阅读说明：本技术 具有减少的模具结垢的可固化有机硅组合物 (Curable silicone compositions with reduced mold fouling ) 是由 M·伯克马 S·登特 P·德康 S·利德利 J·麦克唐纳 K·范蒂格伦 F·德拜尔 M 于 2018-05-17 设计创作，主要内容包括：本发明提供一种可固化有机硅组合物,其包含：(A)含烯基的有机聚硅氧烷,该含烯基的有机聚硅氧烷包含：(A-1)在每个分子中平均具有至少两个烯基基团的二烷基聚硅氧烷)；和(A-2)含烯基的树脂形式的有机聚硅氧烷,该有机聚硅氧烷包含SiO<Sub>4/2</Sub>单元、R<Sup>1</Sup><Sub>2</Sub>R<Sup>2</Sup>SiO<Sub>1/2</Sub>单元和R<Sup>1</Sup><Sub>3</Sub>SiO<Sub>1/2</Sub>单元；(B)在每个分子中平均具有至少三个硅键合的氢原子的有机聚硅氧烷,其中组分(B)为包含以下的有机聚硅氧烷：(B-1)以组分(B)的50质量％至100质量％的有机聚硅氧烷,该有机聚硅氧烷包含至少0.7质量％的硅键合的氢,并且包含在每1摩尔SiO<Sub>4/2</Sub>单元1.50摩尔至2.50摩尔HR<Sup>3</Sup><Sub>2</Sub>SiO<Sub>1/2</Sub>单元范围内的比率的SiO<Sub>4/2</Sub>单元和HR<Sup>3</Sup><Sub>2</Sub>SiO<Sub>1/2</Sub>单元；以及(B-2)以组分(B)的0质量％至50质量％的直链有机聚硅氧烷,该直链有机聚硅氧烷含有至少0.3质量％的硅键合的氢；以及(C)硅氢加成反应催化剂。(The present invention provides a curable silicone composition comprising: (A) an alkenyl-containing organopolysiloxane comprising: (a-1) a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule); and (A-2) an organopolysiloxane in the form of an alkenyl-containing resin, the organopolysiloxane comprising SiO 4/2 Unit, R 1 2 R 2 SiO 1/2 Unit and R 1 3 SiO 1/2 A unit; (B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms in each molecule, wherein component (B) is an organopolysiloxane comprising: (B-1) an organopolysiloxane containing at least 0.7 mass% of silicon bonds, in an amount of 50 to 100 mass% of component (B)And is contained in each 1 mol of SiO 4/2 Units from 1.50 molar to 2.50 molar HR 3 2 SiO 1/2 SiO of ratio in the range of the unit 4/2 Unit and HR 3 2 SiO 1/2 A unit; and (B-2) from 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, based on component (B); and (C) a hydrosilylation reaction catalyst.)

1. A curable silicone composition comprising

(A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising

(A-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, based on component (A), and

(A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains the alkenyl group in a range of at least 1% by mass to less than 3.5% by mass;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen in component (B) per 1 mole of total alkenyl groups in component (A),

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10Alkyl radicals, and

(B-2) 0 to 50 mass%, based on component (B), of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, wherein the silicon-bonded group other than the silicon-bonded hydrogen is C_1-10An alkyl group; and

(C) a catalytic amount of a hydrosilylation reaction catalyst.

2. A highly transparent cured silicone material provided by thermosetting a curable silicone composition comprising: (A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising

(A-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, based on component (A), and

(A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains the alkenyl group in a range of at least 1% by mass to less than 3.5% by mass;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen in component (A) per 1 mole of total alkenyl groups in the component,

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10Alkyl radicals, and

(B-2) 0 to 50 mass%, based on component (B), of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, wherein the silicon-bonded group other than the silicon-bonded hydrogen is C_1-10An alkyl group; and

(C) a catalytic amount of a hydrosilylation reaction catalyst.

3. The highly transparent cured silicone material according to claim 2, which has a hardness in a range of at least 30 to not more than 90 measured using a type a durometer specified in JIS K6253, an elongation of at least 50% specified in JIS K6251, a parallel light transmittance at 25 ℃ of at least 90% measured on a 6mm optical path according to JIS K7105, and a parallel light transmittance at 200 ℃ is a value of at least 99% of the parallel light transmittance at 25 ℃.

