Temporary adhesive composition, and method of producing thin wafer

A solution of a temporary adhesive composition comprising:

• (A) a cured product of an organopolysiloxane having a weight-average molecular weight of at least 15,000, obtained by a hydrosilylation reaction between an alkenyl group-containing organopolysiloxane (A1) and a hydrosilyl group-containing compound (A2) in presence of a platinum group metal-based catalyst, wherein
• (A1) is an alkenyl group-containing organopolysiloxane having a weight-average molecular weight exceeding 2,000, comprising:
• (I) 35 to 99 mol % of siloxane units represented by R1SiO3/2 (T units),
• (II) 0 to 49 mol % of siloxane units represented by R2R3SiO2/2 units (D units) and
• (III) 1 to 25 mol % of siloxane units represented by R4R5R6SiO1/2 units (M units),
• wherein each of R1 to R6 represents an unsubstituted or substituted monovalent hydrocarbon group of 1 to 10 carbon atoms,
• in which alkenyl groups bonded to silicon atoms represent at least 2 mol % of all organic groups bonded to silicon atoms, and
• (A2) is a hydrosilyl group-containing compound comprising:
• an organohydrogenpolysiloxane represented by an average composition formula (1):
• R7aHbSiO(4-a-b)/2 (1)
• wherein R7 represents a monovalent hydrocarbon group other than an alkenyl group, and a and b are numbers that respectively satisfy 0.75≦a≦2.5, 0.05≦b≦1.0, and 0.8≦a+b≦2.6,
• and having at least two hydrogen atoms bonded to silicon atoms within each molecule, or
• a bis-hydrosilyl compound represented by a general formula (2):
• wherein each of R8 and R9 independently represents a monovalent hydrocarbon group other than an alkenyl group, and X represents a divalent organic group, or
• a combination thereof,
• in an amount sufficient to provide 0.4 to 1.0 mols of hydrogen atoms bonded to silicon atoms per 1 mol of all the alkenyl groups within the organopolysiloxane (A1), and
• (B) an organic solvent having a boiling point of not more than 220° C.