JPH04320465A - Cationic electrodeposition coating composition - Google Patents

Abstract

PURPOSE:To provide the title composition excellent in film smoothness, heat stability, etc., free from seeding, settling, etc., and excellent in coating stability. CONSTITUTION:This composition is prepared by mixing 100 pts.wt. (in terms of solid centent) resin with 1-80 pts.wt. low-oil absorption silica pigment having an oil absorption of 80 or below and a mean particle diameter of 10mum or below and a water solubles content of 1 pts.wt. or below.

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 with improved coating film smoothness and coating stability.

0002

[Prior Art] As an example of the use of fine particle silica in cationic electrodeposition paints, for example, Japanese Patent Application Laid-Open No. 64-66278 describes the use of fine-particle silica as a means for improving end-face corrosion resistance and thread rust resistance (JIS K 5101-78). ) containing 5% or more of the pigments, and the total oil absorption of the pigments is 1,000 to 10
,000 particulate silica is proposed.

[0003] However, the fine particle silica having a large oil absorption as described above has structural viscosity, which causes the problem that the viscosity of the coating increases and the smoothness of the electrodeposited coating decreases.

Furthermore, since natural silica pigments are hard and difficult to disperse, they have poor stability in paints and have problems such as the formation of lumps and sedimentation due to aggregation.

[0005]

[Problems to be Solved by the Invention] The present invention provides a cationic electrodeposition coating composition that has excellent coating film smoothness, thermal stability, etc., and also has excellent coating stability without the occurrence of lumps or sedimentation.
The purpose is to

[0006]

[Means for Solving the Problems] In order to achieve the above object, if a low oil absorption silica pigment is used, which has an oil absorption of 80 or less, an average particle diameter of 10 μm or less, and a water-soluble content of 1 part by weight or less,
The present inventors have discovered that this method has excellent results and have come up with the present invention.

That is, the present invention provides low oil absorption silica pigments 1 to 8 with an oil absorption of 80 or less, an average particle diameter of 10 mμ or less, and a water-soluble content of 1 part by weight or less, per 100 parts by weight of the resin (solid content equivalent).
Provided is a cationic electrodeposition coating composition containing 0 parts by weight.

The resin component of the cationic electrodeposition paint used in the present invention is not particularly limited as long as it is a resin commonly used for cationic electrodeposition. These cationic electrodeposition resins are disclosed, for example, in JP-A-49-99337, JP-A-51-126225, and JP-A-51-103135.
No. 51-117799, Japanese Patent Application Laid-Open No. 1982-117799
-18746 publication, JP-A-52-87498 publication,
JP-A-53-43800, JP-A-53-6532
Publication No. 7, JP-A-53-65329, JP-A-47
-759, JP 48-51924, JP 52-11228, JP 54-4978, JP 54-15449, JP 54-15
936, JP 54-93024, JP 55-31889, JP 55-31890, JP 55-115476, JP 56-3
4186, JP 56-49725, JP 56-79163, JP 57-112687
Publication No. 3, Japanese Unexamined Patent Publication No. 57-139147, Special Publication No. 6
2-61077, JP 63-86766, JP 63-139909, JP 1-605
16, JP-A-54-97632, and JP-A-55-137174.

The resin used in the present invention may be any of these resins, but particularly preferred is a cationic resin obtained by reacting an epoxy resin with a compound having an amino group. Of course, the material is not limited thereto, and may be a phenol resin having a cationic group, a polybutadiene resin, an acrylonitrile resin, a styrene resin, a maleindiene compound resin, or a copolymer resin thereof.

A dryer such as a melamine resin, a blocked polyisocyanate, an ester/amide exchanger, and/or a manganese compound is added to these resin systems as necessary.

[0011] The coating material is prepared by mixing the resin with acetic acid, propionic acid,
It is prepared by dissolving or dispersing it in water containing an organic acid such as lactic acid or an inorganic acid such as phosphoric acid, or an aqueous medium containing an organic solvent (alcohol, ketone, ether, etc.) that is miscible with water.

The aqueous or aqueous medium solution or dispersion thus obtained further contains a low oil absorption silica pigment. The low oil absorption silica pigment used in the present invention has an oil absorption of 80 or less, preferably 50 or less. If the oil absorption exceeds 80, the smoothness of the coating film will deteriorate, which is not preferable. The average particle size of the low oil absorption silica pigment is 10 μm or less, preferably 5 μm or less. If the average particle size exceeds 10 μm, the stability of the coating material deteriorates, which is not preferable. Further, the water-soluble content (for example, Na, K, Ca ions, etc.) of the low oil absorption silica pigment is 1 part by weight or less, preferably 0.1 part by weight or less. If the water-soluble content exceeds 1 part by weight, it is undesirable because it adversely affects electrodeposition characteristics and performance.

