JPH04110065A - Method of forming coating film - Google Patents

Abstract

PURPOSE:To obtain a coating film of good appearance and high performance by first applying an electrodeposition coating material having low initiating temp. of curing on a material to be coated, then applying a coating material containing a specified amt. of hydrophilic solvent and ketone solvent by wet- on-wet method, and curing both films at one time. CONSTITUTION:First, an electrodeposition coating material having 100-140 deg.C initiating temp. of curing is applied on the material to be coated. During this coating film is not hardened, a coating material containing a hydrophilic solvent by 15-100wt.% to the whole amt. of solvent on coating, and ketone solvent by the max. 10wt.% is applied thereon. Then, both coating films are cured at one time. By this method, the coating films are formed by wet-on-wet state, which gives high performance excellent in appearance, weather resistance and chipping resistance, and the obtd. film is especially suitable for outside boards of automobiles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention makes it possible to form a coating film with a high degree of appearance, weather resistance, and chimping resistance in a shortened process. In particular, the present invention relates to a coating film forming method suitable for painting exterior panels of automobiles.

[Conventional technology] Generally, painting of metal materials such as automobile exterior panels and home appliances is done by first performing electrodeposition coating, baking the formed coating film, and then applying intermediate coating and top coating. However, in recent years, wet-on-uni coating has omitted the baking process during electrodeposition coating in order to save energy, resources, and labor.

Consideration is underway to paint it using

In this case, the electrodeposited coating before baking and drying has a 2 to 10
% of water, it is more suitable to use a water-based paint material than a solvent-based paint material to coat the upper part of the paint. However, since most of the volatile components of water-based paints are water, they tend to drip into the paint film and pinholes tend to form during baking, making them significantly inferior to solvent-based paints in terms of workability. be.

In order to solve the above-mentioned problems, improvements have been proposed from a process perspective, such as controlling the temperature and humidity of the booth, extending the setting zone, and adding bleed heat treatment, but the workability is still not comparable to that of solvent-based paints. Not obtained.

Against this background, we adjusted the solvent composition of the solvent-based paint that is applied wet-on-wet, and replaced 20% by weight of the total organic solvent in the solvent-based paint with a hydrophilic organic solvent that dissolves at least 5% by weight in water. A painting method using paint was developed by Ganto Honda (Japanese Patent Application Laid-open No. 193568/1983).
.

(Problems to be Solved by the Invention) When the above-described special solvent-based paint is used, wrinkles, cracks, curing distortion, lack of gloss, and
It is possible to reduce defects such as poor image clarity, poor adhesion, dents, and repelling.

Therefore, a high-performance coating film can be formed in a process that omits the baking step during electrodeposition coating.

However, this method still has some shortcomings in effectively eliminating the above-mentioned defective phenomena, and is particularly suitable for painting exterior panels of automobiles, which requires the highest quality coating performance and coating appearance. However, there was still room for improvement.

As a result of repeated research into wet-on-wet coating conditions, the present inventors found that an electrodeposition coating with a lower coating film curing initiation temperature than conventional coatings, a specific amount of internally crosslinked micro resin particles, and/or non-gelling If an electrodeposition paint containing a polymeric resin is used and a specific amount of hydrophilic solvent is used as an on-wet paint, and if a limited amount is used if it contains a ketone solvent, defects in the formed paint film, especially wrinkles, may occur. The present invention was developed based on the discovery that cracks, curing distortion, poor gloss, poor image clarity and adhesion, as well as dents in the mist area and repelling, can be extremely effectively reduced.

Accordingly, an object of the present invention is to provide a method for forming a coating film that provides an appearance and coating performance particularly suitable for painting exterior panels of automobiles through a shortened process.

[Means to solve the problem]

The first coating film forming method according to the present invention for achieving the above object is characterized in that the following steps are sequentially performed.

(1) The coating material has a coating film curing start temperature of 100 to 140°C.
The first step is to apply the electrodeposition paint.

(2) When the electrodeposition coating film obtained in the first step is uncured,
A second step of applying a paint in which the maximum content of hydrophilic solvents and ketone solvents is 15 to 100% by weight based on the total solvent used at the time of coating, and is 10% by weight.

(3) A third step of simultaneously curing the electrodeposited film from the first step and the paint film from the second step.

The second coating film forming method according to the present invention has the second step and the third step common to the first invention, and the first step is
The object to be coated contains 1 to 60 parts by weight of internally crosslinked fine resin particles and/or non-gelling polymer resin as a solid content per 100 parts by weight of the solid content of the coating film forming resin, and the coating film curing initiation temperature is 100 parts by weight. The gist of the structure is to replace the process with an electrodeposition paint at a temperature of ~140°C.

The entire coating process that is the premise of the present invention is electrodeposition coating.
These are commonly used processes such as intermediate coating, baking, top coating, baking, electrodeposition coating - intermediate coating (^) - baking - (polishing) - intermediate coating (B) - baking, top coating - baking, or electrodeposition coating - top coating - baking. . Therefore, in the second step of wet-on-wet painting, there are cases in which not only an intermediate coat but also a direct top coat is applied.

Hereinafter, the conditions for each step, the components used, etc. will be explained in detail.

In the present invention, the state of an uncured electrodeposited coating film is determined by, for example, using a pendulum type viscoelasticity meter, and the logarithmic attenuation rate of the coating film increases from its minimum value:
It is measured by a detection method that measures the temperature at an inflection point.

The reason for selecting and using an electrodeposition paint with a coating film curing start temperature of 100 to 140°C in the first step of the first coating film forming method is that if the coating film curing start temperature is less than 100°C, the intermediate coating in the second step When baked after painting, there are problems such as overhakes, poor paint film performance, yellowing, and poor paint stability.
If the temperature exceeds 140°C, curing distortion will occur due to the difference in the curing start temperature of the intermediate coating or top coating that is commonly used in the second process, and defective phenomena such as shrinkage, insufficient image clarity, and insufficient interlayer adhesion will occur. This is because it cannot be effectively prevented. Therefore, by setting the curing start temperature of the electrodeposited coating at 100 to 140°C, the occurrence of defective phenomena can be effectively prevented, and at the same time, it is possible to shorten the baking time after intermediate coating and lower the baking temperature. becomes.

