JP2000319352A - Cationically electrodepositable resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cationically electrodepositable resin composition capable of being formed into a coated film having a uniform coated surface, and small difference of film thicknesses and excellent in gloss and flatness. SOLUTION: This cationically electrodepositable resin composition comprises a cationic resin having a cross-linkable functional group, e.g. a polyamine resin, a blocked polyisocyanate compound and benzoic acid and/or salicylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationically electrodepositable resin composition capable of forming a coating film having a uniform coating surface, a small difference in film thickness, and excellent gloss and smoothness.

[0002]

2. Description of the Related Art Cathodic electrodeposition paints have excellent throwing power and are required to have such properties in order to form a coating film having excellent durability and anticorrosion properties. It is widely used for undercoating of metal objects such as metal. Prior to the electrodeposition coating, the surface of the object to be coated is often subjected to a chemical conversion treatment with zinc phosphate or the like in order to improve the corrosion resistance and adhesion of the electrodeposition coating film.

[0003] However, the chemical conversion coating often causes sagging marks and streak-like unevenness, resulting in a non-uniform thickness of the coating. As a result, there is a disadvantage that a difference in film thickness is apt to occur in the electrodeposition coating film, and the gloss and smoothness of the coated surface are reduced.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to provide:
Even if the thickness of the chemical conversion coating is uneven, the electrodeposition coating formed on the surface is uniform, the difference in the film thickness is extremely small, and a cationic electrode can form a coating having excellent gloss and smoothness. It is to provide a resin composition that can be attached.

The present inventors have conducted intensive studies to achieve the above object. As a result, this time, the resin composition for a cationic electrodeposition coating composition was made to further contain an aromatic carboxylic acid so that the coating surface was uniform and the film was uniform. The present inventors have found that a cationic electrodeposition paint capable of forming a coating film having an extremely small difference in thickness and excellent gloss and smoothness can be obtained, and have completed the present invention. Thus, the present invention comprises (A) a cationic resin having a crosslinkable functional group, (B) a blocked polyisocyanate compound, and (C) an aromatic carboxylic acid compound selected from benzoic acid, salicylic acid and a mixture thereof. It is another object of the present invention to provide a cationically electrodepositable resin composition.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the cationic electrodeposition coating composition of the present invention will be described in detail.

A cationic resin having a crosslinkable functional group
(A) : As the cationic resin (A) in the present invention, those conventionally used as a base resin in a cationic electrodeposition paint can be similarly used.
A resin having a crosslinkable functional group such as a hydroxyl group and a cationic group such as a primary, secondary or tertiary amino group in one molecule can be used. The resin skeleton is, for example, an epoxy resin or an acrylic resin. And polybutadiene, alkyd resin, polyester resin, and the like. Among them, a polyamine resin obtained by adding an amine to an epoxy resin is generally suitable from the viewpoint of excellent corrosion protection.

As an amine-added epoxy resin, for example,
(I) Adducts of polyepoxide compounds with primary mono- or polyamines, secondary mono- or polyamines, mixed primary and secondary polyamines and the like (for example, US Pat. No. 3,984,299)
(Ii) adducts of polyepoxide compounds with ketiminated secondary mono- or polyamines having primary amino groups (see, for example, US Pat. No. 4,017,438).
(Iii) a product obtained by an etherification reaction between a polyepoxide compound and a ketiminated hydroxyl compound having a primary amino group (see, for example, JP-A-59-43013). Is raised.

A polyepoxide compound used for producing an amine-added epoxy resin has two epoxy groups in one molecule.
Compounds having at least 200, generally at least 200,
Preferably the number average molecular weight is in the range of 400 to 4000 and generally at least 190, preferably 300 to 20.
Those having an epoxy equivalent in the range of 00 are suitable, especially those obtained by the reaction of a polyphenol compound with epichlorohydrin. Examples of the polyphenol compound which can be used for forming such a polyepoxide compound include bis (4-hydroxyphenyl) -2,2-propane, 4,4-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1, 1
-Ethane, bis (4-hydroxyphenyl) -1,1-
Isobutane, bis (4-hydroxy-tert-butylphenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene,
Bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane,
4,4-dihydroxydiphenyl sulfone, phenol novolak, cresol novolak and the like can be mentioned.

