JP7353026B2 - Room temperature curable polyorganosiloxane composition and cured product thereof - Google Patents

Description

The present invention relates to a room temperature curable polyorganosiloxane composition and a cured product thereof.

Curable polyorganosiloxane compositions that exhibit fluidity in an uncured state and form a rubber-like elastic body (silicone rubber) upon curing are classified into condensation reaction type and addition reaction type, depending on the curing mechanism. The former cures at room temperature and takes a long time to cure, but is characterized by good adhesion. The latter can be cured in a short time by heating, and has excellent curability even in areas where moisture in the air is not sufficiently supplied.

Silicone rubber is known as a material with excellent heat resistance, cold resistance, weather resistance, and electrical insulation properties, and is used in parts such as O-rings, packings, and gaskets in various industrial fields. As an addition reaction type curable polyorganosiloxane composition that produces such silicone rubber, for example, a curable polyorganosiloxane composition that imparts solvent resistance to silicone rubber has been proposed (for example, Patent Document 1 reference.).

In addition, in condensation reaction type (room temperature) curable polyorganosiloxane compositions, fluidity, non-sag properties, extrudability, adhesive properties, and adhesive durability are improved by incorporating additives such as fillers and light stabilizers. Curable polyorganosiloxane compositions have been proposed (see, for example, Patent Documents 2 and 3).

Japanese Patent Application Publication No. 2009-138038 Japanese Patent Application Publication No. 2001-152020 Japanese Patent Application Publication No. 2002-302606

However, conventional room-temperature-curable polyorganosiloxane compositions, especially those with high hardness, have a problem of poor adhesiveness and elongation properties. This is because room-temperature-curable polyorganosiloxane compositions that are highly filled with fillers that provide mechanical strength, especially fillers with high specific gravity, may experience interfacial peeling at the adhesive interface between the cured product and the substrate to be bonded. One of the reasons is that thin film failure tends to occur and cohesive failure is difficult to occur.

Furthermore, room temperature curable polyorganosiloxane compositions sometimes have poor adhesion to metal members and plastics (engineering plastics) such as polyphenylene sulfide and polybutylene terephthalate.

The present invention was made with the aim of solving the above-mentioned problems, and includes a room-temperature-curable polyorganosiloxane composition that has excellent adhesion to various substrates and provides excellent elongation properties to the cured product. The purpose is to provide a cured product thereof.

The room temperature curable polyorganosiloxane composition of the present invention comprises (A) 100 parts by mass of a linear polyorganosiloxane having two or more alkoxy groups in one molecule;
(B1) 1 to 100 parts by mass of mica powder,
(B2) 3 to 50 parts by mass of fumed silica,
(C) General formula: R ¹ _a Si(OR ² ) _4-a
(In the formula, R ¹ is a monovalent hydrocarbon group, R ² is an alkyl group or an alkoxy-substituted alkyl group, and a is 0, 1, or 2.)
It is characterized by containing 0.5 to 15 parts by mass of an alkoxysilane and/or its partially hydrolyzed condensate represented by: and 0.1 to 10 parts by mass of (D) a titanium chelate catalyst.

According to the room temperature curable polyorganosiloxane composition of the present invention, it has excellent adhesion to various substrates and can provide a cured product with excellent elongation properties.

It is a figure explaining the method of observing the presence or absence of foaming and the occurrence of cracks in a cured product.

The room temperature curable polyorganosiloxane composition of the present invention comprises (A) 100 parts by mass of a linear polyorganosiloxane having two or more alkoxy groups in one molecule;
(B1) 1 to 100 parts by mass of mica powder,
(B2) 3 to 50 parts by mass of fumed silica,
(C) General formula: R ¹ _a Si(OR ² ) _4-a
(In the formula, R ¹ is a monovalent hydrocarbon group, R ² is an alkyl group or an alkoxy-substituted alkyl group, and a is 0, 1, or 2.)
It is characterized by containing 0.5 to 15 parts by mass of an alkoxysilane or a partially hydrolyzed condensate thereof represented by: and 0.1 to 10 parts by mass of (D) a titanium chelate catalyst.
Hereinafter, each component contained in the room temperature curable polyorganosiloxane composition according to the embodiment of the present invention will be explained.

