JP2013173879A - Silicone rubber composition, method of manufacturing the same, and silicone rubber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain: a silicone rubber composition that can form a silicone rubber in which workability of rubber formation is improved, and that is excellent in extensibility on an assumption that reduction of cracking of a main chain of a silicone rubber, reduction of yellowing, prolongment of a life cycle, and reduction of foaming at vulcanization are attempted; and a silicone rubber to cure the same.SOLUTION: A silicone rubber composition includes at least: two kinds of terminal silanol modified polyorganosiloxanes with different weight average molecular weights (Mw); an alkoxysilane; a curable catalyst consisting of an aluminum alkoxide or a curable catalyst consisting of a mixture of an aluminum alkoxide and a hydroxy acid ester, and a method of manufacturing the same and a silicone rubber are disclosed.

Description

  The present invention relates to a silicone rubber composition, a method for producing the same, and a silicone rubber obtained by curing the silicone rubber composition.

  Silicone rubbers that are vulcanized by heating are roughly classified into the following two types. One is to cure by radical reaction using an organic peroxide as a vulcanizing agent (see, for example, Patent Document 1). The other is a method in which a platinum compound is used as a catalyst and cured by an addition reaction thereof (see, for example, Patent Document 2).

JP 2004-161930 A JP 2006-182911 A

  However, a silicone rubber cured with an organic peroxide as a vulcanizing agent generates a product due to decomposition of the organic peroxide, and this product may cause cracking of the main chain of the silicone rubber. There is also a problem of yellowing due to coloring during heat vulcanization. In the case of curing using a platinum compound as a catalyst, a silicone rubber is formed by addition reaction of a vinyl group-containing silicone raw rubber with hydrogen organosiloxane as a crosslinking agent. However, there is a problem that the life cycle is short and long-term storage is not possible. There is also a problem of foaming during vulcanization. On the other hand, in common with both types, there are a problem that workability is inferior because of the two-component type, and a problem that the degree of expansion as rubber is small.

  The present invention has been made in view of the above problems, and is based on the premise of reducing cracking of the main chain of silicone rubber, reducing yellowing, extending the life cycle and reducing firing during vulcanization. An object of the present invention is to obtain a silicone rubber composition capable of improving the workability of rubber formation and forming a silicone rubber excellent in extensibility and a silicone rubber obtained by curing it.

  In order to achieve the above object, the present inventors do not use an organic peroxide-based or platinum-based catalyst conventionally used as a catalyst, use a novel curable catalyst, and further use a one-component type. The form of silicone rubber composition was adopted. In order to improve extensibility, two types of polyorganosiloxanes having different weight average molecular weights (Mw) were used as polyorganosiloxanes as the main component of the silicone rubber composition. Specifically, it is as follows.

  A silicone rubber composition according to an aspect of the present invention is a curable catalyst comprising two types of terminal silanol-modified polyorganosiloxanes having different weight average molecular weights (Mw), alkoxysilanes, and aluminum alkoxides, or aluminum alkoxides and hydroxy acid esters. And a curable catalyst comprising a mixture of the following.

  In the silicone rubber composition according to another embodiment of the present invention, the ratio of the weight average molecular weight of the two types of terminal silanol-modified polyorganosiloxanes is 8 or more.

  The silicone rubber composition according to another aspect of the present invention further uses a hydroxy acid ester as a malic acid ester.

  In the silicone rubber composition according to another aspect of the present invention, the alkoxysilane is methyltrimethoxysilane or phenyltrimethoxysilane.

  In the silicone rubber composition according to another embodiment of the present invention, the terminal silanol-modified polyorganosiloxane is further changed to both terminal silanol-modified polydimethylsiloxane.

  The silicone rubber composition according to another embodiment of the present invention further includes a filler.

  A method for producing a silicone rubber composition according to an embodiment of the present invention includes a curable catalyst or aluminum alkoxide comprising two types of terminal silanol-modified polyorganosiloxanes having different weight average molecular weights (Mw), alkoxysilane, and aluminum alkoxide. A mixing step of mixing at least a curable catalyst comprising a mixture of hydroxy acid esters, a polymerizing step of heating the mixture obtained by the mixing step to polymerize the polyorganosiloxane, and after the polymerizing step A depressurizing step of depressurizing.

  In the method for producing a silicone rubber composition according to another embodiment of the present invention, the mixing step further comprises one of the two types of terminal silanol-modified polyorganosiloxane, one terminal silanol-modified polyorganosiloxane, alkoxysilane, and a curable catalyst. And mixing at least one terminal silanol-modified polyorganosiloxane other than one terminal silanol-modified polyorganosiloxane in the mixture obtained through the first mixing step. The second mixing step is performed during the polymerizing step.

  In the method for producing a silicone rubber composition according to another aspect of the present invention, the ratio of the weight average molecular weights of the two types of terminal silanol-modified polyorganosiloxane is 8 or more.

  In the method for producing a silicone rubber composition according to another aspect of the present invention, the hydroxy acid ester is further converted to malic acid ester.

  In the method for producing a silicone rubber composition according to another aspect of the present invention, the alkoxysilane is methyltrimethoxysilane or phenyltrimethoxysilane.

  In the method for producing a silicone rubber composition according to another aspect of the present invention, the terminal silanol-modified polyorganosiloxane is further changed to both terminal silanol-modified polydimethylsiloxane.

  The silicone rubber according to an embodiment of the present invention is obtained by curing any of the above silicone rubber compositions.

  According to the present invention, on the premise of reducing the cracking of the main chain of silicone rubber, reducing yellowing, extending the life cycle and reducing firing during vulcanization, the workability of rubber formation is improved, Silicone rubber having excellent extensibility can be obtained.

