HK1182412B - Formaldehyde free coating for panels - Google Patents

Abstract

The invention provides a curable, formaldehyde free coating composition comprising a composition comprising a polyacid copolymer crosslinked with a hydroxyl group-containing compound and calcium aluminosilicate powder, panels coated with the coating composition, and a method of coating a panel with the coating composition.

Description

Formaldehyde-free coating for panels

Background

The present invention relates to polymeric or polymerizable formaldehyde-free materials for imparting sag resistance to panels, such as fibrous panels, and acoustical panels, such as ceiling tiles.

Sound-absorbing panels (or tiles) are specially designed systems intended to improve sound absorption by absorbing sound in indoor spaces (such as rooms, hallways, conference halls, etc.) and/or reducing sound transmission therein. While there are numerous types of sound absorbing panels, sound absorbing panels of the general type such as that disclosed in U.S. patent No. 1,769,519 are generally constructed of mineral wool fibers, fillers, colorants, and a binder. These materials can be used to provide, among many other substances, sound absorbing panels having desirable acoustic properties as well as other characteristics such as color and appearance.

To prepare the panel, a selected combination of fibers, fillers, extenders, binders, water, surfactants, and other additives are combined to form a slurry and processed. The cellulosic fibers are typically in the form of recycled newsprint. The extender is typically expanded perlite. Fillers may include clay, calcium carbonate, or calcium sulfate. Binders can include starch, latex, and reconstituted, cross-linked paper products to create a binding system that helps lock all ingredients into a desired structural matrix.

Organic binders such as starch are often the primary component providing structural adhesion to the panel. Starch is a preferred organic binder because, among other reasons, it is relatively inexpensive. For example, panels comprising newsprint, mineral wool, and perlite can be economically bonded together with the aid of starch. Starch imparts both strength and durability to the panel structure, but is sensitive to problems caused by moisture. Moisture can cause the panels to soften and sag, which is unsightly in the ceiling and can lead to weakening of the panels.

One method for dealing with problems caused by moisture in panels is to back coat the panels with a melamine formaldehyde resin based coating with or without a urea formaldehyde component. When such a formaldehyde resin based coating is exposed to moisture or humidity, it tends to resist the compressive forces on the back surface resulting from downward sagging motion.

When properly cured, the cured melamine formaldehyde resin has a rigid and brittle cross-linked structure. This rigid structure acts to resist compressive forces on the back surface resulting from downward sagging motion. However, formaldehyde resins tend to emit formaldehyde, a known environmental irritant.

To reduce formaldehyde emissions, formaldehyde reactive materials (such as urea) have been added to scavenge free formaldehyde. Unfortunately, such small molecule scavengers end-cap the reactive groups of the formaldehyde resin, which prevents significant levels of crosslinking from occurring. As a result, a characteristic highly crosslinked polymer structure is never formed. The resulting coating is weak and will not resist sagging.

While there are a number of commercially available acoustical panel products classified as low Volatile Organic Chemical (VOC) emitters, these products emit detectable levels of formaldehyde due to the presence of a variety of different formaldehyde emitting components used in these panels. Although formaldehyde emissions produced during thermal exposure in the manufacturing process can be vented into the chimney or thermal oxidizer, the resulting product will still contain residual formaldehyde, which is emitted upon installation. In those locations where sound absorbing panels are installed (such as public buildings, including schools, healthcare facilities, or office buildings), the reduction of formaldehyde emissions or elimination of such emissions would provide improved indoor air quality.

What is needed is a coating that can counteract the moisture sensitivity of these panels without emitting environmental irritants.

Brief summary of the invention

The present invention provides a curable, formaldehyde-free coating composition for use in coating acoustic panels. The coating composition comprises (i) a composition comprising (a) a polyacid copolymer comprising at least two carboxylic acid groups, anhydride groups, or salts thereof, (b) a hydroxyl group-containing compound bearing at least two hydroxyl groups, and (c) a phosphorus-containing catalyst; and (ii) a calcium alumino silicate powder having a total alkali content of less than about 2wt.%, based on the total weight of the calcium alumino silicate powder, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said hydroxyl groups is from about 1/0.01 to about 1/3.

The present invention further provides a coated panel comprising: (a) a panel having a backing side and an opposite facing side; and (b) a formaldehyde-free coating layer supported by the backing side of the panel, the coating layer comprising: (i) a composition comprising (a) a polyacid copolymer comprising at least two carboxylic acid groups, anhydride groups, or salts thereof, (b) a hydroxyl group-containing compound having at least two hydroxyl groups as a separate compound, and (c) a phosphorus-containing catalyst; and (ii) a calcium alumino silicate powder having a total alkali content of less than about 2wt.%, based on the total weight of the calcium alumino silicate powder, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said hydroxyl groups is from about 1/0.01 to about 1/3.

The invention further provides a method of coating a panel comprising: (i) providing a panel having a backing side and an opposite facing side; and (ii) applying directly or indirectly to the backing side of the panel a curable, formaldehyde-free coating composition comprising (a) a polyacid copolymer comprising at least two carboxylic acid groups, anhydride groups, or salts thereof; (b) a hydroxyl group-containing compound having at least two hydroxyl groups as an independent compound; and (c) a phosphorus-containing catalyst; and (b) a calcium alumino silicate powder having a total alkali content of less than about 2wt.%, based on the total weight of the calcium alumino silicate powder, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said hydroxyl groups is from about 1/0.01 to about 1/3.

Brief description of several views of the drawings

Fig. 1 schematically illustrates a perspective view of a coated panel having a back-side coating, according to an embodiment of the invention.

