JPH0193330A - Application of heat seal material - Google Patents

Abstract

PURPOSE:To form a continuous heat seal material layer having a given thickness at the part of a vessel or a lid which is to be applied with heat seal without generating any film scrap by converting a tubular peripheral surface into a horizontal peripheral surface utilizing the heat shrinkable property of a heat sealing resin film. CONSTITUTION:A heat shrinkable film 4 is manufactured by employing a low- density polyethylene, for example. A cup type deep draw vessel 7, consisting of a tinplate and formed with a flange for heat seal, is prepared. The vessel 7 is put on a supporting table 9 and a tubular film 4 is fixed so that the tip end 5 of the same is projected while the projected part 5 is heated by hot air to shrink it. In this case four sheets of jigs 11 made of nylon, are employed to fix the film and a circumferential heat seal layer 6 is formed without affecting the parts of the film except the projected part 5. Then, the circumferential heat seal layer 6 is fixed to the flange 8 of the vessel 7 by high-frequency induction heating method and, finally, the vessel 7 is cut and separated from the tubular film 4 by employing a heating wire.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of applying a layer of heat sealing material around the circumference of a container or lid to be heat sealed, and more particularly to a method of applying a layer of heat sealing material around the circumference of a container or lid to be heat sealed. This invention relates to a method of applying a resin film around a container or lid without wasting material.

(Prior art) Sealing techniques using heat sealing are widely used to seal various containers, such as plastic containers, plastic-metal foil composite containers, metal cans, and glass bottles. It is possible to use a lid with a layer of sealant, use a container with a layer of heat sealant on the entire inner surface, or use a container with a heat sealant coated around the area to be heat sealed. It is being said.

Olefin resins such as polyethylene and polypropylene are excellent heat-sealing materials, but in order to apply this resin only to the parts of the container or lid that need to be heat-sealed, it is necessary to apply the resin in the form of a powder or dispersion. Alternatively, the resin film is punched into a shape corresponding to the heat-sealed part, for example, a ring shape,
It is necessary to apply this to the area to be heat sealed.

(Problems to be Solved by the Invention) However, in the method of applying the heat sealing material in the form of powder or dispersion, the thickness of the heat sealing material layer is relatively thin, ranging from several μm to 10 μm. When foreign matter or the like adheres to the surface of the layer, it is often difficult to form a seal structure with reliable sealing. Further, the heat sealing material layer obtained by this method has a large variation in thickness, and furthermore, coating defects such as pinholes are likely to occur in the heat sealing material layer.

On the other hand, the method of applying by punching a film eliminates the drawbacks of the powder or dispersion coating method, but
The film after punching out the circumferential heat sealing material layer becomes scrap, and the flexible heat sealing material layer must be applied to the container or lid in an accurately positioned state. I am still unsatisfied with this because it is cumbersome to operate.

By the way, applying heat sealing material only to the parts of the container or lid that need to be heat sealed is necessary in the case of inner-coated metal containers or glass containers, and it is necessary to apply heat sealing material only to the parts of the container or lid that should be heat sealed. In a container sealed by
The opening starting part, if not the inner hook, of the sealing part has a laminated structure with the plurality of container materials and an intermediate material inserted therebetween, and the intermediate material and one of the plurality of container materials are in a tight seal, and The intermediate material and the other of the plurality of container materials are easy-to-open seals, and the inner edge of the easy-to-open seal portion is located closer to the center than the inner edge of the tight seal portion, and An easy-open sealed food container characterized in that, at the opening start position, the outer peripheral edge of the easy-open seal part is located at the same position as the outer peripheral edge of the tight seal part, or closer to the center than the outer peripheral edge of the tight seal part ( (patent pending).

Therefore, an object of the present invention is to apply a heat sealing material in the form of a film only to the portion of the container or lid to be heat sealed, and to
It is an object of the present invention to provide a method that can be easily applied to other processes without producing film scraps.

Another object of the present invention is to use a heat-shrinkable film of heat-sealing resin as a heat-sealing material so that the material can be applied to the heat-sealing surface of a container or lid without the need for die-cutting the film. We are here to provide you with a method.

