JP2008106134A - Cationic electrodeposition coating composition and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simultaneously satisfying both the surface smoothness and the end-face coatability of a cationic electrodeposition coating material. <P>SOLUTION: The cationic electrodeposition coating composition having excellent smoothness and end-face coatability gives an uncured deposition coating film formed by the electrodeposition coating of the cationic electrodeposition coating composition and having a storage elastic modulus (G') of 80-500 dyn/cm<SP>2</SP>at 140°C and a loss elastic modulus (G") of 10-150 dyn/cm<SP>2</SP>at 80°C. The invention further provides a method for satisfying the smoothness and the end-face coatability by using the coating composition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cationic electrodeposition coating composition excellent in smoothness and end face coverage, and to a method for achieving both smoothness and end face coverage of a cationic electrodeposition coating film using the same.

  Electrodeposition coating is a coating method performed by immersing an object to be coated in an electrodeposition coating composition and applying a voltage. In this method, even an object to be coated having a complicated shape can be painted in detail, and can be painted automatically and continuously, so that it has a large and complicated shape, particularly for an automobile body. Widely used as an undercoating method for objects to be coated.

  Even if it is electrodeposition coating, since it is coating coating on articles | goods, it is desirable that the coating surface is smooth. In addition, a metal punched portion or the like has an acute end surface, and the anticorrosion performance deteriorates if the coating film is not sufficiently coated on the portion. Therefore, both surface smoothness and end face coverage are performances required by the electrodeposition coating film. On the other hand, the surface smoothness is fluidized and smoothed by lowering the viscosity of the uncured coating during bake curing, but the end surface coverage is sagging by preventing the viscosity of the uncured coating from decreasing. It is necessary to suppress and to leave a coating film on an acute end face. In other words, smoothness and end face coverage are contradictory performances.

  As a technique for examining the coating film viscosity of the electrodeposition coating film, there is JP-A-2002-285077 (Patent Document 1), and the minimum coating film viscosity in the coating film curing process is between 30 and 150 PaS. An electrodeposition coating composition for electric wires is described (claim 3). Patent Document 1 describes that by adjusting the minimum coating film viscosity in the coating film curing process, there is no sagging at the time of melting, and edge coverage and the like can be improved.

In JP-A-6-65791 (Patent Document 2), an uncured coating surface formed by applying a cationic electrodeposition coating is coated with a chipping-resistant primer, and further an intermediate coating or top coating is applied to form a three-layer coating. In the method of simultaneously curing the cationic electrodeposition paint, it is disclosed that the minimum melt viscosity when the coating film is cured is 10 ⁴ to 10 ⁸ cps. It is disclosed that this coating film can shorten the coating process because three layers are baked at a time, is excellent in edge cover property, and the formed multilayer coating film is excellent in finish and chipping resistance. This publication discloses the finish and edge cover properties of the multilayer coating film, but does not discuss the finish and edge cover properties of the electrodeposition coating film itself. On the other hand, in the general paint including the cationic electrodeposition paint of the present invention, it has been conventionally performed to control the viscosity of the coating film using particles described later.
JP 2002-285077 A JP-A-6-65791

  In the present invention, as described above, it is an object to provide a method for making the contradictory performances of surface smoothness and end face coverage compatible in cationic electrodeposition coatings.

That is, the present invention is a cationic electrodeposition coating composition, and the storage elastic modulus (G ′) at 140 ° C. of an uncured deposited coating obtained by electrodeposition coating of the cationic electrodeposition coating composition is 80. Provided is a cationic electrodeposition coating composition excellent in smoothness and end face coverage, which is ˜500 dyn / cm ² and has a loss elastic modulus (G ″) at 80 ° C. of 10 to 150 dyn / cm ² .

  The cationic electrodeposition coating composition preferably contains a cationic epoxy resin, a blocked isocyanate curing agent, resin particles and / or a pigment component.

Further, the present invention relates to a method for forming a cationic electrodeposition coating film by immersing an object to be coated in a cationic electrodeposition coating material and applying a voltage. By adjusting the storage elastic modulus (G ′) at 80 to 500 dyn / cm ² and adjusting the loss elastic modulus (G ″) at 80 ° C. to 10 to 150 dyn / cm ² , A method for achieving both end face coverage is provided.

  The storage elastic modulus and loss elastic modulus are preferably adjusted by adding crosslinked resin particles or blending an inorganic pigment. In the case of crosslinked resin particles, the average particle size is preferably 1.0 to 3.0 μm, and the amount added is The amount is preferably 3 to 15% by weight in the solid content of the coating resin in the cationic electrodeposition coating composition.

  Adjustment of the storage elastic modulus and loss elastic modulus with an inorganic pigment is preferably performed by blending the inorganic pigment in an amount of 10 to 20% by weight in the solid content of the cationic electrodeposition coating composition.

  The storage elastic modulus and loss elastic modulus can be adjusted by both the inorganic pigment and the crosslinked resin particles, the crosslinked resin particles have an average particle diameter of 1.0 to 3.0 μm, and the inorganic pigment is a cationic electrodeposition coating. It is preferably used in an amount of 0.5 to 10% by weight in the solid content of the composition.

  In the case of adjusting the storage elastic modulus and loss elastic modulus by both the inorganic pigment and the crosslinked resin particles, the crosslinked resin particles are blended in an amount of 3 to 15% by weight in the coating resin solid content of the cationic electrodeposition coating composition. Is preferred.

  According to the present invention, smoothness and end face coverage can be achieved by simultaneously adjusting the loss elastic modulus G ″ and the storage elastic modulus G ′ among the dynamic viscoelasticity of the uncured coating deposited in the electrodeposition coating. In the prior art, smoothness was ensured only by controlling the minimum melt viscosity by controlling the complex viscosity η * in the dynamic viscoelasticity measurement. In the present invention, in the dynamic viscoelasticity of the uncured coating film of the cationic electrodeposition paint, a loss is caused when controlling the smoothness. It was found that it is important to control the elastic modulus: G ″ (viscosity term) within a specific range. Further, it has been found that it is important to control the storage elastic modulus G ′ (elastic term) within a specific range when controlling the end face coverage. Furthermore, in the present invention, the loss elastic modulus G ″ is controlled to a specific range, and at the same time, the storage elastic modulus G is secured in order to ensure both smoothness and end face coverage of the electrodeposition coating film, which has been regarded as a reciprocal event. The electrodeposition coating film obtained by finding that it is important to control 'to a specific range, and by controlling these parameters to a specific range, assuming that G ″ and G ′ are independent parameters. This achieves both smoothness and end face coverage.

