JP2005126565A - Rubber composition for keypad and keypad using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition for keypads having high dynamic fatigue durability ( nailing durability ), and to provide keypads using the same. <P>SOLUTION: The rubber composition for keypads comprises (A) an organopolysiloxane ≥100 in polymerization degree having in the molecule at least two alkenyl groups bound to a silicon atom, (B) an ethylene-α-olefin-nonconjugated polyene random copolymer rubber, wherein the nonconjugated polyene is made from at least one terminal vinyl group-containing norbornene compound represented by formula(I)( wherein, (n) is an integer of 0 or 1-10; R<SP>1</SP>is H or a 1-10C alkyl; and R<SP>2</SP>is H or a 1-5C alkyl ) or formula(II) ( wherein, R<SP>3</SP>is H or a 1-10C alkyl ), (C) reinforcing silica ≥50 m<SP>2</SP>/g in specific surface area and (D) a curing agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition for a keypad and a keypad comprising a cured product of the rubber composition.

  Keypad materials are widely used in mobile phones, personal computer keyboards, and the like, and the required characteristics of these keypad materials are that there is little change in load when keys are pressed. Normally, when the keystroke of a molding key is repeated, the load on the key decreases as the number of keystrokes increases. As the decrease in peak load is smaller, the key characteristics are better, and a material exhibiting such load characteristics is excellent as a keypad material.

A material made of silicone rubber is widely used as such a keypad material. JP-A-6-145523 (Patent Document 1), JP-A-9-132712 (Patent Document 2), JP-A 2000-309710 (Patent Document 3), JP-A 2001-164111 (Patent Document 4), etc. Has proposed a silicone rubber composition for keypads.
However, in recent years, as the shape of the key to be molded has become more complex, the distortion on the key itself has become larger. Things are increasing. For this reason, the dynamic fatigue durability is not fully satisfied with the recent severe requirements.

  Japanese Patent Application Laid-Open No. 2001-31810 (Patent Document 5) proposes a rubber composition based on a non-conjugated polyene and an alkenyl group-containing organopolysiloxane. However, there is no description about application to a keypad. Not.

JP-A-6-145523 JP-A-9-132712 JP 2000-309710 A JP 2001-164111 A JP 2001-31810 A

    The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a keypad rubber composition and a keypad excellent in dynamic fatigue durability (keystroke durability).

  As a result of intensive studies to achieve the above object, the present inventor has found that an organopolysiloxane having a degree of polymerization of 100 or more and having at least two alkenyl groups bonded to a silicon atom and a nonconjugated polyene have the general formula [I ] Or a composition containing reinforcing silica in a specific ratio mixture of ethylene / α-olefin / non-conjugated polyene random copolymer rubber comprising at least one terminal vinyl group-containing norbornene compound represented by [II] It has been found that a keypad material excellent in keystroke durability can be obtained by vulcanizing, and the present invention has been made.

Accordingly, the present invention provides (A) a degree of polymerization of 100 or more and an organopolysiloxane having at least two alkenyl groups bonded to a silicon atom in an amount of 20 to 99 parts by mass (B) non-conjugated polyene represented by the following general formula [ I] or [II]

（式中、ｎは０又は１〜１０の整数であり、Ｒ¹は水素原子又は炭素数１〜１０のアルキル基であり、Ｒ²は水素原子又は炭素数１〜５のアルキル基である。）

(In the formula, n is 0 or an integer of 1 to 10, R ¹ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ² is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. )

（式中、Ｒ³は水素原子又は炭素数１〜１０のアルキル基である。）
で表される少なくとも１種の末端ビニル基含有ノルボルネン化合物よりなるエチレン・α−オレフィン・非共役ポリエンランダム共重合体ゴム
８０〜１質量部
（但し、（Ａ）成分と（Ｂ）成分の合計は１００質量部である）
（Ｃ）比表面積５０ｍ²／ｇ以上の補強性シリカ ３〜１００質量部
（Ｄ）硬化剤 有効量
を含有するキーパッド用ゴム組成物を提供する。

(In the formula, R ³ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.)
An ethylene / α-olefin / non-conjugated polyene random copolymer rubber comprising at least one terminal vinyl group-containing norbornene compound represented by
80 to 1 part by mass (however, the sum of component (A) and component (B) is 100 parts by mass)
(C) Reinforcing silica having a specific surface area of 50 m ² / g or more 3 to 100 parts by mass (D) Curing agent A rubber composition for a keypad containing an effective amount is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for keypads used as the keypad excellent in dynamic fatigue durability (keystroke durability) can be obtained.

