KR20090046905A - Conductivity control agent for cationic electrodeposition paint and electric conductivity adjustment method of cationic electrodeposition paint using the same - Google Patents

Abstract

An object of the present invention is to provide a technique for preventing lowering of conductivity and uniform electrodeposition in a low solid content and low ash cationic electrodeposition coating composition, and a low solid type cation having a paint solid concentration of 0.5 to 9.0% by weight. A conductivity control agent for cationic electrodeposition paints used in electrodeposition paints, comprising an amino group-containing compound having a molecular weight of 500 to 20,000 and an amine number of 200 to 500 mmol / 100 g, and adjusting the electrical conductivity to 900 to 2,000 μS / cm A method for adjusting the electrical conductivity of a solvent control agent and a cationic electrodeposition paint, comprising the steps of: incorporating a conductivity control agent into a low solid type cationic electrodeposition paint having a paint solid concentration of 0.5 to 9.0% by weight; And adjusting the electrical conductivity of the solid cationic electrodeposition paint to 900 to 2,000 µS / cm. Agent is directed to a method including the amino group-containing compound is an amine value of 200 to 500mmol / 100g.

Description

CONDUCTIVITY CONTROL AGENT FOR CATIONIC ELECTRODEPOSITION COATING MATERIAL AND METHOD OF REGULATING ELECTRIC CONDUCTIVITY OF CATIONIC ELECTRODEPOSITION COATING MATERIAL USING THE SAME}

TECHNICAL FIELD This invention relates to the adjustment of the electrical conductivity of the conductivity control agent of a cationic electrodeposition coating material, and a cationic electrodeposition coating material using the same.

Since the cationic electrodeposition coating can be applied to the details of a complicated shape, it can be applied to the details and can be applied automatically and continuously, so that the undercoat of a large and complicated shape such as an automobile body, in particular, can be applied. It is widely used as a method. Cationic electrodeposition coating is performed by immersing a workpiece as a cathode in a cationic electrodeposition paint and applying a voltage.

The cationic electrodeposition paint is conventionally an aqueous coating composition having a solid content concentration of about 20% by weight, and when left without stirring, a pigment or the like precipitates and a precipitate is formed in an electrodeposition bath. Normally, the cationic electrodeposition paint is circulated by a pump or stirred with a stirrer to prevent sediment formation.

However, since the cationic electrodeposition bath is a large-scale facility in which the automobile body is immersed, the energy required for circulation and agitation, the equipment related thereto, and the cost for maintaining the facility become enormous. Reducing or eliminating such circulation or agitation makes a significant contribution to energy savings in cationic electrodeposition coating. For this reason, it is effective to use a cationic electrodeposition paint that does not produce precipitates or to have a small amount of sediment, specifically, a low solid content or a low ash cationic electrodeposition paint, and such cationic electrodeposition paints are being studied.

For example, Japanese Unexamined Patent Application Publication No. 2004-231989 (Patent Document 1) discloses using a cationic electrodeposition coating material having a pigment ash content of 3 to 10% by weight and a solid content concentration of 5 to 12% by weight. An environment-adaptive electrodeposition coating method is disclosed. This cationic electrodeposition paint has less sediment, less energy costs for agitation and circulation, and can be said to be excellent. In practice, however, as the solid content of the paint decreases, the conductivity decreases, so-called "throwing power". The performance that a coating film is formed from electrodeposition coating to every corner of a to-be-painted thing called this worsens.

It is generally known that the desired uniform electrodeposition can be imparted by adjusting the conductivity of the paint to an appropriate value. As a patent document, what was mentioned about the electroconductivity and uniform electrodeposition property of coating material exists in Unexamined-Japanese-Patent No. 2004-269627 (patent document 2). This cation electrodeposition coating composition mix | blends a sulfonium modified epoxy resin, and control of membrane resistance is needed.

Examining the amine value of the base resin of the cationic electrodeposition paint is Japanese Patent Laid-Open No. 2005-232397 (Patent Document 3) and Japanese Patent Laid-Open No. 7-150079 (Patent Document 4) ) And the like. Patent Document 3 describes that the amine titer of urethane resin (gas resin) is preferably 20 to 60 mgKOH / g (in terms of 35.7 to 107.0 mmol / 100 g), and the cation electrodeposition property of Patent Document 4 is also described. The resin has an amine value of 3 to 200 mg KOH / g (in terms of 5.3 to 356 mmol / 100 g) described as a preferred range. These are the values of the conventional amine number and are basically low.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-231989

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-269627

Patent Document 3: Japanese Patent Laid-Open No. 2005-232397

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

(Initiation of invention)

(Tasks to be solved by the invention)

In low solid content and / or low ash cationic electrodeposition paint, there exists a tendency for conductivity to fall compared with normal cation electrodeposition paint. In this invention, the low solid content and / or low ash cationic electrodeposition coating composition WHEREIN: The technique which prevents the fall of the uniform electrodeposition property by the fall of conductivity is provided.

(Means to solve the task)

That is, the present invention is a conductivity control agent for cationic electrodeposition paints used for low solid type cationic electrodeposition paints having a paint solid content concentration of 0.5 to 9.0 wt%, containing amino groups having a molecular weight of 500 to 20,000 and an amine number of 200 to 500 mmol / 100 g. Provided is a conductivity control agent for a cationic electrodeposition paint comprising a compound and adjusting the electrical conductivity to 900 to 2,000 μS / cm. In the cationic electrodeposition paint, this conductivity control agent exists as an emulsion separate from the cationic epoxy resin, a hardening | curing agent, and a pigment which are coating film forming components, and is mix | blended as a 3rd component actually.

It is preferable that the amino group containing compound used as said conductivity control agent is obtained by modifying the epoxy group contained in an epoxy resin with an amine compound as an amine modified epoxy resin.

Moreover, it is preferable that the said amino group containing compound is obtained by modifying the epoxy group of the acrylic resin which has an epoxy group by an amine compound as an amine modified acrylic resin.

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

The present invention also provides a low solid type cationic electrodeposition paint having a paint solid concentration of 0.5 to 9.0% by weight, comprising a conductivity controlling agent containing an amino group-containing compound having an amine number of 200 to 500 mmol / 100 g, and having an electrical conductivity of 900 to It provides a low solids type cationic electrodeposition paint of 2,000 µS / cm.

The present invention also provides a method for adjusting the electrical conductivity of the cationic electrodeposition paint,

A process of blending a conductivity control agent with a low solid type cationic electrodeposition paint having a paint solid content concentration of 0.5 to 9.0 wt%;

And adjusting the electrical conductivity of the low solid type cationic electrodeposition paint in the compounding step to 900 to 2,000 µS / cm,

The conductivity control agent provides a method comprising an amino group containing compound having an amine number of 200 to 500 mmol / 100 g.

The present invention also provides a method for replenishing a conductivity control agent in a cationic electrodeposition paint.

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

And adjusting the electrical conductivity of the low solid type cationic electrodeposition paint in the diffusion step to 900 to 2,000 µS / cm,

The conductivity control agent provides a method comprising an amino group containing compound having an amine number of 200 to 500 mmol / 100 g.

(Effects of the Invention)

According to the present invention, the conductivity control agent of a specific cationic electrodeposition paint is blended in the cationic electrodeposition paint to reduce uniform electrodeposition properties due to the decrease in conductivity of the cationic electrodeposition paint, which is a drawback of the low ash and / or low solid type cationic electrodeposition paint. Can be solved.

1 is a perspective view illustrating an example of a box used when evaluating uniform electrodeposition property.

It is sectional drawing which shows typically the evaluation method of uniform electrodeposition property.

(Explanation of the sign)

10... Boxes 11 to 14. Zinc Phosphated Steel Sheet

15... Through hole 20. Electrodeposition coating container

21. Electrodeposition paint 22. Counter electrode

(The best mode for carrying out the invention)

The conductivity control agent for the cationic electrodeposition paint of the present invention is composed of an amino group-containing compound having an amine value of 200 to 500 mmol / 100 g. Any amino group-containing compound may be used as long as the conductivity control agent for the cationic electrodeposition paint of the present invention has an amine value in the above range, but usually an amine-modified epoxy resin or an amine-modified acrylic resin is preferable.

The conductivity control agent for the cationic electrodeposition paint of the present invention may be neutralized with an acid as necessary. The amine titer is preferably 250 to 450 mmol / 100 g, more preferably 300 to 400 mmol / 100 g. If the amine value is less than 200 mmol / 100 g, the amount of addition necessary for adjusting the liquid conductivity of the cationic electrodeposition paint of low solid content concentration to an optimum value increases, which may impair corrosion resistance. Moreover, when it exceeds 500 mmol / 100g, it has a fault that precipitation property is reduced and a desired uniform electrodeposition is not obtained. In addition, the zinc steel sheet aptitude is also reduced.

The amino group-containing compound as the conductivity control agent for the cationic electrodeposition paint in the present invention is considered to be a low molecular weight to a high molecular weight, but usually include a high molecular weight compound such as an amine-modified epoxy resin or an amine-modified acrylic resin. Examples of the low molecular weight amino group-containing compound include monoethanolamine, diethanolamine, dimethylbutylamine, and the like.

In this invention, high molecular weight amino group containing compound, especially an amine modified epoxy resin and an amine modified acrylic resin are preferable. An amine modified epoxy resin is obtained by modifying the epoxy group of an epoxy resin with an amine compound. Although an epoxy resin can use a general thing, what has a molecular weight of 500-20000 is suitable as a bisphenol-type epoxy resin, t-butylcatechol type epoxy resin, a phenol novolak-type epoxy resin, and a cresol novolak-type epoxy resin. Among these epoxy resins, phenol novolac type epoxy resins and cresol novolac type epoxy resins are most preferred. In particular, these epoxy resins are commercially available. For example, phenol novolak-type epoxy resin DEN-438 by Dow Chemical Japan, cresol novolak-type epoxy resin YDCN-703 by Doto Chemical Co., Ltd. is mentioned.

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 the reaction of an epoxy group with a diol or dicarboxylic acid.

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

As a compound which introduce | transduces an amino group into an acrylic resin containing an epoxy resin or an epoxy group, primary amine, secondary amine, tertiary amine, etc. are mentioned. As these specific examples, butylamine, octylamine, diethylamine, dibutylamine, dimethylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-di In addition to methyl ethanolamine acetate, a diethyl disulfide acetic acid mixture, etc., the secondary amine which the primary amines, such as diketimine of aminoethyl ethanolamine and diketimine of diethyl hydroamine, blocked. A plurality of amines may be used.

As described above, the number average molecular weight of these amine-modified epoxy resins and amine-modified acrylic resins is preferably from 500 to 20,000. If the number average molecular weight is less than 500, there is a possibility that the corrosion resistance is impaired, and the reason cannot be determined. However, a decrease in uniform electrodeposition property and a decrease in zinc steel sheet aptitude appear. When the number average molecular weight is larger than 20000, there is a fear of causing a deterioration of the finish appearance.

