Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
  • C08G77/04—Polysiloxanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/14—Peroxides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K9/00—Use of pretreated ingredients
  • C08K9/04—Ingredients treated with organic substances
  • C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
  • C08L83/04—Polysiloxanes

Definitions

• the present invention relates to a millable silicone rubber composition and a cured silicone rubber.
• silicone rubber is excellent in weather resistance, durability, heat resistance, colorability, and is physiologically inactive. in use.
• linear organopolysiloxane which is a raw material for silicone rubber
• a method of polymerizing a low-molecular-weight cyclic or linear organopolysiloxane by an equilibration reaction using an acidic or basic catalyst is known. It is however, in this polymerization method, as a result of simultaneous formation and cleavage of siloxane bonds, the resulting high-molecular-weight linear organopolysiloxane contains a large amount of low-molecular-weight cyclic siloxanes (hereinafter referred to as low-molecular-weight siloxanes).
• BCF Bioconcentration Factor
• BCF is a method to test how much chemical substances accumulate in fish in water, and experiments are conducted under a constant concentration of chemical substances. Therefore, this method is not suitable for evaluating the accumulation of poorly water-soluble substances and highly volatile substances.
• Tetramer, pentamer and hexamer low-molecular-weight siloxanes (D4-6) have been shown to have low accumulation and little toxicity in actual environments, but their BCF values are high. are shown and regulated.
• D4-6 is designated as SVHC (Substances of Very High Concern).
• D5 which had sufficient data in Japan, was not designated as a monitoring chemical substance, but D4 and D6, which lacked data, were designated as monitoring chemical substances.
• reduction of low-molecular-weight siloxane is required.
• Patent Document 1 discloses that an organopolysiloxane having at least one hydroxyl group at the molecular chain end is added with magnesium hydroxide, calcium hydroxide, strontium hydroxide and water.
• a method of adding a hydroxide selected from barium oxide and conducting a polycondensation reaction to obtain a polymer is disclosed.
• the degree of polymerization of the product obtained is low, and it is difficult to obtain a crude rubber-like substance.
• Patent Document 2 a method of obtaining a polymer by adding a silane or siloxane having a bifunctional dialkylaminosilyl group to an organopolysiloxane or triorganosilanol having a silanol group at both ends of a molecular chain and conducting a polycondensation reaction. disclosed.
• Patent Document 3 discloses a silicone rubber composition containing a low content of volatile low-molecular-weight siloxane, which is composed of a polyorganosiloxane-silethylene copolymer, reinforcing filler silica, and an organic peroxide.
• Patent Document 4 an organopolysiloxane obtained by heating an organopolysiloxane having silanol groups at both molecular chain ends and a silane or siloxane having two hydrolyzable groups in the molecule is added with finely divided silica.
• a blended silicone rubber composition is disclosed.
• Patent Document 5 a mixture of an organopolysiloxane having silanol groups at both ends of the molecule, an end blocking agent such as triorganosilanol, a silane or siloxane having two dialkylaminosilyl groups in the molecule, and a reinforcing filler is used.
• An end blocking agent such as triorganosilanol, a silane or siloxane having two dialkylaminosilyl groups in the molecule
• a reinforcing filler is used.
• a silicone rubber composition having a reduced low-molecular-weight siloxane content obtained by heating is disclosed.
• a cured product of these conventional organopolysiloxanes containing a small amount of low-molecular-weight siloxane may have a large compression set.
• the packing when used as a packing, the packing remains crushed and the effect as the packing is weakened.
• the tube when used as a tube, if the tube is crushed or bent, it may not return to its original shape, and when used as a roll, it may remain crushed. was there.
• the silicone rubber composition of Patent Document 3 uses an organic peroxide as a curing agent, there are restrictions on its use, such as yellowing of the cured silicone rubber due to decomposition residues, and the inability to use it in applications where it comes into contact with food.
• the present inventors have made intensive studies to solve the above problems, and as a result, the following millable type silicone rubber containing an organopolysiloxane component having a specific alkenyl group content and a specific surface-treated treated silica
• the inventors have found that the composition can achieve the above objects, and completed the present invention. That is, the present invention provides the following millable type silicone rubber composition and its cured silicone rubber cured product.
• the component (B) is treated silica treated with the vinyl group-containing alkoxysilane and/or vinyl group-containing organosilazane in an amount such that the number of vinyl groups is 0.0001 mol or more per 100 parts by mass of silica. 1>, the millable type silicone rubber composition.
• ⁇ 3> The millable type silicone rubber composition according to ⁇ 1> or ⁇ 2>, wherein the component (C) is an addition reaction curing agent that is a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.
• component (C) is an addition reaction curing agent that is a combination of an organohydrogenpolysiloxane and a hydrosilylation catalyst.
• component (C) is an organic peroxide curing agent.
• ⁇ 5> A cured product of the millable silicone rubber composition according to any one of ⁇ 1> to ⁇ 4>.
• ⁇ 6> The cured product according to ⁇ 5>, wherein the total amount of low-molecular-weight siloxane components having a degree of polymerization of 20 or less contained in the cured product is less than 5,000 ppm.
• the mixture obtained by blending the above components (A) and (B) and before blending the curing agent is referred to as a (millable type) silicone rubber compound. type) is called a silicone rubber composition.
• the total amount of low-molecular-weight siloxane components having a degree of polymerization of 20 or less is less than 5,000 ppm, and the weather resistance, durability, heat resistance, etc. inherent to silicone rubber are excellent. Furthermore, it is possible to obtain a silicone rubber cured product which has a small compression set, can maintain its shape even when deformed in use, and can be used for various purposes.
• component (A) is the main component (base polymer) in the millable type silicone rubber composition, and (A-1) the content of low-molecular-weight siloxane having a degree of polymerization of 20 or less is less than 5,000 ppm.
• General formula (1) (In formula (1), R 1 may be the same or different and is a monovalent hydrocarbon group having 1 to 12 carbon atoms, and m is a number of 2 to 1,000.)
• each R 1 is independently a monovalent hydrocarbon group having 1 to 12 carbon atoms.
• the monovalent hydrocarbon group those having 1 to 8 carbon atoms are particularly preferred, and specific examples include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group and octyl group; cyclopentyl group and cyclohexyl group.
• Cycloalkyl groups such as; vinyl, allyl, propenyl, butenyl, alkenyl groups such as hexenyl; cycloalkenyl groups such as cyclohexenyl; aryl groups such as phenyl, tolyl; benzyl, 2-phenyl
• An aralkyl group such as an ethyl group and the like are included.
• a methyl group, a vinyl group and a phenyl group are preferred, and a methyl group and a vinyl group are particularly preferred.
• the degree of polymerization of component (A-1) is 2 to 1,000, preferably 10 to 800. If the degree of polymerization is greater than 1,000, it is difficult to remove low-molecular-weight siloxanes having a degree of polymerization of 20 or less.
• the degree of polymerization refers to the number average degree of polymerization measured by gel permeation chromatography (GPC) under the conditions shown below, using polystyrene as a standard substance.
• the component (A-1) may be used singly or as a mixture of two or more different molecular weights (degrees of polymerization) and molecular structures.
• the organopolysiloxane is also characterized in that the content of low-molecular-weight siloxanes with a degree of polymerization of 20 or less (the total content of two or more types of low-molecular-weight siloxanes) is less than 5,000 ppm. .
• the content is preferably 3,000 ppm or less, more preferably 1,000 ppm or less (in terms of mass).
• the content of the low-molecular-weight siloxane is 5,000 ppm or more, it is not preferable because contact failure tends to occur in the cured product containing the low-molecular-weight siloxane, and environmental problems occur.
• the content of low-molecular-weight siloxane having a degree of polymerization of 20 or less is measured by gas chromatography under the following conditions using n-tetradecane as an internal standard.
• low-molecular-weight siloxane having a degree of polymerization of 20 or less in the organopolysiloxane having silanol groups at both ends of the molecular chain represented by general formula (1) is 5,000 ppm or more
• low-molecular-weight siloxane is obtained by a conventionally known method.
• the component (A-1) is used in the present invention when the content is reduced to less than 5,000 ppm.
• Various methods are known for removing low-molecular-weight siloxanes having a degree of polymerization of 20 or less from organopolysiloxanes, and include heating distillation, vacuum distillation, thin-film distillation, and the like. In order to efficiently remove the low-molecular-weight siloxane, it is preferable to use a high temperature under reduced pressure. However, if the temperature is too high, cracking of the organopolysiloxane occurs.
• Component (A-2) has two dialkylaminosilyl groups in one molecule and condenses with the silanol groups of component (A-1) to form a highly viscous polyorganosiloxane.
• each R 2 is independently a monovalent hydrocarbon group having 1 to 12 carbon atoms.
• the monovalent hydrocarbon group those having 1 to 8 carbon atoms are particularly preferred, and specific examples include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group and octyl group; cyclopentyl group and cyclohexyl group.
• Cycloalkyl groups such as; vinyl, allyl, propenyl, butenyl, alkenyl groups such as hexenyl; cycloalkenyl groups such as cyclohexenyl; aryl groups such as phenyl, tolyl; benzyl, 2-phenyl
• An aralkyl group such as an ethyl group and the like are included.
• R 2 is preferably a methyl group, an ethyl group and a vinyl group.
• each R 3 is independently an alkyl group having 1 to 4 carbon atoms.
• Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, propyl group and butyl group, with methyl group and ethyl group being preferred.
• Examples of component (A-2) include bis(dimethylamino)dimethylsilane, bis(dimethylamino)diethylsilane, bis(diethylamino)methylvinylsilane, bis(diethylamino)dimethylsilane and bis(diethylamino)methylvinylsilane.
• component (A-2) may be used singly or as a mixture of two or more different molecular structures.
• the condensate of (A) components (A-1) and (A-2) is obtained by mixing (A-1) and (A-2) and heating the mixture.
• (A-1) and (A-2) may be uniformly mixed, and heating may be performed at a temperature of 30 to 230°C, preferably 70 to 200°C.
• the amount of component (A-2) added is such that the molar ratio of the dialkylaminosilyl groups of component (A-2) to the silanol groups of component (A-1) is 0.5 to 3.0. is preferred. If the amount of component (A-2) added is less than 0.5 mol per 1 mol of the silanol groups of component (A-1), the condensation polymerization will be insufficient and the organopolysiloxane obtained by heating will not be produced. Due to its small molecular weight, it may not be a millable type silicone rubber. Further, if the amount of component (A-2) added is more than 3.0 mol per 1 mol of silanol groups of component (A-1), unreacted component (A-2) must be removed by heating. and is not economical.
• Alkenyl groups bonded to silicon atoms in components (A-1) and (A-2) are alkenyl groups other than alkenyl groups bonded to silicon atoms in components (A-1) and (A-2). It is 0.03 to 0.30 mol % with respect to the substituent. If the alkenyl group content is less than 0.03 mol %, the addition vulcanization is difficult and the compression set is unfavorably increased.
• the alkenyl group may be present in either R 1 of the component (A-1) or R 2 of the component (A-2), or may be present in both.
• the organopolysiloxane obtained by heating and mixing the components (A-1) and (A-2) is a mixture of two or more different molecular weights (degrees of polymerization) and molecular structures, even if one type is used alone. may be
• Component (B) is treated silica having a degree of hydrophobicity of 40 or more, preferably 50 to 70, and treated with a vinyl-containing alkoxysilane and/or a vinyl-containing organosilazane (alkenyl-containing organosilane). treated silica. If the degree of hydrophobization of the treated silica is less than 40, the plasticity reversion of the silicone rubber compound becomes large, and it becomes difficult to incorporate it into the organopolysiloxane.
• the degree of hydrophobicity is an index indicating how much the silica surface is treated for hydrophobicity, and refers to a value measured by the following methanol titration method.
• the treated silica of component (B) is treated with vinyl group-containing alkoxysilane and/or vinyl group-containing organosilazane in an amount such that the number of vinyl groups is 0.0001 mol or more per 100 parts by mass of silica. is preferred.
• the vinyl group-containing alkoxysilane and/or vinyl group-containing organosilazane to be added has a vinyl group content of 0.0001 mol or more, the compression set of the cured product is favorable.
• the treated silica can be obtained, for example, by charging fumed silica into a high-speed mixer, rotating the mixer, and when the rotation is stabilized, spraying a hydrophobizing agent to obtain wet silica, and then heating the wet silica.
• the blending amount of the treated silica of component (B) is 5 to 100 parts by mass, preferably 10 to 60 parts by mass, per 100 parts by mass of organopolysiloxane of component (A). If the amount of the component (B) is too small, no reinforcing effect can be obtained, and if it is too large, the workability will be poor and the mechanical strength will be lowered.
• Alkenyl-containing organosilanes for treating silica are vinyl-containing alkoxysilanes and/or vinyl-containing organosilazanes.
• the vinyl group-containing alkoxysilane is not particularly limited, but vinyltriethoxysilane, vinyltrimethoxysilane, divinyldimethoxysilane, vinyltris(methoxyethoxy)silane and the like are suitable.
• vinyl group-containing organosilazanes include, but are not limited to, 1-vinylpentamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-dimethyl-1,1, Examples thereof include 3,3-tetravinyldisilazane, 1,3-divinyl-1,1,3,3-tetravinyldisilazane, and 1,3-divinyl-1,1,3,3-tetramethyl Disilazanes are preferred.
• the silica is pretreated with such an alkenyl group-containing organosilane, not only is there no effect of the low-molecular-weight siloxane derived from the surface treatment agent, but the change in plasticity of the silicone rubber compound is small, and compression is permanent. It is possible to give a silicone rubber cured product with a small strain.
• the curing agent is not particularly limited as long as it can cure the silicone rubber compound, and includes the following (C-1) addition reaction curing agent and (C-2) organic peroxide curing agent.
• C-1) Addition Reaction Curing Agent
• an organohydrogenpolysiloxane and a hydrosilylation catalyst are used in combination.
• the organohydrogenpolysiloxane has 2 or more, preferably 3 or more, more preferably 3 to 200, and still more preferably about 4 to 100 silicon-bonded hydrogen atoms (i.e., hydrosilyl group), its molecular structure may be linear, cyclic, branched or three-dimensional network structure.
• the organohydrogenpolysiloxane a known organohydrogenpolysiloxane can be used as a cross-linking agent for addition reaction-curable silicone rubber compositions. can be used.
• R 4 represents an unsubstituted or substituted monovalent hydrocarbon group, which may be the same or different, and preferably excludes aliphatic unsaturated bonds. .
• those having 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms are specifically alkyl groups such as methyl group, ethyl group and propyl group; cycloalkyl groups such as cyclohexyl group; phenyl group, tolyl group and the like.
• r is 0 ⁇ r ⁇ 3, preferably 0.5 ⁇ r ⁇ 2.2, more preferably 1.0 ⁇ r ⁇ 2.0, and s is 0 ⁇ s ⁇ 3, preferably 0.002 ⁇ s ⁇ 1.1, more preferably 0.005 ⁇ s ⁇ 1, and r+s is 0 ⁇ r+s ⁇ 3, preferably 1 ⁇ r+s ⁇ 3, more preferably 1.002 ⁇ r+s ⁇ 2.7.
• the organohydrogenpolysiloxane has two or more, preferably three or more, hydrosilyl groups in one molecule, which may be present at the end of the molecular chain, in the middle of the chain, or both. good too.
• the organohydrogenpolysiloxane preferably has a viscosity at 25° C. of 0.5 to 10,000 mPa ⁇ s, particularly 1 to 300 mPa ⁇ s.
• the viscosity is a value measured by a rotational viscometer at 25°C (same below).
• organohydrogenpolysiloxanes include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy ) methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane/dimethylsiloxane cyclic copolymer, both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked Dimethylsiloxane/methylhydrogensiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane/methylhydrogensiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogensi
• the amount of the organohydrogenpolysiloxane to be blended is preferably 0.1 to 40 parts by mass per 100 parts by mass of component (A).
