JPS59122564A - Coating composition for cathode electrodeposition - Google Patents

Abstract

PURPOSE:The titled composition that contains a resin having a specific number of basic groups and nonconjugated carbon-carbon unsaturated bonds and a specific blocked polyisocyanate, thus giving coating films which show high thrawing power and stability in a satisfactory film thickness and contributing to pollution reduction. CONSTITUTION:The objective composition is obtained by combining (A) a resin more than 0.5 of basic groups and nonconjugated carbon-carbon unsaturated bonds, respectively, per 100g of the resin such as polycondensation polymer, polymerization polymer or polyaddition polymer with (B) a polyisocyanate blocked with more than 10mol% (based on the total blocking agent) of a basic group-free polymeric monohydroxy compound such as monohydroxyalkyl acrylate and/or monohydroxyalkyl methacrylate at a solid weight ratio of (95-50): (50-5). EFFECT:The resultant composition can lower the baking temperature in practice.

Description

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

In recent years, many types of resins have been developed as coating compositions for cathode electrodeposition. For example, JP-A-51-51-1O3,
JP-A-52-18746 and JP-A-51-36
No. 280 discloses a cathode electrodeposition coating composition containing an epoxy resin as a main resin and a blocked isocyanate as a curing agent. By using these coating compositions, it has become possible to cure the coating film at a practical coating film curing temperature, and a coating film having extremely high corrosion resistance and solvent resistance has been obtained. However, even in these coating compositions, improvements in flexibility, adhesion, and moisture resistance are still required.

Special Publication No. 54-44686 and Special Publication No. 55-35
No. 432 discloses a polycondensation resin, a polymer resin, or a polyaddition resin that optionally has self-crosslinking, a basic group and α,
A coating composition for cathode electrodeposition is described in which, by using a basic urethane compound having a β-double bond, the coating composition is expected to be cured mainly by thermal polymerization of the double bond during coating film baking.

On the other hand, the inventors of the present application previously filed a patent application for a coating composition for cathode electrodeposition, which contains a copolymer of a diene compound such as butadiene/acrylonitrile and an epoxy resin as main components, and uses a blocked isocyanate as a curing agent.
Japanese Patent Publication No. 56-41760 and Japanese Patent Publication No. 55-13
Publication No. 7174). Although this coating composition is particularly excellent in corrosion resistance, flexibility, and adhesion, it still has drawbacks such as hardening of the coating film at low temperature baking and a large amount of scattered matter in the furnace during coating baking. There were some points that were unsatisfactory in practical terms.

The present invention consists of (A) a resin having at least 0.5 basic groups and non-conjugated carbon-carbon unsaturated bonds per 1000 g of resin, and (B) a block blocked with a polymerizable monohydroxy compound containing no basic groups. A coating composition for cathode electrodeposition comprising a polyisocyanate is provided.

The above composition provides high adhesion, sufficient coating thickness, and good coating stability, and is also capable of significantly lowering the practical coating baking temperature compared to when conventional blocked isocyanate components are used. At the same time, it was found that the amount of flying blocks from the blocking agent in the baking furnace was reduced, which greatly contributed to resource conservation and a reduction in pollution caused by baking furnace exhaust gas. 1. The electrodeposited coating obtained from the composition has excellent corrosion resistance, flexibility, and adhesion similar to conventional cathodic electrodeposition coatings.

In the present invention, resins having a basic group and non-conjugated carbon-carbon unsaturated bonds include polycondensation resins, synthetic resins, polymer resins, polyaddition resins, and modified resins thereof, such as epoxy resins, epoxidized butadiene polymers, Glycidyl methacrylate polymers, alkyd resins, etc., for example, butadiene homo or copolymers having active hydrogen such as -COOH1-OH1-NHR at the molecular end, unsaturated fatty acids having 12 or more carbon atoms, α, β-unsaturated carboxylic acids, Examples include resins modified with hydroxy (meth)acrylic acid, glycidyl (meth)acrylic acid, and the like.

The main resin in one of these trees is itself a resin component 1.
000P, has at least 0.5, preferably 2 to 3, non-conjugated carbon-carbon double bonds, and has a resin component of 100
01i', #M resin which may have at least 0.5, preferably 1 to 2 basic groups or does not have these groups and a resin having the above groups in the above ratio. They may be blended in a certain amount ratio. In any case, resins without the above groups cannot be used alone.

