Two-component polyurethane composition

Abstract

The two-component polyurethane composition contains (A) an aqueous dispersion containing 5% by weight to 50% by weight of a hydroxyl-containing acrylic emulsion polymer containing hydroxy-functional alkyl (meth)acrylate structural units, based on the weight of the hydroxyl-containing acrylic emulsion polymer, and 2% by weight to 20% by weight of a branched polyether polyol, based on the weight of the hydroxyl-containing acrylic emulsion polymer, wherein the branched polyether polyol has a hydroxyl functionality of 4 to 10 and a molecular weight per branch of 1200 to 2500 grams per mole, and contains 20% by weight to 40% by weight of ethylene oxide units, based on the weight of the branched polyether polyol, and (B) a polyisocyanate.

Description

[Technical field]

[0001] The present invention relates to a two-component polyurethane composition and a process for preparing the same. [Background technology]

[0002] Water-based two-component polyurethane compositions are increasingly being used in the coating industry due to their zero or lower volatile organic compounds (VOCs) compared to solvent-based polyurethane compositions. Although two-component water-based polyurethane compositions can provide coatings with acceptable appearance (e.g., gloss and fullness) and similar mechanical properties to solvent-based polyurethane compositions, they cannot provide a sufficiently long pot life, as indicated by foaming problems and / or loss of gloss of the coating after storage. Incorporating isocyanates with hydrophilic modifications ("hydrophilic isocyanates") into two-component polyurethane coating compositions can extend pot life due to better water dispersibility compared to unmodified polyisocyanates. However, many customers prefer to use unmodified isocyanates due to better chemical and water resistance, thicker bubble-free film thickness, and lower cost compared to hydrophilic isocyanates.

[0003] Therefore, there remains a need to provide an aqueous two-component polyurethane composition that has an extended pot life without compromising other properties such as appearance. Summary of the Invention

[0004] The present invention provides an aqueous two-component polyurethane composition that is particularly suitable for coatings by combining a hydroxyl-containing acrylic emulsion polymer and a specific branched polyether polyol with a polyisocyanate. The polyurethane composition of the present invention provides acceptable initial gloss and distinctness of image (DOI) while having excellent pot life, as shown by a 60° gloss of greater than 75 after 3 hours storage at 35° Celsius (° C). These properties can be measured according to the test methods described in the Examples section below.

[0005] In a first aspect, the present invention provides a two-component polyurethane composition comprising: (A) 10% to 50% by weight, based on the weight of the hydroxyl-containing acrylic emulsion polymer, of a hydroxyl-functional alkyl (meth)acrylate structural unit; an aqueous dispersion comprising 2% to 20% by weight of a branched polyether polyol, based on the weight of the hydroxyl group-containing acrylic emulsion polymer, the branched polyether polyol having a hydroxyl functionality of 4 to 10 and a molecular weight per branch of 1200 to 2500 grams per mole, and containing 20% ​​to 40% by weight of ethylene oxide units, based on the weight of the branched polyether polyol; (B) a polyisocyanate.

[0006] In a second aspect, the invention is a process for preparing the two-component polyurethane composition of the first aspect, the process comprising admixing an aqueous dispersion (A) with a polyisocyanate (B). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Test methods refer to the test method most recent at the priority date of this document unless a date is given with the test method number. Reference to a test method includes both a reference to the testing society and the test method number. The following test method abbreviations and identifiers apply herein: ASTM refers to ASTM International methods.

[0008] Products identified by trade names refer to compositions available under those trade names as of the priority date of this document. "And / or" means "and, or alternatively." All ranges are inclusive of endpoints unless otherwise indicated.

[0009] By "aqueous" dispersion herein is meant that the particles are dispersed in an aqueous medium. By "aqueous medium" herein is meant water and 0-30% by weight, based on the weight of the medium, of a water-miscible compound(s), such as, for example, an alcohol, a glycol, a glycol ether, a glycol ester, or a mixture thereof.

[0010] A "structural unit," also known as a "polymerized unit," of a specified monomer refers to the remainder of the monomer after polymerization, i.e., the polymerized monomer or the polymerized form of the monomer. For example, the structural unit of methyl methacrylate is:

[0011] [ka] where the dotted lines represent the points of attachment of the structural units to the polymer backbone.

[0012] "Acrylic emulsion polymer" herein refers to an emulsion homopolymer of an acrylic monomer or an emulsion copolymer of an acrylic monomer with a different acrylic monomer or with other monomers such as styrene and vinyl acetate. "Acrylic monomer" as used herein includes (meth)acrylic acid, alkyl (meth)acrylates, (meth)acrylamides, (meth)acrylonitrile, and modified forms thereof, such as hydroxyalkyl (meth)acrylates. Throughout this document, the fragment "(meth)acrylic" refers to both "methacrylic" and "acrylic". For example, (meth)acrylic acid refers to both methacrylic acid and acrylic acid, and methyl (meth)acrylate refers to both methyl methacrylate and methyl acrylate.

[0013] The "functionality" or "Fn" of a polyol herein refers to the number of hydroxyl (OH) groups per molecule. The functionality (Fn), the concentration of ethylene oxide, propylene oxide and butylene oxide units for the polyether polyol, and the chemical structure of the initiator for preparing the polyether polyol are determined according to standard methods. 13 Determined by C nuclear magnetic resonance (NMR) analysis.

[0014] By "branched" polyether polyol herein is meant a polyether polyol having a functionality >2.

[0015] The two-component polyurethane composition of the present invention typically comprises Part A and Part B, where Part A comprises an aqueous dispersion comprising a hydroxyl-containing acrylic emulsion polymer and a branched polyether polyol, and Part B comprises one or more polyisocyanates. The branched polyether polyol is represented by the formula (I): R-[O-(AO) x -H] y (I) wherein R represents a polyvalent aliphatic hydrocarbon radical; each AO is independently selected from ethylene oxide units (-CH-CH-0-), propylene oxide units (-CH-CH(CH)-0-), butylene oxide units (-CH-CH(CHCH)-0-), or combinations thereof, with the proviso that the ethylene oxide units are present in a total concentration of 20% to 40% by weight, based on the weight of the branched polyether polyol; The subscript x refers to the average moles of alkylene oxide and can range from 20 to 55; The subscript y refers to the functionality of the polyether polyol, which can range from 4 to 10.

[0016] Each AO in formula (I) may be in block or random order. The value of subscript x may be sufficient to provide a branched polyether polyol having a desired molecular weight per branch, as described below.

[0017] "Multivalent" radicals include radicals with a valence of four or more. The R group can be derived from an initiator used in the preparation of a polyether polyol having 4 to 10 hydroxyl groups by removing active hydrogen in the initiator. R can be a saturated hydrocarbon group, typically having 4 to 10 carbon atoms. Examples of R groups can be pentaerythrityl, sorbityl, or glycosyl.

[0018] Specific examples of branched polyether polyols include those represented by formula (II):

[0019] [ka] (In the formula, R''=

[0020] [ka] m is 5 to 23, and n is 12 to 35.

