JPH04342780A - Water-dispersible resin composition and coating using the same - Google Patents

Abstract

PURPOSE:To obtain the title composition capable of giving coatings of excellent coating film characteristics such as stability, water resistance, adhesiveness or flexibility by dispersing in water a reaction product formed by reaction between a partially neutralized acrylic resin and aromatic epoxy resin at a specified ratio. CONSTITUTION:The objective composition can be obtained by dispersing in water a reaction product prepared by reaction between (A) an acrylic resin obtained by partially neutralizing with ammonia or an amine a carboxyl- functional polymer 500-12000 (pref. 7000-10000) in number-average molecular weight and 230-350 (pref. 250-300) in acid value produced by polymerizing a copolymerizable unsaturated monomer mixture containing an ethylenically unsaturated aliphatic carboxylic acid and (B) an aromatic epoxy resin having in one molecule 1.25-1.5 epoxy groups on average, 2.7-3.2 (pref. 2.8-3.1) in molecular weight distribution (Mw/Mn) and 4500-8000 (esp. 6000-7000 in number-average molecular weight at M weight ratio A/B=(5:95)-(40:60) [pref. (10:90)-(40:60)].

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-dispersible resin composition useful for paints, adhesives, etc., and paints using the same.

0002

BACKGROUND OF THE INVENTION In recent years, there has been a strong demand for labor-saving and energy-saving coatings, adhesives, etc. for automobiles, industrial machinery, steel furniture, electrical appliances, etc. Furthermore, in recent years, there has been a shift from conventional solvent-based paints to water-based paints in order to prevent air pollution caused by organic solvents emitted from paints.

[0003] Epoxy resins, which have excellent various properties, are being developed into water-based paints. In particular, various methods have been proposed in which epoxy resins are modified with acrylic resins and dispersed in water.

For example, in JP-A-55-3481 and JP-A-55-3482, an epoxy resin is esterified into a carboxyl functional polymer in the presence of an amine esterification catalyst until the oxirane functional groups are consumed. A method for producing a self-emulsifying epoxy ester copolymer by partially reacting the reaction product with a base is disclosed.

However, the polymer mixture obtained by the method described in the publication had poor curability and poor paint stability. In order to solve these drawbacks, JP-A-56-109243 discloses that a reaction product obtained by reacting an alkali-neutralized acrylic resin with a specific molecular weight with an aromatic epoxy resin with a specific molecular weight is treated with ammonia or Aqueous resin compositions are described which are dispersed in an aqueous medium in the presence of an amine.

[0006]

[Problems to be Solved by the Invention] However, according to the studies of the present inventors, even the resin composition described in JP-A-56-109243 does not have sufficient paint stability. It is difficult to say that the properties of the coating film are satisfactory. Moreover, there is still no other solution that satisfactorily solves these problems.

The present invention solves these problems by using a water-dispersible resin made by reacting a partially neutralized specific carboxyl-functional polymer with a specific aromatic epoxy resin, and applying a cured coating. The purpose of the present invention is to provide a water-dispersible resin composition and a paint that have excellent film resistance, adhesion, flexibility, etc., and also have excellent paint stability.

[0008]

[Means for Solving the Problems] That is, the present invention provides a method for polymerizing a copolymerizable unsaturated monomer mixture consisting of an ethylenically unsaturated aliphatic carboxylic acid and other copolymerizable unsaturated monomers. Acrylic resin (A
) and has an average of 1.25 to 1.5 epoxy groups in one molecule, a molecular weight dispersity (weight average molecular weight / number average molecular weight) of 2.7 to 3.2, and a number average molecular weight of 4 ,5
An epoxy resin/acrylic resin reaction product obtained by reacting an aromatic epoxy resin (B) with a weight ratio of 00 to 8,000 at a weight ratio of (A)/(B) of 5/95 to 40/60 is water-dispersed. The present invention relates to the resulting water-dispersed resin composition and a coating material using the same.

The acrylic resin of component (A) of the present invention contains an ethylenically unsaturated aliphatic carboxylic acid such as acrylic acid, methacrylic acid, maleic acid, itaconic acid, and other copolymerizable unsaturated monomers. It is an acrylic resin obtained by copolymerization.