Detailed description of the invention

The present invention is directed to a curable, formaldehyde-free coating composition comprising a composition and a calcium aluminosilicate powder. The composition comprises (a) a polyacid copolymer comprising at least two carboxylic acid groups, anhydride groups, or salts thereof, (b) a hydroxyl group-containing compound bearing at least two hydroxyl groups, and (c) a phosphorus-containing catalyst; and (ii) a calcium alumino silicate powder having a total alkali content of less than about 2wt.%, based on the total weight of the calcium alumino silicate powder, wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said hydroxyl groups is from about 1/0.01 to about 1/3.

The present invention was predicated, at least in part, on the unexpected and unexpected discovery of a curable coating composition that helps impart strength and sag resistance to panels (with particular application in panels), is formaldehyde-free. The inventors have found that certain polymeric binders and back-coats used in surface treatments inherently contain, release, emit or generate formaldehyde. In addition, additives such as wet preservatives or biocides included in surface treatments and backcoatings can also release, emit, or produce detectable and quantifiable levels of formaldehyde. Thus, while formaldehyde may not be a component of the polymeric binder or biocide as used in the acoustic panel, the inventors have surprisingly discovered that the panel may still release, emit, or generate formaldehyde for a number of reasons, including, for example, degradation of the polymeric binder and/or biocide. Advantageously, the present invention provides a coating that provides sufficient rigidity to impart strength and avoid sagging, while at the same time avoiding formaldehyde emissions, thereby improving indoor air quality.

The coating composition of the present invention is suitable for coating the front and/or back side of a panel, such as a fibrous panel (e.g., an acoustic panel such as a ceiling tile). The coating composition of the present invention may be used with sound absorbing panels known in the art and prepared by methods known in the art, including from a single type of sound absorbing panelAcoustical panels prepared by aqueous felting, e.g. autoratoneCeiling tiles (USG IORs, Inc.) together with acoustical panels prepared by wet slurry molding or casting, such as ACOUSTONECeiling tiles (USG interlaors, Inc.). For example, sound absorbing panels and their preparation are described in, for example, U.S. Pat. Nos. 1,769,519, 3,246,063, 3,307,651, 4,911,788, 6,443,258, 6,919,132, and 7,364,015, each of which is incorporated herein by reference.

The formaldehyde-free composition includes a polyacid copolymer including at least two carboxylic acid groups, anhydride groups, or salts thereof. Without wishing to be bound by any particular theory, it is believed that the composition described herein acts as a binder for the calcium alumino silicate powder and is referred to herein as a binder composition. Preferably, the compound is a carboxylated acrylic polymer. The polyacid must be sufficiently nonvolatile that it will remain substantially available for reaction with the polyol in the composition during the heating and curing operation. The polyacid may be a compound having a molecular weight of less than 1000 or it may be an addition polymer or oligomer (including, e.g., polymerized units, carboxylic acid-functional monomers) containing at least two carboxylic acid groups, anhydride groups, or salts thereof, such as, for example, citric acid, butane tricarboxylic acid, and cyclobutanetetracarboxylic acid. Other suitable carboxylic acid group containing monomers include, for example, methacrylic acid, acrylic acid, crotonic acid, fumaric acid, maleic acid, 2-methyl maleic acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid, 2-methyl itaconic acid, alpha-methyleneglutaric acid, monoalkylmaleic acid, and monoalkylfumaric acid, and salts thereof. Suitable anhydride group-containing monomers include, for example, maleic anhydride, itaconic anhydride, acrylic anhydride, and methacrylic anhydride, and salts thereof.

Preferably, the adhesive composition comprises a compound containing carboxylic acid groups, and more preferably, the adhesive composition comprises a compound containing methacrylic and/or acrylic acid groups. Such carboxylic acid group-containing compounds can include any suitable amount of monomers, including carboxylic acid groups, anhydride groups, or salts. Typically, the compound comprises about 1% or more, such as about 2% or more, or about 5% or more, or about 10% or more, or about 20% or more, or 30% or more, based on the weight of the polymer, of monomers comprising carboxylic acid groups, anhydride groups, or salts. Alternatively or additionally, the compound includes about 99% or less, such as about 98% or less, or about 95% or less, or about 90% or less, or about 80% or less, monomers including carboxylic acid groups, anhydride groups, or salts, based on the weight of the polymer. Thus, the carboxylic acid group-containing compound can include monomers comprising carboxylic acid groups, anhydride groups, or salts in an amount that is constrained by any two of the above endpoints recited for the monomers. For example, such compounds containing carboxylic acid groups can include about 1% to about 99%, about 2% to about 98%, about 5% to about 95%, or about 10% to about 90% of monomers comprising carboxylic acid groups, anhydride groups, or salts, based on the weight of the polymer.

The adhesive composition further includes a hydroxyl group-containing compound having at least two hydroxyl groups. The hydroxyl group-containing compound may be present as a separate compound in the curable adhesive composition or may be incorporated into the polyacid copolymer backbone. The hydroxyl group-containing compound can be any suitable polyol that is sufficiently nonvolatile that it will remain substantially available for reaction with the polyacid in the composition during heating and curing. The polyol desirably is a compound having a molecular weight of less than about 1000, the compound bearing at least two hydroxyl groups, such as, for example, ethylene glycol, glycerol, pentaerythritol, trimethylolpropane, sorbitol, sucrose, glucose, resorcinol, catechol, pyrogallol, glycolated urea, 1, 4-cyclohexanediol, diethanolamine, triethanolamine and certain reactive polyols, such as, for example, beta-hydroxyamines, such as, for example, bis- [ N, N-bis (. beta. -hydroxyethyl) ] adipamide, as may be prepared according to the teachings of U.S. Pat. No. 4,076,917, or it may be an addition polymer containing at least two hydroxyl groups, such as, for example, polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, and homopolymers or copolymers of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and the like. Preferably, the hydroxyl group-containing compound is a hydroxyl group-containing amine selected from the group consisting of: diisopropanolamine, 2- (2-aminoethyl) ethanolamine, triethanolamine, tris (hydroxymethyl) aminomethane, and diethanolamine.