Hereinafter, the present invention will be described in more detail.
The component (A) of the rubber composition of the present invention is an organopolysiloxane having a degree of polymerization of 100 or more and having at least two alkenyl groups bonded to silicon atoms, and is represented by the following average composition formula (IV): The one is representative.
R _a SiO _{(4-a) / 2} (IV)
(In the formula, R represents the same or different unsubstituted or substituted monovalent hydrocarbon group, and a is a positive number of 1.95 to 2.05.)

  In the above average composition formula (IV), R represents the same or different unsubstituted or substituted monovalent hydrocarbon group, usually having 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, specifically, methyl Group, ethyl group, propyl group, butyl group, hexyl group, octyl group and other alkyl groups, cyclopentyl group, cyclohexyl group and other cycloalkyl groups, vinyl group, allyl group, propenyl group and other alkenyl groups, cycloalkenyl group, phenyl Groups, aryl groups such as tolyl groups, aralkyl groups such as benzyl groups and 2-phenylethyl groups, or groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms or cyano groups, and the like. Group, vinyl group, phenyl group and trifluoropropyl group are preferable, and methyl group and vinyl group are particularly preferable.

  Specifically, the main chain of the organopolysiloxane is composed of a dimethylsiloxane unit, or a phenyl group, a vinyl group, a 3,3,3-trifluoropropyl group, etc. are formed on a part of the main chain of the dimethylpolysiloxane. Those having a diphenylsiloxane unit, a methylvinylsiloxane unit, a methyl-3,3,3-trifluoropropylsiloxane unit or the like introduced therein are suitable.

  The organopolysiloxane of component (A) must have two or more alkenyl groups, preferably vinyl groups, in one molecule, and 0.01 to 20 mol%, particularly 0.02 to 10 mol% is an alkenyl group. Preferably there is.

  The alkenyl group may be bonded to a silicon atom at the molecular chain end, or may be bonded to a silicon atom in the middle of the molecular chain, or both, but at least the silicon atom at the molecular chain end It is preferable that it is couple | bonded with. Note that a is a positive number of 1.95 to 2.05, which is basically linear, but may be branched within a range not impairing rubber elasticity.

The polymerization degree of the organopolysiloxane (A) is 100 or more, preferably 3,000 to 100,000, and particularly preferably 5,000 to 20,000. If the degree of polymerization is less than 100, sufficient rubber strength cannot be obtained.
Further, the organopolysiloxane of component (A) may be used alone or in combination of two or more having different molecular structures and polymerization degrees.

  Such an organopolysiloxane can be obtained, for example, by (co) hydrolytic condensation of one or more organohalogenosilanes, or by ring-opening polymerization of a cyclic polysiloxane using an alkaline or acidic catalyst. Can do.

  (A) The compounding quantity of a component is 20-99 mass parts, Preferably it is 30-97 mass parts, Most preferably, it is 50-95 mass parts. Even if it is less than 20 parts by mass or more than 99 parts by mass, the synergistic effect of using the component (A) and the component (B) together becomes insufficient.

  Component (B) is an ethylene / α-olefin / non-conjugated polyene random copolymer rubber in which the non-conjugated polyene is composed of at least one terminal vinyl group-containing norbornene compound represented by the above general formula [I] or [II]. .

  Examples of at least one terminal vinyl group-containing norbornene compound represented by the above general formula [I] or [II] include 5-vinyl-2-norbornene, 5-methylene-2-norbornene, and 5- (2-propenyl)- 2-norbornene, 5- (3-butenyl) -2-norbornene, 5- (4-pentenyl) -2-norbornene, 5- (5-hexenyl) -2-norbornene, 5- (6-heptenyl) -2- Examples include norbornene, 5- (7-octenyl) -2-norbornene, and 5- (5-ethyl-5-hexenyl) -2-norbornene, and 5-vinyl-2-norbornene and 5-methylene-2-norbornene are preferable. In particular, 5-vinyl-2-norbornene is preferred.

