Silicone rubber compound and silicone rubber composition containing the same

Abstract

To provide a silicone rubber compound having suppressed reversion to plasticization over time.SOLUTION: A millable-type silicone rubber compound comprises: (A) 100 pts.mass of an organopolysiloxane represented by the average composition formula (I): R1aSiO(4-a) / 2 (where R1 represents identical or different unsubstituted or substituted monovalent C1-10 hydrocarbon groups, 0.01 to 20 mol% of the total R1 groups being C2-C10 alkenyl groups, and a is 1.5 to 2.8), the organopolysiloxane having a viscosity at 25°C of 9,000,000 to 100,000,000 mPa s; and (B) 0.3 to 10 pts.mass of an organopolysiloxane represented by the formula (II): R3O(SiR22O)mR3 (where R2 represents identical or different unsubstituted or substituted monovalent C1-10 hydrocarbon groups, each R3 independently represents a C1-10 alkyl group or a hydrogen atom, and m is 1 to 50), the organopolysiloxane having a viscosity at 25°C of 10 to 1,000 mPa s.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a silicone rubber compound and a silicone rubber composition containing the same.

Background Art

[0002] A silicone rubber composition or a cured product obtained by curing the same has characteristics such as excellent weather resistance, electrical properties, low compression set properties, heat resistance, and cold resistance, and thus is widely used in various fields including electrical equipment, automobiles, construction, medical, and food.

[0003] A cured product obtained by curing a silicone rubber composition is usually produced by kneading a silicone rubber compound containing an organopolysiloxane together with a curing agent and the like and then curing the mixture.

[0004] However, it is known that a silicone rubber compound exhibits a phenomenon of curing over time (reversion to plasticity). When a silicone rubber compound reverts to plasticity, kneading may not be properly performed, and as a result, there arises a problem that the processability into a silicone rubber composition or the like deteriorates. Therefore, it is important to suppress the reversion to plasticity of the silicone rubber compound.

[0005] Regarding a method for suppressing the reversion to plasticity, for example, Patent Document 1 proposes mixing a silicone rubber raw rubber and finely powdered wet silica with a polyorganohydrogensiloxane and a polyether-modified polyorganosiloxane.

[0006] Further, Patent Document 2 proposes blending calcium carbonate having a specific surface area of 1 m 2 / g or more together with a predetermined organohydrogenpolysiloxane and reinforcing silica.

[0007] Furthermore, in Patent Document 3, it is proposed to blend (D) an alkali metal salt of phosphoric acid into a silicone rubber composition containing (A) an organopolysiloxane having a polymerization degree of 100 or more and at least two alkenyl groups in one molecule, (B) an organopolysiloxane or organosilane having an alkoxy group or a hydroxyl group at the molecular chain ends, and (C) a reinforcing silica having a specific surface area of 50 m 2 / g or more.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, in the methods for suppressing plasticization reversion proposed in Patent Documents 1 to 3, it has been clarified by the study of the present applicant that there are variations in the degree of plasticization reversion of the silicone rubber compound. Therefore, it cannot be said that the methods disclosed in Patent Documents 1 to 3 can necessarily suppress the plasticization reversion of the silicone rubber compound.

[0010] One object of the present disclosure is to provide a silicone rubber compound in which plasticization reversion over time is suppressed.

Means for Solving the Problems

[0011] As a result of intensive studies, the present applicant has found that the relaxation time of the organopolysiloxane contained in the silicone rubber compound affects the plasticization reversion of the silicone rubber compound. The present disclosure is based on such findings.

[0012] According to one embodiment of the present disclosure, (A) an average compositional formula (I): (Chemical formula 1) R 1 a SiO (4-a) / 2 (I) (In the formula, R 1 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, 0.01 to 20 mol% of all R 1 groups are C 2~10 alkenyl groups, a is 1.5 to 2.8) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 9,000,000 to 100,000,000 mPa·s represented by, and (B) formula (II): (Chemical formula 2) R 3 O(SiR 2 2O) m R 3 (II) (In the formula, R 2 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, each R 3 is independently a C 1~10 alkyl group or a hydrogen atom, m is 1 to 50) 0.3 to 10 parts by mass of an organopolysiloxane having a viscosity at 25°C of 10 to 1,000 mPa·s represented by A mirable type silicone rubber compound containing, The relaxation time τ (seconds) of the component (A) and the parts by mass of the component (B) satisfy the following mathematical formula: (Equation 1) (A) Component relaxation time τ × 0.207 - 14 ≤ (B) Component parts by mass and The relaxation time τ of the above component (A) provides a millable silicone rubber compound measured by the rheology test method disclosed in this specification.

Advantages of the Invention

[0013] The silicone rubber compound with suppressed plasticization return according to the present disclosure is advantageous in terms of easy processing. The silicone rubber compound according to the present disclosure is particularly advantageous in terms of easy processing into a silicone rubber composition and / or a cured product obtained by curing the same.

Brief Description of the Drawings

[0014]

Figure 1

Modes for Carrying Out the Invention

[0015] [Definitions] In the present disclosure, the "monovalent C 1~10 hydrocarbon group" means a group containing 1 to 10 carbon atoms and hydrogen atoms. The monovalent C1-C 10 hydrocarbon group may be linear, branched or cyclic, and may be saturated or unsaturated. Also, the monovalent C1-C 10 hydrocarbon group may contain one or more ring structures. The monovalent C1-C 10 hydrocarbon group may have one or more nitrogen atoms, oxygen atoms, sulfur atoms, etc. at its terminal or in the molecular chain. The monovalent C1-C 10 hydrocarbon group includes, but is not limited to, for example, C1-C 10 alkyl group, C2-C 10 alkenyl group, C2-C 10 alkynyl group, C3-C 10 cycloalkyl group, C3-C 10 cycloalkenyl group, C6-C 10 aryl group, C3-C 10 heteroaryl group, etc.

[0016] In the present disclosure, "C1-C 10 alkyl group" means a saturated linear or branched hydrocarbon group containing 1 to 10 carbon atoms. C1-C 10 alkyl groups include, but are not limited to, for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl (e.g., n-hexyl), heptyl (e.g., n-heptyl), octyl (n-octyl, isooctyl, 2,2,4-trimethylpentyl), nonyl (e.g., n-nonyl), decyl (e.g., n-decyl), and the like. "C1-C8 alkyl group" in the present disclosure means a saturated linear or branched hydrocarbon group containing 1 to 8 carbon atoms. "C1-C5 alkyl group" in the present disclosure means a saturated linear or branched hydrocarbon group containing 1 to 5 carbon atoms.

[0017] In the present disclosure, "C2-C 10 alkenyl group" means a linear or branched hydrocarbon group containing 2 to 10 carbon atoms and having at least one unsaturated double bond. C2-C 10 alkenyl groups include, but are not limited to, for example, ethenyl (vinyl), propenyl, isopropenyl, butenyl, pentenyl, hexenyl, and the like. "C2-C8 alkenyl group" in the present disclosure means a linear or branched hydrocarbon group containing 2 to 8 carbon atoms and having at least one unsaturated double bond. "C2-C5 alkenyl group" in the present disclosure means a linear or branched hydrocarbon group containing 2 to 5 carbon atoms and having at least one unsaturated double bond.

