Technical field
[0001]The present invention, on the excellent rust corrosion resistance of the end face, the scratch resistance and moisture absorption resistance of the coating film regarding good precoated steel sheet. More particularly, the present invention is, for example, an electric product, in fields such as architecture, environment wet with water, a chromate-free type precoated steel sheet used in an outdoor environment, particularly exposed to rainwater, moisture absorption resistance of the coating film in addition to excellent relates chromate-free type precoated steel sheet excellent in scratch resistance.
BACKGROUND
[0002]When installed precoat steel plate outdoors is exposed to a high temperature and rainy environments such as rainy, problems red rust in a short period of no coating film cutting end face are known. To solve this problem, pre-coated steel sheet having an end face rust corrosion have been proposed.
[0003]
　As an example, Patent Document 1, the end face rust inhibitory precoated steel sheet with the addition of anticorrosive pigments showing red rust inhibiting effect at least in one surface of the coating of the plated steel sheet is described. This means that when the end faces of the precoated steel sheet was immersed in water, anticorrosive pigment is eluted from the coating film, the component is intended to suppress the occurrence of red rust by protecting the end surface. Sodium tungstate may be mentioned as an example of the effect is largely put into practical use as anticorrosive pigment, to the addition have been found various anticorrosive pigments showing red rust inhibiting effect, various which contains them in the coating film Pre-coated steel plate has been proposed. Patent Document 2 describes a chromium-free coated steel sheet having excellent end surface rust corrosion like, phosphates of alkali metals and hypophosphite chloride and alkaline earth metal, a rust inhibiting effect it is described that can be used as anticorrosive pigments shown.
[0004]
　The precoated steel sheet described in Patent Documents 1 and 2, since the anticorrosive pigment is assumed to be eluted from in the coating by any wet, these anticorrosive pigments deliquescence at high humidity high water-solubility They have in common that they are substances having. Coatings containing such deliquescent anticorrosive pigment is easy to absorb moisture in a high humidity environment, problems in a state where the coating film surface wet are obvious. For example, when using precoated steel sheet as a housing of the equipment, when a state results in which the coating surface is wet, when pasting the painted surface with an adhesive foam material or the like for the notes stickers and airtightness improves , a problem occurs where the pressure-sensitive adhesive can not be bonded.
[0005]
　Patent Document 3, precoated steel sheet painted on one surface of the plated steel sheet was impermeable to water tends coating layer (hereinafter referred to as "water-permeable coating") have been described. This is because the easily water in the film to reach the surface of the steel sheet permeated original plate, causing positively coupled current between the plating and the base steel of the cut end faces of the steel plate, the end face by the sacrificial protection effect of zinc it is intended to suppress the occurrence of red rust from. Examples of the water-permeable coating is containing a predetermined amount of pigment in a relatively thin film in, and at least part thereof by a pigment of relatively large particle size, external moisture passes through the coating film of zinc coatings designed to make it easier to reach the system plating layer has been proposed.
[0006]
　The precoated steel sheet described in Patent Document 3, the film so the Patent Documents 1 and 2, but the film is not likely problem exists moisture, only the sacrificial protection effect of zinc is insufficient rust inhibiting effect of the end face, and it can not be avoided the occurrence of white rust of a steel plate surface by dissolution of zinc.
[0007]
　As precoated steel sheet to solve the problem in the technique of Patent Document 1 to 3, the present inventors have developed a pre-coated steel sheet described in Patent Document 4. This makes the surface of the coating film containing an effective anticorrosive pigment red rust prevention of the end surface, the liquid water for effective expression of the anticorrosive pigment through but, due to deliquescence of anticorrosive pigment in the coating film of moisture causative gas water (steam) is precoated steel sheet so as to cover the top layer coating which does not transmit (water permeable water vapor impermeable coating).
[0008]
　Advance a coating film is shipped to form, in the precoat steel plate is molded by omitting the coating step at the user generally good processability (bending workability, such as press workability) is also required. As a technique to meet such a demand, it is known that the addition of wax coating, for example, Patent Document 4, water permeable, water vapor impermeable coating provided on coating containing anticorrosive pigment the film, it is described that the inclusion of ingredients such as wax.
　Further, Patent Document 5, the addition of wax to the coating film hydrophilic treatment, by controlling the projected area ratio on the coating surface of the wax, with the expression of excellent formability according waxes, tetraalkoxysilane rain excellent by partial hydrolysis condensate of it has been proposed to express anyone pollution improvement. The coated steel plate described in Patent Document 5, the end face corrosion resistance of the steel sheet is not considered.
CITATION
Patent Document
[0009]
Patent Document 1: WO 2011/071175 Patent
Patent Document 2: JP 2009-045923 Patent Publication
Patent Document 3: JP 2010-083075 Patent Publication
Patent Document 4: JP 2016-193593 Patent Publication
Patent Document 5: JP 2013-018263 JP
Summary of the Invention
Problems that the Invention is to Solve
[0010]
　The present inventors, when practical use of precoated steel sheet as described in Patent Document 4 was developed, in order to improve its workability, water permeable, water vapor impermeable on coating containing anticorrosive pigment the coating film was generally contain low-melting waxes. However, the content of the wax in such a low-melting, increasing as close to normal amounts such that the effect is obtained, it has been found that the end face rust corrosion resistance of the precoated steel sheet is lost. That is, the wax to be contained in the water-permeable water vapor impermeable coating of the precoated steel sheet of Patent Document 4 was developed has been found that it is necessary to limit the amount.
[0011]
　On the other hand, limiting the amount of the wax to be contained in the water-permeable water vapor impermeable coating of the precoated steel sheet of Patent Document 4, it was found that no sufficient scratch resistance can not be obtained. More specifically, for example, when the coating of the design side of precoated steel sheet (side where the coating does not contain rust preventive pigment for the end face rust corrosion resistance expression) is thin, stacked for shipment to the user, or coiling in the precoated steel sheet, decorative side coating for sliding during transport or peeled from the underlying steel sheet, phenomena such as galling coating during molding of the user is generated was observed.