[0021] The branched polyether polyols useful in the present invention have a functionality (Fn) of 4 or more, and can be 5 or more, or even 6 or more, but at the same time, generally 10 or less, 9 or less, 8 or less, or even 6 or less. Desirably, each branch of the polyether polyol has one hydroxyl group. A mixture of two or more polyether polyols can be used, which may differ in functionality, amount of ethylene oxide units, and / or molecular weight per branch. When two or more polyols with different functionalities are used, Fn refers to the average functionality of these polyols. For example, for a mixture of 1 mole of polyol with Fn=6 and 2 moles of polyol with Fn=4, the average functionality=(1 * 6+2 * 4) / (1+2)=4.67.

[0022] The branched polyether polyols useful in the present invention may contain ethylene oxide units (-(CHCH-O)-) in a concentration of 20% or more, and can be 22% or more, 24% or more, 25% or more, 26% or more, 28% or more, 30% or more, 32% or more, or even 35% or more by weight, based on the weight of the branched polyether polyol, while at the same time generally being 40% or less, and can be 39% or less, 38% or less, 37% or less, 36% or less, or even 35% or less by weight.

[0023] The branched polyether polyols useful in the present invention may also contain propylene oxide units, butylene oxide units, or mixtures thereof in a concentration of 60% by weight or more, and can be 61% by weight or more, 62% by weight or more, 63% by weight or more, 64% by weight or more, or even 65% by weight or more, but at the same time generally not more than 80% by weight, and can be 78% by weight or less, 76% by weight or less, 75% by weight or less, 74% by weight or less, 72% by weight or less, 70% by weight or less, 68% by weight or less, or even 65% by weight or less. Desirably, the branched polyether polyol contains 20% by weight to 40% by weight of ethylene oxide units and 60% by weight to 80% by weight of propylene oxide units, more desirably 20% by weight to 35% by weight of ethylene oxide units and 65% by weight to 80% by weight of propylene oxide units, based on the weight of the branched polyether polyol.

[0024] The branched polyether polyol may have a molecular weight (also referred to as "total MW") of 4,800 grams per mole (g / mol) or more, and can be 5,000 g / mol or more, 5,200 g / mol or more, 6,200 g / mol or more, 6,500 g / mol or more, 7,000 g / mol or more, 8,000 g / mol or more, 9,000 g / mol or more, 10,000 g / mol or more, 11,000 g / mol or more, or even 12,000 g / mol, but at the same time generally not more than 25,000 g / mol, and can be not more than 20,000 g / mol, not more than 17,500 g / mol, not more than 15,000 g / mol, or even not more than 12,000 g / mol. The molecular weight of the branched polyether polyol can be calculated according to the following equation: Total MW=56100 / (OHV x Fn) where Total Mw represents the molecular weight of the polyol, OHV represents the hydroxyl number as measured by ASTM D4274, and Fn represents the functionality of the polyol.

[0025] The branched polyether polyols useful in the present invention may have a molecular weight per branch of 1,200 g / mol or more, 1,300 g / mol or more, 1,400 g / mol or more, 1,500 g / mol or more, 1,600 g / mol or more, 1,700 g / mol or more, 1,800 g / mol or more, 1,900 g / mol or more, or even 2,000 g / mol or more, but at the same time generally 2,500 g / mol or less, 2,400 g / mol or less, 2,300 g / mol or less, 2,200 g / mol or less, 2,100 g / mol or less, or even 2,000 g / mol or less. The molecular weight per branch (also referred to as "Mw per branch") can be determined as follows. Mw per branch = [total MW-MW(initiator)] / Fn where Total MW and Fn are as defined above, and MW(initiator) represents the molecular weight of the initiator used to prepare the polyol. MW(initiator) is 13 It can be determined based on the structure of the initiator as characterized by C NMR analysis.

[0026] The branched polyether polyols useful in the present invention can be obtained in a conventional manner by reacting an alkylene oxide, such as ethylene oxide, propylene oxide, butylene oxide, or a combination thereof, with an initiator in the presence of a catalyst for the ring-opening polymerization of the alkylene oxide. The polymerization can be bulk or solution polymerization. The initiator can have 4 to 10 active hydrogen atoms to prepare a branched polyether polyol having a hydroxyl functionality ranging from 4 to 10. Examples of suitable initiators include pentaerythritol, sorbitol, glucose, or mixtures thereof. Catalysts useful for the polymerization of alkylene oxides can be either anionic or cationic, such as KOH, boron trifluoride, or mixed cyanide complex (DMC) catalysts, such as zinc hexacyanocobaltate. The alkylene oxide is typically fed to a reactor containing dry initiator and catalyst at a temperature varying from 50° C. to 140° C. Polymerization is usually considered complete when the pressure in the reactor returns to approximately the same pressure as before the alkylene oxide was fed.

[0027] The branched polyether polyols useful in the present invention may be present in a concentration of 2 wt% or greater, based on the weight of the hydroxyl group-containing acrylic emulsion polymer, such as 2.1 wt% or greater, 2.2 wt% or greater, 2.3 wt% or greater, 2.4 wt% or greater, 2.5 wt% or greater, 3 wt% or greater, 3.5 wt% or greater, 4 wt% or greater, 4.5 wt% or greater, 5 wt% or greater, 5.5 wt% or greater, 6 wt% or greater, 6.5 wt% or greater, 7 wt% or greater, 7.5 wt% or greater, 8 wt% or greater, 9 wt% or greater, 10 wt% or greater, 11 wt% or greater, 12 wt% or greater, 13 wt% or greater, 14 wt% or greater, 15 wt% or greater, 16 wt% or greater, 17 wt% or greater, 18 wt% or greater, 19 wt% or greater, 20 wt% or greater, 21 wt% or greater, 22 wt% or greater, 23 wt% or greater, 24 wt% or greater, 25 wt% or greater, 26 wt% or greater, 27 wt% or greater, 28 wt% or greater, 29 wt% or greater, 30 wt% or greater, 31 wt% or greater, 32 wt% or greater, 33 wt% or greater, 34 wt% or greater, 35 wt% or greater, 36 wt% or greater, 37 wt% or greater, 38 wt% or greater, 39 wt% or greater, 40 wt% or greater, 40 wt% or greater, 40 wt% or greater, 40 wt% or greater, 4 %, 8.5% or more, 9% or more, 9.5% or more, or even 10% or more by weight, but at the same time, generally not more than 20% by weight, and can be not more than 19% by weight, not more than 18% by weight, not more than 17% by weight, not more than 16% by weight, not more than 15% by weight, not more than 14.5% by weight, not more than 14% by weight, not more than 13.5% by weight, not more than 13% by weight, not more than 12.5% ​​by weight, not more than 12% by weight, not more than 11.5% by weight, not more than 11% by weight, or even not more than 10.5% by weight. "Weight of hydroxyl-containing acrylic emulsion polymer" refers to the dry weight of acrylic emulsion polymer.

