Toyo Seikan Kaisha, Ltd.

Yoichi Kitamura

Hisashi Hotta

Chikara Yurita

Makoto Ito

Hiroshi Ueno

Seishichi Kobayashi

Toshimasa Kodaira

Hiroshi Matsubayashi

Michiko Tsurumaru

Makoto Horiguchi

Yoshiro Togo

Yoshiteru Akae

A very thin coating layer having a thickness of the order of 1-100 angstroms of a hydroxymethyl substituted phenol is applied to the surface of a metal material. The hydroxylmethyl substituted phenol, such as saligenin, is applied in the gaseous phase to the surface of the metal material maintained at a high temperature. By forming this ultra-thin coating layer, the heat bondability of a thermoplastic resin layer to the metal material can be effectively improved. This technique is advantageously used in various fields, for example, for production of bonded cans. The metal material comprises a steel plate substrate and a chromium-containing layer on the surface of the substrate, and the very thin layer is applied on the chromium-containing layer.

Surface-treated steel plate and bonded structure of metal material

A very thin coating layer having a thickness of the order of angstroms of a hydroxymethyl substituted phenol is applied to the surface of a metal material. The hydroxylmethyl substituted phenol, such as saligenin, is applied in the gaseous phase to the surface of the metal material maintained at a high temperature. By forming this ultra-thin coating layer, the heat bondability of a thermoplastic resin layer to the metal material can be effectively improved. This technique is advantageously used in various fields, for example, for production of bonded cans.

Process for surface treatment of metal materials

A method of making a welded can body wherein the opposite marginal edge portions of a metallic blank are overlapped to form a can body preform with an overlapped portion, and then the overlapped portion is electric-resistance mash-seam welded by using a pair of wire electrodes abutting on both the surfaces of the overlapped portion. At least one of the pair of the wire electrodes is formed with a flat main portion and a marginal projection including a slope contiguous to the flat main portion on the surface thereof, which surface is adapted to abut on the surface of the overlapped portion. The overlapped portion of the can body preform is fed in between the pair of wire electrodes such that the edge face of one of the marginal edge portions may be positioned on an area of the flat main surface portion in the vicinity of the slope or be positioned on the slope, allowing the marginal edge beside the edge face to flow outwardly in the circumferential direction of the can body preform along the slope during the welding.

Method of making a welded can body

Surface treatment of metal blanks is achieved by applying an oxirane ring-containing compound in the gas phase to the surface of a metal blank maintained at a high temperature. According to this method, a covering layer which is much thinner than a conventional so-called adhesive primer coating layer and has a thickness of the angstrom order is formed on the surface of a metal blank. If a thermoplastic resin layer is coated on the metal surface treated with this oxirane ring-containing compound, the initial adhesion and the adhesion after lapse of time are highly improved over these adhesions attainable by the conventional methods. Even if a lacquer containing a thermosetting resin instead of the thermoplastic resin is coated and dried on the metal surface treated with this bonding compound, a similar effect can be attained. Accordingly, when an organic material is bonded or laminated to the so-treated metal surface or when metal-to-metal bonding is performed, a strong bonding can be maintained in the bonded portion.

Method for surface treatment of metal blanks

Disclosed is a process for the preparation of welded cans, which comprises forming a blank comprised of a surface-treated steel plate into a cylinder and passing a lap portion of the formed cylinder between a pair of electrode rollers through an electrode wire to effect electric resistance welding, wherein said surface-treated steel plate comprises a layer of metallic tin or a tin-iron alloy formed on the steel plate substrate in an amount of 0.05 to 1.0 g/m.sup.2 as calculated as metallic tin and a hydrated chromium oxide layer formed on said tin layer in an amount of 0.005 to 0.05 g/m.sup.2 as calculated as metallic chromium and electric resistance welding is carried out in an inert atmosphere in the state where an electrode wire having a plating layer of tin or a tin alloy having a thickness of 0.1 to 20 .mu.m is kept in close contact with the surface of said surface-treated steel plate. In the inner and outer surface portions of the side seam of a welded can prepared according to this process, the thickness of the oxide layer is controlled below 400 .ANG. and the amount of tin in these inner and outer surface portions is at least 60% of the amount of tin in the starting surface-treated steel plate, and this welded can is excellent in the corrosion resistance, lacquer adhesion and appearance characteristics of the seam.

