JPH0621239B2 - Resin composition for cationic electrocoating - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin composition for cationic electrodeposition coating.

[Conventional technology]

In recent years, the one-coat finishing electrodeposition coating that has been adopted in the industrial field of electric appliances, office equipment, etc., uses a coating material that uses an acrylic or polyester resin composition as a binder. The coating film needs to have both aesthetics and performance. However, the coating film coated with the conventional anionic resin composition as a binder is aside from its aesthetic appearance, the electrochemical reaction during electrodeposition coating causes the elution of the anode metal substrate and the surface of the anode metal substrate. It is said that the elution of the chemical conversion treatment film applied to and the elution of ions into the coating film are essentially unavoidable, and as a result of the deposited film being contaminated, the physical properties of the coating film such as corrosion resistance and alkali resistance are not always sufficient. It had drawbacks.

Therefore, the present inventors have set out to develop a resin composition for cationic electrodeposition coatings in order to solve these problems, and as a result, as described in JP-A-55-21459, amine imides have been developed. A cation type resin composed of a copolymer obtained by copolymerizing an ethylenically unsaturated monomer having a group and an ethylenically unsaturated monomer having a hydroxyl group was obtained.

[Problems to be solved by the invention]

From the above cationic resin, excellent corrosion resistance, an electrodeposition coating film exhibiting alkali resistance can be obtained, but due to the improvement of the required quality for coating film physical properties in the subsequent industrial field,
In some cases, the cationic resin may not be sufficiently satisfactory in corrosion resistance and alkali resistance.

[Means for solving problems]

Therefore, as a result of further intensive research, the present inventors have found that
It was found that the cationic resin can be greatly improved in coating film physical properties such as corrosion resistance and alkali resistance by adding an amino-modified polyepoxide to which a partially blocked polyisocyanate is added, and the present invention is completed. It has come.

That is, the present invention is a copolymer 50 obtained by copolymerizing an ethylenically unsaturated monomer having an amine imide group, an ethylenically unsaturated monomer having a hydroxyl group and another ethylenically unsaturated monomer. The present invention relates to a resin composition for a cationic electrodeposition coating composition, which comprises ˜95% by weight and 5 to 50% by weight of an amino-modified polyepoxide having a number average molecular weight of 500 to 3000 and a partially blocked polyisocyanate added thereto.

The ethylenically unsaturated monomer having an amine imide group used in the present invention has the following general formula: (In the formula, n is 1 or 2, R ₁ is a residue of a monovalent or divalent unsaturated carboxylic acid, and R ₂ , R ₃ and R ₄ are each 1 to 8 carbon atoms.
Of 1,1,1-trimethylamine methacrylimide, 1,1-dimethyl-1-ethylamine methacrylimide, 1,1-dimethyl-1- (2). -Hydroxypropyl) amine methacrylimide, 1,1,1-trimethylamine acrylimide, 1,1-dimethyl-1-
(2-Hydroxyethyl) amine cinnamyl imide, bis 1,1,1-trimethylamine maleimide, bis 1,1,1-trimethylamine fumarimide and the like can be mentioned.

Examples of the ethylenically unsaturated monomer having a hydroxyl group used in the present invention include acrylic acid 2-
Examples thereof include hydroxyethyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate and the like.

Examples of the other ethylenically unsaturated monomer used in the present invention include ethylene, propylene, styrene, α-methylstyrene, vinyltoluene, methyl acrylate, ethyl acrylate, methyl methacrylate, butyl acrylate, acrylic acid. n-octyl, acrylic acid 2
-Ethylhexyl, vinyl methacrylate, vinyl chloride,
Vinyl acetate, vinyl propionate, vinylidene chloride, isoprene, butadiene, pentadiene, chloroprene,
Methylvinyltoluene, vinylpyrrolidone, acrylonitrile, acrylamide, butyl crotonate, diethyl maleate, diethyl fumarate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate , Dimethylaminopropyl methacrylate, diethylaminopropyl acrylate, diethylaminopropyl methacrylate and the like.

