WO2011127641A1

WO2011127641A1 - Phosphate group-containing resin and use thereof

Info

Publication number: WO2011127641A1
Application number: PCT/CN2010/071693
Authority: WO
Inventors: Chih-Hung Tsai
Original assignee: Deuchem (Shanghai) Chemical Co., Ltd.
Priority date: 2010-04-12
Filing date: 2010-04-12
Publication date: 2011-10-20

Abstract

Disclosed are a cross-linkable phosphate group-containing resin, which comprises as polymerized units: a polymerizable unsaturated polyester having at least one phosphate group and/or having at least one phosphoric acid group, a (meth)acrylate-based polymerizable monomer, an alkoxylated (meth)acrylic acid polymerizable monomer, and carbonyl-containing (meth)acrylic polymerizable monomer; use of the phosphate-group containing resin as a treating agent for a metallic pigment or an inorganic pigment, especially in a water-based coating composition; and a water-based coating composition comprising water as a medium, the phosphate group-containing resin, a metallic pigment or an inorganic pigment, and a binder.

Description

PHOSPHATE GROUP-CONTAINING RESIN AND USE THEREOF TECHNICAL FIELD

The present application relates to resin and use thereof. The present application also relates to a composition comprising such resin.

BACKGROUND ART

It is well known to use metallic pigments, such as aluminum flakes, or inorganic pigments in coating compositions to provide metallic glamour or a desired color, chiefly on exterior panels of automobiles, motorcycles, etc. The use of these pigments in solvent based coating compositions results in relatively few problems. In recent years, use of water based coating compositions is strongly required from the viewpoint of prevention of environmental pollution.

However, when being utilized in water based coating compositions, the pigments, particularly aluminum flakes, react with water and any acid components present in such coating compositions. Then, the pigments deteriorate and can cause the generation of hydrogen gas. Furthermore, the finish appearances resulting from such coating compositions have a reduced brightness and glamour.

In order to avoid such problem, phosphated random polymers have been added to water based coating compositions to protect the surface of the pigments based on the mechanism that the phosphated portion of the polymers provides passivation of the pigments so as to inhibit the reaction caused by direct contact of water with the pigments. l In this regard, Du Pont has disclosed a series of phosphated polymers which are added to pigment-containing coating compositions to protect the surface of pigments. Concerning the phosphated polymers disclosed by Du Pont Company, a phosphate group is provided by the reaction of glycidyl (meth)acrylate polyacrylate with phosphoric acid ester. For example, US Patent No. 5,104,922, issued on April 14, 1992, has disclosed a water based metallic coating material comprising a phosphated linear polymer. US Patent No. 5,530,070, issued June 25, 1996, has disclosed a water based metallic coating material comprising a phosphated graft copolymer having macromonomer side chains.

Kansai Paint Company has further disclosed a series of phosphated polymers which are added to pigment-containing coating compositions to protect the surface of pigments. For the phospated polymers disclosed by Kansai Paint Company, phosphate group is provided by phosphated acrylic monomer, instead of by the reaction of glycidyl (meth)acrylate polyacrylate with phosphoric acid ester. For example, US Patent No. 6,099,968, issued on August 8, 2000, has disclosed a water based metallic coating material comprising a phosphated polymer obtained by copolymerizing: styrene, alkyl (meth)acrylate, phosphoric ester group-containing polymerizable unsaturated monomer, carboxyl-containing polymerizable unsaturated monomer, and hydroxy 1-containing polymerizable unsaturated monomer. US Patent No. 6,617,409, issued on September 9, 2003, has disclosed a water based metallic coating material comprising a phosphated polymer obtained by copolymerizing: a polymerizable monomer having a phosphate group, a polymerizable monomer having a phosphoric acid group, and a (meth)acrylate based polymerizable monomer having two tertiary alkyl groups in a molecule.

However, there is still a need for coating compositions having further improved performances.

