Compositions and methods for reducing formaldehyde in acrylic or styrene-acrylic polymer products

Abstract

There is provided a unique aqueous polymer composition comprising an aqueous dispersion of polyacrylic or polystyrene-acrylic particles, a combination of at least one cyclic polycarbonyl compound and at least one hydroxyl group functionalized amine compound, wherein the combination can significantly reduce or even completely eliminate formaldehyde in acrylic or styrene-acrylic products (such as coating materials, paints, primers, adhesives, sealants, etc.) produced therefrom without causing any deterioration in the performance characteristics of the products. A method for preparing the product and a method for reducing or eliminating formaldehyde in the product are also provided.

Description

Technical Field

[0001] The present disclosure relates to formaldehyde emission control, and more particularly to a technique for reducing the emission of free formaldehyde from acrylic or styrene - acrylic polymer products. Background Art

[0002] Formaldehyde (FA) is commonly contained in various commercial products such as coating materials, adhesives, building materials, interior decorations, etc., and has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). Free formaldehyde contained in acrylic / styrene - acrylic coatings or adhesives can be a more serious problem because the free formaldehyde emitted from clear primers, cementitious waterproof coatings, decorative layers, or other interior building components formed with acrylic / styrene - acrylic coatings or adhesives will accumulate in the enclosed indoor building environment and pose risks to nearby construction workers and residents. Many countries have established regulatory standards regarding the health risks associated with free formaldehyde. For example, Chinese standards JG / T 468 - 2015, "Interface Treating Agent for Interior Building Wall", JC / T 907 - 2018, "Interface Treating Agent for Concrete", and GB 50325 - 2020, "Standard for Indoor Environmental Pollution Control of Civil Building Engineering" require that the concentration of free formaldehyde should be maintained at a level less than 100 mg / kg (i.e., less than 100 ppm).

[0003] In the past few decades, considerable efforts have been made to reduce or eliminate the environmental and health risks associated with free formaldehyde emissions and to meet the increasingly stringent environmental protection requirements worldwide. For example, researchers in the coating field have carefully designed coating formulations to minimize any formaldehyde or formaldehyde - generating substances (e.g., sodium formaldehyde sulfoxylate) contained therein. However, to date, all commercial manufacturing still has to make compromises between environmental production and other factors such as manufacturing costs, performance characteristics of coatings / adhesives, etc. In addition, even if any formaldehyde - containing or formaldehyde - generating components have been strictly excluded from the acrylic coating / adhesive formulation, trace amounts of formaldehyde may still be introduced as by - products or inevitable contaminants.

[0004] Several formaldehyde scavengers have been reported as supplementary means to mitigate existing problems, but various drawbacks still exist. For example, the scavenging efficiency of these formaldehyde scavengers may be so insufficient that the preparation of formaldehyde-free acrylic coatings / adhesives is impracticable or must be accomplished by using an undesirably high additional amount of scavenger. The addition of the scavenger may lead to the formation of a large amount of harmful by-products (such as volatile organic amines, etc.) and the deterioration of performance characteristics (such as stability). Another problem is that most of these formaldehyde scavengers require rather high pH conditions or high scavenger addition amounts, which may cause addition problems such as unpleasant odors, color changes (e.g., light brown / light yellow). In addition, scavengers suitable for other coating / adhesive systems (e.g., PU-based systems that are usually polymerized under anhydrous conditions) are generally not suitable for waterborne acrylic-based systems, which further increases the difficulty of developing new formaldehyde removal technologies for waterborne acrylic-based systems.

[0005] In view of the above, there is a great desire for a technology that can effectively reduce the formaldehyde concentration in acrylic coatings / adhesives within a normal pH range, such as 2 to 10, while maintaining various performance characteristics and avoiding the drawbacks described above, in order to meet the requirements of customers and existing and future environmental protection regulations and further improve product competitiveness.

[0006] After continuous exploration, a technology that can achieve the above goals has been surprisingly developed. Summary of the Invention

[0007] In a first aspect of the present disclosure, the present disclosure provides a unique aqueous polymer composition, which comprises: (a) an aqueous dispersion of polymer particles, the polymer particles comprising an acrylic polymer, a styrene-acrylic polymer, or a combination thereof, wherein the aqueous dispersion contains formaldehyde; (b) at least one cyclic polycarbonyl compound; and (c) at least one hydroxyl group-functionalized amine compound; wherein the at least one cyclic polycarbonyl compound and the at least one hydroxyl group-functionalized amine compound are formaldehyde-scavenging.

[0008] In a second aspect of the present disclosure, there is provided a product obtained from the aqueous polymer composition of the present disclosure, wherein the aqueous product is an adhesive, a coating material, a paint, or a sealant, and the free formaldehyde concentration of the product is lower than the free formaldehyde concentration in the aqueous dispersion.

[0009] In a third aspect of the present disclosure, there is provided a method for preparing a product with reduced formaldehyde by using the aqueous polymer composition of the present disclosure, wherein the product is an adhesive, a coating material, a paint or a sealant, and the method comprises the step of combining an aqueous dispersion comprising polymer particles with a cyclic polycarbonyl compound and a hydroxyl group-functionalized amine compound, and these polymer particles comprise an acrylic polymer, a styrene-acrylic polymer or a combination thereof.

