JPH0260984A - Production of heat-bondable silicone adhesive composition - Google Patents

Abstract

PURPOSE:To obtain the title composition excellent in storage stability, adhesiveness, etc., by heating a solution of an organopolysiloxane mixture of a specified composition in an organic solvent and mixing the formed reaction mixture with an organopolysiloxane resin. CONSTITUTION:100 pts.wt. compound (A) obtained by kneading 60-90 pts.wt. diorganopolysiloxane having 1-3 alkenyl groups with 40-10 pts.wt. fine particulate silica and an organohydrogenpolysiloxane (B) having 2-3 Si-bonded hydrogen atoms in the molecule and a catalytic amount of a hydrosilylation catalyst (C) (components A and B are used in such a ratio that the Si-bonded hydrogen atoms of component B to the alkenyl groups of component A is 1:0.1-0.8) are dissolved in an organic solvent. The solution is heated to react component A with component B. 20-200 pts.wt. organopolysiloxane resin comprising units of the formula (wherein R<1> is an alkyl, an alkenyl or a hydroxyl) and SiO2 units and having an Si-bonded hydroxyl content <=10wt.% is dissolved in the reaction to obtain the title adhesive composition.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a heat-adhesive silicone adhesive composition, and more specifically to a silicone adhesive composition that has excellent storage stability, and has a high The present invention relates to a method for producing a heat-adhesive silicone adhesive composition that exhibits cohesive strength and high adhesive strength in a high-temperature atmosphere.

[Conventional technology]

Silicone adhesive has tackiness and adhesive strength at room temperature.

It has excellent properties such as adhesive strength, and in addition, it has properties such as heat resistance, cold resistance, and electrical properties unique to silicone, so it can be used for electrical insulation tapes that require a high degree of reliability, heat resistance, It is widely used in adhesives and various pressure-sensitive adhesives that require cold resistance.

Such silicone adhesive compositions generally include:
A composition that is made of a mixture of dimethylpolysiloxane raw rubber and methylpolysiloxane resin and is cured by an organic peroxide is used. Apart from this, a composition is used which is made of a mixture of an alkenyl group-containing diorganopolysiloxane, an organohydrodiene polysiloxane, and an organopolysiloxane resin and is cured by a platinum catalyst.

[Problem to be solved by the invention]

However, the adhesive composition has a drawback that it has poor storage stability and cannot be stored in a single container.Usually, the components constituting the adhesive composition are stored separately in separate containers. The conventional method was to add and mix a catalyst immediately before use. In addition, since all of the above adhesive compositions exhibit strong tackiness and high adhesion and adhesive strength at room temperature, when these are applied to the surface of various base materials and processed into tape-shaped adhesives, There was a drawback that the coated surface and the back surface of the tape-like base material adhered to each other and could not be peeled off. therefore.

In order to put this into practical use, it was necessary to perform a mold release treatment on the back side of the tape-shaped base material. Furthermore, when processing sheet-like adhesives and storing them in a stacked manner, it is necessary to insert a release material between the adhesive-coated surface and the back surface of the sheet-like base material.

The object of the present invention is to provide a silicone adhesive composition with excellent storage stability, and a heat-adhesive silicone adhesive that exhibits high cohesive strength and high adhesive strength in high-temperature atmospheres by removing organic solvents. The present invention provides a method for producing a composition.

[Means for solving problems and their effects]

The present invention relates to a method for producing a heat-adhesive silicone adhesive composition, which is characterized by comprising the following steps (I) to (I[).

(1) An organ prepared by kneading (A) 60 to 90 parts by weight of a diorganopolysiloxane having an average of 1 to 3 alkenyl groups per molecule and (b) 10 to 40 parts by weight of finely divided silica. polysiloxane compound
100 parts by weight.

(B) Organohydrodiene polysiloxane containing on average 2 to 3 silicon-bonded hydrogen atoms per molecule The number of silicon-bonded hydrogen atoms in the main component and the diorganopolysiloxane in component (a) An amount having a molar ratio of (1:0.1) to (1:0.8) with the vinyl group in the hydrosilylation reaction catalyst and (C) a catalytic amount of the hydrosilylation reaction catalyst dissolved in an organic solvent. A step of dispersing and obtaining an organic solvent solution of an organopolysiloxane composition, (II) Next, by heating the organic solvent solution, the diorganopolysiloxane in the component (a) and (b)
a step of reacting the organohydrodiene polysiloxane component to obtain a reaction mixture of the organopolysiloxane composition, (■) then adding (D) to the reaction mixture;
) R13SiO, 2 units (wherein, R1 is an alkyl group,
Selected from alkenyl groups and hydroxyl groups, at least 99 mol% of all R2 groups are methyl groups. ) and Sin, units, and a step of dissolving 20 to 200 parts by weight of an organopolysiloxane resin having a silicon atom-bonded hydroxyl group content of 10% by weight or less per 100 parts by weight of component (A). ” related.

