JP6083372B2 - Method for producing addition-curable liquid silicone rubber composition - Google Patents

Description

  In the present invention, when 1-ethynyl-1-cyclohexanol is used as the control agent, the control agent is surely dispersed in the silicone rubber composition without solvent, without crystallization of the control agent. The present invention relates to a method for producing an addition-curable low-viscosity liquid silicone rubber composition for stabilization, and a silicone rubber molding comprising a cured product of the addition-curable liquid silicone rubber composition produced by the production method. In particular, since the present invention does not use a hydrocarbon solvent used as a dispersion aid for the control agent, it is easy to reduce the composition of VOC (volatile organic compounds), such as electrophotographic printers and copiers. Fix the problem of hydrocarbon volatiles that are harmful to the human body when used in sealed spaces such as fixing rolls / fixing belts, paper feed rolls, developing rolls, structural members, adhesives, and automotive airbag materials in image forming devices. It is particularly useful for preventing.

  Certain silicone rubber compositions generally contain a platinum catalyst inhibitor that retards the hydrosilylation addition reaction at room temperature, and many platinum catalyst inhibitors are known, particularly US Pat. No. 3,445,420. An acetylenic compound described in (issued on May 20, 1969, Patent Document 1) is preferably used. In particular, 1-ethynyl-1-cyclohexanol is widely used in the silicone industry because it has a high control effect and is inexpensive.

  However, since 1-ethynyl-1-cyclohexanol has a melting point of 30 to 33 ° C., when the silicone rubber composition is added to and mixed with the silicone rubber composition, the silicone rubber composition exceeds the melting point of 1-ethynyl-1-cyclohexanol. If the temperature is not controlled, solidification occurs, and there is a disadvantage that good dispersion, that is, good control effect cannot be obtained. Especially in cold regions where the silicone raw material itself is cold, or even in warming regions, the above phenomenon may be significant and problematic in winter.

  For this reason, the silicone raw material is preheated and mixed, the composition is heated using a manufacturing apparatus equipped with a warming jacket, or stirring heat is generated with a mixer or the like before adding the control agent. Although there is a method of adding a control agent while maintaining a temperature of 33 ° C. or higher, in the case of a low-viscosity liquid silicone raw material, it is difficult to increase the temperature by stirring heat, and heating by a manufacturing apparatus equipped with a heater or steam is possible. It is common.

  Moreover, as a method of eliminating coagulation at the time of addition of 1-ethynyl-1-cyclohexanol, it is dissolved in an organic solvent such as toluene, xylene, isoparaffin or the like to prevent crystallization of the control agent and added to the silicone rubber composition In recent years, there has been a demand for low VOC measures for silicone materials in general due to environmental concerns and concerns about the impact on the human body. As represented by the European BAM standards, silicone rubber There is an increasing demand for users to avoid mixing organic solvents in the composition.

  On the other hand, as for the control agent having a high melting point, as shown in Japanese Patent No. 2665881 (Patent Document 2), by using a long-chain acetylene alcohol, normal temperature volatility is suppressed, and generation of gel and improvement in workability are achieved. Examples include a target method and a method that enables stable production of a peelable cured film of a thin film by using acetylene alcohol having different boiling points in combination as in Japanese Patent No. 3098946 (Patent Document 3). However, these are not described as measures for solving the problems related to coagulation and poor dispersion of acetylene alcohol at low temperature, and are not useful for silicone rubber compositions having low viscosity. I can't. In particular, there is no description at all regarding the measures for achieving a low VOC composition.

  Also, cetylene alcohol having a long chain length and a low melting point is difficult and expensive to synthesize, and since the acetylene alcohol unit is lower than the molecular weight, a large amount of control agent is added to obtain the necessary control effect. Therefore, there is a disadvantage that the cost of the control agent is increased, and 1-ethynyl-1-cyclohexanol, which is inexpensive and has a high control effect, is easily dispersible in particular in a low-viscosity silicone rubber composition without coagulation. Was strongly sought after.

U.S. Pat. No. 3,445,420 Japanese Patent No. 2665881 Japanese Patent No. 3098946

  The present invention has been made in view of the above circumstances, and in the method for producing a low-viscosity silicone rubber composition, for example, 1-ethynyl-1-cyclohexanol was used as a control agent in an extremely cold production place such as below freezing point. Even if the control agent does not crystallize, the control agent is reliably dispersed in the silicone rubber composition without solvent, and has a stable control effect, and has a low VOC addition-curable liquid silicone rubber composition. It is an object of the present invention to provide a method for producing a product, and a silicone rubber molded article comprising a cured product of an addition-curable liquid silicone rubber composition produced by the production method.

As a result of intensive studies to achieve the above object, the present inventors have found that (A) an organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule, and (B) one molecule. In the method for producing an addition-curable liquid silicone rubber composition comprising an organohydrogenpolysiloxane having a hydrogen atom bonded to at least two silicon atoms, (C) an addition reaction catalyst, and (D) a control agent. As
(A) 1-ethynyl-1-cyclohexanol, and (b) acetylene alcohol having a freezing point or melting point other than the above component (a) of 15 ° C. or less, and (a) component and (b) component A control agent in which the pre-mixed pre-mixture has a crystal precipitation temperature of 25 ° C. or lower is used, and the pre-mix is mixed with at least a part of the component (A) or at least a part of the component (A) and the component (B). Even if the temperature of the silicone rubber composition is less than 33 ° C. and 1-ethynyl-1-cyclohexanol is used as a control agent, Without the crystallization of the control agent, the control agent is reliably dispersed in the silicone rubber composition without a solvent, and a stable control effect can be obtained even though the composition has a low VOC. Heading the door, the present invention has been accomplished.

