JP2023172784A - Millable silicone rubber compound, millable silicone rubber composition and method for producing millable silicone rubber composition - Google Patents

Abstract

To provide a millable silicone rubber compound that exhibits performance on par with traditional ones without the need for heat treatment.SOLUTION: A millable silicone rubber compound includes the following components (A)-(D). (A) 100 pts.mass of organopolysiloxane raw rubber having two or more alkenyl groups binding to silicon atoms in one molecule, with an average degree of polymerization of 1,000-100,000, (B) 5-100 pts.mass of reinforcing silica with a specific surface area of 50-450 m2/g, determined by the BET adsorption method, (C) 1.0-50.0 pt.mass of an organosiloxane having hydroxy silyl groups at both terminals, represented by the general formula (1) (R1's independently represent a C1-8 monovalent hydrocarbon group and m represents an integer of 1-50), and (D) 0.0001-0.1 pt.mass of an amine compound that is liquid at 25°C, with a boiling point of 30-60°C at 1013 hPa.SELECTED DRAWING: None

Description

The present invention relates to a millable silicone rubber compound, a millable silicone rubber composition, and a method for producing a millable silicone rubber composition.

To produce silicone rubber, it is necessary to knead a reinforcing filler into organopolysiloxane. In this case, a surface treatment agent called a dispersant is used, and when reinforcing silica is dispersed as a filler, an organosilane or siloxane having a silanol group is used. However, since the step of dispersing silica using this method takes time, it is desired to shorten this time.

In addition to this dispersion step, a heat treatment step at high temperature is also essential, and the heat treatment step requires a large amount of electric power. The environmental impact is also a problem because the process takes a long time and consumes a lot of electricity. In order to solve this problem, attempts have been made to use a small amount of a silazane compound in combination with the dispersant as a condensation catalyst for the dispersant. However, even this method does not lead to a fundamental solution.

In order to solve the above problems, Patent Document 1 states that by increasing the amount of the silazane compound used in combination with the dispersant, the heat treatment step is not necessary and the compounding time can be shortened. This method is said to produce a millable silicone rubber compound with performance comparable to conventional ones, but on an industrial scale, the excess silazane compound cannot be completely removed. Therefore, if this silicone rubber compound is used in an addition-curing silicone rubber composition, the physical properties of the cured rubber product may not be stable or the surface may feel sticky. Therefore, there has been a desire for an easily removable catalyst for promoting the condensation reaction between the dispersant and the silanol groups on the reinforcing silica surface.

JP2012-025846A

The present invention has been made in view of the above circumstances, and provides a millable silicone rubber compound that does not require heat treatment and has the same performance as conventional silicone rubber compounds, and a silicone rubber composition containing a kneaded product of the silicone rubber compound. With the goal.

（式中、Ｒ^１は独立して炭素数１～８の１価炭化水素基であり、ｍは１～５０の整数である。）
（Ｄ）１０１３ｈＰａにおける沸点が３０～６０℃である２５℃で液体のアミン化合物：０．０００１～０．１質量部
を含むものであるミラブル型シリコーンゴムコンパウンドを提供する。 In order to solve the above problems, the present invention
Components (A) to (D) below (A) Organopolysiloxane raw rubber having two or more alkenyl groups bonded to silicon atoms in one molecule and having an average degree of polymerization of 1,000 to 100,000: 100 parts by mass,
(B) Reinforcing silica with a specific surface area of 50 to 450 m ² /g by BET adsorption method: 5 to 100 parts by mass,
(C) Organosiloxane having hydroxysilyl groups at both ends, represented by the following general formula (1): 1.0 to 50.0 parts by mass, and

(In the formula, R ¹ is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 1 to 50.)
(D) A millable silicone rubber compound containing 0.0001 to 0.1 part by mass of an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa is provided.

If this is the case, the millable type silicone rubber compound will have the same performance as the conventional one in which heat treatment is performed, even though heat treatment is not necessary for the surface treatment of the reinforcing silica.

The present invention also provides a millable silicone rubber composition containing a kneaded product obtained by kneading the above-mentioned millable silicone rubber compound and (E) a curing agent.

If such a product is used, a cured product can be obtained by reacting the component (A) with the component (E).

It is preferable that the component (E) is a curing agent for a hydrosilylation reaction, which is a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

Such a material is suitable for the millable silicone rubber compound of the present invention since it contains fewer impurities that inhibit addition curing.

It is preferable that the component (E) is an organic peroxide.

Organic peroxides are also suitable as curing agents.

In addition, the present invention involves kneading the above-mentioned millable silicone rubber compound, and applying heat of stirring while surface-treating the component (B) with the component (C) in the presence of the component (D) as a catalyst. A method for producing a millable silicone rubber composition is provided, in which a curing agent (E) is added after the component (D) is removed.

With such a manufacturing method, it is possible to release the unnecessary component (D) while proceeding with the surface treatment of the component (B) with the component (C).

