JPH03200884A - Thermosetting paint composition - Google Patents

Abstract

PURPOSE:To improve the acid, marring, water and solvent resistances by using a binder comprising a resin composition consisting of an acrylic and/or polyester resin, an amino resin, and a polyorganosiloxane. CONSTITUTION:5-90 pts.wt. hydroxylated resin having a hydroxyl number of 20 to 150 and an acid value of 50 or lower, selected from an acrylic resin of a number-average molecular weight of 1,000 to 50,000 and a polyester resin of a number-average molecular weight of 800 to 50,000 is mixed with 5-50 pts.wt. amino resin (e.g. melamine resin) and 1-90 pts.wt. polyorganosiloxane having an average number of silanol groups in the molecule of at least 2 and a number- average molecular weight of 500 or higher so as to provide a total of 100 pts.wt., thus giving a binder comprising a resin mixture. The binder is mixed, if necessary, with an organic solvent having a boiling point of 150 deg.C or lower (e.g. toluene), a pigment, an ultraviolet absorber, a coated surface modifier, a curing catalyst, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermosetting coating composition, more specifically, a thermosetting coating composition suitable for a top coating that can form a coating film with excellent acid resistance and scratch resistance. paint composition.

(Prior art and its problems) Conventionally, materials such as metals have been coated with paint films to impart rust prevention and cosmetic properties.

In recent years, damage caused by acid rain has become a serious social problem as air pollution increases and forests wither. There are problems such as etching of the paint film, whitening, staining, etc. on the paint film, and there is a strong demand for a paint film with good acid resistance.

Additionally, top coats, such as those applied to automobile exterior panels, are susceptible to scratches due to collisions with sand, dust, etc. while driving, or friction from cleaning brushes, etc., which is one of the causes of deterioration in appearance. In particular, the occurrence of scratches is very noticeable in dark colored paint films such as black, navy blue, and brown, and there is a strong demand for improving the scratch resistance of the top coat film.

Currently, paints containing hydroxyl group-containing resins and amino resins as binders are widely used as thermosetting top coat paints, but none that satisfy both acid resistance and scratch resistance have yet to be obtained.

(Means for Solving the Problems) The present inventors have made a leap forward in acid resistance and scratch resistance without impairing the weather resistance, solvent resistance, water resistance, mechanical properties, and appearance of the paint film. With the aim of achieving improved performance, we investigated the glass transition point, molecular weight, composition, etc. of hydroxyl group-containing resins and amino resin systems. As a result, although some effects were observed by changing these, it was still insufficient.

As a result of extensive research on polymer blends, the present inventors have developed a coating material by blending a silanol group-containing polyorganosiloxane that forms crosslinking points through the reaction between silanol groups and the reaction between silanol groups and hydroxyl groups. A coating film with significantly improved acid resistance and scratch resistance can be obtained without impairing the performance or appearance of the film, and in addition to these properties, a coating film with excellent water resistance and solvent resistance can be obtained. This discovery led to the completion of the present invention.

That is, the present invention comprises the following components (A), (B) and (C).
) in a total amount of 100 parts by weight, 5 to 90 hydroxyl group-containing resins (A) selected from acrylic resins and polyester resins
parts by weight, 5 to 50 parts by weight of amino resin (B), and a number average molecular weight of 500 having an average of 2 or more silanol groups in one molecule.
The present invention provides a thermosetting coating composition characterized in that the resin composition containing the above polyorganosiloxane (C) in a proportion of 1 to 90 parts by weight is used as a binder.

The binder in the coating composition of the present invention contains a hydroxyl group-containing resin (A), an amine resin (B), and a polyorganosiloxane (C) as essential components.

The hydroxyl group-containing resin (A) in the present invention is a hydroxyl group-containing resin selected from acrylic resins and polyester resins, and may be one type or a mixture of two or more of these resins.

Examples of the acrylic resin include copolymers of hydroxyl group-containing vinyl monomers and other vinyl monomers. As a hydroxyl group-containing vinyl monomer,
For example, C2-C24 hydroxyalkyl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, etc.: N-methylol acrylamide, N-methylol methacrylamide, N- Hydroxyethyl acrylamide, N-hydroxyethylmethacrylamide, N,N-dihydroxyethyl acrylamide,
Mono- or di-acrylic acid or methacrylic acid such as N,N-dihydroxyethyl methacrylamide, etc.
Examples include C1-C1□hydroxyalkylamides.