(Means for Solving the Problems) According to the present invention, there is provided a method of applying a layer of heat sealing material circumferentially to a container or lid to be heat sealed, the method comprising applying a layer of heat sealing material in a circumferential manner to a container or lid that is slightly larger than the outer dimensions of said container or lid. Prepare a heat-shrinkable tubular film made of a heat-sealing material resin having the following dimensions, and insert the tip of this tubular film by an amount equivalent to the heat-sealing width from a mold corresponding to the container, lid, or their heat-sealed portion. By protruding outward and heating the protruding portion of the tubular film to shrink it, a circumferential heat sealing layer is formed along the heat sealing surface, and this heat sealing layer is adhered to the container or lid. A method of applying a heat sealing material characterized by a method of applying a layer of heat sealing material circumferentially to a container or a lid to be heat sealed, the method comprising applying a layer of the heat sealing material in a circumferential manner to a container or a lid to be heat sealed, the method comprising: Prepare a heat-shrinkable tape made of a heat-sealing material resin, and apply this tape to the outer periphery of a container, a lid, or a mold corresponding to the heat-sealed portion thereof, so that only an amount corresponding to the heat-sealing width protrudes outward. By wrapping and fixing the tape in a similar manner, and heating and shrinking the protruding part of the tape, a circumferential heat-sealing layer is formed along the heat-sealing surface, and this heat-sealing layer is adhered to the container or lid. A method of applying the featured heat sealant is provided.

(Function) In FIG. 1 for detailed explanation of the present invention, a mold 1 has an outer shape 2 corresponding to the outer shape of a container or a lid, and has an upper surface 3 corresponding to a heat-sealed portion of the container or lid. .

A heat-shrinkable tubular film 4 made of a heat-sealing resin and having dimensions slightly larger than the external dimensions of the container or lid.
This film 4 is arranged around the outer periphery of the mold 1, and the tip 5 of the film 4 is made to protrude outward from the mold 1 by an amount corresponding to the heat sealing layer. (Step A) The protruding portion 5 of the tubular film 4 is heated and shrunk using, for example, hot air. As a result, the protruding portion of the film contracts along the upper surface 3 of the mold 1 to form a circumferential heat sealing layer 6 along the heat sealing surface. (Step B) That is, according to the present invention, the cylindrical circumferential surface is converted into a horizontal circumferential surface by utilizing the heat shrinkability of the heat-sealable resin film.

Subsequently, the circumferential heat-sealing layer 6 is cut from the remaining tubular film 4 by means such as cutting.

(Step C) Finally, the cut horizontal and circumferential heat sealing layer 6 is adhered to the heat sealing portion (flange) 8 of the container 7 to form a heat sealing container. (Step D) In Figure 1, it should be understood that a container or lid can be used instead of the mold 1 and a horizontal circumferential heat sealing layer 6 can be applied directly to the heat sealing portion of the container or lid. . It is also understood that instead of cutting the horizontal, circumferential heat-sealing layer 6 from the tubular film and then adhering it, the heat-sealing layer 6 can be glued to the container or lid and then cut from the tubular film. Should.

In FIG. 2 for explaining the method 542 of the present invention, a heat-shrinkable tape 4a made of a heat-sealing material resin is wrapped and fixed around the heat-sealing part 8 of the container 7, and then cut from the remaining tape. do. (Step A) This heat-shrinkable tape 4a has a width slightly larger than the heat-sealing layer of the container 7, and is wound so that only the width corresponding to the heat-sealing layer protrudes outward.

Next, the protruding portion 5a of the tape is heated and shrunk using means such as hot air. Thereby, a horizontal and circumferential heat sealing layer 6 is similarly formed along the surface of the heat sealing portion 8. (Step B) This heat-sealing layer 6 is adhered to the heat-sealing portion 8 of the container by means such as thermal bonding. (Step C) “According to the present invention, by utilizing the heat shrinkability of the heat-sealable resin film to convert the cylindrical circumferential surface into a horizontal circumferential surface, there is virtually no generation of film scraps. It becomes possible to form a continuous heat-sealing material layer 6 with a constant thickness only on the portion of the container or lid that is to be heat-sealed.

(Description of preferred embodiments) Heat-shrinkable film In the present invention, a film made of a resin having heat-sealability and also having heat-shrinkability is used.

Such resins include olefins such as polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers with a vinyl acetate content of 10 to 45% by weight, ethylene-acrylic ester copolymers, and ionomers. Polyester resins are preferably used, and polyesters are also suitable.

Resins such as polyester, copolyester, and polyamide are also applicable.