Accordingly, the present invention provides a method for producing the following addition-curable liquid silicone rubber composition and a silicone rubber molded article.
[1]
(A) an organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule; (B) an organohydrogenpolysiloxane having a hydrogen atom bonded to at least two silicon atoms in one molecule; In the method for producing an addition-curable liquid silicone rubber composition containing (C) an addition reaction catalyst and (D) a control agent,
(A) 1-ethynyl-1-cyclohexanol and, (b) a solid or melting point coagulation is Ri der 15 ℃ below, the following general formula (1)
CH≡C—C (R ² ) (OH) R ¹ (1)
(In the formula, R ¹ is a linear or branched monovalent hydrocarbon group having 5 to 15 carbon atoms, and R ² is a linear monovalent hydrocarbon group having 1 to 3 carbon atoms. .)
A control agent containing one or more of acetylene alcohols represented by the formula (1) and having a crystal precipitation temperature of 25 ° C. or lower in a premixed mixture of the components (a) and (b). And including adding and mixing the pre-mixture to at least a part of the component (A) or a blend containing at least a part of the component (A) and the component (B) at a temperature of less than 33 ° C. A method for producing an addition-curable liquid silicone rubber composition.
[2]
The acetylene alcohol as the component (b) is 3,7,11-trimethyl-1-dodecin-3-ol, 3-methyl-1-dodecin-3-ol, 3-methyl-1-pentadecin-3-ol, 3 Production of addition-curable liquid silicone rubber composition according to [1], which is at least one selected from -methyl-1-tridecin-3-ol and 3-ethyl-6-ethyl-1-nonin-3-ol Method.
[3]
[1] or [2], wherein the mixing mass ratio (a) / (b) of the component (a) and the component (b) in the premix is a ratio of 95/5 to 30/70 A method for producing an addition-curable liquid silicone rubber composition.
[4]
The composition temperature at the end of mixing when preparing the silicone rubber composition is 40 ° C. or lower, and the composition viscosity before curing at 23 ° C. is 400 Pa · s or lower [1] to [3] The method for producing an addition-curable liquid silicone rubber composition according to any one of [3].
[5]
The produced addition-curable liquid silicone rubber composition is cured into a 2 mm-thick silicone rubber sheet by a press cure at 120 ° C./10 minutes, and the 2 mm-thick silicone rubber sheet is heated at 190 ° C./1 hour for headspace gas The addition curing according to any one of [1] to [4], wherein when the volatile hydrocarbon component is analyzed by chromatographic analysis, the amount of the volatile hydrocarbon component is 20 μg / g or less. For producing a mold-type liquid silicone rubber composition.
[6]
[5] The addition-curable liquid silicone rubber according to [5], which is for structural members, adhesives, image forming members, automotive airbag coating members, or LED optical materials used in office machine image forming apparatuses A method for producing the composition.
[7]
[1] A silicone rubber molding comprising a cured product of an addition-curable liquid silicone rubber composition produced by the production method according to any one of [6].

  According to the method for producing an addition-curable liquid silicone rubber composition of the present invention, the control agent is used even when 1-ethynyl-1-cyclohexanol is used as the control agent in an extremely cold production place such as below freezing point. Without crystallization, the control agent is reliably dispersed in the silicone rubber composition without solvent, and the control effect can be stabilized while being a low VOC composition, especially for office machines. Structural members, adhesives used in image forming apparatuses, image forming members (especially rolls, belts, pressure pads) and automotive airbag coating members, LED optical materials (especially LED element sealing materials and lens materials) It is useful as a method for producing a low-viscosity silicone rubber composition used in (1).

Hereinafter, the present invention will be described in detail.
The production method of the addition-curable liquid silicone rubber composition of the present invention is (a) 1-ethynyl-1-cyclohexanol, which is inexpensive and highly available as a control agent, and has a freezing point or melting point of 15 ° C. or less. A control agent containing a component (a) and an acetylene alcohol (b) having a different structure, and having a crystal precipitation temperature of a premixed mixture of the components (a) and (b) in advance of 25 ° C. or less is prepared. After that, the premix is added to the addition-curable liquid silicone rubber composition composed of the remaining components excluding the control agent. By using this method, the composition can be controlled in a low VOC state. Crystallization of the agent at low temperature can be prevented.

The addition-curable liquid silicone rubber composition obtained by the present invention is
(A) an organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule;
(B) an organohydrogenpolysiloxane having hydrogen atoms bonded to at least two silicon atoms in one molecule;
(C) An addition reaction catalyst and (D) a control agent are contained.

-(D) Control agent-
The control agent used in the present invention is:
It contains (a) 1-ethynyl-1-cyclohexanol, and (b) acetylene alcohol having a freezing point or melting point (mp) other than the component (a) of 15 ° C. or less.