Examples of amines that can be added to these polyepoxide compounds include amine compounds such as primary amines, secondary amines, tertiary amines, and polyamines. Here, as the primary amine compound, for example,
Methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, n-propanolamine, isopropanolamine and the like;
As the secondary amine compound, for example, diethylamine,
Diethanolamine, di-n-propanolamine, diisopropanolamine, N-methylethanolamine,
And tertiary amine compounds such as triethylamine, triethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, N, N-diethylethanolamine and N-ethyl. And diethanolamine. Examples of the polyamine include ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminoethylamine, and dimethylaminopropylamine.

Further, a basic compound such as ammonia, hydroxylamine, hydrazine, hydroxyethylhydrazine, N-hydroxyethylimidazoline or the like is used as a cationizing agent to react with an epoxy group, and the basic group formed thereby is acidified. It may be a group capable of being cationized by protonation. As the acid that can be used here, for example, a water-soluble organic carboxylic acid such as formic acid, acetic acid, glycolic acid, and lactic acid is preferable.

Blocked polyisocyanate compound
(B) : The blocked polyisocyanate compound (B) in the present invention is a substance that acts as a curing agent for the above-mentioned cationic resin as the base resin, and generally uses a full-block addition reaction product of the polyisocyanate compound. be able to.

The polyisocyanate compound is a compound having at least two isocyanate groups in one molecule, for example, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate. Aromatic, alicyclic or aliphatic polyisocyanate compounds such as methylene diisocyanate and isophorone diisocyanate, and excessive amounts of these polyisocyanate compounds, ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol,
The molecular weight having a terminal isocyanate group obtained by reacting a low molecular weight active hydrogen-containing compound such as castor oil is usually 1
Prepolymers in the range of 50 to 5000 are exemplified.

On the other hand, the blocking agent is a compound for adding to the isocyanate group of the polyisocyanate compound and temporarily blocking it. The blocked polyisocyanate compound formed by the addition is stable at room temperature, Higher than the dissociation temperature (for example, 100 ° C
When heated above, the blocking agent is dissociated to regenerate the isocyanate group and undergo a crosslinking reaction with the crosslinking functional group of the cationic resin (A). Such blocking agents include, for example, ε
-Lactam compounds such as caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol, p-
phenolic compounds such as t-butylphenol and cresol; aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcoholic compounds such as phenyl carbitol and methylphenyl carbitol; ethers such as ethylene glycol monobutyl ether Alcohol compounds and the like can be mentioned. Of these, oxime-based and lactam-based blocking agents dissociate at a relatively low temperature, and are therefore suitable from the viewpoint of the low-temperature curability of the electrodeposition paint.

The relative proportion of the cationic resin (A) and the blocked polyisocyanate compound (B) in the resin composition of the present invention is based on the total solid weight of these two components. Is typically 50-90%,
In particular, 65 to 80%, and the compound (B) is generally 50 to 80%.
A range of 10%, especially 35-20% is suitable.

Aromatic carboxylic acid compound (C) : The aromatic carboxylic acid compound (C) is a compounding component of the composition of the present invention. By containing the carboxylic acid compound (C), even if the thickness of the chemical conversion coating on the surface of the substrate is uneven, the electrodeposited surface is uniform and the difference in film thickness is small, and the gloss and smoothness are further improved. An excellent coating film can be formed.

As the aromatic carboxylic acid (C), benzoic acid or salicylic acid can be used alone, or a mixture of benzoic acid and salicylic acid may be used. In that case, there is no limitation on the mixing ratio, and the mixture can be used by mixing at an arbitrary ratio.

The content of the aromatic carboxylic acid compound (C) in the resin composition of the present invention is 10 times in total of the cationic resin (A) and the blocked polyisocyanate compound (B).
0 to 5 parts by weight (solid content), generally 0.1 to 5 parts by weight,
In particular, it is suitable in the range of 0.3 to 3.5 parts by weight, more preferably 0.5 to 2 parts by weight.

The cationically electrodepositable resin composition : The cationically electrodepositable resin composition of the present invention includes, for example, the above-mentioned cationic resin (A), blocked polyisocyanate compound (B) and aromatic carboxylic acid. It can be prepared by mixing and dispersing compound (C) in an aqueous medium. In this case, examples of the neutralizing agent for cationization by neutralizing the cationic group in the cationic resin (A) include organic or inorganic acids such as formic acid, acetic acid, lactic acid, methanesulfonic acid, and phosphoric acid. These may be added to the cationic resin (A) in advance, or may be added to the aqueous medium together with the components (A), (B) and (C) during the mixing and dispersion.

