JPS63309516A - Aqueous resin dispersion - Google Patents

Abstract

PURPOSE:To obtain an aqueous resin dispersion which form a smooth film surface free of coating defects when applied with a roller coater and excels in film properties, by dispersing a composition containing a reaction product of a specified modified epoxy resin with a specified polymerizable monomer in an aqueous medium by neutralizing it with an amine or the like. CONSTITUTION:An aqueous resin dispersion is prepared by dispersing a composi tion containing a reaction product of a modified epoxy resin (i) prepared by reacting 100pts.wt. aromatic epoxy resin of a number-average MW of 1,000-8,000 with 0.1-10pts.wt. (meth)acrylic acid and 3-100pts.wt. nonpolymerizable polybasic carboxylic acid (e.g., adipic acid) with polymerizable monomer (ii) containing 12-80wt.% monobasic carboxylic acid monomer [e.g., (meth)acrylic acid] as an essential component in an aqueous medium by at least partially neutralizing it with an amine (e.g., 2-dimethylaminoethanol) or ammonia. This dispersion has excellent roller coatability and properties as a baking coating composition intended for metals, especially, as a can interior paint.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an aqueous resin dispersion, and more specifically, as a coating composition for baking on metals, particularly for the inner surface of cans. This invention relates to an aqueous resin dispersion that has both excellent roll coatability and physical properties as a paint.

(Prior Art) It has been desired to use water-based paints for can inner surfaces and anticorrosion paints from the viewpoints of resource saving, energy saving, and environmental pollution. The same applies to water-based systems as in the case of melt-cut types.

Epoxy resins have been mainly studied, and various methods have been proposed for dispersing epoxy resins in water.

For example, methods using anionic and nonionic surfactants are known as methods for dispersing epoxy resins using surfactants, but they have poor storage stability, hygiene, chemical and mechanical performance, and It is unsuitable as a commercial paint.

As a solution to this problem, various self-emulsifying epoxy resins have been proposed in which epoxy resins are modified with acrylic resins and segments with emulsifying power are introduced into the molecules.

For example, JP-A-53-1228 discloses a grafted epoxy resin obtained by polymerizing a monomer mixture containing a carboxylic acid monomer using a free radical generator such as benzoyl peroxide in the presence of an epoxy resin. have been shown to be able to be stably dispersed in aqueous media containing bases.

JP-A-53-14963 and JP-A-55-94
Publication No. 33 discloses that a partial reactant containing an excess of carboxyl groups obtained by reacting an acrylic resin with a relatively high molecular weight aromatic epoxy resin can be stably dispersed in an aqueous medium in the presence of ammonia or an amine. It is shown. JP-A No. 55-3481 and JP-A No. 55-3482 disclose self-emulsifying compounds in which substantially no oxirane groups of epoxy resins obtained by converting carboxyl group-functional polymers into amine esters are self-emulsified in water with a base. Emulsifying epoxy ester copolymers are disclosed. JP-A-57-105418 and JP-A-58-1985
No. 13 discloses that an epoxy group in one molecule obtained by partially reacting an aromatic epoxy resin and (meth)acrylic acid,
Polymerizing a monomer mixture containing acrylic acid or methacrylic acid into a low molecular compound having an acryloyl group,
Aqueous dispersion compositions obtained by neutralization with basic compounds are disclosed.

Since the self-emulsifying epoxy resin obtained by the above technique does not contain a surfactant in the coating material, a strong coating film can be obtained by itself.

There are various methods for applying these aqueous resin dispersions to non-painted substrates such as metal plates, such as spray painting, dip painting, and curtain flow coaters, but roll coater painting requires less cost for painting equipment. It has the advantage of being able to stably coat even a relatively small amount of coating, so it has become the mainstream for coating metal plates for single cans, especially coiled or sheet steel plates. ing. However, the above-mentioned self-emulsifying epoxy resin has a characteristic of being highly thixotropic, and it has been found that the following problems occur when coating with a roll coater due to the resin's viscoelastic properties. In other words, the transfer from the paint supply roll to the application roll is unstable, and the amount of coating film formed becomes unstable. In addition, when the paint is transferred from the application roll to the metal plate, the flow is poor and paint ribs occur on the metal plate.
This can cause defects in the coating film that are fixed to the formed coating film and have an extremely thin coating thickness.