As a heat-shrinkable film, the shrinkage rate defined by the following % formula % L+, L2 = length of the film before shrinkage and after shrinkage is in the direction of shrinkage (circumferential direction) 10 to 7
0%, especially 15 to 40% is suitable.

Such a heat-shrinkable film is produced, for example, by the following methods: (1) flat two-stage biaxial stretching method (2) flat simultaneous biaxial stretching method (2) tube-type two-stage stretching method (4) tube-type two-stage stretching method.

The thickness of the film varies depending on the application, but in the state before shrinkage, it is 10 to 200 μm, especially 15 to 100 μm.
Preferably, it is in the μm range.

The heat-shrinkable film may be made of a single resin, or may be made of multiple types of resins.

For example, blends of polypropylene or propylene-ethylene copolymers and polyethylene are known to exhibit a wide range of seal strengths relative to polypropylene or polyethylene depending on the blend ratio.

When a heat-sealing material layer is formed from a heat-shrinkable film made of this blend, so-called easily peelable heat-sealing (peelable heat-sealing) can be performed. Further, the heat-shrinkable film may be a laminated film. For example, if a laminated film consisting of a polypropylene base and a propylene-ethylene copolymer surface layer is used, heat sealing can be performed at a relatively low temperature.

Container and lid The container and lid can be made of any container-forming material known per se, such as resin, metal, paper, glass, ceramic, or a laminate thereof.

A suitable example of the container is a three-dimensional container having a heat-sealable part such as a flange part, a curl part, a bead part, etc. at the opening, for example,
These include wide-mouth bottles, squeezed cans, squeezed cans, two-piece cans, cup-shaped containers, tray-shaped containers, etc.

Suitable containers and lids are made of a resin that has heat-sealing properties at least on the inner surface of the heat-shrinkable film described above, such as low-medium high density polyethylene, tactical polypropylene, propylene-ethylene copolymer, etc. Olefin resins such as olefin resins graft-modified with polymers, ethylene-vinyl acetate copolymers, ethylenically unsaturated carboxylic acids or their anhydrides; polyamide or copolyamide resins with relatively low melting points or low softening points; relatively It is made of polyester or copolyester resin with a low melting point or low softening point.

The container body may be a container formed from these resins alone, or may be a laminated container including a metal foil such as aluminum foil, m-foil, or tin foil as an intermediate layer.

The lid can be made of metal foil such as aluminum foil, tin foil, steel foil, or tin foil.
The base material is a thermoplastic resin film such as a biaxially oriented polyethylene terephthalate film, a biaxially oriented nylon film, a polycarbonate film, various fibers, or a laminate thereof, and the above-mentioned heat-sealable resin layer is used as an inner material. It may be a layered structure.

For example, if the heat-shrinkable film is a polypropylene film, a tight seal will be formed if the inner surface of the lid or the inner surface of the container is made of polypropylene. In addition, the inner surface of the lid or container may be made of polypropylene or other polymers,
For example, polyethylene, ethylene-vinyl acetate copolymer,
If it is made of a blend of ethylene-propylene rubber or the like, an easy-to-open seal will be formed. In addition, if the intermediate material is made of a laminated structure of a polypropylene layer and the blend layer, and both the inner surface of the lid and the inner surface of the container are made of polypropylene, the polypropylene layer side has a tight seal and the blend layer side has an easy-to-open seal. A seal will form.

In the method of the present invention, the width of the heat-shrinkable film that protrudes outward from the mold corresponding to the container, lid, or their heat-sealed portion is the width of the horizontal, circumferential heat-sealed film formed after heat shrinkage. The width of the material layer is such that it will provide the necessary heat sealing portion, and can be determined empirically depending on the heat shrinkage conditions and the type of film. Generally, the protruding width or protruding width is 50 to 3 m.
It is particularly desirable that m is in the range of 30 to 5+ nm.

Heating of the protruding or protruding portions can be performed using hot air, heated steam, infrared radiation, etc. The heating temperature varies depending on the type of film, but for example, in the case of polyethylene, it is 80 to 130 ° C., in the case of polypropylene, A range of 120 to 180°C is suitable. It is preferable to cut the film by fusing, and for this purpose, a laser beam, contact with a heating wire or heating plate, etc. are used.

