JP7626099B2 - Room temperature curable organopolysiloxane compositions and articles - Google Patents

Description

The present invention relates to a room-temperature curable organopolysiloxane composition of the condensation curing type that crosslinks (cures) by hydrolysis and condensation reactions due to moisture (water) in the air at room temperature (23°C ± 15°C), in particular, a room-temperature curable organopolysiloxane composition in which the elimination compound released and generated from the crosslinking agent (curing agent) by the hydrolysis reaction during curing is a cyclic ketone compound such as cyclobutanone or cyclopentanone, which cures well by condensation reaction and gives a silicone rubber cured product (elastomeric organopolysiloxane cured product) that has excellent adhesion, good long-life coolant (LLC) resistance, and good moist heat resistance, and various articles containing the composition or its cured product (silicone rubber). In particular, the room-temperature curable organopolysiloxane composition of the present invention can be suitably used as a sealant (adhesive, potting agent, coating agent) for electric and electronic parts.

Room temperature curable organopolysiloxane compositions that cure at room temperature to become silicone rubber have been known for some time and have been widely used in industry. Known mechanisms for curing at room temperature include a mechanism that cures by hydrosilylation addition reaction, a mechanism that cures by radical curing with ultraviolet light, and a mechanism that cures by condensation reaction between hydrolyzable groups bonded to silicon atoms and hydroxyl groups. Among these, room temperature curable organopolysiloxane compositions that cure by condensation reaction have the advantage that they can be easily cured at room temperature and are less susceptible to curing inhibition by impurities that occur in hydrosilylation addition reactions, etc. For this reason, they are widely used in fields such as automotive gaskets and sealing materials, construction sealants, and electrical and electronic parts.

Room temperature curable organopolysiloxane compositions that cure by a condensation reaction contain a hydrolyzable organosilane compound having a hydrolyzable group in the molecule as a curing agent (crosslinking agent), and examples of curing agents that have already been widely used include deoxime-type hydrolyzable organosilane compounds that release oxime compounds such as 2-butanone oxime upon curing, and dealcohol-type hydrolyzable organosilane compounds that release alcohol compounds such as methanol. Rubber-like cured products obtained by curing compositions containing these curing agents have high heat resistance, chemical resistance, and weather resistance derived from silicone (siloxane structure), and are therefore widely used as sealants for electric and electronic components.
On the other hand, oxime compounds such as 2-butanone oxime generated during curing of deoxime-type curing agents are suspected to be carcinogenic, and methanol and the like generated during curing of alcohol-free curing agents are toxic to the human body and designated as deleterious substances, making them undesirable from the viewpoint of human health. Furthermore, in some cases, these compositions use tin catalysts as curing catalysts, which are subject to stronger regulations as environmentally hazardous substances, making them undesirable from the viewpoint of environmental protection.

Furthermore, the curing agents (crosslinking agents) used in the alcohol-free type room-temperature curable organopolysiloxane compositions are less reactive than those used in the oxime-free type room-temperature curable organopolysiloxane compositions, and therefore cure slowly, and the compounds released from the oxime-free type corrode copper-based materials, limiting the scope of application in electrical and electronic components. Furthermore, there have been cases in which these conventional curing systems have insufficient moisture resistance and LLC resistance.
In recent years, in anticipation of the rapid electrification of automobiles and the spread of next-generation communications such as 5G, the use of silicone adhesives in electrical and electronic applications is increasing. Electrical and electronic applications require resistance to moisture, particularly LLC resistance and moist heat resistance.
From the standpoint of protecting the environment, preventing damage to the health of workers, and improving the productivity and reliability of electronic components, there is a particular demand for products that are more environmentally and safety-conscious and also have excellent curability and durability, and there is an increasing demand for room-temperature-curable organopolysiloxane compositions that have excellent performance and contain highly safe compounds that are eliminated.

JP 2018-515634 A (Patent Document 1) proposes a condensation-curing organopolysiloxane composition that releases an α-hydroxycarboxylic acid ester compound, typically ethyl lactate, as an alternative to dealcohol-removing and oxime-removing curing agents. In this system, the leaving group, ethyl lactate, is a highly safe compound, but the use of a tin catalyst is essential. Tin catalysts have been noted as being harmful to aquatic organisms, and the use of tin catalysts is undesirable from the perspective of environmental protection.

JP 51-39673 B (Patent Document 2) proposes a condensation-curing organopolysiloxane composition that releases a ketone compound, typically acetone. Compared to 2-butanone oxime or methanol, acetone is a compound that is less harmful to the human body, and it also provides a composition that cures faster and has better durability than conventional curing forms. However, acetone has a low flash point of -20°C and is highly volatile, which limits the environment in which it can be used.

Special table 2018-515634 publication Special Publication No. 51-39673

The present invention has been made in consideration of the above circumstances, and aims to provide a room-temperature curable organopolysiloxane composition that has no reported health hazards, such as carcinogenicity or reproductive toxicity, to the human body, or environmental hazards, such as toxicity to aquatic organisms, and that uses a hydrolyzable organosilane compound having a cyclic ketone compound, such as cyclobutanone or cyclopentanone, with a relatively high flash point as a leaving group (leaving compound), as a curing agent, and that has the same curing properties as conventional dealcohol-free or oxime-free room-temperature curable organopolysiloxane compositions without using a tin catalyst, while also reducing the harmful effects on the human body and the environmental load, and that can give a silicone rubber cured product having good rubber properties, adhesion, LLC resistance, and moisture resistance after curing, and an electric/electronic part, adhesive, potting agent, coating agent, etc. that has this composition or a cured product (silicone rubber) obtained by curing this composition.

（式中、Ｒ²は炭素数１～１０の一価炭化水素基であり、ｎは１～８の整数であり、ｍは３又は４である。） [0011] As a result of intensive research conducted in order to achieve the above-mentioned object, the present inventors have found that a room-temperature-curable organopolysiloxane composition containing as a curing agent (crosslinking agent) a hydrolyzable organosilane compound which leaves and releases a cyclic ketone compound such as cyclobutanone or cyclopentanone as a leaving group (leaving compound), and/or a partial hydrolysis condensate thereof, as represented by the following general formula (2), solves the above-mentioned problems of toxicity and safety to the human body and the environment, and have further found that even when a basic organic compound is added as a curing catalyst to this composition, the composition exhibits curability and cured product performance equivalent to those when a tin catalyst is added, and further that the cured product has excellent LLC resistance and moist heat resistance (durability in high temperature and high humidity environments), which has led to the completion of the present invention.

(In the formula, ^R2 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, n is an integer from 1 to 8, and m is 3 or 4.)

