JP3756301B2 - Conductive silicone rubber composition for sponge and conductive silicone sponge using the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a conductive silicone rubber composition for sponge and a conductive silicone rubber sponge using the same, and more specifically, conductive conductivity for sponge capable of obtaining fine cells with good workability and moldability. The present invention relates to a silicone rubber composition.
[0002]
[Technical background of the invention and its problems]
Silicone rubber is excellent in heat resistance, weather resistance, cold resistance, electrical properties, flame retardancy, heat insulation, and the like, and is used in many applications by taking advantage of these properties.
In addition, carbon black, graphite powder, metal powder, metal oxide, etc. are blended with this silicone rubber and are widely used as conductive silicone rubber. Further, it is also used as a conductive silicone rubber sponge by blending a foaming agent with conductive silicone rubber. This conductive silicone rubber sponge is basically foamed by heating a composition containing a foaming agent and a curing agent to a conductive silicone rubber base above the decomposition temperature of the foaming agent (generally 150 to 400 ° C). Can be obtained.
Applications of this conductive silicone rubber sponge are used for gaskets, various packings, rolls of office automation equipment such as PPCs, printers, and fax machines. In this case, the conductive sponge is required to have a high expansion ratio, fine cells, and good compression set. In response to such demands, a method using a peroxyketal organic peroxide (Japanese Patent Publication No. 62-49895) and a method using a percarbonate organic peroxide (Japanese Patent Laid-Open No. 5-43802) ), A method in which a percarbonate organic peroxide and an addition type crosslinking are used in combination (Japanese Patent Laid-Open No. 7-292146), a method in which an alkyl perester based organic peroxide is used (Japanese Patent Laid-Open No. 7-316330) A method of foaming and curing using two molds (JP-A-8-3356) has been proposed. However, these conventional methods contain a silicone and a conductive material which are inherently incompatible with each other, and therefore, it has been impossible to obtain a conductive silicone rubber sponge having a high expansion ratio, fine cells, and good compression set.
Further, although a method using a thermosetting resin fine particle catalyst containing a platinum-based catalyst (JP-A-7-247436) has been proposed, it is difficult to obtain a uniform thermosetting resin fine particle catalyst, Since the familiarity between the silicone and the conductive material was not improved, a fine cell could not be obtained.
On the other hand, a conductive silicone rubber sponge having a high expansion ratio, fine cells, and small compression set has been strongly desired for rolls of OA equipment such as PPC, printer, and FAX.
[0003]
OBJECT OF THE INVENTION
The present invention has been made for such problems. The present invention provides a conductive silicone rubber sponge having good workability and moldability, high foaming ratio, fine cells, and low compression set. An object of the present invention is to provide a conductive silicone rubber composition for sponge that can be used as a sponge.
[0004]
[Structure of the invention]
As a result of intensive studies to achieve the above object, the inventors of the present invention have a phenyl group-containing organic compound whose terminal is blocked with a hydroxyl group or an alkoxy group with respect to a polyorganosiloxane containing a conductivity-imparting material and finely powdered fumed silica. A conductive silicone rubber composition for sponges containing a silicon compound in combination and an organic foaming agent and a curing agent is found to have good workability and moldability, a high expansion ratio, and a fine cell sponge can be obtained. The present invention has been completed.
That is, the present invention
(a) Average unit formula: R _a SiO _{(4-a) / 2}
(Wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, and a represents a number in the range of 1.98 to 2.02) 100 parts by weight of a polyorganosiloxane having an average degree of polymerization of 3000 to 10,000
(b) Average unit formula: R _b (C ₆ H ₅ ) _c SiO _{(4- (b + c)) / 2}
(Wherein R is a substituted or unsubstituted monovalent hydrocarbon group, b and c are numbers satisfying 0 ≦ b ≦ 3, 0 <c ≦ 3, and 0 <b + c ≦ 4) 0.5 to 20 parts by weight of a phenyl group-containing organosilicon compound having an average polymerization degree of 3 to 1000 and having a terminal blocked with a hydroxyl group or an alkoxy group
(c) Fine powder fumed silica 5 to 200 parts by weight
(d) 3 to 300 parts by weight of a conductive material selected from acetylene black and ketjen black
(e) Organic blowing agent (excluding 1,1′-azo-bis (1-acetoxy-1-phenyl-ethane)) 0.1-20 parts by weight
(f) Curing agent The present invention relates to a conductive silicone rubber composition for sponge, characterized by comprising a necessary amount.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The polyorganosiloxane of component (a) used in the present invention has an average unit formula: R _a SiO _{(4-a) / 2 wherein} R is a substituted or unsubstituted monovalent hydrocarbon group, R 1 represents an alkyl group such as a methyl group, an ethyl group, and a propyl group, a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, an alkenyl group such as a vinyl group and an allyl group, Aryl groups such as cycloalkenyl groups, tolyl groups, and phenyl groups, and chloromethyl groups, chloropropyl groups, and the like in which some or all of the hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms or cyano groups, 3 An unsubstituted or substituted monovalent hydrocarbon group such as a 1,3,3-trifluoropropyl group or a 2-cyanoethyl group. The R groups may be the same or different. The value of a is preferably a positive number selected from the range of 1.98 to 2.02 to obtain a rubber elastic body, and preferably contains an alkenyl group such as a vinyl group as a part of the R group. In particular, among the organic groups bonded to the silicon atom of the polyorganosiloxane (a), those having an alkenyl group in the range of 0.01 to 1 mol% are preferred.
