JP2010043189A - Replenishing paint for cationic electrodeposition paint, and method for replenishing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make possible supply of electrodeposition paints in one pack by examining component of the replenishing paint. <P>SOLUTION: The replenishing paint for cationic electrodeposition paint to be replenished to a bathtub of electrodeposition paints is so controlled that its viscosity measured by the E-type viscometer at 5 rpm and at 25°C is 100-500 mPa s, and its thixotropy index (Ti-value) is in the range of 2-4, and the method of replenishing the cationic electrodeposition paint bath is to use the replenishing paint in one pack. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a replenishment paint containing a high concentration resin to be replenished to a cationic electrodeposition paint and a method for replenishing a cationic electrodeposition paint using the same.

  Cationic electrodeposition coating is a coating method performed by immersing an object to be coated in a cationic electrodeposition coating composition as a cathode and applying a voltage. In this method, even a workpiece having a complicated shape can be applied to the details, and can be applied automatically and continuously. It has been widely put into practical use as an undercoating method for objects to be coated.

  The cationic electrodeposition coating is subjected to an electrodeposition coating treatment in an electrodeposition bath installed in a large factory such as an automobile assembly factory, and then baked to form a cured undercoat film. A cationic electrodeposition coating bath is a water-based low-viscosity coating liquid, and as described above, applying a voltage causes the coating components to deposit on the substrate to form a coating film. During this time, the pigment and the resin component are taken out together with the object to be coated, and the coating film forming component of the coating is reduced in the cationic electrodeposition coating bath. Therefore, generally, in the cationic electrodeposition paint bath, a high-concentration paint called a replenishment paint is transported from the paint company to the automobile assembly factory and replenished to the cationic electrodeposition paint bath.

  In the case of a replenishing paint that is used repeatedly and applied to a cationic electrodeposition paint bath having a reduced solid content, the replenishing paint generally has a high solid content and a high specific gravity of the pigment to be blended. Furthermore, since the viscosity of the replenishing paint is low, precipitation of the blended pigment tends to occur. When the replenishment paint in which the pigment has settled is replenished to the cationic electrodeposition paint bath, it is necessary to sufficiently stir and redisperse the settled pigment. However, when redispersing, not only a great amount of energy is consumed, but if the redispersion of the pigment is insufficient, the active ingredient cannot be replenished as designed, resulting in the composition of the cationic electrodeposition paint bath. Ingredients may become out of design and cause various problems. This is because the viscosity of the cationic electrodeposition coating resin replenisher (resin emulsion containing a curing agent) is very low. Accordingly, if the pigment dispersion paste and the cationic electrodeposition paint resin replenisher are handled separately (two-pack), the pigment dispersion paste having a high viscosity can be kept relatively stable because the sedimentation is moderated. On the other hand, the two-packing of the above-mentioned cationic electrodeposition replenishing paint causes an increase in transportation cost, and the paint user wants to develop a replenishing paint that is made into one liquid again and solves the above problems. It was.

  Although there is very little conventional technology in which the concept of replenishing paint for cationic electrodeposition paints is considered, for example, Japanese Patent Application Laid-Open No. 2005-126749 (Patent Document 1) reduces storage space for replenishing paint and maintenance for storage. In order to do this, it is described that the replenishing paint is put in the moving body equipped with the delivery container. This Patent Document 1 merely describes a method for reducing the place where the replenishing paint is placed at the user (customer), and is not a patent relating to the components of the replenishing paint.

  Japanese Patent Application Laid-Open No. 2002-256495 (Patent Document 2) describes that when the hue of one cationic electrodeposition paint is shifted to another hue, the hue is gradually shifted by changing the hue of the replenisher. ing. This replenishing paint is merely different in color and does not consider the components of the replenishing paint itself.

  Japanese Patent Application Laid-Open No. 7-188987 (Patent Document 3) discloses a solution in which an organic acid salt of dimethyllaurylamine is blended in a replenisher of a cationic electrodeposition coating. This is merely an addition of an organic acid salt of dimethyllaurylamine in order to control the composition ratio of the acid component / base component of the electrodeposition bath, and this is not a control of the component of the replenishing paint.

