Polyesters molecular weight

It has been hypothesized that cross-linked polymers would have better mechanical properties if interchain bridges were located at the ends rather than the center of chains. To test this, low molecular weight polyesters were synthesizedf... 

To produce a spandex fiber by reaction spinning, a 1000—3500 molecular weight polyester or polyether glycol reacts with a diisocyanate at a molar ratio of about 1 2. The viscosity of this isocyanate-terrninated prepolymer may be adjusted by adding small amounts of an inert solvent, and then extmded into a coagulating bath that contains a diamine so that filament and polymer formation occur simultaneously. Reactions are completed as the filaments are cured and solvent evaporated on a belt dryer. After appHcation of a finish, the fibers are wound on tubes or bobbins and rewound if necessary to reduce interfiber cohesion. 

In addition, polyester polyols are made by the reaction of caprolactone with diols. Poly(caprolactone diols) are used in the manufacture of thermoplastic polyurethane elastomers with improved hydrolytic stabiHty (22). The hydrolytic stabiHty of the poly(caprolactone diol)-derived TPUs is comparable to TPUs based on the more expensive long-chain diol adipates (23). Polyether/polyester polyol hybrids are synthesized from low molecular weight polyester diols, which are extended with propylene oxide. 

Thermoplastic polyurethane elastomers are produced from prepolymers by polycondensation (12,13). A relatively high molecular-weight polyester or polyether with terminal hydroxy groups (a polyglycol) first reacts with an excess of a diisocyanate. 

The major PET manufacturers are depolymerizing scrap PET with glycols (glycolysis) or methanol (methanolysis) to form low-molecular-weight polyester diols (and BHET) and dimethyl terephthalate.3 The purified products are then used to make new products. Goodyear uses glycolysis to make REPETE, a new product which contains 10-20% recycled PET. Hoechst Celanese used methanolysis to produce DMT for repolymerization. Eastman Chemicals uses depolymerization of PET to recover used X-ray scrap. 

Alkyl esters often show low reactivity for lipase-catalyzed transesterifications with alcohols. Therefore, it is difficult to obtain high molecular weight polyesters by lipase-catalyzed polycondensation of dialkyl esters with glycols. The molecular weight greatly improved by polymerization under vacuum to remove the formed alcohols, leading to a shift of equilibrium toward the product polymer the polyester with molecular weight of 2 x 10" was obtained by the lipase MM-catalyzed polymerization of sebacic acid and 1,4-butanediol in diphenyl ether or veratrole under reduced pressure. ... 

The enzymatic synthesis of polyesters from activated diesters was achieved under mild reaction conditions. The polymerization of bis(2,2,2-trichloroethyl) glutarate and 1,4-butanediol proceeded in the presence of PPL at room temperature in diethyl ether to produce the polyesters with molecular weight of 8.2 x 10. Vacuum was applied to shift the equilibrium forward by removal of the activated alcohol formed, leading to the production of high molecular weight polyesters. The polycondensation of bis(2,2,2-trifluoroethyl) sebacate and aliphatic diols took place using lipases BC, CR, MM, and PPL as catalyst in diphenyl ether. Under the... 

Camauba wax is obtained from the leaves of several species of palm trees in South America, such as Copemicia cerifem which grows in Brazil. It is made up of esters of long chain alcohols and acids with high carbon number, high molecular weight polyesters of hydroxyacids, and derivatives of p-hydroxy- and p-methoxycinnamic acid [84]. 

High molecular weight polyester, 20 23 High molecular weight poly(ethylene oxide) resins, 10 674... 

Duh, B., Method for production of a high molecular weight polyester prepared from a prepolymer polyester having an optimal carboxyl content, US Patent 4 238 593, 1980. 

Moore, L. D., Rule, M. and Wicker, H., Process for preparing high molecular weight polyesters, US Patent 4 446 303, 1984. 

SSP can be carried out batchwise or continuously, either in vacuo or supported by an inert gas flow. Another variation of SSP is the so-called suspension process in the swollen state, which allows for the production of extremely high-molecular-weight polyesters [3], This technology is more of academic interest than for commercial application since it requires complete removal of the high-boiling suspending oils. 

---