[0012]
　Thus, in the precoated steel sheet of Patent Document 4, as well as excellent in moisture absorption resistance to prevent wetting of the coating surface containing anticorrosive pigment for the end face rust corrosion expression, scratch resistance of the coating film, it has become a relief of particular problem that the front and back coating not have to but also excellent coating galling of scratch resistance and the molding process for the sliding during transport.
[0013]
　The present invention seeks to solve this problem.
Means for Solving the Problems
[0014]
　We, the end face rust (simply hereinafter sometimes referred to as "anti-rust pigment") corrosion resistance rust pigments for expressing coating containing (hereinafter, referred to as "lower coat layer") on the water-permeable water vapor causes the effect of the end face rust corrosion resistance anticorrosive pigment by addition of waxes to impermeable top layer coating (also referred hereinafter simply "top layer coating") is impaired, as follows It was discussed.
[0015]
　The inclusion of a low melting point common wax in the uppermost layer coating, the wax is melted during heating and drying to form a top layer coating. Wax surface tension is less hydrophobic, the melted wax may block this by entering the water permeability path in spread or coating wet coating surface. Therefore, pre-coated steel sheet can not be transmitted through the top layer coating water when wet with water, by elution of the anticorrosive pigment in the lower coat layer is prevented, the expression of the end face rust corrosion is inhibited.
[0016]
　Continue considering this discussion based, inventors, not the type of wax which melts by heating, by using a wax in the form of scattered protrudes island from the coating film in particulate after the formation of the coating film It was found that at the same time guaranteeing the end face rust corrosion, it is possible to improve the sliding properties to ensure scratch resistance. In addition, the wax used is a particulate having an average particle size of 1 ~ 8 [mu] m, at a content of 1 to 10 wt% with respect to the dry coating mass is present in a state partially projecting from the surface of the coating film It found that the is preferable. The present invention has been completed based on these findings.
[0017]
　Precoated steel sheet of the present invention was thus completed, the thin coating than in water permeable water vapor impermeable coating in precoated steel sheet of Patent Document 4, hit the material obtained by adding granular wax described above, specifically that gist is as follows.
[0018]
　[1] A zinc-plated steel sheet both sides chromate-free type chemical conversion treatment layer of was formed thereon, chromate-free type precoated steel sheet having a plurality of coating films including at least a top layer coatings and lower coat layer adjacent thereto a is,
　condition of the top layer coating of one side (1) to (5) below:
　　(1) water contact angle of the uppermost surface of the coating film 65 ~ 75 °,
　　(2) film of the uppermost layer coating thickness 0.5 ~ 5 [mu]
　　m, (3) the top layer coating comprises a first pigment, 15 to 70% by weight content with respect to the dry coating weight of the
　　pigment, (4) the first pigment of the total amount of the average primary particle size 1μm or more of the dry coating mass to 5% by mass or more, and
　　(5) the top layer coating film, a granular wax having an average particle size of 1 ~ 8 [mu] m dry film weight to It is contained at a content of 1 to 10 wt%, the least of the particulate wax particles Some are present in a state of partially projecting from the coating surface,
the filled
　and the lower layer coating adjacent to the top layer coating, one effective in preventing red rust of the end face or two or more deliquescent characterized in that it contains a second pigment is a sexual anticorrosive pigments, chromate-free type precoated steel sheet.
　[2] the wax, PTFE wax, polyethylene / PTFE covariance waxes, and characterized in that it is selected from the group consisting of high molecular weight polyethylene waxes, chromate-free type precoated steel sheet according to [1].
　[3] the second pigment, characterized in that the selected tungstate and silicates, phosphates and chlorides of alkali metals, as well as from the group consisting of hypophosphite alkaline earth metal , chromate-free type precoated steel sheet according to [1] or [2].
　[4] the tungstate, sodium tungstate, calcium tungstate, ammonium tungstate, lithium tungstate, characterized in that it is a tungstate magnesium or mixtures thereof, chromate-free type described in [3] Pre-coated steel plate.
　[5] the silicate, sodium silicate, potassium silicate, characterized in that it is a lithium silicate or mixtures thereof, chromate-free type precoated steel sheet according to the above [3].
　[6] wherein the alkali metal phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium tripolyphosphate, sodium dihydrogen phosphate monohydrate, sodium dihydrogen phosphate dihydrate characterized in that it is a hydrate, or a mixture thereof, chromate-free type precoated steel sheet according to the above [3].
　[7], wherein the alkali metal chloride is sodium chloride, chromate-free type precoated steel sheet according to the above [3].
　[8] The hypophosphorous acid salt characterized in that it is a calcium hypophosphite, chromate-free type precoated steel sheet according to the above [3].
The invention's effect
[0019]
　According to the present invention, in addition to being able to avoid the wetting of the white no rust, and coating in a high humidity environment while exhibiting an end face rust inhibiting effect from the steel sheet surface, the coating resistance during molding galling resistance, and the use of chromate-free type precoated steel sheet with sufficient scratch resistance such as front and back coating scratch resistance for the sliding during transport is possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
FIG. 1 is a diagram showing a wetting evaluation due to moisture absorption of the back coating film in Example.
DESCRIPTION OF THE INVENTION
[0021]
　The precoated steel sheet of the present invention which aims to improve the scratch resistance of the coating film, and a chromate-free type chemical conversion treatment layer formed on the surface of the galvanized steel sheet, which is formed on the chromate-free type chemical conversion treatment layer, the end face rust anticorrosive pigments for corrosion resistance expression (hereinafter, "second pigment" also referred to) a coating containing (hereinafter, referred to as "lower coat layer") and, on the lower-layer coating film, in contact with the under layer coating the upper surface having a top layer coating of water-permeable water vapor impermeability formed to.