The acetylene alcohol (b) used in the present invention is not particularly defined, but is preferably an acetylene alcohol represented by the following general formula (1).
CH≡C—C (R ² ) (OH) R ¹ (1)
(In the formula, R ¹ is a linear or branched monovalent hydrocarbon group having 5 to 15 carbon atoms, and R ² is a linear monovalent hydrocarbon group having 1 to 3 carbon atoms. .)

In the above formula (1), R ¹ is a linear or branched monovalent hydrocarbon group having 5 to 15 carbon atoms, specifically, a pentyl group, neopentyl group, hexyl group, heptyl group, octyl And alkyl groups such as a group, nonyl group, decyl group, undecyl group and dodecyl group, and alkenyl groups such as a pentenyl group, a hexenyl group and a heptenyl group. When the carbon number of the monovalent hydrocarbon group of R ¹ is less than 5, the control agent is highly volatile and the silicone rubber composition may not be stably controlled, and the freezing point may be high. . On the other hand, when the number of carbon atoms is larger than 15, the active ingredient of acetylene alcohol per mol is reduced and the control effect is weakened, so that a large amount of the control agent needs to be added, and the synthesis of the control agent becomes difficult. There is a risk that the price may be a high control agent. The carbon number of R ¹ is more preferably 6 to 14, and most preferably 8 to 12.

R ² is a linear monovalent hydrocarbon group having 1 to 3 carbon atoms, specifically, an alkyl group such as a methyl group, an ethyl group, or an n-propyl group, a vinyl group, an allyl group, Examples thereof include alkenyl groups such as n-propenyl group. The carbon number of the monovalent hydrocarbon group of R ² is 1 to 3, and the desirable carbon number is 1 or 2. In the case of R ^2, the smaller the number of carbon atoms, the easier the control effect of the silicone rubber composition is, and more preferably a methyl group.

  Examples of the acetylene alcohol (b) include 3-methyl-1-butyn-3-ol (mp: 3 ° C.), 3,7,11-trimethyl-1-dodecin-3-ol (mp). : -65 ° C), 3-methyl-1-dodecin-3-ol (mp: -2 to -4 ° C), 3-methyl-1-pentadecin-3-ol (mp :-) 5 ° C. or less), 3-methyl-1-tridecin-3-ol (mp: −3 to −5 ° C.), 3-ethyl-6-ethyl-1-nonin-3-ol (mp) : At least −5 ° C.) or the like.

  The freezing point (or melting point) of the component (b) is 15 ° C. or less, preferably 5 ° C. or less, more preferably −1 to −200 ° C. When the freezing point (or melting point) of the component (b) exceeds 15 ° C, it is difficult to set the crystal precipitation temperature of the premixed mixture with the component (a) to 25 ° C or lower. In addition, the component (b) does not have to be one type in particular, and it is optional to use two or more types of control agents as long as they are control agents having a freezing point (or melting point) of 15 ° C. or lower. .

  In the production method of the present invention, the control agent is prepared by premixing (a) 1-ethynyl-1-cyclohexanol and (b) acetylene alcohol, and then adding this premixed mixture to the addition-curable liquid silicone comprising the remaining components. It is essential to add it to the rubber composition.

Here, the crystal precipitation temperature of the premixed mixture of (a) 1-ethynyl-1-cyclohexanol and (b) acetylene alcohol needs to be 25 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 It is below ℃. Here, in order to set the crystal precipitation temperature of the preliminary mixture to 25 ° C. or lower, when preparing the preliminary mixture, the mixing ratio (mass ratio) of the component (b) to the component (a) is increased, or ( When preparing component a) and component (b) at a specific mixing ratio, component (b) has a lower freezing point or melting point (for example, acetylene alcohol having a freezing point or melting point of −1 ° C. or lower) The crystal precipitation temperature of the premix can be reduced by a method such as
The crystal precipitation temperature of the preliminary mixture can be measured as the temperature at which crystals start to precipitate when the temperature is lowered from the melting temperature at 0.5 ° C./hour.

  The addition ratio of the (b) component to the (a) component may be a ratio (mass ratio) at which the crystal precipitation temperature of the premixed mixture of the (a) and (b) components is 25 ° C. or less. For example, it is appropriately selected depending on the characteristics (molecular weight, molecular structure, freezing point, melting point, etc.) of the acetylene alcohol of component (b), and in particular, the mass mixing ratio of component (a) and component (b) (a) / (b) Is preferably a ratio of 95/5 to 30/70, more preferably a ratio of 90/10 to 50/50, and still more preferably 80/20 to 60/40. In the present invention, it is desirable to add 1-ethynyl-1-cyclohexanol as the component (a) at a concentration as high as possible, but (a) / (b) should be 95/5 or more. If increased, crystals will precipitate at a temperature higher than 25 ° C., making it difficult to disperse in the silicone rubber composition, and a sufficient control effect may not be obtained, and (a) / (b) is 30/70 or less. If the component (a) is reduced, the crystal precipitation temperature tends to be 25 ° C. or lower. However, the control agent becomes difficult because the acetylene alcohol unit per mole decreases and the control effect is difficult to obtain, or the expensive component (b) increases. The average unit price of may increase.

  As an example, for example, when 3,7,11-trimethyl-1-dodecin-3-ol is used as the component (b) and (a) / (b) is mixed at a mass mixing ratio of 70/30, The crystal precipitation temperature of a) and (b) the premix (mixing control agent) is −1 ° C. or lower, and the control agent does not crystallize even when the raw material temperature of the silicone rubber composition is as low as 10 ° C., for example. It is possible to uniformly disperse. In addition, since there is no need for a heating mechanism in the mixing apparatus for the silicone rubber composition, and no heating time is required, quality and production efficiency can be greatly improved.

