JP4762669B2 - Manufacturing method of coated plate with excellent stain resistance and workability - Google Patents

Description

The present invention relates to a method for producing a coated plate having a coating having excellent contamination resistance on the surface. In the present coated plate, a surface layer film mainly composed of an alkoxide and a lower layer binder resin form a mixed layer state and exhibit excellent stain resistance and workability. Contamination may include contamination due to dripping, other carbon contamination due to being left outdoors, and contamination due to indoor food, etc. The present invention is effective for such contamination.

  In the present invention, excellent contamination resistance means rain dripping contamination (adhesion of dust and carbon in the air), food contamination (adhesion of curry, mustard, juice, tobacco, etc.), heat oil contamination (Adhesion of tempura oil, food oil, etc.)

  The “painted plate” here is defined as a plate material in which a coating film is formed on at least one side of the substrate. As the substrate, in addition to metal, paper, wood, plywood, etc., polypropylene (PP), polyethylene terephthalate (PET) A plate of a material such as resin can be used.

Patent Document 1 discloses the hydrolysis of one or both of organosilane (represented by the formula R ¹ _n Si (OR ² ) _4-n ) and its partial hydrolysis condensate with a urethane resin having a specific silyl group. It is disclosed that a coating film excellent in substrate adhesion, hot water resistance, alkali resistance, weather resistance, stain resistance, etc. is formed by applying an aqueous coating composition based on a decomposition condensation reaction product. . Although many of the conventional coating compositions are organic solvent-based coatings, which are environmental problems, the coating of Patent Document 1 is a water-based organic-inorganic composite resin coating.

  Patent Document 2 describes a coating film having an octane contact angle in water of 102 degrees or more in order to prevent the occurrence of rain lines. This coating film is coated with a surface treatment agent containing (A) a hydrolyzate of 1 to 3 functional hydrolyzable silane compounds, a silicon compound that is an alkali silicate or colloidal silica, and (B) a synthetic resin film-forming component. It is formed by. The treatment agent of Patent Document 2 is suitable for application to the surface of a hydrophobic synthetic resin coating film in which spotted stains are likely to occur due to rainwater.

  Patent Document 3 discloses a top coating composition that forms a coating film excellent in weather resistance, water resistance, chemical resistance, stain resistance, and scratch resistance. This coating composition comprises a curing agent component having a functional group capable of reacting with a hydroxyl group, a resin component having a hydroxyl group at a terminal obtained by a reaction between a cyclic compound and a hydroxyl group, and a hydrolyzable alkoxy group or aryl directly bonded to a silicon atom. Contains compounds having an oxy group.

  Patent Document 4 discloses an outer plate coating film having raindrop-fouling resistance and having a water dynamic backward tension (Tr) of 47 dyn / cm or more. The coating film described in this document contains at least one of an organic polymer having an alkoxyl group and a partial hydrolysis-condensation product of an organosilicon compound, and a film-forming resin.

  Patent Document 5 describes an outer coating film having raindrop-stain resistance and having a water dynamic receding tension (Tr) of 55 dyn / cm or more. This coating film contains a partially hydrolyzed condensate of tetramethoxysilane that defines a molar ratio of silanol groups to methoxysilyl groups, a film-forming resin, and an organosilica sol having a particle size of 10 to 100 nm.

  In Patent Document 6, a liquid compound containing a hydrolyzate of alkoxysilane and a polyester resin is applied to a metal surface and dried to provide a metal having excellent weather resistance, acid resistance, stain resistance, and scratch resistance. A coating method for obtaining a surface is described.

  All the paints described in Patent Documents 1 to 6 are intended to improve stain resistance, and adhere to the surface using the action of hydrophilic silanol (SiOH) groups on the surface of the coating film. The pollutant is washed away with rain water. Each of the paints in Patent Documents 1 to 6 contains a film-forming resin (urethane resin, polyester resin, or the like).

  As a paint for steel plates that copes with contamination by foods without using organometallic paints such as organosilanes, for example, Patent Document 7 describes a paint that crosslinks a polyester resin with an isocyanate-based crosslinking agent. The polyester resin having an average functional group number of 2.1 to 2.6, a number average molecular weight of 8000 to 22000, and a glass transition temperature of 0 to 30 ° C., a methylated methylol melamine resin, a butylated methylol melamine resin, an acid catalyst, and an amine compound A coating composition for a coated metal plate containing as an essential component is described.

JP 2003-147266 A JP-A-7-109435 JP 2002-146295 A JP-A-10-130581 JP-A-11-124518 JP-A-7-68217 JP 63-301217 A JP-A-8-100150

  Conventional stain-resistant paints, as described in Patent Documents 1 to 6, are metal element alkoxides such as organic silicate compounds (silicon is an element generally classified as a semimetal, but in the description here, It is common to form a film on a substrate by mixing a film-forming binder (polyester resin, etc.) with a film-forming binder (polyester resin, etc.) if it is simply referred to as “metal” for the sake of strictness. .

Problems of the stain-resistant paint using such a film-forming binder are described below.
In the conventional stain-resistant paint, a hydrolyzate (silanol, etc.) of an organometallic compound that exhibits hydrophilicity is mixed and buried in the resin binder for film formation, so that good stain resistance is obtained. Absent.

  When forming a cured coating film by using an inorganic binder having an alkoxysilyl group as a curing reactive group and generating a Si—O—Si or Si—O—C bond by a hydrolysis / condensation reaction of the SiOR group It is important to leave SiOR groups that form hydrophilic SiOH groups upon hydrolysis in the coating film. However, in conventional coatings, if the thermal curing is advanced to increase the hardness of the resulting coating film, the SiOR groups are consumed by the curing reaction, so that a sufficient amount of SiOR groups does not remain on the coating surface, so The amount of hydrophilic SiOH groups obtained by the decomposition reaction became insufficient, and as a result, the hydrophilicity of the coating film was not maintained, and good contamination resistance could not be realized.

