GB2067212A - Room Temperature Curing Silicone Resin Compositions - Google Patents

Abstract

A room temperature-curing silicone resin composition comprising: (a) 100 parts by weight of an organopolysiloxane resin having the average unit formula: <IMAGE> wherein R' is a substituted or unsubstituted monovalent hydrocarbon radical, n is 0.80 to 1.80 and m is such that the hydroxyl radicals are at least 0.01 weight percent of the weight of the resin; (b) 0.5-50 parts by weight of an alpha, omega- dihydroxydiorganopolysiloxane having the general formula: HO(R''2SiO)qH wherein R'' is a substituted or unsubstituted monovalent hydrocarbon radical, q is at least 2; and (c) (i) a silane R'''aSiX4-a, wherein a is 0, 1 or 2, and X is a hydrolysable group; or (ii) the partial hydrolysis and condensation product of the silane (i), the amount of (c) being such that the composition may be stored under anhydrous conditions but is curable at room temperature in the presence of water, to produce water-repellent, mould-releasing, readily peelable and soil-resistant films.

Description

SPECIFICATION Room Temperature Curing Silicone Resin-Composition This invention deals with a silicone resin-containing composition which is curable at room temperature in the presence of moisture.

More specifically, this invention describes compositions which may be stored under essentiaily dry conditions and then cured at room temperature in the presence of moisture to produce films which are water repellent, give good mould release and peelability and have soil, heat, weather and chemical resistance when cured.

Usually, organopolysiloxane resins containing silicon-bound hydroxyls (which is the means by which they are cured) are cured by baking them at elevated temperatures, such as 1500--2000C and above.

Some applications, however, cannot tolerate the elevated temperatures and it has therefore been proposed that resins be developed which will cure at room temperature.

U.S. Patent No. 3,350,349, for example, describes a room-temperature curing silicone resin composition composed of aminoalkylalkoxysilanes and organopolysiloxane resins which contain silicon-bonded hydroxyl groups. However, when the aminoalkylalkoxysilane is combined with a solution of an organopolysiloxane resin which contains silicon-bonded hydroxyl groups, gelling occurs in a short time. The storaye stability is therefore quite poor. Due to this gelling, mixing must be carried out immediately before use which reduces the working time of the resin. Furthermore, the silicone resin film obtained by this method does not exhibit good water repellency or mould release.

In order to improve the water repellency and mould release, a methylpolysiloxane which contains silicon-bonded hydroxyl groups was added as is shown in Japanese Publication No. Sho 43 [1 968]- 1 5696. This resin composition must be cured, however, at elevated temperatures. For this reason, it cannot be employed on a part which cannot be heated. This restriction on practical use is disadvantageous.

On the other hand, methylphenylpolysiloxane resins which contain a methylpolysiloxane with a small number of hydroxyl groups do not exhibit good film-forming properties and cannot produce uniform films.

Clark, in U.S. Patent No. 2,934,519 shows hydroxylated resins which have been reacted with acyloxysilanes to render the resins curable at room temperature in the presence of moisture. It should be noted that Clark requires two resins whereas the instant invention contains only one resinous component.

Hartlein et al., in U.S. Patent No. 3,629,228, shows alkoxy-functional block copolymers which are curable at room temperature. These block copolymers consist of pre-reacted blocks (not mixtures) of siloxane resins and siloxane linear fluids. The resins and linear fluids are first coupled together by using trifunctional silanes and, thereafter, the block copolymer is rendered alkoxyfunctional by reacting the block copolymer with additional trifunctional, hydrolysable silanes. The Hartlein patent disciosure therefore clearly differs from the present invention in requiring a laborious, time-consuming preparation of the block copolymers, a procedure which is not required in accordance with the present invention. McKellar et al., in U.S.Patent No. 3,576,905, disclose room temperature-vulcanizable siloxanes which are very similar to those of Hartlein just referred to. The primary difference is the use by McKellar of ketoxime-functional silanes which allow the inclusion of various different blocks in the copolymer and therefore allow for different properties in the final product. Again, McKellar (loc. cit) differs from the instant invention in the use of prereacted block copolymers.

