JP3288971B2 - Method for reusing cold-setting aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Explanation of Terms] Terms used in the present invention will be described in detail with reference to FIGS. The “collecting liquid” denoted by reference numeral 4 in FIG. 1 refers to a solution for dissolving and recovering excess coating composition (21) generated during coating, and is usually a coating booth (1). Used in the form of a water curtain (3). In the present invention,
As shown in FIGS. 1 and 2, the “paint diluent (6)” refers to the excess paint composition (2) collected by the collection liquid (4).
Refers to a solution containing 1). Thereafter, as shown in more detail in FIG. 2, the “paint diluent (6)” is subjected to filtration and concentration several times using an ultrafiltration device (7) including a membrane (71), whereby “ Filtrate (20) '' and `` intermediate concentrated paint (1
6)). The "filtrate (20)" contains water and a solvent, and is also referred to as "separate solution (9)" in the present invention. The “final concentrated paint (16 ′)” refers to a paint that can be reused as a cold-setting aqueous paint composition by subsequently adjusting the paint particle size and the like.

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reusing surplus paint after applying a reusable cold-setting water-based paint to an object. Specifically, the present invention, the coating composition, collected by a collection liquid in a coating booth,
The present invention relates to a method of filtering and concentrating the resultant to separate it into a concentrated paint and a separated liquid, and then re-adjusting and reusing each.

[0003]

2. Description of the Related Art Conventionally, automotive parts, industrial machines, agricultural equipment and the like have been coated with a rust-proofing water-based paint as a primer. Such a water-based paint must be dried and cured at the temperature of an object to be coated (usually 80 ° C. or lower) for a work that cannot improve heat resistance or has a large heat capacity, and is usually called a room temperature-curable water-based paint. ing.

[0004] When the room-temperature-curable water-based paint is spray-painted in a coating booth, a large amount of paint dust that is not applied to an object to be coated is generated. Such paint spray dust is collected by being dissolved or dispersed in booth water in a coating booth. Since the collected paint dust is very large, discarding the paint dust as it is results in loss of paint and also leads to environmental pollution.

Therefore, it has been studied to collect and reuse the paint collected in the booth water.
A recovery method as disclosed in JP-A-9-51324 has been proposed. In the method described in JP-A-49-51324, first, spray dust of an aqueous coating composition is collected with water to obtain coating dilution water. The coating composition is recovered and concentrated by filtering the water through the obtained coating dilution water through a reverse osmosis membrane or an ultrafiltration membrane. afterwards,
The concentrated coating composition is readjusted so as to have the same nonvolatile content as the original aqueous coating composition, and then reused. Here, the non-volatile component refers to a water-soluble resin or pigment for forming a coating film such as a water-soluble alkyd resin or a water-soluble acrylic resin contained in the water-based coating composition.

A disadvantage of the method described in Japanese Patent Application Laid-Open No. 49-51324 is that when the paint dilution water collected in water is separated and concentrated by an ultrafiltration membrane or the like, the aqueous liquid separated by filtration is separated. Is generated in large quantities. The recovered paint is reused, but the aqueous liquid containing water needs to be disposed of. Therefore, it has been proposed that this aqueous liquid be returned to the coating booth and reused as washing water.

However, the concentrated paint and the aqueous liquid separated from the paint dilution water cause various inconveniences when reused repeatedly. For example, in the collected concentrated paint, the concentration of volatile components is reduced, so that the amount of neutralized amine in the volatile components is also reduced, whereby the pH of the paint itself is gradually reduced. Further, in the separated aqueous liquid, low-molecular components (for example, residual monomers and by-products contained in the base material of the paint, generated during the neutralization of the resin varnish and during storage) are separated from the paint composition by filtration. The concentration of decomposition products of the resin increases with each reuse. As such concentrated paints and aqueous liquids continue to be reused, the solvent composition and pH of the paint composition that determine the suitability for reuse (recycling)
The hydration stability of the resin with respect to changes in the composition gradually decreases, and eventually, the hydration stability of the resin in the coating composition may decrease, resulting in aggregation or separation of the paint.

As a method for eliminating the above-mentioned inconveniences,
Methods have also been proposed to increase the hydrophilicity of the resin in the original aqueous coating composition, thereby increasing the hydration stability of the resin upon reuse. However, when such a method is used, the coating film performance (for example, salt spray resistance, water resistance, etc.) of the paint may decrease. Further, although there is a cold-setting water-based paint having anticorrosion properties, there is no one that can overcome the above-mentioned disadvantages and impart recyclability.
In addition, the method described above does not improve the disadvantage of reusing the filtered and separated aqueous liquid as washing water.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the efficiency of filtration and concentration of paint diluting water by preventing the separation of resin and pigment in a cold-setting aqueous coating composition having anticorrosion properties. It is an object of the present invention to provide a method for reusing said coating composition which can be enhanced. Further, an object of the present invention is to use a coating composition in which the acid value of the resin for forming a coating film is selected so as to correspond to the composition ratio and the pH of the collecting liquid, and to use the coating composition and the collecting liquid. Is also to provide a way to reuse.