The cationic electrodeposition coating material to which the conductivity control agent for the cationic electrodeposition paint of the present invention can be applied is not limited to a low solid type cationic electrodeposition coating material having a solid content concentration of 0.5 to 9.0% by weight, and usually has a solid content concentration of about 20% by weight. It is also possible to apply to the cationic electrodeposition paint of. Even in normal cationic electrodeposition paints, the conductivity may decrease, and when electrodeposition coating is performed as it is, uniform electrodeposition may be insufficient. When such a defect occurs, the conductivity can be controlled to an appropriate value by adding the conductivity control agent for the cationic electrodeposition paint to the ordinary cationic electrodeposition paint, and as a result, it becomes possible to secure sufficiently uniform electrodeposition property.

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

Electrodeposition Paint Composition

The conductivity control agent for the cationic electrodeposition paint of the present invention can suitably adjust the electrical conductivity of the electrodeposition paint by adjusting the blending amount into the cationic electrodeposition paint. Examples of the cationic electrodeposition coating composition include a cationic epoxy resin, a curing agent, and, if necessary, a pigment and an additive. Hereinafter, each component is demonstrated.

Cationic Epoxy Resin (Cationically Modified Epoxy Resin as Coating Film Forming Component)

The cationic epoxy resin used in the present invention includes an epoxy resin modified with an amine. The cationic epoxy resin is typically ring-opened with an active hydrogen compound capable of introducing a cationic group to all of the epoxy rings of the bisphenol-type epoxy resin, or some of the epoxy rings are ring-opened with other active hydrogen compounds, and the remaining epoxy It is prepared by ring opening with an active hydrogen compound capable of introducing a cationic group. The cationic epoxy resin of the cationic electrodeposition paint preferably has an amine value of 50 to 200 mmol / 100 g, which is smaller than the amine value of the conductivity control agent for the cationic electrodeposition paint (200 to 500 mmol / 100 g). If the amine value is less than 50 mmol / 100 g, the dispersibility to the water of the cation-modified epoxy resin cannot be ensured. If the amine value is more than 200 mmol / 100 g, the water resistance of the resulting coating film may deteriorate, which is not preferable.

Typical examples of the bisphenol type epoxy resin are bisphenol A type or bisphenol F type epoxy resins. As commercially available products of the former, Epicoat 828 (manufactured by Emulsified Shell Epoxy Co., Ltd., epoxy equivalents 180 to 190), Epicoat 1001 (Vinvents Co., Ltd., epoxy equivalents 450 to 500), Epicoat 1010 (Pelants, Epoxy equivalents 3000 to 4000), and the like In addition, the latter commercial item includes Epicoat 807 (manufactured by Ep., Epoxy Equivalent 170).

The oxazolidone ring containing epoxy resin represented by following formula described in Unexamined-Japanese-Patent No. 5-306327 can be used for a cationic epoxy resin. It is because the coating film excellent in heat resistance and corrosion resistance is obtained.

[Wherein R is a residue except a glycidyloxy group of a diglycidyl epoxy compound, R 'is a residue except an isocyanate group of a diisocyanate compound, and n is a positive integer.]

As a method of introducing an oxazolidone ring into an epoxy resin, for example, a block polyisocyanate and a polyepoxide blocked with a lower alcohol such as methanol are heated and insulated in the presence of a basic catalyst to produce a lower alcohol as a by-product. It is obtained by distillation from.

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 the reaction of an epoxy group with a diol or dicarboxylic acid.

These epoxy resins are preferably ring-opened with an active hydrogen compound such that 50 to 200 mmol / 100 g of amine value after ring-opening, more preferably 5 to 50% of them are occupied by primary amino groups.

Active hydrogen compounds capable of introducing cationic groups include acid, sulfide and acid mixtures of primary amines, secondary amines, tertiary amines. In order to prepare primary, secondary or / and tertiary amino group-containing epoxy resins, acid salts of primary amines, secondary amines and tertiary amines are used as active hydrogen compounds capable of introducing cationic groups.

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

Hardener

The curing agent used in the present invention is preferably a block polyisocyanate obtained by blocking a polyisocyanate with a blocking agent, wherein the polyisocyanate is a compound having two or more isocyanate groups in one molecule Say As polyisocyanate, any of aliphatic type, alicyclic type, aromatic type, aromatic-aliphatic type, etc. may be sufficient, for example.

Specific examples of the polyisocyanate include tolylenediisocyanate (TDI), diphenylmethanediisocyanate (MDI), p-phenylenediisocyanate, and naphthalenediisocyanate Aromatic diisocyanates such as nates and the like; Aliphatic diisocyanates having 3 to 12 carbon atoms, such as hexamethylenediisocyanate (HDI), 2,2,4-trimethylhexanediisocyanate and lysine diisocyanate; 1,4-cyclohexanediisocyanate (CDI), isophoronediisocyanate (IPDI), 4,4'-dicyclohexyl methanediisocyanate (hydrogenated MDI), methylcyclohex Cedar isocyanate, isopropylidenedicyclohexyl-4,4'-diisocyanate and 1,3-diisocyanatomethylcyclohexane (hydrogenated XDI), hydrogenated TDI, 2,5- Or alicyclic diisocyanates having 5 to 18 carbon atoms, such as 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also called norbornene isocyanate); Aliphatic diisocyanates having an aromatic ring such as xylylenediisocyanate (XDI) and tetramethylxylylenediisocyanate (TMXDI); And modified products of these diisocyanates (uretainide, carbodiimide, uretodione, uretoimine, biuret and / or isocyanurate modified). 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 in an NCO / OH ratio of 2 or more can also be used as curing agents. have.