（式中、Ｒ²は炭素数１～１０の一価炭化水素基であり、ｎは１～８の整数であり、ｍは３又は４である。）
（Ｃ）有機強塩基性硬化触媒：０．０１～１質量部、
（Ｄ）下記一般式（３）で示されるシランカップリング剤及び／又はその部分加水分解縮合物：０．０１～１０質量部、及び
Ｒ³Ｒ⁴ _bＳｉＸ_3-b （３）
（式中、Ｒ³は窒素原子、硫黄原子及び酸素原子から選ばれる１種以上のヘテロ原子を含む官能性基（但し、グアニジル基を除く）を少なくとも１個有する炭素数１～２０の一価炭化水素基である。Ｒ⁴は炭素数１～１０の非置換又は置換の一価炭化水素基であり、Ｘは加水分解性基である。ｂは０、１又は２である。）
（Ｅ）無機質充填剤：１～５００質量部
を含有し、ロングライフクーラントの５０質量％水溶液に１００℃、１，０００時間浸漬した後の引張り強度及び切断時伸びの変化率が、初期状態と比較してそれぞれ－４０％以上、＋８０％以下である硬化物を与えるものである室温硬化性オルガノポリシロキサン組成物。
［２］
８５℃、８５％ＲＨの環境下に１，０００時間暴露した後の引張り強度及び切断時伸びの変化率が、初期状態と比較してそれぞれ－４０％以上、＋８０％以下である硬化物を与えるものである［１］に記載の室温硬化性オルガノポリシロキサン組成物。
［３］
（Ｂ）成分の加水分解性オルガノシラン化合物及び／又はその部分加水分解縮合物が、加水分解によって環状ケトン化合物を脱離するものである［１］又は［２］に記載の室温硬化性オルガノポリシロキサン組成物。
［４］
脱離する環状ケトン化合物がシクロブタノン又はシクロペンタノンである［３］に記載の室温硬化性オルガノポリシロキサン組成物。
［５］
（Ｅ）成分が、炭酸カルシウム、煙霧質シリカ、沈降性シリカ、カーボンブラック及び酸化アルミニウムから選ばれる１種又は２種以上の無機質充填剤である［１］～［４］のいずれかに記載の室温硬化性オルガノポリシロキサン組成物。
［６］
［１］～［５］のいずれかに記載の室温硬化性オルガノポリシロキサン組成物の硬化物を有する電気・電子部品。
［７］
［１］～［５］のいずれかに記載の室温硬化性オルガノポリシロキサン組成物を含有する電気・電子部品用接着剤。
［８］
［１］～［５］のいずれかに記載の室温硬化性オルガノポリシロキサン組成物を含有する電気・電子部品用ポッティング剤。
［９］
［１］～［５］のいずれかに記載の室温硬化性オルガノポリシロキサン組成物を含有する電気・電子部品用コーティング剤。 That is, the present invention provides the following room temperature curable organopolysiloxane composition, and electric/electronic parts, adhesives, potting agents, coating agents, etc., which contain said composition or a cured product thereof.
[1]
(A) 100 parts by mass of an organopolysiloxane having a viscosity of 20 to 1,000,000 mPa·s at 23° C. and represented by the following general formula (1):
HO-(SiR ¹ ₂ O) _a -H (1)
(In the formula, R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and each R ¹ may be the same or different, and a is an integer of 50 or more.)
(B) a hydrolyzable organosilane compound represented by the following general formula (2) and/or a partial hydrolysis condensate thereof: 1 to 40 parts by mass,

(In the formula, ^R2 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, n is an integer from 1 to 8, and m is 3 or 4.)
(C) organic strong basic curing catalyst: 0.01 to 1 part by mass,
(D) 0.01 to 10 parts by mass of a silane coupling agent represented by the following general formula (3) and/or a partial hydrolysis condensate thereof, and R ³ R ⁴ _b SiX _3-b (3)
(In the formula, ^R3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms and having at least one functional group (excluding a guanidyl group) containing one or more heteroatoms selected from a nitrogen atom, a sulfur atom, and an oxygen atom; ^R4 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms; X is a hydrolyzable group; and b is 0, 1, or 2.)
(E) A room-temperature-curable organopolysiloxane composition containing 1 to 500 parts by mass of an inorganic filler, which gives a cured product in which, after immersion in a 50% by mass aqueous solution of a long-life coolant at 100°C for 1,000 hours, the rate of change in tensile strength and elongation at break, compared to the initial state, is at least -40% and at most +80%, respectively.
[2]
The room-temperature-curable organopolysiloxane composition according to [1] gives a cured product in which the rate of change in tensile strength and elongation at break after exposure for 1,000 hours to an environment of 85°C and 85% RH is at least -40% and at most +80%, respectively, compared to the initial state.
[3]
The room-temperature-curable organopolysiloxane composition according to [1] or [2], wherein the hydrolyzable organosilane compound and/or partial hydrolysis condensate thereof of component (B) is one that releases a cyclic ketone compound by hydrolysis.
[4]
The room-temperature-curable organopolysiloxane composition according to [3], wherein the cyclic ketone compound that is eliminated is cyclobutanone or cyclopentanone.
[5]
The room-temperature-curable organopolysiloxane composition according to any one of [1] to [4], wherein component (E) is one or more inorganic fillers selected from the group consisting of calcium carbonate, fumed silica, precipitated silica, carbon black, and aluminum oxide.
[6]
An electric or electronic part having a cured product of the room-temperature-curable organopolysiloxane composition according to any one of [1] to [5].
[7]
An adhesive for electric and electronic components, comprising the room-temperature-curable organopolysiloxane composition according to any one of [1] to [5].
[8]
A potting agent for electric and electronic parts, comprising the room-temperature-curable organopolysiloxane composition according to any one of [1] to [5].
[9]
A coating agent for electrical and electronic parts, comprising the room-temperature-curable organopolysiloxane composition according to any one of [1] to [5].

In the room temperature curable organopolysiloxane composition of the present invention, the compound (elimination compound) generated from the curing agent (crosslinking agent) by the hydrolysis/condensation reaction during curing is a highly safe cyclic ketone compound such as cyclobutanone or cyclopentanone, and the composition has excellent curability and adhesion after curing, and the composition gives a silicone rubber cured product (elastomeric organopolysiloxane cured product) that is also good in durability. Therefore, the composition can be suitably used as various adhesives, potting agents, coating agents, etc. that take into consideration human health and safety. Furthermore, the room temperature curable organopolysiloxane composition of the present invention shows sufficient curability and cured product performance by using a basic organic compound as a curing catalyst without using a tin catalyst, and furthermore, the cured product has excellent LLC resistance and moist heat resistance (durability in high temperature and high humidity environments), so the composition can be suitably used as various adhesives, potting agents, coating agents, etc. for electrical and electronic components that are environmentally friendly (load reduction) and have excellent durability.