The degree of polymerization of this polyorganosiloxane is preferably 3000 to 10,000. If it is less than 3000, workability and formability deteriorate, and if it exceeds 10,000, blending of the filler becomes difficult and the formability deteriorates.
[0006]
(b) The component phenyl group-containing organosilicon compound has an average unit formula: R _b (C ₆ H ₅ ) _c SiO _{(4- (b + c)) / 2} (wherein R is a substituted or unsubstituted monovalent) Wherein b and c are numbers satisfying 0 ≦ b ≦ 3, 0 <c ≦ 3, and 0 <b + c ≦ 4), and the terminal is a hydroxyl group or a methoxy group, ethoxy Group, an alkoxy group such as a propoxy group, and the like, but more preferably a hydroxyl group and a methoxy group.
R is an alkyl group such as a methyl group, an ethyl group or a propyl group, a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a cycloalkenyl group or a tolyl group, and these Non-hydrogen groups such as chloromethyl, chloropropyl, 3,3,3-trifluoropropyl, 2-cyanoethyl, etc., in which some or all of the hydrogen atoms bonded to the carbon atom of the group are substituted with halogen atoms, cyano groups, etc. Examples thereof include substituted or substituted monovalent hydrocarbon groups. The R groups may be the same or different.
[0007]
It is assumed that b and c are 0 ≦ b ≦ 3, 0 <c ≦ 3, and 0 <b + c ≦ 4. The average degree of polymerization of this product is preferably 3 to 1000 . 1000 not the molecule is obtained increases and the effect exceeds that there Ru.
The amount of component (b) is preferably 0.5 to 20 parts by weight per 100 parts by weight of the polyorganosiloxane base polymer of component (a). More preferably, it is 1 to 10 parts by weight. If the amount is less than 0.5 parts by weight, the effect may not be obtained. If the amount exceeds 20 parts by weight, no further effect is obtained, and the workability and mechanical strength may be lowered.
[0008]
(c) The component finely powdered fumed silica is a component necessary for improving workability, moldability, mechanical strength, etc., and may be one generally used conventionally, but has a surface area of 50 m. ² / g or more is preferable. Moreover, this thing may be used as it is, and what was surface-treated with organosiloxane, polyorganosiloxane, hexaorganosilazan, etc. may be used.
The blending amount of the fine powder fumed silica as the component (c) is preferably 5 to 200 parts by weight with respect to 100 parts by weight of the polyorganosiloxane base polymer as the component (a). If the blended amount of finely powdered fumed silica is less than 5 parts by weight, the plasticity of the resulting compound will be low, workability and moldability will be poor, and there is a possibility that a fine cell sponge cannot be obtained. If it exceeds, blending is difficult, the compound becomes too hard, and a sponge with a high foaming ratio may not be obtained.
[0009]
component (d) of the conductive imparting agent is a component necessary for obtaining the conductive acetylene black or Ketjen black is used.
Specific examples of acetylene black include Denka Black (manufactured by Electrochemical Co., Ltd.), Shaunigan acetylene black (manufactured by Shaunigan Chemical Co., Ltd.), and the like. Chain Black EC-600 JD (manufactured by Ketjen Black International Co., Ltd.) can also be used. Of these, acetylene black is particularly excellent in conductivity because it has a secondary structure structure with few impurities, and is particularly preferably used in the present invention. Also, Ketjen Black EC and Ketjen Black EC-600 JD indicating excellent conductivity even at low loadings from having excellent specific surface area even Ru can preferably be used.
