FIBROUS GLASS BINDERS

Abstract: A fibrous glass binder comprises a copolymer of a carboxy functional monomer with a hydroxy functional monomer, and catalyst comprising an alkali metal salt of a phosphorous containing acid.

Description: FIBROUS GLASS BINDERS TECHNICAL FIELD This invention relates generally to fibrous glass binders. More particularly, the invention is directed to a low viscosity binder for application to a fibrous glass mat, which binder rigidly cures to form a fibrous glass bat having excellent compression recovery characteristics. BACKGROUND ART Fibrous glass insulation products generally comprise matted glass fibers bonded together by a cured thermoset polymeric material. Molten streams of glass are drawn into fibers of random lengths and blown into a forming chamber where they are randomly deposited as a mat onto a traveling conveyor. The fibers, while in transit in the forming chamber and while still hot from the drawing operation, are sprayed with an aqueous binder. A phenol-formaldehyde binder is currently used throughout the fibrous glass insulation industry. The residual heat from the glass fibers and the flow of air through the fibrous mat during the forming operation are generally sufficient to volatilize a majority of all of the water from the binder, thereby leaving the remaining components of the binder on the fibers as a viscous or semi-viscous high-solids liquid. The coated fibrous mat, which is formed in a compressed state due to the tremendous flow of air through the mat in the forming chamber, is then transferred out of the forming chamber to a transfer zone where the mat vertically expands due to the resiliency of the glass fibers. This vertical expansion is extremely important to the successful manufacture of commercially acceptable fibrous glass thermal or acoustical insulation products. Thereafter, the coated mat is transferred to a curing oven where heated air is blown through the mat to cure the binder and rigidly bond the glass fibers together. Phenol-formaldehyde binders are widely used because they have a low viscosity in the uncured state, yet form a rigid thermoset polymeric matrix for the glass fibers when cured. A low binder viscosity in the uncured state is required to allow the maximum vertical expansion of the coated mat when it exits the forming chamber. A binder which forms a rigid matrix when cured is required so that a finished fibrous glass thermal or acoustical insulation product, when compressed for packaging and shipping, will recover to its as-made vertical dimension when installed in a building. Insulation manufacturers have long desired an alternative polymeric binder system for fibrous glass products. However, low molecular weight, low viscosity binders S which allow maximum vertical expansion of the mat in the transfer zone generally cure to form a nonrigid plastic matrix in the finished product, thereby reducing the attainable vertical height recovery of the finished insulation product when installed. Conversely, high viscosity binders which generally cure to form a rigid matrix in the finished product do not allow maximum vertical expansion of the coated, uncured mat. 0 Accordingly, the industry continuously is searching for nonphenol formaldehyde binders having a low viscosity when uncured and structural rigidity when cured. U.S. Patent No. 5,318,990 discloses a binder which meets this need. The binder comprises a polycarboxy polymer, a monomeric trihydric alcohol, and catalyst comprising an alkali metal salt of a phosphorous-containing organic acid. U.S. Patent No. 5,340,868 also discloses a low viscosity, nonphenol binder. This binder comprises a polycarboxy polymer, a β-hydroxyalkylamide, and trifunctional monomeric carboxylic acid. DISCLOSURE OF INVENTION I now have discovered another nonphenol formaldehyde binder having a low viscosity when uncured and structural rigidity when cured. My binder comprises an aqueous solution of a copolymer composed of a carboxy containing monomer with an hydroxy C 2 - C 8 alkyl acrylate or methacrylate; and an alkali metal salt of a phosphorous-containing acid. The binder is useful for fibrous glass insulation. BEST MODE FOR CARRYING OUT THE INVENTION The binder according to the present invention comprises an aqueous solution of a copolymer consisting of a carboxy containing monomer and a hydroxy alkyl acrylate, and a catalyst. The viscosity of the binder is kept low through use of a low molecular mass copolymer, and provides a maximized vertical expansion of the fibrous glass mat as it exits the forming chamber, similar to the vertical expansion provided by the well-known phenol-formaldehyde binders. Generally, binders