The copolymer of the present invention is produced by mixing an ethylenically unsaturated monomer having an amine imide group, an ethylenically unsaturated monomer having a hydroxyl group, and a mixture of other ethylenically unsaturated monomers (hereinafter, referred to as a unit amount It is convenient to carry out radical polymerization of the mixture (referred to as body mixture) in an organic solvent using a radical-forming polymerization initiator. As the organic solvent at that time,
The copolymer obtained is insoluble in water and can be mixed with water because of the necessity of dispersion, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, tert-butyl alcohol, acetone, methyl ethyl ketone, diethyl ketone, dioxane, tetrahydrofuran, ethyl. Cellosolve, butyl cellosolve and the like are preferable.

Further, as the radical-forming polymerization initiator, organic peroxides such as benzoyl peroxide, tert-butyl pen benzoate, ditertiary butyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide;
Alternatively, azonitrile compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobisisopropionitrile can be used. However, since amine imides are easily oxidized, it is preferable to use the azonitrile compound.

The radical-generating polymerization initiator is preferably added in an amount of 0.05 to 10% by weight with respect to the monomer mixture.

The ethylenically unsaturated monomer having an amine imide group is used in an amount of 2 to 40% by weight in the monomer mixture. If it is less than 2% by weight, the water solubility will be poor and at the time of curing. If a sufficient crosslink density cannot be obtained and the amount exceeds 40% by weight, the polymerization rate becomes low, which is unsuitable, and it is also expensive, which is economically undesirable.

The ethylenically unsaturated monomer having a hydroxyl group is used in an amount of 5 to 40% by weight in the monomer mixture, and when it is less than 5% by weight, a coating film having a low crosslink density is excellent. Is not obtained, and when it exceeds 40% by weight, the moisture resistance of the coating film tends to be poor.

Other ethylenically unsaturated monomers, in the monomer mixture,
It is the balance of the total amount of the ethylenically unsaturated monomer having an amine imide group and the ethylenically unsaturated monomer having a hydroxyl group.

The partially modified polyisocyanate-added amino-modified polyepoxide used in the present invention includes a secondary amine added to the epoxy group of the polyepoxide to partially block the hydroxyl group of the amino-modified polyepoxide having no residual epoxy group. The above polyisocyanate is added.

The polyepoxide is a compound having one or more 1,2 epoxy groups, for example, polyglycidyl ether of polyphenol (obtained by etherifying polyphenol with epichlorohydrin or dichlorohydrin in the presence of alkali). And so on.

Here, as the polyphenol, for example, 2,2-bis (4-hydroxyphenyl) propane (hereinafter referred to as bisphenol A), 1,1-bis (4-hydroxyphenyl) ethane, 2-methyl-1 1,1-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxy-3)
Examples thereof include -t-butylphenyl) propane, bis (2-hydroxynaphthyl) methane, and 1,5-dihydroxynaphthalene.

Further, oxyalkylated adducts of polyphenols (for example, ethylene oxide adducts of polyphenols, propylene oxide adducts, etc.), novolac type phenol resins, and polyphenol resins similar to these are used.

Next, other polyepoxides include, for example, epoxidized polyalkadiene resins, polyglycidyl ethers of hydroxyl group-containing resins, and polyglycidyl esters of carboxyl group-containing resins.

The polyepoxide is further reacted to cause chain extension,
It may be epoxidized after increasing its molecular weight. As the chain extender in that case, an active hydrogen-containing compound having reactivity with an epoxy group, for example, a compound containing a hydroxyl group, an amino group, an imino group, a thiol group, a carboxyl group (for example, glycol, diamine, polyether polyol, Dimer acid, hydantoin, bisphenol A, polyaminoamide, amino acid, etc.) and the like.