(Problems to be Solved by the Invention) As a result of studies, the present inventors discovered that the water solubility and viscoelasticity of self-emulsifying epoxy resins have a large effect on the paintability of roll coater coating, leading to the present invention. 2 The present invention improves the above-mentioned conventional drawbacks, and forms a coating film as good as that of solvent-based paints during roll coater coating, that is, no coating defects occur and a smooth coating surface is formed. can,
The present invention also provides an aqueous resin dispersion that has excellent coating film properties.

[Structure of the invention]

(Means for Solving the Problems) That is, the present invention provides for
A modified epoxy resin obtained by reacting 100 parts by weight of an aromatic epoxy resin with 0.1 to 10 parts by weight of acrylic acid or methacrylic acid and 3 to 100 parts by weight of a non-polymerizable polybasic carboxylic acid. .

A composition containing a reaction product with a polymerizable monomer containing 12 to 80% by weight of a monobasic carboxylic acid monomer as an essential component is prepared in an aqueous medium by at least partially neutralizing it with an amine or ammonia. It is an aqueous resin dispersion obtained by dispersing the resin.

The aromatic epoxy resin used in the present invention includes an epoxy resin made by reacting bisphenols such as bisphenol A, bisphenol B, and bisphenol F with epichlorohydrin in the presence of an alkali catalyst, and a commercially available product is Epicoat manufactured by Cheshi Chemical Co., Ltd. 828. Epicote 1001. Epicote 1004. Epicote 1007. Epicote 1009, Epicote 1
010. Examples include Epicor 1-1100L. In addition, dehydrated castor oil fatty acid is added to the epoxy group or hydroxyl group of the bisphenol type epoxy resin.

Soybean oil fatty acid, coconut oil fatty acid or bisphenol A
It is also possible to use epoxy resins modified with, etc.

The modified epoxy resin in the present invention includes a compound in which the epoxy group of an aromatic epoxy resin is esterified with acrylic acid or methacrylic acid and/or a non-polymerizable polybasic carboxylic acid. As for the reaction order, it is preferable to perform modification with acrylic acid or methacrylic acid followed by modification with polybasic carboxylic acid, but this order is not specified, and modification with acrylic acid or methacrylic acid is performed after modification with polybasic carboxylic acid. In some cases, both compounds may be reacted simultaneously.

Modification with acrylic acid or methacrylic acid.

80℃~200℃ without catalyst or using an alkali catalyst
The reaction can be carried out at a reaction temperature of 1 to 10 hours. The blending amount of acrylic acid or methacrylic acid is 0.00 parts by weight per 100 parts by weight of aromatic epoxy resin.
1 to 10 parts is preferred. If the amount of acrylic acid or methacrylic acid blended is less than 0.1 part by weight, a reaction with the polymerizable additive described below may occur, that is, the epoxy resin cannot become a self-emulsifying type.

On the other hand, if the amount is more than 10 parts by weight, many reactive double bonds will be introduced into the epoxy resin, and as a result, gelation will easily occur during reaction with monopolymerizable monomers.

Modification with a polybasic carboxylic acid may be performed under the same conditions as above. Examples of polybasic carboxylic acids used here include adipic acid, pimelic acid, and speric acid.

Azelaic acid, sebacic acid, phthalic acid, terephthalic acid,
There are non-polymerizable aliphatic or aromatic dicarboxylic acids such as isophthalic acid, and non-polymerizable tricarboxylic acids such as trimellitic acid and trimellitic anhydride, as well as pyromellitic acid and pyromellitic anhydride. There are non-polymerized tetravalent carboxylic acids such as acids. The amount of polybasic carboxylic acid used is preferably 3 to 100 parts, more preferably 5 to 30 parts, based on 100 parts by weight of the aromatic epoxy resin. If the amount of the polybasic carboxylic acid used is less than 3 parts by weight, the properties of the final aqueous dispersion will become highly thixotropic, making it difficult to obtain roll coatability. If the amount increases, the water resistance of the coating film will deteriorate, which is not preferable.

In order to make the epoxy resin self-emulsifying in the present invention, the modified epoxy resin obtained above is reacted with a polymerizable monomer containing 12 to 80% by weight of a monobasic carboxylic acid monomer as an essential component. This reaction is.

This is a polymerization reaction between the acryloyl group or methacryloyl group of a modified epoxy resin and a polymerizable monomer.

That is, a monomer mixture consisting of a monobasic carboxylic acid monomer such as acrylic acid or methacrylic acid and other copolymerizable monomers is mixed with an ordinary radical polymerization initiator such as azobisisobutyronitrile or benzoyl peroxide in an organic solvent. Copolymerization is carried out at a temperature of 80°C to 150°C. The above copolymerizable monomers include methyl acrylate, ethyl acrylate, isopropyl acrylate,
n-butyl acrylate, isobutyl acrylate, n-amyl acrylate.