According to the present invention, there is provided a millable silicone rubber compound that has the same performance as conventional ones without the need for forced heat treatment during the surface treatment of the filler, and a silicone rubber compound obtained by blending a curing agent into a kneaded product of the compound. A rubber composition is obtained.

As a result of intensive studies to achieve the above object, the present inventor discovered that when preparing a silicone rubber compound by using an organopolysiloxane and reinforcing silica with an organosiloxane having silanol groups at both ends, a specific amine We have discovered that by blending a small amount of a compound, it is possible to quickly surface-treat silica without heat treatment. This is because the heat of stirring generated when organopolysiloxane and silica are mixed can quickly surface-treat the silica. Furthermore, as the surface treatment reaction progresses, the amine compound that is not subjected to the reaction is discharged from the system by the heat of stirring, making it easy to create millable silicone rubber compounds that have the same performance as conventional ones without heat treatment. The present inventors have discovered that it is possible to obtain the desired results, and have come up with the present invention.

（式中、Ｒ^１は独立して炭素数１～８の１価炭化水素基であり、ｍは１～５０の整数である。）
（Ｄ）１０１３ｈＰａにおける沸点が３０～６０℃である２５℃で液体のアミン化合物：０．０００１～０．１質量部
を含むものであるミラブル型シリコーンゴムコンパウンドである。 That is, the present invention
Components (A) to (D) below (A) Organopolysiloxane raw rubber having two or more alkenyl groups bonded to silicon atoms in one molecule and having an average degree of polymerization of 1,000 to 100,000: 100 parts by mass,
(B) Reinforcing silica with a specific surface area of 50 to 450 m ² /g by BET adsorption method: 5 to 100 parts by mass,
(C) Organosiloxane having hydroxysilyl groups at both ends, represented by the following general formula (1): 1.0 to 50.0 parts by mass, and

(In the formula, R ¹ is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 1 to 50.)
(D) A millable silicone rubber compound containing 0.0001 to 0.1 part by mass of an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa.

In the present invention, a mixture of the above components (A) to (D) before adding a curing agent is referred to as a silicone rubber compound, and a kneaded product of this compound mixed with a curing agent is referred to as a silicone rubber composition. It is called a thing.

The present invention will be explained in more detail below.

（式中、Ｒ^１は独立して炭素数１～８の１価炭化水素基であり、ｍは１～５０の整数である。）
（Ｄ）１０１３ｈＰａにおける沸点が３０～６０℃である２５℃で液体のアミン化合物：０．０００１～０．１質量部
を含むものである。 [Mirable silicone rubber compound]
The millable silicone rubber compound of the present invention is
Components (A) to (D) below (A) Organopolysiloxane raw rubber having two or more alkenyl groups bonded to silicon atoms in one molecule and having an average degree of polymerization of 1,000 to 100,000: 100 parts by mass,
(B) Reinforcing silica with a specific surface area of 50 to 450 m ² /g by BET adsorption method: 5 to 100 parts by mass,
(C) Organosiloxane having hydroxysilyl groups at both ends, represented by the following general formula (1): 1.0 to 50.0 parts by mass, and

(In the formula, R ¹ is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 1 to 50.)
(D) Contains 0.0001 to 0.1 part by mass of an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa.

Moreover, the millable silicone rubber composition of the present invention contains (E) a curing agent in the kneaded product of the above-mentioned millable silicone rubber compound.

Among these, it is preferable that the curing agent component is a curing agent for a hydrosilylation reaction, which is a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.

-(A) Component-
In the present invention, component (A) is an organopolysiloxane raw rubber having two or more silicon-bonded alkenyl groups in one molecule and having an average degree of polymerization of 1,000 to 100,000.

The alkenyl group is preferably an alkenyl group having 2 to 8 carbon atoms, more preferably an alkenyl group having 2 to 6 carbon atoms. Specific examples include vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, and cyclohexenyl group. Among these, a vinyl group is preferred.

Substituents other than the above alkenyl groups include monovalent hydrocarbon groups having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms. Specifically, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, and octyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group, aryl groups such as phenyl group and tolyl group, benzyl group , aralkyl groups such as 2-phenylethyl group, and the like. Note that a fluoroalkyl group in which a part of the alkyl group is substituted with a fluorine atom may also be used. Among these, methyl group and phenyl group are preferred, and methyl group is particularly preferred.

Further, the above component (A) has two or more alkenyl groups in one molecule, preferably 2 to 50 alkenyl groups, and more preferably 2 to 20 alkenyl groups. Among these, those having a vinyl group are particularly preferred. In this case, it is preferable that 0.01 to 20 mol%, particularly 0.02 to 10 mol% of all siloxane units in the organopolysiloxane be siloxane units having alkenyl groups. Note that this alkenyl group may be bonded to a silicon atom at the end of the molecular chain, or may be bonded to a silicon atom in the middle of the molecular chain (non-terminal of the molecular chain), or both, but at least Preferably, it is bonded to the silicon atom at the end of the molecular chain.

