An object of the present invention is to provide a photocuring method, which makes it possible to rapidly and efficiently obtain a crosslinked product (resin), a compound used in the photocuring method, and a photocuring resin composition containing the compound. The present invention relates to a photocuring method, which comprises a step 1 and a step 2 performed after the step 1, a compound used in the photocuring method, and a photocuring resin composition containing the compound. Step 1: this is a step in which in the presence of (A) compound having a carbonyl group generating a radical by photoirradiation and a carboxyl group decarboxylated by photoirradiation, (B) silane coupling agent having a mercapto group or a (meth)acryl group is reacted with (C) water under acidic conditions to obtain (D) silane compound having a mercapto group or a (meth)acryl group and at least one silanol group. Step 2: this is a step in which in the presence of the compound (A) and (E) compound having a carbonyl group generating a radical by photoirradiation and a group generating a base by being decarboxylated by photoirradiation, the compound (A) and the compound (E) are irradiated with light to create alkaline conditions in a reaction system by decarboxylating the carboxyl group of the compound (A) and generating a base from the compound (E), and radicals are generated from the compound (A) and the compound (E) to generate a crosslinked product containing a constitutional unit derived from the silane compound (D) from the silane compound (D) and, if necessary, from (F) compound having two or more polymerizable unsaturated groups.

An object of the present invention is to provide a photocuring method, which makes it possible to rapidly and efficiently obtain a crosslinked product (resin), a compound used in the photocuring method, and a photocuring resin composition containing the compound. The present invention relates to a photocuring method, which comprises a step 1 and a step 2 performed after the step 1, a compound used in the photocuring method, and a photocuring resin composition containing the compound. Step 1: this is a step in which in the presence of (A) compound having a carbonyl group generating a radical by photoirradiation and a carboxyl group decarboxylated by photoirradiation, (B) silane coupling agent having a mercapto group or a (meth)acryl group is reacted with (C) water under acidic conditions to obtain (D) silane compound having a mercapto group or a (meth)acryl group and at least one silanol group. Step 2: this is a step in which in the presence of the compound (A) and (E) compound having a carbonyl group generating a radical by photoirradiation and a group generating a base by being decarboxylated by photoirradiation, the compound (A) and the compound (E) are irradiated with light to create alkaline conditions in a reaction system by decarboxylating the carboxyl group of the compound (A) and generating a base from the compound (E), and radicals are generated from the compound (A) and the compound (E) to generate a crosslinked product containing a constitutional unit derived from the silane compound (D) from the silane compound (D) and, if necessary, from (F) compound having two or more polymerizable unsaturated groups.

A silicone elastomer cured product having radical reactivity obtained by curing a composition is disclosed. The composition comprises (A) a chain organopolysiloxane having a curing reactive group, and optionally (B) an organohydrogen polysiloxane, (C1) a curing agent, and (D) an organopolysiloxane resin. The surface of the cured product has radical reactivity with, for example, an adhesive, and is easily removable along with, for example, adhesive tape after use as a protective material. In general, the cured product has excellent heat resistance and flexibility and exhibits good adhesion and conformity to a substrate so as not to separate from a substrate even when the cured product is cut together with the substrate while remaining easily removable from the substrate when desired. A protective material for an electronic component made of the cured product is also disclosed.

A defoaming agent obtainable by a process, the process including the step of: (i) polymerizing (B) at least one defoaming agent monomer in (A) a polymerization solvent under coexistence of (C) a polymer soluble in the polymerization solvent.

A defoaming agent obtainable by a process, the process including the step of: (i) polymerizing (B) at least one defoaming agent monomer in (A) a polymerization solvent under coexistence of (C) a polymer soluble in the polymerization solvent.

