JP2009067952A - Rust proof coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rust proof coating composition which is capable of forming a film having good adhesiveness to metal parts and excellent in rust-proofing properties when coated thereon. <P>SOLUTION: The rust proof coating composition is prepared by using an emulsion containing particles having a heterogeneous structure obtained by multistage emulsion polymerization in the presence of an anionic surfactant. In the composition, at least one phase of the particles having the heterogeneous structure is formed of a copolymer prepared by emulsion polymerizing a cationic functional group-containing monomer and a copolymerizable α,β-ethylenically unsaturated monomer except carboxyl group-containing monomers, at least one phase of the particles having the heterogeneous structure is formed of a copolymer prepared by emulsion polymerizing a carboxyl group-containing monomer and a copolymerizable α,β-ethylenically unsaturated monomer except cationically functional group-containing monomers, and the sum total of the cationic functional group-containing monomer units and the carboxyl group-containing monomer units in the particles having the heterogeneous structure is <10 mass% based on the total monomer units of the particles having the heterogeneous structure. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rust-preventing coating composition, and particularly to a rust-preventing coating composition capable of forming a coating film excellent in metal adhesion, rust-preventing property, and water resistance.

  Conventionally, organic solvent-based alkyd phthalate paints and urethanes are used for rust prevention of automobile chassis and other metal parts, tanks, bridges, water pipes, mechanical structures such as machinery, buildings, furniture, and home appliances. Although paints and epoxy resin paints have been used, there is a demand for a shift from organic solvent-based paints to water-based resin paints from the viewpoints of global environmental problems, energy saving, fire risk, and the like. In particular, from the viewpoint of workability and handling convenience, the use of a one-component water-based resin paint is required, but conventional water-based resin paints are rust-proof, metal-adhesive, top-coat paint-adhesive, and water-resistant. Various properties such as resistance and alkali resistance are inferior to those of organic solvent-based paints, which is insufficient as an alternative to organic solvent-based paints.

In the background as described above, various attempts have been made to overcome the above-mentioned drawbacks of water-based resin paints. For example, a water-dispersible resin composition for an anticorrosive coating obtained by emulsion copolymerization of an unsaturated monomer having styrene, (meth) acrylic acid ester, unsaturated carboxylic acid and glycidyl group in the presence of a reactive emulsifier is disclosed. Although it has been described (see, for example, Patent Document 1), rust prevention and metal adhesion enough to replace conventional solvent-based paints were not obtained. In addition, a method for improving the rust prevention property by mixing an organic solvent such as industrial gasoline and mineral spirit with an emulsion having a specified molecular weight and glass transition temperature to improve the film forming property is disclosed (for example, patents). However, there is a problem in terms of rust prevention durability.
JP-A-5-1244 JP 2006-52247 A

  The present invention has been made against the background of the problems of the prior art as described above, and is obtained by a general multistage emulsion polymerization method. In the present invention, no agglomerates are formed during emulsion polymerization, and the storage stability is good. It is a coating composition for rust prevention using emulsion containing heterophasic structure particles that is extremely easy to make, and when coated, it can form a coating film with good adhesion to metal parts and excellent rust prevention properties It aims at providing the coating composition for rust prevention.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have determined that each of the cationic functional group-containing monomer and the carboxyl group-containing monomer by multi-stage emulsion polymerization using an anionic surfactant. Emulsion polymerization in a separate stage, that is, those monomers are not emulsion polymerized in the mixed state, and these monomers are used in combination with other copolymerizable α, β-ethylenically unsaturated monomers, respectively. Emulsion containing different phase structure particles obtained by a multistage emulsion polymerization method in which emulsion polymerization is performed in multiple stages, and the total amount of the cationic functional group-containing monomer units and carboxyl group-containing monomer units in the different phase structure particles It is found that the above-mentioned object can be achieved by making a coating composition for anticorrosion using a specific emulsion having different phase structure particles containing less than 10% by mass of the total monomer units of the different phase structure particles. Reached Ming.

