JP2009221408A - Cationic electrodeposition coating composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationic electrodeposition coating composition which exhibits excellent film smoothness without lowering coating film quality and coating work efficiency. <P>SOLUTION: The cationic electrodeposition coating composition comprises (A) a cationic amine-modified epoxy resin (base resin) obtained by cationizing an amine-modified epoxy resin obtained by reacting an epoxy resin, obtained by bringing glycidyl ether of a polyol, glycidyl ether of a dihydric phenol, and a dihydric phenol into a reaction with an amine, (B) a blocked polyisocyanate (curing agent), and (C) an extender pigment having an average primary particle size of 0.01-1 μm, wherein D50 and D90 as indices of its particle size distribution are 110-140% and 210-240% of the average primary particle size, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cationic electrodeposition coating composition that exhibits excellent coating film smoothness.

  Electrodeposition coating has better throwing power and less environmental pollution compared to air spray coating and electrostatic spray coating for automobile body and its parts, and parts with a bag structure such as electric appliances. Therefore, it is widely used as a primer coating. For the purpose of improving the finish of the process coating film, resin-like and pigment-like technical techniques have been introduced in order to improve the smoothness of the electrodeposition coating film.

  Representative technical techniques for improving smoothness include adjustment of the molecular weight and Tg of the base resin, adjustment of the particle diameter of the emulsion, adjustment of the pigment amount (P / B) in the coating film, etc. It is put into practical use with each technology.

  Cationic electrodeposition coating compositions incorporating these technical techniques include electrodeposition coating compositions in which the molecular weight, Tg, and emulsified particle diameter of the resin are adjusted (see Patent Document 1 and Patent Document 2), and pigments in the coating film. The composition (refer patent document 3) which adjusted the quantity can be mentioned. However, these technologies are based on conventional standard cationic electrodeposition coating compositions in terms of chemical properties (rust prevention quality, chemical resistance), physical properties (impact resistance, coating strength), and coating workability. There is a problem that sufficient results cannot be obtained.

Also, taking into account the circumstances of the recent work, the smoothness of the surface has changed greatly, and it does not depend on the degree of smoothness of the work, and always exceeds a certain level. There is an increasing demand for smoothness to be achieved, but these techniques are insufficient.
JP-A-8-3488 JP 2004-307773 A Japanese Patent Laid-Open No. 10-43674

  The present invention was devised in view of the problems of the prior art, and the object thereof is not accompanied by a decrease in coating film quality and painting workability as compared with conventional standard cationic electrodeposition coating compositions. And it is providing the novel cationic electrodeposition coating composition which exhibits the coating surface smoothness superior to the conventional thing even when the smoothness of to-be-coated material is impaired.

  As a result of diligent investigations to achieve the above object, the present inventor has selected an extender pigment having a small average particle size and a narrow particle size distribution, and a base resin to be combined with the glycidyl ether of polyol and 2 Using a cationic amine-modified epoxy resin obtained from an epoxy resin obtained by reacting a glycidyl ether of a monohydric phenol with a dihydric phenol, excellent surface smoothness is achieved without deteriorating the coating quality and coating workability. As a result, the present invention has been completed.

  That is, the present invention provides (A) a cation obtained by cationizing an amine-modified epoxy resin obtained by reacting an amine with an epoxy resin obtained by reacting a glycidyl ether of a polyol, a glycidyl ether of a dihydric phenol and a dihydric phenol. Amine-modified epoxy resin (base resin), (B) blocked polyisocyanate (curing agent), and (C) the average primary particle diameter is 0.01 to 1 μm, preferably 0.01 to 0.5 μm, A cationic electrodeposition coating composition comprising an extender pigment having D50 as an index of particle size distribution of 110 to 140% of an average primary particle diameter and D90 of 210 to 240%.

