JPH07207195A - Pigment-dispersing resin for electrodeposition coating - Google Patents

Abstract

PURPOSE:To provide a pigment-dispersing resin for electrodeposition coating which has a specific structure and shows excellent stability with lapse of time, pigment dispersion and corrosion resistance. CONSTITUTION:The resin of the formula (Ep is residue of epoxy resin having 150 to 2,000 epoxy equivalents; R1 is hydroxymethyl 2-hydroxyethyl, 3- hydroxypropyl, 4-hydroxybutyl, 2,3-dihydroxypropyl; A<-> is a counter anion; m is 0.1 to 4.0). The objective resin is obtained by reaction of an epoxy resin of 150 to 2,000 epoxy equivalent with a sulfide of the formula: R<1>SCH2CH(OH) CH2OH in the presence of an acid such as formic acid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationic resin which can be suitably used as a pigment-dispersing resin in an electrodeposition paint and a pigment-dispersing paste containing the same.

[0002]

2. Description of the Related Art Electrodeposition coating is a method in which a water-based coating material is filled in a tank and the coating components are electrophoresed on an object to be coated in the same bath and the surface of the coating is electroprecipitated. This coating method is mainly used for anticorrosion coating of automobile bodies and is industrially important.

Generally, the electrodeposition coating composition contains a pigment and a pigment dispersant. Before introducing pigments into paint,
A pigment-dispersed paste in which a pigment is dispersed in an aqueous medium at a high concentration is used as an intermediate composition. A dispersant is used to impart sufficient storage stability to this pigment dispersion paste. This dispersant is required to have the property of increasing the dispersion stability of the pigment-dispersed paste and the ability to keep the paint stable for a long period of time when it is used as an electrodeposition coating by diluting the pigment-dispersed paste with an aqueous medium. It In recent years, cationic resins have been generally used as pigment dispersants for electrodeposition coatings.

For example, Japanese Examined Patent Publication Nos. 53-47143 and 54-497.
No. 8 discloses a cationic resin used as a dispersant for electrodeposition coatings. Further, JP-A-1-182377 discloses a cationic resin which also functions as a catalyst in a curing reaction between an α, β-unsaturated carbonyl group and a hydroxyl group. Here, a cationic resin having a tertiary sulfonium salt is disclosed as a cationic resin having an inhibitory effect in a moderately basic and corrosive environment for catalytic activity.

Further, Japanese Patent Application Laid-Open No. 63-23919 discloses a sulfonium resin useful as a pigment crushing and color-developing agent, and the most preferable example is 3 derived from thiodiethanol.
Cationic resins having primary sulfonium salts are mentioned.

However, since the pigment-dispersed resin disclosed herein is inferior in pigment dispersibility during long-term storage, there is a problem that a pigment-dispersed paste and electrodeposition coating having excellent storage stability cannot be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above-mentioned conventional problems, and an object of the present invention is to provide excellent pigment dispersibility and high anticorrosion property with excellent stability over time. An object of the present invention is to provide a pigment-dispersed resin capable of preparing an electrodeposition coating material, and a pigment-dispersed paste containing the resin and excellent in stability over time.

[0008]

The present invention is based on the formula

[0009]

[Chemical 2]

[Wherein Ep is a residue of an epoxy resin having an epoxy equivalent of 150 to 2000, and R ¹ is hydroxymethyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl. Or a 2,3-dihydroxypropyl group, A ^- is a counter anion, and m is a number from 0.1 to 4.0. ] To provide a pigment-dispersed resin, which achieves the above object.

The pigment-dispersed resin of the present invention comprises 30 to 500, especially 5
It preferably has a tertiary sulfonium value of 0 to 150.
If the tertiary sulfonium value exceeds 500, the corrosion resistance decreases and
This is because if it is less than 0, the dispersion becomes poor. The tertiary sulfonium value in the present invention is represented by milliequivalents of sulfonium groups in 100 g of resin.