In addition, preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more of all siloxane units in the organopolysiloxane, particularly preferably all siloxane units other than siloxane units having an alkenyl group are dialkylsiloxy A group, especially a dimethylsiloxy group, is preferred.

The molecular structure of the organopolysiloxane, component (A), is preferably linear or linear with a partially branched structure. Specifically, the repeating structure of the diorganosiloxane units constituting the main chain of the organopolysiloxane consists of repeating only dimethylsiloxane units, or as a part thereof, diphenylsiloxane units, methylphenylsiloxane units, methyl Those into which diorganosiloxane units such as vinylsiloxane units and methyl-3,3,3-trifluoropropylsiloxane units are introduced are suitable.

Further, both ends of the molecular chain are preferably blocked with a group selected from, for example, a trimethylsiloxy group, a dimethylphenylsiloxy group, a vinyldimethylsiloxy group, a divinylmethylsiloxy group, a trivinylsiloxy group, etc. Particularly preferred is blockade with a group.

Examples of the organopolysiloxane of component (A) include methylvinylpolysiloxane, methylphenylvinylpolysiloxane, methyltrifluoropropylvinylpolysiloxane, and the like.

Such organopolysiloxanes can be produced, for example, by (co)hydrolyzing and condensing one or more organohalogenosilanes, or by converting cyclic polysiloxanes (siloxane trimers, tetramers, etc.) into alkaline or It can be obtained by ring-opening polymerization using an acidic catalyst.

The average degree of polymerization of the organopolysiloxane is 1,000 to 100,000, preferably 2,000 to 50,000, more preferably 2,500 to 30,000, particularly preferably 3,000 to 20. ,000. Moreover, the properties of this organopolysiloxane are so-called raw rubber-like (non-liquid) without self-flowing properties at room temperature (25° C.). If the average degree of polymerization is too small, problems such as roll adhesion will occur when compounded, and roll workability will deteriorate. Note that this degree of polymerization can be measured as a weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis.

The above-mentioned component (A) may be used alone or in a mixture of two or more having different molecular weights (degrees of polymerization) and molecular structures.

-(B) Component-
Component (B), reinforcing silica, is a filler added to obtain a silicone rubber composition with excellent mechanical strength, and for this purpose, it has a specific surface area (BET adsorption method) of 50 to 450 m2 ^. /g, preferably 100 to 450 m ² /g, more preferably 100 to 300 m ² /g. If the specific surface area is less than 50 m ² /g, the mechanical strength of the cured product will be low.

Examples of such reinforcing silica include fumed silica, precipitated silica (wet silica), and those whose surfaces have been hydrophobized with chlorosilane, hexamethyldisilazane, etc. Suitably used. Among these, fumed silica is preferred because of its excellent dynamic fatigue properties.

The above component (B) may be used alone or in combination of two or more.

The amount of the reinforcing silica as the component (B) is 5 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the organopolysiloxane as the component (A). If the amount of the component (B) is too small, no reinforcing effect will be obtained, and if it is too large, workability will deteriorate, mechanical strength will decrease, and dynamic fatigue durability will deteriorate. It ends up.

（式中、Ｒ^１は独立して炭素数１～８の１価炭化水素基であり、ｍは１～５０の整数である。） -(C) Component-
In the present invention, as component (C), an organosiloxane having hydroxysilyl groups (silanol groups) at both ends, which is represented by the following general formula (1), is used.

(In the formula, R ¹ is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 1 to 50.)

Here, R ¹ is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, and specifically, R 1 is a monovalent hydrocarbon group having 1 to 8 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, etc. It is preferably an alkenyl group having 2 to 8 carbon atoms such as an alkyl group, a vinyl group, or an allyl group, or an aryl group having 6 to 8 carbon atoms such as a phenyl group or tolyl group, and more preferably a methyl group or a vinyl group. .

Further, m is an integer of 1 to 50, preferably 2 to 20.

The amount of component (C) used is 1.0 to 50.0 parts by weight, preferably 2.0 to 20.0 parts by weight, per 100 parts by weight of component (A). If the amount of organopolysiloxane endblocked with silanol groups at both ends is too small, plasticity reversion (creep hardening) will be large, and if it is too large, the plasticity of the compound will be too low and roll stickiness will occur when kneading means such as a roll mill are used. This deteriorates roll workability.

-(D) Component-
Component (D) is a condensation reaction catalyst. This is for causing a condensation reaction between the hydroxysilyl groups (silanol groups) present on the silica surface of the component (B) and the hydroxysilyl groups (silanol groups) of the component (C).

The condensation reaction catalyst of component (D) is an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa. Specific examples of such component (D) include propylamine (melting point: -83°C, boiling point: 49°C), isopropylamine (melting point: -101°C, boiling point: 33°C), and tert-butylamine (melting point: - 72.65°C, boiling point: 46°C), and lower dialkylamines such as diethylamine (melting point: -50°C, boiling point: 56°C). Note that the melting point and boiling point described above are the temperatures described in the SDS published by Fuji Film Wako Pure Chemical Industries, Ltd.

