JP2568583B2 - Manufacturing method of low temperature heat sealable laminated sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The low-temperature heat-sealing laminated sheet obtained by the production method of the present invention is a resin or glass hollow such as a lactic acid bacterium beverage container, a fruit jelly container, a mayonnaise container, and a ketchup container. It is useful as a seal lid for closing the discharge port of containers and coffee containers, as a label for shampoo containers and motor oil containers, as a book cover, and as a material for forming milk boxes.

(Prior art)

Conventionally, as such a sealing lid, a laminated layer provided with a low-density iriethylene (melting point of 118 to 123 ° C.) film layer or an ethylene / vinyl acetate (5 to 22% by weight) copolymer film layer laminated on an aluminum foil by melt extrusion. Using a sheet, apply it to the discharge port (bottle opening) of a polypropylene, high-impact polystyrene, or glass container.
The film is melted at a heat sealing temperature of 0 to 230 ° C. to seal the sealing lid to the bottle mouth.

However, removing the seal lid from the bottle mouth by hand requires a fairly strong pulling force. To lower the heat seal strength, the heat seal temperature may be lowered, but there is no guarantee that the heat seal is sufficiently performed.

On the other hand, there is also known a laminated sheet that can be subjected to low-temperature heat sealing (100 to 120 ° C.) in which an aqueous emulsion of an ethylene / vinyl acetate copolymer is applied to the surface of an aluminum foil and dried to form a film (Japanese Patent Application Laid-Open (JP-A) No. 2002-110630). No. 56-101845).

Although this laminated sheet is used for easy peelable bags, it is not used as a seal lid for the bottle mouth because of its low sealing strength. There is a correlation between the film thickness of the film and the heat seal strength that the heat seal strength linearly increases with an increase in the film thickness. However, since the drying property of the emulsion and the cost of the emulsion are high, the film thickness of the film is limited to at most 10 microns.

Therefore, the appearance of a balanced laminated sheet that can be easily peeled and has a sufficient sealing strength is desired.

The appearance of such a laminated sheet is also desirable as a paper box forming material such as a milk container for milk.

[Specific means to solve the problem]

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

That is, the present invention relates to a base material obtained by laminating and integrating a base material sheet (A) selected from an aluminum foil, an aluminum vapor-deposited film and paper and an olefin-based resin film (B) having a melting point of 145 ° C. or less. On the resin film (B) surface,
A method for producing a low-temperature heat-sealable laminated sheet, comprising applying an aqueous emulsion of ethylene-based resin particles having a melting point lower by at least 5 ° C. than the melting point of the olefin-based resin to form a film (C). Is what you do.

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

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

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

(Olefin-based resin film) Raw resin of the olefin-based resin film (B) to be bonded and laminated on the base sheet (A) includes low-density polyethylene, linear low-density polyethylene, ethylene-methacrylic acid copolymer and its metal. Salt (K, Na, Zn, Al, etc.), ethylene / vinyl acetate (2-22% by weight) copolymer, ethylene (1.5-6% by weight) / propylene random copolymer, ethylene / maleic anhydride random copolymer Coalescence, propylene (85-95%), ethylene (0.5-6%), butene-1
(2 to 8%) copolymer or the like is used.

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

This film (B) has the effect of improving the low-temperature heat sealing strength of the film (C) obtained from the emulsion. The thickness of the film (B) is preferably 2 to 50 microns. The surface of the film (B) may be subjected to corona discharge treatment, plasma treatment, or primer treatment.

(Coating) As an aqueous emulsion of ethylene-based resin particles giving 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), a melt flow rate is 20 g / 10 min or more. An aqueous emulsion of a copolymer of ethylene and a comonomer having a comonomer content of 5 to 50% by weight is used.

Examples of the comonomer include vinyl acetate, methacrylic acid, acrylic acid, lower alkyl acrylate (having 1 to 8 carbon atoms in the alkyl group), lower alkyl methacrylate, and maleic anhydride. Specific examples of the ethylene-based resin include ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymer, and metal salts of ethylene-methacrylic acid copolymer (Na ⁺ , K ⁺ , Li ⁺ , Zn ⁺⁺ , Al ⁺⁺⁺ ), ethylene / lower alkyl ester of acrylic acid / maleic anhydride copolymer, etc., which can be used simply or in combination of two or more.