It is preferable that polyisocyanate is aliphatic polyisocyanate or alicyclic polyisocyanate. It is because the formed coating film is excellent in weatherability.

Preferred embodiments of aliphatic polyisocyanate or alicyclic polyisocyanate include hexamethylenediisocyanate, hydrogenated TDI, hydrogenated MDI, hydrogenated XDI, IPDI, norbornene isocyanate, two of them. Bimer, trimer (isocyanurate), and the like.

The blocking agent is added to the polyisocyanate group and is stable at normal temperature, but can be recovered from free isocyanate group by heating above the dissociation temperature.

As a block agent, when low temperature hardening (160 degrees C or less) is desired, lactam system block agents, such as (epsilon) -caprolactam, (delta) -valerolactam, (gamma)-butyrolactam, and (beta)-propiolactam, and form aldoxin, It is preferable to use oxime-based blocking agents such as acetaldehyde, acetoxime, methyl ethyl ketoxime, diacetyl monooxime and cyclohexane oxime.

The binder containing a cationic epoxy resin and a hardening | curing agent is generally contained in the electrodeposition coating composition in the quantity which occupies 25 to 85 weight%, preferably 40 to 70 weight% of the total solid of an electrodeposition coating composition.

Pigment

The electrodeposition coating composition used in the present invention may contain a pigment which is usually used. Examples of pigments that can be used include inorganic pigments commonly used, for example colored pigments such as titanium white, carbon black and colcothar; Filler pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; Zinc Phosphate, Iron Phosphate, Aluminum Phosphate, Calcium Phosphate, Zinc Phosphite, Zinc Cyanide, Zinc Oxide, Tripolyphosphate, Zinc Molybdate, Aluminum Molybdate, Calcium Molybdate and Aluminum Molybdate, Zinc Phosphate, Bismuth Hydroxide And rust preventive pigments such as bismuth oxide, basic bismuth carbonate, bismuth nitrate, bismuth benzoate, bismuth citrate and bismuth silicate.

The pigment is generally contained in the electrodeposition coating composition in an amount that accounts for 1 to 35% by weight, preferably 10 to 30% by weight of the total solids of the electrodeposition coating composition.

Pigment dispersion paste

When the pigment is used as a component of the electrodeposition paint, the pigment is generally dispersed in a high concentration in an aqueous medium in advance with a resin called a pigment dispersion resin to form a paste. It is because it is difficult to disperse | distribute a pigment in one process in the low concentration uniform state used for an electrodeposition coating composition, because a pigment is powder form. Such pastes are generally referred to as pigment dispersion pastes.

The pigment dispersion paste is prepared by dispersing a pigment in an aqueous medium together with a pigment dispersion resin varnish. 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 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 varnish is used in a solid content ratio of 5 to 40 parts by weight and a pigment of 10 to 30 parts by weight.

After mixing 10-1000 weight part of said resin dispersion varnishes and pigments with respect to 100 weight part of resin solid content, a ball mill, a sand grinding mill, etc. until the particle diameter of the pigment in this mixture turns into a predetermined uniform particle size. It disperse | distributes using the usual dispersing apparatus of, and a pigment dispersion paste is obtained.

The said cationic electrodeposition coating composition of this invention needs to be 0.5-9.0 weight% of paint solid content concentration. If the paint solid content concentration is lower than the lower limit, no cationic electrodeposition coating film is obtained. On the other hand, when the paint solid content concentration exceeds the upper limit, the pigment component contained in the cationic electrodeposition paint left in the unstirred state is precipitated, which is not preferable.

Preparation of Electrodeposition Coating Composition

The electrodeposition coating composition is prepared by dispersing a cationic epoxy resin, a curing agent and a pigment dispersion paste in an aqueous medium. Also, usually, the aqueous medium contains a neutralizing agent 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 which achieves a neutralization rate of at least 20%, preferably 30 to 60%.

The amount of curing agent should be 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 at the time of curing to give a good cured coating film, generally cationic It is represented by the solid content weight ratio with respect to the hardening | curing agent of an epoxy resin, and is generally the range of 90/10-50/50, Preferably it is 80/20-65/35.

The electrodeposition paint may contain tin compounds such as dibutyl tin dilaurate and dibutyl tin oxide, or may include a common urethane cracking catalyst. Since it is preferable to contain substantially no lead, it is preferable that the quantity is 0.1 to 5 weight% of a block polyisocyanate compound.

The electrodeposition coating composition may include a commercial paint additive such as a water miscible organic solvent, a surfactant, an antioxidant, a UV absorber, and a pigment.

Although the cation electrodeposition coating composition of this invention contains a component of the said base material, although it will not specifically limit, The cationic electrodeposition coating material which the conductivity control agent for cation electrodeposition coating materials of this invention acts effectively is a thing of low solids type. In addition, the cationic electrodeposition paint of the present invention may be a low ash type.

The low solid type cationic electrodeposition coating material has a solid content concentration of less than about 20 wt% of the conventional solid content, in particular 0.5 to 9 wt%, and more preferably 3 wt%. If it is less than 0.5 weight%, since a pigment component precipitates in an unstirred state, it is unpreferable. On the other hand, although it may be more than 9% by weight, there is a possibility that the need to adjust the electrical conductivity of the paint by adding a conductivity regulator for the cationic electrodeposition paint is eliminated.

As a method of reducing the solid content concentration of the cationic electrodeposition paint, when the method of reducing the pigment component is employed, the ash content in the paint (that is, the weight of the solid material remaining when the paint is burned is divided by the weight of the solid content of the paint, 100 Multiplied by Therefore, the cationic electrodeposition paint used in the present invention can also be said to be a low ash type. The ash content is 15 to 40% by weight in the case of the normal cationic 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.

It is preferable that the to-be-painted thing in the case of carrying out electrodeposition coating using an electrodeposition coating composition is a conductor previously surface-treated, such as zinc phosphate treatment by immersion, a spray method, etc., Even if such surface treatment is not performed good. In addition, a conductor does not have a restriction | limiting in particular as long as it can become a cathode in carrying out electrodeposition coating, A metal base material is preferable.

The conditions under which electrodeposition is carried out are generally the same as those used for other types of electrodeposition coatings. The applied voltage may vary greatly, or may range from 1 volt to several hundred volts. Current densities usually range from about 10 A / m 2 to 160 A / m 2 and tend to decrease during electrodeposition.

After electrodeposition by the electrodeposition coating method of the present invention, the film is baked in an ordinary method such as a baking furnace, a baking oven or an infrared heat lamp under elevated temperature. The baking temperature is usually about 140 ° C to 180 ° C. After the final water washing, the coating material coated with the cationic electrodeposition paint of the present invention is dried and baked to form a cured electrodeposition coating film, whereby the coating step is completed.

Adjustment of Electrical Conductivity

In the present invention, the liquid conductivity of the paint is ensured by adding the above-described liquid conductivity control agent for the cationic electrodeposition paint to the cationic electrodeposition paint. As described above, the low solid type cationic electrodeposition paint tends to have a low liquid conductivity compared to a normal cationic electrodeposition paint having a solid content of about 20% by weight. It adjusts by mix | blending. By increasing the amine value of the cation-modified epoxy resin as the coating film forming component, the conductivity can be maintained at an appropriate value and the uniform electrodeposition property can be ensured. However, when the amine number of the cation-modified epoxy resin is more than 200 mmol / 100 g, the water resistance of the resulting coating film may deteriorate, which is not preferable. The electrical conductivity required to obtain the desired uniform electrodeposition property is 900 to 2000 µS / cm, and the liquid conductivity of the low solid type electrodeposition paint can be controlled in this range by adding the conductivity control agent for the cationic electrodeposition paint of the present invention. The lower limit of conductivity is preferably 1000 µS / cm, and the upper limit is preferably 1800 µS / cm. If the conductivity is less than 900 µS / cm, there is a drawback that the desired uniform electrodeposition is not obtained. If the conductivity is larger than 2000 µS / cm, there is a drawback that a coating film defect called a gas pinhole is likely to occur during zinc coating. In addition, conductivity is measured on the conditions of 25 degreeC of liquid temperature using the commercially available liquid conductivity meter.

The compounding quantity of the conductivity control agent for cationic electrodeposition paints to a cationic electrodeposition paint is not specifically limited, A predetermined electrical conductivity may be obtained, Specifically, 0.5-30 weight% based on paint solid content, Preferably it is 1 To 30% by weight, more preferably 1 to 15% by weight. Although at least better than 0.5% by weight, sufficient electrical conductivity may not be obtained in some cases. In addition, although the compounding quantity may exceed 50 weight%, the increase of the electrical conductivity proportional to the addition amount is not seen.

As mentioned above, the low solid type cationic electrodeposition paint which adjusted conductivity is a low ash and a low solid type cationic electrodeposition paint, and can secure favorable uniform electrodeposition property. Also in such a cationic electrodeposition paint, it is necessary to replenish the coating film-forming component to the cationic electrodeposition paint tank in the process of repeatedly coating the object on the coating line. At this time, the electrical conductivity of the cationic electrodeposition paint in the bath may deviate from the range of 900 to 2,000 µS / cm desired by the present application. When the electrical conductivity is 900 μS / cm or less, by adding the conductivity regulator of the present invention to the cationic electrodeposition paint tank separately, the conductivity of the cationic electrodeposition paint in the bath is maintained at 900 to 2,000 weight while maintaining the solid content concentration at 0.5 to 9.0% by weight. It can be adjusted in the range of μS / cm.

(Example)

The present invention will be described more specifically by way of examples. This invention should not be interpreted as being limited to these Examples. In the examples, parts and percentages are based on weight unless otherwise indicated.

Example A-1

Into a flask equipped with a reflux condenser and a stirrer, 295 parts of methyl isobutyl ketone (hereinafter abbreviated as "MIBK"), 37.5 parts of methylethanolamine and 52.5 parts of diethanolamine were kept at 100 ° C while stirring. 205 parts of cresol novolak-type epoxy resins (a clay chemicals, brand name YDCN-703) are gradually added to this, and it is made to react for 3 hours after complete addition. 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.

Example A-2

To 140 parts of the amino modified resin solution obtained in Example A-1, 5.5 parts of formic acid and 1254.5 parts of deionized water were added, followed by stirring for 30 minutes while maintaining the temperature at 80 ° C. The organic solvent was removed under reduced pressure to obtain a liquid conductivity controller A having a solid content of 7.0%.