　In the present invention, the top layer coating film, the following (1) to (5), it is important particularly satisfying (5).
　　(1) water contact angle of the uppermost surface of the coating film 65 ~ 75
　　°, (2) film thickness of the uppermost coating is 0.5 ~ 5 [mu]
　　m, (3) the top layer coating comprises a first pigment 15 to 70 mass% content of a dry coating weight of the first pigment,
　　(4) first of pigments, the total amount of the average primary particle size 1μm or more of 5 mass with respect to the dry coating weight % or more, and
　　(5) the top layer coating film, and contains at a content of 1 to 10% by weight of particulate wax dry coating weight with respect to the average particle size of 1 ~ 8 [mu] m, at least of the particulate wax particles some are present in a state of partially projecting from the coating surface, and the top layer coating the lower layer coating adjacent to the one effective in preventing red rust of the end face or two or more deliquescent It contains a second pigment is a sexual anticorrosive pigment.
　Therefore, in the precoated steel sheet of the present invention, in accordance with this condition, with at least a portion is partially protruding from the coating surface of the wax particles in the top layer coating, scattered and dispersed like islands. Thus, most of the top layer coating surface is not lost water permeability, therefore rust agent when precoated steel sheet has been exposed to water can be eluted through the top layer coating, sufficient end surface rust corrosion resistance collateral It is.
[0022]
　On the other hand, when the coating film was rubbed with an object, wax protruding from the coating film by partially Midori Kowasuru, sliding resistance can be obtained. Thus, it is possible to prevent the design side coating for sliding during transport in coiled precoated steel sheet or stack is peeled off from the substrate steel sheet, problems such as galling coating during molding of the user is generated.
[0023]
　At least a portion of the particulate wax used in the uppermost layer coating of the precoated steel sheet of the present invention, interspersed protrudes islands from remain partially coating the particulate after the formation of the coating. To meet this requirement, as the particulate wax, those exceeding heat drying temperature of the melting point to form a coating film, or even if melted during heat drying of the coating film, the protruding island from the coating after the deposition melt viscosity to the extent that granular form enough to scattered is not lost to use high. Since heat drying temperature during film formation is generally about 200 ° C., the melting point of the wax is preferably greater than 200 ° C., more preferably above 250 ° C., more preferably greater than 300 ° C.. Meanwhile, a wax having a melt viscosity enough to particulate form be melted during heat drying of the coating film is not lost, 2000 mPa · s or more at the temperature during heat drying of the coating, preferably 2500 mPa · s or more, more preferably shows a viscosity of greater than or equal to 3000mPa · s.
[0024]
　Waxes meeting these conditions, polytetrafluoroethylene (PTFE) waxes, polyethylene / PTFE covariance waxes, such as high molecular weight polyethylene wax. As an example, and the like SST series wax supplied from Shamrock Technologies, Inc. (USA).
[0025]
　Particulate wax used in the present invention, it is preferable that the average particle size of 1 ~ 8 [mu] m. Granular waxes average particle size of less than 1μm are on availability is difficult, it is difficult to obtain a sufficient projection height from the coating film surface. The average particle size of greater than 8μm is coating wax greatly from the surface protrudes after the film formation, since the wax tends to fall off when the coating was rubbed, undesirable. More preferred average particle size of the particulate wax is 3 ~ 5 [mu] m.
[0026]
　Height particulate wax protruding from the uppermost layer coating surface (the distance from the coating surface of the coating film surface and the wax particles to a farthest end) is preferably about 0.1 ~ 3 [mu] m. Is less than 0.1 [mu] m, the sliding resistance is difficult to obtain due hexane corrupted protrusions, it exceeds 3 [mu] m, the wax is transferred to the mold frequently need arises to clean the mold during press molding of steel sheets. More preferred projected height of 0.5 ~ 2 [mu] m.
[0027]
　The film thickness of the presence state, and each layer of the coating film in the uppermost layer coating of the particulate wax, the test pieces of the precoated steel sheet embedded in a resin, can be confirmed by coating section observation by polishing the cross section. The thickness of the top layer coating is the average value of the thickness of non-existent portion of the particulate wax.
[0028]
　The content of the particulate wax in the top layer coating film is preferably 1 to 10% by weight based on the dry coating weight. In less than 1 wt%, the effect of the wax addition is not sufficiently expressed, and when it exceeds 10 wt%, cohesive force of the coating film is not easily deposited drops. Top layer coating of the present invention, because they contain a large amount of the first pigment than usual in order to obtain a water permeable and water vapor impermeable, essentially cohesive force is small, a large amount of wax addition will be further reduced cohesive force of the coating film, which is particularly disadvantageous. More preferable content of the particulate wax is about 1 to 5% by weight, based on dry coating weight.
[0029]
　To further illustrate the precoated steel sheet of the present invention, it is a chromate-free type chemical conversion treatment layer on both sides of at least a zinc-based plated steel sheet, the lower coat layer formed thereon, the top layer which is formed adjacent to the lower-layer coating film It has a coating film. These coatings, and zinc chromate free type chemical treatment from the surface side in the order of the plated steel sheet layer, and the lower coat layer, a top layer coating, but are formed in this order, and the top layer coating film under layer coating if neighboring i.e. provided in contact with the upper surface of the lower coat layer, the structure is not limited. For example, other coating film may be provided between the chromate-free type chemical conversion treatment layer and lower coat layer. Specifically, a primer coating layer formed on the chromate-free type chemical conversion treatment layer, or may be a structure in which a plurality of coating films, such as one or more upper-layer coating film thereon.