[0018] In the present disclosure, "C2-C 10 alkynyl group" means a linear or branched hydrocarbon group containing 2 to 10 carbon atoms and having at least one unsaturated triple bond. C2-C 10 alkynyl groups include, but are not limited to, for example, ethynyl, propargyl, and the like.

[0019] In the present disclosure, "C3-C 10 cycloalkyl group" means a saturated monocyclic or bicyclic hydrocarbon group containing 3 to 10 carbon atoms. C3-C 10 Cycloalkyl groups include, but are not limited to, for example, cyclopropyl, cyclobutyl, cyclohexyl, cycloheptyl, and the like.

[0020] In the present disclosure, "C3-C 10 cycloalkenyl group" means a monocyclic or bicyclic hydrocarbon group containing 3 to 10 carbon atoms and having at least one unsaturated double bond. C3-C 10 Cycloalkenyl groups include, but are not limited to, for example, cyclopropenyl, cyclobutenyl, cyclohexenyl, and the like.

[0021] In the present disclosure, "C6-C 10 aryl group" may be either monocyclic or polycyclic (e.g., bicyclic or tricyclic) and contains 6 to 10 carbon atoms in the ring structure. Examples include, but are not limited to, phenyl, naphthyl, and the like.

[0022] In the present disclosure, "C3-C 10 heteroaryl group" may be either monocyclic or polycyclic (e.g., bicyclic or tricyclic) as long as it contains 3 to 10 carbon atoms in the ring structure and also contains one or more oxygen atoms, nitrogen atoms, and / or sulfur atoms in the ring structure. Examples include, but are not limited to, furyl, thienyl, pyridyl, indolyl, quinolyl, isoquinolyl, imidazolyl, and the like.

[0023] In the present disclosure, "the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group" refers to the above-mentioned monovalent C 1~10 hydrocarbon group in which one or more hydrogen atoms may or may not be substituted by substituents, and may be substituted by the same or different substituents, a monovalent C 1~10Means a hydrocarbon group. Such substituents include, but are not limited to, for example, the above-mentioned monovalent hydrocarbon group, -OH group, C1-C 10 alkoxy group, aldehyde group (-C(=O)H), ester group, acyloxy group, amide group, amino group, halogen group, thiol group (-SH), imino group, oxime group, etc.

[0024] In the present disclosure, "C1-C 10 The "alkoxy group" means a group having the structure of "-O-C1-C 10 alkyl group", and includes, but is not limited to, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, etc.

[0025] In the present disclosure, the "ester group" means a group having the structure of "-C(=O)O-R" (wherein R represents the above-mentioned monovalent hydrocarbon group). means.

[0026] In the present disclosure, the "acyloxy group" means a group having the structure of "-O-C(=O)-R" (wherein R represents the above-mentioned monovalent hydrocarbon group).

[0027] In the present disclosure, the "amide group" means a group having the structure of "-C(=O)NR(R')" (wherein R and R' independently represent hydrogen or the above-mentioned monovalent hydrocarbon group). The amide group includes, but is not limited to, for example, carbamoyl group (-C(=O)NH2), monoalkylcarbamoyl group (e.g., methylcarbamoyl group), dialkylcarbamoyl group (e.g., dimethylcarbamoyl group), etc.

[0028] In the present disclosure, the "amino group" means a group represented by "-NR2" (wherein each R independently represents hydrogen or the above-mentioned monovalent hydrocarbon group). When all Rs are hydrogen, the amino group is a primary amino group; when one R is hydrogen, the amino group is a secondary amino group; when neither of the two Rs is hydrogen, the amino group is a tertiary amino group.

[0029] In the present disclosure, examples of the "halogen group" include fluorine, chlorine, bromine, and iodine.

[0030] In the present disclosure, the "imino group" means a group having the structure of "RN=C(R')-" (wherein R and R' independently represent any substituent).

[0031] In the present disclosure, the "oxime group" means a group having the structure of "R2C=N-O-" (wherein each R independently represents any substituent).

[0032] [Mirable-type silicone rubber compound] According to one embodiment of the present disclosure, in the mirable-type silicone rubber compound, (A) the average composition formula (I): (Chemical formula 3) R 1 a SiO (4-a) / 2 (I) (wherein R 1 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, 0.01 to 20 mol% of all R 1 groups are C 2~10 alkenyl groups, a is 1.5 to 2.8) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 9,000,000 to 100,000,000 mPa·s, represented by (B) formula (II): (Chemical formula 4) R 3 O(SiR 2 2O) m R 3 (II) (wherein R 2 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, each R3 is, independently of each other, C 1~10 an alkyl group or a hydrogen atom, m is from 1 to 50) 0.3 to 10 parts by mass of an organopolysiloxane having a viscosity at 25 °C of 10 to 1,000 mPa·s, represented by containing the relaxation time τ (seconds) of the above component (A) and the parts by mass of the above component (B) satisfy the following formula: (Equation 2) (A) relaxation time τ of component × 0.207 - 14 ≤ (B) parts by mass of component satisfying The relaxation time τ of the above component (A) is measured by the rheology test method disclosed in this specification. Hereinafter, the millable silicone rubber compound of the present disclosure will be described in detail.

[0033] [(A) component] According to one embodiment of the present disclosure, the component (A) has an (A) average composition formula (I): (Chemical formula 5) R 1 a SiO (4-a) / 2 (I) (wherein R 1 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, 0.01 to 20 mol% of all R 1 groups are C 2~10 alkenyl groups, a is from 1.5 to 2.8) an organopolysiloxane having a viscosity at 25 °C of 9,000,000 to 100,000,000 mPa·s (also referred to as "(A) component" in the present disclosure).

[0034] (A) component may be linear, or may include a branched structure and / or a cyclic structure. According to one embodiment of the present disclosure, the (A) component has a linear structure in which both ends of the molecular chain are blocked with triorganosiloxy groups and the main chain consists of a repetition of diorganosiloxane units.

[0035] R 1 is preferably a C such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, octyl group, nonyl group, decyl group, etc. 1~10 alkyl group; C such as cyclohexyl group, etc. 1~10 cycloalkyl group; C6-C such as phenyl group, naphthyl group, etc. 10 aryl group; C2-C such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, octenyl group, etc. 10 alkenyl group; C3-C such as cyclohexenyl group, etc. 10 cycloalkenyl group; etc. unsubstituted monovalent hydrocarbon groups, substituted monovalent hydrocarbon groups such as chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, tolyl group, xylyl group, benzyl group, phenylethyl group, phenylpropyl group, etc.

[0036] The R in the (A) component 1 The C in 2~10 The alkenyl groups may be of one kind or two or more kinds. The C in R 1 The C in 2~10 The alkenyl groups may be bonded to the silicon atom at the molecular chain end, the silicon atom in the middle of the molecular chain, or both of them. From the viewpoint of imparting excellent mechanical properties when the millable silicone rubber compound is cured, the above C 2~10 alkenyl groups are preferably present at least at the molecular chain ends of the (A) component. The C in R 1 The C in 2~10 As the alkenyl group in R, preferably, it is a C 2~8 alkenyl group, more preferably, it is a C 2~5 alkenyl group, and even more preferably, it is a vinyl group.

[0037] (A) component, all R 1 Among the groups, C 2~10 The alkenyl group is preferably from 0.01 to about 10 mol%, more preferably from 0.01 to about 5 mol%, still more preferably from 0.01 to about 1 mol%, and even more preferably from 0.01 to about 0.5 mol%.