As such a means, it is effective to use a resin (hereinafter referred to as "main component resin") whose coating film curing initiation temperature is in the range of 100 to 140 DEG C. as the main component constituting the coating film.

The main component resin of the coating material may be an anionic resin type or a cationic resin type, and may be a water-soluble type or a dispersion type. For example, α,β ethylenically unsaturated dibasic acids or their anhydride adducts of drying oils or liquid rubbers such as polybutadiene, those whose main skeleton is optionally epoxidized resins, and modified derivatives thereof, such as maleic Oil resins, maleated polybutadiene resins, amine-modified epoxidized polybutadiene resins, etc.; those whose main skeleton is fatty acid esters of resinous polyols and their modified derivatives, such as epoxy resins, esterified resins, etc.; acrylic resins whose main skeleton is Examples include those whose main skeleton is acrylic resin.

Depending on the mechanism of the curing reaction, these resins are of the self-crosslinking type, in which the resin itself is cured by radical polymerization or oxidative polymerization, or in the case of self-curing, which is cured by a curing agent such as melamine resin or prosodic polyisocyanate compound. There are hardening agent types and types that use rain sound in combination, and in these cases, frJA compounds such as manganese, cobalt, nickel, and Lm can be used as catalysts.

Among these, specific examples of main component resins as anionic resin systems are listed below.

(1) Containing a side chain bond block, at least one of the terminal epoxy groups is ring-opened by reaction with an active hydrogen compound capable of reacting with the epoxy group, and introduced by reacting with a diisocyanate compound half-blocked with hydroxocarboxylic acid. A modified epoxy resin having a carboxyl group at the end of its main chain (Japanese Unexamined Patent Publication No. 1-236224).

(2) Sorbic acid, maleic anhydride, number average molecular weight 50
A resin obtained by condensing a 0 or more epoxy resin, an unsaturated resin acid, a monovalent to trivalent organic acid, and a monovalent to tetravalent alcohol (Japanese Unexamined Patent Publication No. 81261/1982).

(3) Free carboxylic acid group in the side chain and/or main chain,
A resin obtained by modifying either a drying oil or a conjugated diene polymer or copolymer having a conjugated diene-bonded α,β-unsaturated monocarboxylic acid residue (JP-A-1-1469)
Publication No. 71).

(4) 0.1 to 10% by weight based on the total amount of the acrylic copolymer (1) containing a carboxyl group and a hydroxyl group and/or an alkoxyalkyl group bonded to a nitrogen atom and the aminoplast resin (II) An electrodeposition coating composition comprising a sulfonic acid group-containing polymer (I[I) (Japanese Patent Application Laid-open No. 62-53383).

Furthermore, examples of the main component resin of the cationic resin system include the following.

(1) Functional groups that can react with cationic groups and isocyanate groups (e.g., hydroxyl groups, amino groups, imino groups, etc.)
A mixture of a cationic base resin having the following properties and a blocked polyisocyanate blocked with a blocking agent that dissociates at a temperature of 70 to 140°C.

(2) Iodine value 50-500, basic group solid content 100
30-300 mmol per g and number average molecular weight 500
The resin (A) has at least two benzene nuclei and at least one ethylenic vinyl group in one molecule, and has an acidic group of 5 to 35 per 100 g of solid content.
0 mmol and a resin (B) having a number average molecular weight of 500 to 5000 in a ratio of 0.03 to 0.5 mol of acidic groups of component (B) per 1 mol of basic groups of component (A), and a negative electrodeposition coating composition containing at least a portion neutralized with an acid (Japanese Patent Application Laid-open No. 1-271467).

(3) Ester group-containing compound (
B) contains a group that forms an amide or ester with a carboxylic acid, consisting of a microcle addition reaction product (A) obtained by carrying out a microcle addition reaction on a compound (C) containing at least two double bonds capable of undergoing a microcle addition reaction. In the curable component for synthetic resins, the reaction product (A) has on average at least one polymerizable double bond and at least two transesterifiable or transamidable ester groups per molecule, and Compound (B) is (bl)CH
- Paint preparation using the above-mentioned curable component for synthetic resins, characterized in that it is a reaction product consisting of an activated alkyl ester and (b2) polyisocyanate
192463).

(4) (i) Formation of a film having a sulfonium group or phosphonium group Item C) A portion capable of crosslinking with (1) and a portion capable of catalyzing the crosslinking reaction between (item 1) (i) and (ii) An aqueous cationic electrodepositable coating composition having a positive electrodepositable source (Japanese Patent Application Laid-open No. 179983/1983).

(5) A coating composition containing an onium group-containing polymer and an aminoplast curing agent (JP-A-60-1265).

Among these, (1) is the most desirable. The cationic base resin constituting (1) includes well-known epoxy resins and acrylic resins, but specific examples of such cationic base resins include those with active hydrogen and amino groups. Examples include epoxy resins containing.

The epoxy resin is a compound having one or more epoxy groups per molecule on average, and epoxy resins having two epoxy groups are particularly preferred.

Useful epoxy resins include bisphenol F, an epoxy resin obtained from bisphenol A and epichlorohydrin;
and epichlorohydrin or hydrogenated bisphenol A
Examples include polyglynodyl ether obtained from and epichlorohydrin.

Particularly preferred are epoxy resins obtained by the reaction of bisphenol A and epichlorohydrin.

In addition, an acrylic polymer having an epoxy group may be used. Such polymers are obtained by polymerization of unsaturated epoxy group-containing polymers, such as glycidyl (meth)acrylate, with one or more other polymerizable ethylenically unsaturated monomers.

Examples of such polymers are disclosed in U.S. Pat. No. 4,001,156 at column 3, line 59 to line 51'M, line 60.

As a cationizing agent, the basic amino compound used in the amino group-containing epoxy resin may be any of primary amines, secondary amines, tertiary amines, polyamines, and alkanolamines. Preferred basic amino compounds include diethylamine, dipropylamine, N-methylethanolamine, jetanolamine, ethylenediamine, diethylenetriamine, dimethylcyclohexylamine, dimethylethanolamine, diethylenetriamine, and the like. When using a polyamine such as diethylenetriamine, it is preferable to react the primary amine group with a ketone such as acetone, methyl ethyl ketone, or methyl isobutyl ketone to obtain a ketimine derivative. The ketimine production reaction proceeds easily by heating to 100° C. or higher and distilling off the produced water. When using a tertiary amine having no active hydrogen, it is used in place of an acid amine salt with an appropriate acid such as boric acid, phosphoric acid, sulfuric acid, acetic acid, lactic acid, etc.

