Method for producing room-temperature curable organopolysiloxane compositions

Abstract

To provide an inexpensive method for producing room temperature curable organopolysiloxane compositions in which terminal silanol groups of an organopolysiloxane whose both terminals of the molecular chain are blocked by silanol groups, which is the main agent (base polymer), can be inexpensively blocked with hydrolyzable silyl groups during producing process of the room temperature curable organopolysiloxane compositions and after curing the room temperature curable organopolysiloxane compositions do not discolor significantly even under high temperature conditions or exposure to ultraviolet rays.SOLUTION: There is provided a method for producing room temperature curable organopolysiloxane compositions including a step of blocking terminal silanol groups of the main agent (base polymer) with hydrolyzable silyl groups during production of the compositions by mixing the organopolysiloxane being base polymer whose both terminals of the molecular chain are blocked by silanol groups with hydrolyzable organosilane compounds and / or partially hydrolyzed condensate thereof in the presence of a condensation catalyst, wherein a mixture prepared by uniformly mixing a carboxylic acid and an amine compound in advance is used as the condensation catalyst.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a room-temperature curable organopolysiloxane composition that is excellent in storage stability, heat and weather resistance (discoloration resistance), ultraviolet resistance, etc. at low cost, starting from an organopolysiloxane having a terminal silanol group as a main ingredient (base polymer).

Background Art

[0002] Room-temperature curable silicone rubber compositions that crosslink by moisture are easy to handle and have excellent weather resistance and electrical properties, so they are used in various fields such as sealing materials for building materials and adhesives in the electrical and electronic fields. These room-temperature curable silicone rubber compositions are often designed starting from an organopolysiloxane having a silanol group at the terminal, and a tin catalyst was frequently used from the viewpoint of reactivity. However, in recent years, there are concerns about toxicity to the human body and the environment, and environmental regulations have become stricter, so its use has been avoided.

[0003] Titanium catalysts, which are considered as an alternative to tin catalysts, have high reactivity and are difficult to adjust because they gel when starting from an organopolysiloxane having a silanol group at the terminal. There is also a method of using a catalyst obtained by mixing a Lewis acid, a Lowry-Bronsted acid, and an amine to block the silanol group terminal, but the addition of a titanium catalyst is essential, and it is difficult to use it in combination with other catalysts. By using an organopolysiloxane that is pre-terminally blocked with an alkoxysilyl group, such problems can be avoided, but there are drawbacks such as increased costs.

[0004] <000^017>As a solution to the above problems, it is possible to block the silanol group terminal during the production process by using a specific amino group-containing silane as a terminal blocking catalyst, and obtain a room-temperature curable organopolysiloxane composition having excellent storage stability. [[ID=I21]] However, when an amino group-containing silane is used as the terminal blocking catalyst, the cured product of the organopolysiloxane may be significantly discolored when exposed to high-temperature conditions or ultraviolet rays after curing. The following documents are examples of prior art related to the present invention. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 63-83166 [Patent Document 2] Japanese Patent Application Publication No. 63-99236 [Patent Document 3] Special Publication No. 7-39547 [Overview of the initiative] [Problems that the invention aims to solve]

[0006] The present invention has been made in view of the above circumstances, and aims to provide an inexpensive method for producing a room-temperature curable organopolysiloxane composition in which the terminal silanol groups of a main component (base polymer), a molecular chain-end-end-silanol-group-blocked organopolysiloxane, can be inexpensively blocked with hydrolyzable silyl groups during the manufacturing process of the room-temperature curable organopolysiloxane composition, and which does not undergo significant discoloration even when exposed to high temperatures or ultraviolet light after curing. [Means for solving the problem]

[0007] The present inventors, through diligent research to solve the above problems, have discovered that by using a mixture of a carboxylic acid and an amine compound uniformly mixed beforehand as a condensation catalyst, and mixing a main component (base polymer) of an organopolysiloxane with silanol groups sealed at both ends of the molecular chain and a hydrolyzable organosilane compound and / or a partially hydrolyzed condensate thereof in the presence of the condensation catalyst, the terminal silanol groups of the base polymer are sealed with hydrolyzable silyl groups during the composition manufacturing process, thereby enabling the inexpensive production of a room-temperature curable organopolysiloxane composition. Furthermore, the inventors have found that the cured product of the room-temperature curable organopolysiloxane composition produced through this process does not significantly discolor even when exposed to high temperatures or ultraviolet light, thus completing the present invention.