The polyacid copolymer is polyesterified with a hydroxyl group-containing compound to form a formaldehyde-free composition as a polyester. The ratio of the number of equivalents of the carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of the hydroxyl groups is from about 1/0.01 to about 1/3 (e.g., from about 1/0.05 to about 1/2.5, or about 1/0.1 to about 1/2).

The binder composition further includes a phosphorus-containing catalyst. The phosphorus containing catalyst may be any suitable compound. Preferably the phosphorus containing catalyst is selected from the group consisting of: alkali metal hypophosphite (such as sodium hypophosphite, for example), alkali metal phosphate (such as sodium phosphate, for example), alkali metal polyphosphate, alkali metal dihydrogen phosphate, polyphosphoric acid, C_1-22Alkyl phosphinic acids, or various combinations thereof.

Preferably, the adhesive composition is an Aquaset available from Dow Chemical Co. (Dow Chemical Co., Ltd.) (Midland, MI)^TMA polymer. More preferably, the binder composition is Aquaset available from Dow Chemical Co^TM600 polymer.

In other embodiments, the phosphorus-containing catalyst is an oligomer or polymer bearing phosphorus-containing groups, such as, for example, an oligomer or polymer of acrylic acid and/or maleic acid formed in the presence of sodium hypophosphite; addition polymers such as, for example, the copolymer component of the present invention prepared from ethylenically unsaturated monomers in the presence of a phosphonium salt chain transfer agent or terminator; and addition polymers containing acid functional monomer residues, such as, for example, copolymerized phosphoethyl methacrylate, and similar phosphonates and copolymerized vinyl sulfonic acid monomers and their salts. In one embodiment of the invention, the hydroxyl-containing compound and the phosphorus-containing compound are present in the same addition polymer. Preferably, such phosphorus-containing catalysts may be used at a level of about 0wt.% or more, for example about 5wt.% or more, or about 10wt.% or more, based on the weight of the oligomer or polymer. Alternatively or additionally, the phosphorus-containing catalyst may be used at a level of about 40wt.% or less, for example about 35wt.% or less, or about 30wt.% or less, or about 25wt.% or less, or about 20wt.% or less, based on the weight of the oligomer or polymer. Thus, the phosphorus-containing catalyst may be used at a level constrained by any two of the above endpoints recited for the phosphorus-containing catalyst. For example, the phosphorus-containing catalyst may be used at a level of from about 0wt.% to about 40wt.%, e.g., from about 0wt.% to about 30wt.%, from about 0wt.% to about 20wt.%, or from about 0wt.% to about 10wt.%, based on the weight of the oligomer or polymer.

In addition to the curable formaldehyde-free binder composition, the coating composition of the present invention includes a powder comprising, consisting essentially of, or consisting of a calcium aluminosilicate powder. As used herein, the term "glass powder" or "glass filler" is intended to mean one or more powders including powders comprising, consisting essentially of, or consisting of calcium aluminosilicate powder. The calcium aluminosilicate powder may be any suitable calcium aluminosilicate powder. The desirable calcium aluminosilicate powders provide chemical inertness with very low oil and water absorption. While not wishing to be bound by theory, applicants believe that the low water absorption characteristic allows for higher loading levels of calcium aluminosilicate powder filler in the coating composition without an excessive increase in viscosity. Suitable calcium aluminosilicate powders include powders made from glass fibers (e.g., glass fibers recovered from post-industrial glass feedstocks). Preferably, the calcium alumino silicate powder has a total alkali content of less than about 2wt.% (e.g., E-glass), based on the total weight of the calcium alumino silicate powder. Desirably, the calcium aluminosilicate powder does not comprise a substantial amount, or any amount, of chopped calcium aluminosilicate fibers such that the calcium aluminosilicate powder has an average aspect ratio of about 5:1 or less, preferably about 3:1 or less, or more preferably about 2:1 or less (e.g., about 1.5:1 or less).

The calcium alumino-silicate powder may have any suitable median particle size and/or surface area. Typically such calcium alumino-silicate powders have a median particle size of about 250 microns or less, preferably 100 microns or less, and more preferably 20 microns or less (e.g., about 15 microns or less, or about 10 microns or less). Such calcium alumino-silicate powders desirably have about 1m²G to about 3m²A surface area per gram and preferably about 1.2m²G to about 2.4m²Surface area in g. While not wishing to be bound by theory, applicants believe that the finely dispersed abrasive powder provides higher surface area for maximum interaction with the coating binder, enhances and improves the mechanical properties of the curable coating composition, and increases the stiffness and strength of the thin film coating (once applied to the panel), thereby improving sag resistance.

The coating composition may optionally further comprise one or more components selected from the group consisting of: dispersants, mineral fillers, pigments, surfactants, pH modifiers, buffers, viscosity modifiers, stabilizers, defoamers, flow modifiers, and various combinations thereof.

Is suitable forDispersants include, for example, tetrapotassium pyrophosphate (TKPP) (FMC Corp.), sodium polycarboxylates such as Tamol731（Rohm&Haas), and nonionic surfactants such as Triton^TMCF-10 alkylaryl polyether (Dow chemical). Preferably, the coating composition includes a surfactant selected from the group consisting of nonionic surfactants (e.g., Triton)^TMCF-10 alkylaryl polyether (Dow chemical)).

Suitable mineral fillers (in addition to the calcium aluminosilicate powders discussed above) include, for example, brighteners, clays (e.g., kaolin), mica, sand, barium sulfate, silica, talc, gypsum, wollastonite, zinc oxide, zinc sulfate, hollow beads, bentonite salts, or mixtures thereof. Preferably, the coating composition does not contain mineral fillers (e.g., the coating composition does not contain mica). However, if desired, mineral fillers such as mica may be included in the composition, either alone or in combination with another filler (such as the calcium aluminosilicate powder described herein). If included in some embodiments of the coating composition, the mica can have a particle size of about 250 microns or less, preferably 100 microns or less, and more preferably 20 microns or less (e.g., about 15 microns or less, or about 10 microns or less).

