JPS58136667A - Composition for electrodeposition coating - Google Patents

Abstract

PURPOSE:To provide a compsn. for electrodeposition coating capable of forming a film excellent not only in appearance and corrosion resistance but also in resistance to flexing, impact and moisture, prepared by blending a hydroxyl group- rich resin with a specified resin. CONSTITUTION:1-3mol of partly blocked isocyanate (e.g., a reaction product of toluene diisocyanate and a proper amount of 2-ethylhexanol is reacted with 1mol of hydroxy-terminated butadiene/acrylonitrile copolyme (pref. having an acrylonitrile content of about 8-40wt%, about 1.5-2.5 terminal hydroxyl groups per molecule on average and a number-average molecular weight of about 500- 5,000) to obtain a reaction product. The titled compsn. is prepared by blending 100pts.wt. hydroxyl group-rich resin (e.g. epoxy-modified amino resin) with 5- 120pts.wt. said reaction product.

Description

[Detailed description of the invention] The present invention relates to a composition for electrodeposition coating.

Electrodeposition paints are used in a wide range of applications, including as primers for automobiles, and their performance has been significantly improved as there has been a strong demand for improved performance of durable consumer products from the standpoint of resource conservation. For example, Japanese Patent Application Publication No. 51. The electrodeposition paints described in Publications No.-103135 and No. 52-18746 exhibit extremely excellent corrosion resistance, solvent resistance, etc.
It is highly valued as a paint. However, even with these electrodeposition coatings, there remain problems to be solved in terms of flexibility, adhesion, moisture resistance, etc.

In order to solve such problems, the applicant first added a partially blocked isocyanato group-containing compound and an amide 7 group-containing compound to a reaction mixture of an epoxy group-containing compound and a carboxyl group-containing butadiene acrylonitrile copolymer. A cathode electrodeposition coating composition containing a resin obtained by the reaction or a reaction product of an epoxy group-containing compound and a carboxyl group-containing butadiene acrylonitrile copolymer and a resin obtained by mixing a completely blocked isocyanate group-containing compound. Application related to (Japanese Unexamined Patent Publication No. 54-9763
No. 2), and a butadiene-acrylonitrile copolymer having a number average molecular weight of about 500 to about 5,000, containing about 8 to about 40% by weight of an acrylonyl-IJ component, and having a reactive terminal group, about 5 to 50% by weight. % and about 95 to about 50% by weight of resin components other than the copolymer.Resin obtained by reaction or mixing (however, the dicarboxyl group-containing butadiene acrylonitrile copolymer is added to 1 equivalent of the epoxy group of the epoxy group-containing compound) The free carboxyl tea scoop is 0.2~0.7
The carboxyl group-containing butane is reacted with a partially blocked isocyanato group-containing compound and an amino group-containing compound simultaneously or separately to react the cationic resin and the epoxy group-containing compound in an equivalent ratio. Contains a reaction product obtained by reacting a gen-acrylonitrile copolymer at a ratio of 0.2 to 0.7 equivalents of free carboxyl groups with an amino group-containing compound and a completely blocked isocyanate group-containing compound. An application was filed (Japanese Patent Application Laid-Open No. 137174/1983) regarding an electrodeposition coating composition containing cationic resins (excluding cationic resins).

Based on the above invention, the present inventor conducted research on the use of butadiene acrylonitrile copolymers having various reactive groups in electrodeposition coatings, and found that butadiene acrylonitrile copolymers having a hydroxyl group at the terminal were partially produced. By combining a resin component obtained by reacting a blocked incyanate with a polyhydroxyl group-containing resin component, the above-mentioned conventional problems can be improved, and an electrodeposition coating composition having more favorable properties than the conventional one can be obtained. They investigated this and completed the present invention.

That is, the gist of the present invention is to contain 5 to 120 parts by weight of a reaction product with 1 mol of a terminal hydroxyl group-containing butadiene acrylonitrile copolymer and 1 to 3 mols of a partially blocked diisocyanate, per 100 parts by weight of a polyhydroxyl group-containing resin. An electrodeposition coating composition is provided.

The terminal hydroxyl group-containing butadiene-acrylonitrile copolymer used in the present invention refers to a copolymer having a butadiene component and an acrylonitrile component as main chains or side chains, and a hydroxyl group at the molecular end. Preferred copolymers contain about 60-92% by weight of the butadiene component and about 8-40% by weight of the acrylonitrile component. It is particularly preferred that about 1.5 to 2.5 terminal hydroxyl groups exist in one molecule. The number average molecular weight of the copolymer is about 500 to 5000, preferably about 2
000-3500. If the number average molecular weight is less than 500, corrosion resistance, flexibility, and impact resistance will not be sufficient;
If it is more than 00, the water dilutability of the resin is poor, and the smoothness of the resulting electrodeposited surface is sharply reduced.