  This copolymer is a random copolymerization of ethylene, propylene and a non-conjugated diene (for example, 5-vinyl-2-norbornene) in the presence of a catalyst containing, for example, a vanadium catalyst and an organoaluminum catalyst as main components. Can be obtained.

Specific examples of the catalyst include VOCl ₃ and VO (OC ₂ H ₅ ) ₃ as vanadium catalysts, and triethylaluminum and diethylaluminum ethoxide as organoaluminum catalysts. The polymerization temperature at this time is 30 to 60 ° C., more preferably 30 to 50 ° C., the polymerization pressure is 4 to 12 kgf / cm ² , particularly 5 to 8 kgf / cm ² , and the supply amount of non-conjugated polyene and ethylene is It is obtained by random copolymerization of ethylene, propylene and a non-conjugated diene (for example, 5-vinyl-2-norbornene) under the condition that the molar ratio is (non-conjugated polyene / ethylene) 0.01 to 0.2. The copolymerization is preferably performed in a hydrocarbon medium.

  The diene component to be copolymerized is exemplified below in addition to at least one terminal vinyl group-containing norbornene compound represented by the above general formula [I] or [II] within a range not impairing the object of the present invention. A diene compound can be used in combination.

  Examples of the diene compound include 5- (1-methyl-2-propenyl) -2-norbornene, 5- (1-methyl-3-butenyl) -2-norbornene, and 5- (1-methyl-4-pentenyl)-. 2-norbornene, 5- (2,3-dimethyl-3-butenyl) -2-norbornene, 5- (2-ethyl-3-butenyl) -2-norbornene, 5- (3-methyl-5-hexenyl)- 2-norbornene, 5- (3,4-dimethyl-4-pentenyl) -2-norbornene, 5- (3-ethyl-4-pentenyl) -2-norbornene, 5- (2-methyl-6-heptenyl)- Norbornene such as 2-norbornene, 5- (1,2-dimethyl-5-hexenyl) -2-norbornene, 5- (1,2,3-trimethyl-4-pentenyl) -2-norbornene, 1,4 Hexadiene, 3-methyl-1,4-hexadiene, 4-methyl-1,4-hexadiene, 5-methyl-1,4-hexadiene, 4,5-dimethyl-1,4-hexadiene, 7-methyl-1, Chain non-conjugated dienes such as 6-otadiene, methyltetrahydroindene, 5-ethylidene-2-norbornene, 5-isopropylidene-2-norbornene, 5-vinylidene-2-norbornene, 6-chloromethyl-5-isopropenyl- Cyclic non-conjugated dienes such as 2-norbornene and dicyclopentadiene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, etc. A triene etc. are mentioned.

  The (B) component ethylene / α-olefin / non-conjugated polyene random copolymer has a ratio of (a) ethylene unit and (b) α-olefin [molar ratio of (a) / (b)] of 40/60 to 95. / 5, preferably 50/50 to 90/10, more preferably 55/45 to 85/15, particularly preferably 60/40 to 80/20. When this molar ratio is within the above range, a keypad rubber composition having excellent heat aging resistance, strength characteristics and rubber elasticity, as well as excellent cold resistance and processability can be obtained.

  The iodine value of the copolymer of component (B) is preferably 0.5 to 50 (g / 100 g), more preferably 0.8 to 40 (g / 100 g), still more preferably 1 to 30 (g / 100 g). ), Particularly preferably 1.5 to 25 (g / 100 g). When the iodine value is within the above range, a rubber composition for a keypad having high crosslinking efficiency, high impact resilience, and excellent dynamic fatigue durability can be obtained. If the iodine value exceeds 50, it may be disadvantageous in terms of cost.

  (B) The compounding quantity of a component is 1-80 mass parts (however, the sum total with (A) component is 100 mass parts), Preferably it is 3-70 mass parts, Most preferably, it is 5-50 mass parts. If it is less than 1 part by mass or more than 80 parts by mass, the synergistic effect used in combination with the component (A) becomes insufficient.

Component (C) Reinforcing silica having a specific surface area of 50 m ² / g or more is added to obtain a rubber composition for a keypad having excellent mechanical strength. It requires more 50 m ² / g, preferably from 100 to 400 m ² / g. When the specific surface area is less than 50 m ² / g, the mechanical strength of the cured product is lowered.

