JPH04165098A - Electrodeposition coating method - Google Patents

Abstract

PURPOSE:To form a coating film with its edge excellent in corrosion resistance by successively electrodepositing the uncured electrodeposition coating films of the different kinds of cationic electrodeposition coating compositions on a material under specified conditions, baking and curing the films. CONSTITUTION:Emulsion polymerization is carried out using a cationic reaction emulsifier. A cationic electrodeposition coating composition (I) contg. a cationic electrodepositing gelled particulate polymer having a clad-core structure contg. hydrolyzable alkoxysilane and hydroxyl groups as the core component and the urethane coupling and hydroxyl groups as the clad component is deposited on a material to be coated to form an uncured electrodeposition coating film. A cationic electrodeposition coating composition (II) with the minimum electrodeposition current density controlled to <=0.7mA/cm<2> and the emulsification degree to >=80wt.% is deposited on the coating film to form an uncured double-layer coating film (about 15-80mu film thickness), which is baked and cured. Consequently, a well-finished coating film free of pinholes and with the edge excellent in corrosion resistance is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a cationic electrodeposition coating method, and more specifically, the present invention relates to a cationic electrodeposition coating method, and more specifically, it has excellent smoothness and can be applied to corners of cut surfaces, bent corners, i-origins, etc. The present invention relates to a cationic electrodeposition coating method capable of forming a thick electrodeposition coating film twice on edge portions.

(Conventional technology and its problems) Cationic electrodeposition coating has excellent throwing power and uniformity of film thickness.
It has excellent anti-corrosion properties on flat surfaces, and is widely used as an undercoat for automobile bodies. However, although cationic electrodeposition coatings generally have low melt viscosity and are excellent in smoothness, on the other hand, little or no cured coating is formed on the edges, resulting in significantly poor rust prevention properties at the edges. This defect is likely to occur.

In order to improve the rust prevention properties of the edges, for example, a rust-proof steel plate is used, or after electrodeposition coating and baking, self-preventive paint is applied to the edges with a roller or spatula. However, the cost and number of steps are significant. In addition, various attempts have been made to incorporate large amounts of pigments into electrodeposition coatings, or to reduce the amount of plasticizing components. '') is difficult to achieve at the same time as achieving smoothness of the coating film.Additionally, attempts have also been made to achieve double-circle coating, and the electrodeposition coating used in the first layer has a high pigment concentration or a high oil absorption amount. A method has also been proposed in which edge cover is achieved by using pigments and smoothness is achieved in the second layer.
This method has a problem in that poor finishing occurs due to pigment settling, particularly in the horizontal portions of the bag structure of the object to be coated.

Therefore, the present inventors investigated an electrodeposition coating method that has both excellent edge cover and coating surface smoothness and does not cause poor finish due to pigment sedimentation. A cationic electrodeposition paint containing gelled polymer fine particles made by dispersing a copolymer in water and cross-linking the copolymer is applied as the first layer of electrodeposition paint, and then a specific electrodeposition paint is applied on top of this. proposed an electrodeposition coating method in which an uncured electrodeposited multi-layer coating film formed by the above method is baked (see Japanese Patent Laid-Open No. 17895/1993).

This method is effective in preventing repelling and improving edge coverage, adhesion, and chipping resistance of cationic electrodeposition coatings without impairing edge coverage, coated surface smoothness, and corrosion resistance; however, edge coverage deteriorates slightly over time. This has the drawback of lowering the performance, which is unsatisfactory in practical terms.

(Means for Solving the Problems) Therefore, the present inventors have improved edge coverage, coating surface smoothness,
As a result of intensive research to develop an electrodeposition coating method that does not impair corrosion resistance (and edge coverage that does not deteriorate over time), we have developed a hydrolyzable alkoxy core component formed by emulsion polymerization using a cationic reactive emulsifier. The cationic electrodepositable gelling fine particle polymer, which has a core shell structure containing silane groups and hydroxyl groups and also contains urethane bonds and hydroxyl groups as shell components, has very good dispersion stability in cationic electrodeposition paints. , and is suitable for cationic electrodeposition, and in two-time inspection coating, the first layer of cationic electrodeposition paint contains a cationic electrodepositionable gelling fine particle weight having a core structure containing urethane bonds and hydroxyl groups. By incorporating a coalescing agent, the stability of the electrodeposition bath for the first layer is not impaired (also, during baking, the urethane bonds in the shell component condense with hydroxyl groups, resulting in interparticle crosslinking and crosslinking with the base resin). At the same time, the silanol groups in the core component also take part in the crosslinking reaction, which improves the repellency prevention and edge coverage of cationic electrodeposition coatings without impairing the coating's water resistance, corrosion resistance, and coating surface smoothness. The present invention was completed based on the findings that it is extremely effective in improving adhesion and chipping resistance, and that edge coverage does not deteriorate over time.

(Thus, according to the present invention, a core containing a hydrolyzable alkoxysilane group and a hydroxyl group as a core component and a urethane bond and a hydroxyl group as a shell component, which is obtained by emulsion polymerization using a cationic reactive emulsifier) A minimum amount of Deposition current density is 0.7
mA/cm” or less and emulsion degree is 80% by weight
An electrodeposition coating method is provided, which comprises baking and curing an uncured electrodeposited multilayer coating formed by electrodeposition of the above cationic electrodeposition coating composition (II).