[0038] According to one embodiment of the present disclosure, the (A) component has, in one molecule, C bonded to a silicon atom 2~10 containing two or more alkenyl groups (preferably from 2 to about 50, more preferably from 2 to about 30, still more preferably from 2 to about 20).

[0039] According to one embodiment of the present disclosure, in the (A) component, about 90 mol% or more (preferably 95 mol% or more, more preferably 98 mol% or more, still more preferably 99 mol% or more) of all R 1 is a C 1~10 alkyl group (preferably a C 1~8 alkyl group, more preferably a C 1~5 alkyl group, still more preferably a methyl group). According to a preferred embodiment of the present disclosure, in the (A) component, R 1 is such that all except the C 2~10 alkenyl group are C 1~10 alkyl groups (preferably C 1~8 alkyl groups, more preferably C 1~5 alkyl groups, still more preferably methyl groups), that is, R 1 is composed of a C 2~10 alkenyl group and a C 1~10 alkyl group (preferably a C 1~8 alkyl group, more preferably a C 1~5 alkyl group, still more preferably a methyl group).

[0040] a is preferably from about 1.8 to about 2.5, more preferably from about 1.95 to about 2.05.

[0041] The viscosity of component (A) at 25°C is preferably from 9,000,000 to about 70,000,000 mPa·s, more preferably from 9,000,000 to about 50,000,000 mPa·s, and even more preferably from 9,000,000 to about 40,000,000 mPa·s. When component (A) has such a viscosity, it is advantageous in that when the mirable type silicone rubber compound is cured, excellent mechanical strength, tear strength, crack resistance, etc. are imparted even at high temperatures. In addition, the viscosity of component (A) in the present disclosure means the viscosity (DIN EN ISO 3219) measured using a rotational viscometer (shearing rate: 0.1 / s) at 25°C unless otherwise specified.

[0042] The average degree of polymerization (average chain length) of component (A) is not particularly limited, but may be, for example, about 3,000 to about 10,000, preferably about 4,000 to about 8,000, and more preferably about 5,000 to about 7,000.

[0043] Component (A) may be one kind or a mixture of two or more kinds.

[0044] According to a preferred embodiment of the present disclosure, component (A) has the formula (Ia): (Chemical formula 6) -Si(CH3)2O- (Ia) contains in the molecule a dimethylsiloxane unit represented by the formula (Ib): (Chemical formula 7) -Si(CH3)(CH=CH2)O- (Ib) and a methylvinylsiloxane unit represented by the formula (Ib).

[0045] According to a more preferred embodiment of the present disclosure, the component (A) contains, in the molecule, about 90 mol% or more (preferably, about 95 mol% or more, more preferably, about 98 mol% or more, still more preferably about 99 mol% or more, and even more preferably, about 99.5 mol% or more) of dimethylsiloxane units represented by the above formula (Ia), and 0.01 to about 10 mol% (preferably, 0.01 to about 5 mol%, more preferably, 0.01 to about 2 mol%, still more preferably, 0.01 to about 1 mol%, and even more preferably, 0.01 to about 0.5 mol%) of methylvinylsiloxane units represented by the above formula (Ib).

[0046] [Component (B)] According to one embodiment of the present disclosure, the component (B) is represented by the formula (II): [Chemical formula 8] R 3 O(SiR 2 2O) m R 3 (II) (wherein R 2 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, each R 3 is independently a C 1~10 alkyl group or a hydrogen atom, m is 1 to 50) and is an organopolysiloxane having a viscosity at 25°C of 10 to 1,000 mPa·s (also referred to as "component (B)" in the present disclosure).

[0047] Component (B) may be linear, or may include a branched structure and / or a cyclic structure. According to one embodiment of the present disclosure, component (B) has a linear structure in which both ends of the molecular chain are blocked with dimethylsilanol groups and the main chain consists of a repetition of diorganosiloxane units.

[0048] R 2is preferably a C such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, octyl group, nonyl group, decyl group, etc. 1~10 alkyl group; C such as cyclohexyl group, etc. 1~10 cycloalkyl group; C6-C such as phenyl group, naphthyl group, etc. 10 aryl group; C2-C such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, octenyl group, etc. 10 alkenyl group; C3-C such as cyclohexenyl group, etc. 10 cycloalkenyl group; etc., unsubstituted monovalent hydrocarbon groups, substituted monovalent hydrocarbon groups such as chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, tolyl group, xylyl group, benzyl group, phenylethyl group, phenylpropyl group, etc. More preferably, R 2 is 1~10 alkyl group (preferably C 1~8 alkyl group, more preferably C 1~5 alkyl group, still more preferably methyl group) and contains at least one.

[0049] According to one embodiment of the present disclosure, R in component (B) 2 is C2-C 10 alkenyl group (preferably C 2~8 alkenyl group, more preferably C 2~5 alkenyl group, still more preferably vinyl group). When R in component (B) 2 contains a C 2~10 alkenyl group, the C 2~10 alkenyl group may be one kind or two or more kinds. The C 2 in R 2~10 alkenyl group is preferably C 2~8 alkenyl group, more preferably C 2~5 alkenyl group, still more preferably vinyl group.

[0050] (B) R in the component 2 as C2-C 10When an alkenyl group is included, all R 2 In the C of the group 2~10 The alkenyl group may be, for example, about 0 to about 100 mol%, preferably about 0 to about 50 mol%, more preferably about 0 to about 25 mol%.

[0051] According to one embodiment of the present disclosure, the component (B) contains 0 or more (preferably 0 to about 10, more preferably 0 to about 5, still more preferably 0 to 2) C atoms bonded to a silicon atom in one molecule. 2~10 Alkenyl groups (preferably 0 to about 10, more preferably 0 to about 5, still more preferably 0 to 2).

[0052] According to one embodiment of the present disclosure, in the component (B), 0 to about 100 mol% (preferably 0 to about 50 mol%, more preferably 0 to about 30 mol%, still more preferably 0 to about 10 mol%) of all R 2 is C 1~10 Alkyl group (preferably C 1~8 Alkyl group, more preferably C 1~5 Alkyl group, still more preferably methyl group). According to one embodiment of the present disclosure, in the component (B), R 2 is C 2~10 All other than the alkenyl group are C 1~10 Alkyl group (preferably C 1~8 Alkyl group, more preferably C 1~5 Alkyl group, still more preferably methyl group), that is, R 2 is composed of a C 2~10 Alkenyl group and a C 1~10 Alkyl group (preferably C 1~8 Alkyl group, more preferably C 1~5 Alkyl group, still more preferably methyl group).

[0053] According to a preferred embodiment of the present disclosure, at least one of the structures at both ends in the component (B) is the following formula II-1: (Chemical formula II-1) R 3 O-Si(CH3)R 2 O- (II-1) (In the formula, R3 and R 2 is as defined above) has. According to a more preferred embodiment of the present disclosure, both terminal structures in the component (B) have the structure of the above formula II-1.

[0054] According to another preferred embodiment of the present disclosure, at least one of the terminal structures at both ends in the component (B) is the following formula II-2: (Chemical formula II-2) R 3 O-Si(CH2CH)R 2 O- (II-2) (wherein R 3 and R 2 is as defined above) has. According to a more preferred embodiment of the present disclosure, both terminal structures in the component (B) have the structure of the above formula II-2.

