JP4116929B2 - High gloss pre-coated metal plate with excellent corrosion resistance - Google Patents
High gloss pre-coated metal plate with excellent corrosion resistance Download PDFInfo
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- JP4116929B2 JP4116929B2 JP2003158168A JP2003158168A JP4116929B2 JP 4116929 B2 JP4116929 B2 JP 4116929B2 JP 2003158168 A JP2003158168 A JP 2003158168A JP 2003158168 A JP2003158168 A JP 2003158168A JP 4116929 B2 JP4116929 B2 JP 4116929B2
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- 229910052751 metal Inorganic materials 0.000 title claims description 72
- 239000002184 metal Substances 0.000 title claims description 72
- 238000005260 corrosion Methods 0.000 title claims description 34
- 230000007797 corrosion Effects 0.000 title claims description 33
- 239000011347 resin Substances 0.000 claims description 50
- 229920005989 resin Polymers 0.000 claims description 49
- 229910000831 Steel Inorganic materials 0.000 claims description 38
- 239000010959 steel Substances 0.000 claims description 38
- 239000000049 pigment Substances 0.000 claims description 33
- 239000011230 binding agent Substances 0.000 claims description 28
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 27
- 239000011247 coating layer Substances 0.000 claims description 24
- 239000000126 substance Substances 0.000 claims description 23
- 239000000377 silicon dioxide Substances 0.000 claims description 22
- 229910001424 calcium ion Inorganic materials 0.000 claims description 20
- 238000006243 chemical reaction Methods 0.000 claims description 20
- 229910000990 Ni alloy Inorganic materials 0.000 claims description 17
- RGPUVZXXZFNFBF-UHFFFAOYSA-K diphosphonooxyalumanyl dihydrogen phosphate Chemical compound [Al+3].OP(O)([O-])=O.OP(O)([O-])=O.OP(O)([O-])=O RGPUVZXXZFNFBF-UHFFFAOYSA-K 0.000 claims description 17
- 239000007787 solid Substances 0.000 claims description 16
- 229920000642 polymer Polymers 0.000 claims description 15
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 13
- 229910052804 chromium Inorganic materials 0.000 claims description 13
- 239000011651 chromium Substances 0.000 claims description 13
- 239000010410 layer Substances 0.000 claims description 13
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical group [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims description 11
- 230000001588 bifunctional effect Effects 0.000 claims description 11
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- 150000001875 compounds Chemical class 0.000 claims description 10
- 125000000524 functional group Chemical group 0.000 claims description 9
- 238000006116 polymerization reaction Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 7
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 3
- 229910052725 zinc Inorganic materials 0.000 claims description 3
- 239000011701 zinc Substances 0.000 claims description 3
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- 239000011342 resin composition Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 description 124
- 239000011248 coating agent Substances 0.000 description 119
- 238000011282 treatment Methods 0.000 description 44
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 33
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- 238000012360 testing method Methods 0.000 description 18
- QELJHCBNGDEXLD-UHFFFAOYSA-N nickel zinc Chemical compound [Ni].[Zn] QELJHCBNGDEXLD-UHFFFAOYSA-N 0.000 description 17
- 238000000034 method Methods 0.000 description 16
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 14
- 239000000463 material Substances 0.000 description 14
- 238000005096 rolling process Methods 0.000 description 13
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 12
- 229920000877 Melamine resin Polymers 0.000 description 11
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- 238000001035 drying Methods 0.000 description 10
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- 229920000728 polyester Polymers 0.000 description 8
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- 239000004640 Melamine resin Substances 0.000 description 7
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 7
- 150000002513 isocyanates Chemical class 0.000 description 7
- 238000007747 plating Methods 0.000 description 7
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- 239000005057 Hexamethylene diisocyanate Substances 0.000 description 4
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 4
- 239000008199 coating composition Substances 0.000 description 4
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- RRAMGCGOFNQTLD-UHFFFAOYSA-N hexamethylene diisocyanate Chemical compound O=C=NCCCCCCN=C=O RRAMGCGOFNQTLD-UHFFFAOYSA-N 0.000 description 4
- 229910052759 nickel Inorganic materials 0.000 description 4
- 239000002987 primer (paints) Substances 0.000 description 4
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- 229920000178 Acrylic resin Polymers 0.000 description 3
- 239000004925 Acrylic resin Substances 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
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- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
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- 150000003839 salts Chemical class 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- RTTZISZSHSCFRH-UHFFFAOYSA-N 1,3-bis(isocyanatomethyl)benzene Chemical compound O=C=NCC1=CC=CC(CN=C=O)=C1 RTTZISZSHSCFRH-UHFFFAOYSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 229920003270 Cymel® Polymers 0.000 description 2
- 101100379079 Emericella variicolor andA gene Proteins 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 2
- QPLNUHHRGZVCLQ-UHFFFAOYSA-K aluminum;[oxido(phosphonooxy)phosphoryl] phosphate Chemical compound [Al+3].OP([O-])(=O)OP([O-])(=O)OP(O)([O-])=O QPLNUHHRGZVCLQ-UHFFFAOYSA-K 0.000 description 2
- 229920003180 amino resin Polymers 0.000 description 2
- 239000011668 ascorbic acid Substances 0.000 description 2
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010894 electron beam technology Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- JBKVHLHDHHXQEQ-UHFFFAOYSA-N epsilon-caprolactam Chemical compound O=C1CCCCCN1 JBKVHLHDHHXQEQ-UHFFFAOYSA-N 0.000 description 2
- NAQMVNRVTILPCV-UHFFFAOYSA-N hexane-1,6-diamine Chemical compound NCCCCCCN NAQMVNRVTILPCV-UHFFFAOYSA-N 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 229920005906 polyester polyol Polymers 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- KTSHEKDQKNFWGQ-UHFFFAOYSA-N silver zinc Chemical compound [Zn][Ag][Ag] KTSHEKDQKNFWGQ-UHFFFAOYSA-N 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 239000001993 wax Substances 0.000 description 2
- 239000005995 Aluminium silicate Substances 0.000 description 1
- KSPIHGBHKVISFI-UHFFFAOYSA-N Diphenylcarbazide Chemical compound C=1C=CC=CC=1NNC(=O)NNC1=CC=CC=C1 KSPIHGBHKVISFI-UHFFFAOYSA-N 0.000 description 1
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 1
- 229910001335 Galvanized steel Inorganic materials 0.000 description 1