There is no particular restriction on the method of adding the above (D) component, but after adding the above (D) component to the above (C) component, it should be immediately added to the pot into which the above (B) component was added. It is preferable. By doing so, the condensation reaction between the hydroxysilyl group (silanol group) of the component (B) and the hydroxysilyl group (silanol group) of the component (C) can proceed efficiently. Furthermore, in order to make it easier to knead the component (D) using a two-roller, kneader, etc., the component (D) may be made into a paste with organopolysiloxane or the like in advance.

The amount of component (D) added is 0.0001 to 0.1 parts by mass, preferably 0.001 to 0.1 parts by mass, and more preferably 0.01 parts by mass, per 100 parts by mass of component (A). ~0.05 part by mass. If the amount of component (D) used is too small, the time required for surface treatment of the reinforcing silica may become longer, or the degree of surface treatment may become lower, making it impossible to obtain a silicone rubber compound. On the other hand, if the amount of component (D) used is too large, component (D) cannot be removed from the resulting silicone rubber compound, and the plasticity of the silicone rubber compound may increase over time, or if a platinum catalyst is used. When obtaining silicone rubber using addition curing, there is a possibility that the physical properties of the obtained rubber may not be stable or that tack (adhesion) may develop on the rubber surface due to insufficient curing.

The millable silicone rubber compound of the present invention is preferably produced using an apparatus capable of uniformly kneading predetermined amounts of the components (A) to (D) described above. Although there are no particular restrictions on the equipment that can uniformly knead, in consideration of the reactivity of the component (D) and its removal after the reaction is completed, it is preferable to use equipment that easily generates heat of stirring. Specifically, a millable silicone rubber compound can be obtained by kneading using a kneader, a Banbury mixer, a roll mill, etc. Among these, it is particularly preferable to produce using a kneader.

When mixing the above components (A) to (D), the organosiloxane blocked at both ends with hydroxysilyl groups (silanol groups), which is the above component (C), acts as a wetter for the reinforcing silica, which is the above component (B). In order to enhance the effect of the wetter, it is effective to add a condensation reaction catalyst, which is the component (D). By adding this component, the reinforcing silica, which is component (B), quickly acts as a wetter. In order to effectively treat the surface of component (B), it is essential that both ends of component (C) be hydroxysilyl groups (silanol groups).

Here, the temperature for mixing the above components (A) to (D) is preferably 0 to 120°C, more preferably 30 to 100°C, and still more preferably 30 to 90°C. Further, the time for mixing the above components (A) to (D) is not particularly limited, but considering production efficiency, it is preferably 1 to 300 minutes, more preferably 10 to 120 minutes. is desirable.

When the above-mentioned components (A) to (D) are mixed by the above method, heat of stirring is generated. The stirring heat varies depending on the degree of polymerization of the component (A) used, the amount of reinforcing silica as the component (B), and the ratio of the component (A) to the component (B). If the composition is suitable for a compound, ie, a conventional millable silicone rubber compound, stirring heat of about 30 to 120° C. is generated. The component (D) used in the present invention is a liquid when blended, so it is easy to handle and has excellent reactivity between the component (B) and the component (C). In addition, since the boiling point at normal pressure of 1013 hPa is 30 to 60°C, the component (D) can be removed from the millable silicone rubber compound using only the stirring heat generated during compounding. Therefore, it is possible to supply the same millable type silicone rubber compound to the market while contributing to the current decarbonized society and environmental issues such as reducing CO ₂ emissions.

The millable silicone rubber compound obtained as described above is kneaded and then blended with a curing agent (E) to be described later, to obtain a millable silicone rubber composition.

[Millable silicone rubber composition and manufacturing method]
The millable silicone rubber composition of the present invention is obtained by removing the component (D) from the millable silicone rubber compound by kneading and adding the component (E) described below.

Specifically, the above-mentioned millable silicone rubber compound is kneaded, and in the presence of the above-mentioned (D) component, which is a catalyst, the above-mentioned (B) component is surface-treated with the above-mentioned (C) component, and the above-mentioned mixture is heated by stirring. A method for producing a millable silicone rubber composition is provided, in which a curing agent (E) is added after removing component (D).

-(E) Component-
The millable silicone rubber composition of the present invention contains a kneaded product obtained by kneading the above millable silicone rubber compound and (E) a curing agent.

(E) The curing agent is not particularly limited as long as it can cure the component (A), but it is of the (E1) addition reaction (hydrosilylation reaction) type generally known as a rubber curing agent. A curing agent for the hydrosilylation reaction, consisting of a combination of an organohydrogenpolysiloxane (crosslinking agent) and a hydrosilylation catalyst, or (E2) an organic peroxide is preferred.

Among these, the millable silicone rubber compound of the present invention is suitable for use as an addition reaction type curing agent because it contains almost no impurities that inhibit addition curing.