  Further, the addition amount of the control agent (preliminary mixture of the components (a) and (b)) to the silicone rubber composition is specified as long as it is an addition amount necessary for the control of the silicone rubber composition of the present invention. Although it is not, usually 0.001-1.0 mass part, more preferably 0.01-0.1 mass part is added per 100 mass parts of silicone rubber (total of (A) and (B) component), and it crosslinks. The speed can be adjusted. If the addition amount is less than 0.001 part by mass, the control effect of the obtained silicone rubber composition may not be obtained. If the addition amount exceeds 1.0 part by mass, the control is too effective and the rubber does not harden (hardening failure). ) There are cases.

  In addition, although the constituent material of the silicone rubber composition used in the present invention is described below, the following is an example, and the composition is not limited by the following description.

-(A) Organopolysiloxane-
The organopolysiloxane used in the present invention contains an alkenyl group bonded to at least two silicon atoms in one molecule, and is preferably a liquid or raw rubber-like diorganopolysiloxane at room temperature (23 ° C.). What is shown by average composition formula (2) can be used.
R ³ _a SiO _{(4-a) / 2} (2)
Wherein R ³ is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and a is 1.5 to 2.8, preferably 1 A positive number in the range of .8 to 2.5.)

Here, the unsubstituted or substituted monovalent hydrocarbon group for R ³ includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group. Group, cyclohexyl group, octyl group, nonyl group, alkyl group such as decyl group, aryl group such as phenyl group, tolyl group, xylyl group, naphthyl group, aralkyl group such as benzyl group, phenylethyl group, phenylpropyl group, vinyl Groups, allyl groups, propenyl groups, isopropenyl groups, butenyl groups, hexenyl groups, cyclohexenyl groups, octenyl groups and other alkenyl groups, and some or all of the hydrogen atoms of these groups are halogens such as fluorine, bromine, chlorine, etc. Substituted with atoms, cyano groups, etc., such as chloromethyl, chloropropyl, bromoethyl, Fluoropropyl group, but cyanoethyl group, etc., more than 90 mole% of the total R ³ is, in particular, it is preferable that all of R ^3, except for the alkenyl group is a methyl group.

Further, at least two of R ³ must be alkenyl groups (preferably those having 2 to 8 carbon atoms, more preferably those having 2 to 6 carbon atoms, and particularly preferably vinyl groups). . The alkenyl group content in the organopolysiloxane is 1.0 × 10 ^{−6 to} 5.0 × 10 ⁻³ mol / g, particularly 5.0 × 10 ^{−6 to} 1.0 × 10 ⁻³ mol / g. g is preferable. When the amount of the alkenyl group is less than 1.0 × 10 ⁻⁶ mol / g, crosslinking is insufficient and gelation occurs, and when the amount is more than 5.0 × 10 ⁻³ mol / g, the crosslinking density is low. There is a possibility that the rubber becomes too high and becomes brittle rubber.

  The alkenyl group may be bonded to the silicon atom at the end of the molecular chain, may be bonded to the silicon atom in the middle of the molecular chain (that is, non-terminal of the molecular chain), or may be bonded to both.

  The molecular weight may be liquid or raw rubber at room temperature, and a plurality of polymers having different viscosities may be mixed and used. The degree of polymerization of the polymer is preferably from 30 to 10,000, more preferably from 50 to 5,000. In addition, this polymerization degree is an average polymerization degree measured as a weight average value in terms of polystyrene by gel permeation chromatography (GPC) analysis (hereinafter the same).

The structure of this organopolysiloxane basically has a main chain, for example, a diorganosiloxane unit such as a dimethylsiloxane unit, a diphenylsiloxane unit, a methylphenylsiloxane unit, a methyltrifluoropropylsiloxane unit, or a vinylmethylsiloxane unit. (R ³ ₂ SiO _2/2 ), and both ends of the molecular chain are, for example, trimethylsiloxy group, vinyldimethylsiloxy group, divinylmethylsiloxy group, trivinylsiloxy group, vinyldiphenylsiloxy group, vinylmethylphenylsiloxy Has a linear structure blocked with a triorganosiloxy group (R ³ ₃ SiO _1/2 ) such as a phenyl group, phenyldimethylsiloxy group, diphenylmethylsiloxy group, etc., but partially branched structure, cyclic structure, etc. (R ³ is as described above.) .

-(B) Organohydrogenpolysiloxane-
The organohydrogenpolysiloxane (B) used in the present invention is an organohydrogenpolysiloxane containing a hydrogen atom (SiH group) bonded to at least two silicon atoms in one molecule, and contains the alkenyl group. It acts as a crosslinking agent for curing the composition by an organopolysiloxane and hydrosilylation addition reaction, and is represented by the following average composition formula (3). At least 2, preferably 3 or more (usually in one molecule) , About 3 to 200), more preferably 3 to 100, particularly 3 to 50 silicon atom-bonded hydrogen atoms (SiH groups) are preferably used.
R ⁴ _b H _c SiO _{(4-bc) / 2} (3)
(Wherein R ⁴ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. B is 0.7 to 2.1, particularly 0.8 to 2.0, and c is 0. 0.001 to 1.0, and b + c is a positive number satisfying 0.8 to 3.0, particularly 1.0 to 2.5.)