• the proportion of hydrogen atoms (hydrosilyl groups) bonded to silicon atoms is 0.5 to 10 per aliphatic unsaturated bond (alkenyl group, diene group, etc.) in components (A) and (B). is suitable, and preferably a range of 0.7 to 10 is suitable. If the number of silicon-bonded hydrogen atoms (hydrosilyl groups) per aliphatic unsaturated bond in components (A) and (B) is 0.5 or more, sufficient cross-linking and sufficient mechanical strength are achieved. is obtained, and if it is 10 or less, the physical properties after curing do not deteriorate, and the heat resistance in particular does not deteriorate, and the compression set does not increase.
• the hydrosilylation catalyst performs hydrosilylation addition between the alkenyl group (if present) of component (A) or the alkenyl group (vinyl group) of component (B) and the silicon-bonded hydrogen atom (hydrosilyl group) of the organohydrogenpolysiloxane. It is the catalyst for the reaction.
• hydrosilylation catalysts include platinum group metal-based catalysts, including simple platinum group metals and compounds thereof, and conventionally known catalysts for addition reaction-curable silicone rubber compositions can be used.
• platinum metal adsorbed on a carrier such as silica, alumina or silica gel
• platinum catalyst such as platinic chloride, chloroplatinic acid, alcoholic solution of chloroplatinic acid hexahydrate, palladium catalyst, rhodium catalyst, etc. platinum or platinum compounds (platinum catalysts) are preferred.
• the amount of the catalyst to be added is sufficient as long as it can promote the addition reaction, and is usually used in the range of 1 mass ppm to 1 mass% in terms of the amount of platinum group metal relative to the silicone rubber compound, but 10 to 500 mass ppm. A range is preferred. When the amount added is 1 mass ppm or more, the addition reaction is sufficiently accelerated and curing is sufficient.
• an addition reaction inhibitor may be used for the purpose of adjusting the curing speed, depending on the purpose of the present invention. Specific examples thereof include acetylene alcohol-based control agents such as ethynylcyclohexanol and tetracyclomethylvinylpolysiloxane.
• the addition reaction controller may be used singly or in combination of two or more.
• Organic peroxide curing agent (C-2)
• organic peroxide curing agent examples include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methyl benzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6 -hexanediol-bis-t-butyl peroxycarbonate and the like.
• the amount of the organic peroxide curing agent added is preferably 0.1 to 10 parts by mass, particularly preferably 0.2 to 5 parts by mass, per 100 parts by mass of component (A). If the amount is 0.1 parts by mass or more, curing will not be insufficient, and if the amount is 10 parts by mass or less, the cured silicone rubber will not turn yellow due to decomposition residues of the organic peroxide curing agent. .
• an addition reaction curing agent and an organic peroxide curing agent are added to the component (A) by combining the components (C-1) and (C-2) within the ranges of the above amounts.
• a co-vulcanized silicone rubber composition can also be used.
• the (C-1) component and (C-2) component can be used properly depending on the purpose.
• an addition reaction curing agent is used for an electric wire or the like, problems such as adhesion to the core wire may occur, so the use of an organic peroxide curing agent is preferable.
• use of an addition reaction curing agent is preferred because there is concern about the influence of decomposition residues of the organic peroxide curing agent.
• the silicone rubber composition of the present invention may optionally contain fillers such as crushed quartz, crystalline silica, diatomaceous earth, calcium carbonate, coloring agents, tear strength improvers, acid acceptors, alumina and Various alkoxysilanes, especially phenyl group-containing alkoxysilanes and their hydrolysates, diphenylsilanediol, carbon functional silanes, etc., as thermal conductivity improvers such as boron nitride, release agents, reaction control agents, and dispersants for fillers. Addition of known fillers and additives in thermosetting silicone rubber compositions is optional.
• fillers such as crushed quartz, crystalline silica, diatomaceous earth, calcium carbonate, coloring agents, tear strength improvers, acid acceptors, alumina and Various alkoxysilanes, especially phenyl group-containing alkoxysilanes and their hydrolysates, diphenylsilanediol, carbon functional silanes, etc.,
• the millable type silicone rubber composition of the present invention can be cured under known curing conditions by a known curing method. Specifically, the composition can be cured usually by heating at 25 to 200°C, preferably 80 to 160°C. The heating time may be about 0.5 minutes to 5 hours, particularly about 1 minute to 3 hours.
