Laminated Film

Laminated film, method for production thereof, bag and package using the laminated film, and method for separation thereof

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Laminated Film Abstract
A laminated film includes an outer-layer-film, a water-soluble film, and an intermediate layer interposed between the outer-layer-film and the water-soluble film. The intermediate layer contains high-pressure polyethylene oxidized to a prescribed degree on a surface thereof contiguous to the water-soluble film. The outer-layer-film and the intermediate layer adhere fast to each other. The intermediate layer and the water-soluble film directly contact each other and adhere so weakly to each other as to be peelable.

Laminated Film Claims
What is claimed is:

1. A bag comprising at least one laminated film, said at least one laminated film being formed in the shape of a bag opened on one side thereof;

wherein said at least one laminated film comprises:

an outer film including at least one layer;

a water-soluble film; and

an intermediate film interposed between said outer film and said water-soluble film;

said outer film and said intermediate film are adhered fast to each other;

said intermediate film and said water-soluble film directly contact each other and are adhered weakly to each other so as to be peelable from each other;

said outer film, said intermediate film and said water-soluble film are superposed with respect to each other so that said water-soluble film is positioned inside of said outer film;

portions of the laminated film are heat-sealed so that parts of said water-soluble film that face each other at the heat-sealed portions are fused to each other;

a non-heat-sealed portion enclosed by heat-sealed portions formed in an outside area that is outside of a heat-sealed portion that encloses an area of the laminated film for accommodating a commodity in a sealed condition including after said intermediate film and said water-soluble film have been peeled from each other;

perforations formed in said outside area for excising a part of said outside area;

one end of a boundary line between a non-heat sealed portion and a heat-sealed portion, which are mutually adjoining in said outside areas remaining after the excision of said part of said outside area is disposed at said perforations;

at least a part of a peripheral edge of said non-heat-sealed portion remaining after the excision of said part in said outside area coincides with said perforations, one end of said at least a part of the peripheral edge of said non-heat-sealed portion remaining after the excision being disposed at said boundary line; and

at least a part of a peripheral edge of said heat-sealed portion remaining after the excision of said part in said outside area coincides with said perforations, one end of said at least a part of the peripheral edge of said heat-sealed portion remaining after the excision being disposed at said boundary line.

2. A bag according to claim 1, wherein a portion of said heat-sealed portion remaining after the excision of said part in said outside area has a narrow width.

3. A bag according to claim 1, wherein said intermediate film is an adhesive layer.

4. A package, comprising:

a hermetically sealed bag made of at least one laminated film; and

a commodity placed in said bag;

wherein said at least one laminated film comprises:

an outer film including at least one layer;

a water-soluble film; and

an intermediate film interposed between said outer film and said water-soluble film;

said outer film and said intermediate film are adhered fast to each other;

said intermediate film and said water-soluble film directly contact each other and are adhered weakly to each other so as to be peelable from each other;

said outer film, said intermediate film and said water-soluble film are superposed with respect to each other so that said water-soluble film is positioned inside of said outer film;

prescribed portions of the laminated film are heat-sealed so that parts of said water-soluble film that face each other at the prescribed portions are fused to each other;

a non-heat-sealed portion enclosed with heat-sealed portions formed in an outside area that is outside a heat-sealed portion enclosing an area of the laminated film for accommodating said commodity, said commodity being maintained in a sealed condition in said area of the laminated film including after said intermediate film and said water-soluble film have been peeled from each other;

perforations formed in said outside area for excising a part of said outside area;

5. A package according to claim 4, wherein a portion of said heat-sealed portion remaining after the excision of said part in said outside area has a narrow width.

6. A package according to claim 4, wherein said intermediate film is an adhesive layer.

Patent Information Search Body

Laminated Film Description
BACKGROUND OF THE INVENTION

The present invention relates to a laminated film, a method for the production thereof, a bag and a package both using the laminated film, and a method of the peeling (or separating) thereof.

Heretofore, for the purpose of accommodating agricultural chemicals and other various commodities, bags which are made of a laminated film having the component layers thereof joined by lamination so strongly as to be impossible to peel have been used. The conventional laminated film has for the innermost layer thereof a film (such as, for example, LLD-PE (linear low-density polyethylene) film) that is thermally adhesive (namely heat-sealable) to itself. A commodity is placed in a hermetically sealed bag produced by superposing this laminated film so that the thermally adhesive film is positioned inside, and heat-sealing the prescribed portions of the superposed laminated film so that the parts of the thermally adhesive film facing to each other at the prescribed portions are fused to each other.

