JPH04323273A - Cationic electrodeposition coating composition - Google Patents

Abstract

PURPOSE:To a cationic electrodeposition coating composition capable of providing a coating film having excellent throwing power and having excellent smoothness without making gas pinholes, etc., also to zinc plated steel plate. CONSTITUTION:A cationic electrodeposition coating composition containing 0.05-10 pts.wt. polybasic acid having <=7.0 pKa based on 100 pts.wt. (expressed in terms of solid content) base resin.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to cationic electrodeposition coating compositions. More specifically, the present invention relates to a cationic electrodeposition coating composition that has excellent coverage and provides a coating film with excellent smoothness and no gas pinholes even on galvanized steel plates and the like.

0002

BACKGROUND OF THE INVENTION Conventionally, as a method of improving the adhesion of a paint to a base material, it has been carried out to reduce the solvent content of the paint or to make the base resin polymeric.

Furthermore, JP-A-2-127481 proposes the use of sulfamic acid instead of the above-mentioned monobasic acid for neutralization. However, these paints
For example, when coating galvanized steel sheets for automobiles, a new problem arises in that gas pinholes are likely to occur.

0004

[Problems to be Solved by the Invention] The present invention provides a coating film that has excellent adhesion to the base material and has excellent smoothness without generating gas pinholes even on galvanized steel sheets etc. An object of the present invention is to provide a cationic electrodeposition coating composition.

[0005]

[Means for Solving the Problems] In order to achieve the above-mentioned object, it has been discovered that excellent results can be achieved by neutralizing the base resin of a paint using a polybasic acid, and the present invention has been completed.

That is, the present invention provides base resin (solid content equivalent) 1
0.00 parts by weight, 0.00 parts by weight of a polybasic acid with a pKa of 7.0 or less.
A cationic electrodeposition coating composition containing 05 to 10 parts by weight,
I will provide a.

The base resin used in the cationic electrodeposition paint of the present invention may be any known base resin. For example, amine-modified epoxy resin systems such as Japanese Patent Publication No. 54-4978 and Japanese Patent Publication No. 56-34186, Japanese Patent Publication No. 54-15449,
Amine-modified polyurethane polyol resins such as No. 55-115476, amine-modified polybutadiene resins such as JP-B No. 62-61077 and JP-A No. 63-86766, JP-A-63-139909, and JP-B No. 1-605.
These include amine-modified acrylic resins such as No. 16. Sulfonium group-containing resin systems, phosphonium group-containing resin systems, etc. are also known.

[0008] These resin systems are blended with a crosslinking agent, a melamine resin, a blocked polyisocyanate or an ester/amide exchanger, and/or a dryer such as a manganese compound, if necessary. In some cases, organic solvents (alcohols, ketones, ethers, etc.) are also blended.

[0009] The polybasic acid to be blended into the paint of the present invention has a pKa of 7.0 or less, preferably a pKa2 of 7.0.
Hereinafter, pKa2 is more preferably 6.0 or less. When pKa2 exceeds 7.0, the base resin cannot be sufficiently neutralized and water-solubilized due to low neutralization ability. Further, the organic dibasic acid has a water solubility (that is, solubility in 100 g of water at 25° C.) of 1 g/100 g (25° C. water) or more, preferably 5 or more. Water solubility is 1g/100g (25℃
water), the acid concentration in the dilution water will be non-uniform and uniform neutralization and emulsification will not be possible.

Examples of such organic dibasic acids include tartaric acid, fumaric acid, malonic acid, oxalic acid, etc.
One or more of these may be used.

Examples of other polybasic acids include citric acid.

The amount of the polybasic acid added to the paint is 0.0 parts by weight based on 100 parts by weight of the base resin (solid content).
It is 5 to 10 parts by weight, preferably 0.1 to 5.0 parts by weight. 0
．． If it is less than 0.05 parts by weight, the effect of the present invention cannot be obtained, and
Exceeding the weight part is not preferable as it will result in poor smoothness.

[0013] It is believed that the polybasic acid causes ionic bonds between the base resin molecules to further increase the molecular weight, thereby increasing the coating resistance during precipitation and improving the coverage.

