JP2000326383A - Manufacture of laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a laminate obtained by laminating a resin layer having excellent adhesive properties with a base material of metal, workability, durability against contraction and shear and good pasteurization durability on the material, by extrusion laminating a polyolefin resin, laminating the resin on the material, and irradiating the laminated layer with an electron beam. SOLUTION: A resin layer is obtained by melting a polyolefin resin by an extruder, then the layer is extruded for laminating it so as to be brought into contact with a plate-like or cylindrical metal base material such as a metal foil of copper, aluminum or the like supplied to a flat die and heated. The laminated resin is irradiated with an electron beam. A flat plate-like resin laminated metal plate before working is irradiated with an electron beam by using an accelerator of a Cockcroft type or van de Graaff type electron beam generation source, and then to remove a curing strain due to crosslinking, the plate is heated to a temperature of a predetermined range based on a glass transition temperature of the cured resin irradiated with the beam. Thus, the laminate of the resin layer having adhesive properties with the material, workability, durability against contraction and shear and good pasteurization durability and the material is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminate in which a polyolefin resin layer having good adhesion to a metal substrate, workability, and sterilization resistance is formed on a metal, and particularly to a can, The present invention relates to a method for producing a laminate suitable for can lid applications.

[0002]

2. Description of the Related Art Conventionally, as a resin laminated metal plate used for cans, a biaxially stretched thermoplastic film which has been thermally laminated to a metal plate directly or via an adhesive has been used. Was.

However, a biaxially stretched thermoplastic film has poor processability and poor adhesion to a metal substrate.
Normal drawing and ironing (DI processing, drawning and ironi
ng) cannot be tolerated.

[0004] Extrusion and lamination of a molten thermoplastic resin are required for workability, which is a necessary function for making a can, and adhesion to a metal as a base material, and for a function required for a can after the can is made. It was difficult to achieve compatibility with certain sterilization resistance.

An object of the present invention is to provide a resin having a resin layer having excellent adhesion and workability to a metal substrate, capable of withstanding DI processing, and having good sterilization resistance. The purpose is to obtain a laminate.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have extruded and laminated a polyolefin resin, laminated it on a metal substrate, and then irradiated the laminated resin layer with an electron beam. By this, it is possible to obtain a laminate in which a resin layer having excellent adhesion and workability with a metal base material, being able to withstand DI processing, and having good sterilization resistance is obtained, and achieving the above object. The invention has been completed.

Thus, the present invention provides a method for manufacturing a laminate, comprising extruding and laminating a polyolefin resin on a heated metal substrate, and irradiating the laminated polyolefin resin layer with an electron beam. It provides a method.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described in detail below. The polyolefin-based resin used in the method of the present invention can be used without any particular limitation as long as it is a polyolefin resin or a modified polyolefin resin that can be formed into an extruded film and can be thermally fused to a substrate. In the present invention, the modified polyolefin resin means a resin in which the amount of olefin constituting the resin is 50% or more.

As the polyolefin resin, for example,
Low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ethylene and other α
-Copolymer with olefin, ethylene-vinyl acetate copolymer, ethylene-unsaturated carboxylic acid ester copolymer,
Copolymers of ethylene and cyclic olefins, propylene and C ₄ or more α- olefins and copolymers; unsaturated carboxylic acid-modified polyolefin obtained by modifying these polyolefin resins with an unsaturated carboxylic acid or its derivative Resins and the like can be mentioned.

Other α-olefins constituting the copolymer of ethylene and other α-olefins include propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene, 1-octene and the like. Decene, 1-tetradecene,
Examples thereof include 1-octadecene and the like, and these can be used alone or in combination of two or more.

The unsaturated carboxylic acid ester constituting the ethylene-unsaturated carboxylic acid ester copolymer includes methyl acrylate, ethyl acrylate, propyl acrylate, n-, i- or t-butyl acrylate, acrylic acid 2-ethylhexyl, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-, i-acrylate
Or t-butyl, 2-ethylhexyl methacrylate, lauryl methacrylate, etc. can be mentioned, and these can be used alone or in combination of two or more.

Commercially available copolymers of ethylene and cyclic olefin include, for example, Apel (trade name) series manufactured by Mitsui Chemicals, Inc. These can be used alone or in combination of two or more.

The unsaturated carboxylic acid or its derivative as a modifier used in the production of the unsaturated carboxylic acid-modified polyolefin resin includes acrylic acid, maleic acid, and the like.
Unsaturated carboxylic acids such as fumaric acid, tetrahydrophthalic acid, itaconic acid, crotonic acid, citraconic acid, nadic acid R (endosis-bicyclo [2,2,1] hept-5-ene-2,3-dicarboxylic acid); Or derivatives thereof, for example, acid halides, amides, imides, anhydrides, esters and the like. Specific examples include maleenyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate. Eat and the like. The unsaturated carboxylic acid-modified polyolefin-based resin can be obtained, for example, by graft-polymerizing the above-mentioned unsaturated carboxylic acid or a derivative thereof as the modifier to the polyolefin-based resin.

