JPH06136330A - Heat-bondable laminated composite film and its production - Google Patents

Abstract

PURPOSE:To obtain a heat-bondable film having high bonding strength to a metallic surface, scarcely changes in its thickness when used in bonding by melting under applied heat and pressure, is excellent in dimensional accuracy after bonding and is useful especially for e.g. sealing a metallic electrode of a thin battery. CONSTITUTION:The film is one prepared by laminating a 5-500mum-thick film of a modified polyolefin prepared by grafting an unsaturated carboxylic acid or its anhydride onto a polyolefin on each surface of a polyolefin film of a thickness of 5mum or above. The title production process comprises laminating the polyolefin on the modified polyolefin in a molten state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated composite film for heat welding, and is particularly suitable for laminating a metal surface to a metal surface or a metal surface to a polyolefin etc. for sealing the metal electrodes of the positive and negative electrodes of thin batteries. And a laminated composite film for heat welding.

[0002]

2. Description of the Related Art Conventionally, when a metal surface and a metal surface or a metal surface and a polyolefin film or a polyolefin molded product are adhered by a welding film, a film laminated metal sheet obtained by laminating a modified polyolefin on the metal surface is used as the welding film, Alternatively, a single layer of the modified polyolefin film was interposed between the metal surface and the metal surface or between the metal surface and the polyolefin film or the polyolefin molded product, and the metal layer was heated to a temperature not lower than the melting point of the modified polyolefin and pressure-bonded.

[0003]

SUMMARY OF THE INVENTION In such a method,
There is a problem that the modified polyolefin film melted by heat and pressure flows out to the surroundings and the thickness of the adhesive layer changes, and the dimensional accuracy in the adhesive direction cannot be obtained. There is a problem that the modified polyolefin layer becomes thin and the adhesive strength becomes insufficient. Further, when the metal surface and the metal surface are bonded with a modified polyolefin film to electrically insulate the modified polyolefin film, there is a problem that the modified polyolefin flows out to cause insulation failure. An object of the present invention is to solve the above-mentioned problems, to provide a uniform thickness of an adhesive layer, and to provide a laminated film for heat-welding capable of ensuring adhesive strength, electrical insulation and the like.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that welding is performed using a composite film obtained by laminating a modified polyolefin film having a lower melting point than the polyolefin film on the polyolefin film. Thus, the inventors have found that the dimensional accuracy and the adhesive strength are good when the metal surface is bonded to the metal surface or the metal surface is bonded to the polyolefin film, and the present invention has been completed. That is, the present invention is a modified polyolefin obtained by graft-polymerizing an unsaturated carboxylic acid or an anhydride thereof having a thickness of 5 to 500 μm, which has a melting point of at least 5 ° C. lower than that of the polyolefin film, on both sides of a polyolefin film having a thickness of 5 μm or more. Is a laminated composite film for thermal fusion bonding, and a method for producing the same, which comprises laminating a polyolefin and a modified polyolefin in a molten state. Hereinafter, the present invention will be described in detail.

(1) Polyolefin Film As the polyolefin for the polyolefin film used in the present invention, ethylene homopolymer, ethylene as a main component and α-olefin other than ethylene, vinyl ester (for example, vinyl acetate) or unsaturated carboxylic acid ester ( Examples thereof include a copolymer with ethyl acrylate), a propylene homopolymer, or a copolymer with propylene as a main component and an α-olefin (including ethylene) other than propylene, and the like, and these are used in combination of two or more kinds. be able to.

