JP2010037481A - Cationic electrodeposition paint composition and cationic electrodeposition coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cationic electrodeposition paint composition capable of giving a cured electrodeposition film having good film appearance when an object to be coated, which has been treated with an environmentally-friendly chemical conversion treating agent or an untreated object to be coated is subjected to electrodeposition coating. <P>SOLUTION: The cationic electrodeposition paint composition is used for electrodeposition coating of an object to be coated, which has been treated with a zirconium-based chemical conversion treating agent or an untreated object to be coated. The cationic electrodeposition paint composition contains at least a cationic epoxy resin, a blocked isocyanate curing agent and a conductivity control agent and has a paint solid concentration of 0.5-9.0 mass%. The resin component contained in the cationic electrodeposition paint composition has an SP value of ≤11.7. An electrodeposition film obtained from the cationic electrodeposition paint composition has a film viscosity at 50°C of ≤3,000 Pa s. The time required for resistance formation is within 12 s. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a cured electrodeposition coating film having a good coating film appearance in the case of electrodeposition coating on an object to be coated or an untreated object that has been treated with a chemical conversion treatment agent having a low environmental impact. The present invention relates to a cationic electrodeposition coating composition and a cationic electrodeposition coating method.

  When the electrodeposition coating is performed, a chemical conversion treatment is usually applied to the article to be coated in order to improve the corrosion resistance and the coating film adhesion. As a chemical conversion treatment agent, there is one containing zinc phosphate (for example, JP-A-10-204649 (Patent Document 1)).

  However, since the zinc phosphate chemical conversion treatment agent is a highly reactive treatment agent having a high metal ion and acid concentration, there is a disadvantage that the economical efficiency and workability in wastewater treatment are inferior. Moreover, when performing metal surface treatment using a zinc phosphate chemical conversion treatment agent, salts that are insoluble in water are generated and precipitated as precipitates. In the case of using a zinc phosphate-based chemical conversion treatment agent, it is costly to remove this precipitate (sludge) generated in the coating process.

Japanese Patent Laid-Open No. 10-204649 JP-A-7-310189

  As a treatment agent other than the zinc phosphate-based chemical conversion treatment agent, a metal surface treatment agent made of, for example, a zirconium compound is known (for example, JP-A-7-310189 (Patent Document 2)). By using a metal surface treatment agent comprising a zirconium compound, there is an advantage that the amount of sludge can be remarkably reduced.

  On the other hand, even when electrodeposition coating is applied to an untreated object as it is, if there is a means capable of obtaining a cured electrodeposition coating film having a good coating film appearance, the coating process can be shortened. Therefore, it is considered more preferable.

  The present invention solves the above-mentioned conventional problems, and the object of the present invention is when electrodeposition coating is performed on an object to be coated or an untreated object that has been treated with a chemical conversion treatment agent containing zirconium ions. The object of the present invention is to provide a cationic electrodeposition coating composition capable of obtaining a cured electrodeposition coating film having a good coating film appearance.

The present invention
A cationic electrodeposition coating composition used for electrodeposition coating of a coating treated with a chemical conversion treatment agent containing zirconium ions or an untreated coating,
This cationic electrodeposition coating composition contains at least a conductivity control agent comprising a cationic epoxy resin, a blocked isocyanate curing agent, and an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g. A cationic electrodeposition coating composition of 0.5 to 9.0% by mass,
The SP value of the resin component contained in this cationic electrodeposition coating composition is 11.7 or less,
The electrodeposition coating obtained from this cationic electrodeposition coating composition has a coating film viscosity at 50 ° C. of 3000 Pa · s or less, and in electrodeposition coating under a predetermined condition using this cationic electrodeposition coating composition, The time from the start of voltage application until the coating resistance value of the deposited electrodeposition coating film reaches 30 kΩ · cm ² is within 12 seconds, and this predetermined condition is determined by applying voltage for 180 seconds at a coating temperature of 30 ° C. It is a condition for forming a coating film having a dry film thickness of 15 μm.
A cationic electrodeposition coating composition is provided, whereby the above object is achieved.

  More preferably, the cationic electrodeposition coating composition further comprises a non-crosslinked acrylic resin having a solubility parameter of 10.4 to 11.0, a glass transition temperature of 20 to 80 ° C. and a number average molecular weight of 2500 to 3500. .

  The blocked isocyanate curing agent is more preferably a blocked isocyanate obtained by blocking an aromatic diisocyanate or an aromatic polyisocyanate.

The present invention further includes
A cationic electrodeposition coating method for forming an electrodeposition coating on an object to be coated or an untreated object treated with a chemical conversion treatment agent containing zirconium ions,
This cationic electrodeposition coating composition is the above cationic electrodeposition coating composition,
In electrodeposition coating under a predetermined condition at a coating temperature of 30 ° C., the time from the start of voltage application until the coating resistance value of the deposited electrodeposition coating reaches 30 kΩ · cm ² is within 12 seconds. The predetermined condition is a condition in which a coating film having a dry film thickness of 15 μm is formed by applying a voltage for 180 seconds at a coating temperature of 30 ° C.,
A cationic electrodeposition coating method is also provided.

  In the present specification, an uncured electrodeposition coating film before baking and curing is referred to as an “electrodeposition coating film”, and a coating film after baking and curing is referred to as a “cured electrodeposition coating film”.

  The cationic electrodeposition coating composition of the present invention has a coating solid content concentration as low as 0.5 to 9.0% by mass, so that there is little sedimentation of the pigment or resin component, and the energy during electrodeposition coating is effectively reduced. In addition, it has excellent water washability after electrodeposition coating. The cationic electrodeposition coating composition of the present invention also has good throwing power despite the low coating solids concentration. The cationic electrodeposition coating composition of the present invention is electrodeposited on a coating having a thin chemical conversion treatment film formed by a zirconium-based chemical conversion treatment agent, or an untreated coating that has not been subjected to chemical conversion treatment. Even in the case of painting, it has a feature that a cured electrodeposition coating film having a good coating film appearance can be obtained in the same manner as in the case of painting on an object treated with a zinc phosphate chemical conversion treatment agent. .

Cationic electrodeposition coating composition The cationic electrodeposition coating composition of the present invention comprises an aqueous solvent, a cationic epoxy resin dispersed in or dissolved in an aqueous solvent, a blocked isocyanate curing agent, and an uncrosslinked acrylic resin as required. Contains binder resin, conductivity control agent, neutralizing acid, organic solvent, and optionally pigment.

In the cationic electrodeposition coating composition, the conductivity control agent “conductivity control agent” is an emulsion separate from the binder resin and pigment containing a cationic epoxy resin and a blocked isocyanate curing agent, which are coating film forming components. Existing. Therefore, this conductivity control agent functions as a third component other than the binder resin and the pigment. The conductivity control agent is composed of an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g. The conductivity control agent may be any amino group-containing material as long as the amine value has the above range, but is usually preferably an amine-modified epoxy resin or an amine-modified acrylic resin. Moreover, the electrical conductivity control agent of this invention may be neutralized with the acid as needed. The amine value is preferably 250 to 450 mmol / 100 g, and most preferably 300 to 400 mmol / 100 g. If the amine value is smaller than 200 mmol / 100 g, the amount required to adjust the electric conductivity of the cationic electrodeposition coating composition having a low solid content concentration to an optimum value increases, which may impair the corrosion resistance. Moreover, when it exceeds 500 mmol / 100g, there exists a fault that precipitation property falls and desired throwing power cannot be obtained. In addition, the suitability of the galvanized steel sheet also decreases.

  The amino group-containing compound may be a low-molecular compound or a high-molecular compound, and usually includes a high-molecular-weight amino group-containing compound such as an amine-modified epoxy resin or an amine-modified acrylic resin. Examples of the low molecular weight amino group-containing compound include monoethanolamine, diethanolamine, and dimethylbutylamine.

  In the present invention, high molecular weight amino group-containing compounds, particularly amine-modified epoxy resins and amine-modified acrylic resins are preferred. The amine-modified epoxy resin can be obtained by modifying an epoxy group of an epoxy resin with an amine compound. A general epoxy resin can be used, but it is a bisphenol type epoxy resin, a t-butylcatechol type epoxy resin, a phenol novolac type epoxy resin, or a cresol novolac type epoxy resin, and has a number average molecular weight of 500 to 20000. Those are preferred. Of these epoxy resins, phenol novolac resins and cresol novolac resins are most desirable. These phenol novolac resins and cresol novolac resins are commercially available. Examples thereof include phenol novolac resin DEN-438 manufactured by Dow Chemical Japan, and cresol novolak resin YDCN-703 manufactured by Tohto Kasei.

  These epoxy resins may be modified with resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. In addition, the epoxy resin can be chain-extended using a reaction between an epoxy group and a diol or dicarboxylic acid.

  As the amine-modified acrylic resin, for example, a homopolymer of dimethylaminoethyl methacrylate which is an amino group-containing monomer or a copolymer with another polymerizable monomer may be used as it is. Alternatively, it can be obtained by modifying a glycidyl group of a homopolymer of glycidyl methacrylate or a copolymer with another polymerizable monomer with an amine compound.

  Examples of the compound that introduces an amino group into an epoxy resin or an acrylic resin containing an epoxy group include primary amines, secondary amines, and tertiary amines. Specific examples thereof include butylamine, octylamine, diethylamine, butylamine, dimethylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, diethyl disulfide, In addition to acetic acid mixtures, secondary amines blocked with primary amines such as diketimines of aminoethylethanolamine and diketimines of diethylhydroamine can be mentioned. A plurality of amines may be used.

