JP2019026765A - Method for producing silicone sponge - Google Patents

Abstract

To provide a method for producing a silicone sponge capable of easily obtaining a fine silicone sponge by an injection molding method.SOLUTION: A method for producing a silicone sponge includes a step of preparing a silicone sponge composition which contains (A) thermally expandable resin fine particles and (B) an addition-curable silicone composition, where when an expansion start temperature of the component (A) is T(°C) and a crosslinking rate T10 at 130°C of the component (B) is t(sec), a value of T/tis 1.9 to 2.9, and a step of foaming the prepared silicone sponge composition in a metal mold 6 by an injection molding machine 100. In the method for producing the silicone sponge, 0.1 to 10 pts.mass of the thermally expandable resin fine particles having Ta of the component (A) of 80-130°C is used based on 100 pts.mass of the component (B).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing an in-mold foamed silicone sponge.

  Silicone (rubber) sponge is a sponge having excellent physical properties such as heat resistance, cold resistance, electrical insulation, flame retardancy, compression set, and the like specific to silicone rubber. Silicone rubber sponges having such characteristics are used for OA equipment, automobiles, building materials, and the like to promote low thermal conductivity and light weight.

  Silicone rubber sponges are produced by various methods from their molded and foamed forms, depending on their use. As one of them, there is a method of obtaining a sponge by blending thermally expandable resin fine particles (thermally expandable microcapsules) encapsulated with a solvent or an already expanded resin hollow filler into a polymer (Patent Documents 1 to 4). The above-described thermally expandable resin fine particles, which are encapsulated in an unexpanded state in the organic resin shell while the solvent is in a liquid state, are those in which the solvent in the organic resin shell expands at a high temperature. And the particle diameter after expansion becomes the size of the sponge cell.

  On the other hand, with regard to the blending of the thermally expandable resin fine particles, there is no concern of capsule breakage during the production of the silicone rubber composition, but the resin fine particles must be expanded and the rubber cured at the same time during molding. Therefore, since it is difficult to adjust the curing timing, HAV atmospheric pressure hot air crosslinking (HAV: Hot Air Vulcanization, hereinafter abbreviated as HAV crosslinking) is particularly used (Patent Documents 3 and 4).

  HAV sponge molded product is a suitable molding method for producing lump-like and plate-like products, but is not suitable for applications that require dimensional accuracy such as O-rings, connector packings, and component housings (three-dimensional types). is there. In such applications, there is a great merit in the use of mold molding (injection molding) or the like, and in particular, a highly efficient production method using an injection molding system of an addition curable liquid silicone rubber composition is desirable.

  However, it is difficult to mold a silicone composition in which expanded resin hollow filler and thermally expandable resin fine particles are mixed in in-mold foaming, and in particular, the expanded resin hollow filler compounded composition absorbs the injection pressure by the hollow filler. Therefore, the problem that the material does not enter the mold occurs. As a solution to such a problem, proposals have been made to make the composition have a very low viscosity and to avoid it by a method using a groove in the mold (Patent Document 4).

  However, the technique of Patent Document 4 is a technique in which an already expanded resin hollow filler is blended into a low-viscosity uncrosslinked silicone composition, and is not a technique in which a silicone composition blended with thermally expandable resin fine particles is foamed in a mold, It is impossible to injection mold, and a large amount of reinforcing silica cannot be added, and a sponge having excellent rubber strength cannot be produced. In addition, there is no description regarding a sponge injection molding method using an addition-curable silicone rubber or a corresponding method in which a material is injected into a mold at a high pressure.

  In addition, regarding the thermally expandable resin fine particle blended composition, it is possible to inject the resin into the mold, but since the resin expands in the injection pressure and the heated mold, the pressure in the mold is very high. Therefore, there arises a problem that a foam cannot be obtained.

JP-A-5-209080 JP-A-8-012888 JP 2000-143986 A Japanese Patent Laid-Open No. 9-137063

  In view of the above circumstances, an object of the present invention is to provide a method for producing a silicone sponge, which can easily obtain a fine silicone sponge by an injection molding method.

In order to solve the above problems, in the present invention,
The following (A) and (B) component (A) thermally expandable resin fine particles (B) addition-curable silicone composition, the expansion start temperature of the component (A) is T _a (° C.), the component (B) A step of preparing a silicone sponge composition having a value of T _a / t _b of 1.9 to 2.9 when the crosslinking rate T10 at 130 ° C. is t _b (seconds), and the prepared silicone sponge And a step of foaming the composition in a mold by injection molding.

  If it is the manufacturing method of silicone sponge like this invention, it is possible to obtain a fine silicone sponge easily.

Further, as the component (A), 0.1 to 10 parts by mass of thermally expandable resin fine particles having _a T _a (° C.) of 80 to 130 ° C. is used with respect to 100 parts by mass of the component (B). Is preferred.

  If the production method using such thermally expandable resin fine particles as the component (A), the produced silicone sponge does not foam, the sponge density increases, the rubber elasticity after crosslinking deteriorates, the surface There is no fear of an increase in tack, and there is no need to slow down the crosslinking rate of the silicone composition.

Moreover, as said (B) component, the following (B1)-(B5) component (B1) 1 molecule of 2 or more alkenyl groups, and a liquid organopolysiloxane at 25 degreeC: 100 mass part (B2) 1 molecule Organopolysiloxane having two or more silicon atom-bonded hydrogen atoms: The molar ratio of silicon atom-bonded hydrogen atoms in component (B2) to silicon-bonded alkenyl groups in component (B1) is 0.5: 1 to Amount of 10: 1 (B3) Reinforcing silica powder: 1.0-60 parts by mass (B4) Platinum-based catalyst: 0.1-1,000 ppm in terms of platinum-based metal relative to component (B1) Amount (B5) Reaction control agent: 1.9 ≦ T _a / t _b ≦ 2.9.
It is preferable to use an addition-curable silicone composition containing

  With such a production method using the component (B), it is possible to easily obtain a finer silicone sponge.

  The component (A) includes an organic resin outer shell and a solvent encapsulated in the outer shell, and the outer shell includes vinylidene chloride, acrylonitrile, methacrylonitrile, acrylate ester, and methacrylate ester. It is preferable to use thermally expandable resin fine particles having an outer shell made of a polymer of a selected monomer or two or more kinds of copolymers among the monomers.

