JP2006342218A - Water-dispersible resin composition for coating steel plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-dispersible resin composition excellent in antirusting tendency, adhesivity to metal, adhesivity to topcoating material, alkali resistance, etc. <P>SOLUTION: The water-dispersible resin composition for coating steel plate comprises a copolymer resin emulsion that is obtained by emulsion copolymerization of an unsaturated monomer mixture comprising (a) a polymerizable unsaturated monomer containing neither epoxy group, acid group, hydroxy group and hydrolyzable silyl group, (b) an epoxy group-containing polymerizable unsaturated monomer, (c) an acid group-containing polymerizable unsaturated monomer, (d) a hydroxyl-containing polymerizable unsaturated monomer and (e) a hydrolyzable silyl group-containing polymerizable unsaturated monomer. In this composition, the copolymer resin has a weight-average molecular weight of 30,000-500,000, and the resin particles as a constituent of the emulsion has an average size of 70 nm or smaller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-dispersible resin composition, and particularly to a water-dispersible resin composition useful as a steel sheet coating. More specifically, the present invention relates to rust prevention, adhesion to metals, paints such as alkyd paints, urethane paints, epoxy paints, adhesives with top coating materials such as foamed polyurethane and foamed polyethylene as heat insulating materials for building materials, and water resistance. Water-dispersible resin composition suitable for surface treatment and post-treatment of general steel plates and galvalume steel plates, which is excellent in boiling water resistance, alkali resistance and blocking resistance, and does not require addition of chromic acid or chromate pigments Related to things.

  Conventionally, undercoating paint for interior and exterior of buildings, furniture, home appliance casings, agricultural vinyl pipes, roofing materials for livestock sheds, pre-painted steel sheets for metal structures such as automobile bodies, chassis, engine surroundings and cans ( Organic solvent-based alkyd phthalate paints, urethane paints, and epoxy resin paints have been used as undercoat paints for (pre-coated metal). However, in recent years, the use of water-based resin paints in place of conventional organic solvent-based paints has been required due to global environmental problems caused by organic solvents, fire hazards, and the like. In particular, in view of convenience in handling such as workability, use of a water-dispersible resin coating that can be used as it is in one liquid is required. However, conventional water-dispersible resin coatings are inferior in rust prevention, adhesion to metals, adhesion to top coating materials, water resistance, boiling water resistance, alkali resistance, blocking resistance, slipping properties, etc. It was not sufficient to replace the paint. In addition, water-based urethane dispersions are very suitable as conventional water-dispersible resin coatings, but have the disadvantages of low weather resistance and high price. Accordingly, there has been almost no water-based resin paint that sufficiently satisfies the above-mentioned demand. For building materials and the like, a metal plate is used in which a resin liquid is coated with a thin film after plating on a Galvalume steel plate, and urethane foam or the like is coated thereon. Conventionally, although this is a water-based coating agent, a resin liquid in which a chromium-based rust preventive agent is mixed in two liquids has been used.

  In the background as described above, various attempts have been made to overcome the above disadvantages of the water-dispersible resin composition. For example, JP-A-5-1244 discloses a water dispersible resin composition for an anticorrosive coating obtained by emulsion copolymerization of styrene, a (meth) acrylic ester, an unsaturated carboxylic acid, and an unsaturated monomer having a glycidyl group. Disclosure. However, the rust prevention property, metal adhesion property, top coating adhesion property, alkali resistance, etc. that can be replaced with conventional solvent-based resins cannot be exhibited. Japanese Patent Laid-Open No. 6-136241 discloses an aqueous epoxy resin, an epoxy acrylic resin having an aromatic epoxy unsaturated carboxylic acid ester monomer unit, and a water dispersibility containing an acrylic resin having an unsaturated carboxylic acid monomer unit. A resin is disclosed. Although this resin composition is sufficient as the performance of the paint, the production method is complicated. In addition, it contains a large amount of organic solvent even if it is aqueous, and uses a large amount of strontium chromate, a hexavalent chromium that is extremely harmful when making paints, from the viewpoint of global environmental pollution. Was retreating significantly.

  In particular, aluminum-containing metal steel plates are used in large quantities without being painted as building materials, and aluminum is easily corroded by alkali when exposed to strong alkalis in cement materials such as concrete, resulting in black rust. There was a problem. For this reason, the coating material which forms the film | membrane with high density | concentration on the steel plate surface and can provide the outstanding alkali resistance by apply | coating to such a metal steel plate was desired.

JP-A-5-1244 JP-A-6-136241

The object of the present invention is to overcome the drawbacks of the above conventional water-dispersible resin coatings, and to prevent rust, adhere to metal, adherence to topcoat materials such as alkyd paints and urethane foam, water resistance and boiling water resistance. Another object of the present invention is to provide a water-dispersible resin composition having excellent alkali resistance, blocking resistance and slipperiness.
Another object of the present invention is to provide a water-dispersible resin composition that does not contain chromate pigments and is suitable as a resin composition for steel sheet coating for post-treatment and undercoating of general steel sheets and galvalume steel sheets. There is.

  As a result of intensive studies, the present inventor has obtained a water-dispersible composition comprising a copolymer resin emulsion obtained by emulsion polymerization of an unsaturated monomer mixture having a specific composition. The above object is achieved by the water-dispersible resin composition in which the weight average molecular weight of the resin is in a specific range and the average particle diameter of the resin particles constituting the copolymer resin emulsion is in a specific range. The headline and the present invention were completed.

  That is, the present invention comprises a polymerizable unsaturated monomer (a) containing no epoxy group, acid group, hydroxyl group or hydrolyzable silyl group, a polymerizable unsaturated monomer (b) having an epoxy group, and an acid group. An unsaturated monomer mixture comprising a polymerizable unsaturated monomer (c), a hydroxyl group-containing polymerizable unsaturated monomer (d), and a polymerizable unsaturated monomer (e) having a hydrolyzable silyl group is emulsion-polymerized. A water-dispersible resin composition comprising the copolymer resin emulsion prepared, wherein the copolymer resin has a weight average molecular weight of 30,000 to 500,000 and the average particle size of the resin particles constituting the copolymer resin emulsion Provided is a water-dispersible resin composition for coating steel sheets having a diameter of 70 nm or less.

  The glass transition temperature of the copolymer resin is preferably 20 ° C. or higher.

  Polymerizable unsaturated monomer (b) having an epoxy group, acid group-containing polymerizable unsaturated monomer (c), hydroxyl group-containing polymerizable unsaturated monomer (d), polymerizable unsaturated monomer having a hydrolyzable silyl group (e ) Is preferably about 0.1 to 10% by weight based on the total amount of the polymerizable unsaturated monomers (a), (b), (c), (d) and (e).

  As the polymerizable unsaturated monomer (a) which does not contain any of an epoxy group, an acid group, a hydroxyl group and a hydrolyzable silyl group, an alkyl group having 1 to 18 carbon atoms (meth) acrylic acid alkyl ester (a- 1) or (meth) acrylic acid alkyl ester (a-1) having 1 to 18 carbon atoms of the alkyl group, styrene monomer (a-2), (meth) acrylonitrile (a-3), amide Preferably used is a monomer mixture with at least one monomer selected from the group consisting of a bond-containing polymerizable unsaturated monomer (a-4) and a polyfunctional vinyl group-containing polymerizable unsaturated monomer (a-5). It is done.

  The copolymer resin emulsion includes 0.3 to 6% by weight of a reactive surfactant based on the total amount of polymerizable unsaturated monomers (a), (b), (c), (d) and (e). It is preferable that the unsaturated monomer mixture is emulsion-polymerized in the presence of. The copolymer resin emulsion is preferably one obtained by emulsion polymerization of an unsaturated monomer mixture in the presence of the radical chain transfer agent (f).