Examples of other vinyl monomers include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, 1so-butyl acrylate, 3-pentyl acrylate, hexyl acrylate, 2-hebutyl acrylate, octyl acrylate, 2-octyl acrylate, C of acrylic acids such as nonyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-ethyl butyl acrylate
1-C24 alkyl esters, and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, is.

-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, 2-ethylhexyl acrylate, butyl methacrylate, lauryl methacrylate,
C1 ~ of methacrylic acid such as stearyl methacrylate
Examples include C24 alkyl esters and carboxyl group-containing vinyl monomers such as acrylic acid and methacrylic acid, as well as styrene, vinyltoluene, and glycidylmethacrylate.

In order to copolymerize these monomers, conventionally known methods are used, and they can be made into an organic solvent solution type or a non-aqueous dispersion type by the polymerization method, and either form can be used. Further, the acrylic resin has a number average molecular weight of 1
000-50000, preferably 3000-30000
It is desirable that it be within the range of .

In the present invention, the polyester resins that can be used as the hydroxyl group-containing resin (A) include both oil-free polyester resins and alkyd resins, including phthalic acid and its acid anhydrides, isophthalic acid, terephthalic acid, trimellitic acid, and Polybasic acid components such as its acid anhydride, hexahydrofucric acid and its acid anhydride, succinic acid, adipic acid, pimelic acid, sebacic acid, brassic acid, ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, Included are those obtained by condensation polymerization of polyol components such as 1.6-hexanediol, trimethylolpropane, glycerin, penquerythritol, and tricyclodecane dimetatool according to a conventional method.

In the above condensation polymerization reaction, the molecular weight may be adjusted by using, for example, benzoic acid, pt-butylbenzoic acid, etc. as an end-capping agent, or by further blending an oil or fat with the above acid component and polyol component. or after oil modification using fatty acids such as coconut oil fatty acids, tall oil fatty acids, and castor oil fatty acids as part of the acid component. In addition, 6 may be used since the polymer is modified by chain extension with an aliphatic polyisocyanate such as 1,6-hexamethylene diisocyanate or ε-caprolactone.

The above polyester resin has a number average molecular weight of 800 to 50.
000, preferably in the range of 2000 to 20000.

Both the acrylic resin and the polyester resin, which are the hydroxyl group-containing resins (A), must have hydroxyl groups that serve as crosslinking reaction points, and the hydroxyl value of these resins is 20 to 150, preferably Suitably, the acid value is in the range of 30-130, and the acid value is preferably 50 or less, preferably 5-30.

The hydroxyl group-containing resin (A) may be any of the above acrylic resins and polyester resins, but acrylic resins are more preferred from the viewpoint of weather resistance.

In the present invention, the amine resin used as component (B) acts as a crosslinking agent, and is obtained by the reaction of an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, or dicyandiamide with an aldehyde. Examples include methylolated amino resins. Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Additionally, this methylolated amino resin can also be used after being etherified with a suitable alcohol. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n
-propyl alcohol, i-propyl alcohol, n-
Examples include butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol, and the like. Amino resins include melamine with a high degree of etherification, that is, melamine in which an average of three or more methyl ethers per triazine nucleus, and melamine resins in which a portion of the methoxy groups are substituted with alcohols having two or more carbon atoms. In addition, a low molecular weight melamine having an average degree of condensation of about 2 or less and a mononuclear proportion of about 50% by weight or more is preferable from the viewpoint of scratch resistance. It is preferable to add a commonly used curing catalyst.

Polyorganosiloxane (C
) is a polyorganosiloxane having an average of 2 or more, preferably 2 to 10 silanol groups in one molecule and a number average molecular weight of 500 or more, preferably 1,000 to 50,000. This polyorganosiloxane preferably has a ladder structure portion, and can be obtained, for example, by hydrolyzing and condensing a silane compound containing a trifunctional silane represented by (I) below as an essential component.

R,5i(OR')4-, --(I) (wherein R and R' may be the same or different, and have 1-1 carbon atoms
3 represents a hydrocarbon group, and X represents 1.) Examples of the above R and R' include a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, a benzyl group, a phenethyl group, etc. It will be done.