  If it is a manufacturing method using (A) component which has such an outer shell, even if it knead | mixes with the mixer attached to a molding machine in the state where the viscosity of the silicone sponge composition for injection molding is high, it is preferable. It is possible to obtain a silicone sponge having an expansion ratio.

  Further, as the component (A), it is preferable to use thermally expandable resin fine particles that expand into hollow particles having an average particle diameter of 20 to 500 μm after crosslinking.

  With such a production method using the component (A), it is possible to easily obtain a silicone sponge having a desired sponge magnification.

  The silicone sponge composition is preferably molded by filling an injection mold with an amount corresponding to 40 to 90% by volume of the mold volume.

  With such a manufacturing method, even if the composition expands and becomes a sponge, there is not enough material, and the molded product may be short-circuited or chipped. There is no fear that the density of the rear sponge will be 1.0 or more.

  As described above, according to the method for producing a silicone sponge of the present invention, a fine silicone sponge can be easily produced by injection molding. The manufactured silicone sponge is composed of sponge gaskets and cushioning materials for seats, transport sponges for automobiles, railway vehicles, airplanes, ships, etc., space and architecture, seat surface sponges, sound deadening sponges and flame retardant sponges, and the sponges. It is useful for producing an electrophotographic image forming member having at least one layer, a paper feed roll, a pressure pad, and the like.

It is a figure which shows the one aspect | mode of the injection molding machine used for the manufacturing method of the silicone sponge of this invention. It is a figure which shows another aspect of the injection molding machine used for the manufacturing method of the silicone sponge of this invention. 2 is a photograph showing a state of a sponge cell of Example 1. FIG.

  As described above, development of a method for producing a silicone sponge that can easily obtain a fine silicone sponge by an injection molding method has been demanded.

  As a result of intensive studies to achieve the above object, the present inventors have blended thermosetting liquid silicone sponge composition with thermally expandable resin fine particles that thermally expand at a specific temperature, and thereby thermosetting liquid silicone. It was found that a highly foamed sponge can be obtained by injection molding by adjusting the curing start timing of the sponge composition with a certain rule to the expansion timing of the thermally expandable resin fine particles. The present inventors have found that a sponge can be molded and have completed the present invention.

That is, the present invention
The following (A) and (B) component (A) thermally expandable resin fine particles (B) addition-curable silicone composition, the expansion start temperature of the component (A) is T _a (° C.), the component (B) A step of preparing a silicone sponge composition having a value of T _a / t _b of 1.9 to 2.9 when the crosslinking rate T10 at 130 ° C. is t _b (seconds), and the prepared silicone sponge And a step of foaming the composition in a mold by injection molding.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.
The present invention comprises (A) a step of preparing a silicone sponge composition for injection molding comprising thermally expandable resin fine particles and (B) a silicone composition, and the prepared silicone sponge composition for injection molding using an injection molding machine. And a step of producing a silicone sponge by foaming in a mold.

  In the injection mold in the method for producing a silicone sponge of the present invention, the events in the time series of the temperature rise of the silicone sponge composition for injection molding will be described. First, the components (A) and (B) were mixed. The silicone sponge composition for injection molding is injected into a heated injection mold in a volume smaller than the mold volume, and the silicone sponge composition for injection molding is warmed. When the thermally expandable resin fine particle (A) is heated to the expansion start temperature, it foams in the silicone sponge composition for injection molding and forms an expanded resin hollow body corresponding to the silicone sponge cell. Thereafter, curing of the silicone sponge composition for injection molding is started to obtain a silicone sponge as a sponge cured product.

<Preparation process of silicone sponge composition for injection molding>
[(A) component: thermally expandable resin fine particles]
In the method for producing a silicone sponge of the present invention, it is essential to use the component (A) which is a thermally expandable resin fine particle. The component (A) is usually composed of an organic resin outer shell and a solvent contained in the outer shell. The component (A) is such that the outer shell is softened by heat and the solvent is vaporized and expanded almost simultaneously, so that the outer shell expands in a balloon shape (the thermally expandable resin fine particles in which the outer shell expands in a balloon shape are In this way, a spherical sponge cell can be formed inside the silicone sponge. As the outer shell of the component (A), it is desirable that the outer shell exhibits high hardness and strength at normal temperature and does not break even when kneaded with a mixer attached to the molding machine in a state where the viscosity of the silicone sponge composition is high.

  Examples of the organic resin forming the outer shell include a polymer of a monomer selected from vinylidene chloride, acrylonitrile, methacrylonitrile, acrylic acid ester, and methacrylic acid ester, or a copolymer of two or more of the above monomers. Of these, acrylonitrile and methacrylonitrile are preferred.

  Examples of the solvent encapsulated in the outer shell include solvents such as linear or branched aliphatic hydrocarbons having 3 to 8 carbon atoms or linear alicyclic hydrocarbons having 3 to 8 carbon atoms ( And aliphatic hydrocarbons such as isobutane, isopentane, n-hexane, and cyclohexane), and preferably isobutane and isopentane.

  (A) The manufacturing method of a component can use a well-known thing, For example, it can manufacture by the method etc. of Japanese Patent Publication No.42-26524.

  The present invention uses unexpanded thermally expandable resin fine particles as the component (A), and an expanded resin hollow body that has already expanded is unsuitable for the present invention. This is because the outer shell of the expanded resin hollow body is thin, and if the viscosity of the silicone composition is high, the outer shell made of resin will be destroyed during kneading or transfer through an injection molding machine, and the solvent inside will leak out. For this reason, a predetermined expansion ratio cannot be obtained, and abnormal foaming due to the solvent occurs.

  The sponge cell formed using the component (A) is different from the sponge cell using the organic foaming agent, by adjusting the softening point of the outer shell polymer of the capsule to be used, the boiling point of the solvent, The maximum inflated diameter can be arbitrarily adjusted, and the volume in the balloon state after inflating can be controlled by the amount of solvent contained and the particle diameter before foaming. Therefore, it is possible to prevent bubble breakage and cracking due to excessive foaming or outgassing, and it is possible to easily obtain a silicone rubber sponge.

The expansion start temperature T _a (° C.) of the component (A) is preferably 80 to 130 ° C., more preferably 85 to 120 ° C., and still more preferably 85 to 110 ° C.

If the expansion starting temperature T _a is 80 ° C. or more, bubbling timings becomes appropriate, an outer shell of heat-expandable resin particles are destroyed before cross-linking of the silicone composition, or not foamed, sponge density high This is preferable because there is no fear of Further, if the expansion starting temperature T _a is at 130 ° C. or less, there is no need to slow down to match it to the crosslinking rate of the silicone composition, the rubber elasticity is deteriorated after crosslinking, increase surface tackiness of the produced silicone sponge It is preferable because there is no fear of becoming.

