Cyclic siloxane, adhesion aid, silicone composition, and adhesive

Abstract

To provide a cyclic siloxane which is excellent in chemical resistance and serves as an adhesion aid capable of stably imparting adhesiveness even when exposed to a high-temperature and high-humidity environment for a long time, a silicone composition containing the same, and an adhesive.SOLUTION: The cyclic siloxane is represented by general formula (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cyclic siloxane, an adhesive coagent, a silicone composition containing the same, and an adhesive. [Background technology]

[0002] Materials used for bonding around automatic transmission fluid (ATF) and long life coolant (LLC) used in automobile engines are required to maintain their adhesive properties even when exposed to these liquids for long periods of time in high temperature and humidity environments.

[0003] Cyclic siloxanes having functional groups are used as adhesion aids in silicone compositions used in adhesives and sealants to impart adhesion to various substrates. For example, Patent Document 1 proposes a cyclic siloxane that has excellent adhesion to metals and resins, particularly polycarbonate resins, and is capable of imparting stable adhesion even when exposed to high-temperature, high-humidity environments such as 85°C and 85% RH for long periods of time. However, there has been a demand for improved LLC resistance under more severe conditions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2024-044151 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a cyclic siloxane that serves as an adhesion aid that has excellent chemical resistance and is capable of imparting stable adhesion even when exposed to high-temperature, high-humidity environments for extended periods of time, a silicone composition containing the same, and an adhesive. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides a cyclic siloxane represented by the following general formula (1). [ka] (In the formula, R 1 are independently an alkyl group having 1 to 4 carbon atoms, and R 2 are independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 3 and R 4 are independently an alkylene group having 1 to 8 carbon atoms, X is independently a glycidyloxy group, a trimethoxysilyl group, or a triethoxysilyl group, p is an integer of 1 to 3, q ​​is an integer of 1 to 3, r is an integer of 1 to 3, and the sum of p, q, and r is 4 to 6. The order of arrangement of the siloxane units is arbitrary.

[0007] Such cyclic siloxanes have excellent chemical resistance and adhesive durability in high-temperature, high-humidity environments.

[0008] The present invention also provides an adhesion promoter comprising the above cyclic siloxane.

[0009] Such an adhesive aid has excellent chemical resistance and adhesion durability in high-temperature, high-humidity environments.

[0010] The present invention also provides a silicone composition containing the above cyclic siloxane.

[0011] Such a silicone composition has excellent chemical resistance and exhibits stable adhesive properties even when exposed to high-temperature, high-humidity environments for extended periods of time.

[0012] The present invention also provides an adhesive comprising the above silicone composition.

[0013] Such an adhesive has excellent chemical resistance and maintains stable adhesive properties even when exposed to high temperature and humidity environments for a long period of time. [Effects of the Invention]

[0014] As described above, the cyclic siloxane of the present invention has excellent chemical resistance and maintains adhesiveness even when exposed to high-temperature, high-humidity environments for extended periods of time, making it useful as an adhesion promoter for imparting adhesiveness to silicone compositions, etc. It can be particularly well suited for use in automotive applications where reliability in high-temperature, high-humidity environments such as those found around automatic transmission fluids (ATFs) and LLCs is required. DETAILED DESCRIPTION OF THE INVENTION

[0015] As described above, there has been a need for the development of a cyclic siloxane that can serve as an adhesion aid that has excellent chemical resistance and is capable of imparting stable adhesion even when exposed to a high-temperature, high-humidity environment for a long period of time.

[0016] As a result of extensive research to achieve the above object, the present inventors have discovered that a specific cyclic siloxane has excellent chemical resistance and high adhesive durability in high-temperature, high-humidity environments, and have completed the present invention.

[0017] That is, the present invention is a cyclic siloxane represented by the following general formula (1). [ka] (In the formula, R 1 are independently an alkyl group having 1 to 4 carbon atoms, and R 2 are independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 3 and R 4 are independently an alkylene group having 1 to 8 carbon atoms, X is independently a glycidyloxy group, a trimethoxysilyl group, or a triethoxysilyl group, p is an integer of 1 to 3, q ​​is an integer of 1 to 3, r is an integer of 1 to 3, and the sum of p, q, and r is 4 to 6. The order of arrangement of the siloxane units is arbitrary.

[0018] The present invention will be described in detail below, but the present invention is not limited thereto.