[0028] The aqueous dispersion (A) in the polyurethane composition comprises one or more hydroxyl-containing acrylic emulsion polymers. The acrylic emulsion polymers typically exist in the form of an aqueous dispersion (also referred to as "primary dispersion") synthesized by emulsion polymerization. The hydroxyl-containing acrylic emulsion polymers comprise one or more structural units of hydroxy-functional alkyl (meth)acrylates. Examples of suitable hydroxy-functional alkyl (meth)acrylates include hydroxyethyl (meth)acrylates, such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate; hydroxypropyl (meth)acrylates, such as 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, and 3-hydroxypropyl methacrylate; hydroxybutyl (meth)acrylates, such as 3-hydroxybutyl acrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate; 6-hydroxyhexyl acrylate; 6-hydroxyhexyl methacrylate; 3-hydroxy-2-ethylhexyl acrylate; 3-hydroxy-2-ethylhexyl methacrylate; and mixtures thereof. Desirably, the hydroxy-functional alkyl (meth)acrylates include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, or mixtures thereof.The hydroxyl-containing acrylic emulsion polymer may contain hydroxy-functional alkyl (meth)acrylate structural units in a concentration of 5% or more by weight, based on the weight of the hydroxyl-containing acrylic emulsion polymer, and can be 10% or more, 12% or more, 15% or more by weight, and can be more than 15%, 17% or more, 20% or more, 23% or more, 25% or more, 27% or more, or even 30% or more by weight, but at the same time, generally 50% or less by weight, and can be 48% or less, 45% or less, 42% or less, 40% or less, 38% or less, 36% or less, 35% or less, 34% or less, 32% or less, or even 30% or less by weight.

[0029] The hydroxyl-containing acrylic emulsion polymer may include structural units of one or more acid monomers, their salts, or mixtures thereof. The acid monomers may include carboxylic acid monomers, sulfonic acid monomers, phosphorus-containing acid monomers, or mixtures thereof. Examples of suitable phosphorus-containing acid monomers and their salts include phosphoalkyl(meth)acrylates, such as phosphoethyl(meth)acrylate, phosphopropyl(meth)acrylate, and phosphobutyl(meth)acrylate; salts thereof; or mixtures thereof; CH2=C(R1)-C(O)-O-(R2O) q-P(O)(OH)2 (wherein R1 = H or CH3, R2 = alkylene such as an ethylene group, a propylene group, or a combination thereof, q = 1 to 20), such as SIPOMER PAM-100, SIPOMER PAM-200, SIPOMER PAM-300, SIPOMER PAM-600, and SIPOMER PAM-4000 (all available from Solvay); phosphoalkoxy (meth)acrylates such as phosphoethylene glycol (meth)acrylate, phosphodiethylene glycol (meth)acrylate, phosphotriethylene glycol (meth)acrylate, phosphopropylene glycol (meth)acrylate, phosphodipropylene glycol (meth)acrylate, phosphotripropylene glycol (meth)acrylate; salts thereof; or mixtures thereof. Desirably, the phosphorus-containing acid monomer and its salt are selected from phosphoethyl (meth)acrylate, phosphopropyl (meth)acrylate, phosphobutyl (meth)acrylate, or allyl ether phosphate; their salts; or mixtures thereof. More desirably, the phosphorus-containing acid monomer is phosphoethyl methacrylate (PEM). The carboxylic acid monomer can be an α,β-ethylenically unsaturated carboxylic acid, a monomer having an acid-forming group that generates or can be subsequently converted to such an acid group (e.g., anhydride, (meth)acrylic anhydride, or maleic anhydride), and mixtures thereof. Specific examples of carboxylic acid monomers include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, 2-carboxyethyl acrylate, and mixtures thereof. The sulfonic acid monomer and its salt can include sodium vinyl sulfonate (SVS), sodium styrene sulfonate (SSS), acrylamido-methyl-propane sulfonate (AMPS), or their salts; or mixtures thereof. The acid monomers can be a combination of carboxylic acid monomers and / or salts thereof and phosphorus-containing acid monomers and / or salts thereof. Desirably, the acid monomers are selected from acrylic acid, methacrylic acid, itaconic acid, or phosphoethyl methacrylate; salts thereof; or mixtures thereof.The hydroxyl group-containing acrylic emulsion polymer may contain structural units of acid monomers and their salts in a concentration of 0.1% by weight or more, and can be 0.2% by weight or more, 0.3% by weight or more, 0.5% by weight or more, 0.8% by weight or more, 1.0% by weight or more, 1.3% by weight or more, 1.5% by weight or more, 1.7% by weight or more, 2.0% by weight or more, or even 2.2% by weight or more, but at the same time, generally 10% by weight or less, 8.0% by weight or less, 7.0% by weight or less, 6.0% by weight or less, 5.0% by weight or less, 4.5% by weight or less, 4.0% by weight or less, 3.5% by weight, 3.0% by weight or less, or even 2.5% by weight or less, based on the weight of the hydroxyl group-containing acrylic emulsion polymer.

[0030] The hydroxyl-containing acrylic emulsion polymers useful in the present invention may or may not contain structural units of one or more ethylenically unsaturated functional monomers (other than those mentioned above) having at least one functional group selected from amide, acetoacetate, carbonyl, ureido, silane, or amino groups. Suitable ethylenically unsaturated functional monomers include, for example, amino-functional monomers such as dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate; ureido-functional monomers such as hydroxyethylethylene urea methacrylate, hydroxyethylethylene urea acrylate, for example SIPOMER WAM from Solvay. II; monomers having an acetoacetate functional group, such as acetoacetoxyethyl methacrylate (AAEM), acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxypropyl acrylate, allyl acetoacetate, acetoacetoxybutyl methacrylate, acetoacetoxybutyl methacrylate, acetoacetamidoethyl methacrylate, acetoacetamidoethyl acrylate; monomers having a carbonyl-containing group, such as diacetone acrylamide (DAAM), diacetone methacrylamide; monomers having an amide functional group, such as acrylamide and methacrylamide; vinyl trialkoxysilanes, such as vinyl trimethoxysilane, vinyl triethoxysilane, vinyl tris(2-methoxyethoxy)silane, vinyl dimethyl ethoxysilane vinyl methyl diethoxysilane or (meth) acryloxy alkyl trialkoxysilanes, such as (meth) acryloxy ethyl trimethoxysilane and (meth) acryloxy propyl trimethoxysilane; or mixtures thereof.The hydroxyl group-containing acrylic emulsion polymer may contain structural units of ethylenically unsaturated functional monomers in a concentration of 0% by weight or more, and the concentration can be 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, or even 2% by weight or more, while generally being 10% by weight or less, 8% by weight or less, 6% by weight or less, 5% by weight or less, or even 3% by weight or less, based on the weight of the hydroxyl group-containing acrylic emulsion polymer.

[0031] The hydroxyl group-containing acrylic emulsion polymer useful in the present invention may contain structural units of one or more monoethylenically unsaturated nonionic monomers other than the above hydroxy-functional alkyl (meth)acrylates and ethylenically unsaturated functional monomers. In this specification, "nonionic monomer" refers to a monomer that does not have an ionic charge between pH=1-14. The monoethylenically unsaturated nonionic monomer may be selected from vinyl aromatic monomers, alkyl (meth)acrylates, acrylonitrile, or mixtures thereof. Suitable vinyl aromatic monomers may include, for example, styrene; substituted styrenes such as methylstyrene, alpha-methylstyrene, trans-beta-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, butylstyrene, and p-methoxystyrene; o-, m-, and p-methoxystyrene; and p-trifluoromethylstyrene; or mixtures thereof. The alkyl (meth)acrylates may be selected from C1-C 20 Alkyl, C1-C 18 Alkyl, C1-C 12The alkyl (meth)acrylate may be an alkyl or a C1-C4 alkyl (meth)acrylate. Specific examples of alkyl (meth)acrylates include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, iso-butyl acrylate, iso-butyl methacrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, cyclohexyl methacrylate, cyclohexyl acrylate, tert-butyl cyclohexyl methacrylate, trimethylcyclohexyl methacrylate, isobornyl methacrylate, isobornyl acrylate, tetrahydrofuran methacrylate, dicyclopentadienyl acrylate, dicyclopentadienyl methacrylate, and combinations thereof. Desirably, the monoethylenically unsaturated nonionic monomer comprises styrene in combination with one or more alkyl (meth)acrylates. Desirably, the monoethylenically unsaturated nonionic monomer is selected from styrene, methyl methacrylate, 2-ethylhexyl acrylate, butyl acrylate, or mixtures thereof. The monoethylenically unsaturated nonionic monomer structural unit may be present in a concentration of 40% by weight or more, and can be 45% by weight or more, 50% by weight or more, 55% by weight or more, 60% by weight or more, or even 65% by weight or more, based on the weight of the hydroxyl group-containing acrylic emulsion polymer, while generally being 94.9% by weight or less, and can be 94.8% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 77% by weight or less, 75% by weight or less, 74% by weight or less, 72% by weight or less, or even 70% by weight or less.

