JP2661423B2 - Heat fusion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heat-sealing a container material, and more particularly, to a method for simultaneously heat-sealing a surface composed of a polyolefin portion and a polyester portion and a polyester surface.

[0002]

2. Description of the Related Art Containers for liquid drinks such as milk drinks, fruit drinks, and sake are conventionally made of paper as a base material because of their hygiene, water resistance, moisture proofness, and heat sealability. Of the container is processed by using a polyolefin or the like.

[0003] Among such container constituent materials, for example, in the case of a container having a body as shown in Fig. 2, especially when the contents are sake or the like, the joint is formed such that the end face of the constituent material is exposed inside the container. It does not come into contact with the contents. That is, the portion shown in FIG.
As shown as an enlarged cross-sectional view, when one material end is bent inward at a predetermined length necessary for bonding, and when bonding the outer surface of the bent portion and the corresponding inner surface of the other material end, In advance, the vicinity of the center in the thickness direction from the tip of the portion corresponding to the bent portion, that is, the outer portion of the paper portion is removed at a fixed length from the tip, and the remaining inner half thickness portion is removed to the outer removed portion. The method of folding is usually used. Therefore, at the portion indicated by X, the inner surfaces of the constituent materials are bonded together, and at the portion indicated by Y, the outer surface and the inner surface of the constituent material are bonded.

[0004] Conventionally, as a container constituting material as described above,
Polyolefin was used for both the inner surface and the outer surface. However, when a polyolefin is used for the inner surface of the container, the polyolefin has a property of adsorbing or permeating a flavor component of the beverage, and thus there is a problem that the original aroma and taste of the beverage are not maintained. When it is prepared by extrusion coating, there is also a problem that oxidation is apt to occur, which causes an unpleasant odor.

In order to solve the above-mentioned problems, in recent years, instead of polyolefin, polyester, particularly polyester having excellent heat sealing properties, has been used as a container constituting material instead of polyolefin as an inner surface layer of the container.

[0006]

In the case where the heat-sealable polyester is used as described above, in the case of a material mainly composed of paper, even if heat sealing is performed to form an adhesive portion at the end. However, since the paper acts as a heat insulating material, it is actually difficult to perform heat fusion. For this reason,
Both surfaces to be heat-sealed are burned with a gas burner or the like,
After being heated and melted, a so-called flame treatment of superimposing and fusing is performed. As described above, when one surface has two or more kinds of materials, that is, a polyester portion and a polyolefin portion, the polyester surface is treated by the flame treatment. In this case, a lower oxide was formed, and the oxide hindered the adhesion between the polyesters. Therefore, the adhesion at the portion X in FIG. 3 was insufficient.

The inventors of the present invention have also proposed a method of simultaneously heat-sealing a surface composed of a polyolefin portion and a polyester portion and a polyester surface, which is an object of the present invention, after treating a surface composed of a polyolefin portion and a polyester portion with a flame. A method has been proposed in which hot air treatment is performed, while the polyester surface is subjected to hot air treatment, and then both surfaces are pressed against each other and thermally fused (Japanese Patent Application No. Hei 2-237).
29), however, there is a drawback that by subjecting the surface composed of the polyolefin portion and the polyester portion to a frame treatment, the polyester portion is oxidized or hydrolyzed, which adversely affects the heat fusion property between the polyesters.

Accordingly, an object of the present invention is to provide a method capable of simultaneously heat-sealing a surface comprising a polyolefin portion and a polyester portion and a polyester surface with good adhesive strength.

The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, the object of the present invention is to provide a member in which at least the surface of the polyolefin portion and the surface of the polyester portion are aligned on the same surface. In the method of heat-sealing a first surface which is a region including both surfaces and a second surface which is a polyester surface of a member having a polyester portion on the surface, of the first surface, The polyolefin portion is subjected to hot air treatment after flame treatment, and the polyester portion is subjected to hot air treatment but not flame treatment, while the second surface is subjected to hot air treatment but not flame treatment. It has been found that the first surface and the second surface can be attained by a heat fusion method characterized in that the first surface and the second surface are pressed against each other and heat-sealed.

