JP3063455B2 - Method for producing resin for water-based paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a water-based paint resin synthesized when a specific solvent composition is adjusted. Specifically, when the acrylic monomer and polymerization initiator are dropped into the modified epoxy resin, the optimum reaction temperature is easily maintained at a constant level, and a solvent composition that provides a reflux state effective to improve the uniformity in the system is synthesized. The present invention relates to a method for producing a resin for an aqueous paint to be used.

[0002]

2. Description of the Related Art In recent years, the use rate of water-based paints has been remarkably increased, particularly on the inner surface of a can. However, its storage stability is not always satisfactory. Originally, the water-based paint for the inner surface of a can which does not include a solvent removing step has a limited amount of an organic solvent that can be used for resin synthesis. In addition, with increasing awareness of environmental issues in recent years, the amount of organic solvents contained in paints has been reduced. On the other hand, when the amount of the organic solvent is small, the resin solid content during the reaction becomes high, so that the viscosity becomes high and the production becomes difficult, which causes gelation or poor water dispersion.

For example, when a modified epoxy resin and a mixed acrylic monomer described in Japanese Patent Application Laid-Open No. 58-198513 are polymerized, a high viscosity due to a small amount of an organic solvent and a slight variation during synthesis (for example, a reaction Due to temperature fluctuations and contamination in the system), its molecular weight is significantly increased. Such resins are difficult to solubilize in water, and paints using aqueous dispersions of such resins have poor storage stability.

[0004]

When an aqueous coating material is actually produced, contamination in the system can be sufficiently considered, and there is a risk of an increase in molecular weight, gelation and poor water dispersion. In addition, by reducing the amount of organic solvent used,
It is conceivable that the above will be further promoted. As a result of the study, the present inventors believe that it is necessary to synthesize the acryl-epoxy resin with a constant molecular weight of 30,000 to 70,000 in order to prevent the above-mentioned gelation and poor water dispersion. The present invention is directed to a self-emulsifiable water-based coating resin which improves the above-mentioned various disadvantages and is excellent in production stability and storage stability.

[0005]

According to the present invention, when an acrylic monomer is dropped together with a polymerization initiator onto a modified epoxy resin obtained by modifying an epoxy resin with methacrylic acid, the solvent in the system is an alkyl alcohol and an ether alcohol, This is a method for producing a water-based paint resin having a ratio of 5/5 to 8/2. A feature of the present invention is that when an acrylic monomer is dropped together with a polymerization initiator onto a modified epoxy resin obtained by modifying an epoxy resin with methacrylic acid, foaming is caused by adjusting the solvent composition in the system, and the uniformity in the system is reduced. To increase

[0006] The term "modified epoxy resin" means that (A) bisphenol A type epoxy resin is mixed with methacrylic acid at 1 / 0.04
(B) (i) acrylic acid or methacrylic acid 20;
To 80% by weight, (b) aromatic vinyl monomer 10 to 60
(C) 90 to 10 parts by weight of an acrylic monomer comprising 1 to 50% by weight of an alkyl ester of an α, β-ethylenically unsaturated carboxylic acid in the presence of a polymerization initiator.
Polymerize at 140 ° C. After that, the aqueous dispersion is obtained by partially or completely neutralizing with a basic compound. (A) and (B)
In the present invention, it is important that the solvent composition in the system is adjusted to 5/5 to 8/2, preferably 6/4 to 7/3 by the ratio of the alkyl alcohol and the ether alcohol in the system to cause foaming. is there. The reason for this is that the uniformity in the system can be enhanced, the molecular weight of the resin is kept constant between 30,000 and 70,000, and subsequent gelation, poor water dispersion, and unstable storage can be prevented.

