United States Patent (113,607,865

(72) Inventors John Dyer (56) References Cited Media; UNITED STATES PATENTS Lyle H. Phifer, West Chester, both of Pa. 2,694,723 l l 11954 Schramm ...... 260/455 B 2l Appl. No. 732,551 2,761,247 9/1956 Meadows.... a 260/216 22 Filed May 28, 1968 2,825,655 3/1958 Meadows...... 260/216 45) Patented Sept. 21, 1971 2,910,466 101959 Watt...... 260/216 73) Assignee FMC Corporation Philadelphia, Pa. 3,103,5073.14102 9/19637/1964 O'Boyle...Knoevenagel. 260/234 Primary Examiner-Lewis Gotts (54) PREPARATION OFXANTHATES Assistant Examiner-Johnnie R. Brown 10 Claims, No Drawings Attorneys-Thomas R. O'Malley, George F. Mueller and Robert G. Hoffmann 52) U.S.C...... 260/234 R, 260/26, 260/455 B 51 int. Cl...... C07c69132 ABSTRACT: A method of forming alcohol xanthates utilizing 50 Field of Search...... 260/455 B, a transXanthation reaction between an alcohol xanthate and 234,216 an alcohol, is disclosed herein. 3,607,865 PREPARATION OFXANTHATES erythritol Alcohol xanthic acids and their derivatives are known to be sorbital useful for a variety of applications including mineral flotation glucose agents, sulfidizing agents, rubber vulcanization accelerators, mannitol adhesives and as intermediates in the preparation of shaped 2-methoxyethanol articles, for example, regenerated cellulose fibers and films. 2-ethoxyethanol In general, alcohol xanthates have been derived by reacting 2-butoxyethanol carbon disulfide with simple and complex alcohols under al diethyleneglycol ethylether kaline conditions. Reactions of this type have been known for polyethylene glycols many years and may be seen, for example, in many prior U.S. 10 2,3-epoxy propanol Pat. Nos., including. 520,770, 1,440,962, 1,507,089, pinacol 1,642,587, 1819, 112, 1,872,452, 2,037,717-8, 2,608,572, phenol and 2,668,820, to mention a few. phenyl ethyl alcohol The derivative of the alcohol xanthic acid is formed as a salt phenyl propyl alcohol during the preparation under alkaline conditions, or may be 15 chloro-phenyl ethyl alcohol formed by replacing the salt-forming metal ion with another 1-phenyl propanol.2 metal ion, an ester-forming group, carboxylic acid group, or benzyl 1, 4 ganic phosphorous group or the like, as is well known in the o-hydroxybenzyl 1, 5 art. dihydroxybenzyl alcohol In the above prior art method of obtaining alcohol 20 trihydroxybenzyl alcohol xanthates, undesirable byproducts are formed during the reac 1,4-butandiol tions involving alkali, free carbon disulfide and products of the 1,5-pentandiol reaction. Furthermore, in the aqueous xanthate preparing systems of the prior art, xanthates of various alcohols are un polyvinyl alcohol stable and this, coupled with the byproduct formation, 25 partial esters of polyvinyl alcohol decreases process efficiency in working with the xanthate partial ethers of polyvinyl alcohol products. SCOSc Therefore, it is an object of this invention to provide a raffinose method for the preparation of an alcohol xanthate in the starch absence of an alkali and/or free carbon disulfide. 30 dextrin It is another object of this invention to provide a method for gums the preparation of an alcohol xanthate by a transxanthation chitin reaction. pentosans These and other objects are accomplished in accordance galactanes with the present invention which is a method comprising con 35 pectins tacting is a substantially water-free liquid medium at a pH cellulose ranging from at least about 1 to no greater than about 12, a The simple alcohols, including monohydric aliphatic al derivative of an alcohol xanthic acid with an excess of a free cohols having from 1 to 18 carbon atoms and the alcohol differing from the alcohol moiety of the xanthate for a polysaccharides, are probably the most useful alcohols for the time sufficient for a transxanthation reaction to occur. The 40 preparation of the dithiocarbonate derivatives or xanthates. derivatives of alcohol xanthic acid as referred to above may Cellulose, of course, is useful in various forms, including, e.g., also be termed O-substituted dithiocarbonates. cotton, regenerated cellulose, microcrystalline cellulose and The alcohols useful in the above method, both for the al partially esterified or etherified cellulose. cohol moiety of the xanthic acid derivative and the free al If the free alcohol for this process is a liquid at normal or cohol, are intended to include alcohols in the broadest sense, 45 elevated temperature, it can be employed as the liquid medi and, in general, are those organic compounds which have one um of the invention, or it may be mixed with another nonaque or more reactive hydroxyl groups available in their chemical ous liquid with which it is miscible. However, dilution with structure and will react, either by conventional xanthating another liquid will tend to slow up the transxanthation reac procedures or through transxanthation to form a xanthic acid tion. If the alcohol is a solid material, it can be dissolved or or derivative thereof. These