The blending amount of the component (d) conductivity imparting agent is preferably 3 to 300 parts by weight with respect to 100 parts by weight of the polyorganosiloxane base polymer (a). If the blending amount of the conductive material is less than 3 parts by weight, the desired conductivity may not be obtained, and if it exceeds 300 parts by weight, a conductive silicone rubber sponge having a high expansion ratio may not be obtained. Because. Moreover, these conductivity-imparting materials may be used alone or in combination of two or more.
[0010]
The organic foaming agent (e) is a component necessary for making a sponge, is stable at room temperature, and decomposes to generate gas when exposed to high temperatures. As the foaming agent, those usually used for silicone rubber may be used, such as azobisisobutyronitrile, dinitrosopentamethylenetetramine, benzenesulfonhydrazide, N, N-dinitroso-N, N′-dimethylterephthalamide, azodicarbonamide Ami de, etc. you can use.
The amount of the organic foaming agent as component (e) is 0.1 to 20 parts by weight, particularly preferably 0.5 to 10 parts by weight, per 100 parts by weight of the polyorganosiloxane base polymer as component (a). If the amount is less than 0.1 part by weight, a sponge cannot be obtained, and if it exceeds 20 parts by weight, no further effect can be obtained and the mechanical strength may be reduced.
[0011]
The component (f) curing agent is added to cure the composition and is appropriately selected according to the reaction mechanism. As its reaction mechanism, (1) a crosslinking method using an organic peroxide vulcanizing agent, (2) a method using an addition reaction, etc. are known, and depending on the reaction mechanism, (a) component and (f) component, ie, a curing catalyst It is well known that preferred combinations with crosslinkers are determined. That is, in the case of applying the above crosslinking method (1), the base polymer of the component (a) is not particularly limited, but preferably at least one of organic groups bonded to silicon atoms in one molecule. A polydiorganosiloxane in which is a vinyl group is used. The curing agent for component (f) includes benzoyl peroxide, orthomethylbenzoyl peroxide, paramethylbenzoyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, t-butylperoxide. Organic peroxide vulcanizing agents such as oxybenzoate, t-butylperoxy-2-ethylhexanoate, dicumyl peroxide, cumyl-t-butyl peroxide are used. These organic peroxide vulcanizing agents are used as one kind or a mixture of two or more kinds. The blending amount of the organic peroxide which is the curing agent of the component (f) is preferably in the range of 0.05 to 15 parts by weight with respect to 100 parts by weight of the base polymer of the component (a). When the amount of the organic peroxide is less than 0.05 parts by weight, the vulcanization is not sufficiently performed, and when it exceeds 15 parts by weight, there is no particular effect, and the physical properties of the obtained silicone rubber sponge This is because it may adversely affect
[0012]
As the base polymer of the component (a) when the addition reaction (2) is applied, a polyorganosiloxane in which at least one of the organic groups bonded to the silicon atom in one molecule is a vinyl group is used. In addition, as the curing agent of the component (f), a platinum catalyst such as chloroplatinic acid, platinum olefin complex, platinum vinylsiloxane complex, platinum black, platinum triphenylphosphine complex, etc. is used as a curing catalyst. As the agent, a polyorganosiloxane having an average of at least two hydrogen atoms bonded to silicon atoms in one molecule is used. Among the curing agents of component (f), the blending amount of the curing catalyst is preferably in the range of 1 to 1000 ppm in terms of platinum element with respect to the base polymer of component (a). If the blending amount of the curing catalyst is less than 1 ppm, curing does not proceed sufficiently, and if it exceeds 1000 ppm, no improvement in curing speed can be expected. The blending amount of the crosslinking agent is preferably such that 0.5 to 10.0 hydrogen atoms are present in the crosslinking agent, more preferably 1.0 to 5.0, per alkenyl group in component (a). . If the amount of hydrogen atoms is less than 0.5, curing does not proceed sufficiently, and if it exceeds 10.0, the heat resistance after curing decreases.
[0013]
The conductive silicone rubber composition for sponge of the present invention includes, in addition to the above (a) to (f), quartz powder, diatomaceous earth, titanium oxide, cerium hydroxide, cerium oxide, platinum compound, processing aid, silazane. You may mix | blend a compound, a silane coupling agent, etc.
