JPH111270A - Cover material for heat sealing - Google Patents

Abstract

(57) [Problem] To provide a cover material including paper applied to a container having a polyolefin-based resin formed on the inner surface, a wide range of heat sealing conditions, stable peel strength, and no peeling even when stored at high temperatures. An object is to provide a heat-sealing lid material having heat resistance. SOLUTION: A base film 1 containing at least paper,
In the heat-sealing lid member 10 made of a heat-sealing film, the heat-sealing film is composed of a “carrier layer 6” and a “heat-sealing layer 7 made of a mixture of a polystyrene resin and a polyethylene resin”. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION At least in a paper container or a lid material for a plastic molded container whose inner surface is made of a polyethylene resin, the heat sealant layer of the lid material has excellent sealing properties even at high temperatures. But not
It belongs to a heat-sealing lid material that can be easily peeled off without peeling the paper at the flange portion of the paper container at the time of opening.

[0002]

2. Description of the Related Art Conventionally, paper cup containers having a polyolefin resin on the inner surface thereof are used for dessert foods such as yogurt, pudding and jelly, liquid drinks such as fruit juice, coffee, cocoa, milk drinks, instant noodles and snack foods. Widely used as packaging containers. Many lids for sealing these containers are heat-sealed from the viewpoints of confidentiality of the containers, storability of contents, and hygiene. The heat sealing portion is required to be easily opened from the convenience of opening and use.

[0003] Therefore, as an important function of the lid material, the adhesive strength (peeling strength) when the lid material is heat-sealed with the flange of the container body and opened at the time of use is not peeled at the distribution stage, and is not peeled at the time of opening. A well-balanced material that can be easily peeled is required. Then, there is a demand for a material which does not impair the appearance of the peeled portion such as the heat sealant layer remaining when the package is opened and the peeling of the flange portion (particularly, the paper container) of the container.

[0004] These lids are composed of at least paper and a heat sealant layer mainly composed of hot melt.
Aluminum foil, plastic film,
A functional film such as a barrier material coated film has been laminated on either or both sides of the paper. And between each layer, it was laminated | stacked by sandwich lamination using a thermoplastic resin, or dry or wet lamination.

[0005]

The wax-modified hot-melt heat sealant layer used in the conventional lid material can fill the gap of the joint portion of the paper container and can be sealed, and has a stable peel strength. It has something. However, there is a problem in that the container filled with the content and sealed is melted and peeled off at room temperature or at a high temperature during distribution, which lacks heat resistance. In addition, the heat sealant layer obtained by denaturing a thermoplastic resin mainly composed of polyethylene has excellent heat resistance, but the width of the temperature and pressure heat sealing conditions is restricted in order to obtain an appropriate peel strength. For example, when the lid material is heat-sealed by applying high temperature and high pressure, the paper of the lid material or the paper of the flange of the container is destroyed when the lid material is opened, and "paper peeling" is caused, or the lid material is formed. And peeling off only the paper leaving the film (other layer) in the opening of the container. Conversely, when the temperature and pressure are insufficient, the adhesive strength between the container and the lid material is insufficient, and the container may be peeled off during the distribution process, and it is difficult to set and maintain appropriate heat sealing conditions. there were.

According to the present invention, there is provided a lid material including the above paper,
An object of the present invention is to provide a heat-sealing lid material having a wide range of heat sealing conditions, moderately stable peel strength, and heat resistance that does not peel even when stored at a high temperature.

[0007]

In order to solve the above-mentioned problems, a cover material of the present invention comprises a base film containing at least paper and a heat-sealable film (hereinafter referred to as HS film). In the laminate, the HS film is a heat-sealing lid made of a “carrier layer” and a “heat-sealing layer made of a mixture of a polyethylene resin and a polystyrene resin”. The heat sealing lid has a thickness of the carrier layer in the HS film of 10 to 65 μm and a thickness of the heat sealing layer of 3 to 20 μm.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A heat sealing lid 1 according to the present invention shown in FIG.
0 denotes a laminate 10 comprising at least a base film 1 containing paper and an HS film 5, wherein the HS film is made of a “carrier layer 6” and a heat seal made of a mixture of a polyethylene resin and a polystyrene resin. Layer 7 ". And the HS
The thickness of the carrier layer 6 occupying the film 5 is 10 to 65 μm
m, and the thickness of the heat seal layer 7 is 3 to 20 μm.
The heat sealing lid member 10 is as follows.

The base film defines the surface shape and physical properties of the lid material, and is formed by laminating paper or another functional film as shown in FIG. The paper that constitutes the base film 1 is art paper, coated paper, matte kraft paper, imitation paper, woodfree paper, kraft paper, tissue paper,
From parchment paper, glassine paper, etc., basis weight 15-200 g / m ²
Is selected depending on the application and processing method. And
Preferably, it can be supplied in a wound shape suitable for a laminating step with a functional film or an HS film.

