Abstract: In a process for producing an aromatic polyester fiber by heat-treating a fiber obtained by melt-spinning an aromatic polyester exhibiting anisotropy in its molten state, an aromatic polyester fiber having high strength and high modulus of elasticity can be produced with suppressed fusion between single filaments during the heat treatment by (a) subjecting the fiber obtained by melt spinning to heat treatment in an organic liquid heating medium or (b) adhering to the fiber obtained by melt spinning at least one member selected from the group consisting of suspensions having a concentration of 0.05 to 20% by weight of organic polymer powders having a melting point or a softening temperature higher than the heat treatment temperature, and suspensions having a concentration of 0.1 to 20% by weight of barium sulfate powder or barium titanate powder, and then subjecting the resulting fiber to heat treatment.

Abstract: An optical communication cable with less breakage or damage during the preparation and handling which comprises an optical fiber strand, a tension-resistant material, and a synthetic resin coating layer, the tension-resistant material being provided between the optical fiber strand and the synthetic resin coating layer and being fibers obtained by melt spinning an aromatic polyester showing an anisotropy in the molten state.

Abstract: A polyester fiber suitable for reinforcing resin can be obtained by subjecting a fiber obtained by melt-spinning a polyester which exhibits anisotropy in its molten state to(a) a treatment comprising adhering to the fiber a solution of an epoxy group-containing compound dissolved in an organic solvent which is inert to the said compound, and then drying the resulting fiber; or(b) a treatment comprising making the fiber contact with at least one member selected from the group consisting of sulfur trioxide, chlorosulfonic acid, fluorosulfonic acid, and an aqueous sulfuric acid solution having a concentration of 30 to 95% by weight.

Abstract: A method for treating fibers to obtain treated fibers suitable as a reinforcing material which comprises treating a fiber obtained from a polyester which shows anisotropy in the molten state in an aqueous solution of at least one compound selected from the group consisting of hydroxides, carbonates, bicarbonates, and organic carboxylic acid salts of lithium, sodium, potassium, magnesium and calcium at 20.degree. to 120.degree. C. for at least one minute.The above-mentioned treatment provides treated fibers suitable as a reinforcing material which exhibit an excellent adhesion to matrices to be reinforced and can give a satisfactory strength to the resulting composite material.

Abstract: An aromatic polyester showing anisotropy in the molten state is melt spun stably for a long period of time by controlling an extrusion pressure at a nozzle portion to 3 kg/cm.sup.2 G or higher and an atmospheric temperature T.sub.N at a nozzle outlet to a degree satisfying the following formula: (T.sub.F -100).ltoreq.T.sub.N .ltoreq.T.sub.F, wherein T.sub.F is a flowing temperature of the aromatic polyester, and preferably controlling the pressure of a polymer melt at a tip outlet of an extruder to 15 kg/cm.sup.2 G or higher, whereby a highly orientated fiber of fine denier is obtained.

Abstract: A process for producing an aromatic polyester by polycondensation of either(1)(a) aromatic hydroxycarboxylic acids containing at least 50 mole % of p-hydroxybenzoic acid, and/or ester-forming derivatives of these acids,(b) an aromatic dicarboxylic acid and/or an ester-forming derivative of aromatic dicarboxylic acid, and(c) an aromatic dihydroxy compound and/or an ester-forming derivative of aromatic dihydroxy compound,wherein the (a):(b) molar ratio and the (a):(c) molar ratio are each from 1:0 to 1:4, or(2)(d) aromatic dicarboxylic acids containing at least 50 mole % of terephthalic acid, and/or ester-forming derivatives of these acids and(e) aromatic dihydroxy compounds containing at least 50 mole % of at least one of hydroquinone, substituted hydroquinone, 4,4'-dihydroxydiphenyl, and substituted 4,4'-dihydroxydiphenyl, and/or ester-forming derivatives of these dihydroxy compounds,characterized in that the polycondensation is carried out by using a liquid compound which has a higher boiling point at normal

Abstract: A method for treating fibers which comprises modifying the surface of a fiber of a polyester which shows anisotrophy in the molten state by subjecting the fiber to a low-temperature plasma irradiation, said method enabling to obtain fibers which comprise highly oriented molecules, are highly crystalline and hence exhibit a high tenacity and a high modulus of elasticity.The fibers thus obtained are suitable as a reinforcing material, exhibit an excellent adhesion to matrices to be reinforced and can give a satisfactory strength to the resulting composite material.

Abstract: In the method for producing aromatic polyesters having excellent moldability, good thermal resistance and little dependence on molding temperature and providing molded products having little anisotropy, obtained from (A) one or more compounds selected from aromatic dicarboxylic acids and their derivatives and (B) one or more compounds selected from aromatic dihydroxy compounds and their derivatives, or (A), (B) and (C) one or more compounds selected from aromatic hydroxycarboxylic acids and their derivatives, a method characterized in that polymerization is carried out in a reaction system containing, together with (A), (B) and optionally (C), a quinone compound (D) and/or a complex obtained from (B) and (D) as well as an organic carboxylic acid anhydride, or a reaction product thereof.

