WO2021016785A1

WO2021016785A1 - Aqueous dispersion of polymeric particles and method of preparing the same

Info

Publication number: WO2021016785A1
Application number: PCT/CN2019/098132
Authority: WO
Inventors: Caiyun Li; Fu ZHAN; Baoqing ZHENG; Juan ZHAO; Qian SHEN
Original assignee: Dow Global Technologies Llc; Rohm And Haas Company
Priority date: 2019-07-29
Filing date: 2019-07-29
Publication date: 2021-02-04
Also published as: TW202104277A

Abstract

An aqueous dispersion of polymeric particles comprising an acrylic polymer and a polyurethane, wherein the acrylic polymer comprises, by weight based on the weight of the acrylic polymer, from 0.1%to 10%of structural units of a (meth) acrylate functional siloxane, from 0.1%to 8%of structural units of a multiethylenically unsaturated monomer, and structural units of a monoethylenically unsaturated nonionic monomer; wherein the polymeric particles have a Tg of 0℃ or lower, and the weight ratio of polyurethane to acrylic polymer in the polymeric particles is from 20: 80 to 99: 1; a method of preparing the aqueous dispersion; and an aqueous coating composition comprising the aqueous dispersion.

Description

Aqueous Dispersion of Polymeric Particles and Method of Preparing the Same

FIELD OF THE INVENTION

The present invention relates to an aqueous dispersion of polymeric particles and a method of preparing the same.

INTRODUCTION

Aqueous acrylic polymer emulsions are used in a wide range of coating applications. For example, acrylic emulsion polymers can be used for adhesion and early film softness development in applications such as leather basecoats. However, these polymers have limited use in leather topcoats which require balanced flexibility and abrasion resistance properties. Simply increasing the glass transition temperature (Tg) of acrylic emulsion polymers may improve abrasion resistance but adversely impact the resulting flexibility and softness of the coatings they produce, particularly at low temperatures (e.g., -10℃ or lower) . In many applications such as automotives, it is also desirable that coating compositions provide a substrate with relatively low gloss finish with a gloss level of 2.0 or lower on a 60° Gardner Gloss scale. Therefore, there remains a need to provide an aqueous dispersion particularly suitable for coating compositions that provide coatings with balanced properties of flexibility, abrasion resistance, and low gloss.

SUMMARY OF THE INVENTION

The present invention provides a novel aqueous dispersion of polymeric particles comprising an acrylic polymer and a polyurethane, which can be prepared by incorporation of a specific amount of the polyurethane in the process of polymerization of the acrylic polymer. An aqueous coating composition comprising such aqueous dispersion can provide coatings made therefrom with balanced cold bally flexibility (-10℃) rated as 3, abrasion resistance as indicated by wet rubbing fastness and Gakushin rubbing fastness both showing rating of 3, and preferably a gloss level (60°) of 2.0 or lower. These properties can be measured according to the test methods described in the Examples section below.

In a first aspect, the present invention is an aqueous dispersion of polymeric particles comprising an acrylic polymer and a polyurethane, wherein the acrylic polymer comprises, by weight based on the weight of the acrylic polymer,

from 0.1%to 10%of structural units of a (meth) acrylate functional siloxane of formula (I) ,

where R ₁ is a linear or branched C ₁-C ₁₀ alkylene group, R ₂ is hydrogen or a methyl group, n is from 0 to 100, p is from 0 to 100, provided that n+p is from 5 to 100;

from 0.1%to 8%of structural units of a multiethylenically unsaturated monomer, and

structural units of a monoethylenically unsaturated nonionic monomer;

wherein the polymeric particles have a Tg of 0℃ or lower, and the weight ratio of polyurethane to acrylic polymer in the polymeric particles is from 20: 80 to 99: 1.

In a second aspect, the present invention is a method of preparing the aqueous dispersion of the first aspect. The method comprises forming an acrylic polymer in an aqueous medium by emulsion polymerization in the presence of a polyurethane to give the aqueous dispersion of polymeric particles comprising an acrylic polymer and a polyurethane, wherein the acrylic polymer comprises, by weight based on the weight of the acrylic polymer,

where R ₁ is linear or branched C ₁-C ₁₀ alkylene group, R ₂ is hydrogen or a methyl group, n is from 0 to 100, p is from 0 to 100, provided that n+p is from 5 to 100;

structural units of a monoethylenically unsaturated nonionic monomer;

In a third aspect, the present invention is an aqueous coating composition comprising the aqueous dispersion of the first aspect, further comprising a matting agent, an additional polyurethane dispersion, a hand feel modifier, a thickener, a leveling agent, a crosslinking agent, or mixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION

“Aqueous” dispersion herein means that particles dispersed in an aqueous medium. By “aqueous medium” herein comprises water and from 0 to 30%, by weight based on the weight of the medium, of water-miscible compound (s) such as, for example, alcohols, glycols, glycol ethers, glycol esters, and the like.

“Acrylic” as used herein includes (meth) acrylic acid, alkyl (meth) acrylate, (meth) acrylamide, (meth) acrylonitrile and their modified forms such as (meth) hydroxyalkyl acrylate. Throughout this document, the word fragment “ (meth) acryl” refers to both “methacryl” and “acryl” . 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.

“Structural units” , also known as “polymerized units” , of the named monomer, refers to the remnant of the monomer after polymerization, that is, polymerized monomer or the monomer in polymerized form. For example, a structural unit of methyl methacrylate is as illustrated:

where the dotted lines represent the points of attachment of the structural unit to the polymer backbone.

The aqueous dispersion of the present invention comprises polymeric particles comprising an acrylic polymer and a polyurethane (also as “an aqueous polyurethane/acrylic hybrid dispersion” ) . The polymeric particles may be obtained by forming the acrylic polymer in an aqueous medium by an emulsion polymerization in the presence of the polyurethane, typically a dispersion of polyurethane particles.

The acrylic polymer useful in the present invention may comprise structural units of one or more (meth) acrylate functional siloxanes of formula (I) :

where R ₁ is a linear or branched C ₁-C ₁₀ alkylene group, R ₂ is hydrogen or a methyl group, n is from 0 to 100, p is from 0 to 100, provided that n+p is from 5 to 100. R ₁ can be a linear or branched C ₁-C ₈, C ₁-C ₆, or C ₁-C ₃ alkylene group, preferably - (CH ₂) ₃-. n and p may be each independently from 0 to 60, from 0 to 50, from 0 to 40, from 0 to 30, or from 0 to 20. Preferably, n+p is from 5 to 60, from 8 to 50, from 10 to 40, from 10 to 30, or from 10 to 20.

The acrylic polymer useful in the present invention may comprise, by weight based on the weight of the acrylic polymer, 0.1%or more, 0.2%or more, 0.3%or more, 0.4%or more, 0.5%or more, 0.6%or more, 0.7%or more, 0.8%or more, 0.9%or more, 1.0%or more, 1.1%or more, 1.2%or more, 1.5%or more, or even 2%or more, and at the same time, 10%or less, 9.0%or less, 8.0%or less, 7.0%or less, 6.0%or less, 5.0%or less, or even 4.0%or less of structural units of the (meth) acrylate functional siloxane.

The acrylic polymer useful in the present invention may comprise structural units of one or more multiethylenically unsaturated monomers. “Multiethylenically unsaturated monomers” means monomers have two or more ethylenically unsaturated bonds. Examples of suitable multiethylenically unsaturated monomers include allyl (meth) acrylate, hexanediol di(meth) arcylate, ethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, butanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinyl benzene, allyl (meth) acrylamide, allyl oxyethyl (meth) acrylate, crotyl (meth) acrylate, diallyl maleate, or mixtures thereof. Preferred multiethylenically unsaturated monomers is allyl methacrylate. The acrylic polymer may comprise structural units of the multiethylenically unsaturated monomer in an amount of from 0.1%to 8%, for example, 0.1%or more, 0.2%or more, 0.3%or more, 0.4%or more, 0.5%or more, 0.6%or more, 0.7%or more, 0.8%or more, 0.9%or more, 1.0%or more, 1.1%or more, 1.2%or more, 1.3%or more, 1.4%or more, 1.5%or more, 1.6%or more, 1.7%or more, 1.8%or more, 1.9%or more, or even 2.0%or more, and at the same time, 8.0%or less, 7.5%or less, 7.0%or less, 6.5%or less, 6.0%or less, 5.5%or less, 5.0%or less, 4.5%or less, 4.0%or less, 3.5%or less, 3.0%or less, or even 2.5%or less, by weight based on the weight of the acrylic polymer.

