JP2563147B2 - Aqueous resin dispersion - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous resin dispersion, and more specifically, the present invention has a high curing rate, excellent hygiene and flexibility, and a color change when applied to a metal substrate. The present invention relates to an aqueous resin dispersion that can be used in an aqueous paint that can form a coating film having an extremely small size.

[0002]

2. Description of the Related Art Conventionally, in can paints and anticorrosion paints,
From the viewpoints of energy saving, environment and pollution, a shift from a solvent system to a water system is desired, and various studies have been made. The main one is a self-emulsifying type resin in which a functional group having emulsifying power is introduced into the molecule by modifying an epoxy resin with an acrylic resin, and a phenol resin is cold-blended as a curing agent. Alternatively, a hot-blended type paint is known.

However, the phenolic resins conventionally used as curing agents tend to undergo self-condensation during baking and curing, which leads to a decrease in flexibility of the cured coating film, and changes the color of the coating film during curing. It had the problem of causing it.

Further, when a conventional phenol resin is used as a curing agent for can paints and anticorrosion paints, low molecular weight components due to the phenol resin are eluted after the paint is dried by heating and cured, which is a safety and health concern. There's a problem. Especially tinplate,
When the above-mentioned coating material is used for an iron-based base material such as a nickel-plated steel sheet, in order to improve the corrosion resistance of the cured coating film, it is generally necessary to add a large amount of a phenol-based resin as a curing agent. It has the drawback that the problem becomes noticeable.

[0005]

DISCLOSURE OF THE INVENTION The object of the present invention is to overcome the drawbacks of the prior art, to have a high curing speed, to have high adhesion to a metal substrate when applied to a metal substrate, and to improve hygiene and hygiene. Another object of the present invention is to provide an aqueous resin dispersion which is excellent in flexibility, chemical resistance and the like and which can form a coating film having an extremely small color change.

[0006]

According to the present invention, there is provided an aqueous resin dispersion which can achieve the above object.

[0007]

That is, the present invention is an aqueous solution obtained by dispersing an acrylic resin (A), an epoxy resin (B) and a phenolic resin (C) containing a carboxyl group in an aqueous medium in the presence of an amine. In the resin dispersion, 20% or more and less than 80% of the phenolic hydroxyl groups of the phenolic resin as the phenolic resin (C) are allyl etherified, the weight average molecular weight is 250 to 800, and the molecular weight is less than 250. An allyl ether type phenol resin having a content of a low molecular weight component of 10% by weight or less is used, and the phenol resin (C) is a spare with a carboxyl group-containing acrylic resin (A) and / or epoxy resin (B). The present invention relates to an aqueous resin dispersion characterized by being condensed.

The carboxyl group-containing acrylic resin (A) used in the present invention is a benzoylperoxide containing a monomer mixture containing a monobasic carboxylic acid monomer such as acrylic acid or methacrylic acid and another copolymerizable monomer. It can be obtained by copolymerizing at a temperature of 80 to 150 ° C. using a usual radical polymerization initiator such as oxide. Other copolymerizable monomers include acrylates such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, methyl methacrylate Methacrylates such as propyl methacrylate, n-butyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, styrene, vinyltoluene,
Styrene-based monomers such as methylstyrene and chlorostyrene, hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate, N-methylol acrylamide, N-butoxymethyl acrylamide and the like N Examples thereof include substituted acrylic monomers, epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile. These other copolymerizable monomers may be used in combination of two or more, if necessary.

The copolymerization ratio of the monobasic carboxylic acid monomer and the other copolymerizable monomer is such that 30 to 90% by weight of the monobasic carboxylic acid monomer and the other copolymerizable monomer 7 are used.
It is preferably 0 to 10% by weight.