(A) Polyorganosiloxane is the base polymer of the room temperature curable polyorganosiloxane composition. (A) Polyorganosiloxane has two or more (preferably two or more on average) alkoxy groups in one molecule.

In the polyorganosiloxane (A), the alkoxy group is a group that has hydrolyzability and can undergo hydrolytic condensation with the alkoxy group contained in the component (C). (A) Since the polyorganosiloxane has an alkoxy group as a hydrolyzable group, it is possible to reduce the adverse effect on the member to which the room temperature curable polyorganosiloxane composition is applied. In the polyorganosiloxane (A), examples of the alkyl group possessed by the alkoxy group include more general alkoxy groups that are lower alkyl groups such as methyl, ethyl, propyl, and butyl groups.

In component (A), organic groups other than alkoxy groups bonded to silicon atoms include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, and dodecyl group. , cycloalkyl groups such as cyclohexyl group, alkenyl groups such as vinyl group and allyl group; aryl groups such as phenyl group, tolyl group and xylyl group; aralkyl groups such as 2-phenylethyl group and 2-phenylpropyl group, etc. be done. Further, examples of the halogenated hydrocarbon group include a chloromethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, etc., and examples of the cyanoalkyl group include a 2-cyanoethyl group, a 3-cyanopropyl group, etc. can be mentioned. Organic groups other than alkoxy groups are easy to synthesize, component (A) has a low viscosity relative to its molecular weight, and it is easy to achieve both workability of the composition and good mechanical properties of the cured product. It is preferable that 85% or more of the whole group is a methyl group, and it is more preferable that substantially all organic groups other than alkoxy groups are methyl groups. The plurality of organic groups other than the alkoxy group bonded to the silicon atom may be the same or different.

In particular, when imparting heat resistance, radiation resistance, cold resistance, or transparency to the cured product, a necessary amount of phenyl group is added as part of the organic group other than the alkoxy group bonded to the silicon atom to provide oil resistance, When imparting solvent resistance, 3,3,3-trifluoropropyl group or 3-cyanopropyl group is used as part of the organic group other than the alkoxy group, and when imparting a surface with paintability, The structure of the organic group can be arbitrarily selected depending on the purpose, such as using a long-chain alkyl group or an aralkyl group in combination with a methyl group as part of the organic group other than the alkoxy group.

Component (A) may have an oxy group or a divalent hydrocarbon group between the bond between silicon atoms or the bond between silicon atoms and oxygen atoms that form a molecular chain. Examples of the divalent hydrocarbon group include alkylene groups such as methylene group, ethylene group and trimethylene group; phenylene group and the like. Since synthesis is easy, X is preferably an oxy group or an ethylene group, and an oxy group is particularly preferred.

The viscosity of component (A) at 25° C. is preferably 0.02 to 1000 Pa·s, more preferably 0.1 to 500 Pa·s. The degree of polymerization of component (A) is such that the viscosity at 25° C. falls within the range described above, and specifically, it is preferably from 20 to 2,500, more preferably from 80 to 2,000. The higher the viscosity of component (A), the better the surface curability tends to be. However, if the viscosity of component (A) is too low, the rubber elasticity after curing will be poor, and if it is too high, workability will be reduced.

(A) The number of alkoxy groups that the polyorganosiloxane has is two or more per molecule, preferably four or more. (A) The polyorganosiloxane preferably has at least one alkoxy group at both ends of its molecular chain. In particular, (A) the polyorganosiloxane is either a trialkoxysilyl group-blocked polyorganosiloxane having three alkoxy groups at each end, or a dialkoxysilyl group-blocking polyorganosiloxane at both ends having two alkoxy groups at each end. Preferably it is a capped polyorganosiloxane or a mixture of both. By using a polyorganosiloxane endblocked with trialkoxysilyl groups at both ends, it is possible to improve the adhesion of the cured product to the base material, and also to improve the elongation properties such as tensile strength and elongation of the cured product. Furthermore, by using a polyorganosiloxane endblocked at both ends with a trialkoxysilyl group and a polyorganosiloxane endblocked at both ends with a dialkoxysilyl group, the extrudability and curing speed of the room temperature curable polyorganosiloxane composition can be adjusted.

