JP4579129B2 - Fluorine-clear coated stainless steel sheet and method for producing the same - Google Patents

Description

  The present invention comprises a thermosetting resin composition comprising a block isocyanate resin and an amino resin as a resin for crosslinking and curing to a fluororesin, and a P-toluenesulfonic acid catalyst as a curing catalyst. The present invention relates to a fluorine-clear coated stainless steel sheet excellent in adhesion, weather resistance, scratch resistance and stain resistance, and a method for producing the same.

  Clear coated stainless steel sheet has a high-grade appearance utilizing the metallic luster and has a very high surface luster. Therefore, it has been used in many cases for housing, interior materials and cover materials of home appliances. In recent years, clear-coated stainless steel sheets for outdoor use are required, and some highly weather-resistant clear-coated steel sheets with lubricity coated with fluororesin have been partially produced. However, for example, Japanese Patent Laid-Open No. 2001-198522 (Patent Document 1) discloses that a fluororesin powder is dispersed and put in an acrylic resin in order to exhibit lubricity. However, the fluororesin powder is difficult to disperse. Therefore, there is a drawback that it is difficult to obtain a uniform coating film.

  JP-A-2001-137775 (Patent Document 2) discloses that a scaly inorganic additive having an average particle diameter of 10 to 200 μm, specifically glass flakes, etc. is added to the coating material to increase the hardness of the fluororesin coating film. A patent for blended high hardness and excellent wear resistance has been filed, but this also has the disadvantage that it is difficult to obtain a uniform coating film because of its large particle size, as described above.

JP 2001-198522 A JP 2001-137775 A

  As described above, the conventional fluorine-clear coated stainless steel sheet has a problem that it is difficult to obtain a uniform coating film. Furthermore, it is also difficult to produce a fluororesin clear-coated stainless steel plate having a high productivity and one coat. It is an object of the present invention to provide a highly functional fluorine-clear stainless steel sheet with excellent adhesion, weather resistance, scratch resistance, and contamination resistance that can be produced with a single coat having a uniform coating film and excellent productivity. It is a problem.

As a result of earnestly examining means for solving the above problems, the present inventors have found that a thermosetting resin composition having excellent adhesion, wrinkle resistance, and contamination resistance as well as weather resistance, which is a characteristic of a fluororesin, and A fluorine-clear coated stainless steel sheet comprising the composition and a method for producing the same were established.
(1) It has a stainless steel plate and a coating film produced by applying and baking a thermosetting resin composition to the stainless steel plate, and the thermosetting resin composition mainly has a glass transition point of 10 to 60. ° C., number and fluororesin having an average molecular weight of 3,000 to 20,000, a crosslinking agent for crosslinking curing the fluorine resin include a polyolefin wax, the crosslinking agent, Ri blocked isocyanate resins and amino resins der, the polyolefin The wax is contained in an amount of 0.25 to 5 parts by mass per 100 parts by mass of the solid content of the thermosetting resin composition, and the chemical conversion treatment before forming the coating film is a non-chromate treatment. Fluorine clear coated stainless steel sheet with excellent adhesion, weather resistance, scratch resistance, and contamination resistance.

(2) The thermosetting resin composition comprises a P-toluenesulfonic acid-based catalyst as a curing catalyst for the amino resin in a solid content of 0.5 to 8 parts by mass per 100 parts by mass of the solids of the thermosetting resin composition. A fluorine-clear coated stainless steel sheet having excellent adhesion, weather resistance, scratch resistance, and stain resistance as described in (1) .

(3) The thermosetting resin composition was 1~10μm coated with 1 coating to a stainless steel plate, comprising the step of producing a coating film by baking the surface temperature of the stainless steel plate as 180 to 250 ° C., the thermosetting The resin composition includes, as main components, a fluororesin having a glass transition point of 10 to 60 ° C. and a number average molecular weight of 3000 to 20000, a crosslinking agent for crosslinking and curing the fluororesin, and a polyolefin wax, and the crosslinking agent Is a blocked isocyanate resin and an amino resin, and the polyolefin wax is contained in an amount of 0.25 to 5 parts by mass in solid content per 100 parts by mass of the solid matter of the thermosetting resin composition, and the coating film A method for producing a fluorine-clear coated stainless steel sheet excellent in productivity, characterized in that the chemical conversion treatment before forming the steel is a non-chromate treatment .
(4) Before the step of producing the coating film, the method further includes a step of chemical conversion treatment of the stainless steel plate, and in the step of chemical conversion treatment of the stainless steel plate, the adhesion amount is ² to 50 mg / m ² (in the fluorescent X-rays) The non-chromate metal surface treatment agent is applied so that the amount of SiO ₂ is measured), and the stainless steel plate is dried at a surface temperature of 60 to 140 ° C. Productivity as described in (3) above Method of fluorine-clear coated stainless steel sheet with excellent resistance.