  As described above, the number average molecular weight of these amine-modified epoxy resin and amine-modified acrylic resin is preferably 500 to 20000. If the number average molecular weight is less than 500, corrosion resistance may be impaired, and although the reason is not clear, a decrease in throwing power and a decrease in suitability for galvanized steel sheets are observed. If the number average molecular weight is larger than 20000, the finished appearance may be deteriorated. In the present specification, the number average molecular weight can be calculated from the measurement result of gel permeation chromatography (GPC) using polystyrene as a standard.

  These amine-modified epoxy resins and amine-modified acrylic resins can be used after neutralizing with a neutralizing acid in advance. Acids used for neutralization are inorganic acids or organic acids such as hydrochloric acid, nitric acid, phosphoric acid, sulfamic acid, formic acid, acetic acid and lactic acid.

  The cationic electrodeposition coating composition contains a conductivity control agent, so that the coating solid content concentration is 0.5 to 9.0% by mass, which is excellent even though it is a low solid content type cationic electrodeposition coating composition. The throwing power can be secured. By using the conductivity control agent, the conductivity can be controlled to an appropriate value, and as a result, sufficient throwing power can be ensured. Further, since the cationic electrodeposition coating composition is of a low solid content type, it has a feature that there are few precipitates even when it is allowed to stand for a long time. Further, the water washing usually performed after the electrodeposition coating can be performed more easily, which has the advantage that the occurrence of secondary sagging can be prevented.

Cationic epoxy resin (cationic epoxy resin as a film-forming component)
Examples of the cationic epoxy resin as the coating film-forming component include amine-modified epoxy resins. As the amine-modified epoxy resin, an amine-modified epoxy resin generally used in an electrodeposition coating composition can be used without particular limitation. As the amine-modified epoxy resin, an amine-modified epoxy resin known to those skilled in the art and a commercially available epoxy resin obtained by amine modification can be used.

  A preferred amine-modified epoxy resin is an amine-modified epoxy resin obtained by modifying an epoxy group in a resin skeleton of an epoxy resin with an organic amine compound. A typical example of the starting resin for the epoxy resin is a polyphenol polyglycidyl ether type epoxy resin which is a reaction product of a polycyclic phenol compound such as bisphenol A and epichlorohydrin.

  The following formula described in JP-A-5-306327

[Wherein R represents a residue excluding the glycidyloxy group of the diglycidyl epoxy compound, R ′ represents a residue excluding the isocyanate group of the diisocyanate compound, and n represents a positive integer. The oxazolidone ring-containing epoxy resin represented by the above formula may be used for the preparation of an amine-modified epoxy resin to prepare an amine-modified oxazolidone ring-containing epoxy resin. This is because a coating film excellent in heat resistance and corrosion resistance can be obtained. As a method for introducing an oxazolidone ring into an epoxy resin, for example, a blocked isocyanate curing agent blocked with a lower alcohol such as methanol and a polyepoxide are heated and kept in the presence of a basic catalyst, and a by-product lower alcohol is formed in the system. There is a method of further distilling off.

  These epoxy resins may be modified with suitable resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. In addition, the epoxy resin can be chain-extended using a reaction between an epoxy group and a diol or dicarboxylic acid.

  In addition, before the ring opening reaction of the epoxy group with amines, for the purpose of adjusting the molecular weight or amine equivalent, improving heat flow, etc., 2-ethylhexanol, nonylphenol, Monohydroxy compounds such as ethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono n-butyl ether, and propylene glycol mono-2-ethylhexyl ether can also be added and used.

  Examples of amines that can be used to open an epoxy group of an epoxy resin and introduce an amino group include primary amines such as butylamine and N, N-dimethylbenzylamine, secondary amines, and tertiary amines. Mention may be made of amines and / or their acid salts. Further, ketimine block primary amino group-containing secondary amine such as aminoethylethanolamine methyl isobutyl ketimine, diethylenetriamine diketimine can also be used. These amines must be reacted with at least an equivalent amount with respect to the epoxy group in order to open all the epoxy groups.

  The number average molecular weight of the amine-modified epoxy resin is preferably in the range of 1500 to 5000, and more preferably in the range of 1600 to 3000. By setting the number average molecular weight to 1500 or more, good solvent resistance and corrosion resistance can be obtained when a cured coating film is formed. Moreover, the viscosity of a resin solution can be controlled to an appropriate range by making a number average molecular weight into 5000 or less.

  The amine-modified epoxy resin is preferably molecularly designed so that the amine value is in the range of 50 to 200 mmol / 100 g. If the amine value is less than 50 mmol / 100 g, the emulsification dispersion failure in the aqueous medium due to the acid treatment described in detail below may be caused. On the other hand, when it exceeds 200 mmol / 100 g, an excess amino group remains in the coating film after curing, and as a result, the water resistance may decrease.

The blocked isocyanate curing agent cationic electrodeposition coating composition contains a blocked isocyanate curing agent obtained by blocking polyisocyanate with a blocking agent. Here, the polyisocyanate means a compound having two or more isocyanate groups in one molecule. The polyisocyanate may be, for example, any of aliphatic, alicyclic, aromatic and aromatic-aliphatic.

  Specific examples of polyisocyanates include aromatic diisocyanates or aromatic polyisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), crude MDI, p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI) ), 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate, and the like; C3-C12 aliphatic diisocyanates; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′- Dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4′-diiso Anate, and 1,3-diisocyanatomethylcyclohexane (hydrogenated XDI), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (norbornane diisocyanate C5-C18 alicyclic diisocyanate such as xylylene diisocyanate (XDI) and aliphatic diisocyanate having an aromatic ring such as tetramethylxylylene diisocyanate (TMXDI); Modified diisocyanates (urethanes, carbodiimides, uretdiones, uretoimines, burettes and / or isocyanurates). These may be used alone or in combination of two or more.

  Adducts or prepolymers obtained by reacting polyisocyanates with polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropane, and hexanetriol at an NCO / OH ratio of 2 or more may also be used as the block isocyanate curing agent.

  Preferred specific examples of the aliphatic polyisocyanate or alicyclic polyisocyanate include hexamethylene diisocyanate, hydrogenated TDI, hydrogenated MDI, hydrogenated XDI, IPDI, norbornane diisocyanate, their dimer (biuret), and trimer. (Isocyanurate) etc. are mentioned.

  A blocked isocyanate curing agent is a compound in which a free isocyanate group of an isocyanate group terminal precursor is reacted with an active hydrogen group-containing compound (blocking agent) to make it inactive at room temperature. When heated, the blocking agent dissociates. The isocyanate group is regenerated.

  Examples of the blocking agent for the blocked isocyanate curing agent include aliphatic or heterocyclic alcohols such as 1-chloro-2-propanol, phenols such as phenol, oximes such as methyl ethyl ketone oxime, active methylene compounds such as acetylacetone, and ε- And aromatic alcohols such as caprolactam and ethers such as ethylene glycol monomethyl ether. These blocking agents may be used alone or in combination of two or more.

  In the present invention, it is more preferable to use a blocked isocyanate obtained by blocking an aromatic diisocyanate or an aromatic polyisocyanate as the blocked isocyanate curing agent. Although it depends on the type of the cationic epoxy resin, it is easy to adjust the SP value of the resin component contained in the electrodeposition coating composition to 11.7 or less by using such a blocked isocyanate curing agent. Become. Thereby, even if the electrodeposition coating film is in an uncured state, the resin component in the electrodeposition coating film is fused. And the flow of excessive current in the coating film deposition part is suppressed, the occurrence of coating film abnormality such as gas pinholes is suppressed, and the coating film appearance of the obtained cured electrodeposition coating film becomes good. .

The non-crosslinked acrylic resin cationic electrodeposition coating composition may further contain a specific non-crosslinked acrylic resin. Here, “non-crosslinked acrylic resin” means a resin prepared without using a crosslinkable monomer that provides internal crosslinking, such as that used in the preparation of general crosslinked resin particles.

  The non-crosslinked acrylic resin has a solubility parameter of 10.4 to 11.0, a glass transition temperature of 20 to 80 ° C., and a number average molecular weight of 2500 to 3500, and all parameters of solubility parameter, glass transition temperature and number average molecular weight. It is required to be within the above range. The solubility parameter (also referred to as SP value) is a measure of solubility. The larger the value, the higher the polarity, and the smaller the value, the lower the polarity. When the solubility parameter of the non-crosslinked acrylic resin exceeds 11.0, it is difficult to adjust the SP value of the resin component contained in the cationic electrodeposition coating composition within a favorable range. Further, when the solubility parameter of the non-crosslinked acrylic resin is less than 10.4, it is difficult to use in the cationic electrodeposition coating composition because it has strong hydrophobicity and may cause repellency of the coating film.

The solubility parameters 10.4 to 11.0 of the non-crosslinked acrylic resin in the present invention are lower than those of the cation-modified acrylic resin contained in the conventional cationic electrodeposition coating composition. The solubility parameter of a general acrylic component of a cation-modified acrylic resin (such as an amino group-containing acrylic resin) contained in a conventional cationic electrodeposition coating composition is about 10.9 to 11.4. Since the non-crosslinked acrylic resin in the present invention is thus hydrophobic and has a low SP value, the SP value of the resin component contained in the cationic electrodeposition coating composition can be adjusted to a favorable range, thereby The time from the start of voltage application until the coating resistance value of the deposited electrodeposition coating reaches 30 kΩ · cm ² can be made within 12 seconds. That is, by including the non-crosslinked acrylic resin in the cationic electrodeposition coating composition, the coating film resistance value of the coating film deposited by the start of voltage application rises in a short time from the start of voltage application (coating film resistance value). The rise of is early.) And, since the rise of the coating resistance value is quick at the portion where the electrodeposition coating film is deposited, the excessive current flow at the coating deposition portion is suppressed, and the occurrence of coating film abnormality such as gas pinholes occurs. It is suppressed and the coating film appearance of the obtained cured electrodeposition coating film becomes good.