Isoamyl acrylate, n-hexyl acrylate.

Acrylic acid esters such as 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, and dodecyl acrylate, and methyl methacrylate.

Propyl methacrylate, n-butyl methacrylate.

Isobutyl methacrylate, n-amyl methacrylate.

Methacrylic acid esters such as n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, styrene, vinyltoluene, 2-methylstyrene,
Styrenic monomers such as t-butylstyrene and chlorstyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate, N-methylol (meth)acrylamide, N
N-substituted (meth)acrylic monomers such as -butoxymethyl (meth)acrylamide, glycidyl acrylate.

It can be selected from one or more of epoxy group-containing monomers such as glycidyl methacrylate and acrylonitrile.

The amount of the monobasic carboxylic acid heptamer used is 12 to 80% by weight based on the amount of the copolymerizable monomer.

If the amount used is less than 12% by weight, the dispersion stability of the resin in the aqueous medium, the adhesion of the painted film to metal, and the solvent resistance will deteriorate, which is undesirable.On the other hand, if the amount used is more than 80% by weight, This is not preferred because the water resistance of the coating film becomes poor.

In the present invention, the aqueous resin dispersion is prepared by adding ammonia or amine to a composition containing a reaction product of a modified epoxy resin and a copolymerizable monomer in an amount such that the final composition has a pH of 4 to 11. It may be dispersed in an aqueous medium, but if high-boiling solvents are used in the previous step, it is preferable to remove these solvents in advance under reduced pressure.

The above amine is, for example, trimethylamine.

Alkylamines such as triethylamine and butylamine, alcohol amines such as 2-dimethylaminoethanol, jetanolamine, triethanolamine, and aminomethylpropanol, 2-morpholine, and the like are used. Polyvalent amines such as ethylenediamine and diethylenetriamine can also be used.

In the present invention, the aqueous medium means water alone or a mixture with a hydrophilic organic solvent in which at least 10% by weight is water, and examples of the hydrophilic organic solvent include methanol, ethanol, n-propanol, isopropanol, n-propanol, -Butanol, 5ec-butanol + tart-butanol, alkyl alcohols such as isobutanol, ether alcohols such as methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, methyl calpitol, ethyl carpitol, methyl cellosolve acetate, ethyl cellosolve acetate and other ether esters such as dioxane, dimethylformamide, dioxane alcohol, etc. are used.

The aqueous resin dispersion of the present invention can be improved in curability and adhesion to metal by adding a curing agent such as a Fehr resin or an amino resin, if necessary. Furthermore, although the aqueous resin dispersion according to the present invention itself has good paintability, it is possible to further improve the paintability by adding a surfactant, an antifoaming agent, etc. as necessary. .

Applicable base materials include untreated steel sheets and treated steel sheets.

Metal plates such as galvanized steel plates and tin plates are suitable, and roll coating is the most preferred coating method, but air spray, airless spray, electrostatic spray coating, dipping coating, electrodeposition coating, etc. are also possible. It is. Further, the baking conditions can be selected from the range of 2 to 30 minutes at a temperature of 150° C. to 230° C. for 9 hours.

The aqueous resin dispersion of the present invention can be used in antirust sprays, printing inks, anticorrosive paints, etc. by adding appropriate rust preventive agents, pigments, fillers, etc., depending on the purpose.

Example 1 [Preparation of acryloyl group-containing epoxy resin solution] 100 parts of Epicote 1009, 1.0 part of acrylic acid, 1.0 part of 1% sodium hydroxide solution, and 100 parts of ethylene glycol monobutyl ether were placed in a flask and the epoxy resin was dissolved. After that, the mixture was reacted at 135°C for 4 hours. Final acid value 0.1. An epoxy resin solution with a solid content of 50% was obtained.

[Preparation of modified epoxy resin solution]

202 parts of the above acryloyl group-containing epoxy resin (100 parts of unmodified epoxy resin) and 15 parts of adipic acid were charged into a flask and reacted at 160°C for 5 hours. Initial acid value 10
What was 0 became 63 after the reaction. A modified epoxy resin solution with a solid content of 53% was obtained.

[Preparation of phenolic resin solution]

228 parts of bisphenol A, 227 parts of a 37% formaldehyde aqueous solution, and 20 parts of 25% aqueous ammonia were charged into a flask and reacted at 95° C. for 90 minutes.

