Binder solution with low temperature curing

Abstract

An aqueous binder solution for nonwoven mats such as insulation comprises a polycarboxylate polymer and a beta-hydroxyalkylamide hardener, such as N, N, N', N'-tetrakis-(beta-hydroxyethyl)adipamide, in an acidic solution. The polycarboxylate polymer is made using a phosphorus-containing accelerator. The solution has a pH below 3.

Description

[0001] BINDER SOLUTION WITH LOW TEMPERATURE CURING

[0002] FIELD

[0003] This invention relates to the field of insulation.

[0004] INTRODUCTION

[0005] Insulation that contains a nonwoven fiber mat is commonly made using the following process:

[0006] • Raw materials such as glass, minerals, or other inorganics are melted at high temperature, spun and extruded through a die to form fibers, and cooled. The resulting fibers are collected as a nonwoven mat. In insulation products, the nonwoven mat is often called batt or batting.

[0007] • An aqueous solution containing a binder is sprayed onto the extruded fibers or nonwoven mat of fibers.

[0008] • The nonwoven mat treated with the binder is heated to drive off the aqueous solvent and cure the binder.

[0009] • The cured nonwoven mat is cut to desired shape and size.

[0010] Traditional binders are made using phenolic resins that are produced by the reaction of formaldehyde and phenol. However, regulatory concerns about formaldehyde have driven producers to use new binders that are free of formaldehyde.

[0011] One class of common formaldehyde-free binder is aqueous solutions that contain a polycarboxylate polymer and a polyol hardener. On heating, the polycarboxylate polymer and the polyol hardener react to form ester linkages that cross-link the polymer.

[0012] The polycarboxylate polymer is frequently poly(acrylic acid) (“PAA”), although polymers of methacrylic acid, maleic acid, itaconic acid, maleic anhydride and methacrylic anhydride can also be used. Copolymers containing one or more monomers can also be used. The polycarboxylate polymer is made by polymerizing the monomers in water in the presence of a free-radical initiator and an accelerator / a chain transfer agent. Two different accelerator / chain transfer agents are commonly used, which produce different polymers. Bisulfite accelerators, such as sodium bisulfite, produce a polymer that has sulfur-based terminal groups. Phosphorous-based accelerators produce a polymer that has phosphorus-based internal (within chain) and terminal groups. Phosphorus-based accelerators are generally alkali metal salts of phosphorous acid, hypophosphorous acid and / or polyphosphoric acids. Examples of the salts include 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. Mixtures of two or more of the salts can also be used.

[0013] The polyol hardener is typically a low molecular weight compound containing at least two hydroxyl groups. A common polyol hardener is triethanolamine, but diethanolamine, ethylene glycol, glycerol, glucose, trimethylolpropane, 1,2, 4- butanetriol, 1,3-propane diol, 1,4-butanediol, 1,6-hexanediol, pentaerythritol, sorbitol, and mixtures thereof are also used.

[0014] The polycarboxylate binders are free of formaldehyde, but they are known to be more difficult to cure, requiring higher temperatures and longer curing times than formaldehyde-phenol binders. Higher curing temperatures are undesirable because they require higher energy usage and higher energy costs to effect the full cure. Longer curing times also require higher energy expenditure and slower line speeds, ft is important to fully cure the binder because failure to adequately cure the binder results in a product with poor physical strength, such as tensile strength, especially if the binder becomes wet.

[0015] A binder is needed that cures rapidly and at low temperature to provide adequate physical strength.

[0016] SUMMARY

[0017] One aspect of this invention is an aqueous binder solution that comprises:

[0018] (a) a polycarboxylate polymer that comprises internal or terminal phosphonate or phosphinate functional groups; and

[0019] (b) a hardener composition comprising beta-hydroxyalkylamide hardener, wherein the ratio of the hardener composition to the polycarboxylate polymer is suitable for the hardener composition to cross-link the polycarboxylate polymer, and the aqueous binder solution has a pH below 3.0. The word “or” in this application permits one option or the other option or both options simultaneously, in the sense of “and / or”; the word “or” does not require selection of just one option.

[0020] A second aspect of this invention is a process to make a cured nonwoven fiber mat comprising the steps of:

[0021] (a) providing a nonwoven mat of inorganic fibers;

[0022] (b) applying an aqueous binder solution to the inorganic fibers; and

[0023] (c) heating the nonwoven mat to dry and cure the binder, wherein (and characterized in that) the aqueous binder solution is an aqueous binder solution of the first aspect of this invention.

[0024] A third aspect of this invention is a nonwoven fiber mat comprising inorganic fibers and at least 1 weight percent of a cured binder that comprises the reaction product of (a) a polycarboxylate polymer that comprises internal or terminal phosphonate or phosphinate functional groups and (b) a hardener composition that comprises beta-hydroxyalkylamide hardener.

