JP2661427B2 - Heat fusion method of container body - 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 polyester surface and a surface comprising a polyolefin portion and a polyester portion.

[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, in a container having a body as shown in FIG. 3, for example, especially when the contents are sake or the like, the joint portion 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, as shown in an enlarged sectional view in FIG. 4, the portion shown in FIG. 3A is formed by bending one end of the material inward at a predetermined length required for bonding, and the outer surface of the bent portion and the other corresponding surface are bent. When bonding the inner surface of the material end portion, 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 from the tip at a fixed length, and the remaining inner portion is removed. A method of folding a half-thick portion into an outer removed portion 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. In the case where the resin is prepared by extrusion coating, there is a problem that the resin is easily oxidized, thereby generating 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 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. 4 was insufficient.

Accordingly, it is an object of the present invention 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.

[0008]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies and as a result, the object of the present invention is to provide a polyolefin surface layer on one surface side of a substrate, One end of the polyester surface layer of the laminate film having a polyester surface layer on the surface side is folded back to the polyolefin surface layer side, the end having a surface composed of a polyolefin portion and a polyester portion, and the other surface A method of heat-sealing the container body by heat-sealing the end of the polyester surface layer on the side, wherein the surface of the polyolefin portion at the end having a surface composed of the polyolefin portion and the polyester portion is frame-treated. The surface of the polyester portion is subjected to hot air treatment, the end of the polyester surface layer on the other surface side is subjected to hot air treatment, and then both ends are treated. The surface of respectively and pressed together and found to be achieved by the method of thermal fusion bonding container body, characterized by heat sealing. In a preferred embodiment, after the polyolefin portion on the surface comprising the polyolefin portion and the polyester portion is flame-treated, the polyester portion is subjected to hot air treatment.

[0009] Actually, the polyolefin portion and the polyester portion are adjacent to each other, and the frame and hot air applied to each portion are applied to the portions slightly adjacent to each other, which hinders the object of the present invention. It is acceptable within the range not to do.

Hereinafter, the present invention will be described in more detail.

FIG. 1 is a schematic process diagram showing one example of the production of a container body by the heat fusion method of the present invention. In FIG.
A laminated film 1 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 surface 2 'at one end 4 thereof.
As shown in FIG. 1 (A), the polyolefin surface 3 on the back side of the end portion 4 is subjected to a frame treatment with a gas burner 5, and then the polyester surface 2 'is subjected to hot air treatment with a hot air treatment nozzle 6.

When polyester is exposed to a high temperature in the presence of moisture, it undergoes hydrolysis and its physical properties such as heat sealability are deteriorated. Therefore, prior to the flame treatment using a gas flame containing a large amount of moisture, polyester is used. It is preferable to perform hot air treatment after that. In other words, if hot air is first applied to the polyester and then the frame is applied to the polyolefin, the polyester is already sufficiently heated and may be affected by the frame applied to the adjacent polyolefin, causing hydrolysis. Although expensive, the polyester will not be heated and will not hydrolyze if flame treatment is performed first.

On the other hand, the other end of the polyester surface 2 is subjected to hot air treatment by hot air treatment nozzles 6 'and 6 ". After such treatment, the end 4 is bonded. As shown in FIG. 1 (B), the inner surface is folded inward by a predetermined length, and the outer surface thereof and the other polyester surface which has been subjected to the hot air treatment are combined with each other, press-bonded and heat-fused. As a result, an adhered container body as shown in (C) is obtained.

In the present invention, the flame treatment for treating the polyolefin portion on the surface composed of the polyolefin portion and the polyester portion is mainly performed to oxidize the polyolefin to introduce a polar group. Is 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 0.001 to
It is 1.5 seconds, more preferably 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, and the adhesion between the polyolefin and the polyester becomes insufficient. If the contact time exceeds 1.5 seconds, the polyolefin melts and is lost or burns in some cases. Further, as described above, the adjacent polyesters may be hydrolyzed by the presence of moisture and heat contained in the frame, and the adhesiveness may be reduced.