Thus, various methods have been examined to eliminate the above-mentioned defects.

We have now invented a silicone resin composition which may be stored under dry conditions for a long period of time, and may be cured at room temperature under humid conditions to produce a water-repelling, mould-releasing, easily peelable and soil-resistant film.

This invention therefore consists in a composition of matter which is a room temperature-curing silicone resin composition composed of: (a) 100 parts by weight of an organopolysiloxane resin having the average unit formula: RlnSiO4~n~m(0H)m 2 wherein R' is a substituted or unsubstituted monovalent hydrocarbon radical, n has a value of 0.80 to 1.80 and m has a value such that the amount of hydroxyl radicals bonded to silicon atoms in the organopolysiioxane resin is equal to or greater than 0.01 weight percent based on the weight of the organopolysiloxane resin; (b) 0.5-50 parts by weight of an alpha, omega-dihydroxydiorganopolysiloxane having the general formula: HO(R"2SiO)H wherein R" is a substituted or unsubstituted monovalent hydrocarbon radical, and q is an integer equal to or greater than 2; and (c) a silicone compound selected from: (i) a silane having the general formula R"'aSiX4~a, wherein a is 0, 1 or 2 and X is a group which is hydrolysable in the presence of water and ambient temperature, and (ii) the partial hydrolysis and condensation product of the silane in (i), the amount of (c) in the total composition being such that, in admixture with the components (a) and (b), the entire composition may be stored under anhydrous conditions but is curable at room temperature in the presence of water.

Component (a), the organopolysiloxane resin which contains silicon-bonded hydroxyl groups, is the principal component of the resin composition of this invention. It can be synthesized by methods known in the art and it is commercially available.

Generally, it can be produced by the hydrolysis in an organic solvent of a mixture of chlorosilanes which contain 0.8-1.8 organic groups per silicon atom. The hydrolysed organopolysiloxane resin can be used as it is produce or it may be further heat treated to produce an organopolysiloxane whose silanol groups are partly condensed.

For the purposes of this invention R', the monovalent hydrocarbon group bonded to silicon, may be an alkyl group such as methyl, ethyl, propyl, t-butyl, 2-ethylhexyl, dodecyl or octadodecyl; an alkenyl group such as vinyl, allyl or hexadienyl; an aryl group such as phenyl or naphthyl; or a substituted alkyl group such as chloromethyl, 3,3,3-trifluoropropyI, 3,3,4,4,5,5,5-heptafluoropentyl or difluoromonochloropropyl. Alkyl groups, alkenyl groups and alkyl halides are preferred. The methyl group is most preferred. The organopolysiloxane resin is preferably dissolved in a solvent.Such solvents include aromatic organic solvents such as benzene, toluene, xylene, trimethylbenzene, tetramethylbenzene and diethylbenzene; aliphatic organic solvents such as cyclohexane, methylcyclohexane and dimethylcyclohexane; chlorinated organic solvents such as trichloroethylene, 1 1,1-trichloroethane, carbon tetrachloride and chloroform and aliphatic saturated hydrocarbon solvents such as hexane and industrial grade gasoline.

Component (b), the diorganopolysiloxane in which both ends contain silicon-bonded hydroxyl groups, increases the mould releasability, the ease of peeling and the water repellency of the film. It can also be produced by known methods and is commercially available.

Examples of R" in accordance with this invention are alkyl groups such as methyl, ethyl, propyl, tbutyl, 2-ethylhexyl, dodecyl and octadecyl; alkenyl groups such as vinyl, allyl, decenyl and hexadienyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; cycloalkenyl-groups such as cyclopentencyl and cyciohexenyl; aryl groups such as phenyl and naphthyl; aralkyl groups such as benzyl, phenylethyl and xylyl; alkaryl groups such as tolyl and dimethylphenyl and substituted hydrocarbon groups such as chloromethyl, 3,3,3-trifluoropropyl, 3,3,4,4,5,5,5-heptafluoropentyl, perchlorophenyl, 3,4dibromocyclohexyl, alpha,alpha,alpha-trifluorotolyl and 2,4-dibromobenzyl. Alkyl groups, alkenyl groups and alkyl halides are preferred.The methyl group is the most preferred The integer q for the purposes of this invention is greater than, or equal to, 2, and is preferably less than, or equal to, 1,000.