FIG. 1 shows a flow of a manufacturing method by an exemplary simultaneous mixing method of a silicone rubber composition according to an embodiment of the present invention. FIG. 2 shows a flow of a manufacturing method by an exemplary two-stage mixing method of the silicone rubber composition according to the embodiment of the present invention. FIG. 3 shows the elongation at break of the silicone rubber produced in Examples 1-9. FIG. 4 shows the strength at break of the silicone rubber produced in Examples 1-9. FIG. 5 shows the elongation at break of the silicone rubber produced in Examples 10-12. FIG. 6 shows the strength at break of the silicone rubber produced in Examples 10-12. FIG. 7 shows that the silicone rubber prepared in Example 13 (Adjustment Method A), the silicone rubber prepared in Example 1 (Adjustment Method B), and PDMS (Mw = 3000) are 2 mol, and PDMS (Mw = 26000). The elongation at break of a silicone rubber (adjustment method C) prepared by mixing 1 mol of MTMS and 0.1 mol of catalyst A at the same time with the other conditions being the same as in Example 1 is shown. FIG. 8 shows the strength at break of the three types of silicone rubber shown in FIG. FIG. 9 shows the gel fraction of the silicone rubber produced in Example 13 (two-stage adjustment) compared with that of Example 1 (simultaneous adjustment). FIG. 10 shows the hot water resistance of the silicone rubber prepared in Example 13 (two-stage adjustment) compared with that of Example 1 (simultaneous adjustment). FIG. 11 shows the elongation at break of each silicone rubber produced in Examples 16-21. FIG. 12 shows the breaking strength of each silicone rubber produced in Examples 16-21. FIG. 13 shows the elongation at break of each silicone rubber produced in Examples 22-25. FIG. 14 shows the strength at break of each silicone rubber produced in Examples 22-25. FIG. 15 shows the elongation at break of each silicone rubber produced in Example 13 of Experiment 3 and Examples 26 to 28 of Experiment 7. FIG. 16 shows the breaking strength of each silicone rubber produced in Example 13 of Experiment 3 and Examples 26 to 28 of Experiment 7. FIG. 17 shows the gel fraction of each silicone rubber produced in Example 13 and Examples 26 to 28 in comparison. FIG. 18 shows the elongation at break of each silicone rubber produced in Examples 29-32. FIG. 19 shows the strength at break of each silicone rubber produced in Examples 29-32. FIG. 20 shows the elongation at break of each silicone rubber produced in Example 32 of Experiment 8 and Examples 33 to 35 of Experiment 9. FIG. 21 shows the breaking strength of each silicone rubber produced in Example 32 of Experiment 8 and Examples 33 to 35 of Experiment 9. FIG. 22 shows the elongation at break of each silicone rubber produced in Examples 36-38. FIG. 23 shows the strength at break of each silicone rubber produced in Examples 36-38. FIG. 24 shows the elongation at break of each silicone rubber produced in Example 37 of Experiment 10 and Examples 39 and 40 of Experiment 11. FIG. 25 shows the breaking strength of each silicone rubber produced in Example 37 of Experiment 10 and Examples 39 and 40 of Experiment 11. FIG. 26 shows the visible light transmittance of the silicone rubber produced in Example 36 and Example 37 in comparison with liquid crystal glass and commercially available silicone rubber (commercially available product).

  Next, each embodiment of the silicone rubber composition according to the present invention, its production method, and silicone rubber will be described.

"1. Silicone rubber composition"
The silicone rubber composition according to this embodiment is
(A) Two types of terminal silanol-modified polyorganosiloxanes having different weight average molecular weights (Mw);
(B) alkoxysilane;
(C) a curable catalyst comprising an aluminum alkoxide or a curable catalyst comprising a mixture of an aluminum alkoxide and a hydroxy acid ester;
At least.

  Moreover, the silicone rubber composition according to this embodiment preferably includes (D) a filler.

(A) Terminal silanol-modified polyorganosiloxane The both-end silanol-modified polyorganosiloxane suitably used in this embodiment is represented by the following general formula (1). However, the polyorganosiloxane which not only silanol-modified both ends but also silanol-modified only one end may be used. In formula (1), R ¹ and R ² are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 4 to 10 carbon atoms, or an aryl or aryl having 6 to 10 carbon atoms. It is a substituted hydrocarbon group. Examples of the linear or branched alkyl group having 1 to 20 carbon atoms include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, pentyl, neopentyl, and hexyl. , Heptyl, octyl, nonyl, decyl, undecyl, dodecyl, and the like can be given as preferred examples. Moreover, as a C4-C10 cycloalkyl group, each functional group, such as cyclopentyl and cyclohexyl, can be mentioned as a suitable example. Furthermore, as a C6-C10 aryl group or aryl substituted hydrocarbon group, each functional group, such as phenyl, toluyl, xylyl, ethylphenyl, benzyl, phenethyl, can be mentioned as a suitable example. A particularly preferred terminal silanol-modified polyorganosiloxane is a both-end silanol-modified polydimethylsiloxane.

  The viscosity at 23 ° C. of the terminal silanol-modified polyorganosiloxane is 10 to 100,000 mPa · s, preferably 20 to 50,000 mPa · s, and more preferably 30 to 10,000 mPa · s. The terminal silanol-modified polyorganosiloxane is preferably a both-end silanol-modified polydimethylsiloxane.

  The terminal silanol-modified polyorganosiloxane (hereinafter simply referred to as “polyorganosiloxane”) is used by mixing two types having different weight average molecular weights (Mw). Mw is preferably selected from two types in the range of 300 to 1,000,000. Furthermore, the ratio of the two types of Mw (referred to as Mw1 and Mw2) is at least Mw2 / Mw1 = 6 or more, further 8 or more, and more preferably in the range of 8 to 26 in order to increase the elongation at break of the cured product It is preferable to do this.

  As specific Mw values, when a polyorganosiloxane having Mw1 = 1000 is used, the other polyorganosiloxane used by mixing with it is Mw2 = 6000 or more, and further Mw2 = 8000 or more. It is preferable to use an organosiloxane. When a polyorganosiloxane having Mw1 = 3000 is used, it is preferable to use a polyorganosiloxane having Mw2 = 18000 or more, more preferably Mw2 = 24000 or more, as another polyorganosiloxane used by mixing with it. In order to increase both the elongation at break and the strength at break, it is preferable to use a mixture of two types of polyorganosiloxanes of Mw1 = 2000 to 4000 and Mw2 = 16000 to 32000.

(B) Alkoxysilane Tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane; methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxy Silane, ethyltriethoxysilane, ethyltripropoxysilane, methyltributoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-propyltripropoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, n- Butyltrimethoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, hexyltrimethoxysilane, Xyltriethoxysilane, hexyltripropoxysilane, octyltrimethoxysilane, octyltriethoxysilane, octyltripropoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, hexadecyltri Methoxysilane, hexadecyltriethoxysilane, octadecyltrimethoxysilane, octadecyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, benzyltrimethoxysilane, benzyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3 -Glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltri Trialkoxysilanes such as toxisilane, 3-mercaptopropyltriethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3-aminopropyltrimethoxysilane; dimethyldimethoxysilane, Examples thereof include dialkoxysilanes such as dimethyldiethoxysilane, dimethyldipropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldipropoxysilane, diphenyldimethoxysilane, and diphenyldiethoxysilane.

