JPH02145666A - Thermosetting coating composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition giving a coating film having excellent water-resistance, acid resistance, chemical resistance, etc., by adding a blocked polyisocyanate compound to an organic solvent-type coating composition containing a glycidyl-containing resin and a carboxyl-containing resin as vehicle components. CONSTITUTION:The objective composition is produced by adding (A) a blocked polyisocyanate compound to an organic solvent-type coating composition composed of (B) a resin having glycidyl group (preferably acrylic resin having a number-average molecular weight of 1,000-20,000) and (C) a resin having carboxyl group (preferably an acrylic resin having a number-average molecular weight of 3,000-20,000) as vehicle components.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a thermosetting resin coating composition.

(Prior Art and its Problems) Conventionally, materials such as metals are coated with paint to impart rust prevention and cosmetic properties. Particularly in the automobile industry, this demand is becoming even stronger.

The currently mainstream paint for automobile bodies uses a combination of hydroxyl group-containing resin and melamine resin as a vehicle component, but this paint produces many by-products during curing, which can cause minute wrinkles in the paint film. The drawback is that a coating film with excellent texture, gloss, and texture cannot be obtained.

As a coating composition that improves the above-mentioned drawbacks, a coating composition containing a combination of glycidyl group-containing resin/carboxyl group-containing resin as a vehicle component does not generate by-products during curing and produces a coating film with an excellent finished appearance. In recent years, it has been viewed as promising because of its ability to form.

However, this coating composition cures the coating film by utilizing the reaction between glycidyl groups and carboxyl groups, but in this reaction, new hydrophilic hydroxyl groups are generated, resulting in poor water resistance of the cured coating film. There is a drawback. In addition, the cured coating film has a lower crosslinking density than a cured coating film whose vehicle component is a combination of hydroxyl group-containing resin/melamine resin, so the coating film has good water resistance, solvent resistance, acid resistance, scratch resistance, etc. The reality is that the problem of insufficient performance remains.

(Means for Solving the Problems) The present inventors have conducted extensive research in order to solve the conventional problems as described above. As a result, when a blocked polyisocyanate compound is added to a paint containing a conventional glycidyl group-containing resin/carboxyl group-containing resin as a vehicle component, it is possible to eliminate the hydroxyl groups generated during coating film curing and form a coating film with a high crosslinking density. They discovered this and completed the present invention.

That is, the present invention provides a blocked polyisocyanate compound (
The present invention relates to a thermosetting coating composition characterized by adding C).

The glycidyl group-containing resin (A) used in the composition of the present invention can be selected from conventionally known resins without particular limitations as long as it has a glycidyl group that reacts with the carboxyl group of the resin (B). Examples of the TH resin include acrylic resins, polyester resins, alkyd resins, and epoxy resins. Among these, acrylic resins are preferred because they provide coating films with excellent weather resistance.

The acrylic resin includes (1) glycidyl group-containing vinyl monomers such as glycidyl acrylate, glycidyl methacrylate, glycidyl methacrylamide, and allyl glycidyl ether; (2) 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl. Hydroxyalkyl esters of acrylic acid or methacrylic acid having 1 to 8 carbon atoms, such as acrylate, hydroxypropyl methacrylate, etc.: (3) Methyl acrylate, butyl methacrylate,
Ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl meccrylate, i-butyl acrylate, i-butyl methacrylate, tert
-butyl acrylate, tert-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate,
Alkyl or cycloalkyl esters of acrylic acid or methacrylic acid having 1 to 24 carbon atoms, such as lauryl acrylate, stearyl acrylate, stearyl methacrylate, decyl acrylate, etc.: (4) styrene, vinyltoluene, vinyl propionate, Vinyl monomers such as α-methylstyrene, vinyl acetate, acrylonitrile, methacrylonitrile, vinyl propionate, vinyl vivalate, Beoba monomer (Shell Chemicals); the above (1) monomers and (2) to ( 4)
It is a copolymer with at least one monomer selected from the following.

