JP7772098B2 - Platinum-phosphite complex-containing hydrosilylation catalyst, method for producing the same, and curable organopolysiloxane composition and article - Google Patents

Description

The present invention relates to a platinum-phosphite ester complex-containing hydrosilylation catalyst and a method for producing the same. It also relates to a curable organopolysiloxane composition containing the hydrosilylation catalyst, and an article having a cured product thereof.

This addition-curable silicone composition (addition-curable organopolysiloxane composition; the term "addition-curable silicone composition" as used herein refers to a composition whose cured product can be either a rubber-like cured product (an elastomer) such as silicone rubber or a gel-like cured product (a low-stress non-elastic material that does not exhibit a significant rubber hardness value), with no restrictions on the hardness after curing) contains an organopolysiloxane having alkenyl groups bonded to silicon atoms as the base polymer, an organohydrogenpolysiloxane having hydrosilyl groups (hydrogen atoms bonded to silicon atoms (i.e., SiH groups)) as the curing agent (crosslinking agent), and a platinum-based catalyst as the curing catalyst. The cured product is obtained by the addition reaction of the hydrosilyl groups with the alkenyl groups. The silicone rubber, silicone gel, and other silicone cured products obtained by heat-curing this addition-curable silicone composition have excellent heat resistance, weather resistance, oil resistance, cold resistance, and electrical insulation properties. For this reason, addition-curable silicone compositions are used in a wide range of applications, including electrical and electronic components, optical components, building materials, and automotive sealing materials.

When one-component addition-curable silicone compositions like those mentioned above are exposed to high temperatures during storage, they can experience problems such as changes in properties, such as thickening and gelation, as well as changes in physical properties after curing. To avoid these problems, one approach is to create a mixed silicone composition by separating the components into two or more components and mixing them immediately before use. Another approach is to transport one-component silicone compositions at low temperatures. The former raises concerns about changes in the physical properties of the cured silicone due to formulation variations or uneven mixing. Furthermore, highly advanced formulation and mixing techniques are required, making them unsuitable for everyone. The latter, meanwhile, requires low-temperature storage from storage to use, which increases transportation and storage costs, making them commercially disadvantageous. Against this backdrop, there has been a growing demand in recent years for one-component addition-curable silicone compositions that maintain their properties and performance even when stored for long periods at room temperature (hereafter referred to as 23°C ± 15°C).

Against this background, Japanese Patent Publication No. 2849027 (Patent Document 1) proposes a method of adding an amine compound with an ethylenediamine skeleton. However, this publication suffers from the problem of corrosion of electronic substrates and a deterioration in electrical properties due to the addition of an amine compound. Furthermore, Japanese Patent Publication No. 4530147 (Patent Document 2) proposes a method of using a catalyst prepared by heat-aging a specific phosphite ester compound with a platinum catalyst. However, this method suffers from the problem of unstable catalyst activity due to the heat-aging process. Furthermore, the use of an organic peroxide in combination with the catalyst poses handling limitations. Furthermore, prolonged exposure to room temperature can cause thickening and gelation, necessitating low-temperature storage and transportation to ensure stable performance.

Also, overseas, European Patent Application Publication No. 2050768A1 and U.S. Patent No. 6706840 (Patent Documents 3 and 4) propose methods using platinum-phosphite complexes. However, even in these two publications, thickening and gelation occur when exposed to room temperature for long periods of time, so low-temperature conditions are essential during storage and transportation to ensure performance stability.

Furthermore, U.S. Patent No. 4,256,616 (Patent Document 5) proposes a method using a platinum-phosphite complex and tin salt. However, because this method uses a tin compound, there are concerns about its harmfulness to the human body. Furthermore, if exposed to room temperature for a long period of time, thickening and gelation occur, so low-temperature conditions are essential during storage and transportation to maintain performance stability.

Furthermore, U.S. Patent No. 4,329,275 (Patent Document 6) proposes a method using a platinum catalyst, a phosphorus compound, and an organic peroxide that does not contain a hydroperoxide group. Even with the composition proposed in this method, thickening and gelation occur when exposed to room temperature for long periods of time, so low-temperature conditions are essential during storage and transportation to ensure performance stability.

Recently, German Patent Application Publication No. 60316102T2 (Patent Document 7) describes a one-component organopolysiloxane gel composition made from a platinum catalyst, a phosphite triester, and an organic peroxide. The phosphite triester is tris(2,4-di-tert-butylphenyl) phosphite. It also proposes a method in which the amount of organic peroxide present is at least 2 equivalents based on the phosphite triester. Furthermore, Japanese Patent Publication No. 2018-503709 (Patent Document 8) proposes a method using tris(2,4-di-tert-butylphenyl) phosphite. However, these methods require the use of a hydrocarbon organic solvent such as xylene to dissolve tris(2,4-di-tert-butylphenyl) phosphite. This has led to the problem of hydrocarbon organic solvents being contained in the resulting silicone composition.

More recently, Japanese Patent Application Laid-Open No. 2021-042323 (Patent Document 9) proposes a method for improving storage stability by using a specific phosphite ester compound. While the method described in the above publication does dramatically improve storage stability, high temperatures of around 150°C are required to obtain a fully cured silicone product. Furthermore, due to the high hydrolysis potential of the phosphite ester compound, storage stability in air is poor.

Therefore, there is a demand for a platinum-phosphite complex-containing hydrosilylation catalyst that is free of hydrocarbon organic solvents and is liquid at 23°C. If such a catalyst could be obtained, it would be possible to obtain a one-part addition-curable silicone composition that is free of hydrocarbon organic solvents and has stable properties and physical characteristics. Therefore, there has been a growing demand for a platinum-phosphite complex-containing hydrosilylation catalyst that is free of hydrocarbon organic solvents and is liquid at 23°C.

Patent No. 2849027 Patent No. 4530147 European Patent Application Publication No. 2050768A1 U.S. Patent No. 6,706,840 U.S. Pat. No. 4,256,616 U.S. Patent No. 4,329,275 German Patent Application Publication No. 60316102T2 Special table 2018-503709 publication Japanese Patent Application Laid-Open No. 2021-042323

The present invention was made to solve these problems, and aims to provide a platinum-phosphite ester complex-containing hydrosilylation catalyst that is liquid at 23°C and has good storage stability, free of environmentally hazardous hydrocarbon organic solvents, and a method for producing the same. Another aim is to provide a hydrocarbon-free curable organopolysiloxane composition containing the catalyst that exhibits stable properties and physical characteristics even when exposed to room temperature (23°C ± 15°C) for extended periods of time, as well as an article comprising the cured product.

The present inventors have conducted extensive research to achieve the above object and have come to the following findings.
First, the following general formula (1)
(wherein ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).
A solution is prepared by dissolving a phosphite compound represented by the following general formula (1) in a hydrocarbon organic solvent having a boiling point of 80°C or less. To this solution, a platinum catalyst containing no hydrocarbon organic solvent is added, and the platinum catalyst is selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid, or a chloroplatinate salt and an alkenyl group-containing siloxane, and the mixture is dispersed and dissolved to prepare a solution containing a platinum-phosphite complex composed of platinum and the phosphite compound represented by the above general formula (1). To this complex solution, a platinum catalyst represented by the following general formula (2) is added.
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)
An organopolysiloxane compound having a unit represented by the formula (2) is added to the platinum-phosphite complex and dispersed and dissolved therein to prepare a solution containing an association of the platinum-phosphite complex and the siloxane compound represented by the formula (2). Further, acetylene alcohol is added to this association solution and dispersed therein to stabilize the platinum-phosphite complex and the association of the platinum-phosphite complex and the siloxane compound represented by the formula (2). The hydrocarbon organic solvent having a boiling point of 80°C or less is then removed from the solution to obtain the desired platinum-phosphite complex-containing hydrosilylation catalyst of the present invention, which is liquid at 23°C and does not contain any hydrocarbon organic solvent.
The present inventors also discovered that by using the platinum-phosphite complex-containing hydrosilylation catalyst obtained above, it is possible to obtain a one-component curable organopolysiloxane composition that does not contain a hydrocarbon organic solvent, and that the properties and physical characteristics of the resulting one-component curable organopolysiloxane composition remain stable even when exposed to room temperature for long periods of time, leading to the completion of the present invention.
In this specification, the term "one-component composition" refers to a composition in which all components are configured as one composition, and is also called "one-liquid type."

Accordingly, the present invention provides the following platinum-phosphite complex-containing hydrosilylation catalyst and method for producing the hydrosilylation catalyst. The present invention also provides a curable organopolysiloxane composition containing the hydrosilylation catalyst, and an article having a cured product thereof.
[1]
Platinum and the following general formula (1)
(In the formula, ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms.)
and a platinum-phosphite ester complex comprising a phosphite ester compound represented by the formula:
The following general formula (2)
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)
and an acetylene alcohol having a melting point of 35°C or less.
The platinum-phosphite complex-containing hydrosilylation catalyst is liquid at 23°C and does not contain any hydrocarbon organic solvent.
[2]
The platinum-phosphite complex-containing hydrosilylation catalyst according to [1], wherein the organopolysiloxane compound having a unit represented by general formula (2) is a cyclic organopolysiloxane compound.
[3]
The platinum-phosphite complex-containing hydrosilylation catalyst according to [1] or [2], wherein 0.01 to 100 mol % of the platinum-phosphite complex is associated with an organopolysiloxane compound having a unit represented by general formula (2).
[4]
The platinum-phosphite complex-containing hydrosilylation catalyst according to any one of [1] to [3], wherein the alkenyl group-containing siloxane compound further comprises at least one compound selected from the group consisting of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and linear dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups.
[5]
The platinum-phosphite complex-containing hydrosilylation catalyst according to any one of [1] to [4], wherein the acetylene alcohol has one ethynyl group and one hydroxy group per molecule.
[6]
The platinum-phosphite complex-containing hydrosilylation catalyst according to [1], wherein the organopolysiloxane compound having the unit represented by formula (2) is composed exclusively of the unit represented by formula (2) except for the molecular chain terminals.
[7]
The platinum-phosphite complex-containing hydrosilylation catalyst according to [1], wherein n in formula (2) is an integer of 4 to 10.
[ 8 ]
A curable organopolysiloxane composition containing only the platinum-phosphite complex-containing hydrosilylation catalyst according to any one of [1] to [ 7 ] as a curing catalyst .
[ 9 ]
The curable organopolysiloxane composition according to [ 8 ], which does not contain a hydrocarbon organic solvent.
[ 10 ]
An article comprising a cured product of the curable organopolysiloxane composition according to [ 8 ] or [ 9 ].
[ 11 ]
A method for producing a platinum-phosphite complex-containing hydrosilylation catalyst, comprising the following steps (a) to (e):
(a) preparing a solution of a phosphite ester compound represented by the following general formula (1) in a hydrocarbon organic solvent having a boiling point of 80°C or less;
(In the formula, ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms.)
(b) adding to the solution a platinum catalyst containing no hydrocarbon organic solvent, the platinum catalyst being selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid or a chloroplatinate salt and an alkenyl group-containing siloxane, and dispersing and dissolving the catalyst to prepare a solution containing a platinum-phosphite complex composed of platinum and the phosphite compound represented by the general formula (1);
(c) adding an organopolysiloxane compound having a unit represented by the following general formula (2) to the solution obtained in step (b), and dispersing and dissolving the compound to prepare a solution containing an association product of a platinum-phosphite ester complex and an organopolysiloxane compound having a unit represented by the following general formula (2);
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)
and,
(d) adding an acetylene alcohol having a melting point of 35°C or less to the solution obtained in step (c);
(e) A step of removing the hydrocarbon organic solvent having a boiling point of 80° C. or less from the solution obtained in the step (d).
[ 12 ]
The method for producing a platinum-phosphite complex-containing hydrosilylation catalyst according to [ 11 ], wherein 0.01 to 500 moles of an organopolysiloxane compound having a unit represented by general formula (2) are added per mole of platinum atoms in the platinum-phosphite complex.
[ 13 ]
The method for producing a platinum-phosphite complex-containing hydrosilylation catalyst according to [ 11 ] or [ 12 ], wherein 0.50 to 800 moles of acetylene alcohol are added per mole of platinum atom in the platinum-phosphite complex.

The platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is liquid at 23°C even without containing a hydrocarbon organic solvent, resulting in extremely stable catalyst properties. In addition, the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention contains acetylene alcohol, resulting in excellent storage stability as a catalyst. Therefore, when the catalyst is incorporated into a one-component curable organopolysiloxane composition, it can be easily and uniformly dispersed while remaining stable, resulting in a curable organopolysiloxane composition that is free of hydrocarbon organic solvents. The resulting one-component curable organopolysiloxane composition that is free of hydrocarbon organic solvents provides a composition with stable properties and physical characteristics even when exposed to room temperature for long periods of time. Furthermore, because it does not contain hydrocarbon organic solvents, it is possible to obtain a very safe cured product.

FIG. 1 shows ¹⁹⁵ Pt-NMR profiles for each step in the preparation of the platinum-phosphite complex-containing hydrosilylation catalyst of Example 1, where (a) is a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution, (b) is the result when a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution is added to a solution containing a phosphite compound, (c) is the result when a vicinal alkenyl group-containing organopolysiloxane compound is further added, and (d) is the result when acetylene alcohol is further added.

[Platinum-phosphite complex-containing hydrosilylation catalyst]
The platinum-phosphite ester complex-containing hydrosilylation catalyst of the present invention comprises platinum and a compound represented by the following general formula (1):
(wherein ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).
and a platinum-phosphite ester complex composed of a phosphite ester compound represented by the following general formula (2):
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)
and an acetylene alcohol having a melting point of 35°C or less, and the platinum-phosphite complex-containing hydrosilylation catalyst is liquid at 23°C and does not contain any hydrocarbon organic solvent.
In the present invention, a platinum-phosphite complex-containing hydrosilylation catalyst that is liquid at 23°C refers to a platinum-phosphite complex-containing hydrosilylation catalyst in which the platinum-phosphite complex and/or the phosphite compound are not crystallized (a state in which no crystallized components are present).

The platinum-phosphite ester complex-containing hydrosilylation catalyst of the present invention preferably contains a platinum-phosphite ester complex associated with an organopolysiloxane compound having units represented by general formula (2). In other words, the platinum-phosphite ester complex and the organopolysiloxane compound having units represented by general formula (2) preferably comprise an association of the platinum-phosphite ester complex and the platinum-phosphite ester complex with the siloxane compound represented by general formula (2), or more preferably comprise an association of the platinum-phosphite ester complex with the siloxane compound represented by general formula (2). Specifically, it is preferred that 0.01 to 100 mol %, and particularly 0.02 to 100 mol %, of the platinum-phosphite ester complex be associated with the organopolysiloxane compound having units represented by general formula (2). If the content is less than 0.01 mol%, the platinum-phosphite ester complex in the platinum-phosphite ester complex-containing hydrosilylation catalyst may crystallize and become cloudy during long-term storage. It is believed that an association complex is quantitatively and easily formed in accordance with the blending ratio between a platinum-phosphite ester complex and an organopolysiloxane compound having units represented by general formula (2) when the platinum-phosphite ester complex is dispersed or dissolved in the organopolysiloxane compound in a free (liquid) state and then contacted with the organopolysiloxane compound, and the presence of this association complex is believed to suppress crystallization of the platinum-phosphite ester complex (see Examples 1, 2, and 3 described below). In contrast, alkenyl-containing siloxane compounds other than organopolysiloxane compounds having units represented by general formula (2) are believed not to effectively form association complexes even when in contact with a platinum-phosphite ester complex (see Comparative Example 1 described below).

In the present invention, by further adding an acetylene alcohol with a melting point of 35°C or less to the platinum-phosphite complex-containing hydrosilylation complex, the complex state of the platinum-phosphite complex can be stabilized, and the association state of the association between the platinum-phosphite complex and the organopolysiloxane compound having units represented by general formula (2) can be stabilized, thereby improving the storage stability of the catalyst.

It is preferable that 0.01 to 100 mol %, and particularly 1.0 to 100 mol %, of the platinum-phosphite complex component contained in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention be stabilized with the above-mentioned acetylene alcohol. If less than 0.01 mol %, the expected improvement in storage stability may not be achieved when used in a composition.

<Platinum-phosphite complex>
The platinum-phosphite complex contained in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is composed of platinum and a phosphite compound represented by the general formula (1) described below.

[Phosphite ester compounds]
In the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention, the phosphite compound represented by the following general formula (1) contained as the platinum-phosphite complex is an essential component, and by forming a complex with platinum (platinum-phosphite complex), it is possible to significantly improve the storage stability of the properties and physical properties of the curable organopolysiloxane composition containing the catalyst of the present invention.
(wherein ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).

In the above formula (1), R ¹ is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms, preferably a monovalent aliphatic hydrocarbon group having 1 or 2 carbon atoms, and more preferably a methyl group.

Specific examples of the phosphite compound represented by the above formula (1) include phosphite compounds in which R 1 has the same number of carbon atoms, such as tris(2,4-dimethylphenyl)phosphite, tris(2,4-di-tert-butylphenyl)phosphite, tris(2,4-bis(3-ethylpentan-3-yl)phenyl)phosphite, and tris(2,4-bis(4-propylheptan-4-yl)phenyl)phosphite, as well as phosphite compounds in which R ¹ has a different number of carbon atoms, such as tris(4-(tert-butyl)-2-methylphenyl)phosphite, tris(4-(tert-butyl)-2-ethylphenyl)phosphite, tris(2-(tert-butyl)-4-(3-ethylpentan-3-yl)phenyl)phosphite, and ^tris (2-(tert-butyl)-4-(3-methylhexan-3-yl)phenyl)phosphite. Among these, it is particularly preferable to use tris(2,4-di-tert-butylphenyl)phosphite, which is easily available and has excellent storage stability.

In the platinum-phosphite complex, the phosphite compound represented by the general formula (1) is preferably present in an amount of more than 0.6 moles but not more than 1.9 moles, and preferably 0.8 to 1.5 moles, per mole of platinum atom. At 0.6 moles or less, the resulting curable organopolysiloxane composition containing the platinum-phosphite complex-containing hydrosilylation catalyst may exhibit poor storage stability or gelation. Furthermore, at an amount exceeding 1.9 moles, the platinum-phosphite complex in the resulting platinum-phosphite complex-containing hydrosilylation catalyst may crystallize at room temperature (23°C ± 15°C, the same applies hereinafter), potentially preventing it from remaining liquid (liquid phase).

<Alkenyl Group-Containing Siloxane Compound>
The alkenyl group-containing siloxane compound contained in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is liquid at 23°C and contains an organopolysiloxane compound having a unit represented by general formula (2) described below.

[Organopolysiloxane Compound]
The organopolysiloxane compound contained in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is characterized by having a unit represented by the following general formula (2): This is an essential component that, by associating with the platinum-phosphite complex, prevents the platinum-phosphite complex in the platinum-phosphite complex-containing hydrosilylation catalyst from crystallizing at room temperature.
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)

The organopolysiloxane compound having the bifunctional siloxane unit represented by the above general formula (2) has n of 2 or more (i.e., has two or more bifunctional siloxane units represented by [(R ² )(R ³ )SiO _2/2 ]), and therefore is an organopolysiloxane having two or more alkenyl groups (hereinafter sometimes referred to as adjacent alkenyl groups) in the molecule bonded to each of the silicon atoms at non-terminal positions (in the middle of the molecular chain) present in adjacent bifunctional siloxane units via ether oxygen atoms that form siloxane bonds (Si—O—Si).
It is preferable that the organopolysiloxane compound having units represented by the general formula (2) be composed solely of units represented by the formula (2) other than the molecular chain terminals (triorganosiloxy units or diorganohydroxysiloxy units).

In the above formula (2), ^R2 is an alkenyl group having 2 to 10 carbon atoms, preferably an alkenyl group having 2 to 4 carbon atoms (such as a vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, or isobutenyl group), and more preferably a vinyl group.
In the above formula (2), ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, preferably a monovalent saturated aliphatic hydrocarbon group (alkyl group) having 1 to 4 carbon atoms, and more preferably a methyl group.
In the formula (2), n is an integer of 2 to 200, preferably an integer of 3 to 100, more preferably an integer of 4 to 40, and even more preferably an integer of 4 to 10.

The terminals of the organopolysiloxane compound having the bifunctional siloxane unit represented by the general formula (2) are not particularly limited. For example, when the organopolysiloxane compound is linear or branched, the molecular chain terminals may be silanol group-containing siloxy groups (diorganohydroxysiloxy groups) or triorganosiloxy groups such as trimethylsiloxy groups or dimethylvinylsiloxy groups. Furthermore, when the organopolysiloxane compound is cyclic, there are no molecular chain terminals.
The organopolysiloxane compound having two or more adjacent alkenyl groups each having a unit represented by general formula (2) is a component that prevents crystallization of the platinum-phosphite ester complex by associating with the platinum-phosphite ester complex. Therefore, when the compound is dispersed or mixed with the platinum-phosphite ester complex and brought into contact with the platinum-phosphite ester complex, it must be in a liquid state in which the molecules are individually free.

Specific examples of the organopolysiloxane compound include organoalkenylcyclopolysiloxanes such as 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (the organo group here means an alkyl group), vicinal alkenyl group-containing cyclic polysiloxanes such as organoalkenylsiloxane-diorganosiloxane cyclic copolymers (same as above), and vicinal alkenyl group-containing siloxane polymers (vicinal alkenyl group-containing linear methylvinylpolysiloxanes) obtained by linear ring-opening polymerization of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane via an equilibration reaction. As mentioned above, there are no particular restrictions on the terminals of the vicinal alkenyl group-containing siloxane polymer (vicinal alkenyl group-containing linear methylvinylpolysiloxane) that has been linearly ring-opening polymerized by an equilibration reaction, but polymers containing trimethylsiloxy groups, silanol group-containing siloxy groups (dimethylhydroxysiloxy groups), or dimethylvinylsiloxy groups are preferably used.
Among these, the organopolysiloxane compound having a unit represented by the above general formula (2) is preferably a cyclic organopolysiloxane compound (organocyclopolysiloxane compound) that can reduce the viscosity of the platinum-phosphite complex-containing hydrosilylation catalyst itself.