  According to the present invention, it is possible to evaluate the coexistence of surface smoothness and end face coverage only by controlling the loss elastic modulus and storage elastic modulus of the uncured coating film deposited during electrodeposition. A useful performance inspection or performance management method for electrodeposition paints can be provided.

  Dynamic viscoelasticity is an elastic modulus observed when a vibration (periodic) strain or force is applied to a linear viscoelastic body, and is related to frequency and temperature. The following descriptions of dynamic viscoelasticity include: lecture rheology (edited by the Japan Society of Rheology), Chapter 2 Rheology of Polymer Liquids, p31-39 and Introduction to Polymer Chemistry (Seizo Okamura, Akio Nakajima, Shigeharu Onoki, Yasunori Nishijima, Higashimura Toshinobu and Norio Ise), Chapter 4 Performances of Polymeric Materials, Viscoelasticity, p149-155.

The stress and strain at the angular velocity ω (2π × frequency f) are given by the following equations.
Strain γ (t) = γ ₀ e ^iωt (dyn / cm ² )
Stress σ (t) = σ ₀ e ^{i (ωt + δ)} (dyn / cm ² )
(Where γ (t) is the strain at time t, σ (t) is the stress at time t, γ ₀ is the strain at t = 0, σ ₀ is the stress at t = 0, and δ is the phase difference. )
The complex elastic modulus G ^{* at} this time is
G ^* = (σ ₀ / γ ₀ ) e ^iδ = (σ ₀ / γ ₀ ) (cos δ−i sin δ)
It is represented by The complex viscosity η ^* = G ^* / ω (poise), which is generally used as a viscosity control factor of a paint, is a quantification of viscoelasticity having both the viscosity and elasticity of the paint.

That is, in the present invention, both the smoothness and the end face coverage can be achieved by separately treating the viscosity and elasticity and controlling them. In order to ensure smoothness, it is necessary to control the flow of the paint during the baking process. This flow is associated with a viscous property, which is expressed by the following equation from the relationship between stress and strain.
Loss modulus (viscosity) G ″ = G ^* sin δ (dyn / cm ² )

On the other hand, in order to ensure end face coverage, it is necessary to control the force to stay in place during the baking process, and this force is related to the elastic property, which is based on the relationship between stress and strain. It is represented by the following formula.
Storage elastic modulus (elasticity) G ′ = G ^* cos δ (dyn / cm ² )

  In the case of general paints including cationic electrodeposition paints, the uncured coating film is governed by the viscosity term at the initial stage of baking, and is greatly affected by the loss elastic modulus G ″. The gelation point (apparently connected from end to end) is reached by cross-linking, after which it becomes governed by the elastic term and is greatly influenced by the storage elastic modulus G '. The relationship between the loss elastic modulus G ″ (viscosity term) and the storage elastic modulus G ′ (elastic term) of the behavior is the temperature at which the loss elastic modulus G ″ <the storage elastic modulus G ′. It means a point that changes to term rule.

  In the present invention, smoothness is controlled by controlling the loss elastic modulus G ″ at a temperature below the gel point (80 ° C.) and controlling the storage elastic modulus G ′ at a temperature above the gel point (140 ° C.). The present invention has been completed.

The present invention will now be described by describing the process leading to the completion of the invention. First, the following was performed as a preliminary experiment.
Viscoelastic behavior was measured with some paints, specifically, conventional paint systems containing pigments, those without them, and those with various crosslinked resin particles. As the temperature rises, the viscosity starts to decrease from 40 to 80 ° C., the viscosity increases slightly between about 80 and 100 ° C., and when the temperature exceeds 100 ° C., the viscosity greatly decreases and flows. After this flow, the curing reaction starts to start, the viscosity starts to increase again, gradually begins to increase to around 150 ° C., and then the viscosity rapidly increases to complete the curing. In order to check the dynamic viscoelasticity of the paint while confirming it, five kinds of paints were measured using Rheosol-G3000 of BM Co., Ltd., and the temperature was 0.5 degree and the frequency was 0.02 Hz. The strain value γ (t) with respect to the applied stress value σ (t) and the phase difference δ between stress and strain were measured under the condition of an increase rate of 2 ° C./min. From the relationship between the obtained stress value σ (t), strain value γ (t) and phase difference δ, the storage elastic modulus (G ′), loss elastic modulus (G ″), and complex viscosity (η ^* ) are calculated according to the above formula. 1 to 3 are shown in Fig. 1 to Fig. 3. The coating materials used in Fig. 1 to 3 are as follows: "STD" is PN-310 (Nippon Paint Co., Ltd .: Cationic electrodeposition coating) ”Pigment free” is obtained by removing the pigment component from PN-310 (PWC = 0%), and “resin particle 1” is 15% by weight of “pigment free” with crosslinked resin particles (average particle diameter of 1 to 3 μm). For “Resin particles 2”, 5% by weight of crosslinked resin particles (average particle size 100 nm) are blended with “Pigment free”, and for “Resin particles 3”, “Resin particles 2” are added to “Pigment free”. Crosslinked resin particles (average) Child diameter 100 nm) is obtained by blending 10 wt%.

  As is apparent from FIGS. 1 to 3, it can be seen that the behavior varies considerably depending on the paint. Roughly divided into three modes (40 to 80 ° C., 80 to 100 ° C., and 100 ° C. or more), the dynamic viscoelastic behavior may change greatly depending on the composition of the paint, particularly the presence of particles and the like. It can also be seen that the graphs drawn by the five types of paints are different. Therefore, it can be seen that the viscoelastic behavior can be optimally controlled by changing the composition.