Preferably, the pigment dispersion resin of the present invention is prepared by reacting an epoxy resin with a sulfide corresponding to the above-mentioned tertiary sulfonium group. This reaction is
Generally, it is carried out at a reaction temperature of 50 to 80 ° C, preferably 60 to 75 ° C, by mixing and stirring the epoxy resin, sulfide, acid and deionized water. The preferred reaction ratio is 1 to 4 equivalents of sulfide with respect to the epoxy groups of the epoxy resin, and the same amount of acid with epoxy. As an acid,
What can be a counter anion of sulfonium can be used. Examples thereof include formic acid, lactic acid, acetic acid, propionic acid, butyric acid, dimethylolpropionic acid, boric acid, phosphoric acid, hydrochloric acid, sulfuric acid, and the like.However, when an inorganic acid is used, halogen compounds that lead to reduced corrosion resistance Carboxylic acids such as formic acid, lactic acid, acetic acid, propionic acid, butyric acid, and dimethylolpropionic acid are preferable because they may be mixed.

The epoxy resin which can be used in the present invention is a so-called polyepoxide having an average of one or more 1,2-epoxy groups in one molecule. The epoxy equivalent of these epoxy resins is preferably 150 to 2000, more preferably 4
It is from 00 to 1500. If the epoxy equivalent is less than 150, a coating cannot be obtained because a film cannot be formed during electrodeposition, and if it exceeds 2000, the amount of cationic groups per molecule is insufficient and sufficient water solubility cannot be obtained. The epoxy resin also has a number average molecular weight of 300 to 10,000, preferably 800 to 5,000. When the number average molecular weight is more than 10,000, the viscosity becomes high, resulting in poor dispersion, and when the number average molecular weight is less than 300, corrosion resistance is reduced.

Examples of such epoxy resins include polyglycidyl ethers of polyphenols and acrylic polymers having 1,2-epoxy groups as pendant groups.

Polyglycidyl ethers of polyphenols are generally obtained by reacting polyphenols with epichlorohydrin or dichlorohydrin in the presence of alkali. Examples of polyphenols include bis (4-hydroxyphenyl) -2,2-propane, 4,4-dihydroxybenzophenone, bis (4-hydroxyphenyl)-
Examples include 1,1-ethane and its analogs. The acrylic polymer having a 1,2-epoxy group as a pendant group is
Generally, it can be obtained by copolymerizing an acrylic monomer having a 1,2-epoxy group, such as glycidyl methacrylate, alone or with another acrylic monomer.

The sulfide which can be used in the present invention has a formula R ¹ SCH ₂ CH (OH) CH ₂ OH [wherein R ¹ has the same meaning as described above. ]]. Such a sulfide is generally obtained by reacting a thiol with an epoxy compound.

Specific examples of the sulfide usable in the present invention include 1- (2-hydroxyethylthio) -2,3-methanediol, 1- (2-hydroxyethylthio) -2,3-ethanediol, 1 -(2-hydroxyethylthio) -2,3-propanediol, 1- (2-hydroxyethylthio) -2,3-butanediol, 2,2'-thiobis (2,3-propanediol), 1- (2-Hydroxypropylthio) -2,3-propanediol and the like can be mentioned.

The pigment dispersion resin of the present invention thus obtained and the pigment are mixed in a weight ratio of 1: 0.05 to 1:10, preferably 1: 0.1 to 1: 0.5, by a method well known to those skilled in the art. The pigment-dispersed paste of the present invention can be prepared by blending with.

The pigment is not particularly limited as long as it is usually used, and examples thereof include iron oxide, strontium chromate, carbon black, titanium dioxide, talc, barium sulfate, cadmium yellow, cadmium red, chromic yellow, and phosphomolybdenum. Examples thereof include aluminum oxide, zinc phosphomolybdate, and combinations thereof.

Further, the obtained pigment dispersion paste is mixed with deionized water and a cationic resin, and further as an auxiliary agent, another resin, a solvent, an antioxidant, a surfactant, and other components used in the electrodeposition process. The electrodeposition paint is obtained by adding additives well known to those skilled in the art such as auxiliary agents.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, "part" is based on weight.