The amount of organopolysiloxane compound having units represented by general formula (2) is preferably 0.01 to 500 moles per mole of platinum atoms in the platinum-phosphite complex, more preferably 0.02 to 200 moles, even more preferably 0.03 to 100 moles, and most preferably 0.05 to 50 moles. If the amount is less than 0.01 mole, the platinum-phosphite complex in the platinum-phosphite complex-containing hydrosilylation catalyst may crystallize at room temperature, making it unable to retain liquid, or may cause problems such as poor dispersibility and reduced blending workability when the catalyst is blended into a curable organopolysiloxane composition. Furthermore, if the amount exceeds 500 moles, the effective platinum amount of the platinum-phosphite complex-containing hydrosilylation catalyst itself will decrease, and therefore, when preparing a curable organopolysiloxane composition incorporating this catalyst, an extremely large amount will need to be incorporated. This will increase the amount of organopolysiloxane compound having a unit represented by general formula (2) added, increasing the likelihood of problems such as reduced mechanical properties and reduced curability.

[Other alkenyl group-containing siloxane compounds]
The alkenyl group-containing siloxane compound may include an alkenyl group-containing siloxane compound other than the organopolysiloxane compound having the unit represented by the general formula (2). Examples include vinyl group-containing disiloxanes such as 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3-diallyl-1,1,3,3-tetramethyldisiloxane, 1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane, and 1,3-divinyl-1,1,3,3-tetraphenyldisiloxane, as well as linear dimethylpolysiloxanes capped at both molecular chain ends with dimethylvinylsiloxy groups. Examples of such vinyl group-containing disiloxanes include those blended with the platinum catalyst used to prepare the platinum-phosphite complex in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention.

The content of alkenyl group-containing siloxane compounds other than organopolysiloxane compounds having units represented by general formula (2) is preferably 0 to 5.0% by mass, and more preferably 0 to 3.0% by mass, of the alkenyl group-containing siloxane compounds. If the content of this compound is too high, the purity of the organopolysiloxane compounds having units represented by general formula (2) will decrease, and the platinum-phosphite complex in the platinum-phosphite complex-containing hydrosilylation catalyst may crystallize and become cloudy during long-term storage.

<Acetylene alcohol>
The acetylene alcohol contained in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is an essential component for stabilizing the platinum-phosphite complex and the association between the platinum-phosphite complex and the alkenyl group-containing siloxane compound.
The acetylene alcohol is characterized by having a melting point of 35°C or lower. Among these, those having one ethynyl group having a carbon-carbon triple bond and one hydroxy group, which is an alcoholic hydroxyl group, per molecule are preferred. In addition, considering that the platinum-phosphite ester complex and the association of the platinum-phosphite ester complex with the alkenyl group-containing siloxane compound are liquids at 23°C, the melting point of the acetylene alcohol must be 35°C or lower.

Specific examples of acetylene alcohols used in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention include 1-ethynyl-1-cyclohexanol (melting point: 30°C), 3-methyltridec-1-yn-3-ol (melting point: no information, liquid at 20°C), 3-butyn-1-ol (melting point: -63.6°C), 2-methyl-3-butyn-2-ol (melting point: 2.6°C), and 3-methyl-1-pentadecyn-3-ol (melting point: no information, liquid at 20°C). Of these, 1-ethynyl-1-cyclohexanol (melting point: 30°C) and 3-methyltridec-1-yn-3-ol (melting point: no information, liquid at 20°C) are more preferred. These may be used alone or in combination.

The content of acetylene alcohol used in the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is preferably 0.50 to 800 moles, and more preferably 1.0 to 500 moles, per mole of platinum atom in the platinum-phosphite complex. If the acetylene alcohol content is too high, the resulting platinum-phosphite complex-containing hydrosilylation catalyst may separate or form a precipitate, making it difficult to obtain a catalyst with uniform properties. Conversely, if the acetylene alcohol content is too low, it will take time to stabilize the resulting platinum-phosphite complex-containing hydrosilylation catalyst, which will cause variations in the storage stability of one-component curable organopolysiloxane compositions using this catalyst.

The platinum-phosphite complex-containing hydrosilylation catalyst of the present invention does not contain a hydrocarbon organic solvent. Hydrocarbon organic solvents are compounds consisting only of carbon and hydrogen, and examples thereof include the hydrocarbon organic solvents used to dissolve the phosphite compounds used in the method for producing the platinum-phosphite complex-containing hydrosilylation catalyst described below. Because hydrocarbon organic solvents are compounds consisting only of carbon and hydrogen, they do not include acetylene alcohols with melting points of 35°C or below, or vinyl-containing siloxanes with approximately 2 to 4 silicon atoms, such as tetramethyldivinyldisiloxane, trimethyltrivinylcyclotrisiloxane, and tetramethyltetravinylcyclotetrasiloxane. "Doing without a hydrocarbon organic solvent" means that the content of the hydrocarbon organic solvent is 1.0% by mass or less.

[Method for producing a platinum-phosphite complex-containing hydrosilylation catalyst]
The platinum-phosphite complex-containing hydrosilylation catalyst described above can be produced stably through the following five steps.
(a) preparing a solution of the phosphite compound represented by the general formula (1) in a hydrocarbon organic solvent having a boiling point of 80°C or less;
(b) adding to the solution a platinum catalyst containing no hydrocarbon organic solvent, the platinum catalyst being selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid or a chloroplatinate salt and an alkenyl group-containing siloxane, and dispersing and dissolving the catalyst to prepare a solution containing a platinum-phosphite complex composed of platinum and the phosphite compound represented by the general formula (1);
(c) adding an organopolysiloxane compound having a unit represented by the general formula (2) to the solution obtained in the step (b), and dispersing and dissolving the compound to prepare a solution containing an association product of a platinum-phosphite ester complex and an organopolysiloxane compound having a unit represented by the general formula (2); and
(d) adding an acetylene alcohol having a melting point of 35°C or less to the solution obtained in step (c);
(e) A step of removing the hydrocarbon organic solvent having a boiling point of 80° C. or less from the solution obtained in the step (d).

Each step will be described in detail below.
First step: (a)
The first step is to prepare a solution in which a phosphite compound represented by the following general formula (1) is dissolved in a hydrocarbon organic solvent having a boiling point of 80° C. or less.
(wherein ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).

This is an essential step for quickly forming a complex with the platinum added in the subsequent step, as many phosphite ester compounds represented by general formula (1) are solid at room temperature.

[Phosphite ester compounds]
The phosphite ester compound represented by the general formula (1) is as described above, and among them, it is particularly preferable to use tris(2,4-di-tert-butylphenyl)phosphite, which is easily available and has excellent storage stability.

[Hydrocarbon-based organic solvent having a boiling point of 80°C or less]
The phosphite ester compound represented by the general formula (1) is often a solid at room temperature. Therefore, when the phosphite ester compound is mixed with a platinum catalyst (described later) to form a platinum-phosphite ester complex in the second step, the phosphite ester compound must be dissolved in a hydrocarbon organic solvent having a boiling point of 80°C or lower to form a solution. As mentioned above, hydrocarbon organic solvents are compounds consisting only of carbon and hydrogen, and therefore the acetylene alcohol used in the present invention, which has a melting point of 35°C or lower, does not fall under this category.

Hydrocarbon organic solvents with a boiling point of 80°C or less are primarily composed of linear or branched saturated hydrocarbons, preferably linear or branched saturated hydrocarbons. Specific examples of hydrocarbon organic solvents with a boiling point of 80°C or less include n-pentane (boiling point: 36°C), n-hexane (boiling point: 68°C), 2-methylbutane (boiling point: 30°C), 2,2-dimethylbutane (boiling point: 50°C), 2,3-dimethylbutane (boiling point: 58°C), 2-methylpentane (boiling point: 62°C), and 3-methylpentane (boiling point: 63°C). Among these, n-hexane (boiling point: 68°C) is particularly suitable for industrial use, as it is relatively easy to handle and easily removed in the subsequent removal process.

The reason a boiling point of 80°C or lower is required is that, in the hydrocarbon organic solvent removal step described below, it is preferable to remove the solvent by vacuum distillation. By setting the vacuum distillation temperature at 50°C or lower, the hydrocarbon organic solvent can be removed, making it possible to obtain a stable platinum-phosphite complex-containing hydrosilylation catalyst. In the case of hydrocarbon organic solvents with boiling points above 80°C, the vacuum distillation temperature must be above 50°C in order to completely remove the used hydrocarbon organic solvent. This can result in residual hydrocarbon organic solvent remaining in the platinum-phosphite complex-containing hydrosilylation catalyst, or the platinum-phosphite complex-containing hydrosilylation catalyst decomposing due to the thermal history of the solvent removal step, resulting in the precipitation of crystals.

The amount of hydrocarbon organic solvent with a boiling point of 80°C or less used is not particularly limited, but it is preferably 100 to 10,000 parts by mass, and particularly 1,000 to 5,000 parts by mass, per 100 parts by mass of the phosphite ester compound represented by general formula (1).

The temperature at which the phosphite compound represented by general formula (1) is dissolved in the hydrocarbon organic solvent is preferably 40° C. or lower, more preferably in the range of 0 to 35° C. If the phosphite compound is dissolved at a temperature exceeding 40° C., the phosphite compound is likely to be hydrolyzed by the water contained in the hydrocarbon organic solvent. As a result, the phosphite compound is likely to be converted to a phosphate ester compound, and the stability of the resulting catalyst is reduced.
The dissolution time is not particularly limited as long as the phosphite ester compound represented by general formula (1) is dissolved in the hydrocarbon organic solvent, and specifically, it is about 10 minutes to 24 hours. As for the container for dissolution, it is preferable to select a container that can block oxygen.

Second step: (b)
The second step is a step of adding a platinum catalyst containing no hydrocarbon organic solvent, selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid, or a chloroplatinate salt and an alkenyl group-containing siloxane, to the solution obtained in step (a), and dispersing and dissolving the catalyst to prepare a solution containing a platinum-phosphite complex composed of platinum and the phosphite compound represented by the general formula (1) above.

[Platinum catalyst]
The platinum catalyst used as an intermediate raw material in the preparation of the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is a platinum catalyst containing no hydrocarbon organic solvent, selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid, or a chloroplatinate salt and an alkenyl group-containing siloxane. This platinum catalyst is typically itself a curing catalyst contained in an addition-curable silicone composition, which contributes to the hydrosilylation addition reaction between alkenyl groups in the alkenyl group-containing organopolysiloxane base polymer and hydrosilyl groups in the organohydrogenpolysiloxane crosslinker.

In the present invention, the platinum catalyst is further dispersed and dissolved in a solution containing the phosphite ester compound represented by the general formula (1) described above. This results in a platinum-phosphite ester complex-containing hydrosilylation catalyst, which contains a platinum-phosphite ester complex composed of platinum and the phosphite ester compound represented by the general formula (1), and is used as a curing catalyst for an addition-curable silicone composition. This significantly improves the storage stability of the properties and physical characteristics of the target curable organopolysiloxane composition.

Among the platinum catalysts serving as intermediate raw materials, examples of the alkenyl group-containing siloxane in the platinum-alkenyl group-containing siloxane complex include 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3-diallyl-1,1,3,3-tetramethyldisiloxane, 1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane, 1,3-divinyl-1,1,3,3-tetraphenyldisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, and 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane. Examples of the structures of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane, and 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane are shown below.

In a platinum catalyst containing no hydrocarbon organic solvent _, the platinum catalyst is selected from one or more platinum-alkenyl group-containing siloxane complexes formed from a platinum compound selected from platinum chloride (PtCl ₄ ), chloroplatinic acid (H ₂ PtCl ₆ ), and chloroplatinic acid salt _(H 2 PtCl 6 .6H ₂ O) and an alkenyl group-containing siloxane such as a vinyl group-containing siloxane. Specific examples of the platinum-alkenyl group-containing siloxane complex include platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (Karstedt complex), platinum-1,3-diallyl- Examples of suitable platinum catalysts include 1,1,3,3-tetramethyldisiloxane complex, platinum-1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane complex, platinum-1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane complex, platinum-1,3-divinyl-1,1,3,3-tetraphenyldisiloxane complex, and platinum-1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane complex. The platinum-alkenyl group-containing siloxane complex is preferably at least one selected from these groups, and it is essential that the complex does not contain a hydrocarbon organic solvent. Among the platinum catalysts listed above, it is particularly preferred to use a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (Karstedt complex).

A preferred platinum catalyst, platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex (Karstedt complex), is believed to have the following structure:

The platinum catalysts shown here must be free of basic hydrocarbon organic solvents, such as aromatic hydrocarbon organic solvents such as toluene and xylene, and alcohol organic solvents such as ethanol, n-butanol, and 2-ethylhexyl alcohol, due to concerns that these may have adverse effects on the human body.

This hydrocarbon organic solvent-free platinum catalyst, selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid, or chloroplatinate salts and alkenyl group-containing siloxanes, is preferably in the form of a silicone solution using as a diluent (solvent) an alkenyl group-containing organopolysiloxane (typically a linear organopolysiloxane end-capped with vinyldiorganosiloxy groups at both molecular chain terminals and having no adjacent alkenyl groups in the molecule, such as a linear dimethylpolysiloxane end-capped with dimethylvinylsiloxy groups) that is the same or different from the alkenyl group-containing siloxane that forms the ligand of the platinum-alkenyl group-containing siloxane complex. The platinum atom content of this solution is preferably 0.001 to 0.010 mol %. Converting this to mass %, the amount of platinum (mass concentration) contained in the silicone solution is approximately 0.2 to 2.0 mass %. Within this range, the stability of the platinum-alkenyl group-containing siloxane complex can be improved.

The optimum ratio of the platinum catalyst and phosphite ester compound is greater than 0.6 molecules and less than 1.9 molecules of phosphite ester compound per platinum atom in the platinum catalyst. A ratio of 0.8 molecules to 1.5 molecules of phosphite ester compound per platinum atom in the platinum catalyst is more desirable. If the ratio of phosphite ester compound is 0.6 molecules or less per platinum atom in the platinum catalyst, the resulting curable organopolysiloxane composition containing the platinum-phosphite ester complex-containing hydrosilylation catalyst may have poor storage stability or may be at high risk of gelation. On the other hand, if the ratio of phosphite ester compound is greater than 1.9 molecules per platinum atom in the platinum catalyst, the platinum-phosphite ester complex-containing hydrosilylation catalyst may not be able to remain liquid at 23°C in the subsequent step. The reason for this is believed to be that even if the platinum-phosphite ester complex obtained in this step is associated with the organopolysiloxane compound, the platinum-phosphite ester complex in the resulting platinum-phosphite ester complex-containing hydrosilylation catalyst is likely to precipitate. Furthermore, when the platinum-phosphite ester complex-containing hydrosilylation catalyst is blended into a curable organopolysiloxane composition, problems such as poor dispersibility and reduced blending workability may occur.

In this process, there are no particular limitations on the method of adding the platinum catalyst. It may be added all at once, or added dropwise.

In this step, the dispersion and dissolution of the platinum catalyst is preferably carried out at a temperature of 40°C or less, particularly 0 to 35°C, for 30 minutes or more, particularly 30 minutes to 4 hours. As with the first step, it is preferable to select a container that can block oxygen for this step, and the container used in the first step can be used as is.

By dispersing and dissolving under the above conditions, a platinum-phosphite ester complex composed of platinum and the phosphite ester compound represented by the above general formula (1) is formed.

Third step: (c)
The third step is a step of adding an organopolysiloxane compound having a unit represented by the following general formula (2) to the solution obtained in step (b), and dispersing and dissolving the compound to prepare a solution containing an association product of a platinum-phosphite ester complex and an organopolysiloxane compound having a unit represented by the following general formula (2):
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)

The present invention associates at least a portion of a platinum-phosphite ester complex with an organopolysiloxane compound having units represented by the general formula (2) above, thereby obtaining a platinum-phosphite ester complex-containing hydrosilylation catalyst that is liquid at 23°C without containing a hydrocarbon organic solvent and has excellent dispersibility and property stability. Furthermore, when this platinum-phosphite ester complex-containing hydrosilylation catalyst is used as a curing catalyst in an addition-curable silicone composition, it provides a composition that has stable properties and physical characteristics even when exposed to room temperature for long periods of time, and it is possible to create a composition that does not contain a hydrocarbon organic solvent.

Here, the organopolysiloxane compound having units represented by general formula (2) is as described above. The organopolysiloxane compound having units represented by general formula (2) is a component that associates with a platinum-phosphite ester complex to prevent the platinum-phosphite ester complex from crystallizing. The organopolysiloxane compound is characterized by the fact that, although it associates with the complex, the molecules are in a liquid state in which they are individually free. In this respect, it differs from alkenyl-group-containing siloxanes, such as vinyl-group-containing siloxanes, which serve as ligands that form complexes with platinum atoms in the platinum catalyst.

In the step (b), when the alkenyl-containing siloxane, such as the vinyl-containing siloxane, which is a ligand in the platinum catalyst, is liberated from the platinum-phosphite ester complex, the following may occur depending on the structure of the liberated alkenyl-containing siloxane, such as the vinyl-containing siloxane.
First, if the released alkenyl-containing siloxane, such as a vinyl-containing siloxane, is an alkenyl-containing siloxane, such as a vinyl-containing siloxane, other than an organopolysiloxane compound having a unit represented by general formula (2), it is believed that the alkenyl-containing siloxane, such as a vinyl-containing siloxane, will not associate with the platinum-phosphite complex, as described above. Therefore, by mixing and contacting the alkenyl-containing siloxane with an organopolysiloxane compound having a unit represented by general formula (2) in this step, it is possible to reliably form an association with the platinum-phosphite complex.
On the other hand, when the liberated alkenyl-group-containing siloxane, such as a vinyl-group-containing siloxane, corresponds to an organopolysiloxane compound having units represented by general formula (2), it is believed that the alkenyl-group-containing siloxane, such as a vinyl-group-containing siloxane, can also form an association with the platinum-phosphite complex. In this case, the role of this step is to prepare a platinum-phosphite complex, and then mix and contact it with an organopolysiloxane compound having units represented by general formula (2), thereby more reliably forming an association with the platinum-phosphite complex.

The amount of organopolysiloxane compound having units represented by general formula (2) used is preferably in the range of 0.01 to 500 moles, particularly 0.02 to 50 moles, per mole of platinum atom in the platinum-phosphite ester complex obtained in the previous step. If the amount of organopolysiloxane compound having units represented by general formula (2) per mole of platinum atom in the platinum-phosphite ester complex is less than 0.01 mole, the amount of organopolysiloxane compound having units represented by general formula (2) associated per mole of platinum atom will be very small. As a result, it becomes difficult to maintain liquid properties at 23°C, and crystals will precipitate. This can lead to problems such as poor dispersibility and reduced compounding workability when attempting to incorporate the catalyst into a curable organopolysiloxane composition. Furthermore, if the amount of organopolysiloxane compound having units represented by general formula (2) exceeds 500 moles per mole of platinum atoms in the platinum-phosphite complex, the viscosity of the resulting platinum-phosphite complex-containing hydrosilylation catalyst will be significantly affected, which may result in problems such as reduced workability when compounding the catalyst.

In this process, there are no particular limitations on the method for adding the organopolysiloxane compound having units represented by the general formula (2) above. It may be added all at once, or added dropwise. However, because adding dropwise takes time, adding it all at once or adding it is preferable.

In this step, dispersion and dissolution are preferably carried out at a temperature of 40°C or less, particularly 0 to 35°C, for 60 minutes or more, and particularly 60 minutes to 24 hours. Dispersion and dissolution under the above conditions allows for the production of an association of at least a portion of the platinum-phosphite ester complex with an organopolysiloxane compound having a unit represented by general formula (2). As with the first and second steps, it is preferable to select a container for this step that can block oxygen, and the container used in the first or second step can be used as is.

By dispersing and dissolving under the above conditions, a solution containing an association of the platinum-phosphite ester complex with an organopolysiloxane compound having units represented by the above general formula (2) can be prepared.

Fourth step: (d)
The fourth step is to add an acetylene alcohol having a melting point of 35°C or lower to the solution obtained in step (c), and by dispersing the acetylene alcohol, it is possible to stabilize the complex state of the platinum-phosphite ester complex in the solution and the association state of the association product of the platinum-phosphite ester complex and the organopolysiloxane compound having a unit represented by general formula (2). Such an acetylene alcohol has a boiling point of more than 80°C, preferably 100°C or higher.

The amount of acetylene alcohol used is preferably 0.50 to 800 moles, and particularly 1.0 to 500 moles, per mole of platinum atom in the platinum-phosphite ester complex obtained in the previous step. Using less than 0.50 moles of acetylene alcohol per mole of platinum atom in the platinum-phosphite ester complex is undesirable because the storage stability of one-component curable organopolysiloxane compositions using that catalyst will vary. Furthermore, using more than 800 moles of acetylene alcohol may result in separation or precipitate formation in the resulting platinum-phosphite ester complex-containing hydrosilylation catalyst, making it difficult to obtain a uniform catalyst.

In this process, there are no particular limitations on the method of adding acetylene alcohol. It can be added all at once, or added dropwise. However, because adding dropwise takes time, adding it all at once or adding it is preferable.

In this step, the addition and dispersion are preferably carried out at a temperature of 40°C or below, particularly 0 to 35°C, for 10 minutes or longer, and particularly 30 to 400 minutes. Addition and dispersion under the above conditions provides the resulting platinum-phosphite complex-containing hydrosilylation catalyst with excellent storage stability and property stability, and when added to a composition, dramatically improves the storage stability of the composition. As with steps 1, 2, and 3, it is preferable to select a container for this step that can block oxygen; the container used in steps 1, 2, or 3 can be used as is.

Fifth step: (e)
The fifth step is a step of removing the hydrocarbon organic solvent having a boiling point of 80° C. or lower from the solution obtained in the previous step (d). This step is an essential step for removing the hydrocarbon organic solvent having a boiling point of 80° C. or lower from the solution obtained in steps (a) to (d) and obtaining a platinum-phosphite complex-containing hydrosilylation catalyst that is free of hydrocarbon organic solvents.

The solvent removal method used here is preferably a vacuum distillation method in which the solvent is distilled off under reduced pressure at low temperatures to avoid reactivating the platinum-phosphite complex-containing hydrosilylation catalyst stabilized in the previous step. The vacuum distillation temperature in this vacuum removal step must be 50°C or lower, preferably 0 to 45°C, to obtain a stable platinum-phosphite complex-containing hydrosilylation catalyst. The vacuum distillation time is not particularly limited, but is preferably 30 minutes to 4 hours. Furthermore, while the pressure varies depending on the boiling point of the hydrocarbon organic solvent used, a pressure of 50 hPa or lower, preferably 1 to 30 hPa, allows for complete removal of the hydrocarbon organic solvent used. It is preferable that these conditions are such that the acetylene alcohol added in the fourth step is not removed.

Whether the hydrocarbon organic solvent used has been completely removed can be confirmed by checking the mass ratio of the total mass of the phosphite ester compound, platinum catalyst, siloxane compound, and acetylene alcohol used to the mass of the platinum-phosphite ester complex-containing hydrosilylation catalyst obtained after completion of the fifth step. If the mass of the resulting platinum-phosphite ester complex-containing hydrosilylation catalyst is greater than the total mass of the phosphite ester compound, platinum catalyst, siloxane compound, and acetylene alcohol used, residual hydrocarbon organic solvent remains, and complete removal of the hydrocarbon organic solvent can be achieved by adding additional time to this step.

The present invention associates at least a portion of a platinum-phosphite ester complex with an organopolysiloxane compound having units represented by the general formula (2) above, resulting in a liquid at 23°C. Adding the acetylene alcohol then yields a platinum-phosphite ester complex-containing hydrosilylation catalyst with even better dispersibility and property stability. When this platinum-phosphite ester complex-containing hydrosilylation catalyst is used as a curing catalyst in an addition-curable silicone composition, it provides a composition with more stable properties and physical characteristics, even when exposed to room temperature for long periods of time, and it is possible to create a composition that does not contain hydrocarbon organic solvents.

[Curable organopolysiloxane composition containing a platinum-phosphite complex-containing hydrosilylation catalyst]
The platinum-phosphite complex-containing hydrosilylation catalyst described above can be used in applications such as curing catalysts for various resins and purification catalysts, but its characteristics are particularly apparent when used as a curing catalyst for one-component (one-liquid) addition reaction-curable curable organopolysiloxane compositions that undergo a hydrosilylation reaction to form silicone resins (silicone rubber or silicone gel). Furthermore, it is preferable that the curable organopolysiloxane composition does not contain hydrocarbon organic solvents, which have a significant environmental impact.

The reasons for this are mainly the following four points.
(1) When heated, it has curability substantially equivalent to that of a platinum catalyst selected from one or more of the platinum compounds selected from platinum chloride, chloroplatinic acid, and chloroplatinate salts, which have been conventionally used, and platinum-alkenyl group-containing siloxane complexes formed from alkenyl group-containing siloxanes such as vinyl group-containing siloxanes, and acetylene alcohols.
(2) When stored at room temperature, the phosphite ester compound forms a complex with platinum, suppressing catalytic activity and causing the hydrosilylation reaction to proceed very slowly. As a result, the properties and physical properties of the resulting curable organopolysiloxane composition are stable even when exposed to room temperature for long periods of time.
(3) By associating at least a portion of the platinum-phosphite complex with an organopolysiloxane compound having a unit represented by general formula (2), it becomes possible to maintain the state of the resulting platinum-phosphite complex-containing hydrosilylation catalyst in a liquid state at 23°C.
(4) The platinum-phosphite ester complex and the associated complex of the platinum-phosphite ester complex with an organopolysiloxane compound having a unit represented by general formula (2) are stabilized with acetylene alcohol. This enhances the stability of the resulting platinum-phosphite ester complex-containing hydrosilylation catalyst, further improving the reactivity of the catalyst itself. Furthermore, the production stability of the platinum-phosphite ester complex-containing hydrosilylation catalyst can also be improved.

For the reasons stated above, using the platinum-phosphite ester complex-containing hydrosilylation catalyst of the present invention in a curable organopolysiloxane composition has the advantages of improving workability and facilitating uniform dispersion.

Here, the curable organopolysiloxane composition that is particularly preferred is a one-component, addition-reaction-type organopolysiloxane composition that uses an organopolysiloxane containing alkenyl groups as the base polymer and blends an organohydrogenpolysiloxane that has a hydrogen atom bonded to a silicon atom (i.e., a hydrosilyl group) as the curing agent (crosslinking agent).

When the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is incorporated into a curable organopolysiloxane composition, the amount incorporated is preferably 0.1 to 1,000 ppm, more preferably 1 to 500 ppm, and even more preferably approximately 5 to 300 ppm, calculated as the mass of platinum atoms in the platinum-phosphite complex-containing hydrosilylation catalyst relative to the total composition. Furthermore, when the platinum-phosphite complex-containing hydrosilylation catalyst is used in the form of a catalyst solution, such as a silicone solution containing a solvent other than a hydrocarbon organic solvent, such as an alkenyl-terminated organopolysiloxane (alkenyl-terminated silicone oil), for example, when the platinum-phosphite complex-containing hydrosilylation catalyst solution has a platinum atom concentration of 1 mass %, the amount of the catalyst solution blended is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.05 to 3 parts by mass, per 100 parts by mass of the alkenyl group-containing organopolysiloxane (base polymer). If the amount of platinum-phosphite complex-containing hydrosilylation catalyst solution (1 mass % platinum atoms) blended is less than 0.001 part by mass (or the mass of platinum atoms relative to the total composition is less than 0.1 ppm), the strength of the cured product of the resulting curable organopolysiloxane composition may be reduced, or the curing may be insufficient. Conversely, if the amount of platinum-phosphite complex-containing hydrosilylation catalyst solution (1 mass % platinum atoms) exceeds 10 parts by mass (or 1,000 ppm platinum atom mass), the resulting curable organopolysiloxane composition will become discolored, the time until curing will be shortened, and the composition will be unaffordable. The activity of the catalyst, i.e., the curability, can be controlled by increasing or decreasing the concentration of the platinum-phosphite complex-containing hydrosilylation catalyst added.

The curable organopolysiloxane composition of the present invention may be exemplified by the following one-component millable silicone rubber composition.
(A) 100 parts by mass of a linear diorganopolysiloxane gum having at least two silicon-bonded alkenyl groups per molecule and an average degree of polymerization of 100 or more;
(B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule: 0.01 to 50 parts by mass;
(C) reinforcing silica having a specific surface area of 50 m ² /g or more: 5 to 100 parts by mass,
(D) The platinum-phosphite complex-containing hydrosilylation catalyst of the present invention: 0.001 to 10 parts by mass

-(A) Linear diorganopolysiloxane raw rubber-
The linear diorganopolysiloxane gum of component (A) is the main component (base polymer) of the composition, and contains at least two, preferably 2 to 10,000, and more preferably 2 to 500 silicon-bonded alkenyl groups per molecule, with an average degree of polymerization of 100 or greater.

The component (A) is preferably one represented by the following average composition formula (I).
R ¹¹ _n1 SiO _(4-n1)/2 (I)
(In formula (I), R ¹¹ are each independently the same or different monovalent hydrocarbon groups having 1 to 20 carbon atoms, and n1 is a positive number of 1.95 to 2.04.)

In the above average composition formula (I), R ¹¹ is the same or different monovalent hydrocarbon group having 1 to 20 carbon atoms, preferably 1 to 12, and more preferably 1 to 8 carbon atoms. Examples of the monovalent hydrocarbon group represented by ^{R 11} include alkyl groups such as methyl, ethyl, propyl, and butyl; cycloalkyl groups such as cyclohexyl; alkenyl groups such as vinyl, allyl, butenyl, and hexenyl; aryl groups such as phenyl and tolyl; and aralkyl groups such as β-phenylpropyl. Some or all of the hydrogen atoms bonded to the carbon atoms of these groups may be substituted with halogen atoms, such as 3,3,3-trifluoropropyl. Of these, methyl, vinyl, phenyl, and trifluoropropyl groups are preferred, and methyl and vinyl groups are more preferred. Among these, it is particularly preferred that 50 mol % or more of the monovalent hydrocarbon groups represented by R ¹¹ in the molecule are methyl groups, more preferably 80 mol % or more of the monovalent hydrocarbon groups represented by R 11, and particularly preferably 95 mol % or more of the monovalent hydrocarbon groups represented by R 11, and even more preferably all of the monovalent hydrocarbon groups represented by R ¹¹ other than the alkenyl groups are methyl groups.

In the above average composition formula (I), n1 is a positive number between 1.95 and 2.04, and preferably between 1.98 and 2.02. If the n1 value is not within the range of 1.95 to 2.04, the resulting cured product may not exhibit sufficient rubber elasticity.

Furthermore, the linear diorganopolysiloxane raw rubber of component (A) must have at least two alkenyl groups per molecule, and in the above formula (I), it is preferable that 0.001 to 10 mol %, and especially 0.01 to 5 mol %, of R ¹¹ be alkenyl groups. Preferred alkenyl groups are vinyl groups and allyl groups, with vinyl groups being especially preferred.

The average degree of polymerization of the organopolysiloxane of component (A) is 100 or more (usually 100 to 100,000), more preferably in the range of 1,000 to 100,000, even more preferably in the range of 3,000 to 50,000, and particularly preferably in the range of 4,000 to 20,000. If the average degree of polymerization is less than 100, the silicone rubber composition of the present invention will no longer satisfy the properties required for millable rubber, and roll kneading properties and the like will be significantly impaired, which is undesirable.

The average degree of polymerization is determined from the weight average molecular weight in terms of polystyrene in a GPC (gel permeation chromatography) analysis measured under the following conditions.
(Measurement conditions)
Developing solvent: toluene Flow rate: 1 mL/min
Detector: Refractive index detector (RI)
Column: KF-805L x 2 (Shodex)
Column temperature: 25°C
Sample injection volume: 30 μL (toluene solution with a concentration of 0.2% by mass)

The linear diorganopolysiloxane gum of component (A) is not particularly limited as long as it satisfies the requirements for alkenyl group and average degree of polymerization, but is preferably a linear diorganopolysiloxane gum whose main chain consists of repeating diorganosiloxane units ( ^RSiO , _where ^R _is the same as above, and the same applies _below ) and whose molecular chain is end-blocked with triorganosiloxy groups ₍ ^RSiO ), and those whose molecular chain is end-blocked with trimethylsiloxy groups, dimethylvinylsiloxy groups, dimethylhydroxysiloxy groups, methyldivinylsiloxy groups, trivinylsiloxy groups, etc. are preferred, and those whose molecular chain is end-blocked with siloxy groups containing at least one vinyl group are particularly preferred. These organopolysiloxanes may be used alone, or two or more with different degrees of polymerization or molecular structures may be used in combination.

The (A) component is preferably contained in the composition of the present invention in an amount of 43 to 96% by mass, more preferably 50 to 90% by mass, and even more preferably 50 to 80% by mass.

-(B) Organohydrogenpolysiloxane-
Component (B) is an organohydrogenpolysiloxane having at least two, and preferably three or more, silicon-bonded hydrogen atoms (SiH groups) per molecule. Component (B) acts as a curing agent (crosslinking agent) for curing the one-component millable silicone rubber composition of the present invention, which cures (crosslinks) via a hydrosilylation addition reaction; the SiH groups in component (B) crosslink with the alkenyl groups in component (A) via a hydrosilylation addition reaction to cure the composition.

Component (B) may be a conventional organohydrogenpolysiloxane contained in addition reaction-curable organopolysiloxane compositions. It preferably has at least two, preferably three or more, more preferably 3 to 100, and even more preferably 4 to 50 silicon-bonded hydrogen atoms (SiH groups) per molecule.

The SiH group content in the organohydrogenpolysiloxane is preferably 0.0005 to 0.02 mol/g, and particularly preferably 0.001 to 0.017 mol/g. If the amount of SiH groups is below the lower limit, crosslinking may be insufficient. If the amount is above the upper limit, volatility may be high, and some of the organohydrogenpolysiloxane may volatilize out of the composition during compounding, manufacturing, or product storage.

Organohydrogenpolysiloxanes containing 2 to 300 silicon atoms per molecule, particularly 3 to 150, and especially 4 to 100 silicon atoms, which are liquid at room temperature (23°C ± 15°C, the same applies below), are preferred. The hydrogen atoms bonded to the silicon atoms may be located at either the ends of the molecular chain, midway along the molecular chain (non-terminal), or both. The molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or three-dimensionally network-like.

The organohydrogenpolysiloxane (B) is represented, for example, by the following average composition formula (II):
R ¹² _b H _c SiO _(4-bc)/2 (II)

In formula (II), R ¹² are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms. b is a positive number from 0.7 to 2.1, c is a positive number from 0.001 to 1.0, and b+c is a positive number that satisfies the range of 0.8 to 3.0. The organohydrogenpolysiloxane contains silicon-bonded hydrogen atoms (SiH groups) in the above-mentioned amount, and preferably has the above-mentioned number of silicon atoms.
In the above formula (II), examples of the monovalent hydrocarbon group represented by R ¹² include the groups exemplified above for R ^11. Among these, groups having no aliphatic unsaturated bonds are preferred.

In the above formula (II), b is a positive number between 0.7 and 2.1, preferably between 0.8 and 2.0, c is a positive number between 0.001 and 1.0, preferably between 0.01 and 1.0, and b+c is a positive number between 0.8 and 3.0, preferably between 1.0 and 2.5.

(B) Organohydrogenpolysiloxane, for example, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, methylhydrogenpolysiloxane blocked at both ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer blocked at both ends with trimethylsiloxy groups, dimethylpolysiloxane blocked at both ends with dimethylhydrogensiloxy groups, dimethylsiloxane blocked at both ends with dimethylhydrogensiloxy groups, Methylsiloxane-methylhydrogensiloxane copolymer, methylhydrogensiloxane-diphenylsiloxane copolymer both ends blocked with trimethylsiloxy groups, methylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymer both ends blocked with trimethylsiloxy groups, methylhydrogensiloxane-methylphenylsiloxane-dimethylsiloxane copolymer both ends blocked with trimethylsiloxy groups, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymer both ends blocked with dimethylhydrogensiloxy groups, methylhydrogensiloxane-dimethylsiloxane-methylphenylsiloxane copolymer both ends blocked with dimethylhydrogensiloxy groups, (CH Examples include a copolymer consisting of ( _CH3 )2HSiO1 _{/2 units} , ( _CH3 ) _{3SiO1 /2} units, and SiO4 _{/2 units} , a copolymer consisting of ( _CH3 )2HSiO1 _/2 units and SiO4 _/2 units, a copolymer consisting of _{( CH3} )2HSiO1 _/2 units, SiO4 _/2 units, and ( _C6H5 )SiO3 _{/2 units} , and copolymers in which some or all of the methyl groups in these exemplary compounds have been substituted with other alkyl groups, phenyl groups, etc.

In addition, the organohydrogenpolysiloxane (B) may be a polyvalent aromatic ring-containing organohydrogenpolysiloxane in which, in the compounds exemplified above, part of the siloxane skeleton (-Si-O-Si-) that constitutes the molecule (usually part of the position of the oxygen atom that forms the siloxane bond) contains a hydrocarbon skeleton (e.g., a phenylene skeleton, a bisphenylene skeleton, a bis(phenylene)ether skeleton, a bis(phenylene)methane skeleton, a 2,2-bis(phenylene)propane skeleton, a 2,2-bis(phenylene)hexafluoropropane skeleton, etc.) that is typically divalent to tetravalent and contains an aromatic ring.

The amount of component (B) blended is 0.01 to 50 parts by mass, preferably 0.1 to 30 parts by mass, per 100 parts by mass of component (A). Furthermore, it is preferable that the molar ratio (SiH groups/alkenyl groups) of the hydrogen atoms bonded to silicon atoms in component (B) to the total number of alkenyl groups bonded to silicon atoms in components (A) and (B) (particularly component (A)) is 0.6 to 10, particularly 1 to 5. If this ratio is less than 0.6, curing (crosslink density) may be insufficient, resulting in a sticky rubber. If it is greater than 10, the resulting silicone rubber composition may foam during curing or may be difficult to release from a mold.

-(C) Reinforcing Silica-
The reinforcing silica of component (C) acts as a filler that imparts excellent mechanical properties to the resulting silicone rubber composition. The reinforcing silica may be either precipitated silica (wet silica) or fumed silica (fumed silica or dry silica), and surface-untreated reinforcing silica typically has numerous silanol (SiOH) groups present on its surface. In the present invention, the specific surface area of the reinforcing silica of component (C), as measured by the BET method, must be 50 m ² /g or greater, preferably 100 to 450 m ² /g, and more preferably 100 to 300 m ² /g. If this specific surface area is less than 50 m ² /g, the reinforcing effect of component (C) will be insufficient.

The reinforcing silica of component (C) may be used untreated, or, if necessary, may be surface-treated (hydrophobized) with an organosilicon compound such as organopolysiloxane, organopolysilazane, chlorosilane, or alkoxysilane. These reinforcing silicas may be used alone or in combination of two or more. The reinforcing silica of component (C) can be a commercially available product. Examples thereof include the Aerosil series, such as Aerosil 130, Aerosil 200, Aerosil 300, Aerosil R-812, Aerosil R-972, and Aerosil R-974 (manufactured by Nippon Aerosil Co., Ltd.), Cabosil MS-5 and MS-7 (manufactured by Cabot Corporation), and Reolosil QS-102, 103, and MT-10 (manufactured by Tokuyama Corporation), which are surface-untreated or surface-hydrophobized (i.e., hydrophilic or hydrophobic) fumed silica, and Tokusil US-F (manufactured by Tokuyama Corporation), NIPSIL-SS, and NIPSIL-LP (manufactured by Nippon Silica Co., Ltd.), which are surface-untreated or surface-hydrophobized precipitated silica.

The amount of reinforcing silica (component (C)) blended is 5 to 100 parts by mass, preferably 10 to 80 parts by mass, and more preferably 20 to 70 parts by mass per 100 parts by mass of organopolysiloxane (component (A)). If the blending amount deviates from this range, not only will the processability of the resulting silicone rubber composition be reduced, but the mechanical properties such as tensile strength and tear strength of the cured silicone rubber obtained by curing the silicone rubber composition will be insufficient.

-(D) Platinum-phosphite complex-containing hydrosilylation catalyst-
The platinum-phosphite complex-containing hydrosilylation catalyst of the present invention described above is used as the platinum-phosphite complex-containing hydrosilylation catalyst of component (D).
The amount of the platinum-phosphite complex-containing hydrosilylation catalyst (D) is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, and even more preferably 0.05 to 3 parts by mass, per 100 parts by mass of component (A). If the amount of platinum-phosphite complex-containing hydrosilylation catalyst is less than 0.001 part by mass, the strength of the resulting cured product may be reduced, or the product may be poorly cured. Conversely, if the amount of platinum-phosphite complex-containing hydrosilylation catalyst exceeds 10 parts by mass, the resulting composition may become discolored, the time required for curing may be shortened, and the product may be cost-inefficient. The activity of the catalyst, i.e., curability, can be controlled by increasing or decreasing the concentration of the platinum-phosphite complex-containing hydrosilylation catalyst.
The acetylene alcohol contained in component (D) acts as a reaction inhibitor in the composition, making it possible to inhibit the curing of the millable silicone rubber composition at room temperature for an extended period of time.

-Other ingredients-
In addition to the above components, the one-component millable silicone rubber composition of the present invention may optionally contain, within the scope of the effects of the present invention, dispersants (wetters) for fillers such as reinforcing silica (component (C)), reinforcing inorganic fillers other than component (C) such as calcium carbonate and fumed titanium dioxide, non-reinforcing inorganic fillers such as calcium silicate, titanium dioxide, ferric oxide and carbon black, various fillers such as inorganic fillers with or without surface hydrophobic treatment, organic resin balloons, silane coupling agents (for example, alkoxysilanes containing a monovalent hydrocarbon group having a functional group (e.g., epoxy group, (meth)acryloxy group, mercapto group) containing a heteroatom selected from oxygen atoms, nitrogen atoms and sulfur atoms), etc. The optional components that can be blended include adhesion promoters such as hydrolyzable organosilane compounds and/or partial hydrolysis condensates thereof, plasticizers such as non-functional silicone oils that do not contain functional groups involved in hydrosilylation addition reactions, such as alkenyl groups or hydrosilyl groups (SiH groups) in the molecule, such as dimethylpolysiloxanes terminally capped with trimethylsilyl groups (dimethylsilicone oils), dimethylsiloxane-diphenylsiloxane copolymers terminally capped with trimethylsilyl groups, and dimethylsiloxane-methylphenylsiloxane copolymers terminally capped with trimethylsilyl groups (methylphenylsilicone oils), addition reaction regulators, and additives such as pigment pastes and reinforcing silicone resins.

-Method for producing the composition-
The one-component millable silicone rubber composition of the present invention can be obtained by kneading the components that make up the composition under shear stress using a known kneader such as a kneader, Banbury mixer, two-roll mill, etc. In this case, the remainder of component (A), if any, is added to a base compound containing some or all of the organopolysiloxane of component (A) and the reinforcing silica of component (C), along with the organohydrogenpolysiloxane of component (B), and the platinum-phosphite complex-containing hydrosilylation catalyst of component (D), and the mixture is kneaded using a kneader such as a two-roll mill, thereby easily obtaining the desired one-component millable silicone rubber composition with excellent storage stability.

The essential curing condition for the curable organopolysiloxane composition containing the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention is that it must be cured by heating. The heating temperature is preferably in the range of 60 to 250°C, and more preferably in the range of 80 to 150°C. There are no particular restrictions on the curing time, but a time of approximately 10 to 120 minutes is more suitable.

[Articles Having Cured Products of Curable Organopolysiloxane Compositions Containing Platinum-Phosphite Complex-Containing Hydrosilylation Catalysts]
The curable organopolysiloxane compositions containing the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention can be used in articles such as potting materials for electrical and electronic devices, IGBTs, and the like; articles using adhesives for various electronic substrates and resin cases; rubber contacts used as rubber contacts in remote controllers, typewriters, word processors, computer terminals, musical instruments, and the like; construction gaskets; various rolls such as copier rolls, developing rolls, transfer rolls, charging rolls, and paper feed rolls; vibration-isolating rubber for audio equipment, and the like; packing for compact discs used in computers; polymer insulators for electric wires, and articles used in medical equipment, such as rubber hoses and nipples.

The present invention will be described in further detail below using examples and comparative examples to clarify the effects of the present invention, but the present invention is not limited thereto. In the examples, "parts" means "parts by mass," and "%" means "% by mass" unless otherwise specified.

[Example 1]
0.3311 parts of tris(2,4-di-tert-butylphenyl)phosphite was weighed into a transparent glass container, and 9.6689 parts of n-hexane (boiling point: 68°C) was added. The container was then sealed and allowed to dissolve for approximately 1 hour at room temperature (23°C). After visually confirming that the tris(2,4-di-tert-butylphenyl)phosphite crystals had dissolved, 10.0 parts of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution containing 1% Pt atoms (solvent: dimethylpolysiloxane with a degree of polymerization of 180 and capped at both ends with vinyldimethylsiloxy groups) was added. The container was then sealed and stirred for 30 minutes to obtain a uniform solution (preparation of a silicone solution containing a platinum-phosphite ester complex).
Thereafter, 2.50 parts of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane was added, the flask was sealed, and the mixture was stirred for 60 minutes to achieve uniformity. Then, 1.0 part of 3-methyltridec-1-yn-3-ol was added to the solution, the flask was sealed, and the mixture was stirred for 60 minutes to achieve uniformity. The solution was then transferred to a 100 ml eggplant-shaped flask, and n-hexane was removed under reduced pressure using a rotary evaporator (conditions: 40°C x 2 hours/approximately 35 hPa). The 100 ml eggplant-shaped flask yielded 13.6 g of a pale yellow, transparent liquid (yield: 98.3%). This silicone solution of platinum-phosphite complex-containing hydrosilylation catalyst was designated "Catalyst I."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 14.2 moles per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 9.3 moles per mole of platinum atoms in the platinum-phosphite complex.)

[Example 2]
0.3311 parts of tris(2,4-di-tert-butylphenyl)phosphite was weighed into a transparent glass container, and 9.6689 parts of n-hexane was added. The container was then sealed and allowed to dissolve at room temperature for approximately 1 hour. After visually confirming that the tris(2,4-di-tert-butylphenyl)phosphite crystals had dissolved, 10.0 parts of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution containing 1% Pt atoms (solvent: dimethylpolysiloxane with a degree of polymerization of 180 and capped at both ends with vinyldimethylsiloxy groups) was added, the container was sealed, and the mixture was stirred for 30 minutes to obtain a uniform solution (preparation of a silicone solution containing a platinum-phosphite ester complex).
Thereafter, 2.5 parts of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane was added, the flask was sealed, and the mixture was stirred for 60 minutes to achieve uniformity. Then, 2.0 parts of 1-ethynyl-1-cyclohexanol was added to the solution, the flask was sealed, and the mixture was stirred for 60 minutes to achieve uniformity. The solution was then transferred to a 100 ml eggplant-shaped flask, and n-hexane was removed under reduced pressure using a rotary evaporator (conditions: 40°C x 2 hours/approximately 32 hPa). The 100 ml eggplant-shaped flask yielded 14.8 g of a pale yellow, transparent liquid (yield: 99.8%). This silicone solution of platinum-phosphite complex-containing hydrosilylation catalyst was designated "Catalyst II."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 14.2 moles per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 18.6 moles per mole of platinum atoms in the platinum-phosphite complex.)

[Example 3]
0.3311 parts of tris(2,4-di-tert-butylphenyl)phosphite was weighed into a transparent glass container, and 9.6689 parts of n-hexane was added. The container was then sealed and allowed to dissolve at room temperature for approximately 1 hour. After visually confirming that the tris(2,4-di-tert-butylphenyl)phosphite crystals had dissolved, 10.0 parts of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution containing 1% Pt atoms (solvent: dimethylpolysiloxane with a degree of polymerization of 180 and capped at both ends with vinyldimethylsiloxy groups) was added, the container was sealed, and the mixture was stirred for 30 minutes to obtain a uniform solution (preparation of a silicone solution containing a platinum-phosphite ester complex).
Next, 0.1765 parts of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane was added, the flask was sealed, and the mixture was stirred for 60 minutes to achieve uniformity. Next, 1.0 part of 3-methyltridec-1-yn-3-ol was added to the solution, the flask was sealed, and the mixture was stirred for 60 minutes to achieve uniformity. The solution was then transferred to a 100 ml eggplant-shaped flask, and n-hexane was removed under reduced pressure using a rotary evaporator (conditions: 40°C x 2 hours/approximately 32 hPa). The 100 ml eggplant-shaped flask yielded 11.47 g of a transparent yellow liquid (yield: 99.7%). This silicone solution of platinum-phosphite complex-containing hydrosilylation catalyst is designated "Catalyst III."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 1.0 mole per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 9.3 moles per mole of platinum atoms in the platinum-phosphite complex.)

[Comparative Example 1]
The same procedure as in Example 1 was carried out, except that 2.5 parts of 1,1,3,3,5,5,7,7-octamethylcyclotetrasiloxane was used instead of 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane. As a result, 13.7 g of a transparent yellow liquid was obtained in a 100 ml recovery flask (yield: 99.1%). This silicone solution of a platinum-phosphite complex-containing hydrosilylation catalyst is designated "Catalyst IV."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 0 mole per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 9.3 moles per mole of platinum atoms in the platinum-phosphite complex.)

[Comparative Example 2]
The same procedure as in Example 1 was repeated, except that 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane was not used. As a result, 11.15 g of a transparent yellow liquid was obtained in a 100 ml recovery flask (yield: 98.4%). This silicone solution of a platinum-phosphite complex-containing hydrosilylation catalyst was designated "Catalyst V."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 0 mole per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 9.3 moles per mole of platinum atoms in the platinum-phosphite complex.)

[Comparative Example 3]
The same procedure as in Example 1 was repeated, except that 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane and 3-methyltridec-1-yn-3-ol were not used. As a result, 10.33 g of a colorless, transparent liquid was obtained in a 100 ml recovery flask (yield: 99.9%). This silicone solution of a platinum-phosphite complex-containing hydrosilylation catalyst is designated "Catalyst VI."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 0 mole per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 0 mole per mole of platinum atoms in the platinum-phosphite complex.)

[Comparative Example 4]
The same procedure as in Example 1 was carried out, but without using n-hexane. As a result, a brown, transparent liquid (yield: 13.8 g) with white crystals dispersed therein was obtained in a 100 ml eggplant-shaped flask; a colorless, transparent liquid was not obtained (yield: 99.8%). This silicone solution of a platinum-phosphite complex-containing hydrosilylation catalyst is designated "Catalyst VII."
(The amount of the phosphite compound was 1.0 mole per mole of platinum atoms in the platinum catalyst, the amount of the vicinal alkenyl group-containing organopolysiloxane compound was 14.2 moles per mole of platinum atoms in the platinum-phosphite complex, and the amount of the acetylene alcohol was 9.3 moles per mole of platinum atoms in the platinum-phosphite complex.)

[test]
The following appearance tests were carried out using the silicone solutions of the platinum-phosphite complex-containing hydrosilylation catalysts (Catalysts I to VII) obtained in Examples 1 to 3 and Comparative Examples 1 to 4. The results, along with the yields, are shown in Table 1.

〔exterior〕
The platinum-phosphite ester complex-containing hydrosilylation catalysts obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were each stored in a sealed container filled with nitrogen. The appearance was then checked immediately after production (23°C), after 3 days at 23°C, and after 3 months. Those that showed no crystal formation in the container were judged to be acceptable, and those that showed crystal formation in the container were judged to be unacceptable.

[evaluation]
The platinum-phosphite complex-containing hydrosilylation catalysts obtained in Examples 1 to 3 satisfy the requirements of the present invention. In all of Examples 1 to 3, the amount of phosphite compound blended was 1.0 mole per mole of platinum atom in the platinum catalyst. The platinum-phosphite complex-containing hydrosilylation catalysts obtained in Examples 1 to 3 showed suppressed crystal precipitation even after being left at 23°C for 3 months under sealed conditions, demonstrating that platinum-phosphite complex-containing hydrosilylation catalysts with highly stable properties have been obtained.

The amount of phosphite compound was varied in 0.1 mol increments from 1.0 mol to 1.9 mol per mole of platinum atom in the platinum catalyst, but the procedure was otherwise the same as in Example 1 to prepare platinum-phosphite complex-containing hydrosilylation catalysts. All of the catalysts yielded colorless to pale yellow, transparent liquids at 23°C, and it was confirmed that the liquid remained the same color even after 3 months at 23°C.

In contrast, the platinum-phosphite complex-containing hydrosilylation catalysts of Comparative Examples 1 to 3 did not contain an organopolysiloxane compound (vicinal alkenyl group-containing organopolysiloxane compound) having units represented by general formula (2). Therefore, although the platinum-phosphite complex-containing hydrosilylation catalyst was initially produced as a transparent yellow liquid, it had poor long-term stability and crystals precipitated over time. Furthermore, the platinum-phosphite complex-containing hydrosilylation catalyst of Comparative Example 4 was produced by coordinating the phosphite compound to the platinum catalyst without dissolving it in a hydrocarbon organic solvent, but instead produced a liquid in which the phosphite compound did not dissolve and crystals were dispersed.

As is clear from the above results, the present invention provides a stable, liquid platinum-phosphite complex-containing hydrosilylation catalyst.
In Example 1, the structure of the Pt catalyst was confirmed by ¹⁹⁵ Pt-NMR in each step of preparing the platinum-phosphite complex-containing hydrosilylation catalyst. The results are shown in Table 2 and FIG. 1.

[evaluation]
In the case of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex containing a Pt atom, a single peak was observed near approximately -6,130 ppm. However, when a phosphite ester compound was added, the peak shifted to approximately -5,600 ppm and approximately -5,660 ppm, and split. The change in peak position suggested that the platinum catalyst and the phosphite ester compound used formed a complex. When a vicinal alkenyl group-containing organopolysiloxane compound was added to this complex, multiple peaks appeared near approximately -5,540 ppm to approximately -5,700 ppm. These results suggest that the platinum-phosphite ester complex and the vicinal alkenyl group-containing organopolysiloxane compound are associated with each other. Furthermore, when acetylene alcohol was added to this association, numerous peaks were confirmed in the range of approximately -5,540 ppm to approximately -5,700 ppm, but the results showed that the peaks clearly had different intensities than before the addition of acetylene alcohol. Therefore, it is presumed that the acetylene alcohol stabilizes unstable structures in the association between the platinum-phosphite ester complex and the adjacent alkenyl group-containing organopolysiloxane compound, resulting in a change in peak intensity.

[Examples of Curable Organopolysiloxane Compositions Utilizing Hydrosilylation Catalysts Containing Platinum-Phosphite Complexes]
In order to clarify the effects of the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention, the catalysts obtained in Examples 1 to 3 and Comparative Examples 1 to 4 (storage sealed at 23°C for 3 months) and examples and comparative examples relating to curable organopolysiloxane compositions utilizing a general platinum catalyst will be described in more detail below. Note that although the following examples and comparative examples are directed to one-component millable curable organopolysiloxane compositions, the present invention is not limited thereto.

[Composition Example 1]
100 parts of dimethylpolysiloxane gum (corresponding to n1 = 2.00 in formula (I)) consisting of 99.85 mol% dimethylsiloxane units, 0.125 mol% methylvinylsiloxane units, and 0.025 mol% dimethylvinylsiloxy units and having an average degree of polymerization of 6,000, 55 parts of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 ^m2 /g, 12 parts of dimethyldimethoxysilane, 0.2 parts of vinyltrimethoxysilane, 12 parts of dimethylpolysiloxane having silanol groups at both ends, an average degree of polymerization of 4, and a viscosity at 23°C of 15 mPa·s, and 0.15 parts of 3% potassium siliconate were added, and the mixture was heated at 170°C for 2 hours under mixing in a kneader to prepare base compound (1).

To 100 parts of dimethylpolysiloxane gum, 1.7 parts of an organohydrogenpolysiloxane represented by the following formula (hydrosilyl group amount: 0.00726 mol/g, corresponding to b = 1.5 and c = 0.05 in formula (II) above), 0.05 parts of "Catalyst I" prepared in Example 1, and 0.00080 parts of ethynylmethyldecylcarbinol were added, and the mixture was uniformly mixed using a twin roll mill to produce a one-component millable curable organopolysiloxane composition I in the form of a gum.

Composition Example 2
A one-component millable curable organopolysiloxane composition II was prepared in the same manner as in Example 1, except that 0.05 parts of "catalyst II" was used in place of "catalyst I".

Composition Example 3
A one-component millable curable organopolysiloxane composition III was prepared in the same manner as in Example 1, except that 0.05 parts of "catalyst III" was used in place of "catalyst I".

[Comparative Composition Example 1]
A one-component millable curable organopolysiloxane composition IV was prepared in the same manner as in Example 1, except that 0.05 parts of "catalyst IV" was used in place of "catalyst I".

[Comparative Composition Example 2]
A one-component millable curable organopolysiloxane composition V was prepared in the same manner as in Example 1, except that 0.05 parts of "catalyst V" was used in place of "catalyst I".

[Comparative Composition Example 3]
A one-component millable curable organopolysiloxane composition VI was prepared in the same manner as in Example 1, except that 0.05 parts of "catalyst VI" was used in place of "catalyst I".

[Comparative Composition Example 4]
A one-component millable curable organopolysiloxane composition VII was prepared in the same manner as in Example 1, except that 0.05 parts of "Catalyst VII" was used in place of "Catalyst I".

[Comparative Composition Example 5]
One-component millable curable organopolysiloxane composition VIII was prepared in the same manner as in Example 1, except that 0.05 parts of a platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution containing 1% Pt atoms (solvent: dimethylpolysiloxane having a degree of polymerization of 180 and capped at both ends with vinyldimethylsiloxy groups) was used in place of "catalyst I."

[Comparative Composition Example 6]
In Composition Example 1, instead of 0.05 parts of "Catalyst I," 0.046 parts of "Catalyst I'" prepared in the same manner as in Example 1, except that 1.0 part of 3-methyltridec-1-yn-3-ol was not added in the production process of the catalyst of Example 1, was added. The mixture was then uniformly mixed and dispersed using a twin roll mill in the same manner as in Composition Example 1, and 0.004 parts of 3-methyltridec-1-yn-3-ol was added, and the mixture was uniformly mixed and dispersed using a twin roll mill to produce one-component millable curable organopolysiloxane Composition IX.

[test]
The following tests were carried out using the one-component millable curable organopolysiloxane compositions obtained in Composition Examples 1 to 3 and Comparative Composition Examples 1 to 6. The results, along with a pass/fail rating for the appearance of the catalyst, are shown in Table 3.

[Workability during preparation of one-component millable curable organopolysiloxane composition (workability during catalyst addition)]
When preparing the one-component millable curable organopolysiloxane compositions prepared in Composition Examples 1 to 3 and Comparative Composition Examples 1 to 6, those in which the platinum-phosphite complex-containing hydrosilylation catalyst was liquid at 23°C and no problems occurred when it was added were judged to pass. Conversely, those in which the platinum-phosphite complex and/or the phosphite compound in the platinum-phosphite complex-containing hydrosilylation catalyst had crystallized and problems occurred in workability when it was added were judged to fail.

[Storage Stability of One-Component Millable Curable Organopolysiloxane Composition]
The storage stability of the one-component millable curable organopolysiloxane compositions prepared in Composition Examples 1 to 3 and Comparative Composition Examples 1 to 6 was evaluated by measuring the initial curability of the resulting one-component millable curable organopolysiloxane compositions and their curability after 6 and 12 months of storage at 23°C using a rheometer (ALPHA TECHNOLOGIES RUBBER PROCESS ANALYZER RPA2000) at a measurement temperature of 150°C. The curing torque of the one-component millable curable organopolysiloxane composition was measured over time, and the time (T50) from the start of measurement to reach 50% of the maximum torque value was confirmed and compared. Furthermore, compositions that could be evaluated up to 12 months at 23°C were judged to pass.

*1) Platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complex solution containing 1% by mass of Pt atoms

[Composition Evaluation]
The platinum-phosphite ester complex-containing hydrosilylation catalysts obtained in Examples 1 to 3 fulfilled the requirements of the present invention, and the one-component millable curable organopolysiloxane compositions of Examples 1 to 3 using these catalysts demonstrated good workability upon addition of the catalyst and cured in 10 minutes at 150°C even after long-term storage at 23°C, demonstrating curability virtually unchanged from that at the time of production.

In contrast, the platinum-phosphite ester complex-containing hydrosilylation catalysts of Comparative Examples 1 to 3 failed the appearance judgment of the catalyst itself because crystals precipitated after 3 months or 3 days at 23°C. Furthermore, they also failed in workability because it became necessary to add the required amount of catalyst while removing the crystalline components when adding the catalyst. Furthermore, the one-component millable-type curable organopolysiloxane compositions of Comparative Examples 1 to 3 that used these catalysts hardened to a rubbery state after 1 year of storage at 23°C, demonstrating poor storage stability.
Furthermore, the platinum-phosphite complex-containing hydrosilylation catalyst of Comparative Example 4 was prepared without using a hydrocarbon organic solvent, which resulted in poor complex formation between the phosphite compound and platinum. As a result, the one-component millable curable organopolysiloxane composition of Comparative Example 4 prepared using this catalyst had poor storage stability.
Comparative Composition Example 5 is an example of a one-component millable curable organopolysiloxane composition in which a typical platinum catalyst (i.e., a platinum catalyst containing no hydrocarbon organic solvent, selected from one or more platinum-vinyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid, or chloroplatinic acid salts and vinyl group-containing siloxanes) was used directly without complexing with a phosphite ester or associating with a siloxane compound. The one-component millable curable organopolysiloxane composition of Comparative Composition Example 5 produced using this catalyst resulted in reduced storage stability.
Comparative Composition Example 6 represents a case in which a platinum-phosphite complex-containing hydrosilylation catalyst of the present invention was used, but without the addition of acetylene alcohol. This Comparative Composition Example 6 contains the same amounts of platinum-phosphite complex-containing hydrosilylation catalyst and acetylene alcohol added separately as in Composition Example 1, and the components and blending amounts shown in Composition Example 1 are the same. However, after storing the composition of Comparative Composition Example 6 at 23°C for 12 months (1 year), it hardened into a rubber-like state, indicating poor storage stability. Therefore, even when the same components are added in the same amounts, the composition of the present invention, which uses a platinum-phosphite complex-containing hydrosilylation catalyst to which acetylene alcohol has been added in advance, demonstrates significantly superior storage stability.

The above results demonstrate that the one-component millable curable organopolysiloxane composition using the platinum-phosphite ester complex-containing hydrosilylation catalyst obtained in this invention exhibits excellent performance in terms of improved workability and storage stability.

The platinum-phosphite complex-containing hydrosilylation catalyst of the present invention, unlike conventional platinum-phosphite complex-containing hydrosilylation catalysts that tend to form crystals, is able to maintain its liquid state at 23°C without the use of hydrocarbon organic solvents. Therefore, the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention improves the stability of the hydrosilylation catalyst itself and improves the workability of producing curable organopolysiloxane compositions using this catalyst. Furthermore, the absence of hydrocarbon organic solvents makes it extremely safe from an industrial perspective, resulting in minimal adverse effects on the human body and a highly robust composition. Furthermore, curable organopolysiloxane compositions incorporating the platinum-phosphite complex-containing hydrosilylation catalyst of the present invention exhibit excellent storage stability, maintaining stable properties and physical characteristics even when exposed to room temperature for extended periods of time. This makes them suitable for a wide range of applications, including electrical equipment, automobiles, construction, medicine, and food.

Claims (13)

Platinum and the following general formula (1)
(wherein ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).
and a platinum-phosphite ester complex comprising a phosphite ester compound represented by the formula:
The following general formula (2)
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)
and an acetylene alcohol having a melting point of 35°C or less.
The platinum-phosphite complex-containing hydrosilylation catalyst is liquid at 23°C and does not contain any hydrocarbon organic solvent. The platinum-phosphite ester complex-containing hydrosilylation catalyst according to claim 1, wherein the organopolysiloxane compound having a unit represented by general formula (2) is a cyclic organopolysiloxane compound. The platinum-phosphite ester complex-containing hydrosilylation catalyst according to claim 1 or 2, in which 0.01 to 100 mol % of the platinum-phosphite ester complex is associated with an organopolysiloxane compound having a unit represented by general formula (2). The platinum-phosphite ester complex-containing hydrosilylation catalyst according to any one of claims 1 to 3, wherein the alkenyl group-containing siloxane compound further contains one or more compounds selected from 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and linear dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups. The platinum-phosphite ester complex-containing hydrosilylation catalyst according to any one of claims 1 to 4, wherein the acetylene alcohol has one ethynyl group and one hydroxy group per molecule. The platinum-phosphite complex-containing hydrosilylation catalyst according to claim 1, wherein the organopolysiloxane compound having units represented by formula (2) is composed exclusively of units represented by formula (2) except for the molecular chain terminals. 2. The platinum-phosphite complex-containing hydrosilylation catalyst according to claim 1, wherein n in formula (2) is an integer of 4 to 10. A curable organopolysiloxane composition comprising the platinum-phosphite complex- containing hydrosilylation catalyst according to any one of claims 1 to 5 as the only curing catalyst . 9. The curable organopolysiloxane composition according to claim 8 , which does not contain a hydrocarbon organic solvent. An article comprising a cured product of the curable organopolysiloxane composition according to claim 8 or 9 . A method for producing a platinum-phosphite complex-containing hydrosilylation catalyst, comprising the following steps (a) to (e):
(a) preparing a solution of a phosphite ester compound represented by the following general formula (1) in a hydrocarbon organic solvent having a boiling point of 80°C or less;
(wherein ^R1 is independently a hydrogen atom or a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).
(b) adding to the solution a platinum catalyst containing no hydrocarbon organic solvent, the platinum catalyst being selected from one or more platinum-alkenyl group-containing siloxane complexes formed from platinum chloride, chloroplatinic acid or a chloroplatinate salt and an alkenyl group-containing siloxane, and dispersing and dissolving the catalyst to prepare a solution containing a platinum-phosphite complex composed of platinum and the phosphite compound represented by the general formula (1);
(c) adding an organopolysiloxane compound having a unit represented by the following general formula (2) to the solution obtained in step (b), and dispersing and dissolving the compound to prepare a solution containing an association product of a platinum-phosphite ester complex and an organopolysiloxane compound having a unit represented by the following general formula (2);
(In the formula, ^R2 is an alkenyl group having 2 to 10 carbon atoms, ^R3 is a monovalent aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer from 2 to 200.)
and,
(d) adding an acetylene alcohol having a melting point of 35°C or less to the solution obtained in step (c);
(e) A step of removing the hydrocarbon organic solvent having a boiling point of 80° C. or less from the solution obtained in the step (d). The method for producing a platinum-phosphite complex-containing hydrosilylation catalyst according to claim 11 , wherein 0.01 to 500 moles of an organopolysiloxane compound having a unit represented by general formula (2) are added per mole of platinum atoms in the platinum-phosphite complex. 13. The method for producing a platinum-phosphite complex-containing hydrosilylation catalyst according to claim 11 , wherein 0.50 to 800 moles of acetylene alcohol are added per mole of platinum atom in the platinum-phosphite complex.