The solubility parameter can be measured by, for example, the following method [Reference: SUH, CLARKE, J. et al. P. S. A-1, 5, 1671-1681 (1967)].
Measurement temperature: 20 ° C
Sample: Weigh 0.5 g of resin in a 100 ml beaker, add 10 ml of good solvent using a whole pipette, and dissolve with a magnetic stirrer.
solvent:
Good solvent ... tetrahydrofuran poor solvent ... n-hexane, ion-exchanged water, etc. Muddy point measurement: The poor solvent is dropped using a 50 ml burette, and the point at which turbidity is produced is defined as the amount dropped.

  The solubility parameter δ of the resin is given by:

V _i : Molecular volume of solvent (ml / mol)
φ _i : Volume fraction of each solvent at cloud point δ _i : SP value of solvent ml: Low SP poor solvent mixed system mh: High SP poor solvent mixed system

  The number average molecular weight of the non-crosslinked acrylic resin can be calculated from the measurement result of gel permeation chromatography (GPC) using polystyrene as a standard. When the number average molecular weight of the non-crosslinked acrylic resin is less than 2500, the end face coverage is inferior, and when the number average molecular weight of the non-crosslinked acrylic resin exceeds 3,500, the coating film smoothness is inferior. Examples of the method for adjusting the number average molecular weight of the non-crosslinked acrylic resin in the range of 2500 to 3500 include a method of adjusting by controlling the synthesis temperature and a method of controlling by adjusting the blending amount of the radical generation initiator.

  The glass transition temperature of the non-crosslinked acrylic resin can be measured by detecting a thermal change accompanying the glass transition of the resin using a differential scanning calorimeter. Examples of the differential scanning calorimeter that can be used include DSC220C manufactured by Seiko Denshi Kogyo. When the glass transition temperature of the non-crosslinked acrylic resin is less than 20 ° C., the coating film smoothness is inferior. When the glass transition temperature of the non-crosslinked acrylic resin exceeds 80 ° C., the coating film smoothness and the end face coverage are inferior.

  As a method of adjusting the glass transition temperature of the non-crosslinked acrylic resin to a range of 20 to 80 ° C., for example, adjustment by any monomer combination can be mentioned.

  For the non-crosslinked acrylic resin in the present invention, for example, a hydroxyl group-containing ethylenically unsaturated monomer (i), an acidic group-containing ethylenically unsaturated monomer (ii), and other ethylenically unsaturated monomers (iii) are arbitrarily selected, It can be prepared by polymerization.

Examples of the hydroxyl group-containing ethylenically unsaturated monomer (i) include, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. , Polypropylene glycol mono (meth) acrylate, allyl alcohol, adducts of hydroxyethyl (meth) acrylate and ε-caprolactone, and the like.
Examples of acidic group-containing ethylenically unsaturated monomers (ii) include carboxylic acids such as (meth) acrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, fumaric acid, etc. Examples include acid group-containing ethylenically unsaturated monomers; sulfonic acid group-containing ethylenically unsaturated monomers such as t-butylacrylamidesulfonic acid.
Other ethylenically unsaturated monomers (iii) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n- (meth) acrylate Butyl, t-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, (Meth) acrylic acid alkyl esters such as tridecyl methacrylate;
An addition reaction product of an oil fatty acid and an acrylic acid or methacrylic acid ester monomer having an oxirane structure (for example, an addition reaction product of stearic acid and glycidyl methacrylate);
An addition reaction product of an oxirane compound containing C ₃ or more alkyl groups and acrylic acid or methacrylic acid;
Aryl group-containing ethylenically unsaturated monomers such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, benzyl (meth) acrylate, vinylpyridine;
Itaconic acid ester (dimethyl itaconate), maleic acid ester (such as dimethyl maleate), fumarate ester (such as dimethyl fumarate), etc .; in addition, acrylonitrile, methacrylonitrile, methyl isopropenyl ketone, vinyl acetate, veova monomer (shell) Chemical brand name, vinyl propionate, vinyl pivalate, vinyl propionate, ethylene, propylene, butadiene, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, acrylamide;
Etc.

When the non-crosslinked acrylic resin is produced, the amount of each monomer is 100% by mass as the total amount of monomers.
20-30% by mass of styrene,
15-50% by weight of isobutyl methacrylate,
5 to 40% by mass of ethyl hexyl acrylate,
Ethyl acrylate 0-40% by mass,
5-20% by weight of hydroxyethyl methacrylate,
It is more preferable that By producing a non-crosslinked acrylic resin using each monomer in the above mass range, the solubility parameter of the non-crosslinked acrylic resin can be suitably adjusted to a range of 10.4 to 11.0.

  The polymerization of the non-crosslinked acrylic resin can be performed by a conventional method such as a solution polymerization method, and is preferably performed, for example, in the presence of a radical polymerization initiator. Examples of the radical polymerization initiator include azo initiators such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, lauryl peroxide, Examples include t-butyl peroctoate. If necessary, a chain transfer agent such as dodecyl mercaptan or 2-ethylhexyl thioglycolate may be used. In general, the polymerization reaction is preferably performed in a temperature range of about 60 to 160 ° C. for about 1 to 15 hours.

  The non-crosslinked acrylic resin preferably has a hydroxyl value of 30 to 50 mgKOH / g. The non-crosslinked acrylic resin having a hydroxyl value of 30 to 50 mgKOH / g can be obtained by adjusting the amount of the hydroxyl group-containing ethylenically unsaturated monomer by a method well known to the equivalent person.

  When the non-crosslinked acrylic resin is used, the content of the non-crosslinked acrylic resin is preferably 1 to 15% by mass, and 8 to 12% by mass with respect to the resin solid content in the cationic electrodeposition coating composition. Is more preferable. If it is less than 1% by mass, it is difficult to control the SP value and viscosity by the non-crosslinked acrylic resin, and if it exceeds 15% by mass, the coating performance such as corrosion resistance may be deteriorated.

Pigment The electrodeposition coating composition used in the present invention may contain a commonly used pigment. Examples of pigments that can be used include commonly used pigments such as colored pigments such as titanium white, carbon black and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; phosphorus Zinc oxide, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and aluminum phosphomolybdate, aluminum phosphomolybdate Examples thereof include rust preventive pigments such as zinc, bismuth hydroxide, bismuth oxide, basic bismuth carbonate, bismuth nitrate, bismuth benzoate, bismuth citrate, and bismuth silicate.

  In the cationic electrodeposition coating composition of the present invention, the pigment is added to the electrodeposition coating composition in an amount of 2 to 7% by mass, preferably 3 to 5% by mass, based on the total solid content of the electrodeposition coating composition. Contained.

Pigment-dispersed paste When a pigment is used as a component of an electrodeposition coating composition, the pigment is generally dispersed in an aqueous medium at a high concentration in advance together with a resin called a pigment-dispersed resin to form a paste. This is because the pigment is in a powder form, and it is difficult to disperse in a single step in a low concentration uniform state used in the electrodeposition coating composition. Such a paste is generally called a pigment dispersion paste.

  The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin in an aqueous medium. As the pigment dispersion resin, a cationic polymer such as a cationic or nonionic low molecular weight surfactant or a modified epoxy resin having a quaternary ammonium group and / or a tertiary sulfonium group is generally used. As the aqueous medium, ion-exchanged water or water containing a small amount of alcohol is used. Generally, the pigment dispersion resin is used at a solid content ratio of 5 to 40 parts by mass, and the pigment is used at a solid content ratio of 10 to 30 parts by mass.

  The pigment dispersion resin and the pigment are mixed and dispersed using a normal dispersing device such as a ball mill or a sand grind mill until the particle size of the pigment in the mixture becomes a predetermined uniform particle size, and the pigment dispersion paste Get.

Other Components The cationic electrodeposition coating composition may contain a dissociation catalyst for dissociating the blocking agent of the blocked isocyanate curing agent in addition to the above components. As such a dissociation catalyst, organic tin compounds such as dibutyltin laurate, dibutyltin oxide and dioctyltin oxide, amines such as N-methylmorpholine, metal salts such as strontium, cobalt and copper can be used. The concentration of the dissociation catalyst is preferably 0.1 to 6 parts by mass with respect to 100 parts by mass of the total of the cationic epoxy resin and the blocked isocyanate curing agent in the cationic electrodeposition coating composition.

Preparation of cationic electrodeposition coating composition The cationic electrodeposition coating composition is prepared by dispersing a cationic epoxy resin, a curing agent, a conductivity control agent and a pigment dispersion paste in an aqueous medium. Further, the aqueous medium usually contains a neutralizing agent in order to improve the dispersibility of the cationic epoxy resin. Neutralizing agents are inorganic or organic acids such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, lactic acid. The amount is that which achieves a neutralization rate of at least 20%, preferably 30-60%.

  The amount of the blocked isocyanate curing agent is sufficient to react with active hydrogen-containing functional groups such as primary, secondary or / and tertiary amino groups and hydroxyl groups in the cationic epoxy resin during curing to give a good cured coating film. It must be sufficient, generally expressed in terms of the solids mass ratio of the cationic epoxy resin to the curing agent, generally in the range of 90/10 to 50/50, preferably 80/20 to 65/35.

  The amount of the conductivity control agent contained in the cationic electrodeposition coating composition is not particularly limited, but specifically, 0.5 to 30 mass based on the solid content of the cationic electrodeposition coating composition. %, More preferably 1 to 30% by mass, and even more preferably 1 to 15% by mass. The amount of the conductivity control agent may be less than 0.5% by mass, but sufficient electrical conductivity may not be obtained. Moreover, although the quantity of an electrical conductivity control agent may exceed 30 mass%, the increase in electrical conductivity proportional to the addition amount is not seen.