[0010]

According to the present invention, i) a composition ratio:
Epoxy resin (a) / fatty acid (b) / ethylenically unsaturated monomer (c) = 20-70: 20-50: 3-50
(% By weight) (where a + b + c = 100) and a reusable cold-setting aqueous coating composition containing an acrylic-modified epoxy ester resin having an acid value of 25 to 60 were collected in a coating booth at a pH adjusted beforehand. Liquid to obtain a paint diluent, ii) filtering and concentrating the paint diluent to separate it into a concentrated paint and a separated liquid, and iii) containing a hydrophilic solvent in the separated liquid. A method for reusing a reusable cold-curable aqueous coating composition, comprising adjusting the amount to 1.5 to 20% by weight and adjusting the pH to 8 to 10 to reuse as a collecting liquid. .

[0011] In the method for reusing the cold-setting aqueous coating composition, the filtration and concentration step ii) is particularly preferably performed by an ultrafiltration device.

The method of the present invention can be reused repeatedly by limiting the acid value of the resin in the cold-setting aqueous coating composition (that is, by limiting the degree of hydrophilicity of the resin).

Further, in the method of the present invention, the acid value of the resin in the cold-setting aqueous coating composition to be used is selected depending on the pH value of the collecting liquid or the content of the hydrophilic solvent in the collecting liquid. It is also possible.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. A cold-curable aqueous coating composition suitable for use in the method of the present invention comprises an acrylic-modified epoxy ester resin as a main component and other additives. The solvent for the coating composition comprises water and a hydrophilic solvent.

The acrylic-modified epoxy ester resin can be synthesized from an epoxy resin (a), a fatty acid (b) and an ethylenically unsaturated monomer (c). Acrylic-modified epoxy ester resin is firstly epoxy resin (a)
After synthesizing an epoxy ester resin from a fatty acid (b) and an appropriate ethylenically unsaturated monomer (c),
It may be acrylic-modified. The acryl-modified epoxy ester resin preferably contains a styrene monomer in the acryl-modification step from the viewpoint of easy modification.

Examples of the epoxy resin (a) include “Epicoat 828”, “Epicoat 1001”, “Epicoat 1002”, “Epicoat 1004”, and “Epicoat 100”.
7 "and" Epicoat 1009 "(both made of shell, bisphenol A type epoxy resin) and" Epototo
YD-128, Epototo YD-011, Epototo YD-01
Commercially available epoxy resins such as "2", "Epototo YD-014", "Epototo YD-017" and "Epototo YD-019" (a bisphenol A type epoxy resin manufactured by Toto Kasei) can be used. One or more of the above epoxy resins may be used simultaneously.

As the fatty acid (b), any of natural or synthetic fatty acids can be used. For example, tung oil, linseed oil, castor oil, dehydrated castor oil, safflower oil, tall oil, soybean oil, coconut oil, etc. The resulting fatty acids are mentioned.
One or more of the above fatty acids may be used simultaneously.

The synthesis of the epoxy ester resin from the epoxy resin (a) and the fatty acid (b) can be performed by a conventionally known method. For example, the epoxy resin (a) and the fatty acid (b) are mixed with a suitable solvent. (For example, toluene, xylene, etc.) using a conventional condensation catalyst, if necessary, under an inert gas (for example, nitrogen gas) atmosphere.
The reaction can be carried out at ~ 250 ° C until the desired acid value is reached. As the condensation catalyst, dibutyltin oxide, tetra-n-butylammonium bromide or the like is used.

Next, the above-mentioned epoxy ester resin is reacted with the ethylenically unsaturated monomer (c) to obtain an acryl-modified epoxy ester resin. As the ethylenically unsaturated monomer (c), styrene, (meth) acrylic acid,
Examples include unsaturated carboxylic acids such as maleic anhydride and itaconic acid, (meth) acrylates, and mixtures thereof. It is essential that at least one of the above acrylic monomers contains a carboxylic acid group, and one or more acrylic monomers are used as a mixture with styrene.

The reaction between the epoxy ester resin and the ethylenically unsaturated monomer (c) is carried out in the presence of a polymerization initiator.
Under an inert gas (eg, nitrogen gas) atmosphere,
The reaction can be performed in a temperature range of 80 to 150 ° C. until a desired acid value is obtained.

As the polymerization initiator used in the above reaction between the epoxy ester resin and the ethylenically unsaturated monomer (c), any of those known in the art such as peroxides and azo compounds can be used. "Kayabutyl B (alkyl perester type)" manufactured by Kazaku Akzo Corporation or the like can be used in an amount of 0.1 to 20% by weight based on the total amount of monomers used.