If the nonconjugated carbon-carbon double bond is less than 0.5, the curing performance of the bake-cured coating film will be poor. Moreover, if it exceeds 30, it may adversely affect the stability of the paint bath over time.

If the number of basic groups is less than 0.5, the resulting cathode electrodeposition coating composition may have poor water solubility and may not be put to practical use. Moreover, if there are more than 3, the liquid electrical conductivity of the cathode electrodeposition coating composition becomes too high, and the water during electrodeposition coating becomes difficult to use. a+ 1
．． <The decomposition reaction is significantly accelerated, and a large amount of hydrogen gas generated may cause deterioration of the surface condition of the electrodeposition coating.

Among the above resins used in the present invention, particularly preferred resins are modified epoxy resins. Epoxy tree 11L!
ru epichlorohydrin and hisphenol A,
Examples include polycondensation resins of epichlorohydrin and hisphenol F that are resistant to l-condensation fats. Examples of these include Ebicotorna 828, -1!1001゜≠1004 (hereinafter manufactured by Shell Chemical Co., Ltd.) and Ebikuron 83o (made by Shell Chemical Co., Ltd.). Inu Nippon Ink Chemical Co., Ltd.) is exemplified.

-coon among the compounds having a non-conjugated carbon-carbon double bond that modify the above-mentioned epoxy resin.

-0H1-NHR and other butadiene-based homo or copolymers having active hydrogen include PBC-1000, PBcL2000, and PB commercially available from Nippon Soda Co., Ltd.
G-1000-PBG-2000, PBa-aooo-
Hiker〇TB-2000, Hi-h-CTBN-13
00. Hiker ATBN-1800, Hiker HTBN
An example is -130o.

Examples of unsaturated fatty acids having 12 or more carbon atoms include drying oils of natural oils, unsaturated fatty acids synthesized from semi-drying oils, tall oil,
Examples include dimer acid and the like.

Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, sorbic acid, and fumaric acid.

Polyisocyanate blocked with a polymerizable monohydroxy compound that does not contain basic groups reduces the baking temperature of the coating film, which is one of the important objectives of the present invention, and suppresses baking furnace exhaust gas pollution caused by scattering of the blocking agent. It is the most important ingredient in

Examples of polyisocyanates include aromatic polyisocyanates, such as toluene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, and dibenzyl isocyanate; aliphatic polyisocyanates, such as tetramethylene diisocyanate; Examples include hexamethylene diisocyanate, dicyclohexyl diisocyanate, and inphorone diisocyanate. Furthermore, polyols with molecules less than Btooo are added to these diisocyanates by NC.
A urethane prepolymer having an incyanato group at the molecular end by reacting at a 010H equivalent ratio of 1.1 or more may be used. Moreover, polyincyanates may be used alone or in combination of two or more types.

Examples of polymerizable monohydroxy compounds used as flocking agents include hydroxy-alkyl esters of acrylic acid or methacrylic acid, tri- or (d-tetrapropylene glycol mono(meth)acrylate, 1-trimethylolpropane-cy(meth)acrylate, Pentaerythritol-tri(meth)acrylate.

There are saturated or unsaturated monoalcohols having at least 6 carbon atoms, cellosolves and calpitols which can be used in combination with the polymerizable monohydroxy compound described in tI+iJ.

Examples of these include hexanol, nonanol, decanol, lauryl alcohol, stearyl alcohol,
- Saturated monoalcohols such as ethylhexanol, unsaturated monoalcohols such as oleyl alcohol, elycyl alcohol, lylunyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, methyl calpitol, ethyl carpitol and carpitols such as butylcarpitol.

When a polymerizable monohydroxyl compound is used in part or all of the blocking agent for blocked isocyanate that does not contain a basic group, at least 1 of the total number of moles of all blocking agent components is used.
It is also important to block at least 0%, preferably at least 30%, with a polymerizable monohydroxyl compound. When the polymerizable monohydroxyl compound is 10% or less, this is one of the important properties of the present invention. The advantages of resource saving due to the reduction in practical baking salinity and low pollution due to the reduction of baking furnace exhaust gas are significantly excluded.

