To provide a cation exchange membrane which is less susceptible to swelling or elongation during electrolysis of a potassium chloride aqueous solution even without permitting water absorption or swelling immediately prior to mounting it in an electrolyzer, and a method whereby it possible to stably produce a potassium hydroxide aqueous solution without necessity to conduct an operation for water absorption or swelling immediately prior to mounting the membrane in the electrolyzer. A cation exchange membrane comprising a polymer having cation exchange groups, wherein in cations (100 mol %) contained in the cation exchange membrane, the total of potassium ions and sodium ions is at least 99 mol %, and in the total (100 mol %) of potassium ions and sodium ions contained in the cation exchange membrane, the potassium ions are 80-98 mol % and the sodium ions are 20-2 mol %,

A process for the preparation of a semifinished product including a PAEK-based resin and reinforcing fibers, including the stages of: a. preparation of a dispersion including a PAEK-based resin in the pulverulent form dispersed in an aqueous phase including a surfactant; b. bringing the reinforcing fibers into contact with said aqueous dispersion; c. drying the fibers impregnated with dispersion; and d. heating the impregnated fibers to a temperature sufficient for the melting of the resin, so as to form a semifinished product, wherein the surfactant is a thermally stable surfactant. Also, semifinished products capable of being obtained from the process and their use in the manufacture of composite materials.

A flame-retardant composition is provided. The flame-retardant composition comprises: (A) a compound having the structure of formula (I), ##STR00001## (B) a maleimide compound; and (C) an allyl-containing compound, having a structure different from formula (I), wherein the flame-retardant composition has a phosphorus content ranging from 0.5 wt % to 1.4 wt % based on the total weight of the flame-retardant composition excluding solvent.

An encapsulant includes a cross-linked polymer, an acrylate component, and a photoinitiator. The cross-linked polymer is formed by subjecting a vinyl fluoride-vinyl ether copolymer to a cross-linking reaction with a tetracarboxylic dianhydride. The vinyl fluoride-vinyl ether copolymer has a weight-average molecular weight ranging from 10000 to 50000, and a hydroxyl value ranging from 40 mg KOH/g to 170 mg KOH/g. The tetracarboxylic dianhydride is represented by formula (I)

##STR00001## (I). R represents a tetravalent organic group containing fluorine and an aromatic group. The acrylate component includes an acrylate monomer selected from a monoacrylate monomer, a monomethacrylate monomer, a diacrylate monomer, a dimethacrylate monomer, a triacrylate monomer, a trimethacrylate monomer, and combinations thereof.

A production method capable of producing a hollow fine particulate containing a perfluororesin, having a large average particle size, and having a monoporous structure. A method for producing a hollow fine particulate including: a step A of dispersing a solution containing a perfluoromonomer and a non-polymerizable solvent capable of dissolving the perfluoromonomer and having an SP value of 9.00 to 9.80 (cal/cm.sup.3).sup.1/2 into water to provide a dispersion; a step B of polymerizing the perfluoromonomer to provide a phase-separated fine particulate containing a perfluororesin and having a monoporous structure; and a step C of removing the non-polymerizable solvent in the phase-separated fine particulate to provide a hollow fine particulate having a monoporous structure.