The polymerization ratio of the glycidyl group-containing vinyl monomer (1) is in the range of 5 to 80% by weight, preferably 10 to 60% by weight of the monomers constituting the copolymer, and the copolymer is
500-50,000, preferably 1.000-20,
000 number average molecular weight. If the polymerization ratio of the glycidyl group-containing vinyl monomer is less than 5% by weight, a sufficiently cured coating film cannot be obtained, while if it is more than 80% by weight, it will become expensive and will not be more effective in terms of physical properties. I can't expect that. Furthermore, if the number average molecular weight is less than 500, solvent resistance and weather resistance will be poor;
If it is larger, workability, finish quality, etc. will be inferior.

Carboxyl group-containing resin (B) used in the composition of the present invention
is a resin for obtaining a cured coating film in combination with the glycidyl group-containing resin (A), and conventionally known polycarboxylic acid resins can be used.

Examples of the polycarboxylic acid resin include acrylic resin, polyester resin, and alkyd resin. Among these, acrylic resins are preferred because they provide coating films with excellent weather resistance.

The acrylic resin includes (8) ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, iconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxyethyl (meth)acrylate, and the above-mentioned Examples include copolymers with at least one monomer selected from monomers (2) to (4).

The polymerization ratio of ethylenically unsaturated carboxylic acid in the above copolymer is 2% to 20% by weight, preferably 3% to 20% by weight.
10% by weight, and the copolymer has a content of 1°0% by weight.
00-70.000, preferably 3.000-20.0
It can have a number average molecular weight of 0.00. If the amount of ethylenically unsaturated carboxylic acid is less than 2% by weight, a sufficiently cured coating film cannot be obtained.On the other hand, if it is more than 20% by weight, the resin has a high viscosity and high polarity (which results in poor compatibility with glycidyl group-containing acrylic resins). If the number average molecular weight is less than 1.000, the solvent resistance and weather resistance will be poor, while if it is greater than 70.000, the resin viscosity will be very high and the finish will be poor. .

The blocked polyisocyanate compound (C) used in the composition of the present invention is a polyisocyanate compound having an average of at least two isocyanate groups in one molecule, and the incyanate groups are blocked with a blocking agent.

Examples of the polyisocyanate compound include m- or p-xylylene diisocyanate, 24- or 2.
Amount of aromatic diisocyanate compounds such as 6-dolylene diisocyanate, m- or p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, etc. 4
．． Aliphatic (alicyclic ) Diisocyanate compound: Adduct of the above diisocyanate compound and polyol (ethylene glycol, trimethylolpropane, etc.): Examples include polymers of the above diisocyanate compound and billet type polyisocyanate compounds.

Volatile low-molecular active hydrogen compounds are used as blocking agents for polyisocyanates, examples of which include methanol, ethanol, propatool, butanol, hexanol, cyclohexanol, benzyl alcohol,
Aliphatic or aromatic monoalcohols such as ethylene glycol monoethyl ether (hereinafter abbreviated as cellosolve), ethylene glycol motubutyl ether (hereinafter abbreviated as butyl cellosolve), hydroxy tertiary amines such as dimethyl- or diethylaminoethanol,
Examples include oximes such as acetoxime and methyl ethyl ketone oxime, active methylene compounds such as acetylacetone, acetoacetate, and malonic acid ester, lactams such as ε-caprolactam, and phenol. Among these, aliphatic monoalcohols, oximes, and caprolactam are particularly preferred.

The composition of the present invention can be obtained by dissolving or dispersing the components (A) to (C) in an organic solvent.

The blending ratio of glycidyl group-containing resin (A) and carboxyl group-containing resin (B) is usually 0.5 carboxyl group in resin (B) per glycidyl group in resin (A).
-1.5 pieces, preferably 0.8-1.2 pieces can be blended.

In addition, the blending ratio of the blocked polyisocyanate compound (C) is the OH produced by the resin (A) and the resin (B).
The number of isocyanate groups in component (C) may be approximately one per one group.

Examples of the organic solvent include aromatic hydrocarbons such as xylene and toluene; esters such as ethyl acetate, propyl acetate, and butyl acetate; ketones such as acetone and methyl ethyl ketone; and ethylene glycol, cellosolve, butyl cellosolve, and cellosolve acetate. Examples include ether type.

These organic solvents can be used alone or in combination of two or more. Further, from the viewpoint of curability, those having a boiling point of about 150 parts or less are preferable, but are not limited thereto.

The organic solvent can be blended as a paint stock solution (paint before being adjusted to a coating viscosity) in an amount of 30 to 60% by weight in terms of solid content.

The composition of the present invention contains, for example, organic pigments (for example, quinacridone series such as quinacridone series, azo series such as Pigment Red, phthalocyanine series such as phthalocyanine blue and phthalocyanine green, etc.), inorganic pigments (for example, titanium oxide, barium sulfate, carbonate, etc.). Calcium, Balik, clay, silica, etc.), carbon-based pigments (carbon black), scaly metallic powders (e.g. aluminum, micaceous iron oxide, stainless steel, etc.), and anti-rust pigments (e.g. red iron oxide, strontium chromate, etc.) can be used. .

In addition to the pigments described above, additives such as ultraviolet absorbers, coating surface conditioners, curing catalysts, and pigment dispersants can be used in the composition of the present invention.

The composition of the present invention can be applied to metals (e.g. steel plates, surface-treated steel plates, etc.)
It can be applied directly to the material to be coated, such as plastic, or to the coated surface of the material to be coated with a brimer or brimer/intermediate coat. In addition, when used as a top coat for automobile paints, it can be used as a base coat metallic paint such as 2 coats 1 bake, 2 coats 2 bakes, etc., and a clear paint for top coats such as solid color paints such as 1 coat 1 bake. .

To give an example of a coating method when used as an automobile top coat, for example, the coating is adjusted to a coating viscosity of about 12 to 30 seconds (20 degrees Celsius), and then electrostatically coated (bell-shaped). , REA type, etc.), air spray coating, etc., to a dry film thickness of about 10 to 60 μm.

The baking conditions for the paint are approximately 120-180℃, 1
The duration is approximately 0 to 30 minutes.

(Actions and Effects of the Invention) The paint of the present invention has water resistance by reacting free hydroxyl groups in the paint film newly generated by the reaction between glycidyl groups and carboxyl groups with a blocked polyisocyanate compound to reduce the hydroxyl groups. A coating film with excellent properties and acid resistance is formed. In addition, the urethane bond produced by the reaction between the hydroxyl group and the blocked polyisocyanate compound is chemically stable, so it has excellent chemical resistance and water resistance, as well as excellent mechanical properties and coating surface condition (sag, flow). A coating is formed. Furthermore, crosslinking with the blocked polyisocyanate compound forms a cured coating film with a high crosslinking density, making it possible to exhibit excellent solvent resistance and scratch resistance.

(Example) The present invention will be described in more detail with reference to Examples. "Parts" and "%" in Examples and Comparative Examples are based on weight.

Production Example 1 Styrene 30 parts, n
- By reacting monomers of 20 parts of butyl methacrylate, 20 parts of 2-ethylhexyl acrylate, and 30 parts of glycidyl methacrylate.

Glycidyl group-containing acrylic resin (G-1) with a number average molecular weight of 1800, resin solid content of 50%, and Gardner foam viscosity of A
I got it.

Production Example 2 Styrene 30 parts, n
-20 parts of butyl methacrylate, 10 parts of 2-ethylhexyl acrylate, 30 parts of glycidyl methacrylate,
10 parts of 2-hydroxyethyl acrylate monomer was reacted to obtain a number average molecular weight of 2000. Resin solid content 50%
A glycidyl group-containing acrylic resin (G-2) having a Gardner foam viscosity of C was obtained.

Production Example 3 30 parts of styrene, 40 parts of n-butyl methacrylate, in an organic solvent of 85 parts of Kijirole and 15 parts of n-butanol.
20 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid
By reacting 0 parts of monomer, the number average molecular weight is 6000,
A carboxyl group-containing acrylic resin (A-1) with a resin solid content of 50% and a Gardner foam viscosity of ■ was obtained.