[0014]
The composition of the present invention can be obtained by kneading the above components using a mixer such as a roll, kneader, Banbury mixer, etc., but in order to obtain a finer cell, (a), (b), ( c) The components (d), (e) and (f) are preferably blended at a temperature of less than 100 ° C. after kneading the components at 100 to 200 ° C., and (a), (b), ( More preferably, the components (e) and (f) are blended at a temperature lower than 100 ° C., preferably 60 ° C. or lower, after kneading the components (c) and (d) at 100 to 200 ° C. The heating and kneading may be carried out by mixing and kneading while heating at 100 to 200 ° C, or after mixing at less than 100 ° C, the kneading may be carried out at 100 to 200 ° C.
[0015]
The conductive silicone rubber composition for sponge obtained as described above is foam-cured to obtain a conductive silicone rubber sponge. This foam-curing may be performed by a known method. That is, this foam curing may be carried out by mold molding, extrusion molding, etc. In the case of mold molding, the above-mentioned conductive silicone rubber composition for sponge is applied to the mold at 1/5 to 4/5 of its total volume. Heat at 100 to 200 ° C for 1 minute to 30 minutes, and when extruding, press at a temperature of 200 to 400 ° C for 10 seconds to 30 minutes. However, this may be done with a fluidized bed heating or UHF vulcanization. The conductive silicone rubber sponge thus produced may be in any shape such as a tube shape, a rod shape, or a sheet shape. In the case of a roll, it may be formed into a tube shape in advance and a cored bar may be inserted, or may be foamed and cured after being coated on the cored bar. The obtained conductive silicone rubber sponge is a charging roll, a developing roll, a transfer roll, a cleaning roll, a pressure roll, a paper feed roll, a heat insulating material, a cushioning material, etc. for OA equipment such as a gasket, packing, PPC, printer, and fax machine. Very useful to.
[0016]
【The invention's effect】
The silicone rubber composition obtained in the present invention can provide a conductive silicone rubber sponge having good workability and moldability, high foaming ratio, fine cells, and good compression set. The obtained silicone rubber sponge is very useful as a gasket, a conductive roll, a heat insulating material, a cushioning material and the like.
[0017]
【Example】
Next, examples of the present invention will be described, but the present invention is not limited to the following examples. Moreover, the part in an example represents a weight part.
Example 1
100 parts of polyorganosiloxane having a polymerization degree of 6000, comprising 99.88 mol% of (CH ₃ ) ₂ SiO units, 0.12 mol% of (CH ₃ ) (CH ₂ ═CH) SiO units, and capped with dimethylvinylsilyl groups at the ends. Knead 5 parts of a phenyl group-containing organosilicon compound represented by the following formula (1) and 45 parts of fumed silica (AEROSIL 130) with a kneader mixer until uniform, and then knead at 150 ° C. for 2 hours at room temperature. After cooling to 20 parts, 20 parts of Denka Black (manufactured by Electrochemical Co., Ltd.) were blended and kneaded until uniform to obtain a base compound 1. HO [(CH ₃ ) (C ₆ H ₅ ) SiO] ₄ [(CH ₃ ) ₂ SiO] ₁₆ H (1)
Next, 100 parts of this base compound 1 were added to 1 part of 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 0.5 part of t-butylperoxy-2-ethylhexanoate, azoisobutyro After mixing 3 parts of nitrile with 2 rolls and dispensing to 10mm thickness, foam and cure for 15 minutes in an oven at 200 ° C, and then vulcanize for 4 hours at 200 ° C to form a conductive silicone rubber sponge. Obtained.
Next, the expansion ratio, compression set, and volume resistivity of the conductive silicone rubber sponge were measured. Further, a cross section of 1 cm @ 2 was observed with a microscope, and the average of the maximum cell diameter and 10 cell diameters was measured.
[0018]
Example 2
(CH _{3) 2} SiO units 99.8 _{mol%, (CH 3) (CH} 2 = CH) of SiO units 0.2 mol%, terminals blocked with dimethyl vinyl silyl group, a polyorganosiloxane 100 parts of polymerization degree 7000 , 3 parts of a phenyl group-containing organosilicon compound represented by the following formula (2), 30 parts of fumed silica (AEROSIL R-972) whose surface was treated with dimethyldichlorosilane until kneaded with a kneader mixer, Next, the mixture is heated and kneaded at 150 ° C. for 2 hours, cooled to room temperature, then mixed with 7 parts of Ketjen Black EC-600 JD (manufactured by Ketjen Black International Co., Ltd.) and kneaded until uniform to obtain base compound 2. It was.