The acrylic polymer useful in the present invention may comprise structural units of one or more monoethylenically unsaturated nonionic monomers. The term “nonionic monomers” herein refers to monomers that do not bear an ionic charge between pH=1-14. Suitable examples of ethylenically unsaturated nonionic monomers include alkyl esters of (meth) acrylic acid, preferably having an alkyl with 1-32 carbon atoms, for example, C ₁-C ₁₈- alkyl esters of (meth) acrylic acid, C ₁-C ₁₂-alkyl esters of (meth) acrylic acid, or C ₁-C ₄-alkyl esters of (meth) acrylic acid, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate, butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, decyl acrylate, isodecyl methacrylate, isobornyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate; (meth) acrylonitrile; vinyl aromatic monomers including styrene and substituted styrenes, or mixtures thereof; butadiene; ethylene, propylene, α-olefins such as 1-decene; and vinyl monomers such as vinyl acetate, vinyl butyrate, vinyl chloride, vinylidene chloride, vinyl versatate and other vinyl esters, cycloalkyl (meth) acrylates including cyclohexyl (meth) acrylate, methcyclohexyl (meth) acrylate, dihydrodicyclopentadienyl (meth) acrylate, trimethylcyclohexyl (meth) acrylate, t-butyl (meth) cyclohexyl acrylate; or combinations thereof. Preferred monoethylenically unsaturated nonionic monomers are selected from the group consisting of butyl acrylate, butyl methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, and mixtures thereof. The acrylic polymer may comprise, by weight based on the weight of the acrylic polymer, 72%or more, 77%or more, 80%or more, 82%or more, 84%or more, 85%or more, 90%or more, or even 92%or more, and at the same time, 99.8%or less, 99.7%or less, 99.6%or less, 99.5%or less, 99%or less, 98.5%or less, or even 98%or less of structural units of the monoethylenically unsaturated nonionic monomer.

The acrylic polymer useful in the present invention may comprise structural units of one or more monoethylenically unsaturated functional monomers carrying at least one functional group selected from an amide, ureido, carboxyl, carboxylic anhydride, hydroxyl, sulfonic acid, sulfonate, phosphoric acid, or phosphate group, a salt thereof, or mixtures thereof, that are different from the monoethylenically unsaturated nonionic monomer described above. Examples of suitable monoethylenically unsaturated functional monomers include α, β-ethylenically unsaturated carboxylic acids including an acid-bearing monomer such as methacrylic acid, acrylic acid, itaconic acid, maleic acid, or fumaric acid; or a monomer bearing an acid-forming group which yields or is subsequently convertible to, such an acid group such as anhydride, (meth) acrylic anhydride, or maleic anhydride; vinyl phosphonic acid; allyl phosphonic acid; phosphoalkyl (meth) acrylates such as phosphoethyl (meth) acrylate, phosphopropyl (meth) acrylate, phosphobutyl (meth) acrylate; salts thereof; and mixtures thereof; CH ₂=C (R) -C (O) -O- (R ^lO) _q-P (O) (OH) ₂, wherein R=H or CH ₃, R ¹=alkylene, and q=1-10, such as SIPOMER PAM-100, SIPOMER PAM-200, SIPOMER PAM-300 and SIPOMER PAM-600 all available from Solvay; phosphoalkoxy (meth) acrylates such as phospho ethylene glycol (meth) acrylate, phospho di-ethylene glycol (meth) acrylate, phospho tri-ethylene glycol (meth) acrylate, phospho propylene glycol (meth) acrylate, phospho di-propylene glycol (meth) acrylate, phospho tri-propylene glycol (meth) acrylate, salts thereof; sodium styrene sulfonate, sodium vinyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, sodium salt of 2-acrylamido-2-methyl-1-propanesulfonic acid, ammonium salt of 2-acrylamido-2-methyl-1-propane sulfonic acid; sodium salt of allyl ether sulfonate; acrylamide, methacrylamide, monosubstituted (meth) acrylamide, N-methylacrylamide, N-ethylacrylamide, N-isopropylacrylamide, N-butylacrylamide, N-tertiary butylacrylamide, N-2-ethylhexylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide; hydroxy-functional alkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; ureido-functional monomers such as hydroxyethyl ethylene urea methacrylate, hydroxyethyl ethylene urea acrylate, such as SIPOMER WAM II, methylacrylamidoethyl ethylene urea, or mixtures thereof. Preferred ethylenically unsaturated functional monomers are acrylic acid, sodium styrene sulfonate, acrylamide, methacrylamide, methacrylic acid, or mixtures thereof. Although it is possible for the acrylic polymer to include structural unites of the monoethylenically unsaturated functional monomer such as the carboxylic acid monomer, it is preferred that the acrylic polymer comprises a substantial absence of structural units of the monoethylenically unsaturated functional monomer. As used herein, a substantial absence means less than 10%, less than 6%, less than 5%, less than 3%, less than 1%, less than 0.5%, less than 0.2%, less than 0.1%, or even zero of structural units of the monoethylenically unsaturated functional monomer, by weight based on the weight of the acrylic polymer.

In some embodiments, the acrylic polymer useful in the present invention may comprise, by weight based on the weight of the acrylic polymer, from 0.2%to 10%of structural units of the (meth) acrylate functional siloxane, from 0.2%to 8%of structural units of the multiethylenically unsaturated monomer such as allyl methacrylate, and from 72%to 99.6%of structural units of the monoethylenically unsaturated nonionic monomer, and optionally from 0 to 10%of structural units of the monoethylenically functional monomer such as α, β-ethylenically unsaturated carboxylic acids. Preferably, the acrylic polymer in the polymeric particles comprises, by weight based on the weight of the acrylic polymer, from 0.2%to 8%of structural units of the (meth) acrylate functional siloxane, from 0.2%to 8%of structural units of the multiethylenically unsaturated monomer, from 84%to 99.6%of structural units of the monoethylenically unsaturated nonionic monomer, and optionally, from 0 to less than 5%of structural units of the monoethylenically unsaturated functional monomer.

The polyurethane useful in the present invention may be a reaction product of one or more polyols with one or more isocyanate compounds. “Polyols” refers to any products having two or more hydroxyl groups per molecule. Polyols useful in preparing the polyurethane may include polyether diols, polyester diols, polycarbonate polyols, multi-functional polyols, or mixtures thereof. The polyols may be selected from polyether polyols, polyester polyols, polycarbonate polyols, or mixtures thereof.

The polyether polyols useful in preparing the polyurethane may contain a -C-O-C-group. They can be obtained by reacting starting compounds that contain reactive hydrogen atoms such as water or diols, with alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, epichlorohydrin, or mixtures thereof. Preferred polyether polyols include poly (propylene glycol) with a molecular weight of from 400 to 3,000, polytetrahydrofuran and copolymers of poly (ethylene glycol) and poly (propylene glycol) . The diols useful in preparing the polyether polyols may include alkylene glycols, preferably ethylene glycol, diethylene glycol and butylene glycol.

The polyester polyols useful in preparing the polyurethane are typically esterification products prepared by the reaction of organic polycarboxylic acids or their anhydrides with a stoichiometric excess of a diol (s) . Examples of suitable polyester polyols useful in preparing the polyurethane include poly (glycol adipate) , poly (ethylene terephthalate) polyols, polycaprolactone polyols, alkyd polyols, orthophthalic polyols, sulfonated and phosphonated polyols, and the mixture thereof. The diols useful in preparing the polyester polyols include those described above for preparing the polyether polyols. Suitable carboxylic acids useful in preparing the polyester polyols may include dicarboxylic acids, tricarboxylic acids and anhydrides, such as maleic acid, maleic anhydride, succinic acid, glutaric acid, glutaric anhydride, adipic acid, suberic acid, pimelic acid, azelaic acid, sebacic acid, chlorendic acid, 1, 2, 4-butane-tricarboxylic acid, phthalic acid, the isomers of phthalic acid, phthalic anhydride, fumaric acid, dimeric fatty acids such as oleic acid, and the like, or mixtures thereof. Preferred polycarboxylic acids useful in preparing the polyester polyols include aliphatic and aromatic dibasic acids.

