Room-temperature-curable organopolysiloxane composition and article

Abstract

This room-temperature-curable organopolysiloxane composition comprises, in a specific proportion: (A) an organopolysiloxane having a specific structure; (B) surface-treated calcium carbonate having a BET specific surface area in a specific range and having been treated in a specific fatty-acid amount; (C) a hydrolyzable organosilicon compound and / or a product of partial hydrolytic condensation thereof, the hydrolyzable organosilicon compound having at least three silicon-atom-bonded hydrolyzable groups in the molecule and being neither (A) component nor (D) component; (D) a silane coupling agent having a specific molecular structure having a carboxylic acid silyl ester bond; and (E) a curing catalyst. The composition has a low viscosity and high thixotropic properties and hence has excellent applicability. The composition cures at room temperature with moisture in the air (crosslinking by condensation reaction), thereby giving a cured silicone rubber which has satisfactory adhesion to die-cast aluminum.

Description

Room temperature curable organopolysiloxane compositions and articles

[0001] The present invention relates to a room-temperature curable organopolysiloxane composition that hardens at room temperature to form a silicone rubber, and more particularly to a room-temperature curable organopolysiloxane composition that has low viscosity and high thixotropy before curing, resulting in excellent workability, and provides a cured product with excellent adhesion to aluminum die castings and the like after curing, and to an article containing an aluminum die-cast substrate bonded with the composition.

[0002] Moisture-curing silicone rubber compositions, which crosslink (cure) into an elastomer-like silicone rubber cured product at room temperature (23°C ± 15°C) due to humidity in the atmosphere, are easy to handle, and the resulting cured silicone rubber product has excellent weather resistance and electrical properties. Therefore, they are used in a variety of fields, such as automotive sealants, building sealants, and adhesives in the electrical and electronic fields.

[0003] For automotive applications, metals are used for components due to their durability and the strength of the base material. Die casting is widely used because it allows for the mass production of highly precise castings in a short time. Among these, aluminum alloy die casting (hereinafter also referred to as aluminum die casting) is the most widely used die casting alloy due to its light weight, excellent corrosion resistance, and minimal dimensional change over time, accounting for approximately 97% of all die casting alloys.

[0004] However, aluminum alloy die castings are known to be extremely difficult to adhere to. One reason for this difficulty in adhesion is thought to be the uneven distribution of trace metal components such as silicon, copper, and iron, which are additives, on the surface of the aluminum alloy die casting, resulting in the formation of grain boundaries. Furthermore, the release agent applied to the mold remains as carbides after heating.

[0005] Several methods have been proposed to improve the adhesion between aluminum alloy die-casts and resins. Patent No. 6439455 (Patent Document 1) proposes a method in which perforations with openings are formed on the surface of a metal member by laser irradiation, thereby improving adhesion through an anchoring effect. Furthermore, Patent No. 6351902 (Patent Document 2) and Patent No. 6568983 (Patent Document 3) propose a method in which a laser is irradiated onto the joining surface to melt the surface layer of the joining surface, thereby removing grain boundaries and carbide films that cause poor adhesion, and then plasma treatment is performed to generate hydroxyl groups and improve adhesion. In all of these cases, the surface of the substrate is treated with a laser to improve adhesion, which increases the number of steps involved.

[0006] Furthermore, Japanese Patent Publication No. 6988736 (Patent Document 4) and Japanese Patent Publication No. 7176527 (Patent Document 5) propose that the adhesion to magnesium alloys can be improved by using a silane coupling agent having a carboxylate silyl ester group, which is also used in this composition. However, there is no mention of adhesion to aluminum alloy die castings.

[0007] Patent No. 6439455 Patent No. 6351902 Patent No. 6568983 Patent No. 6988736 Patent No. 7176527

[0008] The object of the present invention is to provide a room-temperature curable organopolysiloxane composition that has low viscosity and high thixotropy, resulting in a cured product with excellent workability and adhesion to aluminum die-castings, and an article containing an aluminum die-casting substrate bonded with the composition.

[0009] To achieve the above objective, the present inventors have discovered that a room-temperature curable organopolysiloxane composition containing in a specific proportion (A) an organopolysiloxane represented by general formula (1) and / or (2) described later, (B) surface-treated calcium carbonate having a specific BET specific surface area and treated with a specific amount of fatty acids, (C) a hydrolyzable organosilicon compound other than components (A) and (D) and / or a partially hydrolyzed condensate thereof having at least three hydrolyzable groups bonded to silicon atoms in one molecule, (D) a silane coupling agent having a specific molecular structure with a carboxylate silyl ester bond, and (E) a curing catalyst provides a silicone rubber cured product that has excellent workability and hardens at room temperature by atmospheric moisture (crosslinking by condensation reaction) to provide good adhesion to aluminum die-castings, thus leading to the present invention.

