JPH07188588A - Resin composition for powder coating - Google Patents

Abstract

PURPOSE:To obtain a thermally curable resin composition for powder coating providing a coating film having excellent smoothness and finishing appearance such as vividness, showing improved pigment dispersibility and storage stability, containing a specific modified resin and a dibasic carboxylic acid as essential components. CONSTITUTION:This composition contains (A) a resin obtained by modifying a vinyl-based copolymer obtained from a glycidyl group-containing monomer (e.g. glycidyl acrylate) and an ethylenic unsaturated monomer (e.g. methyl acrylate) copolymerizable with the monomer with a compound containing orthophosphate group in the molecule (preferably dibutyl phosphate or diethylhexyl phosphate) and (B) a dibasic carboxylic acid (e.g. maleic acid) as essential components.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a new and useful resin composition for powder coatings. More specifically, the present invention comprises, as essential components, a specific resin modified with a compound having a specific group called an orthophosphoric acid group and a dibasic carboxylic acid. Thermosetting powder that gives a coating film that has a so-called finished appearance, such as high image quality and sharpness, and that has excellent pigment dispersibility and storage stability of the powder coating material. The present invention relates to a coating resin composition.

[0002]

2. Description of the Related Art In recent years, powder coatings, which are low-pollution coatings,
It is used in a wide range of fields. While using a glycidyl group-containing vinyl copolymer as a resin component, as a curing agent, a thermosetting powder coating in the form of using a dibasic carboxylic acid compound, particularly a coating excellent in weather resistance It is widely used because it can be formed.

However, since the powder coating composition does not use a solvent, the finished appearance such as the smoothness of the obtained coating film tends to be inferior to that of the solvent type composition, but that is not the case. For this reason, in particular, the development of a powder coating having excellent pigment dispersibility and an excellent finished appearance is eagerly desired.

As a measure for improving the finished appearance by improving the pigment dispersibility described above, Japanese Patent Publication No. 3-47304 attempts to modify a vinyl copolymer with a phosphorous acid ester. However, when this method is followed, although the effect of improving the pigment dispersibility is recognized,
Storage stability of powder coatings, especially the problem that the glycidyl group-containing vinyl copolymer reacts with the curing agent during long-term storage and the coating film appearance deteriorates (that is, solid-phase reactivity) There is.

[0005]

However, the inventors of the present invention have various problems in the prior art as described above, in particular, as described above, the pigment dispersibility and the storage stability of the powder coating material. From the point of satisfying both, the development of a powder coating of extremely high practicality was raised as a problem to be solved by the present invention, and earnest research was started.

[0006] Therefore, the problem to be solved by the present invention is, in particular, for a powder coating which is excellent in pigment dispersibility and storage stability, that is, the so-called practical performance is improved. To provide a resin composition, that is, a powder coating material.

[0007]

Therefore, the present inventors have
Focusing on the problems to be solved by the invention as described above, as a result of intensive studies, as a result, a glycidyl group-containing vinyl-based copolymer, such as an orthophosphoric acid diester, was formed in one molecule in one molecule. By modifying with a compound having a phosphoric acid group, the pigment dispersibility is dramatically improved, and in addition, it is also found that the storage stability of the powder coating is also excellent. The present invention has been completed.

That is, in the present invention, basically, a vinyl copolymer obtained from a glycidyl group-containing monomer and an ethylenically unsaturated monomer copolymerizable with the glycidyl group-containing monomer is positively incorporated into the molecule. A resin modified with a compound having a phosphoric acid group,
A dibasic carboxylic acid, which is intended to provide a resin composition for powder coating, which comprises containing as an essential component,

Specifically, one of the glycidyl group-containing monomers is
0-60% by weight and 90-40% by weight of an ethylenically unsaturated monomer which can be copolymerized therewith are obtained, and the softening point is within the range of 70-150 ° C. and the number average. A vinyl-based copolymer having a molecular weight of 1,000 to 30,000,

A resin modified with a compound having one orthophosphoric acid group in one molecule, and a dibasic carboxylic acid,
The present invention intends to provide a resin composition for powder coatings, which is contained as an essential component, has excellent pigment dispersibility and storage stability, and is extremely highly practical.

Here, in order to modify the glycidyl group-containing vinyl copolymer with the above-mentioned compound having an orthophosphoric acid group in the molecule, particularly, a compound having one orthophosphoric acid group in one molecule. The orthophosphoric acid group-containing compound is added to the copolymer solution or the melt after desolvation and uniformly dispersed, and the temperature is about 80 ° C to about 180 ° C for about 1 to about 5 hours. A method of heating for a while to react with the glycidyl group is generally adopted.

Specific examples of such orthophosphoric acid group-containing compounds include only typical ones such as dimethyl phosphate, dibutyl phosphate, dioctyl phosphate, di2-ethylhexyl phosphate, dilauryl phosphate and diphenyl phosphate. Fate,
Dinaphthyl phosphate, dicresyl phosphate, di (nonylphenyl) phosphate, methyl octyl phosphate,

Cetylphenyl phosphate, diisodecyl phosphate, monobutyl butylphosphonate, 2
-Ethylhexyl phosphonate mono-2-ethylhexyl and the like, among which the use of orthophosphoric acid dialkyl ester is desirable, and in particular, orthophosphoric acid dialkyl ester having 4 or more carbon atoms, dibutyl phosphate or di2-ethylhexylphosphate. It is preferable to use fate or the like.

The amount of the orthophosphoric acid group-containing compound used is 0.0 with respect to 100 parts by weight of the vinyl copolymer.
The range of 1 to 10% by weight is suitable, and if it is less than 0.01% by weight, the effect of improving the pigment dispersibility and the like cannot be expected, and

On the other hand, when it is used in an excessively large amount exceeding 10% by weight, the physical properties of the coating film, such as image clarity and weather resistance, tend to be deteriorated, which is not preferable. .

When the content of the glycidyl group-containing monomer component in the vinyl copolymer is less than 10% by weight based on the total amount of the monomers, the coating strength and the adhesion to metal are inevitable. On the other hand, when it is used in an excessively large amount exceeding 60% by weight, the excessive curing reaction inevitably lowers the smoothness of the coated surface. This is also not preferable.

The vinyl-based copolymer preferably has a softening point (ring and ball method) of about 70 to about 150 ° C., and has a number average molecular weight of about 1,
It is desirable to use those within the range of 000 to about 30,000.

When the softening point of the vinyl-based copolymer is lower than 70 ° C., the storage stability of the powder coating is inevitably deteriorated. On the other hand, when it exceeds 150 ° C. and becomes too high. , Inevitably, the heat fluidity will decrease, and the smoothness of the coated surface will deteriorate, so
Either case is not preferable.

When the number average molecular weight is less than 1,000, the strength of the coating film is inevitably lowered. On the other hand, when it exceeds 30,000 and is too large,
In any case, the smoothness of the coated surface will be deteriorated, which is not preferable in any case.

The glycidyl group-containing monomer used in the preparation of the vinyl-based copolymer is only a representative one, and glycidyl acrylate, β-methylglycidyl acrylate, glycidyl methacrylate or Various (meth) acrylic acid (β-
Methyl) glycidyl ester,

A variety of epoxy group-containing (meth) compounds such as 3,4-epoxycyclohexyl acrylate, 3,4-epoxycyclohexylmethyl acrylate, 3,4-epoxycyclohexyl methacrylate or 3,4-epoxycyclohexylmethyl methacrylate. ) Acrylic acid esters or ε-caprolactone modified products thereof;

Alternatively, allyl alcohol (methyl)
Examples thereof include glycidyl ether, (methyl) glycidyl ether of methallyl alcohol, and N-glycidyl acrylic acid amide vinyl sulfonate glycidyl.

It goes without saying that these may be used alone or in combination of two or more kinds.

On the other hand, the monomer copolymerizable with such a glycidyl group-containing monomer belongs to the area of ethylenically unsaturated monomers and has a low reactivity with an epoxy group. It is also possible to use a monomer which can be radically copolymerized with such a glycidyl group-containing monomer.

[0025] Only typical representative ethylenically unsaturated monomers copolymerizable with the glycidyl group-containing monomer will be exemplified, and known and commonly used acrylic acid esters or methacrylic acid, respectively. In addition to esters, there are known and commonly used vinyl monomers.

It goes without saying that these may be used alone or in combination of two or more.