When the copolymerization ratio of the other copolymerizable monomer is less than 10% by weight, the resulting acrylic resin (A) containing a carboxyl group has poor dispersibility in an aqueous medium. Further, the copolymerization ratio of the other copolymerizable monomer is 7
When the content is more than 0% by weight, not only the viscosity of the carboxyl group-containing acrylic resin (A) becomes too high to produce the resin smoothly, but also the aqueous resin dispersion is prepared using the acrylic resin (A). When adjusted, the water resistance of the coating film formed from the aqueous resin dispersion becomes poor.

The weight average molecular weight of the acrylic resin (A) containing a carboxyl group is preferably in the range of 10,000 to 50,000, and if the weight average molecular weight is less than 10,000, the processability of the coating film is deteriorated. When the weight average molecular weight is more than 50,000, dispersibility in an aqueous medium becomes poor.

The epoxy resin (B) used in the present invention is obtained by condensing bisphenol A and epichlorohydrin in the presence of an alkali catalyst, and has an average of 1 to 2 molecules per molecule. Those having an epoxy group and having a number average molecular weight of 900 or more are preferable. As commercially available products, there are Epicoat 1009 manufactured by Shell Chemical Co., Ltd., YD-017, YD-019 manufactured by Tohto Kasei Co., Ltd., and the like. A modified epoxy resin obtained by reacting a vegetable oil fatty acid such as dehydrated castor oil or a modifying agent such as bisphenol A with an epoxy group of the bisphenol A type epoxy resin can also be used.

In the present invention, the phenolic resin (C)
Allyl ether type phenol resin used as
First, 1 to 1 mol of phenols and phenols
In the presence of a high-concentration alkali catalyst, 4 mol of formaldehyde is reacted at a relatively low temperature of room temperature to 60 ° C for a long time, and further, if necessary, the temperature is raised to 70 to 90 ° C to promote the condensation and phenol. Formaldehyde is added to the compounds and the weight average molecular weight of the product reaches a desired value, and a low molecular weight component having a molecular weight of less than 250 is 10%.
A phenolic resin is synthesized by performing a condensation reaction until the temperature becomes below. Then, 0.2 to 0.8 mol of allyl halide was reacted with 1 mol of the phenolic hydroxyl group of this phenolic resin to substitute the allyl ether for the phenolic hydroxyl group, and then purified by a conventional method. It is obtained by removing impurities such as a catalyst.

In the allyl ether type phenol resin used in the present invention, 20% or more and less than 80% of the phenolic hydroxyl group in the phenolic resin is allyl etherified, the weight average molecular weight is 250 to 800, and the molecular weight is The content of low molecular weight components less than 250 is 10% by weight or less.

When an allyl ether type phenol resin having an allyl etherification rate of less than 20% is used, the remarkable effects of the present invention due to allyl etherification cannot be obtained. When an allyl ether type phenolic resin having an allyl etherification rate of 80% or more is used, the curing speed tends to be slow.

When an allyl ether type phenol resin having a weight average molecular weight of less than 250 is used,
Processability and hygiene tend to be poor, and when the weight average molecular weight exceeds 800, dispersibility and compatibility are poor.

Further, when an allyl ether type phenol resin having a low molecular weight component having a molecular weight of less than 250 and a content of more than 10% by weight is used, hygiene is poor.

The allyl etherification rate of the allyl ether type phenol resin can be identified by the ratio of the phenolic hydroxyl group around 9 ppm and the allyl ether group around 5.2 ppm by ¹ H-NMR.

The weight average molecular weight of the allyl ether type phenol resin can be measured by gel permeation chromatography (GPC).

The phenols used to synthesize the phenolic resin include phenol, cresol,
Alkylphenols such as ethylphenol, butylphenol, octylphenol, bisphenol A,
Examples thereof include bisphenols such as bisphenol F, and these can be used in combination of two or more kinds.

As the alkali catalyst, alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth hydroxides such as calcium hydroxide and magnesium hydroxide can be used.

As the allyl halide, allyl chloride,
Allyl bromide, allyl iodide and the like can be mentioned.

