Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations

1948 Some furfural condensation products John Henry Jensen Jr. Iowa State College

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Recommended Citation Jensen, John Henry Jr., "Some furfural condensation products " (1948). Retrospective Theses and Dissertations. 13870. https://lib.dr.iastate.edu/rtd/13870

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SOME FURFURiiL CONDENSATION PRODUCTS

by

John Henry Jensen, Jr.

A Thesis Submitted to the Graduate Faculty for the Degree of D-DCXOR'o;f" PlHIliOSOPHY

Major'SUbj.^6t.:i' C|he$ical Engineering

Approved;

Signature was redacted for privacy.

Signature was redacted for privacy. Head of Major epartment

Signature was redacted for privacy. Dean of Grkdu^te College

Iowa State College 1948 UMI Number: DPI 3302

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ProQuest information and Learning Company 300 North Zeeb Road P.O. Box 1346 Ann Arbor, Ml 48106-1346 A ^ TABLE OF CONTENTS Page INTRODUCTION 1

PYROLYSIS OF ACID-POLYMERIZED FURFURAL 13

MODIFIED THIOKOL 16 Introduction 15 Experimental 16 Reaultfl 19

VINYL PURAL 20 Introduction SO Experimental 28 Sulphuric acid catalyst 23 Phosphorus pentoxide catalyst 32 Azeotropic distillation 35 Calcium chloride catalyst 36 Preparation of resins 37 Testing methods 51 Results 65 DISCUSSION OP RESULTS 56

CONCLUSIONS 59 SUMMARY 62

SELECTED REFERENCES 63

ACKNOWLEDGMENT S 72

APPENDIX 73 INTRODUCTION

Throughout industrial practice, there is the problem of reducing losses, both of material and energy, to increase the return on investment, or even to prevent becoming enjoined to cease operations when wastes have become a nuisance to the

general public. In some cases the elimination of wastes result® in increased yields, but in many others utilization of wastes results in by-products which may in time even become primary products, as in the case of the production of butanol and acetone by fez*mentation. In this case the butanol was at first a waste when acetone was needed for powder manufacture in World War I, but subsequently the alcohol became of primary importance with the advent of the lacquer industry in which it was extensively used as a solvent. The waste problem is present particularly in agricultural industry; in most crops only a small part of the total plant is harvested for market—in forestry it is commonly said that only about 10 per cent of a tree becomes finished lumber. Con­ version of these wastes to useful products is an intriguing problem, not only because of the increased revenue it would bring from the nation's farm Iwd, but also because such conversion might conceivably be a considerable contribution to the conservation of the exhaustible resources of the country. 2.

It Is currently a matter of discussion whether or not this

country Is even now changing from a "have" to a "have not''

nation. In the light of this, utilisation of wastes becomes of Increasing significance. Such use would mean drawing upon reserves which are replenished annually» instead of draining more or less fixed reserves which at best can be extended only by new discoveries and by working deposits more and more nearly the marginal minimum which can be processed with ad­ vantage.

In considering the possible uses of agricultural wastes it is convenient to consider their components. Plant materials in general are comprised of three main classes of materials, llgnln, cellulose, and hemi-cellulose. Cellulose has received much attention. It is available in some sources in high con­ centration, as in cotton. Familiar present-day products derived from cellulose Include the acetate, nitrate, and other derivatives now marketed in the forms of fibers, films, and molded products. Lignin has yielded fewer articles of trade. Though it is very abundant in paper mill wastes, it is a complex material, the composition of which is still not well under- stood, certainly^not as well as that of cellulose. The studies of research groups such as those at the Iowa State

College and the Paper Institute however have yielded signifi­ cant advances. Jahn ( 33) summarized the research on lignin a few years ago. At that time Its uses were not many, though 3.

It was being used to produce plastics, bonded materials, and

vanillin. It was also a source of various organic compounds;

hydrocarbons, phenols, and cyclohexanols have been prepared by various processes.

That the pentosan fraction Is an Important part of agri­

cultural wastes may be seen from examination of data pertaining to cornstalks which Peterson and Hlxon (51) showed to contain

about 28 per cent pentosan. Many other wastes have similar proportions.

Because of this pentosan content there have been attempts to found an Industry based upon hydrolysis by dilute acid to xylose, a five carbon sugar. A snail plant for manufacture of xylose from the pentosan content of cottonseed-hull bran was. In fact, in operation for a short time by the Swann Company at Annlston, Alabama In cooperation with the University of Alabama and the Alabama Polytechnic Institute under a project of the

National Bureau of Standards. The work was described by

Schrelber, Gelb, VSfingfleld,and Acree (59). A pjroject of the

Experiment Station at the Iowa State College was established to investigate this problem. The results were reported in the unpublished doctoral thesis of B. 6. Firstenberger (22).

Of much greater commercial interest, however, has been the further hydrolysis of the pentosans to furfural. This is done by the Quaker Oats Company at their plant in Cedar Rapids,

Iowa (39). Finely divided oat hulls are placed in digesters 4.

and cooked with an aqueous solution containing 2 per cent

sulphuric acid. Steam is admitted to the reactor both to supply heat and to sweep out the furfural vapor to frac­ tionating columns. In the fractionating columns furfural and water form an aseotropic mixture boiling at 90®C, which is taken out near the top of the column, the overhead being lower molecular weight by-products. Upon being condensed, the ateotrope separates into a furfural layer containing 4.8 per cent water, and a water layer containing 8.3 per cent fur­ fural (43) • The furfural layer is either sold as such or is optionally purified to remove the water content, while the water layer is returned to the oolumn to be stripped of its furfural content. Thus the only waste is water. Although N furfural was first discovered and reported by Dobereiner in 1832 (l8) when he was studying the production of formic acid from sugar and manganese dioxide, it was the advent of the process described above which reduced it fx^>m a laboratory curiosity to an item of commerce. Only eight years after

DiSbereiner's discovery Stenhouse (67) reported preparation of larger quantities of this material than had previously been made by others. With such quantities, he was able to make a beginning on the determination of the properties of what he still termed "das sogennante kunstliche Amelsen^l". Analysis indicated the empirical formula 05^402, the specific gravity was found to be 1.1006, and the boiling point 168®C. These 5. properties differ but slightly from those now accepted, via.

specific gravity 1.159 and boiling point 161.7®C.

Fownes ( 23) attached the name by which this oil was to be Identified. Because It could be made readily from yegetable materials, particularly brans, he suggested the name "furfurol"

(furfur - bran, ^1 - oil). It was not until the aldehydlc nature of the compound was subsequently Identified that the spelling was changed to "furfural" to be consistent with the systematic naming of compounds In which the suffix >01 Is reserved for alcohols rather than aldehydes.

With the common reagents at hand It was natural that even the early Investigators became familiar with the tendency of this material to polymerise, In fact It was In the Stenhouse paper of 1840 that the condensation resulting from the action of hydrochloric acid or sulphuric acid was described, and In a later paper In 1850 ( he described additional reactions and derivatives. Since then there has been a continuous stream of work on the chemistry of furan compounds In general.

Furfurea, when freshly distilled. Is a mobile fluid, light-straw to colorless and with a peculiar empyreumatlc odor.

Upon standing It gradually darkens, but this may be deterred or prevented by keeping It away from light and air and par- tlciilarly by the addition of snail quantities of antioxidants such as hydroqulnone.

The structure of the furfural molecule, consisting of 6.

an aldehyde group attached to an unsaturated heterocycllo ring,

results in marked activity, especially because there is a

H-C^ - gC-H

H-C® - C«0

V/0 H•

conjugated system of single and double bonds extending out to

the aldehyde group. The very presence of the oxygen atom in

the ring contributes to the activity of furan compounds in

general as has been pointed out by Penn (50). In thiophene—

in which the ring is identical except for the presence of

sulphur in place of oxygen—there is almost no tendency to

polymerise as in the furan compounds, though it has been repor­

ted that thiophene will oondense with diphenylohloromethane

in the presence of stannic chloride (66). On the other hand,

pyri^le and cyclopentadiene, which are similar to furane H-G - C-H H-C - C-H II II II II H-C C-H H-C. C-H I ' \ H H H

(the parent compound from which furfural may be considered

derived) except that they contain respectively an NH and CHg group in place of the oxygen in the furane ring, both polymer­

ize readily.

It was quite logical that as commereial quantities of

furfural became available at a reasonable price it was applied 7. to the manufacture of realns for the plastics Iduatry, as the production of phenol-forraaldchyde resins was already veil under way in the early twenties and here was another chemical­ ly active aldehyde. The resins produced from phenol and fur­ fural were dark in color but possessed exceptional strength, so found acceptance in the market, particuleurly in the manufac­ ture of articles subject to serere abuse such as laminated gears.

The greatest use of furfural has been found in the appli­ cation of its properties as a selectire solvent. It has been extensively used as a purifying reagent for lubricating oils.

In this application furfural has the property of being able to remove sludge-forming and other laidesirable constituents present in oils and leave a superior grade of oil. This property has also been used to remove dark-colored substances present in wood rosin so that a product results which is much lighter in color and therefore able to command a better market.

Particularly in^ortant during the war was its use as a selec­ tive solvent in the purification of butadiene for the synthetic rubber program. For polymerization into Buna 3, butadiene must be very nearly pure; even 2 per cent of impurities in the monomer greatly impede, if not entirely prevent, the proper course of the copolymerisation. Without furfural, the requisite purity might have been very difficult to achieve.

As previously mentioned, Stenhouse (9 ) long ago reported 8.

that In the presenoe of some mineral acids and bases furfural

yielded a hard black polymer except that with nitric acid the

result was that the furfural was oxidized to oxalic acid.

The mechanism of this action has puzzled many investigators.

However, not long ago Penn (50) pointed out some analogies in

chemical behavior which seem plausible elucidations of the

matter.

Penn pointed out that from consideration of the struc-> ture of the molecule it should be possible for furfural to polymerize or condense in the following manners:

1. By the double bond 2-3.

2. By the double bond 4-5.

3. By condensation of the aldehyde group.

4. By condensation with the use of the 5 hydrogen

atom •

5. By splitting of the double bonds in the 2-5 and

3-4 positions in preference to the 2-3 and 4-5

positions.

Demonstration that all of these may occur has been seen through study of the behavior of other compounds much like furane and furfural.

For example, coumarone (benzo-furane) condenses by means H

H-C C C-H I II |i

I H 9. of the double bonds of the furane ring present; hence, by analogy It would seem that furane compounds should behave similarly, I.e. polymerize by way of the 2-3 or 4-5 double bond. It is conceivable that one of these double bonds may be used to build the polymer chain and then the other used to cross-link between chains to build up the extreme hardness found in the resins. Evidenoe of which double bond may be used to build the chains is taten, again by inference, from study of polymerization of coumarone. As would be expected from the principle of steric hindrance 1—methyl coumarone H H-? S - if-H

I H polymerizes less readily than the parent body, and dimethyl- coumarone polymerizes only with great difficulty, if at all. H i? -

I H

Hence, by analogy, it would seem that for polymerization of this aort to proo«ed in furane compounds requires that first the unhindered 4-5 bond be used and then subsequently the 2-3 bond if it be used at all.

Then considering the conjugated system of single and double bonds it may be conjectured that furane bodies may polymerize by acting as dienes, i.e. through the 2 and 6 10, positions, leaving a double bond between positions 3 and 4.

Numerous studies of the furane compounds have shown the 2 and 5 positions to be more reactive. In many oases substitu­ tion for the hydrogen atoms at positions 3 and 4 is impossible until the 2 and 5 positions have been blocked to prevent re­ action there. This is seen also in pyrrole, which upon hydro- genation gives 2-.5 dihydropyrrole. Similar action is seen with 2-methyl pyrrole smd pyrrole-2-aldehyde. Also in the case of oyolopentadiene, studies (12) of the residual un- saturation indicate for lower polymers two double bonds per chain requiring a structure u , u n \ — C - C-H

X H / H X H H / H H n

but for higher polymers one residual double bond per chain unit requiring the structure ( 9 ) 11.