As the esters of acrylic acid or methacrylic acid, only typical ones are exemplified, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n acrylate.
-Butyl, isobutyl acrylate, tert acrylate
-Butyl, cyclohexyl acrylate, acrylic acid 2-
Ethylhexyl, octyl acrylate, acrylic acid 2-
Ethyl octyl, dodecyl acrylate or benzyl acrylate,

Alternatively, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-methacrylate Various (meth) acrylic acid esters such as ethylhexyl, octyl methacrylate, 2-ethyloctyl methacrylate, dodecyl methacrylate, benzyl methacrylate or phenyl methacrylate, and

2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate or methacrylic acid 4
-Various hydroxyl group-containing (meth), such as hydroxybutyl
Acrylic acid esters and the like.

Further, only typical examples of other ethylenically unsaturated monomers are exemplified, and various unsaturated dicarboxylic acid dialkyl esters such as fumaric acid dialkyl ester or itaconic acid dialkyl ester are exemplified. Various aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene or vinyltoluene;

Or various cyano group-containing vinyl monomers such as acrylonitrile or methacrylonitrile; acrylamide or methacrylamide,
Various amide bond-containing vinyl monomers, etc.,

Further, various vinyl monomers containing an oxazolyl group such as vinyl oxazoline; vinyl acetate, vinyl propionate or "Veova" (of a branched aliphatic monocarboxylic acid manufactured by Shell Co. of the Netherlands). Various vinyl esters such as vinyl ester);

Furthermore, various vinyl ethers such as lauryl vinyl ether; various halogen-containing vinyl monomers such as vinyl chloride or vinylidene chloride; or vinyltrimethoxysilane or γ-methacryloyloxypropyltrimethoxysilane. And various silicon-containing vinyl monomers.

In the present invention, examples of the above-mentioned dibasic carboxylic acid used as a curing agent component include aliphatic or aromatic polyvalent carboxylic acids,
Of the typical ones, only typical ones among them are glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and 1,10-decane. Diacid, 1,12-dodecanedioic acid, 1,20-eicosanedioic acid or 1,24-tetraicosanedioic acid,

Alternatively, maleic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, hexahydrophthalic acid or cyclohexene-1,2-
Examples thereof include dicarboxylic acid, 1,3-cyclohexyldicarboxylic acid, and 1,4cyclohexyldicarboxylic acid.

Further, various carboxylic acid anhydrides such as succinic anhydride, sebacic anhydride, phthalic anhydride and itaconic anhydride may be used. Above all, 1,10-decanedioic acid,
Saturated aliphatic dibasic dicarboxylic acids of the type of 1,12-dodecanedioic acid or 1,20-eicosanedioic acid are particularly desirable because they can easily balance various performances.

The dibasic carboxylic acid can be used in any combination, but the ratio of the dibasic carboxylic acid and the glycidyl group in the glycidyl group-containing vinyl copolymer is the same as that of the dibasic carboxylic acid. It is desirable to use it in such a ratio that the equivalent ratio to the carboxyl group in the carboxylic acid falls within the range of 0.5 to 1.5.

The thus obtained resin composition for powder coating of the present invention contains various synthetic resins such as epoxy resin, polyester resin or polyamide; various colorants such as pigments or dyes. Including kinds,

Furthermore, there are usually used classes of powder coatings, such as flow control agents, antiblocking agents, UV absorbers, antistatic agents, antioxidants or benzoin. As, a variety of known and commonly used paint additives,

If desired, one or more of these may be added. Therefore, the resin composition for powder coating of the present invention may be further added with or without such various additives. It can be put to practical use as a powder coating.

Using the resin composition for powder coating of the present invention,
In order to prepare the intended powder coating, any well-known and commonly used method can be adopted, but usually, after mixing the various components listed above,

About 80 to about 1 by various melt kneaders such as a heating roll or an extruder.
Melt and mix well at a temperature of about 80 ° C, then
After cooling it, crush it.
It is especially recommended to use the powder coating method.

Also, as a coating method, the object to be coated is coated by a well-known and commonly used coating method such as an electrostatic spraying method or a fluidized-bed method, and then the thus-obtained coated article is usually roughly coated. It is possible to obtain a coating film by powder coating by performing baking in a baking oven in the range of 150 to 210 ° C.

The resin composition for powder coating of the present invention is mainly used for coating of steel products, and is used for various purposes such as automobiles, building materials, home electric appliances or vending machines. It is intended to be used for.