The above-mentioned silane compound to be hydrolyzed and condensed may be only the trifunctional silane of formula (I), but if necessary,
In addition to the functional silane, it may contain a di- or l-functional silane in which the value of X in formula (1) is 2 or 3, and in the silane compound, the silane of formula (I) The content is preferably 30% by weight or more, and 80% by weight.
It is more preferable that the content is above.

Representative examples of the silane of formula (I) include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, ethyltrimethoxysilane, and benzyltrimethoxysilane. Examples include silane and phenethyltrimethoxysilane.

Difunctional or monofunctional which may be used in combination with the silane of formula (1)
Examples of the functional silane include dimethyldimethoxysilane, diphenyldimethoxysilane, diphenyljethoxysilane, diisobutyldimethoxysilane, diisobutyldipropoxysilane, and trimethylmethoxysilane.

The hydrolytic condensation of the silane compound is carried out by mixing the silane compound with a water-soluble solvent (e.g., alcohol solvent, cellosolve solvent, etc.) as necessary, and then mixing the silane compound with a water-soluble solvent (e.g., alcohol solvent, cellosolve solvent, etc.) and using a mineral acid such as hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, etc. The hydrolysis and condensation reactions are carried out in the presence of an organic acid and water, preferably at a pH of 6 or lower, at about 20 DEG C. to 100 DEG C. and stirring for about 30 minutes to 20 hours.

The molecular weight of polyorganosiloxane depends on the amount of water used,
It can be adjusted as appropriate depending on the type and amount of catalyst, reaction temperature, reaction time, etc.

If the average number of silanol groups in one molecule of polyorganosiloxane is less than two, crosslinking will be insufficient and the resulting coating film will have poor acid resistance and scratch resistance. Furthermore, if the number average molecular weight of the polyorganosiloxane is less than 500, the acid resistance of the coating film will not be sufficient. The number average molecular weight is 10 for acid resistance.
More preferably, it is 00 or more.

In the present invention, a hydroxyl group-containing resin (A
), amino resin (B) and polyorganosiloxane (C
) is the total amount of the three components (resin solid content) 10
Based on 0 parts by weight, 5 to 90 parts by weight of hydroxyl group-containing resin,
Preferably 30 to 60 parts by weight, amino resin 5 to 50 parts by weight, preferably 10 to 40 parts by weight, curable resin (C) 1
~90 parts by weight, preferably 5 to 60 parts by weight, more preferably 10 to 40 parts by weight.

If the amount of the hydroxyl group-containing resin (A) is less than 5 parts by weight, the adhesion to the base will decrease, while if it exceeds 90 parts by weight, the resulting coating film will have poor scratch resistance and iiiM properties. If the blending ratio of the amino resin (B) is less than 5 parts by weight, the crosslinking density of the hydroxyl group-containing resin (A) will be low and the water resistance and scratch resistance will be significantly impaired. If the blending ratio exceeds 50 parts by weight, the mechanical properties will deteriorate. Also, problems such as poor adhesion to the substrate occur. In addition, if the blending ratio of the curable resin (C) is less than 1 part by weight, the effect of auxiliary crosslinking will be small and the acid resistance and scratch resistance of the coating film will not be improved; on the other hand, if it exceeds 90 parts by weight , problems such as poor adhesion to the substrate arise.

The thermosetting coating composition of the present invention includes, in addition to the paint goo containing the above components (A), (Bl and (C)) as essential components, an organic solvent, a pigment, an ultraviolet absorber, a coating surface conditioner,
It may contain additives such as a curing catalyst and a pigment dispersant.

Examples of the organic solvents 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; 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, 6 having a boiling point of about 150 parts or less is preferable, but 6 is not limited thereto.

Examples of pigments that may be contained in the composition of the present invention include organic pigments (e.g., quinacridone-based pigments such as quinacridone red, azo-based pigments such as pigment red, and phthalocyanine-based pigments such as fucrocyanine blue and phthalocyanine green).
, inorganic pigments (e.g. titanium oxide, barium sulfate, calcium carbonate, valine, clay, silica, etc.), carbon-based pigments (
carbon black), scaly metallic powder (e.g. aluminum, micaceous iron oxide, stainless steel, etc.),
Antirust pigments (eg red iron, strontium chromate, etc.) can be used.

