Classifications

• • 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
  • C08K5/16—Nitrogen-containing compounds
  • C08K5/34—Heterocyclic compounds having nitrogen in the ring
  • C08K5/3467—Heterocyclic compounds having nitrogen in the ring having more than two nitrogen atoms in the ring
  • C08K5/3472—Five-membered rings
  • C08K5/3475—Five-membered rings condensed with carbocyclic rings
• • 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
  • C08G77/06—Preparatory processes
  • C08G77/08—Preparatory processes characterised by the catalysts used
• • 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
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • 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
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica
• • 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
• • 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
  • C08G77/12—Polysiloxanes containing silicon bound to hydrogen
• • 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
  • C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
• • 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
  • C08G77/80—Siloxanes having aromatic substituents, e.g. phenyl side groups
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2201/00—Properties
  • C08L2201/08—Stabilised against heat, light or radiation or oxydation

Definitions

• the present invention relates to an oil-bleeding silicone rubber composition capable of improving heat resistance and giving a silicone rubber cured product with low compression set.
• silicone rubber has been widely used in various fields such as building materials, electrical/electronic parts, automobile parts, and OA equipment parts due to its excellent heat resistance, weather resistance, durability, and electrical properties.
• the spread as automobile parts is remarkable, and it is used for oil seals, wire connector packing, rubber plugs, O-rings, diaphragms, grommets for distributors, etc.
• oil-bleeding silicone rubber that bleeds oil onto the surface of the molded product has been recognized as effective. anti-corrosive silicone rubbers are widely used.
• oil-bleeding silicone rubber when used as a gasket such as an O-ring or packing, a low compression set is required to prevent seal leakage.
• a low compression set is required to prevent seal leakage.
• Patent Document 1 Japanese Patent Publication No. 2016-518461
• Patent Document 2 Japanese Patent Application Laid-Open No. 2014-031408
• metal oxides titanium oxide, iron oxide in the previous report, hydrous cerium oxide, hydrous oxide in the latter report, zirconium
• the addition of the metal oxide can improve the heat resistance of the silicone rubber composition.
• the inclusion of a metal oxide causes the resulting cured product to be colored, making it difficult to color even if other colors are desired.
• Patent Document 3 Japanese Patent Application Laid-Open No. 7-1304264 describes an oil-bleed waterproof connector containing a hydrosilylation reaction catalyst composed of a platinum-based catalyst and a non-silicone thermoplastic resin in a silicone rubber composition.
• a sealing component for an air conditioner is disclosed.
• the above catalysts merely shorten the molding time and are advantageous in terms of cost, and for heat resistance, a heat-resistant agent (rare earth oxide, cerium silanolate, cerium fatty acid salt, etc.) must be added separately.
• Patent Document 4 JP-A-6-32983
• a phthalate ester is added to a silicone rubber composition as an oil that does not cause electrical contact failure, and an oil-bleeding silicone rubber having the inherent heat resistance of silicone rubber is molded. goods are disclosed.
• phthalate esters merely maintain the inherent heat resistance of silicone rubber, and do not improve the physical properties and heat resistance of silicone rubber compositions.
• Patent Document 5 Japanese Unexamined Patent Application Publication No. 2000-118361 discloses that a functional wiper blade made of a molded body of a silicone rubber composition containing silicone oil as a water repellent is superior in heat resistance to conventional wiper blades. is stated. However, there is no specific heat resistance test, and the heat resistance required for wiper blades is insufficient as the heat resistance (for example, 200° C. or higher) required by the present invention. Also, the silicone oil that bleeds out is only used as a water repellent.
• Patent Document 6 JP-A-6-93186 describes an oil-bleeding silicone rubber composition containing two types of bleeding oils (that is, a phenyl silicone oil and a phenyl group-containing low molecular weight silicone oil). . It is reported that a combination of the two types of bleed oil can suppress tackiness while obtaining a bleed effect and improve roll workability, but does not mention heat resistance.
• Patent Document 7 Japanese Patent Application Laid-Open No. 2-242854 describes that an addition-curable silicone rubber composition to which a triazole compound is added can reduce the compression set without secondary vulcanization. However, heat resistance is not discussed.
• the present invention has been made in view of the above circumstances, and improves the heat resistance of the cured product without adding conventional additives such as metal oxides and antioxidants that improve the heat resistance, and improves the compression set.
