Silicone rubber composition, silicone rubber, and silicone rubber foam

Abstract

The present invention prevents silicone rubber from decomposing into combustible low-molecular siloxane at high temperatures, and inhibits weight loss. This silicone rubber composition comprises: polyorganosiloxane represented by formula (A1) (component a); a weight loss inhibitor (component b); and an organic peroxide crosslinking agent (component c), wherein weight loss when silicone rubber obtained by crosslinking the silicone rubber composition is heated from 30°C to 900°C at a temperature increase rate of 150°C / minute in nitrogen atmosphere is less than 0.4 g / cm3.

Description

Silicone rubber composition, silicone rubber, and silicone rubber foam

[0001] The present invention relates to a silicone rubber composition, a silicone rubber, and a silicone rubber foam.

[0002] The silicone rubber composition contains at least a polyorganosiloxane and a crosslinking agent, and the crosslinked silicone rubber is formed by crosslinking the polyorganosiloxane with the crosslinking agent. The silicone rubber composition also contains a foaming agent in addition to the polyorganosiloxane and crosslinking agent, and a silicone rubber foam is obtained as the silicone rubber by crosslinking and foaming. Silicone rubber is a material with excellent properties such as weather resistance and heat resistance, and is used in a variety of fields.

[0003] In recent years, in order to improve the flame retardancy of silicone rubber, a technique of adding various flame retardants to a silicone rubber composition has been proposed.

[0004] Japanese Patent Publication No. 44-2591, Japanese Patent Laid-Open No. 48-96650, Japanese Patent Laid-Open No. 53-130753, Japanese Patent Laid-Open No. 2004-149693, Japanese Patent Laid-Open No. 2009-144024,

[0005] However, conventional silicone rubbers can decompose when exposed to high temperatures. This can result in the generation of flammable low-molecular-weight siloxanes, which can lead to a loss of weight. Therefore, to improve safety, it is necessary to suppress the generation of flammable low-molecular-weight siloxanes.

[0006] Therefore, an object of the present invention is to provide a silicone rubber composition, silicone rubber, and silicone rubber foam that can effectively prevent the decomposition of flammable low-molecular-weight siloxanes from silicone rubber at high temperatures and prevent the weight of the silicone rubber from decreasing.

[0007] The silicone rubber composition of the present invention contains (component a), (component b), and (component c). (Component a) is a polyorganosiloxane represented by the following formula (A1).

[0008] (In formula (A1), R １ represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group, and R ２ represents an alkenyl group, and R ３ are each independent R １ or R ２ where n and m represent the total number of repeating units obtained by random polymerization or block polymerization, respectively, and n+m+2, which is the sum of n and m plus 2, the number of terminal groups, represents the mass average degree of polymerization.) In addition, (component a) has a mass average degree of polymerization of 1,000 or more and 10,000 or less, and does not contain R ２ in a mass content of 0.001 mmol / g or more and less than 2.0 mmol / g, and R ２ (Component b) is a weight loss inhibitor. (Component c) is an organic peroxide crosslinking agent. In the silicone rubber composition, when a silicone rubber obtained by crosslinking the silicone rubber composition is heated from 30°C to 900°C at a temperature increase rate of 150°C / min in a nitrogen atmosphere, the weight loss is 0.4 g / cm. ３ It will be less than.

[0009] The present invention can provide a silicone rubber composition, silicone rubber, and silicone rubber foam that can effectively prevent the decomposition of flammable low-molecular-weight siloxanes from silicone rubber at high temperatures and prevent the weight of the silicone rubber from decreasing.

[0010] FIG. 1 shows the weight loss of the silicone rubber (W M (g / cm ３ 1 is a graph showing the relationship between the content of platinum atoms in the platinum compound (component c) relative to the polyorganosiloxane (component a), CL (ppm).

[0011] [A] Silicone Rubber Composition The silicone rubber composition of this embodiment contains (component a) polyorganosiloxane, (component b) weight loss inhibitor, and (component c) crosslinking agent. In addition, the silicone rubber composition of this embodiment preferably contains (component d) reinforcing silica. As a result, in the silicone rubber composition of this embodiment, the polyorganosiloxane (component a) is crosslinked by the crosslinking agent (component c), and a silicone rubber is formed, which is a crosslinked product of the polyorganosiloxane. In the silicone rubber composition of this embodiment, when a silicone rubber obtained by crosslinking the silicone rubber composition is heated from 30°C to 900°C at a heating rate of 150°C / min under a nitrogen atmosphere, the weight loss is 0.4 g / cm. ３ It will be less than.

