TWI679245B - Curable polysiloxane rubber composition and polysiloxane rubber member - Google Patents

Abstract

The present invention provides a curable polysiloxane rubber composition which is hardened to provide a hardened polysiloxane rubber hardened product, and a polysiloxane rubber member for a keypad obtained by curing the composition.

A curable polysiloxane rubber composition comprising the following components as a main component: (A) The following average composition formula (I) R _a SiO _{(4-a) / 2} (I)

(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number from 1.95 to 2.05.)

The organopolysiloxane with a degree of polymerization shown as 100 or more, (B) a reinforcing silica having a specific surface area of 50 m ² / g or more obtained by the BET adsorption method, (C) is represented by the following general formula (II)

(Wherein R ¹ and R ² are each independently an unsubstituted or substituted monovalent hydrocarbon group or alkenyl group which does not have the same or different aliphatic unsaturated bond, and at least one of R ¹ and R ² is an alkenyl group .N is an independent integer ranging from 1 to 10.)

The silazane compound shown.

(D) Hardener

Description

Curable polysiloxane rubber composition and polysiloxane rubber member

The present invention relates to a curable polysiloxane rubber composition which is excellent in durability of a polysiloxane rubber hardened material which is excellent in durability against dynamic fatigue such as repeated stretching, buckling, etc. after molding, and is made by curing the composition Silicone rubber member for keypad.

Polysiloxane rubber (rubber-like elastomer hardened with a silicone rubber composition) is characterized by excellent weather resistance, electrical properties, low compression set, heat resistance, and cold resistance. It is widely used in various fields such as electrical equipment, automobiles, construction, medical treatment, and food. Examples include rubber keys used for rubber contacts of remote controls, computer terminals, musical instruments, construction gaskets, photocopier rollers, development rollers, transfer rollers, charging rollers, paper feed rollers, etc. Anti-vibration rubber for audio equipment, gaskets for optical discs, mobile phones, computer keyboards, etc.

Among them, materials used in keypad materials, automotive connector sleeves, and the like are subject to repeated deformations such as stretching and buckling. Therefore, the silicone rubber used in this application requires high dynamic fatigue durability. For example, the characteristics of a small keyboard require less load change when typing. Generally, if the key is repeatedly typed, the weight of the key decreases as the number of keystrokes increases. The smaller the peak load reduction is, the better the key characteristics are. A material system exhibiting such a weight characteristic can be used as a good keypad material.

As a material excellent in such dynamic fatigue characteristics, a silicone rubber is widely used at present. Japanese Patent Laid-Open No. 6-145523 (Patent Document 1), Japanese Patent Laid-Open No. 9-132712 (Patent Document 2), Japanese Patent Laid-Open No. 2000-309710 (Patent Document 3), and Japanese Patent Laid-Open No. 2001-164111 Proposals (Patent Document 4), Japanese Patent Application Laid-Open No. 2013-221090 (Patent Document 5), and Japanese Patent No. 3184231 (Patent Document 6) have proposed polysiloxane rubber compositions having excellent dynamic fatigue durability.

However, in recent years, with the miniaturization of the equipment used, the number of people who have added large curved shapes due to materials has also increased. Therefore, with regard to the stringent requirements in recent years, there has not been sufficient satisfaction regarding dynamic fatigue durability.

On the other hand, as a patent for a silicone rubber composition in which a silazane compound having an alkenyl group is formulated, Japanese Patent Laid-Open No. 54-146850 (Patent Document 7), Japanese Patent Laid-Open No. 5- Japanese Patent No. 65417 (Patent Document 8). However, only those described as high-strengthening or silicon dioxide treatment agents are described, and no improvement in fatigue durability is described.

[Prior technical literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 6-145523

[Patent Document 2] Japanese Patent Application Laid-Open No. 9-132712

[Patent Document 3] Japanese Patent Laid-Open No. 2000-309710

[Patent Document 4] Japanese Patent Laid-Open No. 2001-164111

[Patent Document 5] Japanese Patent Laid-Open No. 2013-221090

[Patent Document 6] Japanese Patent No. 3184231

[Patent Document 7] Japanese Patent Laid-Open No. 54-146850

[Patent Document 8] Japanese Unexamined Patent Publication No. 5-65417

The present invention has been made in view of the above circumstances, and an object thereof is to provide a hardenable silicone rubber composition which is hardened and provides a silicone rubber hardened material excellent in dynamic fatigue durability, and a keypad obtained by hardening the composition. Constructed with silicone rubber.

The present inventors have devoted themselves to the results of the research in order to achieve the above-mentioned object, and have found that by formulating an organopolysiloxane having a polymerization degree of 100 or more (especially 1,000 or more), and reinforcing silica, the The curable polysiloxane rubber composition of an alkenyl silazane compound is hardened, and knowledge of a polysiloxane rubber hardened body (rubber-like elastomer) excellent in dynamic fatigue characteristics is obtained, and the present invention has been completed.

Therefore, the present invention provides the following curable polysiloxane rubber composition and a polysiloxane rubber member obtained by curing the composition.

[1]

A stiffening poly siloxane silicone rubber composition, which will be based component as a main component from the following: (A) represented by the following average compositional formula _{(I) R a SiO (4} -a) / 2 (I)

(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number from 1.95 to 2.05.)

100 parts by mass of an organopolysiloxane having a polymerization degree of 100 or more, (B) 5 to 70 parts by mass of reinforcing silica having a specific surface area of 50 m ² / g or more obtained by the BET adsorption method, (C ) With the following general formula (II)

(Wherein R ¹ and R ² are each independently an unsubstituted or substituted monovalent hydrocarbon group or alkenyl group which does not have the same or different aliphatic unsaturated bond, and at least one of R ¹ and R ² is an alkenyl group .N is an independent integer of 1-10. 0.01 to 10 parts by mass of the silazane compound shown in (D) an effective amount of a hardener.

[2]

As in the hardening polysiloxane rubber composition of [1], in the general formula (II) of the component (C), R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, and R At least one of the ² series is an alkenyl group.

[3]

The curable polysiloxane rubber composition according to [1] or [2], wherein the silazane compound of the component (C) is represented by the following general formula (III).

[4]

The polysiloxane rubber composition according to any one of [1] to [3], further as the (E) component, for each 100 parts by mass of the total of the (A) component and the (B) component, the following general formula (IV)

(In the formula, R ³ is the same or different alkyl or hydrogen atom, R ⁴ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and m is an integer from 0 to 50.)

The organosilane or organosiloxane shown contains 0.1 to 50 parts by mass.

[5]

The silicone rubber composition according to any one of [1] to [4] is hardened and A 100% elongation fatigue test of a silicone rubber hardened product of more than 2 million times.

[6]

A polysiloxane rubber member for a keypad is obtained by curing a curable polysiloxane rubber composition according to any one of [1] to [5].

According to the present invention, a curable polysiloxane rubber composition capable of providing a polysiloxane rubber cured material having excellent dynamic fatigue durability can be obtained.

Hereinafter, the present invention will be described in more detail.

-(A) Ingredient-

In the present invention, the component (A) is an organic polysiloxane having a degree of polymerization of 100 or more (particularly 1,000 or more) represented by the following average composition formula (I) as the main agent (matrix polymer) of the composition ).

R _a SiO _{(4-a) / 2} (I)

(In the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number from 1.95 to 2.05.)

In the above average composition formula (I), R represents the same or different non-substituted or substituted monovalent hydrocarbon group, and usually has 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms. Specific examples include: Methyl, ethyl, propyl, butane Alkyl, hexyl, octyl, etc., cyclopentyl, cyclohexyl, etc. cycloalkyl, vinyl, allyl, propenyl, etc. alkenyl, cycloalkenyl, phenyl, tolyl, etc. aryl Aralkyl, benzyl, 2-phenylethyl, etc., or a part or all of the hydrogen atoms of these groups substituted with a halogen atom or a cyano group, etc., preferably methyl, vinyl, benzene And trifluoropropyl, particularly preferably methyl and vinyl.

In particular, the organopolysiloxane as the component (A) has two or more in one molecule, usually 2 to 50, and especially 2 to 20 aliphatic unsaturated groups such as alkenyl and cycloalkenyl groups. A base is preferred, and a vinyl base is particularly preferred. At this time, 0.01 to 20 mole% of all R, especially 0.02 to 10 mole% of aliphatic unsaturated groups such as alkenyl groups are preferred. In addition, the aliphatic unsaturated group may be bonded to the silicon atom at the end of the molecular chain, and the silicon atom on the way to the molecular chain (non-terminal of the molecular chain) may also be the two. A silicon atom to the end of the molecular chain is preferred.

In addition, in the total R, 90 mole% or more, preferably 95 mole% or more, more preferably all R except for the aliphatic unsaturated group is an alkyl group, and especially a methyl group is most preferable.

In addition, a is 1.95 to 2.05, preferably 1.98 to 2.02, and more preferably a positive number of 1.99 to 2.01.

Specifically, the repeating structure of the two organosiloxane units (R ₂ SiO _2/2 , where R is the same as the above, and the same below) constituting the main chain of the organopolysiloxane is composed only of repeated dimethyl groups. Siloxane units, or as a part of the dimethyl polysiloxane structure composed of the repeating dimethylsiloxane units constituting this main chain, introduce phenyl, vinyl, 3 Diphenylsiloxane units, methylphenylsiloxane units, methylvinylsiloxane units, methyl 3,3,3- A trifluoropropylsiloxane unit or the like is preferably an organosiloxane unit.

The two ends of the molecular chain are, for example, trimethylsilyloxy, dimethylphenylsilyloxy, vinyldimethylsilyloxy, divinylmethylsilyloxy, trivinylsilyloxy, etc. Tertiary organic silyloxy (R ₃ SiO _1/2 ) or hydroxy diorganosilyloxy (R ₂ (HO) SiO _1/2 ), such as hydroxydimethylsilyloxy, is preferred for capping.

Examples of the organopolysiloxane as the component (A) include trimethylsilyloxy, dimethylphenylsilyloxy, dimethylvinylsilyloxy, methyl, and the like at the end of the molecular chain. Triorganosilyloxy (R ₃ SiO _1/2 ) such as divinylsilyloxy, trivinylsilyloxy or hydroxydiorganosilyloxy (R ₂ (HO ) SiO _1/2 ) end cap, the main chain is a straight chain composed of the aforementioned repeating two organosiloxane units (R ₂ SiO _2/2 ). Particularly preferred as the type of the substituent in the molecule (that is, a non-substituted or substituted monovalent hydrocarbon group bonded to a silicon atom) include methyl vinyl polysiloxane, methyl phenyl ethylene Polysiloxane, methyltrifluoropropylvinylpolysiloxane and the like.

Such organic polysiloxanes can be obtained by, for example, (co) hydrolyzing and condensing one or two or more organic halogenated silanes, or by using a basic or acidic catalyst to cyclic polysiloxanes (silicone). (Three-body, four-body, etc.) are obtained by ring-opening polymerization. These systems are basically linear diorganopolysiloxanes, but the component (A) may be a mixture of two or more types having different molecular weights (degrees of polymerization) or molecular structures.

The degree of polymerization (or the number of silicon atoms in the molecule) of the above-mentioned organic polysiloxane is 100 or more (usually 100 to 100,000), preferably 1,000 to 100,000, more preferably 2,000 to 50,000, and particularly preferably 3,000 to 20,000. There is no self-flow at room temperature (25 ° C), so-called raw rubber (non-liquid) is preferred. If the polymerization degree is too small, it is difficult to obtain a so-called kneading type when preparing a compound (that is, a non-liquid state that can be uniformly mixed under shear stress using a kneading machine such as a rolling mill and has no self-flowing property at room temperature. (1) The silicone rubber compound causes problems such as sticking of the roller, and deteriorates the workability of the roller. The polymerization degree (or molecular weight) is a weight average polymerization degree (or weight average molecular weight) in terms of polystyrene, which can be measured by gel permeation chromatography (GPC) using toluene or the like as a developing solvent.

-(B) ingredients-

(B) Reinforcement of the component Silicon dioxide is a reinforcing filler added to obtain a silicone rubber composition having excellent mechanical strength. For this purpose, the specific surface area (BET adsorption method) must be 50 m ² / g. Above, it is preferably 100 to 450 m ² / g, and 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 hardened product will be lowered.

Examples of such reinforcing silica include aerosol silica (smoke silica), precipitated silica, and the like. In addition, chlorosilane or hexamethyldisilazane is used on the surface of these substances. It can also be used suitably, such as a hydrophobizing process. Among them, fumed silica with excellent dynamic fatigue characteristics is preferred. (B) A component may use 1 type or 2 or more types together.

(B) The compounding amount of component-reinforcing silica is relative to (A) 100 parts by mass of the organopolysiloxane is 5 to 70 parts by mass, preferably 10 to 50 parts by mass. (B) When the blending amount of the component is too small, the reinforcing effect cannot be obtained, and when it is too large, the workability is deteriorated, and the mechanical strength is reduced, and the dynamic fatigue durability is also deteriorated.

-(C) component-

(C) The component is represented by the following general formula (II)

(Wherein R ¹ and R ² are each independently an unsubstituted or substituted monovalent hydrocarbon group or alkenyl group which does not have the same or different aliphatic unsaturated bond, and at least one of R ¹ and R ² is an alkenyl group .N is an independent integer of 1-10.)

The silazane compound shown.

In the above formula (II), the duplication number n of the two-functional organosiloxane units (R ² ) ₂ SiO _2/2 ) is independent of each other, preferably about 1 to 10, particularly preferably 3 ~ 7 or so.

In addition, R ¹ and R ² are each independently an unsubstituted or substituted monovalent hydrocarbon group or alkenyl group which does not have the same or different aliphatic unsaturated bond, and at least one of R ¹ and R ² is an alkenyl group. Examples of the non-substituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond include those in which R is the same as the group other than the alkenyl group in the exemplification of R in the component (A), and particularly methyl, Alkyl groups having about 1 to 6 carbon atoms are preferred. Examples of the alkenyl group include a carbon number of 2 to 10, such as a vinyl group, an allyl group, and a propenyl group. Particularly preferred is a carbon number of about 2 to 4, and particularly preferred is a vinyl group.

In addition, the silazane compound as the component (C) has one or more alkenyl groups in the molecule, preferably has two or more alkenyl groups, and particularly preferably has three or more and 20 or less, especially four or more and 12 or less. Those are better. In addition, this alkenyl group exists as R ¹ (that is, as a terminal alkenyl group) which is a silicon atom bonded to a tertiary organosilyloxy group ((R ¹ ) ₃ SiO _1/2 ), and serves as a bond. The presence of R ² (that is, as a side alkenyl group) of a silicon atom in a bifunctional diorganosiloxane unit ((R ² ) ₂ SiO _2/2 ) exists from the viewpoint of improving dynamic fatigue durability Is better.

Specific examples of the component (C) include vinyl-containing silazane compounds represented by the following general formulae (III), (V), (VI), (VII), but the general formula (III) The vinyl-containing silazane compounds shown are particularly preferred.

The compounding amount of the organosilazane compound containing a vinyl group in the component (C) is 0.01 to 10 parts by mass, preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the organopolysiloxane in the component (A). When the blending amount of the component (C) is too small, the effect of improving dynamic fatigue durability cannot be obtained, and when it is too large, the hardness of the obtained rubber becomes too high, and it is also uneconomical.

-(D) ingredients-

The curing agent for the component (D) is not particularly limited if it is obtained by curing the component (A), but it is generally known as a rubber curing agent (i) addition reaction (hydrosilylation reaction) type curing agent Organohydrogenpolysiloxane (Crosslinking agent) A combination with a hydrosilylation catalyst or (ii) an organic peroxide is preferred.

The organohydrogenpolysiloxane which is a crosslinking agent of the above (i) addition reaction (hydrosilylation reaction) is one that contains at least two hydrogen atoms (SiH groups) bonded to silicon atoms in one molecule, A conventionally known organohydrogenpolysiloxane represented by the following average composition formula (i) can be applied.

R ⁵ _b H _c SiO _{(4-bc) / 2} (VIII)

(Here, R ⁵ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, preferably one having no aliphatic unsaturated bond. As specific examples, methyl, ethyl, propyl, and isopropyl are used.) Non-substituted, such as alkyl, butyl, isobutyl, third butyl, pentyl, hexyl, etc., cyclohexyl, cycloalkyl, phenyl, aryl, benzyl, etc. Monovalent hydrocarbon groups, 3,3,3-trifluoropropyl, cyanomethyl, and the like are substituted monovalent hydrocarbon groups in which at least a part of the hydrogen atoms of the aforementioned monovalent hydrocarbon groups are substituted with halogen atoms or substituted alkyl groups such as cyano groups. B 0.7 to 2.1, c is 0.01 to 1.0, and b + c is 0.8 to 3.0, preferably b is 0.8 to 2.0, c is 0.10 to 1.0, preferably 0.18 to 1.0, more preferably 0.2 to 1.0, and b + c is a positive number that satisfies 1.0 ~ 2.5.)

In addition, the molecular structure of the organohydrogenpolysiloxane may be any of a linear structure, a cyclic structure, a bifurcated structure, and a three-dimensional mesh structure. In this case, those having 2 to 300 silicon atoms (or a degree of polymerization) in one molecule can be suitably used, especially those having a liquid state of about 4 to 200 at room temperature. In addition, the hydrogen atom (SiH group) bonded to the silicon atom may be at the end of the molecular chain, or at the side chain (in the middle of the molecular chain), or both of them. It is used in one minute. The seed contains at least 2 (usually 2 to 300), preferably 3 or more (for example, 3 to 200), and preferably 4 to 150 or so.

Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisilaxane, 1,3,5,7-tetramethylcyclotetrasiloxane, and methyl hydrogen. Cyclopolysiloxane, methylhydrosiloxane, dimethylsiloxane cyclic copolymer, tris (dimethylhydrosilane) methylsilane, tris (dimethylhydrosilane) phenylsilane, Trimethylsiloxy-terminated methylhydrogen polysiloxane on both ends, trimethylsiloxy-terminated dimethylsiloxane on both ends, methylhydrosiloxane copolymer, dimethylhydrogen on both ends Silanol-terminated dimethylpolysiloxane, dimethylhydrosiloxy-terminated dimethylsiloxane-terminated, methylhydrosiloxane copolymer, trimethylsiloxy-terminated at both terminals Methylhydrosiloxane, diphenylsiloxane copolymer, trimethylsiloxy terminated methylhydrosiloxane, diphenylsiloxane, dimethylsiloxane copolymer, cyclic Methylhydrogenpolysiloxane, cyclic methylhydrosiloxane, dimethylsiloxane copolymer, cyclic methylhydrosiloxane, diphenylsiloxane, dimethylsiloxane copolymer It was made (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units consisting of Copolymer, a (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units and a copolymer (C ₆ H ₅₎ SiO _3/2 units, or constituting the respective compound shown embodiment, a part of methyl Or all substituted with other alkyl groups such as ethyl and propyl, or aryl groups such as phenyl. Moreover, as such an organic hydrogen polysiloxane, the compound of a following structural formula is illustrated specifically.

(Where k is an integer from 2 to 10, and s and t are integers from 0 to 10.)

As the organohydrogen polysiloxane, the viscosity at 25 ° C is 0.5 to 10,000 mPa · s, particularly preferably 1 to 300 mPa · s. Viscosity can be measured by a rotating viscometer.

The compounding amount of the organohydrogen polysiloxane is 100 parts by mass with respect to the organopolysiloxane of the component (A), preferably 0.1 to 30 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.3 to 10 Parts by mass.

The organohydrogenpolysiloxane is a hydrogen atom of a silicon atom bonded to an organohydrogen polysiloxane with respect to an aliphatic unsaturated group such as an alkenyl group of a silicon atom bonded to the component (A). (That is, SiH group), the molar ratio is 0.5 to 10 mol / mol, preferably 0.8 to 6 mol / mol, and more preferably 1 to 5 mol / mol. good. If it is less than 0.5 Moore / Mole, the cross-linking may not be sufficient, and sufficient mechanical strength may not be obtained. If it exceeds 10 Moore / Mole, physical properties after hardening are reduced, especially heat resistance and A case where the compression distortion is significantly deteriorated.

In addition, the hydrosilylation catalyst used in the above-mentioned (i) addition reaction (hydrosilylation reaction) is a crosslinking reaction in which an aliphatic unsaturated group (such as an alkenyl group) in the component (A) is used as a crosslinking agent. A catalyst in which the silicon atom in the above-mentioned organic hydrogen polysiloxane is bonded to a hydrogen atom (SiH) to perform an addition reaction. Examples of the hydrogenated silylation catalyst system include a platinum group metal catalyst, and a platinum group metal monomer and the compound. Among them, the catalyst is a conventional addition reaction-hardening polysiloxane rubber composition. You can use a well-known person. Examples include fine particles of platinum metal adsorbed on a carrier such as silica, alumina, or silica gel, platinum tetrachloride, chloroplatinic acid, an alcohol solution of chloroplatinic acid hexahydrate salt, and palladium. Catalyst, rhodium catalyst, etc., but platinum or a platinum compound is preferred.

The addition amount of the hydrosilylation catalyst can promote the addition reaction, that is, the so-called catalyst amount is sufficient. Usually, it is converted to the mass of the platinum group metal with respect to the (A) component, and it is used within the range of 1 ppm to 1% by mass. , But a range of 10 to 500 ppm is preferred. If the added amount is less than 1 ppm, the addition reaction cannot be sufficiently promoted and hardening may be insufficient. On the other hand, if it exceeds 1% by mass, even if the amount is increased beyond this amount, the effect on reactivity will be small and it may become Uneconomic situation.

In addition, in addition to the above-mentioned catalysts, for the purpose of adjusting the curing speed, an addition crosslinking control agent can also be used. Specific examples include ethynylcyclohexanol and tetramethyltetravinylcyclotetrasiloxane.

On the other hand, examples of (ii) organic peroxides include benzamyl peroxide, 2,4-dichlorobenzyl peroxide, and p-methylbenzyl peroxide. , O-methylbenzylidene peroxide, 2,4-bisisophenylpropyl peroxide, 2,5-dimethyl-bis (2,5-tert-butyl peroxide) Hexane, di-third butyl peroxide, third butyl perbenzoate, 1,6-hexanediol-bis-peroxy third butyl carbonate, and the like.

The addition amount of the organic peroxide is preferably 0.1 to 15 parts by mass, and particularly preferably 0.2 to 10 parts by mass, with respect to 100 parts by mass of the component (A). If the added amount is too small, the cross-linking reaction does not proceed sufficiently, and the hardness may decrease, the rubber strength may be insufficient, and the compression set may increase, such as deterioration in properties. If the added amount is too large, it is not only economically unsatisfactory, but also has degradation products of the hardener. It may be generated in large quantities, and the compression set may be increased, such as an increase in permanent deformation, or the discoloration of the obtained sheet may increase.

In the polysiloxane rubber composition of the present invention, in addition to the above-mentioned components, it may be used as an optional component as required, and further as a component (E), containing both ends of a molecular chain represented by the following general formula (IV). Silanol groups (hydroxyl groups bonded to silicon atoms) or alkoxy-terminated organosilanes or organosiloxanes are used as dispersants for the above-mentioned reinforcing silica dioxide fillers. By adding this component, the dispersibility of the silica filler into the rubber can be improved, and the processability can also be improved.

(In the formula, R ³ is the same or different alkyl or hydrogen atom, R ⁴ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and m is an integer from 0 to 50.)

Here, R ³ is the same or different alkyl or hydrogen atom, and the organosilane or organosiloxane represented by the general formula (IV) above has an alkoxy group or a hydroxyl group at both ends of the molecular chain. Examples of R ^{3 include} a hydrogen atom or an alkyl group having 1 to 4 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and third butyl, methyl, ethyl, and hydrogen. Atoms are better.

R ⁴ is usually 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms. Specific examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and tert-butyl. Alkyl and other alkyl groups, cyclohexyl and other cycloalkyl groups, vinyl, allyl, propenyl, isopropenyl, butenyl, isobutenyl, hexenyl, cyclohexenyl and other alkenyl and phenyl groups , Aryl groups such as tolyl, aralkyl groups such as β-phenylpropyl, or some or all of the hydrogen atoms of carbon atoms bonded to these groups are replaced with halogen atoms, cyano groups, etc., such as chloroform And the like, methyl, vinyl, phenyl, and trifluoropropyl are preferred, and methyl and vinyl are particularly preferred. From the viewpoint of compatibility with the organopolysiloxane of the component (A), it is preferably the same as the monovalent hydrocarbon group of the component (A) (that is, R in the formula (1)).

m is an integer from 0 to 50, preferably from 1 to 30. If m exceeds 50, the effect may be reduced as a treating agent for treating the reinforcing silica of the component (B).

(E) component is an arbitrary component added as needed, but when formulating (E) component, the blending amount of (E) component is 100 parts by mass per 0.1 (A) component and (B) component, 0.1 ~ It is preferably 50 parts by mass, particularly 0.5 to 30 parts by mass, and especially 0.5 to 20 parts by mass. If it is less than 0.1 parts by mass, it may be difficult to knead, and the plastic reset may become large. If it exceeds 50 parts by mass, the obtained silicone rubber composition may have adhesiveness.

In the polysiloxane rubber composition of the present invention, in addition to the above components, as long as the purpose of the present invention is not impaired, a conductivity imparting agent such as carbon black, such as iron oxide, or a flame retardant such as a halogen compound, may be added Property imparting agent, softener, anti-aging agent, ultraviolet absorber, colorant, etc.

The polysiloxane rubber composition of the present invention can be obtained by kneading a specific amount of the above-mentioned components with two rollers, a kneader, a Banbury mixer, or the like.

The polysiloxane rubber composition of the present invention is mainly used as a keypad. In order to form the keypad, it is necessary to harden the polysiloxane rubber composition, but the hardening conditions are not particularly limited. In general, a keypad can be obtained by heating and hardening at 80 to 300 ° C, especially at 100 to 250 ° C for 5 seconds to 1 hour, especially about 30 seconds to 30 minutes. In addition, post curing can be performed at 100 to 200 ° C for about 10 minutes to 10 hours.

The molding method is not particularly limited, but press molding is preferred.

The polysiloxane rubber composition of the present invention is a polysiloxane obtained by curing under conditions of pressure curing (primary curing) at 165 ° C / 10 minutes and post-curing (secondary curing) at 200 ° C / 4 hours. The 100% elongation fatigue test of the hardened rubber is more than 2 million times, especially more than 3 million times, and especially more than 3.5 million times. If the 100% elongation fatigue test is less than 2 million times, dynamic fatigue durability may be poor when molded into a keypad. In addition, in order to obtain a polysiloxane rubber hardened product that has reached 2 million times or more in a 100% elongation fatigue test, at least as an essential component, the above-mentioned (A) to (D) components are uniformly used at the above-mentioned specific blending ratio Ground The kneaded and mixed polysiloxane rubber composition may be used.

[Example]

Hereinafter, examples and test examples will be described to specifically explain the present invention, but the present invention is not limited to the following examples. The parts in the following examples represent parts by mass. The measurement methods of physical properties and the evaluation methods of dynamic fatigue properties are shown below.

Physical property test

The test sheets obtained in the examples and comparative examples were used to measure hardness (hardness meter type A), tensile strength, and elongation at the time of cutting in accordance with JIS K6249. The results are shown in Table 1.

Test method for dynamic fatigue characteristics

The dynamic fatigue durability is measured by the following method.

[100% tensile fatigue test]

Using the test sheet obtained in the examples and comparative examples, the test piece was punched out with a No. 3 dumbbell-shaped body, and the ruled lines were set so that the distance between the ruled lines became 20 mm. It is set on the De Mattia testing machine in a way that the marking line is changed from 20mm to 40mm (0 ~ 100% stretch), and repeatedly stretched at a speed of 300 times per minute. The number of times until the dumbbell-shaped body was broken was measured. The results are shown in Table 1.

[Example 1]

A dimethylsiloxane unit containing 99.850 mole% of diorganosiloxane units constituting the main chain and a 0.125 mole% of methylvinylsiloxane unit, and a dimethylvinylsilane as a terminal end of the molecular chain 100 parts of linear organic polysiloxane (raw rubber) with an average degree of polymerization of 0.025 mole% of oxygen groups of about 6,000, and a fuming silica (trade name AEROSIL 200, Japan AEROSIL Corporation) with a BET specific surface area of 200 m ² / g (Manufactured) 30 parts, as a dispersant, has two ends of a silanol group, 3 parts of dimethyl polysiloxane having an average degree of polymerization of 5, and 1.19 parts of a silazane compound represented by the following general formula (III) and kneaded with a kneader The compound was prepared by heat-treating at 170 ° C for 2 hours.

For 100 parts of the above compound, 0.4 part of 2,5-dimethyl-2,5-bis (third butyl peroxide) hexane was added as a cross-linking agent, and after homogeneous mixing, the temperature was 70 kgf / cm ² at 165 ° C. Under the conditions, pressure curing was performed for 10 minutes, and a test sheet having a thickness of 2 mm was produced. Then, post-curing was performed at 200 ° C for 4 hours.

[Example 2]

Instead of the silazane compound represented by the general formula (III), 1.11 parts of the silazane compound represented by the following general formula (V) was added. Manufactured the same.

[Example 3]

The same procedure as in Example 1 was carried out except that the silazane compound represented by the general formula (III) was replaced with 1.11 parts of the silazane compound represented by the following general formula (VI).

[Example 4]

The same procedure as in Example 1 was carried out except that the silazane compound represented by the general formula (III) was replaced with 1.50 parts of the silazane compound represented by the following general formula (ii).

[Comparative Example 1]

In addition to replacing the silazane compound represented by the general formula (III), Except for 1.07 parts of the silazane compound represented by the following general formula (i), a system was produced in the same manner as in Example 1.

[Comparative Example 2]

It produced similarly to Example 1 except having replaced the silazane compound represented by general formula (III), and adding 0.28 parts of silazane compounds represented by the following general formula (X).

[Comparative Example 3]

It produced similarly to Example 1 except having replaced the silazane compound represented by general formula (III), and adding 0.33 parts of silazane compounds represented by the following general formula (XI).

Claims (5)

A stiffening poly siloxane silicone rubber composition, which is based following ingredients together as a main component, (A) represented by the following average compositional formula _{(I) R a SiO (4} -a) / 2 (I) ( in the formula, R is the same or different unsubstituted or substituted monovalent hydrocarbon group, a is a positive number of 1.95 to 2.05) 100 parts by mass of an organopolysiloxane having a polymerization degree of 100 or more, and (B) is obtained by a BET adsorption method 5 to 70 parts by mass of reinforcing silica having a specific surface area of 50 m ² / g or more, (C) is expressed by the following general formula (II) (Wherein R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, R ² is each independently an unsubstituted or substituted monovalent hydrocarbon group or an alkenyl group, and at least one of R ² is Alkenyl, n are independently independent integers of 3 to 10) 0.01 to 10 parts by mass of a silazane compound having 3 or more alkenyl groups in the molecule, and an effective amount of (D) a hardener. The curable polysiloxane rubber composition according to claim 1, wherein the silazane compound of the component (C) is represented by the following general formula (III), The polysiloxane rubber composition according to claim 1, further comprising the following general formula (IV) as the component (E) per 100 parts by mass of the total of the components (A) and (B). (Wherein R ³ is the same or different alkyl or hydrogen atom, R ⁴ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and m is an integer of 0 to 50) Alkane contains 0.1 to 50 parts by mass. The polysiloxane rubber composition according to claim 1, wherein the polysiloxane rubber composition is cured to give a 100% elongation fatigue test of 2 million or more times. A polysiloxane rubber member for a keypad is obtained by curing a curable polysiloxane rubber composition according to any one of claims 1 to 4.