[0025] The beta-hydroxyalkylamide hardeners used in this invention can cure rapidly with polycarboxylate polymers at low temperatures to strongly adhere fiber mats together, if the polycarboxylate polymer is made using a phosphorous-based accelerator and the binder solution has an acidic environment. DETAILED DESCRIPTION

[0026] This invention uses an aqueous binder solution that comprises a polycarboxylate polymer and a hardener composition, wherein the hardener composition comprises a beta-hydroxyalkylamide hardener.

[0027] The polycarboxylate polymer is made by polymerizing unsaturated carboxylate monomers in the presence of a free-radical initiator and a phosphorous-based accelerator. The resulting polymer has pendant carboxylic acid groups. The resulting polymer also has internal or terminal phosphonate or phosphinate groups.

[0028] Unsaturated carboxylate monomers comprise an unsaturated aliphatic moiety linked to one or more carboxylic acid groups. In some embodiments, the carboxylic acid group is in the form of an acid. In some embodiments, the carboxylic acid group is in the form of an acid derivative, such as an acid salt or an anhydride; monomers that comprise these derivative groups are also carboxylate monomers. Examples of suitable carboxylate monomers include acrylic acid, methacrylic acid, maleic acid, maleic anhydride and itaconic acid and their derivatives. In some embodiments, the carboxylate monomer is acrylic acid. In some embodiments, the carboxylate monomer is methacrylic acid. In some embodiments, the carboxylate monomers arc a blend of acrylic and methacrylic acid.

[0029] In some embodiments, the polycarboxylate polymer consists of or consists essentially of repeating units derived from unsaturated carboxylate monomers.

[0030] In some embodiments, the polycarboxylate polymer may also comprise repeating units derived from comonomers that copolymerize with the unsaturated carboxylate monomers. Examples of suitable comonomers include acrylate ester monomers, such as methyl methacrylate and butyl acrylate. In some embodiments, the comonomers and their proportions are selected such that the polycarboxylate polymer is water-soluble or water-dispersible. In some embodiments, at least 80 mole percent of the monomers are unsaturated carboxylate monomers, or at least 85 mole percent or at least 90 mole percent or at least 95 mole percent or 100 mole percent. In some embodiments, 0 mole percent of the monomers are other unsaturated monomers, or no more than 5 mole percent or no more than 10 mole percent or no more than 15 mole percent or no more than 20 mole percent.

[0031] Polymerization takes place in an aqueous solvent. The aqueous solvent comprises primarily water but may optionally further comprise water-miscible cosolvents such as acetone. The ratio of solvent to monomers is not critical, as long as all monomers are dispersed in the solvent. In some embodiments, the solution comprises at least 10 weight percent solids or at least 20 weight percent or at least 25 weight percent or at least 30 weight percent or at least 35 weight percent or at least 40 weight percent or at least 45 weight percent. In some embodiments, the solution comprises at most 70 weight percent solids or at most 60 weight percent or at most 55 weight percent or at most 50 weight percent or at most 45 weight percent.

[0032] In some embodiments, a base such as sodium hydroxide or potassium hydroxide is added to the solvent to raise the pH of the reaction mixture and control the growth of viscosity in the reaction mixture. In some embodiments, the reaction mixture has a pH of at least 2.0 or at least 2.1 or at least 2.2 or at least 2.3 or at least 2.4 or at least 2.5 or at least 2.6 or at least 2.7. In some embodiments, the solvent has a pH of at most 4.0 or at most 3.6 or at most 3.2 or at most 3.0 or at most 2.6.

[0033] The polymerization takes place in the presence of a free -radical initiator. Suitable initiators are known and commercially available. Common initiators used in polymerization of polycarboxylate polymers are peroxodisulfate salts, such as sodium or ammonium salts. In some embodiments, the ratio of initiator to monomers is at least 1 weight percent or at least 3 weight percent or at least 5 weight percent. In some embodiments, the ratio of initiator to monomers is at most 15 weight percent or at most 12 weight percent or at most 10 weight percent.

[0034] The polymerization takes place in the presence of a phosphorous-containing accelerator. The accelerator performs up to three roles in the polymerization. First, the accelerator may act as a chain transfer agent, limiting the growth of polymer chains and controlling molecular weight. Second, the accelerator may add internal and / or terminal phosphonate or phosphinate functional groups to the polycarboxylate polymer. For example, some polycarboxylate polymer chains may be terminated by phosphinate (-PO2H2) or phosphonate (-PO3H2) groups (“terminal groups”), or may be bridged by a phosphinate (-PO2H-) group (“internal groups”), or salts thereof. Third, a fraction of the accelerator may remain unincorporated in the polymer chains in its native form as hypophosphite, or it will exist as phosphorus acid species (H3PO3, H3PO4), or salts thereof.