[0010] In a fourth aspect of the present disclosure, there is provided a method for reducing the formaldehyde content in the product of the present disclosure, wherein the method comprises the following steps: providing an aqueous dispersion comprising polymer particles, and these polymer particles comprise an acrylic polymer, a styrene-acrylic polymer or a combination thereof, wherein the aqueous dispersion has a first free formaldehyde concentration; and adding a cyclic polycarbonyl compound and a hydroxyl group-functionalized amine compound to the aqueous dispersion to reduce the formaldehyde to a second free formaldehyde concentration, wherein the second free formaldehyde concentration is less than 90% of the first free formaldehyde concentration.

[0011] It should be understood that the foregoing general description and the following detailed description are merely exemplary and explanatory, and are not limiting of the invention as claimed. Description of the Drawings

[0012] Figure 1 A schematic process flow chart showing an embodiment according to the present disclosure is shown. Detailed Description

[0013] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, all publications, patent applications, patents and other references mentioned herein are incorporated by reference. As disclosed herein, "and / or" means "and, or as an alternative". Unless otherwise specified, all ranges include the endpoints.

[0014] As used herein, the terms "reduced formaldehyde", "reducing formaldehyde" and "reduced free formaldehyde concentration" are interchangeable and refer to scavenging the free formaldehyde contained in an acrylic or styrene-acrylic aqueous dispersion to any extent before adding a binary formaldehyde scavenging system, such as less than 70%, or less than 50%, or less than 30% of the original free formaldehyde concentration.

[0015] As used herein, the content of free formaldehyde is characterized by high performance liquid chromatography (HPLC), and can be characterized, for example, according to GB / T 30982-2014.

[0016] According to an exemplary embodiment, the present disclosure provides an aqueous polymer composition comprising: (a) an aqueous dispersion comprising polymer particles, the polymer particles comprising an acrylic polymer, a styrene-acrylic polymer, or a combination thereof; (b) at least one cyclic polycarbonyl compound; and (c) at least one hydroxyl group-functionalized amine compound.

[0017] According to some embodiments, the aqueous polymer composition of the present disclosure can be regarded as a "raw material package" or "precursor package" for preparing acrylic or styrene-acrylic products with reduced formaldehyde, and the products can be adhesives, coating materials, primers, paints, sealants, etc. For example, formaldehyde-free acrylic or styrene-acrylic products can be prepared by combining all components of the "raw material package" or "precursor package". According to an embodiment, the polymer particles in the aqueous dispersion (a) are the solid components or precursor components of the acrylic or styrene-acrylic products, and the aqueous dispersion can include an aqueous suspension, an emulsion, or an aqueous latex. According to an embodiment, based on the weight of the aqueous dispersion, the aqueous dispersion contains 5 wt% to 60 wt% of polymer particles, such as 10 wt% to 55 wt%, or 20 wt% to 52 wt%, or 30 wt% to 50 wt%, or 40 wt% to 57 wt% or within the numerical range obtained by combining any two of the above-mentioned end points. According to another embodiment, the aqueous dispersion comprising polymer particles can have a first free formaldehyde concentration, which needs to be further reduced, for example, to meet the regulations of a specific country / region or to further improve the product competitiveness. For example, the first free formaldehyde concentration can be 10 ppm to 2,000 ppm, or 12 ppm to 1,000 ppm, or 15 ppm to 500 ppm, or 20 ppm to 200 ppm, or 50 ppm to 100 ppm, or within the numerical range obtained by combining any two of the above-mentioned end points. According to an embodiment, the aqueous dispersion comprising polymer particles (a) may have been recognized as a commercial product (e.g., an adhesive, a coating material, a primer, a paint, a sealant, etc.) because its first free formaldehyde concentration meets the requirements of local environmental regulations, and components (b) and (c) are added thereto to further reduce the first free formaldehyde concentration (e.g., to a reduced second free formaldehyde concentration), thereby improving the quality and competitiveness of the product. According to an embodiment, the aqueous dispersion does not contain organic solvents.

[0018] Figure 1 A schematic process flow chart showing a process for reducing the free formaldehyde concentration of a styrene-acrylic dispersion (latex) and a method for producing a styrene-acrylic product (e.g., a waterproof adhesive) is shown. As Figure 1As shown, the process includes: Step A) dissolving a cyclic polycarbonyl compound (b) and a hydroxyl group-functionalized amine compound (c) in an aqueous solvent (e.g., water) to form an aqueous solution, which is referred to as a "complex solution" as it is a complex of a binary formaldehyde scavenging system; Step B) providing an aqueous dispersion (a) containing polymer particles, for example, by preparation or purchase; and Step C) adding the complex solution to the aqueous dispersion to produce a styrene-acrylic-based product with a reduced formaldehyde content.

[0019] According to an embodiment, in Step A), the cyclic polycarbonyl compound and the hydroxyl group-functionalized amine compound are dissolved in an aqueous solvent (such as water) to form two separate aqueous solutions for each compound or one aqueous solution containing both. Based on the total weight of the solution, the aqueous solution can have a solids content of 5 wt% to 40 wt%, such as 10 wt% to 30 wt%, or 20 wt% to 25 wt% by weight. As used herein, the aqueous solution is referred to as a "complex solution" as it is a complex of a binary formaldehyde scavenging system. According to an embodiment, the aqueous solution does not contain an organic solvent, i.e., only water is used as the solvent for the complex solution. According to an embodiment, the preparation of the complex aqueous solution can be carried out at any temperature, and an elevated temperature can be employed to facilitate dissolution. According to a specific embodiment, the complex aqueous solution is prepared at ambient temperature.

