JP3918944B2 - Addition-curing silicone composition - Google Patents

Description

  The present invention provides a cured product that has excellent curing stability, heat resistance, and excellent adhesion, and adheres well to various substrates such as resins and metals, and adheres to electrical and electronic parts and automotive parts. The present invention relates to an addition-curable silicone composition that can be suitably used as an agent or the like.

  In order to obtain an addition-curable silicone adhesive having adhesiveness to various substrates, studies have been conventionally made to add an adhesion-imparting component to a curable silicone resin to develop adhesiveness. For example, an addition-curable silicone rubber composition containing an organohydrogensiloxane having an alkoxysilyl group (described in Japanese Patent Publication No. 53-21026) or an addition-curable silicone rubber composition containing an organohydrogensiloxane having an epoxy group Products (described in Japanese Patent Publication No. 53-13508) have been proposed.

  However, conventional addition-curable silicone adhesives are difficult to self-adhere to some substrates, particularly resins, and may not exhibit adhesive properties unless a primer component is used. Examples of the hardly-adhesive resin include polycarbonate and polyphenylene sulfite. Recently, there is an increasing need for an addition-curable silicone adhesive that can easily adhere to such a resin.

  Therefore, in order to obtain an addition-curable silicone adhesive that self-adheres to a hardly adhesive resin, for example, a technique of adding a nitrogen compound (Japanese Patent Publication No. 52-147963), a hydrolysis catalyst for alkoxysilane added as an adhesion-imparting material As techniques for adding organotin compounds, organotitanium compounds, and organoaluminum compounds have been developed and are publicly known.

However, these techniques may affect the curability of the addition-curable silicone adhesive as described below, and none of the methods is satisfactory. That is, when a nitrogen compound is added to the addition-curable silicone adhesive, the catalytic ability of the platinum atom, which is an addition reaction catalyst, is significantly inhibited, and the curability becomes very unstable. In addition, when an organotin compound, an organotitanium compound, an organoaluminum compound, or the like is added, the organohydrogensiloxane in the addition-curable silicone adhesive is deactivated, and when heated, the siloxane bond in the silicone polymer is cleaved. For this reason, the heat resistance of the cured product is reduced.
Japanese Patent Publication No.53-21026 Japanese Patent Publication No.53-13508 Japanese Patent Publication No. 52-147963

  The present invention has been made in view of the above circumstances, and is an addition that gives a cured product that has excellent curing stability and thermal stability, has excellent adhesiveness, and can adhere well to difficult-to-adhere resins. An object is to provide a curable silicone composition.

  As a result of intensive studies to achieve the above object, the present inventor has found that an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule represented by the following average composition formula (1): Adhesion to an addition-curable silicone composition comprising an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule represented by the average composition formula (2), platinum or a platinum compound. When (meth) acryloxyalkyl-modified organopolysiloxane having a viscosity of 5 to 10,000 centipoise at 25 ° C. and having a linear or cyclic organopolysiloxane structure is blended as an improver, this (meth) acryloxy An alkyl-modified organopolysiloxane is present in the composition (ie, organopolysiloxane matrix). In addition, the (meth) acrylic group in the molecule shows high affinity for the substrate and has excellent adhesion without adversely affecting the curability and thermal stability of the composition. It has been found that an addition-curable silicone composition can be obtained that gives a cured product that can be satisfactorily adhered even to difficult-to-adhere resins such as polycarbonate and polyphenylene sulfite, and has led to the present invention.

Therefore, the present invention
(A) The following average composition formula (1)
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, R ² is an alkenyl group, a is 1.4 to 2.0, and b is 0.0001. -0.5, a + b = 1.9-2.05.)
100 parts by weight of an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule represented by (B) The following average composition formula (2)
R ³ _c H _d SiO _{(4-cd) / 2} (2)
Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, c is 0.7 to 2.0, d is 0.005 to 1.2, c + d = 0.8 to 3.0)
An organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule represented by
0.4 to 0.4 silicon-bonded hydrogen atoms per alkenyl group in the composition
Amount that can be supplied (C) Platinum or platinum compound Amount of catalyst (D) Viscosity at 25 ° C. is 5 to 10,000 centipoise and has a cyclic organopolysiloxane structure, or a molecular chain terminal is a silanol group It is characterized by containing 0.0001 to 3 parts by weight of (meth) acryloxyalkyl-modified organopolysiloxane having a linear organopolysiloxane structure terminated with or blocked with a triorganosiloxy group. An addition-curable silicone composition is provided.