[0030]
　Precoated steel sheet of the present invention, one surface of the uppermost layer coating film (1) satisfies the condition - (5), lower coat layer adjacent to the galvanized steel sheet side of the uppermost layer coating film, effectively on the end face rust corrosion It contains a second pigment is one or more deliquescent anticorrosive pigments. In the present invention, the lower coat layer is required to contain a deliquescent anticorrosive pigments, as long as it satisfies this requirement, any other coating which is positioned below the uppermost layer coating film described above anticorrosive it is also possible to contain a pigment.
[0031]
　The second pigment is a valid deliquescent anticorrosive pigment on the end face corrosion resistance, tungstates and silicates, phosphates and chlorides of alkali metals, as well as consisting of hypophosphite alkaline earth metal it can be exemplified one or two or more selected from the group.
[0032]
　The tungstate, for example, sodium tungstate, calcium tungstate, ammonium tungstate, can be used lithium tungstate or tungstic acid magnesium, may be used mixtures thereof. Tungstate may be mixed about 6 ~ 50 wt% in the coating. When the content is less than 6 wt%, insufficient for the expression of the end face rust corrosion resistance, becomes more than 50 wt%, tungstate excessively eluted when the coating film after film formation is exposed to a humid environment, Ya blistering of the coating film peeling could occur. Tungstate content in the coating film is more preferably 7 ~ 40 wt%, most preferably 10 ~ 30 wt%.
[0033]
　The silicate, e.g., sodium silicate, can be used potassium silicate or lithium silicate, it may also be used mixtures thereof. Silicates can be mixed about 5 ~ 50 wt% in the coating. If less than 5 wt%, insufficient for the expression of the end face rust corrosion resistance, becomes more than 50 wt%, silicate excessively eluted when the coating film after film formation is exposed to a humid environment, Ya blistering of the coating film peeling could occur. Silicate content in the coating film is more preferably 7 ~ 40 wt%, most preferably 10 ~ 30 wt%.
[0034]
　Tungstate or silicate used in the present invention is a powder at room temperature, in consideration of the thickness of the contaminating coating, maximum particle diameter 5 ~ 20 [mu] m, more preferably paint until about 5 ~ 10 [mu] m it is preferable to disperse and use a medium.
[0035]
　In the present invention, as the addition of anticorrosive pigments expressing end face rust corrosion, phosphates and chlorides of alkali metals, or it is also possible to use alkaline earth metal hypophosphite. The alkali metal phosphates, e.g., sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium tripolyphosphate, sodium dihydrogen phosphate monohydrate, or sodium dihydrogen phosphate dihydrate things can be used, it may be used mixtures thereof. The alkali metal chloride may be used, for example sodium chloride. The hypophosphite, can be used, for example calcium hypophosphite. Suitable content of the rust preventing pigment in the coating was 0.5 ~ 30wt%, 1 ~ 20wt% is more preferable.
[0036]
　Anticorrosive pigment used in the present invention can also be any combination of the aforementioned materials.
[0037]
　Constituents other than the active anticorrosive pigments for expression of the end face rust corrosion in the lower coat layer adjoining the top layer film may be those used in the coating layer of conventional precoated steel sheet.
[0038]
　Lower coating has a thickness is preferably 2 ~ 20 [mu] m. When it is less than 2 [mu] m, insufficient absolute amounts of anticorrosive pigment added it can not be obtained a sufficient end face rust corrosion resistance, at the same time more than 20 [mu] m, to saturate the effect of the end face rust corrosion and uneconomical, during processing adhesion decreases. More preferred thickness is 3 ~ 15 [mu] m, more preferably 5 ~ 10 [mu] m. Here, the film thickness to say, the average of the distance between the interface and the average thickness, namely the interface and underlying the upper layer of the coating layer of the coating layer. The film thickness can be measured by the following method. The precoated steel sheet was embedded cured epoxy resin, after polishing the cross-sectional direction, performing sectional microscopy of the coated film, to measured the upper and lower interface distance. Considering that an interface distance between the upper and lower fluctuates by measurement location, range of sectional microscopic observation is preferably at least 10mm or more. If the particle size of the added anti-corrosion pigment is protruded from the increased resin of the coating film, it views the protruding pigment surface and the interface between the upper and lower layers of the coating layer.
[0039]
　As described above, the uppermost layer coating adjacent the lower coat layer containing a second pigment, in addition to the conditions of (5) above [1],
　　the contact angle to water of (1) coating the surface 65 ~ 75
　　°, (2) the thickness of the coating film is 0.5 ~ 5 [mu]
　　m, (3) coating comprises a first pigment, the content of the first pigment is dry coating weight relative to 15 to 70 mass %, and
　　(4) the first of the pigment, the total amount of the average primary particle size 1μm or more of the dry coating mass to 5% by weight or more,
it is necessary condition that. The "first pigment" herein, coloring and, or refers to a whole pigment for the purpose of such rust, but does not include deliquescent anticorrosive pigment present in the lower layer. Also, as the ingredient forming the dry film mass (mass in the dry state of the coating film), a binder, pigment, and other components such as beads. Thickness referred to herein is the average of the distance between the interface and the average film thickness, that is, the surface and the lower coat layer, excluding the protruding portion of the particulate wax uppermost coating layer of the coating layer. Film thickness can be performed in conjunction with the time of measurement of a thickness of the above-described lower-layer coating film. Incidentally, if the particle size of the anticorrosive pigment in a second pigment was added to the bottom layer coating protrudes into the uppermost layer coating of resin greatly lower coat layer, and the lower coating layer and the protruding surface of the pigment regarded as the interface.
[0040]
　The contact angle to water of the coating film surface is required to be 65 ~ 75 °. If it is less than 65 °, insufficient effect as a barrier layer against water vapor can not be sufficiently suppressed moisture absorption by deliquescence action of anticorrosive pigments in lower coat layer adjoining it exceeds 75 °, immersion in water It was inhibited elution of anticorrosive pigments from the lower layer coating time, because not obtained sufficient end face rust corrosion resistance.
