Liquid crystal polyester resin mixture

Details Liquid crystal polyester resin mixture Liquid crystal polyester resin mixture

2002-06-25

2004-03-09

Wu, Shean C. (Department: 1756)

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

C252S299010, C252S299500, C525S132000, C525S397000, C524S539000

Reexamination Certificate

active

06702956

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a liquid crystal polyester resin mixture, a liquid crystal polyester resin molded artyicles of the liquid crystal polyester resin mixture, and a method for producing of the molded articles.
BACKGROUND OF THE INVENTION
The liquid crystal polyester resin, generally called as a thermotropic crystal liquid polymer, is remarkably excellent in melt fluidity and heat resistant at 300° C. or higher, so that a molded article of the resin is employed for electronic parts as well as OA (office automation equipment) parts, AV parts, heat resistant containers and the like.
Such molded article is generally produced by injection molding method. It is required for the injection molding method that the time for steps of plasticizing resin and metering plasticized resin (plastication time) in an injection unit is kept constant and stable. If the plastication time is shortened, the time taken for a cooling molten resin (cooling time) in mold unit could be shortened. However, in the case of the liquid crystal polyester resin, the plastication time is hardly kept constant and stable and therefore, plasticizing resin is not sometimes completed within the cooling time to result in problems that it is difficult to finish molding in constant cycles. And consequently, the productivity is decreased and the quality of the obtained molded article is deteriorated.
As a means for solving such problems, a composition comprising a thermotropic liquid crystal polymer, a higher fatty acid metal salt, and a higher fatty acid is disclosed in Japanese Unexamined Patent Publication No. 5-125259.
Also, Japanese Unexamined Patent Publication No. 5-125258 discloses a particle mixture comprising a thermotropic liquid crystal polymer particle, a higher fatty acid metal salt and a fatty acid. Further, Japanese Unexamined Patent Publication No. 9-143347 discloses that a fatty acid ester is added to a liquid crystal polyester resin composition comprising a liquid crystal polyester resin and a filler and Japanese Unexamined Patent Publication No. 8-12863 discloses that a fluoro resin is added to a liquid crystal polyester resin composition comprising a liquid crystal polyester resin and a filler.
However, in above cases, since compounds having a low melting point and being easy to be decomposed at a high temperature is used with heat resistant liquid crystal polymers, there are problems that the gas evolved by the decomposition deteriorates the surface appearance.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a liquid crystal polyester resin mixture having a stabilized plasticization time, possible to be molded in constant cycles, and making it possible to produce a molded article excellent in mechanical properties and heat stability.
Inventors of the present invention have made enthusiastic investigations to achieve the above-described object and consequently found out that a liquid crystal polyester resin mixture obtained by adding specified amount of a specified fatty acid amide or a specified polyethylene to a liquid crystal polyester resin composition has a stable plastication time and is possible to be molded in constant cycles. Moreover, inventors have found out that an obtained molded article is excellent in mechanical properties and heat stability and accordingly have completed the present invention. That is, the invention is to provide a liquid crystal polyester resin mixture comprising 100 parts by weight of a liquid crystal polyester resin composition which comprises 100 parts by weight of a liquid crystal polyester and from 0 to 150 parts by weight of a filler, and either from 0.001 to 5 parts by weight of a fatty acid amide having a formula; R
1
—CO—NH
2
(wherein R
1
denotes a saturated or unsaturated hydrocarbon of 10 to 30 carbons) or from 0.001 to 2 parts by weight of a high molecular weight polyethylene with a molecular weight of 10,000 or higher.
DETAILED DESCRIPTION OF THE INVENTION
The liquid crystal polyester to be used for the invention is a polyester called as a thermotropic liquid crystal polymer and includes, for example, the following;
(1) a polymer comprises one or more kinds of aromatic hydroxycarboxylic acids;
(2) a polymer comprises aromatic dicarboxylic acid(s) and aromatic diol(s);
(3) a polymer comprises aromatic hydroxycarboxylic acid(s), aromatic dicarboxylic acid(s) and aromatic diol(s); and
(4) a polymer prepared by reacting aromatic hydroxycarboxylic acid(s) with polyesters such as polyethylene terephthalate.
Such polymers form anisotropic melt at a temperature of 400° C. or lower. Additionally, in place of aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids and aromatic diols, their ester-formable derivatives may be included. The ester-formable derivatives of the carboxylic acids include, for example, derivatives which are produced by converting carboxyl groups into highly reactive acid chlorides, acid anhydrides and the like and capable of promoting the reaction of polyester production and derivatives which are produced by esterificating carboxyl groups with alcohols and ethylene glycol and capable of forming polyesters by ester interchange reaction.
The ester-formable derivatives of phenolic hydroxyl groups include, for example, derivatives of compounds having the phenolic hydroxyl groups esterified with carboxylic acids and capable of forming polyesters by ester interchange reaction.
Further, the aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids, and aromatic diols may be substituted with an alkyl such as methyl and ethyl; a halogen atom, and an aryl to the extent that these substituent groups do not interfere with the ester formability.
The repeating monomer unit of the liquid crystal polyester can be exemplified as follows, however it is not limited to the following examples.
The repeating monomer units derived from aromatic hydroxycarboxylic acids:
The above exemplified repeating monomer units may be substituted with a halogen atom or an alkyl group.
The repeating monomer units derived from aromatic dicarboxylic acids:
The above exemplified repeating monomer units may be substituted with a halogen atom, an alkyl group, or an aryl group.
The repeating monomer units derived from aromatic diols:
The above exemplified repeating monomer units may be substituted with a halogen atom, an alkyl group, or an aryl group.
In the above exemplified repeating monomer units derived from the aromatic hydroxycarboxylic acids, aromatic dicarboxylic acids, and aromatic diols, the alkyl is preferably an alkyl of 1 to 6 carbons, the aryl is preferably an aryl of 6 to 20 carbons.
From a viewpoint of the balance of heat resistance, mechanical properties, and processibility, the liquid crystal polyester containing 30% by mole of the foregoing repeating monomer unit defined as (A
1
) is preferable.
Preferable combinations of the repeating monomer units are the following examples (a) to (f).
(a): a combination of (A
1
), (B
1
) and (C
1
), or a combination of (A
1
), a mixture of (B
1
) and (B
2
), and (C
1
),
(b): a combination of (A
1
) and (A
2
),
(c): the same combination as (a) expect partly replacing (A
1
) with (A
2
),
(d): the same combination as (a) expect partly replacing (B
1
) with (B
3
),
(e): the same combination as (a) expect partly replacing (C
1
) with (C
3
), and
(f): the combination of (A
1
), (A
2
), (B
1
) and (C
2
).
The liquid crystal polyester to be employed for the invention can be produced by a well-known method. For example, the liquid crystal polyesters defined as the (a) and (b) can be produced by methods described in Japanese Patent Publication No. 47-47870, Japanese Patent Publication No. 63-3888 and the like.
In the present invention, a filler may be added to the liquid crystal polyester. In the case of adding a filler, the filler is added in not more than 150 parts by weight, preferably 10 to 100 parts by weight, to 100 parts by weight of the liquid crystal polyester. If the addition ratio of the filler exceeds 150 parts by weight, the melt viscosity of the resu

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