Component (A) is obtained by condensing a silanol group-terminated polyorganosiloxane with a molar excess of tetraalkoxysilane relative to the silanol groups of the polyorganosiloxane in the presence or absence of a catalyst. As this catalyst, known amines, carboxylic acids, metal carboxylates such as zinc, tin, iron, etc. are used. When the condensation reaction is carried out in the absence of a catalyst, it is preferred to heat the reaction mixture to the reflux temperature of the tetraalkoxysilane. The molar ratio of tetraalkoxysilane/SiOH in the condensation reaction is preferably about 5 to 15.

Component (A) can also be obtained by adding trialkoxysilane to a vinyl group-terminated polyorganosiloxane, or by adding vinyltrialkoxysilane to a hydrogen group-terminated polyorganosiloxane.

In the room-temperature-curable polyorganosiloxane composition of the present embodiment, the base polymer may contain components other than component (A) as long as the effects of the present invention are not impaired; however, it must consist only of component (A). is preferred. Components other than component (A) that may be included as a base polymer in the room temperature curable polyorganosiloxane composition of the present embodiment include, for example, a polyorganosiloxane endblocked with alkoxysilyl groups having branches in the molecule, and These include polyorganosiloxanes having alkoxy groups and end-blocked with alkoxysilyl groups.

In the room temperature curable polyorganosiloxane composition of this embodiment, the mica powder as component (B1) acts as an inorganic filler and imparts excellent elongation properties and adhesive properties to the cured product. (B1) Mica powder is generally flat or scaly. (B1) Since mica powder is flat or scaly, it is thought that by dispersing it in the room temperature curable polyorganosiloxane composition of this embodiment, fine layered voids will be formed in the composition. It will be done. This makes it easier for by-products generated when the room-temperature-curable polyorganosiloxane composition is cured to be released to the outside of the composition through the layered voids, suppressing the generation of microbubbles in the cured product, and preventing the formation of microbubbles in the cured product. It is possible to achieve excellent adhesion to various base materials while imparting excellent elongation properties. Therefore, compared to, for example, calcium carbonate or quartz powder, which have a high specific gravity, sufficient strength, excellent elongation characteristics, and excellent adhesion to various base materials can be achieved with a small amount.

The average particle size of the mica powder (B1) is preferably 1 to 100 μm, in order to achieve both excellent elongation properties and adhesive properties of the cured product, and to improve extrudability and storage stability. More preferably, the diameter is 1 to 60 μm. Furthermore, the aspect ratio of (B1) mica powder is preferably 10 to 250, more preferably 20 to 150.

(B1) The average particle size of mica powder is calculated as the average value of the maximum diameter of the flat surface, and the aspect ratio is calculated as the ratio of the maximum diameter of the flat surface to the maximum thickness (maximum diameter of the flat surface / maximum thickness). can do. The value of the average particle size is the value measured by image analysis using an electron microscope, the average particle size calculated from the 50% diameter based on mass conversion from the particle size distribution, and the average particle size based on number measured by laser diffraction/scattering method. It may be either the diameter or the value determined by sieving particle size distribution measurement. In addition, the maximum diameter of the flat surface of mica particles can be determined by, for example, the average value of the maximum diameter of the flat surface measured by laser diffraction/scattering method, or by electron microscopy of 10 to 100 randomly selected mica particles. The average value of the maximum diameter of the flat surface obtained by image analysis can be used, and similarly, the maximum thickness of mica particles can be determined by the number average of the maximum thickness obtained by image analysis of the 10 to 100 mica particles randomly selected above. The values can be used to determine the aspect ratio of the mica particles.

In addition, when using a commercial product as (B1) mica powder, its average particle diameter and aspect ratio may be the values declared by the vendor.

As the mica powder which is the component (B1), in addition to natural mica such as muscovite, phlogopite, and biotite, synthetic mica can be used. Muscovite is preferred because it contains fewer impurities and provides excellent elongation properties to the cured rubber-like elastic body.

The blending amount of mica powder, component (B1), is 1 to 100 parts by mass, and 6 to 50 parts by mass, per 100 parts by mass of component (A), in order to achieve both excellent elongation properties and adhesive properties of the cured product. Preferably.

The room temperature curable polyorganosiloxane composition of this embodiment can improve the mechanical properties of a cured product by containing (B2) fumed silica.

In the room temperature curable polyorganosiloxane composition of the present embodiment, the specific surface area of the fumed silica (B2) measured by the BET method is preferably, for example, about 100 to 300 mm ² /g from the viewpoint of dispersibility.

