United States Patent (19) 11 Patent Number: 4,883,857 Guillet et al. 45) Date of Patent: Nov. 28, 1989

(54 PRODUCTION OF PHOTODEGRADABLE 4,042,568 8/1977 Guillet et al...... 528/229 POLYESTER PLASTICS 4,145,516 3/1979 Guillet et al...... 528/85 (75) Inventors: James E. Guillet, Don Mills; Ilse Primary Examiner-John Kight Treurnicht; Ruey S. Li, both of Assistant Examiner-S. A. Acquah Toronto, all of Canada Attorney, Agent, or Firm-Nixon & Vanderhye 73 Assignee: Ecoplastics Limited, Ontario, Canada 57) ABSTRACT 21 Appl. No.: 252,799 Condensation copolymers such as polyesters are ren (22 Filed: Sep. 30, 1988 dered photodegradable, by subjecting them to condi tions under which they undergo ester interchange effec (30) Foreign Application Priority Data tively causing polymer chain scission, in the presence of Sep. 30, 1987 CA Canada ...... 550526 a keto carbonyl containing compound having chemical 51) Int. Cl* ...... C08G 63/02 groups reactive with the condensation polymer prod 52 U.S. C...... 528/272; 528/302; ucts formed by the ester interchange. The compound 528/304; 528/308.2; 528/220; 523/125 reacts chemically with the polymer products to reform 58) Field of Search ...... 528/272, 302, 304,308.2, the high molecular weight condensation copolymer, but 528/220; 523/125 with the keto carbonyl groups chemically linked into the polymer chains to confer photodegradability (56) References Cited thereon. U.S. PATENT DOCUMENTS 3,878,169 4/1975 Guillet et ai...... 528/220 19 Claims, 1 Drawing Sheet

OO 5O 2OO 250 RRAD. HRS. U.S. Patent Nov. 28, 1989 4,883,857 FIG. I.

O 5O IOO 15O 20O 25O RRAD. HRS.