To explain this, (A)
The diorganopolysiloxane component (a) used in the component organopolysiloxane compound must contain an average of 1 to 3 alkenyl groups in one molecule.

The molecular structure of this component may be linear, 9-branched, cyclic, network-like, or three-dimensional.6 Also, its molecular weight is not particularly limited, but it may be difficult to mix with other components or exhibit adhesive properties. For ease of handling, it is preferred that at least half of the chain be linear or branched, and that the viscosity at 25° C. be 1,000,000 centipoise or less.

The alkenyl group bonded to the silicon atom of such diorganopolysiloxane is a vinyl group.

Allyl group, propenyl group, butenyl group, pentenyl group,
Examples include hexenyl group, heptenyl group, octenyl group, nonenyl group, and decenyl group. The bonding position of the alkenyl group is preferably at the end opposite to the silicon atom because the reactivity of the curing reaction is better. In addition to alkenyl groups, organo groups bonded to silicon atoms include methyl and ethyl groups.

Alkyl groups such as propyl, butyl, pentyl and hexyl; Aryl groups such as phenyl, tolyl and xylyl; Aralkyl groups such as benzyl and phenethyl; trifluoropropyl and chloromethyl groups Examples include halogenated alkyl groups such as. In addition, as groups bonded to silicon atoms, small amounts of hydrogen atoms, hydroxyl groups,
It may also contain an alkoxy group. From the viewpoint of economy and good adhesion, it is preferable that half or more of the organo groups bonded to silicon atoms be methyl groups.

Finely powdered silica, which is component (b) in component (A) used in the present invention, functions to eliminate the tackiness and adhesiveness at room temperature of the adhesive composition obtained by the production method of the present invention. , Also, when used in combination with component (D) used in step (m), it functions to impart high adhesiveness by heating.

Such fine powder silica includes dry silica, which is produced by reacting tetrachlorosilane etc. in an oxyhydrogen flame, and wet silica, which is obtained by reacting water glass with acid and then removing water and salt. be.

In the present invention, either dry silica or wet silica may be used, but dry silica is generally preferred because it has higher adhesive strength under heating.

Component (A) in the present invention is an organopolysiloxane compound obtained by kneading the above-mentioned components (a) and (b), and the production of this compound is essential to achieving the object of the present invention.

This kneading method is not particularly limited as long as it can uniformly knead components (a) and (b) and achieve the purpose of the present invention, but generally, kneading is carried out under heating conditions. It is preferable.

Examples of such methods include, for example, adding component (b) to component (a) and kneading it to some extent at room temperature, and then thoroughly kneading it under heating; adding component (b) to component (a); After sufficiently kneading the mixture, the mixture may be thoroughly kneaded at room temperature or under heating, or the mixture may be left to mature under heating. This heating temperature is usually 100℃~220℃
is within the range of In addition, various plasticizers may be added to make this kneading easier. Examples of such plasticizers include diorganopolysiloxane containing hydroxyl groups at both ends of the molecular chain, and hexamethyldisiloxane. Examples include silazane.

The organohydride diene polysiloxane as the component (B) used in the present invention is a component that reacts with the component (A) in the presence of the hydrosilylation reaction catalyst as the component (C).

This component is an organopolysiloxane having an average of 2 to 3 silicon-bonded hydrogen atoms in one molecule, and there are no restrictions on its molecular structure or molecular weight. Examples of the organo group bonded to the silicon atom include those similar to the organo groups mentioned in the explanation of component (A), but specific examples of the component, most of which are preferably methyl groups, include: , dimethylsiloxane-methylhydrodienesiloxane copolymer with trimethylsiloxy groups blocked at both ends, dimethylpolysiloxane with dimethylhydrodiensiloxy groups blocked at both ends, dimethylsiloxane-methylhydrodienesiloxane copolymer blocked with dimethylhydrogensiloxy groups at both ends Combined.

Cyclic dimethylsiloxane-methylhydrodienesiloxane copolymer + (CHa)zH8lox 12 units.