As the fumed silica, either fumed silica whose surface has been treated with a surface treatment agent or fumed silica whose surface has not been treated may be used, but surface-treated fumed silica is preferred. By blending the surface-treated fumed silica, it is possible to improve the dispersibility of the mica powder (B1) in the composition and improve the mechanical properties such as elongation properties and hardness of the cured product. As the surface treatment agent, organochlorosilanes, polyorganosiloxanes, organosilazanes, etc. can be used. Among the above-mentioned surface treatment agents, it is preferable to use organosilazanes from the viewpoint of high degree of treatment and amount of treatment. Here, the fumed silica surface-treated with the above-mentioned surface treatment agent has an alkyl group carbon on the surface. The carbon content of the surface-treated fumed silica is preferably 2.0% by mass or more, for example, from the viewpoint of storage stability, especially viscosity stability (workability).

When the room temperature curable polyorganosiloxane composition of the present embodiment contains fumed silica, the amount of fumed silica is 3 to 3 to 100 parts by mass of component (A) in terms of improving mechanical properties. The amount is 50 parts by weight, and preferably 3 to 30 parts by weight from the viewpoint of viscosity and workability. In addition, when using the above-mentioned surface-treated fumed silica, the amount of fumed silica is calculated based on the mass after surface treatment.

In addition, the room temperature curable polyorganosiloxane composition of the present embodiment may contain, in addition to the above (B1) mica powder and (B2) fumed silica, a room temperature curable polyorganosiloxane composition, as long as the effects of the present invention are not impaired. It may also contain other inorganic fillers blended with. Other inorganic fillers include wet silica such as precipitated silica, dry silica such as calcined silica, fine quartz powder, calcium carbonate, carbon black, diatomaceous earth, aluminum oxide, zinc oxide, aluminosilicate, and the like.

In the room temperature curable polyorganosiloxane composition of the present embodiment, the alkoxysilane or its partially hydrolyzed condensate as component (C) has the general formula (C): R ¹ _a Si(OR ² ) _{4- a} (wherein R ¹ is a monovalent hydrocarbon group, R ² is an alkyl group or an alkoxy-substituted alkyl group, and a is 0, 1, or 2) or a partially hydrolyzed condensate thereof (hereinafter referred to as "alkoxysilane etc.").

In the above formula (C), R ¹ is a monovalent hydrocarbon group, and examples thereof include the same groups as R ⁴ described above. R ² is an alkyl group or an alkoxy-substituted alkyl group. Further, a is 0, 1 or 2.

Specifically, the alkoxysilane includes methyltrimethoxysilane, vinyltrimethoxysilane, decyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, methyltri(ethoxymethoxy)silane, tetramethoxysilane, tetraethoxysilane, Examples include dimethyldimethoxysilane, dimethyldiethoxysilane, and diphenyldimethoxysilane.

The room temperature curable polyorganosiloxane composition of the present embodiment may contain either the alkoxysilane represented by the above general formula or its hydrolyzed condensate as the alkoxysilane (C), or may contain both. May contain. From the viewpoint of improving the adhesion of the cured product to the substrate, it is preferable to contain both an alkoxysilane and a hydrolyzed condensate thereof.

When the room temperature curable polyorganosiloxane composition of the present embodiment contains both an alkoxysilane represented by the above general formula and a hydrolyzed condensate of the alkoxysilane as the alkoxysilane (C), the alkyl having these It is preferable that the groups are different from each other, that is, it is preferable to use alkoxysilanes having different combinations of R ¹ and R ² in the above general formula (C) and hydrolyzed condensates of alkoxysilanes from the viewpoint of improving adhesion to the substrate. In addition, the ratio of both the alkoxysilane and the hydrolyzed condensate of alkoxysilane is 1 in terms of the mass ratio of alkoxysilane/hydrolyzed condensate of alkoxysilane, from the viewpoint of improving the adhesiveness of the cured product to the substrate. The ratio is preferably from /2 to 2/1.