[0010] Accordingly, the present invention provides an article comprising the following room-temperature curable organopolysiloxane composition and an aluminum die-cast substrate. [1] (A) Organopolysiloxane represented by the following general formula (1) and / or (2): 100 parts by mass, HO(SiR2O) n H (1) (wherein R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, either identical or different, and n is an integer of 10 or more.) (In the formula, R and n are as described above, X is independently an oxygen atom or an alkylene group having 2 to 5 carbon atoms, and m is independently 0 or 1 for each silicon atom to which it is bonded.) (B) BET specific surface area of ​​13 to 25 m² 2 Surface-treated calcium carbonate having a concentration of / g, wherein the surface of the calcium carbonate particles is treated with a fatty acid, and the surface of the calcium carbonate is treated with 0.5 to 2.0 parts by mass of fatty acid per 100 parts by mass of calcium carbonate: 15 to 200 parts by mass, (C) hydrolyzable organosilicon compounds other than components (A) and (D) and / or partially hydrolyzed condensates thereof, having at least three hydrolyzable groups bonded to silicon atoms in one molecule: 0.1 to 50 parts by mass, (D) silane coupling agent represented by the following general formula (3): 0.05 to 10 parts by mass, and (In the formula, R 1 , R2 , R 3 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different, k is independently an integer of 3 to 14, a is independently an integer of 0 to 2 for each silicon atom to which it binds, and b is an integer of 0 to 3. ) (E) Curing catalyst: A room-temperature curable organopolysiloxane composition containing 0.001 to 15 parts by mass. [2] The room-temperature curable organopolysiloxane composition according to [1], wherein the component (C) is a hydrolyzable organosilane compound represented by the following general formula (4) and / or a partial hydrolysis condensate thereof. R 4 d SiR 5 4-d (4) (In the formula, R 4 is a monovalent hydrocarbon group, and R 5 is independently a hydrolyzable group. d is 0 or 1. ) [3] The room-temperature curable organopolysiloxane composition according to [1] or [2], which is used for aluminum die-cast adhesion. [4] An article containing a base material of aluminum die-cast adhered by the room-temperature curable organopolysiloxane composition according to any one of [1] to [3].

[0011] According to the present invention, a room-temperature curable organopolysiloxane composition is obtained which has excellent workability due to its low viscosity and high thixotropy, and gives a cured product having excellent adhesion to aluminum die-cast.

[0012] [(A) component] The organopolysiloxane of the (A) component used in the room-temperature curable organopolysiloxane composition of the present invention acts as the main agent (base polymer) of the composition of the present invention, and is represented by the following general formula (1) and / or (2). HO(SiR2O) n H (1) (In the formula, R is a non-substituted or halogen atom-substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different, and n is an integer of 10 or more.) (In the formula, R is a non-substituted or halogen atom-substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different, n is an integer of 10 or more, X is independently an oxygen atom or an alkylene group having 2 to 5 carbon atoms, and m is independently 0 or 1 for each silicon atom to which it binds.) [[ID=​In general formulas (1) and (2), R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, which is either unsubstituted or substituted with a halogen atom. Examples include alkyl groups such as methyl, ethyl, and propyl groups; cycloalkyl groups such as cyclohexyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; and groups in which the hydrogen atoms bonded to the carbon atoms of these groups are partially substituted with halogen atoms, such as 3,3,3-trifluoropropyl group. Among these, methyl, vinyl, phenyl, and 3,3,3-trifluoropropyl groups are preferred, and methyl groups are particularly preferred. The multiple Rs in general formulas (1) and (2) may be the same group or different groups.

[0014] Furthermore, n is an integer of 10 or more, and in particular, an integer such that the viscosity of these organopolysiloxanes at 23°C is in the range of 25 to 500,000 mPa·s, preferably in the range of 500 to 100,000 mPa·s. If the viscosity is lower than 25 mPa·s, the rubber elasticity after curing will be poor, and if it is higher than 100,000 mPa·s, the workability will decrease. Note that the viscosity is the value at 23°C measured by a rotational viscometer (e.g., BL type, BH type, BS type, cone plate type, rheometer, etc.). Specifically, the value of n that gives such viscosity is usually an integer of about 10 to 2,000, preferably 20 to 1,500, and more preferably 50 to 1,000.

[0015] Furthermore, in general formula (2), X is independently an oxygen atom or an alkylene group having 2 to 5 carbon atoms. Examples of alkylene groups having 2 to 5 carbon atoms include ethylene, propylene, and butylene groups. Among these, oxygen atoms and ethylene groups are preferred as X.

[0016] m is independently 0 or 1 for each silicon atom to which it is bonded.