The aqueous resin dispersion of the present invention is characterized in that the phenol resin (C) is pre-condensed with the carboxyl group-containing acrylic resin (A) and / or epoxy resin (B). .

[0025]

As a method for obtaining the aqueous resin dispersion of the present invention in which the above-mentioned acrylic resin (A) and / or epoxy resin (B) containing a carboxyl group and phenolic resin (C) are precondensed. , For example (a) ~
Method (c) can be mentioned.

(A) Acrylic resin (A) and / or epoxy resin (B) containing a carboxyl group and phenolic resin (C) in a hydrophilic solvent in the presence or absence of amine in a hydrophilic solvent 70 ~ 30 minutes at a temperature of 120 ℃ ~
A method of reacting for 2 hours.

(B) Carboxyl group-containing acrylic resin (A) and epoxy resin (B) in a hydrophilic solvent in the presence or absence of an amine at a temperature of 50 to 150 ° C. for 30 minutes to After preliminarily reacting for 3 hours to partially bond the acrylic resin (A) containing a carboxyl group and the epoxy resin (B), the phenolic resin (C) is added, and further at 70 to 120 ° C. for 30 minutes. Method of reacting for 2 minutes to 2 minutes.

(C) After dissolving the epoxy resin (B) and the phenol resin (C) in a hydrophilic solvent, 70 to 1
A method in which a precondensation reaction is performed at 20 ° C. for 30 minutes to 2 hours, and then the acrylic resin (A) containing a carboxyl group is reacted in the presence or absence of an amine.

In the aqueous resin dispersion of the present invention, the proportion of the acrylic resin (A), the epoxy resin (B) and the phenol resin (C) containing a carboxyl group used is (A) in terms of solid content weight ratio. / (B) = 100/200 ~
500 and (A) + (B) / (C) = 95/5
It is preferably about 70/30.

Examples of the amine include alcohol amines such as aqueous ammonia solution, monoethanolamine and dimethylamine ethanol. The amine may be used in a ratio such that the pH of the aqueous resin dispersion is within the range of 4 to 11, and specifically, the acrylic resin (A), the epoxy resin (B) and the carboxyl group-containing acrylic resin (B) and It is about 1% based on the total weight of the phenolic resin (C).

The hydrophilic solvent is, for example, n
-Butanol, butyl cellosolve and the like.

In the present invention, the aqueous medium means a mixture of water and a hydrophilic solvent. The proportion of the hydrophilic solvent is preferably 20% by weight or less in the aqueous resin dispersion.

In the aqueous resin dispersion of the present invention, confirmation of a partially bound product of the acrylic resin (A) containing a carboxyl group and the epoxy resin (B) can be confirmed by the molecular weight distribution chart by GPC. . Confirmation of a precondensate of a carboxyl group-containing acrylic resin (A) and / or epoxy resin (B) and a phenolic resin (C) can be confirmed by ¹ H-NMR from 2.5 to 2.9.
It can be known from the measurement of the amount of oxirane observed in ppm and the chart of the molecular weight distribution by GPC.

If necessary, a surfactant, an antifoaming agent or the like may be added to the aqueous resin dispersion of the present invention to improve the coatability. Further, an appropriate rust inhibitor, pigment, filler or the like may be blended depending on the use and used for a rust-preventive primer, a printing ink, an anti-corrosion paint and the like.

As a base material to be applied, a metal plate such as an untreated steel plate, a treated steel plate, a tin plate and an aluminum plate is suitable, and a coating method includes spray coating such as air spray and airless spray, and a roll coater. A method such as painting can be used.

[0037]

[Function] When a conventional phenolic resin is used as a curing agent, in addition to the reaction between the epoxy resin and the phenolic resin, the self-condensation of the phenolic resin also proceeds at the same time, so that a uniform cured coating film can be obtained. Therefore, the cured coating film partially takes a sea-island structure, and it is presumed that the cured coating film has poor flexibility. In the present invention, since the allyl ether type phenol resin in which the phenolic hydroxyl group of the conventional phenol resin is partially allyl etherified is used, the self-condensation rate of the phenol resin is suppressed and the flexibility is uniform. It is presumed that such a cured coating film can be obtained.