Hiker HTBN (B,
F, commercially available from Gudrich Co., Ltd.), and the like.

The hydroxyl groups of the copolymer may be partially modified. It may also be partially copolymerized with other polymerizable monomers, such as methacrylonitrile, acrylic esters, methacrylic esters, styrene, chloroprene, isoprene, etc. It is included within the technical scope of the present invention.

The partially blocked isocyanate used in the present invention is obtained by reacting an organic polyisocyanate, preferably an organic diisocyanate, with a blocking agent, and includes, for example, those described in Japanese Patent Publication No. 52-6306.

The organic polyisocyanate is not particularly limited, and all polyisocyanates conventionally used as vehicle components for electrodeposition paints can be used. For example, aliphatic diisocyanates, cycloaliphatic diisocyanates, aromatic diisocyanates, aliphatic-aromatic diisocyanates,
Examples include nuclear-substituted aromatic diisocyanates (eg, dianisidine diisocyanate), but also prepolymers derived from polyether diols, polyester diols, and other simple diols (eg, alkylene glycols, etc.).

Examples of the reflocking agent for partially blocking the organic polyisocyanate include amino alcohols (alkanol tertiary amines are particularly preferred), aliphatic alcohols (aliphatic alcohols having 1 to 8 carbon atoms are particularly preferred), and aromatic alkyl alcohols. (e.g. phenyl carbinol, etc.), ether bond-containing alcohols (3 to 1 carbon atoms)
cellosolves are particularly preferred), phenols, and oximes (such as methyl ethyl ketoxime). Systems using incyanate partially blocked with alkanol tertiary amines have significantly improved dispersibility and stability, and incyanates partially blocked with oximes and phenols are unblocked at relatively low temperatures. preferable.

Furthermore, even a blocking agent having a high molecular weight and being relatively nonvolatile may be used in a small amount.

The above partially blocked incyanate is added at a ratio of 1 to 3 moles per mole of the terminal hydroxyl group-containing butadiene acrylonitrile copolymer under conventional reaction conditions (for example, 100%
The reaction is carried out at a temperature below .degree. C., optionally using a catalyst such as dibutyltin laurate. If the reaction ratio of the partially blocked incyanate is less than 1 mole per mole of the base material, the coating film will not be sufficiently cured by baking and good coating performance will not be obtained. Moreover, if the amount exceeds 3 moles, it becomes difficult to control the reaction such as gelation due to reaction with the copolymer.

Examples of the polyhydroxyl group-containing resin used in the present invention include anionic and cationic electrodeposition coating resins having an average of two or more hydroxyl groups in one molecule. Examples of cationic type ψ compounds include epoxy-modified amino resins (JP-A-52-18746, JP-A-53-86735, JP-A-53-47143, JP-A-53-8568, etc.), amino-modified maleingiene compounds. Resin-based (Unexamined Japanese Patent Publication No. 5
3-97034), amino-modified polyurethane polyol resin systems (JP-A-54-154497, JP-A-54-55)
-115476 publications, etc.), as well as amine group-containing resins,
Examples include resins containing sulfonium groups and phosphonium groups, and examples of anionic types include RJIOI (styrene-allyl alcohol copolymer resin commercially available from Monsanto Co.) and EPON#1001 (bisphenol A type epoxy resin commercially available from Shell Chemical Co.) Examples include resins obtained by esterifying with adipic acid or the like or with an oil fatty acid, and then maleating or halfestering with phthalic anhydride or the like to anionize.

However, particularly suitable polyhydroxyl group-containing resins for use in the present invention are those based on epoxy-modified amino resins, which will be described in further detail.

The epoxy group-containing compound may be either a monomer or a polymer. In particular, epoxy compounds produced from polyglycidyl ethers of polyphenols such as bisphenol A, novolak resins, similar phenolic resins, and others are industrially available and suitable. Typically a compound containing a 1,2-epoxy group (especially an epoxy equivalent of about 3
00 to 1000 is preferred). These epoxy group-containing compounds may themselves have a hydroxyl group, and may also contain alcohols such as polypropylene glycol, polyethylene glycol, caprolactam,
It may be partially etherified with diols or the like.

Further, it may be partially esterified with carboxylic acid, dimer acid, adipic acid, sebacic acid, etc.