O 4O 8O 20 6O 20O RRAD. HRS. FIG 2 4,883,857 1. 2 terious side effects to the polymer. The effective result PRODUCTION OF PHOTODEGRADABLE is that the keto carbonyl group containing compound POLYESTER PLASTICS inserts itself into the condensation polymer chain, to produce a U.V. photodegradable polymer of high mo FIELD OF THE INVENTION lecular weight. This invention relates to photodegradable plastics From another aspect, the present invention provides materials and processes for their preparation. More novel keto carbonyl group containing compounds, hav particularly, it relates to high molecular weight conden ing at least two condensable groups per molecule, and sation polymers which will degrade upon exposure to capable of condensation reaction with polymeric frag ultraviolet radiation, e.g. direct sunlight, and processes O ments produced by catalytic thermal treatment of a for the preparation of such condensation polymers. condensation polymer, to insert themselves into a con densation polymer chain. BACKGROUND AND PRIOR ART Thus the present invention allows one to effect chem It is known that the incorporation of ketone carbonyl ical modification to a high molecular weight condensa groups into a polymeric backbone can render polymers 15 tion copolymer, to introduce the property of U.V. photodegradable upon exposure to ultraviolet radiation. photodegradability into it. Such condensation copoly The keto carbonyl groups can be located in the poly mers, e.g. polyesters, are readily available, inexpensive meric backbone chains, or in a side chain adjacent to the commodity items. Compounds containing keto car main polymeric backbone chain. For example, U.S. Pat. bonyl groups for incorporation therein can be prepared No. 4,042,568 Guillet et al. discloses condensation poly 20 mers such as polyamides, polyesters, polyurethanes, in straightforward economic manner. The process of polyepoxides, polyamide esters, polyurethanes and compounding the polymer and incorporating the keto polyamino acids, which are photodegradable on expo compounds therein can be simply and economically sure to U.V. light, due to the presence in the copolymer performed, e.g. in an extruder. This also may be accom backbone of keto carbonyl groups located in side chains 25 plished as the polymer is molded into the desired fin adjacent to the main chain of the copolymer backbone, ished article. Accordingly, the present invention pro in small amounts. vides relatively cheap, easily produced U.V. photode Condensation polymers such as polyesters have re gradable condensation polymers, capable of economic cently assumed an increased measure of commercial use in disposable commodity items such as beverage importance as disposable containers, e.g. for beverages, 30 bottles, wrapping films, containers and the like. where they have received food grade approval for use The U.V. photodegradable polymeric materials of in containers for soft drinks, beer, etc. As the volume of the present invention may be used directly for the man usage of such polyester containers increases, they be ufacture of finished thermoplastic articles therefrom. In come cheap, disposable, throw away items and pose a the alternative, they may be used as masterbatches, and potential litter and environmental pollution problem. 35 blended in appropriate proportions with standard con Such problems could be alleviated by making the con densation copolymers, to form a polymeric composition tainers of U.V. photodegradable polymers, so that they which is wholly U.V. photodegradable. The rate of would degrade and effectively disappear eventually, if photodegradation is largely determined by the molar discarded in an outdoor environment where they would concentration of keto carbonyl groups in the polymer encounter incident direct and indirect sunlight. This 40 or polymeric composition. Accordingly, when the keto would be particularly beneficial in remote rural areas, carbonyl containing polymers of the present invention where collection of litter is uneconomic. Materials such are to be used as masterbatch materials, they should as those described and exemplified in U.S. Pat. No. contain a higher concentration of carbonyl than other 4,042,568 are satisfactorily U.V. degradable, and fulfill wise. Satisfactory rates of U.V. photodegradation are most of the requirements in this regard. They are, how 45 achieved with carbonyl concentrations in the polymer ever, relatively expensive, since they are prepared by or polymeric blend of from 0.1-5 mole percent, prefera polymerization of special keto-containing condensable bly 0.5-3 mole percent. monomers. If photodegradable condensation polymers The invention can be applied to substantially any are to complete successfully with regular condensation condensation copolymer which effectively exists in polymers in high volume, disposable food and beverage 50 equilibrium with its monomeric components, such as packaging applications, they must be price competitive polyesters, polyamides, polyurethanes, polyepoxides, therewith. polyamide esters, polyureas and polyamino acids. The condensation copolymer must be capable of chain scis SUMMARY OF THE INVENTION sion upon heating, in the substantial absence of oxygen. The present invention provides, from one aspect, a 55 The keto carbonyl group containing compound should novel process for preparing U.V. photodegradable con be chosen in conjunction with the condensation copoly densation polymers containing keto carbonyl groups, mer so that it consists essentially of a compound or either in the backbone polymeric chain or in a side monomer of the type from which the condensation group adjacent to the backbone polymeric chain, in copolymer is derived. Thus in the case of polyesters, the which a preformed high molecular weight thermoplas 60 compound should be a keto carbonyl group containing tic condensation polymer is subjected to thermal treat hydroxyl compound or acid, preferably a hydroxy-acid. ment effectively causing polymer chain scission thereof, In the case of polyamides, it should be an amine or acid, in the presence of a keto carbonyl group containing preferably an amino acid. compound, containing at least two chemical groups reactive with the condensation polymer products so 65 DESCRIPTION OF THE PREFERRED formed, the thermal treatment being conducted under EMBODIMENTS conditions such that said compound joins to two or Most preferred among the condensation polymers are more such polymer products, and without serious dele polyesters, on account of their ease of undergoing ester 4,883,857 3 interchange, and so the invention will be further de scribed and illustrated with specific reference to polyes X-M-A-Q-Y (III) ters, especially polyethylene terephthalate, although it is not to be construed as limited thereto. in which M and Q are independently selected from The common polyethylene terephthalate (PET) is a 5 alkylene and aralkylene, optionally being interrupted by polyester condensation product derived from tereph an acyl group thalic acid or esters thereof and ethylene glycol. Com monly, the starting material is dimethyl terephthalate, (-O-C-), of formula: 10 O O O (I) the alkylene portion thereof having from 2-10 carbon atoms; CH3.O.C C.O.CH3 A represents a keto carbonyl group of formula 15 and ethylene glycol. On heating with a suitable catalyst, R each methyl ester group of terephthalic dimethyl ester -C- or -C- DMT condenses with a hydroxyl group of ethylene I l. glycol, releasing methanol and forming the condensa O f=o tion polymer. Two repeating units of polyethylene tere 20 R phthalate PET can thus be illustrated as follows:

O O O (II) I oal-al-ol-O-o- However, this condensation copolymerization reac in which: tion is, in fact, an equilibrium between the monomers 30 Ris hydrogen, lower alkyl or lower alkaryl, and R' and the condensation polymer. Upon heating, normally is lower alkyl or lower alkaryl; in the presence of a suitable catalyst, such as antimony and X and Y are independently selected from car trioxide or an organic acid, ester interchange takes boxyl, lower alkyl carboxylic ester, phenyl car place at the ester groups, thus incorporating the mono boxylic acid ester, lower alkaryl carboxylic acid mers into the polymer. The heating may cause melting 35 ester, haloacyl and hydroxy, one but not both of of the polymer, or stop short of the melting point. X and Y being hydroxy. Whilst the mechanism and resulting chemical groupings Fragments of the polyester produced on thermal are not fully elucidated and understood, it appears that treatment either recombine with one another to reform groups readily reactable with hydroxyl groups and the starting material, or recombine with the compound groups readily reactable with acid groups are formed as of formula (III) as a linking compound. The molecular end groups on the polymeric fragments so produced, weight of the compound of formula (III) thus inserted i.e. effectively forming an acid-terminated fraction and into the polymeric chain is insignificant in comparison a hydroxyl-terminated fraction. According to the in with the high molecular weight of the thermoplastic vention, therefore, in its preferred embodiments, such polyester starting material. Compounds of the formula ester interchange by heating is undertaken in the pres 45 (III) having groups M and Q similar to or the same as ence of material containing a reactive hydroxyl group those to be found in the high molecular weight polyes and a reactive acid or acid functional derivative group, ter are also preferred, so as to minimize the risk of unde and which also contains in its structure a keto carbonyl sired modification of other properties of the final ther group, either in linear relationship to the acidic and moplastic polymer. hydroxyl groups of the compound, or in a position 50 Compounds of formula (III) in which M is an alkyl adjacent to the linearly arranged claims terminated by ene chain interrupted by acyl, and X and Y are as de the acidic or hydroxyl groups. As a result, at least some fined above, are novel, and constitute a feature of the of the keto carbonyl containing compounds form links present invention. They may be prepared by transesteri between the polymeric chain fragments so produced to fication methods, e.g. by reaction of a keto containing reform the high molecular weight polyester chains, but 55 diacid of diester with a diol such as ethylene glycol, to with keto carbonyl groups located therein, to effect form a keto containing diol, followed by reaction with photodegradability on exposure to U.V. radiation on a diester. Keto substituted dicarboxylic acids and esters the resulting polymers. for use as starting materials are known. When these are The keto carbonyl containing compounds can be reacted with ethylene glycol in the presence of suitable represented by the following general formula (III): catalysts such as zinc and calcium acetates, transesterifi cation occurs to form keto substituted diol compounds, according to the following general reaction scheme:

RO--(CH2)-cH-(CH2)--ORI + 2CH-OH O O CH-OH R Ca acetate Zn acetate 4,883,857

-continued

Hochscho--CH2-H-CH2--och,O O chority - 2ROH where R' is independently selected from hydrogen and interchange at one chain end only of the compound of lower alkyl. formula (IV). When the polyester to be modified is In the above formulae, x and y are independently 10 polyethylene terephthalate, this diacid or diester is pref. selected integers from 1-10. When, in the above scheme, erably dimethyl phthalate, a commercially available x is 1, y is 1, R is methyl and R is hydrogen, the starting compound, so as to provide in the compound of formula diacid is 3-acetylglutaric acid, a known compound. (III) chemical groups M and Q substantially identical Other analogous keto-substituted diacids are known and with those in polyethylene terephthalate. Thus the reac can be used, for example y-acetyl pimelic acid, y-benz- 15 tion can be represented as follows: Ho-CH, CH, osch-H-CH)--oh, CH, OH -- (H, O g-o o R C