（式中、Ｒ^２は独立して、水素原子、または炭素数１～８のアルキル基、炭素数６～１０のアリール基、及び炭素数７～１０のアラルキル基から選ばれる基であり、１分子中２個以上のＲ^２が水素原子である。なお、同じケイ素原子上に２個以上の水素原子が存在することはない。ａは２≦ａ≦３０の整数、ｂは０≦ｂ≦３００の整数、ｃは０≦ｃ≦１０の整数、及びｄは０≦ｄ≦３０の整数である。なお、各シロキサン単位の結合はブロックであってもランダムであってもよい。） The organohydrogenpolysiloxane used as the crosslinking agent in the addition reaction type curing agent (E1) preferably has two or more hydrosilyl groups in one molecule. Particularly preferred is an organohydrogenpolysiloxane represented by the following general formula (2).

(In the formula, R ² is independently a hydrogen atom or a group selected from an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, and 1 Two or more R ² in the molecule are hydrogen atoms. Two or more hydrogen atoms cannot exist on the same silicon atom. a is an integer of 2≦a≦30, and b is 0≦b≦ 300 integer, c is an integer of 0≦c≦10, and d is an integer of 0≦d≦30. Note that the bonding of each siloxane unit may be block or random.)

Here, R ² is independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, preferably 6 to 8 carbon atoms, and an aryl group having 7 to 8 carbon atoms. It is a group selected from 10, preferably 7 to 9 aralkyl groups. However, 2 or more, preferably 2 to 200, more preferably 2 to 130 R ² atoms in one molecule are hydrogen atoms. Examples of alkyl groups include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, hexyl group, and cycloalkyl groups such as cyclohexyl group. It will be done. Examples of the aryl group include phenyl group, tolyl group, and the like. Examples of aralkyl groups include benzyl group and 2-phenylpropyl group. Note that a fluoroalkyl group in which a part of the alkyl group is substituted with a fluorine atom may also be used. Further, a is an integer of 2≦a≦30, preferably 2≦a≦20. b is an integer of 0≦b≦300, preferably 3≦b≦200. c is an integer of 0≦c≦10, preferably 0≦c≦5. and d is an integer of 0≦d≦30, preferably 0≦d≦20.

Furthermore, the molecular structure of the organohydrogenpolysiloxane may be linear, cyclic, branched, or three-dimensional network structure. In this case, the number of silicon atoms (or degree of polymerization) in one molecule is 2 to 300, particularly about 4 to 200, and a liquid at 25° C. is preferably used. Note that the hydrosilyl group may be present at the end of the molecular chain, at a side chain (in the middle of the molecular chain), or at both.

Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane. Dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, methylhydrogenpolysiloxane blocked with trimethylsiloxy groups on both ends, dimethylsiloxane/methylhydrogen blocked with trimethylsiloxy groups on both ends Siloxane copolymer, dimethylpolysiloxane with dimethylhydrogensiloxy groups blocked at both ends, dimethylsiloxane/methylhydrogensiloxane copolymer blocked with dimethylhydrogensiloxy groups at both ends, methylhydrogensiloxane/diphenylsiloxane copolymer blocked with trimethylsiloxy groups at both ends Polymer, methylhydrogensiloxane/diphenylsiloxane/dimethylsiloxane copolymer blocked with trimethylsiloxy groups at both ends, cyclic methylhydrogenpolysiloxane, cyclic methylhydrogensiloxane/dimethylsiloxane copolymer, cyclic methylhydrogensiloxane/diphenylsiloxane・Dimethylsiloxane copolymer, a copolymer consisting of (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units, (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units, and (C ₆ H ₅ )SiO _3/2 units, etc., and in each of the above-mentioned exemplified compounds, some or all of the methyl groups are other alkyl groups such as ethyl group or propyl group, or aryl groups such as phenyl group. Examples include those that have been replaced. Moreover, as such an organohydrogenpolysiloxane, a compound having the following structural formula can be specifically exemplified.

（式中、ｋは２～１０の整数、ｓ及びｔはそれぞれ０～１０の整数である。）

(In the formula, k is an integer of 2 to 10, and s and t are each integers of 0 to 10.)

The organohydrogenpolysiloxane preferably has a viscosity of 0.5 to 10,000 mPa·s, particularly preferably 1 to 300 mPa·s, at 25°C. Note that the viscosity is a value measured using a rotational viscometer according to the method described in JIS K7117-1:1999.

This organohydrogenpolysiloxane also has a molar ratio of silicon-bonded hydrogen atoms (i.e., hydrosilyl groups) in the organohydrogenpolysiloxane to silicon-bonded alkenyl groups in component (A) (hydrosilyl groups). /alkenyl group) is preferably 0.5 to 10, more preferably 0.8 to 6, still more preferably 1 to 5. If it is 0.5 or more, crosslinking will be sufficient and sufficient mechanical strength will be obtained. Moreover, if it is 10 or less, physical properties after curing will not deteriorate, and in particular, heat resistance and compression set resistance will not deteriorate.