The heat-shrinkable film is bonded to the container or lid by heating the film above its softening temperature, for example, by bar sealing, rotary roll sealing, high frequency sealing, impulse sealing, ultrasonic sealing, or the like.

(Effects of the Invention) According to the present invention, by converting a cylindrical circumferential surface into a horizontal circumferential surface by utilizing the heat shrinkability of a heat-sealable resin film, there is virtually no generation of film scraps. It is possible to form a continuous heat-sealing material layer with a constant thickness only on the portion of the container or lid that is to be heat-sealed. The effect of reducing the amount of film used is greater as the circumference of the portion to be heat sealed is longer and the width is narrower.

Further, it is possible to apply the heat sealing material layer in a correctly positioned state not only when the heat sealing part is circumferential, but also when the heat sealing part is triangular, square, or other polygonal.

(Example) Example 1 Using low-density polyethylene with a melt index of 3.0, a film with a thickness of 30 μm and a circumferential diameter of 85 was produced by tube-stage stretching at a blow-up ratio of 5 and a winding speed of 15 m/min.
A heat-shrinkable film of mm was produced. The inner surface has an epoxy/phenol coating film containing maleic anhydride-modified polyethylene powder (15P) IR, and has an outer diameter of 80+n+.
A cup-shaped deep-drawn container made of a 0.2 mm tin plate was prepared with a heat-sealing flange having a width of 6 mm.

The above film was applied as a heat sealant to the flange of this container by the method shown in FIG. The application conditions will be explained below.

First, the container 7 was placed on a support stand 9 having an outer diameter of 83+nm and fixed so that the tip 5 of the tubular film 4 protruded by 15 mm (Step A). Next, the protrusion 5 was heated and shrunk with hot air at 120'C (Step B). At this time, four nylon jigs 11 shown in FIG. 5(b) were used to fix the film. As a result, the circumferential heat sealing layer 6. was formed. Then, this circumferential heat sealing layer 6 was sealed to the flange 8 of the container 7 by high frequency induction heating method (Step C
). Finally, the container 7 was separated from the tubular film 4 using a heating wire (Step D).

The film loss rate by this method was approximately 30%.

Example 2 Using a zinc-based ionomer with a melt index of 1.5, a heat-shrinkable film with a thickness of 20 μm and a circumference of 400+nm was produced by a tube-stage stretching method under the conditions of a blow-up ratio of 4.5 and a winding speed of 10 m/min. was created. This film was applied as a heat-sealing material to a 50 μm aluminum foil in the same manner as shown in FIG. 1 to produce a heat-sealed lid. The application conditions will be explained below.

First, the vertical 10
The tip 5 of the tubular film 4 was fixed to a mold 1 with a diameter of 0 mm and a width of 100 mm so that it protruded by 10 mm (Step A), and the protruding portion 5 was heated with an infrared heater to shrink it (Step B).
). At this time, in order to fix the film, as shown in Fig. 5 (a)
) Four jigs 10 made of polytetrafluoroethylene were used. As a result, the circumferential heat sealing layer 6 was formed without affecting the parts other than the protruding parts. Next, this circumferential heat-sealing layer 6 was separated from the tubular film 4 by impulse fusing, and in step C), it was sealed to aluminum foil by an impulse sealing method. There was no loss of film with this method, and the amount of film used was less than 50% of that when the film was applied over the entire surface of the aluminum foil.

Example 3 The first layer is a polypropylene layer with a melt index of 1.0, and the second layer is an ethylene-propylene copolymer with a melt index of 3.0 and 35 weight of an ethylene-α-olefin copolymer with a melt index of 3.4. % blended layers was prepared, and this was stretched 3 times lengthwise and crosswise using a biaxial stretching machine to obtain a simultaneous 2@stretched film with a thickness of 50 μm. Next, this film is sealed by impulse welding so that the circumference is 83mm so that the blend layer is on the inside.
It was processed into a tubular heat-shrinkable film of mm. Using this film, the outer diameter is 80 mm,
It was applied to a polypropylene round cup having a heat-sealing flange with a width of 7 mm. After application, the adhesive strength between the heat sealing material and the container is such that it can be easily peeled off (0.8 to 1.2 k).
g715mm width). The application conditions will be explained below.

