HK1050025B - One-part organopolysiloxane rubber composition for use as a corrosion protection coating - Google Patents

Description

One-component organopolysiloxane rubber composition for use as an anti-corrosion coating

Technical Field

The present invention relates to one-component room temperature vulcanizable organopolysiloxane rubber compositions which are free of Volatile Organic Compounds (VOC) and can be crosslinked in the presence of moisture to form coatings for corrosion protection, water protection, soil protection or aging protection of surfaces, or as secondary seal coatings for liquid spills, or high voltage insulator coatings.

Background

In many different applications, it is important to protect surfaces from environmental influences. For example, metals and other surfaces such as concrete that are exposed to moisture such as rain or fog and polluted atmospheres such as found in industrial sites are subject to extensive corrosive effects unless protected in some way from the corrosive atmosphere. Other potentially corrosive environments include coastal areas where salt spray occurs and areas where agricultural chemicals are widely used. In addition, metal and concrete surfaces that come into direct contact with water, such as marine structures and containers, also have the potential to suffer from various types of corrosion. Currently, these surfaces are most often protected by painting with alkyd-type paints. These paints form a relatively rigid coating on the surface, they become brittle and, when subjected to stress, flake or chip, exposing the underlying surface to corrosive elements. In addition, these paints are generally susceptible to UV damage, further reducing their useful lifetime.

Two-component organopolysiloxane rubber compositions have been developed for use as corrosion-resistant coatings for metals. For example, Lampe in U.S. patent No.4,341,842 describes a room temperature vulcanizable two-component composition for coating the underside of a vehicle to protect the metal from rusting or corrosion by road salt or other similar compounds. However, such two-component compositions have a great disadvantage in that they require the use of complicated two-component mixing nozzle arrangements or, when used with conventional spray equipment, require premixing and immediate use on site. If ordinary spray equipment is used, the amount of premix material must be precise to avoid waste because the composition has a limited pot life.

One-component compositions for surface coating have also been described. These compositions generally utilize volatile organic solvents such as naphtha, toluene, petroleum ether and chlorinated hydrocarbons as diluents to improve work efficiency and facilitate application of the coating composition. If no solvent is used, the coating composition is difficult to apply due to the high viscosity. The use of solvents creates environmental pollution and potential threats to worker health as they evaporate.

Yaginurua et al, in US patent No.5,445,873, describe solventless coatings that cure by condensation reaction at room temperature. The coating is designed for packaging circuit boards and does not require high physical strength. The composition utilizes a low molecular weight organopolysiloxane having a viscosity in the range of 20 to 500 centipoise.

Another solventless coating consisting of a polysiloxane resin and a polydiorganosiloxane fluid has been described in US patent 4,780,338. The coatings require high temperatures for curing, which requires heating the substrate or oven drying after application of the coating.

US patent 4,929,703 also describes solventless coatings consisting of a) a polysiloxane resin reaction product prepared by hydrolysis followed by neutralization of an equilibrium mixture of silane and diorganopolysiloxane, B) silane, and C) diorganopolysiloxane fluid. As a result of the siloxane condensation reaction to form the matrix, the coating cures upon exposure to moisture.

Many other applications in which silicone coatings are used include, inter alia, water-repellent, stain-resistant, and high voltage insulating coatings. These applications generally use one-or two-component compositions as described above, which suffer from the same problems. Thus, there remains a need for one-part room temperature vulcanizable silicone coating compositions that are easily applied to a surface as a protective coating and that are free of Volatile Organic Compounds (VOC).

Disclosure of Invention

The present invention provides VOC free one-part room temperature vulcanizable coating for simple and convenient application by common methods such as dip coating, flow coating or spray coating. The coatings avoid environmental impact and provide high physical strength and adhesion obtained with suitable blends of reinforcing and extending fillers.