  On the other hand, in order to maintain the hydrophilicity of the coating film surface, if the SiOR group is left in the coating film, not only the desired coating film hardness can be obtained, but also the hydrolysis / condensation reaction of the SiOR group occurs inside the coating film. As a result, defects such as coating film cracks occurred.

  In addition, for the purpose of fixing a metal alkoxide (organic silicate) compound to a binder resin and promoting hydrolysis, various catalysts are added to the resin. Since it absorbs moisture and cures, there is a problem that storage stability is extremely poor and coating workability is deteriorated.

The paints described in Patent Documents 7 and 8 that deal with food contamination by improving the organic resin to be used and devising the composition of the crosslinking agent without using organometallic paints such as organosilanes are also becoming increasingly demanding from customers. Performance is not enough to satisfy.
In addition, the use of an expensive fluorine-based resin is also conceivable, but it is economically disadvantageous and has a problem that the fluorine-based resin is oleophilic and is weak against oil stains.

  An object of the present invention is to solve the above-mentioned problems of the prior art and provide a coated plate with improved stain resistance and workability and a method for producing the same.

The gist of the present invention is as follows .
(1 ) Mainly composed of one or more metalloid elements selected from silicon, titanium, zirconium and boron, or a metal alkoxide and / or a partial polycondensate (I) generated by hydrolysis of the alkoxide on the substrate. It has a surface layer film and a lower layer film mainly composed of a binder resin (II) having a functional group that reacts with the alkoxide and / or its partial condensate (I), and both layers are mixed. A method for producing a coated plate excellent in stain resistance and workability, wherein one or more metalloid elements or metal alkoxides selected from silicon, titanium, zirconium and boron and / or the alkoxides are hydrolyzed. A coating for the surface layer coating mainly composed of the resulting partial polycondensate (I) and a buffer having a functional group that reacts with the alkoxide and / or its partial condensate (I). The coating for the lower layer film mainly composed of the inder resin (II) is applied on the substrate, and the two coatings are simultaneously dried and baked. The viscosity of the coating for the surface layer film is equal to the viscosity of the coating for the lower layer film. Contamination resistance and processability, characterized in that the difference between the surface tension of the coating for the surface coating and the surface tension of the coating for the lower coating is 5 × 10 ⁻³ N / m or less . The manufacturing method of the coating board excellent in.
( 2 ) The paint for surface coating and the coating for lower layer coating are simultaneously applied to a substrate by a multi-layer curtain method, and the coating plate having excellent stain resistance and workability described in ( 1 ) above Production method.
( 3 ) Contamination resistance and workability as described in ( 2 ) above, wherein the coating for the surface layer coating and the coating for the lower layer coating are simultaneously applied to the substrate by the multi-layer curtain method using a slide coater. The manufacturing method of the coating board excellent in .

In the coated plate obtained by the method for producing a coated plate of the present invention, a metalloid alkoxide such as silicon or boron or a metal alkoxide such as titanium or zirconium and / or such a metalloid element or metal alkoxide is hydrolyzed. The resulting surface polycondensate (A) is mainly composed of a surface layer coating that contains no or even no binder resin, and exhibits excellent stain resistance. In addition, the semi-metal or metal alkoxide Since the partial polycondensate itself has good weather resistance, the accompanying effect that the weather resistance is improved is also obtained. Further, the lower layer film mainly composed of the binder resin fulfills the function of ensuring the adhesion of the surface layer film. Further, in the coated plate of the present invention, since the surface layer alkoxide and the lower layer binder resin are in a mixed state, the adhesion between the surface layer and the lower layer film is further improved, and excellent workability is exhibited. As a synergistic effect, the coated plate of the present invention can maintain excellent stain resistance over a long period of time.

  In the method for producing a coated plate of the present invention, the functions of the surface layer coating material and the lower layer coating material are separated, and both are applied on the substrate in a wet state and simultaneously dried and baked. Since the mixed layer state is formed without impairing the respective functions of the lower layer coating, it is possible to obtain a coated plate that exhibits excellent stain resistance over a long period of time. In particular, multi-layer simultaneous coating such as using a slide coater can be used, so that the two coating paints can be stored separately until just before application, making it easier to store the paint and improving the efficiency of the application work. To do. In conventional painting work to obtain stain-resistant coated plates, metal alkoxides such as organic silicates and hydrolysis-promoting catalysts (acids such as acetic acid and hydrochloric acid, amines, bases such as alkali metal hydroxides, etc.) And the binder resin were previously blended into one liquid, the paint stability was poor, and the paint that deteriorated with time was discarded.

The coated plate obtained by the coated plate manufacturing method of the present invention has a coating film of a mixed layer structure of a surface layer coating and a lower layer coating on the substrate, and the surface layer coating is a semi-metallic element such as silicon or boron, titanium, zirconium or the like The metal alkoxide and / or the partial polycondensate (A) produced by hydrolysis of such a semi-metal element or metal alkoxide is the main component, and the lower layer coating is composed of the alkoxide and / or its partial polycondensate (A). The binder resin (B) having a reactive functional group is mainly used.
The mixed layer structure in the present invention refers to a state in which the boundary between the surface layer and the lower layer is not flat but disturbed, and is a concept confronting a multilayer structure in which the boundary is flat.
In addition, the mixed layer structure of the present invention includes a state in which a thin layer is partially separated and dispersed in an island shape in a thick layer. Details of the mixed layer structure will be described later.

<Board>
The board | substrate used for this invention is not specifically limited, Resin plates, such as a polypropylene (PP) and a polyethylene terephthalate (PET), etc. other than a metal plate, paper, wood, a plywood, etc. can be used.

  Examples of the metal plate include a steel plate, an aluminum plate, a stainless steel plate, a titanium plate, and a copper plate. Among these, as examples of steel plates, cold-rolled steel plates, hot-rolled steel plates, galvanized steel plates, alloyed galvanized steel plates, zinc-iron alloy-plated steel plates, zinc-aluminum alloy-plated steel plates, aluminum-plated steel plates, chrome-plated steel plates, nickel-plated steel plates , Zinc-nickel alloy plated steel sheet, tin plated steel sheet and the like.