Further, in the conventional phenolic resin, the low molecular weight component having a molecular weight of less than 250 has water solubility to some extent, which is presumed to reduce the hygiene of the cured coating film. It is assumed that the hygiene will be improved by reducing it as much as possible.

Further, the color change of the cured coating film when a conventional phenolic resin is used as a curing agent is mainly due to the dehydrogenation reaction due to the oxidation of the phenolic hydroxyl group and the formation of the coloring pigment due to the oxidation of the methylene bond. The allyl etherification of the phenolic hydroxyl group in the present invention can suppress the oxidation of the phenolic hydroxyl group, which is the first step of this coloring mechanism, and thus does not generate an unnecessary coloring dye at the time of curing, and therefore, coloring It is assumed that a coating film with extremely small change can be obtained.

[0040]

The present invention will be described below in more detail with reference to examples and comparative examples. In the examples and comparative examples,
Unless otherwise specified, "part" and "%" indicate "part by weight" and "% by weight", respectively.

Various test methods used in Examples and Comparative Examples are as follows.

(1) Adhesion Using a knife on the coated surface, a width of 1.5 mm and a length and width of 1
The number of unstripped portions of the gobang when a single cut is made and a cellophane adhesive tape having a width of 24 mm is closely adhered to the cut and strongly peeled off is shown.

(2) MEK rubbing This is the number of reciprocations when the tin plate surface is exposed by reciprocating a 2 pound hammer with a gauze sufficiently impregnated with MEK (methyl ethyl ketone) on the cured coating film.

(3) Workability Using a special goby folding type DuPont impact tester, put a sample painted on a tin plate folded in two at the bottom and place a 1 kg iron weight with a flat contact surface from a height of 50 cm. The length of the crack in the bent portion generated when dropped was measured. 0-10mm ... ○ 10-20mm… △ 20mm or more …… ×

(4) Resistance to boiling water A test panel coated on a tin plate was treated in water at 100 ° C. for 30 minutes, and then the coating film was judged by the same evaluation as the visual observation and the adhesion property of (1).

(5) Acid resistance 30 vol% sulfuric acid was added dropwise to the coating film and stored at 50 ° C. for 3 hours, and then the sulfuric acid content was wiped off.

(6) Hygiene The coating film and 1 ml of pure water per 1 cm ^{2 of} coating film were put in a pressure resistant bottle, and 1
After treating at 30 ° C. for 30 minutes, the measurement was performed according to the test method (dissolution test) described in the Food Sanitation Law. 10ppm or less ... ○ 10ppm or more ... ×

Example 1Synthesis of acrylic resin solution (A)  Styrene 300 parts Ethyl acrylate 210 parts Methacrylic acid 90 parts Butyl cellosolve 388 parts Benzoyl peroxide 12 parts

One-third of the mixture having the above composition was charged into a four-necked flask whose atmosphere was replaced with nitrogen gas, heated to 90 ° C., and the remaining whole amount was added dropwise at that temperature over 1 hour and 30 minutes.
After completion of the dropwise addition, the mixture was further reacted at that temperature for 2 hours and then cooled to obtain an acrylic resin solution (A) having an acid value of 110 and a solid content of 60.2%. The weight average molecular weight of the acrylic resin is 2
It was 1,000.