Incidentally, (A) expansion starting temperature T _a of the component, after the sample before expansion that takes into glass bottles and 5 minutes hot air heating in an oven at a predetermined temperature, allowed to cool for 30 minutes at ambient temperature, the size of the expansion after the particles This was confirmed with an optical microscope, and the temperature was set so that the particle radius after expansion was larger by 10% or more than the particle radius before expansion.

  The average particle size of the component (A) used in the present invention is preferably 10 to 70 μm in an unexpanded state. If it is 10 micrometers or more, since the quantity of the solvent component to include becomes sufficient and desired sponge foaming magnification can be obtained, it is preferable. If it is 70 micrometers or less, since there is no possibility that a sponge cell turns into a rough silicone sponge, it is preferable. In addition, in this invention, an average particle diameter shall point out the value measured as a weight average value using the particle size distribution measuring apparatus by a laser beam diffraction method etc.

  Further, the component (A) used in the present invention is preferably thermally expandable resin fine particles that expand into hollow particles (expanded resin hollow bodies) having an average particle diameter of 20 to 500 μm after crosslinking.

  It is preferable that the compounding quantity of (A) component is 0.1-10 mass parts with respect to 100 mass parts of silicone composition of (B) component. More preferably, it is selected in the range of 0.5 to 6.0 parts by mass, and more preferably 1.0 to 5.0 parts by mass. If the component (A) is 0.1 part by mass or more, a sufficient foaming ratio can be obtained. If the component is 10 parts by mass or less, rubber elasticity is obtained, and the molded product is damaged by deformation such as compression. In addition to being difficult, the resin component remaining in the rubber is reduced, and the mechanical strength is not greatly reduced.

[(B) component: addition-curable silicone composition]
The addition curable silicone composition as component (B) will be described. This (B) component can become the main ingredient of the silicone sponge manufactured by the manufacturing method of the silicone sponge of this invention. The component (B) preferably has a viscosity enabling injection molding. Specifically, the viscosity at 25 ° C. measured by a method using a rotational viscometer described in JIS K 7117-1: 1999 is 50 to 10,000 Pa. · It is preferably s, more preferably 60 to 8,000 Pa · s, still more preferably 100 to 5,000 Pa · s.

The (B) component addition-curable silicone composition comprises the following (B1) to (B5) components (B1) organopolysiloxane having at least two alkenyl groups in one molecule: 100 parts by mass (B2) in one molecule Organopolysiloxane having at least two silicon-bonded hydrogen atoms: The molar ratio of silicon-bonded hydrogen atoms in component (B2) to silicon-bonded alkenyl groups in component (B1) is 0.5: 1 to 10: 1 (B3) reinforcing silica powder: 1.0-60 parts by mass
(B4) Platinum-based catalyst: an amount of 0.1 to 1,000 ppm in terms of platinum-based metal relative to the component (B1) (B5) reaction control agent: 1.9 ≦ T _a / t _b ≦ 2.9 It is preferable that the addition-curable silicone composition contains an amount of Hereinafter, the components (B1) to (B5) will be described in detail.

((B1) component: organopolysiloxane having an alkenyl group)
The organopolysiloxane containing an alkenyl group bonded to two or more silicon atoms in one molecule, which is the component (B1), is usually a known organopolymer that is used as a base polymer of an addition-curable silicone rubber composition. Polysiloxane, which is liquid at 25 ° C.

  In the present invention, the viscosity of the component (B1) is a value at 25 ° C. measured by a method using a rotational viscometer described in JIS K 7117-1: 1999, and is in a range of 1 to 1,000 Pa · s. Preferably, it is 5 to 500 Pa · s, more preferably 10 to 300 Pa · s. If the viscosity of the component (B1) is 1 Pa · S or more, the mechanical strength of the silicone sponge foam obtained by curing the composition is sufficient, which may cause a practical problem as a foam molded product. Absent. Moreover, if the viscosity is 1,000 Pa · s or less, the viscosity of the composition becomes too high, and it is difficult to transfer by the material supply pump of the injection molding machine, and the supply time is not increased. The property is good.

The component (B1) is usually an organopolysiloxane represented by the following average composition formula.
R _a SiO _{(4-a) / 2} (I)

  In the above formula, R is independently an alkyl group such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, hexyl group, cyclohexyl group, vinyl group, allyl group, propenyl group, Examples thereof include alkenyl groups such as isopropenyl group and butenyl group, aryl groups such as phenyl group, tolyl group and xylyl group, aralkyl groups such as benzyl group, and the like, preferably methyl group and vinyl group. The plurality of substituents may be different or the same, but it is necessary that the molecule contains two or more alkenyl groups (usually 2 to 50, preferably 2 to 20). . This alkenyl group may be bonded to a silicon atom at the end of the molecular chain, may be bonded to a silicon atom in the middle of the molecular chain (non-terminal of the molecular chain), or may be bonded to both of these, It preferably contains at least an alkenyl group bonded to silicon atoms at both ends of the molecular chain. a is a number in the range of 1.9 to 2.4, preferably 1.95 to 2.05.

The organopolysiloxane represented by the formula (I) may be linear or RSiO _3/2 units (R is as described above) or branched containing SiO _4/2 units. Usually, the main chain consists of repeating diorganosiloxane units R ₂ SiO _2/2 (R is as described above), and both ends of the molecular chain are triorganosiloxy groups R ₃ SiO _1/2 (R is as described above) It is preferably a linear diorganopolysiloxane blocked with. The substituent bonded to the silicon atom may be basically any of the above, but the alkenyl group is preferably a vinyl group, and the other substituents are preferably a methyl group or a phenyl group. .

  The degree of polymerization of the organopolysiloxane represented by the formula (I) is preferably 100 to 3,000, more preferably 150 to 2,000, and still more preferably 200 to 1,500. . In the present invention, the degree of polymerization can be determined as the number average degree of polymerization in terms of polystyrene in gel permeation chromatography (GPC) analysis using toluene as a developing solvent measured under the following measurement conditions.

・ Measurement condition developing solvent: THF (tetrahydrofuran)
Flow rate: 0.350 mL / min
Detector: Differential refractive index detector (RI)
Column: TSKgel SuperMultipore HZ-H
(Both manufactured by TOSOH)
Column temperature: 40 ° C

((B2) component: organopolysiloxane having silicon-bonded hydrogen atoms)
The organopolysiloxane having a silicon atom-bonded hydrogen atom as the component (B2) has a hydrogen atom (hydrosilyl group) bonded to two or more silicon atoms in one molecule, and the component (B1) in the component (B1) It is a component that acts as a crosslinking agent in an addition (hydrosilylation) reaction with an alkenyl group.

  As the component (B2), there is no particular limitation on the molecular structure, and various kinds of conventionally produced, for example, linear, cyclic, branched, and three-dimensional network structures can be used. It is necessary to contain 2 or more (usually 2 to 200) in the molecule, preferably 3 or more (for example, 3 to 150), more preferably 4 to 100.

  The group bonded to the silicon atom other than the hydrosilyl group (B2) is a substituted or unsubstituted monovalent hydrocarbon group similar to the monovalent hydrocarbon group R in the average composition formula (I), but an alkenyl group, etc. Those not containing an aliphatic unsaturated bond are preferred, and a methyl group or a phenyl group is particularly preferred.

  Component (B2) preferably has 2 to 300 silicon atoms (or degree of polymerization) in one molecule, more preferably 3 to 200, still more preferably 4 to 100. .

As the component (B2), for example, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyltetracyclosiloxane, 1,3,5,7,8-pentamethylpentacyclo Siloxane oligomers such as siloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, tris (dimethylhydrogensiloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane; Blocked methyl hydrogen polysiloxane, molecular chain both ends trimethylsiloxy group blocked dimethyl siloxane / methyl hydrogen siloxane copolymer, molecular chain both ends silanol group blocked methyl hydrogen polysiloxane, molecular chain both ends Nol group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, molecular chain both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, molecular chain both ends dimethylhydrogensiloxy group-blocked methylhydrogenpolysiloxane, molecular chain both ends dimethylhydro Gensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, etc .; consisting of R ₂ (H) SiO _1/2 units and SiO _4/2 units, optionally R ₃ SiO _1/2 units, R ₂ SiO _{2 / 2} units, R (H) SiO _2/2 units, (H) SiO _3/2 units or RSiO _3/2 units (wherein R is the same as R in the above-mentioned average composition formula (I)) Are preferably free of aliphatic unsaturated bonds such as alkenyl groups). It can be exemplified corn resin or the like.

  The blending amount of the component (B2) is such that the molar ratio of the amount of the hydrosilyl group of the component and the amount of the alkenyl group of the component (B1) is hydrosilyl group: alkenyl group = 0.5: 1 to 10: 1. It is sufficient that the amount is within a range of 0.8: 1 to 5: 1. If the blending amount of the component (B2) is not less than the above lower limit value, the crosslinking density is not lowered, and there is no possibility of adversely affecting the heat resistance of the foam molded product. Further, if the blending amount of the component (B2) is not more than the above upper limit value, the hydrosilyl group will not be excessive, and there is no fear that the rubber hardness will be lowered by not forming the interpolymer network structure by crosslinking, and the component (B2) The problem of abnormal foaming due to the intramolecular dehydrogenation reaction does not occur, and the heat resistance is not adversely affected.

((B3) component: reinforcing silica powder)
The reinforcing silica powder of component (B3) is a substance necessary for improving the processability, mechanical strength, etc. of the silicone sponge composition, and preferably has a specific surface area of 50 m ² / g or more. The thing of -400m < ² > / g is more preferable.

  Examples of the component (B3) include fumed silica (dry silica) and precipitated silica (wet silica). Of these, fumed silica (dry silica) is preferable. Moreover, you may use what hydrophobized these surfaces with organopolysiloxane, organopolysilazane, chlorosilane, alkoxysilane, etc. As the component (B3), these silicas may be used alone or in combination of two or more. In addition, the addition amount of (B3) component is 1.0-60 mass parts with respect to 100 mass parts of (B1) component, It is preferable that it is 5.0-50 mass parts, It is 10-40 mass parts. More preferably. If the amount of component (B3) added is 1.0 part by mass or more, a sufficient reinforcing effect is obtained, and if it is 60 parts by mass or less, the processability of the silicone sponge is good, and the physical properties of the resulting silicone sponge The viscosity of the silicone sponge composition before crosslinking does not become too high, and the density of the sponge can be easily reduced.

((B4) component: platinum-based catalyst)
The (B4) component platinum-based catalyst is a component in which the (B1) component and the (B2) component are hydrosilylated to form a silethylene bond (addition reaction). For example, platinum black, second platinum chloride, chloroplatinic acid And a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and olefins, a platinum-based catalyst such as platinum bisacetoacetate, a white metal metal catalyst such as a palladium-based catalyst and a rhodium-based catalyst.

  The blending amount of the component (B4) can be a catalytic amount, and is usually 0.1 to 1,000 ppm, preferably 1 to 500 ppm as a platinum group metal (in terms of mass) with respect to the component (B1). This is the amount.

((B5) component: reaction control agent)
The reaction control agent for component (B5) is not particularly limited as long as it is a compound having an effect of adjusting the reaction rate of the curing reaction with respect to component (B4), and conventionally known compounds may be used alone or in combination. Can do. Of these, acetylene alcohols are preferred. Specific examples of acetylene alcohols include 1-ethynyl-1-cyclohexanol, 3-methyl-1-butyn-3-ol, 3,7,11-trimethyl-1-dodecin-3-ol, 3- Methyl-1-dodecin-3-ol, 3-methyl-1-pentadecin-3-ol, 3-methyl-1-tridecin-3-ol, 3-ethyl-6-ethyl-1-nonin-3-ol, etc. Is mentioned. In addition, phosphorus-containing compounds such as triphenylphosphine, compounds containing nitrogen atoms such as tributylamine, tetramethylethylenediamine, and benzotriazole, compounds containing sulfur atoms, hydroperoxy compounds, maleic acid derivatives, etc. may be used. it can. Further, the reaction control agent may be encapsulated with a resin or resin that melts at a constant temperature.

The blending amount of the component (B5) needs to be adjusted to the optimum amount for each reaction control agent to be used because the degree of the action of adjusting the reaction rate of the curing reaction of the reaction control agent varies depending on the chemical structure. is there. Particularly in the present invention must adjust the crosslinking rate of the expansion starting temperature T _a by component (B) of the silicone composition of the component (A).

Specifically, the value indicated by T _a / t _b at the expansion start temperature T _a (° C.) of the component (A) and the rate t _b (second) of the crosslinking rate T10 at 130 ° C. of the component (B). It is necessary to adjust the foaming and cross-linking balance so that becomes 1.9 to 2.9. Incidentally, the crosslinking rate T10 _{(t b)} used a value measured under the following conditions.

・ Measurement method of cross-linking speed T10 (t _b (seconds)) JIS K 6300- using a rubber vulcanization tester (trade name “moving die rheometer MDR”, manufactured by Alpha Technologies, closed torsional vibration type conical die method). 2: Based on 2001, a crosslinking property was measured by performing a crosslinking property test at 130 ° C. for 2 minutes. Calculate the minimum value (ML) (unit: dN · m) of the torque before crosslinking of the silicone composition and the maximum value (MH) (unit: dN · m) of the torque after crosslinking, and T10 (unit: seconds) ) And T90 (unit: second). T10 and T90 are required for the torque to increase by 10% from the minimum torque (ML) when “maximum torque (MH) −minimum torque (ML)” is 100%. It is a display meaning the time and the time required to increase by 90%.

[Other ingredients]
The silicone sponge composition prepared by the method for producing a silicone sponge of the present invention may contain a semi-reinforcing or non-reinforcing filler other than the reinforcing silica (B3) in addition to the above-described components. it can. Examples of the semi-reinforcing or non-reinforcing filler include pulverized silica, diatomaceous earth, metal carbonate, clay, talc, mica, and titanium oxide. Further, heat-resistant additives, flame retardants, antioxidants, processing aids and the like conventionally used in the silicone rubber composition can be blended. Furthermore, a conductive sponge can be obtained by adding conductive carbon, conductive metal oxide fine particles (conductive zinc white, titanium oxide, tin antimony-based fine particles) or the like.

  The silicone sponge composition can be further imparted with thermal conductivity as required. Sponges can be produced by adding powders that have been added to silicone, such as pulverized quartz, zinc oxide, alumina, aluminum oxide, metal silicon powder, silicon carbide, and fibrous carbon fiber as the thermally conductive material.

  Moreover, you may add dispersing agents, such as alkoxysilane, diphenylsilanediol, carbon functional silane, a both-ends silanol blockade low molecular siloxane, etc.

<Injection molding process>
The silicone sponge composition is characterized by being molded by a liquid injection molding method. Although the manufacturing method of the silicone sponge by liquid injection molding is demonstrated with reference to drawings, this invention is not limited to these.

[Injection molding method of one-component addition-curable liquid silicone sponge composition]
FIG. 1 shows an embodiment of an injection molding machine used in the method for producing a silicone sponge of the present invention. The component (A), the component (B), and other components as necessary are mixed in one liquid to prepare an unfoamed silicone sponge composition (mixture), and then the injection molding machine shown in FIG. 100 can be molded. The silicone sponge composition placed in the tank 1 is supplied to the cylinder portion 4 through the material supply line 3 by the metering discharge pump 2, transferred to the metering portion by the screw 5, and simultaneously kneaded by the rotation of the screw 5. The injection amount is measured by a measuring unit in the cylinder unit 4 or a measuring device separately connected to the cylinder unit 4, and injected from the cylinder unit 4 to the mold 6.

[Method of Injection Molding of Two-Component Addition-Curable Liquid Silicone Sponge Composition]
FIG. 2 shows another aspect of the injection molding machine used in the method for producing a silicone sponge of the present invention. The addition curable silicone sponge composition used in the method for producing a silicone sponge according to the present invention is divided into two liquids, liquid A and liquid B, in order to prevent transportation and stability during storage and curing, and is shown in FIG. You may shape | mold with the injection molding machine 101. FIG. The composition divided into the two liquids is merged by the regulator 7 through the material supply lines 3a and 3b at a predetermined ratio from the tanks 1a and 1b by the metering discharge pumps 2a and 2b, and the pressure is adjusted. The mixed material is further mixed by a static mixer 9 through a line 8. The mixed material is supplied to the cylinder part 4 of the injection molding machine through the line 10, transferred to the metering part by the screw 5, and simultaneously kneaded by the rotation of the screw 5. After the measurement, it is injected from the cylinder part 4 into the mold 6.

  The composition injected into the mold 6 is preferably 40 to 90% by volume of the capacity of the mold 6, more preferably 50 to 80% by volume, and further preferably 60 to 70% by volume. preferable. Casting in an amount of 40% by volume or more is preferable because there is no risk of shorting or chipping in the molded product due to insufficient material even if the composition becomes a sponge after expansion, and if it is 90% by volume or less, It is preferable that the thermally expandable resin fine particles cannot be foamed by the injection pressure and the density of the sponge after curing does not become 1.0 or more.

  As the curing conditions for the composition, the composition is usually injected into the mold 6 in a state where the temperature in the mold 6 is preheated to a curing temperature range of less than 200 ° C., preferably 120 ° C. to 180 ° C. It is preferable to cure in a time of 1 second to 60 minutes.

  If the temperature in the mold 6 is 120 ° C. or higher, the component (A) is easy to foam and the silicone sponge composition does not become insufficiently cured. If the temperature in the mold 6 is 180 ° C. or lower, the foaming of the component (A) is not suppressed by the curing of the silicone sponge composition, and it is preferable to make a sponge easily.

  After molding by the injection molding machines 100 and 101, the silicone sponge may be subjected to secondary heat treatment for the purpose of stabilizing rubber physical properties. The heat treatment temperature and time at this time are not particularly limited, but are preferably 100 to 250 ° C. and 30 minutes to 5 hours.

  The silicone sponge obtained according to the present invention has a density of 0.20 to 0.99, preferably 0.30 to 0.90, more preferably 0.40 to 0.80.

  With such a method for producing a silicone sponge of the present invention, a fine silicone sponge can be easily produced by injection molding.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

開始温度：マイクロカプセルが膨張を開始する温度（Ｔ_ａ）
終了温度：マイクロカプセルが最大膨張径となる温度
最大膨張倍率：膨張前の平均粒子体積に対する最大膨張体積の倍率 [Component (A) (thermally expandable resin fine particles): C1 to C4]
As the component (A), the following thermally expandable resin fine particles C1 to C4 were used. The expansion start temperature T _a (° C.) and other properties are shown in Table 1 below.

Starting temperature: temperature at which the microcapsule starts to expand (T _a )
End temperature: Temperature at which the microcapsule has the maximum expansion diameter Maximum expansion ratio: Ratio of the maximum expansion volume to the average particle volume before expansion

[Production of Component (B) (Addition-Curable Silicone Composition)]
(Synthesis Example 1: 1 liquid addition curable liquid silicone rubber composition 1)
Both ends are blocked with dimethylvinylsiloxy groups, the degree of polymerization is 700, the viscosity at 25 ° C. is 30 Pa · s, 90 parts by mass of dimethylpolysiloxane with a vinyl content of 0.00004 mol%, both ends are blocked with trimethylsiloxy groups The specific surface area is 300 m ² / g in 10 parts by mass of dimethylpolysiloxane having a degree of polymerization of 150 having a methylvinylsiloxy group in the side chain, a viscosity at 25 ° C. of 0.5 Pa · s, and a vinyl content of 0.0014 mol%. 40 parts by mass of fumed silica (Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.), 8 parts by mass of hexamethyldisilazane, and 2.0 parts by mass of water were mixed at room temperature for 30 minutes with a biaxial tangential kneader (simplex blade). Thereafter, the temperature was raised to 150 ° C., and stirring was continued for 3 hours, followed by cooling to obtain a silicone rubber base.

  After mixing 0.10 parts by mass of platinum catalyst (Pt concentration 1%) for 15 minutes with 100 parts by mass of the obtained silicone rubber base, 0.12 parts by mass of ethynylcyclohexanol was similarly kneaded for 15 minutes as a reaction control agent. . Next, 5 parts by mass of methylhydrogenpolysiloxane having hydrosilyl groups at both ends and side chains (polymerization degree 40, hydrosilyl group amount 0.007 mol / g) as a cross-linking agent is added, and stirring is continued for 15 minutes. An addition-curable liquid silicone rubber composition 1 was obtained. The viscosity of the one-component addition-curable liquid silicone rubber composition 1 was 1,000 Pa · s.

  A one-component addition curable liquid silicone rubber composition 1 is set in a rubber vulcanization tester (trade name “Moving Dye Rheometer MDR”, manufactured by Alpha Technologies Co., Ltd.) with 4.5 g of the composition, and JIS K 6300-2: 2001. The crosslinkability test was performed under the conditions of 130 ° C. for 2 minutes and T10 and T90 were measured, and T10 = 43 (seconds) and T90 = 105 (seconds).

(Synthesis Example 2: 1-component addition-curable liquid silicone rubber composition 2)
One solution by the same production method as the one-component addition-curable liquid silicone rubber composition 1 except that the platinum catalyst (Pt concentration: 1%) was 0.20 parts by mass and the reaction control agent was 0.07 parts by mass of ethynylcyclohexanol. An addition-curable liquid silicone rubber composition 2 was obtained.

  The viscosity of the one-component addition-curable liquid silicone rubber composition 2 was 1,000 Pa · s. Further, when the crosslinking rate of the one-component addition-curable liquid silicone rubber composition 2 was measured in the same manner as in Synthesis Example 1, T10 = 22 (seconds) and T90 = 55 (seconds).

(Synthesis Example 3: Two-component addition-curable liquid silicone rubber composition 3A, 3B)
Both ends are blocked with dimethylvinylsiloxy groups, the degree of polymerization is 700, the viscosity at 25 ° C. is 30 Pa · s, 80 parts by mass of dimethylpolysiloxane with a vinyl content of 0.00005 mol%, both ends are blocked with trimethylsiloxy groups The specific surface area is 300 m ² / g in 20 parts by mass of dimethylpolysiloxane having a degree of polymerization of 150 having a methylvinylsiloxy group in the side chain, a viscosity at 25 ° C. of 0.5 Pa · s, and a vinyl content of 0.0014 mol%. 25 parts by mass of fumed silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.), 3 parts by mass of hexamethyldisilazane, and 1.0 part by mass of water were mixed at room temperature for 30 minutes with a biaxial tangential method kneader (simplex blade). Thereafter, the temperature was raised to 150 ° C., and stirring was continued for 3 hours, followed by cooling to obtain a silicone rubber base. 100 parts by mass of the obtained silicone rubber base was mixed with 0.4 parts by mass of a platinum catalyst (Pt concentration 1%) using a planetary mixer (straight blade) to obtain a two-component addition-curable liquid silicone rubber composition 3A. .

  Similarly, 18.0 parts by mass of 100 parts by mass of the obtained silicone rubber base with methylhydrogenpolysiloxane having a hydrosilyl group at both ends and side chains as a crosslinking agent (polymerization degree 40, hydrosilyl group amount 0.007 mol / g). Part, 0.22 parts by mass of ethynylcyclohexanol was added as a reaction control agent, and stirring was continued for 15 minutes to obtain a two-component addition-curable liquid silicone rubber composition 3B.

  The viscosity of the two-component addition curable liquid silicone rubber composition 3A was 580 Pa · s, and the viscosity of the two-component addition curable liquid silicone rubber composition 3B was 500 Pa · s.

  Further, the crosslinking rate of the two-component addition-curable liquid silicone rubber composition 3A, 3B was determined. Two-component addition-curable liquid silicone rubber compositions 3A and 3B were weighed in 50 g portions into 200 cc high-density polyethylene containers and mixed and stirred by hand for 5 minutes using a metal spatula with a total length of 15 cm. Next, a sample subjected to defoaming for 3 minutes at a reduced pressure of −0.06 MPa using a vacuum pump was tested for crosslinkability with a rubber vulcanization tester in the same manner as the one-component addition-curable liquid silicone rubber composition 1. And T10 and T90 were measured and T10 = 30 (seconds) and T90 = 65 (seconds).

(Synthesis Example 4: Two-component addition-curable liquid silicone rubber composition 4A, 4B)
2 by the same production method as the two-component addition-curable liquid silicone rubber composition 3 except that 0.30 parts by mass of platinum catalyst (Pt concentration 1%) and 0.25 parts by mass of ethynylcyclohexanol were used as the reaction control agent. Liquid addition curable liquid silicone rubber compositions 4A and 4B were obtained.

  The viscosity of the two-component addition curable liquid silicone rubber composition 4A was 580 Pa · s, and the viscosity of the two-component addition curable liquid silicone rubber composition 4B was 500 Pa · s.

  Further, when the crosslinking speed was measured for the two-component addition curable liquid silicone rubber compositions 4A and 4B in the same manner as the two-component addition curable liquid silicone rubber compositions 3A and 3B, T10 = 48 (seconds) and T90 = 112 ( Second).