The present invention will be described in detail below. In the present invention, the viscosity is a value measured using a rotational viscometer in accordance with the method specified in JIS Z 8803. Unless otherwise specified, "room temperature" refers to a temperature of 23°C ± 15°C and a humidity of 50% RH ± 5% RH.

[Component (A): Organopolysiloxane]
Component (A) used in the room temperature curable organopolysiloxane composition of the present invention is an organopolysiloxane represented by the following general formula (1) and having a viscosity at 23° C. of 20 to 1,000,000 mPa·s.
HO-(SiR ¹ ₂ O) _a -H (1)
(In the formula, R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and each R ¹ may be the same or different. a is an integer of 50 or more.)

Component (A) is a linear diorganopolysiloxane whose main chain consists of repeating diorganosiloxane units as shown in formula (1) and whose molecular chain is terminated at both ends with hydroxyl groups (silanol groups) bonded to silicon atoms, and whose viscosity at 23°C is 20 to 1,000,000 mPa·s, and which acts as the main agent (base polymer) of the room temperature curable organopolysiloxane composition of the present invention.

In the above formula (1), R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms, such as alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, 2-ethylhexyl, nonyl, and decyl, cycloalkyl groups such as cyclohexyl, alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, and hexenyl, aryl groups such as phenyl and tolyl, and aralkyl groups such as benzyl and phenylethyl. Alternatively, the hydrogen atoms of these hydrocarbon groups may be partially substituted with halogen atoms such as chlorine, fluorine, and bromine, such as a trifluoropropyl group. The unsubstituted or substituted monovalent hydrocarbon group of ^R1 is preferably one that does not contain an aliphatic unsaturated bond, more specifically, an alkyl group such as a methyl group, an aryl group such as a phenyl group, and particularly preferably a methyl group. The ^R1s may be the same group or different groups.

In the above formula (1), a, which indicates the number of repetitions (or degree of polymerization) of the bifunctional diorganosiloxane units (SiR ¹ ₂ O _2/2 ) that constitute the main chain, is an integer of 50 or more, preferably an integer from 50 to 2,000, more preferably an integer from 100 to 1,500, and particularly preferably an integer from 200 to 1,200.
In the present invention, the degree of polymerization (or molecular weight) can be determined, for example, as a polystyrene-equivalent number average degree of polymerization (or number average molecular weight) in gel permeation chromatography (GPC) analysis using toluene, tetrahydrofuran (THF) or the like as a developing solvent.

The organopolysiloxane of component (A) has a viscosity at 23°C of 20 to 1,000,000 mPa·s, preferably 100 to 300,000 mPa·s, more preferably 1,000 to 200,000 mPa·s, and particularly preferably 10,000 to 100,000 mPa·s. If the viscosity of the organopolysiloxane is less than the lower limit (20 mPa·s), a large amount of component (C), described below, is required, which is economically disadvantageous. Also, if the viscosity of the organopolysiloxane exceeds the upper limit (1,000,000 mPa·s), workability decreases, which is not preferable.

The organopolysiloxane of component (A) may be used alone or in combination of two or more types.

（式中、Ｒ²は炭素数１～１０の一価炭化水素基であり、ｎは１～８の整数であり、ｍは３又は４である。） [Component (B): Hydrolyzable organosilane compound and/or partial hydrolysis condensate thereof]
The component (B) used in the room-temperature-curable organopolysiloxane composition of the present invention is a hydrolyzable organosilane compound represented by the following general formula (2) and/or a partial hydrolysis condensate thereof, which is used as a crosslinking agent (curing agent) and is characterized in that it releases a cyclic ketone compound such as cyclobutanone or cyclopentanone as a leaving group (leaving substance) upon hydrolysis.
In the present invention, the term "partial hydrolysis condensate" refers to an organosiloxane oligomer having three or more, preferably four or more, residual hydrolyzable groups in the molecule, which is produced by partially hydrolyzing and condensing the hydrolyzable organosilane compound.

(In the formula, ^R2 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, n is an integer from 1 to 8, and m is 3 or 4.)

In the above general formula (2), R ² is a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms, and examples of R ² include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, 2-ethylhexyl, nonyl, and decyl groups, alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, and hexenyl groups, aryl groups such as phenyl and tolyl groups, and aralkyl groups such as benzyl and phenylethyl groups. Among these, methyl, ethyl, vinyl, and phenyl groups are preferred, and methyl, vinyl, and phenyl groups are particularly preferred.

In the above general formula (2), n is an integer of 1 to 8, preferably an integer of 2 to 6, more preferably an integer of 2 to 4, and even more preferably 2 or 3. When n is 0, a cyclic structure is not formed. When n is an integer of 9 or more, the molecular weight of the hydrolyzable organosilane becomes large, making purification by distillation difficult and increasing the amount of addition required to ensure storage stability, which is disadvantageous in terms of cost.

As mentioned above, m is 3 or 4. If this number is less than 3 (i.e., if m is 0, 1, or 2), rubber hardening by crosslinking reaction does not occur, and the compound is not suitable as a crosslinking agent for room temperature curable organopolysiloxane compositions.

The leaving group (leaving compound) generated by hydrolysis of the hydrolyzable organosilane compound represented by the above general formula (2) is a cyclic ketone compound such as cyclopropanone, cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, cyclononanone, cyclodecanone, etc., preferably cyclobutanone and cyclopentanone, more preferably cyclopentanone. There have been no reports of cyclobutanone and cyclopentanone being harmful to human health, such as carcinogenicity or reproductive toxicity, or environmentally harmful, such as toxicity to aquatic organisms. Cyclopentanone is also mass-produced industrially, is easily available, and is highly cost-competitive, so it is also advantageous for the production of the hydrolyzable organosilane compound of component (B), as described below.

The hydrolyzable organosilane compound of component (B) can be produced, for example, by reacting (e.g., dehydrochlorination reaction) a chlorosilane compound corresponding to the product hydrolyzable organosilane compound represented by general formula (2) with a cyclic ketone compound in the presence of a catalyst and a basic substance. This reaction formula is represented, for example, by the following formula [1].

（式中、Ｒ²、ｎ、ｍは前記の通りである。）

(In the formula, R ² , n, and m are as defined above.)

Examples of the chlorosilane compound include the following.

Examples of the cyclic ketone compound include the following.

The amount of the cyclic ketone compound to be reacted with the chlorosilane compound is preferably 0.95 to 3.0 moles, more preferably 0.99 to 2.5 moles, and even more preferably 1.0 to 2.0 moles, per mole of chlorine atoms in the chlorosilane compound. If the amount of the cyclic ketone compound added is small, the reaction may not terminate, and if the amount of the cyclic ketone compound added is too large, purification may take a long time, which may increase the production time.