As described above, this is due to the excellent smoothness of the coating film and the stability of the coating material over a long period of time.
An extremely large application can be expected where a resin composition for a powder coating having an extremely high practicality is required.

[0046]

EXAMPLES Next, the present invention will be described with reference to Examples, Examples, Comparative Examples,
Although more specific description will be given with reference to application examples or comparative application examples, in the following, all parts and% are based on weight unless otherwise specified.

Reference Example 1 (Preparation Example of Glycidyl Group-Containing Vinyl Copolymer) In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 66.7 parts of xylene was added and heated. Then, the air in the reaction vessel was replaced with nitrogen and then heated to reflux.

Then, a mixture of the monomers in the amounts shown in Table 1 and the polymerization initiator was added thereto over 4 hours. Further, the mixture was kept under reflux for 1 hour and then cooled to give 0.5 of azobisisobutyronitrile.
Parts were added, and the remaining monomers were copolymerized at 80 to 100 ° C. to complete the copolymerization.

Thereafter, a phosphorus compound in an amount as shown in Table 1 was added, the mixture was heated at 120 ° C. for 2 hours, and the solvent was removed to obtain a solid vinyl copolymer. It was

[0050]

[Table 1]

<< Footnote of Table 1 >>"HEA" ..... Abbreviation of "2-hydroxyethyl acrylate""AIBN" ..... Abbreviation of "azobisisobutyronitrile"

[0052]

[Table 2]

[0053]

[Table 3]

<< Footnotes in Table 1 >>"MGMA" ......... Abbreviation of "β-methylglycidyl methacrylate"

[0055]

[Table 4]

[0056]

[Table 5]

[0057]

[Table 6]

Examples 1 to 7 and Comparative Examples 1 to 3 "Bus Conneader PR-46 type" (single screw extruder manufactured by Buss, Switzerland) was used with the composition ratios shown in Table 2. Then, various powder coating resin compositions were prepared by a conventional method.

[0059]

[Table 7]

<< Footnotes in Table 2 >>"Modaflow" ......... Leveling agent manufactured by Monsanto, USA

[0061]

[Table 8]

[0062]

[Table 9]

[0063]

[Table 10]

<< Footnote in Table 2 >> Abbreviation of "1,12-DDDA" ........... "1,12-dodecanedioic acid"

Application Examples 1 to 9 and Comparative Application Examples 1 to 3 In each of these examples, various resin compositions for powder coatings were actually used as powder coatings and various properties of the respective compositions were evaluated. , For comparative examination. This will clarify the application characteristics as a powder coating.

First, Examples 1 to 9 and Comparative Examples 1 to 3
Each of the resin compositions for powder coatings obtained in 1. is shown in Table 3 on a 0.8 mm thick satin finished steel sheet which has been treated with zinc phosphate by an electrostatic spray coating machine for powder coatings. Painted so as to have such a film thickness, baked at 180 ° C for 20 minutes, and then coated with a test plate (test plate).
Was produced.

Next, with respect to each test plate as a baked coating film, the coating film was evaluated and the storage stability of the powder coating material was tested for each item as shown in Table 3. The results are shown together in the same table.

Each evaluation examination or test was carried out in the following manner.

The film thickness was measured by an electromagnetic film thickness measuring method.

The pellet flow was measured by forming 0.5 g of each powder coating into pellets having a diameter of 10 mmφ, fixing the pellets on a metal plate, and holding the pellets at an angle of 45 °. The length (mm) flowing down during curing was measured.

Evaluation Criteria (1) A: extremely excellent smoothness B: normal smoothness C: poor smoothness

The solvent resistance was evaluated by visually observing the condition of the coated surface after rubbing for 20 reciprocations with gauze impregnated with methyl ethyl ketone.

Evaluation Criteria (2) ∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙

For the evaluation and examination of weather resistance, a test for 800 hours was conducted by using a sunshine weatherometer, and the ratio of 60-degree gloss (that is, 60-degree specular reflectance) before and after such a test, that is, gloss The retention rate (%) was displayed.

The storage stability was evaluated by examining the coatings after storage at 40 ° C. for 60 days, from the smoothness of the coating film, the pellet flow (mm) and the glossy surface of the coating film, respectively. A comprehensive evaluation decision was made.