[0008] Accordingly, the present invention provides a method for producing the following room-temperature curable organopolysiloxane composition. [1] (A) Organopolysiloxane in which both ends of the molecular chain are sealed with silanol groups: 100 parts by mass, (B) Branched saturated aliphatic monocarboxylic acids A condensation catalyst consisting of a mixture of a compound and an amine: 0.01 to 30 parts by mass, (C) Hydrolyzable organosilane compounds and / or partially hydrolyzed condensates thereof: 0.1 to 30 parts by mass, and (D) Filler: 1 to 1,000 parts by mass A method for producing a room-temperature curable organopolysiloxane composition containing, [i] A step of mixing component (A) with some or all of component (C) in the presence of component (B) to encapsulate the silanol groups at both ends of the molecular chain of the organopolysiloxane of component (A) with hydrolyzable silyl groups, then, [ii] A step of mixing the remainder of component (C) and component (D) into a reaction mixture obtained by mixing and reacting component (A), component (B), and some or all of component (C) obtained in step [i]. A method for producing a room-temperature curable organopolysiloxane composition containing the above. [2] In step [ii], further, (E) Curing catalyst other than component (B): 0.001 to 15 parts by mass per 100 parts by mass of component (A), (F) Adhesion-improving agent: 0.1 to 30 parts by mass per 100 parts by mass of component (A), and (G) Preservative: 0.1 to 10 parts by mass per 100 parts by mass of component (A) A method for producing a room-temperature curable organopolysiloxane composition according to [1], comprising mixing at least one selected from [1]. [3] A method for producing a room-temperature curable organopolysiloxane composition according to [1] or [2], comprising the step of adding a basic substance to a reaction mixture obtained by mixing and reacting component (A), component (B), and some or all of component (C) after step [i] to neutralize the reaction reaction. 4 (B) component is an amine compound having a silane structure or a silicone structure (siloxane structure) in the molecule, and is a method for producing a room-temperature curable organopolysiloxane composition described in [1] or [2]. [5] A method for producing a room-temperature curable organopolysiloxane composition according to [1] or [2], wherein the branched saturated aliphatic monocarboxylic acid used in component (B) has 5 to 22 carbon atoms in the molecule. [6] A method for producing a room-temperature curable organopolysiloxane composition according to [1] or [2], wherein the branched saturated aliphatic monocarboxylic acid used in component (B) is one or more selected from tert-butylacetic acid, 2-methylbutyric acid, 2-methylbutanoic acid, 2,2-dimethylbutyric acid, 2,2-dimethylvaleric acid, 3,3,5-trimethylhexanoic acid, 3-methylcrotonic acid, 2-ethylhexanoic acid, 2-hexyldecanoic acid, and neodecanoic acid. [7] A method for producing a room-temperature curable organopolysiloxane composition according to [1] or [2], wherein the branched saturated aliphatic monocarboxylic acid used in component (B) is 2-ethylhexanoic acid, 2-hexyldecanoic acid, or neodecanoic acid.

Advantages of the Invention

[0009] By the production method of the present invention, a room-temperature curable organopolysiloxane composition using a molecular chain both-ends hydrolyzable silyl group-blocked base polymer prepared during the production process using a specific mixed catalyst does not significantly discolor the cured product (silicone rubber cured product) even when the cured product is exposed to high-temperature conditions or ultraviolet rays (UV).

Modes for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0011] (A) component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, the (A) component used as the base polymer of the room-temperature curable organopolysiloxane composition is an organopolysiloxane (main agent) in which both ends of the molecular chain are blocked with silanol groups (hydroxyl groups bonded to silicon atoms).

[0012] Specifically, as the organopolysiloxane of the (A) component, a linear diorganopolysiloxane in which both ends of the molecular chain are blocked with silanol groups represented by the following formula (1) is preferably mentioned.

Chemical Formula

[0013] The viscosity of the diorganopolysiloxane represented by formula (1) above at 23°C is preferably 100 to 1,000,000 mPa·s, and more preferably 300 to 100,000 mPa·s. The viscosity is measured using a rotational viscometer (e.g., BL type, BH type, BS type, cone plate type, etc.) (the same applies hereafter). Furthermore, the number of repeating units (m) or degree of polymerization of the diorganosiloxane units in the diorganopolysiloxane shown in formula (1) above was determined as the number-average degree of polymerization (or number-average molecular weight) in polystyrene terms using gel permeation chromatography (GPC) analysis with toluene or the like as the developing solvent.

[0014] In formula (1) above, R can be an unsubstituted or substituted alkyl group having 1 to 12 carbon atoms or an unsubstituted or substituted aryl group having 6 to 10 carbon atoms. Examples include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; aryl groups such as phenyl, tolyl, xylyl, and α-,β-naphthyl groups; and groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as F, Cl, and Br, or cyano groups, such as 3-chloropropyl, 3,3,3-trifluoropropyl, and 2-cyanoethyl groups. Among these, alkyl groups such as methyl and ethyl groups are preferred, and methyl groups are particularly preferred.

[0015] In the above formula (1), Y is an oxygen atom or a divalent hydrocarbon group having 1 to 8 carbon atoms, and as a divalent hydrocarbon group having 1 to 8 carbon atoms, -(CH2) q1 -(q1 represents 1-8), or -(CH=CH) q2 -(q2 represents 1 to 4) is preferred. Among these, oxygen atoms, -CH2CH2-, -CH2CH2CH2-, or -CH=CH- are particularly preferred.

[0016] Examples of the linear diorganopolysiloxane structure represented by formula (1) above include diorganopolysiloxanes with silanol groups sealed at both ends of the molecular chain, diorganohydroxysilylethyl groups sealed at both ends of the molecular chain, diorganohydroxysilylpropyl groups sealed at both ends of the molecular chain, and diorganohydroxysilylethenyl groups sealed at both ends of the molecular chain.

[0017] (A) Organopolysiloxanes, in which both ends of the molecular chain of component (A) are sealed with silanol groups, may be used alone or in combination of two or more types with different structures and degrees of polymerization.