Abstract: In a method for producing aromatic polyesters having improved moldability by the polycondensation ofA: one or more compounds selected from the group consisting of aromatic hydroxycarboxylic acids and their functional derivatives such as acylated or esterified compounds thereof,or A withB: one or more compounds selected from the group consisting of aromatic dicarboxylic acids and their functional derivatives such as esterified compounds or acid halides thereofandC: one or more compounds selected from the group consisting of aromatic diphenols and their functional derivatives such as acylated compounds thereof,the improvement comprising adding to the reaction system, either in bulk, or gradually during polycondensationD: one or more compounds selected from the group consisting of 1,3,5-trihydroxybenzene, 3,5-dihydroxybenzoic acid, 5-hydroxyisophthalic acid and their functional derivatives such as acylated or esterified compounds thereof,whereby D is included in the reaction.

Abstract: In a process for producing an aromatic polyester fiber of high strength and high modulus of elasticity represented by the prescribed general formula, a process comprising grinding a polymer of the prescribed general formula to form ground particles having diameters of less than 3 mm and an average particle diameter of 0.5 mm or smaller; heat-treating the particles for 0.5 to 30 hr at a temperature between 100.degree. and 350.degree. C., at which temperature the particles do not fuse; melt-spinning the heat-treated particles at a temperature of 250.degree. to 450.degree. C. if the particles have a melt property such that the temperature at which the particles possess a shear rate of 51/sec (48,000 poise as melt viscosity) under a shear stress of 2.45.times.10.sup.6 dynes/cm.sup.2 is in the range of 200.degree. to 350.degree. C.; and thereafter heat-treating the resulting fiber for 0.5 to 50 hr at a temperature between 250.degree. and 450.degree. C., at which temperature the fiber does not fuse.

Abstract: A process for producing an aromatic polyester composition, which is characterized in that in producing an aromatic polyester represented by the general formula A, ##STR1## (wherein X is an alkylene group having 1 to 4 carbon atoms, --O--, --SO.sub.2 --, --S--, or --CO--; m and n are each 0 or 1; the ratio of d to e is in the range of from 1:1 to 10:1; the ratio of e to f is in the range of from 9:10 to 10:9; and the substituents attached to the benzene ring are in para or meta position to one another), the polymerization is carried out by the method of bulk polymerization, using substantially no solvent, and in the presence of at least one polymer selected from the group consisting of polyalkylene terephthalates, polyphenylene sulfides, aromatic polysulfones, and aromatic polyesters represented by the general formula B, ##STR2## wherein (p+q) is in the range of from 10 to 100 and p/(p+q).gtoreq.0.8.

Abstract: In a process for producing an aromatic polyester by reacting under application of heat (A) an aromatic dicarboxylic acid and/or an ester-forming derivative thereof, (B) an aromatic hydroxycarboxylic acid and/or an ester-forming derivative thereof, and (C) a dihydroxy aromatic compound produced by the method of alkali fusion and containing 4,4'-dihydroxydiphenyl as major constituent and/or an ester-forming derivative of said dihydroxy aromatic compound, the improvement which comprises employing as said 4,4'-dihydroxydiphenyl, a 4,4'-dihydroxydiphenyl of such a quality that a solution of 1 part by weight of it dissolved in 100 parts by weight of a mixture comprising methanol and water in a weight ratio of 70:30 will show a pH of 6.6 to 7.4. The polyester produced by the improved process shows little discoloration and is excellent in thermal resistance and mechanical properties.

Abstract: A process for producing by bulk polycondensation an aromatic polyester of the formula, ##STR1## wherein X is a hydrocarbon radical having 1 to 20 carbon atoms, --O--, --SO.sub.2 --, --S--, or --CO--, m is 0 or 1 and n is 0 or 1; when p=0, q=r=an integer of 3 to 600; when q=r=0, p=an integer of 3 to 600; when p.noteq.0, q.noteq.0 and r.noteq.0, p+q+r=3 to 600; p, q, r are integers and q=r, which comprises using a horizontal jacketed reactor provided with one or two agitator shafts bearing impellers fixed thereto and carrying out the bulk polycondensation in said reactor while circulating a heat-transfer medium through the jacket, agitator shaft(s), and, if necessary, impellers to heat or cool the reaction system to obtain a particulate material having a weight-average particle size of 0.5 to 20 mm.

Abstract: A process for producing oxybenzoyl copolyesters comprising 3 to 300 of repeating unit of the formula, ##STR1## wherein m and n are each 0 or 1, and W is --O--, --SO.sub.2 --, --S-- or --CO--, which comprises reacting a compound of the formula, ##STR2## wherein R.sup.1 is a hydrogen atom, a benzyl, lower alkyl or phenyl group, and Y is a hydrogen atom or a lower alkanoyl group, with a compound of the formula, ##STR3## wherein X is a halogen atom, in the presence of an aliphatic, alicyclic or aromatic hydrocarbon solvent having a boiling point of 100.degree. to 260.degree. C. under atmospheric pressure to produce bis(carboxyphenyl)phthalate, adding a compound of the formula, ##STR4## wherein W is --O--, --SO.sub.2 --, --S-- or --CO--, Z is a hydrogen atom or an alkanoyl group, and m and n are each 0 or 1, and optionally a compound of the formula, ##STR5## wherein R.sup.2 and R.sup.