The catalyst used in the reaction includes monovalent or divalent metallic copper compounds, such as, but not limited to, copper chloride, copper bromide, copper iodide, copper sulfate, copper nitrate, copper carbonate, basic copper carbonate, copper formate, copper acetate, and copper butyrate.
The amount of catalyst (metallic copper compound) added is preferably 0.001 to 0.5 mol, more preferably 0.002 to 0.2 mol, and even more preferably 0.003 to 0.1 mol, per mol of the chlorosilane compound. If the amount of catalyst added is too small, the reaction may not be completed, whereas if the amount of catalyst added is too large, it is disadvantageous in terms of cost.

The basic substance used in the reaction may be a basic substance having low nucleophilicity, such as trimethylamine, triethylamine, tripropylamine, tributylamine, urea, diazabicycloundecene, diazabicyclononene, etc. Among these, trimethylamine, triethylamine, and tributylamine are preferred, and triethylamine is particularly preferred.
The amount of the basic substance added is preferably 0.95 to 2.5 mol, more preferably 0.99 to 2.0 mol, and even more preferably 1.0 to 1.5 mol, per mol of chlorine atoms in the chlorosilane compound. If the amount of the basic substance added is small, the reaction may not be completed, whereas if the amount of the basic substance added is too large, it is economically disadvantageous.

[0043] A commonly used solvent may be used in the production of the hydrolyzable organosilane compound of component (B). Examples of the solvent include organic solvents such as 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.
The amount of the solvent used is not particularly limited, but is usually in the range of 10 to 500 parts by mass, preferably 30 to 400 parts by mass, and more preferably 50 to 300 parts by mass, per 100 parts by mass of the cyclic ketone compound used.

The reaction conditions for the chlorosilane compound and the cyclic ketone compound are usually such that the chlorosilane compound is dropped into the cyclic ketone compound at a temperature of 0 to 120°C, preferably 0 to 100°C, and the reaction is carried out at 50 to 120°C, preferably 60 to 100°C, for 1 to 48 hours, more preferably 3 to 30 hours. If the reaction temperature is too low, the reaction may not be completed, and if the reaction temperature is too high, the product may become significantly colored. In addition, if the reaction time is too short, the reaction may not be completed, and if the reaction time is too long, this is detrimental to productivity.
After the reaction is completed, purification can be performed by distilling the target product under reduced pressure, the degree of reduction being preferably 1×10 ⁻⁵ to 3,000 Pa, more preferably 1×10 ⁻⁵ to 2,000 Pa, and the temperature during purification being preferably 100 to 250° C., more preferably 120 to 230° C. If the pressure during reduction (degree of reduction) is too high, distillation may become difficult. If the temperature during purification is too low, purification by distillation may become difficult, and if it is too high, coloration or decomposition of the reaction product may occur.

Specific examples of the hydrolyzable organosilane compound of component (B) include those represented by the following formula: In this case, Me represents a methyl group.

The component (B) may be used alone or in combination of two or more types.
The amount of component (B) is 1 to 40 parts by mass, preferably 3 to 30 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of component (A). If the amount of component (B) is less than the lower limit of 1 part by mass, the shelf life of the composition may deteriorate when stored in a sealed container. If the amount of component (B) is more than the upper limit of 40 parts by mass, the curability of the room-temperature-curable organopolysiloxane composition may decrease significantly, and the adhesiveness may also deteriorate.
The hydrolyzable organosilane compound and/or partial hydrolysis condensate thereof of component (B) is clearly distinguished from the silane coupling agent and/or partial hydrolysis condensate thereof of component (D) as an optional component described later in detail below, in that it does not have in its molecule a monovalent hydrocarbon group having at least one functional group containing one or more atoms selected from a nitrogen atom, a sulfur atom, and an oxygen atom.

[Component (C): Organic Strong Basic Curing Catalyst]
Component (C) is a curing catalyst made of a strongly basic organic substance, and imparts good curing properties to the composition of the present invention. Examples of component (C) include amine compounds such as triethylamine, hexylamine, tetramethylguanidine, diazabicycloundecene (DBU), and diazabicyclononene (DBN), and guanidyl group-containing alkoxysilane compounds such as γ-tetramethylguanidylpropyltrimethoxysilane and γ-tetramethylguanidylpropyltriethoxysilane, as well as salts thereof (strongly basic organic curing catalysts). At least one of these, i.e., one type, may be used alone, or two or more types may be used in combination.

The amount of component (C) is 0.01 to 1 part by mass, preferably 0.1 to 0.8 parts by mass, and more preferably 0.2 to 0.6 parts by mass, per 100 parts by mass of component (A). If the amount of component (E) is less than the lower limit of 0.01 part by mass, the catalytic effect is not obtained, and if it exceeds the upper limit of 1 part by mass, the durability of the composition deteriorates.

[Component (D): Silane coupling agent and/or partial hydrolysis condensate thereof]
Component (D) is a silane coupling agent represented by the following general formula (3) (i.e., a hydrolyzable organosilane compound or carbon functional silane having a functional group-containing monovalent hydrocarbon group) and/or a partial hydrolysis condensate thereof, and is an essential component for imparting good adhesion to the cured product of the room-temperature-curable organopolysiloxane composition of the present invention.
R ³ R ⁴ _b SiX _3-b (3)
(In the formula, ^R3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms and having at least one functional group (excluding a guanidyl group) containing one or more heteroatoms selected from a nitrogen atom, a sulfur atom, and an oxygen atom; ^R4 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms; X is a hydrolyzable group; and b is 0, 1, or 2.)

In the above formula (3), R ³ is a monovalent hydrocarbon group having 1 to 20 carbon atoms and having at least one functional group containing one or more heteroatoms selected from a nitrogen atom, a sulfur atom, and an oxygen atom (for example, an unsubstituted or substituted amino group, an unsubstituted or substituted imino group, an amide group, a ureido group, a mercapto group, an epoxy group, a (meth)acryloxy group, etc., but excluding a guanidyl group), and specifically, a β-(2,3-epoxycyclohexyl)ethyl group, a β-(3,4-epoxycyclohexyl)ethyl group, a γ-glycidoxypropyl group, a γ-methacryloxypropyl group, a γ-glycid ... Examples of monovalent hydrocarbon groups preferably having 3 to 20 carbon atoms, more preferably 3 to 14 carbon atoms, containing at least one heteroatom selected from a nitrogen atom, a sulfur atom, and an oxygen atom, such as a γ-acryloxypropyl group, a γ-acryloxypropyl group, an N-β-(aminoethyl)-γ-aminopropyl group [also known as an N-2-(aminoethyl)-3-aminopropyl group], a γ-aminopropyl group, an N-phenyl-γ-aminopropyl group, a γ-ureidopropyl group, a γ-mercaptopropyl group, and a γ-isocyanatopropyl group. As R ⁵ , a γ-glycidoxypropyl group, a γ-aminopropyl group, and an N-β-(aminoethyl)-γ-aminopropyl group are particularly preferred.