of phenol-formaldehyde or of the acrylate type require multiple components or require an extended synthesis process. Suφrisingly, it has been discovered that an aqueous solution of a simple copolymer containing both an hydroxy function and a carboxy function in conjunction with a catalyst will maintain low viscosity when applied and will cure into a rigid thermoset. The copolymer of the present invention comprises a monomer or monomers containing hydroxy and/or carboxy groups. The copolymer preferably contains more than one pendant carboxy group and more than one pendant hydroxy group. The carboxy portion of the copolymer may come from unsaturated carboxylic acid monomers including, but not limited to, acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, maleic acid, cinnamic acid, 2-methylmaleic acid, itaconic acid, 2-methylitaconic acid, α, β-methyleneglutaric acid and the like. Alternatively, the carboxy containing monomer may come from unsaturated anhydrides including, but not necessarily limited to, maleic anhydride, itaconic anhydride, acrylic anhydride, methacrylic anhydride and the like and mixtures thereof. Preferably, the carboxy containing monomer is acrylic acid. The hydroxy functional monomers useful for this invention are hydroxy C 2 - C g alkyl acrylates or methacrylates. Preferably, the monomers are hydroxy C 2 - C 4 alkylacrylates or methacrylates such as hydroxyethyl, hydroxypropyl, and hydroxybutyl acrylate or methacrylate and mixtures thereof. Methods of copolymerizing these monomers are well known in the chemical art. The acid containing monomer content of the copolymer may be present at a concentration of from about 10 mole% to 90 mole%. Preferably, the acid containing monomer content of the copolymer is present at a concentration of from 50 mole% to 70 moIe%. The hydroxy containing monomer content of the copolymer may be present at a concentration of from about 90 mole% to 10 mole%. Preferably, the hydroxy containing monomer content of the copolymer is present at a concentration of from 50 mole% to 30 mole%. The copolymer of this invention ha< an average number molecular weight ranging from greater than zero to less than 30,000. The copolymer of the present invention may additionally comprise another monomer of one or more vinyl compounds including, but not necessarily limited to, styrene α-methylstyrene, acrylonitrile, methacrylonitrile, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, glycidyl methacrylate, vinyl methyl ether, vinyl acetate and the like. Methods for producing these copolymers are well known in the art. The catalyst I use comprises an alkali metal salt of a phosphorous-containing inorganic acid; particularly alkali metal salts of phosphorous acid, hypophosphorous acid, and polyphosphoric acids. Examples of such catalysts include, but are not necessarily limited to, sodium hypophosphite, sodium phosphite, potassium phosphite, disodium pyrophosphate, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, potassium .phosphate, potassium polymetaphosphate, potassium polyphosphate, potassium tripolyphosphate, sodium trimetaphosphate, and sodium tetrametaphosphate, as well as mixtures thereof. Preferred catalysts include sodium hypophosphite and sodium phosphite, as well as mixtures thereof. The carboxy/hydroxy containing copolymer and alkali metal salt may be mixed in any conventional mixing device. Based on the combined weight of the copolymer and alkali metal salt, the amount of alkali metal salt varies over wide limits from about 1% to about 15% by weight. Preferably, the amount may vary from about 4% to about 8% by weight. Water may be added to the mixture in any amount which would produce an aqueous binder having a viscosity and a flow rate suitable for its application to a forming fibrous glass mat by any convenient method, such as spraying. Conveniently, water may comprise up to about 95% by weight of the binder. The binders of the present invention may optionally contain conventional adjuvants such as, for example, coupling agents, dyes, oils, fillers, thermal stabilizers, flame retarding agents, lubricants, and the like, in conventional amounts generally not exceeding 20% of the weight of the binder. In operation, the inventive binder is applied to glass fibers as they are being produced and formed into a mat, water is volatilized from the binder, and the high-solids binder-coated fibrous glass mat is heated to cure the binder and thereby produce a finished fibrous glass bat which may be used as a thermal or acoustical insulation product, a reinforcement for a subsequently produced composite, etc. The industry generally produces a porous mat of fibrous glass by fiberizing