JP7124533B2 - Silicone rubber-based curable composition and structure - Google Patents

Description

The present invention relates to silicone rubber-based curable compositions and structures.

Various studies have so far been made on silicone rubber. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes an addition-curable silicone rubber composition containing organopolysiloxane, silica and a platinum catalyst (claim 1, Table 1, etc. of Patent Document 1).

JP 2017-105930 A

However, upon investigation by the present inventors, it was found that the silicone rubber-based curable composition described in Patent Document 1 has room for improvement in terms of compression set and fluidity during curing.

As a result of further investigation, the present inventors found that by using an organic peroxide as a cross-linking agent for a silicone rubber compound containing two types of organopolysiloxane, silica particles, and a silane coupling agent, In comparison, the inventors found that the compression set is reduced and the fluidity at the time of curing is improved, leading to the completion of the present invention.

According to the invention,
a vinyl group-containing organopolysiloxane (A) containing a low vinyl group-containing linear organopolysiloxane (A1-1) and a high vinyl group-containing linear organopolysiloxane (A1-2);
an organic peroxide (B) having an —O—O— structure in the molecule;
silica particles (C);
a silane coupling agent (D);
A silicone rubber-based curable composition is provided comprising:

Further, according to the present invention, there is provided a structure comprising a cured product of the silicone rubber-based curable composition.

INDUSTRIAL APPLICABILITY According to the present invention, a silicone rubber-based curable composition and a structure having reduced compression set and excellent fluidity during curing are provided.

The silicone rubber-based curable composition of this embodiment will be described.

The silicone rubber-based curable composition of the present embodiment contains a vinyl group containing a low vinyl group-containing linear organopolysiloxane (A1-1) and a high vinyl group-containing linear organopolysiloxane (A1-2). It may contain an organopolysiloxane (A), an organic peroxide (B) having an —O—O— structure in its molecule, silica particles (C), and a silane coupling agent (D).

<<Vinyl group-containing organopolysiloxane (A))>>
The silicone rubber-based curable composition of this embodiment contains a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) is a polymer that is the main component of the silicone rubber-based curable composition of the present embodiment.

The vinyl group-containing organopolysiloxane (A) can contain a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, and the vinyl groups serve as crosslinking points during curing.

The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but for example, it preferably has two or more vinyl groups in the molecule and is 15 mol % or less. , 0.01 to 12 mol %. As a result, the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1) is optimized, and a network can be reliably formed with each component described later.

In the present specification, "-" means including upper and lower limits unless otherwise specified.
In the present specification, the vinyl group content is the mol % of the vinyl group-containing siloxane units when the total units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mol %. However, one vinyl group is considered to be one vinyl group-containing siloxane unit.

Although the degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, it is, for example, preferably in the range of about 1,000 to 10,000, more preferably in the range of about 2,000 to 5,000. The degree of polymerization can be determined, for example, as a polystyrene-equivalent number-average polymerization degree (or number-average molecular weight) in GPC (gel permeation chromatography) using chloroform as a developing solvent.

Although the specific gravity of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, it is preferably in the range of about 0.9 to 1.1.

As the vinyl group-containing linear organopolysiloxane (A1), the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber can be improved by using those having the degree of polymerization and specific gravity within the ranges described above. can be improved.

As the vinyl group-containing linear organopolysiloxane (A1), those having a structure represented by the following formula (1) are particularly preferable.

In formula (1), R ¹ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group of a combination thereof having 1 to 10 carbon atoms. The alkyl group having 1 to 10 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferable. The alkenyl group having 1 to 10 carbon atoms includes, for example, vinyl group, allyl group, butenyl group, etc. Among them, vinyl group is preferred. The aryl group having 1 to 10 carbon atoms includes, for example, a phenyl group.

In formula (1), R ² is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group having 1 to 10 carbon atoms, or a combination thereof. The alkyl group having 1 to 10 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferable. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl groups, allyl groups and butenyl groups. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

In formula (1), R ³ is a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms, an aryl group, or a hydrocarbon group combining these. The alkyl group having 1 to 8 carbon atoms includes, for example, methyl group, ethyl group, propyl group, etc. Among them, methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

Examples of substituents for R ¹ and R ² in formula (1) include methyl group and vinyl group, and examples of substituents for R ³ include methyl group.

In formula (1), a plurality of R ¹ are independent of each other and may be different or the same. Furthermore, the same applies to R ² and R ³ . In formula (1), at least one of multiple R ¹ and R ² is an alkenyl group.

Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), m is an integer of 0 to 2000, and n is 1000 to 10000. is an integer of m is preferably 0-1000 and n is preferably 2000-5000.

Further, specific structures of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) include, for example, those represented by the following formula (1-1).

In formula (1-1), R ¹ and R ² are each independently a methyl group or a vinyl group, and at least one is a vinyl group.

As the vinyl group-containing linear organopolysiloxane (A1), a first vinyl group-containing linear organopolysiloxane having a vinyl group content of 2 or more vinyl groups in the molecule and not more than 0.4 mol %. A chain organopolysiloxane (A1-1) (sometimes referred to as "low-vinyl group-containing linear organopolysiloxane (A1-1)") and a vinyl group content of 0.5 to 15 mol% a second vinyl group-containing linear organopolysiloxane (A1-2) (sometimes referred to as "high vinyl group-containing linear organopolysiloxane (A1-2)") is preferred.

As crude rubber, which is a raw material of silicone rubber, a first vinyl group-containing linear organopolysiloxane (A1-1) having a general vinyl group content and a second vinyl group-containing linear organopolysiloxane having a high vinyl group content were used. By combining with the chain organopolysiloxane (A1-2), the vinyl groups can be unevenly distributed, and the crosslink density can be more effectively formed in the crosslink network of the silicone rubber. As a result, the tear strength of silicone rubber can be increased more effectively.

Specifically, as the vinyl group-containing linear organopolysiloxane (A1), for example, a unit in which R ¹ is a vinyl group and/or a unit in which R ² is a vinyl group in the above formula (1-1) , a first vinyl group-containing linear organopolysiloxane (A1-1) having 2 or more in the molecule and containing 0.4 mol% or less, and a unit in which R ¹ is a vinyl group and / or R It is preferable to use a second vinyl group-containing linear organopolysiloxane (A1-2) containing 0.5 to 15 mol % of units in which ² is a vinyl group.

In addition, the first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of, for example, 0.01 to 0.2 mol%, more preferably 0.02 to 0.15 mol%. is more preferred. The second vinyl group-containing linear organopolysiloxane (A1-2) preferably has a vinyl group content of, for example, 0.5 to 12 mol %, more preferably 0.8 to 8 mol %.

Furthermore, when combining the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2), (A1-1) and (A1-2) is not particularly limited. , more preferably 80:20 to 90:10.

The first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may be used singly or in combination of two or more. good.

Also, the vinyl group-containing organopolysiloxane (A) may contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

<<Organic Peroxide (B)>>
The silicone rubber-based curable composition of this embodiment contains an organic peroxide (B). By using the organic peroxide (B), the fluidity of the silicone rubber-based curable composition during curing can be improved while reducing the compression set of the silicone rubber.