  According to the cationic electrodeposition coating composition of the present invention, the conventional standard cationic electrodeposition is possible even in a state where the surface smoothness of the object to be coated is poor without deteriorating the coating film quality and the coating workability. Surface smoothness superior to that of the coating composition is achieved. Therefore, the cationic electrodeposition coating composition of the present invention is extremely useful for electrodeposition coating of automobile bodies, parts thereof, electric appliances and the like.

  The present invention includes (A) a specific cationic amine-modified epoxy resin (base resin), (B) a blocked polyisocyanate (curing agent), and (C) an extender pigment having a specific average primary particle size and particle size distribution. A cationic electrodeposition coating composition comprising

  The (A) cationic amine-modified epoxy resin (base resin) of the present invention is obtained by reacting an amine with an epoxy resin obtained by reacting a glycidyl ether of a polyol, a glycidyl ether of a dihydric phenol and a dihydric phenol. It is obtained by cationizing the amine-modified epoxy resin obtained. As an epoxy equivalent of an epoxy resin, 300-5000 are preferable, Most preferably, it is 400-2000.

  The (A) cationic amine-modified epoxy resin (base resin) of the present invention comprises a dihydric phenol moiety that imparts appropriate hardness to the molecular chain, and a polyol moiety that imparts appropriate flexibility to the molecular chain. Since it is shared, the effect of the coated surface smoothness of the (C) extender pigment of the present invention can be sufficiently manifested. When the cationic amine-modified epoxy resin is composed only of glycidyl ether of polyol, the smoothness of the coating film is ensured to some extent, but a problem is caused in the rust prevention quality. Moreover, when comprised only with the glycidyl ether of a bihydric phenol, the smoothness of a coating film is not ensured but a malfunction arises also in a physical property.

  Examples of the glycidyl ether of the polyol include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, diethylene glycol diglycidyl ether, triethylene glycol diglycidyl ether, 1 , 4-cyclohexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polytetramethylene glycol diglycidyl ether, or a mixture thereof.

  Examples of the divalent phenol glycidyl ether include resorcin diglycidyl ether, hydroquinone diglycidyl ether, bisphenol A diglycidyl ether, 4,4'-dihydroxybenzophenone diglycidyl ether, 1,1-bis- (4-hydroxyphenyl). ) -Methane diglycidyl ether, 4,4′-dihydroxybiphenyl diglycidyl ether, or a mixture thereof.

  Examples of the dihydric phenol include resorcin, hydroquinone, bisphenol A, 4,4′-dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl) -methane, 1,1- (2,4′-dihydroxy. Phenyl) -methane, 1,1-bis- (4-hydroxyphenyl) -ethane, 4,4′-dihydroxybiphenyl, and the like, or a mixture thereof.

  As amines to be reacted with the epoxy resin, methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, diethylamine, diethanolamine, N-methylethanolamine, N-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine , Ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine and the like, or a mixture thereof. In the reaction between the epoxy resin and the amine, the primary amino group may be blocked by reacting with a ketone in advance, and then the remaining active hydrogen may be reacted with the epoxy group.

  The reaction of the diglycidyl ether of polyol, the diglycidyl ether of dihydric phenol and the dihydric phenol can be carried out in a melt without a solvent, but can also be carried out in a system to which a small amount of solvent is added. The solvent used for the reaction is not particularly limited as long as it does not react with the epoxy group. The reaction temperature is suitably 70 to 180 ° C. The amination in which an amine is reacted with an epoxy resin can be carried out in a solvent or in a melt without a solvent, and the reaction temperature is suitably 40 to 150 ° C.

  The cationization of the amine-modified epoxy resin can be performed by neutralizing the amino group with a proton acid. Preferred examples of the protonic acid include formic acid, lactic acid, acetic acid, propionic acid, citric acid, malic acid, sulfamic acid, and the like, or a mixture thereof.