SUMMARY

In one aspect, the present application provides a cross-linkable phosphate group-containing resin comprising, as polymerized units: (a) a polymerizable unsaturated polyester having at least one phosphate group and/or having at least one phosphoric acid group, (b) a (meth)acrylate based polymerizable monomer, (c) an alkoxylated (meth)acrylic acid polymerizable monomer, and (d) a carbonyl-containing (meth)acrylic polymerizable monomer. In one embodiment, the (meth)acrylate based polymerizable monomer may contain 0.01-40% wt.% styrene.

In another aspect, the present application provides use of the phosphate-group containing resin as a treating agent for a metallic pigment or an inorganic pigment, especially used in a water-based coating composition.

The cross-linkable phosphate group-containing resin according to the present application allows pigments to have an improved dispersivity in water based coating compositions, thereby improving metallic brightness of coating film, and in addition offers an improved protection to pigments against the reaction with water over a long period of time, thereby improving the stability of coating compositions formulated with pigments. More importantly, it is unexpected to find that the novel phosphate group-containing resin provided by the present application, as a pigment treating agent, makes the resulting coating compositions containing the pigment get significantly improved in cohesion after cured.

In yet another aspect, the application provides a water-based coating composition comprising water as a medium, the phosphate group-containing resin of the present application, a metallic pigment or an inorganic pigment, and a binder. In an embodiment, the water-based coating composition further comprises conventional additives such as a water-dispersible resin, color pigment, color space effect pigments, extender pigment, organic solvent, viscosity modifier, UV screener, defoaming agent and surface modifier.

DETAILED DESCRIPTION

The present application provides a cross linkable phosphate group-containing resin comprising, as polymerized units:

(a) a polymerizable unsaturated polyester having at least one phosphate group represented by a formula [-OPOiOR^OH)], wherein R¹ represents a hydrocarbon group having 1 to 10 carbon atoms and/or having at least one phosphoric acid group represented by a formula [-OPO(OH)₂],

(b) a (meth)acrylate based polymerizable monomer which may contain 0.01-40 wt% styrene,

(c) an alkoxylated (meth)acrylic acid polymerizable monomer, and

(d) a carbonyl-containing (meth)acrylic polymerizable monomer.

In an embodiment, the polymerizable unsaturated polyester (a) is a polyester having at least one phosphate group represented by a formula [-OPOCOF^XOH)] and/or having at least one phosphoric acid group represented by a formula [-OPO(OH)₂] and at least one polymerizable double bond in a molecule, wherein R¹ represents a hydrocarbon group having 1 to 10 carbon atoms, and to be specific, it includes, for example, linear or branched chain Ο_1-10 alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, octyl, 2-ethylhexyl, decyl and isodecyl. Preferably, R¹ represents a hydrocarbon group having 1 to 4 carbon atoms, and to be specific, it includes, for example, linear or branched chain C_1- alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl and tert-butyl.

In another embodiment, the phosphate group contained in the polymerizable unsaturated polyester (a) can be obtained by reacting, for example, one acidic hydroxyl group contained in a phosphoric acid monoester represented by (HO)₂PO(OR¹), for example, phosphate such as monobutyl phosphate and monoisodecyl phosphate with a glycidyl group-containing polyester having at least one polymerizable double bond.

In other embodiments, the polyester group contained in the polymerizable unsaturated polyester (a) can be obtained by copolymerizing an acid and a hydroxyl-containing compound, wherein the acid is, for example, selected from the group consisting of 2-ethyl hexyl acid, benzoic acid, adipic acid, tetrahydrogen phthalic anhydride, isophthalic acid, terephthalic acid, maleic anhydride, cyclohexane dicarboxylic acid, trimellitic anhydride and mixtures thereof, and the hydroxyl-containing compound is, for example, selected from the group consisting of octanol, ethylene glycol, propanediol, butanediol, diethylene glycol, hexanediol, butyl ethyl propanediol, trimethylolpropane, ethoxylated trimethylolpropane, glycerin, neopentyl glycol, cyclohexane dimethanol, pentaerythritol, di-pentaerythritol, sorbitol and mixtures thereof.

