JP2001294630A - Aqueous resin and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aqueous resin capable of producing a coating film forming agent capable of stably advancing crosslinking with an unsaturated monomer even in a high concentration of an ethylene-unsaturated carboxylic acid copolymer being a seed particle, having excellent solvent resistance, alkali resistance, corrosion resistance and topcoating adhesivity and to obtain the aqueous resin obtained by the method. SOLUTION: An unsaturated monomer comprising an epoxy group-containing unsaturated monomer and/or a polyfunctional unsaturated monomer as an essential component is subjected to emulsion polymerization by using a water dispersion of an ethylene-unsaturated carboxylic acid copolymer as seed particles in the presence of a colloidal silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing an aqueous resin capable of forming a film having excellent solvent resistance, alkali resistance and corrosion resistance, and an aqueous resin obtained therefrom.

[0002]

2. Description of the Related Art There have been known various aqueous resins used as film-forming materials such as paints and rust preventives. However, especially for coating a metal, a film having excellent adhesion and corrosion resistance is used. In order to obtain the above, an aqueous dispersion of an ethylene-unsaturated carboxylic acid copolymer is often used. In order to obtain higher corrosion resistance, colloidal silica is often added to and mixed with the aqueous dispersion of the ethylene-unsaturated carboxylic acid copolymer. Further, in order to improve the storage stability of the coating agent using the above-mentioned aqueous dispersion and the adhesion of the top coat to the coating film, other resins may be blended or composited.

For example, JP-A-60-228510 discloses a method for producing an aqueous resin obtained by emulsion-polymerizing an unsaturated monomer in an ethylene-unsaturated carboxylic acid copolymer dispersion. Also, Japanese Unexamined Patent Publication No.
No. 3 discloses an aqueous solution in which an unsaturated monomer is added to an ethylene-unsaturated carboxylic acid copolymer dispersion, emulsion-polymerized, and post-crosslinking is performed after polymerization, and a water-based resin obtained by adding a colloidal sol such as SiO ₂ to the aqueous resin. A method for treating a chromate-coated plated steel sheet is described. Further, JP-A-10-176
No. 119 discloses a metal surface treating agent obtained by emulsion polymerization of an unsaturated monomer in an aqueous dispersion of an alkali metal neutralized product of an ethylene-unsaturated carboxylic acid copolymer (ionomer) and an aqueous polyester resin. It has been disclosed.

[0004] However, in the invention of Japanese Patent Application Laid-Open No. 60-228510, in the case of a neutralized product with ammonia or an organic amine, the dispersion stability may be impaired at the time of polymerization of the unsaturated monomer due to its high viscosity. Yes, JP
In the invention disclosed in Japanese Patent No. 73083, the crosslinking is further performed after the emulsion polymerization. Therefore, particularly when it is desired to increase the degree of crosslinking, agglomerates are generated or the viscosity is increased, and the dispersion stability is impaired. Furthermore, the invention of JP-A-10-176119 has the problem that the hydrolysis resistance of the aqueous polyester resin is sometimes low, and the solvent resistance of the formed film is low due to lack of crosslinking reactivity. .

Thus, emulsion polymerization of an unsaturated monomer in an aqueous dispersion of an ethylene-unsaturated carboxylic acid copolymer is effective for a composite of an ethylene-unsaturated carboxylic acid copolymer and an acrylic resin. However, since the viscosity of the ethylene-unsaturated carboxylic acid copolymer serving as seed particles is high, it has been difficult to stably proceed polymerization under high concentration conditions.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to stably promote the crosslinking with unsaturated monomers even when the ethylene-unsaturated carboxylic acid copolymer as seed particles is at a high concentration, Solvent resistance, alkali resistance,
An object of the present invention is to provide a method for producing an aqueous resin capable of producing a film-forming agent excellent in corrosion resistance and top coat adhesion, and an aqueous resin obtained by this method.

[0007]

According to the process for producing an aqueous resin of the present invention, an aqueous dispersion of an ethylene-unsaturated carboxylic acid copolymer is used as seed particles, and an epoxy group-containing unsaturated monomer is used in the presence of colloidal silica. And / or emulsion polymerization of unsaturated monomers containing a polyfunctional unsaturated monomer as an essential component. An aqueous resin selected from an aqueous polyurethane resin, an aqueous polyester resin, and an aqueous acrylic resin may be used in combination as the seed particles.