In the case of the furane ring, the unaaturation found for low degrees of polymerization (theriao-plastlo resins) and the fact that oxidation with peracetie acid Introduces an extra oxygen atom per unit indicates the action as a diene (7).

In this case however the activity of the ring laakes further action of the remaining 3-4 bond quite likely to orosa-linfc

or further bind the same chain.

3o far this has considered only the possibilities for polymerization dependent upon the linkages between cso'bon atoms. It is also possible for condensations to occur invol>

Ting the 5-hydrogen atom and the aldehyde group.

For the former node of condensation evidence is seen in the behavior of furfuryl alcohol. Three aolecxiles of fur- furyl alcohol will condense to form an identifiable, more complex iK)leoule capable of reacting similarly to increase further the length of the chain (19).

^ n H 9 9 9 6 - C C-C C-C C-C I I H II II 9 II II 9 II II H H-C^o/O - g - OH

This suggests the likelihood of a form of aldol condensation- in the case of furfural involving again the 5-hydrogen-atom— to give 1£>,

In addition to all the above mechanleras it la possible

that the presence of hydrohalogen add may cause cleavage of the ether linkage nrhloh closes the ring thereby leading to an additional series of possibilities of reactions as an aliphatic compound.

Passing from consideration of the simple polymerization of furfural alone to its reactions to form resins with phenols« amines, etc. opens a wide number of poBSibllities for polymer­ ization or condensation, separately or simultaneously. The early work in this field is well reviewed by Ellis (20). The study of the use of furfural in phenolic resins has led to oommercial plaatice under the trade name of Durite. It has also been the subject of various researches at the Experiment

Station of the Iowa State College. Hence this field was not studied in this work. The purpose of this work is to investigate some of the other possible applications of furfural to the general field of plastics. 13.

PYR0LY3IS OF ACID-POLYMERIZED FURFURAL

Three thousand iBlllllltera of furfural was polymerized

by adding to It 300 ml, of concentrated sulphuric acid. After this had stood for one week, it was crushed. A 60 gram por­ tion was selected for test. This portion would pass through an eight-mesh Tyler screen, and be retained on a twenty-mesh screen.

This sample was placed in a distillation flask with a water-cooled condenser attached to the side arm. Heat was applied by flame directed at an asbestos-centered wire gauze supporting the flask. At 95®C. a few drops of liquid appeared in the receiver attended by a strongly acrid odor. A total of 4 ml. was collected. The liquid was acid to litmua and produced a white precipitate with silver nitrate which dissolved upon addition of nitric acid. With barium chloride there was formed a white precipitate insoluble in hydrochloric acid.

Thus the presence of sulphate ion was indicated. Two 0.2 ml. samples required 1.10 and 1.15 ml. of 0.0983 N sodium hydrox­ ide to reach neutralization with phenolphthalein indicator.

Thus the acid product was 0.55 N. Further heating produced no detectable change although a thermoneter inserted among the solid grains indicated a 14. temperature of 360®C. and the lower part of the sample was heated Bufflclently to soften the Pyrex glass flask. The solid grains showed no sign of melting or decomposition.

After heating, the grains appeared no different than before. 15.

MODIFIED THIOKOL

Introduotlon

In casting about to dlsoover a fruitful field for

applications of furfural In the plastics Industry, one of

those selected early was the field of the thloplasts because

of the aTallablllty of the materials and ease of handling.

The history of the thloplasts extends many years back. These materials In the early days suffered the same neglect

as did many other compounds; a hundred years ago investigators

seemed to have little interest in tars and gums resulting from

experiments (particularly orgeurtlc), but seemed interested only

if the product was crystalline so that it might readily be characterised. Thus Meyer (4-5) in 1867 had made an amorphous

ethylene sulphide by boiling ethylene dlbromide with potassium sulphide, but since the product was not crystalline, his interest apparently oeased. It was about fifty years later that this simple reaction came into its own along with the

Ifevlved interests in many another of the earlier chemists'

"gunks*. J. C, Patrick (3, p.273) was searching for a new antl. freeze fluid when he mixed ethylene dlchloride and sodium poly- sulphide, but instead of finding a new fluid, he discovered 16.

a gummy mass.

Fortunately, he had the acumen to follow this discovery

by Investigating its possibilities. It was found that the

product, known as Thiokol A, had both good and bad properties.

It, like natural rubber, softened at high temperatures and

became brittle when cold and even at best had a rather low

strength. Ofi the other hand it was inert, or nearly so, to

almost all solvents and was cheap so that it found a ready

market, for example in the manufacture of hose for handling

petroleum products, a service in which the flexibility and

inertness were much needed. Many modifications have since been devised. Among the obvious were the use of other dihalides (dichloroethers,

dichlorohydrins, etc.), after-treatments such as boiling with

40 per cent caustic to remove labile sulphur, and vulcaniza­ tion with or without additional fillers, etc. These have had the effects of improving the strength, the temperature stabil­ ity, decreasing the odor, etc.

Although it was not known what might be the effect of incorporation of furfural Into this mixture it was never­ theless tried.

Experimental

To acquaint the workers with the procedure of formation of Thlokol in bulk, the procedure given by Barron In "Modern 17.

Synthetic Rubbers" (3, p. 274) was tried. This procedure was

Dissolve 750 g. sodium sulfide In water and boll with 300 g, of sulfur. This gives a solution containing chiefly sodium tetrasulfIde. It is diluted, 500 oc. ethylene dlchlorlde added and refluxed at 70®C. for a few hours. found to be quite satisfactory. The ethylene dlchlorlde layer

lay below the v/ater layer so, as heat was applied and the

dlchlorlde began to boil, the vapors passed up through the

water layer where the tetrasulflde was In solution. If the

tetrasulfide solution were too concentrated, of course, the layers would be reversed. The product from one-fifth of the above recipe (and using potaaislum sulfide in place of sodium

sulfide which was not available) appeared within twenty minutes as a guDuny, gray-green mass. If this mass were taken from the reaction vessel while still hot and pliable little difficulty was had; but after cooling, it became quite hard and con­ sequently impossible to remove without reheating or breaking the vessel.

A second test was made with one-half the ethylene dlchlorlde replaced by an equal volume of furfural. In this experiaent it was found that the product instead of being hard and gray-green was now quite plastic and dark-brown In color.

The oonsistenoy was found to be something like that of a soft asphalt or "bouncing putty"; it stretches or compresses easily, but it does not snap back, it returns slowly to its original shape. Upon being left standing, it slowly deforms 18. to a flat cake. This plastic nature is retained even after a few yeara; aamplea three years old have much the same properties as when they were prepared.

Yflth this encouraging result, It was decided to prepare a series of samples with varying fractions of furfural incor­ porated. A batch of six raols of potassium tetrasulflde (two- thirds of Barron's recipe) was prepared. The recipe required 600 ml, of ethylene dlchloride; this is

2 I 500 ml. I 1.287 g. I mol , 4.24 mols 31 1 ml. I 99 g. i.e. the recipe requires approximately 3 mols of potassium tetrasulflde to 2 mols of the ethylene diohlorlde. The tet­ rasulflde solution was diluted to a total volume of 1200 ml.

Thus each 100 ml, portion (0.5 mol) required two-thirds (0.5 mol) or 0,33 mol of ethylene dlchloride or its equivalent.

A series of samples was prepared according to the following schedule: Tatle 1 Modified Thiokol Preparations Potassium Ethylene Furfural Specimen tetrasulflde dlchloride ml. mols ml. mole ml. mols

0 100 0.5 26.30 0.330 0.00 0.00 1 100 0.5 23,70 0.296 2.63 0.032 2 100 0.5 21,00 0.264 5.26 0.064 3 100 0.5 18.40 0.231 7,90 0.095 4 100 0.5 15.80 0.198 10.50 0.127 5 100 0.5 13.15 0,165 13.15 0.159 6 100 0.5 10.50 0,132 15,80 0.191 7 100 0.5 7.90 0.099 18.40 0.222 8 100 0.5 5.76 0,072 21.00 0.254 9 100 0.5 2.63 0,033 23.70 0.286 10 100 0.5 0.00 0,000 26.30 0.318 19.

Results

It waa found that the effect was that of plastlclzlng,

I.e. the more furfural present, the softer and more sticky the product.

It might be questioned whether this plastlclzlng effect

mtght not be achieved equally well by Incorporating the fur­

fural Into finished Thlokol, for example by kneading the

polymer with furfural. With the equipment available such was

not found to be possible. It seemed necessary, and certainly

much simpler, to add the furfural to the ethylene dlchlorlde

(with which it Is misclble in all proportions) in the re­

action mixture. 20.

VINYL FURAL

Introduotlon

Vinyl resins as a class may be considered as Just one

example of polymers formed from deriYatives of ethylene as they contain the group H-C s C- ; however, they have their H H origin commercially in acetylene.

Manufacture from acetylene begins with the production first of vinyl acetate (61, p. 909). This is done by passing a stream of acetylene gas through anhydrous acetic acid con­ taining a mercury-acetate-sulphate catalyst. The vapors pass out the top of the reaction vessel and are subsequently purified by rectification to produce pure vinyl acetate, ethylidene acetate, and by-product acetone. H H 0 HC S CH + CHgCOOH —> HC = C - 0 - C - CH3

The sludge from the reactor is reworked for its mercury con­ tent. Polymerization inhibitors must be added to the pure liquid to prevent eventual solidification, as the fluid polymerizes in time under the influence of air and light alone.

Vinyl acetate is polymerized by the use of peroxide catalysts. With the admixture of some water, a little basic material such as soda ash, and a peroxide catalyst such as benzoyl peroxide or hydrogen pe7.*oxide, the monomer polymerizes 21.

readily. Polymerization may be done either in bulk or In

emulsion. As in all polymerizations the average size of

polymer molecule produced la decreased by the use of greater

quantities of catalyst, higher temperature, etc., i.e. by

conditions which favor the formation of many nuclei of growing

polymer chains. Conversely, the higher molecular weight products are produced by employment of minimum catalyst,

temperature, etc.

Polyvinyl acetate by itself is not very suitable as a

plastic resin because of Its tendency to be tacky when warm,

if not even at room temperature; however, this very property

has made its application as an adhesive of luiportance. Plastics more generally useful are formed by copolymerlsatlon

of vinyl acetate and vinyl chloride.

H H H CH3COO-C = CHg + H-C = 6-CI —>

n H H H H H H H H I I t 1 I1 1 1 1t 1 -c - c - c C - C - C - C - C - C 1 1 I I I 1 1 1 1 1 1 CI H 0 H 0, H CI H 0 CsO C«0 CstO II i CHg CHjj CHg

Polyvinyl acetate may be hydrolyzed to Its component

parts, polyvinyl alcohol and aoetic acid, just like any mono-

merle ester. 22.

H H H H H H I 1J 1 1 1 t C - C - C - c - C- 1 1 1 1 H 0 H 0 H 0 acid 1 1 1 CsO c=o c=o or base 1 1 CHg CH3 CH3

H H H H H H -C - C - C - C - C - C- + CH- COOH H 0 H 0 H 0 I I I H H H

This may be done either In acid or alkaline medium, but it has been reported (27) that "alkali-prepared* polyvinyl alcohol is not aa pure as that prepared by acid hydrolysis as it has a strong tendency for adsorption of inorganic salts.

Thus the alkali acetate formed upon such alkaline hydrolysis would to some extent be adsorbed upon the px*oduot.

This impurity of polyvinyl alcohol prepared by hydrolysis in alkaline medium was confirmed in t his work. Thus 256 g. of polyvinyl acetate was dissolved in 4 1. of redistilled solox

(denatured ethanol), and 4 mols of potassium hydroxide was also dissolved in solox. The acetate solution was added drop- wise » with stirring, to the alcoholic potassium hydroxide.