The secondary amine to which the epoxy group of these polyepoxides is added may be one having at least one imino group in one molecule, and examples of such a compound include diethylamine, diisopropylamine, diethanolamine, methylethanolamine. , Diisopropanolamine and the like, and secondary amines in which all amino groups are blocked with ketimine (hereinafter referred to as ketimine-blocked amino group-containing polyamine) and the like.

Here, as the ketimine-blocked amino group-containing polyamine, a polyamine (for example, diethylenetriamine,
The amino group in dipropylenetriamine, dibutylenetriamine, triethylenetetramine, etc.) is converted into ketimine by reaction with a ketone (eg, acetone, methylethylketone, methylisobutylketone, etc.). After the ketimine-blocked amino group-containing polyamine reacts with the epoxy group, the ketimine group is decomposed and the amino group is regenerated by the addition of water.

The addition of the secondary amine to the polyepoxide is carried out by a usual method, and its basic steps are as follows.

Charge some or all of the polyepoxide in the reaction vessel,
Mix under an inert gas stream to form a uniform liquid. If necessary in this step, heating, addition of a suitable organic solvent, preliminary reaction between polyepoxide and other components (for example, bisphenol A, etc.) can be carried out. Then, the addition of the secondary amine is carried out by a method such as total charging, divided charging, and dropping charging while stirring the above-mentioned homogeneous liquid substance under an inert gas stream at an appropriate temperature. The type and amount of the secondary amine can be changed depending on the time. At this stage, heating, cooling, reflux of volatile components, addition of a part of polyepoxide, an organic solvent and the like can be performed. After the addition of the secondary amine is completed, if necessary, the reaction is continued at an appropriate temperature and time, and if necessary, other components are added and reacted, and steps such as dilution with an organic solvent, distillation and excess are performed. be able to.

Here, the reaction temperature and reaction time required for the addition reaction of the secondary amine are 80 to 120 ° C. and 1 to 3 hours.

The organic solvent used in this case is preferably a solvent having no active hydrogen, such as toluene, xylene, methyl isobutyketone, diisopropyl ketone, mineral spirits, ethylene glycol monoethyl ether acetate, diethylene glycol dimethyl ether, butyl acetate, etc. Can be given.

The partially blocked polyisocyanate added to the hydroxyl group of the amino-modified polyepoxide is preferably one derived from diisocyanate.

Examples of such diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexathylene diisocyanate, 1,2-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 4,4′-
Diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,4
-Xylylene diisocyanate, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, 4,
Examples include 4'-diphenyl ether diisocyanate.

Other polyisocyanates include, for example, polyfunctional isocyanates (such as triisocyanates such as 1,3,5-triisocyanate benzene and 2,4,6-triisocyanate toluene), polymerizable polyisocyanates (such as the above diisocyanates). A dimer of
And a prepolymer derived from a polyisocyanate such as polyether polyols, polyester polyols, and other simple polyols such as alkylene glycols.

Examples of the blocking agent that partially blocks the above polyisocyanate include n-butanol,
Aliphatic alcohols such as 2-ethylhexanol, aromatic alkyl alcohols such as phenylcarbinol and methylphenylcarbinol, ether bond-containing alcohols such as ethyl cellosolve and butyl cellosolve,
Examples thereof include phenols such as phenol and cresol, oximes such as acetone oxime and methyl ethyl ketoxime, and lactams such as ε-caprolactam and γ-caprolactam.

The reaction between the blocking agent and the polyisocyanate is performed at 20 to 70 ° C. for 0.5 to 6 hours.

The reaction between the partially blocked polyisocyanate and the amino-modified polyepoxide is performed at 50 to 80 ° C. for 1 to 3 hours.

The number of isocyanate groups in the partially blocked polyisocyanate in the amino-modified polyepoxide added with the partially blocked polyisocyanate is, when the electrodeposition coating film is baked, the hydroxyl groups in the resin composition are unblocked, It is sufficient that the number is sufficient for reaction curing with an amino group and the like, and a range from the same number as the number of free active hydrogen contained in the resin composition to 1/10 is appropriate. The number can be freely determined according to the mixing ratio of the copolymer with the amino-modified polyepoxide to which the polyisocyanate blocked physically is added.

The partially modified polyisocyanate-added amino-modified polyepoxide thus obtained is
Those having a number average molecular weight in the range of 500 to 3000 are used. When the number average molecular weight is less than 500 and 30
If it exceeds 00, the water dispersion stability of the obtained coating material and the coating film physical properties of the obtained coating film may be deteriorated.

The resin composition of the present invention may be prepared by simply mixing the copolymer and the amino-modified polyepoxide to which the partially blocked polyisocyanate is added, but in order to obtain the electrophoretic property and the uniformity of the coating film, It is preferable to heat and mix at 60 to 100 ° C.

Further, the mixing ratio of the copolymer and the amino-modified polyepoxide to which the partially blocked polyisocyanate is added is 50 to 95% by weight of the solid content of the copolymer, and the partially blocked polyisocyanate is added. The amount of the amino-modified polyepoxide used is 5 to 50% by weight. When the amount of amino-modified polyepoxide added with partially blocked polyisocyanate is less than 5% by weight, the coating film obtained is not sufficiently improved in performance such as corrosion resistance and alkali resistance. The resulting coating has a reduced gloss, and the appearance as a one coat is impaired, and the weather resistance is reduced.

The resin composition of the present invention thus obtained is neutralized with an inorganic acid or an organic acid, and water is added while being sufficiently mixed to obtain an electrodepositable aqueous dispersion.

The inorganic acid or organic acid at that time is, for example, hydrochloric acid,
Examples include phosphoric acid, formic acid, acetic acid, propionic acid, and lactic acid.

A coating material using the resin composition of the present invention basically comprises a copolymer, an amino-modified polyepoxide to which a partially blocked polyisocyanate is added, and an acid which is a neutralizing agent. Plasticizers, which are components used in cationic electrodeposition paints, surfactants, pigments, organic solvents, water, etc. are added as appropriate, and are usually used in the production of paints such as dissolvers, homomixers,
Mix and disperse evenly with a mixer or disperser such as a sand grind mill, attritor, or roll mill.
It is a cationic electrodeposition coating composition which is an aqueous dispersion having a solid content of the resin component of approximately 10 to 25% by weight.

In the obtained cationic electrodeposition coating bath, electrodeposition coating is performed in the same manner as in ordinary cationic electrodeposition coating, using the electroconductive object as a cathode, followed by washing with water and baking at 130 to 170 ° C. for 20 to 40 minutes. Thus, a cured coating film is obtained.

〔The invention's effect〕

The cured coating film obtained from the resin composition of the present invention has corrosion resistance,
It has excellent coating film physical properties such as alkali resistance and pencil hardness.

Also, during baking of the coating film, amines generated by thermal decomposition of amine imide groups volatilize quickly, so
The slightly generated amount is reduced as compared with the conventional blocked polyisocyanate type alone.

〔Example〕

Next, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples. In the examples, parts are parts by weight and% is% by weight.

Production example 1. (Preparation of Copolymer Solution-1) A reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, a dropping funnel and a nitrogen gas inlet was charged with 126.6 parts of isopropyl alcohol and heated under a nitrogen gas flow,
Stirring was started to 80 ° C. Then, while maintaining the temperature at 80 ° C., the following mixture was added dropwise over about 2 hours.

1,1-Dimethyl-1- (2-hydroxypropyl) 40.2 parts Amine methacrylimide 2-hydroxyethyl methacrylate 45.0〃 Styrene 28.5〃 Butyl acrylate 44.4〃 2-Ethylhexyl acrylate 15. 3 〃 2,2'-azobisisobutyronitrile 5.1 〃 After dropping, the reaction was continued at 80 ° C for 3 hours to obtain a pale yellow transparent copolymer solution-1 having a solid content of 56.8%. .