In the present invention, the "cationic electrodepositable gelling fine particle polymer" contained in the cationic electroacoustic paint composition (I) is prepared as a first step by using a cationic reactive emulsifier containing an allyl group in the molecule. , (a) a polymerizable unsaturated vinyl silane monomer containing a vinylic double bond and a hydrolyzable alkoxysilane group; (b) a polymerizable monomer containing a few (both two) radically polymerizable unmaturing groups in the molecule; (c) a polymerizable unsaturated monomer containing a vinyl double bond and a hydroxyl group, and (d) other polymerizable unsaturated monomers are subjected to emulsion polymerization, and then in the first step In the presence of the obtained aqueous gelatinized fine particle polymer, as a second step, (e) a block mono- or polyisocyanate in which at least one incyanate group in the molecule is blocked with a radically polymerizable monohydroxy compound; , (f) a polymerizable unsaturated monomer containing a vinyl double bond and a hydroxyl group, and (g) a monomer component (B) consisting of another polymerizable unsaturated monomer, and the emulsion polymerization This is a cationic electrodepositable gelling fine particle polymer characterized by using a water-soluble azoamide compound as a polymerization initiator.

The vinyl silane monomer of (a) above has the following general formula % formula % where Q represents a polymerizable unsaturated group such as γ-methacryloxypropyl group or vinyl group, and R represents an acetoxy group or This is a compound represented by the following, which represents an alkoxy group having a carbon atom.

Examples of such alkoxy groups include methoxy, ethoxy, propoxy, butoxy, imbutoxy, pentoxy, hexoxy, and the like, as well as methoxymethoxy, ethoxymethoxy, alkoxyallyloxy, ethoxyphenoxy, and the like. Preferred R is a methoxy or ethoxy group. The silane monomers are known per se or are prepared analogously to those known per se. Specific examples of such silane monomers include:
Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-
Examples include methacryloxypropyltrimethoxysilane and vinyltriacetoxysilane, and among these, γ-methacryloxypropyltrimethoxysilane is particularly preferred.

The polymerizable monomers containing at least two radically polymerizable unsaturated groups in the molecule of (b) above include polymerizable unsaturated monocarboxylic acid esters of polyhydric alcohols, polymerizable unsaturated alcohols of polybasic acids, etc. These include esters, aromatic compounds substituted with two or more vinyl groups, and specific examples thereof include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1.3-butylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate,
1,4-butanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol diacrylate erythritol tetramethacrylate,
glycerol dimethacrylate, glycerol diacrylate, glycerol aryloxy dimethacrylate,
1,1゜l-trishydroxymethylethane diacrylate, 1,1.1-trishydroxymethylethane triacrylate, 1,1.1-trishydroxymethylethane dimethacrylate, 1,1.1-trishydroxymethylethane triacrylate Methacrylate, 1,1.1-trishydroxymethylpropane diacrylate, 1,1.1
=) Lishydroxymethylpropane triacrylate,
1,1゜1-trishydroxymethylpropane dimethacrylate, 1,1.1-trishydroxymethylpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl terephthalate, diallyl phthalate and divinyl Examples include benzene.

The polymerizable unsaturated monomers containing a vinyl double bond and a hydroxyl group (C) and (f) are monomer components useful for introducing a hydroxyl group into the gelled fine particle polymer,
The introduced hydroxyl group functions as a parent group or a functional group for a crosslinking reaction between dispersed particles when producing a gelled fine particle polymer. Examples of the unsaturated monomers of components (C) and (f) include 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and the like.

The blocked mono- or polyisocyanate (e) in which at least one incyanate group in the molecule is blocked with a radically polymerizable monohydroxy compound can improve the water resistance of the coating film, which is one of the important objects of the present invention. It is an important component for improving the repellency prevention, edge coverage, adhesion, chipping resistance, etc. of cationic electrodeposition coatings without impairing corrosion resistance or coated surface smoothness.

The monoisocyanates used in the above component (e) include phenyl isocyanate, p-chlorophenylisocyanate, 0-chlorophenylisocyanate, m-chlorophenylisocyanate, 3,4-dichlorophenylisocyanate, 2,5-dichlorophenylisocyanate, Examples include chlorphenylisocyanate, methylisocyanate, ethylisocyanate, n-butylisocyanate, n-propylisocyanate, and octadecylisocyanate. These monoisocyanates may be used alone or in combination of two or more.

Further, as polyisocyanates, aromatic polyisocyanates such as toluene diisocyanate, naphthalene diisocyanate, xylylene diisocyanate,
Hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, dibenzyl isocyanate, etc.: Aliphatic polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, dicyclohexyl diisocyanate, isophorone diisocyanate, etc. are exemplified. Furthermore, polymers and billet forms of these polyisocyanate compounds can also be used. The above polyisocyanates may be used alone or in combination of two or more.

Blocking agents used to block the above mono- and polyisocyanates include, for example, radically polymerizable monohydroxy compounds, specific examples of which include hydroxyalkyl esters of acrylic or methacrylic acid, tri- or tetra- Propylene glycol mono(merota) acrylate, trimethyl propanedi(meth)
Examples include acrylate, pentaerythritol tri(meth)acrylate, and the like.

