FIELD OF THE INVENTION

The present invention relates to a self-emulsifying blocked polyisocyanate dispersion and a process for preparing the self-emulsifying blocked polyisocyanate dispersion.

BACKGROUND OF THE INVENTION

Cathodic electrodeposition coating materials have been widely used in various fields due to excellent application performance thereof and excellent properties of the obtained coating films. Cathodic electrodeposition coating materials generally comprise a part of binder dispersion comprising a resin component (e.g., cationic amino-containing epoxy resin) and a curing agent component (e.g., blocked polyisocyanate) in an aqueous medium, and a part of pigment paste. The binder dispersion is generally prepared by mixing the resin component and the curing agent component, and then neutralizing and dispersing in an aqueous medium. The neutralized resin component and the curing agent will be present together in form of charged micelles in the binder dispersion. There is a fair chance for the two components to react with each other during storage of cathodic electrodeposition coating composition and the long-term circulation of electrodeposition coating bath.

During electrodeposition coating, the substrate to be coated is used as the cathode. A current is applied between the cathode and an anode as counter electrode such that the micelles containing the neutralized resin component and the curing component in the coating bath are deposited on the metal substrate to form a coating film. The substrate as coated is then subjected to heating in order to cure the coating film, commonly at a temperature of higher than 160°C.

In recent years, there is an emerging demand for cathodic electrodeposition coating materials that are able to perform curing at a lower temperature, particularly from original equipment manufacturer (OEM) in automotive fields, blocked polyisocyanateTo achieve that, curing agents active at a lower temperature are introduced to the cathodic electrodeposition coating compositions, which, however, leads to a worse storage stability and/or working stability during electrodeposition coating. Consequently, the obtained coating films tend to have poor appearance and properties.

Solutions to the problem have been proposed. For example, EP3415574B describes a process for producing an electrodeposition coating composition having a curability at low temperatures. The electrodeposition coating composition was prepared by mixing an aqueous dispersion of an amino group-containing epoxy resin (A), an aqueous dispersion of a blocked polyisocyanate compound (B), and a pigment dispersion paste (C), wherein an emulsifier is required to provide the aqueous dispersion of a blocked polyisocyanate compound (B). An emulsifier or surfactant needs to be synthesized and added into the component (B), which cause additional work to prepare an electrodeposition coating composition.

Therefore, it is still required to provide a self-emulsifying blocked polyisocyanate compound, as one critical component to prepare an electrodeposition coating composition which has a good storage stability and the obtained coating films show satisfying performance. .

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a blocked polyisocyanate curing agent that can endow binder dispersions containing it and a resin component and thus cathodic electrodeposition coating materials with improved stability.

A further object of the present invention is to provide a process for preparing a blocked polyisocyanate curing agent.

It has surprisingly been found that the objects were achieved by a self-emulsifying curing agent dispersion, which curing agent comprises blocked polyisocyanate having neutralized amine.

Accordingly, the present invention provides an aqueous dispersion of blocked polyisocyanate having neutralized amine, which is obtainable or obtained by a process comprising steps of

(a) reacting a polyurethane prepolymer having isocyanate groups as polyisocyanate with a blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen, to provide an amine-containing blocked polyisocyanate, and

(c) neutralizing the amine-containing blocked polyisocyanate with an acid and dispersing in water.

Further, the present invention provides a process for preparing an aqueous dispersion of blocked polyisocyanate having neutralized amine, which comprises steps of

(a) reacting a polyurethane prepolymer having isocyanate groups as polyisocyanate with a blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen, to provide an amine-containing blocked polyisocyanate, and

(c) neutralizing the amine-containing blocked polyisocyanate with an acid and dispersing in water.

It has been found by the inventors that the aqueous dispersion of blocked polyisocyanate having neutralized amine as described herein are particularly useful for preparing binder dispersions having excellent storage stability, even eliminating the need of using an emulsifier or dispersing agent in the dispersions.

DETAILED DESCRIPTION OF THE INVENTION The present invention now will be described in details hereinafter. It is to be understood that the present invention may be embodied in many different ways and shall not be construed as limited to the embodiments set forth herein. Unless mentioned otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

Herein, the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.

The terms “comprise”, “comprising”, etc. are used interchangeably with “contain”, “containing”, etc. and are to be interpreted in a non-limiting, open manner. That is, e.g., further components or elements may be present. The expressions “consists of” or “consists essentially of” or cognates may be embraced within “comprises” or cognates.

The term “self-emulsifying” as used herein within the context of the blocked polyisocyanate means that the blocked polyisocyanate can form a stable dispersion without the necessity of using added surfactants, such as emulsifier or dispersing agent.

The term “prepolymer” as used herein within the context means a monomer or system of monomers that have been reacted to an intermediate molecular mass state that is capable of further polymerization by reactive groups to a fully cured high molecular weight state.

The polyurethane prepolymer having isocyanate groups in step (a) may be those derived from polyisocyanate compounds and polyols.

Useful polyisocyanate compounds for deriving the polyurethane prepolymer having isocyanate groups may include aliphatic, cycloaliphatic and aromatic diisocyanates and polyisocyanates containing three or more isocyanate groups per molecule.

Examples of aliphatic diisocyanates may include, but are not limited to, 1,3-trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1 ,6- hexamethylene diisocyante, 1,2-propylene diisocyanate, ethylethylene diisocyanate, 1- methyltrimethylene diisocyanate, 2-methylpetane diisocyanate, 2,2,4-trimethylhexane diisocyanate, isomers and oligomers thereof.

Examples of cycloaliphatic diisocyanates may include, but are not limited to, isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, dicyclohexylmethane diisocyanate, isomers and oligomers thereof.

Examples of aromatic diisocyanates may include, but are not limited to, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1 ,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5- naphthylene diisocyanate, biphenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'- diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2,2-diphenylpropane-4,4'-diisocyanate, isomers or oligomers thereof.

Examples of triisocyanates may include, but are not limited to 1,3,5-triisocyanatobenzene,

2.4.6-triisocyanatotoluene, 1,8-diisocyanato-4-(isocyanatomethyl) octane, lysine triisocyanate, isomers or oligomers thereof.

The oligomers as mentioned above may for example be dimers, dimers, trimers, and higher oligomers such as tetramers, pentamers, hexamers, or a mixture thereof.

According to the present invention, particularly suitable polyisocyanate compounds for deriving the polyurethane prepolymer are those comprising one or more oligomers of 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1 ,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5- naphthylene diisocyanate, biphenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'- diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate and 2,2-diphenylpropane-4,4'-diisocyanate.

Preferably, the polyurethane prepolymer having isocyanate groups is derived from a polyisocyanate compound comprising one or more oligomers of 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate.