[0055] Each R 3 is preferably such that at least one is a hydrogen atom. More preferably, each R 3 is a hydrogen atom. According to one embodiment of the present disclosure, the component (B) has at least one end being a diorganosilanol end (more preferably, a dialkylsilanol end, even more preferably, a dimethylsilanol end). According to a preferred embodiment of the present disclosure, both ends of the component (B) are diorganosilanol ends (more preferably, dialkylsilanol ends, even more preferably, dimethylsilanol ends). When at least one of each R 3 is (preferably, both are) a hydrogen atom, it is advantageous in that it forms a hydrogen bond with the hydroxyl groups on the surface of other components (for example, the component (C) such as silica described later) and enhances the affinity.

[0056] According to a preferred embodiment of the present disclosure, the component (B) has about 0.1 to about 10% by mass, preferably about 0.5 to about 8% by mass, more preferably about 1 to about 5% by mass of SiOH in the molecule.

[0057] m is preferably from 1 to about 50, more preferably from 2 to about 30, and even more preferably from 3 to about 25.

[0058] (B) The viscosity of the component at 25°C is preferably from 10 to about 500 mPa·s, more preferably from about 15 to about 100 mPa·s, and even more preferably from about 20 to about 80 mPa·s. By having such a viscosity of the (B) component, it becomes possible to reduce the amount of the (B) component contained in the millable silicone rubber compound, which is advantageous in that it can prevent a decrease in the rubber physical properties due to a large amount of the (B) component being compounded. In addition, the viscosity of the (B) component in the present disclosure means the viscosity (DIN EN ISO 3219) measured using a rotational viscometer (shearing rate: 0.9 / s) at 25°C unless otherwise specified.

[0059] (B) The component may be one kind or a mixture of two or more kinds.

[0060] (B) The amount of the component is preferably from about 0.4 to about 8 parts by mass, more preferably from about 0.5 to about 7.5 parts by mass, based on 100 parts by mass of the above (A) component.

[0061] According to a preferred embodiment of the present disclosure, the (B) component is of formula (IIa): (Chemical formula IIa) HOSi(CH3)2O(Si(CH3)2O) m-2 Si(CH3)2OH (IIa) (wherein m is as defined above) and contains an organopolysiloxane represented by.

[0062] According to one embodiment of the present disclosure, the relaxation time τ (seconds) of the above (A) component and the parts by mass of the above (B) component are represented by the following mathematical formula: (Equation 3) (A) Relaxation time τ of the component × 0.207 - 14 ≤ (B) Parts by mass of the component satisfies

[0063] In the present disclosure, the "relaxation time" means the time from when a certain strain is applied to the (A) component until the strain is eliminated. The relaxation time τ of the (A) component in the present disclosure is measured by the rheology test method described below.

[0064] [(C) component] According to one embodiment of the present disclosure, the above-mentioned mirable silicone rubber compound further contains (C) silica (also referred to as "(C) component" in the present disclosure).

[0065] (C) component is not particularly limited and may be dry silica (for example, fumed silica), wet silica, etc. From the viewpoint of imparting good mechanical properties to the above-mentioned mirable silicone rubber compound, the mirable silicone rubber composition described below and / or their cured products, dry silica is preferred.

[0066] According to one embodiment of the present disclosure, (C) component is preferably reinforcing silica because it can impart better mechanical properties to the above-mentioned mirable silicone rubber compound, the mirable silicone rubber composition described below and / or their cured products.

[0067] (C) component may be one having any surface area. As (C) component, for example, the specific surface area by the BET method is about 50 m 2 / g or more, preferably about 100 to about 500 m 2 / g, more preferably about 100 to about 300 m 2 / g may be used. From the viewpoint of obtaining good strength in the above-mentioned mirable silicone rubber compound, the mirable silicone rubber composition described below and / or their cured products, (C) component preferably has a specific surface area of about 50 m 2 / g or more.

[0068] (C) component may be used as it is, may be used in combination with a surface treatment agent, or may be used after being pre-treated with a surface treatment agent or the like. Examples of the surface treatment agent include, but are not limited to, alkylalkoxysilane, alkylchlorosilane, alkylsilazane, silane coupling agent, titanate-based treatment agent, fatty acid ester, etc. These may be used alone or in combination of two or more (simultaneously or at different timings).

[0069] (C) The amount of the component is not particularly limited as long as the object of the present disclosure can be achieved. When the mirable type silicone rubber compound contains the above (C) component, the amount of the (C) component is, for example, about 0.1 to about 150 parts by mass, preferably about 1 to about 100 parts by mass, more preferably about 2 to about 70 parts by mass, still more preferably about 3 to about 40 parts by mass with respect to 100 parts by mass of the above (A) component. From the viewpoint of preventing compression set in the mirable type silicone rubber compound and / or its cured product, the amount of the (C) component is preferably 150 parts by mass or less with respect to 100 parts by mass of the above (A) component.

[0070] [(D) component, (E) component] According to one embodiment of the present disclosure, the mirable type silicone rubber compound further contains at least one selected from the group consisting of (D) filler (also referred to as “(D) component” in the present disclosure) and (E) non-functional organosiloxane (also referred to as “(E) component” in the present disclosure).

[0071] (D) component is preferably defined as “filler (excluding silica)”, preferably “filler (excluding reinforcing silica)” from the viewpoint of distinguishing it from the silica (preferably reinforcing silica) of the above (C) component.

[0072] (D) component may use any filler, which may be an inorganic filler or an organic filler. Examples of (D) component include, but are not limited to, inorganic fillers such as iron oxide, zinc oxide, titanium oxide, magnesium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, magnesium carbonate, calcium carbonate, barium sulfate, magnesium silicate (talc), aluminum silicate (clay), diatomaceous earth, calcium metasilicate, zeolite, hydrotalcite, quartz, alumina, etc.; organic fillers such as graphite, carbon black, polyparaphenylene terephthalamide (e.g., Kevlar (registered trademark)), cellulose nanofiber, expanded graphite, etc. These may be used alone or in combination of two or more.

[0073] (E) component may use any non-functional organosiloxane. Examples of (E) component include, but are not limited to, octamethylcyclotetrasiloxane, polydimethylsiloxane, etc. These may be used alone or in combination of two or more.

[0074] The amounts of (D) component and (E) component are not particularly limited as long as the object of the present disclosure can be achieved, and those skilled in the art can appropriately adjust them.

[0075] [Other components] The above-mentioned mirable type silicone rubber compound may contain other components such as mold release agents, pigments, reaction inhibitors, heat resistance imparting agents, flame retardants, dispersants, preservatives, stabilizers, etc., in addition to the above-mentioned components as necessary as long as the object of the present disclosure can be achieved. Note that, from the viewpoint of distinguishing from the mirable type silicone rubber composition described later, it is preferable that the above-mentioned mirable type silicone rubber compound does not contain a curing agent.

[0076] Examples of the release agent include, for example, carboxylic acid-based release agents, ester-based release agents, ether-based release agents, ketone-based release agents, alcohol-based release agents, etc. These may be used alone or in combination of two or more.