[0018] (B) Component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, the room-temperature curable organopolysiloxane composition includes, as component (B), a condensation catalyst consisting of a mixture of a carboxylic acid and an amine compound obtained by pre-mixing them uniformly. If the carboxylic acid and the amine compound are each individually (as separate components) incorporated into the room-temperature curable organopolysiloxane composition, exothermic reactions due to neutralization reactions may occur during the formulation process, potentially affecting the composition by causing gelation or delaying the curing process. Furthermore, depending on the combination, crystallization and gelation may occur, and if incorporated individually, the reaction may proceed during stirring, potentially forming clumps (localized gels) in the composition.

[0019] The condensation catalyst of component (B) is a mixture obtained by uniformly mixing a carboxylic acid and an amine compound at room temperature (23°C ± 15°C) beforehand. It acts as a condensation catalyst (end-blocking catalyst) for blocking the silanol groups at both ends of the molecular chain in component (A) with the hydrolyzable silyl groups in the hydrolyzable organosilane compound and / or its partially hydrolyzed condensate of component (C) described later, and also acts as a condensation catalyst (curing catalyst) to promote the condensation and curing reaction of the entire composition. The condensation catalyst of component (B) contains an ammonium salt (ammonium carboxylate) of the carboxylic acid and the amine compound, which is formed by uniformly mixing the carboxylic acid and the amine compound at room temperature (23°C ± 15°C) beforehand.

[0020] The carboxylic acid used when preparing the condensation catalyst of component (B) may be one or more selected from saturated aliphatic carboxylic acids, unsaturated aliphatic carboxylic acids, and aromatic carboxylic acids (carboxylic acids in which the carboxyl group is bonded to a carbon atom constituting an aromatic ring), containing one or more (especially one or two) carboxyl groups (C(=O)OH) in the molecule and having one or more carbon atoms. The aliphatic carboxylic acid (carboxylic acid in which the carboxyl group is bonded to a carbon atom constituting an aliphatic hydrocarbon group) may be a carboxylic acid having a linear, branched, or aliphatic cyclic hydrocarbon chain, or an aliphatic carboxylic acid having an aromatic cyclic hydrocarbon chain in the molecule.The carboxylic acid is preferably one having 1 to 30 carbon atoms in the molecule, particularly 1 to 22. Specific examples include methaneic acid (formic acid), ethaneic acid (acetic acid), propanoic acid (propionic acid), butanoic acid (butyric acid), pentanoic acid (valeric acid), hexanoic acid (caproic acid), heptanoic acid (enanthic acid), octanoic acid (caprylic acid), nonanoic acid (pelargonic acid), decanoic acid (capric acid), dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), and hexanoic acid. Saturated aliphatic monocarboxylic acids such as decanoic acid (palmitic acid), heptadecanoic acid, octadecanoic acid (stearic acid); unsaturated aliphatic monocarboxylic acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, sorbic acid; saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid; benzoic acid, phthalic acid, isophthalic acid Examples include acids, aromatic carboxylic acids such as terephthalic acid and salicylic acid, branched saturated aliphatic monocarboxylic acids such as tert-butylacetic acid, 2-methylbutyric acid, 2-methylbutanoic acid, 2,2-dimethylbutyric acid, 2,2-dimethylvaleric acid, 3,3,5-trimethylhexanoic acid, 3-methylcrotonic acid, 2-ethylhexanoic acid, 2-hexyldecanoic acid, and neodecanoic acid, saturated aliphatic monocarboxylic acids having saturated aliphatic cyclic hydrocarbon chains such as cyclopropanecarboxylic acid, cyclopentanecarboxylic acid, cyclohexanecarboxylic acid, cyclopropylcarboxylic acid, cyclohexylcarboxylic acid, and cyclopropylcarboxylic acid, unsaturated aliphatic monocarboxylic acids having unsaturated aliphatic cyclic hydrocarbon chains such as 1-cyclohexene-1-carboxylic acid, aliphatic carboxylic acids having aromatic cyclic hydrocarbon chains in the molecule such as biphenylacetic acid, and saturated aliphatic monocarboxylic acids containing a carbonyl group in the saturated aliphatic hydrocarbon group such as levulinic acid. In particular, those containing branched chains, such as 2-ethylhexanoic acid and 2-hexyldecanoic acid, and having low odor are preferred.

[0021] The amine compounds used when preparing the condensation catalyst of component (B) are compounds containing one or more (particularly one or two) primary amines (-NH2) or secondary amines (-NH-) in the molecule. Specific examples include primary amine compounds such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, isopentylamine, tert-pentylamine, hexylamine, octylamine, 2-ethylhexylamine, nonylamine, decylamine, vinylamine, allylamine, aniline, toluidine, anisidine, 2,4-dimethylaniline, 2,4,6-trimethylaniline, 2,6-diethylaniline, cyclohexylamine, and 2-phenylethylamine, as well as secondary amine compounds such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, N-methylethylamine, N-ethylisobutylamine, N-methylaniline, and piperidine. Furthermore, as amine compounds, silane compounds and siloxane compounds having one or more (particularly one or two) primary amines (-NH2) or secondary amines (-NH-) in the molecule are preferred because they have excellent compatibility with component (A) and other silicone-based components such as component (C) described later, in that they have a silane structure or silicone structure (siloxane structure) in the molecule. Examples of silane compounds and siloxane compounds having one or more primary amines (-NH2) or secondary amines (-NH-) in the molecule include amino-functional group-containing alkoxysilanes such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyl(methyl)dimethoxysilane, and 3-aminopropyltris(trimethylsiloxy)silane, as well as partially hydrolyzed condensates of the amino-functional group-containing alkoxysilanes (amino-functional group-containing siloxane oligomers).