The polymerizable monohydroxy compound can be used in combination with other blocking agents, and examples of blocking agents that can be used in combination include saturated or unsaturated monoalcohols having at least 6 carbon atoms, cellosolves, calpitols, and oximes. Can be mentioned.

Specific examples thereof include hexanol, nonanol, decanol, lauryl alcohol, stearyl alcohol,
Saturated monoalcohols such as 2-ethylhexanol, unsaturated monoalcohols such as oleyl alcohol and lilunyl alcohol, methyl cellosolve, ethyl cellosolve,
Examples include cellosolves such as butyl cellosolve and hexyl cellosolve, carpitols such as methyl calpitol, ethyl carpitol and butyl carpitol, oximes such as methyl ethyl ketoxime, acetone oxime, methyl isobutyl ketoxime, and cyclohexanone oxime. I can do it.

The other polymerizable unsaturated monomers (d) $ and (g) are the remaining components constituting the gelling fine particle polymer, and are, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, etc. ) acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl acrylate, etc. Alkyl (C+ to C1,) of (meth)acrylic acid Ester; Vinyl aromatic monomers such as styrene, α-methylstyrene, and vinyltoluene; (meth)acrylic acid amide compounds; (meth)acrylonitrile; can do.

These monomers are appropriately selected depending on the desired properties,
Each may be used alone, or two or more types may be used in combination.

The monomer component (A
) The polymerization ratio of the monomers (a) to (d) constituting the [core component] is not strictly limited, and can be changed depending on the desired physical properties of the gelled fine particle polymer to be produced. However, it can generally be within the range described below.

(a) Monomer: 0.5 to 10% by weight, preferably 1 to 10% by weight
5% by weight; (b) monomer: 1 to 50% by weight, preferably 3 to 40% by weight
Weight%; (C) monomer: 1 to 30% by weight, preferably 2 to 1O
Weight%; (d) Monomer: 10 to 97.5% by weight, preferably 4
5-94% by weight.

Furthermore, the polymerization ratio of the monomers (e) to (g) constituting the monomer component (B) [shell component] is not strictly limited. Although it can be changed depending on the situation, it can generally be within the following range.

(e) Monomer = 10-40% by weight, preferably 15-40% by weight
30% by weight, (f) monomer: 1 to 30% by weight, preferably 2 to 10%
Weight%; (g) Monomer: 30-89% by weight, preferably 6
0-83% by weight.

Monomer component (A) [core component] and monomer component (B) [
Selection of the blending ratio with the shell component] is also one of the important factors in putting the present invention into practical use. The weight ratio of the sum of monomer components (A) to the sum of monomer components (B) is generally conveniently in the range of 10-90:90-10, preferably 40-60:60-40. When the content ratio of monomer component (A) is less than 10% or more than 90%, there is a tendency for the edge coverage of the resulting baked coating to decrease.

The monomer component (A
) is typically used as a cationic reactive emulsifier containing an allyl group in the molecule, and is represented by the following general formula (I) R, OH, where R1 has a substituent. R2 and R3 each represent a hydrocarbon group having 1 to 22 carbon atoms;
-3 alkyl group, R4 represents a hydrogen atom or a methyl group, and Ae represents a monovalent anion. Reactive emulsifiers containing a quaternary ammonium salt represented by the following are included. The above-mentioned emulsifiers are known per se (see Japanese Patent Application Laid-Open No. 60-78947), and include those commercially available as Latemul-180 (trade name, manufactured by Kao Corporation). In the emulsion polymerization of the monomer component (A) of the gelatinized fine particle polymer in the present invention, a cationic reactive emulsifier that is gradually incorporated into the polymer during polymerization is suitable, and among them, allyl, which is a relatively low-reactivity group, is suitable. Any cationic reactive emulsifier containing a group can be used without being limited to those mentioned above. Furthermore, the amount of the cationic reactive emulsifier containing an allyl group is not strictly limited, and may vary depending on the type of monomer component (A) and the physical properties desired for the type of gelled fine particle polymer produced. can vary, but generally
Normally 0 parts per 100 parts by weight of gelled fine particle polymer solid content
．． It is preferably used within the range of 1 to 30% by weight, preferably 0.5 to 5% by weight.

In addition, as a polymerization initiator, the following general formula (II) OCH,
CH,0 In the formula, X represents a straight chain or branched alkylene group having 2 to 12 carbon atoms, or the following general formula (m) X'CH2CH3CHI CH2X' In the formula, x
A water-soluble azoamide compound in which ', x'' and X3 are small (one represents a hydroxyl group and the others represent hydrogen) is particularly suitable.

These compounds are known per se (Japanese Unexamined Patent Publication No. 6
1-218618, JP-A-61-63643), for example, those commercially available as VA series (trade name, manufactured by Wako Pure Chemical Industries, Ltd.). The polymerization initiator can be used in amounts commonly used in the art, but generally the optimum amount is 0.1 to 1.0 parts by weight per 100 parts by weight of gelled particulate polymer solids.
is within the range of parts by weight.