  The cationic electrodeposition coating composition of the present invention has a solid content concentration lower than the conventional 20% by mass, particularly 0.5 to 9% by mass, and more preferably 3 to 9% by mass. If it is less than 0.5% by mass, an electrodeposition coating film as an undercoat coating film may not be obtained. On the other hand, when the solid content concentration exceeds 9% by mass, there is a possibility that the pigment component contained in the cationic electrodeposition coating composition settles in a stationary and unstirred state. In addition, it may not be necessary to add a conductivity control agent to adjust the electrical conductivity of the paint.

  The SP value of the resin component contained in the cationic electrodeposition coating composition of the present invention is 11.7 or less. Here, the “resin component contained in the cationic electrodeposition coating composition” means a cationic epoxy resin, a blocked isocyanate curing agent, a conductivity control agent, and a non-crosslinked acrylic resin used in a preferred embodiment. The SP value of the resin component contained in the cationic electrodeposition coating composition is determined using the SP values of the cationic epoxy resin, blocked isocyanate curing agent, conductivity controller, and non-crosslinked acrylic resin, respectively. It can obtain | require by calculating an average value based on solid content mass ratio in the inside. The SP value of each of the cationic epoxy resin, blocked isocyanate curing agent, conductivity control agent, and non-crosslinked acrylic resin should be measured by the above-described cloud point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion-exchanged water). Can do.

  The cationic electrodeposition coating composition of the present invention is excellent in settling stability due to a low coating solid content concentration, and in addition to being excellent in throwing power, in addition to an object to be coated or untreated treated with a zirconium-based chemical conversion treatment agent. Even when the object to be coated is applied by electrodeposition, it is possible to achieve a coating film appearance that is inferior to the case of coating the object treated with the zinc phosphate chemical conversion treatment agent. In general, the film thickness of the chemical conversion treatment film formed with the zirconium-based chemical conversion treatment agent is very thin, about 1/10 to 1/30 of the film thickness of the chemical conversion treatment film formed with the zinc phosphate-based chemical conversion treatment agent. Moreover, since the electrical conductivity control agent which a cationic electrodeposition coating composition contains has a high amine number, it is easy to flow an electric current. Therefore, when electrodeposition is applied to an object on which a zirconium-based conversion coating is formed, the coating resistance value is lower even in the portion where the electrodeposition coating is deposited than when a zinc phosphate conversion coating is formed. turn into. The same applies when electrodeposition is applied to an untreated object. Since the object to be coated is untreated, the resistance value of the coating film is lowered even in the portion where the electrodeposition coating film is deposited, as compared with the case where the zinc phosphate-based chemical conversion film is formed. As a result, an excessive current flow occurs in the coating film deposition portion, and coating film abnormalities such as gas pinholes are likely to occur.

In contrast, the present invention provides a cationic electrodeposition coating composition containing a low solid content type conductivity control agent by setting the SP value of the resin component contained in the cationic electrodeposition coating composition to 11.7 or less. Also, hydrophobicity can be ensured. As a result, the time from the start of voltage application in electrodeposition coating until the coating resistance value of the deposited electrodeposition coating reaches 30 kΩ · cm ² is within 12 seconds. That is, by adjusting the SP value of the resin component contained in the cationic electrodeposition coating composition to 11.7 or less, the coating film resistance value of the coating film deposited by the start of voltage application can be reduced within a short time from the start of voltage application. It rises (the rise of the coating film resistance value is fast). And, since the rise of the coating resistance value is quick at the portion where the electrodeposition coating film is deposited, the excessive current flow at the coating deposition portion is suppressed, and the occurrence of coating film abnormality such as gas pinholes occurs. It is suppressed and the coating film appearance of the obtained cured electrodeposition coating film becomes good. The lower limit of the SP value is preferably 10.0. By making the SP value 10.0 or more, it is possible to prevent the occurrence of uneven drying on the deposited coating film.

  Examples of a method for adjusting the SP value of the resin component contained in the cationic electrodeposition coating composition to 11.7 or less include, for example, a method of including a non-crosslinked acrylic resin in the cationic electrodeposition coating composition, and an aromatic as a blocked isocyanate curing agent. And a method using a blocked isocyanate obtained by blocking an aromatic diisocyanate or an aromatic polyisocyanate.

  The electrodeposition coating film obtained from the cationic electrodeposition coating composition of the present invention has a coating film viscosity at 50 ° C. of 3000 Pa · s or less. The uncured electrodeposition coating film obtained by precipitation from the cationic electrodeposition coating composition has a coating film viscosity at 50 ° C. of 3000 Pa · s or less, so that the electrodeposition coating film is in an uncured state. Fusion of the resin component inside will occur. And the flow of excessive current in the coating film deposition part is suppressed, the occurrence of coating film abnormality such as gas pinholes is suppressed, and the coating film appearance of the obtained cured electrodeposition coating film becomes good. . The viscosity is preferably 500 Pa · s or more. By setting the viscosity to 500 Pa · s or more, good throwing power can be obtained.

  In the present invention, the reason for measuring the viscosity of the electrodeposition coating film at 50 ° C. is as follows. An electrodeposition coating film is a coating film deposited on the surface of an object to be coated by application of a voltage. In general, the electrodeposition coating film is designed to have a higher viscosity (high Tg) than the top coating composition and the intermediate coating composition in order to ensure corrosion resistance. Therefore, when the viscosity of the electrodeposition coating film is measured at a general electrodeposition bath temperature (for example, 30 ° C.), the measurement may be impossible due to the very high viscosity. For this reason, it is difficult to measure the viscosity of the electrodeposition coating film at 30 ° C. On the other hand, the deposited electrodeposition coating film is heated to generate a heat flow, the viscosity is lowered, and the coating film surface becomes smooth. By further heating, the blocking agent of the blocked isocyanate curing agent contained in the electrodeposition coating film is thermally dissociated, and this undergoes a crosslinking reaction with hydroxyl groups, amino groups, etc. in the cationic epoxy resin, and the coating film viscosity rapidly increases. To do. As a result, the electrodeposition coating film is cured to form a cured electrodeposition coating film. That is, the viscosity of the electrodeposition coating film is once lowered by heating, and then the viscosity is increased.

  Furthermore, at the time of electrodeposition coating, Joule heat is generated, and the vicinity of the object to be coated is raised to about 40 to 50 ° C. That is, it can be said that the viscosity measurement at 50 ° C. is a state in which the physical properties at the time of electrodeposition coating deposition are reproduced. From the above, the temperature of 50 ° C. is a preferable temperature for the measurement of the viscosity of the coating film from the above properties of the electrodeposition coating composition, and the temperature at which the binder resin is not crosslinked, that is, the deposition of the uncured electrodeposition coating film It is considered that the temperature is appropriate for judging the nature of time.

  In the cationic electrodeposition coating composition of the present invention, as a method of adjusting the coating viscosity at 50 ° C. of an uncured electrodeposition coating obtained by precipitation from the cationic electrodeposition coating composition to 3000 Pa · s or less, for example, A method of using a dicarboxylic acid-modified cationic epoxy resin as a cationic epoxy resin, a method of adjusting the amount of a solvent contained in an electrodeposition coating composition, and a method of adjusting a mixing ratio of a cationic epoxy resin and a blocked isocyanate curing agent Etc. Other methods include a method of adding a cationic acrylic resin and a method of adjusting Tg of the non-crosslinked acrylic resin.

  In addition, the coating-film viscosity of an electrodeposition coating film can be measured as follows. First, electrodeposition coating is carried out for 180 seconds so that the film thickness is about 15 μm to form an electrodeposition coating film, which is washed with water to remove the excessively deposited electrodeposition coating composition. Next, after removing excess moisture adhering to the surface of the electrodeposition coating film, the coating film is taken out immediately without drying to prepare a sample. The sample thus obtained can be measured for coating film viscosity at 50 ° C. using a dynamic viscoelasticity measuring apparatus.

Articles to be coated Examples of the objects to be coated in the present invention include metal substrates capable of cationic electrodeposition. The metal substrate is not particularly limited as long as it can be cationically electrodeposited. Examples thereof include iron-based metal substrates, aluminum-based metal substrates, and zinc-based metal substrates. .

In the case of chemical conversion treatment, a general chemical conversion treatment agent containing zirconium ions can be used. In the present specification, this chemical conversion treatment agent may be referred to as a “zirconium-based chemical conversion treatment agent”.

  The concentration of zirconium ions in the chemical conversion treatment agent is preferably 10 to 10,000 ppm. More preferable lower and upper limit values are 100 ppm and 500 ppm, respectively.

  In addition, the description about the concentration of the metal ion in the chemical conversion treatment agent as the chemical conversion treatment agent in the present specification focuses on only the metal atom in the complex or oxide when the complex or oxide is formed. And expressed in terms of metal element equivalent. Therefore, the metal ion concentration in the chemical conversion treatment agent as the chemical conversion treatment agent in the present specification is a metal in a case where it is dissociated 100% and exists as a metal ion regardless of whether or not a part thereof is present as a non-ion. Refers to ion concentration.

  Further, it contains zirconium ions and tin ions, the zirconium ion concentration is 10 to 10,000 ppm, the concentration ratio of tin ions to zirconium ions is 0.005 to 1 in terms of mass, and the pH is 1.5 to 6.5. A chemical conversion treatment agent that is or a chemical conversion treatment agent containing titanium or hafnium may be used.

Chemical conversion treatment A chemical conversion treatment film (which may be referred to as a “coating” in the present specification for omission) is formed by performing treatment on an object to be coated using the chemical conversion treatment agent. The chemical conversion treatment is performed by bringing the chemical conversion treatment agent into contact with the metal substrate that is the object to be coated. Specific examples of the method for bringing the chemical conversion treatment agent into contact with the article to be coated include an immersion method, a spray method, a roll coating method, and a pouring treatment method.