• the millable type silicone rubber composition of the present invention described above uses a combination of component (A) organopolysiloxane and component (B) treated silica to reduce low-molecular-weight siloxane components and reduce compression of the cured product. A millable type silicone rubber composition having a small permanent set can be obtained.
• the silicone rubber cured product of the present invention is a cured product of the millable type silicone rubber composition of the present invention. Therefore, the silicone rubber cured product of the present invention has a small amount of low-molecular-weight siloxane components and a small compression set.
• the total content of low-molecular-weight siloxane components having a degree of polymerization of 20 or less can be less than 5,000 ppm.
• Treated Silica 2 was prepared in the same manner as in Preparative Example 1, except that 0.6 g of vinyltrimethoxysilane was used. The resulting treated silica 2 had a degree of hydrophobicity of 61 determined by the methanol titration method.
• Treated Silica 3 was prepared as in Preparative Example 1, except that no vinyltrimethoxysilane was added. The resulting treated silica 3 had a degree of hydrophobicity of 60 determined by the methanol titration method.
• Treated Silica 4 was prepared in the same manner as in Preparation Example 1 except that 10 g of dimethylpolysiloxane having both terminal silanol groups, an average degree of polymerization of 4 and a viscosity at 25° C. of 15 mPa ⁇ s was used. The resulting treated silica 4 had a degree of hydrophobicity of 35 determined by the methanol titration method.
• Both terminal silanol dimethylsiloxanes used in the following synthesis examples (A-1-1), (A-1-2), (A-1-3), (A-1-4), (A-1-5) and the content of low-molecular-weight siloxane components having a degree of polymerization of 20 or less contained in Polymers 1 to 8 were obtained under the following conditions. Since low-molecular-weight siloxanes with a degree of polymerization of 2 or less were not detected, the content of low-molecular-weight siloxane components with a degree of polymerization of 20 or less determined under the following conditions may be expressed as ⁇ D3-20.
• Base compounds (1) to (12), silicone rubber compositions (1) to (13), and test sheets (1) to (13) were prepared as follows.
• the physical properties of the silicone rubber compound (base compound) and cured silicone rubber (test sheet) were measured as follows.
• Compression set was measured by a method according to JIS K 6262:2013 using a test piece for measurement of compression set prepared in accordance with JIS K 6262:2013.
• Example 1 After adding 35 parts by mass of treated silica 1 prepared in Preparation Example 1 to 100 parts by mass of Polymer 1 synthesized in Synthesis Example 1, the mixture was mixed with a kneader to prepare a base compound (1).
• the base compound (1) With respect to 100 parts by weight of the base compound (1), 0.9 parts by weight of methylhydrogenpolysiloxane having a hydrosilyl group in a side chain as a curing agent (degree of polymerization: 38, hydrosilyl group: 0.00725 mol/g), reaction 0.04 parts by mass of ethynylcyclohexanol as a control agent and 0.05 parts by mass of a platinum catalyst (Pt concentration of 1% by mass) are added with a double roll and uniformly mixed to obtain a raw rubber-like silicone rubber composition (1).
• the composition was press-cured for 10 minutes under conditions of 120°C and 70 kgf/cm 2 to prepare a test sheet (1) having a thickness of 2 mm. Elongation at break was measured. Also, the compression set was measured for a cured product obtained by press curing the composition under conditions of 120° C. and 70 kgf/cm 2 for 15 minutes. Table 4 shows the measurement results.
• Example 2 A base compound (2) was prepared in the same manner as in Example 1 except that polymer 2 synthesized in Synthesis Example 2 was used instead of polymer 1, and silicone rubber composition (2) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (2) was prepared in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 4 shows the measurement results.
• Example 3 A base compound (3) was prepared in the same manner as in Example 1 except that polymer 3 synthesized in Synthesis Example 3 was used instead of polymer 1, and silicone rubber composition (3) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (3) was produced in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 4 shows the measurement results.
• Example 4 A base compound (4) was prepared in the same manner as in Example 1 except that polymer 4 synthesized in Synthesis Example 4 was used instead of polymer 1, and silicone rubber composition (4) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (4) was prepared in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 4 shows the measurement results.
