KR20040082338A - Method for coated composite film - Google Patents

Abstract

PURPOSE: A preparation method of a coated composite film is provided to produce a film excellent in anti-chipping and an appearance, particularly gloss by a three-coat one-bake process. CONSTITUTION: The preparation method of a coated composite film comprises the steps of: forming an electrically coated film on a substrate, applying an intermediate paint, a base paint and a transparent paint continuously in a wet-on-wet process and then baking and hardening the applied three layers at one time, wherein the baking and hardening comprises a low temperature heating step for heating at a temperature of 25 to 80% of a hardening temperature for a time of 5 to 30% of a hardening time and a high temperature heating step for heating at a temperature of 80 to 120% of a hardening temperature for a time of 30 to 130% of a hardening time.

Description

Manufacturing method of coated composite film {METHOD FOR COATED COMPOSITE FILM}

The present invention relates to a method for producing a coated composite film, and more particularly to a method for producing a coated composite film by a three-coat one-bake method.

There are two methods for producing the coated composite film. One method is to bake and cure all coated films after coating. Another is a method of making a coated composite film by coating two or more coatings without curing and then curing them all at once. For example, a two coat one firing method is commonly carried out to form a metal coating. JP-A 11-114489 discloses a coated composite comprising successively forming a color base coating film, a metal base coating film and a transparent coating film and then simultaneously firing and curing three layers to improve film appearance. A method of making a film is disclosed.

In the case of forming the intermediate coating film, the base coating film and the transparent coating film by the three coating single baking method, the baking oven for curing the intermediate coating can be eliminated. Thus, the energy and operating time consumed are reduced, which is greatly beneficial in terms of economics and environmental friendliness.

However, in the three coating one firing method, the three layers of the coating film are in a wet or semi-dry state. For this reason, the escape route of the solvent is reduced and limited, so that the nonvolatile components in the coated composite film are increased when compared with the conventional continuous firing method or the two-coating single firing method. As a result, the solvent contained in one coating film migrates to the adjacent coating film, especially when heated. This solvent migration easily increases the phenomenon that adjacent coating films, called phase mixing, in firing and curing are dissolved in each other so that the components contained in each coating film are mixed. If phase mixing occurs, the appearance of the resulting composite film deteriorates considerably. In particular, phase mixing has a significant adverse effect on the appearance gloss of the coated composite film.

On the other hand, JP-A 2000-84463 proposes a method of forming a coating film excellent in flatness by using a solution thermosetting paint, and a method of carrying out a firing and curing step under two heating conditions. In this method, roughness of the coating film surface is prevented by the relaxed evaporation solvent contained in the coated layer.

However, the three coating one firing method has the following problems, for example:

In some cases, the coating film is peeled off by the so-called chipping when the gravel is splashed by the running vehicle and collides with the coating film. In conventional coated composite film production methods, such as firing each coating and coating two coatings, the bottom coating film and the intermediate coating film are fired and cured independently. Thus, an anti-chipping coating film is formed on or below the intermediate coating film, or the brightness of the topcoating film and the brightness of the intermediate coating film are adjusted to form an intermediate coating film where no chipping is recognized. As a result, a method of processing chipping can be adopted.

For example, JP-A 2002-249699 and JP-A 9-208882 describe chipping primer coating compositions and methods of forming anti-chip coating films on coated composite films.

In addition, although JP-A 6-256714 or JP-A 6-254482 has been studied to improve the chipping prevention properties in terms of the composition of the intermediate coating, the degree of improvement is insufficient to be used in the three-coating single firing method.

SUMMARY OF THE INVENTION The present invention solves the conventional problems, and an object of the present invention is to provide a method for producing a coated composite film having excellent appearance, in particular glossiness, and anti-chipping properties, by a three-coating single firing method.

The present invention,

Forming an electrocoated film on the substrate, successively applying an intermediate paint, a base paint and a transparent paint in a wet-on-wet manner, and then firing and curing all three applied layers at once. and;

At this time, the firing and curing are performed at a low temperature heating step of heating at a temperature of 25 to 80% of the curing temperature for a time of 5 to 30% of the curing time, and at least 80% of the curing temperature for a time of 30 to 130% of the curing time. A high temperature heating step of heating at a temperature of 120% or less,

It provides a method for producing a coated composite film.

Coating film forming

In the method of manufacturing the coated composite film of the present invention, the intermediate coating film by the intermediate paint, the base coating film by the base paint, and the transparent coating film by the transparent paint, wet-on-wet (wet-wet) method It is formed continuously on the substrate.

When an automobile body is used as a substrate, as an anti-corrosion film (generally called an "undercoat film"), an electrodeposition film is previously formed on the body steel sheet. In the method of applying the intermediate paint, the paint is applied by a multi-step coating, preferably by a two-step coating via air electrostatic spray coating, or by a "μ (micro micro) bell", "μ (micro) The film can be formed by a combination coating method of a rotation atomizing electrostatic coating machine called a "bell" or "metabell" and an air electrostatic spray coating.

The thickness of the dried coating film made of the intermediate paint varies depending on the intended use. In many cases, a thickness of 10 to 60 μm is useful. When the thickness exceeds the upper limit, the transparency is reduced, and in some cases, the disadvantage is that the coating is uneven or completely extinguished. If the thickness is less than the lower limit, the surface may be concealed and a non-smooth coating may be formed.

In the coated composite film production method of the present invention, on the uncured intermediate coating film, the base paint and the transparent paint are coated in a wet-wet manner to form the base coating film and the transparent coating film.

The base paint used to form the base coating film can be applied by electrostatic spray coating or by using a rotary spray electrostatic coating machine such as metabell, μ bell, μ bell and the like. The dried thickness of the coating film may be set to 5 to 35 μm, preferably 7 to 25 μm. When the thickness of the base coating film exceeds 35 μm, the sharpness is reduced and in some cases it is not smooth or completely out. If the thickness is less than 5 μm, surface concealability is insufficient and in some cases an unsmooth coating (discontinuous film state) occurs.