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 229920000297 Rayon Polymers 0.000 description 1
- MZZSDCJQCLYLLL-UHFFFAOYSA-N Secalonsaeure A Natural products COC(=O)C12OC3C(CC1=C(O)CC(C)C2O)C(=CC=C3c4ccc(O)c5C(=O)C6=C(O)CC(C)C(O)C6(Oc45)C(=O)OC)O MZZSDCJQCLYLLL-UHFFFAOYSA-N 0.000 description 1
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 description 1
- BZHJMEDXRYGGRV-UHFFFAOYSA-N Vinyl chloride Chemical compound ClC=C BZHJMEDXRYGGRV-UHFFFAOYSA-N 0.000 description 1
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 239000002390 adhesive tape Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 235000012211 aluminium silicate Nutrition 0.000 description 1
- 239000003429 antifungal agent Substances 0.000 description 1
- 229940121375 antifungal agent Drugs 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- QHIWVLPBUQWDMQ-UHFFFAOYSA-N butyl prop-2-enoate;methyl 2-methylprop-2-enoate;prop-2-enoic acid Chemical compound OC(=O)C=C.COC(=O)C(C)=C.CCCCOC(=O)C=C QHIWVLPBUQWDMQ-UHFFFAOYSA-N 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000007809 chemical reaction catalyst Substances 0.000 description 1
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 1
- 239000004927 clay Substances 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000007766 curtain coating Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
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- 238000007607 die coating method Methods 0.000 description 1
- 125000005442 diisocyanate group Chemical group 0.000 description 1
- 238000007598 dipping method Methods 0.000 description 1
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- 238000009713 electroplating Methods 0.000 description 1
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- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 1
- 239000008397 galvanized steel Substances 0.000 description 1
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 1
- 238000007602 hot air drying Methods 0.000 description 1
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 1
- 239000010687 lubricating oil Substances 0.000 description 1
- 239000012860 organic pigment Substances 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002964 rayon Substances 0.000 description 1
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- 125000006850 spacer group Chemical group 0.000 description 1
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- 238000003756 stirring Methods 0.000 description 1
- NVKTUNLPFJHLCG-UHFFFAOYSA-N strontium chromate Chemical compound [Sr+2].[O-][Cr]([O-])(=O)=O NVKTUNLPFJHLCG-UHFFFAOYSA-N 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 229920001187 thermosetting polymer Polymers 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- DVKJHBMWWAPEIU-UHFFFAOYSA-N toluene 2,4-diisocyanate Chemical compound CC1=CC=C(N=C=O)C=C1N=C=O DVKJHBMWWAPEIU-UHFFFAOYSA-N 0.000 description 1
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- LRXTYHSAJDENHV-UHFFFAOYSA-H zinc phosphate Chemical compound [Zn+2].[Zn+2].[Zn+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LRXTYHSAJDENHV-UHFFFAOYSA-H 0.000 description 1
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Landscapes
- Application Of Or Painting With Fluid Materials (AREA)
- Laminated Bodies (AREA)
- Chemical Treatment Of Metals (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、プレス成形後の耐食性に優れた表面処理金属板に関するものであり、家電用、建材用、土木用、機械用、自動車用、家具用、容器用等において、特に環境上問題があるとされている6価クロムを用いずに、プレス成形時の塗膜密着性と防錆効果を発揮することを特徴とする。
【０００２】
【従来の技術】
家電用、建材用、自動車用等に、従来の加工後塗装されていたポスト塗装製品に代わって、着色した塗膜を被覆したプレコート金属板が使用されるようになってきている。この金属板は、金属用前処理を施した金属板に塗料を被覆したもので、塗料を塗装した後に切断しプレス成形されて使用されることが一般的である。そのため、塗膜が被覆されていない金属が露出する切断端面部の耐食性とプレス加工時の塗膜剥離がプレコート金属板の問題点となっていたが、金属用前処理としてクロメート処理を施し、且つ塗膜中に6価クロム系の防錆顔料を含有することでこれらの問題点が解決され、現在では汎用的に使用されている。しかし、6価クロムは環境負荷物質であるため、6価クロムを排除する動きが近年盛んである。
【０００３】
化成処理の技術としては、特開平9-828291号公報、特開平10-251509号公報、特開平10-337530号公報、特開2000-17466号公報、特開2000-248385号公報、特開2000-273659号公報、特開2000-282252号公報、特開2000-265282号公報、特開2000-167482号公報等が開示されている。
【０００４】
一方、特開平9-12931号公報では、6価クロム系防錆顔料の代わりにリン酸系防錆顔料とイオン交換シリカ系防錆顔料とを併用したポリエステル系並びにエポキシ系の塗料により切断端面部の耐食性に優れたプレコート鋼板を提供する技術が開示されている。
【０００５】
その一方で、プレコート鋼板の性能として、光沢や鮮映性の高い塗膜が要求される。前述の特開平9-12931号公報の実施例に例示されているプレコート鋼板では、高光沢のプレコート鋼板を得ることは困難であり、更には、加工部の耐食性に劣る。特開昭62-116138号公報、特開平2-205201号公報、特開平7-150326号公報、特開昭58-61292号公報等では、粗度調整した圧延ロールにてプレコート鋼板やその原板を圧延加工することで、プレコート鋼板の塗装後鮮映性を向上させる技術が開示されている。しかし、プレコート鋼板やその原板粗度を圧延ロールにて調整すると、製造工程が増えることによるコストアップや作業効率の低下の問題が発生する。
【０００６】
特開平1-304934号公報では、金属板上に数平均分子量5000〜70000のエポキシ変成ポリエステル樹脂にアミノ樹脂を配合した下塗り塗料と数平均分子量2000〜10000のポリエステル樹脂に架橋速度の異なる2種以上のアミノ樹脂を配合した上塗り塗料を形成させることで高鮮映性を得る技術が開示されている。しかし、上塗り塗料に分子量の低い塗料を適用すると、密着曲げや深絞り成形等の厳しい加工性が施されると塗膜にクラックが入り易く、更にはこの塗膜のクラック部から腐食が発生し易いため、加工部耐食性が劣る。
【０００７】
特開平10-66931号公報には、金属板に有機塗料を塗布し、更にその上にクリヤー樹脂を含む溶液を塗布することで塗膜に鮮映性を付与する技術が開示されている。しかし、この様に乾燥前の塗料上にクリヤー樹脂を含む溶液を均一に且つ安定的に塗布することは困難である。その一方で、乾燥後の塗膜上にクリヤー塗料等を塗布乾燥させることは容易であるが、この場合、外観意匠性と耐食性を両立するために防錆力を付与した下塗り塗装、着色を施した中塗り塗装、上塗りであるクリヤー塗装と3層以上の塗装を施さなければならない。しかし、プレコート鋼板を製造する連続塗装ラインでは、2回塗装2回焼付(一般に2コート2ベイクと呼ばれる)が一般的であり、3層以上の塗装を施すことは困難である。2コート2ベイク方式で上塗りクリヤータイプの塗装を施す場合は、防錆塗膜層を省略して、着色を施した下塗り塗装として、上塗り塗装にトップクリヤーを施すことが一般的であるが、防錆塗膜層を省力しているために耐食性に劣る。このようなタイプの場合、着色層に防錆顔料を添加することが一般的であるが、従来の6価クロム系防錆顔料は黄色系であるため、塗膜中に着色顔料と共に添加すると、目的の色がでにくい欠点を有していた。
【０００８】
【特許文献１】
特開平9-828291号公報
【特許文献２】
特開平10-251509号公報
【特許文献３】
特開平10-337530号公報
【特許文献４】
特開2000-17466号公報
【特許文献５】
特開2000-248385号公報
【特許文献６】
特開2000-273659号公報
【特許文献７】
特開2000-282252号公報
【特許文献８】
特開2000-265282号公報
【特許文献９】
特開2000-167482号
【特許文献１０】
特開平9-12931号公報
【特許文献１１】
特開昭62-116138号公報
【特許文献１２】
特開平2-205201号公報
【特許文献１３】
特開平7-150326号公報
【特許文献１４】
特開昭58-61292号公報
【特許文献１５】
特開平1-304934号公報
【特許文献１６】
特開平10-66931号公報
【０００９】
【発明が解決しようとする課題】
本発明は、従来技術における上記問題点を解決し、6価クロムを含まなくても加工部耐食性に優れ、さらに、高光沢高鮮映性を有する2コート2ベークのプレコート金属板を提供することをその課題としている。
【００１０】
【課題を解決するための手段】
発明者らは、６価クロムを含まない化成処理を施した亜鉛−ニッケル合金めっき鋼板上に、防錆顔料としてトリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカと着色顔料とを含むベース塗膜層を施し、更にその上にクリヤー塗膜層を施すことで、加工性（特にプレスによる深絞り加工性）に優れ、且つ、６価クロムを用いずに加工部耐食性に優れた高光沢プレコート金属板を得ることができることを見出した。本発明は、かかる知見を基に完成させたものであって、本発明がその要旨とするところは、以下の通りである。
（１） 亜鉛−ニッケル合金めっき鋼板の片面もしくは両面上に、６価のクロムを含まない化成処理層、その上に、バインダー樹脂と（ａ）着色顔料を必須成分として含み、且つ防錆顔料として（ｂ）トリポリリン酸二水素アルミニウム又は（ｃ）カルシウムイオン交換シリカの一方又は双方を含むベース塗膜層、更にその上にクリヤー塗膜層を有する金属板であって、前記ベース塗膜層中のバインダー樹脂固形分１００質量部に対し、（ｂ）の添加量が０〜５０質量部、（ｃ）の添加量が０〜５０質量部、且つ（ｂ）と（ｃ）の合計添加量が１〜５０質量部であると共に、（ａ）、（ｂ）、（ｃ）の合計添加量がバインダー樹脂固形分１００質量部に対し１質量部超３００質量部以下であることを特徴とする加工部耐食性に優れた高光沢プレコート金属板。
（２） 前記ベース塗膜層のバインダー樹脂又はクリヤー塗膜層の樹脂の一方又は双方が、両端に官能基を有する直鎖状重合体である樹脂と２官能化合物からなる塗料組成物を加熱によって直鎖上重合体の更なる直鎖状重合反応を促進させて成膜させてなる樹脂である（１）記載の高光沢プレコート金属板。
（３） 前記金属板の表面粗度Ｒａが１．０以下である（１）記載の高光沢プレコート金属板。
【００１１】
【発明の実施の形態】
本発明は、亜鉛−ニッケル合金めっき鋼板の片面もしくは両面上に、６価のクロムを含まない化成処理層、その上に、バインダー樹脂と（ａ）着色顔料を必須成分として含み、且つ防錆顔料として（ｂ）トリポリリン酸二水素アルミニウム又は（ｃ）カルシウムイオン交換シリカの一方又は双方を含むベース塗膜層、更にその上にクリヤー塗膜層を有するプレコート金属板であって、前記ベース塗膜層中のバインダー樹脂固形分１００質量部に対し、（ｂ）の添加量が０〜５０質量部、（ｃ）の添加量が０〜５０質量部、且つ（ｂ）と（ｃ）の合計添加量が１〜５０質量部であると共に、（ａ）、（ｂ）、（ｃ）の合計添加量がバインダー樹脂固形分１００質量部に対し１質量部超３００質量部以下であることを特徴とする加工部耐食性に優れた高光沢プレコート金属板によって達せられる。
【００１３】
本願発明は、亜鉛−ニッケル合金めっき鋼板を用いる。
【００１４】
ニッケルを含む合金めっきを施した金属板（例えば亜鉛−ニッケル合金めっき鋼板）は、熱反射性に優れる。
【００１５】
