JP4483372B2 - Resin coated tin alloy plated steel sheet - Google Patents

Description

  The present invention relates to a surface-treated steel sheet for cans used in food cans, beverage cans, general cans, and the like, and relates to a resin-coated tin alloy-plated steel sheet coated with a thermoplastic resin.

  Conventionally, in order to produce food cans, beverage cans, general cans, etc., surface-treated steel sheets obtained by coating tin-plated steel sheets or thin chrome-plated steel sheets have been used. Painting is often performed multiple times, and not only is the baking process of the paint complicated, but most of the paint used for painting is an organic solvent that can cause pollution problems when released into the atmosphere. There is a problem that the equipment cost is increased because the equipment to be processed is required. In order to avoid the use of organic solvent paints, water-based paints have also been developed. However, since the coating film performance is inferior, the level of practical use has not yet been reached.

  In order to solve these problems, many attempts have been made to laminate a thermoplastic resin film, and studies have been made to laminate a film of polyolefin resin such as polyethylene resin or polypropylene resin or a film of polyester resin such as polyethylene terephthalate resin. It was conducted.

Furthermore, Patent Documents 1 and 2 disclose a so-called extrusion laminating technique in which a molten resin is directly contacted with a metal plate and coated. Such a technique can be laminated at a lower cost than the film laminating technique.
JP-A-57-203545 JP-A-2-241737

  However, even for laminated steel sheets to which film laminating technology or extrusion laminating technology is applied, in the case of contents containing a solvent or alcohol that swells the film, it is difficult to maintain the barrier properties of the film. Rust was observed in the processed and welded parts, which was a practical problem. In such a case, there is a method of improving the corrosion resistance by applying a primer made of a thermosetting resin to the lower layer of the film, but this has been a problem because the cost is greatly increased.

  On the other hand, as the surface-treated steel sheet for cans, there are a tin-plated steel sheet and a thin chrome-plated steel sheet, which are conventionally called tinplate.

  For tin-plated steel sheets, the tin oxide is usually plated with tin, then immersed in an aqueous solution containing a hexavalent chromium compound such as dichromic acid or chromic acid, or electrolyzed in this solution. Or it is common to form the chromate film which consists of metal chromium and chromium oxide.

  Moreover, a thin chromium plating steel plate forms the layer which consists of metal chromium and a chromium oxide by the electrolytic treatment in the aqueous solution of chromic acid for the same original plate. There is chromium oxide in the outermost layer of these surface-treated steel sheets for cans, and this chromium oxide is known to have an effect of improving adhesion to a polyethylene film.

  However, when immersion treatment or electrolytic treatment is performed with an aqueous solution using a hexavalent chromium compound such as dichromic acid or chromic acid, not only is it necessary to ensure safety in the working environment and wastewater treatment, but also in the unlikely event. If the chromate treatment liquid leaks due to an accident, etc., there is a great risk of serious damage to the environment. Due to recent environmental problems, movements to regulate chromium are progressing in various fields, and the need for chemical conversion treatment to improve adhesion to laminate resin without using chromium in surface-treated steel sheets for cans has increased. ing.

  As a technology relating to chemical conversion treatment instead of chromate treatment of the surface-treated steel sheet for cans, for example, Patent Document 3 contains Cr on a tin-plated steel sheet by direct current electrolysis using a tin-plated steel sheet as a cathode in a phosphoric acid solution. The surface treatment method of the tin plating steel plate which formed the chemical conversion film which does not carry out is disclosed, and patent document 4 makes P or P and Al contain in a chemical conversion film, and tin-plates the chemical conversion film which does not contain Cr An electroplating tin for seamless cans applied to the surface of the layer is disclosed.