(CH ₃ ) O [(C ₆ H ₅ ) ₂ SiO] ₃ [(CH ₃ ) ₂ SiO] ₁₀ (CH ₃ ) (2)
Next, 100 parts of this base compound 2 were added to 1 part of 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 0.5 part of t-butylperoxy-2-ethylhexanoate, azoisobutyro After mixing 3 parts of nitrile with 2 rolls and dispensing to 10mm thickness, after foaming and curing for 15 minutes in an oven at 200 ° C, vulcanize at 200 ° C for 4 hours to make conductive silicone rubber sponge. Obtained and evaluated .
[0019]
Comparative Example 1
In Example 1, a conductive silicone rubber sponge was obtained in the same manner as in Example 1 except that the compound represented by the following formula (7) was used instead of the phenyl group-containing organosilicon compound represented by the above formula (1). And evaluated.
HO [(CH ₃ ) ₂ SiO] ₂₀ H (7)
Comparative Example 2
In Example 2, a conductive silicone rubber sponge was obtained in the same manner as in Example 2 except that the compound represented by the following formula (8) was used instead of the phenyl group-containing organosilicon compound represented by the above formula (1). And evaluated.
(CH ₃ ) [(C ₆ H ₅ ) ₂ SiO] ₆ [(CH ₃ ) ₂ SiO] ₁₅ Si (CH ₃ ) ₃ (8)
Comparative Example 3
A conductive silicone rubber sponge was obtained and evaluated in the same manner as in Example 1 except that in Example 1, fumed silica was replaced with Nipsil LP (manufactured by Nippon Silica Industry Co., Ltd.), which is precipitated silica.
Comparative Example 4
In Example 1, a conductive silicone rubber sponge was obtained in the same manner as in Example 1 except that the compound represented by the following formula (9) was used instead of the phenyl group-containing organosilicon compound represented by the above formula (1). And evaluated.
HO [(CH ₃ ) (C ₆ H ₅ ) SiO] ₃₀₀ [(CH ₃ ) ₂ SiO] ₃₀₀₀ H (9)
These results are summarized in Table 1.
[0020]
[Table 1]

Claims (6)

(a) Average unit formula: R _a SiO _{(4-a) / 2}
(Wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, and a represents a number in the range of 1.98 to 2.02)
(b) Average unit formula: R _b (C ₆ H ₅ ) _c SiO _{(4- (b + c)) / 2}
(Wherein R represents a substituted or unsubstituted monovalent hydrocarbon group, b and c represent numbers satisfying 0 ≦ b ≦ 3, 0 <c ≦ 3, and 0 <b + c ≦ 4) 0.5 to 20 parts by weight of a phenyl group-containing organosilicon compound having an average degree of polymerization of 3 to 1000 and having a terminal blocked with a hydroxyl group or an alkoxy group
(c) Fine powder fumed silica 5 to 200 parts by weight
(d) 3 to 300 parts by weight of a conductive material selected from acetylene black and ketjen black
(e) Organic blowing agent (excluding 1,1′-azo-bis (1-acetoxy-1-phenyl-ethane)) 0.1-20 parts by weight
(f) Curing agent A conductive silicone rubber composition for sponge, comprising a necessary amount.   (f) The conductive silicone rubber composition for sponge according to claim 1, wherein the curing agent is an organic peroxide.   (f) The conductive silicone rubber composition for sponge according to claim 1, wherein the curing agent is an addition type curing agent.   A method for producing a conductive silicone rubber composition for sponges comprising the components (a) to (f) according to claim 1, wherein the components (a), (b) and (c) are heated at 100 to 200 ° C. A method for producing a conductive silicone rubber composition for sponge, comprising mixing the components (d), (e), and (f) at a temperature of less than 100 ° C. after kneading.   A method for producing a conductive silicone rubber composition for sponges comprising the components (a) to (f) according to claim 1, wherein the components (a), (b), (c) and (d) are added to 100 to 100%. A method for producing a conductive silicone rubber composition for sponge, characterized by mixing the components (e) and (f) at a temperature of less than 100 ° C after heat-kneading at 200 ° C.   A conductive silicone rubber sponge obtained by heating and foaming / curing the composition according to claim 1.