[0017] [Component (B)] The surface-treated calcium carbonate of component (B) is a characteristic component of the present invention, and has a BET specific surface area of ​​13 to 25 m². 2The viscosity is / g, and it is an essential condition that the calcium carbonate particles have a surface treated with fatty acids. In particular, by using surface-treated calcium carbonate in which 0.5 to 2.0 parts by mass of fatty acids are applied to the surface of the calcium carbonate per 100 parts by mass of calcium carbonate, thixotropy is achieved with sufficiently low viscosity, and adhesion to aluminum die casting is improved.

[0018] As mentioned above, surface-treated calcium carbonate has a BET specific surface area of ​​13 to 25 m². 2 The value is / g, preferably 15 to 20m 2 It is / g. 25m 2 When the amount exceeds 13m / g, the resulting viscosity becomes high, making it difficult to work with. 2 If the amount is less than / g, the thixotropy of the composition decreases, and its shape retention decreases.

[0019] The optimal amount of fatty acid used for surface treatment varies depending on the BET specific surface area of ​​the calcium carbonate raw material before treatment. However, within the BET specific surface area range described above, it is preferable to treat with 0.5 to 2.0 parts by mass of fatty acid per 100 parts by mass of calcium carbonate, and particularly preferable to treat with 1.0 to 1.8 parts by mass of fatty acid. Generally, if the amount of surface treatment agent is too small, the viscosity of the composition will be high and the thixotropy will decrease, while if the amount of treatment is too large, the adhesion of the resulting cured product will decrease.

[0020] Examples of fatty acids used for surface treatment include lauric acid, myristic acid, palmitic acid, oleic acid, and stearic acid.

[0021] In the present invention, a method for surface-treating a calcium carbonate surface with a fatty acid is to add a surface treatment agent, selected from fatty acids, sodium salts of fatty acids, potassium salts of fatty acids, and esters of fatty acids, to a slurry of calcium carbonate particles, stir, and then perform the treatment. It is believed that the surface treatment agent added to the slurry of calcium carbonate particles reacts with the calcium present on the calcium carbonate surface to form calcium salts of fatty acids.

[0022] The blending amount of component (B) is preferably 15 to 200 parts by mass, particularly preferably 30 to 150 parts by mass, based on 100 parts by mass of component (A). When it is less than 15 parts by mass, the thixotropic property of the composition decreases. When it exceeds 200 parts by mass, the viscosity of the composition becomes too high and the desired workability cannot be obtained.

[0023] [(C) component] The (C) component used in the room-temperature curable organopolysiloxane composition of the present invention acts as a crosslinking agent (curing agent) and has at least three hydrolyzable groups bonded to silicon atoms in one molecule. It is a hydrolyzable organosilicon compound other than components (A) and (D) and / or its partial hydrolysis condensate. The organosilicon compound of this (C) component usually does not contain heteroatoms such as nitrogen atoms, oxygen atoms, and sulfur atoms in the molecule other than the hydrolyzable groups. As the (C) component, a hydrolyzable organosilane compound represented by the following general formula (4) and / or its partial hydrolysis condensate (that is, an organosiloxane oligomer having at least two, preferably three or more remaining hydrolyzable groups in the molecule formed by partially hydrolyzing and condensing the organosilane compound) is preferable. R 4 d SiR 5 4-d (4) (In the formula, R 4 is a monovalent hydrocarbon group, and R 5 is independently a hydrolyzable group. d is 0 or 1, preferably 1.)

[0024] In the general formula (4), the hydrolyzable group R 5Examples thereof include an alkoxy group, an acyloxy group, an alkenyloxy group, a ketoxime group, etc. Specifically, alkoxy groups having 1 to 4 carbon atoms, particularly 1 or 2 carbon atoms, such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group; acyloxy groups having 2 to 4 carbon atoms, such as an acetoxy group, a propionoxy group; alkenyloxy groups having 2 to 4 carbon atoms, such as a vinyloxy group, an allyloxy group, a propenoxy group, an isopropenoxy group; ketoxime groups having 3 to 8 carbon atoms, such as a dimethylketoxime group, a methylethylketoxime group, a methylisobutylketoxime group, etc. can be exemplified.

[0025] Further, the remaining group R bonded to the silicon atom other than the hydrolyzable group 4 is not particularly limited as long as it is a monovalent hydrocarbon group. Specifically, monovalent hydrocarbon groups having 1 to 10 carbon atoms such as alkyl groups such as a methyl group, an ethyl group, a propyl group, a butyl group; alkenyl groups such as a vinyl group; aryl groups such as a phenyl group are exemplified. Among these, a methyl group, an ethyl group, a vinyl group, and a phenyl group are preferable.

[0026] Specific examples of such component (C) include alkoxysilanes such as methyltrimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, tetramethoxysilane, vinyltriethoxysilane, tetraethoxysilane; acetoxysilanes such as methyltriacetoxysilane, vinyltriacetoxysilane; isopropenoxysilanes such as methyltriisopropenoxysilane, vinyltriisopropenoxysilane, phenyltriisopropenoxysilane; and ketoximesilanes such as tetrakis(methylethylketoxime)silane, methyltris(dimethylketoxime)silane, methyltris(methylethylketoxime)silane, ethyltris(methylethylketoxime)silane, methyltris(methylisobutylketoxime)silane, vinyltris(methylethylketoxime)silane, and partial hydrolysis condensates of these silanes. These may be used alone or in combination of two or more.