However, in the laminate, none of the chemical conversion films described in the above-mentioned publications can be said to have sufficient adhesion as compared with a conventional chromate film formed by dichromic acid or a chromic acid solution.
Japanese Patent Publication No.55-24516 Japanese Patent Publication No. 1-332308

  The object of the present invention is to provide a coating resin without containing Cr, which is undesirable from an environmental problem, in the chemical conversion film formed on the upper layer of the tin alloy plating layer as a tin-based plated steel sheet having excellent corrosion resistance. It is to provide a resin-coated tin alloy-plated steel sheet having a resin coating layer excellent in corrosion resistance, even for a content containing a solvent or alcohol that swells a thermoplastic resin and has excellent adhesion to the resin. .

The present invention is described in further detail below.
When a chemical conversion film not containing Cr is formed on the tin alloy layer using the above-described conventional technique, it is difficult to satisfy the adhesiveness to the laminate resin.

  For this reason, the inventors have conducted extensive research to solve the above-described problems in the surface-treated steel sheet. As a result, when a chemical conversion film containing P and Si is formed on the upper layer of the tin alloy layer, the laminate resin and It has been found that sufficient adhesion can be satisfied. More specifically, if a chemical conversion film containing an appropriate amount of P and Si is formed on the upper layer of the tin alloy layer, preferably by a chemical conversion treatment solution containing P and a silane coupling agent, the silane coupling agent. It was found that the reactive groups present in the film orientate and greatly contribute to the improvement of the resin adhesion.

The surface-treated steel sheet of the present invention has a tin alloy layer containing one or two selected from Fe and Ni on the steel sheet surface, and 0.5 to 100 mg / m ² P and 0.1 to 0.1 to the upper layer. It has a chemical conversion film containing 250 mg / m ² of Si, and the surface of the chemical conversion film has an adhesive resin layer as a lower layer, and a water repellent resin layer having a surface contact angle with water at 25 ° C. of 87 degrees or more as an upper layer. have a composite resin layer to the water-repellent resin layer (1) fluorine blend resin of the resin and the thermoplastic resin containing, (2) a resin containing silicon and thermoplastic resin blends of resins, Or (3) a blend resin obtained by mixing a silane coupling agent having a fluorine atom or an alkyl group with a thermoplastic resin. In the blend resin shown in (1), the content of the fluorine-containing resin in the blend resin is 0. 5 to 15% by mass, and (2 In the blend resin shown in FIG. 4, the content of the silicon-containing resin in the blend resin is 0.5 to 15% by mass, and in the blend resin shown in (3), the content of the silane coupling agent in the blend resin Is 0.5 to 5.0 mass% . In addition, it is preferable to make Si / P ratio (mass ratio) in a chemical conversion film into the range of 0.05-100.

  Moreover, it is preferable to form the said chemical conversion film with the chemical conversion liquid containing P and a silane coupling agent, and it is more suitable that the said silane coupling agent has an epoxy group.

Furthermore, it is preferable that the adhesion amount of Sn in the tin alloy layer is 0.1 to 3.0 g / m ² .

  According to the present invention, the chemical conversion film formed on the upper layer of the tin alloy layer has a function of improving the film characteristics, but does not contain Cr, which is undesirable due to environmental problems. It is possible to provide a resin-coated tin alloy-plated steel sheet having a resin coating layer excellent in corrosion resistance, even for contents containing a solvent or alcohol that swells thermoplastic resins and has excellent adhesion.

Embodiments of the present invention will be described in detail below.
The tin alloy-plated steel sheet used for the resin-coated tin alloy-plated steel sheet of the present invention is obtained by forming a tin alloy layer on a normal tin plate, and the “tin alloy layer” in the present invention is from among Fe and Ni It means a tin alloy layer containing one or two selected types.

  Ordinary tinplate is Sn plating on tin plate, or it is left as it is or is subjected to general heat treatment (reflow treatment) for heating and melting Sn (in this case, tin plate and Sn plating layer) Since most of the surface is metal Sn, the Sn oxide grows on the surface of the metal Sn when the storage period until use is long. . Since this Sn oxide is fragile, film peeling is likely to occur after lamination, starting from this Sn oxide, and the film adhesion is remarkably deteriorated.

  In order to solve this drawback, conventionally, it has been dealt with by chromate treatment, but even if chromate treatment is carried out, it can completely suppress the growth of Sn oxide that tends to occur on the surface of metal Sn. Can not.