In the above formula (3), R ⁴ is a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, and may be, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, or a decyl group; a cycloalkyl group such as a cyclohexyl group; an alkenyl group such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, or a hexenyl group; an aryl group such as a phenyl group or a tolyl group; or an aralkyl group such as a benzyl group or a phenylethyl group. Alternatively, a group in which the hydrogen atoms of these hydrocarbon groups are partially substituted with a halogen atom such as chlorine, fluorine, or bromine, such as a trifluoropropyl group, may be mentioned. Among these, a methyl group, an ethyl group, a propyl group, or an isopropyl group is preferable. Note that R ⁴ may be the same group or different groups.

In the above formula (3), examples of the hydrolyzable group X include, for example, a ketoxime group, an alkoxy group, an alkoxyalkoxy group, an acyloxy group, and an alkenyloxy group. Specifically, examples include ketoxime groups having 3 to 8 carbon atoms, such as dimethylketoxime group, diethylketoxime group, methylethylketoxime group, and methylisobutylketoxime group; alkoxy groups having 1 to 4 carbon atoms, preferably 1 or 2 carbon atoms, such as methoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, and tert-butoxy group; alkoxyalkoxy groups having 2 to 4 carbon atoms, such as methoxymethoxy group and methoxyethoxy group; acyloxy groups having 2 to 4 carbon atoms, such as acetoxy group and propionoxy group; and alkenyloxy groups having 2 to 4 carbon atoms, such as vinyloxy group, allyloxy group, propenoxy group, and isopropenoxy group. X is preferably a methoxy group. The hydrolyzable groups X may be the same or different.

Specific examples of the silane coupling agent represented by formula (3) of component (D) include aminosilanes such as γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, 3-2-(aminoethylamino)propyltrimethoxysilane [also known as N-2-(aminoethyl)-3-aminopropyltrimethoxysilane], epoxysilanes such as γ-glycidoxypropyltrimethoxysilane and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, (meth)acrylicsilanes such as γ-(meth)acryloxypropyltrimethoxysilane and γ-(meth)acryloxypropyltriethoxysilane, mercaptosilanes such as γ-mercaptopropyltrimethoxysilane, and isocyanatesilanes such as γ-isocyanatopropyltrimethoxysilane.

The silane coupling agent and/or partial hydrolysis condensate thereof as the component (D) may use one type alone, or two or more types may be used in combination.
The amount of component (D) is 0.01 to 10 parts by mass, and preferably 0.1 to 8 parts by mass, per 100 parts by mass of component (A). If it is less than 0.01 part by mass, the cured product will not exhibit sufficient adhesive performance, and if it is blended in excess of 10 parts by mass, the rubber strength after curing will decrease and the curability will decrease.

[Component (E): Inorganic Filler]
The inorganic filler of component (E) is a reinforcing or non-reinforcing filler for imparting rubber properties to the room temperature curable organopolysiloxane composition of the present invention. Examples of the inorganic filler of component (E) include silica-based fillers such as dry silica such as calcined silica and fumed silica, wet silica such as precipitated silica and sol-gel silica, which are surface-hydrophobized or untreated, carbon black, talc, bentonite, calcium carbonate, zinc carbonate, magnesium carbonate, calcium oxide, zinc oxide, magnesium oxide, aluminum oxide, aluminum hydroxide, etc., among which calcium carbonate, fumed silica, precipitated silica, carbon black, and aluminum oxide are preferred, and calcium carbonate, fumed silica, precipitated silica, carbon black, and aluminum oxide, which are surface-hydrophobized inorganic fillers, are more preferred. In this case, it is preferred that these inorganic fillers have a low water content.
There are no particular limitations on the type, amount, treatment method, etc. of the surface treatment agent (hydrophobic treatment agent). Representative examples of the surface treatment agent that can be used include organosilicon compounds such as chlorosilanes, alkoxysilanes, and organosilazanes, fatty acids, paraffins, silane coupling agents, and titanium coupling agents.

The inorganic filler of component (E) may be used alone or in combination of two or more kinds.
The amount of component (E) blended is 1 to 500 parts by mass, preferably 3 to 400 parts by mass, more preferably 5 to 300 parts by mass, and even more preferably 10 to 250 parts by mass, relative to 100 parts by mass of component (A). If the amount is less than 1 part by mass, sufficient rubber strength cannot be obtained, resulting in a problem that the composition is not suitable for the intended use, whereas if the amount exceeds 500 parts by mass, the ejection properties from the cartridge deteriorate, storage stability decreases, and the mechanical properties of the resulting rubber properties also decrease.

[Other ingredients]
In addition, the room temperature curable organopolysiloxane composition of the present invention may contain other commonly known additives in addition to the above-mentioned components, as long as they do not impair the purpose of the present invention.Additives include polyethers as thixotropy improvers, silicone oils (nonfunctional organopolysiloxanes) as plasticizers, isoparaffins, etc., and if necessary, colorants such as pigments, dyes, and fluorescent whitening agents, bioactive additives such as antifungal agents, antibacterial agents, and marine organism repellents, surface modifiers such as phenyl silicone oils, fluorosilicone oils, and organic liquids incompatible with silicone as bleeding oils, solvent volatile oils, and solvents such as low-boiling isoparaffins.It is preferable that the room temperature curable organopolysiloxane composition of the present invention does not contain organometallic catalysts such as tin catalysts, titanium catalysts, and organic bismuth catalysts as curing catalysts.

The room temperature curable organopolysiloxane composition of the present invention can be obtained by uniformly mixing the above-mentioned components and the above-mentioned various additives in a dry atmosphere in predetermined amounts. The room temperature curable organopolysiloxane composition of the present invention cures when left at room temperature, and the molding method, curing conditions, etc. can be known methods and conditions according to the type of composition.

The room temperature curable organopolysiloxane composition of the present invention, particularly the one-component composition, is stored in the absence of moisture, i.e., in a sealed container that is protected from moisture, and is easily cured at room temperature (23°C ± 15°C) by exposing it to moisture in the air when used.