亜鉛−ニッケル合金めっき鋼板は、加工部の耐食性に優れる。亜鉛−ニッケル合金めっき鋼板とは、めっき層にニッケルを１〜３０質量％、好ましくは５〜１５質量％含む亜鉛系合金めっき鋼板のことであり、新日本製鐵社製の「ジンクライト」（新日本製鐵の登録商標）等を使用することができる。
【００１６】
更に、本発明に用いる亜鉛−ニッケル合金めっき鋼板の表面粗度Ｒａが１．０以下であると、プレコート金属板の塗装後鮮映性が向上するためより好適である。亜鉛−ニッケル合金めっき鋼板の表面粗度は、表面粗度を調整した調質圧延ロールにて亜鉛−ニッケル合金めっき鋼板を圧延することや、鋼板にめっきを施した後に表面粗度を調整した調質圧延ロールにて圧延する、もしくは、めっきを施す前の鋼板原板に表面粗度を調整した調質圧延ロールにて圧延した後にめっきすることで、粗度を調整することができる。ここで、Ｒａとは、ＪＩＳ．Ｂ．０６０１．３に記載された算術平均粗さ（Ｒａ）のことである。
【００１７】
亜鉛−ニッケル合金めっき鋼板上に処理する化成処理は、６価クロム含まないものであることを特徴とする。６価クロムは、環境負荷物質であるため、これを含むものは不適である。６価クロムを含まない化成処理としては、一般に公知のもの、電解クロメート処理、反応クロメート処理、リン酸亜鉛系処理、ジルコニア系処理、チタニア系処理、シランカップリング系処理を使用することができ、具体例としては、特開平９−８２８２９１号公報、特開平１０−２５１５０９号公報、特開平１０−３３７５３０号公報、特開２０００−１７４６６号公報、特開２０００−２４８３８５号公報、特開２０００−２７３６５９号公報、特開２０００−２８２２５２号公報、特開２０００−２６５２８２号公報、特開２００００−１６７４８２号公報、等に記載された技術や、日本パーカライジング社製のクロムを含まない化成処理「ＣＴ−Ｅ３００」や「ＣＴ−Ｅ２００」、日本ペイント社製の３価クロム型化成処理「サーフコートＮＲＣ１０００」等を使用することができる。なお、電解クロメート処理や反応クロメート処理は、処理過程において６価クロムを含む処理液を用いるが、処理過程で行われる還元反応において、全ての６価クロムが３価クロムとなるため、これを施したプレコート金属板には最終的に６価クロムが含まれないため、本発明ではこれらも６価クロムを含まない化成処理と言える。
【００１８】
本発明のプレコート金属板は、化成処理を施した亜鉛−ニッケル合金めっき鋼板上に、バインダー樹脂とトリポリリン酸二水素アルミニウム、カルシウムイオン交換シリカ、着色顔料を含むベース塗膜層を形成することを特徴とする。
【００１９】
本発明のベース塗膜層は、バインダー樹脂として一般に公知のプレコート金属板用塗料に、トリポリリン酸二水素アルミニウム、カルシウムイオン交換シリカ、着色顔料を添加したものを成膜させることで形成できる。
【００２０】
本発明のベース塗膜層中にはトリポリリン酸二水素アルミニウムが含まれる。トリポリリン酸二水素アルミニウムを含まないと塗膜密着性が劣り、プレス加工時に塗膜がプレス金型によって擦り取られる（一般に型かじりとも呼ばれる）恐れがある。さらに、トリポリリン酸二水素アルミニウムは薄い白色であるため、ベース塗膜を着色顔料で色付けする際に色調に悪影響を及ぼさないため好適である。トリポリリン酸二水素アルミニウムの添加量は塗膜のバインダー樹脂固形分１００質量部に対し０〜５０質量部にする必要があり、５０質量部超ではベース塗膜の色調が調整できなくなるため、不適である。
【００２１】
本発明のベース塗膜層中にはカルシウムイオン交換シリカが含まれる。カルシウムイオン交換シリカは、シリカ表面にカルシウムイオンを吸着したようなタイプのもので、グレイス社製の「シールデックス」（グレイス社の登録商標）等を使用することができる。カルシウムイオン交換シリカは、耐食性に優れる上、薄い白色であるため、ベース塗膜を着色顔料で色付けする際に色調に悪影響を及ぼさないため好適である。カルシウムイオン交換シリカの添加量は、バインダー樹脂固形分１００質量部に対し０〜５０質量部にする必要があり、５０質量部超ではベース塗膜の色調が調整できなくなるため不適である。
【００２２】
更に、トリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカとの合計の添加量が塗膜のバインダー樹脂固形分１００質量部に対し１〜５０質量部にする必要がある。１質量部未満では、耐食性や密着性が劣り、５０質量部超ではベース塗膜の色調が調整できなくなるため不適である。
【００２３】
本発明のベース塗膜中には前記トリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカについては、どちらか一方が含まれていれば良いが、トリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカの双方が含まれていると、耐食性や加工性密着性がより向上し、より好適である。
【００２４】
本発明のベース塗膜層中に含まれる着色顔料は、一般に公知の着色顔料を使用することができる。例えば、酸化チタン(TiO2)、酸化亜鉛(ZnO)、酸化ジルコニウム(ZrO2)、炭酸カルシウム(CaCO3)、硫酸バリウム(BaSO4)、アルミナ(Al2O3)、カオリンクレー、カーボンブラック、酸化鉄(Fe2O3、Fe3O4)等の無機顔料や、有機顔料等を使用することができる。着色顔料の添加量は、特に規定するものではなく、求める色調を得るのに必要な量を添加できる。しかし、リン酸アルミ系顔料とシリカ系防錆顔料と全着色顔料との合計は、塗膜のバインダー樹脂固形分100質量部に対し1質量部超300質量部以下にする必要がある。1質量部以下では、耐食性や密着性が劣り、300質量部超では塗膜の加工性が劣るため不適である。
【００２５】
バインダー樹脂としてのプレコート金属板用塗料とは、溶剤中にバインダー成分である有機物や無機物が溶解もしくは分散しているものであり、熱を加えて短時間(5〜400秒)で成膜可能な塗料のことである。ベース塗膜に用いるバインダー樹脂成分は特に規定するものではなく、一般に塗料用バインダー樹脂として公知のもの、例えば、ポリエステル樹脂、アクリル樹脂、メラミン樹脂、エポキシ樹脂、フッ素樹脂、塩化ビニル樹脂等の一般に公知の塗料用樹脂等を使用することができる。これらの樹脂には、硬化剤としてイソシアネートやメラミン樹脂等を添加しても良い。
【００２６】
本発明者らがこれまでに得た知見によれば、メラミン硬化型ポリエスエル系、イソシアネート硬化型ポリエステル系の樹脂をバインダー成分として用いると、塗膜の加工性に優れ好適であり、特に、次のものが好適であるが、これらは一例であり、これらに限定されるものではない。
【００２７】
メラミン硬化型ポリエスエル系の場合、ポリエステル樹脂の分子量は、数平均分子量で2000〜30000が好適であり、ポリエステル樹脂のTgは-10〜130℃が好適であり、メラミン樹脂の添加量は、ポリエステル樹脂100質量部に対して5〜70質量部が好適である。
【００２８】
ポリエステル樹脂の分子量が2000未満では塗膜の加工性が低下し、30000超では、樹脂が溶剤に溶解したときに粘度が高すぎるため塗装しにくくなる恐れがある。ポリエステル樹脂のTgが-10℃未満では塗膜が成膜しない恐れがあり、130℃超では塗膜が硬すぎるため、加工性が低下する恐れがある。メラミン樹脂の添加量がポリエステル100質量部に対して5質量部未満であると、塗膜が未硬化となる恐れがあり、70質量部超では、塗膜が硬くなりすぎて加工性が低下する恐れがある。
【００２９】
使用するポリエステル樹脂は、一般に市販されているもの、例えば、東洋紡績社製の「バイロンTM」や、住化バイエルウレタン社製「デスモフェンTM」等を使用することができる。使用するメラミン樹脂も、一般に市販されているもの、例えば、三井サイテック社製「サイメルTM」、「マイコートTM」、大日本インキ化学工業社製「ベッカミンTM」、「スーパーベッカミンTM」等を使用することができる。
【００３０】
イソシアネート硬化型ポリエステル系の場合、ポリエステル樹脂の分子量は、数平均分子量で2000〜30000が好適であり、ポリエステル樹脂のTgは-10〜70℃が好適であり、イソシアネートの添加量は、[イソシアネートのNCO基当量]/[ポリエステル樹脂のOH基当量]=0.8〜1.2であると好適である。
【００３１】
[イソシアネートのNCO基当量]/[ポリエステル樹脂のOH基当量]の値が0.8未満もしくは1.2超では、塗膜生成時に塗膜が未硬化となりやすい。ポリエステル樹脂の分子量が2000未満では塗膜の加工性が低下し、30000超では、樹脂が溶剤に溶解したときに粘度が高すぎるため、塗装しにくくなる恐れがある。ポリエステル樹脂のTgが-10℃未満では、塗膜が成膜しない恐れがあり、70℃超では塗膜が硬すぎるため、加工性が低下する恐れがある。
【００３２】
使用するポリエステル樹脂は、一般に市販されているもの、例えば、東洋紡績社製の「バイロンTM」、住化バイエルウレタン社製「デスモフェンTM」等を使用することができる。
【００３３】
使用するイソシアネートも、一般に市販されているもの、例えば、住化バイエルウレタン社製「スミジュールTM」、「デスモジュールTM」、三井武田ケミカル社製「タケネート」(三井武田ケミカル社の登録商標)等を使用することができる。
【００３４】
本発明プレコート金属板は、トリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカと着色顔料とを含むベース塗膜層上にクリヤー塗膜を形成することを特徴とする。クリヤー塗膜は、ベース塗膜と同様の一般に公知のプレコート金属板用塗料を使用することができる。一般には、有機樹脂のみを溶剤に溶融もしくは分散させ、成膜したときに透明となるものである。クリヤー塗膜に用いる有機樹脂は、ベース塗膜のバインダーとして例示したものを使用することができ、特にベース樹脂のバインダーとして例示したメラミン硬化型ポリエスエル系、イソシアネート硬化型ポリエステル系の樹脂であるとより好適である。また、成膜したとき透明性が担保できる範囲であれば、僅かな着色顔料や防錆顔料等を添加しても良い。クリヤー塗料中には、必要に応じて一般に公知の界面活性剤、ワックス、スリップ材、レベリング材、消胞剤等の添加剤を添加することができる。特にクリヤー塗膜層にワックスを添加すると、プレコート鋼板表面の摩擦係数が低くなり、プレス成形性が向上するためより好適である。塗膜の透明性については特に規定するものではなく、ベース塗膜の色彩が透けて見えなければならない。樹脂の種類や添加剤の種類や添加量によって透明性は異なるため、必要に応じてこれらを選定する必要がある。
【００３５】
また、本発明のプレコート金属板に塗装するベース塗膜層のバインダー樹脂又はクリヤー塗膜の樹脂が、両端に官能基を有する直鎖状重合体である樹脂と2官能化合物からなる塗料組成物を加熱によって直鎖上重合体の更なる直鎖状重合反応を促進させて成膜させるタイプのものであると、加工部の耐食性が向上し、更に好適である。このように焼付過程で直鎖状重合反応を促進させて成膜させた塗膜は、見かけ上、高分子の熱可塑型塗膜となる。そのため、これらの塗膜を被覆したプレコート鋼板を加工すると、加工部で塗膜樹脂中の分子鎖のズレが発生し、加工により伸張された塗膜の内部応力が架橋された熱硬化型塗膜と比べて緩和し易くなる。そのため、直鎖重合を促進させた塗膜を塗装したプレコート鋼板は加工部での塗膜内部応力が一般の熱硬化性塗膜の時と比べて小さくなるため、加工部の耐食性がより向上するものと推定される。
【００３６】
両端に官能基を有する2官能の直鎖状重合体は、一般に公知の直鎖状ポリエステル、直鎖状エポキシ、直鎖状アクリル等を使用することができる。例えば、直鎖状ポリエステルの場合、大日本インキ化学工業社製の「ベッコライトTM M-6207-40」、「ベッコライトTM 57-206-40」、東洋紡社製の「バイロンTM 600」、「バイロンTM 290」等を、直鎖状エポキシ樹脂の場合、大日本インキ化学工業社製の「エピクロンTM 7050-40S」、ジャパンエポキシレジン社製の「エピコート1007」、「エピコート1009」等を、直鎖状アクリル樹脂の場合、三菱レイヨン社製の「LR-635」や大日本インキ化学工業社製の「アクリディックTM A-405」等を使用することができる。
【００３７】
両端に官能基を有する直鎖状重合体と反応し得る2官能化合物としては、ジイソシアネート化合物、ジカルボキシル基化合物が挙げられる。ジイソシアネート化合物としては、キシレンジイソシアネート、トルエンジイソシアネート、ヘキサメチレンジイソシアネート等がある。また、ポリエステルポリオール、アクリルポリオールの両端を前述のジイソシアネート又はヘキサメチレンジアミン、ポリエステルポリオールジカルボン酸、グリシジル変性アクリル樹脂等で変性した樹脂等が挙げられる。ジイソシアネート化合物としては、ブロック化イソシアネート化合物でも良い。
【００３８】
両端に官能基を有する2官能の直鎖状重合体と2官能化合物との比率は、2官能化合物/直鎖状重合体の官能基比で0.5〜10が好適である。0.5未満もしくは10超であると、直鎖重合反応が促進しない恐れがある。両端に官能基を有する直鎖状重合体である樹脂と2官能化合物からなる塗料組成物については、特開2002-249725号公報に記載の技術を使用することができる。
【００３９】
本発明のベース塗膜やクリヤー塗膜の塗装方法は、一般に公知の塗布方法、例えば、ロールコート、カーテンフローコート、ローラーカーテンコート、ダイコート、エアースプレー、エアーレススプレー、電着塗装、粉体塗装、浸漬、バーコート、刷毛塗りなどで行うことができる。ただし、ロールコートやカーテンフローコート、ローラーカーテンコートを完備した一般的コイルコーティングライン、シートコーティングラインと呼ばれる連続塗装ラインで塗装すると、塗装作業効率が良く大量生産が可能であるため、より好適である。塗料の乾燥焼付方法は、熱風オーブン、直火型オーブン、塩赤外線オーブン、誘導加熱型オーブン等の一般に公知の乾燥焼付方法を用いることができる。塗料が紫外線硬化型塗料の場合は一般に公知の紫外線照射装置、電子線硬化型塗料の場合は一般に公知の電子線照射装置を使用することができる。
【００４０】
本発明のプレコート金属板の塗膜厚は、特に限定するものではないが、ベース塗膜が乾燥膜厚にして10μm以上、ベース塗膜と上塗りクリヤー塗膜との合計膜厚が20μm以上であると、光沢や鮮映性、色調が向上し、より好適である。ベース塗膜の膜厚が10μm未満であると、塗膜の隠蔽性が劣り、色調が悪くなる恐れがある。ベース塗膜と上塗りクリヤー塗膜との合計膜厚が20μm未満であると、光沢や鮮映性が低下する恐れがある。これらの塗膜の上限は、特に規定するものではないが、膜厚が厚すぎると塗装焼付の工程でワキと呼ばれる塗装欠陥が発生したり、均一膜厚で塗装しにくい等の問題が発生する恐れがあるので、ベース塗膜及び上塗りクリヤー塗膜の各塗膜の膜厚は100μm以下が好ましい。
【００４１】
また、本発明のプレコート金属板は、本発明の塗膜を両面に施しても良いし、片面に施しても良い。片面にのみ本発明の塗膜を施した場合、他方の面には一般に公知のプレコート鋼板用塗膜を被覆しても良い。
【００４２】
【実施例】
以下、実験に用いた供試材について詳細を説明する。
【００４３】
まず、次に示す2種類のクリヤー塗料を作製した。
クリヤー塗料 -1
東洋紡社製の非晶性ポリエステル樹脂である「バイロンTM 270」を、有機溶剤(質量比でシクロヘキサノン:ソルベッソ150=1:1に混合したものを使用)に、樹脂固形分濃度が30質量%となるように溶解した。次に、硬化剤として三井サイテック社製のメラミン樹脂「サイメルTM 303」を添加した。メラミン樹脂の添加量は、樹脂固形分の質量比で、ポリエステル樹脂固形分:メラミン樹脂固形分=85:15となるように添加した。さらに、このポリエステル樹脂とメラミン樹脂の混合溶液に、三井サイテック社製の酸性触媒「キャタリストTM 600」を0.5質量%添加し、これらを攪拌することで、クリヤー塗料を得た。
クリヤー塗料 -2
東洋紡社製の直鎖型非晶性ポリエステル樹脂である「バイロンTM 600」を、有機溶剤(質量比でシクロヘキサノン:ソルベッソ150=1:1に混合したものを使用)に、樹脂固形分濃度が30質量%となるように溶解した。次に、2官能化合物である住化バイエルウレタン社製のヘキサメチレンジイソシアネート(HDI)「スミジュールTM BL3175」を、HDIのNCO基/ポリエステル樹脂のOH基の比で1.0となるように添加した。更に、反応触媒として、三井武田ケミカル社製の「タケネートTK-1」を添加し、攪拌することでクリヤー塗料を得た。
【００４４】
次に、ベース塗料の作製方法を示す。上記2種のクリヤー塗料を用いて、テイカ社製のトリポリリン酸二水素アルミニウム「K-WHITE#105」(以下、リン酸アルミと称す)、グレイス社製のカルシウムイオン交換シリカ「シールデックスC303」(以下、Caシリケートと称す)、石原産業社製の白色の着色顔料「タイペークCR95」(以下、着色顔料と称す)を添加し、攪拌することでベース塗料を得た。なお、作製した塗料の詳細を表1に記載する。
【００４５】
【表１】
また、比較として、次に示す市販のプレコート鋼板用塗料も使用した。
市販プライマー塗料
日本ファインコーティング社製プライマー塗料「FL641プライマー」(塗膜中にクロム酸ストロンチウムを10質量%含むものを使用)
市販トップ塗料
日本ファインコーティング社製「FL100HQ」(酸化チタンのみにて白色に着色したもので、その他の添加顔料を含まないものを使用)
以下、実験に用いたプレコート金属板について詳細を説明する。
【００４７】
新日本株式会社製の亜鉛-ニッケル合金めっき鋼板「ジンクライト」(以下、ZLと称す)を原板として準備した。板厚は0.6mmのものを使用した。また、電気めっきラインにてめっきする前の工程にて、焼鈍した冷延鋼板に表面の粗度を調整した圧延ロールにて調質圧延を施すことで、亜鉛-ニッケル合金めっき鋼板の表面粗度を変えた材料も準備した。本実験で用いた亜鉛-ニッケル合金めっき鋼板のめっき付着量は片面20g/m2、めっき層中のニッケル量は12%であった。
【００４８】
更に、原板として新日本製鐵株式会社製の溶融亜鉛めっき鋼板「シルバージンク」(以降、GIと称す)とも準備した。「シルバージンク」(新日本製鐵の登録商標)は、板厚0.6mm、亜鉛付着量Z08(片面20g/m2)のものを用いた。化成処理は施していない未処理材を用いた。また、必要に応じて、既にめっきを施したGIを調整した圧延ロールにて調質圧延を施すことで、GIの表面粗度を変えた材料も準備した。
【００４９】
次に、準備した原板を必要に応じてFC-4336(日本パ−カライジング製)の2質量%濃度、50℃温度の水溶液にてスプレー脱脂し、水洗後、乾燥した後に電解クロメート処理、ノンクロメート処理、3価クロム処理、6価クロム処理を行った。電解クロメート処理は、クロム酸50g/L、硫酸0.3g/Lの浴中で、電流密度10A/dm2で所定の電気量を通電して、電解型クロメート処理を施し、水洗した後、熱風乾燥炉を用いて到達板温80℃で乾燥することで、処理した。電解クロメート処理の付着量はクロム付着量で15mg/m2とした。また、ノンクロメート処理、3価クロム処理、6価クロム処理は、それぞれの処理液をロールコーターにて塗布し、熱風オーブンにて乾燥させた。熱風オーブンでの乾燥条件は、鋼板の到達板温で60℃とした。
【００５０】
なお、ノンクロメート処理液は日本パーカライジング社製の「CT-E300」を使用し、全固形分付着量として50mg/m2となるように塗布した。3価クロム処理液は日本ペイント社製の「サーフコートNRC1000」を使用し、クロム付着量として50mg/m2となるように、6価クロム処理液は日本パーカライジング社製の「ZM1300AN」を使用し、クロム付着量として50mg/m2となるようにした。
【００５１】
次に、化成処理を施した金属板の片方の面にベース塗料を(以降こちらの面を表面と称す)、他方の面に裏面塗料を(以降、こちらの面を裏面と称す)ロールコーターにて塗装し、熱風を吹き込んだ誘導加熱炉にて金属板の到達板温が210℃となる条件で乾燥硬化することでベース塗膜層を得た。そして乾燥焼付後に、塗装された金属板へ水をスプレーにて拭きかけ、水冷した。更に、表面のベース塗膜層の上に、クリヤー塗料をローラーカーテンコーターにて塗装し、熱風を吹き込んだ誘導加熱炉にて金属板の到達板温が230℃となる条件で乾燥硬化させることでクリヤー塗膜層を得た。そして、乾燥焼付後に、塗装された金属板へ水をスプレーにて吹きかけ、水冷することで、プレコート金属板サンプルを得た。また、比較材として、６価クロム処理を施した金属板上に市販プライマー塗料を前記ベース塗料と同条件で塗装焼き付けし、更にその上に、市販トップ塗料と表1中の塗料-13をトップ塗料としてクリヤー塗料と同条件で塗装焼付したプレコート金属板も作製した。
【００５２】
なお、表2に、作製したプレコート金属板の詳細を記載する。また、裏面塗料は、全てのサンプルにおいて日本ペイント社製の「FL100HQ」(グレー色に着色したもの)を乾燥膜厚にして5μm塗装した。
【００５３】
【表２】
以下、作製したプレコート金属板の評価方法の詳細を記載する。
1. 光沢測定
JIS.K.5400.7.6に準じて作製したプレコート金属板の表面の光沢度を測定した。測定条件は入射角及び受光角を20°とした。更に、測定した値が80%のものを○、60%以上80%未満のものを△、60%未満のものを×と評価した。
2. 鮮映性測定
携帯用鮮明度光沢度計「PGD」(東京光電社製)にてGd値を測定した。更に、測定したGd値が0.3以上のものを○、0.1以上0.3未満のものを△、0.1未満のものを×と評価した。
3. 色調測定
JIS.K.5400.7.4.2に準じて色の計測を行った。本実験では、全てのプレコート金属板サンプルを白色に着色しているため、白色度の指標であるL値に着目し、L値が90以上のものを○、70以上90未満のものを△、70未満のものを×と評価した。
4. 塗膜加工密着性試験
作製したプレコート金属板を、180°折り曲げ加工(密着曲げ加工)し、加工部の塗膜を目視で観察し、塗膜の割れの有無を調べた。なお、180°折り曲げを行う際には、プレコート金属板の表面が曲げの外側となるように折り曲げ、さらに曲げの内側にはプレコート金属板と同じ板厚のスペーサーを2枚挟んだ状態で密着曲げを行った(一般に2T曲げとして知られている)。また、加工部に粘着テープを貼り付け、これを勢い良く剥離したときの塗膜の残存状態を目視にて観察した。
【００５５】
塗膜割れ及び剥離の評価は、塗膜割れや剥離の全くない時を○、塗膜に僅かな亀裂や剥離が認められる時を△、塗膜に明確な大きな割れや剥離がある時を×として評価した。
5. ビードによる塗膜かじり試験
プレコート金属板をプレス成形したときに、プレス金型でプレコート金属板の塗膜をかじることによって発生する塗膜の剥離を再現する試験方法である「ビードによる塗膜かじり試験法」(公開技報95-1078)を実施した。まず、作製したプレコート金属板を30mm(幅)×300mm(長さ)の試験片に切り出し、この試験片を平面の金型と半径4mmRのビードを設けた金型とで挟み込む。この際に試験片の表面(評価面)に金型のビードが押し付けられるように挟み込み、さらに1tの荷重を加えて金型のビード部をプレコート金属板の評価面に押し付けた。この状態で、プレコート金属板を200mm/minの速度で引き抜き、ビードにて擦られたプレコート金属板の評価面の塗膜剥離状態を目視にて観察し、評価した。
【００５６】
評価は、塗膜が全く剥離していない場合を◎、極部分的に剥離している場合を○、ビードで擦られた部分の面積率にして20%程度以上が剥離している場合を△、全面剥離している場合を×とした。
6. 耐食性試験
作製したプレコート金属板を油圧式エリクセンタイプの20tプレス加工試験機を用いて円筒絞り試験した。円筒絞り試験は、ポンチ径φ50mm、ポンチ肩R3mm、ポンチコーナーR3mm、ダイス肩R3mm、絞り比2.0、しわ押さえ圧1tの条件で行い、金属板が金型から絞り抜けるまで加工を行った。なお、本試験においては、市販の潤滑油を金属板に塗布した条件でプレス加工を行い、また、加工材カップの外側が表面となるように加工した。さらに、これら絞り加工を施したプレコート鋼板加工材をJIS.Z.2371に準じて塩水を120時間噴霧した。なお、プレス加工されたサンプルの切断端面は特にシール等はせずに、切断端面が露出する状態で腐食試験を行った。また、塩水は加工材のカップ外側に噴霧した。耐食性試験後の加工サンプル表面の端面部からの腐食程度を観察し、評価した。端面部の評価基準は、加工端面からの最大赤錆発生幅及び最大膨れ幅が2mm以下の場合◎、2mm超3mm以下の場合○、3mm超4mm以下の場合○△、4mm超5mm以下の場合△、5mm超の場合×と評価した。
7. 6価クロム含有量の測定
作成したプレコート金属板に6価クロムが含まれるか否かを判定するために、次の方法にて評価を行った。
【００５７】
まず、作製したプレコート金属を50mm×50mmサイズに切断し、試験片を作製した。次に、ビーカーにイオン交換水を500ml入れ、ヒーターにて沸騰させ、この沸騰水中に試験片を30分間浸漬した。そして、試験片を取り出した残溶液中に含まれるクロム濃度をJIS.K.0102のジフェニルカルバジド吸光光度法に準じて測定した。そして、得られたクロム濃度から、作製した試験片から沸騰水中に溶出したクロムトータル量を算出し、これを試験片に含まれるトータル6価クロム量とした。更に、算出したトータル6価クロム量を試験片の面積(2500mm2)で割ることで、作製したプレコート金属板の面積当たりに含まれる6価クロム量を算出し、そして、この6価クロム含有量が0.3mg/m2以下の場合は○(6価クロムを含まない)と評価し、0.3mg/m2超の場合は×(6価クロムを含む)と評価した。
【００５８】
【表３】
以下、評価結果について詳細を記載する。表３に作製したプレコート金属板の評価結果を示す。本発明のプレコート金属板（本発明例Ｎｏ．１〜１６、１９〜２２）は、高光沢、鮮映性、色調に優れ、更には加工性、加工後の耐食性に優れる。更に、プレコート金属板に塗装した塗膜のバインダー樹脂又はクリヤー塗膜の樹脂が、両端に官能基を有する直鎖状重合体である樹脂と２官能化合物からなる塗料組成物を加熱によって直鎖状重合体の更なる直鎖状重合反応を促進させて成膜させたものであると、加工部の耐食性が更に向上し、より好適である（本発明例Ｎｏ．１、１３、１４と本発明例Ｎｏ．８、１６との比較）。この直鎖重合体の直鎖重合反応を促進させたタイプの皮膜は、ベース塗膜、クリヤー塗膜のいずれか一方への適用で、加工部耐食性に効果を発揮するが、ベース塗膜、クリヤー塗膜の双方に適用すると加工部耐食性が更に向上するため、より好適である（本発明例Ｎｏ．１、１３、１４と本発明例Ｎｏ．８、１６と本発明例Ｎｏ．２１、２２との比較）。また、本発明のプレコート金属板の原板に用いる亜鉛−ニッケル合金めっき鋼板の表面粗度Ｒａが１．０超のもの（本発明例Ｎｏ．１０）は光沢や鮮映性が少し低下するため、原板に用いる亜鉛−ニッケル合金めっき鋼板の粗度Ｒａは１．０以下がより好適である。本発明の如く亜鉛−ニッケル合金めっき鋼板を使用すると、耐食性が良好である（本発明例Ｎｏ．１、９、１０と参考例Ｎｏ．１７、１８との比較）。また、本発明のプレコート金属板で、下塗り塗膜の膜厚を８μｍとし、且つ下塗り塗膜と上塗り塗膜との合計膜厚を１８μｍとしたもの（本発明例Ｎｏ．１２）は、若干光沢、鮮映性、色調が劣るため、下塗り塗膜の膜厚を１０μｍ以上とし、且つ下塗り塗膜と上塗り塗膜との合計膜厚を２０μｍ以上とすることがより好ましい。
【００６０】
プレコート金属板のベース塗膜中にトリポリリン酸二水素アルミニウム又はカルシウムイオン交換シリカのどちらか一方しか添加されていないもの（本発明例Ｎｏ．１９、２０）は、ビードカジリ性や耐食性が低下するため、トリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカの双方を含むものの方がより好ましい。
【００６１】
プレコート金属板のベース塗膜中に含まれるトリポリリン酸二水素アルミニウムの添加量や、カルシウムイオン交換シリカのどちらか一方の添加量もしくは両方の合計添加量が、ベース塗膜のバインダー樹脂１００質量部に対して５０質量部超のもの（比較例Ｎｏ．２２、２３、２４）は、色調に劣るため不適である。プレコート金属板のベース塗膜中に含まれるトリポリリン酸二水素アルミニウムとカルシウムイオン交換シリカと着色顔料との合計添加量がベース塗膜のバインダー樹脂１００質量部に対して３００質量部超のもの（比較例Ｎｏ．２５）は、加工性に劣るため不適である。また、６価クロムを含む化成処理を用いたプレコート金属板は、環境負荷物質であるクロムが溶出し易いため、不適である。なお、６価クロムを含まない化成処理であれば、ノンクロメート化成処理、３価クロム化成処理、電解クロメート化成処理のいずれでも良く、光沢、鮮映性、色調、加工性、ビードかじり性、加工部耐食性等の諸性能は好適である（本発明例Ｎｏ．１とＮｏ．１３とＮｏ．１４との比較、もしくは本発明例Ｎｏ．８とＮｏ．１５とＮｏ．１６との比較）。
【００６２】
【発明の効果】
本発明により、環境上の影響が懸念される6価クロムを使用せずに、高光沢、高鮮映性を有し、且つ、塗膜の加工密着性、耐食性に優れ、プレス成形に非常に適した高意匠性プレコート金属板を提供することが可能となった。従って、本発明は工業的価値の極めて高い発明であるといえる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface-treated metal plate having excellent corrosion resistance after press molding, and particularly has environmental problems in home appliances, building materials, civil engineering, machinery, automobiles, furniture, containers, and the like. It is characterized by exhibiting coating film adhesion and antirust effect during press molding without using hexavalent chromium.
[0002]
[Prior art]
For home appliances, building materials, automobiles, and the like, pre-coated metal sheets coated with a colored coating film have been used in place of conventional post-painted products that have been painted after processing. This metal plate is obtained by coating a metal plate that has been subjected to metal pretreatment, and is generally used after being cut and press-molded after the paint is applied. Therefore, the corrosion resistance of the cut end face part where the metal not coated with the coating film is exposed and the coating film peeling at the time of press processing were problems of the pre-coated metal plate, but the chromate treatment was applied as a pretreatment for metal, and These problems have been solved by including a hexavalent chromium-based rust preventive pigment in the coating film, and it is currently used for general purposes. However, since hexavalent chromium is an environmentally hazardous substance, movements to eliminate hexavalent chromium have become popular in recent years.