At this time, the criteria for evaluating the smoothness of the coating film were the same as those for the above evaluation criteria (1).

[0077]

[Table 11]

<< Footnote in Table 3 >> μm is a unit of length representing micron.

[0079]

[Table 12]

[0080]

[Table 13]

[0081]

[Table 14]

Thus, in comparison with the respective products of the present invention obtained in Examples 1 and 3, Comparative Examples 1 and 3
All of the control products obtained in 1) are in the form of using no orthophosphoric acid diester, and
Inferior in smoothness,

Further, in comparison with the product of the present invention obtained in Example 2, the control product obtained in Comparative Example 2 is a form in which the orthophosphoric acid diester is changed to the phosphorous acid diester. Although there is no problem with smoothness, the storage stability of the powder coating is extremely poor.

After all, the respective products of the present invention obtained in Examples 1 to 9 were all gritty, and in particular, in terms of smoothness, storage stability, weather resistance and mechanical performance. Is excellent.

Therefore, in order to improve the finished appearance and the storage stability of the powder coating, it is effective to modify the vinyl copolymer with a compound having an orthophosphoric acid group in the molecule. It can be said that it is a means to become.

[0086]

As described in detail above, the resin composition for powder coatings of the present invention is particularly excellent in the storage stability of powder coatings, and has good smoothness and sharpness of the coated surface. It is extremely highly practical and has a so-called finished appearance of the coating film.

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[Procedure amendment]

[Submission date] February 14, 1994

[Procedure Amendment 1]

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Further, if only representative examples of other ethylenically unsaturated monomers are given, various unsaturated dicarboxylic acid dialkyl esters such as fumaric acid dialkyl ester or itaconic acid dialkyl ester are exemplified. Various aromatic vinyl monomers such as styrene, α-methylstyrene or vinyltoluene;

[Procedure Amendment 2]

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In the present invention, examples of the above-mentioned dibasic carboxylic acid used as a curing agent component include aliphatic or aromatic polyvalent carboxylic acids,
Of the typical ones, only typical ones among them are glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and 1,10-decane. Dicarboxylic acid, 1,12-
Dodecanedicarboxylic acid, 1,20-eicosandicarboxylic acid or 1,24-tetraicosandicarboxylic acid,

[Procedure 3]

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Alternatively, maleic acid, citraconic acid, itaconic acid, glutaric acid, phthalic acid, isophthalic acid, hexahydrophthalic acid, cyclohexene-1,2-dicarboxylic acid or 1,3-cyclohexyldicarboxylic acid or 1,4-cyclohexyl Examples include dicarboxylic acids.

[Procedure amendment 4]

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[0059]

[Table 7]

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[0061]

[Table 8]

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[0062]

[Table 9]

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[0063]

[Table 10]

[Procedure Amendment 8]

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<< Footnotes in Table 2 >>"DDA" ... Abbreviation of "1,10-decanedicarboxylic acid"

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Claims (5)

[Claims] 1. A vinyl copolymer obtained from a glycidyl group-containing monomer and an ethylenically unsaturated monomer copolymerizable therewith is modified with a compound having an orthophosphoric acid group in the molecule. A resin composition for powder coating, comprising a resin and a dibasic carboxylic acid as essential components. 2. A softening point of 70 which is obtained by polymerizing 10 to 60% by weight of a glycidyl group-containing monomer and 90 to 40% by weight of an ethylenically unsaturated monomer copolymerizable therewith.
Within a range of up to 150 ° C. and a number average molecular weight of 1,0
The vinyl copolymer in the range of 00 to 30,000,
A resin composition for powder coating, comprising a resin modified with a compound having one orthophosphoric acid group in one molecule and a dibasic carboxylic acid as essential components. 3. The composition according to claim 1, wherein the compound having one orthophosphoric acid group in one molecule is an orthophosphoric acid dialkyl ester. 4. The composition according to claim 1, wherein the compound having one orthophosphoric acid group in one molecule is di2-ethylhexyl phosphate or dibutyl phosphate. 5. The amount of the compound having one orthophosphoric acid group in one molecule is the same as that of the above vinyl-based copolymer.
The composition according to any one of claims 1 to 4, which is in a range of 0.01 to 10.0 parts by weight with respect to 00 parts by weight.