[0050]Preparation of epoxy resin solution (B)  Epicoat 1009 (number average molecular weight 5,300) 300 parts Butyl cellosolve 200 parts

An epoxy resin solution (B) having a solid content of 60% was placed in a four-necked flask in which the above components were replaced with nitrogen gas, heated to 120 ° C. and completely cooled.
I got

[0052]Allyl ether type phenolic resin solution
Adjustment of (C-I)  Phenol 94 parts, 37% formalin water 243 parts, 25
% 160% sodium hydroxide solution in a 4-necked flask
Charge, react at 40 ° C for 6 hours, and further at 70 ° C for 1 hour
It was made to react. The phenolic resin is then added to the chloride
After charging 38.3 parts of the mixture and reacting at 40 ° C. for 4 hours,
The separated water was removed. Then, add 10% phosphoric acid aqueous solution.
After adjusting the pH to 3.2 and repeating washing 4 times with water,
Water was removed under reduced pressure and n-butanol was added to the solid content.
60% allyl ether type phenolic resin solution (C-
I) was obtained. Obtained allyl ether type phenolic tree
The weight average molecular weight of the fat solution (measured by GPC) is 480.
And the content of low molecular weight components having a molecular weight of less than 250 is
It was 4.3% by weight. In addition,¹By H-NMR
Allyl ether of rill ether type phenolic resin solution
When the conversion rate was measured, the allyl ether conversion rate was 48%.
there were.

[0053]Preparation of aqueous resin dispersion  Acrylic resin solution (A) 25 parts Epoxy resin solution (B) 100 parts n-Butanol 10 parts Butyl cellosolve 10 parts Dimethylaminoethanol 1 part Dimethylaminoethanol 5 parts Allyl ether type phenolic resin solution (CI) 31 parts Deionized water 205 parts Nitrogen gas-substituted four-necked flask was charged with
After raising the temperature to 00 ° C, add dropwise and incubate at 100 ° C for 2 hours.
I responded. Then add, and then add 1
Hold at a temperature of 00 ° C for 10 minutes and then add
A stable aqueous resin dispersion of 25% form was obtained.

Example 2Preparation of allyl ether type phenolic resin solution (C-II)
Order  In Example 1, allyl ether type phenolic resin
When preparing the solution (CI), the charged amount of allyl chloride was adjusted to 6
The reaction was carried out in the same manner as in Example 1 except that the amount was changed to 1.2 parts.
Allyl ether type phenolic resin solution with 60% form factor
(C-II) was obtained. Obtained allyl ether type pheno
The weight average molecular weight of the resin resin solution is 550.
The content of low molecular weight component of less than 250 is 3.1% by weight
there were. Also, allyl ether type phenolic resin solution
The rate of allyl etherification of
The conversion rate was 78%.

[0055]Preparation of aqueous resin dispersion  In Example 1, allyl was added during the preparation of the aqueous resin dispersion.
Instead of the ether type phenolic resin solution (CI)
Allyl ether type phenolic resin solution (C-II)
Same as the preparation of the aqueous resin dispersion of Example 1 except that it was used
Stable aqueous resin content with solid content of 25% depending on the composition and method
I got a scatter.

Example 3Preparation of allyl ether type phenolic resin solution (C-III)
Order  Bisphenol A 228 parts, 37% formalin water 324
Parts, 160 parts of 25% aqueous sodium hydroxide solution in 4 mouths
The mixture was placed in a Rasco and reacted at 60 ° C. for 5 hours. Then
38 parts of allyl chloride was charged and reacted at 40 ° C. for 4 hours.
Separate the aqueous layer and adjust the pH to 3.4 with 10% aqueous phosphoric acid.
And repeat washing 4 times with water, and then add water under reduced pressure.
Remove and add n-butanol to remove ants with 60% solids.
A ether type phenolic resin solution (C-III) was obtained.
Weight of the obtained allyl ether type phenolic resin solution
It has an average molecular weight of 420 and a low molecular weight of less than 250.
The content of the molecular weight component was 0% by weight. In addition,
Measurement of allyl etherification rate of ether type phenolic resin
As a result, the allyl etherification rate was 22%.