[0020] According to an embodiment, in Figure 1 Step B) as shown, the aqueous dispersion is provided by the polymerization of at least one acrylic monomer or a combination of at least one acrylic monomer and at least one styrene monomer. According to an alternative embodiment, in Figure 1 Step A) as shown, the aqueous dispersion is provided by a commercial supplier.

[0021] As used herein, the term "acrylic" in the present invention includes (meth)acrylic acid, (meth)acrylic acid alkyl esters, (meth)acrylamide, (meth)acrylonitrile, and their modified forms, such as (meth)acrylic acid hydroxyalkyl esters. For example, (meth)acrylic acid refers to both methacrylic acid and acrylic acid, and (meth)acrylic acid methyl ester refers to both methyl methacrylate and methyl acrylate. According to an embodiment of the present application, the acrylic monomer used to prepare the acrylic or styrene-acrylic particles (a) can be a linear or branched (meth)acrylic acid (C1-C 22 ) alkyl ester, (meth)acrylic acid (C3-C 22 ) cycloalkyl ester, or (meth)acrylic acid (C6-C 22)aryl esters, and exemplary acrylic monomers can be selected from the group consisting of: acrylic acid, methacrylic acid, 2-hydroxyethyl methacrylate, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 3-butanediol dimethacrylate, acrylonitrile, isobutyl (meth)acrylate, hexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, acrylamide, methacrylamide, allyl (meth)acrylate, 2-methylallyl (meth)acrylate, allyl (meth)acrylamide, 2-methylallyl (meth)acrylamide, allyloxyethyl (meth)acrylate, 2-methylallyloxyethyl (meth)acrylate, crotyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenylethyl (meth)acrylate, diallyl maleate, and any combination thereof. According to an embodiment, based on the total weight of the acrylic polymer, the acrylic polymer comprises 59 wt% to 100 wt% of the above-described acrylic monomers; such as 65 wt% to 95 wt%, or 70 wt% to 90 wt%, or 75 wt% to 85 wt%, or 78 wt% to 85 wt%, or within the numerical range obtained by combining any two of the above-described endpoints.

[0022] According to another embodiment, the styrene monomer for the acrylic-styrene polymer can be styrene or a substituted styrene having one, two, three, four, or five substituents selected from the group consisting of: hydroxyl, straight-chain or branched C1-C12 alkyl, straight-chain or branched C1-C12 alkoxy, C3-C12 cycloalkyl, halogen, and nitrile groups. Based on the total weight of the styrene-acrylic polymer, the styrene-acrylic polymer can comprise 0.1 wt% to 90 wt%, or 10 wt% to 80 wt%, or 20 wt% to 70 wt%, or 30 wt% to 60 wt%, or 40 wt% to 50 wt% of the above-described styrene monomer, and 10 wt% to 90 wt%, or 20 wt% to 80 wt%, or 30 wt% to 70 wt%, or 40 wt% to 60 wt%, or 45 wt% to 55 wt% of the above-described acrylic monomers.

[0023] According to another embodiment, the monomer raw materials for preparing acrylic polymers or acrylic-styrene polymers may further comprise one or more additional ethylenically unsaturated monomers, and based on the total weight of the polymer, the content of these ethylenically unsaturated monomers may be 0.1 wt% to 20 wt%, or 1 wt% to 15 wt%, or 5 wt% to 10 wt%. The ethylenically unsaturated monomers may be selected from the group consisting of itaconic acid, fumaric acid, maleic acid, maleic anhydride, itaconic anhydride, N-vinylformamide, N-vinylpyrrolidone, N-methyl-2-methyleneoxazolidine, 2-methylene-1,3-thiolene, ethylene, propylene, isobutene, butadiene, isoprene, vinyl methyl ether, vinyl isobutyl ether, vinylpyridine, β-aminoethyl vinyl ether, aminopentyl vinyl ether, vinyl acetate, sodium vinyl sulfonate, and any combination thereof.

[0024] According to some embodiments, the aqueous dispersion (a) of polymer particles comprising an acrylic polymer or a styrene-acrylic polymer can be prepared by any suitable method, such as by free radical polymerization (e.g., emulsion polymerization), wherein the above-described acrylic monomers, styrene monomers, and optionally additional ethylenically unsaturated monomers react to produce a dispersion of acrylic or styrene-acrylic polymer particles dispersed in an aqueous medium. The free radical polymerization can be carried out at ambient temperature or at an elevated temperature, such as 30°C to 150°C, or 50°C to 130°C, or 60°C to 100°C, or 70°C to 90°C.

[0025] Common additives, such as catalysts, cocatalysts, chain transfer agents, initiators, surfactants, etc., can be appropriately introduced during the polymerization.

