JP2018009089A - Silicone rubber sponge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicone rubber sponge which is excellent in productivity, is reduced in compression permanent and has open cells.SOLUTION: A silicon rubber sponge is formed by foaming and curing a silicone rubber composition which contains (A) a base polymer formed of (A1) and (A2), where a ratio of (A1) is 1-30 mass% with respect to the total of (A), and has an alkenyl group content of 0.001-0.1 mmol/g. (A1) is polyorganosiloxane diol having viscosity at 25°C of 1-200 Pas and (A2) polyorganosiloxane having an average degree of polymerization of 3,000-8,000; (B) silica powder having a specific surface area of 100-380 m/g; (C) organosilazane; (D) an inorganic filler having an average particle diameter of 1-30 μm; (E) a heat decomposition type foaming agent; and (F) an organic peroxide crosslinking agent, in each predetermined amount.SELECTED DRAWING: None

Description

  The present invention relates to a silicone rubber sponge, and more particularly to a silicone rubber sponge suitably used for various rolls for OA equipment.

  Silicone rubber is used in various applications by taking advantage of its excellent characteristics. In particular, in a fixing roll in which a thermoplastic resin toner is heat-pressed and fixed on paper in a printer, a silicone rubber having excellent heat resistance, flexibility, and low compression strain is used. Furthermore, the silicone rubber sponge having air bubbles inside has more flexibility than ordinary silicone rubber. By using this for the fixing roll, a wider nip width can be obtained, and the printing quality and speed are improved.

  In recent years, in addition to print quality and speed, there has been a strong demand for energy saving and reduction of chemical substances discharged from printers. Low thermal conductivity and the amount of silicone resin used as a source of volatile chemical substances. The use of fewer silicone rubber sponge rolls is increasing. Usually, a silicone rubber sponge for a roll is manufactured by extruding a millable silicone rubber to which a foaming agent has been added in a tube shape and continuously curing it simultaneously with foaming by heating. According to this method, it is possible to efficiently produce a silicone rubber sponge with stable quality.

  However, since the silicone rubber sponge produced by this method is usually composed of closed cells, the print quality deteriorates, such as dimensional changes due to expansion and contraction of air in the bubbles, and time required for shape recovery. Cause.

  On the other hand, a method of obtaining a silicone rubber sponge having open cells using liquid silicone rubber is known (see, for example, Patent Document 1). In this method, a sponge with relatively small compression set and uniform open cells can be obtained, but the liquid silicone rubber mixed with water is cured while holding water, and then the water is removed by heating. Since a process is required, it is inferior in mass productivity, and enormous energy is required to evaporate water by heating.

  Moreover, the method of obtaining the silicone rubber sponge which has open cells with a millable silicone rubber is known (for example, refer patent document 2). Although the silicone rubber sponge obtained by this method recovers its shape in a short time because the bubbles are reamed, the ingredients formulated for reaming worsen the compression set of the silicone rubber itself. The level of compression set currently required is not reached.

JP 2003-226774 A JP 2006-307008 A

  The present invention has been made from the above viewpoint, and an object of the present invention is to provide a silicone rubber sponge which is excellent in productivity, has a high open cell ratio, and has a reduced compression set.

The present invention provides a silicone rubber sponge obtained by foaming and curing a silicone rubber composition containing the following components (A) to (F).
(A) It consists of the following (A1) and (A2), the ratio of (A1) is 1 to 30% by mass with respect to the whole (A), and the alkenyl group content is 0.001 to 0.1 mmol / 100 parts by weight of the base polymer which is g,
(A1) Polyorganosiloxane diol represented by the following formula (1) having a viscosity of 1 to 200 Pas at 25 ° C. HO [(R ¹ ₂ ) SiO] _n1 [R ¹ R ² SiO] _n2 H (1)
(In formula (1), R ¹ is each independently a monovalent unsubstituted or substituted hydrocarbon group not containing an alkenyl group, R ² represents an alkenyl group. N1 and n2 in formula (1) are And the total number of each repeating unit subjected to random polymerization or block polymerization, n1 is an integer of 200 to 1500, and n2 is an integer of 0 to 50.)
(A2) Polyorganosiloxane represented by the following formula (2) (R ³ ₃ ) SiO — [(R ³ ₂ ) SiO] _m —OSi (R ³ ₃ ) (2)
(In Formula (2), each R ³ independently represents a monovalent unsubstituted or substituted saturated or unsaturated hydrocarbon group not containing a hydroxyl group. M + 2 represents an average degree of polymerization, and the average degree of polymerization is 3000. ˜8000.)
(B) 1 to 30 parts by mass of silica powder having a specific surface area of 100 to 380 m ² / g,
(C) 0.1 to 10 parts by mass of organosilazane,
(D) 10 to 60 parts by mass of an inorganic filler having an average particle size of 1 to 30 μm,
(E) 0.1 to 10 parts by mass of the thermally decomposable foaming agent with respect to 100 parts by mass in total of the components (A) to (D), and (F) the organic peroxide crosslinking agent (A) to (D) 0.1-5 mass parts with respect to 100 mass parts in total of a component

  According to the present invention, it is possible to provide a silicone rubber sponge which is excellent in productivity, has a high open cell ratio, and has a reduced compression set. The silicone rubber sponge of the present invention can be suitably used for various rolls for OA equipment by having such properties.

Embodiments of the present invention will be described below.
The silicone rubber sponge of the present invention is obtained by foaming and curing a silicone rubber composition containing the above-mentioned predetermined amounts of the components (A), (B), (C), (D), (E) and (F). Obtained.

[Silicone rubber composition]
Each component of (A) to (F) contained in each predetermined amount of the silicone rubber composition for producing the silicone rubber sponge of the embodiment will be described below.

((A) component)
The component (A) is a base polymer of a silicone rubber composition comprising a specific polyorganosiloxane diol and a specific polyorganosiloxane not containing a hydroxyl group and containing a predetermined amount of alkenyl groups.

(A) component consists of following (A1) and (A2), the ratio of (A1) is 1-30 mass% with respect to the whole (A), and the ratio of (A2) is 99 with respect to the whole (A). -70 mass%. The component (A) has an alkenyl group content of 0.001 to 0.1 mmol / g.
That is, when (A) component mixes the following (A1) component and (A2) component in the ratio from which the ratio of (A1) component will be 1-30 mass% with respect to the whole (A) component, ( A) It is obtained by mixing so that the alkenyl group content as a whole component is 0.001 to 0.1 mmol / g.

  The component (A1) is a polyorganosiloxane diol represented by the following formula (1) having a viscosity at 25 ° C. of 1 to 200 Pas. Hereinafter, the polyorganosiloxane diol represented by the formula (1) is also referred to as polyorganosiloxane diol (1). In the present specification, “viscosity” refers to a viscosity at 25 ° C. unless otherwise specified.

HO [(R ¹ ₂ ) SiO] _n1 [R ¹ R ² SiO] _n2 H (1)
(In formula (1), R ¹ is each independently a monovalent unsubstituted or substituted hydrocarbon group not containing an alkenyl group, R ² represents an alkenyl group. N1 and n2 in formula (1) are And the total number of each repeating unit subjected to random polymerization or block polymerization, n1 is an integer of 200 to 1500, and n2 is an integer of 0 to 50.)

The above formula (1) does not necessarily mean a block copolymer. That is, n1 indicating the number of polymerized units — (R ¹ ₂ ) SiO— and n2 indicating the number of —R ¹ R ² SiO— do not indicate the number in the block, and each unit is included in the entire molecule. Indicates the total number of each. That is, the polyorganosiloxane diol represented by the formula (1) may be a random copolymer. The siloxane skeleton of the polyorganosiloxane diol (1) is substantially linear since it can synthesize a polymer having a predetermined viscosity with a high degree of polymerization with good control. There may be a plurality of branches therein.

  The component (A1) may be composed of one type of polyorganosiloxane diol (1), or may be composed of two or more types. When it consists of 1 type of polyorganosiloxane diol (1), the viscosity of polyorganosiloxane diol (1) is 1-200 Pas. When the viscosity of the polyorganosiloxane diol (1) is two or more, the viscosity of the polyorganosiloxane diol (1) is not necessarily the above as long as the viscosity is within the above range as the component (A1) obtained by mixing them. Although it does not need to be in the range, preferably, in each polyorganosiloxane diol (1), the viscosity is 1 to 200 Pas.

  When the (A1) component has a viscosity of 1 to 200 Pas, it can be adjusted to 5000 to 40000 Pas, which is a preferable viscosity as the (A) component, when blended with the (A2) component at a predetermined ratio. The viscosity of the polyorganosiloxane diol (1) is preferably 5 to 200 Pas, more preferably 5 to 100 Pas.

  The average degree of polymerization of the polyorganosiloxane diol (1), that is, the average number of siloxane units in the molecule of the polyorganosiloxane diol (1) is represented by the total number (n1 + n2) of n1 and n2 in the formula (1). As long as the viscosity of the polyorganosiloxane diol (1) is in the above range, the average degree of polymerization is not particularly limited. In the polyorganosiloxane diol (1) having a viscosity in the range of 1 to 200 Pas, the average degree of polymerization is about 200 to 1500.

Polyorganosiloxane diol (1) whether having R ² is an alkenyl group in a molecule is arbitrary. That is, as long as the alkenyl group content in the component (A) is 0.001 to 0.1 mmol / g, the polyorganosiloxane diol (1) may have R ² that is an alkenyl group in the molecule. You don't have to.

Note that has alkenyl groups in the polyorganosiloxane diol (1) molecule is that the formula (1) has a -R ¹ R ² SiO- polymerized units, n2 indicating the number of the polymerized units It means 1 or more. The number of n2 depends on the alkenyl group content of the polyorganosiloxane diol (1). The alkenyl group contained in the polyorganosiloxane diol (1) is not present in the terminal O _1/2 -Si—OH unit but is present bonded to the intermediate Si—O _2/2 unit.

Specific examples of the alkenyl group represented by R ² in Formula (1) include a vinyl group, an allyl group, a 3-butenyl group, a 4-pentenyl group, and a 5-hexenyl group. R ² is preferably a vinyl group because the synthesis and handling of the polyorganosiloxane diol (1) is easy and the addition reaction is easily performed. If R ² there are a plurality in the formula (1), a plurality of R ² may be the same or different, but from the viewpoint of easy synthesis, but are preferably the same.

In the formula (1), each R ¹ is a monovalent unsubstituted or substituted hydrocarbon group that does not contain an alkenyl group. Specific examples of R ¹ include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, and hexyl group; aryl groups such as phenyl group, xenyl group, naphthyl group, tolyl group, and xylyl group; Aralkyl groups such as benzyl group and phenethyl group; cycloalkyl groups such as cyclohexyl group; cycloaryanyl groups such as cyclohexenyl group; chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, 3 -Substituted hydrocarbon groups such as cyanopropyl group and 3-methoxypropyl group. In the formula (1), a plurality of R ¹ may be the same or different. In terms of easy synthesis, R ¹ is preferably the same, but different groups may be introduced into a part thereof depending on the physical properties required of the resulting silicone rubber.

Synthesis and handling of the polyorganosiloxane diol (1) is easy, since the excellent heat resistance can be obtained, it is preferably 50% or more of R ¹ is a methyl group, all of R ¹ is a methyl group Is particularly preferred.

For the purpose of imparting oil resistance and / or solvent resistance to the resulting silicone rubber, a part of R ¹ is a 3,3,3-trifluoropropyl group, and the remaining R ¹ is all a methyl group. Combinations can be used. In this case, a combination in which R ^{1 of the} unit surrounded by n1 in the formula (1) is partially a 3,3,3-trifluoropropyl group and the remaining R ¹ is all methyl groups is preferable.

In the case where the component (A) contains the component (A2) having an alkenyl group and the above alkenyl group content of the component (A) can be achieved only by the component (A2), the polyorganosiloxane diol (1) is alkenyl. It does not have to have a group. In that case, the polyorganosiloxane diol (1) is a compound represented by HO [(R ¹ ₂ ) SiO] _n1 H, which does not have a —R ¹ R ² SiO— unit. Hereinafter, polyorganosiloxane diol (1) having an alkenyl group is referred to as polyorganosiloxane diol (11), and polyorganosiloxane diol (1) having no alkenyl group is referred to as polyorganosiloxane diol (12).

  (A1) component consists of 1 or more types chosen from polyorganosiloxane diol (11) and polyorganosiloxane diol (12), and adjusts the kind and content combination with (A2) component to contain together. The alkenyl group content and viscosity as component (A) are adjusted.

  The polyorganosiloxane diol (11) is a polyorganosiloxane diol having n2 of 1 or more in the formula (1). Examples of the polyorganosiloxane diol (11) include polyorganosiloxane diol (11) in which n1 in the formula (1) is 200 to 1500 and n2 is 1 to 50. Moreover, as alkenyl group content in polyorganosiloxanediol (11), 0.001-0.5 mmol / g is mentioned, for example.