  The addition-curable silicone composition of the present invention is excellent in curing stability and thermal stability, and can also exhibit excellent adhesion to various substrates, particularly difficult-to-adhere resins such as polycarbonate and polyphenylene sulfite. It gives a cured product and is useful as an adhesive for electrical and electronic parts and on-vehicle parts.

Hereinafter, the present invention will be described in more detail. The component (A) of the addition-curable silicone composition of the present invention is a component that is a main component of the composition of the present invention, and the following average composition formula (1)
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, R ² is an alkenyl group, a is 1.4 to 2.0, and b is 0.0001. 0.5, a + b = 1.9 to 2.05, preferably a is 1.9 to 2.0, b is 0.001 to 0.1, and a + b = 1.95 to 2.02. .) Is an organopolysiloxane containing at least two alkenyl groups bonded to silicon atoms in one molecule.

  The molecular structure of the organopolysiloxane of the above formula (1) is not particularly limited, and may be linear, partially branched or cyclic, and a polymer composed of a single siloxane unit. Alternatively, it may be a copolymer composed of two or more types of siloxane units, but usually, both ends of the molecular chain are blocked with triorganosiloxy groups, and the main chain basically consists of repeating diorganosiloxane units. Generally, it is a chain diorganopolysiloxane. In addition, the alkenyl group in the molecule may be bonded to either the silicon atom at the end of the molecular chain or the silicon atom in the middle of the molecular chain, or may be bonded to both. In view of the above, it is preferable to contain an alkenyl group bonded to silicon atoms at both ends of the molecular chain.

Here, the substituted or unsubstituted monovalent hydrocarbon group represented by R ¹ in the above formula (1) is preferably one having 1 to 12 carbon atoms, more preferably one having 1 to 8 carbon atoms. For example, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, hexyl group, 2-ethylhexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl Group, cycloalkyl group such as cycloheptyl group, aryl group such as phenyl group, tolyl group, xylyl group and naphthyl group, aralkyl group such as benzyl group, phenylethyl group and phenylpropyl group, or carbon of these hydrocarbon groups Substituted hydrocarbons in which some or all of the hydrogen atoms bonded to the atoms are substituted with halogen atoms such as fluorine atoms and chlorine atoms, nitrile groups, etc. Groups such as trifluoropropyl group, chloromethyl group, a substituted alkyl group such as a cyanoethyl group and the like. R ¹ may be the same or different from each other, but among these, all are preferably methyl groups from the standpoint of chemical stability and ease of synthesis. If necessary for characteristics, a part of the methyl group may be substituted with a phenyl group or a trifluoropropyl group.

On the other hand, as the alkenyl group represented by R ² , those having 2 to 8 carbon atoms, particularly those having 2 to 4 carbon atoms are preferable, for example, vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, isobutenyl group. And a hexenyl group, a pentenyl group, etc. are exemplified, and a vinyl group or an allyl group is particularly preferable, and a vinyl group is most preferable from the viewpoint of ease of synthesis and chemical stability.

  The viscosity of the organopolysiloxane (A) at 25 ° C. is preferably 10 centistokes (cs) or more, usually 50 to 1,000,000 cs, particularly preferably 100 to 500,000 cs. When the viscosity is lower than 10 cs, the cured product becomes brittle and may not be able to cope with the deformation of the base material. When the viscosity exceeds 1,000,000 cs, the viscosity of the composition before curing increases and the workability is improved. May decrease. These organopolysiloxanes may be used in combination of two or more if the viscosity is in the above range.

The organohydrogenpolysiloxane of component (B) has the following average composition formula (2)
R ³ _c H _d SiO _{(4-cd) / 2} (2)
Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, c is 0.7 to 2.0, d is 0.005 to 1.2, c + d = 0.8 to 3.0, preferably c is 0.9 to 2.0, d is 0.1 to 1.0, and c + d = 1.0 to 2.5.)
1 molecule has at least 2, preferably 3 or more hydrogen atoms bonded to silicon atoms (that is, SiH groups). This organohydrogenpolysiloxane is an alkenyl in which silicon-bonded hydrogen atoms (that is, SiH groups) in a molecule are bonded to silicon atoms in the component (A) in the presence of platinum or a platinum compound as the component (C) described later. It reacts with the group at room temperature or under heating to act as a crosslinking agent that gives a three-dimensional network structure.