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 primer or intermediate coat. When used as a top coat for automobile paints, it can be used, for example, as top enamel paints such as 2-coat 1-bake, 2-coat 2-bake, clear paint for top coat; solid color paint such as 1-coat 1-bake.

To illustrate the method of applying the composition of the present invention when used as an automobile top coat, for example, the coating composition of the present invention may be coated for about 12 to 30 seconds () Ord Cup No. 4.
．． This can be done by adjusting the coating viscosity to a temperature of 20°C), and then applying it to a dry film thickness of about 10 to 60 μ using electrostatic coating (bell type, REA type, etc.) or air spray coating. The appropriate temperature is about 120 to about 180°C for about 10 to 30 minutes.

(Actions and Effects of the Invention) The composition of the present invention contains a polyorganosiloxane (having two or more silanol groups in one molecule) as a binder component.
C), and upon heating, reactions between silanol groups and reactions between silanol groups and hydroxyl groups in the hydroxyl group-containing resin occur, resulting in a strong, dense, and crosslinked structure with excellent hydrolysis resistance. It is thought that this is because the acid resistance and scratch resistance can be significantly improved, and a coating film with excellent water resistance and solvent resistance can be obtained. Also,
By keeping the blending amounts of binder components (A), (B), and (C) within a specific range, it was possible to avoid impairing the weather resistance, mechanical properties, and appearance of the paint film. It is something.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, hereinafter, "parts" and "%" each refer to "parts by weight".
and "% by weight".

Production Example 1 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 form a hydroxyl group-containing acrylic resin solution (resin solid content 50%, Gardner foam viscosity (25°C) J). A-1
) was obtained. The obtained resin had a number average molecular weight of 6,600.

Production Example 2 Monomers of 30 parts of styrene, 30 parts of n-butyl methacrylate, 15 parts of 2-ethylhexyl acrylate, and 25 parts of 2-hydroxyethyl acrylate were reacted in an organic solvent of 85 parts of quijirole and 15 parts of n-butanol. Thus, a hydroxyl group-containing acrylic resin solution (A-2) with a resin solid content of 50% and a Gardner foam viscosity (25° C.) of B was obtained. The obtained resin had a number average molecular weight of 5,000.

Production Example 3 Isophthalic acid 0.29 mol, fucuric acid 0123 mol, hexahydrophthalic acid 0.43 mol, trimethylolpropane 0.4 mol, neopentyl glycol 0.6 mol,
Add 0.1 mol of coconut oil fatty acid to the reaction vessel and add 200 to 23
A coconut oil-modified polyester resin having an acid value of 8 and a hydroxyl value of 72 was obtained by condensation polymerization at 0°C. The polyester resin 100
43 parts of xylene was added to the mixture to obtain a resin solution (A-3) with a resin solid content of 60%. The viscosity of this resin solution is Y-+25
°C, Gardner bubble viscosity).

Production Example 4 was mixed, and after reacting at 60°C for 5 hours, methanol was removed under reduced pressure, and Kijirol was added to obtain polyorganosiloxane liquid C-1 with solid content of 50% and Gardner viscosity (25°C) AB. . The obtained polyorganosiloxane had a number average molecular weight of about 5,000 and had an average of 6 silanol groups per molecule.

Production Example 5 was mixed, and after reacting at 60°C for 10 hours, methanol was removed under reduced pressure, and butyl acetate was added to reduce the solid content to 50%.
A polyorganosiloxane liquid C-2 having a Gardner viscosity (25° C.) of D was obtained. The obtained polyorganosiloxane has a number average molecular weight of about 15,000, with an average molecular weight of 10
It had silanol groups.

Example 1 100 parts (solid content: 50 parts) of the resin solution (A-1) obtained in Production Example 1, 33.3 parts of Kneepan 20SE (Note 1) (
20 parts by solid content), the resin solution obtained in Production Example 4 (C-1
) 60 parts (30 parts solids) and 1 part Raybow #3 (Note 2) was stirred, and then Swasol 1000
(Note 3) to make the paint viscosity 25 seconds (Ford Cup #4
/25°C) and used for the test.

(Note 1) Knee pants 20SE...manufactured by Mitsui Toatsu Chemical ■.

Butyl etherified melamine resin solution with a solid content of approximately 60%,
Product name.