  The content of the OH group bonded to the silicon atom in the component (A1), that is, the silanol group (Si—OH group) is preferably 0.01 to 0.15 mmol / g, more preferably 0.02 to 0.1 mmol / g. Preferably, 0.02 to 0.08 mmol / g is more preferable. If the content of the silanol group in the component (A1) is in the above range, it is preferable because the content of the silanol group as the component (A) can be easily adjusted to the range described later.

The component (A2) is a polyorganosiloxane represented by the following formula (2). Hereinafter, the polyorganosiloxane represented by the formula (2) is also referred to as polyorganosiloxane (2).
(R ³ ₃ ) SiO-[(R ³ ₂ ) SiO] _m —OSi (R ³ ₃ ) (2)
(In Formula (2), each R ³ independently represents a monovalent unsubstituted or substituted saturated or unsaturated hydrocarbon group not containing a hydroxyl group. M + 2 represents an average degree of polymerization, and the average degree of polymerization is 3000. ˜8000.)

  In the polyorganosiloxane (2), the siloxane skeleton represented by the formula (2) may have some branches, but a polymer having a high degree of polymerization such as the average degree of polymerization shown above is synthesized with good control. Therefore, it is preferably linear. The polyorganosiloxane (2) may be a homopolymer or a copolymer.

Specific examples of R ³ in Formula (2) include the unsubstituted or substituted hydrocarbon groups exemplified in R ¹ (but not including a hydroxyl group), the alkenyl groups exemplified in R ² , and the like. In addition, although R < ³ > in Formula (2) shows the said monovalent group each independently, not all of R < ³ > is an alkenyl group. The preferred embodiment of R ³ is also the same as the preferred embodiment of the unsubstituted or substituted hydrocarbon group in R ^{1 and} the preferred embodiment of the alkenyl group in R ² .

Polyorganosiloxane (2) may be R ³ is a compound having no alkenyl group may be a compound part of R ³ is an alkenyl group. Hereinafter, polyorganosiloxane (2) having an alkenyl group is referred to as polyorganosiloxane (21), and polyorganosiloxane (2) having no alkenyl group is referred to as polyorganosiloxane (22). The component (A2) may be composed of one type of polyorganosiloxane (2), or may be composed of two or more types.

In the polyorganosiloxane (21), the alkenyl group may be bonded to any silicon atom in the molecule, but since it exhibits excellent reactivity, a part of the alkenyl group is bonded to the silicon atom at the molecular end. It is preferable. That is, it is preferable that a part of R ³ of the terminal M unit represented by —OSi (R ³ ₃ ) is an alkenyl group. In the polyorganosiloxane (21), one R ³ of M unit at both ends is one each. A polyorganosiloxane (21) containing both alkenyl groups, which is an alkenyl group, is preferred. In both terminal alkenyl group-containing polyorganosiloxane (21), the intermediate unit _{^{- [(R 3 2) SiO}} ] - R 3 may be partially alkenyl group for. As described above, the alkenyl group is preferably a vinyl group because the synthesis and handling of the polyorganosiloxane (21) is easy and the addition reaction is easily performed.

In the polyorganosiloxane (21) having alkenyl groups at both ends having an alkenyl group as an intermediate unit, up to about 2.3% of m intermediate units is an intermediate unit in which one of two R ³ is an alkenyl group. be able to. The intermediate unit having an alkenyl group is contained in the polyorganosiloxane (21) containing both alkenyl groups at random or in a block.

Groups other than the alkenyl group in the polyorganosiloxane (21) are easy to synthesize and handle the polyorganosiloxane (21) and have excellent heat resistance. Therefore, 50% or more of R ³ other than the alkenyl group is methyl. It is particularly preferable that all of them are methyl groups. In particular, when heat resistance, cold resistance or radiation resistance is required, phenyl group, and 3,3,3-trifluoropyrrolyl group, etc. should be used appropriately when oil resistance and / or solvent resistance is required. Can do.

  The alkenyl group content in the polyorganosiloxane (21) is used in combination with the type, content, and combination when the polyorganosiloxane (22) component is contained as the component (A2) in addition to the polyorganosiloxane (21). Depending on the type and content of the polyorganosiloxane diol (1), 0.001-0.2 mmol / g is preferable, 0.001-0.1 mmol / g is more preferable, and 0.005-0.05 mmol / g is Further preferred. The alkenyl group content as the component (A2) is also preferably in the same range as described above.

  (A2) The average degree of polymerization of a component is 3000-8000, and 4000-7500 are preferable. Further, the viscosity of the component (A2) is preferably 5,000 to 50,000 Pas, more preferably 10,000 to 40,000 Pas. If the average degree of polymerization of the component (A2) is 3000 to 8000, the viscosity is about 5000 to 50000 Pas, and if the average degree of polymerization is 4000 to 7500 in the preferred range, the viscosity is about 10,000 to 40000 Pas. is there. (A2) By making the viscosity of a component into 5000-50000Pas, when mix | blending with a (A1) component and a predetermined ratio, it is easy to adjust to 5000-40000Pas which is a preferable viscosity as (A) component.

  When the component (A2) is composed of two or more kinds of polyorganosiloxane (2), the average degree of polymerization is not necessarily in the above range in each polyorganosiloxane (2). The average degree of polymerization should just be in the said range as (A2) component which mixed 2 or more types of polyorganosiloxane (2). In addition, when using 2 or more types of polyorganosiloxane (2), it is preferable in each polyorganosiloxane (2) that an average degree of polymerization exists in the said range.

  In the component (A), one or more types are appropriately selected from the polyorganosiloxane (21) having an alkenyl group and the polyorganosiloxane (22) having no alkenyl group, depending on the component (A1) combined with the component (A2). (A2). Since the content of the component (A2) in the component (A) is 99 to 70% by mass, if the polyorganosiloxane (21) is used as the component (A2), the alkenyl group content (0) as the component (A) 0.001 to 0.1 mmol / g) is preferable because it is easy to adjust.

  (A) component consists of such (A1) component and (A2) component, the ratio of (A1) component is 1-30 mass% with respect to the whole (A) component, and the ratio of (A2) is (A) It is 99-70 mass% with respect to the whole. The component (A) has an alkenyl group content of 0.001 to 0.1 mmol / g. Adjustment of the alkenyl group content and viscosity in the component (A) is performed by adjusting the types and blending ratios of the component (A1) and the component (A2). The proportion of the component (A1) and the component (A2) in the component (A) is such that the proportion of the component (A1) is 5 to 25% by mass with respect to the entire component (A), from the viewpoint of giving appropriate workability to the compound. Preferably, 5-15 mass% is more preferable.

  The alkenyl group content in the component (A) is preferably 0.005 to 0.05 mmol / g, and more preferably 0.01 to 0.05 mmol / g. If the alkenyl group content of the component (A) is less than 0.001 mmol / g, the physical strength of the resulting silicone rubber sponge is not sufficient, and if it exceeds 0.1 mmol / g, the resulting silicone rubber sponge becomes brittle, The necessary flexibility cannot be obtained.

  The viscosity of the component (A) at 25 ° C. is preferably 5000 to 40000 Pas, more preferably 10,000 to 30000 Pas. If the viscosity of the component (A) is less than 5000 Pas, the resulting silicone rubber composition may become too sticky and roll workability may deteriorate, and if it exceeds 40,000 Pas, the viscosity of the silicone rubber composition becomes too high. Kneading may be difficult.

  The content of the OH group bonded to the silicon atom in the component (A), that is, the silanol group (Si—OH group) is preferably 0.0002 to 0.045 mmol / g, more preferably 0.0005 to 0.02 mmol / g. Preferably, 0.001 to 0.015 mmol / g is more preferable. (A) The silanol group of component not only suppresses the plasticization return of the silicone composition by (B) component by carrying out condensation reaction with the silanol group which exists in the surface of the silica powder of (B) component. Give moderate viscosity to things. When the silanol group content in the component (A) is within the above range, the silicone rubber composition is not sticky and roll workability is not deteriorated, or the mechanical properties of the cured product are not deteriorated. It can sufficiently condense with silanol groups present on the surface of the component silica powder.

((B) component)
In the silicone rubber composition used in the present invention, the component (B) is a silica powder having a specific surface area of 100 to 380 m ² / g, and the content is 1 to 30 mass relative to 100 parts by mass of the component (A). Part. Hereinafter, unless otherwise specified, the content of each component is represented by parts by mass with respect to 100 parts by mass of the component (A), and may be simply represented as. The component (B) is a component having a function of imparting appropriate fluidity to the silicone rubber composition and imparting excellent mechanical strength to the silicone rubber obtained by curing the composition.

The silica powder of the component (B) has a specific surface area of 100 to 380 m ² / g in order to add to the silicone rubber composition according to the present invention and perform the above function. In addition, in this specification, a specific surface area says the specific surface area by BET method. Hereinafter, the silica powder having a specific surface area of 100 to 380 m ² / g is also referred to as silica powder (B). 100-360 m < ² > / g is preferable and, as for the specific surface area of a silica powder (B), 130-300 m < ² > / g is more preferable. The type of silica is not particularly limited, but precipitated silica, fumed silica (fumed silica), and the like are preferably used. From the viewpoint of reinforcement, fumed silica is preferred.

  In general silicone rubber compositions, since silica powder is used after being surface-treated as necessary, surface-untreated silica powder and surface-treated silica powder are referred to as “silica powder” without distinction. However, in the silicone rubber composition according to the present invention, the silica powder of the component (B) shows only the untreated surface silica powder that has not been subjected to surface treatment.

A commercially available product may be used as the silica powder (B). Commercially available products are fumed silica, all of which are EVONIC trade names, Aerosil 130 (specific surface area: 130 m ² / g), Aerosil 200 (specific surface area: 200 m ² / g), Aerosil 300 (specific surface area: 300 m). ² / g). Silica powder (B) may use 1 type, or may use 2 or more types together.

  Content of (B) component in the silicone rubber composition which concerns on this invention is 1-30 mass parts with respect to 100 mass parts of (A) component, and 1-25 mass parts is preferable. When the content of the component (B) exceeds 30 parts by mass, the viscosity of the silicone rubber composition is remarkably increased, making it difficult to mix the component (B) into the component (A), and conversely, the content is less than 1 part by mass. In addition, the extrusion workability of the silicone rubber composition deteriorates, and the properties such as mechanical strength of the resulting silicone rubber sponge become insufficient.

  The silicone rubber composition used in the present invention is a millable silicone rubber composition that is suitable for extrusion molding and has both good shape stability and low hardness of the extrusion molded product, by blending a smaller amount of silica powder than usual. Is obtained. If such a millable silicone rubber composition is used, a silicone rubber sponge with reduced compression set can be obtained.

((C) component)
The silicone rubber composition used in the present invention contains 0.1 to 10 parts by mass of organosilazane as the component (C).

  (C) component has the effect | action which silylated the silanol group of the surface of the silica powder of (B) component. Thereby, the stability of the silicone compound which contains (E) component and (F) component in addition to the base compound which consists of (A) component, (B) component, (C) component, (D) component, and base compound. Improved. Furthermore, ammonia is by-produced during the silylation, and the ammonia promotes the condensation reaction between the terminal silanol groups of the polyorganosiloxane diol (A1) and the silanol groups on the surface of the silica powder (B), Thereby, the viscosity suitable for roll workability | operativity is provided to a base compound or a silicone rubber composition.

  As the component (C), hexamethyldisilazane, 1-vinylpentamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-dimethyl-1,1,3 Hexaorganodisilazane such as 1,3-tetravinyldisilazane, octaorganotrisilazane such as octamethyltrisilazane, 1,5-divinylhexamethyltrisilazane, and the like. The component (C) may be composed of one of these or may be composed of two or more.

  As the component (C), hexamethyldisilazane and 1,3-divinyl-1,1,3,3-tetramethyldisilazane are preferable. Hexamethyldisilazane, hexamethyldisilazane and 1,3-divinyl-1 1,3,3-tetramethyldisilazane is more preferred.

  (C) Content of a component is 0.1-10 mass parts with respect to 100 mass parts of (A) component organopolysiloxane. The content of the component (C) is preferably 0.3 to 8 parts by mass, more preferably 0.5 to 3 parts by mass. Moreover, 1-40 mass parts is preferable with respect to 100 mass parts of (B) component, and, as for content of (C) component, 5-30 mass parts is more preferable.

  When the content of the component (C) is too small, a sufficient amount of the component (B) for obtaining the mechanical strength cannot be blended, and the storage stability of the blend is deteriorated. When too large, workability | operativity of a formulation deteriorates and it is not preferable economically.

  (C) Component (B) Component (B) Silica powder on the surface of the silanol group on the surface Silyl group by-produced ammonia and low molecular siloxane, such as hexamethyldisiloxane, and further unreacted organosilazane Can be easily removed by heat treatment in the production process described later.

((D) component)
The silicone rubber composition used for this invention contains 10-60 mass parts of inorganic fillers (D) whose average particle diameter is 1-30 micrometers.

