JPH06306325A - Resin composition for water-base coating material - Google Patents

Abstract

PURPOSE:To provide the title compsn. which is excellent in storage stability and sprayability and gives a coating film excellent in gloss, resistances to water, corrosion, and chemicals, etc. CONSTITUTION:The compsn. (100 pts.wt.) is prepd. by compounding 85-30 pts.wt. water-base acrylic resin mainly comprising an acrylic emulsion resin having a number-average mol.wt. of 30,000 or lower, 5-30 pts.wt. acryl-modified epoxy resin obtd. by reacting a carboxylated copolmyer formed from an ethylenically unsatd. carboxylic acid and a copolymerizable monomer and having an acid value of 50-350 with a resin partially neutralized with an amine, and 10-40 pts.wt. amino resin.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a resin composition for water-based paint.

[0002]

2. Description of the Related Art In recent years, metal paints used in automobiles, industrial machines, steel furniture, home appliances, etc. have been replaced with conventional solvent-based paints from the viewpoints of effective use of petroleum resources, environmental protection, safety measures, etc. The transition to water-based paints is progressing. As such a water-based paint, there is a thermosetting paint made of a combination of an acrylic emulsion resin or a water-soluble acrylic resin and an amino resin, but the coating film is inferior in water resistance, corrosion resistance, chemical resistance and the like. Further, in JP-A-1-132667 and JP-A-2-212570, a molecular weight of 4,000 to 3 produced from an aqueous modified epoxy resin and an organic solvent is disclosed.
A thermosetting water-based coating composition comprising a combination of 50,000 water-based acrylic resins and amino resins is disclosed, and it is described that the coating film has good water resistance and corrosion resistance. However, when used for automobiles, steel furniture, home appliances, and the like, spray coating causes cracking and sagging, and a coating film having a high gloss and an excellent appearance cannot be obtained.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and is excellent in spray paintability.
It is an object of the present invention to provide a resin composition for water-based coatings capable of forming a coating film having excellent gloss, water resistance, corrosion resistance, chemical resistance and the like.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that an aqueous acrylic resin containing an acrylic emulsion resin having a number average molecular weight of 30,000 or less as a main component has good compatibility with the aqueous acrylic resin. The present invention has been completed by finding that the above object can be achieved by combining a specific water-based acrylic modified epoxy resin and an amino resin as a curing agent. That is, the present invention provides (A) an aqueous acrylic resin having an acrylic emulsion resin having a number average molecular weight of 30,000 or less as a main component, and (B) an ethylenically unsaturated carboxylic acid and a copolymerizable monomer having an acid value of 50. ~ 35
Acrylic-modified epoxy resin and (C) amino resin obtained by reacting an aromatic epoxy resin with a resin obtained by partially neutralizing a carboxyl group-containing copolymer of 0 with an amine,
/ (B) / (C) (weight ratio) is 85 to 30/5 to 30 /
The present invention relates to a resin composition for an aqueous coating composition containing 10 to 40 so that the total amount becomes 100.

Next, each component used in the resin composition for aqueous paint of the present invention will be described. The water-based acrylic resin used as the component (A) contains an acrylic emulsion resin having a number average molecular weight of 30,000 or less obtained by emulsion polymerization as a main component. This acrylic emulsion resin gives a tough coating film and gives it a property that does not easily sag during spray coating. Examples of the monomer used for producing the acrylic emulsion resin include 2-hydroxyethyl acrylate or methacrylate, hydroxyalkyl ester of α, β-monoethylenically unsaturated carboxylic acid such as 2-hydroxypropyl acrylate or methacrylate, acrylic acid and methacrylic acid. Α, β-monoethylenically unsaturated carboxylic acids such as acids, crotonic acid, itaconic acid, maleic acid and fumaric acid, esters of methacrylic acid and acrylic acid with alkanols having 1 to 12 carbon atoms, acrylonitrol, methacrylonitrile, Acrylamide, methacrylamide, styrene, vinyltoluene, vinylpyrrolidone, N, N-dimethylaminoethyl acrylate or methacrylate, vinyl pyridine, polyethylene glycol monoacrylate or methacrylate And the like.