  As described above, according to the present invention, a fluorine-clear coated stainless steel sheet that is chromate-free and has excellent hardness, workability, weather resistance, stain resistance, scratch resistance, detergent resistance, and chemical resistance. It can be manufactured with a highly productive one coat, and can provide a fluorine-clear coated stainless steel sheet that is optimal for building material exteriors, home appliances, and building material interior materials, and a method for manufacturing the same.

Hereinafter, the present invention will be described in detail.
As the fluororesin in the present invention, a commercially available product manufactured by a known method as a resin for coating can be used, and hardness, workability, weather resistance, stain resistance, scratch resistance, detergent resistance, Since a fluorine-clear coated stainless steel sheet with excellent chemical properties can be obtained, the productivity is remarkably superior compared to a 2-coat product. A highly clear coated stainless steel sheet with high productivity can be made by adding a specified amount of a polyolefin wax of a certain size having a high lubricating effect to the fluororesin. In addition, to achieve lubricity, polyolefin wax is used without using fluororesin powder, and melamine resin is used without adding scale-like inorganic additives, specifically glass flakes, etc., to increase hardness and wear resistance. Bring that effect. Therefore, since the paint is a clear type, a very uniform coating film can be obtained.

  The above fluororesin is, for example, heat polymerization of fluoroolefins such as tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) and various copolymerizable monomers in the presence of an organic solvent and a polymerization initiator in a high-pressure reactor. Can be used. 10-60 degreeC is preferable and, as for the glass transition point which is a parameter of the hardness of resin, More preferably, it is 20-50 degreeC. When the glass transition point of the resin is less than 10 ° C., the temperature of the steel sheet surface rises to 80 to 100 ° C. due to friction and heat generated during continuous pressing, resulting in softening of the coating film. Resin adheres. Moreover, when it exceeds 60 degreeC, workability | operativity at the time of coating, such as a pinhole and insufficient leveling, is bad.

  The number average molecular weight is preferably 3000 to 20000, and more preferably 4000 to 15000. If it is less than 3000, the reactivity with the crosslinking agent is too poor to form a coating film, and if it exceeds 20000, the solubility in the solvent is insufficient and the resin liquid is not formed. Commercially available products are Zeffle GK500, GK550, GK570 (Daikin Kogyo Co., Ltd.), Cefral Coat A402B, A610X, A670X (Central Glass Co., Ltd.), Lumiflon LF100, LF200, LF302, LF400, LF504, LF600 (manufactured by Asahi Glass Co., Ltd.) May be used alone or in combination. The crosslinking agent which is another component of the fluororesin-based thermosetting resin component is a blocked isocyanate resin and an amino resin.

  The blocked isocyanate compound is a compound having two or more isocyanate groups in one molecule, and aliphatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate, etc. Diisocyanate, isophorone diisocyanate, cycloaliphatic diisocyanate and other alicyclic diisocyanates, burette type adducts of the polyisocyanates, isocyanuric ring type adducts, etc., and these polyisocyanates are phenols, oximes, active methylenes, ε -Blocked with a blocking agent such as caprolactams, triazoles, pyrazoles, etc. Full BL1100, BL1265MPA / X, VPLS2253, BL3475BS / SN, BL3272MPA, BL3370MPA, BL4265SN, Dessumsum 2170, Sumidur 3175 (manufactured by Sumika Bayer Urethane Co., Ltd.) Duranate 17B-60PX, TPA-B80X, MF-B60X, MF-K60X (above, Asahi Kasei Kogyo Co., Ltd.) Barnock DB-980K, D-550, B3-867, B7-887-60 (above, Dainippon Ink & Chemicals, Inc.), Coronate 2515, 2507, 2513 (manufactured by Nippon Polyurethane Industry Co., Ltd.) and the like may be used alone or in combination.

  Amino resin is a generic term for resins modified with alcohol by addition reaction of amino compounds (melamine, guanamine, urea) and formaldehyde (formalin), and melamine resin, benzoguanamine resin, urea resin, butylated urea resin, There are butylated urea melamine resin, glycoluril resin, acetoguanamine resin, and cyclohexylguanamine resin. Among them, melamine resin is preferable from the viewpoint of fingerprint resistance, scratch resistance and chemical resistance due to thermosetting.

