JPH09309177A - Polyolefin resin film laminated steel panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin resin laminated steel panel excellent in design effect by laminating a polyolefin resin film on a steel panel without damaging embossed appearance. SOLUTION: Two polyolefin resin films different in m.p. are laminated on the surface of a steel panel through an adhesive layer containing an acid modified polyolefin resin and embossing processing is applied to the surfaces of the polyolefin resin films and the relation of T1<=T2-10 and T3<=T2-10 is formed between the m.p. T1( deg.C) of the polyolefin resin layer on the side of the adhesive layer. the m.p. T2( deg.C) of the polyolefin resin layer on a surface side and the m.p. T3( deg.C) of the acid modified polyolefin resin layer contained in the adhesive layer. As the polyolefine resin films, a film wherein a printing layer is provided between two polyolefin resin layers can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin laminated steel sheet used as an exterior material, an interior material, a surface material, etc. as a substitute material for a vinyl chloride steel sheet.

[0002]

2. Description of the Related Art Conventionally, PVC steel sheets have been used for outer panels of home electric appliances and the like. The vinyl chloride steel plate has a high degree of freedom regarding the color tone because the vinyl chloride resin forming the surface thereof exhibits excellent physical properties by the formulation of a plasticizer, a stabilizer and the like, and an arbitrary pigment can be added. Further, embossing can enhance the design, and the thick film effect gives a heavy feeling. However, since vinyl chloride resin contains chlorine, it poses a problem in terms of environmental measures, and the use of PVC steel sheet tends to deteriorate the image of the product, and further the corporate image. Therefore, switching to coated steel sheets with properties equivalent to PVC steel sheets is being promoted. As a substitute material for a PVC steel sheet, a polyolefin resin laminated steel sheet is known to satisfy the required characteristics. The polyolefin resin is a difficult-to-adhere plastic like the fluororesin, and it is necessary to adopt a heat fusion method for adhesion. In order to improve the adhesiveness between the polyolefin resin and the steel sheet, it has been studied to interpose a polyolefin resin adhesive that is adhesively modified with maleic anhydride or the like between the steel sheet and the polyolefin resin film. For example, JP-A-54-71
In 1890, a polyolefin resin / metal substrate is prepared by adjusting the polar group and crystallinity of a polar group-containing ethylenically unsaturated monomer-modified olefin resin, and by adjusting the amount and amount of a film-forming base resin. The adhesive strength between them is increased.

[0003]

However, Japanese Patent Application Laid-Open No.
The material targeted in No. 71189 is a sealing member such as a crown or a container lid, and in order to obtain a sufficient adhesive force between the metal substrate and the polyolefin resin, the polyolefin resin surface is completely melted and a smooth surface is obtained. Becomes Therefore, it cannot be applied to lamination on a polyolefin resin laminated steel sheet that has been embossed in advance, and it cannot be used as a substitute for a vinyl chloride steel sheet whose design is improved by embossing. Therefore, the present inventors, like the embossing of vinyl chloride sol coated steel for exterior building materials applications, after laminating the polyolefin resin film, using a embossing roll when the polyolefin resin film is in a molten state I examined how to do it. However, as compared with a plasticized vinyl chloride resin that exhibits amorphous polymer-like properties, a polyolefin resin that exhibits clear crystallinity has a marked decrease in the viscosity of the molten resin in the temperature range above the melting point. Therefore, in a polyolefin resin film laminated on a steel sheet having a sufficient amount of heat for maintaining the molten state of the polyolefin resin, the embossed pattern applied to the surface instantly flows, and as a result, a clear appearance is not expressed. The present invention has been devised to solve such a problem, and by adjusting the melting points of the polyolefin resin film and the polyolefin film in the adhesive layer, the embossed polyolefin resin film has an embossed appearance. It is an object of the present invention to provide a polyolefin resin laminated steel sheet which can be laminated on a steel sheet without damaging the resin and has excellent designability.