4. The highly transparent cured silicone material as set forth in any one of claims 2 or 3 wherein the thermosetting is carried out at a temperature of from 120 ℃ to 180 ℃.

5. A cured silicone composite comprising a substrate forming a single article having a cured silicone layer provided by thermosetting the curable silicone composition of claim 1 at a temperature of 120 ℃ to 180 ℃.

6. The highly transparent cured silicone material according to claim 2, having a hardness in the range of at least 50 to not more than 90 measured using the type a durometer specified in JIS K6253.

7. The curable silicone composition according to claim 1, wherein (B) is an amount that provides 1.5 to 2.0 moles of silicon-bonded hydrogen per 1 mole of the total alkenyl groups in component (a).

8. The highly transparent cured silicone material according to any one of claims 2 to 7, further comprising an additional ingredient selected from the group consisting of: inhibitors, mold release agents, fillers, adhesion promoters, heat stabilizers, flame retardants, reactive diluents, antioxidants, and combinations of any two or more thereof.

9. The highly transparent cured silicone material according to any one of claims 2 to 7, the dialkylpolysiloxane (A-1) having a viscosity of from 10,000mPas to 500,000mPas at 25 ℃.

10. A method of forming a highly transparent cured silicone material, the method comprising the steps of: heating a curable silicone composition at a temperature of 120 ℃ to 180 ℃, the curable silicone composition comprising: (A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising

(A-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, based on component (A), and

(A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains the alkenyl group in a range of at least 1% by mass to less than 3.5% by mass;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups other than the silicon-bonded hydrogen are C_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen in component (A) per 1 mole of total alkenyl groups in the component,

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10Alkyl radicals, and

(B-2) 0 to 50 mass%, based on component (B), of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, wherein the silicon-bonded group other than the silicon-bonded hydrogen is C_1-10An alkyl group; and

(C) catalytic amount of hydrosilylation catalyst

To form a highly transparent cured silicone material.

11. The method of claim 10, further comprising coating a mold with the curable silicone composition of claim 1 and heating the mold to cure the curable silicone composition.

12. The method of claim 11, wherein the method further comprises removing a cured silicone composition from the mold, recoating the mold with the curable silicone composition, and curing the curable silicone composition.

13. The method of claim 12, wherein recoating the mold with the curable silicone composition is repeated and the curable silicone composition is cured more than 1000 times before cleaning or replacing the mold.

Technical Field

The present invention relates to a curable silicone composition that provides a cured silicone material that is flexible and highly transparent and reduces mold fouling during the molding process. The present invention also relates to a cured silicone composition formed by thermosetting the curable silicone composition. The present invention also relates to a method for curing a silicone composition, which comprises thermosetting a curable silicone composition in a mold.

Background

Curable silicone compositions containing organopolysiloxanes in the form of resins and providing highly transparent cured silicone materials are known. For example, JP 2005-042099A (equivalent to US 2005-0006794A1) describes a method comprisingThe silicone rubber composition of (1): an organopolysiloxane having at least two aliphatic unsaturated bonds in each molecule; has a resin structure and contains SiO₂Unit, R having 2 to 3 vinyl groups₃SiO_0.5Units and R having 0 to 1 vinyl group₃SiO_0.5Organopolysiloxanes of units wherein the non-vinyl groups R in these formulae are monovalent hydrocarbon groups free of aliphatic unsaturation, such as methyl groups and the like; an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule; and platinum group metal-based catalysts. Hereinafter, SiO₂The cell is called Q cell, and R₃SiO_0.5The cells are referred to as M cells.

The polyorganosiloxane composition described in JP 2006-335857A provides a transparent cured material and comprises: a linear polyorganosiloxane containing silicon-bonded alkenyl groups and having a thickness of 10mm at 23 DEG C²S to 10,000mm²Viscosity per second; a branched polyorganosiloxane comprising a Q unit, an M unit having one vinyl group, and an M unit having no aliphatic unsaturated bond; a polyalkylhydrosiloxane comprising Q units, M units having one silicon-bonded hydrogen atom, and M units not containing silicon-bonded hydrogen; and a platinum group metal compound.