  In particular, it can be understood that the viscoelastic behavior near 80 ° C. and the viscoelastic behavior near 140 ° C. are the standards that greatly differ between the respective paints with reference to FIGS.

Based on this standard, the following experiment was further conducted. PN-310 (Cation Electrodeposition Paint manufactured by Nippon Paint Co., Ltd.) and PN-310 paint with the amount of inorganic pigment component changed, PN-310 with the inorganic pigment component removed, and the paint containing crosslinked resin particles Several types with different types and blending amounts were created and their viscous behavior was measured. From these viscoelastic results, FIG. 4 shows three viscoelastic behaviors at 80 ° C., that is, G ′ value, electrodeposition skin (FIG. 4A), η ^* value, and electrodeposition so that changes at each temperature can be easily understood. The skin (FIG. 4B) and G ″ value and electrodeposition skin (FIG. 4C) are all displayed, and FIG. 5 also shows three viscoelastic behaviors at 140 ° C., namely G ′ value and electrodeposition skin (FIG. 5A), η ^* Values and electrodeposited skin (FIG. 5B) and G ″ values and electrodeposited skin (FIG. 5C) were all displayed. The electrodeposited skin was represented by surface roughness (Ra). The electrodeposition skin evaluated here means the appearance of the electrodeposition coating film described later, that is, smoothness, and is indicated by the measured value of the arithmetic average roughness (Ra) of the roughness curve. That is, the relationship between the electrodeposited skin and the viscoelastic behavior was observed by looking at the smoothness described above on the electrodeposited skin.

  As apparent from the behaviors of FIGS. 4 and 5, the electrodeposition skin at 80 ° C. is recognized to have a certain relationship in the relationship between the measurement points and the change in viscoelasticity of the measurement paint and the electrodeposition skin. (See FIG. 4C). Moreover, what measured the three behaviors of end face coverage and viscoelastic behavior is similarly described in FIGS. As is apparent from FIGS. 6 and 7, it can be seen that the relationship between the storage elastic modulus (G ′) at 140 ° C. and the end face coverage shows a correlation (see FIG. 7A). That is, the change in the viscosity value and the electrodeposition skin (smoothness) or end face coverage are correlated. Here, the end face coverage is determined by an evaluation method described later. The “coverability” displayed in FIGS. 6 and 7 has the same meaning as the “end surface coverage” herein.

From this measurement result, in the present invention, a loss elastic modulus (G ″) of 80 ° C. is used for electrodeposited skin (smoothness), and a storage elastic modulus (G ′) of 140 ° C. is used as a reference for end face coverage. In this way, the present invention has been completed, and the preferred ranges of storage elastic modulus (G ′) and loss elastic modulus (G ″) can be obtained by referring to FIGS. You can choose. That is, G ′ at 140 ° C. is preferably 80 to 500 dyn / cm ² with reference to FIG. 7A, and G ″ at 80 ° C. is 10 to 150 dyn / cm ² with reference to FIG. 4C (the electrodeposition skin Ra is smaller can be selected good) smoothness. preferably, the storage elastic modulus (G ') is 90~500dyn / cm ^2, more preferably 100~500dyn / cm ^2. also, 80 The loss elastic modulus (G ″) at ° C. is preferably 10 to 120 dyn / cm ² , more preferably 10 to 100 dyn / cm ² .

  If the storage elastic modulus G ′ is less than the desired lower limit, the end face coverage of the obtained electrodeposition coating film may be deteriorated, and if it exceeds the desirable upper limit, the smoothness may be lowered. If the loss elastic modulus G "is less than the desired adjustment, the smoothness is improved, but the end face coverage of the obtained electrodeposition coating film may be deteriorated, and if it exceeds the desired upper limit, the smoothness may be lowered.

  Here, the storage elastic modulus G ′ and the loss elastic modulus G ″ described above are the elastic moduli of the uncured deposited coating, and the uncured is obtained by electrodeposition-coating a cationic electrodeposition paint. The state where the deposited coating is still not baked and cured.

  In the composition for cationic electrodeposition coating, crosslinked resin particles and / or inorganic pigments are added or blended as described above. In addition to these, an aqueous medium, a cationic epoxy resin and a block dispersed or dissolved in the aqueous medium It contains a binder resin containing an isocyanate curing agent, a neutralizing acid, and an organic solvent.

  In order to adjust the viscoelastic behavior, there is a method of adding crosslinked resin particles as a first method. The average particle diameter of the crosslinked resin particles is preferably 1.0 to 3.0 μm. When the particle size is smaller than 1.0 μm, the ratio of the surface area increases, and the interaction with the cationic epoxy resin, which is a binder resin component contained in the cationic electrodeposition coating composition, increases, and the deposited coating film Since the viscosity of the liquid increases rapidly, it is difficult to adjust the viscoelastic behavior as described above. On the other hand, when the particle diameter is larger than 3.0 μm, the smoothness decreases due to sedimentation when the electrodeposition paint is not stirred and accumulation of particles on the horizontal surface during the electrodeposition paint. Here, the average particle diameter can be measured by the following method.

  The average particle diameter of the resin particles was measured by a granular particle permeation measurement method using MICROTRAC 9340UPA manufactured by Nikkiso Co., Ltd. Further, with this measuring instrument, the particle size distribution of the resin particles was measured, and the average particle diameter at the cumulative relative frequency F (x) = 0.5 was calculated from the measured value. In these measurements and calculations, a solvent (water) refractive index of 1.33 and a resin refractive index of 1.59 were used.

It is essential that the crosslinked resin particles have a crosslinked structure. When there is no cross-linked structure, the value of the storage elastic modulus G ′ at 140 ° C. is 80 dyn / cm ² or less, which is not preferable because end face coverage cannot be secured. The crosslinked resin particles are preferably used in an amount of 3 to 15% by weight based on the resin solid content of the cationic electrodeposition coating composition. If it is less than 3% by weight, it becomes difficult to achieve both smoothness and end face coverage, and if it exceeds 15% by weight, the coating performance such as corrosivity may be deteriorated. Here, the above-mentioned “resin solid content” means all the resin solid contents including the crosslinked resin particles contained in the cationic electrodeposition coating composition.