[0022] In the condensation catalyst of component (B), the mixing ratio of the carboxylic acid and the amine compound is preferably 1:9 to 9:1 in molar ratio, and particularly preferably 2:8 to 6:4. If there is too much amine compound (too little carboxylic acid) or too much carboxylic acid (too little amine compound), the function of the condensation catalyst may be significantly impaired.

[0023] In the condensation catalyst of component (B), the method of mixing the carboxylic acid and the amine compound is sufficient as long as both components are uniformly mixed in the mixture without uneven distribution. Examples include mixing at room temperature (23°C ± 15°C) for 10 minutes to 2 hours, particularly 10 minutes to 1 hour, using a shaker or the like under moisture-free conditions. However, depending on the combination and mixing ratio, there is a risk of severe heat generation, so it is more preferable to mix gradually by dropwise addition while maintaining room temperature (23°C ± 15°C). This mixing yields a mixture containing a liquid salt (for example, a salt of 2-ethylhexanoic acid and diethylamine, a salt of 2-ethylhexanoic acid and γ-aminopropyltrimethoxysilane, or a salt of 2-hexyldecanoic acid and 3-aminopropyltris(trimethylsiloxy)silane).

[0024] The amount of condensation catalyst component (B) is 0.01 to 30 parts by mass, preferably 0.05 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of organopolysiloxane in which both ends of the molecular chain of component (A) are sealed with silanol groups. If there is too little condensation catalyst, the sealing reaction of the terminal silanol groups of component (A) to hydrolyzable silyl groups may not proceed sufficiently, which may reduce the storage stability of the composition. If there is too much catalyst, the curing rate may slow down, which may reduce the mechanical properties of the resulting cured product.

[0025] (C) Component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, the room-temperature curable organopolysiloxane composition includes, as component (C), a hydrolyzable organosilane compound and / or a partially hydrolyzed condensate thereof, which acts as a chelating agent for sequestering the silanol groups at both ends of the molecular chain in component (A) with hydrolyzable silyl groups in the presence of the condensation catalyst of component (B) described above, and as a crosslinking agent (curing agent) for improving the crosslinking density of the cured product, in particular a hydrolyzable organosilane compound and / or a partially hydrolyzed condensate thereof having three or more (particularly three or four) hydrolyzable groups bonded to silicon atoms in the molecule. In the present invention, "partially hydrolyzed condensate" means an organosiloxane oligomer having three or more residual hydrolyzable groups in the molecule, produced by partially hydrolyzing and condensing a hydrolyzable organosilane compound.

[0026] Examples of hydrolyzable groups bonded to silicon atoms in the hydrolyzable organosilane compound and / or its partially hydrolyzed condensate of component (C) include ketoxime groups with 3 to 7 carbon atoms such as dimethylketoxime group, methylethylketoxime group, and diethylketoxime group; alkoxy groups with 1 to 10 carbon atoms such as methoxy group, ethoxy group, propoxy group, isopropoxy group, and butoxy group; acyloxy groups with 2 to 10 carbon atoms such as acetoxy group, octanoyloxy group, and benzoyloxy group; and alkenyloxy groups with 2 to 4 carbon atoms such as vinyloxy group, allyloxy group, propenoxy group, and isopropenoxy group, with alkoxy groups with 1 to 4 carbon atoms and isopropenoxy groups being preferred. Examples of organo groups (monovalent hydrocarbon groups) bonded to silicon atoms other than the hydrolyzable groups in the hydrolyzable organosilane compound and / or its partially hydrolyzed condensate include alkyl groups having 1 to 10 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl groups, alkenyl groups having 2 to 10 carbon atoms such as vinyl and allyl groups, and aryl groups having 6 to 10 carbon atoms such as phenyl and tolyl groups, with alkyl groups having 1 to 4 carbon atoms being preferred. Furthermore, the hydrolyzable organosilane compound of component (C) may be a bissilyl type hydrolyzable silane compound or a trisilyl type hydrolyzable silane compound in which multiple (2 or 3) silyl groups having hydrolyzable groups are linked together by a divalent hydrocarbon group such as an alkylene group.

[0027] Specific examples of component (C) include alkoxysilanes such as methyltrimethoxysilane, octyltrimethoxysilane, dimethyldimethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, and 2-ethylhexyl α-(dimethoxymethylsilyl)propionate; isopropenoxy group-containing silanes such as methyltriisopropenoxysilane, ethyltriisopropenoxysilane, vinyltriisopropenoxysilane, and phenyltriisopropenoxysilane; acetoxysilanes such as methyltriacetoxysilane, ethyltriacetoxysilane, and vinyltriacetoxysilane; and partially hydrolyzed condensates of these silanes. These can be used individually or in combination of two or more. Furthermore, the hydrolyzable organosilane compounds of component (C) and / or their partially hydrolyzed condensates are clearly distinguishable from the hydrolyzable silanes and siloxanes of component (E) and the adhesion-imparting agents of component (F), described later, in that they do not contain monovalent hydrocarbon groups with functional groups containing heteroatoms selected from nitrogen, oxygen, and sulfur as groups other than hydrolyzable groups in their molecules.