  Depending on the type of alcohol to be modified, it is divided into methylated melamine resin, n-butylated melamine resin, isobutylated melamine resin, mixed alkylated melamine resin and the like. Commercially available methylated melamine resins include Cymel 300, 301, 303, 350, 370, 771, 325, 327, 703, 712, 715, 701, 267, 285, 232, 235, 236, 238, 211, 254. 204, 212, 202, 207 (Mitsui Cytec Co., Ltd.), LUWIPAL063, 066, 068, 069, 072, 073 (BASF), Super Becamine L-105 (Dainippon Ink Chemical Co., Ltd.) (Made by company) Melan 522, 523, 620, 622, 623 (above, manufactured by Hitachi Chemical Co., Ltd.), Mycoat 506, 508 (above, made by Mitsui Cytec Co., Ltd.), Uban 20SB, 20SE, 21R, 22R, 122, 125, 128, 22 225, 228, 28-60, 20HS, 2020, 2021, 2028, 120 (above, manufactured by Mitsui Chemicals), PLASTOPAL EBS 100A, 100B, 400B, 600B, CB (above, manufactured by BASF) Super Becamine J- 820, L-109, L-117, L-127, L-164 (above, Dainippon Ink & Chemicals, Inc.), Melan 21A, 22, 220, 2000, 8000 (above, made by Hitachi Chemical Co., Ltd.) Tesazine 3020, 3021, 3036 (manufactured by Hitachi Chemical Co., Ltd.), and isobutylated melamine resins are Uban 60R, 62, 62E, 360, 361, 165, 166-60, 169, 2061 (all, Mitsui Chemicals, Inc.) Company-made), Super Becamine G-821, L-145, L-1 0, L-125 (above, Dainippon Ink & Chemicals, Inc.), PLASTOPAL EBS 4001, FIB, H731B, LR8824 (above, made by BASF) Melan 27, 28, 28D, 245, 265, 269, 289 (above, Hitachi Chemical Co., Ltd.), Tesazine 3027, 3028, 3029, 3030, 3037 (Hitachi Chemical Polymer Co., Ltd.) and mixed alkylated melamine resins are Cymel 267, 285, 232, 235, 236, 238, 211. 254, 204, 212, 202, and 207 (manufactured by Mitsui Cytec Co., Ltd.) and the like may be used alone or in combination.

  In general, a sulfonic acid-based catalyst is used as a curing catalyst for an amino resin, but a P-toluenesulfonic acid-based catalyst is preferable among the sulfonic acid-based catalysts to enable short-time baking, and the thermosetting resin composition and It is desirable to contain 0.5 to 8 parts by mass, preferably 2 to 4 parts by mass in solid content per 100 parts by mass of the solid material of the crosslinked resin composition. If it is 0.5 parts by mass or less, the effect cannot be obtained, and if it is 8 parts by mass or more, not only the curing is saturated, but also workability and boiling water resistance are deteriorated.

  Further, a curing catalyst for promoting curing of the blocked isocyanate compound may be included. Examples of the curing catalyst include dibutyltin dilaurate, tetra-nbutyl, 1.3 diacetoxycystanoxane and the like, and they may be mixed and used as necessary. Furthermore, leveling agents, antifoaming agents, antioxidants, UV absorbers, matting agents, silane coupling agents, etc. may be mixed as additives used for general paints to form paints, or pigments or dyes may be dispersed. It is also possible to make the color clear. Moreover, you may contain an epoxy resin, a silicon resin, an acrylic resin, a polyester resin etc. as needed.

  The polyolefin-based wax contains 0.25-5 parts by mass of a polyolefin wax in a solid content per 100 parts by mass of the thermosetting resin composition and the resin solid, and the polyolefin-based wax includes paraffin, microclostalline, Examples thereof include hydrocarbon waxes such as polyethylene and polyethylene-fluorine. During processing, the film temperature rises due to processing heat and frictional heat of the material, so the melting point of the wax is suitably 70 to 160 ° C. If it is less than 70 ° C., it softens and melts during processing and has excellent characteristics as a solid lubricating additive. When the temperature exceeds 160 ° C., the friction characteristics are lowered due to the presence of hard particles on the surface, so that high moldability cannot be obtained.