The aqueous resin of the present invention is obtained by the above-mentioned production method, and may have an average particle diameter of 10 to 80 nm.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The ethylene-unsaturated carboxylic acid copolymer used as seed particles in the production method of the present invention is a copolymer obtained by radically polymerizing ethylene and an unsaturated carboxylic acid such as (meth) acrylic acid under high temperature and high pressure. Preferably, the copolymerization amount of the unsaturated carboxylic acid accounts for 15 to 20% by mass of the total amount and the melt index is 100 to 3000. As such an ethylene-unsaturated carboxylic acid copolymer, for example, an ethylene-acrylic acid copolymer is sold by Dow Chemical Company under the trade names Primacol 5980 and 5990, and by Mitsui / Dupont Polychemical Company under the name of Nucrel N5130H. ing. An aqueous dispersion is obtained by neutralizing a part or all of the carboxyl groups contained in these ethylene-unsaturated carboxylic acid copolymers with a water-soluble amine such as ammonia, a metal hydroxide and a metal oxide. Can be obtained.

An aqueous resin selected from an aqueous polyurethane resin, an aqueous polyester resin, and an aqueous acrylic resin can be used as seed particles together with the ethylene-unsaturated carboxylic acid copolymer. These aqueous resins may be used alone or in combination of two or more.

As an example of the aqueous polyurethane resin, a hydrophilic NCO-terminated prepolymer having a nonionic group or an anionic group is synthesized from diisocyanate and diol, added with water, dispersed, and then chain-extended with an amine. And the like. Examples of the aqueous polyester resin include those obtained by neutralizing a polyester having a carboxyl terminal obtained by dehydration condensation of a polyol and a dibasic acid with an amine and dispersing in water, and the like. Examples of the water-based acrylic resin include a polymer obtained by radical polymerization of an unsaturated monomer essentially including an unsaturated carboxylic acid in an organic solvent, which is neutralized with an amine, dispersed in water, and then desolventized, or an interface. Examples thereof include those obtained by emulsion polymerization of an unsaturated monomer in an aqueous activator solution.

The solid content of the particles selected from the above-mentioned aqueous polyurethane resin, aqueous polyester resin and aqueous acrylic resin is preferably equal to or less than the mass of the solid content of the ethylene-unsaturated carboxylic acid copolymer. ,
Exceeding this range may cause a decrease in adhesion to metals and corrosion resistance.

The production method of the present invention is characterized in that emulsion polymerization is carried out in the presence of colloidal silica. Colloidal silica has a significantly lower viscosity than aqueous resins. Therefore, if this is made to coexist with the above-mentioned seed particles, the viscosity is lowered during the polymerization and the stability is increased. As a result, fine water-dispersed particles can be stably obtained even when the resin concentration is relatively high.

The colloidal silica used in the production method of the present invention preferably has a pH stability in a range from neutral to alkaline, and has good coexistence stability with seed particles. Examples of colloidal silica meeting such conditions include Snowtex N, Snowtex C (manufactured by Nissan Chemical Industries, Ltd.), Cataloid S-20L, and Cataroid SA (manufactured by Catalysis Kasei Kogyo). The addition amount is in the range of 10 to 100 parts by mass, more preferably 15 to 50 parts by mass, based on the resin solid content of the seed particles. If the addition amount is less than 10 parts by mass, the hardness and corrosion resistance of the formed film are reduced, and if it exceeds 100 parts by mass, the film-forming property and water resistance may be reduced.

The unsaturated monomers used for emulsion polymerization in the production method of the present invention contain an epoxy group-containing unsaturated monomer and / or a polyfunctional unsaturated monomer as essential components. Examples of the epoxy group-containing unsaturated monomer include glycidyl esters of unsaturated carboxylic acids such as glycidyl (meth) acrylate and allyl glycidyl ether. Examples of the polyfunctional unsaturated monomer include ethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, glycerin dimethacrylate, divinylbenzene, trimethylolpropane triacrylate, and pentaerythritol triacrylate.

In addition, other radically polymerizable unsaturated monomers other than the epoxy group-containing unsaturated monomer and / or the polyfunctional unsaturated monomer can be appropriately used in combination. Such a radical polymerizable unsaturated monomer is not particularly limited, but is preferably a hydrophobic one, and examples thereof include the following. Vinyl compounds such as styrene, α-methylstyrene, acrylonitrile, and vinyl acetate, and methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-
(Meth) acrylic acid alkyl esters such as ethylhexyl (meth) acrylate. In addition to the above-mentioned hydrophobic monomers, hydroxyl-containing compounds such as 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate; carboxyl-containing compounds such as acrylic acid, methacrylic acid, and itaconic acid; and ( Hydrophilic monomers such as amide compounds such as (meth) acrylamide and N, N-dimethylacrylamide can also be used.

The total solids content of the unsaturated monomers is preferably from 20 to 200 parts by mass, more preferably from 30 to 120 parts by mass, based on 100 parts by mass of the solid content of the ethylene-unsaturated carboxylic acid copolymer. Department is good. If the amount used is less than 20 parts by mass, no composite effect is observed, and if it exceeds 200 parts by mass, the particle size becomes large or the film-forming property is reduced, so that the adhesion and the corrosion resistance are reduced.