The isocyanate compounds useful in preparing the polyurethane have two or more isocyanate groups on average, preferably two to three isocyanate groups per molecule. The isocyanate compounds typically comprise about 5 to 20 carbon atoms and include aliphatic, cycloaliphatic, aryl-aliphatic, and aromatic polyisocyanates, oligomers thereof, or mixtures thereof. Preferred isocyanate compounds are diisocyanates such as toluene diisocyanate, hexamethylene isocyanate and isophorone isocyanate.

Suitable aliphatic isocyanate compounds in the present invention may include, for example, omega-alkylene diisocyanates having from 5 to 20 carbon atoms, such as hexamethylene-1, 6-diisocyanate, 1, 12-dodecane diisocyanate, 2, 2, 4-trimethyl-hexamethylene diisocyanate, 2, 4, 4-trimethyl-hexamethylene diisocyanate, 2-methyl-1, 5-pentamethylene diisocyanate, and the mixture thereof. Preferred aliphatic polyisocyanates are hexamethylene-1, 6-diisocyanate, 2, 2, 4-trimethyl-hexamethylene-diisocyanate, 2, 4, 4-trimethyl-hexamethylene diisocyanate, or mixtures thereof. Examples of suitable cycloaliphatic isocyanate compounds include dicyclohexylmethane diisocyanate (for example, DESMODUR polyisocyanates from Covestro) , isophorone diisocyanate, 1, 4-cyclohexane diisocyanate, 1, 3-bis- (isocyanatomethyl) cyclohexane, or mixtures thereof. Preferred cycloaliphatic isocyanate compounds are selected from dicyclohexylmethane diisocyanate and isophorone diisocyanate. Examples of suitable araliphatic isocyanate compounds include m-tetramethyl xylylene diisocyanate, p-tetramethyl xylylene diisocyanate, 1, 4-xylylene diisocyanate, 1, 3-xylylene diisocyanate, or mixtures thereof. A preferred araliphatic isocyanate compound is tetramethyl xylylene diisocyanate. Examples of suitable aromatic isocyanate compounds include 4, 4'-diphenylmethylene diisocyanate, toluene diisocyanate, their isomers, naphthalene diisocyanate, their oligomeric forms, or mixtures thereof. A preferred aromatic isocyanate compound is toluene diisocyanate.

The polyurethane dispersion useful in the present invention may be prepared by techniques known in the art, for example, first preparing a polyurethane by reacting at least one polyol and at least one isocyanate compound described above, optionally in the presence of a catalyst, a solvent or mixtures thereof; dispersing the obtained polyurethane in water optionally typically in the presence of a surfactant; and optionally adding polyamines before, during and/or after dispersing the polyurethane in water.

The polyurethane useful in the present invention may have a hydroxyl (OH) number of from 0 mgKOH/g to 50 mgKOH/g, for example, 40 mgKOH/g or less or 30 mgKOH/g or less, as measured by ASTM D 1957-86 (2001) method. The polyurethane useful in the present invention may have an acid number of from 10 mgKOH/g to 100 mgKOH/g, for example, 10 mgKOH/g or more, 15 mgKOH/g or more, or even 20 mgKOH/g or more, as determined by ASTM D 974 (2008) method.

The polyurethane useful in the present invention may have a number average molecular weight of 2,000 g/mol or more, 3,000 g/mol or more, 4,000 g/mol or more, 5,000 g/mol or more, 6,000 g/mol or more, 8,000 g/mol or more, or even 10,000 g/mol or more, as measured by gel permeation chromatography (GPC) with polystyrene standard. The polyurethane is typically supplied in the form of an aqueous dispersion. Polyurethane particles in the aqueous polyurethane dispersion may have a particle size in the range of from 30 nm to 500 nm, from 40 nm to 300 nm, or from 50 nm to 100 nm. The particle size herein means the average particle size as measured by Brookhaven 90Plus Particle Size Analyzer described in the Examples section below.

The weight ratio of polyurethane to acrylic polymer in the polymeric particles may be from 20: 80 to 99: 1, from 22.5: 77.5 to 95: 5, from 25: 75 to 90: 10, from 27.5: 72.5 to 87.5: 12.5, from 30: 70 to 85: 15, from 32.5: 67.5 to 82.5: 17.5, from 35: 65 to 80: 20, from 40: 60 to 77.5: 22.5, from 42.5: 57.5 to 75: 25, from 45: 55 to 70: 30, from 47.5: 52.5 to 65: 35, from 50: 50 to 60: 40, or from 50: 50 to 55: 45.

The aqueous dispersion of polymeric particles of the present invention may be prepared by emulsion polymerization of monomers used for preparing the acrylic polymer in an aqueous medium in the presence of the polyurethane. During polymerization, the acrylic polymer grafted polyurethane may be formed. Without being bound by a theory, after polymerization process, the acrylic polymer is embedded in the polymeric particles. Emulsion polymerization techniques for preparing the acrylic polymer are well known in the art. Temperature suitable for emulsion polymerization may be lower than 100℃, in the range of from 15 to 95℃, or in the range of from 30 to 90℃. Monomers for preparing the acrylic polymer may include the (meth) acrylate siloxane, the multiethylenically unsaturated monomer, the monoethylenically unsaturated nonionic monomer, and optionally the monoethylenically unsaturated functional monomer described above. Total weight concentration of the monomers used to prepare the acrylic polymer is equal to 100%. The weight ratio of the polyurethane to total weight of the monomer for preparing the acrylic polymer can be the same as the weight ratio of polyurethane to acrylic polymer as described above, for example, in the range of from 20: 80 to 99: 1.

The preparation of the aqueous dispersion of the polymeric particles may be conducted by first providing the polyurethane, preferably an aqueous dispersion of polyurethane, and then loading and polymerizing a mixture of monomers that form structural units of the acrylic polymer in the presence of the polyurethane to obtain the aqueous dispersion of polymeric particles. The mixture of monomers may include the monomers described above, the (meth) acrylate functional siloxane, the multiethylenically unsaturated monomer, and the monoethylenically unsaturated nonionic monomer. The mixture of monomers for preparing the acrylic polymer may be added neat or as an emulsion in water; or added in one or more additions or continuously, linearly or nonlinearly, over the polymerization reaction period, or combinations thereof. Temperature suitable for emulsion polymerization processes may be lower than 100℃, in the range of from 15 to 95℃, or in the range of from 30 to 90℃. Multistage free-radical polymerization using the monomers described above can be used, which at least two stages are formed sequentially, and usually results in the formation of the multistage polymer comprising at least two polymer compositions.

In the emulsion polymerization, free radical initiators may be used. The emulsion polymerization process may be 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, perphosphoric acid, and salts thereof; potassium permanganate, and ammonium or alkali metal salts of peroxydisulfuric acid. The free radical initiators may be used typically at a level of 0.01 to 3.0%by weight, based on the total weight of monomers. Redox systems comprising the above described initiators coupled with a suitable reductant may be used in the polymerization process. Examples of suitable reductants include sodium sulfoxylate formaldehyde, ascorbic acid, isoascorbic acid, alkali metal and ammonium salts of sulfur-containing acids, such as sodium sulfite, bisulfite, thiosulfate, hydrosulfite, sulfide, hydrosulfide or dithionite, formadinesulfinic acid, acetone bisulfite, glycolic acid, hydroxymethanesulfonic acid, glyoxylic acid hydrate, lactic acid, glyceric acid, malic acid, tartaric acid and salts of the preceding acids. Metal salts of iron, copper, manganese, silver, platinum, vanadium, nickel, chromium, palladium, or cobalt may be used to catalyze the redox reaction. Chelating agents for the metals may optionally be used.

In the emulsion polymerization, one or more surfactants may be used. The surfactants may be added prior to or during the polymerization of the monomers, or combinations thereof. A portion of the surfactant can also be added after the polymerization. These surfactants may include anionic and/or nonionic emulsifiers. Examples of suitable surfactants include alkali metal or ammonium salts of alkyl, aryl, or alkylaryl sulfates, sulfonates or phosphates; alkyl sulfonic acids; sulfosuccinate salts; fatty acids; polymerizable surfactants; and ethoxylated alcohols or phenols. The surfactant used is usually from 0.1%to 6%or from 0.3%to 1.5%, by weight based on the total weight of monomers used for preparing the acrylic polymer.