• Example 5 A base compound (5) was prepared in the same manner as in Example 1 except that polymer 5 synthesized in Synthesis Example 5 was used instead of polymer 1, and silicone rubber composition (5) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (5) was produced in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 4 shows the measurement results.
• Example 6 Add 0.6 parts by mass of 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane as a curing agent to 100 parts by mass of the base compound (2) with a double roll, and uniformly After mixing to produce a crude rubber-like silicone rubber composition (6), the composition was press-cured at 165°C and 70 kgf/cm 2 for 10 minutes to prepare a test sheet (6) having a thickness of 2 mm. , hardness, tensile strength and elongation at break were measured in the same manner as above. In addition, the compression set was measured in the same manner as above for a cured product obtained by press curing the composition under conditions of 165° C. and 70 kgf/cm 2 for 15 minutes. Table 4 shows the measurement results.
• Example 7 A base compound (6) was prepared in the same manner as in Example 2 except that the treated silica 2 prepared in Preparation Example 2 was used instead of the treated silica 1, and the silicone rubber composition (7) was prepared in the same manner as in Example 1. was prepared. Using the obtained composition, a test sheet (7) was produced in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 4 shows the measurement results.
• Example 1 A base compound (7) was prepared in the same manner as in Example 1 except that polymer 6 synthesized in Synthesis Example 6 was used instead of polymer 1, and silicone rubber composition (8) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (8) was produced in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 5 shows the measurement results.
• Example 2 A base compound (8) was prepared in the same manner as in Example 1 except that Polymer 7 synthesized in Synthesis Example 7 was used instead of Polymer 1, and silicone rubber composition (9) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (9) was produced in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 5 shows the measurement results.
• a base compound (9) was prepared in the same manner as in Example 1 except that polymer 8 synthesized in Synthesis Example 8 was used instead of polymer 1, and silicone rubber composition (10) was prepared in the same manner as in Example 1. prepared. Using the obtained composition, a test sheet (10) was produced in the same manner as in Example 1, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 5 shows the measurement results.
• Example 4 A base compound (10) was prepared in the same manner as in Example 2 except that the treated silica 3 prepared in Comparative Preparation Example 1 was used instead of the treated silica 1, and the silicone rubber composition (11) was prepared in the same manner as in Example 2. ) was prepared. Using the obtained composition, a test sheet (11) was produced in the same manner as in Example 2, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 5 shows the measurement results.
• Example 5 A base compound (11) was prepared in the same manner as in Example 2 except that the treated silica 4 prepared in Comparative Preparation Example 2 was used instead of the treated silica 1, and the silicone rubber composition (12) was prepared in the same manner as in Example 2. ) was prepared. Using the obtained composition, a test sheet (12) was produced in the same manner as in Example 2, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 5 shows the measurement results.
• a base compound (12) was prepared in the same manner as in Example 6 except that Polymer 6 synthesized in Synthesis Example 6 was used instead of Polymer 1, and a silicone rubber composition (13) was prepared in the same manner as in Example 6. prepared. Using the obtained composition, a test sheet (13) was produced in the same manner as in Example 6, and the hardness, tensile strength, elongation at break, and compression set were measured in the same manner as described above. Table 5 shows the measurement results.
• Example 2 has a higher compression set than Comparative Example 4 using treated silica 3 that does not use vinyltrimethoxysilane and Comparative Example 5 using treated silica 4 with a hydrophobicity of less than 40. turned out to be small.
• Example 6 containing an organic peroxide curing agent is a comparative example using an organopolysiloxane having a vinyl group content of less than 0.03 mol% relative to the methyl groups bonded to the silicon atoms of the silanol dimethylsiloxane at both ends and the aminosilane. 6, it was found that the compression set was small.
• the millable type silicone rubber composition of the present invention is suitable for use in contact with food (e.g., food containers, packaging materials, etc.), and when an organic peroxide curing agent is used as the curing agent (C), it can be suitably used for electric wires.
• food e.g., food containers, packaging materials, etc.
• organic peroxide curing agent used as the curing agent (C)
• it can be suitably used for electric wires.

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