Further, when two or more types of alkoxysilanes etc. represented by the above general formula (C) are included, it is preferable to use two types with different values of a in the above general formula (C), and in this case, a It is preferable that the smaller the value of , the smaller the number of carbon atoms in R ¹ and R ² . For example, when using a tetrafunctional alkoxysilane etc. where the value of a is 0 and a trifunctional alkoxysilane etc. where the value of a is 1, at least one of R ¹ and R ² possessed by the trifunctional alkoxysilane etc. First, it is preferable that the number of carbon atoms is smaller than the number of carbon atoms of R ¹ and R ² of the tetrafunctional alkoxysilane, etc., and the number of carbon atoms of both R ¹ and R ² of the functional alkoxysilane, etc. is It is preferable that the number of carbon atoms in R ¹ and R ² is smaller than that of the alkoxysilane and the like.

In the room temperature curable polyorganosiloxane composition of the present embodiment, the content of (C) alkoxysilane, etc. is 0.1 to 15 parts by mass, and 0.5 parts by mass, based on 100 parts by mass of component (A). The amount is preferably 10 parts by mass.

In an embodiment of the present invention, the titanium chelate catalyst as component (D) is tetra(isopropoxy)titanium, tetrabutoxytitanium, a partial hydrolyzate of tetra(isopropoxy)titanium, or a partial hydrolyzate of tetrabutoxytitanium. alkoxytitaniums such as tetrabutoxyzirconium and its partially hydrolyzed alkoxyzirconiums, (diisopropoxybis(ethylacetoacetate) titanium, diisopropoxybis(methylacetoacetate)titanium, diisopropoxybis(acetylacetone) ) titanium, dibutoxybis(ethyl acetoacetate) titanium, dimethoxybis(ethyl acetoacetate) titanium, and other known titanium chelate compounds; Examples include zirconium, butoxytris(ethylacetoacetate)zirconium, and tributoxy(ethylacetoacetate)zirconium. Among them, titanium chelate compounds are preferred because of their curing catalytic ability.

The amount of the titanium chelate catalyst (D) is 0.1 to 10 parts by weight, preferably 1 to 5 parts by weight, per 100 parts by weight of the polyorganosiloxane (A).

It is preferable that the room temperature curable polyorganosiloxane composition of the present embodiment further contains (E) an adhesion imparting agent in order to further improve adhesiveness and adhesive durability.

(E) As the adhesion imparting agent, an isocyanurate compound such as 1,3,5-tris[3-(trimethoxysilyl)propyl] isocyanurate represented by the following formula (3) can be used.

(E) The isocyanurate compound used as an adhesive agent includes a (trimethoxysilyl)propyl group bonded to the nitrogen atom of the above-mentioned isocyanuric acid 1,3,5-tris[3-(trimethoxysilyl)propyl]. A compound in which one or two of these groups are converted to a 2-propenyl group or a (dimethoxysilylmethyl)propyl group may also be used.

Furthermore, as the adhesion imparting agent (E), a silane compound represented by the general formula: R ⁷ _4-q SiY _q may be used. In the formula, R ⁷ represents a substituted or unsubstituted monovalent hydrocarbon group which may be the same or different from each other, and Y represents a hydrolyzable group. Moreover, q is a number that exceeds 2 and is 4 or less on average. Examples of R ⁷ include a substituted amino group, epoxy group, isocyanato group, (meth)acryloxy group, mercapto group, or an alkyl group or phenyl group substituted with a halogen atom. Examples of the substituted alkyl group include a substituted methyl group, a 3-substituted propyl group, and a 4-substituted butyl group, and a 3-substituted propyl group is preferred because it is easy to synthesize.

(E) Silane compounds having the above general formula that can be used as adhesive properties include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltriisopropoxysilane, 3-aminopropyl Triacetamidosilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-methyl-3-aminopropyltrimethoxysilane, Substituted or unsubstituted amino group-containing silanes such as N-phenyl-3-aminopropyltrimethoxysilane, N,N-dimethyl-3-aminopropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3- Epoxy group-containing silanes such as glycidoxytrimethoxysilane, 3-glycidoxymethyldimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane; 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropylmethyldimethoxysilane isocyanato group-containing silanes such as; Examples include group-containing silanes; mercapto group-containing silanes such as 3-mercaptopropyltrimethoxysilane; and halogen atom-containing silanes such as 3-chloropropyltrimethoxysilane. Among these, epoxy group-containing silanes and isocyanato group-containing silanes, which have less influence on the titanium chelate catalyst (D) described above, are more preferred. Further, it is preferable to use a mixture or a reactant of an amino group-containing silane and an epoxy group-containing silane.