[0012] When a silicone rubber foam is obtained as the silicone rubber, the silicone rubber composition of this embodiment further contains (component e) a foaming agent, which crosslinks and foams the silicone rubber composition of this embodiment to obtain the silicone rubber foam.

[0013] As will be described in more detail below, the silicone rubber composition of this embodiment can effectively prevent the decomposition of flammable low-molecular-weight siloxanes from the silicone rubber at high temperatures, thereby preventing the weight of the silicone rubber from decreasing.

[0014] The components constituting the silicone rubber composition of this embodiment will be described in detail below.

[0015] [A-1] (Component a) Polyorganosiloxane (Component a) Polyorganosiloxane is a base polymer of peroxide-cured heat-cured rubber (HCR) and is represented by formula (A1).

[0016]

[0017] In formula (A1), R １ represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group. Specifically, R １is an alkyl group (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl), an aryl group (e.g., phenyl, tolyl, xylyl), an aralkyl group (e.g., benzyl, phenethyl), etc. Furthermore, R is a monovalent substituted hydrocarbon group. １ is an m-chloromethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a 3-cyanopropyl group, a 3-methoxypropyl group, etc. In order to facilitate the synthesis and handling of (component a) polyorganosiloxane and to obtain excellent heat resistance, in formula (A1), R １ It is preferable that 50% or more of the total of R are methyl groups, and particularly, １ When heat resistance, cold resistance, or radiation resistance is required for the polyorganosiloxane (component a), it is preferable that all of R １ When oil resistance and solvent resistance are required for the polyorganosiloxane (component a), it is preferable that R １ It is preferable that the alkyl group contains a 3,3,3-trifluoropropyl group or the like.

[0018] In formula (A1), R ２ represents an alkenyl group. Specifically, R ２ is a vinyl group, an allyl group, a 3-butenyl group, a 4-pentenyl group, a 5-hexenyl group, etc. The polyorganosiloxane (component a) is easy to synthesize and handle, and the addition reaction is easily carried out, so that R ２ is preferably a vinyl group.

[0019] In formula (A1), R ３ are each independent R １ or R ２ That is, R ３ is R １ (a monovalent unsubstituted or substituted hydrocarbon group containing no aliphatic unsaturated groups) and R ２ and the group shown as (alkenyl group). ３ As mentioned above, a part of ２Preferably, the alkenyl group is the alkenyl group shown below.

[0020] In formula (A1), n ​​and m each represent the total number of randomly polymerized or block-polymerized repeating units. The sum of n and m plus 2, which is the number of terminal groups, (n + m + 2) corresponds to the mass-average degree of polymerization.

[0021] The polyorganosiloxane (component a) may be a block copolymer or a random copolymer. The polyorganosiloxane (component a) is preferably substantially linear, but may have some branching in the siloxane skeleton.

[0022] The mass average degree of polymerization (n + m + 2) of the polyorganosiloxane (component a) is in the range of 1000 to 10000. If it is smaller than the lower limit, the necessary workability cannot be obtained, and sufficient mechanical strength cannot be obtained. If it is larger than the upper limit, polymerization becomes difficult. Therefore, the mass average degree of polymerization is preferably in the range of 2000 to 8000.

[0023] In the polyorganosiloxane (component a), R ２ In order to form a crosslinked product, two or more R groups are contained in one molecule of (component a) polyorganosiloxane. ２ (R ３ R in the terminal unit shown as ２ The content per mass of R is 0.001 mmol / g or more and less than 2.0 mmol / g. If it is less than the lower limit, the strength of the crosslinked body may be insufficient. If it is greater than the upper limit, the crosslinked body may become brittle. For this reason, in formula (A1), R ２ The content is preferably 0.005 mmol / g or more and 0.3 mmol / g or less, and more preferably 0.01 mmol / g or more and 0.1 mmol / g or less.

[0024] In the silicone rubber composition of this embodiment, the polyorganosiloxane (component a) may be one type or multiple types.

[0025] [A-2] (Component b) Weight Loss Inhibitor The (component b) weight loss inhibitor is added to silicone rubber to inhibit the decomposition of (component a) polyorganosiloxane, which constitutes the main chain of the silicone rubber, from producing flammable low-molecular-weight siloxanes when the silicone rubber is exposed to high temperatures. Examples of the weight loss inhibitor include (component b1) inorganic filler, (component b2) platinum compound, and (component b3) ligand (a ligand capable of coordinating with the platinum atom constituting the (component b2) platinum compound). [A-2-1] (Component b1) Inorganic Filler The (component b1) inorganic filler is a mixture of crystalline silica (quartz) and Fe ３ O ４ and TiO ２ and at least one of the following.