[0035] Examples of suitable phosphorus-based accelerators include phosphorous acid, hypophosphorous acid, polyphosphoric acids and their alkali metal salts. Examples of the salts include 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 and combinations thereof. In some embodiments, the ratio of accelerator to monomers is at least 1 weight percent or at least 2 weight percent or at least 3 weight percent or at least 4 weight percent or at least 5 weight percent or at least 6 weight percent or at least 7 weight percent. In some embodiments, the ratio of accelerator to monomers is at most 25 weight percent or at most 20 weight percent or at most 18 weight percent or at most 15 weight percent or at most 12 weight percent or at most 10 weight percent or at most 8 weight percent. In the foregoing ratios, the weight of accelerator is based on the anhydrous weight of the accelerator. However, in many embodiments the accelerator added to the reaction mixture will not be anhydrous when added to the polymerization reaction. In some embodiments, the phosphorus-based accelerator is in a hydrated form when added to the reaction mixture, such as sodium hypophosphate monohydrate. In some embodiments, the phosphorus-based accelerator is added to the reaction mixture in the form of an aqueous solution.

[0036] In some embodiments, at least 20 weight percent of the phosphorous used in the polymerization is incorporated into polycarboxylate polymer as terminal or internal phosphonate or phosphinate functional groups, or at least 30 weight percent or at least 40 weight percent or at least 45 weight percent or at least 50 weight percent or at least 60 weight percent or at least 70 weight percent or at least 75 weight percent or at least 80 weight percent or at least 85 weight percent or at least 90 weight percent. In some embodiments, at most 95 weight percent of the phosphorous used in the polymerization is incorporated into polycarboxylate polymer as terminal or internal phosphonate or phosphinate functional groups, or at most 90 weight percent or at most 85 weight percent or at most 80 weight percent or at most 75 weight percent or at most 70 weight percent or at most 65 weight percent.

[0037] The polymerization takes place at an elevated temperature, such as at least 50°C or at least 60°C or at least 70°C or at least 80°C or at least 90°C. The temperature is generally below 100°C to prevent the solvent from boiling.

[0038] In some embodiments, the polycarboxylate polymer has a weight average molecular weight (Mw) of at least 800 Da or at least 1000 Da or at least 1200 Da or at least 1400 Da or at least 1500 Da or at least 1600 Da or at least 1800 Da or at least 2000 Da. In some embodiments, the polycarboxylate polymer has a weight average molecular weight (Mw) of at most 20,000 Da or at most 10,000 Da or at most 8000 Da or most 6000 Da or most 5000 Da.

[0039] Suitable polycarboxylate polymers are commercially available and include polycarboxylate polymer commercially available from The Dow Chemical Company under the AQUASET™ and ACUMER™ trademarks.

[0040] The beta-hydroxyalkylamide (b-HAA) hardener used in the hardener composition is a compound characterized by having on average at least two beta-hydroxyalkylamide (b-HAA) moieties per molecule. Each b-HAA moiety is illustrated in Formula 1. wherein

[0041] • R2and R3arc each independently hydrogen or a hydrocarbyl moiety.

[0042] • “y” is a number of hydro xyalkyl moieties (-CR22-CR32-OH) bonded to the amide nitrogen, and each “y” is independently either 1 or 2 on each b-HAA moiety.

[0043] • R1is not present when “y” is 2, and is a moiety independently selected from hydrogen or a hydrocarbyl moiety when “y” is 1.

[0044] In some embodiments, hydrocarbyl moieties in R1, R2and R3are aryl. In some embodiments, hydrocarbyl moieties in R1, R2and R3are aliphatic. In some embodiments, hydrocarbyl moieties in R1, R2and R3are alkyl.

[0045] We hypothesize, without intending to be bound, that the b-HAA moieties may gain reactivity by forming cyclic species, such as an oxazolinium cations, that react with carboxylate groups in the polycarboxylate polymer. In some embodiments, R1, R2and R3are selected to reduce or avoid interference with these reactions. • In some embodiments, the R3moieties in each hydroxyalkyl moiety collectively comprise on average no more than 4 carbon atoms or no more than 3 carbon atoms or no more than 2 carbon atoms or no more than 1 carbon atoms or 0 carbon atoms. In some embodiments, both R3moieties are hydrogen.

[0046] • In some embodiments, the R2moieties in each hydroxyalkyl moiety collectively comprise on average no more than 6 carbon atoms or no more than 4 carbon atoms or no more than 2 carbon atoms or no more than 1 carbon atoms or 0 carbon atoms. In some embodiments, both R2moieties are hydrogen.

[0047] • In some embodiments, the R1moieties in each b-HAA moiety collectively comprise on average no more than 6 carbon atoms or no more than 4 carbon atoms or no more than 2 carbon atoms or no more than 1 carbon atoms or 0 carbon atoms. In some embodiments, R1is hydrogen.