The curable silicone composition described in JP 2007-131694A (equivalent to US2009-0118441 a1) comprises: at least one diorganopolysiloxane having at least two alkenyl groups per molecule; at least two organopolysiloxanes in the form of resins having different mass average molecular weights, each organopolysiloxane comprising Q units, M units having one vinyl group, and M units containing no aliphatic unsaturated bond; an organopolysiloxane having at least two silicon-bonded hydrogen atoms in each molecule; and a hydrosilylation reaction catalyst.

JP 2006-328102A (equivalent to US2006-0264583 a1) describes a silicone polymer composition for lens molding, characterized in that a colorless and transparent cured material is provided and comprises: as a result of whichAn organopolysiloxane of a base component, the organopolysiloxane having at least two aliphatic unsaturated bonds in each molecule and having a viscosity of at least 100mPa · s at 25 ℃; an organohydrogenpolysiloxane having at least three H (CH) s in each molecule₃)₂SiO_1/2A unit; and a platinum group metal catalyst.

US 8,859,693 describes a curable silicone composition for optical devices comprising: (A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising: (a-1) a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of at least 1,000 mPa-s to not more than 50,000 mPa-s at 25 ℃, in a range of 50% by mass to not more than 80% by mass of component (a); and (A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 20 to not more than 50 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is alkenyl, and the organopolysiloxane contains alkenyl groups in the range of at least 0.5 mass% to less than 3.5 mass%; (B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups, other than silicon-bonded hydrogen, are C_1-10An alkyl group in an amount to provide 0.8 to 2 moles of silicon-bonded hydrogen in component (a) per 1 mole of total alkenyl groups in component; and (C) a catalytic amount of a hydrosilylation reaction catalyst, and provides a highly transparent cured silicone material characterized by having a hardness in the range of at least 30 to not more than 80 measured using a type A durometer specified in JIS K6253, an elongation of at least 50% specified in JIS K6251, a parallel light transmittance at 25 ℃ of at least 90% measured on a 6mm optical path according to JIS K7105, and the parallel light transmittance at 200 ℃ is a value of at least 99% of the parallel light transmittance at 25 ℃.

However, these curable silicone compositions are prone to mold fouling prematurely during the production process. During the molding process, silicon-based deposits may build up on the mold. Over time, these silicone deposits can grow in size and the molded part replicates the shape of these deposits, which is undesirable in many cases. This process is known as mold fouling. Mold fouling is particularly disadvantageous in optical applications where defects in the molded article can interfere with the optical path, transmission and intensity, and mold fouling is more pronounced in complex molds. Thus, this premature fouling or build-up of deposits requires interruption of the production process to clean these silicon-based deposits in the mold. Such cleaning of the mold may shorten the service life of the mold and increase the production cost by reducing the production efficiency and increasing the frequency of mold replacement.

Disclosure of Invention

The present invention relates to a curable silicone composition comprising

(A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising: (a-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, as component (a); and (A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains an alkenyl group in the range of at least 1 mass% to less than 3.5 mass%;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups, other than silicon-bonded hydrogen, are C_1-10Alkyl groups, the organopolysiloxane being one which provides from 1.2 moles to less than 2.2 moles of total alkenyl groups in component (A) per 1 mole of the componentWherein component (B) is an organopolysiloxane comprising: (B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10An alkyl group; and (B-2) 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, based on component (B), wherein the silicon-bonded group other than silicon-bonded hydrogen is C_1-10An alkyl group; and (C) a catalytic amount of a hydrosilylation reaction catalyst.

The present invention also relates to a method of forming a highly transparent cured silicone material, the method comprising the steps of: heating at 120 ℃ to 180 ℃ a curable silicone composition comprising: (A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising: (a-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, as component (a); and (A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains an alkenyl group in the range of at least 1 mass% to less than 3.5 mass%; (B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups, other than silicon-bonded hydrogen, are C_1-10Alkyl groups, the organopolysiloxane being one which provides from 1.2 moles to less than 2.2 moles of total alkenyl groups in component (A) per 1 mole of the componentWherein component (B) is an organopolysiloxane comprising: (B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10An alkyl group; and (B-2) 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, based on component (B), wherein the silicon-bonded group other than silicon-bonded hydrogen is C_1-10An alkyl group; and (C) a catalytic amount of a hydrosilylation reaction catalyst.