Example B-1

255 parts of MIBK and 75 parts of methylethanolamine were thrown into the flask provided with the reflux cooler and the stirrer, and it kept at 100 degreeC, stirring. 180 parts of phenol novolak-type epoxy resins (the Dow Chemical Japan company make, brand name DEN-438) are added gradually, and it makes it react for 3 hours after whole quantity addition is complete | finished. 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.

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 were added, followed by stirring for 30 minutes while maintaining the temperature at 80 ° C. The organic solvent was removed under reduced pressure to obtain a liquid conductivity controller B having a solid content of 7.0%.

Example C-1

50 parts of methyl isobutyl ketones (MIBK) are added to the flask provided with a reflux condenser, a nitrogen inlet tube, a dropping funnel, and a stirrer, and it keeps at 100 degreeC, stirring. The mixed liquid which consists of 100 parts of glycidyl methacrylate and 2 parts of azobis isobutyronitrile (AIBN) was dripped at constant speed for 2 hours by the dropping funnel. It kept at 100 degreeC and continued stirring for 30 minutes. Then, 52.5 parts of MIBK and 0.5 parts of AIBN were dripped over 1 hour. Furthermore, stirring was continued for 1 hour and reaction was complete | finished.

Example C-2

47.5 parts of MIBK and 52.8 parts of methylethanolamine were put into the flask provided with the reflux condenser and the stirrer, and kept at 100 ° C while stirring. 205 parts of the reactants obtained in Example C-1 were slowly added thereto, followed by reaction for 3 hours after the addition of the entire amount was completed. The molecular weight was measured and found to be 9,800. The amine titer (MEQ (B)) of the obtained amino modified resin was measured, and it was 450 mmol / 100 g.

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 were added, followed by stirring for 30 minutes while maintaining the temperature at 80 ° C. The organic solvent was removed under reduced pressure to obtain a liquid conductivity controller C having a solid content of 7.0%.

Comparative Example D

463.4 parts of deionized water and 13.5 parts of formic acid are added to the glass beaker and stirred. While stirring, 23.1 parts of dimethylethanolamine whose molecular weight is 89 was added gradually. Amine value (MEQ (B)) of the active ingredient was 740 mmol / 100 g, and a liquid conductivity controller D having an active ingredient concentration of 7% was obtained.

Preparation Example 1 Preparation of Cationic Electrodeposition Coating Composition

Preparation Example 1-1 Preparation of Cationic Modified Epoxy Resin

92 parts of 2,4- / 2,6-tolylene diisocyanate (weight ratio = 8/2) and the methyl isobutyl ketone (to a flask equipped with a stirrer, a cooling tube, a nitrogen introduction tube, a thermometer, and a dropping funnel) Hereinafter, 95 parts of abbreviations (MIBK) and 0.5 parts of dibutyltin dilaurate were added. After stirring the reaction mixture, 21 parts of methanol was dripped. The reaction started from room temperature and was raised to 60 ° C by exotherm. 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. In addition, 53 parts of bisphenol A-propylene oxide 5 mole adducts were added to the reaction mixture. The reaction was mainly in the range of 60 to 65 ° C, and continued in the measurement of the IR spectrum until the absorption based on the isocyanate group was lost.

Next, 365 parts of epoxy equivalents of 188 epoxy equivalent synthesize | combined from bisphenol A and epichlorohydrin by the method known previously were added to the reaction mixture, and it heated up to 125 degreeC. Thereafter, 1.0 part of benzyldimethylamine was added and reacted at 130 ° C until the epoxy equivalent was 410.

Subsequently, 61 parts of bisphenol A and 33 parts of octylic acid were added and reacted at 120 degreeC, and the epoxy equivalent was 1190. Thereafter, the reaction mixture was cooled, and 11 parts of diethanolamine, 24 parts of N-ethylethanolamine and 25 parts of 79% by weight MIBK solution of ketimide of aminoethylethanolamine were added and reacted at 110 ° C for 2 hours. Thereafter, the mixture was diluted to a nonvolatile content of 80% in MIBK to obtain an amine-modified epoxy resin (80% resin solid content).

Preparation Example 1-2 Preparation of Block Isocyanate Curing Agent

1250 parts of diphenylmethane diisocyanate and 266.4 parts of MIBK were put into a reaction container, and after heating to 80 degreeC, 2.5 parts of dibutyltin dilaurates were added. Here, what melt | dissolved 226 parts of (epsilon) -caprolactam in 944 parts of butyl cellosolves was dripped at 80 degreeC over 2 hours. After heating at 100 DEG C for 4 hours thereafter, in the measurement of the IR spectrum, it was confirmed that the absorption based on the isocyanate group was lost and allowed to cool, and then 336.1 parts of MIBK were added to have a glass transition temperature of 0 DEG C. A block isocyanate curing agent was obtained.

Preparation Example 1-3 Preparation of Pigment Dispersion Resin

First, 222.0 parts of isophorone diisocyanate (hereinafter abbreviated as IPDI) were put into a reaction vessel equipped with a stirring device, a cooling tube, a nitrogen introduction tube, and a thermometer, and diluted with 39.1 parts of MIBK, followed by dibutyl. 0.2 part of tin dilaurate was added. Then, after heating up this at 50 degreeC, 131.5 parts of 2-ethylhexanols were dripped over 2 hours in dry nitrogen atmosphere under stirring. The reaction temperature was maintained at 50 ° C by cooling appropriately. As a result, 2-ethylhexanol half-blocking IPDI (resin solid content 90.0%) was obtained.

