WO2000005314A1

WO2000005314A1 - Coating composition and method of use

Info

Publication number: WO2000005314A1
Application number: PCT/CA1999/000670
Authority: WO
Inventors: Dennis Figiel; Noel Austin Winter; Michael Kenneth St. Germain
Original assignee: Siltex International Corporation
Priority date: 1998-07-23
Filing date: 1999-07-23
Publication date: 2000-02-03
Also published as: AU4892899A; CA2243800A1

Abstract

The application describes a coating composition including 25 % to 99 %, by weight, of a waterborne silicone resin and 1 to 75 % by weight of a crumb rubber selected from the group consisting of natural rubber, synthetic butyl rubber, ethylene propylene diene monomer (EPDM) rubber or a combination thereof. The coating according to the present invention, is useful as a marine coating, an acoustic coating, for caulking and chinking, an automotive coating (i.e. undercoating) as well as an architectural coating for stucco, stipple and roofing.

Description

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A coating composition comprising: 25% to 99%, by weight, of a water-borne silicone resin and 1 to 75% by weight of a granular form of elastomeric rubber

2. The coating composition of claim 1 wherein the elastomeric rubber is selected from the group consisting of natural rubber, butyl rubber, ethylene propyiene diene monomer rubber or a combination thereof.

3. The coating composition of claim 1 wherein the elastomeric rubber is granulated to between 5 and 400 mesh.

4. The coating composition of claim 1 wherein the elastomeric rubber has a roughened outer surface.

5. The coating composition of claim 1 wherein the elastomeric rubber is obtained by a mechanical grinding process.

6. The coating composition of claim 1 wherein the elastomeric rubber is obtained from used vehicle tires.

7. The coating composition of claim 1 further comprising a grit material.

8. The coating composition of claim 7 wherein the grit material is selected from the group consisting of fumed silica, perlite, or sand.

9. The coating composition of claim 1 further comprising a tinting pigment. - 8 - -^"

10. The coating composition of claim 1 wherein the water-borne silicone resin is a water/alcohol diluted tin-catalysed, calcium carbonate filled water-borne silicone resin.

11. The coating composition of claim 1 comprising 25% to 70%, by weight, of a water-borne silicone resin and 30 to 75% by weight of a granular form of elastomeric rubber.

12. A method for producing a coating composition comprising: mixing 1 to 75% by weight of a granular form of elastomeric rubber into 25% to 99%, by weight, of a water-borne silicone resin.

13. The method of claim 12 wherein the elastomeric rubber is selected from the group consisting of natural rubber, butyl rubber, ethylene propyiene diene monomer rubber or a combination thereof.

14. The method of claim 12 wherein prior to mixing the elastomeric rubber into the water-borne silicone rubber, the elastomeric rubber is wetted.

15. The method of claim 14 wherein the elastomeric rubber is wetted by soaking in water and draining.

16. The method of claim 14 wherein the elastomeric rubber is wetted by rinsing in a mixture of alcohol and water.

17. The method of claim 12 wherein prior to mixing the elastomeric rubber into the water-borne silicone rubber, the elastomeric rubber is (a) soaked in water, (b) drained, (c) rinsed in a mixture of alcohol and water and (d) drained. 18. The method of claim 17 wherein the alcohol water mixture is 20 to 40% water and 60 to 80% glycol, by volume.

19. The method of claim 12 wherein the elastomeric rubber is granulated to between 5 and 400 mesh.

20. The method of claim 12 wherein the elastomeric rubber has a roughened outer surface.

21. The method of claim 12 wherein the elastomeric rubber is obtained by a mechanical grinding process.

22. The method of claim 12 wherein the elastomeric rubber is obtained from used vehicle tires.

23. The method of claim 12 further comprising mixing a grit material into the water- borne silicone resin.

24. The method of claim 12 wherein the grit material is selected from the group consisting of fumed silica, perlite, or sand.

25. The method of claim 12 further comprising mixing a tinting pigment into the water-borne silicone resin.

26. The method of claim 12 wherein the water-borne silicone resin is a water/alcohol diluted tin-catalysed, calcium carbonate filled water-borne silicone resin.

27. A method for coating a surface comprising: providing a coating composition including 1 to 75% by weight of a granular form of elastomeric rubber and 25% - 10 - - ^'

to 99%, by weight, of a water-borne silicone resin; and applying the coating composition to a structure.

28. The method of claim 27 wherein the structure is a building and the coating is applied as stucco.

COATING COMPOSITION AND METHOD OF USE

Field of the Invention

This invention is related to a coating composition and method of use thereof.