  The metal plate can be pretreated as necessary. Examples of the pretreatment include water washing, hot water washing, pickling, alkali degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, composite oxide film treatment and other non-chromate treatments. These can be used alone or in combination for pre-coating treatment. What is necessary is just to select the conditions of pre-coating treatment suitably.

<Surface coating>
The surface layer coating on the coated plate obtained by the method for producing a coated plate of the present invention comprises one or both of a semimetal element or metal alkoxide and a partial polycondensate obtained by hydrolysis of such a metalloid element or metal alkoxide. It is formed from the main paint. That is, the coating material contains one or both of a metalloid element or metal alkoxide and a partial polycondensate thereof as essential components, and may contain other components as necessary.

A metalloid element or metal alkoxide is represented by the general formula M (OR) _n, where M represents a metal such as silicon or boron, or a metal such as titanium or zirconium, and R is generally an alkyl group. Represents. Preferred alkyl groups are methyl group, ethyl group, propyl group, butyl group and the like. n varies depending on the valence of the metal element or the metalloid element, and is not particularly limited, but many are about 2 to 5. A compound in which a part of the OR group is replaced with another group such as a phenyl group or an element such as F can also be used and used together.

  As the metal alkoxide, organic titanate and organic zirconate are preferable, and as the metalloid alkoxide, organic silicate and organic borate are preferable, but both are not limited thereto. Examples of typical metalloid alkoxides include silicon tetramethoxide, silicon tetraethoxide, silicon tetra-n-proxyd, silicon tetra-sec-butoxide, boron trimethoxide, boron triethoxide, boron tri-n-propoxide. And boron tri-iso-butoxide. Examples of typical metal alkoxides include titanium tetramethoxide, titanium tetraethoxide, titanium tetra-iso-propoxide, titanium tetra-tert-butoxide, zirconium tetramethoxide, zirconium tetraethoxide, zirconium-n-butoxide, Etc.

  A single alkoxide or a partial polycondensate thereof may be used, or a mixture of alkoxides or a partial polycondensate thereof may be used.

  Metal alkoxides other than those mentioned above or metal alkoxides can also be used. For example, organic borates can be used as a crosslinking agent for the alkoxides described above. Moreover, in order to improve heat resistance, what substituted some phenyl groups by the phenyl group, such as phenyl triethoxysilane, can also be added. Moreover, what substituted some alkoxy groups for other elements, such as fluorotriethoxysilane, can also be used.

  In particular, since organic zirconate has excellent alkali resistance, it effectively acts on alkaline contaminants. Organic zirconates have been rarely used so far in paints that exhibit stain resistance. The reason seems to be that when blended in the binder paint, it did not float on the surface of the coating film, so that sufficient hydrophilicity could not be exhibited. In the present invention, the surface coating film having an organic zirconate or a partial polycondensate thereof is positioned on the lower layer coating containing the binder resin, which does not contain the binder resin but has a lower binder resin content than the conventional coating. This conventional problem is solved. Further, in the present invention, the surface layer and the lower layer show a mixed layer state in which the boundary surface is disturbed, and the boundary surface is wider as compared with the flat multi-layer state, so that the adhesion between both layers is greatly enhanced.

The coating for the surface layer film used in the present invention forms the surface layer film by the following mechanism.
The basic reaction of film formation is represented by M (OR) _n + n / 2H ₂ O → MO _{n / 2} + nROH.
In the presence of water, the alkoxide is hydrolyzed to produce M-OH, which is polymerized to form MO _{n / 2} , which forms a continuous film. Actually, it shows complex behavior depending on the reaction conditions. When a functional group that reacts with M-OH is contained in the lower layer, the reaction between the M-OH and the functional group occurs in the process of film formation, and the lower layer and the surface layer are more firmly adhered to each other. Will improve.

A small amount of a binder component (A ₁ ) is added to the coating for the surface coating as a solid component for the purpose of improving the film-forming property and improving the workability of coating (for example, the stability of the coating curtain during curtain coating). May be. Examples of materials suitable for use as the binder include polyester resins, urethane resins, fluororesins, acrylic resins, and the like.

Basic substances such as various amines and alkali metal hydroxides may be added to the coating for the surface layer coating as a hydrolysis promoting catalyst (A ₂ ). The addition amount of the hydrolysis promoting catalyst may be appropriately selected depending on the type of the catalyst and the content of the alkoxide component, but generally it is preferably in the range of 0.05 to 5% by mass with respect to the solid content of the paint. It is. If it is less than 0.05% by mass, the catalytic action is insufficiently exhibited, and if it exceeds 5% by mass, the hydrolysis reaction may be rapid, and the performance as a film, particularly the stain resistance, may be reduced.

The surface layer coating material may further contain a catalyst (A ₃ ) that promotes the hydrolytic condensation reaction of alkoxysilyl groups. The catalyst (A ₃ ) is not particularly limited, and examples thereof include aluminum acetylacetonate. The addition amount of the catalyst (A ₃ ) is preferably 0.1 to 10% by mass in the resulting coating composition. If it is less than 0.1% by mass, the effect of addition of the catalyst cannot be obtained, and if it exceeds 10% by mass, the hydrolysis condensation reaction occurs too early, which is not preferable. More preferably, it is 1-5 mass%.

An organic solvent (A ₄ ) may be added to the surface layer coating material. As the organic solvent (A ₄ ), it is preferable to use an alcoholic organic solvent or a glycol derivative in consideration of the decomposition of the SiOR group during storage. It is also possible to use a mixture of two or more solvents. Examples of the alcohol-based organic solvent include butanol, octanol, diacetone alcohol, and the like. Examples of glycol derivatives include ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, Examples thereof include ethylene glycol monomethyl ether acetate and propylene glycol monoethyl ether acetate.

<Undercoat>
The lower layer coating in the coated plate of the present invention is a binder resin having a functional group capable of reacting with a semi-metal element or metal alkoxide of the essential component (I) of the surface layer coating, a partial polycondensate thereof, or both. It is formed from a paint mainly composed of (II). That is, this lower layer coating material contains a binder resin having such a functional group as an essential component, and may contain other components as necessary.