In a particular embodiment, the polymerizable unsaturated polyester (a) has a weight average molecular weight of 300-10000 g/mole, preferably 500-3000 g/mole, a hydroxyl number of 50-400 mg KOH/g, preferably 100-300 mg KOH/g, and an acid number of 100-350 mg KOH/g, preferably 200-300 mg KOH/g.

In some embodiments, the (meth)acrylate based polymerizable monomer (b) used in the present application is of the general formula (I)

in which R 2 is hydrogen or methyl, and R 3 is a linear or branched alkyl having 1-22 carbon atoms. Preferably, the (meth)acrylate based polymerizable monomer is selected from the group consisting of acrylic acid, methacrylic acid, alkyl (meth)acrylate, 2-hydroxyl ethyl (meth)acrylate and mixtures thereof, wherein the alkyl is a linear or branched alkyl having 8-18 carbon atoms. More preferably, the (meth)acrylate based polymerizable monomer is selected from the group consisting of acrylic acid, methacrylic acid, alkyl (meth)acrylate, 2-hydroxyl ethyl (meth) aery late and mixtures thereof, wherein the alkyl is a linear or branched alkyl having 12-13 carbon atoms. In some embodiments, the (meth) aery late based polymerizable monomer may contain styrene. The amount of styrene may range from: 0.01 to 40 wt.%. In other embodiments, the alkoxylated (meth)acrylic acid polymerizable monomer (c) is obtained by alkoxylating (meth)acrylic acid polymerizable monomer. Preferably, the alkoxylated moiety of alkoxylated (meth)acrylic acid polymerizable monomer (c) comprises at least one segment of

C₂H₄0- ^■C₃H₆0- n

and at least one segment of , wherein m is an integer of 5 to 50, preferably 5 to 30 and n is an integer of 5 to 50, preferably 5 to 30. More preferably, the alkoxylated (meth)acrylic acid polymerizable monomer (c) is ethoxylated (meth)acrylic acid polymerizable monomer having a weight average molecular weight of 300 to 1500 g/mole,

C₂H₄0- which comprises one segment of , wherein m is an integer of

5 to 30. The carbonyl-containing (meth)acrylic polymerizable monomer (d) may comprise at least one ketone group and/or at least one methylene carbonyl

O

Q_|__| Q II

group ( ² ). Preferably, the carbonyl-containing (meth)acrylic polymerizable monomer is selected from the group consisting of diacetone acrylamide, acetoacetoxyethyl methacrylate, glycidyl (meth)acrylate-levulinic acid adduct, and mixtures thereof. In some embodiments, the phosphate group-containing resin of the present application can be produced by copolymerizing the polymerizable components (a) to (d) each described above in the presence of a polymerization initiator by a conventionally known method, for example, a solution polymerization method. The proportions of these polymerizable components in copolymerization shall not strictly be restricted and can be changed over a wide range depending on characteristics desired to the phosphate group-containing resin produced. In general, the components (a) to (d) are copolymerized in the following proportions based on the total weight of these components. The proportion of the polymerizable unsaturated polyester (a) is 1 to 30 % by weight, preferably 2 to 25 % by weight. The proportion of the (meth)acrylate based polymerizable monomer (b) is 10 to 50% by weight, preferably 15 to 40% by weight. The proportion of the alkoxylated (meth)acrylic acid polymerizable monomer (c) is 2 to 30% by weight, preferably 5 to 20% by weight. The proportion of carbonyl-containing (meth)acrylic polymerizable monomer (d) is 2 to 50% by weight, preferably 5 to 40% by weight.

In preferred embodiments, the phosphate group-containing resin of the present application can have a weight average molecular weight falling within a range of usually 1,000 to 100,000 g/mole, preferably 1,000 to 50,000 g/mole and particularly preferably 1,500 to 30,000 g/mole, an acid number falling within a range of 0 to 250 mg KOH/g, particularly 0 to 120 mg KOH/g and further particularly 0 to 100 mg KOH/g originating from a phosphoric acid group and carboxylic acid group, and hydroxyl number falling in a range of 0 to 250 mg KOH/g, particularly 0 to 120 mg KOH/g and further particularly 0 to 80 mg KOH/g.

