JPS61154846A - Sealant film and manufacture thereof - 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 [Field of Industrial Application] The present invention relates to a film used as an adhesive layer when, for example, the opening of a container is heat-sealed with a lid, and a method for manufacturing the same.

[Prior art and its problems]

As mentioned above, a heat-bonded lid is required to have excellent sealing performance, but in general, completely fused lids have good sealing performance, but the lid cannot be peeled off by hand when opening. figure,
The package had been opened by cutting it open with a knife.

Therefore, various adhesives (sealants) have been devised that have excellent sealing properties and also have good removability. One of these is a mixed resin of polyethylene and polypropylene. By appropriately controlling the mixing ratio, this mixed resin has excellent sealing properties for polypropylene containers or polyethylene containers, can be easily opened, and has the property of being resistant to retort sterilization. but,
On the other hand, due to the characteristics of low elongation and low tensile strength,
Since it is very easy to cut and tear, it is difficult to form it into a film, and the selection and blending ratio of resins are limited to a narrow range.

Therefore, it is currently almost impossible to provide sealant films with various sealing strengths and to control the thickness of the sealant film to the fullest.

Additionally, current sealant films often have defects such as pinholes and tears.

Furthermore, there is a problem that sealant films made of mixed resins are expensive.

[Purpose of the invention]

Therefore, this invention has no defects such as pinholes, and
It is an object of the present invention to provide a sealant film that allows the mixing ratio etc. to be selected over a wide range and is low in cost, and a method for manufacturing the same.

[Structure of the invention]

In order to achieve the above object, in this invention, an adhesive layer with a thickness of 3 to 15 μm made of a mixed resin of polyethylene and polypropylene is laminated on a 10 to 10 μm thick flavor-retaining layer made of polyethylene or polypropylene. It was made into a sealant film. In addition, to manufacture this sealant film, a laminated cylindrical body is obtained by coextrusion using an inflation method (in-die lamination method) with an adhesive layer made of a mixed resin on the inside and a support layer on the outside. After flattening, the edges on both sides are removed.

[For production]

The adhesive layer of the sealant film itself has a small elongation at break and is easily torn, but by laminating it on a support layer, it becomes possible to form an extremely thin adhesive layer.

In addition, in the manufacturing method, by coextruding with the adhesive layer inside, the influence of outside air can be eliminated and controlled air can be blown up, thereby avoiding rapid cooling of the adhesive layer.

Further, by co-pressing using an in-die lamination method, it is possible to completely prevent the adhesive layer from breaking, and a two-layer blown film with good adhesion can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the sealant fill film 1 is
An adhesive layer 2 is laminated on a support layer 3.

The adhesive layer 2 is made of a mixed resin of polyethylene and polypropylene, and has a thickness of about 3 to 15 μm.

In general, it is preferable to make it as thin as possible, but if it is less than 3 μm, it is very difficult to form a film, and as an adhesive, it is difficult to form a film.
A thickness of μ or more is hardly required.

Note that the mixing ratio of polyethylene and polypropylene may be appropriately selected depending on the mating resin to be bonded, adhesive strength, etc. Further, its apparent density is 0.5 to 0, sg/ys, preferably 0.6 to 0.75 g/cA.

The support layer 3 is made of high-density polyethylene, linear low-density polyethylene, low-strength polyethylene, or polypropylene, and has a thickness of about 10 to 50 microns. If it is less than 10μ, there will be a problem with the ability to support the adhesive layer, and if it is less than 50μ
The above is neither necessary nor economical.

In order to improve the adhesion when the sealant film 1 as described above is bonded to other base materials, surface treatment such as corona treatment can be applied to the outer surface (lower surface in FIG. 1) of the support layer 3. .

FIG. 2 shows a container lid material in which a base material 5 and a sealant film 6 are bonded together with an adhesive 4 interposed therebetween.

As the base material 5, a single substance such as a synthetic resin film, cellophane, aluminum foil, paper, or a composite material thereof may be used. It may be printed on its outer or inner surface.

Further, as the adhesive 4, polyurethane, polyethylene, etc. are used.

Next, a method for manufacturing the sealant film 1 will be described.

mass, inflation method (inner die method),
Coextrusion is carried out with the adhesive layer 2 on the inside and the support layer 3 on the outside. The reason why the adhesive layer 2 is placed on the inside is to prevent this mixed resin, which has poor film-forming properties, from being directly exposed to indoor air discharged from a blower.

This is because the indoor cloud atmosphere changes significantly, and the extremely thin mixed resin may break or change due to rapid cooling. On the other hand, blowing up air with the mixed resin inside can eliminate the influence of outside air (at the same time, the temperature of the air for ink can be easily controlled, so it can be slowly cooled). , breakage, etc. can be prevented.

Since the film coextruded as described above is in the form of a cylinder, it is flattened with a roll as shown in FIG. In the figure, 6 is a flat cylindrical body,
A support layer 3 surrounds the outer surface. Here, if a corona treatment is performed as necessary, the adhesiveness of the support layer 3 will be improved when the sealant film 1 is later bonded to another base material. Therefore, there is also meaning here of coextruding with the support layer 3 on the outside.

By cutting off the outer edge of the flattened cylindrical body 6 as described above, a two-ply sealant film 1 with the adhesive layer 2 on the inside is obtained.

〔effect〕

The sealant film of the present invention has an adhesive layer made of a mixed resin that is easily broken and supported by another synthetic resin layer, so the adhesive layer can be made extremely thin and has no pinholes. Moreover, it is inexpensive because only a small amount of expensive mixed resin is required, and the flexibility of the support layer can be utilized, so that the reliability and stability of adhesion can be improved.

Next, in the manufacturing method, the adhesive layer is co-extruded with the support layer on the inside, so it can be easily formed without breaking the adhesive layer, and the thickness of the adhesive layer can be freely selected. The selection of resins to be mixed and their blending ratio can also be selected within a wide range.

In addition, the support layer provides a sealant film with good elongation and strength, which makes subsequent processing very easy, and many other effects can be seen.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a sealant film, FIG. 2 is a sectional view of a container lid, and FIG. 3 is a cutaway side view of a flattened cylindrical body obtained by coextrusion. In the figure, 1 is a sealant film, 2 is an adhesive layer, 3 is a support layer, and 6 is a cylindrical body.

Claims (2)

[Claims] (1) A sealant film in which a 3-15 μm thick adhesive layer made of a mixed resin of polyethylene and polypropylene and a 10-50 μm thick support layer made of polyethylene or polypropylene are laminated. (2) Co-extrusion is carried out using an in-die lamination method with a mixed resin of polyethylene and polypropylene on the inside and polyethylene or polypropylene on the outside, and after the obtained cylindrical body is made flat, both sides of the body are cut off, A method for producing a sealant film in which an adhesive layer made of the above mixed resin and a support layer made of polyethylene or polypropylene are laminated.