• An object of the present invention is to provide an oil-bleeding silicone rubber composition that reduces the
• an addition-curable silicone rubber composition comprising the components (A) to (C) described below as essential components is added with a predetermined (D) phenyl Addition of group-containing organopolysiloxane, (E) non-functional dimethylpolysiloxane and (F) benzotriazole derivative imparts oil-bleeding properties to the cured product, improves heat resistance, and reduces compression set.
• D phenyl Addition of group-containing organopolysiloxane
• E non-functional dimethylpolysiloxane
• benzotriazole derivative imparts oil-bleeding properties to the cured product, improves heat resistance, and reduces compression set.
• the inventors have found that and completed the present invention.
• the present invention provides the following oil-bleeding silicone rubber composition.
• A an organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule: 100 parts by mass;
• B an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule: 0.2 to 20 parts by mass;
• C platinum group metal-based catalyst: 0.5 to 500 ppm as platinum group metal (in terms of mass) with respect to the total mass of components (A) and (B);
• D phenyl group-containing organopolysiloxane represented by the following formula (1): 1 to 10 parts by mass,
• R 3 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an aliphatic unsaturated bond, which is the same as or different from each other, and at least one is a phenyl group.
• n is a positive number from 3 to 50
• m+n is a positive number that satisfies 3 to 50.
• E a non-functional dimethylpolysiloxane represented by the following formula (2): 1 to 25 parts by mass, and (In the formula, Me is a methyl group and p is an integer of 2 to 600.)
• R 4 is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms
• R 5 is a monovalent hydrocarbon group having 1 to 15 carbon atoms or a group represented by the following formula (4). be.
• R 6 is -(CH 2 ) L -Si(OR 7 ) 3
• R 7 is an alkyl group having 1 to 4 carbon atoms or SiR 8 3 group
• R 8 is an alkyl group having 1 to 4 carbon atoms group
• L is an integer of 1 to 6. * indicates a point of attachment.
• An oil-bleeding silicone rubber composition comprising: 2.
• the silicone rubber cured product obtained by curing the above silicone rubber composition has a compressibility of 25% and a compression set (in accordance with JIS-K6262:2013) of 40% or less after compression at 150° C. for 70 hours.
• the reduction rate of the elongation at break (according to JIS K6249:2003) after heating the cured silicone rubber obtained by curing the above silicone rubber composition at 225° C. for 72 hours is 30% or less relative to the initial elongation at break.
• the heat resistance of a cured oil-bleeding silicone rubber can be improved by using only a component that imparts oil-bleeding properties without adding conventional additives such as metal oxides for improving heat resistance.
• the compression set can be lowered by adding a triazole derivative.
• the silicone rubber composition of the present invention does not require conventional additives such as metal oxides for improving heat resistance, the cured product is colorless to milky white, and can be easily cured by coloring agents such as pigments. can be colored to any desired color.
• the oil-bleeding silicone rubber composition of the present invention contains the following components (A) to (F).
• the rate of decrease in elongation at break is 30% or less, preferably 25% or less, and the compression set is measured at 150 ° C. for 70 hours at a compression ratio of 25% (JIS-K6262: 2013). It gives a cured product of 40% or less.
• Component (A) is an organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule, and is the main ingredient (base polymer) of the present composition.
• this component (A) those represented by the following average compositional formula (5) can be used.
• R1aSiO(4 - a )/2 (5) (wherein R 1 is the same or different, unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, a is a positive number of 1.5 to 2.8, It is preferably a positive number of 1.8 to 2.5, more preferably a positive number of 1.95 to 2.05.)
• the unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms represented by R 1 includes methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, Alkyl groups such as pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, and decyl group; Aryl groups such as phenyl group, tolyl group, xylyl group, and naphthyl group; Benzyl group, phenylethyl group, phenylpropyl Alkenyl groups such as aralkyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, octenyl group, etc.,
• At least two of R 1 must be alkenyl groups (preferably those having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms), preferably vinyl groups.
• the alkenyl group content in the organopolysiloxane is preferably 1.0 ⁇ 10 -6 to 5.0 ⁇ 10 -3 mol/g, more preferably 1.0 ⁇ 10 -5 to 2.0 ⁇ 10 -3 mol/g. mol/g is more preferable. If the alkenyl group content is 1.0 ⁇ 10 ⁇ 6 to 5.0 ⁇ 10 ⁇ 3 mol/g, a rubber-like substance can be obtained.
• This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, to a silicon atom in the middle of the molecular chain, or to both.