Although the melt flow rate of the polyolefin resin is not particularly limited, it is usually 0.05 to 50 g / 10 min, 0.1 to 20 g / 10 from the viewpoint of moldability.
Preferably it is in the range of minutes.

Among the polyolefin resins, polyethylene resins and modified polyethylene resins are preferred from the viewpoint of curability by electron beam irradiation. Further, it is preferable from the viewpoint of heat resistance that the copolymer be a copolymer of ethylene and a cyclic olefin, and that the glass transition temperature (Tg) be in the range of 50 to 100 ° C.

In the method of the present invention, the metal substrate on which the above-mentioned polyolefin resin is extruded and laminated may be, for example, a metal foil, a plate or a tube. , Copper, aluminum, tin-free steel, tinplate, titanium, and the like, and metals conventionally used as packaging base materials. Also,
The metal substrate may be the metal itself, or may be a metal such as kraft paper or a plastic film or sheet adhered to the back surface of the metal.

In the method of the present invention, as a method of extruding and laminating a polyolefin-based resin, for example, the polyolefin-based resin is melted by an extruder, and after being melted, supplied to a T-die (flat die) and heated to a heated metal. A method of extruding and laminating in contact with a substrate can be exemplified. The temperature of the metal surface of the heated metal substrate during lamination is usually [Tg (1)] based on the glass transition temperature [Tg (1)] of the polyolefin resin.
The temperature is preferably in the range of not less than +20] ° C. and not more than the extrusion temperature of the resin, from the viewpoint of adhesion and ease of cooling after lamination. The thickness of the polyolefin resin layer to be laminated is not particularly limited, but is usually 5 μm.
It is preferable that the thickness be in the range of about m to 100 μm.

In the method of the present invention, after laminating a polyolefin-based resin, an electron beam is applied to the laminated polyolefin-based resin layer to obtain a desired laminate. The electron beam irradiation may be performed after molding the resin-laminated metal plate, but is usually performed on the plate-shaped resin-laminated metal plate before processing, and subsequently, the electron beam irradiation is performed to remove the curing distortion due to crosslinking. [Tg (2) +20] ° C to 280 ° C, preferably 1 ° C, based on the glass transition temperature [Tg (2)] of the cured resin thus obtained.
It is preferable to heat (heat set) in the range of 80 to 250 ° C.

In the present invention, the processability and the adhesion of the polyolefin resin layer to the metal substrate can be greatly improved by performing electron beam irradiation. The present inventors believe that the reason for this is that the cohesive force of the polyolefin-based resin layer is improved by inter-polymer crosslinking by hydrogen abstraction of the olefin unit.

The accelerators of the electron beam source used for electron beam irradiation include Cockcroft type, Cockcroft-Walton type, Van de Graf type, Resonant transformer type, Transformer type, Insulated core transformer type, Dynamitron type , A linear filament type, an area beam type, a high frequency type and the like. The electron beam energy is 100 keV or more.
300 keV, preferably 150 keV to 200 keV
Is appropriate. The irradiation dose is 0.2Mrad ~ 2
0 Mrad is suitable, especially 3 Mrad to 15 Mrad,
It is suitable in terms of processability, adhesion, and economy. The irradiation time of the electron beam can be generally about 1 second or less.

The polyolefin-based resin-laminated metal sheet obtained by the method of the present invention can be used for beverage cans, food cans, morsels,
It is suitably used for cans such as gallon cans and metal lids such as caps, and can also be applied to outer surfaces of household appliances such as magic bottles and refrigerators.

[0022]

The present invention will be described more specifically with reference to the following examples.

Example 1 An aluminum plate having a thickness of 0.22 mm was heated to 150 ° C., and a low-density polyethylene resin was applied on the plate at a resin temperature of 240 ° C. using an extruder equipped with a T-die. Thickness 2
The resin-coated surface was melt-extruded so as to have a thickness of 0 μm, laminated between a cooling roll and a nip roll, and then irradiated with an electron beam of 10 Mrad under a nitrogen atmosphere to obtain a laminate (A).

Example 2 The laminate (A) obtained in Example 1 was further subjected to 60 ° C. at 230 ° C.
Heating (heat setting) for 2 seconds gave a laminate (B).

Example 3 In Example 1, "Apel APL6509T" (manufactured by Mitsui Chemicals, Inc.) was used in place of the low density polyethylene resin.
A laminate (C) was obtained in the same manner as in Example 1 except that a trade name, a copolymer of ethylene and a cyclic olefin) was used.