The polyisocyanate compound can be used alone or as a mixture of two or more species for deriving the polyurethane prepolymer having isocyanate groups.

The polyols for deriving the polyurethane prepolymer having isocyanate groups may be for example polyhydric alkanols, polyhydric phenols, (poly)ether polyols, (poly)ester polyols, and polycarbonate polyols.

Examples of polyhydric alkanols may include, but are not limited to glycols such as ethylene glycol, 1 ,2-propanediol, 1,3-propanediol, 1 ,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2- pentanediol, 1,4-pentanediol, 1,5-pentanediol, neopentyl glycol, 1 ,4-hexanediol, 1 ,5-hexanediol,

1.6-hexanediol, 2,5-hexanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1 ,8- octanediol, 1,9-nonanediol, 2,2-diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2,4- trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol, 2-n-hexadecane-1 ,2-ethylene glycol, 2-n- eicosane-1 ,2-ethylene glycol and 2-n-octacosane-1,2-ethylene glycol, hydrogenated bisphenol A; and trihydric or higher polyhydric alkanols such as glycerol, trimethylolethane, trimethylolpropane, 1 ,2,6-hexanetriol, pentaerythritol, sorbitol and mannitol.

Examples of polyhydric phenols may for example be polyphenols. Suitable polyphenols may include, but are not limited to bisphenol A, bisphenol F and polyalkoxylated derivatives thereof, for example polyethoxylated bisphenol A. Suitable polyphenols also include, but are not limited to 4,4’-dihydroxybenzophenone, 1,1-bis(4-hydroxyphenyl)ethane, 1 , 1-bis(4- hydroxyphenyl)isobutane, 2,2-bis(4-hydroxy-tert-butylphenyl)propane, bis(2- hydroxynaphthyl)methane, 1 ,5-dihydroxynaphthalene, and polyalkoxylated derivatives thereof.

Examples of (poly)ether polyols may include, but are not limited to, oligomeric ether polyols such as diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, diglycerol, triglycerol and dipentaerythritol, and polyether polyols such as polyethylene glycols, polypropylene glycols, polybutylene glycols, polytetrahydrofuran (PolyTHF), which polyether polyols preferably have an average molecular weight (Mn) of no higher than 1000, more preferably no higher than 800, most preferably no higher than 700.

Examples of (poly)ester diols may include, but are not limited to, (poly)condensate of polyhydric alcohols such as ethylene glycol, propylene glycol, neopentyl glycol, 1 ,4-butanediol, 1 ,4- butenediol, 1 ,6-hexanediol, furan dimethanol and cyclohexane dimethanol, with polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, adipic acid, isophthalic acid, terephthalic acid, phthalic anhydride, dimethyl terephthalate, dimer acids and derivatives thereof.

Examples of polycarbonate polyols may include, but are not limited to, the reaction product of C2-C20-polyols with diaryl- or dialkyl carbonates such as diphenyl carbonate and dimethyl carbonate, or phosgene. The C2-C20-polyols may be, for example, ethylene glycol, 1 ,2- propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,6-hexanediol, 1 ,8-octanediol, neopentyl glycol, 1 ,4-bishydroxymethylcyclohexane, 2-methyl-1 ,3-propanediol, 2,2,4-trimethylpentane-1 ,3-diol, bisphenol A, diethylene glycol, tetraethylene glycol, glycerol, trimethylolethane, trimethylolpropane, 1 ,2,6-hexanetriol, pentaerythritol, or any combinations thereof.

Examples of commercial polycarbonate polyols are the products from Bayer Material Science AG obtainable under the tradenames Desmophen® C 2100, Desmophen® C 2200, Desmophen® C XP 2613, Desmophen® C 3100 XP, Desmophen® C 3200 XP and Desmophen® C XP 2716.

The polyurethane prepolymer having isocyanate groups as described herein may be commercially available or may be prepared in situ before reacting with a blocking agent in step (a).

Suitable polyurethane prepolymer having isocyanate groups may have a content of isocyanate groups in a range of from 70% to 90% by molar, preferably from 70% to 80% by molar, based on the total amount of isocyanate groups and urethane groups contained in the polyurethane prepolymer.

In some embodiments, the polyurethane prepolymer having isocyanate groups as prepared in situ is used to react with the blocking agent in step (a). Particularly, the polyurethane prepolymer may be prepared by dosing a polyol as described above into a polyisocyanate compound. Any catalysts and organic solvents known for preparing polyurethane may be used without any particular restrictions. In this case, the partially blocked polyisocyanate is obtainable or obtained by a process comprising steps of (a-1) preparing a polyurethane prepolymer having isocyanate groups by reacting a polyisocyanate with a polyol, and (a-2) reacting the polyurethane prepolymer having isocyanate groups obtained from step (a-1) with at least one blocking agent selected from oximes, pyrazoles and active methylene compounds.

Accordingly, in preferable embodiments, the present invention provides an aqueous dispersion of blocked polyisocyanate having neutralized amine, which is obtainable or obtained by a process comprising steps of

(a-1) preparing a polyurethane prepolymer having isocyanate groups by reacting a polyisocyanate with a polyol,

(a-2) reacting the polyurethane prepolymer having isocyanate groups obtained from step (a-1) with at least one blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen, to provide an amine-containing blocked polyisocyanates, and

(c) neutralizing the amine-containing blocked polyisocyanates with an acid, and dispersing in water.

Preferably, the polyol is dosed into the polyisocyanate compound over a period of time in step (a-1). Any catalysts and organic solvents known for preparing polyurethane may be used in step (a-1), without any particular restrictions. The polyol and the polyisocyanate compound as used in step (a-1) are those as described herein above.

The polyurethane prepolymer having isocyanate groups as obtained from step (a-1) may have a content of isocyanate groups in a range of from 70% to 90% by molar, preferably from 70% to 80% by molar, based on the total amount of isocyanate groups and urethane groups contained in the polyurethane prepolymer.

The blocking agent in step (a) or (a-2) may be selected from oximes. Examples of useful oximes may include, but are not limited to formamide oxime, acetaldoxime, acetoxime, methylethyl ketoxime, methylisobutyl ketoxime, diethyl ketoxime, diacetyl monoxime, benzophenoxime, cyclopentanoneoxime, cyclohexanoneoxime, or any combinations thereof. Preferably, methylethyl ketoxime is used as the blocking agent.