  The copolymer resin emulsion is preferably a core / shell type resin emulsion.

In the present invention, the glass transition temperature (Tg) of the copolymer resin is the glass transition temperature Tgi (i = 1) of each homopolymer of the monomer Mi (i = 1, 2,..., I) used for the polymerization. , 2,..., I) and each weight fraction Xi (i = 1, 2,..., I) of the monomer Mi, the following formula:
1 / Tg = Σ (Xi / Tgi)
It is a theoretical value calculated by a good approximation.

  The water-dispersible resin composition of the present invention has a resin having a weight average molecular weight in a specific range and a small particle size of resin particles, so that the denseness of the coating film is high, rust prevention, alkyd paint, and urethane foam. Excellent adhesion to topcoat materials such as. Moreover, it has high alkali resistance, and is excellent in adhesion to metal, water resistance, boiling water resistance, blocking resistance, and slipperiness. Furthermore, it does not require the addition of chromic acid or chromate pigments, and is excellent from the viewpoint of protecting the global environment. As a resin composition for steel sheet coating for the purpose of post-treatment and undercoating of general steel sheets and galvalume steel sheets. Is preferred.

  The water-dispersible resin composition of the present invention contains a copolymer resin emulsion obtained by emulsion polymerization of monomer components (a), (b), (c), (d) and (e).

  As a typical example of the polymerizable unsaturated monomer (a) that does not contain any of an epoxy group, an acid group, a hydroxyl group, and a hydrolyzable silyl group, the alkyl group has 1 to 18 carbon atoms (meth). Acrylic acid alkyl ester (a-1), styrenic monomer (a-2), (meth) acrylonitrile (a-3), amide bond-containing polymerizable unsaturated monomer (a-4), polyfunctional vinyl group-containing polymerizable And unsaturated monomers (a-5). The polymerizable unsaturated monomer (a) can be used alone or in combination of two or more.

  Examples of the (meth) acrylic acid alkyl ester (a-1) having 1 to 18 carbon atoms in the alkyl group include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, ( N-butyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, (meth) Examples include decyl acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, and the like. These 1 type (s) or 2 or more types are used in combination as appropriate. Among them, (meth) acrylic acid alkyl ester having 1 to 10 carbon atoms in the alkyl group is preferable.

  Examples of the styrene monomer (a-2) include α-methylstyrene, vinyltoluene and the like in addition to styrene. These monomers can be used alone or in combination of two or more.

  Examples of the amide bond-containing vinyl monomer (a-4) include acrylamide, methacrylamide, α-ethylacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, diacetone. (Meth) acrylamide, N-methylolacrylamide, N-methylolmethacrylamide, methylenebisacrylamide, methylenebismethacrylamide, N-vinylpyrrolidone and the like can be mentioned. These can be used alone or in combination of two or more.

  Examples of the polyfunctional vinyl group-containing polymerizable unsaturated monomer (a-5) include divinylbenzene, ethylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and allyl (meth). In addition to divinyl compounds such as acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) An acrylate etc. are mentioned. These may be used alone or in combination of two or more.

  As the polymerizable unsaturated monomer (a) which does not contain any of an epoxy group, an acid group, a hydroxyl group and a hydrolyzable silyl group, at least the above (meth) is used in order to obtain good film formability and high coating film hardness. The acrylic acid alkyl ester (a-1) is preferably used, and it is particularly preferable to use the (meth) acrylic acid alkyl ester (a-1) and the styrenic monomer (a-2) in combination. Further, together with the (meth) acrylic acid alkyl ester (a-1), or the (meth) acrylic acid alkyl ester (a-1) and the styrenic monomer (a-2), (meth) acrylonitrile (a-3), It is also preferable to use at least one monomer selected from an amide bond-containing polymerizable unsaturated monomer (a-4) and a polyfunctional vinyl group-containing polymerizable unsaturated monomer (a-5).

  When (meth) acrylonitrile (a-3) is used as a copolymerization monomer, a dense and tough film is formed due to the orientation and crystallization effect of the cyano group in the polymer, thereby adversely affecting water and rust prevention. Permeation is suppressed, and rust prevention is further improved. Moreover, since the coating film hardness is increased, blocking resistance and slipperiness are also improved.

  When the polymerizable unsaturated monomer (a-4) containing an amide bond is used as a copolymerization monomer, the emulsion's Newtonian viscosity is imparted and the leveling and workability of the paint are improved. Thickness uniformity is increased, and the generation of rust from thin portions can be prevented.

  When a polyfunctional vinyl group-containing polymerizable unsaturated monomer (a-5) is used as a copolymerization monomer, crosslinking within the emulsion particles is promoted, and the hardness of the paint film is increased, and at the same time, blocking resistance, abrasion resistance, slippage are increased. Improved. It also has an effect of improving water resistance and alkali resistance.

  The amount of the (meth) acrylic acid alkyl ester (a-1) is, for example, 20 to 100% by weight, preferably 30 to 80% by weight, more preferably, based on the total amount of the polymerizable unsaturated monomer (a). It is about 35 to 70% by weight. The amount of the styrenic monomer (a-2) is, for example, 0 to 80% by weight, preferably 20 to 70% by weight, more preferably 30 to 60% by weight, based on the total amount of the polymerizable unsaturated monomer (a). Degree. The amount of (meth) acrylonitrile (a-3) is usually 0 to 20% by weight (for example 1 to 20% by weight), preferably 0 to 10%, based on the total amount of the polymerizable unsaturated monomer (a). It is about weight% (for example, 1 to 10 weight%). The amount of the amide bond-containing polymerizable unsaturated monomer (a-4) is usually 0 to 20% by weight (eg 1 to 20% by weight), preferably based on the total amount of the polymerizable unsaturated monomer (a). Is about 0 to 10% by weight (for example, 1 to 10% by weight), and the amount of the polyfunctional vinyl group-containing polymerizable unsaturated monomer (a-5) is the total amount of the polymerizable unsaturated monomer (a). On the other hand, it is usually 0 to 10% by weight (eg 1 to 10% by weight), preferably 0 to 5% by weight (eg 1 to 5% by weight).

  Examples of the polymerizable unsaturated monomer (b) having an epoxy group include monomers having a glycidyl group such as glycidyl acrylate, glycidyl methacrylate (GMA), glycidyl chlorate, glycidyl allyl ether, β-glycidyl methacrylate, (3 , 4-epoxychlorohexyl) methyl methacrylate, 3-epoxychloro-2-hydroxypropyl methacrylate and the like. Usually, a monomer having a glycidyl group such as glycidyl methacrylate is often used.

  By using the polymerizable unsaturated monomer (b) having an epoxy group, synergy between the affinity of the epoxy group on the metal surface and the adhesion of the acid group-containing polymerizable unsaturated monomer (c) to the metal surface Due to the effect, adhesion to the metal is further promoted, and a great effect is exhibited for further improvement of the rust prevention effect. Furthermore, a three-dimensional network structure is formed by a cross-linking reaction between an epoxy group and a carboxyl group in the resin composition, and the resin composition has the effect of imparting water resistance, boiling water resistance, alkali resistance, blocking resistance, and slipperiness. Demonstrated.