Manufacturing example 2. (Preparation of Copolymer Solution-2) 104.1 parts of ethyl cellosolve was placed in the same reaction vessel as in Production Example 1, heated under nitrogen gas flow, and stirred to start at 90 ° C. Then, while maintaining the temperature at 90 ° C, the following mixture was added dropwise over about 2 hours.

1,1,1-trimethylamine acrylic 26.7 parts imide 2-hydroxyethyl methacrylate 45.0〃 styrene 35.5〃 butyl acrylate 50.5〃 2-ethylhexyl acrylate 16.5〃 2,2'-azo After adding 4.5 〃 bisisobutyronitrile, continue the reaction at 100 ℃ for 2 hours, then
Add 1.0 parts of 2,2'-azobisisobutyronitrile,
The reaction was continued at 100 ° C for 2 hours to give a light yellow transparent solid content of 6
A 1.6% copolymer solution-2 was obtained.

Manufacturing example 3. (Preparation of partially modified polyisocyanate-added amino-modified polyepoxide solution-1) A reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser was charged with 2,4-tolylene diisocyanate 652 under a nitrogen gas stream. 0.0 parts, methyl isobutyl ketone 297.0
Then, while maintaining the temperature at 30 ° C. under stirring, 536.0 parts of 2-ethylhexanol was added dropwise over about 5 hours to give 2,
A 2-ethylhexanol half-blocked product of 4-tolylene diisocyanate was obtained.

Separately, after placing 495.0 parts of methyl isobutyl ketone in the same reaction vessel as above, 950.0 of epoxy resin A (Epicote # 1001 manufactured by Yuka Shell Epoxy Co., Ltd.)
Was added, the mixture was heated and dissolved at 100 ° C., and then cooled.

Then, 204.0 parts of diethanolamine was added at 80 ° C., and the temperature was raised to 100 ° C. over 1 hour while paying attention to heat generation.
After keeping the temperature at 100 ° C and reacting for 1 hour,
Cooled.

Then, after adding 356.8 parts of methyl isobutyl ketone, 247.5 parts of the 2-ethyhexanol half-blocked compound of the above 2,4-tolylene diisocyanate was added dropwise at 70 ° C. over 1 hour to 90 ° C. Warm, then 1
The temperature was raised to 100 ° C. for a reaction.

Then, after the temperature was raised to 120 ° C., the pressure inside the reaction vessel was reduced, and the methyl isobutyl ketone was desolvated over about 1 hour.

Then, the inside of the reaction vessel was returned to atmospheric pressure, 135.0 parts of ethyl cellosolve was added at 100 ° C., and after thoroughly stirring, cooled to 80 ° C. to obtain a yellowish brown viscous solid content of 85.0.
%, And an amino-modified polyepoxide solution-1 to which a partially blocked polyisocyanate having a number average molecular weight of 1300 was added was obtained.

Manufacturing example 4. (Preparation of Amino-Modified Polyepoxide Solution-2 with Partially Blocked Polyisocyanate Addition) 517.0 parts of methyl isobutyl ketone were placed in the same reaction vessel as in Production Example 3, and then epoxy resin B was added.
(Yukaka Shell Epoxy Co., Ltd., Epicoat # 1004)
950.0 parts were added, and the mixture was heated and melted at 100 ° C. and then cooled.

Then, at 80 ° C., diethylenetriamine ketiminated with methyl isobutyl ketone (Yukaka Shell Epoxy Co., Ltd.)
Manufactured by Epikiure H-1) (256.0 parts) was added, and the temperature was raised to 100 ° C. in 1 hour while paying attention to heat generation.
The temperature was maintained at 0 ° C., the reaction was further performed for 1 hour, and then the mixture was cooled.

Then, after adding 377.0 parts of methyl isobutyl ketone, 270.3 parts of a 2-ethylhexanol half-blocked product of 2,4-tolylene diisocyanate obtained in Production Example 3 was added dropwise at 70 ° C. over 1 hour. Meanwhile, the temperature was raised to 90 ° C. and further raised to 100 ° C. in 1 hour for reaction.