[0048] • In some embodiments, the R1, R2and R3moieties in each b-HAA moiety collectively comprise on average no more than 8 carbon atoms or no more than 6 carbon atoms or no more than 4 carbon atoms or no more than 3 carbon atoms or no more than 2 carbon atoms or no more than 1 carbon atom or 0 carbon atoms. In some embodiments, all of the R1, R2and R3moieties on a b- HAA moiety are hydrogen.

[0049] • In some embodiments, y is 1. In some embodiments, y is 2.

[0050] In some embodiments, the b-HAA hardener is illustrated in Formula 2 wherein R1, R2and R3and y have the meaning and embodiments previously described, R4is an organic moiety, “x” is a number of b-HAA moieties pendant from R4, and “x” and “y” are selected such that the b-HAA hardener comprises at least 2 hydroxyalkyl moieties per molecule.

[0051] In some embodiments, R4is aryl. In some embodiments, R4is aliphatic. In some embodiments, R4is alkyl. In some embodiments, R4is alkaryl. In some embodiments, R4comprises on average no more than 12 carbon atoms or no more than 10 carbon atoms or no more than 8 carbon atoms or no more than 6 carbon atoms or no more than 5 carbon atoms or no more than 4 carbon atoms. R4comprises at least 1 carbon atom. In some embodiments, R4comprises on average at least 2 carbon atoms or at least 3 carbon atoms or at least 4 carbon atoms.

[0052] In some embodiments, “x” and “y” are selected such that the b-HAA hardener comprises on average at least 2.5 hydroxyalkyl moieties per molecule or at least 3.0 hydroxyalkyl moieties per molecule or at least 3.5 hydroxyalkyl moieties per molecule or at least 3.9 hydroxyalkyl moieties per molecule or at least 4.0 hydroxyalkyl moieties per molecule. In some embodiments, “x” and “y” are selected such that the b-HAA hardener comprises on average at most 6.0 hydroxyalkyl moieties per molecule or at most 5.5 hydroxy alkyl moieties per molecule or at most 5.0 hydro xy lkyl moieties per molecule or at most 4.5 hydroxyalkyl moieties per molecule or at most 4.1 hydroxyalkyl moieties per molecule or at most 4.0 hydroxyalkyl moieties per molecule.

[0053] In some embodiments, the b-HAA hardener is soluble in water up to at least 5 weight percent or at least 10 weight percent or at least 20 weight percent or at least 25 weight percent or at least 30 weight percent or at least 35 weight percent or at least 40 weight percent or at least 45 weight percent or at least 50 weight percent.

[0054] Examples of suitable b-HAA hardeners include N,N,N',N'-tetrakis(2-hydroxyethyl)-adipamide, which is commercially available, such as under the Primid or Prosid product names, from EMS Griltech and Sir Industrial, respectively. See, for example, Formula 3. adipamide

[0055] These and other b-HAAs can be synthesized by known processes, such as by the reaction of a suitable alkanolamine or dialkanolamine and a multi-functional carboxylic acid or an alkyl ester of a multifunctional carboxylic acid.

[0056] In some embodiments, the hardener composition comprises other hardeners in addition to the b-HAA hardener. Common hardeners for polycarboxylate polymers include polyols and poly mines, and particularly lower molecular weight polyols and poly amines. Examples of suitable other hardeners include glycerol, bisphenol A, ethanolamine, diethanolamine, triethanolamine, trimethylolpropane, l,2,4.butanetriol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, pentaerythritol, and sorbitol. In some embodiments, the b-HAA hardeners make up at least 50 weight percent of the hardener composition or at least 60 weight percent or at least 70 weight percent or at least 80 weight percent or at least 90 weight percent or 100 weight percent. In some embodiments, the b-HAA hardeners provide at least 30 mole percent of the hydroxyl groups in the hardener composition, or at least 40 mole percent or at least 50 mole percent or at least 60 mole percent or at least 70 mole percent or at least 80 mole percent or at least 90 mole percent or 100 mole percent.

[0057] The ratio of the hardener composition to the polycarboxylate polymer should be suitable for the hardener composition to form crosslinks between the polycarboxylate polymer molecules. The crosslinking occurred by formation of ester linkages between hydroxyl groups on the hardener molecules and carboxylate groups on the polycarboxylate polymer. In some embodiments, the molar ratio of hydroxyl groups in the hardener composition to carboxylate groups on the poly carboxyl ate polymer is at least 15 percent or at least 20 percent or at least 25 percent or at least 27 percent or at least 30 percent or at least 35 percent or at least 40 percent or at least 45 percent or at least 48 percent or at least 50 percent. In some embodiments, the molar ratio of hydroxyl groups in the hardener composition to carboxylate groups on the polycarboxylate polymer is at most 100 percent or at most 80 percent or at most 75 percent or at most 70 percent or at most 65 percent or at most 60 percent or at most 55 percent or at most 54 percent or at most 50 percent. For example, the molar ratio of hydroxyl groups in the hardener composition to carboxylate groups on the polycarboxylate polymer may be from 20 percent to 70 percent or from 25 percent to 65 percent or from 45 percent to 65 percent or from 40 percent to 60 percent.