(2) Modified Polyolefin Film The modified polyolefin film for use in the present invention, which is modified by graft polymerization of an unsaturated carboxylic acid or its anhydride, is usually produced by graft-polymerizing these compounds with polyolefin. To be done. Modified polyolefin: Examples of the polyolefin used in the production of the modified polyolefin include ethylene homopolymer, ethylene as a main component, and α-olefin other than ethylene, vinyl acetate, (meth) acrylic acid or its ester, etc. Examples thereof include a combination, a propylene homopolymer, and a copolymer of propylene as a main component and an α-olefin (including ethylene) other than propylene. Modifier: Examples of the unsaturated carboxylic acid or its anhydride of the modifier to be graft-polymerized with the above-mentioned polyolefin include
Examples thereof include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, citraconic acid, citraconic anhydride, itaconic acid, itaconic anhydride, and the like. Of these, acrylic acid and maleic anhydride are preferable, and maleic anhydride is most preferable.

Modification method: As a method of graft-polymerizing the above-mentioned modifier to the polyolefin, there are a slurry method, a solution method, a melt-kneading method and the like, but from the economical viewpoint, the solution method and the melt-kneading method are preferable. In the case of the melt kneading method, an unsaturated carboxylic acid or its anhydride and, if necessary, a radical reaction initiator such as an organic peroxide or an azobis compound are added to the raw material powder or pellets of Henschel according to a conventional method at a predetermined mixing ratio. Dry blend with a mixer or the like, or dissolve unsaturated carboxylic acid or its anhydride and, if necessary, a radical reaction initiator in an organic solvent, spray to a powder or pellets of polyolefin, and blend with a Henschel mixer or the like. A kneading machine in which the system is replaced with nitrogen gas in the blended polyolefin powder or pellets,
For example, the modified polyolefin can be obtained by charging it in a Banbury mixer, a double screw mixer or the like and melt-kneading at a temperature of 120 to 300 ° C. for 0.1 to 30 minutes.

Here, the amount of the radical reaction initiator used is 0.1% by weight or less, preferably 0.1% by weight, based on the polyolefin.
It is in the range of 001 to 0.05% by weight. Examples of the organic peroxide used as the above initiator include benzoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butyl peroxylaurate, dicumyl peroxide, α, α′-bis (t-butyl peroxide). Isopropyl) benzene, 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, t
-Butyl peroxybenzoate, n-butyl-4,4
-Bis (t-butylperoxy) valerate, octanoyl peroxide, p-menthane hydroperoxide and the like can be mentioned, and examples of the azobis compound include azobisisobutyronitrile and 2,2'-azobis (2,2). 4,4-trimethylvaleronitrile), 2,2 '
-Azobis (2-cyclopropylpropionitrile) and the like.

The modified polyolefin referred to in the present invention includes the modified polyolefin obtained as described above, a blend of two or more thereof, or a blend of the above polyolefin and the above modified polyolefin. The amount of unsaturated carboxylic acid or its anhydride contained in the modified polyolefin thus obtained is 0.01 to 3
%, Preferably 0.02 to 2% by weight, particularly preferably 0.05 to 1% by weight. If it is less than 0.01% by weight or exceeds 3% by weight, sufficient adhesive strength cannot be obtained.

Melting point of modified polyolefin: The melting point of the modified polyolefin film used in the present invention is required to be at least 5 ° C. lower than the melting point of the polyolefin film used. It is preferably 10 ° C or higher. When the difference in melting point is less than 5 ° C., the laminated composite film for heat welding is inserted between the metal surfaces, and the modified polyolefin film is mainly melted by heating from the metal side to form the metal surface and the metal surface. In the case of adhering, the inner polyolefin film is melted and flows out to the surrounding to change the thickness of the adhesive layer,
There is a problem that dimensional accuracy in the bonding direction cannot be obtained. Here, the melting point is a peak point of melting when 5 mg of a measurement sample is set in a differential scanning calorimeter and measurement is performed at a temperature rising rate of 10 ° C./min.

