JPH0193349A - Laminated sheet having low temperature heat sealing property - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The low-temperature heat-sealable laminate sheet of the present invention is suitable for use in resin or glass hollow containers such as lactic acid bacteria beverage containers, fruit jelly containers, mayonnaise containers, ketchup containers, and coffee containers. It is useful as sealing lids that block discharge ports, labels for shampoo containers and motor oil containers, book covers, and milk box forming materials.

[Prior art]

Conventionally, such sealing lids have been made by laminating aluminum foil with a low-density polyethylene (melting point 118-123°C) film layer or an ethylene-vinyl acetate (5-22% by weight) copolymer film layer laminated by melt extrusion. Using a sheet, apply this to the outlet (bottle mouth) of a polypropylene, high-impact polystyrene, or glass container, melt the film at a heat sealing temperature of 140 to 230°C, and fuse the seal lid to the bottle mouth. ing.

However, removing this seal lid from the bottle mouth by hand requires a fairly strong pulling force. Although the heat sealing strength can be lowered by lowering the heat sealing temperature, there is no guarantee that the heat sealing will be performed satisfactorily.

On the other hand, there is also known a laminated sheet that can be heat-sealed at low temperatures (100-120°C) by coating the surface of aluminum foil with an aqueous emulsion of ethylene/vinyl acetate copolymer and drying it to form a film. Showa 56-101845
issue).

Although this laminated sheet is used for easy-peelable bags, it is not used as a sealing lid for the bottle mouth because the sealing strength is weak. There is a correlation between the film thickness of the film and the heat seal strength, such that the heat seal strength increases linearly as the film thickness increases.

However, due to the high cost of drying the emulsion and the cost of the emulsion, the actual situation is that the film thickness used is only 10 microns at most.

Therefore, it is desired to develop a well-balanced laminated sheet that can be easily brewed and has sufficient sealing strength.

The appearance of such a laminated sheet is also desirable as a material for forming paper boxes such as milk pure pack containers.

[Specific measures to solve the problem]

In the present invention, the sealing strength of the film is improved by providing a film formed from an extruded low-temperature heat-sealable film and an emulsion in a laminated structure on a base sheet.

That is, in the present invention, an olefin resin film (B) having a melting point of 145° C. or less is laminated on the surface of a base sheet selected from aluminum foil, aluminum vapor-deposited film, or paper, and furthermore, this resin film (B) Provided is a low-temperature heat-sealable laminate sheet on the surface of which is formed a film C) formed from an aqueous emulsion of ethylene resin particles having a melting point at least 5° C. lower than the melting point of the olefin resin. .

(Base Sheet) As the base sheet, aluminum foil, art paper, white cardboard, coated paper, aluminum-deposited polyethylene terephthalate or polypropylene sheet, etc. are used.

Printing may be applied to the opposite side of the base sheet on which the olefin resin film (B) is laminated.

The thickness of the base sheet is usually 5 to 500 microns.

(Olefin Resin Film) The raw material resins for the olefin resin film (B) adhesively laminated on the base sheet (A) include low density polyethylene, linear low density polyethylene, ethylene/methacrylic acid copolymer, and its metal. Salt (KXNa, Zn-, l'J-
etc.), ethylene/vinyl acetate (2 to 22% by weight) copolymer, ethylene (1.5 to 6% by weight)/propylene random copolymer, ethylene/maleic anhydride random copolymer, propylene (85 to 6% by weight), etc. 98%)・Ethylene (0,5
~6%) and Phthene-1 (2~8%) copolymers are used.

The melting point of the olefin resin of this film (B) is 80
~145°C, preferably 1d80~135°C.

This film (B) is a film obtained from an emulsion (
It has the effect of improving the low temperature heat sealing strength of C).

The thickness of this film (B) is preferably 2 to 50 microns. In addition, this film (B) was subjected to corona discharge treatment on the surface,
It may be subjected to plasma treatment or primer treatment.

(Coating) An aqueous emulsion of ethylene resin particles that provides a coating (C) of a resin having a melting point at least 5°C lower than the melting point of the resin of the film (B) has a melt flow rate of 20 pZl or more for 0 minutes or more. , an aqueous emulsion of a comonomer of ethylene and a comonomer is used in which the content of the comonomer to be copolymerized is from 5 to 50% by weight.

Examples of the comonomer include vinyl acetate, methacrylic acid, acrylic acid, lower alkyl acrylate (the alkyl group has 1 to 8 carbon atoms), lower alkyl methacrylate, maleic anhydride, and the like. Specific examples of ethylene-based resins include metal salts of engineered ethylene/vinyl acetate copolymers, ethylene/acrylic acid copolymers, ethylene/maleic anhydride copolymers, and ethylene/methacrylic acid copolymers (
(Na'', K+, Li+, zn++, Al''), ethylene/lower alkyl acrylate/maleic anhydride copolymer, etc. can be used, and these may be used alone or in combination of two or more.

In addition to these ethylene resins, so-called tackifiers such as rosin and its derivatives, terpenes and its derivatives, petroleum resins, and hydrogenated products thereof; paraffin wax, microcrystalline wax, carnauba wax, and Futscher Tropus are added as necessary. Waxes such as wax; inorganic fine powder anti-blocking agents such as silica, talc, and zeolite; organic slip agents such as erucic acid amide, oleic acid amide, and stearic acid amide; and ingredients that improve cohesive force and adhesive strength. As such, thermoplastic polyurethane, thermoplastic polyester, chlorinated polypropylene, chlorinated polyethylene, etc. may be blended.

In order to obtain a post-dispersed aqueous emulsion of these ethylene resins, JP-A-58-118843, JP-A-58-1206
As described in Publication No. 55, etc., ethylene resin is supplied to a twin-screw extruder, melt-kneaded, and a dispersant is added through a liquid introduction pipe provided in the compression region or vent region of the extruder. By introducing water and rotating the screw, the molten styrene-based resin and water are kneaded, and this kneaded material is phase-reversed from the W10 state to the 0/W state in the housing of the extruder, and the exit of the extruder It is obtained by discharging from a nozzle into a low pressure region, usually an atmospheric pressure region, and storing it in a storage tank.

The particle size of the ethylene resin particles in the emulsion is 0.01
~3 microns, with a solids concentration of 8-60% by weight, preferably 20-50% by weight.

As a method for applying the aqueous ethylene resin emulsion onto the film (B), any of a gravure coater, a reverse coater, a Meyer bar coater, an air knife coater, etc. can be used. The dry film thickness of the aqueous dispersion is 0.
．． It is 3-10μ, preferably 1-5μ. If it is less than 0.3μ, the heat sealing strength will be poor. Moreover, if it exceeds 10 μm, not only is the drying property inferior, but also no improvement in heat sealing strength is observed, making it uneconomical.

(Laminated sheet) To manufacture a laminated sheet, a laminated base material is manufactured in advance by extruding and laminating a molten olefin resin film on the surface of a base sheet, then an aqueous ethylene resin emulsion is applied, and the film is formed by drying. It is obtained by forming (C).

Further, after coating the surface of the base sheet (A) with a mixture of a polyether resin or a polyester resin base and a curing agent of an incyanate compound, it is dried, and then an olefin resin film (B) is applied to this surface. It can also be obtained by dry laminating, then applying an aqueous ethylene resin emulsion and drying.

Furthermore, when the low-temperature heat-sealable laminated sheet is required to have directional tearability, it is preferable to use a uniaxially oriented film as the olefin resin film.

This low-temperature heat-sealable laminated sheet can be used as a bag by heat-sealing the coated surfaces together.

Also, as a sealing lid, it is applied to the mouth of a hollow container, injection container, or glass container made of high-impact polystyrene, low-density polyethylene, high-density polyethylene, polypropylene, polyamide, polyethylene terephthalate, or polycarbonate, and is heat-sealed at 90 to 230°C. used.

Example-1 Aluminum foil (30μ) was coated with linear low-density polyethylene (specific gravity 0.925, MI 4y/1o min, melting point 123°C
) film (30μ) was laminated by a dry lamination method onto a base material, and an ethylene/vinyl acetate copolymer aqueous dispersion (raw fat: melting point 74°C, vinyl acetate 28% by weight, melt ratio 70 - 150 - 710 minutes) , solid content 50% by weight) was gravure coated to a film thickness of 5 μm after drying, and dried by heating at IZO° C. to form a film to obtain a low-temperature heat-sealable laminate sheet.

The coating surface of this laminated sheet was overlapped with a sheet of i-impact polystyrene (250μ) at 100°C for 1
Heat-sealed from the aluminum side under the conditions of 2#/-13 seconds at each temperature of 20℃ and 140℃, cut into strips with a width of 15fIa, and measured the beer strength at 180℃ with a chopper.The beer strength was 1 for each. ,000 t71
5m, 1,200 f/15 songs, 1. zsor/xs■
Met.