  The inorganic filler of component (D) communicates the bubbles formed by the pyrolytic foaming agent of component (E) when a silicone rubber sponge is produced using the silicone rubber composition, that is, between the bubbles. The silicone rubber sponge has a function of increasing the open cell property (communication rate) of the resulting silicone rubber sponge by breaking through the wall of the silicone rubber existing in the container. In order to make the bubbles communicate efficiently, the average particle size of the component (D) is 1 to 30 μm. The average particle size of the component (D) is preferably 2 to 20 μm, and more preferably 2 to 10 μm. In addition, in this specification, the average particle diameter of (D) component means the average primary particle diameter measured by a laser diffraction scattering method.

  The particle shape of the inorganic filler of component (D) is preferably a shape that allows bubbles to communicate by breaking through the walls between the bubbles formed in the silicone rubber by the pyrolytic foaming agent of component (E). Specifically, the particle shape of the inorganic filler is preferably a non-spherical shape such as a plate shape, a needle shape, or a scale shape.

  Specific examples of the inorganic filler (D) include quartz fine powder, diatomaceous earth, mica, metal oxide, graphite, calcium carbonate, and clay having an average particle diameter of 1 to 30 μm. Examples of the metal oxide include aluminum oxide, zinc oxide, magnesium oxide and the like. Among these, quartz fine powder, diatomaceous earth, and the like are preferable from the viewpoint of efficiently communicating bubbles. (D) As a component, it may consist of 1 type of these, and may consist of 2 or more types.

  (D) As an inorganic filler of a component, you may use a commercial item. Commercially available products include Radiolite F (trade name, manufactured by Showa Chemical Industry Co., Ltd., average particle size: 7 μm), which is a baked flux of diatomaceous earth, and Crystallite VX-S (trade name, Tatsumorisha) as quartz fine powder. And an average particle diameter of 4 μm).

  Content of (D) component in the silicone rubber composition which concerns on this invention is 10-60 mass parts with respect to 100 mass parts of (A) component, and 20-60 mass parts is preferable. When the content of the component (D) exceeds 60 parts by mass, it becomes difficult to mix the component (D). Conversely, when the content is less than 10 parts by mass, the resulting silicone rubber sponge has sufficient open cell properties (communication rate). Not.

((E) component)
The (E) component pyrolytic foaming agent is a type of foaming agent in which a molded product containing this is decomposed by heating to generate a gas, thereby forming a foam. The silicone rubber composition according to the present invention contains (E) component pyrolytic foaming agent, so that the silicone rubber crosslinked with the silicone rubber composition can be foamed by heating. can get. During the foaming, the component (D) breaks through the walls of the silicone rubber existing between the bubbles, thereby allowing the bubbles to communicate with each other and improving the open cell property.

  The (E) component pyrolytic foaming agent is not particularly limited as long as it can generate a gas by thermal decomposition, but is known as an organic foaming agent known as a rubber foaming agent incompatible with silicone. Inorganic foaming agents can be used. A foaming agent having a decomposition temperature of 50 to 250 ° C. is preferred. When the decomposition temperature of the pyrolytic foaming agent is less than 50 ° C., handling and storage stability may be a problem, and when it exceeds 250 ° C., productivity may be affected.

  Specific examples of organic foaming agents include nitroso compounds such as N, N′-dimethyl-N, N′-dinitrosoterephthalamide and N, N′-dinitrosopentamethylenetetramine; azodicarbonamide, azobisisobuty Ronitrile, azocyclohexylnitrile, azodiaminobenzene, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 1,1′-azobis (1- Acetoxy-1-phenylethane), azodicarbonamide, barium azodicarboxylate, and other organic azo compounds; benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, P, P′-oxybis (benzenesulfonylhydrazide), diphenylsulfone-3,3 ′ -Disulfonylhydrazide, 4,4'-oxybi (Benzenesulfonyl hydrazide), sulfonyl hydrazide compounds such as p-toluenesulfonyl hydrazine; calcium azide, and 4,4-diphenyl-sulfonyl azide, etc. azide compounds such p- toluenesulfonyl Le azide is

  Specific examples of the inorganic foaming agent include sodium hydrogen carbonate (sodium bicarbonate), sodium carbonate, ammonium hydrogen carbonate, ammonium carbonate, ammonium nitrite and the like. In addition, (E) component may use 1 type or may use 2 or more types together.

  Among these, as the pyrolytic foaming agent of the component (E), an organic foaming agent having a decomposition temperature of 80 to 200 ° C. is preferably used from the viewpoint of productivity and ease of handling. As such an organic foaming agent, specifically, azobisisobutyronitrile (decomposition temperature: 102 ° C.), 1,1′-azobis (1-acetoxy-1-phenylethane) (decomposition temperature: 106 ° C.) Azo compounds such as azodicarbonamide (decomposition temperature: 205 ° C.), N, N′-dinitrosopentamethylenetetramine (decomposition temperature: 203 ° C.), N, N′-dimethyl-N, N′-dinitroso And nitroso compounds such as terephthalamide (decomposition temperature: 105 ° C.).

  In the silicone rubber composition according to the present invention, the content of the pyrolyzable foaming agent of the component (E) is 0.1 to 10 parts by mass with respect to 100 parts by mass in total of the components (A) to (D), Preferably it is 0.5-5 mass parts. When the content of the component (E) is less than 0.1 parts by mass, a sufficient amount of gas is not generated by decomposition, and a silicone rubber sponge cannot be obtained. Further, when the content of the component (E) exceeds 10 parts by mass, the resulting silicone rubber sponge is easily deformed and the quality of the silicone rubber sponge is deteriorated.

((F) component)
The organic peroxide crosslinking agent of component (F) used in the present invention is a silicone rubber composition, in particular, a silicone rubber by crosslinking the base polymer of component (A).

  Specific examples of the organic peroxide crosslinking agent as component (F) include acyl peroxides such as benzoyl peroxide and p-methylbenzoyl peroxide, t-perbutylbenzoate, and 2,5-dimethyl-2,5. Ester esters such as dibenzoylperoxyhexane, 1,1-bis-t-butylperoxy-3,3,5-trimethylcyclohexane, 2,2-bis-t-butylperoxybutane, n- Ketal peroxides such as butyl-4,4-bis-t-butylperoxybutane and n-butyl-4,4-bis-t-butylperoxyvalerate, 2,5-dimethyl-2,5-di- Examples include t-butylperoxyhexane.

  In the present invention, when the organic peroxide crosslinking agent of component (F) is selected to decompose at a temperature higher than the decomposition temperature of the pyrolytic foaming agent of component (E), the open cell ratio of the resulting silicone rubber sponge Is preferable because of high. This is because, in the process of foaming and curing the silicone rubber composition by heating, foaming by the pyrolytic foaming agent of component (E) is started prior to curing by the organic peroxide crosslinking agent of component (F). This is because the component (D) easily breaks through the wall of the silicone rubber between the bubbles in a state where the curing of the silicone rubber has not sufficiently progressed after the start of foaming.

