JPH0579703B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to room temperature curable silicone rubber compositions which, when cured, exhibit excellent adhesion. More specifically, the present invention provides a room temperature curable polydiorganosiloxane in which the silicon atom at each polymer chain end is terminated with at least two hydrolyzable groups, a nonchelating condensation catalyst, and a metal chelate adhesion promoter. The present invention relates to silicone rubber compositions. BACKGROUND OF THE INVENTION Various metal carboxylate salts, metal chelates,
It is well known in the art prior to the present invention that organic acids and organic bases can be used. Evans, U.S. Pat. No. 3,622,529, discloses a composition that is stable under substantially anhydrous conditions but capable of curing to an elastic solid state in the presence of moisture; Chain-stopped polydiorganosiloxane, formula:

[In the formula, R and R ² are each hydrocarbyl,
An organic group having 18 or less carbon atoms selected from halohydrocarbyl, nitrohydrocarbyl and alkoxyhydrocarbyl, R ¹ is hydrogen or a group selected from hydrocarbyl, halohydrocarbyl and cyanoalkyl, and R ³ is hydrogen or hydrocarbyl, halohydrocarbyl. , nitrohydrocarbyl, alkoxyhydrocarbyl, dialkylamino and

An organic group with 18 or less carbon atoms selected from
R ⁴ is aliphatic hydrocarbyl, aliphatic halohydrocarbyl, aliphatic nitrohydrocarbyl and

[Chemical formula] R ⁵ and R ⁶ are each an aliphatic hydrocarbyl, a is an integer of 2-4, b is an integer of 0-2, and d is 0 or 1.
where the sum of a, b, and d is 4], and optionally a small amount of a carboxylate and/or chelate of a metal in the electrochemical series of metals from lead to manganese. A composition that is stable under substantially anhydrous conditions but capable of curing to an elastic solid state, disclosed in U.S. Pat. No. 3,708,467 to Smith et al.
(OR ¹ ) _4-n [R and R ¹ in the formula are hydrocarbyl,
silanes having about 8 or less carbon atoms selected from the group consisting of halohydrocarbyl and cyano-lower alkyl; and salts, alkoxides, hydroxides or It contains a catalyst system that includes a first catalyst that is an oxide and a second catalyst that is a titanium chelate. The present invention provides improved adhesion when a polydiorganosiloxane in which the silicon atom at the end of each polymer chain is terminated with at least two hydrolyzable groups is used in combination with a nonchelating condensation catalyst and a metal chelate adhesion promoter. This was based on this surprising finding. SUMMARY OF THE INVENTION It is an object of the present invention to provide a room temperature curable silicone rubber composition that exhibits excellent adhesion to a variety of substrates when cured. Another object of the present invention is to provide a method for producing room temperature curable silicone rubber compositions which, when cured, exhibit excellent adhesion to a variety of substrates. According to a first aspect of the invention, (a) a polydiorganosiloxane in which the silicon atom at each polymer chain end is terminated with at least two hydrolyzable groups; (b) an effective amount of a non-chelating condensation catalyst; c) A room temperature curable silicone rubber composition is provided that exhibits excellent adhesion upon curing, comprising an effective amount of a metal chelate adhesion promoter. DETAILED DESCRIPTION Room temperature curable silicone rubber compositions of the present invention that cure to an elastic solid state upon exposure to moisture and exhibit improved adhesion to a variety of substrates include (a) each polymer chain terminus; (b) an effective amount of a nonchelating condensation catalyst; and (c) an effective amount of a metal chelate adhesion promoter. Polydiorganosiloxanes in which the silicon atom at the end of each polymer chain is terminated with at least two hydrolyzable groups are already known in the art. Such polydiorganosiloxane can be represented by the following general formula.