Suitable pigments include conventional pigments familiar to those of ordinary skill in the art. Care must be taken to avoid pigments that would raise the pH of the coating and thus inhibit the binder from curing. Preferably, the coating composition is uncolored when used as a backcoating to promote sag resistance.

Suitable surfactants are preferably nonionic surfactants. Non-limiting examples of suitable nonionic surfactants include ethoxylated nonylphenols, such as IgepalCO-630 (Rhodia Canada, Inc.) in Rodiya, Canada).

Suitable pH modifiers and buffers include sulfuric acid and phosphoric acid and various combinations thereof. These additives are designed to provide a suitable pH environment for curing of the adhesive. Preferably, the coating composition includes a pH modifier selected from either sulfuric acid or phosphoric acid.

Suitable viscosity modifiers include hydroxyethyl cellulose such as Natrosol(Hercules, Inc.), carboxymethylcellulose (CMC), sodium bentonite (Volclay), kaolin, e.g., as Snowbrite Clay (Whittaker, Clark)&Daniels), and various combinations thereof.

Suitable defoamers include oil-based defoamers such as Hi-Mar DFC-19 (Hi-Mar Specialties, Inc.).

The binder composition is formaldehyde-free. As used herein, "formaldehyde-free" means that the binder composition is not made with formaldehyde or formaldehyde-generating chemicals and does not release formaldehyde under normal use conditions. Desirably, the coating composition comprising the formaldehyde-free binder composition is also formaldehyde-free, or at least substantially formaldehyde-free. The term "substantially free of formaldehyde" is defined to mean that an incidental or background amount of formaldehyde (e.g., less than 100 ppb) may be present in the coating composition and is within the scope of the present invention.

The amount of formaldehyde present in the coating composition can be determined according to ASTM D5197 by heating the dried coated sample to 115 ℃ in a humidified Markes microchamber and then collecting emissions under controlled conditions using a 2, 4-Dinitrophenylhydrazine (DNPH) sampling tube (cartridge). After exposure, the DNPH sample tube was washed with acetonitrile, the acetonitrile wash was diluted to a volume of 5ml, and the sample was analyzed by liquid chromatography. Results are reported in μ g/mg of coated sample and compared to a control sample. Samples that were within experimental error of the control sample over a significant set of tests were substantially formaldehyde free.

The coating composition can include any suitable amount of the formaldehyde-free binder composition. Preferably, the coating composition comprises about 10wt.% or more, for example about 15wt.% or more, or about 20wt.% or more, or about 30wt.% or more of the formaldehyde-free binder composition, based on the total weight of the dry components of the coating composition. Alternatively or additionally, the coating composition comprises about 60wt.% or less, for example about 55wt.% or less, or about 50wt.% or less, of the formaldehyde-free binder composition based on the total weight of the dry components of the coating composition. Thus, the coating composition can include the formaldehyde-free binder composition in an amount that is constrained by any two of the above endpoints recited for the formaldehyde-free binder composition. For example, the coating composition can include about 10wt.% to about 60wt.%, about 20wt.% to about 55wt.%, or about 20wt.% to about 50wt.% of the formaldehyde-free binder composition, based on the total weight of the dry components of the coating composition. In addition, the coating composition can include any suitable amount of calcium aluminosilicate powder. Preferably, the coating composition comprises about 5wt.% or more, for example about 10wt.% or more, or about 20wt.% or more, or about 30wt.% or more, of calcium aluminosilicate powder, based on the total weight of the dry components of the coating composition. Alternatively or additionally, the coating composition comprises about 80wt.% or less, for example about 70wt.% or less, or about 65wt.% or less, of calcium aluminosilicate powder, based on the total weight of the dry components of the coating composition. Thus, the coating composition may include the calcium aluminosilicate powder in an amount constrained by any two of the above endpoints recited for the calcium aluminosilicate powder. For example, the coating composition may comprise about 30wt.% to about 80wt.%, about 35wt.% to about 75wt.%, or about 40wt.% to about 75wt.% calcium aluminosilicate powder, based on the total weight of the dry components of the coating composition.

The curable coating composition can be prepared by mixing the binder composition, calcium aluminosilicate powder, and other optional components using conventional mixing techniques. Typically, the coating particles or solids are suspended in an aqueous carrier. Typically, the adhesive composition is added to and mixed with the aqueous carrier, followed by other optional components in descending order according to the amount of dry wt.%. Desirably, calcium aluminosilicate powder is added to the mixture to ensure that the powder is properly wetted.

The solids content of the coating composition of the present invention can be as high as is practical for a particular application. For example, one limiting factor with respect to the choice and amount of liquid carrier used is the viscosity obtained with the desired amount of solids. Thus, spraying is most sensitive to viscosity, while other methods are less sensitive. An effective range for the solids content of the coating composition is about 15% or more, for example about 20wt.% or more, or about 25wt.% or more, or about 30wt.% or more, or about 35wt.% or more, or about 40wt.% or more, or about 45wt.% or more. Alternatively or additionally, the solids content of the coating composition is about 90wt.% or less, or about 85wt.% or less, or about 80wt.% or less, or about 75wt.% or less. Thus, the solids content of the coating composition can be constrained by any two of the above endpoints recited for the solids content of the coating composition. For example, the solids content of the coating composition may be from about 15wt.% to about 90wt.%, from about 35wt.% to about 80wt.%, or from about 45wt.% to about 75 wt.%.

The present invention is further directed to a panel (e.g., an acoustic panel) coated with the coating composition of the present invention. A coated panel 10 according to one aspect of the invention, as schematically illustrated in fig. 1, includes a panel core 20 having a backing side 30 and a facing side 40. The panel may optionally further include a backing layer 35 in communication with the backing side 30, and/or a facing layer 45 in communication with the facing side 40. A back coating layer 50 is in communication with the backing side 30 or optional backing layer 35. Optionally, a further front coating layer 60 is in communication with the facing side 40 or the optional facing layer 45.

The backside coating layer 50 counteracts the sagging force of gravity in wet conditions, thus applying this layer to the backing side 30 of the panel core 20 (or the backing layer 35 if present). The backing side 30 may be the side directed to forced ventilation on a panel in a suspended ceiling tile system. The coated panel 10 may be an acoustic panel for sound attenuation. One illustrative procedure for producing the panel core 20 is described in U.S. patent No. 1,769,519. In one aspect, the panel core 20 includes a mineral wool fiber and a starch, wherein the mineral wool fiber may include fibers such as slag wool, rock wool, and/or basalt wool. In another aspect of the invention, the starch component may be starch gel, which acts as a binder for mineral wool fibers, as disclosed in U.S. Pat. Nos. 1,769,519, 3,246,063 and 3,307,651. In another aspect of the present invention, the panel core 20 may comprise a fiberglass panel.

The panel core 20 of the coated panel of the present invention may also include a variety of other additives and agents. For example, the panel core 20 can include a calcium sulfate material (e.g., stucco, gypsum, and/or anhydrite), boric acid, and Sodium Hexametaphosphate (SHMP). Kaolin and guar gum can replace stucco and boric acid when making acoustical tiles.

The core of the coated panel of the present invention can be prepared using a variety of techniques. In one embodiment, the panel core 20 is prepared by a wet felting or water felting process, as described in U.S. patent nos. 4,911,788 and 6,919,132. In another embodiment, the panel core 20 is prepared by combining starch and additives in water and mixing to provide a slurry. The slurry is heated to cook the starch and produce a starch gel, which is then mixed with the mineral wool fibers. The combination of gel, additive, and mineral wool fibers (known as "pulp") is metered into a plurality of trays in a continuous process. Metering into itThe bottom of the tray into which the pulp is added may optionally contain a backing layer 35 (e.g., bleached paper, unbleached paper, or kraft-backed aluminum foil, hereinafter referred to as kraft/aluminum foil) that is used to help release material from the tray, but remains as part of the final product. The surface of the pulp may be patterned and the trays containing the pulp may be subsequently dried, for example by conveying them through a convection tunnel dryer. The dried product or slab may then be fed into a finishing line where it is cut to size to provide panel cores 20. The panel core 20 may then be converted into a panel of the present invention by applying the coating composition of the present invention. The coating composition is preferably applied to the panel core 20 after the core has been formed and dried. In yet another embodiment, the panel core 20 is prepared according to the method described in U.S. patent 7,364,015, which is incorporated herein by reference. Specifically, the panel core 20 includes a sound-absorbing layer that includes a composite gypsum of interlocking matrices, which may be a unitary layer or may be a multi-layer composite. Desirably, the panel core 20 is prepared on a conventional gypsum wallboard manufacturing line in which a ribbon of the acoustical panel precursor is formed by casting a mixture of water, calcined gypsum, foaming agent, and optionally cellulosic fibers (e.g., paper fibers), lightweight aggregate (e.g., expanded polystyrene), binder (e.g., starch, latex), and/or reinforcing material (e.g., sodium trimetaphosphate) on a conveyor belt. In a preferred embodiment, the panel core comprises a backing sheet (e.g., paper, metal foil, or combinations thereof), a precursor (including calcined gypsum and having at least about 35 lbs/ft) that may optionally be coated with a scrim layer (e.g., paper, woven or non-woven fiberglass), and/or a densified layer³Density of (d). In yet another embodiment, the panel core 20 is prepared according to a wet felting process. In the wet felting process, an aqueous solution of the material (including mineral wool, expanded perlite, starch, and minor amounts of additives) that will form the panelThe slurry is placed on a moving wire screen, such as a fourdrinier or cylinder former. A wet mat is formed by dewatering the aqueous slurry by gravity and then optionally by vacuum suction on the wire screen of a fourdrinier paper machine. The wet mat is pressed to a desired thickness between press rolls for additional dewatering. The pressed felt was dried in an oven and then cut to produce an acoustic panel. The panel core 20 may then be converted into a panel of the present invention by applying the coating composition of the present invention. The coating composition is preferably applied to the panel core 20 after the core has been formed and dried.

In another embodiment, the panel core 20 may include one or more formaldehyde-free biocides as a preservative, as described in U.S. patent application publication 2007/0277948a1, which is incorporated herein by reference. Suitable formaldehyde-free biocides include 1, 2-benzisothiazolin-3-one as ProxelGXL or ProxelCRL（ARCH Chemicals）、Nalcon （Nalco）、Canguard^TMBIT (Dow chemical), and Rocima^TM BT 1S（Rohm&Haas). Other isothiazolin-3-ones include various blends of 1, 2-benzisothiazolin-3-one and 2-methyl-4-isothiazolin-3-one asMBS (Acti-Chem) is available. Additional isothiazolin-3-ones include 5-chloro-2-methyl-4-isothiazolin-3-one, and blends thereof. The blend of 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one is as Kathon^TM LX（Rohm & Haas）、K14 (Troy Chemical), and251 (Drew Chemical). Another suitable formaldehyde-free biocide includes Zinc 1-hydroxy-2 (1H) -pyrithione, as zincs(ARCH Chemicals) are available and are preferably effective in both the dry and wet states. Zinc 1-hydroxy-2 (1H) -pyrithione may also be used with Zinc oxide as ZincEmulsions are available. Other suitable formaldehyde-free biocides include 2-n-octyl-4-isothiazolin-3-one as Kathon^TM893 andM-8（Rohm&haas) and 2- (4-thiazolyl) -benzimidazoles asTK-100 (LanXess).