Other copolymerizable unsaturated monomers include:
2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate,
α,β-ethylenically unsaturated monomers having hydroxyl groups such as 2-hydroxypropyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, methacrylic acid Alkyl esters of α,β-monoethylenically unsaturated carboxylic acids such as n-butyl, acrylamide derivatives such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, glycidyl acrylate, methacrylic acid Glycidyl esters of α,β-monoethylenically unsaturated carboxylic acids such as glycidyl, vinyl esters of saturated carboxylic acids such as vinyl acetate and vinyl propionate, aromatic unsaturated monomers such as styrene, α-methylstyrene, and vinyltoluene. There are bodies, etc.

The above polymerization is carried out in the presence of a radical catalyst such as azobisisobutyronitrile, t-butyl peroxybenzoate, benzoyl peroxide, dibutyl peroxide, or cumene hydroperoxide.
This can be done by heating to 160°C.

The obtained acrylic resin before neutralization has an acid value of 23
It is adjusted to 0-350, preferably 250-300. If the acid value is too small than 230, after epoxy grafting,
Poor water solubility or water dispersibility, resulting in poor paint stability. Moreover, if the acid value is too large than 350, the coating film properties (especially hot water resistance) will deteriorate. It also tends to gel when epoxy grafted.

[0013] The number average molecular weight (GPC method, standard polystyrene equivalent value) of the acrylic resin obtained is 5,000.
~12,000, preferably 7,000-10,000
is adjusted to If the number average molecular weight is less than 5,000, the hot water resistance and processability will be poor, and if it exceeds 12,000, the viscosity of the final product will be high.

Next, the obtained acrylic resin is partially neutralized with ammonia or amine, and then water-solubilized or water-dispersed to obtain a partially neutralized acrylic resin (A). Suitable amines include, for example, monopropylamine, monobutylamine, diethylamine, dibutylamine, triethylamine, tributylamine, monoethanolamine, ethylmonoethanolamine, monocyclohexylamine, dimethylaminoethanol, 2-amino-2-methyl Primary, secondary and tertiary aliphatic or cycloaliphatic amines such as -1-propanol, morpholine and piperidine can be used. Ammonia and amine are preferably used in an amount of 0.6 or more and less than 1.0 mol per equivalent of acid group. When the amount of amine is less than 0.6 mole, water dispersibility or water solubility tends to be poor, and when it is more than 1.0 mole, the viscosity of the final product tends to be high.

The aromatic epoxy resin (B) used in the present invention has an average of 1.25 to 1.5 epoxy groups in one molecule, and has a molecular weight dispersity (weight average molecular weight/number average molecular weight). is 2.7 to 3.2 and the number average molecular weight is 4,500
~8,000.

[0016] If the number of epoxy groups in one molecule is less than 1.25 on average, the viscosity tends to increase during reaction with the acrylic resin (A), and stability during water dispersion and coating viscosity decrease, On the other hand, if it exceeds 1.5, the flexibility, workability, and adhesion of the cured coating film will decrease.

[0017] If the molecular weight dispersity is less than 2.7, the flexibility of the cured coating will decrease, while if it exceeds 3.2, the processability and adhesion of the cured coating will decrease, and the coating will deteriorate. The viscosity increases and the stability of the paint decreases. From the viewpoint of these characteristics, 2.8 to 3.1 is preferable.

Furthermore, if the number average molecular weight is less than 4,500, the processability and adhesion of the cured coating film will decrease;
If it exceeds 000, gelation tends to occur during the reaction with the acrylic resin (A), the viscosity of the paint increases, and the stability of the paint decreases. In terms of these characteristics, 5,500
-7,500 is preferable, especially 6,000-7,000
is preferred.

[0019] Although there are no restrictions on the method for producing such an epoxy resin, for example, D
It can be easily produced by using ER343 (diglycidyl ether of bisphenol A, trade name) and bisphenol A. The present inventors conducted a similar study using Shell Chemical's Epon 829 (glycidyl ether of bisphenol A, trade name), but the above epoxy resin could not be easily produced due to the large amount of low molecular weight substances. . This is thought to be due to the type of catalyst for molecular chain elongation, and the complex of ethyltriphenylphosphonium acetate and acetic acid contained in DER343 is considered to be effective in producing the above-mentioned epoxy resin.