One or more of the above monomers may be used, but 5 to 20% by weight of the above hydroxyalkyl ester of α, β-monoethylenically unsaturated carboxylic acid should be used. Is preferred and 5% by weight
If it is less than 20% by weight, crosslinking tends to be insufficient and a tough coating film tends to be difficult to obtain, and if it exceeds 20% by weight, the processability of the coating film tends to be poor. Further, the α, β-monoethylenically unsaturated carboxylic acid is preferably used in an amount of 1 to 10% by weight, more preferably 2 to 8% by weight. If this α, β-monoethylenically unsaturated carboxylic acid is less than 1% by weight, crosslinking tends to be insufficient and a tough coating film tends to be difficult to obtain, and if it exceeds 10% by weight, the processability and water resistance of the coating film will be poor. Tends to be inferior. The acrylic emulsion resin can be produced by a known method by emulsion polymerization, and is preferably produced at a temperature of 30 to 100 ° C. in the presence of a radical polymerization catalyst.
As the emulsifier, an anionic and / or nonionic surfactant or a reactive surfactant capable of reacting with the (meth) acrylic monomer can be used. Further, a chain transfer agent such as carbon tetrachloride or mercaptans may be used to control the molecular weight.

The emulsion after emulsion polymerization is neutralized with a tertiary amine such as triethylamine or dimethylaminoethanol (adjusted to pH 7 to 9) to give an aqueous acrylic emulsion resin. The amount of the tertiary amine used is preferably 0.5 to 1 mol per 1 mol of the carboxyl group contained in the emulsion before neutralization. The acrylic emulsion resin thus produced has a number average molecular weight of 30,000 or less. When the number average molecular weight exceeds 30,000, gloss decreases. The lower limit of the number average molecular weight is preferably 3,000. If the number average molecular weight is less than 3,000, the water resistance, corrosion resistance, phase hiding property, chemical resistance, etc. tend to be poor.

In the present invention, the water-based acrylic resin as the component (A) may contain other water-based acrylic resin in addition to the above-mentioned acrylic emulsion resin. Examples of other water-based acrylic resins include solution polymerization-type water-based acrylic resins. As the monomer for producing the solution-polymerizable water-based acrylic resin, the same ones as those mentioned above as the monomers for the acrylic emulsion resin can be used, except that hydroxyalkyl of α, β-monoethylenically unsaturated carboxylic acid is used. It is preferable to use 5 to 20% by weight of the ester, and if the amount is less than 5% by weight, crosslinking tends to be insufficient and a tough coating film tends to be difficult to obtain. is there. The α, β-monoethylenically unsaturated carboxylic acid is preferably used in an amount of 5 to 20% by weight, more preferably 7 to 15% by weight. If this α, β-monoethylenically unsaturated carboxylic acid is less than 5% by weight, the stability of the aqueous resin tends to decrease, and if it exceeds 20% by weight, the coating film tends to have poor water resistance and corrosion resistance.

The solution polymerization type aqueous acrylic resin is synthesized by a known method in an organic solvent in the presence of a radical polymerization catalyst. As the organic solvent, a hydrophilic organic solvent such as butyl cellosolve, isopropanol, 3-methyl 3-methoxybutanol and the like is preferable. The solution-polymerized polymer is neutralized with a tertiary amine such as triethylamine or dimethylaminoethanol (adjusted to pH 7 to 9) to give an aqueous solution-polymerizable aqueous acrylic resin. The amount of the tertiary amine used is preferably 0.5 to 1 mol per 1 mol of the carboxyl group contained in the emulsion before neutralization. The number average molecular weight of the solution-polymerizable water-based acrylic resin is preferably 3,000 to 30,000.
When the number average molecular weight is less than 3,000, water resistance, stain resistance, chemical resistance and the like tend to be poor, and when it exceeds 30,000, water solubility and water dispersibility tend to be poor. Solution-polymerizable water-based acrylic resin has the following properties: dispersibility of pigments, resistance to armpits during spray coating (creating bubbles in the coating layer and leaving craters after the bubbles burst), and coating smoothness. Has the effect of improving. The amount of the solution-polymerizable aqueous acrylic resin used is preferably such that the weight ratio of acrylic emulsion resin / solution-polymerizable aqueous acrylic resin is 100 to 40 / 0-60, and more preferably 95 to 50/5 to 50. preferable. If the amount of the solution-polymerizable water-based acrylic resin is too large, sagging tends to occur, and if it is too small, the effect of suppressing armpits tends to be small.