As means for enabling commodities to be contained in hermetically sealed bags that are made of the laminated film mentioned above, the two methods called "bag supplying method" and "automatic packaging method" are known. The bag supplying method comprises a manufacturer of bags initially producing bags open in one side from the laminate film mentioned above and a manufacturer of commodities then receiving the supply of these bags, filling the bags with their commodities via the openings thereof, and thereafter occluding the openings of the bags by heat-sealing. The automatic packaging method comprises a manufacturer, for example, of commodities forwarding the laminated film mentioned above through the sequential steps of the process of production of bags such as, for example, superposing the laminated film upon itself, heat-sealing the prescribed portions of the superposed laminated film, and filling the formed bags with their commodities, and finally obtaining hermetically sealed bags accommodating the commodities therein. Irrespectively of the choice between these two methods, automatic machines adapted to automate the steps of manufacture mentioned above have been finding extensive adoption by the manufacturers of commodities. In the case of the bag supplying method, for example, such automatic machines as are capable of automatically filling the bags opened in one side with the commodities and then automatically heat-sealing the openings of the filled bags are used. In the case of the automatic packaging method, such automatic machines as are capable of automating the process of automatic packaging mentioned above are used.

Generally, even when the commodity to be contained happens to be a powdery agricultural chemicals (which is generally diluted with water prior to use), for example, it is directly contained in the bag that is made of the conventional laminated film mentioned above. When a user of the agricultural chemicals opens the bag, the powdery agricultural chemicals is drifted up through the opened side of the bag possibly to be inhaled by the user or suffered to impinge on the user's hands, with the result that the powder will do harm to the user's system. When the user transfers the powdery agricultural chemicals from the bag into a tank for the purpose of diluting it with water, the powdery agricultural chemicals is likewise drifted up and suffered to do harm to the user's system. Even after the agricultural chemicals has been extracted from the bag, the remnant thereof adheres to the inner wall of the bag. If the bag in this condition is discarded among the household rubbish, therefore, it will form a cause for environmental pollution.

For the purpose of safeguarding the environment against this danger, therefore, the practice of containing a given powdery agricultural chemicals in a bag made of a water-soluble film, hermetically sealing this bag, further containing the bag of the water-soluble film accommodating the agricultural chemicals in a bag formed of the conventional laminated film mentioned above, and hermetically sealing the outer bag has been in vogue in recent years. In this case, the bag of the water-soluble film serves as an inner bag and the bag of the conventional laminated film as an outer bag. The reason for using the outer bag in this manner is that the water-soluble film succumbs readily to the degeneration by the ambient condition and possesses no sufficient strength.

When the inner bag and the outer bag are used as described above, the outer bag can be opened without entailing the danger of drifting up the agricultural chemicals and the inner bag containing the agricultural chemicals can be directly placed in a tank and diluted with the water accommodated in the tank (because the inner bag of the water-soluble film dissolves on contact with water), with the result that the composite bag will ensure perfect ease of handling because the agricultural chemicals accommodated therein no longer has the possibility of doing harm to the user's system or jeopardizing the safety of the environment. After the agricultural chemicals has been extracted from the outer bag, absolutely no remnant thereof is adhering to the inner wall of the outer bag. When the outer bag is discarded as it is among household rubbish, therefore, it entails absolutely no problem.

The foregoing remarks hold good not only for the powdery agricultural chemicals mentioned above but also for a granular or liquid agricultural chemicals and other various commodities.

The conventional practice of using both an inner bag and an outer bag, however, incurs a huge cost. This conventional practice of using both an inner bag and an outer bag, for example, requires inner bags to be separately produced and necessitates an extra cost for this production. The operation of placing the inner bag accommodating a given commodity in the outer bag, for example, necessitates the use of new devices at an extra cost of equipment because this operation does not permit use of the aforementioned existing automatic machines which fit the bag supplying method and the automatic packaging method mentioned above.