From the viewpoint of compatibility in the room-temperature curable polyorganosiloxane composition, when component (E) is blended, the amount thereof is 0.01 to 5 parts by mass per 100 parts by mass of component (A). It is preferable. When the blending amount of component (E) is 0.01 or more per 100 parts by mass of component (A), a sufficient adhesion improvement effect can be obtained, and the effect is quickly developed. In addition, when the amount is 5 parts by mass or less, separation during storage and shrinkage of the cured product can be suppressed, and storage stability and workability can be suppressed, and yellowing phenomenon can be suppressed. The blending amount of component (E) is more preferably in the range of 0.1 to 2 parts by weight per 100 parts by weight of component (A).

The room-temperature curable polyorganosiloxane composition of the present embodiment may contain a thixotropic agent, a viscosity modifier, a fluidity modifier, a pigment, a flame retardant, an organic solvent, a fungicide, an antibacterial agent, and an ultraviolet absorber, as necessary. It may contain various functional additives such as additives and heat resistance improvers.

The room temperature curable polyorganosiloxane composition of the present embodiment is prepared by uniformly mixing predetermined amounts of each of the components (A) to (D), the optional component (E), and the other optional components described above in a dry atmosphere. By doing so, a one-component room temperature curable composition is obtained. When this composition is exposed to air, a crosslinking reaction proceeds due to moisture, and it hardens into a rubber elastic body. It can also be prepared as a two-component room temperature curable composition. In a two-component composition, the base ingredients (e.g., components (A), (B1), and (B2)) and the curing agent (e.g., components (C) and (D)) are mixed in air. It cures in the same way as a one-component room temperature curable composition.

The room temperature curable polyorganosiloxane composition of the embodiment also has a cured product obtained by curing the composition as described above, which has excellent elongation and tensile strength, and has excellent adhesion to various substrates. Are better. For example, a cured product having an elongation measured according to JIS K 6249 of 80% or more can be obtained.

Therefore, the room temperature curable polyorganosiloxane composition of the embodiment can be used as an adhesive for coating, potting, fixing parts, etc., as well as various mechanical parts such as automobile parts such as O-rings, packings, and gaskets. Suitable for this purpose.

Examples of the present invention will be described below, but the present invention is not limited to these Examples. In the following Examples and Comparative Examples, the viscosity is the value at 25°C. Note that, except for two examples, "Example 2" and "Example 3," all the remaining "Examples" are "Reference Examples."

Each component used in the following Examples and Comparative Examples is as follows.
A1: Polydimethylsiloxane with both ends capped with trimethoxysilyl groups (viscosity: 10,400 mPa・s, average degree of polymerization: 800)
A2: Polydimethylsiloxane with both ends capped with methyldimethoxysilyl groups (viscosity: 11,000 mPa・s, average degree of polymerization: 800)

B1: Mica powder (muscovite powder with average particle size: 22 μm, aspect ratio: 70)

b1: Quartz powder (average particle size: 4.2 μm)
b2: Calcium carbonate (average particle size (number-based particle size distribution 50%): 2.2 μm: specific surface area: 4.5 m ² /g)
B21: Trimethylsilyl surface-treated fumed silica (specific surface area by BET method before surface treatment: 200 m ² /g, carbon (C) content: 3.3% by mass)
B22: Trimethylsilyl surface-treated fumed silica (specific surface area by BET method before surface treatment: 200 m ² /g, carbon (C) content: 2.0% by mass)
B23: Dimethylsilyl surface-treated fumed silica (specific surface area by BET method before surface treatment: 200 m ² /g, carbon (C) content: 1.09% by mass)
B24: Dimethylsilyl surface-treated fumed silica (specific surface area by BET method before surface treatment: 130 m ² /g, carbon (C) content: 0.79% by mass)
B25: Fumed silica surface-treated with octamethylcyclotetrasiloxane (specific surface area by BET method before surface treatment: 200 m ² /g)

C1: Methyltrimethoxysilane C2: Methyltriethoxysilane C3: Methyl silicate C4: Ethyl silicate

D: Bis(ethyl acetoacetate) diisopropoxy titanium E1: 1,3,5-tris[3-(trimethoxysilyl)propyl] isocyanurate
E2: 3-glycidoxypropyltrimethoxysilane