The organic peroxide (B) is a derivative of hydrogen peroxide (H—O—O—H) and has a structure in which one or two hydrogen atoms of hydrogen peroxide are replaced with organic free radicals. and is not particularly limited as long as it is a compound having an —O—O— structure in the molecule. This organic peroxide (B) is easily decomposed by heat or light to generate free radicals.

In the present embodiment, by using the organic peroxide (B) as a cross-linking agent, compared with the case of platinum, it is less susceptible to curing inhibition due to impurities, and a compound containing a nitrogen atom, a phosphorus atom, a sulfur atom, etc. Even in the case of combined use, it is possible to suppress the occurrence of curing inhibition.

The organic peroxide (B) includes ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, peroxyesters and peroxydicarbonates. It can contain one or more selected from the group consisting of Among these, diacyl peroxides or dialkyl peroxides are preferred from the viewpoint of ease of handling, and dialkyl peroxides are preferred from the viewpoint of vinyl group reactivity. These may be used alone or in combination of two or more.

The organic peroxide (B) can contain dialkyl peroxides represented by the following general formula (I) or (II). Dialkyl peroxides represented by the following general formula (I) are preferable from the viewpoint of excellent tear strength over a wide range of hardness.
R ¹ —O—O—R ² General formula (I)
R ¹ —O—O—R ³ —O—O—R ² General formula (II)

In general formula (I) above, R ¹ and R ² , which may be the same or different independently of each other, represent a substituted or unsubstituted alkyl group or cycloalkyl group, a phenyl group, an alkylphenyl group, a cycloalkyl group; , or may be substituted with an alkylcycloalkyl group. Either one of R ¹ and R ² may be a hydrogen atom.

In general formula (II) above, R ¹ to R ³ may be independently the same or different, R ¹ and R ² each represent a substituted or unsubstituted alkyl group or cycloalkyl group, a phenyl group, It may be substituted with an alkylphenyl group, a cycloalkyl group, or an alkylcycloalkyl group, and R ³ represents an alkylene group. Either one of R ¹ and R ² may be a hydrogen atom.

In general formula (I) or (II) above, the alkyl group for R ¹ and R ² is, for example, a straight chain having 1 to 16 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 4 to 8 carbon atoms. Branched or branched alkyl groups can be used. One or more terminal hydrogen atoms of this alkyl group may be substituted with a phenyl group.
In general formula (I) or (II) above, the cycloalkyl group for R ¹ and R ² can be, for example, a cycloalkyl group having 5 to 8 carbon atoms.
In general formula (II) above, the alkylene group for R ³ is, for example, a linear or branched alkylene group having 1 to 16 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 4 to 8 carbon atoms. can be used.

Specific examples of the dialkyl peroxides include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl -2,5-di-(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethyl Cyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl perbenzoate, tert- Butyl peroxy isopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butyl cumyl peroxide, di-t-butyl peroxy-3,3,5-trimethylcyclohexane, t-butyl cumyl peroxide, di-2,5 amyl peroxide , t-butyl hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxine)hexyne-3, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2, 5-dimethyl-2,5-mono(t-butylperoxy)hexane, α,α'-bis(t-butylperoxy-m-isopropyl)benzene and the like.
The lower limit of the content of the organic peroxide (B) is, for example , 0.001 parts by weight or more, preferably 0.005 parts by weight or more, more preferably 0.01 parts by weight or more. Thereby, the minimum strength as a cured product can be ensured. On the other hand, the upper limit of the content of the organic peroxide (B) is the total of 100 parts by weight of the vinyl group-containing organopolysiloxane (A), the silica particles (C) and the silane coupling agent (D). , for example, 10 parts by weight or less, preferably 5 parts by weight or less, more preferably 3 parts by weight or less. Thereby, the influence by a by-product can be suppressed.

<<Silica particles (C)>>
The silicone rubber-based curable composition of the present embodiment contains silica particles (C).

Silica particles (C) are not particularly limited, but for example, fumed silica, pyrogenic silica, precipitated silica and the like are used. These may be used alone or in combination of two or more. The silica particles (C) may contain one or more silica particles surface-treated with a silane coupling agent (D).

The silica particles (C) have a BET specific surface area of, for example, 30 to 500 m ² /g, preferably 50 to 400 m ² /g, more preferably 100 to 400 m ² /g. . Also, the average primary particle size of the silica particles (C) is, for example, preferably 1 to 100 nm, more preferably about 5 to 20 nm.

By using silica particles (C) having a specific surface area and an average particle size within the above ranges, the hardness and mechanical strength of the silicone rubber formed can be improved, particularly the tensile strength can be improved.

<<Silane coupling agent (D)>>
The silicone rubber-based curable composition of this embodiment contains a silane coupling agent (D).
Silane coupling agent (D) can have a hydrolyzable group. The hydrolyzable group is hydrolyzed with water to form a hydroxyl group, and the hydroxyl group undergoes a dehydration condensation reaction with the hydroxyl group on the surface of the silica particle (C), thereby modifying the surface of the silica particle (C).

The silane coupling agent (D) can contain a silane coupling agent having a hydrophobic group. A silane coupling agent having a trimethylsilyl group can be used as the silane coupling agent having a hydrophobic group. As a result, the hydrophobic group is imparted to the surface of the silica particles (C), so that the cohesive force of the silica particles (C) in the silicone rubber-based curable composition and further in the silicone rubber is reduced (hydrogen aggregation due to bonding is reduced), and as a result, it is presumed that the dispersibility of the silica particles in the silicone rubber-based curable composition is improved. This increases the interface between the silica particles and the rubber matrix, increasing the reinforcing effect of the silica particles. Furthermore, it is presumed that the slipperiness of the silica particles in the matrix is improved when the rubber matrix is deformed. The improved dispersibility and slipperiness of the silica particles (C) improve the mechanical strength (for example, tensile strength and tear strength) of the silicone rubber due to the silica particles (C).

Moreover, the silane coupling agent (D) can contain a silane coupling agent having a vinyl group. As a result, vinyl groups are introduced onto the surfaces of the silica particles (C). Therefore, when a network (crosslinked structure) is formed during curing of the silicone rubber-based curable composition, the vinyl groups possessed by the silica particles (C) also participate in the crosslinking reaction. C) will also be incorporated. As a result, it is possible to reduce the hardness and increase the modulus of the formed silicone rubber.

As the silane coupling agent (D), a silane coupling agent having a hydrophobic group and a silane coupling agent having a vinyl group can be used in combination. The silane coupling agent (D) may be used alone or in combination of two or more.

Examples of the silane coupling agent (D) include those represented by the following formula (4).

_Yn -Si-(X) _4-n (4)
In the above formula (4), n represents an integer of 1-3. Y represents a functional group having a hydrophobic group, a hydrophilic group or a vinyl group, and when n is 1 it is a hydrophobic group, and when n is 2 or 3 at least one of It is a hydrophobic group. X represents a hydrolyzable group.