Reaction, at room temperature, was immediate. The product separated in granules. It was observed that later (after the first portions of product had been filtered out) the product was lighter in color; i.e. as the base was diluted by the 23.

addition of the solvent added with the polyvinyl acetate the

color of the product changed from buff to nearly white.

Analysis of the dried product for ash gave the data shown In

Table 2.

Table 2

Analytical Data from Ash Determination on Polyvinyl Alcohol Prepared by Alkaline Hydrolysis of Polyvinyl Acetate

Gram weight Test 1 Test 2 Test 3

Crucible and sample 9.9840 10.0235 9.7937

Crucible 8.9836 9.0046 8.7896

Sample 1.0004 1.0189 1.0041

Crucible and ash 9.0289 9.0557 8.8382

Ash 0.0453 0.0511 0.0486

Per cent ash 4.53 5.02 4.84

It may be postulated that the ash content might be les­ sened by working with more dilute solutions of base and poly­ vinyl acetate, but this was not tested In view of the fact that it Is known that acid hydrolysis yields material of greater purity. Subsequent work was done with polyvinyl alcohol (trade name Elvanol) obtained from the Electrochemicals

Department of S. I. du Pont de Nemours and C!o., Inc., Niagara

Palls, N. Y. using their medium viscosity type B, Grade 71-24.

It should be noted in passing that polyvinyl alcohol must be prepared by this round-about procedure as the monomer 24.

Is unknown. All attempts to prepare monomerlc 7lnyl alcohol

have resulted Instead In the formation of aoetaldehyde, with

which it is tautomeric.

Polyvinyl alcohol is useful in some ways by itself, e.g.

as an emulsifying agent, but possesses the general handicap

for many purposes that it is soluble in water if it is not too

highly polymerized.

Still further modification of the polyvinyl chain leads

to other extremely useful materials. Since the chain possesses

hydroxyl groups on alternate carbon atoms, it lends itself to

the formation of acetals.

H H H H H I I I I I _C-C-C-C-C I I I I I H 0 H 0 H I I H 0 H I C-H I R

The products are conveniently prepared by omitting the opera­ tion of hydrolysis of the polyvinyl acetate to the alcol:u)l as a separate step and proceeding from the acetate directly. By this method the hydrolysis and subsequent acetal foz*mation are performed in the same reaction vessel and at very nearly the same time. This is done by dispersing ("Alssolving") the polyvinyl acetate in a suitable solvent, such as acetic acid, and then treating it with the desired aldehyde In the presence 25. of a small amount of add catalyst, such as sulphuric acid.

Anhydrous conditions are needed as the reaction requires the

elimination of water.

The use of formaldehyde in such a process leads to the formation of a hard resin which may derive some if not much of its hardness from cross-linkages between chains. This has been used to some considerable extent as wire insulation.

However, the acetal most noted at present is that formed by the reaction with butyrsildehyde. This product seems to have

Just the right degree of resistance to cold and also of ad­ hesion to smooth surfaces to make it the best material known at present for use as an interlayer in safety glass.

Based upon this knowledge and a brief statement in

Barron's "Modern Synthetic Rubbers" (3, p. 307) it was de­ cided to investigate the use of furfural in the formation of what might be termed "polyvinyl fural" by analogy with the names of similar products made from other aldehydes. However, here one encounters two dilemmas. It is quite well known that when fui*fural is treated with a mineral acid (except nitric acid) it readily polymerizes by Itself to give an extremely hard but brittle resin, so hard and brittle that it does not lend Itself to commeroial use. Yet an acid catalyst is ordinarily used to promote the formation of acetals. This method was tried In this work even so. Later,

Improvements were made. Also there was the problem of a 26. suitable reaction medium. In this work the starting material was one which is quite Insoluble In most common solvents except water and yet water Is the very thing not desired, as the reaction requires the elimination of water, i.e. anhydrous conditions.

To summarize, beginning from the Industrial raw materials of acetylene and aoetlc acid there are many variables attend­ ant upon the total sequence of reactions.

H H 0 I I II 1. H-C • C-K + CH3COOH —H-C s C - 0 - C - CH3

0 H H H H H II M 1 1 1 1 1 c - CH3 ^ -c .. C - C .. C - C- [ 1 1 1 1 1 1 1 1 H 0 H 0 H 1 1 CsO c=o 1 1 CH3 CHg

H H H H H H H H H H 1 1 1 1 1 1 1 acid 1 1 1 1 I 3. -CC - C - c - C - c- + •C - C - C - G C- 1 1 1 1 1 1 1 1 or 1 1 1 1 I H 0 H 0 H H 0 H 0 H 1 1 H H c=o c=o 1 1 CH3 CH3 27.

H-C - C-H H H H H H 1 1 1 1 1 1 1 I 4. H-C C-CsO 4 -C - C - C C- 1 1 i1 I V0 " H 0 H 0 H H H

H H I I -C I f H H

At each step the usual variables of time, temperature, and ratio of reactants exert their effect. As was pointed out,

the molecular weight of the polymer is established prin­

cipally in the polymerization reaction where it is governed

by the temperature, time, and amount of catalyst. Next, the

hydrolysis of the ester may be carried to a greater or lesser

degree leaving few or many residual acetyl giroups in the poly­ vinyl alcohol chain according to the intensity of the hydrol­ ysis. In this work these variables were eliminated by having requested the supplier to deliver a grade of polyvinyl alcohol of moderate molecular weight and high degree of conversion to alcohol. Thus the only variables encountered here were those dealing with the final step of conversion to the acetal. Of 28.

the variables studied, the major worlt was done on that of the

length of time allowed for the reaction.

Hlxperl mental

Sulphuric acid catalyst.

Again, In order that the workers might become feunlllar

with the procedure, an Initial test was made In which the pro­

cedure given by D'Alello (13, p. 61) for the preparation of poly­

vinyl formal from polyvinyl acetate was followed precisely.

First, from freshly redistilled vinyl acetate, some poly­

vinyl acetate was prepared according to the instructions of

German Patent 615,995 of 1935 (l) viz. 200 g. vinyl acetate

and 200 g. of water were placed in a flask fitted for reflux.

To this were added 10 ml. of 3 per cent aqueous hydrogen peroxide solution (in lieu of 1 ml. of 30 per cent aqueous

hydrogen peroxide directed by the patent) and 1 g. of sodium carbonate. After the mixture was boiled for about twenty minutes the polymer became of sufficient molecular weight to separate front the liquid system as a solid mass. While still warm and pliable it was removed from the flask.

Subsequent tests indicated that the proportion of peroxide catalyst is not critical. Satisfactory polymerization resulted with as little as one-tenth of the amount described here.

This product was then dispersed in glacial acetic acid 29.

and treated with formaldehyde In the presence of sulphuric

acid catalyst. The product was recovered several hours later

by adding water to the mixture while it was stirred rapidly.

This changed the mixture from an acid to an aqueous system.

The product so obtained was In the form of hard, slightly

amber grains. That a change had occurred was indicated by

the faot that whereas the original polyvinyl acetate would

disperse in alcohol, the formal would not.

Next the direct substitution of furfural for formalde­

hyde was tried. With 50 g. of polyvinyl acetate D'Alello suggests 42 g. of formalin of 40 per cent strength, i.e.

16,8 g. of pure formaldehyde. As the molecular weight of formaldehyde is 30, this amounts to 0.56 mol. To replace this with furfural (molecular weight 96) requires 53.8 g.

The specific gravity of furfural is 1.16 so 53.8 g. of fur­ fural is obtained by using 46 ml. Fifty milliliters was used.

Also, it was thought that since it had been observed that polyvinyl acetate would disperse in furfural it might be possible to form the acetal from the two without the aid of further solvent except as diluent. To test this, 50 g. of polyvinyl acetate was added (in small chunks) to 50 ml. of furfural. To obtain a smooth dispersion required that the mixture be allowed to stand overnight.

The next day, while the mixture was slowly stirred, the catalyst (3.5 ml. of concentrated sulphuric acid) was added. 33.

This Imtaediately caused the mass to set to the usual black porous mass. Thus, at least with this catalyst. It was evident that a diluent or solvent is needed.

Considering the need of diluent, It was decided to try benzene as It was found that a thick syrup of polyvinyl acetate

"dissolved" in furfural was mlsclble with benzene. Riegel

(58, p. 628) states that the sulfonating power of sulphuric acid is exhausted when ita strength is down to 77 per cent.

Consequently, it was thought that if only a small amount of acid \fere present, as in this case, it would exert catalytic rather than sulfonating action. It was yet possible that the furfural alone might be polymerized in the system.

The procedure followed here was to add 100 ml. of ben­ zene to a mixture of 50 g. of polyvinyl acetate and 50 ml. of furfural. To this was added 3.4 g. of concentrated sul­ phuric acid. This nilxture was stirred slowly and warmed; the result was that it set to a sticky jelly in about two hours. Then arose the problem of how to separate the reacting materials from the solvent. A technique was not apparent. Possibly kneading the mass in water would accomplish this by virtue of the insolubility of benzene in water. The equip­ ment for so doing, however, was not available. Compared to the previous test this one shows that the presence of the diluent does retard the reaction.

In view of the problem of separating the solvent, it 31.

was thought that a retuim to D'Alello's suggeatlon of glacial

acetic acid might be acceptable, 'fhla had previously been

avoided because It was known that furfural will form a crys­

talline dlacetate; but when the acid was tried as a solvent for furfural alone, no evidence of Interaction was apparent after three hours.

Hence, a batch was prepared In which there were placed

93 g. of glacial acetic add, 1 g. of concentrated sulphuric acid catalyst, and 50 g. of polyvinyl acetate. This was slowly stirred while being kept at 85 to 90®C. over a water bath until the resin was smoothly dispersed. By this time It had darkened noticeably though no furfural was yet added.

To this was added 50 ml. of furfural. The mixture was then warmed over a water bath. In two hours the liquid mixture stiffened to a tough Jelly which "climbed" up the shaft of the stirrer. It was then poured out Into cold water and kneaded some by hand to assist In the removal of the add diluent. The washings were decanted and discarded.

The product from this procedure Is still tough and plastic after three years. Addition of plastlclaers to portions of this product was made by working them in on a set of equal-speed mixing rolls in the laboratory of the Chemical Engineering section of the Engineering Experiment Station. The rolls were warmed by the use of two large infra-red lights. The material was 32.

first warmed and sheeted out on one roll, then the liquid

plastlclzer (tri-cresyl phosphate for one saaple, and butyl

ethyl dig^ycol oarbonate for another) was added dropwlse and

worked In by cutting and foldlng-^ver the sheeted-out resin. Sheets so made still retain their desirable p]*operties of flexibility and water resistance after two-and-one-half years.

It is oonoelTable that there may be in these sheets some

proportion of unconverted polyvinyl acetate. The absenoe of

polyvinyl alcohol from acid hydrolysis of the polyester Is

indicated by the inertness to boiling water. That the fur­

fural has combined Is shown by the dark color of the product

and the negative aniline-acetate color reaction test on the

washings. Prom this evidence alone, however, it is not

possible to state whether the furfural has entered the chain

in acetal formation or i^ether this be merely a case of ad­

mixture of two resins. At any rate it Is true that the resulting product does have desirable properties although It is black in color.

Phosphorus pentoxide catalyst.

Considering that the presence of the sulphuric acid in the reaction mixture'might cause excessive condensation of the furfural with itself rather than the desired acetal for­ mation, it was decided to try other methods for promoting the reaction. It seemed plausible to try the use of phosphorus 33.

pentoxlde, relying on its affinity for water to cause forma­ tion of the acetal before hydrolysis of some of the oxide would give rise to excess acidity.

To test this premise there was placed in a three-neoked flaefc a mixture of 83.4 g. of polyvinyl alcohol, 76.7 g. of phosphorus pentoxlde, and 500 ml. of furfural. But even be­ fore heat was applied, this mixture became very hot from the reaction ensuing so that it first boiled and then later set to a hard black mass. Thus it seemed that far too much phos­ phorus pentoxlde had been employed.