Examples include copolymers consisting of (CHa)islOxzz units, Sin units, and the like.

The amount of this component added is such that the molar ratio of silicon-bonded hydrogen atoms in this component to alkenyl groups in component (a) is (1:0.
The amount is in the range of 1) to (1:0.8). Further, it is preferable that the total number of silicon-bonded hydrogen atoms in this component and the number of alkenyl groups in the diorganopolysiloxane of component (a) is less than 6. This is because when the total amount is 6 or more, the adhesive composition obtained by the production method of the present invention tends to gel during storage, and
This is because the fluidity tends to decrease and it becomes impossible to uniformly coat various substrates.

The organic solvent used in the present invention is used to facilitate the reaction between component (A) and component (B), and is used to facilitate the reaction between component (A) and component (B), and to It is a diluent to make it easier to apply on the substrate, and it contains component (a) and (B).
Any material may be used as long as it can dissolve component () and CD) and disperse component (b). Specific examples of these include toluene,
Examples include xylene, benzene, mineral spirit, solvent naphtha, n-hexane, n-hebutane, isopropyl alcohol, perchloroethylene, trichloroethylene, and the like. Further, these organic solvents may be used alone or in combination. The amount of such an organic solvent to be used is appropriately selected upon use, and is therefore not particularly limited and is an arbitrary amount.

The hydrosilylation reaction catalyst used in the present invention is (A)
It is a catalyst for promoting the reaction between the components and the component (B), particularly the addition reaction between the alkenyl group of the component (a) in the component (A) and the silicon-bonded hydrogen atom in the component (B). Such catalysts include chloroplatinic acid, complexes of chloroplatinic acid and olefins, complexes of chloroplatinic acid and vinylsiloxanes,
Alternatively, examples include platinum supported on a fine support such as alumina, and a complex of rhodium and vinyl siloxane. Further, the amount added is sufficient for the reaction of component (a) and component (b), and is a catalytic amount.

In the present invention, the above components (A) to (C) are dissolved in an organic solvent to obtain an organic solvent solution of the organopolysiloxane composition, but the dissolution method is not particularly limited. However, generally, it is advantageous to uniformly dissolve and disperse component (A) in an organic solvent, then add components (B) and (C), and then uniformly mix and dissolve them.

Step (n) involves heating the organic solvent solution of the organopolysiloxane composition obtained in step (1).
) component, especially the diorganopolysiloxane as the component (a) in the component (A), and the organohydrodiene polysiloxane as the component (B) are subjected to an addition reaction to obtain a reaction mixture of the organopolysiloxane composition. However, the heating temperature here is not particularly limited as long as it is a temperature at which the above reaction can occur, and is usually carried out within the range of 20°C to 110°C.

In step (m), the reaction mixture obtained in step (II) is added (
D) component R13Si0□7□ units (wherein R1 is selected from an alkyl group, an alkenyl group and a hydroxyl group,
At least 90 mole percent of all R1 groups are methyl groups. )
This is a process of adding and dissolving organopolysiloxane resin consisting of is selected from alkyl groups such as methyl, ethyl and propyl groups, alkenyl groups such as vinyl and allyl groups, and hydroxyl groups, and 90 mol% of all R1 groups are methyl groups.

And R1, SiO□1. Unit To Sin, Unit (7)
It is preferable that the MoJLI ratio is within the range of (0,6:1) to (1,0:1). This is because in R13SiO, when the □ unit is less than 0.6, the adhesive strength tends to decrease, and when it exceeds 0.9, the cohesive strength tends to decrease. Also (D
) The content of hydroxyl groups bonded to silicon atoms in the component is 10
It is not more than 6% by weight, preferably not more than 6% by weight. The amount added is 20 parts by weight per 100 parts by weight of component (A).
~200 parts by weight.

Such an organopolysiloxane resin is used as described above (I[
) There are many methods for dissolving the resin in the reaction product obtained in the process, but generally an effective method is to add the organopolysiloxane resin to the reaction product and stir it at room temperature or under heating. .

In the method of the present invention, if it is necessary to obtain an adhesive composition having even higher adhesive strength, after dissolving the organopolysiloxane resin of component (D) in the reaction mixture obtained in step (II) above, It is preferable to heat-treat this by stirring under heating conditions or the like.

〔Example〕

Next, one embodiment of the present invention will be explained with reference to examples. In the example.

Parts represent parts by weight, and C8 represents centistokes. Further, each characteristic shown in the examples was measured by the following method.