(Example 1)
(A1) 25 parts by mass of mica powder (muscovite powder with average particle size: 22 μm, aspect ratio: 70) added to 100 parts by mass of polyorganosiloxane consisting of polydimethylsiloxane whose both ends are blocked with trimethoxysilyl groups. (B21) 20 parts by mass of trimethylsilyl surface-treated fumed silica (original BET specific surface area 200 m ² /g, carbon content: 3.3%), (C1) 1 part by mass of methyltrimethoxysilane, (C3) Methyl silicate 1 part by mass, (D) 3 parts by mass of diisopropoxybis(ethyl acetoacetate) titanium, and 2 parts by mass of (E1) tri(3-(trimethoxysilyl)propyl)isocyanurate to form a polyorganosiloxane composition. I got something.

(Examples 2 to 14, Comparative Examples 1 to 4)
Polyorganosiloxane compositions of Examples 2 to 14 and Comparative Examples 1 to 4 were obtained by changing the types and blending amounts of components (A) to (E) as shown in Table 1.

Next, the hardness, tensile strength, elongation, adhesive strength, and tack-free time of the cured product of the polyorganosiloxane composition obtained above were measured and evaluated by the following methods. Furthermore, the extrusion force, liquid separation property, and specific gravity of the polyorganosiloxane composition were measured and evaluated using the following methods. The results of these measurements and evaluations are shown in the lower column of Table 1.

[Hardness, tensile strength and elongation]
The polyorganosiloxane composition was dispensed and formed into a 2 mm sheet, and then left to cure in an atmosphere of 23° C. and 50% RH for 7 days to obtain a cured product of the polyorganosiloxane composition. The hardness (initial hardness) of the obtained cured product was measured using a type A hardness meter. In addition, tensile strength was measured in accordance with JIS K 6249. Furthermore, elongation was measured in accordance with JIS K 6249.

[Adhesive strength]
The composition was applied to the surface of an aluminum base material (Bare Al) that had not undergone surface treatment so that the length was 10 mm, the width was 25 mm, and the thickness was 1 mm, and the same aluminum substrate as above was superimposed on it. Then, the sample was left to stand in an atmosphere of 23° C. and 50% RH for 7 days to be cured to obtain a test piece. Then, a tensile test was performed on the obtained test piece using an Autograph manufactured by Shimadzu Corporation at a tensile speed of 10 mm/min, and the shear adhesive strength (MPa) and cohesive failure rate (%) were measured.
In the same manner as above, adhesive strength was evaluated using aluminum die cast (Al-DC) and polyphenylene sulfide (PPS) as base materials.

[Tack free time]
The polyorganosiloxane composition was applied to the surface of an aluminum Petri dish with a diameter of 5 cm, the surface of which had been cleaned with an organic solvent, and was dried by touching the surface with a finger under an environment of 23 ° C. and 50% relative humidity (RH). We measured the time it took to confirm that this was the case.

[Extrusion force]
The polyorganosiloxane composition was filled into a 333 ml cartridge manufactured by Showa Marutsutsu Co., Ltd., and the composition was extruded from a nozzle attached to the tip of the cartridge (inner diameter of the tip: 6.2 mm). At this time, the plunger at the bottom of the cartridge was pressed and the force for extruding the composition (discharge force) was measured using an Autograph manufactured by Shimadzu Corporation. In this way, the extrusion force of the polyorganosiloxane composition was measured initially and after standing at 70° C. for 5 days.

[specific gravity]
The specific gravity of the cured product of the polyorganosiloxane composition was measured based on the substitution method specified in JIS K 6220, based on the mass ratio with water at a water temperature of 23±2°C.

[Liquid separation]
The polyorganosiloxane composition was left at room temperature and pressure for 5 days. The state of the composition was observed after 1 day or 5 days to confirm whether the filler ((B1) mica powder, quartz powder, or calcium carbonate) had separated. The composition of the example was mixed evenly even after 5 days, whereas in the composition of the comparative example, some of the filler (quartz powder or calcium carbonate) separated and turned grayish after 5 days. Observed as a shadow.