Hence, a second attempt was made with a mixture of 50 ml. of furfural, 8.33 g. polyvinyl alcohol, and 2.0 g. of phos­ phorus pentoxlde. There was no appgurent immediate reaction as before so the mixture was slowly heated while being stirred.

When the temperature had reached 64®C. the mixture became more viscous and so the heat was removed. Even so the tem­ perature continued to rise to 72®C. and the mixture became quite black. It was then turned out onto a sheet of paper and allowed to cool. After it was washed it was found to be quite pliable, easily worked by hand, and somewhat elastic.

In view of the previous success with acetic acid diluent it was decided to attempt a similar use with this catalyst.

For this purpose there was prepared a mixture of 50 ml. of furfural, 50 ml. of glacial acetic acid, 8.33 g. of polyvinyl alcohol, and 2.0 g. of phosphorus pentoxlde. The mixture was 34.

Slowly heated until, again at 64®C., it turned dark and quite viscous. Heating was then discontinued; the reaction did not cease even so. The reaction continued a little longer, giving a viscous, clear, purple-colored liquid.

When this mixture was added to water and then the liquid material drained off there was found a light-purple-colored, elastic material, not at all sticky. It appeared to be made of tough sinewy fibres containing a few pockets of black con­ densed furfural and light polyvinyl acetate. Thus it was seen that although a reaction had occurred, there were still some admixed chunks of condensed furfural.

To prove that the product obtained depended upon the presence of both furfural and polyvinyl alcohol two tests were made in which all ingredients were present but one of these two.

When acetic acid, furfural, and phosphorus pentoxide were mixed and heated very little reaction was noticeable.

Some small solid particles of condensed furfural did separate, but the viscosity did not increase as in the previous tests. When acetic acid, polyvinyl alcohol, and phosphorus pentoxide were mixed and heated to boiling there again seemed little evidence of reaction. The viscosity did increase slightly, but nothing like the previous product appeared.

It was demonstrated that both furfural and polyvinyl alcohol must be present in order that an elastic product be formed. 35.

Azeotropic dlatlllatlon.

The work deaorlbed In the preceding section demonstrated that a polymeric product could be formed from polyvinyl alco­ hol and furfural. However, there was some question as to whether phosphoznjia pentoxlde might be too strong a dehydrating agent. It was lutown that furfural and water form an azeo- troplc mixture boiling at 97.9®C, under normal barometric pressure. Consequently, It was thought It might be possible to remove the water formed In the reaction by this means.

Polyvinyl alcohol and excess furfural could be charged to a reaction vessel and heated. As the water formed It would distill out Into a reflux column for separation of the azeotrope from anhydrous furfural vapor and then pass to a condenser. After being condensed the azeotrope would separate

Into two layers; the water layer would be discarded and the furfural layer returned to the reaction vessel If desired.

The apparatus used was comprised of a three-necked flask fitted with a reflux column to which a water-cooled condenser was attached, a separatory funnel, and provided with a motor- driven stirring device. Into this the furfural and polyvinyl alcohol were charged. The reaction vessel was heated by use of a Bunsen burner.

The removal of water from the reaction by azeotroplc dlatlllatlon by thla method was not significantly successful.

Heating alone accelerates the natural tendency of furfural 36. to polymerize. This resulted In a product contaminated with polymerized furfural. Consequently this method waa dis­

carded even though there was some Indication that the water formed could he removed In this manner.

Calcium chloride catalyst.

From the preceding work It was Icnown that a desirable product could be formed by admixture, at least, of vinyl and furfural resins, and that acetic acid was a suitable solvent.

In view of the doubt existing as to whether or not the acetal had actually formed and whether the product might not actually be merely what might be termed "contaminated" polyvinyl acetate, It was decided to eliminate the latter doubt by eliminating the polyvinyl acetate. For this purpose commer­ cial polyvinyl alcohol was employed.

Also, at this stage of the investigation there was dis­ covered a French patent issued to the I. G. ParbenIndustrie

(29) in which the use of calcium chloride as a dehydrating agent for formation of acetals was recommended. As this would be a less severe reagent with less tendency to cause the typical furfural-acid resin formation, the change to calcium chloride catalyst was made. Since the reaction of 1 aol of aldehyde with the alcohol requires the removal of 1 mol of water (which may be removed in forming cross-links between chains as well as in forming 37. additions to one ohain) then the proportions baaed on 50 ml.

(0.56 mol) of furfural require the removal of 0.56 mol (10 g.) of water. If anhydrous caloium chloride be used, it is pos­ sible that it may be converted to the raonohydrate, dihydrate, or hexahydrate. Assuraing conversion of the anhydrous form

(moleculsur weight 111) only to the monohydrate means that to remove the 10 g. of water would require 94 g. of the anhydrous calcium chloride. On the other hand, conversion to the hexa­ hydrate would require only one-sixth as much, or (nearly) 16 g.

Preparation of reains. Abatch hereinafter designated as VP-1 was prepared by mixing 100 g. of polyvinyl alcohol with 750 ml. glacial acetic acid, 500 ml. furfural, and 20 g. anhydrous calcium chloride in a 3 1. beaker. This represents a considerable excess of furfural, serving as additional diluent as well as exerting a mass-action effect. The mix­ ture was heated to 60®C. for one-half hour on an electric hot plate. In this time the original suspension of the polyvinyl alcohol cleared. The piroduot was then precipitated by the alow addition of an equal volume of water while the mixture was rapidly stirred. The product so precipitated was left standing in the mother liquor as it was difficult to filter due to the fact that there seemed to be some gelatinizing effect (it was later found that this difficulty could be reduced by adequate washing which seems to harden the 38. gelatinized particles).

Three discs were molded from this resin for testing pur­

poses. Five gram samples of the unfilled resin were molded without filler under pressing conditions of 150°C. and 10,000 ITd. total pressure for a time of three minutes each. The resultant discs were li in. in diameter and ahout 0.2 in. in

thickness, dimensions upon which this work is standardized.

The discs made of this resin had good smooth surfaces and

showed sharp edges; they were slightly translucent and of a

dark brown color.

To investigate the effect of time of reaction, a second batch, smaller in amount, was prepared. In this case the

quantities used were 400 ml. of glacial acetic acid, 400 ml.

of furfural, smd 20 g. of anhydrous calcium chloride. These were mixed and heated to 70°C. After the calcium chloride had

dissolved there was added 50 g. of polyvinyl alcohol. In

about ten minutes the fluid system beoame a thick syrup as

before, but this time the reaction was continued with the

result that after one hour it had become a thick Jelly. It was transferred from the original 1 1. beaker to a 4 1.

beaker and an attempt to dilute the resin was made by trying

to incorporate an additional quantity of 400 ml. of acetic

acid. It was found that this is very difficult to do. It

was found that it would be far better to have the necessary

amount of solvent present at the beginning, for as the attempt 39. at dilution was being made the reaction was continuing.

Thereby the purpose of the attempted dilution was defeated.

Consequently, it was impossible to precipitate the reain in granules as in the previous batch; in this case it was necessary to place the thick Jelly in a dog-leg mixer and knead it while water was passed in. A screen was placed over the upoer rim of the container so ao to prevent the loss of resin particles, but permit the wash water to pass out of the machine. The resultant resin in this case was a mass of irregular pieces, much darker in color than in the previous case; it is likely that because of the problem of physical handling in this case the washing was not as efficient as before. This material is designated as VF-2.

V/hen discs were molded of this resin It was found that a somewhat higher temperature was required to soften the grains to cause suitable flow in the mold.

At this time it was apparent that it might be of value to prepare a series of samples of this resin with varying reaction time allowed to ascertain whether such variation would appreciably affect the properties of the resin.

Sample VF-3 was prepared by heating at 70°C, for one and one-half hours a mixture of 400 ml, furfural, SO g. of »n- hydrous oslcium chloride, 2 1. of glacial acetic acid, and

60 g. of polyvinyl alcohol. In this case a sufficient amount of solvent was present to prevent the difficulties encountered with the preparation of sample VF-2, so precipitation was

successfully achieved by the addition of water to the thick

resin sj/rup while stirring, as in the preparation of VF-1.

The procedure gave a yield of 60.8 g. of resin after it was

washed, filtered, and dried. Discs were molded at 160°C.

for five minutes at a load of 10,000 lb.

Sample VF-4 was prepared fi?om the same proportions in

the mixture as in VP-3 but with the reaction allowed to pro­

ceed for five hours before the resin was precipitated as in

the preparation of VF-1. The product was washed and dried

as usual. The yield was 39.4 g. Discs were molded at 170°0. for five minutes under a load of 10,000 lb.

Sample VF-5 was prepared from a mixture of 1 1. of

acetic acid, 500 ml. of furfural, 50 g. of polyvinyl alcohol, and 20 g. of anhydrous calcium chloride. Reaction time was fifteen minutes; the yield was 50 g. of Ichakl-colored grains.

Sample VF-6 was prepared from a mixture of 1200 ml. of glacial acetic acid, 400 ml. of furfural, 50 g. of polyvinyl alcohol, and 20 g, of anhydrous calcium chloride. The re­ action mixture was kept at a temperature of 70°G. for one hour and ten minutes. The yield was 56.8 g. The preparation of sample VF-7 followed the procedure of the preparation of VF—3, except that in addition to the in­ gredients noted there, there was added 50 g. of asbestos floe to serve as filler. The asbestos was added to the mixture 41.

before the reaction began. The reaction was allowed to pro­

ceed for five houre. The product precipitated then was quite

light in color, contrary to what was expected from the previous

experiments. Based upon the color of the previous prepara­

tions also allowed to react for some time, it is to be sus­

pected that in this case the addition of the asbestos retarded the reaction. Discs molded at 160®C. for five minutes under

a load of 10,000 lb. showed an average specific gravity of

1.48 by measurement of the dimensions of the discs.

Sample VP-d was prepared with the identical proportions

as were used in sample 7F-7 except that the asbestos was not

added until the end of the reaction time of five hours. At

that time the sample was split into two equal parts; one was

precipitated by the addition of water to the mixture as it

was, while to the other part was added 25 g. of asbestos floe

before precipitation with water. The latter was distinguished

by the designation VF-8a.

At this stage of the investigation it was decided to

begin study with larger size preparations to permit a more

extensive testing program. It was first necessary to make a

trial test or two for the purpose of learning suitable tech­

nique. It was decided to begin with nearly foxirfold prepara­

tions. This required the use of a much larger reaction

vessel, so use was made of a 10 gallon stoneware crook with a maaonite fume cover. This was heated during time of reaction 42. by being placed In a water bath arrangement comprised of water heated in a steam-Jacketed open kettle In the Unit Operations

Laboratory of the Department of Chemical Engineering. A suitable stirring mechanism was at first devised by using a small high speed stirring motor with a speed reducer comprised of pulleys and a rubber belt. This was subsequently replaced by a motor with a worm-gear speed reducer attached.

Throughout this work the problem of fume nuisance from the acid solvent remained unsolved. It would be preferable to work with a closed reactor but such was not available.

The use of a closed reactor would have the additional merit of permitting the use of reflux of solvent vapors thereby reducing solvent losses.

In all remaining cases, the procedure with this apparatus was to charge the acid, catalyst, and polyvinyl alcohol first.

These were then warmed to the reaction temperature, and stirred until the mixture was a uniform dispersion, or nearly so. Then the furfural was added.

The first preparation so made, designated VF.9, was made by use of 200 g. of polyvinyl alcohol, 3000 ml. of glacial acetic acid, 80 g. of anhydrous calcium chloride, and 1500 ml. of furfural. These materials were heated for one hour at approximately 70®C. Then it was found that the reaction had proceeded too far to permit the use of a high-speed stirrer while precipitating the resin with the addition of water. 43.

Consequently, It was again necessary to uae the procedure of

kneading while water was passed Into the kneading machine.

The yield from this test was 171 g. of dried resin.