As described above, there are very few examples of examining the replenishment paint of the cationic electrodeposition paint.
Japanese Patent Laid-Open No. 2005-126749 JP 2002-256495 A JP-A-7-188987

  The object of the present invention is to examine the components of the replenishing paint of the cationic electrodeposition paint, which has hardly been studied in the prior art, and to reduce the replenishing paint from one pack to a one pack and at the same time prevent sedimentation of the paint components.

  The present invention relates to a replenishing paint to be replenished to a cationic electrodeposition paint bath, wherein the replenishing paint has a viscosity of 100 to 500 mPa · S at 25 rpm at 25 ° C. according to an E-type viscometer and a thixotropy index (Ti value) of 2 A replenishing paint for a cationic electrodeposition paint characterized by being in the range of 4.

  The present invention also provides a replenishing paint for cationic electrodeposition paint having a solid content concentration of 30% by mass or more.

  Furthermore, the present invention provides that the replenishing paint performs viscosity adjustment by blending a viscosity modifier.

  Furthermore, the present invention provides a replenishing coating material for a cationic electrodeposition coating material containing a viscosity modifier in an amount of 0.1 to 0.5% by mass relative to the resin solid content in the coating material.

  The present invention also provides a pigment dispersion paste and a high-concentration cationic electrode instead of a two-pack replenishment of the pigment dispersion paste and the high-concentration cationic electrodeposition paint resin replenisher when replenishing the paint to the cationic electrodeposition paint bath. One-pack replenishment paint containing a coating resin replenisher is made to have a viscosity of 100 to 500 mPa · S and a thixotropy index (Ti value) of 2 to 4 at 25 rpm at 25 ° C. using an E-type viscometer. A method for supplying replenishment paint to a paint is provided.

  In the present invention, by simply blending a viscosity modifier in the replenishment paint of the cationic electrodeposition paint, it has been replenished with a two-pack of the pigment dispersion paste and the high-concentration cationic electrodeposition paint resin replenisher until now. It became possible to make one pack. If a viscosity modifier is blended and the viscosity at 5 rpm at 25 ° C. by an E-type viscometer is adjusted to 100 to 500 mPa · S and the thixotropy index (Ti value) is adjusted to a range of 2 to 4, precipitation of the pigment is suppressed. Since it can be replenished as it is without the need for redispersion, there are significant advantages such as the preparation of a replenishing paint being only one solution and the fact that it can be delivered to customers in one solution.

  Viscosity modifiers are usually blended in general viscous paints, whereas cationic electrodeposition paints usually do not require viscosity modifiers. This is because the electrodeposition paint is a so-called shabu-shabu paint having a low viscosity as described above, and thus it is not necessary to adjust the viscosity. In addition, adding a viscosity modifier to the electrodeposition paint increases the solid content to about 90% by weight at the time of coating. However, the flowability of the coating film deteriorates due to the presence of the viscosity modifier. Therefore, the finished skin becomes worse. According to the present invention, the two-pack paint can be made into one pack by blending the viscosity modifier, which has not been blended with the cationic electrodeposition paint composition, into the replenishment paint of the electrodeposition paint. The industrial contribution is immense. When the viscosity modifier is blended in the replenishing paint, the viscosity adjusting action is greatly reduced by dilution in the main electrodeposition tank. Moreover, the bad influence (deterioration of flow property) which a viscosity modifier brings can be made low by selecting what is not concentrated in the coating film applied as a viscosity modifier.

  The reason why the viscosity of the electrodeposition paint is lowered is that, as described above, since the viscosity of the emulsion containing the curing agent is low, the viscosity of the entire electrodeposition paint is lowered. When replenishing this paint, the conventional replenishing paint is used as it is because it is not designed as a one-pack replenishing paint with a high concentration of the conventional electrodeposition paint. Even if it is made into one pack, there is a possibility that a problem that the pigment component contained in the replenishing paint settles may occur. In order to solve this problem, conventionally, the component of the replenishing paint is made into a two-pack consisting of a pigment dispersion paste and an electrodeposition paint resin replenishing solution, or the one-packed replenishing paint is continuously stirred. It was necessary to take measures. When two-packed, the pigment dispersion paste has a relatively high viscosity, so that the pigment hardly settles even in a stationary state, and the electrodeposition resin replenisher does not contain a pigment component that is likely to settle. Therefore, although the above-described problems have been solved, there has been a problem of transportation costs as described above. In the present invention, the problem can be solved only by adjusting the viscosity of the replenishing paint without using means such as two-packing.

  A viscosity modifier is blended in the replenishing coating composition for cationic electrodeposition coating of the present invention. Various commercially available products can be used as the viscosity modifier. The solid content concentration of the cationic electrodeposition replenishing coating composition containing the viscosity control agent is preferably 30% by mass or more. This is because if the solid content concentration of the replenishing coating composition is below the desired lower limit, it is not preferable because sufficient solid content cannot be replenished in the cationic electrodeposition coating bath that has been used repeatedly and has a reduced solid content concentration.

  Even if the composition of the replenishing paint for the cationic electrodeposition paint, which was a conventional two-pack, is made into a one-pack, the viscosity of the whole paint such as replenishment is low, so the problem that the pigment component contained in the replenishing paint settles occurs. There is a fear.

  The viscosity adjusting agent that can be used in the present invention may be either organic or inorganic, and in particular, the viscosity at 100 ° C. and 500 mPa · s at 25 rpm at 25 ° C. by an E-type viscometer of the replenishing paint In addition, it is only necessary that the Ti value can be in the range of 2 to 4. Specific examples include fatty acid amide swelling dispersions, amide fatty acids, polyamides such as long-chain polyaminoamide phosphates (such as the Dispalon series manufactured by Enomoto Kasei Co., Ltd.), organic acid smectite clay, montmorillonite, etc. Organic bentonite-based (such as thixogel series manufactured by Sud Chemie Catalyst), inorganic pigments such as aluminum silicate and barium sulfate (such as Takehara Chemical), flat pigments that develop viscosity depending on the shape of the pigment, polyester-modified urethane emulsion, Examples include various modified urethane compounds such as polyether-modified urethane emulsion (BYK series manufactured by BYK Chemie), and the like.

  Among these, various modified urethanes are preferable.

In this specification, the thixotropy index (Ti value) is an index indicating thixotropy, and the thixotropy means the property of becoming a sol when stirred at a constant temperature and returning to a gel state when left untreated. To do. Although it depends on the characteristics of the pigment particles and the vehicle, it is a property often seen in dispersions. This is because the internal structure of the gel is destroyed by the external force and the fluidity is increased, but the bonds between the particles are reproduced when left standing. Generally, in a dispersion system such as a paste, the viscosity value decreases according to the rotation speed, but the thixotropy index is obtained by taking a ratio of viscosity values at different rotation speeds a and b (a> b). In the present invention, measurement is performed at ₅ rpm and 50 rpm using an E-type viscometer, and the ratio of the viscosity, η _{5 /} η _50, is set as the Ti value (measurement temperature: 25 ° C.).

  The viscosity modifier is an amount of 0.1 to 0.5% by mass, preferably 0.1 to 0.3% by mass, more preferably 0, based on the replenishing coating resin solid content of the replenishing coating composition for cationic electrodeposition coatings. It mix | blends in the quantity of 15-0.25 mass%. If it is less than 0.1% by mass, the effect of adjusting the viscosity cannot be obtained, and it becomes difficult to make the replenishing paint into a one-pack type. Even if the amount exceeds 0.5% by mass, the effect of adjusting the viscosity cannot be obtained, and conversely, there are defects due to high viscosity such as detergency and surface drying.

  In the present invention, the viscosity of the replenishment paint for the cationic electrodeposition paint is in the range of 100 to 500 mPa · S, preferably 200 to 400 mPa · S, more preferably 300 to 400 mPa · S at 5 rpm (25 ° C.) of an E-type viscometer. To adjust. This viscosity is measured with an E-type viscometer. When it is less than 100 mPa · S, the viscosity of the replenishing paint is insufficient and the pigment is precipitated. When it is higher than 500 mPa · S, the viscosity is too high, and there are defects such as cleanability and surface drying.

  Furthermore, in the present invention, it is necessary to prepare the Ti value of the replenishing paint for the cationic electrodeposition paint to be 2 to 4, preferably 3 to 4. When the Ti value is less than 2, the sedimentation stability of the pigment is deteriorated, and when it exceeds 4, the viscosity of the paint is excessively increased, and the storage stability is adversely affected. .

Cationic electrodeposition paint composition The cationic electrodeposition paint composition used in the replenishment paint for the cationic electrodeposition paint of the present invention has a high concentration because it is a replenishment paint, but it is a composition used in a general cationic electrodeposition paint composition. It may be the same thing. Each component will be described below.

Cationic Epoxy Resin The cationic epoxy resin used in the replenishment paint for the cationic electrodeposition paint of the present invention includes an epoxy resin modified with an amine. Cationic epoxy resins typically open all of the epoxy rings of a bisphenol-type epoxy resin with an active hydrogen compound capable of introducing a cationic group, or some epoxy rings with other active hydrogen compounds. It is produced by opening the ring and opening the remaining epoxy ring with an active hydrogen compound capable of introducing a cationic group.

  A typical example of the bisphenol type epoxy resin is a bisphenol A type or bisphenol F type epoxy resin. As the former commercial product, there are Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Epoxy Equivalent 180-190), Epicoat 1001 (Same, Epoxy Equivalent 450-500), Epicoat 1010 (Same, Epoxy Equivalent 3000-4000), etc. Examples of the latter commercially available product include Epicoat 807 (same as above, epoxy equivalent 170).

  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. An oxazolidone ring-containing epoxy resin represented by the above formula may be used as the cationic epoxy resin. This is because a coating film having excellent heat resistance and corrosion resistance can be obtained.

  As a method for introducing an oxazolidone ring into an epoxy resin, for example, a block polyisocyanate 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 introduced from the system. Obtained by distilling off.

  It is known that an epoxy resin containing an oxazolidone ring can be obtained by reacting a bifunctional epoxy resin with a diisocyanate blocked with a monoalcohol (ie, bisurethane). Specific examples and production methods of the oxazolidone ring-containing epoxy resin are described in, for example, paragraphs 0012 to 0047 of JP-A No. 2000-128959 and are publicly known.

  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.

  These epoxy resins are ring-opened with an active hydrogen compound so that an amine equivalent of 0.3 to 4.0 meq / g is obtained after ring opening, and more preferably 5 to 50% of them are occupied by primary amino groups. It is desirable to do.

  Active hydrogen compounds that can introduce a cationic group include primary amines, secondary amines, tertiary amine acid salts, sulfides and acid mixtures. In order to prepare a primary, secondary or / and tertiary amino group-containing epoxy resin, an acid salt of a primary amine, secondary amine or tertiary amine is used as an active hydrogen compound capable of introducing a cationic group.

  Specific examples include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, diethyl disulfide / acetic acid mixture, etc. In addition, there are secondary amines in which primary amines such as aminoethylethanolamine ketimine and diethylenetriamine diketimine are blocked. A plurality of amines may be used in combination.

Curing Agent The curing agent used in the present invention is preferably a blocked polyisocyanate obtained by blocking polyisocyanate with a blocking agent, where polyisocyanate refers to 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 such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2,4- C3-C12 aliphatic diisocyanates such as trimethylhexane diisocyanate and lysine diisocyanate; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI) , Methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and 1,3-diisocyanatomethylcyclo Carbon such as xane (hydrogenated XDI), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also referred to as norbornane diisocyanate). Aliphatic diisocyanates having a number of 5 to 18; aliphatic diisocyanates having aromatic rings such as xylylene diisocyanate (XDI) and tetramethylxylylene diisocyanate (TMXDI); modified products of these diisocyanates (urethanes, carbodiimides, Uretdione, uretoimine, burette and / or isocyanurate modified product); and the like. 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 curing agents.

  The polyisocyanate is preferably an aliphatic polyisocyanate or an alicyclic polyisocyanate. This is because the formed coating film is excellent in weather resistance.

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

  The blocking agent is added to a polyisocyanate group and is stable at ordinary temperature, but can regenerate a free isocyanate group when heated to a temperature higher than the dissociation temperature.

  As a blocking agent, when low temperature curing (160 ° C. or lower) is desired, lactam blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam and β-propiolactam, and formaldoxime, acetoald It is preferable to use an oxime blocking agent such as oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, and cyclohexane oxime.

  In general, the total amount of the cationic epoxy resin and the curing agent may be 25 to 85% by mass, preferably 40 to 70% by mass, based on the total solid content of the replenishing coating material for the cationic electrodeposition coating material.

Pigment The replenishing paint used in the present invention may contain a commonly used pigment. Examples of pigments that can be used include commonly used inorganic pigments, for example colored pigments such as titanium white, carbon black and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; Zinc phosphate, iron phosphate, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and aluminum phosphomolybdate, phosphomolybdic acid Examples include rust preventive pigments such as aluminum zinc.

  The pigment is generally contained in the replenishing paint in an amount of 1 to 35% by weight, preferably 3 to 25% by weight, based on the total solid content of the replenishing paint.

Pigment-dispersed paste When a pigment is used as a component of a replenishing paint, 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 in an aqueous medium together with a pigment dispersion resin varnish. As the pigment-dispersed resin varnish, 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.

  After the pigment dispersion resin varnish and the pigment are mixed in a solid content ratio of 20 to 100 parts by mass with respect to 100 parts by mass of the pigment, a ball mill or sand is used until the particle size of the pigment in the mixture reaches a predetermined uniform particle size. A pigment dispersion paste is obtained by dispersing using a normal dispersing device such as a grind mill.

Replenishment Paint Composition Preparation A replenishment paint is prepared by dispersing a cationic epoxy resin, a curing 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 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. In general, it is generally in the range of 90/10 to 50/50, preferably 80/20 to 65/35, expressed as a solid mass ratio of the cationic epoxy resin to the curing agent.

  The replenishing paint may contain a tin compound such as dibutyltin dilaurate or dibutyltin oxide, or a normal urethane cleavage catalyst. Since what does not contain lead substantially is preferable, it is preferable that the quantity shall be 0.1-5 mass% of the block polyisocyanate compound which is a hardening | curing agent.

  The replenishing coating composition can contain conventional coating additives such as water miscible organic solvents, surfactants, antioxidants, and UV absorbers.

  According to the present invention, in a method for replenishing a paint to a cationic electrodeposition paint bath, a two-pack (pigment-dispersed paste and a high concentration having a solid content concentration of 30% by mass or more is obtained by incorporating a viscosity modifier in the replenished paint. Provided is a paint replenishing method in which a cationic electrodeposition paint resin replenisher) is made into one pack. Thereby, when this paint is replenished to the cationic electrodeposition paint bath, it returns to the normal viscosity, and the influence of the viscosity control agent hardly exists due to the dilution effect. In addition, the cationic electrodeposition paint to which the replenishment paint is replenished is completely the same as the components of the conventional cationic electrodeposition paint, so that there is no appearance and no defects, and electrodeposition coating is possible. The solid content concentration of the one-pack replenishment paint is 30% by mass or more, while the initial solid content concentration in the cationic electrodeposition paint bath is about 20% by mass. For this reason, even if it is repeatedly used and the solid content concentration falls below 20% by mass, the solid content concentration in the cationic electrodeposition paint bath is set to the initial value by replenishing the one-pack replenishment paint. Can be recovered.

  The invention is explained in more detail by means of examples. The present invention should not be construed as being limited to these examples.

Production Example 1 Production of Blocked Isocyanate Curing Agent 199 parts of hexamethylene diisocyanate trimer (Coronate HX: manufactured by Nippon Polyurethane Co., Ltd.) and methyl in a flask equipped with a stirrer, cooler, nitrogen injection tube, thermometer and dropping funnel 32 parts of isobutyl ketone and 0.03 part of dibutyltin dilaurate were weighed, and 87.0 parts of methyl ethyl ketoxime was added dropwise from the dropping funnel over 1 hour while stirring and bubbling nitrogen. The temperature was increased from 50 ° C. to 70 ° C. Thereafter, the reaction was continued for 1 hour, and the reaction was continued until the absorption of the NCO group disappeared with an infrared spectrometer. Thereafter, 0.74 parts of n-butanol and 39.93 parts of methyl isobutyl ketone were added to obtain a nonvolatile content of 80%.

Production Example 2 Production of Emulsion Containing Cationic Epoxy Resin and Cationic Epoxy Resin and Curing Agent A flask equipped with a stirrer, a cooler, a nitrogen injection tube and a dropping funnel was charged with 2,4 / 2,6-tolylene diisocyanate (80 / 20 wt%) 71.34 parts, 111.98 parts of methyl isobutyl ketone and 0.02 part of dibutyltin dilaurate were weighed, and 14.24 parts of methanol was added dropwise from the dropping funnel over 30 minutes while stirring and nitrogen bubbling. did. The temperature was raised from room temperature to 60 ° C. due to heat generation. Thereafter, the reaction was continued for 30 minutes, and then 46.98 parts of ethylene glycol mono-2-ethylhexyl ether was added dropwise from the dropping funnel over 30 minutes. The temperature was raised to 70 to 75 ° C. due to heat generation. After continuing the reaction for 30 minutes, 41.25 parts of bisphenol A propylene oxide (5 mol) adduct (BP-5P manufactured by Sanyo Chemical Industries, Ltd.) was added, the temperature was raised to 90 ° C., and the IR spectrum was measured. The reaction was continued until the NCO group disappeared.

  Subsequently, 475.0 parts of a bisphenol A type epoxy resin having an epoxy equivalent of 475 (YD-7011R manufactured by Toto Kasei Co., Ltd.) was added and dissolved uniformly, then the temperature was raised from 130 ° C. to 142 ° C., and azeotrope with MIBK To remove water from the reaction system. After cooling to 125 ° C., 1.107 parts of benzyldimethylamine was added to carry out an oxazolidone ring formation reaction by a demethanol reaction. The reaction was continued until an epoxy equivalent of 1140.

  Thereafter, the mixture was cooled to 100 ° C., 24.56 parts of N-methylethanolamine, 11.46 parts of diethanolamine and 26.08 parts of aminoethylethanolamine ketimine (78.8% methyl isobutyl ketone solution) were added, and 110 ° C. for 2 hours. Reacted. Thereafter, 20.74 parts of ethylene glycol mono-2-ethylhexyl ether and 12.85 parts of methyl isobutyl ketone were added to dilute to adjust to 82% non-volatile matter. The number average molecular weight (GPC method) was 1380, and the amine equivalent was 94.5 meq / 100 g.

  In a separate container, 145.11 parts of ion-exchanged water and 5.04 parts of acetic acid were weighed, and 320.11 parts (75.0 parts as a solid content) of the above cationic epoxy resin heated to 70 ° C. and Production Example 1 A mixture of 190.38 parts of the blocked isocyanate curing agent (25.0 parts as a solid content) was gradually added dropwise and stirred to disperse uniformly. Thereafter, ion exchange water was added to adjust the solid content to 36%.

Production Example 3 Production of Pigment Dispersion Resin Varnish To a flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer and a dropping funnel, 382.20 parts of bisphenol A type epoxy resin (trade name DER-331J) having an epoxy equivalent of 188 Then, 111.98 parts of bisphenol A was weighed, heated to 80 ° C. and dissolved uniformly, and then 1.53 parts of a 1% solution of 2-ethyl-4-methylimidazole was added and reacted at 170 ° C. for 2 hours. . After cooling to 140 ° C., 196.50 parts of 2-ethylhexanol half-blocked isophorone diisocyanate (non-volatile content: 90%) was added thereto and reacted until the NCO group disappeared. To this was added 205.00 parts of dipropylene glycol monobutyl ether, followed by 408.00 parts of 1- (2-hydroxyethylthio) -2-propanol and 134.00 parts of dimethylolpropionic acid. 0.000 part was added and it was made to react at 70 degreeC. The reaction was continued until the acid value was 5 or less. The resulting resin varnish was diluted to 350.5% non-volatile content with 1150.50 parts of ion exchange.

Production Example 4 Production of Pigment Dispersion Paste 238 parts of the pigment dispersion resin varnish obtained in Production Example 3 in a sand grind mill, 100 parts of titanium dioxide and 44 parts of ion-exchanged water are dispersed until the particle size is 10 μm or less. A dispersion paste was obtained (solid content 48.0%).

Examples 1-4 and Comparative Examples 1-3
Preparation of Replenishing Paint for Cationic Electrodeposition Paint Emulsion comprising the cationic epoxy resin obtained in Production Example 2 and a curing agent and the blocked isocyanate curing agent obtained in Production Example 1 are uniformly at a solid content ratio of 80/20 It mixed so that it might become. Glacial acetic acid was added to this so that the milligram equivalent (MEQ (A)) of the acid per 100 g of resin solid content was 30, and further ion-exchanged water was slowly added for dilution. By removing MIBK under reduced pressure, an emulsion having a solid content of 40% was obtained.

  1370 parts of this emulsion and 67 parts of the pigment dispersion paste obtained in Production Example 4, 13 parts of ion-exchanged water and 8 parts of dibutyltin oxide were mixed, and after stirring, thickeners described in Table 1 below ( (Viscosity modifier) was blended (the blending amount was 0.15 to 0.5 wt% with respect to the solid content), and a replenishing paint for a cationic electrodeposition paint having a solid content of 40% and an ash content of 3% was prepared. The viscosity of this replenishing paint was measured with an E-type viscometer. In addition, a reference | standard is an example without a thickener, Comparative Examples 1-3 mix | blends a viscosity regulator, but the viscosity measured at 25 rpm at 5 rpm with the E-type viscosity meter in the range of 100-500 mPa * S. It does not enter.

  Further, the coating amount and the change in ash content after one week and the appearance (surface roughness) after electrodeposition coating were measured for the paint.

The measuring method was as follows.
(1) Viscosity measurement E type viscosity, 5 rpm, 50 rpm (respective viscosity is η ₅ , η ₅₀ ), measurement temperature: 25 ° C.
(2) Ti value The Ti value was represented by the value of η _{5 /} η ₅₀ of the viscosity determined by the above viscosity measurement.
(3) Sedimentation test Put the above replenisher into a test tube (350 mm x 20 mm in diameter) and let stand at 40 ° C for one week, then measure the pigment sedimentation amount (visual observation) and the ash content (upper layer and lower layer of the test tube). .
(4) Appearance evaluation After the above replenisher was diluted to 7% solids with deionized water, electrodeposition coating was performed at a voltage of 200 volts at 30 ° C for 3 minutes, and baked at 160 ° C for 15 minutes. The Ra value of the film was measured using an evaluation type surface roughness measuring machine (manufactured by Mitutoyo Corporation, SURFTEST SJ-201P) in accordance with JIS-B0601. Measurement was performed 7 times using a sample with a 2.5 mm width cut-off (number of sections: 5), and an Ra value was obtained by an average of vertical erase. The results are shown in Table 1. It can be said that the smaller the Ra value, the less the unevenness and the better the coating film appearance.

基準は増粘剤がない例である。

The standard is an example without a thickener.

  Thickener A is a non-urethane associative thickener made by Sud Chemie Catalyst, Optiflo L100, and thickener B is Optiflo L150. Thickener C is a urethane-modified polyether, Additol VXW6388, manufactured by Ito Oil. Thickener D is Bermodol PUR2150 (urethane modified polyether) manufactured by Akzo Nobel. Thickener E is BYK-425 which is a urea-modified urethane type thickener manufactured by Big Chemie. Thickener F is Rheolate 288 (urea modified urethane-based associative thickener) commercially available from Elementis.

As described above, the replenishment paint for cationic electrodeposition paints containing the viscosity modifier is greatly improved in settling property than that without the viscosity modifier. Examples 1 to 4 having a viscosity η ₅ of 100 to 500 mPa · s at 25 rpm at 25 ° C. with an E-type viscometer are excellent because there is no amount of pigment deposited and almost no change in ash content. be able to.

Claims (6)

  In the replenishment paint to be replenished to the cationic electrodeposition paint bath, the replenishment paint has a viscosity of 100 to 500 mPa · S at 25 ° C. at 25 ° C. with an E-type viscometer, and a thixotropic index (Ti value) in the range of 2 to 4. A replenishing paint for a cationic electrodeposition paint characterized by being.   2. The replenishing coating material for cationic electrodeposition coating material according to claim 1, wherein the solid content concentration is 30% by mass or more.   The replenishing paint for cationic electrodeposition paints according to claim 1, wherein the replenishing paint is adjusted by blending a viscosity modifier.   The replenishment paint for cationic electrodeposition paints according to claim 1, wherein the viscosity modifier is contained in an amount of 0.1 to 0.5% by mass relative to the resin solid content in the replenishment paint.   In the method of replenishing paint to the cationic electrodeposition paint bath, in place of the two-pack replenishment of the pigment dispersion paste and the high concentration cationic electrodeposition paint resin replenisher, the pigment dispersion paste and the high concentration cationic electrodeposition paint resin replenisher To a cationic electrodeposition paint bath characterized by having a viscosity of 100 to 500 mPa · S at 25 rpm at 25 ° C. and a thixotropy index (Ti value) of 2 to 4 using an E-type viscometer. How to replenish paint.   6. A method of electrodeposition coating using a cationic electrodeposition paint bath in which a replenishment paint is replenished by the replenishment method according to claim 5.