JP2016145301A - Addition reaction curable liquid silicone rubber composition - Google Patents

Abstract

Even when a silicone raw rubber component is added to a liquid silicone rubber composition mainly composed of an organopolysiloxane that is liquid at room temperature, the homogenous dispersibility is good, the viscosity is not increased over time, and the storage stability is excellent. An addition-curable liquid silicone rubber composition that can be cured to give a low-hardness silicone rubber (cured product). An organopolysiloxane that is liquid at room temperature containing two or more silicon-bonded alkenyl groups, and a linear organopolysiloxane that has a specific end group blocking ratio and a specific weight average molecular weight and is in the form of a raw rubber at room temperature. An addition-curable liquid silicone rubber composition comprising a combination of siloxane and reinforcing silica (fumed silica). [Selection figure] None

Description

  The present invention is excellent in dispersibility of the raw rubber component and storage stability of the composition even when a silicone raw rubber component is added to a liquid silicone rubber composition containing an organopolysiloxane that is liquid at room temperature as a main component (base polymer). The present invention relates to an addition-curable liquid silicone rubber composition that can provide a liquid silicone rubber composition. More specifically, even when a raw rubber component is blended, it is excellent in homogeneous dispersibility, can reduce the thickening of the composition over time, and preferably has a hardness after curing (durometer A) of 1 to 1. The present invention relates to an addition-curable liquid silicone rubber composition capable of providing a low-hardness silicone rubber of about 30.

  Silicone rubber is heat-resistant, cold-resistant, safe, good appearance (transparency), soft to the touch, and also has good durability, especially for infant playground equipment, tableware and toothbrushes, especially for baby bottle nipples and babies Widely used as a material for molding pacifiers and tableware covers. In particular, the addition reaction curing type silicone rubber composition does not produce a by-product due to the decomposition of the organic peroxide unlike the organic peroxide curing type silicone rubber composition. It is used favorably.

  Currently, silicone rubber nipples (durometer A), which are widely used, have a hardness of 40-50, but it is even lower for diversifying their designs or for babies with weak suction. Hardness was desired. Moreover, as a use of low-hardness silicone rubber, low-hardness silicone rubber may be used in a portion that contacts the face of the mask. When low hardness rubber is used for the mask material, it is possible to reduce discomfort during wearing. However, if the amount of reinforcing silica is reduced in order to produce a silicone rubber with low hardness, the strength will be lost and the rubber will crack when the molded product is removed from the mold after molding. The rubber will be cut. In addition, if the balance of addition crosslinks is lost and the hardness is reduced without reducing the reinforcing silica, the rubber becomes sticky or the surface becomes sticky. It becomes inappropriate.

  In order to solve the above problems, a method has been proposed in which a silicone raw rubber is added to a liquid silicone rubber composition to reduce the hardness and stickiness of the rubber (Patent Document 1: Japanese Patent No. 4006581). However, when a silicone raw rubber component is added to a liquid silicone rubber composition containing an organopolysiloxane that is liquid at room temperature as a main component (base polymer), the dispersibility of the raw rubber component is poor, and even if it does not contain a crosslinking agent component over time. The viscosity increased remarkably and storage stability was problematic.

Japanese Patent No. 4006581

  The present invention has been made in order to improve the above circumstances, and even when a silicone raw rubber component is added to a liquid silicone rubber composition containing an organopolysiloxane that is liquid at room temperature as a main ingredient (base polymer), homogeneous dispersibility is obtained. An object of the present invention is to provide an addition-curable liquid silicone rubber composition that is good, has little viscosity increase over time, has excellent storage stability, and can be cured to give a low hardness silicone rubber (cured product). And

  As a result of intensive studies to achieve the above object, the present inventors have obtained organopolysiloxane liquid at room temperature containing at least two silicon atom-bonded alkenyl groups in one molecule, and a specific end group blocking ratio. In combination with linear organopolysiloxane that is raw rubber-like at room temperature with a specific weight average molecular weight and reinforcing silica (fumed silica), it is excellent in homogeneous dispersibility of raw rubber and increases in viscosity over time It has been found that an addition-curable liquid silicone rubber composition can be obtained which is low in storage stability and can be cured to give a low hardness silicone rubber (cured product). It is.

Accordingly, the present invention provides the following addition-curable liquid silicone rubber composition.
[1]
(A) alkenyl group-containing organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule at room temperature: 100 parts by mass
(B) A raw rubber-like organopolysiloxane at room temperature having a weight average molecular weight of 450,000 to 850,000 and a terminal blockage of 90 mol% or more: 1 to 200 parts by mass,
(C) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 0.2 to 20 parts by mass with respect to 100 parts by mass in total of components (A) and (B) ,
(D) Fumed silica whose specific surface area by BET method is 200 m ² / g or more: 5 to 50 parts by mass with respect to 100 parts by mass in total of the components (A) and (B),
(E) Organosilane and / or organopolysiloxane having one or two silanol groups in one molecule: 0 to 10 parts by mass with respect to 100 parts by mass in total of components (A) and (B),
(F) Addition reaction catalyst: an addition-curable liquid silicone rubber composition containing a catalytic amount.
[2]
The viscosity at a shear rate of 0.9 s ⁻¹ at 23 ° C. when the silicone rubber mixture in which the components (A) to (D) and, if necessary, the component (E) were uniformly mixed was stored at 105 ° C. for 3 days was [1] The addition-curable liquid silicone rubber composition according to [1], which has a viscosity of 1.5 times or less at 23 ° C. and a shear rate of 0.9 s ⁻¹ .