[0014] In addition to the polybasic acids mentioned above, an organic monobasic acid may also be blended into the coating material of the present invention for the purpose of improving water solubility. The organic monobasic acid is not particularly limited, and may be any known organic acid such as acetic acid and lactic acid.

The blending weight ratio of the organic monobasic acid to the organic dibasic acid (organic monobasic acid/organic dibasic acid) is 0.
/100-95/5, preferably 70/30-90/1
It is 0. When the blending weight ratio exceeds 95/5, there is no effect of improving the running properties.

The cationic electrodeposition paint of the present invention may optionally contain extender pigments such as aluminum silicate, precipitated barium sulfate, kaolin, precipitated potassium carbonate, titanium dioxide, carbon black, zinc white, Bengara, Coloring pigments such as manganese dioxide, anti-rust pigments such as strontium chromate, lead chromate, basic lead silicate, and aluminum molybdate are blended. Other additives, e.g. surfactants,
Flow control agents, ultraviolet absorbers, etc. are also added as necessary.

[0017] Formation of a coating film using the cationic electrodeposition paint of the present invention is carried out by a conventional method. For example, after electrodeposition on the substrate surface until a desired coating thickness is obtained, the coating is washed with water and then baked at a temperature of 120°C or higher, for example 180°C. The base material is not particularly limited as long as it can be used for electrodeposition, and examples thereof include cold-rolled steel sheets, galvanized steel sheets, aluminum alloys, and the like.

[0018]

Effects of the Invention The present invention provides a cationic electrodeposition coating composition that has excellent coverage and provides a coating film with excellent smoothness and no gas pinholes even on galvanized steel sheets. It will be done.

[0019]

[Examples] The present invention will be specifically explained below with reference to Examples. In addition, unless otherwise specified, "parts" represent parts by weight.

(Preparation Example 1 - Preparation of quaternizing agent)
Ingredients
Weight part Solid content 2-ethylhexanol 320.0
304 Half-capped TDI (in methyl isobutyl ketone) Dimethylethanolamine 8
7.2 87.2 Lactic acid aqueous solution
117.6
88.2 Butyl cellosolve
39.2
−

According to the above composition, 2-ethylhexanol semi-capped toluene diisocyanate (TDI) was added to dimethylethanolamine at room temperature using a suitable reaction vessel. The mixture exothermed and was stirred at 80° C. for 1 hour. Next, lactic acid was charged and butyl cellosolve was added. The reaction mixture was stirred at 65° C. for about half an hour to obtain a quaternizing agent.

(Preparation Example 2 - Preparation of resin vehicle)
Ingredients
Weight part Solid content Ebon 8291) 71
0.0 681.2 Bisphenol A
289.6
289.6 2-ethylhexanol
406.4 386.1 Half-capped TDI (in methyl isobutyl ketone) Quaternizing agent from Preparation Example 1
496.3 421.9 Deionized water
71.
2 Butyl cellosolve
56.761) Epon 829: Bisphenol A type epoxy resin, epoxy equivalent weight 193-203, manufactured by Ciel Chemical Company.

According to the above compositions, Epon 829 and Bisphenol A were charged into a suitable reaction vessel and heated to 150 to 160°C under a nitrogen atmosphere. An initial exothermic reaction occurred. The reaction mixture was allowed to react at 150-160°C for about 1 hour, then after cooling to 120°C, 2-ethylhexanol semi-capped TDI was added. The reaction mixture was 110-1
It was kept at 20°C for about 1 hour and then butyl cellosolve was added. The mixture was then cooled to 85-95°C, homogenized, water was added, and the quaternizing agent of Preparation Example 1 was added. The reaction mixture was maintained at 80-85° C. until the acid value reached 1 to obtain a resin vehicle.

(Preparation Example 3 - Preparation of pigment paste)
Ingredients
Part by weight Solid content Resin vehicle diluted solution of Preparation Example 2 2)
833.3 250 Carbon Black 23
23 Titanium dioxide
91
7 917 Lead silicate

60 60 Deionized water
666.7 -2) 429 parts of the resin vehicle of Preparation Example 2 was added to 101 parts of butyl cellosolve.
1 part and diluted with 470 parts deionized water to give a solids content of 30%.