Therefore, in this invention, the steel plate (tinplate original plate) surface, having a place tin alloy layer of Sn oxide is grown metal easily Sn layer, and forming a conversion coating on the upper layer of the tin alloy layer Thereby, excellent adhesion can be obtained.

  As a means for forming the tin alloy layer, a method of forming a Fe—Sn alloy layer by completely alloying Sn with base metal by heat treatment after tin plating is often used. Further, if a Ni-based pretreatment is applied to the steel sheet surface before tin plating, a denser Fe—Sn—Ni alloy layer can be formed.

  As Ni-based pretreatment, Ni flash plating treatment for plating a small amount of Ni and Ni diffusion treatment for heat treatment after Ni plating are often used. In the Ni flash plating process, alloying proceeds even at room temperature with Sn plating applied to the upper layer, and alloying occurs when the ratio of Ni and Sn is 1: 3, so the ratio of Ni amount to Sn amount is set to 1: 3. In this case, a Ni—Sn alloy layer can be obtained without heat treatment. In the Ni diffusion treatment, an Fe—Ni alloy layer that is a Ni diffusion layer exists below the tin alloy layer.

  Furthermore, as another method for forming a tin alloy layer, the tin alloy layer is formed by performing Sn alloy plating using a Sn plating solution containing Fe ions and / or Ni ions, regardless of the diffusion alloying reaction after plating. May be formed.

Moreover, in this invention, it is preferable that the adhesion amount of Sn in a tin alloy layer is the range of 0.1-3.0 g / m < ² >. If the Sn adhesion amount in the tin alloy layer is less than 0.1 g / m ² , sufficient adhesion may not be obtained. If it exceeds 3.0 g / m ² , the performance is sufficient but the cost is low. This is because it is not preferable because it becomes high, and in the case of alloying by heat treatment, it is necessary to perform alloying at a high temperature for a long time, which is not preferable from the viewpoint of productivity. In addition, Sn adhesion amount can be measured by a coulometric method or surface analysis by fluorescent X-rays.

Furthermore, the tin alloy layer in the present invention is not particularly limited as long as it is a tin alloy layer containing one or two selected from Fe and Ni. In the case of a Sn—Fe alloy layer, FeSn ₂ alloy layer or FeSn alloy layer is preferable. In the case of Sn—Ni alloy layer, Sn ₃ Ni alloy layer or SnNi alloy layer is preferable, and in the case of Sn—Fe—Ni alloy layer. The (Fe · Ni) Sn ₂ alloy layer or the (Fe · Ni) Sn alloy layer is preferable.

Then, the main features of the structure of the present invention, the upper layer of the tin alloy layer has a conversion coating containing 0.5 to 100 mg / m ² of P and 0.1 to 250 mg / m ² of Si, the chemical conversion coating on the surface of the adhesive resin layer and a lower layer, and have a composite resin layer of the water repellent resin layer and upper layer surface contact angle is 87 degrees or more relative to water at 25 ° C., the water-repellent resin layer, (1 ) A blend resin of a fluorine-containing resin and a thermoplastic resin, (2) a blend resin of a silicon-containing resin and a thermoplastic resin, or (3) a silane coupling agent having a fluorine atom or an alkyl group. It consists of a blend resin mixed with a plastic resin. In the blend resin shown in (1), the content of the fluorine-containing resin in the blend resin is 0.5 to 15% by mass. In the blend resin shown in (2), Of silicon-containing resin in blend resin In the blend resin shown in (3) above, the content of the silane coupling agent in the blend resin is 0.5 to 5.0 mass%. is there.

(1) The P content in the chemical conversion film should be 0.5-100 mg / m ² in terms of the amount of adhesion in this invention. In this invention, the P content in the chemical conversion film should be 0.5-100 mg / m in terms of the amount of adhesion. A range of ² is necessary. If it is less than 0.5 mg / m ² , sufficient adhesion cannot be obtained, and if it exceeds 100 mg / m ² , defects are likely to occur in the chemical conversion film, and the adhesion deteriorates. Note that the P adhesion amount can be measured by surface analysis using fluorescent X-rays.

Further, as a method for forming a chemical conversion film containing P, for example, it is preferable to carry out by phosphoric acid-based chemical conversion treatment. In this case, as a supply source of P in the chemical conversion treatment liquid, phosphate ions (PO ₄ ^{3 -} ) It is more preferable to use 1 to 80 g / l of metal salt such as phosphoric acid, sodium phosphate, aluminum phosphate, potassium phosphate and / or monohydrogen phosphate in terms of conversion.

Note that the chemical conversion treatment liquid, Sn, Fe, Ni metal salts, for example, can be appropriately added metal salts, such as _{SnC1 2, FeC1 2, NiC1 2} , SnSO 4, FeSO 4, NiSO 4. In this case, an oxidizing agent such as sodium chlorate or nitrite, or an etching agent such as fluorine ion may be added as an accelerator.

  A chemical conversion film containing P can be formed by immersing or electrolytically treating the steel sheet on which the tin alloy layer is formed in the phosphoric acid-based chemical conversion treatment solution.

(2) The Si content in the chemical conversion film is adjusted to the range of 0.1 to 250 mg / m ² in this invention. In this invention, the adhesion amount of Si contained in the chemical conversion film has a remarkable effect of improving adhesion. The range of 0.1 to 250 mg / m ^{2 that} appears. If it is less than 0.1 mg / m ² , the effect of improving adhesion cannot be obtained sufficiently. If it exceeds 250 mg / m ² , unreacted Si components remain, especially when a silane coupling agent is used. This is because the silane coupling agent is self-condensed and the effect of improving adhesion is reduced. In order to contain Si in the chemical conversion film, it is preferable to treat with a solution containing a silane coupling agent. Note that the amount of Si adhesion can be measured by surface analysis using fluorescent X-rays.

  As a method for forming a chemical conversion film containing P and Si, a chemical conversion film containing P is formed using the above-described phosphoric acid-based chemical conversion treatment solution, and more preferably a solution obtained by diluting a silane coupling agent in water. It can be done by processing. In addition, when the silane coupling agent is treated with a solution diluted with water and the surface wettability is poor, if repelling occurs, a solution diluted with alcohol can be used. For example, it can be uniformly treated with a solution in which ethanol is 50 mass% or more, the silane coupling agent is 0.5 to 20 mass%, and the remainder is water. The treatment using the solution containing the silane coupling agent may be performed by application of the solution, drying or immersion treatment.

The general chemical formula of the silane coupling agent is X—Si—OR _2or3 (OR: alkoxy group). In the silane coupling agent, an alkoxysilyl group (Si-OR) is hydrolyzed with water to form a silanol group, and is adhered to each other by a dehydration condensation reaction with an OH group on the metal surface. Further, in the upper layer of the steel plate, a reactive group corresponding to X in the general chemical formula is oriented and is compatible or bonded with the resin.

As the silane coupling agent, 3-methacryloxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2- ( Aminoethyl) 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, 3-mercapto Propylmethoxysilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, N-2- (aminoethyl) 3-aminopropyltrimethoxysilane with amino group, N- 2- (Aminoethyl) 3-amino Propyl methyl dimethoxy silane, 3-aminopropyl, etc. triethoxysilane but can be used, in particular there are epoxy groups X of _X-Si-OR 2or3 in the general formula of the silane coupling agent 2- (3,4-epoxy cyclo Hexyl) ethyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane are preferred.

  The chemical conversion film is preferably formed by a chemical conversion treatment solution containing P and a silane coupling agent.

  By adding a silane coupling agent to the phosphoric acid-based chemical conversion treatment solution, which is a method for forming a chemical conversion film containing P, it is possible to form a chemical conversion film containing P and Si in one liquid. In this case, the pH is preferably in the range of 1.5 to 5.5. That is, if the pH of the chemical conversion treatment liquid is adjusted to a range of 1.5 to 5.5, the silane coupling agent can be uniformly dissolved in the chemical conversion treatment liquid, and excellent adhesion can be obtained. This is because if the pH is outside the above range, it becomes difficult to uniformly dissolve the silane coupling agent in the chemical conversion solution, and the effect of improving the adhesion tends to be insufficient.

(3) On the surface of the chemical conversion film, having a composite resin layer having an adhesive resin layer as a lower layer and a water repellent resin layer having a surface contact angle with water at 25 ° C. of 87 ° or more as an upper layer, On the surface of the chemical conversion film, a composite resin layer is formed with an adhesive resin layer as a lower layer and a water repellent resin layer having a surface contact angle with water at 25 ° C. of 87 ° or more as an upper layer.

  In the conventional laminating technology for coating thermoplastic resin, when a container can be filled with water-soluble paints, water-soluble resins, surfactants, etc. containing organic solvent components such as methyl ethyl ketone, toluene, xylene and alcohols In many cases, the water content in the contents reaches the metal surface and rusts starting from the processed part or welded part, and it is difficult to maintain good corrosion resistance.

  For this reason, as a result of intensive studies to solve the above-mentioned problems in the thermoplastic resin-laminated steel sheet, the inventors have found that when a water repellent component having a small surface energy is present in the uppermost layer of the film, It has been discovered that moisture is removed from the resin layer by the water repellent effect of the film, and as a result, has excellent corrosion resistance even when the film layer is swollen by a solvent or alcohol. Furthermore, when arranged by the contact angle with water on the outermost surface, it was found that it has good corrosion resistance when it has 87 degrees or more in an atmosphere of 25 ° C., more specifically, in an air atmosphere of 25 ° C. and 1 atm. . This is because the water-repellent resin having a water surface contact angle of less than 87 degrees has a low water-repellent effect on the moisture contained in the content and does not improve the corrosion resistance of the content.

For the water-repellent resin layer, a blend resin of fluorine-containing resin and thermoplastic resin, a blend resin of silicon-containing resin and thermoplastic resin, or a silane coupling agent having a fluorine atom or an alkyl group is thermoplastic. It consists of blend resin mixed with resin .

  When the water repellent resin layer is made of a blend resin of a fluorine-containing resin and a thermoplastic resin, examples of the fluorine-containing resin include ethylene trifluoride resin and tetrafluoroethylene resin. Examples of the plastic resin include polyethylene resin, polypropylene resin, ethylene-propylene copolymer, and polyester. When tetrafluoroethylene resin is used as the fluorine-containing resin, the molecular weight is relatively small, 200 to 2 million, and excellent dispersibility can be obtained for polyolefin resins such as polyethylene resin and polypropylene resin. Is preferable.

Moreover, content of the fluorine-containing resin in blend resin shall be 0.5-15 mass% . When the content of the fluorine-containing resin exceeds 15 wt%, it is because delamination de repellent resin layer and the lower layer of the resin layer (e.g., adhesive resin layer) is that likely to occur, it is less than 0.5 mass%, sufficient corrosion resistance is because not be obtained.

  When the water-repellent resin layer is made of a blend resin of a silicon-containing resin and a thermoplastic resin, a siloxane-modified polyolefin, for example, a dimethylpolysiloxane-modified ethylene-butene copolymer is suitable as the silicon-containing resin.

In addition, as the thermoplastic resin constituting the blend resin together with the resin containing silicon, for example, polyethylene resin, polypropylene resin, ethylene-propylene copolymer, polyester resin, etc. are used as in the case of the above-mentioned fluorine-based blend resin. It is preferable to do. At this time, the content of the silicon-containing resin is set to 0.5 to 15% by mass . When the content of the silicon-containing resin exceeds 15% by weight, because in the water-repellent organic layer and the underlying resin layer that delamination easily occurs, is less than 0.5 mass%, such a sufficient corrosion resistance can not be obtained it is from the stomach.