  In the present invention, room temperature or room temperature means 20 ° C. ± 10 ° C., particularly 25 ° C. In addition, raw rubber or raw rubber-like means that organopolysiloxane has a high degree of polymerization (high molecular weight) and is non-liquid (solid or pasty) having no (or almost no) self-fluidity at room temperature. means.

  According to the present invention, an organopolysiloxane which contains at least two silicon-bonded alkenyl groups per molecule and is liquid at room temperature, and has a specific end group blocking ratio and a specific weight average molecular weight at room temperature. With a specific amount of a combination of linear organopolysiloxane and reinforcing silica (fumed silica), it is excellent in homogeneous dispersibility of raw rubber, can reduce viscosity increase even after long-term storage after production, and Preferably, an addition-curable liquid silicone rubber composition capable of providing a low-hardness silicone rubber having a hardness after curing (durometer A) of about 1 to 30 can be provided.

Hereinafter, the present invention will be described in more detail.
First, the component (A), an alkenyl group-containing organopolysiloxane that is liquid at room temperature (25 ° C., the same shall apply hereinafter) is the main component (base polymer) of the present composition, preferably at the ends of the molecular chains (both). An organopolysiloxane having an alkenyl group bonded to a silicon atom and having an alkenyl group bonded to at least two silicon atoms in one molecule and generally having a number average degree of polymerization of 1,500 or less. In the composition of the present invention, the alkenyl group-containing organopolysiloxane which is liquid at room temperature (that is, has self-fluidity) is composed only of this organopolysiloxane (component (A)).

Here, as the organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule, a liquid at room temperature represented by the following average composition formula (I) can be used.
R ¹ _a SiO _{(4-a) / 2} (I)
Wherein R ¹ 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 .8 to 2.5, more preferably a positive number in the range of 1.95 to 2.05.)

The unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms bonded to the silicon atom represented by R ¹ includes a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. Alkyl groups such as isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, Aralkyl groups such as benzyl, phenylethyl, and phenylpropyl, alkenyl such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, octenyl, and the like Hydrogen atoms partially or wholly substituted with halogen atoms such as fluorine, bromine and chlorine, cyano groups, etc. Chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, but cyanoethyl group and the like, Preferably, at least 90 mol% of all R ¹ is a methyl group.

Further, at least two of R ¹ must be alkenyl groups (preferably having 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms, and particularly preferably a vinyl group).
The alkenyl group content in the organopolysiloxane is 1.0 × 10 ⁻⁶ mol / g to 3.0 × 10 ⁻³ mol / g, particularly 1.0 × 10 ⁻⁵ mol / g to 2.0. It is preferable to set it as x10 < ^-3 > mol / g. If the amount of the alkenyl group is less than 1.0 × 10 ⁻⁶ mol / g, the rubber hardness may be too low to form a gel, and if it exceeds 3.0 × 10 ⁻³ mol / g, the crosslinking density Becomes too high, the hardness becomes extremely high, and the elasticity of the rubber may be lost.

  The structure of the organopolysiloxane basically has a linear structure in which both ends of the molecular chain are blocked with triorganosiloxy groups and the main chain is composed of repeating diorganosiloxane units. It may be a branched structure having an organosilsesquioxane unit, a cyclic structure, or the like.

  Further, the alkenyl group may be bonded to the silicon atom at the molecular chain end or may be bonded to the silicon atom in the middle of the molecular chain (molecular chain non-terminal). In the component (A) of the present invention, It is preferable that the molecule contains at least one, preferably two or more alkenyl groups bonded to the silicon atom at the end of the molecular chain (that is, the silicon atom in the triorganosiloxy group). The alkenyl group bonded to the silicon atom in the diorganosiloxane unit or monoorganosilsesquioxane unit may or may not be contained. If at least one, preferably two or more alkenyl groups bonded to the silicon atom at the end of the molecular chain are not contained, a rubber cured product having low hardness and high tear strength may not be obtained.

  Regarding the degree of polymerization (the number of silicon atoms or the number of difunctional diorganosiloxane units in the molecule), the average degree of polymerization (number average degree of polymerization, the same shall apply hereinafter) is usually 1,500 or less, preferably 100 to 1. , 500, more preferably from 150 to 1,100. If it is less than 100, sufficient rubber feeling may not be obtained, and if it is higher than 1,500, the viscosity becomes high and molding may be difficult. Here, the molecular weight or the degree of polymerization can be determined, for example, as a polystyrene-converted value in gel permeation chromatography (GPC) analysis using toluene as a developing solvent. Usually, the average degree of polymerization is the number average degree of polymerization, etc. Is preferably obtained as a weight average molecular weight or the like (the same applies hereinafter).