[0010] The functional film has a barrier property against water vapor, oxygen gas, light and the like required for the packaging material, and at the same time, tears when the lid material is peeled off.
It has the strength to prevent the occurrence of pinholes due to the contents and projections from the outside. Also, when a design effect with a glossy surface is required, the back side is printed using a functional film with excellent printability, and a lid with a glossy film as the outermost layer by laminating the printing surface and paper. Materials can also be configured.

The functional film is a stretched or unstretched film made of polyethylene, polypropylene, polystyrene, polycarbonate, saponified ethylene / vinyl acetate copolymer, acrylic resin, polyamide, polyester, polyvinyl chloride, cellulose acetate, or
These films are coated with polyvinylidene chloride, polyvinyl alcohol, etc., or silicon oxide (Si
O _x ), ZrO ₂ , ITO, and metal aluminum include a film provided with a barrier layer by vapor deposition or sputtering. And these films are not only single-layer
A three-layer structure may be used.

[0012] Lamination of paper and a functional film can be performed by "dry lamination" using a curable adhesive or a pressure-sensitive adhesive, "wet lamination" using an adhesive of an aqueous medium such as emulsion, starch or casein, or "thermal lamination". And a conventional method such as sandwich lamination of forming an adhesive resin layer by melt extrusion of a "plastic resin".

When the heat-sealing lid material of the present invention is fed to a filling machine as a single sheet, in order to prevent curling, paper which expands and contracts by absorbing and desorbing moisture may be sandwiched with a non-hygroscopic film or a moisture-proof material may be applied to the paper surface. It is preferable to apply a material that prevents expansion and contraction due to moisture absorption of paper. In addition, a base film having a symmetrical top and bottom centered on paper may be used.

The HS film of the present invention comprises a heat seal layer made of a blend of a polyethylene resin and a polystyrene resin, and a carrier layer laminated with the heat seal layer. The heat-sealing layer is a layer that is directly heat-sealed with the container, and the carrier layer is formed by laminating the heat-sealing film so that the film-forming process can be stably performed while the heat-sealing layer is formed of a thin film. is there. Then, polyethylene having stable film forming properties is used.

Examples of the polystyrene resin constituting the heat seal layer include a block copolymer of styrene and butadiene, a hydrogenated product of a block copolymer of styrene and butadiene, high-impact polystyrene, general-purpose polystyrene, or a mixture of these. A mixture of more than one type.

The polystyrene resin contained in the HS film is preferably from 10 to 80% by weight, and if it is less than 10% by weight, the heat sealing strength is so strong that it is hard to peel off. May drop.
On the other hand, if the polystyrene resin is 80% by weight or more, the peel strength is weak and the sealing property cannot be maintained, and the resin may be opened at the time of distribution. The polystyrene resin contained in the heat seal layer of the present invention has an action of uniformly causing cohesive failure in the heat seal layer when the mixture is peeled off after heat sealing, and the peel strength due to the strength of the heat sealing conditions. This has the effect of reducing the difference.

The polyethylene constituting the heat seal layer by blending with the polystyrene resin has a density of 0.9.
0.5-0.940 g / cm ³ of polyethylene, or ethylene / α-olefin copolymer, ethylene / vinyl acetate copolymer, ethylene / acrylic acid copolymer, ethylene / acrylic acid ester copolymer, ionomer, etc. In order to adjust the peel strength depending on the material of the container, the type and the mixing ratio are appropriately selected and used.

The HS film is prepared by co-extrusion of a polystyrene-based resin and a resin to be a carrier layer on a base film through a primer layer, if necessary, by melt coating, or by a multi-layer co-extrusion film forming method in a separate process. What did
Dry lamination or low-density polyethylene can be provided as an adhesive resin layer by sandwich lamination.

The thickness of the heat seal layer constituting the HS film is preferably 3 to 20 μm, and if it is 3 μm or less, the peel strength from the container may be partially high, and the flange may be peeled off. On the other hand, when the thickness of the heat seal layer exceeds 20 μm, the absolute amount of the heat seal layer which has been coagulated and separated and remains in the container increases, which impairs the appearance of the separated portion. Accordingly, the thickness of the corresponding carrier layer is set within a range in which a film can be formed by co-extrusion.
It is preferable that the total thickness of the S film is 10 μm to 70 μm from the viewpoint of the film forming process. When the total thickness of the HS film is 10 μm or less, it is impossible to perform the film forming process using the current technology. When the total thickness is 70 μm or more, resources are wasted and the heating time in the heat sealing process is prolonged.

When the base film is processed by coextrusion coating, the total thickness of the HS film is 15 to 30 μm.
It is. When performing coextrusion coating, it is preferable to provide an isocyanate compound as a primer layer or perform corona discharge treatment or the like depending on the type of the coated surface of the base film. Also,
The total thickness when the HS film is formed by a circular die or T-die method in another step is preferably set to 25 to 60 μm from the viewpoint of the step. The lamination with the base film is processed by ordinary dry lamination using a polyester-isocyanate-based resin or polyether-isocyanate-based resin as an adhesive, or sandwich lamination using polyethylene as an adhesive resin layer.

Hereinafter, the present invention will be described in detail with reference to examples.

FIG. 2 shows a structure as shown in FIG.
/ M ² coated paper (trade name, manufactured by Cormorant Fuji Processing Co., Ltd.) 2 and aluminum foil 9 μm (functional film 4) were laminated by sandwich lamination using polyethylene (adhesive resin layer 3). On the other hand, when the thickness is 20
An HS film 5 having a total thickness of 30 μm, comprising a carrier layer 6 made of low-density polyethylene having a thickness of 10 μm and a heat seal layer 7 having a composition shown in Table 1 and having a thickness of 10 μm, was prepared by coextrusion. Then, the aluminum foil of the carrier film 1 and the carrier layer 6 of the HS film are
Lamination was performed by sandwich lamination using polyethylene (adhesive resin layer 3) having a thickness of 20 μm to form lids 10 for heat sealing of Examples 1 to 4.

[0022]

[Comparative example]

(Comparative Examples 1 and 2) The heat-sealing lids of Comparative Examples 1 and 2 were prepared in the same manner as in Example except that the composition of the polystyrene resin and the polyethylene of the heat seal layer of the HS film shown in Table 1 was changed. Configured.

(Comparative Example 3) As shown in Table 1, in place of the HS film, the base film 1 was replaced with a hot-melt heat sealant H-425 (manufactured by Toyo Petrolite Co., Ltd.).
(Trade name) at a coating amount of 25 g / m ² to form a lid for heat sealing of Comparative Example 3 provided by gravure hot melt coating.

The following items were evaluated for the heat-sealing lid materials prepared in Examples and Comparative Examples. Table 1 shows the results. Peel strength: The ring sealer was used to bond the heat-sealing layer of the heat-sealing lid material and the polyethylene of the flange of a 200-ml paper cup prepared from a low-density polyethylene base paper (basis weight 250 g / m ² ) provided with 20 μm. At 140 ° C., 1 kg / cm ² for 1 second. After 24 hours heat sealing, JISZ1707
The film was peeled at a width of 15 mm and peeled at 180 ° to measure the peel strength. Peeling appearance: The peeling state of the sample whose peel strength was measured at the flange portion of the paper cup was evaluated according to the following criteria. ：: No peeling of paper, and cohesive peeling of the heat seal layer. Δ: The polyethylene on the side of the cup base paper was cut, and the paper was partially peeled off. X: The peel strength is strong, and the paper is peeled as a whole. Alternatively, the peel strength is too small to be practical. Heat resistance test: The paper cups heat-sealed with the lids of Examples and Comparative Examples were left at 50 ° C. for 1 week, and the sealing condition of the lids was evaluated according to the following criteria. ：: The sealed state of the lid is maintained. ×: The lid material peels off. (Below)

[0025]

[Table 1] HS layer: Heat seal layer HIPS: High impact polystyrene SBR: Block copolymer of styrene and butadiene LDPE: Low density polyethylene LLDPE: Linear polyethylene

[0026]

As described above, the heat sealant layer of the lid material for heat sealing of the present invention comprises a heat seal layer which undergoes cohesive peeling as described above and a carrier layer which has the necessary strength when forming the film. It is composed of the constituted HS film. Heat seal layer containing polystyrene resin, the peel strength of the heat seal portion is stable,
It has an easy-opening strength that can withstand the conventionally used hot melt, and can be peeled off without causing paper peeling at the flange portion of the paper cup. Further, even if the paper cup heat-sealed with the lid material of the present invention is left under a high temperature,
An effect of maintaining a sealed state without causing peeling as seen in a lid material for heat sealing using a conventional hot melt is exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a heat-sealing lid material of the present invention.

FIG. 2 is a schematic cross-sectional view of a heat sealing lid material according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base film 2 Paper 3 Adhesive resin layer 4 Functional film 5 HS film 6 Carrier layer 7 Heat seal layer 10 Heat sealing lid material

Claims (2)

[Claims] 1. A laminate comprising a base film containing at least paper and a heat-sealing film, wherein the heat-sealing film is a heat-sealing layer comprising a carrier layer and a mixture of a polyethylene resin and a polystyrene resin. A lid material for heat sealing, comprising: 2. The heat-sealing film according to claim 1, wherein the thickness of the carrier layer occupies 10 to 65 μm.
And a heat sealing layer having a thickness of 3 to 20 [mu] m.