[0028] The amount of component (C) is usually 0.1 to 30 parts by mass per 100 parts by mass of component (A), but preferably 0.2 to 20 parts by mass, and more preferably 0.5 to 15 parts by mass. If the amount is 0.1 parts by mass or more, the end-sealing reaction and cross-linking (curing) reaction will proceed sufficiently. If the amount of component (C) is too little, the end-sealing reaction and cross-linking (curing) reaction will not proceed sufficiently. If the amount of component (C) is too much, the cured product may become too hard, and it will also be economically disadvantageous.

[0029] (D) Component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, the room-temperature curable organopolysiloxane composition contains a filler (component (D)) for providing sufficient mechanical strength to the cured product. Known fillers can be used, for example, silicon oxides such as fine silica powder, aerosol silica, silica aerogel, precipitated silica, and diatomaceous earth; metal oxides such as iron oxide, zinc oxide, and titanium oxide, or those whose surfaces have been treated with silane; metal carbonates such as calcium carbonate, magnesium carbonate, and zinc carbonate; inorganic fillers such as asbestos, glass wool, carbon black, fine mica, and molten silica powder; or synthetic resin powders such as polystyrene, polyvinyl chloride, and polypropylene.

[0030] The amount of component (D) is 1 to 1,000 parts by mass per 100 parts by mass of component (A), preferably 5 to 200 parts by mass. By adding 1 part by mass or more of component (D), the cured product obtained from the room-temperature curable organopolysiloxane composition will have sufficient mechanical strength, and if the amount added is 1,000 parts by mass or less, the viscosity of the composition will not increase, making it difficult to work with, nor will the rubber strength of the cured product decrease, resulting in poor rubber elasticity.

[0031] (E) Component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, the room-temperature curable organopolysiloxane composition may contain, as an optional component, a curing catalyst other than the above-mentioned component (B) (component (E)). Component (E) is a curing catalyst other than component (B) (a non-metallic organic catalyst and / or a metallic catalyst), and is intended for use as a curing catalyst for the room-temperature curable organopolysiloxane composition.

[0032] As the nonmetallic organic catalyst for the curing catalyst, any known catalysts used as curing accelerators for condensation-curing type organopolysiloxane compositions can be used, and are not particularly limited. Examples include phosphazene-containing compounds such as N,N,N',N',N'',N''-hexamethyl-N'''-(trimethylsilylmethyl)-phosphorimidictriamide, amine compounds or salts thereof such as n-octylamine, hexylamine, dodecylamine phosphate, and tetramethylguanidine, quaternary ammonium salts such as benzyltriethylammonium acetate, dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine, hydrolyzable silanes and siloxanes having a guanidyl group such as tetramethylguanidylpropyltrimethoxysilane, tetramethylguanidylpropylmethyldimethoxysilane, and tetramethylguanidylpropyltris(trimethylsiloxy)silane, but the nonmetallic organic catalyst is not limited to these. Furthermore, the nonmetallic organic catalyst may be used alone or in combination of two or more types.

[0033] As the metal-based catalyst for the curing catalyst, any known catalysts used as curing accelerators for condensation-curing organopolysiloxane compositions can be used, and are not particularly limited. For example, alkyltin ester compounds such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctoate, dioctyltin dineodecanoate, and di-n-butyl-dimethoxytin; titanate esters or titanium chelate compounds such as tetraisopropoxytitanium, tetra-n-butoxytitanium, tetrakis(2-ethylhexoxy)titanium, dipropoxybis(acetylacetonate)titanium, and titanium isopropoxyoctylene glycol; zinc naphthenate, zinc stearate, zinc-2-ethyloctoate, and iron- Examples of metal catalysts include alkole-aluminum compounds such as 2-ethylhexoate, cobalt-2-ethylhexoate, manganese-2-ethylhexoate, cobalt naphthenate, aluminum isopropylate, and aluminum secondary butyrate; aluminum chelate compounds such as aluminum alkyl acetate diisopropylate and aluminum bisethylacetoacetate monoacetylacetonate; and lower fatty acid salts of alkali metals such as potassium acetate, sodium acetate, and lithium oxalate; however, metal catalysts are not limited to these. Furthermore, metal catalysts may be used individually or in combination of two or more types.

[0034] The amount of curing catalyst component (E) is 0 to 15 parts by mass per 100 parts by mass of component (A), preferably 0.001 to 15 parts by mass, and more preferably 0.01 to 10 parts by mass. If the amount of component (E) is too high, the curing will be too fast, resulting in insufficient working time and potentially being economically disadvantageous.

[0035] (F) component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, the room-temperature curable organopolysiloxane composition may contain an adhesion-imparting agent of component (F) as an optional component that may be added as needed. Preferred adhesion-imparting agents of component (F) include, for example, amino-functional group-containing alkoxysilanes such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and N-2-(aminoethyl)-3-aminopropyl(methyl)dimethoxysilane; epoxy-functional group-containing alkoxysilanes such as γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; and silane coupling agents (carbon functional hydrolyzable silanes) such as isocyanate-functional group-containing alkoxysilanes.

[0036] The amount of the adhesion-imparting agent component (F) is 0 to 30 parts by mass per 100 parts by mass of the organopolysiloxane component (A). When added, it is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.2 to 10 parts by mass. If the amount exceeds 30 parts by mass, it may be economically disadvantageous or the stability of the composition may decrease.

