Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-08-10
2002-07-23
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C528S272000, C528S275000, C528S296000, C528S300000, C528S302000, C528S307000, C528S308000, C528S308600
Reexamination Certificate
active
06423789
ABSTRACT:
BACKGROUND OF THE INVENTION
Polyesters which incorporate poly(alkylene ether) glycols are well known within the art. Said polyesters are typically produced by adding poly(alkylene ether)glycols at the beginning of the polyester polymerization stage. For example, Shivers, in U.S. Pat. No. 3,023,192, teaches the production of segmented copolyetherester elastomers, which incorporate poly(alkylene ether)glycols, by adding the poly(ethylene glycol) to dimethyl terephthalate, ethylene glycol and catalysts followed by polymerization. Further art teachings of similar production processes include, for example, U.S. Pat. Nos. 3,243,413, 3,558,557, 3,651,014, 3,701,755, 3,763,109, 3,766,146, 3,784,520, 3,880,976, 4,136,715, 4,262,114, 4,315,882, 4,467,595, 4,670,498, 4,906,729, and 4,906,714.
Occasionally, it has been generally taught that the poly(alkylene ether)glycol may be added to the polyester and incorporated through reesterification. For example, Frohlich, et al., in U.S. Pat. No. 3,663,653 teach that “Another possibility of preparing the block copolyesters of the invention consists in admixing the polytetrahydrofurandiol to the polyester melt. Owing to a reesterification reaction the polytetrahydrofuran blocks are bound to the polyester through their hydroxyl terminal groups.” (U.S. Pat. No. 3,663,653, column 2, lines 6-10). As an additional example, Wolfe, in U.S. Pat. No. 3,775,374, teaches that “Such prepolymers can also be prepared by a number of alternative esterification of ester interchange processes; for example, the long chain glycol can be treated with a high or low molecular weight short chain ester homopolymer or copolymer in the presence of catalyst until randomization occurs.” (U.S. Pat. No. 3,775,374, column 4, lines 40-45). A similar teaching may be found by Hoeschele as taught in U.S. Pat. No. 3,801,547. As a further example, Buxbaum, et al., in U.S. Pat. Nos. 4,156,774 and in 4,315,882, teach, “However, it is also possible to follow a procedure such that block polyesters are obtained by, for example, subjecting precondensates of homopolyesters (for example polyethylene terephthalate and polydiethylene glycol terephthalate) in appropriate quantity ratios to a polycondensation reaction, specifically on their own or together with a polyester of terephthalic acid and polybutylene glycol”. As yet a further example, Tanaka, et al., in U.S. Pat. No. 4,251,652, teach that such polyesters may be prepared by “polycondensing at a temperature of from 210 to 270° C. at least one dicarboxylic acid and at least one diol to provide a polyester and then polycondensing the resultant polyester with TERATHANE® at a temperature from 200 to 250° C.”Nelsen, in U.S. Pat. No. 4,355,155, teaches that “the long chain glycol can be reacted with a high or low molecular weight short chain ester homopolymer”. Greene, in U.S. Pat. No. 5,128,185, teaches “For example, long chain glycol can be reacted with high or low molecular weight short chain ester homopolymer or copolymer in the presence of catalyst until randomization occurs.” However, none of these references exemplify such processes within their disclosures. They exemplify production processes through the monomeric species, as discussed above.
Rarely, it has been exemplified within the background art to produce said polyesters which incorporate poly(alkylene ether)glycols from the interaction of preformed polyesters with the poly(alkylene ether)glycols. For example, Still, et al., in U.S. Pat. Nos. 4,968,778 and 4,970,275, teach a process to produce polyesters which incorporate poly(alkylene ether)glycols which consists “of a low molecular weight polyester formed by the reaction of terephthlaic acid and ethylene glycol (1:1.4 TA:EG)” combined with a poly(alkylene glycol)ether and catalysts followed by heating and finishing.