The resulting condensation product was extracted into a mixed solvent consisting of 50 parts of MIBK, 50 parts of cyclohexanone, and 100 parts of xylene, and dehydrated by heating and refluxing for 120 minutes, resulting in a number average molecular weight of 680. A phenol resin solution with a solid content of 50% was obtained.

[Adjustment of aqueous resin dispersion]

25 parts of styrene to 300 parts of the above modified epoxy resin solution,
60 parts of methacrylic acid, 2.5 parts of N,N-azobisisobutyronitrile, and 80 parts of n-butanol were added and mixed uniformly. Pour 117 parts of this mixed solution into a flask and
The remaining mixture was added dropwise over a period of 120 minutes while the temperature was maintained at .degree. C., and after the addition of 2 drops, the reaction was continued for an additional 60 minutes. Thereafter, 120 parts of the above phenol resin was added, and while stirring, 30 parts of 2-dimethylaminoethanol was added for neutralization.

After boiling, 600 parts of ion-exchanged water was gradually added while stirring, resulting in a solid content of 20% and a viscosity of 390 cps (at 25°C).
A milky-white dispersion was obtained, in which all viscosities below are measured at 25°C).

Example 2 [Preparation of methacryloyl group-containing epoxy resin solution] 100 parts of Epicoat 1007, 1.3 parts of methacrylic acid,
A flask was charged with 1.0 part of a 1% calcium hydroxide solution and ethylene glycol monoethyl ether acetate-zoos to dissolve the epoxy resin, and then reacted at 130°C for 5 hours. Final acid value 0.3. An epoxy resin solution with a solid content of 50% was obtained.

[Preparation of modified epoxy resin solution]

202 parts of the above methacryloyl group-containing epoxy resin solution (100 parts of unmodified epoxy resin), 8.0 parts of phthalic acid, and 0.005 parts of dimethylbenzylamine were charged into a flask and reacted at 130° C. for 3 hours. The initial acid value was 50, but it became 27. A modified epoxy resin solution with a solid content of 52% was obtained.

[Adjustment of aqueous resin dispersion]

To 300 parts of the above acid-modified epoxy resin solution, 14 parts of styrene, 5 parts of ethyl acrylate, 28 parts of methacrylic acid, N,
2.5 parts of N-azobisisobutyronitrile.

50 parts of n-butanol was added and mixed uniformly. 100 parts of this mixed solution was placed in a flask and heated to 90°C.

The remaining mixture was added dropwise over 120 minutes while keeping the temperature of the liquid in the flask at 90°C, and after 2 drops, the reaction was continued for an additional 120 minutes. Thereafter, 15 parts of Cymel 303 (a water-soluble amino resin manufactured by Mitsui Toatsu) was added. Further, while stirring, 18 parts of 25% aqueous ammonia was added to effect neutralization. Thereafter, 600 parts of ion-exchanged water was gradually added while stirring to obtain a milky white dispersion with a solid content of 21% and a viscosity of 4 socps. The obtained dispersion was stored at 50°C for 3 months, but no abnormalities were observed.

Example 3 [Preparation of modified epoxy resin solution] Acryloyl group-containing epoxy resin solution 202 of Example 1
(100 parts of unmodified epoxy resin) and 5.0 parts of trimellitic acid were charged into a flask and reacted at 200°C for 1 hour. The initial acid value was 38, but it became 19 after the reaction.

A modified epoxy resin solution with a solid content of 51% was obtained.

[Adjustment of aqueous resin dispersion]

23 parts of acrylic acid and 18 parts of 2-ethylhexyl acrylate were added to 300 parts of the above modified epoxy resin solution.

5 parts of methyl methacrylate, 3 parts of N,N-azobisisobutyronitrile, and 40 parts of n-butanol were added and mixed uniformly. Pour 100 parts of this mixture into a flask and
The temperature was raised to 00°C. The remaining mixture was added dropwise over 120 minutes while keeping the liquid temperature in the flask at 90°C, and after 9 drops, the reaction was continued for another 120 minutes. Thereafter, 120 parts of the phenol resin of Example 1 was added, and 12 parts of 25% aqueous ammonia was further added with stirring to effect neutralization.

Thereafter, 600 parts of ion-exchanged water was gradually added while stirring to obtain a milky white dispersion with a solid content of 23% and a viscosity of 510 cps. The obtained dispersion was stored at 50°C for 3 months, but no abnormalities were observed.

Example 4 [Preparation of modified epoxy resin solution] Methacryloyl group-containing epoxy resin solution 2 of Example 2
02 parts (100 parts of unmodified epoxy resin).