[0032] The hydroxyl group-containing acrylic emulsion polymer useful in the present invention may or may not contain structural units of one or more multi-ethylenically unsaturated monomers, including di-, tri-, tetra-, or higher multifunctional ethylenically unsaturated monomers. Examples of suitable multi-ethylenically unsaturated monomers include butadiene, allyl (meth)acrylate, divinylbenzene, ethylene glycol dimethacrylate, butylene glycol dimethacrylate, and mixtures thereof. The structural units of multi-ethylenically unsaturated monomers may be present at a concentration of 0% by weight or more, can be 0.1% by weight or more, or even 0.2% by weight or more, based on the weight of the hydroxyl group-containing acrylic emulsion polymer, but at the same time, generally 5% by weight or less, can be 3% by weight or less, 1% by weight or less, can be less than 1% by weight, 0.5% by weight or less, or even 0% by weight.

[0033] Desirably, the hydroxyl-containing acrylic emulsion polymer useful in the present invention contains, by weight based on the weight of the hydroxyl-containing acrylic emulsion polymer, 5% to 35% structural units of a hydroxy-functional alkyl (meth)acrylate, 0.2% to 5% structural units of an acid monomer, salt thereof, or mixture thereof, and 60% to 94.8% structural units of a monoethylenically unsaturated nonionic monomer other than a hydroxy-functional alkyl (meth)acrylate.

[0034] The hydroxyl group-containing acrylic emulsion polymers useful in the present invention may have a weight average molecular weight of 50,000 g / mol or less, as measured by gel permeation chromatography (GPC), including but not limited to 48,000 g / mol or less, 45,000 g / mol or less, 42,000 g / mol or less, 40,000 g / mol or less, 38,000 g / mol or less, 35,000 g / mol or less, 32,000 g / mol or less, 30,000 g / mol or less, 28,000 g / mol or less, 25,000 g / mol or less, 23,000 g / mol or less, 20,000 g / mol or less, 18,000 g / mol or less, and preferably 19,000 g / mol or less. 00 g / mol or less, or even 17,000 g / mol or less, but at the same time it is generally 3,000 g / mol and can be 4,000 g / mol or more, 5,000 g / mol or more, 6,000 g / mol or more, 7,000 g / mol or more, 8,000 g / mol or more, 9,000 g / mol or more, 10,000 g / mol or more, 11,000 g / mol or more, 12,000 g / mol or more, 13,000 g / mol or more, 14,000 g / mol or more, 15,000 g / mol or more, or even 16,000 g / mol or more (further details are given in the GPC analysis below).

[0035] The particle of hydroxyl-containing acrylic emulsion polymer dispersed in aqueous dispersion (A) may have a particle size of 30 nanometers (nm) or more, can be 50nm or more, 60nm or more, 70nm or more, or even 80nm or more, but at the same time, generally is 500nm or less, can be 300nm or less, 200nm or less, 150nm or less, 120nm or less, or even 100nm or less.Particle size in this specification refers to the number average particle size measured by Brookhaven BI-90 Plus Particle Size Analyzer.

[0036] The hydroxyl-containing acrylic emulsion polymers useful in the present invention can be present in a concentration of 20% to 70%, 30% to 55%, 35% to 50%, or 40% to 45% by weight, dry or solid weight based on the total weight of the aqueous dispersion (A).

[0037] The hydroxyl group-containing acrylic emulsion polymer useful in the present invention can be prepared by emulsion polymerization of the above monomers in an aqueous medium, preferably in the presence of a surfactant. The surfactant can be added before or during polymerization of the monomers or combinations thereof, different from the branched polyether polyols. A portion of the surfactant can also be added after polymerization. These surfactants can be anionic or nonionic, and desirably can be anionic surfactants, such as sulfate surfactants, sulfonate surfactants, or mixtures thereof. These surfactants can be used in an amount of 0.1% by weight or more, and can be 0.3% by weight or more, 0.5% by weight or more, 0.7% by weight or more, 0.9% by weight or more, or even 1.2% by weight or more, based on the total weight of the monomers for preparing the hydroxyl group-containing acrylic emulsion polymer, but at the same time, it is generally 5% by weight or less, and can be 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1.5% by weight or less.

[0038] The monomers may be added neat or as an emulsion in water, or may be added in one or more portions or continuously, linearly or non-linearly, over the reaction time to prepare the hydroxyl-containing acrylic emulsion polymer. The total weight concentration of the monomers for preparing the hydroxyl-containing acrylic emulsion polymer is equal to 100% based on the total weight of the monomers. The weight concentration of each monomer based on the total weight of the monomers for preparing the hydroxyl-containing acrylic emulsion polymer can be the same as the above-mentioned weight concentration of the structural unit of such monomer based on the weight of the hydroxyl-containing acrylic emulsion polymer. The temperature suitable for polymerization of the monomers can be less than 100°C, in the range of 10-95°C, or in the range of 50-92°C. A multi-stage emulsion polymerization can be used using the above-mentioned monomers, whereby at least two stages are formed successively, usually forming a multi-stage polymer comprising at least two polymer compositions.

[0039] In the polymerization process, a free radical initiator can be used. The polymerization process may be a thermally initiated or redox initiated emulsion polymerization. Examples of suitable free radical initiators include hydrogen peroxide, t-butyl hydroperoxide, cumene hydroperoxide, ammonium and / or alkali metal persulfates, sodium perborate, superphosphate, and salts thereof; potassium permanganate, and ammonium or alkali metal salts of peroxydisulfate. Free radical initiators can typically be used at levels of 0.01 to 3.0% by weight, based on the total weight of monomers. Redox systems comprising the above initiators in combination with a suitable reducing agent can be used in the polymerization process. Examples of suitable reducing agents include sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids (such as sulfites, bisulfites, thiosulfates, hydrosulfites, sulfides, hydrogen sulfides or dithionites, formadinesulfinic acid, acetonate bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid, etc.), and salts of the aforementioned acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt may be used to catalyze the redox reaction. Chelators for the metals may be optionally used.