[0003]
As the chemical conversion treatment technology, JP-A-9-828291, JP-A-10-251509, JP-A-10-337530, JP2000-17466, JP2000-248385, JP2000 JP-A-273659, JP-A-2000-282252, JP-A-2000-265282, JP-A-2000-167482, and the like are disclosed.
[0004]
On the other hand, in Japanese Patent Laid-Open No. Hei 9-29331, a cut end face portion is formed by using a polyester-based and epoxy-based paint in which a phosphate-based rust preventive pigment and an ion-exchange silica-based rust preventive pigment are used in place of a hexavalent chromium-based rust preventive pigment A technique for providing a precoated steel sheet having excellent corrosion resistance is disclosed.
[0005]
On the other hand, as a performance of the pre-coated steel sheet, a coating film having high gloss and sharpness is required. With the pre-coated steel sheet exemplified in the above-mentioned example of JP-A-9-2931, it is difficult to obtain a high-gloss pre-coated steel sheet, and further, the corrosion resistance of the processed part is inferior. In JP-A-62-116138, JP-A-2-205201, JP-A-7-150326, JP-A-58-61292, etc., a pre-coated steel plate or its original plate is used with a rolling roll adjusted in roughness. A technique for improving the post-painting sharpness of a precoated steel sheet by rolling is disclosed. However, when the precoated steel plate or the roughness of the original plate is adjusted with a rolling roll, there are problems of cost increase and work efficiency reduction due to an increase in manufacturing steps.
[0006]
In JP-A-1-304934, two or more types having different crosslinking speeds for an undercoat paint in which an amino resin is blended with an epoxy-modified polyester resin having a number average molecular weight of 5000 to 70000 on a metal plate and a polyester resin having a number average molecular weight of 2000 to 10,000. A technique for obtaining a high definition by forming a top coating containing an amino resin is disclosed. However, when a low molecular weight coating is applied to the top coating, cracks are likely to occur in the coating film when severe workability such as adhesion bending or deep drawing is applied, and further, corrosion occurs from the crack portion of the coating film. Since it is easy, the corrosion resistance of a processed part is inferior.
[0007]
Japanese Patent Application Laid-Open No. 10-66931 discloses a technique for imparting clarity to a coating film by applying an organic paint to a metal plate and further applying a solution containing a clear resin thereon. However, it is difficult to uniformly and stably apply the solution containing the clear resin onto the paint before drying as described above. On the other hand, it is easy to apply and dry a clear paint on the dried coating film, but in this case, in order to achieve both appearance design and corrosion resistance, undercoating and coloring with anti-corrosion ability are applied. The intermediate coating, the clear coating that is the top coating, and three or more layers of coating must be applied. However, in a continuous coating line for producing a pre-coated steel sheet, two-time coating and two-time baking (generally referred to as two-coat two-bake) are common, and it is difficult to apply three or more layers. When top coat clear type coating is applied by the 2-coat 2-bake method, it is common to omit the rust-preventive coating layer and apply top clear to the top coat as a colored undercoat. It is inferior in corrosion resistance because it saves the rust coating layer. In the case of such a type, it is common to add a rust preventive pigment to the colored layer, but since the conventional hexavalent chromium-based rust preventive pigment is yellow, when added together with the color pigment in the coating film, It had the disadvantage that the target color was difficult to appear.
[0008]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-828291
[Patent Document 2]
Japanese Patent Laid-Open No. 10-251509
[Patent Document 3]
JP-A-10-337530
[Patent Document 4]
Japanese Unexamined Patent Publication No. 2000-17466
[Patent Document 5]
JP 2000-248385 A
[Patent Document 6]
Japanese Unexamined Patent Publication No. 2000-273659
[Patent Document 7]
JP 2000-282252 A
[Patent Document 8]
JP 2000-265282 A
[Patent Document 9]
JP 2000-167482 A
[Patent Document 10]
Japanese Patent Laid-Open No. 9-12931
[Patent Document 11]
JP 62-116138 A
[Patent Document 12]
JP-A-2-205201
[Patent Document 13]
JP-A-7-150326
[Patent Document 14]
JP 58-61292 A
[Patent Document 15]
JP-A-1-304934
[Patent Document 16]
Japanese Patent Laid-Open No. 10-66931
[0009]
[Problems to be solved by the invention]
The present invention solves the above-mentioned problems in the prior art, and provides a 2-coat 2-bake pre-coated metal sheet having excellent processed portion corrosion resistance even without hexavalent chromium, and having high gloss and high definition. Is the issue.
[0010]
[Means for Solving the Problems]
The inventors performed a chemical conversion treatment not containing hexavalent chromium.Zinc-nickel alloy plated steelOn the board,Aluminum dihydrogen triphosphate as anticorrosive pigmentWhenCalcium ion exchanged silicaBy applying a base coating layer that contains a color pigment and a clear coating layer on it, it is excellent in workability (especially deep drawing workability by pressing) and is processed without using hexavalent chromium. It has been found that a high-gloss precoated metal sheet having excellent partial corrosion resistance can be obtained. The present invention has been completed based on such knowledge, and the gist of the present invention is as follows.
(1)Zinc-nickel alloy plated steelA chemical conversion treatment layer containing no hexavalent chromium on one or both sides of the plate, on which a binder resin and (a) a color pigment are included as essential components; andAs anti-rust pigment(B)Aluminum dihydrogen phosphateOr (c)Calcium ion exchanged silicaThe base coating layer containing one or both of the above, and further a clear coating layer on the base coating layer, with respect to 100 parts by mass of the binder resin solid content in the base coating layer, the addition amount of (b) 0 to 50 parts by mass, the addition amount of (c) is 0 to 50 parts by mass, and the total addition amount of (b) and (c) is 1 to 50 parts by mass, and (a), (b), A high-gloss precoated metal sheet excellent in processed part corrosion resistance, wherein the total addition amount of (c) is more than 1 part by weight and not more than 300 parts by weight with respect to 100 parts by weight of the binder resin solid content.