When the quantity of alpha,omega-dihydroxydiorganopolysiloxane is less than 0.5 part by weight in the composition, the mould releasability and water-repellency of the cured film are unsatisfactory.

When the quantity exceeds 50 parts by weight, the durability of the cured film is insufficient. For this reason, the quantity of (b) should be 0.5-50 parts by weight and preferably 1-15 parts by weight relative to 100 parts by weight of component (a).

Component (c), the silicone compound, is used for curing the composition of this invention at room temperature. R"' in the general formula R"' aSlX4a can be monovalent hydrocarbon group.

Examples of alkyl groups are methyl, ethyl, propyl, t-butyl, 2-ethylhexyl, dodecyl and octadecyl; the alkenyl groups can be vinyl, allyl and hexadienyl; the cycloalkyl groups can be cyclopentyl and cyclohexyl; the cycloalkenyl groups can be cyclopentenyl and cyclohexenyl; the aryl groups can be phenyl and naphthyl; the aralkyl groups can be benzyl, phenylethyl and xylyl; the alkaryl groups can be'- tolyl and dimethylphenyl; the halogenated hydrocarbon groups can be chloromethyl, 3,3,3trifluoropropyl, perchlorophenyl, 3,4-dibromocyclohexyl, 2,2,2-trifluorotolyl and 2,4-dibromobenzyl and the cyanoalkyl groups can be beta-cyanoethyl, gamma-cyanopropyl, omega-cyanobutyl, betacyanopropyl, gamma-cyanobutyl and omega-cyanooctadecyl. R"' is preferably alkyl, alkenyl or the haloalkyl group.The methyl or the vinyl group is the most preferred. X is a group which is hydrolysable in the presence of moisture. Examples of this group are diorganoketoxime, acyloxy, monoorganoamino, diorganoamino, N-organoacylamino, N,N-diorganoaminoxy, alkoxy and alpha,beta-substituted vinyloxy.

Diorganoketoxime, acyloxy, alpha,beta-substituted vinyloxy, monoorganoamino and diorganoamino are preferred from the standpoint of the ease of production of a composition which is storable under dry conditions for long periods of time. The value of a is 0, 1 or 2, and is preferably 1.

Examples of component (c) for the purposes of this invention are methylvinyldi(dimethyl ketoxime)silane, methyltri(dimethyl ketoxime)silane, methyltri(methyl ethyl ketoxime)silane, vinyltri(methyl ethyl ketoxime) silane, methyletoxydi(methyl ethyl ketoxime)silane, dimethyltetra(methyl ethyl ketoxime),disiloxane, methyltriacetoxysilane, vinyltriacetoxysilane, ethyltriacetoxysilane, phenyltriacetoxysiiane, methylethoxydiacetoxysilane, tetraacetoxysilane, methyltri(N-butylamino)silane, vinyltri(N-cyclohexylamino)silane, propyltri(N,N-dipropylamino)silane, dimethyldi(N-methylacetamide)silane, methyltri(N-methylacetamide)silane, dimethyldi(N,N- diethylhydroxylamino)silane, methyltri(N,N-diethylhydroxamino)silane, methyltriethoxysilane, vi nyltriethoxysila ne, tetra(isopropenyloxy)silane and methyltri(isopropenyloxy)silane.

The quantity of this component in the composition depends on the quantity of silicon-bonded hydroxyl groups in component (a), the quantity of silicon-bonded hydroxyl groups in component (b) and the quantity of hydrolysable groups in component (c). The amount of component (c) has to be balanced against the amount of hydroxyl in the composition to give a composition which is storable under dry conditions for long periods of time, and is thereafter curable at room temperature in the presence of moisture.