Cationic electrodeposition coating A general electrodeposition coating process includes a process of immersing an object to be coated in an electrodeposition coating composition, and applying a voltage between the object to be coated as a cathode and an anode to deposit a film. Process. The energization time varies depending on the electrodeposition conditions, but is generally about 2 to 4 minutes. As the applied voltage, for example, a voltage of 50 to 450 V is applied between the object to be coated and the anode.

In the electrodeposition coating at a coating temperature of 30 ° C. using the cationic electrodeposition coating composition of the present invention, from the start of voltage application until the coating resistance value of the deposited electrodeposition coating reaches 30 kΩ · cm ^2. The time (this time is referred to as “resistance formation time” in this specification) is within 12 seconds. The voltage in this electrodeposition coating is a voltage that results in a film thickness in the range of 15 μm when energized for about 3 minutes. A specific method for measuring the resistance formation time is as follows. First, “the voltage at which the film thickness becomes 15 μm by energization for 180 seconds” in the case of performing electrodeposition coating using a specific electrodeposition coating composition is determined. This voltage determination method is determined by, for example, a method of calculating a voltage with a film thickness of 15 μm based on a film thickness measurement result when an arbitrary voltage (50 V, 100 V) is applied. Thereafter, under the condition of applying the determined voltage, a new object is electrodeposited, and the time until the coating resistance value of the electrodeposition coating reaches 30 kΩ · cm ² in this case (resistance formation time) ) Is measured.

  After electrodeposition coating, perform water washing as necessary. Next, usually, a cured electrodeposition coating film is formed by baking at 140 to 180 ° C. for 10 to 30 minutes.

  The chemical conversion treatment agent that can be used in the present invention contains zirconium ions and tin ions, the zirconium ion concentration is 10 to 10,000 ppm, and the concentration ratio of tin ions to zirconium ions is 0.005 to 1 in terms of mass, And a chemical conversion treatment agent having a pH of 1.5 to 6.5. Since this chemical conversion treatment agent seems to improve the stability of the chemical conversion treatment film, iron-based substrates such as cold-rolled steel sheets or galvanized steel sheets that were not suitable for pretreatment with conventional chemical conversion treatment agents containing zirconium It is possible to satisfactorily form the chemical conversion treatment film. Further, by using the electrodeposition coating composition in the present invention, excellent throwing power is exhibited.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. In the examples, “parts” and “%” are based on mass unless otherwise specified.

Production Example 1 Production of chemical conversion treatment agent
Production Example 1-1 Preparation of Aminosilane Hydrolysis Condensate As aminosilane, KBE603 (3-aminopropyl-triethoxysilane, effective concentration 100%, manufactured by Shin-Etsu Chemical Co., Ltd.), 5 parts by mass from a dropping funnel, deionized water 47 After dropping uniformly in a mixed solvent of 5 parts by mass and 47.5 parts by mass of isopropyl alcohol (solvent temperature: 25 ° C.) over 60 minutes, the reaction was performed at 25 ° C. for 24 hours in a nitrogen atmosphere. Thereafter, the reaction solution was depressurized to evaporate isopropyl alcohol, and deionized water was further added to obtain a hydrolysis-condensation product of aminosilane having an active ingredient of 5%.

Production Example 1-2 Preparation of Chemical Conversion Treatment Agent 40% zirconic acid aqueous solution as a zirconium ion supply source in such an amount that the zirconium ion concentration becomes 500 ppm and tin acetate as the tin ion supply amount in which the tin ion concentration becomes 30 ppm Then, the aminosilane hydrolysis condensate of Production Example 1-1 is added in an amount of 200 ppm, aluminum nitrate is added in an amount of aluminum ion concentration of 200 ppm, hydrofluoric acid is added, and nitric acid and sodium hydroxide are added. Was used to adjust the pH to 3.5 to obtain a chemical conversion treatment agent. The Sn / Zr ratio in the obtained chemical conversion treatment agent was 0.06. Moreover, the free fluorine ion concentration when measured using a fluorine ion meter when this treatment agent was adjusted to pH 3.0 was 5 ppm.

Production Example 2 Production Example for Cationic Electrodeposition Coating Composition
Production Example 2-1 Preparation of Conductivity Control Agent In a flask equipped with a reflux condenser and a stirrer, 295 parts of methyl isobutyl ketone (hereinafter abbreviated as “MIBK”), 37.5 parts of methylethanolamine, 52.5 diethanolamine The parts were charged and kept at 100 ° C. with stirring. To this, 205 parts of a cresol novolac type epoxy resin (product name YDCN-703, manufactured by Tohto Kasei Co., Ltd.) was gradually added. It was 2100 when the number average molecular weight was measured. The amine value (MEQ (B)) of the obtained amino-modified resin was measured and found to be 340 mmol / 100 g.

  To 140 parts of the resulting amino-modified resin solution, 5.5 parts of formic acid and 1254.5 parts of deionized water were added and stirred for 30 minutes while maintaining at 80 ° C. The organic solvent was removed under reduced pressure to obtain a conductivity control agent having a solid content of 7.0%. The SP value of the conductivity control agent was 14.3 as measured by a turbid point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion exchange water).

Production Example 2-2 Preparation of Cationic Epoxy Resin (1)
In a flask equipped with a stirrer, a condenser tube, a nitrogen inlet tube, a thermometer and a dropping funnel, 92 parts of 2,4- / 2,6-tolylene diisocyanate (mass ratio = 8/2), methyl isobutyl ketone (hereinafter, MIBK) Abbreviated to 95 parts) and 0.5 part of dibutyltin dilaurate. While stirring the reaction mixture, 21 parts of methanol was added dropwise. The reaction was started from room temperature and heated to 60 ° C. due to heat generation. Then, after continuing reaction for 30 minutes, 50 parts of ethylene glycol mono-2-ethylhexyl ether was dripped from the dropping funnel. Further, 53 parts of a bisphenol A-propylene oxide 5 mol adduct was added to the reaction mixture. The reaction was mainly carried out in the range of 60 to 65 ° C. and continued until absorption based on the isocyanate group disappeared in the measurement of IR spectrum.

  Next, 365 parts of epoxy resin with an epoxy equivalent of 188 synthesized from bisphenol A and epichlorohydrin by a known method was added to the reaction mixture, and the temperature was raised to 125 ° C. Thereafter, 1.0 part of benzyldimethylamine was added and reacted at 130 ° C. until the epoxy equivalent was 410.

  Subsequently, 61 parts of bisphenol A and 33 parts of octylic acid were added and reacted at 120 ° C., resulting in an epoxy equivalent of 1190. Thereafter, the reaction mixture was cooled, 11 parts of diethanolamine, 24 parts of N-ethylethanolamine and 25 parts of a 79% by weight MIBK solution of ketimine of aminoethylethanolamine were added and reacted at 110 ° C. for 2 hours. Then, it diluted with MIBK until it became non-volatile content 80%, and obtained the cationic epoxy resin (1) (resin solid content 80%). The SP value of this cationic epoxy resin was measured by a turbid point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion-exchanged water) and found to be 11.6.

Production Example 2-3 Preparation of Cationic Epoxy Resin (2)
In a flask equipped with a stirrer, condenser, nitrogen inlet, thermometer and dropping funnel, 35 parts of 2,4- / 2,6-tolylene diisocyanate (mass ratio = 8/2), methyl isobutyl ketone (hereinafter referred to as MIBK) 94 parts and dibuciltin dilaurate 0.5 part were charged. While stirring the reaction mixture, 7 parts of methanol was added dropwise. The reaction was started from room temperature and heated to 60 ° C. due to heat generation. Then, after continuing reaction for 30 minutes, 12 parts of ethylene glycol mono-2-ethylhexyl ether was dripped from the dropping funnel. Further, 33 parts of a bisphenol A-propylene oxide 5 mol adduct was added to the reaction mixture. The reaction was mainly carried out in the range of 60 ° C. to 65 ° C. and continued until absorption based on the isocyanate group disappeared in the measurement of IR spectrum. Next, 383 parts of an epoxy resin having an epoxy equivalent of 188 synthesized from bisphenol A and epichlorohydrin by a known method was added to the reaction mixture, and the temperature was raised to 125 ° C. Thereafter, 1.0 part of benzyldimethylamine was added and reacted at 130 ° C. until the epoxy equivalent was 266.

  Subsequently, when 90 parts of bisphenol A, 47 parts of octylic acid and 71 parts of dimer acid were added and reacted at 120 ° C., an epoxy equivalent of 1460 was obtained.

  The obtained reaction product was then cooled, and then 31 parts of diethanolamine and 39 parts of a 79% by weight MIBK solution of ketimine product of aminoethylethanolamine were added and reacted at 110 ° C. for 2 hours. Thereafter, it was diluted with MIBK to a non-volatile content of 88%. Thus, a cationic epoxy resin (2) was obtained. The SP value of the cationic epoxy resin (2) was measured by a cloud point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion-exchanged water) and found to be 11.6.

Production Example 2-4 Preparation of Pigment Dispersing Resin First, 222.0 parts of isophorone diisocyanate (hereinafter abbreviated as IPDI) was placed in a reaction vessel equipped with a stirrer, a cooling tube, a nitrogen introduction tube, and a thermometer, and MIBK 39.1. Then, 0.2 part of hedibutyltin dilaurate was added. Then, after heating this to 50 degreeC, 131.5 parts of 2-ethylhexanol was dripped over 2 hours in dry nitrogen atmosphere, stirring. The reaction temperature was maintained at 50 ° C. by cooling appropriately. As a result, 2-ethylhexanol half-blocked IPDI (resin solid content: 90.0%) was obtained.

  Next, 87.2 parts of dimethylethanolamine, 117.6 parts of 75% aqueous lactic acid solution, and 39.2 parts of ethylene glycol monobutyl ether are added to a suitable reaction vessel in this order, and the mixture is stirred at 65 ° C. for about half an hour to form quaternization. An agent was prepared.