Subsequently, 87.2 parts of dimethylethanolamine, 117.6 parts of 75% lactic acid aqueous solution, and 39.2 parts of ethylene glycol monobutyl ether were sequentially added to a suitable reaction vessel, and the mixture was stirred at 65 ° C. for about half an hour to obtain a quarterizing agent. Prepared).

Next, 710.0 parts of EPON 829 (the bisphenol A type epoxy resin, epoxy equivalents 193-203 made by Shell Chemical Company, Inc.) and 289.6 parts of bisphenol A were put into a suitable reaction container, and it was made into 150-160 degreeC under nitrogen atmosphere. As a result of heating, an initial exothermic reaction occurred. The reaction mixture was reacted at 150 to 160 ° C. for about 1 hour, and then cooled to 120 ° C., and then 498.8 parts of 2-ethylhexanol half-blocked IPDI (MIBK solution) prepared earlier was added.

The reaction mixture was kept at 110 to 120 ° C. for about 1 hour, then 463.4 parts of ethylene glycol monobutyl ether were added, the mixture was cooled to 85 to 95 ° C., homogenized, and then 196.7 parts of the quaternizing agent prepared first Added. The reaction mixture was maintained at 85 to 95 ° C until the acid value became 1, and then 964 parts of deionized water was added to terminate the quaternization in the epoxy-bisphenol A resin to obtain a resin for pigment dispersion having a quaternary ammonium salt portion. (50% resin solids).

Preparation Example 1-4 Preparation of Pigment Dispersion Paste

100 parts of the pigment dispersion resin, 100.O parts of titanium dioxide and 100.O parts of ion-exchanged water were added to a sand grind mill and dispersed until the particle size became 10 μm or less, thereby dispersing the pigment dispersion paste. (50% solids).

Preparation Example 1-5 Preparation of Emulsions

The amine-modified epoxy resin obtained in Production Example 1-1 and the block isocyanate curing agent obtained in Production Example 1-2 were mixed so as to be uniform with a solid ratio of 80/20. Glacial acetic acid was added to this so that the milligram equivalent (MEQ (A)) of acid per 100g of resin solid content might be 30, and ion-exchange water was slowly added and diluted on it. Removal of MIBK under reduced pressure yielded an emulsion with 36% solids.

Comparative Example 1

319 parts of the emulsion obtained in Preparation Example 1-5 and 133 parts of the pigment dispersion paste, 543 parts of ion-exchanged water, 2 parts of 10% cerium acetate aqueous solution and 3 parts of dibutyltin oxide were mixed to obtain an electrodeposition paint having a solid content of 20%. Composition F was obtained. The density | concentration of the pigment contained in solid content of this cationic electrodeposition coating composition was 23 weight%. Moreover, paint solid content can be calculated | required as a percentage with respect to the original mass of the mass of the residue after heating for 30 minutes at 180 degreeC. (According to JIS K5601) The electrodeposition coating composition F obtained here was used as Comparative Example 1 as it is. . The liquid conductivity was 1600 μS / cm.

Comparative Example 2

158 parts of the emulsion and 8 parts of the pigment dispersion paste obtained in Preparation Example 1-5, 831 parts of ion-exchanged water, 2 parts of 10% cerium acetate aqueous solution, and 1 part of dibutyltin oxide were mixed to obtain an electrodeposition coating composition having a solid content of 7%. 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 is. Liquid conductivity was 890 μS / cm.

Example 1

By adding 6 parts of the liquid conductivity control agent A obtained in Example A-2 with respect to 1000 parts of the electrodeposition coating composition G obtained first, the electrodeposition coating composition H in which the liquid conductivity was adjusted to 1200 µS / cm was obtained. This electrodeposition coating composition H was used as Example 1.

Example 2

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

Example 3

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

Example 4

By adding 400 parts of ion-exchanged water to 1000 parts of the electrodeposition coating composition G obtained first, the solid content concentration was reduced from 7% to 5%. By this operation, the liquid conductivity was lowered from 890 µS / cm to 640 µS / cm. By adding 8 parts of the liquid conductivity control agent A obtained in Example A-2 to this, an electrodeposition coating composition K in which the liquid conductivity was adjusted to 1100 µS / cm was obtained. This electrodeposition coating composition K was used as Example 4.

Comparative Example 3

The electrodeposition coating composition L having the liquid conductivity adjusted to 1200 µS / cm was obtained by adding 1 part of the liquid conductivity regulator D obtained in Comparative Example D with respect to 1000 parts of the electrodeposition coating composition G obtained first. This electrodeposition coating composition L was used as Comparative Example 3.

The cationic electrodeposition coating composition obtained by the Example and the comparative example and the cationic electrodeposition coating film obtained by baking were evaluated by the following method.

Uniform electrodeposition

Uniform electrodeposition property was evaluated by the so-called four-box method (4BOX method). That is, as shown in FIG. 1, four zinc phosphate-treated steel sheets (Surdyne SD-5000 (manufactured by Nihon Paint Co., Ltd.) of JIS G3141 SPCC-SD) 11 to 14 were placed in parallel at a distance of 20 mm in a standing state. It arrange | positioned and the box 10 which sealed both lower side surfaces and the bottom surface with insulators, such as a cloth adhesive tape, was prepared. In addition, the steel sheets 11 to 13 other than the steel sheet 14 are provided with a through hole 15 having a diameter of 8 mm in the lower portion.