  The amount of the polymerizable unsaturated monomer (b) having an epoxy group is, for example, 0.1 to 10 weights based on the total amount of the monomer components (a), (b), (c), (d) and (e). %, Preferably about 1 to 7% by weight. By setting the amount of the polymerizable unsaturated monomer (b) having an epoxy group within this range, when the resin composition containing the copolymer resin emulsion is used as a paint, the affinity of the coating film to the metal surface is improved. As a result, the adhesion is improved, and at the same time, an excellent rust prevention power is obtained. If the said usage-amount of an epoxy-group-containing polymerizable unsaturated monomer (b) is less than 0.1 weight%, the rust prevention power of a coating film is weak, and water resistance, boiling water resistance, and blocking resistance will fall easily. On the other hand, if the amount exceeds 10% by weight, the internal structure of the resin coating will be unevenly microgel-like, causing cracks due to strain, water permeation, and rusting catalyst components such as chloride ions and sulfuric acid. In order to facilitate the permeation of ions, the rust preventive power is weak and the strength of the coating film tends to decrease.

  As the acid group-containing polymerizable unsaturated monomer (c), for example, an ethylenically unsaturated compound having in the molecule thereof at least one acid group selected from a carboxyl group, a sulfonic acid group, a phosphoric acid group and the like can be used.

  Among the acid group-containing polymerizable unsaturated monomers (c), examples of the carboxyl group-containing polymerizable unsaturated monomers include acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, α-ethylacrylic acid, β-ethylacrylic acid, Examples thereof include β-propylacrylic acid, β-isopropylacrylic acid, itaconic acid, maleic anhydride and fumaric acid. Examples of the sulfonic acid group-containing polymerizable unsaturated monomer include p-vinylbenzenesulfonic acid, p-acrylamidepropanesulfonic acid, t-butylacrylamidesulfonic acid and the like. Examples of the phosphoric acid group-containing polymerizable unsaturated monomer include phosphoric acid monoester of 2-hydroxyethyl acrylate, phosphoric acid monoester of 2-hydroxypropyl methacrylate, etc., and these are trade names “Light Ester PM” (Kyoeisha). (Available from Chemical Co., Ltd.). The acid group-containing polymerizable unsaturated monomer (c) can be used alone or in combination of two or more.

  By using the acid group-containing polymerizable unsaturated monomer (c) as a copolymerization component, the storage composition, mechanical stability, and freezing of a resin composition containing a copolymer resin emulsion and a water-based paint using the same are used. Various stability such as stability can be obtained. In addition, because of the strong adhesion to the metal substrate during the formation of the coating film, water enters the interface between the metal substrate and the coating film. Therefore, it is possible to obtain a high rust preventive power.

  The amount of the acid group-containing polymerizable unsaturated monomer (c) is, for example, 0.1 to 10 weights based on the total amount of the monomer components (a), (b), (c), (d) and (e). %, Preferably 1 to 7% by weight. When the amount of the acid group-containing polymerizable unsaturated monomer (c) used is less than 0.1% by weight, the polymerization stability of the resin and the various stability are deteriorated, and the adhesion of the coating film to the metal surface and the rust-preventing power. Tends to be weak. On the other hand, when it exceeds 10% by weight, the polymerization stability of the resin and the above-mentioned various stability deteriorate, and the water resistance and alkali resistance of the obtained coating film tend to be weak.

  The hydroxyl group-containing polymerizable unsaturated monomer (d) is not particularly limited as long as it is an unsaturated monomer having a hydroxyl group. Examples thereof include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxy methacrylate. Examples thereof include hydroxyl-containing acrylic monomers such as propyl, hydroxybutyl acrylate, hydroxybutyl methacrylate, and ε-caprolactone-modified acrylic monomer. These 1 type (s) or 2 or more types are used in combination. As the ε-caprolactone-modified acrylic monomer, trade names “Placcel FA-1”, “Placcel FA-2”, “Placcel FA-3”, “Placcel FA-4”, “Placcel FA” manufactured by Daicel Chemical Industries, Ltd. -5 "," Placcel FM-1 "," Placcel FM-2 "," Placcel FM-3 "," Placcel FM-4 "," Placcel FM-5 "and the like.

  By using the hydroxyl group-containing polymerizable unsaturated monomer (d) as a copolymerization component, the hydrophilicity of the resin composition containing the copolymer resin emulsion and the water-based paint using the same increases, and as a building material heat insulating material after the coating film is formed. Affinity with top coating materials such as foamed polyurethane, foamed polyethylene, and top coating is increased, and adhesion is improved.

  The amount of the hydroxyl group-containing polymerizable unsaturated monomer (d) is, for example, 0.1 to 10% by weight based on the total amount of the monomer components (a), (b), (c), (d) and (e), Preferably it is 1 to 7 weight%. When the amount of the hydroxyl group-containing polymerizable unsaturated monomer (c) used is less than 0.1% by weight, the affinity with the top coating material is poor and the adhesion tends to be poor. On the other hand, if it exceeds 10% by weight, the hydrophilicity is too strong and the water resistance of the coating film tends to be weak.

  The polymerizable unsaturated monomer (e) having a hydrolyzable silyl group is not particularly limited as long as it is an unsaturated monomer having a hydrolyzable silyl group in the molecule. For example, γ- (meth) acryloxypropyl Monomers containing alkoxysilyl groups such as trimethoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropyltriethoxysilane Can be mentioned.

  By using a polymerizable unsaturated monomer (e) having a hydrolyzable silyl group as a copolymerization component, the water resistance of a resin composition containing a copolymer resin emulsion and an aqueous paint film using the same is increased. As a result, the rust prevention power is improved. Moreover, blocking resistance and slipperiness are also improved by crosslinking.

  The amount of the polymerizable unsaturated monomer (e) having a hydrolyzable silyl group is, for example, 0.1% based on the total amount of the monomer components (a), (b), (c), (d) and (e). -10% by weight, preferably 1-5% by weight. If the said usage-amount of the polymerizable unsaturated monomer (e) which has a hydrolyzable silyl group is less than 0.1 weight%, the water resistance of a coating film will be weak and it will become the tendency for rust prevention power to be inferior. On the other hand, if it exceeds 10% by weight, the polymerization stability of the synthetic resin emulsion tends to decrease.

  The glass transition temperature (Tg) of the copolymer resin in the present invention is preferably 20 ° C. or higher, more preferably 35 ° C. or higher. When a resin composition containing a copolymer resin emulsion having a copolymer resin Tg of 20 ° C. or higher is used as a rust preventive paint for a pre-coated metal based on a general steel plate or a galbarium steel plate, the adhesiveness of the coating film is small. Good blocking resistance. Moreover, even when immersed in warm water or boiling water, the resin is hardly deformed due to high temperature, and exhibits excellent warm water resistance, boiling water resistance, and rust resistance.

  When the Tg of the copolymer resin is less than 20 ° C., the adhesiveness of the coating film is large, the mechanical strength is often insufficient, the blocking resistance is inferior, and at the same time, the hot water resistance, boiling water resistance, and rust prevention power are low. Become. Although the upper limit of Tg of copolymer resin is not specifically limited, For example, it is about 100 degreeC.

  In the emulsion polymerization of the present invention, a radical chain transfer agent (f) is used as necessary. When the radical chain transfer agent (f) is used, the emulsion polymerization proceeds smoothly, and the weight average molecular weight and particle diameter of the resulting resin are relatively low, so that the coating is uniform and dense (small gaps between resin particles). A film is formed smoothly, and alkali resistance, adhesion to a substrate, and rust prevention can be improved. Such a radical chain transfer agent (f) is not particularly limited as long as the molecular weight can be adjusted at the time of the polymerization reaction. For example, mercaptan compounds (thiol compounds), alcohols, amines, halogenated hydrocarbons, Examples thereof include terpenoid compounds and oligomers of monomers having an ethylenically unsaturated bond (such as oligomers of styrene monomers). The radical chain transfer agent (f) can be used alone or in combination of two or more.