In the emulsion polymerization, one or more chain transfer agents may be used. Examples of suitable chain transfer agents include 3-mercaptopropionic acid, dodecyl mercaptan, methyl 3-mercaptopropionate, butyl 3-mercaptopropionate, benzenethiol, azelaic alkyl mercaptan, or mixtures thereof. The chain transfer agent may be used in an effective amount to control the molecular weight of the acrylic polymer, for example, from 0 to 2.5%, from 0.03%to 1%, or from 0.05%to 0.5%, by weight based on the total weight of monomers used for preparing the acrylic polymer.

After completing the emulsion polymerization, the obtained aqueous dispersion of polymeric particles may be neutralized by one or more bases as neutralizers to a pH value, for example, at least 6, from 6 to 10, or from 7 to 9. The bases may lead to partial or complete neutralization of the ionic or latently ionic groups of the acrylic polymer. 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 triethyl amine, ethylamine, propylamine, monoisopropylamine, monobutylamine, hexylamine, ethanolamine, diethyl amine, dimethyl amine, di-n-propylamine, 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; and mixtures thereof. The aqueous dispersion of polymeric particles of the present invention preferably has a coagulum content of 0.6%or less, 0.5%or less, 0.4%or less, 0.3%or less, or even 0.25%or less.

The coagulum content was measured according to the test method described in the Examples section below. The polymeric particles in the aqueous dispersion of the present invention may have a Tg of 0℃ or lower, for example, -2℃ or lower, -5℃ or lower, -8℃ or lower, or even -10℃ or lower, and at the same time, -60℃ or higher, -55℃ or higher, -50℃or higher, -45℃ or higher, -40℃ or higher, -35℃ or higher, -30℃ or higher, -28℃ or higher, or even -25℃ or higher. Tg values of the polymeric particles are measured by DSC as described in the Examples section below.

The polymeric particles in the aqueous dispersion of the present invention may have a particle size of from 30 nanometers (nm) or more, 40 nm or more, 50 nm or more, or even 60 nm or more, and at the same time, 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, 300 nm or less, 200 nm or less, 150 nm or less, or even 120 nm or less. The particle size herein means the average particle size determined by Brookhaven 90Plus Particle Size Analyzer as described in the Examples section below.

The present invention also relates to an aqueous coating composition comprising the aqueous dispersion of polymeric particles described above. The aqueous coating composition may comprise, by solids weight based on the solids weight of the aqueous coating composition, 20%or more, 25%or more, 30%or more, or even 35%or more, and at the same time, 80%or less, 70%or less, 60%or less, 50%or less, or even 40%, of the aqueous dispersion of polymeric particles.

The aqueous coating composition of the present invention may further comprise an additional polyurethane dispersion. The polyurethane dispersion may be the same or different from those polyurethane dispersions used in preparation of the aqueous dispersion of polymeric particles described above. The additional polyurethane dispersion may be present in the aqueous coating composition, by solids weight based on the total solids weight of the coating composition, from 0 to 80%, from 5%to 50%, or from 10%to 40%.

The aqueous coating composition of the present invention may further comprise one or more thickeners, also known as “rheology modifiers” . Examples of suitable thickeners include alkali swellable emulsions (ASE) ; hydrophobically modified alkali swellable emulsions (HASE) ; associative thickeners such as hydrophobically modified ethoxylated urethanes (HEUR) ; and cellulosic thickeners such as methyl cellulose ethers, hydroxymethyl cellulose (HMC) , hydroxyethyl cellulose (HEC) , hydrophobically-modified hydroxy ethyl cellulose (HMHEC) , sodium carboxymethyl cellulose (SCMC) , sodium carboxymethyl 2-hydroxyethyl cellulose, 2-hydroxypropyl methyl cellulose, 2-hydroxyethyl methyl cellulose, 2-hydroxybutyl methyl cellulose, 2-hydroxyethyl ethyl cellulose, and 2-hydoxypropyl cellulose. Preferred thickener is HEUR, HASE or ASE. The thickener may be present, by solids weight based on the total solids weight of the aqueous coating composition, in an amount of from 0 to 7%, from 0.01%to 6%, from 0.1%to 5%, from 0.2%to 4%, or from 0.5%to 3%.

The aqueous coating composition of the present invention may also comprise one or more leveling agents. “Leveling agents” refers to chemical substances which enable the coating composition to more uniformly wet substrate and decrease surface defects. Examples of suitable leveling agents include polydimethylsiloxane, modified polydimethylsiloxane, polyacrylate, fluorocarbon surfactants, or mixtures thereof. The leveling agent may be present, by weight based on the total solids weight of the coating composition, from 0 to 10%, from 0.1%to 7%, from 0.3%to 6%, from 0.5%to 5%, or from 0.7%to 4%.

The aqueous coating composition of the present invention may further comprise one or more matting agents. “Matting agents” herein refer to any inorganic or organic particles that provide matt effect. Matting agents usually have an average particle size of 3.5 microns or more, according to ASTM E2651-10 (2010) Standard Guide for Powder Particle Size Analysis. Suitable matting agents useful in the present invention may include silica matting agents, polyurea matting agents, polyacrylate matting agents, polyethylene matting agents, polytetrafluoroethene matting agents, and mixtures thereof. Preferred matting agent are silica matting agents, polyacrylate matting agents, polyurea matting agents, and mixtures thereof. Suitable commercially available matting agents may include ACEMATT TS-100 and OK520 silica matting agents both available from Evonik, DEUTERON MK polyurea matting agent available from Deuteron, SYLOID Silica 7000 matting agent available from Grace Davison, PARALOID ^TM PRD 137B emulsion based on polyacrylate available from The Dow Chemical Company (PARALOID is a trademark of The Dow Chemical Company) ; ULTRALUBE D277 emulsion based on HDPE/plastic, ULTRALUBE D818 emulsion based on montan/PE/plastic, and ULTRALUBE D860 emulsion based on PE/ester matting agents all available from Keim-Additec; and mixtures thereof. The matting agent may be present, by solids weight based on the solids weight of the aqueous coating composition, in an amount of 2%or more, 3%or more, 4%or more, or even 5%or more, and at the same time, 60%or less, 50%or less, 40%or less, 30%or less, 25%or less, 20%or less, 15%or less, or even 10%or less.

The aqueous coating composition of the present invention may also comprise one or more hand feel modifiers. “Hand feel modifiers” refers to chemicals which are added into coating formulations with the purpose to endow dried films made therefrom with pleasant hand feeling. Examples of suitable hand feel modifiers include silicones, wax emulsions, polyacrylic polymer and mixtures thereof. The hand feel modifier may be present, by solids weight based on the total solids weight of the coating composition, from 0 to 40%, from 2%to 30%, from 4%to 25%, or from 6%to 20%.

The aqueous coating composition of the present invention may further comprise one or more crosslinking agents. Examples of suitable crosslinking agents include polyfunctional aziridines, polycarbodiimide, or polyisocyanates. The polyisocyanates crosslinking agents may include the isocyanate compounds described above in preparing the polyurethane dispersion, preferably their oligomeric forms, and more preferably water-dispersible polyisocyanates. The polyisocyanates useful in the present invention may have two or more isocyanate (NCO) groups on average, preferably two to four isocyanate groups per molecule. The polyisocyanates typically comprise from 5 to 100 carbon atoms, from 10 to 80 carbon atoms, or from 15 to 50 carbon atoms. The polyisocyanates are preferably aliphatic or cycloaliphatic polyisocyanates. More preferably, the polyisocyanates are hexamethylene diisocyanate homopolymers, hexamethylene diisocyanate adducts, isophorone diisocyanate homopolymers, isophorone diisocyanate adducts, or mixtures thereof. The crosslinking agent in the aqueous coating composition may be present, by solids weight (i.e., dry weight) based on the total solids weight of the aqueous coating composition, in an amount of from 0 to 50%, for example, 5%or more, 10%or more, 15%or more, 20%or more, 25%or more, or even 30%or more, and at the same time, 50%or less, 45%or less, 40%or less, or even 35%or less.

The aqueous coating composition of the present invention may further comprise one or more coalescents. Examples of suitable coalescents include 2-n-butoxyethanol, dipropylene glycol n-butyl ether, propylene glycol n-butyl ether, dipropylene glycol methyl ether, propylene 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, or mixtures thereof. The coalescents may be present, by weight based on the total weight of the coating composition, in an amount of from 0 to 15%, from 0.01%to 10%, or from 0.1%to 5%.