The method for producing an aqueous resin of the present invention is carried out as follows. The mixture obtained from the aqueous dispersion of the ethylene-unsaturated carboxylic acid copolymer, colloidal silica, and the aqueous resin selected from the aqueous polyurethane resin, the aqueous polyester resin, and the aqueous acrylic resin, if necessary, is appropriately heated while stirring. Here, unsaturated monomers containing an epoxy group-containing unsaturated monomer and / or a polyfunctional unsaturated monomer as an essential component are added together with a polymerization initiator. As the initiator, those commonly used in emulsion polymerization can be used, for example, ammonium persulfate, persulfates such as potassium persulfate, azobiscyanovaleric acid,
Azo compounds such as azobisisobutyronitrile can be mentioned. The addition of the unsaturated monomer and the polymerization initiator is preferably performed not at once, but continuously, or divided into several portions, from the viewpoint of preventing an excessive reaction. The reaction can be carried out according to a known seed emulsion polymerization method, the temperature can be 30 to 90 ° C., the time can be 30 minutes to 8 hours, and the solid content concentration can be 15 to 45% by mass.

When emulsion polymerization is carried out in the presence of colloidal silica, the particles hardly agglomerate. Therefore, the particle size of the resulting aqueous resin depends on the particle size of the seed particles, the mass ratio of the seed resin, and the amount of colloidal silica added. And particle size,
The average particle diameter becomes 10 to 80 nm. When the particle diameter is in this range, the film-forming properties are good and a dense film can be formed, so that various properties are excellent.

The unsaturated monomers contain an epoxy group and / or a plurality of unsaturated bonds, and other functional groups such as a carboxyl group. Therefore, the crosslinking reaction by emulsion polymerization proceeds between the carboxyl group of the seed particles and the unsaturated monomers, and / or between the unsaturated monomers. Further, the polymer particles formed in the seed particles by the three-dimensional crosslinking of the unsaturated monomers are physically entangled with the seed particles, and in some cases, are chemically bonded. Will be tough.

[0021]

Next, the present invention will be described more specifically with reference to examples and comparative examples.

Example 1 Synthesis of Aqueous Resin An ethylene-acrylic acid copolymer (Primacol 5980, manufactured by Dow Chemical Co.) was added to ammonia in a flask equipped with a stirrer, temperature controller, dropping funnel, nitrogen inlet tube and condenser. 400 g (solid content: 25% by mass) of an aqueous dispersion adjusted to a neutralization ratio of 80% with water, 300 g of colloidal silica (Snowtex N, manufactured by Nissan Chemical Industries, solid content: 20% by mass), and an aqueous polyurethane resin (Adecabon Titer HUX) −32
0, manufactured by Asahi Denka Kogyo Co., Ltd., solid content: 32% by mass) and heated to 83 ° C.

Subsequently, under a nitrogen atmosphere, 1/10 of the monomer mixture obtained from 35 g of glycidyl methacrylate, 21 g of styrene and 14 g of methyl methacrylate was added and stirred for 10 minutes, and 1 g of azobiscyanovaleric acid was added to N, N- A quarter amount of a polymerization initiator aqueous solution neutralized with 0.6 part of dimethylaminoethanol and dissolved in 60 g of deionized water was charged to initiate polymerization. Ten minutes after the addition of the polymerization initiator, the remaining monomer mixture and the aqueous initiator solution were dropped uniformly over 60 minutes and 70 minutes, respectively. After the completion of the dropwise addition, aging was continued for 120 minutes at the same temperature to complete the reaction.
After cooling, the mixture was filtered through a wire mesh, solid content was 28% by mass, and average particle size was 40
nm aqueous resin dispersion was obtained.

The film-forming degreasing, melting 55 wt% aluminum washed thickness 0.5 mm - on the surface of the zinc alloy coated steel sheet (commercially available), the aqueous resin dispersion obtained above, a dry film thickness of 1. 5 g / m ²
Apply with a bar coater so that it becomes 260
C. and dried for 8 seconds. At this time, the temperature at which the object was reached was 80 ° C. The cooled one is used as a test plate,
The solvent resistance, corrosion resistance, alkali resistance and adhesion of the topcoat paint were evaluated by the following methods, and the results are shown in Table 1.

Evaluation Method <Average Particle Diameter> A part of the obtained aqueous resin was diluted with deionized water and measured with a dynamic light scattering analyzer (ELS-800, manufactured by Otsuka Electronics Co., Ltd.).