The above-mentioned epoxy group-containing compound is reacted with an amino group-containing compound such as a primary amine, a secondary amine, a tertiary amine, a polyamine, an alkanolamine, etc. to form a cationic resin.

Suitable amino group-containing compounds include ethylenediamine,
Examples include diethylenetriamine, dimethylcyclohexylamine, dimethylethanolamine, methyljetanolamine, dimethylamino-2-propanolamine, diethylaminoethoxyethanol, di-n-propanolamine, and particularly preferred are ethylenediamine and methylethanolamine. Note that the tertiary amine having no active hydrogen is used by converting it into an acid amine salt with an appropriate acid such as boric acid, phosphoric acid, sulfuric acid, acetic acid, lactic acid, etc.

The blending ratio of the resin obtained by reacting the above terminal hydroxyl group-containing butadiene acrylonitrile copolymer with the partially blocked isocyanate and the above polyhydroxyl group-containing resin is 5 to 120 parts by weight of the former to 100 parts by weight of the latter. If the amount of the former is less than 5 parts by weight, it is difficult to obtain a cured coating film with sufficient flexibility, and if it exceeds 120 parts by weight, it is not only difficult to cure the coating film sufficiently under the conventional baking conditions. ,
This is not preferable because it also reduces corrosion resistance.

Depending on the purpose, the resin component used in the present invention may be further modified with other resin components or paint raw materials, such as amino resins, phenol resins, completely blocked isocyanates, polyamides, polyethers, polyesters, etc., or It may be used by appropriately mixing with these components.

To dissolve or disperse the cationic resin used in the present invention in water, it can be dissolved or dispersed in water using an appropriate acid, such as an inorganic acid such as boric acid, phosphoric acid, sulfuric acid, or hydrochloric acid, or an organic acid (preferably an organic acid) such as lactic acid or acetic acid. They can be used together for neutralization.

In order to dissolve or disperse the anionic resin used in the present invention in water, it is neutralized with an appropriate base such as ammonia, diethylamine, triethylamine, ethanolamine, caustic soda, caustic potash, etc. (preferably an organic amine) alone or in combination. do it.

In addition to the above-mentioned components, the composition for electrodeposition coating according to the present invention may appropriately contain conventional additives such as pigments, solvents, antioxidants, and surfactants.

The properties of the coating film obtained by using the composition for electrodeposition coating according to the present invention are different from the appearance of the coating film after baking compared to the properties of the coating film obtained from the composition for electrodeposition coating that has been conventionally used. Not only are they comparable in terms of quality, coating hardening, and corrosion resistance, but they particularly surpass the latter in terms of bending resistance, impact resistance, and moisture resistance.

Although the present invention is primarily intended for electrodeposition paints, it can also be effectively applied to conventional water-based paints, solvent-based paints, and the like.

Hereinafter, the present invention will be explained by examples.

Example 1 Toluene diisocyanate (2,,
130 parts by weight of 2-ethylhexanol (containing 1 drop of dibutyltin laurate) was added to 174 parts by weight of an 80:20 mixture of 4-toluene diisocyanate and 2.6-1-toluene diisocyanate so that the reaction temperature was 100°C or less. was cooled externally and gradually added to Nakara to prepare diurethane of toluene diisocyanate, and then a butadiene acrylonitrile copolymer containing terminal hydroxyl groups (B, F,
Good Rich Commercial Product Hiker-H"rBN 130
0X17; molecular weight 3500, OH equivalent 1700) 18
00 parts by weight and dibutyltin urate o, os were added and allowed to react at 121°C for 90 minutes (substantially complete consumption of incyanato groups was confirmed by infrared spectroscopy). The resulting reaction mixture was diluted with 500 parts by weight of ethylene glycol heptanoethyl ether (component A).

Separately, 1000 parts by weight of EPON 1004 (polyglycidyl ether of bisphenol A, available from Shell Chemical Company; epoxy equivalent: 910) was heated to 70°C while stirring.
277 parts by weight of n-methylpyrrolidone was added and dissolved, and further 80.3 parts by weight of diethylamine (
(substantially the same stoichiometric equivalent to the epoxy groups present)
was added and reacted at 100°C for 2 hours to prepare an amine-epoxy adduct (component B).

A mixture consisting of 271 parts by weight of component A and 1357.3 parts by weight of component B was neutralized with 30 parts by weight of glacial acetic acid and then diluted with 950 parts by weight of deionized water to give a non-volatile composition of approximately 5 parts by weight.
A 0% by weight resin vehicle I was prepared.

A steel plate treated with zinc phosphate was cathodically electrodeposited in an electrodeposition bath prepared according to the following formulation to a coating thickness of 20 μm, and the coated product was baked at 200° C. for 30 minutes.