4 liters of cationic electrodeposition paints were transferred to a vinyl chloride container to obtain a first electrodeposition bath. As shown in FIG. 2, the said box 10 was immersed in the electrodeposition paint container 20 which put the electrodeposition paint 21 as a to-be-coated object. In this case, the paint 21 penetrates into the box 10 only through the through holes 15.

The coating material 21 was stirred with the magnetic stirrer (not shown). Each of the steel sheets 11 to 14 was electrically connected to each other, and a counter electrode 22 was disposed such that the distance from the nearest steel sheet 11 was 150 mm. A voltage was applied to each of the steel sheets 11 to 14 as a cathode and the counter electrode 22 as an anode, and the steel plates were subjected to cation electrodeposition coating. The coating is stepped up to a voltage at which the film thickness of the coating film formed on the A surface of the steel sheet 11 for 5 seconds from the start of application is increased to 15 µm, and then the voltage is maintained for 175 seconds in normal electrodeposition and 115 seconds in short electrodeposition. Carried out.

Each steel sheet after coating is baked for 25 minutes at 170 ° C. after water washing, 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 counter electrode. The film thickness of the coating film formed in the G surface of the steel plate 14 furthest from (22) is measured, and uniform electrodeposition property is according to the ratio (G / A value) of film thickness (G surface) / film thickness (A surface). Evaluated. The case where this value exceeds 50% was good (legend; A), and the case where this value was 50% or less was judged as bad (legend; B).

<Zinc sheet aptitude>

The alloyed hot-dip galvanized steel sheet subjected to the chemical conversion treatment was boosted up to 220 V in 5 seconds, followed by electrodeposition at 175 seconds, followed by water washing, and baking at 170 ° C. for 25 minutes to observe the coating state. It was judged that the case where the coating film abnormality was not recognized was good (legend A), the case where a little abnormality was recognized, the abnormality was established (legend B), and the case where remarkable abnormality was recognized was bad (legend C).

<Horizontal appearance>

The external appearance after the baking of the electrodeposition coated plate which was placed in a horizontal state in the unstirred cation electrodeposition coating material and electrodeposited and coated was visually evaluated.

A: Good without problems, B: Pigment settles a little, there is a little roughness, C: Pigment settles, and appearance is bad.

<Conductivity>

The conductivity of the cation electrodeposition coating composition obtained by the Example and the comparative example was measured on the conditions of 25 degreeC of solution temperature using the conductivity meter (CM-305 by Doa Radio Industry Co., Ltd. product).

In Examples 1-4, it is a cation electrodeposition coating material containing a liquid conductivity control agent, liquid conductivity is in a suitable range, and defects are not seen in uniform electrodeposition property and a coating-film external appearance. Comparative Example 1 is a cationic electrodeposition paint of ordinary paint solids (20% by weight), and the liquid conductivity is in the scope of the present invention, but the paint solids are high and the horizontal appearance is deteriorated. Comparative Example 2 is a cationic electrodeposition coating material having a low paint solid content concentration of 7% by weight. The liquid conductivity of the electrodeposition coating material is insufficient, and uniform electrodeposition property is lowered. In the comparative example 3, although the amino group containing compound is mix | blended with the cationic electrodeposition paint of the comparative example 2, since the amine titer of an amino group containing compound exceeds the range of this invention, neither uniform electrodeposition property nor zinc steel plate aptitude worsens.

Claims (8)

A conductivity control agent for cationic electrodeposition paints used in low solids type cationic electrodeposition paints having a paint 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 and an amine number of 200 to 500 mmol / 100 g, To adjust the electrical conductivity from 900 to 2,000μS / cm Conductivity control agent for cationic electrodeposition paints. The method of claim 1, A conductivity control agent for cationic electrodeposition paints, wherein the amino group-containing compound is an amine-modified epoxy resin or an amine-modified acrylic resin. The method of claim 2, The conductivity control agent for cationic electrodeposition paints obtained by modifying the epoxy group contained in the epoxy resin by the amine-modified epoxy resin with an amine compound. The method of claim 2, A conductivity control agent for cationic electrodeposition paints obtained by modifying an epoxy group of an acrylic resin having an epoxy group with an amine compound. The method of claim 3, wherein The said epoxy resin is a bisphenol-type, t-butylcatechol type, the phenol novolak-type, or the cresol novolak-type conductivity control agent for cation electrodeposition paints. A low solids type cationic electrodeposition paint having a paint solid concentration of 0.5 to 9.0% by weight, A conductivity controlling agent containing an amino group-containing compound having an amine number of 200 to 500 mmol / 100 g, Electrical conductivity between 900 and 2,000 μS / cm Low solid type cationic electrodeposition paint. As a method of adjusting the electrical conductivity of the cationic electrodeposition paint, A process of blending a conductivity control agent with a low solid type cationic electrodeposition paint having a paint solid content concentration of 0.5 to 9.0 wt%, and Process of adjusting the electrical conductivity of the low solid type cationic electrodeposition paint in the compounding step to 900 to 2,000μS / cm And The conductivity control agent comprises an amino group containing compound having an amine number of 200 to 500 mmol / 100 g. As a method of replenishing a conductivity control agent in a cationic electrodeposition paint, Supplying a conductivity control agent to a low solid type cationic electrodeposition paint having a paint solid concentration of 0.5 to 9.0% by weight, and A step of adjusting the electrical conductivity of the low solid type cationic electrodeposition paint in the diffusion step to 900 to 2,000μS / cm And The conductivity control agent comprises an amino group containing compound having an amine number of 200 to 500 mmol / 100 g.

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