  A suitable particle size of these waxes is 0.1 to 7.0 μm. If it exceeds 7.0 μm, the distribution of the solidified wax becomes non-uniform, resulting in low gloss and unfavorable wrinkle resistance. On the other hand, when the thickness is less than 0.1 μm, the lubrication effect does not appear and the workability is insufficient. The amount of the polyolefin wax is suitably 0.25 to 5 parts by mass per 100 parts by mass of the thermosetting resin composition and the resin solid. If it is less than 0.25 parts by mass, the workability is insufficient, and if it exceeds 5 parts by mass, unevenness occurs on the surface of the coating film, and the appearance of the clear steel plate is impaired.

The chemical conversion treatment before coating the stainless steel plate is suitable for a metal-coated steel material, and a non-chromate metal surface treatment agent that does not contain chromium and is used as a pretreatment for paint is used. In general, metal surface treatment agents contain one or two aminosilane and epoxysilane coupling agents and their hydrolyzed condensates, water-dispersible silica, and water-soluble acrylic resins and phenol resins to improve processability. It is preferable that the amount of adhesion is ² to 50 mg / m ² (the amount of SiO ₂ is measured by fluorescent X-ray) and the surface temperature (MT) of the stainless steel plate material is dried at 60 to 140 ° C. . When the adhesion amount exceeds 50 mg / m ² , the water-soluble component of the chemical conversion treatment increases and blisters are generated on the coating surface. Preferably it is 2-10 mg / m < ² >.

  As aminosilane coupling agents, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, propyltriethoxysilane Examples of epoxy silane coupling agents include silanes such as 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane. A coupling agent is mentioned.

  The treatment liquid can be applied using a method such as spraying, roll coater, curtain flow coating, electrostatic coating or the like. Drying may be performed by evaporating moisture, and the temperature is suitably 60 to 140 ° C. In this treatment, a known pretreatment such as alkali degreasing, acid or alkali etching may be performed as necessary.

  Although the chromate treatment is slight but contains hexavalent chromium, it is harmful and when the chromium treatment is converted to a chemical treatment, the stainless steel surface is slightly yellowish, but the clear treatment is colorless and transparent. In addition, by applying 1 to 10 μm of the coating film of claims 1 and 2 of the present invention and baking it at a surface temperature (MT) of 180 to 250 ° C. of a stainless steel material, a fluorine-clear coated stainless steel sheet having high whiteness can be obtained. it can.

Hereinafter, the present invention will be specifically described with reference to examples.
As shown in Table 1, paints were prepared by blending each component, applied with a bar coater so that the coating film became 5 μm, and stainless steel plate SUS430 / No. 4 The surface finish of the polishing finish was baked so as to be in the table, and a fluorine-clear coated stainless steel plate was produced by 1 coat and 1 bake. Before coating the stainless steel plate, the aminosilane-based chemical conversion coating solution is applied with a roll coater so that the SiO ₂ is ₂ to 50 mg / m ² with fluorescent X-rays, and the plate temperature is 100 ° C. It was made to dry. For comparison, a stainless steel plate whose clear coating is out of the scope of the present invention was treated in the same manner as in the above-mentioned invention examples, and comparative example Nos. 1 to 13 stainless steel sheets were obtained.
For these test materials, the processability, hardness, weather resistance, wrinkle resistance, stain resistance, detergent resistance, and chemical resistance of the coating film were examined. The results are shown in Tables 1 and 2.

The evaluation method of the coating film is as follows.
(1) Workability of coating film It was evaluated according to JIS K5600 5-2 (cupping resistance).
5: 7 mm or more (pass)
4: Less than 5-7mm (pass)
3: Less than 3 to 5 mm (failed)
2: Less than 1 to 3 mm (failed)
Less than 1: 1 mm (failed)

(2) Hardness Evaluation was performed according to JIS K5600 5-4 scratch hardness (pencil method).
5: 6H or more (pass)
4: 5H (pass)
3: 4H (failed)
2: 3H (failed)
1: 2H or less (failed)

(3) Weather resistance It evaluated by the gloss retention (%) after SWOM test 4000 hr.
5: Gloss retention 80-100% (pass)
4: Gloss retention 60 to less than 80% (pass)
3: Gloss retention 40 to less than 60% (failed)
2: Gloss retention 20 to less than 40% (failed)
1: Gloss retention 0 to less than 20% (failed)

(4) A household detergent “JIF” (manufactured by Riba Japan) containing a wrinkle-resistant abrasive is dropped on four sheets of gauze and rubbed 100 times with a load of 1 kg to evaluate the wrinkle property.
5: No wrinkle (pass)
4: Flaws are hardly noticeable (pass)
3: A wrinkle can be clearly confirmed (failed)
2: Gloss of the paint film is lost with blemish (failed)
1: The coating film is scraped and reaches the substrate (failed)