  Examples of the mercaptan compound include methyl mercaptan, ethyl mercaptan, butyl mercaptan, n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, mercaptoethanol. , Mercaptopropanol, mercaptobutanol, mercaptoacetic acid, mercaptopropionic acid, thiomalic acid, trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptopropionate), benzyl mercaptan, phenyl mercaptan, cyclohexyl mercaptan 1-thioglycerol, 2,2'-dimercaptodiethyl ether, 2,2'-dimercaptodip Pyrether, 2,2'-dimercaptodiisopropyl ether, 3,3'-dimercaptodipropyl ether, 2,2'-dimercaptodiethyl sulfide, 3,3'-dimercaptodipropyl sulfide, octanethiol, decanethiol , Dodecanethiol and the like.

  Examples of the alcohol include methanol, ethanol, isopropanol, n-butanol, n-propanol, isobutanol, t-butanol, pentanol, hexanol, benzyl alcohol, octanol, decanol, dodecanol, octadecanol and the like.

  Examples of the amine include methylamine, ethylamine, isopuramine, n-butylamine, n-propylamine, isobutylamine, t-butylamine, pentylamine, hexylamine, benzylamine, octylamine, decylamine, dodecylamine, octadecylamine and the like. Is mentioned.

  Examples of the halogenated hydrocarbon include dichloromethane, dibromomethane, carbon tetrachloride, carbon tetrabromide and the like. Examples of the terpenoid compound include terpinolene, myrcene, limonene, α-pinene, β-pinene and the like. Moreover, as an oligomer of a monomer having an ethylenically unsaturated bond, for example, a monomer dimer having an ethylenically unsaturated bond such as α-methylstyrene dimer (for example, a dimer of a styrene monomer) Etc.

  The amount of the radical chain transfer agent (f) used is, for example, 0.01 to 10% by weight with respect to the total amount of the monomer components (a), (b), (c), (d) and (e), preferably 0.01 to 5% by weight. When the amount of the radical chain transfer agent (f) used is less than 0.01% by weight, a resin having a large molecular weight and particle diameter is formed, and the denseness of the coating film tends to be lowered. Is not preferable because the molecular weight is reduced and various functions as a resin (adhesion, water resistance, rust resistance, etc.) are likely to be lowered.

  In the emulsion polymerization of the present invention, an emulsifier is usually used. The emulsifier may be a non-reactive general emulsifier, but it is advantageous in terms of the performance of the adhesive to use a reactive surfactant for the reason described later.

  Although it does not restrict | limit especially as a non-reactive general emulsifier, For example, a hydrocarbon group which has a C6 or more carbon atom, carboxylate, sulfonate, sulfate partial ester, phosphate An anionic or nonionic (nonionic) emulsifier selected from micelle compounds having a hydrophilic moiety such as a phosphate partial ester in the same molecule; micelle compounds having a polyoxyalkylene group in the molecule Used. Among these, as an anionic emulsifier, alkali metal salt or ammonium salt of sulfuric acid half ester of alkoxyphenols or higher alcohols; alkali metal salt or ammonium salt of alkyl or allyl sulfonate; polyoxyethylene alkylphenyl ether, polyoxyethylene Examples thereof include alkali metal salts or ammonium salts of alkyl ether or polyoxyethylene allyl ether sulfate half ester. Examples of nonionic emulsifiers include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene allyl ether. These non-reactive emulsifiers can be used alone or in combination of two or more. These general-purpose anionic and nonionic emulsifiers are various anions having radically polymerizable unsaturated double bonds in the molecule, that is, having groups such as acrylic, methacrylic, propenyl, allyl, allyloxy, and maleic acid groups. And nonionic reactive surfactants are used in appropriate combination.

  The reactive surfactant is not particularly limited, and includes a group containing a reactive group such as a polymerizable unsaturated group and a group that exhibits a surface active action such as a nonionic hydrophilic group or an anionic hydrophilic group. Any reactive surfactant having may be used. Examples of the group containing a reactive group such as a polymerizable unsaturated group include a vinyl group, an allyl group, a methacryl group, an allyloxy group, a methallyloxy group, an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group. It is done.

  Representative reactive surfactants include, for example, compounds represented by the following formula (1), (2), (3), (4), (5), (6) or (7). .

（式中、Ａ¹は炭素数２〜４の置換若しくは無置換のアルキレン基、Ｒ¹は水素原子又はメチル基、Ｒ²は炭素数７〜２４の炭化水素基又は炭素数７〜２４のアシル基、Ｘは水素原子、又はノニオン系若しくはアニオン系の親水基、ｍは０〜１００の整数を示す）

(In the formula, A ¹ is a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R ¹ is a hydrogen atom or a methyl group, R ² is a hydrocarbon group having 7 to 24 carbon atoms or an acyl having 7 to 24 carbon atoms. Group, X is a hydrogen atom, or a nonionic or anionic hydrophilic group, m represents an integer of 0 to 100)

（式中、Ａ²は炭素数２〜４の置換若しくは無置換のアルキレン基、Ｒ³は炭素数１〜１８の炭化水素基、Ｒ⁴は水素原子又は炭素数１〜１８の炭化水素基、ｐは２〜２００の整数、Ｍはアルカリ金属又はＮＨ₄を示す）

(In the formula, A ² is a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R ³ is a hydrocarbon group having 1 to 18 carbon atoms, R ⁴ is a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, p is an integer of 2 to 200, M represents an alkali metal or NH ₄ )

（式中、Ａ³は炭素数２〜４の置換若しくは無置換のアルキレン基、Ｒ⁵は水素原子又はメチル基、Ｒ⁶は水素原子又はアルキル基、ｑは０〜１００の整数、Ｍはアルカリ金属又はＮＨ₄を示す）

(In the formula, A ³ represents a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents a hydrogen atom or an alkyl group, q represents an integer of 0 to 100, and M represents an alkali. Represents metal or NH ₄ )

（式中、Ｒ⁷は置換基を有していてもよい炭化水素基、Ｒ⁸は水素原子又はメチル基、Ｍはアルカリ金属又はＮＨ₄を示す）

(In the formula, R ⁷ is a hydrocarbon group which may have a substituent, R ⁸ is a hydrogen atom or a methyl group, M is an alkali metal or NH ₄ )

（式中、Ｒ⁹は置換基を有していてもよい炭化水素基、Ｒ¹⁰は水素原子又はメチル基、Ｍはアルカリ金属又はＮＨ₄を示す）

(In the formula, R ⁹ is a hydrocarbon group which may have a substituent, R ¹⁰ is a hydrogen atom or a methyl group, M is an alkali metal or NH ₄ )

（式中、Φは多官能フェニル基、Ａ⁴、Ａ⁵は、それぞれ炭素数２〜４の置換若しくは無置換のアルキレン基、Ｒ¹¹は水素原子又はメチル基、ｒ、ｓは、それぞれ１〜１００の整数、Ｍはアルカリ金属又はＮＨ₄を示す）

(Wherein Φ is a polyfunctional phenyl group, A ⁴ and A ⁵ are each a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R ¹¹ is a hydrogen atom or a methyl group, and r and s are each 1 to 1. An integer of 100, M represents an alkali metal or NH ₄ )

（式中、Ａ⁶は炭素数２〜４の置換若しくは無置換のアルキレン基、Ｒ¹²は水素原子又はメチル基、Ｍはアルカリ金属又はＮＨ₄を示す）

(In the formula, A ⁶ represents a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, R ¹² represents a hydrogen atom or a methyl group, M represents an alkali metal or NH ₄ )

In the formula (1), examples of the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ¹ include, for example, ethylene, propylene, trimethylene, tetramethylene group, and halogen atom (fluorine atom, chlorine atom). Etc.), an alkylene group to which a substituent such as a hydroxyl group or an alkoxy group (C _1-4 alkoxy group such as methoxy or ethoxy group) is bonded. Examples of the hydrocarbon group having 7 to 24 carbon atoms in R ² include alkyl groups such as octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl and octadecyl groups; alkenyl groups such as octenyl and decenyl groups; 4-methylphenyl, Examples thereof include alkylaryl groups such as 4-propylphenyl, 4-octylphenyl, 4-nonylphenyl, 4-decylphenyl, 4-dodecylphenyl, 4-tetradecylphenyl and 4-hexadecylphenyl groups. Examples of the acyl group having 7 to 24 carbon atoms in R ² include aliphatic, alicyclic or aromatic acyl groups such as octanoyl, nonanoyl, dodecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl and 4-nonylbenzoyl groups. Is mentioned. m is preferably an integer of about 0 to 50.