Regarding the amounts of amino compounds reacting with each other and the epoxy resin used, the relative amounts will vary based on the amount of cationic salt, eg, the amount of cationic base formation desired, and will also depend on the molecular weight of the epoxy resin. The amount of cationic base formed and the molecular weight of the reaction product are selected such that the resulting cationic polymer forms a stable dispersion when mixed with an aqueous medium.

The reaction between these basic amino compounds and the epoxy resin generally occurs even when they are mixed at room temperature, but in order to complete the reaction, it is necessary to complete the reaction at a temperature of about 20 to 200 degrees Celsius, preferably about 50 degrees centigrade.
It is preferable to heat at 50° C. for about 1 to 5 hours.

The above reaction and reaction product can be used, for example, in JP-A-51-1
03135, JP 55-32385, JP 53-65327, JP 53-65328
It may be manufactured by the method described in Japanese Patent Application Publication No. 52-87498 and the like.

The blocked polyisocyanate used with these cationic base resins is obtained by adding a blocking agent to polyisocyanate, and the blocking agent dissociates within a temperature range of 70°C to 140°C to generate isocyanate groups. It reacts with the functional groups in the base resin and cures.

Blocked polyisocyanates include all polyisocyanates conventionally used as vehicle components for electrodeposition paints.
Blocking agents can be used, but it is necessary to select a blocking agent for low-temperature curing. Typical polyisomers are exemplified below. Trimethylene diisocyanate, tetramethylene diisocyanate, bentamethylene diisocyanate, hexamethylene diisocyanate, 1.2-
Propylene diison anate, 1,2-petylene diison anate? -t, 2,3-butylene diisocyanate, 13
- Aliphatic compounds such as butylene diisocyanate, ethylidene diisocyanate, phenylene diisocyanate, 1.3-7 clobentanediisocyanate, 1.4-
Aliphatic cyclic compounds such as cyclohexane diisocyanate and 12-cyclohexane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 44'-diphenyl diisocyanate, L5-
Aromatic compounds such as naphthalene diisocyanate, 1.4-naphthalene diisocyanate, 4.4'-diphenylmethane diisocyanate, 2.4- or 26-toluene diisocyanate or mixtures thereof, 4.4
'-Aliphatic-aromatic compounds such as toluidine diisocyanate and 14-xylene diisocyanate, nuclear-substituted aromatic compounds such as dianisidine diisocyanate, 44'-diphenyl ether diisonoanate, and chlorodiphenylnoisonoanoate, triphenylmethane -4,4
'4' triisonanate, 1.3.5-triisocyanate, 2,4.6-1-liisocyanate toluene, 4,4'
-diphenyl-trimethylmethane-2,2', 5.5
Examples include polymerized polyisocyanates such as tetraisocyanate such as '-tetraisocyanate, toluene diisonanate dimer, and toluene diisocyanate trimer.

As a pro-removal agent that dissociates at a temperature of 70 to 140℃,
It may be in the presence of a catalyst. Such blocking agents include, for example, in the case of aromatic polyisocyanates, halogenated hydrocarbons such as 1-chloro-2-propanol, ethylene chlorohydrin, n-propanol, furfuryl alcohol, and alkyl groups. Aliphatic or heterocyclic alcohols such as substituted furfuryl alcohol, phenols such as phenol, m-ditrophenol, p-chlorophenol, nonylphenol, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, acetone oxime , oximes such as cyclohexane oxime, active methylene compounds such as acetylacetone, ethyl acetoacetate, and ethyl malonate, and caprolactam. Particularly preferred are oximes, and among alcohols, furfuryl alcohol and alkyl group substituted Furfuryl alcohol. In the case of aliphatic polyisocyanates, phenols and oximes are preferred among the above.

Note that another blocking agent (b) may be mixed with a blocking agent that dissociates at 70 to 140° C. (hereinafter referred to as "blocking agent (a)").

The blocking agent (b) is preferably one having a dissociation temperature of less than 160''C, such as aliphatic alcohols such as methanol, ethanol, and isopanol, aromatic alcohols such as benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl Examples include ethers such as ether, ethylene glycol monobutyl ether, and diethylene glycol monomethyl ether.The method for mixing the blocking agent (b) is to block the blocking agents (a) and (b) in a fixed ratio with polyisocyanate, or or Prosoc polyisocyanate blocked with blocking agent (a) and blocking agent (
In b), a method is adopted in which the frozen solid polyisocyanate is mixed in a fixed ratio. The mixing ratio of the blocking agent (a) and the blocking agent (b) is preferably set in the range of (a):(b)=lO:O to lO:5 in terms of equivalent ratio.

As the dissociation catalyst for the blocking agent, tin compounds such as dibutyltin laurate, dibutyltin oxide, and dioctyltin, amines such as N-methylmorpholine, and metal salts such as lead acetate can be used.

The concentration of the catalyst is usually 0.3 to 5% by weight based on the solid content of the film-forming resin in the cationic electrodeposition coating.

In the first step of the second coating film forming method of the present invention, the coating film curing initiation temperature is 100 to 140"C as described above, and the internal crosslinking is minute with respect to 100 parts by weight of the coating film forming resin solid content. It is required to coat the object with an electrodeposition paint containing 1 to 60 parts by weight of resin particles and/or non-gelled polymer resin including solid content, and by applying this process, it is possible to achieve an even higher appearance and higher quality. It becomes possible to form a coating film with high weather resistance and high chipping resistance in a shortened process.

The inclusion of internally crosslinked microscopic resin particles and non-gelling polymer resin alone or in combination in the electrodeposition coating increases the melt viscosity during curing of the electrodeposition coating, allowing smooth coating in the uncured state. It's for a reason. For this purpose, for example, it is effective to add pigment components at a weight ratio of 35% or more to the total resin solid content in the electrocoating paint bath, but in this case, the smoothness of the coating film and the There are problems with stability.