The room-temperature-curable organopolysiloxane composition of the present invention has a rate of change in tensile strength and elongation at break (((physical properties after durability - initial physical properties)/initial physical properties) x 100%) after immersion of a cured product in a 50% by mass aqueous solution of long-life coolant at 100°C for 1,000 hours that is -40% or more and +80% or less, preferably -30% or more and +50% or less, compared to the initial state. If the rate of change in tensile strength and elongation at break is less than -40%, sufficient physical properties cannot be obtained as a sealing agent for long-life coolant (LLC), and if it exceeds +80%, the change from the initial physical properties will be too great, which is not preferred in terms of product design.
The cured product of the room-temperature curable organopolysiloxane composition is a 2 mm thick rubber sheet obtained by pouring the composition into a 2 mm mold and curing it at 23° C. and 50% RH for 7 days, and the tensile strength and elongation at break are values measured in accordance with JIS K 6249.
In the present invention, in order to achieve the above-mentioned ranges of change in tensile strength and elongation at break after immersion in a 50% by mass aqueous solution of long-life coolant at 100°C for 1,000 hours, a specific amount of a specific organosilicon compound (component (B)) having a cyclic ketone as a leaving group is used as a crosslinking component, and a specific range of an organic strong basic catalyst (component (C)) is added as a curing catalyst (0.01 to 1 part by mass per 100 parts by mass of component (A)), and further, a specific range of an inorganic filler (component (E)) is used in combination (1 to 500 parts by mass per 100 parts by mass of component (A)). In particular, when the amount of the organic strong basic catalyst (component (C)) blended exceeds 1 part by mass per 100 parts by mass of component (A), the resistance to the long-life coolant decreases.

Furthermore, the rate of change in tensile strength and elongation at break of the room-temperature-curable organopolysiloxane composition of the present invention after a cured product is exposed to an environment of 85° C. and 85% RH for 1,000 hours (((physical properties after durability−initial physical properties)/initial physical properties)×100%) compared to the initial state is preferably −40% or more and +80% or less, and more preferably −25% or more and +40% or less. If the rate of change in tensile strength and elongation at break is less than −40%, sufficient physical properties may not be obtained as an airtight sealant, whereas if it exceeds 80%, the change from the initial physical properties will be too great, which may be undesirable from the perspective of product design.
The cured product of the room-temperature curable organopolysiloxane composition is a 2 mm thick rubber sheet obtained by pouring the composition into a 2 mm mold and curing it at 23° C. and 50% RH for 7 days, and the tensile strength and elongation at break are values measured in accordance with JIS K 6249.
In the present invention, in order to achieve the above-mentioned ranges of change in tensile strength and elongation at break after 1,000 hours of exposure to an environment of 85°C and 85% RH, it is effective to use a specific amount of a specific organosilicon compound having a cyclic ketone as a leaving group (component (B)) as a crosslinking component, add an organic strong basic catalyst (component (C)) as a curing catalyst in a specific range (0.01 to 1 part by mass per 100 parts by mass of component (A)), and further use an inorganic filler of component (E) in a specific range (1 to 500 parts by mass per 100 parts by mass of component (A)). In particular, when the amount of the organic strong basic catalyst of component (C) exceeds 1 part by mass per 100 parts by mass of component (A), resistance to a moist heat test may decrease.

In the room temperature curable organopolysiloxane composition of the present invention, the compound generated from the crosslinking agent by the hydrolysis reaction during curing is a highly safe cyclic ketone compound such as cyclopentanone, and is therefore considered to be safe for the human body and the environment. Furthermore, cyclopentanone has a flash point of 35°C, which is higher than that of dealcohol-type compositions that release alcohol compounds such as methanol when the composition is cured, and is therefore highly safe. Such a room temperature curable organopolysiloxane composition of the present invention exhibits good curing properties by using various existing catalysts, and the cured product (silicone rubber) is also excellent in adhesion, LLC resistance, and moist heat resistance. In addition, a tin catalyst is not used, making it possible to provide a composition that takes environmental impact into consideration.

Therefore, the room temperature curable organopolysiloxane composition of the present invention is particularly useful as an adhesive, potting agent, coating agent, or the like for electrical and electronic applications. The room temperature curable organopolysiloxane composition of the present invention can be used as an adhesive, potting agent, or coating agent according to a conventional method.

Examples of items that are subject to this regulation include automobile parts, electrical and electronic parts, etc.

The present invention will be described in more detail below with reference to synthesis examples, working examples, and comparative examples, but the present invention is not limited to the following examples. The viscosity is measured at 23°C using a rotational viscometer according to the method specified in JIS Z 8803. Me represents a methyl group.

[Synthesis Example 1] Synthesis of hydrolyzable organosilane compound 1 834g (9.9mol) of cyclopentanone, 825g (8.2mol), 5g (0.05mol) of copper (I) chloride, and 1,500ml of hexane were charged into a 5,000mL four-necked separable flask equipped with a mechanical stirrer, a thermometer, a reflux tube, and a dropping funnel, and 400g (2.47mol) of vinyltrichlorosilane was dropped over about 2 hours in the range of 40 to 60°C. After that, after stirring at 80°C for 12 hours, the generated triethylamine hydrochloride was removed by filtration, and hexane was distilled from the filtrate at 100°C and normal pressure, and then distilled at 180°C and 300 Pa to obtain hydrolyzable organosilane compound 1 (yield 532g, yield 69%). This reaction formula is represented by the following formula [2].

[Synthesis Example 2] Synthesis of hydrolyzable organosilane compound 2 834g (9.9mol) of cyclopentanone, 825g (8.2mol), 5g (0.05mol) of copper (I) chloride, and 1,500ml of hexane were charged into a 5,000mL four-necked separable flask equipped with a mechanical stirrer, a thermometer, a reflux tube, and a dropping funnel, and 368g (2.47mol) of methyltrichlorosilane was dropped over about 2 hours at a temperature of 40 to 60°C. After stirring at 80°C for 12 hours, the generated triethylamine hydrochloride was removed by filtration, and hexane was distilled from the filtrate at 100°C and normal pressure, followed by distillation at 170°C and 300 Pa to obtain hydrolyzable organosilane compound 2 (yield 519g, yield 71%). This reaction formula is represented by the following formula [3].

[Synthesis Example 3] Synthesis of hydrolyzable organosilane compound 3 834g (9.9mol) of cyclopentanone, 825g (8.2mol), 5g (0.05mol) of copper (I) chloride, and 1,500ml of hexane were charged into a 5,000mL four-necked separable flask equipped with a mechanical stirrer, a thermometer, a reflux tube, and a dropping funnel, and 522g (2.47mol) of phenyltrichlorosilane was dropped over about 2 hours in the range of 40 to 60°C. After that, after stirring at 80°C for 12 hours, the generated triethylamine hydrochloride was removed by filtration, and hexane was distilled from the filtrate at 100°C and normal pressure, and then distilled at 200°C and 300 Pa to obtain hydrolyzable organosilane compound 3 (yield 568g, yield 65%). This reaction formula is represented by the following formula [4].