In other aspect, the present application also relates to use of the phosphate group-containing resin of the application as a treating agent for a metallic pigment or an inorganic pigment in a water-based coating composition. Typical metallic flake pigments that can be used are aluminum flake, bronze flake, nickle flake, stainless steel flake and the like. Aluminum flake is preferred since it imparts an automotive finish with the desired metallic glamour. Typical inorganic pigments that can be used are titanium dioxides, zinc sulfides, zinc oxides, iron oxides, magnetite, manganese iron oxides, chromium oxides, nickel or chromium antimony titanium oxides, manganese titanium rutiles, cobalt oxides, mixed oxides of cobalt and aluminum, rutile mixed-phase pigments, sulfides of rare earths, spinels of cobalt with nickel and zinc, spinels based on iron and chromium with copper, zinc and manganese, bismuth vanadates, pearl effect pigments, and extender pigments.

Therefore, the present application also relates to a water-based coating composition comprising water as a medium, the phosphate group-containing resin of the present application, a metallic pigment or an inorganic pigment, and a binder, and when required, conventional additives such as a water-dispersible resin, color pigment, color space effect pigments, extender pigment, organic solvent, viscosity modifier, UV screener, defoaming agent and surface modifier.

In the manufacture of the water-based coating composition, the phosphate group-containing resin of the present application is first used to treat a metallic pigment or an inorganic pigment in a suitable organic solvent, followed by mixing with a paint formulation comprising a binder resin to form a waterborne coating composition which is then subjected to a curing procedure to form the water-based coating composition. If necessary, the water-based coating composition can comprises conventional additives as mentioned above in a suitable amount depending on the effect of the coating composition to be achieved.

Examples of the suitable organic solvents comprises, for examples, butylene glycol, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol n-propyl ether, propylene glycol t-butyl ether, propylene glycol n-butyl ether, dipropylene glycol monoethyl ether, dipropylene glycol n-propyl ether, or dipropylene glycol n-butyl ether, or mixtures thereof.

In some embodiments, the paint formulation suitable for preparing the waterborne coating composition comprises a binder resin wherein the binder contains a carbonyl group and/or a polyamine group. In general, the binder resin is conventionally known in the art, and examples thereof may refer to those shown in US Patent Nos. 5147926 and 5571861. These carbonyl-containing binders can be obtained by using epoxy resin and levulinic acid adduct to prepare polyurethane dispersion or using ketone containing monomer such as diacetone acrylamide, acetoacetoxyethyl methacrylate to prepare the acrylic emulsion. This emulsion is capable of crosslinking with polyamine compound such as adipic acid dihydrazide to form a self-cross-linkable binder system. The curing reaction of carbonyl and amine follow a condensation mechanism. During the drying procedure, the phosphate group-containing resin and the binder resin are cross-linked by reaction of the carbonyl group in the phosphate group-containing resin and/or the carbonyl group in the binder with the polyamine group in the binder. As a result, such cross-linking reaction makes the resulting coating compositions exhibit significantly improved in cohesion after cured.

The phosphate group-containing resin of the present application is suitable for the production of coatings, such as anticorrosion coatings and/or intermediate coatings for a wide variety of applications, such as in the sector of automotive finishing and plastics coating.

The coating composition obtained by using the phosphate group-containing resin of the present application and a metallic pigment or an organic pigment can be applied by any of the application methods known to a person skilled in the art, including brushing, roller coating, pouring, knife-coating, dipping and spraying, etc..

The phosphate group-containing resin of the present application allows pigments to have an improved dispersivity in water based coating compositions, and in addition offers an improved protection to pigments against the reaction with water over a long period of time, thereby improving the stability of coating compositions formulated with pigments. Most importantly, the phosphate group-containing resin of the present application makes the resulting coating compositions get significantly improved in cohesion after cured.

The present application will be illustrated below with reference to following examples, without any intention thereby to restrict the application. All parts and percentages are on a weight basis unless otherwise indicated.