  Examples of such reinforcing silica include fumed silica, precipitated silica, and the like, and those whose surfaces are hydrophobized with chlorosilane, hexamethyldisilazane, or the like are also preferably used.

  The amount of the reinforcing silica (C) added is preferably 3 to 100 parts by mass, more preferably 10 to 70 parts by mass, with respect to 100 parts by mass in total of the components (A) and (B). If the amount is less than 3 parts by mass, the added amount is too small to obtain a reinforcing effect, and if it exceeds 100 parts by mass, the workability deteriorates and the mechanical strength is lowered, and the dynamic fatigue durability of the molding key. (Keystroke durability) will also deteriorate.

  The curing agent for component (D) is not particularly limited as long as it can cure the rubber composition of the present invention, but (i) a crosslinking reaction by addition reaction known as a curing agent for rubber, Organohydrogenpolysiloxane and hydrosilylation catalyst, (ii) organic peroxide are preferred.

  The hydrosilylation catalyst used in the above-mentioned (i) crosslinking reaction by addition reaction includes aliphatic unsaturated bonds (alkenyl groups, diene groups, etc.) of component (A) and silicon atom-bonded hydrogen atoms (SiH groups) of organohydrogenpolysiloxane. ) Is an addition reaction.

  Examples of the hydrosilylation catalyst include a platinum group metal catalyst, which includes a platinum group metal and a compound thereof, and 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, chloroplatinic acid hexahydrate alcohol solution, palladium catalyst, rhodium catalyst, etc. Platinum or platinum compounds are preferred. The addition amount of the catalyst only needs to accelerate the addition reaction, and is usually used in the range of 1 ppm to 1% by weight in terms of the amount of platinum-based metal, but is preferably in the range of 10 to 500 ppm. If the addition amount is less than 1 ppm, the addition reaction may not be sufficiently promoted and curing may be insufficient. On the other hand, if it exceeds 1% by weight, there is little influence on the reactivity even if it is added more than this amount. It may be an economy.

  In addition to the above catalyst, an addition crosslinking controller may be used for the purpose of adjusting the curing rate. Specific examples include ethynylcyclohexanol and tetracyclomethylvinylpolysiloxane.

The organohydrogenpolysiloxane may be linear, cyclic or branched as long as it contains 2 or more, preferably 3 or more SiH groups in one molecule. A known organohydrogenpolysiloxane can be used as a crosslinking agent for the silicone rubber composition, and for example, an organohydrogenpolysiloxane represented by the following average composition formula (V) can be used.
R ⁶ _p H _q SiO _{(4-pq) / 2} (V)

In the average composition formula (V), R ⁶ represents an unsubstituted or substituted monovalent hydrocarbon group, which may be the same or different, and excludes an aliphatic unsaturated bond. preferable. Usually, those having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms are preferred. Specifically, alkyl groups such as methyl group, ethyl group and propyl group, cycloalkyl groups such as cyclohexyl group, vinyl group, allyl group and butenyl. Groups, alkenyl groups such as hexenyl groups, aryl groups such as phenyl groups and tolyl groups, aralkyl groups such as benzyl groups, 2-phenylethyl groups and 2-phenylpropyl groups, and some or all of the hydrogen atoms of these groups Is a group substituted with a halogen atom or the like, for example, a 3,3,3-trifluoropropyl group. Note that p and q are 0 ≦ p <3, preferably 1 ≦ p ≦ 2.2, 0 <q ≦ 3, preferably 0.002 ≦ q ≦ 1, 0 <p + q ≦ 3, preferably 1.002 ≦. It is a positive number satisfying p + q ≦ 3.

  Organohydrogenpolysiloxane has 2 or more, preferably 3 or more, SiH groups in one molecule, which may be present at both ends of the molecular chain or in the middle of the molecular chain. Also good. Moreover, as this organohydrogenpolysiloxane, it is preferable that the viscosity in 25 degreeC is 0.5-10,000 cSt, especially 1-300 cSt.

  Specific examples of such organohydrogenpolysiloxanes include compounds having the following structural formula.