Batch VF-10 meanwhile was prepared as a duplicate of

VF-8a. The proportions used were smaller, only 30 g. of

polyvinyl alcohol, and 30 g, of asbestos floe (added at the time of precipitation with water) were used.

Sample VP-11 represented a return to the procedure for

preparation of larger specimens. In this case the propor­

tions used were 200 g. of polyvinyl alcohol, 1000 ml. of fur­

fural, 3000 ml. of glacial acetic acid, and 80 g. of anhyd­ rous calcium chloride. In this case precipitation was

accomplished while the mixture was being stirred with an Alsop mixer.

An attempt to duplicate this success by preparation of an Identical batch, VP-12, resulted again in a preparation too thick to permit use of the high-speed stirrer for pre­ cipitation; again the kneading machine was used.

As a consequence of this seeming erratic behavior when time alone was the criterion for reaction, it was thought that perhaps it might be of more value to follow the change in viscosity of the reacting system. The method of viscosity check thought suitable for this work was the use of a dip- cup. A dip-cup was made of a 50 ml. beaker with an opening in the bottom. This was held by means of a copper strap and 44.

handle when it was dipped Into the reaction system. Vis­

cosity checks were made by noting the time required for the liquid to run out of the beaker back into the reactor. The cup was such that water at 20®C. would drain from the cup in

13.4 seconds. It was thought that It might be possible to note the change of viscosity by observing the change in the current drawn by the stirring motor when the geared-down type was used, but the change in current was not sufficiently detect­ able with the instruments available. The viscosity check procedure was initiated with the preparation of batch VF-13. The reactor was charged with 200 g. of polyvinyl alcohol, 1000 ml. of furfural, 5000 ml. of glacial acetic acid, and 60 g. of anhydrous calcium chloride. Table 3 Viscosity Change During Preparation of VF-IS Time of reaction Time to drain dip-cup 3:45 (start) 3:60 0.200 mln 3:55 0,260 4:00 0.285 4:10 0.340 4:20 0.360 4:25 0.395 4:30 0.400 4:40 0.410 4:45 0.440

The change in viscosity Is indicated by the data shown in

Table 3. At the end of these viscosity checks, the sample was 45.

precipitated by the use of the high-speed stirrer while water

was Blowly added. The product was in the form of light-brown

grains of quite small size, readily filtered after washing.

The yield was 228 g. Table 4

Viscosity Change During Preparation of VF-14

Time of Time to drain dip-cup Temperature reaction min. ®C. 11:35 a.m. (start) 0.257 70 11:40 0.258 11:45 0.327 11:55 0.362 12:05 p.m. 0.382

12:15 0.382 12:25 0.382 80 12:35 0.396 12:40 0.410 12:50 0.420

1:00 0.520 72 1:10 0.640 1:20 0.840 65 1:35 1.130 67 1:43 1.200 70 1:53 1.300 2:02 1.500

In Tiew of the success of this method of preparation another saople was prepared, allowing time for longer observa­ tion of the change in viscosity. The reacting proportions used were the same as in the preceding preparation. The change in viscosity during the reaction period is indicated in Table 4. This preparation was designated as VF-14. 46.

Subsequently, It was desired to Investigate the effect of the addition of a filler on the properties of these last two preparations. Mixtures of each with varying proportions of asbestos floo were made as shown in Table 5.

Table 5 Proportions Used for Mixtures of Resins VF-13 and VP-14 With Asbestos Floe

Designation Resin Asbestos floe K. K. VF-13a, VP-14a 10 40 VF-13b, VP-14b 20 30 VF-13C, VF-140 30 20 VP-13d, VP-14d 40 10

These were first mixed by passing the individual mixtures through a small hand-powered grinder, but this method was found to be unsuitable as the asbestos seemed to adhere to the metal walls of the grinder and thereby defeat the purpose of passing the mixture through. A suitable method was found to be that of tumbling the mixture in a Jar mill using rubber stoppers in place of the usual grinding stones. Sample VP-15 was prepared by use of the same proportions aa used in the previous two preparations, but with the ad­ dition of 200 g« of asbestos floe filler at the time of pre­ cipitation. This was to peralt the comparison of resins prepared by the two procedures of mechanically mixing the filler with the dried resin powder, and by precipitating the resin on the filler. The viscosity changes during preparation of thla sample are shown in Table 6.

Table 6

Vlaooaity Change During Preparation of VP-16

Time of reaction Time to drain dip-cup min.

2:45 0.250 2:50 0.308 2:58 0.333 3:05 0.333 3:10 0»360

3:15 0.350 3:23 0.350 3:30 0.383 3:37 0.417 3:46 0.366

3:48 0.383 3:52 0.417 3:59 0.467

Because It was felt that all variables were perhaps not

sufficiently well controlled to permit complete Justification

of comparisons of one batch with another, a final batch (VF'16}

was prepared in which portions were withdrawn at intervals

during the reaction period. In this case the reacting pro­ portions were 13.7 1. of glacial acetic acid, 600 g. of polyvinyl alcohol, 200 g. of anhydrous calcium chloride, and

2000 ml. of furfural. The viscosity changes are shown in Table 7. 48.

Table 7

Viscosity Change During Preparation of VP-16

Time of Time to drain Temper- Notes reaction dip-cup ature mln. ®C.

1:50 start 2J00 0.242 63 2:10 0.447 65 2:20 0.453 69.5 2:30 0.566 70

2:40 0.596 69 2:50 0.700 69 .*5:00 0.709 68 13 lb. removed and 3:15 0.750 69 precipitated (VF-16a) 3:25 0.833 69

3:35 0.890 69 3:45 0.904 69 3:55 0.900 70 4:05 0.984 70 13 lb. removed and 4:20 1.283 65 precipitated (VF-16b)

4:40 1.418 68 too thlct for further checks 5:05 remainder precipitated

As the data were accumulated regarding moisture absorption by discs molded of the resins described above it iras observed that the moisture absorption was less for those specimens molded from reain preparations obtained as a result of short reaction duration. Because it was Icnown that polyvinyl al­ cohol is quite appreciably affected by water it was expected that the water absorption might decrease with increasing time of reaction. To check the effect of water on the type of 49. polyvinyl alcohol at hand a test was made on the water ab. sorption of discs prepared from it. Three samples tested showed water absorption values of 13.74, 16.79, and 37.00 per cent; In fact it was difficult to weigh the discs correct­ ly after they had been soaked because they were somewhat dis­ integrated by the twenty-four hour soaking. Hence it was thought desirable to make some "blank" tests to ascertain whether the pi^jduct obtained in the resin preparations were really a new material or merely a precipitated portion of the original reactants.

The procedure followed was similsir to that described in the work with phosphorus pentoxide, i.e. furfural was omitted from the reaction mixture. A mixture was prepared consisting in 2000 ml. of glacial acetic acid, 50 g. of polyvinyl alco­ hol, and 20 g. of anhydrous calcium chloride. This was then heated to 70®C. for one and one-half hours. At the end of the heating period, water was added aa was customary, but no precipitate appeared as it had when furfural was present.

As a further check the above procedure was repeated except that Just prior to the addition of water there was added

400 ml. of furfural. Again no precipitate appeared. Hence, it was concluded that the resin being tested was a new mater­ ial formed only when both furfural and polyvinyl alcohol were present during the reaction period. Nevertheless, it is true that although polyvinyl alcohol is appreciably affected by water 50,

the realns made from the reaction with furfural show more

resistance to water as the reaction time ie decreased.

A test was also made to see what might be the effect

of various organic reagents on this type of resin. Several

1 g. portions of resin powder were placed in test tubes with

10 g. portions of each of the following solvents: toluene,

Skelly B, benzene, N>butanol, methanol, N-butyl formate, raetiiyl-isobutyl ketone, methyl-ethyl ketone, N-butyl acetate, vinyl acetate, amyl acetate, propyl acetate, dichloropentane, and ethyl acetate. In most all of these solvents the effect was only that the powder was wetted by the solvent. Even after one year only a slight swelling effect was observed on the specimens placed in toluene, benzene, butanol, methanol,

methyl-ethyl ketone, and ethyl acetate. In no case did solution of the powder occur. So this type of resin appears to be very little affected by common solvents.

It was also found that suitable prefoirms could be made by dry-pressing the resin powder. These were not used much, however, as the "spring-back" of the formed powder after it was removed from the cold mold was sufficient that it did not easily slip back into the same mold for subseciuent curing.

It is necessary to have preform molds slightly smaller than those used for curing; such a double set of molds was not available. 51.

Testing methods. For the purpose of comparing the realn

preparations described In the previous section, three teats were employed. These were the water absorption test, the

Paige Impact teat, and the Charpy Impact test. The first was

used because the extent of water absorption by plastic ma­

terials Is considered Indicative of their worth In many other

respects. The other tests were chosen because It was dis­ covered early In this work that the molded resin did have

exceptional toughness; consequently Its Impact strength seemed

to be a suitable Index of comparative value.

The procedure used for the water absorption test was a

close approximation to the A.B.7.M. procedure designated

A.S.T.M. D570-42 (2, p. 443). Briefly, this consists In

measuring and weighing the dlsc-ehaped specimen, conditioning

It (heating for one hour at 105 to 110°C.), rewelghlng, planing In water at room temperature for twenty-four hours, rewelghlng, reconditioning, and rewelghlng. From these data the per cent Increase In weight on Immersion Is obtained by subtracting the weight after conditioning from the weight after soaking and dividing by the weight after conditioning.

The purpose of reconditioning Is to ascertain whether the specimen may be partially soluble In water. The per cent soluble material In the specimen Is obtained from the data as follows: 52.

Per cent soluble s

conditioned weight - reconditioned welgrht conditioned weight *

In the above expression, If the weight after reconditioning be greater than the weight after the first conditioning, the per cent soluble Is reported as "none".

The per cent water absorption Is the sum of the per cent

Increase In weight after Immersion and the per cent soluble.

In addition, observations of warping, cracking, etc. are noted.

Specimens made In this work deviated from the A.S.T.M. specifications of 1/8 In. thickness and 2 In. diameter; In this work the discs were made about 0.2 In. thick, and li In.

In diameter because of the alae of the mold available.

The Paige Impact teat consists briefly In dropping a

5 lb. weight onto a disc-shaped specimen to ascertain how far the weight must be dropped In order to break the specimen.

The specimen Is laid on a firm Iron support. An Iron cylinder with one end hemispherical In shape Is then set upon the specimen with the hemispherical end on the specimen. This cylinder Is held loosely by a guide. The weight then Is raised so as to fall on the cylinder from an elevation of

1 In. If the specimen does not fall at this elevation, the weight is again raised and allowed to drop from a height of

2 In. If the specimen still does not fall, the free fall of 53» the weight la increased by Increments of 1 In. until It does.

Failure Is denoted by the presence on either surface of the specimen of a crack which extends to the periphery.

This test takes more time than the Charpy test, but it

Is much easier to prepare the specimens. It is less likely that they may be cured unevenly as the 5 g. discs are much smaller than the 15 g. bars used in the Charpy test, hence uniform heating during curing is easier to attain.

The Chax^y impact test was performed on several apeci~ mens according to directions of the A.S.T.M. procedure D256-

43T, Method B (24, p. 264). A Charpy impact test machine was available in the laboratories of the Chemical Engineering section of the Engineering Experiment Station. This machine is so constructed that the maximum force which may be ex­ pended to break a specimen is 57 inch-pounds.

A bar-shaped specimen 5 in. by ^ by about ^ in. was used as test piece. This was molded with the molding pressure applied on the i by 5 in. face. After conditioning (heating forty-eight hours at 50®C.) the bar was placed on the rigid support of the machine in such a way that the pendulum swing of the striker struck the bar on the i by 5 in. face in simple- beam loading. A few tests were first made with no bar in the machine to ascertain the average reading for a free swing of the striker. Then a bar specimen was placed in the machine and the owing of the striker after breaking the specimen was I

54.