[0037] (G) Component In the method for producing a room-temperature curable organopolysiloxane composition of the present invention, a preservation enhancer for component (G) may be added to the room-temperature curable organopolysiloxane composition as an optional component to improve the storage stability of the composition. Examples of preservation enhancers for component (G) include organosilazane compounds such as hexamethyldisilazane, hexaethyldisilazane, 1,3-divinyl-1,1,3,3-tetramethyldisilazane, 1,3-divinyl-1,1,3,3-tetraethyldisilazane, heptamethyldisilazane, and 1,1,3,3-tetraethyldisilazane, as well as oligomers thereof, and one type may be used alone or two or more types may be used in combination.

[0038] The amount of preservative enhancer (G) is 0 to 10 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of organopolysiloxane (A). If the amount is less than 0.1 parts by mass, the preservation properties may be poor, and if the amount exceeds 10 parts by mass, the curability of the composition may decrease.

[0039] -Other additives- Furthermore, in the method for producing the room-temperature curable organopolysiloxane composition of the present invention, in addition to the above-mentioned components (A) to (D) (or components (A) to (G) as needed), the room-temperature curable organopolysiloxane composition may further contain at least one known additive selected from pigments, dyes, antioxidants, antioxidants, antistatic agents, flame retardants such as antimony oxide and paraffin chloride, viscosity modifiers such as unfunctionalized diorganopolysiloxanes such as trimethylsilyl group-blocked dimethylpolysiloxane (unfunctionalized dimethyl silicone oil), etc., to the extent that it does not impair the objectives of the present invention. Furthermore, polyethers as thixotropic enhancers, or antifungal agents, antibacterial agents, adhesive aids, etc., may also be added to the composition to the extent that it does not impair the objectives of the present invention.

[0040] [Method for producing room-temperature curable organopolysiloxane compositions] In the present invention, a room-temperature curable organopolysiloxane composition is produced by the following method. That is, with respect to the above-mentioned components (A) to (D) (or components (A) to (G)), [i]: A step of mixing all of component (A) and part or all of component (C) in the presence of component (B) (total amount) to encapsulate the silanol groups at both ends of the molecular chain of the organopolysiloxane of component (A) with hydrolyzable silyl groups, then, [ii]: A step of mixing the remainder of component (C) and all of component (D) into a reaction mixture obtained by mixing and reacting all of component (A), all of component (B), and part or all of component (C) obtained in step [i]. It is manufactured by a manufacturing method that includes steps [i] and [ii].

[0041] Of the components of (C), the amount blended in step [i] as a terminal chelating agent and crosslinking agent (curing agent) for sequestering the silanol groups at both ends of the molecular chain of component (A) with hydrolyzable silyl groups in the presence of the condensation catalyst of component (B) described above is preferably 40% by mass or more (40-100% by mass), particularly 50% by mass or more (50-100% by mass), and more preferably 60% by mass or more (60-100% by mass) of the total components of (C). Therefore, the remainder of the components of (C) blended in step [ii] is preferably 60% by mass or less (0-60% by mass), particularly 50% by mass or less (0-50% by mass), and more preferably 40% by mass or less (0-40% by mass) of the total components of (C).

[0042] Furthermore, there are no particular restrictions on the order in which optional components such as component (E), component (F), component (G), and other additives are added as needed, but it is preferable that they be added in step [ii].

[0043] In step [i], the mixing of component (A) and some or all of component (C) in the presence of component (B) is sufficient if the silanol groups at both ends of the molecular chain in component (A) are encapsulated by the hydrolyzable silyl groups in component (C). The mixing conditions are typically 10 minutes to 5 hours, preferably 30 minutes to 3 hours, at room temperature (usually 0 to 40°C, preferably 10 to 30°C) under moisture barrier conditions. Furthermore, the mixing is preferably carried out under atmospheric pressure.

[0044] In step [ii], the reaction mixture obtained by mixing and reacting components (A), (B), and some or all of component (C) obtained in step [i] is mixed with the remainder of component (C) and component (D). The mixing conditions are as follows: under moisture barrier, the mixture is heated to room temperature or, if necessary, to about 40 to 120°C; the mixing time should be sufficient to ensure that the components are homogenized, usually 10 minutes to 3 hours, preferably 30 minutes to 3 hours. Furthermore, it is preferable to perform the mixing under normal pressure or reduced pressure.

[0045] Furthermore, the reaction mixture obtained by mixing and reacting some or all of the above components (A), (B), and (C) in step [i] may be neutralized by adding a basic substance such as amine compounds like methylamine, dimethylamine, ethylamine, diethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, dibutylamine, pentylamine, heptylamine, nonylamine, ethylenediamine, hexamethylenediamine, aniline, phenethylamine, toluidine, pyrrolidine, piperidine, piperazine, morpholine, pyrrole, pyrazole, imidazole, etc. to the reaction mixture after step [i] (i.e., before step [ii], during step [ii], or after step [ii]).

[0046] The room-temperature curable organopolysiloxane composition produced as described above undergoes a rapid crosslinking (curing) reaction at room temperature (23°C ± 15°C) due to atmospheric moisture, yielding cured organopolysiloxane products such as cured silicone rubber (elastomer elastic material) and cured silicone gel. Furthermore, the cured product (cured silicone rubber or cured silicone gel) does not discolor or undergoes significantly reduced discoloration even when exposed to UV (ultraviolet) light under high-temperature conditions. Moreover, the room-temperature curable organopolysiloxane composition obtained by this manufacturing method of the present invention can be suitably used as a coating agent, adhesive, or sealing material. [Examples]

[0047] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, the compositions were prepared at 23°C, and the viscosity is a measurement taken with a rotational viscometer at 23°C. Room temperature refers to 23°C.