[0040] In order to control the molecular weight of hydroxyl-containing acrylic emulsion polymer, one or more chain transfer agents may be used in the polymerization process.Examples of suitable chain transfer agents include 3-mercaptopropionic acid, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, n-dodecyl mercaptan, n-hexadecanethiol, tert-dodecyl mercaptan, n-octadecanethiol, benzenethiol, azelaic acid alkyl mercaptan, hydroxyl-containing mercaptan, such as hydroxyethyl mercaptan, mercaptopropionic acid, and mixtures thereof. The chain transfer agent may be used in a concentration of more than 0.3% by weight, and can be 0.4% by weight or more, 0.5% by weight or more, 0.6% by weight or more, 0.8% by weight or more, 1% by weight or more, 1.3% by weight or more, 1.5% by weight or more, or even 2.0% by weight, based on the total weight of the monomers, while at the same time generally being 20% ​​by weight or less, 15% by weight or less, 13% by weight or less, 10% by weight or less, 8% by weight or less, 6% by weight or less, 4% by weight or less, 3% by weight or less, or even 2.5% by weight or less.

[0041] The types and levels of the above monomers can be selected to give the resulting hydroxyl-containing acrylic emulsion polymer a glass transition temperature (Tg) suitable for different applications. The hydroxyl-containing acrylic emulsion polymer may have a Tg in the range of 0-80°C, which can be 0°C or higher, 10°C or higher, 15°C or higher, 20°C or higher, 25°C or higher, 30°C or higher, 35°C or higher, or even 40°C or higher, but at the same time, it is generally 80°C or lower, and can be 75°C or lower, 70°C or lower, 65°C or lower, 60°C or lower, 55°C or lower, or even 50°C or lower. As used herein, "Tg" can be determined by differential scanning calorimetry (DSC) (further details are given in the GPC analysis below).

[0042] After completing the polymerization process, the resulting hydroxyl-containing acrylic emulsion polymer dispersion can be neutralized with one or more bases to a pH value, for example, of at least 5, 5.5-10, 6.0-9, 6.2-8, 6.4-7.5, or 6.6-7.2. Examples of suitable bases include ammonia; alkali metal or alkaline earth metal compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, zinc oxide, magnesium oxide, sodium carbonate; primary, secondary, and tertiary amines such as triethylamine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethylamine, dimethylamine, di-npropylamine, tributylamine, triethanolamine, dimethoxyethylamine, 2-ethoxyethylamine, 3-ethoxypropylamine, dimethylethanolamine, diisopropanolamine, morpholine, ethylenediamine, 2-diethylaminoethylamine, 2,3-diaminopropane, 1,2-propylenediamine, neopentanediamine, dimethylaminopropylamine, hexamethylenediamine, 4,9-dioxadodecane-1,12-diamine, polyethyleneimine, or polyvinylamine; aluminum hydroxide; or mixtures thereof.

[0043] The polyurethane composition of the present invention further comprises one or more (B) polyisocyanates useful as crosslinkers. The polyisocyanate may comprise any molecule having two or more isocyanate (NCO) groups, or a mixture of two or more such molecules. The polyisocyanate may be an aliphatic, cycloaliphatic, or aromatic polyisocyanate, or a mixture thereof. An aliphatic polyisocyanate is a polyisocyanate in which the NCO group is not directly attached to an aromatic ring. The polyisocyanate may be a biuret, a trimer isocyanurate, a dimeric uretdione, an asymmetric trimer iminooxadiazinedione, or an allophanate. The polyisocyanate may have an average functionality of greater than 2 (>2) or from 2.5 to 10. Examples of suitable polyisocyanates include aliphatic diisocyanates and their dimers and trimers, such as tetramethylene diisocyanate and hexamethylene diisocyanate (HDI), C2-C8 alkylene diisocyanates such as 1,12-dodecane diisocyanate, 2,2,4-trimethyl-hexamethylene diisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate; alicyclic diisocyanates and their dimers and trimers, such as isophorone diisocyanate (IPDI) and dicyclohexyl methane diisocyanate (DMC). diisocyanate (HMDI), 1,4-cyclohexane diisocyanate, and 1,3-bis-(isocyanatomethyl)cyclohexane; aromatic diisocyanates and their dimers and trimers, such as toluene diisocyanate (TDI) and diphenyl methane diisocyanate (MDI). Desirably, the polyisocyanate comprises an aliphatic polyisocyanate. More desirably, the polyisocyanate is selected from hexamethylene diisocyanate homopolymer, hexamethylene diisocyanate adduct, isophorone diisocyanate homopolymer, isophorone diisocyanate adduct, or mixtures thereof.Trimers (or isocyanurates) in polyisocyanates can be prepared by methods known in the art, for example, as disclosed in US Patent Publication No. 2006 / 0155095(A1), by trimerizing cycloaliphatic diisocyanates (e.g., isophorone diisocyanate) in the presence of one or more trimerization catalysts, such as tertiary amines or phosphines, or heterogeneous catalysts, and optionally in the presence of solvents and / or auxiliaries, such as cocatalysts, conveniently at elevated temperatures, until the desired NCO content is reached, followed by deactivation of the catalyst using inorganic and organic acids, the corresponding acid halides and alkylating agents, and preferably heating. Similarly, isocyanurate compositions containing isocyanurates from aliphatic diisocyanates can be formed by cyclizing aliphatic diisocyanates in the presence of one or more trimerization catalysts, followed by deactivation of the catalyst. Any of the isocyanurates can be further modified by conventional methods to contain urethane, urea, imino-s-triazine, uretonimine, or carbodiimide moieties. Desirably, the polyisocyanate is selected from aliphatic diisocyanates, their dimers and trimers, or mixtures thereof. More desirably, the polyisocyanate is selected from aliphatic trimers, such as, in particular, HDI trimer, or mixtures of HDI trimer and IPDI dimer.

[0044] The polyisocyanates useful in the present invention may include one or more polyisocyanate prepolymers, which may be formed by the reaction of HDI trimer and / or another aliphatic diisocyanate / trimer with a monol, diol, diamine, or monoamine. Such prepolymers may further include polyalkoxy or polyether chains. Still further, suitable polyisocyanates may be modified with ionic compounds such as aminosulfonic acids. Commercially available polyisocyanates may include, for example, DESMODUR™ N3300, N3600, and N3900 polyisocyanates, and BAYHYDUR™ XP2655, 401-60, and 401-70 polyisocyanates (Covestro); Tolonate HDT, HDT-LV, and HDT-LV2, and Easaqua L 600 polyisocyanates (Vencorex Chemicals); DURANATE TLA-100 and TMA-100 polyisocyanates (Asahi Kasei); and AQUOLIN 268, 269, and 270 polyisocyanates (Wanhua Chemicals).

[0045] The polyisocyanates useful in the present invention can be used alone or diluted with one or more solvents to form a polyisocyanate solution before mixing with Part A. Such solvents can reduce the viscosity of the polyisocyanate and are non-reactive with the polyisocyanate. The solvents can be used in amounts of 5% to 150%, 15% to 130%, 20% to 120%, or 30% to 100% by weight based on the weight of the polyisocyanate. Suitable solvents can include, for example, propylene glycol diacetate, propylene glycol methyl ether acetate, dipropylene glycol dimethyl ether, or mixtures thereof.

[0046] The polyisocyanate can be present in an amount sufficient to provide a molar ratio of the total moles of isocyanate groups in the polyisocyanate, which can include two or more different polyisocyanates, to the total moles of hydroxyl groups in the hydroxyl group-containing acrylic emulsion polymer and the branched polyether polyol in the range of 0.8:1 to 2.5:1, 0.9:1 to 2.0, or 1:1 to 1.5:1.