In one aspect, the present invention provides a one-part room temperature vulcanizable organopolysiloxane rubber composition for use as a protective coating. The composition comprises a product obtained by mixing:

a) from about 20 to about 60 weight percent of one or more polydiorganosiloxane fluids of the formula:

R″O[(R)₂SiO]_nR′

wherein R is a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or phenyl, R ' is H, a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or phenyl, R ' is H, or a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or phenyl, and n has an average value such that the viscosity at 25 ℃ is from about 1 to about 100,000 centipoise, wherein R ' of at least one of the polyorganosiloxane fluids is H, and n has an average value such that the viscosity at 25 ℃ is in the range of 1,000-100,000 centipoise, preferably 3,000-40,000 centipoise;

b)0 to about 40 weight percent of a cyclic organosiloxane of the formula:

[(R)₂SiO]_n

wherein R is a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or a phenyl group which may be optionally substituted with an alkyl group having 1 to 8 carbon atoms, and n has an average value of 3 to 10;

c)0 to about 40 weight percent of an inorganic extending or non-reinforcing filler;

d) about 0.5 to about 10 wt% of the surface area is about 100-250m²Amorphous SiO between/g and in the particle size range between about 0.01 and 0.03 microns₂A reinforcing filler;

e) about 1 to about 7 weight percent of an oximinosilane crosslinker of the formula:

RSi(ON＝CR′₂)₃

wherein R and R' are independently selected from a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or a phenyl group which may be optionally substituted with an alkyl group having 1 to 8 carbon atoms;

f) from about 0.2 to about 3 weight percent of an adhesion promoter of the formula:

wherein R is²And R³Each independently selected from monovalent alkyl groups having 1 to 8 carbon atoms, b is an integer between 0 and 3, and R¹Is a saturated, unsaturated or aromatic hydrocarbon radical having from 1 to 10 carbon atoms, which contains an amino function; and

g) about 0.02 to about 3 weight percent of an organotin salt as a condensation catalyst.

In one aspect of the invention, the composition is for coating high voltage electrical insulators and further comprises about 36 to about 48 weight percent of an alumina trihydrate having a median particle size of 13 μm and containing 65.1 percent Al₂O₃34.5% of bound water, 0.3% of Na₂O，0.02％CaO，0.01％SiO₂And having a specific gravity of 2.42, the alumina trihydrate being present in a proportion of 90 to 110 parts by weight per 100 parts by weight of polyorganosiloxane.

The present invention also provides a method of protecting an exposed surface, particularly a metal or concrete surface, from the environment. The method comprises applying a thin layer of the above one-part organopolysiloxane rubber composition on the surface and allowing the coating of the one-part organopolysiloxane rubber composition to cure to a silicone elastomer at room temperature.

The present invention also provides a surface coated with a silicone elastomer formed from the curing of the one-part organopolysiloxane rubber composition.

Detailed Description

The one-part organopolysiloxane rubber composition of the present invention is ideally suited for protecting surfaces from environmental influences. Such protection includes the protection of metal or concrete surfaces and buildings from corrosion by salt spray and chemical environments, including direct contact with salt water, salt spray, gases and other industrial contaminants. The composition of the invention can also be used to coat metal surfaces of motor vehicles which are exposed to high salt conditions in the winter season. Compositions with suitable additives also provide protection against ageing effects, especially from exposure to UV radiation. The compositions of the present invention are particularly useful for antifouling coatings on marine structures such as ship hulls, oil well drilling equipment, docks, piers, buoys, water intake pipes and various underwater structures. The coating composition of the present invention can also be used for coating power transmission towers and bridges for corrosion protection of metal or concrete buildings in direct contact with salt water and industrial pollution, especially sulphur forms. The compositions containing alumina trihydrate can be used as protective coatings on electrical insulators that provide corrosion protection and electrical leakage. The coating composition can also be used to form impermeable coatings by coating textiles such as Geo Tech or nylon, cotton or other fabrics for use as chemical containers or as tents, awnings, canopies and the like. The absence of Volatile Organic Compounds (VOCs) in the coating composition makes it desirable for use in controlled areas where a minimum level of VOCs is required.

The one-part organopolysiloxane rubber composition of the present invention used as a protective coating contains from about 20 to about 60 weight percent of one or more polydimethylsiloxane fluids of the formula:

R″O[(R)₂SiO]_nR′

wherein R is a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or phenyl, R 'is H, a monovalent alkyl or alkylene group having 1 to 8 carbon atoms, or phenyl, R' is H or a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or phenyl, and n has an average value such that the viscosity at 25 ℃ is from about 1 to about 100,000 centipoise. At least one of the polyorganosiloxane fluids is a high viscosity siloxane having reactive groups wherein R' is H and n has an average value such that the viscosity is in the range of 1,000-100,000 centipoise, preferably 3,000-40,000 centipoise at 25 ℃. The polydimethylsiloxane may contain small amounts of monomethylsiloxane units, and the methyl groups are replaced with small amounts of other groups as impurities, as found in commercial products, but the preferred fluid contains only polydimethylsiloxane.