Specifically, as the organopolysiloxane of component (A), molecular chain both ends diorganoalkenylsiloxy group-blocked diorganopolysiloxane, molecular chain both ends organodialkenylsiloxy group-blocked diorganopolysiloxane, molecular chain Both ends trialkenylsiloxy group-blocked diorganopolysiloxane, molecular chain both ends triorganosiloxy group-blocked diorganosiloxane / organoalkenylsiloxane copolymer, both ends chain diorganoalkenylsiloxy group-blocked diorganosiloxane / organoalkenylsiloxane Examples of the polymer include a diorganosiloxane / organoalkenylsiloxane copolymer in which one end of a molecular chain is blocked with a diorganoalkenylsiloxy group and the other end is a triorganosiloxy group blocked. Diorganoalkenylsiloxy group-capped diorganopolysiloxane, diorganoalkoxysiloxy group-capped diorganopolysiloxane, diorganosiloxane / organoalkenylsiloxane copolymer, and / or diorganoalkenylsiloxy group-capped diorganosiloxane with molecular chain both ends -An organoalkenylsiloxane copolymer. The “organo group” in each siloxane means the same as the unsubstituted or substituted monovalent hydrocarbon group excluding the alkenyl group among R ¹ in the formula (I). The alkenyl group-containing organopolysiloxane of component (A) is clearly different from the component (E) described later in that it does not contain silanol groups (that is, hydroxyl groups bonded to silicon atoms) in the molecule. It will be

Next, the component (B) has a weight average molecular weight of 450,000 to 850,000 and a raw rubber-like (that is, self-flowing) at room temperature (25 ° C.) where the end group blocking ratio is 90 mol% or more. Non-liquid), preferably linear organopolysiloxane, and the organopolysiloxane may be one represented by the following average composition formula (II).
R ² _b SiO _{(4-b) / 2} (II)
Wherein R ² is an unsubstituted or substituted monovalent hydrocarbon group having the same or different carbon number of 1 to 10, preferably 1 to 8, and b is 1.8 to 2.5, preferably 1 .9 to 2.1, more preferably a positive number in the range of 1.98 to 2.01.)

Here, examples of the unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms bonded to the silicon atom represented by R ² include those similar to the above R ¹ . Alkyl group such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, cyclohexyl group, octyl group, nonyl group, decyl group, phenyl group Aryl groups such as tolyl group, xylyl group and naphthyl group, aralkyl groups such as benzyl group, phenylethyl group and phenylpropyl group, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl Groups, alkenyl groups such as octenyl groups, and some or all of the hydrogen atoms of these groups are halogenated such as fluorine, bromine and chlorine. Chloromethyl group, chloropropyl group, bromoethyl group, trifluoropropyl group, cyanoethyl group, etc., but 90 mol% or more of the total R ² is a methyl group and the remainder is a residue. A vinyl group is preferred.

In R ² , an alkenyl group (having 2 to 8 carbon atoms is preferable, more preferably 2 to 6 and particularly preferably a vinyl group) may or may not be included. In the organopolysiloxane of component (B), the content of the alkenyl group is 0.0026 mol / 100 g or less (0 to 0.0026 mol / 100 g), particularly 0.0014 mol / 100 g or less (0 To 0.0014 mol / 100 g). When the amount of the alkenyl group is more than 0.0026 mol / 100 g, the curing rate may be remarkably lowered. 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, or may be bonded to both.

  The structure of this organopolysiloxane is basically a linear structure in which both ends of the molecular chain are blocked with triorganosiloxy groups and the main chain is composed of repeating diorganosiloxane units, as in the case of component (A). However, a partially branched structure, a ring structure, or the like may be used.

  The weight average molecular weight is 450,000 to 850,000, preferably 500,000 to 800,000, and is a raw rubber (that is, non-liquid without self-fluidity) at room temperature (25 ° C.). When the weight average molecular weight exceeds 850,000, the liquid silicone rubber composition is poorly dispersed and dissolved. When the weight average molecular weight is less than 450,000, surface tack force of the rubber cured product is generated.

  Moreover, the terminal group blocking ratio is 90 mol% or more (90 to 100 mol%), preferably 91 to 100 mol%, more preferably 92 to 100 mol%. When the terminal group blocking ratio is less than 90 mol%, the viscosity increase with time is remarkable. The terminal group blocking rate is the both ends of the repeating structure of the diorganosiloxane unit constituting the main chain of the component (B) (in the case of raw rubber-like highly polymerized organopolysiloxane, the polymerization terminal of the polymer is usually , Silanol group or hydroxydiorganosiloxy group) is blocked by a triorganosiloxy group (for example, trimethylsiloxy group or vinyldimethylsiloxy group) (mol%).