The copolymerization of the unsaturated monomers (a) to (d) and (e) to (g) above can be carried out by emulsion polymerization, which is a method known per se for producing acrylic copolymers. First, the above monomer mixtures (a) to (d)
For example, continue the reaction in an aqueous medium in the presence of a cationic reactive emulsifier containing an allyl group and a water-soluble azoamide compound polymerization initiator at a reaction temperature of usually about 50 to about 100°C for about 1 to about 20 hours, In this way, an aqueous gelatinized fine particle polymer can be produced.

Next, the mixtures (e) to (g) are added, and the reaction is further continued at a reaction temperature of about 50 to about 100°C for about 1 to about 20 hours. As a result, a cationically electrodepositable gelling fine particle polymer having a core-core structure can be obtained.

The cationic electrodepositable gelling fine particle polymer in the present invention is
Typically, the aqueous dispersion will have a resin solids content of about 10-40% by weight, based on total weight. The gelatinized fine particle polymer usually has a diameter of 500 nm or less, preferably 10 to 10 nm.
It may have a particle size in the range of 300nm, more preferably 50-1100n. The particle size can be adjusted by adjusting the amount of the cationic reactive emulsifier containing an allyl group in the molecule, and a desired range can be easily obtained.

The cationic electrodeposition coating composition (I) that is first coated according to the method of the present invention contains the above-mentioned cationic electrodeposition gelling fine particle polymer having the specific core shell structure.
It can be composed of the same component composition as in ordinary cationic electrodeposition coating compositions.

Therefore, the above-mentioned cationic electrodeposition coating composition (I) contains, as a resin component, a resin (hereinafter referred to as cationic electrodeposition (Sometimes called paint resin)
For example, polyamine resins such as amine-added epoxy resins, such as (1) polyepoxide compounds and primary mono- and polyamines, secondary mono- and polyamines, or 1.
adducts with secondary mixed polyamines (e.g. U.S. Pat. No. 3,
984,299); (ii) adducts of polyepoxide compounds with secondary mono- and polyamines having ketiminated primary amine groups (e.g., U.S. Pat.
(j) Reactants obtained by etherification of a polyepoxide compound and a hydroxy compound having a ketiminated primary amino group (see, for example, JP-A-59-43013), etc. may contain.

The polyepoxide compound used in the production of the polyamine resin is a compound having two or more epoxy groups (-CH-CH,)\1 in one molecule, generally at least 200, preferably 400 to . Those having a number average molecular weight in the range of 4,000, more preferably 800 to 2,000 are suitable, and those obtained by the reaction of polyphenol compounds and epichlorohydrin are particularly preferred. Examples of the polyphenol compound used for forming the polyepoxide compound include bis(4-
hydroxyphenyl)-2,2-propane, 4,4'-
Dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-
tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, 1,5-dihydroxynaphthalene, bis(2,4-dihydroxyphenyl)methane, tetra(4-hydroxyphenyl)-1,
Examples include 1,2,2-ethane, 4.4'-dihydroxydiphenylsulfone, phenol novolak, and cresol novolak.

The polyepoxide compound may be one partially reacted with a polyol, polyether polyol, polyester polyol, polyamide amine, polycarboxylic acid, polyisocyanate compound, etc. Furthermore, it may be one that is partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamide amine, a polycarboxylic acid, a polyisocyanate compound, etc. Furthermore, the polyepoxide compound may be one that is partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamide amine, a polycarboxylic acid, a polyisocyanate compound, or the like. It may also be something that has been done.

In addition, when good weather resistance is required for the composite cured coating film formed according to the method of the present invention, a resin component with excellent weather resistance may be used as a resin component other than the above-mentioned cationic electrodepositable gelling fine particle polymer. It is convenient to use the amino group-containing acrylic resin or the nonionic acrylic resin alone or in combination with the amine-added epoxy resin.

The amine-added epoxy resin described above can be cured using a polyisocyanate compound blocked with an alcohol, if necessary.

In addition, amine-added epoxy resins that can be cured without using blocked isocyanate compounds can also be used, such as resins in which β-hydroxyalkyl carbamate groups are introduced into polyepoxide materials (for example, in JP-A-59-155470). (see Japanese Patent Publication No. 55-80436); vine-type resins that are cured by transesterification (for example, see Japanese Patent Application Laid-open No. 80436/1983) can also be used.

The above-mentioned cationic aqueous solution or dispersion of the cationic electrodeposition coating resin is usually prepared by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid, or lactic acid to make it water-solubilized or water-dispersed. be able to.

The cationic electrodeposition paint resin solution or aqueous dispersion obtained by (including resin solid content during coalescence), preferably 1 to 50% by weight, more preferably 5 to 35% by weight
Cationic electrodeposition coating composition (I) can be obtained by mixing so as to obtain the following. When the content of the cationic electrodepositable gelatinized fine particle polymer in the cationic electrodeposition coating composition (I) is less than 1% by weight based on the total resin solid content, the baking of the electrodeposition coating will occur when the coating melts. On the other hand, if it exceeds 50% by weight, the control effect on viscosity reduction is small (and the edge coverage of the electrodeposited coating film is likely to be insufficient). The leveling effect due to heat flow becomes insufficient, and the smoothness of the electrodeposited coating tends to be poor.