（式中、Ａ⁷は炭素数２〜４の置換若しくは無置換のアルキレン基、Ｍはアルカリ金属又はＮＨ₄、ｎは０〜１００の整数を示す）
で表される基が例示される。Ａ⁷における炭素数２〜４の置換若しくは無置換のアルキレン基としては、前記Ａ¹における炭素数２〜４の置換若しくは無置換のアルキレン基と同様のものが挙げられる。Ｍにおけるアルカリ金属としては、例えば、ナトリウム、カリウムなどが挙げられる。ｎは、好ましくは０〜３０程度の整数である。 Examples of the nonionic or anionic hydrophilic group in X include various groups including a polyoxyalkylene group, a sulfonic acid group, a carboxyl group, and the like. As a representative group, the following formula (8)

(In the formula, A ⁷ represents a substituted or unsubstituted alkylene group having 2 to 4 carbon atoms, M represents an alkali metal or NH ₄ , and n represents an integer of 0 to 100)
The group represented by these is illustrated. Examples of the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ⁷ include the same as the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ¹ . Examples of the alkali metal in M include sodium and potassium. n is preferably an integer of about 0 to 30.

In the formula (2), the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms for A ^2, are the same as those of the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in the A ^1. Examples of the hydrocarbon group having 1 to 18 carbon atoms in R ³ and R ⁴ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, hexyl, octyl, nonyl, decyl, dodecyl, Alkyl groups such as hexadecyl and octadecyl groups; alkenyl groups such as vinyl, allyl, hexenyl, octenyl, nonenyl and decenyl groups; aralkyl groups such as benzyl, 2-phenylethyl, 3-phenylpropyl and 4-phenylbutyl groups It is done. Among these, a hydrocarbon group having 4 to 18 carbon atoms is particularly preferable. The alkali metal in M is the same as described above. p is preferably an integer of about 2 to 50.

In the formula (3), examples of the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ³ include the same as the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ¹ . Examples of the alkyl group in R ⁶ include about 1 to 20 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, t-butyl, hexyl, octyl, nonyl, decyl, dodecyl, and hexadecyl groups. And the like. q is preferably an integer of about 0 to 50. The alkali metal in M is the same as described above.

In formula (4) and formula (5), examples of the hydrocarbon group optionally having a substituent in R ⁷ and R ⁹ include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, alkyl groups such as t-butyl, hexyl, octyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl groups; alkenyl groups such as vinyl, allyl, hexenyl, octenyl, decenyl groups; cycloalkyl groups such as cyclohexyl groups; phenyl groups, etc. Aryl groups; aralkyl groups such as benzyl and 2-phenylethyl; or a halogen atom (fluorine atom, chlorine atom, etc.), hydroxyl group, alkoxy group (C _1-4 alkoxy group such as methoxy, ethoxy group, etc.), etc. And a hydrocarbon group to which the substituents are bonded. M is the same as described above.

In formula (6), the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ⁴ and A ⁵ is the same as the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ¹ . Can be mentioned. r and s are preferably integers of about 1 to 50. The alkali metal in M is the same as described above. As the reactive surfactant represented by the formula (6), a trade name “Antox MS-60” manufactured by Nippon Emulsifier Co., Ltd. is commercially available.

In Formula (7), examples of the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ⁶ include the same as the substituted or unsubstituted alkylene group having 2 to 4 carbon atoms in A ¹ . The alkali metal in M is the same as described above.

  The reactive surfactant is copolymerized or grafted with the monomer components (a), (b), (c), (d) and (e), and is present as a structural unit of a high molecular weight polymer after polymerization. To do. For this reason, non-reactive general emulsifiers remain in the water phase in the low-molecular form in the water phase even after polymerization, and the cast film of the resin dispersion finally obtained is therefore water and boiling resistant. The cast film of the resin dispersion obtained using a reactive surfactant, while having poor alkali resistance, rust resistance, solvent resistance and adhesion, has high water resistance, boiling water resistance, Demonstrates alkali resistance, rust prevention, solvent resistance and adhesion.

  The amount of the reactive surfactant used in the emulsion polymerization is, for example, about 0.3 to 6% by weight with respect to the total amount of the monomer components (a), (b), (c), (d) and (e). It is. When the amount used is less than 0.3% by weight, the stability of emulsion polymerization is poor, grit is likely to occur during the polymerization, the stability of the resin dispersion obtained after the polymerization is poor, and the commercial value is poor. It tends to be a thing. On the other hand, if it exceeds 6% by weight, water resistance, boiling water resistance, alkali resistance, rust resistance, solvent resistance and adhesiveness may be hindered, and there may be a problem in economy. Is not preferable.

  In the present invention, in addition to the monomer components (a), (b), (c), (d) and (e), as long as the properties such as rust prevention, adhesion, water resistance and alkali resistance are not impaired, Alternatively, in addition to these and a chain transfer agent, other polymerizable unsaturated monomers may be copolymerized. The amount of the polymerizable unsaturated monomer used is, for example, 20% by weight or less, preferably 10% with respect to the total amount of the monomer components (a), (b), (c), (d) and (e). % Or less, more preferably 5% by weight or less.

  In the present invention, the copolymer resin emulsion is particularly preferably a core / shell type resin emulsion. Here, as the definition of the core / shell, in the emulsion polymerization, when the polymerization is performed in multiple stages (for example, two stages), the resin component that is the core formed in the first stage polymerization is referred to as the core, and the second A resin component that becomes a shell formed on the surface of the core in the polymerization after the step is referred to as a shell. For example, when the monomer is dropped in two stages and the polymerization is performed, the monomer is dropped in the first stage, the resin component formed by the polymerization corresponds to the core, and after the core formation, the monomer in the second stage The resin component formed by polymerization corresponds to the shell.

  In the core-shell type synthetic resin emulsion, the ratio of the core part to the shell part is 20% by weight to 95% by weight, preferably 30% by weight to 90% by weight, based on the total weight, It is desirable that the shell portion is in the range of 5 wt% to 80 wt%, preferably 10 wt% to 70 wt%.

  The reason why the core / shell type synthetic resin emulsion is particularly preferable in the present invention is that a tougher and harder resin film is obtained compared to the homopolymerized emulsion, and the film is tough and has a high hardness even when used as a paint film. Therefore, it is advantageous in terms of blocking resistance and slipperiness. Such features are difficult to obtain in any case outside the range of the core and shell.

  In the core-shell type synthetic resin emulsion, the monomer composition used for the core part and the shell part as a whole is composed of the monomer components (a), (b), (c), (d) and (e), The Tg of the synthetic resin (copolymer resin) calculated from the total monomer composition may be 20 ° C. or higher, but the Tg of the shell portion is preferably 10 ° C. or higher (particularly 20 ° C. or higher) higher than the core portion. When the Tg difference between the shell part and the core part is less than 10 ° C., or conversely, when the Tg of the core part is higher than the Tg of the shell part, it is difficult to obtain sufficient coating film hardness, which tends to be disadvantageous in blocking resistance and slipperiness. . The Tg of the shell portion (when the shell portion is a multilayer, the outermost layer Tg) is preferably 50 ° C. or higher (eg, 50 to 100 ° C.), more preferably 60 ° C. or higher (eg, 60 to 100 ° C.). is there. Moreover, it is preferable that the polymerizable unsaturated monomer (b) which has an epoxy group is contained in the monomer component which comprises a shell part at least.