The idea of preparing a laminated film having an outer-layer-film and a water-soluble film weakly joined to each other in a peelable manner through the adhesive of weak adhesive force (adhesive strength or peel strength) and, in accordance with the conventional bag supplying method or automatic packaging method mentioned above, superposing this laminated film so that the water-soluble film is positioned inside, heat-scaling the prescribed portions of the superposed laminated film so that the parts of the water-soluble film facing to each other a the prescribed portions are fused to each other, thereby forming a hermetically sealed bag, and containing a commodity in this bag is conceivable in the circumstance. Incidentally, the water-soluble film is generally thermally adhesive to itself.

According to this method employing the adhesive, the bag made of the laminated film mentioned above has a double-wall structure consisting of an outer-layer-film functioning as an outer bag and a water-soluble film functioning as an inner bag. The user of the commodity contained in this bag, similarly to the aforementioned composite bag consisting of an inner bag and an outer bag, is only required to peel (or separate) the outer-layer-film to obtain the commodity as contained in the inner bag of the water-soluble film without entailing the danger of drifting up the commodity such as, for example, agricultural chemicals. He is then required to place the inner bag still accommodating the commodity in the tank and dilute it with the water accommodated in the tank (because the bag made of the water-soluble film dissolves on contact with water), with the result that the user will enjoy perfect ease of handling because the commodity accommodated therein no longer has the possibility of doing harm to his system or jeopardizing the safety of the environment.

Since the laminated film mentioned above can be handled during the insertion of a given commodity therein in the same manner as the conventional laminated film, the existing automatic machines and other devices can be used in their unmodified form. The bag incurs no noticeable addition to the cost of production because it obviates the necessity of separately producing inner bags unlike the aforementioned composite bag consisting of an inner bag and an outer bag.

In the method resorting to an adhesive agent, the adhesive agent is not easily obtained as vested with ideal properties for the adhesion contemplated by the method. The product of this method, therefore, has the possibility that the properties of the adhesive and the water-soluble film will vary with the elapse of time because of the reaction between the components of the adhesive and the water-soluble film. The possibility that the outer-layer-film will not be easily peeled off from water-soluble film when the user seeks to use the commodity accommodated in the bag, the outer-layer-film will peel from the water-soluble film before the bag reaches the user, the water-soluble film will sustain pinholes therein, or the water-soluble film will suffer degradation of the water-solubility thereof, therefore, is undeniable. Further, the possibility exists that part of the adhesive will remain on the water-soluble film and go to impair the solubility of the water-soluble film after the outer-layer-film has been peeled from the water-soluble film and the components of the adhesive will react with the components of the commodity such as, for example, agricultural chemicals in the tank accommodating water and degenerate the commodity after the water-soluble film has been dissolved in the water during the use of the commodity.

In the method described above, the user of the commodity accommodated in the bag incurs inconvenience in peeling the outer-layer-film unless the bag is provided with a part which becomes a beginning for peeling the outer-layer-film.

SUMMARY OF THE INVENTION

The present invention has been produced in view of the circumstances mentioned above. The present invention has an object of providing a laminated film capable of producing by the use of existing facilities a bag having a double-wall structure essentially consisting of an outer bag and an inner bag made of a water-soluble film and excelling in the peeling property of the outer bag, a method for producing the laminated film, and a bag and a package both using the laminated film.

The present invention has another object of providing a bag and a package which both have a double-wall structure essentially consisting of an outer bag and an inner bag made of a water-soluble film, permit effective use of the existing facilities for the production thereof, and allows the outer bag film thereof to be easily peeled when the commodity accommodated therein is used, and a method for the peeling thereof.

To solve the problems mentioned above, a laminated film according to a first aspect of the present invention comprises: an outer-layer-film including one or more layers; a water-soluble film; and an intermediate layer interposed between the outer-layer-film and the water-soluble film, the intermediate layer containing high-pressure polyethylene oxidized to a prescribed degree at least on a surface thereof contiguous to the water-soluble film. The outer-layer-film and the intermediate layer adhere fast to each other. The intermediate layer and the water-soluble film directly contact each other and adhere so weakly to each other as to be peelable (or separable ).

The term "fast adhesion" as used herein means the union of two faces with such adhesive force as to render their peeling substantially difficult and the term "weak adhesion" means the union of two faces with such adhesive force as is weaker than that of the fast adhesion mentioned above and is capable of allowing the joined faces to peel.

A laminated film according to a second aspect of the present invention is a laminated film according to the first aspect, wherein the intermediate layer contains an ethylene.cndot..alpha.-olefin copolymer elastomer mixed with the high-pressure polyethylene.