The epoxy resin used in the present invention is preferably a bisphenol A type epoxy resin which is a condensate of bisphenol A and epichlorohydrin, and has an epoxy equivalent of 900 to 4,000. Epoxy equivalent is 9
If it is less than 00, the flexibility of the coating film is poor, and if it is more than 4,000, the viscosity is too high to obtain a good polymerized product,
There is a disadvantage that the storage stability of the aqueous dispersion is poor.
The reaction between the epoxy resin and methacrylic acid is 1 / 0.04-1.
/0.5 at a molar ratio of 110 to 15 using the reaction catalyst.
It can proceed at a temperature of 0 ° C.

As a catalyst, an alkali metal hydroxide or an alkali metal inorganic or organic salt is used. The reaction is continued until free methacrylic acid is consumed. When the reaction molar ratio is 1 /
When the aqueous dispersion composition obtained in the range of 0.04 or less has poor storage stability, and when the ratio is 1 / 0.5 or more, the formation of a high molecular weight during polymerization is remarkable, gelation is likely to occur during polymerization, and it is difficult to make aqueous. It is. The acrylic monomer used is (a) 20 to 80% by weight of acrylic acid or methacrylic acid, (b) 10 to 60% by weight of an aromatic vinyl monomer, (c) alkyl ester of α, β-ethylenically unsaturated carboxylic acid 1 When the amount of acrylic acid or methacrylic acid is 20% by weight or less, the storage stability of the aqueous dispersion is poor. When the amount is 80% by weight or more, the aqueous dispersion tends to gel during polymerization, which is not preferable.

If the amount of the aromatic vinyl monomer is less than 10% by weight, the corrosion resistance is not good, and if it is more than 60% by weight, the storage stability of the aqueous dispersion is poor. If the alkyl ester of α, β-ethylenically unsaturated carboxylic acid is 1% by weight or less, the flexibility of the coating film is insufficient, and if it is 50% by weight or more, the boiling water resistance of the coating film is poor. Examples of the aromatic vinyl monomer used in the present invention include styrene, α-methylstyrene, and vinyl toluene. Examples of alkyl esters of α, β-ethylenically unsaturated carboxylic acids include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and the like.
Examples thereof include alkyl acrylates such as 2-ethylhexyl acrylate and alkyl methacrylates corresponding to the above alkyl esters.

In the present invention, the ratio of the modified epoxy resin (A) and the mixed acrylic monomer (B) is (A) 10 to 90.
(B) 90 to 10 parts by weight with respect to parts by weight.
Examples of the polymerization initiator used when reacting (A) and (B) include a peroxide, a persulfate, an azobis compound, and a redox system combining these reducing agents. The solvent used in the present invention is an alkyl alcohol and an ether alcohol. The alkyl alcohol is, for example, methanol, ethanol, propanol, butanol and the like, and the ether alcohol is, for example, propylene glycol monomethyl ether, propylene glycol monopropyl ether, ethylene glycol monoether. Examples thereof include butyl ether, propylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, and ethylene glycol monohexyl ether.

In the present invention, the modified epoxy resin (A)
When the acrylic monomer (B) is polymerized, it is important to bring the inside of the system to a reflux state at 100 to 130 ° C. using the above two kinds of solvents. As a result, the uniformity in the system can be improved, the molecular weight of the resin can be kept constant, and subsequent gelation, poor water dispersion, and unstable storage can be prevented. For this purpose, the ratio of alkyl alcohol to ether alcohol is 5 /
If the ratio of alkyl alcohol is small, the resin will not be in a reflux state at 100 to 140 ° C., and the uniformity is not maintained, so that the molecular weight of the resin is not constant and the molecular weight is increased.
Gelation is likely to occur, and if the proportion of alkyl alcohol is high, the reaction temperature tends to decrease, and the molecular weight of the resin increases, causing gelation.