The blocking agent in step (a) or (a-2) may be selected from pyrazoles. Examples of useful pyrazoles may include, but are not limited to pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-benzyl-3,5-dimethylpyrazole, methyl 5-methylpyrazole-3-carboxylate, 3-methyl-5-phenylpyrazole and 3,5-dimethylpyrazole-4- carboxanilide. The blocking agent in step (a) or (a-2) may be selected from active methylene compounds. Examples of useful active methylene compounds may include, but are not limited to dimethyl malonate, diethyl malonate, diisopropyl malonate, ethyl acetoacetate, isopropyl acetoacetate, methyl acetoacetate, isopropyl acetoacetate and acetylacetone.

The reaction between polyisocyanate and the blocking agent may be carried out conventionally, preferably by dosing the blocking agent into polyisocyanate over a period time. Heating may be applied to the reaction mixture, for example after completion of dosing the blocking agent, to promote the reaction between the polyisocyanate and the blocking agent.

Preferably, the partially blocked polyisocyanate as obtained from step (a) or (a-2) may have a content of remaining isocyanate groups in a range of from 10% to 25% by molar, preferably from 10% to 20% by molar, based on the total amount of isocyanate groups, blocked polyisocyanate groups and urethane groups contained in the partially blocked polyisocyanate.

The amine compound having active hydrogen as used in step (b) may be selected from C3-C20- amine compounds having active hydrogen, such as diethanolamine, methyldiethanolamine (MDEA), triethanolamine (TEA), dimethylethanolamine (DMEA), diethylethanolamine (DEEA), 3- dimethylaminopropane-1,2-diol (DMAPD), 3-diethylaminopropane-1,2-diol (DEAPD), 2- dimethylaminopropane-1 ,3-diol, 2-diethylaminopropane-1 ,3-diol, 2-(hydroxyethyl)-2- dimethylaminopropane-1,3-diol (DMTA), 2-(hydroxyethyl)-2-diethylaminopropane-1,3-diol (DETA), N,N-dimethyl-N-(2-hydroxypropyl)amine (DMPA), t-butoxyaminoethoxyethanol (TBAEE), 2- [[2-(dimethylamino)ethyl]methylamino]ethanol (DMAEA), N,N,N'- trimethylaminoethylethanolamine (TMAEEA), tetra(2-hydroxypropyl)ethylenediamine, N,N - bis(2-hydroxyethyl)ethylenediamine, tetramethylhexamethylenediamine (TMHMDA), 2-(2- aminoethylamine)ethanol, 3-(N,N-dimethylamino)propylamine (DMAPA), bis-(3- dimethylaminopropylamine) (BDMAPA), or any combinations thereof. Preferably, the amine compound having active hydrogen is selected from diethanolamine, methyldiethanolamine (MDEA), 2-[[2-(dimethylamino)ethyl]methylamino]ethanol (DMAEA), 3-(N,N- dimethylamino)propylamine (DMAPA), bis-(3-dimethylaminopropylamine) (BDMAPA), and any combinations thereof.

The reaction between the partially blocked polyisocyanate with the amine compound having active hydrogen may be carried out conventionally, preferably by dosing the partially blocked polyisocyanate into the amine compound having active hydrogen over a period time, and vice versa. Heating may be applied to the reaction mixture, for example after completion of dosing, to promote the reaction between the partially blocked polyisocyanate and the amine compound having active hydrogen.

The amine-containing blocked polyisocyanates as obtained in step (b) are substantially free of isocyanate groups, particularly comprises no detectable isocyanate groups. o

Any suitable organic solvents and optionally catalysts known for the reaction between the partially blocked polyisocyanate with the amine compound having active hydrogen may be used in step (b).

The reactions in step (a) (or steps (a-1) and (a-2)) and in step (b) may be carried out in same or different organic solvent or solvent mixture. Particularly, the reactions in step (a) (or steps (a-1) and (a-2)) and in step (b) are carried out in the same organic solvent or solvent mixture.

Suitable solvents may be, for example, acetone, butanone, methyl isobutyl ketone (MIBK), cyclohexanone, N-methyl-2-pyrrolidone (NMP), acetonitrile, dimethyl sulfoxide (DMSO), tetrahydrofurane (THF), 1 ,4-dioxane and Ci-C4-alkyl-Ci-C4-alkanoates, and any combinations thereof. The organic solvent or solvent mixture, if used in any step(s), may not be removed from the reaction mixture as obtained from the step(s), and thus will be comprised in the aqueous dispersion of blocked polyisocyanate having neutralized amine.

The amine-containing blocked polyisocyanate as obtained in step (b) may contain 30 to 200, preferably 50 to 180 millimoles (mmol) of amine, per 100g of the amine-containing blocked polyisocyanates, calculated on a basis of solid content.

The amine-containing blocked polyisocyanates may be neutralized with any inorganic or organic acids as a neutralizing agent in step (c). Suitable inorganic acids may be, for example, hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid and perchloric acid. Suitable organic acids may for example be mono- or poly-carboxylic acids which is optionally substituted with a hydroxy group. Particularly, the organic acids may be C1-C10- monocarboxylic acids, Ci-Cw-dicarboxylic acids, Ci-Cio-tricarboxylic acids, C1-C10- hydroxymonocarboxylic acids, Ci-Cio-hydroxydicarboxylic acids, Ci-Cio-hydroxytricarboxylic acids, and any combinations thereof. Examples of the organic acids may include, but are not limited to formic acid, acetic acid, propanoic acid, butanoic acid, lactic acid, glycolic acid, 3- hydroxy butanoic acid, 2-hydroxyisobutanoic acid, malic acid, oxalic acid, malonic acid, methyl malonic acid, succinic acid, methyl succinic acid, adipic acid, pimelic acid, suberic acid, glutaric acid, citric acid, tartaric acid, fumaric acid, benzoic acid, and any combinations thereof. Suitable organic acids may particularly be selected from formic acid, acetic acid, propanoic acid, lactic acid, glycolic acid, malic acid, oxalic acid, adipic acid, citric acid, succinic acid, fumaric acid, benzoic acid, and any combinations.

The neutralizing may be carried out in the presence of water, for example by introducing the acid as the neutralizing agent in form of an aqueous solution thereof.

The neutralizing may be carried out with the acid in an equivalent amount in a range of from 20% to 125%, preferably from 30% to 100%, and more preferably from 30% to 90%, based on the amount by molar of amino groups in the amine-containing blocked polyisocyanates.

The dispersing in water in step (c) may be carried out conventionally, for example by means of stirring. It will be understood that the dispersing may be carried out during the neutralizing or after the neutralizing. Preferably, a separate dispersing operation was carried out after the neutralizing.

According to the present invention, no emulsifier or surfactant is necessarily used for the dispersing.

In some embodiments, the dispersing in step (c) is carried out by mixing the neutralized mixture with water in the absence of any added emulsifier or dispersing agent.