Hereinafter, the present invention will be described in more detail. FIG.
FIG. 2 is a schematic process diagram showing an example of manufacturing a container body by the heat fusion method of the present invention. In FIG. 1, a polyester film 2 having a polyester surface 2 corresponding to the inner surface of the container, a polyolefin surface 3 corresponding to the outer surface of the container on the back surface thereof, and a polyester film 2 having a polyester surface 2 at one end 4 thereof are shown in FIG. Then, the polyolefin portion at the end 4 is flame-processed by a gas burner 5 and then hot-air-processed by a hot-air processing nozzle 6, and the polyester portion at the end 4 is also hot-air-processed at the same time. on the other hand,
The other end of the polyester surface is subjected to hot air processing by a hot air processing nozzle 6. After such treatment, the end portion 4 is folded inside a predetermined length necessary for bonding, and the outer surface thereof and the other end of the polyester surface subjected to hot air treatment as shown in FIG. Are bonded to each other, pressed and thermally fused to obtain a bonded container body as shown in FIG. 1 (C).

In the present invention, the flame treatment for treating the polyolefin portion of the surface composed of the polyolefin portion and the polyester portion is mainly performed to oxidize the polyolefin and introduce a polar group. Preferably, a method of contacting with a flame burned with a mixed gas of a combustible gas such as propane gas and air, and the contact time is preferably 0.0
The time is from 01 to 1.5 seconds, more preferably from 0.1 to 0.6 seconds. That is, if the contact time is less than 0.001 second, the activation of the polyolefin is insufficient, the adhesion between the polyolefin and the polyester becomes insufficient, and if the contact time exceeds 1.5 seconds, the polyolefin portion is overheated,
In some cases, the adhesiveness or the surface properties of the non-adhesive portion may be reduced.

Further, the hot air treatment performed on the surface composed of the polyolefin portion and the polyester portion subjected to the frame treatment and the polyester surface is performed to soften the surface portion. Normally, heated air at 300 to 1000 ° C.
This is done by spraying each side through a nozzle for 2-5 seconds. In particular, when the surface composed of the polyolefin portion and the polyester portion is treated, it is not usually necessary to immediately carry out the treatment after the flame treatment, but it is preferable to carry out the treatment by in-line treatment.

In the present invention, after both surfaces are subjected to hot air treatment, preferably, both surfaces are quickly and preferably laminated and press-bonded to perform heat fusion, thereby bonding the both surfaces in a softened state. On this occasion,
The pressure bonding is preferably performed at a pressure of 0.05 kg / cm ² or more.

In the present invention, a member having a surface composed of at least a polyolefin portion and a polyester portion is a portion where at least the polyolefin is exposed on the surface, for example, a Y portion in FIG. 3, and a portion where the polyester is exposed on the surface, for example in FIG. It has an X portion. As such a polyolefin, polyethylene, polypropylene or the like is used. As polyester, a heat-sealable polyester resin having excellent heat-sealability is preferably used in consideration of formation of a container. Examples of the heat-sealable polyester resin include a low-crystalline or non-crystalline polyester resin having a glass transition temperature Tg of 50 to 150 ° C.

When a polyester resin having a glass transition temperature Tg of 50 ° C. or less is used, blocking or the like due to softening stickiness of the resin may occur during processing of a packaging material or during storage, which may cause a problem in work. If a polyester resin having a temperature of 150 ° C. or higher is used, it may be difficult to make a bag or box during heat sealing. Further, a polyester resin having high crystallinity has a disadvantage that heat sealability is reduced and the resin is brittle.

The polyester resin comprises a copolymer of a polybasic acid and a polyhydric alcohol. As such a polybasic acid, one containing terephthalic acid as a main component is preferable, and as the polyhydric alcohol, one containing ethylene glycol as a main component is preferable. The polybasic acids and polyhydric alcohols can each contain other polybasic acids and other polyhydric alcohols as comonomer components.