Further, the resin composition of the present invention may contain, if necessary, a compound containing a metal selected from bismuth, lanthanum and molybdenum; an anticorrosive such as a lead-containing compound;
A curing catalyst such as an organotin compound; a pigment; an organic solvent;

The compound containing a metal selected from bismuth, lanthanum and molybdenum is useful for promoting the curability of the formed electrodeposition coating film and improving the corrosion resistance,
Specifically, water-soluble or water-insoluble metal-containing compounds exemplified below can be used.

Examples of the bismuth-containing compound include bismuth lactate, bismuth silicate, triphenylbismuth,
Bismuth gallate, bismuth hydroxide, bismuth trioxide,
Bismuth nitrate, bismuth benzoate, bismuth citrate,
Examples thereof include bismuth oxycarbonate. Of these, bismuth lactate, bismuth silicate and bismuth hydroxide are particularly preferable.

Examples of the lanthanum-containing compound include lanthanum acetate, lanthanum lactate, lanthanum oxalate, lanthanum nitrate, lanthanum hydroxide, lanthanum oxide and lanthanum tungstate. Lanthanum acid is preferred.

As the molybdenum-containing compound, for example,
Examples thereof include zinc molybdate, aluminum molybdate, zinc phosphomolybdate, and aluminum phosphomolybdate.

These metal-containing compounds can be used usually in the form of a powder, and the particle size thereof is generally 10 μm or less, preferably 0.1 to 3 μm. The amount of the metal is generally 0.1 to 10 parts by weight, particularly 0.3, in terms of metal per 100 parts by weight (solid content) of the cationic resin (A) and the blocked polyisocyanate compound (B).
A suitable range is from 5 to 7 parts by weight, more preferably from 0.5 to 5 parts by weight.

Examples of the lead-containing compound used as an anticorrosive include lead silicate and lead acetate, and examples of the organotin compound include dioctyltin benzoate, dibutyltin benzoate, dibutyltin oxide, and dioctyltin. Examples include tin oxide, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin diacetate.

As the pigments, those generally used in the field of paints can be used in the same manner. System, anthraquinone system, thioindigo system, perylene system, quinacridone system, titanium yellow, monoazo system, disazo system, condensed azo system, anthorapyrimidine system,
Inorganic and organic coloring pigments such as cobalt green, phthalocyanine green, ultramarine, cobalt blue, phthalocyanine blue, and cobalt violet; calcium carbonate, kaolin, clay, diatomaceous earth, hydrous silica, talc, barite, barium sulfate, and carbonic acid Barium, silica sand,
Extender pigments such as glass beads and mica; zinc dust, zinc phosphate, calcium phosphate, aluminum phosphate, aluminum polyphosphate such as aluminum tripolyphosphate, aluminum orthophosphate, calcium orthophosphate, boric acid-based protection Rust pigments, rust-preventive pigments such as alkaline earth metals and zinc oxide, tungstic acid-based rust-proof pigments, phosphorous acid-based rust-proof pigments, hypophosphite-based rust-proof pigments, nitrite-based rust-proof pigments, vanadic acid-based Anticorrosive pigments such as anticorrosive pigments are included, and Zr (OH) ₄ , Mg ₄ Al ₂ (OH) ₁₂ CO _{3.
3H 2 O, Mg 6 Al 2} (OH) 16 CO 3 · 5H 2 O, Mg 6 A
compounds such as _{l 7 (OH) 16 CO 3} · 4H 2 O can be used as a rust preventive pigment.

These pigments generally have a particle size of 10
μm or less, particularly preferably in the range of 0.01 to 3 μm, and the amount thereof can be arbitrarily selected according to the purpose. Usually, the cationic resin (A) and the blocked polyisocyanate compound (B 100)
0.5 to 50 parts by weight, especially 1 part by weight (solid content)
A range of ３０30 parts by weight is suitable.