Specific examples of such an organopolysiloxane of component (B) include those containing no alkenyl groups in the molecule, such as triorganosiloxy group-capped diorganopolysiloxane raw rubber with molecular chains at both ends, Dialkenyl group-containing diorganoalkenylsiloxy group-capped diorganopolysiloxane raw rubber, molecular-chain both end organodialkenylsiloxy group-capped diorganopolysiloxane raw rubber, molecular chain both-end trialkenylsiloxy Blocked diorganopolysiloxane raw rubber, triorganosiloxy group-blocked diorganosiloxane / organoalkenylsiloxane copolymer raw rubber, molecular chain both ends diorganoalkenylsiloxy group-blocked diorganosiloxane / organoalkenylsiloxa Copolymer raw rubber, diorganosiloxane / organoalkenylsiloxane copolymer raw rubber having one end of a molecular chain blocked with a diorganoalkenylsiloxy group and the other end of a triorganosiloxy group blocked, preferably, Molecular chain both ends triorganosiloxy group-capped diorganopolysiloxane raw rubber, molecular chain both ends diorganoalkenylsiloxy group-capped diorganopolysiloxane raw rubber, molecular chain both ends triorganosiloxy group-capped diorganosiloxane / organoalkenylsiloxane copolymer Raw rubber and / or diorganoalkenylsiloxy group-blocked diorganosiloxane / organoalkenylsiloxane copolymer raw rubber with both ends of the molecular chain. The “organo group” in each siloxane means the same as the unsubstituted or substituted monovalent hydrocarbon group excluding the alkenyl group among R ² in the formula (II). In addition, the raw rubber-like organopolysiloxane of the component (B) is clearly different from the component (E) described later in that it does not substantially contain a silanol group (that is, a hydroxyl group bonded to a silicon atom) in the molecule. It is differentiated by.

  (B) A component is 1-200 mass parts with respect to 100 mass parts of (A) component, Preferably it is 3-150 mass parts, More preferably, it is the range of 5-120 mass parts. If the blending amount is less than 1 part by mass, the rubber hardness (durometer A) of the cured silicone rubber cannot be sufficiently lowered, and if it exceeds 200 parts by mass, the composition has a high viscosity and is difficult to mold. .

  The component (C) is an organohydrogenpolysiloxane having at least 2, preferably 3 or more hydrogen atoms (SiH groups) bonded to silicon atoms, and the SiH groups in the molecule are the above (A). And it bridge | crosslinks with the alkenyl group couple | bonded with the silicon atom in (B) component by hydrosilylation addition reaction, and acts as a hardening | curing agent for hardening a composition.

The organohydrogenpolysiloxane of component (C) is represented by the following average composition formula (III), and is at least 2, preferably 3 or more, more preferably 3 to 100, and still more preferably in one molecule. Those having 4 to 50 silicon-bonded hydrogen atoms (SiH groups) are preferably used.
R ³ _c H _d SiO _{(4-cd) / 2} (III)
Wherein R ³ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, which are the same or different from each other. C is 0.7 to 2.1, d Is 0.001-1, and c + d is a positive number satisfying 0.8-3.)

Here, examples of the monovalent hydrocarbon group for R ³ include the same groups as those exemplified for R ¹ , but those having no aliphatic unsaturated group are preferred.
C is 0.7 to 2.1, preferably 0.8 to 2, d is 0.001 to 1, preferably 0.01 to 1, and c + d is 0.8 to 3, preferably It is a positive number satisfying 1 to 2.5, and the molecular structure of the organohydrogenpolysiloxane may be any of linear, cyclic, branched, and three-dimensional network.

  In this case, the number of silicon atoms in one molecule (or the degree of polymerization) is preferably 2 to 300, particularly 4 to 150 at room temperature (25 ° C.). In addition, the hydrogen atom couple | bonded with a silicon atom may be located in any of the molecular chain terminal and the middle of a molecular chain, and may be located in both.

Examples of the organohydrogenpolysiloxane of the component (C) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, tris (hydrogendimethylsiloxy) methylsilane, Tris (hydrogendimethylsiloxy) phenylsilane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane / dimethylsiloxane cyclic copolymer, trimethylsiloxy group-blocked methylhydrogenpolysiloxane at both ends, trimethylsiloxy group-blocked dimethylsiloxane at both ends Methyl hydrogen siloxane copolymer, both ends dimethyl hydrogen siloxy group-capped dimethyl polysiloxane, both ends dimethyl hydrogen siloxy group capped dimethyl siloxane methyl high Rogen siloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane copolymer, trimethylsiloxy group-blocked methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, both-end trimethylsiloxy group-blocked Methylhydrogensiloxane / methylphenylsiloxane / dimethylsiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane / diphenylsiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked methylhydrogensiloxane / dimethylsiloxane-methylphenylsiloxane copolymer, (CH _{3) 2} HSiO _1/2 units and (CH _{3) 3} SiO _1/2 units and SiO _4/2 Position and a copolymer, (CH ₃₎ a copolymer consisting of ₂ HSiO _1/2 units and SiO _4/2 units, and (CH _{3) 2} HSiO _1/2 units and SiO _4/2 units (C Examples thereof include copolymers comprising ₆ H ₅ ) SiO _3/2 units, and compounds obtained by substituting a part or all of methyl groups with other alkyl groups or phenyl groups in these exemplified compounds.

  Further, as the organohydrogenpolysiloxane of component (C), in the compounds exemplified above, a part of the siloxane skeleton constituting the molecule is usually a divalent to tetravalent aromatic ring-containing hydrocarbon skeleton ( For example, phenylene skeleton, bisphenylene skeleton, bis (phenylene) ether skeleton, bis (phenylene) methane skeleton, 2,2-bis (phenylene) propane skeleton, 2,2-bis (phenylene) hexafluoropropane skeleton, etc.) Alternatively, it may be a polyvalent aromatic ring-containing organohydrogenpolysiloxane.