alcohols are simple monohydric, 50 dispersed in an inert liquid medium, such as a liquid hydrocar dihydric and polyhydric compounds, as well as complex al bon, ether, ketone, amide, sulfoxide, a less reactive alcohol, or cohols and polymeric alcohols. Aliphatic and aromatic al the like, for example, acetone, dioxane, dimethyl sulfoxide, cohols are well-known and need no exhaustive list to describe cyclohexane, dimethyl formamide, isopropanol, etc. and enumerate them, but some of the more common and The acidity of the liquid medium in which the method of readily available are listed below, and their xanthate deriva 55 this invention is carried out ranges in pH from at least about 1 tives are known or are obvious: to no greater than about 12, and preferably from about 2 to 8. methanol Buffers and pH adjusting components may be included. ethanol The rate of the transxanthation reaction tends to be slower propanol when the alcohol moiety of the xanthate is more acidic than isopropanol 60 the free alcohol, while the rate of reaction tends to increase l, 3-dichloropropanol-2 when the free alcohol is more acidic. In highly acidic reaction n-butanol media, i.e., below pH l, the transxanthation reaction is re s-butanol tarded owing to the more extensive protonation of the xanthic t-butanol acid. On the other hand, increased alkalinity will also retard isobutanol 65 transxanthation, since it suppresses the acidity of the free al pentanol cohol. Thus, the above limitations for the pH range for the hexanol reaction are dictated by practical reasons. octanol Lewis acids and other acids may be used as catalysts for the decanol reaction. It is to be expected that catalysts used to accelerate cetyl alcohol 70 transesterification reactions, e.g., as in polyester production, ceryl alcohol would also accelerate transxanthation reactions. melissyl alcohol The temperature of the reaction may be between the freez ethylene glycol ing and boiling points of the liquid reaction medium at at propylene glycol mospheric pressure, although a temperature within the range glycerol 75 of Oto 40°C. is preferred. 3,607,865 3 4. During the transxanthation reaction, alcohol which is Transxanthation reactions of the above type were carried formed from the exchange reaction and which is readily out in the presence of different diluent liquids or solvents. In recoverable, can be removed to help increase the transxantha all cases, the alcohol concentration was greatly in excess of tion yield, if desired. the xanthate. The xanthates were insoluble in the non-polar When the transxanthation reaction is complete, or substan solvents, cyclohexane and ether, and soluble in dioxane, water tially complete, the transxanthated product and/or the alcohol and acetone. The rate of exchange was not influenced by the or incompletely regenerated alcohol from the original alcohol alcohol to solvent ratio in cyclohexane and ether; however, in xanthate can be recovered by any practical means, including acetone, dioxane and water, exchange was retarded by decantation, centrifugation, precipitation, and distillation, de decrease alcohol to solvent ratio. The retarding effect was pending on the nature of the product itself and any inert sol O greatest for water, vent which may have been used. The following examples are set forth to demonstrate the EXAMPLE IV method of this invention. Solutions of potassium ethylxanthate in methanol mixtures 5 were prepared wherein the acid concentration was varied to EXAMPLE provide solution pH's ranging from 5 down to about 0.5. As A solution of 0.1 g of potassium ethylxanthate in 5 mi. of the acidity of the solution was increased, the exchange rate in methanol was allowed to stand for forty hours at ambient tem creased and passed through a maximum at about 1.5 and perature (22-26° C.). At the end of this time, the xanthate decreased rapidly at lower pH, It should be noted that some mixture comprised 74.3 percent ethyl and 25.7 percent xanthate decomposition also occurs in acidic solution mix methyl derivative. At the end of 10 days, the mixture, tures. Useful acids include organic and mineral acids, for ex precipitated by the addition of a larger volume of ether, com ample, acetic, phosphoric, hydrochloric and sulfuric acids. Al prised 6 percent of potassium ethylxanthate and 94 percent kali metal salts may be included for this buffering action. potassium methyl xanthate. The activation energy for the reaction was calculated as 25.6 kilocalories. The reaction 25 EXAMPLEV theoretically proceeds according to the chemical equation: Water and alkali were removed from thin films of viscose by washing with sodium sulfate and ethanol. The cellulose xanthate films were contacted with ethylene glycol. After ap proximately 4 hours at ambient temperature, the cellulose was 30 completely regenerated as a clear film and all the xanthate was recovered as the ethylene glycol derivative. wherein the formation in brackets is an unstable transition EXAMPLE WI complex. 