  As the binder resin, polyester, acrylic, fluorine, urethane resin and the like are suitable. A mixture of two or more binder resins can also be used. This binder resin is selected from a methylol group, an isocyanate group, an epoxy group, a carboxyl group, a hydroxyl group, and an alkoxyl group as a functional group capable of reacting with the alkoxide of (I), a partial polycondensate thereof, or both. Contains one or more.

  If necessary, fine particle fillers, pigments and other additives may be added to the coating for the lower layer coating, or an organic solvent may be added.

The particulate fillers, for _{example, SiO 2, TiO 2, Al} 2 O 3, Cr 2 O 3, ZrO 2, Al 2 O 3 · SiO 2, 3Al 2 O 3 · 2SiO 2, such as silicate Zirconia Fine particles can be used. As the pigment, for example, color pigments such as titanium dioxide, carbon black, iron oxide, various calcined pigments, cyanine blue, and cyaning ray, and extender pigments such as calcium carbonate, clay, and barium sulfate can be used. In addition, for example, metal powder such as aluminum powder, matting agents such as silica and alumina, antifoaming agents, leveling agents, anti-sagging agents, surface conditioners, viscosity modifiers, dispersants, UV absorbers, waxes, etc. Additives used in ordinary paints can be used. Similarly, organic solvents are commonly used in ordinary paints such as aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, and ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone. A typical solvent can be used.

<Composition of coating>
As is apparent from the above description, in the coated plate obtained by the method for producing a coated plate of the present invention, the surface layer is mainly composed of a partial polycondensate produced by hydrolysis of a metalloid element or a metal alkoxide, and has a SiOR group. A film formed from a paint containing a hydrophilic group such as TiOR group or ZrOR group is provided. The blending of the binder resin into the surface layer film is kept to a minimum, and the binder resin may not be blended depending on the kind of metalloid element or metal alkoxide and the required performance level of the product. For this reason, since the reaction product of the metalloid alkoxide or metal alkoxide in the surface layer film becomes a high concentration, the desired contamination resistance can be maintained even if the surface layer film is partially dispersed in an island shape by the mixed layer.

  Under the surface film, a film formed from a paint mainly composed of a binder resin containing a functional group that reacts with a metalloid alkoxide or a metal alkoxide of the surface layer paint or a partial polycondensate thereof is provided. The reactive functional group of the binder resin of the lower layer coating material reacts with the metalloid element or metal alkoxide or partial polycondensate thereof of the surface layer coating material to maintain a strong bond with the surface layer coating. This reaction is accelerated by simultaneously drying the surface layer and lower layer coating materials to form a stronger bond. Accordingly, it is advantageous that the coating for the surface layer coating and the coating for the lower layer coating are simultaneously heated and dried. In particular, the present invention is characterized by a mixed layer state in which the boundary surface of the boundary region between the surface layer coating and the lower layer coating enters and is disturbed, thereby achieving a stronger bond.

  A cured film of the surface layer formed from a paint mainly composed of a metalloid alkoxide or a metal alkoxide or a partial polycondensate thereof exhibits excellent hydrophilicity even if it is a thin film. Even if the exposed area ratio is reduced to 70%, the desired contamination resistance can be maintained. Since the lower layer film formed from the coating material having reactivity with the constituent components of the surface layer film is excellent in adhesion to the surface layer film, it serves as a support layer for the surface layer.

The optimum thickness (dry) of the mixed surface layer and lower layer is 0.6 to 35 μm. When the thickness is less than 0.6 μm, the contamination resistance cannot be sufficiently secured, and when the thickness is more than 35 μm, the economy is inferior and the workability may be lowered.
In order to expose the surface layer coating to the surface of the coating film in an area of 70% or more, it is necessary to secure an average film thickness of the surface layer of at least about 0.1 μm, depending on the degree of the mixed layer.

<Measuring method of film thickness>
For the measurement of the average film thickness, any of the known methods may be used. For convenience, the intensity of the semi-metal element or metal element contained in the sample whose film thickness is to be measured is measured using fluorescent X-rays. The average film thickness can be obtained from a calibration curve prepared in advance. The calibration curve can be obtained from the film thickness measured in advance by the gravimetric method. It is also possible to measure by the gravimetric method from the beginning without using the fluorescent X-ray method.

  The thickness of the lower layer film may be appropriately determined from the performance such as workability, corrosion resistance, and colorability, but the generally preferred film thickness is 0.5 to 30 μm. If it is thinner than 0.5 μm, it is inferior in corrosion resistance, and if it is thicker than 30 μm, it is inferior in economic efficiency and workability may be reduced.

In the coated plate obtained by the method for producing a coated plate of the present invention, even if the binder resin is not included or contained, the surface layer coating with a small content serves a function of stain resistance, and the lower layer coating mainly composed of the binder resin It fulfills the function of ensuring the adhesion of the surface coating. In addition to these, the surface layer film is provided with functions such as designability (by coloring of the film), weather resistance, and workability, and the lower layer film is also provided with designability (by coloring, etc.), workability, and weatherability. Further, it is possible to impart functions such as corrosion resistance, and by adding these functions, it is possible to obtain a coated plate having a higher function. Moreover, since the boundary part between layers is a mixed layer state, the coating film of this invention has a unique design property according to the grade of a mixed layer. This is particularly noticeable when the exposure rate of the surface coating to the coating surface is less than 100%.

<Definition of mixed layer structure>
The mixed layer structure in the present invention has a first condition that the boundary surface between the surface layer and the lower layer is not flat but has wavy irregularities. The degree of unevenness depends on the film thickness, but when the cross section is observed with a 400 times SEM (scanning electron microscope) image, the unevenness is recognized, and the difference in height (A) between the boundary surface is The case where the total average film thickness (B) is 1/4 or more is defined as a mixed layer structure. On the other hand, when the above criteria are applied, in the case where the average film thickness of the lower layer is thicker than the average film thickness of the surface layer, it is actually a mixed layer state intended by the inventors. There is a possibility that it is determined not to be in a mixed state. That is, when the average film thickness (C) of the surface layer is ¼ or less of the total average film thickness (B) of the surface layer and the lower layer, the above criterion is not applied, and the height difference (A) of the unevenness is the average of the surface layer. If the thickness is greater than (C), it is defined as having a mixed layer structure.