Preparation Example 1 Preparation of Polyurethane Crosslinking Agent A hexamethylene diisocyanurate 199. was added to a reaction vessel equipped with a stirrer, a cooling tube, a nitrogen introducing tube and a thermometer.
Add 1 part, dilute with methyl isobutyl ketone (hereinafter abbreviated as MIBK) 31.6 parts, then add dibutyltin dilaurate 0.2
Added parts. After heating to 50 ° C, methyl ethyl ketoxime
87 parts were added dropwise with stirring in a dry nitrogen atmosphere to maintain the reaction temperature at 50 ° C. Keep at 70 ° C until the isocyanate groups disappear by infrared absorption spectrum, then MIBK35.8
Parts, and 4.0 parts of n-butanol were diluted to obtain a polyurethane crosslinking agent.

Preparation Example 2 Preparation of Aminated Epoxy Resin A reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introducing pipe and a thermometer was placed in Epicoat 1001 (produced by Yuka Shell Epoxy Co., bisphenol A type epoxy resin having an epoxy equivalent of 475). ) 99.8 parts, Epicoat 1004 (produced by Yuka Shell Epoxy Co.,
Epoxy equivalent 950 bisphenol A type epoxy resin) 85
0.2 parts, nonylphenol 55 parts, MIBK 193.3 parts and benzyldimethylamine 4.5 g are added, and the temperature is 140 ° C.
And reacted for 4 hours to obtain a resin having an epoxy equivalent of 1175. Here ethylene glycol n-hexyl ether 69.1
Parts, 35.4 parts of MIBK solution of 2-aminoethylethanolamine MIBK ketimine compound (78% by weight of solid content), 26.5 parts of N-methylethanolamine and 37.1 parts of diethanolamine were added. This was reacted at 120 ° C. for 2 hours to obtain a target resin.

Example 1 Preparation of Half-Blocked Diisocyanate 222.2 parts of isophorone diisocyanate (hereinafter abbreviated as IPDI) was placed in a reaction vessel equipped with a stirrer, a nitrogen introducing tube, and a cooling tube, and methyl isobutyl ketone (hereinafter abbreviated as MIBK). ) After diluting with 39.1 parts, 0.2 part of dibutyltin dilaurate was added. After the temperature was raised to 50 ° C., 131.5 parts of 2-ethylhexanol was dropped and reacted in a dry nitrogen atmosphere for 2 hours while stirring. The reaction temperature was maintained at 50 ° C. to obtain 2-ethylhexanol half-blocked IPDI (solid content 90%).

Preparation of Pigment Dispersion Resin A reaction vessel equipped with a stirrer, a nitrogen inlet tube, and a cooling tube is charged with Epon.
828 (Epoxy resin made by Shell Chemical Co., epoxy equivalent: 190)
Charge 351.6 parts and 99.2 parts of bisphenol A, heat to 130 ° C under nitrogen atmosphere, and add benzyldimethylamine 1.4.
By adding 1 part and reacting at 170 ° C. for about 1 hour,
A bisphenol type epoxy resin having an epoxy equivalent of 445 was obtained. Then, after cooling to 140 ° C, 2-ethylhexanol half-blocked IPDI 218.3 parts (solid content 196.5 parts) prepared above was added and reacted.

After keeping it at 140 ° C. for 1 hour, 172.3 parts of dipropylene glycol monobutyl ether was added to dilute it, and then the reaction mixture was cooled to 100 ° C. to give 1- (2-hydroxyethylthio) -2,3. -Propanediol 408.0 parts (solid content 136.0 parts), dimethylolpropionic acid 134.0 parts and deionized water 144.0 parts were added. It has an acid value of 2.0 at 70-75 ℃.
The reaction was carried out until the following conditions were obtained to obtain a pigment dispersion resin having a tertiary sulfonium conversion rate of 72%. This was diluted with 324.8 parts of dipropylene glycol monobutyl ether to obtain a pigment dispersion resin (resin solid content 50%).

Example 2 In Example 1, 408.0 parts of 1- (2-hydroxyethylthio) -2,3-propanediol (solid content 182.0 parts) was replaced with 2,2'-thiobis.
(2,3-Propanediol) The reaction was carried out in the same manner except that the amount was changed to 546.0 parts to obtain a pigment-dispersed resin having a tertiary sulfonium conversion rate of 82%. This was diluted with 324.8 parts of dipropylene glycol monobutyl ether to obtain a pigment dispersion resin (resin solid content 50%).