  Considering that the average particle size of the crosslinked resin particles is 1.0 to 3.0 μm, it is preferably produced by suspension polymerization. Production by other methods such as emulsion polymerization is also possible if the particle size satisfies the above range, but suspension polymerization is preferred from the viewpoint of aligning the particle size within a desired range.

  The cross-linked resin particles are not particularly limited. For example, resin particles made of a resin having a cross-linked structure obtained mainly from an ethylenically unsaturated monomer, resin particles made of an internally cross-linked urethane resin, and internally cross-linked. Examples thereof include fine resin particles made of melamine resin.

  The resin having a cross-linked structure obtained mainly from the ethylenically unsaturated monomer is not particularly limited. For example, a single monomer containing a cross-linkable monomer as an essential component and containing an ethylenically unsaturated monomer. An aqueous dispersion prepared by subjecting a body composition to suspension polymerization in an aqueous medium, internally crosslinked resin particles obtained by a method such as solvent replacement of the aqueous dispersion, or a low SP organic such as an aliphatic hydrocarbon In a non-aqueous organic solvent that dissolves the monomer but does not dissolve the polymer, such as an organic solvent having a high SP, such as a solvent or ester, ketone, alcohol, etc., an ethylenically unsaturated monomer Examples thereof include internally crosslinked resin particles obtained by a method such as the NAD method or precipitation method in which internally crosslinked resin particles obtained by copolymerizing a monomer composition containing a body are dispersed.

  As a second method for adjusting the above viscous behavior, the inorganic pigment is used in an amount of 10 to 20% by weight (hereinafter also referred to as “PWC”) in the solid content of the cationic electrodeposition coating composition. There is. In the conventional cationic electrodeposition coating, the PWC is more than 20% by weight and not more than 25% by weight, and it has been impossible to achieve both smoothness and end face coverage, but this PWC is 10 to 20% by weight. By using in the range, it is possible to achieve both of these performances. Here, PWC refers to the ratio of the resin component and the pigment component contained in the cationic electrodeposition coating composition to the solid content. If the PWC of the inorganic pigment is less than 10% by weight, the resin content increases, and the resin softens due to an increase in temperature. Therefore, the desired high viscosity cannot be obtained, and the above viscous behavior is adjusted. I can't. On the other hand, if the PWC exceeds 20% by weight, the amount of pigment increases, and the fusing effect by the resin cannot be obtained. As a result, the high viscosity is not exhibited, and it becomes difficult to control the viscoelasticity. In inorganic pigments, PWC affects the viscous behavior as described above, but its particle size does not significantly affect the viscous behavior.

  The inorganic pigment used here is not particularly limited as long as it is a pigment usually used in an electrodeposition coating composition. Examples of pigments include commonly used inorganic pigments, for example colored pigments such as titanium white and bengara; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica and clay; zinc phosphate, phosphorus Iron oxide, aluminum phosphate, calcium phosphate, zinc phosphite, zinc cyanide, zinc oxide, aluminum tripolyphosphate, zinc molybdate, aluminum molybdate, calcium molybdate and aluminum phosphomolybdate, aluminum zinc phosphomolybdate, bismuth series Examples thereof include rust preventive pigments such as compounds and cerium compounds.

  A third method for adjusting the above viscoelastic behavior is a method in which the crosslinked resin particles and an inorganic pigment are used in combination. In this case, the average particle diameter of the crosslinked resin particles is 1.0 to 3.0 μm, and the amount used is 3 to 15% by weight in the solid content of the paint. On the other hand, the amount of the inorganic pigment used can be reduced to a range of 0.5 to 10% by weight in the solid content (PWC) of the cationic electrodeposition coating composition. The lower limit is preferably 1% by weight, more preferably 2% by weight. On the other hand, the upper limit is preferably 7% by weight, more preferably 5% by weight. If it is used in an amount exceeding 10% by weight, the amount of the pigment is increased more than necessary, and the horizontal appearance may be deteriorated due to the sedimentation of the pigment. On the other hand, if it is less than 0.5% by weight, the color hiding property may be lowered.

  By using both the inorganic pigment and the crosslinked resin particles, the amount of the inorganic pigment can be further reduced, and as a result, reduction of energy and labor for preventing sedimentation of the solid content of the electrodeposition paint can be expected. Further, when the viscous behavior is adjusted using only the crosslinked resin particles without using the inorganic pigment, the energy and labor for preventing the settling of the solid content can be greatly reduced. In addition, if the inorganic pigment is not contained or is contained in a very small amount, the object to be coated is washed with water after electrodeposition coating, but the washing process is greatly shortened, simplifying equipment and using resources. A great effect is achieved.

  Next, components used in a general cationic electrodeposition coating composition will be described.

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

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

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

[Wherein R represents a residue excluding the glycidyloxy group of the diglycidyl epoxy compound, R ′ represents a residue excluding the isocyanate group of the diisocyanate compound, and n represents a positive integer. An oxazolidone ring-containing epoxy resin represented by the above formula may be used as the cationic epoxy resin. This is because a coating film having excellent heat resistance and corrosion resistance can be obtained.

  As a method for introducing an oxazolidone ring into an epoxy resin, for example, a blocked isocyanate curing agent blocked with a lower alcohol such as methanol and a polyepoxide are heated and kept in the presence of a basic catalyst, and a by-product lower alcohol is formed in the system. It is obtained by further distilling off.

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

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

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

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

Blocked isocyanate curing agent The polyisocyanate used in the blocked isocyanate curing agent of the present invention refers to a compound having two or more isocyanate groups in one molecule. The polyisocyanate may be any of aliphatic, alicyclic, aromatic and aromatic-aliphatic, for example.