A laminated film according to a third aspect of the present invention is a laminated film according to the first or the second aspect, wherein the carbonyl groups of the oxidized high-pressure polyethylene on the surface of the intermediate layer are bound to the hydroxyl groups of a surface of the water-soluble film.

A laminated film according to a fourth aspect of the present invention is a laminated film according to any of the first through third aspects, wherein the water-soluble film comprises at least one material selected from the group consisting of polyvinyl alcohol, vinyl acetate, vinyl acetate type resin, polyacrylamide, polyethylene oxide, and polyvinylpyrrolidone.

A laminated film according to a fifth aspect of the present invention is a laminated film according to any of the first through the fourth aspects, wherein the water-soluble film has the surface thereof contiguous to the intermediate layer subjected to a corona treatment.

A method for producing a laminated film according to a sixth aspect of the present invention comprises: a step of extruding a melted and thermally oxidized high-pressure polyethylene in the form of a film between an outer-layer-film including one or more layers and a water-soluble film; and a step of compressing and meanwhile cooling the outer-layer-film, the water-soluble film and the film of high-pressure olyethylene.

A method for producing a laminated film according to a seventh aspect of the present invention comprises: a step of extruding a melted and thermally oxidized mixture containing a high-pressure polyethylene and an ethylene.cndot..alpha.-olefin copolymer elastomer in the form of a film between an outer-layer-film including layers and a water-soluble film; and a step of compressing and meanwhile cooling the outer-layer-film, the water-soluble film and the film of the mixture.

A method for producing a laminated film according to a eighth aspect of the present invention is a method according to the sixth or the seventh aspect, further comprising: a step, performed prior to the step of compressing, of blowing ozone against the surface of the film of high-pressure polyethylene or the film of the mixture destined to contact with the water-soluble film.

A method for producing a laminated film according to a ninth aspect of the present invention is a method according to any of the sixth through the eighth aspects, further comprising: a step, performed prior to the step of compressing, of subjecting the surface of the water-soluble film destined to contact with the outer-layer-film to a corona treatment.

A bag according to a tenth aspect of the present invention is made of at least one laminated film set forth in any of the first through the fifth aspects. The at least one laminated film is formed in the shape of a bag opened on one side. The at least one laminated film is superposed so that the water-soluble film is positioned inside. Prescribed portions of the superposed laminated film are heat-sealed so that the parts of the water-soluble film facing to each other at the prescribed portions are fused to each other.

A package according to a eleventh aspect of the present invention comprises a hermetically sealed bag made of at least one laminated film set forth in any of the first through fifth aspects; and a prescribed commodity placed in the bag. The at least one laminated film is superposed so that the water-soluble film is positioned inside. Prescribed portions of the superposed laminated film are heat-sealed so that the parts of the water-soluble film facing to each other at the prescribed portions are fused to each other.

A package according to a twelfth aspect of the present invention is a package according to the eleventh aspect, wherein perforations for tearing are formed in the heat-sealed portion of the package.

A package according to a thirteenth aspect of the present invention comprises: a hermetically sealed bag made of at least one laminated film set forth in any of the first through the fifth aspects, the water-soluble film not being formed on prescribed edge portions of the outer-layer-film; and a prescribed commodity placed in the bag. The at least one laminated film is superposed so that the water-soluble film is positioned inside and that the edge portions are shifted and faced to each other. Prescribed portions of the superposed laminated film are heat-sealed so that the parts of the water-soluble film facing to each other at the prescribed portions arc fused to each other.

A package according to a fourteenth aspect of the present invention is a package according to the eleventh aspect, wherein the bag has a non-heat-sealed portion enclosed with the heat-sealed portions and taking no part in accommodating the commodity; and the bag has a notched part for tearing formed in the edge portion corresponding to the non-heat-sealed portion.

A package according to a fifteenth aspect of the present invention is a package according to any of the eleventh through the fourteenth aspects, wherein the commodity is agricultural chemicals, medicament, food, or ground bait.

Here, the inferable basic principle of the weak adhesion in the laminated film according to the first through the fifth aspects will be described below.