The composition may contain a second linear dimethylpolysiloxane of low molecular weight acting as a viscosity reducing agent for the composition, for application of the composition to a surface. The low molecular weight linear dimethylsiloxane is an end-capped oligomeric compound of the above formula wherein R, R 'and R' may be the same or different and are independently selected from the group consisting of monovalent alkyl or alkylene groups having 1 to 8 carbon atoms, or phenyl groups. The average value of n is between 4 and 24, preferably between 4 and 20.

If the composition contains two different polysiloxanes as given above, the total amount of polysiloxanes is generally about 40-60 wt%, wherein the relative amounts of the two polysiloxanes are selected according to the desired properties of the final coating. Generally, each polysiloxane will be present in a ratio of about 30 wt% to about 70 wt%, based on the total weight of the polysiloxane fluid.

In addition to, or instead of, the low molecular weight linear dimethylpolysiloxane, the composition may contain up to about 40 wt%, more preferably 20 to 30 wt%, of a cyclic organosiloxane of the formula:

[(R)₂SiO]_n

wherein R is a monovalent alkyl or alkenyl group having 1 to 8 carbon atoms, or a phenyl group which may be optionally substituted with an alkyl group having 1 to 8 carbon atoms, and n has an average value of 3 to 10. The preferred cyclic organosiloxane is cyclic dimethylsiloxane and is used in a similar manner to the use of low molecular weight linear dimethylpolysiloxanes, the viscosity of the composition being reduced to make it suitable for application by spraying, brushing or dipping.

The composition also contains from 5 to 40 wt%, more preferably from 15 to 30 wt% of an inorganic extending or non-reinforcing filler to increase the resistance of the coating to environmental effects, including the high temperature stability of the cured product. The extending filler is preferably selected from inorganic substances such as calcium carbonate, barium sulphate, iron oxide, diatomaceous earth, melamine, quartz, crystalline silica, titanium dioxide, alumina trihydrate, zinc oxide, zirconium oxide and chromium oxide. The choice of filler will depend on the desired properties and the end use of the composition. Thus, for applications where high temperature resistance is not required, such as corrosion protection coatings for electrical power systems, roof coatings, etc., the preferred filler will be calcium carbonate, diatomaceous earth or quartz. For applications where high temperature stability is required, such as coating exhaust pipes or mufflers of motor vehicles, preferred fillers would be melamine, iron oxide, zinc oxide, titanium dioxide, zirconium oxide or zinc chromate. For coatings requiring higher strength, crystalline silica is utilized, while for coatings of electrical insulators, the composition contains alumina trihydrate to provide electrical leakage protection. In one aspect of the invention, the composition is for coating a high voltage electrical insulator and further comprises about 36 to about 48 weight percent of an alumina trihydrate having a median particle size of 13 μm and containing 65.1 percent Al₂O₃34.5% bound H₂O，0.3％Na₂O，0.02％CaO，0.01％SiO₂And has a specific gravity of 2.42, the alumina trihydrate being present in a proportion of 90 to 110 parts by weight per 100 parts by weight of polyorganosiloxane. The amount of filler can be increased within this range to improve the desired properties.

The composition contains about 0.5-5 wt% of amorphous SiO₂A reinforcing filler havingA surface area of between about 100 and 250m/g and a particle size range of between about 0.01 and 0.03 microns. The specific gravity of the filler is preferably about 2.2.

The composition also contains about 1-7 wt%, preferably 2-5 wt%, of the oximinosilane crosslinker. Preferably, the oximinosilane crosslinker has the formula RSi (ON ═ CR'₂)₃Wherein R and R' are independently selected from monovalent alkyl or alkenyl groups having 1 to 8 carbon atoms, or phenyl, preferably alkyl such as methyl, ethyl, propyl, butyl, or alkylene such as vinyl, allyl, or phenyl. Preferred R and R' are alkyl or vinyl groups, most preferably methyl and ethyl groups.

