MXPA99000414A

MXPA99000414A - Coating with high reflectance luminaire and durable board for the te

Info

Publication number: MXPA99000414A
Application number: MXPA/A/1999/000414A
Authority: MX
Inventors: G Caldwell Kenneth; H Fernando Raymond
Original assignee: Armstrong World Industries Inc
Priority date: 1998-01-09
Filing date: 1999-01-08
Publication date: 2000-12-06

Abstract

A coating composition for roof boards that includes water, a binder and a filler material, the filler material has large particles with an average particle size of a minimum of about 50 microns, average particles with an average particle size in the range from about 1.2 to about 30 microns, and small particles which have an average particle size in the range from about 0.1 to about 1.0 micrometer

Description

COVER WITH HIGH REFLECTANCE LUMINAIRE AND DURABLE BOARD FOR CEILING BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The invention is directed to a coating composition for roof boards. The coating described herein has qualities of high light reflectance and durability. The paint coatings used in the roof boards require special features which are desired for the board. Two of the most important are durability and high light reflectance. A roof tile covering that has these characteristics is highly beneficial. Known coatings for roof boards include a coating described by U.S. Patent 5,674,594 which is for an acoustic roof board. This paint coating contains a latex emulsion and filler particles of two different sizes; of approximately 40 to 150 mesh and 325 mesh and finer. REF. 29050 Another coating is described in US 4,900,611. This coating contains reflective flakes of light which are approximately 10 to 100 micrometers transverse. U.S. Patent 3,755,238 contains particles of a finely divided polyolefin; these particles are less than 50 micrometers. Another patent, that of Great Britain 1,144,767 also describes a coating with small particles having a maximum size of about 44 microns.

BRIEF DESCRIPTION OF THE INVENTION A coating composition for roof boards comprises water, a binder and a filler, the filler material having large particles with an average particle size of a minimum of about 50 microns, average particles with an average particle size in the range of about 1.2 to about 30 microns, and small particles which have an average particle size in the range of from about 0.1 to about 1.0 microns. With small particles an average particle size of less than about 0.1 micrometer is not used because it has been noted that when the average particle size is less than about 0.1, the particles become virtually transparent and provide unacceptable light reflectance. It has also been noted that although it is possible to use a filler material having an average particle size greater than about 300 microns in the coating composition, when this is done, the durability of the coating actually decreases. Therefore, preferably, to maximize durability, the large particles should have an average particle size in the range of from about 50 to about 300 microns. From about 40 to about 70% of the total wet (liquid) coating volume will be constituted of solids; this will allow discontinuous coating to be produced by the composition. These solids include both filler material and particles in the binder which coalesce into a solid when the coating dries. The dry filler content of the total wet (liquid) coating volume is from about 25 to about 65% (by volume).