  The (B) blocked polyisocyanate (curing agent) of the present invention is a reaction product of a polyisocyanate and a blocking agent. The polyisocyanate is an aromatic or aliphatic (including alicyclic) polyisocyanate, such as 2,4- or 2,6-tolylene diisocyanate and a mixture thereof, p-phenylene diisocyanate, diphenylmethane-4,4 ′. -Diisocyanate, polymethylene polyphenyl diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 1,3 or 1,4-bis- (isocyanate methyl) -cyclohexane, dicyclohexylmethane-4,4'-diisocyanate, bis- ( Isocyanatomethyl) -norbornane, 3 or 4-isocyanatomethyl-1-methylcyclohexyl isocyanate, m- or p-xylylene diisocyanate, m- or - tetramethylxylylene diisocyanate, more may be mentioned biuret modified product of the isocyanate or isocyanurate modified products and the like.

  Furthermore, some of the isocyanate groups of the isocyanate are ethylene glycol, propylene glycol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, 1,4-cyclohexanediol and other low molecular diols, polyethylene glycol, Examples thereof include oligomeric diols such as polypropylene glycol, polytetramethylene glycol and polylactone diol, polyisocyanates linked by polyols such as trimethylolethane, trimethylolpropane and pentaerythritol, or mixtures thereof.

  Examples of the blocking agent include aliphatic alcohol compounds such as methanol, ethanol, n-butanol and 2-ethylhexanol, cellosolve compounds such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether. Carbitol compounds, acetone oximes, oxime compounds such as methyl ethyl ketone oxime, cyclohexanone oxime, lactam compounds such as ε-caprolactam, phenol compounds such as phenol, cresol and xylenol, active methylene such as ethyl acetoacetate and diethyl malonate Group-containing compounds can be mentioned.

  The reaction between the polyisocyanate and the blocking agent can be carried out in a solvent or in a melt. Solvents used for the reaction include solvents that do not react with polyisocyanates, such as ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexane, and isophorone, and aromatics such as benzene, toluene, xylene, chlorobenzene, and nitrobenzene. Examples thereof include hydrocarbons, cyclic ethers such as tetrahydrofuran, and halogenated hydrocarbons such as chloroform. Although there is no limitation in particular about reaction temperature, Preferably it is 30-150 degreeC.

  The extender pigment (C) of the present invention is used mainly for the purpose of reinforcing and increasing the coating film, and is a pigment having a relatively low refractive index. As the extender pigment (C) of the present invention, special grades of hydrous aluminum silicate such as kaolin, clay, porcelain clay, and China clay, hydrous magnesium silicate such as talc, and barium sulfate such as precipitated barium can be used. Hydrous aluminum silicate and barium sulfate are preferable, and in particular, Silicolloid P87, Siritin Z86 Puriss manufactured by Hoffman Minerals, BLANC FIX # 100, BARIFINE BF-30 series manufactured by Sakai Chemical Industry Co., Ltd. are preferable.

  The (C) extender pigment of the present invention has an average primary particle diameter of 0.01 to 1 μm, and D50 as an index of the particle size distribution is 110 to 140% of the average primary particle diameter, and D90 is 210 to 240%. It is necessary to be. Here, D50 and D90 respectively represent 50% and 90% cumulative particle size distribution from the smaller particle size in the particle size distribution measurement, and the smaller the number, the smaller the particle size. This means that the distribution width is small. The general kaolin used in the conventional standard cationic electrodeposition coating composition has D50 = 1.2 μm and D90 = 3.8 μm with respect to an average primary particle diameter of 0.4 μm. I can not use it. On the other hand, silica colloid P87, which is an extender that can be used in the present invention, has an average primary particle size of 0.5 μm, D50 = 0.6 μm, and D90 = 1.1 μm, and BARIFINE BF-30 has an average primary particle size of 0.3 μm. D50 = 0.4 μm and D90 = 0.7 μm. When general kaolin with a large particle size distribution width is used, the difference between the maximum and minimum primary particle sizes becomes large even if the average primary particle size is the same. As a result, a coating film with good smoothness cannot be obtained. By using the extender having a narrow particle size distribution width defined in the present invention, a coating film having excellent smoothness can be obtained even when the surface smoothness of the article to be coated is poor.

