Aromatic copolyamides, process for preparing them and their use

Details Aromatic copolyamides, process for preparing them and their use Aromatic copolyamides, process for preparing them and their use

1993-08-11

1995-05-30

Kight, III, John

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

Synthetic resins

From carboxylic acid or derivative thereof

C08G 6926

Patent

active

054202310

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

Aromatic copolyamides, process for preparing them and their use for the production of shaped structures. This application is a 371 of PCT/EP92/00392 filed Feb. 25, 1992.
Aromatic polyamides are known as materials of high mechanical, chemical and heat stability. Fibers and films of these materials exhibit high strengths and high initial moduli (modulus of elasticity), which renders them particularly suitable for industrial fields of use, for example for reinforcing plastics or as filter materials.
Such polymers are usually prepared by reaction of aromatic diamines with aromatic dicarboxylic acid chlorides in aprotic organic solvents of the amide type, for example N,N-dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP), alkali metal chlorides or alkaline earth metal chlorides being added, if appropriate, to improve the solubility and the hydrogen chloride formed subsequently being neutralized, for example with calcium oxide (DE-A-19 29 713, DE-B-22 19 703).
However, the preparation and processing of such polyamides proves to be very expensive. Because of its poor solubility in organic solvents, even in the presence of organic salts, such as lithium chloride or calcium chloride, as solubilizing agents, the polymer already precipitates out of the reaction medium shortly after its formation. It must be isolated, washed and dried, and then dissolved again in a solvent suitable for the processing.
These polymers are preferably spun from concentrated sulfuric acid, but this causes particular problems in handling (work safety, corrosion) and disposal.
Sparingly soluble polyamides, such as poly(p-phenyleneterephthalamide), have bonds arranged in parallel or coaxially to one another starting from the aromatic units. To achieve better solubility, it is possible to employ comonomers which are intended to serve to interrupt the parallel or coaxial pattern of bonds along the polymer chains.
Aromatic copolyamides of terephthalic acid, p-phenylenediamine and 3,4'-diaminodiphenyl ether can be processed from the NMP solutions obtained during the preparation process to give fibers and films having good strengths. However, synthesis of 3,4'-diaminodiphenyl ether and purification thereof are very expensive because of the asymmetric structure. Modifications of poly(p-phenylene-terephthalamide) which are industrially simpler, for example by incorporation of meta-linkage units (for example m-phenylenediamine) result in a deterioration in the mechanical properties (DE-B-30 07 063).
It is furthermore known that polyamides of p-phenylenediamine and 2,5-furandicarboxylic acid derivatives can be processed from NMP with addition of lithium chloride to give fibers and films (EP-A-0 256 606). In this process, the monomers are polymerized with one another directly in the presence of phosphorous acid triphenyl ester and pyridine. The resulting polymers have intrinsic viscosities of more than 1.5 dl/g (measured at 30.degree. C. in 98% strength sulfuric acid).
An alternative synthesis process for the preparation of poly(p-phenylene-2,5-furandicarboxamide) which is achieved without additions which are ecologically unacceptable or are often regarded as toxic, such as phosphorus compounds or pyridine, is described in Polymer Communications, 26, 246-249 (1985). However, in contrast to the products obtained by a direct polycondensation, the products obtained by this route have considerably lower intrinsic viscosities.
The present invention is therefore based on the object of discovering an aromatic copolyamide which has comparably good mechanical properties to poly(p-phenylene-terephthalamide), has a very good solubility in organic solvents and can be processed directly from these solutions to give high-quality fibers and films; whereby the process for the preparation of these polyamides should be economically and ecologically favorable and readily accessible diamines and dicarboxylic acid derivatives should be employed as starting substances.
The object is achieved by the present invention. The invention relates to an aromatic copo

REFERENCES:
patent: 5077378 (1991-12-01), Mueller et al.
Chemical Abstracts, vol. 83, No. 14, 1975, Columbus, Ohio.
Chemical Abstracts, vol. 75, No. 16, 1971, Columbus, Ohio.
Chemical Abstracts, vol. 75, No. 6, 1971, Columbus, Ohio.

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