  Among the alkoxysilanes exemplified above, tetraalkoxysilanes and trialkoxysilanes are preferable for increasing the elongation at break when cured, and tetramethoxysilane, methyltrimethoxysilane, and phenyltrimethoxysilane. 3-glycidoxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane are more preferable, and tetramethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane and 3-aminopropyltrimethoxysilane are more preferable. Also, trialkoxysilanes are preferable for increasing the strength at break when cured, and methyltrimethoxysilane and phenyltrimethoxysilane are more preferable.

  The amount of alkoxysilane added is preferably in the range of 0.6 to 1.5 mol, more preferably in the range of 0.8 to 1.2 mol, particularly preferably 1.0 mol, per mol of polyorganosiloxane. To do.

(C) Curable catalyst It is preferable to use only the aluminum alkoxide or a mixture of aluminum alkoxide and hydroxy acid ester as the curable catalyst. Preferable examples of the aluminum alkoxide include aluminum isopropoxide, aluminum-sec-butoxide, and aluminum ethoxide.

  Hydroxy acid esters include methyl formate, ethyl formate, methyl acetate, ethyl acetate, vinyl acetate, propyl acetate, octyl acetate, cyclohexyl acetate, ethyl propionate, methyl acetate, ethyl valerate, ethyl caproate, ethyl chloroacetate, dichloro Aliphatic monocarboxylic esters such as ethyl acetate, ethyl hydroxyacetate, ethyl acrylate, methyl methacrylate, ethyl crotonic acid; diethyl oxalate, dibutyl malonate, dimethyl succinate, diethyl glutarate, diethyl malate, diethyl tartrate, Aliphatic polycarboxylic acid polyesters such as triethyl citrate, ethyl lactate, diethyl chlorosuccinate, diethyl maleate and dimethyl fumarate; alicyclic carboxylic acid esters such as ethyl cyclohexanecarboxylate; ethyl benzoate , Aromatic carboxylic acid esters such as benzine benzoate, methyl toluate, methyl anisate and dimethyl phthalate; lactones such as γ-butyrolactone, δ-valerolactone, coumarin and phthalide; sulfonate esters such as methyl benzenesulfonate Preferred examples include inorganic acid esters such as dimethyl sulfate, ethyl nitrate, triethyl phosphate, and diethyl carbonate.

  In order to increase the elongation at break when the silicone rubber composition is cured, it is more preferable to add aluminum alkoxide alone or a mixture of aluminum alkoxide and diethyl malate. In order to increase the strength at break, it is preferable to add a mixture of an aluminum alkoxide and a hydroxy acid ester as compared with aluminum alkoxide alone.

  The curable catalyst is preferably added in an amount of less than 0.2 mol per mol of the polyorganosiloxane, particularly preferably less than 0.1 mol, and more preferably in the range of 0.05 to 0.1 mol. It is more preferable to add at.

(D) Filler The silicone rubber composition according to this embodiment may contain an inorganic or organic filler. Inorganic fillers include silica (silicon dioxide), calcium carbonate, magnesium carbonate, barium sulfate, magnesium sulfate, aluminum silicate, zirconium silicate, iron oxide, titanium oxide, aluminum oxide, zinc oxide, potassium titanate, kaolin, talc, glass Examples thereof include beads, sericite activated clay, bentonite, aluminum nitride, and silicon nitride. Examples of the organic filler include polymethyl methacrylate, polyester fine particles, polyurethane fine particles, and the like. Among them, silica that can easily obtain finer particulate fillers is preferable in ensuring the transparency of the silicone rubber.

  In terms of increasing the elongation at break when the silicone rubber composition is cured, the amount of the filler is preferably 3% by mass or more based on the total mass of the silicone rubber composition including the filler. Henceforth, the meaning of the mass% of a filler is the same meaning. Further, the amount of the filler is preferably 3 to 10% by mass, particularly 3 to 8% by mass for increasing the strength at break.

  The filler may have any shape such as a plate shape, a particle shape, or a fiber shape. In order to increase the elongation at break and the strength at break when the silicone rubber composition is cured, the size of the filler is preferably 5 nm or more in diameter in terms of a sphere, and particularly preferably 50 nm or more. .

“2. Manufacturing method of silicone rubber composition”
FIG. 1 shows a flow of a manufacturing method by an exemplary simultaneous mixing method of the silicone rubber composition according to this embodiment.

  First, two types of polyorganosiloxanes Mw1 and Mw2 having different Mw, alkoxysilane, and a curable catalyst are mixed (step 1: mixing step). In step 1, a filler can also be mixed. Moreover, it is preferable to dilute and mix a curable catalyst in 0.5-20 mass% with respect to the total amount of a curable catalyst and an organic solvent with organic solvents, such as toluene. The organic solvent is preferably one that does not easily evaporate at room temperature. Next, while heating to 40-80 degreeC, it stirs and polymerizes polyorganosiloxane (Step 2: Polymerization process). Next, the pressure is reduced at room temperature (around 25 ° C.) (step 3: pressure reduction step). Through these treatments, the silicone rubber composition is completed. In the polymerizing step of Step 2, stirring may be performed using any stirring means, and may be performed by, for example, ultrasonic dispersion using an ultrasonic cleaner, stirring using a stirring blade or a stirring bar. The stirring speed can be appropriately changed according to the contents, and is preferably set to, for example, 300 to 800 rpm, more preferably 400 to 500 rpm. In addition, the temperature in the polymerization step is particularly preferably in the range of 50 to 70 ° C. This is because the polymerization of the polyorganosiloxane is promoted and the semi-cured state (gel) is set to such an extent that the polymerization is not terminated. The time for heating in the polymerization step can be appropriately changed according to the temperature. For example, when heating at 50 to 70 ° C., it is preferably in the range of 24 to 120 hours. In the decompression step of Step 3, preferably, the solvent in the silicone rubber composition is volatilized by using a vacuum desiccator device at room temperature (around 25 ° C.), and without completely drying, Concentrate in jelly form.

  FIG. 2 shows a flow of a manufacturing method by an exemplary two-stage mixing method of the silicone rubber composition according to this embodiment.