[0047] The polyurethane composition of the present invention may or may not include one or more catalysts to accelerate curing. The catalyst may be any suitable catalyst for two-component polyurethane compositions, including metal-based catalysts such as tin-, bismuth-, zinc-, aluminum-, zirconium-containing catalysts, or tertiary amine catalysts, including mono-, di-, and tri-amine aliphatic and cycloaliphatic tertiary amine catalysts, and mixtures thereof. Examples of suitable metal-based catalysts include dibutyltin dilaurate, dibutyltin mercaptide, dibutyltin sulfide, dimethyltin mercaptide, dibutyltin mercaptoester, zirconium dionate, Al dionate, bismuth neodecanoate, and zinc amine compounds. Suitable tertiary amine catalysts can include, for example, triethylenediamine, triethyleneamine, 1,4-diazabicyclo[2.2.2]octane, 6-(dibutylamino)-1,8-diazabicyclo[5.4.0]undec-7-ene, dimethylcyclohexylamine, and mixtures thereof. The catalyst can be present in an amount of 0.01% to 2.5% by weight, or 0.1% to 1.0% by weight, based on the total weight of the polyisocyanate and hydroxyl-containing components (e.g., hydroxyl-containing acrylic emulsion polymer and branched polyether polyol) solids.

[0048] The polyurethane composition of the present invention may or may not include one or more pigments, one or more extenders, or mixtures thereof. The term "pigment" herein refers to a particulate inorganic or organic material that can substantially contribute to the opacity, color, or hiding power of a coating. Typically, inorganic pigments having a refractive index greater than 1.8 can include, for example, titanium dioxide (TiO2), zinc oxide, zinc sulfide, iron oxide, barium sulfate, barium carbonate, or mixtures thereof. Examples of suitable organic pigments include phthalo blue, phthalo green, monoazo yellow, carbon black, or mixtures thereof. The preferred pigment used in the present invention is TiO2. The term "extender" refers to a particulate material having a refractive index less than or equal to 1.8 and greater than 1.3. Examples of suitable extenders include calcium carbonate, aluminum oxide (Al2O3), clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, ceramic beads, and opaque polymers, such as ROPAQUE™ Ultra E available from The Dow Chemical Company (ROPAQUE is a trademark of The Dow Chemical Company), or mixtures thereof. The pigment and / or extender are typically present in Part A of the polyurethane composition. The polyurethane composition may have a pigment volume concentration (PVC) of 0-75%, 5-50%, or 10-30%. The PVC may be determined according to the following formula: PVC=[volume (pigment+extender) / volume (pigment+extender+emulsion polymer+branched polyether polyol)]×100%.

[0049] The polyurethane composition of the present invention may or may not contain one or more coalescent agents. A "coalescent agent" herein refers to a solvent that fuses polymer particles into a continuous film under ambient conditions (10-30°C, relative humidity: 30-80%). Examples of suitable coalescent agents include dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, propylene glycol methyl ether, 2-n-butoxyethanol, dipropylene glycol methyl ether, propylene glycol n-propyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, triethylene glycol monobutyl ether, dipropylene glycol n-propyl ether, n-butyl ether, aromatic hydrocarbons such as the Solvesso series from ExxonMobil, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate such as the Texanol ester alcohol from Eastman, or mixtures thereof. The coalescent agent is typically present in Part A of the polyurethane composition. The concentration of the coalescent can be 0-50% by weight, 5%-40% by weight, or 10%-25% by weight based on the weight of the hydroxyl-containing acrylic emulsion polymer.

[0050] The polyurethane compositions of the present invention may or may not contain conventional additives such as, for example, light stabilizers, ultraviolet (UV) absorbing compounds, leveling agents, wetting agents, dispersants, neutralizing agents, defoamers, or rheology modifiers, or mixtures thereof. These additives may be present in amounts of 0 to 20% by weight, 1% to 10% by weight, based on the weight of the polyurethane composition.

[0051] The polyurethane composition of the present invention can be prepared using techniques known in the art. The process for preparing the polyurethane composition typically includes the steps of (i) providing part A, which includes an aqueous dispersion containing a hydroxyl-containing acrylic emulsion polymer and a branched polyether polyol, and optionally a pigment and other ingredients as described above, and (ii) mixing part A from step (i) with a polyisocyanate. The aqueous dispersion of part A can be prepared by providing a hydroxyl-containing acrylic emulsion polymer prepared by hydroxyl-containing acrylic emulsion polymerization of the monomers described above, and adding and mixing the resulting emulsion polymer with a branched polyether polyol. Alternatively, the branched polyether polyol can be added before and / or during the polymerization of the monomers used to prepare the hydroxyl-containing acrylic polymer. Desirably, all of the branched polyether polyol in the polyurethane composition is mixed with the hydroxyl-containing acrylic emulsion polymer after its polymerization. The polyisocyanate in part B is preferably diluted with a solvent. Part A and part B can be mixed immediately before application. The polyurethane composition can be cured at ambient temperature (10-30° C.) or at a temperature ranging from 4° C. to 150° C., desirably from 25° C. to 80° C. The curing temperature can vary depending on the substrate. Curing times generally range from 10 minutes at a temperature of 50° C. to 90° C., or from 1 to 14 days at a temperature of 10 to 35° C. Examples of suitable substrates include metal, wood, plastic, concrete, cementitious substrates, masonry, asphalt, elastomeric substrates, glass, or fabric.

[0052] The polyurethane composition of the present invention is useful for producing coatings with or without pigments or extenders, adhesives, sealants, primers, and caulking compositions. The polyurethane composition can expand the window for formulations with extended pot life. By "extended pot life" is meant that the polyurethane composition after 3 hours storage at 35°C can provide a 60° gloss of higher than 75 for coatings made therefrom (further details are given in the gloss test below). For example, the novel combination of hydroxyl group-containing acrylic emulsion polymer and branched polyether polyol in Part A allows the use of various types of polyisocyanates, such as aliphatic polyisocyanates without polyalkoxy chain or ionic compound modification ("unmodified polyisocyanates"), or aliphatic polyisocyanates with hydrophilic modification, such as modified by polyalkoxy chains or ionic compounds (e.g., hydrophilic polyisocyanates), thereby forming a two-component polyurethane composition with the above-mentioned extended pot life. The two-component polyurethane composition can also provide coatings made therefrom with a distinctness of image (DOI) of 70 or higher. Distinctness of image (DOI) measures the clarity of a reflected image on a surface (e.g., a coating surface) and is an indication of the perfection of the reflection and the absence of surface haze or "orange peel". The polyurethane composition can provide coatings made therefrom having a 60° gloss of 75 or greater. DOI and gloss can be measured according to the test methods described in the Examples section below.

[0053] The present invention further provides a polyurethane coating made from the two-component polyurethane composition on any of the above substrates. Such coatings can be multi-layer coatings on a primer layer, and can optionally be base coats or color coats. The coatings can be agricultural, construction and earthmoving coatings; architectural coatings; general industrial finishing coatings; marine and protective coatings; automotive coatings; auto refinish coatings; plastic coatings; wood coatings, coil coatings; and civil engineering coatings. EXAMPLES

[0054] Some embodiments of the present invention will now be described in the following examples. All percentage (%) values ​​are weight percentages based on the weight of the composition. Table 1 lists the materials used in the synthesis of the sample polymer dispersions and coating compositions described herein below. OROTAN, DOWANOL, and ACRYSOL are all trademarks of The Dow Chemical Company.