  Specific examples of polyisocyanates include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), p-phenylene diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate (HDI), 2,2,4- C3-C12 aliphatic diisocyanates such as trimethylhexane diisocyanate and lysine diisocyanate; 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI) , Methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, and 1,3-diisocyanatomethylcyclo Carbon such as xane (hydrogenated XDI), hydrogenated TDI, 2,5- or 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also referred to as norbornane diisocyanate). Aliphatic diisocyanates having a number of 5 to 18; aliphatic diisocyanates having an aromatic ring such as xylylene diisocyanate (XDI) and tetramethyl xylylene diisocyanate (TMXDI); Uretdione, uretonimine, burette and / or isocyanurate modified product); These may be used alone or in combination of two or more.

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

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

  As a blocking agent, normally used epsilon caprolactam, butyl cellosolve, etc. can be used.

  When the crosslinked resin particles are used as a component of the electrodeposition paint, they may be blended at any stage of producing the electrodeposition paint, but a method of adding directly to the produced cationic electrodeposition paint is preferred.

  When an inorganic pigment is used as a component of an electrodeposition paint, generally, the inorganic pigment is previously dispersed in an aqueous medium at a high concentration to form a paste (pigment dispersion paste). This is because the inorganic pigment is in a powder form, and it is difficult to disperse it in a single step in a low concentration uniform state used in the electrodeposition coating composition. Such a paste is generally called a pigment dispersion paste.

  The pigment dispersion paste is prepared by dispersing an inorganic pigment in an aqueous medium together with a pigment dispersion resin varnish. As the pigment dispersion resin, a cationic polymer such as a cationic or nonionic low molecular weight surfactant or a modified epoxy resin having a quaternary ammonium group and / or a tertiary sulfonium group is generally used. As the aqueous medium, ion-exchanged water or water containing a small amount of alcohol is used.

  In general, the pigment dispersion resin is used in an amount of 20 to 100 parts by mass with respect to 100 parts by mass of the inorganic pigment. After the pigment dispersion resin varnish and the pigment are mixed, the pigment is dispersed using a normal dispersing device such as a ball mill or a sand grind mill until the particle size of the pigment in the mixture reaches a predetermined uniform particle size. Obtain a dispersion paste.

  In addition to the above components, the cationic electrodeposition coating composition used in the present invention includes organic tin compounds such as dibutyltin laurate, dibutyltin oxide and dioctyltin oxide, amines such as N-methylmorpholine, strontium, cobalt, A metal salt such as copper may be included as a catalyst. These can act as a catalyst for the dissociation of the blocking agent of the curing agent. The concentration of the catalyst is preferably 0.1 to 6 parts by mass with respect to 100 parts by mass of the total of the cationic epoxy resin and the curing agent in the electrodeposition coating composition.

Preparation of cationic electrodeposition coating composition The cationic electrodeposition coating composition of the present invention comprises the above-described cationic epoxy resin, blocked isocyanate curing agent, and optionally crosslinked resin particles and / or pigment dispersion paste and catalyst. Can be prepared by dispersing in an aqueous medium. Usually, the aqueous medium contains a neutralizing acid in order to neutralize the cationic epoxy resin and improve the dispersibility. The neutralizing acid is inorganic acid or organic acid such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, lactic acid, sulfamic acid, acetylglycine. The aqueous medium in this specification is water or a mixture of water and an organic solvent. It is preferable to use ion exchange water as water. Examples of organic solvents that can be used include hydrocarbons (for example, xylene or toluene), alcohols (for example, methyl alcohol, n-butyl alcohol, isopropyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, propylene glycol), ethers (For example, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, propylene glycol monoethyl ether, 3-methyl-3-methoxybutanol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether), ketones (for example, Methyl isobutyl ketone, cyclohexanone, isophorone, acetylacetone), esters (eg, ethylene glycol monoester) Ether acetate, ethylene glycol monobutyl ether acetate) or mixtures thereof.

  The amount of blocked isocyanate curing agent must be sufficient to react with active hydrogen-containing functional groups such as primary, secondary amino groups, hydroxyl groups, etc. in the cationic epoxy resin during curing to give a good cured coating In general, it is generally 90/10 to 50/50, preferably 80/20 to 65/35 in terms of solid content weight ratio (epoxy resin / curing agent) between the cationic epoxy resin and the blocked isocyanate curing agent. is there. The amount of neutralizing acid is that which is sufficient to neutralize at least 20%, preferably 30-60%, of the cationic groups of the cationic epoxy resin.

  The organic solvent is indispensable as a solvent when preparing resin components such as a cationic epoxy resin and a blocked isocyanate curing agent, and complicated operation is required for complete removal.

  Examples of the organic solvent usually contained in the coating composition include ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethyl hexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, propylene glycol monophenyl ether and the like.

  In addition to the above components, the cationic electrodeposition coating composition may contain commonly used coating additives such as a plasticizer, a surfactant, an antioxidant, and an ultraviolet absorber.

Method for applying cationic electrodeposition coating composition The above-mentioned cationic electrodeposition coating composition is electrodeposited on an object to form an electrodeposition coating film. The material to be coated is not particularly limited as long as it is electrically conductive, and examples thereof include iron plates, steel plates, aluminum plates, those obtained by surface treatment thereof, and molded products thereof.

  The electrodeposition coating of the cationic electrodeposition coating composition is usually performed by applying a voltage of 50 to 450 V between the object to be coated as a cathode and the anode. When the applied voltage is less than 50V, electrodeposition is insufficient, and when it exceeds 450V, the coating film is destroyed and an abnormal appearance is obtained. At the time of electrodeposition coating, the bath temperature of the coating composition is usually adjusted to 10 to 45 ° C.

  The electrodeposition coating step is composed of a step of immersing an object to be coated in a cationic electrodeposition coating composition, and a step of applying a voltage between the above object to be coated as a cathode and an anode to deposit a film. . Moreover, although the time which applies a voltage changes with electrodeposition conditions, generally it can be made into 2 to 4 minutes.