[Example 1]
50 parts by mass of the two-component addition-curable liquid silicone rubber composition 3A was added to 1.5 parts by mass of the thermally expandable resin fine particles (C1) as the component (A) (unexpanded average particle diameter 20 μm, started to expand at 70 ° C. and 110 The mixture was stirred and mixed under reduced pressure for 15 minutes with a planetary mixer (straight blade) to obtain a silicone sponge composition (Ex. 1-A). Similarly, 1.5 parts by mass of C1 was added to and mixed with the two-component addition-curable liquid silicone rubber composition 3B to obtain a silicone sponge composition (Ex. 1-B).

  The silicone sponge compositions (Ex. 1-A) and (Ex. 1-B) were set in the tanks 1a and 1b of the injection molding machine 101 shown in FIG. 2 and prepared for injection molding. The silicone sponge compositions (Ex. 1-A) and (Ex. 1-B) were transferred by the metering discharge pumps 2a and 2b and the material supply lines 3a and 3b, and mixed by the regulator 7 and the static mixer 9. After the mixed composition was supplied to the cylinder part 4, 80% of the volume was metered and injected into the cavity of the mold 6 at an injection pressure of 100 MPa to produce a low specific gravity silicone sponge molded product. The mold temperature was 150 ° C., and the molding cycle was 80 seconds / time. The mold shape was dumbbell No. 2 conforming to the tensile test of JIS K 6249: 2003, and a sheet-like molded product having a thickness of 2 mm was obtained. The finished silicone sponge molded product (dumbbell sheet) is allowed to stand at room temperature for 8 hours, and then the density (JIS K 6249: 2003 standard), Asker C hardness (JIS S 6050: 2008 standard), average cell diameter (cross section measured with an electron microscope) ), The expansion rate of the molded product was measured, and the results are shown in Table 2. Moreover, the electron micrograph which shows the state of a sponge cell was shown in FIG.

  The expansion ratio of the molded product was calculated as a percentage by measuring the finest details (constricted portion) of the dumbbell with a caliper and dividing the size of the obtained silicone sponge molded product against the mold size.

[Example 2]
50 parts by mass of the two-component addition curable liquid silicone rubber composition 4A was added to 1.5 parts by mass of the thermally expandable resin fine particles (C3) as the component (A) (unexpanded average particle diameter of 60 μm, started to expand at 120 ° C., and 160 The mixture was stirred and mixed under reduced pressure for 15 minutes with a planetary mixer to obtain a silicone sponge composition (Ex. 2-A). Similarly, 1.5 parts by mass of (C3) was added to and mixed with the two-component addition-curable liquid silicone rubber composition 4B to obtain a silicone sponge composition (Ex. 2-B).

  Silicone sponge compositions (Ex. 2-A) and (Ex. 2-B) are set in the tanks 1 a and 1 b of the injection molding machine 101 shown in FIG. 2, respectively, and a volume of 70% is placed in the cavity of the mold 6. A silicone sponge molded product having a low specific gravity was obtained in the same manner as in Example 1 except that molding was performed by metering injection.

  The obtained silicone sponge molded product was allowed to stand at room temperature for 8 hours, and then various properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[Example 3]
As the component (A), 3.0 parts by mass of thermally expandable resin fine particles (C2) (unexpanded average particle diameter of 30 μm, starting to expand at 80 ° C. and expanding to 90 times volume at 120 ° C.) was used. Except for this, silicone sponge compositions (Ex. 3-A) and (Ex. 3-B) were obtained in the same manner as Example 1.

  Silicone sponge compositions (Ex. 3-A) and (Ex. 3-B) are set in the tanks 1 a and 1 b of the injection molding machine 101 shown in FIG. 2, respectively, and a volume of 60% is placed in the cavity of the mold 6. A silicone sponge molded product having a low specific gravity was obtained in the same manner as in Example 1 except that molding was performed by metering and injection.

  The obtained silicone sponge molded product was allowed to stand at room temperature for 8 hours, and then various properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[Example 4]
To 100 parts by mass of the one-component addition-curable liquid silicone rubber composition 1, 4.0 parts by mass of thermally expandable resin fine particles (C2) as the component (A) are mixed by stirring for 15 minutes using a planetary mixer. A composition (Act 4) was obtained. Set the silicone sponge composition (actual 4) as it is in the tank 1 of the one-liquid injection molding machine 100 shown in FIG. 1, and weigh and inject 50% of the volume into the cavity of the mold 6 Injection molding was performed under the same conditions as in Example 1 to obtain a silicone sponge molded product having a low specific gravity.

  The obtained silicone sponge molded product was allowed to stand at room temperature for 8 hours, and then various properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[Example 5]
A low specific gravity was obtained in the same manner as in Example 4 except that the silicone sponge composition having the same contents as in Example 4 was molded by metering 85% of the volume into the cavity of the mold 6 by the injection molding machine 100. A silicone sponge molded product was obtained. The silicone sponge molded product (rubber sponge sheet) of Example 5 expanded greatly as soon as the mold was opened, and became a sponge molded product that was clearly larger than the mold size even after standing at room temperature for 8 hours. The obtained silicone sponge molded product was allowed to stand at room temperature for 8 hours, and various properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[Example 6]
A low specific gravity was obtained in the same manner as in Example 3 except that a silicone sponge composition having the same contents as in Example 3 was molded by injection-molding a volume of 40% into the cavity of the mold 6 with an injection molding machine 101. A silicone sponge molded product was obtained. The obtained silicone sponge molded product was allowed to stand at room temperature for 8 hours, and various properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[Example 7]
50 parts by mass of the two-component addition curable liquid silicone rubber composition 4A, 1.5 parts by mass of thermally expandable resin fine particles (C4) as the component (A) (unexpanded average particle diameter of 40 μm, expansion starts at 140 ° C. and 180 The mixture was stirred and mixed under reduced pressure for 15 minutes with a planetary mixer to obtain a silicone sponge composition (Ex. 7-A). Similarly, 1.5 parts by mass of (C4) was added to and mixed with the two-component addition-curable liquid silicone rubber composition 4B to obtain a silicone sponge composition (Ex. 7-B).