[0026] According to some embodiments, examples of surfactants include, but are not limited to, cationic surfactants, anionic surfactants, zwitterionic surfactants, nonionic surfactants, and combinations thereof. Examples of anionic surfactants include, but are not limited to, alkylphenol ether sulfates, carboxylates and phosphates, sodium dodecylbenzenesulfonate, alkyl alkoxylate sulfates / carboxylates or phosphates, wherein the alkyl group has 8 to 20 carbon atoms. Examples of nonionic surfactants include, but are not limited to, linear or branched aliphatic alcohol ethoxylates or alkoxylates, fatty acid methyl ethoxylate esters, sorbitan derivatives.

[0027] According to some embodiments, the initiator can be either a thermal initiator or a redox initiator. Exemplary thermal initiators include, but are not limited to, sodium persulfate and ammonium persulfate, and examples of redox initiators consist of at least one reducing agent, such as ascorbic acid, metabisulfite, or isoascorbic acid; and at least one oxidizing agent, such as a peroxide or a persulfate.

[0028] According to some embodiments, a chain transfer agent may optionally be used in the polymerization. Exemplary chain transfer agents include long-chain alkyl mercaptans (such as tert-dodecyl mercaptan), methyl 3-mercaptopropionate, alcohols (such as isopropyl alcohol, isobutyl alcohol, lauryl alcohol, or tert-octyl alcohol), carbon tetrachloride, tetrachloroethylene, and bromotrichloroethane.

[0029] According to some embodiments, at least one additive may optionally be post-added to the polymer. Examples of the at least one additive include, but are not limited to, thickeners, defoamers, wetting agents, mechanical stabilizers, pigments, fillers, freeze-thaw agents, neutralizing agents, plasticizers, tackifiers, adhesion promoters, and any combination thereof.

[0030] According to another embodiment, the aqueous dispersion (a) comprising polymer particles may be commercially available.

[0031] According to some embodiments, the aqueous dispersion (a) comprising polymer particles (prepared via polymerization or purchased from a supplier) has a first free formaldehyde concentration as indicated above, which needs to be further reduced in order to meet the environmental regulations of a specific country / region or to further improve the product competitiveness.

[0032] According to some embodiments, the dispersion provided in step B) has a pH value between 2.0 and 10.0, such as between 3.0 and 9.0, or between 4.0 and 7.5, or between 5.0 and 6.6.

[0033] In step C) as Figure 1 shown, the complex solution prepared in step A) is added to the aqueous dispersion provided in step B) and reacted with the free formaldehyde contained therein, thereby reducing the free formaldehyde concentration to a second free formaldehyde concentration, where the second free formaldehyde concentration is less than 90% of the first free formaldehyde concentration, such as less than 70% of the first free formaldehyde concentration, or less than 50%, or less than 30%, or less than 25%, or less than 20%, or less than 15%, or less than 10%, or less than 5%, or less than 1%. According to some embodiments, based on the weight of the resulting product, the second free formaldehyde concentration is less than 100 ppm, such as from 0.1 ppm to 50 ppm, or from 0.5 ppm to 20 ppm, or from 0.8 ppm to 10 ppm, or from 1 ppm to 5 ppm, or less than 2 ppm based on the weight of the resulting product. An aqueous solution of the compound (b) and the compound (c) can be directly added to the aqueous dispersion (a) containing the particles, and the blend is thoroughly mixed by stirring to promote the formaldehyde scavenging reaction. According to one embodiment, the formaldehyde scavenging reaction can be carried out at ambient temperature or at an elevated temperature such as from 15°C to 100°C, or from 20°C to 80°C, or from 25°C to 60°C, or from 30°C to 50°C.

[0034] According to some embodiments, the cyclic polycarbonyl compound has a structure represented by any one of Formulas I to XVI,

[0035]

[0037] wherein each of R1, R2, R3, and R4 is independently selected from the group consisting of: hydrogen, straight-chain or branched C1-C 12 alkyl, straight-chain or branched C1-C 12 alkoxy, C3-C 12 cycloalkyl, C6-C 12 aryl, halogen, and nitrile groups. According to specific embodiments, each of R1, R2, R3, and R4 is independently selected from the group consisting of: hydrogen, straight-chain or branched C1-C6 alkyl, straight-chain or branched C1-C6 alkoxy, C3-C6 cycloalkyl, and C6-C9 aryl.