[0077] Examples of the pigment include, for example, titanium oxide, aluminum silicate, iron oxide, zinc oxide, calcium carbonate, carbon black, rare earth oxides, cerium silanolate, aluminum oxide, aluminum hydroxide, titanium yellow, chrome yellow, cobalt blue, etc. These may be used alone or in combination of two or more.

[0078] Examples of the reaction inhibitor include, for example, acetylene-based compounds, hydrazines, triazoles, phosphines, mercaptans, etc. (for example, acetylene alcohol, vinyl group-containing polyorganopolysiloxane, triallyl cyanurate, triallyl isocyanurate, triacryl formal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropynyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, triallyl phosphate, acetylene group-containing silane, siloxane), etc. These may be used alone or in combination of two or more.

[0079] Examples of the heat resistance-imparting agent include, for example, carbon black, cerium organic acid, cerium hydroxide, cerium oxide, iron oxide, iron organic acid, fumed titanium dioxide, etc. These may be used alone or in combination of two or more.

[0080] Examples of the flame retardant include, for example, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc carbonate, silica, carbon black, carbon nanotubes, ceramic powder, pulverized powder of cured silicone rubber, halogen compounds, phosphorus compounds, etc. These may be used alone or in combination of two or more.

[0081] The amounts of these other components are not particularly limited as long as the objects of the present disclosure can be achieved, and can be appropriately adjusted by those skilled in the art.

[0082] [Rheology test method for measuring relaxation time τ] The rheology test method for measuring the relaxation time τ of the component (A) in the present disclosure is as follows in terms of the apparatus and measurement procedure. Note that 1% strain means the state where D = 0.01 when the shear rate D is expressed by the following formula in a cone-plate type rotational viscometer, and 100% strain means the state where D = 1 when the shear rate D is expressed by the following formula in a cone-plate type rotational viscometer. Generally, φ in the following formula is in the range of 0.005 to 0.05 (corresponding to 0.3 to 3°). [Apparatus] Cone-plate type rotational viscometer (Modular Compact Rheometer, MCR 302, manufactured by Anton Paar) [Measurement procedure] Procedure 1. Apply pre-shear to the sample ((A) component) under the following conditions. Fixture PP25 d (sample thickness) 1 mm Temperature 25°C γ (strain) 1% f (frequency) 100 Hz Time 100 seconds Procedure 2. Remove the strain and give an interval of 20 seconds. Procedure 3. Instantaneously apply 100% strain to the sample by rotating the motor and observe the change in stress (observation time: 1000 seconds, number of measurement points: 264 points (logarithmic up and down: 0.01 to 30 seconds)). Procedure 4. Taking the start of Procedure 3 as the starting point, the time required until the stress falls below 100 Pa is defined as the relaxation time τ.

[0083] [Equation (4)] D = 0.1047 N / Φ D: Shear rate N: Rotational speed (rpm) Φ: Angle (radian) between the cone surface and the plate

[0084] The present inventors have clarified through this study that the relaxation time τ of component (A) exhibits additivity. Therefore, when component (A) is a mixture of two or more types, the relaxation time τ of component (A) can be measured for each organopolysiloxane as described above and calculated by the following formula.

[0085] (Equation 5) Relaxation time τ = (τ1 × M1 + τ2 × M2 + [...]+ τ n × M n ) / (M1 + M2 + [...]+ M n ) τ1: Relaxation time of organopolysiloxane 1 τ2: Relaxation time of organopolysiloxane 2 τ n : Relaxation time of organopolysiloxane n M1: Parts by mass of organopolysiloxane 1 M2: Parts by mass of organopolysiloxane 2 M n : Parts by mass of organopolysiloxane n n: Natural number

[0086] For example, when component (A) is a mixture of three types (M1, M2, M3), the relaxation time τ of component (A) is the value of "(τ1 × M1 + τ2 × M2 + τ3 × M3) / (M1 + M2 + M3)".

[0087] [Method for producing a mirable silicone rubber compound] The above mirable silicone rubber compound can be produced by any method. For example, a method of mixing the above component (A) and the above component (B), and, if necessary, the above component (C), the above component (D), the above component (E) and / or the above other components with an arbitrary kneader can be mentioned. Conditions such as temperature and time during kneading can be appropriately adjusted by those skilled in the art.

[0088] [Use of the mirable silicone rubber compound] The above-mentioned mirable silicone rubber compound can be advantageously used as an intermediate for producing a mirable silicone rubber composition and / or a silicone rubber cured product described later.

[0089] According to another embodiment of the present disclosure, there is provided the above-mentioned mirable silicone rubber compound for producing a mirable silicone rubber composition. According to another embodiment of the present disclosure, there is provided the use of the above-mentioned mirable silicone rubber compound for producing a mirable silicone rubber composition.

[0090] According to another embodiment of the present disclosure, there is provided the above-mentioned mirable silicone rubber compound for producing a silicone rubber cured product. According to another embodiment of the present disclosure, there is provided the use of the above-mentioned mirable silicone rubber compound for producing a silicone rubber cured product.

[0091] [Mirable silicone rubber composition]

[0092] According to another embodiment of the present disclosure, there is provided a mirable silicone rubber composition containing the above-mentioned mirable silicone rubber compound and a (F) curing agent (also referred to as the “(F) component” in the present disclosure).

[0093] [(F) component] The (F) component is not particularly limited as long as it can cure the mirable silicone rubber compound to a desired hardness. Examples of the (F) component include addition-curing type curing agents, peroxide-curing type curing agents, etc., and these may be used alone or in combination of two or more.

[0094] Examples of the addition-type curing agent include, but are not limited to, noble metals (e.g., platinum group metals such as platinum, rhodium, palladium, osmium, iridium, ruthenium, etc.), or those in which these are fixed to particulate carrier materials (e.g., activated carbon, aluminum oxide, silicon oxide); halides of noble metals (e.g., platinum halide, dicyclopentadiene-platinum dichloride, cyclooctadiene-platinum dichloride, cyclopentadiene-platinum dichloride); complexes of noble metals (e.g., platinum-olefin complex, platinum-alcohol complex, platinum-alcoholate complex, platinum-vinylsiloxane complex); those containing iron (e.g., iron-carbonyl complex catalyst, iron catalyst having a cyclopentadienyl group as a ligand, iron catalyst having a terpyridine-based ligand or a terpyridine-based ligand and a bistrimethylsilylmethyl group, iron catalyst having a bisiminopyridine ligand, iron catalyst having a bisiminoquinoline ligand, iron catalyst having an aryl group as a ligand, iron catalyst having a cyclic or acyclic olefin group having an unsaturated group, iron catalyst having a cyclic or acyclic olfinyl group having an unsaturated group); and others containing cobalt, vanadium, samarium, nickel and / or manganese; etc. These may be used alone or in combination of two or more.