Example 3 In Example 1, 408.0 parts of 1- (2-hydroxyethylthio) -2,3-propanediol was added to 1- (2-hydroxypropylthio) 2,3
-Propanediol 498.0 parts (solid content 166.0 parts) was changed in the same manner as above, and a pigment dispersion resin having a tertiary sulfonium conversion rate of 70% was obtained. This was diluted with 324.8 parts of dipropylene glycol monobutyl ether to obtain a pigment dispersion resin (resin solid content 50%).

Example 4 500 parts of ethylene glycol monobutyl ether was charged into a reaction vessel equipped with a stirrer, a nitrogen introducing tube, and a cooling tube, and heated to 120 ° C. with stirring. A mixture of 285.0 parts of glycidyl methacrylate, 205.0 parts of styrene, 250.0 parts of 2-hydroxyethyl methacrylate, 250.0 parts of n-butyl acrylate and 28.0 parts of t-butyl peroxyoctoate was added dropwise over 3 hours. After that, 210 parts of ethylene glycol monobutyl ether, 500 parts of 1- (2-hydroxyethylthio) -2,3-propanediol and 134.0 parts of dimethylolpropionic acid were added and further reacted at 70 ° C. Then dipropylene glycol monobutyl ether 324.8
It was diluted with 1 part to obtain a pigment-dispersed resin (resin solid content 50%).

COMPARATIVE EXAMPLE 1 Preparation of Pigment Dispersion Resin Obtained from Thiodiethanol Ethanol was added to a reaction vessel equipped with a stirrer, nitrogen introducing tube and cooling tube.
828 533.2 parts, bisphenol A 199.6 parts, and nonylphenol 19.2 parts were charged and heated to 130 ° C. in a nitrogen atmosphere. Here, ethyl triphenylphosphonium iodide 0.
By adding 75 parts and reacting at 170 ° C. for about 1 hour, a bisphenol A type epoxy resin having an epoxy equivalent of 490 was obtained. Then, after cooling to 140 ° C, 2-ethylhexanol half-blocked isophorone diisocyanate 198.4
Parts (solid content 178.6 parts) were added and the mixture was kept at 140 ° C. for 1 hour. The epoxy resin thus obtained was diluted with 161.8 parts of ethylene glycol monobutyl ether, cooled to 100 ° C., and 122.1 parts of 2,2′-thiobis (ethanol), 134.0 parts of dimethylolpropionic acid and 144.0 parts of deionized water were added. added. This mixture was reacted at 70 to 75 ° C until the acid value became 5.0 to obtain a resin having a tertiary sulfonium conversion rate of 82%. Then, it was diluted with 353.5 parts of ethylene glycol monobutyl ether to obtain a pigment dispersion resin (resin solid content 50%).

Comparative Example 2 Preparation of Quaternizing Agent 174.0 parts of tolylene diisocyanate (hereinafter abbreviated as TDI) was placed in a reaction vessel equipped with a stirrer, a nitrogen introducing tube and a cooling tube,
Dibutyltin dilaurate 0. after dilution with 33.9 parts MIBK.
Two parts were added. After heating to 50 ° C, 2-ethylhexanol 13
1.5 parts of the mixture was reacted dropwise in a dry nitrogen atmosphere for 2 hours while stirring. The reaction temperature was maintained at 50 ° C. to obtain 2-ethylhexanol half-blocked TDI. This 2-ethylhexanol half-blocked TDI 320.0 parts (solid content 30
(4.0 parts) was added to 87.2 parts of dimethylethanolamine at room temperature, and an exotherm was observed. After stirring this at 80 ° C for 1 hour, 117.6 parts of 75% lactic acid aqueous solution (solid content 88.2 parts) was added, and further ethylene glycol monobutyl ether 39.2
Added parts. The reaction mixture was stirred at 65 ° C. for about half an hour to give the quaternizing agent.