  The content of (C) extender pigment used in the cationic electrodeposition coating composition of the present invention is similar to that of the prior art, and (C) extender pigment / resin ((A) base resin + (B) curing agent) The weight ratio is generally 5 to 20%. (C) In order to sufficiently exhibit the effect of the extender pigment, the weight ratio is preferably selected in the range of 8 to 15%. As a result, the effects of both the components (C) extender pigment and (A) base resin can be exhibited synergistically. As a result, the coating film is superior to the conventional standard cationic electrodeposition coating composition. Performance and coating workability are ensured, and the smoothness of the electrodeposited surface that cannot be obtained by the conventional method can be achieved regardless of the level of smoothness of the object to be coated. This is a feature of the present invention and cannot be achieved in other prior art.

  The content ratio of (A) cationic amine-modified epoxy resin (base resin) and (B) blocked polyisocyanate (curing agent) is 90 to 40/10 to 60 in terms of solid content, preferably 85 to 85. It is 40 / 15-60, More preferably, it is 80-55 / 20-45. Further, a part of the component (A) can be blended in place of a resin obtained by cationizing a normal amine-modified epoxy resin other than the component (A), but the amount thereof is 30% by weight with respect to the component (A). % Or less is preferable.

  In addition to the components (A), (B) and (C) described above, the cationic electrodeposition coating composition of the present invention may further contain conventional coating additives such as titanium white, carbon black, bengara, etc. Color pigments, zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate, bismuth compounds Additives such as foaming agents and repellency inhibitors, aqueous solvents, curing catalysts, and the like can be included. Further, other resins such as an acrylic resin, a polyester resin, a urethane resin, and a butadiene resin can be contained.

  The cationic electrodeposition coating composition of the present invention can be usually applied to the surface of a desired substrate by a known cationic electrodeposition coating method in a state dispersed in water. Specifically, the solid content concentration of the paint is preferably about 5 to 40% by weight, more preferably 15 to 25% by weight, the pH is adjusted to 5 to 8, the bath temperature is 15 to 35 ° C., and the load voltage is 100. Under the condition of ~ 450V, the object to be coated can be applied as a cathode. After the coating of the coating object, the cured coating film can be obtained by washing the coating object with water and baking at 100 to 200 ° C. for 10 to 30 minutes in a baking oven. Although there is no restriction | limiting in particular in the film thickness of the coating film obtained from the cationic electrodeposition coating composition of this invention, 5-60 micrometers in a cured coating film, Preferably 10-40 micrometers is suitable.

  The excellent effects of the cationic electrodeposition coating composition of the present invention are shown by the following examples, but the present invention is not limited thereto.

(Manufacture of base resin A1)
Base resin A1 was manufactured by the method shown below using the raw materials shown in Table 1. Raw materials (1), (2), (3), and (4) were charged into a 5-liter four-necked flask equipped with a stirrer, thermometer, and cooling tube, and the temperature was raised to 150 ° C. by stirring and heating. . After holding at 150 ° C. for 6 hours, the raw material (5) was gradually added and cooled to 80 ° C. Next, the raw material (6) was charged and the temperature was raised to 100 ° C. After maintaining at 100 ° C. for 2 hours, the base resin A1 was taken out by cooling to 80 ° C. The obtained base resin A1 had a solid content of 70%.

(Manufacture of base resin A2)
Base resin A2 was manufactured by the method shown below using the raw materials shown in Table 2. Raw materials (1), (2), (3), and (4) were charged into a 5-liter four-necked flask equipped with a stirrer, thermometer, and cooling tube, and the temperature was raised to 150 ° C. by stirring and heating. . After holding at 150 ° C. for 6 hours, the raw material (5) was gradually added and cooled to 80 ° C. Next, the raw material (6) was charged and the temperature was raised to 100 ° C. After maintaining at 100 ° C. for 2 hours, the base resin A2 was taken out by cooling to 80 ° C. The obtained base resin A2 had a solid content of 70%.