An organopolysiloxane emulsion composition which contains a polyoxyalkylene-modified organopolysiloxane compound represented by formula (1) as an emulsifying agent or as an emulsifying assistant.
(LR.sub.2SiO.sub.1/2).sub.a(R.sub.3SiO.sub.1/2).sub.b(R.sub.2SiO.sub.2/2).sub.c(RSiO.sub.3/2).sub.d(SiO.sub.4/2).sub.e(1)
(In the formula, L represents a polyoxyalkylene group represented by formula (2); R represents a hydrogen atom, a hydroxy group, an alkyl group, an aryl group, an aralkyl group or an alkoxy group; a represents a number of 2-4; b represents a number of 0-2; c represents a number of 50-1,000; and each of d and e represents 0 or 1.)
H.sub.2CCH.sub.2(CH.sub.2).sub.rO-(EO).sub.s-(AO).sub.tR.sup.1(2)
(In formula (2), EO represents an oxyethylene group; AO represents a linear or branched oxyalkylene group having 3-10 carbon atoms; R.sup.1 represents an alkyl group, a hydrogen atom, a carboxy group, an acyl group or a phenyl group; r represents a number of 0-10; s represents a number of 1-100, t represents a number of 0-150; and (s+t) represents a number of 15 or more.)

A defoaming agent including a polymer, the polymer including a repeating unit represented by the following general formula (1); and a repeating unit represented by the following general formula (3): ##STR00001##
wherein in the general formula (1), X.sup.1 is a repeating unit obtainable by polymerization of a first ethylenic unsaturated group; Y.sup.1 is a side chain including a linear or branched polysiloxane structure, the polysiloxane structure having a polymerization degree of 5 to 300; and Z.sup.1 is a linking group linking the repeating unit X.sup.1 and the side chain Y.sup.1; ##STR00002##
wherein in the general formula (3), X.sup.2 is a repeating unit obtainable by polymerization of a second ethylenic unsaturated group, Y.sup.2 is a C.sub.1-30 hydrocarbyl side chain; and Z.sup.2 is a linking group linking the repeating unit X.sup.2 and the side chain Y.sup.2.

A defoaming agent including a polymer, the polymer including a repeating unit represented by the following general formula (1); and a repeating unit represented by the following general formula (3): ##STR00001##
wherein in the general formula (1), X.sup.1 is a repeating unit obtainable by polymerization of a first ethylenic unsaturated group; Y.sup.1 is a side chain including a linear or branched polysiloxane structure, the polysiloxane structure having a polymerization degree of 5 to 300; and Z.sup.1 is a linking group linking the repeating unit X.sup.1 and the side chain Y.sup.1; ##STR00002##
wherein in the general formula (3), X.sup.2 is a repeating unit obtainable by polymerization of a second ethylenic unsaturated group, Y.sup.2 is a C.sub.1-30 hydrocarbyl side chain; and Z.sup.2 is a linking group linking the repeating unit X.sup.2 and the side chain Y.sup.2.

A defoaming agent comprising: a polymer comprising a repeating unit represented by the following general formula (1): ##STR00001##
where in the general formula (1), X.sup.1 is a repeating unit obtainable by polymerization of an ethylenic unsaturated group; Y.sup.1 is a side chain comprising a linear or branched polysiloxane structure, the polysiloxane structure comprising a repeating unit represented by the following general formula (2) and having a polymerization degree of 5 to 300; and Z.sup.1 is a linking group linking the repeating unit X.sup.1 and the side chain Y.sup.1; ##STR00002##
wherein in the general formula (2), R.sup.1 and R.sup.2 are each independently an organic group having a carbon number of 1 to 18.

A defoaming agent comprising: a polymer comprising a repeating unit represented by the following general formula (1): ##STR00001##
where in the general formula (1), X.sup.1 is a repeating unit obtainable by polymerization of an ethylenic unsaturated group; Y.sup.1 is a side chain comprising a linear or branched polysiloxane structure, the polysiloxane structure comprising a repeating unit represented by the following general formula (2) and having a polymerization degree of 5 to 300; and Z.sup.1 is a linking group linking the repeating unit X.sup.1 and the side chain Y.sup.1; ##STR00002##
wherein in the general formula (2), R.sup.1 and R.sup.2 are each independently an organic group having a carbon number of 1 to 18.