When irregularities are present or the gloss pigment is contained due to the base coating film, a transparent coating film is formed to protect the film by hiding the minute irregularities generated therefrom. As a coating method, it is particularly desirable to form the coating film with a rotary spray electrostatic coater such as μ bell, μ bell and the like.

The dry thickness of the transparent coating film is preferably about 10 to 80 mu m, more preferably about 20 to 60 mu m. When the thickness exceeds the upper limit, in some cases, a disadvantage arises in that the lid and the lid are extinguished upon application. When the thickness is less than the lower limit, the surface irregularities cannot be concealed.

The coated composite film is then cured by simultaneous heating. This method is generally referred to as three coating, one firing method. The film thickness of the coated composite film is usually 30 to 300 mu m, preferably 50 to 250 mu m. If the thickness exceeds the upper limit, the physical properties of the film, such as temperature cycle tests, are reduced. If the thickness is less than the lower limit, the strength of the film is reduced.

In order to sufficiently cure the coated layer applied to the substrate surface, curing conditions are set for the thermosetting paint. When the thermosetting paint cures under conditions that do not satisfy the curing conditions, the crosslinking of the coated composite film is insufficient, and the coated composite film performance is reduced. Generally, as curing conditions of the thermosetting paint, a curing temperature (° C.) and a curing time are set.

The curing temperature refers to the temperature of the environment in which the coated composite film is placed when the coated film is baked and cured by a conventional one-step heating method. Generally, it is the temperature set for the drying oven into which the coated composite film is inserted. The curing temperature is determined depending on the reaction temperature of the crosslinking system of the coated composite film and the ease of practical application line applied.

Curing time refers to the time required to cure the coated composite film at the curing temperature. With the curing time, the optimum value is determined experimentally depending on the type of paint and the thickness of the coated composite film. The curing time is determined by the time at which the substantially required coated composite film performance is obtained, taking into account the ease and curing temperature of the actual application line applied.

In the process of the invention, the step of calcining-curing the coated three layers is divided into a low temperature heating step, an alc high temperature heating step, and each step is carried out for a predetermined time. When the low temperature heating step is carried out within a short time, the entire heating time is not quite long and the working efficiency is not reduced. By carrying out the low temperature heating step, the deposited volatile components can be increased, thus preventing layer mixing from occurring.

In the low temperature heating step of the present invention, the thermosetting paint layer formed on the surface of the substrate is 5 to 30% of the curing time, preferably 10 to 20, at a temperature of 25 to 80% of the curing temperature, preferably 35 to 60%. Heated for% time. If the curing temperature and curing time are out of the range, the technical effect is insufficient. For example, when the curing temperature is 140 ° C, the low temperature heating temperature is 35 to 112 ° C, preferably 49 to 84 ° C. When the curing temperature is 100 ° C, the low temperature heating temperature is 25 to 80 ° C, preferably 35 to 60 ° C. Furthermore, when the curing time is 30 minutes, the low temperature heating time is 2 to 9 minutes, preferably 3 to 6 minutes. When the curing time is 60 minutes, the low temperature heating temperature is 3 to 18 minutes, preferably 6 to 12 minutes.

In the high temperature heating step, the thermosetting paint layer is further heated at a temperature of 80% or more and 120% or less, preferably 90 to 110% of the curing temperature, for a time of 30 to 130% of the curing time, preferably 50 to 100%. do. If the curing temperature and curing time exceed the upper limit, stress builds up and in some cases cracks occur in the coated composite film. For example, when hardening temperature is 140 degreeC, high temperature heating temperature is 112 degreeC or more and 168 degreeC, Preferably it is 126-154 degreeC. When curing temperature is 100 degreeC, high temperature heating temperature is 80 degreeC or more and 120 degrees C or less, Preferably it is 90-110 degreeC. Furthermore, when the curing time is 30 minutes, the high temperature heating time is 10 to 40 minutes, preferably 15 to 30 minutes. When the curing time is 60 minutes, the high temperature heating time is 18 to 78 minutes, preferably 30 to 60 minutes.

Heating is carried out using methods known to those skilled in the art. Generally, articles coated with a thermoset paint may be housed in a drying oven controlled to a high temperature.

In particular, the method may include the following process:

Placing the article to be coated, which is coated with a thermosetting paint, in a drying oven accommodated for a low temperature heating time and controlled at a low temperature heating temperature, and then accommodated for a high temperature heating time and adjusting the temperature of the drying oven to a high temperature heating temperature;

Prepare a tunnel type dryer with the inlet and outlet open at both ends, divide the inside of the tunnel into a low temperature section and a high temperature section, adjust the temperature of the low temperature section with the low temperature heating temperature, and adjust the temperature of the high temperature section with the high temperature heating temperature. Passing the object through the low temperature portion for a time period, and then moving the object through the high temperature portion during the high temperature heating time while moving the object into the tunnel by the belt conveying device; And

Prepare the first drying oven adjusted to the temperature of the low temperature heating temperature, and the second drying oven adjusted to the temperature of the high temperature heating temperature, and then the article to be coated with the thermosetting paint coated thereon in the first drying oven for the low temperature heating time. Accommodating and storing the goods in a second drying oven during the high temperature heating time.

Middle coating film

In the coating film manufacturing method of the present invention, an intermediate paint is used to prepare an intermediate coating film, and the intermediate paint is (a) urethane-modified polyester resin, (b) melamine resin, (c) blocked isocyanate compound, ( d) non-aqueous dispersion resins having a core-shell structure, and (e) flaky pigments. The intermediate paint may further comprise organic or inorganic various colored pigments and filler pigments.