Selection of the blending ratio of component A and component B is also an important factor in putting the present invention into practical use. The blending ratio of component A should be selected with particular consideration to the stability of the cathode electrodeposition coating composition. In other words, the content ratio in the ingredients is 50%
Below this, the stability of the cathode electrodeposition coating composition generally decreases. Moreover, when it exceeds 95%, the hardenability of the baked coating film is significantly reduced.

Next, actual examples of the cathode electrodeposition coating composition of the present invention will be shown. In these cathode electrodeposition coating compositions, it is also possible to use urethane cleavage catalysts such as laurate, tin octate, and argyltin oxide, and color pigments and extender pigments such as titanium oxide, carbon black, and pen handles, as necessary. Ru.

Unless otherwise specified, terms such as medium, part, or % are expressed as weight.

Example 1 Prescription Parts by weight Epon 100
2 416...Squid〇TBN
1800-13” 104 Methylethanolamine 37.6 Butyl Cellosolve
42.3 Wednesday
2799 acetic acid
14(1) Polycarbogysibutadiene acrylonitrile copolymer (USA B, F, Goodri (
h Chemica 1) In the above formulation, Epon 1002 and No-Ika-CTB
Heat N1800-18 at 180-150°C for about 2 hours, then add 2-hydroxyethyl methacrylate blocked toluene diisocyanate and heat to 110°C f71.
D fever. Furthermore, add methylethanolamine to 120
Keep at °C and add butyl cellosolve to this. Water and acetic acid are added and mixed to obtain a composition for cathode electrodeposition with a solid content of 20%.

Note that 2-hydroxyethyl methacrylate blocked toluene diincyanate is prepared as follows.

Prescription Parts by weight Toluene diincyanate 1742-Hydroxyethyl methacrylate V-) Hydroquinone 0.6n-Butanol 196 Charge toluene diincyanate into a container equipped with a stirrer, cool to 40-80°C, and keep at that temperature. 2 Carefully and gradually add the IIEMA/Hydrogynone mixture. After the entire amount was added, the reaction vessel was heated at 180°C, and then heated at 180°C.
Continue the reaction at 30-140°C. The reaction mixture was sampled over time, the absorption of -NCO was confirmed by IR, and -NCO
When absorption of the mixture ceased, the temperature was lowered to 110°C, and n-butanol was added to make a fest with a solid content of 70%.

Example 2 A composition for cathode electrodeposition with a solid content of 20% was obtained in the same manner as in Example 1, except that the 2-hydroxyethyl methacrylate block toluene diisocyanate (70% solution) was prepared as follows. Ta.

Preparation of 2-hydroxyethyl methacrylate blocked toluene diisocyanate (70% solution): Formulation
Part by weight Toluene diisocyanate
1742HEMA
862-ethylhexanol 200
Hydroquinone 0.6n-
Buta/-ol 196 Example 3 2-Hydroxyethyl methacrylate pro-nctoluene diisocyanate (70% soluble GL) was prepared in the same manner as in Example 1, except that the solid content was 20%.
A composition for cathode electrodeposition was obtained.

Preparation of 2-hydroxyethyl methacrylate propylene diisocyanate (70% solution): Prescription
Weight department. Nate L (2)
3112HEMA
148 Hydroquinone
0.6n-butanol
81(2): Toluene diisocyanate/trimethylolpropane, prepolymer (solid content 75%) (manufactured by Nippon Polyurethane Industries Co., Ltd.).

Example 4 Introduction of basic groups: Prescription Parts by weight (3) Epoxidized liquid polybutadiene 1000 Butyl cellosolve 269 Methylethanolamine 75 (3) Oxirane Oxygen content 6
~9% (BF-1000 manufactured by Nippon Shudatsu Co., Ltd., R-45EPI manufactured by Idemitsu Oil Co., Ltd., E-1 manufactured by Nippon Oil Co., Ltd.
800-65 etc.).

In the above recipe, epochinated 1-night-type phytadiene is charged into a container equipped with a stirrer, heated at 60 to 80°C while introducing N2 gas little by little, and then methyl cellosolve is added and the temperature is further increased to 100 to 110°C. °CK rise i=-. Then add methylethanolamine and add 180 to 14
After reacting at 0°C for 5 hours, it is cooled.