The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group having a combination thereof, and examples thereof include a methyl group, an ethyl group, a propyl group, a phenyl group, and the like. Methyl groups are preferred.

Moreover, the hydrophilic group includes, for example, a hydroxyl group, a sulfonic acid group, a carboxyl group, a carbonyl group, etc. Among them, a hydroxyl group is particularly preferable. The hydrophilic group may be contained as a functional group, but is preferably not contained from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

Further, the hydrolyzable group includes an alkoxy group such as a methoxy group and an ethoxy group, a chloro group, a silazane group, and the like. Among them, a silazane group is preferable because of its high reactivity with the silica particles (C). A compound having a silazane group as a hydrolyzable group has two structures of (Y _n —Si—) in the above formula (4) due to its structural characteristics.

Specific examples of the silane coupling agent (D) represented by the above formula (4) are as follows.
Those having a hydrophobic group as the functional group include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, alkoxysilanes such as n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane; hexamethyldisilazane. is mentioned. Among these, a silane coupling agent having a trimethylsilyl group containing one or more selected from the group consisting of hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, and trimethylethoxysilane is preferred.

Examples of those having a vinyl group as the functional group include methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, and vinyltrimethoxysilane. alkoxysilanes such as silane and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane. Among these, methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, divinyltetramethyldisilazane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinyl A silane coupling agent having a vinyl group-containing organosilyl group containing one or more selected from the group consisting of methyldimethoxysilane is preferred.

Further, when the silane coupling agent (D) contains two kinds of a silane coupling agent having a trimethylsilyl group and a silane coupling agent having a vinyl group-containing organosilyl group, those having a hydrophobic group include hexamethyldisilazane, Divinyltetramethyldisilazane is preferably included as one having a vinyl group.

When the silane coupling agent (D1) having a trimethylsilyl group and the silane coupling agent (D2) having a vinyl group-containing organosilyl group are used in combination, the ratio of (D1) and (D2) is not particularly limited, but for example, (D1):(D2) in a weight ratio of 1:0.001 to 1:0.35, preferably 1:0.01 to 1:0.20, more preferably 1:0.03 to 1:0 .15. Desired physical properties of the silicone rubber can be obtained by setting it to such a numerical range. Specifically, the dispersibility of silica in the rubber and the crosslinkability of the rubber can be balanced.
<<Water (E)>>
Further, the silicone rubber-based curable composition of the present embodiment may contain water (E) in addition to the above components (A) to (D).

Water (E) is a component that functions as a dispersion medium for dispersing each component contained in the silicone rubber-based curable composition and contributes to the reaction between the silica particles (C) and the silane coupling agent (D). . Therefore, the silica particles (C) and the silane coupling agent (D) can be linked to each other more reliably in the silicone rubber, and uniform properties can be exhibited as a whole.

Furthermore, the silicone rubber-based curable composition of the present embodiment may contain, in addition to the above components (A) to (E), known additive components blended in silicone rubber-based curable compositions. Examples thereof include diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, and mica. In addition, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, thermal conductivity improvers and the like can be added as appropriate.

In addition, although the content ratio of each component in the silicone rubber-based curable composition is not particularly limited, it is set as follows, for example.

In the present embodiment, the upper limit of the content of the silica particles (C) may be, for example, 60 parts by weight or less, preferably 50 parts by weight, with respect to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). It may be 35 parts by weight or less, more preferably 35 parts by weight or less. This makes it possible to balance mechanical strength such as hardness and tensile strength. Moreover, the lower limit of the content of the silica particles (C) is not particularly limited to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A), but may be, for example, 20 parts by weight or more.

The content of the silane coupling agent (D) is, for example, 1 part by weight or more and 50 parts by weight or less, preferably 5 parts by weight or more and 45 parts by weight or less, relative to 100 parts by weight of the vinyl group-containing organopolysiloxane (A). It is more preferably 8 parts by weight or more and 40 parts by weight or less. By making it equal to or higher than the above lower limit, the dispersibility of the silica particles (C) in the silicone rubber-based curable composition can be reliably improved.

Other catalysts may be used in combination with the organic peroxide (B) of the catalyst. Other catalysts such as platinum or platinum compounds are used. As the platinum or platinum compound, known ones can be used, for example, platinum black, platinum supported on silica, carbon black, etc., chloroplatinic acid or an alcohol solution of chloroplatinic acid, chloroplatinic acid and Complex salts of olefins, complex salts of chloroplatinic acid and vinyl siloxane, and the like are included.

Furthermore, when water (E) is contained, its content can be set as appropriate. and more preferably 30 to 70 parts by weight. This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

<Method for producing silicone rubber>
Next, a method for producing the silicone rubber of this embodiment will be described.
As a method for producing the silicone rubber of the present embodiment, the silicone rubber can be obtained by preparing a silicone rubber-based curable composition and curing the silicone rubber-based curable composition.
Details will be described below.

First, each component of the silicone rubber-based curable composition is uniformly mixed using any kneading device to prepare the silicone rubber-based curable composition.

[1] For example, a vinyl group-containing organopolysiloxane (A), silica particles (C), and a silane coupling agent (D) are weighed in predetermined amounts, and then kneaded with an arbitrary kneading device, A kneaded material containing these components (A), (C) and (D) is obtained.

The kneaded product is preferably obtained by previously kneading the vinyl group-containing organopolysiloxane (A) and the silane coupling agent (D), and then kneading (mixing) the silica particles (C). This further improves the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A).

Further, when obtaining this kneaded product, water (E) may be added to the kneaded product of each component (A), (C), and (D), if necessary. This allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

Further, the kneading of the components (A), (C) and (D) is preferably carried out through a first step of heating at a first temperature and a second step of heating at a second temperature. As a result, in the first step, the surface of the silica particles (C) can be surface-treated with the coupling agent (D), and in the second step, the silica particles (C) and the coupling agent (D) By-products generated in the reaction can be reliably removed from the kneaded material. After that, if necessary, the component (A) may be added to the obtained kneaded product and further kneaded. This can improve the familiarity of the components of the kneaded product.

The first temperature is preferably, for example, about 40 to 120.degree. C., and more preferably, for example, about 60 to 90.degree. The second temperature is, for example, preferably about 130 to 210.degree. C., more preferably about 160 to 180.degree.

Moreover, the atmosphere in the first step is preferably an inert atmosphere such as a nitrogen atmosphere, and the atmosphere in the second step is preferably a reduced-pressure atmosphere.

Furthermore, the time for the first step is preferably, for example, about 0.3 to 1.5 hours, more preferably about 0.5 to 1.2 hours. The time for the second step is, for example, preferably about 0.7 to 3.0 hours, more preferably about 1.0 to 2.0 hours.

By setting the first step and the second step under the above conditions, the above effect can be obtained more significantly.

[2] Next, a predetermined amount of the organic peroxide (B) is weighed, and then the organic peroxide (B) is kneaded with the kneaded product prepared in the above step [1] using an arbitrary kneading device. By doing so, a silicone rubber-based curable composition is obtained. The obtained silicone rubber-based curable composition may be a paste containing a solvent.