[0027] The amount of component (C) is used in the range of 0.1 to 50 parts by mass, preferably 5 to 30 parts by mass, per 100 parts by mass of component (A). If it is less than 0.1 parts by mass, sufficient crosslinking cannot be obtained, making it difficult to obtain a composition with the desired rubber elasticity, and if it exceeds 50 parts by mass, the resulting cured product tends to have reduced mechanical properties.

[0028] Furthermore, component (C) is clearly different from the organopolysiloxane of component (A) described above in that n in formula (1) or (2) is less than 10, and is also clearly differentiated from the silane coupling agent of component (D) described later in that it does not have a silyl carboxylate bond in its molecule.

[0029] [Component (D)] The silane coupling agent of component (D) used in the room-temperature curable organopolysiloxane composition of the present invention has 1 to 4 silyl carboxylate bonds in its molecule and is essential for imparting good adhesion to aluminum die castings to the cured product (silicone rubber) obtained by curing the composition of the present invention at room temperature. In the silane coupling agent having silyl carboxylate groups used in the present invention, the carboxyl group is protected by a silyl group when uncured, but the silyl group is removed by hydrolysis during curing, regenerating the carboxyl group and improving adhesion to aluminum die castings. Furthermore, by protecting the highly active carboxyl group with a silyl group, improved storage stability and chemical resistance are also achieved.

[0030] The silane coupling agent containing a carboxylate silyl ester group according to the present invention has a structure represented by the following general formula (3). (In the formula, R 1 , R 2 , R 3 (where is the same or different monovalent hydrocarbon group having 1 to 10 carbon atoms, k is an integer from 3 to 14, a is an integer from 0 to 2 for each silicon atom to which it is bonded, and b is an integer from 0 to 3.)

[0031] In general formula (3), OR 1 R is a hydrolyzable group in the silane coupling agent. 1This refers to an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, such as alkyl groups such as methyl, ethyl, and propyl groups; cycloalkyl groups such as cyclohexyl groups; saturated or unsaturated aliphatic hydrocarbon groups such as alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; and aromatic hydrocarbon groups such as aralkyl groups such as benzyl and phenylethyl groups. Among these, alkyl groups such as methyl, ethyl, and propyl groups are preferred, and methyl and ethyl groups are particularly preferred.

[0032] Furthermore, the value of a in the formula is an integer from 0 to 2, independently for each silicon atom to which it is bonded, and is preferably 0.

[0033] Also, in general formula (3), R 2 This refers to an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, such as alkyl groups such as methyl, ethyl, and propyl groups; cycloalkyl groups such as cyclohexyl groups; saturated or unsaturated aliphatic hydrocarbon groups such as alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; and aromatic hydrocarbon groups such as aralkyl groups such as benzyl and phenylethyl groups. Among these, alkyl groups such as methyl, ethyl, and propyl groups, and aryl groups such as phenyl groups are preferred, with methyl and phenyl groups being particularly preferred.

[0034] In general formula (3), R 3 The carboxyl group is derived from a silyl group that protects the carboxyl group, and is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples include alkyl groups such as methyl, ethyl, and propyl groups; cycloalkyl groups such as cyclohexyl groups; saturated or unsaturated aliphatic hydrocarbon groups such as alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; and aromatic hydrocarbon groups such as aralkyl groups such as benzyl and phenylethyl groups. Among these, alkyl groups such as methyl, ethyl, and propyl groups, alkenyl groups such as vinyl groups, and aryl groups such as phenyl groups are preferred, with methyl, vinyl, and phenyl groups being particularly preferred.

[0035] Furthermore, the value of b in the formula is an integer from 0 to 3, preferably an integer from 1 to 3, more preferably 2 or 3, and when the value of b is 2 or 3, R 3 The structures may be identical or different from each other.

[0036] In general formula (3), k is an integer from 3 to 14, and represents the number of repeating saturated hydrocarbon groups in the spacer that connects the hydrolyzable alkoxysilyl group and the silyl carboxylate group of the silane coupling agent. The value of k in the formula is an integer from 3 to 14, preferably an integer from 3 to 13, and more preferably an integer from 3 to 11. If the value of k is less than 3, synthesis becomes difficult, and if the value of k is greater than 14, the molecular weight may become too large, potentially reducing adhesion.

[0037] The following compounds are examples of silane coupling agents containing silyl carboxylate groups.