[0038] According to some embodiments, the cyclic polycarbonyl compound is selected from the group consisting of: cyclohexane-1,3-dione, 5,5-dimethylcyclohexane-1,3-dione, 5,5-diethylcyclohexane-1,3-dione, 6-methylcyclohexane-1,3-dione, 6-ethylcyclohexane-1,3-dione, cyclohexane-1,3,5-trione, pyrazolidine-3,5-dione, 1,2-dimethylpyrazolidine-3,5-dione, 1,2-diethylpyrazolidine-3,5-dione, 1-methylpyrazolidine-3,5-dione, 1-ethylpyrazolidine-3,5-dione, pyran-3,5-dione, 2-methyl-pyran-3,5-dione, pyran-2,4-dione, 6-methyl-pyran-2,4-dione, 6-ethyl-pyran-2,4-dione, 6-isopropyl-pyran-2,4-dione, 6-(n)-butyl-pyran-2,4-dione, 6-isobutyl-pyran-2,4-dione, 6-pentyl-pyran-2,4-dione, 6-isopentyl-pyran-2,4-dione, [1,3]-dioxane-4,6-dione, 2,2-dimethyl-[1,3]-dioxane-4,6-dione, 2,2-diethyl-[1,3]-dioxane-4,6-dione, 2,2-dipropyl-[1,3]-dioxane-4,6-dione, 2-phenyl-[1,3]-dioxane-4,6-dione, 2,4,6-trioxo-hexahydropyrimidine, 1-methyl-2,4,6-trioxo-hexahydropyrimidine, 1,3-dimethyl-2,4,6-trioxo-hexahydropyrimidine, 1,3-diethyl-2,4,6-trioxo-hexahydropyrimidine, 1-phenyl-2,4,6-trioxo-hexahydropyrimidine, furan-2,4(3H,5H)-dione, 3-methyl-furan-2,4(3H,5H)-dione, 3,3-dimethyl-furan-2,4(3H,5H)-dione, 3-ethyl-furan-2,4(3H,5H)-dione, 3,3-diethyl-furan-2,4(3H,5H)-dione, and any combination thereof. For example, the cyclic polycarbonyl compound can be cyclohexane-1,3-dione or 5,5-dimethylcyclohexane-1,3-dione.

[0039] According to some embodiments, the hydroxy group-functionalized amine compound has a structure represented by Formula A:

[0040]

[0041] wherein X is a direct bond, a methylene group, a methine group or a quaternary carbon group, n is an integer of 1, 2 or 3, and each of R5, R6 and R7 is independently selected from the group consisting of: hydrogen, hydroxy, straight-chain or branched C1-C 12 alkyl, C6-C 12 aryl, straight-chain or branched C1-C 12 hydroxyalkyl, C6-C 12Hydroxyaryl, -NR8R9, C1-C 12 Alkylene-NR8R9, C1-C 12 Hydroxyalkylene-NR8R9, C6-C 12 Arylene-NR8R9 and C6-C 12 Hydroxyarylene-NR8R9, wherein each of R8 and R9 is independently selected from the group consisting of: hydrogen, straight-chain or branched C1-C 12 Alkyl, C6-C 12 Aryl, straight-chain or branched C1-C 12 Hydroxyalkyl and C6-C 12 Hydroxyaryl; provided that at least one of R5, R6 and R7 comprises one or more hydroxy groups. According to specific embodiments, each of R5, R6 and R7 is independently selected from the group consisting of: hydrogen, hydroxy, straight-chain or branched C1-C6 alkyl, C6-C9 aryl, straight-chain or branched C1-C6 hydroxyalkyl, C6-C9 hydroxyaryl, -NR8R9, C1-C6 alkylene-NR8R9, C1-C6 hydroxyalkylene-NR8R9, C6-C9 arylene-NR8R9 and C6-C9 hydroxyarylene-NR8R9, wherein each of R8 and R9 is independently selected from the group consisting of: hydrogen, straight-chain or branched C1-C6 alkyl, C6-C9 aryl, straight-chain or branched C1-C6 hydroxyalkyl and C6-C9 hydroxyaryl; provided that at least one of R5, R6 and R7 comprises one or more hydroxy groups.

[0042] According to some specific embodiments, when X is a direct bond, a methylene group, a methine group or a quaternary carbon group, respectively, the hydroxy group-functionalized amine compound has a structure represented by Formula AI, Formula AII, Formula AIII or Formula AIV,

[0043]

[0044] wherein R5, R6 and R7 are as indicated above.

[0045] According to some specific embodiments, the hydroxy group-functionalized amine compound has a hydroxy functionality of 2 to 4, for example, a hydroxy functionality of 3.

[0046] According to some specific embodiments, the hydroxy group-functionalized amine compounds are selected from the group consisting of: ethanolamine, diethanolamine, 1,1,1-tris(hydroxymethyl)methylamine, 1,1-bis(hydroxymethyl)-1-(hydroxyethyl)methylamine, 1-bis(hydroxyethyl)-1,1-(hydroxyethyl)methylamine, 1,1,1-tris(hydroxyethyl)methylamine, 2-amino-1-butanol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol, 2-amino-1-methyl-1,3-propanediol, N-methylethanolamine, N-butylethanolamine, monoisopropanolamine, 2-amino-2(hydroxymethyl)propane-1,3-diol, diisopropanolamine, monosecondary butanolamine, di-secondary butanolamine, N-isopropylhydroxylamine, N-ethylhydroxylamine, N-methylhydroxylamine, N-butylhydroxylamine, N-(secondary butyl)hydroxylamine, their salts, and any combination thereof. For example, the hydroxy group-functionalized amine compound can be 1,1,1-tris(hydroxymethyl)methylamine.