[Chemical formula] where R is a monovalent substituted or unsubstituted C _(1-13) hydrocarbon group, preferably methyl, or a large amount of methyl and a small amount of phenyl, cyanoethyl,
trifluoropropyl, vinyl or a mixture thereof; R ¹ is selected from the group consisting of alkyl, alkyl ether, alkyl ester, alkyl ketone and alkyl cyano group;
C _(1-8) aliphatic organic group or C _(7-13) aralkyl group; R ² is a monovalent substituted or unsubstituted C _(1-13) hydrocarbon group; X is amide, amino , carbamato, enoxy, imidato, isocyanato, oximato, thioisocyanato, and ureido group, and a is 0.
or 1, b is 0-2, and the sum of a+b is 0-3
, where n is an integer up to about 2500. Preferably R ¹ and R ² are methyl. Polydiorganosiloxanes within the above formulas are known in the art, for example in commonly assigned US Pat.
There is one described in No. 4395526. It is particularly preferred that at least two alkoxy groups are bonded to the silicon atom at each polymer chain end of the polydiorganosiloxane (a). These polyalkoxy-terminated polydiorganosiloxanes can be made, for example, according to the teachings of Chung, US Pat. No. 4,515,932. Condensation catalyst (b) used in carrying out the present invention
can be any condensation catalyst known in the art other than metal chelates. The reason for excluding metal chelates is that in the present invention, metal chelates, which are commonly used as condensation catalysts, are used as adhesion promoters. Accordingly, those skilled in the art recognize that although metal chelates primarily function as condensation catalysts, in the present invention metal chelates are used primarily as a means to improve the adhesion of cured silicone compositions to various substrates. It should be done. Therefore, for the purposes of the present invention, the condensation catalyst is
For example, it can be selected from metal salts of monocarboxylic acids and dicarboxylic acids, metal alkoxides, organic bases, organic acids, and the like. Preferably, the condensation catalyst is a metal salt of a carboxylic acid, in particular a tin compound, such as dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dimethoxide, carbomethoxyphenyltin trisuberate, tin octoate,
Particularly preferred are dimethyltin dibutyrate, triethyltin tartrate, tin oleate and tin naphthenate. Dibutyltin diacetate is particularly preferred. Examples of other metal condensation catalysts include zirconium octoate, lead 2-ethyl octoate, iron 2-ethylhexanoate, cobalt 2-ethylhexanoate,
- manganese ethylhexanoate, zinc 2-ethylhexanoate, antimony octoate, bismuth naphthenate, zinc naphthenate and zinc stearate. Examples of non-metallic condensation catalysts include hexylammonium acetate and benzyltrimethylammonium acetate. Other suitable condensation catalysts will be apparent to those skilled in the art;
This can be easily confirmed without excessive experimentation. Generally, an effective amount of condensation catalyst is from about 0.001 to about 2 parts by weight per 100 parts by weight of polydiorganosiloxane (a). Polydiorganosiloxane condensation catalyst
Preferably, amounts ranging from about 0.1 to about 1 part by weight per 100 parts by weight of (a) are used. Metal chelates used as adhesion promoters (c) in the practice of this invention include lead, tin, zirconium, antimony, zinc, chromium, cobalt, nickel,
Chelates may be based on aluminum, gallium, germanium or titanium. However, titanium chelate is more preferred as the metal chelate. Specific examples of titanium chelate compounds useful in practicing the present invention include Weyenberg U.S. Pat. No. 3,334,067, Smith et al. U.S. Pat. Described in No. 4438039. Examples of preferred titanium chelates include:

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embedded image The following compounds are also preferred. Diisostearoyl ethylene titanate, Titanium dimethacrylate oxyacetate, Titanium diacrylate oxyacetate, Titanium di(cumyl phenolate) oxyacetate, Titanium di(dioctyl phosphate) oxyacetate, Di(dioctyl phosphate) ethylene titanate, Titanium di(dioctyl pyro) phosphate) oxyacetate, di(dioctylpyrophosphate) ethylene titanate. The titanates listed below are particularly suitable.