If the boundary surface between the surface layer and the lower layer shows remarkable unevenness as described above, it is defined as a mixed layer in the present invention even if the boundary surface maintains continuity. Of course, even when a discontinuous portion is formed in a part of the boundary surface and a coating film is formed only with the resin of the surface layer or the lower layer only (second condition), the unevenness is remarkable. If so, it is defined as a mixed layer structure.
When either or both of the first and second conditions are satisfied (a state where the boundary surface is continuous and the discontinuous portion is mixed), the coating film shows a mixed layer structure. It is considered.

<Judgment method of mixed layer structure>
Reference is made to FIGS. In these figures, 1 is the lower layer, 2 is the surface layer, and (A) is the position where the thickness of the surface layer is the thickest and the thinnest (if the boundary is not continuous as shown in FIG. (B) is the total average film thickness of the surface layer and the lower layer, and (C) is the average film thickness of the surface layer.
1) Take 10 cross-section samples of the coating film at any part of the product.
2) Each cross-sectional sample is observed with a 400 times SEM (scanning electron microscope) image, and three measurement samples having a length of 500 μm are arbitrarily selected.
3) The interface between the surface layer and the lower layer is observed for each measurement sample, and the distance (A) between the position where the thickness of the surface layer is the thickest and the position where it is the thinnest is measured. When the boundary surface is not continuous, the distance (A) is measured from the boundary surface to the position where the surface layer enters most.
4) When the distance (A) satisfies the following relationship with respect to the total average film thickness (B) of the surface layer and the lower layer, the mixed layer structure is determined.
When C> 1 / 4B: A / B ≧ 1/4
When C ≦ 1 / 4B: A ≧ C
5) It is judged whether or not each measurement sample (3 places) has a mixed layer structure, and the same inspection is performed for other cross-sectional samples (10 samples).
6) When 3 locations × 10 samples = 30 samples are inspected and the number of samples determined to be in the mixed layer structure exceeds 20, the product is determined to have a mixed layer structure.
To form a mixed layer structure, make the paint used for the surface layer high viscosity, make the paint used for the lower layer low viscosity, or make the surface tension of the surface paint larger than that of the lower paint, or the surface tension of the lower paint is high. Even in such a case, a method of reducing the difference can be adopted.

<Coating method>
As described above, the surface layer coating and the lower layer coating are simultaneously heated and dried to form a mixed layer state at the boundary portion. For this purpose, it is necessary to form a plurality of coating films of coating materials in a wet state. Any coating method may be used as long as a plurality of wet coating films can be formed. For example, a multi-layer curtain coating using a slide coater, a slot die, an extrusion die, or the like is preferable. . In addition, a wet-on-wet coating method can be used. There is no need for one coating for the surface coating or one for the lower coating. For example, in order to improve the adhesion with the outermost layer coating material on the lower layer coating material, the coating may be formed with another surface layer coating material.

  In the case of curtain coating, it is difficult to apply a thin film of a surface layer coating material mainly composed of a metalloid element or metal alkoxide or a partial polycondensate thereof with a single layer curtain because a stable thin film cannot be formed. However, when a multilayer curtain is applied simultaneously with a thin film of a lower layer coating material mainly composed of a binder resin, there is an advantage that it can be stably applied even if the surface layer coating material film becomes thinner.

  When using the multilayer simultaneous coating method, a method of mixing layers at the boundary between wet layers is employed.

The present invention is characterized in that the upper and lower layers are mixed, but the realization of the mixed layer is that the coating used for the surface layer has a high viscosity and the coating used for the lower layer has a low viscosity, or the surface tension of the surface coating is reduced. It is possible to make it larger than that of the lower layer paint or to reduce the difference even when the surface tension of the lower layer paint is large. As a particularly preferable method, the viscosity of the surface coating is set to be equal to or higher than the viscosity of the lower coating, preferably the difference is 50 mPa · s or more, and / or the difference in surface tension (interface tension) between the upper and lower layers. Is 5 × 10 ⁻³ N / m or less, more preferably 3 × 10 ⁻³ N / m or less. If the viscosity of the surface layer paint is lower than that of the lower layer paint, a desired mixed layer hardly occurs between the upper and lower layers. Even when the difference in surface tension (interfacial tension) between the upper and lower layers is larger than 1.0 × 10 ⁻² N / m, a desired mixed layer hardly occurs between the upper and lower layers. Further, the mixed layer or the degree thereof may vary depending on the coating method and conditions and the heating and drying conditions described below.

<Heat drying>
The method of simultaneously heating and drying the coating layer for the surface layer coating and the coating layer for the lower layer coating is not particularly limited. For example, hot air or induction heating can be used, and a plurality of methods may be used in combination. . In the case of a radiation curable coating layer, radiation irradiation can be used in combination. From the viewpoint of productivity, although not as preferable as baking by forced heating drying, the coating layer may be naturally dried.

  In the case of heating, the substrate temperature is generally raised to 40 to 250 ° C. When a heat-resistant binder resin component is used, the binder resin component may be heated to a higher temperature. However, since the metalloid alkoxide component or the metal alkoxide component becomes difficult to be hydrolyzed when it is made into a ceramic, the heating temperature is preferably 350 ° C. or less.

<Additional coating>
If necessary, another coating is applied on the metal plate and cured and dried to form an additional film, for example, as an undercoat layer for improving corrosion resistance or a base treatment layer for improving adhesion. You may form the lower layer film and surface layer film of invention. The type of paint for the additional coating is not particularly limited, and examples thereof include polyester resin, epoxy resin, urethane resin, and acrylic resin. The selected paint is applied to the required film thickness using a roll coater, curtain flow coater, roller curtain coater, electrostatic coating machine, brush, blade coater, die coater, etc., then left at room temperature or in a hot air oven, induction heating The additional coating layer is obtained by curing and drying in a furnace, a near infrared furnace, a far infrared furnace, an energy beam curing furnace or the like.