Background of the Invention

In the industry of building construction, stucco is commonly used as a coating composition for structures. Stucco is now available in two forms: cement based and polymer based. These two forms of stucco are essentially inflexible when set. Thus, in areas such as the California coast of the United States where earth tremors and quakes can occur, stucco can sometimes crack compromising the outer coating of the structure. This leaves the envelope of the structure compromised and the interior open for damage due to the weather. The cracking is facilitated by the inclusion in the base of fillers, such as sand and perlite.

In addition, each of these stucco products have inherent problems including one or more of fading, undesirable fire rating and lack of adhesion to some surfaces.

Summary of the Invention

A coating composition has been invented which exhibits superior elasticity and shear strength over previous stucco coating compositions. In addition, a coating composition according to the present invention has exhibited favourable acoustic damping properties. The present coating composition is fire retardant, resistant to fungal and mildew growth, is breathable and is washable. Through experimentation the product has exhibited superior application characteristics in its ability to float and release over conventional stucco products. The superior application characteristics permit the formation of various textured appearances. In addition, the coating composition of the present invention can accept a higher percentage of filler than previously possible using polymer-based stuccos, which serves to reduce the cost of the product. Thus, the coating according to the present invention, is useful as a marine coating, an acoustic coating, for caulking and chinking, an automotive coating (i.e. undercoating) as well as an architectural coating for stucco, stipple and roofing.

Thus, in accordance with a broad aspect of the present invention, there is provided a coating composition comprising: 25% to 99%, by weight, of a water-borne silicone resin and 1 to 75% by weight of a granular form of elastomeric rubber.

Detailed Description of the Present Invention

Applicant has discovered that a water-borne silicone resin filled with a granular form of rubber, commonly called crumb rubber, is very useful as a coating composition. The silicone resin exhibits strong adhesion to the crumb rubber particles. The silicone resin will adhere more strongly to rubber than to sand particles, which are commonly used as a filler in coating compositions. In addition, the crumb rubber particles are flexible and elastic and flex with the silicone resin base to enhance the flexibility and shear strength of the final coating composition.

The coating composition according to the present invention includes 25% to 99%, by weight, of a water-borne silicone resin and 1 to 75%, by weight, of an elastomeric crumb rubber. Suitable crumb rubbers are those selected from the group consisting of natural rubber, butyl rubber (i.e. synthetic butyl rubber), ethylene propyiene diene monomer (EPDM) rubber, other rubbers having similar elastomeric and chemical resistant properties and which are capable of adhering to silicone resin or combinations of any of the foregoing. To produce a more cost effective coating, the percentage of crumb rubber should be increased relative to the silicone resin with consideration as to - 3 - -^"

the shear characteristics of the coating increasing the percentage of crumb rubber in the coating will eventually reduce the shear strength of the coating. The preferred concentration of crumb rubber for any coating application can be determined by gradually increasing or decreasing the concentration of crumb rubber while noting the shear strength of the coating. These results can be plotted to show what shear strength reduction occurs with increased concentrations of crumb rubber, and the value of the shear strength can be plotted against the cost savings of increased crumb rubber concentration to find an economically useful coating composition. One preferred coating composition includes 25% to 70%, by weight, of a water-borne silicone resin and 30 to 75% by weight of a crumb rubber and shows superior overall properties with consideration as to cost, elongation, texture, finish, adhesion and shear strength when compared to coating compositions according to the present invention and having lower concentrations of crumb rubber.

The water-borne silicone resin preferably is based on a tin-catalysed, calcium carbonate filled water-borne silicone which meets the slump test as defined in test method CTM 0062 such as that produced by Dow Corning Corporation, Midland, Michigan, USA and known as Q3-L237™. One particularly preferred resin is available from Siltex International Corporation, Calgary, Alberta, Canada and is known as Siltex 1000™. Siltex 1000™ is a water/alcohol diluted water-borne silicone resin based on a tin- catalysed, calcium carbonate filled water-borne silicone resin.

Crumb rubber, as is known is granular cured rubber. The crumb rubber preferred in the present invention is selected from the group consisting of natural rubber, synthetic butyl rubber, EPDM rubber or any combination thereof. The crumb rubber is in particulate form and is preferably between 5 and 400 mesh. The size of the rubber crumb particles will determine the surface texture, ease of float, acoustic properties and elongation of the final coating composition, when cured. In particular, while all coating compositions according to the present invention exhibit excellent float characteristics, particles of higher mesh size (ie. smaller size particles) give a coating having better float characteristics than lower mesh size particles. With respect to acoustic properties, larger size crumb rubber particles create a more random surface in the coating and provide better acoustic damping than smaller size crumb rubber particles. The elongation property of the composition is improved by use of smaller size particles when compared to coatings using larger size granules. To facilitate handling, preferably the crumb particles are between 10 to 200 mesh. For some applications, it is preferred that the crumb rubber particles be of a substantially uniform size (i.e. have a high aspect ratio). A coating composition containing crumb rubber particles of uniform size will have a uniform appearance and will perform uniformly.