  Next, 710.0 parts of EPON 829 (bisphenol A type epoxy resin manufactured by Shell Chemical Company, epoxy equivalent 193 to 203) and 289.6 parts of bisphenol A were charged into a suitable reaction vessel, and the reaction was conducted under a nitrogen atmosphere. When heated to 150 to 160 ° C., an initial exothermic reaction occurred. The reaction mixture was reacted at 150-160 ° C. for about 1 hour, then cooled to 120 ° C., and 498.8 parts of 2-ethylhexanol half-blocked IPDI (MIBK solution) prepared above was added.

  The reaction mixture is kept at 110-120 ° C. for about 1 hour, then 463.4 parts of ethylene glycol monobutyl ether are added, the mixture is cooled to 85-95 ° C. and homogenized, and then the quaternizing agent 196 prepared above is used. 7 parts were added. After maintaining the reaction mixture at 85 to 95 ° C. until the acid value becomes 1, 964 parts of deionized water is added to finish quaternization in the epoxy-bisphenol A resin, and a pigment dispersion having a quaternary ammonium salt portion A resin was obtained (resin solid content 50%). The SP value of this pigment-dispersing resin was measured by a turbid point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion-exchanged water) and found to be 14.0.

Production Example 2-5 Preparation of Pigment Dispersion Paste (1) Into a sand grind mill, 100 parts of the pigment dispersion resin obtained in Production Example 2-4, 100.0 parts of titanium dioxide and 100.0 parts of ion-exchanged water were added. Dispersion was carried out to 10 μm or less to obtain a pigment dispersion paste (1) (solid content 50%).

Production Example 2-6 Preparation of Non-Crosslinked Acrylic Resin (1) In a five-necked flask equipped with a reflux condenser, stirrer, dropping funnel, and nitrogen inlet tube, 300.0 parts of n-butyl acetate was charged under a nitrogen atmosphere. Heated to 120 ° C. To this, 250.0 parts of styrene, 35.7 parts of methyl methacrylate, 48.2 parts of n-butyl acrylate, 380.0 parts of isobornyl methacrylate, 278.4 parts of hydroxyethyl methacrylate, 7.7 parts of methyl acrylate, acetic acid A mixture of 60.0 parts of n-butyl and 150.0 parts of t-butyl peroctoate was dropped from a dropping funnel over 3 hours. After the completion of dropping, the mixture was kept at 120 ° C. for about 1 hour, and then a mixture of 30.0 parts of n-butyl acetate and 10.0 parts of t-butyl peroctoate was dropped, and the mixture was kept at 120 ° C. for about 30 minutes. A solution of 70.3% acrylic resin was obtained.
The non-crosslinked acrylic resin (1) obtained had a solubility parameter of 11.0, a glass transition temperature of 80 ° C., and a number average molecular weight of 2700.

Production Example 2-7 Production of Non-Crosslinked Acrylic Resin (2) In a five-necked flask equipped with a reflux condenser, a stirrer, a dropping funnel, and a nitrogen introduction tube, 300.0 parts of n-butyl acetate was charged under a nitrogen atmosphere. Heated to 120 ° C. To this, 200.0 parts styrene, 325.6 parts isobutyl methacrylate, 150.2 parts 2-ethylhexyl acrylate, 138.6 parts ethyl acrylate, 185.6 parts hydroxyethyl methacrylate, 60.0 parts n-butyl acetate, and A mixture of 130.0 parts of t-butyl peroctoate was added dropwise from the dropping funnel over 3 hours. After the completion of dropping, the mixture was kept at 120 ° C. for about 1 hour, and then a mixture of 30.0 parts of n-butyl acetate and 10.0 parts of t-butyl peroctoate was dropped, and the mixture was kept at 120 ° C. for about 30 minutes. A solution of 70.5% acrylic resin was obtained.
The non-crosslinked acrylic resin (2) obtained had a solubility parameter of 10.6, a glass transition temperature of 20 ° C., and a number average molecular weight of 3,200.

  In addition, the glass transition temperature (Tg) of each component in this specification was measured using DSC (Differential Scanning Colorimeter) Seiko Electronics Industry.

Production Example 2-8 Preparation of Blocked Isocyanate Curing Agent (1) 1250 parts of diphenylmethane diisocyanate and 266.4 parts of MIBK were charged into a reaction vessel, which was heated to 80 ° C., and then 2.5 parts of dibutyltin dilaurate was added. . A solution prepared by dissolving 226 parts of ε-caprolactam in 944 parts of butyl cellosolve was added dropwise at 80 ° C. over 2 hours. Furthermore, after heating at 100 degreeC for 4 hours, in the measurement of IR spectrum, it confirmed that absorption based on an isocyanate group disappeared, and after standing to cool, MIBK336.1 part was added and block isocyanate hardening | curing agent (1) was obtained. (Solid content 80%). The SP value of the blocked isocyanate curing agent (1) was 11.3 as measured by a cloud point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion exchange water).

Comparative Production Example 2-1 Preparation of Blocked Isocyanate Curing Agent (2) 840 parts of hexamethylene diisocyanate and 172.2 parts of MIBK were charged into a reaction vessel and heated to 80 ° C., and then 2.5 parts of dibutyltin dilaurate was added. added. To this, 870 parts of methyl ethyl ketoxime was added dropwise at 80 ° C. over 2 hours. Furthermore, after heating at 100 degreeC for 4 hours, in the measurement of IR spectrum, it confirmed that the absorption based on an isocyanate group disappeared, and after standing to cool, MIBK101.3 part was added and block isocyanate hardening | curing agent (2) was obtained. (Solid content 85%). The SP value of the blocked isocyanate curing agent (2) was measured by a cloud point measurement method using a good solvent (tetrahydrofuran) and a poor solvent (ion-exchanged water) and found to be 12.6.

Production Example 2-9 Preparation of Binder Resin Emulsion (1) The cationic epoxy resin (2) obtained in Production Example 2-3 and the blocked isocyanate curing agent (1) obtained in Production Example 2-8 were mixed in solid content. It mixed so that it might become uniform by ratio 60/40. Glacial acetic acid was added so that the milligram equivalent (MEQ (A)) of the acid per 100 g of resin solid content was 30, and ion-exchanged water was slowly added for dilution. By removing MIBK under reduced pressure, an emulsion having a solid content of 36% was obtained.

Production Example 2-10 Preparation of Binder Resin Emulsion (2) Cationic Epoxy Resin (1) Obtained in Production Example 2-2, Blocked Isocyanate Curing Agent (1) Obtained in Production Example 2-8, and Production Example 2 An emulsion having a solid content of 36% was obtained in the same manner as in Production Example 2-9 except that the non-crosslinked acrylic resin (1) obtained in -6 was uniformly mixed at a solid content ratio of 50/40/10. It was.

Production Example 2-11 Preparation of Binder Resin Emulsion (3) Cationic Epoxy Resin (2) Obtained in Production Example 2-3, Blocked Isocyanate Curing Agent (1) Obtained in Production Example 2-8, and Production Example 2 An emulsion having a solid content of 36% was obtained in the same manner as in Production Example 2-9 except that the non-crosslinked acrylic resin (2) obtained in -7 was uniformly mixed at a solid content ratio of 50/40/10. It was.

Comparative Production Example 2-2 Preparation of Binder Resin Emulsion (4) Comparative production with the cationic epoxy resin (2) obtained in Production Example 2-3 and the blocked isocyanate curing agent (1) obtained in Production Example 2-8 Emulsion having a solid content of 36% in the same manner as in Production Example 2-9 except that the blocked isocyanate curing agent (2) obtained in Example 2-1 was uniformly mixed at a solid content ratio of 60/24/16. Got.

Comparative Production Example 2-3 Preparation of Binder Resin Emulsion (5) The cationic epoxy resin (1) obtained in Production Example 2-2 and the blocked isocyanate curing agent (1) obtained in Production Example 2-8 were solidified. An emulsion having a solid content of 36% was obtained in the same manner as in Production Example 2-9 except that the mixture was uniformly mixed at a fraction ratio of 60/40.

Example 1
Preparation of Cationic Electrodeposition Coating Composition 123.4 parts of binder resin emulsion (1) obtained in Production Example 2-9, 47.6 parts of conductivity control agent obtained in Production Example 2-1, Production Example 2- A cationic electrodeposition coating composition was prepared by mixing 4.5 parts of the pigment dispersion paste obtained in 5 and 2 parts of a 10% aqueous cerium acetate solution, 0.7 parts of dibutyltin oxide and 821.8 parts of ion-exchanged water. did. The resulting solid coating content of the cationic electrodeposition coating composition was 5% by mass. The solid content of the paint can be determined as a percentage of the original mass of the residue after heating at 180 ° C. for 30 minutes (according to JIS K5601). The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.6.

Chemical conversion treatment and electrodeposition coating In the liquid of the chemical conversion treatment agent of Production Example 1 heated to 40 ° C., the surface to be coated (cold rolled steel sheet) washed with water after degreasing treatment was immersed for 60 seconds to perform surface treatment. The coating amount of the chemical conversion treatment film was 75 mg / m ² . The coating amount is included in the chemical conversion treatment agent using “XRF1700” (Shimadzu X-ray fluorescence analyzer) after the cold-rolled steel sheet after the water washing treatment is dried at 80 ° C. for 5 minutes in an electric drying furnace. The total amount of metal was analyzed. The “coating amount of the chemical conversion treatment film” indicates the total amount of metals contained in the chemical conversion treatment agent.
The coated object thus formed with the chemical conversion film was then sprayed with tap water for 30 seconds and further sprayed with ion-exchanged water for 10 seconds.