○Measurement of ball tack After applying a heat-adhesive silicone adhesive composition to the surface of the substrate at a solid content of 5.0 μs, dry it in a dryer at 110°C for 5 minutes.
The organic solvent was removed by leaving it for a minute to prepare a pressure-sensitive adhesive sheet.

This adhesive sheet is pasted on the pole tack tester (manufactured by Tester Sangyo) on the inclined surface 306 with the adhesive side facing up. A ball is rolled and the diameter of the largest steel ball that stops on a sticky surface of 10a1 length is shown in 1/32 inch units6.
For example, the display lO.

It shows that a steel ball with a diameter of 10/32 inches was the largest steel ball that could be stopped on this adhesive surface.

0 Measurement of adhesion force The adhesive sheet made by the pole tack measurement method was
Stainless steel plate polished with No. 0 waterproof abrasive paper (SUS3
04) Attach on top using a 2 kg rubber roller at 25°C (room temperature adhesion).

In addition, the adhesive side of the adhesive sheet and the above stainless steel plate were stacked and bonded together using an iron heated to about 110°C (thermal adhesion), and after standing at 25°C for 1 hour, a tensile test was performed. The adhesive force when peeled off was measured using a tensilon machine (manufactured by Toyo Baldwin ■) at a tensile speed of 0.3 m/win, and expressed in units of g72.5 am.

Measurement of o'M collection force Adhesive tape made using the same method as above for measuring adhesion was placed on a stainless steel plate (surface polished with No. 280 water-resistant abrasive paper).
S U 5304), length 20m.

An area of width 10+m is heated and bonded using an iron at about 110°C. A load of 500 g was applied to the lower end of this adhesive tape, and the tape was hung in a dryer at 100° C. for 2 hours, after which the shift distance was measured using a reading microscope and expressed in units of 1.

Example 1 To 78 parts of dimethylpolysiloxane raw rubber with dimethylvinylsiloxy groups blocked at both ends, 9 parts of dimethylpolysiloxane with hydroxyl groups blocked at both ends with a viscosity of 25C8 was added as a plasticizer, and further 22 parts of dry silica having a specific surface area of 130 m/g were added and mixed. I practiced. Next, the mixture was heat-treated at 180° C. for 2 hours while being kneaded to obtain an organopolysiloxane compound. Next, this was dissolved and dispersed in 300 parts of xylene, and the viscosity was further increased to 4.
1.2 parts of 5C8 dimethylpolysiloxane endblocked with dimethylhydrodienesiloxy groups at both ends was added and dissolved.Next, while stirring this solution, a complex of chloroplatinic acid and divinyltetramethyldisiloxane was dissolved at 180p in terms of platinum.
pm, and after raising the temperature to 90℃,
The reaction was carried out for 0 minutes to obtain a reaction mixture of an organopolysiloxane composition. Next, after cooling this solution to room temperature, add it to (
CHi) Consists of islOzz unit and Sin, unit,
The molar ratio is 0.7:1.0, and the hydroxyl group content is 1.
．． 80 parts of 0% by weight methylpolysiloxane resin was added and dissolved to obtain a silicone adhesive composition (Sample 1). Similarly, 110 parts of this methylpolysiloxane resin was added and dissolved to obtain a silicone adhesive composition (Sample 2). Silicone adhesive compositions were obtained in the same manner as above except that a mixture of 78 parts of dimethylpolysiloxane blocked with siloxy groups and 8 parts of dimethylpolysiloxane crude rubber blocked with both hydroxyl groups was used (Sample 3, Sample 4). The silicone adhesive composition was applied to a thickness of 38. The adhesive sheet was coated onto a polyester film having a thickness of 50 μm in terms of solid content, and the solvent was removed in a dryer at 110° C. to prepare a pressure-sensitive adhesive sheet. Ball tack, adhesive force, and cohesive force were measured using this adhesive sheet. The results were as shown in Table 1. For comparison, the properties of silicone adhesives (Samples 5 and 6) prepared in the same manner as above except that the dry silica having a specific surface area of 130 rd/g was not used in Samples 1 and 2 were measured in the same manner as above. The results are also listed in Table 1.

Table 1 It was found that Samples 1 to 4 of the present invention had no tackiness or adhesiveness at room temperature, but showed high adhesive strength when heated.