（式中、ｋは２〜１０の整数、ｓ及びｔは０〜１０の整数である。）

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

  The amount of the organohydrogenpolysiloxane is preferably 0.1 to 40 parts by weight per 100 parts by weight of component (A). In addition, it is appropriate that the ratio of hydrogen atoms bonded to silicon atoms (≡SiH groups) is 0.5 to 10 for one aliphatic unsaturated bond (alkenyl group, diene group, etc.) of component (A). A range of 0.7 to 5 is preferable. If it is less than 0.5, crosslinking may not be sufficient, and sufficient mechanical strength may not be obtained. If it exceeds 10, physical properties after curing will be deteriorated, and particularly heat resistance and compression set will be remarkably deteriorated. There is a case.

  (Ii) Examples of the organic peroxide include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5 -Dimethyl-bis (2,5-t-butylperoxy) hexane, di-t-butylperoxide, t-butylperbenzoate, 1,6-hexanediol-bis-t-butylperoxycarbonate, etc. . The addition amount of the organic peroxide is preferably from 0.1 to 15 parts by weight, particularly preferably from 0.2 to 10 parts by weight, based on 100 parts by weight of the component (A).

  In addition to the above components, the rubber composition of the present invention preferably further contains an organosilane or siloxane represented by the following general formula (III) as the component (E).

（式中、Ｒ⁴は同一又は異種のアルキル基又は水素原子、Ｒ⁵は同一又は異種の非置換又は置換一価炭化水素基、ｍは１〜５０の正数である。）

(In the formula, R ⁴ is the same or different alkyl group or hydrogen atom, R ⁵ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and m is a positive number of 1 to 50.)

Here, R ⁴ is the same or different alkyl group or hydrogen atom, and the organosilane or siloxane represented by the general formula (III) has an alkoxy group or a hydroxyl group at the molecular chain terminal. Examples of R ⁴ include a hydrogen atom or an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, and a methyl group, an ethyl group, or a hydrogen atom is preferable. As the R ⁵ group, those having 1 to 12 carbon atoms, particularly 1 to 8 carbon atoms are preferred, and specifically, alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group, and a cycloalkyl group such as a cyclohexyl group. , An alkenyl group such as a vinyl group, an allyl group, a butenyl group or a hexenyl group, an aryl group such as a phenyl group or a tolyl group, an aralkyl group such as a β-phenylpropyl group, or a hydrogen bonded to a carbon atom of these groups Examples include a chloromethyl group, a trifluoropropyl group, a cyanoethyl group, etc. in which some or all of the atoms are substituted with a halogen atom, a cyano group, etc., preferably a methyl group, a vinyl group, a phenyl group, a trifluoropropyl group, A group and a vinyl group are more preferable. In particular, at least one R ^{5 in} the molecule is preferably an alkenyl group, particularly a vinyl group. When it has an alkenyl group, the dynamic fatigue durability is further improved.

  m is a positive number of 1 to 50, and a range of 1 to 30 is preferable. When m exceeds 50, the effect may be reduced as a treatment agent for treating the reinforcing silica of component (C).

  (E) The compounding quantity of a component is 0.1-50 mass parts per 100 mass parts in total of (A) component and (B) component, and 0.5-30 mass parts is especially preferable. If the amount is less than 0.1 parts by mass, the effect of addition may be insufficient, and the plastic return may increase. If the amount exceeds 50 parts by mass, the resulting rubber composition may be sticky.

  Moreover, it is preferable to add (F) mold release agent to the rubber composition of this invention. As release agents, higher fatty acid salts such as stearic acid, palmitic acid, oleic acid, lauric acid, higher fatty acid metal salts such as zinc stearate, nickel stearate, calcium stearate, magnesium stearate, zinc oleate, calcium oleate, Higher fatty acids such as ethyl stearate, stearic acid stearate, ethyl oleate, butyl oleate, castor oil (ricinoleic acid ester of glycerin), higher fatty acids such as stearic acid amide, oleic acid amide, palmitic acid amide The amides are exemplified.

  The release agent of component (F) is preferably 0 to 3 parts by weight, particularly 0.01 to 2 parts by weight, based on 100 parts by weight of the total of components (A) and (B). If the amount added is too large, physical properties such as compression set may deteriorate.