[0055] [Table 1] * "Secondary dispersion" refers to an aqueous dispersion made by a process that involves solution polymerization of monomers in an organic solvent, neutralization of the resulting polymer, and phase inversion to obtain an aqueous dispersion.

[0056] [Table 2] * All of the polyether polyols listed in Table 2 are commercially available from The Dow Chemical Company and can be prepared following a similar procedure to the synthesis of Polyether Polyol 1 below, except for the feeding sequence and / or amount of alkylene oxide. EO (ethylene oxide)

[0057] [ka] PO (propylene oxide) stands for

[0058] [ka] It represents.

[0059] Synthesis of polyether polyol 1 Branched polyether polyol 1 was prepared based on the initiator sorbitol, followed by a step of alkoxylation under known alkoxylation conditions utilizing KOH as a catalyst. Sorbitol was added to the reactor together with KOH (2000 ppm active weight, 50% concentration by weight in aqueous solution). The reactor was closed and the reactor contents were stirred at 250 revolutions per minute (RPM) and heated to 80°C. A vacuum was applied to remove residual water from the reactor while maintaining the reactor contents at 80°C. The reactor contents were then heated to 120°C and ethylene oxide was slowly added to the reactor while maintaining the pressure in the reactor below 4.5 bar (450 kilopascals). After the addition of ethylene oxide (EO), the reactor contents were maintained at 120°C for digestion and the reactor pressure was monitored until the reactor pressure was close to the initial pressure (before EO was added). As a second feeding step, propylene oxide (PO) was also slowly added to the reactor at 120°C while maintaining the pressure in the reactor below 4.5 bar. The reactor contents were then maintained at 120°C for digestion and monitored until the reactor pressure was close to the pressure before PO addition and stable for 2 hours. The reactor was then purged with nitrogen and vacuum three times to remove any remaining propylene oxide. The reactor contents were cooled to 60°C and neutralized with acetic acid to prepare a polyether polyol represented by formula I. Based on the total weight of the blended ingredients used in the preparation of polyether polyol 1, the weight ratio of EO was about 35% and the weight ratio of PO was about 63%.

[0060] Synthesis of polyether polyol 2 Polyether polyol 2 was prepared according to the same procedure as for the synthesis of polyether polyol 1 above, except that the order of EO and PO feed was swapped, and the weight ratio of EO used was about 20% and the weight ratio of PO used was about 78%, based on the total weight of the blend ingredients used in the preparation of polyether polyol 2.

[0061] In the examples and in determining the properties and characteristics described herein, the following standard analytical equipment and methods are used.

[0062] Particle size measurement The particle size of the polymer particles in the aqueous dispersion refers to the number average particle size measured by a Brookhaven BI-90 Plus Particle Size Analyzer.

[0063] Tg measurement Tg was measured by DSC. Five to ten milligrams (mg) of sample were analyzed in sealed aluminum pans on a TA Instruments DSC Q2000 equipped with an autosampler under nitrogen atmosphere. The DSC Tg measurements used three cycles including -40 to 180°C at 10°C / min (first cycle, then held for 5 minutes (min) to erase the thermal history of the sample), 180 to -40°C at 10°C / min (second cycle), and -40 to 180°C at 10°C / min (third cycle). The Tg was taken from the third cycle by taking the midpoint in the heat flow versus temperature transition as the Tg value.

[0064] GPC analysis GPC analysis of acrylic polymers was typically performed on an Agilent 1200. Samples were dissolved in tetrahydrofuran (THF) / formic acid (FA) (5%) at a concentration of 2 mg / mL (milliliter) and then filtered through a 0.45 micrometer (μm) polytetrafluoroethylene (PTFE) filter prior to GPC analysis. GPC analysis was performed using the following conditions:

[0065] Columns: one PLgel GUARD column (10 μm, 50 millimeters (mm) × 7.5 mm), two Mixed B columns (7.8 mm × 300 mm) in tandem; column temperature: 40 °C; mobile phase: THF / FA (5%); flow rate: 1.0 mL / min; injection volume: 100 microliters (μL); detector: Agilent refractive index detector, 40 °C; and calibration curve: using PL Polystyrene I Narrow standards with molecular weights ranging from 2,329,000 to 580 g / mol, polynom 3 fitness.

[0066] Gloss Test Initial Gloss Gloss measurements were performed at a given angle (60 degrees (°)) using a BYK Gardener Micro TRI Glossmeter (BYK-Gardner USA, Columbia, Md.) according to ASTM D523 (1999). The two-component polyurethane composition was drawn down onto an aluminum panel (Q-panel A-46) at a wet thickness of 150 μm immediately after mixing all the formulation components therein. After drying at room temperature for 20 minutes, the coated panel was further dried at 60° C. for 40 minutes and then the gloss was measured. The average of three separate readings was reported as the "initial gloss". An acceptable initial gloss (60°) is 84 or greater.

[0067] Gloss after storage The two-component polyurethane compositions were stored at 35°C for 1.5 hours and 3 hours, respectively, immediately after mixing all the formulation components therein. Coating panels were then prepared by using the polyurethane compositions obtained after 1.5 hours storage or 3 hours storage, following the same procedure and drying conditions used above in determining the initial gloss. The resulting coating panels were then measured for 60° gloss, and were designated as "Gloss (35°C / 1.5 hours)" and "Gloss (35°C / 3 hours)", respectively. The average of three separate readings was reported. A gloss (60° gloss) of 75 or greater after 3 hours storage indicates acceptable pot life. Otherwise, if the gloss (60° gloss) after 3 hours storage is less than 75, the pot life test is failed.

[0068] Clearness of Image (DOI) Test DOI measurements were performed according to ASTM D5767-95(2004) (Standard Test Methods for Instrumental Measurement of Distinctness-of-Image Gloss of Coating Surfaces) using a BYK Gardner microwave scan meter (BYK-Gardner USA, Columbia, MD). The two-component polyurethane composition was drawn down onto an aluminum panel (Q-panel A-36) at a wet thickness of 200 μm immediately after mixing all the formulation components therein. After drying at room temperature for 20 minutes, the panel was further dried at 60° C. for 40 minutes. For each panel, the average of three separate readings was reported as the DOI value. If the DOI is 70 or greater (≧70), the sample passes the DOI test. Otherwise, i.e., the sample has a DOI less than 70, it fails.

[0069] Solid content The solids content of the sample was measured by weighing 0.7±0.1 grams (g) of the sample (the wet weight of the sample is denoted as "W1") and placing it in an aluminum pan (the weight of the aluminum pan is denoted as "W2") in a 150°C oven for 25 minutes, then cooling the aluminum pan containing the dried sample and weighing its total weight, denoted as "W3". The solids content of the sample is calculated as (W3-W2) / W1. * Calculate at 100%.

[0070] Synthesis of Hydroxyl-containing Acrylic Emulsion Polymer Dispersion ("HA-01") The monomer emulsion was prepared as follows.