(DMT)

Cec O CH3 (V) Ho Choo CH-)- sh- (CHyochroco CO-O-CH3 O i-o O R oyl pimelic acid, y-acetyl suberic acid, y-acetyl azelaic acid and the like, and functional derivatives thereof which behave as acids, such as esters, acyl halides, an This compound of formula (V) can now be reacted hydrides, etc. They are described in aforementioned 40 with polyethylene terephthalate, by subjecting the U.S. Pat. No. 4,042,568 Guillet et al. Processes for their polyethylene terephthalate to ester interchange in the preparation are also known, for example from U.S. Pat. presence of compound (V), and compound (V) will No. 2,438,961 Boese, and from U.S. Pat. No. 2,342,606 effectively insert itself into the polymer chains of poly Bruson. ethylene terephthalate, to impart U.V. degradability When group A in the compound of formula (III) is to 45 thereto. be a keto group C-O, to provide backbone keto car In the alternative to the use of keto carbonyl contain bonyl containing polyesters, the diacid starting material ing compounds of formula III, one can use keto group contains a keto group in its backbone, instead of in a side containing low molecular weight condensation copoly chain, but the preparation of a compound similar to mers (oligomers) which upon thermal treatment will compound (IV) proceeds analogously to the transesteri 50 undergo chain scission reaction to yield keto group fication shown above. An example of a known such containing fragments. These fragments each have end diacid is y-ketopimelic acid. groups capable of reaction with the polyester fragments As noted, it is within the scope of the invention, al resulting from the thermal chain scission of the high though not preferred, to prepare compounds of formula molecular weight polyester. Consequently thermal (III) starting from keto-containing glycols, and regular, 55 treatment of a mixture of polyester and oligomeric keto unsubstituted diacids such as glutaric acid, pimelic acid, containing polyester results in ester interchange reac suberic acid, succinic acid and the like. Keto-containing tions between the fragments of the two starting materi glycols are known, for example from aforementioned als, with random insertion of keto group containing U.S. Pat. No. 4,042,568. Examples include y-acetylpen fragments into the high molecular weight polyester. A tamethylene-a, c)-glycol and y-acetylhexamethylene-a, 60 photodegradable high molecular weight polyester re a)-glycol. Compounds analogous to those of formula IV sults. can thus be formed, but in which the acyl groups are An example of such an oligomer is that produced by effectively "reversed' with respect to the keto carbonyl condensation copolymerization of keto pimelate with a groups. glycol such as ethylene glycol. Such an oligomer con Then, to form the compound of formula (III), ready 65 tains a high concentration of keto groups, and will pro for reaction to insert into the polyester, the diol com duce a relatively large number of keto group containing pound such as compound (IV) is reacted with a diacid fragments for random insertion into polyethylene tere or diester, under conditions controlled to effect ester phthalate for example. 4,883,857 7 8 The conditions under which the polyester is reacted of oxygen. The process is thus extremely economically with the keto carbonyl containing monomer should be conducted. such as to avoid substantial side reaction and oxidation When a keto group containing oligomeric polyester is of the high molecular weight polymer. Thus, the reac used for ester interchange, the reaction may also be tion should be conducted on the polymer in the molten conducted under extruder conditions as previously de state, in the substantial absence of oxygen, and prefera scribed. The oligomers are normally semisolid, paste bly under conditions in which the reaction mixture can like materials, so that they are readily compounded with be vented so as to remove low molecular weight mole the high molecular weight polyester in the extruder cules produced in the condensation reaction. Subjecting barrel. Alternatively, however, some or all of the ester the polymer to mixing in the molten state in an extruder, 10 interchange reaction may take place in the solid state from which air is excluded, is satifactory. It may be after the mixture has issued from the extruder. When necessary to have a catalyst present, to effect satisfac operating in this manner, the oligomer is compounded tory chain scission of the polyester. Suitable catalysts with the high molecular weight polyester in an ex include those which effect ester interchange in polyeth truder, and the mixture is extruded therefrom in pellet ylene terephthalate and polybutylene terephthalate pro 15 form. Then the pellets are maintained at a temperature duction. A discussion of such catalysts, and a listing of just below the melting point of the polyester for several representative examples, is to be found in "Encyclope hours, to drive the reaction to completion. Very high dia of Polymer Science and Technology” Kirk-Othmer, molecular