In the present invention, the component (B) is a resin obtained by partially neutralizing a carboxyl group-containing copolymer having an acid value of 50 to 350, which is composed of an ethylenically unsaturated carboxylic acid and a copolymerizable monomer, with an amine. An acrylic-modified epoxy resin obtained by reacting the above with an aromatic epoxy resin is used. The carboxyl group-containing copolymer used here is
It is obtained by copolymerization of an α, β-monoethylenically unsaturated carboxylic acid such as (meth) acrylic acid, maleic acid, itaconic acid, fumaric acid and a monomer copolymerizable therewith. Examples of the monomer copolymerizable with α, β-monoethylenically unsaturated carboxylic acid include α, β-monoethylenically unsaturated carboxylic acid such as 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Hydroxyalkyl ester, ester of (meth) acrylic acid and alkanol having 1 to 12 carbon atoms, (meth) acrylonitrol, (meth) acrylamide, styrene, vinyltoluene, vinylpyrrolidone, N, N-dimethylaminoethyl (meth) Examples thereof include acrylate, vinyl pyridine, polyethylene glycol mono (meth) acrylate and the like.

The amount of α, β-monoethylenically unsaturated carboxylic acid is adjusted so that the resulting copolymer has an acid value of 50 to 350. When the acid value is less than 50, the stability of the acrylic modified epoxy resin after grafting with the epoxy resin is poor, and when the acid value is more than 350, the water resistance of the coating film is lowered, and during the reaction with the epoxy resin, Easy to gel. The number average molecular weight of such a carboxyl group-containing copolymer is preferably 3,000 to 20,000. If this number average molecular weight is less than 3,000, the water resistance tends to decrease, and if it exceeds 20,000, the viscosity of the final product tends to be too high. Such a carboxyl group-containing copolymer is partially neutralized with a tertiary amine such as triethylamine or dimethylaminoethanol, and then reacted with an aromatic epoxy resin.

Aromatic epoxy resins that can be used include
Commercially available epoxy resin, for example, Epicoat 1001, 1004, 1007, 100 manufactured by Shell Chemical Co., Ltd.
9 etc. are mentioned. Further, bisphenol A and a diglycidyl ether of bisphenol A can be used by synthesizing one having a molecular weight adjusted to a purpose. The use ratio of the carboxyl group-containing copolymer / aromatic epoxy resin is preferably in the range of 5/95 to 40/60 by weight. If it is less than 5/95, the stability tends to decrease, and if it exceeds 40/60, the corrosion resistance and chemical resistance of the coating film tend to decrease.

The resin composition of the present invention contains an amino resin as the component (C). Examples of amino resins that can be used include those obtained by subjecting formaldehyde to an addition reaction with urea, melamine, benzoguanamine, acetoguanamine, spiroguanamine and the like, and further alkyletherifying with an alcohol having 4 or less carbon atoms. In order to obtain a coating film with good gloss, it is preferable to use an alkyl etherified amino resin which is alkyl etherified with an alcohol having 2 or less carbon atoms.

The resin composition of the present invention comprises (A) / (B) /
The weight ratio of the component (C) is 85 to 30/5 to 30/10 to 4
The components (A) to (C) are contained in a ratio of 0 (however,
(A) + (B) + (C) component = 100). The use ratio is preferably 85 to 50/5 to 20/10 to 30. If the amount of component (B) is low, the corrosion resistance and chemical resistance are reduced, and if it is too high, the phase rebound property of the coating film (when applied repeatedly, the coating film applied later is better than the previously applied coating film). Adhesion property) and weather resistance are deteriorated. On the other hand, if the amount of component (C) is too small, the crosslinking density will be low, and the hardness, water resistance, stain resistance and chemical resistance will decrease, and if it is too large, the processability of the coating film will decrease.

Further, an acid catalyst such as an inorganic acid such as hydrochloric acid or phosphoric acid or an organic acid such as paratoluenesulfonic acid may be added to the resin composition for an aqueous coating material of the present invention. As the hydrophilic organic solvent, butyl cellosolve, ethyl cellosolve, 3-methyl 3-methoxybutanol, isopropanol, butanol, etc. can be used, and these are appropriately selected and used from the viewpoints of spray coatability, smoothness of coating film, gloss, etc. Preferably. In the resin composition for water-based paint of the present invention,
If necessary, pigments and other additives can be further added. Further, the resin composition for water-based paint of the present invention can be applied to various coating methods, and as the coating method, for example, spray coating, roll coater coating, dipping coating and the like can be adopted.

[0016]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In the following, "%" means "% by weight" unless otherwise specified.