The acryl-modified epoxy ester resin synthesized in this manner comprises an epoxy resin (a) / fatty acid (b) /
The composition ratio of the ethylenically unsaturated monomer (c) is 20 to 7
It is preferably in the range of 0:20 to 50: 3 to 50 (% by weight). In the above composition ratio, the epoxy resin (a)
If the amount is less than 20%, the corrosion resistance of the coating film composed of the prepared coating composition will be reduced, and if it exceeds 70%, the resin viscosity will be too high, so that the synthesis is difficult. In the above composition ratio, when the amount of the fatty acid (b) is less than 20%, the water resistance of the coating film deteriorates, and when it exceeds 50%, the initial hardness of the coating film is low. Handleability becomes worse. Further, in the above composition ratio,
When the amount of the ethylenically unsaturated monomer (c) is less than 3%, the water dispersibility of the synthesized resin becomes poor, and 50%
When it exceeds, the corrosion resistance of the coating film is reduced.

The acrylic-modified epoxy ester resin has a high degree of water solubility (degree of hydrophilicity) in order to reliably prevent paint separation when the paint is collected and reused.
It is preferable to have Such a degree of water solubility can be represented by an acid value. That is, the acid value of the preferred acrylic-modified epoxy ester resin for use in the method of the present invention may be 25-60, especially 30-50. When the acid value of the resin is less than 25, the degree of water-solubilization of the water-soluble resin (that is, the degree of hydrophilicity) is reduced, and separation or the like may occur in the concentration process. When the acid value exceeds 60,
The degree of water-solubility of the resin becomes too high, which may cause a problem in water resistance of the coating film.

After the synthesis of the acrylic-modified epoxy ester resin, an amine compound (eg, ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine,
Mono-n-propylamine, dimethyl-n-propylamine, monoethanolamine, dimethanolamine, triethanolamine, N-methylethanolamine, N-methyldiethanolamine, dimethylethanolamine,
(Isopropanolamine, diisopropanolamine, etc.), especially 100% neutralized with triethylamine, dispersed in water and a hydrophilic solvent, and then usually used at a non-volatile content of 60 to 10%, but is particularly limited to this range. Not something. The hydrophilic solvent used here is
Any material that volatilizes when forming a coating film may be used, and examples thereof include glycol derivatives such as butyl cellosolve, butyl glycol, butyl diglycol, and propylene glycol.

The coating composition is prepared by mixing the above water-dispersed varnish in an amount of 50 to 90% by weight based on the total weight of the coating composition. And defoamers, etc.).

As the pigment which can be added to the above coating composition, any of pigments such as titanium dioxide, carbon and quinacridone, and extender pigments such as barium sulfate, talc and clay can be used. 10 to 250
It can be blended in the range of weight%.

[0027] A dryer is added to the aqueous coating composition used in the method of the present invention because of a curing reaction by oxidative polymerization. As a dryer that can be used, any substance known in the art (that is, lead, manganese, and a cobalt-based compound) can be used, and for example, DICNATE 3111 (a cobalt-based compound) manufactured by Dainippon Ink and Chemicals, Inc. can be used.

The method of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic sectional view showing a recycling system for a reusable cold-setting aqueous coating composition of the present invention.

In step i) of the method of the present invention, the cold-setting aqueous coating composition is applied to an object 11 using a coating gun 2 in a coating booth 1. At this time, the excess coating composition 21 is collected by the water curtain 3 made of the collecting liquid 4. In the composition of the collection liquid 4, in order to stably disperse the excess coating composition 21 in water, any of those mentioned as the hydrophilic solvent contained in the coating composition can be used, Particularly, it is preferable to contain butyl diglycol. The solution containing the coating composition 21 collected by the collection liquid 4 is used as the coating diluent 6 here.
Call. The paint diluent 6 is sent into the concentration tank 5.

In the above step, the collecting liquid can be prepared, for example, by the following procedure. First, a collection liquid is prepared from water and a hydrophilic solvent. The content of the hydrophilic solvent in the collection liquid is preferably in the range of 2.5 to 10% by weight. As the hydrophilic solvent, any of those mentioned as the solvent contained in the coating composition can be used, and butyl diglycol is particularly preferred.

Next, the collected liquid is treated with an amine compound.
The pH is adjusted to H8-10, particularly preferably to pH 9.5. As the amine compound used to adjust the pH of the collection liquid, any of the above-described amine compounds used to neutralize the acrylic-modified epoxy ester resin can be used, and dimethylethanolamine is particularly preferred in terms of amine volatilization. It is preferred to use. Here, in the case where the collected liquid is adjusted to pH 9.5 or less, the collected liquid is lowered to a predetermined pH by open stirring.

The collected liquid thus prepared has a pH of
If the value is less than 8, the concentrated paint collected cannot be concentrated due to aggregation, and if the pH exceeds 10, hydrolysis is promoted in the coating composition during use or storage of the collected concentrated paint. This is not preferable because the low-molecular component may increase and the coating may thicken.