In the present invention, specific examples of the heat-sealable polyester include (1) a co-condensation polymer of two or more dibasic acids mainly containing terephthalic acid and a dihydric alcohol, and (2) terephthalic acid. Examples include a co-condensation polymer of an acid and two or more dihydric alcohols, (3) polyethylene terephthalate, or a polymer alloy of the co-condensation polymer of (1) or (2) and a modified polyolefin.

Other dibasic acids which may be included as comonomer components with terephthalic acid include isophthalic acid,
Aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenoxyethane dicarboxylic acid, diphenyl ether dicarboxylic acid and diphenyl sulfone dicarboxylic acid; alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid; adipic acid And aliphatic dicarboxylic acids such as sebacic acid and azelaic acid; and oxyacids such as P-β-hydroxyethoxybenzoic acid, P-oxybenzoic acid, and ε-oxycaproic acid.

Examples of the dihydric alcohol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-dicyclohexanedimethanol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, and the like. Neopentylene glycol, diethylene glycol, 1,1-cyclohexane dimethylol, 1,4-cyclohexane dimethylol, 2,2-bis (4-β-hydroxyethoxyphenyl) propane, bis- (4-β
-Hydroxyethoxyphenyl) sulfonecyclohexanediol, 1,4-bis (β-hydroxyethoxy)
Glycols such as benzene and 1,3-bis (β-hydroxyethoxy) benzene are exemplified.

Examples of the modified polyolefin include a copolymer of ethylene and an unsaturated carboxylic acid or an ester thereof, or an ionomer. Examples of the unsaturated carboxylic acid or its ester include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate and the like. As a copolymer of ethylene and an unsaturated carboxylic acid or an ester thereof, one having an unsaturated carboxylic acid content of 3 to 20% by weight is preferable, and in the case of an ester, the content of the ester component is 1 to 20% by weight. % Is preferred.

In the present invention, the polyester resin may contain a nucleating agent or various additives such as a lubricant, an antiblocking agent, a stabilizer, an antifogging agent, a coloring agent, and the like. As such a nucleating agent, polyolefin or inorganic fine particles having a particle size of 2 to 10 μm are used. Examples of polyolefins include low-density polyethylene, high-density polyethylene, linear low-density polyethylene, and polypropylene.Examples of inorganic substances include carbon black, talc, gypsum, silica, alumina, calcium carbonate, titanium dioxide, graphite, and powdered glass. , Powdered metal and the like.

In the present invention, the member having a polyester surface refers to a member having a polyester surface only, and such a polyester is the same as the heat-sealable polyester resin described above.

In the present invention, the member having a surface composed of at least a polyolefin portion and a polyester portion and the member having a polyester surface may be separate film members, respectively. A laminate film having a polyester surface layer on one side and a polyolefin surface layer having an end composed of a polyester side and a polyolefin side as shown in FIG. 3 on the other side is used. The folded width of the portion including the polyester surface in FIG. 3, that is, the length of the X portion is preferably 1 to 15 mm from the viewpoint of container production.
As the above-mentioned laminated film, for example, a film having a layer structure of polyester / adhesive layer / stretched plastic / metal foil / adhesive resin / paper / polyethylene is used.
In the above-mentioned layer constitution, the above-mentioned ones are used for each of the polyester layer and the polyethylene layer, and the thickness thereof is preferably 5 to 60 μm and 5 to 50 μm, respectively.