  First, one polyorganosiloxane (Mw1) of two types of polyorganosiloxanes having different Mw, alkoxysilane, and a curable catalyst are mixed (step 11: first mixing step). Next, while heating to 40-80 degreeC and stirring, polyorganosiloxane is polymerized (step 12: Polymerization process). During heating and stirring, a polyorganosiloxane (Mw2) different from the polyorganosiloxane mixed in Step 11 and a curable catalyst are added to the stirring mixture (Step 13: second mixing step). You may mix a filler in a 2nd mixing process. The second mixing step is preferably performed in the early stage of the polymerization step of Step 12, for example, when the total time of the polymerization step is 70 to 80 hours, this step is started for 0.5 to 8 hours. It is preferable to carry out in the range, and more preferably in the range of 1 to 5 hours. The filler may be mixed in the first mixing step, or may be mixed in both the first mixing step and the second mixing step. Further, alkoxysilane can be added not only in the first mixing step but also in the second mixing step. The polyorganosiloxane Mw2 mixed in the second mixing step may have a weight average molecular weight larger or smaller than the polyorganosiloxane Mw1 mixed in the first mixing step. Next, the pressure is reduced at room temperature (around 25 ° C.) (step 14: pressure reduction step). Through these treatments, the silicone rubber composition is completed. The polymerizing step in step 12 and the depressurizing step in step 14 can be performed in the same manner as step 2 and step 3 shown in FIG. 1, respectively.

“3. Silicone rubber”
Silicone rubber is obtained by heating a silicone rubber composition. The heating temperature is 100 to 180 ° C, preferably 110 to 170 ° C, more preferably 140 to 160 ° C. The heating is preferably performed by gradually raising the temperature from room temperature to the above range.

  Next, examples of the present invention will be described.

1. 1. Components of Silicone Rubber Composition 1.1 Polyorganosiloxane As polyorganosiloxane, Mw = 1000 (manufactured by Shin-Etsu Chemical Co., Ltd.), Mw = 3000 (manufactured by Shin-Etsu Chemical Co., Ltd.), Mw = 4200 (Alfa Aesar Co., Ltd.) ), Mw = 18000 (manufactured by Gelest Co., Ltd.), Mw = 26000 (manufactured by Gelest Co., Ltd.), Mw = 49000 (manufactured by Gelest Co., Ltd.), 6 types of silanol-modified polydimethylsiloxanes (hereinafter referred to as “PDMS”) ) Was used.

1.2 Alkoxysilane As alkoxysilane, methyltrimethoxysilane (MTMS) manufactured by Tokyo Chemical Industry Co., Ltd., tetramethoxysilane (TMOS) manufactured by Tokyo Chemical Industry Co., Ltd., phenyltrimethoxysilane manufactured by Tokyo Chemical Industry Co., Ltd. (PhTMS), 5-glycidoxypropyltrimethoxysilane (product name: KBM403) manufactured by Shin-Etsu Chemical Co., Ltd. and 3-aminopropyltrimethoxysilane (product name: KBM903) manufactured by Shin-Etsu Chemical Co., Ltd. Silane was used.

1.3 Curable Catalyst As the curable catalyst (hereinafter simply referred to as “catalyst”), five types of metal alkoxides and four types of hydroxy acid esters were used. Examples of the metal alkoxide include aluminum-s-butoxide (ALsB) manufactured by Wako Pure Chemical Industries, Ltd., aluminum isopropoxide (ALiP) manufactured by Tokyo Chemical Industry Co., Ltd., and aluminum ethoxide (ALE) manufactured by Tokyo Chemical Industry Co., Ltd. Titanium tetraethoxide (TTE) manufactured by Kanto Chemical Co., Ltd. and dibutyltin dilaurate (DBTDL) manufactured by Gelest Co., Ltd. were used. Examples of hydroxy acid esters include diethyl malate (MAdE) manufactured by Tokyo Chemical Industry Co., Ltd., diethyl tartrate (TAdE) manufactured by Tokyo Chemical Industry Co., Ltd., triethyl citrate (CAtE) manufactured by Wako Pure Chemical Industries, Ltd., and Tokyo Chemical Industry. Kogyo Corp. ethyl lactate (LAe) was used.

1.4 Filler Fumed silica manufactured by Nippon Aerosil Co., Ltd. was used as the filler.

1.5 Solvent Toluene was used as the solvent.

2. 2. Evaluation Method 2.1 Mechanical Properties After curing the silicone rubber composition, the cured silicone rubber was used in the form of dumbbell-shaped No. 6 (approximately 4.0 mm in the center in the length direction, 4.0 mm in width, 20 mm in total length, 1.5 mm in thickness). ) To obtain a test piece. Using the tensile strength tester (model number: RTC1250A) manufactured by A & D Co., Ltd., hold both ends of the test piece and pull it to both sides in the length direction of the test piece at a pulling speed of 500 mm / min. The elongation and stress of the test piece at the time of fracture were measured. The elongation at break (unit:%) was obtained by subtracting the length of the original test piece (unit: mm, excluding the distance gripped by the test device) from the length of the test piece at break (unit: mm). The value was expressed as a percentage by dividing by the length of the original test piece (unit: mm, excluding the distance gripped by the test apparatus). The strength at break (unit: MPa) was expressed by dividing the test force at break (unit: N) by the fracture cross-sectional area (width × thickness, unit: mm ² ) of the test piece.

2.2 Gel fraction of test piece The weight ratio of the test piece for mechanical property evaluation before and after being immersed in toluene for 48 hours is shown as a percentage. The smaller the weight after immersion in toluene, the lower the gel fraction (unit:%).

2.3 Hot water resistance A test piece for mechanical property evaluation was immersed in warm water at 120 ° C. for 120 hours, and the weight ratio before and after immersion was shown as a percentage. It means that hot water resistance is so low that the weight after immersion in warm water is small.

2.4 Visible light transmittance (transparency)
Using a spectrophotometer (model number: U4100) manufactured by Hitachi, Ltd., the test piece was irradiated with visible light having a wavelength of 780 to 380 nm, and the transmittance (unit:%) was determined from the difference in the amount of light after transmission.

2.5 Composition Evaluation of Silicone Rubber Using an energy dispersive X-ray fluorescence analyzer (model number: EDX-800) manufactured by Shimadzu Corporation, main components constituting the test piece were analyzed.