[Example 1]
To 100 parts by mass of (A) linear dimethylpolysiloxane (dimethylpolysiloxane in the above general formula (1) where R ¹ =methyl group and a =about 620) having a viscosity of 20,000 mPa·s at 23° C. and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and thoroughly mixed, and then 8 parts by mass of (B-1) hydrolyzable organosilane compound 1 was added and thoroughly mixed. Finally, 1 part by mass of (D-1) γ-aminopropyltrimethoxysilane (product name: KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.4 parts by mass of (C-1) γ-tetramethylguanidylpropyltrimethoxysilane were added and thoroughly mixed under reduced pressure to obtain composition 1.

[Example 2]
To 100 parts by mass of (A) a linear dimethylpolysiloxane (dimethylpolysiloxane corresponding to the above general formula (1) where R ¹ = methyl group and a = approximately 620) having a viscosity of 20,000 mPa·s at 23° C. and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B-1) the above hydrolyzable organosilane compound 1 was added and thoroughly mixed. Finally, 1 part by mass of (D-1) γ-aminopropyltrimethoxysilane (product name: KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.4 parts by mass of (C-1) γ-tetramethylguanidylpropyltrimethoxysilane were added and thoroughly mixed under reduced pressure to obtain Composition 2.

[Example 3]
To 100 parts by mass of (A) a linear dimethylpolysiloxane (dimethylpolysiloxane corresponding to the above general formula (1) where R ¹ = methyl group and a = approximately 620) having a viscosity of 20,000 mPa·s at 23° C. and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B-1) the above hydrolyzable organosilane compound 1 was added and thoroughly mixed. Finally, 1 part by mass of (D-1) γ-aminopropyltrimethoxysilane (product name: KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.25 parts by mass of (C-2) diazabicycloundecene were added and thoroughly mixed under reduced pressure to obtain composition 3.

[Example 4]
To 100 parts by mass of (A) a linear dimethylpolysiloxane (dimethylpolysiloxane corresponding to the above general formula (1) where R ¹ = methyl group and a = approximately 620) having a viscosity of 20,000 mPa·s at 23° C. and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B-1) the above hydrolyzable organosilane compound 1 was added and thoroughly mixed. Finally, 1 part by mass of (D-2) N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (product name: KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.25 parts by mass of (C-2) diazabicycloundecene were added and thoroughly mixed under reduced pressure to obtain Composition 4.

[Example 5]
To 100 parts by mass of (A) a linear dimethylpolysiloxane (dimethylpolysiloxane in the above general formula (1) where R ¹ = methyl and a = approximately 620) having a viscosity of 20,000 mPa·s at 23°C and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B-2) the above hydrolyzable organosilane compound 2 was added and thoroughly mixed. Finally, 1 part by mass of (D-1) γ-aminopropyltrimethoxysilane (product name: KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.4 parts by mass of (C-1) γ-tetramethylguanidylpropyltrimethoxysilane were added and thoroughly mixed under reduced pressure to obtain Composition 5.

[Example 6]
To 100 parts by mass of (A) a linear dimethylpolysiloxane (dimethylpolysiloxane corresponding to the above general formula (1) where R ¹ = methyl group and a = approximately 620) having a viscosity of 20,000 mPa·s at 23° C. and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B-3) the above hydrolyzable organosilane compound 3 was added and thoroughly mixed. Finally, 1 part by mass of (D-2) N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (product name: KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.4 parts by mass of (C-1) γ-tetramethylguanidylpropyltrimethoxysilane were added and thoroughly mixed under reduced pressure to obtain Composition 6.

[Comparative Example 1]
To 100 parts by mass of (A) linear dimethylpolysiloxane (dimethylpolysiloxane in the above general formula (1) where R ¹ =methyl group and a =about 620) having a viscosity of 20,000 mPa·s at 23°C and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and thoroughly mixed, and then 8 parts by mass of (B') methyltrismethylethylketoximesilane was added and thoroughly mixed. Finally, 1 part by mass of (D-1) γ-aminopropyltrimethoxysilane (product name: KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.1 part by mass of (C') dioctyltin dilaurate were added and thoroughly mixed under reduced pressure to obtain Composition 7.

[Comparative Example 2]
To 100 parts by mass of (A') linear dimethylpolysiloxane (dimethylpolysiloxane corresponding to the above general formula (1) where R ¹ = methyl group, a = approximately 620) having a viscosity of 20,000 mPa·s at 23°C and both molecular chain terminals are blocked with methyldimethoxy groups, 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B'') methyltrimethoxysilane was added and thoroughly mixed. Finally, 1 part by mass of (D-1) γ-aminopropyltrimethoxysilane (product name: KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) and 0.1 part by mass of (C′) dioctyltin dilaurate were added and thoroughly mixed under reduced pressure to obtain composition 8.

[Comparative Example 3]
To 100 parts by mass of (A) a linear dimethylpolysiloxane (dimethylpolysiloxane corresponding to the above general formula (1) where R ¹ = methyl group and a = approximately 620) having a viscosity of 20,000 mPa·s at 23° C. and both molecular chain terminals are blocked with silanol groups (hydroxyl groups bonded to silicon atoms), 100 parts by mass of (E-1) heavy calcium carbonate the surface of which has been treated with a paraffin-based material (product name: MC Coat P-20, manufactured by Maruo Calcium Co., Ltd.) and 10 parts by mass of (E-2) fumed silica the surface of which has been treated with dimethyldichlorosilane (product name: MU-215, manufactured by Shin-Etsu Chemical Co., Ltd.) were added and thoroughly mixed, and then 8 parts by mass of (B-1) the above hydrolyzable organosilane compound 1 was added and thoroughly mixed. Finally, 1 part by mass of (D-2) N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (product name: KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) and 2 parts by mass of (C-1) γ-tetramethylguanidylpropyltrimethoxysilane were added and thoroughly mixed under reduced pressure to obtain Composition 9.

[Test Method]
The following evaluations were carried out for each of the compositions (room-temperature-curable organopolysiloxane compositions) prepared in the above Examples 1 to 6 and Comparative Examples 1 to 3. The evaluation results are shown in Table 1 below, together with the blending amounts of Examples 1 to 6 and Comparative Examples 1 to 3.

(Initial evaluation)
As an initial evaluation, the following tack-free time, curing speed, rubber properties, adhesion, and electrical properties were evaluated using each of the compositions immediately after preparation.
Tuck Free Time
Using each of the compositions prepared in the above Examples and Comparative Examples, the tack-free time (touch-dry time) was measured in accordance with the method specified in JIS A 5758.

Curing speed The curing speed test method was to fill a glass petri dish with an inner diameter of 10 mm with each composition prepared in the above Examples and Comparative Examples, and after one day (24 hours) at 23°C and 50% RH, a probe was inserted into the dish to measure the cured thickness (depth) from the part exposed to air.

Each composition prepared in the above Examples and Comparative Examples was poured into a 2 mm mold and cured at 23° C. and 50% RH for 7 days to obtain a 2 mm thick rubber sheet. The rubber properties (type A durometer hardness, tensile strength, and elongation at break) were measured in accordance with JIS K 6249.