That is, the antirust coating composition of the present invention is an antirust coating composition using an emulsion containing heterophasic particles obtained by a multistage emulsion polymerization method in the presence of an anionic surfactant. At least one phase of the structured particles is obtained by emulsion polymerization of a cationic functional group-containing monomer and another copolymerizable α, β-ethylenically unsaturated monomer other than the carboxyl group-containing monomer. Formed of a copolymer,
At least one phase of the heterophasic structure particles is obtained by emulsion polymerization of a carboxyl group-containing monomer and another copolymerizable α, β-ethylenically unsaturated monomer other than the cationic functional group-containing monomer. Formed from a copolymer obtained by
Furthermore, the total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the heterophasic structure particles is less than 10% by mass of the total monomer units of the heterophasic structure particles.
It is characterized by that.

  The emulsion containing heterophasic structure particles used in the antirust coating composition of the present invention does not generate agglomerates during the emulsion polymerization, has good storage stability, and is extremely easy to make into a paint. The rust coating composition is a water-based coating that exhibits excellent metal adhesion and rust prevention.

The present invention is described in detail below.
The emulsion containing heterophasic particles used in the anticorrosive coating composition of the present invention is obtained by a multistage emulsion polymerization method in the presence of an anionic surfactant, and at least one phase of the heterophasic particles is a cationic functional group. Formed of a copolymer obtained by emulsion polymerization of a monomer containing a monomer and other copolymerizable α, β-ethylenically unsaturated monomer other than a carboxyl group-containing monomer, At least one phase of the structured particles is obtained by emulsion polymerization of a carboxyl group-containing monomer and another copolymerizable α, β-ethylenically unsaturated monomer other than the cationic functional group-containing monomer. Formed of a copolymer.

  The multi-stage emulsion polymerization method employed in the production of the emulsion containing heterophasic particles used in the anticorrosive coating composition of the present invention is a combination of any one of the above monomers in water (for example, a cationic functional group-containing monomer). And other copolymerizable α, β-ethylenically unsaturated monomers other than the carboxyl group-containing monomer), anionic surfactants and polymerization initiators, and chain if necessary An aqueous emulsion containing a transfer agent, an emulsion stabilizer, and the like is formed, and emulsion polymerization is carried out under a conventionally known emulsion polymerization method, usually at 60 to 90 ° C., and then the other monomer combination (For example, a combination of a carboxyl group-containing monomer and another copolymerizable α, β-ethylenically unsaturated monomer other than a cationic functional group-containing monomer) Emulsion polymerization, usually under heating at 60-90 ° C The emulsion copolymer is repeatedly subjected to two or more steps, usually 2 to 5 steps, so that the emulsion copolymer has a different phase structure, that is, particles composed of an outermost phase having different characteristics and one or more internal phases. This is a multistage emulsion polymerization method to be formed.

  Examples of the cationic functional group-containing monomer include dimethyl diallylammonium salt, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethylmethyl chloride salt methacrylate and the like.

  Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, and the like.

  As other copolymerizable α, β-ethylenically unsaturated monomers, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, sec-butyl Acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-methoxyethyl acrylate 2-ethoxyethyl acrylate, 2-butoxyethyl acrylate, 2-phenoxyethyl acrylate, ethyl carbitol acrylic Rate, allyl acrylate, glycidyl acrylate, dimethylaminoethyl acrylate, sodium acrylate, trimethylolpropane acrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, pentaerythritol triacrylate Acrylate monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, propyl methacrylate, benzyl methacrylate , Isopropyl methacrylate, se -Butyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, allyl methacrylate, ethylene glycol methacrylate, triethylene glycol methacrylate, tetraethylene glycol methacrylate, 1,3-butylene glycol methacrylate, tri Mention may be made of methacrylic acid ester monomers such as methylolpropane methacrylate, 2-ethoxyethyl methacrylate and 2-methoxyethyl methacrylate.

  In addition to the above acrylic monomers, α, β-ethylene having a carbonyl group such as acrolein, diacetone acrylamide, diacetone methacrylamide, formyl styrene, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone, etc. As a copolymerization component, a vinyl monomer such as an unsaturated monomer, acrylamide, acrylonitrile, vinyl acetate, styrene, ethylene, propylene, isobutylene, butadiene, isoprene, or chloroprene can be used.