• the structure of this organopolysiloxane basically has a straight-chain structure in which both ends of the molecular chain are blocked with triorganosiloxy groups and the main chain consists of repeating diorganosiloxane units, but it is partially branched. structure, a cyclic structure, or the like.
• organopolysiloxane represented by the above formula (5) examples include, for example, both terminal dimethylvinylsiloxy group-blocked dimethylpolysiloxane, both terminal dimethylvinylsiloxy group-blocked dimethylsiloxane/methylvinylsiloxane copolymer, both terminal dimethylvinylsiloxy Group-blocked dimethylsiloxane/diphenylsiloxane copolymer, both-terminal dimethylvinylsiloxy-blocked dimethylsiloxane/methylvinylsiloxane-diphenylsiloxane copolymer, both-terminal dimethylvinylsiloxy-blocked methyltrifluoropropylpolysiloxane, both-terminal dimethylvinylsiloxy Group-blocked dimethylsiloxane/methyltrifluoropropylsiloxane copolymer, dimethylvinylsiloxy group-blocked dimethylmethyl
• the average degree of polymerization (number average degree of polymerization Mn, hereinafter the same) is preferably 1,500 or less, more preferably 100 to 1,500, and even more preferably 150 to 1,000. If the average degree of polymerization is from 100 to 1,500, a rubber-like substance can be obtained with good moldability.
• This average degree of polymerization can usually be determined as a polystyrene-equivalent value in GPC (gel permeation chromatography) analysis using toluene as a developing solvent (hereinafter the same).
• the viscosity of the component (A) organopolysiloxane is not particularly limited, the viscosity at 25° C. is 200 to 150,000 mPa ⁇ s from the viewpoint of good handling workability of the composition and good strength of the resulting cured product. 400 to 100,000 mPa ⁇ s is more preferable.
• the viscosity can be measured with a rotational viscometer, and the rotor and rotation speed are appropriately selected according to the viscosity (hereinafter the same).
• component (A) if it is an organopolysiloxane containing alkenyl groups bonded to silicon atoms at both ends of the molecular chain, one or two or more of them having different molecular structures and degrees of polymerization may be used in combination. can be done.
• Component (B) is an organohydrogenpolysiloxane having at least two, preferably three or more, silicon-bonded hydrogen atoms (SiH groups) per molecule, and the SiH groups in the molecule are It acts as a curing agent (crosslinking agent) for curing the composition by crosslinking with alkenyl groups bonded to silicon atoms in the component through a hydrosilylation addition reaction.
• SiH groups silicon-bonded hydrogen atoms
• the organohydrogenpolysiloxane of component (B) is, for example, represented by the following average compositional formula (6), and has at least 2, preferably 3 or more, more preferably 3 to 100 per molecule, and particularly Those having 4 to 50 silicon-bonded hydrogen atoms (SiH groups) are preferably used.
• R2bHcSiO ( 4-bc)/2 ( 6) (In the formula, R 2 is the same or different from each other and is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms.
• the number c is a positive number between 0.001 and 1.0, and b+c is a positive number satisfying 0.8 to 3.0.)
• R 2 the same ones as those exemplified for R 1 can be mentioned, but those having no aliphatic unsaturated group are preferred.
• b is a positive number of 0.7 to 2.1, preferably a positive number of 0.8 to 2.0
• c is a positive number of 0.001 to 1.0, preferably 0.01 to 1 is a positive number of 0.0
• b+c is a positive number satisfying 0.8 to 3.0, preferably a positive number satisfying 1.0 to 2.5
• the molecular structure of the organohydrogenpolysiloxane is: It may have a straight-chain, cyclic, branched-chain, or three-dimensional network structure.
• the content of SiH groups in the organohydrogenpolysiloxane is preferably 0.0005 to 0.020 mol/g, particularly 0.001 to 0.017 mol/g. If the amount of SiH groups is less than 0.0005 mol/g, the crosslinking may be insufficient, and if it exceeds 0.020 mol/g, the organohydrogenpolysiloxane may become an unstable substance.
• the number (or the degree of polymerization) of silicon atoms in one molecule is 2 to 300, particularly 3 to 150, especially 4 to 100, and liquid at room temperature (25°C) is preferably used.
• the hydrogen atoms bonded to the silicon atoms may be located either at the molecular chain terminal, in the middle (non-terminal) of the molecular chain, or at both.