[0057]Preparation of aqueous resin dispersion  In Example 1, allyl was added during the preparation of the aqueous resin dispersion.
Instead of the ether type phenolic resin solution (CI)
Allyl ether type phenolic resin solution (C-III)
Same as the preparation of the aqueous resin dispersion of Example 1 except that it was used
Stable aqueous resin dispersion with solid content of 25% by various blending methods
Got the body

Comparative Example 1Preparation of allyl ether type phenolic resin solution (C-IV)
Order  Phenol 94 parts, 37% formalin water 243 parts, 25
% 160% sodium hydroxide solution in a 4-necked flask
After charging and reacting at 40 ° C for 6 hours, the temperature was raised to 70 ° C.
And allowed to react at that temperature for 1 hour. Then this pheno
7.7 parts of allyl chloride was added to a resin and the mixture was mixed at 40 ° C
After reacting for 10 hours, add 10% phosphoric acid aqueous solution to adjust the pH.
Was adjusted to 3.2. After washing with water 4 times, under reduced pressure
To remove water and add n-butanol, solid content 60%
Allyl ether type phenolic resin solution (C-IV)
Obtained. Obtained allyl ether type phenolic resin solution
Has a weight average molecular weight of 550 and a molecular weight of less than 250
The content of the low molecular weight component was 4.2% by weight. Well
Allyl ether type phenolic resin
The conversion rate was 9.5%.

[0059]Preparation of aqueous resin dispersion  In Example 1, allyl was added during the preparation of the aqueous resin dispersion.
Instead of the ether type phenolic resin solution (CI)
Allyl ether type phenolic resin solution (C-IV)
Same as the preparation of the aqueous resin dispersion of Example 1 except that it was used
Stable aqueous resin dispersion with solid content of 25% by various blending methods
Got the body

Comparative Example 2Preparation of allyl ether type phenolic resin solution (CV)
Order  Phenol 94 parts, 37% Formalin 243 parts, 25%
160 parts of sodium hydroxide aqueous solution is prepared in a 4-necked flask.
And reacted at 40 ° C. for 6 hours. Then allyl chloride
Charge 76.5 parts and react at 40 ° C for 4 hours, then separate
The water removed was removed. Then, add 10% phosphoric acid aqueous solution
The pH was adjusted to 3.2. Washing with water was repeated 4 times
After that, water was removed under reduced pressure, and n-butanol was added to solidify.
Allyl ether type phenolic resin solution with 60% form factor
(CV) was obtained. Obtained allyl ether type pheno
Resin solution has a weight average molecular weight of 280 and a molecular weight of 25.
The content of low molecular weight components less than 0 is 42.6% by weight, ant
The rate of ruthelation was 94%.

[0061]Preparation of aqueous resin dispersion  In Example 1, allyl was added during the preparation of the aqueous resin dispersion.
Instead of the ether type phenolic resin solution (CI)
Allyl ether type phenolic resin solution (CV)
Same as the preparation of the aqueous resin dispersion of Example 1 except that it was used
Stable aqueous resin dispersion with solid content of 25%
Obtained.

The aqueous resin dispersions obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were applied to tin plates to a thickness of 8 to 10 microns and baked at 210 ° C. for 10 minutes to prepare test panels. did. The test results are shown in Table 1.

[0063]

[Table 1]

[0064]

As is apparent from the results of the examples, the aqueous resin dispersion of the present invention can form a coating film having extremely high flexibility and hygiene when applied to a metal substrate. .

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Claims (1)

(57) [Claims] 1. An aqueous resin dispersion comprising a carboxyl group-containing acrylic resin (A), an epoxy resin (B) and a phenolic resin (C) dispersed in an aqueous medium in the presence of an amine. As the phenolic resin (C), 20% or more and less than 80% of the phenolic hydroxyl groups of the phenolic resin are allyl etherified,
An allyl ether type phenolic resin having a weight average molecular weight of 250 to 800 and a low molecular weight component having a molecular weight of less than 250 is 10% by weight or less, and the phenolic resin (C) is a carboxyl group-containing acrylic resin. An aqueous resin dispersion characterized by being pre-condensed with a resin (A) and / or an epoxy resin (B).