In the light of the conventional technical common sense prevalent in the field of laminated films, it is thought that direct adhesion (adhesion in the absence of an adhesive) between high-pressure polyethylene and a water-soluble film is difficult to attain. Absolutely no case of effecting this form of adhesion has ever been reported to date in the field of laminated films. The techniques of lamination include the extrusion lamination in which a plurality of films directly are adhered to each other without using an adhesive, besides the adhesive lamination. However, in the field of techniques of lamination, the extrusion lamination has been established as a technique of attaining fast adhesion of a plurality of films into an integral composite. Absolutely no idea has been conceived of using the extrusion lamination for attaining so weak adhesion of a plurality of films as permits the joined films to be separated by peeling. Absolutely no case of using the extrusion lamination for weak adhesion of a plurality of films has ever been reported. Particularly, absolutely no case of using the extrusion lamination for direct adhesion between a high-pressure polyethylene and a water-soluble film has ever been known.

The high-pressure polyethylene has a repeating unit represented by the following chemical formula (1), having a hydrogen bond, nonpolar in behavior, for the terminal group thereof.

On the other hand, a water-soluble film has the polar group of the form of hydroxyl-OH-- for the terminal group thereof. It is, therefore, thought that the direct adhesion (through no medium such as an adhesive) of the two members under discussion is difficult.

The present inventors, after a study, have found that when the surface of a film including high-pressure polyethylene therein is oxidized, union is attained with adhesive force (peeling force) in accordance with to the extent of the oxidation between high-pressure polyethylene and a water-soluble film.

Specifically, when the high-pressure polyethylene is oxidized, the part of the high-pressure polyethylene that responds to the oxidation becomes a composition represented by the following chemical formula (2). ##STR1##

On the other hand, the substance of the water-soluble film such as, for example, polyvinyl alcohol has a repeating unit represented by the following chemical formula (3) and a chemical structure represented by the following chemical formula (4).

It is, therefore, made possible to generate linkage of relatively weak binding strength between the carbonyl group of the oxidized high-pressure polyethylene and the hydroxyl group of the polyvinyl alcohol as represented by the following chemical formula (5). ##STR3##

This linkage generates adhesive force between the film of the oxidized high-pressure polyethylene and the film of the polyvinyl alcohol and allows direct adhesion of the two films. Since the amount of the carbonyl group in the oxidized high-pressure polyethylene varies with the degree of the oxidation, the adhesive force between the film of the oxidized high-pressure polyethylene and the film of the polyvinyl alcohol can be adjusted by the extent to which the high-pressure polyethylene is oxidized. Since other water-soluble films likewise have a hydroxyl group, the principle described above applies not only to the film of polyvinyl alcohol but also to the other water-soluble films.

It is thought based on the principle described above that in the laminated film according to the first aspect mentioned above, the water-soluble film and the intermediate layer containing high-pressure polyethylene oxidized to a prescribed degree at least on the surface thereof contiguous to the water-soluble film directly contact each other and can adhere so weakly to each other as to permit the joined films to be separated by peeling.

For the layer of the outer-layer-film that approximates most to the intermediate layer in the first aspect mentioned above, for example, it suffices to employ a layer to which the high-pressure polyethylene can be joined by thermal adhesion (that is, a layer to which the high-pressure polyethylene in a molten state is capable of adhering fast). As a result, the fast adhesion can be realized between the outer-layer-film and the intermediate layer.

For the outer-layer-film to be used in the present invention, various outer-layer-films which have been used in the conventional laminated films mentioned above may be employed. More specifically for the outer-layer-film, (1) simple polyester film, (2) simple paper, (3) a composite having polyester film thermally adhered to paper (with the paper on the intermediate layer side), (4) a composite obtained by superposing a polyester film, an adhesive layer, an aluminum foil layer, an adhesive layer, and a polyester film sequentially in the order mentioned and dry-laminating the superposed layer by means of the adhesive layers mentioned above, and (5) a composite obtained by superposing an aluminum-evaporated polyester film (polyester film having aluminum evaporated thereon), an adhesive layer, and a polyester film sequentially in the order mentioned and dry-laminating the superposed layers by means of the adhesive layer mentioned above (with the polyester film on the intermediate layer side), for example, may be employed.