(2) One or both of the binder resin of the base coating layer and the resin of the clear coating layer are linearly heated by heating a coating composition composed of a resin that is a linear polymer having functional groups at both ends and a bifunctional compound. The high-gloss precoated metal sheet according to (1), which is a resin formed by accelerating further linear polymerization reaction of the upper polymer.
(3The high gloss pre-coated metal plate according to (1), wherein the metal plate has a surface roughness Ra of 1.0 or less.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present inventionZinc-nickel alloy plated steelA chemical conversion treatment layer containing no hexavalent chromium on one or both sides of the plate, on which a binder resin and (a) a color pigment are included as essential components; andAs anti-rust pigment(B)Aluminum dihydrogen phosphateOr (c)Calcium ion exchanged silicaA pre-coated metal plate having one or both of a base coating layer and a clear coating layer on the base coating layer, wherein (b) is added to 100 parts by mass of the binder resin solid content in the base coating layer The amount is 0-50 parts by mass, the addition amount of (c) is 0-50 parts by mass, and the total addition amount of (b) and (c) is 1-50 parts by mass, and (a), (b) The total addition amount of (c) is more than 1 part by weight and not more than 300 parts by weight with respect to 100 parts by weight of the binder resin solid content, and is achieved by a high-gloss precoated metal plate excellent in processed part corrosion resistance.
[0013]
The present invention is, Zinc-nickel alloy plated steel sheetUsingThe
[0014]
DMetal plate with alloy plating including nickel (for example, zinc-nickel alloy plated steel plate))Excellent heat reflectivityBe.
[0015]
AsiaLead-nickel alloy-plated steel sheet has excellent corrosion resistance of the machined partTheThe zinc-nickel alloy plated steel sheet is a zinc-based alloy plated steel sheet containing 1 to 30% by weight, preferably 5 to 15% by weight of nickel in the plating layer. (Registered trademark of Nippon Steel Corporation) can be used.
[0016]
Furthermore, it uses for this invention.Zinc-nickel alloy plated steelWhen the surface roughness Ra of the plate is 1.0 or less, it is more preferable since the sharpness after painting of the precoated metal plate is improved.Zinc-nickel alloy plated steelThe surface roughness of the plate is measured by a temper rolling roll with adjusted surface roughness.Zinc-nickel alloy plated steelRolling the plate,steelRolling with a temper rolling roll with adjusted surface roughness after plating on the plate, or before platingsteelThe roughness can be adjusted by plating the plate raw plate after rolling with a temper rolling roll whose surface roughness is adjusted. Here, Ra is JIS. B. It is the arithmetic average roughness (Ra) described in 0601.3.
[0017]
Zinc-nickel alloy plated steelThe chemical conversion treatment performed on the plate is characterized by not containing hexavalent chromium. Hexavalent chromium is an environmentally hazardous substance, so it is not suitable to contain it. As the chemical conversion treatment not containing hexavalent chromium, generally known ones, electrolytic chromate treatment, reaction chromate treatment, zinc phosphate treatment, zirconia treatment, titania treatment, silane coupling treatment can be used. Specific examples include JP-A-9-828291, JP-A-10-251509, JP-A-10-337530, JP-A-2000-17466, JP-A-2000-248385, JP-A-2000-273659. No. 2000, Japanese Patent Laid-Open No. 2000-282252, Japanese Patent Laid-Open No. 2000-265282, Japanese Patent Laid-Open No. 2000-167482, etc., or a chemical conversion treatment “CT-E300 containing no chromium” manufactured by Nihon Parkerizing Co., Ltd. ”And“ CT-E200 ”, a trivalent chromium type chemical conversion treatment“ Surf ”manufactured by Nippon Paint Co., Ltd. It can be used over door NRC1000 "and the like. Electrolytic chromate treatment and reaction chromate treatment use a treatment solution containing hexavalent chromium in the treatment process, but all hexavalent chromium is converted to trivalent chromium in the reduction reaction performed in the treatment process. Since the pre-coated metal plate does not contain hexavalent chromium finally, it can be said that these are chemical conversion treatments that do not contain hexavalent chromium in the present invention.
[0018]
The pre-coated metal plate of the present invention was subjected to chemical conversion treatment.Zinc-nickel alloy plated steelOn the board, with binder resinAluminum dihydrogen phosphate,Calcium ion exchanged silicaA base coating film layer containing a color pigment is formed.
[0019]
The base coating layer of the present invention is a commonly known pre-coated metal sheet paint as a binder resin.Aluminum dihydrogen phosphate,Calcium ion exchanged silicaIt can be formed by depositing a color pigment added.
[0020]
In the base coating layer of the present inventionIs aluminum dihydrogen triphosphateIncludedThe Aluminum dihydrogen phosphateIf it is not contained, the coating film adhesion is inferior, and the coating film may be scraped off by a press die during press processing (generally also referred to as mold galling). further,Aluminum dihydrogen phosphateIs a pale white color and is therefore suitable because it does not adversely affect the color tone when the base coating film is colored with a coloring pigment.Aluminum dihydrogen phosphateIt is necessary to make the addition amount of 0 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content of the coating film, and if it exceeds 50 parts by mass, the color tone of the base coating film cannot be adjusted.
[0021]
In the base coating layer of the present inventionIs calcium ion exchanged silicaIncludedThe Calcium ion exchanged silicaIs a type in which calcium ions are adsorbed on the silica surface, and “Sealdex” (registered trademark of Grace) manufactured by Grace Co., Ltd. can be used.Calcium ion exchanged silicaIn addition to being excellent in corrosion resistance and being pale white, it is suitable because it does not adversely affect the color tone when coloring the base coating film with a coloring pigment.Calcium ion exchanged silicaIt is necessary to make 0 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content, and if it exceeds 50 parts by mass, the color tone of the base coating film cannot be adjusted.
[0022]
Furthermore,Aluminum dihydrogen phosphateWhenCalcium ion exchanged silicaThe total addition amount must be 1 to 50 parts by mass with respect to 100 parts by mass of the binder resin solid content of the coating film. If it is less than 1 part by mass, the corrosion resistance and adhesion are poor, and if it exceeds 50 parts by mass, the color tone of the base coating film cannot be adjusted.
[0023]
In the base coating film of the present invention,Aluminum dihydrogen phosphateWhenCalcium ion exchanged silicaAs for, it is good if either one is included,Aluminum dihydrogen phosphateWhenCalcium ion exchanged silicaWhen both of these are contained, corrosion resistance and workability adhesiveness will improve more and it is more suitable.
[0024]
As the color pigment contained in the base coating layer of the present invention, generally known color pigments can be used. For example, titanium oxide (TiO2), Zinc oxide (ZnO), zirconium oxide (ZrO)2), Calcium carbonate (CaCOThree), Barium sulfate (BaSOFour), Alumina (Al2OThree), Kaolin clay, carbon black, iron oxide (Fe2OThree, FeThreeOFour) And the like, organic pigments, and the like can be used. The addition amount of the color pigment is not particularly defined, and an amount necessary for obtaining a desired color tone can be added. However, the total of the aluminum phosphate pigment, the silica-based rust preventive pigment, and all the colored pigments needs to be more than 1 part by mass and less than 300 parts by mass with respect to 100 parts by mass of the binder resin solid content of the coating film. If it is 1 part by mass or less, the corrosion resistance and adhesion are inferior, and if it exceeds 300 parts by mass, the processability of the coating film is inferior.
[0025]
Pre-coated metal plate paint as a binder resin is a solution in which organic or inorganic substances as binder components are dissolved or dispersed in a solvent, and can be formed in a short time (5 to 400 seconds) by applying heat. It is a paint. The binder resin component used for the base coating is not particularly specified, and is generally known as a binder resin for paints, for example, polyester resins, acrylic resins, melamine resins, epoxy resins, fluororesins, vinyl chloride resins, etc. The resin for paints and the like can be used. To these resins, isocyanate, melamine resin, or the like may be added as a curing agent.
[0026]
According to the knowledge obtained by the present inventors so far, when a melamine curable polyester resin or an isocyanate curable polyester resin is used as a binder component, it is excellent in workability of the coating film. Although these are suitable, these are examples and are not limited thereto.
[0027]
In the case of a melamine curable polyester system, the molecular weight of the polyester resin is preferably 2000 to 30000 in number average molecular weight, the Tg of the polyester resin is preferably -10 to 130 ° C., and the addition amount of the melamine resin is the polyester resin 5-70 mass parts is suitable with respect to 100 mass parts.
[0028]
When the molecular weight of the polyester resin is less than 2000, the processability of the coating film is lowered, and when it exceeds 30000, the viscosity is too high when the resin is dissolved in a solvent, which may make it difficult to paint. If the Tg of the polyester resin is less than −10 ° C., the coating film may not be formed, and if it exceeds 130 ° C., the coating film is too hard and the workability may be reduced. If the added amount of melamine resin is less than 5 parts by mass with respect to 100 parts by mass of polyester, the coating film may become uncured. If it exceeds 70 parts by mass, the coating film becomes too hard and processability decreases. There is a fear.
[0029]
The polyester resin to be used is generally commercially available, for example, “Byron” manufactured by Toyobo Co., Ltd.TM"Sumika Bayer Urethane" DesmophenTMCan be used. The melamine resin used is also generally available on the market, for example, “Cymel” manufactured by Mitsui Cytec.TM, "My coatTM"Beccamin" manufactured by Dainippon Ink & Chemicals, Inc.TM"," Super BecamineTMCan be used.
[0030]
In the case of an isocyanate curable polyester system, the molecular weight of the polyester resin is preferably 2000 to 30000 in terms of number average molecular weight, the Tg of the polyester resin is preferably -10 to 70 ° C., and the addition amount of the isocyanate is [isocyanate NCO group equivalent] / [OH group equivalent of polyester resin] = 0.8 to 1.2 is preferable.
[0031]
When the value of [NCO group equivalent of isocyanate] / [OH group equivalent of polyester resin] is less than 0.8 or more than 1.2, the coating film tends to be uncured when the coating film is formed. When the molecular weight of the polyester resin is less than 2000, the processability of the coating film is lowered, and when it exceeds 30000, the viscosity is too high when the resin is dissolved in a solvent, which may make it difficult to paint. If the Tg of the polyester resin is less than −10 ° C., the coating film may not be formed, and if it exceeds 70 ° C., the coating film is too hard and the workability may be reduced.
[0032]
The polyester resin to be used is generally commercially available, for example, “Byron” manufactured by Toyobo Co., Ltd.TM"Desmophen" manufactured by Sumika Bayer Urethane Co., Ltd.TMCan be used.
[0033]
Isocyanate used is also generally available on the market, for example, “Sumidule” manufactured by Sumika Bayer Urethane Co., Ltd.TM, "Death ModuleTM"Takenate" manufactured by Mitsui Takeda Chemical Co., Ltd. (registered trademark of Mitsui Takeda Chemical Co., Ltd.) can be used.