The composition also contains about 0.2 to 3 weight percent of an organofunctional silane as an adhesion promoter. Preferably, the organofunctional silane has the following structural formula:

wherein R is²And R³Independently selected from monovalent alkyl or alkenyl radicals having 1 to 8 carbon atoms, or phenyl, b is an integer between 0 and 3, preferably 0, and R¹Is a saturated, unsaturated or aromatic hydrocarbon group having 1 to 10 carbon atoms, which may be further functionalized with a group selected from amino, ether, epoxy, isocyanate, cyano, acryloxy and acyloxy groups and combinations thereof. R²And R³Preference is given to alkyl, such as methyl, ethyl, propyl, butyl, or alkylene, such as vinyl and allyl. More preferably, R²And R³Is an alkyl group, most preferably methyl, ethyl, or propyl. Preferably R¹Is an alkyl group, more preferably further functionalized with one or more amino groups. The most preferred organofunctional silane is N- (2-aminoethyl-3-aminopropyl) trimethoxysilane.

In all of the above compounds, alkyl includes straight chain, branched or cyclic groups. Wherein alkyl is C_1-8Straight-chain or branched alkyl radicals, e.g. methyl, ethyl, propylAlkyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl and the like, cycloalkyl is C_3-8Cycloalkyl, e.g. cyclopropyl, cyclobutyl, cyclohexyl, etc., alkylene being C_1-8Alkylene groups such as vinyl and allyl. The above groups as well as the phenyl group may be further functionalized with groups included in the chain or ring structure selected from amino, ether, epoxy, isocyanate, cyano, acryloxy, acyloxy and combinations as the case may be, provided that the functionalization does not adversely affect the desired properties of the compound.

The composition additionally contains from about 0.02 to about 3 weight percent of an organotin salt of a carboxylic acid as a condensation catalyst which accelerates the aging of the composition. Preferably, the organotin salt is selected from the group consisting of dibutyltin diacetate, stannous octoate, dibutyltin dioctoate, and dibutyltin dilaurate. Most preferably, the organotin salt is dibutyltin dilaurate of the formula:

(C₄H₉)₂Sn(OCOC₁₀H₂₀CH₃)₂

the composition may contain minor amounts of other optional ingredients, such as pigments and other fillers, provided that the addition of these ingredients does not cause a reduction in the desired properties of the cured coating prepared from the composition. One commonly used optional ingredient is a pigment, preferably a gray pigment, most preferably present in an amount up to about 1% by weight.

The organopolysiloxane compositions of the invention are prepared by mixing the ingredients together in the absence of moisture. The silane is moisture sensitive and will undergo crosslinking in the presence of moisture so that when the silane is added, the mixture must be substantially free of moisture and remain in a moisture free state until cure is desired.

A preferred method of mixing involves mixing the polysiloxane fluid with the extending and reinforcing fillers and other optional fillers and pigments. Thereafter, the oximinosilane and organofunctional silane were added and mixed under a nitrogen atmosphere. The organotin salt is added to the mixture, and the mixture is then dispensed into sealed containers for storage prior to use.

The surface to be protected is coated with the composition by conventional methods such as dipping, brushing or spraying. Preferably, the surface to be protected is applied by spraying one or more passes of the composition of the present invention. The thickness of the coating will depend on the particular requirements of the application and the level of protection desired. The coating typically has an average thickness of 250-. After the coating is formed on the surface, the surface is exposed to normal atmosphere for crosslinking and curing of the coating.

The improved coatings of the present invention are capable of protecting surfaces from environmental effects, including preventing corrosion of metal and concrete surfaces in the presence of moisture, such as rain or fog, and contaminating the atmosphere, salt spray or fog, or direct contact with salt water. The improved coating of the present invention is particularly useful for protecting metal surfaces that are in direct contact with salt water. These surfaces include the hulls of ships and other vessels, oil well rigs, port and dock buildings, and the like. When the coating is used on a ship's hull, other benefits than corrosion protection, such as fouling resistance, are obtained. The coating does not make marine animals, such as Ming He Medium, easily contact the surface. Any such animals that attempt to adhere to the surface are typically removed from the surface by a high pressure washing device. In addition, the cleaning of surfaces is typically accomplished by high pressure washing and/or hand or mechanical wiping, without the scraping operations typically used in hull cleaning of ships or other marine facilities. Because the cleaning of the surface coated with the composition of the invention is easily accomplished, the composition can also be used as a scratch-resistant coating for the surface.