The oxidation of the high-pressure polyethylene may be the oxidation caused by heating the high-pressure polyethylene to an elevated temperature (for imparting a molten state to the high-pressure polyethylene, for example) and enabling the oxygen in the air to induce oxidation owing to the elevated temperature (this oxidation referred to hereinafter as "thermal oxidation"), the oxidation induced forcedly, for example, by blowing ozone thereto (this oxidation referred to hereinafter as "forced oxidation"), or the oxidation due to the combination of the thermal oxidation and the forced oxidation. For example, in the case of the thermal oxidation, the amount of the oxidation can be adjusted by suitably varying the temperature of the high-pressure polyethylene, and in the case of the forced oxidation, the amount of the oxidation can be adjusted by suitably varying the concentration of the ozone.

It has been found that when the mixture of the high-pressure polyethylene with an ethylene.cndot..alpha.-olefin copolymer elastomer is used for the intermediate layer as in the second aspect mentioned above, the adhesive force between the intermediate layer and the water-soluble film can be adjusted by the ratio of combination of the mixture. Further, the mixture thus incorporating the ethylene.cndot..alpha.-olefin copolymer elastomer therein enables the intermediate layer to gain in flexibility. As a result, although the water-soluble film readily expands and contracts, the intermediate layer can follow the expansion and contraction of the water-soluble film, so the possibility that the expansion and contraction of the water-soluble film will induce unintentional peeling or the like between the intermediate layer and the water-soluble film is decreased. A substance which has a similar chemical nature as the ethylene.cndot..alpha.-olefin copolymer elastomer may be used in the place or in addition to the elastomer in the mixture.

The water-soluble film may be formed of various substances as cited in the fourth aspect mentioned above. For example, the water-soluble film may be the film of such a water-soluble synthetic polymer as partially saponified polyvinyl alcohol. A water-soluble polyvinyl alcohol type film, for example, may be used as the water-soluble film. As concrete examples of the water-soluble polyvinyl alcohol type film, partially saponified polyvinyl acetate, or polyvinyl alcohol denatured with maleic acid, itaconic acid or the like. The degree of saponification may be in the range of 70-98 mol % and the degree of polymerization may be in the range of 500-3000. These degrees of saponification and polymerization can be suitably determined in respect of the degree of water-solubility, the strength of the film, and the speed of solution in water.

For example, the water-soluble film may be (1) the film of a partially saponified polyvinyl alcohol not being denatured, (2) the film of polyvinyl alcohol denatured with a carboxylic acid, (3) the film of a denatured polyvinyl alcohol incorporating therein an oxyalkylene group or a cationic group, or (4) the film of a denatured polyvinyl alcohol containing a sulfonic acid group. As a concrete example of the water-soluble film of a denatured polyvinyl alcohol containing a sulfonic acid group, the water-soluble film of a denatured polyvinyl alcohol which is disclosed in JP-A-07-118,407 may be cited. This water-soluble film is produced by forming in the shape of a film a denatured polyvinyl alcohol containing 0.1-20 mol % of a sulfonic acid group-containing unit represented by the following chemical formula (6). ##STR4##

In the chemical formula (6), R.sub.1 is a hydrogen atom or a lower alkyl group, R.sub.2 is an alkyl group, R.sub.3, R.sub.4 and R.sub.5 are each independently a hydrogen atom or an alkyl group, and M is a hydrogen atom, an alkali metal atom, an ammonium group, or an amine.

The water-soluble film may have the surface thereof contiguous to the intermediate layer subjected to corona treatment as in the fifth embodiment mentioned above. The corona treatment is generally means for modifying the surface of a given material, particularly a macromolecular material, by virtue of corona discharge in the air under a pressure of not less than 100 mmHg, generally, under the atmospheric pressure. It is useful for enhancing such properties as adhesion. Since a trace amount of ozone gas is generated by corona discharge when the corona treatment is performed, this ozone gas can be used for causing the forced oxidation of the surface of the high-pressure polyethylene by blowing this ozone gas against the high-pressure polyethylene in a molten state.

For example, the laminated film according to any of the first through the fifth aspects mentioned above can be produced by the methods for production according to the sixth through the ninth aspects mentioned above. These methods for production are based on the technique of extrusion lamination. Since these methods for production use the high-pressure polyethylene in a molten state, the high-pressure polyethylene has a high temperature and, therefore, is subjected to thermal oxidation. The amount of the oxidation by the thermal oxidation is determined by the temperature of the high-pressure polyethylene and the duration of the exposure thereof to the ambient air and the like. Incidentally, in the eighth aspect mentioned above, the blowing of ozone is performed for the purpose of further increasing the amount of oxidation of the high-pressure polyethylene. As the ozone for blowing, the ozone which is generated by the corona treatment mentioned above or the ozone which is produced by an ozone generator may be used.