  For the above reasons, it is preferable that the organic peroxide crosslinking agent of component (F) is appropriately selected depending on the decomposition temperature of the thermally decomposable foaming agent of component (E) used. The decomposition temperature of the organic peroxide crosslinking agent of component (F) is equal to or higher than the decomposition temperature of the thermally decomposable foaming agent of component (E) to be combined, and is 20 to 100 ° C. higher than the decomposition temperature from the viewpoint of productivity. Is preferred. As the component (F), one type may be used, or two or more types may be used in combination.

  The content of the organic peroxide crosslinking agent as the component (F) in the composition of the present invention is 0.1 to 5 parts by mass, preferably 100 parts by mass with respect to the total of the components (A) to (D). 0.5 to 2 parts by mass. When the content of the component (F) is less than 0.1 part by mass, the function of the organic peroxide crosslinking agent cannot be performed sufficiently. Moreover, when content of (F) component exceeds 5 mass parts, characteristics, such as heat resistance, will fall in the silicone rubber sponge obtained.

(Optional component)
In addition to the components (A) to (F) described above, the silicone rubber composition used in the present invention contains various additives conventionally used according to various purposes within a range that does not impair the effects of the present invention. You may mix | blend. Examples of such additives include inorganic fillers other than the above components (B) and (D), conductive fillers such as carbon black, pigments, thixotropic agents, and viscosity for improving extrusion workability. Examples include regulators, ultraviolet inhibitors, fungicides, heat resistance improvers, flame retardants, antioxidants, and the like.

  The silicone rubber composition used in the present invention can be prepared by uniformly kneading the components (A) to (F), the processing aid, and other components by a mixing means such as a universal kneader or a kneader.

  Also, for example, (E) component, (F) component involved in foaming and curing, and other components, that is, a mixture of components (A) to (D) are stored separately to produce a silicone rubber sponge. It may be prepared by kneading just before the preparation.

  The silicone rubber sponge of the present invention is obtained by foaming and curing the above silicone rubber composition. More specifically, the silicone rubber sponge of the present invention is produced by molding the above silicone rubber composition and curing and foaming the resulting molded product. Molding includes silicone rubber sponge properties and target shapes such as extrusion (including multi-axis extrusion with other materials), calendar molding, injection molding, transfer molding, press molding, and casting. Any method can be selected accordingly. As the molding method, extrusion molding is preferred because mass production is easy.

  The molded product obtained above is heat-treated at a temperature equal to or higher than the decomposition temperature of the pyrolyzable foaming agent of component (E), and is foamed and cured to form a silicone rubber sponge. The temperature of the heat treatment is not particularly limited as long as it is equal to or higher than the decomposition temperature of the pyrolytic foaming agent of component (E) and the decomposition temperature of the organic peroxide crosslinking agent of component (F). A temperature higher by ˜150 ° C. is preferred. However, when these decomposition temperatures are 150-250 degreeC, it is preferable from a viewpoint of preventing the thermal deterioration of a composition that the upper limit of heat processing temperature shall be 300 degreeC. Moreover, it is preferable that the time of heat processing shall be 0.5 to 12 hours. Examples of the heat treatment method include a heat treatment method using an oven or the like.

  The above heat treatment is performed at a temperature equal to or higher than the decomposition temperature of the thermally decomposable foaming agent of component (E) and lower than the decomposition temperature of the organic peroxide crosslinking agent of component (F). ) Crosslinking may be promoted by heat treatment at a temperature equal to or higher than the decomposition temperature of the component organic peroxide.

  The silicone rubber sponge of the present invention thus obtained is a silicone rubber sponge having excellent productivity, high open cell ratio, and reduced compression set.

For example, the expansion ratio of the silicone rubber sponge of the present invention is preferably 120 to 400%, more preferably 150 to 350%. In addition, the expansion ratio in this specification means the expansion ratio [%] measured by the method for measuring the expansion ratio used in a normal silicone rubber sponge. That is, based on the density (Dsolid (g / cm ³ )) of the base rubber in the following method for measuring the open cell ratio (%), D solid (g / cm ³ ) is used as the density of the obtained silicone rubber sponge. It is a value (Dsolid / Dsponge × 100 (%)) obtained by multiplying the value divided by (Dsponge (g / cm ³ )) by 100%.

  The open cell rate of the silicone rubber sponge of the present invention is, for example, preferably 50% or more, and more preferably 70% or more. Here, the open cell rate is measured by the following method.

[Measurement method of open cell rate (%)]
(Measurement procedure)
1. The density of the silicone rubber sponge (hereinafter also simply referred to as “sponge”), the density of the base rubber, and the dry mass of the sponge are measured. The base rubber refers to an unfoamed silicone rubber obtained by curing a silicone rubber composition (excluding (E) a pyrolytic foaming agent) used for the production of sponge.
2. A specimen cut into a dice with a side of 1 to 2 cm is used, and the test temperature is 23 ° C.
3. The test specimen is submerged in water, decompressed to about 30 mmHg, and left for 3 minutes. After returning to normal pressure and leaving the specimen immersed in water for 3 minutes, the specimen is taken out and wiped off the surface moisture, and the mass of the sponge after water absorption is measured (in-water replacement method).

(Calculation)
The dry mass of the sponge is expressed as Wdry (g),
The weight of the sponge after water absorption is Wwet (g),
The sponge density is D sponge (g / cm ³ ),
The density of the base rubber is Dsolid (g / cm ³ )
In this case, the total volume A of the cell is a value obtained by subtracting the volume of the sponge from the volume of the base rubber, and is obtained by the following formula (a).
Total volume of the cell A = (Wdry / Dsponge) − (Wdry / Dsolid) (a)

Moreover, the volume B of the cell formed into a continuous bubble is calculated | required by the following formula | equation (b), when the density of water is 1 g / cm < ³ >.
The volume B of the open cell B = Wwet-Wdry (b)

Then, open cell ratio (%) is calculated | required by the following formula | equation (c) as a ratio (percentage) of the volume B of the cell formed into the open cell with respect to the total volume A of a cell.
Open cell ratio (%) = 100 × (B / A) (c)

  The silicone rubber sponge of the present invention is useful as a roll, a heat insulating material, a cushioning material, etc. because of its high open cell ratio and low compression set, and in particular, various rolls for copying machines and printers (for example, fixing rolls, It is suitably used for cleaning rolls, conductive charging rolls containing carbon black, developing rolls, toner supply rolls, electrostatic removal rolls, and the like. Among these, the silicone rubber sponge of the present invention is more preferably used for the fixing roll.

