Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-05-18
2001-11-13
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S507000, C524S538000, C524S539000, C524S588000, C524S590000, C524S591000, C524S788000, C524S839000, C524S871000, C525S123000, C525S440030, C525S457000, C525S474000, C525S478000, C525S054220, C525S054300, C525S455000, C156S331400
Reexamination Certificate
active
06316535
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to coating compositions, and more specifically to filled water-based polymeric coating compositions for substrates, such as mineral fiber boards.
BACKGROUND OF THE INVENTION
Aqueous coating compositions for substrates, such as mineral fiber boards, are becoming increasingly important for both economic and ecological reasons. It is desirable to reduce the use of volatile organic solvents, which can be harmful, resulting in an increased desire for waterborne (i.e., water-based) mixtures. There are, however, some disadvantages associated with the use of waterborne mixtures.
Disadvantages of aqueous solutions include the difficulty, in some cases, of effecting sufficient water dispersibility and solubility of the binder components of the coating composition in water. Where good dispersibility and solubility are achieved, one often encounters lowered resistance of the cured coatings to water. This is less of a problem with coating compositions that are soluble only in organic solvents. In addition, there are processing problems that result from the high viscosity of aqueous coating compositions. These problems have, in some situations, previously been overcome through the use of organic auxiliary solvents in conjunction with water. The use of these auxiliary solvents, however, dampens the economic and ecological advantages of using water in the first place.
One solution, at least as it pertains to coating mineral fiber boards, involves the use of one component waterborne, latex-based coatings. These coatings are based on waterborne latex polymers or polymer solutions including ethylene vinyl chloride, vinyl acrylic, starch, or melamine formaldehyde. Such coatings are either self-crosslinking or coalesce upon drying by use of ovens. Mineral fiber boards are typically used as ceiling tiles and serve to improve thermal and acoustic insulation.
Similarly, two component systems use crosslinking to achieve rapid curing at room temperature without the use of ovens. These two component systems, however, often take up to several hours to cure. Such a limitation on manufacturing and production methods is undesirable, and reduced processing times would be beneficial in many instances.
SUMMARY OF THE INVENTION
The present invention provides an aqueous system for coating a substrate. The system comprises two components. The first component contains a first polymer which has hydroxyl functional groups or amine functional groups and optionally a catalyst, preferably an organotin catalyst. The second component comprises a second polymer which is a polyisocyanate containing isocyanate functional groups. A filler (i.e., an extender pigment) is included in either the first component, second component, or both components. Preferably, at least one filler is incorporated in both the first component and the second component. Alternatively, the filler may only be present in one component. In the latter case the filler is present in an amount above about 50% by dry volume.
Preferably, the filler is selected from calcium carbonate, titanium dioxide, sand, clay, mica, dolomite, silica, talc, perlite, gypsum, wallastonite, aluminum trihydrate, zinc oxide, barium sulfate, zinc sulfate, and combinations thereof. The polymer of the first component is preferably selected from a polyester polyol, an acrylic polyol, a urethane polyol, a polyether polyol, a polyamine, an aldimine, a short oil alkyd, a silicone polyol, a cellulose ester, a vinyl polyol, and combinations thereof. A preferred polyamine is a polyaspartic ester.
The present invention also provides methods of coating a substrate. According to one embodiment, the method comprises the steps of applying to the substrate a first component which contains the first polymer containing hydroxyl functional groups or amine functional groups and optionally a catalyst to form a partially coated substrate. Then, a second component which contains a second polymer (which is a polyisocyanate containing isocyanate functional groups) is applied to the partially coated substrate. In another method, the second component is applied to the substrate first. Alternatively, the two components can first be mixed and the mixture applied to the substrate. Regardless of the particular method, at least one filler is preferably incorporated in both the first component and the second component. Alternatively, the filler may only be present in one component. In the latter case, the filler is present at an amount above about 50% by dry volume.
A third aspect to the present invention is the coating formed by applying to the substrate a coating system of the present invention using the methods of the present invention.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is an aqueous system for coating a substrate. The system comprises two components. The first component contains a first polymer which has hydroxyl functional groups or amine functional groups and optionally a catalyst. The second component comprises a second polymer which is a polyisocyanate containing isocyanate functional groups. Preferably, at least one filler is incorporated in both the first component and the second component. Alternatively, the filler may only be present in one component. In the latter case, the filler is present at an amount above about 50% by dry volume of that component.
The two polymer components serve as binders in known ways. For example, when the first polymer includes hydroxyl groups, the hydroxyl groups react with the isocyanate groups to form urethane groups in a crosslinked polymer. Similarly, when the first polymer includes amine groups, the amine groups react with the isocyanate groups to form urea groups in a crosslinked polymer. The first polymer can be any known compatible polymer, capable of being dispersed or dissolved in water, having hydroxyl groups or amine groups used to react with polyisocyanate to form a crosslinked polymer. For example, the first polymer may be selected from, but not limited to, a polyester polyol, an acrylic polyol, a urethane polyol, a polyamine, an aldimine, a short oil alkyd, a silicone polyol, a cellulose ester, or a vinyl polyol. A preferred formula includes the use of a polyester polyol in the first component and a polyisocyanate in the second component.
It is important that the polymers contain minimum concentration of hydroxyl or amine functionality for sufficient cross-linking to occur. A preferred equivalent ratio of isocyanate functional groups to hydroxyl or amine functional groups is in the range of about 0.1:1 to about 10:1. A more preferred equivalent ratio of isocyanate functional groups to hydroxyl or amine functional groups is in the range of about 0.5:1 to about 5:1.
The catalyst can preferably be an organo-metallic catalyst used to speed the overall curing rate. Catalysts are, of course, used in an effective amount to speed the overall curing rate. One suitable catalyst can be any long chain tertiary amine. Preferred catalysts include dibutyl-tin-laurate and zinc octoate.
In the embodiment in which at least one filler is incorporated in both components, the filler may be a mixture or a single ingredient in both components; the fillers may also be the same or different in each component. A filler can be selected from the group consisting of calcium carbonate, titanium dioxide, sand, clay, mica, dolomite, silica, talc, perlite, gypsum, limestone, wallastonite, calcite, aluminum trihydrate, zinc oxide, barium sulfate, zinc sulfate and mixtures thereof. Preferably, calcium carbonate is used, and it may either be prepared synthetically or derived from natural sources, such as from limestone or calcite. Mixtures of filler in each component will also work. In this embodiment, the fillers should be included in both components in an amount of at least about 40% by dry volume of the total system after the two component
Caldwell Kenneth G.
Fernando Raymond H.
Pidugu Vijaya K.
Armstrong World Industries Inc.
Szekely Peter
Womble Carlyle Sandridge & Rice PLLC
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