Production Example 1 (Production of Acrylic Emulsion Resin) 592 g of ion-exchanged water and Monogen Y1 were placed in a flask equipped with a stirrer, a reflux condenser, an inert gas inlet and a thermometer.
00 g (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was charged, and after heating to 60 ° C., 1.5 g of ammonium persulfate was added, to which 200 g of styrene and 60 of β-hydroxyethyl acrylate were added.
g, methacrylic acid 10 g, butyl acrylate 130 g
And 2 g of a mixture of 0.5 g of dodecyl mercaptan.
The solution was added dropwise over a period of time, and after the completion of the addition, a mixed solution of 0.5 g of ammonium persulfate and 5 g of water was added. After incubating for 2 hours, 8 g of triethylamine was added to give a number average molecular weight of 1
A milky white acrylic emulsion resin having a heating residue of 40.1% was obtained.

Production Example 2 (Production of Solution Polymerizable Aqueous Acrylic Resin) 300 g of 3-methyl-3-methoxybutanol was charged in the same flask as in Production Example 1 and heated to 110 ° C., then 200 g of styrene and β-hydroxyethyl methacrylate. 7
5 g, methacrylic acid 50 g, butyl acrylate 175
g and 10 g of azobisisobutyronitrile were added dropwise over 2 hours, and then the mixture was kept warm for 2 hours and cooled,
50 g of triethylamine and 160 g of water were added to obtain an aqueous acrylic resin having a number average molecular weight of 7,000 and a heating residue of 50%.

Production Example 3 (Production of Acrylic Modified Epoxy Resin) (a) Production of Solution of Copolymer Containing Carboxyl Group In a flask similar to Production Example 1, 175 g of butyl cellosolve was added.
And 100 g of butanol were charged and heated to 130 ° C., and 140 g of styrene and 13 parts of ethyl acrylate were added to the mixture.
A mixture of 0 g, 230 g of methacrylic acid and 3 g of p-butylperbenzoate was added dropwise over 3 hours, and then 25 g of butyl cellosolve and 115 g of butanol were added to the mixture.
The mixture was added dropwise over 0 minutes and kept warm for 2 hours. After cooling to 100 ° C, 155 g of dimethylaminoethanol and 235 g of water
Was added, and water was further added to adjust the heating residue to 37%. The acid value of the carboxyl group-containing copolymer thus obtained was 300 (solid content conversion) and the number average molecular weight was 8,000.

(B) Production of Aromatic Epoxy Resin Epoxy Resin DER343 (manufactured by Dow Chemical Co.) 405
g and bisphenol A 220 g were charged and reacted at 190 ° C. for 2 hours. An epoxy resin having a number average molecular weight of 6,500 and a weight average molecular weight of 19,000 was obtained.

(C) Production of Acrylic Modified Epoxy Resin One part of 625 g of the aromatic epoxy resin produced in the above (b) is added.
After heating to 00 ° C., 50 g of butanol and 435 g of a solution of the carboxyl group-containing copolymer prepared in the above (a) were added. Then, the mixture was stirred at 80 ° C. for 30 minutes to obtain an acrylic modified epoxy resin having an acid value of 34 and a number average molecular weight of 8,000. Further, 1100 g of water was added dropwise over 1 hour and adjusted with water so that the heating residue was 30% to obtain a milky white water-dispersed resin.

Production Example 4 (Production of Modified Epoxy Resin, Based on Example of JP-A-2-212570) In a flask similar to Production Example 1, 145 g of ethyl cellosolve was added.
And 5 g of propyl mercaptan were charged and heated to 115 ° C., then α-methylstyrene 20 g and acrylic acid 5
g, 2-hydroxypropyl acrylate 40 g, a mixture of ethyl acrylate 35 g and benzoyl peroxide 0.1 g was added dropwise over 3 hours, and after keeping the temperature for 1 hour, 0.8 g of benzoyl peroxide was further added, and the mixture was further reacted for 1 hour. After cooling, the ethyl cellosolve was distilled off under reduced pressure at 80 ° C. to obtain an acrylic resin solution having a number average molecular weight of 2,100 and a solid content of 85%. Next, Epicoat 1001 is 97.4.
After charging g, heating to 90 ° C., adding 10 g of orthophosphoric acid, heating to 130 ° C., reacting until the epoxy equivalent became 12,000 or more, and cooling, 121 g of ethyl cellosolve, 18.2 g of butyl cellosolve, dimethyl Aminoethanol (18.2 g) and water (100 g) were added to obtain a modified epoxy resin having a heating residue of 50%.

