Bonded body of galvanized steel sheet and adherend, and manufacturing method thereof

Abstract

The invention is a technique for strongly integrating a galvanized steel sheet and a resin molded article. A hot-dip galvanized steel sheet “Z18” is immersed in an aqueous solution for aluminum degreasing at 75° C. for 7 minutes, to form roughness having an RSm of 0.8 to 2.3 μm and an Rz of 0.3 to 1.0 μm on the surface. The surface is covered with convex protrusions having a diameter of about 100 nm, and a chromate treatment layer appears in the surface. In other words, three conditions suitable for bonding are satisfied thereby. A resin composition comprising 70 to 97 wt % of polyphenylene sulfide and 3 to 30 wt % of a polyolefin resin is injected onto the surface. The resin composition penetrates into ultra-fine irregularities and is cured in that state, whereby a composite in which the galvanized steel sheet and the resin molded article are strongly integrated is obtained. The shear rupture strength of the composite is extremely high, in excess of 20 MPa.

1 . A bonded body of a galvanized steel sheet and an adherend,
 wherein the surface of said galvanized steel sheet has micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, and ultra-fine irregularities having a period of 10 to 300 nm are formed within the surface having the micron-scale roughness, the surface layer being a thin layer of a metal oxide or a metal phosphate,   said adherend is a resin molded article of a thermoplastic resin composition having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide and an aromatic polyamide, and   said galvanized steel sheet and said resin molded article are bonded by way of said thermoplastic resin composition that penetrates into said ultra-fine irregularities and is cured.   
     
     
         2 . The bonded body of a galvanized steel sheet and an adherend according to  claim 1 ,
 wherein said thermoplastic resin composition comprises 70 to 97 wt % of polybutylene terephthalate and 3 to 30 wt % of polyethylene terephthalate and/or a polyolefin resin.   
     
     
         3 . The bonded body of a galvanized steel sheet and an adherend according to  claim 1 ,
 wherein said thermoplastic resin composition comprises 70 to 97 wt % of polyphenylene sulfide and 3 to 30 wt % of a polyolefin resin.   
     
     
         4 . The bonded body of a galvanized steel sheet and an adherend according to  claim 1 ,
 wherein said thermoplastic resin composition comprises 50 to 100 wt % of an aromatic polyamide and 0 to 50 wt % of an aliphatic polyamide.   
     
     
         5 . (canceled) 
     
     
         6 . A bonded body of a galvanized steel sheet and an adherend,
 wherein the surface of said galvanized steel sheet has micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, and ultra-fine irregularities having a period of 10 to 300 nm are formed within the surface having the micron-scale roughness, the surface layer being a thin layer of a metal oxide or a metal phosphate,   said adherend is a resin molded article of a hard, highly crystalline resin having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide, an aromatic polyamide, an aliphatic polyamide and a liquid crystal polymer, and   said galvanized steel sheet and said resin molded article are bonded by way of said highly crystalline resin that penetrates into said ultra-fine irregularities and is cured.   
     
     
         7 - 9 . (canceled) 
     
     
         10 . A bonded body of a galvanized steel sheet and an adherend,
 wherein said adherend is a metal alloy,   the surfaces of both said galvanized steel sheet and said metal alloy have micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, and ultra-fine irregularities having a period of 10 to 300 nm are formed within the surfaces having the micron-scale roughness, the surface layers being thin layers of a metal oxide or a metal phosphate, and   the galvanized steel sheet and the metal alloy are strongly bonded by way of a thermosetting adhesive, being one type of thermosetting adhesive selected from among (1) to (3), namely (1) an epoxy adhesive, (2) a phenolic adhesive and (3) an unsaturated polyester adhesive, that penetrates into the ultra-fine irregularities of both said galvanized steel sheet and said metal alloy, and is cured in that state.   
     
     
         11 . (canceled) 
     
     
         12 . A method for manufacturing a bonded body of a galvanized steel sheet and an adherend, comprising:
 a surface treatment step of performing a liquid treatment for creating, on the surface of a galvanized steel sheet, micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, forming ultra-fine irregularities having a period of 10 to 300 nm within the surface having the micron-scale roughness, and making the surface layer into a thin layer of a metal oxide or a metal phosphate;   an inserting step of inserting the galvanized steel sheet, having undergone said surface treatment step, into an injection molding mold; and   an integrating step of injecting a thermoplastic resin composition having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide and an aromatic polyamide, onto the surface of said inserted galvanized steel sheet, and curing the injected thermoplastic resin composition after having penetrated into said ultra-fine irregularities, to thereby strongly integrate said galvanized steel sheet and a molded article of the thermoplastic resin composition.   
     
     
         13 . A method for manufacturing a bonded body of a galvanized steel sheet and an adherend, comprising:
 a surface treatment step of performing a liquid treatment for creating, on the surface of a galvanized steel sheet, micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, forming ultra-fine irregularities having a period of 10 to 300 nm within the surface having the micron-scale roughness, and making the surface layer into a thin layer of a metal oxide or a metal phosphate;   a resin molded article production step of producing a resin molded article of a resin composition having, as a main component, one or more selected from among polybutylene terephthalate, polyphenylene sulfide, an aromatic polyamide, an aliphatic polyamide and a liquid crystal polymer;   a heating step of heating the surface of the galvanized steel sheet, having undergone said surface treatment step, to a temperature not lower than a melting temperature of said resin composition; and   a press-fusion bonding step of pressing said resin molded article against the surface of said galvanized steel sheet having undergone said heating step, to put the resin composition in a molten state, placing the galvanized steel sheet and the resin molded article under reduced pressure, increasing the pressure thereafter to cause the molten resin composition to penetrate into said ultra-fine irregularities, and curing the resin that has penetrated, to thereby fusion-bond the galvanized steel sheet and the resin molded article.   
     
     
         14 . A method for manufacturing a bonded body of a galvanized steel sheet and an adherend, comprising:
 a surface treatment step of performing a liquid treatment for creating, on the surface of a galvanized steel sheet, micron-scale roughness having a peak-valley average spacing (RSm) of 0.8 to 10 μm and a maximum height roughness (Rz) of 0.2 to 5 μm, forming ultra-fine irregularities having a period of 10 to 300 nm within the surface having the micron-scale roughness, and making the surface layer into a thin layer of a metal oxide or a metal phosphate;   a coating step of coating one type of thermosetting adhesive selected from among (1) to (3), namely (1) an epoxy adhesive, (2) a phenolic adhesive and (3) an unsaturated polyester adhesive, onto the surface of the galvanized steel sheet having undergone said surface treatment step;   a joining preliminary step of placing the galvanized steel sheet, having undergone said coating step, into a hermetic container that is depressurized and then pressurized to cause the applied thermosetting adhesive to penetrate into said ultra-fine irregularities;   a fixing step of closely adhering and fixing an adherend to the surface of said galvanized steel sheet having undergone said joining preliminary step; and   a curing step of heating said fixed galvanized steel sheet and adherend, to thereby cure the adhesive component.   
     
     
         15 - 22 . (canceled)