Then, after the temperature was raised to 120 ° C., the pressure inside the reaction vessel was reduced, and methyl isobutyl ketone was removed over about 1 hour.

Then, the inside of the reaction vessel was returned to atmospheric pressure, 142.0 parts of ethyl cellosolve was added at 100 ° C., and after thoroughly stirring, cooled to 80 ° C. to obtain a yellowish brown viscous solid content of 85.0.
%, And an amino-modified polyepoxide solution-2 to which a partially blocked polyisocyanate having a number average molecular weight of 2400 was added was obtained.

Manufacturing Example 5. (Preparation of Amino-Modified Polyepoxide Solution-3 with Partially Blocked Polyisocyanate Added) 250.0 parts of methyl isobutyl ketone was placed in the same reaction vessel as in Production Example 3, and then epoxy resin C was added.
(Yukaka Shell Epoxy Co., Ltd., Epicoat # 828) 3
800.0 parts were added and mixed while heating at 80 ° C.

Then, 204.0 parts of diethanolamine was added at 80 ° C., and the temperature was raised to 100 ° C. over 1 hour while paying attention to heat generation.
After keeping the temperature at 100 ° C and reacting for 1 hour,
Cooled.

Then add 182.0 parts of methyl isobutyl ketone,
2-Ethylhexanol half-blocked product of 2,4-tolylene diisocyanate obtained in Production Example 3 at 70 ° C
0.8 part was added dropwise over 1 hour to 90 ° C., and the temperature was further increased to 100 ° C. in 1 hour to cause reaction.

Then, after the temperature was raised to 120 ° C., the pressure inside the reaction vessel was reduced, and methyl isobutyl ketone was removed over about 1 hour.

Then, the inside of the reaction vessel was returned to atmospheric pressure, 68.0 parts of ethyl cellosolve was added at 100 ° C., and after sufficiently stirring,
Amino-modified polyepoxide solution obtained by cooling to 80 ° C. and adding a partially blocked polyisocyanate having a yellowish brown viscous solid content of 85.0% and a number average molecular weight of 690-3
Got

Examples 1-9. Comparative Examples 1-2 Based on the formulations shown in Table 1, cationic electrodeposition coating baths of Examples 1-9 and Comparative Examples 1-2 were obtained as follows.

A reaction vessel equipped with a thermometer, a stirrer and a reflux condenser was charged with a copolymer solution and an amino-modified polyepoxide solution to which a partially blocked polyisocyanate had been added (however, in the comparative example, the copolymer solution only). Preparation,
The temperature was maintained at 85 ° C., and the mixture was stirred and mixed for 1 hour to prepare a resin solution (solid content is shown in Table 1).

A 10% acetic acid aqueous solution was added to the obtained resin solution, and the mixture was stirred for 20 minutes, and then deionized water was gradually added with stirring to mix them to obtain a cationic electrodeposition coating bath having a solid content of 10%.

A direct current of 240 V is applied to the obtained cationic electrodeposition coating bath for 2 minutes to perform cathodic electrodeposition coating, and after washing with water, 160
It was heated at 0 ° C. for 30 minutes to obtain an electrodeposition coating film (film thickness is shown in Table 1).

The performance of the resulting electrodeposition coating film is shown in Table 2.

As is clear from Table 2, Examples 1 to 9 are Comparative Example 1
It can be seen that the pencil hardness, the corrosion resistance, and the alkali resistance are superior to those of Nos.

Claims (1)

[Claims] 1. A copolymer 50 to be obtained by copolymerizing an ethylenically unsaturated monomer having an amine imide group, an ethylenically unsaturated monomer having a hydroxyl group and another ethylenically unsaturated monomer. Amino-modified polyepoxide having a number average molecular weight of 500 to 3000 and a polyisocyanate partially blocked with 95% by weight of 5 to 50
A resin composition for a cationic electrocoating, which comprises 10% by weight.