• the organohydrogenpolysiloxane of component (B) includes 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 terminal dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both terminal dimethylhydrogensiloxy group-blocked dimethylsiloxane-methylhydrogensiloxane copolymer, both terminal trimethylsiloxy group-b
• organohydrogenpolysiloxane of the component (B) in the compounds exemplified above, a part of the siloxane skeleton (—Si—O—Si—) constituting the molecule (generally, an oxygen some of the atomic positions), usually divalent to tetravalent, aromatic ring-containing hydrocarbon skeleton (e.g., phenylene skeleton, bisphenylene skeleton, bis (phenylene) ether skeleton, bis (phenylene) methane skeleton, 2, 2-bis(phenylene)propane skeleton, 2,2-bis(phenylene)hexafluoropropane skeleton, etc.) and polyvalent aromatic ring-containing organohydrogenpolysiloxane.
• aromatic ring-containing hydrocarbon skeleton e.g., phenylene skeleton, bisphenylene skeleton, bis (phenylene) ether skeleton, bis (phenylene) methane skeleton, 2,
• the amount of organohydrogenpolysiloxane as component (B) is 0.2 to 20 parts by mass, preferably 0.3 to 10 parts by mass, per 100 parts by mass of component (A).
• the molar ratio (SiH group/alkenyl group) to the total amount of alkenyl groups bonded to atoms is preferably 0.8-10, more preferably 1.0-5. If this ratio is less than 0.8, the curing (crosslinking density) may be insufficient and the rubber may become sticky. release from the mold may become difficult.
• Component (C) includes platinum black, platinum chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, and platinum group metals such as platinum bisacetoacetate. system catalysts.
• the component (C) platinum group metal-based catalyst may be used alone or in combination of two or more.
• the amount of the platinum group metal-based catalyst can be a catalyst amount, and is usually 0.5 to 500 ppm as a platinum group metal (in terms of mass) with respect to the total mass of the components (A) and (B). Yes, preferably 1 to 200 ppm.
• Component (D) is added to the silicone rubber composition containing components (A) to (C) in the method for improving the heat resistance of the composition. It is a component that, when added together with siloxane, imparts oil-bleeding properties to the cured product and improves heat resistance, and is represented by the following general formula (1).
• R 3 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an aliphatic unsaturated bond, which is the same as or different from each other, and at least one is a phenyl group.
• m is a positive number from 0 to 3
• n is a positive number from 3 to 50
• m+n is a positive number that satisfies 3 to 50.
• each R 3 is independently an unsubstituted group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms, and still more preferably 1 to 3 groups other than a phenyl group. or substituted monovalent hydrocarbon groups, at least one of which is a phenyl group. It is also distinguished from component (A) in that R 3 does not have an aliphatic unsaturated bond, particularly an alkenyl group.
• the bonding order of each siloxane unit is not limited to the following (the same shall apply hereinafter).
• Monovalent hydrocarbon groups containing no aliphatic unsaturated bonds include, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, Alkyl groups such as cyclohexyl group, octyl group, nonyl group and decyl group; aryl groups such as cycloalkyl group, phenyl group and tolyl group; aralkyl groups such as benzyl group; and preferably a methyl group or a phenyl group.
• At least one of R 3 in the formula is a phenyl group, and two of the diorganosiloxane units are preferably phenyl groups, or one is a phenyl group and the other is a methyl group. Furthermore, the content of phenyl groups is preferably 3 mol % or more, more preferably 10 to 50 mol %, even more preferably 15 to 40 mol %, of all R 3 .
• m and n are positive numbers satisfying 0 ⁇ m ⁇ 3, preferably 1 ⁇ m ⁇ 3, 3 ⁇ n ⁇ 50, preferably 3 ⁇ n ⁇ 49, more preferably 3 A positive number that satisfies ⁇ n ⁇ 30 and 3 ⁇ m + n ⁇ 50, preferably 4 ⁇ m + n ⁇ 50, more preferably 4 ⁇ m + n ⁇ 40, further preferably 4 ⁇ m + n ⁇ 31, particularly preferably 4 ⁇ m+n ⁇ 30.
• component (D) dissolves in the base polymer (component (A)) and bleeding properties cannot be obtained.
• m+n exceeds 50, entanglement between the base polymer (component (A)) and component (D) becomes preferential, resulting in a decrease in bleeding property.
• the component (D) and the base polymer (component (A)) become immiscible in a well-balanced manner, and the repulsive force causes oil-bleeding (the degree of oil bleeding and exudation). ease of use) can be improved.
