Organopolysiloxane, method of manufacturing thereof, curable silicone composition, and cured product thereof

A curable silicone composition comprising:

• (A) an organopolysiloxane represented by the following average structural formula:
• R1aSiO(4-a)/2
• {wherein R1 designates a substituted or non-substituted monovalent hydrocarbon group, an alkoxy group, a hydroxyl group, or an organopolysiloxane residue of the following general formula:
• —X—(SiR22O)mSiR23
• (wherein R2 are the same or different, substituted or unsubstituted monovalent hydrocarbon groups;
• X represents a bivalent hydrocarbon group;
• and “m” is an integer equal to or greater than 1);
• however, at least one R1 in one molecule is the aforementioned organopolysiloxane residue, at least one R1 is a monovalent hydrocarbon group having aliphatic carbon-carbon double bonds, and “a” is a positive number that satisfies the following condition:
• 0<a<2)};
• (B) an organic silicon compound having in one molecule at least two silicon-bonded hydrogen atoms {this component is used in such an amount that the content of silicon-bonded hydrogen atoms of this component ranges from 0.1 to 10 moles per 1 mole of the monovalent hydrocarbon groups having aliphatic carbon-carbon double bonds of the aforementioned component (A)};
• and
• (C) a catalytic amount of a hydrosilylation catalyst.

A method of manufacturing an organopolysiloxane represented by the following average structural formula:

• R1aSiO(4-a)/2
• {wherein R1 designates a substituted or unsubstituted monovalent hydrocarbon group, an alkoxy group, a hydroxyl group, or an organopolysiloxane residue of the following general formula:
• —X—(SiR22O)mSiR23
• (wherein R2 are the same or different, substituted or unsubstituted monovalent hydrocarbon groups;
• X represents oxygen atoms or a bivalent hydrocarbon group;
• and “m” is an integer equal to or greater than 1);
• however, at least one R1 in one molecule is the aforementioned organopolysiloxane residue, and “a” is a positive number that satisfies the following condition:
• 0<a<2)}, said method comprising the step of reacting:
• (i) an organopolysiloxane represented by the following average structural formula:
• R3aSiO(4-a)/2
• (wherein R3 represents a substituted or unsubstituted monovalent hydrocarbon group, an alkoxy group, or a hydroxyl group, in one molecule at least one R3 is monovalent hydrocarbon group having aliphatic carbon-carbon double bond;
• and “a” is a positive number that satisfies the following condition:
• 0<a<2), and
• (ii) a diorganopolysiloxane represented by the following general formula:
• H(SiR42O)mSiR43
• (wherein R4 designates substituted or unsubstituted monovalent hydrocarbon groups that can be identical or different and that are free of unsaturated aliphatic bonds, and “m” is an integer equal to or greater than 1) {constituent (ii) is used in such an amount that the content of silicon-bonded hydrogen atoms of this constituent is less than 1 mole per 1 mole of the monovalent hydrocarbon groups having aliphatic carbon-carbon double bonds of constituent (i) },
• the reaction being carried out in the presence of (iii) a hydrosilylation catalyst.