  In the emulsion polymerization, the monomer components (a), (b), (c), (d) and (e) are used in an aqueous liquid, using a radical polymerization initiator, and a general emulsifier and / or a reactive surfactant. , And if necessary, by heating in the presence of the radical chain transfer agent (f) with stirring. The reaction temperature is preferably about 30 to 100 ° C. and the reaction time is preferably about 1 to 10 hours, for example. The reaction temperature is adjusted by adding the radical chain transfer agent (f) and the monomer mixture liquid or monomer pre-emulsion liquid all at once or dropping them into a reaction vessel charged with water and a general emulsifier and / or reactive surfactant. Good.

  As the radical polymerization initiator, known initiators usually used in emulsion polymerization of acrylic resins can be used. Specifically, as a water-soluble free radical polymerization initiator, for example, persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, etc., these oxidizing agents, sodium bisulfite, thio So-called redox initiators composed of a combination with a reducing agent such as sodium sulfate, Rongalite, and ascorbic acid are each used, for example, in the form of an aqueous solution.

  In addition, in the emulsion polymerization, the use of an auxiliary agent (chain transfer agent) for molecular weight adjustment such as mercaptan compounds and lower alcohols, in order to advance the emulsion polymerization, for example, smooth and uniform formation of the coating film In many cases, it is preferable to improve the adhesion to the base material and improve the rust prevention property.

  Emulsion polymerization methods include any one of the following, such as the usual one-stage continuous monomer uniform dropping method, the core-shell polymerization method which is a multistage monomer feed method, and the power feed polymerization method in which the monomer composition fed continuously during the polymerization is changed. Can be legal.

  Thus, the copolymer resin emulsion in the present invention is prepared. The weight average molecular weight of the copolymer resin is about 30,000 to 500,000, preferably 50,000 to 400,000, and more preferably about 60,000 to 300,000. When the weight average molecular weight is 30,000 or less, the water resistance, boiling water resistance, alkali resistance, acid resistance, and rust resistance are likely to decrease. When the weight average molecular weight exceeds 500,000, the adhesion to the metal substrate, alkali resistance, and rust resistance are reduced. Is prone to decline. Moreover, the molecular weight distribution (Mw / Mn; Mw is a weight average molecular weight, Mn is a number average molecular weight) of copolymer resin is 2-10, for example, Preferably it is 2-8, More preferably, it is the range of 2-5. A weight average molecular weight and a number average molecular weight can be measured by GPC method (polystyrene conversion).

  The average particle diameter of the copolymer resin particles constituting the copolymer resin emulsion in the present invention is 70 nm or less (for example, 25 to 70 nm), preferably 60 nm or less (for example, 25 to 60 nm), and more preferably 50 nm or less ( For example, 25 to 50 nm). The average particle diameter of the resin particles can be measured with an electrophoretic light scattering particle size distribution analyzer. When the average particle diameter is 70 nm or less, a highly dense coating film with small voids (holes) between the resin particles can be formed, so that water resistance, boiling water resistance, alkali resistance, acid resistance, rust resistance, etc. It can improve and prevent the generation of voids and blisters. On the other hand, if the average particle diameter exceeds 70 nm, a film with low density is likely to be formed, water resistance, boiling water resistance, alkali resistance, acid resistance, rust resistance and the like are lowered, and voids, blisters and the like are generated.

  In the present invention, the smaller the particle size distribution of the copolymer resin particles (the more uniform the particles), the better. When the particle size distribution of the copolymer resin particles is narrow, the resin particles are closely arranged and the voids (holes) between the resin particles are smaller, so that a highly dense coating film can be formed. Accordingly, the water resistance, boiling water resistance, alkali resistance, acid resistance, rust resistance and the like are remarkably improved.

  The weight average molecular weight and molecular weight distribution of the copolymer resin are, for example, the type and amount of monomer constituting the resin, the type and amount of the radical chain transfer agent (f), the polymerization temperature, the dropping rate of the monomer, the polymerization initiator It can be adjusted by selecting the type and amount.

  The water-dispersible resin composition of the present invention may contain an additive such as a basic compound, mainly based on the copolymer resin emulsion. As the basic compound, ammonia, various amines, alkali metal salts and the like are used. By adding a basic compound, a part or all of the acid contained in the copolymer resin emulsion is neutralized, and the stability of the copolymer resin emulsion is ensured.

  The water-dispersible resin composition of the present invention can be used as it is to form a clear film as a coating agent as it is, or a colored pigment, extender pigment, aqueous urethane resin dispersion, dispersant, curing can be added to the resin composition. Various additives such as an agent, a wetting agent, an antifoaming agent, a zirconium compound as a rust preventive or rust preventive pigment, zinc phosphate, aluminum tripolyphosphate, and a wax emulsion as a slipping agent can be blended and used as a paint. Examples of the color pigment include titanium oxide and iron oxide. As extender pigments, calcium carbonate, clay, mica, talc and the like are used. As the curing agent, melamine resin, isocyanate resin, or the like is used.

  The content of the copolymer resin in the water-dispersible resin composition can be appropriately set according to the use, but is generally about 10 to 70% by weight.

  The water-dispersible resin composition of the present invention is particularly useful as a paint for coating steel sheets. In addition, rust prevention, adhesion to metals, paints such as alkyd paint, urethane paint, epoxy paint, adhesion to topcoat materials such as foamed polyurethane and foamed polyethylene as building material insulation, water resistance and boiling water resistance and resistance to water Since it is excellent in alkali resistance and blocking resistance, it can be suitably used particularly as a precoat metal primer. Moreover, it is suitable for surface treatment and post-treatment of general steel plates and galvalume steel plates.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited by these Examples. In the examples and comparative examples, “parts” and “%” are based on weight unless otherwise specified. In addition, a gel permeation chromatograph (manufactured by Shimadzu Corporation, trade name “LC-10”) is used for measurement of weight average molecular weight and molecular weight distribution, and electrophoretic light scattering is used for measurement of particle diameter (average particle diameter). A particle size distribution analyzer (trade name “ELS-800” manufactured by Otsuka Electronics Co., Ltd.) was used. Moreover, the standard deviation of the particle diameter was calculated | required with respect to 100 resin particles extracted at random, and CV value (variation coefficient) of the particle diameter was computed from the said formula.