The temperature at which the organic peroxide (B) is kneaded is, for example, preferably about 10 to 70°C, more preferably about 25 to 30°C, as the set temperature of the rolls.

Further, the kneading time is preferably about 5 minutes to 1 hour, more preferably about 10 to 40 minutes.

By setting the temperature within the above range in steps [1] and [2], the progress of the reaction of the vinyl group-containing organopolysiloxane (A) can be more accurately prevented or suppressed. In addition, by setting the kneading time within the above range in steps [1] and [2], each component (A) to (E) can be more reliably dispersed in the silicone rubber-based curable composition. can be done.

The kneading device used in steps [1] and [2] is not particularly limited, but for example, a kneader, two rolls, a Banbury mixer (continuous kneader), a pressure kneader, etc. can be used.

In step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded product. As a result, even if the temperature of the kneaded material is set to a relatively high temperature, the progress of the reaction of the vinyl group-containing organopolysiloxane (A) can be more accurately prevented or suppressed.

[3] Next, a silicone rubber is formed by curing the silicone rubber-based curable composition.

In the present embodiment, the curing step of the silicone rubber-based curable resin composition includes, for example, heating at 100 to 250° C. for 1 to 30 minutes (primary curing), followed by post-baking at 200° C. for 1 to 4 hours (secondary curing). curing).
The silicone rubber of the present embodiment is obtained through the steps described above.

Next, the properties of the silicone rubber (cured product of the silicone rubber-based curable composition) of this embodiment will be described.

The upper limit of the durometer hardness A of the cured product of the silicone rubber-based curable composition is not particularly limited, but may be 80 or less, preferably 75 or less, more preferably 70 or less. Thereby, the cured properties of the silicone rubber can be balanced. Moreover, from the viewpoint of ease of deformation, the upper limit of the durometer hardness A may be 50 or less, 45 or less, or 40 or less. As a result, in the silicone rubber, it is possible to increase the ease of deformation in which deformation such as bending and stretching is facilitated. On the other hand, the lower limit of the durometer hardness A is not particularly limited, but may be, for example, 10 or more, preferably 20 or more, more preferably 25 or more. This increases the mechanical strength of the silicone rubber. Moreover, the shape retention of the structure can be enhanced.

(Measurement conditions for durometer hardness A)
A sheet-shaped test piece was prepared using the cured product of the silicone rubber-based curable composition, and the durometer hardness A of the obtained sheet-shaped test piece was measured at 25°C in accordance with JIS K6253 (1997). do.

The lower limit of the tear strength of the cured product of the silicone rubber-based curable composition is, for example, 25 N/mm or more, preferably 28 N/mm or more, more preferably 30 N/mm or more, and still more preferably 33 N/mm or more. , more preferably 35 N/mm or more. This can improve the scratch resistance and mechanical strength of the silicone rubber. In addition, the durability of silicone rubber can be improved during repeated use. On the other hand, the upper limit of the tear strength is not particularly limited, but may be, for example, 70 N/mm or less, or 60 N/mm or less. Thereby, various properties of the silicone rubber can be balanced.

(Measurement conditions for tear strength)
A crescent-shaped test piece is prepared using the cured silicone rubber-based curable composition, and the tear strength of the obtained crescent-shaped test piece is measured at 25° C. in accordance with JIS K6252 (2001).

The lower limit of the tensile strength of the cured product of the silicone rubber-based curable composition is, for example, 5.0 MPa or higher, preferably 6.0 MPa or higher, and more preferably 7.0 MPa or higher. Thereby, the mechanical strength of the silicone rubber can be improved. In addition, it is possible to realize a highly durable structure that can withstand repeated deformation. On the other hand, the upper limit of the tensile strength is not particularly limited, but may be, for example, 15 MPa or less, or 13 MPa or less. Thereby, various properties of the silicone rubber can be balanced.

(Conditions for measuring tensile strength)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was subjected to the Measure the tensile strength.

The upper limit of the tensile stress M100 at ₁₀₀ % elongation of the cured product of the silicone rubber-based curable composition is, for example, 4.0 MPa or less, preferably 3.0 MPa or less, more preferably 2. It is 0 MPa or less, more preferably 1.0 MPa or less. As a result, easiness of deformation can be ensured. The lower limit of the tensile stress _M100 is not particularly limited, but may be, for example, 0.1 MPa or more, or 0.3 MPa or more. Thereby, the mechanical strength of the cured product can be improved.

(Measurement conditions for tensile stress)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was subjected to the The stress at 100% elongation (tensile stress M ₁₀₀ ) is measured.

The lower limit of the elongation at break of the cured product of the silicone rubber-based curable composition is, for example, 300% or more, preferably 400% or more, and more preferably 500% or more. Thereby, the high stretchability and durability of the silicone rubber can be improved. On the other hand, the upper limit of the elongation at break is not particularly limited, but may be, for example, 2000% or less, 1500% or less, or 1100% or less. Thereby, various properties of the silicone rubber can be balanced.

(Measurement conditions for breaking elongation)
A dumbbell-shaped No. 3 test piece was prepared using the cured product of the silicone rubber-based curable composition, and the obtained dumbbell-shaped No. 3 test piece was subjected to the Measure the elongation at break.

(Compression set)
The lower limit of the compression set of the cured product of the silicone rubber-based curable composition is not particularly limited, but is, for example, 0.1% or more, preferably 0.5% or more, and more preferably 1.5%. It may be 0% or more. Thereby, the physical properties of the silicone rubber can be balanced. On the other hand, the upper limit of the compression set is, for example, 20.0% or less, preferably 16.0% or less, more preferably 13.0% or less. As a result, the silicone rubber can be made to have excellent restorability.
(Conditions for measurement of compression set)
A disk-shaped test piece was prepared using the cured product of the silicone rubber-based curable composition, and the resulting disk-shaped test piece was subjected to compression rate of 25%, 150 ° C., 22 ° C. according to JIS K6262 (2013) Compress under time conditions and measure the compression set.

The lower limit of t _c (10) of the silicone rubber-based curable composition measured at 170° C. with a curastometer may be, for example, 30 seconds or longer, preferably 60 seconds or longer, and more preferably 90 seconds or longer. Thereby, fluidity at the time of molding can be secured. The upper limit of t _c (10) is not particularly limited, but may be, for example, 420 seconds or less, preferably 360 seconds or less, more preferably 300 seconds or less. Thereby, short-time curability can be secured.

<Induction time (measurement conditions for _tc (10) at 170°C in a curastometer>
The curing torque of the above silicone rubber-based curable composition is measured over time using a curastometer in accordance with JIS K6300-2 (2001) at a mold temperature of 170°C. Based on the measurement results, _{M E} (M _E = M _H - _{M L} ). Calculate the induction time t _c (10), which is the time from the start of measurement until reaching 10% of M _E .

In this embodiment, when measuring the hardness, tensile stress, elongation at break, tensile strength, tear strength, compression set, and induction time t _c (10) of the silicone rubber-based curable composition, the object to be heated and the object to be measured As the cured product of the silicone rubber-based curable composition can be used. As this cured product, for example, a silicone rubber-based curable composition is pressed at 170° C. and 10 MPa for 15 minutes to form a sheet having a thickness of 1 mm, and is subjected to primary curing, followed by primary curing at 200° C. for 4 hours. A sheet-shaped silicone rubber (cured product of a silicone rubber-based curable composition) obtained by heating and secondary curing may also be used.

In the present embodiment, for example, by appropriately selecting the type and amount of each component contained in the silicone rubber-based curable composition, the preparation method of the composition for forming the silicone rubber-based curable composition, etc. , the hardness, tensile stress, elongation at break, tensile strength, tear strength and compression set can be controlled. Among these, for example, appropriate control of the type and blending ratio of resins constituting the silicone rubber-based curable composition, cross-linking density and cross-linking structure of the resin, and adjustment of the type and amount of peroxide added. , Improving the mixing ratio of the inorganic filler and the dispersibility of the inorganic filler are factors for setting the hardness, tensile stress, elongation at break, tensile strength, tear strength, and compression set within the desired numerical range. mentioned.

As a result of examination by the present inventor, the following findings were obtained. It was found that if the amount of filler in silicone rubber is reduced, the hardness and tensile stress can be reduced, but on the other hand, the tear strength is lowered and the durability of the silicone rubber is lowered.

Therefore, as a result of intensive studies, by appropriately selecting a resin composition such as a vinyl group-containing organopolysiloxane (A), it is possible to control the uneven distribution of cross-linking density and cross-linking structure, and to achieve low stress and low hardness in a wide strain range. It was found that the tear strength of the silicone rubber can be increased while realizing this. Moreover, it turned out that the tensile strength of silicone rubber can also be improved. Although the detailed mechanism is not clear, the combination of high-vinyl group-containing organopolysiloxane and low-vinyl group-containing organopolysiloxane makes it possible to control uneven distribution of the crosslinked structure, thereby increasing the tear strength of silicone rubber while reducing hardness. It is considered possible. Thus, by increasing the tear strength while maintaining other physical properties, the durability of the silicone rubber can be increased.

Structures comprising a cured product (silicone rubber) of the silicone rubber-based curable composition of the present embodiment include, for example, medical applications such as medical instruments and equipment; automotive applications; robot applications such as industrial robots; Applications; production facilities and daily life applications such as vibration-proof materials, seismic-isolating materials, and food hoses; roller members; The silicone rubber of the present embodiment can be processed and molded into various shapes such as a sheet, a cylinder, and a bag according to various uses.

The silicone rubber of the present embodiment is used as an example of medical applications such as medical instruments and devices, such as medical tube materials; sealing materials; packing materials; connector materials; You can configure the department. For example, by applying the resin-made movable member of the present embodiment to a medical tube, the medical tube has excellent kink resistance, scratch resistance, insertability, transparency, and further excellent resilience. Become. Moreover, medical tubes include, for example, medical catheters, manipulators, leads, and the like.

The silicone rubber of the present embodiment, as an example of robot applications such as industrial robots, for example, constitutes a part of drive mechanisms such as joints; wiring mechanisms such as wiring cables and connectors; operating mechanisms such as manipulators; can be done.

The silicone rubber of the present embodiment is used for electronic devices such as wearable devices that can be worn on the human body, for example, elastic wiring or wiring substrate; optical fiber, flat cable, wiring structure, cable Cables such as guides; sensors such as touch panels, force sensors, MEMS, and seat sensors;

In addition, the silicone rubber of the present embodiment is a packaging material such as a gas barrier film; cooking utensils; hoses; fixing belts; switches; sheet materials; You can configure the department.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can also be adopted.
Examples of reference forms are added below.
1. a vinyl group-containing organopolysiloxane (A) containing a low vinyl group-containing linear organopolysiloxane (A1-1) and a high vinyl group-containing linear organopolysiloxane (A1-2);
an organic peroxide (B) having an —O—O— structure in the molecule;
silica particles (C);
a silane coupling agent (D);
A silicone rubber-based curable composition comprising:
2. 1. The silicone rubber-based curable composition according to
The organic peroxide (B) includes ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, peroxyesters and peroxydicarbonates. A curable silicone rubber composition comprising at least one selected from the group consisting of
3. 1. or 2. The silicone rubber-based curable composition according to
The organic peroxide (B) is a silicone rubber-based curable composition containing a dialkyl peroxide represented by the following general formula (I) or (II).
R ¹ —O—O—R ² General formula (I)
R ¹ —O—O—R ³ —O—O—R ² General formula (II)
(In general formula (I) above, R ¹ and R ² may be the same or different independently of each other and represent a substituted or unsubstituted alkyl group or cycloalkyl group, a phenyl group, an alkylphenyl group, a cycloalkyl or an alkylcycloalkyl group, and either one of R ¹ and R ² may be a hydrogen atom.
In general formula (II) above, R ¹ to R ³ may be independently the same or different, R ¹ and R ² each represent a substituted or unsubstituted alkyl group or cycloalkyl group, a phenyl group, It may be substituted with an alkylphenyl group, a cycloalkyl group, or an alkylcycloalkyl group, and R ³ represents an alkylene group. Either one of R ¹ and R ² may be a hydrogen atom. )
4. 1. ~3. The silicone rubber-based curable composition according to any one of
The content of the organic peroxide (B) is 0 with respect to 100 parts by weight of the total of the vinyl group-containing organopolysiloxane (A), the silica particles (C) and the silane coupling agent (D). 001 parts by weight or more and 10 parts by weight or less of the silicone rubber-based curable composition.
5. 1. ~ 4. The silicone rubber-based curable composition according to any one of
The ratio (A1-1) of the low vinyl group-containing linear organopolysiloxane (A1-1) and the high vinyl group-containing linear organopolysiloxane (A1-2): (A1-2) is the weight A silicone rubber-based curable composition having a ratio of 50:50 to 95:5.
6. 1. ~ 5. The silicone rubber-based curable composition according to any one of
A curable silicone rubber composition, wherein the silane coupling agent (D) contains a silane coupling agent having a trimethylsilyl group and a silane coupling agent having a vinyl group-containing organosilyl group.
7. 6. The silicone rubber-based curable composition according to
A curable silicone rubber composition, wherein the silane coupling agent having a trimethylsilyl group contains one or more selected from the group consisting of hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, and trimethylethoxysilane.
8. 6. or7. The silicone rubber-based curable composition according to
The silane coupling agent having a vinyl group-containing organosilyl group is methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, divinyltetramethyldisilazane, A silicone rubber-based curable composition containing at least one selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane.
9. 1. ~8. The silicone rubber-based curable composition according to any one of
The content of the silane coupling agent (D) is 1 part by weight or more and 50 parts by weight or less per 100 parts by weight of the vinyl group-containing organopolysiloxane (A).
10. 1. ~ 9. The silicone rubber-based curable composition according to any one of
The low vinyl group-containing linear organopolysiloxane (A1-1) has a vinyl group content of 0.01 to 0.4 mol%,
A curable silicone rubber composition, wherein the high vinyl group-containing linear organopolysiloxane (A1-2) has a vinyl group content of 0.5 to 15 mol %.
11. 1. ~ 10. The silicone rubber-based curable composition according to any one of
The low vinyl group-containing linear organopolysiloxane (A1-1) or the high vinyl group-containing linear organopolysiloxane (A1-2) contains a compound represented by the above general formula (1), Silicone rubber-based curable composition.
(In the above formula (1), m is an integer of 1 to 1000, n is an integer of 3000 to 10000, and R ¹ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or A hydrocarbon group combining these, R ² is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, or a hydrocarbon group combining these, R ³ is a substituted group having 1 to 8 carbon atoms or an unsubstituted alkyl group, an aryl group, or a hydrocarbon group combining these, and at least one of a plurality of R ¹ and R ² is an alkenyl group.)
12. 1. ~ 11. A structure comprising a cured product of the silicone rubber-based curable composition according to any one of .