[0041]
　Contact angle measurements are sufficiently produced by the shearing of the coated steel plate was cut out in a size of 30 mm × 60 mm test piece of wet test conditions (temperature 49 ° C., relative humidity 90-95%) from the left for 15 hours in a blower after drying, the measuring the contact angle with water of the uppermost coating of the surface provided with the coating containing an effective anticorrosive pigment to the end face rust corrosion (water permeable water vapor impermeable coating) . The contact angle with water of 30 seconds after dropping a water droplet on the uppermost layer coating from a microsyringe, a general-purpose contact angle measuring instrument (e.g., manufactured by Kyowa Interface Science Co., Ltd. of CA-A type contact angle measuring instrument, etc.) It is measured using a.
[0042]
　Satisfies the condition of (1) to (4), while the hydrophilic top layer coating surface, is contained a first pigment of a predetermined amount in the relatively thin top layer coating, and at least that one parts are by a pigment of relatively large particle size, the top layer coating is a barrier layer against water (steam) as a gas in contact with the top layer paint film, the second in adjacent lower-layer coating film in while suppressing moisture absorption by deliquescence action of anticorrosive pigment, by allowing the liquid water in contact with the top layer coating film to reach the lower-layer coating film surface by capillary action of the coating film, rust allowing the expression of the red rust preventing effect of the end face due to the elution of the pigment. At the same time, since no liquid water reaching the lower-layer coating film surface containing the anticorrosive pigment is in contact with the zinc plating layer of the steel sheet surface, generation of white rust of a steel plate surface by dissolution of zinc is avoided that.
[0043]
　Top layer coating thus is an in and impermeable to water vapor and water permeability is mainly composed of a binder and a first pigment, and the aforementioned granular wax, contains other components as required .
[0044]
　Binder, a curing agent and a binder resin which is a main component, and a other components.
[0045]
　Type of binder resin, practically is appropriately selected according to performance required as a coated steel sheet, epoxy resins, polyurethane resins, and polyester resins, also uses various types of resins that have been used for coating steel far be able to. However, in the present invention must be a contact angle to water of the uppermost layer coating surface to 65 ~ 75 °, therefore in this range the contact angle at the time of forming the uppermost layer coating by adding other ingredients the use of a resin that can be is determined. Such resins, epoxy resins, polyurethane resins, polyester resins as a base resin, for example, was contained partially hydrolyzed condensate of tetraalkoxysilane resins.
[0046]
　Examples of tetraalkoxysilane, methyl silicate 51, ethyl silicate 40, ethyl silicate 48 (manufactured by Colcoat Co., Ltd.) and include products including commercial products such as MKC silicate MS51, MS56 (manufactured by Mitsubishi Chemical Corporation). Further, tetramethoxysilane, tetraethoxysilane, it may be hydrolytic condensation by adding water and catalyst to monomer such as tetrapropoxysilane.
[0047]
　The curing agent to be combined with the binder resin, for example, melamine resins, polyisocyanate compounds and the like. If necessary, it may be blended a crosslinking catalyst.
[0048]
　Content relative to dry coating weight of the binder component is preferably 30 to 85 mass%. When the content of the binder component is excessively large reduces the amount of relatively first pigment, with the number of pores available for transmission of the liquid will be insufficient, corrosion resistance is lowered or, or it becomes difficult coloring of desired color tone. On the other hand, if the content is too low, although the hardness of the coating film itself is improved elevated 耐疵 with resistance, since the elongation of the coating film itself is lowered, workability is lowered. A particularly preferred content range is 40 to 60% by weight, based on the dry coating weight.
[0049]
　The first kind of the pigment except that not the same as the second pigment is not particularly limited, may be either anticorrosive pigments, color pigments and the like. Examples of anticorrosive pigments, aluminum tripolyphosphate, Zn phosphate and phosphorous acid, Mg, Al, Ti, Zr, and Ce salts, Ca ion exchange silica and oil absorption 100 ~ 1000 ml / 100 g, a specific surface area of 200 ~ 1000 m 2 / g, like amorphous silica particles having an average particle size of 2 ~ 30 [mu] m is.
[0050]
　Examples of coloring pigments, zinc oxide, titanium oxide, calcium carbonate, inorganic pigments such as kaolin, copper phthalocyanine, an organic pigment such as toluidine red, more like carbon black.
[0051]
　Top layer coating of the present invention contains a large amount of the first pigment than usual in order to obtain a water permeable and water vapor impermeability. Content of the first pigment is from 15 to 70% by weight, based on the dry coating weight. In less than 15 wt% content of the pigment, for liquid water is less likely to transmit the coating film, impeded dissolution of anticorrosive pigment in the lower coat layer, the effect of preventing red rust of the end face becomes difficult to appear . On the other hand, when the content of the pigment is more than 70 mass%, workability becomes difficult to satisfy the other properties required for precoated steel sheets, etc. decreases.
[0052]
　Also, among the first pigment, the total amount for the dry coating weight of more pigments having an average primary particle diameter of 1 [mu] m, is required to be 5 mass% or more. It is important to allow the transmission of liquid water such particle size is present in relatively large pigment. The upper limit of the total content for the dry coating weight of more pigments having an average primary particle size 1μm is not particularly set, it is preferable that 70 mass% or less for reasons of workability maintenance after painting. In contrast, the total content for the dry coating weight of more pigments having an average primary particle size 1μm, more preferably 5 to 30 mass%, particularly preferably 5 to 15 mass%.
[0053]
　Preferably has an average primary particle size of the first pigments is less than the thickness of the coating. The average primary particle size of the pigment when an excessively large larger than the thickness of the coating film, corrosion resistance of the painted surface is a concern may decrease.