The following examples are provided to illustrate preferred embodiments of the present invention and to demonstrate the usefulness of the coating, but are in no way intended to limit the scope of the invention.

Example 1

To 36 parts by weight of a dimethylpolysiloxane fluid having a viscosity of 16,750 cps at 25 ℃ and 22 parts by weight of a cyclic dimethylsiloxaneTo the alkane was added 35 parts by weight of a mixture having a specific gravity of 2.2 and about 130m²A mixture of amorphous and crystalline silica fillers per gram of surface area. Then, 2 parts by weight of pigment was added and the composition was mixed in a mixer to a uniform consistency. Then, 3 parts by weight of methyltris- (methylethylketoximino) silane and 1 part by weight of N- (2-aminoethyl-3-aminopropyl) trimethoxysilane were added under a nitrogen atmosphere and mixed. Finally, 0.1 part of dibutyltin dilaurate was added to the dispersion and mixed until a uniform consistency was obtained.

Samples prepared from stainless steel and carbon steel and aluminum sheets were applied with the mixture by dipping into the composition prepared according to example 1, and the samples were exposed to normal atmosphere for crosslinking. Samples with an average coating thickness of 300 microns were subjected to salt spray testing in an electric (ozone generating) environment. After 2000 hours of continuous exposure, the coating showed no signs of degradation or separation from the original metal surface. Uncoated coupons of both metals showed severe etching and corrosion.

A sample of carbon steel sheet was coated with the mixture by dipping into the composition prepared according to example 1 and the sample was exposed to normal atmosphere for crosslinking. The test specimens having an average coating thickness of 320 microns were exposed to accelerated heat aging at 260 ℃. After 7 consecutive days of exposure, the coating showed no signs of deterioration or separation from the original metal surface.

Carbon steel coupons coated to a thickness of 500 microns with the composition of example 1 were immersed in an algae-producing environment in seawater for 30 days at room temperature. There are considerable deposits of seaweed which are easily removed by wiping with a wet cloth. The initial surface of the coating showed no changes, scratches or deformations.

The improved flexibility of the coating and its resistance to cracking was demonstrated using carbon steel coupons coated with a 300 micron thick coating. The specimen was bent 180 ° along the curve and showed no cracking or separation from the substrate.

Example 2

By makingA composition useful for high temperature protection was prepared using 37 parts by weight of a dimethylpolysiloxane fluid having a viscosity of 3,300 centipoise at 25 deg.C and 20 parts by weight of cyclic dimethylsiloxane, and 4 parts by weight of titanium dioxide was added. Then 3 parts by weight of methyl tris- (methylethylketoximino) -silane, 1 part by weight of N- (2-aminoethyl-3-aminopropyl) trimethoxysilane and 0.05 part by weight of dibutyltin dilaurate were added under a nitrogen atmosphere. Then, 32 parts by weight of a lubricant having a specific gravity of 2.2 and a particle size of 150m were added²A mixture of amorphous and crystalline silica fillers per gram of surface area. Finally, 6 parts by weight of melamine were added and mixed thoroughly to give a uniform consistency.

Adhesion testing of the above formulations was performed by applying thin coatings on stainless steel, carbon steel, aluminum, wood and glass. The coating was cured for 7 days under standard conditions (room temperature 25 ℃ and 50% relative humidity) and then peeled off by applying a cut on the surface. The coating exhibited excellent adhesion to all tested materials.

Several sheets of 200 micron thickness were prepared from the above product and cured for 7 days under standard conditions. Physical properties such as elongation, tensile stress, tear resistance and hardness were tested on each sheet before and after immersion in 150 ℃ motor oil, e.g., Mobile10W-30, Valvoline10W-30 and automatic transmission fluids. No deterioration or significant reduction in physical properties was found. The product exhibits excellent oil resistance at high temperatures.