[0020] In order to obtain the above characteristics using DER343, the weight ratio of bisphenol A/DER343 must be 33.4.
It is preferable to react at a ratio of /66.6 to 32/68. Further, this reaction is preferably carried out at a reaction temperature of 180 to 190°C. Here, if the reaction temperature is less than 180°C,
It takes a long time to reach the final target molecular weight, and the content of low molecular weight compounds increases. On the other hand, if the temperature exceeds 190°C, it becomes difficult to control the reaction. Moreover, it is better not to use a reaction solvent. When a reaction solvent is used, the reaction time becomes longer and the content of low molecular weight substances increases.

[0021] Incidentally, Epicoat 1004, 1007, and 1 manufactured by Shell Chemical Co., Ltd., which are commercially available epoxy resins described in Japanese Patent Application Laid-Open No. 109243/1982 and which have been used conventionally,
009, Epon 829, Epiclon 4050, 7050 manufactured by Dainippon Ink Chemical Co., Ltd., and Dow DER668, 667, 669 manufactured by Dow Chemical Company, etc., do not satisfy the characteristics of the epoxy resin of the present invention. However, it is not possible to obtain excellent coating film properties and coating stability. For example, the most commonly used Epikote 1007 and 1009 have a molecular weight dispersity of 3.4 to 3.8.
Because of its large size, processability, adhesion, paint stability, etc. are not sufficient.

In the present invention, the reaction between the partially neutralized acrylic resin (A) and the aromatic epoxy resin (B)
Partially neutralized acrylic resin (A) was added to aromatic epoxy resin (B) kept at 100°C, and then heated to 65°C.
It is preferable to react at 85°C for 10 to 45 minutes. Control of the reaction can be measured by changing the acid value, measuring oxirane (%), etc.

The weight (%) ratio of partially neutralized acrylic resin (A)/aromatic epoxy resin (B) is 5/95 to 40.
/60, preferably in the range of 10/90 to 40/60. When the amount of component (A) used increases, the processability and corrosion resistance of the coating film decreases, and when the amount of component (B) increases, the dispersibility and stability of the paint decrease.

The water-dispersed resin composition of the present invention contains hydrochloric acid,
A catalyst such as an inorganic acid such as phosphoric acid or an organic acid such as para-toluenesulfonic acid may be added. The amount used is preferably 1 part by weight or less per 100 parts by weight of component (A) (solid content).

The water-dispersed resin composition of the present invention contains butyl cellosolve, ethyl cellosolve, methyl cellosolve, diacetone alcohol, 3-methoxy-3-methylbutane-
It can be used after being diluted to an appropriate solid content with a mixed solvent of water and a water-soluble solvent such as 1-ol, isopropanol, ethanol, and methanol. The mixing ratio of water and water-soluble organic solvent is preferably 95/5 to 80/20 in terms of water/organic solvent weight ratio.

The viscosity when diluted with the above preferred mixed solvent to a solid content of 30% by weight is 150 cps to 2,000 cps.
cps is preferred. If it is less than 150 cps, the viscosity decreases, resulting in a thinner coating film and a tendency to reduce workability. On the other hand, if it exceeds 2,000 cps, the workability during painting will decrease and the stability of the paint will decrease. There is a tendency to

When the water-dispersible resin composition of the present invention is used as a coating material, pigments and other additives may be used depending on the purpose. Further, as a coating method, spray coating, coating with a roll coater, dipping, etc. can be adopted.

[0028]

[Examples] The present invention will be specifically explained below with reference to Examples. In the examples, parts indicate parts by weight. A partially neutralized acrylic resin was produced as follows. In addition, the molecular weight was measured by high performance liquid chromatography under the following conditions. Column: Gelpack R440, R450, R400H (
Three cables (all manufactured by Hitachi Chemical Co., Ltd.) are connected in series. Flow rate: 2.0ml/min Detector: RI