[0019] [Cyclic siloxane] The present invention is a cyclic siloxane represented by the following general formula (1). [ka] (In the formula, R 1 are independently an alkyl group having 1 to 4 carbon atoms, and R 2 are independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R 3 and R 4 are independently an alkylene group having 1 to 8 carbon atoms, X is independently a glycidyloxy group, a trimethoxysilyl group, or a triethoxysilyl group, p is an integer of 1 to 3, q ​​is an integer of 1 to 3, r is an integer of 1 to 3, and the sum of p, q, and r is 4 to 6. The order of arrangement of the siloxane units is arbitrary.

[0020] R 1 are independently an alkyl group having 1 to 4 carbon atoms, and the alkyl group may be linear, branched, or cyclic. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group, and a methyl group and an ethyl group are preferred.

[0021] R 2 are independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and the alkyl group may be linear, branched, or cyclic. Specific examples include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. 2 is preferably a hydrogen atom, a methyl group, or an ethyl group.

[0022] R 3 and R 4are independently an alkylene group having 1 to 8 carbon atoms, and the alkylene group may be linear, branched, or cyclic. Specific examples include a methylene group, an ethylene group, a trimethylene group, a propylene group, a tetramethylene group, an isobutylene group, a dimethylethylene group, a pentamethylene group, a 2,2-dimethyltrimethylene group, a hexamethylene group, a heptamethylene group, and an octamethylene group. A methylene group, an ethylene group, or a trimethylene group is preferred, and an ethylene group or a trimethylene group is particularly preferred.

[0023] The sum of p, q and r is 4 to 6, preferably 4 or 5, and particularly preferably 4.

[0024] p is an integer of 1 to 3, preferably 2 or 3, and particularly preferably 2.

[0025] q is an integer of 1 to 3, preferably 1 or 2, and particularly preferably 1.

[0026] r is an integer of 1 to 3, preferably 1 or 2, and particularly preferably 1.

[0027] Specific examples of such cyclic siloxanes include those represented by the following structural formulas, but are not limited to these structures. [ka]

[0028] [ka]

[0029] [Adhesion aid] The adhesive aid of the present invention comprises the above-mentioned cyclic siloxane. Such an adhesive aid has excellent chemical resistance and excellent adhesion durability in high-temperature, high-humidity environments.

[0030] [Silicone composition] The silicone composition of the present invention contains the above-described cyclic siloxane. Such a silicone composition has excellent chemical resistance and exhibits stable adhesive properties even when exposed to high-temperature, high-humidity environments for extended periods of time.

[0031] The components contained in the silicone composition of the present invention are not particularly limited, but examples include silicone compositions containing (A) an organopolysiloxane having two or more aliphatic unsaturated hydrocarbon groups bonded to silicon atoms per molecule, (B) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, (C) a platinum group metal catalyst, (D) a reaction inhibitor, (E) the cyclic siloxane of the present invention, and (F) an inorganic filler.

[0032] The amount of the cyclic siloxane (E) of the present invention added to the silicone composition is preferably 0.05 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, per 100 parts by mass of component (A). When the amount of component (E) is within the above range, appropriate adhesiveness can be imparted. Only one component (E) may be added, or two or more components may be used simultaneously.

[0033] [glue] The adhesive of the present invention comprises the silicone composition described above. Such an adhesive has excellent chemical resistance and maintains stable adhesion even when exposed to high-temperature, high-humidity environments for extended periods of time.

[0034] [Method for producing cyclic siloxane] The method for producing the cyclic siloxane of the present invention is not particularly limited. For example, the cyclic siloxane of the present invention can be produced by reacting a cyclic methylhydrogenpolysiloxane represented by the following general formula (2) with a compound represented by the following general formula (3) and a compound represented by the following general formula (4) in the presence of a platinum group metal catalyst. [ka] (In the formula, n is an integer of 4 to 6.) [ka] (In the formula, R 5 is an alkenyl group having 2 to 8 carbon atoms, and R 1 and R 2 is the same as above.) [ka] (In the formula, R 5 and X are the same as above.)

[0035] n is an integer of 4 to 6, preferably 4 or 5, and particularly preferably 4.

[0036] R 5 R is an alkenyl group having 2 to 8 carbon atoms, and the alkenyl group may be linear, branched, or cyclic. Specific examples include a vinyl group, an allyl group, a propenyl group, a butenyl group, and a hexenyl group, with a vinyl group and an allyl group being preferred. 1 , R 2 and X is the same as above.

