WO2008015968A1

WO2008015968A1 - Conductivity control agent for cationic electrodeposition coating material and method of regulating electric conductivity of cationic electrodeposition coating material using the same

Info

Publication number: WO2008015968A1
Application number: PCT/JP2007/064743
Authority: WO
Inventors: Satoru Uchidoi; Takefumi Yamamoto
Original assignee: Nippon Paint Co., Ltd.
Priority date: 2006-08-01
Filing date: 2007-07-27
Publication date: 2008-02-07
Also published as: AU2007279812A1; GB0901963D0; JP2008037889A; GB2454123A; US20090321270A1; TW200813177A; CN101522823A; KR20090046905A

Abstract

A technology that prevents any deterioration of conductivity and throwing power in a cationic electrodeposition coating material composition of low solid and low ash contents. For example, there is provided a conductivity control agent for cationic electrodeposition coating material for use in a cationic electrodeposition coating material of solid content as low as 0.5 to 9.0 wt.%, comprising an aminated compound of 500 to 20,000 molecular weight and 200 to 500 mmol/100g amine value so as to attain a regulation of electric conductivity to 900 to 2000 μS/cm. Further, there is provided a method of regulating the electric conductivity of cationic electrodeposition coating material, comprising the steps of mixing a conductivity control agent with a cationic electrodeposition coating material of solid content as low as 0.5 to 9.0 wt.%; and regulating the electric conductivity of the cationic electrodeposition coating material of low solid content after the mixing step to 900 to 2000 μS/cm, wherein the conductivity control agent contains an aminated compound of 200 to 500 mmol/100g amine value.

Description

Specification

Conductivity control agent for cationic electrodeposition coating and method for adjusting electric conductivity of cationic electrodeposition coating using the same

Technical field

TECHNICAL FIELD [0001] The present invention relates to a conductivity control agent for a cationic electrodeposition coating and adjustment of the electric conductivity of a cationic electrodeposition coating using the same.

Background art

[0002] Cationic electrodeposition coating is capable of applying even fine details even to an object having a complicated shape, and can be applied automatically and continuously. It is widely used as a method for undercoating undercoating with large and complex shapes. Cationic electrodeposition coating is performed by immersing an object to be coated in a cationic electrodeposition coating material as a cathode and applying a voltage.

[0003] Conventionally, cationic electrodeposition paints are water-based paint compositions having a solid content concentration of about 20% by weight, and when left without stirring, pigments and the like precipitate and precipitates are formed in the electrodeposition bath. Normally, cationic electrodeposition paints are circulated with a pump or stirred with a stirrer to prevent precipitation.

[0004] However, since the cationic electrodeposition bath is a large-scale force that can immerse the car body, it is a powerful facility that can circulate and agitate, the energy involved, the equipment involved, and the power to maintain the equipment, and the cost involved. Will be enormous. Reducing or eliminating such circulation and agitation greatly contributes to energy saving in cationic electrodeposition coating. Therefore, it is effective that the cationic electrodeposition coating does not produce a precipitate or has a small amount of sediment. Specifically, it is effective to use a cationic electrodeposition coating having a low solid content or a low ash content. For the first time, electrodeposition paints are being studied!

[0005] For example, Japanese Patent Application Laid-Open No. 2004-231989 (Patent Document 1) discloses a cationic electrodeposition paint having a ash content of 3 to 10% by weight and a solid content concentration of 5 to 12% by weight. There is a disclosure of an environmentally-friendly electrodeposition coating method using paint. This cationic electrodeposition paint is excellent in that it has less sediment and power for agitation and circulation and less energy costs. S, in fact, as the solid content of the paint decreases, the electrical conductivity decreases, V. The performance of forming a coating film to every corner of the film will deteriorate.

[0006] It is generally known that a suitable throwing power can be imparted by adjusting the electrical conductivity of the paint to an appropriate value. Japanese Patent Application Laid-Open No. 2004-269627 (Patent Document 2) is cited as a patent document that mentions the electrical conductivity and throwing power of the paint. This cationic electrodeposition coating composition contains a sulfone-modified epoxy resin and requires control of film resistance.

[0007] The amine value of the base resin of the cationic electrodeposition coating is being studied, such as JP-A-2005-232397 (Patent Document 3) and JP-A-7-150079 (Patent Document 4). Exists. According to Patent Document 3, the amine value of urethane resin (substrate resin) is preferably 20 to 60 mgK OH / g (35.7-107.0 mmol / 100 g in terms of conversion), and the cationic electrodeposition property of Patent Document 4 The resin is described as having a desirable amine value of 3 to 200 mg KOH / g (in terms of conversion, 5.3-356 mmol / 100 g). These are the conventional ammine values, which are basically low.

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004_231989

Patent Document 2: JP 2004-269627 Koyuki

Patent Document 3: Japanese Unexamined Patent Publication No. 2005-232397

Patent Document 4: Japanese Patent Laid-Open No. 7-150079

Disclosure of the invention

Problems to be solved by the invention

[0009] The cationic electrodeposition coating composition having a low solid content and / or low ash content tends to have a lower electrical conductivity than a normal cationic electrodeposition coating composition. The present invention provides a technique for preventing a decrease in throwing power accompanying a decrease in conductivity in a cationic solid electrodeposition coating composition having a low solid content and / or a low ash content.