The urethane-modified polyester resin (a) can be obtained by reacting a hydroxyl group-containing polyester resin with an aliphatic isocyanate compound.

Generally, polyester resins can be prepared by polycondensing monovalent or polyhydric alcohols with acid components such as carboxylic acids, acid anhydrides and acid chlorides. The hydroxyl group-containing polyester resin used in the present invention contains at least 80 mol% (based on the total moles of acid components) of isophthalic acid in the acid component used in the polycondensation reaction. When the amount of isophthalic acid in the acid component is less than 80 mol%, the glass transition temperature (Tg) of the resulting hydroxyl group-containing polyester resin is lower than the desired range.

Examples of acid components other than isophthalic acid include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, forceic anhydride, trimellitic acid, and trimeric Mellitic anhydride, pyromellitic acid, pyromellitic anhydride, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, succinic anhydride, dodecenyl succinic acid, dodecenyl succinic anhydride And the like. Alternatively, the acid component may contain an acid other than the polyhydric carboxylic acid and acid anhydride conventionally used in the preparation of the polyester resin. Examples of such acids are monocarboxylic acids and hydroxycarboxylic acids. As the acid used to prepare the hydroxy group-containing polyester resin, isophthalic acid can be used alone or in combination with other acids.

Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2, 3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, 2,2-dimethyl-3-hydroxypropyl-2,2-dimethyl-3-hydroxypropio Nate, 2,2,4-trimethyl-1,3-pentanediol, polytetramethylene ether glycol, polycaprolactone polyol, glycerin, sorbitol, anitol, trimethylolethane, trimethylolpropane, trimethylolbutane, hexanetriol , Pentaerythritol, dipentaerythritol, and the like.

In the preparation of the hydroxyl group-containing polyester resin, in addition to the acid component and the polyhydric alcohol, other components that can react with these components may be used. Examples of these other components include acid chlorides, acid derivatives of lactones, epoxide compounds and dry oils and semi-dry oils and fatty acid derivatives thereof. Lactone can form graft chains by ring-opening addition of polyhydric carboxylic acids and polyhydric alcohols to polyester resins. Examples of lactones include β-propiolactone, dimethyl propiolactone, butyl lactone, γ-valerolactone, ε-caprolactone, γ-caprolactone, γ-caprylactone, crotolactone, δ-valerolactone, ? -caprolactone and the like. In particular, ε-caprolactone is most preferred. Specific examples include lactones and monoepoxide compounds such as Carjula E (manufactured by Shell Chemical Co., Ltd.).

The hydroxyl group-containing polyester resin has a glass transition temperature (Tg) of 40 to 80 ° C, preferably 45 to 75 ° C. When the glass transition temperature (Tg) is less than 40 ° C, the film hardness decreases. When the glass transition temperature is higher than 80 ° C., the chipping prevention performance is reduced.

Examples of aliphatic isocyanate compounds include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, methylcyclohexane diisocyanate and isophorone diisocyanate. Include.

In particular, it is preferable to use hexamethylene diisocyanate or trimethylhexamethylene diisocyanate from the viewpoint of the chipping prevention performance and weather resistance of the coating film. Burettes, isocyanurates and adducts thereof may also be used.

By a method known to those skilled in the art, the reaction of the hydroxy group-containing polyester resin with the aliphatic isocyanate compound can be carried out.

The urethane-modified polyester resin (a) has a number average molecular weight (Mn) of 1,500 to 3,000, preferably 1,700 to 2,500. If the molecular weight is less than 1500, coating workability and curability are not sufficient. If the molecular weight exceeds 3,000, the nonvolatile fraction becomes too small during application, and the coating workability deteriorates backwards. In the present application, the number average molecular weight is determined by the GPC method using polystyrene as a reference.

The urethane-modified polyester resin (a) preferably has a hydroxyl group value (OHV) of 30 to 180, more preferably 40 to 160. If the hydroxyl group value exceeds 180, the water resistance of the coating film is reduced. When the hydroxyl group value is smaller than 30, the hardenability of the coating film is reduced. In addition, the resin preferably has an acid value (AV) of 3 to 30 mgKOH / g, more preferably 5 to 25 mgKOH / g. If the acid value exceeds 30 mgKOH / g, the water resistance of the coating film is reduced. When the acid value is less than 3 mgKOH / g, the hardenability of the coating film is reduced.

The amount of urethane-modified polyester resin (a) contained in the intermediate paint is 40 to 56% by weight, preferably 43 to 50% by weight, based on the weight of the resin solids content in the paint. When this amount is less than 40 weight%, chipping prevention performance will become inadequate. When this component exceeds 56% by weight, the hardness of the coating film is reduced.

By including the urethane-modified polyester resin as a component of the intermediate paint, it is believed that the elasticity of the coating film is improved and the anti-chipping properties of the coating film are also improved.

The melamine resin (b) and the blocked isocyanate compound (c) described below are components for curing the urethane-modified polyester resin (a).

The melamine resin (b) is not particularly limited, but a methylated melamine resin, a butylated melamine resin or a methyl-butyl mixed melamine resin can be used. Examples include "Cymel 303", "Cymel 254", "Urban 128" and "Urban 20N60" available from Mitsui Toatsu Co., Ltd., and Sumitomo Chemical Company, Limited (Sumitomo). Chemical Co., Ltd.) and "Sumimar Series" commercially available.

The amount of melamine resin (b) contained in the intermediate paint is 10 to 30% by weight, more preferably 15 to 25% by weight, based on the weight of the resin solids content in the paint. When the content of the melamine resin is less than 10% by weight, curing of the coated composite film becomes insufficient. If the content is more than 20% by weight, the cured coated composite film is too hard and brittle.