The curable silicone composition and method of forming a highly transparent cured silicone material of the present invention provides a flexible and highly transparent cured silicone material without prematurely fouling the mold during repeated curing.

Detailed Description

A curable silicone composition comprising

(A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising

(A-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, based on component (A), and

(A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains an alkenyl group in the range of at least 1 mass% to less than 3.5 mass%;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups, other than silicon-bonded hydrogen, are C_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen in component (A) per 1 mole of total alkenyl groups in component,

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10Alkyl radicals, and

(B-2) 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, wherein the silicon-bonded group other than the silicon-bonded hydrogen is C, based on component (B)_1-10An alkyl group; and

(C) a catalytic amount of a hydrosilylation reaction catalyst.

A method of forming a highly transparent cured silicone material, the method comprising the steps of: heating at a temperature of 120 ℃ to 180 ℃ a curable silicone composition comprising: (A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising

(A-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, based on component (A), and

(A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains an alkenyl group in the range of at least 1 mass% to less than 3.5 mass%;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups, other than silicon-bonded hydrogen, are C_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen in component (A) per 1 mole of total alkenyl groups in component,

wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10Alkyl radicals, and

(B-2) 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, wherein the silicon-bonded group other than the silicon-bonded hydrogen is C, based on component (B)_1-10An alkyl group; and

(C) a catalytic amount of a hydrosilylation reaction catalyst.

The alkenyl-containing organopolysiloxane (a) comprises: (a-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, as component (a); and (A-2) an organopolysiloxane in the form of an alkenyl group-containing resin that contains SiO in an amount of 40 to not more than 80 mass% of component (A)_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains an alkenyl group in a range of at least 1% by mass to less than 3.5% by mass. The dialkylpolysiloxane (a1) having an average of at least two alkenyl groups per molecule in an amount of 20 to not more than 60 mass% of component (a) and having a viscosity of 5000 to 1,000,000mPas at 25 ℃.

Component (A-1) has an average of at least two alkenyl groups per molecule. The component (A-1) has a substantially linear molecular structure, but a part of the molecular chain may be slightly branched. The alkenyl group in the component (A-1) can be exemplified by vinyl, allyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl groups, of which vinyl is preferable. The bonding position for the alkenyl group is not limited, and may be, for example, a terminal position on the molecular chain and/or a side chain position, with the terminal position on the molecular chain being preferred. The alkyl group in the component (A-1) may be represented by C_1-10Alkyl groups such as methyl, ethyl, propyl, cyclopentyl, cyclohexyl, and the like are exemplified, with methyl being preferred.

The viscosity of component (A-1) at 25 ℃ is in the range of 5,000 to 1,000,000mPas, or in the range of 10,000 to 500,000mPas, or in the range of 15,000 to 200,000 mPas, or in the range of >50,000 to 200,000 mPas. When component (A-1) is a mixture of two or more alkenyl-functional dialkylpolysiloxanes, the viscosity of the mixture at 25 ℃ must be in the immediately alternative range described above (i.e., 5,000 to 1,000,000mPas, or 10,000 to 500,000mPas, or 15,000 to 200,000 mPas, or >50,000 to 200,000 mPas). Component (A-1) may be a mixture of a small amount of an alkenyl-functional dialkylpolysiloxane gum and an alkenyl-functional dialkylpolysiloxane that is liquid at 25 ℃ as long as the viscosity at 25 ℃ is within the specified range. The foregoing reasons are as follows: when the viscosity of component (a-1) at 25 ℃ is less than the above lower limit, the cured silicone material provided by curing of the composition of the present invention tends to have unsatisfactory flexibility; on the other hand, when the viscosity of component (a-1) at 25 ℃ exceeds the above upper limit, the transparency of the cured silicone material provided by curing of the composition of the present invention tends to decrease at high temperatures, whereas the composition of the present invention assumes that the viscosity is too high and the handling characteristics tend to decrease.

This component (A-1), diorganopolysiloxane, is exemplified by the following: dimethylpolysiloxanes capped with dimethylvinylsiloxy groups at both molecular chain ends, dimethylsiloxane x methylvinylsiloxane copolymers capped with dimethylvinylsiloxy groups at both molecular chain ends, methylvinylpolysiloxanes capped with trimethylsiloxy groups at both molecular chain ends, dimethylsiloxane x methylvinylsiloxane copolymers capped with trimethylsiloxy groups at both molecular chain ends, and mixtures of two or more of the foregoing.

