Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1992-11-02
1994-06-21
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528340, 528342, 528347, C08G 6928
Patent
active
053229231
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to semi-crystalline, semi-aromatic copolyamides derived from terephthalic acid and mixtures comprising an alkylpentamethylenediamine and hexamethylenediamine, which have a bending temperature under load (abbreviated BTUL; standards : NF T 51005) under 1.8 MPa of at least 240.degree. C., when these copolyamides are filled with one or more padding or reinforcing fillers of fibrous type and moulded. The present invention also relates to processes for the production of these copolyamides, as well as compositions, in particular for moulding, produced from these copolyamides.
Polyamides derived from aliphatic diamine(s) and aliphatic or aromatic carboxylic diacid(s) have already been known for a long time. Depending on their composition, these polyamides are semi-crystalline polymers having high melting points (m.p.) or completely amorphous substances having relatively low glass transition temperatures (Tg).
Semi-crystalline polyamides are advantageously used when it is desired to produce formed articles which have a good thermomechanical stability at high temperature. The best known of the semi-crystalline polyamides is polyamide 6.6 (polymer of hexamethylenediamine and adipic acid); this polyamide is easily convertible by the melt route, but, because of a low Tg of about 50.degree. C., it finds fields of application which are restricted to those involving use temperatures which remain below 100.degree. C. Other semi-crystalline polyamides have been disclosed which have a higher Tg and, consequently, a better retention of the mechanical property values as a function of temperature. A polyamide of this type which is of particular value is that obtained from terephthalic acid and 2-methylpentamethylene-1,5-diamine (cf. JP-A-69/019.551) because of the possibility of obtaining a Tg of the order of 142.degree. C.; the stability to heat is clearly noted with a polyamide of this type, but it has been found that:
if this polymer is filled with a padding or reinforcing filler of fibrous type and then converted by injection moulding under industrially economic conditions using a cold mould, that is to say a mould kept at a temperature of between 100.degree. and 150.degree. C., with short cooling times (the time concerned is the minimum time for which the injected material must be kept in the mould to enable the part to be ejected without deformation or to enable the moulded product to fall from the mould without difficulty), that is to say cooling times of between 20 and 40 seconds,
it is not possible to obtain a high BTUL under 1.8 MPa able to reach and exceed 240.degree. C. It has been found that this BTUL is, for example, 145.degree.-150.degree. C. for moulded articles filled with 10 to 60% by weight of glass fibres (relative to the weight of the total polyamide+filler) and obtained by the cold mould technique. The production, under these moulding conditions, of a low value for the BTUL is to be related to a low capacity for crystallisation of the polyamide under consideration obtained from terephthalic acid and alkylpentamethylenediamine, which has the result that when cooled rapidly, in particular when it is injected into a cold mould, the said polyamide does not crystallise or does so only partially. The articles obtained may then be amorphous; moreover, they are liable to change as a result of a crystallisation during reheating. It is understood that this type of semi-aromatic polyamide is useable only when using a hot mould, that is to say a mould kept at a temperature of between 170.degree. and 200.degree. C., with long cooling times, that is to say cooling times of between 2 and 4 minutes, and consequently their development remains very limited.
European Patent No. 0,347,848 also discloses semi-crystalline polyamides obtained from terephthalic acid, 2-methylpentamethylenediamine and an aromatic emine.
The use of a semi-crystalline, semi-aromatic polyamide based on recurring units derived from terephthalic acid and alkylpentamethylenediamine, for moulding under industrially economic
REFERENCES:
patent: 4111921 (1978-09-01), Bier et al.
patent: 4163101 (1979-07-01), Schade et al.
patent: 5109106 (1992-04-01), Lahary et al.
Coquard Jean
Lahary Pierre-Yves
Foelak Morton
Rhone-Poulenc Chimie
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