[0004]

In order to achieve the object of the polyolefin resin laminated steel sheet of the present invention, a film obtained by laminating two polyolefin resin layers having different melting points is provided with an adhesive layer containing an acid-modified polyolefin resin. Has a structure laminated on the surface of the steel sheet, and the surface of the polyolefin resin film is embossed. The melting point T ₁ (° C.) of the polyolefin resin layer on the adhesive layer side, the melting point T of the polyolefin resin layer on the surface side ₂ (° C.) and the melting point T ₃ (° C.) of the acid-modified polyolefin resin contained in the adhesive layer, the relationship of T ₁ ≦ T ₂ −10 and T ₃ ≦ T ₂ −10 is established. Characterize. As the polyolefin resin film, a film having a printing layer provided between two polyolefin resin layers can be used.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In order to bond a polyolefin resin film to a steel plate, it is necessary to interpose an acid-modified polyolefin resin for bonding the polyolefin resin film and the steel plate, and a layer containing the acid-modified polyolefin resin is used as an adhesive layer. To do. Further, at the time of adhesion, the steel sheet / acid-modified polyolefin resin-containing layer / polyolefin resin film is heated to a temperature not lower than the melting point of the acid-modified polyolefin resin contained in the polyolefin resin film and the adhesive layer to melt the acid-modified polyolefin resin-containing layer. While adhering to the steel plate surface, the polyolefin resin film is melted to make the acid-modified polyolefin resin-containing layer and the polyolefin resin film compatible with each other. In order to make the steel plate / acid-modified polyolefin resin-containing layer / polyolefin resin film a strong adhesive body in this bonding process, it is necessary to melt the polyolefin resin film. As a result, even with a polyolefin resin film that has been embossed in advance, embossing flows during bonding and a clear embossed pattern cannot be retained.

In the present invention, a polyolefin resin film comprising two polyolefin resin layers having different melting points is used in order to prevent the embossed pattern applied to the polyolefin resin film from collapsing. The melting point T ₂ of the polyolefin resin arranged on the surface side is set to be higher than the melting point T _{1 of the} polyolefin resin arranged on the adhesive layer side and the melting point T ₃ of the acid-modified polyolefin resin contained in the adhesive layer by 10 ° C. or more. There is. The bonding temperature between the polyolefin resin film and the adhesive layer depends on the melting points T ₁ and T ₃ , and theoretically the melting point T is set under the condition that the bonding time is set to be extremely long.
_The higher one of ₁ and T _{3 is} the lower limit temperature for bonding. However, assuming a continuous laminated steel plate manufacturing facility used in actual operation, each resin does not flow at the temperature of melting point T ₁ or T ₃ necessary for bonding, and a temperature of melting point + several degrees C is required. Become. On the other hand, the polyolefin resin on the surface side exhibits a slight fluidity even if it is lower than the melting point T ₂ , and the emboss may flow even at T ₂ −several degrees Celsius due to the roll pressure, and the appearance may be impaired.

In this respect, if there is a difference of 10 ° C. or more between the melting points T ₁ and T ₃ and the melting point T ₂ , the embossed pattern attached to the polyolefin resin layer on the surface side is not broken and the polyolefin resin film and the base material are not broken. Strongly adheres to the steel plate. On the other hand, the difference between the melting points T ₁ and T ₃ and the melting point T ₂ is 1
If the temperature is less than 0 ° C., when the polyolefin resin film and the adhesive layer are bonded to each other, the polyolefin resin layer on the surface side is also partially fluidized, and the embossed pattern on the surface is damaged. Considering the laminate temperature control in the actual continuous laminated steel sheet manufacturing equipment, it is preferable that the melting point difference of 20 ° C. or more is between the melting points T ₁ and T ₃ and the melting point T ₂ . The steel sheet used may be phosphating, if necessary,
Zn-plated steel sheet that has undergone coating-type chromate treatment, Zn
There are various plated steel plates such as an Al plated steel plate and an Al plated steel plate, an aluminum plate, and a stainless steel plate.

The resin component of the adhesive is a mixture of an acid-modified polyolefin resin and a solvent-soluble thermosetting resin. The acid-modified polyolefin resin is obtained by graft-polymerizing an acid anhydride having an ethylenically unsaturated group such as maleic anhydride onto a polyolefin resin such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer. Copolymers of olefins such as ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers with carboxylic acids having an ethylenically unsaturated group are used as monomers or mixtures. In addition,
Since the polyolefin resins are compatible with each other, the melting point can be adjusted by mixing. As the solvent-soluble thermosetting resin, a polyester resin, a polyurethane resin, an epoxy resin, or the like is used. Examples of the curing agent include general block type isocyanate and melamine resin.

The adhesive is not a limitation of the present invention, but is prepared by, for example, dispersing an acid-modified polyolefin resin pulverized into a powder in a solvent solution of a solvent-soluble thermosetting resin. Coloring pigments, rust preventive pigments, extender pigments, etc. can be added to the adhesive as required. The adhesive layer is
The dry coating film thickness is preferably 2 to 20 μm. As a coating method, since the adhesive is thixotropic, it is preferable to adopt a top feed type full reverse type roll coating method. The polyolefin resin film of the film laminated on the steel sheet via the adhesive layer is a homopolymer or copolymer of a monomer selected from ethylene, propylene and α-olefin, and kneaded with ethylene-propylene rubber. Crosslinked with a crosslinking agent, ethylene, propylene, a copolymer of ethylene-propylene rubber having a block portion of a homopolymer or copolymer of a monomer selected from α-olefins, A kneaded product of a homopolymer or a copolymer of a monomer selected from ethylene, propylene and α-olefin is used.

Since the polyolefin resins are compatible with each other, the melting point can be adjusted by mixing various polyolefin resins. When a copolymer is used for a polyolefin resin, the melting point can be adjusted by the polymerization composition ratio of the monomer. In the homopolymer, the higher the composition ratio of the monomer having a high melting point, the higher the melting point of the copolymer. A polyolefin resin film composed of two polyolefin resin layers having different melting points is manufactured by various methods. For example, it is manufactured by forming each polyolefin resin into a film, heating and laminating, heat-sealing, immediately embossing and cooling. Alternatively, it is produced by forming a film by a two-layer extrusion molding method, immediately performing embossing and cooling. When a polyolefin resin containing a large amount of rubber component is used, it can be formed into a film by the calender method, but ethylene, propylene, α
In a homopolymer or copolymer of a monomer such as olefin,
Extrusion molding is employed.

A pigment and various additives are blended with the polyolefin resin as required. The thickness of the polyolefin resin film is not particularly limited, but when considering the manufacturability, handleability and various performances, the adhesive layer side is 50
.About.200 .mu.m, and the surface side preferably has a thickness of about 50 to 150 .mu.m. A printed layer may be provided between the two polyolefin resin layers. In this case, after forming the adhesive layer-side polyolefin resin layer into a film, the printed surface is subjected to an easy-adhesion treatment such as corona discharge, if necessary, to form a printed layer by a method such as gravure printing, and the film-formed surface side A laminated film is manufactured by heating and laminating with a polyolefin resin to be the above, heat-sealing, immediately embossing and cooling. Printing inks used in gravure printing include those in which a pigment and various additives are mixed with a base resin such as a vinyl chloride-vinyl acetate copolymer type, an acrylic type, a polyester type, or a polyurethane type.

The steel sheet coated with the adhesive is heated in an oven to be solvent-dried, and the acid-modified polyolefin resin contained in the adhesive is melted. A polyolefin resin film is laminated on the upper surface of the resin, and immediately cooled to obtain the polyolefin. Manufacture resin laminated steel sheet. When the steel sheet coated with the adhesive is heated in an oven, the heating temperature is such that when the films are laminated, the polyolefin resin on the adhesive layer side is melted by the heat quantity of the steel sheets, and the acid-modified polyolefin resin contained in the adhesive is used. It is necessary to maintain a molten state and set the temperature at which the polyolefin resin on the surface side does not melt. In laminating, when the laminate roll in contact with the polyolefin resin surface on the surface side is a cooling roll, the embossed pattern on the surface of the polyolefin resin film is maintained in a more stable state.

[0013]

[Example] With a plate thickness of 0.5 mm, the weight per unit surface of Zn is 45.
A g / m ² hot-dip Zn-plated steel sheet was coated with chromate, coated with a bar coater to a dry film thickness of 5 μm, baked, and immediately laminated with a polyolefin resin film on its upper surface with a laminator. Then, it was immediately water-cooled to obtain a polyolefin resin laminated steel sheet. Table 1 shows the manufacturing conditions at this time. The adhesive used was a mixture of a thermosetting epoxy resin paint (curing agent: methylated melamine) and an acid-modified polyolefin resin at a weight ratio of 30:70. Each of the polyolefin resin films was manufactured by heating and laminating film-formed polyolefin resins on the adhesive side and the surface side, heat-sealing them, and immediately applying satin embossing and cooling. A 100 μm thick film containing no pigment was used on the surface side, and a 150 μm thick film containing 10% by weight of titanium oxide was used on the adhesive layer side. The 60-degree reflective gloss of the embossed surface in the film state was 8, and the emboss retention of the polyolefin resin laminated steel sheet was evaluated by the change in gloss. Regarding test No. 8, after the corona discharge treatment was applied to the adhesive layer side film and the polyester printing ink black was gravure printed, the surface side film was laminated and heat fused and immediately subjected to satin embossing. Cooled.

The adhesive strength of the thus obtained polyolefin resin laminated steel sheet was investigated. In the adhesive strength test, the peel strength when subjected to the 180-degree peel test was measured. As the adhesive strength, preferably, the material of the polyolefin resin film is broken or the adhesive strength of 50 N / 10 mm or more is required. As can be seen from Table 1 showing the investigation results, in all of the polyolefin resin laminated steel sheets according to the present invention, film breakage occurred, and the polyolefin resin film adhered to the steel sheet with good adhesive strength. Moreover, the glossiness of the polyolefin resin laminated steel sheet did not substantially change from the original polyolefin resin film, and a good embossed pattern was retained. On the other hand, in the polyolefin resin laminated steel sheet of the comparative example, the change in gloss after adhesion was large and the embossed pattern was broken.

[0015]

[0016]

As described above, the polyolefin resin laminated steel sheet of the present invention uses a polyolefin resin film obtained by laminating two layers of polyolefin resins having different melting points, and the acid-modified polyolefin resin contained in the adhesive layer. And, by making the melting point of the polyolefin resin on the surface side higher than the melting point of the polyolefin resin layer on the adhesive layer side by 10 ° C. or more, the embossed pattern applied on the surface side is not broken by the heating at the time of bonding, and good adhesive strength is obtained. The polyolefin resin film is adhered to the steel plate with. for that reason,
The obtained polyolefin resin laminated steel sheet utilizes an embossed pattern excellent in design and is used in a wide range of fields such as exterior materials, interior materials, and exterior materials.

Claims (2)

[Claims] 1. Two polyolefin resin layers having different melting points are used.
The laminated film has a structure laminated on the steel plate surface via an adhesive layer containing an acid-modified polyolefin resin,
The surface of the polyolefin resin film is embossed, and the melting point T ₁ (° C.) of the polyolefin resin layer on the adhesive layer side and the melting point T ₂ of the polyolefin resin layer on the surface side
(° C.) and the melting point T ₃ (° C.) of the acid-modified polyolefin resin contained in the adhesive layer, T ₁ ≦ T ₂ −10 and T ₃ ≦
A polyolefin resin laminated steel sheet satisfying the relationship of T ₂ -10. 2. The polyolefin resin film according to claim 1, wherein the polyolefin resin laminated steel sheet has a printed layer between two polyolefin resin layers.