  When the silicone rubber sponge is used for the above various rolls, the silicone rubber sponge is not used alone, and usually a silicone rubber sponge is formed into a layer on the outer peripheral surface of a core bar such as a cored bar.

  When a roll is manufactured using the silicone rubber sponge of the present invention, for example, when a silicone rubber sponge layer is formed in a form adhered to a metal surface such as a core metal, a primer is applied to the metal surface in advance. Accordingly, after baking at a temperature of 100 to 300 ° C. for 1 minute or longer, the silicone rubber composition is extruded, wound, filled or injected, and then molded and cured in the same manner as described above. When the roll having the silicone rubber sponge layer obtained in this manner requires heat resistance like a fixing roll, a heat resistance improver such as iron sesquioxide (Bengara) is added to the silicone rubber composition. It is preferable to mix.

  In addition, when a roll is manufactured using a silicone rubber sponge, the silicone rubber sponge is molded into a tube shape, and the silicone rubber sponge tube is arranged in layers so as to cover the outer peripheral surface of a cored bar, etc. It may be a roll.

  When silicone rubber sponge is used as a pressure roll, particularly in a dry toner fixing part, if necessary, an insulating or conductive silicone rubber adhesive is applied to the surface of the roll having the obtained silicone rubber sponge as a surface layer. After coating, it is preferable to provide a resin layer or rubber layer such as a fluororesin layer or a fluororubber layer as the outermost layer.

When the roll using the silicone rubber sponge is a conductive roll such as a charging roll, the silicone rubber composition is mixed with carbon black, and if necessary, a carbon balloon is further blended to obtain a volume resistivity of the silicone rubber sponge. Can be in the range of 10 ¹ to 10 ¹⁰ Ω · cm. These rolls may polish the surface or may be used as they are.

  In addition, when using a roll having a conductive silicone rubber sponge layer in contact with the photosensitive drum, in order to prevent contamination due to the transfer of low molecular weight siloxane to the photosensitive drum, the surface of the roll other than silicone is used. In other words, it is preferable to form a rubber film such as NBR or a resinous film such as a fluororesin.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  In the following examples and comparative examples, the following polyorganosiloxane was used as the component (A1) and the component (A2). The siloxane unit is indicated by the following symbols.

M unit: (CH ₃ ) ₃ SiO _1/2 −
M ^Vi unit: (CH ₃ ) ₂ (CH ₂ ═CH) SiO _1/2 −
M ^OH unit: (CH ₃ ) ₂ (OH) SiO _1/2 −
D unit: — (CH ₃ ) ₂ SiO—
^DH unit: — (CH ₃ ) HSiO—
D ^Vi unit: — (CH ₃ ) (CH ₂ ═CH) SiO—

  As the polyorganosiloxane diol of the component (A1) and the polyorganosiloxane of the component (A2), the structural formula, viscosity [Pas], average polymerization degree, silanol group content [mmol / g] shown in the following Table 1, Each linear polyorganosiloxane polymer having an alkenyl group content [mmol / g] was used.

Further, in Examples and Comparative Examples, (B) component, (C) component, (D) component, (E) component, (F) component, etc., respectively, as silica powder, organosilazane, inorganic filler, heat Decomposable foaming agents, organic peroxide crosslinking agents, colorants, and the like were used.
(B) component; fumed silica B1; Aerosil 300 (trade name, manufactured by EVONIC), specific surface area of 300 m ² / g
B2: Aerosil 200 (trade name, manufactured by EVONIC), specific surface area of 200 m ² / g
B3: Aerosil 130 (trade name, manufactured by EVONIC), specific surface area of 130 m ² / g
Bcf: Aerosil 130 treated with dimethyldichlorosilane (silica surface carbon content: 1.0 mass%)

Component (C): organosilazane C1; hexamethyldisilazane C2; 1,3-divinyl-1,1,3,3-tetramethyldisilazane

Component (D); inorganic filler D1; radiolite F (trade name, manufactured by Showa Chemical Industry Co., Ltd.), diatomaceous earth flux fired product, average particle size: 7 μm
D2: Crystallite VX-S (trade name, manufactured by Tatsumori), quartz fine powder, average particle size 4 μm

(E) Thermal decomposition type foaming agent E1; azobisisobutyronitrile E2; OT _AZO- 15 (trade name, manufactured by Otsuka Chemical Co., Ltd.) 1,1′-azobis (1-acetoxy-1-phenylethane)

(F) Organic peroxide crosslinking agent F1; 2,5-dimethyl-2,5-di-t-butylperoxyhexane (decomposition temperature: 179 ° C.)
F2: p-methylbenzoyl peroxide (decomposition temperature: 128 ° C.)

(Coloring agent); Bengala

(Process oil)
PO1; M ^OH D ₂₀ M ^OH , viscosity 0.07 Pas
_{^{PO2; M OH D 10 M OMe}} ; viscosity 0.01Pas, Me represents a methyl group

[Manufacture of base compounds 1-9]
Base compounds 1 to 9 for the silicone rubber composition having the composition shown in Table 2 were produced as follows. That is, the component (A1), the component (A2) and the component (B) were mixed with a kneader for 30 minutes. (C) component was mix | blended with this with the kneader, adding continuously over 20 to 60 minutes, and it knead | mixed at 50 degreeC for 1 hour. Furthermore, after adding (D) component and kneading for 30 minutes with two rolls, it heat-kneaded at 150 degreeC for 2 hours, this was cooled to 40 degrees C or less, and the base compound was produced.

  However, when the component (B2) is contained as the component (B), after the component (C) is added and kneaded in the above, the component B2 is added and kneaded in a kneader for 30 minutes, and then the component (D) is added. . Moreover, when it did not contain (D) component, the base compound was manufactured except the mixing process in the above.

[Manufacture of base compounds 10, 11]
After mixing all the components of the composition shown in Table 3 uniformly with a kneader, the mixture was heated and kneaded at 150 ° C. for 2 hours, and cooled to 40 ° C. or lower to prepare a base compound. In Tables 2 and 3, the blank indicates the blending amount “0”.

(Evaluation of base compound)
The obtained base compound was evaluated for plasticity and extrusion processability by the following methods. Moreover, the mechanical property was measured about the hardened | cured material which added the (F) organic peroxide crosslinking agent to the base compound by the following method, shape | molded it in the sheet form, and was hardened | cured. The results are shown in the lower column of Tables 2 and 3. In addition, although the extrusion processability was evaluated with the base compound, the extrusion processability of the silicone rubber compositions used in Examples 1 to 8 and Comparative Examples 1 to 7 corresponds to the extrusion processability of the base compound used in each example. To do.