[0038] The silane coupling agent containing a silyl carboxylate group represented by the above general formula (3) can be produced, for example, by first preparing a silyl carboxylate compound having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at the terminal, represented by the following general formula (5), through a dehalogenation reaction between a carboxylic acid having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at the terminal and a halosilane, and then reacting the silyl carboxylate compound with an alkoxysilane having an SiH group (hydrosilyl group) in the presence of a catalyst. (In the formula, R 3 (b and k are the same as above.)

[0039] Silyl carboxylate compounds having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at the terminal, represented by general formula (5), can be produced by the following method: General formula (6) A carboxylic acid having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at its terminus, represented by the following general formula (7) (In the formula, R 3 A halosilane represented by (where b is the same as above, and X' represents a halogen atom) can be produced by reacting it in the presence of a hydrogen halide scavenger at, for example, 0 to 150°C, preferably 0 to 60°C, for about 30 minutes to 10 hours.

[0040] In formula (7) above, the halogen atom of X' can be a fluoro group, a chloro group, a bromo group, or an iodine group, but a chloro group is preferred due to its availability.

[0041] The reaction ratio between a carboxylic acid having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at the terminal, represented by formula (6), and a halosilane represented by formula (7) is preferably such that the molar ratio of halogen atoms in the halosilane to carboxyl groups in the carboxylic acid having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) is 1 to 2, and more preferably 1.0 to 1.4.

[0042] Examples of hydrogen halide scavengers include tertiary amine compounds such as trimethylamine, triethylamine, tributylamine, and pyridine. The amount of hydrogen halide scavenger used is preferably 0.8 to 3 moles, particularly 1 to 2 moles, per mole of halogen atoms in the halosilane represented by formula (7).

[0043] The organosilicon compound according to the present invention can be produced by reacting a silyl carboxylate compound having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at the terminal end, represented by the general formula (5) obtained in this way, with an alkoxysilane having an SiH group (hydrosilyl group), in the presence of a catalyst.

[0044] That is, the following general formula (8) (In the formula, R 1 , R 2The compounds are obtained by reacting an alkoxysilyl compound represented by (a) (a hydrosilyl group-containing (organo)alkoxysilane) with a silyl carboxylate compound having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at its terminus, represented by the above general formula (5), in the presence of a platinum group metal catalyst, for example, at 40 to 200°C, preferably 60 to 120°C, for about 30 minutes to 15 hours.

[0045] At this time, the reaction ratio between the alkoxysilyl compound represented by formula (8) (hydrosilyl group-containing (organo)alkoxysilane) and the carboxylate silyl ester compound represented by formula (5) having an aliphatic unsaturated group (ethylenically unsaturated group or alkenyl group) at the terminal is preferably such that the molar ratio of the SiH group of the alkoxysilyl compound to the terminal aliphatic unsaturated group of the carboxylate silyl ester compound (SiH group / terminal aliphatic unsaturated group) is 0.5 to 2, more preferably 1 to 2, and even more preferably 1.0 to 1.5.

[0046] Examples of platinum group metal catalysts used here include chloroplatinic acid, an alcoholic solution of chloroplatinic acid, a reaction product of chloroplatinic acid and alcohol, platinum olefin compound complexes, platinum vinyl group-containing siloxane complexes, and platinum-supported carbon. The amount of platinum group metal catalyst used is a so-called catalytic amount, preferably 0.1 to 1,000 ppm in terms of the mass of the platinum group metal relative to the total mass of the carboxylate silyl ester compound having an aliphatic unsaturated group at the terminal and the alkoxysilane having an SiH group, and particularly preferably 0.3 to 100 ppm.

[0047] Furthermore, in all of the above manufacturing methods, a solvent may be added during the reaction. The solvent is not particularly limited, but examples include aromatic hydrocarbons such as toluene, xylene, and benzene; aliphatic hydrocarbons such as pentane, hexane, heptane, nonane, octane, and decane; ethers such as dimethyl ether, methyl ethyl ether, tetrahydrofuran, and dioxane; halogenated hydrocarbons such as perchloroethane, perchloroethylene, trichloroethane, chloroform, and carbon tetrachloride; amides such as dimethylformamide; and esters such as ethyl acetate, methyl acetate, and butyl acetate.

[0048] The amount of the silane coupling agent containing a silyl carboxylate group in component (D) is 0.05 to 10 parts by mass, preferably 0.2 to 8 parts by mass, per 100 parts by mass of component (A). If the amount is less than 0.05 parts by mass, adhesion to the aluminum die casting cannot be obtained, and if it is more than 10 parts by mass, the cured product will be hard and brittle, which is also disadvantageous in terms of cost.