According to the above composition, the above components were dispersed using a sand grind mill to obtain a particle size of 10 μm or less. Total solids 50.0%, resin solids 10.0%, pigment solids 40.
A 0% pigment paste was obtained.

(Preparation Example 4 - Preparation of polyurethane crosslinking agent)
In a suitable reaction vessel, add TDI (2,4-/2,6-isomer=
80:20) 218 parts of 2-ethylhexanol were added to 291 parts of the mixture under stirring in a dry nitrogen atmosphere, and the mixture was cooled to maintain the reaction temperature at 38°C. After keeping at the same temperature for half an hour,
The temperature was raised to 60°C, and 75 parts of trimethylolpropane and 0.08 parts of dibutyltin dilaurate were added. The mixture was maintained at 121° C. for 1.5 hours until the absorption of isocyanate groups substantially disappeared according to an infrared absorption spectrum, and then diluted with 249 parts of ethylene glycol monoethyl ether. Resin solid content 70.1%.

(Preparation Example 5 - Preparation of polycaprolactone diol chain extended polyether) Epicoat 1001 (epoxy resin manufactured by Yuka Ciel Epoxy Co., Ltd.) was placed in a suitable reaction vessel.
970 parts and polycaprolactone diol (trade name: TO
265 parts of NE0200 (manufactured by UCC) were charged. This was heated to 100° C. under a nitrogen atmosphere, and 0.46 part of benzylmethylamine was added. The reaction mixture was further heated to 130° C. and maintained at this temperature for approximately 1.5 hours. The batch was cooled to 110°C, 110 parts of methyl isobutyl ketone were added, and then 39.8 parts of diethylenetriamine in methyl isobutyl diketimine 73% solution of methyl isobutyl ketone was added.
parts by weight and an additional 100 parts by weight of methyl isobutyl ketone. Continue cooling until the batch temperature reaches 70°C.
At the same temperature, 53.1 parts of diethylamine was added, and the bath temperature was raised to 12.
It was kept at 0°C for 3 hours and then taken out.

Preparation of cationic electrodeposition paint (Example 1) Components
Department
Polycaprolactone diol of Preparation Example 5
576 Chain-extended polyether Polyurethane crosslinking agent of Preparation Example 4
310 Ethylene glycol monohexyl ether 71 Tartaric acid
15.4 Deionized water
705.5 Preparation example 3
pigment paste
342 Deionized water

2424

[0029] With the above composition, the polycaprolactone diol chain-extended polyether of Preparation Example 5 and Preparation Example 4
The polyurethane crosslinker was mixed with ethylene glycol monohexyl ether, neutralized with tartaric acid, and then slowly diluted with deionized water. Add the pigment paste from Preparation Example 3 to this, mix evenly, and add the remaining deionized water to make a solid 20%
% cationic electrodeposition coating composition A was obtained.

(Example 2) A cationic electrodeposition coating composition was obtained in the same manner as in Example 1, except that 2.4 parts of fumaric acid and 9.8 parts of acetic acid were used in place of 15.4 parts of tartaric acid. .

(Example 3) Part 1 Nisseki Polybutadiene B-2000 (number average molecular weight 2
000, 1,2 bonds (65%) was epoxidized using peracetic acid to produce epoxidized polybutadiene with an oxirane oxygen content of 6.4%.

1000g of this epoxidized polybutadiene
After charging 354 g of ethyl cellosolve and ethyl cellosolve into a 2 liter autoclave, 62.1 g of dimethylamine was added,
The reaction was carried out at 0°C for 5 hours. After distilling off unreacted amine,
After cooling to 120°C, a mixture of 79.3 g of acrylic acid, 7.6 g of hydroquinone and 26.4 g of ethyl cellosolve was added, and the mixture was further reacted at 120°C for 3 hours and 45 minutes to produce resin solution C1. The amine value of this product is 85.
2 mmol/100g, acid value 10.0 mmol/10
0 g, and the solid content concentration was 75.0% by weight.