It will be contemplated that an added emulsifier or dispersing agent will improve the stability of a dispersion, and thus the dispersing in step (c) may be carried out in the presence of an added emulsifier or dispersing agent, although the emulsifier or dispersing agent are not indispensable. In this case, the aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention will comprise an emulsifier or dispersing agent.

Any conventional emulsifier or dispersing agent for preparing aqueous dispersions of blocked polyisocyanates may be used, including nonionic, anionic, cationic or zwitterionic emulsifier or dispersing agents. Particularly, a nonionic emulsifier or dispersing agent may be mentioned.

Suitable nonionic emulsifier or dispersing agent may be selected from polyalkylene oxides such as polyethylene oxides and polypropylene oxides, ethoxylated or propoxylated fatty alcohols, ethoxylated or propoxylated alkylphenols, ethoxylated or propoxylated fatty acids, ethoxylated or propoxylated fatty esters, sorbitan derivatives, sucrose esters and derivatives, ethylene oxide-propylene oxide block copolymers, fluorinated alkyl polyoxyethylene ethanols, and any combinations thereof.

The aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention may further comprises additional components, for example organic solvent, colorant or pigment, viscosity modifier, leveling agent, anti-gel forming agent, light stabilizer, antioxidant, ultraviolet absorber, heat resistance improver, inorganic or organic filler, plasticizer, lubricant, softening agent, antistatic agent, reinforcing agent, and any combinations thereof.

The additional components, if comprised, may be introduced into the aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention after step (b), for example, before the neutralizing in step (c), between the neutralizing and the dispersing in step (c) or during the dispersing in step (c).

The aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention may have one or more of following properties, i) a pH value in a range of from 3.0 to 8.0, preferably from 3.5 to 8.0, and more preferably from 4.0 to 8.0, measured at 20 °C according to DIN 55659-1 ; ii) a conductivity in a range of from 2 to 10 mS/cm, preferably from 3 to 8 mS/cm, measured at 20°C according to DIN EN ISO 15091; iii) a Z-average particle size in a range of from 60 to 200 nm, preferably from 60 to 160 nm, measured according to DIN ISO 13321; iv) a polydispersity index (PDI) of less than 0.2, an indicator of particle size distribution, measured according to DIN ISO 13321; v) a solid content of from 10% to 40% by weight, preferably from 15% to 35% by weight, measured according to DIN EN ISO 3251, under 130 °C for 60 mins; vi) a molar equivalent of acid (MEQ-A) in a range of from 20 to 150 mmol/100g, preferably from 30 to 120 mmol/100g, measured according to DIN EN ISO 15880; and vii) a molar equivalent of base (MEQ-B) in a range of from 30 to 200 mmol/100g, preferably from 50 to 180 mmol/100g, measured according to DIN EN ISO 15880.

The aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention are particularly useful for preparing binder dispersions having excellent storage stability, even eliminating the need of using an emulsifier or dispersing agent in the dispersions. It is believed that the benefits of the aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention are related to the introduction of the neutralized amine into the blocked polyisocyanate curing agent and may also related to the particular design of blocking, introducing amine and neutralization.

Accordingly, the present invention further provides a process for preparing an aqueous dispersion of blocked polyisocyanates having neutralized amine, which comprises steps of

(a) reacting a polyurethane prepolymer having isocyanate groups with at least one blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen, to provide an amine-containing blocked polyisocyanates , and

(c) neutralizing the amine-containing blocked polyisocyanates with an acid, and dispersing in water.

In step (a), the polyurethane prepolymer containing isocyanate groups having a content of isocyanate groups in a range of from 70% to 90% by molar, preferably from 70% to 80% by molar, based on the total amount of isocyanate groups and urethane groups contained in the polyurethane prepolymer.

Preferably, the present invention further provides a process for preparing an aqueous dispersion of blocked polyisocyanates having neutralized amine, which comprises steps of (a-1) preparing a polyurethane prepolymer containing isocyanate groups from a polyisocyanate compound and a polyol,

(a-2) reacting the polyurethane prepolymer containing isocyanate groups from (a-1) with a blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen, to provide amine-containing blocked polyisocyanates amine, and (c) neutralizing the amine-containing blocked polyisocyanates with an acid and dispersing in water.

In step (a-1), the preparation may provide a polyurethane prepolymer having a content of isocyanate groups in a range of from 70% to 90% by molar, preferably from 70% to 80% by molar, based on the total amount of isocyanate groups and urethane groups contained in the polyurethane prepolymer.

In step (a) or (a-2), the blocking agent may be used in an amount such that the partially blocked polyisocyanate as obtained will have a content of remaining isocyanate groups in a range of from 10% to 25% by molar, preferably from 10% to 20% by molar, based on the total amount of isocyanate groups, blocked polyisocyanate groups and urethane groups contained in the partially blocked polyisocyanate.

In step (b), the amine compound may be used in an amount such that the amine-containing blocked polyisocyanates as obtained do not contain free isocyanate groups.

Any general description and preferences of reacting materials and conditions provided hereinabove within the context of preparation of the aqueous dispersion of blocked polyisocyanates having neutralized amine according to the present invention may be applied for the processes here.

Embodiments

Various embodiments are listed below. It will be understood that the embodiments listed below may be combined with all aspects and other embodiments in accordance with the scope of the invention.

Embodiment 1

An aqueous dispersion of blocked polyisocyanate having neutralized amine obtainable or obtained by a process comprising steps of

(a) reacting a polyurethane prepolymer having isocyanate groupspolyisocyanate with at least one blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen, to provide an amine-containing blocked polyisocyanate, and

(c) neutralizing the amine-containing blocked polyisocyanate with an acid and dispersing in water.

Embodiment 2

The aqueous dispersion of blocked polyisocyanate according to Embodiment 1, wherein said polyurethane prepolymer having isocyanate groups is obtainable or obtained from a reaction of polyisocyanate and polyol. Embodiment 3

The aqueous dispersion of blocked polyisocyanate according to Embodiment 2, wherein said polyisocyanate is at least one selected from aliphatic, cycloaliphatic and aromatic diisocyanates and polyisocyanates containing at least three isocyanate groups per molecule.

Embodiment 4

The aqueous dispersion of blocked polyisocyanate according to Embodiment 3, wherein said polyisocyanate is at least one selected from a group consisting of monomers, isomers and oligomers of 1 ,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1 ,4-xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, biphenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'- diphenyl ether diisocyanate and 2,2-diphenylpropane-4,4'-diisocyanate.

Embodiment 5

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 2 to 4, wherein said polyol is at least one selected from polyhydric alkanols, polyhydric phenols, (poly)ether polyols, (poly)ester polyols, and polycarbonate polyols.