  A known pigment or additive can be added to the additional coating layer as necessary. Although the film thickness is arbitrary, in the case of a coated metal plate, a dry film thickness of about 1 to 30 μm, particularly 3 to 12 μm is common. The drying conditions may be appropriately selected according to the type of paint and the performance to be obtained, but the conditions are such that the maximum plate temperature is 150 to 240 ° C. and the arrival time is about 10 to 200 seconds in a hot air furnace, induction heating furnace, near infrared furnace or the like. Is common. There may be no additional coating layer, and it may be a single layer or a multilayer.

  EXAMPLES Next, although an Example demonstrates this invention further, this invention is not limited to these examples.

Non-chromate ground treatment is applied to hot dip galvanized steel sheets with a zinc adhesion of 60 g / m ² (per side) using E300N (Nippon Parkerizing Co., Ltd.) under standard conditions, and then primer PDN1 (polyester resin system from Nippon Paint Co., Ltd.) Primer paint) was applied to a dry film thickness of 5 μm and baked under standard conditions to produce a substrate.

  On this substrate, using the slide coater, the following coating materials A-1 to A-3 for the lower layer coatings have the dry film thicknesses shown in Table 1, and the following coating materials B-1 are used as the coating materials for the surface layer coatings. -B-4 was similarly applied so as to have a dry film thickness shown in Table 1. After the application, baking was performed using a hot-air drying oven under conditions where the maximum plate temperature reached 240 ° C.

-Paint A-1: FLC7000 (Nippon Paint's hydroxyl group-containing polyester resin-based paint, including a methylol group-containing melamine resin as a crosslinking agent. Beige) was diluted with a solvent, and a surface conditioner and a rheology-imparting agent were added. Things (Surface tension 25-30 × 10 ^-3 N / m, Viscosity 50-100mPa · s)
・ Paint A-2: FLC1520 (blocked isocyanate group-containing polyester resin-based paint manufactured by Nippon Paint Co., Ltd.) diluted with a solvent and added with a surface conditioner and a rheology imparting agent (surface tension 25-30 × 10 ⁻³ N / m, viscosity 50-100mPa · s)
・ Paint A-3: A surface conditioner is added to WS4000 (a silanol group-containing urethane resin manufactured by Mitsui Takeda Chemical Co., Ltd.) and colloidal silica (Snowtex N manufactured by Nissan Chemical Co., Ltd., 100/20 added in terms of solid content). (Surface tension 50-60 × 10 ^-3 N / m, viscosity 15-20mPa · s)

-Paint B-1: Polycondensate of tetraethoxysilane / dimethylmethoxysilane / tetramethoxyzirconium = 50/40/10 (molar ratio) (alcohol solvent; weight average molecular weight 4000) (surface tension 25-30 × 10 ⁻³ N / m, viscosity 150-200mPa · s)
Paint B-2: polycondensate of tetraethoxysilane / ethyltriethoxysilane = 30/70 (molar ratio) (water-alcohol mixed solvent; weight average molecular weight 5000) (surface tension 50 to 55 × 10 ⁻³ N / m, viscosity 50-100mPa · s)
-Paint B-3: polycondensate of tetraethoxysilane / dimethylmethoxysilane = 80/20 (molar ratio) (alcohol solvent; weight average molecular weight 4500) (surface tension 25-30 × 10 ⁻³ N / m, viscosity 100 ~ 150mPa · s)
-Paint B-4: Polycondensate of tetramethoxysilane (alcohol solvent; weight average molecular weight 3000) (surface tension 25-30 × 10 ⁻³ N / m, viscosity 100-150 mPa · s)

As a comparative example, on the above substrate, the following paints C-1 and C-2 are individually shown to have a dry film thickness of 18 μm, and D-1 to D-3 and E-1 to E-3 are displayed. Each of the combinations shown in 1 was applied to form a paint film.
-Paint C-1: 10 parts by mass of tetramethoxysilane polycondensate (weight average molecular weight 2200) is added to 100 parts by mass of FLC7000-Paint C-2: FLC7000 is used as it is

-Paint D-1: FLC7000 (Nippon Paint's hydroxyl group-containing polyester resin-based paint, including methylol group-containing melamine resin as a crosslinking agent. Beige color) (surface tension 30 to 35 × 10 ^-3 N / m, viscosity 350 ~ 500mPa · s)
Paint D-2: FLC1520 (blocked isocyanate group-containing polyester resin paint manufactured by Nippon Paint Co., Ltd.) (surface tension 30 to 35 × 10 ⁻³ N / m, viscosity 350 to 500 mPa · s)
-Paint D-3: Paint in which colloidal silica (Snowtex N manufactured by Nissan Chemical Co., Ltd.) is added to WS4000 (silanol group-containing urethane resin manufactured by Mitsui Takeda Chemical Co., Ltd.) at a solid content mass ratio of 100/20 (surface tension 60-80) × 10 ^-3 N / m, Viscosity 15-20mPa · s)

-Paint E-1: Polycondensate of tetraethoxysilane / dimethylmethoxysilane / tetramethoxyzirconium = 50/40/10 (molar ratio) (weight average molecular weight 1500) (surface tension 20-25 × 10 ⁻³ N / m , Viscosity 20-100mPa · s)
・ Paint E-2: Polyethoxysilane / dimethylmethoxysilane = 80/20 (molar ratio) polycondensate (weight average molecular weight 2000) (surface tension 20 to 25 × 10 ⁻³ N / m, viscosity 20 to 100 mPa) s)
-Paint E-3: Tetramethoxysilane polycondensate (weight average molecular weight 2200) (surface tension 20 to 25 × 10 ⁻³ N / m, viscosity 20 to 100 mPa · s)

<Confirmation of mixed layer>
The presence or absence of the mixed layer was confirmed by the method described above with reference to FIGS.

<Surface layer exposed area ratio>
The surface layer exposed area ratio indicates the ratio of the surface layer exposed on the outer surface of the coating film. As the mixing progresses, the lower layer binder resin floats on the outer surface of the coating film and the surface layer resin is not uniformly distributed.
In the present invention, since the surface layer contains a high-concentration metal alkoxide (organic silicate) compound, even if the exposed area ratio of the surface layer is reduced to 70%, sufficient contamination resistance is exhibited.
The exposed area ratio can be measured by the following method.

５）各測定用サンプル（３箇所）の露出面積率を平均して平均露出面積率を算出する。更に他の断面試料（１０試料）についても同様の検査を行う。
６）１０試料の平均露出面積率を更に平均して、最終の露出面積率とする。 <Measurement method of exposed area ratio>
Please refer to FIG. In FIG. 6, 1 is the lower layer, 2 is the surface layer, Xn is the length of the exposed portion of the surface layer, and Y is the sample length (500 μm).
1) Take 10 cross-section samples of the coating film at any part of the product.
2) Each cross-sectional sample is observed with a 400 times SEM (scanning electron microscope) image, and three measurement samples having a length of 500 μm (corresponding to Y in FIG. 6) are arbitrarily selected.
3) The interface between the surface layer and the lower layer is observed for each measurement sample, and the length of the portion where the surface layer is exposed (Xi in FIG. 6) is measured.
4) The total of the length (Xi) of the exposed portion of the surface layer with respect to the sample length (Y) is compared, and the exposed area ratio is calculated by the following formula.

5) The average exposed area ratio is calculated by averaging the exposed area ratios of the respective measurement samples (three places). Further, the same inspection is performed on other cross-sectional samples (10 samples).
6) The average exposed area ratio of 10 samples is further averaged to obtain the final exposed area ratio.

Further, when the surface layer film contains zirconium, the exposed area ratio can be calculated more easily using EPMA. That is,
1) Take 10 samples at any part of the product.
2) Using an SEM (scanning electron microscope) with an EPMA (electron beam analyzer), observe the above sample with a 400x image, and arbitrarily place three 500μm × 500μm measurement samples. select.
3) For each measurement sample, the area (Z) of the region where the EPMA spectrum of zirconium is detected in the region is measured.
4) Measure the exposed area ratio using the following formula.
Exposed area ratio = Z / (500 μm) ² × 100
In this measurement, the measurement can be performed more easily by using a device such as a CMA with an image processing device using a computer.

<Rain dripping resistance>
The dripping resistance was examined as follows. The manufactured pre-coated steel sheet is cut into a width of 110 mm and a length of 245 mm, arranged so that the length direction is vertical, and is bent so that the evaluation surface is upward at 100 mm from the top of the length direction (bending R is 10 mm). It was installed on a stand for outdoor exposure so that the lower part in the length direction was vertical. The exposure test was conducted for 6 months as it was, and the raindrop on the vertical surface was visually observed and evaluated according to the following criteria.
◎: No raindrops ○: Raindrops are slightly △: Raindrops are clearly recognizable ×: Raindrops are 20 meters away

<Karakushi stain resistance>
The rust resistance and stain resistance were evaluated as follows. The manufactured pre-coated steel sheet was cut into 50 mm squares, and a Japanese style bean paste from SSB Foods Co., Ltd. was applied to an area of about 30 mmΦ on the evaluation surface and left at 20 ° C. for 24 hours. After standing, it was washed with water, and the color of the area where the mustard was applied was measured to determine the color difference (ΔE) from before the test and evaluated according to the following criteria.
A: ΔE ≦ 1.0
○: 1.0 <ΔE ≦ 2.0
Δ: 2.0 <ΔE ≦ 3.0
×: ΔE> 3.0

<Magic ink (registered trademark) stain resistance>
Evaluation of anti-magic ink (registered trademark) contamination was carried out as follows. The manufactured precoated steel sheet was cut into 50 mm squares, three lines were drawn on the evaluation surface with red magic ink (registered trademark), left in an atmosphere of 20 ° C. for 24 hours, and then the lines were wiped with ethanol. The color residue of the ink was visually determined and evaluated according to the following criteria.
◎: No trace remaining ○: Slight color residue △: Color residue present ×: Almost disappears

<Processability>
The workability was evaluated as follows. The manufactured pre-coated steel sheet was bent so that the evaluation surface was on the front side, and the occurrence of cracks in the coating film in the bent portion was observed with a 10-fold magnifier.
At the time of bending, the same steel plate was sandwiched between T sheets, and the minimum number of sheets T without cracks was determined. For example, if the thickness of the plate is T, 0T means that the coating does not crack even if it is folded without sandwiching the plate, and 2T means that the coating does not crack even if it is folded between two plates. However, when a sheet is sandwiched and bent, the coating film is cracked.

<Coating hardness>
The coating film hardness was evaluated by pencil hardness.
The pencil hardness was determined so that the coating film was not damaged by the method of JIS G 3312.

<Contamination life>
The method for measuring the contamination-resistant life was as follows.
The same test is performed again after one year for each of the raindrop stain resistance, mustard stain resistance, and magic ink (registered trademark) stain resistance, and the determination is made based on the results. That is, with regard to raindrop resistance, the outdoor exposure test is continued as it is, and the same evaluation is made after one year and six months. For rust resistance and magic contamination resistance, the same test is performed on test materials stored indoors for one year and evaluated according to the same standards. These test results were determined on the basis of the following criteria in comparison with the previous test results, and were defined as the anti-contamination life.
◎: Evaluation equal to or better than that in all tests ○: Degradation of only one level in one test △: Degradation of only one level in two tests ×: Degradation in all tests or specific Evaluation decreased by 2 or more levels in the test

The evaluation results are shown in Tables 1-2.
Examples 1 to 3 have a hydroxyl group-containing polyester resin-based paint (A-1) containing a methylol group-containing melamine resin as a crosslinking agent as a lower layer, and a molar ratio of tetraethoxysilane / dimethylmethoxysilane / tetramethoxyzirconium of the present invention. The polycondensate (B-1) of 50/40/10 was applied as a surface layer while changing the surface area exposed area ratio. A remarkable mixed layer was formed in the coating film, and as a result, good workability was exhibited. In addition, although both the contamination resistance and the contamination resistance life were good, there was a tendency for both the contamination resistance and the contamination resistance life to decrease as the exposed area ratio of the surface layer decreased.