(5) Contamination resistance The test specimen was written with oil-based magic and the magic adhesion of the coating film when wiped off was evaluated. 5: No trace at all (passed)
4: Traces are slightly recognized (pass)
3: Traces are slightly noticeable (failed)
2: Mark remains dark (failed)
1: Peel off (failed)

(6) Detergent resistance The specimen was put on Magiclin for 72 hours at 40 ° C., and the state of the coating film was observed and evaluated.
5: No trace at all (passed)
4: Traces are slightly recognized (pass)
3: Traces are slightly noticeable (failed)
2: Mark remains dark (failed)
1: Peel off (failed)

(7) Chemical resistance 2 mL of 5% sulfuric acid and 5% NaOH were dropped on the test material, and after capping, the state of the coating film after 16 hours was observed and evaluated.
5: No trace at all (passed)
4: Traces are slightly recognized (pass)
3: Traces are slightly noticeable (failed)
2: Mark remains dark (failed)
1: Peel off (failed)

According to the present invention, a fluorine-clear coated stainless steel sheet that is chromate-free and has excellent hardness, workability, weather resistance, stain resistance, scratch resistance, detergent resistance, and chemical resistance is highly productive. 1 coat and 1 bake can be obtained.
On the other hand, in the comparative example, the resin is not a fluororesin, but an acrylic resin or a polyester resin, which is outside the scope of the present invention (Comparative Examples No. 1 and 2) is inferior in stain resistance, scratch resistance and weather resistance. When the amount of the crosslinking agent is out of the range of the present invention (Comparative Examples No. 3 and 4), the scratch resistance and the processability of the coating film are inferior. When the amount of the catalyst is outside the range of the present invention (Comparative Examples No. 5 and 6), the scratch resistance and the processability of the coating film are inferior. When the amount of the polyolefin wax is out of the range of the present invention (Comparative Examples Nos. 7 to 12), the processability, scratch resistance and gloss of the coating film are inferior. Comparative Example No. Since the amount of polyolefin wax 13 deviates from the scope of the present invention, the processability, hardness and scratch resistance of the coating film are not sufficient, and in particular, the productivity is poor because it is produced by 2-coat 2-bake.

Claims (4)

It has a stainless steel plate and a coating film produced by applying and baking a thermosetting resin composition to the stainless steel plate, and the thermosetting resin composition mainly has a glass transition point of 10 to 60 ° C. fluororesin having an average molecular weight 3,000 to 20,000, a crosslinking agent for crosslinking curing the fluorine resin include a polyolefin wax, the crosslinking agent, Ri blocked isocyanate resins and amino resins der, the polyolefin wax, The solid content of 0.25-5 parts by mass per 100 parts by mass of the thermosetting resin composition, and the chemical conversion treatment before forming the coating film is a non-chromate treatment. Fluorine-clear coated stainless steel sheet with excellent adhesion, weather resistance, scratch resistance, and stain resistance. The thermosetting resin composition contains a P-toluenesulfonic acid-based catalyst as a curing catalyst for the amino resin in a solid content of 0.5 to 8 parts by mass per 100 parts by mass of the solids of the thermosetting resin composition. The fluorine-clear coated stainless steel sheet having excellent adhesion, weather resistance, scratch resistance, and contamination resistance according to claim 1. The thermosetting resin composition includes a step of applying a thermosetting resin composition to a stainless steel plate in a single coat in an amount of 1 to 10 μm and baking the surface temperature of the stainless steel plate at 180 to 250 ° C. to produce a coating film. Includes, as main components, a fluororesin having a glass transition point of 10 to 60 ° C. and a number average molecular weight of 3000 to 20000, a crosslinking agent for crosslinking and curing the fluororesin, and a polyolefin wax. It is an isocyanate resin and an amino resin, and the polyolefin wax is contained in an amount of 0.25 to 5 parts by mass in solid content per 100 parts by mass of the solid of the thermosetting resin composition, and forms the coating film. A method for producing a fluorine-clear coated stainless steel sheet excellent in productivity, characterized in that the previous chemical conversion treatment is a non-chromate treatment . Before the step of producing the coating film, the method further includes a step of chemical conversion treatment of the stainless steel plate, and in the step of chemical conversion treatment of the stainless steel plate, the adhesion amount is 2 to 50 mg / m. ²  (SiO2 with fluorescent X-ray ₂  The non-chromate metal surface treatment agent is applied so that the amount of the fluorine is excellent, and the surface temperature of the stainless steel plate is dried at 60 to 140 ° C. Manufacturing method of clear coated stainless steel sheet.