Welded can and process for preparation thereof

Disclosed is a process for the preparation of welded cans, which comprises forming a blank comprised of a surface-treated steel plate into a cylinder and passing a lap portion of the formed cylinder between a pair of electrode rollers through an electrode wire to effect electric resistance welding, wherein said surface-treated steel plate comprises a layer of metallic tin or a tin-iron alloy formed on the steel plate substrate in an amount of 0.05 to 1.0 g/m.sup.2 as calculated as metallic tin and a hydrated chromium oxide layer formed on said tin layer in an amount of 0.005 to 0.05 g/m.sup.2 as calculated as metallic chromium and electric resistance welding is carried out in an inert atmosphere in the state where an electrode wire having a plating layer of tin or a tin alloy having a thickness of 0.1 to 20 .mu.m is kept in close contact with the surface of said surface-treated steel plate. In the inner and outer surface portions of the side seam of a welded can prepared according to this process, the thickness of the oxide layer is controlled below 400 A and the amount of tin in these inner and outer surface portions is at least 60% of the amount of tin in the starting surface-treated steel plate, and this welded can is excellent in the corrosion resistance, lacquer adhesion and appearance characteristics of the seam.

A method of manufacturing a welded can body from tinplate or a tin-iron alloy plated steel sheet comprises overlapping the opposite marginal portions of a blank of the tinplate or the tin-iron plated steel sheet to form a can body preform having an overlapping portion, applying at least to the cut edges of the marginal portions of the blank a fluxing agent promoting wetting of steel with molten tin, and electrical resistance seam welding the overlapping portion in a nonoxidizing atmosphere by employing a pair of wire electrodes each covered by a layer of metallic tin on the surface thereof facing the overlapping portion. The welded portion has improved corrosion resistance, as an extruded weld portion and a remaining cut edge surface portion thereof are covered with tin transferred from the surfaces of the wire electrodes and/or the tinplate during the welding operation.

Method of manufacturing a welded can body

Disclosed is a process for the preparation of welded cans, which comprises forming a blank into a cylinder and passing a lap portion of the formed cylinder between a pair of electrode rollers through an electrode wire to effect electric resistance welding, wherein said blank is a tin-free steel blank comprising a steel plate substrate, a layer of metallic chromium formed on the surface of the steel plate substrate and a layer of chromium oxide formed on the metallic chromium layer, and electric resistance welding is carried out in an inert atmosphere in the state where an electrode wire having a plated layer of a soft metal selected from the group consisting of tin and alloys thereof, the thickness of said plated layer being 0.1 to 20 .mu.m, is kept in close contact with the chromium oxide layer of the tin-free steel blank. The inner and outer surfaces of the side seam of a welded can according to this process are covered with a continuous or discontinuous protecting covered layer including a metallic chromium layer and a chromium oxide layer formed thereon, and the thickness of steel oxide exposed through this discontinuous portion is controlled below 400 A. Since exposure of steel in the inner and outer surfaces of the seam is thus controlled, the corrosion resistance, lacquer adhesion and appearance charcteristics of the seam are highly improved in this welded can.