Means for solving the problem

[0010] That is, the present invention is a conductivity control agent for a cationic electrodeposition paint used for a low solid content type cationic electrodeposition paint having a paint solid content concentration of 0.5 to 9.0 wt%, Molecular weight 50 Conductivity for cationic electrodeposition paints containing an amino group-containing compound with an amine value of 200-500 mmol / 100 g and adjusting the electric conductivity to 900-2,000 S / cm. Provide a degree control agent. This conductivity control agent exists in cationic electrocoating paints as a separate emulsion from the cationic epoxy resin, curing agent and pigment, which is a film-forming component, and is actually formulated as the third component. To do.

[0011] The amino-containing compound used as the conductivity control agent is an amine-modified epoxy resin, and is preferably obtained by modifying an epoxy group contained in the epoxy resin with an amine compound.

[0012] The amino group-containing compound is also preferably an amine-modified acrylic resin obtained by modifying an epoxy group of an acrylic resin having an epoxy group with an amine compound.

[0013] The epoxy resin may be a bisphenol type, a t-butylcatechol type, a phenol novolac type, or a cresol nopolac type, and may have a number average molecular weight of 500 to 20,000.

[0014] The present invention is also a low solid content type cationic electrodeposition paint having a paint solid content concentration of 0.5 to 9.0% by weight and containing an amino group having an amine value of 200 to 500mmol / 100g. Provided is a low solid content type cationic electrodeposition coating comprising a conductivity control agent containing a compound and having an electrical conductivity of 900 to 2,000 S / cm.

[0015] The present invention further relates to a method for adjusting the electrical conductivity of a cationic electrodeposition coating material, comprising a low solid content type cationic electrodeposition coating material having a coating solid content concentration of 0.5 to 9.0% by weight. Adding a conductivity control agent;

Adjusting the electrical conductivity of the low solid content type cationic electrodeposition coating in the blending step to 900 to 2,00 11 S / cm,

The conductivity control agent comprises an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g.

I will provide a.

[0016] The present invention is also a method for supplying a conductivity control agent to a cationic electrodeposition paint. Supplying a conductivity control agent to a low solid content type cationic electrodeposition paint having a solid content concentration of 0.5 to 9.0% by weight;

Adjusting the electric conductivity of the low solid content type cationic electrodeposition coating in the replenishment step to 900 to 2,00 11 S / cm,

I will provide a.

The invention's effect

[0017] According to the present invention, by incorporating a conductivity control agent for a specific cationic electrodeposition paint into the cationic electrodeposition paint, the disadvantage of the low ash type and / or low solid content type cationic electrodeposition paint is achieved. This is to eliminate the decrease in throwing power that accompanies the decrease in conductivity of a cationic electrodeposition paint.

Brief Description of Drawings

[0018] FIG. 1 is a perspective view showing an example of a box used for evaluating throwing power.

FIG. 2 is a cross-sectional view schematically showing a throwing power evaluation method.

Explanation of symbols

[0019] 10. .box,

11 ~; 14... Zinc phosphate treated steel sheet,

15.Through hole,

20 .. Electrodeposition coating container,

21 ... Electrodeposition paint,

22. Counter electrode.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] The conductivity control agent for cationic electrodeposition paints of the present invention is composed of an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g. The conductivity control agent for cationic electrodeposition coating of the present invention may be any amino group-containing compound as long as the amine value has the above range, but usually an amine-modified epoxy resin or an amine-modified acrylic resin is preferred. . Moreover, the conductivity control agent for cationic electrodeposition paints of the present invention may be neutralized with an acid, if necessary. 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 200 mmol / 100 g / J or more, the amount required to adjust the liquid conductivity of the low solid content cationic electrodeposition paint to the optimum value increases, which may impair the corrosion resistance. On the other hand, if it exceeds 500 mmol / 100 g, the precipitation property is lowered and the desired throwing power cannot be obtained. In addition, the suitability of galvanized steel sheets is also reduced.

[0021] The amino group-containing compound as the conductivity control agent for cationic electrodeposition coatings in the present invention can be considered to have a low molecular weight to a high molecular weight ordinary amine-modified epoxy resin diamine-modified acrylic resin, etc. And high molecular weight compounds. Examples of the low molecular weight amino group-containing compound include monoethanolamine, diethanolamine, and dimethylbutylamine.

[0022] 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 the epoxy group of the epoxy resin with an amine compound. Epoxy resins that can be used in general include bisphenol type epoxy resin, t-butylcatechol type epoxy resin, phenol nopolac type epoxy resin, and cresol nopolac type epoxy resin, having a molecular weight of 500 to 20000. Those having the following are preferred. Of these epoxy resins, phenol nopolac type epoxy resins and cresol nopolac type epoxy resins are most desirable. In particular, these epoxy resins are commercially available. Examples thereof include phenolic nopolak type epoxy resin DEN-438 manufactured by Dow Chemical Japan, and cresol nopolac type epoxy resin YDCN-703 manufactured by Tohto Kasei Co., Ltd.

[0023] These epoxy resins may be modified with resins such as polyester polyols, polyether polyols, and monofunctional alkylphenols. Epoxy resins can also be chain-extended using the reaction of epoxy groups with diols or dicarboxylic acids.

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 is used as it is. Alternatively, it may be used by modifying the glycidyl group of a homopolymer of glycidyl metatalylate or a copolymer with other polymerizable monomer with an amine compound.