Embodiment 6

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 5, wherein said partially blocked polyisocyanate is obtainable or obtained by a process comprising steps of

(a-1) preparing a polyurethane prepolymer having isocyanate groups by reacting a polyisocyanate with a polyol, and

(a-2) reacting the polyurethane prepolymer having isocyanate groups obtained from step (a-1) with at least one blocking agent selected from oximes, pyrazoles and active methylene compounds.

Embodiment 7

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 6, wherein said blocking agent is at least one selected from a group consisting of formamide oxime, acetaldoxime, acetoxime, methylethyl ketoxime, methylisobutyl ketoxime, diethyl ketoxime, diacetyl monoxime, benzophenoxime, cyclopentanoneoxime and cyclohexanoneoxime.

Embodiment 8

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 7, wherein said amine compound having active hydrogen is at least one selected from C3-C20- amine compounds having active hydrogen, and preferably at least one selected from a group consisting of diethanolamine, methyldiethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, 3-dimethylaminopropane-1,2-diol, 3-diethylaminopropane-1,2-diol, 2- dimethylaminopropane-1 ,3-diol, 2-diethylaminopropane-1 ,3-diol, 2-(hydroxyethyl)-2- dimethylaminopropane-1,3-diol, 2-(hydroxyethyl)-2-diethylaminopropane-1,3-diol, N,N-dimethyl- N-(2-hydroxypropyl)amine, t-butoxyaminoethoxyethanol, 2-[[2- (dimethylamino)ethyl]methylamino]ethanol, N,N,N'-trimethylaminoethylethanolamine, tetra(2- hydroxypropyl)ethylenediamine, N,N'-bis(2-hydroxyethyl)ethylenediamine, tetramethylhexamethylenediamine, 2-(2-aminoethylamine)ethanol, 3-(N,N- dimethylamino)propylamine and bis-(3-dimethylaminopropylamine).

Embodiment 9

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 8, wherein said polyurethane prepolymer having isocyanate groups has a content of isocyanate groups in a range of from 70% to 90% by molar and preferably from 70% to 80% by molar, based on the total amount of isocyanate groups and urethane groups in said polyurethane prepolymer.

Embodiment 10

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 9, wherein said partially blocked polyisocyanatehas a content of remaining isocyanate groups in a range of from 10% to 25% by molar and preferably from 10% to 20% by molar, based on the total amount of remaining isocyanate groups, blocked polyisocyanate groups and urethane groups in said partially blocked polyisocyanate.

Embodiment 11

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 10, wherein said acid in step (c) is selected from inorganic acids and preferably at least one selected from a group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid and perchloric acid.

Embodiment 12

The aqueous dispersion of blocked polyisocyanate according to any one of claims 1 to 10, wherein said acid in step (c) is selected from organic acids, preferably mono- or poly-carboxylic acids optionally substituted by hydroxyl groups and more preferably at least one selected from a group consisting of Ci-Cio-monocarboxylic acids, Ci-Cio-dicarboxylic acids, C1-C10- tricarboxylic acids, Ci-Cw-hydroxymonocarboxylic acids, Ci-Cio-hydroxydicarboxylic acids and Ci-Cio-hydroxytricarboxylic acids.

Embodiment 13

The aqueous dispersion of blocked polyisocyanate according to any one of Embodiments 1 to 12, wherein it has at least one property of i) a pH value in a range of from 3.0 to 8.0, preferably from 3.5 to 8.0 and more preferably from 4.0 to 8.0, measured at 20°C according to DIN 55659-1; ii) a conductivity in a range of from 2 to 10 mS/cm, preferably from 3 to 8 mS/cm, measured at 20°C according to DIN EN ISO 15091; iii) a Z-average particle size in a range of from 60 to 200 nm, preferably from 60 to 160 nm, measured according to DIN ISO 13321; iv) a polydispersity index of less than 0.2, measured according to DIN ISO 13321; v) a solid content of from 10% to 40% by weight, preferably from 15% to 35% by weight, measured under 130 °C for 60 mins according to DIN EN ISO 3251 ; vi) a molar equivalent of acid in a range of from 20 to 150 mmol/100g, preferably from 30 to 120 mmol/100g, measured according to DIN EN ISO 15880; and vii) a molar equivalent of base in a range of from 30 to 200 mmol/100g, preferably from 50 to 180 mmol/100g, measured according to DIN EN ISO 15880.

Embodiment 14

A process for preparing an aqueous dispersion of blocked polyisocyanate havingneutralized amine comprising steps of

(a) reacting a polyurethane prepolymer having isocyanate groups polyisocyanatewith at least one blocking agent selected from oximes, pyrazoles and active methylene compounds, to provide a partially blocked polyisocyanate,

(b) reacting remaining isocyanate groups in the partially blocked polyisocyanate with an amine compound having active hydrogen to provide an amine-containing blocked polyisocyanate containing amine building units, and

(c) neutralizing the amine-containing blocked polyisocyanate containing amine with an acid and dispersing in water.

Embodiment 15

The process according to Embodiment 14, wherein said polyurethane prepolymer having isocyanate groups is obtainable or obtained by a reaction of polyisocyanate and polyol.

Embodiment 16

The process according to Embodiment 15, wherein said polyisocyanate is at least one selected from aliphatic, cycloaliphatic and aromatic diisocyanates and polyisocyanates having at least three or more isocyanate groups per molecule.

Embodiment 17

The process according to Embodiment 16, wherein said polyisocyanate is at least one selected from a group consisting of monomers, isomers and oligomers of 1 ,3-phenylene diisocyanate, 1 ,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1 ,3-xylylene diisocyanate, 1 ,4-xylylene diisocyanate, 1 ,4-naphthylene diisocyanate, 1 ,5-naphthylene diisocyanate, biphenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate and 2,2- diphenylpropane-4,4'-diisocyanate.

Embodiment 18

The process according to any one of Embodiments 15 to 17, wherein said polyol is at least one selected from polyhydric alkanols, polyhydric phenols, (poly)ether polyols, (poly)ester polyols, and polycarbonate polyols.

Embodiment 19

The process according to any one of Embodiments 14 to 18, wherein said partially blocked polyisocyanate is obtainable or obtained by a process comprising steps of(a-1) preparing a polyurethane prepolymer having isocyanate groups by reacting a polyisocyanate with a polyol, and

(a-2) reacting the polyurethane prepolymer having isocyanate groups obtained from step (a-1) with at least one blocking agent selected from oximes, pyrazoles and active methylene compounds.

Embodiment 20

The process according to any one of Embodiments 14 to 19, wherein said blocking agent is at least one selected from a group consisting of formamide oxime, acetaldoxime, acetoxime, methylethyl ketoxime, methylisobutyl ketoxime, diethyl ketoxime, diacetyl monoxime, benzophenoxime, cyclopentanoneoxime and cyclohexanoneoxime.