The aqueous coating composition of the present invention may further comprise pigments and/or extenders. “Pigment” herein refers to a particulate inorganic material which is capable of materially contributing to the opacity or hiding capability of a coating. Such materials typically have a refractive index greater than 1.8. Inorganic pigments may include, for example, titanium dioxide (TiO ₂) , zinc oxide, iron oxide, zinc sulfide, barium sulfate, barium carbonate, or mixture thereof. In a preferred embodiment, pigment used in the present invention is TiO ₂. TiO ₂ typically exists in two crystal forms, anatase and rutile. TiO ₂ may be also available in concentrated dispersion form. The aqueous coating composition may also comprise one or more extenders. “Extender” herein refers to a particulate material having a refractive index of less than or equal to 1.8 and greater than 1.3. Examples of suitable extenders include calcium carbonate, clay, calcium sulfate, aluminosilicates, silicates, zeolites, mica, diatomaceous earth, solid or hollow glass, ceramic beads, nepheline syenite, feldspar, diatomaceous earth, calcined diatomaceous earth, talc (hydrated magnesium silicate) , silica, alumina, kaolin, pyrophyllite, perlite, baryte, wollastonite, opaque polymers such as ROPAQUE ^TM Ultra E available from The Dow Chemical Company (ROPAQUE is a trademark of The Dow Chemical Company) , or mixtures thereof. The pigments and/or extenders may be present, by weight based on the total solids weight of the coating composition, in a combined amount of from 0 to 30%, from 2%to 25%, or from 4%to 20%.

In addition to the components described above, the aqueous coating composition of the present invention may further comprise any one or combination of the following additives: buffers, neutralizers, freeze/thaw additives, humectants, mildewcides, biocides, anti-skinning agents, colorants, anti-oxidants, plasticizers, thixotropic agents, adhesion promoters, and grind vehicles. These additives may be present in a combined amount of from 0 to 10%, from 0.3%to 5%, or from 0.5%to 3%, by solids weight based on the solids weight of the aqueous coating composition.

The solids content of the aqueous coating composition may be in the range of from 10%to 60%, from 15%to 50%, or from 25%to 45%, by weight based on the weight of the coating composition.

The aqueous coating composition of the present invention may be prepared by mixing the aqueous dispersion of polymeric particles with other optional components, for example, matting agents, thickeners, leveling agents and/or crosslinking agents as described above. Components in the aqueous coating composition may be mixed in any order to provide the aqueous coating composition of the present invention. Any of the above-mentioned optional components may also be added to the composition during or prior to the mixing to form the aqueous coating composition.

The aqueous coating composition of the present invention may be applied to architectural substrates or industrial substrates including, for example, flexible substrates including leather (e.g., natural leather, artificial leather, synthetic leather, and vinyl leather) such as leather upholstery, for example, automotive upholstery, metals, plastics, foams, stones, elastomeric substrates, fabrics, paper, cardboard, paperboard, wood, or cementitious substrates by any known method, such as, for example, brushing, dipping, rolling and spraying. The coating composition is particularly suitable for automotive leather finishing. The aqueous coating composition may be applied to unfinished or basecoat finished leather such as, for example, mineral tanned or vegetable tanned leather including full-grain leather, buffed or corrected-grain leather, and split leather; or to paper; by curtain coater and spraying methods such as, for example, air-atomized spray, air assisted spray, airless spray, high volume low pressure spray, and air-assisted airless spray, by roll coating or knife coating. The aqueous coating composition can be applied directly onto leather or indirectly coated over a primer layer. The primer can be a conventional primer comprising a (meth) acrylic polymer, a polyurethane, a polyacrylonitrile, a polybutadiene, a polystyrene, a polyvinyl chloride, a polyvinylidene chloride, a polyvinyl acetate, and combinations thereof.

The present invention also provides a method of preparing a coating on a substrate, optionally coated with a basecoat, comprising: applying the substrate the aqueous coating composition of the present invention, and drying, or allowing to dry, the applied coating composition to produce the coating. The substrate is preferably leather surface. The aqueous coating composition can provide the coatings with cold bally flexibility (-10℃) , wet rubbing fastness and Gakushin rubbing fastness all showing rating of 3. The aqueous coating composition may also provide the coatings with a gloss level of 2.0 or lower, preferably, 1.6 or lower, 1.5 or lower, 1.4 or lower, 1.3 or lower, or even 1.2 or lower, on a 60° Gardner Gloss scale. These properties are measured according to the test methods described in the Examples section below. The present invention also relates to a process of using the aqueous coating composition, comprising forming the aqueous coating composition, applying the aqueous coating composition to leather surface, and drying, or allowing to dry the applied coating composition. Drying may be performed in a known manner such as, for example, air drying or heat drying at temperatures that will not damage the substrate, for example, from 50 to 130℃, from 60 to 125℃, or from 70 to 120℃.

EXAMPLES

Some embodiments of the invention will now be described in the following Examples, wherein all parts and percentages are by weight unless otherwise specified. The following materials are used in the examples:

BAYDERM Finish 91UD dispersion (40%solids) available from The Dow Chemical Company, is a polyurethane dispersion with an average particle size of about 60-80 nm as measured by Brookhaven 90Plus Particle Size Analyzer described below.

Sodium lauryl sulfate (SLS) , available from Solvay, is used as a surfactant.

Sodium lauryl benzene sulfonate (DS-4) , available from Solvay, is used as a surfactant.

Methyl methacrylate (MMA) , butyl acrylate (BA) , acrylic acid (AA) , methacrylic acid (MAA) , and allyl methacrylate (ALMA) are monomers all available from The Dow Chemical Company.

BRUGGOLITE FF6 reductant is available from Brueggemann Chemical.

Kathon LXE (1.5%solids) and Kathon LX (14.2%solids) biocides are available from The Dow Chemical Company.

A reactive silicone (hereinafter “RS 123” ) , available from The Dow Chemical Company, has the structure as follows,

where n+p = 12～25.

Silok 3560 methacrylate silicone, available from Guangzhou Silok Polymer Co., Ltd., is a crosslinkable silicone resin with reactive functional organic polysiloxane (molecular weight: around 60000 and degree of unsaturation: around 4.5%) .

Silok 3572 allyl polyether silicone, available from Guangzhou Silok Polymer Co., Ltd., contains unsaturated groups (–CH ₂CH=CH ₂) and has a molecular weight of around 8000 and a degree of unsaturation of around 0.5%.

Aquaderm Fluid H (100%solids) , available from Lanxess Chemical, is a polysiloxane/polyether copolymer leveling agent.

OPTI-MATT ^TM UD-4 duller (25%solids) , available from Dow Chemical Company, is an aqueous dispersion of an organic dulling agent combined with silica.

ROSILK ^TM 2229 hand feel modifier (58%solids) , available from The Dow Chemical Company, is an aqueous silicone emulsion.

ACRYSOL ^TM RM-819W thickener (23%solids) , available from The Dow Chemical Company, is a hydrophobically modified ethoxylated urethane.

ACRYSOL RM-2020 thickener (20%solids) , available from The Dow Chemical Company, is a non-ionic urethane rheology modifier.

BINDER LS-3486-HS (51%solids) , available from The Dow Chemical Company, is a reactive aliphatic polyisocyanate resin supplied in ethyl 3-ethoxypropionate for use as a crosslinking agent.

OPTI-MATT, ROSILK, HYDRHOLAC, and ACRYSOL are trademarks of The Dow Chemical Company.

The following standard analytical equipment and methods are used in the Examples.

Differential scanning calorimetry (DSC) method

DSC was used to measure polymer Tgs. A 5-10 milligram (mg) sample was analyzed in a sealed aluminum pan on a TA Instrument DSC Q2000 fitted with an auto-sampler under a nitrogen (N ₂) atmosphere. Tg measurement was conducted with three cycles including, from -60 to 200℃ at a rate of 10℃/min followed by holding for 5 min (1 ^st cycle) , from 200 to -60℃at a rate of 10℃/min (2 ^nd cycle) , and from -60 to 200℃ at a rate of 10℃/min (3 ^rd cycle) . Tg was obtained from the 3 ^rd cycle by taking the mid-point in the heat flow versus temperature transition as the Tg value.