3. Preparation of catalyst In an organic synthesizer (model number: CP-160, manufactured by Shibata Kagaku Co., Ltd.), a temperature of 1 mol of ALsB and 1 mol of MAdE can be kept constant under a nitrogen atmosphere. The mixture was stirred and mixed for 72 hours at 25 ° C. and a rotational speed of 550 rpm, and then diluted to 2 wt% (ALsB + MAdE = 2 wt%, toluene = 98 wt%) with toluene. This is referred to as catalyst A. In the same procedure, 1 mol of ALsB and 1 mol of TAdE were mixed and diluted with toluene. This is referred to as catalyst B. In the same procedure, 1 mol ALsB and 1 mol CAtE were mixed and diluted with toluene. This is referred to as catalyst C. In the same procedure, 1 mol of ALsB and 1 mol of LAe were mixed and diluted with toluene. This is designated as Catalyst D. Only 1 mol of ALsB was diluted to 2 wt% (ALsB = 2 wt%, toluene = 98 wt%) with toluene at a temperature of 25 ° C. in a nitrogen atmosphere. This is designated as Catalyst E. 1 mol of ALiP and 1 mol of MAdE were mixed in the same procedure as in Catalyst A and diluted with toluene. This is referred to as catalyst F. In the same procedure, 1 mol of ALE and 1 mol of MAdE were mixed and diluted with toluene. This is referred to as catalyst G. In the same procedure, 1 mol of TTE and 1 mol of MAdE were mixed and diluted with toluene. This is referred to as catalyst H. In the same procedure as for catalyst E, only 1 mol of DBTDL was diluted to 2 wt% with toluene (DBTDL = 2 wt%, toluene = 98 wt%). This is designated as Catalyst I.

4). Experiment 1 (Simultaneous mixing of two types of PDMS with different Mw / Examination of catalyst type)
4.1 Various Preparation Conditions for Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 1 to 9>
In an atmosphere in which nitrogen is flowed in a glove box (manufactured by As One Co., Ltd., model number: Galaxy), 1 mol of PDMS (Mw = 3000), 1 mol of PDMS (Mw = 26000), 1 mol of MTMS, 0 .1 mol of catalyst A and 3 wt% of filler having an average particle diameter of 50 nm (product name: NAX50) with respect to the total mass of the silicone rubber composition including the filler are put in a container and the organic synthesis apparatus described above at 60 ° C. For 72 hours. In addition, the meaning of the content rate (wt%) of a filler is the same meaning also in a subsequent example. Next, mixing was stopped and the pressure in the silicone rubber composition was removed by reducing the pressure at room temperature (around 25 ° C.) using a vacuum desiccator. By this series of operations, a silicone rubber composition was completed. Next, the silicone rubber composition is transferred to a thin container, and held at 60 ° C. for 12 hours using a dry oven (manufactured by ASONE, model number: DOV-300), followed by holding at 120 ° C. for 6 hours. Then, it hold | maintained at 150 degreeC for 6 hours, and produced the sheet-shaped silicone rubber (Example 1).

  A sheet-shaped silicone rubber was prepared in the same procedure as in Example 1 except that Catalyst A was changed to Catalyst B (Example 2). A sheet-shaped silicone rubber was prepared in the same procedure as in Example 1 except that the catalyst A was changed to the catalyst C (Example 3). A sheet-shaped silicone rubber was produced in the same procedure as in Example 1 except that Catalyst A was changed to Catalyst D (Example 4). A sheet-shaped silicone rubber was produced in the same procedure as in Example 1 except that Catalyst A was changed to Catalyst E (Example 5). A sheet-shaped silicone rubber was prepared in the same procedure as in Example 1 except that the catalyst A was changed to the catalyst F (Example 6). A sheet-shaped silicone rubber was produced in the same procedure as in Example 1 except that the catalyst A was changed to the catalyst G (Example 7). A sheet-shaped silicone rubber was produced in the same procedure as in Example 1 except that the catalyst A was changed to the catalyst H (Example 8). A sheet-shaped silicone rubber was produced in the same procedure as in Example 1 except that Catalyst A was changed to Catalyst I (Example 9).

4.2 Evaluation The silicone rubber compositions prepared in Examples 1 to 7 using the catalysts A to G were sufficiently cured at 150 ° C. and could be evaluated thereafter. On the other hand, the silicone rubber compositions prepared in Examples 8 and 9 using the catalysts H and I are not sufficiently cured at 150 ° C., and are sufficiently cured even after being heated to 200 ° C. and held for 6 hours. The subsequent evaluation was impossible. From this result, it is considered that aluminum alkoxide or a mixture of aluminum alkoxide and hydroxy acid ester is excellent as a catalyst.

  3 and 4 show the elongation at break and the strength at break of the silicone rubber produced in Examples 1 to 9, respectively. However, since Examples 8 and 9 could not be evaluated, they were plotted at zero values on each graph.

  The silicone rubbers of Examples 1 to 7 have a large elongation at break of 400% or more. Among them, Example 1 (using catalyst A), Example 5 (using catalyst E), Example 6 ( The elongation at break of Catalyst F) and Example 7 (Catalyst G) was a very large value exceeding 700%. In terms of elongation at break, it has been found that it is advantageous to use a catalyst made of a single aluminum alkoxide or a catalyst obtained by mixing aluminum alkoxide and MAdE. In addition, the silicone rubber of Example 5 (using catalyst E) exhibits a lower strength at break (about 0.1 MPa) than the others, and the strength at break of other silicone rubbers is 0.25 to 0.6 MPa. Range. Therefore, in order to increase both the elongation at break and the strength at break, it is advantageous to use a catalyst obtained by mixing aluminum alkoxide and MAdE instead of a catalyst of aluminum alkoxide alone. all right.

5. Experiment 2 (Simultaneous mixing of two types of PDMS with different Mw / examination of catalyst amount)
5.1 Preparation Conditions of Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 10 to 12>
Using catalyst A (ALsB + MAdE), the amount of addition was changed to three levels of 0.05, 0.1 and 0.2 mol, and a silicone rubber composition was prepared under the same conditions as in Example 1, (Catalyst A = 0.05 mol: Example 10, Catalyst A = 0.1 mol: Example 11 (same as Example 1), Catalyst A = 0.2 mol: Example 12).

5.2 Evaluation FIGS. 5 and 6 show the elongation at break and strength at break of the silicone rubbers produced in Examples 10-12, respectively.