(Manufacture of base resin A3)
Base resin A3 was manufactured by the method shown below using the raw materials shown in Table 3. Raw materials (1), (2), and (3) were charged into a 5-liter four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, and the temperature was raised to 100 ° C. by stirring and heating. After holding at 100 ° C. for 1 hour, it was cooled to 80 ° C. Next, the raw materials (4) and (5) were added and the temperature was raised to 100 ° C. After maintaining at 100 ° C. for 2 hours, the base resin A3 was taken out by cooling to 80 ° C. The obtained base resin A3 had a solid content of 70%.

(Manufacture of base resin A4)
Using the raw materials shown in Table 4, a comparative base resin A4 was produced by the method shown below. The raw material (1) was charged into a 5 liter four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, and the temperature was raised to 80 ° C. by stirring and heating. Next, the raw materials (2) and (3) were added and the temperature was raised to 100 ° C. After maintaining at 100 ° C. for 2 hours, the base resin A4 was taken out by cooling to 80 ° C. The obtained base resin A4 had a solid content of 100%.

(Production of curing agent B)
Using the raw materials shown in Table 5, a curing agent B was produced by the method shown below. Raw materials (1) and (2) were charged into a 5 liter four-necked flask equipped with a stirrer, a thermometer, and a cooling tube, and the temperature was raised to 100 ° C. by stirring and heating. Thereafter, a solution of the raw material (4) previously dissolved in the raw material (3) was charged over 1 hour while keeping the temperature in the flask at 100 ° C., and reacted at 100 ° C. for 2 hours. Next, the raw material (5) was added dropwise over 1 hour while maintaining the same temperature. After the addition, the raw material (5) was further maintained at 100 ° C. for 2 hours, and then cooled to 80 ° C. to take out the curing agent B. The obtained curing agent B had a solid content of 75%.

Examples 1-4, Comparative Examples 1-4
With the formulation shown in Table 6, the mixture of the base resin and the curing agent was charged into a mixed solution of diethylene glycol monobutyl ether, formic acid, and deionized water with good stirring to obtain each resin aqueous dispersion. Next, base resin, formic acid, deionized water, carbon black, titanium oxide, extender pigment (BF-30 (manufactured by Sakai Chemical Industry Co., Ltd .: barium sulfate), silicocolloid P87 (Hoffman Mineral Co., Ltd.) with the formulation shown in Table 6 Manufactured by Kaolin) or ASP-200 (manufactured by ENGELHARD: Kaolin)), dibutyltin oxide and bismuth hydroxide are sufficiently stirred with a dissolver, and then dispersed with a horizontal sand mill until the particle gauge particle size is 10 μm or less. Got. BF-30 used at this time has an average primary particle size = 0.3 μm, D50 = 0.4 μm, D90 = 0.7 μm, and Siricolloid P87 has an average primary particle size = 0.5 μm, D50 = 0.6 μm, D90 = 1.1 μm, ASP-200 had an average primary particle size = 0.4 μm, D50 = 1.2 μm, D90 = 3.8 μm. These resin water dispersions and pigment pastes were mixed in the weight ratios shown in Table 6 to obtain cationic electrodeposition paints of Examples 1 to 4 and Comparative Examples 1 to 4.

  Using the cationic electrodeposition paint obtained above, a carbon electrode as an anode, a degreased cold-rolled steel sheet (Partec, 0.8 × 70 × 150 mm, no chemical conversion treatment) as a cathode, and a film after baking Electrodeposition coating was performed under the condition that the thickness was 20 μm, and baking was performed at 170 ° C. for 20 minutes to obtain test plates.