[0047] According to some specific embodiments, based on the total weight of the aqueous dispersion, the combined concentration of the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound is from 20 ppm to 1,000 ppm, such as from 50 ppm to 800 ppm, or from 100 ppm to 700 ppm, or from 200 ppm to 600 ppm, or from 250 ppm to 500 ppm, or from 300 ppm to 500 ppm, or within any numerical range obtained by combining any two of the above-mentioned endpoints. According to an alternative embodiment, when it is estimated that the aqueous dispersion (a) containing particles further contains some potential formaldehyde-generating substances, a higher amount of the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound can be used, and the potential formaldehyde-generating substances may further emit free formaldehyde during long-term storage and use. For example, the combined molar content of the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound can be more than one-fold, such as 1 to 50 times, such as 1 to 30 times, or 1 to 25 times, or 1 to 10 times the total formaldehyde (i.e., the sum of free formaldehyde and potential formaldehyde-generating substances) contained in the aqueous dispersion (a) containing particles. According to some embodiments, the molar ratio between the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound is from 1:1 to 1:10, such as from 1:1 to 1:5, or from 1:1 to 1:2.5, or from 1:1.25 to 1:2.5, or from 1:2 to 1:2.5, or within the range obtained by combining any two of the above ratios.

[0048] According to some embodiments, after the treatment in step C), after incorporating the complex solution, the pH of the aqueous dispersion does not change significantly. For example, the aqueous dispersion may have a pH value between 2.0 and 10.0, such as 3.0 to 9.0, or 4.0 to 7.5, or 5.0 to 6.6.

[0049] One or more additional steps (not shown in Figure 1 ) may optionally be carried out before or after each of steps A) to C) according to actual needs, and examples of such additional steps include concentration, dilution, filtration, pH adjustment or incorporation of any additives as described above.

[0050] The aqueous dispersion produced after step C) described above can be used as products including adhesives, coating materials, paints, primers, sealants, etc., which can be used in various applications such as building components, automotive parts, furniture, interior decoration, containers, packaging materials, household appliances, manufacturing equipment, analytical devices, etc.

[0051] Based on the specially designed compositions and methods, the following benefits have been successfully achieved:

[0052] a) Effective removal of free formaldehyde in acrylic-based or styrene-acrylic-based aqueous dispersions;

[0053] b) Long-term inhibition of formaldehyde emission;

[0054] c) Excellent color fastness and viscosity stability;

[0055] d) Applicability at weak acidic, neutral and weak basic pH values; and

[0056] e) Excellent cost-effectiveness.

[0057] Example

[0058] Some embodiments of the present invention will now be described in the following examples, where all parts and percentages are by weight unless otherwise specified. However, the scope of the present disclosure is of course not limited to the formulations described in these examples. On the contrary, the examples are merely for illustrative purposes of the present disclosure.

[0059] All raw materials are commercial products and are used as received. The water used in the examples is deionized water, and the information of the main raw materials is listed in Table 1 below:

[0060] Table 1. Raw materials used in the examples

[0061]

[0062] Characterization technique :

[0063] 1. Characterization of free formaldehyde concentration 。

[0064] In the following examples, the concentration of free formaldehyde in any sample was characterized by HPLC according to GB / T30982-2014 "Limit of Hazardous Substances in Construction Adhesive", and specifically according to the following procedure: Approximately 0.1 g of DNPH was dissolved in 10 ml of phosphoric acid by vortexing for more than 2 minutes, and the resulting solution was designated as the "DNPH solution". A stock standard with a concentration of 1000 mg / L purchased from J&K Chemical was diluted with ACN to produce a series of standards. 0.5 ml of the standard solution and 0.5 ml of acetonitrile were transferred to a 20 ml glass vial with a pipette, and then derivatized with 0.05 ml of the "DNPH solution" for 24 hours. A blank sample was also prepared and characterized to obtain a calibration curve.

[0065] The sample to be measured was dissolved in acetonitrile at a dilution factor of 8, and then 0.5 ml of the resulting sample solution and 0.5 ml of acetonitrile were transferred to a 20 ml glass vial with a pipette and derivatized with 0.05 ml of the "DNPH solution" for 24 hours. A blank sample was also prepared and characterized to obtain a calibration curve. The sample was tested by HPLC coupled with a UV detector having a peak wavelength of 360 nm. The instrument information and process conditions for HPLC analysis are summarized in Table 2 below:

[0066] Table 2: Instrument information and process conditions for HPLC analysis

[0067]

[0068] 2. Color test

[0069] Approximately 23 g of the liquid latex samples prepared in each of the following examples were separately poured into plastic trays and heated overnight in an oven at 70 °C to form films. The L / A / B / ΔE values of the films were measured on a DATACOLOR Spectro 1000 spectrophotometer to evaluate the color change in the films.

[0070] 3. pH value

[0071] The pH value of each liquid sample was measured with a pH meter.

[0072] 4. Viscosity

[0073] The viscosity of each liquid sample was measured using a Brookfield LV#2 viscometer.

[0074] 5. Accelerated thermal aging of the sample

[0075] The liquid latex samples prepared in each of the following examples were heated in an oven at 54 °C for one to six weeks. After the predetermined duration, the samples were taken out and subjected to color testing and free formaldehyde concentration testing as described above.

[0076] Example 1 of the present invention :

[0077] In this example, a stock latex was prepared by free radical polymerization of an aqueous emulsion of styrene and MMA. The stock latex is an aqueous dispersion of styrene-acrylic polymer particles, which has a solids content of 47.0 wt%, a pH of 6.6, and a viscosity of less than 75 cps. Although the raw materials have been carefully selected to minimize the introduction of any aldehyde-generating components into the reaction system, detectable amounts of formaldehyde are still present in this stock latex.