[0026] [A-2-2] (Component b2) Platinum Compound Examples of the platinum compound (component b2) include chloroplatinic acid, reaction products of chloroplatinic acid and alcohol, platinum-olefin complexes, platinum-vinylsiloxane complexes, platinum-ketone complexes, and platinum-phosphine complexes. Of these, platinum-vinylsiloxane complexes are preferred because they are compatible with and easily dispersible in the polyorganosiloxane (component a), with platinum-1,1,3,3-tetramethyl-1,3-divinyldisiloxane complex and platinum-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex being particularly preferred. The platinum compound (component b2) may be of one type or multiple types.

[0027] [A-2-3] (Component b3) Ligand The (Component b3) ligand is a compound capable of coordinating with the platinum atom constituting the (Component b2) platinum compound. The (Component b3) ligand is, for example, a phosphite or a nitrogen-containing aryl compound. Specifically, the (Component b3) ligand is preferably triphenyl phosphite or 2,2'-bipyridyl.

[0028] [A-3] (Component c) Crosslinking Agent (Component c) is an organic peroxide.

[0029] Specifically, organic peroxides used as the crosslinking agent (component c) include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-chlorobenzoyl peroxide, dicumyl peroxide, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexyne, di-t-butyl peroxide, t-butyl peroxybenzoate, and bis(4-t-butylcyclohexyl)peroxydicarbonate.

[0030] [A-4] (Component d) Reinforcing Silica (Component d) is a powder such as precipitated silica, fumed silica, or pyrogenic silica. (Component d) Reinforcing silica may be of one type or of multiple types.

[0031] (Component d) reinforcing silica is added to the silicone rubber composition to provide it with appropriate fluidity and to provide high mechanical strength to the silicone rubber, which is a crosslinked product of the silicone rubber composition. In order to obtain the above functions, (Component d) reinforcing silica is selected from those having a BET specific surface area (specific surface area measured by the BET method) of 50 m ２ / g or more 350m ２ / g or less is preferable.

[0032] The reinforcing silica (component d) is preferably subjected to a hydrophobic treatment to hydrophobize the surface where silanol groups (Si—OH groups) are present, which effectively prevents the silicone rubber composition from increasing in viscosity or experiencing significant replasticization.

[0033] In the hydrophobic treatment of (component d) reinforcing silica, for example, an organosilicon compound is used as a surface treatment agent. Specific examples of the organosilicon compound used as a surface treatment agent include hexaorganodisilazanes such as 1,3-divinyltetramethyldisilazane, 1,3-dimethyltetravinyldisilazane, and hexamethyldisilazane; organosilazanes such as octamethyltrisilazane and 1,5-divinylhexamethyltrisilazane; alkyltrialkoxysilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, and butyltrimethoxysilane; dialkyldialkoxysilanes such as dimethyldimethoxysilane, diethyldimethoxysilane, dimethyldiethoxysilane, and diethyldiethoxysilane; vinyltriethoxysilane, vinyltrimethoxysilane, and vinyltris(methoxyethoxy)silane. alkenyltrialkoxysilanes; dialkenyldialkoxysilanes such as divinyldimethoxysilane and divinyldiethoxysilane; trialkylalkoxysilanes such as trimethylmethoxysilane and triethylmethoxysilane; trialkenylalkoxysilanes such as trivinylmethoxysilane and trivinylethoxysilane; organochlorosilanes such as trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, vinyltrichlorosilane, divinyldichlorosilane and trivinylchlorosilane, and silane coupling agents such as chloropropyltrimethoxysilane, dimethylpolysiloxanes (including cyclic structures), low molecular weight polyorganosiloxanes end-blocked with hydroxyl groups or alkoxy groups, organohydrogenpolysiloxanes, etc. The organosilicon compound used as a surface treatment agent may be a partial hydrolysis reaction product of the above-mentioned substances. Among the above substances, it is particularly preferable to use silane coupling agents in which the substituent bonded to the silicon atom other than the hydrolyzable group is a methyl group, cyclic dimethylpolysiloxanes, low-molecular-weight polyorganosiloxanes whose ends are blocked with hydroxyl groups or alkoxy groups, and organosilazanes.

[0034] [A-5] (Component e) Foaming Agent (Component e) is added to obtain a silicone rubber foam from the silicone rubber composition by decomposing upon heating to generate a gas.

[0035] The decomposition temperature of the blowing agent (component e) is preferably 50°C or higher and 250°C or lower. If the decomposition temperature is lower than the lower limit, handling is difficult and storage stability is poor. On the other hand, if the decomposition temperature is higher than the upper limit, productivity decreases. For this reason, the decomposition temperature of the blowing agent is preferably 80°C or higher and 200°C or lower.