  In Examples 4 and 5, the type of the surface layer resin was changed to a polycondensate (B-3) having a molar ratio of tetraethoxysilane / dimethylmethoxysilane of 80/20 and a polycondensate of tetramethoxysilane (B-4). For example, in all cases, remarkable mixing occurred and excellent workability was exhibited. Moreover, since the surface layer exposed area ratio was set as high as 95%, both the stain resistance and the pencil hardness were satisfactory. Also, the contamination-resistant life was very good.

  Examples 6 and 7 are examples in which the type of the lower layer resin was changed to a silanol group-containing urethane resin-based paint blended with a blocked isocyanate group-containing polyester resin-based paint and colloidal silica. Was recognized. In addition, both contamination resistance and contamination resistance life were extremely good.

In Examples 9 to 13, the influence was examined by changing the film thickness of the surface layer and the lower layer, but even when the film thickness was changed and the surface layer exposure rate was changed, the generation of a mixed layer was observed. On the other hand, when the film thickness of the surface layer became thinner and the exposed area ratio of the surface layer decreased, the contamination resistance tended to decrease. The contamination-resistant life tended to decrease slightly compared with the case where the surface layer was thick.
Comparative Example 1 is obtained by applying a mixture of a binder resin (hydroxyl group-containing polyester resin) and a polycondensate of tetramethoxysilane to the above substrate, and the stain resistance is that of the example of the present invention. Although it is not good compared with many examples, it is within the usable range depending on the application. On the other hand, this comparative example has a poor workability and is inferior in stain resistance as compared with Example 7 having the same workability. In addition, when compared with Example 11 and Example 14 that showed equivalent stain resistance, the workability was inferior, and overall, the result was better than the Example. It's hard to say.

  In Comparative Example 2, a hydroxyl group-containing polyester resin-based paint containing a methylol group-containing melamine resin was applied as a crosslinking agent used as the binder resin of Comparative Example 1, but for all the pollutants tested. It did not show stain resistance.

  Comparative Examples 3 to 9 are paints having the same components as in the examples, and the paints having different surface tension and viscosity are used. The paint used in the comparative example has a higher surface tension than the paint used in the example and is a highly viscous paint. That is, it is a paint property that is extremely difficult to generate a mixed layer as compared with the paint used in the examples. As shown in Table 1, no intermixing occurred in Comparative Examples 3 to 9. In the comparative example in which the mixed layer does not occur, the stain resistance, the contamination resistant life, and the pencil hardness are as good as in the example, but the workability is slightly inferior to the example in which the mixed layer is generated (implemented). The processability of the examples was 0T to 1T, and that of the comparative examples was 1T to 2T).

  As described above, it has been clarified that the mixed layer state can be obtained by the method described in the examples, and the workability is improved as an effect. The method for realizing the mixed layer state is not particularly limited, but it can be easily achieved by setting the surface tension and viscosity of the coating material for forming the surface layer film and the lower layer film to an appropriate range.

The coated plate obtained by the coated plate manufacturing method of the present invention can be applied to various applications as pre-coated metal (PCM). For example, it can be applied to roofs, exterior walls, interior materials, various exteriors, tunnel interior materials, guardrails, etc. as building materials, exterior materials for various machine parts, various containers (cans, boxes), various household appliances (refrigerators, laundry) Machine, air conditioning equipment), cooking utensils, transportation equipment (cars, motorcycles), etc.
In addition, the method for producing a coated plate according to the present invention is not limited to pre-coated metal, but is applied to the production of a coated plate in which a substrate made of a material such as paper, wood, plywood or resin, which is required to be resistant to various types of dirt, is applied. Is also possible.

It is a figure explaining the definition of the mixed layer whose boundary surface is continuous. It is a figure explaining the definition of the mixed layer whose boundary surface is continuous. It is a figure explaining the definition of the mixed layer whose boundary surface is continuous. It is a figure explaining the definition of the mixed layer whose boundary surface is discontinuous. It is a figure explaining the definition of the mixed layer whose boundary surface is discontinuous. It is a figure explaining the measuring method of a surface layer exposure area rate.

Explanation of symbols

1 Lower layer 2 Surface layer

Claims (3)

A surface coating mainly comprising a partial polycondensate (I) produced by hydrolysis of one or more metalloid elements or metal alkoxides selected from silicon, titanium, zirconium and boron and / or the alkoxides on a substrate; And a lower layer film mainly composed of a binder resin (II) having a functional group that reacts with the alkoxide and / or a partial condensate thereof (I), and both layers are mixed, and is resistant to contamination. A method for producing a coated plate excellent in workability and workability, wherein one or more metalloid elements or metal alkoxides selected from silicon, titanium, zirconium and boron and / or partial weights produced by hydrolysis of the alkoxides Coating for surface layer coating mainly composed of condensate (I), and binder having functional group that reacts with alkoxide and / or partial condensate (I) thereof The coating material for the lower film mainly made of resin (II), is applied to a substrate, there is simultaneously dried baked two paint, the same or viscosity of the coating for the surface layer coating and the viscosity of the paint for the lower layer film greater, and / or the difference in surface tension surface tension and lower film-coating material of the surface layer coating paint is characterized in that 5 × is 10 ^-3 N / m or less, excellent workability and stain resistance A method of manufacturing painted plates. The method for producing a coated plate excellent in stain resistance and workability according to claim 1 , wherein the coating for the surface layer coating and the coating for the lower layer coating are simultaneously applied to the substrate by a multilayer curtain method. The coating with excellent stain resistance and workability according to claim 2 , wherein the coating for the surface layer coating and the coating for the lower layer coating are simultaneously applied to the substrate by a multilayer curtain method using a slide coater. A manufacturing method of a board.

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