[0078] A solution was prepared by dissolving 30.00 g of Tris-A and 17.00 g of dimedone in 188.00 g of DI water. 200.00 g of the stock latex was weighed and transferred to a kettle equipped with a stirrer paddle. Then, 0.501 g of the solution was weighed and slowly added dropwise to the kettle under gentle stirring using a dropper. After adding the solution, the mixture in the kettle was further stirred for about 10 minutes to form a homogeneous aqueous dispersion.

[0079] The samples prepared in this example were subjected to color testing, free formaldehyde concentration testing, and accelerated heat aging testing as described above, and the characterization results are summarized in Table 3.

[0080] Comparative Examples 1 to 5

[0081] Comparative Examples 1 to 5 were carried out by repeating the above-described procedures and parameters of Example 1 of the present invention, except that the solution of Tris-A and dimedone was omitted in Comparative Example 1, and for Comparative Examples 2, 3, 4, and 5, they were respectively replaced with solutions of HPA-X, DETA, TETA, and PEI in DI water at the same concentration.

[0082] The samples prepared in these comparative examples were similarly subjected to color testing, free formaldehyde concentration testing, and accelerated heat aging testing as described above, and the characterization results are summarized in Table 3.

[0083] Table 3. Characterization results of Example (Ex.) 1 and Comparative Examples (Co.Ex.) 1-5 of the present invention

[0084]

[0085]

[0086] As can be seen from the experimental results summarized in Table 3, the sample of Example 1 of the present invention exhibits excellent free formaldehyde removal efficiency, long-term formaldehyde generation inhibition, and good colorfastness. In addition, it can be seen that the sample of Example 1 of the present invention is the only one that is very suitable for a weakly acidic pH value.

[0087] Example 2 of the present invention

[0088] Example 2 of the present invention was carried out by repeating the above-described procedures and parameters of Example 1 of the present invention, except that the addition amounts were adjusted while keeping the total mass of Tris-A and dimedone constant. Specifically, a solution was prepared by dissolving 24.41 g of Tris-A and 22.59 g of dimedone in 188.00 g of DI water. 200.00 g of the stock latex was weighed and transferred to a kettle equipped with a stirring paddle, and then 0.501 g of the solution was weighed and slowly added dropwise to the kettle under gentle stirring using a dropper. After adding the solution, the mixture in the kettle was further stirred for about 10 minutes to form a uniform aqueous dispersion.

[0089] The sample prepared in this example was subjected to the free formaldehyde concentration test as described above, and the characterization results are listed in Table 4.

[0090] Example 3 of the present invention

[0091] Example 3 of the present invention was carried out by repeating the above-described procedures and parameters of Example 1 of the present invention, except that the addition amounts were adjusted while keeping the total mass of Tris-A and dimedone constant. Specifically, a solution was prepared by dissolving 21.79 g of Tris-A and 25.21 g of dimedone in 188.00 g of DI water. 200.00 g of the stock latex was weighed and transferred to a kettle equipped with a stirring paddle, and then 0.501 g of the solution was weighed and slowly added dropwise to the kettle under gentle stirring using a dropper. After adding the solution, the mixture in the kettle was further stirred for about 10 minutes to form a uniform aqueous dispersion.

[0092] The sample prepared in this example was subjected to the free formaldehyde concentration test as described above, and the characterization results are listed in Table 4.

[0093] Table 4. Formulations and free formaldehyde removal results of Examples 1-3 of the present invention 。

[0094]

[0095]

[0096] The formaldehyde removal results of all Examples 1-3 of the present invention are summarized in Table 4. It can be seen therefrom that the relative content of dimedone / Tris-A used in Example 1 of the present invention can achieve the highest formaldehyde scavenging effect.

Claims

1. An aqueous polymer composition, the aqueous polymer composition comprising (a) an aqueous dispersion of polymer particles, the polymer particles comprising an acrylic polymer, a styrene-acrylic polymer, or a combination thereof, wherein the aqueous dispersion comprises formaldehyde; (b) at least one cyclic polycarbonyl compound; and (c) at least one hydroxyl group-functionalized amine compound, wherein the at least one cyclic polycarbonyl compound and the at least one hydroxyl group-functionalized amine compound are formaldehyde scavenging.

2. The aqueous polymer composition according to claim 1, wherein the cyclic polycarbonyl compound has a structure represented by any one of Formulas I to XVI, wherein each of R1, R2, R3 and R4 is independently selected from the group consisting of: hydrogen, straight-chain or branched C1-C 12 alkyl, straight-chain or branched C1-C 12 alkoxy, C3-C 12 cycloalkyl, C6-C 12 aryl, halogen and nitrile groups.