In the above formula (2), the substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond of R ³ is preferably a group having 1 to 12 carbon atoms, particularly preferably having 1 to 8 carbon atoms. The same thing as the thing illustrated in the said R < ¹ > is mentioned, Although it may be same or mutually different, it is preferable that all are methyl groups from the ease of a synthesis | combination and chemical stability. If necessary for characteristics, a part of the methyl group may be substituted with a phenyl group or a trifluoropropyl group. In addition, you may use these organohydrogen polysiloxanes individually by 1 type or in combination of 2 or more types.

The organohydrogenpolysiloxane of component (B) is not particularly limited in terms of its molecular structure, and may be any of linear, branched, cyclic, and three-dimensional network (resin), and silicon. Even a polymer composed only of siloxane units having an atom-bonded hydrogen atom (that is, SiH group) is one or more of triorganosilyl units, diorganosiloxane units, monoorganosiloxane units, and SiO ₂ units. The copolymer may be used.

Specific examples of the (B) component organohydrogenpolysiloxane include methylhydrogensiloxane cyclic polymer, methylhydrogen / dimethylsiloxane cyclic copolymer, trimethylsiloxy group-blocked methylhydrogenpolysiloxane, trimethyl at both ends Siloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both ends dimethylhydrogensiloxy group-blocked dimethylpolysiloxane, both ends dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, both ends dimethylhydrogen Siloxy group-blocked dimethylsiloxane / methylhydrogensiloxane / diphenylsiloxane copolymer, dimethylsiloxy group-blocked dimethylsiloxy at both ends Diphenylsiloxane copolymer, both ends dimethylhydrogensiloxy group blocked methylhydrogensiloxane diphenylsiloxane copolymer, both ends trimethylsiloxy group blocked methylhydrogensiloxane diphenylsiloxane copolymer, both ends trimethylsiloxy group blocked Methylhydrogensiloxane / diphenylsiloxane / dimethylsiloxane copolymer, a copolymer comprising (CH ₃ ) ₂ HSiO _1/2 units and SiO _4/2 units, (CH ₃ ) ₃ SiO _1/2 units and (CH ₃ ) Copolymer comprising ₂ HSiO _1/2 units and SiO ₂ units, comprising (CH ₃ ) ₂ HSiO _1/2 units, SiO _4/2 units and (C ₆ H ₅ ) SiO _3/2 units. copolymer, copolymerization consisting of (CH ₃₎ HSiO _2/2 units and (CH ₃₎ SiO _3/2 units and / or HSiO _3/2 units Body and the like.

  The organohydrogenpolysiloxane is not particularly limited in the degree of polymerization, but the number of silicon atoms in one molecule (or the degree of polymerization) from the viewpoint of compatibility with the component (A) and ease of synthesis. Is preferably 3 to 200, more preferably 4 to 150.

  The blending amount of the component (B) is a hydrogen atom (SiH group) bonded to a silicon atom contained in the organohydrogenpolysiloxane in the component (B) with respect to one alkenyl group in the component (A). Is sufficient to be 0.4 to 10, preferably 1.2 to 5. If it is less than 0.4, the curing becomes insufficient and the required strength of the cured product cannot be obtained, and if it exceeds 10, the foaming occurs at the time of curing or the physical properties change over time.

  In the composition of the present invention, as a conventionally known adhesion-imparting agent, organo having at least one SiH group and at least one epoxy functional group, ester functional group or alkoxy functional group in the molecule. Addition of hydrogen polysiloxane or the like is optional, but in this case, for each alkenyl group in component (A), organohydrogen poly other than components (B) and (B) The respective components are blended so that the total of all SiH groups in the siloxane is 0.4 to 10, preferably 1.2 to 5.

  The component (C), platinum or a platinum compound, is used as a catalyst for promoting the addition curing reaction (hydrosilation) of the alkenyl group-containing organopolysiloxane and the organohydrogenpolysiloxane. Things can be used. Specific examples include platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, complexes of chloroplatinic acid and olefins, aldehydes, vinyl siloxanes, acetylene alcohols, and the like.

  Furthermore, in the present invention, when the use of the composition is taken into consideration, mixing of corrosive components is not desirable. For this reason, it is preferable that the platinum or the platinum compound is free of chlorine ions. Therefore, as platinum or a platinum compound, a zero-valent platinum complex having a chlorine ion of 5 ppm or less is preferably used. Specifically, US Pat. No. 3,715,334, US Pat. No. 3,775,452, The vinyl siloxane / platinum complex etc. which were described in US Patent 3,814,730 etc. are mentioned.

  The amount of platinum or platinum compound added can be a catalytic amount and may be appropriately increased or decreased depending on the desired curing rate. The range of 0.1 to 2,000 ppm, particularly 1 to 200 ppm in terms of platinum metal amount (weight conversion) is preferable with respect to the total of component (B).