[0025] 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 butynoreamine, talented cutinoleamine, jetinoreamine, dibutinoreamine, dimethylenobutyneamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine. In addition to acetate, jetyl disulfide'acetic acid mixture, etc., primary amine-blocked secondary amines such as aminoethylethanolamine diketimine, jetylhydroamine diketimine and the like can be mentioned. A plurality of amines may be used.

[0026] As described above, the number average molecular weight of these amine-modified epoxy resins and amine-modified acrylic resins 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 greater than 20000 !, there is a risk of causing a decrease in the finished appearance.

The cationic electrodeposition paint to which the conductivity control agent for cationic electrodeposition paint of the present invention can be applied is not limited to a low solid content type cationic electrodeposition paint having a solid content concentration of 0.5 to 9.0% by weight. It is also possible to apply to a normal cationic electrodeposition paint having a solid content concentration of about 20% by weight. Even with normal cationic electrodeposition paints, the electrical conductivity may be reduced, and if the electrodeposition is applied as it is, the throwing power may be insufficient. When such a problem occurs, the conductivity can be controlled to an appropriate value by adding the above-mentioned conductivity control agent for cationic electrodeposition paints to normal cationic electrodeposition paints. Therefore, sufficient throwing power can be secured.

[0028] These amine-modified epoxy resin and amine-modified acrylic resin can be used after neutralization 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.

[0029] Electrodeposition coating composition

The conductivity control agent for cationic electrodeposition paints according to the present invention has a compounding amount in cationic electrodeposition paints. By adjusting, the electric conductivity of the electrodeposition coating material can be suitably adjusted. Cationic electrodeposition coating compositions include those containing a cationic epoxy resin, a curing agent, and optionally pigments and additives. Hereinafter, each component will be described.

[0030] Cationic epoxy resin (cation-modified epoxy resin as a film-forming component)

The cationic epoxy resin used in the present invention includes an epoxy resin modified with amine. Cationic epoxy resins typically have the ability to open with active hydrogen compounds that can introduce cationic groups into all of the epoxy rings of bisphenol type epoxy resins, or some epoxy rings to other It is produced by opening a ring with an active hydrogen compound and opening the remaining epoxy ring with an active hydrogen compound capable of introducing a cationic group. Power of cationic electrodeposition paint Thion-based epoxy resin preferably has an amine value of 50 to 200 mmol / 100 g, which is smaller than the amine value (200 to 500 mmol / 100 g) of the conductivity control agent for cationic electrodeposition paint. It has a great value. If the amine value is less than 50 mmol / 100 g, the dispersibility of the cation-modified epoxy resin in water cannot be ensured, and if it exceeds 200 mmol / 100 g, the water resistance of the resulting coating film may be deteriorated.

[0031] A typical example of the bisphenol type epoxy resin is a bisphenol A type or bisphenol F type epoxy resin. As for the former commercial products, Epicoat 828 (manufactured by Yuka Shell Epoxy Co., Epoxy Equivalent 180 ~; 190), Epico 1001 (Equivalent Epoxy Equivalent 450 ~ 500), Epicote 1010 (Equipment Equivalent Equivalent 3000 ~ 4000), etc. The latter commercial products include Epicoat 807 (epoxy equivalent 170).

[0032] The following formula described in JP-A-5-306327

[0033] [Chemical 1]

[Wherein, R represents a residue excluding the glycidyloxy group of the diglycidyl epoxy compound, R ′ represents an isocyanato group of the diisocyanate compound, and n represents a positive integer. The oxazolidone ring-containing epoxy resin represented by Moyore. This is because a coating film having excellent heat resistance and corrosion resistance can be obtained.

[0035] 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 to produce a by-product lower product. Obtained by distilling off alcohol from the system.

[0036] These epoxy resins may be modified with an appropriate resin such as polyester polyol, polyether polyol, and monofunctional alkylphenol. Epoxy resins also have the ability to extend the chain using the reaction of epoxy groups with diols or dicarboxylic acids.

[0037] These epoxy resins are ring-opened with an active hydrogen compound so that an amine value of 50 to 200 mmol / 100 g is obtained after ring opening, and more preferably 5 to 50% of them are occupied by primary amino groups. Is desirable.

[0038] The active hydrogen compounds capable of introducing 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, primary amine, secondary amine, or tertiary amine acid salts are used as active hydrogen compounds capable of introducing cationic groups.

[0039] Specific examples include butylamine, octylamine, jetylamine, dibutylamine, methylbutyramine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, jetyl disulfide. 'There is a secondary amine that blocks primary amines, such as a mixture of acetic acid, ketimine of aminoethylethanolamine, diketimine of dimethyltriamine. Amines can be used in combination.

[0040] Curing agent

The curing agent used in the present invention is preferably a blocked polyisocyanate obtained by blocking a polyisocyanate with a blocking agent. Here, a polyisocyanate means two isocyanate groups in one molecule. A compound having the above. The polyisocyanate may be, for example, any of aliphatic, alicyclic, aromatic and aromatic aliphatic. [0041] Specific examples of polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate. 1 to 4 aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), 2, 2, 4 trimethylhexane diisocyanate, lysine diisocyanate and the like; Hexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylenomethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidenedicyclohexane Hexolux 4,4'-diisocyanate and 1,3-diisocyanatomethylcyclohexane (hydrogenated XDI), hydrogenated TDI, 2, 5 or 2, 6 C5-C18 alicyclic diisocyanates such as bis (isocyanatomethyl) monobicyclo [2.2.1] heptane (also called norbornane diisocyanate); xylylene diisocyanate (XDI ) And aliphatic diisocyanates having an aromatic ring such as tetramethylxylylene diisocyanate (TMXDI); modified products of these diisocyanates (urethanes, carpositimides, uretdiones, uretoimines, burettes and / or Isocyanurate modified product); and the like. These can be used alone or in combination of two or more.