  In the production of the emulsion containing the different phase structure particles, an anionic surfactant is used as an emulsifier in order to obtain miscibility with the coating material. Examples of the anionic surfactant include fatty acid salts such as sodium lauryl sulfate, alkylbenzene sulfonates such as higher alcohol sulfate esters and sodium dodecylbenzenesulfonate, polyoxyethylene alkyl ether sulfates, and polyoxynonyl phenyl ether sulfones. Examples thereof include ammonium sulfate, polyoxyethylene-polyoxypropylene glycol ether sulfate, and so-called reactive surfactants having a sulfonic acid group or a sulfate group and a polymerizable unsaturated group in the molecule. Moreover, a nonionic surfactant can also be used together with an anionic surfactant. When a nonionic surfactant is used in combination, the mechanical stability and freeze-thaw stability of the paint are improved.

  As the above polymerization initiator, those conventionally used for radical polymerization can be used, but water-soluble ones are preferred, for example, persulfates such as potassium persulfate and ammonium persulfate. 2,2′-azobis (2-aminodipropane) hydrochloride, 4,4′-azobis-cyanovaleric acid, 2,2′-azobis (2-methylbutanamidooxime) dihydrochloride tetrahydrate Azo compounds such as hydrogen peroxide, peroxides such as t-butyl hydroperoxide, and the like. Furthermore, a redox system in which a reducing agent such as L-ascorbic acid or sodium thiosulfate is combined with ferrous sulfate or the like can also be used.

  Examples of the chain transfer agent include long-chain alkyl mercaptans such as n-dodecyl mercaptan, aromatic mercaptans, and halogenated hydrocarbons. Examples of the emulsion stabilizer include polyvinyl alcohol, hydroxyethyl cellulose, and polyvinyl pyrrolidone.

  In each stage of multi-stage emulsion polymerization employed in the production of emulsion containing heterophasic structure particles, the monomer batch feeding method in which the monomer mixture is batch fed, and the monomer dropping in which the monomer mixture is dripped continuously. It is possible to employ a method, a pre-emulsion method in which a monomer mixture, water, and an anionic surfactant are preliminarily mixed and emulsified and added dropwise, or a combination thereof.

  In the present invention, the total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the heterophasic structure particles needs to be less than 10% by mass of the total monomer units of the heterophasic structure particles. Preferably, it is 2-9 mass%, More preferably, it is 3-8 mass%. When the total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the heterophasic structure particles is larger than the above range, a coating formed from the obtained antirust coating composition is used. This leads to a decrease in the water resistance of the membrane, resulting in a decrease in rust prevention (salt water spray resistance). Moreover, when the total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the heterophasic structure particles is too small, the intended effect tends to be insufficient.

  In the present invention, the “cationic functional group-containing monomer unit” in the heterophasic particles is satisfactory in that both the adhesion and antirust property of the coating film formed with the antirust coating composition are satisfied at the same time. The mass ratio of “carboxyl group-containing monomer unit” is preferably 0.5 to 5: 1, more preferably 1 to 4: 1, and 1.5 to 3: 1. Is more preferable.

  In the heterophasic structure particles contained in the heterophasic particle-containing emulsion used in the anticorrosive coating composition of the present invention, the outermost phase is a cationic functional group-containing monomer in the presence of an anionic surfactant, and a carboxyl group-containing When the emulsion is formed from a copolymer obtained by emulsion polymerization of other copolymerizable α, β-ethylenically unsaturated monomer other than the monomer, such emulsion having different phase structure particles The stability of the rust-preventive coating composition of the present invention using the coating composition is increased, and adhesion with the base material is improved by applying such a rust-preventive coating composition, so that it is such an outermost phase. It is preferable.

  In the heterophasic structure particles contained in the heterophasic particle-containing emulsion used in the anticorrosive coating composition of the present invention, at least one of the phases constituting the heterophasic structure particles is formed of an emulsion copolymer having an internal cross-linked structure. It may be. The emulsion copolymer particles having such an internal cross-linked structure are divinylbenzene, ethylene glycol di () as a part of a monomer mixture added at a predetermined stage of multi-stage emulsion polymerization for forming a phase having an internal cross-linked structure. Method of emulsion polymerization using a monomer having two or more polymerizable unsaturated double bonds in the molecule such as (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, emulsion polymerization reaction Combinations of functional group-containing monomers that react with each other at a certain temperature, for example, an ethylenically unsaturated monomer having a functional group such as a carboxyl group and a glycidyl group, or a hydroxyl group and an isocyanate group. A method of emulsion polymerization using a monomer mixture, (meth) acryloxypropyltrimethoxysilane in which hydrolysis condensation reaction occurs, A method of emulsion polymerization using a monomer mixture containing an ethylenically unsaturated monomer having a silyl group such as (meth) acryloxypropyltriethoxysilane, (meth) acryloxypropylmethyldimethoxysilane, etc. It can be manufactured by a method.