<Polymerization Stability> The state of the aqueous resin after polymerization was evaluated according to the following criteria. ：: Filterable and no aggregates Δ: Difficult to filter and / or the amount of aggregates generated is 2% by mass or more ×: Unfilterable and / or the amount of aggregates generated is 5% by mass or more

<Solvent resistance> The test plate was set on a rubbing tester, and 0.5 kg of gauze impregnated with xylene was used.
After pressing and reciprocating 10 times at f / cm ² , the state of the film on the surface of the test plate was visually observed. ：: scarcely scarred △: slightly scratched ×: scratched all over

<Alkali Resistance> After the test plate was immersed in a 1% aqueous NaOH solution for 30 minutes, the surface appearance was visually measured. ：: almost no blackening △: slightly blackening ×: blackening of the entire surface

<Corrosion Resistance> The test plate was subjected to a salt spray tester based on JISZ2371 to measure the rust generation area after 72 hours, and evaluated according to the following criteria. The results shown in Table 1 were obtained. ：: less than 10% △: 10% or more to less than 50% ×: 50% or more

<Adhesion of Topcoat> A melamine alkyd resin paint (Olga Select 200, manufactured by Nippon Paint Co., Ltd.) was applied on a test plate with a bar coater so as to have a dry film thickness of 30 μm. And baked to make a painted plate. Using a cutter knife, 100 grids at 1 mm intervals were formed on the coating film of the painted plate, and an adhesive tape was stuck thereon and peeled vertically. Then, the number of grids where the coating film remained was measured and evaluated according to the following criteria. : 100 remaining number △: ９９ 99 to 51 ×: ５０ 50 or less

Examples 2 to 4 The same apparatus as in Example 1 except that the formulations shown in Table 1 were changed.
The reaction was performed according to the procedure to obtain an aqueous resin dispersion. Further, a test plate was prepared and evaluated in the same manner as in Example 1. Table 1 shows the obtained results.

Comparative Example 1 The same apparatus as in Example 1 except that the formulation was changed to the formulation shown in Table 1,
The reaction was performed according to the procedure to obtain an aqueous resin dispersion. To this was added 300 parts by mass of Snowtex N to prepare a coating solution, which was then prepared and evaluated in the same manner as in Example 1. Table 1 shows the obtained results.

Comparative Examples 2 to 4 The same apparatus as in Example 1 except that the formulations shown in Table 1 were changed.
The reaction was performed according to the procedure to obtain an aqueous resin dispersion. Further, a test plate was prepared and evaluated in the same manner as in Example 1. Table 1 shows the obtained results.

[0034]

[Table 1]

As is clear from the contents of Table 1, the aqueous resin produced in this example had an average particle diameter of 40 to 52 nm and high polymerization stability. The formed film is
It had excellent solvent resistance, alkali resistance, corrosion resistance, and overcoat adhesion.

[0036]

The aqueous resin of the present invention can be stably emulsion-polymerized by using a seed polymerization method without using an emulsifier. In addition to this, colloidal silica is allowed to coexist in the reaction system, so that the viscosity of the reaction solution is reduced, the polymerization stability is improved, and fine particles can be synthesized.

In addition, since the ethylene-unsaturated carboxylic acid copolymer and the epoxy group-containing unsaturated monomer and / or the polyfunctional unsaturated monomer are polymerized in a complex manner, the adhesion of the topcoat paint is improved by improving the compatibility of each resin. , The alkali resistance of the coating film is improved by lowering the average acid value of the resin, and the corrosion resistance, solvent resistance, and alkali resistance are improved by increasing the molecular weight by crosslinking.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C09D 123/08 C09D 123/08 133/02 133/02 151/00 151/00 163/10 163/10 F Terms (reference) 4J011 AA05 AA08 KA11 KB08 KB13 KB19 KB22 KB29 4J026 AA12 AA43 AA45 AB02 AB07 AC17 AC23 BA05 BA07 BA16 BA20 BA25 BA27 BA28 BA30 BA31 BA34 BA38 BB02 DB04 DB12 DB14 DB25 DB28 DB30 4J01 CB061 CB061 CB061 CB061 CG06 CG141 CG161 CG171 CH031 CH051 CH061 CH071 CH121 CH171 DD041 DD042 DD241 DD242 DG051 DG052 DG061 DG062 DG261 DG262 HA156 HA446 KA08 LA02 MA08 MA10 NA03 NA04 NA12

Claims (4)

[Claims] 1. An aqueous dispersion of an ethylene-unsaturated carboxylic acid copolymer is used as seed particles, and an epoxy group-containing unsaturated monomer and / or a polyfunctional unsaturated monomer is an essential component in the presence of colloidal silica. A method for producing an aqueous resin, comprising subjecting an unsaturated monomer to emulsion polymerization. 2. The method for producing an aqueous resin according to claim 1, wherein an aqueous resin selected from an aqueous polyurethane resin, an aqueous polyester resin and an aqueous acrylic resin is further used as the seed particles. 3. An aqueous resin obtained by the method according to claim 1. 4. The aqueous resin according to claim 3, having an average particle size of 10 to 80 nm.