[0048] Preparation of condensation catalyst 1 used in Examples 1 and 4 below 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane were mixed at room temperature for 1 hour using a shaker under moisture-free conditions to ensure homogeneity, thereby preparing a mixture containing a liquid salt (condensation catalyst 1).

[0049] Preparation of condensation catalyst 2 used in Example 2 below 1.2 parts by mass of 2-ethylhexanoic acid and 0.5 parts by mass of diethylamine were mixed at room temperature for 1 hour using a shaker under moisture-free conditions to ensure homogeneity, thereby preparing a mixture containing a liquid salt (condensation catalyst 2).

[0050] Preparation of condensation catalyst 3 used in Example 3 below 0.8 parts by mass of 2-ethylhexanoic acid and 0.8 parts by mass of γ-aminopropyltrimethoxysilane were mixed at room temperature for 1 hour using a shaker under moisture-free conditions to ensure homogeneity, thereby preparing a mixture containing a liquid salt (condensation catalyst 3).

[0051] Preparation of condensation catalyst 4 used in Example 5 below 0.3 parts by mass of 2-hexyldecanoic acid and 0.2 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane were mixed at room temperature for 1 hour using a shaker under moisture-free conditions to ensure homogeneity, thereby preparing a mixture containing a liquid salt (condensation catalyst 4).

[0052] [Example 1] A reaction mixture was prepared by adding 1.7 parts by mass of a mixture (condensation catalyst 1) prepared by pre-mixing 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane to 100 parts by mass of dimethylpolysiloxane (in formula (1) above, R = methyl group, Y = oxygen atom, m = approximately 800) in which both ends of the molecular chain are encapsulated with hydroxyl groups (silanol groups) bonded to silicon atoms, with a viscosity of 50,000 mPa·s, 5.0 parts by mass of methyltrimethoxysilane, and 42.3 parts by mass of dimethylpolysiloxane with trimethylsilyl groups encapsulated at both ends, with a viscosity of 100 mPa·s. The mixture was then uniformly mixed at room temperature for 30 minutes under moisture barrier conditions to prepare the reaction mixture (step [i]). Next, 15 parts by mass of fuming silica (MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) was added to the reaction mixture and mixed under reduced pressure at room temperature for 40 minutes. Then, 3.3 parts by mass of a partially hydrolyzed condensate of methyltrimethoxysilane (methoxy group-containing methylsiloxane oligomer, degree of polymerization: 2-8) was added and mixed at room temperature for 20 minutes, and then mixed under reduced pressure at room temperature for 15 minutes to obtain composition 1 (step [ii]).

[0053] [Example 2] Composition 2 was obtained in the same manner as in Example 1, except that in step [i], instead of 1.7 parts by mass of a mixture (condensation catalyst 1) prepared by pre-mixing 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane uniformly beforehand, 1.7 parts by mass of a mixture (condensation catalyst 2) prepared by pre-mixing 1.2 parts by mass of 2-ethylhexanoic acid and 0.5 parts by mass of diethylamine uniformly beforehand was used.

[0054] [Example 3] Composition 3 was obtained in the same manner as in Example 1, except that in step [i], instead of 1.7 parts by mass of a mixture (condensation catalyst 1) prepared by pre-mixing 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane uniformly beforehand, 1.6 parts by mass of a mixture (condensation catalyst 3) prepared by pre-mixing 0.8 parts by mass of 2-ethylhexanoic acid and 0.8 parts by mass of γ-aminopropyltrimethoxysilane uniformly beforehand was used.

[0055] [Example 4] Composition 4 was obtained in the same manner as in Example 1, except that in step [ii], 3.3 parts by mass of a partially hydrolyzed condensate of methyltrimethoxysilane (methoxy group-containing methylsiloxane oligomer) and 0.8 parts by mass of hexamethyldisilazane were added simultaneously.

[0056] [Example 5] In the manufacturing method of Example 1, in step [i], instead of 1.7 parts by mass of a mixture (condensation catalyst 1) prepared by pre-mixing 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane uniformly, 0.5 parts by mass of a mixture (condensation catalyst 4) prepared by pre-mixing 0.3 parts by mass of 2-hexyldecanoic acid and 0.2 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane uniformly was used. In step [ii], 3.3 parts by mass of a partially hydrolyzed condensate of methyltrimethoxysilane (methoxy group-containing methylsiloxane oligomer) and 0.8 parts by mass of hexamethyldisilazane were added simultaneously, mixed at room temperature for 20 minutes, and then 0.3 parts by mass of dioctyl tin dineodecanoate was added and mixed at room temperature for 10 minutes. The process was carried out in the same manner as in Example 1 to obtain composition 5.