The adhesive layer is formed of an adhesive resin, a laminate of the adhesive resin and polyolefin, or an adhesive or a primer coating agent. Examples of the adhesive resin include an ethylene-α-olefin copolymer having a density of 0.910 or less, and an unsaturated carboxylic acid-modified polyolefin. Polyolefins include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-α
Olefin copolymers and the like can be mentioned. Here, the unsaturated carboxylic acid-modified polyolefin means the above-mentioned polyolefin copolymerized or graft-polymerized with a carboxylic acid group, an acid anhydride group and a derivative thereof, and as a carboxylic acid group, an acid anhydride group and a derivative thereof. Specific examples include methacrylic acid, maleic acid, fumaric acid, methacrylic anhydride, maleic anhydride, ethyl methacrylate, glycidyl acrylate, and diglycidyl methacrylate. Examples of the adhesive include one- or two-component reactive urethane-based adhesives, polyester-based adhesives, acryl-urethane-based adhesives, and epoxy-urethane-based adhesives. Examples of the primer coating agent include polyethyleneimine. And alkyl titanates.

A stretched plastic layer can be provided to prevent permeation of the contents due to cracks in the metal foil. As the stretched plastic contained in the stretched plastic layer, a biaxially stretched polyester formed by molding a polyester resin or a nylon resin, biaxially stretching 4 to 6 times in the longitudinal direction and 4 to 6 times in the lateral direction, and then biaxially stretching and then heat-setting. A resin or a biaxially stretched nylon resin is preferably used.

The base material constituting the laminate according to the present invention is not particularly limited as long as it can be used as a structural support of the container. Preferably, the base material contains paper in the layer structure. Is preferred. As the paper constituting the base material, white paperboard having a basis weight of 100 to 400 g / m ² , base paper for milk cartons, acid-resistant paper, and the like are preferably used.

[0027] A metal foil is usually provided on the paper to prevent the permeation of the beverage, and the metal foil has a thickness of 6 to 20 mm.
Those made of 0 μm aluminum are preferably used. Such a metal foil is provided on the paper using, for example, the same unsaturated carboxylic acid-modified polyolefin, ionomer resin, or the like as that used as the adhesive resin.
Further, instead of the metal foil, a plastic film on which glass is deposited can be used.

The container to which the method of the present invention can be preferably applied is a liquid beverage having a high permeability, such as alcohol, whiskey, juice, coffee, barley tea, oolong tea, mineral water, and soups. Container.

[0029]

In the above-mentioned method for heat-sealing containers, the adhesion between the polyolefin and the polyester is insufficient if only the hot air treatment is performed, and the adhesion between the polyesters if only the frame treatment is performed. Insufficient or impossible. However, by using the present invention, the polyolefin is subjected to hot air treatment after the flame treatment, and the polyester is subjected to only hot air treatment, and thereafter, is subjected to heat bonding by press-bonding to each other. Good adhesion is achieved in any of the comrades.

[0030]

【Example】

<Example 1> One end of a laminate having the following layer constitution was removed from the inner layer of paper from the polyethylene layer by a predetermined length from the end, and as shown in FIG. Wrap with a wrap width of 8 mm so that
A laminated film having a surface composed of a polyester surface and a polyethylene surface was prepared. Polyester (PET, thickness 60μm) / Biaxially stretched polyester (OPET, thickness 12μm) / Aluminum foil (Al, thickness 9μm) / Ionomer (thickness 20μm)
/ Paper (basis weight 320g / m ² ) / Polyethylene (PE, thickness 20μm) However, as a polyester, a sealer made of terephthalic acid, isophthalic acid and ethylene glycol (Sela)
r) PTX207 (manufactured by Dupont Mitsui Polychemicals)
Was used.

As shown in FIG. 1, the polyethylene film of the polyester film and the polyethylene film was exposed to the above-prepared film for 0.5 second with a frame made of a mixed gas of propane and air, and subjected to a frame treatment. Thereafter, hot air of 400 ° C. was blown from the hot air processing nozzle 6 to the above-mentioned flame-treated polyethylene portion, polyester portion, and the other polyester surface for 1.5 seconds to perform hot air treatment. Then, both surfaces subjected to the hot air treatment were immediately pressure-bonded at a pressure of 0.2 kg / cm ³ , heat-sealed, and the adhesive strength was examined. The results are shown in the following (Table 1).