[0049] [Component (E)] Examples of curing catalysts for component (E) include organic carboxylates and alkoxides of metals such as tin, titanium, zirconium, iron, antimony, bismuth, and manganese; organic titanates and organic titanium chelate compounds. More specifically, examples include tin compounds such as dibutyltin dilaurate, dibutyltin dioctoate, dioctyltin dilaurate, dibutyltin maleate, dimethyltin dineodecanoate, dibutyltin dimethoxide, dioctyltin dineodecanoate, and stanus octoate; titanium compounds such as tetrabutyl titanate, diisopropoxybis(acetylacetonate) titanium, and diisopropoxybis(ethylacetoacetate) titanium; amine compounds such as dibutylamine, laurylamine, tetramethylguanidine, and tetramethylguanidylpropyltrimethoxysilane, and their salts. One or more components can be used individually or in combination. Because the composition of the present invention exhibits excellent curing properties such as rapid curing and deep curing, it is preferable to add an organotin compound or an organotitanium compound, and an organotitanium compound is even more preferable.

[0050] The amount of component (E) added is 0.001 to 15 parts by mass, preferably 0.01 to 10 parts by mass, per 100 parts by mass of component (A). If the amount is less than 0.001 parts by mass, curing will be insufficient and the performance will not be realized, and if it exceeds 15 parts by mass, curing will be too fast, making it difficult to use and resulting in poor durability such as heat resistance.

[0051] [Other Components] In addition, generally known additives other than those described above may be used, as long as they do not hinder the effects of the present invention. Examples of additives include dry silica, wet silica, quartz powder, titanium dioxide powder, diatomaceous earth powder, aluminum hydroxide powder, magnesium hydroxide powder, finely powdered alumina, magnesia powder, zinc oxide powder, zinc carbonate powder, barium sulfate powder, and inorganic fillers other than calcium carbonate in the form of fine powder obtained by surface treatment of these with silanes, silazanes, low-polymerization polysiloxanes, etc. In addition, calcium carbonate other than component (B) may be used as long as it does not hinder the effects of the composition. When such inorganic fillers are incorporated, the amount added is preferably 1 to 200 parts by mass, and more preferably 5 to 150 parts by mass, per 100 parts by mass of component (A).

[0052] Other additives include dimethylpolysiloxane with trimethylsiloxy groups sealed at both ends, isoparaffins, triacetin as a preservative stabilizer, 3-methoxysilyl-N-(1,3-dimethylbutyldena)propylamine and 3-ethoxysilyl-N-(1,3-dimethylbutyldena)propylamine as adhesion-promoting components other than component (C), platinum compounds as flame retardants, zinc carbonate powder, polyethers as thixotropy modifiers, colorants such as pigments, dyes, and fluorescent whitening agents, heat-resistant agents such as red iron oxide and cerium oxide, cold-resistant agents, rust inhibitors, fungicides, and antibacterial agents. Solvents such as toluene, xylene, solvent volatile oils, cyclohexane, methylcyclohexane, and low-boiling point isoparaffins may also be added. These other additives can be blended in a manner that does not impair the objectives of the present invention.

[0053] The method for preparing the room-temperature curable organopolysiloxane composition of the present invention is not particularly limited and can be obtained by mixing predetermined amounts of each of the above components in accordance with conventional methods.

[0054] The viscosity of the room-temperature curable organopolysiloxane composition of the present invention at 23°C is preferably 20 to 100 Pa·s, and more preferably 25 to 80 Pa·s. If the viscosity is less than 20 Pa·s, thixotropy is difficult to develop, and the material may sag, resulting in poor workability. If it exceeds 100 Pa·s, the viscosity becomes too high, resulting in poor workability. Note that viscosity is measured at a shear rate of 20 (S). -1 ) can be measured using a capillary rheometer or the like.

[0055] The room-temperature curable organopolysiloxane composition of the present invention can be cured at room temperature without the need for heating or cooling, typically at 0 to 50°C, preferably 5 to 40°C. The curing time is typically 1 hour to 2 weeks, preferably 3 hours to 1 week. Known methods and conditions can be used for curing conditions depending on the type of composition.

[0056] The room-temperature curable organopolysiloxane composition of the present invention exhibits excellent adhesion to aluminum die castings, making it suitable for applications using aluminum die castings as a substrate. It is particularly suitable for use as a waterproof and dustproof sealing material in automotive applications.

[0057] Articles containing an aluminum die-cast substrate bonded with the room-temperature curable organopolysiloxane composition of the present invention are used for cases and covers of automotive parts.