• m may be 0, but is preferably 1 or more, so that the structure of formula (1) has a branched structure, and the oil bleeding property of the cured product can be changed. It is possible to control the amount of oil that exudes from the molded product (cured product) at the beginning of molding and the time that the oil exudes. Moreover, by setting m to 1 or more, the heat resistance of the cured product can be further improved.
• the blending amount of component (D) is 1 to 10 parts by mass, preferably 3 to 8 parts by mass, per 100 parts by mass of component (A). If the amount is less than the above lower limit, sufficient oil bleeding will not appear, and if it exceeds the above upper limit, the physical properties and heat resistance of the resulting cured product will decrease, and mold contamination will occur during molding. There is a risk of
• Examples of the phenyl group-containing organopolysiloxane (silicone oil) represented by the above formula (1) include compounds represented by the following formulas (1-1) and (1-2). (Phenyl group 19 mol%) (Phenyl group 35 mol%) (In the above formula, Me is a methyl group and Ph is a phenyl group.)
• the non-functional dimethylpolysiloxane of the component (E) is represented by the following general formula (2). It is a component that, when added to the rubber composition together with the component (D), imparts oil-bleeding properties to the cured product and improves heat resistance. (In the formula, Me is a methyl group and p is an integer of 2 to 600.)
• p average degree of polymerization
• p is an integer of 2-600, preferably an integer of 10-550. If p is less than 2, it is likely to volatilize and escape from the system, so it does not function as an active ingredient. If p exceeds 600, the surface of the cured silicone rubber will become sticky even with a small amount of the silicone rubber compounded, increasing the load during release from the metal plate.
• the blending amount of component (E) is 1 to 25 parts by mass, preferably 1 to 23 parts by mass, more preferably 2 to 21 parts by mass, per 100 parts by mass of component (A). If the above compounding amount is less than 1 part by mass, not only will the bleeding property be poor, but the heat resistance effect will not be sufficiently obtained. end up
• the total amount of component (D) and component (E) is preferably 2 to 35 parts by mass, more preferably 2 to 30 parts by mass, and further 3 to 25 parts by mass with respect to 100 parts by mass of component (A). 5 to 25 parts by mass is particularly preferred. If the amount is more than 35 parts by mass, the rubber physical properties and heat resistance of the cured product may be remarkably deteriorated, and mold contamination may occur.
• the blending mass ratio (D)/((D)+(E)) ⁇ 100% in the total blending amount of components (D) and (E) is preferably 2 to 98%, more preferably 4 to 96%.
• the cured product obtained by curing the composition of the present invention exhibits excellent oil bleeding and heat resistance.
• the intended effect can be obtained without containing an additive such as a metal oxide, the hardness can be made low.
• (F) benzotriazole derivative] (F) component is the following general formula (3) [In the formula, R 4 is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, and R 5 is a monovalent hydrocarbon group having 1 to 15 carbon atoms or a group represented by the following formula (4). (In the formula, R 6 is -(CH 2 ) L -Si(OR 7 ) 3 , R 7 is an alkyl group having 1 to 4 carbon atoms or SiR 8 3 group (R 8 is an alkyl group having 1 to 4 carbon atoms group), and L is an integer of 1 to 6.
• a benzotriazole derivative represented by which can reduce the compression set of silicone rubber after curing and provide a sufficient pot life for working. Further, by interacting with the platinum group metal catalyst of component (C), the heat resistance can be improved, especially when the amount of the platinum group metal catalyst is large.
• the benzotriazole derivatives of component (F) may be used singly or in combination of two or more.
• R 4 is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms
• the monovalent hydrocarbon group having 1 to 6 carbon atoms is a methyl group, an ethyl group, a propyl group, an isopropyl group or a butyl group.
• a hydrogen atom or a methyl group is preferred from the viewpoint of synthesis.
• R 5 is a monovalent hydrocarbon having 1 to 15 carbon atoms or a group represented by the above formula (4). Examples of specific benzotriazole derivatives are shown below.
• L is an integer of 1 to 6
• R 7 is an alkyl group or a trialkylsilyl group.
• the blending amount of component (F) is 2 to 100 mol, preferably 5 to 75 mol, more preferably 10 to 50 mol, per 1 mol of platinum group metal atoms of component (C). If the blending amount is less than 2 mol, the compression set cannot be lowered sufficiently, and a pot life sufficient for working cannot be obtained. If it exceeds 100 mol, the curability will be lowered.