The film thickness of the electrodeposition coating film can generally be formed in the range of 5 to 25 μm. If the film thickness is less than 5 μm, the rust prevention property may be insufficient. The film resistance of the electrodeposition coating film is preferably 1000 to 1600 kΩ / cm ² at a film thickness of 15 μm. If the film resistance of the coating film is less than 1000 kΩ / cm ^2, it is in a state where sufficient electrical resistance is not obtained, and there is a risk of poor throwing power, and if it exceeds 1600 kΩ / cm ² , the coating film appearance may be inferior. There is. The film resistance of the coating film is more preferably 1100 to 1500 kΩ / cm ² .

The film resistance value of the coating film is determined by the following formula from the residual current value (A) of the coating film at the final coating voltage (V).
Membrane resistance value (FR) = V / A

  The electrodeposition coating film obtained as described above is cured by baking at 120 to 260 ° C., preferably 140 to 220 ° C. for 10 to 30 minutes after completion of the electrodeposition process, or after washing with water. An electrodeposition coating is obtained.

  The following examples further illustrate the present invention, but the present invention is not limited thereto. Unless otherwise specified, “parts” represents parts by weight.

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

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

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

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

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

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

Production Example 4 Production of Pigment Dispersion Paste 120 parts of pigment dispersion resin varnish obtained in Production Example 3 in a sand grind mill, 100 parts of kaolin, 92 parts of titanium dioxide, 8.0 parts of dibutyltin oxide and 184 parts of ion-exchanged water The pigment dispersion paste was obtained by dispersing until the particle size became 10 μm or less. (Solid content 48%)

Production Example 5 Production of Crosslinked Resin Particles 120 parts of butyl cellosolve was placed in a reaction vessel and heated to 120 ° C. with stirring. A solution prepared by mixing 2 parts of t-butylperoxy-2-ethylhexanoate and 10 parts of butyl cellosolve, 15 parts of glycidyl methacrylate, 50 parts of 2-ethylhexyl methacrylate, 20 parts of 2-hydroxyethyl methacrylate and n-butyl methacrylate A monomer mixture consisting of 15 parts and having an SP value of 10.1 was dropped in 3 hours. After aging for 30 minutes, a solution in which 0.5 part of t-butylperoxy-2-ethylhexanoate and 5 parts of butyl cellosolve were added dropwise in 30 minutes, and after aging for 2 hours, the mixture was cooled. . To this, 7 parts of N, N-dimethylaminoethanol and 15 parts of 50% lactic acid aqueous solution were added, followed by quaternization by heating and stirring at 80 ° C. When the acid value became 1 or less and the viscosity increase stopped, heating was stopped to obtain an acrylic resin having an ammonium group. The number of ammonium groups per molecule of the acrylic resin having ammonium groups was 6.0.

  To the reaction vessel, 120 parts of an acrylic resin having an ammonium group and 270 parts of deionized water were added and stirred with heating at 75 ° C. To this, 1.5 parts of 2,2′-azobis (2- (2-imidazolin-2-yl) propane) 1.5% acetic acid neutralized aqueous solution was added dropwise over 5 minutes. After aging for 5 minutes, 30 parts of methyl methacrylate was added dropwise over 5 minutes. After further aging for 5 minutes, 170 parts of methyl methacrylate, 40 parts of styrene, 30 parts of n-butyl methacrylate, 5 parts of glycidyl methacrylate, and neopentyl were added to a solution obtained by mixing 170 parts of an acrylic resin having an ammonium group and 250 parts of deionized water. A pre-emulsion obtained by adding and stirring an α, β-ethylenically unsaturated monomer mixture consisting of 30 parts of glycol dimethacrylate was added dropwise over 40 minutes. After aging for 60 minutes, the mixture was cooled to obtain a dispersion of crosslinked resin particles 1. The resulting dispersion of the crosslinked resin particles had a nonvolatile content of 35%, a pH of 5.0, and an average particle size of 100 nm.

Production Example 6 Production of Non-crosslinked Resin Particles 2 parts of lauroyl peroxide was dissolved in a solution in which 104 parts of styrene, 20 parts of 2-ethylhexyl methacrylate, and 76 parts of lauryl methacrylate were mixed. This was added with stirring to 497 parts of an aqueous solution obtained by dissolving 8 parts of polyvinyl alcohol (Gosenol GH-17, manufactured by Nihon Gosei Co., Ltd.) in deionized water, and homomic line flow type 30 (manufactured by Tokushu Kika Kogyo Co., Ltd.). The suspension was prepared at 3500 rpm.

  This suspension is subjected to suspension polymerization for 5 hours at a stirring speed of 150 rpm and a reaction temperature of 81 to 83 ° C. using a normal batch reaction vessel. After cooling, the obtained dispersion is filtered through a 200 mesh screen. Non-crosslinked resin particles were obtained. The non-crosslinked resin particle dispersion obtained had a non-volatile component of 30% and an average particle size of 3 μm.

Example 1
2222 parts of the emulsion obtained in Production Example 2 and 417 parts of the pigment dispersion paste obtained in Production Example 4 and 2361 parts of ion-exchanged water were mixed to obtain PWC = 16.5%, crosslinked resin particles 0% by weight, A cationic electrodeposition coating composition having a solid content of 20% by weight was obtained.

Comparative Example 1
738 parts of emulsion obtained in Production Example 2 and 4 parts of dibutyltin oxide were mixed with 4598 parts of ion-exchanged water, and a cationic electrodeposition coating composition having PWC = 0%, crosslinked resin particles 0% by weight, and solid content 5% by weight. A composition was obtained.

Comparative Example 2
702 parts of the emulsion obtained in Production Example 2, 38 parts of the crosslinked resin particles obtained in Production Example 5 and 4 parts of dibutyltin oxide, and 4596 parts of ion-exchanged water were mixed to obtain PWC = 0%, crosslinked resin particles 5 A cationic electrodeposition coating composition having a weight percentage of 5% and a solid content of 5% was obtained.