weight polyesters containing keto carbonyl Vol. II, pages 111-112, and in J. Polymer Sci., 54, 20 groups are produced in this way. 385-410 (1961), R. E. Wilfong. Suitable among such The preformed polyester which is modified accord catalysts is antimony trioxide. Indeed, commercially ing to the present invention may be newly manufac available polyethylene terephthalate commonly con tured, virgin resin, or previously used, recycle polyester tains sufficient amounts of a catalyst for use in the pres resin. The invention in fact provides a means by which ent invention without addition of separate quantities of 25 scrap polyester resin may be recycled and reused. At catalyst. present, disposal of scrap polyester resin is a significant The most preferred way of conducting the process of economic problem. The present invention allows scrap the present invention is by formation of the keto-con polyester to be converted to photodegradable form, taining monomer of formula (III) in situ in the presence re-used as a plastic (although perhaps not in food pack of the polyester into which the monomer is to be in 30 aging applications) and will subsequently be more serted, and under conditions which will permit such readily disposable on account of its photodegradability. insertion as the monomer of formula III is formed. In The products of the present invention, photodegrada this way, a most economical, one step process can be ble condensation polymers, may be used in substantially utilized. Thus there is prepared a mixture of the polyes any application where the corresponding non-photode ter, and the ingredients required to react to form the 35 gradable condensation polymers have previously been monomer of formula (III), namely a diol and a diacid, used. Beads or the like obtained from the extruder or diester, diacylhalide, etc., one of which contains the solid state reactor as described above may be repro keto carbonyl group. There is no need to recover the cessed to yield desirable products. The degree of homo compound of formula (III) before it is mixed with the geneity of the product is further improved as a result of polyester. In this manner of proceeding, however, sub such reprocessing. The physical and chemical proper stantially equimolar quantities of ingredients forming ties of the final products remain substantially unaltered, the compound of formula (III) should be used. If there other than the addition of the property of photodegrad is a molar excess of either the diol or the diacid etc., ability. there is a risk that this excess will react with polymer The invention is further illustrated in the following fragments of the polyester formed in the transesterifica 45 tion process to effect chain termination thereof. This specific examples. will undesirably affect the molecular weight of the EXAMPLE 1. resultant polyester. In this preferred way of operating, it is thus simply Preparation of the diglycol ester of 2-acetyl-glutaric necessary to mix the polyester, diol and diacid or the 50 acid (DGAG) like, optionally in the presence of added catalyst, and DGAG was synthesized by transesterification of the subject the mixture to high temperatures (e.g. 220-280 diethyl ester of 2-acetyl glutaric acid (an acid with a C.) with adequate protection from oxidation and with ketone group in a side chain) with ethylene glycol in the facilities to allow removal of low molecular weight presence of zinc and calcium acetates. condensation reaction products (normally water or 55 0.006 g calcium acetate and 0.003 g zinc acetate were lower alcohols). Such conditions are to be found in dissolved in 4.66 g ethylene glycol (0.075M) in a glass conventional plastics extruders and solid state reactors. tube (2.5 cm ODX20 cm ht). The solution was heated Thus, to conduct the preferred process of the invention, with 6.9 g diethyl 2-acetyl glutarate (0.03M) in an alu when operating above or below the melting point of the minum heating block which had a cavity sized to ac polyester, one merely mixes the materials in an extruder commodate the glass tube. The contents were heated at or solid state reactor, and obtains the modified, 180°-200 C. for 2 hours. 2.8g of a colourless conden photodegradable polyester from the extruder, without sate boiling at about 80 C. was collected. A slightly in fact having to include any significant additional pro yellowish brown liquid residue was obtained in the glass cessing step or equipment into a regular plastics pro tube after reaction. This residue was extracted with cessing operation. Solid state reactors commonly oper 65 methylene chloride and water, and the two phases al ate at temperatures from about 5 C. to about 40 C. lowed to separate. Unreacted glycol was contained in below the polymer melting point, and either under vac the aqueous phase. The ester in the methylene chloride uum or under flush of nitrogen, for substantial exclusion phase was purified with activated charcoal and recov 4,883,857 9 10 ered. An approximately 80% yield of ester was ob tained. EXAMPLE 3