  A silicone rubber having an elongation at break of 600% or more was obtained with any amount of catalyst, and in particular, the elongation at break of the silicone rubber increased when the catalyst A was 0.05 and 0.1 mol. . However, the strength at break did not show a large difference regardless of the amount of catalyst A added.

6). Experiment 3 (Examination of stepwise mixing of two types of PDMS with different Mw)
6.1 Various Preparation Conditions for Silicone Rubber Composition and Silicone Rubber Cured with It <Example 13>
1 gm PDMS (Mw = 3000), 1 mol MTMS, and 0.1 mol catalyst A are put in a container in an atmosphere in which nitrogen is flowed in a glove box (manufactured by ASONE Co., Ltd., model number: Galaxy). Using the above-described organic synthesizer, mixing was performed at 60 ° C. for 3 hours (first stage). Next, 1 mol of PDMS (Mw = 26000), 0.1 mol of catalyst A, and 3 wt% filler with an average particle diameter of 50 nm (product name: NAX50) were added to the vessel, and 72 ° C. at 72 ° C. Time mixing was performed (second stage). Next, mixing was stopped, pressure reduction under the same conditions as in Experiment 1 was performed, and a silicone rubber composition was produced. Subsequent curing conditions were the same as in Experiment 1, and a sheet-shaped silicone rubber was produced (Example 13).

6.2 Evaluation FIGS. 7 and 8 show the elongation at break and the strength at break of the silicone rubber prepared in Example 13 (Adjustment Method A), respectively. As a comparison, the value of the silicone rubber (adjustment method B) produced in Example 1 of the simultaneous mixing method is also shown. In addition, PDMS (Mw = 3000) was 2 mol, PDMS (Mw = 26000) was not added, 1 mol of MTMS and 0.1 mol of catalyst A were simultaneously mixed, and other conditions were the same as in Example 1. The silicone rubber produced as (adjustment method C) was subjected to comparison with Example 13 and Example 1 (Comparative Example 1).

  As shown in FIGS. 7 and 8, it was found that in Example 13 in which two types of PDMS having different Mw in two stages were mixed, both the elongation at break and the strength at break of the silicone rubber were extremely large. In Example 1 in which two types of PDMS having different Mw were mixed at the same time, both the elongation at break and the strength at break were lower than in Example 13, but in Comparative Example 1 prepared from one type of Mw PDMS. In comparison, the elongation at break was much higher.

  FIG. 9 and FIG. 10 show the gel fraction and hot water resistance of the silicone rubber (two-stage adjustment) prepared in Example 13 in comparison with those of Example 1 (simultaneous adjustment), respectively.

  As shown in FIG. 9, the silicone rubber produced by the two-stage mixing method has a larger residual weight in toluene than that produced by the simultaneous mixing method. On the other hand, in the hot water resistance, as shown in FIG. 10, there was no significant difference between the silicone rubber produced by the two-stage method and the silicone rubber produced by the simultaneous mixing method.

7). Experiment 4 (Stepwise mixing of two types of PDMS with different Mw / comparison with commercial products)
7.1 Preparation Conditions for Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 14 and 15>
A silicone rubber composition was produced under the same conditions as in Experiment 3 except that no filler was added, and a sheet-shaped silicone rubber was produced (Example 14). A silicone rubber composition was prepared under the same conditions as in Example 14 except that the PDMS mixed in the first stage was changed to that of Mw = 1000, and a sheet-shaped silicone rubber was prepared (Example 15).

7.2 Evaluation Table 1 shows the fluorescent X-ray analysis results and elongation at break of the silicone rubber produced in Example 14 and Example 15. For comparison, a commercially available silicone rubber (manufactured by Tomita Matex Co., Ltd., product number: TSCE4000) was also subjected to the same evaluation.

As shown in Table 1, the silicone rubber produced under any of the conditions of Examples 14 and 15 had a higher elongation at break than commercially available products. Also, the silicone rubber (Example 15) prepared by mixing both types of PDMS with Mw = 1000 and 26000 is compared with the silicone rubber (Example 14) prepared by mixing both types of PDMS with Mw = 3000 and 26000. The elongation at break was about 1.5 times larger. However, even when the compositions of Si, O, Al, and CH ₃ were compared by fluorescent X-ray analysis, no relationship with the elongation at break was observed.

8). Experiment 5 (Stepwise mixing of two types of PDMS with different Mw / Mw study)
8.1 Preparation Conditions for Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 16 to 21>
Table 2 shows combinations of PDMS Mw mixed in the first stage and PDMS Mw mixed in the second stage.

  1 mol of PDMS (Mw = 1000) was used as the PDMS to be mixed in the first stage, and 1 mol of PDMS (Mw = 26000) was used as the PDMS to be mixed in the second stage, and the other conditions were the same as in Experiment 3. A silicone rubber composition was produced to produce a sheet-shaped silicone rubber (Example 16: Sample A). A silicone rubber composition was prepared under the same conditions as in Example 16 except that 1 mol of PDMS (Mw = 3000) was used as the PDMS to be mixed in the first stage, thereby producing a sheet-shaped silicone rubber (Example 17: Sample B). A silicone rubber composition was prepared under the same conditions as in Example 16 except that 1 mol of PDMS (Mw = 4200) was used as the PDMS to be mixed in the first stage, thereby preparing a sheet-shaped silicone rubber (Example 18: Sample C). A silicone rubber composition was prepared under the same conditions as in Example 16 except that PDMS mixed in the first stage and PDMS mixed in the second stage were reversed from Example 17, and a sheet-shaped silicone rubber was prepared ( Example 19: Sample D). Silicone rubber under the same conditions as in Example 16 except that 1 mol of PDMS (Mw = 3000) was used as the PDMS mixed in the first stage and 1 mol of PDMS (Mw = 18000) was used as the PDMS mixed in the second stage. A composition was prepared to produce a sheet-shaped silicone rubber (Example 20: Sample E). A silicone rubber composition was prepared under the same conditions as in Example 16 except that 1 mol of PDMS (Mw = 49000) was used as the PDMS to be mixed in the second stage, thereby preparing a sheet-shaped silicone rubber (Example 21: Sample F).

8.2 Evaluation FIGS. 11 and 12 show the elongation at break and strength at break of the silicone rubbers produced in Examples 16 to 21, respectively.