  The component (D) component (meth) acryloxyalkyl-modified organopolysiloxane is a basic compound of the present invention, and exhibits excellent adhesiveness due to the high affinity of the (meth) acrylic group in the compound for the substrate. Is.

  Here, as the (meth) acryloxyalkyl-modified organopolysiloxane (that is, acryloxyalkyl-modified organopolysiloxane and / or methacryloxyalkyl-modified organopolysiloxane, the same shall apply hereinafter), siloxane in the molecule (≡Si—O A structure having a chain structure of -Si≡) -chain is used. Since this (meth) acryloxyalkyl-modified organopolysiloxane moves to the substrate interface while diffusing in the composition during heat curing, those having a linear or cyclic siloxane easily diffuse in the composition, Although the effect can be sufficiently exhibited, when the siloxane has a branched structure, the diffusion of molecules is hindered, and the effect of the present invention cannot be obtained. In the case of a linear organopolysiloxane, the molecular chain terminal is terminated with a silanol group (silicon-bonded hydroxyl group) or blocked with a triorganosiloxy group such as a trimethylsiloxy group.

  Furthermore, the (meth) acryloxyalkyl-modified organopolysiloxane of component (D) is preferably one that does not have hydrogen atoms (SiH groups) bonded to silicon atoms in the organopolysiloxane molecule, and has SiH groups. When the product is used, the addition reaction between the components (D) proceeds, and the (meth) acryloxyalkyl-modified organopolysiloxane is separated from the (A) component and the (B) component organopolysiloxane, thereby imparting adhesion. The effect may be unstable or the adhesiveness may be inferior.

  As such (meth) acryloxyalkyl-modified organopolysiloxane, those represented by the following general composition formula (3) are suitable.

Examples of the alkyl group and aryl group for R ⁴ include the same as those exemplified for R ¹ above, and a methyl group, an ethyl group, a propyl group, a phenyl group and the like are preferable, and a methyl group is particularly preferable.

  Since the (meth) acryloxyalkyl-modified organopolysiloxane is more likely to exhibit adhesiveness by increasing the affinity, the concentration of (meth) acrylic groups contained in the organopolysiloxane may be high. Preferably, the (meth) acryl equivalent is 140 to 500, particularly 170 to 340. If the (meth) acrylic equivalent is greater than 500, the adhesion may be inferior, and if it is less than 140, the compound may be unstable or synthesis may be difficult.

  Further, the (meth) acryloxyalkyl-modified organopolysiloxane has a viscosity at 25 ° C. of 5 to 10,000 centipoise (cp), preferably 5 to 5,000 cp, more preferably 10 to 1,000 cp. There is a need. When the viscosity is less than 5 cp, the solubility of the (A) component and the (B) component in the organosiloxane increases, and the (D) component (meth) acryloxyalkyl-modified organopolysiloxane is present at the interface with the adherend. It cannot be used and the adhesiveness is inferior, and if it exceeds 10,000 cp, the molecular weight is too large and the diffusion rate in the composition decreases.

  In addition, this linear or cyclic organopolysiloxane has a number of silicon atoms in one molecule (or degree of polymerization) from the viewpoint of affinity with a diffusible substrate in the composition, stability of the molecule, etc. 2 to 40, particularly 3 to 30, especially about 4 to 20, and at least two (meth) acryloxyalkyl groups in the molecule, particularly 3 to 20, and more preferably 4 to It is preferable to have 10 for the same reason.

  The blending amount of the (D) component (meth) acryloxyalkyl-modified organopolysiloxane is 0.0001 to 3 parts by weight, preferably 0.0005 to 1 part by weight per 100 parts by weight of the (A) organopolysiloxane. Parts, more preferably 0.001 to 0.8 parts by weight. If the blending amount is less than 0.0001 parts by weight, a satisfactory adhesive improvement effect cannot be obtained, and if it exceeds 3 parts by weight, the balance of the three-dimensional crosslinking reaction is lost due to the addition reaction between the component (A) and the component (B). A sufficient rubber hardness cannot be obtained.

  Furthermore, in the present invention, since these materials are put to practical use, when it is necessary to adjust the curing time, conventionally known addition curing type control agents can be used. Examples of the control agent include vinyl group-containing organopolysiloxanes such as vinylcyclotetrasiloxane, triallyl isocyanurate, alkyl maleates, acetylene alcohols and silanes, modified siloxanes, hydroperoxides, tetramethylethylenediamine, benzotriazole, The mixture etc. are mentioned, One type of the compound chosen from these can be used individually or in combination of 2 or more types. In addition, the addition amount of these control agents can be used in the range which does not have a bad influence on target sclerosis | hardenability and preservability.