35 Methanol, ethanol, propanol and isopropanol were con EXAMPLE II tacted with films of cellulose xanthate as in example V. The rate of simple alcohol xanthate formation was in the order A solution of 0.1 g of potassium ethylxanthate in 5 ml. of a mixture of methanol and 4 percent potassium hydroxide stood MeOHEtOH>ProHo di-ProH 40 hours at ambient temperature (22-26 C.). At the end of 40 this time, the xanthate mixture comprised 84.3 percent ethyl EXAMPLE WI and 15.7 percent methyl derivative. The activation energy for Phenol xanthate was formed when potassium ethylxanthate the reaction was calculated as 26.6 kilocalories. As may be was dissolved in molten phenol. seen from the above, the addition of alkali retards the xantha Some of the advantages of the method of this invention are: tion reaction. 45 i. The preparation of xanthates without the use of alkali and free carbon disulfide is possible. EXAMPLE III 2. Recovery and reuse of alcohol byproduct is possible. Solutions of 0.1 g., of potassium ethyl xanthate in n 3. Xanthates produced through this method are not subject propanol and in methanol were allowed to stand for a period to hydrolytic degradation. of days at ambient temperature (22-26°C.), and the percent 50 4. Xanthates produced through this method are more stable age of exchange or transxanthation was observed. The per in the absence of water. centage of exchange in relation to time is set forth in the fol 5. The method involves little or no undesirable byproduct lowing table: formation. 6. An alkaline alcoholic preparation of cellulose or other TABLE 55 polysaccharide xanthate may be formed into a shaped article and at least partially regenerated in an acidic alcohol solution by transxanthation. The free alcohol and the alcohol xanthate MethanoSolution N-Propanol Solution formed may be recovered and reused. 60 Other advantages for the method of this invention will be Age %. Ethyl % Ethyl readily apparent to those skilled in this art. (days) Xanthate Remaining Xanthate Remaining Various changes and modifications may be made practicing this invention without departing from the spirit and scope 70 96.2 3 44.7 86.3 thereof, and therefore, it is not to be limited except as in 7 2.4 63.5 65 dicated by the appended claims. O 6. S2.6 We Claim: 1. A method for the preparation of an alcohol xanthate which comprises contacting in a substantially water-free liquid The results of the above table indicate a slower reaction rate medium at a pH ranging from at least about 1 to no greater for the less acidic alcohol, n-propanol. The reaction proceeds 70 than about 12 and in the absence of a catalyst or in the more rapidly toward acidic free alcohols, other factors presence of an acidic catalyst, a derivative of an alcohol remaining constant. xanthic acid with an excess of a free alcohol differing from the The activation energy for the transxanthation reaction with alcohol moiety of the alcohol xanthic acid for a time sufficient n-propanol and potassium ethyl xanthate was calculated as for a transxanthation reaction to occur, said free alcohol and 29. kilocalories. 75 said alcohol moiety of the xanthate consisting of alcohols 3,607,865 S 6 selected from aliphatic alcohols, phenol, phenyl lower alkyl al 6. The method of claim 1 wherein the pH ranges from about cohols and polysaccharides 2 to about 8. 2. The method of claim 1 wherein the alcohol moiety of said 7. The method of claim 1 wherein the temperature at which derivative of an alcohol. xanthic acid is derived from a the transxanthation reaction is carried out ranges from about monohydric aliphatic alcohol having from 1 to 18 carbon 5 0 to about 40°C. atons. 8. The method of claim 1 wherein a transxanthated deriva 3. The method of claim 1 wherein said free alcohol is a tive product is recovered. monohydric aliphatic alcohol having from 1 to 18 carbon 9. The method of claim 1 wherein the alcohol or in atons. 4. The method of claim 1 wherein the alcohol moiety of said O completely regenerated alcohol from said derivative of al derivative of an alcohol xanthic acid is derived from a cohol xanthate is recovered as a shaped article. polysaccharide. 10. The method of claim 9 wherein the alcohol is cellulose 5. The method of claim wherein said free alcohol is a or an incompletely regenerated cellulose. polysaccharide. 15

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75 PO - " ) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 6 OT 86.5 Dated September 21, 97. Inventor(s) John Dyer and Lyle H. Phifer

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below: - - Column l, line 36, "is" should read -- in --. Column 2, iine l7, "benzyl ill, 4" should read -- benzyl alcohol -- Column 2, line l8, "o-hydroxybenzyl i, 5" should read -- O - hydroxybenzyl alcohol - - - Column. 4, line 9, "decrease" shoulid read -- decreased --. Signed and Sealed this 25th day of April 1972.

... ii., it -- it': i.TCill, JR. ROBERT GOTTS CiAEK Attesting Officer CorzitlissiCrier of Patents