[0058] The following describes examples and comparative examples of the present invention, but these are representative embodiments of the present invention and the present invention is not limited to the following examples. The viscosity in the examples was measured using a B-type rotational viscometer (BH-type) at 23°C. Furthermore, the adhesion, viscosity, and non-flowability of the room-temperature curable organopolysiloxane composition of the present invention were evaluated according to the following method. The surface-treated calcium carbonate used below was the product shown below, with the surface treatment agent amount and BET specific surface area shown in Table 1. A: Shiraishi Kogyo Co., Ltd.'s Shirotsuya CC-R B: Shiraishi Kogyo Co., Ltd.'s Shirotsuya CCR-S C: Maruo Calcium Co., Ltd.'s Carlex 300 D: Shiraishi Kogyo Co., Ltd.'s Viscolite-HL E: Shiraishi Kogyo Co., Ltd.'s Viscolite-OS F: Shiraishi Kogyo Co., Ltd.'s Viscoexcel 30K G: Shiraishi Kogyo Co., Ltd.'s Vigot 15 H: Maruo Calcium Co., Ltd.'s MC Coat P-20

[0059]

[0060] [Example 1] 100 parts by mass of dimethylpolysiloxane with hydroxyl groups sealed at both ends and a viscosity of 1,500 mPa·s, and a thixotropy modifier with a viscosity of 270 mm 2 0.5 parts by mass of / s polyether and 80 parts by mass of surface-treated calcium carbonate shown in A of Table 1 were added and mixed uniformly. Then 5.2 parts by mass of methyltrimethoxysilane, 1 part by mass of triacetin, 1 part by mass of 11-trimethoxysilylundecanoate trimethylsilyl ester, and 4 parts by mass of diisopropoxybis(ethylacetoacetate)titanium were added and mixed uniformly under moisture barrier conditions to obtain room-temperature curable organopolysiloxane composition 1.

[0061] [Example 2] A room-temperature curable organopolysiloxane composition 2 was obtained in the same manner as in Example 1, except that 80 parts by mass of the surface-treated calcium carbonate shown in Table 1, B was used instead of the surface-treated calcium carbonate shown in Table 1, A.

[0062] [Example 3] A room-temperature curable organopolysiloxane composition 3 was obtained in the same manner as in Example 1, except that 80 parts by mass of the surface-treated calcium carbonate shown in Table 1 C was used instead of the surface-treated calcium carbonate shown in Table 1 A.

[0063] [Example 4] 0.5 parts by mass of 3-methoxysilyl-N-(1,3-dimethylbutyldena)propylamine was added to the room-temperature curable organopolysiloxane composition of Example 1 to obtain room-temperature curable organopolysiloxane composition 4.

[0064] [Example 5] A room-temperature curable organopolysiloxane composition 5 was obtained in the same manner as in Example 1, except that 1 part by mass of 4-trimethoxysilylbutanoate trimethylsilyl ester was used instead of 11-trimethoxysilylundecanoate trimethylsilyl ester.

[0065] [Comparative Example 1] A room-temperature curable organopolysiloxane composition 6 was obtained in the same manner as in Example 1, except that 80 parts by mass of the surface-treated calcium carbonate shown in Table 1 D was used instead of the surface-treated calcium carbonate shown in Table 1 A.

[0066] [Comparative Example 2] A room-temperature curable organopolysiloxane composition 7 was obtained in the same manner as in Example 1, except that 80 parts by mass of the surface-treated calcium carbonate shown in Table 1E was used instead of the surface-treated calcium carbonate shown in Table 1A.

[0067] [Comparative Example 3] A room-temperature curable organopolysiloxane composition 8 was obtained in the same manner as in Example 1, except that 80 parts by mass of the surface-treated calcium carbonate shown in Table 1F was used instead of the surface-treated calcium carbonate shown in Table 1A.

[0068] [Comparative Example 4] A room-temperature curable organopolysiloxane composition 9 was obtained in the same manner as in Example 1, except that 80 parts by mass of surface-treated calcium carbonate shown in Table 1 G was used instead of surface-treated calcium carbonate shown in Table 1 A.

[0069] [Comparative Example 5] A room-temperature curable organopolysiloxane composition 10 was obtained in the same manner as in Example 1, except that 1 part by mass of N-[3-(trimethoxysilyl)propyl]-1,3-benzenedimethanamine was used instead of 11-trimethoxysilylundecanoate trimethylsilyl ester.

[0070] [Comparative Example 6] A room-temperature curable organopolysiloxane composition 11 was obtained in the same manner as in Example 1, except that 80 parts by mass of surface-treated calcium carbonate shown in Table 1, H was used instead of surface-treated calcium carbonate shown in Table 1, A.

[0071] The room-temperature curable organopolysiloxane compositions of these examples and comparative examples were measured and compared using the following method.

[0072] [Shear Adhesion and Cohesive Failure Rate] To evaluate the adhesion to aluminum die casting, each room-temperature curable organopolysiloxane composition obtained in the above examples and comparative examples was applied to an aluminum die casting (ADC-12) measuring 25 mm in width and 50 mm in length, covering an area of ​​250 mm². 2 The material was applied to a thickness of 1 mm, and the same aluminum die-cast material was placed on top. The material was then cured at 23°C and 50% RH for 7 days to prepare shear adhesion test specimens. The shear adhesion strength (MPa) and cohesive failure rate (%) of these shear adhesion test specimens were determined in accordance with JIS K6850.