Results of oil resistance of the cured product

Test specimen	Elongation at Break (%)	Tensile Strength (psi)	Shore hardness A (dot)	Tear resistance (psi)
					Curing for 7 days under standard conditions	183	309	56	36
Cured sheet impregnated with oil at 150 deg.C (Mobile10W-30) for 70 hours	180	290	50	22
					Cured sheet impregnated with oil (automatic drain change) at 150 ℃ for 70 hours	180	274	48	25

The formulations were also tested for flame retardancy by Underwriter Laboratories Inc. (UL 94-V-0), and the products successfully passed the flame retardancy test.

Example 3

By mixing 30 parts by weight of a dimethylpolysiloxane fluid having a viscosity of 20,000 cps at 25 ℃ with 20 parts by weight of a cyclic dimethylsiloxane, and then adding 2 parts by weight of a mixture having a specific gravity of 2.2 and about 150m²Amorphous silica per g surface area to prepare a first composition for coating an electrical insulator. Then, 2 parts by weight of methyltris- (methylethylketoximino) silane and 1 part by weight of N- (2-aminoethyl-3-aminopropyl) trimethoxysilane were added and mixed under a nitrogen atmosphere. Then, 35 parts by weight of alumina trihydrate were added and mixed well to a uniform consistency. The viscosity and sagging of the mixture were checked and adjusted to 1000. + -. 300 centipoise and 35. + -. 10 (according to the Leneta standard) by adding an excess of cyclic dimethoxypolysiloxane and amorphous silica, respectively. Finally, 0.1 part by weight of dibutyltin dilaurate was added and mixed thoroughly.

Example 4

By mixing 30 parts by weight of a dimethylpolysiloxane fluid having a viscosity of 20,000 cps at 25 ℃ with 29 parts by weight of a linear dimethylpolysiloxane having a viscosity of 50 cps at 25 ℃, and then adding 2 parts by weight of a mixture having a specific gravity of 2.2 and about 150m²Per gram of surface area amorphous silica. Then, 2 parts by weight of methyltris- (methylethylketoximino) silane and 1 part by weight of 1 were added under a nitrogen atmosphereParts by weight of N- (2-aminoethyl-3-aminopropyl) trimethoxysilane and mixing. Then, 35 parts by weight of alumina trihydrate were added and mixed well to a uniform consistency. The viscosity and sagging of the mixture were checked and adjusted to 1000. + -. 300 centipoise and 35. + -. 10 (according to the Leneta standard) by adding an excess of linear dimethoxypolysiloxane and amorphous silica, respectively. Finally, 0.1 part by weight of dibutyltin dilaurate was added and mixed thoroughly.

The compositions of the present invention may also be used to protect other types of surfaces from corrosive environments. For example, the compositions of the present invention are particularly useful for protecting the surface of leak seals used around oil reservoirs and the like. The composition may be applied to a heavy duty fabric which is then used to line the interior of a leak shut-off well around a tank farm. Samples of heavy sickness Geo fabric were sprayed with the composition of the present invention to coat the fabric. Fabrics were contacted with these materials for up to 7 days by placing caustic soda solution, diesel, furnace oil on the surface of treated and untreated fabric samples. It was found that the treated fabric did not deteriorate and the deposits of material could be easily washed away without any significant loss of weight of the material. In contrast, the untreated fabric did not retain the material on the surface and the caustic soda solution caused deterioration of the untreated fabric material within 24 hours.

The compositions of the present invention are useful in many situations where it is desirable to protect a surface from the environment. These compositions include the compositions exemplified above as well as other compositions, the formulation of which is well within the skill of the ordinary artisan. The selection of the various components and their proportions will be evident depending on the desired properties of the final coating. The composition of the present invention overcomes many of the problems associated with prior art compositions in that it is a one-part coating composition that is easy to apply using any commonly used method and is VOC free, thus eliminating or reducing the environmental pollution and potential health hazards to workers caused by VOC containing compositions.

While the present invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes and substitutions can be made therein without departing from the true spirit and scope of the invention. All such modifications are intended to be included within the scope of the appended claims.