  Except that the compositions (Act 7-A) and (Act 7-B) are set in the tanks 1a and 1b of the injection molding machine 101, and 70% volume is metered and injected into the cavity of the mold 6. Obtained a silicone sponge molded article having a low specific gravity in the same manner as in Example 1. The rubber sponge sheet of Example 7 expanded greatly as soon as the mold was opened, and became a sponge molded product that was clearly larger than the mold size even after standing at room temperature for 8 hours. The obtained low-specific gravity silicone sponge molded product was allowed to stand at room temperature for 8 hours, and various properties were measured in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 1]
(A) The one-component addition-curable liquid silicone rubber composition 2 that does not contain the component is set as it is in the tank 1 of the one-component injection molding machine 100, and a volume of 100% is measured in the cavity of the mold 6. Injection molding was performed under the same conditions as in Example 1. The obtained sheet was solid, and after standing at room temperature for 8 hours, various characteristics were measured in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 2]
To 100 parts by mass of the one-component addition-curable liquid silicone rubber composition 2, 5.0 parts by mass of thermally expandable resin fine particles (C1) were mixed under reduced pressure with a planetary mixer for 15 minutes to obtain a silicone sponge composition (ratio 2). ) A silicone sponge composition (ratio 2) is set in the tank 1 of an injection molding machine 100 for one liquid, and 70% volume is metered into the cavity of the mold 6 and injected under the same conditions as in Example 5. Molded. When the mold 6 was opened, the silicone sponge composition of Comparative Example 2 (ratio 2) was hardly foamed, and the sponge molded product was not spread in the mold (short state). The obtained molded product was allowed to stand at room temperature for 8 hours, and various characteristics other than the expansion rate of the molded product were measured in the same manner as in Example 1. Table 2 shows the results.

[Comparative Example 3]
To 100 parts by mass of the one-component addition-curable liquid silicone rubber composition 1, 3.0 parts by mass of thermally expandable resin fine particles (C1) were mixed under reduced pressure with a planetary mixer for 15 minutes to obtain a silicone sponge composition (ratio 3). ) The silicone sponge composition (ratio 3) is set as it is in the tank 1 of the injection molding machine 100 for one liquid, and a volume of 70% is metered and injected into the cavity of the mold 6, and the same as in the first embodiment. Injection molding was performed under the conditions. The silicone sponge composition of Comparative Example 3 had a large warp after taking out the mold, and part of the sponge cell was broken and solidified. The obtained molded product was allowed to stand at room temperature for 8 hours, and various characteristics were measured in the same manner as in Example 1. The results are shown in Table 2.

[Comparative Example 4]
50 parts by mass of the two-component addition curable liquid silicone rubber composition 3A was mixed with 2.0 parts by mass of thermally expandable resin fine particles (C3) under reduced pressure with a planetary mixer for 15 minutes to obtain a silicone sponge composition (ratio 4). -A) was obtained. Similarly, 2.0 parts by mass of (C3) was added to and mixed with the two-component addition-curable liquid silicone rubber composition 3B to obtain a silicone sponge composition (ratio 4-B). Silicone sponge compositions (ratio 4-A) and (ratio 4-B) are set in the tanks 1a and 1b of the injection molding machine 101, respectively, and 85% volume is metered and injected into the cavity of the mold 6. Except that, a silicone sponge molded article having a low specific gravity was obtained in the same manner as in Example 1. The obtained molded product was allowed to stand at room temperature for 8 hours, and various characteristics other than the expansion rate of the molded product were measured in the same manner as in Example 1. Table 2 shows the results.

  As shown in Table 2, in Examples 1 to 7 using the method for producing a silicone sponge of the present invention, a fine silicone sponge having good conditions such as hardness and density could be easily produced. On the other hand, in Comparative Examples 1 to 4 in which the method for producing a silicone sponge of the present invention was not used, the molded product was in a solid state or had a sheet warp, and a fine silicone sponge could not be produced.

  From the above, according to the present invention, it is possible to easily obtain a fine silicone sponge by an injection molding method.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

100, 101 ... injection molding machine, 1, 1a, 1b ... tank,
2, 2a, 2b ... metering discharge pumps, 3, 3a, 3b, 8, 10 ... material supply lines,
4 ... Cylinder part, 5 ... Screw, 6 ... Mold, 7 ... Regulator,
9: Static mixer.

Claims (6)

The following (A) and (B) component (A) thermally expandable resin fine particles (B) addition-curable silicone composition, the expansion start temperature of the component (A) is T _a (° C.), the component (B) A step of preparing a silicone sponge composition having a value of T _a / t _b of 1.9 to 2.9 when the crosslinking rate T10 at 130 ° C. is t _b (seconds), and the prepared silicone sponge And a step of foaming the composition in a mold by injection molding. As the component (A), 0.1 to 10 parts by mass of thermally expandable resin fine particles having _a T _a (° C.) of 80 to 130 ° C. is used with respect to 100 parts by mass of the component (B). The method for producing a silicone sponge according to claim 1. As the component (B), the following (B1) to (B5) component (B1): an organopolysiloxane having two or more alkenyl groups in one molecule and liquid at 25 ° C .: 100 parts by mass (B2) in one molecule Organopolysiloxane having two or more silicon-bonded hydrogen atoms: The molar ratio of silicon-bonded hydrogen atoms in component (B2) to silicon-bonded alkenyl groups in component (B1) is 0.5: 1 to 10: (B3) Reinforcing silica powder: 1.0 to 60 parts by mass (B4) Platinum-based catalyst: An amount that is 0.1 to 1,000 ppm in terms of platinum-based metal amount (B1) component ( B5) Reaction control agent: 1.9 ≦ T _a / t _b ≦ 2.9.
The method for producing a silicone sponge according to claim 1 or 2, wherein an addition-curable silicone composition containing the above is used.   The component (A) comprises an organic resin outer shell and a solvent encapsulated in the outer shell, and the outer shell is selected from vinylidene chloride, acrylonitrile, methacrylonitrile, acrylate ester and methacrylate ester. The silicone according to any one of claims 1 to 3, wherein thermally expandable resin fine particles having an outer shell made of a monomer polymer or a copolymer of two or more of the monomers are used. Sponge manufacturing method.   The silicone sponge according to any one of claims 1 to 4, wherein as the component (A), thermally expandable resin fine particles that expand into hollow particles having an average particle size of 20 to 500 µm after crosslinking are used. Manufacturing method.   The silicone sponge composition is molded by filling an injection mold with an amount corresponding to 40 to 90% by volume of the mold volume. 2. A method for producing a silicone sponge according to item 1.

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