[0012]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, parts represent parts by weight, and% represents% by weight. Example 1 (Production of modified epoxy resin) (1) 43 parts of propylene glycol monopropyl ether (2) 100 parts of Epicoat 1007 (manufactured by Yuka Shell Epoxy Co., Ltd.) (3) 0.1 part of 10% sodium hydroxide 0.1 part (4) Hydroquinone 0.004 parts (5) Methacrylic acid 0.87 parts (6) n-butanol 52 parts (1) and (2) in a four-necked flask filled with nitrogen gas.
And stirred under heating at 120 ° C. for 2 hours to dissolve the epoxy resin. Thereafter, the temperature was raised, (3) to (5) were charged while stirring at 130 ° C., the reaction was carried out at 130 ° C. for 5 hours, and after cooling, the product was taken out. The obtained resin solution had a solid content of 51% and a resin acid value of 0.2 (per solid content).

(Production of epoxy-acrylic resin) (1) 196 parts of the above modified epoxy resin (2) 17 parts of styrene (3) 1.7 parts of ethyl acrylate (4) 15.3 parts of methacrylic acid (5) propylene glycol 9.3 parts of monopropyl ether (6) 1.7 parts of n-butanol (7) 2.0 parts of azobisisobutyronitrile 2.0 parts (8) 0.6 parts of azobisisobutyronitrile Four parts filled with nitrogen gas Charge (1) in a neck flask,
While heating and refluxing at 125 ° C., the mixed solution of (2) to (7) was added dropwise over 3 hours. 60 minutes after the completion of the dropwise addition, (8) was added. After reacting for an additional 60 minutes, it was cooled. The molecular weight of the self-emulsifying epoxy-acrylic resin was 40,000 by weight and the solid content was 55%.

(Production of Aqueous Dispersion) (1) 243.6 parts of epoxy-acrylic resin (2) 4.8 parts of dimethylaminoethanol (3) 414 parts of ion-exchanged water 414 parts cooled to 70 ° C. (1) 2) was added and (3) was added dropwise over 2 hours to obtain an aqueous dispersion. In the self-emulsifying epoxy-acrylic resin, the neutralization ratio of carboxyl groups contained in the acrylic resin is 30.3 mol%, and the solid content is 20.
2%, solvent amount 16%, viscosity 1 in # 4 Ford cup
5 seconds / 25 ° C.

The paint was aged at 50 ° C. for one month.
There were no abnormalities such as gelation. The viscosity was 14 seconds / 25 ° C in a # 4 Ford cup. Example 2 (Production of Modified Epoxy Resin) (1) 33 parts of propylene glycol monobutyl ether (2) 100 parts of Epicoat 1004 (manufactured by Yuka Shell Epoxy Co., Ltd.) 100 parts (3) 0.1 part of 10% sodium hydroxide 0.1 part ( 4) Hydroquinone 0.004 parts (5) Methacrylic acid 1.86 parts (6) n-butanol 48.7 parts In a four-necked flask filled with nitrogen gas, (1) and (2)
And stirred under heating at 120 ° C. for 2 hours to dissolve the epoxy resin. Thereafter, the temperature was raised, (3) to (5) were charged while stirring at 130 ° C., the reaction was carried out at 130 ° C. for 5 hours, and after cooling, the product was taken out. The obtained resin solution had a solid content of 54.2% and a resin acid value of 0.2 (per solid content).

(Production of epoxy-acrylic resin) (1) 183.7 parts of the above modified epoxy resin (2) 17 parts of styrene (3) 1.7 parts of ethyl acrylate (4) 15.3 parts of methacrylic acid (5) Propylene glycol monobutyl ether 15.7 parts (6) Benzoyl peroxide 2.0 parts (7) Benzoyl peroxide 0.6 parts Charge (1) into a four-necked flask filled with nitrogen gas,
While heating and refluxing at 120 ° C., the mixed solution of (2) to (6) was added dropwise over 3 hours. 60 minutes after the completion of the dropwise addition, (7) was added. After reacting for an additional 60 minutes, it was cooled. The molecular weight of the self-emulsifying epoxy-acrylic resin was 30,000 by weight and the solid content was 57.4%.