If necessary, so-called tackifiers such as rosin and derivatives thereof, terpenes and derivatives thereof, petroleum resins and hydrogenated products thereof; paraffin wax, microcrystalline wax, carnava wax, Waxes such as Itsuyatropuswaxu;
Inorganic fine powder antiblocking agents such as silica, talc and zeolite; erucamide, oleamide,
Organic slip agents such as stearic acid amide, etc., further, as a component to improve cohesion, adhesion, thermoplastic polyurethane, thermoplastic polyester, chlorinated polypropylene,
Chlorinated polyethylene or the like may be blended.

In order to obtain a post-dispersion aqueous emulsion of these ethylene resins, an ethylene resin is supplied to a twin-screw extruder as described in JP-A-58-118843, JP-A-58-120655, etc., and melt-kneading is performed. Then, water containing a dispersant is introduced from a liquid introduction pipe provided in a compression section area or a vent area of the extruder,
The molten ethylene resin and water are kneaded by rotating the screw, and the kneaded material is placed in the housing of the extruder.
It is obtained by inverting the phase from the W / O state to the O / W state, releasing the phase from the exit nozzle of the extruder to 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 from 0.01 to
3 microns, solids concentration 8-60% by weight, preferably 20
~ 50% by weight.

As a method for applying the aqueous emulsion of the ethylene resin on the film (B), any of a gravure coater, a reverse coater, a Meyer bar coater, an air knife coater and the like can be used. The film thickness of the dried film of the aqueous dispersion is
It is 0.3-10 μm, preferably 1-5 μm. If it is less than 0.3 μm, the heat sealing strength will be poor. On the other hand, if it is 10 μm or more, not only is the drying property inferior, but also no improvement in heat seal strength is observed, which is uneconomical.

(Laminated sheet) In order to produce a laminated sheet, a laminated substrate is prepared by extruding and laminating a molten olefin-based resin film on the surface of the substrate sheet (A), and then applying an aqueous ethylene-based resin emulsion and drying. To form a film (C).

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

Further, when a directional tear property is required for the low-temperature heat-sealing laminated sheet, a uniaxially oriented film may be used as the olefin-based resin film.

This low-temperature heat-sealable laminated sheet can be used as a bag as a heat seal between film surfaces.

In addition, high impact polystyrene, low-density polyethylene, high-density polyethylene, polypropylene, polyamide, polyethylene terephthalate, a hollow container made of polycarbonate, an injection container, a glass container as a sealing lid, and heat sealed at 90 to 230 ° C. Used.

Example 1 A film (30 μm) of linear low-density polyethylene (specific gravity 0.925, MI 4 g / 10 min, melting point 123 ° C.) was placed on an aluminum foil (30 μm).
μ) on a substrate laminated with a dry lamination method, an aqueous dispersion of ethylene / vinyl acetate copolymer (resin resin; melting point
74 ℃, vinyl acetate 28% by weight, melt flow rate 150g
/ 10 minutes, solid content 50% by weight. ) Was gravure coated to a film thickness of 5 μm after drying, and dried by heating at 120 ° C. to form a film, thereby obtaining a low-temperature heat-sealing laminated sheet.

The film surface of this laminated sheet is superimposed on a high impact polystyrene sheet (250μ), and
Heat sealed from the aluminum side under the conditions of ² kg / cm ² and 3 seconds at each temperature of 40 ° C, cut out into strips of 15 mm width, and determined the 180 degree peel strength with a shopper. The peel strength was 1,000 g / each. 15mm, 1,200g / 15mm, 1,260g / 15mm
It was.

Comparative Example-1 An aqueous dispersion was directly applied to an aluminum foil without providing a linear low-density polyethylene film layer in Example 1, and dried to form a film. Strength is 150g / 15mm, 240g / 15m respectively
m, 230g / 15mm.

Example 2 A low-temperature heat-sealable laminated 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 similarly. .

 The results are shown in the same table.

Example-3, Comparative Examples 2-3 An ethylene / acrylic acid copolymer (acrylic acid content: 4% by weight, melt flow rate: 6 g / 10 minutes, melting point: 108 ° C) film was placed on an aluminum foil (20μ) at 240 ° C. Extrusion lamination was performed to a film thickness of 30 μm.