The cationic electroacoustic paint composition (I) may further contain conventional paint additives, for example, coloring pigments such as titanium white, carbon black, red iron, yellow lead, etc.; extender pigments such as talc, calcium carbonate, mica, etc. , clay, silica, etc.: rwm pigments such as strontium chromate,
Chromium pigments such as zinc chromate, basic lead silicate,
A lead pigment such as lead chromate may also be included.

The cationic electrostatic storage paint composition (I) can be applied to the surface of a desired base material by cationic electrocoating. Cationic electrodeposition coating generally has a solid content concentration of approximately 5 to 40% by weight.
Dilute with deionized water etc. so that the pH is 5.
．． This can be carried out using an electrodeposition bath consisting of the cationic electrodeposition coating composition (I) adjusted within the range of 5 to 8.0.

Next, according to the method of the present invention, the cationic electrodeposition coating composition (II) to be applied on the uncured electrostatic coating film of the above-mentioned cationic electrodeposition coating composition (I) is The current density is 0.7 mA/cm" or less, preferably 0.5 mA/cm" or less, more preferably 0.3 mA/cm" or less.
rnA/am2 or less, and the degree of emulsification of the electrodeposition coating resin is 80% by weight or more, preferably 8
The content is preferably 5% by weight or more, more preferably 90% by weight or more.

Cationic electrodeposition coating composition used as the second layer (II
), when the minimum electrodeposition current density is 0.7 mA/c, it becomes difficult for electrodeposition to occur, and the thickness of the second layer tends to decrease (and the degree of emulsification of the electrodeposition paint resin decreases). If the amount is less than 80% by weight, the coating properties approach a solution state, the deposited coating film becomes extremely dense, and the first layer and second layer are mixed, making it difficult to achieve the intended purpose.

The above "minimum deposition current density" is a value measured by the following method; A platinum plate with a surface area of 1ea2 and an insulated back side is used as the opposite electrode of the object to be coated, and a distance of 15 cm is set so that the two surfaces face each other. and place it in the electrodeposition paint. At 28°C, a constant current was applied without stirring, the time and voltage were recorded, and the current density was set to 0.
05 mA/cm2, the voltage rises rapidly due to increased resistance due to electrolytic deposition of paint for 3 minutes or 3 minutes.
The current density when the current density occurs in the vicinity of more than 1 minute is defined as the minimum deposition current density.

Furthermore, the "emulsification degree" is an index representing the proportion (wt%) of particles truly suspended as particles in the electrodeposition paint, and is determined by the following procedure: First, the solid content is 15 to 20%. Approximately 35 cc of clear emulsion of 28% by weight was placed in a cell and sealed.
, M, for 60 minutes. 2 cc of the supernatant of the separated sample is taken out with a pipette and dried at 120° C. for 1 hour, and the nonvolatile content (N, f%) is measured.

Next, turn the cell upside down, drain off the supernatant, and add another 10
Invert for a minute and remove the supernatant layer. After homogenizing the remaining sediment layer with a glass rod, accurately weigh 1.5 to 2.0 g, and
After drying at 0° C. for 1 hour, the non-volatile content (Nzc%) is measured.

Next, about 2 cc of the clear emulsion was accurately weighed, dried at 120°C for 1 hour, and the nonvolatile content (N, f%) was measured. The degree of emulsification is a value determined by the following formula.

The cationic electroacoustic paint composition (II) has a coating film melting minimum viscosity of 101 to 106 centiboise at the initial stage of curing,
Preferably, it is within the range of 101 to 102 centimeters from the viewpoint of improving the smoothness of the coated surface.

The cationic electroacoustic paint composition (II) used as the second layer in the method of the present invention is not particularly limited as long as it satisfies the above-mentioned minimum deposition current density and emulsification degree requirements. It can be composed of the same component composition as in the cationic electrostatic coating composition, and the cationic electrocoating coating resin component is selected from those mentioned above for the cationic electrostatic coating composition (I) used as the first layer. (The resin component may be the same as that in the cationic electrodeposition coating composition (I) as the first layer or may be of a different type).

The minimum electrodeposition current density of the cationic electroacoustic paint composition (II) to be used can be adjusted by appropriately adjusting the type and amount of the cationizing agent (amino compound) in the base resin component and/or the type and amount of the acid required for neutralization. This can be done empirically (through small-scale experiments) by changing the

Further, the degree of emulsification can also be easily adjusted by the same method as adjusting the minimum electrodeposition current density.

The above cationic charge storage paint composition (II) may also contain conventional paint additives, such as carbon black,
Colored pigments such as titanium white and red iron; extender pigments such as clay, talc, and calcium carbonate; rust-preventing pigments such as strontium dichromate and lead chromate; or other additives may be added. Other additives include, for example, dispersion aids (nonionic surfactants); coating surface anti-repellents (acrylic resins, fluororesins, silicone resins, etc.); curing accelerators (for example, lead, bismuth, tin, etc.). metal salts), etc.

The above-mentioned cationic electrodeposition coating composition (II) is diluted with deionized water as appropriate before use, so that the solid content concentration is about 5 to about 40.
The weight percent and pH can be adjusted to be within the range of about 5.5 to about 8.

In the present invention, the method and apparatus for electrocoating the object to be coated using the coating compositions (I) and (II) include methods and apparatus known per se that have been conventionally used in cationic electrodeposition coating. equipment can be used. In this case, it is desirable to use the object to be coated as a cathode and to use a carbon plate as an anode. The vine electrodeposition coating conditions used are not particularly limited, but generally the bath temperature for each coating composition is: 15 to 35°C (preferably 20 to 30°C)
, voltage: 100-400V (preferably 200-30V
0V), current density: 0.01 to 3A/dm", current application time = 30 seconds to 10 minutes, pole area ratio (A/C): 6/1 to 1/
6. Distance between electrodes: 10 to 100 cm. Electrodeposition is preferably performed under stirring.

The film thickness (dry state) of the first layer of electroacoustic coating film formed using the above-mentioned electro@coating method is 5 to 30P, preferably 10P.
-25P, and the thickness (dry state) of the second layer of electrostatic coating film formed thereon is conveniently in the range of 5-70F, preferably 10-50F.

In the present invention, after the first 'rl@ coating, excess 1i@ paint adhering to the object to be coated is removed by washing with reverse osmosis membrane filtrate or deionized water using a dipping method or spray method, and then It is convenient to carry out a second electrodeposition coating. In addition, it is preferable and necessary to perform the second electrodeposition coating while the first one-layer coating is uncured, in order to form a composite coating and from the viewpoint of adhesion. The conditions are, for example, after washing with water, the first electrodeposition coating is coated with 12
Heating may be performed for a short time at a temperature of 0°C or less, or heating may be performed to the extent that moisture is removed using hot air. It should be understood that this includes:

The two-layer electrodeposition coating film formed on the object to be coated is preferably washed with deionized water or reverse osmosis membrane filtrate, and then heated at a temperature equal to or higher than the curing start temperature of the coating composition (II), preferably 10
Both coatings are cured by heating to 0 to 250°C, more preferably 150 to 200°C.

The thickness of the capacitor coating film is generally desirably within the range of 15 to 80P as the total thickness of the first capacitor coating film thickness and the thickness of the second capacitor coating film. The electrodeposition coating film thus formed can be finished by appropriately applying a top coat as necessary.

When the first and second electrodeposition coatings are performed according to the method of the present invention, the single-layer coating film applied in the second coating is deposited on the surface of the first electrostatic coating film, and A coating film is formed in a multi-layer state of the electrodeposited layer and the second electrodeposited layer. Therefore, if the coating method of the present invention is used, the edges can be covered with the first layer of capacitive coating, and the coating surface smoothness and uniform film formation can be improved with the second capacitive coating. can be secured.

As a result, the two-layer coating film has excellent corrosion resistance at the edges, and also has an excellent coating surface condition with no poor finish due to pigment sedimentation or pinhole defects. Furthermore, since the first layer paint also has good bath stability, a coating film with a good finish can be obtained even over time.

According to the electrodeposition coating method of the present invention, the corrosion resistance of the edges of the object to be coated, which was a weak point of conventional electric W coatings, is significantly improved, and a multilayer coating film with excellent coating surface smoothness can be created. can be formed. In particular, the cationic electrodepositable gel fine particle polymer contained in the cationic electrodeposition coating composition (I) used for the first electrodeposition coating can be added to normal cationic electrodeposition coating to prevent aggregation and abnormal electrodeposition. It is co-electrodeposited without causing problems such as sedimentation, acts as a flow regulator during heat curing of the electrodeposited coating, and exhibits excellent repellency prevention effects and edge covering effects. The electrodeposition coating method of the present invention, which has an excellent effect of improving edge coverage that does not deteriorate over time, can be widely applied as an anticorrosive coating method in a wide range of industrial coating fields such as automobiles, electrical equipment, and prefabricated steel frames. .

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. In Examples and Comparative Examples, "part" and "%" are respectively "parts by weight. ” and “% by weight”.

Production example 1 2 equipped with a stirrer, air introduction pipe, cooling pipe, and temperature control device
A flask was charged with 222 parts of inphonodiisocyanate and 50 parts of methyl isobutyl ketone, and the mixture was stirred and heated to 70°C while blowing dry air into the liquid phase. 0.3 parts of dibutyltin dilaurate was added thereto, and then 116 parts of 2-hydroxyethyl acrylate was added dropwise over 1 hour, and the temperature was maintained at 70'C for another 1 hour after the addition was completed.

Subsequently, 115 parts of methyl isobutyl ketoxime was added dropwise over 1 hour. Even after the completion of the dropwise addition, the mixture was heated and kept at 70°C. The reaction mixture was collected over time and the absorption of -NCO was confirmed by IR. The end point of the reaction was defined as the point in time when the amount disappeared.

In this way, a 90% isophorone diisocyanate/2-hydroxyethyl acrylate/methyl isobutyl ketoxime block solution was obtained. The 70% solid foam viscosity of this product (solvent composition: 10% methyl isobutyl ketone, 20% n-butyl acrylate) was DE.

Production Examples 2 to 6 Using the same formulation as Production Example 1 and using the raw materials shown in Table 1, 90% solutions of various radically polymerizable blocked isocyanate monomers were obtained. 70 of these monomers
The % solid foam viscosity is also shown in Table-1.

9' Production Example 7 of Cationic Gel 'LEjLIi' I equipped with a stirring device, thermometer, cooling tube and heating mantle
In a J2 flask, add 700 parts of deionized water and Latemul-
180 (manufactured by Kao Corporation, 25% aqueous solution) was added, and the temperature was raised to 90"C without stirring. To this was added 2 parts of VA-086 (manufactured by Wako Junwara Industries, Ltd.), which is a polymerization initiator. 20 percent of the aqueous solution dissolved in 100 parts of deionized water was added. After 15 minutes, 10 parts of component (A), the following mixture, was added.

Styrene 32 parts n-butyl acrylate 32 parts 1,6-hexanediol diacrylate 30 parts 2-hydroxyethyl acrylate 4 parts KBMT-
503" 2 parts * γ-Meccryloxybrobyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Next, after further stirring for 30 minutes, dropping of the remaining monomer mixture of component (A) and the aqueous polymerization initiator solution was started. ( A) The component monomer mixture was supplied for 1.5 hours, and the polymerization initiator aqueous solution was supplied for 4.5 hours. (A)
After the completion of dropping the component monomer mixture, the polymerization temperature was kept at 9 ℃ for 1 hour.
After maintaining the temperature at 0''C, dropwise addition of the following monomer mixture as component (B) was started.

Styrene 38 parts n-butyl acrylate 38 parts 2-hydroxyethyl acrylate 4 parts Monomer solution obtained in Production Example 1
22 parts (B) The monomer mixture of component (B) was heated for 30 minutes even after the dropwise addition of the aqueous solution of polymerization initiator supplied for 1.5 hours, kept at 90°C, cooled to room temperature, and heated to fP using a furnace cloth.
31A and took it out. Thus, solids content 20.0%, pH
Viscosity of 3, 9, 50 cps (BM type rotational viscometer, No.
2 spindle) and an average particle diameter of 74r+m (measured with Coulter Nanosizer N-4), a gelled fine particle polymer dispersion was obtained.

Production Examples 8 to 13 and Comparative Production Examples 1 to 7 In Production Example 7, the amount of initially charged deionized water, the type of polymerization initiator, (A)
Component monomer composition, (B) component monomer composition and (A
Emulsion polymerization was carried out using the same recipe as in Production Example 7, except that the ratio of component (B) to component (B) was changed as shown in Table 2.
A gelled fine particle polymer dispersion having the properties shown in Table 2 was obtained.

Comparative Production Example 8 1 equipped with a stirring device, thermometer, cooling tube and heating mantle
In a °C flask, add 700 parts of deionized water and -1 part of Latemul.
80 was added, and the temperature was raised to 90°C while stirring. To this was added 20 percent of an aqueous solution of 2 parts of VA-086, a polymerization initiator, dissolved in 100 parts of deionized water. After 15 minutes, 10 parts of the following monomer mixture, which is a mixture of components (A) and (B) in Production Example 7, was added.

Styrene 70 parts n-butyl acrylate 70 parts 1゜6-hexanediol diacrylate 30 parts 2-hydroxyethyl acrylate 8 parts KBM-5
032 parts 22 parts of the monomer solution obtained in Production Example 1 Then, after further stirring for 30 minutes, dropping of the remaining monomer mixture and the aqueous polymerization initiator solution was started. The monomer mixture is 3
The aqueous polymerization initiator solution was supplied every 3.5 hours, and the polymerization temperature was maintained at 90°C. After the dropwise addition of the aqueous polymerization initiator solution was completed, the mixture was heated for 30 minutes and kept at 90°C, then cooled to room temperature, filtered using a furnace cloth, and taken out. Thus, solid content 19.9%, pH 3, 9, viscosity of 60 cps (BM type rotational viscometer, No. 2 spindle), average particle size 72n.
A dispersion liquid of gelled fine particle polymer of m was obtained.

Example 1 of manufacturing the first cationic ζ product 572 parts of a 35% solids cationic electrodepositing clear emulsion (trade name, Nileclone 9450, manufactured by Kansai Paint Co., Ltd.) consisting of a polyamide-modified epoxy resin and a completely blocked diisocyanate were added to Production Example 7. 75 parts of the obtained gelled fine particle polymer with a solid content of 20% and 139.4 parts of the following pigment paste (A) with a solid content of 43% were added with stirring, diluted with 588.5 parts of deionized water, and cationic electrolyte was added. @Paint (I
)-1 was obtained.

Preparation Examples 2 to 15 In Preparation Example 1, cationic electrolysis was performed in the same manner as in Preparation Example 1, except that 75 parts of the dispersions obtained in Preparation Examples 8 to 13 and Comparative Preparation Examples 1 to 8 were used as the gelled fine particle polymer. Paints (I)-2 to (1)-15 were obtained.

Example of preparation of two-layer cationic material I■ Example 16 Clear emulsion for cationic electrodeposition (manufactured by Kansai Paint Co., Ltd., trade name: NILCLON No. 9600) 626 parts with a solid content of 4
139.4 parts of 3% pigment paste (A) was added with stirring and diluted with 550 parts of deionized water to obtain cationic electrodeposition paint (II)-1.

The minimum electrodeposition current density of this paint was 0.25 mA/cm2. The degree of emulsification of the clear emulsion used was 90%.