The hydrosilylation catalyst used in the addition reaction curing agent (E1) is a catalyst that promotes the addition reaction between the alkenyl group in the component (A) and the hydrosilyl group in the organohydrogenpolysiloxane as a crosslinking agent. It is. Examples of the hydrosilylation catalyst include platinum group metal catalysts such as ruthenium and platinum. Platinum group metal catalysts include simple platinum group metals and their compounds. For this purpose, conventionally known catalysts for addition reaction-curable silicone rubber compositions can be used. For example, particulate platinum metal adsorbed on a carrier such as silica, alumina or silica gel, platinum chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohol, complexes of chloroplatinic acid and olefins. , a complex of chloroplatinic acid and a vinyl group-containing (poly)siloxane, a palladium catalyst, a rhodium catalyst, a ruthenium catalyst, and the like. Among these, platinum or platinum compounds are particularly preferred.

The amount of the hydrosilylation catalyst to be added may be any so-called catalytic amount that can promote the addition reaction, and is usually in the range of 1 ppm to 1% by mass in terms of platinum group metal mass relative to the amount of component (A) above. It is preferably used in a range of 10 to 500 ppm. If the amount added is 1 ppm or more, the addition reaction will be sufficiently promoted and curing will be sufficient. Further, if it is 1% by mass or less, the effect on reactivity is commensurate with the amount added, which is economical.

Further, in addition to the above-mentioned catalyst, an addition crosslinking control agent may be used for the purpose of adjusting the curing rate. Specific examples include ethynylcyclohexanol and tetramethyltetravinylcyclotetrasiloxane.

On the other hand, examples of the organic peroxide (E2) include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, and 2,4-dicumyl peroxide. , 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6-hexanediol-bis-t-butylperoxy carbonate etc.

The amount of organic peroxide added is preferably 0.1 to 15 parts by weight, particularly preferably 0.2 to 10 parts by weight, per 100 parts by weight of component (A). If the amount added is sufficient, the crosslinking reaction will proceed sufficiently, and physical property deterioration such as decreased hardness, insufficient rubber strength, and increased compression set will not occur. Further, when the amount added does not exceed the above, it is economically preferable, and the amount of decomposed products of the curing agent is sufficiently small, so that deterioration of physical properties such as increased compression set and discoloration of the obtained sheet are not increased.

In addition to the above-mentioned components, the millable silicone rubber composition of the present invention includes conductivity imparting agents such as carbon black, flame retardancy imparting agents such as iron oxide and halogen compounds, softeners, anti-aging agents, and ultraviolet absorbers. , colorants, etc. can be added.

The thus obtained millable silicone rubber composition of the present invention can be cured as a silicone rubber by curing at 80 to 300°C, particularly 100 to 200°C, for 5 seconds to 1 hour, especially 30 seconds to 30 minutes. You can get things.

EXAMPLES Hereinafter, the present invention will be specifically explained by showing examples, reference examples, and comparative examples, but the present invention is not limited to the following examples. The melting point and boiling point are at 1013 hPa, the average degree of polymerization is measured as the weight average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC) analysis, and the viscosity is determined by the method described in JIS K7117-1:1999. This is the value measured using a rotational viscometer.

[Example 1]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average polymerization degree of 4, and a viscosity at 25°C of 15 mPa·s, and 0.01 parts of isopropylamine (melting point: -101°C, boiling point: 33°C) Parts by mass were added and kneaded uniformly. The temperature before kneading was 27°C, but rose to 64°C one hour after the start of kneading (sampling 1). After 2 hours of kneading, the temperature reached 75°C (sampling 2). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 3).

[Example 2]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average degree of polymerization of 4, and a viscosity at 25°C of 15 mPa·s, and 0.01 parts by mass of diethylamine (melting point: -50°C, boiling point: 56°C). 1 part was added and kneaded uniformly. The temperature before kneading was 24°C, but rose to 67°C one hour after the start of kneading (sampling 4). After 2 hours of kneading, the temperature reached 78°C (sampling 5). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 6).

[Example 3]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average polymerization degree of 4, and a viscosity at 25°C of 15 mPa·s, tert-butylamine (melting point: -72.65°C, boiling point: 46°C) 0.01 part by mass was added and kneaded uniformly. The temperature before kneading was 20°C, but rose to 63°C one hour after the start of kneading (sampling 7). After 2 hours of kneading, the temperature reached 75°C (sampling 8). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 9).

[Example 4]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average polymerization degree of 4, and a viscosity at 25°C of 15 mPa·s, and 0.05 parts of isopropylamine (melting point: -101°C, boiling point: 33°C). Parts by mass were added and kneaded uniformly. The temperature before kneading was 23°C, but rose to 62°C one hour after the start of kneading (sampling 10). After 2 hours of kneading, the temperature reached 72°C (sampling 11). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 12).

[Example 5]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average degree of polymerization of 4, and a viscosity at 25°C of 15 mPa·s, and 0.10 parts of isopropylamine (melting point: -101°C, boiling point: 33°C). Parts by mass were added and kneaded uniformly. The temperature before kneading was 22°C, but rose to 64°C one hour after the start of kneading (sampling 13). After 2 hours of kneading, the temperature reached 78°C (sampling 14). Thereafter, for reference, this silicone rubber compound was heat treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 15).

[Comparative example 1]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average polymerization degree of 4, and a viscosity at 25°C of 15 mPa・s, hexamethyldisilazane (melting point: -78°C, boiling point: 125°C) 0 01 part by mass was added and kneaded uniformly. The temperature before kneading was 24°C, but rose to 66°C one hour after the start of kneading (sampling 16). After 2 hours of kneading, the temperature reached 76°C (sampling 17). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 18).

[Comparative example 2]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. 6.0 parts by mass of dimethylpolysiloxane, which has silanol groups at both ends, has an average degree of polymerization of 4, and a viscosity at 25°C of 15 mPa·s, and 0.30 parts of isopropylamine (melting point: -101°C, boiling point: 33°C). Parts by mass were added and kneaded uniformly. The temperature before kneading was 18°C, but rose to 60°C one hour after the start of kneading (sampling 19). After 2 hours of kneading, the temperature reached 73°C (sampling 20). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 21).

[Comparative example 3]
In a 3L kneader, 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units, and 0.025 mol% of dimethylvinylsiloxy units were added, with an average of vinyl groups bonded to silicon atoms per molecule. 100 parts by mass of organopolysiloxane raw rubber having an average degree of polymerization of 6,000 having 12 elements, 40 parts by mass of fumed silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) having a BET specific surface area of 200 m ² /g, and a dispersant. Then, 6.0 parts by mass of dimethylpolysiloxane having silanol groups at both terminals, an average degree of polymerization of 4, and a viscosity at 25° C. of 15 mPa·s was added and uniformly kneaded. The temperature before kneading was 19°C, but rose to 73°C one hour after the start of kneading (sampling 22). After 2 hours of kneading, the temperature reached 88°C (sampling 23). Thereafter, for reference, this silicone rubber compound was heat-treated at 160° C. for 2 hours to confirm the difference in physical properties from the above two samples (Sampling 24).

[test]
A millable silicone rubber composition was prepared using the kneaded products of each silicone rubber compound obtained as the compositions of Examples 1 to 5 and the compositions of Comparative Examples 1 to 3 and each silicone rubber compound, and then molded. Table 1 shows the results of the test using the test sheet.

○Plasticity measurement The sampled silicone rubber compound kneaded under each condition was kneaded 15 times using three rolls, and the William plasticity was measured 10 minutes later (initial stage), and then after 1 day at 40°C. The plasticity was measured for each, and the change over time after one day at 40°C with respect to the initial value was calculated. If the calculated result (change in plasticity) is within ±50 compared to the heat-treated silicone rubber compound kneaded product, it passes (equivalent to the conventional product), and if it deviates from this, it is rejected (different from the conventional product). ). Note that the compared values can be obtained using the following formula.
(Compared values) = (Change in plasticity of the heat-treated kneaded product) - (Change in plasticity of the kneaded product of the present invention)

で示されるオルガノハイドロジェンポリシロキサン（信越化学工業（株）製）０．８５質量部を添加し、均一に混合して、ミラブル型シリコーンゴム組成物を調製した後、この組成物を１２０℃で１０分間プレスキュアを行った試験用シートと、前述条件に更に、２００℃で４時間のポストキュアを行った試験用シートを作製した。両条件にて作成した試験用シートについて密度、硬さ（デュロメーターＡ）、引張強さ、切断時伸び、反発弾性率、及び圧縮永久歪み（１５０℃／２２時間、２５％圧縮）を測定した。その数値が、熱処理を行ったシリコーンゴムコンパウンドの混練物を用いて作成した試験用シートの結果と比較して誤差±２０％以内であるものを合格（従来品同等）、これに逸脱したものは不合格（従来品と異なる）と判定した。なお、比較した値は下記式で求めることができる。
（誤差）＝｛（本発明の混練物を用いて得られた硬化物の物性の値）－（熱処理を行った混練物を用いて得られた硬化物の物性の値）｝÷（熱処理を行った混練物を用いて得られた硬化物の物性の値）

○Measurement of physical properties A platinum catalyst containing 1% by mass of chloroplatinic acid-divinyldisiloxane complex as an addition reaction curing agent in terms of platinum atomic mass based on 100 parts by mass of the kneaded silicone rubber compound sampled under each condition. (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.01 part by mass and the following formula

After adding 0.85 parts by mass of organohydrogenpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) shown by and mixing uniformly to prepare a millable silicone rubber composition, this composition was heated at 120°C. A test sheet that was pre-cured for 10 minutes and a test sheet that was post-cured for 4 hours at 200° C. under the above conditions were prepared. The density, hardness (durometer A), tensile strength, elongation at break, rebound modulus, and compression set (150° C./22 hours, 25% compression) of the test sheets prepared under both conditions were measured. If the value is within ±20% of the result of a test sheet made using a kneaded product of heat-treated silicone rubber compound, it will pass (equivalent to conventional products), and if it deviates from this, it will pass. It was determined that the product failed (different from the conventional product). Note that the compared values can be obtained using the following formula.
(Error) = {(Value of physical properties of cured product obtained using the kneaded product of the present invention) - (Value of physical properties of cured product obtained using the kneaded product subjected to heat treatment)} ÷ (Value of physical properties of cured product obtained using the kneaded product subjected to heat treatment) physical property values of the cured product obtained using the kneaded product)

[Evaluation results]
Each silicone rubber compound obtained in Examples 1 to 5 satisfies the requirements of the present invention, and the physical properties of the kneaded product of each silicone rubber compound and the millable silicone rubber composition prepared using them are as follows. The physical properties of the molded test sheet of the cured product are almost the same as when using a silicone rubber compound manufactured using conventional heat treatment, which means that it shows the same performance as the conventional product. I understand.

On the other hand, in Comparative Example 1, since the boiling point of hexamethyldisilazane instead of the amine compound used in the present invention is high, when the same amount is mixed, the plasticity change of the silicone rubber compound is caused by heat treatment. It can be seen that it is larger when compared with the manufactured silicone rubber compound. As a result, the stability of silicone rubber compounds over time has decreased. Further, when the stirring time was 1 hour, the compression set after post-curing was also large.

In Comparative Example 2, the amine compound shown in the present invention is used, but the blending amount is different. Therefore, the amine compound cannot be removed from the silicone rubber compound by stirring heat alone, and the change in plasticity of the silicone rubber compound is extremely large compared to a silicone rubber compound produced using heat treatment. In such a case, the molded test sheet of the millable silicone rubber composition prepared using this silicone rubber compound was cured, but if a large amount of amine compound remained, the platinum catalyst was deactivated by the amine compound. Deviations in the blending amount can be said to be a fatal drawback, as there is a possibility that a molded test sheet cannot be obtained. Furthermore, when the silicone rubber compound was not heat treated, the compression set after press curing was also large. Further, when the stirring time was 1 hour, the elongation at cutting was large.

Furthermore, in Comparative Example 3, a silicone rubber compound was obtained without using a condensation reaction catalyst. In this case, as in Comparative Examples 1 and 2, the change in plasticity of the silicone rubber compound is greater than that of the silicone rubber compound produced using heat treatment. Therefore, in this case as well, the stability of the silicone rubber compound over time is reduced. Further, when the stirring time was 1 hour, the elongation at cutting after post-curing was reduced.

From the above results, the kneaded product of the silicone rubber compound obtained by the production method of the present invention shows the same aging stability as before even without forced heat treatment, and the silicone rubber composition prepared using it shows the same stability over time as before. It was found that the physical properties of the material also showed performance equivalent to that of the conventional method. As a result, even if the heat treatment step is omitted, a kneaded product of silicone rubber compound equivalent to the conventional one can be obtained, thereby contributing to energy saving and a decarbonized society.

The method for producing a millable silicone rubber compound of the present invention and the method for producing a silicone rubber composition obtained by adding a curing agent to a kneaded product of the compound have the same properties as conventional ones without forced heat treatment. A millable silicone rubber compound having the following properties can be easily obtained. Therefore, it is possible to achieve the recent energy savings and contribute to a decarbonized society. Furthermore, silicone rubber compositions using this silicone rubber compound can be expected to have a wide range of applications, including electrical equipment, automobiles, architecture, medical care, and food fields.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of

Claims (5)

Components (A) to (D) below (A) Organopolysiloxane raw rubber having two or more alkenyl groups bonded to silicon atoms in one molecule and having an average degree of polymerization of 1,000 to 100,000: 100 parts by mass,
(B) Reinforcing silica with a specific surface area of 50 to 450 m ² /g by BET adsorption method: 5 to 100 parts by mass,
(C) Organosiloxane having hydroxysilyl groups at both ends, represented by the following general formula (1): 1.0 to 50.0 parts by mass, and

(In the formula, R ¹ is independently a monovalent hydrocarbon group having 1 to 8 carbon atoms, and m is an integer of 1 to 50.)
(D) A millable silicone rubber compound comprising 0.0001 to 0.1 part by mass of an amine compound that is liquid at 25°C and has a boiling point of 30 to 60°C at 1013 hPa. A millable silicone rubber composition comprising a kneaded product obtained by kneading the millable silicone rubber compound according to claim 1 and (E) a curing agent. 3. The millable silicone rubber composition according to claim 2, wherein the component (E) is a curing agent for hydrosilylation reaction consisting of a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst. The millable silicone rubber composition according to claim 2, wherein the component (E) is an organic peroxide. The millable silicone rubber compound according to claim 1 is kneaded, and in the presence of the component (D) which is a catalyst, the component (B) is subjected to surface treatment with the component (C) while the heat of stirring is applied to the component (B). A method for producing a millable silicone rubber composition, which comprises adding (E) a curing agent after removing component D).