Particle Size Measurement

Particle size of polymer particles in an aqueous polymer dispersion was measured by using Brookhaven Instruments 90Plus Particle Size Analyzer, which employs the technique of photon correlation spectroscopy (light scatter of sample particles) . This method involved diluting 2 drops of the aqueous polymer dispersion to be tested in 20 ml of 0.01 M NaCl solution, and further diluting the resultant mixture in a sample cuvette to achieve a desired count rate (K) (e.g., K ranging from 250 to 500 counts/sec for diameter in the range of 10-300 nm, and K ranging from 100 to 250 counts/sec for diameter in the range of 300-500 nm) . Then the particle size of the aqueous polymer dispersion was measured and reported as an average diameter by intensity.

Coagulum Content of Aqueous Dispersion of Polymeric Particles

An aqueous dispersion of polymeric particles was filtered through a 44 micron (325 mesh) sieve. The residue remaining on the sieve was washed with water and put in an oven at 150℃ for 15 min. Coagulum content was determined by the dry weight of the residue on the sieve divided by the original total wet weight of the aqueous dispersion. The lower the coagulum content, the more stable polymerization process in preparing the aqueous dispersion.

Properties of Coating Compositions

First, a basecoat was sprayed on a leather substrate in an amount of 66 g/m ² (6 g/ft ²) . The basecoat was composed of deionized (DI) water (100 g) , Bayderm Finish CTG s (870 g, 28%solids) (dispersion of polyurethane, polyacrylic, and other additive, Lanxess Chemical) , Aquaderm additive SF (30 g, 50%solids) (silicon emulsion for softy and waxy touch feeling, Lanxess Chemical) , EUDERM Black B-N pigment dispersion (100 g, 23%solids) (Lanxess Chemical) , BINDER LS-3486-HS (30 g, 51%solids) , and RM-2020 thickener in an amount of 0-10 grams to adjust the viscosity of the basecoat to 25 seconds measured by Viscosity Cup (Ford #4) . Then a coating composition to be tested was sprayed onto the resulting basecoat in an amount of 20 g/m ² (1.8 g/ft ²) twice with drying at 90℃ for 5-10 min for each time. After further drying at room temperature for 2 days, the obtained finished leather samples were tested according to the methods below:

● Gloss

Gloss (60°) of the finished leather samples was measured using a gloss meter (BYK Gardner USA 25 MICRO-TRI-GLOSS meter, catalogue number 4520) . The maximum acceptable gloss (60°) is 2.0.

● Wet Rubbing Fastness Test

Wet rubbing fastness was determined in accordance with ASTM D 5053-03 (2009) (Standard Test Method for Color fastness of Crocking Leather) . The wet rubbing fastness test was conducted using a rub fastness (Satra Footware Technology Center model STM421) . A 11.5 cm x 3.5 cm Swatch was removed from the finished crust. To determine the finish fastness of the as prepared finished leather samples, a 1.5 cm x 1.5 cm felt rubbing pad was saturated with water and placed on the equipment rubbing head (total weight of rubbing head was 1 kilogram) . To complete the testing, the leather Swatch was inserted into the rub fastness tester and stretched an additional 10%, the water saturated felt rubbing pad was applied to the finished surface of the leather Swatch, and 300 rubbing cycles were completed.

The finished surface of the leather Swatch was visually evaluated to assess damage. The felt rubbing pad used for the test was visually evaluated for pigment transfer as compared to a control felt rubbing pad (unused felt rubbing pad) . The wet rub fastness is rated on a scale of 1-3:

1 means the topcoat and basecoat are totally damaged so that the felt rubbing pad becomes black with the damaged basecoat attached to it;

2 means the topcoat is damaged and the basecoat is slightly damaged so that the felt rubbing pad becomes slightly black;

3 means the topcoat and basecoat show no damage so that the felt rubbing pad shows no change on color.

● Cold Bally Flexibility

Cold bally flexibility was measured in accordance with ASTM D6182-00 (2010) (Standard Test Method for Flexibility and Adhesion of Finished Leather) by repeatedly flexing a leather specimen over 30,000 cycles at -10℃. After flexing, the leather samples were observed by the naked eye to assess damage to the surface of the leather samples. The finish showing no cracking or white crazing is rated as “Pass” . Otherwise, cracking or white crazing on the finish is rated as “Fail” .

● Gakushin Rubbing Fastness

The Gakushin rubbing fastness was conducted by using GT-7020 from Gotech according to the following procedure: an abrasive cloth (#6 duct cloth) was fixed to a platen and a strip of a finished leather sample obtained above was fixed to a head. The duct cloth and the finished leather samples were contacted together and a total head weight above the leather of 1 kilogram (kg) was set in place. The test was activated and the platen moved back and forth at a rate of 30 cycles per minute (min) enabling the duct cloth to rub across the surface of the leather samples with the pressure of 1 kg applied. Around 9,000 cycles were applied for each leather sample. The leather sample finished with Example 2 (prepared as below) was set as a standard sample with rating of 3, other leather samples with comparable or better Gakushin properties than Example 2 are rated with 3.

The Gakushin property is rated on a scale of 1-3:

1 means the topcoat and basecoat of the finished leather samples are totally damaged and the leather substrate is exposed so that the rub area of the duct cloth becomes black;

2 means the topcoat is damaged and the basecoat of the leather samples is damaged partially so that the rub area of the duct cloth becomes slightly black;

3 means the topcoat and basecoat of the finished leather samples show no damage so that the rub area of the duct cloth has no color change.

Example (Ex) 1 Polymer Dispersion 1 (PD-1)

A monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (126 g) , MMA (150 g) , BA (352 g) , RS 123 (5g) , and ALMA (10 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was added 91UD (1285 g, 40%solids) and DI water (395 g) , and stirring was initiated. The contents of the flask were heated to 28-32℃ under a nitrogen atmosphere. The monomer emulsion (322 g) was fed into flask over 25 min and held for 30 min. FeSO ₄.7H ₂O (0.010g) in DI water (5g) mixed with ethylenediamine tetraacetic acid (EDTA) salt (0.039g) in DI water (5g) , a solution of t-butyl hydroperoxide (t-BHP, 0.3g t-BHP (70%solution) in 16g DI water) and a solution of Bruggolite FF6 (FF6, 0.2g FF6 in 16g DI water) were all added to the flask. After 20 min, the monomer emulsion (322 g) was fed into the flask over 25 min and held for 30 min. A solution of t-BHP (0.3 g t-BHP (70%solution) in 16g DI water) and a solution of FF6 (0.2g FF6 in 16g DI water) were added into the flask. At the end of polymerization, a solution of t-BHP (1.65g t-BHP (70%solution) in 40g DI water) and a solution of FF6 (1g FF6 in 41g DI water) were all added to the flask over 50 min, followed by a solution of Kathon LXE (2.6g (1.5%solution) in 15g DI water) , to obtain the polymer dispersion.

Ex 2 PD-2

The polymer dispersion of Ex 2 was prepared as in Ex 1 except the monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (123 g) , BA (339 g) , ALMA (10 g) , RS 123 (10 g) , and MMA (146 g) together to produce a stable monomer emulsion.

Ex 3 PD-3

The polymer dispersion of Ex 3 was prepared as in Ex 1 except the monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (123 g) , BA (329 g) , ALMA (10 g) , RS 123 (25 g) , and MMA (141 g) together to produce a stable monomer emulsion.

Ex 4 PD-4

The polymer dispersion of Ex 4 was prepared as in Ex 1 except the monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (123 g) , BA (356 g) , ALMA (10 g) , RS 123 (1 g) , and MMA (150 g) together to produce a stable monomer emulsion.

Ex 5 PD-5

The polymer dispersion of Ex 5 was prepared as in Ex 1 except the monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (123 g) , BA (354.5 g) , ALMA (10 g) , RS 123 (2.5 g) , and MMA (149 g) together to produce a stable monomer emulsion.

Ex 6 PD-6

A monomer emulsion was prepared by mixing SLS surfactant (11 g, 28%) , DI water (74 g) , BA (204 g) , ALMA (6 g) , RS 123 (6 g) , and MMA (88 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was added 91UD (2269 g, 40%solids) and DI water (232 g) , and stirring was initiated. The contents of the flask were heated to 28-32℃ under a nitrogen atmosphere. The monomer emulsion (189 g) was fed into flask over 25 min and held for 30 min. FeSO ₄.7H ₂O (0.006g) in DI water (5g) mixed with EDTA salt (0.023g) in DI water (5g) , a solution of t-BHP (0.17g t-BHP (70%solution) in 9g DI water) and a solution of FF6 (0.12g FF6 in 9g DI water) were all added to the flask. After 20 min, the monomer emulsion (189 g) was fed into the flask over 25 min and held for 30 min. A solution of t-BHP (0.17g t-BHP (70%solution) in 9g DI water) and a solution of FF6 (0.12g FF6 in 9g DI water) were added into the flask. At the end of polymerization, a solution of t-BHP (0.97g t-BHP (70%solution) in 23g DI water) and a solution of FF6 (0.58g FF6 in 24g DI water) were all added to the flask over 50 min, followed by a solution of Kathon LXE (1.56g (1.5%solution) in 9g DI water) , to obtain the polymer dispersion.