[0058] To form the aqueous binder solution, the polycarboxylate polymer and the hardener composition are dissolved or dispersed together in an aqueous solvent. The aqueous solvent comprises water.

[0059] In some embodiments, the aqueous solvent further comprises an organic solvent that is miscible with water. In some embodiments, the water-miscible organic solvent has no moieties that can react with the polycarboxylate polymer or the hardener, such as no hydroxyl, no amine, or no acid groups. Examples of water-miscible solvents include acetone, acetonitrile, dimethyl sulfoxide, dimethylformamide, and dimethylacetamide. In some embodiments, the solvent comprises less than 50 weight percent organic solvent or less than 40 weight percent or less than 30 weight percent or less than 20 weight percent or less than 10 weight percent or less than 5 weight percent or 0 weight percent.

[0060] The aqueous binder solution has a pH less than 3. In some embodiments, the pH is at most 2.95 or at most 2.90 or at most 2.85 or at most 2.80 or at most 2.75 or at most 2.70 or at most 2.65 or at most 2.60 or at most 2.55 or at most 2.50. In some embodiments, the pH is at least 2.00 or at least 2.05 or at least 2.10 or at least 2.15 or at least 2.20 or at least 2.25 or at least 2.30 or at least 2.35 or at least 2.40 or at least 2.45. For example, in some embodiments, the pH is 2.10 to 2.90 or from 2.20 to 2.70 or from 2.35 to 2.55 or from 2.4 to 2.5. The pH can be controlled by adding inorganic acids, such as sulfuric acid, sulfurous acid, hydrochloric acid, nitric acid, nitrous acid or phosphorous acid. In some embodiments, the acid is sulfuric acid or hydrochloric acid.

[0061] The ratio of solvent to solids (polycarboxylate polymer and hardener composition) should be high enough such that all solids are stably dissolved, dispersed, or suspended in the solvent and the viscosity of the aqueous binder solution is suitable to apply to fiber mat, such as by spraying. In some embodiments, the solids content (the percent of the total aqueous solution that is made up of the solids) is kept high to minimize the energy needed to evaporate the solvent and to maintain a viscosity suitable to apply to the fiber mat without excessive running.

[0062] In some embodiments, the solids content of the aqueous binder solution is at least 1 weight percent or at least 2 weight percent or at least 3 weight percent or at least 4 weight percent or at least 5 weight percent or at least 6 weight percent or at least 7 weight percent or at least 8 weight percent or at least 9 weight percent or at least 10 weight percent. In some embodiments, the solids content of the aqueous binder solution is at most 60 weight percent solids (polycarboxylate polymer and hardener) or at most 55 weight percent or at most 40 weight percent or at most 40 weight percent or at most 30 weight percent or at most 25 weight percent or at most 20 weight percent or at most 15 weight percent or at most 12 weight percent. For example, in some embodiments, the solids content of the aqueous binder solution, when it is applied to the fiber mat, is from 5 to 25 weight percent or from 7 to 15 weight percent or from 8 to 12 weight percent. In some embodiments, the aqueous binder solution may have a higher solids content when produced, such as from 30 to 60 weight percent solids or from 45 to 55 weight percent solids, and may be diluted to prepare it for use. The higher solids content may be more convenient for storage and transportation of the aqueous binder solution.

[0063] In some embodiments, the aqueous binder solution has a viscosity of at least 50 cps or at least 100 cps or at least 500 cps. In some embodiments, aqueous binder solution has a viscosity of at most 2500 cps or at most 1500 cps or at most 1000 cps.

[0064] In some embodiments, the aqueous binder solution may comprise additives such as silicone- based and / or silane- or alkoxysilane-containing species, rheology modifiers, hydrophobic additives such as organic waxes or inorganic species, and corrosion inhibitors. In some embodiments, additives make up no more than 25 weight percent of the aqueous binder solution or no more than 20 weight percent or no more than 15 weight percent or no more than 10 weight percent or no more than 5 weight percent or 0 weight percent.

[0065] In some embodiments, the aqueous binder solution starts curing (as measured by DMA) at a temperature of no more than 150°C or no more than 140°C or no more than 130°C or no more than 128°C or no more than 125°C or no more than 120°C or no more than 118°C. In some embodiments, the aqueous binder solution starts curing (as measured by DMA) at a temperature of at least 100°C or at least 105°C or at least 110°C or at least 112°C or at least 115°C.

[0066] The aqueous binder solution may be used as a binder in a non-woven mat or fiber-based article, such as batting in insulation products, according to known processes.

[0067] In a process of this invention, the aqueous binder solution is applied to a nonwoven fiber mat that comprises inorganic fibers. Suitable non-woven mats are known and commercially available. In some embodiments, the fibers are fiberglass. In some embodiments, the fibers are mineral fibers. In some embodiments, the fibers of made from cullet, a mixture of glass pieces which is often recycled, mixed with sand, limestone, soda, borax, and / or dolomite. In some embodiments, the raw materials are crushed stone. The raw materials are melted into a liquid state, such as at 1000°C or more, and then transferred to a “spinner”, which is a centrifuge containing holes designed to allow molten material to flow through and form fibers. The fibers are cooled and collected in a non-woven mat.

[0068] In some embodiments, the nonwoven fiber mat is at least 2 cm thick or at least 4 cm or at least 6 cm. In some embodiments, the nonwoven fiber mat is at most 40 cm thick or at most 30 cm or at most 25 cm.

[0069] The aqueous binder solution is applied to the inorganic fibers before or after they are collected in the mat by known means such as spraying, pouring, or dipping. In some embodiments, the weight ratio of aqueous binder solution in the fiber mat, based on the weight of solids applied excluding solvent, is at least 1 weight percent or at least 2 weight percent or at least 3 weight percent or at least 4 weight percent. In some embodiments, the weight ratio of aqueous binder solution in the fiber mat, based on the weight of solids applied excluding solvent, is at most 20 weight percent or at most 15 weight percent or at most 12 weight percent or at most 10 weight percent or at most 8 weight percent or at most 6 weight percent. The resulting product is an impregnated fiber mat.

[0070] In some embodiments, the impregnated fiber mat is dried before curing. For example, drying may be carried out with flow of air or nitrogen at a temperature of at least 50°C or at least 60°C or at least 70°C or at least 80°C or at least 85°C or at least 90°C. In some embodiments, the drying temperature is no more than 120°C or no more than 110°C or no more than 100°C or no more than 95 °C or no more than 90°C.

[0071] The impregnated fiber mat is cured by exposure to heat, such as in an oven, to cause the polycarboxylate polymer and the hardener to react and cross-link. In some embodiments, the curing temperature is at least 150°C or at least 175°C or at least 190°C or at least 200°C. In some embodiments, the curing temperature is no more than 400°C or no more than 350°C or no more than 320°C or no more than 300°C.

[0072] In some embodiments, residence time for the mat at the curing temperature is at most 600 seconds (s) or at most 300 s or at most 240 s or at most 180 s or at most 150 s or at most 120 s minutes or at most 90 s or at most 60 s. In some embodiments, residence time for the mat at the curing temperature is at least 30 seconds or at least 60 s or least 90 s. Several factors may influence the residence time needed to fully cure the aqueous binder solution, including the temperature at which curing occurs, the thickness of the impregnated fiber mat, the extent to which fibers in the fiber mat are hot before curing (such as due to the temperature at which they are formed), and the curing temperatures of the binder. In general, higher cure temperatures and selecting a binder with lower cure temperatures reduces the required residence time.

[0073] The process makes a nonwoven fiber mat comprising inorganic fibers and at least 1 weight percent of a cured binder that comprises the reaction product of (a) a polycarboxylate polymer that comprises internal or terminal phosphonate or phosphinate functional groups and (b) a hardener composition comprising beta-hydroxyalkylamide hardener. The polycarboxylate polymer and the hardener composition have the description and optional embodiments that are previously described. In the reaction product, ester linkages between the hardener molecules and the polycarboxylate polymer molecules crosslink the polycarboxylate polymer. The cured binder on the mat comprises terminal or internal phosphonate or phosphinate functional groups like the polycarboxylate polymer, or their reaction products. The ratio of inorganic fibers to cured binder is as previously described for the ratio of fiber mat to aqueous binder solution. The binder adheres the fibers to each other to form a stable mat. Test Methods

[0074] Unless stated otherwise, measurements listed in this application are made using the following test methods:

[0075] Examples

[0076] The following examples illustrate specific embodiments of the invention, but do not limit the broadest scope of the invention. The materials in Table 1 are used for the Examples:

[0077] Table 1

[0078] Preparation of Binder Pl (made with phosphorus-based accelerator)

[0079] The preparation of Pl is carried out using a 5 L four neck flask equipped with mechanical stirrer, reflux condenser, and thermocouple. Deionized water (745 g), sodium hydroxide (50 wt%, 26.2 g), and 110.4 g of SHP solution are added to the flask and the contents are stirred and heated. At a temperature of 85 °C, separately prepared solutions of acrylic acid (1844.3 g) and deionized water (326 g), sodium persulfate (18.4 g) in deionized water (113.4 g), and SHP solution (257.6 g) are fed to the reactor contents over the course of 120 min, 125 min, and 105 min, respectively. The temperature of the reactor contents is allowed to increase over time to 92°C during the process. At the end of feeding, each vessel containing a solution is rinsed to the reactor with deionized water (8 g). The reactor contents are held at 90°C for 15 min and then cooled to room temperature. SHP solution (22.5 g) is added to the reactor contents, followed by deionized water (485 g). The reactor contents have pH 2.3, and a solids content of 52.5%. The resulting polycarboxylate polymer has a weight-average molecular weight of 2950 Da and a number average molecular weight of 1530 Da, measured according to the Test Methods.