[0095] When using an addition-curing hardener as the (F) component, an organohydrogenpolysiloxane or the like may be used in combination. Examples of the organohydrogenpolysiloxane include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris(hydrogendimethylsiloxy)methylsilane, tris(hydrogendimethylsiloxy)phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogen siloxane-dimethylsiloxane cyclic copolymer, trimethylsiloxy-terminated methylhydrogenpolysiloxane, trimethylsiloxy-terminated dimethylsiloxane-methylhydrogen siloxane copolymer, dimethylhydrogensiloxy-terminated dimethylpolysiloxane, dimethylhydrogensiloxy-terminated dimethylsiloxane-methylhydrogen siloxane copolymer, trimethylsiloxy-terminated methylhydrogen siloxane-diphenylsiloxane copolymer, trimethylsiloxy-terminated methylhydrogen siloxane-diphenylsiloxane-dimethylsiloxane copolymer, trimethylsiloxy-terminated methylhydrogen siloxane-methylphenylsiloxane-dimethylsiloxane copolymer, dimethylhydrogensiloxy-terminated methylhydrogen siloxane-dimethylsiloxane-diphenylsiloxane copolymer, dimethylhydrogensiloxy-terminated methylhydrogen siloxane-dimethylsiloxane-methylphenylsiloxane copolymer, (CH3)2HSiO 1 / 2 units and (CH3)3SiO 1 / 2 units and SiO 4 / 2 units and copolymers composed of, (CH3)2HSiO 1 / 2 units and SiO 4 / 2 units and copolymers composed of, (CH3)2HSiO 1 / 2 units and SiO 4 / 2 units and (C6H5)3SiO 1 / 2 units and copolymers composed of, etc. In the above-exemplified compounds, those in which part or all of the methyl groups are substituted with other alkyl groups, phenyl groups, etc. may be mentioned.

[0096] According to one embodiment of the present disclosure, the above (F) component contains an addition-type curing agent. According to a preferred embodiment of the present disclosure, when the above (F) component is an addition-type curing agent, the above mirrorable silicone rubber composition further contains an organohydrogenpolysiloxane.

[0097] According to one embodiment of the present disclosure, the above (F) component contains a curing agent of the organic peroxide curing type.

[0098] Examples of the curing agent of the organic peroxide curing type include, but are not limited to, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, di-t-butyl peroxide, t-butyl perbenzoate, 1,6-hexanediol-bis-t-butylperoxycarbonate, 1,6-bis(t-butylperoxycarboxy)hexane, etc. These may be used alone or in combination of two or more.

[0099] The (F) component may be microencapsulated in fine particle solids or the like (for example, those containing the above precious metals or the like in a thermoplastic resin (for example, a polyester resin or a silicone resin)). Further, the (F) component may be included in an inclusion compound (for example, cyclodextrin).

[0100] The amount of the (F) component is not particularly limited as long as it can cure the above mirrorable silicone rubber composition to a desired hardness. The amount of the (F) component may be, for example, about 0.05 to about 10 parts by mass, preferably about 0.1 to about 8 parts by mass, more preferably about 0.2 to about 5 parts by mass, based on 100 parts by mass of the above mirrorable silicone rubber composition.

[0101] Further, when the component (F) is an addition-type curing agent, the amount of the addition-type curing agent in the above-mentioned millable silicone rubber composition can be appropriately adjusted by those skilled in the art according to the desired curing temperature and curing time. The amount of the addition-type curing agent may be, for example, about 0.01 to about 1,000 ppm, preferably about 0.1 to about 500 ppm, more preferably about 1 to about 100 ppm as the metal element in the curing agent, based on the total amount of the above-mentioned millable silicone rubber composition.

[0102] The above-mentioned millable silicone rubber composition can be produced by any method. For example, a method of mixing the above-mentioned millable silicone rubber compound and the component (F) under any conditions (temperature, time), etc. can be mentioned. These conditions can be appropriately adjusted by those skilled in the art.

[0103] The above-mentioned millable silicone rubber composition may be used as a silicone rubber cured product by curing. According to another embodiment of the present disclosure, there is provided the above-mentioned millable silicone rubber composition for producing a silicone rubber cured product. According to another embodiment of the present disclosure, there is provided the use of the above-mentioned millable silicone rubber composition for producing a silicone rubber cured product.

[0104] [Silicone rubber cured product] According to another embodiment of the present disclosure, there is provided a silicone rubber cured product obtained by curing the above-mentioned millable silicone rubber composition.

[0105] The above-mentioned silicone rubber cured product can be produced by any method. For example, a method of curing the above-mentioned silicone rubber composition under any conditions (temperature, time, pressure, etc.) can be mentioned. These conditions can be appropriately adjusted by those skilled in the art.

[0106] [Kit] According to another embodiment of the present disclosure, there is provided a kit for a millable silicone rubber composition, which contains the above-mentioned millable silicone rubber compound and the component (F).

[0107] According to another embodiment of the present disclosure, there is provided a kit for a silicone rubber cured product, which includes the above-mentioned moldable silicone rubber compound and the above-mentioned component (F).

[0108] Further, according to one embodiment of the present disclosure, the following is provided. [1] (A) Average composition formula (I): (Chemical formula 10) R 1 a SiO (4-a) / 2 (I) (In the formula, R 1 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, 0.01 to 20 mol% of all R 1 groups are C 2~10 alkenyl groups, a is 1.5 to 2.8) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 9,000,000 to 100,000,000 mPa·s, represented by and (B) formula (II): (Chemical formula 11) R 3 O(SiR 2 2O) m R 3 (II) (In the formula, R 2 is the same or different unsubstituted or substituted monovalent C 1~10 hydrocarbon group, each R 3 is independently a C 1~10 alkyl group or a hydrogen atom, m is 1 to 50) 0.3 to 10 parts by mass of an organopolysiloxane having a viscosity at 25°C of 10 to 1,000 mPa·s, represented by A moldable silicone rubber compound containing The relaxation time τ (seconds) of the above-mentioned component (A) and the parts by mass of the above-mentioned component (B) are represented by the following mathematical formula: (Number 6) (Relaxation time τ of component (A) × 0.207 - 14 ≤ parts by mass of component (B)) satisfies The relaxation time τ of the above component (A) is a millable silicone rubber compound measured by the rheology test method disclosed in this specification. [2] The millable silicone rubber compound according to [1], wherein the relaxation time τ of the component (A) is 30 to 100. [3] The component (B) is of formula (IIa): (Chemical formula 12) HO(Si(CH3)2O) m H (IIa) (wherein m is as defined above) The millable silicone rubber compound according to [1] or [2], containing an organopolysiloxane represented by [4] The millable silicone rubber compound according to any one of [1] to [3], further containing (C) silica. [5] (D) filler, and (E) non-functional organosiloxane The millable silicone rubber compound according to any one of [1] to [4], further containing at least one selected from the group consisting of [6] The millable silicone rubber compound according to any one of [1] to [5], and (F) curing agent A millable silicone rubber composition containing [7] The millable silicone rubber composition according to [6], wherein the component (F) contains an addition-curing type curing agent. [8] The millable silicone rubber composition according to [6], wherein the component (F) contains an organic peroxide-curing type curing agent. [9] A silicone rubber cured product obtained by curing the millable silicone rubber composition according to any one of [6] to [8].[[]END]

Example

[0109] Examples are given below to explain the present disclosure in more detail, but the present disclosure is not limited to these examples. The raw materials used in the examples and reference examples described below are as follows. · Organopolysiloxane raw rubber 1: Consisting of 99.73 ± 0.03 mol% of dimethylsiloxane units and 0.29 ± 0.07 mol% of vinylmethylsiloxane units, and having a viscosity at 25°C of 14,000,000 to 22,000,000 mPa·s of organopolysiloxane (manufactured by Wacker Chimie) · Organopolysiloxane raw rubber 2: Consisting of 99.95 ± 0.01 mol% of dimethylsiloxane units and 0.08 ± 0.04 mol% of vinylmethylsiloxane units, and having a viscosity at 25°C of 22,000,000 to 31,000,000 mPa·s of organopolysiloxane (manufactured by Wacker Chimie) · Dimethylsilanol-terminated dimethylpolysiloxane 1: Having dimethylsilanol groups at both ends and having a viscosity at 25°C of 30 to 50 mPa·s of dimethylpolysiloxane (manufactured by Wacker Chimie) · Dimethylsilanol-terminated dimethylpolysiloxane 2: Having dimethylsilanol groups at both ends and having a viscosity at 25°C of 30 to 50 mPa·s of dimethylpolysiloxane (manufactured by Wacker Chimie) · Silica: Untreated fumed silica (HDK V15D, manufactured by Wacker Chimie) with a BET specific surface area of 130 to 170 m 2 / g · Quartz powder (CRYSTALITE 5X, manufactured by Tatsumori Co., Ltd.)