Further, the hot air treatment performed on the polyester portion on the surface comprising the frame-treated polyolefin portion and the polyester portion, and on the polyester surface to be fused with the polyolefin portion and the polyester portion, This hot air treatment is usually performed to soften the surface.
This is performed by blowing heated air at 0 to 1000 ° C. through a nozzle onto each surface for 0.2 to 5 seconds. In particular, when the polyester portion on the surface comprising the polyolefin portion and the polyester portion is to be treated, it is usually not necessary to carry out the treatment immediately after the flame treatment, but it is preferable to carry out the treatment in an in-line treatment.

In the present invention, after both sides are subjected to a frame treatment and a hot air treatment, preferably, both sides are overlapped and pressed quickly and heat-fused, and the both sides in a softened state are bonded. At this time, it is preferable to perform the pressure bonding 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 refers to a portion where at least the polyolefin is exposed on the surface, for example, a Y portion in FIG. 4, 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, the softening of the resin, blocking due to stickiness, etc. may occur during processing of the packaging material or during storage, which may cause a problem in work. When using polyester resin of 150 ° C or higher,
Box making may be difficult. Further, a polyester resin having a high crystallinity has a definite melting point, so that it has poor heat-sealing properties at low temperatures and has a disadvantage of being 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 cocondensation polymer of two or more dibasic acids mainly containing terephthalic acid and a dihydric alcohol, (2) terephthalic acid. Examples thereof 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 that can 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 the copolymer of ethylene and an unsaturated carboxylic acid or an ester thereof, those having an unsaturated carboxylic acid content of 3 to 20% by weight are preferable. 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 whose surface is made of only polyester, and the same polyester as the heat-sealable polyester resin is used as such a polyester.

In the present invention, the member having a surface comprising 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 surface layer having an end portion composed of a polyester side and a polyolefin side as shown in FIG. 4 on the other side is used. The width of the folded portion including the polyester surface in FIG. 4, 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.
The thickness is preferably 5 to 60 μ and 5 to 50 μ, respectively.

The adhesive layer is made of an adhesive resin, a laminate of the adhesive resin and a polyolefin, or an adhesive or a primer coating agent.

As the adhesive resin, for example, a density of 0.91
0 or less ethylene-α-olefin copolymer, unsaturated carboxylic acid-modified polyolefin and the like. Examples of the polyolefin include polyethylene, polypropylene, polybutene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, ethylene-α-olefin copolymer, and the like. 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 the contents from being transmitted due to cracks in the metal foil. As the stretched plastic contained in the stretched plastic layer, a polyester resin or a nylon resin is biaxially stretched 4 to 6 times in a longitudinal direction and 4 to 6 times in a transverse direction after molding, and then biaxially stretched and then heat-fixed. A polyester resin or a biaxially stretched nylon resin is preferably used.

The substrate 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 substrate contains paper in the layer constitution. 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.

A metal foil is usually provided on the paper to prevent permeation of beverages, to provide gas barrier properties for preventing oxygen from entering from outside, and to provide light-shielding properties. Those made of 200 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.

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

[0034]

EXAMPLES The present invention will be described more specifically with reference to the following examples.

Example 1 One end of the laminate having the following layer constitution was removed from the inner paper layer by a predetermined length from the inner side of the paper layer to the polyethylene layer side, and as shown in FIG. The laminate was folded back at a folding width of 8 mm so as to be an outer layer, to prepare a laminate film having a surface composed of a polyester surface and a polyethylene surface.

Polyester (PET) / biaxially oriented polyester (OPET) / aluminum foil (Al) / (60μ) (12μ) (9μ) ionomer / paper / polyethylene (PE) (20μ) (320g / m ² ) (20μ) )

However, as the polyester, a sealer (Selar) PTX 207 (manufactured by Du Pont-Mitsui Polychemicals) comprising terephthalic acid, isophthalic acid and ethylene glycol was used.