[0080] Preparation of Binder P2 (made with sulfite-based accelerator)

[0081] The preparation of Pl is carried out using a 5 L four neck flask equipped with mechanical stirrer, reflux condenser, and thermocouple. Deionized water (142 g), iron (II) sulfate heptahydrate (0.015 wt%, 4.0 g), and sodium metabisulfite (12.6 g) in deionized water (19.5 g) are added to the flask and the contents are stirred and heated. At a temperature of 70°C, separately prepared solutions of acrylic acid (1252.8 g) and deionized water (271.8 g), sodium persulfate (18.0 g) in deionized water (161.7 g), and sodium metabisulfite (180.0 g) in deionized water (279.2 g) are fed to the reactor contents over the course of 90 min, 95 min, and 85 min, respectively. At the end of feeding, the vessel containing the monomer solution is rinsed to the reactor with deionized water (6.3 g) and the vessels containing the sodium persulfate and sodium metabisulfite are rinsed to the reactor with deionized water (3.1 g). The reactor contents are held at 70°C for 15 min and then cooled to room temperature. Deionized water (132.7 g) is added to the reactor contents, followed by sodium hydroxide (50 wt%, 278.3 g) and deionized water (6.3 g). Hydrogen peroxide (35 wt%, 43.3 g) and deionized water (3.1 g) are added to the reactor contents over 10 min, followed by a 15 min hold. Finally, deionized water (75 g) is added to the reactor contents. The reactor contents have pH 3.7 and a solids content of 48.0%. The resulting polycarboxylate polymer has a weight-average molecular weight of 2960 Da and a number average molecular weight of 1200 Da, measured according to the Test Methods.

[0082] Preparation of Inventive and Comparative Solutions:

[0083] Resin solutions shown in Table 2 as Inventive Examples 1 to 5 (IE1 to IE5) and Comparative Examples 1 to (CE1 to CE8) are mixed together as follows:

[0084] • Hardener 1 from Table 1 is mixed with water to form a 50 weight percent solution. Hardener 2 from Table 1 is used as a pure (98%+) material.

[0085] • The hardener solution is mixed with binders from Table 1 to form a mixture that has the hydroxyl-to-acid ratio shown in Table 2.

[0086] • If required in Table 2, powdered SHP is added to the solution.

[0087] • Aqueous acid as shown in Table 2 (or aqueous base in the case of CE3) is added to the solution to achieve the pH shown in Table 2.

[0088] Preparation of Composite Samples for DMA Testing:

[0089] Resin solutions shown in Table 2 are diluted with water to 10% solids. Binder-free, borosilicate glass filter paper from Whatman® (GF / B, CAT No. 1821-150) is impregnated with the resin solution using a Birch Brother padder. The impregnated paper is pre-dried in an oven at 80°C for 15 min. DMA testing is performed strength according to the Test Methods. Average results are shown in Table 2.

[0090] Preparation of Composite Samples for Tensile Testing:

[0091] Resin solutions shown in Table 2 are diluted with deionized water to 6% solids. Binder-free, borosilicate glass filter paper from Whatman® (GF / A CAT No. 1820-866) is impregnated with the resin solution using a Birch Brother padder. The paper is dried in a Mathis oven at 90 °C for 90 sec and then cured in a second Mathis oven at either 160 °C or 190 °C for 3 min.

[0092] Samples are cut into ten 1 x 4 inch strips. Five strips are used for dry tensile testing. Five strips are used for wet tensile testing. Samples for wet testing are soaked for 30 min in 90°C water, blotted dry and tested within a few hours.

[0093] Samples are tested for tensile strength according to the Test Methods. Average results are shown in Table 2.

Claims

CLAIMS:

1. A non wo ven fiber mat comprising inorganic fibers and at least 1 weight percent of a cured binder wherein the cured binder comprises the reaction product of (a) a polycarboxylate polymer that comprises internal or terminal phosphonate or phosphinate functional groups and (b) a hardener composition that comprises beta-hydroxyalkylamide hardener.

2. The nonwoven fiber mat of Claim 1 wherein (b) the hardener composition comprises at least 50 weight percent of a beta-hydroxyalkylamide hardener that meets Formula 2:wherein:(a) R4is an organic moiety that comprises on average from 1 to 12 carbon atoms;(b) R2and R3are each independently hydrogen or a hydrocarbyl moiety;(c) “x” is on average at least 1;(d) “y” is a number of hydroxyalkyl moieties (-CR22-CR32-OH) bonded to the amide nitrogen, and each “y” is independently either 1 or 2;(e) “x” and “y” are selected such that the beta-hydroxyalkylamide hardener comprises at least 2 hydroxyalkyl moieties per molecule; and(f) R1is not present when “y” is 2, and is a moiety independently selected from hydrogen or a hydrocarbyl moiety when “y” is 1.

3. The nonwoven fiber mat of Claim 1 wherein (b) the hardener composition comprises at least 50 weight percent N, N, N’, N’-tetrakis-(beta-hydroxyethyl)adipamide.

4. An aqueous binder solution comprising:(a) a polycarboxylate polymer that comprises internal or terminal phosphonate or phosphinate functional groups; and(b) a hardener composition comprising beta-hydroxyalkylamide hardener, wherein the ratio of the hardener composition to the polycarboxylate polymer is suitable for the hardener composition to cross-link the polycarboxylate polymer, and the aqueous binder solution has a pH below 3.0.

5. The aqueous binder solution of Claim 4 wherein the polycarboxylate polymer has a weight average molecular weight from 1,000 Da to 10,000 Da.

6. The aqueous binder solution of Claim 4 wherein (b) the hardener composition comprises at least 50 weight percent of a beta-hydroxyalkylamide hardener that meets Formula 2:wherein:(a) R4is an organic moiety that comprises on average from 1 to 12 carbon atoms;(b) R2and R3are each independently hydrogen or a hydrocarbyl moiety;(c) “x” is on average at least 1 ;(d) “y” is a number of hydroxyalkyl moieties (-CR22-CR32-OH) bonded to the amide nitrogen, and each “y” is independently either 1 or 2;(e) “x” and “y” are selected such that the beta-hydroxy alkyl amide hardener comprises at least 2 hydroxyalkyl moieties per molecule; and(f) R1is not present when “y” is 2, and is a moiety independently selected from hydrogen or a hydrocarbyl moiety when “y” is 1.

7. The aqueous binder solution of Claim 6 wherein the R1, R2and R3moieties in each betahydroxyalkylamide moiety collectively comprise on average from 0 to 8 carbon atoms; and R4comprises on average from 1 to 12 carbon atoms.

8. The aqueous binder solution of Claim 6 wherein “x” and “y” are selected such that the beta- hydroxyalkylamidc hardener comprises on average from 2.5 to 4 hydroxyalkyl moieties per molecule.

9. The aqueous binder solution of Claim 4 wherein the molar ratio of hydroxyl groups in the hardener to carboxylate groups on the polycarboxylate polymer is from 25 percent to 75 percent.

10. The aqueous binder solution of Claim 4 wherein the aqueous binder solution has a pH from 2.10 to 2.90.

11. The aqueous binder solution of Claim 6 wherein:(a) the R1, R2and R3moieties in each beta-hydroxyalkylamide moiety collectively comprise on average from 0 to 8 carbon atoms; and(b) R4is alkyl, aryl or alkaryl; and(c) “x” and “y” are selected such that the beta-hydroxyalkylamide hardener comprises on average from 2.5 to 4 hydroxyalkyl moieties per molecule; and(d) the molar ratio of hydroxyl groups in the hardener to carboxylate groups on the polycarboxylate polymer is from 45 percent to 65 percent; and(e) the aqueous solvent has a pH from 2.20 to 2.70.

12. The aqueous binder solution of Claim 1 1 wherein the aqueous binder solution starts curing (as measured by DMA) at a temperature from 105°C to 130°C.

13. The aqueous binder solution of Claim 11 wherein the beta-hydroxyalkylamide hardener is N, N, N’ , N' -tetrakis-(beta-hydroxyethyl)adipamide.

14. The aqueous binder solution of Claim 11 wherein the polycarboxylate polymer is the product of polymerization of unsaturated carboxylate monomers in the presence of sodium hypophosphite, sodium phosphite, potassium phosphite, disodium pyrophosphate, tetrasodium pyrophosphate, sodium tripolyphosphate, sodium hexametaphosphate, potassium phosphate, potassiumpolymetaphosphate, potassium polyphosphate, potassium tripolyphosphate, sodium trimetaphosphate, or sodium tetrametaphosphate or a combination thereof.

15. A process to make a cured nonwoven fiber mat comprising the steps of:(a) providing a nonwoven mat of inorganic fibers;(b) applying an aqueous binder solution to the inorganic fibers; and(c) heating the nonwoven mat to dry and cure the binder, wherein the aqueous binder solution is a solution as described in any one of Claims 4 to 14.

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