HO-CH2-CH-OH + C2H5-O.CO.CH2-CH-CH-CO.O.C2H5

y coCH3 Hoch-chococh-ch-ch-cooch. CH-OH co DGAG CH3

Preparation of the diglycol ester of acetone dicarboxylic acid (DGAD)

CH2COOMe 20 O Ych.cooMe + 2HOCH2CH2OH-Ge. EXAMPLE 2 CH2COOCH2CH2OH Insertion into polyethylene terephthalate of DGAG and dimethyl terephthalate 25 o=c, -- 2MeOH 0.009 of antimony trioxide was mixed with 0.7 g of Ych.coochchyoh DGAG and 0.49 g dimethyl terephthalate (1:1 mole ratio). The mixture was added to 21.7 g pulverized Calcium acetate (0.006 g) and zinc acetate (0.003 g) commercial bottle grade polyethylene terephthalate 30 were dissolved in ethylene glycol (4.66g, 0.075M) in a resin and placed in a glass tube, lined inside with alumi glass tube. The dimethyl ester of acetone dicarboxylic num foil, as mentioned in example 1. The contents and acid (5.25 g, 0.03M) was added and the reaction mixture aluminum foil were then heated, in the glass tube, under heated in an aluminum heating block at 160-185° C. for a high vacuum (30-300 microns) at 250-280 C. for 2 2.5 hrs. Approximately 4 ml of condensate was col hours in an aluminum block heater. After cooling to 35 lected at a vapour temperature of about 60° C. A room temperature, the vacuum was released, and the slightly yellowish liquid product was obtained in the aluminum foil tube containing the product was re tube. The crude product was purified by dissolution in moved. The slightly grayish product in the aluminum water (10 ml) followed by extraction with hexanes tube was dissolved with trifluoroacetic acid-methy (2x25 ml). The hexane extracts were discarded. The lene chloride mixture (1:3) and a film was cast on Tedlar aqueous layer was further extracted with methylene film. The film was then extracted (Soxhlet) overnight chloride (2x30 ml). The combined methylene chloride with methanol. extracts were passed through a charcoal column to give After drying, the film was aged in the Weather-Ome an almost colourless solution. After evaporation of the ter. The intrinsic viscosities of the aged films along with solvent, the purified product was obtained as a thick oil PET films as controls were determined using a standard 45 in 80% yield. viscosity measurement technique. The molecular EXAMPLE 4 weights were calculated from the intrinsic viscosity, using the Mark-Houwink equation, with k value of Insertion of DGAD into polyethylene terephthalate 0.0021 and alpha value of 0.58. The rate of photodegra The diglycolester of acetone dicarboxylic acid dation was illustrated on a graph, FIG. 1, where there 50 (DGAD, 0.65 g) was mixed with an equimolar amount was plotted as ordinate the value Mo/MT-1, in which (based on DGAD) of dimethyl terephthalate (0.49 g). Mois the molecular weight of the initial resin, MTis its Pulverised commercial bottle grade polyethylene tere molecular weight after time T of exposure to ultraviolet phthalate (21.7 g) was added to the reaction mixture, radiation in the Weather-Ometer. When this ratio which was in turn transferred to a glass tube lined with Mo/MT is unity, no reduction in molecular weight, i.e. 55 aluminum foil. The reaction vessel was heated in the no polymer chain scission has occurred. When this ratio cavity of an aluminum block heater at 260-280 C. for is two, the molecular weight has halved, i.e. an average 2 hours, under a vacuum of 100-300 microns. After one break per polymer chain has occurred. The value of cooling to room temperature, the vacuum was released. Mo/MT less one, as plotted, is thus proportional to the The fused product was dissolved in trifluoroacetic acid average number of chain scissions per polymer mole 60 methylene chloride mixture (1:3) and a film was cast on cule. Acclelerated degradation of the product of this a glass plate. The dried film was extracted overnight example, compared with an unmodified polyethylene with boiling methanol in a soxhlet extractor. terephthalic acid, was thus demonstrated. Photodegradation of the film was studied as de On FIG. 1, the circles and continuous curve are de scribed in Example 2, and the results are presented rived from the product of this example. The square 65 graphically on FIG. 2 in the same format and with the plots and broken line curve are derived from similar same notations. Accelerated photodegradation as com testing of the unmodified polyethylene terephthalate pared with the unmodified polyethylene terephthalate resin. resin is clearly demonstrated. 