As shown in FIG. 1, the polyethylene film on the surface composed of the polyester surface and the polyethylene surface was blown on the above-prepared film for 0.5 second with a flame of a mixed gas of propane and air, and after hot-air Hot air of 400 ° C from processing nozzle 6
For a second, hot air treatment was performed by spraying the polyester portion on the surface consisting of the polyester surface and the polyethylene surface and the other end of the polyester surface. Then, both surfaces treated as described above were immediately pressure-bonded at a pressure of 0.2 kg / cm ² , heat-sealed, and the adhesive strength was examined.

Table 1 shows the results.

The adhesive strength was measured by the following method.

Measurement of adhesive strength: The obtained laminate was 15 mm wide.
, And peeled off between both sides at a tensile speed of 300 mm / min, and the strength was measured.

Examples 2 to 5 The polyester in Example 1 was replaced with PET G 5116 (manufactured by Eastman Kodak Co.), which is a condensate of a glycol component containing 1,4-cyclohexanedimethanol and a dibasic acid component. Example 2 was the same as Example 1 except for the above.
In addition, Examples 3 to 5 were performed in the same manner as in Example 1 except that the hot air processing time or the frame processing time in Example 1 was changed as shown in Table 1. In each case, the adhesive strength was measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Examples 1 to 3 Comparative Example 1 was performed in the same manner as in Example 1 except that the frame processing was not performed. Comparative Example 1 was the same as Comparative Example 1 except that the hot air treatment time was changed as shown in Table 1.
Comparative Examples 2 and 3 were performed in the same manner as described above. Comparative Examples 1 to
In each of the three samples, the adhesive strength was measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Examples 4 to 7 Comparative Example 4 was performed in the same manner as in Example 1 except that the hot air treatment was not performed. Further, 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. Comparative Examples 4 to 7
In each case, the adhesive strength was measured in the same manner as in Example 1.
Table 1 shows the results.

[0045]

[Table 1] As is clear from Table 1, in Comparative Examples 1 to 3 in which only the hot air treatment was performed, the adhesion between the polyolefin and the polyester was insufficient, and in Comparative Examples 4 to 7 in which only the frame treatment was performed, the adhesion between the polyesters was poor. Insufficient or impossible, but as in Examples 1-5, good adhesion both at polyolefin / polyester and between polyesters by applying flame treatment and hot air treatment to predetermined sites, respectively. Was done.

[0046]

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 heat-sealed simultaneously and in-line with good adhesive strength. be able to.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of the step (A) in FIG. 1 as viewed from the direction of travel.

FIG. 3 is a schematic perspective view showing a body of an example of a container made by the method of the present invention.

FIG. 4 is an enlarged cross-sectional view of a portion A in FIG. 3, showing an example of a portion bonded by the method of the present invention.

[Explanation of symbols]

 Reference Signs List 1 laminated film 2, 2 'polyester surface 3 polyolefin surface 4 end 5 gas burner 6, 6', 6 "nozzle for hot air treatment 7 polyester layer 8 adhesive layer 9 biaxially oriented polyester layer 10 paper 11 aluminum foil 12 polyolefin Layer A Edge heat-sealed 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 Pat. , A)

Claims (2)

(57) [Claims] 1. One end of the polyester surface layer of a laminate film having a polyolefin surface layer on one side of the substrate and a polyester surface layer on the other side is placed on the polyolefin surface layer side. A method for heat-sealing a container body for heat-sealing an end having a surface composed of a polyolefin portion and a polyester portion formed by folding, and an end of a polyester surface layer on the other surface side, wherein the polyolefin portion is And the surface of the polyolefin portion of the end having the surface consisting of the polyester portion and the surface of the polyester portion and the surface of the polyester portion is subjected to hot air treatment, the other surface side of the polyester surface layer is subjected to hot air treatment, Then, the respective surfaces of both ends are pressure-bonded to each other and heat-sealed. 2. The method according to claim 1, wherein the polyester portion is subjected to hot air treatment after the polyolefin portion on the surface comprising the polyolefin portion and the polyester portion is subjected to a flame treatment.