The resin composition of the present invention is capable of cationic electrodeposition, and can be advantageously used as a cationic electrodeposition coating in the preparation of an electrodeposition bath and the electrodeposition coating of substrates such as automobile bodies and electric appliances. For example, the resin composition of the present invention is diluted with deionized water or the like so that the solid content becomes about 5 to 40% by weight, and the pH is further adjusted to form an electrodeposition bath of 5.5 to 9.0. Prepared, bath temperature 15-35 ° C, load voltage 100-40
Electrodeposition coating can be performed by immersing an object to be coated as a cathode under a condition of 0 V and applying a current. The thickness of the coating film can be changed according to the use of the object to be coated, etc., but generally it is preferably in the range of 10 to 40 μm as a cured coating film. After energization, the object to be coated is pulled up from the electrodeposition bath and washed with water, and then about 100 to about 2
00 ° C, preferably 10 to 40 at about 140 to about 180 ° C.
By heating for about a minute, the coating film can be cured.

[0030]

As described above, in the cationic electrodeposition coating film formed using the resin composition of the present invention, the thickness of the coating film formed on the surface of the substrate by the chemical conversion treatment is not uniform. However, the cationic electrodeposition paint according to the present invention formed on the surface has a constant film thickness, has almost no change in the film thickness, and has a remarkable effect of being excellent in gloss and smoothness.

[0031]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. Parts and percentages are in principle based on weight. The thickness of the coating film is based on the cured coating film.

Comparative Example 1 "Epon 1004" (product name, bisphenol A type epoxy resin, epoxy equivalent: about 950, manufactured by Yuka Shell Co., Ltd.) 1
900 parts were dissolved in 1012 parts of butyl cellosolve,
After heating to １００100 ° C., 124 parts of diethylamine were added dropwise, and the mixture was kept at 120 ° C. for 2 hours to obtain an amine-added epoxy resin having an amine value of 47. On the other hand, an amine value of 100
Dimer acid-type polyamide resin ("Versamide 46
0 ", manufactured by Henkel Hakusui Co., Ltd., 1000 parts, and dissolved in 429 parts of methyl isobutyl ketone.
The resulting amide resin was converted to ketimine by terminating the generated water by evaporation and kept at 150 ° C. for about 3 hours, and then cooled to 60 ° C. after the distillation of water was stopped. Then, this was added to the amine-added epoxy resin to obtain 10
Heat to 0 ° C., hold for 1 hour, cool to room temperature,
A varnish (a) of an amine-added epoxy resin-polyamide modified resin having 8% and an amine value of 65 was obtained.

Varnish (a) 103 parts (70 in resin solids)
Parts), 30 parts of a 2-ethylhexyl alcohol blocked product of tolylene diisocyanate (solid content), 15 parts of a 10% acetic acid aqueous solution and 72.5 parts of a pigment paste (Note 1) were mixed, and water was further added to solid content. A 20% comparative cationic electrodeposition paint was obtained.

(Note 1) Pigment paste: 5 parts (solid content) of the varnish (a), 10 parts of titanium oxide pigment, 0.5 part of carbon black, 20 parts of clay, 20 parts of 10% bismuth lactate aqueous solution and water A paste prepared by adding and mixing and dispersing 35 parts.

Example 1 To the electrodeposition coating composition of Comparative Example 1, benzoic acid was added in an amount of 1 part per 100 parts of the total solid content of the varnish (a) and the blocked 2-ethylhexyl alcohol of tolylene diisocyanate. To prepare a cationic electrodeposition coating composition.

Example 2 According to the present invention, salicylic acid was added to the electrodeposition coating composition of Comparative Example 1 in an amount of 1 part per 100 parts of the total solid content of the varnish (a) and the blocked 2-ethylhexyl alcohol of tolylene diisocyanate. A cationic electrodeposition paint was prepared.

Comparative Example 2 A cationic electrodeposition coating was prepared in the same manner as in Example 1 except that benzoic acid in Example 1 was replaced with oleic acid in the same amount.

Comparative Example 3 A cationic electrodeposition paint was prepared in the same manner as in Example 1 except that benzoic acid in Example 1 was replaced with linoleic acid in the same amount.

Comparative Example 4 A cationic electrodeposition paint was prepared in the same manner as in Example 1 except that benzoic acid in Example 1 was replaced with decanoic acid in the same amount.

Comparative Example 5 A cationic electrodeposition paint was prepared in the same manner as in Example 1 except that benzoic acid in Example 1 was replaced with stearic acid in the same amount.