Table 8 Summary of Resin Preparation Dat

Batch Acetic Furfural Polyvinyl Calcium Asbestos acid alcohol chloride g. ml. ml. K. K, Polyvinyl alcohol

VF-11 3000 1000 200 80 VF-6 1000 500 50 20 VF-9 3000 1500 200 80

VF-13 5000 1000 200 80 VF-16a 13700 2000 600 200 VF-6 1200 400 50 20

VF-3 2000 400 50 20 VF-16b 13700 2000 600 200 VF-14 5000 1000 200 80

VP-16C 13700 2000 600 200 VF-4 2000 400 50 20 VF-8 2000 400 50 20

VF-13b 5000 1000 200 80 see Table 5 VF-13C 5000 1000 300 80 see Table 5 VF-13d 5000 1000 200 80 see Table 5

VF-IS 5000 1000 200 80 200 VF-14c 5000 1000 200 80 see Table 6 VF-14d 5000 1000 200 80 see Table 5

VF-7 2000 400 50 20 60 VP-8a 2000 400 50 20 25 to 1/2 bat<

*6 blows from 24 in. elevation to oause failure

••added to mixture at the time of precipitation of the resin

54.

Table 8 Preparation Data and Physical Testing Results

Asbestos Time Per cent Paige impact Charpy impact water test test hiV; absorption in^ ft.~lb./in.

22.51 1.39

• 0.75 12,6x24*,14x24 1/4 1.15 24,17,10 1 2.18

1 2.48 16,16,6x24 5.86 1 1/6 1.67 12,9,10 5.21 1 1/6 4.96 24,13,12

1 1/2 2.40 11,8,7 2 1/4 3.36 24,24,16 5.52 2 1/2 1.39 20,15,8 5.47

3 1/4 4.02 10,10,9 4.84 5 5.20 9,7,7 8 6.54 7.6,2

see Table 5 1 15.20 see Table 5 1 6.49 see Table 5 1 2.79

200** 1 1/4 12.30 2.99 see Table 5 2 1/2 8.48 see Table 5 2 1/2 2.17

50 5 3.02 25 to 1/2 batch 5 6.06

55.

noted. The difference between the two was the energy expended

in breaking the bar« expressed in foot-pounds per inch of

thickness of the bar. In some oases notched bars are used, but the bars used in this work were unnotched because it was thought that uncertainties in uniformity of notching different specimens outweighed the likelihood of an Irregular fracture.

Results. The significant notes regarding physical aspect of the resin powders and appearance of shapes molded from them have been Inserted with the descriptions of the individual preparations. In general the powders were light- brown, khaki, or brown-violet in color and all the shapes molded from them were dark brown or black in color, and good sharp moldings.

Pertinent data concerning preparation of the samples and specimens and the results of the physical testing program are shown in the data presented in Table 8. The original data from which the water absoirption and Charpy impact test results were obtained are presented in the Appendix. 56.

DISCUSSION OP RESULTS

The pyrolysis teat establiahed that the polymer formed

upon treatment of furfural with sulphurlo acid Is practically

unaffected hy hl^h temperature. Various other testa on this

type of resin have been reported by others, but the effect of

high temperature had not been seen.

That the Incorporation of furfural Into a Thlokol prepa­

ration renders It softer and leas offensive Is noteworthy.

Although these effects have both been achieved by other means,

It Is of Interest to find that this might be another market

for furfural. The methods employed In this work for the formation of vinyl fural proved to result In technically useful materials

In all oases except that of the attempt to employ the prin­

ciple of azeotroplc distillation. In this one case the tem­

perature necessitated by atmospheric pressure was detrimental

to the furfural used. It may be possible that If the reaction

were carried out under diminished pressure the azeotrope would

pass out of the system at a temperature sufficiently low to

cause little or no polymerization of the fiu*fural with Itself.

The product obtained from the use of sulphuric acid as

catalyst was made Into flexible sheets. These show desirable aging characterlstloa under exposure to light and air. It 67.

Is conceivable that some of the slight surface stickiness

might be alleviated by the Incorporation of an Inert filler

material such as clay or chalk. Furthermore, the product

might possibly find market acceptance If coated onto fabric

as a filling, binding, and waterproofing agent. The compound­

ing work was not too satisfactorily done on the equal-speed

mixing rolls. It Is felt that mixing could be achieved more quickly and perhaps more unlfomnly by the use of differential-

speed mixing rolls or an Intensive mixer such as the Banbury mixer.

It Is also conceivable that the resin prepared by the

use of anhydrous calcium chloit'lde catalyst might be formed

Into similar flexible sheets If a suitable plastlclzer (and

possibly a filler) were Incorporated, The work done here was

concerned only with the suitability of this material as a

molding resin characterized by exceptional Impact strength

without excessive moisture absoz^ition. It is to be noted that

the Charpy impact test data are high values for molded materials

and that these values were obtained with the unplastlclzed resin. The addition of proper plastlclzers would decrease

brittleness and still further increase the impact strength.

It is thought that of the two impact test methods employed the Charpy method is preferable. It is a much quicker test

and appeared to yield more nearly reproducible values. Fur­ thermore, its acceptance as a standard by the American Society 58. for Testing Materials would seem to make It the preferred method.

The chief difficulty attendant on the use of the Charpy impact test is the preparation of the specimens. As has been mentionedt it is much simpler to achieve a uniform cure on the small disc specimens than on the bars made in this work. The problem is principally one of obtaining uniform heating. This could be achieved if the mold were equipped for heating by the admission of high pressure steam to the internal channel now used only for cooling and for temperature measurement. Steam at 100 p.s.i. gauge pressure has a tem­ perature of 170®C., Just slightly above that upon which this work was standardized. This temperature is not sufficiently above that used in this work (165°C.) to be detrimental to the molded shapes. The production of bars would be simplified by use of multiple-cavity type molda having a piping arrangement to permit admission of either 100 p.s.i. steam or cold water.

This would be a benefit to the physical testing program. 59.

CONCLUSIONS

1. Furfural polymerized by sulphuric add Is practically unaffected by temperatures up to the softening point of Pyrex glass. It neither melts nor shows evidence of decomposition.

2. Thlokol may be plastlolzed and partly deodorized by the Incoi-poratlon of furfural In the reaction mixture.

3. A plastic resin Is formed by the reaction between furfural and polyvinyl acetate with sulphuric acid catalyst.

4. A useful flexible sheet material Is formed when the resin described In Conclusion No. 3 Is plastlclzed with either trl-cresyl phosphate or butyl ethyl dlglycol carbonate.

5. A polymeric product Is formed from the reaction of polyvinyl alcohol and furfural with the aid of sulphuric acid, phosphorus pentoxlde, or anhydrous calcium chloride catalyst by heating, suitably at 70®C.

6. The polymeric product formed from the reaction of polyvinyl alcohol and furfural with phosphorus pentoxlde catalyst Is a blacX guiBiny substance. 7. The resin formed by the reaction of polyvinyl alcohol and furfural with anhydrous calcium chloride catalyst makes good sharp moldings when formed under molding conditions of five minutes, 165®C., and 3260 p.s.l.

8. The water absorption of such molded specimens varies proportionally with the time allowed for the resln-formatlon 60.

reaction, varying from about 1 per cent absorption for sped-.

mens molded from a resin prepared in fifteen minutes to around

4 per cent for a resin prepared in three and one-fourth hours.

9. The resistance to the Paige impact-strength test of such molded specimens varies widely.

10. The Charpy impact-strength test of such molded speci­ mens shows great resistance to impact. For standard bars made of unfilled resin the values exceeded 5 ft.-lb. per inch of thickness. Standard bars having asbestos floe filler re­ quired an average of 2.99 ft.-lb. per inch of thickness. 11. The use of asbestos floe filler appreciably increased the moisture absorption of molded shapes and decreased their resistance to impact.

12. The specific gravity of such molded specimens is about

1.25 for unfilled moldings, and about 1.48 for specimens with asbestos floe filler.

13. Asbestos floe filler may be Incorporated into such resins either by mechanical mixing of the dry materials or by precipitating the resin on the filler.

14. Glacial acetic acid is a suitable reaction medlvim for the formation of the resin from the reaction of furfural and polyvinyl alcohol with sulphuric acid, phosphorus pentoxide, or anhydrous calcium chloride catalyst.

15. The resin is suitably precipitated from the system mentioned in Conclusion No. 14 by adding water to it slowly 61. while the mixture Is rapidly stirred.

16. When the precipitated resin Is thoroughly washed It Is easily filtered.

17. Suitable oold-preased preforms may be made from the dry resin powder.

18. It la suitable to follow the course of the reaction by observing the change In the •lacoslty of the reaction mixture. 62.

SUMMikRY

In this work It was found that acid-polymerized furfural

is practically unaffected by heat, that Thlokol may "be softened

and lt3 odor dlralnlahed by the Incorporation of furfural In the

reaction mixture, and that a polymeric product suitable for

proceasing into flexible sheets or molded shapes having excep­

tional resistance to Impact may be formed by the reaction of

polyvinyl alcohol and furfural with either sulphuric acid,

phosphorus pentoxlde, or anhydrous calcium chloride catalyst.

Inclusion of asbestos floe filler in the molding powder has a

deleterious effect on the pz*opertlea of shapes molded from such a resin. Increasing the reaction time allowed for formation of the resin causes an Increase in the water absorption of molded shapes prepared from it, and decreases their resistance to

impact. 69.

SELEOTSD R£P£R£NC£B

1. Alexander WaokerOesellsobaft fur eleotrochealacho Indus- trie Q-.m.b.H., German Patent 618,995, July 17, 1935. Abstracted in C.A., 29, 8177 (1936).

Description of procedure for preparation of poly, •inyl acetate from Tinyl acetate.

2. American Society for Testing Materials, A.S.T.H. Standards on Plastics, Philadelphia, American Society for Testing Materials, 1946.

5. Barron, H., Modem Synthetic Rubbers, Second Edition, London, Chapman and Hall, Ltd., 194S.

4. Barry, T. H., and Light, L., Furfural Plasties: Recent Progress, Brit. Plastics, 5, 535-8 (1934). Abstracted in C.A., 28, 4545 (1934).

6. Beckmamn, £., and Oehn, £., Action of Furfural on Phenols, 3itb. kgl. preuss. Akad. Wiss., Berlin, 1S01<-21 (1918). Abstracted in C.A., 14, 642 (1920).

Description of resins formed from reaction of fur­ fural with acid materials cmd salts. 6. Blaikie, K. a., and Crosier, R. K., II. S. Patent 2,166,856, July 18, 1939. Abstracted in C.A., 33, 8857 (1939).

Formation of polyvinyl acetal resin incorporating aliphatic aldehydes.

7. Boeseken, J.; VermiJ, C. 0. G.; Bunge, H.; and ran Meeuwen, C., The Oxidation of Some Furan DeriTatives by Means of Per Acids, Rec. Tray. Chim., 50, 1023-34 (1931).

8. Bruins, R. W., The Use of Polymers from Furfural in the Fabrication of Molded Products, Unpublished Ph.D. Thesis, Ames, Iowa, Iowa State College Library, 1934.

Preparations of resins from furfural and furfurin and various catalysts. 64.

9. Bruson, H. A., and Staudlnger, H., Cyolopentadiene Rubber, Ind. Eng. Chem., 18, S81-5 (1926).

10. Calloway, N. 0., Condensation Reactions of Furfural and Its Derivatives, Unpublished Ph.D. Thesis, Ames, Iowa, Iowa State College Library, 1933.

A study of furfural condensations and condensation preventatives. 11. Canadian Electro Products Co., Ltd., French Patent 692,718, Mar. 25, 1930. Abstracted In C.A. 25, 1692 (1931).

Formation of an aoetal resin from a vinyl ester and acetaldehyde or formaldehyde. ^2. German Patent 664,648, Sept. 2, 1938. Abstracted In C.A., 33, 875 (1939).