DETAILED DESCRIPTION Due to the presence of three different particle sizes of the filler material, the present coating composition provides a coating with both good durability and high light reflectance. The large filler particles provide durability, and are present in an amount which is high enough to be effective and provide durability, but which is low enough to effectively allow small and medium sized particles to reflect light . Durability can be measured by the scraping test described in the examples. Although a scraping resistance of 20 can be tolerated, it is preferred that the minimum performance level of the test be 22, more preferably 25. The concentration of large particles can be as low as about 15% dry solids by volume to obtain a scraping resistance of 20. Preferably they are present large particles in the composition in an amount in the range from about 20 to about 55% of the total volume of dry solids. The small particles are present in an effective amount to provide part of the light reflectance which is necessary for a coating composition that will provide a dry coating having a light reflectance of at least about 0.84.; when small particles are present in a minimum amount of about 3%, at least part of this light reflectance is provided. The maximum amount of small particles will be low enough to be effective to provide the coating with viscosity that will allow the liquid coating to be applied by spray. When the concentration of small particles is too high, the coating composition is too viscous to allow spray coating. Since the maximum amount of small particles must be limited to keep the viscosity low, the concentration of small particles in itself is not able to provide adequate reflectance for light. Medium particles should be added in an amount necessary to be effective, to carry out the reflectance of the light to at least about 0.84, as measured by ASTM E1477-92. Acceptable, small particles are present in the composition in an amount in the range from about 3 to about 25% of the total volume of dry solids to reasonably improve light reflectance. Even where a minimum acceptable light reflectance is desired, the small particles alone (without the medium size particles) can not be used in an amount high enough to provide reflectance to the light since the viscosity of the coating composition would be too high. elevated Medium sized particles should be used. The medium size particles are present in an amount effective to provide the coating with a light reflectance of at least about 0.84 (preferably higher). However, with the present coatings, which contain these three specific sizes of filler particles (including filler particles), light reflectance values as high as 0.89 (using ASTM E 1477-92) have been measured. Preferably, medium sized particles are present in a minimum amount of about 25% by dry volume of solids; this will provide a reasonably good light reflectance with a reasonably good (low) application viscosity to allow the spray coating application technique to be used. Spray coating can be performed at viscosities up to about 10,000 centipoise (measured using a Brookfield viscometer at 10 revolutions per minute (rpm)). However, alternatively, the viscosity can be used at a slightly higher level by decreasing the medium size particles to about 22.5% dry volume of solids and using a higher concentration of small particles. However, preferably, medium-sized particles are present in an amount in the range of from about 25 to about 70% dry volume of solids. Although the binder can be used at concentrations which will be familiar to those usually familiar with the art, it is preferred that the coating binder concentration be in the range of from about 2 to about 30% by weight; or more preferably from about 3 to about 50% by volume. Water can also be maintained at family concentrations for those usually familiar with the technique; however, preferably the water can be used in an amount ranging from about 5 to about 30% of the total wet volume, or from about 3 to about 20% by weight. Preferably, the coatings of the present invention include a dispersing agent. This can also be used in a familiar amount for those usually familiar with the technique. However, preferably, the dispersing agent is present in an amount of up to about 3% in total wet volume, or more preferably in the range from about 0.5 to about 2.5% by total weight (weight) of the liquid coating. The coatings of the present invention preferably also include a thickening agent. This can also be used in a familiar amount for those usually familiar with the technique. However, preferably, the thickening agent is present in an amount of up to about 3% by total wet volume, or more preferably in the range of from about 0.2 to about 2.5% by total weight (weight) of the liquid coating. The coating compositions of the present invention can be made by mixing dry ingredients in the wet ingredients. Coating compositions having the amounts of filler material in the suggested amounts will have a suitable viscosity so that the spray coating technique is used to apply the coating. The fillers which can be used with the present invention with either large, medium or small particles include: calcium carbonate, limestone, titanium dioxide, sand, barium sulfate, clay, mica, dolomite, silica, talc , perlite, polymers, gypsum, wollastonite, calcite, aluminum trihydrate, pigments, zinc oxide and zinc sulfate. The preferred filler material for large particle sizes is preferably selected from the group consisting of: limestone, dolomite and sand, and mixtures thereof. The preferred filler material for the median particle sizes are preferably selected from the group consisting of: limestone, dolomite and milled silica, and mixtures thereof. The preferred filler material for the small particle sizes are preferably selected from the group consisting of: calcium carbonate, titanium dioxide, clay and mixtures thereof. Binders which can be used with the present invention include epoxies, urethanes, melamine, polyesters, natural and modified natural polymers and vinyl polymers. The polymers may include one or more of the following vinyl acetate monomers,. vinyl propionate, vinyl butyrate, ethylene, vinyl chloride, vinylidene chloride, vinyl fluoro, vinylidene fluoride, ethyl acrylate, methyl acrylate, propyl acrylate, butyl acrylate, ethyl methacrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, styrene, butadiene, urethane, epoxy, melamine and an ester. Examples of modified natural and natural polymers are proteins and carbohydrate polymers such as starch. Preferred binders are polymers of one or more of the following monomers: methyl methacrylate, butyl acrylate and vinyl acetate. Preferably, these coatings are used on acoustic substrates (such as roof boards). The visual surface of the substrate may include a thin canvas which is fixed to the board for the roof. The coating can be applied directly to the thin canvas before it is fixed to the board, or to the thin canvas after it has been fixed on a board. You can use any thin canvas. Suitable thin canvases include thin canvases made of cellulose, polypropylene, polyethylene, glass, polyester, polyamide and mixtures thereof. The coatings made by the present coating composition are discontinuous, and therefore provide a discontinuous finish required to allow the sound to pass through to an acoustic substrate. Preferably, these coating compositions are used in any substrate material having a fluid reduction coefficient (NRC) equal to or greater than 55.