Blocking isocyanate compounds (c) can be obtained by adding blocking agents to aliphatic isocyanates or derivatives thereof. When heating the blocked isocyanate compound, the blocking agent dissociates to produce isocyanate groups, which react with the hydroxyl groups of the urethane-modified polyester resin to cure the material.

Examples of aliphatic isocyanates and derivatives thereof include compounds used in the preparation of urethane-modified polyester resins. Examples of blocking agents include compounds having active methylene groups such as acetyl acetone, ethyl acetoacetate and ethyl malonate. By using a blocking agent, the film is improved in elasticity and the anti-chipping properties of the film are also improved.

Blocked isocyanate compounds are commercially available, for example, as "Duranate MF-K60X" which is an active methylene-type blocked isocyanate from Asahi Chemical Industry Co., Ltd.

The amount of blocked isocyanate compound (c) contained in the intermediate coating paint may be 15 to 30% by weight, preferably 17 to 25% by weight, based on the weight of the resin solids content in the paint. When this amount is less than 15 weight%, sclerosis | hardenability becomes inadequate. If this amount exceeds 30% by weight, the cured film becomes too hard and easily breaks.

A non-aqueous dispersion resin (d) having a core-shell structure was prepared by copolymerizing a monomer copolymerizable with the dispersion stability resin in a mixed solution with an organic solvent to obtain a resin as uncrosslinked resin particles insoluble in the mixed solution. can do. The monomers copolymerized in the presence of dispersion stable resins to obtain uncrosslinked resin particles are not particularly limited as long as they are radical-polymerizable unsaturated monomers.

In order to synthesize the dispersion stability resin and the non-aqueous dispersion, it is preferable to use a polymerizable monomer having a functional group, because the non-aqueous dispersion having the functional group reacts with the curing agent together with the dispersion stability resin containing the functional group in three dimensions. Because it can form a crosslinked coated composite film.

The dispersion stability resin is not particularly limited as long as the non-aqueous dispersion can be stably synthesized in an organic solvent. Specifically, a hydroxyl group value of 10 to 250, preferably 20 to 180, an acid value of 0 to 100 mgKOH / g, preferably 0 to 50 mgKOH / g, and a number average of 800 to 100,000, preferably 1,000 to 20,000 It is preferable to use an acrylic resin having a molecular weight, a polyester resin, a polyether resin, a polycarbonate resin, a polyurethane resin and the like. If these variables exceed the upper limit, the handling properties of the resin are reduced and the handling properties of the non-aqueous dispersion itself are also reduced. If the parameters are below the lower limit, there is a possibility that the coated film is peeled off and the stability of the particles is reduced when formulated into the coating film.

The method of synthesizing the dispersion stable resin is not particularly limited, but preferably includes a method of obtaining a resin by radical polymerization in the presence of a radical polymerization initiator and a method of obtaining a resin by a condensation method or an addition reaction. In addition, the monomers used to obtain the dispersion stable resins described above may be appropriately selected depending on the properties of the resins, but the functional groups (e.g., hydrates) treated by the polymerizable monomers described thereafter used to synthesize the non-aqueous dispersions may be used. It is preferable to use a monomer having a hydroxyl group, an acid group, etc.), and if necessary, a monomer having a functional group such as glycidyl group, isocyanate group or the like may be used.

In addition, the weight ratio of the dispersion stable resin and the polymerizable monomer may be arbitrarily selected according to the purpose. For example, it is preferred that the dispersion stability resin is 3 to 80% by weight, in particular 5 to 60% by weight and 97 to 20% by weight, especially 95 to 40% by weight, based on the total weight of the two components. In addition, the total concentration of the dispersion stable resin and the polymerizable monomer in the organic solvent is preferably 30 to 80% by weight, in particular 40 to 60% by weight, based on the total weight.

Non-aqueous dispersions can be obtained by polymerizing radically polymerizable monomers in the presence of dispersion stable resins. In the non-aqueous dispersion, the hydroxyl value is 50 to 400, preferably 100 to 300, the acid value is 0 to 200 mgKOH / g, preferably 0 to ₅₀ mgKOH / g, and the average particle diameter (D ₅₀ ) is 0.05 to It is preferable that it is 10 micrometers, Preferably it is 0.1-2 micrometers. Particle morphology cannot be maintained if these variables are below the lower limit. If the variables exceed the upper limit, they are less stable when dispersed in paint.

Representative polymerizable monomers having functional groups used to synthesize non-aqueous dispersions are hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxymethyl (meth) Monomers having hydroxyl groups such as acrylate, allyl alcohol, and adducts of hydroxyethyl (meth) acrylate and ε-caprolactone.

On the other hand, examples of the monomer having an acidic group include a polymerizable monomer having a carboxyl group, a sulfonic acid group and the like. Examples of the monomer having a carboxyl group include (meth) acrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, fumaric acid and the like. Examples of polymerizable monomers having sulfonic acid groups include t-butylacrylamide sulfonic acid and the like. When using a polymerizable monomer having an acidic group, it is preferable that a part of the acidic group is a carboxyl group.

Further examples of polymerizable monomers having functional groups include glycidyl group-containing unsaturated monomers such as glycidyl (meth) acrylate, and m-isopropenyl-α, α-dimethylbenzyl isocyanate, isocyanatoethyl acrylate Isocyanate group-containing unsaturated monomers such as the like and the like.

Examples of other polymerizable monomers are methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (Meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate and tri (Meth) acrylic acid alkyl esters such as decyl (meth) acrylate; Addition reaction products of an acrylic acid or methacrylic acid ester monomer having an oxirane structure and an oil fatty acid (e.g., an addition reaction product of stearic acid and glycidyl methacrylate), an oxirane compound containing an alkyl group having at least C ₃ and acrylic acid or Addition reaction products of methacrylic acid, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, pt-butylstyrene, benzyl (meth) acrylate, itaconic acid esters (dimethyl itaconate ), Maleic acid ester (dimethyl maleate), fumaric acid ester (dimethyl fumarate), and acrylonitrile, methacrylonitrile, methylisopropenyl ketone, vinyl acetate, Veoba Monomer (Shell Chemical Company, Limited, trade name) ), Vinyl propionate, vinyl pivalate, ethylene, propylene, butadiene, N, N-dimethylaminoethyl acrylate, N, N-dimethyl Mino methacrylate, acrylamide and vinylpyridine include other polymerizable monomers, such as.

