JP2661402B2 - Water-dispersed resin composition and paint using the same - Google Patents

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 a paint or an adhesive, and a paint using the same.

[0002]

2. Description of the Related Art In recent years, there has recently been a strong demand for labor-saving and energy-saving with respect to coatings, adhesives and the like for automobiles, industrial machines, steel furniture, electric products and the like. In recent years, in order to prevent air pollution due to organic solvents emanating from paint,
The transition from conventional solvent-based paints to water-based paints is advancing.

[0003] Water-based coatings for epoxy resins excellent in various properties are also being actively pursued. In particular, various methods have been proposed in which an epoxy resin is modified with an acrylic resin and dispersed in water.

For example, JP-A-55-3481 and JP-A-55-3482 disclose that an epoxy resin is esterified with a carboxyl-functional polymer until an oxirane functional group is consumed in the presence of an amine esterification catalyst. A method is disclosed in which a reaction product obtained by the polymerization reaction is partially reacted with a base to form a self-emulsifying epoxy ester copolymer.

[0005] However, the polymer mixture obtained by the method described in the publication has poor curability and poor paint stability. As a solution to such a drawback, JP-A-56-109243 discloses a reaction product obtained by reacting an alkali-neutralized acrylic resin having a specific molecular weight and an aromatic epoxy resin having a specific molecular weight with ammonia or ammonia. An aqueous resin composition which is dispersed in an aqueous medium in the presence of an amine is described.

[0006]

However, according to the study of the present inventors, even the resin composition described in JP-A-56-109243 has sufficient paint stability. It is difficult to say that the coating properties are not sufficient. There is no other solution to these problems.

The present invention solves such a problem, and uses a water-dispersed resin obtained by reacting a partially neutralized specific carboxyl-functional polymer and a specific aromatic epoxy resin, and curing and coating the resin. An object of the present invention is to provide a water-dispersed resin composition and a coating material which are excellent in water resistance, adhesion, flexibility and the like of a film and also excellent in coating stability.

[0008]

That is, the present invention relates to a method for polymerizing a copolymerizable unsaturated monomer mixture comprising an ethylenically unsaturated aliphatic carboxylic acid and another copolymerizable unsaturated monomer. Acrylic resin (A) obtained by partially neutralizing a carboxyl-functional polymer having an average molecular weight of 5,000 to 12,000 and an acid value of 230 to 350 with ammonia or an amine, and having an average molecular weight of 1.25 to 1.5 per molecule. An aromatic epoxy resin (B) having an epoxy group, having 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. ) With (A) / (B) weight ratio of 5/95 to 40/6
The present invention relates to a water-dispersed resin composition obtained by dispersing an epoxy resin / acrylic resin reactant reacted in step 0 with water, and a paint using the same.

The acrylic resin of the component (A) of the present invention comprises an ethylenically unsaturated aliphatic carboxylic acid such as acrylic acid, methacrylic acid, maleic acid or itaconic acid, and another copolymerizable unsaturated monomer. An acrylic resin obtained by copolymerization.

Other copolymerizable unsaturated monomers include:
2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate,
Α, β-ethylenically unsaturated monomer having a hydroxyl group 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, diacetoneacrylamide, 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, and aromatics such as styrene, α-methylstyrene and vinyltoluene There is such as unsaturated monomer.

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

The obtained acrylic resin before neutralization has an acid value of 23.
It is adjusted to 0 to 350, preferably 250 to 300.
If the acid value is less than 230, after epoxy grafting,
Poor water solubility or water dispersibility, resulting in poor paint stability. On the other hand, if the acid value is too large, the properties of the coating film (particularly, warm water resistance) will be reduced. In addition, it tends to gel during epoxy grafting.

The obtained acrylic resin has a number average molecular weight (GPC method, standard polystyrene conversion value) of 5,000.
~ 12,000, preferably 7,000-10,000
It is adjusted to. If the number average molecular weight is less than 5,000, hot water resistance and processability are poor, and if it exceeds 12,000, the viscosity of the final product becomes high.

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

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.

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

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

Further, when the number average molecular weight is less than 4,500, the processability and adhesion of the cured coating film decrease, while
If it exceeds 000, gelation tends to occur during the reaction with the acrylic resin (A), and the viscosity of the coating material increases, and the stability of the coating material decreases. In view of these properties, 5,500
~ 7,500 is preferred, especially 6,000 ~ 7,000
Is preferred.

There is no limitation on the method for producing such an epoxy resin. For example, D.C.
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 Epon 829 (glycidyl ether of bisphenol A, trade name) manufactured by Shell Chemical, but could not easily produce the epoxy resin because of a large amount of low molecular weight substances. . This is considered to be due to the type of catalyst for elongating the molecular chain, and the complex of ethyltriphenylphosphonium acetate and acetic acid contained in DER 343 is considered to be effective for the production of the epoxy resin.

In order to obtain the above characteristics using DER 343, the weight ratio of bisphenol A / DER 343 is 33.
The reaction is preferably carried out at 4 / 66.6 to 32/68.
This reaction is preferably performed at a reaction temperature of 180 to 190 ° C. Here, when the reaction temperature is lower than 180 ° C.,
It has a long time to obtain the final target molecular weight and also has a high content of low molecular substances. On the other hand, when the temperature exceeds 190 ° C., it becomes difficult to control the reaction. It is better not to use a reaction solvent. When a reaction solvent is used, there are disadvantages that the reaction time is prolonged and the content of low molecular weight substances is increased.

It is to be noted that EP-coats 1004, 1007, 1 manufactured by Shell Chemical Co., which are commercially available epoxy resins described in JP-A-56-109243 and conventionally used.
No. 009, Epon 829, Epicron 4050, 7050 manufactured by Dainippon Ink and Chemicals, Inc., Dow DER 668, 667, 669 manufactured by Dow Chemical Co., Ltd. do not satisfy the properties of the epoxy resin of the present invention. If used, excellent coating film properties and paint stability cannot be obtained. For example, the most frequently used epicoats 1007 and 1009 have a molecular weight dispersity of 3.4 to 3.8.
Therefore, 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) is 80 to 80.
Acrylic resin (A) partially neutralized was added to aromatic epoxy resin (B) kept at 100 ° C., and then 65 to 65 ° C.
The reaction is preferably performed at 85 ° C. for 10 to 45 minutes. The control of the reaction can be measured by a change in acid value, measurement of oxirane (%), or the like.

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

The aqueous dispersion type resin composition of the present invention contains hydrochloric acid,
A catalyst such as an inorganic acid such as phosphoric acid and an organic acid such as paratoluenesulfonic acid may be added. The amount used is preferably 1 part by weight or less based on 100 parts by weight of the component (A) (solid component).

The water-dispersed resin composition of the present invention comprises 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, or methanol. The mixing ratio of water and the water-soluble organic solvent is preferably 95/5 to 80/20 in weight ratio of water / organic solvent.

The viscosity when diluted to a solid content of 30% by weight with the above preferred mixed solvent is 150 cps to 2,000.
cps is preferred. Here, when the viscosity is less than 150 cps, the viscosity tends to decrease, so that the thickness of the coating film tends to be thin and the workability tends to decrease. Tend to.

When the water-dispersed resin composition of the present invention is used as a paint, a pigment and other additives may be used according to the purpose. As a coating method, spray coating, coating with a roll coater, dipping, or the like can be employed.

[0028]

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

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

Production Example 2 Using the same apparatus 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.
Heat up 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 part by weight of t-butyl peroxybenzoate was dropped into the flask in 3 hours. . Then butyl cellosolve, 5 parts by weight, butanol 2
3 parts by weight were added dropwise over 20 minutes, and then the temperature was kept for 2 hours to obtain an acrylic resin. The acid value at this time was 250 (in terms of solid content). 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 26 parts by weight of dimethylaminoethanol was further added at 80 ° C. to obtain a partially neutralized acrylic resin. Then, water was added, and the heating residue was 37
It adjusted so that it might become weight%.

Production Example 3 Production of Aromatic Epoxy Resin Diglycidyl ether type DE of bisphenol A
Weigh 405 parts by weight of R343 (manufactured by Dow Chemical Company) and 220 parts by weight of bisphenol and stirrer, reflux condenser,
It was charged into a flask equipped with a thermometer and an inert gas inlet. Adjust the heating to reach about 130 ° C in 30 minutes,
Thereafter, the heating was stopped, and the temperature was raised to 190 ° C. using the heat of reaction. The reaction was performed at that temperature for 2 hours to synthesize an epoxy resin. The average number of epoxies in one molecule was 1.35. At this time, the number average molecular weight (Mn) is 6,55.
0, the weight average molecular weight (Mw) was 19,600, and the molecular weight dispersity was 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, and the mixture was thoroughly stirred. When the temperature reached 100 ° C., the partially neutralized acrylic resin synthesized in Production Example 1 was obtained. Resin 4
35 parts by weight (epoxy resin / acrylic resin =
80/20; solid fraction). The mixture was stirred at 80 ° C. for 30 minutes to obtain an epoxy-acrylic reactant. 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-dispersible resin. This resin is solidified for 30 minutes.
Water was further adjusted to weight percent. 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, and the mixture was stirred well, cooled to 100 ° C., and then partially neutralized acrylic resin synthesized in Production Example 2 43
5 parts by weight (epoxy resin / acrylic resin = 8)
0/20; solid fraction). Stirring was further continued at 80 ° C. for 30 minutes to obtain an epoxy-acrylic reactant. At this time, the acid value was 30. Thereafter, 1,100 parts by weight of water was added over 1 hour to obtain a white water-dispersible resin. This resin was adjusted with water so as to have a solid content of 30% by weight. At this time, the viscosity 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., and 30 parts by weight of butanol was added.
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 fraction ratio). The mixture was stirred at 80 ° C. for 30 minutes to obtain an epoxy-acrylic reactant. 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 solid 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 The acrylic resin of Example 1 was used, and as an aromatic epoxy resin, Epon 1009 (manufactured by Shell Chemical Co., Mn: 8,59)
0, 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., and then 50 parts by weight of butanol was further cooled, 435 parts by weight of a partially neutralized acrylic resin was added at 100 ° C., and 30 parts at 80 ° C.
After holding for 1 minute (acid value 35), 1,100 parts by weight of water was added to obtain a white water-dispersible resin. Further, the heating residue of this resin was adjusted to 30% by weight with water. The viscosity is
It was 7,800 cps (B-type viscosity: 6 rpm).

COMPARATIVE EXAMPLE 2 The aromatic epoxy resin of Comparative Example 1 was prepared using Epon 1007 (manufactured by Shell Chemical Co., Mn: 4,480, Mw: 19,600 M).
w / Mn = 3.37), and a white water-dispersible resin was obtained in the same manner as in Comparative Example 1. The heating residue of this resin is 30
By weight, the viscosity was 250 cps (B-type viscosity 6 rp.
m).

The coating tests of the water-dispersed resin compositions obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were measured under the following conditions.
Each resin composition adjusted to 30% by weight was applied to a tin plate with a bar coater # 18 (the film thickness was 5 to 7 μm after baking).
m. ). 190, 200, 210
Baking was carried out at 5 ° C. for 5 minutes each. Then, it was left at room temperature for 24 hours to conduct a coating film test. Table 1 shows the results.

Coating film test method: Pencil hardness: evaluated by JIS K5400 using Mitsubishi Uni. -Impact value: Measured by a DuPont impactor 1/2 "-500.-Boiling water resistance: Immersion in boiling water for 1 hour, then take out,
Its appearance was determined.・ Adhesion of boiling water resistance; 1 m in coating film after immersion in boiling water for 1 hour
One hundred squares with a size of mx 1 mm were cut, and the cellophane tape was peeled off, and the peeling ratio was determined. -Erichsen value after boiling water resistance: After immersion in boiling water for 1 hour, the film was extruded by 5 mm using an Erichsen test, and the appearance of the coating film was observed. Stability: The composition was left at room temperature (25 ° C.) for 60 days, and the appearance of the paint was measured.

[0039]

[Table 1]

[0040]

The water-dispersed resin composition obtained by the present invention and the paint using the same are excellent in stability and
Excellent in various properties of the coating film, especially water resistance, adhesion, and flexibility.

Claims (3)

(57) [Claims] 1. A number average molecular weight of 5,000 to 5,000 obtained by polymerizing a copolymerizable unsaturated monomer mixture comprising an ethylenically unsaturated aliphatic carboxylic acid and another copolymerizable unsaturated monomer.
Acrylic resin (A) obtained by partially neutralizing a carboxyl-functional polymer having an acid value of 230 to 350 with ammonia or an amine, and an average of 1.25 to 25 per molecule
An aromatic group 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 (A) / (B) of the epoxy resin (B) is 5/95.
A water-dispersed resin composition obtained by dispersing an epoxy resin / acrylic resin reactant reacted at a rate of about 40/60 in water. 2. A water / organic solvent weight ratio of 95/5 to 80.
The water-dispersed resin composition according to claim 1, wherein the viscosity when the solid content is diluted to 30% by weight with a mixed solvent of / 20 is from 150 cps to 2,000 cps. 3. A paint comprising the water-dispersed resin composition according to claim 1 or 2.