Embodiment 21

The process according to any one of Embodiments 14 to 20, wherein said amine compound having active hydrogen is at least one selected from C3-C2o-amine compounds having active hydrogen, and preferably at least one selected from a group consisting of diethanolamine, methyldiethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, 3- dimethylaminopropane-1 ,2-diol, 3-diethylaminopropane-1 ,2-diol, 2-dimethylaminopropane-1 ,3- diol, 2-diethylaminopropane-1,3-diol, 2-(hydroxyethyl)-2-dimethylaminopropane-1 ,3-diol, 2- (hydroxyethyl)-2-diethylaminopropane-1,3-diol, N,N-dimethyl-N-(2-hydroxypropyl)amine, t- butoxyaminoethoxyethanol, 2-[[2-(dimethylamino)ethyl]methylamino]ethanol, N,N,N'- trimethylaminoethylethanolamine, tetra(2-hydroxypropyl)ethylenediamine, N,N'-bis(2- hydroxyethyl)ethylenediamine, tetramethylhexamethylenediamine, 2-(2- aminoethylamine)ethanol, 3-(N,N-dimethylamino)propylamine and bis-(3- dimethylaminopropylamine).

Embodiment 22

The process according to any one of Embodiments 14 to 21, wherein said polyurethane prepolymer having isocyanate groups has a content of isocyanate groups in a range of from 70% to 90% by molar and preferably from 70% to 80% by molar, based on the total amount of isocyanate groups and urethane groups in said polyurethane prepolymer.

Embodiment 23

The process according to any one of Embodiments 14 to 22, wherein said partially blocked polyisocyanatehas a content of remaining isocyanate groups in a range of from 10% to 25% by molar and preferably from 10% to 20% by molar, based on the total amount of remaining isocyanate groups, blocked polyisocyanate groups and urethane groups in said partially blocked polyisocyanate.

Embodiment 24

The process according to any one of Embodiments 14 to 23, wherein sad acid in step (c) has an equivalent amount in a range of from 20% to 125%, preferably from 30 % to 100% and more preferably from 30% to 90%, based on the total amount by molar of amino groups in the amine- containing blocked polyisocyanate. Embodiment 25

The process according to any one of Embodiments 14 to 24, wherein said acid in step (c) is selected from inorganic acids and preferably at least one selected from a group consisting of hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, boric acid and perchloric acid.

Embodiment 26

The process according to any one of claims 14 to 24, where said acid in step (c) is selected from organic acids, preferably mono- or poly-carboxylic acids optionally substituted by hydroxyl groups and more preferably at least one selected from a group consisting of C1-C10- monocarboxylic acids, Ci-Cw-dicarboxylic acids, Ci-Cio-tricarboxylic acids, C1-C10- hydroxymonocarboxylic acids, Ci-Cio-hydroxydicarboxylic acids and Ci-Cio-hydroxytricarboxylic acids.

Examples

The invention will be further illustrated by following Examples, which set forth particularly advantageous embodiments. While the Examples are provided to illustrate the present invention, they are not intended to limit it.

Description of Materials and Measurements in Examples

Materials:

Lupranate® M20S: Solvent-free polymeric product based on 4,4'-diphenylmethane diisocyanate (MDI) containing oligomers and isomers, having an average functionality of about 2.7, and NCO content 31.5g/100g according to ASTM D 5155, available from BASF;

Desmophen® C3100 XP: Linear aliphatic polycarbonate diol with a molecular weight of approx. 1,000 g/mol, available from Covestro;

BE-188EL: liquid Bisphenol A epoxy resin having an epoxy equivalent of approx. 188 g/mol, available from Chang Chun Group;

PPG 600: Pluriol® P 600 available from BASF;

PPG 900: Pluriol® P 900 available from BASF;

PPG 1000: Polypropylene Glycol available from Aladdin Chemicals;

PolyTHF® 650: Poly(tetramethylene ether) glycol, available from BASF;

Bisphenol A 6EO: Bisphenol A ethoxylate with 3 EO/phenol, available from Sigma-AIrdrich;

MIBK: Methyl isobutyl ketone, a solvent;

MEKO: Methyl ethyl ketoxime, a blocking agent;

MDEA: N-methyl diethanolamine;

DMAPA: N,N-dimethylaminopropylamine;

BDMAPA: Bis(N,N-dimethylaminopropylamine);

DMAEA: 2-[[2-(Dimethylamino)ethyl]methylamino]ethanol.

Measurements: The methods and devices as described in following Table were used for the measurements in Examples.

I. Preparation of self-emulsifying blocked polyisocyanate dispersion

Example 1

A reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet, was charged with 150.9 parts by weight of MEKO, 19.7 parts by weight of 1,2-propanediol, 408 parts by weight of methyl isobutyl ketone (MIBK), and 0.18 parts by weight of dibutyltin dilaurate (DBTL). This initial charge was heated to 30°C. Thereafter, over a period of 60 mins, 400 parts by weight of Lupranate®M20Swas being dosed into the reactor in a uniform rate with constant stirring. After finishing dosing, the reaction temperature was cooled down to 60°C and stirred for another 60 mins. Then, after cooling to 30°C, 41.3 parts by weight of MDEA was dosed into the reactor with a dosing rate such that the temperature was not higher than 80°C. 30 mins after finishing dosing, the reaction mixture was raised up to a temperature of 80°C and stirred for another 60 mins, obtaining an organic system comprising MEKO-blocked polyisocyanates containing amine building units. A mixture of 510 parts by weight of water and 23.1 parts by weight of formic acid (86%) was then added into the organic system with an intensive string to obtain an aqueous dispersion of blocked polyisocyanates containing neutralized amine building units. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 2

500 parts by weight of Lupranate® M20S, 121.4 parts by weight of MIBK and 0.23 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. This initial charge was heated to 30°C. Then, 31.2 parts by weight of 1,2- propanediol was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 303.6 parts by weight of MIBK was then added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 190.8 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 67.1 parts by weight of DMAPA was initially charged into the second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up to 60°C and stirred for another 15 mins. The obtained organic system was transferred into a plastic container. A mixture of 36.9 parts by weight of water and 19.9 g formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1700 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 3

450 parts by weight of Lupranate® M20S, 131.6 parts by weight of MIBK, and 0.20 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. The initial charge was heated to 30°C. Then, 309.0 parts by weight of Bisphenol A 6EO was being dosed into the reactor in a uniform rate over 60 min with continuous stirring. 328.9 parts by weight of MIBK was subsequently added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 171.0 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 60.2 parts by weight of DMAPA was initially charged into this second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up 60°C again and stirred for another 15 mins. The obtained organic system was transferred into a plastic container. A mixture of 35.8 parts by weight of water and 18.9 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 2050 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 4