[0036] The blowing agent (component e) is, for example, an organic blowing agent. Specifically, the organic blowing agent is an azo compound such as azobisisobutyronitrile (decomposition temperature: 102°C), 1,1'-azobis(1-acetoxy-1-phenylethane) (decomposition temperature: 106°C), or azodicarbonamide (decomposition temperature: 205°C), or a nitroso compound such as dinitrosopentamethylenetetramine (decomposition temperature: 203°C) or N,N-dimethyl-N,N-dinitrosoterephthalamide (decomposition temperature: 105°C). The above blowing agents decompose when heated to a temperature above their decomposition temperature, releasing N ２ Gas and CO ２ The foaming agent (component e) may be one type or multiple types.

[0037] In order to adjust the foaming temperature, a regulator such as urea or an organic acid may be used in combination with the organic foaming agent.

[0038] [A-6] Blending [A-6-1] Blending (Component b1) In the silicone rubber composition of this embodiment, the inorganic filler (component b1) is preferably added in an amount of 0.1 to 200 parts by mass per 100 parts by mass of the polyorganosiloxane (component a). If the proportion of the inorganic filler (component b1) added is less than the lower limit of this range, when the silicone rubber is exposed to high temperatures, the decomposition and generation of flammable low-molecular-weight siloxanes cannot be sufficiently suppressed, making it difficult to suppress weight loss of the silicone rubber. Furthermore, if the proportion of the inorganic filler (component b1) added is greater than the upper limit of this range, the flexibility of the silicone rubber may be lost. For this reason, the inorganic filler (component b1) is preferably added in an amount of 0.2 to 200 parts by mass, and more preferably 0.5 to 150 parts by mass.

[0039] [A-6-2] Blending of (Component b2) In the silicone rubber composition of this embodiment, the platinum compound (component b2) is added so as to contain 1 ppm to 300 ppm of platinum atoms relative to the polyorganosiloxane (component a). If the proportion of the platinum compound (component b2) added is less than the lower limit of this range, the decomposition of flammable low-molecular-weight siloxanes from the silicone rubber at high temperatures may not be sufficiently suppressed, making it difficult to suppress weight loss of the silicone rubber. Furthermore, if the proportion of the platinum compound (component b2) added is greater than the upper limit of this range, it may be difficult to achieve cost reduction. For this reason, the platinum compound (component b2) is preferably added in an amount of 1 ppm to 200 ppm of platinum atoms relative to the polyorganosiloxane (component a), and more preferably 5 ppm to 150 ppm of platinum atoms.

[0040] [A-6-3] Blending of (Component b3) In the silicone rubber composition of this embodiment, the (Component b3) ligand is preferably added in an amount of 1 mol to 40 mol per mol of platinum atoms contained in the (Component b2) platinum compound. If the addition ratio of the (Component b3) ligand is less than the lower limit of this range, the decomposition of flammable low molecular weight siloxanes from the silicone rubber at high temperatures may not be sufficiently suppressed, making it difficult to suppress weight loss of the silicone rubber. Furthermore, if the addition ratio of the (Component b3) ligand is greater than the upper limit of this range, the effect of suppressing the decomposition of low molecular weight siloxanes becomes saturated. For this reason, the (Component b3) ligand is preferably added in an amount of 1 mol to 20 mol, and more preferably 2 mol to 15 mol, per mol of platinum atoms contained in the (Component b2) platinum compound.

[0041] [A-6-4] Blending of (Component c) In the silicone rubber composition of this embodiment, the (component c) crosslinking agent is preferably added in an amount of 0.001 parts by mass or more and 10 parts by mass or less, based on 100 parts by weight of the (component a) polyorganosiloxane. If the addition ratio of the (component c) crosslinking agent is less than the lower limit of this range, sufficient crosslinking may not be achieved, resulting in insufficient strength. Furthermore, if the addition ratio of the (component c) crosslinking agent is greater than the upper limit of this range, a problem may arise in which a long post-cure period is required to remove the decomposition products of the excess (component c) crosslinking agent. For this reason, the (component c) crosslinking agent is preferably added in an amount of 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.1 parts by mass or more and 1 part by mass or less.

[0042] [A-6-5] Blending of (Component d) In the silicone rubber composition of this embodiment, the addition of (Component d) reinforcing silica is optional, but it is preferably added in an amount of 1 part by mass to 100 parts by mass per 100 parts by mass of (Component a) polyorganosiloxane. If the addition ratio of (Component d) reinforcing silica is less than the lower limit of this range, the mechanical strength of the silicone rubber may be insufficient. Furthermore, if the addition ratio of (Component d) reinforcing silica is more than the upper limit of this range, the viscosity of the silicone rubber composition may increase, which may deteriorate the workability during molding. For this reason, it is preferable that (Component d) reinforcing silica is added in an amount of 1 part by mass to 60 parts by mass, and more preferably 5 parts by mass to 50 parts by mass.

[0043] [A-6-6] Blending of (Component e) In the silicone rubber composition of this embodiment, the foaming agent (component e) is preferably added in an amount of 0.1 to 10 parts by mass per 100 parts by mass of the polyorganosiloxane (component a). If the amount of foaming agent (component e) added is less than the lower limit of this range, the amount of gas generated by decomposition may be insufficient, making it difficult to produce a silicone rubber foam. Furthermore, if the amount of foaming agent (component e) added is greater than the upper limit of this range, the amount of gas generated by decomposition may be so large that deformation of the silicone rubber foam may occur. For this reason, it is more preferable that the foaming agent (component e) be added in an amount of 0.5 to 7 parts by mass.

[0044] [A-7] Others In addition to the above components, the silicone rubber composition of this embodiment may contain other additives as needed.

[0045] For example, when the silicone rubber composition of this embodiment contains reinforcing silica (component d), it may contain a surface treatment agent (component f) to hydrophobize the silanol groups present on the surface of the reinforcing silica (component d). The surface treatment agent (component f) is a low-viscosity silicone oil, silicone resin, silane compound, or the like, having a silanol group or an alkoxy group at its terminal. In particular, the surface treatment agent (component f) is preferably a polydimethylsiloxane having silanol groups at both terminals and having a mass-average degree of polymerization of approximately 4 to 200. The blending ratio of the surface treatment agent (component f) is appropriately set depending on the type and blending ratio of the reinforcing silica (component d). However, the blending ratio is preferably 0.1 to 20 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the reinforcing silica (component d).

[0046] In addition, the silicone rubber composition of the present embodiment may contain conductive fillers (carbon black, etc.), pigments, thixotropy-imparting agents, viscosity modifiers for improving extrusion workability, ultraviolet protection agents, mildew inhibitors, heat resistance improvers, flame retardants, antioxidants, etc.

[0047] [B] Method for Producing Silicone Rubber Composition The silicone rubber composition of this embodiment is produced by kneading the components.

[0048] For example, when preparing the silicone rubber composition of this embodiment, first, (component a) polyorganosiloxane, (component b1) inorganic filler, (component b2) platinum compound, (component b3) ligand, (component d) reinforcing silica, and (component f) surface treatment agent are uniformly mixed using a kneader or the like. If necessary, the mixture is further kneaded in a heated state to perform a surface treatment of the (component d) reinforcing silica with the (component f) surface treatment agent. The resulting mixture is further kneaded with (component c) crosslinking agent at room temperature using a kneader or two-roll mill. This produces the silicone rubber composition of this embodiment.

[0049] When the silicone rubber composition of this embodiment contains a foaming agent (component e), the polyorganosiloxane (component a), the inorganic filler (component b1), the platinum compound (component b2), the ligand (component b3), the reinforcing silica (component d), and the surface treatment agent (component f) are mixed uniformly in the same manner as described above, and then the crosslinking agent (component c) and the foaming agent (component e) are mixed at room temperature using a kneader or a two-roll mill.

[0050] [C] Actions and Effects The silicone rubber composition of this embodiment contains (component a) polyorganosiloxane, (component b) weight loss inhibitor, and (component c) crosslinking agent. In the silicone rubber composition of this embodiment, a crosslinked product obtained by crosslinking the silicone rubber composition at a temperature of 300°C or less is heated from 30°C to 900°C at a temperature increase rate of 150°C / min in a nitrogen atmosphere, and the weight loss is 0.4 g / cm. ３ (Component b) weight loss suppression is added so that the weight loss is less than. In this embodiment, the components that make up the silicone rubber composition interact with each other, and the silicone rubber, which is a crosslinked product of the silicone rubber composition, converts into a dense crosslinked product at high temperatures by promoting bonding between the hydrocarbon groups and silicon atoms of the linear polyorganosiloxane that makes up the silicone rubber. As a result, in this embodiment, the generation of cyclic low-molecular-weight siloxanes due to decomposition of the siloxane bonds of the linear polyorganosiloxane is suppressed, and weight loss of the silicone rubber is effectively suppressed.

[0051] Weight reduction is 0.4g / cm ３ When the weight loss is less than 0.4 g / cm, the crosslinked body of the silicone rubber composition can maintain its shape even when exposed to high temperatures. ３ When a crosslinked body having a cross-linking strength of less than 1 / 2 mm is used as a cushioning material between opposing components, the crosslinked body can maintain its shape even after being exposed to high temperatures, and therefore can function as a spacer between the opposing components, maintaining electrical insulation between the components and suppressing heat propagation.

[0052] The same effects as above can also be obtained with a silicone rubber composition that further contains a foaming agent (component e) for producing a silicone rubber foam.

[0053] Examples and Comparative Examples will be described below with reference to Tables 1 and 2. Each table shows the composition and test results of each example. In each table, (EX1) to (EX14) correspond to Examples, and (C EX1) to (C EX7) correspond to Comparative Examples.

[0054]

[0055]

[0056] [1] Materials for each component used in preparing the silicone rubber composition of each example The components used in preparing the silicone rubber composition of each example will be described below.

[0057] In the following description, the siloxane units are described using the following symbols:

[0058] M unit: (CH ３ ) ３ SiO １／２ - M ｖｉ Unit: (CH ３ ) ２ (CH ２ =CH)SiO １／２ - M ＯＨ Unit: (CH ３ ) ２ (OH)SiO １／２ - D unit: - (CH ３ ) ２ SiO-.D ｖｉ Unit: -(CH ３ ) (CH ２ =CH)SiO-

[0059] [1-1] (Component a) Polyorganosiloxane In each example, the following was used as (component a) polyorganosiloxane.

[0060] (a-1) M ｖｉ D ｎ D ｖｉ ｍ M ｖｉ (n=7980, m=22, 0.04 mmol / g Vi) (a-2) MD ｎ D ｖｉ ｍM (n=3660, m=340, 1.14 mmol / g Vi)

[0061] That is, in each example, (component a-1) has both ends M ｖ The intermediate units are D and D ｖｉ The mass average degree of polymerization (n+m+2=7980+22+2) is 8004, and the content of vinyl groups (R ２ The vinyl group content of component a-2 in each example is 0.04 mmol / g. Both ends of component a-2 are capped with M units, and the middle units are D units and D units. ｖｉ It is a linear polydimethylsiloxane consisting of units, and has a mass average degree of polymerization (n+m+2=3660+340+2) of 4002 and a vinyl group (R ２ ) is a polyorganosiloxane gum having a vinyl group content of 1.14 mmol / g.

[0062] In each example, (component a-1) is R １ is a methyl group, and R ２ is a vinyl group, and R ３ is R ２ In each example, (component a-2) is a vinyl group, similar to the above formula (A1). １ is a methyl group, and R ２ is a vinyl group, and R ３ is a methyl group.

[0063] [1-2] (Component b) Weight Loss Inhibitor [1-2-1] (Component b1) Inorganic Filler In each example, the following was used as (Component b1) inorganic filler.

[0064] (b1-1) Crystalline silica (quartz) (trade name: Crystalite VX-S; manufactured by Takimori Co., Ltd.) (b1-2) Fe ３ O ４ (Product name: KN-320; manufactured by Toda Kogyo Co., Ltd.) (b1-3) TiO ２ (Product name P-25; manufactured by EVONIK)

[0065] [1-2-2] (Component b2) Platinum Compound In each example, the following was used as (Component b2) platinum compound.

[0066] Platinum-2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane complex (mass content of platinum atoms: 1.8%)

[0067] [1-2-3] (Component b3) Ligand (capable of coordinating with platinum atom constituting (Component b2) platinum compound) In each example, the following was used as (Component b3) ligand.

[0068] (b3-1) Triphenyl phosphite (b3-2) 2,2'-bipyridyl

[0069] [1-3] (Component c) Crosslinking Agent In each example, the following was used as (component c) crosslinking agent.

[0070] 2,5-bis(t-butylperoxy)-2,5-dimethylhexane

[0071] [1-4] (Component d) Reinforcing Silica In each example, the following was used as (Component d) reinforcing silica.

[0072] (Component d-1) Fumed silica (BET specific surface area 130 m ２ / g) (trade name Aerosil 130; manufactured by EVONIK) (Component d-2) Fumed silica (BET specific surface area 200 m ２ / g) (trade name Aerosil 200; manufactured by EVONIK) (Component d-3) precipitated silica (BET specific surface area 185 m ２ / g) (trade name SIPERNAT 268; manufactured by EVONIK)

[0073] [1-5] (Component f) Surface Treatment Agent In each example, the following was used as (Component f) surface treatment agent.

[0074] ・(Component f-1) M ＯＨ D ８ M ＯＨ ・(Component f-2) M ＯＨ D ３０ M ＯＨ

[0075] That is, (component f-1) and (component f-2) have both ends MＯＨ It is a polysiloxane in which the intermediate unit is composed of D units.

[0076] [2] Preparation of Silicone Rubber Compositions of Each Example The procedure for preparing the silicone rubber compositions of each example will be described.