Example 2 10 parts of hexamethyldisilazane as a plasticizer and 1 part of water were added to 80 parts of dimethylpolysiloxane crude rubber endblocked with dimethylvinylsiloxy groups at both ends, and further a specific surface area of 200
20 parts of dry silica of rd/g were added and kneaded.
Next, this organopolysiloxane compound was dissolved in 300 parts of toluene, and the compound had a viscosity of 60C8, with both ends of the molecular chain being blocked with dimethylhydrodienesiloxy groups and containing on average one silicon-bonded hydrogen atom in the side chain.
1.1 parts of dimethylsiloxane/methylhydrogensiloxane copolymer was added and dissolved. Next, while stirring this solution, a complex of chloroplatinic acid and divinyltetramethyldisiloxane was added in an amount of 150 ppm in terms of platinum, and the temperature was raised to 90°C and reacted for 30 minutes to form an organopolysiloxane composition. A reaction mixture was obtained.

This reaction mixture was then added with CCHl)asi01t2 units and Sun.

After adding and dissolving 70 parts of methylpolysiloxane resin with a molar ratio of OJ: 1.0 and a hydroxyl group content of 1.5% by weight, the resin was heated at 90°C for 6 hours to form a silicone adhesive. I got something. (Sample 7).

Similarly, 100 parts of the above methylpolysiloxane resin was added to the above reaction mixture and dissolved, followed by heat treatment at 95° C. for 6 hours to obtain a silicone adhesive composition (Sample 8).

These samples were coated on the surface of aluminum foil with a thickness of 50 mm to a thickness of 50 parts m in terms of solid content, and then heated at 100°C.
The solvent was removed in a dryer to create an adhesive sheet. Pole tack using this adhesive sheet.

Adhesive force, cohesive force, and high temperature adhesive force in an atmosphere of 250°C were measured. These results were as shown in Table 2.

For comparison, dimethylsiloxane/methylvinylsiloxane copolymer raw rubber having a vinyl group content of 0.06% by weight was used in place of the dimethylpolysiloxane endblocked with dimethylvinylsiloxy groups at both ends.

A silicone adhesive composition (Sample 9) was prepared in the same manner as above except that dimethylsiloxane/methylvinylsiloxane copolymer raw rubber having a vinyl group content of 0.21% by weight was used.
．． 10) was obtained. Further, a silicone adhesive composition (Sample 11 was prepared) in the same manner as Sample 7 except that no platinum compound catalyst was added.

Table 2 Samples 7 and 8 had no tack, stickiness, or adhesive properties at room temperature, but showed high adhesive strength when heated to approximately 110°C and exhibited high adhesive strength even in an atmosphere of 25.0°C. .

Comparative Samples 9 and 10 became gel-like during the preparation of the silicone adhesive composition, and the surfaces coated with the silicone adhesive compositions also became gel-like.

Example 3 Both ends of the molecular chain are blocked with dimethylvinylsiloxy groups,
Viscosity 120,000C8 containing one vinyl group on average in the side chain
dimethylsiloxymethylvinylsiloxane copolymer 7
To 2 parts, 13 parts of diphenylsilanediol as a plasticizer was added, and further 27 parts of fumed silica having a specific surface area of 200 m/g were added, and the mixture was uniformly kneaded to obtain an organopolysiloxane compound. Next, this compound was allowed to stand at room temperature for 7 days, kneaded again, and then dissolved in 300 parts of toluene. To this solution was added and dissolved 1.4 parts of dimethylpolysiloxane having a viscosity of 45C8 and endblocked with dimethylno)hydrogensiloxy groups at both ends.

Next, while stirring this solution, add 150pp in terms of platinum.
m of chloroplatinic acid was added, the temperature was raised to 90°C, and the mixture was reacted for 1 hour. Next, add (CHi)3slOtz to this solution.
Consists of z unit and 5lot unit, the molar ratio of which is 0.7
: Add 80 parts of methylpolysiloxane resin with a pH of 1.0 and a hydroxyl group content of 2.0% by weight, and add 80 parts of methylpolysiloxane resin with stirring.
A silicone adhesive composition (Sample 12) was obtained by heat treatment at 5° C. for 6 hours.

For comparison, in the above, instead of the dimethylsiloxane/methylvinylsiloxane copolymer, a viscosity of 120,000 C8 was used.
A silicone adhesive composition was prepared in the same manner as above except that a dimethylpolysiloxane endblocked with trimethylsiloxy groups at both ends and containing no vinyl groups was used (Sample 13).
).