400 parts by weight of Lupranate® M20S, 132.7 parts by weight of MIBK, and 0.18 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. The initial charge was heated to 30°C. Then, 190.4 parts by weight of polypropylene glycol 600 (PPG 600) was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 398.0 parts by weight of MIBK was then added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 152.0 parts by weight of MEKO was slowly dosed into the reactor over 30 min. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 53.5 parts by weight of DMAPA was initially charged into this second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up 60°C again and stirred for another 15 mins. The obtained organic system was transferred into a plastic container. A mixture of 40.8 parts by weight of water and 21.8 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1784 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 5

450 parts by weight of Lupranate® M20S, 130.6 parts by weight of MIBK, and 0.20 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. The initial charge was heated to 30°C. Then, 235.9 parts by weight of polyTHF® 650 was quickly added into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. 261.2 parts by weight of MIBK was subsequently added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 168.6 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C again and continued for another 30 mins. Then the content in the reactor was cooled to 30°C, followed by quickly charging 59.3 parts by weight of DMAPA into the reactor. 20 mins after finishing charging, the reaction mixture was raised up to 60°C again and stirred for another 30 mins. The obtained organic system was afterwards transferred into a plastic container. A mixture of 43.6 parts by weight of water and 23.5 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 2290 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 6

350 parts by weight of Lupranate® M20S, 121.0 parts by weight of MIBK, and 0.16 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. The initial charge was heated to 30°C. Then, 176.0 parts by weight of polycarbonate diol (Desmophen® C3100XP) was quickly added into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. 362.9 parts by weight of MIBK was subsequently added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 147.6 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C again and continued for another 30 mins. Then, the content in the reactor was cooled to 30°C, followed by quickly charging 51.9 parts by weight of DMAPA into the reactor. 20 mins after finishing charging, the reaction mixture was raised up 60°C again and stirred for another 30 mins. The obtained organic system was afterwards transferred into a plastic container. A mixture of 30.5 parts by weight of water and 16.3 g formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1647 g water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

7 400 parts by weight of Lupranate® M20S, 105.3 parts by weight of MIBK, and 0.18 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. This initial charge was heated to 30°C. Then, 22.2 parts by weight of 1,2- propanediol was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 263.3 parts by weight of MIBK was then added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 152.7 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 109.5 parts by weight of BDMAPA was initially charged into the second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up to 60°C again and stirred for another 15 mins. The obtained organic system was transferred into a plastic container. A mixture of 70.1 parts by weight of water and 37.5 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1617 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 8

450 parts by weight of Lupranate® M20S, 114.3 parts by weight of MIBK, and 0.20 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. This initial charge was heated to 30°C. Afterwards, 25.0 parts by weight of 1,2-propanediol was being dosed into the reactor at a constant rate within 60 mins with continuous stirring. 285.8 parts by weight of MIBK was subsequently added into the reactor, and the content in the reactor was cooled to 30°C. At 30 °C, 171.8 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was heated up to 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 96.1 parts by weight of DMAEA was initially charged into the second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor at a constant rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up to 60°C again and stirred for another 15 mins. The obtained organic system was transferred into a plastic container. A mixture of 39.9 parts by weight of water and 21.9 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1787 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

575 parts by weight of Lupranate® M20S, 150.4 parts by weight of MIBK, and 0.26 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. This initial mixture was heated to 30°C. Then, 35.37 parts by weight of 1,2-propanediol was quickly charged into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. Next, 451.3 parts by weight of MIBK was added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 216 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 76 parts by weight of DMAPA was initially charged into the second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up to 60°C again and stirred for another 15 mins. The obtained organic system was added with 41.7 parts by weight of PPG 600 under intensive mixing, and then transferred into a plastic container. A mixture of 41.8 parts by weight of water and 22.5 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 2033.4 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 10

400 parts by weight of Lupranate®M20S, 104.9 parts by weight of MIBK, and 0.18 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. This initial mixture was heated to 30°C. Then, 24.3 parts by weight of 1,2- propanediol was quickly charged into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. Subsequently, 318.8 parts by weight of MIBK was charged into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 148.3 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 52.2 parts by weight of DMAPA was initially charged into the second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up to 60°C again and stirred for another 15 mins. The obtained organic system was added with 6.3 parts by weight of PPG 1000 under intensive mixing, and then transferred into a plastic container. A mixture of 30.4 parts by weight of water and 16.4 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1405 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

Example 11

400 parts by weight of Lupranate®M20S, 104.9 parts by weight of MIBK, and 0.18 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. This initial mixture was heated to 30°C. Then, 24.3 parts by weight of 1,2- propanediol was quickly charged into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. Subsequently, 318.8 parts by weight of MIBK was charged into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 148.3 parts by weight of MEKO was slowly dosed into the reactor over 20 mins. After finishing dosing MEKO, the reaction was raised up to a temperature of 60°C and continued for another 30 mins. The obtained intermediate was immediately transferred to a dropping funnel, and then installed into a second clean reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. 52.2 parts by weight of DMAPA was initially charged into the second reactor, and heated to 30°C. Thereafter, the intermediate in the dropping funnel was being dosed into the reactor in a uniform rate over 60 mins with continuous stirring. 30 mins after finishing dosing, the reaction mixture was raised up to 60°C again and stirred for another 15 mins. The obtained organic system was added with 31.3 parts by weight of Bisphenol A 6EO under intensive mixing, and then transferred into a plastic container. A mixture of 30.4 parts by weight of water and 16.4 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1405 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

450.0 parts by weight of Lupranate® M20S, 117.9 parts by weight of MIBK, and 0.20 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. The initial charge was heated to 30°C. Then, 27.5 parts by weight of 1,2- propanediol was quickly added into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. 353.6 parts by weight of MIBK was subsequently added into the reactor, and the content in the reactor was cooled to 30°C. At 30°C, 170.3 parts by weight of ethyl propyl amine was slowly dosed into the reactor over 20 mins. After finishing dosing, the reaction was raised up to a temperature of 60°C again and continued for another 30 mins. Then, the content in the reactor was cooled to 30°C, followed by quickly charging 59.2 parts by weight of DMAPA into the reactor. 20 mins after finishing charging, the reaction mixture was raised up 60°C again and stirred for another 30 mins. The obtained organic system was afterwards transferred into a plastic container. A mixture of 182 parts by weight of water and 18.6 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1450 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

The dispersion is very unstable due to high particle size. An obvious phase separation was observed within 2 hours after dispersing.