Examples and Comparative Examples Cationic electrodeposition paints (I)-1 to (1) obtained in Preparation Examples 1 to 15
I)-15, each of 0, 8 x 300 x 90 mm cold-rolled dull steel plates (angle between end face and flat part is 45 degrees) chemically treated with Pearl Bond #3030 (manufactured by Nippon Bar Ising ■, zinc phosphate system). was immersed in the liquid and used as a cathode for electrocoating. The electrodeposition coating conditions are: electrodeposition paint bath temperature 3
0°C, pH 6.5, voltage 300V, an electrodeposition coating film with a film thickness (based on dry film thickness) of 10P was formed, the coating film was washed with water after electrodeposition, and this was further coated with cationic electrodeposition paint ( II)-
i, and electrodeposition coating was performed using it as a cathode. N@ Painting conditions are bath temperature 30℃, pH 6.7, voltage 30
0■, and the film thickness of the electrodeposition paint (II) was 20 Pm. After washing this with water, it was baked at 180° C. for 30 minutes to produce a board.

Table 3 shows the combinations of electrodeposition paints (1) and (II), the measurement results of the coating melt viscosity, and the performance test results of the obtained coated plates.

Furthermore, 30% of the cationic 1i coating obtained in Preparation Examples 1 to 15 was added.
The samples were stored for one month under closed stirring at ℃, and the electrodeposition test described above was also conducted on them. The results are also shown in Table 3 below.

[Performance test method] (*1) Coating film melt viscosity The melt viscosity of the electrodeposited film during baking was measured using the rolling ball viscosity measurement method (JIS
- Z-0237) was evaluated based on the thermal fluid appearance of the scratch marks. The numerical value indicates the lowest viscosity (centivoise).

(*2) Edge coverage A test plate is prepared by electrodeposition coating on a steel plate having an edge angle of 45° under conditions such that the cured film thickness of the flat portion is 20F11, and hardening under predetermined baking conditions. Set the test plate on the Tsuruto Slaying device so that the edge part is vertical, and
The corrosion resistance of the edge portion after 168 hours is evaluated by the 5-Z-2371 salt water test.

0: No rust at all ○: Slight rust occurrence ×: Significant rust occurs (*3) Smoothness of painted surface Visually evaluate the finish of the electrodeposited surface.

○: Good ■ = Poor △: Slightly poor (*4) Impact resistance 0 weight 500g in an atmosphere of 20°C according to JIS-5400-19796, 13, 3B method
, indicates the maximum height without causing paint film damage under the conditions of the tip radius of the center of impact (cm), with 50 cm being the highest value.

(*5) Chipping resistance Baked electrodeposition coated board is further coated with thermosetting intermediate coating and top coating, and the following tests are conducted on the heated and cured plate.

■Test equipment: Q-G-R grameter (Q Panel Company product) ■Stone to be sprayed: Crushed stone with a diameter of 15-20 m/m■Capacity of stone to be sprayed: Approximately 500〇-■ Spraying The air pressure is approximately 4 kg/c.Temperature during the test: approximately 20℃.The test specimen is attached to the test specimen holder, and the air pressure of approximately 4 kg/am'' is used to fire approximately 500-kg crushed stone onto the test specimen. After that, the condition of the painted surface was evaluated.The condition of the painted surface was visually observed and evaluated according to the following criteria.

(Evaluation) 0 (Good): Only a few scratches due to impact were observed on a part of the top coat, and no peeling of the electrical storage coating was observed.

(Slightly poor) There are scratches caused by impact on the second and intermediate coats, and slight peeling of the electrodeposited film is observed.

Δ (Poor) Many scratches due to impact were observed on the second and intermediate coats, and considerable peeling of the electrodeposited coating was observed.

(*6) Secondary adhesion after immersion in hot water After being immersed in water at 40°C for 20 days, JIS-5
400-19796, 15, and adhesive cellophane tape was attached to the surface of the coating, and the coated surface was evaluated after it was suddenly peeled off.

0 Good with no abnormalities △: Slight peeling of the edges of the gongs ×: Part of the gongs are peeling off (*7) Cross-cut scratches were made on the electric @ coating film with a knife to reach the anti-corrosion base. 840 according to JIS 22371
A time salt spray test was conducted and evaluation was made based on rust from knife scratches and blistering width.

○, the maximum width of rust or blisters is IIT1m from the cut part
Less than (one side).

◎: The maximum width of rust or blisters is 1 from the cut part △: The maximum width of rust or blisters is 2 or more and less than 31 from the cut part (
one side) and the blisters are quite noticeable on the flat surface.

×: The maximum width of the blemishes or blisters is 3 mm or more from the cut portion, and the occurrence of pristle is observed on the entire painted surface.

Claims (1)

[Claims] 1. Cationic electrodepositable product made by emulsion polymerization using a cationic reactive emulsifier and having a core-shell structure containing a hydrolyzable alkoxysilane group and a hydroxyl group as a core component and a urethane bond and a hydroxyl group as a shell component. Cationic electrodeposition coating composition containing gelled particulate polymer (I)
A cation having a minimum electrodeposition current density of 0.7 mA/cm^2 or less and an emulsion degree of 80% by weight or more on an uncured electrodeposition coating film obtained by electrodeposition coating on an object. An electrodeposition coating method characterized by baking and curing an uncured electrodeposited multilayer coating film formed by electrodeposition coating composition (II).