Example 1 The solution-polymerizable water-based acrylic resin produced in Production Example 2 was used in an amount of 10
After milling g (solid content), 30 g of diethylene glycol monobutyl ether and 100 g of titanium white with a sand mill, 60 g of acrylic emulsion resin (solid content) produced in Production Example 1 and 10 g of acrylic modified epoxy resin produced in Production Example 3 (solid content) ) And hexamethoxymethylated melamine (CYMEL 303 manufactured by Mitsui Toatsu Co., Ltd.) (solid content) were mixed, water was added, and the temperature was adjusted to 40 seconds with a Ford cup # 4.

Examples 2 to 4 and Comparative Examples 1 to 5 Resin compositions were prepared in the same manner as in Example 1 except that the composition was changed as shown in Table 1. Examples 1 to 4 and Comparative Examples 1 to 5
The resin composition prepared in 1. was made into a paint, and dried on a 0.6 mm thick bonderite # 144 treated steel sheet using an Iwata Wider 61 at a dry film thickness of 28 μm at 22 ° C. and 50% relative humidity.
The coating properties and coating film performance were tested by the following methods, and the results are shown in Tables 1 and 2.

Paintability test In spray coating, the coating amount was changed, the plate was stood and dried at 80 ° C. for 10 minutes, then baked at 160 ° C. for 20 minutes, and the armpit and sag limit film thickness were visually measured. The smoothness was evaluated according to the following criteria. ◎ ・ ・ ・ Very good ○ ・ ・ ・ Good

Coating Performance (a) Gloss: Expressed as reflectance at 60 ° gloss. (B) Hardness: Based on the pencil scratch test (JIS K5400). (C) Goglan eye test 1mm with a cutter 1mm (2mm at boiling water test)
It was cut into 00 pieces, and peeled off with a cellophane tape, and the number of burrs in the remaining coating film was measured. (D) Contamination with Magic A stain was contaminated with a red marker, and after 24 hours, it was wiped off with ethanol, and the contamination trace was visually judged. (E) Salt Water Sprayability After scratching the coating film with a cutter, the film was placed in a salt water spray tester, taken out after 100 hours, and the peeling width on one side when peeled off with cellophane tape was measured in mm. (F) Weather resistance The gloss retention of the coating film after 500 hours of the sunshine weatherometer test is shown. (G) Phase-retaining property The coating film was baked at 170 ° C. for 30 minutes, then applied again in the same manner and baked at 160 ° C., and the coating film was subjected to a scoring test. With respect to the coating film applied later, the number of burrs in the remaining coating film was measured.

[0027]

[Table 1]

[0028]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the resin compositions of the present invention produced in Examples 1, 2 and 3 show satisfactory results in coatability and coating film performance.
Example 4 is a case where the solution-polymerizable aqueous acrylic resin component is not included, but the smoothness of the coated surface is slightly inferior. Comparative Examples 1 and 2 are those in which the acrylic emulsion resin component is low or absent at all, and it easily sags, is inferior in boiling water resistance, chemical resistance, and phase clinging property, and is also insufficient in stain resistance. Further, Comparative Example 3 is a resin composition described in Examples of JP-A-2-212570, which has a gloss higher than that of Comparative Example 2.
The boiling water resistance and stain resistance are reduced. Further, in Comparative Example 4, the acrylic emulsion resin component is small and the modified epoxy resin component is large, but the gloss, boiling water resistance,
Stain resistance, weather resistance, and phase hiding resistance are reduced. Comparative Example 5 is a case where the modified epoxy resin is not contained, but the corrosion resistance is poor and the boiling water resistance is slightly lowered.

[0030]

EFFECT OF THE INVENTION The resin composition for water-based paints of the present invention has excellent storage stability, fast curing property, spray coating property, etc., and using this, good adhesion, gloss, water resistance, corrosion resistance, weather resistance. ,
It is possible to obtain a coating film having excellent chemical resistance, compatibility and the like.

Claims (2)

[Claims] 1. An acid value consisting of (A) an aqueous acrylic resin mainly composed of an acrylic emulsion resin having a number average molecular weight of 30,000 or less, and (B) an ethylenically unsaturated carboxylic acid and a copolymerizable monomer having an acid value of 50 to 50. Acrylic-modified epoxy resin and (C) amino resin obtained by reacting 350 carboxyl group-containing copolymer partially neutralized with amine with aromatic epoxy resin are (A) / (B) / (C)
(Weight ratio) 85-30 / 5-30 / 10-40, The resin composition for water-based paints contained so that the total amount may be 100. 2. The resin composition for an aqueous coating composition according to claim 1, wherein the aqueous acrylic resin as the component (A) contains a solution-polymerizable aqueous acrylic resin together with an acrylic emulsion resin.