molten glass and immediately forming a fibrous glass mat on a moving conveyor. Glass is melted in a tank and supplied to a fiber forming device such as a spinner or a bushing. Fibers of glass are attenuated from the device and are blown generally downwardly within a forming chamber. The glass fibers typically have a diameter from about 2 to about 9 microns and have a length from about V* inch (6.4 mm) to about 3 inches (76 mm). Preferably, the glass fibers range in diameter from about 3 to about 6 microns, and have a length from about X Λ inch (12.7 mm) to about VΛ inches (38 mm). The glass fibers are deposited onto a perforated, endless forming conveyor. The binder is applied to the glass fibers as they are being formed by means of suitable spray applicators so as to result in a distribution of the binder throughout the formed mat of fibrous glass. The glass fibers, having the uncured resinous binder adhered thereto, are gathered and formed into a mat on the endless conveyor within the forming chamber with the aid of a vacuum drawn through the mat from below the forming conveyor. The residual heat contained in the glass fibers, as well as the air flow through the mat, causes a majority of the water to volatilize from the mat before it exits the forming chamber. As the high-solids resin-coated fibrous glass mat emerges from the forming chamber, it expands vertically due to the resiliency of the glass fibers. The expanded mat is then conveyed to and through a curing oven wherein heated air is passed through the mat to cure the resin. Flights about and below the mat slightly compress the mat to give the finished product a predetermined thickness and surface finish. Typically, the curing oven is operated at a temperature from about 200°C to about 325°C. Preferably, the temperature ranges from about 250°C to about 300°C. Generally, the mat resides within the oven for a period of time from about l Δ minute to about 3 minutes. For the manufacture of conventional thermal or acoustical insulation products, the time ranges from about % minute to about l y 2 minutes. The fibrous glass having a cured, rigid binder matrix emerges from the oven the form of a bat which may be compressed for packaging and shipping and which will thereafter substantially fully recover its as-made vertical dimension when unconstrained. By way of example, a fibrous glass mat which is about 1 V* inches (32 mm) thick as it exits from the forming chamber, will expand to a vertical thickness of about 9 inches (229 mm) in the transfer zone, and will be slightly compressed to a vertical thickness of about 6 inches (152 mm) in the curing oven. Example 1 An example of a copolymer which may be used as an ingredient for this binder may be prepared as follows: Reagent Weight Used acrylic acid 125.0 g 2-hydroxyethyl acrylate 125.0 g sodium hypophosphite hydrate 0.5 g cupric acetate monohydrate 0.5 g 30% aqueous hydrogen peroxide 2.5 g distilled water 645.0 g In a 2 L 3 -necked flask fitted with a reflux condenser, a nitrogen inlet, a temperature controller, and an overhead stirrer is added 500 g of distilled water. A solution of the sodium hypophosphite and cupric acetate is prepared in the remaining 145 g of distilled water. The hydrogen peroxide is added and stirred into the solution of cupric acetate and sodium hypophosphite. This solution is added to the 2 L flask. Nitrogen is sparged through the solution for 15 minutes with oxygen-free nitrogen. The sparge is removed, and the reactor is blanketed with nitrogen. Once the solution is sparged, the monomers are added with stirring. The solution is heated to 80°C at which time an exotherm occurs. Once the exotherm subsides, heating is continued for three hours at 85°C. Example 2 A binder containing the following ingredients is prepared and is applied to fibrous glass as it is formed into a mat. Ingredients Weight Copolymer from Example 1 (@29% solids) 2074.9 g Sodium Hypophosphite 36.1 g Silane (A-l 100, 100%) 1.2 g Water 4255.0 g Comparison binder: Formulated phenol-formaldehyde resin (@10% solids in water) 1 Example 3 The mats coated with the above two binders vertically expand to approximately the same height as they exit the forming section. Thereafter, the mats are slightly compressed to a nominal thickness of about 8 inches (203 mm) while being cured off-line in a large oven at a temperature of about 185°C. The cured bats exhibit the following recoveries after being compressed for the stated length of time. Recovery (% of nominal thickness) Binder 24 Hour 1 Week Example 2 89% 88% Comparison 90% 89% 1 Formulation also contains a small amount of aminosilane coupling agent and an oil emulsion for dust control.