  When samples A, B, and C were compared, it was found that the elongation at break became smaller as the Mw of the first stage PDMS increased. It was found that even when the Mw of the first stage PDMS was made larger than the Mw of the second stage PDMS as in Sample D, the elongation at break increased. From this, it is considered that a large difference in Mw between the first-stage PDMS and the second-stage PDMS has a deep relationship with increasing the elongation at break. Comparing the ratio of Mw of PDMS of the first stage and Mw of PDMS of the second stage and the elongation at break, sample A (ratio: 26), samples B and D (ratio: 8) having a relatively high Mw ratio .7) and Sample F (ratio: 16.3) had a high elongation at break of 800% or more.

  Regarding the strength at break, no correlation was found for the difference between the Mw of the first stage PDMS and the Mw of the second stage PDMS. From the viewpoint of increasing both the elongation at break and the strength at break, Sample B or Sample F is considered preferable.

9. Experiment 6 (staged mixing of two types of PDMS with different Mw / examination of the amount of PDMS in the second stage)
9.1 Preparation Conditions of Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 22 to 25>
PDMS mixed in the second stage was 0.5 mol, and the other conditions were the same as in Experiment 3, and a silicone rubber composition was produced to produce a sheet-shaped silicone rubber (Example 22). PDMS mixed in the second stage was changed to 0.75 mol, and other conditions were the same as those in Experiment 3, and a silicone rubber composition was produced to produce a sheet-shaped silicone rubber (Example 23). PDMS mixed in the second stage was 1.0 mol, and other conditions were the same as those in Experiment 3, and a silicone rubber composition was prepared to produce a sheet-shaped silicone rubber (Example 24). PDMS mixed in the second stage was changed to 1.25 mol, and other conditions were the same as those in Experiment 3, and a silicone rubber composition was prepared to produce a sheet-shaped silicone rubber (Example 25).

9.2 Evaluation FIG. 13 and FIG. 14 show the elongation at break and strength at break of each silicone rubber produced in Examples 22 to 25, respectively.

  As shown in FIG. 13, it was found that the elongation at break increases as the amount of PDMS mixed in the second stage increases. Further, as shown in FIG. 14, no correlation was observed between the strength at break and the amount of PDMS mixed in the second stage. From the viewpoint of increasing both the elongation at break and the strength at break, Example 24 (PDMS = 1 mol) is considered preferable.

10. Experiment 7 (Stepwise mixing of two types of PDMS with different Mw / Examination of types of alkoxysilane)
10.1 Production Conditions of Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 26 to 28>
A silicone rubber composition was produced under the same conditions as in Experiment 3 except that MTMS was changed to TMOS, and a sheet-shaped silicone rubber was produced (Example 26). A silicone rubber composition was produced under the same conditions as in Experiment 3 except that MTMS was changed to KBM403, and a sheet-shaped silicone rubber was produced (Example 27). A silicone rubber composition was prepared under the same conditions as in Experiment 3 except that MTMS was changed to KBM903, and a sheet-shaped silicone rubber was produced (Example 28).

10.2 Evaluation FIGS. 15 and 16 show the elongation at break and strength at break of the silicone rubbers produced in Example 13 of Experiment 3 and Examples 26 to 28 of Experiment 7, respectively.

  As shown in FIG. 15, a deep correlation between the type of alkoxysilane and the elongation at break was not recognized, and a silicone rubber having a large elongation at break of 800% or more was obtained. On the other hand, as shown in FIG. 16, a correlation between the type of alkoxysilane and the strength at break was recognized, and it was found that a silicone rubber having a greater strength at break can be obtained by using MTMS.

  In FIG. 17, the gel fraction of each silicone rubber produced in Example 13 and Examples 26-28 is compared and shown.

  As shown in FIG. 17, it was found that the silicone rubber produced using MTMS as the alkoxysilane has the highest gel fraction. From this, it is considered that when MTMS is used, the density of cross-linking points is increased, but when TMOS, KBM403, or KBM903 is used, there is a high possibility that an unreacted portion with PDMS remains.

11. Experiment 8 (gradual mixing of two types of PDMS with different Mw / examination of filler particle size)
11.1 Production Conditions of Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 29 to 32>
Using four types of fumed silica (manufactured by Nippon Aerosil Co., Ltd.) having primary particle sizes of 7 nm, 12 nm, 30 nm, and 50 nm, the relationship between the particle size of the filler and the properties of the silicone rubber was examined. A silicone rubber composition was prepared under the same conditions as in Experiment 3 except that fumed silica having a primary particle diameter of 7 nm was added, to produce a sheet-shaped silicone rubber (Example 29). A silicone rubber composition was prepared under the same conditions as in Example 29 except that fumed silica having a primary particle size of 12 nm was added, and a sheet-shaped silicone rubber was prepared (Example 30). A silicone rubber composition was prepared under the same conditions as in Example 29 except that fumed silica with a primary particle size of 30 nm was added, to produce a sheet-shaped silicone rubber (Example 31). A silicone rubber composition was prepared under the same conditions as in Example 29 except that fumed silica having a primary particle size of 50 nm was added, and a sheet-shaped silicone rubber was prepared (Example 32).

11.2 Evaluation FIGS. 18 and 19 show the elongation at break and strength at break of each silicone rubber produced in Examples 29 to 32, respectively.

  As shown in FIGS. 18 and 19, when the particle size of the filler was increased, both the elongation at break and the strength at break were observed to increase.

12 Experiment 9 (Stage mixing of two types of PDMS with different Mw / examination of filler addition)
12.1 Production Conditions for Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 33 to 35>
Using fumed silica (manufactured by Nippon Aerosil Co., Ltd.) having a primary particle diameter of 50 nm, the relationship between the amount of filler added (0 to 8 wt%) and the properties of silicone rubber was examined. A silicone rubber composition was prepared under the same conditions as in Experiment 3 except that fumed silica having a primary particle size of 50 nm was not added, to produce a sheet-shaped silicone rubber (Example 33). A silicone rubber composition was prepared under the same conditions as in Example 33 except that 5 wt% of fumed silica having a primary particle diameter of 50 nm was added (Example 34). A silicone rubber composition was prepared under the same conditions as in Example 33 except that 8 wt% of fumed silica having a primary particle diameter of 50 nm was added (Example 35).

12.2 Evaluation FIGS. 20 and 21 show the elongation at break and strength at break of each silicone rubber produced in Example 32 of Experiment 8 and Examples 33 to 35 of Experiment 9, respectively.