[0054]
　Top layer coatings, in addition to the above binder and a first pigment component, if necessary, a leveling agent, to obtain an uneven appearance beads, such as conductive powder for improving the weldability and electromagnetic shielding properties it may contain other components. However, when the content of these components is increased, because it causes a decrease in the intrinsic properties of the top layer coating film of the barrier effect, etc. to water permeability and gas liquid water, dry film of these other components the total content with respect to the mass is preferably set to 20 mass% or less, and particularly preferably 10 mass% or less.
[0055]
　The thickness of the top layer coating and 0.5 ~ 5 [mu] m. If it is less than 0.5μm, the barrier effect is less of a gas to water (water vapor). On the other hand, the uppermost layer coating of the present invention, because it contains a large amount of the first pigment than usual in order to obtain a water permeable and water vapor impermeable, essentially cohesive force is small. Coating not withstand the shearing forces due to rubbing of the film thickness is increased when the coating surface is to become easier to cohesive failure. Debris of the back coating film was peeled off by rubbing with front surface coating, also to damage the front surface coating film, resulting in scratches to enter both the front and back surfaces. Further, since the water permeable the film thickness of the uppermost layer coating film becomes thick to decrease the end face rust corrosion dissolution deliquescent corrosion inhibitor from the lower layer is inhibited is reduced. For these reasons, the thickness of the top layer coating is 1 ~ 5 [mu] m, less than 1 ~ 2 [mu] m is more preferable. As described above, the thickness of the coating is preferably in a first average primary particle diameter or less on the pigment which contains.
[0056]
　Coating, such as use as a top layer coating of the present invention is similar to the coating described in Patent Document 3 as the water passes through. The role of water permeability of the coating film in Patent Document 3 satisfies the voids in the coating film water when liquid water touches the coating film is freely transmitted through the coating, plating under the coating the surface is wettable by the liquid (water). In the present invention, the role of the coating film of the lower layer adjacent to the uppermost layer coating film is a coating layer containing a deliquescent anticorrosive pigment rather than plating layer is infiltrated liquid water into the lower layer, JP is the same as in 3. That is, when the precoat steel products that are installed outdoors has been exposed to water in rainfall, in order to suppress the red rust from the cutting edge is deliquescent rust to exert rust prevention effect by eluting into water pigment eluting certainly deliquescent anticorrosive pigment from the lower coat film containing, it is necessary to act on the cut edge. Therefore, the uppermost layer coating, the water impregnated in the coating, the deliquescent anticorrosive pigment eluted from the lower layer, functions to freely diffuse to towards the water that wets the surface of the precoated steel sheet products It is not borne.
[0057]
　On the other hand, in the present invention, in addition to the above role, thereby also borne yet another role in the top layer coating. It if water as a gas (water vapor) touches the top layer coating film, suppressing role of deliquescence anticorrosive pigment absorbs moisture contained in the lower layer and the uppermost layer coating film becomes a barrier layer is there. As described above, the present invention is a coating layer underlying adjacent to the uppermost layer coating film contains a deliquescent anticorrosive pigment rather than plating layer. If the lower layer is a coating layer, adhesion of the top layer coating and the lower coating layer is better than if the lower layer is a plated layer. Then, the gap for transmitting water in the upper layer becomes a structure in which one end is sealed with the lower coating layer, although capillary water can reach the lower-layer coating film layer, in the case of gas, the lower coat since the lower portion of the air gap of the top layer coating in a portion contacting the membrane is sealed, the gas present in the void is difficult to replace. For this reason, liquid water is believed although permeate new mechanism that does not transmit is expressed. As a result, by the upper layer of the deliquescent anticorrosive pigment-containing layer provided a top layer coating described above, as the precoat steel plate surface in direct contact to the environment even under a high humidity environment does not reach the readily wets it can be.
[0058]
　Above in the present invention as, in the water permeable coating film of Patent Document 3, in addition to the conventional functions, and further play a new function can say effect opposite direction from that. That is, if the liquid water in the uppermost layer coating was touched not interfere with the dissolution of the deliquescent anticorrosive pigments from the lower (conventional function), a function not readily elute in the case where water of gas was touched a (new function).
[0059]
　In the chromate-free type precoated steel sheet of the present invention, provided on one above [1] (1) to (5) satisfy the uppermost layer coating film and the non-lower coat layer deliquescent anticorrosive pigment containing adjacent thereto of coating (including all of the coating on the opposite surface) can be formed from a common material used in the production of chromate-free type precoated steel sheet. Meanwhile, all of the coating film both surfaces, normal manufacturing equipment, can be easily formed by the production process, it falls short of will now be described in detail about them.
[0060]
　The steel sheet as a base material for the precoated steel sheet of the present invention, a galvanized steel sheet. The zinc-plated steel sheet, for example, galvanized steel sheet, electro-galvanized steel sheets, Al- galvanized steel sheet, is any such Al-Mg-Si- galvanized steel sheet can be used. Among them, when using the Al-Mg-Si- galvanized steel sheet, improved 耐赤 rust resistance is particularly remarkable, preferable.
[0061]
　On the surface of the galvanized steel sheet as a pretreatment layer for applying a coating paint, providing a normal chromate-free type chemical conversion treatment layer. As an example, the chemical conversion treatment layer, silica, silane coupling agent, tannic or tannic acid, zirconium compounds, there can be used a film containing any two or more and the resin of the titanium compound. Chemical conversion layer, dip coating and chemical conversion treatment liquid, a roll coater coating, wringer roll coating, brush coating, can be formed by a spray coating.
Example
[0062]
　The invention will now be described by way of examples. Needless to say, the following examples are intended for purposes of illustration, the present invention is not limited to the following examples.