EXAMPLES

EXAMPLE A

Preparation of Polyester (A)

112.17 parts of trimethylol propane, 55.79 parts of neopentyl glycol, 58.05 parts of phthalic anhydride, 58.85 parts of adipic acid and 38.39 parts of maleic anhydride were placed in a glass reaction vessel, heated to 150 °C, and then heated to 230 °C over a period of 4 hours. The reaction was maintained at 230 °C until the acid number reached 70 mg KOH/g. The temperature was lowered to 90 °C, then 50 parts of propylene glycol monomethyl ether acetate were added, giving a polyester (A).

EXAMPLE B

Preparation of Polyester (B)

163.59 parts of trimethylol propane, 118.53 parts of adipic acid and 39.78 parts of maleic anhydride were placed in a glass reaction vessel, heated to 150 °C, and then heated to 230 °C over a period of 4 hours. The reaction was maintained at 230 °C until the acid number reached 70 mg KOH/g. The temperature was lowered to 90 °C, then 50 parts of propylene glycol monomethyl ether acetate were added, giving a polyester (B). Examples 1-3

The reagents used to prepare phosphoric ester polymers of Examples 1-3 are shown in Table 1.

Weight- average molecular weight Mw for each sample was determined by gel permeation chromatography (GPC). Three Waters (Styragel) columns 7.8 mm I.D. 300 mm (HR4, HR3, HR 0.5 in a series) were used for GPC analysis with THF (1 ml/ min) as the mobile phase. Waters 2410 RI detector is set at 35°C. Column Oven is set at 40 °C. Using PMMA as standards

Example 1 : Preparation of phosphoric ester polymer I

100.0 parts of polyester (A), 20.0 parts of propylene glycol monomethyl ether acetate were added in a glass reaction vessel. The temperature was heated to 80 °C after which, 30.0 parts of polyphosphoric acid were added at 80 °C. The temperature was maintained at 80 °C for 3 hours. Then 399.7 parts of propylene glycol monomethyl ether were added to the vessel. The temperature was heated to 110 °C. A mixture containing 65.6 parts of styrene, 43.7 parts of SLMA, 131.1 parts of GAM-adduct, 52.5 parts of AE-400 and 8.9 parts of Luperox-26 was added over a period of 2 hours. The reaction was maintained at 110 °C for another 2 hours. The phosphoric ester polymer solution was obtained. Phosphoric ester polymer I was determined to have a weight average molecular weight of 16600 g/mole.

Example 2: Preparation of phosphoric ester polymer II

100.0 parts of polyester (B) and 20.0 parts of propylene glycol monomethyl ether acetate were added in a glass reaction vessel and then heated to 80 °C after which, 30.0 parts of polyphosphoric acid were added at 80 °C. The reaction temperature was maintained at 80 °C for 3 hours. To this solution, 399.7 parts of propylene glycol monomethyl ether were added to the vessel and the temperature was increased to 110 °C. Then a mixture containing 65.6 parts of styrene, 43.7 parts of SLMA, 131.1 parts of DAAM, 52.5 parts of AE-400 and 8.9 parts of Luperox-26 was added over a period of 2 hours. The reaction was maintained at 110 °C for another 2 hours. The phosphoric ester polymer II was obtained. Phosphoric ester polymer II was determined to have a weight average molecular weight of 16300 g/mole.

Example 3: Preparation of phosphoric ester polymer III

100.0 parts of polyester (A) and 20.0 parts of propylene glycol monomethyl ether acetate were added in a glass reaction vessel and then heated to 80 °C after which, 30.0 parts of polyphosphoric acid were added at 80 °C. The reaction temperature was maintained at 80 °C for 3 hours. To this solution, 399.7 parts of propylene glycol monomethyl ether were added to the vessel and the temperature was increased to 110 °C. Then a mixture containing 65.6 parts of styrene, 43.7 parts of SLMA, 131.1 parts of AAEM, 52.5 parts of AE-400 and 8.9 parts of Luperox-26 was added over a period of 2 hours. The reaction was maintained at 110 °C for another 2 hours. The phosphoric ester polymer III was obtained. Phosphoric ester polymer III was determined to have a weight average molecular weight of 15400 g/mole.