[0013] The above-mentioned low oil absorption silica pigment can be obtained, for example, by pulverizing a natural product, refining it, and adjusting the particle size. For example, it is commercially available under brands such as Minisil and Microcrystal Silica.

The content of the low oil absorption silica pigment in the coating composition is based on 100 parts by weight of the resin (in terms of solid content):
The amount is 1 to 80 parts by weight, preferably 2 to 40 parts by weight. If the content is less than 1 part by weight, there will be no effect on the viscosity of the coating film, and if it exceeds 80 parts by weight, the smoothness of the electrodeposition coating film will be poor.

The cationic electrodeposition paint of the present invention may optionally contain extender pigments such as aluminum silicate (mica), precipitated barium sulfate, kaolin, precipitated calcium carbonate, and talc, titanium dioxide, carbon black, and zinc white. , coloring pigments such as Bengara, manganese dioxide, and lead oxide, and rust-preventing pigments such as strontium chromate, lead chromate, basic lead silicate, and aluminum molybdate. Other additives, such as surfactants, flow control agents, ultraviolet absorbers, etc., may also be added as necessary.

[0016] Formation of the electrodeposition coating film according to the present invention is carried out by a conventional method. That is, the substrate is crushed in an electrodeposition bath, and after electrodeposition, the coating film is washed with water and baked at a temperature of 120°C or higher, for example, 180°C, until the desired coating thickness is obtained. The above-mentioned base material may be a metal conventionally generally coated by electrodeposition, such as iron, steel, galvanized steel, alloys thereof, or may be chemically treated.

[0017]

[Effects of the Invention] According to the present invention, by using a low oil absorption silica pigment, the viscosity of the electrodeposited coating during the baking process is kept low, flowability is increased, and the smoothness of the coating is improved. I can point it out.

Furthermore, according to the present invention, the use of a low oil absorption silica pigment increases the pigment dispersibility, prevents the formation of lumps and sedimentation due to aggregation, and improves the storage stability of pigment pastes and paints. .

[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) Components
Part by weight 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
- With the above composition, using a suitable reaction vessel, at room temperature
- Ethylhexanol Half-capped toluene diisocyanate (TDI) was added to dimethylethanolamine. The mixture exothermed and was stirred at 80° C. for 1 hour. Next, lactic acid was added, 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 Epon 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. With the above composition, Epon 8
29 and bisphenol A were charged into a suitable reaction vessel and heated to 150-160°C under 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. 1 of the reaction mixture
It was kept at 10-120°C for about 1 hour, and then butyl cellosolve was added. Next, the mixture was cooled to 85 to 95°C and homogenized, water was added, and the quaternizing agent of Preparation Example 1 was further added. acid value is 1
The reaction mixture was maintained at 80-85° C. until the resin vehicle was obtained.

(Preparation Example 3 - Preparation of polycaprolactone diol chain extended polyether) In a suitable reaction vessel, Epicoat 1001 (epoxy resin manufactured by Yuka Ciel Epoxy Co., Ltd.)
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 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 of pigment paste and cationic electrodeposition paint (Example 1) Preparation of pigment paste (I): Components
Weight part
Solid content Resin vehicle diluted solution 2 of Preparation Example 2) 1666.7 500
Carbon black
81 81
Low oil absorption silica pigment 3)
791.8 791.8 Lead silicate
67.2 67.2
dibutyltin oxide
60 60 Deionized water
217.9 -2)
429 parts of the resin vehicle of Preparation Example 2 was added to 1 part of butyl cellosolve.
01 parts and 470 parts of deionized water to give a solids content of 30 parts.
%. 3) Minisil low oil absorption silica pigment: It is a modified silica with an oil absorption of 44 and an average particle diameter of 1.6 μm. Fig. 1 shows a 10,000x electron micrograph.

Each component of the above composition was dispersed using a sand grind mill to obtain a particle size of 10 μm or less. Furthermore, deionized water was added to obtain a pigment paste (I) having a total solid content of 52.0%, a resin solid content of 17.3%, and a pigment solid content of 34.7%.