[0077] In preparing the silicone rubber composition of each example, the components were mixed in the proportions shown in Tables 1 and 2. Specifically, first, (component a) polyorganosiloxane, (component b1) inorganic filler, (component d) reinforcing silica, and (component f) surface treatment agent were mixed using a kneader and kneaded in a heated state (150°C, 1 hour) to obtain a kneaded mixture. Then, after cooling the kneaded mixture to room temperature, (component b2) platinum compound, (component b3) ligand, and (component c) crosslinking agent were further kneaded into the kneaded mixture using a two-roll mill. In this way, the silicone rubber composition of each example was prepared.

[0078] Tables 1 and 2 show the parts by mass of components other than (component a) added relative to 100 parts by mass of (component a) polyorganosiloxane. In the "Composition" column of Tables 1 and 2, "-" indicates that no component is added.

[0079] In Tables 1 and 2, the weight of platinum atoms in the platinum compound (component b2) is shown as a ratio (ppm) to the weight of the polyorganosiloxane (component a). Similarly, in Tables 1 and 2, the amount (mol) of the ligand (component b3) per 1 mol of the platinum compound (component b2) is also shown.

[0080] [3] Preparation of Silicone Rubber of Each Example The procedure for preparing the silicone rubber of each example (crosslinked product of silicone rubber composition) will be described.

[0081] The silicone rubber composition prepared as described above was placed in a mold (20 cm long x 20 cm wide x 2 mm thick) and crosslinked under pressure for 10 minutes at 170°C, yielding a silicone rubber sheet in which the silicone rubber composition was crosslinked. This silicone rubber sheet was then subjected to a post-cure treatment at 200°C for 4 hours using a hot air circulation oven.

[0082] [4] Evaluation of each silicone rubber example Evaluation of each silicone rubber example will be described.

[0083] Here, as shown in Tables 1 and 2, the weight loss of the silicone rubber in each example was evaluated.

[0084] To evaluate the weight loss of the silicone rubber, a thermogravimetric differential thermal analyzer (product name TG / DTA6200; manufactured by SII NanoTechnology) was used. Approximately 10 mg of the silicone rubber sheet prepared as described above was heated in a nitrogen atmosphere (nitrogen gas with a purity of 99.9995% by volume or higher, flow rate 220 ml / min). The silicone rubber was heated from room temperature (30°C) to 1000°C at a heating rate of 150°C / min. The weight loss rate WL (%) at 900°C was measured for each silicone rubber example.

[0085] Then, for each example, the density DE (g / cm 3 ) of the silicone rubber was calculated as shown in the following formula: ３ ) to calculate the weight loss of silicone rubber per unit volume W (g / cm ３ ) was sought.

[0086] WM=DE*WL / 100

[0087] FIG. 1 shows the weight loss of the silicone rubber (W M (g / cm ３ 1 is a graph showing the relationship between the content of platinum atoms in the platinum compound (component c) relative to the polyorganosiloxane (component a), CL (ppm). In FIG. 1, diamond markers indicate the results of (EX1) to (EX14), and circular markers indicate the results of (C EX1) to (C EX7).

[0088] As shown in Tables 1 and 2 and in Figure 1, (EX1) to (EX14) (diamond markers in Figure 1) represent the weight loss of silicone rubber per unit volume, W (g / cm ３ ) is 0.4 g / cm ３ On the other hand, (C EX1) to (C EX7) (circular markers in Figure 1) indicate the weight loss of silicone rubber per unit volume, W M (g / cm ３ ) is 0.4 g / cm３ Thus, (EX1) to (EX14) can reduce the weight loss WM of the silicone rubber per unit volume more than (C EX1) to (C EX7).

[0089] As described above, the silicone rubber compositions (EX1) to (EX14) have a weight loss of 0.4 g / cm when the crosslinked product obtained by crosslinking the silicone rubber composition at a temperature of 300°C or less is heated from 30°C to 900°C at a heating rate of 150°C / min in a nitrogen atmosphere. ３ (Component b) weight loss suppression is added so that the total weight loss is less than 100 parts by mass. In particular, the silicone rubber compositions (EX1) to (EX14) contain 0.1 to 200 parts by mass of (component b1) inorganic filler per 100 parts by mass of (component a) polyorganosiloxane, (component b2) platinum compound added so that it contains 1 ppm to 300 ppm of platinum atoms relative to the (component a) polyorganosiloxane, and (component b3) ligand added so that it contains 1 mol to 40 mol per mol of platinum atoms contained in the (component b2) platinum compound. Therefore, the components constituting the silicone rubber compositions (EX1) to (EX14) interact with each other, and the silicone rubber, which is a crosslinked product of the silicone rubber composition, is prevented from decomposing flammable low-molecular-weight siloxanes from the silicone rubber at high temperatures, effectively preventing weight loss of the silicone rubber.