As discussed above, coated panels according to the present invention may optionally include a backing layer 35. A wide variety of materials may be used for the backing layer 35 including unbleached paper, bleached paper, kraft/aluminum foil, and the like. A flame retardant backcoating may optionally be applied in combination with a bleached or unbleached paper backing to improve the surface burn characteristics of these products. The flame retardant backcoating may include components such as, for example, water, flame retardants, and biocides. The backing layer 35 may also be used to improve sag resistance and/or sound control. In addition, a filler coating or a plurality of filler coatings may also be applied to the backing layer 35. The filled coating may include components such as, for example, water, fillers, binders, and various other additive types, such as defoamers, biocides, and dispersants.

In one embodiment of the present invention, the coating composition of the present invention further comprises one or more components selected from the group consisting of: dispersants, organic fillers, mineral fillers, pigments, surfactants, pH modifiers, buffers, viscosity modifiers, stabilizers, defoamers, flow modifiers, and combinations thereof.

A further embodiment of the present invention includes a method of coating a panel comprising the steps of applying the coated composition. The coating composition may be applied to one or more surfaces of a panel, preferably an acoustical panel or acoustical tile substrate, using a variety of techniques known and available to those of ordinary skill in the art. Such techniques include, for example, airless spray systems, air-assisted spray systems, and the like. The coating may be applied by such methods as roll coating, flow coating, spray coating, curtain coating, extrusion, knife coating, and various combinations thereof. An effective range for such coating application rates is from about 2g/ft on a dry basis²To about 200g/ft²From 3g/ft²About to about 20g/ft²And from about 4.0g/ft²To about 10g/ft². In one embodiment, the coating composition of the present invention is applied to the backing layer 30 of the panel. In another embodiment, the coating composition of the present invention is applied to the backing layer 35 of the panel.

After the curable coating composition of the present invention has been applied to the panel, it is heated to complete drying and curing. Drying the resulting product removes any water used as a carrier for the coating composition or any of its components and converts the polymeric binder into a structural, rigid network to provide a surface treatment. "curing" herein refers to a chemical or morphological change sufficient to alter the properties of the polymer, such as, for example, by covalent chemical reaction, ionic interaction or aggregation, improved adhesion to the faceplate, phase transformation or inversion, hydrogen bonding, and the like.

The duration and temperature of the heating will affect the drying rate of the heated substrate, the ease of processing and handling, and the development of properties. The heat treatment may be performed at from about 100 ℃ to about 400 ℃ (e.g., about 175 ℃ to about 370 ℃, or about 200 ℃ to about 215 ℃) for a period of time from about 3 seconds to about 15 minutes. For acoustic panels, treatment at 175 ℃ to 280 ℃ is preferred. Overall, a coating surface temperature of about 200 ℃ indicates complete cure.

If desired, drying and curing may be accomplished in two or more distinct steps. For example, the curable coating composition may be first heated at a temperature and for a period of time sufficient to substantially dry but not substantially cure the composition, and then heated at a higher temperature for a second period of time and/or for a longer period of time to complete the cure. Such a procedure, called "B-staging", can be used to provide coated panels according to the present invention.

The coated panels of the present invention have increased resistance to permanent deformation (sag resistance). Desirably, the coated panels of the present invention have a sag resistance of less than about 0.4 inches per two feet of length of the coated panel, preferably less than about 0.3 inches per two feet of length of the coated panel, and more preferably less than about 0.2 inches per two feet of length of the coated panel, as determined according to ASTM C367-09.

The coated panel of the present invention is desirably substantially formaldehyde free, meaning that it meets the special environmental requirements of High Performance school associates (Collaparity for High Performance school) 01. sup. thOne level of 350 knots to release or emit formaldehyde. To be considered substantially formaldehyde free, the coated panel should provide 16.5 μ g/m³Or a lesser calculated formaldehyde concentration.

The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.

Example 1

This example demonstrates the sag resistance characteristics of an acoustical panel prepared and coated with one of the coating compositions of the present invention.

In this example, a series of coated acoustic panels were produced and the sag resistance was tested. A first panel was prepared using a conventional melamine formaldehyde binder and used as a control (composition 1A). The next four panels were prepared using a coating composition comprising a formaldehyde-free binder composition comprising Aquaset600 polymeric binder (Dow Construction Polymers) incorporates one of four different calcium aluminosilicate powders: having a median particle size of 7.27 microns and 2.1m²LA-7 of surface area/g^TM(Vitro Minerals) glass powder (composition 1B); LA100^TM(Vitro Minerals) glass powder (composition 1C); having a median particle size of 10.46 microns and 1.2m²LA300 of surface area/g^TM(Vitro Minerals) glass powder (composition 1D); has a median particle size of 7.04 microns and 2.1m²LA400 of surface area/g^TM(Vitro Minerals) glass powder (composition 1E). The compositions of each of these coatings are listed in table 1A.

TABLE 1A

Each composition was applied to an acoustical panel (pressed 2310 Auratone without a coating or other finishing step applied) using a two-step application methodBase felt), the two-step application method consisting of: first (at 18 g/ft)²) Apply 12g of coating and then (at 18 g/ft)²) 6g of paint was applied. The resulting coating was cured at 260 ℃ for 10 minutes. All coating compositions (1B-1E) of the present invention have coating applications and sag resistance properties equal to or better than the melamine formaldehyde control (1A). The sag resistance properties of each panel were measured according to ASTM C367-09 after three cycles of 40 ℃/95% humidity for 12 hours followed by 21 ℃/50% humidity for 12 hours. The sag resistance was measured as the Total Movement (TM) of the panel and the position relative to the plane (PRFP). Table 1B summarizes these characteristics.