Adhesion Each of the compositions prepared in the above Examples and Comparative Examples was cured between two aluminum plates of 25 mm width and 100 mm length at 23°C and 50% RH for 7 days to form a silicone rubber cured layer with an adhesive area of 2.5 ^cm2 and an adhesive thickness of 1 mm on the upper and lower aluminum plates, to prepare a shear adhesion test specimen. The shear adhesive strength and cohesive failure rate to aluminum were measured using each of these test specimens according to the method specified in JIS K 6249.

Electrical properties (breakdown voltage, volume resistivity)
Each composition prepared in the above Examples and Comparative Examples was poured into a 1 mm mold and cured at 23° C. and 50% RH for 7 days to obtain a rubber sheet having a thickness of 1 mm. The dielectric breakdown voltage and volume resistivity were measured according to JIS K 6249.

(Evaluation of humidity and heat resistance)
In order to confirm the moist heat resistance performance, the obtained cured silicone rubber sheet and the shear adhesion test specimen were exposed to an environment of 85°C and 85% RH and allowed to deteriorate for 1,000 hours, and then tests (rubber properties, adhesion) similar to those performed at the initial stage of production (initial evaluation) were performed to confirm the moist heat resistance.

(LLC resistance evaluation)
In order to confirm LLC resistance, the obtained cured silicone rubber sheet and shear adhesion test specimen were immersed in a 50 mass % aqueous solution of long life coolant (Toyota genuine super long life coolant, manufactured by Toyota Motor Corporation) and subjected to thermal degradation at 100°C for 1,000 hours, and then tests (rubber properties, adhesion) similar to those performed at the initial stage of production (initial evaluation) were performed to conduct a confirmation test of LLC resistance.

(Rate of change and judgment)
The compositions in which the rate of change in tensile strength and elongation at break after the LLC resistance test and the 85°C, 85% RH test, respectively, was -40% or more and +80% or less, compared with the initial state, were judged as passing, and the rest were judged as failing.
The rate of change was calculated as ((physical properties after durability test--initial physical properties)/initial physical properties)×100%.

From the above results, it was shown that the room temperature curable organopolysiloxane composition of the present invention has good curability (tack-free time, curing speed), rubber properties and adhesion in the initial evaluation, even without using a tin catalyst, and also has good properties in the moist heat resistance test and LLC resistance test. The properties of the room temperature curable organopolysiloxane composition of the present invention are superior to the commonly used oxime-free and alcohol-free compositions of Comparative Examples 1 and 2 in terms of moist heat resistance and LLC resistance. However, the composition of Comparative Example 3, which contains a large amount of strong base catalyst as a curing catalyst, was inferior in durability to the composition of the present invention. In addition, there was no difference in electrical properties between the Examples and Comparative Examples, and the results showed high insulating properties specific to silicone.
Furthermore, the compound released during curing from the compositions of the Examples is cyclopentanone, a highly safe compound with no reported health hazards, such as carcinogenicity or reproductive toxicity, to the human body, or environmental hazards, such as toxicity to aquatic organisms. On the other hand, the compounds released during curing from the compositions of Comparative Examples 1 and 2 are both labeled with health hazards in SDS (Safety Data Sheets) or the like, and are 2-butanone oxime, which may be carcinogenic and is toxic to aquatic organisms, and methanol, which is designated as a deleterious substance and is highly harmful to the human body. This shows that the room-temperature-curable organopolysiloxane composition of the present invention is superior in terms of human health and environmental protection.

The above results confirm that the room temperature curable organopolysiloxane composition of the present invention releases safer compounds during curing, has good curing properties without the use of a tin catalyst, and the cured product has good physical properties, adhesion, durability (moisture heat resistance, LLC resistance), and insulating properties, making it suitable for use in electrical and electronic applications (adhesives, potting agents, coating agents, etc.).

Claims (9)

(A) 100 parts by mass of an organopolysiloxane having a viscosity of 20 to 1,000,000 mPa·s at 23° C. and represented by the following general formula (1):
HO-(SiR ¹ ₂ O) _a -H (1)
(In the formula, R ¹ is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and each R ¹ may be the same or different, and a is an integer of 50 or more.)
(B) a hydrolyzable organosilane compound represented by the following general formula (2) and/or a partial hydrolysis condensate thereof: 1 to 40 parts by mass,

(In the formula, ^R2 is a monovalent hydrocarbon group having 1 to 10 carbon atoms, n is an integer from 1 to 8, and m is 3 or 4.)
(C) organic strong basic curing catalyst: 0.01 to 1 part by mass,
(D) 0.01 to 10 parts by mass of a silane coupling agent represented by the following general formula (3) and/or a partial hydrolysis condensate thereof, and R ³ R ⁴ _b SiX _3-b (3)
(In the formula, ^R3 is a monovalent hydrocarbon group having 1 to 20 carbon atoms and having at least one functional group (excluding a guanidyl group) containing one or more heteroatoms selected from a nitrogen atom, a sulfur atom, and an oxygen atom; ^R4 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms; X is a hydrolyzable group; and b is 0, 1, or 2.)
(E) A room-temperature-curable organopolysiloxane composition containing 1 to 500 parts by mass of an inorganic filler, which gives a cured product in which, after immersion in a 50% by mass aqueous solution of a long-life coolant at 100°C for 1,000 hours, the rate of change in tensile strength and elongation at break, compared to the initial state, is at least -40% and at most +80%, respectively. The room temperature curable organopolysiloxane composition according to claim 1, which gives a cured product in which the rate of change in tensile strength and elongation at break after exposure for 1,000 hours to an environment of 85°C and 85% RH is -40% or more and +80% or less, respectively, compared to the initial state. The room-temperature curable organopolysiloxane composition according to claim 1, wherein the hydrolyzable organosilane compound and/or its partial hydrolysis condensate of component (B) releases a cyclic ketone compound by hydrolysis. The room temperature curable organopolysiloxane composition according to claim 3, wherein the cyclic ketone compound that is eliminated is cyclobutanone or cyclopentanone. The room temperature curable organopolysiloxane composition according to claim 1, wherein component (E) is one or more inorganic fillers selected from calcium carbonate, fumed silica, precipitated silica, carbon black, and aluminum oxide. An electric or electronic part having a cured product of the room temperature curable organopolysiloxane composition according to any one of claims 1 to 5. An adhesive for electrical and electronic components containing the room temperature curable organopolysiloxane composition according to any one of claims 1 to 5. A potting agent for electrical and electronic components containing the room temperature curable organopolysiloxane composition according to any one of claims 1 to 5. A coating agent for electrical and electronic parts containing the room temperature curable organopolysiloxane composition according to any one of claims 1 to 5.