[0037] The compounds represented by the general formulas (3) and (4) may be used either individually or in combination of two or more. [Example]

[0038] The present invention will be specifically explained below using synthesis examples, examples, and comparative examples, but the present invention is not limited to these. 1 H-NMR spectra were measured in deuterated chloroform using TMS (tetramethylsilane) as a reference substance with an AVANCE-III 400 MHz (manufactured by BRUKER).

[0039] [Synthesis Example 1] Synthesis of Cyclic Siloxane 1 24.05 g (0.1 mol) of 2,4,6,8-tetramethylcyclotetrasiloxane and 55 g of toluene were placed in a 500 mL four-neck flask equipped with a coil condenser and a thermometer, and while stirring at 70°C, 0.02 g of a toluene solution of platinum-divinyltetramethyldisiloxane complex (platinum concentration 0.5 wt%) was added, and 16.42 g (0.1 mol) of eugenol was added dropwise over 30 minutes, followed by a reaction at 70°C for 2 hours. 1 After confirming that the signal derived from the allyl group had disappeared in the H-NMR spectrum, 14.82 g (0.1 mol) of trimethoxyvinylsilane was added dropwise over 30 minutes, and the reaction was carried out at 70° C. for 2 hours. 1 After confirming that the signals derived from vinyl groups had disappeared in the H-NMR spectrum, the mixture was cooled to 25°C, 0.3 g of activated carbon was added, and the mixture was stirred for 5 hours, after which the activated carbon was removed by filtration. Next, the mixture was concentrated under reduced pressure at 80-90°C and 2 mmHg for 2 hours to remove the toluene, yielding cyclic siloxane 1 represented by the following formula (5) (yield: 84%). 1 H NMR(400MHz,CDCl3) δ=0.05(m,12H,SiC H 3), 0.40-0.86(m, 6H, SiC H 2), 1.44(m,2H,SiCH2C H 2), 2.40(m, 2H, C H 2C6H3), 3.38(s, 9H, SiOC H 3), 3.70(s, 3H, OC H 3), 4.55(s, 2H, Si H ), 5.60(s,H,O H ), 6.46-6.60(m,3H,C6 H 3).

[0040] [ka] (In the formula, the order of the siloxane units is not specified.)

[0041] [Synthesis Example 2] Synthesis of Cyclic Siloxane 2 Into a 500 mL four-neck flask equipped with a coil condenser and a thermometer, 24.05 g (0.1 mol) of 2,4,6,8-tetramethylcyclotetrasiloxane and 55 g of toluene were added at 70°C while stirring, and 0.02 g of a toluene solution of platinum-divinyltetramethyldisiloxane complex (platinum concentration 0.5 wt%) was added, and 17.82 g (0.1 mol) of 4-allyl-1,2-dimethoxybenzene was added dropwise over 30 minutes, followed by a reaction at 70°C for 2 hours. 1 After confirming that the signal derived from the allyl group had disappeared in the H-NMR spectrum, 14.82 g (0.1 mol) of trimethoxyvinylsilane was added dropwise over 30 minutes, and the reaction was carried out at 70° C. for 2 hours. 1 After confirming that the vinyl group-derived signals had disappeared in the H-NMR spectrum, the mixture was cooled to 25°C, 0.3 g of activated carbon was added, and the mixture was stirred for 5 hours, after which the activated carbon was removed by filtration. Next, the mixture was concentrated under reduced pressure at 80-90°C and 2 mmHg for 2 hours to remove the toluene, yielding cyclic siloxane 2 represented by the following formula (6) (yield: 87%). 1 H NMR(400MHz,CDCl3) δ=0.03(m,12H,SiC H 3), 0.38-0.90(m, 6H, SiC H 2), 1.48(m,2H,SiCH2C H 2), 2.40(m, 2H, C H 2C6H3), 3.44(s, 9H, SiOC H 3), 3.68(s, 6H, OC H 3), 4.50(s, 2H, Si H ), 6.55-7.10(m,3H,C6 H 3).

[0042] [ka] (In the formula, the order of the siloxane units is not specified.)