This was coated on aluminum foil to a thickness of 501 U in terms of solid content, and the solvent was removed in a dryer at 70° C. to prepare an adhesive sheet. The results of evaluation using this adhesive sheet are as shown in Table 3.

Table 3 Sample 12 was extremely superior to Comparative Example Sample 13 in terms of cohesive force and adhesive strength under a high temperature atmosphere of 250°C.

Example 4 Adding 15 parts of diphenylsilanediol to 70 parts of dimethylsiloxane/methylphenylsiloxane copolymer (phenyl group content: 3 mol%) containing an average of one vinyl group at both ends of the molecular chain and on the side chain. death.

Next, the specific surface area is 130rr? /g of wet process silica (Nip Seal manufactured by Nippon Silica) was added thereto, and heat treated at 180° C. for 3 hours while kneading to obtain an organopolysiloxane compound. Next, this compound was dissolved in 300 parts of toluene, and 1.1 parts of dimethylpolysiloxane having a viscosity of 45CS and having dimethylhydrodiene siloxy groups endblocked at both ends was added and dissolved.

While stirring this solution, a complex of chloroplatinic acid and divinyltetramethyldisiloxane was added in an amount of 120 ppm in terms of platinum, and after the temperature was raised to 90° C., the mixture was reacted for 1 hour. Next, to this solution was added a methylpolysiloxane resin 7 consisting of 72 units of (CH3)35 lots and SiO□ units in a molar ratio of 0.8:1.0 and a hydroxyl group content of 1.5% by weight.
A silicone adhesive composition (Sample 14) was obtained by adding 5 parts of the silicone adhesive composition and heating it at 95° C. for 6 hours while stirring.

This is applied on the surface of aluminum foil at a solid content of 50. A pressure-sensitive adhesive sheet was prepared by applying a thick coating and removing the solvent in a dryer at 70°C. The results of evaluation using this pressure-sensitive adhesive sheet are as shown in Table 4.

For comparison, see the above. Methylhydrodienesiloxane dimethyl with a viscosity of 7C8, which has both ends blocked with trimethylsiloxy groups and contains an average of 5 silicon-bonded hydrogen atoms in one molecule, instead of dimethylpolycimexane blocked with methylhydrogensiloxy groups. A silicone adhesive was prepared in the same manner as above except that a siloxane copolymer was used.

When this silicone adhesive was applied to the surface of aluminum foil in the same manner as above, it became gel-like and no pressure-sensitive adhesive sheet could be formed.

(Margins below) Table [Effects of the Invention] The production method of the present invention consists of the steps (I) to Cm) as described above, so it has excellent storage stability and does not require the addition of a catalyst before use. The present invention is characterized in that it is possible to easily produce a heat-adhesive silicone adhesive composition that exhibits high cohesive strength and high adhesive strength in a high-temperature atmosphere simply by removing the solvent.

Claims (1)

[Scope of Claims] 1. A method for producing a heat-adhesive silicone adhesive composition, characterized by comprising the following steps [I] to [III]. [I] (A) (a) Diorganopolysiloxane 60-60 containing on average 1 to 3 alkenyl groups in one molecule
Organopolysiloxane compound 10 obtained by kneading 90 parts by weight and (b) 10 to 40 parts by weight of finely divided silica.
0 parts by weight, (B) an organohydrodiene polysiloxane containing an average of 2 to 3 silicon-bonded hydrogen atoms per molecule; the silicon-bonded hydrogen atoms in the main component and the diorganohydrogen polysiloxane in the component (a); The molar ratio of alkenyl groups in polysiloxane is (1:0.1) to (1:0.8)
) and (C) a catalytic amount of a hydrosilylation reaction catalyst in an organic solvent to obtain an organic solvent solution of the organopolysiloxane composition. [II] Next, by heating the organic solvent solution,
The diorganopolysiloxane in the component (a) and (B)
A step of reacting the organohydrodiene polysiloxane component to obtain a reaction mixture of the organopolysiloxane composition, [III] Thereafter, adding (D) R^1_3 to the reaction mixture;
SiO_1_/_2 units (in the formula, R^1 is an alkyl group,
Selected from alkenyl groups and hydroxyl groups, at least 90 mol% of all R^1 groups are methyl groups. ) and SiO_
It consists of 2 units, and the silicon atom-bonded hydroxyl group content is 10
% by weight or less of the organopolysiloxane resin as described above (A
) A step of dissolving 20 to 200 parts by weight per 100 parts by weight of the components.