Claims (18)

1. A one-component organopolysiloxane rubber composition for use as an anti-corrosion coating for metals, comprising the product obtained by mixing:

a)20 to 50 weight percent of one or more polydiorganosiloxane fluids of the formula:

R″O[(R)₂SiO]_nR′

wherein R is a monovalent alkyl group having 1 to 8 carbon atoms or phenyl group, R ' is H, a monovalent alkyl group having 1 to 8 carbon atoms, or phenyl group, R ' is H, a monovalent alkyl group having 1 to 8 carbon atoms, or phenyl group, and n has an average value such that the viscosity at 25 ℃ is in the range of 1 to 100,000 centipoise, wherein R ' of at least one of the polyorganosiloxane fluids is H, and n has an average value such that the viscosity at 25 ℃ is in the range of 1,000-100,000 centipoise;

b)0 to 40 weight percent of a cyclic organosiloxane of the formula:

[(R)₂SiO]_n

wherein R is a monovalent alkyl group having 1 to 8 carbon atoms, or a phenyl group which may be optionally substituted with an alkyl group having 1 to 8 carbon atoms, and n has an average value of 3 to 10;

c)0-40 wt% of an inorganic extending or non-reinforcing filler;

d)0.5-10 wt% of surface area of 100-²Between/g amorphous SiO₂A reinforcing filler;

e)1-7 wt% of an oximinosilane crosslinker of the formula:

RSi(ON＝CR′₂)₃

wherein R and R' are independently selected from monovalent alkyl groups having 1 to 8 carbon atoms, or phenyl groups which may be optionally substituted with alkyl groups having 1 to 8 carbon atoms;

f)0.2 to 3 wt% of an adhesion promoter of the formula:

wherein R is²And R³Independently selected from monovalent alkyl groups having 1 to 8 carbon atoms, b is an integer between 0 and 3, and R¹Is a saturated, unsaturated or aromatic hydrocarbon radical having from 1 to 10 carbon atoms, which contains an amino function; and

g)0.02 to 3 wt% of an organotin salt as condensation catalyst.

2. A composition according to claim 1 wherein the composition contains only one polyorganosiloxane fluid wherein R and R' are each an alkyl group and 20 to 30 wt% of the cyclic organosiloxane.

3. The composition according to claim 2, wherein R and R' are methyl.

4. A composition according to claim 3, wherein the adhesion promoter is a compound of the formula:

wherein Me is methyl.

5. A composition according to claim 1 or 4, wherein the organotin salt is an organotin carboxylate salt selected from the group consisting of dibutyltin diacetate, stannous octoate and dibutyltin dioctoate.

6. The composition of claim 5 wherein the organotin carboxylate salt is a compound of the formula:

(C₄H₉)₂Sn(OCOC₁₀H₂₀CH₃)₂。

7. a composition according to claim 1 or 6, wherein the inorganic extending or non-reinforcing filler is one or more materials selected from the group consisting of calcium carbonate, barium sulphate, iron oxide, diatomaceous earth, melamine, quartz, crystalline silica, titanium dioxide, alumina trihydrate, zinc oxide, zirconium oxide and chromium oxide.

8. A composition according to claim 7, wherein the inorganic extending or non-reinforcing filler is a combination of 0.5 to 5.0% by weight of crystalline silica and 36 to 48% by weight of alumina trihydrate having a median particle size of 13 μm and containing 65.1% Al₂O₃34.5% of bound water, 0.3% of Na₂O，0.02％CaO，0.01％SiO₂And having a specific gravity of 2.42, the alumina trihydrate being present in a proportion of 90 to 110 parts by weight per 100 parts by weight of polyorganosiloxane.

9. A composition according to claim 7, wherein the inorganic extending or non-reinforcing filler is one or more materials selected from melamine, iron oxide, zinc oxide, titanium dioxide, zirconium oxide or zinc chromate.

10. A composition according to claim 9 wherein the inorganic extending or non-reinforcing filler is melamine.

11. A composition according to claim 1, comprising:

a)36 weight percent of a hydroxyl terminated dimethylpolysiloxane fluid having a viscosity of 10,000 and 20,000 centipoise at 25 ℃;

b) 35% by weight of a mineral having a specific gravity of 2.2 and at most 130m²Amorphous and crystalline SiO in terms of surface area/g₂A mixture of fillers;

c)3 wt% methyl tris- (methyl ethyl ketoximino) silane;

d) 1% by weight of N- (2-aminoethyl-3-aminopropyl) trimethoxysilane;

e) 0.1% by weight of dibutyltin dilaurate;

f)22 wt% cyclic dimethylsiloxane; and

g) 0.8% by weight of a grey pigment.