Table 1

1) Misubish gas, SLMA

2) Nippon Oil & Fats Co., Ltd., AE-400 3) Cognis, MPEG350MA

4) Glycidyl methacrylate-Levulinic acid adduct

5) KYOWA HAKKO CHEMICAL CO., LTD., Diacetone Acrylamide

6) Eastman, acetoacetoxyethyl methacrylate

7) Arkema Inc. Luperox-26

Comparison Example 1 : Preparation of phosphoric ester polymer IV 100.00 parts of polyester (B) and 20 parts of propylene glycol monomethyl ether acetate were added in a glass reaction vessel and then heated to 80 °C after which, 30 parts of polyphosphoric acid were added at 80 °C. The reaction temperature was maintained at 80 °C for 3 hours. To this solution, 399.7 parts of propylene glycol monomethyl ether were added to the vessel and the temperature was increased to 110 °C. Then a mixture containing 65.6 parts of styrene, 43.7 parts of SLMA, 52.5 parts of AE-400 and 8.9 parts of Luperox-26 was added over a period of 2 hours. The reaction was maintained at 110 °C for another 2 hours. The phosphoric ester polymer IV was obtained.

Example 4

Preparation and application of a coating composition

An aluminum pigment paste solution I was prepared using the amounts of ingredients listed below.

I I Parts by weight Aluminum pigment paste ^!) 37.0

Butyl glycol 55.5

Phosphoric ester polymer I, II, III or IV 3.7

The ingredients were mixed for 10 minutes and maintained at room temperature for 2 hours before further application.

A waterborne paint I was prepared using the ingredients listed below.

1) Conventional aluminum pigment paste (Silver-Dollar)

2) Cytec, self-crosslinkable emulsion, Daotan 6462, an urethane-acyl hybrid resin.

3) BYK-Chemie, Defoamer, BYK-024

4) Elementis Specialties, PU thickener, WT-105A

5) Elementis Specialties, HASE thickener, Rheolate 416

6) Elementis Specialties, waterbase organic clay, Bentone DE

UV Curable Overcoat

1) Elementis Specialties, UV oligomer, UA-M6

2) Elementis Specialties, UV monomer, UM-562

3) Ciba, photo initiator, Irgacure- 184

4) Elementis Specialties, leveling agent, Levasilp 875

A waterborne metallic paint (i.e. the coating composition) was prepared as follows: 18.8 parts of aluminum pigment paste solution I were added to waterborne paint I under intensive mixing for 15 minutes. The resulting paint was sprayed over ABS plastic substrate and then baked at 80 °C for 30 minutes. The UV curable overcoat was then applied followed by drying at 70 °C for 5 minutes to remove the solvents, and UV curing under air at line speed lOm/min, radiation intensity 340 mj/cm 2 , illumination intensity 1000 mw/cm 2 , single medium mercury lamp, 120 W/cm. Adhesion of the UV cured coatings was measured according to ASTM D3359 (cross-hatch adhesion). Transparent tape (3M No. 600) was applied on the scribed cross-hatch area, pressed down, and then stripped away sharply in a direction perpendicular to the surface of the coated panels. The coating was then visually inspected to see whether any of the coating was removed from the panel by the tape. Results are shown in the table below.

*Base coat cohesion failed

The specific ASTM ratings for the adhesion test versus the percentage coating removed are shown in the below Table.

2B 15 - 35%

IB 35 - 65%

OB > 65%

The adhesion testing data show that a coating composition made using the phosphate group-containing resin (i.e. phosphoric ester polymer I, II or III) as prepared in Examples 1-3 has much higher adhesion compared to a coating composition made with a phosphate containing resin which does not contain a carbonyl-containing (meth)acrylic polymerizable monomer (i.e. phosphoric ester polymer IV).