Prescription Weight part Epon +-10
01900 Butylcerone Lube 245 Acrylic Acid 144N,N'-Dimethylethanolamine 5 High F Quinone
11-butyl cellosolve
Pour 306 Epon + 1001 into a container with a stirrer 9
After raising the temperature to 0 to 100°C, butyl cellosolve is added and dissolved uniformly, a mixed solution of hydroquinone and acrylic acid is added, and the mixture is stirred at 90 to 100°C until the mixture becomes uniform. Thereafter, dimethylethanolamine was added at 100°C, and the reaction was carried out at 110-120°C for 2-3 hours. When the acid value reached 4-6, the reaction vessel was cooled and the desired reaction product (
n) is obtained.

Preparation of composition for cathodic electrodeposition coating: The components (■) and (II) and blocked isocyanate are mixed in the following formulation and then water-solubilized to prepare a composition for cathodic electrodeposition coating with a solid content of 20%.

Prescription Weight parts Ingredients [I]
β7,5 block toluene diincyanate acetic acid 1,8 pure water
485.7(4) Same as block incyanate of Example 1.

Comparative Example 1 In place of the 2-hydroxyethylmethane 1-V-toblock toluene diisocyanate of Example 1, 2-ethylhexanol methacrylate/lectluene diisocyanate obtained from the following formulation was used. Proceed to Example 1 except that the same amount is used.

Formula Parts by weight Toluene diincyanate 1742-ethylhexanol 286n-butanol
197 Comparative Example 2 The same amount of 2-ethylhexanol-blocked toluene diisocyanate shown in Comparative Example 1 was used instead of the 2-hydroxyethyl methacrylate-blocked toluene diisocyanate in the cathodic electrodeposition coating composition formulation of Example 4. Same as Example 4.

To the cathode electrodeposition coating compositions obtained in Examples 1 to 4 and Comparative Examples 1 and 2 above! , zinc phosphate treated steel sheet (0,8
X 70 This was washed with pure water and baked at 165°C for 20 minutes. (However, the samples used for the baked paint film weight loss test were dried at 105 to 110°C for 3 hours and then baked under the above conditions.) The properties of the baked paint films obtained are shown in Table 1.

Evaluation and test conditions: Appearance: ◎ Very good ○ Good (2) Pencil hardness: The breaking hardness of the coating film is shown when measured at a load of 1 kg in accordance with JIS-5400, items 6 to 14.

(3) 4vt I B K-y Pink: Gauze was impregnated with MIBK (1st grade reagent), and the condition of the coating film was evaluated with the naked eye when the coating was rubbed 20 times with this cloth.

◎ No faeces on the paint film ○ Some gloss fading × Paint film melts and exposes the base (4) Tsuruto Spray: JIS-Z-2871,50
After 0 hours, measure the rust on the cut part of the paint film and 1/2 of the bulge width.

○ l ~ 3 cutting Δ 3 ~ 5 distribution (5) Baked coating film I $, periodic measurement conditions: Wash the electrocoated steel plate with water, and measure the weight A after baking at △ 105 ~ 110 ° C for 3 hours. Then, the weight B after baking at 165°C for 20 hours is measured. It is expressed by the following formula.

A-B Baked paint film reduction--X 100 Patent applicant: Nippon Paint Co., Ltd.

Claims (1)

[Scope of Claims] 1. (A) a resin having at least 0.5 basic groups and nonconjugated carbon-carbon unsaturated bonds per 1000 f of resin; and (B) a resin at least partially containing basic groups; A coating composition for cathode electrodeposition, which contains a blocked polyisocyanate blocked with a polymerizable monohydroxy compound. 2. The composition according to item 1, wherein the resin is a polycondensation resin, a polymer resin, or a polyaddition resin. 3. The composition of item 1, wherein the polymerizable monohydroxy compound is at least 10 mol% of the total blocking agent. 4. Solid weight ratio of resin to block isocyanate is 9.
5-50:5-5o composition according to paragraph 1. 5. The composition according to item 1, wherein the nonconjugated carbon-carbon unsaturated bond is introduced into the resin by a diene compound and/or an α,β unsaturated carboxylic acid. 6. The composition according to item m1, wherein the polymerizable monohydroxy compound is monohydroxyalkyl acrylate and/or monohydroxyalkyl methacrylate.