  The compounding amount of the organohydrogenpolysiloxane as component (C) is 0.2 to 20 parts by mass, preferably 0.3 to 10 parts per 100 parts by mass in total of the components (A) and (B). Part by mass. Further, the molar ratio (SiH groups / SiH groups) of hydrogen atoms bonded to silicon atoms (SiH groups) in the organohydrogenpolysiloxane and the total amount of alkenyl groups bonded to silicon atoms in the components (A) and (B). The amount by which the alkenyl group) is 0.8 to 10, particularly 1.0 to 5 is preferred. If this ratio is less than 0.8, crosslinking may be insufficient, resulting in a sticky rubber. If it is more than 10, foaming is observed in the molded product, or release from the mold becomes difficult. There is a risk of becoming.

Component (D), fumed silica, is essential in order to give sufficient strength to the resulting silicone rubber. BET specific surface area of the fumed silica, 200 meters ² / g or more, usually, 200 to 400 m ² / g, preferably ^{200~380m 2 / g, 200m 2 /} g is less than sufficient strength can not be obtained In addition, the transparency of the molded product is lowered, and if it is larger than 400 m ² / g, blending may become difficult or the color may be changed.

  (D) The compounding quantity of the fumed silica of a component is 5-50 mass parts with respect to a total of 100 mass parts of (A) component and (B) component, and it is preferable that it is 10-40 mass parts. If the blending amount is less than 5 parts by mass, sufficient rubber strength cannot be obtained.

As the fumed silica as the component (D), it is usually preferable to use one having a hydrophobic surface. Without surface treatment, dispersibility in silicone oil is poor, and silica agglomerates may be formed or blending may be difficult. The silica surface treatment may be a direct treatment in a powder state or a surface treatment by heating and mixing with the (G) silica surface treatment agent described later when mixing with the component (A). Good.
As a usual treatment method, it can be treated by a generally known technique. For example, the untreated silica fine powder and a silica surface treatment agent (G) described later are added to a mechanical kneader or a fluidized bed sealed at normal pressure. If necessary, mixing treatment is performed at room temperature or heat treatment in the presence of an inert gas. In some cases, a catalyst may be used to facilitate the treatment. After kneading, the treated silica fine powder can be produced by drying.

  The silica surface treating agent of component (G) can be used to hydrophobically treat the surface of fumed silica as component (D) as described above, and the silica surface treating agent of component (G) Specifically, silazanes such as hexamethyldisilazane, divinyltetramethyldisilazane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, butyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane , Vinyltriethoxysilane, vinyltrimethoxysilane, trimethylmethoxysilane, triethylmethoxysilane, vinyltris (methoxyethoxy) silane, trimethylchlorosilane, dimethyldichlorosilane, divinyldimethoxysilane, chloropropyltrimethoxysilane, etc. Silane coupling agent, polymethylsiloxane, organosilicon compounds such as organohydrogen polysiloxanes. As the treating agent, silane coupling agents or silazanes are particularly preferable.

  (G) When using a component, it is preferable that it is 0.1-50 mass parts with respect to 100 mass parts of (D) component, and it is more preferable that it is 0.5-30 mass parts. If the blending amount is less than 0.1 parts by mass, the surface treatment of silica may be insufficient. If the blending amount is more than 50 parts by mass, the addition reaction may be inhibited or the reinforcing effect may be reduced.

  The organosilane and / or organopolysiloxane having one or two silanol groups in one molecule of the component (E) is usually a liquid component at room temperature (25 ° C.), and the component (B) and ( D) A component that prevents a thickening phenomenon of the entire composition due to the interaction of the component, and is an optional component that can be used in the present composition. Specifically, trimethylsilanol, triethylsilanol, dimethylvinylsilanol, dimethylsilanediol, diphenylsilanediol and the like, organosilane compounds which are liquid at room temperature (25 ° C.), branched siloxane compounds such as tris (trimethylsiloxy) silanol, Examples thereof include linear organopolysiloxane compounds that are liquid at room temperature (25 ° C.), such as dimethylpolysiloxane blocked with dimethylhydroxysiloxy group blocked at both ends of the molecular chain, dimethylpolysiloxane blocked with dimethylhydroxysiloxy group / one terminal trimethylsiloxy group . In particular, in the case of an organosilane compound or a branched siloxane compound, trimethylsilanol or tris (trimethylsiloxy) silanol is preferable from the viewpoint of synthesis. In the case of a linear organopolysiloxane compound, the (number average) degree of polymerization is 100 or less (usually 2 to 100), preferably 80 or less (particularly about 5 to 80), at room temperature (25 ° C.). Liquid one-end or both-end dimethylhydroxysiloxy group-blocked dimethylpolysiloxane is preferred. If the degree of polymerization of the linear organopolysiloxane compound exceeds 100, the effect of preventing the thickening phenomenon may not be sufficiently exhibited. The component (E) is more preferably trimethylsilanol, a linear organopolysiloxane having silanol groups at both ends of the molecular chain and having an average degree of polymerization of 100 or less and liquid at room temperature.

  In addition, the organosilane and / or organopolysiloxane of the component (E) are those that contain substantially no silanol groups in the molecule in that they contain one or two silanol groups in the molecule. The above-mentioned (A) component and (B) component are clearly differentiated.

  (E) The compounding quantity in the case of mix | blending a component is 0.1-10 mass parts with respect to a total of 100 mass parts of (A) component and (B) component, Preferably it is 0.1-8 mass parts, More preferably Is 0.1 to 5 parts by mass. When the addition amount is less than 0.1 parts by mass, the effect of preventing thickening may not be sufficiently exhibited. When the addition amount exceeds 10 parts by mass, foaming occurs during curing.

Examples of the addition reaction catalyst for component (F) include platinum black, platinous chloride, chloroplatinic acid, a reaction product of chloroplatinic acid and a monohydric alcohol, a complex of chloroplatinic acid and an olefin, platinum bisacetoacetate, etc. Platinum-based catalysts, palladium-based catalysts, rhodium-based catalysts, and the like.
In addition, the compounding quantity of this addition reaction catalyst can be made into a catalyst quantity, and 0.5-1,000 ppm with respect to the total mass of (A)-(E) component normally as a platinum group metal (mass conversion). In particular, it is about 1 to 500 ppm.

  In the addition curable liquid silicone rubber composition of the present invention, as other components, if necessary, a filler such as precipitated silica, quartz powder, diatomaceous earth, calcium carbonate, carbon black, conductive zinc white, metal Conductive agents such as powder, nitrogen-containing compounds and acetylene compounds, phosphorus compounds, nitrile compounds, carboxylates, tin compounds, mercury compounds, sulfur compounds and other hydrosilylation reaction control agents, heat-resistant agents such as iron oxide and cerium oxide, dimethyl Internal mold release agent such as silicone oil, adhesion imparting agent (especially containing at least one functional group selected from alkenyl group, epoxy group, amino group, (meth) acryloxy group, mercapto group, etc. in the molecule) In addition, an organosilicon compound such as alkoxysilane that does not contain a SiH group in the molecule), a thixotropic agent, etc. are blended. It is arbitrary and.

  In addition, the addition curable liquid silicone rubber composition of the present invention, when all of the components (A) to (F) are mixed, causes the crosslinking reaction to proceed over time even at room temperature. It is preferable to store the component (C) and the component (F) separately.

A composition in which the component (C) and the component (F) are separated, that is, a silicone rubber mixture obtained by uniformly mixing the components (A), (B) and (D) to (F), and (A) to ( E) The viscosity of the silicone rubber mixture obtained by uniformly mixing the components is usually 30 to 10,000 Pa · s when the shear rate is 0.9 s ⁻¹ at 23 ° C. when used for injection molding. Preferably, it is in the range of 50 to 5,000 Pa · s, more preferably 100 to 3,000 Pa · s. Even if this viscosity is less than 30 Pa · s, it may be difficult to mold even if it exceeds 10,000 Pa · s. The viscosity at these specific shear rates is measured by, for example, a precision rotational viscometer HAAKE Rheostress 6000 (manufactured by Thermo scientific) or a precision rotational viscometer Rotovisco RV1 type (manufactured by HAAKE). This can be done using a meter.

The silicone rubber mixture obtained by uniformly mixing the components (A), (B) and (D) to (F), and the silicone rubber mixture obtained by uniformly mixing the components (A) to (E) The viscosity at a shear rate of 0.9 s ^-1 at 23 ° C. when stored at 105 ° C. for 3 days is not more than 1.5 times the viscosity at a shear rate of 0.9 s ⁻¹ at 23 ° C. immediately after production. (1 to 1.5 times), particularly 1.3 times or less (1 to 1.3 times) is preferable.
If the material viscosity is higher than 1.5 times the setting in the injection molding, the molding may be difficult unless the molding conditions are changed, and the time for sucking the material with the pump may become longer. Thus, in order to make the increase in viscosity over time 1.5 times or less, it is desirable to mix the components (B), (D) and (E) in appropriate amounts in the above mixture.

  As a method for molding and curing the silicone rubber composition, a conventional method can be adopted, but a liquid injection molding method is suitably employed as the molding method. Further, as the curing conditions, heat treatment conditions of 120 to 230 ° C. for 3 seconds to 10 minutes, preferably 150 to 210 ° C. for about 5 seconds to 3 minutes may be employed. The silicone rubber composition of the present invention has a hardness (durometer A) based on JIS-K6249 of a silicone rubber elastic body (elastomer) obtained by curing under such conditions, preferably 1-30, more preferably 5-5. 25, and more preferably, a low hardness silicone rubber of about 5 to 20 can be provided. In addition, in order for the silicone rubber obtained to have values such as the above hardness, it can be achieved by blending the components (A) to (D) at an appropriate ratio (mass ratio) in the composition.

  The addition-curable liquid silicone rubber composition of the present invention has little viscosity increase over time even when a silicone raw rubber is added, and has excellent storage stability, and is useful for injection molding applications.

