Provided is a method for producing a rubber composition that includes a rubber component (A) including natural rubber, at least one filler (B) selected from an inorganic filler and carbon black, and a monohydrazide compound (C) supported on a solid. The monohydrazide compound (C) is represented by general formula (I): R—CONHNH.sub.2, where R represents an alkyl group having from 1 to 30 carbon atoms, a cycloalkyl group having from 3 to 30 carbon atoms, or an aryl group. The method comprises compounding in an optional preliminary compounding stage and a plurality of compounding stages, and adding the monohydrazide compound (C) supported on the solid and kneading in the preliminary compounding stage and/or a first compounding stage. Also provided is a rubber composition produced with this method.

The present invention relates to a thermally curable composition comprising: (a1) a solid rubber in an amount of 2.5% by mass or more, (a2) an olefinic double bond-containing polymer which is liquid or pasty at 22° C. in an amount of less than 5% by mass, (a3) a hydrocarbon resin in an amount of, in total with said component (a2), 5% by mass or more and 20% by mass or less, and (a4) a liquid polydiene in an amount of 15% by mass or more based on the total mass of the composition as a component (a); and at least one selected from the group consisting of the following (b1) to (b3): (b1) sulfur and one or more accelerator(s), (b2) peroxidic vulcanization system or disulfidic vulcanization system, and (b3) quinones, quinone dioximes or dinitrosobenzene, as a vulcanization system (b).

The present invention relates to a thermally curable composition comprising: (a1) a solid rubber in an amount of 2.5% by mass or more, (a2) an olefinic double bond-containing polymer which is liquid or pasty at 22° C. in an amount of less than 5% by mass, (a3) a hydrocarbon resin in an amount of, in total with said component (a2), 5% by mass or more and 20% by mass or less, and (a4) a liquid polydiene in an amount of 15% by mass or more based on the total mass of the composition as a component (a); and at least one selected from the group consisting of the following (b1) to (b3): (b1) sulfur and one or more accelerator(s), (b2) peroxidic vulcanization system or disulfidic vulcanization system, and (b3) quinones, quinone dioximes or dinitrosobenzene, as a vulcanization system (b).

An object of the invention is to provide a crosslinking agent with which a crosslinked polymer that suffers little coloring with the lapse of time and shows excellent viscosity stability is obtained. The crosslinking agent of the invention includes a compound which contains two or more alkylhydrazide groups represented by the following general formula (1). ##STR00001##
(In formula (1), R.sup.1 represents an alkyl group having 1-10 carbon atoms, and symbol * is a linking bond.)

An object of the invention is to provide a crosslinking agent with which a crosslinked polymer that suffers little coloring with the lapse of time and shows excellent viscosity stability is obtained. The crosslinking agent of the invention includes a compound which contains two or more alkylhydrazide groups represented by the following general formula (1). ##STR00001##
(In formula (1), R.sup.1 represents an alkyl group having 1-10 carbon atoms, and symbol * is a linking bond.)

An object of the invention is to provide a crosslinking agent with which a crosslinked polymer that suffers little coloring with the lapse of time and shows excellent viscosity stability is obtained. The crosslinking agent of the invention includes a compound which contains two or more alkylhydrazide groups represented by the following general formula (1). ##STR00001##
(In formula (1), R.sup.1 represents an alkyl group having 1-10 carbon atoms, and symbol * is a linking bond.)

Disclosed is a copolymer of polyglycolide and one or more additives. The copolymer may have a weight-average molecular weight (Mw) in the range of 10,000-1,000,000 and a ratio of a weight-average molecular weight to a number-average molecular weight (Mw/Mn) in the range of 1.0 to 10.0. The copolymer may have a melt index (MFR) in the range of 0.1 to 1000 g/10 min. The copolymer has good mechanical properties, thermal stability and hydrolytic stability. Also provided is a process for preparing the copolymer.

Disclosed is a copolymer of polyglycolide and one or more additives. The copolymer may have a weight-average molecular weight (Mw) in the range of 10,000-1,000,000 and a ratio of a weight-average molecular weight to a number-average molecular weight (Mw/Mn) in the range of 1.0 to 10.0. The copolymer may have a melt index (MFR) in the range of 0.1 to 1000 g/10 min. The copolymer has good mechanical properties, thermal stability and hydrolytic stability. Also provided is a process for preparing the copolymer.

Provided is a polycarbonate-based resin composition, including: 50 mass % or more to 99 mass % or less of a polycarbonate-based resin (S) containing 0.1 mass % or more to 100 mass % or less of a polycarbonate-polyorganosiloxane copolymer (A), which contains a polycarbonate block (A-1) formed of a specific repeating unit and a polyorganosiloxane block (A-2) containing a specific repeating unit, and 0 mass % or more to 99.9 mass % or less of an aromatic polycarbonate-based resin (B) except the polycarbonate-polyorganosiloxane copolymer (A); 1 mass % or more to 50 mass % or less of a polyester-based resin (C); and 0.001 part by mass or more to 1 part by mass or less of an amide compound (D) with respect to 100 parts by mass of a total amount of the polycarbonate-based resin (S) and the polyester-based resin (C).

Provided is a polycarbonate-based resin composition, including: 50 mass % or more to 99 mass % or less of a polycarbonate-based resin (S) containing 0.1 mass % or more to 100 mass % or less of a polycarbonate-polyorganosiloxane copolymer (A), which contains a polycarbonate block (A-1) formed of a specific repeating unit and a polyorganosiloxane block (A-2) containing a specific repeating unit, and 0 mass % or more to 99.9 mass % or less of an aromatic polycarbonate-based resin (B) except the polycarbonate-polyorganosiloxane copolymer (A); 1 mass % or more to 50 mass % or less of a polyester-based resin (C); and 0.001 part by mass or more to 1 part by mass or less of an amide compound (D) with respect to 100 parts by mass of a total amount of the polycarbonate-based resin (S) and the polyester-based resin (C).