The paint diluent 6 is used in step i of the method of the present invention.
In i), after passing through a filtration and concentration step, it can be separated into an intermediate concentrated paint 16 and a filtrate 20. In the method of the present invention, the filtration and concentration are preferably performed by using an ultrafiltration device 7.
This is performed using

The paint diluent 6 is passed through the ultrafiltration device 7 several times and concentrated until it has a viscosity equal to or higher than the coating viscosity, thereby obtaining a final concentrated paint 16 '. At the same time, the water and the solvent, which are the filtrate 20 after the filtration, are collected as the separation liquid 9.

The above-mentioned final concentrated paint 16 'is supplied to the paint tank 10
Transported to The final concentrated paint 16 ′ has a proper value (for example, the paint particle size is 30 μm or less, and the gloss retention ratio to the initial paint> 90
%), And can be reused as a cold-setting aqueous coating composition. Confirmation of the paint particle size at the time of readjustment can be performed by a conventionally known method.

The content of the hydrophilic solvent with respect to the volatile matter is 20%
Above the above, the amount of the solvent in the paint increases, which causes problems in the labor safety law and the solvent regulation.

Separation liquid 9 recovered in ii) of the method of the present invention
Can be adjusted to a desired pH (pH
After adjusting to 8 to 10), it can be reused as a collected liquid [Step (iii)]. Here, the purpose of adjusting the pH of the separated solution is as follows:
The purpose is to replenish the neutralized amine scattered (volatilized) during the coating of the coating composition to prevent a change in the solvent composition ratio and a decrease in pH of the coating composition to be reused. By preventing a change in the solvent composition ratio of the coating composition and a decrease in pH, the hydration stability of the resin in the coating composition is improved, and the suitability for recycling the coating is also improved.

In the method of the present invention, after the above step ii), by re-adjusting the concentration of the separated final concentrated paint in the paint tank 10, it can be reused as a cold-setting aqueous paint composition. it can.

According to the present invention, depending on the acid value of the acrylic-modified epoxy ester resin, which is the main component of the coating composition, the pH of the collecting liquid and the separating liquid used for collecting the coating and the amount of the hydrophilic solvent contained therein Depends on the method of reusing the cold-curable aqueous coating composition, or the pH of the collecting liquid used for collecting the coating (including the recovered separated liquid) or the amount of the hydrophilic solvent contained therein. Thus, two modes of the method for reusing the coating composition for determining the acid value of the acrylic-modified epoxy ester resin can be considered. The description so far corresponds to the former method ().

In the first embodiment of the latter method (), when the pH of the collection liquid is adjusted to 9.5, the acid value of the acrylic-modified epoxy ester resin is represented by the following formula:

AV ≧ −12.00x + 63.5 (where AV represents an acid value and a number from 25 to 60, and x is the content (% by weight) of the hydrophilic solvent in the collection liquid. ) And the number is from 1.5 to 20.) A reusable cold-setting aqueous coating composition prepared and blended with the resin so as to satisfy 1.5) can be used.

In the second embodiment of the latter method (), when the pH of the separated solution is adjusted to 8.5, the acid value of the acrylic-modified epoxy ester resin is represented by the following formula:

AV ≧ −3.22 × + 61.5 (where AV represents an acid value and a number from 25 to 60, and x is the content (% by weight) of the hydrophilic solvent in the collection liquid. ) And the number is from 1.5 to 20.) A reusable cold-setting aqueous coating composition prepared and blended with the resin so as to satisfy 1.5) can be used.

Further, in the third mode of the latter method (), the amount of the hydrophilic solvent contained in the collected liquid is 2.5.
When adjusted to 10% by weight, the acid value of the acrylic-modified epoxy ester resin is represented by the following formula:

AV ≧ −1.88x−20.62y + 230.34 (where AV represents an acid value and a number from 25 to 60, and x is the content of the hydrophilic solvent in the collection liquid) (Weight%), and is a number from 2.5 to 10, and y represents the pH of the collected liquid and satisfies 8 ≦ y ≦ 10.) The reusable cold-setting water-based coating composition can be used.

[0043]

The present invention will be described below with reference to examples.
The present invention is not limited to the following examples. Preparation Example 1 Epicoat 1001 (shell product, epoxy resin) 609.2
Parts by weight, 295.4 parts by weight of dehydrated castor oil fatty acid, 295.4 parts by weight of safflower oil fatty acid, and Kisir 2 for circulation
4.0 parts by weight were placed in a reaction vessel and stirred under a nitrogen gas atmosphere until the acid value reached 3.7.
The condensation reaction was carried out at 0 ° C. for about 10 hours. After the reaction, the mixture was diluted by adding 500 parts by weight of butyl cellosolve to obtain a nonvolatile matter of 68.
Epoxy ester resin Ep of 8% by weight and acid value of 3.7
-I got 1.