450.0 parts by weight of Lupranate® M20S, 132.6 parts by weight of MIBK, and 0.20 parts by weight of DBTL were charged into a reactor equipped with a condenser, a nitrogen gas inlet and a nitrogen gas outlet. The initial charge was heated to 30°C. Then, 27.7 parts by weight of 1,2- propanediol was quickly added into the reactor. The reaction continued for 60 mins with continuous stirring at 60°C. 397.7 parts by weight of MIBK was subsequently added into the reactor, and the content in the reactor was cooled to 30°C. At 30 °C, 258.2 parts by weight of bis(2-methoxyethyl)amine was slowly dosed into the reactor over 20 mins. After finishing dosing, the reaction was raised up to a temperature of 60°C again and continued for another 30 mins. Then, the content in the reactor was cooled to 30°C, followed by quickly charging 59.4 parts by weight of DMAPA into the reactor. 20 mins after finishing charging, the reaction mixture was raised up 60°C again and stirred for another 30 mins. The obtained organic system was afterwards transferred into a plastic container. A mixture of 247 parts by weight of water and 19.2 parts by weight of formic acid (86%) was then slowly added into that organic system to create water in oil phase. Then, additional 1592.3 parts by weight of water was charged for phase inversion to oil in water phase. The characteristics of the resulting aqueous dispersion are shown in Table 1 below.

The process for dispersion is difficult to be conducted. Further, the dispersion is very unstable due to high particle size. An obvious phase separation was observed within 2 hours after dispersing.

Stable aqueous self-emulsifying blocked polyisocyanate dispersions were not prepared successfully with ethyl propyl amine or bis(2-methoxyethyl)amine as a blocking agent.

able 1

II. Preparation of an aqueous dispersion of cationic amino-containing epoxy resin

Example 12

An amino-containing epoxy resin was prepared with reference to US 6274649B1 , column 9, lines 15 to 35. 1128 parts by weight of a liquid Bisphenol A epoxy resin (BE-188EL), 262 parts by weight of dodecylphenol, 31.4 parts by weight of xylene and 228 parts by weight of bisphenol A were charged into a reactor fitted with stirrer, reflux condenser, thermometer and inert-gas inlet. The reactor was heated to 127°C, to which 1.6 g of triphenylphosphine are added with stirring under nitrogen to start an exothermic reaction, and the temperature rose to 160°C. The mixture was cooled again to 130°C and the epoxide content was then checked. Once the epoxide content indicated that >98% of the phenolic OH groups have reacted, 297.5 parts by weight of PPG 900 was then added with simultaneous cooling. After 5 min, 131.25 parts by weight of diethanolamine (DEOLA) was added at 120°C with further cooling. When the temperature has dropped to 110°C, 63.75 parts by weight of N,N-dimethylaminopropylamine (DMAPA) was added. After brief exothermicity (T _m ax of 140°C), the mixture was allowed to react further at 130°C for 2 hours until the viscosity remains constant, to obtain an organic system comprising the amino-containing epoxy resin.

Thereafter, the organic system comprising the amino-containing epoxy resin was immediately transferred into a plastic container containing a mixture of 3840 parts by weight of water and 48.8 parts by weight of formic acid (86%) with stirring, to obtain an aqueous dispersion of cationic amino-containing epoxy resin. The characteristics of the resulting dispersion are shown in Table 2 below.

Table 2

III. Preparation of 1 K binder dispersions comprising a resin component and a curing agent component

Example 13

1345.5 parts by weight of the blocked polyisocyanate dispersion from Example 1 as the curing agent component and 2300 parts by weight of the resin dispersion from Example 12 were mixed together with moderate stirring to get a homogeneous mixture. The resulting 1 K binder dispersion was characterized and evaluated for storage stability. The results are shown in Table 3 below.

The storage stability of the binder dispersion was evaluated by visually observing the appearance of the dispersion in a transparent container after standing for a period of time at a certain temperature. The dispersion is evaluated as “unstable”, if a phase separation (serious) or a sedimentation (mild) occurs,

Serious: obvious phase separation in the container;

Mild: slight sedimentation of particles, which can be observed by flipping the container upside down.

Table 3

Example 14

The preparation as described in Example 13 was repeated except that 650.8 parts by weight of the blocked polyisocyanate dispersion from Example 2 and 1450 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 4 below.

Table 4

Example 15 The preparation as described in Example 13 was repeated except that 900 parts by weight of the blocked polyisocyanate dispersion from Example 3 and 1800 parts by weight of the resin dispersion from 12 were used. The characterization and stability evaluation results are shown in Table 5 below.

Table 5

Example 16

The preparation as described in Example 13 was repeated except that 773.8 parts by weight of the blocked polyisocyanate dispersion from Example 4 and 1526.2 parts by weight of the resin dispersion from 12 were used. The characterization and stability evaluation results are shown in Table 6 below.

Table 6

Example 17 The preparation as described in Example 13 was repeated except that 1086 parts by weight of the blocked polyisocyanate dispersion from Example 5 and 1800 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 7 below.

Table 7

Example 18

The preparation as described in Example 13 was repeated except that 998 parts by weight of the blocked polyisocyanate dispersion from Example 6 and 1422 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 8 below.

Table 8

Example 19

The preparation as described in Example 13 was repeated except that 989.5 parts by weight of the blocked polyisocyanate dispersion from Example 7 and 1749.6 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 9 below.

Table 9

Example 20

The preparation as described in Example 13 was repeated except that 965.9 parts by weight of the blocked polyisocyanate dispersion from Example 8 and 1703 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 10 below.

Table 10 Example 21

The preparation as described in Example 13 was repeated except that 774 parts by weight of the blocked polyisocyanate dispersion from Example 9 and 1800 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 11 below.

Table 11

Example 22

The preparation as described in Example 13 was repeated except that 1296.6 parts by weight of the blocked polyisocyanate dispersion from Example 10 and 2010 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 12 below.

Table 12

Example 23

The preparation as described in Example 13 was repeated except that 807 parts by weight of the blocked polyisocyanate dispersion from Example 11 and 1500 parts by weight of the resin dispersion from Example 12 were used. The characterization and stability evaluation results are shown in Table 13 below. Table 13

It can be seen, the binder dispersions from Examples 14 to 23 comprising a curing agent component from Examples 2 to 11 respectively show significantly higher storage stability than that of the binder dispersion from Example 13 comprising a curing agent component from Example 1. Without being bound by any theory or mechanism, it is believed that the good stability is related to starting the synthesis with a polyurethane prepolymer containing isocyanate groups. It is also believed that the particular sequence of conducting blocking before introducing amine can provide blocked polyisocyanate curing agents with desirable application properties.