Ex 7 PD-7

A monomer emulsion was prepared by mixing SLS surfactant (11 g, 28%) , DI water (74 g) , BA (204 g) , ALMA (6 g) , RS 123 (6 g) , and MMA (88 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was added 91UD (324 g, 40%solids) and DI water (232 g) , and stirring was initiated. The contents of the flask were heated to 28-32℃ under a nitrogen atmosphere. The monomer emulsion (189 g) was fed into flask over 25 min and held for 30 min. FeSO ₄.7H ₂O (0.006g) in DI water (5g) mixed with EDTA salt (0.023g) in DI water (5g) , a solution of t-BHP (0.17g t-BHP (70%solution) in 9g DI water) and a solution of FF6 (0.12g FF6 in 9g DI water) were all added to the flask. After 20 min, the monomer emulsion (189 g) was fed into the flask over 25 min and held for 30 min. A solution of t-BHP (0.17g t-BHP (70%solution) in 9g DI water) and a solution of FF6 (0.12g FF6 in 9g DI water) were added into the flask. At the end of polymerization, a solution of t-BHP (0.97g t-BHP (70%solution) in 23g DI water) and a solution of FF6 (0.58g FF6 in 24g DI water) were all added to the flask over 50 min, followed by a solution of Kathon LXE (1.56g (1.5%solution) in 9g DI water) , to obtain the polymer dispersion.

Ex 8 PD-8

A monomer emulsion was prepared by mixing SLS surfactant (11 g, 28%) , DI water (74 g) , BA (204 g) , ALMA (6 g) , RS 123 (6 g) , and MMA (88 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was added 91UD (504 g, 40%solids) and DI water (232 g) , and stirring was initiated. The contents of the flask were heated to 28-32℃ under a nitrogen atmosphere. The monomer emulsion (189 g) was fed into flask over 25 min and held for 30 min. FeSO ₄.7H ₂O (0.006g) in DI water (5g) mixed with EDTA salt (0.023g) in DI water (5g) , a solution of t-BHP (0.17g t-BHP (70%solution) in 9g DI water) and a solution of FF6 (0.12g FF6 in 9g DI water) were all added to the flask. After 20 min, the monomer emulsion (189 g) was fed into the flask over 25 min and held for 30 min. A solution of t-BHP (0.17g t-BHP (70%solution) in 9g DI water) and a solution of FF6 (0.12g FF6 in 9g DI water) were added into the flask. At the end of polymerization, a solution of t-BHP (0.97g t-BHP (70%solution) in 23g DI water) and a solution of FF6 (0.58g FF6 in 24g DI water) were all added to the flask over 50 min, followed by a solution of Kathon LXE (1.56g (1.5% solution) in 9g DI water) , to obtain the polymer dispersion.

Comparative (Comp) Exs 1-5 and 8

The polymer dispersions Comp Ex 1-5 and 8 were prepared as in Ex 1 except monomer emulsions used are prepared as follows,

Comp Ex 1 CPD-1

A monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (126 g) , BA (357 g) , ALMA (10 g) , and MMA (149 g) together to produce a stable monomer emulsion.

Comp Ex 2 CPD-2

A monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (123 g) , BA (352 g) , RS 123 (10 g) and MMA (154 g) together to produce a stable monomer emulsion.

Comp Ex 3 CPD-3

A monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (126 g) , BA (340 g) , ALMA (10 g) , Silok 3560 (27 g) , and MMA (139 g) together to produce a stable monomer emulsion.

Comp Ex 4 CPD-4

A monomer emulsion was prepared by mixing SLS surfactant (18 g, 28%) , DI water (123 g) , BA (135 g) , ALMA (10 g) , RS 123 (10 g) , and MMA (360 g) together to produce a stable monomer emulsion.

Comp Ex 5 CPD-5

A monomer emulsion was prepared mixing SLS surfactant (18 g, 28%) , DI water (146 g) , BA (339 g) , ALMA (10 g) , Silok 3572 (10 g) , and MMA (146 g) together to produce a stable monomer emulsion.

Comp Ex 8 CPD-8

A monomer emulsion was prepared by mixing SLS surfactant (11 g, 28%) , DI water (74 g) , BA (182 g) , ALMA (6 g) , RS 123 (45g) , and MMA (70 g) together to produce a stable monomer emulsion.

Comp Ex 6 CPD-6

A monomer emulsion was prepared by mixing SLS surfactant (37 g, 28%) , DS-4 surfactant (37g, 22.5%) , DI water (321 g) , BA (958 g) , RS 123 (9.3g) , and AA (34.8 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was DI water (1212 g) , and stirring was initiated. The contents of the flask were heated to 33-37℃under a nitrogen atmosphere. The monomer emulsion (345 g) was fed into flask over 5 min. FeSO ₄.7H ₂O (0.008g) in DI water (4g) , a solution of ammonium persulfate (APS) (0.25g APS in 24g DI water) and a solution of Lykopon (0.5g Lykopon in 24g DI water) were all added to the flask. After 20 min, the monomer emulsion (1052 g) and a solution of t-BHP (0.55g t-BHP (70%solution) in 8g DI water) and a solution of sodium sulfoxylate formaldehyde (SSF, 0.44g SSF in 24g DI water) was fed into the flask over 50 min. After 30 min, 248 g of MMA was fed into the flask over 5 min. A solution of t-BHP (1.13 g t-BHP (70%solution) in 12g DI water) and a solution of SSF, (0.86g SSF in 28g DI water) were added into the flask. At the end of polymerization, a solution of t-BHP (1.87g t-BHP (70%solution) in 28g DI water) and a solution of FF6 (1.62g FF6 in 32g DI water) were added to the flask over 30 min, followed by a solution of SLS (88g, 28%) and triethyl amine (23g) in 168g DI water, and a solution of Kathon LX (0.35g (14.2%solution) in 16g DI water) , to obtain the polymer dispersion.

Comp Ex 7 CPD-7

The polymer dispersion Comp Ex 7 was prepared as in Comp Ex 6 except the monomer emulsion was prepared by mixing SLS surfactant (37 g, 28%) , DS-4 surfactant (37 g, 22.5%) , DI water (321 g) , MMA (88 g) , BA (953 g) , RS 123 (19 g) , and AA (35 g) together to produce a stable monomer emulsion.

Comp Ex 9 CPD-9

A monomer emulsion was prepared by mixing SLS surfactant (11 g, 28%) , DI water (74 g) , MMA (88 g) , BA (204 g) , RS 123 (6 g) , and ALMA (6 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was added 91UD (134 g, 40%solids) and DI water (232 g) , and stirring was initiated. The contents of the flask were heated to 28-32℃ under a nitrogen atmosphere. The monomer emulsion (194.5 g) was fed into flask over 25 min and held for 30 min. FeSO ₄.7H ₂O (0.0058g) in DI water (3g) mixed with EDTA salt (0.0232g) in DI water (3g) , a solution of t-BHP (0.174g t-BHP (70%solution) in 9.5g DI water) and a solution of FF6 (0.116g FF6 in 10g DI water) were all added to the flask. After 20 min, 194.5 g of the monomer emulsion was fed into the flask over 25 min and held for 30 min. A solution of t-BHP (0.17g t-BHP (70%solution) in 9.3g DI water) and a solution of FF6 (0.12g FF6 in 10g DI water) were added into the flask. At the end of polymerization, a solution of t-BHP (0.97g t-BHP (70%solution) in 23g DI water) and a solution of FF6 (0.58g FF6 in 24g DI water) were all added to the flask over 50 min, followed by a solution of Kathon LXE (0.9g (1.5%solution) in 10g DI water) , to obtain the polymer dispersion.