Claims

What is claimed is:

1. A phosphate group-containing resin comprising, as polymerized units :

(a) a polymerizable unsaturated polyester having at least one phosphate group represented by the formula [-OPOiOR^OH)], wherein R¹ represents a hydrocarbon group having 1 to 10 carbon atoms and/or having at least one phosphoric acid group represented by a formula [-OPO(OH)₂];

(b) a (meth)acrylate based polymerizable monomer,

(c) an alkoxylated (meth)acrylic acid polymerizable monomer, and

(d) a carbonyl-containing (meth)acrylic polymerizable monomer.

2. The phosphate group-containing resin according to claim 1, wherein R¹ represents a hydrocarbon group having 1 to 4 carbon atoms.

3. The phosphate group-containing resin according to claim 1, wherein R¹ represents an alkyl group having 1 to 4 carbon atoms.

4 The phosphate group-containing resin according to claim 1, wherein the (meth)acrylate based polymerizable monomer (b) contains 0.01 to 40 wt. % styrene.

5. The phosphate group-containing resin according to claim 4, wherein the (meth)acrylate based polymerizable monomer (b) is selected from the group consisting of acrylic acid, methacrylic acid, alkyl (meth)acrylate, 2-hydroxyl ethyl (meth)acrylate and mixtures thereof, wherein the alkyl is a linear or branched alkyl having 8-18 carbon atoms.

6. The phosphate group-containing resin according to claim 5, wherein the alkyl has 12-13 carbon atoms.

7. The phosphate group-containing resin according to claim 1, wherein the alkoxylated moiety of the alkoxylated (meth)acrylic acid polymerizable

C₂H₄0- monomer (c) comprises at least one segment of and at least

^■C₃H₆0- one segment of , wherein m is an integer of 5 to 50, and n is an integer of 5 to 50.

8. The phosphate group-containing resin according to claim 7, wherein the alkoxylated (meth)acrylic acid polymerizable monomer (c) is ethoxylated (meth)acrylic acid polymerizable monomer having one segment of

— -C₂H₄0^

J m

, wherein m is an integer of 5 to 30.

9. The phosphate group-containing resin according to claim 8, wherein the ethoxylated (meth)acrylic acid polymerizable monomer has a weight average molecular weight of 300-1500 g/mole.

10. The phosphate group-containing resin according to claim 1, wherein the carbonyl-containing (meth)acrylic polymerizable monomer (d) comprises at least

O

Q_|__| Q I I one keto group and/or at least one methylenecarbonyl group ( ² ).

11. The phosphate group-containing resin according to claim 1, wherein the polymerizable unsaturated polyester (a) has a weight average molecular weight of 300-10000 g/mole, a hydroxyl number of 50-400 mg KOH/g, and an acid number of 100-350 mg KOH/g.

12. The phosphate group-containing resin according to claim 1, wherein the phosphate group-containing resin has a weight average molecular weight of 1000-100,000 g/mole, an acid number of 0-250 mg KOH/g, and hydroxyl number of 0-250 mg KOH/g.

13. The phosphate group-containing resin according to claim 1, obtained by copolymerizing 1 to 30% by weight of the polymerizable unsaturated polyester (a), 10 to 50% by weight of the (meth)acrylate based polymerizable monomer (b), 2 to 30% by weight of the alkoxylated (meth)acrylic acid polymerizable monomer (c), and 2 to 50% by weight of the carbonyl-containing (meth)acrylic polymerizable monomer (d), based on the total amount of the components (a) to (d).

14. Use of the phosphate group-containing resin according to claim 1 as a treating agent for a metallic pigment or an inorganic pigment.

15. Use according to claim 14, wherein the pigment is used in a water-based coating composition comprising a binder resin containing a carbonyl group, a polyamine group or combinations thereof.

16. A water-based coating composition comprising water as a medium, the phosphate group-containing resin of claim 1, a metallic pigment or an inorganic pigment, and a binder.

17. The water-based coating composition of claim 16 further comprising conventional additives such as a water-dispersible resin, color pigment, color space effect pigments, extender pigment, organic solvent, viscosity modifier, UV screener, defoaming agent and surface modifier.