（式中、Ｒはアルキル基を示し、ｑは０〜１００の整数を示す）
で表される反応性界面活性剤［商品名「アデカリアソープＳＲ−２０」、旭電化工業（株）製］（f1）５部を仕込み、７５℃に昇温した。別途、次に示すモノマー、乳化剤及び水の混合液を高圧ホモジナイザーを用いて均一に乳化し、第１段目モノマー乳化液として滴下ロートに仕込んだ。
（第１段目モノマー乳化液）
反応性界面活性剤（f1） ４部
ＭＭＡ（メタクリル酸メチル）（a1） ４５部
ＳＭ（スチレン）（a2） ７５部
２ＥＨＡ（アクリル酸２−エチルヘキシル）（a3） ５０部
アクリロニトリル（ＡＮ）（a4） １０部
ＭＡＡ（メタクリル酸）（c1） ５部
２ＨＥＭＡ（２−ヒドロキシエチルメタクリレート）（d1） １０部
加水分解性シリル基含有重合性不飽和モノマー［商品名「Ａ−１７４」、γ−メタクリロキシプロピルトリメトキシシラン、日本ユニカー（株）製］（e1） ５部
ＰＥＭＰ［トリメチロールプロパントリス（３−メルカプトプロピオネート）：連鎖移動剤］ １部
水 １３０部
また、別途、次に示すモノマー混合液を第２段目モノマーとして滴下ロートに仕込んだ。
（第２段目モノマー）
ＭＭＡ（メタクリル酸メチル）（a1） ９０部
ＳＭ（スチレン）（a2） ５０部
アクリロニトリル（ＡＮ）（a4） ５部
ＧＭＡ（グリシジルメタクリレート）（b1） ２０部
ＭＡＡ（メタクリル酸）（c1） １０部
２ＨＥＭＡ（２−ヒドロキシエチルメタクリレート）（d1） １０部
２ＨＥＡ（２−ヒドロキシエチルアクリレート）（d2） １５部
さらに、別途、次に示す滴下用開始剤水溶液を別の滴下ロートに仕込んだ。
（滴下用開始剤水溶液）
過硫酸カリウム ３部
水 ５０部
次に、前記反応容器内に、前記第１段目モノマー乳化液の５％を添加し、７５℃に加熱後、前記滴下用開始剤水溶液の５％を投入し、１０分間プレ重合反応を行った。この間反応容器の内温は自動的に８０℃に上昇した。その後、残りの第１段目モノマー乳化液を８０℃で３時間かけて、また滴下用開始剤水溶液を８０℃で６時間かけて一定速度で同反応容器内に滴下した。第１段目モノマー乳化液の滴下終了後、８０℃に保持して１時間熟成反応を行い、第２段目モノマーを２時間かけて滴下した。その後、８０℃に１時間保ち、熟成を行い、室温に冷却した後、アンモニア水（２５％）４部を反応容器内に投入し、水分散性樹脂組成物（コア−シェル型エマルジョン）を得た。得られた樹脂のコア部の理論Ｔｇは３８℃、シェル部の理論Ｔｇは７６℃、オーバーオールの理論Ｔｇは５６℃であり、重量平均分子量は１９３０００、分子量分布は４．３、平均粒子径は４９ｎｍであった。 Example 1 (two-stage polymerization)
In a reaction vessel for producing an ordinary acrylic resin emulsion equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 407 parts of water and the following formula (9)

(In the formula, R represents an alkyl group, and q represents an integer of 0 to 100)
5 parts of a surfactant (trade name “ADEKA rear soap SR-20” manufactured by Asahi Denka Kogyo Co., Ltd.) (f1) was charged, and the temperature was raised to 75 ° C. Separately, the following mixture of monomers, emulsifier and water was uniformly emulsified using a high-pressure homogenizer, and charged into the dropping funnel as a first-stage monomer emulsion.
(First stage monomer emulsion)
Reactive surfactant (f1) 4 parts MMA (methyl methacrylate) (a1) 45 parts SM (styrene) (a2) 75 parts 2EHA (2-ethylhexyl acrylate) (a3) 50 parts Acrylonitrile (AN) (a4) 10 parts MAA (methacrylic acid) (c1) 5 parts 2HEMA (2-hydroxyethyl methacrylate) (d1) 10 parts Hydrolyzable silyl group-containing polymerizable unsaturated monomer [trade name “A-174”, γ-methacryloxypropyl Trimethoxysilane, manufactured by Nippon Unicar Co., Ltd.] (e1) 5 parts PEMP [trimethylolpropane tris (3-mercaptopropionate): chain transfer agent] 1 part water 130 parts Was charged into the dropping funnel as the second stage monomer.
(Second stage monomer)
MMA (methyl methacrylate) (a1) 90 parts SM (styrene) (a2) 50 parts Acrylonitrile (AN) (a4) 5 parts GMA (glycidyl methacrylate) (b1) 20 parts MAA (methacrylic acid) (c1) 10 parts 2HEMA (2-Hydroxyethyl methacrylate) (d1) 10 parts 2HEA (2-hydroxyethyl acrylate) (d2) 15 parts Further, the following initiator solution for dropping was separately charged in another dropping funnel.
(Initiator aqueous solution for dripping)
Potassium persulfate 3 parts Water 50 parts Next, 5% of the first stage monomer emulsion is added to the reaction vessel, heated to 75 ° C., and then 5% of the dropping initiator aqueous solution is added. A prepolymerization reaction was performed for 10 minutes. During this time, the internal temperature of the reaction vessel automatically increased to 80 ° C. Thereafter, the remaining first-stage monomer emulsion was dropped into the reaction vessel at a constant rate over 3 hours at 80 ° C. and the initiator aqueous solution for dropping over 6 hours at 80 ° C. After completion of dropping of the first stage monomer emulsion, aging reaction was carried out for 1 hour while maintaining at 80 ° C., and the second stage monomer was added dropwise over 2 hours. Thereafter, the mixture was kept at 80 ° C. for 1 hour, matured, cooled to room temperature, and then 4 parts of ammonia water (25%) was put into the reaction vessel to obtain a water-dispersible resin composition (core-shell type emulsion). It was. The theoretical Tg of the core part of the obtained resin is 38 ° C., the theoretical Tg of the shell part is 76 ° C., the theoretical Tg of the overall is 56 ° C., the weight average molecular weight is 193,000, the molecular weight distribution is 4.3, and the average particle diameter is It was 49 nm.

（式中、Φは多官能フェニル基、ｒ、ｓは、それぞれ１〜１００の整数、Ｍはアルカリ金属又はＮＨ₄を示す）
で表される反応性界面活性剤［商品名「アントックスＭＳ−６０」、ビス（ポリオキシエチレン多環フェニルエーテル）メタクリレート硫酸エステル塩、日本乳化剤（株）製］（f4）を用いた以外は、すべて実施例１と同様にして重合を行い、水分散性樹脂組成物を得た。得られた樹脂の重量平均分子量は１８２０００、分子量分布は３．７、平均粒子径は４８ｎｍであった。 Example 2
In Example 1, instead of the reactive surfactant (trade name “ADEKA rear soap SR-20”) (f1), the same amount of the following formula (10)

(Wherein Φ is a polyfunctional phenyl group, r and s are each an integer of 1 to 100, and M is an alkali metal or NH ₄ )
Except that the reactive surfactant represented by the formula [trade name “ANTOX MS-60”, bis (polyoxyethylene polycyclic phenyl ether) methacrylate sulfate ester, manufactured by Nippon Emulsifier Co., Ltd.] (f4) was used. All were polymerized in the same manner as in Example 1 to obtain a water-dispersible resin composition. The obtained resin had a weight average molecular weight of 182,000, a molecular weight distribution of 3.7, and an average particle size of 48 nm.

Example 3
In Example 1, polymerization was carried out in the same manner as in Example 1 except that 1 part of n-dodecyl mercaptan was used instead of PEMP as a chain transfer agent to obtain a water-dispersible resin composition. The obtained resin had a weight average molecular weight of 131,000, a molecular weight distribution of 4.8, and an average particle diameter of 52 nm.

Example 4
In Example 1, polymerization was carried out in the same manner as in Example 1 except that 8 parts of α-methylstyrene dimer was used instead of PEMP as the chain transfer agent to obtain a water-dispersible resin composition. The obtained resin had a weight average molecular weight of 214,000, a molecular weight distribution of 4.0, and an average particle diameter of 36 nm.

Example 5 (two-stage polymerization)
In Example 1, instead of 75 parts of the first-stage monomer SA, 50 parts of 2EHA, SM45 parts, 2EHA0 parts, 80 parts of EA (ethyl acrylate), second-stage monomer MMA90 parts, instead of 2HEA15 parts, MMA75 parts, Emulsion polymerization was carried out in the same manner as in Example 1 except that 2 HEA was 0 parts and EA was 25 parts to obtain a water-dispersible resin composition. The theoretical Tg of the core part of the obtained resin is 41 ° C., the theoretical Tg of the shell part is 75 ° C., the theoretical Tg of the overall is 56 ° C., the weight average molecular weight is 141,000, the molecular weight distribution is 3.9, and the average particle diameter is It was 41 nm.