• the silicone rubber composition of the present invention preferably further contains reinforcing silica powder as component (G), preferably fine reinforcing silica powder.
• the (G) component reinforcing silica powder may be used alone or in combination of two or more.
• the reinforcing silica powder of component (G) is not particularly limited in the type of silica, and examples thereof include fumed silica (dry silica), calcined silica, precipitated silica (wet silica), etc., and is generally used as a reinforcing agent for silicone rubber. Any silica may be used, but fumed silica is preferred because it improves the strength of silicone rubber.
• reinforcing silica powder those used in conventional silicone rubber compositions can be used, but reinforcing silica powder having a BET specific surface area of 50 m 2 /g or more is preferred. Reinforcing silica powder having a BET specific surface area of 50 to 400 m 2 /g, particularly 100 to 350 m 2 /g, is preferably used.
• the surface of the reinforcing silica powder may be hydrophobized with a surface treatment agent such as a (usually hydrolyzable) organosilicon compound such as chlorosilane, alkoxysilane, or organosilazane.
• the silica fine powder may be one that has been previously powdered and has been directly surface-hydrophobicized with a surface-treating agent, or silicone oil (for example, the alkenyl group-containing organopolysiloxane of component (A) above). ) may be subjected to surface hydrophobizing treatment by adding a surface treatment agent during kneading.
• a surface-treating agent for example, the alkenyl group-containing organopolysiloxane of component (A) above.
• the surface can be treated by a well-known technique.
• the untreated silica fine powder and the surface treatment agent are placed in a mechanical kneading device or fluidized bed sealed under normal pressure, and if necessary Mixing treatment is performed at room temperature or heat treatment (under heating) in the presence of an inert gas.
• a catalyst such as a hydrolysis accelerator
• Surface-treated silica fine powder can be produced by drying after kneading.
• the amount of the surface treatment agent to be blended may be at least the amount calculated from the coverage area of the treatment agent.
• surface treatment agents include silazanes such as hexamethyldisilazane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, vinyl Silane coupling agents such as triethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris(methoxyethoxy)silane, trimethylchlorosilane, dimethyldichlorosilane, divinyldimethoxysilane and chloropropyltrimethoxysilane, polymethylsiloxane , organosilicon compounds such as organohydrogenpolysiloxane, etc., which are surface-treated and used as hydrophobic silica fine powder.
• a silane coupling agents such as trie
• the blending amount is preferably 5 to 100 parts by mass, more preferably 5 to 80 parts by mass, and further 5 to 60 parts by mass based on the total 100 parts by mass of component (A). preferable. If the amount is less than 5 parts by mass, the reinforcing effect may not be obtained, and if it exceeds 100 parts by mass, the viscosity of the silicone rubber composition may become too high, resulting in poor workability and processability.
• the oil-bleeding silicone rubber composition of the present invention may optionally contain other components such as reaction control agents such as ethynylcyclohexanol, fillers such as quartz powder, diatomaceous earth, and calcium carbonate, carbon black, and conductive materials.
• reaction control agents such as ethynylcyclohexanol
• fillers such as quartz powder, diatomaceous earth, and calcium carbonate, carbon black, and conductive materials.
• Conductive agents such as zinc white and metal powders, adhesion imparting agents (especially at least one functional group selected from alkenyl groups, epoxy groups, amino groups, (meth)acryloxy groups, mercapto groups, etc. in the molecule) and an organic silicon compound such as alkoxysilane containing no SiH group in the molecule), a thixotropic agent, a coloring agent such as a pigment, a benzotriazole derivative, and the like.
• the oil-bleeding silicone rubber composition of the present invention should be improved in heat resistance without adding heat resistance improvers, specifically metal oxides such as iron oxide, titanium oxide and cerium oxide. Therefore, the content of these components can be set to 20% by mass or less in the composition, preferably none.
• the oil-bleeding silicone rubber composition of the present invention can be prepared by appropriately mixing the above-described essential components (A) to (F) and other prescribed components, and the order of blending is not particularly limited. However, first, it is preferable to combine (B) component, (D) component, (E) component and (F) component together or separately with the above component (A). Here, together means blending the three components at the same time. Separately means to blend the components (B), (D), (E) and (F) in random order. Finally, component (C) is added and mixed. A cured product obtained from the composition thus obtained is excellent in oil-bleeding property and heat resistance during use.
• the oil-bleeding silicone rubber composition thus obtained does not require additives such as metal oxides, it is colorless and transparent to milky white, and can be easily colored with a coloring agent such as a pigment. can do.
• a coloring agent such as a pigment. can do.
• colorless to milky white means a change in the degree of cloudiness from colorless and transparent to gradually losing transparency and becoming whitish (colorless and translucent), and finally to milky white (no transparency).
• the molding and curing method for this oil-bleeding silicone rubber composition conventional methods can be adopted, but the molding method most suitable for the purpose is selected from injection molding, transfer molding, injection molding, compression molding, and the like. It is possible.
• heat treatment primary vulcanization
• secondary vulcanization post-curing
• the cured product (silicone rubber cured product) of the oil-bleeding silicone rubber composition obtained in this way preferably has a hardness (JIS K 6249:2003, by durometer A hardness tester) of 10 or more, preferably 10 to 70. More preferably, 20-60 is even more preferable. It is preferable that the hardness of the cured silicone rubber does not substantially change even after heating the cured silicone rubber at 225° C. for 72 hours in the atmosphere. For example, the change rate of the durometer A hardness after heating at 225 ° C. for 72 hours in an air atmosphere relative to the initial durometer A hardness is preferably within ⁇ 7 degrees, more preferably within ⁇ 5 degrees. .
• this cured silicone rubber has oil bleeding properties.
• oil-bleeding means that the silicone oil contained in the cured product oozes (bleeds) onto the surface of the cured silicone rubber over time. Here, it is sometimes simply referred to as bleeding property.
• this cured silicone rubber has excellent heat resistance.
• the rate of decrease in the elongation at break (according to JIS K6249:2003) relative to the initial elongation at break is preferably 30% or less, more preferably 25% or less. preferable.
• the method for improving the heat resistance of the cured oil-bleeding silicone rubber or lowering the compression set according to the present invention includes: Components (A) to (C) below (A) Organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule: 100 parts by mass, (B) an organohydrogenpolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule: 0.2 to 20 parts by mass; (C) platinum group metal-based catalyst: 0.5 to 500 ppm as platinum group metal (in terms of mass) with respect to the total mass of components (A) and (B) 1 to 10 parts by mass of the following (D) to (F) components (D) phenyl group-containing organopolysiloxane represented by the following formula (1), (In the formula, R 3 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms and not containing an alipha
• n is a positive number from 3 to 50
• m+n is a positive number that satisfies 3 to 50.
• E a non-functional dimethylpolysiloxane represented by the following formula (2): 1 to 25 parts by mass, and (In the formula, Me is a methyl group and p is an integer of 2 to 600.)
• R 4 is a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms
• R 5 is a monovalent hydrocarbon group having 1 to 15 carbon atoms or a group represented by the following formula (4). be.
• R 6 is -(CH 2 ) L -Si(OR 7 ) 3
• R 7 is an alkyl group having 1 to 4 carbon atoms or SiR 8 3 group
• R 8 is an alkyl group having 1 to 4 carbon atoms group
• L is an integer of 1 to 6. * indicates a point of attachment.
• the above silicone rubber composition further contains 5 to 100 parts by mass of reinforcing silica powder as component (G) per 100 parts by mass of component (A).
• components (A) to (G) are the same as the components in the oil-bleeding silicone rubber composition of the present invention described above, and have the effect of improving heat resistance (elongation at break) and reducing compression set. is the same as above.
• a part means a mass part.
• room temperature means 25°C.
• Me represents a methyl group and Ph represents a phenyl group.
• the amount of phenyl groups in component (D) described below is the ratio (mol%) of the number of moles of phenyl groups to the total number of moles of R 3 in formula (1).
• the viscosity is a value measured using a rotational viscometer at 25°C.
• Preparation Example 1 Vinyldimethylsiloxy group-blocked dimethylpolysiloxane (A1) having a viscosity of about 30,000 mPa ⁇ s and an average degree of polymerization Mn of 750 (vinyl group content: 3.6 ⁇ 10 ⁇ 5 mol/g) 60 parts, 40 parts of fine powder silica (G) (trade name: Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) having a specific surface area of about 300 m 2 /g by the BET method, 8 parts of hexamethyldisiloxane as a surface treatment agent, and 2 parts of water. The parts were mixed in a kneader for 1 hour.