Similar to above. 13. D'Alello, 0. F., A Laboratory Manusa of Plastics and Synthetic Resins, New York, J. Wiley and Sons, Inc., 1943. 14. Darling:, E. R., Furfurol as a Dye Base, Textile Am., 37, No. 3,pp. 17, 25 (1922). Abstracted in C.A., 16, 1321 (1922).

Formation of dyes from furfural and tannic acid with alkali polysulfides and aromatic compounds.

15. Delmonte, J,, Producing Furfural Resins, Plastics, 2, No. 2, 60, 62-3, 110-12 (1945).

Description of furfural manufacture, phenolic resins, and trends in use of furfural. Furfural Resin Adheslves for Aircraft Use, Pacific Plastics, 2, No. 4, 14 (April 1944).

Furfural is a constituent in "Resin X** which is an adhesive suitable for aircraft manufacture.

The Technology of Adheslves, New York, Relnhold Publishing Co., 1947. In preparation of polyvinyl acetals it is suggested that the reaction medium be isopropyl alcohol or benzene. 65.

18. Dbberelner, J. W., Ueber die medlolnleche und chemlsohe Anwendung und die vorteilhafte Darstellung der Ameiseneaure, Ann., 3, 141^6 (1832).

The report of the dlacovery of furfural.

19. Dunlop, A. 0., and Peters, F.M., The Nature of Furfuryl Alcohol, Ind. Eng. Ohem., 34, 814-17 (1942).

Includes description of a mechanism of polymerlza. tlon of furfuryl alcohol.

20. Ellis, C,, The Chemistry of Synthetic Resins, New York, Relnhold Publishing Co., 1935.

An extensive review of the plastics field to that date.

21. U. S. Patent 1,558,442, Oct. 20, 1925. Abstracted In C.A., 20, 290 (1926).

Acld-polymerlaed furfural Is modified by the In­ clusion of nitrate or acetate In the reaction mixture. 22. Plrstenberger, B. G., The Data, Design, and Specifications for a Plant to Produce Xylose from Cornstalks, Un­ published Ph.D. Thesis, Ames, Iowa, Iowa State College Library, 1942. 23. Pownes, G., Kunstllche Blldung elner organlschen Base, Ann, 54, 52-66 (1845).

The name "furfuirol* is proposed for the aldehyde in the course of the description of furfuramlde and fur- furin.

24. Oenln, G., Furfured and Its Application In the Plastics Industry, Rev. gen. mat. plastlques, 7, 89-95 (1931). Abstracted in C.A,, 25, 2817 (1931).

A review of the properties and constitution of fur­ fural and of its applications as a solvent and as an ingredient in synthetic resins.

25. Gulnot, H. M. E., U. S. Patent 2,273.484, Feb. 17, 1942. Abstracted in C.A., 36, 4371 (1942).

A type of synthetic rubber may be made from furfural via sylvan and plperylene. 66.

86, Herrman, W. 0., and Deutach, H,, U. S. Patent 1,767,759, June 24, 1930. Abstracted In G.A., 24, 4409 (1930).

Resins may be formed by the interaction of alkaline substanoes such as sodium or sodium sulfide and aliphatic aldehydes.

(I 27. Herrman, W. 0., and Haehnel, W,, Uber den Poly-vinyl alkohol, Ber., 60, 1658-63 (1927).

In discussing preparation of polyvinyl alcohol it is stated that that prepared by acid hydrolysis of the ester is less contaminated by the reaction medium.

28. Hull, S. M., U. S. Patent 1,711.025, April 30, 1929. Abstracted in C.A., 23, 3060 (1989).

A resin may be formed from a protein material such as casein and furfural condensed in presence of ester gum.

29. I. G. Farbenlndustrie, A. Q., French Patent 755,316, Nov. 23, 1933. Abstracted in C.A., 28, 1560, 1934.

Calcium chloride is a suitable dehydrating agent for the formation of a polyvinyl acetal. 30. German Patent 731,684, Jan. 14, 1943. Abstracted in C.A., 38, 550 (1944).

An emulsified polyvinyl ester forms an acetal in the presence of an sdcohol and subsequently a carbonyl compound. 31. Jahn, E. C., Utilization of Lignln, Ind. Eng. Chem., News Ed., 18, 993-6 (1940).

Known uses for lignln are described. 32. Kappeler, H., Brit. Patent 293,872, July 14, 1927. Abstracted in C.A., 23, 1729, 1929. Fia»fural and urea may be condensed with or without a catalyst and other materials. 33. Swiss Patent 133,387, July 14, 1927. Abstracted in fl.A., 24, 476 (1930). A black infusible plastic may be made from furfural and thiourea with or without a catalyst, solvent, and diluent. 67.

Swlaa Patent 133,707 to 133,712, July 14, 1927. Abstracted In C.A., 24, 476, 1930.

A resin may be made from furfural and urea and one of several other organic bases with or without a catalyst, solvent, and diluent.

Brit. Patent 345,891, June 12, 1929. Abstracted in C.A., 26, 2073 (1932).

A resin may be formed by condensing furfural or a derivative with another aldehyde or its polymer in the presence of an acid. French Patent 697,169, June 10, 1930. Abstracted in C.A., 25, 2822 (1931}.

Similar to above. Swiss Patent 146,561, June 12, 1929. Abstracted in C.A., 26, 2287 (1932).

A hard black resin may be made by condensing fur­ fural with acetaldehyde by means of an acid.

38. ^(J. 3. Patent 1,873,599, Aug. 23, 1932. Abstracted in C.A., 26, 6081 (1932). An inflexible black; resin may be made by condensing furfural with another aldehyde by means of an acid condensing agent.

39. Killeffer, D. H., Furfural Steps into Industry, Ind. Eng. Chem., 18, 1217-19 (1926).

Description of process for manufacture used at plant of Quaker Oats Co. at Cedar Rapids, Iowa.

40. Lewis, H. F., U. 3. Patent 2,267,830, Dec. 30, 1941. Abstracted in C.A., 36, 2647 (1942). A resin suitable for coating laboratory furniture may be formed from a mixture containing furfural and vinyl acetate. 41. Libbey-Owens-Ford C^lass Co., Brit. Patent 502,906, March 21, 1939. Abstracted in C.A., 33, 6993 (1939).

A polyvinyl acetal may be formed with aliphatic modifiers. 68.

Light, L.| Furfural Plastics, Brit. Plastics, 11, 314-15 (1939). Abstracted in C.A., 34, 1771 (1940).

A survey of recent developments.

Mains, G. H., The System Furfural-Water, I, Chem. Met. Eng., 26, 779-784 (1922).

A study of phase relationships in the furfural- water system.

Meunier, 0., Application of Furfural to the Manufacture of Varnish Resins, Mat. grasses, 9.4516-7 (1916). Abstracted in C.A., 10, 2806 (1916).

Varnish resins may be formed by the condensation in alkaline medium of furfural and substances such as aniline and acetone.

Meyer, V., Ueber 7hiodiglykolverbindungen, Ber., 19, 3259-3266 (1886). An early research into mustard gas formation with notes on the formation of some tars. Moss, W. H., and White, Blanche B., Can. Patent 303,697, S^t. 2, 1930. Abstracted in C.A., 24, 5518 (1930). A resin may be formed from p-toluene sulfonamide and furfural in the presence of an alkaline catalyst. Novotny, E. E., and Johnson, W. W., 0. 3. Patent 1,827,824, Oct. 20, 1931. Abstracted in C.A., 26, 862 (1932). Heating furfural and urea or a derivative with an acid or basic catalyst gives a plastic resin which becomes infusible on further heating.

Ogawa, W.; Hanyu, T.; and Yanigihashi, T., Furfural Resins as Electrical Insulating Material, Researches Electro-Tech. Lab., Tokyo, Japan, No. 178, 1926. Abstracted in C.A., 21, 669 (1927).

Most furfural condensation products were found Inferior to bakellte as electrical insulating material, but they were found to have good black color and ultra­ violet absorption. 69.

49. Patrick, J. C., U. S. Patent 1,996,487, April 2, 1935. Abstracted In C.A., 29, 3421 (1935). Reaction of furfural and an alkaline polyaulflde glV€Bproducts suitable for electrical insulation.

50. Penn, S., Polymerisation and Structure of Furfural Resins, Brit. Plastics, 16, 286-92 (1944). Speculation as to mechanism of polymerization of furfural,

51. Peterson, C. J., and Hlxon, R. M., Chemical Examination of the Tissue of the Cornstalk, Ind. Eng. jShem., Analytical Edition, 1, 65-7 (1927).

52. Phillips, M., IJ. S. Patent 1,750,903, March 18, 1930. Abstracted in C.A., 24, 2623 (1930).

Condensation of furfural in presence of hydrochloric acid gives a black resin.

53. Phlllipa, M., and Mains, 0. H., U. S. Patent 1,441,598, Jan. 9, 1923. Abstracted in C.A., 17, 1724 (1923).

Condensation products may be made from furfural and various amines and ketones in presence of an acid or base. Many are suitable for baking enamels.

54. Porai-Koshitz, A. E., Russian Patent 31,012. Sept. 30, 1933. Abstracted in C.A., 28, 3424 (1934). A furfural condensation product is made with free or sulfonated fatty acids alone or together with alkali salts of sulphur dioxide, borio or phosphoric acids or their salts. 55. Potts, H. E., and Carbide and Carbon Chemicals Corp., Brit. Patent 497,146. Dec. 9, 1938. Abstracted in C.A., 33, 3490 (1939).

A resin suitable for manufacture of safety glass is made from polyvinyl alcohol and an aliphatic aldehyde in a hydrochloric acid medium.

56. Richardson, L. T., U. S. Patent 1,584,144, May 11, 1926. Abstracted in Official Oaiette U. S. Pat. Office, 346,393 (1926). A resin is made of furfural and acetone by treating with alkali and later with acid. 70.

57. U. S. Patent 1,682,934, Sept. 4, 1928. Abstrac­ ted In C.A., 22, 3999 (1928).

Furfural and an acidic inorganic material react to form a resin.

68. Riegel, E. R., Industrial Chemistry, Fourth Ed., New York, Reinhold Publishing Co., 1942.

59. Schreiber, W. T., Geib, N.V., Wincfield, B., and Acree, 3. F., Semi-Commercial Production of Xylose, Ind. Eng. Chein., 22, 497-501 (1930).

60. Shawinigan Chemicals, Ltd., Brit. Patent 416,413, Sept. 10, 1934. Abstracted in C.A., 29, 1177 (1935).

A partly hydrolyzed polyvinyl ester may be condensed with eji aldehyde solution (also containing other modi­ fiers) to form a resin suitable for impregnating, making films, adhesives, or polish.

61. Shreve, R. N,, The Chemical Process Industries, First Ed., New Yorl:, UcGraw-Hill Book Co., 1945.

62. Snell, H. S., U. S. Patent 1,678,713. July 31, 1928. Abstracted in G.A., 22, 3747 (1928).

A condensation product may be made from furfural and an insoluble proteinate such as aluminum soy-bean or milk caseinate.

63. Snelling, W. 0., U. S. Patent 1,716,606, June 11, 1929. Abstracted in C.A., 23, 3783 (1929).

A mixture of furfural, hydrochloric acid, and water gives a solid non-resinous product suitable for making crayons, porous carbon, decolorizing material, etc.

64. Societe Nobel franoaise, French Patent 777,251, Feb. 15, 1935. Abstracted in C.A., 29, 4104 (1935). A polyvinyl ester may be condensed with formaldehyde and acetaldehi'de. If the mixture be rich in formalde­ hyde the product will be less soluble but will possess good physical characteristics. 65. Somerville, I. A., U, S. Patent 1,770,635, July 15, 1930. Abstracted in C.A., 24, 4524 (1930). 71.

