Polyarylene sulfide resin

Details Polyarylene sulfide resin Polyarylene sulfide resin

2003-04-22

2004-09-07

Truong, Duc (Department: 1711)

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

Synthetic resins

From carboxylic acid or derivative thereof

C528S321000, C528S322000, C528S373000, C528S374000, C528S397000, C528S488000

Reexamination Certificate

active

06787631

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
This invention relates to novel polyarylene sulfide resins and, more particularly, to polyarylene sulfide resins which are moldable with reduced generation of flash.
BACKGROUND TECHNOLOGY
Polyphenylene sulfide resins (hereinafter referred to as PPS resins) are high-melting heat-resistant crystalline resins with excellent properties in respect to flow, resistance to organic solvents, electrical properties and flame retardance. On account of these features, PPS resins are widely used in recent years as materials in the manufacture of parts of electrical and electronic instruments, automobiles and chemical instruments. However, the problem facing PPS resins is their tendency to generate flash in injection molding of articles, for example, connectors and the like. The following methods are disclosed to solve this problem; to blend linear PPS resins with crosslinked PPS resins which melt turning gel-like, to blend PPS resins with polyphenylene ether resins (JP 1997-157525 A), to blend low-viscosity PPS resins with high-viscosity PPS resins (JP 1995-278432 A) and to blend PPS resins with polybutylene naphthalate resins (JP 1998-292099 A). However, any of these methods partly damages the excellent characteristics of PPS resins as the result of blending. Improvement of moldability by copolymerization of PPS resins with polymers containing specified epoxy radicals is disclosed in JP 1990-182726 A, but partial damage of PPS resins also occurred here.
An object of this invention is to provide novel polyarylene sulfide resins moldable with reduced generation of flash when molded by themselves or as part of resin compositions.
DISCLOSURE OF THE INVENTION
This invention relates to a polyarylene sulfide resin comprising 0.5-10% by weight of the constituent unit represented by the following general formula (1) and 80-99.5% by weight of the constituent unit represented by the following general formula (2):
—(Ar
1
—S—)
n
  (1)
—(Ar
2
—S—)
m
  (2)
wherein Ar
1
is the radical represented by general formula (3), Ar
2
is phenylene or alkyl-substituted phenylene radical, R
1
-R
7
are independently hydrogen atoms or lower alkyl groups containing 1-3 carbon atoms and n and m are integers of 1 or more.
Further, this invention relates to a polyarylene sulfide resin composition comprising the aforementioned polyarylene sulfide resin.
Still further, this invention relates to a process for preparing a polyarylene sulfide resin by polymerizing polychloro aromatic compounds comprising 0.5-10% by weight of a dichloroarylene represented by the following general formula (4)
(wherein R
1
-R
7
are as defined earlier) and 80-99.5% by weight of a dichlorobenzene represented by the following general formula (5) (wherein Ar2 is phenylene or alkyl-substituted phenylene radical) in the presence of an alkali metal sulfide.
Cl—Ar
2
—Cl  (5)
This invention will be described in detail below. The polyarylene sulfide resin of this invention comprises 0.5-10% by weight, preferably 1-8% by weight, of the constituent unit represented by the aforementioned general formula (1) and 80-99.5% by weight, preferably 92-99% by weight, of the constituent unit represented by the aforementioned general formula (2).
In the first place, a process and raw materials generally used for the preparation of the resin of this invention will be explained. Since the following account is an example, it is needless to say that any resin comprising the aforementioned constituent units at the specified ratio is satisfactory as the resin of this invention.
A compound which generates the radical represented by general formula (3) as the constituent unit of the resin of this invention is at least one of the compounds represented by the aforementioned general formula (4). A compound of this kind can be obtained from phthalic anhydride or its derivative and 2,5-dichloroaniline or its derivative. Here, the radicals R
1
-R
7
are independently hydrogen atoms or lower alkyl groups containing 1-3 carbon atoms and preferably they are all hydrogen atoms.
A compound which generates the radical represented by the aforementioned general formula (2) is represented by the aforementioned general formula (5). Here, Ar
2
is phenylene or alkyl-substituted phenylene radical, preferably phenylene radical. Concretely, it is one kind or more of dichlorobenzenes selected from dichlorobenzene and alkyl-substituted dichlorobenzenes, and it is generally dichlorobenzene. There are ortho-, meta- and para-isomers for dichlorobenzenes and para-isomers are preferable. More preferable is p-dichlorobenzene. In the case of alkyl-substituted dichlorobenzenes, the alkyl radical preferably contains 3 or less carbon atoms.
To be precise, a compound represented by general formula (4) and a dichlorobenzene are so used that the proportions of the radical represented by general formula (1) and the radical represented by general formula (2) remain in the aforementioned range. However, since the proportions in the raw material roughly coincide with those in the resin, the raw materials are taken so that the compound represented by general formula (4) accounts for 0.5-10% by weight, preferably 1-8% by weight, and the dichlorobenzene accounts for 80-99.5% by weight, preferably 92-99% by weight. If the proportion of the compound represented by general formula (4) becomes less than 0.5% by weight, there would substantially be produced no effect for reducing generation of flash. On the other hand, if the proportion exceeds 10% by weight, the melt viscosity would become excessively high during molding thereby deteriorating moldability.
The polychloro aromatic compounds to be used as raw materials may be the compounds represented by the aforementioned general formulas (4) and (5) alone or may additionally contain a small amount of other polychloro aromatic compounds. In the latter case, the amount of other polychloro compounds is kept preferably at or below 10% by weight of the total polychloro aromatic compounds. The use of other polychloro aromatic compounds introduces constituent units other than those represented by general formulas (1) and (2) in proportion to the amounts of other polychloro aromatic compounds used.
The aforementioned other polychloro aromatic compounds include dichlorobiphenyl, dichlorodiphenyl ether, dichlorodiphenyl ketone and dichloronaphthalene. The compounds cited have isomers and preferable are those compounds which have chlorine atoms in a symmetrical position, for example, para isomers and 2,6- or 2,7-dichloronaphthalene. If necessary, trichlorobenzene and the like may be used.
The resin of this invention can be prepared according to a process publicly known for the preparation of PPS resins. For example, a process for preparing polymers of relatively low molecular weight disclosed in JP 70-3368 B and a process for preparing linear polymers of relatively high molecular weight disclosed in JP 1977-12240 B are available.
In addition, a process for polymerization in the presence of sulfur, a process for polymerization in the presence of an alkali metal sulfide and a process for self-polymerization of a raw material such as p-chlorothiophenol are available. A variety of additives, catalysts and solvents may be used in the aforementioned reactions.
A preferred process is the one which effects polymerization in the presence of sulfur or an alkali metal sulfide. The amount of sulfur source, that is, sulfur or an alkali metal sulfide is 0.9-1.1 mole per 1 mole of polychloro aromatic compound.
The process for polymerization in the presence of an alkali metal sulfide is based on the reaction to be effected in a polar solvent in the presence of an alkali metal sulfide. A typical alkali metal sulfide is sodium sulfide, but a combination of hydrated sodium sulfide, sodium sulfide or sodium hydrosulfide and sodium hydroxide or a combination of hydrogen sulfide and sodium hydroxide may be used. Polar solvents useful for the reaction include aprotic organic polar solvents such as amides, lactams and urea compounds, N-met

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