Production Example 1 In a flask equipped with a stirrer, a reflux condenser, a thermometer, and an inert gas inlet, 35 parts by weight of butyl cellosolve and 20 parts by weight of butanol were charged and heated. The temperature was raised to 130°C, and a mixed solution consisting of 28 parts by weight of styrene, 26 parts by weight of ethyl acrylate, 46 parts by weight of methacrylic acid, and 0.6 parts by weight of t-butyl peroxybenzoate was poured into the flask over 3 hours. I let it drip. Then, 5 parts by weight of butyl cellosolve and 23 parts by weight of butanol were added dropwise over 20 minutes.
Thereafter, the mixture was kept warm for 2 hours to obtain an acrylic resin. The acid value at this time was 300 (in terms of solid content). Further, the number average molecular weight was 9,700, and the weight average molecular weight was 24,200. Thereafter, the mixture was cooled to 100°C, 47 parts by weight of water was added, and further 31 parts by weight of dimethylaminomethanol was added at 80°C to obtain a partially neutralized acrylic resin. Thereafter, water was added to adjust the heating residue to 37% by weight.

Production Example 2 Using the same equipment as in Production Example 1, 35 parts by weight of butyl cellosolve and 20 parts by weight of butanol were charged and heated to 130°C.
Increase the temperature to. A mixed solution consisting of 32 parts by weight of styrene, 30 parts by weight of ethyl acrylate, 38 parts by weight of methacrylic acid, and 0.6 parts by weight of t-butylperoxybenzoate was dropped into the flask over 3 hours. . Then butyl cellosolve, 5 parts by weight, butanol 23
Parts by weight were added dropwise over 20 minutes, and then kept warm for 2 hours to obtain an acrylic resin. The acid value at this time was 250 (calculated as solid content). Further, the number average molecular weight was 9,600 and the weight average molecular weight was 21,300. Thereafter, the mixture was cooled to 100°C, 47 parts by weight of water was added, and further, 26 parts by weight of dimethylaminoethanol was added at 80°C to obtain a partially neutralized acrylic resin. Thereafter, water was added to adjust the heating residue to 37% by weight.

Production Example 3 Production of aromatic epoxy resin Diglycidyl ether type DE of bisphenol A
Weighed 405 parts by weight of R343 (manufactured by Dow Chemical Company) and 220 parts by weight of bisphenol, and placed them in a stirrer, a reflux condenser,
The mixture was placed in a flask equipped with a thermometer and an inert gas inlet. Heating was adjusted so that the temperature reached about 130°C in 30 minutes, then heating was stopped and the temperature was raised to 190°C using the heat of reaction. The reaction was carried out at that temperature for 2 hours to synthesize an epoxy resin. The average number of epoxy molecules in one molecule was 1.35. In addition, the number average molecular weight (Mn) at this time is 6,550
, weight average molecular weight (Mw) of 19,600, and molecular weight dispersity of 2.99.

Example 1 The epoxy resin obtained in Production Example 3 was cooled to 130°C, 50 parts by weight of butanol was added, stirred well, and when the temperature reached 100°C, the partially neutralized acrylic resin synthesized in Production Example 1 was added. resin 4
35 parts by weight was added (epoxy resin/acrylic resin=
80/20; solid content ratio). The mixture was stirred at 80°C for 30 minutes to obtain an epoxy-acrylic reaction product. The acid value at this time was 34. Thereafter, 1,100 parts by weight of water was added over 1 hour to obtain a white water-dispersed resin. This resin has a solid content of 30
The weight percentage was further adjusted with water. The viscosity at this time is 450c
ps (B type viscosity 6 rpm) (organic solvent/water: 13/87).

Example 2 The epoxy resin obtained in Production Example 3 was cooled to 130°C, 50 parts by weight of butanol was added, stirred thoroughly, and after cooling to 100°C, the partially neutralized acrylic resin synthesized in Production Example 2 was obtained. 43
5 parts by weight were added (epoxy resin/acrylic resin = 8
0/20; solid content ratio). Stirring was further continued at 80° C. for 30 minutes to obtain an epoxy-acrylic reaction product. The acid value at this time was 30. Thereafter, 1,100 parts by weight of water was added over 1 hour to obtain a white water-dispersed resin. This resin was adjusted with water to have a solid content of 30% by weight. The viscosity at this time was 250 cps (B type viscosity 6 rpm) (organic solvent/water = 13/87).

Example 3 The epoxy resin obtained in Production Example 3 was cooled to 130°C, 30 parts by weight of butanol was added, stirred well, and further cooled to 130°C.
When the temperature reached 00°C, 910 parts by weight of the partially neutralized acrylic resin synthesized in Production Example 1 was added (epoxy resin/acrylic resin = 65/35; solid content ratio). The mixture was stirred at 80°C for 30 minutes to obtain an epoxy-acrylic reaction product. The acid value at this time was 65. Thereafter, 800 parts by weight of water was added to obtain a white water-dispersed resin. This resin was further adjusted to a solids content of 30% by weight with water. The viscosity at this time is 390 cps (B
Mold viscosity 6r. p. m) (organic solvent/water = 18/
82).

Comparative Example 1 Using the acrylic resin of Example 1, Epon 1009 (manufactured by Shell Chemical Co., Ltd., Mn: 8,590) was used as an aromatic epoxy resin.
, Mw; 28,900, Mw/Mn=3.82) to obtain a water-dispersed resin in the same manner. That is, 625 parts by weight of Epon 1009 was heated to 130°C, then 50 parts by weight of butanol was used, further cooled, 435 parts by weight of partially neutralized acrylic resin was added at 100°C, and kept at 80°C for 30 minutes (acid After that, 1,100 parts by weight of water was added to obtain a white water-dispersed resin. Furthermore, the residual content of this resin after heating was adjusted to 30% by weight with water. The viscosity is 7
, 800 cps (B type viscosity 6 rpm).

Comparative Example 2 The aromatic epoxy resin of Comparative Example 1 was mixed with Epon 1007 (manufactured by Shell Chemical Co., Ltd., Mn: 4,480, Mw: 19,600
A white water-dispersed resin was obtained in the same manner as in Comparative Example 1 using Mw/Mn=3.37). The heating residue of this resin is 3
0% by weight, the viscosity is 250 cps (B type viscosity 6 r.p.
m).

Coating film tests of the water-dispersed resin compositions obtained in Examples 1 to 3 and Comparative Examples 1 to 2 were carried out under the following conditions. Each resin composition adjusted to 30% by weight was coated on a tin plate using a bar coater #18 (film thickness was 5 to 7 μm after baking).
It was m. ). This coating plate is 190, 200, 210
Baking was performed at ℃ for 5 minutes each. Then, it was left at room temperature for 24 hours and a coating test was conducted. The results are shown in Table 1.

Coating film test method/Pencil hardness: Evaluated according to JIS K5400 using Mitsubishi Uni.・Impact value: Measured using a DuPont impactor 1/2″-500. ・Boiling water resistance: Immersed in boiling water for 1 hour, then taken out.
Its appearance was judged.・Boiling water resistant adhesion; after 1 hour immersion in boiling water, 1 m of paint film
100 m x 1 mm goblets were cut, peeled off with cellophane tape, and the rate of peeling was determined. - Erichsen value after boiling water resistance: After being immersed in boiling water for 1 hour, it was extruded to 5 mm using the Erichsen test and the appearance of the coating film was observed. - Stability: The appearance of the above paint was measured after being left at room temperature (25°C) for 60 days.

[0039]

[Table 1]

[0040]

Effects of the Invention The water-dispersed resin composition obtained by the present invention and the coating material using the same have excellent stability, and
It has excellent coating properties, especially water resistance, adhesion, and flexibility.

Claims (3)

[Claims] Claim 1: A copolymerizable unsaturated monomer mixture consisting of an ethylenically unsaturated aliphatic carboxylic acid and other copolymerizable unsaturated monomers having a number average molecular weight of 5,000.
12,000 and an acrylic resin (A) partially neutralized with ammonia or amine, a carboxyl functional polymer having an acid value of 230 to 350 and an average of 1.25 to 1.25 per molecule
Aromatic type having an epoxy group of 1.5, a molecular weight dispersity (weight average molecular weight/number average molecular weight) of 2.7 to 3.2, and a number average molecular weight of 4,500 to 8,000. The weight ratio of epoxy resin (B) to (A)/(B) is 5/95
A water-dispersed resin composition obtained by water-dispersing an epoxy resin/acrylic resin reactant reacted at a ratio of ~40/60. Claim 2: The weight ratio of water/organic solvent is 95/5 to 8.
The water-dispersed resin composition according to claim 1, which has a viscosity of 150 cps to 2,000 cps when the solid content is diluted to 30% by weight with a 0/20 mixed solvent. 3. A paint comprising the water-dispersed resin composition according to claim 1 or 2.