[0071] To 318 g of deionized (DI) water, 23 g of DISPONIL Fes 993 surfactant (30% active), 173 g of MMA, 306 g of ST, 204 g of EHA, 304 g of HEMA, 16 g of MAA, 16 g of PEM, and 21 g of n-DDM were added and mixed together to produce a stable monomer emulsion. To DI water (600 g) under a nitrogen atmosphere at 90° C., Fes 993 surfactant (30% active) (42.6 g), aqueous ammonia (28%, 2.5 g) in DI water (16.9 g), 29 g of the monomer emulsion and ammonium persulfate (APS) (2.03 g) in DI water (16.9 g), followed by DI water (3.75 g) were added to form a reaction mixture. The remaining monomer emulsion was then added over 160 minutes at 86° C., followed by DI water (30 g). At the end of the polymerization, FeSO4.7H2O (0.005 g) in DI water (15.75 g) mixed with tetrasodium salt of ethylenediaminetetraacetic acid (0.005 g) in DI water (15.75 g), a solution of t-butyl hydroperoxide (70%, 1.6 g) in DI water (32.76 g), a solution of isoascorbic acid (0.78 g) in DI water (34.32 g), a solution of t-butyl hydroperoxide (0.78 g) in DI water (16.41 g), and a solution of isoascorbic acid (0.39 g) in DI water (17.19 g) were all added at 60° C., followed by ammonia (28%, 7.02 g) in DI water (16.65 g) at 50° C. to obtain an aqueous dispersion. The resulting aqueous dispersion was characterized according to the test methods described above and had the following characterization results: particle size: 76 nm, pH: 6.96, solids: 42.75%, viscosity: 3589 centipoise at 25° C. measured using a Brookfield viscometer DV-I Primer (60 RPM and spindle #2), Tg: 43° C. measured by DSC, number average molecular weight (Mn): 6629 g / mol measured by GPC, Mw: 16,586 g / mol measured by GPC.

[0072] IE1-4 and CE-A-CE-J paint formulation samples Tables 3 and 4 list the formulations for preparing the paint formulation (i.e., coating composition) samples, with the amount of each component reported in grams (g). The molar ratio of NCO groups to OH groups in each paint formulation was 1.2:1. The components for preparing the grind were mixed using a high speed Cowles disperser at 1,500 RPM for 30 minutes to form the grind. The components in the letdown were then added to the grind using a conventional laboratory mixer to obtain Part A. Part A of each paint formulation sample was allowed to sit overnight, and then the components of Part B were added to Part A and mixed using a high speed Cowles disperser at 600 RPM for 10 minutes, thereby forming the paint formulation sample. The solids content of each paint formulation sample is shown in Tables 3 and 4. The resulting paint formulation samples were characterized according to the test methods described above, and the characterization results are shown in Tables 3 and 4, respectively.

[0073] As shown in Table 3, all of the paint formulation samples IE-1, IE-2, IE-3 and IE-4 provided high gloss (60° initial gloss ≧84) and passed the DOI test (initial DOI ≧70), while also exhibiting long pot life (60° gloss ≧75 after 3 hours storage at 35° C.).

[0074] In contrast, as shown in Table 4, the paint formulation sample without branched polyether polyol (CE-A) exhibited unacceptable initial gloss and pot life. Paint formulation samples containing branched polyether polyols with lower MW per branch (CE-B) or branched polyether polyols with lower concentrations of ethylene oxide units and / or lower functionality (CE-C through CE-H) all exhibited shorter pot life. Secondary dispersions of hydroxyl acrylic resins, with or without the addition of branched polyether polyol 1, provided paint formulation samples (CE-I and CE-J) with unacceptably shorter pot life compared to the HA-01 emulsion polymer dispersion.

[0075] [Table 3] 1 Polyol concentration: weight percent of branched polyether polyol relative to the solids content of the hydroxyl acrylic polymer dispersion.

[0076] [Table 4] 1 Polyol concentration: weight percent of branched polyether polyol relative to the solids content of the hydroxyl acrylic polymer dispersion.

Claims

1. 1. A two-component polyurethane composition comprising: (A) a hydroxyl-containing acrylic emulsion polymer comprising 5% to 50% by weight, based on the weight of the hydroxyl-containing acrylic emulsion polymer, of hydroxy-functional alkyl (meth)acrylate structural units; an aqueous dispersion comprising: 2% to 20% by weight of a branched polyether polyol, based on the weight of the hydroxyl group-containing acrylic emulsion polymer, said branched polyether polyol having a hydroxyl functionality of 4 to 10 and a molecular weight per branch of 1200 to 2500 grams per mole, and containing 20% ​​to 40% by weight of ethylene oxide units, based on the weight of the branched polyether polyol; (B) a polyisocyanate.

2. The branched polyether polyol is represented by the formula (I): -[O-(AO) ｘ -+] ｙ (I) 2. The two-component polyurethane composition of claim 1 having the structure: wherein R represents a polyvalent aliphatic hydrocarbon group; each AO is independently selected from ethylene oxide units, propylene oxide units, butylene oxide units, or combinations thereof, with the proviso that the ethylene oxide units are present in a total concentration of 20% to 40% by weight based on the weight of the branched polyether polyol; x is a number in the range of 20 to 55; and y is a number in the range of 4 to 10.

3. 3. The two-component polyurethane composition according to claim 1 or 2, wherein the branched polyether polyol contains 20% to 40% by weight of ethylene oxide units and 60% to 80% by weight of propylene oxide units, based on the weight of the branched polyether polyol.

4. The two-component polyurethane composition according to any one of claims 1 to 3, wherein the polyisocyanate is an aliphatic diisocyanate trimer.

5. The two-component polyurethane composition according to any one of claims 1 to 4, wherein the aqueous dispersion (A) comprises from 5% by weight to 10% by weight of the branched polyether polyol, based on the weight of the hydroxyl group-containing acrylic emulsion polymer.

6. 6. The two-component polyurethane composition according to any one of claims 1 to 5, wherein the hydroxy-functional alkyl (meth)acrylate is selected from 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, or mixtures thereof.

7. The two-component polyurethane composition according to any one of claims 1 to 6, wherein the hydroxyl-containing acrylic emulsion polymer has a weight average molecular weight of 50,000 g / mol or less.

8. The two-component polyurethane composition according to any one of claims 1 to 7, wherein the hydroxyl-containing acrylic emulsion polymer has a glass transition temperature of from 10°C to 80°C.

9. The two-component polyurethane composition according to any one of claims 1 to 8, wherein the hydroxyl group-containing acrylic emulsion polymer comprises, based on the weight of the hydroxyl group-containing acrylic emulsion polymer, 5% to 35% by weight of structural units of the hydroxy-functional alkyl (meth)acrylate, 0.2% to 5% by weight of structural units of acid monomers, their salts, or mixtures thereof, and 60% to 94.8% by weight of structural units of monoethylenically unsaturated nonionic monomers other than the hydroxy-functional alkyl (meth)acrylate.

10. 10. The two-component polyurethane composition according to claim 1, wherein the molar ratio of total isocyanate groups to total hydroxyl groups in said aqueous dispersion (A) is in the range of 0.8:1 to 2.5:

1.

11. A two-component polyurethane composition according to any one of claims 1 to 10, wherein the branched polyether polyol has a molecular weight of from 4800 to 15000 grams per mole.

12. A process for preparing the two-component polyurethane composition according to any one of claims 1 to 11, comprising admixing said aqueous dispersion (A) with said polyisocyanate (B).

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