Examples The ingredients for the coatings were mixed in the following examples to form the coating composition. Subsequently, the coatings were used to coat a fiber roof board that has a thin glass canvas surface. The board samples are then subjected to the tests indicated for each example. The tongue scraping test (also referred to as the finger scraping test) for each of the samples is used to test the scrap resistance of the coating surface with paint from the roof board samples which were prepared. This test is carried out and can be repeated according to the following description. Metal tabs (also called "fingers") are placed firmly, regularly in a row and each has a protruding length of approximately 4.7 cm (1875 inches). The tongues are made of steel, they are retained at the same level and have thicknesses which increase advancing from left to right. The thicknesses of the tabs are: (254, 305, 356, 406, 457, 508, 559 and 635 micrometers (10, 12, 14, 16, 18, 20, 22, and 25 thousandths of an inch) each. The board is placed on a stand under this set of tabs and the tabs are allowed to overlap through the top edge of the board a distance of about 5.5 mm (7/32 inches). Then the tabs are lowered across the board at a speed of 51 cm / min (20 inches per minute). A thicker tongue will cause a scraping more easily. A thinner tongue will scrape less easily. Therefore, the "scratch resistance" rating provided on the board tested in these examples is the thickness of the thinner bead which leaves a scrape on the board after the tabs run through it. Thus, for example, under example 5, the board is scraped at 508, 509 and 635 micrometer (20, 22, and 25 mil) gauge thicknesses, then its scrap resistance is less than 20. #1 % solids by volume = 49.69 Viscosity = 1200 cps (Brookfield - 10 rpm) Light reflectance »0.89 [Good reflectance to light] Resistance to scraping« 25 [Good scratch resistance] Example # 2 - Size filler of large minimum particle: % solids by volume = 49.41 Viscosity = 1200 cps (Brookfield - 10 rpm) Light reflectance »0.89 [Good reflectance to light] Resistance to scraping - 25 [Good scraping resistance] Example # 3 - Filling material of minimum average particle size: % solids by volume = 49.71 Viscosity = 1200 cps (Brookfield - 10 rpm) Light reflectance »0.89 [Good reflectance to light] Resistance to scraping - 25 [Good scraping resistance] Example # 4 - Filling material of minimum small particle size: % solids by volume = 49.35 Viscosity = 1200 cps (Brookfield - 10 rpm) Light reflectance «0.85 [Good reflectance to light] Resistance to scraping - 25 [Good scraping resistance] Example # 5 - having a low concentration of filler material with large particle size: % solids by volume = 49.62 Viscosity = 1200 cps (Brookfield - 10 rpm) Reflectance to light »0.90 Resistance to scraping - 20 [Low scraping resistance] Example # 6 - having a low concentration of the filler material with average particle size: % solids by volume = 49.7 Viscosity = 1200 cps (Brookfield - 10 rpm) Reflectance to light »0.83 [Low reflectance to light] Resistance to scraping «25 Example # 7 - having a low concentration of filler material with small particle size: % solids in volume = 49.7 Viscosity = 1200 cps (Brookfield - 10 rpm) Reflectance in light «0.80 [Low reflectance to light] Scrape resistance step «25 Example # 8 - having a high concentration of filler material with small particle size: % solids by volume = 49.99 Viscosity = 1800 cps (Brookfield - 10 rpm) [Too thick for proper application] Reflectance to light «0.89 Scrape resistance step« 25 It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims

l. A coating composition for roof boards characterized in that it comprises water, a binder and a filler material, the filler material contains large particles with an average particle size of a minimum of about 50 microns, these large "stew" particles present in an "effective amount" to obtain a coating composition which will produce a durable and scrap resistant coating, medium particles with an average particle size in the range of about 1.2 to about 30 microns, and small particles which have a Average particle size in the range of from about 0.1 to about 1.0 microns, small particles are present in a minimum amount of about 3% by dry solids volume, the amount is low enough to be effective in maintaining the coating composition to a vi If the viscosity is low enough for spray application, the medium size particles are present in an amount which is effective to provide the coating with the ability to produce a coating having a light reflectance of at least about 0.84, as measured by ASTM. E 1477-92.
2. The coating composition according to claim 1, characterized in that it has a large particle size in the range from about 50 to about 300 microns.
3. The coating composition according to claim 1, characterized in that it has large particles present at a concentration as low as about 15% of the volume of dry solids.
4. The coating composition according to claim 1, characterized in that it has small particles present at a concentration of from about 3 to about 25%.
5. The coating composition according to claim 1, characterized in that it has large particles present in a concentration from about 20 to about 55% of the total volume of dry solids.
6. The coating composition according to claim 1, characterized in that it has average particles present at a concentration from about 25 to about 70.
7. The coating composition according to claim 1, characterized in that it has a total solids content. in the range from about 40 to about 65%.
8. The coating composition according to claim 1, characterized in that the filler material for the large particle sizes is selected from the group consisting of: limestone, dolomite, sand and mixtures thereof.
9. The coating composition according to claim 1, characterized in that the filling material for the average particle sizes is selected from the group consisting of: limestone, dolomite, ground silica and mixtures thereof.
10. The coating composition according to claim 1, characterized in that the filler material for the small particle sizes are selected from the group consisting of: calcium carbonate, titanium dioxide, clay and mixtures thereof. The coating composition according to claim 1, characterized in that the binder is a polymer having one or more of the following monomers, vinyl acetate, vinyl propionate, vinyl butyrate, ethylene, vinyl chloride, vinylidene, vinyl fluoride, vinylidene fluoride, ethyl acrylate, methyl acrylate, propyl acrylate, butyl acrylate, ethyl methacrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl, methylacrylate, styrene, butadiene, urethane, epoxy resin , melamine and an ester. 12. The coating composition according to claim 1, characterized in that the small, medium and large filling materials can be a material selected from the group consisting of calcium carbonate, limestone, titanium dioxide, sand, barium sulfate, clay, mica, dolomite, silica, talc , pearlite, polymers, gypsum, olastonite, calcite, aluminum trihydrate, pigments, zinc oxide, zinc sulfate and mixtures thereof. 13. A coated board for the roof, characterized in that it comprises a substrate having a visual surface which has a discontinuous coating that includes a binder and a filling material, the filling material contains large particles with an average particle size of one at a minimum of about 50 microns, these large particles are present in an effective amount to obtain a coating composition which will produce a durable, scrap resistant coating, medium particles with an average particle size in the range of from about 1.2 to about 30 microns , and small particles which have an average particle size in the range from about 0.1 to about 1.0 microns, small particles are present in a minimum amount of about 3% dry solids volume, the amount is low enough to be ef Elective to maintain the coating composition at a sufficiently low viscosity for spray application, the middle particles are present in an amount which is effective to provide the coating with the ability to produce a coating having a light reflectance. less about 0.84, measured by ASTM E 1477-92. 14. The roof board, according to claim 13, characterized in that the substrate is a roof board that has a noise reduction coefficient equal to or greater than 55. 15. The board for the roof, in accordance with Claim 13, characterized in that the coating is on a thin canvas. 16. The roof board, according to claim 15, characterized in that the thin canvas is made of a material that is selected from the group consisting of cellulose, polypropylene, polyethylene, glass, polyester, polyamide and mixtures thereof.