The content of the component (a-1) in the composition of the present invention is an amount of at least 20% by mass to not more than 60% by mass of the component (a), or an amount of at least 20% by mass to less than 50% by mass of the component (a). The reason for this is as follows: when the content of component (a-1) exceeds the limit of the range, the flexibility and/or hardness of the cured silicone material provided by curing of the composition of the present invention tends to decrease, and the composition fouls the mold too quickly during repeated curing of the composition in the same mold.

The organopolysiloxane (a-2) in the form of an alkenyl group-containing resin of 40 to not more than 80 mass% of component (a) imparts satisfactory hardness and flexibility to the cured silicone material provided by curing of the composition of the present invention, and contains SiO_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is alkenyl and contains alkenyl groups in the range of at least 1 to less than 3.5 mass%. In these formulae, R¹Is C_1-10Alkyl, such as methyl, ethyl, propyl, cyclopentyl, cyclohexyl, and the like, and R²Is an alkenyl group such as vinyl, allyl, isopropenyl, butenyl, hexenyl, cyclohexenyl and the like, with vinyl being preferred。

The organopolysiloxane in the form of an alkenyl-containing resin of component (a-2) contains at least 1 mass% to less than 3.5 mass% of alkenyl groups, or contains at least 1.0 mass% to not more than 2.5 mass% of alkenyl groups. The reason for this is as follows: when the alkenyl group content in component (a-2) is less than the lower limit, the hardness of the cured silicone material provided by curing of the composition of the present invention tends to decrease; on the other hand, when the alkenyl group content in component (a-2) exceeds the upper limit, the flexibility of the cured silicone material provided by curing of the composition of the present invention tends to decrease, and the transparency of the cured silicone material provided by curing of the composition of the present invention tends to decrease at high temperatures. Component (a-2) may be a mixture of two or more organopolysiloxanes in the form of an alkenyl group-containing resin, in which case it is considered that such a mixture must contain at least 1% by mass to less than 3.5% by mass of alkenyl groups, and alternatively contain at least 1.0% by mass to not more than 2.5% by mass of alkenyl groups.

R in component (A-2)¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2The total number of moles of units and 1 mole of SiO_4/2The ratio of the units is preferably in the range of 0.50 to 1.80, and particularly preferably in the range of 0.70 to 1.10. The reason for this is as follows: r in the component (A-2)¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2The total number of moles of units and 1 mole of SiO_4/2When the ratio of the units is less than the lower limit, the molecular weight of the component (a-2) is too large, and the transparency of the cured silicone material provided by curing of the composition of the present invention may decrease; on the other hand, when R in the component (A-2)¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2The total number of moles of units and 1 mole of SiO_4/2When the ratio of the units exceeds the above upper limit, the cured silicone material provided by curing of the composition of the present invention may have unsatisfactory strength.

The component (A-2) has a mass average molecular weight preferably in the range of 3,000 to 7,000, and more preferably in the range of 4,000 to 6,000 on a standard polystyrene basis by gel permeation chromatography. Component (a-2) may be a mixture of two or more kinds of organopolysiloxanes in the form of an alkenyl-containing resin, and is preferably a mixture containing organopolysiloxanes in the form of an alkenyl-containing resin having a mass average molecular weight in the range of 3,000 to 7,000 on a standard polystyrene basis by gel permeation chromatography.

The content of the component (a-2) in the composition of the present invention is an amount of at least 40% by mass to not more than 80% by mass of the component (a), or an amount of more than 50% by mass to not more than 80% by mass of the component (a). The reason for this is as follows: when the content of component (a-2) is less than the lower limit of the range, the hardness of the cured silicone material provided by curing of the composition of the present invention tends to decrease; on the other hand, when the content of component (a-2) exceeds the upper limit of the range, the flexibility of the cured silicone material provided by curing of the composition of the present invention tends to decrease, the transparency of the cured silicone material provided by curing of the composition of the present invention tends to decrease at high temperatures, and the mold fouling rate increases.