[0043] [Examples 1-1, 1-2, Comparative Examples 1-1 and 1-2] Preparation of Silicone Composition The following components (A) to (F) were mixed in the blending ratios (parts by mass) shown in Table 1 to prepare a silicone composition. Component (F) was added to component (A) and mixed using a three-roll mill, then components (C) and (D) were added and mixed in that order, and finally components (B) and (E) were added and mixed, followed by degassing under reduced pressure to obtain a silicone composition.

[0044] [Adhesiveness] The resulting silicone composition was sandwiched between two aluminum plates to give a bonding area of ​​25 mm x 10 mm and a bonding thickness of 2 mm, and heated in an oven at 120°C for 60 minutes to cure the silicone composition, producing test specimens in which the aluminum plates were bonded together with a cured layer of the silicone composition. The shear adhesive strength to aluminum of each test specimen was measured according to the method specified in JIS K 6249:2003. The results are shown in Table 1.

[0045] [Chemical resistance] LLC liquid (a 50:50 mass% solution of Toyota Super Long Life Coolant and ion-exchanged water) was placed in a pressure-resistant container, and each test specimen prepared in the above adhesion test was immersed in it, then sealed and exposed to a 120°C environment for 500 hours and 1000 hours. After the specified time had elapsed, the test specimens were removed from the LLC liquid, washed with water, dried, and then their shear adhesive strength was measured according to the method specified in JIS K 6249:2003. The results are shown in Table 1.

[0046] Component (A) (A-1): Dimethylpolysiloxane capped at both ends with trivinylsilyl groups (kinematic viscosity at 25°C: 100,000 mm 2 / s, vinyl group content 0.0025 mol / 100g) (A-2):Me3SiO 1 / 2 Units, Me2ViSiO 1 / 2 Units and SiO 4 / 2 It is a polysiloxane (MeSiO 1 / 2 Unit: Me2ViSiO 1 / 2 Unit: SiO 4 / 2 Molar ratio of units 7:1:10, weight average molecular weight 4,000, vinyl group content 0.08 mol / 100g) (A-3): Dimethyl polysiloxane capped at both ends with dimethylvinylsilyl groups (kinematic viscosity at 25°C: 100,000 mm 2 / s, vinyl group content 0.0025 mol / 100g)

[0047] Component (B): Methylhydrogenpolysiloxane represented by the following formula: [ka]

[0048] Component (C): Toluene solution of platinum-divinyltetramethyldisiloxane complex (platinum concentration 0.5% by mass)

[0049] Component (D): Ethynylcyclohexanol (reaction inhibitor)

[0050] (E) Component (E-1): Cyclic siloxane 1 obtained in Synthesis Example 1 (E-2): Cyclic siloxane 2 obtained in Synthesis Example 2 (E-3): Cyclic siloxane (comparison component) represented by the following structural formula [ka] (E-4): A cyclic siloxane (comparative component) represented by the following structural formula, described in Synthesis Example 1 of JP-A-2024-044151. [ka]

[0051] (F) Component: Surface-treated with hexamethyldisilazane, BET specific surface area 300m 2 / g fumed silica

[0052] [Table 1]

[0053] As shown in Table 1, the silicone composition containing the cyclic siloxane of the present invention exhibited good adhesion to aluminum plates and maintained its adhesion even after being exposed to an environment of 120°C in LLC liquid for 1,000 hours (Examples 1-1 and 1-2).

[0054] On the other hand, in Comparative Example 1-1, in which a glycidyl ether-type cyclic siloxane, which has conventionally been known as an adhesive aid, was used instead of the cyclic siloxane of the present invention, and in Comparative Example 1-2, in which the cyclic siloxane described in Synthesis Example 1 of JP-A No. 2024-044151 was used, adhesion to aluminum could not be maintained after 500 hours of exposure to an environment of 120°C in LLC liquid.

[0055] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention.

Claims

1. A cyclic siloxane characterized by being represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ are independently alkyl groups having 1 to 4 carbon atoms, and R ２ are independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ３ and R ４ are independently an alkylene group having 1 to 8 carbon atoms, X is independently a glycidyloxy group, a trimethoxysilyl group, or a triethoxysilyl group, p is an integer of 1 to 3, q ​​is an integer of 1 to 3, r is an integer of 1 to 3, and the sum of p, q, and r is 4 to 6. The order of arrangement of the siloxane units is arbitrary.

2. An adhesion promoter comprising the cyclic siloxane of claim 1.

3. A silicone composition comprising the cyclic siloxane of claim 1.

4. An adhesive comprising the silicone composition according to claim 3.

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