As a means for producing the internally crosslinked fine resin particles used, for example, from a fine resin particle dispersion obtained by subjecting an ethylenically unsaturated monomer to a crosslinkable comonomer and a crosslinking comonomer in an aqueous medium by subjecting them to subenzidine polymerization or emulsion polymerization. Ethylenically unsaturated, low SP organic solvents such as aliphatic hydrocarbons or non-aqueous organic solvents that dissolve monomers but do not dissolve polymers, such as high SPN organic solvents such as esters, ketones, alcohols, etc. A method called NAD method or precipitation method, in which a monomer and a crosslinkable copolymerizable monomer are copolymerized and the resulting internally crosslinked fine resin particles are dispersed, can be applied.

The ethylenically unsaturated monomers used in the above method include:
Alkyl esters of acrylic acid or methacrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; Other monomers having ethylenically unsaturated bonds that can be copolymerized with this, such as styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, ethylene, propylene, vinyl acetate, vinyl propionate, (meth)acrylonitrile , dimethylaminoethyl (meth)acrylate, etc. Two or more types of these monomers may be used. The crosslinkable copolymerizable monomer is a monomer having two or more radically polymerizable ethylenically unsaturated bonds in the molecule and/or two types of ethylenically unsaturated monomers each carrying mutually reactive groups. Contains group-containing monomers.

Monomers having two or more radically polymerizable ethylenically unsaturated groups in the molecule include polymerizable unsaturated monocarboxylic acid esters of polyhydric alcohols, polymerizable unsaturated alcohol esters of polybasic acids, and There are aromatic compounds substituted with one or more vinyl groups, examples of which include the following compounds.

Ethylene glycol di(meth)acrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1.3 butylene glycol dimethacrylate, trimethylolpropane tri(meth)acrylate, 1.4 butanediol diacrylate, neopentyl glycol diacrylate , 1,6-hexanediol diacrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(
Meth) acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol dimethacrylate-1, glycerol di(meth)acrylate, glycerol aryloquine dimethacrylate, 1. Ll-1-
Lishydroxomethylethane di(meth)acrylate,
1,1.1- Trishydroxymethylethanetri(
meth)acrylate, 11.1-)Lischtloquinomethylprobane di(meth)acrylate, 1,1. i-
Trishydroxymethylpropane tri(meth)acrylate, triallyl/americate, triallylisoannule-1-, triallyl trimellitate, diallyl terephthalate, diallyl phthalate and divinylhairamine.

In addition, examples of monomers having two types of ethylenically unsaturated groups, each carrying a group that can react with each other, include an epoxy group-containing ethylenically unsaturated monomer such as glycidyl (meth)acrylate; ) Ethylenically unsaturated monomers containing carboxyl groups such as acrylic acid and crotonic acid are the most representative, but mutually reactive groups are not limited to these, for example, amine and carbonyl, Epoxides and carboxylic acid anhydrides, amines and carboxylic acid chlorides, alkyleneimines and carbonyls, orca-alkoxysolanes and carfoquinols, hytroquine and isoneanates, and 11 more! and the present invention includes these.

For fine resin particles produced in an aqueous medium or a non-aqueous organic medium, internally crosslinked fine resin particles are isolated by a method such as filtration, spray drying, or freeze drying, and the internally crosslinked fine resin particles are isolated as they are or ground to an appropriate particle size using a mill or the like. It can also be used as
．． Furthermore, the synthesized dispersion can be used as it is, or by replacing the solvent (V) with the medium.

As a method for producing internally crosslinked fine resin particles different from the above,
An emulsion obtained by emulsifying a film-forming aqueous resin (A) that is chargeable in water and a water-insoluble crosslinking agent (B) that can self-crosslink and/or crosslink with the aqueous resin (A) in an aqueous medium. In the case of charged gel particles containing a pigment in the core portion, the pigment is dispersed in the crosslinking agent (B) and then the There is a method in which the aqueous resin (A) is added and emulsified in an aqueous medium, and the resulting emulsion is heat-treated as described above.

Typical examples of film-forming aqueous resins (A) used in this method include maleated oil or maleated polybutadiene half esters and anionic acrylic resins for the anionic type, and aminated polybutadiene and amines for the cationic type. Examples include chemically modified epoxy resins.

Water-insoluble thermosetting H11FI (
B) is melamine resin for anionic water-based resin,
There are methylolphenols or etherified methylolphenols, etc. For cationic water-based resins, etherified methylolphenols, and when the cationic water-based resin is aminated polybutadiene resin, tetrabromobisphene,! -L A can also be used as a crosslinking agent.

Pigments contained in the core part include pigment substances commonly used in electrodeposition paints, such as iron oxide, lead oxide, strontium chromate, warp, carbon blank, titanium dioxide, talc, aluminum silicate, precipitated barium sulfate,
In addition to basic lead silicate, aluminum phosphomolybdate, etc., there are metal pigments such as zinc dust and other body II materials.

In order to maintain a stable dispersion state in paint and bathing, the internally crosslinked fine resin particles preferably have an ionizable group having the same polarity as the main component resin. That is, in the case of anionic electrodeposition, it is preferable to carry an anionic group such as a carboxyl group or a sulfonic acid group, and in the case of a cationic group, it is preferable to carry a cationic group such as an amino group or a quaternary ammonium group. becomes. To achieve this,
In the case of carrying an anionic group, a monomer having an ethylenically unsaturated bond and a carboxyl group, such as (meth)acrylic acid, is used, and in the case of carrying a cationic group, a monomer having an ethylenically unsaturated bond and a basic group is used. Monomers such as dimethylaminoethyl (meth)acrylate, vinyl pyridines, etc., are added to the monomer mixture during the synthesis of internally crosslinked fine resin particles, or during the synthesis of internally crosslinked fine resin particles. There is a method of polymerizing a monomer mixture using an initiator that provides a cationic end.

If the polymer constituting the internally crosslinked microscopic resin particles itself is nonpolar, an appropriate emulsifier, especially an oligosoap, polysorb, or a reactive emulsifier having amphoteric ionic groups, may be used to synthesize the internally crosslinked microscopic resin particles. It is also possible to stably disperse resin particles.