Example 4 The laminate (C) obtained in Example 3 was further subjected to 60 ° C. at 230 ° C.
Heating (heat setting) was performed for 2 seconds to obtain a laminate (D).

Example 5 Example 1 was repeated except that a high-density polyethylene resin was used in place of the low-density polyethylene resin.
And a laminate (E) was obtained.

Example 6 The laminate (E) obtained in Example 5 was further subjected to 60 ° C. at 230 ° C.
Heating (heat setting) was performed for 2 seconds to obtain a laminate (F).

Example 7 A laminate (G) was obtained in the same manner as in Example 1, except that a linear low-density polyethylene resin was used instead of the low-density polyethylene resin.

Example 8 The laminate (G) obtained in Example 5 was further subjected to 60 ° C. at 230 ° C.
Heating (heat setting) was performed for 2 seconds to obtain a laminate (H).

COMPARATIVE EXAMPLE 1 In Example 1, the same procedure was performed up to the laminating step.
Example 1 except that electron beam was not irradiated after lamination
To obtain a laminate (I).

Comparative Example 2 The laminate (I) obtained in Comparative Example 1 was further treated at 230 ° C. with 60
After heating (heat setting) for 2 seconds, a laminate (J) was obtained.

Each of the laminates obtained in the above Examples and Comparative Examples was subjected to various tests based on the following test methods. The test results are shown in Table 1 below.

Test Method Adhesion: 6 parallel vertical and horizontal straight lines were drawn at 2 mm intervals on the resin-coated surface of each laminated body with a cutter knife at intervals of 2 mm so as to form 25 squares of 2 mm × 2 mm. Individual pieces were prepared, a cellophane adhesive tape was adhered to the surface thereof, and the peeling condition when the tape was instantaneously peeled was evaluated according to the following criteria.

◎: No peeling of the resin film was observed at all. な い: No squares were removed, but turning-up was observed at the edges of the squares. Δ: Squares were separated, but no more than two. : Three or more squares fall off.

Deep drawing workability: Using a deep drawing machine, the resin-coated surface of the laminate is placed outside, and the drawing ratio is 50%.
Was subjected to deep drawing, and the peeling state of the processed side surface was visually evaluated based on the following criteria.

◎: No peeling of the resin film was observed at all. な い: No peeling was observed at the side surface, but turning-up was observed at the end. Δ: A slight peeling of the resin film was observed at the side surface. ×: Even at the side surface. Remarkable peeling of the resin film is observed.

Resistance to retort adhesion: A deep drawn sample prepared by the above test for deep drawing workability was subjected to 12
The peeling state of the sample after the retort sterilization treatment in steam at 5 ° C. for 30 minutes was visually evaluated according to the following criteria.

：: No peeling of the resin film was observed at all. ：: No peeling was observed at the side surface, but the edge was turned up. Δ: A slight peeling of the resin film was observed at the side surface. ×: Even at the side surface. Remarkable peeling of the resin film is observed.

Water mark resistance: Water marks generated when the unprocessed laminates were subjected to the retort sterilization treatment in the above retort adhesion test were visually evaluated according to the following criteria.

：: No water mark is observed. Δ: A little water mark is observed. X: Remarkable water mark is observed.

[0042]

[Table 1]

[0043]

According to the method of the present invention, a resin layer having excellent adhesion and workability to a metal base material, being able to withstand DI processing, and having good sterilization resistance is laminated on the base material. A resin laminate can be obtained.

The polyolefin resin-laminated metal sheet, which is a laminate obtained by the method of the present invention, is suitably used for cans such as beverage cans, food cans, miscellaneous cans, and 5 gallon cans, and for metal lids such as caps. Can be.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08J 7/00 305 C08J 7/00 305 // C08L 23:00 F term (reference) 4F073 AA32 BA06 BA07 BB01 CA42 4F100 AB01A AB10 AK03B AK04B AK06 BA02 EH112 EH23B EH232 EJ421 EJ532 GB16 GB23 JA05B JC00 JK06 JL01 YY00B 4F207 AA03 AA04 AD03 AD08 AD29 AG03 KA01 KB11 KF01 KJ05 KJ09 KK42 KK82 KW33

Claims (4)

[Claims] 1. A method for producing a laminate, comprising: extruding and laminating a polyolefin-based resin on a heated metal substrate; and irradiating the laminated polyolefin-based resin layer with an electron beam. 2. The method for producing a laminate according to claim 1, wherein the constituent monomer component of the polyolefin resin is mainly composed of ethylene. 3. The polyolefin resin according to claim 1, wherein the polyolefin resin is a polyolefin resin containing a cyclic olefin.
A method for producing the laminate according to the above. 4. The method for producing a laminate according to claim 1, wherein the glass transition temperature of the polyolefin resin is in the range of 40 to 100 ° C.