On this ethylene / acrylic acid copolymer resin film layer, an ethylene / acrylic acid resin (acrylic acid content: 8% by weight, melt flow rate: 300 g / 10 minutes, melting point: 102 ° C.) aqueous dispersion (solid content: 45% by weight) Was subjected to gravure coating so that the film thickness after drying became 2 μm, and dried at 140 ° C. to form a film, thereby obtaining a low-temperature heat-sealing laminated sheet. This laminated sheet is 2mm glass plate and 200kg, 230 ℃, pressure 2kg
/ cm ² , heat sealing at a time of 3 seconds, and a 90 ° peel test was measured with a shopper at a pulling speed of 200 mm. As a result, the peel strengths were 2,130 g / 15 mm and 2,400 g / 15 mm, respectively. In the case where the aqueous dispersion was not applied (Comparative Example-2), the values were 810 g / 15 mm and 840 g / 15 mm,
When the aqueous dispersion was directly applied to the aluminum foil (Comparative Example-3), it was 1,230 g / 15 mm and 1,470 g / 15 mm.

Example-4, Comparative Examples 4-5 Low density polyethylene (specific gravity 0.918, melt flow rate 4 g / 10 min, melting point 113) on white cardboard (250 μm thick)
℃) to a thickness of 20μ on a substrate laminated by extrusion lamination at 330 ℃, the ethylene
The acrylic acid copolymer aqueous dispersion was gravure-coated so as to have a thickness of 4 μm after drying, and dried at a temperature of 140 ° C. to form a film, thereby obtaining a low-temperature heat-sealing laminated sheet. This laminated sheet was heat-sealed with a polyester film of 100 μm and at a temperature of 120 ° C., 150 ° C. and 180 ° C. from the polyester film side at 2 kg / cm ² for 2 seconds, and evaluated in the same manner as in Example-1. The peel strength was 750 g / 15 mm, 920 g / 15 mm, and 1,030 g / 15 mm, respectively. In addition, when applying the aqueous dispersion, it is 50g / 15mm
(Comparative Example-4) When the aqueous dispersion was directly applied to white cardboard, the results were 230 g / 15 mm, 270 g / 15 mm, and 310 g.
/ 15 mm (Comparative Example-5).

Examples -5 to 6, Comparative Example -6 A uniaxially stretched ethylene-acrylic acid copolymer film (acrylic acid content of 4% by weight) was dry-laminated on an aluminum-deposited biaxially stretched polyester film (thickness: 12 µ). A substrate having a melting point of 108 ° C. and a film thickness of 20 μ) was obtained. Corona treatment is applied to the ethylene-acrylic acid copolymer film layer of the base material, and the ethylene-acrylic acid copolymer aqueous dispersion shown in Table 2 is coated with a Mayer bar so that the film thickness after drying becomes 1 μm. Then, the resultant was dried at 130 ° C. to obtain a low-temperature heat-sealing laminated base material. The aqueous dispersion liquid application surfaces of the base material are superposed on each other, and 105 ° C, 115
It heat-sealed from the polyester side under the conditions of ² kg / cm ² and 0.5 seconds at a temperature of 125 ° C. and 125 ° C., and evaluated in the same manner as in Example-1. Table 2 shows the results.

Claims (3)

(57) [Claims] 1. A substrate sheet (A) selected from aluminum foil, aluminum vapor-deposited film and paper, having a melting point of 14
Ethylene-based resin particles having a melting point lower by at least 5 ° C. than the melting point of the olefin-based resin on the resin film (B) surface of the substrate obtained by laminating and integrating the olefin-based resin film (B) having a temperature of 5 ° C. or lower. A method for producing a low-temperature heat-sealable laminated sheet, comprising applying a water-based emulsion of (1) to form a film (C). 2. The film (B) has a thickness of 2 to 50 microns.
The method for producing a laminated sheet according to claim 1, wherein the thickness of the film (C) is 0.3 to 10 microns. 3. The method for producing a laminated sheet according to claim 1, wherein the olefin resin film (B) is uniaxially oriented.