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to the description of these Examples.

Raw material components used in Examples and Comparative Examples shown in Table 1 are shown below.
(Vinyl group-containing organopolysiloxane (A))
Low-vinyl group-containing linear organopolysiloxane (A1-1): a vinyl group-containing dimethylpolysiloxane synthesized according to Synthesis Scheme 1 (the structure represented by the above formula (1-1), where only R ¹ (terminal) is vinyl underlying structure)
High-vinyl group-containing linear organopolysiloxane (A1-2): a vinyl group-containing dimethylpolysiloxane synthesized according to Synthesis Scheme 2 (a structure represented by the above formula (1-1) in which R ¹ and R ² are vinyl groups structure that is

・有機過酸化物（Ｂ－２）：下記式で表されるジターシャリーブチルパーオキサイド（ジアルキルパーオキサイド類、モメンティブ社製、ＴＣ－４Ｎ）

(Organic peroxide (B))
- Organic peroxide (B-1): dicumyl peroxide represented by the following formula (dialkyl peroxides, manufactured by Momentive, TC-3)

- Organic peroxide (B-2): ditertiary butyl peroxide represented by the following formula (dialkyl peroxides, manufactured by Momentive, TC-4N)

(Silica particles (C))
・Silica particles (C): Silica fine particles (particle diameter 7 nm, specific surface area 300 m ² /g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL 300"

(Silane coupling agent (D))
- Silane coupling agent (D-1): hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)"
- Silane coupling agent (D-2): divinyltetramethyldisilazane, manufactured by Gelest, "1,3-DIVINYLTETRAMETHYLDISILAZANE (SID4612.0)"

(organohydrogenpolysiloxane)
・Made by Momentive: “TC-25D”
(platinum or platinum compound)
・Made by Momentive: “TC-25A”

(Synthesis of vinyl group-containing organopolysiloxane (A))
[Synthesis Scheme 1: Synthesis of Low Vinyl Group-Containing Linear Organopolysiloxane (A1-1)]
A low vinyl group-containing linear organopolysiloxane (A1-1) was synthesized according to the following formula (5).
That is, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium siliconate were placed in a 300 mL separable flask having a cooling tube and a stirring blade, which was replaced with Ar gas, and the temperature was raised to 120° C. for 30 minutes. Stirred. At this time, an increase in viscosity was confirmed.
After that, the temperature was raised to 155° C. and stirring was continued for 3 hours. After 3 hours, 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added, and the mixture was further stirred at 155° C. for 4 hours.
Furthermore, after 4 hours, it was diluted with 250 mL of toluene and then washed with water three times. The washed organic layer was washed several times with 1.5 L of methanol for reprecipitation purification to separate the oligomer and polymer. The obtained polymer was dried overnight under reduced pressure at 60° C. to obtain a low-vinyl group-containing linear organopolysiloxane (A1-1) (Mn=2,2×10 ⁵ , Mw=4,8×10 ⁵ ). Also, the vinyl group content calculated by ¹ H-NMR spectrum measurement was 0.04 mol %.

[Synthesis Scheme 2: Synthesis of High Vinyl Group-Containing Linear Organopolysiloxane (A1-2)]
In the above synthesis step (A1-1), in addition to 74.7 g (252 mmol) of octamethylcyclotetrasiloxane, 0.5 g of 2,4,6,8-tetramethyl 2,4,6,8-tetravinylcyclotetrasiloxane was added. Except for using 86 g (2.5 mmol), the same synthesis step as in (A1-1) was performed to obtain a high-vinyl group-containing linear organopolysiloxane (A1- 2) was synthesized (Mn=2,3×10 ⁵ , Mw=5,0×10 ⁵ ). Also, the vinyl group content calculated by ¹ H-NMR spectrum measurement was 0.93 mol %.

(Example 1: Preparation of silicone rubber-based curable composition)
In Example 1, a silicone rubber-based curable composition was prepared as follows. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1 below, and then silica particles ( C) was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after the addition of the silica particles (C) includes a first step of kneading for 1 hour under a nitrogen atmosphere at 60 to 90° C. for the coupling reaction, and removal of the by-product (ammonia). For this purpose, a second step of kneading for 2 hours under a reduced pressure atmosphere at 160 to 180 ° C. is performed, followed by cooling, and the remaining 10% of the vinyl group-containing organopolysiloxane (A) is added twice. Add in portions and knead for 20 minutes.
Subsequently, 0.15 parts by weight of the organic peroxide (B-1) was added to 100 parts by weight of the resulting kneaded product (silicone rubber compound) and kneaded with a roll to obtain the silicone rubber-based curability of Example 1. A composition was obtained.

(Example 2: Preparation of silicone rubber-based curable composition)
In Example 2, a silicone rubber-based curable composition was prepared in the same manner as in Example 1. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1, and then silica particles (C) are added to the mixture. was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after adding the silica particles (C) was performed in the same manner as in Example 1.
Subsequently, 0.35 parts by weight of the organic peroxide (B-1) was added to 100 parts by weight of the resulting kneaded product (silicone rubber compound) and kneaded with a roll to obtain the silicone rubber-based curability of Example 2. A composition was obtained.

(Example 3: Preparation of silicone rubber-based curable composition)
In Example 3, a silicone rubber-based curable composition was prepared in the same manner as in Example 1. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1, and then silica particles (C) are added to the mixture. was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after adding the silica particles (C) was performed in the same manner as in Example 1.
Subsequently, 0.25 parts by weight of the organic peroxide (B-1) was added to 100 parts by weight of the resulting kneaded product (silicone rubber compound) and kneaded with a roll to obtain the silicone rubber-based curability of Example 3. A composition was obtained.

(Example 4: Preparation of silicone rubber-based curable composition)
In Example 4, a silicone rubber-based curable composition was prepared in the same manner as in Example 1. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1, and then silica particles (C) are added to the mixture. was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after adding the silica particles (C) was performed in the same manner as in Example 1.
Subsequently, 0.5 parts by weight of the organic peroxide (B-2) was added to 100 parts by weight of the resulting kneaded product (silicone rubber compound) and kneaded with a roll to obtain the silicone rubber curing property of Example 4. A composition was obtained.