[0034]
The pre-coated metal plate of the present invention isAluminum dihydrogen phosphateWhenCalcium ion exchanged silicaA clear coating film is formed on a base coating film layer containing a pigment and a coloring pigment. For the clear coating film, a generally known coating material for a pre-coated metal plate similar to the base coating film can be used. Generally, only an organic resin is melted or dispersed in a solvent and becomes transparent when a film is formed. As the organic resin used for the clear coating film, those exemplified as the binder of the base coating film can be used, and in particular, the melamine curable polyester type and isocyanate curable polyester type resins exemplified as the binder of the base resin. Is preferred. In addition, a slight amount of a color pigment, a rust preventive pigment, or the like may be added as long as the transparency can be ensured when the film is formed. In the clear paint, additives such as generally known surfactants, waxes, slip materials, leveling materials, and antifungal agents can be added as necessary. In particular, the addition of wax to the clear coating layer is more preferable because the coefficient of friction on the surface of the precoated steel sheet is lowered and the press formability is improved. The transparency of the coating film is not particularly specified, and the color of the base coating film must be seen through. Since the transparency varies depending on the type of resin, the type of additive, and the amount added, it is necessary to select them as necessary.
[0035]
In addition, a coating composition comprising a binder resin of a base coating film layer or a resin of a clear coating film coated on the precoated metal plate of the present invention, which is a linear polymer having functional groups at both ends and a bifunctional compound. It is more preferable that the film is formed by promoting further linear polymerization reaction of the linear polymer on heating to improve the corrosion resistance of the processed part. Thus, the coating film formed by promoting the linear polymerization reaction in the baking process is apparently a polymer thermoplastic coating film. Therefore, when pre-coated steel sheets coated with these coating films are processed, the molecular chain shift in the coating resin occurs in the processed part, and the internal stress of the coating film stretched by processing is cross-linked. It becomes easier to relax than. Therefore, the precoated steel sheet coated with a coating that promoted linear polymerization has a lower internal stress in the processed part than in the case of a general thermosetting coating, which further improves the corrosion resistance of the processed part. Estimated.
[0036]
As the bifunctional linear polymer having functional groups at both ends, generally known linear polyester, linear epoxy, linear acrylic and the like can be used. For example, in the case of linear polyester, “Beckolite” manufactured by Dainippon Ink & Chemicals, Inc.TM M-6207-40 "," BeckoliteTM 57-206-40 ", Toyobo's" Byron "TM 600 '', `` ByronTM 290 ", etc., in the case of linear epoxy resin," Epicron "manufactured by Dainippon Ink & Chemicals, Inc.TM 7050-40S ", Japan Epoxy Resin" Epicoat 1007 "," Epicoat 1009 ", etc., in the case of linear acrylic resin, Mitsubishi Rayon" LR-635 "or Dainippon Ink & Chemicals "AcridickTM A-405 "or the like can be used.
[0037]
Examples of the bifunctional compound capable of reacting with a linear polymer having functional groups at both ends include a diisocyanate compound and a dicarboxyl group compound. Examples of the diisocyanate compound include xylene diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate. Moreover, the resin etc. which modified the both ends of the polyester polyol and the acrylic polyol with the above-mentioned diisocyanate or hexamethylene diamine, polyester polyol dicarboxylic acid, a glycidyl modified acrylic resin, etc. are mentioned. The diisocyanate compound may be a blocked isocyanate compound.
[0038]
The ratio of the bifunctional linear polymer having functional groups at both ends to the bifunctional compound is preferably 0.5 to 10 in terms of the functional group ratio of bifunctional compound / linear polymer. If it is less than 0.5 or more than 10, the linear polymerization reaction may not be promoted. For a coating composition comprising a resin that is a linear polymer having functional groups at both ends and a bifunctional compound, the technique described in JP-A-2002-249725 can be used.
[0039]
The coating method of the base coating or clear coating of the present invention is generally known coating methods such as roll coating, curtain flow coating, roller curtain coating, die coating, air spray, airless spray, electrodeposition coating, powder coating. , Dipping, bar coating, brushing, and the like. However, it is more suitable to apply on a continuous coating line called a general coil coating line or sheet coating line complete with roll coat, curtain flow coat, and roller curtain coat, because the painting work efficiency is high and mass production is possible. . As a method for drying and baking the paint, generally known drying and baking methods such as a hot air oven, a direct flame oven, a salt infrared oven, an induction heating oven, and the like can be used. When the coating material is an ultraviolet curable coating material, a generally known ultraviolet irradiation device can be used. When the coating material is an electron beam curable coating material, a generally known electron beam irradiation device can be used.
[0040]
The coating thickness of the precoated metal sheet of the present invention is not particularly limited, but the base coating film is 10 μm or more in dry film thickness, and the total film thickness of the base coating film and the top clear film is 20 μm or more. Further, gloss, sharpness and color tone are improved, which is more preferable. When the film thickness of the base coating film is less than 10 μm, the coating film has poor concealability and the color tone may be deteriorated. When the total film thickness of the base coating film and the top clear coating film is less than 20 μm, there is a possibility that gloss and sharpness may be deteriorated. The upper limit of these coatings is not particularly specified, but if the film thickness is too thick, problems such as a coating defect called waki occur in the coating baking process, and problems such as difficulty in coating with a uniform film thickness occur. Since there is a fear, the thickness of each coating film of the base coating film and the top clear film is preferably 100 μm or less.
[0041]
Moreover, the precoat metal plate of this invention may give the coating film of this invention to both surfaces, and may apply it to one side. When the coating film of the present invention is applied to only one surface, the other surface may be coated with a generally known coating film for a precoated steel sheet.
[0042]
【Example】
Hereinafter, the details of the test material used in the experiment will be described.
[0043]
First, the following two types of clear paints were prepared.
Clear paint -1
Byron, an amorphous polyester resin manufactured by ToyoboTM 270 "was dissolved in an organic solvent (using a mass ratio of cyclohexanone: solvesso 150 = 1: 1) so that the resin solid content concentration was 30% by mass. Next, as a curing agent, the melamine resin “Cymel” manufactured by Mitsui Cytec Co., Ltd.TM 303 "was added. The addition amount of the melamine resin was added so that the ratio of the resin solid content was polyester resin solid content: melamine resin solid content = 85: 15. Furthermore, an acidic catalyst “Catalyst” manufactured by Mitsui Cytec Co., Ltd.TM A clear coating was obtained by adding 0.5% by mass of “600” and stirring them.
Clear paint -2
Byron, a linear amorphous polyester resin manufactured by ToyoboTM 600 "was dissolved in an organic solvent (using a mass ratio of cyclohexanone: solvesso 150 = 1: 1) so that the resin solid content concentration was 30% by mass. Next, hexamethylene diisocyanate (HDI) “Sumijour” manufactured by Sumika Bayer Urethane Co., Ltd. is a bifunctional compound.TM BL3175 "was added so that the ratio of NDI group of HDI / OH group of polyester resin was 1.0. Furthermore, “Takenate TK-1” manufactured by Mitsui Takeda Chemical Co. was added as a reaction catalyst and stirred to obtain a clear paint.
[0044]
Next, a method for producing a base paint will be described. Using the above two clear paints, Teika's aluminum dihydrogen phosphate `` K-WHITE # 105 '' (hereinafter referred to as aluminum phosphate), Grace's calcium ion exchange silica `` Sealdex C303 '' ( (Hereinafter referred to as Ca silicate) and white colored pigment “Taipaque CR95” (hereinafter referred to as colored pigment) manufactured by Ishihara Sangyo Co., Ltd. were added and stirred to obtain a base paint. Details of the prepared paint are shown in Table 1.
[0045]
[Table 1]
For comparison, the following commercially available coatings for precoated steel sheets were also used.
Commercial primer paint
Primer paint "FL641 primer" manufactured by Nippon Fine Coating Co., Ltd. (uses paint containing 10% by mass of strontium chromate)
Commercial top paint
“FL100HQ” manufactured by Nippon Fine Coating Co., Ltd. (Used only with titanium oxide, which is colored white and does not contain other additive pigments)
Hereinafter, the details of the precoated metal plate used in the experiment will be described.
[0047]
A zinc-nickel alloy plated steel sheet “Zinclite” (hereinafter referred to as “ZL”) manufactured by Shin Nippon Co., Ltd. was prepared as a base plate. A plate thickness of 0.6 mm was used. In addition, the surface roughness of the zinc-nickel alloy-plated steel sheet is obtained by subjecting the annealed cold-rolled steel sheet to temper rolling with a rolling roll whose surface roughness is adjusted in the process before plating in the electroplating line. We also prepared materials that changed. The coating amount of the zinc-nickel alloy plated steel sheet used in this experiment is 20 g / m on one side.2The amount of nickel in the plating layer was 12%.
[0048]
Furthermore, a hot dip galvanized steel sheet “Silver Zinc” (hereinafter referred to as GI) manufactured by Nippon Steel Corporation was also prepared as an original plate. "Silver Zinc" (registered trademark of Nippon Steel) has a thickness of 0.6mm and a zinc deposit of Z08 (20g / m on one side)2) Was used. An untreated material that was not subjected to chemical conversion treatment was used. Moreover, the material which changed the surface roughness of GI was prepared by performing temper rolling with the rolling roll which adjusted GI which already plated, as needed.
[0049]
Next, spray degrease the prepared original plate with an aqueous solution of FC-4336 (manufactured by Nihon Parkerizing) at 2 mass% concentration and 50 ° C as necessary, and after washing with water and drying, electrolytic chromate treatment, Chromate treatment, trivalent chromium treatment, and hexavalent chromium treatment were performed. The electrolytic chromate treatment is performed in a chromic acid 50 g / L, sulfuric acid 0.3 g / L bath with a current density of 10 A / dm.2Then, a predetermined amount of electricity was applied, electrolytic chromate treatment was performed, water washing was performed, and drying was performed at an ultimate plate temperature of 80 ° C. using a hot air drying furnace. Electrolytic chromate treatment deposit is 15mg / m in chromium deposit2It was. In the non-chromate treatment, trivalent chromium treatment, and hexavalent chromium treatment, each treatment solution was applied with a roll coater and dried in a hot air oven. The drying conditions in the hot air oven were 60 ° C. at the ultimate temperature of the steel plate.
[0050]
The non-chromate treatment solution uses “CT-E300” manufactured by Nihon Parkerizing Co., Ltd., and the total solid content is 50 mg / m.2It applied so that it might become. Trivalent chromium treatment solution uses “Surf Coat NRC1000” manufactured by Nippon Paint Co., Ltd.2As for the hexavalent chromium treatment solution, use “ZM1300AN” manufactured by Nihon Parkerizing Co., Ltd.2It was made to become.