[0073] [Viscosity] The viscosity of each room-temperature curable organopolysiloxane composition obtained in the above examples and comparative examples was measured using a viscosity measuring device (Netch Corporation, capillary rheometer RH2100) in accordance with ISO 11443, at a shear rate of 20 (S -1 ) was measured.

[0074] [Slump] As a test to confirm non-flowability, a slump test (test temperature 23°C) in accordance with JIS A1439 was performed under vertical conditions using each room-temperature curable organopolysiloxane composition obtained in the above examples and comparative examples, and the length of the room-temperature curable organopolysiloxane composition that dripped was measured.

[0075] The results for the room-temperature curable organopolysiloxane compositions obtained in Examples 1 to 5 are shown in Table 2, and the results for the room-temperature curable organopolysiloxane compositions obtained in Comparative Examples 1 to 6 are shown in Table 3.

[0076]

[0077]

[0078] In the room-temperature curable organopolysiloxane compositions of Examples 1 to 5, which contain calcium carbonate treated with a specific BET specific surface area and a specific amount of surface treatment agent, and further a silane coupling agent containing a silyl carboxylate group, it can be seen that they have high shear adhesion and cohesive failure rate to aluminum die-cast (ADC12), while being low viscosity, non-flowing, and having excellent workability. In Comparative Examples 1 to 3, which use a silane coupling agent containing a silyl carboxylate group but use calcium carbonate treated with an amount of surface treatment agent outside the range of the present invention, adhesion to aluminum die-cast (ADC12) was not observed. Furthermore, in the room-temperature curable organopolysiloxane composition of Comparative Example 3, the BET specific surface area of ​​the calcium carbonate used is higher than the range of the present invention, resulting in high viscosity and poor workability. In Comparative Example 4, a room-temperature curable organopolysiloxane composition, adhesive properties were exhibited to aluminum die-casting because calcium carbonate treated with a specific amount of the surface treatment agent of the present invention, and a silane coupling agent containing a silyl carboxylate group were used. However, because the BET specific surface area of ​​the calcium carbonate used was smaller than the range of the present invention, the thixotropy decreased, the slump could not be measured, and the workability was poor. In Comparative Example 5, since a silane coupling agent containing a silyl carboxylate group was not used, no adhesive properties were exhibited to aluminum die-casting. In Comparative Example 6, a room-temperature curable organopolysiloxane composition, similar to Comparative Example 4, adhesive properties were exhibited to aluminum die-casting because calcium carbonate treated with a specific amount of the surface treatment agent of the present invention, and a silane coupling agent containing a silyl carboxylate group were used. However, because the BET specific surface area of ​​the calcium carbonate used was smaller than the range of the present invention, the thixotropy decreased, the slump could not be measured, and the workability was poor. From the above results, it can be seen that the room-temperature curable organopolysiloxane composition of the present invention has adhesive properties to aluminum die-castings and also exhibits excellent workability due to its low viscosity and high thixotropy.

Claims

1. (A) Organopolysiloxane represented by the following general formula (1) and / or (2): 100 parts by mass, HO(SiR2O) n H (1) (wherein R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, either identical or different, and n is an integer of 10 or more.) (In the formula, R and n are as described above, X is independently an oxygen atom or an alkylene group having 2 to 5 carbon atoms, and m is independently 0 or 1 for each silicon atom to which it is bonded.) (B) BET specific surface area of ​​13 to 25 m² 2 Surface-treated calcium carbonate having a concentration of / g, wherein the surface of the calcium carbonate particles is treated with a fatty acid, and the surface of the calcium carbonate is treated with 0.5 to 2.0 parts by mass of fatty acid per 100 parts by mass of calcium carbonate: 15 to 200 parts by mass, (C) hydrolyzable organosilicon compounds other than components (A) and (D) and / or partially hydrolyzed condensates thereof, having at least three hydrolyzable groups bonded to silicon atoms in one molecule: 0.1 to 50 parts by mass, (D) silane coupling agent represented by the following general formula (3): 0.05 to 10 parts by mass, and (In the formula, R 1 , R 2 , R 3 (E) Curing catalyst: A room-temperature curable organopolysiloxane composition containing 0.001 to 15 parts by mass.

2. The room-temperature curable organopolysiloxane composition according to claim 1, wherein the component (C) is a hydrolyzable organosilane compound represented by the following general formula (4) and / or a partially hydrolyzed condensate thereof. R 4 d SiR 5 4-d (4) (In the formula, R 4 is a monovalent hydrocarbon group, and R 5 is independently a hydrolyzable group. d is 0 or 1.) 3. The room-temperature curable organopolysiloxane composition according to claim 1, for use in bonding aluminum die-castings.

4. An article comprising an aluminum die-cast substrate bonded with a room-temperature curable organopolysiloxane composition according to any one of claims 1 to 3.

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