The composition of this invention can be produced by blending the organopolysiloxane resin (a), the dihydroxydiorganopolysiloxane (b) and the silicone compound (c) under anhydrous conditions. The order of blending is not critical. Component (a) may be combined with a portion of component (c) and the resulting mixture may then be combined with a mixture of component (b) and the rest of component (c). Alternatively, a mixture of component (a) and component (b) may be combined with component (c). Alternatively, a mixture of component (a), part of component (b) and component (c) can be combined with the rest of component (b). Alternatively again, a mixture of component (a) or (b) and component (c) is combined with component (b) or (a).When component (a) is a solid, it should preferably be dissolved in an organic solvent, and the resulting solution is then combined with the other components.

A silane-coupling agent may be added to the composition of this invention as required in order to increase the adhesive capacity relative to various base materials.

Examples of these silane-coupling agents are H2NCH2CH2Si(OC2H5)3, NH2CH2CH2NH(CH2)3Si(OCH3)3,

and mixtures of these compounds. The quantity of the silane-coupling agent should preferably be 0.01-10 wt% of the composition of this invention.

Although this composition can be cured at room temperature, a condensation-accelerating catalyst can be added in order to accelerate curing. An appropriate catalyst is a condensation catalyst for the usual silanol groups.

Examples of such catalyst include tin carboxylates such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dioctoate, stannous octoate, stannous naphthenate, stannous oleate, stannous isobutyrate, stannous linolate, stannous stearate, stannous benzoate, stannous naphthanonate, stannous laurate, stannous o-thymate, stannous beta-benzoylpropionate, stannous crotonate, stannous tropate, stannous p-bromobenzoate, stannous cinnamate, stannous phenylacetate; the iron, manganese and cobalt salts of these carboxylic acids and complexes such as tetraalkyltitanate and dialkyltitanate and organosiloxytitanate. This catalyst should be appropriately selected by taking into consideration the type of hydrolysable groups in component (c).

The composition of this invention can be used over an extremely broad range of applications.

Water repellency, mould releasability and ease of peeling are characteristics of the composition produced by the method of this invention. The heat resistance, weather resistance and solvent resistance of the composition of this invention allow the range of applications to be increased significantly.

The workability and cost of processing can be significantly improved because the composition of this invention rapidly cures at room temperature to form a hard film coat. For this reason, the composition can be applied to large-scale structures which traditionally have been difficult to coat with a thermosetting resin. Since the resin rapidly cures at room temperature, dust rarely adheres to the coat and a glossy film coat can therefore be obtained.

The composition of this invention can be used in any application in which the above-mentioned strong points are effectively utilized. The applications are not limited to the following examples.

Applications include those as a coating agent which suppresses the adhesion of water, oil, snow, ice, paint, soil, food, adhesive agents, pasting agents, paste paper, mud or incrustation; for the removal of snow, ice, food, rubber, plastics, paint, adhesive agents, pasting agents or dust; as a coating agent for peeling or mould release; for protection from grafiti; as a coating agent for material surfaces which are to protected from light, air, water, corrosive gases and corrosive substances such as acids, alkalis or solvents; to improve surface electrical properties and especially the electrical insulation properties of materials or to reduce the viscous resistance of a fluid at a fluid interface.

Materials which can be coated with the composition of this invention include metals such as iron, aluminium, stainless steel, nickel, chromium, tin, copper and zinc; ailoys of these metals; plastics such as polyesters, epoxy resins, polyamides, polyurethane ABS resins; polycarbonates, polyimides, phenolic resins and acrylic resins; ceramics such as china and ceramic wares, glass, wood, rubber, mortar concrete, concrete, brick, tile and slate.

