Curable resin composition, method for producing curable resin composition, and method for measuring surface tackiness of viscoelastic material

A curable resin composition comprising at least one polysiloxane (A) selected from the group consisting of polyorganosiloxane (A1) having not less than 2 alkenyl groups in the molecule and polyorganosiloxysilalkylene (A2) having not less than 2 alkenyl groups in the molecule, and at least one polysiloxane (B) selected from the group consisting of polyorganosiloxane (B1) having not less than 2 hydrosilyl groups in the molecule and polyorganosiloxysilalkylene (B2) having not less than 2 hydrosilyl groups in the molecule, wherein

• the curable resin composition comprises
• at least one polysiloxane selected from the group consisting of polyorganosiloxane represented by the following average unit formula (a-1) and polyorganosiloxysilalkylene represented by the following average unit formula (a-2) as the polysiloxane (A), and
• at least one polysiloxane selected from the group consisting of polyorganosiloxane represented by the following average unit formula (b-1) and polyorganosiloxysilalkylene represented by the following average unit formula (b-2) as the polysiloxane (B),
• when the ratio of the number of a silicon atom in a siloxane unit represented by (R3SiO1/2) to all silicon atoms contained in the curable resin composition is defined as M, the ratio of the number of a silicon atom in a siloxane unit represented by (R2SiO2/2) thereto is defined as D, the ratio of the number of a silicon atom in a siloxane unit represented by (RSiO3/2) thereto is defined as T, and the ratio of the number of a silicon atom in a siloxane unit represented by (SiO4/2) thereto is defined as Q, the curable resin composition satisfies (T+Q)/D>0.3 and M+D+T+Q=1 (wherein R represents a monovalent group),
• the amount of the hydrosilyl groups is 0.9 to 5.0 mol with respect to 1 mol of aliphatic carbon-carbon double bonds present in the curable resin composition, and
• a cured product obtained by curing the curable resin composition by heating under at least one curing condition selected from among conditions involving 25 to 180° C. and 1 to 720 minutes exhibits a separation strength of not more than 0.40 N per mm2 in the following separation load evaluation and/or a total separation load of not more than 0.018 N·mm per mm2 in the following separation load evaluation:
• separation load evaluation:
• an object made of SUS and the cured product are contacted with each other by moving at least one of the object and the cured product from perpendicularly distant positions so as to attain a contact area of 50 to 800 mm2 between the object and the cured product, pressed against each other at a load of 100 N for 2 minutes, and then separated in a perpendicular direction;
• change in stress on the contact face in this operation is recorded;
• a value determined by dividing a maximum stress value from when the object and the cured product start to be separated to when the object and the cured product are completely separated by the contact area is used as the separation strength;
• and a value determined by dividing an area surrounded by a stress curve from when the object and the cured product start to be separated to when the object and the cured product are completely separated and a baseline by the contact area is used as the total separation load, provided that the separation strength and the total separation load are each set to the largest value among values obtained by measurement with rates of the separation set to arbitrary 10 points (wherein adjacent 2 points differ in rate by not less than 5 mm/min) within the range of 5 to 500 mm/min,
• (R1SiO3/2)a1(R12SiO2/2)a2(R13SiO1/2)a3(SiO4/2)a4(X1O1/2)a5 average unit formula (a-1):
• wherein R1 moieties are the same or different and each represent an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, provided that some of the R1 moieties are alkenyl groups in the range of not less than 2 in the molecule;
• X1 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;
• and a1, a2, a3, a4, and a5 represent numerical values satisfying 1>a1≥0, 1>a2≥0, 1>a3>0, 1>a4≥0, 0.05≥a5≥0, a1+a2+a4>0, and a1+a2+a3+a4+a5=1,
• (R22SiO2/2)b1(R23SiO1/2)b2(R2SiO3/2)b3(SiO4/2)b4(RA)b5(X2O1/2)b6 average unit formula (a-2):
• wherein R2 moieties are the same or different and each represent an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, provided that some of the R2 moieties are alkenyl groups in the range of not less than 2 in the molecule;
• RA represents an alkylene group having 1 to 14 carbon atoms;
• X2 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;
• and b1, b2, b3, b4, b5, and b6 represent numerical values satisfying 1>b1≥0, 1>b2>0, 1>b3≥0, 1>b4≥0, 0.7>b5>0, 0.05≥b6≥0, b1+b3+b4>0, and b1+b2+b3+b4+b5+b6=1,
• (R3SiO3/2)c1(R32SiO2/2)c2(R33SiO1/2)c3(SiO4/2)c4(X3O1/2)c5 average unit formula (b-1):
• wherein R3 moieties are the same or different and each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 14 carbon atoms, provided that some of the R3 moieties are hydrogen atoms in the range of not less than 2 in the molecule;
• X3 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;
• and c1, c2, c3, c4, and c5 represent numerical values satisfying 1>c1≥0, 1>c2≥0, 1>c3>0, 1>c4≥0, 0.05≥c5≥0, c1+c2+c4>0, and c1+c2+c3+c4+c5=1, and
• (R42SiO2/2)d1(R43SiO1/2)d2(R4SiO3/2)d3(SiO4/2)d4(RA)d5(X4O)d6 average unit formula (b-2):
• wherein R4 moieties are the same or different and each represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an aryl group having 6 to 14 carbon atoms, provided that some of the R4 moieties are hydrogen atoms in the range of not less than 2 in the molecule;
• RA represents an alkylene group having 1 to 14 carbon atoms;
• X4 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms;
• and d1, d2, d3, d4, d5, and d6 represent numerical values satisfying 1>d1≥0, 1>d2>0, 1>d3≥0, 1>d4≥0, 0.5>d5>0, 0.05≥d6≥0, d1+d3+d4>0, and d1+d2+d3+d4+d5+d6=1.