[0042] Adducts or prepolymers obtained by reacting polyisocyanate with polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropan and hexanetriol at an NCO / OH ratio of 2 or more are also used as curing agents. It's okay.

[0043] The polyisocyanate is preferably an aliphatic polyisocyanate or an alicyclic polyisocyanate! /. This is because the formed coating film is excellent in weather resistance.

[0044] Preferable specific examples of the aliphatic polyisocyanate or alicyclic polyisocyanate include hexamethylene diisocyanate, hydrogenated TDI, hydrogenated MDI, hydrogenated XDI, IPDI, norbornane diisocyanate, and the like. Dimer (biuret), trimer (isocyanurate) and the like.

[0045] The blocking agent is added to a polyisocyanate group and is stable at room temperature, but can regenerate a free isocyanate group when heated to a temperature higher than the dissociation temperature.

[0046] As a blocking agent, when low-temperature curing (160 ° C or less) is desired, ratata series such as ε-force prolatatam, δ-noratalatata, γ-butyroratam and / 3-propiolatata Blocking agents and formaldoxime, acetoaldoxime, acetoxime, methylethyl blocking agents may be used.

[0047] The binder containing the cationic epoxy resin and the curing agent is generally an electrodeposition coating composition in an amount of 25 to 85% by weight, preferably 40 to 70% by weight of the total solid content of the electrodeposition coating composition. Contained in

[0048] 纖

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 inorganic pigments, such as colored pigments such as titanium white, carbon black and bengara; kaolin, talc, aluminum silicate, calcium carbonate, my strength and clay. Extender pigments: zinc phosphate, iron phosphate, ammonium phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and phosphomolybdic acid Examples thereof include anti-mold pigments such as aluminum, aluminum zinc phosphomolybdate, bismuth hydroxide, bismuth oxide, basic bismuth carbonate, bismuth nitrate, bismuth benzoate, bismuth citrate, and bismuth silicate.

[0049] The pigment is generally contained in the electrodeposition coating composition in an amount accounting for the total solid content of the electrodeposition coating composition;! To 35 wt%, preferably 10 to 30 wt%.

[0050] Pigment dispersion paste

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

[0051] The pigment dispersion paste is prepared by dispersing a pigment together with a pigment dispersion resin varnish in an aqueous medium. As the pigment dispersion 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 sulfone group is generally used. Is used. As the aqueous medium, ion-exchanged water or water containing a small amount of alcohol is used. Generally, pigment dispersion resin varnish is 5-40 Part by weight and pigment are used at a solid content ratio of 10 to 30 parts by weight.

[0052] After the pigment-dispersing resin varnish and the pigment are mixed with 100 to 100 parts by weight with respect to 100 parts by weight of the resin solid content, until the particle size of the pigment in the mixture reaches a predetermined uniform particle size, Disperse using a normal dispersing device such as a ball mill or a sand grind mill to obtain a pigment dispersion paste.

[0053] The cationic electrodeposition coating composition of the present invention needs to have a coating solid content concentration of 0.5 to 9.0% by weight. When the solid content concentration of paint is below the lower limit, a cationic electrodeposition coating film cannot be obtained. On the other hand, when the coating solid content concentration exceeds the upper limit, the pigment component contained in the cationic electrodeposition coating material settles in a stationary state without stirring, which is not preferable.

[0054] ϋ

The electrodeposition coating composition is prepared by dispersing a cationic epoxy resin, a curing agent, and a pigment dispersion paste in an aqueous medium. Usually, the aqueous medium 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 an amount that achieves a neutralization rate of at least 20%, preferably 30-60%.

[0055] The amount of the curing agent reacts with active hydrogen-containing functional groups such as primary, secondary or / and tertiary amino groups and hydroxyl groups in the cationic epoxy resin at the time of curing to give a good cured coating film. In general, it is generally in the range of 90/10 to 50/50, preferably in the range of 80/20 to 65/35, expressed as a solid weight ratio of the cationic epoxy resin to the curing agent.

Yes

[0056] The electrodeposition paint may contain a tin compound such as dibutyltin dilaurate and dibutyltin oxide, and a usual urethane cleavage catalyst. Since a lead-free material is preferable, the amount is preferably set to 0.;! To 5% by weight of the block polyisocyanate compound.

[0057] The electrodeposition coating composition may contain conventional coating additives such as a water-miscible organic solvent, a surfactant, an antioxidant, an ultraviolet absorber, and a pigment.

[0058] The cationic electrodeposition coating composition of the present invention is not particularly limited as long as it contains the components described above, but the conductivity control agent for cationic electrodeposition coating of the present invention is effective. The cationic electrodeposition coating used is of the low solids type. The cationic electrodeposition paint of the present invention may be a low ash type.

[0059] The low solid content type cationic electrodeposition coating composition has a solid content concentration of less than the conventional 20% by weight, particularly 0.5 to 9% by weight, and a more preferred lower limit is 3% by weight. If it is less than 0.5% by weight, the pigment component settles without stirring, which is not preferable. On the other hand, although it may exceed 9% by weight, it may not be necessary to adjust the electrical conductivity of the paint by adding a conductivity modifier for cationic electrodeposition paints.