[0032]

[Table 1]

The adhesive strength was measured by the following method. Measurement of adhesive strength: The obtained laminate was cut into a strip having a width of 15 mm, peeled between both sides at a tensile speed of 300 mm / min, and the strength was measured.

Example 2 PET obtained by condensing the polyester of Example 1 with a glycol component containing 1,4-cyclohexanedimethanol and a dibasic acid component
The adhesive strength was measured in the same manner as in Example 1 except that G5116 (manufactured by Eastman) was used. The results are shown in the above (Table 1).

<Embodiments 3 to 5> Except that the hot air processing time or the frame processing time in Embodiment 1 was changed as shown in (Table 1), Embodiments 3 to 5 were performed in the same manner as in Embodiment 1. 5, and the adhesive strength was measured for each.
The results are shown in the above (Table 1).

<Comparative Example 1> The adhesive strength was measured in the same manner as in Example 1 except that the frame treatment was not performed. The results are shown in the above (Table 1).

Comparative Examples 2 and 3 Comparative Examples 2 and 3 were performed in the same manner as in Comparative Example 1 except that the time of the hot air treatment was changed as shown in Table 1 above. The adhesive strength was measured for each. The results are shown in the above (Table 1).

Comparative Example 4 The adhesive strength was measured in the same manner as in Example 1 except that the hot air treatment was not performed. The results are shown in the above (Table 1).

<Comparative Examples 5 to 7> Comparative Examples 5 to 7 were performed in the same manner as in Comparative Example 4 except that the frame processing time in Comparative Example 4 was changed as shown in Table 1 above. The strength was measured. The results are shown in the above (Table 1).

As is clear from the above (Table 1), in Comparative Examples 1 to 3 in which only the hot air treatment was performed, the adhesion between polyolefin / polyester was insufficient, and in Comparative Examples 4 to 7 in which only the frame treatment was performed. In this case, adhesion between polyesters is insufficient or impossible. However, by performing hot air treatment after the frame treatment as in Examples 1 to 5, good adhesion can be obtained both between the polyolefin / polyester and between the polyesters. It was done.

[0041]

As described above in detail, according to the heat-sealing method of the present invention, the surface consisting of the polyolefin portion and the polyester portion and the polyester surface are simultaneously and in-line heat-sealed with good adhesive strength. You can wear it.

[0042]

[Brief description of the drawings]

FIG. 1 is a schematic process diagram showing one embodiment of the heat fusion method of the present invention.

FIG. 2 is a schematic perspective view showing a body of an example of a container produced by the method of the present invention.

FIG. 3 is an enlarged cross-sectional view of a portion A in FIG. 2, showing an example of a portion bonded by the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Laminate film 2 ... Polyester surface 3 ... Surface consisting of polyolefin part and polyester part 4 ... End part 5 ... Gas burner 6 ... Nozzle for hot air treatment 7 ... Polyester layer 8 ... Adhesive layer 9 ... Biaxially stretched polyester layer DESCRIPTION OF SYMBOLS 10 ... Paper 11 ... Aluminum foil 12 ... Polyolefin layer X ... Polyester surface Y ... Polyolefin surface A ... End heat-fusion part

Continuation of the front page (56) References JP-A-49-99371 (JP, A) JP-A-57-135141 (JP, A) JP-A-2-80235 (JP, A) US Patent 4,986,246 (US, A)

Claims (1)

(57) [Claims] 1. A member in which at least a surface of a polyolefin portion and a surface of a polyester portion are arranged on the same side surface, a first surface which is a region including both surfaces, and a member having a polyester portion on the surface. In the method of heat-sealing the second surface which is the polyester surface, the first surface is subjected to hot air treatment after the polyolefin portion is subjected to the flame treatment, and the polyester portion is subjected to the hot air treatment. Is performed, on the other hand, the second surface is subjected to hot air treatment but is not subjected to frame treatment, and thereafter, the first surface and the second surface are pressure-bonded to each other and heat-sealed. A heat fusion method characterized by the following.