Method of welding tin-free steel can

A retortable bonded TFS can coated with an organic lacquer film in which the seaming portion of the can body is bonded with an organic adhesive, characterized in that (1) the amounts of the metallic chromium layer and the chromium oxide layer deposited are 70-130 mg/m.sup.2 and 5-30 mg/m.sup.2, respectively, as metallic chromium; the amount of alkali-soluble chromium in these layers after heating at 210.degree. C. for 10 minutes is not more than 12 mg/m.sup.2 and not more than 70% by weight of the amount of the deposited chromium oxide before heating; the area of thickness unevenness of the chromium oxide is not more than 10%; and the amount of metal exposed is not more than 30 mg/dm.sup.2, expressed as the amount of copper deposited (2) the organic lacquer film layer is a baked and cured film of a mixed lacquer composed of 70 to 85 parts by weight of an epichlorohydrin-bisphenol A type epoxy resin having a number average molecular weight of 2900 to 3750 and 30 to 15 parts by weight of a resol-type phenolic resin derived from a monohydric phenol, bisphenol A and an aldehyde; the phenolic resin has such a molecular weight distribution that the proportion of a high-molecular-weight portion having 3 or more rings is 60 to 70% by weight and the proportion of a low-molecular-weight portion having 2 or less rings is 40 to 30% by weight; and the baked and cured film contains 83 to 87 parts by weight of the epoxy resin and 17 to 13 parts by weight of the phenolic resin, and (3) the adhesive is a linear polyamide adhesive.

Retortable bonded can

Disclosed is a seam welded tinplate can having a side seam formed by welding, wherein the inner and outer surface portions of said side seam comprise an outermost layer formed of an oxide, which has a thickness of 50 to 400 A, and an intermediate layer formed mainly of an iron-tin alloy layer, which has a thickness corresponding to 5 to 100% of the thickness of the total tin layer, and a resin or resin composition containing a polar group selected from the group consisting of carbonyl, hydroxyl, ether and epoxy groups at a concentration of 10 to 2000 millimoles per 100 g of the resin is coated on at least one of said inner and outer surface portions of said side seam.

Side seam-coated tinplate welded can

Disclosed is a welded side-seamed can formed by welding a can blank comprising a steel plate substrate having, formed thereon, a coating layer consisting of a metallic chromium layer and a chromium oxide layer formed on the metallic chromium layer, wherein the so-formed side seam has an exposed steel plate layer consisting of a compact and dense steel oxide formed mainly of magnetite, which has a thickness of 50 to 800 A, especially 50 to 400 A, and a coating of a resin or resinous composition consisting of carbonyl, hydroxyl, ether and epoxy groups at a concentration of 10 to 2000 millimoles per 100 g of the resin is formed on at least one surface portion of said side seam through said steel oxide layer.

Side seam-coated tin-free steel welded can

A can at least a part of which is made of an electrolytically chromated steel sheet, said steel sheet having such a surface that when it is degreased in acetone for 1 minute and analyzed by an Auger electron spectrometer at an incident electron accelerating voltage of 3 KeV, a modulation voltage of 3 V, a modulation frequency of 12 to 20 KHz and a degree of vacuum of at least 6.times.10.sup.-8 torr, the ratio of the peak-peak distance (O.sub.P-P) of KL.sub.2.3 L.sub.2.3 of oxygen to the base-peak distance (Cr.sub.B-P) of L.sub.3 M.sub.2.3 M.sub.4.5 of chromium in the resulting Auger electron spectrum satisfies the following relation:

Can composed of electrolytically chromated steel

Disclosed is a bright welded seam can of tinplate having a side seam formed by welding, wherein each of the inner and outer surfaces of the side seam has an outermost surface layer having a thickness of 50 to 400 A and being composed of oxides and a subsequent intermediate layer composed of an iron-tin alloy, which has a thickness corresponding to 5 to 100% of the thickness of the whole tin layer in the tinplate blank, and wherein the inner and outer surfaces of the side seam have a reflectance corresponding to at least 60% of the reflectance of the tinplate. This bright welded seam can is excellent in the appearance of the seam, the corrosion resistance and the adhesion of the coating.

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Yokohama, Japan

Yoichi Kitamura