  As shown in FIG. 20, the elongation at break was greater when the filler was added than when the filler was not added. However, the elongation at break was almost constant when the amount of filler added was 3 wt% or more. On the other hand, as shown in FIG. 21, the strength at break increased as the amount of filler added increased.

13. Experiment 10 (Stepwise mixing of two types of PDMS with different Mw / No filler added / Mw of PDMS in the first step)
13.1 Production Conditions for Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 36 to 38>
A silicone rubber composition was prepared under the same conditions as in Experiment 3 except that PDMS mixed in the first stage was used without adding a filler and Mw = 1000, and a sheet-shaped silicone rubber was prepared (Example 36). ). A silicone rubber composition was prepared under the same conditions as in Example 36 except that PDMS mixed at the first stage was Mw = 3000, and a sheet-shaped silicone rubber was prepared (Example 37). A silicone rubber composition was prepared under the same conditions as in Example 36 except that PDMS mixed at the first stage was Mw = 4200, and a sheet-shaped silicone rubber was prepared (Example 38).

13.2 Evaluation FIGS. 22 and 23 show the elongation at break and strength at break of the silicone rubbers produced in Examples 36 to 38, respectively.

  As shown in FIG. 22, it is recognized that the elongation at break tends to increase as the Mw of PDMS mixed in the first stage is small and the difference from the Mw (= 26000) of PDMS mixed in the second stage is large. It was. On the other hand, as shown in FIG. 23, the strength at break became substantially constant regardless of the Mw of PDMS mixed in the first stage.

14 Experiment 11 (Stepwise mixing of two types of PDMS with different Mw / No filler added / Examination of types of alkoxysilane)
14.1 Preparation Conditions of Silicone Rubber Composition and Silicone Rubber Cured with It <Examples 39 and 40>
The PDMS mixed in the first stage was Mw = 3000. A silicone rubber composition was prepared under the same conditions as in Example 37 except that the alkoxysilane was changed from MTMS to PhTMS (Example 39). A silicone rubber composition was produced under the same conditions as in Example 39 except that KBM403 was used as the alkoxysilane, and a sheet-shaped silicone rubber was produced (Example 40).

14.2 Evaluation FIGS. 24 and 25 show the elongation at break and strength at break of the silicone rubbers produced in Example 37 of Experiment 10 and Examples 39 and 40 of Experiment 11, respectively.

  As shown in FIG. 24, it was found that the silicone rubber produced using PhTMS or KBM403 as the alkoxysilane has a higher elongation at break than that using MTMS. Moreover, as shown in FIG. 25, it turned out that the silicone rubber produced using PhTMS as an alkoxysilane has a big breaking point strength compared with what was produced using the other alkoxysilane. In order to increase both the elongation at break and the strength at break, it is considered advantageous to use PhTMS as an alkoxysilane.

  Table 3 summarizes the mechanical properties and visible light transmittance of the silicone rubbers produced in Examples 36-40. FIG. 26 shows the visible light transmittance of the silicone rubber produced in Example 36 and Example 37 in comparison with liquid crystal glass and the aforementioned commercially available silicone rubber (commercial product).

  As shown in Table 3, it was found that a silicone rubber having a higher visible light transmittance can be obtained by using MTMS as the alkoxysilane. In particular, it was found that a silicone rubber having a higher visible light transmittance can be obtained when PDW mixed at the first stage uses Mw = 1000 or 3000 than when Mw = 4200 is used. As is clear from FIG. 26, the silicone rubber produced in Example 36 and Example 37 is so transparent that it exhibits a visible light transmittance equivalent to that of liquid crystal glass, and is more visible than commercially available products. The transmittance was high.

  The present invention can be used for a silicone rubber material, an adhesive using the material, a sealant, a paint, and the like.

Claims (13)

Two types of terminal silanol-modified polyorganosiloxanes having different weight average molecular weights (Mw);
Alkoxysilane,
A curable catalyst comprising an aluminum alkoxide or a curable catalyst comprising a mixture of aluminum alkoxide and a hydroxy acid ester;
A silicone rubber composition comprising at least   2. The silicone rubber composition according to claim 1, wherein the two types of terminal silanol-modified polyorganosiloxanes have a weight average molecular weight ratio of 8 or more.   The silicone rubber composition according to claim 1, wherein the hydroxy acid ester is a malic acid ester.   The silicone rubber composition according to any one of claims 1 to 3, wherein the alkoxysilane is methyltrimethoxysilane or phenyltrimethoxysilane.   The silicone rubber composition according to any one of claims 1 to 4, wherein the terminal silanol-modified polyorganosiloxane is a both-end silanol-modified polydimethylsiloxane.   The silicone rubber composition according to any one of claims 1 to 5, further comprising a filler. Mixing at least two kinds of terminal silanol-modified polyorganosiloxanes having different weight average molecular weights (Mw), alkoxysilane and a curable catalyst made of aluminum alkoxide or a curable catalyst made of a mixture of aluminum alkoxide and hydroxy acid ester Process,
A polymerizing step of heating the mixture obtained by the mixing step to polymerize the polyorganosiloxane;
A decompression step of reducing the pressure after the polymerizing step;
The manufacturing method of the silicone rubber composition containing this. The mixing step includes
A first mixing step of mixing one terminal silanol-modified polyorganosiloxane of the two types of terminal silanol-modified polyorganosiloxane, the alkoxysilane, and the curable catalyst;
Second mixing step of mixing at least one terminal silanol-modified polyorganosiloxane other than the one terminal silanol-modified polyorganosiloxane with the mixture obtained through the first mixing step. When,
Divided into
The method for producing a silicone rubber composition according to claim 7, wherein the second mixing step is performed during the polymerizing step.   The method for producing a silicone rubber composition according to claim 7 or 8, wherein the two types of terminal silanol-modified polyorganosiloxanes have a ratio of weight average molecular weight of 8 or more.   The method for producing a silicone rubber composition according to any one of claims 7 to 9, wherein the hydroxy acid ester is malic acid ester.   The method for producing a silicone rubber composition according to any one of claims 7 to 10, wherein the alkoxysilane is methyltrimethoxysilane or phenyltrimethoxysilane.   The method for producing a silicone rubber composition according to any one of claims 7 to 11, wherein the terminal silanol-modified polyorganosiloxane is a both-end silanol-modified polydimethylsiloxane.   A silicone rubber obtained by curing the silicone rubber composition according to any one of claims 1 to 6.

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