In one preferred embodiment, the crumb rubber is produced from larger cured rubber articles. The larger cured rubber articles are processed to form crumbs of a desired size or blend of sizes. Larger cured rubber articles can be, for example, scrap resulting from trimmings from manufacturing operations such as mould extrusions, off- specification rubber products or recycled used products, such as recycled tires. To reduce the cost of the coating material, recycled waste products are preferred for use to form the crumb material.

It has been found that a crumb rubber with a random surface morphology is preferable over a particle having a smooth surface. A rough surface appears to enhance the adhesion of the silicone resin to the crumb particles. A particularly preferred crumb rubber is one resulting from a physical crumbing process such as, for example, grinding rather than a cryogenic crumbing process wherein the surfaces of the resulting crumbs tend to be smooth along the cleaved surface. A particularly preferred crumb rubber is that available from Santee River Rubber Company Ltd., Moncks Corner, South Carolina, USA.

In order to produce the coating composition, the silicone resin and the crumb rubber are combined and mixed to achieve a paste-like consistency. During the mixing, care must be taken to prevent the composition from exceeding a temperature of 105°F, whereabove cross linking of the silicone will occur. In one embodiment, to enhance the adhesion of the silicone resin to the crumb rubber, the crumb rubber is wetted prior to mixing with the resin. Wetting is conducted by applying a liquid to the crumb rubber so that the surfaces of the crumb rubber come into contact with the liquid. The liquid can be any liquid which will not inhibit the adhesion of the silicone to the surface of the crumb particles and which will not adversely affect the structure of the rubber. Suitable liquids are, for example, water, soap water and/or an alcohol. The crumb rubber should remain in the liquid for a time suitable to permit wetting of the surface. Generally, it is desirable to soak the crumb rubber in the liquid as long as economically feasible. Excess liquid should be removed from the crumb rubber before adding the crumb rubber to the silicone resin. Fine mesh size rubber crumb will tend to retain considerable liquid interstitially and, thus, may require greater effort to remove excess liquid. One particularly preferred wetting liquid is water and in a preferred embodiment, the crumb rubber is soaked in water for at least 10 minutes and more preferably at least for 30 minutes. The liquid is then drained from the crumb rubber and the crumb is added to the silicone resin. Another preferred wetting liquid is a mixture of glycol and water such as, for example, 20-40% water and 60-80% glycol, both by volume.

The composition can be used in various ways including as an architectural coating (ie. internal or external stucco, stipple or roof coating or patching), marine coating (ie. for coating a boat hull to prevent barnacle growth), as an acoustic coating for sound proofing or damping, for caulking and chinking or as an automotive coating (i.e. undercoating). The coating can be applied in any desired way such as by spraying, trowelling, paint rolling or brushing. The coating will adhere to most structural surfaces and can be applied directly on concrete, wood, drywall, plastic, previously painted surfaces, metal, fibreglass and cement (i.e. cementitious base coats). The coating can achieve a variety of finished appearances ranging from a smooth finish to a rough "California stucco" appearance as determined by crumb rubber size used and the method of application. The coating can be used as a base coat or as a finish coat. The surface to which the coating is applied should be clean and free of loose material.

In some applications, it may be desirable to include other components to the composition. For example, the coating composition including silicone resin and crumb rubber will be very slippery when water is applied thereto. Thus, to reduce the slip properties of the composition and/or to enhance the abrasion resistance or other properties, a grit material such as, for example, sand, perlite or fumed silica can be added. The grit material is generally less than 10% by volume of the coating composition.

As another example, tinting pigments can be added to the coating, as desired, to obtain a desired colour. The pigments are permanently encapsulated in the resin of the coating.

EXAMPLE

A 80 mesh synthetic butyl rubber crumb was obtained by mechanically grinding used vehicle tires. The crumb rubber was soaked in water for 30 minutes, drained and rinsed with a mixture of 70% glycol and 30% water (by volume). The crumb rubber was drained in preparation for use in the coating composition.

While still wet, 12 litres of the rubber crumb was added to 27 lbs of the water based silicone resin known as Siltex 1000™. Using a paddle mixer, the rubber crumb was mixed into the resin for two minutes while monitoring the mixture to ensure that it did not exceed 80°F.

The resulting mixture was then floated onto a surface and allowed to cure. The resulting coating was able to stretch in excess of 150% of the mil thickness of the application without shearing.

It will be apparent that many other changes may be made to the illustrative embodiments, while falling within the scope of the invention and it is intended that all such changes be covered by the claims appended hereto.