The organopolysiloxane (B) has an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded group is C in addition to the silicon-bonded hydrogen_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen per 1 mole of total alkenyl groups in component (a), wherein organopolysiloxane (B) comprises: (B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10An alkyl group; and (B-2) 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, based on component (B), wherein the silicon-bonded group other than silicon-bonded hydrogen is C_1-10An alkyl group.

There is no limitation on the bonding position of silicon-bonded hydrogen in the component (B), and the silicon-bonded hydrogen may be bonded, for example, at a terminal position on the molecular chain and/or a side chain position on the molecular chain. In component (B), in addition to the silicon-bonded hydrogen, the silicon-bonded groups are alkyl groups such as methyl, ethyl, propyl, cyclopentyl, cyclohexyl, and the like, with methyl being preferred. This provides good compatibility with component (a) and also provides excellent transparency to the cured silicone material provided by curing of the composition of the present invention. Although there is no limitation on the viscosity of component (B), its viscosity at 25 ℃ is preferably 1mm²S to 10,000mm²In the range of/s, and particularly preferably in the range of 1mm²S to 1,000mm²In the range of/s.

Except for SiO_4/2Unit and HR³ ₂SiO_1/2In addition to the units, component (B-1) may further contain R³ ₃SiO_1/2And (4) units. HR in component (B-1)³ ₂SiO_1/2Unit and R³ ₃SiO_1/2The total number of moles of units and 1 mole of SiO_4/2The ratio of units is preferably in the range of 1.50 to 2.50, and more preferably in the range of 1.80 to 2.20. A specific example of the preferred component (B-1) is a compound of (SiO)_4/2)₄(H(CH₃)₂SiO_1/2)₈The organopolysiloxanes are given.

The linear organopolysiloxane (B-2) contains at least 0.3 mass%, and preferably at least 0.7 mass% of silicon-bonded hydrogen. The silicon-bonded group being C, in addition to the silicon-bonded hydrogen_1-10Alkyl groups such as methyl, ethyl, propyl, cyclopentyl, cyclohexyl, and the like, with methyl being preferred. Component (B-2) has a substantially linear molecular structure, but a part of the molecular chain may be slightly branched. Preferable specific examples of the component (B-2) are dimethylsiloxane xmethylhydrogensiloxane copolymer terminated with dimethylhydrogensiloxy groups at both molecular chain terminals, methylhydrogenpolysiloxane terminated with trimethylsiloxy groups at both molecular chain terminals, trimethylsiloxy groups at both molecular chain terminalsGroup-terminated dimethylsiloxane x methylhydrosiloxane copolymers, and mixtures of two or more of the foregoing.

The content of component (B) in the composition of the present invention is an amount that provides 1.2 to less than 2.2 moles, alternatively 1.2 to 2.1 moles, alternatively 1.5 to 2.0 moles, alternatively 1.6 to 1.9 moles of silicon-bonded hydrogen per 1 mole of total alkenyl groups in component (a). The reason for this is as follows: when the content of component (B) is less than the lower limit of the range, curing of the composition tends to be unsatisfactory; on the other hand, when the upper limit of the range is exceeded, the flexibility and/or transparency of the cured silicone material provided by the curing of the composition of the present invention may decrease and mold fouling increases.

The hydrosilylation reaction catalyst as the component (C) is a catalyst for promoting curing of the composition of the present invention, and can be exemplified by a platinum-based catalyst, a rhodium-based catalyst, and a palladium-based catalyst, with the platinum-based catalyst being particularly preferred. These platinum-based catalysts can be exemplified by: platinum fine powder, platinum black, platinum supported on silica fine powder, platinum supported on activated carbon, chloroplatinic acid, alcohol solutions of chloroplatinic acid, and platinum compounds such as olefin complexes of platinum, alkenylsiloxane complexes of platinum, and the like.

The content of the component (C) in the composition of the present invention is a catalytic amount, and specifically an amount providing 0.01 to 1,000 mass ppm, or 0.01 to 10 mass ppm, or 0.01 to 9 mass ppm, or 1 to 7 mass ppm of a catalyst metal atom relative to the composition of the present invention. The reason for this is as follows: when the content of component (C) is less than the lower limit of the range, there is a risk that curing of the resulting composition will not be sufficiently performed; on the other hand, exceeding the upper limit of the range results in a decrease in optical clarity.