3. The aqueous polymer composition according to claim 2, wherein the cyclic polycarbonyl compound is selected from the group consisting of: cyclohexane-1,3-dione, 5,5-dimethylcyclohexane-1,3-dione, 5,5-diethylcyclohexane-1,3-dione, 6-methylcyclohexane-1,3-dione, 6-ethylcyclohexane-1,3-dione, cyclohexane-1,3,5-trione, pyrazolidine-3,5-dione, 1,2-dimethylpyrazolidine-3,5-dione, 1,2-diethylpyrazolidine-3,5-dione, 1-methylpyrazolidine-3,5-dione, 1-ethylpyrazolidine-3,5-dione, pyran-3,5-dione, 2-methyl-pyran-3,5-dione, pyran-2,4-dione, 6-methyl-pyran-2,4-dione, 6-ethyl-pyran-2,4-dione, 6-isopropyl-pyran-2,4-dione, 6-(n)-butyl-pyran-2,4-dione, 6-isobutyl-pyran-2,4-dione, 6-pentyl-pyran-2,4-dione, 6-isopentyl-pyran-2,4-dione, [1,3]-dioxane-4,6-dione, 2,2-dimethyl-[1,3]-dioxane-4,6-dione, 2,2-diethyl-[1,3]-dioxane-4,6-dione, 2,2-dipropyl-[1,3]-dioxane-4,6-dione, 2-phenyl-[1,3]-dioxane-4,6-dione, 2,4,6-trioxo-hexahydropyrimidine, 1-methyl-2,4,6-trioxo-hexahydropyrimidine, 1,3-dimethyl-2,4,6-trioxo-hexahydropyrimidine, 1,3-diethyl-2,4,6-trioxo-hexahydropyrimidine, 1-phenyl-2,4,6-trioxo-hexahydropyrimidine, furan-2,4(3H,5H)-dione, 3-methyl-furan-2,4(3H,5H)-dione, 3,3-dimethyl-furan-2,4(3H,5H)-dione, 3-ethyl-furan-2,4(3H,5H)-dione, 3,3-diethyl-furan-2,4(3H,5H)-dione, and any combination thereof.

4. The aqueous polymer composition according to claim 1, wherein the hydroxyl group-functionalized amine compound has a structure represented by Formula A: wherein X is a direct bond, a methylene group, a methine group or a quaternary carbon group, n is an integer of 1, 2 or 3, and each of R5, R6 and R7 is independently selected from the group consisting of: hydrogen, hydroxy, straight-chain or branched C1-C 12 alkyl, C6-C 12 aryl, straight-chain or branched C1-C 12 hydroxyalkyl, C6-C 12 hydroxyaryl, -NR8R9, C1-C 12 alkylene-NR8R9, C1-C 12 hydroxyalkylene-NR8R9, C6-C 12 arylene-NR8R9 and C6-C 12 hydroxyarylene-NR8R9, wherein each of each of R8 and R9 is independently selected from the group consisting of: hydrogen, straight-chain or branched C1-C 12 alkyl, C6-C 12 aryl, straight-chain or branched C1-C 12 hydroxyalkyl and C6-C 12 hydroxyaryl; provided that at least one of R5, R6 and R7 comprises one or more hydroxy groups.

5. The aqueous polymer composition according to claim 4, wherein the hydroxy group-functionalized amine compound is selected from the group consisting of ethanolamine, diethanolamine, 1,1,1-tris(hydroxymethyl)methylamine, 1,1-bis(hydroxymethyl)-1-(hydroxyethyl)methylamine, 1-bis(hydroxyethyl)-1,1-(hydroxyethyl)methylamine, 1,1,1-tris(hydroxyethyl)methylamine, 2-amino-1-butanol, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol, 2-amino-1-methyl-1,3-propanediol, N-methylethanolamine, N-butylethanolamine, monoisopropanolamine, 2-amino-2(hydroxymethyl)propane-1,3-diol, diisopropanolamine, monosecondary butanolamine, di-secondary butanolamine, N-isopropylhydroxylamine, N-ethylhydroxylamine, N-methylhydroxylamine, N-butylhydroxylamine, N-(secondary butyl)hydroxylamine, their salts, and any combination thereof.

6. The aqueous polymer composition according to claim 1, wherein the aqueous dispersion has a pH value between 2.0 and 10.

0.

7. The aqueous polymer composition according to claim 1, wherein based on the weight of the aqueous dispersion, the combined concentration of the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound is from 20 ppm to 1,000 ppm; and the molar ratio between the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound is from 1:1 to 1:

10.

8. A product obtained from the aqueous polymer composition according to any one of claims 1 to 7, wherein the aqueous product is an adhesive, a coating material, a paint, a primer, or a sealant, and wherein the free formaldehyde concentration of the product is less than the free formaldehyde concentration in the aqueous dispersion.

9. A method for preparing a product with reduced formaldehyde by using the aqueous polymer composition according to any one of claims 1 to 6, wherein the product is an adhesive, a coating material, a paint, a primer, or a sealant, and the method comprises: combining the aqueous dispersion containing polymer particles with the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound to reduce the formaldehyde content contained in the aqueous dispersion, the polymer particles comprising an acrylic polymer, a styrene-acrylic polymer, or a combination thereof.

10. A method for reducing the formaldehyde content in the product according to claim 8, the method comprising: providing an aqueous dispersion containing polymer particles, the polymer particles comprising an acrylic polymer, a styrene-acrylic polymer, or a combination thereof, wherein the aqueous dispersion has a first free formaldehyde concentration; and adding the cyclic polycarbonyl compound and the hydroxy group-functionalized amine compound to the aqueous dispersion to reduce the formaldehyde to a second free formaldehyde concentration, wherein the second free formaldehyde concentration is less than 90% of the first free formaldehyde concentration.

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