More specifically, the applications of the composition produced by the method of this invention include uses for cars, vehicles, ships, various metal moulds, kitchen utensils, dishes, electric poles, guard rails, road signs, the electrical discharge protection of various relay terminals, insulators, spark plugs, print base plates, electric contacts and electrical wires, the interior or liquid supply pipes, building structures such as bridges and buildings, tile joints, the booth, apparatus and tools for painting, engines, metal wheel parts, the windows in aeroplanes, water-supply or sewage pipes and reservoir interiors.

This invention is now illustrated by, but not limited to, the following examples.

"part" in the examples means "part by weight" unless otherwise specified.

The properties described in the examples and comparison examples were measured by the following methods.

Peeling Test: Nitto polyester tape (31 B) (width: 4 cm) was pasted onto the coated surface and allowed to stand under a pressure of 20 g/cm2 for 30 minutes. The peeling resistance (9/4 cm width) was measured in a 1800 peel test at a peeling rate of 30 cm/min.

Pencil Hardness: The pencil lead was piaced on the cured film at an angle of 450 and pushed forward with a pressure of about 500 g. When the cured film was not peeled by the pencil lead, the pencil hardness of the cured film was specified by the hardness of that pencil lead.

Flexibility: The test panel was bent 1 800 around a cylindrical bar (diameter: 8 mm). Crazing and cracks in the bent segment were inspected.

Adhesion: 1 mm squares (100) were scratched in a 1 cm square. Scotch tape was pressed on them and then peeled off with the maximum possible force. The number of squares remaining was counted.

Example 1 A 50 wt% toluene solution of methylpolysiloxane resin (methylsiloxane units: 80 mol%, dimethylsiloxane units: 20 mol%, silicon-bonded hydroxyl groups: 0.9 wt%) was blended with an alpha,omega-dihydroxymethyipolysiloxane (.001 Has), methyltri(methylethyl ketoxime) silane and dibutyltin diacetate. Six (6) silicon resin compositions given in Table i were thus prepared. Each composition was coated onto a 70x 1 50x0.5 mm mild steel plate whose surface had been treated with a primer (whose-principal component was alkoxysilane), and then cured at room temperature for 24 hours. After curing, the peeling resistance was measured. The pencil hardness, flexibility and adhesion properties were measured as properties of the cured film. The results are given in Table II (below).They show that the peeling resistance of the cured film of the composition produced by the method of this invention was extremely low. On the other hand, the peeling resistance of sample No. 1, a comparison example, was extremely high. The peeling resistance of sample No. 6 was low; however, the film was relatively soft. The cured films of samples Nos. 2,3,4 and 5 were treated with 2-3 drops of 40% H2S04, 40% NaOH or 36% hydrochloric acid using a fountain-pen filler and then allower to stand for 2 hours. Two hours after this treatment, the reagents were wiped off with gauze and the films appearances were inspected. The results showed that the films did not undergo change. Test panels whose surfaces had been coated with samples Nos. 2, 3 and 4 and cured at room temperature were aged at 2000C for 24 hours. No changes were observed in the films, Even 6 months later, the polysiloxane compositions were stable and did not gel.

Example 2 A mixture of methylpolysiloxane resin (100 parts, identical to that used in Example 1) and alpha,omega-dihydroxydimethylpolysiloxane (5.0 parts, identical to that used in Example 1) was combined with vinyltri(methylethyl ketoxime)silane (30 parts). The resulting mixture was mixed homogeneously. It was coated onto a 70x 150x0.5 mm aluminium plate, cured at room temperature for 24 hours and then exposed to a Sunshine Weather-O-meter for 1,000 hours. The film was glossy and exhibited excellent ease of peeling, water repellency and mould releasability.

Example 3 A 50% toluene solution (100 parts) of a methylpolysiloxane resin (methylsiloxane unit: 90 mol%), dimethylsiloxane unit: 10 mol%, silicon-bonded hydroxyl group: 2.0 wt%) was blended with methyltri(dimethylketoxime) silane (20 parts), alpha,omega-dihydroxydimethylpolysiloxane (1.0 part, viscosity: 2 Pa.s, silicon-bonded hydroxyl group: 0.2 wt%), dibutyltin diacetate (0.5 parts) and gammaglycidoxypropyltrimethoxysilane (1 part). The resulting mixture was coated onto a mild steel plate and then cured at room temperature for 24 hours. The peeling resistance was measured by the method of Example 1 and was found to exhibit an excellent mould releasability (1 5 g/4 cm width).

The pencil hardness was B, the flexibility was normal and the adhesion was 100%. The abovementioned silicone resin composition was coated onto a concrete electric pole (80 g/m2) using a brush.

The resulting coat was cured for 24 hours. The cured coat was pasted with a sheet of the usual poster paper using starch paste. The poster paper naturally peeled off within several hours. Poster paper similar to that mentioned above was repeatedly pasted onto the above-mentioned coat for 1 year; however, the excellent ease of peeling did not significantly decline.

Example 4 A resin composition was produced by the same method as was employed for producing sample No. 3 of Example 1 with the exception that methyltriacetoxysilane (25 parts), methyltri(Ncyclohexylamino)silane (25 parts) of methyltri(isopropenyloxy)silane (25 parts) was used instead of methyltri(methyl ethyl ketoxime)silane. The resulting composition exhibited the same curing properties and cured film properties as sample No. 3 of Example 1.

Table I Silicone Resin Compositions Sample No.

Component 1 2 3 4 Methylpolysiioxane resin 100 100 100 100 Methyltri(methyl ethyl ketoxime) 25 25 25 25 silane alpha, omega-dlhydroxydimethyl- 0 1.0 3.0 5.0 polysiloxane Dibutyltin diacetate 1.0 1.0 1.0 1.0 Total 127 128 130 132 Sample No.

Component 5 6 Methylpolysiloxane resin 100 100 Methyltri(methyl ethyl ketoxime)silane 25 25 alpha,omega-dihydroxydimethylpolysiloxane 10.0 3.0 Dibutyltin diacetate 1.0 1.0 Total 137 157

Claims (8)

Claims

1. A composition of matter which is a room temperature curing silicone resin composition composed of (a) 100 parts by weight of an organopolysiloxane resin having the average unit formula: RtnSiO4~n m(0H)m 2 wherein R' is a substituted or unsubsituted monovalent hydrocarbon radical, n has a value of 0.80 to 1.80 and m has a value such that the amount of hydroxyl radicals bonded to silicon atoms in the organopolysiloxane resin is equal to, or greater then, 0.01 weight percent based on the weight of the organopolysiloxane resin; (b) 0.5-50 parts by weight of an alpha,omega-dihydroxydiorganopolysiloxane having the general formula: HO(R"2SiO)qH wherein R" is a substituted or unsubstituted monovalent hydrocarbon radical, q is an integer equal to, or greater than 2; and (c) a silicone compound selected from: (i) a silane having the general formula RtaSiX4~a, wherein a is 0, 1 or 2, and X is a group which is hydrolysable in the presence of water and ambient temperature; or (ii) a partial hydrolysis and condensation product of the silane in (i), the amount of the component (c) in the total composition being such that, in admixture with components (a) and (b), the entire composition may be stored under anhydrous conditions but is curable at room temperature in the presence of water.

2. A composition as claimed in claim 1, wherein R', R" and R"' are each selected from alkyl, alkenyl and haloalkyl radicals.

3. A composition as claimed in claim 1 , wherein R' in the component (a) and R" in the component (b) are methyl groups, and R"' in the component (c) is selected from methyl and vinyl groups.

4. A composition as claimed in claim 3 wherein the component (c) is methyltri (methylethylketoxime)silane.

5. A composition as claimed in claim 4, wherein the methyltri-(methylethylketoxime)silane is present in a proportion of 25 parts by weight for every 100 parts of the component (a).

6. A composition as claimed in claim 1, wherein the component (b) is present in a proportion of 1-1 5 parts by weight based on 100 parts of the component (a).

7. A composition as claimed in claim 1 which also contains a catalyst for curing.

8. A composition as claimed in claim 1 substantially as herein described with reference to any of the specific examples.