[0110] The relaxation time τ of the organopolysiloxane raw rubber 1 or organopolysiloxane raw rubber 2 used in the following Examples and Comparative Examples was measured by the following method. Note that 1% strain means a state where D = 0.01 when the shear rate D is expressed by the following formula in a cone-plate type rotational viscometer, and 100% strain means a state where D = 1 when the shear rate D is expressed by the following formula in a cone-plate type rotational viscometer. Generally, φ in the following formula is 0.005 to 0.05 (corresponding to 0.3 to 3°). <Apparatus> Cone-plate type rotational viscometer (Modular Compact Rheometer, MCR 302, manufactured by Anton Paar) <Measurement procedure> Procedure 1. Preliminary shear was applied to the organopolysiloxane raw rubber (sample) under the following conditions. Jig PP25 d (sample thickness) 1 mm Temperature 25°C γ (strain) 1% f (frequency) 100 Hz Time 100 seconds Procedure 2. The strain was removed and an interval of 20 seconds was given. Procedure 3. 100% strain was instantaneously applied to the sample by the rotation of the motor, and the change in stress was observed (observation time: 1000 seconds, number of measurement points: 264 points (logarithmic rise and fall: 0.01 to 30 seconds)). Procedure 4. Starting from the start of Procedure 3, the time required until the stress fell below 100 Pa was defined as the relaxation time τ.

[0111] (Equation 7) D = 0.1047N / Φ D: Shear rate N: Rotational speed (rpm) Φ: Angle (radian) between the cone surface and the plate

[0112] In the examples and reference examples described below, the relaxation time τ of a mixture of organopolysiloxane raw rubber 1 and organopolysiloxane raw rubber 2 (also referred to as "raw rubber mixture" in the present disclosure) was calculated by the following formula. In the examples and reference examples described below, since the total of organopolysiloxane raw rubber 1 and organopolysiloxane raw rubber 2 is 100 parts by mass, the denominator (M1 + M2) of the following mathematical formula becomes 100. (Equation 8) Relaxation time τ of raw rubber mixture = (τ1 × M1 + τ2 × M2) / (M1 + M2) τ1: Relaxation time of organopolysiloxane raw rubber 1 τ2: Relaxation time of organopolysiloxane raw rubber 2 M1: Parts by mass of organopolysiloxane raw rubber 1 M2: Parts by mass of organopolysiloxane raw rubber 2

[0113] [Example 1] 100 parts by mass of organopolysiloxane raw rubber 1 (with a relaxation time τ of 63.0 seconds) was charged into a kneader at 25°C, and 6.47 parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 1 was added in four equal portions at 0.5-hour intervals under a nitrogen atmosphere and mixed. This mixture was further mixed for 0.5 hour to obtain the millable silicone rubber compound of Example 1. The millable silicone rubber compound of Example 1 had no plasticization return.

[0114] [Examples 2 to 4] In Example 1, except that organopolysiloxane raw rubber 1 having a relaxation time τ shown in Table 1 was used instead of organopolysiloxane raw rubber 1 with a relaxation time τ of 63.0 seconds, and the parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 1 were changed to the amounts shown in Table 1, the same method was carried out to obtain the millable silicone rubber compounds of Examples 2 to 4. The millable silicone rubber compounds of Examples 2 to 4 had no plasticization return.

[0115] [Example 5] 100 parts by mass of organopolysiloxane raw rubber 1 (with a relaxation time τ of 31.0 seconds) was charged into a kneader at 25°C. Under a nitrogen atmosphere, 1 / 2 amount of 0.46 parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 1, 8.8 parts by mass of silica, and 15.8 parts by mass of quartz powder were added and mixed for 0.5 hour. The remaining amount of dimethylsilanol-terminated dimethylpolysiloxane 1 was added to the obtained mixture and mixed for 1.5 hours to obtain the millable silicone rubber compound of Example 5. The millable silicone rubber compound of Example 5 had no plasticization return.

[0116] [Examples 6 - 8] In Example 5, instead of organopolysiloxane raw rubber 1 with a relaxation time τ of 31.0 seconds, organopolysiloxane raw rubber 1 having the relaxation time τ described in Table 1 was used, and the parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 1, silica, and powdered quartz were changed to the amounts described in Table 1. Otherwise, the same method was carried out to obtain the millable silicone rubber compounds of Examples 6 - 8. The millable silicone rubber compounds of Examples 6 - 8 had no plasticization return.

[0117] [Example 9] 28.6 parts by mass of organopolysiloxane raw rubber 1 and 71.4 parts by mass of organopolysiloxane raw rubber 2 were charged into a kneader at 25°C under a nitrogen atmosphere and mixed for 1 hour until substantially uniform (the relaxation time τ of the obtained raw rubber mixture was 60.7 seconds). To this raw rubber mixture, 0.505 part by mass of dimethylsilanol-terminated dimethylpolysiloxane 2 and 27.2 parts by mass of silica were added under a nitrogen atmosphere, and the mixture was kneaded for 0.5 hour. To the resulting mixture, 0.337 part by mass of dimethylsilanol-terminated dimethylpolysiloxane 2 was added, and the mixture was kneaded for 0.5 hour under a nitrogen atmosphere. Then, the remaining portion (0.168 part by mass) of dimethylsilanol-terminated dimethylpolysiloxane 2 was added, and the mixture was kneaded at 150 °C for 3.5 hours under a nitrogen atmosphere to obtain the millable silicone rubber compound of Example 9. The millable silicone rubber compound of Example 9 showed no plasticization reversion.

[0118] [Example 10] In Example 9, an organopolysiloxane raw rubber mixture having a relaxation time τ shown in Table 1 was used in place of the organopolysiloxane raw rubber mixture having a relaxation time τ of 60.7 seconds, a mixture of 0.60 part by mass of dimethylsilanol-terminated dimethylpolysiloxane 1 and 1.13 parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 2 was used in place of 1.01 part by mass of dimethylsilanol-terminated dimethylpolysiloxane 2, and the amount in parts by mass of silica was changed to the amount shown in Table 1. Otherwise, the same method was carried out to obtain the millable silicone rubber compound of Example 10. The millable silicone rubber compound of Example 10 showed no plasticization reversion.