80 parts of adipic acid and 149 parts of ethylene glycol monobutyl ether were charged into a flask and reacted at 160°C for 5 hours. The initial acid value was 340, but it became 289 after the reaction. A modified epoxy resin solution with a solid content of 53% was obtained.

[Adjustment of aqueous resin dispersion]

An aqueous resin dispersion was obtained in the same manner as in Example 1 using the above modified epoxy resin solution.

Comparative Example 1 [Preparation of aqueous resin dispersion] Acryloyl group-containing epoxy resin solution of Example 1 300
25 parts of styrene and 60 parts of methacrylic acid.

2.5 parts of N,N-azobisisobutyronitrile, n
- 60 parts of butanol was added and mixed uniformly. Using this mixed solution, an aqueous resin dispersion was obtained in the same manner as in Example 1.

Comparative Example 2 [Preparation of aqueous resin dispersion] Methacryloyl group-containing epoxy resin solution 3 of Example 2
00 parts, 14 parts of styrene, 5 parts of ethyl acrylate, 28 parts of methacrylic acid, 2.5 parts of N,N-azobisisobutyronitrile, and 50 parts of n-butanol were added and mixed uniformly. Using this liquid mixture, an aqueous resin dispersion was obtained in the same manner as in Example 2.

Comparative Example 3 [Preparation of modified epoxy resin solution] 202 parts of the acryloyl group-containing epoxy resin solution of Example 1 (unmodified epoxy resin content: 100 parts), 2.0 parts of adipic acid.
5 parts were charged into a flask and reacted at 160°C for 5 hours.

The initial acid value was 40, but it became 19 after the reaction. A modified epoxy resin solution with a solid content of 51% was obtained.

[Adjustment of aqueous resin dispersion]

An aqueous resin dispersion was obtained in the same manner as in Example 3 using the above acid-modified epoxy resin.

Examples 1-4. The aqueous dispersions obtained in Comparative Examples 1 to 3 were applied onto a tin plate to a thickness of 8 to 10 μm.

The test panels were baked at 165° C. for 5 minutes each and dried. The test results for various resistances are shown in Table ■. Various test methods are as follows.

(1) Adhesion: Approximately 1.5 mm using a knife on the coating surface
Make 11 vertical and horizontal cuts in the width of the goban. When a cellophane adhesive tape with a width of 24 mm is tightly applied and strongly peeled off, the number of unpeeled portions of the goblin area is expressed as a numerator.

(2) Retort resistance: After treatment in water at 125℃ for 30 minutes,
The coating film is judged visually and by peeling off the cellophane adhesive tape.

(3) Workability: This occurs when a special fold-type DuPont impact tester is used, a sample folded in half is placed at the bottom, and an iron weight with a flat contact surface weighing I kg is dropped from a height of 50 cm. The length of the crack in the paint film at the bent part was measured.

0~101m・・・○ mark Work O ~ 20 Tsuru... Δ mark 20wm or more... Indicated by an X mark.

(4) Corrosion resistance: A test piece with an X mark made on the coating surface using a knife is treated in 1% saline at 125°C for 30 minutes, and the degree of corrosion near the X mark is determined.

Items with no abnormality...○ Items with slight corrosion...△ Items with significant corrosion...
... × (5) Painting condition: Using a natural roll coater.

Painting was performed so that the coating film thickness after baking and drying was 5 μm. The height of the flow generated at that time was measured using a surface roughness meter.

0 to 0.7 μm・・・○ mark 0.7~1.5μm・・・△mark 5 μm or more... Indicated by an x mark.

Table ■ [Effects of the Invention] The aqueous resin dispersion of the present invention is stable even when the proportion of water in the aqueous medium is 90% or more, and is suitable for roll coaters.
Since it is suitable for coating, it is possible to perform roll coating, which is the most productive coating material for the inner surface of cans, for example. Moreover, the resulting coating film is excellent in physical properties such as coating adhesion, water resistance, and coating flexibility.

Claims (1)

[Claims] 1. 0.1 to 10 parts by weight of acrylic acid or methacrylic acid and 3 to 100 parts by weight of non-polymerizable polybasic carboxylic acid per 100 parts by weight of aromatic epoxy resin having a number average molecular weight of 1000 to 8000. A composition containing a reaction product of a modified epoxy resin obtained by reacting a monobasic carboxylic acid monomer with a polymerizable monomer containing 12 to 80% by weight of a monobasic carboxylic acid monomer as an essential component is at least partially neutralized with an amine or ammonia. An aqueous resin dispersion that is dispersed in an aqueous medium by mixing.