[0063]
　Precoated steel sheet as a product is generally a coating film that satisfies the design property requirements customers seek to produce a final product by processing it, located outside in the final product one of which is the surface visible to the human is supplied to the consumer in a form which is provided on the surface, the coating on the other surface with respect to it, is not sought design of the requirements as determined in the coating of one surface, coating the other surface contain components which do not affect the design of direct demanded by consumers as the end face rust corrosion pigment. Generally, the surface to be attached with an adhesive foam material or the like for the notes stickers and airtightness improvement, do not touch the human eye in the final product which is a surface of the other. Therefore, in the following, for convenience, the surface of the "front surface" having a coating film performance consumers seek, the surface having a top layer coating adjacent thereto and an end face rust corrosion pigment-containing coating "back" It will be referred to as a.
[0064]
　As original plate, 11% Al-3% Mg -0.2% Si- galvanized steel sheet (0.6 mm thick, single-side coating weight 80 g / m 2 ) (hereinafter referred to as SD), and galvanized steel sheets (0. 6mm thick, single-side coating weight 80 g / m 2 ) (was used hereafter referred to as GI). After alkaline degreasing of the surface of these original sheet, chromate-free chemical conversion solution (silane coupling agent, tannic acid, silica, and a polyester resin mixed system processing solution) by chemical treatment (coating weight: one side 100 mg / m 2 ) was ( hereinafter referred to as processing a). This chemical conversion treatment, a zinc-plated steel sheet surface layer chromate-free type chemical conversion treatment layer was formed.
[0065]
　The front surface, the chemical conversion treated original sheet of chromate-free type chemical conversion treatment layer, general primer layer (Nippon Fine Coatings Co. polyester / melamine + isocyanate combination curable FLC687 resin paint (typically pigmented) ) is formed, a dry film thickness of 2 [mu] m, PMT: dried with hot air at peak metal temperature of 215 ° C.. As a general top coating thereon, the polymer polyester / melamine-curable coating material (Nippon Fine Coatings Co. FLC8500 resin paint (pale beige)) dry film thickness 10 [mu] m, PMT: hot air dried at peak metal temperature of 230 ° C. , to form a top coating.
[0066]
　On the back, the chemical conversion treated original sheet of chromate-free type chemical conversion treatment layer, the lower coat layer was applied three paints. Among two types are those containing 18 wt% sodium tungstate or potassium dihydrogen phosphate as a deliquescent end face rust corrosion pigment (second pigment). The remaining one does not contain an end face rust corrosion pigments deliquescent, a common coating containing only typical pigments (front surface undercoat layer of the same coating material mentioned above). The resins used in these paints are both polyester / melamine + isocyanate combined curing type resins (Nippon Fine Coatings Co. FLC687 resin). These coatings, lower coat layer is coated to a predetermined dry film thickness, formed: and (PMT dried with hot air at peak metal temperature of 215 ° C.).
[0067]
　Lower coat top layer coating film using the substrate coating to be formed on the film (coating prior to the addition of wax) are both above the water permeability of the patent document 4 - the paint used in the vapor impermeable film it is that apply. Among them, the base paint denoted as type I in Table 1, the NKC1200SC clear (Nippon Fine Coatings Co. low fouling property imparting (silanol group surface segregation) baking type polyester resin of the clear type coating material), titania (Ishihara Sangyo Tipaque CR-90) 40wt%, aluminum tripolyphosphate (manufactured by Tayca Corporation K-WHITE # 82) 5wt%, porous silica (Dokai chemical industries, Ltd. H-33) paint was prepared by blending 5 wt% is (pigment content 50 wt% with respect to dry coating weight). The total amount of the average primary particle size 1μm or more pigments in the paint, was calculated to be 10% on the dry coating weight. Other, base paints types IX from the type II is satisfies the condition of the top layer coating of the present application, in which various conditions are formulated to various changes.
[0068]
　These base paint, using amount contain various waxes shown in Table 1 were contained to changed variously paint as the uppermost layer-coating material coating. "PTFE" in the table, "PE / PTFE", "polymeric PE" respectively, Shamrock Technologies Inc. SST series of polytetrafluoroethylene (PTFE) wax (average particle size 2,4,10Myuemu, mp 321 ° C.) , Shamrock Technologies Inc. FLUOROSLIP series polyethylene / PTFE covariance wax (average particle size 4,6,13Myuemu, mp 110 ~ 130 ℃), Shamrock Technologies Inc. TEXTURE series of polyethylene wax (average particle size 5,30Myuemu, represents the melting point 166 ° C.), microcrystalline wax, the melting point of the carnauba wax is respectively 90 ° C., was 80 ° C..
[0069]
　The contact angle of the formed top layer coating film was measured with a contact angle measuring instrument of CA-A type manufactured by Kyowa Interface Science Co. accordance measuring method described above. As a result, the change in contact angle with the substrate coating even when adding any wax was not observed.
[0070]
　On the other hand, the general coating other than Type I ~ IX was used in Japan Fine Coatings Co., Ltd. Polyester / melamine curable FLC100HQ resin as a paint resin. Uppermost coating on the back surface, forming a film thickness shown in Table 1 as a dry film thickness: and (PMT dried with hot air at peak metal temperature of 230 ° C.).
[0071]
　An overview of the pre-coated steel sheet produced is shown in Table 1.
[0072]
[Table 1]

[0073]
[Table 2]

[0074]
　[Evaluation 1] wetting due to moisture absorption of the back coating
　a 50 × 100 mm test pieces cut out from the precoated steel sheet of Examples and Comparative Examples was prepared, was exposed for 30 minutes in the test environment adjusted to different temperatures and relative humidity, It was observed wetting of the coating film due to the back surface of the moisture absorption. The results are summarized in three patterns shown in FIG. 1 (a) ~ (c) , respectively ◎, ○, it was evaluated as ×. A summary of the test results shown in Table 2.