When the water-repellent resin layer is made of a blend resin obtained by mixing a fluorine atom-containing silane coupling agent with a thermoplastic resin, the silane coupling agent preferably has a hydrophobic functional group. It is preferable to use one or two silane coupling agents having an alkylsilane group or a fluorine-containing group. For example, methyltriethoxysilane, methyltrimethoxysilane, n-hexyltriethoxysilane, n- hexyltrimethoxysilane, n- _{octyltriethoxysilane, CF 3 CH 2 CH 2 Si} (OCH 3) 3, CF 3 (CF 2) 3 CH 2 CH 2 Si (OCH 3) 3, CF 3 (CF 2) 6 _{COO (CH 2) 3 Si (} OCH 3) 3 and the like. the thermoplastic resin, as in the case of the fluorine-based blend resin, polyethylene tree , Polypropylene resins, ethylene - propylene copolymer, and a polyester resin.

Content of the silane coupling agent in water-repellent resin shall be 0.5-5.0 mass% . Is less than 0.5% by weight, since no sufficient corrosion resistance can be obtained and, at more than 5.0 mass%, the delamination may turn likely to occur in the resin layer of the underlying water-repellent resin layer.

  Examples of the resin suitable for the adhesive resin layer include polyolefin and polyester.

  Among polyolefin-based polyolefins, carboxyl group-containing polyolefins are preferred, and olefinic monomers such as ethylene, propylene, and butene, and α, β-insoluble such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, maleic anhydride, etc. Those obtained by copolymerization or graft polymerization of saturated carboxylic acids are preferred. In particular, the content of the α, β unsaturated carboxylic acid is preferably 0.01 to 35 parts by weight with respect to 100 parts by weight of the olefin component. This is because if it exceeds 35 parts by weight, the effect becomes saturated and disadvantageous in terms of cost, and if it is less than 0.01 part by weight, sufficient adhesion to the steel sheet may not be obtained.

  In the case of polyester, for example, polyethylene terephthalate modified with isophthalic acid is suitable.

  Further, the thicknesses of the adhesive resin layer and the water-repellent resin layer are not particularly limited, but 5 to 100 μm as the water-repellent resin layer and 2 to 40 μm as the adhesive resin layer are suitable. If the adhesive resin layer is less than 2 μm, the resin adhesion to the steel sheet tends to be insufficient, and if it exceeds 40 μm, there is no problem in performance, but it is disadvantageous in terms of cost. If the water-repellent resin layer is less than 5 μm, the corrosion resistance of the contents may be deteriorated. If it exceeds 100 μm, there is no problem in performance, but it is disadvantageous in terms of cost.

Next, an example of a specific manufacturing method according to the present invention will be described.
The chemical conversion treated tin alloy plated steel sheet is obtained by applying Sn plating to a normal tin plate, Ni flash plating or Ni diffusion treatment, and at a temperature equal to or higher than the melting point of tin (231.9 ° C). A tin alloy-plated steel sheet having a chemical conversion film formed thereon is manufactured by performing a heat melting (reflow) process to alloy Sn with the base iron and subsequently performing a chemical conversion process by a dipping process. In addition, after the reflow treatment, in order to improve the reactivity of the chemical conversion treatment, a cathode treatment of 1 C / dm ² may be performed in a 15 g / l sodium carbonate aqueous solution.

  As the chemical conversion treatment liquid, it contains 1 to 80 g / l phosphoric acid in terms of phosphate ion, 0.001 to 10 g / l stannous chloride in terms of tin ion, and 0.1 to 1.0 g / l sodium chlorate, Further, an aqueous solution to which 0.5 to 20.0 mass% of a silane coupling agent is added is used.

  The conditions for the chemical conversion treatment are preferably a temperature of 40 to 60 ° C. and a treatment (immersion) time of 1 to 5 seconds. The tin alloy plated steel sheet after the chemical conversion treatment is dried with hot air of 35 to 150 ° C.