4,883,857 11 12 Similar results were obtained in the presence of anti addition level. The extruded product filament was mony trioxide (0.009 g) catalyst. cooled in a water trough and pelletized. The reaction product was thermally pressed into EXAMPLE 5 clear films and irradiated in the QUV Accelerated Preparation of the diglycol ester of 4-acetylpimelic acid Weather Tester. The films failed at 92 hours, whereas (DGAP) the control PET resin film remained intact. We claim: CH2CH2CO2Me 1. A process for preparing condensation polymers having accelerated photodegradability and containing Chicoct + 2HOCH2CH2OH-G 10 keto carbonyl groups, either in the backbone polymeric chain or in a side group adjacent to the backbone poly meric chain, which comprises subjecting a high molecu lar weight thermoplastic condensation polymer capable -- 2MeOH of chain scission upon heating, in the substantial absence 15 of oxygen, to thermal treatment to cause polymer ester interchange reaction thereof and so to form condensa Calcium acetate (0.006 g) and zinc acetate (0.003 g) tion polymer products therefrom, in the presence of a were dissolved in ethylene glycol (4.66 g, 0.075M). The keto carbonyl group containing compound containing dimethyl ester of 4-acetylpimelic acid (6.9 g, 0.03M) at least two chemical groups reactive with the conden was added and the mixture was heated in an aluminum 20 sation polymer products so formed, the thermal treat heating block at 180°-200 C. for 2.5 hours. Approxi ment being conducted under conditions such that said mately 1 ml of condensate boiling at about 60° C. was compound chemically reacts with the condensation collected, with an orange coloured liquid product re polymer products to re-form high molecular weight maining in the tube. The crude product was purified by 25 condensation polymer chains containing keto carbonyl dissolution in water (10 ml) followed by extraction with groups. hexane (25 mlx2). The hexane solutions were dis 2. The process of claim 1 wherein said condensation carded and the aqueous layer was extracted with meth polymer is a polyester. ylene chloride (30 mlx2). The organic extracts were 3. The process of claim 2 wherein said polyester is combined and passed through a charcoal column. Sub 30 polyethylene terephthalate. sequent evaporation of the eluents gave an almost co 4. The process of claim 2 wherein the keto carbonyl lourless liquid (DGAP) in 81% yield. group containing compound has a terminal hydroxy EXAMPLE 6 group and a terminal acid functional group. 5. The process of claim 4 wherein the keto carbonyl Insertion of DGAP into polyethylene terephthalate 35 group containing compound has side chain keto car Antimony trioxide (0.009 g) was dispersed in the bonyl groups. diglycolester of 4-acetylpimelic acid (DGAP, 0.65 g). 6. The process of claim 2 wherein said keto carbonyl To this was added an equimolar amount (based on group containing compound corresponds to the general DGAP) dimethyl terephthalate (0.49 g), followed by formula pulverised commercial bottle grade polyethylene glass tube lined with aluminum foil and heated in the cavity of an aluminum block heater at 260-280 C. for 2 hours, under a vacuum of 100-300 microns. After cool in which ing to room temperature, the vacuum was released. The M and Q are independently selected from alkylene fused product was dissolved in trifluoroacetic acid 45 and aralkylene, optionally interrupted by an acyl methylene chloride mixture (1:3) and a film was cast on group (-O-CO-), the alkylene portion thereof a glass plate. The dried film was extracted overnight having from 2-10 carbon atoms; with boiling methanol in a soxhlet extractor. A represents a keto carbonyl group of formula Photodegradation of the film was studied as de scribed in Example 2, and showed accelerated degrada CO or R-C-CO-R' tion when compared with untreated PET resin. 