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[Formula] The effective amount of metal chelate adhesion promoter is generally:
A range of about 0.05 to about 2% by weight of polydiorganosiloxane (a) was found. Of course, larger quantities can be used, but no particular advantage is obtained. The amount of metal chelate used is approximately 0.05% by weight
Below , the strength of the adhesive bond between the silicone elastomer and the substrate is not sufficient for most purposes. In a preferred embodiment, the metal chelate is present in an amount from about 0.1 to about 1.5% by weight of polydiorganosiloxane (a). Of course, mixtures of metal chelates are also contemplated by the present invention. The compositions of the invention may also contain conventional additives such as fillers, plasticizers, crosslinkers, hydroxy functional scavengers, and the like. In the practice of the present invention, the room temperature curable composition can be prepared by stirring, e.g., stirring, the components of the curable composition under conditions substantially free of moisture. The temperature can vary from about 0°C to about 180°C depending on the degree of compounding, type and amount of filler, etc. In a preferred method of making the compositions of the present invention, a polydiorganosiloxane having at least two hydrolyzable groups at each polymer chain end is mixed with a reinforcing filler and a plasticizing fluid to form an RTV base formulation. Create. The silane crosslinker, scavenger for hydroxy functionality, condensation catalyst and metal chelate adhesion promoter are then mixed with the RTV base formulation. The following examples are presented by way of illustration, and not as limitations, to enable those skilled in the art to practice the invention. All parts are parts by weight unless otherwise specified. EXAMPLES Example 1 A vinyl dimethoxy terminated polydimethylsiloxane was prepared. That is, in a 1 gallon Ross mixer equipped with a vacuum line and nitrogen purge line, 100 parts by weight of a silanol-terminated polydimethylsiloxane having a viscosity of 22,000 centipoise at 25°C, 1.5 parts by weight of vinyltrimethoxysilane, 0.2 parts by weight of vinyltrimethoxysilane,
Part by weight of dibutylamine and 0.05 part by weight of acetic acid were charged. This mixture was heated at 100 °C under nitrogen atmosphere for 15
Stir for a minute. Further 45 at 100℃ under 5mmHg vacuum
After mixing for a minute, a storage-stable vinyldimethoxy-terminated polydimethylsiloxane having a viscosity of 26900 centipoise at 25°C was obtained. Example 2 One Gallon Baker-Perkins with Vacuum Line and Nitrogen Purge Tube
In the mixer, 100 parts by weight of the vinyldimethoxy-terminated polydimethylsiloxane prepared in Example 1, a fumed silica filler treated with octamethylcyclotetrasiloxane and hexamethyldisilazane were added.
40 parts by weight of 3000 centipoise t-butylsilanol terminated polydimethylsiloxane, and 15 parts by weight of 50 centipoise silanol terminated polydimethylsiloxane. Add this mixture to 20
The RTV base formulation was created by stirring for 60 minutes under mmHg vacuum. Using a Semco catalyst adder and mixer, 100 parts by weight of the above RTV base formulation was combined with 7 parts by weight of vinyltrimethoxysilane crosslinker, 2 parts by weight of hexamethyldisilazane scavenger for hydroxy functional groups, and dipropoxytitanium. 1.0 part by weight of -bis-(ethyl acetoacetate) and 0.1 part by weight of dibutyltin diacetate were added. After mixing,
