Biodegradable polymers, preparation thereof and use thereof for

Details Biodegradable polymers, preparation thereof and use thereof for Biodegradable polymers, preparation thereof and use thereof for

1997-05-14

2000-01-25

Yoon, Tae

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

525437, 525450, 528288, 528290, 528293, 528296, 528300, 528302, 528304, C08F 2000, C08G 1808, C08G 6312

Patent

active

060180048

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to biodegradable polyesters P1 obtainable by reaction of a mixture consisting essentially of mixtures thereof, thereof or mixtures thereof, and -C.sub.6 -alkanediols and C.sub.5 -C.sub.10 -cycloalkanediols, 1.5:1, with the proviso that the polyesters P1 have a molecular weight (M.sub.n) within the range from 5000 to 50,000 g/mol, a viscosity number within the range from 30 to 350 g/ml (measured in 50:50 w/w o-dichlorobenzene/phenol at a concentration of 0.5% by weight of polyester P1 at 25.degree. C.) and a melting point within the range from 50 to 170.degree. C. and with the further proviso that the polyesters P1 are prepared using from 0.01 to 5 mol %, based on the molar quantity used of component (a1), of a compound D having at least three groups capable of ester formation.
The present invention further relates to polymers and biodegradable thermoplastic molding compositions as claimed in dependent claims, processes for their preparation, their use for producing biodegradable moldings and adhesives, biodegradable moldings, foams and blends with starch obtainable from the polymers or molding compositions of the present invention.
Polymers which are biodegradable, ie. decompose under environmental influences in an appropriate and demonstrable time span have been known for some time. This degradation usually takes place by hydrolysis and/or oxidation, but predominantly by the action of microorganisms such as bacteria, yeasts, fungi and algae.
Y.Tokiwa and T. Suzuki (Nature, 270, (1977) 76-78) describe the enzymatic degradation of aliphatic polyesters, for example including polyesters based on succinic acid and aliphatic diols.
EP-A 565,235 describes aliphatic copolyesters containing [--NH--C(O)O--] groups (urethane units). The copolyesters of EP-A 565,235 are obtained by reacting a prepolyester, which is obtained by reacting essentially succinic acid and an aliphatic diol, with a diisocyanate, preferably hexamethylene diisocyanate. The reaction with the diisocyanate is necessary according to EP-A 565,235 because the polycondensation alone results only in polymers with molecular weights displaying unsatisfactory mechanical properties. A crucial disadvantage is the use of succinic acid or ester derivatives thereof to prepare the copolyesters because succinic acid and derivatives thereof are costly and are not available in adequate quantity on the market. In addition, the polyesters prepared using succinic acid as the only acid component are degraded only extremely slowly.
WO 92/13019 discloses copolyesters based on predominantly aromatic dicarboxylic acids and aliphatic diols, where at least 85 mol % of the polyester diol residue comprises a terephthalic acid residue. The hydrophilicity of the copolyester is increased, and the crystallinity is reduced, by modifications such as the incorporation of up to 2.5 mol % of metal salts of 5-sulfoisophthalic acid or short-chain ether diol segments such as diethylene glycol. This is said in WO 92/13019 to make the copolyesters biodegradable. However, the disadvantage of these copolyesters is that biodegradation by microorganisms has not been demonstrated, on the contrary only the behavior toward hydrolysis in boiling water or, in some cases, also with water at 60.degree. C. has been carried out.
According to the statements of Y.Tokiwa and T.Suzuki (Nature, 270 (1977) 76-78 or J. of Appl. Polymer Science, 26 (1981) 441-448), it may be assumed that polyesters which are substantially composed of aromatic dicarboxylic acid units and aliphatic diols, such as PET (polyethylene terephthalate) and PBT (polybutylene terephthalate), are not enzymatically degradable. This also applies to copolyesters which contain blocks composed of aromatic dicarboxylic acid units and aliphatic diols.
Witt et al. (handout for a poster at the International Workshop of the Royal Institute of Technology, Stockholm, Sweden, Apr. 21-23, 1994) describe biodegradable copolyesters based on 1,3-propanediol, terephthalic ester and adipic or sebacic acid. A disadvantage of th

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