The following performance evaluations (1) to (5) were performed on the electrodeposited test plate.
(1) Surface roughness (Ra): Measured with a Mitutoyo surface roughness meter (cutoff = 2.5 mm). The larger the Ra number, the greater the surface roughness of the coating film.
(2) Solvent resistance: The coating film was wiped with a mixed solution of ethanol / acetone (weight ratio 1/1).
(3) Salt spray resistance: Performed according to JIS-Z-2731. A scratch reaching the substrate was put on the electrodeposited surface with a cutter knife, and the rust width after 480 hours was evaluated. A sample having a rust width of less than 3 mm was marked with ◯, and a sample having a rust width of more than 3 mm was marked with ×.
(4) Salt water immersion test: After immersing the coated test plate in 50%, 5% saline for 480 hours, washing with water and air-drying, and pasting the cellophane adhesive tape on the entire test surface so as not to contain air bubbles, The tape was peeled off, and the ratio (%) of the coating film peeling area to the entire test surface was measured. A case where the ratio of the peeled area was less than 5% was evaluated as ◯, and a case where the ratio was more than that was evaluated as △.
(5) Impact resistance: Measured with a DuPont impact tester (500 g × 50 cm). The case where cracks were not generated in the coating film at 500 g × 50 cm was indicated as “◯”, and the case where cracks were generated was indicated as “Δ”.

Further, the following workability evaluations (6) to (10) were performed on the cationic electrodeposition paint.
(6) Repellency sensitivity: Machine oil / water = 1/9 was placed in an aluminum cup on a wet film and baked under standard conditions, and judged by the number and shape of repelling. ◯ if there are less than 5 shallow replies, △ if there are less than 5 deep replies or less than 5 or less shallow replies, △, if there are 5 or more deep replies or more than 20 shallow replies X.
(7) Contamination trace property: A solution obtained by spot-drying a diluted zinc phosphate treatment solution on a chemical conversion treatment plate is applied as an object to be coated. The thing was made into (triangle | delta).
(8) Finishing property of the horizontal part: The test panel deformed into an L shape was left in the electrodeposition bath solution for 3 minutes without stirring and then energized with the start of stirring. When the gloss ratio of the part to the vertical part is 95% or more, the result is ◯, and when the gloss ratio is 80% or more, the result is △.
(9) Chemical conversion sensitivity: The surface of the zinc phosphate-treated plate half polished with # 400 sandpaper is painted, and the one with no difference in film thickness and appearance between the polished part and the unpolished part is marked with ○. Those with a difference are indicated as Δ.
(10) Drying unevenness: After standard electrodeposition coating, the sample was left for 5 minutes in anhydrous washing, washed with water and baked.

The evaluation results of the cationic electrodeposition paints of Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 7 below.

  From the evaluation results of Table 7, the cationic electrodeposition paints (Examples 1 to 4) of the present invention are conventional standard cationic electrodepositions in terms of coating surface smoothness (surface roughness) and horizontal part finish. It is clear that it is superior to the paint (Comparative Examples 1 to 4).

  The cationic electrodeposition coating composition of the present invention exhibits excellent throwing power, and in a state where the surface smoothness of the object to be coated, which has been a problem, is poor without deteriorating the coating film quality and coating workability. In addition, since smoothness of the coating film superior to the conventional standard cationic electrodeposition coating method is achieved, it is useful for electrodeposition coating of a member having a bag structure such as an automobile body and its parts and an electric appliance. .

Claims (2)

  (A) Cationic amine-modified epoxy resin obtained by cationizing an amine-modified epoxy resin obtained by reacting an amine with an epoxy resin obtained by reacting glycidyl ether of polyol, glycidyl ether of dihydric phenol and dihydric phenol ( Base resin), (B) blocked polyisocyanate (curing agent), and (C) an average primary particle diameter of 0.01 to 1 μm, and D50 as an index of the particle size distribution is 110 of the average primary particle diameter. A cationic electrodeposition coating composition comprising an extender having ˜140% and D90 of 210˜240%.   The cationic electrodeposition coating composition according to claim 1, wherein the extender has an average primary particle size of 0.01 to 0.5 µm.