Production Example 4 30 parts of styrene, 40 parts of n-butyl methacrylate, in an organic solvent of 85 parts of Kijirole and 15 parts of n-butanol.
10 parts of 2-ethylhexyl acrylate, 1 part of acrylic acid
A carboxyl group-containing acrylic resin (A-2) having a number average molecular weight of 5,500, a resin solid content of 50%, and a Gardner foam viscosity of W was obtained by reacting 0 parts of monomers and 10 parts of 2-hydroxyethyl acrylate.

Production Example 5 30 parts of styrene, 40 parts of n-butyl methacrylate, in an organic solvent of 85 parts of Kijirole and 15 parts of n-butanol.
Monomers of 10 parts of 2-ethylhexyl acrylate, 18 parts of 2-hydroxyethyl acrylate, and 2 parts of acrylic acid were reacted to obtain a number average molecular weight of 6600 and a resin solid content of 5.
A hydroxyl group-containing acrylic resin (H-1) with a Gardner foam viscosity of 0% and a Gardner foam viscosity of J was obtained.

Example 1 A mixture of 40 parts of resin (G-1), 60 parts of resin (A-1), and 18 parts of Coronate #2513 (Note 1) was stirred and then mixed with a Turupetz 100 using a Ford cup No. 4. The viscosity was adjusted to 10 seconds and then tested.

(Note 1) Manufactured by Nippon Polyurethane Kogyo Co., Ltd., trade name, non-yellowing type blocked isocyanate Example 2 Mixture of 40 parts of resin (G-1), 60 parts of resin (A-2) and 18 parts of Coronate #2513 (note 1) After stirring, the viscosity was adjusted to 25 seconds using a Trupetz 100 and Ford Cup No. 4, and the mixture was subjected to a test.

Example 3 A mixture of 40 parts of resin (G-2), 60 parts of resin (A-2) and 28 parts of Coronate 12513 (Note 1) was stirred and then stirred for 25 seconds using a Tsurpetz 100 and a Ford cup No. 4. The viscosity was adjusted to 100% and tested.

Comparative Example 1 After stirring a mixture of 40 parts of resin (G-1) and 60 parts of resin (A-1), the viscosity was adjusted to 25 seconds using a Tsurpetz 100 and Ford cup No. 4, and the mixture was subjected to a test. .

Comparative Example 2 70 parts of resin (H-1) and resin kneepants 20SE (Note 2)
) After stirring 30 parts of the mixture, with Tsurpetz 100,
The viscosity was adjusted to 25 seconds using Ford Cup No. 4, and the mixture was tested.

(Note 2) Made by Mitsui Toatsu Chemical Co., Ltd., trade name, melamine resin. The resin blending ratios in the above Examples and Comparative Examples are the amount (C part) converted to solid content, respectively.

(Coating Film Creation Conditions) Painting and cured coating films were created using the compositions of the Examples and Comparative Examples.

Epoxy cationic electrocoating paint was electrocoated on a 0.8 mm thick dull steel plate that had been subjected to zinc phosphate chemical conversion treatment to a dry film thickness of 20μ, and after baking at 170°C for 20 minutes, #400 paint was applied. Polished with sandpaper, wiped with petroleum benzene to degrease, and then air sprayed an automotive interior surfacer to a dry film thickness of approximately 25 μm.
After baking at 40° C. for 30 minutes, it was wet-sanded with #400 sandpaper, drained and dried, and then degreased with petroleum benzine to obtain a test material.

On this material, Magiclon Base Coat HM-22 (manufactured by Kansai Paint Co., Ltd., trade name) was applied using an air spray gun F5 (manufactured by Meiji Kikai Seizo Shin, trade name) to a cured film thickness of approximately 15μ. After opening 1 for about 3 minutes at room temperature, Example 1~
The clear coats of Comparative Examples 1 and 3 and Comparative Examples 1 and 2 were applied to a cured film thickness of about 40μ using the air spray gun F5, and then left at room temperature for about 10 minutes. It was cured by heating at 140° C. for 30 minutes in a hot air dryer.