In the presence of a radical polymerization initiator, preference is given to carrying out the polymerization reaction to obtain a non-aqueous dispersion. Examples of radical polymerization initiators include azo-based initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile), benzoyl peroxide, lauryl peroxide, t-butyl peroctoate and the like. It is preferable that the amount of these initiators is 0.2 to 10 parts by weight, preferably 0.5 to 5 parts by weight per 100 parts by weight of the total polymerizable monomer. It is preferred that the polymerization reaction for obtaining a non-aqueous dispersion in an organic solvent containing a dispersion stable resin is usually carried out at about 60 to 160 ° C. for 1 to 15 hours.

In addition, the non-aqueous dispersion is a particle component in paint different from the crosslinked polymer fine particles, but has a feature of not forming a particle structure in the coating film. That is, the non-aqueous dispersion is different from the crosslinked polymer fine particles in that the particles do not have a crosslinking site and the particle shape changes during the firing process, which may be a resin component.

As well as, for example, Coloring Material, vol. 48 (1975), pp. 28-34, also referred to as NAD (non-aqueous dispersion), and resin particles used in NAD coatings can also be used.

The amount of the non-aqueous dispersion resin (d) contained in the intermediate paint is 4 to 15% by weight, preferably 5 to 12% by weight based on the weight of the resin solids content. When this amount exceeds 15% by weight, the chipping prevention performance is reduced.

By using the non-aqueous dispersion resin (d), it is easy to control the interface of the coating film and the final appearance is improved.

As the flaky pigment (e), mica, alumina, talc and silica can be used, and the use of talc is preferred from the viewpoint of chipping performance.

It is preferable that the flaky pigment (e) has a long diameter size of 1 to 10 mu m and a number average particle diameter of 2 to 6 mu m. When the long diameter is outside the above range, the appearance of the film is inferior and sufficient chipping prevention performance is not obtained. When the number average particle diameter is outside the above range, the appearance of the coating film is similarly poor and sufficient chipping prevention performance is not obtained.

The content of the flaky pigment (e) is 0.4 to 2 parts by weight based on 100 parts by weight of the resin solid content. The content of 0.5 to 1.5 parts by weight is more preferable. If this content is outside the above range, sufficient chipping performance is not obtained since the adhesion property with the bottom coating film is reduced.

Other resins that may be contained are not particularly limited, but examples thereof include acrylic resins, polyester resins, alkyd resins, epoxy resins, and the like. These resins may be used alone or in combination of two or more thereof.

Examples of colored pigments include azo chelate-based pigments, insoluble azo-based pigments, fused azo-based pigments, phthalocyanine-based pigments, indigo pigments, perinone-based pigments, perylene-based pigments, dioxane- as organic bases. Pigments, quinacridone-based pigments, isoindolinone-based pigments, metal complex pigments and the like. As the inorganic base, chrome yellow, yellow iron oxide, blood red, carbon black, titanium dioxide and the like can be used. Moreover, calcium carbonate, barium sulfate, aluminum powder, kaolin, etc. can be used as a filling pigment.

Gray pigmented pigments containing carbon black and titanium dioxide as the main pigments are commonly used. In addition, combinations of various pigments and colored pigments having a color tone compatible with the color tone of the top coating can also be used.

In addition, in order to prevent drape with the top coating film and to maintain coating workability, a viscosity modifier may be added to the intermediate paint. Examples of viscosity modifiers typically include substances that exhibit thixotropic properties, such as polyamide-based modifiers (e.g., swollen dispersions of fatty acid amides, amide fatty acids, phosphates of long-chain polyaminoamides), polyethylene-based modifiers ( Examples include colloidal swollen dispersions of polyethylene oxide), organic bentonite-based modifiers (e.g. organic acid smectite clay, montmorillonite, etc.), inorganic pigments (e.g. aluminum silicate, barium sulfate, etc.), viscosity depending on the shape of the pigment. Flaky pigments, crosslinked resin particles, and the like.

The total amount of solids content of the intermediate paint used in the present invention at the time of application is 30 to 80% by weight, preferably 35 to 65% by weight. If this amount is out of this range, coating stability is inferior. If this amount exceeds the upper limit, the viscosity is too high and the appearance of the coating film is deteriorated. If this amount is less than the lower limit, the viscosity is too low, resulting in deteriorated appearance such as drape and unevenness.

In addition to the components, other additives commonly added to paints, such as surface conditioners, antioxidants, antifoams, and the like, may be incorporated into the intermediate paints used in the present invention. The amount of these incorporated is within the range known to those skilled in the art.

The urethane-modified polyester resin may also contain other resins. Such resins are not particularly limited, but include acrylic resins, polyester resins, alkyd resins, epoxy resins, and the like. These resins may be used alone or in combination of two or more thereof.

Methods of preparing the paint compositions for use in the present invention, including the methods described hereinafter, are not particularly limited, but those skilled in the art such as kneading and dispersing blends of pigments using kneaders, rolls and SG mills All methods well known to the art can be used.

Base coating film

The base paint used in the coating film production method of the present invention is used to form the top coating film together with the transparent paint. This base paint contains a film forming resin, a hardening | curing agent, a coloring pigment, and a glossy pigment as needed.