Next, the non-gelling polymer resin will be described. The non-gelling polymer resin used in the present invention must have the function of increasing melt viscosity during curing of the coating film. This feature is
In the vibration type viscoelasticity measuring method, this can be specifically verified by observing that the minimum logarithmic damping rate (relative viscosity index) increases when a non-gelled polymer resin is used compared to when it is not used.

Examples of the non-gelling polymer resin include various resin systems such as epoxo resin, acrylic resin, polybutadiene resin, polyester resin, and polyether resin. These cannot be limited by molecular weight values, but differ depending on the resin system, composition, polymer structure, type of functional group, main component resin system of the electrodeposition paint to be applied, etc.

Typical examples include epi-bis type epoxy resins, polyether polyols, polyester polyols, polyether polyol-modified polyisocyanates, monoalcohols, carboxylic acid ester-containing diols, carboxyl group-containing butadiene-acrylic copolymers, and terminal carboxyl group-containing diols. butadiene-acrylonitrile copolymer, long chain dibasic acid, polyamine, polyoxyalkylene polyamine,
Polyurethane polyamines, ring-opened polymers of ε-caprolactone, etc. are used to extend the chain, and in the case of using epi-bis type epoxy resin-based cationic electrodeposition paints, butadiene-acrylonitrile copolymers containing terminal carboxyl groups are used. In the case of coalescence, for example, the number average molecular weight is 3500.
As mentioned above, in the case of polyoxyalkylene polyamine, the number average molecular weight is 10,000 or more. When a non-crosslinked acrylic polymer obtained by emulsion polymerization is used in an acrylic resin-based electrodeposition coating, the number average molecular weight is generally 500.
o or above, and when using epoxidized polybutadiene added with an amine and unsaturated fatty acid for an epi-bis type epoxy resin-based cationic electrodeposition paint, a polybutadiene with a number average molecular weight of at least 2200 or more; When used in cationic electrodeposition paints, those having a number average molecular weight of at least 2,500 or more are selected.

The non-gelling polymer resin may be water-soluble or water-insoluble, and may be mixed directly with the electrodeposition paint film-forming resin or mixed directly into the water dispersion of the film-forming resin. Alternatively, it can be added and mixed into the electrocoating paint bath. If it is water-insoluble, it may be dispersed using a surfactant or a solvent. In addition, if it is water-soluble, the electrodeposition paint pI! Having an ionizable group with the same polarity as the film-forming resin has better paint stability.

The amount of internally crosslinked fine resin particles and/or non-gelling polymer resin to be contained in the electrodeposition paint is determined based on the solid content of the film-forming resin 1
The solid content is set in a range of 1 to 60 parts by weight, preferably 2 to 40 parts by weight per 00 parts by weight. This content is 1
If the amount is less than 60 parts by weight, the melt viscosity will hardly increase, so the effect of preventing denting, repelling, etc. caused by intermediate coating overdust mist will not be exhibited, and the corrosion resistance of the steel plate end face will deteriorate (on the other hand, if it exceeds 60 parts by weight) When the trI coating film is cured, the melt viscosity increases too much, resulting in problems such as loss of smoothness of the coating film.

Furthermore, in addition to water as a medium, the following additives, solvents, and pigments can be used in the electrodeposition paint as necessary.

Additives: Additives used when dispersing film-forming resins in aqueous media include, for example, formic acid in the case of cationic resins;
Acids such as acetic acid, lactic acid, and sulfamic acid, bases such as ammonia, amines, and inorganic alkalis in the case of anionic resins, and surface active side.

The concentration of the additive is usually preferably in the range of 0.1 to 15% by weight based on the solid content of the film-forming resin in the electrodeposition coating.

A solvent component used for the purpose of dissolving solvents/resins, adjusting the viscosity of paint films, and adjusting paints, such as kilns, hydrocarbons such as toluene, ethyl alcohol, n-butyl alcohol, isopropyl alcohol, and 2-ethylhexyl alcohol. Alcohols such as nor alcohol, ethylene glycol, propylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, propylene glycol monoethyl ether, 3-methyl 3-methquine butanol, diethylene glycol monoethyl ether,
Ethers such as diethylene glycol monobutyl ether, ketones such as methyl isobutyl ketone, nclohexanone, isophorone, acetylacetone, and esters such as ethylene glycol monoethyl ether acetate and ethylene glycol monobutyl ether acetate, singly or in mixtures. In this case, the solvent concentration for the electrodeposition paint is about 0.01 to 25% by weight, preferably 0.0%.
5 to about 15% by weight.

Pigments: For example, coloring pigments such as carbon black, graphite, titanium oxide, and zinc white, extender pigments such as aluminum silicate and kaolin, and rust-preventing pigments such as strontium chromate, basic lead silicate, basic lead sulfate, and aluminum phosphomolybdate. Alone or in mixtures.

The electrodeposition carried out in the first step of the present invention is carried out at a paint bath temperature of 2
0 to 40℃ 1 Applied voltage 50 to 500cm, Current application time is 30 seconds to 10 seconds with the object to be coated completely immersed in the paint bath.
It is conducted under conventionally used conditions such as minutes. The required thickness of the electrodeposited coating is 5 to 50 μm as a baked coating;
Preferably it is 10-35 μm.

After applying 1N2 coating, water is usually washed to remove excess paint, but if water is not drained properly after washing, dents, splashes, uneven finish, etc. may occur during the second painting process. It is advisable to thoroughly drain the water and blow with air as this may cause wrinkles.

The object to be coated which has been subjected to the T-deposition coating in the first step described above is transferred to the second step of wet-on-wet painting while the electrodeposition coating film is still uncured.

Usually, the second process is carried out as an intermediate coating, which is similar to the general interior coating for automobile exterior panels, and is made by curing resin materials such as polyester, alkynd, urethane-modified, polyester, and acrylic, and melamine resin, flocked isocyanate, etc. It is done using a paint whose main ingredient is a chemical.

In the present invention, the paint used for the intermediate coating or top coating in the second step contains a hydrophilic solvent of 15 to 100% by weight based on the total solvent used during coating, and if it contains a ketone solvent, the maximum content is 10% by weight. It is necessary to select and use a solvent composition that is %. When hydrophilic solvents fall below the above range, rough skin and foaming appear on the coating film, and ketone solvents
When it exceeds 0%, the mist becomes depressed.

Hydrophilic solvents include methyl alcohol, ethyl alcohol, isopropyl alcohol, tertiary phthyl alcohol, normal propyl alcohol, sec-butyl alcohol, isobutyl alcohol, normal butyl alcohol, activated amyl alcohol, isoamyl alcohol, normal amyl alcohol, and normal hexyl alcohol. Alcohols such as alcohol and Hensyl alcohol; propylene glycol monomethyl ether,
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, 3-methoxybutanol, ethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol motsuppi Ether alcohols and ethers such as ether and dioxane; esters and ethers such as methyl acetate, ethylene glycol monomethyl acetate, ethyl lactate, ethylene glycol monoethyl acetate, orthobutyl lactate, diethylene glycol monomethyl acetate, and diethylene glycol heptanoethyl ether Esters: Hydrophilic ketones such as acetone, methyl ethyl ketone, diethyl ketone, soclohexanone, methoxymethylpentanol, and diacetone alcohol can be mentioned.

Ketone solvents with a maximum content of 10% by weight include:
Examples include acetone, methyl ethyl ketone, diethyl ketone, cyclohexane, methoxymethylpentanol, diacetone alcohol, methyl isophthyl ketone, methyl amyl ketone, anone, diisobutyl ketone, isophorone, and cyclohexane.

In the second step of painting, the conditions for conventional intermediate coating or top coating can be applied as they are, and after painting, a baking hardening treatment is performed at the same time as the electrodeposition coating in the first step.

In addition, when a particularly high appearance is required, a painting process is adopted in which the surface of the intermediate coating film is polished and then a second intermediate coating treatment is applied. This secondary intermediate coating can also be applied under the same conditions as conventionally used in the intermediate finishing process for automobile exterior panels.

In addition, the conditions for applying a top coat directly or through an intermediate coat are the same as in the past, using metallic paint, clear paint, or colored paint other than metallic, and using methods such as air spray, electrostatic air spray, Hell-type electrostatic painting, etc. It can be done.

[For production]

According to the first coating film forming method of the present invention, the co-baking temperature after the electrodeposition coating and the intermediate coating can be lowered by adopting the first step using an electrodeposition coating whose coating film curing initiation temperature is 100 to 140°C. Therefore, a conventional intermediate coating process can be applied, and various defects caused by overhakes on the intermediate coating surface can be prevented. Moreover, fuel costs can be reduced.

Furthermore, in the second coating film forming method of the present invention, in addition to the low coating film curing initiation temperature, the electrodeposition coating composition is further made to contain a specific amount of internally crosslinked fine resin particles and/or non-gelling polymer resin. The paint composition is always controlled to a melt viscosity suitable for wet/on-wet painting, and prevents wrinkles, cracks, curing distortion, lack of gloss, lack of image clarity, lack of adhesion, as well as dents in the mist area, cypress, etc. It functions to effectively prevent the occurrence of such phenomena. Therefore, the second step of painting proceeds smoothly without causing any inconvenient phenomena.

Selection and adjustment of the solvent composition of the paint used in the second step reduces the influence of the solvent component on the electrodeposited coating surface during painting, and works together with the viscosity adjustment effect of the electrocoated paint described above to improve the coating surface. It functions effectively to prevent situations such as dents and pinholes from occurring.

Together, these effects make it possible to form a high-performance coating film that always has a high level of appearance, weather resistance, and chipping resistance.

Furthermore, if the present invention is applied, the baking process after electrodeposition coating is omitted, so for example, the process that conventionally required 3c3b (3 coats, 3 bakes) can be changed to 3c2b, and the high appearance painting of 4c4b can be changed to 4c3b. Since it becomes possible to do this, the number of painting steps is significantly reduced.

(Example) Hereinafter, the present invention will be explained based on examples.

Examples 1 to 17, Comparative Examples 1 to 6 Summer cropping bottom for locusts 0.8 m thick treated with zinc phosphate as the first step
Electrodeposition paint (■ ~ [phase] / Table 1) was applied to a dull steel plate of 28℃ at a bath temperature of 28°C, an applied voltage of 250■, and a current application time of 3 minutes to obtain a dry film thickness of about 25cm. An electrodeposited coating film was obtained.

Then, after washing the paint film with water, the air pressure was set to approximately 4 kg/cm.
Blow with compressed air, and after 2 minutes, apply the intermediate coating to a viscosity of 20.
The second step of painting was carried out by air spraying at a rate of 4 seconds (No. 4 feed cup) so that the dry film thickness was approximately 40 μm.

The first and second step coatings were baked and cured at the same time, but were allowed to set for 10 minutes at room temperature before the baking step.

The following examples and comparative examples are based on the basic process described above, and the properties and coating conditions of the electrocoating paint, the properties and coating conditions of the intermediate coating, and the addition of the secondary intermediate coating and top coating were applied. The obtained coating film 5 was subjected to an external appearance investigation and a water resistance test. The results are summarized in Table 322.

In addition, regarding Comparative Example 44, 1 at 160°C including electrodeposition coating film
This was done by baking and drying for 0 minutes and then applying an intermediate coat.

・＼ ′Aゝ 1 stirrer,
Nitrogen introduction pipe, temperature control device, condenser, decanter
1 part of ethylene glycol monomethyl ether (too much weight) was charged into a 2P colchen equipped with the following, and the temperature was raised to 100°C and maintained. Two dropping funnels were prepared, 100 parts by weight of ethylene glycol monomethyl ether was put into one, and 75 parts by weight of N-methyl-N-(vinylhensyl)taurine was dissolved therein. At this time, a small amount of dimethylethanolamine was added as a solubilizing agent.

Furthermore, in one dropping funnel, 50 parts by weight of 2-hydroquine ethyl acrylate, 10 parts by weight of acrylic acid, 110 parts by weight of methyl methacrylate, 110 parts by weight of styrene,
145 parts by weight of n-butyl acrylate and 10 parts by weight of uralyl mercaptan were mixed, and 7 parts of 10 parts by weight of bisisobutyronitrile were dissolved in the mixture.