  The addition-curable liquid silicone rubber composition of the present invention is suitably used as a nipple for baby bottles, a mask material and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to a following example. In addition, a part shows a mass part by the following example. Moreover, the average degree of polymerization of (A) component shows the number average degree of polymerization of polystyrene conversion in the gel permeation chromatography (GPC) analysis which used toluene as the developing solvent, and the average molecular weight of (B) component is also in GPC analysis. The weight average molecular weight in terms of polystyrene is shown.

[Example 1]
70 parts by weight of dimethylpolysiloxane (1) [vinyl group content: 3.9 × 10 ⁻⁵ mol / g] which is liquid at room temperature having an average degree of polymerization of 750, both ends of which are blocked with dimethylvinylsiloxy groups 30 parts of fumed silica (Aerosil 300, manufactured by Nippon Aerosil Co., Ltd.) having a surface area of 300 m ² / g, 8 parts of hexamethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane 1 part and 2.0 parts of water were mixed at room temperature for 30 minutes, heated to 150 ° C., stirred for 3 hours and cooled to obtain a silicone rubber base.
100 parts of this silicone rubber base is 28.5 parts of the above dimethylpolysiloxane (1), both ends of the molecular chain are blocked with dimethylvinylsiloxy groups, the terminal blocking ratio is 92 mol%, and the weight average molecular weight is 800,000. Dimethylpolysiloxane raw rubber [vinyl group content 4.6 × 10 ⁻⁶ mol / g] (2) 28 parts was added, and after stirring for 30 minutes, methylhydrogen poly having SiH groups in the side chain as a crosslinking agent 0.71 part of siloxane (3) (molecular chain both ends trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer having a polymerization degree of 38 and an SiH group amount of 0.0074 mol / g), SiH groups at both ends of the molecular chain Methyl hydrogen polysiloxane (4) having a degree of polymerization of 18 and a molecular chain at both ends divalent with a SiH group content of 0.0014 mol / g 0.91 part of chilled hydrogensiloxy group-blocked dimethylpolysiloxane) (of SiH groups / dimethylpolysiloxane (1) and dimethylpolysiloxane raw rubber (2) in the total of methylhydrogenpolysiloxane (3) and (4)) Total alkenyl group = 1.6 (mol / mol)], 0.05 part of ethynylcyclohexanol was added as a reaction control agent, and stirring was continued for 15 minutes to obtain a silicone rubber mixture.
About this silicone rubber mixture, the result of having measured the viscosity in 23 degreeC and the shear rate of 0.9 s- ¹ immediately after manufacture for 3 days at 105 degreeC with the precision rotational viscometer Rotobisco RV1 type (made by HAAKE) is shown. It was shown in 1.
A silicone rubber composition is prepared by uniformly mixing 100 parts of this silicone rubber mixture with 0.1 part of a platinum catalyst (Pt concentration: 1% by mass), press curing at 120 ° C. for 10 minutes, and then in an oven at 150 ° C. Table 2 shows the results of measuring the hardness of the cured product that had been post-cured for 1 hour based on JIS-K6249 and the result of determining the rubber surface by finger touch.

[Example 2]
In Example 1, a dimethylpolysiloxane raw rubber having both ends of a molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 800,000 [vinyl group content 4.6 × 10 ^{− 6} mol / g] (2) Instead of 28 parts, a dimethylpolysiloxane raw rubber [vinyl] having both ends of the molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 600,000 Group content 7.4 × 10 ⁻⁶ mol / g] (5) 28 parts added [SiH group / dimethylpolysiloxane (1) and dimethyl in the total of methylhydrogenpolysiloxane (3) and (4) A silicone rubber mixture was obtained in the same manner except that the alkenyl group in the total of the polysiloxane raw rubber (5) = 1.6 (mol / mol).
About this silicone rubber mixture, the result of having measured the viscosity in 23 degreeC and the shear rate of 0.9 s- ¹ immediately after manufacture for 3 days at 105 degreeC with the precision rotational viscometer Rotobisco RV1 type (made by HAAKE) is shown. It was shown in 1.
A silicone rubber composition is prepared by uniformly mixing 100 parts of this silicone rubber mixture with 0.1 part of a platinum catalyst (Pt concentration: 1% by mass), press curing at 120 ° C. for 10 minutes, and then in an oven at 150 ° C. Table 2 shows the results of measuring the hardness of the cured product that had been post-cured for 1 hour based on JIS-K6249 and the result of determining the rubber surface by finger touch.

[Example 3]
A silicone rubber mixture was obtained in the same manner as in Example 1, except that 1.0 part of dimethylpolysiloxane (6) having an average degree of polymerization of 10 having both molecular chain ends blocked with dimethylhydroxysiloxy groups was further added. .
About this silicone rubber mixture, the result of having measured the viscosity in 23 degreeC and the shear rate of 0.9 s- ¹ immediately after manufacture for 3 days at 105 degreeC with the precision rotational viscometer Rotobisco RV1 type (made by HAAKE) is shown. It was shown in 1.
A silicone rubber composition is prepared by uniformly mixing 100 parts of this silicone rubber mixture with 0.1 part of a platinum catalyst (Pt concentration: 1% by mass), press curing at 120 ° C. for 10 minutes, and then in an oven at 150 ° C. Table 2 shows the results of measuring the hardness of the cured product that had been post-cured for 1 hour based on JIS-K6249 and the result of determining the rubber surface by finger touch.