TABLE 1B

These data demonstrate that coating compositions according to the present invention comprising formaldehyde-free binder compositions in combination with calcium aluminosilicate powder provide sag resistance characteristics equal to or better than conventional melamine formaldehyde compositions.

Example 2

This example demonstrates the effect of cure temperature on the sag performance of a coating composition according to one embodiment of the present invention.

By applying a coating composition to four 7.6cm x 61cm wet felted test strips (no coating or no other finish applied)Pressed 2310 Auratone for process stepBase mat) to prepare four test strips. The coating composition included 203.7g of Aquaset^TMPolymer adhesive (Dow Construction Polymers) and 158.1g of LA-7^TMGlass powder (Vitro Minerals), 1.38g of Triton CF-10 surfactant (Dow Chemical), 5.50g of Snowbrite^TMclay (Unimin), and 71.30g of water.

The coating composition was applied using a Devilbiss JGA-510 spray gun at 130g/m²Is applied on a 7.6cm x 61cm wet felted test strip. The test strips were dried in an oven at approximately 135 ℃ for 20-30 minutes.

The sag resistance properties of the individual strips were measured according to ASTM C367-09 after three cycles of 40 ℃/95% humidity for 12 hours followed by 21 ℃/50% humidity for 12 hours. One set of six bars was heat treated after initial drying at 135 ℃ for 20-30 minutes. Two strips were tested without additional heating, two strips were heat treated at 177 ℃ for 10 minutes and two strips were heat treated at 177 ℃ for 20 minutes. The second set of six bars was heat treated at 204 ℃ for 0, 10 and 20 minutes, respectively. The anti-sag effect is measured as Total Movement (TM) and position relative to a plane (PRFP). The total shift (TM) of these bar results is listed in table 2A and the position relative to the plane (PRFP) is listed in table 2B.

TABLE 2A (Total Mobile)

TM after 0 min at 177 deg.C	4.69cm
		TM after 10 min at 177 deg.C	4.02cm
TM after 20 minutes at 177 deg.C	2.12cm
		TM after 0 min at 204 ℃	4.47cm
TM after 10 minutes at 204 ℃	1.33cm
		TM after 20 minutes at 204 ℃	1.20cm

TABLE 2B (position relative to flat surface)

PRFP after 0 min at 177 ℃	4.80cm
		PRFP after 10 min at 177 ℃	3.92cm
PRFP after 20 min at 177 ℃	2.21cm
		PRFP after 0 min at 204 ℃	4.58cm
PRFP after 10 minutes at 204 ℃	1.69cm
		PRFP after 20 minutes at 204 ℃	1.47cm

As is clear from these results listed in tables 2A and 2B, the test strips cured at 204 ℃ for 10 minutes exhibited approximately 33% and 43% of the total movement and position relative to a flat surface of the test strips cured at 177 ℃ for 10 minutes. The test strips cured at 204 ℃ for 20 minutes exhibited approximately 57% and 66% of the total movement and position relative to the plane of the test strips cured at 177 ℃ for 20 minutes.

Example 3

This example demonstrates the effect of the particle size of the glass filler on the sag performance of a coating composition according to one embodiment of the invention.

Four coating compositions (compositions 3A-3D) were prepared. Compositions 3A-3D each included 1.50wt.% of a nonionic alkylaryl polyether surfactant (Triton)^TMCF-10, Dow), 0.40wt.% hydroxyethyl cellulose (Cellosize)^TMQP-4400H, Dow Chemical), 1.20wt.% bentonite (Vollclay)^TMAmerican Colloid Company (American Colloid Company)), 6.00wt.% air-separated kaolin (Snowbrite)^TMclay, Unimin), and 40.0wt.% (on a solids basis) of Aquaset^TM600 polymer binder (Dow Construction Polymers). Compositions 3A-3D further included 50.90wt.% of one of the following four glass fillers: composition 3A, LA-7 (Vitro)Minerals), particle size of 10.5 μm; composition 3B, Amerifake ACFT1-300 (ISORCA), particle size 72.1 μm; composition 3C, Grainger 325 mesh (Glass Resources, Inc.), particle size 77.7 μm; and composition 3D, Trivitro^TMVG200, particle size 31.4 μm. The balance of compositions 3A-3D (to achieve a 45% solids coating) was water.

The coating composition was applied to the test panels using a Devilbiss JGA-510 spray gun at an application rate on a wet basis onto 7.6cm x 61cm wet felted test strips as listed in table 3. The coated test strips were then dried in an oven at approximately 135 ℃ and then cured at 177 ℃ for 20 minutes.

The sag resistance properties of each panel were measured according to ASTM C473-95 after three cycles of 12 hours at 40 ℃/95% humidity followed by 12 hours at 21 ℃/50% humidity. The sag resistance was measured as the Total Movement (TM) of the panel and the position relative to the plane (PRFP). The actual coating application, the total movement of the panel, and the final position relative to the plane are listed in table 3.

TABLE 3

As is clear from the results set forth in table 3, composition 3A (which contained glass filler having a particle size of 10.5 μm) exhibited less total movement of the panel and less position relative to the plane (indicating a flatter bar) than compositions 3B, 3C, or 3D (which contained glass filler having particle sizes of 72.1, 77.7 μm, and 31.4 μm, respectively).

Example 4

This example demonstrates that the sag resistance varies with the resin loading of a coating composition according to one embodiment of the present invention.

Seven coating compositions (compositions 4A-4G) were prepared. Compositions 4A-4G each included 1.50wt.% of a nonionic alkylaryl polyether surfactant (Triton)^TMCF-10, Dow), 0.40wt.% hydroxyethyl cellulose (Cellosize)^TMQP-4400H, Dow Chemical), 1.20wt.% bentonite (Vollclay)^TMAmerican Colloid Company (American Colloid Company)), 6.00wt.% air-separated kaolin (Snowbrite)^TMclay, Unimin), a resin (Aquaset)^TM600 polymer binder, Dow Construction Polymers, and glass fillers (LA-7, Vitro Minerals), with the balance being water to achieve a coating of 45% solids. Table 4A lists the compounds formed by Aquaset^TM600 the amount of solids provided by the polymer binder and the amount of glass filler are expressed as wt.%, based on the total weight of these compositions.