Here, as R ^4, there may be mentioned the same groups as R ³ of the alkenyl group-containing organopolysiloxane, and preferably those free of aliphatic unsaturated bonds such as alkenyl radicals.

  This silicon-bonded hydrogen atom is bonded to both silicon atoms bonded to both silicon atoms at the molecular chain end and those bonded to the silicon atom in the middle of the molecular chain (non-terminal molecular chain). It may be a thing.

  The molecular structure of this organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network structures, but the number (or degree of polymerization) of silicon atoms in one molecule is 2 to 1. 1,000, preferably 3 to 500, more preferably 3 to 300, and particularly preferably about 4 to 150 can be used.

Examples of the organohydrogenpolysiloxane include tris (dimethylhydrogensiloxy) methylsilane, tris (dimethylhydrogensiloxy) phenylsilane, 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetra. Methylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane Polymer, both ends dimethylhydrogensiloxy-blocked dimethylpolysiloxane, both ends dimethylhydrogensiloxy-blocked methylhydrogenpolysiloxane, both ends Methylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, both ends trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane A copolymer comprising (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units, (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units and (C ₆ H ₅ ) Copolymers composed of SiO _3/2 units, etc., and in these exemplary compounds, some or all of the methyl groups are substituted with other alkyl groups such as ethyl groups and propyl groups, aryl groups such as phenyl groups, 3, 3 , 3-trifluoropropyl group or the like substituted with a halogen-substituted alkyl group.

  The compounding amount of the organohydrogenpolysiloxane is 0.1 to 50 parts by mass, more preferably 0.1 to 30 parts by mass, and still more preferably 0.3 to 30 parts by mass with respect to 100 parts by mass of the (A) organopolysiloxane. It is desirable to set it as a mass part, Especially preferably, it is 0.3-20 mass part. If the amount of the organohydrogenpolysiloxane is too small, the composition may not be cured due to insufficient crosslinking. If the amount is too large, foaming may occur due to a dehydrogenation reaction, or the rubber elasticity may be reduced and the target hardness or Rubber elasticity may not be obtained. For the same reason, the molar ratio of the silicon atom-bonded hydrogen atom (SiH group) in the component (B) to the silicon atom-bonded alkenyl group in the component (A) is usually 0.3 to 3.0, preferably May be blended in an amount of 0.5 to 2.5, more preferably 0.8 to 2.0.

-(C) addition reaction catalyst (curing catalyst)-
The addition reaction catalyst used in the present invention is a catalyst for promoting the hydrosilylation addition reaction between the alkenyl group bonded to the silicon atom of the organopolysiloxane and the SiH group of the organohydrogenpolysiloxane. Examples of the catalyst include platinum black, secondary platinum chloride, chloroplatinic acid, 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, and a palladium-based catalyst. Examples thereof include platinum group metal catalysts such as catalysts and rhodium catalysts.

  In addition, although the compounding quantity of this addition reaction catalyst can be made into a catalytic quantity, it is normally mix | blended about 0.5-1,000 ppm with respect to the total mass of an organopolysiloxane component as a platinum group metal, especially about 1-500 ppm. It is preferable.

  Curing of the liquid silicone rubber composition of the present invention is addition crosslinking, but an organic peroxide curing agent may be used in combination with the addition crosslinking curing agent. Any organic peroxide curing agent may be used as long as it is used as a catalyst for accelerating the crosslinking reaction of component (A), and conventionally known ones can be used. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, o-methylbenzoyl peroxide, 2,4-dicumyl peroxide, 2,5-dimethyl-bis (2,5- t-butylperoxy) hexane, di-t-butylperoxide, t-butylperbenzoate, 1,1-bis (t-butylperoxycarboxy) hexane, and the like, but are not particularly limited thereto. Absent.

  The addition amount of the organic peroxide curing agent is a catalytic amount and may be appropriately selected depending on the curing rate, but is usually 0.1 to 10 parts by weight, preferably 100 parts by weight of component (A). Can be in the range of 0.2 to 2 parts by weight.

  In addition to the above components, the silicone rubber composition of the present invention contains fumed silica as a reinforcing silica, precipitated silica or fused silica, calcined silica, sol-gel spherical silica, crystalline silica (quartz powder) as necessary. ), Silica fine particles such as diatomaceous earth (note that among these silicas, fused silica and crystalline silica also act as other heat conductive substances), reinforcement such as calcium carbonate, clay, diatomaceous earth, and titanium dioxide. Quasi-reinforcing fillers, silicone resins as reinforcing agents, nitrogen-containing compounds and acetylene compounds other than the above component (D), phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, sulfur compounds, etc. Carbon black may be added as a hydrosilylation reaction control agent, a colorant or a conductivity imparting agent. Moreover, an internal mold release agent such as dimethyl silicone oil, an adhesiveness imparting agent, a thixotropic property imparting agent and the like can be arbitrarily blended within a range not impairing the effects of the present invention. In addition, heat resistance improvers such as cerium oxide, bengara powder, iron octylate, various carbon functional silanes to improve adhesion and moldability, nitrogen compounds that impart flame retardancy, and halogen compounds are added and mixed. May be. A low molecular weight siloxane having a degree of polymerization of 100 or less, a silanol group-containing silane, an alkoxy group-containing silane, or the like may be added as a dispersion aid.

  The mixing method of the silicone rubber composition of the present invention is as follows: (A) organopolysiloxane, (B) organohydrogenpolysiloxane, (C) addition reaction catalyst, (D) using equipment such as a planetary mixer or kneader at room temperature. ) The above-mentioned (a) 1-ethynyl-1-cyclohexanol and (b) acetylene alcohol premixed with a control agent, reinforcing silica, other additives, etc. may all be mixed at the same time, but the liquid silicone rubber composition In general, a catalyst-containing compound (A side: containing an organopolysiloxane, reinforcing silica and an addition reaction catalyst) and a crosslinking agent-containing compound (B side: an organopolysiloxane, reinforcing silica, organohydro) Genpolysiloxane, containing the above-mentioned control agent) is prepared in advance, and the A side (catalyst-containing compound) and the B side It is common to the two-liquid type used by mixing immediately before use a crosslinking agent-containing formulation).

  In preparing the silicone rubber composition, an organopolysiloxane, a fine silica filler, a silanol group-containing silane, etc. are mixed in advance, and an instrument such as a planetary mixer, a kneader, or a dryer is used. A method of preparing a base compound by mixing and heat-treating at a high temperature of 0 ° C. for several minutes to several hours may be used. If necessary, various additives, flame retardants, heat-resistant agents, etc. can be added to this, and the presence or absence of heat treatment of these additives and the timing of heat treatment are arbitrary, and they are similarly mixed in a kneader. It may be prepared by heat treatment.

In the present invention, the remaining silicone rubber composition excluding the control agent (particularly, a blend containing at least a part of the component (A) or at least a part of the component (A) and the component (B)) is The temperature before adding the premix (component (D)) of the silicone rubber composition when the control agent (D) which is a premix of the components a) and (b) is added and mixed is less than 33 ° C., particularly −33 to 33 ° C. It is characterized by being 32.9 ° C. In the production method of the present invention, when the temperature of the remaining silicone rubber composition before the addition of the control agent is in a cooled state of less than 33 ° C., the (a) component (1-ethynyl-1-cyclohexanol) which is the control agent Can be efficiently added and dispersed. That is, when the remaining silicone rubber composition is 33 ° C. or higher, 1-ethynyl-1-cyclohexanol can be dispersed in a liquid state above the freezing point, and the acetylene alcohol compound of component (b) is combined with component (a). There is no need to pre-mix and use together.
Here, when the silicone rubber composition is used as a two-pack type, (A) a part of the organopolysiloxane, (B) the organohydrogenpolysiloxane, (D) the component (a) and the component (b) are mixed in advance. It is necessary to prepare a B-side (crosslinking agent-containing compound) by mixing the control agent composed of the prepared premix and, if necessary, other components at a temperature (low temperature) of less than 33 ° C., particularly −33 to 32.9 ° C. It is useful in some cases, and at the time of use, the B side and the A side (catalyst-containing formulation) containing the remaining (A) organopolysiloxane, (C) addition reaction catalyst and other components as necessary are mixed at 80 ° C. Less than, especially at a temperature of -30 to 50 ° C.
In each of these steps, at least a part of the component (A) means a part or all of the component (A), and a part of the component (A) means 10 to 90 of the whole component (A). It means mass%, preferably 20-80 mass%, more preferably 30-70 mass%, still more preferably 40-60 mass%.

The addition method of the control agent in the present invention is as follows: (A) component alone at 23 ° C. or a silicone rubber compound in which a filler such as reinforcing silica is blended with the (A) component; Is particularly effective when the final silicone rubber composition is mixed to produce a final viscosity of 400 Pa · s or less. When it exceeds 400 Pa · s, it becomes possible to make the silicone rubber composition above the melting point of 1-ethynyl-1-cyclohexanol by kneading heat generated by a planetary mixer or kneader for a long time. . Therefore, the lower the viscosity of the silicone rubber composition of the present invention, the better the benefits of the production method of the present invention. The viscosity of the silicone rubber composition is desirably 300 Pa · s or less, more desirably 0.1 to 150 Pa · s. In particular, when the viscosity is less than 0.1 Pa · s, heat generation by the kneading apparatus cannot be expected, which is a waste of time and power.
In the present invention, the viscosity is a viscosity at a shear rate of 0.9 (1 / s) measured by a shear viscometer. In the present invention, in particular, Thermo Scientific 600 manufactured by Thermo Scientific is used, cone plate used: 20 mm, angle 2 °, setting between GAP: 0.105 mm (volume 0.08 ml), 23 ° C./30 sec. The shear viscosity at 0.9 (1 / s) when measured at an increasing rate of 0.001 (1 / s) → 20 (1 / s) / 300 sec is described.

  In addition, the temperature of the blend (B side) at the end of mixing and stirring (dispersion step) when preparing the crosslinking agent-containing blend (B side) by adding and mixing the component (D) control agent is 40 ° C. or less In particular, it is preferably −30 to 40 ° C. If the temperature of the compound (B side) exceeds 40 ° C., the melting point or freezing point (33 ° C.) of the component (a) is greatly exceeded, and even a large crystal of the component (a) can be easily melted. Therefore, it is not necessary to preliminarily mix the component (a) with the component (b) to lower the crystal precipitation temperature.

  The silicone rubber composition thus obtained was cured into a 2 mm-thick silicone rubber sheet by a press cure at 120 ° C./10 minutes based on the JIS K 6249 test method. When the volatile hydrocarbon component is analyzed by headspace gas chromatography analysis in which the sheet is heated at 190 ° C./1 hour, the amount of the volatile hydrocarbon component is 20 μg / g or less, particularly 5 μg / g or less. preferable. In order to reduce the amount of the volatile hydrocarbon component to 20 μg / g or less, the reaction control agent for component (D) (particularly (a) 1-ethynyl-1-cyclohexane in component (D) is used as in the past. For the purpose of uniformly dissolving and dispersing (hexanol) in the composition (especially in the organopolysiloxane component such as component (A), component (B), etc.), volatile hydrocarbon components (for example, toluene, xylene, paraffin, etc.) ) As a constituent of the composition.

  The silicone rubber composition thus obtained can be produced by various moldings in which a liquid silicone rubber composition is usually molded, such as cast molding, LIM injection molding, mold pressure molding, knife (blade) coating, screen printing, and the like. Although it can shape | mold to the use required by the method, The shaping | molding conditions are not specifically limited, The range of several seconds-1 hour is preferable at 70-400 degreeC. When secondary vulcanization is performed after molding, secondary vulcanization is preferably performed at 150 to 250 ° C. for 1 to 30 hours.

  The silicone rubber composition obtained in the present invention can be suitably used as a structural member, an adhesive, an image forming member, an automotive airbag coating member, or an LED optical material used in an image forming apparatus for office machines.

EXAMPLES Hereinafter, although an Example , a reference example, and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, a part shows a mass part by the following example.

[Examples 1-7 , Reference Example 1 , Comparative Examples 2, 3, 5-10]
100 parts of dimethylpolysiloxane (degree of polymerization 350) blocked at both ends with dimethylvinylsiloxy groups, and hydrophobized fumed silica having a BET specific surface area of 110 m ² / g (manufactured by Nippon Aerosil Co., Ltd., R -972) was put into a planetary mixer in the amount shown in Table 1 below, stirred for 30 minutes at room temperature (23 ° C.), then mixed and heat-treated at a high temperature of 150 ° C. for 4 hours. Silicone bases S1 to S6 having a viscosity of 50 to 1,000 Pa · s were produced.
The silicone bases S1 to S6 were stored in a thermostatic bath at 23 ° C. for 24 hours, and the following blending was performed in a state where the silicone base was cooled to 23 ° C. All raw materials (platinum catalyst, oils, control agents) are mixed at 23 ° C., and mixing is performed at a mixer machine, a kettle temperature, and a mixing atmosphere temperature of 23 ° C.

Platinum catalyst (Pt concentration 1% by mass) is added at a ratio of 0.1 part with respect to the blending amounts of silicone bases S1 to S6 shown in Tables 3 to 5, and stirring is continued for 30 minutes with a planetary mixer. A silicone platinum-containing formulation (A side) was prepared. Similarly, methyl hydrogen polysiloxane having a SiH group at both ends and side chains with respect to the blending amounts of the silicone bases S1 to S6 shown in Tables 3 to 5 (polymerization degree 17, SiH amount 0.0038 mol / g, 5.0 parts of a dimethylhydrogensiloxy group-blocked dimethylhydrogensiloxy group-blocked dimethylhydrogensiloxy group copolymer) and the reaction control agents (preliminary mixture or single control agent) shown in Table 2 are shown in Tables 3-5. It added to the planetary mixer in the ratio used as a quantity, and stirring was continued for 30 minutes, and the silicone crosslinking agent containing compound (B side) was prepared. The above planetary mixer uses Inoue PLM-15 (capacity 15L, frame type 2-shaft 1-pair type, revolution speed 20.5 rpm / min, rotation speed 56.4 pm / min), and the total charge is 8 kg. As a unified production.
These compositions were produced by a planetary mixer, and then immediately filtered through a 100 μm mesh stainless steel mesh to prepare a two-component addition-curable silicone composition.

Next, when each of the above two-component addition-curable silicone compositions is placed in a plastic container in equal amounts, mixed with a 15 cm long spatula for 10 minutes, defoamed for 2 minutes, and then allowed to stand at a crosslinking speed and 23 ° C. The pot life (tack free time) was investigated and the effect of the control agent was investigated.
Also, based on JIS K 6249 test method, it was cured to a 2 mm sheet by press cure at 120 ° C./10 min, measured by Duro A rubber hardness, and headspace gas chromatography analysis in which the 2 mm sheet was heated at 190 ° C./1 hour. The amount of volatile hydrocarbon components (μg / g) was measured.

[Example 8 ]
Silicone base S3 is stored in a thermostatic bath at −5 ° C. for 24 hours, the silicone base is cooled to −5 ° C., and all raw materials (platinum catalyst, oils, control agent), mixer machine A two-component addition curable silicone composition was prepared in the same manner as in Example 2 except that the temperature of the kettle and the blending atmosphere were also set to -5 ° C, and evaluated in the same manner.

[Comparative Example 1]
In order to lower the coagulation temperature of ethynylcyclohexanol, 0.08 part of toluene was premixed with 0.08 part of the control agent A, and then evaluation was performed in the same manner as in Example 1.