The bag according to the tenth aspect mentioned above is an example of the bag which is made of the laminated film according to any of the first through the fifth aspects mentioned above. Generally, in the bag supplying method already described, the bag is supplied from a manufacturer of bags to a manufacturer of commodities to be accommodated therein. The package according to the eleventh aspect mentioned above is the product obtained by placing prescribed commodity in a bag similar to the bag according to the tenth aspect mentioned above using the laminated film according to any of the first through the fifth aspects mentioned above except the bag is in a completely hermetically sealed state. The package constitutes itself the final form in which the commodity reaches the consumer thereof. The package according to the eleventh aspect may be a product produced by using the bag of the tenth aspect in accordance with the bag supplying method mentioned above or a product produced by using the laminated film of any of the first through fifth aspects mentioned above in accordance with the automatic packaging method mentioned above.

In the laminated film according to any of the first through the fifth aspects mentioned above, the outer-layer-film and the intermediate layer adhere fast to each other, and the intermediate layer and the water-soluble film directly contact each other and adhere so weakly to each other as to peelable. The package according to the eleventh aspect mentioned above which uses the laminated film, therefore, has a double-wall structure consisting of the outer-layer-film and the intermediate layer (hereinafter collectively referred to as "outer bag film" for the sake of explanation) which adhere fast to each other and act as an outer bag and the water-soluble film which acts as an inner bag. In this structure, the outer bag film and the water-soluble film adhere so weakly to each other as to be peelable. The user of the commodity in the package, therefore, is only required to peel the outer bag film in gaining access to the commodity accommodated in the inner bag of the water-soluble film similarly to the aforementioned composite package consisting of an inner bag and an outer bag. When the commodity happens to be agricultural chemicals, the outer bag does not suffer the commodity to drift up when it is peeled and the inner bag still accommodating the commodity can be placed in a tank and diluted with the water placed in the tank (because the inner bag made of the water-soluble film dissolves on contact with water). This package, therefore, ensures perfect ease of handling because the commodity accommodated therein no longer has the possibility of doing harm to the user's system or jeopardizing the safety.

Since the laminated film according to any of the first through the fifth aspects mentioned above can be handled during the insertion of the commodity therein in the same manner as the conventional laminated film, the existing automatic machines and other devices can be used in their unmodified form. The bag incurs no noticeable addition to the cost of production because it obviates the necessity of separately producing inner bags unlike the aforementioned composite bag consisting of an inner bag and an outer bag.

In the laminated film according to any of the first through the fifth aspects mentioned above, only linkage occurs between the carbonyl group of the oxidized high-pressure polyethylene and the hydroxyl group of the water-soluble film as described above. There is no possibility that the high-pressure polyethylene and the water-soluble film will induce other chemical reactions with the elapse of time. Unlike the laminated film of the type using an adhesive as mentioned above, the present laminated film can obtain stable adhesive force with the elapse of time between the intermediate layer and the water-soluble film due to a sparing possibility of the change of the properties of the high-pressure polyethylene and the water-soluble film with the elapse of time. As a result, there is no possibility that the outer bag film will not be easily peeled off the water-soluble film when the user seeks to use the commodity accommodated in the bag. There is no possibility that the outer bag film will be peeled off the water-soluble film before the bag reaches the user. There is no possibility that the water-soluble film will have pinholes therein. There is no possibility that the water-soluble film will suffer degradation of the water-solubility thereof. Further, since the adhesive force between the outer bag film and the water-soluble film (namely, between the intermediate layer and the water-soluble film) originates in the union of relatively weak binding strength produced between the carbonyl group of the oxidized high-pressure polyethylene and the hydroxyl group of the polyvinyl alcohol as already described, there is no possibility that the components of the intermediate layer remain on the water-soluble film after peeling the outer bag film. As a result, there is no possibility that, after the water-soluble film has been dissolved in water in preparation for use of the commodity such as the agricultural chemicals accommodated therein, the components of the intermediate layer will react with the components of the commodity such as the agricultural chemicals accommodated in the bag to deteriorate the commodity. Since the intermediate layer, unlike the adhesive, can be formed so as to have a relatively large thickness, the intermediate layer additionally functions as a protector against a mechanical shock. In the case of using adhesive, sufficient moistureproofing ability can not be obtained since the adhesive produces pinholes due to a coating. The intermediate layer functions so as to enhance the moistureproofing ability since intermediate layer does not produce such pinholes thereof.