Cationic electrodeposition paint components

Part Polycaprolactone diol of Preparation Example 3 576 Chain extended polyether Polyurethane crosslinking agent of Preparation Example 4
310 Ethylene glycol monohexyl ether 35.5 Glacial acetic acid
12.3
deionized water
741 Pigment paste (I)
313 Deionized water

2453

With the above composition, the polycaprolactone diol chain-extended polyether of Preparation Example 3 and the polyurethane crosslinker of Preparation Example 4 were mixed with ethylene glycol monohexyl ether, neutralized with glacial acetic acid, and then slowly diluted with deionized water. . Add the above pigment paste (
I) was added and mixed uniformly, and the remaining deionized water was added to obtain a cationic electrodeposition coating composition with a solid content of 20%.

(Example 2) Preparation of pigment paste (II): Ingredients
Weight part
Solid content Resin vehicle diluted solution of Preparation Example 2 1333.3 400.
0 carbon black
36.0 36.
0 titanium dioxide
452.0 452.
0 Low oil absorption silica pigment 3)
400.0 400.0
A-108 Lead silicate
67.2
67.2 Dibutyltin oxide
44.8 44.
8 Deionized water
212.2
-3) Low oil absorption silica pigment: oil absorption 27-31, average particle diameter 1.5 μm. Each component of the above composition was prepared in the same manner as in Example 1, with a total solid content of 55.0% and a resin solid content of 15.7%.
%, and a pigment paste (II) having a pigment solid content of 39.3% was obtained.

Cationic electrodeposition paint components

Part Polycaprolactone diol of Preparation Example 3 576 Chain extended polyether Polyurethane crosslinking agent of Preparation Example 4
310 Ethylene glycol monohexyl ether 21.3 Glacial acetic acid
12.3
deionized water
544.3 Pigment paste (II)
502.1 Deionized water

2467 Each component of the above composition was prepared in the same manner as in Example 1 to obtain a cationic electrodeposition coating composition.

(Comparative Example 1) Preparation of pigment paste (III): Ingredients
Weight part
Solid content Resin vehicle diluted solution of Preparation Example 2 1666.7 500.
0 carbon black
36.0 36.
0 titanium dioxide
441.8 441.
8 Particulate silica 4)
395.0 395.
0 lead silicate
67.2
67.2 Dibutyltin oxide
60.0 60
．． 0 deionized water
245.94) Oil absorption 143-1
83, and a 10,000x electron micrograph is shown in Figure 2. Each component of the above composition was prepared in the same manner as in Example 1 with a total solid content of 51.5%, a resin solid content of 17.2%, and a pigment solid content of 34%.
．． A 3% pigment paste (III) was obtained.

Cationic electrodeposition paint components

Part Polycaprolactone diol of Preparation Example 3 576 Chain extended polyether Polyurethane crosslinking agent of Preparation Example 4
310 Ethylene glycol monohexyl ether 21.3 Glacial acetic acid
12.3
deionized water
964.7 Pigment paste (III)
376.7 Deionized water

2261 Each component of the above composition was prepared in the same manner as in Example 1 to obtain a cationic electrodeposition coating composition.

Storage stability test of pigment paste, smoothness test of cationic electrodeposition coating film and filtration test of cationic electrodeposition paint Storage stability test of pigment paste in Examples 1 to 2 and Comparative Example 1, cation A smoothness test of the electrodeposition coating film and a filterability test of the cationic electrodeposition paint were conducted. The results of these tests are shown in Table-1. Table-1
Example 1
Example 2 Comparative Example 1 Pigment paste
○ ○ Coarse particle generation storage stability 1)
Paint film smoothness 2) 0,35 0,3
0 0,50Ra (μm)

Paint filtration performance 3)
○ ○ ×
1): The pigment paste was stored at 40° C. for one month and the particle size was measured using a grind gauge. ○ represents no change in particle size. 2): Using a cationic electrodeposition paint, a coating film of 20 μm was applied to an SPC steel plate subjected to zinc phosphate chemical conversion treatment at an applied voltage of 200 V for 3 minutes, and after washing with water, it was baked at 180° C. for 20 minutes. The surface roughness (Ra) of this painted steel plate was determined by Surtronic 3P (
(manufactured by Tiller Hobson). 3): 38 after aging at 40℃ for 2 weeks after adjusting the paint.
The filtration condition was examined using a 0-mesh filter net. ◯ indicates good quality, × indicates poor quality.

[0032]

[Brief explanation of the drawing]

FIG. 1 shows the particle structure of a low oil absorption silica pigment used in the present invention.

FIG. 2 shows the particle structure of conventional particulate silica.

Claims (1)

[Claims] Claim 1: Contains 1 to 80 parts by weight of a low oil absorption silica pigment with an oil absorption of 80 or less, an average particle diameter of 10 mμ or less, and a water-soluble content of 1.0 parts by weight or less, per 100 parts by weight of resin (solid content equivalent). A cationic electrodeposition coating composition characterized by: