Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
2002-05-24
2004-03-30
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S213000, C428S214000, C428S216000, C428S328000, C428S461000, C428S463000, C428S516000, C428S520000
Reexamination Certificate
active
06713166
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a laminate film fixedly bonded on the surface of a substrate, and a laminated structure including the laminate film fixedly bonded to the substrate. To be more specific, the present invention relates to a laminate film having a polypropylene resin layer for coating the substrate, and a laminated structure including the polypropylene resin layer with which a surface of the substrate is coated. Above all, the present invention relates to a laminated metal sheet, which is to be processed into a predetermined shape by a draw-forming process or the like, and a laminate film for forming the laminated metal sheet.
BACKGROUND ART
There have been studies and researches on films to be laminated on the surface of a substrate, and it has been desired to develop a highly adhesive film, which is fixedly bonded to a metal substrate (hereinafter referred to as the film for metal lamination). The film for metal lamination is a protective film mainly for protecting the metal substrate from corrosion damage.
In recent years, it has become possible to produce laminate films excellent in adhesion to a metal sheet (hereinafter referred to as the film for metal sheet lamination). The typical conventional film for metal sheet lamination is a two-layer film composed of a resin layer made from polyolefin and an adhesive layer made of an adhesive agent, which is adhesive to metal (hereinafter referred to as the metal adhesive agent). To be more specific, in one such two-layer film, polyethylene, polypropylene, or an ethylene-propylene copolymer is used as polyolefin.
The above-mentioned conventional two-layer films have no problem in being laminated on the surface of a metal material already processed into a predetermined shape. However, when a steel sheet on which a laminate film is fixedly bonded (hereinafter referred to as laminate steel sheet) is processed into a predetermined shape, in particular, by a draw-forming process, the conventional two-layer films are highly likely to whiten or break. To be more specific, when the laminate steel sheet provided with a conventional two-layer film is formed into cans, the yields of quality cans are low due to the whitening or breakage of the conventional two-layer film during the draw-forming process.
DISCLOSURE OF THE PRESENT INVENTION
The present invention has been contrived in view of the aforementioned situation, and its first object is to provide a laminate film which can retard the deterioration of the anticorrosion function of the laminate film caused by its whitening or breakage during a shaping process such as a draw-forming process. The second object of the present invention is to provide a laminated structure to which the laminate film of the present invention is fixedly bonded. The following is a description of the above-mentioned laminate film and the above-mentioned laminated structure.
(I) Laminate Film
The first object can be achieved by a laminate film comprising: an adhesive layer composed of an adhesive agent; a first resin layer composed of a polypropylene resin and the first resin layer being formed above the adhesive layer; and a second resin layer formed between the first resin layer and the adhesive layer, the second resin layer containing a propylene-&agr;-olefin copolymer as a main component, the second resin layer being at least 0.5 times thicker than the first resin layer, the second resin layer having a Vicat softening point lower than that of the first resin layer, and the second resin layer having a melting point lower than that of the first resin layer by 2° C. or more. The laminate film of the present invention is characterized by having the second resin layer disposed between the adhesion layer and the first resin layer.
The first resin layer contains either a polypropylene resin only or a polypropylene resin and an additive agent. When the first resin layer contains the polypropylene resin and the additive agent, it is necessary to contain the polypropylene resin essentially and the additive agent in trace amounts. The polypropylene resin can be a resin composed of propylene homopolymers having a single NMR pentad fraction or a resin obtained by mixing plural kinds of propylene homopolymers having different NMR pentad fractions.
The second resin layer, to be more specific, can be a resin layer exclusively composed of a propylene-&agr;-olefin copolymer, a resin layer exclusively composed of a copolymer of propylene and &agr;-olefin copolymer rubber, or a resin layer composed of a mixture material of a copolymer of propylene and &agr;-olefin copolymer rubber and a rubber material. The second resin layer can be a resin layer further containing a petroleum resin or a resin layer further containing rosin, rosin ester or a terpene resin, or a hydrogenated materials of these.
The “propylene-&agr;-olefin copolymer” cited in the present specification is a copolymer of propylene and &agr;-olefin other than propylene. For example, it can be a copolymer consisting of two components: propylene and one type of &agr;-olefin other than propylene, or a copolymer composed of at least three components: propylene and plural &agr;-olefins which are different in type from each other and other than propylene. The copolymer is a general term for random copolymers, block copolymers, and graft copolymers. To be more specific, the propylene-&agr;-olefin copolymers include a propylene-ethylene random copolymer, a propylene-butene random copolymer, a propylene-ethylene block copolymer, and a propylene-ethylene-butene random copolymer. The “copolymer of propylene and &agr;-olefin copolymer rubber” in this specification means a block polymer of propylene and &agr;-olefin copolymer rubber, and a graft copolymer of propylene and &agr;-olefin copolymer rubber. The “rubber material” cited in this specification means a kind of rubber material included in rubbers. The second resin layer can contain plural types of rubber materials. The rubbers include ethylene-propylene rubber, ethylene-butene rubber, propylene-butene rubber, and hydrogenated styrene-diene rubber. The “petroleum resin” in this specification is an aggregate of polymers obtained by polymerizing fractions mainly composed of a mono-olefin group and a diolefin group as the byproduct in refining ethylene from petroleum in an ethylene plant, and an aggregate of hydrogenated polymers obtained by hydrogenating the polymers. The petroleum resin is a general term for aliphatic petroleum resins, aromatic petroleum resins, and alicyclic petroleum resins.
When the above-mentioned adhesive agent contains an acid-modified propylene polymer, the adhesion between the adhesive layer and the metal substrate is secured. As a result, the film for metal lamination can be provided. The “acid-modified propylene polymer” in this specification means a polymer obtained by substituting the fundamental components (polymer units) of the propylene polymer by acid components or by substituting part of the propylene polymer by acid components. The “propylene polymer” in this specification means a polypropylene or a propylene copolymer mainly composed of propylene. Thus, the acid-modified propylene polymer can be an acid-modified propylene homopolymer, or an acid-modified propylene-&agr;-olefin copolymer.
When the first resin layer has a melting point not less than 155° C., a laminate film fixedly bonded to the substrate through welding can be provided. As a result, in the depositing process the film can be prevented from sticking to the heating device or the cooling device. Thus, it becomes possible to form a substrate which is coated with a laminate film excellent in surface smoothness.
When at least one of the first resin layer, second resin layer, and adhesive layer contains zinc oxide fine particles, the obtained laminate film is capable of suppressing the permeation of a sulfide. This is because the zinc oxide fine particles have the property of absorbing a sulfide such as hydrogen sulfide. (II) Laminated structure
The above-mentioned second object can be achieved by a lami
Gunze Co., Ltd.
Nakarani D. S.
Westerman Hattori Daniels & Adrian LLP
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