Claims: CLAIMS 1. A fibrous glass binder, comprising an aqueous solution of: a copolymer comprising a reaction product of a polymerizable C c£arboxylic acid or anhydride, or mixtures thereof, and an hydroxy C 2 - C 8 alkyl acrylate or methacrylate, or mixtures thereof; and an alkali metal salt of a phosphorous-containing acid. 2. The fibrous glass binder according to claim 1 wherein the acid component of the copolymer is acrylic acid. 3. The fibrous glass binder according to claim 1 wherein the hydroxy component of the copolymer is hydroxyethyl, hydroxypropyl, or hydroxybutyl acrylate or methacrylate. 4. The fibrous glass binder according to claim 1 wherein a nonacid or hydroxy containing monomer is copolymerized with the acid and hydroxy functional monomers. 5. The fibrous glass binder according to claim 1 wherein the alkali metal salt is sodium hypophosphite, sodium phosphite, or a mixture thereof. 6. The fibrous glass binder according to claim 1 wherein the copolymer comprises from 20% to 100% by weight of the anhydrous binder. 7. The fibrous glass binder according to claim 1 wherein the copolymer comprises from 75% to 95% by weight of the anhydrous binder. 8. The fibrous glass binder according to claim 1 wherein the copolymer is comprised of about 10 to 90 mole% of the polymerizable acid containing monomer and about 90 to 10 mole% of the polymerizable hydroxy containing monomer. 9. The fibrous glass binder according to claim 1 wherein the copolymer is comprised of about 50 to 70 mole% of the polymerizable acid containing monomer and about 50 to 30 mole% of the polymerizable hydroxy containing monomer. 10. The fibrous glass binder according to claim 1 wherein the alkali metal salt is present at a concentration from about 2% to about 15% by weight of the total weight of the anhydrous binder. 11. The fibrous glass binder according to claim 1 wherein the alkali metal salt is present at a concentration from about 4% to about 8% by weight of the total weight of the anhydrous binder. 12. The fibrous glass binder according to claim 1 wherein water comprises up to about 95% by weight of the aqueous binder. 13. A fibrous glass binder, comprising an aqueous solution of: a copolymer of acrylic acid and hydroxyethyl acrylate or methacrylate; and sodium hypophosphite, sodium phosphite, or a mixture thereof. 14. A fibrous glass bat, comprising: glass fibers; and adhered to the glass fibers, the cured reaction product of the fibrous glass binder of claim 1. 15. A fibrous glass bat, comprising: glass fibers; and adhered to the glass fibers, the cured reaction product of the fibrous glass binder of claim 13. 16. A copolymer comprising a reaction product of a polymerizable carboxylic acid or anhydride, or mixtures thereof, and an hydroxy C 2 - C t alkyl acrylate or methacrylate, or mixtures thereof. 17. A copolymer according to claim 16 wherein the acid component of the copolymer is acrylic acid. 18. A copolymer according to claim 16 wherein the hydroxy component of the copolymer is hydroxyethyl, hydroxypropyl, or hydroxybutyl acrylate or methacrylate.

Inventors: LOFTUS JAMES E, LOFTUS, JAMES, E.
Applicants: OWENS CORNING FIBERGLASS CORP, OWENS CORNING
Application year: 1995
Main classification: C03C25
IPC codes: C03C25, C08F220, C08K3, C08L33, C09J133, D04H1, D06M23