The contents of the two dropping funnels were allowed to drip for 120 minutes, after which the temperature was maintained at 100'C and stirring continued for 60 minutes. Next, the solvent of this resin solution was removed using a rotary evaporator, and the resin solid content was 96% and the number average molecular weight was 45.
00 acrylic resin was obtained.

After stirring, charge 306 parts by weight of deionized water, 18 parts by weight of the acrylic resin obtained in the above step, and 2.6 parts by weight of dimethylethanolamine into a 1P reaction vessel equipped with a cooling tube and a temperature control device, without stirring. The temperature was raised to 80°C. After the contents were dissolved, the temperature was maintained at 80°C while stirring, and an aqueous solution consisting of 4.8 parts by weight of azobisuneanovaleric acid, 4.5631 parts by weight of dimethylethanolamine, and 48 parts by weight of deionized water was charged. is. Next, 26.6 parts by weight of styrene, 79.8 parts by weight of methyl methacrylate, 53.2 parts by weight of n-butyl acrylate, 53.2 parts by weight of ethylene glycol dimethacrylate, 53.2 parts by weight of ethyl acrylate, and 16 parts by weight of diethylaminoethyl acrylate. A mixed solution consisting of 0 parts by weight was added dropwise over a period of 60 minutes.

After dropping, a mixed aqueous solution consisting of 1.2 parts by weight of azobiscyanovaleric acid, 1.14 parts by weight of trimethylethanolamine and 12 parts by weight of deionized water was further added at the same temperature.
After stirring for 0 minutes, the particle size was 146 nm and the degree of crosslinking was 0.
Cationic internally crosslinked fine resin particles having a concentration of 953 mmol/g and a non-volatile content of 45% were obtained.

74.711 parts of styrene, 74.7 parts by weight of methyl methacrylate, 99.6 parts by weight of n-butyl acrylate, 30 parts by weight of 2-hydroxyethyl acrylate, and 3 parts by weight of ethylene glycol dimethacrylate. The particle size was 132 nm and the degree of crosslinking was 0. 054 mmol/g,
Anionic internally crosslinked fine resin particles having a non-volatile content of 45% were obtained.

Ichiruhi's report by Suga I "'Chefamine D-2000" [Molecular weight is 2゜OO
Jefferson Chemical Co.
1,000 parts by weight of polyoxylapropylene diamine (l) from nChemical Company was charged into a reaction vessel under nitrogen gas, heated to 90°C, and then
R-723” [Dow Chemical Company (now Chemi
Cal Company) Commercially available number average molecular placement piece 752
285 parts by weight of polypropylene glycol jepoxy resin) and 10 parts by weight of ethylene glycol monoethyl ether
0 parts by weight were added. The reaction mixture was heated to 110°C and held for 2 hours, then 25 parts by weight of acetic acid, 287 parts by weight of deionized water
0 parts by weight to obtain a non-gelling polymer resin with a non-volatile content of 30%.

1000 parts by weight of diglycidyl ether of bisphenol A (epoxy equivalent: 910) of the cation I was dissolved in 463 parts by weight of ethylene glycol monoethyl ether while maintaining the temperature at 70"C with stirring, and further 80.3 parts by weight of diethylamine was added. A reaction was carried out at 100° C. for 2 hours to obtain a cationic base resin (a).

80/20 mixture of toluene diisonoanate/2,6-toluene diisocyanate charged in a reaction vessel 2 TD1) 174 parts by weight 4 8 parts by weight of this methyl ethyl ketone oxime was gradually added dropwise while keeping the reaction temperature below 50° C. using an external cooler to obtain a half-flock isocyanate. Next, 45 parts by weight of trimethylolpropane and 0.05 parts by weight of diptyltin dilaurate were added, and the mixture was reacted at 120°C for 90 minutes. The obtained reaction product was diluted with 131 parts by weight of ethylene glycol monoethyl ether to obtain blocked polyisocyanate (b).

Toluene diisocyanate (2,4-) toluene diisocyanate/2,6-toluene diisocyanate 8 charged in a reaction vessel of Frobo 1 isocyanate C
0/20 mixture) 30.5 parts by weight of methyl ethyl ketone oxime was added to 174 parts by weight and the reaction temperature was adjusted to 50% by external cooling.
While keeping the temperature below ℃, slowly add it dropwise to allow complete reaction.
Subsequently, 60.9 parts by weight of furfuryl alcohol was reacted completely in the same manner, and further 35.4 parts by weight of ethylene glycol monobutyl ether were reacted in the same manner to obtain a half-block isocyanate.

Next, 45 parts by weight of trimethylolpropane and 0.05 parts by weight of dibutyltin dilaurate were added, and the mixture was heated at 120'C.
The reaction was carried out for 90 minutes. The obtained reaction product was diluted with 148 parts by weight of ethylene glycol monoethyl ether,
Block polyisocyanate (c) was obtained.

Pro Kupo! Toluene diisocyanate (2,4
-) toluene diisocyanate/2.6- 80/20 mixture of toluene diisocyanate: TDr) 1741
130 parts by weight of 2-ethylhexyl alcohol per 1 m,
While maintaining the reaction temperature at 50° C. or lower by external cooling, the mixture was gradually added dropwise to obtain a half-block isocyanate. Next, 45 parts by weight of trimethylolpropane and 0.05 parts by weight of dibutyltin dilaurate were added, and the mixture was heated at 120°C.
The reaction was allowed to proceed for 0 minutes. The obtained reaction product was diluted with 15 parts of ethylene glycol monoethyl ether (11 parts) to obtain pronoc polyisonate (d).

・Pace's cationic base resin (a) 150 parts by weight glacial acetic acid
6.4 Deionized water
278.6 Carbon black 20 Titanium oxide 122 Kaolin
40 Basic lead silicate 28 Dibutyltin oxide 15 Based on the above formulation, add glacial acetic acid and deionized water to the cationic base resin (a) to dissolve it, then add the pigment and diptyltin oxide and dissolve in a disper. Stirred for about 1 hour. Glass peas were added to this mixture, dispersed in a sand mill to a particle size of 20 nm or less, and the glass peas were filtered out. The resulting pigment paste had a non-volatile content of 50%.

After neutralizing the main component resin consisting of 220 parts by weight of cationic base resin (a) and 146 parts by weight of blocked polyisocyanate (b) with 4.8 parts by weight of glacial acetic acid, 271.2 parts by weight of deionized water was added. A resin composition having a nonvolatile content of about 40% by weight was obtained.