The film-forming resin contained in the base paint is not particularly limited, but preferred examples thereof include acrylic resins, polyester resins, alkyd resins, epoxy resins, urethane resins, and the like. These resins may be used alone or in combination of two or more thereof.

The film forming resin can be used by mixing with a hardening | curing agent. In view of the variety of performance and cost of the resulting coating film, amino resins and / or blocked isocyanate resins are preferably used.

The content of the curing agent is preferably 20 to 60% by weight, more preferably 30 to 50% by weight based on the weight of the solid content of the film-forming resin. When this content is less than 20 weight%, sclerosis | hardenability becomes inadequate. When this content is higher than 60% by weight, the cured film becomes too hard and brittle.

In addition, it may contain, for example, a colored pigment exemplified for the intermediate paint.

The form of the gloss pigment optionally contained in the base paint is not particularly limited. Glossy pigments may exhibit color. For example, a gloss pigment having an average particle diameter (D ₅₀ ) of 2 to 50 µm and a thickness of 0.1 to 5 µm is preferable. In addition, gloss pigments having an average particle diameter of 10 to 35 mu m are excellent and suitably used in terms of gloss appearance. The pigment concentration (PWC) of the luster pigment in the said coating is 20.0 weight% or less normally. This concentration is preferably 0.01 to 18.0% by weight, more preferably 0.1 to 15.0% by weight. When the amount of the gloss pigment exceeds 20.0% by weight, the appearance of the film becomes poor.

Examples of gloss pigments include metals or alloys such as aluminum, copper, zinc, iron, nickel, tin and aluminum oxide and uncolored or colored gloss pigments of mixtures thereof. In addition, interference mica pigments, white mica pigments, graphite and other colored or uncolored flaky pigments may be used together.

The total pigment concentration (PWC) of the gloss pigments and all other pigments in the paint is 0.1 to 50% by weight, preferably 0.5 to 40% by weight, more preferably 1.0 to 30% by weight. When this density | concentration exceeds an upper limit, the external appearance of a coating film will worsen.

In addition, as in the intermediate coating, it is preferable to add a viscosity modifier to the base coating to maintain coating workability. Viscosity modifiers are used to form a smooth and unblemished film, and they may contain a regulator that typically exhibits thixotropy. As such a regulator, for example, a regulator exemplified for the intermediate paint may be contained.

In addition to the above components, additives conventionally added to the paints, such as surface conditioners, thickeners, antioxidants, UV inhibitors and antifoams, may be incorporated into the base paints used in the present invention. The amount of these incorporated is within the range known to those skilled in the art.

The amount of the total solid component of the base paint used in the present invention at the time of application is 10 to 60% by weight, preferably 15 to 50% by weight. When this amount exceeds the upper limit or less than the lower limit, the stability of the paint is reduced. If this amount exceeds the upper limit, the viscosity is too high and the appearance of the coating film is deteriorated. When this amount is less than the lower limit, the viscosity is too low and a deteriorated appearance such as drape and unevenness appears.

Clear coating film

Transparent paint is used to form a transparent coating film. The transparent paint is not particularly limited, but a transparent paint containing a film-forming thermosetting resin and a curing agent can be used. As the type of transparent paint, there are exemplified a solution type, an aqueous type and a powder type.

In view of transparency and resistance to acid etching, preferred examples of solution type transparent paints include acrylic resins and / or polyester resins and amino resin combinations, acrylic resins and / or polyester resins and isocyanate compounds, and carboxylic acids Acrylic resins and / or polyester resins having an epoxy curing system.

Further, examples of the aqueous type of transparent paint include a paint containing a resin obtained by neutralizing the film forming resin contained in the above-described solution-type transparent paint with a base to make the paint aqueous. Neutralization can be carried out by addition of tertiary amines such as dimethylethanolamine and triethylamine before and after polymerization.

On the other hand, as the powder-type transparent coating, conventional powder coating such as thermoplastic and thermosetting powder coating can be used. Thermosetting powder coatings are preferred because coating films with better physical properties are obtained. Embodiments of thermosetting powder paints include epoxy-based, acrylic-based and polyester resin-based powder clear coatings, but acrylic-based powder clear coatings having better weather resistance are particularly preferred.

As powder type transparent paints used in the present invention, epoxy-containing acrylic resins / polyhydric carboxylic acid-based powder paints are particularly preferred because there is no volatile substance upon curing, a better appearance is obtained and little yellowing is caused. .

In addition, as in the intermediate coating, it is preferable to add a viscosity modifier to the transparent coating in order to maintain coating workability. As the viscosity modifier, a modulator that exhibits thixotropy may usually be contained. As the viscosity regulator, for example, a regulator exemplified for the intermediate paint may be contained. If necessary, a curing catalyst, a surface conditioner and the like may be contained.

materials

The method for producing a coating film of the present invention can be advantageously used for various substrates, for example metals, plastics, foam materials and the like, in particular for metal surfaces and cast products. The method can be used particularly suitably for metal products which can be cationic electrocoated.

Examples of the aforementioned metal products include iron, copper, aluminum, tin, zinc and the like and alloys containing these metals. Embodiments include vehicle bodies and parts of automobiles, trucks, motorcycles, buses, and the like. Particular preference is given to surface-treating the metals in advance with phosphates, chromates and the like.

In addition, in the base material used for the metal coating film manufacturing method of this invention, an electrodeposition coating film can be formed on the chemically processed steel plate. As electrodeposition paints for forming electrodeposited coating films, cationic and anionic types can be used, which is preferred because the electrodeposited coating compositions of the cationic type provide a coated composite film with excellent corrosion resistance.

Example

The present invention is described in detail by the following examples, but the present invention is not limited to the following examples. Thereafter, "parts" and "%" are based on weight.