Comparative Example 3
665 parts of the emulsion obtained in Production Example 2, 76 parts of the crosslinked resin particles obtained in Production Example 5 and 4 parts of dibutyltin oxide, and 4596 parts of ion-exchanged water were mixed to obtain PWC = 0%, crosslinked resin particles 10 A cationic electrodeposition coating composition having a weight percentage of 5% and a solid content of 5% was obtained.

Comparative Example 4
665 parts of the emulsion obtained in Production Example 2 and 89 parts of the non-crosslinked resin particles and 4 parts of dibutyltin oxide obtained in Production Example 6 were mixed with 4582 parts of ion-exchanged water so that PWC = 0%, non-crosslinked resin A cationic electrodeposition coating composition having 10% by weight of particles and 5% by weight of solid content was obtained.

Comparative Example 5
389 parts of the emulsion obtained in Production Example 2 and 125 parts of the pigment paste obtained in Production Example 4 and 3486 parts of ion-exchanged water are mixed to obtain PWC = 25%, crosslinked resin particles 0%, solid content 5%. % Cationic electrodeposition coating composition was obtained.

Example 2
702 parts of the emulsion obtained in Production Example 2, cross-linked resin particles (cross-linked resin particles containing methyl methacrylate as a main component; manufactured by Toyobo Co., Ltd., Tuftic ^{(registered trademark)} F-200) and dibutyltin oxide 4 And 4592 parts of ion-exchanged water were mixed to obtain a cationic electrodeposition coating composition having PWC = 0%, crosslinked resin particles 5%, and solid content 5% by weight.

Example 3
665 parts of the emulsion obtained in Production Example 2, crosslinked resin particles (crosslinked resin particles containing methyl methacrylate as a main component; manufactured by Toyobo Co., Ltd., Tuftic ^{(registered trademark)} F-200), and dibutyltin oxide 4 Part and 4587 parts of ion-exchanged water were mixed to obtain a cationic electrodeposition coating composition having PWC = 0%, crosslinked resin particles 10%, and solid content 5% by weight.

Example 4
628 parts of the emulsion obtained in Production Example 2, 127 parts of crosslinked resin particles (crosslinked resin particles mainly composed of methyl methacrylate; manufactured by Toyobo Co., Ltd., Tuftic ^{(registered trademark)} F-200) and dibutyltin oxide 4 Part and 4581 parts of ion-exchanged water were mixed to obtain a cationic electrodeposition coating composition having PWC = 0%, crosslinked resin particles 15%, and solid content 5% by weight.

Example 5
628 parts of the emulsion obtained in Production Example 2, cross-linked resin particles (cross-linked resin particles containing styrene monomer as a main component; manufactured by Soken Chemical Co., Ltd., Chemisnow SX500H, average particle size 3 μm), and 4 parts of dibutyltin oxide Then, 4668 parts of ion-exchanged water were mixed to obtain a cationic electrodeposition coating composition having PWC = 0%, crosslinked resin particles 15%, and solid content 5% by weight.

Example 6
567 parts of the emulsion obtained in Production Example 2, 54 parts of the pigment dispersion paste obtained in Production Example 4 and crosslinked resin particles (crosslinked resin particles containing styrene monomer as a main component; manufactured by Soken Chemical Co., Ltd., Chemisnow SX500H, 40 parts of (average particle diameter 3 μm) and 4739 parts of ion-exchanged water were mixed to obtain a cationic electrodeposition coating composition having PWC = 8%, crosslinked resin particles 15%, and solid content 5% by weight.

  About the cationic electrodeposition coating composition obtained in this way, the loss elastic modulus in 80 degreeC in dynamic viscoelasticity, the storage elastic modulus in 140 degreeC, smoothness, and end surface coverage were evaluated with the following method.

Measurement of loss modulus and storage modulus of electrodeposition coating film Dipping a tin plate in the cationic electrodeposition coating obtained as described above, and coating with a coating voltage such that the film thickness after baking is 15 μm. A film was formed and washed with water to remove excess electrodeposition coating composition. Next, after removing moisture, the uncured coating film piece was taken out immediately without drying to prepare a sample. The sample obtained in this manner was subjected to temperature-dependent measurement in dynamic viscoelasticity using a rotational dynamic viscoelasticity measuring device Rheosol-G3000 (manufactured by UBM Co., Ltd.) under setting conditions: strain 0. The measurement was performed at 5 deg and a frequency of 0.02 Hz. The prepared sample was set and the measurement temperature was kept at 50 ° C. After the measurement was started, the viscosity of the coating film was measured when the electrodeposition coating film was spread uniformly in the cone plate.

Appearance (Smoothness) Evaluation of Electrodeposition Coating Film The appearance evaluation of the electrodeposition coating film was performed by measuring the arithmetic average roughness (Ra) of the roughness curve. An uncured electrodeposition coating film obtained by immersing a cold-rolled steel sheet treated with zinc phosphate in the cationic electrodeposition coating obtained as described above and coating at a coating voltage such that the film thickness after baking is 15 μm. Was baked at 160 ° C. for 10 minutes. Then, Ra value of this cured electrodeposition coating film was measured using an evaluation type surface roughness measuring machine (manufactured by Mitutoyo Corporation, SURFTEST SJ-201P) according to JIS-B0601. Measurement was performed 7 times using a sample with a 2.5 mm width cut-off (number of sections: 5), and an Ra value was obtained by an average of vertical erasure. The results are shown in Tables 1 and 2. It can be said that the smaller the Ra value, the less the unevenness and the better the coating film appearance.

End surface coverage evaluation method A coating material of a cutter knife (OLFA: LB-50K) that has been subjected to zinc phosphate treatment is immersed in a cationic electrodeposition coating composition, and a voltage is applied between the coating material as a cathode and an anode. Is applied to deposit a coating. The electrodeposition conditions were an applied voltage and time adjusted to a cutter knife so that the deposited film thickness was 15 μm. The obtained electrodeposition coating film was washed with water and then baked at 160 ° C. for 10 minutes to obtain a cured electrodeposition coating film.

  Fold the center of the cutter knife covered with the electrodeposition coating film, and measure the film thickness of the electrodeposition coating film coated on the 30-micron region from the tip of the cutter knife (acute angle): Digital microscope (manufactured by Keyence Corporation: VH-8000) Measured with FIG. 8 schematically shows a 30-micron region from the tip of the cutter knife.

  As is apparent from Table 1 above, the dynamic viscoelastic loss elastic modulus (G ″) and storage elastic modulus (G ′) in the predetermined ranges exhibit excellent performance in smoothness and end face coverage. Specifically, in Comparative Example 1, the storage elastic modulus (G ′) is out of the range of the present invention, and the end face coverage is not good, and in Comparative Example 2, the crosslinked resin particles of Production Example 5 are used. Although blended, both the loss elastic modulus (G ″) and the storage elastic modulus (G ′) are out of the scope of the present invention, and neither smoothness nor end face coverage is good. Similar to Comparative Example 2, Comparative Example 3 is a blend of the crosslinked resin particles of Production Example 5. The average particle diameter of the crosslinked resin particles used here was as small as 100 nm, and the value of loss elastic modulus (G ″). This is outside the scope of the present invention and lacks smoothness.Comparative Example 4 contains non-crosslinked particles, and the storage elastic modulus (G ') is outside the scope of the present invention. In addition, Comparative Example 5 contains inorganic pigments instead of resin particles, but the loss elastic modulus (G ″) is out of the range of the present invention, and as a result, the smoothness is not good. In Example 1, the pigment of Production Example 4 was included, and everything was within the scope of the present invention, and the smoothness and end face coverage were excellent. In Examples 2 to 6, by blending specific particles, the storage elastic modulus (G ′) and loss elastic modulus (G ″) are controlled within the scope of the present invention. Both are excellent.

It is a graph which shows the behavior of the loss elastic modulus (G ") value in the dynamic viscoelasticity of five types of coating materials. It is a graph which shows the behavior of the loss elastic modulus (G ') value in the dynamic viscoelasticity of five types of paints. It is a graph which shows the behavior of the complex viscosity ((eta) ^* ) value in the dynamic viscoelasticity of five types of coating materials. It is a graph which shows the relationship between the dynamic viscoelasticity (G ') in 80 degreeC of some coating materials, and electrodeposition skin. It is a graph which shows the relationship between the dynamic viscoelasticity ((eta) ^* ) and electrodeposition skin in 80 degreeC of some coating materials. It is a graph which shows the relationship between the dynamic viscoelasticity (G ") in 80 degreeC of some coating materials, and electrodeposition skin. It is a graph which shows the relationship between the dynamic viscoelasticity (G ') in 140 degreeC of some coating materials, and electrodeposition skin. It is a graph which shows the relationship between the dynamic viscoelasticity ((eta) ^* ) of some coating materials at 140 degreeC, and electrodeposition skin. It is a graph which shows the relationship between the dynamic viscoelasticity (G ") in 140 degreeC of some coating materials, and electrodeposition skin. It is a graph which shows the relationship between the dynamic viscoelasticity (G ') in 80 degreeC of some coating materials, and end surface coverage. It is a graph which shows the relationship between the dynamic viscoelasticity ((eta) ^* ) in 80 degreeC of some coating materials, and end surface coverage. It is a graph which shows the relationship between the dynamic viscoelasticity (G ") in 80 degreeC of some coating materials, and end surface coverage. It is a graph which shows the relationship between the dynamic viscoelasticity (G ') in 140 degreeC of some coating materials, and end surface coverage. It is a graph which shows the relationship between the dynamic viscoelasticity ((eta) ^* ) in 140 degreeC of some coating materials, and end surface coverage. It is a graph which shows the relationship between the dynamic viscoelasticity (G ") in 140 degreeC of some coating materials, and end surface coverage. It is a figure which shows typically a 30 micron site | part from the front-end | tip of a cutter knife.

Claims (8)

A storage elastic modulus (G ′) at 140 ° C. of an uncured deposited coating obtained by electrodeposition coating of the cationic electrodeposition coating composition is a cationic electrodeposition coating composition of 80 to 500 dyn / cm ^2. A cationic electrodeposition coating composition excellent in smoothness and end face coverage, wherein the loss elastic modulus (G ″) at 80 ° C. is 10 to 150 dyn / cm ² .   The cationic electrodeposition coating composition according to claim 1, wherein the cationic electrodeposition coating composition contains a cationic epoxy resin, a blocked isocyanate curing agent, crosslinked resin particles and / or an inorganic pigment component. In a method of forming a cationic electrodeposition coating film by immersing an object to be coated in a cationic electrodeposition coating composition and applying a voltage, the storage modulus at 140 ° C. of the uncured deposited coating film of the cationic electrodeposition coating composition By adjusting (G ′) to 80 to 500 dyn / cm ² and adjusting the loss elastic modulus (G ″) at 80 ° C. to 10 to 150 dyn / cm ² , the smoothness and end face coverage of the cationic electrodeposition coating film can be improved. How to make it compatible.   The method according to claim 3, wherein the storage elastic modulus and loss elastic modulus are adjusted by adding crosslinked resin particles having an average particle size of 1.0 to 3.0 µm to the cationic electrodeposition coating composition.   The method according to claim 4, wherein the crosslinked resin particles are added in an amount of 3 to 15% by weight in the solid content of the coating resin of the cationic electrodeposition coating composition.   The method according to claim 3, wherein the storage elastic modulus and the loss elastic modulus are adjusted by using an inorganic pigment in an amount of 10 to 20% by weight in the solid content of the cationic electrodeposition coating composition.   Cross-linked resin particles having an average particle size of 1.0 to 3.0 μm are added to the cationic electrodeposition coating composition, and the inorganic pigment is added in an amount of 0.5 to 10% by weight in the solid content of the coating resin of the cationic electrodeposition coating composition. The method according to claim 3, wherein the storage elastic modulus and the loss elastic modulus are adjusted by blending in an amount of 5%.   The method according to claim 7, wherein the crosslinked resin particles are added in an amount of 3 to 15% by weight in the solid content of the coating resin of the cationic electrodeposition coating composition.

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