(Production of aqueous dispersion) (1) 233.4 parts of the epoxy-acrylic resin (2) 4.8 parts of dimethylaminoethanol (3) 307.8 parts of ion-exchanged water Cooled to 70 ° C. (1) (2) was added thereto, and (3) was added dropwise over 2 hours to obtain an aqueous dispersion. The neutralization rate of the carboxyl groups contained in the acrylic resin of the self-emulsifying epoxy / acrylic resin is 30.3 mol%, and the solid content is 22%.
%, Solvent amount is 16%, viscosity is 15 with # 4 Ford cup
Sec / 25 ° C.

This paint was aged at 50 ° C. for one month.
There were no abnormalities such as gelation. The viscosity was 14 seconds / 25 ° C in a # 4 Ford cup. Example 3 In the production of the epoxy modified product of Example 2, (2) Epicoat 1004 (manufactured by Yuka Shell Epoxy) 100
Part is Epicoat 1009 (Yukaka Epoxy Co., Ltd.)
100 parts) and 1.86 parts of methacrylic acid of (5).
The production was performed in the same manner as in Example 2 except that the amount was 60 parts to obtain a self-emulsifying epoxy-acrylic resin. The molecular weight of the resin is 45,000
0 The neutralization rate of carboxyl groups contained in the acrylic resin is 3
0.3 mol%, solid content 22,%, solvent amount 16%, viscosity was 15 seconds / 25 ° C with a # 4 Ford cup.

This paint was aged at 50 ° C. for one month.
There were no abnormalities such as gelation. The viscosity was 14 seconds / 25 ° C in a # 4 Ford cup. Comparative Example 1 In the production of the epoxy-modified product of Example 2, (6) n-
The following epoxy-acrylic resin is produced using 48.7 parts of butanol as 22 parts. The reaction temperature is determined at 130 ° C without reflux at 100 to 140 ° C. The remaining 26.7 parts of n-butanol are added after the end of the reaction. The molecular weight of the obtained resin was 80,000, the solid content of the aqueous dispersion was 22%, the amount of solvent was 16%, and the viscosity was 18 seconds / 25 ° C. in a # 4 Ford cup.
Met.

The paint was aged at 50 ° C. for one month, and the viscosity increased.
° C. Some gelation was also observed. Comparative Example 2 In the production of the epoxy modified product of Example 2, (6) n-
48.7 parts of butanol are converted to 48.7 parts of propylene glycol monobutyl ether, that is, the solvent is entirely propylene glycol monobutyl ether. After completion of the dropping of the acrylic monomer, the viscosity was slightly increased, and after 1 hour, stirring became difficult, so the synthesis was stopped. The molecular weight of the resin is beyond the range that can be measured by the instrument, and is probably over 100,000.

[0021]

According to the present invention, by controlling the solvent composition so that the inside of the system is refluxed at the reaction temperature to improve the uniformity, the molecular weight of the obtained resin is reduced to 30,30.
It could be kept between 000 and 70,000, and as a result, a good aqueous dispersion having no storage gelation and excellent storage stability was obtained.

Continuation of front page (56) References JP-A-1-168715 (JP, A) JP-A 1-217023 (JP, A) JP-A-3-296568 (JP, A) JP-A-63-309516 (JP) JP-A-4-351682 (JP, A) JP-A-4-168176 (JP, A) JP-A-57-105418 (JP, A) JP-A-60-106805 (JP, A) 59-1545211 (JP, A) JP-A-58-198513 (JP, A) JP-A-2-77417 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09D 1/00 -201/10 C08F 290/00-290/14 C08F 299/00-299/08 C08G 59/00-59/72

Claims (1)

(57) [Claims] 1. When an acrylic monomer is added dropwise to a modified epoxy resin obtained by modifying an epoxy resin with methacrylic acid together with a polymerization initiator, the solvent in the system is an alkyl alcohol and an ether alcohol, and the ratio thereof is 5/5 to 8 / 2, a method for producing a resin for water-based paint.