  Then, only air drying was performed without passing through a drying process, and then electrodeposition coating was performed. Using the cationic electrodeposition coating composition obtained by the above preparation, electrodeposition was applied at a liquid temperature of 30 ° C. at a coating voltage at which the thickness of the cured electrodeposition coating film was 15 μm. After washing with water, baking was performed at 170 ° C. for 25 minutes to obtain a cured electrodeposition coating film.

Example 2
Preparation of cationic electrodeposition coating composition 180.3 parts of binder resin emulsion (2) obtained in Production Example 2-10, 27.8 parts of conductivity control agent obtained in Production Example 2-1, Production Example 2- A cation electrodeposition coating composition was prepared by mixing 6.3 parts of the pigment dispersion paste obtained in Step 5, 2 parts of a 10% aqueous cerium acetate solution, 1.0 part of dibutyltin oxide, and 782.6 parts of ion-exchanged water. did. The obtained cationic electrodeposition coating composition had a solid content of 7% by mass. The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.5.

  Using the chemical conversion treatment agent of Production Example 1, the surface of the article to be coated (cold rolled steel sheet) was subjected to surface treatment in the same manner as in Example 1. Subsequently, using the obtained cationic electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a cured electrodeposition coating film.

Example 3
Preparation of Cationic Electrodeposition Coating Composition 180.3 parts of binder resin emulsion (3) obtained in Production Example 2-11, 27.8 parts of conductivity control agent obtained in Production Example 2-1, Production Example 2- A cation electrodeposition coating composition was prepared by mixing 6.3 parts of the pigment dispersion paste obtained in Step 5, 2 parts of a 10% aqueous cerium acetate solution, 1.0 part of dibutyltin oxide, and 782.6 parts of ion-exchanged water. did. The obtained cationic electrodeposition coating composition had a solid content of 7% by mass. The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.4.

  Using the chemical conversion treatment agent of Production Example 1, the surface of the article to be coated (cold rolled steel sheet) was subjected to surface treatment in the same manner as in Example 1. Subsequently, using the obtained cationic electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a cured electrodeposition coating film.

Comparative Example 1
Preparation of Cationic Electrodeposition Coating Composition 132.6 parts of binder resin emulsion (1) obtained in Production Example 2-9, 4.5 parts of pigment dispersion paste obtained in Production Example 2-5, 10% aqueous cerium acetate solution 2 parts, 0.7 parts of dibutyltin oxide, and 860.2 parts of ion-exchanged water were mixed to prepare a cationic electrodeposition coating composition. The obtained cationic electrodeposition coating composition had a solid content of 5% by mass. The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.4.

  Using the chemical conversion treatment agent of Production Example 1, the surface of the article to be coated (cold rolled steel sheet) was subjected to surface treatment in the same manner as in Example 1. Subsequently, using the obtained cationic electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a cured electrodeposition coating film.

Comparative Example 2
Preparation of cationic electrodeposition coating composition Binder resin emulsion (4) obtained in Comparative Production Example 2-2 (123.4 parts), Conductivity control agent obtained in Production Example 2-1 (47.6 parts), Production Example 2 4.5 parts of the pigment dispersion paste obtained in -5, 2 parts of 10% cerium acetate aqueous solution, 0.7 parts of dibutyltin oxide, and 821.8 parts of ion-exchanged water were mixed to prepare a cationic electrodeposition coating composition. Prepared. The resulting solid coating content of the cationic electrodeposition coating composition was 5% by mass. The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.8.

  Using the chemical conversion treatment agent of Production Example 1, the surface of the article to be coated (cold rolled steel sheet) was subjected to surface treatment in the same manner as in Example 1. Subsequently, using the obtained cationic electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a cured electrodeposition coating film.

Comparative Example 3
Preparation of Cationic Electrodeposition Coating Composition 180.3 parts of binder resin emulsion (5) obtained in Comparative Production Example 2-3, 27.8 parts of conductivity control agent obtained in Production Example 2-1, Production Example 2 6.3 parts of the pigment dispersion paste obtained in -5, 2 parts of 10% aqueous cerium acetate solution, 1.0 part of dibutyltin oxide, and 782.6 parts of ion-exchanged water were mixed to prepare a cationic electrodeposition coating composition. Prepared. The obtained cationic electrodeposition coating composition had a solid content of 7% by mass. The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.6.

  Using the chemical conversion treatment agent of Production Example 1, the surface of the article to be coated (cold rolled steel sheet) was subjected to surface treatment in the same manner as in Example 1. Subsequently, using the obtained cationic electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a cured electrodeposition coating film.

Comparative Example 4
Preparation of cationic electrodeposition coating composition 530.6 parts of binder resin emulsion (1) obtained in Production Example 2-9, 18.0 parts of pigment dispersion paste obtained in Production Example 2-5, 10% aqueous cerium acetate solution 2 parts, 2.9 parts of dibutyltin oxide, and 446.5 parts of ion-exchanged water were mixed to obtain a cationic electrodeposition coating composition. The solid content of the resulting cationic electrodeposition coating composition was 20% by mass. The SP value of the resin component contained in the obtained cationic electrodeposition coating composition was 11.4.

  Using the chemical conversion treatment agent of Production Example 1, the surface of the article to be coated (cold rolled steel sheet) was subjected to surface treatment in the same manner as in Example 1. Subsequently, using the obtained cationic electrodeposition coating composition, electrodeposition coating was performed in the same manner as in Example 1 to obtain a cured electrodeposition coating film.

  The following measurements and evaluations were performed using the cationic electrodeposition coating compositions obtained in the above examples and comparative examples. The evaluation results are shown in Table 2.

Measurement of coating viscosity at 50 ° C. of electrodeposition coating film Using the cationic electrodeposition coating compositions obtained by the above examples and comparative examples, electrodeposition coating was carried out for 180 seconds so that the film thickness was about 15 μm on the coating object. The electrodeposition coating film was formed, and this was washed with water to remove the excess electrodeposition coating composition. Next, after removing moisture, the coating film was taken out immediately without drying to prepare a sample. The sample thus obtained was subjected to frequency-dependent measurement in dynamic viscoelasticity using a Rheosol G-3000 (manufactured by UBM Co., Ltd.), which is a rotary dynamic viscoelasticity measuring device, and setting conditions: strain 0.5 deg. The frequency was 0.02 Hz. The prepared sample was set and the measurement temperature was kept at 50 ° C. After the measurement was started, the viscosity of the coating film was measured when the electrodeposition coating film was spread uniformly in the cone plate. The obtained results are shown in Table 2 below.

Measurement of electrical conductivity The electrical conductivity of the cationic electrodeposition coating composition obtained by the above examples and comparative examples was measured using a conductivity system (CM-305, manufactured by Toa Denpa Kogyo Co., Ltd.) at a liquid temperature of 25 ° C. The measurement was performed under the following conditions. The obtained results are shown in Table 2 below.

Measurement of time (resistance formation time) until the coating resistance value of the electrodeposition coating reaches 30 kΩ · cm ² Cold- rolled steel sheet washed with water after degreasing treatment is coated with a zinc phosphate-based chemical conversion treatment agent. A steel plate (zinc phosphate-treated steel plate) formed by immersion treatment for 120 seconds in a certain Surfdyne SD-6350 (manufactured by Nippon Paint Co., Ltd., temperature 35 ° C.), 60 seconds in the chemical conversion treatment agent of Production Example 1 Three types of steel plates were used: a steel plate that had been immersed for surface treatment (zircon chemical conversion treatment steel plate) and an untreated steel plate that was not subjected to chemical conversion treatment (untreated steel plate).
4 liters of the cationic electrodeposition coating composition described in each example or each comparative example was transferred to a PVC container to prepare an electrodeposition tank. Next, “the voltage at which the film thickness becomes 15 μm when energized for 180 seconds” in the case where the above-described three types of steel sheets are coated using the cationic electrodeposition coating compositions obtained in the above Examples and Comparative Examples is 150 V. , 200 V, and 250 V were applied based on the results of measuring the film thickness. The obtained applied voltage (V) is shown in the following table.

A vinyl chloride container containing 4 liters of the cationic electrodeposition coating composition described in each example or each comparative example is used as an electrodeposition tank, the above three types of steel plates are used as cathodes, and a pole ratio (coating material and counter electrode (anode )) And the distance between the electrodes (distance between the object to be coated and the counter electrode (anode)) was set to 10 cm. Set the coating temperature to 30 ° C, apply the applied voltage in the above table, and measure the time until the coating resistance value of the deposited electrodeposition coating reaches 30 kΩ · cm ² using an oscilloscope (DATA manufactured by GRAPHTEC). It was measured using PLATFORM DM3100V2). In addition, the coating-film resistance value was computed from the time-voltage curve and time-current curve by a measuring device at the time of electrodeposition coating.

Horizontal appearance A cold-rolled steel sheet, which was subjected to chemical conversion treatment in the same manner as in the method described in Example 1, using the chemical conversion treatment agent used in each Example and Comparative Example, was used for the cationic electrodeposition coating composition described in each Example and Comparative Example. Using the product, electrodeposition coating was performed in a horizontal state in an unstirred cationic electrodeposition coating composition, and the appearance after baking of the electrodeposition coating plate was visually evaluated.
○: Good without problems.
(Triangle | delta): A pigment settles for a while and there is some rough feeling.
X: The pigment settles and the appearance is poor.