Next, 275 parts by weight of pigment paste and 11 parts by weight of deionized water
89 parts by weight were gradually added while stirring at room temperature to prepare a composition (2) for cationic electrodeposition coating.

The cationic electrodeposition paint of the example was prepared according to the above procedure (■) except that the cationic ~ ~blocked polyisocyanate (B) and the internally crosslinked fine resin particles (A) and/or the non-gelling polymer resin were added in different amounts. Compositions ■～■ and Comparative Example Compositions ■～ for Cationic Electrodeposition Paints
@ and [phase] were prepared.

Anion ・9 Into a flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser tube, 520 parts by weight of an epoxy resin obtained by the reaction of bisphenol A and epichlorohydrin with a number average molecular weight of 500 and 1250 parts by weight of epoxy resin was charged. Add and dissolve 289 parts by weight of isobutyl ketone, add N methyl ethane and 154 parts by weight of nolamine under a nitrogen stream, and continue the reaction at a reaction temperature of 80°C until the epoxy value becomes 0. 1087 parts by weight of half-fluoroquiisophorone diisonorate stearate (
solid content) and react at 60°C until the absorption of isonoanate groups disappears in the infrared spectrum.
Next, 238 parts by weight of ε-cabralactone and 1.0 parts by weight of dibutyltin oxide were added, and the reaction was carried out at 120°C for 8 hours to obtain an α, ω-
Obtained a resin gold structure.

On the other hand, pigment paste B was prepared using 12.0 parts by weight of a dispersant (nonylphenol polyethylene ethyne-phosphate ester), 160 parts by weight of aluminum silicate, 220 parts by weight of Bengara, 20 parts by weight of strontium chromate, and 189 parts by weight of deionized water. was prepared. Next, resin A near 0
Part by weight (solid content) and methylated melamine resin (number average molecular weight: 500, unprocessed content: 100% manufactured by Nippon Pein If)
.

Add 30 parts by weight (solid content), remove the solvent, add triethylamine so that the neutralization rate is 50%, then add 40 parts by weight (solid content) of pigment paste) B, stir, and then ion exchange. Anionic electrodeposition coating composition (2) was obtained by diluting water to a solid content of 15%.

An anionic electrodeposition coating composition [phase] of the example was obtained in accordance with (2) above, except that the internally crosslinked fine resin particles (B) were added in an amount of 11 tons.

Anion tank - Into a flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, 1059 parts by weight of an epoxy resin with an epoxy equivalent of 250 and a number average molecular weight of 500, obtained by the reaction of bisphenol A and epichlorohydrin, was added to methyl isobutyl. It was dissolved in 588 parts by weight of ketone and reacted with 314 parts by weight of N-methylethanolamine and 627 parts by weight of phthalic anhydride. This was diluted to a nonvolatile content of 70% with 268 parts by weight of methyl isobutyl ketone to obtain resin a having an acid value of 82.8.

Composition (2) for anionic electrodeposition paint was obtained in the same manner as (2) above, except that resin a was used in place of the α,ω-Sudare II forming resin in composition (2) for anionic electrodeposition paint.

Table 1 shows the composition of each electrodeposition paint prepared above.

The coating film curing start temperature of each electrodeposition paint was determined using a pendulum type viscoelasticity measuring device (made by SENTSUKU, FDOM 0DEL 001).
When measured under the following conditions: weight 7.83 g, vibration period 0.71 seconds, pendulum length 18 cm, heating rate 20°C/min, the logarithmic damping rate of the coating film increased from the minimum value. It was calculated as the temperature at the bending point.

Main] Ue Ebe The intermediate coating is Conventionally, using a paint with the composition shown in Table 2, This was done under the following painting conditions.

Upper J-bi [equipment] Painted as shown below.

(a) Acrylic melamine Silhar hair coat (15
After painting (μ steel), apply wet-on-wet acrylic melamine clear coat (30μm).

(b) Alkyd melamine branoxolind color (4
0μm).

(C) Alkyd melamine white solid color (4
0μm).

i, F) 'Amount,' - (1) Process reduction effect O... Reduction effect exists ×... No reduction effect 2)
Paint film appearance (visual judgment) General surface: ◎...Very good O...Good△...
Slightly abnormal ×...Abnormal Part of intermediate coating overspray: O...Very good O...Good △...Slight dent and adhesion 20...No abnormality ×... Abnormalities ×...Dents present (3) Water resistance Visual appearance after immersion in 50°C warm water for 10 days [Effects of the invention] As described above, according to the coating film forming method of the present invention, the wet period was shortened.・Constant appearance due to on-wet painting process
A high-performance coating film with excellent weather resistance and chipping resistance can be formed.

Therefore, it is extremely useful as a coating process for automobile exterior panels, which particularly requires a high-quality coating film appearance.

Applicant: Nippon Paint Co., Ltd. Agent: Patent Attorney Masaya Takahata

Claims (1)

[Claims] 1. A coating film forming method characterized by sequentially performing the following steps. (1) The coating material has a coating film curing start temperature of 100 to 140°C.
The first step is to apply the electrodeposition paint. (2) When the electrodeposition coating film obtained in the first step is uncured,
A second step of applying a paint having a maximum content of 15 to 100% by weight of a hydrophilic solvent and a ketone solvent based on the total solvent used at the time of application is 10% by weight. (3) A third step of simultaneously curing the electrodeposited film from the first step and the paint film from the second step. 2. A coating film forming method characterized by sequentially performing the following steps. (1) The object to be coated contains 1 to 60 parts by weight of internally crosslinked fine resin particles and/or non-gelling polymer resin as a solid content based on 100 parts by weight of the solid content of the coating film forming resin, and the coating film begins to harden. The first step is to apply electrodeposition paint at a temperature of 100 to 140℃.
Process. (2) When the electrodeposition coating film obtained in the first step is uncured,
A second step of applying a paint in which the maximum content of hydrophilic solvents and ketone solvents is 15 to 100% by weight based on the total solvent used at the time of coating, and is 10% by weight. (3) A third step of simultaneously curing the electrodeposited coating film from the first step and the coating material from the second step.