Performance Test A zinc phosphate-treated steel sheet (Note 2) was immersed in the cationic electrodeposition paints obtained in the above Examples and Comparative Examples as a cathode, and electricity was applied at 200 V for 3 minutes at 30 ° C. to perform electrodeposition coating. After carrying out, it was pulled up, washed with water, and then heated at 170 ° C. for 20 minutes to cure the coating, and the formed electrodeposited surface was evaluated. The thickness of the cationic electrodeposition coating film was about 20 μm. Table 1 shows the results.

(Note 2) Steel sheet treated with zinc phosphate: steel sheet whose surface is treated with zinc phosphate (size 100 × 150 ×
0.8 mm), and the treated coating film on which streaks and sagging traces of the treatment liquid were observed was selected and subjected to a performance test as an object to be coated.

[0043]

[Table 1]

The test methods used to obtain the results shown in Table 1 above are as follows.

Film thickness difference: film thickness meter (HELMUT FISC)
HER GMBH & Co. Made, PERMASCOP
The difference between the maximum film thickness and the minimum film thickness (μ) of the coated steel sheet measured using E ES TYPE ES8e3KB4).
m).

Mitsuzawa: Gloss meter (MURAKAMI CO.)
LOR RESEARCH LABORATORY,
GLOS METER MODEL GM-26D)
60 ° specular reflectance (%) measured using

Smoothness: Determined visually. ○ indicates good smoothness, △
Indicates that the smoothness is slightly inferior, and X indicates that the smoothness is very inferior.

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Claims (15)

[Claims] 1. A composition comprising (A) a cationic resin having a crosslinkable functional group, (B) a blocked polyisocyanate compound, and (C) an aromatic carboxylic acid compound selected from benzoic acid, salicylic acid and a mixture thereof. A cationically electrodepositable resin composition comprising: 2. The composition according to claim 1, wherein the cationic resin (A) is a resin having a hydroxyl group and a primary, secondary or tertiary amino group in one molecule. 3. The composition according to claim 1, wherein the cationic resin (A) is an amine-added epoxy resin. 4. The blocked polyisocyanate compound (B) is tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate, and these polyisocyanate compounds. The composition according to any one of claims 1 to 3, which is a full-block addition reaction product of a polyisocyanate compound selected from the group consisting of isocyanate-terminated prepolymers derived from 5. The composition according to claim 1, wherein the blocked polyisocyanate compound (B) is blocked with an oxime-based or lactam-based blocking agent. 6. The relative proportion of the cationic resin (A) to the blocked polyisocyanate compound (B) is 50 to 90% based on the total solid weight of these two components, The block polyisocyanate compound (B) is in the range of 50 to 10%.
The composition according to any one of the above. 7. The relative ratio of the cationic resin (A) to the blocked polyisocyanate compound (B) is 65 to 80% based on the total solid weight of these two components, The block polyisocyanate compound (B) is in the range of 35 to 20%.
The composition according to any one of the above. 8. An aromatic carboxylic acid compound (C) in an amount within the range of 0.1 to 5 parts by weight per 100 parts by weight of the total solid content of the cationic resin (A) and the blocked polyisocyanate compound (B). The composition according to any one of claims 1 to 7, which comprises: 9. An aromatic carboxylic acid compound (C) in an amount of 0.3 to 3.5 parts by weight per 100 parts by weight of the total solid content of the cationic resin (A) and the blocked polyisocyanate compound (B). The composition according to any one of claims 1 to 8, which is contained in an amount. 10. The composition according to claim 1, further comprising a compound containing a metal selected from bismuth, lanthanum and molybdenum; an anticorrosive; a curing catalyst; a pigment; an organic solvent or an antisettling agent. . 11. A metal-containing compound selected from bismuth, lanthanum and molybdenum is used as a metal in an amount of 0.1 per 100 parts by weight of the total solid content of the cationic resin (A) and the blocked polyisocyanate compound (B). ~
The composition according to claim 10, further comprising 10 parts by weight. 12. A cationic electrodeposition coating comprising the resin composition according to claim 1. 13. A cationic electrodeposition bath comprising the resin composition according to claim 1. 14. A cationic electrodeposition coating method using the resin composition according to any one of claims 1 to 11. 15. An article coated with the resin composition according to claim 1. Description: