JP2010280787A - Method for improving deposition property of cationic electrodeposition coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the throwing power of a high solid content type cationic electrodeposition coating in an electrodeposition coating method using the high solid content type cationic electrodeposition coating, especially the electrodeposition coating method in which a UF filtration washing recovery process of the taken out coating is performed. <P>SOLUTION: The method for improving the throwing power of the high solid content type cationic electrodeposition coating which has a coating solid content concentration of 23.0 to 30.0 mass% and a coating ash content concentration of 25.0 to 30.0 mass% and contains an amine-modified epoxy resin as a coating film-forming component is characterized by including a process for adding an amino group-containing compound having a number-average mol.wt. of ≤2,000 and an amine value of 150 to 500 mmol/100 g to the high solid content type cationic electrodeposition coating. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cationic electrodeposition coating method, and more particularly, to a cationic electrodeposition coating method in which the time required for washing the coating water is shortened.

  Electrodeposition coating can be applied to the details even if the object has a complicated shape, and it can be applied automatically and continuously. It is widely used as an undercoating method for objects to be coated that requires high rust prevention. Moreover, it is economical because the use efficiency of the paint is extremely high compared with other coating methods, and is widely used as an industrial coating method. Cationic electrodeposition coating is performed by immersing an object to be coated in a cationic electrodeposition paint as a cathode and applying a voltage.

  The deposition of the coating film in the process of cationic electrodeposition coating is due to an electrochemical reaction, and the coating film is deposited on the surface of the object to be coated by applying a voltage. Since the deposited coating has insulating properties, the electrical resistance of the coating increases as the deposition of the coating proceeds and the thickness of the deposited film increases in the coating process.

  As a result, the deposition of the coating material on the part is lowered, and instead, the coating film is deposited on the undeposited part. In this way, the coating solids are sequentially deposited on the non-deposited portions to complete the coating. In the present specification, the property that a coating film is sequentially formed on an unattached portion of an object to be coated is referred to as throwing power.

  In the cationic electrodeposition coating, as described above, an insulating coating film is sequentially formed on the surface of the object to be coated, so theoretically it has an infinite wraparound property, and all of the object to be coated is present. It should be possible to form a uniform coating on the part.

  However, in the unattached part of the object to be coated, the applied voltage in the bath is weak compared to the part to be adhered, so that the solid content of the paint is difficult to arrive, and the throwing power of the electrodeposition paint is not always sufficient, Unevenness of film thickness occurs.

As a general technique taken to improve the throwing power of the electrodeposition paint, there is adjustment of the solid content of the paint. If the solid content of the paint is less than 23.0%, there is a risk that the throwing power in the paint will be low. Conversely, if the solid content of the paint exceeds 30.0%, the filter of the pump for circulating and stirring the electrodeposition paint There are problems such as clogging and deterioration of sedimentation stability of the paint, which is not desirable.
In addition, increasing the concentration of ash (pigment) in the paint can also improve the paint coverage. By adding more pigment having a higher electric resistance than that of the resin, the throwing power can be improved by increasing the insulating property of the obtained electrodeposition coating film. If the ash concentration in the paint is 25.0% or less, high film resistance may not be obtained. Conversely, if the ash concentration is 30.0% or more, the coating viscosity becomes too high, and the coating film This is undesirable because it significantly impairs the appearance.

  There is also a factor of reduction in throwing power due to the electrodeposition coating method. In the electrodeposition coating method, the object to be coated is immersed in the electrodeposition paint filled in the electrodeposition tank, the film is formed by energizing the object to be coated, and after the film formation is completed, the electrodeposition paint is removed from the electrodeposition tank. A process of cleaning and baking the excess paint (generally referred to as “take-out paint”) that has been pulled up is performed.

  When electrodeposition coating is performed on an industrial scale, the paint taken out is collected and recycled to the electrodeposition tank for reuse. In order to prevent the composition of the electrodeposition paint from affecting the composition of the electrodeposition paint even if it is circulated through the electrodeposition tank, the filtered electrodeposition paint filled in the electrodeposition tank is filtered. A filtrate from which the high molecular weight component has been removed is used.

  At that time, a filter used for filtering the electrodeposition paint is generally referred to as a “UF filter”. The filtration process is called “UF filtration”. The filtrate obtained by UF filtration is referred to as “UF filtrate”.

  However, in order to shorten the coating water washing process time, when the dripping time of the liquid adhering to the object after the UF filtrate water washing process is shortened, the carry-out amount of the UF filtrate component increases. As a result, a phenomenon occurs in which the components contained in the UF filtrate are selectively gradually reduced from the electrodeposition paint in the electrodeposition tank.

  As the UF filter used for filtration in the electrodeposition coating process, a filter that allows a component having a molecular weight of 3000 or less to pass through is used. When a UF filter that allows components having a molecular weight of greater than 3000 to pass through is used, the concentration of the component dissolved in the washing water in the UF filtrate washing step increases, and the detergency is significantly reduced. On the other hand, when a UF filter having a molecular weight of a component that is smaller than 3000 is used, clogging of the filter is accelerated and the replacement frequency of the UF filter increases, which is not economical. In other words, in the present invention, the UF filtrate component is a component having a molecular weight of 3000 or less, and it has been clarified that when this component is reduced, the molecular weight distribution balance of the coating film forming component is lost and the throwing power is reduced. .

  Cationic electrodeposition coating is usually used for undercoating and is mainly used for rust prevention, etc. It is necessary to make it a predetermined value or more. Therefore, if the film thickness is uneven, the thick part is overcoated, and the coating is performed excessively. Excessive coating means extending the coating time, which is not preferable for improving production efficiency.

  Patent Document 1 describes a technique for improving the throwing power by controlling the conductivity of a cationic electrodeposition paint. For example, when a cationic electrodeposition paint is adjusted to have a low solid content, the conductivity of the paint may decrease and the throwing power may decrease. In such a case, an electrical conductivity control agent may be added to the paint. By increasing the electrical conductivity, the throwing power is also improved. Examples of the conductivity control agent include high molecular weight cationic resins such as amine-modified epoxy resins and amine-modified acrylic resins.

JP 2008-37889 A

  The present invention solves the above-mentioned conventional problems, and the object of the present invention is from an electrodeposition coating method using a high solid content type cationic electrodeposition coating effective for shortening the coating time, particularly from a UF washing tank. It is to maintain and improve the throwing power of the electrodeposition paint in the electrodeposition coating process in which the amount of the UF filtrate taken out is large.

In the present invention, the solids concentration of the paint is 23.0 to 30.0% by mass, the concentration of the paint ash is 25.0 to 30.0% by mass, and a high solid containing an amine-modified epoxy resin as a coating film forming component A method for improving the throwing power of a divided cationic electrodeposition paint,
There is provided a method including a step of adding an amino group-containing compound having a number average molecular weight of 2000 or less and an amine value of 150 to 500 mmol / 100 g to the high solid content type cationic electrodeposition coating composition.

  In one certain form, the process of adjusting the density | concentration of the solid content whose molecular weight in the said high solid content type cationic electrodeposition coating material is 3000 or less to 0.5-1.5 mass% is further included.

  In one certain form, the said amino group containing compound is obtained by making bisphenol A type epoxy resin react with an amine.

By using the method for improving the throwing power of the cationic electrodeposition paint of the present invention and the throwing power improver for the cationic electrodeposition paint, both shortening the coating process time and improving the throwing power are achieved.
The present invention is particularly effective in a cationic electrodeposition coating method using a high solid content and high ash content cationic electrodeposition coating.

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.

Rotating improver for cationic electrodeposition paint The wrapping improver for cationic electrodeposition paint is an additive which is added to the cationic electrodeposition paint and improves the throwing power of the cationic electrodeposition paint. The throwing power improving agent for cationic electrodeposition paints of the present invention needs to improve the electric conductivity of the cationic electrodeposition paint, and is an amino group-containing compound having an amine value of 150 to 500 mmol / 100 g, preferably 250 to 450 mmol / 100 g. Is included. If the amine value is less than 150 mmol / 100 g, the dispersibility in water may be insufficient, and if it exceeds 500 mmol / 100 g, suitability for a galvanized steel sheet may be lowered, which is not preferable.

  The amino group-containing compound has a relatively low molecular weight, such as a number average molecular weight of 2000 or less, preferably 300-1500, more preferably 400-1000.

  In the electrodeposition coating method in the process where the amount of the UF filtrate taken out from the UF water washing tank is large, the removal of the UF filtrate occurs and the non-high molecular weight components are selectively reduced. Do. By replenishing a component having a relatively low molecular weight, the balance of the molecular weight distribution of the coating film forming component contained in the cationic electrodeposition coating material is restored, and the deterioration of the throwing power and the coating film quality is eliminated.

  If the number average molecular weight of the amino group-containing compound is less than 300, the corrosion resistance of the electrodeposition coating film formed may be reduced. Moreover, the maximum value of the molecular weight which passes a UF filter is about 3000, and the component in which molecular weight exceeds 3000 does not pass a UF filter. For this reason, if the number average molecular weight of the amino group-containing compound exceeds 2000, the molecular weight distribution balance of the coating film-forming component may not be properly recovered, and the throwing power and coating film quality may be deteriorated.

  The amino group-containing compound as an adhesion improving agent for cationic electrodeposition coating is preferably an amine-modified epoxy resin. The amine-modified epoxy resin can be obtained by modifying an epoxy group of an epoxy resin with an amine compound. As the epoxy resin, general ones can be used, but bisphenol type epoxy resin, t-butylcatechol type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin having a molecular weight of 300-600. Is preferred. Among these epoxy resins, bisphenol A type epoxy resins are particularly preferable. The bisphenol A type epoxy resin has, for example, a formula

[Wherein n is an integer of 0 or 2 and preferably 0. ]
It is represented by

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.

  Examples of the compound that introduces an amino group into the epoxy resin 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.

  The resulting amine-modified epoxy resin 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.

In the present invention, the cationic electrodeposition paint to be improved in throwing power is a relatively high solid content type cationic electrodeposition paint containing an amine-modified epoxy resin as a film-forming component. . By including an appropriate amount of the wraparound improver for cationic electrodeposition paints of the present invention, the high solid content type cation electrodeposition paint has improved electrical conductivity and improved wrapping power. The high solid content type cationic electrodeposition coating is an electrodeposition coating composition containing a cationic epoxy resin, a curing agent, a pigment, an additive and the like. Hereinafter, each component will be described.

Cationic Epoxy Resin Cationic epoxy resins include amine-modified epoxy resins. The cationic epoxy resin may be a known resin described in JP-A Nos. 54-4978 and 56-34186.

  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).

  A formula as described in JP 2000-128959 A

[Wherein R is a residue obtained by removing an epoxy group from diepoxide, R ′ is a residue obtained by removing an isocyanate group from polyurethane diisocyanate, and n is an integer of 1 to 5.] ]
An oxazolidone ring-containing epoxy resin represented by the formula (1) may be used for 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.

  Particularly preferred epoxy resins are oxazolidone ring-containing epoxy resins. This is because a coating film having excellent heat resistance and corrosion resistance and further excellent impact resistance can be obtained.

  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 this oxazolidone ring-containing epoxy resin are described, for example, in paragraphs 0012 to 0047 of JP-A No. 2000-128959.

  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 the primary, secondary or / and tertiary amino group-containing epoxy resin of the present invention, 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. Use.

  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.

Blocked isocyanate curing agent The polyisocyanate used in the blocked isocyanate curing agent of the present invention 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 the block isocyanate curing agent.

  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 the blocking agent, those usually used such as ε-caprolactam and butyl cellosolve can be used. However, among these, many volatile blocking agents are regulated as targets of HAPs, and it is preferable that the amount used is minimized.

Pigments In general, electrodeposition paints contain pigments as colorants. The cationic electrodeposition paint of the present invention may contain a pigment that is usually used as necessary. Examples of such pigments include colored pigments such as titanium white, carbon black and bengara, extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica, clay and silica, zinc phosphate, iron phosphate, Rust preventive pigments such as aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and aluminum phosphomolybdate, aluminum phosphomolybdate Etc.

Pigment-dispersed paste When a pigment is used as a component of an electrodeposition paint, generally the pigment is dispersed in advance in an aqueous medium at a high concentration to form a paste. This is because the pigment is in a powder form, and it is difficult to disperse it in a single step in a low concentration uniform state used in the electrodeposition paint. 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 20 to 50 parts by mass.

Preparation of cationic electrodeposition coating The cationic electrodeposition coating 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 electrodeposition paint can contain a tin compound such as dibutyltin dilaurate and dibutyltin oxide, and a usual 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 a block polyisocyanate compound.

  The electrodeposition paint can contain conventional paint additives such as water-miscible organic solvents, surfactants, antioxidants, UV absorbers, and pigments.

  The cationic electrodeposition paint used in the method of the present invention is not particularly limited as long as it contains the above-described components, but is preferably a high solid content type. For example, a cationic electrodeposition paint having a paint solid content concentration of 23.0 to 30.0 mass% and a paint ash content concentration of 25.0 to 30.0 mass% corresponds to a high solid content type. This is because such a high solid content type cationic electrodeposition coating is used in an electrodeposition coating method or line for the purpose of shortening the coating time. Here, the ash concentration refers to the ratio of the mass remaining when the present cationic electrodeposition coating is burned to the total solid content of the present cationic electrodeposition coating.

Method for improving throwing power In the present invention, the electroconductivity of the paint is improved by incorporating the throwing power improver for the cationic electrodeposition paint into the cationic electrodeposition paint. In particular, in the line where the dripping time of the UF filtrate washing and collecting process of the carry-out paint is short and the recovery efficiency is low, the coating film forming component having a molecular weight of 3000 or less is preferentially reduced, and the molecular weight distribution of the coating film forming component is reduced. This is because the balance is disturbed and the throwing power and the like are liable to deteriorate.

  The wrapping property improving agent for cationic electrodeposition paint has a solid content concentration of 0.5 to 1.5% by mass, preferably 0.7, which is contained in the high solid content type cationic electrodeposition paint. An appropriate amount is added so that it may become -1.2 mass%, More preferably, it will be 0.8-1.0 mass%. For example, the amino group-containing compounds include those having a molecular weight (number average molecular weight) of 2000 or less among amine-modified epoxy resins contained in a high solid content type cationic electrodeposition coating material as a coating film forming component. Therefore, the amino group-containing compound is contained in the solid content that passes through the UF filter.

  The anti-rotation improver for cationic electrodeposition paints is an electrodeposition paint whose concentration of solids passing through the UF filter is reduced by being used for electrodeposition coating, for example, the concentration of the solids is less than 0.5% by mass. Added directly to the main tank of electrodeposition paint.

  In the electrodeposition coating method in which the UF filtrate washing and recovery step is performed, it is preferable that an amine-modified epoxy resin having a molecular weight enough to pass through a UF filter corresponds to an amino group-containing compound. In addition, molecular weights, such as an amino group compound, can be measured on the basis of polystyrene by gel permeation chromatography.

  The object to be coated when performing electrodeposition coating using a cationic electrodeposition paint is preferably a conductor that has been subjected to surface treatment such as zinc phosphate treatment by dipping or spraying in advance. May not be given. In addition, the conductor is not particularly limited as long as it can become a cathode in performing electrodeposition coating, and a metal substrate is preferable.

The conditions under which electrodeposition is performed are generally the same as those used for other types of electrodeposition coating. The applied voltage may vary greatly and may range from 1 volt to several hundred volts. The current density is typically about 10 amps / m ^{2 to} 160 amps / m ² and tends to decrease during electrodeposition.

  In order to shorten the electrodeposition coating process, in the process in which the sagging time after UF water washing is shortened, the recovery efficiency is deteriorated, and the UF filtrate component having a number average molecular weight of 3000 or less is selectively reduced. Therefore, the method of the present invention is particularly useful for application to such an electrodeposition coating method having poor recovery efficiency.

  After electrodeposition by the electrodeposition coating method of the present invention, the coating is baked at an elevated temperature in a conventional manner, for example, in a baking furnace, in a baking oven or with an infrared heat lamp. The baking temperature is usually about 140 ° C to 180 ° C. The coated product coated with the cationic electrodeposition paint of the present invention is dried and baked after the final water washing to form a cured electrodeposition coating film, thereby completing the coating process.

  The invention is explained in more detail by means of examples. The present invention should not be construed as being limited to these examples. In the examples, parts and percentages are based on mass unless otherwise indicated.

Production Example 1
Production of amine-modified epoxy resin A flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer, and a dropping funnel was prepared. 440 g of an epoxy resin having an epoxy equivalent of 188 ("DER331J" manufactured by Dow Chemical Co.) synthesized from bisphenol A and epichlorohydrin, 30 g of methyl isobutyl ketone, 5 g of methanol, and 6 mol of bisphenol A-ethylene oxide 6 mol adduct (Sanyo Chemical Industries BPE-60) (75 g) and dibutyltin dilaurate (0.01 g) were added, and 60 g of diphenylmethane diisocyanate was added dropwise with stirring. The reaction started from room temperature and was heated to 60 ° C. due to heat generation. Then, after continuing reaction for 30 minutes, reaction was further performed mainly in the range of 60 degreeC-65 degreeC, and continued until the isocyanate group disappeared, measuring IR spectrum. Next, 1 g of dimethylbenzylamine was added, and the reaction was performed at 130 ° C. until an epoxy equivalent of 263 was reached while distilling off by-product methanol using a decanter. Then, according to the infrared spectrometer, 1750 cm < ^-1 > absorption based on the carbonyl group of the oxazolidone ring was confirmed. Subsequently, 135 g of bisphenol A and 50 g of 2-ethylhexanoic acid were added and reacted at 120 ° C. until the epoxy equivalent reached 1118. After cooling, 40 g of N-methylethanolamine and 45 g of aminoethylethanolamine ketiminate (79 mass / methyl isobutyl ketone solution) were added and reacted at 110 ° C. for 2 hours. Then, it diluted with methyl isobutyl ketone until it became non-volatile content 80%, and obtained the base resin containing the oxazolidone ring.

Production Example 2
Production of blocked isocyanate curing agent 1250 parts of diphenylmethane diisocyanate and 266.4 parts of methyl isobutyl ketone (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 the absorption based on an isocyanate group disappeared, and after standing to cool, MIBK 336.1 parts was added and the block isocyanate hardening | curing agent was obtained.

Production Example 3
Manufacture of pigment dispersion resin First, 222.0 parts of isophorone diisocyanate (IPDI) was placed in a reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe and a thermometer, diluted with 39.1 parts of MIBK, 0.2 part of 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%).

Production Example 4
Production of pigment dispersion paste 120 parts of pigment dispersion resin obtained in Production Example 3 in a sand grind mill, 2.0 parts of carbon black, 100.0 parts of kaolin, 80.0 parts of titanium dioxide, 18.0 parts of aluminum phosphomolybdate Part and 144.3 parts of ion-exchanged water were added and dispersed until the particle size became 10 μm or less to obtain a pigment dispersion paste (solid content 56%).

Production Example 5
Production of Cationic Electrodeposition Paint The amine-modified epoxy resin obtained in Production Example 1 and the blocked isocyanate curing agent obtained in Production Example 2 were mixed so as to be uniform at a solid content ratio of 70/30. Glacial acetic acid was added thereto so that the milligram equivalent of the acid per 100 g of resin solid content was 35, and further ion-exchanged water was slowly added for dilution. By removing MIBK under reduced pressure, an emulsion having a solid content of 36% was obtained.

  1875 parts of this emulsion and 564 parts of the pigment dispersion paste obtained in Production Example 4, 1552 parts of ion-exchanged water and 9 parts of dibutyltin oxide were mixed to obtain a solid content of 25.0% by mass and a paint ash concentration of 25. A 0% by weight cationic electrodeposition paint was obtained.

  About the obtained cationic electrodeposition coating material, the density | concentration of the solid content whose molecular weight which permeate | transmits a UF module is 3000 or less was measured so that it might demonstrate below.

Method for Measuring Concentration of Solid Permeating Permeated UF Module A UF filtrate was collected from 4000 g of cationic electrodeposition paint using a UF module (model KCP-1010 manufactured by Asahi Kasei Chemicals Co., Ltd.) having a UF filter with a minimum separation molecular weight of 3000 or more. The UF filtrate was collected every 1000 g, and 1000 g of pure water was added to the cationic electrodeposition paint every time 1000 g was collected, and the amount of the paint was kept at 3000 to 4000 g. The above sorting operation was repeated 6 times.
The obtained 6 filtrate sample totals (UF1 to UF6) were dried by heating at 105 ° C. for 3 hours, and the solid content was measured.

  The measured solid content was as follows.

[Table 1]

  Assuming that this solid content is represented by a geometric sequence of the first term a and a common ratio r, the total Sn is represented by the following equation.

[Equation 1]
Sn = a / (1-r) [when r ≦ 1]

Substituting a = 10.4 and r = 0.68 here results in Sn = 32.5 g. This value is considered to be the total amount of solids that pass through the UF filter contained in 4000 g of the cationic electrodeposition paint, so when calculating its concentration,
32.5 / 4000 × 100 = 0.81%
It becomes.

Production Example 6
Removal of solid content passing through UF filter UF filtration was carried out on 4000 g of the cationic electrodeposition paint obtained in Production Example 5. 2000 g of the obtained UF filtrate was discarded, and 2000 g of pure water was added to the electrodeposition paint. As the UF filter, a filter having a minimum separation molecular weight of 3000 or more (“Microza UF” manufactured by Asahi Kasei Chemicals Corporation) was used.

  The concentration of the solid content passing through the UF filter was measured in the same manner as in Production Example 5 except that the cationic electrodeposition coating material in which this UF filtrate component was partially discarded was used, and it was 0.46% by mass.

Production Example 7
Production of throwing power improver 1 A flask equipped with a stirrer, a cooler, a nitrogen injection tube, a thermometer, and a dropping funnel was prepared. The flask was charged with 490 g of an epoxy resin having an epoxy equivalent weight of 490 (bisphenol A type epoxy resin “E1001” manufactured by Japan Epoxy Resin Co., Ltd.) and 123 g of MIBK (solid content concentration 80%), heated to 50 ° C. and dissolved, and then diethanolamine (DEA ) 105g was divided into 3 parts and charged. At this time, the second charge was cooled to 75 ° C. or lower, and the third charge was cooled to 90 ° C. or lower. After all the DEA was added, the mixture was stirred at 110 to 115 ° C. for 1 hour, and the amine value (mmol / 100 g) and the number average molecular weight were measured. The measurement results are shown in Table 2.

  The reaction product was cooled to 80 ° C., and 10.00 g of 90% acetic acid (neutralization rate: 15%) was added thereto, followed by stirring for 10 minutes. Then, 152.77 g of pure water was added (solid content concentration 60%), 30 minutes later, 97.67 g of pure water was added (solid content concentration 50%), and the mixture was further stirred for 30 minutes, and then 979.00 g of pure water was added. (Solid content concentration 20%). Thus, the throwing power improver 1 made of a DEA-modified epoxy resin was obtained.

Production Example 8
Production of throwing power improver 2 A throwing power improver 2 made of MMA-modified epoxy resin was obtained in the same manner as in Production Example 7 except that 75.1 g of methylmethanolamine (MMA) was used instead of diethanolamine.

Production Example 9
Production of throwing power improver 3 In a flask equipped with the same apparatus as in Production Example 7, 235.0 g of epoxy resin having an epoxy equivalent of 188 (“DER-331J” manufactured by Dow Chemical Company), 125.4 g of bisphenol A and 39.5 g of MIBK (Solid content concentration 90%) and heated to 100 ° C. under a nitrogen atmosphere. Thereafter, 0.9 g of dimethylbenzylamine was added, and the mixture was heated to 130 to 140 ° C. and stirred, and the reaction was continued until the epoxy equivalent reached 2400. Then, after cooling to 110 degreeC, 26.3g of MIBK was added, 47.3g of diethanolamine was added, and it was made to react at 120 degreeC for 1 hour. The amine number and number average molecular weight were measured. The measurement results are shown in Table 2.

  The reaction product was cooled to 80 ° C., and 10.0 g of 90% acetic acid was added thereto and stirred for 10 minutes. Thereafter, 174 g of pure water (solid content concentration 60%) was added, and 30 minutes later, 125.4 g of pure water was added (solid content concentration 50%), and the mixture was further stirred for 30 minutes, and then 292.6 g of pure water was added ( Solid content concentration 36%). Further, after 8 minutes, 836 g was added (solid content 20%) to prepare an emulsion, and a throwing power improver 3 made of DEA-modified epoxy resin was prepared.

[Table 2]
Characteristics of throwing power improver

<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 zinc phosphate-treated steel plates (JIS G3141 SPCC-SD surfdyne SD-5000 (manufactured by Nippon Paint Co., Ltd.) treatment) 11 to 14 in an upright state with an interval of 20 mm. A box 10 was prepared, which was placed in parallel and sealed at the bottom and bottom of both sides 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.

Reference Example 4 liters of the cationic electrodeposition paint obtained in Production Example 5 (Reference Example) or Production Example 6 (Reference Example) was transferred to a PVC container to make a first electrodeposition bath. 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. A voltage was applied to each steel plate 11-14 as a cathode and the counter electrode 22 as an anode, and cationic electrodeposition was applied to the steel plate. The coating was performed by increasing the voltage to 250 V in 5 seconds from the start of application, and then maintaining the voltage 250 V for 115 seconds.

  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). The case where this value exceeded 50% was evaluated as good, and the case where this value was 50% or less was evaluated as poor.

Examples 1 and 2
Subsequently, the throwing power improver 1 (Example 1) or the throwing power improver 2 (Example 2) was added to the electrodeposition paint, and in any case, the concentration of the solid content having a molecular weight of 3000 or less. Was adjusted to 0.79%. Electrodeposition coating was performed in the same manner as above except that the obtained electrodeposition paint was used, and the throwing power of the electrodeposition paint was tested. Table 3 shows the results of these throwing power tests.

Electrodeposition coating was performed in the same manner as in Example 1 except that the same amount of throwing power improving agent 3 as in Example 1 was used instead of using the whirling performance improving agent 1 in Comparative Example. The throwing power of the electrodeposition paint was tested. Table 3 shows the throwing power test results.

※１：ＵＦフィルターを通過する固形分の濃度 [Table 3]

* 1: Concentration of solids passing through UF filter

10 ... box,
11-14 ... Zinc phosphate-treated steel sheet,
15 ... through hole,
20 ... Electrodeposition coating container,
21 ... Electrodeposition paint,
22 ... Counter electrode.

Claims (3)

High solid content type cation battery having a paint solid content concentration of 23.0 to 30.0% by mass and a paint ash content of 25.0 to 30.0% by mass and containing an amine-modified epoxy resin as a coating film forming component It is a method for improving the throwing power of the paint,
A method comprising a step of adding an amino group-containing compound having a number average molecular weight of 2000 or less and an amine value of 150 to 500 mmol / 100 g to the high solid content type cationic electrodeposition coating composition.   The method according to claim 1, further comprising the step of adjusting the concentration of a solid content having a molecular weight of 3000 or less in the high solid content type cationic electrodeposition coating to 0.5 to 1.5 mass%.   The method according to claim 1, wherein the amino group-containing compound is an amine-modified epoxy resin obtained by reacting a bisphenol A type epoxy resin with an amine.

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