  In addition, as another method of forming a chemical conversion film, after treatment with the above chemical conversion treatment liquid not containing a silane coupling agent, a silane coupling treatment liquid for forming a layer containing Si, for example, 50 mass of ethanol. There is a method of uniformly applying a solution containing 0.5% to 20% by mass of a silane coupling agent and the remaining water, and drying so that the steel sheet surface temperature reaches 50 to 150 ° C.

  Thereafter, at least two types of water-repellent resin and adhesive resin are separately heated and melted, and then the adhesive resin and the water-repellent resin resin are formed on the chemical conversion treated tin alloy plated steel sheet, and the adhesive resin layer is the lower layer. The resin-coated tin alloy-plated steel sheet can be obtained by allowing the water-repellent resin layer to flow down and thermally fusing at least a composite resin layer composed of an adhesive resin layer and an upper resin layer. In order to prevent the temperature of the adhesive resin from decreasing as much as possible when the molten adhesive resin is brought into contact with the chemically treated tin alloy-plated steel sheet, the temperature of the chemical-treated tin alloy-plated steel sheet metal plate is Is preferably preheated with a heating device so as to be about the same as the temperature of the adhesive resin, preferably about the melting point of the adhesive resin to the melting point of the adhesive resin + 200 ° C.

  The above description is merely an example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

For example, one or more resin layers may be further provided between the water-repellent resin layer and the adhesive resin layer depending on the application.
In the above description, the case where the resin-coated tin alloy-plated steel sheet is formed by the so-called extrusion laminating technique in which the molten resin is directly contacted and coated on the tin alloy-plated steel sheet on which the chemical conversion film is formed is shown. It is good also as the method of coat | covering with what is called a film lamination technique which laminates after producing a layer as a film. Here, the extrusion laminating method is advantageous and preferable in terms of thinning the resin layer and cost.

Next, embodiments of the present invention will be described in detail below.
Examples 1 to 11
After forming a tin alloy plating layer shown in Table 1 on a tin plate made of low carbon steel or ultra-low carbon steel having a thickness of 0.3 mm, the four types of chemical conversion treatment conditions (AD) shown in Table 2 are used. Either one was applied to form a chemical conversion film. Then, after heating the tin alloy plated steel plate in which the chemical conversion film was formed, any of nine types of resins shown in Table 3 was laminated by an extrusion method to produce a resin-coated tin alloy plated steel plate. About the obtained resin-coated tin alloy-plated steel sheet, the alloy type and Sn adhesion amount of the tin alloy layer, the P and Si adhesion amount in the conversion coating, the type of the coating resin layer, and the surface contact angle with water at 25 ° C (degrees) Is shown in Table 1. In addition, the measurement of the surface contact angle with respect to water was performed as follows.

[Measurement of water contact angle]
It measured, after setting the temperature around a contact angle meter to 25 degreeC using the contact angle meter (CA-S micro type II, Kyowa Interface Science make). After fixing the sample so that there was no deflection on the surface of the steel plate, one drop of pure water was dropped with the attached dripping machine, and the water drop was attached to the surface. Subsequently, a photograph was taken at a magnification of 300 times from a direction parallel to the steel sheet surface, and the contact angle was measured from the photograph with a protractor.

・ Comparative Examples 1-6
For comparison, a resin-coated tin alloy-plated steel sheet in which either one of the P and Si adhesion amounts in the chemical conversion film is outside the proper range of the present invention, or the configuration of the coating resin layer is outside the proper range of the present invention Was also manufactured.

(Performance evaluation)
Each resin-coated tin alloy-plated steel sheet of Examples and Comparative Examples was tested for evaluating resin adhesion and content corrosion resistance.

1. Resin adhesion test Each of the obtained resin-coated tin alloy-plated steel sheets was stretched using a Erichsen tester so that the resin-coated surface was 3 mm convex, and then immersed in boiling water for 5 hours. The resin adhesion was evaluated in three stages according to the criteria shown below according to the peeling state of the convex portions. The evaluation results are shown in Table 1.