(Note 2) Raypaw #3...Made by Raybow Chemical ■.

Silicone surface conditioner liquid with approximately 1% active ingredient, product name 6 (Note 3) Swazol l 000...manufactured by Cosmo Oil■,
Petroleum-based aromatic solvent, trade name.

Examples 2 to 3 and Comparative Examples 1 to 3 The same procedure as in Example 1 was carried out except that the formulation of the mixture before viscosity was as shown in Table 1, and the paint viscosity was 25.
The temperature was adjusted to 25° C. () Ord Cup #4/25° C.) and used for the test.

The blending ratios of Examples and Comparative Examples in Table 1 are amounts (parts) converted to solid content or active ingredient amounts.

Notes in Table 1 are as follows.

(Note 4) Cymel 303...Made by Mitsui Suyanamide ■,
Hexamethoxymethylolmelamine with a solid content of approximately 100%, trade name.

(Note 5) Naicure 5225: Manufactured by King Industries, Inc., USA, neutralized dodecylbenzenesulfonic acid amine with approximately 25% active ingredient, trade name.

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

Electrodeposit epoxy cationic electrolyte paint onto a 0.8mm thick glue steel plate that has been subjected to zinc phosphate chemical conversion treatment to a dry film thickness of 20μ, and then apply an automotive interior coat to the baked electrocoat film. After painting and baking Surf Acer to a dry film thickness of 20F, it was sanded with #400 sandpaper, drained and dried, and then degreased with petroleum benzine to obtain a test material.

On this material, apply Magiclon Baseco-1-HM-22 (manufactured by Kansai Paint Co., Ltd., metallic paint, trade name) using an air spray gun F5 (manufactured by Meiji Kikai Seizo, trade name) to a cured film thickness of approximately 15F. After leaving it at room temperature for about 3 minutes, the viscous paints of Examples 1 to 3 and Comparative Examples 1 to 3 were sprayed using the air spray gun F5 to a cured film thickness of about 40F. After coating, the coating was left at room temperature for about 10 minutes and then cured by heating at 140° C. for 30 minutes in an electric hot air dryer.

Various tests were conducted on each of the baked coated plates obtained.

The test results are shown in Table-1.

The tests in Table 1 were conducted according to the following test method.

Appearance of the paint film: The finished appearance of the paint film was evaluated based on the gloss and texture according to the following criteria.

0: Very good O: Good quality ×: Bad 60° gloss: Specular reflectance was measured at 60°.

Pencil hardness: Pencil scratch value according to JIS K 5400 was displayed.

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

0: No change at all ○ of 6: There is no abnormality on the painted surface, but a slight step was observed at the boundary between the immersed and non-soaked areas ×: Water resistance after the painted surface turned white = 40℃ After being immersed in warm water for 240 hours, the coated surface was washed with water and evaluated based on the following criteria.

0: No change at all O: Slight loss of gloss Solvent resistance: After wiping the painted surface 10 times with gauze impregnated with xylene, the painted surface was inspected and evaluated according to the following criteria.

○: There is almost no change O: There are noticeable scratches on the painted surface Δ: The painted surface swells and tends to whiten. The condition of the painted surface of the coated plate was observed after the car was washed five times. The washing machine used was rPo 20 FWRCJ manufactured by Yasui Sangyo. The evaluation criteria are as follows.

0: Most scratches were found by visual observation. No, passed ○: Some scratches are found, but The severity is extremely minor.

Δ: Failed as light scratches were noticeable by visual observation ×: Rejected due to obvious scratches by visual observation Gel fraction: The free clear film obtained by baking at 140°C for 30 minutes was baked on a 300 meter stainless steel plate. The gel fraction was extracted using a Soxhlet extractor using an acetone/methanol=1/l solvent for 6 hours, and then the gel fraction was calculated according to the following formula.

Claims (1)

[Claims] 1. Total amount of the following components (A), (B) and (C): 10
0 parts by weight, 5 to 90 parts by weight of a hydroxyl group-containing resin (A) selected from acrylic resins and polyester resins, 5 to 50 parts by weight of amino resin (B), and an average of two or more silanol groups per molecule. polyorganosiloxane (C) having a number average molecular weight of 500 or more
A thermosetting coating composition characterized in that the binder is a resin composition containing 90 parts by weight.