First, the container 7 is placed on a support stand 9 with an outer diameter of 81 mm, and fixed using four nylon jigs 11 shown in FIG. 5(b) so that the tip 5 of the tubular film 4 protrudes by 15 mm. In step A), the protrusion 5 was heated and shrunk with hot air of 16 (l) (step B). As a result, a circumferential heat-sealing layer 6 was formed without affecting the parts other than the protrusion. Then, this circumferential heat sealing layer 6 was sealed to the flange 8 of the container 7 by the impulse sealing method (Step C).Finally, the film protruding from the flange was trimmed using a heating wire. The film loss rate was approximately 30%.

Example 4 Using a zinc-based ionomer with a melt index of 1.5, a heat-shrinkable film with a thickness of 30 μm and a circumferential diameter of 270 mm was produced by tube-stage stretching at a blow-up ratio of 3.0 and a winding speed of 10 m/min. was created. A strip of tape with a width of 9 mm was cut out from this film along the longitudinal direction. The thickness of this tape around the mouth is 41111D,
It was applied to a wide mouth bottle with an outer diameter of 150+ nm by the method shown in FIG. The application conditions will be explained below.

First, a heat-shrinkable tape 4a was wrapped around the mouth of a wide-mouthed bottle 7 so that the tip 5 of the tape protruded by 6 mm, and was fixed and cut at the same time using an impulse fusion seal (Step A). Next, the protrusion 5 was heated and contracted using an infrared heater to form a circumferential heat sealing layer 6 (Step B). Then, this circumferential heat-sealing layer 6 was sealed to the mouth of the wide-mouth bottle 7 using a silicone rubber heat-sealing head with good heat dissipation properties (Step C). The heat sealing condition at this time is 140℃
-1 or 2 seconds. There was no loss of film with this method.

Comparative Example Low-density polyethylene with a melt index of 3.0 was extruded using a T-die to produce a flat film. From this film, the outer diameter is 80 mm.

A ring-shaped film having an inner diameter of 68 mm was cut out in a staggered pattern using a punching press. This ring-shaped film has an epoxy/phenol coating film containing 15 PHR of maleic anhydride-modified polyethylene powder on the inner surface, and has an outer diameter of 80 m.
The mixture was applied as a heat-sealing material to a cup-shaped deep-drawn container made of a tin plate with a thickness of 0.2 mm, on which a heat-sealing flange with a width of 6 mm was formed. Application was carried out at 140° C. for 1.2 seconds with a biaxially stretched polyethylene terephthalate film interposed between the heat sealing layer and the heat sealing head. The film loss rate using this method is 75
It was over when it was more than %.

[Brief explanation of the drawing]

1, 2, 3, and 4 are process diagrams illustrating the present invention, and FIG. 5 is a perspective view illustrating the shape of a film fixing jig. Reference number 1 is the type corresponding to the heat sealing part of the container or lid, 2
is its outer shape, 3 is its upper surface, 4 is a tubular heat-shrinkable film, 4a is a tape-like heat-shrinkable film, 5 and 5a are the tips of these heat-shrinkable films, 6 is a circumferential heat-sealing layer, 7
1 is a container, 8 is a heat sealing part, 9 is a support stand for the container, 10 and 1
1 indicates a film fixing jig.

Claims (2)

[Claims] (1) A method of applying a layer of heat sealant circumferentially to a container or lid to be heat-sealed, the heat-shrinkable layer comprising a heat-sealing resin having dimensions slightly larger than the external dimensions of the container or lid. A tubular film is prepared, and the tip of the tubular film is made to protrude outward from the container, the lid, or a mold corresponding to the heat-sealed portion thereof by an amount corresponding to the heat-sealing cloth, and the protruding portion of the tubular film is A method for applying a heat sealing material, which comprises forming a circumferential heat sealing layer along a heat sealing surface by heating and shrinking the material, and adhering this heat sealing layer to a container or a lid. (2) A method of applying a layer of heat sealing material circumferentially to a container or lid to be heat sealed, the heat shrinkable material comprising a heat sealing material resin having a width slightly larger than the heat sealing width of the container or lid. Prepare a plastic tape, wrap this tape around the outer periphery of a container, a lid, or a mold corresponding to the heat-sealed portion thereof, so that only the amount corresponding to the heat-sealing width protrudes outward, and fix the tape. A method for applying a heat sealing material, which is characterized by forming a circumferential heat sealing layer along the heat sealing surface by heating and shrinking the protruding portion of the heat sealing material, and adhering this heat sealing layer to a container or a lid. .