• G fine powder silica
• Example 1 To 100 parts of the base compound (I) obtained above, 6.54 parts of the dimethylpolysiloxane (A1) was further added, and both ends of the molecular chain were blocked with trimethylsiloxy groups (i.e., diorgano dimethyl-methylvinylpolysiloxane copolymer (A2) having an average degree of polymerization Mn of 200 in which 5 mol% of the monovalent groups or atoms bonded to silicon atoms in the siloxane unit) are vinyl groups (vinyl group content 6.5 ⁇ 10 ⁇ 4 mol/g) 1.54 parts, methylhydrogenpolysiloxane (B1) having both molecular chain ends blocked with trimethylsiloxy groups and having SiH groups in side chains (degree of polymerization 38, amount of SiH groups 1.15 parts of 0.00694 mol/g of dimethylsiloxane-methylhydrogensiloxane copolymer with both molecular chain ends blocked with trimethylsiloxy groups,
• composition A was obtained.
• the appearance (visual observation) of the resulting composition A was colorless and translucent.
• This composition A was made to have a thickness of 2 mm and was subjected to press curing at 150° C. for 10 minutes to prepare a test piece of a cured silicone rubber, which was subjected to the following tests.
• the obtained cured product was cut into a sheet piece of 15 mm ⁇ 35 mm, and the sample was allowed to stand at room temperature (25° C.) for 1 day. After that, the presence or absence of oil exuded on the surface of the sample was evaluated by touch with a finger.
• Reduction rate of elongation at break ⁇ (initial elongation at break) - (elongation at break after heating at 225°C for 72 hours) ⁇ /(initial elongation at break) x 100 (%)
• Example 2 To 100 parts of the base compound (I) obtained above, 18.85 parts of the dimethylpolysiloxane (A1) is added, and both ends of the molecular chain are blocked with trimethylsiloxy groups as a cross-linking agent, and have SiH groups in side chains.
• Example 1 a toluene solution (C1) of a complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (1% by mass of platinum atoms) was added, and the mixture was stirred for 30 minutes to obtain a uniform mixture.
• a silicone rubber composition B was obtained.
• the appearance (visual observation) of the resulting composition B was colorless and translucent.
• the resulting composition B was evaluated in the same manner as in Example 1 for oil bleeding property, durometer A hardness, elongation at break, and compression set.
• Example 3 To 100 parts of the base compound (I) obtained above, 6.54 parts of the dimethylpolysiloxane (A1) was further added, and both ends of the molecular chain were blocked with trimethylsiloxy groups to form a side chain (that is, a di Dimethylpolysiloxane (A2) having an average degree of polymerization Mn of 200 (vinyl group content: 6.5 ⁇ 10 -4 mol / g) 1.54 parts, methyl hydrogen polysiloxane (B1) having both ends of the molecular chain blocked with trimethylsiloxy groups and having SiH groups in side chains as a cross-linking agent (degree of polymerization 38, amount of SiH groups 0.00694 mol 1.15 parts of a dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups blocked at both molecular chain ends of /g), and a phenyl group-containing organopolysiloxane having a phenyl
• Example 1 a toluene solution (C1) of a complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (1% by mass of platinum atoms) was added, and the mixture was stirred for 30 minutes to obtain a uniform mixture.
• a silicone rubber composition C was obtained.
• the appearance (visual observation) of the resulting composition C was colorless and translucent.
• the resulting composition C was evaluated in the same manner as in Example 1 for oil bleeding property, durometer A hardness, elongation at break, and compression set.
• E1 non-functional dimethylpolysiloxane having trimethylsiloxy groups at both ends of the molecular chain and 0.08 parts of ethynylcycl
• Example 1 a toluene solution (C1) of a complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (1% by mass of platinum atoms) was added, and the mixture was stirred for 30 minutes to obtain a uniform mixture.
• a silicone rubber composition E was obtained.
• the appearance (visual observation) of the obtained composition E was colorless and transparent.
• the resulting composition E was evaluated in the same manner as in Example 1 for oil bleeding property, durometer A hardness, elongation at break, and compression set.
• D1 phenyl group-containing organopolysiloxane (
• Example 1 a toluene solution (C1) of a complex of platinum and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (1% by mass of platinum atoms) was added, and the mixture was stirred for 30 minutes to obtain a uniform mixture.
• a silicone rubber composition F was obtained.
• the appearance (visual observation) of the obtained composition F was reddish brown.
• the resulting composition F was evaluated in the same manner as in Example 1 for oil bleeding property, durometer A hardness, elongation at break, and compression set.

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