Preparation Example 2 456.8 parts by weight of Epicoat 828 (manufactured by Shell, epoxy resin), 366.3 parts by weight of dehydrated castor oil fatty acid, 376.8 parts by weight of tall oil fatty acid, and 12.0 parts by weight of kissle for circulation were Put in a reaction vessel and under a nitrogen gas atmosphere,
While stirring, 210-23 until the acid value is 3.4.
The condensation reaction was carried out at 0 ° C. for about 10 hours. After the reaction, the nonvolatile content 9
Epoxy ester resin E having 9.0% by weight and an acid value of 3.4
p-2 was obtained.

Preparation Example 3 Epicoat 1001 (made by Shell, epoxy resin) 727.7
Parts by weight, 232.8 parts by weight of dehydrated castor oil fatty acid, 239.5 parts by weight of tall oil fatty acid, 1.9 parts by weight of tetra-n-butylammonium bromide, and 12.0 parts of circil kissil
Parts by weight were placed in a reaction vessel and stirred at 200 ° C. under nitrogen gas atmosphere until the acid value reached 2.7.
For about 5 hours. After the reaction, the nonvolatile content was 99.0.
Epoxy resin Ep-3 having a weight percentage of 2.7 and an acid value of 2.7
I got

Preparation Example 4 Epitote YD-012 (Epoxy resin, manufactured by Toto Kasei) 73
8.2 parts by weight, 690.5 parts by weight of linseed oil fatty acid, 1.4 parts by weight of dibutyltin oxide and kissil for circulation 42.
0 parts by weight are placed in a reaction vessel and stirred under nitrogen gas atmosphere until the acid value reaches 4.4.
The condensation reaction was carried out at 240 ° C. for about 6 hours. After the reaction, 42 parts by weight of butyl cellosolve was added for dilution, and the nonvolatile content was 95.
7% by weight and an acid value of 4.4.
4 was obtained.

Preparation Example 5 1008 parts by weight of the above-mentioned epoxy ester resin Ep-1 and 153.6 parts by weight of butyl cellosolve were placed in a reaction vessel.
The temperature was raised to 40 ° C. At this temperature, 316.8 parts by weight of styrene, 62.4 parts by weight of acrylic acid, and 9.10 parts by weight of a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) were added dropwise over 3 hours at this temperature. After completion of the dropping, aging was performed for 0.5 hour. Next, a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo)
After dropping 2.27 parts by weight, the mixture was aged for 1.5 hours to obtain an acid value of 46.4 and a nonvolatile content of 69.6.
% By weight of an acrylic-modified epoxy ester resin a was obtained.

Preparation Example 6 256.2 parts by weight of an epoxy ester resin Ep-1, 4.4 parts by weight of butyl cellosolve, 4.0 parts by weight of styrene, 15.6 parts by weight of acrylic acid, and a polymerization initiator (Kayabutyl manufactured by Kayaku Akzo) B) Acrylic-modified epoxy ester resin b having an acid value of 62.1 and a nonvolatile content of 70.0% by weight in the same manner as in Preparation Example 5 except that 0.72 part by weight and thereafter 0.08 part by weight were used. I got

Preparation Example 7 203.4 parts by weight of an epoxy ester resin Ep-2 and 24.3 parts by weight of butyl cellosolve were placed in a reaction vessel,
The temperature was raised to ° C. At this temperature, 59.4 parts by weight of styrene, 11.7 parts by weight of acrylic acid and 2.28 parts by weight of a polymerization initiator (Kayabutyl B, manufactured by Kayaku Akzo) were added dropwise over 3 hours at this temperature. After completion of the dropping, aging was performed for 0.5 hour. Then, a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) 0.5
After dropwise addition of 7 parts by weight and 91.6 parts by weight of butyl cellosolve, the mixture was aged for another 1.5 hours to give
An acrylic-modified epoxy ester resin c having an acid value of 30.5 and a nonvolatile content of 70% by weight was obtained.

Preparation Example 8 271.2 parts by weight of epoxy ester resin Ep-3, 121.4 parts by weight of butyl cellosolve, 4.0 parts by weight of styrene,
15.6 parts by weight of acrylic acid, 1.44 parts by weight of a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) and then 0.1 part by weight
An acrylic-modified epoxy ester resin d having an acid value of 42.2 and a nonvolatile content of 70% by weight was obtained in the same manner as in Preparation Example 5 except that 6 parts by weight was used.

Preparation Example 9 In a reaction vessel, 244.0 parts by weight of an epoxy ester resin Ep-4 and 72.5 parts by weight of butyl cellosolve were placed in a reaction vessel.
The temperature was raised to ° C. At this temperature, over 3 hours, 45.0 parts by weight of styrene, 17.9 parts by weight of methyl methacrylate,
33.7 parts by weight of 2-ethylhexyl methacrylate, 18.4 parts by weight of methacrylic acid and 1.15 parts by weight of a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) were added dropwise. After dropping,
Aged for 1.0 hour. Then, 0.50 parts by weight of a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) and 67.0 parts by weight of butyl cellosolve were added dropwise, and the mixture was aged for 2.5 hours to obtain an acid value of 35.0 and a nonvolatile matter of 70 parts by weight. % Of an acrylic-modified epoxy ester resin e.

Preparation Example 10 1008 parts by weight of epoxy ester resin Ep-1, 153.6 parts by weight of butyl cellosolve, 352.7 parts by weight of styrene, 26.5 parts by weight of acrylic acid, and a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) Except that 9.10 parts by weight and then 2.27 parts by weight were used, an acrylic-modified epoxy ester resin f having an acid value of 21.6 and a nonvolatile content of 70% by weight was obtained in the same manner as in Preparation Example 5.

Preparation Example 11 1008 parts by weight of epoxy ester resin Ep-1, 153.6 parts by weight of butyl cellosolve, 346.7 parts by weight of styrene, 32.5 parts by weight of acrylic acid, and a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) Except that 9.10 parts by weight and then 2.27 parts by weight were used, an acrylic-modified epoxy ester resin g having an acid value of 25.4 and a nonvolatile content of 70% by weight was obtained in the same manner as in Preparation Example 5 above.

Preparation Example 12 1008 parts by weight of epoxy ester resin Ep-1, 153.6 parts by weight of butyl cellosolve, 305.4 parts by weight of styrene, 73.8 parts by weight of acrylic acid, and a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) Except that 9.10 parts by weight and then 2.27 parts by weight were used, an acrylic-modified epoxy ester resin h having an acid value of 54.3 and a nonvolatile content of 70% by weight was obtained in the same manner as in Preparation Example 5 above.

Preparation Example 13 1008 parts by weight of epoxy ester resin Ep-1, 153.6 parts by weight of butyl cellosolve, 267.1 parts by weight of styrene, 112.1 parts by weight of acrylic acid, and a polymerization initiator (Kayabutyl B manufactured by Kayaku Akzo) Except that 9.10 parts by weight and then 2.27 parts by weight were used, an acrylic-modified epoxy ester resin i having an acid value of 79.7 and a nonvolatile content of 70% by weight was obtained in the same manner as in Preparation Example 5 above.

Table 1 summarizes the composition ratio, acid value and nonvolatile content of the acrylic-modified epoxy ester resins a to i obtained in Preparation Examples 5 to 13.

[0057]

[Table 1]

Example 1 The acid site of the acrylic-modified epoxy ester resin a was
100% neutralization with trimethylamine. Then
The resin was dispersed in water to form a varnish having a nonvolatile content of 35% by weight.

60.0 parts by weight of the varnish, 0.1% of an antifoaming agent (silica / mineral oil based antifoaming agent, NOPCO 8034L manufactured by San Nopco)
Parts by weight, coloring pigment (titanium dioxide, CR-95 manufactured by Ishihara Sangyo)
31.5 parts by weight, 0.6 part by weight of a dryer (cobalt type, DICNATE3111 manufactured by Dainippon Ink and Chemicals, Inc.) and 8.0 of water
By mixing the parts by weight, a cold-setting aqueous coating composition A was prepared. The amount of the hydrophilic solvent in the volatile components of the coating composition is about 19
% By weight.

Examples 2 to 7 Cold-curable coating compositions C to H were prepared in the same manner as in Example 1 except that the acrylic-modified epoxy ester resins c to h were used, respectively.

Comparative Examples 1 and 2 Cold-curable coating compositions B and I were prepared in the same manner as in Example 1 except that the acrylic-modified epoxy ester resins b and i were used, respectively.

Evaluation item (I) Recyclability of cold-setting water-based paint The paint composition A obtained in Example 1 was treated with a previously prepared collection liquid (solvent composition ratio: water: butyldiglycol = 100: 0-0).
80:20) to dilute the nonvolatile content to 5% by weight to obtain paint dilution water. The paint dilution water was adjusted to pH 9.5 using dimethylethanolamine, and then ultrafiltered and concentrated with NK # 2 cup for at least 30 seconds to obtain concentrated paint A '.
I got Here, the ultrafiltration and concentration were performed by circulating and concentrating the above-mentioned paint dilution water using a UF module manufactured by Asahi Kasei Kogyo equipped with a liquid feed pump.

The coating compositions C to H and the coating compositions B and I obtained in Comparative Examples 1 and 2 were also treated in the same manner as described above, and the corresponding concentrated coatings C ′ to H ′ were respectively treated. And B 'and I' were obtained.

With respect to the concentrated paint thus obtained, suitability for recycling (measurement of particle size and evaluation of appearance of the coating film) was performed in the following procedure.

1) Measurement of particle size The coating composition at the initial stage and after the concentration was measured according to JIS K-540.
The particle size was measured according to 0. The initial coating composition particle size was less than 15 μm. Evaluation criteria Particle size of concentrated paint is less than 30 μm: ○ Particle size of concentrated paint exceeds 30 μm: ×

2) Evaluation of Coating Appearance Evaluation of Gloss of Coating Film The gloss of the concentrated coating film prepared by the following method was evaluated by comparing it with the initial (before the ultrafiltration / concentration step) coating film. Each of the initial paint and the concentrated paint was applied on a glass plate using a 6 miL doctor blade, and then dried at 80 ° C. for 20 minutes. 60 ° of the coating after drying
The gloss was measured and evaluated based on the following criteria, with the result of the initial paint being 100%. Evaluation criteria The gloss retention of the initial paint to the coating film is 90% or more: ○ The gloss retention of the initial coating to the coating film is less than 90%: ×

Salt Spray Resistance Test (JIS K-5400-9) The above concentrated paint was spray-coated on a dull steel plate so as to have a thickness of 25 to 30 μm, dried at 80 ° C. for 20 minutes, and further dried at room temperature. Left for one week. After that, the painted plate is JI
A salt spray test (96 hours) was performed according to S K-5400. Evaluation criteria : Peeling width within 3 mm: ○ Exceeding peeling width: 3 mm: ×

Hot water resistance test (JIS K-5400-8) A dull steel plate having a concentrated paint film was exposed to warm water at 40 ° C. for 10 minutes.
The presence or absence of blisters after immersion for a day was confirmed. Evaluation criteria No blister: ○ Blister: X The evaluation results are shown in Table 2.

[0069]

[Table 2]

From the results shown in Table 2, in the method of the present invention,
When a cold-setting aqueous coating composition having an acid value of 25 to 60 is used, by setting the solvent amount / pH condition of the collection liquid,
It can be seen that the recyclability of the recovered coating composition can be greatly improved.

(II) Specific pH Value of Collection Liquid and Resin for Paint
Relationship between the acid value of the solvent and the content of the hydrophilic solvent in the collecting solution When the pH of the collecting solution is set to a specific value, the corresponding acid value of the corresponding coating resin should be contained in the collecting solution. The desired content of hydrophilic solvent was investigated. Two collection solutions of the same composition were prepared and adjusted to pH 9.5 and 8.5, respectively, using dimethylethanolamine. The nonvolatile content of the collected liquid at the start of concentration was 5% by weight. Each of the two collected liquids was divided into six equal parts. Next, butyl diglycol was added as a hydrophilic solvent to each of the collected liquids so as to be 0, 1.5, 2.5, 5, 10, 10 and 20% by weight based on the total amount of the collected liquid. Then, a total of 12 kinds of collection liquids (pH 9.5 = 6 kinds and pH 8.5 = 6 kinds) were prepared.

In the recycling system of the coating composition of the present invention shown in FIG. 1, the coating compositions A to A obtained from Examples and Comparative Examples were prepared by using the 12 kinds of collecting liquids prepared above.
I was collected, filtered, concentrated and reused. The recyclability (change in particle size and / or gloss retention) of the concentrated paint film after reuse was evaluated. The recyclability was determined based on the particle size <30 μm and the gloss retention> 90% as good (○) or poor (×). The evaluation results are summarized in Tables 3 and 4 below.

[0073]

[Table 3]

[0074]

[Table 4]

From the results in Tables 3 and 4, when the pH of the collection liquid is fixed, the higher the acid value of the acrylic-modified epoxy ester resin in the coating composition and the higher the content of the hydrophilic solvent in the collection liquid. It can be seen that the more preferable, the better. Further, when the pH of the collected liquid is lowered from 9.5 to 8.5, the minimum value of the content of the hydrophilic solvent in the collected liquid is from 1.5% by weight to 2.5%.
It turns out that it is necessary to increase weight%.

To summarize the above results, when the pH of the collection liquid is adjusted to 9.5, the acid value of the acryl-modified epoxy ester resin is represented by the following formula:

Where AV represents an acid value and a number from 25 to 60, and x represents the content (% by weight) of the hydrophilic solvent in the collection liquid. ) And is a number from 1.5 to 20).

Alternatively, when the pH of the collection liquid is adjusted to 8.5, the acid value of the acrylic-modified epoxy ester resin is represented by the following formula:

AV ≧ −3.22x + 61.5 (where AV represents an acid value and a number from 25 to 60, and x is the content (% by weight) of the hydrophilic solvent in the collection liquid. ) And is a number from 1.5 to 20).

(III) The content of the hydrophilic solvent in the collection liquid,
Relationship between Acid Value of Resin and pH of Collection Solution In this example, when the content of the hydrophilic solvent in the collection solution is set to a specific value, the preferable acid value and the collection value of the corresponding coating resin are determined. The desired pH of the liquor was determined. Three collection liquids having the same composition were prepared, each containing 2.5, 5 and 10% by weight of butyl diglycol. The nonvolatile content of the collected liquid at the start of concentration was 5% by weight.