Example 6 (two-stage polymerization)
In Example 1, instead of 45 parts of first stage monomer MMA and 75 parts of SA, MMA 120 parts, SM0 part, second stage monomer MMA 90 parts, SM50 part instead of MMA 140 parts, MMA 140 parts, SM0 part Emulsion polymerization was performed in exactly the same manner as in Example 1 to obtain a water-dispersible resin composition. The theoretical Tg of the core part of the obtained resin is 40 ° C., the theoretical Tg of the shell part is 77 ° C., the theoretical Tg of the overall is 57 ° C., the weight average molecular weight is 81,000, the molecular weight distribution is 3.9, and the average particle diameter is It was 32 nm.

Comparative Example 1
In Example 1, polymerization was carried out in the same manner as in Example 1 except that PEMP as a chain transfer agent was not used to obtain a water-dispersible resin composition. The obtained resin had a weight average molecular weight of 731,000, a molecular weight distribution of 3.1, and an average particle diameter of 48 nm.

Comparative Example 2
In Example 1, the amount of the reactive surfactant used at the time of charging was changed from 5 parts to 1 part, and the amount of the reactive surfactant used in the first-stage monomer emulsion was changed from 4 parts to 8 parts. The emulsion was subjected to emulsion polymerization in exactly the same manner as in Example 1 except that PEMP as a chain transfer agent was not used, and a water-dispersible resin composition was obtained. The obtained resin had a weight average molecular weight of 791,000, a molecular weight distribution of 4.2, and an average particle diameter of 125 nm.

Comparative Example 3
In Example 1, emulsion polymerization was performed in exactly the same manner as in Example 1 except that 90 parts of MMA and 90 parts of GMA were used instead of 90 parts of MMA and 0 parts of GMA to obtain a water-dispersible resin composition. . The theoretical Tg of the core part of the obtained resin is 39 ° C., the theoretical Tg of the shell part is 83 ° C., the theoretical Tg of the overall is 59 ° C., the weight average molecular weight is 91,000, the molecular weight distribution is 3.5, and the average particle diameter is It was 42 nm.

Performance evaluation test To each water-dispersible resin composition obtained in the examples and comparative examples, an aqueous butyl cellosolve solution was added so that the MFT was 20 ° C. or lower in accordance with the respective Tg, and on the surface of the galvalume steel plate. It was coated with a # 8 bar coater so that the dry film thickness was 1 μm, dried for 10 seconds after the plate temperature reached 80 ° C., air-cooled, allowed to stand for 24 hours, and then measured for the following characteristics. The results are shown in Table 1.

(1) Normal adhesion The 100-scale gobang tape test of the coating film was performed at room temperature to measure the normal adhesion. It was displayed as a fraction of the number of galvanic eyes (numerator) remaining without peeling with respect to the number of galvanic eyes 100 (denominator).

(2) Foamed urethane adhesion After the polyurethane foam was heat-sealed on the coating film, it was peeled off and the adhesion state was observed.
○: At the time of peeling, cohesive failure of the polyurethane foam part was observed. Δ: At the time of peeling, cohesive failure of the polyurethane foam part and interface peeling coexisted. ×: Interface peeling occurred on the entire surface.

(3) Corrosion resistance (SS resistance)
A salt spray resistance test (SST) of the coated steel sheet was performed for 200 hours using a salt spray tester, and the blisters and the peeled state of the coated surface were observed.
○: Blister, peeling, etc. were scarce and good. Δ: Blister, peeling, etc. occurred at 1/3 or more and less than 2/3. ×: Blister, peeling, etc. were 2/3 or more of the coating surface. Occurred all over

(4) Blocking resistance The coated surfaces were put together, applied with a load of 200 kg / cm ² at 40 ° C., left for 7 days, then peeled off, and the fixed state was observed.
○: Not fixed △; Slightly fixed ×: Fixed

(5) Alkali resistance After the parts other than the coated surface of the coated plate are sealed with paraffin, they are immersed in a 1% aqueous sodium hydroxide solution at 20 ° C. for 5 hours, and the appearance change of the coated surface, especially the darkened state, is as before the coating. Comparison was made and visual determination was performed.
○: Good with no change in appearance △: About 20% of the whole is dark ×: More than 50% of the whole is dark

(6) Warm water resistance The portions other than the coated surface of the coated plate were sealed with paraffin, and then immersed in water at 80 ° C. for 96 hours to visually determine the appearance of the coated surface, such as the softened state and the blister generation state.
○: There is no blister, etc., and the appearance is good. Δ: Although blisters are generated, the film is in close contact with the metal. ×: A large amount of blisters are generated, and the film is peeled off from the metal surface.

Claims (7)

  Polymerizable unsaturated monomer (a) containing no epoxy group, acid group, hydroxyl group or hydrolyzable silyl group, polymerizable unsaturated monomer (b) having an epoxy group, and acid group-containing polymerizable unsaturated monomer A copolymer resin obtained by emulsion polymerization of an unsaturated monomer mixture comprising (c), a hydroxyl group-containing polymerizable unsaturated monomer (d), and a polymerizable unsaturated monomer (e) having a hydrolyzable silyl group; A water-dispersible resin composition containing an emulsion, wherein the copolymer resin has a weight average molecular weight of 30,000 to 500,000, and an average particle diameter of resin particles constituting the copolymer resin emulsion is 70 nm or less. Water dispersible resin composition for steel sheet coating.   The water-dispersible resin composition for coating steel sheets according to claim 1, wherein the glass transition temperature of the copolymer resin is 20 ° C or higher.   Polymerizable unsaturated monomer (b) having an epoxy group, acid group-containing polymerizable unsaturated monomer (c), hydroxyl group-containing polymerizable unsaturated monomer (d), polymerizable unsaturated monomer having a hydrolyzable silyl group (e 2) is used in an amount of 0.1 to 10% by weight based on the total amount of the polymerizable unsaturated monomers (a), (b), (c), (d) and (e), respectively. Water dispersible resin composition for steel sheet coating.   The polymerizable unsaturated monomer (a) which does not contain any of an epoxy group, an acid group, a hydroxyl group and a hydrolyzable silyl group is a (meth) acrylic acid alkyl ester (a-1) in which the alkyl group has 1 to 18 carbon atoms. ), Or (meth) acrylic acid alkyl ester (a-1) having 1 to 18 carbon atoms, styrene monomer (a-2), (meth) acrylonitrile (a-3), amide bond A monomer mixed with at least one monomer selected from the group consisting of a polymerizable unsaturated monomer (a-4) containing a polyfunctional vinyl group and a polymerizable unsaturated monomer (a-5) containing a polyfunctional vinyl group 1. A water dispersible resin composition for coating steel sheets according to 1.   The copolymer resin emulsion contains 0.3 to 6% by weight of reactive surfactant based on the total amount of polymerizable unsaturated monomers (a), (b), (c), (d) and (e). The water-dispersible resin composition for steel sheet coating according to claim 1, which is a copolymer resin emulsion obtained by emulsion polymerization of an unsaturated monomer mixture in the presence.   The water dispersible resin composition for steel sheet coating according to claim 1, wherein the copolymer resin emulsion is a copolymer resin emulsion obtained by emulsion polymerization of an unsaturated monomer mixture in the presence of the radical chain transfer agent (f).   The water-dispersible resin composition for coating steel sheets according to claim 1, 5 or 6, wherein the copolymer resin emulsion is a core-shell type resin emulsion.