In the package according to the eleventh aspect mentioned above, like that of the fifteenth aspect mentioned above, the commodity accommodated therein is not limited to agricultural chemicals. The commodity accommodated may be other commodities such as, for example, medicament, food, and ground bait. The package may accept still other commodities which are used by placing in liquids capable of dissolving the water-soluble film. It is particularly effective in accommodating such commodities as do harm to the human skin, emit offensive odor, or defile the ambience. The form of the commodity is not limited to powder. The commodity may be a granular substance or a liquid substance. When the liquid commodity is an organic solvent, for example, it has no possibility of dissolving the water-soluble film.

Incidentally, the package according to the eleventh aspect mentioned above compels the user of the commodity accommodated in the bag to experience inconvenience in peeling the outer bag film unless the package is provided with a part which becomes a beginning for peeling the outer bag film. The package according to the twelfth or the thirteenth aspect mentioned above is the case where such a beginning part is formed.

In the package according to the twelfth aspect mentioned above, since the perforations for tearing are formed in the heat-sealed portions, when a part of the heat-sealed portions is torn off along the perforations, the outer bag film and the water-soluble film are stretched in mutually different amounts and consequently the stretched parts of the two films is separated from each other. These stretched parts, therefore, serve as a part which becomes a beginning for peeling the outer bag film.

In the package according to the thirteenth aspect mentioned above, the prescribed edge portions of the outer-layer-film on which the water-soluble film is not formed are sifted and faced to each other, and therefore these portions do not adhere to each other. Thus, these portions function as a part which becomes a beginning for peeling the outer bag film.

In the package according to the fourteenth aspect mentioned above, when a part is torn off from the notched part to the non-heat-sealed portion enclosed with the heat-sealed-portions and taking no part in accommodating the commodity, the outer bag film and the water-soluble film are stretched in mutually different amounts and consequently the stretched parts of the two films are separated from each other. These stretched parts, therefore, serve as a part which becomes a beginning for peeling the outer bag film.

A bag according to a sixteenth aspect of the present invention is made of at least one laminated film. The at least one laminated film is formed in the shape of a bag opened on one side thereof. The at least one laminated film comprises: an outer-layer-film including one or more layers; a water-soluble film; and an intermediate layer interposed between the outer-layer-film and the water-soluble film. The outer-layer-film and the intermediate layer adhere fast to each other. The intermediate layer and the water-soluble film directly contact each other and adhere so weakly to each other as to be peelable. The at least one laminated film is superposed so that the water-soluble film is positioned inside. Prescribed portions of the superposed laminated film are heat-sealed so that the parts of the water-soluble film facing to each other at the prescribed portions are fused to each other. A non-heat-sealed portion and a heat-sealed portion are formed in a mutually adjoining state in the area outside a heat-sealed portion enclosing an area of the superposed laminated film destined to accommodate a commodity. One end of the boundary line between the non-heat-sealed portion in the outside area and the heat-sealed portion in the outside area reaches the outer edge of the bag on which the front side part of the laminated film and the rear side part of the laminated film do not continue into each other. A part of the peripheral edge of the non-heat-sealed portion in the outside area, which continues to the boundary line, forms a part of the outer edge of the bag on which the front side part of the laminated film and the rear side part of the laminated film do not continue into each other. A part of the peripheral edge of the heat-sealed portion in the outside area, which continues to the boundary line, forms a part of the outer edge of the bag on which the front side part of the laminated film and the rear side part of the laminated film do not continue into each other.

A bag according to a seventeenth aspect of the present invention is a bag according to the sixteenth aspect mentioned above, wherein a part of the peripheral edge of the heat-sealed portion in the outside area, which confronts the boundary line, forms a part of the outer edge of the bag on which the front side part of the laminated film and the rear side part of the laminated film do not continue into each other.

A bag according to a eighteenth aspect of the present invention is a bag according to the seventeenth aspect mentioned above, wherein, of the part of the heat-sealed portion in the outside area that lies along the boundary line, at least the part thereof which is positioned on the side of the o