Preparation of Pigment Dispersion Resin Having Quaternary Ammonium Group Epon to a reaction vessel equipped with a stirrer, nitrogen inlet tube, and cooling tube.
828 (Epoxy equivalent 190 bisphenol A made by Yuka Shell Co., Ltd.
Type epoxy resin) 681.2 parts and bisphenol A 289.6
A part was charged and reacted at 150 to 160 ° C. under a nitrogen atmosphere for about 1 hour, then cooled to 120 ° C., and 406.4 parts of 2-ethylhexanol half-blocked TDI (solid content 386.1 parts) was added.
Then, the mixture was cooled to 85 to 95 ° C, homogenized, and 496.3 parts (solid content: 421.9 parts) of the quaternizing agent prepared above and deionized water.
71.2 parts were added. Mix the reaction mixture until the acid number is less than 1.
The temperature was maintained at 80 to 85 ° C., and 85.6 parts of ethylene glycol monobutyl ether was added for dilution to obtain a pigment dispersion resin.

Example 5 Preparation of Pigment Dispersion Paste 1 30.0 parts of pigment dispersion resin prepared in Example 1 (solid content 15.0)
Part), deionized water 75.4 parts, titanium dioxide R-900P 68.9
Part, kaolin 14.4 parts, aluminum phosphomolybdate 15.0 parts and carbon black 1.7 parts were dispersed by a sand grind mill to prepare a pigment dispersion paste having a particle size of 10 μm or less. This pigment-dispersed paste has a total solids content of 56.0
%, Resin solids 7.3%, pigment solids 48.7%.

Example 6 Preparation of Pigment Dispersion Paste 2 A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Example 2 was used in place of the pigment dispersion resin of Example 1.

Example 7 Preparation of Pigment Dispersion Paste 3 A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Example 3 was used in place of the pigment dispersion resin of Example 1.

Comparative Example 3 Preparation of Pigment Dispersion Paste 4 A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Comparative Example 1 was used in place of the pigment dispersion resin of Example 1.

Comparative Example 4 Preparation of Pigment Dispersion Paste 5 A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Comparative Example 2 was used in place of the pigment dispersion resin of Example 1.

Example 8 Evaluation of Dispersion Stability of Pigment Dispersion Paste The pigment dispersion pastes prepared in Examples 5 to 7 and Comparative Examples 3 and 4 were allowed to stand for 2 weeks at 40 ° C. By observing and measuring the yield value, the dispersion stability of the pigment dispersion paste was evaluated. The results of these evaluations are shown in Table 1.

[0039]

[Table 1] Example number Sedimentation state ¹⁾ Change in viscosity ²⁾ Example 5 ○ ○ Example 6 ○ ○ Example 7 ○ ○ Comparative example 3 △ × Comparative example 4 △ ○ 1) Storage at 40 ° C for 2 weeks After the rest, the sedimentation state of the paste was visually evaluated according to the following evaluation criteria. ◯: No sedimentation Δ: Soft sedimentation ×: Hard sedimentation 2) After storage at 40 ° C. for 2 weeks, the viscosity change of the paste was visually evaluated according to the following evaluation criteria. ○: No thickening △: Slightly thickening ×: Remarkably thickening

Example 9 Preparation of Cationic Electrodeposition Coating 1 331.9 parts of the polyurethane cross-linking agent obtained in Preparation Example 1 and 576.0 parts of the aminated epoxy resin obtained in Preparation Example 2 were n-
The mixture was mixed with 30.3 parts of hexyl cellosolve, neutralized with 12.3 parts of glacial acetic acid, and then slowly diluted with 1067.0 parts of deionized water. Then, the organic solvent was removed under reduced pressure until the solid content became 36.0%. To this, 546.8 parts of the pigment dispersion paste prepared in Example 5 was added and mixed uniformly, and 2598.2 parts of deionized water was added to obtain a cationic electrodeposition coating composition having a solid content of 20.0%.

Example 10 Preparation of Cationic Electrodeposition Paint 2 The pigment dispersion paste prepared in Example 5 was used in Example 6
A cation electrodeposition coating composition was obtained in the same manner as in Example 9 except that the one prepared in (4) was used.

Example 11 Preparation of Cationic Electrodeposition Paint 3 The pigment dispersion paste prepared in Example 5 was used in Example 7.
A cation electrodeposition coating composition was obtained in the same manner as in Example 9 except that the one prepared in (4) was used.

Comparative Example 5 Preparation of Cationic Electrodeposition Paint 4 The pigment dispersion paste prepared in Example 5 was used as Reference Example 3.
A cation electrodeposition coating composition was obtained in the same manner as in Example 9 except that the one prepared in (4) was used.

Comparative Example 6 Preparation of Cationic Electrodeposition Paint 5 The pigment dispersion paste prepared in Example 5 was used as Reference Example 4.
A cation electrodeposition coating composition was obtained in the same manner as in Example 9 except that the one prepared in (4) was used.

Example 12 Evaluation of Stability of Cationic Electrodeposition Paints over Time The cationic electrodeposition paints obtained in Examples 9 to 11 and Comparative Examples 5 and 6 were stored at 380 after stirring for 4 weeks at 40 ° C. The temporal stability was evaluated by evaluating the mesh net filterability and the amount of residue. The results are shown in Table 2.

Evaluation of Salt Water Corrosion Resistance of Cationic Electrodeposition Coating Each of the above cationic electrodeposition coatings was electrodeposited on a cold-rolled steel sheet (without zinc phosphate treatment) with a film thickness of 10 μ, and baked at 160 ° C. for 10 minutes. Put a cross cut, then 1 salt spray test (SST)
I went for 20 hours. After this test, firmly stick the 2.4 cm wide adhesive tape (Nichiban Co., Ltd., trade name "Sellotape") on the sample and then peel off the adhesive tape abruptly, and measure the peeling width of the coating film from the steel plate. By doing so, the salt water corrosion resistance of the electrodeposition paint was evaluated. The results are shown in Table 2.

[0047]

[Table 2] Example number Stability over time ¹⁾ Salt water corrosion resistance ²⁾ Example 9 ○ (3 mg) ○ Example 10 ○ (5 mg) ○ Example 11 ○ (5 mg) ○ Comparative example 5 △ (48 mg) ○ Comparison Example 6 Δ (35 mg) ○ 1) The electrodeposited coating was stored for 4 weeks at 40 ° C. under stirring for 4 weeks, and the 380 mesh screen filterability and the amount of residue were used to evaluate the temporal stability of the coating according to the following criteria. The amount of filtration residue is shown in parentheses. ○: Passes well △: Difficult to pass ×: Does not pass through 2) Evaluation criteria for saltwater corrosion resistance ○: Peeling width less than 2 mm △: Peeling width 2-3 mm ×: Peeling width 3 mm or more

[0048]

The pigment-dispersed resin of the present invention has a larger number of hydroxyl groups bonded to the sulfonium group than conventional ones, and the hydrophilicity of the resin is increased. As a result, it was possible to provide a pigment-dispersed resin having excellent stability over time, good pigment dispersibility, and high corrosion resistance.

Claims (4)

[Claims] 1. The formula: [Wherein Ep is a residue of an epoxy resin having an epoxy equivalent of 150 to 2000, and R ¹ is hydroxymethyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl or 2, Is a 3-dihydroxypropyl group, A ^- is a counter anion, and m is 0.1-4.
It is a number of 0. ] A pigment dispersion resin for electrodeposition paint represented by 2. An epoxy resin having an epoxy equivalent of 150 to 2000 and a formula R ¹ SCH ₂ CH (OH) CH ₂ OH, wherein R ¹ has the same meaning as above. ] The pigment-dispersed resin for electrodeposition coating composition according to claim 1, which is obtained by reacting with a sulfide represented by the above formula in the presence of an acid. 3. The pigment dispersion resin for electrodeposition coating composition according to claim 1, which has a tertiary sulfonium value of 30 to 500. 4. A pigment-dispersed paste for electrodeposition paint, which contains the pigment-dispersed resin according to claim 1 in a ratio of 0.05 to 10 with respect to the weight of the pigment.