  In the rubber composition for a keypad of the present invention, in addition to the above-mentioned components, a conductive imparting agent such as carbon black, an iron oxide, a halogen compound, etc. Known additives such as flame retardant, softener, process oil, anti-aging agent, ultraviolet absorber, colorant and the like can be added.

  Although the manufacturing method of the rubber composition of this invention is not specifically limited, It can obtain by knead | mixing the predetermined amount of the component mentioned above with a 2 roll, a kneader, a Banbury mixer, etc. If necessary, heat treatment (kneading under heating) may be performed. Specifically, a method of kneading the components (A) to (C) and then adding the component (D), kneading and heat-treating the components (A) and (C), and kneading the component (B) (this In this case, a part of the component (C) may be kneaded in advance with the component (B)), and then a method of adding the component (D) and the like.

  The rubber composition of the present invention is used for a keypad. In order to form such a keypad, it is necessary to cure the rubber composition, but the curing conditions are not particularly limited. Generally, a keypad can be obtained by heating and curing at 80 to 300 ° C., particularly 100 to 250 ° C., for 5 seconds to 1 hour, particularly 30 seconds to 30 minutes. Moreover, you may post-cure about 10 minutes-10 hours at 100-200 degreeC.

  A method for molding the keypad is not particularly limited, but press molding is preferable.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, the part in the following example shows a mass part. The physical property measurement method, keystroke test method, load measurement method, and keystroke fatigue durability evaluation method are shown below.
Physical property measurement method The rubber composition was cured at 165 ° C./10 minutes, and the hardness (durometer A) and tensile strength were measured according to JIS K6249.
Keystroke test method A rubber composition is press-molded using a mold, a molding key having the shape shown in FIG. 1 is prepared, this molding key is fixed, a load of 250 g is applied from above, and a speed of 3 times per second is prepared. I hit the key.
Mold Key Load Measurement Method The load of the key was measured using a load measuring device (MODEL-1305-DS manufactured by Aiko Engineering Co., Ltd.). When the key is pressed to apply displacement, the click pattern shown in FIG. 2 is usually obtained. F1 of the click pattern was measured as a peak load, and hysteresis loss was determined by the following formula.
Hysteresis loss (%) = [(F1-F4) / F1] × 100
Evaluation Method of Keying Fatigue Durability of Molded Keys The peak load change before and after 200,000 times key pressing was determined by the following formula by the above key pressing test method.
Peak load change (%)
= [F1 value before keystroke test-F1 value after keystroke test] / F1 value before keystroke test] × 100

[Example 1]
75 parts of organopolysiloxane consisting of 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units and having an average degree of polymerization of about 8,000, a polyolefin-based synthetic polymer As an ethylene / propylene / 5-vinyl-2-norbornene copolymer PX-052 [Mitsui Chemicals, Inc.] (ML1 + 4 (100 ° C.): 38, ethylene content 59 mol%, iodine value: 4) 25 parts, 30 parts of silica (Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.)) having a specific surface area of 200 m ² / g, dimethylpolysiloxane having a viscosity of 25 cs (23 ° C.) having silanol groups at both ends and 0.13 mol / 100 g of vinyl groups Five parts were compounded using a pressure kneader to produce a rubber compound.

  To 100 parts of the resulting rubber compound, 3 parts of 1,6-hexanediol-bis-t-butyl peroxycarbonate was added, and a physical property measurement sheet and a key were pressure molded at 165 ° C. for 10 minutes. Table 1 shows the evaluation results of the physical property values and keystroke durability.

[Example 2]
Instead of PX-052 as a polyolefin-based synthetic polymer, an ethylene / propylene / 5-vinyl-2-norbornene copolymer PX-055 [Mitsui Chemicals, Inc.] (ML1 + 4 (100 ° C.): 9, ethylene content: Molding was performed in the same manner as in Example 1 except that 58 mol% and iodine value: 10) were used. Table 1 shows the evaluation results of the physical property values and keystroke durability.

[Example 3]
Instead of PX-052 as a polyolefin-based synthetic polymer, an ethylene / propylene / 5-vinyl-2-norbornene copolymer R5014 [Mitsui Chemicals, Inc.] (ML1 + 4 (100 ° C.): 86, ethylene content: 65 mol %, Iodine value: It was molded by the same method as in Example 1 except that 5) was used. Table 1 shows the evaluation results of the physical property values and keystroke durability.