(3) Laminating Method In the laminated composite film of the present invention, the modified polyolefin film is preferably laminated on both sides of the polyolefin film. As a method of laminating the polyolefin film and the modified polyolefin film, both resins are subjected to an inflation method or a T-die method at 140 to 300 ° C., preferably 16
A method of co-extruding at a temperature of 0 to 230 ° C. and melt-laminating inside or outside the die to form a composite is suitably adopted. When a lamination method other than the coextrusion method is used, for example, both films are formed separately and laminated by heating and pressing,
The film is deformed and the accuracy of the film thickness is impaired, which is not preferable. Therefore, when laminating by a heating and pressing method at a temperature that does not cause deformation, the fusion strength between both films becomes insufficient. Further, a method of forming one film and then melt-extruding the other resin on the film to laminate the film is not preferable because the fusion strength is insufficient.

The thickness of the polyolefin film layer of the heat-welding laminated composite film obtained in the present invention is 5 μm or more, preferably 10 μm or more. When the thickness of the polyolefin film is less than 5 μm, even if the melting point with the modified polyolefin is 5 ° C. or more, the polyolefin film usually melts and flows out to the periphery during melt bonding, and the dimensional accuracy of the adhesive layer cannot be obtained. The thickness of the modified polyolefin film is 5 to 500 μm, preferably 10 to 2
It is 50 μm. If it is less than 5 μm, sufficient adhesive strength cannot be obtained. On the other hand, when the thickness exceeds 500 μm, the amount of the modified polyolefin film melted at the time of bonding increases and flows out to the periphery, and the dimensional accuracy of the adhesive layer cannot be obtained. The total thickness of the laminated composite film for heat-welding obtained in the present invention is preferably 1 mm or less from the viewpoint of adhesive strength and dimensional accuracy, particularly 0.5
mm or less is more preferable. The thickness of each layer, that is, the thickness ratio of the polyolefin film to the modified polyolefin film is preferably 1:50 to 50: 1, and 1:10 to 1
0: 1 is more preferred.

Adhesion method of laminated composite film for heat-welding and metal surface: To adhere the laminated composite film for heat-welding of the present invention to a metal surface, the film is sandwiched between the metal surfaces, The modified polyolefin may be melted and adhered by heating from one or both metal sides.

Application: The laminated composite film for heat-welding of the present invention can be used for adhesion between metals or between a metal and a polyolefin, or can be laminated on a metal surface to obtain a resin laminated metal. In particular, it is suitable for sealing positive and negative metal electrodes for thin batteries.

[0015]

EXAMPLES The present invention will be described in more detail with reference to examples.

Example 1 A modified propylene-ethylene random copolymer modified by graft polymerization of maleic anhydride by a melt-kneading method (density: 0.89 g / cm ³ , melt flow rate (MF
R): 1.2 g / 10 minutes, ethylene content: 5.6% by weight, maleic anhydride content: 0.06% by weight, melting point: 134 ° C.)
At an extrusion temperature of 200 with a 50 mm diameter extruder with L / D = 25.
At ℃, polypropylene (density: 0.90 g / cm ³ ,
MFR: 2 g / 10 minutes, melting point: 165 ° C.), L / D = 23
Of 50 mm diameter extruder at 230 ° C., each of which is connected to a 75 mm diameter three-layer spiral inflation die inside lamination die and laminated and extruded.
Each thickness of the ethylene random copolymer layer is 10μ
An inflation film having a total thickness of 50 μm was molded into m 2 with the thickness of the intermediate polypropylene layer being 30 μm. On both sides of the obtained laminated composite film for heat welding,
50 μm thick stainless steel (JIS: SUS
304) Sheets were stacked and heat-press welded from both sides of the stainless steel sheet at a temperature of 170 ° C. and a pressure of 5 kg / cm ² for 10 seconds to obtain a metal laminated sheet. The test piece of the obtained metal laminated sheet was immersed in hydrochloric acid to dissolve the stainless steel part, the laminated composite film piece for heat welding was taken out, and its cross section was measured for its thickness by a micrograph. Was 47 μm.

