Abstract: A block copolymer composed of polyphenylene sulfide segments and aromatic sulfide sulfone polymer segments and having a logarithmic viscosity [.eta.], determined at 206.degree. C. for its solution in alpha-chloronaphthalene in a polymer concentration of 0.4 g/100 ml of solution and calculated in accordance with the equation [.eta.]=ln (relative viscosity)/polymer concentration, of 0.03 to 1.0. A resin composition comprising the block copolymer and polyphenylene sulfide and/or an aromatic sulfide sulfone polymer and optionally a filler. The block copolymer and the resin composition have improved mechanical strength and are suitable, for example, for encapsulation of electronic component parts.

Abstract: A process for producing a block copolymer composed of polyphenylene sulfide segments and polyphenylene sulfide sulfone segments comprises reacting a polyphenylene sulfide prepolymer with a mixture of a dihalodiphenyl sulfone and a sulfidization agent, or a polyphenylene sulfide sulfone prepolymer with a mixture of a polyhalogenated aromatic compound and a sulfidization agent.

Abstract: A process for producing a polyarylene sulfide polymer, which comprises reacting a polyhaloaromatic compound and a sulfidizing agent in a polar amide solvent in the presence of at least one polymerization additive to form a resinuous liquid consisting of a layer (I) containing a major amount of a polymer having a relatively high molecular weight and a minor amount of a polymer having a relatively low molecular weight and a layer (II) containing a major amount of a polymer having a relatively low molecular weight and a minor amount of a polymer having a relatively high molecular weight, and thereafter fractionating the layer (I) or layer (II) from the resinous liquid.

Abstract: A block copolymer composed of polyphenylene sulfide segments and aromatic sulfide sulfone polymer segments and having a logarithmic viscosity [.xi.], determined at 206.degree. C. for its solution in alpha-chloronaphthalene in a polymer concentration of 0.4 g/100 ml of solution and calculated in accordance with the equation [.xi.]=ln (relative viscosity)/polymer concentration, of 0.03 to 1.0. A resin composition comprising the block copolymer and polyphenylene sulfide and/or an aromatic sulfide sulfone polymer and optionally a filler. The block copolymer and the resin composition have improved mechanical strength and are suitable, for example, for encapsulation of electronic component parts.

Abstract: A resin composition comprising (a) 100 parts by weight of a block copolymer composed of polyphenylene sulfide segments and polyphenylene sulfide sulfone segments and (b) 0.01 to 20 parts by weight of at least one compound selected from the group consisting of epoxy resins, maleimide compounds, N,N'-diarylcarbodiimide compounds and organosilane compounds and as required, (c) an organic filler.

Abstract: A block copolymer composed of polyphenylene sulfide segments and aromatic sulfide sulfone polymer segments and having a logarithmic viscosity [.eta.], determined at 206.degree. C. for its solution in alpha-chloronaphthalene in a polymer concentration of 0.4 g/100 ml of solution and calculated in accordance with the equation [.eta.]=ln (relative viscosity)/polymer concentration, of 0.03 to 1.0. A resin composition comprising the block copolymer and polyphenylene sulfide and/or an aromatic sulfide sulfone polymer and optionally a filler. The block copolymer and the resin composition have improved mechanical strength and are suitable, for example, for encapsulation of electronic component parts.

Abstract: A block copolymer comprising a polyphenylenesulfide portion and a polysulfone portion, and having a logarithmic viscosity [.eta.] in the range of 0.03 to 1.0, said logarithmic viscosity [.eta.] being a value calculated by the following equation from a relative viscosity measured at 206.degree. C. for a solution of a polymer in .alpha.-chloronaphthalene in a polymer concentration of 0.4 g/100 ml.[.eta.]=ln (relative viscosity)/polymer concentration;and a resin composition comprising a block copolymer composed of a polyphenylenesulfide portion and a polysulfone portion, polyphenylenesulfide and/or polysulfone, and if required, a filler.

Abstract: A biaxially oriented crystalline poly(p-phenylene sulfide) film wherein said polymer contains at least 90 mole % of recurring units of the formula ##STR1## and has a melt viscosity of at least 0.12 dl/g and when said film is heat-treated at 270.degree. C. for 10 minutes under relaxation and then stretched at 23.degree. C. at a rate of 200%/min., its tensile strength, stress at 5% stretch and elongation show a percent retention of at least 60%, at least 80%, and 80 to 120%, respectively, based on these properties of the same film which has been stretched under said conditions without the heat-treatment; and a process for producing a crystalline poly(p-phenylene sulfide) film, which comprises heat-treating a biaxially oriented amorphous poly(p-phenylene sulfide) film at a temperature in the range of from 3.degree. C. above its melting point measured by a differential scanning calorimeter to 350.degree. C. at a constant length or under tension or in a moderate relaxed condition.

Abstract: A resin composition comprising (A) a polyphenylene sulfide, (B) an epoxy compound, and as an optional component, a reinforcing material, a filler and/or a fire retardant.

Abstract: A method for purifying polyphenylene sulfide containing impurities mainly comprising an electrolytic component, which comprises heat-treating said polyphenylene sulfide in an organic solvent in the presence of an oxyalkylene compound thereby to reduce the amount of said impurities.

Abstract: A process for production of polyphenylene sulfide which comprises reacting an alkali metal sulfide compound with a polyhalogenated aromatic compound in an organic polar solvent in the presence of an oxyalkylene compound.