Resin vehicle I 100 titanium 8 basic lead silicate
2 carbon black
3 Strontium chromate 2 Dibutyltin laurate 1 Deionized water 209 The coating performance of the obtained painted panel was tested and the results are shown in Table-1.

Example 2 The coating film performance of a painted panel obtained in the same manner as in Example 1 except that 118 parts by weight of ethylene glycol monobutyl ether was used instead of 130 parts by weight of 2-ethylhexanol was tested, and the results are shown in Table 1. Shown below.

Example 3 89 parts by weight of dimethylethanolamine was used instead of 130 parts by weight of 2-ethylhexanol, dibutyltin laurate was not used, 30 parts by weight of glacial acetic acid was replaced by 33 parts by weight,
Furthermore, the coating performance of the coated panel obtained in the same manner as in Example 1 except that 950 parts by weight of deionized water was changed to 947 parts by weight was tested, and the results are shown in Table 1.

Example 4 174 parts by weight of toluene diisocyanate was mixed with 250 parts by weight of MDI (diphenolmethane-4,4'-diisocyanate).
The coating film performance of the obtained painted panel was tested in the same manner as in Example 1 except that the parts by weight were changed, and the results are shown in Table 1.

Example 5 C4f) --HTBN 1300X1'7 1800
Hiker instead of weight part - HTBN 1300 X
27 (B, F.

Coating of a painted panel obtained in the same manner as in Example 1 except that 1800 parts by weight of butadiene acrylonide IJ copolymer containing terminal hydroxyl group (molecular weight 3500, OH equivalent 1700), commercially available from Guts Rich Company, was used. The membrane performance was tested and the results are shown in Table-1.

Example 6 EPON 1004 910 parts by weight, tall oil fatty acid 3
After reacting a mixture consisting of 50 parts by weight and 100 parts by weight at 150°C for 1 hour, 15 parts by weight of phthalic anhydride was added.
0 parts by weight was added and the reaction was further carried out at 150°C for 1 hour.

After adding 250 parts by weight of component A prepared as described in Example 1 to the resulting reaction mixture, 80 parts by weight of triethylamine and 1026 parts by weight of deionized water were further mixed to prepare resin vehicle (2).

A zinc phosphate-treated plate was anodically electrodeposited in an electrodeposition bath prepared according to the following formulation to a coating thickness of 20 μm, and the coated product was baked at 200° C. for 30 minutes.

Resin vehicle ■ 100 titanium
8 basic lead silicate
2 carbon black
Strontium trichromate
2 Deionized water 21
0 The coating film performance of the obtained painted panel was tested and the results are shown below.
Shown in 1.

Comparative Example 1 Hiker-HTBN 1300x17 The coating film performance of the obtained painted panel was tested in the same manner as in Example 1 except that 45 parts by weight of trimethylolpropane was used instead of 1800 parts by weight, and the results are shown in Table-1. show.

Comparative Example 2 Hiker of component A of Example 6 - HTBN 1300x1
7 Trimethylolpropane 4 instead of 1800 parts by weight
The coating performance of a painted panel obtained in the same manner as in Example 6 was tested using the coating material obtained using 5 parts by weight, and the results are shown in Table 1.

Claims (1)

[Claims] 1. (A) 100 parts by weight of polyhydroxyl group-containing resin and (
B) A composition for electrodeposition coating, comprising 5 to 120 parts by weight of a reaction product of 1 mol of a terminal hydroxyl group-containing butadiene acrylonitrile copolymer and 1 to 3 mol of a partially blocked diisocyanate. 2. The composition according to item 1, wherein the polyhydroxyl group-containing resin has an amine group. 3. The composition according to item 2, wherein the polyhydroxyl group-containing resin having 7 amino groups is a bisphenol A type epoxy resin. 4. The terminal hydroxyl group-containing butadiene acrylonitrile copolymer contains 8 to 40% by weight of an acrylonitrile component and has an average of 1.5 to 2.5 terminal hydroxyl groups in one molecule. Compositions as described in Section. 5. The composition according to item 1, wherein the butadiene acrylonitrile copolymer containing a terminal hydroxyl group has a number average molecular weight of about 500 to 5,000. 6. The partially blocked incyanate is partially blocked with one or more monoalcoholic compounds selected from the group consisting of amino alcohols, aliphatic alcohols, aromatic alkyl alcohols, ether bond-containing alcohols, phenols, and oximes. The first thing that has become
Compositions as described in Section. 7. The composition according to item 6, wherein the monoalcoholic compound is an alkanol tertiary amine.