Biodegradable polymers, the preparation thereof, and the use...

Details Biodegradable polymers, the preparation thereof, and the use... Biodegradable polymers, the preparation thereof, and the use...

1997-11-20

2001-07-10

Foelak, Morton (Department: 1711)

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

Synthetic resins

From carboxylic acid or derivative thereof

C521S182000, C521S138000, C528S300000, C528S302000, C528S307000, C528S308000, C528S308600, C528S361000

Reexamination Certificate

active

06258924

ABSTRACT:

The present invention relates to biodegradable polyether esters P1 obtainable by reacting a mixture essentially comprising:
(a1) a mixture essentially comprising:
25-95 mol % of adipic acid or ester-forming derivatives thereof or mixtures thereof,
5-80 mol % of terephthalic acid o r ester-forming derivatives thereof or mixtures thereof, and
0-5 mol % of a compound containing sulfonate groups, where the total of the individual mole percentages is 100 mol %, and
(a2) a mixture of dihydroxy compounds essentially comprising
(a21) from 15 to 99.8 mol % of a dihydroxy compound selected from the group consisting of C
2
-C
6
-alkanediols and C
5
-C
10
-cycloalkanediols,
(a22) from 85 to 0.2 mol % of a dihydroxy compound containing ether functionalities of the formula I:
HO—[(CH
2
)
n
—O]
m
—H  I
where n is 2, 3 or 4 and m is an integer from 2 to 250, or mixtures thereof,
where the molar ratio of (a1) to (a2) is chosen in the range from 0.4:1 to 1.5:1, with the proviso that the polyether ester P1 has a molecular weight (M
n
) in the range from 5000 to 80,000 g/mol, a viscosity number in the range from 30 to 450 g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyether ester P1 at 25° C.) and a melting point in the range from 50 to 200° C., and with the further proviso that from 0 to 5 mol %, based on the molar quantity of component (a1) employed, of a compound D with at least three groups capable of ester formation are employed to prepare the polyether ester P1.
The invention furthermore relates to polymers and biodegradable thermoplastic molding compositions as claimed in the dependent claims, processes for the preparation thereof, the use thereof for producing biodegradable moldings and adhesives, biodegradable moldings, foams and blends with starch obtainable from the polymers and molding compositions according to the 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 alipha tic copolyesters containing [—NH—C(O)O—] groups (urethane units). The copolyesters of EP-A 565,235 ar e obtained by reacting a prepolyester, which is obtained by reacting essentially succinic acid and an aliphatic diol, with a disocyanate, preferably hexamethylene diisocyanate. The reaction with the dasocyanate is necessary according to EP-A 565,235 because the polycondensation alone results only in polymers with molecular weights such that they display 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 92/13020 discloses copolyether esters based on predominantly aromatic dicarboxylic acids, short-chain ether diol segments such as diethylene glycol, long-chain polyalkylene glycols such as polyethylene glycol (PEG) and aliphatic diols, where at least 85 mol % of the polyester diol residue comprise a terephthalic acid residue. The hydrophilicity of the copolyester can be increased and the crystallinity can be reduced by modifications such as in corporation of up to 2.5 mol % of metal salts of 5-sulfoisophthalic acid. This is said in WO 92/13020 to make the copolyesters biodegradable. However, a disadvantage of these copolyesters is that biodegradation by microorganisms was not demonstrated, on the contrary only the behavior towards hydrolysis in boiling water was 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 essentially 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 and copolyether esters which contain blocks composed of aromatic dicarboxylic acid units and aliphatic diols or ether diols.
Witt et al. (handout for a poster at the International Workshop of the Royal Institute of Technology, Stockholm, Sweden, Apr. 21-23, 1994) described biodegradable copolyesters based on 1,3-propanediol, terephthalic ester and adipic or sebacic acid. A disadvantage of these copolyesters is that moldings produced therefrom, especially sheets, have inadequate mechanical properties.
It is an object of the present invention to provide polymers which are degradable biologically, ie. by microorganisms, and which do not have these disadvantages. The intention was, in particular, that the polymers according to the invention be preparable from known and low-cost monomer units and be insoluble in water. It was furthermore the intention that it be possible to obtain products tailored for the desired uses according to the invention by specific modifications such as chain extension, incorporation of hydrophilic groups and groups having a branching action. The aim was moreover that the biodegradation by micro-organisms should not be achieved at the expense of the mechanical properties in order not to restrict the number of applications.
We have found that this object is achieved by the polymers and thermoplastic molding compositions defined at the outset.
We have furthermore found processes for the preparation thereof, the use thereof for producing biodegradable moldings and adhesives, and biodegradable moldings and adhesives obtainable from the polymers and molding compositions according to the invention.
The polyether esters P1 according to the invention have a molecular weight (M
n
) in the range from 5000 to 80,000, preferably from 6000 to 45,000, particularly preferably from 8000 to 35,000, g/mol, a viscosity number in the range from 30 to 450, preferably from 50 to 400, g/ml (measured in o-dichlorobenzene/phenol (50/50 ratio by weight) at a concentration of 0.5% by weight of polyether ester P1 at 25° C.) and a melting point in the range from 50 to 200, preferably from 60 to 160° C.
The polyether esters P1 are obtained according to the invention by reacting a mixture essentially comprising:
(a1) a mixture essentially comprising:
20-95, preferably from 30 to 80, particularly preferably from 40 to 70, mol % of adipic acid or ester-forming derivatives thereof, in particular the di-C
1
-C
6
-alkyl esters such as dimethyl, diethyl, dipropyl, dibutyl, diisobutyl, dipentyl and dihexyl adipate, or mixtures thereof, preferably adipic acid and dimethyl adipate, or mixtures thereof,
5-80, preferably 20-70, particularly preferably from 30 to 60, mol % of terephthalic acid or ester-forming derivatives thereof, in particular the di-C
1
-C
6
-alkyl esters such as dimethyl, diethyl, dipropyl, dibutyl, dipentyl or dihexyl terephthalate, or mixtures thereof, preferably terephthalic acid and dimethyl terephthalate, or mixtures thereof, and
0-5, preferably from 0 to 3, particularly preferably from 0.1 to 2, mol % of a compound containing sulfonate groups, where the total of the individual mole percentages is 100 mol %, and
(a2) a mixture of dihydroxy compounds essentially comprising
(a21) from 15 to 99.8, preferably from 60 to 99.5, particularly preferably from 70 to 99.5, mol % of a dihydroxy compound selected from the group consisting of C
2
-C
6
-alkanediols and C
5
-C
10
-cycloalkanediols,
(a22) from 85 to 0.2, preferably from 0.5 to 40, particularly preferably from 0.5 to 30, mol % of a dihydroxy compound containing ether functionalities of the formula I:

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