As further optional components, the composition of the present invention may contain, for example, a reaction inhibitor in order to adjust the curing rate of the composition of the present invention, for example, acetylenic alcohols such as 2-methyl-3-butyn-2-ol, 3, 5-dimethyl-1-hexyn-3-ol, 1-ethynyl-1-cyclohexanol, phenylbutynol, and the like; alkene-alkyne compounds such as 3-methyl-3-penten-1-yne, 3, 5-dimethyl-3-hexen-1-yne, and the like; and 1,3,5, 7-tetramethyl-1, 3,5, 7-tetravinylcyclotetrasiloxane, 1,3,5, 7-tetramethyl-1, 3,5, 7-tetrahexenylcyclotetrasiloxane, benzotriazole, and the like. The content of the reaction inhibitor in the composition of the present invention is not limited, and the content may be appropriately selected according to the molding method and the curing conditions; however, an amount in the range of 10 mass ppm to 5,000 mass ppm is generally preferred relative to the composition of the present invention.

The composition of the present invention may incorporate, for example, an adhesion promoter, a flame retardant, an inorganic filler, etc., within a range not impairing the object of the present invention. However, in general, from the viewpoint of transparency of the cured silicone material provided by curing of the composition of the present invention, it is preferable not to incorporate an adhesion promoter, a flame retardant and an inorganic filler.

When the cured silicone material provided by curing of the composition of the present invention is used in electrical x-electronic applications, the content of the low molecular weight organopolysiloxane having a molecular weight of not greater than 650 in the composition of the present invention is preferably not greater than 350 ppm.

The viscosity of the composition of the present invention at 25 ℃ is not particularly limited, but from the viewpoint of molding characteristics and handling characteristics, i.e., easiness of pouring or injection, easiness of deaeration, etc., the viscosity of the composition of the present invention at 25 ℃ is preferably 1Pa · s to 100Pa · s, and particularly preferably 2Pa · s to 50Pa · s.

The compositions of the present invention form cured silicone materials when cured by heating to 100 ℃ to 250 ℃. The cured silicone material according to the present invention has a hardness in the range of at least 30 to not more than 80, preferably in the range of at least 50 to not more than 80, and more preferably in the range of at least 60 to not more than 75, as measured using a type a durometer specified in JIS K6253. The reason for this is as follows: when the hardness of the cured silicone material is less than the lower limit of the range, the strength thereof may be insufficient; on the other hand, when the upper limit of the range is exceeded, the flexibility of the cured silicone material under consideration tends to be insufficient. When the cured silicone material is used as an optical member or component, the hardness is particularly preferably in the range of at least 60 to not more than 80 based on the molding characteristics and the handling characteristics, as measured using a type a durometer specified in JIS K6253.

In order to exhibit satisfactory flexibility, the cured silicone material must have an elongation of at least 50% as specified in JIS K6251. The reason for this is that the flexibility of the cured silicone material becomes unsatisfactory below the indicated range.

The cured silicone material of the present invention must have a parallel light transmittance at 25 ℃ of at least 90% measured on a cured silicone material of 6mm thickness, i.e., on an optical path of 6mm, in accordance with JIS K7105, and must have a parallel light transmittance at 200 ℃ that is a value of at least 99% of the parallel light transmittance at 25 ℃. The reason for this is that when the cured silicone material of the present invention has a parallel light transmittance at 200 ℃ of less than 99% of the parallel light transmittance at 25 ℃, defects are liable to occur in optical component applications.

Additionally, the cured silicone material of the present invention can be a composite material in which the cured silicone material is formed into a single article having any of a variety of substrates. The substrate can be exemplified by various metals, thermoplastics, thermosets, rubbers (such as silicone rubbers), and the like, backing fabrics (such as those made of nylon or polyester), electronic parts and components, and light-emitting elements. Such cured silicone composites can be obtained by coating the composition of the present invention on a substrate and then thermally setting.