12. The composition of claim 1 wherein the composition comprises a first polydiorganosiloxane fluid wherein R and R 'are each alkyl groups, R "is H and n is such that the viscosity at 25 ℃ is an average value of 3000 and 30,000 centipoise and a second polydiorganosiloxane fluid wherein R, R' and R" are each alkyl groups and the average value of n is between 4 and 20.

13. A composition according to claim 12 wherein R and R 'of the first polydiorganosiloxane and R, R' and R "of the second polydiorganosiloxane are all methyl.

14. The composition of claim 13 wherein the adhesion promoter is a compound of the formula:

wherein Me is methyl.

15. The composition of claim 14 wherein the organotin carboxylate salt is a compound of the formula:

(C₄H₉)₂Sn(OCOC₁₀H₂₀CH₃)₂。

16. a composition according to claim 15, wherein the inorganic extending or non-reinforcing filler is one or more materials selected from the group consisting of calcium carbonate, barium sulphate, iron oxide, diatomaceous earth, melamine, quartz, crystalline silica, titanium dioxide, alumina trihydrate, zinc oxide, zirconium oxide and chromium oxide.

17. A composition according to claim 7, wherein the inorganic extending or non-reinforcing filler is a combination of 0.5 to 5.0% by weight of crystalline silica and 36 to 48% by weight of alumina trihydrate having a median particle size of 13 μm and containing 65.1% Al₂O₃34.5% of bound water, 0.3% of Na₂O，0.02％CaO，0.01％SiO₂And having a specific gravity of 2.42, the alumina trihydrate being present in a proportion of 90 to 110 parts by weight per 100 parts by weight of polyorganosiloxane.

18. A method of protecting a surface from a corrosive atmospheric environment comprising:

(1) applying to the surface a thin layer of a one-component organopolysiloxane rubber composition comprising the product obtained by mixing:

a)20 to 50 weight percent of one or more polydiorganosiloxane fluids of the formula:

R″O[(R)₂SiO]_nR′

wherein R is a monovalent alkyl group having 1 to 8 carbon atoms or phenyl group, R ' is H, a monovalent alkyl group having 1 to 8 carbon atoms, or phenyl group, R ' is H, a monovalent alkyl group having 1 to 8 carbon atoms, or phenyl group, and n has an average value such that the viscosity at 25 ℃ is in the range of 1 to 100,000 centipoise, wherein R ' of at least one of the polyorganosiloxane fluids is H, and n has an average value such that the viscosity at 25 ℃ is in the range of 1,000-100,000 centipoise;

b)0 to 40 weight percent of a cyclic organosiloxane of the formula:

[(R)₂SiO]_n

wherein R is a monovalent alkyl group having 1 to 8 carbon atoms, or a phenyl group which may be optionally substituted with an alkyl group having 1 to 8 carbon atoms, and n has an average value of 3 to 10;

c)0-40 wt% of an inorganic extending or non-reinforcing filler;

d)0.5-10 wt% of surface area of 100-²Between/g amorphous SiO₂A reinforcing filler;

e)1-7 wt% of an oximinosilane crosslinker of the formula:

RSi(ON＝CR′₂)₃

wherein R and R' are independently selected from monovalent alkyl groups having 1 to 8 carbon atoms, or phenyl groups which may be optionally substituted with alkyl groups having 1 to 8 carbon atoms;

f)0.2 to 3 wt% of an adhesion promoter of the formula:

wherein R is²And R³Independently selected from monovalent alkyl groups having 1 to 8 carbon atoms, b is an integer between 0 and 3, and R¹Is a saturated, unsaturated or aromatic hydrocarbon radical having from 1 to 10 carbon atoms, which contains an amino function; and

g)0.02 to 3 wt.% of an organotin salt as condensation catalyst, and

(2) the coating of the one-component organopolysiloxane rubber composition is cured to a silicone elastomer at room temperature.