TABLE 4A

The coating composition was applied at one application rate to two 7.6cm x 61cm wet felted test strips using a Devilbiss JGA-510 spray gun as listed in table 4B. The coated test strips were then dried in an oven at approximately 135 ℃ and cured at 177 ℃ for 20 minutes.

The sag resistance properties of each bar were measured according to ASTM C473-95 after three cycles of 12 hours at 40 ℃/95% humidity followed by 12 hours at 21 ℃/50% humidity. The sag resistance was measured as the Total Movement (TM) of the strip and the position relative to the plane (PRFP). The actual coating application, the total movement of the strip, and the final position relative to the plane are listed in table 4B. One control bar did not have any coating.

TABLE 4B

As is clear from these results set forth in Table 4B, the final Total Movement (TM) and position relative to plane (PRFP) are at a minimum for compositions 4D and 4E, which contain 40.0wt.% and 50.0wt.% Aquaset on a solids basis, respectively^TM600 polymer binder and 50.90wt.% and 40.90wt.% LA-7 glass filler.

Example 5

This example demonstrates the effect of glass and mica fillers on the sag performance of a coating composition according to one embodiment of the invention.

Two coating compositions (compositions 5A and 5B) were prepared. Each composition contained 1.50wt.% of a nonionic alkyl aryl polyether surfactant (Triton)^TMCF-10, Dow), 0.40wt.% hydroxyethyl cellulose (Cellosize)^TMQP-4400H, Dow Chemical), 1.20wt.% bentonite (Vollclay)^TMAmerican Colloid Company (American Colloid Company)), 6.00wt.% air-separated kaolin (Snowbrite)^TMclay, Unimin), and 39.50wt.% (on a solids basis) of Aquaset^TM600 polymer binder (Dow Construction Polymers). Composition 5A further contained 35.80wt.% glass filler (LA-7)^TMVitro Minerals). Composition 5B further contained 35.80wt.% Mica (Mineral Mica 3X, Mineral Mining Company).

The coating composition was applied using a Devilbiss JGA-510 spray gun at 194g/m on a wet basis²Was applied to two 7.6cm x 61cm wet felted test strips. The coated test strips were then dried in an oven at approximately 135 ℃ and cured at 177 ℃ for 20 minutes.

The sag resistance properties of each bar were measured according to ASTM C473-95 after three cycles of 40 ℃/95% humidity for 12 hours followed by 21 ℃/50% humidity for 12 hours. The sag resistance was measured as the Total Movement (TM) of the strip and the position relative to the plane (PRFP). The total movement of the panel, and the resulting position relative to the plane, are listed in table 5.

TABLE 5

Strip for packaging articles	Composition comprising a metal oxide and a metal oxide	TM(cm)	PRFP(cm)
				1	5A	2.080	2.159
2	5A	3.289	3.432
				3	5B	2.507	2.746
4	5B	2.223	2.469
				5	Control (without coating)	4.376	4.267
6	Control (without coating)	4.747	4.656

As is clear from the results listed in table 5, compositions 5A and 5B (which contained a glass filler and a mica filler, respectively) exhibited approximately equivalent sag resistance as measured by Total Movement (TM) of the panel and position relative to plane (PRFP).

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.

Claims (9)

1. A curable, formaldehyde-free coating composition comprising:

(i) a composition comprising (a) a polyacid copolymer comprising at least two carboxylic acid groups, anhydride groups, or salts thereof; (b) a hydroxyl group-containing compound having at least two hydroxyl groups, either as a separate compound or incorporated into the polyacid copolymer backbone; and (c) a phosphorus-containing catalyst; and

(ii) calcium alumino-silicate powder having a composition based onThe total weight of the calcium aluminosilicate powder is less than 2wt.% of total alkali content, a median particle diameter of 250 microns or less and 1m²G to 3m²The surface area in terms of/g,

wherein the ratio of the number of equivalents of said carboxylic acid groups, anhydride groups, or salts thereof to the number of equivalents of said hydroxyl groups is from 1/0.01 to 1/3.

2. The coating composition of claim 1 comprising 20 to 50wt.% of the binder composition and 40 to 70wt.% of the calcium aluminosilicate powder, based on the total weight of the dry components of the coating composition.

3. The coating composition of claim 1, wherein the hydroxyl group-containing compound is triethanolamine, and/or wherein the polyacid copolymer is a carboxylated acrylic copolymer.

4. The coating composition of claim 1, wherein the calcium alumino silicate powder has a median particle size of 20 microns or less.

5. The coating composition of claim 1, further comprising a filler selected from brighteners, clays, mica, sand, barium sulfate, silica, talc, gypsum, wollastonite, zinc oxide, zinc sulfate, hollow beads, or mixtures thereof, and/or one or more nonionic surfactants.

6. The coating composition of claim 1, further comprising a filler selected from the group consisting of brighteners, mica, sand, barium sulfate, silica, talc, gypsum, wollastonite, zinc oxide, zinc sulfate, hollow beads, or mixtures thereof, and/or one or more of nonionic surfactants and kaolin.

7. The coating composition of claim 1, wherein the composition avoids formaldehyde emissions.

8. The coating composition of claim 1, wherein the calcium alumino-silicate powder has a median particle size of 100 microns or less.

9. The coating composition of any one of claims 1 to 8, further comprising one or more components selected from the group consisting of: dispersants, organic fillers, mineral fillers, pigments, surfactants, pH modifiers, buffers, viscosity modifiers, stabilizers, defoamers, flow modifiers, and combinations thereof.