[0119] [Examples 11 to 16] In Example 9, an organopolysiloxane raw rubber mixture having a relaxation time τ shown in Table 1 was used in place of the organopolysiloxane raw rubber mixture having a relaxation time τ of 60.7 seconds, and the amounts in parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 2 and silica were changed to the amounts shown in Table 1. Otherwise, the same method was carried out to obtain the millable silicone rubber compounds of Examples 11 to 16. The millable silicone rubber compounds of Examples 11 to 16 showed no plasticization reversion.

[0120] [Comparative Examples 1 to 4] In Example 1, except that the organopolysiloxane raw rubber 1 having a relaxation time τ of 63.0 seconds was replaced with the organopolysiloxane raw rubber 1 having a relaxation time τ described in Table 1, and the parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 1 were changed to the amounts described in Table 1, the same method was carried out to obtain the millable silicone rubber compounds of Reference Examples 1 to 4. The millable silicone rubber compounds of Reference Examples 1 to 4 had a plasticization return time of 10 seconds or more.

[0121] [Reference Examples 5 to 7] In Example 5, except that the organopolysiloxane raw rubber 1 having a relaxation time τ of 31.0 seconds was replaced with the organopolysiloxane raw rubber 1 having a relaxation time τ described in Table 1, and the parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 1, silica, and powdered quartz were changed to the amounts described in Table 1, the same method was carried out to obtain the millable silicone rubber compounds of Examples 6 to 8. The millable silicone rubber compounds of Reference Examples 5 to 7 had a plasticization return time of 10 seconds or more.

[0122] [Reference Examples 8 and 9] In Example 9, except that the organopolysiloxane raw rubber mixture having a relaxation time τ of 60.7 seconds was replaced with the organopolysiloxane raw rubber mixture having a relaxation time τ described in Table 1, and the parts by mass of dimethylsilanol-terminated dimethylpolysiloxane 2 and silica were changed to the amounts described in Table 1, the same method was carried out to obtain the millable silicone rubber compounds of Reference Examples 8 and 9. The millable silicone rubber compounds of Reference Examples 8 and 9 had a plasticization return time of 10 seconds or more.

[0123] [Test Example 1: Evaluation of Plasticization Return Time] Using the millable silicone rubber compounds of Examples 1 to 16 and Reference Examples 1 to 9, the plasticization return time was evaluated by the following method. 500 g of each mirable type silicone rubber compound immediately after production was placed on a bank with a gap of 90 mm between the apron plates on two 8-inch rolls (R-2046, manufactured by Nisshin Kagaku Co., Ltd.) with the gap width adjusted to 3 mm. Based on the start time of roll milling (0 seconds), the time (plasticization return time) until each mirable type silicone rubber compound wrapped around the front roll and its surface became smooth (refined) both in appearance and texture was measured. Those with a plasticization return time of less than 10 seconds were judged to have no plasticization return. The results are shown in Table 1.

[0124]

Table 1-1

[0125]

Table 1-2

[0126]

Table 1-3

[0127] As is clear from the results of Test Example 1, the mirable type silicone rubber compounds of Examples 1 to 16 had no plasticization return. Therefore, the mirable type silicone rubber compound of the present disclosure is advantageous in that it has excellent storage stability and can suppress a decrease in processability and the like.

[0128] Although not restricted by theory, when strained, it is the silicone polymer in component (A) that deforms, and it is considered that the stronger the interference between polymer molecular chains, the more time is required to relieve the strain. As the interference between the above molecular chains, entanglement of molecular chains due to a branched structure and crosslinking due to intermolecular forces can be considered. A polymer that is difficult to relieve the plasticization return when the plasticization return occurs is considered to be a polymer with strong interference between the above molecular chains. Therefore, silicone polymers with a long relaxation time τ (for example, Reference Examples 1 to 9) are considered to be difficult to relieve the plasticization return.

[0129] Figure 1 is a plot of the results of Test Example 1 (vertical axis: parts by mass of component (B) / horizontal axis: relaxation time of component (A)). As is clear from Figure 1, it is considered that a mirrorable silicone rubber compound without plasticization return can be obtained when the following mathematical formula is satisfied.

[0130] (Equation 9) (Relaxation time τ of component (A)) × 0.207 - 14 ≤ (parts by mass of component (B))

[0131] Regarding the relaxation time, in Japanese Patent Application Laid-Open No. 2023-089198, a method for measuring the Mooney relaxation rate using a rubber composition (not a polymer such as component (A)) is described. However, this measurement method is a method of measuring after applying shear for 4 minutes at a temperature of 100°C and a rotation speed of 2 rpm, and it can be used for measuring the relaxation time of a very highly viscous substance such as a rubber composition, but it is substantially impossible to measure the relaxation time of a substance with a relatively low viscosity such as the above component (A). On the other hand, the relaxation time measurement method in the present disclosure is advantageous in that it can also measure the relaxation time of a substance with a relatively low viscosity such as the above component (A). Furthermore, in the relaxation time measurement method in the present disclosure, the fact that a correlation appears between the relaxation time of the polymer to be measured (for example, the above component (A)) and the characteristics of the resulting compound (for example, the above mirrorable silicone rubber compound) is a completely unexpected fact.

Claims

1. (A) Average compositional formula (I): (Formula 1) R 1 a SiO (4-a) / 2 (I) (wherein R １ is the same or different unsubstituted or substituted monovalent C １～１０ hydrocarbon group, All R １ 0.01 to 20 mol% of which is C ２～１０ an alkenyl group, a is from 1.5 to 2.8) 100 parts by mass of an organopolysiloxane having a viscosity at 25°C of 9,000,000 to 100,000,000 mPa·s, represented by, and (B) Formula (II): (Formula 2) R 3 O(SiR 2 2 O) m R 3 (II) (wherein R ２ is the same or different unsubstituted or substituted monovalent C １～１０ hydrocarbon group, Each R ３ is, independently of one another, C １～１０ alkyl group or a hydrogen atom, m is from 1 to 50) 0.3 to 10 parts by mass of an organopolysiloxane having a viscosity at 25°C of 10 to 1,000 mPa·s, represented by A mailable silicone rubber compound containing The relaxation time τ (seconds) of the component (A) and the parts by mass of the component (B) satisfy the following mathematical formula: (Equation 1) Relaxation time τ of component (A) × 0.207 - 14 ≤ Parts by mass of component (B) satisfying The relaxation time τ of the component (A) is measured by the rheology test method disclosed in this specification, a mailable silicone rubber compound.

2. The mailable silicone rubber compound according to claim 1, wherein the relaxation time τ of the component (A) is from 30 to 100.

3. The mailable silicone rubber compound according to claim 1, wherein the component (B) contains an organopolysiloxane represented by the formula (IIa): (Formula 3) HO(Si(CH 3 ) 2 O) m H (IIa) (wherein m is as defined above)

4. The mailable silicone rubber compound according to claim 1, further containing (C) silica.

5. (D) A filler, and (E) An organosiloxane having no functional groups The mailable silicone rubber compound according to claim 1, further containing at least one selected from the group consisting of

6. A mailable silicone rubber compound according to any one of claims 1 to 5, and (F) A curing agent A mailable silicone rubber composition containing

7. The mailable silicone rubber composition according to claim 6, wherein the component (F) contains an addition-curing type curing agent.

8. The mailable silicone rubber composition according to claim 6, wherein the component (F) contains an organic peroxide-curing type curing agent.

9. A silicone rubber cured product obtained by curing the mailable silicone rubber composition according to claim 6 ​

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