<Adhesion evaluation criteria>
Rating 3: When the film does not peel Rating 2: When peeling occurs when the film is slightly lifted Rating 1: When peeling occurs when the film is completely lifted

2. Corrosion resistance test of the contents Each resin-coated tin alloy-plated steel sheet was processed with a Dubon impact machine to produce convex parts, and a solvent-containing resin solution of 30 parts by weight of methyl ethyl ketone, 20 parts by weight of toluene and 50 parts by weight of urethane-modified polyester resin was convex. In a state of being filled so as to come into contact with the processed part, the sample was left in a thermostatic chamber at 50 ° C. for 90 days and observed for rusting. The condition of the Dubon impact was that the convex part was processed by pressing a 3/8 ”(inch) punch from the back of the metal plate and dropping a 300g weight onto the evaluation surface (surface) from a height of 30cm. Corrosion resistance was evaluated as “◯” when no rusting occurred on the convex part and “X” when rusting occurred on the convex part. The evaluation results are shown in Table 1.

From the evaluation results shown in Table 1, all of the examples are excellent in content corrosion resistance and resin adhesion.
On the other hand, any one of Comparative Examples 1 to 4 in which either P or Si adhesion amount in the chemical conversion film is outside the proper range of the present invention has poor resin adhesion, and the configuration of the coating resin layer is that of the present invention. In Comparative Examples 5 and 6, which are outside the proper range, the content corrosion resistance is inferior.

  According to the present invention, the chemical conversion film formed on the upper layer of the tin alloy layer has a function of improving the film characteristics, but does not contain Cr, which is undesirable due to environmental problems. It is possible to provide a resin-coated tin alloy-plated steel sheet having a resin coating layer excellent in corrosion resistance, even for contents containing a solvent or alcohol that swells thermoplastic resins and has excellent adhesion.

Claims (5)

On the surface of the steel sheet has a tin alloy layer comprising one or two species selected from among Fe and Ni, containing 0.5 to 100 mg / m ² of P and 0.1 to 250 mg / m ² of Si thereon to have a conversion coating on the surface of the chemical conversion film, an adhesive resin layer and the lower layer, the composite resin layer possess to upper water repellent resin layer is 87 degrees or more surface contact angle to water at 25 ° C. The water-repellent resin layer is made of a blend resin of a fluorine-containing resin and a thermoplastic resin, and the content of the fluorine-containing resin in the blend resin is 0.5 to 15% by mass. Coated tin alloy plated steel sheet. On the surface of the steel sheet has a tin alloy layer comprising one or two species selected from among Fe and Ni, containing 0.5 to 100 mg / m ² of P and 0.1 to 250 mg / m ² of Si thereon to have a conversion coating on the surface of the chemical conversion film, an adhesive resin layer and the lower layer, the composite resin layer possess to upper water repellent resin layer is 87 degrees or more surface contact angle to water at 25 ° C. The water-repellent resin layer is made of a blend resin of a resin containing silicon and a thermoplastic resin, and the content of the silicon-containing resin in the blend resin is 0.5 to 15% by mass. Coated tin alloy plated steel sheet. On the surface of the steel sheet has a tin alloy layer comprising one or two species selected from among Fe and Ni, containing 0.5 to 100 mg / m ² of P and 0.1 to 250 mg / m ² of Si thereon to have a conversion coating on the surface of the chemical conversion film, an adhesive resin layer and the lower layer, the composite resin layer possess to upper water repellent resin layer is 87 degrees or more surface contact angle to water at 25 ° C. The water-repellent resin layer is made of a blend resin in which a silane coupling agent having a fluorine atom or an alkyl group is mixed with a thermoplastic resin, and the content of the silane coupling agent in the blend resin is 0.5 to 5. A resin-coated tin alloy-plated steel sheet, characterized by being 0% by mass . The resin-coated tin alloy-plated steel sheet according to claim 1 , wherein the chemical conversion film is formed by a chemical conversion treatment solution containing P and a silane coupling agent. Resin-coated tin alloy plated steel sheet according to any one of claims 1-4, wherein the amount of adhesion of Sn of the tin alloy layer is 0.1 to 3.0 g / m ^2.