These results are summarized in Table-1.

Paint film appearance: The finished appearance of the paint film was evaluated in terms of gloss and texture using the following criteria.

0: Very good ■＝Good condition ×: Bad 60° gloss: Specular reflectance was measured at 60°.

Pencil hardness: Measured according to JIS K 5400.

Acid resistance: A test coated plate was immersed in a 40% sulfuric acid solution,
After being left at 50°C for 5 hours, it was washed with water and the painted surface was observed and evaluated using the following criteria.

0: No change at all O: There is no abnormality on the painted surface, but there is a slight difference in level between the immersed and non-soaked areas ×: The painted surface has turned white Water resistance: To hot water at 40℃ After immersion for 240 hours, the coated surface was washed with water and evaluated based on the following criteria.

0: No change at all ■ = Slight loss of gloss Solvent resistance: After wiping the painted surface 10 times with gauze impregnated with xylene, the painted surface was observed and evaluated based on the first standard.

0: There is almost no change ◎: There are noticeable scratches on the painted surface △: The painted surface is swollen and has a tendency to whiten Scratch resistance: A car with a test coating plate attached to the roof is washed in a car wash. The condition of the painted surface of the coated plate was observed after the car was washed five times.

The car wash machine is rPo 20 made by Yasui Sangyo. FWRCJ was used. The evaluation criteria are as follows It is as follows.

0: Almost no scratches can be seen by visual observation. I passed without getting it.

○: There are some scratches, but The extent of this is extremely slight.

△: Scratches are noticeable by visual observation. failure.

×: Clearly noticeable spot by visual observation. Failed due to scratches.

Molecular weight between crosslinks: Measured by xylene swelling method.

[Method for Measuring Crosslink Molecular Weight] ■ A clear paint is applied in exactly the same manner as the original painting process, except that the object to be coated is a tin plate, and then heated and cured.

(2) Peel off the clear coating film using a tin plate using the mercury amalgam method to obtain a free clear coating film of approximately 4 cm x 4 cm in size.

■ Fill a desiccator with xylene, place a film on top of the liquid, and gently swell it with xylene vapor.

■ The film was then immersed in xylene and heated at 25°C for 2 hours.
Soak for 4 hours to reach swelling equilibrium.

■ Remove the film from the xylene and place it between filter papers to quickly remove the xylene from the film surface.

■ Place the film in a weighing bottle that has been weighed in advance and weigh it (the weight of the swollen film is Ws).

■ Remove the lid from the weighing bottle and place it in a vacuum dryer to weigh 10 mg.
Dry at 100°C for 3 hours below Hg (the weight of the dry coating film is Wd).

In addition, when the film is easily broken in xylene, it is preferable to place the film in a stainless steel wire mesh, a polyester net, or a porous paper bag and immerse it.

(2) Calculate the molecular weight between crosslinks (Mc) using the following formula (Flory-Riner formula).

However, here, v3 is the volume fraction of the resin in the swollen coating film, and is calculated by the following formula.

Here, ψR is the density of the clear coating film fg/cm"l, ψ
3 is the density of xylene (0,8637 g/cm"1 (25
℃).

vs' is the molar volume of xylene (123cc/mole)
X represents Flo between xylene and clear coating resin.
The ry-Huggins interaction constant is assumed to be 0.4 here.

Gel fraction 2 Prepare a free clear film using the above method (2), place it in a 300 mesh stainless steel mesh container, and extract with a Soxhlet extractor using acetone/methanol = 1/1 solvent for 6 hours. After that, the gel fraction was calculated according to the following formula.

Claims (1)

[Scope of Claims] [1] A blocked polyisocyanate compound (C) is added to an organic solvent-based coating composition containing a glycidyl group-containing resin (A) and a carboxyl group-containing resin (B) as vehicle components. A thermosetting coating composition. [2] The thermosetting coating composition according to claim 1, wherein the glycidyl group-containing resin (A) and the carboxyl group-containing resin (B) are each an acrylic resin.