[0051]
Next, base coating is applied to one side of the metal sheet that has been subjected to chemical conversion treatment (hereinafter this surface is referred to as the front surface), and the back coating is applied to the other surface (hereinafter referred to as the back surface). The base coating layer was obtained by drying and curing in an induction heating furnace in which hot air was blown in a condition where the ultimate temperature of the metal plate was 210 ° C. After drying and baking, water was sprayed onto the painted metal plate and cooled with water. Furthermore, by applying a clear paint on the surface base coating layer with a roller curtain coater and drying and curing it under the condition that the ultimate temperature of the metal plate is 230 ° C. in an induction heating furnace in which hot air is blown. A clear coating layer was obtained. And after drying and baking, water was sprayed on the coated metal plate by spraying and water cooling was performed to obtain a pre-coated metal plate sample. In addition, as a comparative material, a commercial primer coating was baked on a metal plate that had been subjected to hexavalent chromium treatment under the same conditions as the above base coating, and then the top commercial coating and the coating 13 in Table 1 were topped. A pre-coated metal plate was also baked as a paint under the same conditions as the clear paint.
[0052]
Table 2 shows details of the prepared precoated metal sheet. In addition, as for the back surface coating, “FL100HQ” (colored in gray) made by Nippon Paint Co., Ltd. was applied to all samples to a dry film thickness of 5 μm.
[0053]
[Table 2]
Hereinafter, the details of the evaluation method of the prepared precoated metal sheet will be described.
1. Gloss measurement
The glossiness of the surface of the pre-coated metal plate produced according to JIS.K.5400.7.6 was measured. The measurement conditions were an incident angle and a light receiving angle of 20 °. Furthermore, 80% of the measured values were evaluated as ◯, 60% or more and less than 80% were evaluated as Δ, and less than 60% were evaluated as ×.
2. Vividness measurement
The Gd value was measured with a portable sharpness / gloss meter “PGD” (manufactured by Tokyo Kodensha). Furthermore, the measured Gd value of 0.3 or more was evaluated as ◯, the measured value of 0.1 or more and less than 0.3 was evaluated as Δ, and the measured Gd value was evaluated as ×.
3. Color tone measurement
The color was measured according to JIS.K.5400.7.4.2. In this experiment, since all the pre-coated metal plate samples are colored white, pay attention to the L value that is an index of whiteness, ○ that the L value is 90 or more, △ 70 or less than 90, Those less than 70 were evaluated as x.
4. Paint film processing adhesion test
The prepared pre-coated metal plate was subjected to 180 ° bending processing (adhesion bending processing), and the coating film in the processed portion was visually observed to check for cracks in the coating film. When bending 180 °, bend so that the surface of the pre-coated metal plate faces the outside of the bend, and then tightly bend with two spacers of the same thickness as the pre-coated metal plate sandwiched inside the bend (Generally known as 2T bending). Moreover, the adhesive tape was affixed on the process part, and the residual state of the coating film was observed visually when this was peeled off vigorously.
[0055]
Evaluation of coating film cracking and peeling is ○ when there is no coating film cracking or peeling, △ when a slight crack or peeling is observed in the coating film, × when there is a clear large crack or peeling in the coating film × As evaluated.
5. Coating galling test with beads
`` Paint galling test method with beads '' is a test method that reproduces the peeling of the coating film generated by galling the coating film of the precoated metal sheet with a press mold when the precoated metal sheet is press-molded (open technical report) 95-1078). First, the prepared pre-coated metal plate is cut into a 30 mm (width) × 300 mm (length) test piece, and this test piece is sandwiched between a flat mold and a mold provided with beads having a radius of 4 mmR. At this time, the mold bead was sandwiched so as to be pressed against the surface (evaluation surface) of the test piece, and a load of 1 t was further applied to press the bead portion of the mold against the evaluation surface of the precoated metal plate. In this state, the precoated metal plate was pulled out at a speed of 200 mm / min, and the coating film peeling state on the evaluation surface of the precoated metal plate rubbed with a bead was visually observed and evaluated.
[0056]
The evaluation is ◎ when the coating film is not peeled at all, ◯ when it is peeled off extremely partially, △ when the area ratio of the part rubbed with the bead is peeled off by about 20% or more The case where the entire surface was peeled was indicated as x.
6. Corrosion resistance test
The prepared pre-coated metal plate was subjected to a cylindrical drawing test using a hydraulic-type Erichsen type 20t press working tester. The cylindrical drawing test was performed under the conditions of a punch diameter of φ50 mm, a punch shoulder R3 mm, a punch corner R3 mm, a die shoulder R3 mm, a drawing ratio of 2.0, and a wrinkle holding pressure of 1 t until the metal plate was drawn from the die. In this test, pressing was performed under the condition that a commercially available lubricating oil was applied to a metal plate, and processing was performed so that the outside of the workpiece cup was the surface. Further, the precoated steel sheet processed material subjected to the drawing was sprayed with salt water for 120 hours in accordance with JIS.Z.2371. Incidentally, the cut end face of the pressed sample was not particularly sealed, and the corrosion test was performed in a state where the cut end face was exposed. Moreover, the salt water was sprayed on the cup outside of the processed material. The degree of corrosion from the end surface portion of the processed sample surface after the corrosion resistance test was observed and evaluated. The evaluation criteria for the end face are: when the maximum red rust occurrence width and the maximum swollen width from the processed end face are 2 mm or less ◎, when it is more than 2 mm and 3 mm or less, ○ when it is more than 3 mm and 4 mm or less, ○ △, when it is more than 4 mm and 5 mm or less △ In the case of over 5 mm, it was evaluated as x.
7. Measurement of hexavalent chromium content
In order to determine whether or not the prepared precoated metal plate contains hexavalent chromium, evaluation was performed by the following method.
[0057]
First, the prepared precoat metal was cut into a size of 50 mm × 50 mm to prepare a test piece. Next, 500 ml of ion-exchanged water was put into a beaker and boiled with a heater, and the test piece was immersed in this boiling water for 30 minutes. Then, the chromium concentration contained in the residual solution from which the test piece was taken out was measured according to the diphenylcarbazide absorptiometric method of JIS.K.0102. Then, from the obtained chromium concentration, the total amount of chromium eluted from the produced test piece in boiling water was calculated, and this was used as the total hexavalent chromium amount contained in the test piece. Furthermore, the calculated total hexavalent chromium amount is the area of the test piece (2500 mm2) To calculate the amount of hexavalent chromium contained per area of the pre-coated metal plate produced, and this hexavalent chromium content is 0.3 mg / m2In the following cases, it is evaluated as ○ (excluding hexavalent chromium) and 0.3 mg / m2In the case of exceeding, it was evaluated as x (including hexavalent chromium).
[0058]
[Table 3]
Details of the evaluation results will be described below. Table 3 shows the evaluation results of the pre-coated metal plate produced. Pre-coated metal plate of the present invention (Invention Example No. 116, 19 ~22) is excellent in high gloss, sharpness, and color tone, and further excellent in workability and corrosion resistance after processing. Furthermore, a coating composition consisting of a resin and a bifunctional compound in which the binder resin of the coating film or the resin of the clear coating film coated on the pre-coated metal plate is a linear polymer having functional groups at both ends is linearized by heating. When the film is formed by promoting the further linear polymerization reaction of the polymer, the corrosion resistance of the processed part is further improved, which is more preferable (Invention Examples No. 1, 13, 14 and the present invention). Example No. 8, 16 andcomparison). This type of film in which the linear polymerization reaction of the linear polymer is promoted is effective for the corrosion resistance of the processed part when applied to either the base film or the clear film. When applied to both coatings, the corrosion resistance of the processed part is further improved, so that it is more suitable (Invention Examples No. 1, 13, 14 and Invention Examples No. 8, 1).6 andInvention Example No. Comparison with 21, 22). Moreover, it uses for the original plate of the precoat metal plate of this invention.Zinc-nickel alloy plated steelThe surface roughness Ra of the plate exceeds 1.0 (Invention Example No. 10)Is used for the original plate because gloss and sharpness are slightly reduced.Zinc-nickel alloy plated steelThe roughness Ra of the plate is more preferably 1.0 or less.. BookInventionasZinc-nickel alloy plated steel sheetUseAnd corrosion resistanceGood(Invention Examples No. 1, 9, 10 andreferenceExample No. 17 and 18). Further, the precoated metal plate of the present invention, in which the film thickness of the undercoat film is 8 μm and the total film thickness of the undercoat film and the topcoat film is 18 μm (Invention Example No. 12) is slightly glossy Since the sharpness and color tone are inferior, it is more preferable that the film thickness of the undercoat film is 10 μm or more and the total film thickness of the undercoat film and the topcoat film is 20 μm or more.
[0060]
In the base coat of the pre-coated metal plateAluminum dihydrogen phosphateOrCalcium ion exchanged silicaThose having only one of them (Invention Examples No. 19 and 20) have reduced bead galling and corrosion resistance,Aluminum dihydrogen phosphateWhenCalcium ion exchanged silicaThose containing both are more preferred.
[0061]
Included in base coat of pre-coated metal sheetAluminum dihydrogen phosphateAddition amount ofCalcium ion exchanged silicaWhen the amount of either one or the total addition amount of both exceeds 50 parts by mass with respect to 100 parts by mass of the binder resin of the base coating film (Comparative Examples No. 22, 23, 24), the color tone is inferior. Unsuitable. Included in base coat of pre-coated metal sheetAluminum dihydrogen phosphateWhenCalcium ion exchanged silicaIn the case where the total addition amount of the pigment and the color pigment exceeds 300 parts by mass with respect to 100 parts by mass of the binder resin of the base coating film (Comparative Example No. 25), the processability is inferior, which is inappropriate. In addition, a pre-coated metal plate using a chemical conversion treatment containing hexavalent chromium is not suitable because chromium, which is an environmentally hazardous substance, is likely to elute. As long as the chemical conversion treatment does not contain hexavalent chromium, any of non-chromate chemical conversion treatment, trivalent chromium chemical conversion treatment, and electrolytic chromate chemical conversion treatment may be used. Gloss, sharpness, color tone, workability, bead galling, processing Various performances such as partial corrosion resistance are suitable (Comparison between Invention Examples No. 1, No. 13 and No. 14, or Comparison between Invention Examples No. 8, No. 15 and No. 16).
[0062]
【The invention's effect】
According to the present invention, without using hexavalent chromium, which is concerned about the environmental impact, it has high gloss and high image clarity, and has excellent processing adhesion and corrosion resistance of the coating film. It has become possible to provide a suitable high-design pre-coated metal sheet. Therefore, the present invention can be said to be an invention with extremely high industrial value.
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| WO2007013761A1 (en) * | 2005-07-25 | 2007-02-01 | Posco | Pre-sealed steel sheet with improved anti- corrosion and weldability and preparing method thereof |
| JP2007119858A (en) * | 2005-10-28 | 2007-05-17 | Sumitomo Metal Ind Ltd | Chromium-free precoated steel plate |
| JP4734163B2 (en) * | 2006-04-26 | 2011-07-27 | 新日本製鐵株式会社 | Coated substrate and method for producing the same |
| JP6049504B2 (en) * | 2013-03-14 | 2016-12-21 | 日新製鋼株式会社 | Painted steel sheet and method for producing the same |
| TWI521096B (en) * | 2013-04-26 | 2016-02-11 | 新日鐵住金股份有限公司 | Precoated steel sheet and method for manufacturing the same |
| JP6235892B2 (en) * | 2013-12-18 | 2017-11-22 | 日新製鋼株式会社 | Painted steel plate |
| GB201901895D0 (en) * | 2019-02-11 | 2019-04-03 | Applied Graphene Mat Uk Ltd | Corrosion protection for metallic substrates |
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