Preparation Example 1

Preparation of Urethane-Modified Polyester Resin (a)

440 parts of isophthalic acid, 20 parts of hexahydrophthalic acid, 40 parts of azelaic acid, trimethylolpropane 300 in a 2-liter reaction vessel equipped with a nitrogen inlet tube, agitator, temperature controller, addition funnel and cooling tube equipped with a decanter. Part and 200 parts of neopentyl glycol were dissolved, the raw material was dissolved by heating and stirring, and then 0.2 part of dibutyl tin oxide was added thereto and started to stir, and the reaction layer temperature was gradually raised from 180 ° C. to 220 ° C. for 3 hours. . The resulting condensate was distilled out of the system. When the temperature reached 220 ° C., the temperature was maintained for 1 hour and 20 parts of xylene was gradually added to the reaction layer, and then the condensation reaction was carried out in the presence of a solvent. When the resin acid value reached 10 mgKOH / g, the material was cooled to 100 ° C. and 100 parts of hexamethylene diisocyanate were gradually added over 30 minutes. Then, the temperature was maintained for 1 hour, and 200 parts of xylene and 200 parts of butyl acetate were added, and the solid content was 70%, the number average molecular weight was 2000, the acid value was 8 mgKOH / g, the hydroxyl value was 120, and the resin Tg was 60 ° C. Phosphorus urethane-modified polyester resins were obtained.

Preparation Example 2

Preparation of Non-Aqueous Dispersions

(a) Preparation of Dispersion Stability Resin

90 parts of butyl acetate were placed in a vessel equipped with a stirrer, a thermostat and a reflux condenser. Then 20 parts of the solution having the composition shown in Table 2 were added and heated with stirring to raise the temperature:

The remaining 85 parts of the mixed solution was added dropwise at 110 ° C. for 3 hours, and then a solution of 0.5 parts of azobisisobutyronitrile and 10 parts of butyl acetate was added dropwise over 30 minutes. The reaction solution was stirred for further 2 hours at reflux to increase the rate of change of the resin and the reaction was terminated to yield an acrylic resin having a solid content of 50%, a number average molecular weight of 5600 and an SP value of 9.5.

(b) Preparation of non-aqueous dispersion

(a) 60 parts of acrylic resin and 90 parts of butyl acetate obtained in the preparation of the dispersion stability resin were placed in a vessel equipped with a stirrer, a condenser and a temperature controller. Then, a solution having the following composition was added dropwise at 100 DEG C for 3 hours, and then a solution of 0.1 part of azobisisobutyronitrile and 1 part of butyl acetate was added dropwise over 30 minutes:

The reaction solution was continuously stirred for an additional 1 hour to obtain an emulsion having a solid content of 60% and a particle diameter of 180 nm. This emulsion was diluted with butyl acetate to give a core-shell type butyl acetate dispersion having a non-aqueous dispersion content of 40%, viscosity 300 cps (25 ° C.) and particle size 180 nm. This non-aqueous dispersion resin had a Tg of 23 ° C., a hydroxy group value of 162 and an SP value of 11.8, and the difference in SP value of the whole or core portion of this non-aqueous dispersion resin was 2.3.

Example 1

Intermediate paint

107 parts of the urethane-modified polyester resin brightener obtained in the above production example, 280 parts of CR-97 (titanium oxide produced by Ishihara Sangyo Kaisha, Ltd.), MA-100 (Mitsubishi Chemical) 13 parts of carbon black pigment produced by Mitsubishi Chemical Co., Ltd., 7 parts of LMS-100 (talcum produced by Fuji Talc), 47 parts of butyl acetate and 47 parts of xylene Was put into a container, a mixture of the same amount of GB503M (glass beads having a particle diameter of 1.6 mm) was added, and the materials were dispersed at room temperature for 3 hours using a desk size SG mill to obtain a gray pigment paste. The particle size was 5 μm or less at the end of dispersion as measured using a grinding gauge. The glass beads were filtered to obtain a pigment paste. Pigment pastes were prepared as intermediate paints having the compositions shown in Table 3 below. The paint was diluted to 19 seconds / 20 ° C. using a mixed solvent (1: 1) of ethoxyethyl propionate / S-100 (aromatic hydrocarbon solvent produced by Exxon) (using No. 4 Ford cup). ). The nonvolatile component content of the paint at application was 49%.

Base paint

Acrylmelamine-based metal-based pigment "Orga TO H600 18J Green Metallic" produced by Nippon Paint Co., Ltd., produced by Ethoxyethyl Propionate / S-100 (exon) (Diluted aromatic hydrocarbon solvent) / toluene (1: 1: 2) was used to dilute to 17 seconds / 20 ° C (using No. 3 pod cup). The nonvolatile fraction of the paint at application was 31%. The nonvolatile fraction upon deposition was 65%.

Transparent paint

Nippon Paint Co., Ltd. "Mack O-1600 Clear", an acid epoxy curing-based transparent paint produced by Limited, is a mixed solvent of ethoxyethyl propionate / S-100 (aromatic hydrocarbon solvent produced by exon) (1 : 1) was used to dilute to 26 seconds / 20 ° C. (using No. 4 pod cup). The nonvolatile fraction of the paint at the time of application was 50%. In addition, the nonvolatile fraction upon deposition was 61%.

Manufacturing method of coated composite film

Cathode electrodeposition paint "Power Top V-20" (Nippon Paint Company, Limited) was applied to SPC steel plate 0.8mm thick, 30cm long and 10cm wide treated with zinc phosphate to a dry film thickness of 20㎛. , And baked for 30 minutes at 160 ℃ to prepare a coated plate. Then, it was adhered to a moving object, and while moving, the above-described intermediate paint was coated with a "microbell" (electrostatic coating machine of the rotary spray type) to have a dry film thickness of 20 µm, and cured at intervals of 10 minutes after application. .