Comparative Example 1 In Example 1, an aqueous dispersion was applied directly to aluminum foil without a linear low-density polyethylene film layer, and a film was formed by drying. The strength is 150f/15m and 24
I caught a 230t/15 whale at 0f/15m.

Example 2 A low-temperature heat-sealable laminate sheet was obtained in the same manner as in Example 1, except that the thickness of the linear low-density polyethylene film layer was changed as shown in Table 1, and evaluated in the same manner. .

The results are shown in the same table.

Table-1 Example-3, Comparative Examples 2-3 Ethylene-acrylic acid copolymer (acrylic acid content 4% by weight, melt flow rate 6/10 minutes, melting point 108°C) film was placed on aluminum foil (20μ). Extrusion lamination was performed at 240° C. to a film thickness of 3 μm.

On the conoethylene/acrylic acid copolymer resin film layer, ethylene/acrylic acid resin (acrylic acid content: 8% by weight)
, melt 70-ratio 300f/10 minutes, melting point 102
°C) Aqueous dispersion (solid content: 45% by weight) was gravure coated to a film thickness of 2 μm after drying, and dried at 140°C to form a film to obtain a low-temperature heat-sealable laminate sheet.

This laminated sheet is heated to 200℃ and 230℃ with two glass plates.
After heat sealing at a pressure of 2&y/i and a time of 3 seconds, a 90 degree beer test was performed using a Schopper at a pulling speed of 2001, and the beer strength was 2,130 r.
/ 15+111. It showed a seal strength of 2,400 f/15 mm. In addition, when the aqueous dispersion is not applied (Comparative Example-2), the s1oy is 715m and 840t/
15 wa, and when the aqueous dispersion was applied directly to aluminum foil (Comparative Example-3), it was 1,230 wa/w.
15 ■, 1,470 p/l 5 seagulls.

Example-4, Comparative Examples 4-5 Low-density polyethylene (
Specific gravity 0.918, melt 70-ratio 49/10 minutes,
The aqueous dispersion of ethylene/acrylic acid copolymer used in Example-3 was applied to a base material laminated by extrusion lamination at 330°C to a thickness of 20μ (melting point 113℃) to a thickness of 4μ after drying. Gravure coat it so that it looks like this, 14
A film was formed by drying at a temperature of 0° C. to obtain a low-temperature heat-sealable laminate sheet. This laminated sheet was combined with a 100μ polyester film at 120°C, 150°C, and 180°C.
When heat-sealed from the polyester film side at 2 H/d for 2 seconds at various temperatures and evaluated in the same manner as in Example-1, the beer strength was 750? 715m,
It was 920 f/15 ugly, 1.0305'/15m. In addition, when no aqueous dispersion is applied, it is 5.
0? 715 mm (Comparative Example-4) When the aqueous dispersion was applied directly to white cardboard, it was 23 mm.
0f/15kaku, 2705'/15m5, 310f/15
輯(Comparative Example-5).

Examples 5 to 6, Comparative Example 6 A uniaxially stretched ethylene-acrylic acid copolymer film (acrylic acid content: 4% by weight, Melting point 108℃, film thickness 20μ
) was obtained. The ethylene-acrylic acid copolymer film layer of this base material is subjected to corona treatment, and coated with the aqueous ethylene-acrylic acid copolymer dispersion shown in Table 2 using a Mayer bar so that the thickness of the dry layer is 1μ. 13
It was dried at 0°C to obtain a low temperature heat sealable laminated base material. The aqueous dispersion-coated surfaces of this base material are overlapped, and 10
2ky/crI at temperatures of 5°C, 115°C, and 125°C,
Heat sealing was performed from the polyester side for 0.5 seconds, and evaluation was made in the same manner as in Example-1. The results are shown in Table-2.

(Margin below)

Claims (1)

[Claims] 1) The surface of the base sheet (A) selected from aluminum foil, aluminum vapor-deposited film, or paper has a melting point of 1.
An olefin resin film (B) having a temperature of 45° C. or lower is laminated, and an aqueous emulsion of ethylene resin particles having a melting point lower than the melting point of the olefin resin by at least 5° C. is formed on the surface of the resin film (B). A low-temperature heat-sealable laminated sheet on which a film (C) is formed. 2) The laminated sheet according to claim 1, wherein the film (B) has a thickness of 2 to 50 microns, and the coating (C) has a wall thickness of 0.3 to 10 microns. 3) The laminate sheet according to claim 1, wherein the olefin resin film (B) is uniaxially oriented.