(Comparative Example 1: Preparation of silicone rubber-based curable composition)
In Comparative Example 1, a silicone rubber-based curable composition was prepared in the same manner as in Example 1. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1, and then silica particles (C) are added to the mixture. was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after adding the silica particles (C) was performed in the same manner as in Example 1.
Subsequently, 1.81 parts by weight of organohydrogenpolysiloxane (TC-25D) and 0.5 parts by weight of platinum or a platinum compound (TC-25A) were added to 100 parts by weight of the resulting kneaded product (silicone rubber compound). and kneaded with a roll to obtain a silicone rubber-based curable composition of Comparative Example 1.

(Comparative Example 2: Preparation of silicone rubber-based curable composition)
In Comparative Example 2, a silicone rubber-based curable composition was prepared in the same manner as in Example 1. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1, and then silica particles (C) are added to the mixture. was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after adding the silica particles (C) was performed in the same manner as in Example 1.
Subsequently, 3.77 parts by weight of organohydrogenpolysiloxane (TC-25D) and 0.5 parts by weight of platinum or a platinum compound (TC-25A) were added to 100 parts by weight of the resulting kneaded product (silicone rubber compound). and kneaded with a roll to obtain a silicone rubber-based curable composition of Comparative Example 2.

(Comparative Example 3: Preparation of silicone rubber-based curable composition)
In Comparative Example 3, a silicone rubber-based curable composition was prepared in the same manner as in Example 1. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D) and water (E) is pre-kneaded in the proportions shown in Table 1, and then silica particles (C) are added to the mixture. was added and further kneaded to obtain a kneaded product (silicone rubber compound).
Here, the kneading after adding the silica particles (C) was performed in the same manner as in Example 1.
Subsequently, 2.26 parts by weight of organohydrogenpolysiloxane (TC-25D) and 0.5 parts by weight of platinum or a platinum compound (TC-25A) were added to 100 parts by weight of the resulting kneaded product (silicone rubber compound). and kneaded with a roll to obtain a silicone rubber-based curable composition of Comparative Example 3.

(Production of silicone rubber)
In Examples 1 to 4 and Comparative Examples 1 to 3, the silicone rubber curable composition obtained was pressed at 170° C. and 10 MPa for 15 minutes to form a sheet having a thickness of 1 mm and was primarily cured. . Subsequently, it was heated at 200° C. for 4 hours for secondary curing. As described above, a sheet-shaped silicone rubber (cured product of silicone rubber-based curable composition) was obtained.

The obtained sheet-shaped silicone rubber (sheet-shaped elastomer) was evaluated based on the following evaluation items. Table 2 shows the evaluation results. Tensile stress, elongation at break, and tensile strength were measured for three samples, and the average value of the three values was used as the measured value. Five samples were measured for tear strength, and the average value of the five samples was used as the measured value. For hardness, two samples were used, each sample was measured with n=5, and the average value of a total of 10 measurements was used as the measured value. Each average value is shown in Table 2.

<Hardness>
Six 1 mm-thick silicone rubber sheets of each example and comparative example were laminated to prepare a 6 mm test piece. Type A durometer hardness (hardness A) was measured on the obtained test piece at 25° C. in accordance with JIS K6253 (1997).
(Hardness measurement conditions)
The hardness of a sheet-shaped test piece at 25° C. is measured according to JIS K6253 (1997) for sheet-shaped test pieces.

<Tear strength>
A crescent-shaped test piece was prepared according to JIS K6252 (2001) using the obtained 1 mm-thick silicone rubber sheet of each example and comparative example, and the resulting crescent-shaped test piece was tested for tearing. Strength was measured. The unit is N/mm.
(Measurement conditions for tear strength)
The tear strength at 25° C. of a crescent-shaped test piece is measured according to JIS K6252 (2001) for crescent-shaped test pieces.

<Tensile strength>
Dumbbell-shaped No. 3 test pieces were prepared according to JIS K6251 (2004) using the obtained 1 mm-thick sheet-shaped silicone rubber of each example and comparative example, and the obtained dumbbell-shaped 3 The tensile strength of the No.-shaped test piece was measured. The unit is MPa.
(Conditions for measuring tensile strength)
The tensile strength of a dumbbell-shaped No. 3 test piece measured at 25° C. in accordance with JIS K6251 (2004) for a dumbbell-shaped No. 3 test piece.

<Breaking elongation>
Dumbbell-shaped No. 3 test pieces were prepared according to JIS K6251 (2004) using the obtained 1 mm-thick sheet-shaped silicone rubber of each example and comparative example, and the obtained dumbbell-shaped 3 The breaking elongation of the No. 1-shaped test piece was measured. The elongation at break was calculated by [moving distance between chucks (mm)]÷[initial distance between chucks (60 mm)]×100. The unit is %.
(Measurement conditions for breaking elongation)
The breaking elongation at 25° C. of a dumbbell-shaped No. 3 test piece is measured according to JIS K6251 (2004) for dumbbell-shaped No. 3 test pieces.

<Tensile stress>
Dumbbell-shaped No. 3 test pieces were prepared according to JIS K6251 (2004) using the obtained 1 mm-thick sheet-like silicone rubbers of Examples and Comparative Examples, and the tensile speed was 500 mm/min. , the tensile stress M of the obtained dumbbell-shaped No. 3 test piece was measured when it was stretched by a predetermined percentage. The unit is MPa.
(Measurement conditions for tensile stress)
For the dumbbell-shaped No. 3 test piece, the tensile stress at the time of 100% elongation of the dumbbell-shaped No. 3 test piece at 25° C. is M ₁₀₀ .

<Compression set>
(Preparation of disk-shaped test piece)
In Examples 1 to 4 and Comparative Examples 1 to 3, the silicone rubber-based curable composition obtained was pressed at 170° C. and 10 MPa for 15 minutes to form a disc having a diameter of 29 mm and a thickness of 12.5 mm. Together, the primary curing was carried out. Subsequently, it was heated at 200° C. for 4 hours for secondary curing. As described above, a disk-shaped test piece (cured product of the silicone rubber-based curable composition) was obtained.
(Conditions for measurement of compression set)
The obtained disk-shaped test piece was evaluated for compression set. Tests 1 to 7 were used to evaluate the compression set corresponding to the silicone rubber curable compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 3, respectively.
According to JIS K6262 (2013), using a compression set tester (manufactured by Yasuda Seiki Seisakusho) and a spacer with a thickness of 9.38 mm, the disc-shaped test piece was compressed at a compression rate of 25% and fixed. In this state, it was allowed to stand in a constant temperature bath at 150° C. for 22 hours. After that, the test was completed according to the following procedure in accordance with B method described in JIS K6262 (2013). Remove the tester from the constant temperature bath and leave it at 25°C for 1 hour to cool. After that, the test piece was released from the tester and allowed to stand at 25° C. for 30 minutes, then the thickness of the test piece was measured, and the compression set was calculated by the following formula. Three samples were used, and the average value of the three values was used as the measured value. Table 3 shows the average values. The unit is %.
Thickness of disk-shaped test piece before test: h0
Thickness of disc-shaped test piece after test: h1
Spacer height: hs
Compression set (%) = ((h0-h1)/(h0-hs)) x 100