(Plasticity)
According to JISK6249, the plasticity of the base compound was measured using an equilibrium plate plasticity meter (Williams Plastometer) at a re-kneading time of 5 minutes, a standing time of 5 minutes, and a pressing time of 5 minutes.

(Extrudability)
The base compound was extruded horizontally at a speed of 0.5 m / min using a φ50 mm extruder equipped with a breaker plate having 21 φ6 mm holes, and the surface condition of the extruded compound was visually evaluated. .

  When the obtained extrusion-molded product was visually recognized as having a smooth surface free from defects such as shark skin, the extrudability was considered good. The case where the obtained extrusion-molded product was visually recognized as a sharkskin or the like with a smooth surface was regarded as defective.

(Mechanical properties of cured product)
(1) Preparation of test piece 0.5 parts by mass of F1 is added to 100 parts by mass of the base compound obtained above, press-molded into a sheet at 170 ° C. for 10 minutes, and 200 ° C. for 4 hours. Post-curing was performed to obtain a sheet-like cured product (thickness 2 mm). From the sheet-like cured product, dumbbell-shaped No. 2 was prepared as a test piece for measuring mechanical properties (hardness, tensile strength, elongation) based on JIS K6249. In addition, a test piece for compression set (Φ29 mm × 12.5 mm) was produced in the same manner as described above except that a press mold having a predetermined molding size was used.

(2) Measurement of mechanical properties Using a test piece for measuring mechanical properties, the density of the cured product was measured. Further, according to JIS K6249, hardness (Type A), tensile strength [MPa], and elongation [%] were measured. The compression set [%] was measured at 180 ° C. for 22 hours at 25% compression using a compression set test piece in accordance with JISK6249.

[Examples 1-8, Comparative Examples 1-7]
In 100 parts by mass of the base compounds 1 to 11 obtained above, with two rolls, the components (E), (F), and the colorant were added in the amounts shown in Tables 4 and 5 and mixed. 8. Silicone rubber compositions used for Comparative Examples 1-7 were prepared. The obtained silicone rubber composition was crushed to a thickness of about 5 mm using a two-roll, and foamed and cured by heating in an oven at 200 ° C. for 4 hours. Examples 1 to 8 and Comparative Examples 1 to 7 A silicone rubber sponge was prepared.

(Evaluation)
The silicone rubber sponge obtained in each example was evaluated for the following characteristics, and the results are shown in the lower columns of Tables 4 and 5. In Tables 4 and 5, the blank indicates the compounding amount “0” and “−” indicates that the compound is not implemented.
(1) Foaming ratio [%]
The density of the obtained silicone rubber sponge was measured by the underwater substitution method in the same manner as described above. The density of unfoamed silicone rubber measured in the same manner in advance was calculated as the foaming ratio [%] by multiplying the value obtained by dividing by the density of the silicone rubber sponge by 100%.

(2) Sponge hardness (Type E)
Sponge hardness (Type E) was measured according to JIS K6253.
(3) Open cell ratio [%]
The open cell ratio [%] was measured by the above method.

(4) Compression set [%]
The obtained silicone rubber sponge was measured as an appropriately sized test piece at 180 ° C. for 22 hours at 25% compression according to JISK6249.

(5) Foamed state The foamed state of the surface and cross section of the silicone rubber sponge was visually evaluated according to the following criteria.
Good: The surface is smooth and the cells are uniform.
Abnormal foaming: Some cells were abnormally large, and abnormalities such as distortion were observed overall.

  As can be seen from Tables 4 and 5, the silicone rubber sponges of the examples have a good foaming state, a high open cell ratio of 70% or more, and a low compression set.

  The silicone rubber sponge of the present invention is a silicone rubber sponge having open cells with excellent productivity and reduced compression set. The silicone rubber sponge of the present invention is useful as a roll, a heat insulating material, a cushioning material, and the like. In particular, various rolls for copying machines and printers (for example, a fixing roll, a cleaning roll, a conductive charging roll containing carbon black) , Developing roll, toner supply roll, electrostatic removal roll, etc.).

Claims (5)

(A) It consists of the following (A1) and (A2), the ratio of (A1) is 1 to 30% by mass with respect to the whole (A), and the alkenyl group content is 0.001 to 0.1 mmol / 100 parts by weight of the base polymer which is g,
(A1) Polyorganosiloxane diol represented by the following formula (1) having a viscosity of 1 to 200 Pas at 25 ° C. HO [(R ¹ ₂ ) SiO] _n1 [R ¹ R ² SiO] _n2 H (1)
(In formula (1), R ¹ is each independently a monovalent unsubstituted or substituted hydrocarbon group not containing an alkenyl group, R ² represents an alkenyl group. N1 and n2 in formula (1) are And the total number of each repeating unit subjected to random polymerization or block polymerization, n1 is an integer of 200 to 1500, and n2 is an integer of 0 to 50.)
(A2) Polyorganosiloxane represented by the following formula (2) (R ³ ₃ ) SiO — [(R ³ ₂ ) SiO] _m —OSi (R ³ ₃ ) (2)
(In Formula (2), each R ³ independently represents a monovalent unsubstituted or substituted saturated or unsaturated hydrocarbon group not containing a hydroxyl group. M + 2 represents an average degree of polymerization, and the average degree of polymerization is 3000. ˜8000.)
(B) 1 to 30 parts by mass of silica powder having a specific surface area of 100 to 380 m ² / g,
(C) 0.1 to 10 parts by mass of organosilazane,
(D) 10 to 60 parts by mass of an inorganic filler having an average particle size of 1 to 30 μm,
(E) 0.1 to 10 parts by mass of the thermally decomposable foaming agent with respect to 100 parts by mass in total of the components (A) to (D), and (F) the organic peroxide crosslinking agent (A) to (D) The silicone rubber sponge which foamed and hardened the silicone rubber composition containing 0.1-5 mass parts with respect to a total of 100 mass parts of a component.   The silicone rubber sponge according to claim 1, wherein the component (D) is at least one selected from quartz fine powder, diatomaceous earth, mica, metal oxide, graphite, calcium carbonate, and clay.   The silicone rubber sponge according to claim 1 or 2, wherein the extruded product of the silicone rubber composition is foamed and cured.   The silicone rubber sponge according to any one of claims 1 to 3, wherein the expansion ratio is 120 to 400%, and the open cell ratio is 50% or more.   The silicone rubber sponge according to any one of claims 1 to 4, which is used in any of a fixing roll, a cleaning roll, a charging roll, a developing roll, a toner supply roll and an electrostatic removal roll provided in a copying machine or a printer.