[Comparative Example 4]
Evaluation was performed in the same manner as in Example 1 except that a heating device was attached to the planetary mixer and the mixing start temperature was 40 ° C.

※１：制御剤を予備混合後、４０℃より時速０．５℃にて温度低下させた場合の結晶析出開始温度
※２：制御剤を配合物に添加した時には結晶析出している状態で添加
※３：制御剤を添加したときの配合物の温度
※４：プラネタリーミキサーにて３０分間混合した後の終了時温度

* 1: Crystal precipitation start temperature when the temperature is lowered from 40 ° C at 0.5 ° C per hour after pre-mixing the control agent * 2: When the control agent is added to the formulation, it is added in the state of crystal precipitation * 3: Temperature of the compound when the control agent is added * 4: Ending temperature after mixing for 30 minutes with a planetary mixer

※１：制御剤を予備混合後、４０℃より時速０．５℃にて温度低下させた場合の結晶析出開始温度
※２：制御剤を配合物に添加した時には結晶析出している状態で添加
※３：制御剤を添加したときの配合物の温度
※４：プラネタリーミキサーにて３０分間混合した後の終了時温度

* 1: Crystal precipitation start temperature when the temperature is lowered from 40 ° C at 0.5 ° C per hour after pre-mixing the control agent * 2: When the control agent is added to the formulation, it is added in the state of crystal precipitation * 3: Temperature of the compound when the control agent is added * 4: Ending temperature after mixing for 30 minutes with a planetary mixer

※１：制御剤を予備混合後、４０℃より時速０．５℃にて温度低下させた場合の結晶析出開始温度
※２：制御剤を配合物に添加時には結晶析出している状態で添加
※３：制御剤を添加したときの配合物の温度
※４：プラネタリーミキサーにて３０分間混合した後の終了時温度

* 1: Crystal precipitation start temperature when the control agent is premixed and then the temperature is lowered from 40 ° C at 0.5 ° C per hour * 2: When the control agent is added to the formulation, it is added in the state of crystal precipitation * 3: Temperature of the blend when the control agent is added * 4: Ending temperature after mixing for 30 minutes with a planetary mixer

  From the above results, the production method of the addition-curable liquid silicone rubber composition of the present invention can obtain a very stable dispersion and control effect of the control agent even when the raw material temperature of the silicone rubber composition is low. It turns out that it is useful especially for manufacture of the low-hardness silicone rubber composition which is low in viscosity and hardly generates stirring heat during production.

Claims (7)

(A) an organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule; (B) an organohydrogenpolysiloxane having a hydrogen atom bonded to at least two silicon atoms in one molecule; In the method for producing an addition-curable liquid silicone rubber composition containing (C) an addition reaction catalyst and (D) a control agent,
(A) 1-ethynyl-1-cyclohexanol and, (b) a solid or melting point coagulation is Ri der 15 ℃ below, the following general formula (1)
CH≡C—C (R ² ) (OH) R ¹ (1)
(In the formula, R ¹ is a linear or branched monovalent hydrocarbon group having 5 to 15 carbon atoms, and R ² is a linear monovalent hydrocarbon group having 1 to 3 carbon atoms. .)
A control agent containing one or more of acetylene alcohols represented by the formula (1) and having a crystal precipitation temperature of 25 ° C. or lower in a premixed mixture of the components (a) and (b). And including adding and mixing the pre-mixture to at least a part of the component (A) or a blend containing at least a part of the component (A) and the component (B) at a temperature of less than 33 ° C. A method for producing an addition-curable liquid silicone rubber composition. The acetylene alcohol as the component (b) is 3,7,11-trimethyl-1-dodecin-3-ol, 3-methyl-1-dodecin-3-ol, 3-methyl-1-pentadecin-3-ol, 3 The production of an addition-curable liquid silicone rubber composition according to claim 1, which is at least one selected from -methyl-1-tridecin-3-ol and 3-ethyl-6-ethyl-1-nonin-3-ol. Method.   The addition curing according to claim 1 or 2, wherein the mixing mass ratio (a) / (b) of the component (a) and the component (b) in the preliminary mixture is a ratio of 95/5 to 30/70. For producing a mold-type liquid silicone rubber composition.   The composition temperature at the end of mixing when preparing the silicone rubber composition is 40 ° C. or less, and the viscosity of the composition before curing at 23 ° C. is 400 Pa · s or less. 4. The method for producing an addition-curable liquid silicone rubber composition according to any one of 3 above.   The produced addition-curable liquid silicone rubber composition is cured into a 2 mm-thick silicone rubber sheet by a press cure at 120 ° C./10 minutes, and the 2 mm-thick silicone rubber sheet is heated at 190 ° C./1 hour for headspace gas The addition curing according to any one of claims 1 to 4, wherein the amount of the volatile hydrocarbon component is 20 µg / g or less when the volatile hydrocarbon component is analyzed by chromatography analysis. For producing a mold-type liquid silicone rubber composition.   6. The addition-curable liquid silicone rubber according to claim 5, wherein the addition-curable liquid silicone rubber is used for a structural member, an adhesive, an image forming member, an automobile air bag coating member, or an LED optical material used in an image forming apparatus for office machines. A method for producing the composition.   The silicone rubber molding which consists of a hardened | cured material of the addition curable liquid silicone rubber composition manufactured by the manufacturing method of any one of Claims 1-6.