  When an emulsion such as ammonia, triethylamine, or dimethylethanolamine is added to the emulsion containing heterophasic particles used in the anticorrosive coating composition of the present invention and adjusted to pH 6-10, freeze-thaw stability and storage stability The sex becomes even better.

  In addition, sufficient rust prevention effect is not acquired with the coating material using the normal acrylic emulsion obtained from the monomer which does not have a cationic functional group. In the case of an emulsion obtained from a monomer having no carboxyl group, various stability such as polymerization stability, physical stability, and chemical stability are deteriorated, and the carboxyl group-containing monomer and the cationic functional group are deteriorated. When the group-containing monomer is copolymerized at the same time, the polymerization stability is remarkably deteriorated.

  The coating composition for rust prevention of the present invention uses an emulsion containing heterophasic particles obtained by the multistage emulsion polymerization method described above, but in order to impart various functions as a coating, as necessary. , Known additives such as antifoaming agents, antiseptics, antifungal agents, thickeners, freezing stabilizers, wetting agents, UV absorbers, light stabilizers, colored pigments, extender pigments, dispersants, antisettling agents, etc. May be blended.

  The coating composition for rust prevention according to the present invention is a rust preventive pigment composed of Ca, Al, Mg, Zn, Fe phosphate and molybdate in addition to the above-mentioned color pigment and extender pigment. By using the coating composition in an amount of 10 to 120 parts by mass per 100 parts by mass of the solid content of the coating composition, it is possible to constitute a coating having further excellent rust prevention properties.

  The antirust coating composition of the present invention can be applied to various base materials such as inorganic, metal, wood, and plastic. In particular, since it is excellent in rust prevention, metal adhesion, and water resistance, it is suitable as a light anticorrosion paint and an architectural paint.

  Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to these. In Examples and Comparative Examples, “parts” and “%” are based on mass unless otherwise specified.

Examples 1-3
In a reactor equipped with a stirrer, a thermometer, a cooling tube and a dropping device, 260 parts of ion-exchanged water and a non-reactive anionic surfactant “Hytenol NF-13” (Daiichi Kogyo Seiyaku Co., Ltd.) (poly) 2 parts of oxyethylene distyrenated phenyl ether ammonium sulfate and ethylene oxide average added mole number of 13 moles) were charged, respectively, and the temperature inside the reactor was increased to 80 ° C. while replacing the inside with nitrogen.

  Next, 1 part of potassium persulfate (polymerization initiator) was added, and the emulsion (A) having the composition shown in Table 1 that had been previously stirred and mixed in a separate container (the numerical values indicate parts, the same applies hereinafter) was carried out. Emulsions having the composition shown in Table 1 that were continuously dropped over 2 hours for Examples 1 and 3 and 2.5 hours for Example 2 and then stirred and mixed in the same manner as in the first stage. (B) was dripped continuously over 2 hours. After completion of the dropwise addition, the mixture was aged while continuing stirring at 80 ° C. for 2 hours, cooled to 40 ° C., adjusted to pH 9.0 with 50% dimethylethanolamine to obtain a two-phase heterogeneous particle-containing emulsion.

Example 4
Reactive anionic surfactant “AQUALON KH-10” (Daiichi Kogyo Seiyaku Co., Ltd.) [α- in place of 2 parts of the non-reactive anionic surfactant compounded in Examples 1-3 in 260 parts of ion-exchanged water Sulfonato-ω- (1- (allyloxymethyl) alkyloxy) ammonium salt of polyoxyethylene, ethylene oxide average addition mole number 10 mol] 2 parts, emulsion (A) and emulsification of the composition shown in Table 1 Using the product (B), an emulsion having different phase structure particles was obtained in the same manner as in Example 1.