Comparative Examples 1 and 2 Only the modified propylene-ethylene random copolymer film used in Example 1 was extruded through a single spiral inflation die at the same extruder and extrusion temperature, and modified to have thicknesses of 10 μm and 50 μm, respectively. An inflation film of a propylene-ethylene random copolymer was molded. The obtained films of 10 μm and 50 μm were heat-pressed and welded to a stainless steel (SUS 304) sheet having a thickness of 50 μm under the same conditions as in Example 1 to obtain a metal laminated sheet. The two types of metal laminated sheets were treated with hydrochloric acid in the same manner as in Example 1, and the adhesive single-layer resin film pieces were taken out and measured for thickness. The film layers had thicknesses of 4 μm and 20 μm, respectively. As is clear from the above results, the thickness of the film layer of the metal laminated sheet on which the laminated composite film for heat-welding of the present invention is laminated hardly changes, whereas the modified propylene-ethylene random copolymer shown in Comparative Examples is shown. When the film of No. 3 is heated and pressure-welded, the thickness of the film layer changes significantly, and a metal laminated sheet with a good thickness accuracy cannot be obtained.

Example 2 The laminated composite film for heat welding obtained in Example 1 was prepared in the same manner as in Example 1 with a thickness of 50 μm of stainless steel (SUS 3
04) Overlapping sheets, 5kg / c from both sides at 165 ℃
It was heated and pressure-welded at a pressure of m ² for 60 seconds to obtain a metal laminated sheet. Table 1 shows the results obtained by measuring the thickness of the resin film layer of the obtained metal laminated sheet, the adhesive strength (peeling strength in 15 mm) and the electric insulation. However, electrical insulation is ○ when there is no conductivity by the tester, × when there is conductivity
And

[0019]

[Table 1]

Comparative Example 3 A composite film for heat-welding was obtained in the same manner as in Example 1 except that the thickness of each propylene-ethylene random copolymer layer was changed to 3 μm. Using this film, a metal laminated sheet was obtained in the same manner as in Example 2. Table 1 shows the evaluation results
Shown in. The change in thickness of the film layer was small, but the adhesive strength was significantly reduced.

Comparative Examples 4 and 5 Using the modified propylene-ethylene random copolymer films having thicknesses of 10 μm and 50 μm obtained in Comparative Examples 1 and 2, stainless steel / modified propylene-ethylene random copolymer was used in the same manner as in Example 2. A metal laminated sheet of polymer film / stainless steel was obtained. Table 1 shows the evaluation results
Shown in. The thickness of the film layer changed drastically and the insulation was also poor.

[0022]

The laminated composite film for heat welding of the present invention is
Since it is composed of a polyolefin layer with a different melting point and a modified polyolefin layer with excellent melt adhesion, it has a large adhesive strength with the metal surface and a small change in the film thickness due to heating, pressing, and melting. The dimensional accuracy of is excellent.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Morikoshi 1st Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Yokkaichi Research Institute (72) Inventor Norihiro Otsu 1st Toho-cho, Yokkaichi-shi, Mie Mitsubishi Oil (72) Inventor Sadao Higuchi, Toho-cho, Yokkaichi-shi, Mie Mitsubishi Petrochemical Co., Ltd. Inside Yokkaichi Research Institute

Claims (2)

[Claims] 1. A modified polyolefin obtained by graft-polymerizing an unsaturated carboxylic acid or an anhydride thereof having a thickness of 5 to 500 μm, which has a melting point of at least 5 ° C. lower than that of the polyolefin film, on both sides of a polyolefin film having a thickness of 5 μm or more. A laminated composite film for heat-welding, characterized in that the above films are laminated. 2. A laminate of a polyolefin and a modified polyolefin obtained by graft-polymerizing an unsaturated carboxylic acid having a melting point lower than that of the polyolefin by at least 5 ° C. or an anhydride thereof and modifying the laminated polyolefin in a molten state. A method for producing a laminated composite film for heat fusion.