[0090] In contrast, the silicone rubber compositions (C EX1) to (C EX7) differ from the silicone rubber compositions (EX1) to (EX14) in that the weight loss suppression of (component b) is 0.4 g / cm ３) is not added so that the total weight of the silicone rubber composition is less than 100%. In particular, in the silicone rubber compositions (C EX1) to (C EX7), at least one of the components (component b1) of the inorganic filler, (component b2) of the platinum compound, and (component b3) of the ligand does not satisfy the above relationship. Specifically, the silicone rubber composition (C EX1) does not contain the (component b3) ligand. The silicone rubber composition (C EX2) does not contain the (component b2) platinum compound and the (component b3) ligand. The silicone rubber composition (C EX3) does not contain the (component b1) inorganic filler and the (component b2) platinum compound. The silicone rubber composition (C EX4) does not contain the (component b1) inorganic filler. The silicone rubber composition (C EX5) does not contain the (component b1) inorganic filler. The silicone rubber composition (C EX6) does not contain the (component b1) inorganic filler. The silicone rubber composition of (C EX7) does not contain (component b1) an inorganic filler or (component b3) a ligand. Therefore, unlike the compositions of (EX1) to (EX11), the silicone rubbers that are crosslinked from the silicone rubber compositions of (C EX1) to (C EX7) do not inhibit the decomposition of flammable low-molecular-weight siloxanes from the silicone rubber at high temperatures, resulting in a significant reduction in the weight of the silicone rubber.

[0091] <Others> Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0092] According to this embodiment, it is possible to prevent the decomposition of flammable low-molecular-weight siloxane from silicone rubber at high temperatures, and effectively prevent the weight of the silicone rubber from decreasing. Therefore, the present invention can be suitably used in various technical fields where the above effects are required, such as gaskets, cushioning materials, and O-rings.

Claims

1. (Component a) Formula (A1) below (In formula (A1), R １ represents a monovalent unsubstituted or substituted hydrocarbon group that does not contain an aliphatic unsaturated group, R ２ represents an alkenyl group, R ３ are each independent R １ Or R ２ where n and m represent the total number of repeating units randomly polymerized or block polymerized, respectively, and n+m+2, which is the sum of n and m and the number of terminal groups (2), represents the mass average degree of polymerization. ２ The content per mass of the compound is 0.001 mmol / g or more and less than 2.0 mmol / g, and R ２ (Component b) a weight loss inhibitor, and (Component c) an organic peroxide crosslinking agent, wherein the silicone rubber crosslinked with the silicone rubber composition has a weight loss of 0.4 g / cm when heated from 30°C to 900°C at a temperature increase rate of 150°C / min in a nitrogen atmosphere. ３ The silicone rubber composition according to claim 1, 2. The silicone rubber composition according to claim 1, wherein the (component b) weight loss inhibitor comprises: (component b1) an inorganic filler; (component b2) a platinum compound; and (component b3) a ligand, and the (component b3) ligand is capable of coordinating with a platinum atom constituting the (component b2) platinum compound.

3. The silicone rubber composition according to claim 2, wherein the ligand (component b3) is a phosphite or a nitrogen-containing aryl compound.

4. (Component b1) Inorganic filler is crystalline silica, Fe ３ O ４ Or TiO ２ The silicone rubber composition according to claim 2 , wherein 5. The silicone rubber composition according to claim 2, wherein the content of the inorganic filler (component b1) is 0.1 to 200 parts by mass per 100 parts by mass of the polyorganosiloxane (component a).

6. The silicone rubber composition according to claim 2, wherein the platinum compound (component b2) contains 1 ppm or more and 300 ppm or less of platinum atoms relative to the polyorganosiloxane (component a).

7. The silicone rubber composition according to claim 3, wherein the amount of the ligand (component b3) is from 1 mol to 40 mol per 1 mol of platinum atoms of the platinum compound (component b2).

8. (Component d) reinforcing silica is further included, and (Component d) reinforcing silica has a BET specific surface area of ​​50 m ２ / g or more 350m ２ 2. The silicone rubber composition according to claim 1, wherein the polyorganosiloxane content is 1 part by mass or more and 100 parts by mass or less per 100 parts by weight of the polyorganosiloxane (component a).

9. A silicone rubber obtained by crosslinking the silicone rubber composition according to any one of claims 1 to 8.

10. The silicone rubber composition according to claim 1, further comprising (component e) a foaming agent.

11. A silicone rubber foam obtained by crosslinking and foaming the silicone rubber composition according to claim 10.

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