[0075]
　[Evaluation 2] The adhesive material adhesion at high humidity
　were tested adhesion of the adhesive material under high humidity conditions on the back coating layer of each specimen. Each specimen 20 ° C., after standing in a relative humidity of 95% for 30 minutes, to paste the patch used in the air conditioning field to the coating film of the test piece material (adhesive tape) (15 mm width), affixed to immediately It was measured peeling load by pulling in a direction perpendicular to the coating surface at one end of the wood in spring balance. Peeling load ○ the case of more than 1.96 N, was evaluated as × when less than 1.96 N. The results are shown in Table 2.
[0076]
　[Evaluation 3] end face rust corrosion resistance
　was distilled water immersion test. With distilled water immersion test, it has been found that resistance to rust occurring in a short period of time in a wet environment of non-electrolytes can easily evaluated. For each pre-coated steel sheets of Examples and Comparative Examples, respectively 10 × 40 mm test pieces 20 pieces of, and immersed in distilled water 40ml was placed in a Petri dish with a diameter of 80 mm, was observed transition of red rust of the end face.
[0077]
　Normally, when the red rust does not occur in 168 hours, it has been found to be no practical problem. Here, those distilled water immersion time is not at all red rust occurred at 500 hours exceeds ◎, 500 hours extremely slight red rust (diameter 1mm rust following points 5 or less) in which is does not occur in 168 hours produced the ◎ ~ ○, ○ those that do not occur in but 168 hours red rust (rust than six diameters less than 1mm point) is generated in 500 hours, red rust was evaluated as × those generated from less than 168 hours. The results are shown in Table 2.
[0078]
　[Evaluation 4] scratch resistance of the front and back coating
　when transported in a state of coiled or stacked precoated steel plate, scratch resistance and the front and back coatings produced by the sliding of the front and back coating, molding of the user sometimes the galling resistance of the coating film occurs, was evaluated by the following method. The precoated steel sheet of Examples and Comparative Examples were prepared two sheets which were cut into 50 × 50 mm, superposed one front side and the other one of the back, while pressing at a load of 98N from above and below, after one steel plates rotate 90 °, to release the load, it was observed both coated surface was rubbed.
　The case where both the painted surface contains no scratches on the coating film ◎,
　any scratches are found in the coating of one surface is ○ a case where not reached the exposure original plate,
　is wound on the coating of both surfaces If none is found not reached the exposure original plate to ○ ~ △,
　but the back surface scratches were observed on the coating of both surfaces is reached the exposure original plate front surface is not reached the exposure original plate a case where the scratch does not reach the primer layer remains in the top layer △,
　back surface scratches were observed on the coating film of both surfaces has reached the exposure original plate front surface does not reach the exposure original plate the case where things wound has reached up to the primer layer △ -,
　the coating of both surfaces scratch leading to exposure of the original sheet × a case where observed
was evaluated as. The case where the evaluation is the △ or more was passed. The results are shown in Table 2.
[0079]
　Incidentally, the results were also evaluated for separability of wax shown in the remarks column of Table 2. When the back surface side of the coating film of Examples and Comparative Examples were scraped with a metal blade, describing the × to those falling of wax particles were observed. In this case, when performing press molding actually in the mold, the wax is shed by transferring into a mold, often it is necessary to perform the mold cleaning, which is not preferable for practical use.

The scope of the claims

[Requested item 1]And both surfaces chromate-free type chemical conversion treatment layer of galvanized steel sheet, formed thereon, a chromate-free type precoated steel sheet having a plurality of coating films including at least a top layer coatings and lower coat layer adjacent thereto ,
　one side of the top layer coating film the following conditions (1) to (5):
　　(1) contact angle 65 ~ 75 ° with respect to water of the uppermost layer coating surface,
　　the film thickness of (2) uppermost coating 0 .5 ~ 5 [mu]
　　m, (3) the top layer coating comprises a first pigment, the content of the pigment is dry coating weight to 15-70% by
　　weight, (4) the first of the pigment, the average the total amount of primary particle size 1μm or more of the dry coating mass to 5% by mass or more, and
　　(5) the top layer coating film, a granular wax having an average particle size of 1 ~ 8 [mu] m dry coating weight to 1-10 is contained in a content by mass%, at least some of the particulate wax particles Present in a state of partially projecting from the coating surface,
the filled
　and outermost lower coating adjacent to the upper-layer coating film, the end face of the red rust-proof valid one or more deliquescent in preventing characterized in that it contains a second pigment is a rust pigments, chromate-free type precoated steel sheet.
[Requested item 2]
　The wax is, PTFE wax, polyethylene / PTFE covariance waxes, and characterized in that it is selected from the group consisting of high molecular weight polyethylene waxes, chromate-free type precoated steel sheet according to claim 1.
[Requested item 3]
　Said second pigment, characterized in that the selected tungstate and silicates, phosphates and chlorides of alkali metals, as well as from the group consisting of hypophosphite alkaline earth metals, claim chromate-free type precoated steel sheet according to 1 or 2.
[Requested item 4]
　The tungstate, sodium tungstate, calcium tungstate, ammonium tungstate, lithium tungstate, characterized in that it is a tungstate magnesium or mixtures thereof, chromate-free type precoated steel sheet according to claim 3.
[Requested item 5]
　The silicate, sodium silicate, potassium silicate, characterized in that it is a lithium silicate or mixtures thereof, chromate-free type precoated steel sheet according to claim 3.
[Requested item 6]
　The alkali metal phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium tripolyphosphate, sodium dihydrogen phosphate monohydrate, sodium dihydrogen phosphate dihydrate, or characterized in that it is a mixture thereof, chromate-free type precoated steel sheet according to claim 3.
[Requested item 7]
　Characterized in that the alkali metal chloride is sodium chloride, chromate-free type precoated steel sheet according to claim 3.
[Requested item 8]
　Characterized in that said hypophosphite salt is calcium hypophosphite, steel sheet according to claim 3.