Comp Ex 10 CPD-10

A monomer emulsion was prepared by mixing SLS surfactant (22 g, 28%) , DI water (234 g) , BA (590 g) , MMA (241 g) , RS 123 (18 g) , AA (18 g) , MAA (9 g) , and ALMA (17.8 g) together to produce a stable monomer emulsion. To a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was DI water (550 g) and SLS (9 g, 28%) , and stirring was initiated. The contents of the flask were heated to 78-82℃ under a nitrogen atmosphere. The monomer emulsion (92 g) , a solution of ammonium bicarbonate (4.7g in 41g DI water) and a solution of APS (4 g in 13 g DI water) were fed into flask over 3 min. The monomer emulsion (1057.8 g) and a solution of t-BHP (0.63g t-BHP (70%solution) in 8g DI water) and a solution of FF6 (0.27g FF6 in 8g DI water) was fed into the flask over 65 min. At the end of polymerization, FeSO ₄.7H ₂O (0.0021g) in DI water (3 g) mixed with EDTA salt (0.0038 g) in DI water (3 g) , a solution of t-BHP (0.11 g t-BHP (70%solution) in 8g DI water) and a solution of FF6 (0.05g FF6 in 8g DI water) were all added to the flask, followed by a solution of ammonia (6 g (25%solution) in 10g DI water) , a solution of Kathon LXE (2g (1.5%solution) in 10g DI water) , and 91UD (2225 g, 40%solids) , to obtain the polymer dispersion.

Comp Ex 11 CPD-11

The polymer dispersion Comp Ex 11 was prepared as in Comp Ex 9 except that the monomer emulsion was prepared by mixing SLS surfactant (11 g, 28%) , DI water (74 g) , BA (204 g) , MMA (88 g) , RS 123 (6 g) and ALMA (6 g) together to produce a stable monomer emulsion; and to a 5-liter, four-necked round bottom flask equipped with a paddle stirrer, a thermocouple, nitrogen inlet, and reflux condenser was added 91UD (84 g, 40%solids) and DI water (232 g) , and stirring was initiated.

Properties of the above obtained polymer dispersions are given in Table 1. As shown in Table 1, the polymer dispersions of Comp Ex 8 (0.69%) and Comp Ex 11 (0.85%) demonstrated much higher coagulum content as compared to other polymer dispersions.

Table 1. Properties of Polymer Dispersions

¹ Tg of polymeric particles in the obtained polymer dispersions was measured by DSC as described above. ²Viscosity was measured by Brookfield #1, at 60 rpm at 25℃.

Coating Compositions

Aquaderm Fluid H leveling agent (16 g) was added into DI water in a container and stirred for a few minutes. OPTI-MATT UD-4 duller (426.2 g) and ROSILK 2229 hand feel modifier (60 g) were added into the container sequentially with agitation (200 revolutions per minute (rpm) , and then the as-prepared aqueous polymer dispersion (213.1 g) was added. Then BINDER LS-3486-HS (128 g) was added to the container with agitation (200 rpm) to form a mixture. Finally, ACRYSOL RM-819W thickener (3.3 g) was added to the mixture to adjust the viscosity, ideally targeting 24～25 seconds as measured by using a Viscosity testing cup (Ford #4) , to obtain the coating compositions (Coating Exs 1-8 and Comp Coating Exs 1-11) . Types of polymer dispersions used for preparing each coating composition are given in Table 2. These coating compositions were evaluated on leather according to the test methods described above and properties are given in Table 2.

As shown in Table 2, the polymer dispersion that was free of structural units of RS 123 Additive (CPD-1) provided poor wet rubbing fastness and cold bally flexibility performance. The polymer dispersion comprising structural units of other types of reactive silicones (CPD-3 and CPD-5) provided poor Gakushin performance, and/or wet rubbing fastness and cold bally flexibility performance. The polymer dispersion free of structural units of ALMA (CPD-2) provided poor Gakushin and wet rubbing fastness and cold bally flexibility performance. The polymer dispersion with too high Tg (CPD-4) provided leather with poor Gakushin rubbing fastness and cold bally flexibility performance. The polymer dispersions prepared in the absence of PUD (CPD-6 and CPD-7) provided leather with poor cold bally flexibility performance. The polymer dispersion comprising 15%structural units of RS 123 (CPD-8) and the blend of acrylic polymer and PUD (CPD-10) both provided leather with poor Gakushin rubbing fastness and cold bally flexibility performance. The polymer dispersions containing 15%polyurethane (CPD-9) or 10%polyurethane (CPD-11) both provided poor Gakushin rubbing fastness performance. In contrast, the polymer dispersions of Exs 1-8 all provided coatings with satisfactory wet rubbing fastness, cold bally flexibility, Gakushin rubbing fastness, and gloss.

Table 2. Properties of coating compositions (on leather substrate)

Claims

An aqueous dispersion of polymeric particles comprising an acrylic polymer and a polyurethane, wherein the acrylic polymer comprises, by weight based on the weight of the acrylic polymer,

from 0.1%to 10%of structural units of a (meth) acrylate functional siloxane of formula (I) ,

where R ₁ is a linear or branched C ₁-C ₁₀ alkylene group, R ₂ is hydrogen or a methyl group, n is from 0 to 100, p is from 0 to 100, provided that n+p is from 5 to 100;

from 0.1%to 8%of structural units of a multiethylenically unsaturated monomer, and

structural units of a monoethylenically unsaturated nonionic monomer;

wherein the polymeric particles have a Tg of 0℃ or lower, and the weight ratio of polyurethane to acrylic polymer in the polymeric particles is from 20: 80 to 99: 1.
The aqueous dispersion of claim 1, wherein R ₁ in formula (I) is a linear or branched C ₁-C ₆ alkylene group, and n+p is in the range of from 8 to 50.
The aqueous dispersion of claim 1, wherein the acrylic polymer comprises from 0.2%to 8%of structural units of the (meth) acrylate functional siloxane, by weight based on the weight of the acrylic polymer.
The aqueous dispersion of claim 1, wherein the polymeric particles are obtained by forming the acrylic polymer in an aqueous medium by emulsion polymerization in the presence of the polyurethane.
The aqueous dispersion of claim 1, wherein the multiethylenically unsaturated monomer is selected from the group consisting of allyl (meth) acrylate, hexanediol di (meth) arcylate, ethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, butanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinyl benzene, allyl (meth) acrylamide, allyl oxyethyl (meth) acrylate, crotyl (meth) acrylate, diallyl maleate, and mixtures thereof.
The aqueous dispersion of claim 1, wherein the monoethylenically unsaturated nonionic monomer is selected from the group consisting of butyl acrylate, butyl methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and mixtures thereof.
The aqueous dispersion of claim 1, wherein the weight ratio of polyurethane to acrylic polymer in the polymeric particles is from 30: 70 to 85: 15.
The aqueous dispersion of claim 1, wherein the polymeric particles have a particle size of from 30 nm to 800 nm.
The aqueous dispersion of claim 1, wherein the acrylic polymer comprises, by weight based on the weight of the acrylic polymer, from 0.2%to 8%of structural units of the (meth) acrylate functional siloxane, from 0.2%to 8%of structural units of the multiethylenically unsaturated monomer, and from 84%to 99.6%of structural units of the monoethylenically unsaturated nonionic monomer.
A method of preparing the aqueous dispersion of any one of claims 1-9, comprising forming an acrylic polymer in an aqueous medium by emulsion polymerization in the presence of a polyurethane to give the aqueous dispersion of polymeric particles comprising an acrylic polymer and a polyurethane, wherein the acrylic polymer comprises, by weight based on the weight of the acrylic polymer,

from 0.1%to 10%of structural units of a (meth) acrylate functional siloxane of formula (I) ,

where R ₁ is linear or branched C ₁-C ₁₀ alkylene group, R ₂ is hydrogen or a methyl group, n is from 0 to 100, p is from 0 to 100, provided that n+p is from 5 to 100;

from 0.1%to 8%of structural units of a multiethylenically unsaturated monomer, and

structural units of a monoethylenically unsaturated nonionic monomer;

wherein the polymeric particles have a Tg of 0℃ or lower, and the weight ratio of polyurethane to acrylic polymer in the polymeric particles is from 20: 80 to 99: 1.
An aqueous coating composition comprising the aqueous dispersion of any one of claims 1-9, further comprising a matting agent, an additional polyurethane dispersion, a hand feel modifier, a thickener, a leveling agent, a crosslinking agent, or mixtures thereof.