50 in which EXAMPLE 7 R is hydrogen, lower alkyl or lower alkaryl, and R' is Insertion of the di(ethylene glycol) ester of lower alkyl or lower alkaryl; 4-ketopimelic acid (DGKP) into polyethylene 55 and X and Y are independently selected from car terephthalate using a reactive extrusion process boxyl, lower alkyl carboxylic ester, phenyl carbox A Betol BTS 40 twin screw extruder, with corotating ylic ester, lower alkaryl carboxylic acid ester, screws of 40 mm diameter and a 21:1 L/D ratio, was haloacyl and hydroxy, one but not both of X and Y used to conduct the insertion reaction of DGKP into being hydroxy. molten polyethylene terephthalate. 7. The process of claim 6 wherein x in said keto com The PET resin (Kodapak PET 9663 clear) was pre pound of general formula is hydroxy and y therein is dried overnight and mixed with antimony trioxide lower alkyl ester. (0.04% by weight) and dimethyl terephthalate (2.25% 8. The process of claim 6 wherein said keto carbonyl by weight). The mixture was loaded into an AccuRate group containing compound is prepared by transesteri feeder, with feed rate set at 1 kg/hr. The temperature of 65 fication of a keto containing diacid or functional deriva the extruder barrel was kept in the range 220-260 C. tive with a diol, or by transesterification of a keto con DGKP was fed into the PET melt stream through a taining diol with a diacid or functional derivative vent port at a rate controlled to yield a 3% by weight thereof. 4,883,857 13 14 9. The process of claim 8 wherein transesterification 15. The process of claim 12 wherein said conditions is conducted using a keto containing diacid or func are solid state conditions in which the polyester is main tional derivative thereof and a diol. tained at temperatures from about 5” C. to about 40 C. 10. The process of claim 9 wherein the diacid is se below the melting point thereof, under reduced pres lected from acetone dicarboxylic acid, 2-acetyl-glutaric 5 sure with substantial exclusion of oxygen. acid, y-acetyl pimelic acid, y-benzoyl pimelic acid, 16. The process of claim 14 wherein the polyester is ty-acetyl suberic acid and y-acetyl azelaic acid. previously utilized and molded scrap polyester. 11. The process of claim 8 wherein the transesterifica 17. The process of claim 2 wherein the polyester is tion reaction to produce the keto carbonyl group con reacted with a keto carbonyl group containing com taining compound is conducted in the presence of the 10 pound formed in situ by thermal treatment of a keto polyester. group containing oligomeric ester compound. 12. The process of claim 11 wherein said transesterifi 18. The process of claim 17 wherein the oligomeric cation is conducted under conditions causing polymer ester is mixed with the polyester in an extruder. ester interchange reaction of the polyester. 19. The process of claim 18 wherein beads of poly 13. The process of claim 12 wherein said conditions 15 meric mixture are recovered from the extruder and include temperatures sufficient to maintain the polyes maintained at an elevated temperature but below the ter in molten state, mechanical shearing and the substan melting point of the polyester, to pursue the ester inter tial exclusion of oxygen. change reaction. . 14. The process of claim 13 conducted in an extruder. k ck :k : s 20

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