[Comparative Example 1]
In Example 1, a dimethylpolysiloxane raw rubber having both ends of a molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 800,000 [vinyl group content 4.6 × 10 ^{− 6} mol / g] (2) Instead of 28 parts, a dimethylpolysiloxane raw rubber [vinyl] having both ends of the molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 88 mol% and a weight average molecular weight of 800,000 Group content 4.5 × 10 ⁻⁶ mol / g] (7) 28 parts added [SiH group / dimethylpolysiloxane (1) and dimethyl in the total of methylhydrogenpolysiloxane (3) and (4) A silicone rubber mixture was obtained in the same manner except that the alkenyl group in the total of the polysiloxane raw rubber (7) = 1.6 (mol / mol).
About this silicone rubber mixture, the result of having measured the viscosity in 23 degreeC and the shear rate of 0.9 s- ¹ immediately after manufacture for 3 days at 105 degreeC with the precision rotational viscometer Rotobisco RV1 type (made by HAAKE) is shown. It was shown in 1.
A silicone rubber composition is prepared by uniformly mixing 100 parts of this silicone rubber mixture with 0.1 part of a platinum catalyst (Pt concentration: 1% by mass), press curing at 120 ° C. for 10 minutes, and then in an oven at 150 ° C. Table 2 shows the results of measuring the hardness of the cured product that had been post-cured for 1 hour based on JIS-K6249 and the result of determining the rubber surface by finger touch.

[Comparative Example 2]
In Example 1, a dimethylpolysiloxane raw rubber having both ends of a molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 800,000 [vinyl group content 4.6 × 10 ^{− 6} mol / g] (2) Instead of 28 parts, a dimethylpolysiloxane raw rubber [vinyl] having both ends of the molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 440,000 Group content 8.4 × 10 ⁻⁶ mol / g] (8) 28 parts added [SiH group / dimethylpolysiloxane (1) and dimethyl in the total of methylhydrogenpolysiloxane (3) and (4) A silicone rubber mixture was obtained in the same manner except that the alkenyl group in the total of the polysiloxane raw rubber (8) = 1.6 (mol / mol).
About this silicone rubber mixture, the result of having measured the viscosity in 23 degreeC and the shear rate of 0.9 s- ¹ immediately after manufacture for 3 days at 105 degreeC with the precision rotational viscometer Rotobisco RV1 type (made by HAAKE) is shown. It was shown in 1.
A silicone rubber composition is prepared by uniformly mixing 100 parts of this silicone rubber mixture with 0.1 part of a platinum catalyst (Pt concentration: 1% by mass), press curing at 120 ° C. for 10 minutes, and then in an oven at 150 ° C. Table 2 shows the results of measuring the hardness of the cured product that had been post-cured for 1 hour based on JIS-K6249 and the result of determining the rubber surface by finger touch.

[Comparative Example 3]
In Example 1, a dimethylpolysiloxane raw rubber having both ends of a molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 800,000 [vinyl group content 4.6 × 10 ^{− 6} mol / g] (2) Instead of 28 parts, a dimethylpolysiloxane raw rubber having both ends of the molecular chain blocked with dimethylvinylsiloxy groups, a terminal blocking ratio of 92 mol% and a weight average molecular weight of 1,000,000 [Vinyl group content 3.7 × 10 ⁻⁶ mol / g] (9) 28 parts added [SiH group / dimethylpolysiloxane (1) in the total of methylhydrogenpolysiloxane (3) and (4) And dimethylpolysiloxane raw rubber (9) in the total, except that alkenyl group = 1.6 (mol / mol)]. It could not be.

Claims (2)

(A) alkenyl group-containing organopolysiloxane having an alkenyl group bonded to at least two silicon atoms in one molecule at room temperature: 100 parts by mass
(B) A raw rubber-like organopolysiloxane at room temperature having a weight average molecular weight of 450,000 to 850,000 and a terminal blockage of 90 mol% or more: 1 to 200 parts by mass,
(C) Organohydrogenpolysiloxane containing hydrogen atoms bonded to at least two silicon atoms in one molecule: 0.2 to 20 parts by mass with respect to 100 parts by mass in total of components (A) and (B) ,
(D) Fumed silica whose specific surface area by BET method is 200 m ² / g or more: 5 to 50 parts by mass with respect to 100 parts by mass in total of the components (A) and (B),
(E) Organosilane and / or organopolysiloxane having one or two silanol groups in one molecule: 0 to 10 parts by mass with respect to 100 parts by mass in total of components (A) and (B),
(F) Addition reaction catalyst: an addition-curable liquid silicone rubber composition containing a catalytic amount. The viscosity at a shear rate of 0.9 s ⁻¹ at 23 ° C. when the silicone rubber mixture in which the components (A) to (D) and, if necessary, the component (E) were uniformly mixed was stored at 105 ° C. for 3 days was The addition-curable liquid silicone rubber composition according to claim 1, which has a viscosity of 1.5 times or less at 23 ° C and a shear rate of 0.9 s- ¹ .