[0057] [Comparative Example 1] Composition 6 was obtained in the same manner as in Example 5, except that in step [i], 0.3 parts by mass of 2-hexyldecanoic acid and 0.2 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane were pre-mixed uniformly to prepare a mixture (condensation catalyst 4), and 1.3 parts by mass of a compound obtained by the dehydrochlorination reaction of xylylenediamine and 3-chloropropyltrimethoxysilane (N-(aminomethylphenylenemethyl)-3-aminopropyltrimethoxysilane, trade name: CF-73, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of 0.5 parts by mass of a mixture (condensation catalyst 4) prepared by pre-mixing 0.3 parts by mass of 2-hexyldecanoic acid and 0.2 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane.

[0058] [Comparative Example 2] Composition 7 was obtained in the same manner as in Example 1, except that in step [i], 1.0 part by mass of 2-hexyldecanoic acid was used instead of 1.7 parts by mass of a mixture (condensation catalyst 1) prepared by pre-mixing 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane uniformly.

[0059] [Comparative Example 3] Composition 8 was obtained in the same manner as in Example 1, except that in step [i], 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane was used instead of 1.7 parts by mass of a mixture (condensation catalyst 1) prepared by pre-mixing 1.0 part by mass of 2-hexyldecanoic acid and 0.7 parts by mass of 3-aminopropyltris(trimethylsiloxy)silane uniformly.

[0060] [Physical property evaluation test] Each composition prepared in Examples 1-5 and Comparative Examples 1-3 was extruded into a 2 mm thick sheet, exposed to air at 23°C and 50% RH, and then left in the same atmosphere for 7 days. The physical properties (initial properties) of the cured product were measured in accordance with JIS K-6249. The hardness of the cured product was measured using a durometer A hardness tester according to JIS K-6249. The results are shown in Tables 1 and 2.

[0061] [Table 1]

[0062] [Table 2]

[0063] The results in Tables 1 and 2 show that Examples 1-5 and Comparative Example 1 exhibited good reactivity, cured rapidly, and developed rubber elasticity. Comparative Examples 2 and 3 failed to cure the prepared compositions.

[0064] Using the compositions prepared in Examples 1-5 and Comparative Example 1, sheets obtained by the same procedure as described above were placed in a 150°C constant temperature bath for 10 days, or in a UV irradiator (PHLIPS TUV-15W germicidal lamp, irradiation conditions: wavelength 253.7 nm) for 7 days, and the change in the color of the sheets was observed visually. The results are shown in Table 3.

[0065] [Table 3]

[0066] As shown in Table 3, no discoloration was observed in Examples 1-5 even after long-term storage at 150°C or long-term UV irradiation. On the other hand, in Comparative Example 1, yellowing (discoloration) was observed under all conditions.

Claims

1. (A) Organopolysiloxane in which both ends of the molecular chain are sealed with silanol groups: 100 parts by mass, (B) Condensation catalyst consisting of a mixture of a branched saturated aliphatic monocarboxylic acid and an amine compound: 0.01 to 30 parts by mass, (C) Hydrolyzable organosilane compounds and / or partially hydrolyzed condensates thereof: 0.1 to 30 parts by mass, and (D) Filler: 1 to 1,000 parts by mass A method for producing a room-temperature curable organopolysiloxane composition containing, [i] A step of mixing component (A) with some or all of component (C) in the presence of component (B) to encapsulate the silanol groups at both ends of the molecular chain of the organopolysiloxane of component (A) with hydrolyzable silyl groups, then, [ii] A step of mixing the remainder of component (C) and component (D) into a reaction mixture obtained by mixing and reacting component (A), component (B), and some or all of component (C) obtained in step [i]. A method for producing a room-temperature curable organopolysiloxane composition containing the above.

2. In process [ii], further, (E) Curing catalyst other than component (B): 0.001 to 15 parts by mass per 100 parts by mass of component (A) (F) Adhesion-improving agent: 0.1 to 30 parts by mass per 100 parts by mass of component (A), and (G) Preservative: 0.1 to 10 parts by mass per 100 parts by mass of component (A) A method for producing a room-temperature curable organopolysiloxane composition according to claim 1, comprising mixing at least one selected from the above.

3. A method for producing a room-temperature curable organopolysiloxane composition according to claim 1 or 2, further comprising the step of adding a basic substance to a reaction mixture obtained by mixing and reacting component (A), component (B), and some or all of component (C) after step [i] to neutralize the reaction reaction.

4. A method for producing a room-temperature curable organopolysiloxane composition according to claim 1 or 2, wherein the amine compound used in component (B) has a silane structure or a silicone structure (siloxane structure) in its molecule.

5. A method for producing a room-temperature curable organopolysiloxane composition according to claim 1 or 2, wherein the branched saturated aliphatic monocarboxylic acid used in component (B) has 5 to 22 carbon atoms in the molecule.

6. A method for producing a room-temperature curable organopolysiloxane composition according to claim 1 or 2, wherein the branched saturated aliphatic monocarboxylic acid used in component (B) is one or more selected from tert-butylacetic acid, 2-methylbutyric acid, 2-methylbutanoic acid, 2,2-dimethylbutyric acid, 2,2-dimethylvaleric acid, 3,3,5-trimethylhexanoic acid, 3-methylcrotonic acid, 2-ethylhexanoic acid, 2-hexyldecanoic acid, and neodecanoic acid.

7. A method for producing a room-temperature curable organopolysiloxane composition according to claim 1 or 2, wherein the branched saturated aliphatic monocarboxylic acid used in component (B) is 2-ethylhexanoic acid, 2-hexyldecanoic acid, or neodecanoic acid.

Images