Stock material or miscellaneous articles – All metal or with adjacent metals – Composite; i.e. – plural – adjacent – spatially distinct metal...
Patent
1984-08-02
1985-09-17
O'Keefe, Veronica
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite; i.e., plural, adjacent, spatially distinct metal...
148 616, 148 315, 204 141, 428632, 428935, C25D 1138, C25D 304
Patent
active
045420777
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to tin-free steel sheets having improved lacquer adhesion.
TECHNICAL BACKGROUND
Surface treated steel sheets having double coatings, metallic chromium and chromium oxide coatings are designated tin-free steel of chromium type (to be simply referred to as TFS, hereinafter). TFS is regarded as a substitute for tin plates because of its improved properties as can-forming material, and the demand for TFS is increasing in these years. Since TFS has metallic chromium and chromium oxide coatings on the surface, it does not possess sufficient weldability. In manufacturing cans from TFS, a can barrel is formed by applying an epoxy-phenol resin to a blank and bonding the blank with a nylon adhesive.
Recently, the extent of application of TFS cans has been further spread. That is, TFS cans are not only used for so-called cold packs prepared by filling cans with contents such as carbonated beverage and beer at low temperatures, but also used for so-called hot packs prepared by filling cans with contents such as fruit juice and coffee at high temperatures for sterilization as well as retort packs requiring a high temperature retorting treatment for sterilization at the end of packing. In the latter applications, there often occurred accidents of rupture of can barrels.
This can barrel rupture occurs in bonded TFS cans during hot packing and retorting treatment because hot water penetrates through the lacquer film at the barrel junction to deteriorate the interfacial adhesion between the lacquer film and the TFS sheet to eventually separate the lacquer film from the TFS sheet. Extensive investigations have been made to develop TFS sheets which are not susceptible to deterioration of the adhesion between the lacquer film and the TFS sheet.
DISCLOSURE OF THE INVENTION
Particularly, the inventors have made investigations how lacquer adhesion varies in relation to the structure of the TFS surface coating to find that lacquer adhesion is closely correlated to the degree of olation of the chromium oxide coating as analyzed by Fourier transform infrared spectroscopy (to be simply referred to as FIIR, hereinafter), and the present invention is based on this discovery.
According to the present invention, there is provided a tin-free steel sheet having metallic chromium and chromium oxide layers on a steel sheet, characterized in that for improved lacquer adhesion, I.sub.Cr.sup.580 /(I.sub.Cr.sup.580 +I.sub.Cr.sup.660) has a value of 0.5 or more provided that I.sub.Cr.sup.580 is the percent transmission corresponding to ol linkage and I.sub.Cr.sup.660 is the percent transmission corresponding to oxo linkage in the infrared absorption spectrum of said chromium oxide layer as measured by Fourier transform infrared spectroscopy (FIIR).
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a chart of the infrared absorption spectrum of a Cr.sup.OX coating on a TFS sheet as measured by FTIR.
FIG. 2 is an enlarged chart illustrating the infrared absorption spectra near 600 cm.sup.-1 of the surface of TFS sample A having superior lacquer adhesion, sample B having intermediate lacquer adhesion, and sample C having inferior lacquer adhesion.
FIG. 3 illustrates the infrared absorption spectra of TFS before and after heating for analysis of Cr.sup.OX coating structure.
FIG. 4 is a diagram illustrating lacquer adhesion in relation to degree of olation.
FIG. 5 illustrates how to determine the intensity of transmission in an infrared absorption spectrum as measured by FTIR.
FIGS. 6a & b illustrate how to evaluate the adhesion of lacquer to TFS sheets.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to TFS sheets having a metallic chromium coating (to be referred to as Cr.sup.M coating) deposited to 50 to 200 mg/m.sup.2 and a chromium oxide coating (to be referred to as Cr.sup.OX coating, hereinafter) deposited to 10 to 30 mg/m.sup.2 of metallic chromium on each surface of a cold-rolled steel sheet. TFS usually has a Cr.sup.M layer deposited to 50 to 200 mg/m.sup.2 because corrosi
REFERENCES:
patent: 3826628 (1974-06-01), Addinall et al.
patent: 4296182 (1981-10-01), Matsubayashi et al.
patent: 4455355 (1984-06-01), Inui et al.
Ichida Toshio
Irie Toshio
Ogata Hajime
Ohashi Yoshiharu
Tsugawa Shunichi
Kawasaki Steel Corporation
O'Keefe Veronica
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