A series of physical properties of this composition were measured. The results are shown in Table 1. Table 1 Experimental results of Example 2 Characteristics Results of Example 2 Specific gravity 1.085 Coating speed (g/min) 240 Stick-free time (min) 30 Flow (inch) 0.05 Durometer hardness (Shore A) ^* 33 Tensile strength (psi) ^* 519 Elongation (%) ^* 491 Peel adhesion (ppi) ^** Aluminum 2024 80 Cold rolled steel plate 55 Glass 83 Accelerated aging at 100℃ for 48 hours ^** Durometer hardness (Shore A) 35 Tensile strength (psi) 409 Elongation (%) 461 * Cured for 7 days at RH50%, 25°C** Cured for 14 days at RH50%, 25°C Example 3 Example 1 was repeated using 1.5 parts by weight of methyltrimethoxysilane, and cured at 25°C. A methyldimethoxy-terminated polydimethylsiloxane was obtained having a viscosity of 26,500 centipoise. Example 4 An RTV base formulation was made as in Example 2 using the methyldimethoxy-terminated polydimethylsiloxane of Example 3, replacing the vinyltrimethoxysilane crosslinker with 1 part by weight of methyltrimethoxysilane crosslinker. The physical properties of this composition were also measured. The results are shown in Table 2. Table 2 Experimental results of Example 4 Characteristics Results of Example 4 Specific gravity 1.086 Coating speed (g/min) 224 Stick-free time (min) 30 Flow (inch) 0.05 Durometer hardness (Shore A) ^* 35 Tensile strength (psi) ^* 498 Elongation (%) ^* 550 Peel adhesion (ppi) ^** Aluminum 2024 74 Cold rolled steel plate 68 Glass 82 Accelerated aging at 100°C for 48 hours ^** Durometer hardness (Shore A) 31 Tensile strength (psi) 382 Elongation (%) 491 * Cured for 7 days at RH50%, 25°C** Cured for 14 days at RH50%, 25°C Example 5 In this example, Example 4 was prepared without adding titanium chelate.
repeated. The results are shown in Table 3. Table 3 Experimental results of Example 5 Characteristics Results of Example 5 Specific gravity 1.083 Coating speed (g/min) 201 Tack-free time (min) 30 Flow (inch) 0.05 Durometer hardness (Shore A) ^* 31 Tensile strength (psi) ^* 435 Elongation (%) ^* 502 Peel adhesion (ppi) ^** Aluminum 2024 0 Cold rolled steel sheet 0 Glass 0 Accelerated aging at 100°C for 48 hours ^** Durometer hardness (Shore A) 30 Tensile strength (psi) 401 Elongation (%) 398 * Cured for 7 days at 50% RH and 25°C ** Cured for 14 days at 50% RH and 25°C Example 6 Example 4 was repeated again, but this time in place of the titanium chelate, 1.0 part by weight was used. Aminoethylaminopropyltrimethoxysilane was used as an adhesion promoter. The results are shown in Table 4. Table 4 Experimental results of Example 6 Characteristics Results of Example 6 Specific gravity 1.080 Coating speed (g/min) 281 Tack-free time (min) 20 Flow (inch) 0.05 Durometer hardness (Shore A) ^* 41 Tensile strength (psi) ^* 472 Elongation (%) ^* 410 Peel adhesion (ppi) ^** Aluminum 2024 12 Cold rolled steel plate 4 Glass 14 Accelerated aging at 100°C for 48 hours ^** Durometer hardness (Shor A) 38 Tensile strength (psi) 402 Elongation (%) 451 * Cured for 7 days at 50% RH and 25°C ** Cured for 14 days at 50% RH and 25°C Example 7 Example 4 was repeated, but this time 1.0 parts by weight of 1,
3-Dioxypropanethane-bis(acetylacetonate) was used as an adhesion promoter. The test results are shown in Table 5. Table 5 Experimental results of Example 7 Characteristics Results of Example 7 Specific gravity 1.089 Coating speed (g/min) 201 Tack-free time (min) 30 Flow (inch) 0.05 Durometer hardness (Shore A) ^* 42 Tensile strength (psi) ^* 520 Elongation (%) ^* 641 Peel adhesion (ppi) ^** Aluminum 2024 71 Cold rolled steel 58 Glass 86 Accelerated aging at 100°C for 48 hours ^** Durometer hardness (Shore A) 34 Tensile strength (psi) 441 Elongation (%) 519 * Cured for 7 days at RH50%, 25℃** Cured for 14 days at RH50%, 25℃

Claims (1)

[Claims] 1. (a) a polydiorganosiloxane in which the silicon atom at the end of each polymer chain is terminated with at least two hydrolyzable groups; (b) an effective amount of a metal salt of a nonchelating monocarboxylic acid; A curable composition comprising a condensation catalyst of a metal salt of a dicarboxylic acid, a metal alkoxide, or a mixture thereof; (c) an effective amount of a metal chelate adhesion promoter. 2. The polydiorganosiloxane has the general formula:
C _(1-13) hydrocarbon group, R ¹ is selected from the group consisting of alkyl, alkyl ether, alkyl ester, alkyl ketone and alkyl cyano group
C _(1-8) aliphatic organic group or C _(7-13) aralkyl group, R ² is a monovalent substituted or unsubstituted C _(1-13) hydrocarbon group, and X is amido, amino, carbamate. , enoxy, imidato, isocyanato, oximato, thioisocyanato, and ureido group, a is 0 or 1, and b
2. The composition of claim 1, wherein the sum of a+b is equal to 0-3, and n is an integer up to about 2500. 3 R is methyl or a mixture of a large amount of methyl and a small amount of phenyl, cyanoethyl, trifluoropropyl, vinyl or a mixture thereof; R ¹ is methyl and R ² is methyl; Composition according to item 2. 4. The composition of claim 3, wherein the polydiorganosiloxane has at least two methoxy groups bonded to silicon atoms at the ends of each polymer chain. 5. The composition according to claim 1 or 2, wherein the metal is tin. 6. A composition according to claim 1 or claim 2, wherein the condensation catalyst is present in an amount of 0.001-2 parts by weight per 100 parts by weight of polydiorganosiloxane. 7. The composition according to claim 1 or 2, wherein the metal chelate is a metal selected from the group consisting of lead, tin, zirconium, antimony, zinc, chromium, cobalt, nickel, aluminum, gallium, germanium and titanium. thing. 8. The composition according to claim 7, wherein the metal chelate is a titanium chelate. 9 Titanium chelate is polydiorganosiloxane
9. A composition according to claim 8, present in an amount of 0.05-2 parts by weight per 100 parts by weight. 10. A cured composition according to claim 1. 11. A cured composition according to claim 2. 12 (a) a polydiorganosiloxane in which the silicon atom at the end of each polymer chain is terminated with at least two hydrolyzable groups; (b) an effective amount of a nonchelating metal salt of a monocarboxylic acid or a metal salt of a dicarboxylic acid; A method for preparing a curable composition comprising mixing a condensation catalyst of a metal alkoxide, or a mixture thereof, and (c) an effective amount of a metal chelate contact promoter under substantially anhydrous conditions. 13 Polydiorganosiloxane has the general formula: [Chemical formula] where R is a monovalent substituted or unsubstituted
C _(1-13) hydrocarbon group, R ¹ is selected from the group consisting of alkyl, alkyl ether, alkyl ester, alkyl ketone and alkyl cyano group
C _(1-8) aliphatic organic group or C _(7-13) aralkyl group, R ² is a monovalent substituted or unsubstituted C _(1-13) hydrocarbon group, and X is amido, amino, carbamate. , enoxy, imidato, isocyanato, oximato, thioisocyanato, and ureido group, a is 0 or 1, and b
13. The method of claim 12, wherein: is 0-2, the sum of a+b is equal to 0-3, and n is an integer up to about 2500. 14. The method of claim 13, wherein the polydiorganosiloxane has at least two alkoxy groups bonded to silicon atoms at the ends of each polymer chain. 15. The method according to claim 13, wherein the metal is tin. 16 Condensation catalyst is polydiorganosiloxane 100
15. A method according to claim 13 or claim 14, wherein the compound is present in an amount of 0.001-2 parts by weight. 17 Metal chelates include lead, tin, zirconium, antimony, zinc, chromium, cobalt, nickel,
13. A method according to claim 12, based on a metal selected from the group consisting of aluminum, gallium, germanium and titanium. 18. The method according to claim 12, 13, 14 or 15, wherein the metal chelate is a titanium chelate. 19. The method of claim 16, wherein the titanium chelate is present in an amount of 0.05-2 parts by weight per 100 parts by weight of polydiorganosiloxane.