Then, as a second step, the base paint was applied with "microbell" and "metabell" so that the dry film thickness was 15 mu m. There was a 2.5 minute interval between two applications. It hardened | cured for 8 minutes after the 2nd coating. Then, the transparent paint was coated with "microbell" in one step so that the dry film thickness was 35 µm, and then cured for 10 minutes. Curing conditions of the resulting plate-shaped coated composite film were a curing temperature of 140 ° C. and a curing time of 30 minutes.

The coated plates thus prepared were placed in a first drying oven at 40 ° C., held for 5 minutes, transferred to a second drying oven at 140 ° C., and held for 20 minutes. Thereafter, the coated plate was taken out of the drying oven and cooled to room temperature.

The cured coated composite film was visually evaluated for the presence of a glossy appearance. The test results are shown in Table 5.

(2) Then, the state of the surface of the cured coated composite film was measured using "Wave Scan DOI" (coated composite film appearance measuring apparatus produced by Big Chemie). The test results are shown in Table 5.

The measured Wa value means a roughness of 0.1 to 0.3 mm between the surface curvatures and indicates the glossy appearance of the coated composite film. Wc means a degree of roughness of 1 to 3 mm between the surface curvatures, and represents the surface hiding property of the coated composite film. Wd means a roughness of 3 to 10 mm between surface curvatures and indicates the flatness of the coated composite film. The smaller the number, the better each measurement is.

(3) In addition, the chipping prevention of the resulting coated plate was evaluated as follows. The test results are shown in Table 5.

Using a Glabero tester (manufactured by Suga Test Instrument Co., Ltd.), 300 pieces of No. 7 crushed stone at an air pressure of 3.0 kgf / cm ² at a distance of 35 cm The film was hit at a 45 ° angle. After washing with water and drying, a peel test was performed using an industrial adhesive tape manufactured by Nichiban, and then the degree of peeling of the film was visually observed and evaluated in terms of peel diameter and peeling water level.

Examples 2-4

The cured coated composite film was prepared and tested according to the same method as described in Example 1 except that the curing temperature and curing time were changed as shown in Table 5. The test results are shown in Table 5.

Comparative Example 1

A cured coated composite film was prepared according to the same method as described in Example 1 except for the firing and curing step performed by heating the non-cured coated composite film in one step at 140 ° C. for 30 minutes, Tested. The test results are shown in Table 6.

Comparative Example 2

The polyester-melamine-based intermediate paint "Orga TO H870 Gray" produced by Nippon Paint Co., Ltd. is used as the intermediate paint, and the solidification temperature and curing time are shown in Table 6 The cured coated composite film was prepared and tested according to the same method as described in Example 1, except as changed. The test results are shown in Table 6.

Reference Example 1

Cathode electrodeposition paint "Power Top V-20" (Nippon Paint Company, Limited) was applied to SPC steel plate 0.8mm thick, 30cm long and 10cm wide treated with zinc phosphate to a dry film thickness of 20㎛. , And baked for 30 minutes at 160 ℃ to prepare a coated plate. Then, it was adhered to a moving object, and while moving, the above-described intermediate paint was coated with a "microbell" (electrostatic coating machine of the rotary spray type) to have a dry film thickness of 20 µm, and cured at intervals of 10 minutes after application. .

This coated plate was placed in a drying oven set at 140 ° C. and held for 20 minutes. The coated plate was then taken out of the drying oven and cooled to room temperature. Base paints and transparent paints were applied to the coated plate of Example 1 to obtain a coated composite film.

The prepared coated plates were then placed in a drying oven at 140 ° C. and held for 30 minutes. The coated plate was then taken out of the drying oven and cooled to room temperature. According to the same method as described in Example 1, the resulting cured coated composite film was tested. The test results are shown in Table 6.

Reference Example 2

The polyester-melamine-based intermediate paint "Orga TO H870 Gray" produced by Nippon Paint Co., Ltd. is used as the intermediate paint, and the solidification temperature and curing time are shown in Table 6 The cured coated composite film was prepared and tested according to the same method as described in Example 1, except as changed. The test results are shown in Table 6.

In the present invention, even when the coated composite film was formed by the three-coupling one-time baking method, the same glossy appearance as obtained by the three-coating three-time baking method was obtained. Moreover, the coating system implemented in accordance with the present invention exhibited the same anti- chipping properties as the coated composite film obtained by the three coating two baking method, although the firing time was shorter.

Claims (4)

Forming an electrocoated film on the substrate, successively applying an intermediate paint, a base paint and a transparent paint in a wet-on-wet manner, and then firing and curing all three applied layers at once. and; At this time, the firing and curing are performed at a low temperature heating step of heating at a temperature of 25 to 80% of the curing temperature for a time of 5 to 30% of the curing time, and at least 80% of the curing temperature for a time of 30 to 130% of the curing time. A high temperature heating step of heating at a temperature of 120% or less, Method for producing a coated composite film. The method of claim 1, The intermediate paint is obtained by (a) polycondensation of an acid component containing at least 80 mol% of isophthalic acid with a polyhydric alcohol and an aliphatic hydroxyl group-containing polyester resin having a glass transition temperature (Tg) of 40 to 80 ° C. 40 to 56% by weight urethane-modified polyester resin having a number average molecular weight of 1,500 to 3,000 obtained by reacting the isocyanate compound, (b) 10 to 30% by weight melamine resin, (c) 15 to 5 blocked isocyanate compound 30 weight percent, (d) 4 to 15 weight percent of the non-aqueous dispersion resin having a core-shell structure (the amount of (a) to (d) is based on the weight of the resin solids content), and ( e) containing 0.4 to 2 parts by weight of flaky pigment, based on 100 parts by weight of resin solids content, Method for producing a coated composite film. The method of claim 2, A method for producing a coated composite film, wherein the blocked isocyanate compound is blocked with a compound having an active methylene group. A coated composite film made by the method according to any one of claims 1 to 3.