Compositions – Liquid crystal compositions
Reexamination Certificate
2002-12-12
2004-04-06
Huff, Mark F. (Department: 1756)
Compositions
Liquid crystal compositions
C528S181000, C528S176000, C528S190000, C524S777000, C524S785000
Reexamination Certificate
active
06716367
ABSTRACT:
This application claims priority under 35 U.S.C. §§ 119 and/or 365 to Application No. 2001-384459 filed in Japan on Dec. 18, 2001; the entire content of which is hereby incorporated by reference.
TECHNICAL FIELD OF THE INVENTION
The present invention concerns a process for producing a liquid crystalline polymer. More specifically, it relates to a process for producing a liquid crystalline polymer with increased polymerization rate and reduced deposition of monomer-derived substances to a reaction vessel during production by the use of specified metal compound catalysts in combination.
PRIOR ART
As the liquid crystalline polymer, wholly aromatic liquid crystalline polyesters and wholly aromatic liquid crystalline polyester amides are generally known. They are produced, for example, by polycondensation of monomers selected from aromatic hydroxy dicarboxylic acids, aromatic diols, aromatic dicarboxylic acids, aromatic hydroxy amines, aromatic amino carboxylic acids or aromatic diamines.
Bonds of aromatic moiety in the polymer are mainly ester bonds between aromatic carboxyl groups and phenolic hydroxy groups but it is usually difficult to form the ester bonds by direct dehydrating condensation between the carboxylic group and the phenolic hydroxyl group. In view of the above, a method of using an aromatic compound prepared by previously acylating a phenolic hydroxyl group with an acylating agent such as an aliphatic carboxylic acid anhydride like acetic anhydride, for example, 4-acetoxy benzoic acid as a starting material and conducting ester exchange between the obtained compound and the aromatic carboxylic acid thereby producing a polyester while distillating to remove by-produced aliphatic carboxylic acid has been adopted (JP-A 64-33123 and JP-A 63-284221). However, in view of economy, it is desirable to produce by acylation-deacylation in one pot (one step method of starting reaction by charging into an identical reaction vessel).
While the acylation by the aliphatic acid anhydride and the ester exchange reaction between the acylating agent and the carboxylic acid proceeds even under the absence of a catalyst, the reaction can be promoted by use of a catalyst, for which alkali metal carboxylate are generally used. Needless to say, carboxylates of alkali metals are excellent as the acylation catalyst, it is necessary to use the aliphatic acid anhydride in excess for 100% acylation of hydroxyl groups in which discoloration of the polymer or remarkable viscosity increase due to side reaction occurs. Accordingly, when the polymer quality or the productivity is taken into consideration, it is inevitable to transfer to a polycondensation reaction in a state where the acylating reaction rate is somewhat lower than 100%.
The main component of the liquid crystalline polymer often used so far for highly heat resistant and high strength materials is 4-hydroxy benzoic acid. Since this monomer is modified into phenol by decarbonation reaction under the presence of an alkali metal salt and also functions as a splitting group during polymerization, it has a merit capable of compensating the insufficiency of the acylating reaction rate even when it does not reach 100%.
On the other hand, since a homopolymer of 4-hydroxy benzoic acid has a melting point higher than the decomposition point, it is necessary to lower the melting point by copolymerizing various component. Those copolymers with various kinds of comonomers have been proposed but they include a problem such as lowering of heat resistance along with lowering of the melting point. That is, the relation between heat resistance and moldability such as injection or extrusion is antinomy. Accordingly, a polymer of higher heat resistance requires higher temperature for molding fabrication, and there are problems such as violent degradation by decomposition of polymer during molding, swelling of molding articles by polymer decomposition gas (blister deformation), worsening of hue in the molding products (formation of stripe pattern) and easy corrosion of a molding machine due to generated gaseous ingredients. It is shown in JP-A 2002-179776 that a liquid crystalline polyester comprising a 2-hydroxy-6-naphthoic acid unit (8.5 to 30 mol %) and a 4-hydroxy benzoic acid unit (0.1 to 8 mol %) in combination which solved the problems.
By the way, as a result of a further study, it has been found that the function and effect by 4-hydroxy benzoic acid as described above can not be obtained in a case of a polymer at a lower ratio of (or not containing) 4-hydroxy benzoic acid unit and, accordingly, the rate of progress of the acylating reaction gives a significant effect particularly on the subsequent polymerization rate. Namely, in a case of a polymer at a lower ratio of (or not containing) the 4-hydroxy benzoic acid unit, progress of the polycondensation reaction is extremely slow compared with the existent polymer comprising 4-hydroxy benzoic acid as the main component even when an alkali metal catalyst is used and, when it reaches a stage where deacylation proceeds no more, the reaction by monomer elimination proceeds inevitably, to cause remarkable sublimation and deposition of eliminated monomers to the reaction vessel. Because the reaction proceeds with removal of monomers.
DISCLOSURE OF THE INVENTION
The present invention intends to solve the problem upon producing a liquid crystalline polymer at a lower ratio of (or not containing) the 4-hydroxy benzoic acid unit. As a result of the earnest study by the present inventors, it has been found that the use of a specified catalyst is effective for attaining the foregoing object, to accomplish the present invention.
The invention provides a process for producing a liquid crystalline polymer including a constituent unit derived from 4-hydroxy-benzoic acid in an amount of 8 mol % or less, comprising polymerizing monomers in the presence of a catalytic amount of a catalyst comprising a potassium compound and a trivalent cobalt compound in combination.
That is, the invention provides a process for producing a liquid crystalline polymer having a ratio of a constituent unit derived from 4-hydroxy-benzoic acid of 8 mol % or less, in which reaction is conducted in the presence of a catalytic amount of a catalyst system comprising a potassium compound catalyst and a trivalent cobalt compound catalyst in combination.
The obtained liquid crystalline polymer preferably contains constituent units represented by the following formulae (I), (II), (III) and (IV), in which the amount of the constituent unit (I) is 40 to 75 mol %; that of (II), 8.5 to 30 mol %; that of (III), 8.5 to 30 mol %; and that of (IV), 0.1 to 8 mol % based on the entire constituent units:
(where Ar
1
represents 2,6-naphthalene, Ar
2
represents at least one selected from the group consisting of 1,2-phenylene, 1,3-phenylene and 1,4-phenylene, Ar
3
represents at least residue selected from the group consisting of 1,3-phenylene, 1,4-phenylene or a residue of compounds including two or more phenylene groups connected with each other at para-positions and Ar
4
represents 1,4-phenylene).
The process of the invention may further comprising a solid phase polymerization step to increase a polymerization degree of a prepolymer obtained by the melt polycondensation.
DETAILED DESCRIPTION OF THE INVENTION
This invention is to be described specifically. The liquid crystalline polymer as an object for production in this invention has a ratio of the constituent unit derived from 4-hydroxy benzoic acid of 8 mol % or less. There is no particular restriction on other constituent units so long as the liquid crystallinity is exhibited and the polymer is produced, for example, by polycondensation of monomers selected from known aromatic hydroxy dicarboxylic acids, aromatic diols, aromatic dicarboxylic acids, aromatic hydroxy amines, aromatic amino carboxylic acids and aromatic diamines. Particularly preferred is a liquid crystalline polymer containing constituent units represented by the following general formulae (I), (II), (III), and (IV) as an essential
Kanaka Keiichi
Sakamoto Katsutoshi
Burns Doane Swecker & Mathis L.L.P.
Huff Mark F.
Polyplastics Co. Ltd.
Sadula Jennifer R.
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