[Method for observing foaming and cracks]
Prepare a glass plate 2 with a size of 50 mm x 50 mm and a thickness of 1 mm, and place adhesive Teflon (registered trademark, hereinafter the same) in the center of the four sides of this glass plate with a size of 10 mm x 5 mm and a thickness of 0.1 mm. A spacer 3 was created by stacking two tapes and pasting them at four locations in total (FIG. 1(a)).

Sample 1 of the composition to be measured was applied to the center of the glass plate on the side to which the adhesive Teflon tape spacer 3 was attached, with a bead diameter of 1.2 mm and a diameter of 40 mm. At this time, a non-adhesive Teflon spacer 4 with a width of 1 mm and a thickness of 0.2 mm was placed on the surface of the coated sample 1 so as to be perpendicular to the outer periphery of the sample (FIG. 1(b)).

A glass plate similar to that described above was laminated onto the coated sample, and the two glasses were fixed with a double clip. The non-adhesive Teflon spacer 4 was pulled out to form a hole for air release when the pressure in the internal section increases during curing. Then, it was cured at 23° C. and 50% RH for 40 minutes. This was maintained at 85°C for 60 minutes and then allowed to cool to room temperature at 23°C and 50 % RH for 60 minutes. Light from a fluorescent lamp was transmitted through the obtained glass plate with the cured product, and the presence or absence of foaming and cracks was visually observed. A sample in which neither foaming nor cracking occurred was graded as "absent," and a sample in which either foaming or cracking occurred was graded as "presence."

From the above, it can be seen that the polyorganosiloxane compositions of Examples can obtain excellent elongation properties and hardness with a small amount of filler, and also have good adhesion to various substrates. On the other hand, in the polyorganosiloxane composition of the comparative example, the filler separates and high filling is required to obtain the desired hardness, and as a result, it is difficult to achieve excellent elongation properties and adhesive properties. I understand.

1... Sample, 2... Glass plate, 3... Adhesive Teflon tape spacer, 4... Non-adhesive Teflon spacer.

Claims (8)

(A) 100 parts by mass of a linear polyorganosiloxane having two or more silicon-bonded alkoxy groups in one molecule;
(B1) 1 to 100 parts by mass of muscovite powder,
(B2) 3 to 50 parts by mass of fumed silica,
(C) General formula: R ¹ _a Si(OR ² ) _4-a
(In the formula, R ¹ is a monovalent hydrocarbon group, R ² is an alkyl group or an alkoxy-substituted alkyl group, and a is 0, 1, or 2.)
0.5 to 15 parts by mass of an alkoxysilane or a partially hydrolyzed condensate thereof represented by: and 0.1 to 10 parts by mass of (D) a titanium chelate catalyst,
The alkoxysilane (C) or a partially hydrolyzed condensate thereof is
(C2) methyltriethoxysilane;
(C3) methyl silicate or (C4) ethyl silicate;
A room temperature curable polyorganosiloxane composition comprising: (E) further contains 0.01 to 5 parts by mass of an adhesion promoter,
The adhesion imparting agent (E) is
(E1) tri(3-(trimethoxysilyl)propyl)isocyanurate;
(E2) 3-glycidoxypropyltrimethoxysilane,
The room temperature curable polyorganosiloxane composition according to claim 1, comprising: The (B2) fumed silica is surface-treated,
The room-temperature-curable polyorganosiloxane composition according to claim 1 or 2, wherein the carbon content of the surface-treated (B2) fumed silica is 2.0% by mass or more. The room-temperature-curable polyorganosiloxane composition according to any one of claims 1 to 3, wherein the average particle size measured as the average value of the maximum diameter of the flat plane of the muscovite powder (B1) is 1 to 100 μm. . The room-temperature-curable polyorganosiloxane composition according to any one of claims 1 to 4, which contains 6 to 50 parts by mass of the (B1) muscovite powder. The polyorganosiloxane (A) is
(A1) a polyorganosiloxane endblocked with trialkoxysilyl groups at both ends, each having three alkoxy groups at both ends, and
Room temperature curing according to any one of claims 1 to 5, comprising at least one selected from the group consisting of (A2) a polyorganosiloxane endblocked with dialkoxysilyl groups at both ends, each having two alkoxy groups at both ends. polyorganosiloxane composition. A cured product of the room temperature curable polyorganosiloxane composition according to any one of claims 1 to 6. The cured product according to claim 7, which has an elongation measured according to JIS K 6249 of 80% or more.

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