  Further, a reinforcing silica filler in an amount that does not interfere with the effect of the present invention (for example, fumed silica, precipitated silica, crushed silica, etc.), non-reinforcing filler such as quartz powder, diatomaceous earth, calcium carbonate, cobalt blue, etc. It is also possible to add colorants such as inorganic pigments and organic dyes, heat resistance and flame retardancy improvers such as cerium oxide, zinc carbonate, manganese carbonate, bengara, titanium oxide, and carbon black. Furthermore, it is optional to add powdery, whiskered, carbon black having a developed structure, graphite or the like to these compositions for the purpose of improving the conductive stability. In addition, the addition amount of these arbitrary components can be made into a normal amount in the range which does not inhibit the effect of this invention.

  The addition-curable silicone composition of the present invention can be obtained by stirring and mixing the above components by a usual method, and the curing conditions can be set at 40 to 300 ° C. for 0.1 to 10 hours.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, a viscosity means the value in 25 degreeC, Me shows a methyl group and Vi shows a vinyl group in the following example.

Examples and comparative examples
Addition-curable silicone compositions having the compositions shown in Tables 1 and 2 were prepared, and the hardness and shear adhesion were measured by the following methods. The results are shown in Tables 1 and 2. However, the compounding quantity of each component in a table | surface is all a weight part.
Hardness:
The value immediately after curing at 120 ° C. for 60 minutes as the initial mixing value, the value after heating the cured product at 200 ° C. for 500 hours as the value after heat resistance, and the uncured composition as the value after storage The value when the product was cured at 120 ° C. for 60 minutes after being stored at 40 ° C. for 72 hours was measured with an A-type hardness meter in accordance with JIS K 6301.
Shear adhesive strength:
A plate-like (25 mm wide) glass plate or polycarbonate plate is used as the base material, and the two base materials are bonded to each other with a cured silicone rubber (adhesion surface: length 10 mm × width 25 mm × rubber thickness 2 mm), 2 Autograph shows the stress until the adhesive interface between the base material and the cured silicone rubber peels when the base material is pulled in the opposite direction (perpendicular to the rubber thickness) at a speed of 50 mm / min. The shear adhesive force was calculated as the stress per unit area.

Claims (6)

(A) The following average composition formula (1)
R ¹ _a R ² _b SiO _{(4-ab) / 2} (1)
Wherein R ¹ is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, R ² is an alkenyl group, a is 1.4 to 2.0, and b is 0.0001. -0.5, a + b = 1.9-2.05.)
100 parts by weight of an organopolysiloxane having at least two alkenyl groups bonded to silicon atoms in one molecule represented by (B) The following average composition formula (2)
R ³ _c H _d SiO _{(4-cd) / 2} (2)
Wherein R ³ is a substituted or unsubstituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond, c is 0.7 to 2.0, d is 0.005 to 1.2, c + d = 0.8 to 3.0)
An organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule represented by
0.4 to 0.4 silicon-bonded hydrogen atoms per alkenyl group in the composition
Amount that can be supplied (C) Platinum or platinum compound Amount of catalyst (D) Viscosity at 25 ° C. is 5 to 10,000 centipoise and has a cyclic organopolysiloxane structure, or a molecular chain terminal is a silanol group It is characterized by containing 0.0001 to 3 parts by weight of (meth) acryloxyalkyl-modified organopolysiloxane having a linear organopolysiloxane structure terminated with or blocked with a triorganosiloxy group. Addition-curable silicone composition.   The addition-curable silicone composition according to claim 1, wherein the triorganosiloxy group in the component (D) is a trimethylsiloxy group. The addition-curable silicone composition according to claim 1 or 2, wherein the (meth) acryloxyalkyl-modified organopolysiloxane of component (D) is represented by the following general composition formula (3).

The addition-curable silicone composition according to claim 1, 2 or 3, wherein the (meth) acryloxyalkyl-modified organopolysiloxane of component (D) has an acrylic equivalent of 140 to 500. The addition-curable silicone composition according to any one of claims 1 to 4, wherein the (D) component (meth) acryloxyalkyl-modified organopolysiloxane does not have a hydrogen atom directly bonded to a silicon atom. The addition-curable silicone composition according to claim 1, wherein the (meth) acryloxyalkyl-modified organopolysiloxane of component (D) is selected from organopolysiloxanes represented by the following formula.