A tanning- agent may be formed by oondenaation of furfural vrlth napthalene sulfonic aclda. I I 3tadnikoff, 0,, and Goldfarb, I., Uber die Alkyllerung und Acyllerung von thlophen in Anwesenhelt von Zinntetraohlorld, Ber., 61, 2341-2 (1928). Stenhouse, J,, Ueber das eogenannte kunstliche Ameisenol, Ann., 35, 301-4 (1840).

Describes chemical behavior and phyalcal properties of R new material later known aa furfural,

Ueber die Oele, die bei der Elnwlrkung der Schwefelsaure auf verachledene Vegetablllen enstehen, Ann., 74, 278-97 (1850).

rixtanslon of al)Ove.

Trlokey, J. P., and Miner, C. 3., U. S. Patent 1,665,233, April 10, 1928. Abstracted in C.A., 22, 1863 (1928).

Furfural may be condensed by uae of a salt.

U. S. Patent 1,665,237, April 10, 1928. Abstrac­ ted in Official Gazette U. 3. Pat. Office, 369,312 (1928).

A resinous substance may be made by mixing furfural and furfuryl alcohol (or derivatives of either or both) and a catalyst. Ushakov, 3. N.; Markov, I. F.; ana Chilina, E. P., The Synthesis of Acetals of Polyvinyl Alcohol» J. Chem. Ind. U.3.S.R., 18, No. 12, 19-24, 1941. Abstracted in C.A., 38, 3953 (1944).

An ethanol solution of polyvinyl acetate is hydro- lyzed in presence of 100 per cent excess paraldehyde. von Wacek, A,, Furfural, Angew, Chem., 54, 453-8 (1941). Abstracted in C.A., 37, 883 (1943).

A review of the literature since 1930 regarding production, properties, and uses of furfural, Wielenfl, H., Untersuchungen uber Dicyclopentadlen, I., Ber., 39, 1492-9 (1906). 72.

ACKNOWLEDGMENTS

The writer aoknowledgeB hla appreciation of the counsel of Dr. 0. R. Sweeney, who was in charge of this work, and wishes here to thank the several senior students in the

Department of Chemical Engineering who assisted in the experimental work. We are also Indebted to E. I. du Pont de

Nemours & Company, Inc., for a few pounds of Elvanol sent without charge. 73.

APPENDIX 74.

Table 9 Water Absorption Teat Data

Speolnen Original Conditioned Weight after Reconditioned 0aln on of realn weight weight lomeralon weight Immeralbn fiL fiL EL K.' • Polyvinyl alcohol 4.7850 4.7800 5.4370 4.9947 0.6570 4.9441 4.9398 6.7700 5.0067 0.8302 4.85S9 4.8483 6.6400 4.9257 1.7917

VF-3 4.8905 4.8802 4.9965 4.8800 0.1163 4.8675 4.8540 4.9625 4.8910 0.1085 4.8255 4.8150 4.9400 4.7057 0.1250

VF-4 4.8002 4.7940 5.0130 4.8412 0.2190 4.6655 4.6487 5.0085 4.6898 0.3598 5.2045 5.1974 5.3675 5.2449 0.1701

VF-5 4.9545 4.9456 4.9920 4.9497 0.0464 6.0068 4.9783 5.0300 4.9771 0.0517 4.8765 4.7860 4.8550 4,7945 0.0690

VF-6 5.0841 5,0617 5.3068 5.1318 0.2451 4.4777 4.4602 4.6949 4.5382 0.2347 4.9477 4,9150 5.1500 4.9778 0.2350

VF-7 4.3628 4.3495 4.4680 4.3828 0.1186 5.4359 5,4178 5.4852 5.4364 0.0674 4.9824 4,9591 6.2120 5.0154 0.2529

VF-8 4.8910 4.8286 5.1446 4.9832 0.3160

VF.8a 4.5170 4.4876 4.7574 4.5230 0.2698 3.6753 3.6730 3.8294 3.6504 0,1564 5.0368 4.9901 5.3850 5.0134 0.3949

VF-9 4.9400 4.9370 5,0474 4.9718 0,1104 4.9170 4,9160 5,0210 4.9474 0,1050 4.9220 4.9210 5,0274 4.9490 0.1064

VF-10 5.0357 4.9928 5,1627 4.9880 0,1599 5.0216 4.9660 5.1464 4.9757 0.1804 5.0122 4.9565 5.1246 4.9672 0.1690

74.

Table 9 er Absoz»ptlon Test Data

Reconditioned daln on Per cent Soluble Per cent Per cent water weight immersion gain lose soluble absorption £= < £ £

4.9947 0.6570 13.74 13.74 5.0067 0.8302 16.79 16.79 4.9257 1.7917 37.00 37.00

4.8800 0.1163 2.38 2.38 4.8910 0.1085 2.23 2.23 4.7057 0.1250 2.60 2.60

4.8412 0.2190 4.57 4.57 4.6898 0.3598 7.74 7.74 5.2449 0.1701 3.28 3.28

4.9497 0.0464 0.94 0.94 4.9771 0.0517 1.04 1.04 4.7945 0.0690 1.44 1.44

5.1318 0.2451 4.84 4.84 4.5382 0.2347 5.27 5.27 4.9778 0.2350 4.78 4.78

4.3828 0.1185 2.72 2.72 5.4364 0.0674 1.24 1.24 5.0154 0.2529 5.10 5.10

4.9832 0.3160 6.54 6.54

4.5230 0.2698 6.01 6.01 3.6504 0.1564 4.26 0.0226 0.616 4.88 5.0134 0.3949 7.91 7.91

4.9718 0.1104 2.24 2.24 4.9474 0.1050 2.14 2.14 4.9490 0.1064 2.16 2.16

4.9880 0.1599 3.20 0.0048 0.100 3.30 4.9757 0.1804 3.63 3.63 4.9672 0.1690 3.41 3.41

76.

Table 9 (continued}

Speoinen Original Conditioned Weight after Reconditioned Gain on of resin weight weight inunersion weight inuneraion sc. K. K, e.

VF-11 4.9776 4.9574 4.9884 4.9521 0.0310 4.9708 4.9527 4.9837 4,9456 0.0310 4.9388 4.9217 4.9500 4.9138 0.0283

VF-13 4.9060 4.8950 5.0290 4.9300 0.1340 4.8900 4.8860 4.9990 4.9090 0.1140 4.9510 4.9430 6.0650 4.9760 0.1220

VP-13b 8.0419 4.9964 6.8150 5.0002 0.8186 6.0455 4.9870 5.6800 5.0217 0.6930 J VF-13C 4.9081 4.8880 5.2960 4.9440 l' 0.4080 5.1434 5.1101 5.4330 5.1406 0.3226 4.9236 4.9170 5.2120 4.9875 0.2950

VP-13d 4.8347 4.8258 4.9750 4.8608 0.1492 4.9045 4.8989 6.0190 4.9176 0.1201 4.7817 4.7713 4.9070 4.7990 0.1357

VF-14 4.8600 4.8400 4.9140 4.8550 0.0740 4.8880 4.8600 4.9260 4.8710 0.0660 4.9000 4.8880 4.9500 4.9000 0.0620 VP-14C 4.8647 4.8487 5.2770 - 4.9258 0.4283 4.8633 4.8460 5.2420 4.9699 0.3960 4.8466 4.8333 5.2450 4.9772 0.4117

VF-I4d 4.9280 4.9112 5.0030 4.9297 0.0918 4.9312 4.9178 5.0560 4.9425 0.1382 4.8705 4.8616 4.9610 4.8759 ; 0.0894 VF-15 4.9790 4.9213 5.5620 5.0093 i 0.6307 5.0496 5.0135 5.6106 6.2342 0.5971 5.0656 5.0164 5.7263 6.1396 0.6099

VF-16a 4.9320 4.9088 4.9764 4.8948 0.0676 4.9326 4.9080 4.9828 4.8937 0.0748 4.9360 4.9150 4.9738 4.8985 0.0588

j 76. { 1

conditioned Gain on Per cent Soluble Per cent Per cent water Igtit Immersion gain loss soluble abso^tlon g' i % 1 4.9521 0.0310 0.625 0.0053 0.107 0.732 4.9456 0.0310 0.625 0.0071 0.143 0.768 4.9138 0.0283 0.575 0.0079 0.161 0.736 4.9300 0.1340 2.630 2.630 4.9090 0.1140 2.33 2.33 4.9760 0.1220 2.47 2.47

5.0002 0.8186 16.4 16.4 5.0217 i 0.6930 13.9 13.9 i 1.9440 ! 0.4080 8.35 8.35 5.1406 0.3226 6.32 6.32 1.9875 ^ 0.2950 6.00 6.00

1.8608 0.1492 3.09 3.09 1.9176 0.1201 2.45 2.45 1.7990 0.1357 2.84 2.84

1.8550 0.0740 1.53 1.53 1.8710 0.0660 1.36 1.36 1.9000 0.0620 1.27 1.27

1.9258 0.4283 8.75 8.75 1.9699 0.3960 8.17 8.17 1.9772 0.4117 8.52 8.52

1.9297 0.0918 1.87 1.87 1.9425 0.1382 2.81 2.81 1.8759 0.0894 1.84 1.84

>.0093 0.6307 12.8 12.8 >.2342 0.5971 11.9 11.9 5.1396 0.6099 12.2 12.2

1.8948 0.0676 1.38 0.0140 0.286 1.67 t.8937 0.0748 1.53 0.0143 0.292 1.82 L.8985 0.0588 1.20 0.0165 0.336 1.53

76.

Table 9 (oontinuftd)

Speolaen Original Conditioned Weight after Reoonditioned .9ain on of reein weight weight immersion weight immersion g. g. J , S» , ,

Vr-16b 4.9066 4.8678 5.0336 4.8856 0.1668 4.9488 4.8968 5.063S 4.9157 0.1664 4.9646 4.9S22 5.0828 4.9408 0.1606

VP-16C 4.9533 4.9265 5.1178 4.9862 0.1913 4.9259 4.9068 5.0998 4.9671 0.1930 4.9484 4.9212 5.1280 4.9639 0.2088

76.

' ' londitioned Sain on Per cent Soluble Per cent Per cent water ght ifluaeralon gain loss soluble absorption

,1 iK* II I .Ml d ^ . % r.8856 0.1668 3.41 3.41 ^.9167 0.1664 3.40 3.40 X.9408 0.1606 3.27 3.27 t.9862 0.1913 3.88 3.88 t.9671 0.1930 3.93 3.93 t.9639 0.2088 4.26 4.26

77.

Table 10

Charpy Impact Test Data

Specimen Width Thickness In.-lb. Ft.-lb. of resin In. In. to break Der In. Polyvinyl alcohol 0.506 0.273 4.2 1.282 0.505 0.276 4.9 1.49 0.505 0.283 4.3 1.27 0.505 0.277 4.8 1.44 0.505 0.275 4.9 1.49

VF-13 0.506 0.284 18.7 5.49 0.506 0.275 21.0 6.36 0.506 0.284 21.6 S.31 0,507 0.275 16.2 4.91 0.506 0.275 20.7 6.27 0.506 0.282 19.7 5.82 VF-14 0.505 0.275 53.6 16.23 0.506 0.276 19.4 5.66 0.506 0.274 16.7 5.08

VF-15 0.506 0.255 7.7 2.52 0.505 0.252 9.0 2.98 0.504 0.243 10.0 3.43 0.505 0.242 9.1 3.13 0.503 0.262 8.8 2.82

VF-16a 0.506 0.275 14.0 4.24 0.506 0.270 18.2 5.62 0.506 0.267 17.9 5.68 0.506 0.270 11.8 3.64 0.506 0.272 22.7 6.96

VF-16b 0.606 0.275 ^ 16.1 4.42 0.606 0.287 19.1 5.81 0.506 0.271 19.2 5.90 0,606 0.272 21.6 6.62 0.506 0.272 17.4 4.87

VF-160 0.506 0.283 17.0 6.01 0.503 0.276 11.8 3.56 0.606 0.278 16.2 4.86 0.606 0.280 11.4« 2.95 0.506 0.277 19.2 5.77 center void was found.