[Example 4]
To 100 parts of the compound obtained in Example 1, the following formula C ₆ H ₅ Si— (OSiMe ₂ H) ₃
(In the formula, Me represents a methyl group.)
After adding 3.0 parts of an organohydrogenpolysiloxane represented by the formula, 0.06 part of ethynylcyclohexanol as a control agent and 0.05 part of a 5% isopropyl alcohol solution of chloroplatinic acid at two rolls, at 160 ° C. Press molding for 10 minutes. Table 1 shows the evaluation results of the physical property values and keystroke durability.

[Example 5]
75 parts of an organopolysiloxane having 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units and having an average degree of polymerization of about 8,000, a specific surface area of 200 m 30 parts of ² / g silica (Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.)), 5 parts of 25 cs (23 ° C.) dimethylpolysiloxane having silanol groups at both ends and 0.13 mol / 100 g of vinyl groups Blended with a kneader, heat treated at 180 ° C. for 2 hours, cooled to 100 ° C., added 25 parts of polyolefin synthetic polymer PX-052 and mixed for 30 minutes to prepare a rubber compound. In the same manner, a sheet for measuring physical properties and a key were molded, and the evaluation results of physical properties and keystroke durability are shown in Table 1.

[Example 6]
A sheet for measuring physical properties and a key were molded in the same manner as in Example 5 except that 0.1 part of calcium stearate was added simultaneously with the polyolefin-based synthetic polymer. The demoldability of the key from the mold was very good. Table 1 shows the evaluation results of physical property values and keystroke durability.

[Comparative Example 1]
Molding was performed in the same manner as in Example 1 except that EPT-3045 (manufactured by Mitsui Chemicals, Inc. using ethylidene norbornene as the diene component) was used instead of the polyolefin-based synthetic polymer used in Example 1. Table 1 shows the evaluation results of the physical property values and keystroke durability.

[Comparative Example 2]
Organopoly which is composed of 99.825 mol% of dimethylsiloxane units, 0.15 mol% of methylvinylsiloxane units and 0.025 mol% of dimethylvinylsiloxane units without using a polyolefin-based synthetic polymer and having an average degree of polymerization of about 8,000. Molding was performed in the same manner as in Example 1 except that 100 parts of siloxane was used. Table 1 shows the evaluation results of the physical property values and keystroke durability.

[Comparative Example 3]
Molding was performed in the same manner as in Example 1 except that PX-052100 parts was used as a polyolefin-based synthetic polymer without using organopolysiloxane. Table 1 shows the evaluation results of the physical property values and keystroke fatigue durability. The peak weight of the key became too high, and the key was destroyed in the keystroke fatigue test.

It is a side view of the keypad which concerns on this invention.

Claims (5)

(A) Organopolysiloxane having a degree of polymerization of 100 or more and having at least two alkenyl groups bonded to silicon atoms in the molecule
20 to 99 parts by mass of (B) non-conjugated polyene is represented by the following general formula [I] or [II]

(In the formula, n is 0 or an integer of 1 to 10, R ¹ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ² is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. )

(In the formula, R ³ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.)
An ethylene / α-olefin / non-conjugated polyene random copolymer rubber comprising at least one terminal vinyl group-containing norbornene compound represented by
80 to 1 part by mass (however, the sum of component (A) and component (B) is 100 parts by mass)
(C) 3 to 100 parts by mass of reinforcing silica having a specific surface area of 50 m ² / g or more (D) Curing agent A rubber composition for a keypad containing an effective amount. Further, as the component (E), the following general formula (III)

(In the formula, R ⁴ is the same or different alkyl group or hydrogen atom, R ⁵ is the same or different unsubstituted or substituted monovalent hydrocarbon group, and m is a positive number of 1 to 50.)
The rubber composition for keypads of Claim 1 containing the organosilane or siloxane represented by these. The rubber composition for a keypad according to claim 1 or 2, wherein the curing agent is an organic peroxide, or an organohydrogenpolysiloxane and a hydrosilylation catalyst. Furthermore, the rubber composition for keypads of any one of Claims 1-3 which contains a mold release agent as (F) component. The keypad which consists of hardened | cured material of the composition of any one of Claims 1-4.

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