Part 2: 1000 g of bisphenol type epoxy resin having an epoxy equivalent of 950 (trade name Epicote 1004, manufactured by Yuka Ciel Epoxy Co., Ltd.) was dissolved in 343 g of ethyl cellosolve, and 76.3 g of acrylic acid and 10 g of hydroquinone were dissolved.
and 5 g of N,N-dimethylaminoethanol were added, heated to 100° C., and reacted for 5 hours to synthesize resin solution C2. The acid value of this product was 2 mmol/100 g, and the solid content concentration was 75% by weight.

Part 3: 1,400 g of the resin solution C produced in Part 1 above and 2,240 g of the resin solution C produced in Part 2 were mixed until uniform, and then 4.1 g of acetic acid and 5.1 g of tartaric acid were added and thoroughly stirred for neutralization. Next, deionized water was gradually added to prepare an aqueous solution having a solid content concentration of 20% by weight.

2,000 g of this 20% by weight aqueous solution, 4 g of carbon black, 20 g of basic lead silicate and 2,000 g of glass beads were placed in a 5 liter stainless steel beaker and stirred vigorously for 2 hours with a high-speed rotating mixer, and then the glass beads were filtered. Next, deionized water containing 0.32 g of manganese acetate as manganese metal was added so that the solid content concentration was 20.0% to prepare a cationic electrodeposition coating composition C.

(Example 4) Part 1 45 parts of ethylene glycol hexyl ether was put into a reaction vessel equipped with a reflux condenser, a dropping funnel, a stirrer, and a thermometer, and the mixture was heated and maintained at 120°C. 20 parts of styrene, 2
-30 parts of hydroxy methacrylate, 35 parts of ethyl methacrylate, 15 parts of dimethylethyl methacrylate, t
A mixture consisting of 3 parts of -dodecylmercaptan and 2 parts of azobisisobutyronitrile was added dropwise over 2 hours. After the dropwise addition was completed, the temperature was maintained at 120°C for 30 minutes, and then a mixture of 5 parts of ethylene glycol monohexyl ether and 0.2 parts of azobisisobutyronitrile was added dropwise over 5 minutes, and then maintained at 120°C for 1 hour. An acrylic copolymer resin solution having a solid content of about 68% and a weight average molecular weight of about 10,000 was obtained. This is called liquid D1. Next, 155.2 parts of liquid D1 and the polyurethane crosslinking agent of Preparation Example 4 were mixed, and 1.8 parts of glacial acetic acid was added.
The mixture was neutralized with 0.6 parts of tartaric acid and slowly diluted with 243.2 parts of deionized water to obtain an emulsion with a solids content of 30%. 100 parts of the pigment paste of Preparation Example 3 was added to 500 parts of this emulsion liquid and mixed uniformly, and deionized water was added to obtain a cationic electrodeposition coating composition D having a solid content of 20%.

(Comparative Example 1) Glacial acetic acid 1.8 parts, tartaric acid 0.
A cationic electrodeposition paint was obtained in the same manner as in Example 4, except that 2.3 parts of glacial acetic acid was used instead of 6 parts for neutralization.

Paint coverage test A strip of hot-dip galvanized steel plate treated with zinc phosphate coating was inserted into an iron pipe, and each of the cationic electrodeposition paint compositions obtained in Examples 1 to 4 and Comparative Example 1 was tested. The coverage was tested by electrodeposition at a coating temperature of 28° C. and a voltage of 250 volts for 3 minutes. The results are shown in Table-1.

[0039]
Table-1 Example 1 Example 2 Example 3 Example 4 Comparative example 1
Compatibility 24.8 23.3
20.8 20.0
17.3(cm)

Claims (3)

[Claims] Claim 1: 0.05 to 10 parts of a polybasic acid with a pKa of 7.0 or less per 100 parts by weight of the base resin (in terms of solid content).
A cationic electrodeposition coating composition containing parts by weight. 2. The polybasic acid is an organic dibasic acid with a pKa of 27.0 or less, and the cationic electrodeposition coating composition further contains an organic monobasic acid at a blending weight ratio (organic monobasic acid/organic dibasic acid). ) 0/100 to 95/5 of the cationic electrodeposition coating composition according to claim 1. Claim 3: The organic dibasic acid has a water solubility of 1 g/10
The cationic electrodeposition coating composition according to claim 2, having an amount of 0 g (25° C. water) or more.