Appearance evaluation of cured electrodeposition coatings
A cold-rolled steel sheet washed with water after degreasing treatment with a zirconium-based chemical conversion treatment agent was immersed in the chemical conversion treatment agent of Production Example 1 for 60 seconds and subjected to surface treatment (coating amount of the chemical conversion treatment film 75 mg / m ² ). Electrodeposition coating was performed using the cationic electrodeposition coating compositions obtained in the above examples and comparative examples. Electrodeposition coating was performed at a liquid temperature of 30 ° C. at a coating voltage at which the thickness of the cured electrodeposition coating film was 15 μm. After washing with water, baking was performed at 170 ° C. for 25 minutes to obtain a cured electrodeposition coating film. About the formed cured electrodeposition coating film, the coating film appearance was visually evaluated according to the following criteria.
○: The surface of the cured electrodeposition coating film is smooth and the presence of irregularities is not recognized.
X: Unevenness is observed on the surface of the cured electrodeposition coating film.

As a comparison of zinc phosphate-based chemical conversion treatment agents, evaluation was performed on the case where zinc phosphate-based chemical conversion treatment agents were used. The degreased cold-rolled steel sheet is surface-treated at room temperature for 30 seconds using Surffine 5N-8M (manufactured by Nippon Paint Co., Ltd.), and then Surfdyne SD-6350 (Nippon Paint Co., Ltd.), which is a zinc phosphate-based chemical conversion treatment agent. Manufactured at a temperature of 35 ° C. for 120 seconds to form a chemical conversion film. The coating amount of the chemical conversion treatment film was 2200 mg / m ² . The coating amount is included in the chemical conversion treatment agent using “XRF1700” (Shimadzu X-ray fluorescence analyzer) after the cold-rolled steel sheet after the water washing treatment is dried at 80 ° C. for 5 minutes in an electric drying furnace. The total amount of metal was analyzed. The article on which the chemical conversion film was formed was then sprayed with tap water for 30 seconds and further sprayed with ion exchange water for 10 seconds.

Thereafter, only air drying was performed without particularly passing through a drying step, and then electrodeposition coating was performed using the cationic electrodeposition coating composition obtained by the above Examples and Comparative Examples. Electrodeposition coating was performed at a liquid temperature of 30 ° C. at a coating voltage at which the thickness of the cured electrodeposition coating film was 15 μm. After washing with water, baking was performed at 170 ° C. for 25 minutes to obtain a cured electrodeposition coating film. About the formed cured electrodeposition coating film, the coating film appearance was visually evaluated according to the above criteria.
In addition, generation | occurrence | production of sludge was confirmed in the surface treatment using the zinc phosphate chemical conversion treatment agent.

Electrodeposition coating was performed using the cationic electrodeposition coating composition obtained by the said Example and the comparative example by making the untreated cold-rolled steel plate which only washed with water after the untreated steel plate degreasing process to be coated. Electrodeposition coating was performed at a liquid temperature of 30 ° C. at a coating voltage at which the thickness of the cured electrodeposition coating film was 15 μm. After washing with water, baking was performed at 170 ° C. for 25 minutes to obtain a cured electrodeposition coating film. About the formed cured electrodeposition coating film, the coating film appearance was visually evaluated according to the above criteria.

Evaluation of throwing power The throwing power was evaluated by a so-called four-sheet box method. That is, as shown in FIG. 1, four cold-rolled steel plates (JIS G3141 SPCC-SD) 11 to 14 treated with the chemical conversion treatment agent of Production Example 1 are arranged in parallel at an interval of 20 mm, A box 10 was prepared in which the bottom and bottom surfaces of both sides were sealed with an insulator such as cloth adhesive tape. In addition, the steel plates 11 to 13 other than the steel plate 14 are provided with an 8 mmφ through-hole 15 at the bottom.

  4 liters of the cationic electrodeposition coating composition described in each example or each comparative example was transferred to a vinyl chloride container to form a first electrodeposition tank. As shown in FIG. 2, the box 10 was immersed in an electrodeposition paint container 20 containing an electrodeposition paint 21 as an object to be coated. In this case, the paint 21 enters the box 10 only from each through hole 15.

  The coating material 21 was stirred with a magnetic stirrer (not shown). And each steel plate 11-14 was electrically connected and the counter electrode 22 was arrange | positioned so that the distance with the nearest steel plate 11 might be set to 150 mm. Cathode electrodeposition coating was performed on the cold-rolled steel sheet subjected to chemical conversion treatment by applying a voltage with each steel plate 11-14 as a cathode and the counter electrode 22 as an anode. The coating was performed by increasing the voltage up to a voltage at which the film thickness of the coating film formed on the A surface of the steel plate 11 reached 15 μm within 5 seconds from the start of application, and then maintaining the voltage for 175 seconds in normal electrodeposition.

  Each steel sheet after painting is washed with water, baked at 170 ° C. for 25 minutes, and after air cooling, the film thickness of the coating film formed on the A surface of the steel sheet 11 closest to the counter electrode 22 and the farthest from the counter electrode 22 The film thickness of the coating film formed on the G surface of the steel plate 14 was measured, and the throwing power was evaluated by the ratio (G / A value) of film thickness (G surface) / film thickness (A surface). Generally, when this value exceeds 50%, it is good (◯), and when this value is 50% or less, it can be judged as defective (×).

As shown in Table 2 above, in any case of electrodeposition coating using the cationic electrodeposition coating composition of the example, the object to be coated treated with the zirconium-based chemical conversion treatment agent of Production Example 1 is electrodeposited. Even in this case, it was confirmed that a cured electrodeposition coating film having a coating film appearance comparable to that in the case of electrodeposition coating on the object treated with the zinc phosphate chemical conversion treatment agent was obtained.
On the other hand, when using the cationic electrodeposition coating composition of Comparative Example 1 that does not contain a conductivity control agent, it was confirmed that the throwing power was inferior.
Further, when the cationic electrodeposition coating composition of Comparative Example 2 in which the SP value of the resin component contained in the cationic electrodeposition coating composition exceeds 11.7 is used, the coating viscosity at 50 ° C. of the electrodeposition coating is 3000 Pa. In the case of using the cationic electrodeposition coating composition of Comparative Example 3 exceeding s, a cured electrode having a good coating film appearance is applied when an object to be coated treated with a zinc phosphate-based chemical conversion treatment agent is electrodeposited. Although a coated film was obtained, it was confirmed that the appearance of the coated film was inferior when the object to be coated treated with the zirconium-based chemical conversion treatment agent was electrodeposited.
Further, in Comparative Example 4 in which the solid content concentration of the paint is 20% by mass, a cured electrodeposition coating film having a good coating film appearance even in the case of electrodeposition coating of an object treated with a zirconium-based chemical conversion treatment agent. However, since the solid content of the paint was high, it was confirmed that the horizontal appearance in the unstirred paint was inferior.

  In the present invention, even in the case of electrodeposition coating on an object to be treated or an untreated object treated with a zirconium-based chemical conversion treatment agent, the object treated with a zinc phosphate-based chemical conversion treatment agent Similar to the case of coating, it has a feature that a cured electrodeposition coating film having a good coating film appearance can be obtained. For this reason, since there is no need to use a zinc phosphate chemical conversion treatment agent, there are advantages that the load on the environment is small and sludge (sludge) is not generated. And the cationic electrodeposition coating composition of this invention has the characteristics that there are few precipitates even when it is left still for a long time, and also has the outstanding throwing power. In the present invention, in addition to the above-mentioned advantages, constant stirring in the storage of the electrodeposition coating composition and constant stirring of the electrodeposition tank in electrodeposition coating are not required, and stirring is omitted or intermittently stirred. It also has the advantage of being able to. By this invention, the coating cost in coating can be reduced significantly.

It is a perspective view which shows an example of the box used when evaluating throwing power. It is sectional drawing which shows typically the evaluation method of throwing power.

Explanation of symbols

10: Box 11-14: Chemical conversion treatment steel plate 15: Through hole 20: Electrodeposition coating container 21: Electrodeposition paint 22: Counter electrode

Claims (4)

A cationic electrodeposition coating composition used for electrodeposition coating of a coating treated with a chemical conversion treatment agent containing zirconium ions or an untreated coating,
The cationic electrodeposition coating composition contains at least a conductivity control agent comprising a cationic epoxy resin, a blocked isocyanate curing agent, and an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g. A cationic electrodeposition coating composition of 0.5 to 9.0% by mass,
The SP value of the resin component contained in the cationic electrodeposition coating composition is 11.7 or less,
In the electrodeposition coating under a predetermined condition using the cationic electrodeposition coating composition, the coating viscosity at 50 ° C. of the electrodeposition coating obtained from the cationic electrodeposition coating composition is 3000 Pa · s or less, The time from the start of voltage application until the coating resistance value of the deposited electrodeposition coating film reaches 30 kΩ · cm ² is within 12 seconds, and the predetermined condition is that the voltage application is performed at a coating temperature of 30 ° C. for 180 seconds. It is a condition for forming a coating film having a dry film thickness of 15 μm.
Cationic electrodeposition coating composition.   The cationic electrodeposition coating composition further comprises a non-crosslinked acrylic resin having a solubility parameter of 10.4 to 11.0, a glass transition temperature of 20 to 80 ° C, and a number average molecular weight of 2500 to 3500. The cationic electrodeposition coating composition as described.   The cationic electrodeposition coating composition according to claim 1 or 2, wherein the blocked isocyanate curing agent is a blocked isocyanate obtained by blocking an aromatic diisocyanate or an aromatic polyisocyanate. A cationic electrodeposition coating method for forming an electrodeposition coating on an object to be coated or an untreated object treated with a chemical conversion treatment agent containing zirconium ions,
The cationic electrodeposition coating composition is the cationic electrodeposition coating composition according to any one of claims 1 to 3,
In electrodeposition coating under a predetermined condition at a coating temperature of 30 ° C., the time from the start of voltage application until the coating resistance value of the deposited electrodeposition coating reaches 30 kΩ · cm ² is within 12 seconds. The predetermined condition is a condition in which a coating film having a dry film thickness of 15 μm is formed by applying a voltage for 180 seconds at a coating temperature of 30 ° C.,
Cationic electrodeposition coating method.

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