<Induction time (t _c (10) at Curastometer 170° C.)>
In Examples 1 to 4 and Comparative Examples 1 to 3, using the obtained silicone rubber curable compositions, the curing torque was measured over time according to JIS K6300-2 (2001). Based on the measurement results, the induction time t _c (10) was calculated. The corresponding induction time t _c (10) evaluations were given as trials 1-7, respectively.
(Induction time (measuring conditions of _tc (10) at 170° C. in curastometer)
Using a curastometer (manufactured by JSR Trading Co., Ltd., product name: Curastometer V type), the curing torque of 4 g of the resulting silicone rubber-based curable composition was measured over time at a mold temperature of 170°C. A value obtained by subtracting the minimum torque value M _L for 15 minutes after the start of measurement from the maximum torque value M _H for 15 minutes after the start of measurement is defined as M _E (M _E =M _H −M _L ). The induction time t _c (10), which is the time from the start of measurement to _reaching 10% of ME, was calculated. The values are shown in Table 3. The unit is seconds.

Based on the above evaluation results, it was found that the silicone rubber of Test 1 had a lower compression set than that of Test 5, which had comparable hardness. In addition, it was found that the silicone rubbers of Tests 2 and 4 had a reduced compression set compared to Test 6, which had approximately the same hardness. In addition, it was found that the silicone rubber of Test 3 had a lower compression set than that of Test 7, which had approximately the same hardness. Furthermore, it was found that the silicone rubber-based curable compositions of Tests 1-4 had a longer induction time t _c (10) than those of Tests 5-7, and were excellent in heat flow stability. Such a silicone rubber-based curable composition has high fluidity when cured and excellent conformability to molds, so that it can be suitably used as a molding material for mold molding.

From the above, it was found that the silicone rubber-based curable compositions of Examples 1-4 had reduced compression set and excellent fluidity during curing as compared with Comparative Examples 1-3. Moreover, it was found that the silicone rubber-based curable compositions of Examples 1 to 4 can realize silicone rubbers excellent in various mechanical properties.

Claims (11)

Silicone used to form silicone rubber used in medical applications, automotive applications, robot applications, electronic equipment applications, production equipment and daily life applications, or roller members (excluding golf ball core materials and keypad operations) A rubber-based curable composition,
a vinyl group-containing organopolysiloxane (A) containing a low vinyl group-containing linear organopolysiloxane (A1-1) and a high vinyl group-containing linear organopolysiloxane (A1-2);
an organic peroxide (B) having an —O—O— structure in the molecule;
silica particles (C);
a silane coupling agent (D);
including
The silane coupling agent (D) contains a silane coupling agent having a trimethylsilyl group and a silane coupling agent having a vinyl group-containing organosilyl group,
A curable silicone rubber composition, wherein the cured product of the curable silicone composition has a tear strength of 36.4 N/mm or more and 70 N/mm or less, as measured at 25°C in accordance with JIS K6252 (2001). thing. The silicone rubber-based curable composition according to claim 1,
The organic peroxide (B) includes ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, peroxyesters and peroxydicarbonates. A curable silicone rubber composition comprising at least one selected from the group consisting of The silicone rubber-based curable composition according to claim 1 or 2,
The organic peroxide (B) is a silicone rubber-based curable composition containing a dialkyl peroxide represented by the following general formula (I) or (II).
R ¹ —O—O—R ² General formula (I)
R ¹ —O—O—R ³ —O—O—R ² General formula (II)
(In general formula (I) above, R ¹ and R ² may be the same or different independently of each other and represent a substituted or unsubstituted alkyl group or cycloalkyl group, a phenyl group, an alkylphenyl group, a cycloalkyl or an alkylcycloalkyl group, and either one of R ¹ and R ² may be a hydrogen atom.
In general formula (II) above, R ¹ to R ³ may be independently the same or different, R ¹ and R ² each represent a substituted or unsubstituted alkyl group or cycloalkyl group, a phenyl group, It may be substituted with an alkylphenyl group, a cycloalkyl group, or an alkylcycloalkyl group, and R ³ represents an alkylene group. Either one of R ¹ and R ² may be a hydrogen atom. ) The silicone rubber-based curable composition according to any one of claims 1 to 3,
The content of the organic peroxide (B) is 0 with respect to 100 parts by weight of the total of the vinyl group-containing organopolysiloxane (A), the silica particles (C) and the silane coupling agent (D). 001 parts by weight or more and 10 parts by weight or less of the silicone rubber-based curable composition. The silicone rubber-based curable composition according to any one of claims 1 to 4,
The ratio (A1-1) of the low vinyl group-containing linear organopolysiloxane (A1-1) and the high vinyl group-containing linear organopolysiloxane (A1-2): (A1-2) is the weight A silicone rubber-based curable composition having a ratio of 50:50 to 95:5. The silicone rubber-based curable composition according to any one of claims 1 to 5 ,
A curable silicone rubber composition, wherein the silane coupling agent having a trimethylsilyl group contains one or more selected from the group consisting of hexamethyldisilazane, trimethylchlorosilane, trimethylmethoxysilane, and trimethylethoxysilane. The silicone rubber-based curable composition according to any one of claims 1 to 6 ,
The silane coupling agent having a vinyl group-containing organosilyl group is methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, divinyltetramethyldisilazane, A silicone rubber-based curable composition containing at least one selected from the group consisting of vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane. The silicone rubber-based curable composition according to any one of claims 1 to 7 ,
The content of the silane coupling agent (D) is 1 part by weight or more and 50 parts by weight or less per 100 parts by weight of the vinyl group-containing organopolysiloxane (A). The silicone rubber-based curable composition according to any one of claims 1 to 8 ,
The low vinyl group-containing linear organopolysiloxane (A1-1) has a vinyl group content of 0.01 to 0.4 mol%,
A curable silicone rubber composition, wherein the high vinyl group-containing linear organopolysiloxane (A1-2) has a vinyl group content of 0.5 to 15 mol %. The silicone rubber-based curable composition according to any one of claims 1 to 9 ,
The low vinyl group-containing linear organopolysiloxane (A1-1) or the high vinyl group-containing linear organopolysiloxane (A1-2) contains a compound represented by the following general formula (1), A silicone rubber-based curable composition.

(In the above formula (1), m is an integer of 1 to 1000, n is an integer of 3000 to 10000, and R ¹ is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or A hydrocarbon group combining these, R ² is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, or a hydrocarbon group combining these, R ³ is a substituted group having 1 to 8 carbon atoms or an unsubstituted alkyl group, an aryl group, or a hydrocarbon group combining these, and at least one of a plurality of R ¹ and R ² is an alkenyl group.) A structure comprising a cured product of the silicone rubber curable composition according to any one of claims 1 to 10 .