Next, the collected liquid having a butyldiglycol content of 2.5% by weight was divided into five equal parts, and the respective pH values were adjusted to 8.0, 8.5, 9.0, 9.5 using dimethylethanolamine. Prepared at 5 and 10.0. Butyl diglycol content 5
Also, the collected liquid of 10% by weight was equally divided and the pH was adjusted in the same manner as described above. As a result, a total of 15 kinds of collected liquids were prepared. In the recycling system of the coating composition of the present invention shown in FIG. 1, the coating compositions A to I obtained from Examples and Comparative Examples were collected using the above 15 kinds of collection liquids.
It was filtered, concentrated and reused. The recyclability (change in particle size and / or gloss retention) of the concentrated paint film after reuse was evaluated. The recyclability was determined based on the particle size <30 μm and the gloss retention> 90% as good (○) or poor (×). The evaluation results are summarized in Tables 5 to 7 below.

[0080]

[Table 5]

[0081]

[Table 6]

[0082]

[Table 7]

From the results of Tables 5 to 7, it can be seen that when the content of the hydrophilic solvent in the collection liquid is fixed, the higher the acid value of the resin in the coating composition and the higher the pH of the collection liquid, the better. Further, it can be seen that as the content of the hydrophilic solvent in the collection liquid increases, both the pH value of the preferable collection liquid and the acid value of the resin increase.

To summarize the above results, when the amount of the hydrophilic solvent contained in the collection liquid is adjusted to 2.5 to 10% by weight, the acid value of the acrylic-modified epoxy ester resin to be used is represented by the following formula: :

AV ≧ −1.88x−20.62y + 230.34 (where AV represents an acid value and a number from 25 to 60, and x is the content of the hydrophilic solvent in the collection liquid) (Weight%), and is a number from 2.5 to 10, and y represents the pH of the separated liquid and satisfies 8 ≦ y ≦ 10.)

[0085]

According to the present invention, the recyclability of the coating composition is improved without deteriorating the coating properties (for example, salt spray resistance, water resistance, etc.) of the coating composition after reuse. Can be realized. In addition, it is easy to recycle the collected liquid in the coating booth.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a system for recycling a cold-setting aqueous coating composition of the present invention.

FIG. 2 is a schematic flow chart relating to separation of a paint diluent obtained in a system for recycling a cold-setting aqueous paint composition of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Painting booth, 2 ... Painting gun, 3 ... Painting booth water curtain, 4 ... Collection liquid, 5 ... Concentration tank, 6 ... Recovered paint diluent, 7 ... Ultrafiltration device, 8 ... Filtrate tank, 9: separation liquid, 10: paint tank, 11: substrate, 1
6 ... intermediate concentrated paint, 16 '... final concentrated paint, 20 ... filtrate, 21 ... excess paint composition, 71 ... membrane.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C09D 163/10

Claims (7)

(57) [Claims] 1. i) Composition ratio: epoxy resin (a) / fatty acid (b) / ethylenically unsaturated monomer (c) = 20-7.
0:20 to 50: 3 to 50 (% by weight) (however, a + b
+ C = 100), a reusable cold-setting aqueous coating composition containing an acrylic-modified epoxy ester resin having an acid value of 25 to 60 obtained from
H is collected using the adjusted collection liquid to obtain a paint diluent, ii) by filtering and concentrating the paint diluent,
Separation into a concentrated paint and a separated liquid, and iii) Adjusting the content of the hydrophilic solvent in the separated liquid to 1.5 to 20% by weight and adjusting the pH to 8 to 10 to reuse as a collecting liquid. A method for reusing a reusable cold-setting aqueous coating composition comprising the steps of: 2. The method according to claim 1, wherein the filtration and the concentration of the paint diluent are performed by an ultrafiltration device. 3. The method according to claim 1, wherein said collection liquid comprises water and a hydrophilic solvent. 4. The composition ratio of the concentrated paint and the separation liquid is the same as the composition ratio of the collection liquid.
The described method. 5. When adjusting the pH of the collection liquid to 9.5, the acid value of the acrylic-modified epoxy ester resin is determined by the following formula: AV ≧ −12.00x + 63.5 (where, AV Represents an acid value and a number of 25 to 60, and x represents a content (% by weight) of the hydrophilic solvent in the collection liquid and a number of 1.5 to 20. The method of claim 1, wherein said acrylic modified epoxy ester resin is selected to satisfy. 6. When the pH of the collection liquid is adjusted to 8.5, the acid value of the acrylic-modified epoxy ester resin is determined by the following formula: AV ≧ −3.22x + 61.5 (where AV is an integer). Represents an acid value and a number of 25 to 60, and x represents a content (% by weight) of the hydrophilic solvent in the collection liquid and a number of 1.5 to 20. The method of claim 1, wherein said acrylic modified epoxy ester resin is selected to satisfy. 7. When the amount of the hydrophilic solvent contained in the collection liquid is adjusted to 2.5 to 10% by weight, the acid value of the acrylic-modified epoxy ester resin is represented by the following formula: -1.88x-20.62y + 230.34 (where AV represents an acid value and a number from 25 to 60, and x represents the content (% by weight) of the hydrophilic solvent in the collection liquid. And y is a number from 2.5 to 10, and y represents the pH of the separated solution, and satisfies 8 ≦ y ≦ 10.) The method of claim 1.