A method of forming a highly transparent cured silicone material, the method comprising the steps of: heating at a temperature of 120 ℃ to 180 ℃ a curable silicone composition comprising: (A)100 parts by mass of an alkenyl-containing organopolysiloxane comprising

(A-1) 20 to not more than 60 mass% of a dialkylpolysiloxane having an average of at least two alkenyl groups per molecule and having a viscosity of 5000 to 1,000,000mPas at 25 ℃, based on component (A), and

(A-2) as component(A) From 40 to not more than 80% by mass of an organopolysiloxane in the form of an alkenyl-containing resin, the organopolysiloxane comprising SiO_4/2Unit, R¹ ₂R²SiO_1/2Unit and R¹ ₃SiO_1/2Unit of which R¹Is C_1-10Alkyl and R²Is an alkenyl group, and the organopolysiloxane contains an alkenyl group in the range of at least 1 mass% to less than 3.5 mass%;

(B) an organopolysiloxane having an average of at least three silicon-bonded hydrogen atoms per molecule, wherein the silicon-bonded groups, other than silicon-bonded hydrogen, are C_1-10An alkyl group in an amount to provide 1.2 moles to less than 2.2 moles of silicon-bonded hydrogen in component (a) per 1 mole of total alkenyl groups in component, wherein component (B) is an organopolysiloxane comprising

(B-1) an organopolysiloxane that contains at least 0.7 mass% of silicon-bonded hydrogen and is contained at every 1 mole of SiO in an amount of 50 to 100 mass% of component (B)_4/2Units from 1.50 molar to 2.50 molar HR³ ₂SiO_1/2SiO of ratio in the range of the unit_4/2Unit and HR³ ₂SiO_1/2Unit of which R³Is C_1-10Alkyl radicals, and

(B-2) 0 to 50 mass% of a linear organopolysiloxane containing at least 0.3 mass% of silicon-bonded hydrogen, wherein the silicon-bonded group other than the silicon-bonded hydrogen is C, based on component (B)_1-10An alkyl group; and

(C) catalytic amount of hydrosilylation catalyst

To form a cured silicone material.

The curable silicone composition of the method of forming a highly transparent cured silicone material is as described above for the curable silicone composition.

In one aspect of the invention, the method further comprises coating the mold with the curable silicone composition and heating the mold to cure the curable silicone composition. The mold may be coated by methods known in the art. For example, the mold may be coated by injecting a curable silicone composition into the mold. One skilled in the art will know how to coat a mold for curing a curable silicone composition. Heating can be accomplished by methods known in the art, and one skilled in the art will know how to heat the mold to cure the curable silicone composition. Materials for molds used to mold curable silicone compositions are known in the art. Those skilled in the art will appreciate the materials used to form the molds for curing the silicone composition.

The curable silicone composition is heated at a temperature of 120 ℃ to 180 ℃, or 130 ℃ to 170 ℃. The cured silicone material is as described above.

In one aspect of the invention, the method further comprises removing the cured silicone composition from the mold, recoating the mold with the curable silicone composition, and curing the curable silicone composition on the recoated mold.

In another aspect of the invention, recoating the mold with the curable silicone composition is repeated and the curable silicone composition is cured on the recoated mold more than 500 times, or more than 1000 times, or more than 1500 times, or more than 2500 times, without building up any silicon-based deposits on the mold that require cleaning or replacement of the mold. In other words, the mold may be used for 500 cycles, or 100 cycles, or 1500 cycles, or 2500 cycles, wherein one cycle comprises coating the mold with the curable silicone composition, heating the curable silicone composition to cure the curable silicone composition to form a cured silicone material, and removing the cured silicone material from the mold, provided that the mold is not cleaned or replaced between cycles to remove the silicon-based deposit from the mold. The silicon-based deposits in the mold were detected by inspecting the mold using a stereomicroscope at 5 x magnification. The method of determining silicon deposition is described in the examples below.

In another aspect of the present invention, the curable silicone composition has the following provisos: there is less than 1%, alternatively less than 0.01%, alternatively no detectable level of alkoxy groups based on the weight of the curable silicone composition.

The composition of the present invention can be reused in a molding process while substantially reducing mold fouling. The method of the present invention also results in reduced mold fouling compared to prior art compositions during repeated use in the molding process. As described above, mold fouling is the following phenomenon: deposits containing silicon build up on the mold during repeated use, resulting in a reduction in the quality of the molded article when the mold is reused. Mold fouling was observed in the mold under visual inspection at 5 x magnification using a stereoscope.