[0060] As a method of reducing the solid content concentration of the cationic electrodeposition paint, when the method of reducing the pigment component is adopted, the ash content in the paint (that is, the weight of the solid ash remaining when the paint is burned) Divided by the weight of solids and multiplied by 100). Therefore, the cationic electrodeposition coating used in the present invention can be said to be a low ash type. The ash content is 15 to 40% by weight in the case of an ordinary cathodic electrodeposition paint, so the ash content of the low ash type cationic electrodeposition paint is preferably 2 to 7% by weight, more preferably 3 to 5% by weight. is there.

[0061] The object to be coated when electrodeposition coating is performed using the electrodeposition coating composition is preferably a conductor that has been subjected to surface treatment such as zinc phosphate treatment in advance by dipping, spraying, or the like. The surface treatment may not be performed. In addition, the conductor is preferably a metal substrate that is not particularly limited as long as it can serve as a cathode in electrodeposition coating.

[0062] 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 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.

[0063] 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.

[0064] Adjustment of electrical conductivity (conductivity)

In the present invention, the above-described liquid conductivity control agent for cationic electrodeposition coating is used as a cationic electrodeposition coating. By adding, the liquid conductivity of the paint is ensured. As described above, low solid content type cationic electrodeposition coatings tend to have insufficient liquid conductivity compared to ordinary cationic electrodeposition coatings with a solid content concentration of about 20% by weight. Adjust by adding a specific conductivity control agent for cationic electrodeposition coatings. By increasing the amine value of the cation-modified epoxy resin as a coating film forming component, it is possible to maintain electric conductivity at an appropriate value and to ensure throwing power. If the amine value of the cation-modified epoxy resin exceeds 200 mmol / 10 Og, the water resistance of the resulting coating film may be deteriorated, which is not preferable. The electric conductivity necessary for obtaining the desired throwing power is 900 to 2000 S / cm. By adding the conductivity control agent for the cationic electrodeposition paint of the present invention, the low solid content type electrodeposition paint The liquid conductivity of can be controlled within this range. The preferred lower limit of conductivity is 1000 3 /. The preferred upper limit is 1800 S / cm. If the electrical conductivity is less than 900 a S / cm, the desired throwing power cannot be obtained. If the conductivity is more than 2000 μ S / cm, coating defects called gas pins are likely to occur when coating galvanized steel sheets. Have the following disadvantages. Conductivity is measured using a commercially available liquid conductivity meter at a liquid temperature of 25 ° C.

[0065] The blending amount of the conductivity control agent for the cationic electrodeposition coating material in the cationic electrodeposition coating material is not particularly limited as long as a predetermined electric conductivity is obtained. Specifically, it is based on the solid content of the coating material. There are, from 0.5 to 30 weight ^_0/0, preferably 1 to 30 weight ^_0/0, more preferably 1 to; Ru 15 weight% der. Although it may be less than 0.5% by weight, sufficient electrical conductivity may not be obtained. The blending amount may exceed 50% by weight, but no increase in electrical conductivity proportional to the amount added will be observed.

[0066] The low solid content type cationic electrodeposition coating material having the conductivity adjusted as described above is a low ash content and low solid content type cationic electrodeposition coating material, and can ensure suitable throwing power. Even for such cationic electrodeposition paints, it is necessary to replenish the film-forming components in the cationic electrodeposition paint tank in the process of repeatedly coating the object to be coated on the painting line. At this time, the electrical conductivity of the cationic electrodeposition paint in the tank may deviate from the range of 900 to 2,000 S / cm desired by the present application. When the electrical conductivity is 900 S / cm or less, the conductivity adjustment agent of the present invention is separately added to the cationic electrodeposition coating tank to reduce the solid content concentration to 0. The electric conductivity of the cationic electrodeposition paint in the tank can be adjusted to the range of 900 to 2,000 a S / cm while maintaining the content at 5 to 9.0% by weight.

Example

[0067] The present invention will be described in more detail by way of examples. The present invention should not be construed as being limited to these examples. In the examples, parts and percentages are based on weight unless otherwise indicated.

<.

[0068] Example A— 1

A flask equipped with a reflux condenser and a stirrer was charged with 295 parts of methylisoptyl ketone (hereinafter abbreviated as “MIBK”), 37.5 parts of methinorethananolamine, and 52.5 parts of diethanolamine. Hold at 100 ° C. To this, 205 parts of cresol nopolac type epoxy resin (product name: YDCN-703, manufactured by Tohto Kasei) is gradually added, and after the addition is completed, the mixture is allowed to react for 3 hours. The molecular weight was measured and found to be 2,100. The amine value (MEQ (B)) of the obtained amino-modified resin was measured and found to be 340 mmol / 100 g.

[0069] Example A-2

To 140 parts of the amino modified resin solution obtained in Example A-1, 5.5 parts of formic acid and 54.5 parts of deionized water 12 are added and stirred for 30 minutes while maintaining at 80 ° C. The organic solvent was removed under reduced pressure to obtain a liquid conductivity control agent A having a solid content of 7.0%.

[0070] Example B-1

A flask equipped with a reflux condenser and a stirrer is charged with 255 parts of MIBK and 75 parts of methylethanolamine and kept at 100 ° C. while stirring. To this, gradually add 180 parts of phenol nopolak type epoxy resin (trade name DEN-438, manufactured by Dow Chemical Japan Co., Ltd.). The molecular weight was measured and found to be 1,000. The amine value (MEQ (B)) of the obtained amino-modified resin was measured and found to be 390 mmol / 100 g.

[0071] Example B-2

To 140 parts of the amino-modified resin solution obtained in Example B-1, 14 parts of sulfamic acid and 1247 parts of deionized water are added and stirred for 30 minutes while maintaining the temperature at 80 ° C. The organic solvent was removed under reduced pressure to obtain a liquid conductivity control agent B having a solid content of 7.0%. [0072] Example C 1

Charge 50 parts of methyl isobutyl ketone (MIBK) to a flask equipped with a reflux condenser, nitrogen inlet tube, dropping funnel, and stirrer, and maintain at 100 ° C while stirring. A mixed solution consisting of 100 parts of glycidino methacrylate and 2 parts of azobisisobutyronitrile (AIBN) was added dropwise at a constant rate from a dropping funnel in 2 hours. The temperature was kept at 100 ° C and stirring was continued for 30 minutes. Thereafter, a mixture of 52.5 parts of MIBK and 0.5 part of AIBN was added dropwise over 1 hour. Stirring was continued for another hour to complete the reaction.

[0073] Example C 2

A flask equipped with a reflux condenser and a stirrer is charged with 57.5 parts of MIBK and 52.8 parts of methylethanolamine and kept at 100 ° C while stirring. To this, 205 parts of the reaction product obtained in Example C-1 is gradually added, and after the entire amount has been added, the reaction is allowed to proceed for 3 hours. The molecular weight was measured and found to be 9,800. The amine value (MEQ (B)) of the obtained amino-modified resin was measured and found to be 450 mmol / 100 g.

[0074] Example C 3

To 140 parts of the amino modified resin solution obtained in Example C-2, 25.2 parts of lactic acid and 1234.8 parts of deionized water are added and stirred for 30 minutes while maintaining at 80 ° C. The organic solvent was removed under reduced pressure to obtain a liquid conductivity control agent C having a solid content of 7.0%.

[0075] Comparative Example D

Add 463.4 parts deionized water and 13.5 parts formic acid to a glass beaker and stir. While stirring, 23.1 parts of dimethylethanolamine having a molecular weight of 89 were gradually added. Liquid conductivity regulator with an active ingredient's amine value (MEQ (B)) of 740 mmol / 100 g and an active ingredient concentration of 7%

D got.

[0076] Fabrication Example 1 Preparation of cationic electrodeposition coating composition

Production Example 1 1 Preparation of Amine-modified Epoxy Resin

A flask equipped with a stirrer, condenser, nitrogen inlet tube, thermometer and dropping funnel was charged with 95 parts and dibutyltin dilaurate 0.5 parts. While stirring the reaction mixture, 21 parts of methanol was added dropwise. The reaction starts at room temperature and is 60 ° C due to exotherm. The temperature was raised to. Thereafter, the reaction was continued for 30 minutes, and then 50 parts of ethylene glycol mono-2-ethylhexyl ether was added dropwise 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 the absorption based on the isocyanate group disappeared in the IR spectrum measurement.

[0077] Next, an epoxy equivalent synthesized from bisphenol A and epichlorohydrin by a known method

365 parts of 188 epoxy resin 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 an epoxy equivalent of 410 was reached.

[0078] Subsequently, 61 parts of bisphenolanol and 33 parts of octylic acid were added and reacted at 120 ° C. The epoxy equivalent was 1190. The reaction mixture is then cooled and 79 parts by weight of the ketimine product of 11 parts of diethylanolamine, 24 parts of Nethylethanolamine and aminoethylethanolamine! ^ 25 parts of the solution was added and reacted at 110 ° C for 2 hours. Thereafter, it was diluted with MIBK until the non-volatile content became 80% to obtain an amine-modified epoxy resin (resin solid content 80%).

[0079] 1¾ Example 1 2 Block Isocyanate Fossil II

A reactor was charged with 1250 parts of diphenylmethane diisocyanate and 4 parts of MIBK266. This was heated to 80 ° C, and 2.5 parts of dibutyltin dilaurate was added. Here, 226 parts of epsilon prolatatum were dissolved in 944 parts of butylcetone sorb, and dropped at 80 ° C. over 2 hours. After further heating at 100 ° C for 4 hours, in the IR spectrum measurement, it was confirmed that the absorption based on the isocyanate group disappeared, and after cooling, 1 part MIBK336.1 was added to block the glass transition temperature at 0 ° C. An isocyanate curing agent was obtained.

[0080] Production Example 1 3 Preparation of material dispersion fat

First, 220.0 parts of isophorone diisocyanate (hereinafter abbreviated as IPDI) was placed in a reaction vessel equipped with a stirrer, cooling pipe, nitrogen introduction pipe and thermometer, diluted with MIBK 39.1 parts, To this was added 0.2 part of dibutyltin dilaurate. Thereafter, the temperature was raised to 50 ° C., and 131.5 parts of 2-ethylhexanol was added dropwise over 2 hours under stirring in a dry nitrogen atmosphere. The reaction temperature was maintained at 50 ° C by cooling as appropriate. As a result, 2— Ethylhexanol NF-blocked IPDI (resin solid content 90. 0%) was obtained.

[0081] Next, in a suitable reaction vessel, 87.2 parts of dimethylolethanolanolamine, 75% aqueous lactic acid solution

1 1 7. 6 parts and ethylene glycol monobutyl ether 39.2 parts were added in order, and the mixture was stirred at 65 ° C. for about half an hour to prepare a quaternizing agent.

[0082] Next, EPON 829 (Bisphenol A type epoxy epoxies, ephemeral equivalent of 193-203, manufactured by Shell 'Chemical' Company) 71.0. And bisphenol A289.6 咅 are appropriate. When charged in a reaction vessel and heated to 150-160 ° C under a nitrogen atmosphere, an initial exothermic reaction occurred. The reaction mixture was allowed to react at 150-; 160 ° C for about 1 hour, then cooled to 120 ° C, and then 498.8 parts of 2-ethylhexanol half-blocked IPDI (MIBK solution) prepared previously was I got it.

[0083] The reaction mixture was kept at 110-120 ° C for about 1 hour, then 463.4 parts of ethylene glycol monobutyl ether was added, the mixture was cooled to 85-95 ° C, homogenized, and then first. 196. 7 parts of the prepared quaternizing agent was added. After maintaining the reaction mixture at 85 to 95 ° C until the acid value becomes 1, add 964 parts of deionized water to finish quaternization in epoxy bisphenol A resin, and a pigment having a quaternary ammonium salt part A resin for dispersion was obtained (resin solid content 50%).

[0084] ni-paste preparation

Add 100 parts of the pigment dispersion resin obtained in Production Example 1-3 in the sand grind mill, 100.0 parts of titanium dioxide and 10.0 parts of ion-exchanged water, and disperse until the particle size is 10 m or less. A paste was obtained (solid content 50%).

[0085] Example 1 5 Preparation of emulsion

The amine-modified epoxy resin obtained in Production Example 11 and the block isocyanate curing agent obtained in Production Example 12 were mixed so as to be uniform at a solid content ratio of 80/20. 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 ion-exchanged water was slowly added to dilute. Removal of MIBK under reduced pressure yielded an emulsion with a solid content of 36%.

[0086] Comparative Example 1

319 parts of emulsion obtained in Production Example 1-5 and pigment dispersion paste 133 Part, 543 parts of ion-exchanged water, 2 parts of a 10% cerium acetate aqueous solution and 3 parts of dibutyltin oxide were obtained to obtain an electrodeposition coating composition F having a solid content of 20%. The concentration of the pigment contained in the solid content of the cationic electrodeposition coating composition was 23% by weight. The solid content of the paint can be determined as a percentage of the original mass of the mass of the residue after heating at 180 ° C for 30 minutes. (Conforms to JIS K5601) The electrodeposition coating composition F obtained here was used as Comparative Example 1 as it was. The liquid conductivity was 1600 S / cm.

[0087] Comparative Example 2

158 parts of the emulsion obtained in the above Production Example 1-5, 8 parts of pigment dispersion paste, 831 parts of ion-exchanged water, 2 parts of 10% cerium acetate aqueous solution and 1 part of dibutyltin oxide were mixed to obtain a solid content of 7 % Of electrodeposition coating composition G was obtained. The pigment concentration was 5% by weight. The electrodeposition coating composition G obtained here was used as Comparative Example 2 as it was. The liquid conductivity is 890 μcm "C¾>.

[0088] Example 1

By adding 6 parts of the liquid conductivity control agent A obtained in Example A-2 to 1000 parts of the previously obtained electrodeposition coating composition G, the liquid conductivity was reduced to 1200 S / cm. An adjusted electrodeposition coating composition H was obtained. This electrodeposition coating composition H was used as Example 1.

[0089] Example 2

By adding 8 parts of the liquid conductivity control agent B obtained in Example B-2 to 1000 parts of the previously obtained electrodeposition coating composition G, the liquid conductivity was reduced to 1300 S / cm. An adjusted electrodeposition coating composition I was obtained. This electrodeposition coating composition I was used as Example 2.

[0090] Example 3

The liquid conductivity was adjusted to 1100 S / cm by adding 3 parts of the liquid conductivity control agent C obtained in Example C 3 to 1000 parts of the previously obtained electrodeposition coating composition G. An electrodeposition coating composition J was obtained. This electrodeposition coating composition J was used as Example 3.

[0091] Example 4

The solid content concentration was reduced from 7% to 5% by adding 400 parts of ion exchange water to 1000 parts of the electrodeposition coating composition G obtained previously. This operation decreased the liquid conductivity from 890 a S / cm to 640 S / cm. Here, the liquid conductivity control obtained in Example A-2 was used. An electrodeposition coating composition K having a liquid conductivity adjusted to 1100 S / cm was obtained by adding 8 parts of control agent A. This electrodeposition coating composition K was used as Example 4.

[0092] Comparative Example 3

Electrodeposition with the liquid conductivity adjusted to 1200 S / cm by adding 1 part of the liquid conductivity modifier D obtained in Comparative Example D to 1000 parts of the previously obtained electrodeposition coating composition G A paint composition L was obtained. This electrodeposition coating composition L was used as Comparative Example 3.

[0093] The cation electrodeposition coating film obtained by baking with the cationic electrodeposition coating compositions obtained in Examples and Comparative Examples was evaluated by the following method.

[0094] <Throwing power>

The throwing power was evaluated by the 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-50 00 (manufactured by Nippon Paint)) 11 ～; Box 10 was prepared, which was placed in parallel at 20 mm, and the bottom and bottom surfaces of both sides were sealed with an insulating material such as cloth adhesive tape. In addition, the steel plates 11 to 13 other than the steel plate 14 are provided with through holes 15 of 8 mmφ at the bottom.

[0095] 4 liters of cationic electrodeposition paint was transferred to a vinyl chloride container to form 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.

[0096] The coating material 21 was stirred with a magnetic stirrer (not shown). The steel plates 11 to 14 were electrically connected, and the counter electrode 22 was arranged so that the distance between the steel plate 11 and the steel plate 11 was 150 mm. Cathode electrodeposition coating was performed on steel rice with a voltage applied with each steel plate 11-; 14 as a cathode and the counter electrode 22 as an anode. For coating, the pressure is increased to a voltage at which the film thickness of the coating film formed on the A side of steel plate 11 reaches 15 πι in 5 seconds, and then for 175 seconds for normal electrodeposition and 115 seconds for short time electrodeposition. This was done by maintaining the voltage.

[0097] Each steel plate after coating was washed with water, baked at 170 ° C for 25 minutes, air-cooled, and closest to the counter electrode 22, and the film thickness of the coating film formed on the A surface of the steel plate 11 , The farthest from the counter electrode 22! /, And the film thickness of the coating film formed on the G surface of the steel plate 14 was measured, and the ratio (G / A value) of the film thickness (G surface) / film thickness (eight surfaces) The throwing power was evaluated. Good if this value exceeds 50% (Legend; A) A value of 50% or less was judged as bad (legend; B).

[0098] <Zinc steel plate suitability>

The alloyed hot-dip galvanized steel rice subjected to chemical conversion treatment was pressurized to 220V for 5 seconds, electrodeposited for 175 seconds, washed with water, baked at 170 ° C for 25 minutes, and the state of the coating film was observed. Applicable when no abnormalities are observed (Legend; A), slightly abnormalities are observed (Legend; B), markedly abnormal, when abnormalities are observed (Legend; C) It was judged.

[0099] <Horizontal appearance>

The appearance after baking of the electrodeposition coated plate that was electrodeposited in a horizontal state in an unstirred cationic electrodeposition paint was visually evaluated.

A: Good with no problem, B: Slightly settled and slightly rough, C: Sedimented, poor appearance.

[0100] <Conductivity>

The electrical conductivity of the cationic electrodeposition coating compositions obtained in Examples and Comparative Examples was measured using a conductivity meter (CM-305 manufactured by Toa Denpa Kogyo Co., Ltd.) at a liquid temperature of 25 ° C. .

[0101] [Table 1]

Examples;! To 4 are cationic electrodeposition paints containing a liquid conductivity control agent, the liquid conductivity is in an appropriate range, and there are no defects in throwing power and coating appearance. Comparative Example 1 is normal This is a cationic electrodeposition paint with a solid content (20% by weight) of paint, and the liquid conductivity is in the range of the present invention. Comparative Example 2 is a cationic electrodeposition paint having a low solid content concentration of 7% by weight, and the electroconductivity of the electrodeposition paint is insufficient, resulting in a decrease in rolling characteristics. In Comparative Example 3, the strength S in which the amino group-containing compound is blended with the cationic electrodeposition paint of Comparative Example 2, the amine value of the amino group-containing compound exceeds the range of the present invention, and the throwing power is increased. Is also inferior in zinc steel.

Claims

The scope of the claims

[1] A conductivity control agent for a cationic electrodeposition paint used in a low solid content type cationic electrodeposition paint having a solid content concentration of 0.5 to 9.0% by weight,

An amino group-containing compound having a molecular weight of 500 to 20,000, an amine value of 200 to 500 mmol / 100 g,

Adjust the electrical conductivity to 900-2, OOO ^ S / cm,

Conductivity control agent for cationic electrodeposition coatings.

[2] The conductivity control agent for cationic electrodeposition paints according to [1], wherein the amino group-containing compound is an amine-modified epoxy resin or an amine-modified acrylic resin.

3. The conductivity control agent for cationic electrodeposition paints according to claim 2, wherein the amine-modified epoxy resin is obtained by modifying an epoxy group contained in an epoxy resin with an amine compound.

4. The conductivity control agent for cationic electrodeposition paints according to claim 2, wherein the amine-modified acrylic resin is obtained by modifying an epoxy group of an acrylic resin having an epoxy group with an amine compound.

5. The conductivity control agent for cationic electrodeposition paints according to claim 3, wherein the epoxy resin is a bisphenol type, t-butylcatechol type, phenol novolac type or cresol nopolac type.

[6] Conductivity containing an amino group-containing compound having a solid content concentration of 0.5 to 9.0% by weight and a low solid content type cationic electrodeposition paint having an amine value of 200 to 500 mmol / 100 g Containing a control agent,

A low solid content cationic electrodeposition paint having an electric conductivity of 900 to 2,000 S / cm.

[7] A method for adjusting the electrical conductivity of a cationic electrodeposition paint,

A step of blending a conductivity control agent with a low solid content type cationic electrodeposition coating material having a solid content concentration of 0.5 to 9.0% by weight;

The method, wherein the conductivity control agent comprises an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g. A method of supplying a conductivity control agent to a cationic electrodeposition paint,

Supplying a conductivity control agent to a low solid content type cationic electrodeposition paint having a solid content concentration of 0.5 to 9.0% by weight;

The method, wherein the conductivity control agent comprises an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g.