Takanoo, et al., in U.S. Pat. No. 5,331,066, teaches a process for the production of polyesters which incorporate poly(alkylene ether)glycols which comprises conducting polycondensation after or while melting and mixing a polyester polymer of 0.5 dL/g or more intrinsic viscosity and a polyether polymer having hydroxy groups at its terminals and having a number average molecular weight of 200 to 10,000. However, they further teach that “If the quantity of polyether is below one part by weight, desired polymer properties cannot be obtained, and if it is above 60 parts by weight, polyether extremely deteriorates and lowers in quality.”
The present invention overcomes the shortcomings of the background art and provides a process to produce polyesters which incorporate 65 to 90 weight percent poly(alkylene ether)glycols while maintaining adequate thermal properties.
BRIEF SUMMARY OF THE INVENTION
The present invention provides a process for producing a polyester that comprises 65 to 90 wt. % poly(alkylene ether) glycol. The process comprises the step of copolymerizing a preformed polyester polymer having an inherent viscosity of at least 0.4 dL/g and a poly(alkylene ether) glycol, to obtain the polyester comprising 65 to 90 wt. % poly(alkylene ether glycol).
In one embodiment, the process includes mixing and heating preformed polyesters with poly(alkylene ether) glycols, followed by standard finishing processes. The as produced polyesters which incorporate poly(alkylene ether)glycols of the present invention have been found to maintain comparable thermal stability to those produced by background art processes.
DETAILED DESCRIPTION OF THE INVENTION
It has become increasingly understood that there is a need to reduce the environmental footprint of chemical processes. In typical art polyester polymerizations, excesses of the glycol are used and, in turn, must be recovered and repurified. For example, for poly(ethylene terephthalate), generally 40 to 100 percent excess ethylene glycol are used. For poly(1,4-butylene terephthalate) and poly(1,3-propylene terephthalate), the excess glycol utilized is typically in the range from about 20 to 60 percent. In addition, for polyester polymerizations which start from dimethyl terephthalate, as is typical for the preparation of polyesters which incorporate poly(alkylene ether)glycols, significant quantities of methanol must also be recovered and recycled. Such polymerization processes for polyesters which incorporate poly(alkylene ether)glycols are taught within the art in, for example, U.S. Pat. Nos. 3,023,192, 3,243,413, 3,558,557, 3,651,014, 3,701,755, 3,763,109, 3,766,146, 3,784,520, 3,880,976, 4,136,715, 4,262,114, 4,315,882, 4,467,595, 4,670,498, 4,906,729, 4,906,714.
As a means to reduce the amount of volatile organic compounds (VOC) evolved within the processes to produce polyesters which incorporate poly(alkylene ether)glycols, it has been generally taught within the art to start with preformed polyesters. Such general teachings may be found within, for example, U.S. Pat. Nos. 3,663,653, 3,775,374, 3,801,547, 4,156,774, 4,251,652, 4,315,882, 4,355,155 and 5,128,185, said references are hereby incorporated into the present invention through reference. These references do not exemplify said process and therefore are not enabling to one skilled within the art. The use of preformed low molecular weight polyesters in the production of polyesters which incorporate poly(alkylene ether) glycols was taught within U.S. Pat. Nos. 4,968,778 and 4,970,275.
The use of high molecular weight polyesters with intrinsic viscosities of 0.50 dL/g or greater in the production of polyesters which contain 1 to 60 parts by weight, preferably 5 to 35 parts by weight, of poly(alkylene ether)glycols was taught within U.S. Pat. No. 5,331,066, which is hereby incorporated into the present invention by reference. They however strongly teach away from the use of this process in the production of polyesters which incorporate greater than 60 weight percent poly(alkylene ether)glycols due to degradation of the thermal properties.
The present invention has surprisingly found a process to produce polyesters which incorporate between about 65 and 90 weight percent poly(alkylene ether)glycols which significantly r
Acquah Samuel A.
E. I. duPont de Nemours & Company
Krukiel Charles E.
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