Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-12-14
2003-12-16
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S425000, C525S444000, C252S299010, C252S299620, C252S299660, C252S299670
Reexamination Certificate
active
06664341
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a liquid crystal polyester resin composition. More specifically, it relates to a liquid crystal polyester resin composition which comprises specific thermotropic liquid crystal polyester (to be referred to as “liquid crystal polyester” hereinafter) resins in a predetermined ratio, is excellent in metering stability and moldability such as flowability and suppresses the formation of a blister at the time of soldering.
DESCRIPTION OF THE PRIOR ART
Demand for higher performance plastics has been growing in recent years and a large number of polymers having new various properties have been developed. Out of these, an optically anisotropic liquid crystal resin (liquid crystal polyester) characterized by parallel arrangement of molecular chains is attracting much attention for its excellent flowability and mechanical properties and high temperature under load and continuous use temperature according to molecular structure.
A resin composition obtained by filling a liquid crystal polyester having the above properties with a fibrous reinforcement such as a glass fiber and an inorganic filler such as talc is suitable for use as a material for computer-related electric and electronic parts, machine-related parts and precision machine-related parts, and used to relay cases, switches, coil bobbins, capacitors, connectors, speakers, motor parts such as commitators and separator, and encapsulation for coils, quartz oscillators and elements such as IC chips.
In information and communication fields such as personal computers and portable telephones, parts have been becoming more highly integrated, smaller in size and thickness, and lower in height, there have been many cases where an extremely thin portion having a thickness of 0.5 mm or less is formed, and flowability high enough to fill a resin in such a thin portion completely has been desired. Generally speaking, a liquid crystal polyester is superior to other resins in flowability but further improvement of flowability is necessary when the thickness must be made small.
Although the liquid crystal polyester has low viscosity and excellent flowability, it has a problem with metering stability at the time of molding as its conflicting function. Particularly when its molded article is large in size or the amount of a resin to be molded (metering value) is increased to produce a large number of molded articles at one time, molding problems often occur that a short shot and overpacking are repeated alternately due to metering instability and that a mold is not filled with a resin completely due to a back flow (back flow of a resin). These molding problems must be solved to form a part having a thin portion as described above.
When a molded article is left in the high-temperature air or liquid for a long time, or soldered, a swelling called “blister” may be formed on the surface. The cause of this phenomenon is unknown but it is assumed that a decomposition gas generated when the liquid crystal polyester is in a molten state or air contained during molding is introduced into the inside of the molded article and expanded by the subsequent heat treatment at a high temperature, thereby forcing up the surface of the molded article softened by heating and forming a blister.
In order to prevent the formation of such a blister, it is conceivable that air should be removed completely from a vent hole during the melt extrusion of the material, the material should not be retained in a molding machine for a long time at the time of molding, or back pressure is applied. Operation condition ranges for these are narrow and not satisfactory to obtain a molded article free from a blister.
JP-A 11-246653 and JP-A 11-246654 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) disclose that the formation of a blister in a liquid crystal polyester is prevented by acylating an aromatic compound having a phenolic hydroxyl group with a specific amount of a fatty acid anhydride and carrying out an ester exchange reaction between the acylated aromatic compound and an aromatic carboxylic acid. However, as its prevention effect is not satisfactory and balance between flowability and metering stability at the time of molding is not improved, it is difficult to obtain both blister prevention effect and moldability at the same time.
It has been known that two different liquid crystal polyesters are blended together and JP-A 10-219085 discloses that a liquid crystal polyester resin comprising two different liquid crystal polyesters having specific flow temperatures is excellent in flowability in a thin portion and heat resistance. However, the resin is unsatisfactory in terms of metering stability and blister suppression effect at the time of soldering and it is therefore still difficult to obtain both blister prevention effect and moldability at the same time.
Thus, a liquid crystal polyester resin composition which has good balance among metering stability, moldability such as flowability and heat resistance is not found yet.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a liquid crystal polyester resin composition which suppresses the formation of a blister caused by a heat treatment at a high temperature and has excellent moldability.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, the above objects and advantages of the present invention are attained by a liquid crystal polyester resin composition which comprises (A) a liquid crystal polyester comprising at least two aromatic oxycarbonyl recurring units and (B) a liquid crystal polyester comprising at least two aromatic oxycarbonyl recurring units, at least one aromatic dioxy recurring unit and at least one aromatic dicarbonyl recurring unit in a (A)/(B) weight ratio of 90/10 to 30/70.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The liquid crystal polyesters (A) and (B) used in the present invention have aromatic oxycarbonyl recurring units as described above. The recurring units are preferably represented by the following formula (I):
wherein Ar
1
is a benzene ring or naphthalene ring which may be substituted by an alkyl group, alkoxy group, aryl group or halogen atom.
Monomers which can be used to introduce the above recurring units include 4-hydroxybenzoic acid, 3-hydroxybenzoic acid, 2-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-5-naphthoic acid, 3-hydroxy-2-naphthoic acid, 2-hydroxy-3-naphthoic acid, 4′-hydroxyphenyl-4-benzoic acid, 3′-hydroxyphenyl-4-benzoic acid, 4′-hydroxyphenyl-3-benzoic acid, alkyl, alkoxy, aryl and halogen substituted products thereof, and functional derivatives thereof. To produce the liquid crystal polyesters (A) and (B), at least two of the above monomers must be used. For example, three or more of the above monomers may be used.
The liquid crystal polyester (A) preferably consists of the following monomer structural units: 4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid, 4-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid/2-hydroxy-3-naphthoic acid, 4-hydroxybenzoic acid/3-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid, 4-hydroxybenzoic acid/4′-hydroxypheny-4-benzoic acid, and 2-hydroxy-6-naphthoic acid/4′-hydroxyphenyl-4-benzoic acid.
Particularly preferred monomers used in the liquid crystal polyester (A) are 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid. When these two monomers are used, recurring units introduced by these are represented by the following formulas (I)-1 and (I)-2.
The molar ratio of the recurring unit represented by the formula (I)-1 to the recurring unit represented by the formula (I)-2 is preferably in the range of 90/10 to 50/50, more preferably 85/15 to 60/40.
By causing a small amount of another component such as an aromatic aminocarboxylic acid, aromatic monoalcohol, aromatic monocarboxylic acid, aromatic dicarboxylic acid, aromatic amino-alcohol, aromatic monoamine, aromatic
Kitayama Masaya
Kometani Kiichi
Saito Naoshi
Kabushiki Kaisha Ueno Seiyaku Oyo Kenkyusho
Sherman & Shalloway
Short Patricia A.
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