Example 5
Nonionic surfactant “Neugen EA-187” (Daiichi Kogyo Seiyaku Co., Ltd.) (polyoxy) in addition to 2 parts of non-reactive anionic surfactant “Hytenol NF-13” blended in 260 parts of ion-exchanged water Ethylene styrenated phenyl ether, HLB17) 2 parts, emulsion (A) and emulsion (B) having the composition shown in Table 1 were used, and emulsion containing different phase structure particles was carried out in the same manner as in Example 1. Got.

Comparative Example 1
Emulsion by the same operation as in Example 1 except that the emulsion (A) having the composition shown in Table 1 containing both the cationic functional group-containing monomer and the carboxyl group-containing monomer was added dropwise over 4 hours. Got. The obtained emulsion is not an emulsion containing particles having different structure.

Comparative Example 2
Using emulsions (A) and (B) having the compositions shown in Table 1, emulsions having different phase structure particles were obtained in the same manner as in Example 1. The total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the different phase structure particles of the obtained emulsion containing the different phase structure particles is 10% by mass of the total monomer units of the different phase structure particles. Over.

Comparative Example 3
Using emulsions (A) and (B) having the compositions shown in Table 1, emulsions having different phase structure particles were obtained in the same manner as in Example 1. Emulsions (A) and (B) do not contain a cationic functional group-containing monomer.

Comparative Example 4
Using emulsions (A) and (B) having the compositions shown in Table 1, emulsions having different phase structure particles were obtained in the same manner as in Example 1. Emulsions (A) and (B) do not contain a carboxyl group-containing monomer.

The polymerization stability during emulsion polymerization of the emulsions obtained in Examples 1 to 5 and Comparative Examples 1 to 4 was visually evaluated according to the following criteria. The results were as shown in Table 1.
<Polymerization stability>
◎: Almost no agglomerates were generated during polymerization, and a stable emulsion was obtained.
○: Some agglomerates were formed during the polymerization, but a stable emulsion was obtained.
Δ: Polymerization stability was poor and a large amount of aggregates were formed.
X: Polymerization stability was extremely poor and it was difficult to carry out the reaction.

  About the antirust coating composition prepared as follows using the emulsion obtained in Examples 1-5 and Comparative Examples 1-4, the performance evaluation test as an antirust coating was done as follows. The results were as shown in Table 1.

(1) Paint formulation 65.0 parts of the emulsion obtained in any of Examples 1 to 5 and Comparative Examples 1 to 4 are mixed with the following raw materials in the following amounts, and MFT is 0 ° C. or lower. Texanol was added as necessary to produce a coating for rust prevention test.
Natrazole 250HR 0.3 part (Hercules Co., Ltd., hydroxyethyl cellulose)
Deionized water 13.0 parts Ammonia water (28% aqueous solution) 0.2 parts Disperbyk-190 0.2 parts (BIC Chemie Japan Co., Ltd., surfactant)
Surfynol 104E (manufactured by Air Products Co., Ltd., wetting agent) 0.4 parts Primal RM-8W (manufactured by Rohm and Haas Co., Ltd., thickener) 2.0 parts SN deformer 1312 (manufactured by San Nopco Co., Ltd., antifoaming agent) ) 0.4 parts titanium oxide CR-50 (made by Ishihara Sangyo Co., Ltd., titanium oxide) 5.5 parts Bayferrox 130M (Bengara) 5.0 parts micro mica 4.0 parts micro talc 4.0 parts

(2) Coating drying conditions A spray gun with a 2 mm caliber was applied to the paint obtained above so that the dry coating thickness would be 30 μm on the surface of cold rolled steel plate bright (SPCC B 70 mm × 150 mm × 0.8 mm). The coating was applied at a spraying pressure of 3 kg / cm ² (294 kPa), dried at 90 ° C. for 5 minutes, then left at 25 ° C. for 7 days to prepare test pieces, and the following tests were carried out.

(3) Test conditions and evaluation criteria <rust prevention>
A salt spray resistance test (200 hours) according to JIS K-5400 was conducted, and the rust resistance was evaluated according to the following criteria.
A: Rust width 1 mm or less,
○: Rust width 1 to 3 mm,
Δ: Rust width 3 mm,
X: The entire surface is rusted.

<Adhesiveness>
A cross-cut test according to JIS K-5400 was conducted, and the adhesion to metal was evaluated according to the following criteria.
A: 100/100,
○: 80-99 / 100,
Δ: 50-79 / 100,
X: Less than 50/100.

<Water-resistant secondary adhesion>
The test plate produced as described above was immersed in tap water for 168 hours, and after the immersion, dried in a constant temperature room at 23 ° C. for 24 hours. After drying, the same test as the adhesion test was performed to obtain a water resistance secondary adhesion test.
(Criteria)
○: No peeling at all
Δ: Some peeling is observed at the intersection of the cut parts.
X: The whole surface peeling of a cellophane adhesive tape adhesion part is seen.

The storage stability of the paint prepared above was visually evaluated according to the following criteria. The results were as shown in Table 1.
<Paint stability>
(Double-circle): It can paint well and its storage stability is also good.
○: Can be paint without problems
Δ: Can be made into a paint, but there is a problem in storage stability.
X: It is difficult to make a paint.

In addition, the compound of the symbol in Table 1 is as follows.
ST: Styrene MMA: Methyl methacrylate BA: Butyl acrylate EA: Ethyl acrylate 2EHA: 2-ethylhexyl acrylate BMA: Butyl methacrylate HEA: Hydroxyethyl acrylate AA: Acrylic acid MAA: Methacrylic acid GMA: Glycidyl methacrylate DVB: Divinylbenzene DE: Dimethylamino Ethyl methacrylate KH-10: Aqualon KH-10
NF-13: Haitenol NF-13
EA-187: Neugen EA-187

  As is apparent from the data shown in Table 1, the emulsion containing heterophasic particles used in the present invention is excellent in polymerization stability, and the antirust coating composition of the present invention has paint stability, antirust properties, Excellent adhesion and secondary adhesion. On the other hand, in the case of Comparative Example 1 in which the cationic functional group-containing monomer and the carboxyl group-containing monomer were dropped simultaneously as a mixture, the polymerization stability was extremely poor and a stable emulsion could not be obtained. The total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the different phase structure particles of the obtained emulsion containing the different phase structure particles is 10% by mass of the total monomer units of the different phase structure particles. In the case of the comparative example 2 which exceeds and in the case of the comparative example 3 in which neither of the emulsions (A) and (B) contains a cationic functional group-containing monomer, the polymerization stability and the coating stability are improved. Although an excellent emulsion containing heterophasic particles was obtained, rust prevention and adhesion were not preferred. In addition, in the case of Comparative Example 4 in which neither of the emulsions (A) and (B) contains a carboxyl group-containing monomer, the mechanical stability and chemical stability at the time of coating are lacking and stable. No paint was obtained.

  From these results, the emulsion containing heterophasic particles used in the present invention has good stability because the surface of heterophasic particles is covered with an anionic surfactant, and the cationic functional group and carboxyl group are membranes. A strong film can be formed at the time of formation to form a coating film with good rust prevention, adhesion and water resistance.

Claims (4)

A coating composition for rust prevention using an emulsion containing heterophasic particles obtained by a multistage emulsion polymerization method in the presence of an anionic surfactant,
At least one phase of the heterophasic structure particles is obtained by emulsion polymerization of a cationic functional group-containing monomer and another copolymerizable α, β-ethylenically unsaturated monomer other than the carboxyl group-containing monomer. Formed from a copolymer obtained by
At least one phase of the heterophasic structure particles is obtained by emulsion polymerization of a carboxyl group-containing monomer and another copolymerizable α, β-ethylenically unsaturated monomer other than the cationic functional group-containing monomer. Formed from a copolymer obtained by
Furthermore, the total amount of the cationic functional group-containing monomer unit and the carboxyl group-containing monomer unit in the heterophasic structure particles is less than 10% by mass of the total monomer units of the heterophasic structure particles.
An antirust coating composition characterized by the above.   The outermost phase of the heterostructure particles is obtained by emulsion polymerization of a cationic functional group-containing monomer and other copolymerizable α, β-ethylenically unsaturated monomer other than the carboxyl group-containing monomer. The coating composition for rust prevention according to claim 1, wherein the coating composition is formed of a copolymer.   The coating composition for rust prevention according to claim 1 or 2, wherein at least one copolymer of each phase constituting the heterophasic structure particles has an internal crosslinking structure.   4. The mass ratio of “cationic functional group-containing monomer unit”: “carboxyl group-containing monomer unit” in the heterophasic structure particles is 1 to 4: 1. Coating composition for rust prevention.