Methods for producing a self-supporting bag and package

The present invention provides, at low cost, a self-supporting package which is excellent in heat resistance and can be sterilized at high temperatures and the content of which is drunk through a straw. That is, the present invention provides a self-supporting bag which comprises front and back materials consisting of a composite film having a seal layer and having flexibility, and a bottom material consisting of said composite film and folded in the form of the letter W between the front material and the back material, wherein a straw-thrusting film consisting of said composite film is folded in the form of the letter M between the front material and the back material in inverse direction to the bottom material and provided from one side seal to the other side seal of the self-supporting bag, the straw-thrusting film being heat-welded to either one of the front material and the back material, and further provides a self-supporting package comprising said self-supporting bag which is charged with a content and closed by sealing, wherein a seal part is provided in the upper portion of the bag, said seal part having an unsealed part having a width of 2 mm or more in longitudinal direction including therein the upper edge of the straw-thrusting film and a width in lateral direction within the width of the self-supporting bag.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a self-supporting package particularly for
 beverages and for drinking the content through a straw, and to a method
 for producing the same.
 2. Description of the Related Art
 At present, as beverage containers, mention may be made of cans, glass
 bottles, blown bottles, paper packs and the like, but they have both
 merits and demerits in productivity, handleability, saving of resources,
 refuse disposal, preservation, design and the like. Particularly, the
 paper packs to which straws are attached, are very popular and are
 supplied at a low price, while they have demerits that they lack variety
 in shapes and the content cannot be seen. Recently, soft packaging
 containers in the form of a bag made of laminated films which have
 injection-molded spouts and caps have been developed, and these have been
 provided mainly at the field of foods such as beverage containers of small
 capacity owing to their excellent functions such as preservation, heat
 resistance, saving of resources and reclosability. Such soft packaging
 containers with spouts are disclosed in JP-U-61-137539, JP-U-62-90353,
 JP-U-63-34070, and JP-U-63-171350.
 However, structure of these soft packaging containers with spouts is
 complicated, because a bag formed of laminated film is combined with an
 injection-molded spout in order to assure the excellent functions, and
 naturally they are higher in cost than other containers of the same
 capacity. Furthermore, in the case of beverage containers of small
 capacity, mostly the content is drunk up at one time, and hence the
 functions given thereto are superfluous. Thus, cheaper containers have
 been desired from the point of price of the products as a whole. Moreover,
 the soft packaging containers with spouts are not suitable for contents
 which require sterilization at high temperatures, and containers which are
 not limited in their contents have been desired.
 BRIEF SUMMARY OF THE INVENTION
 The object of the present invention is to provide cheap self-supporting
 packages for drinking the content through a straw which are superior in
 heat resistance and can be subjected to sterilization at high
 temperatures.
 The present invention relates to a self-supporting bag (1) which comprises
 a front material (2) and a back material (3) each consisting of a
 composite film having a seal layer and having flexibility, and a bottom
 material (4) consisting of said composite film and folded in the form of
 the letter V between the front material (2) and the back material (3),
 wherein a straw-thrusting film (6) consisting of said composite film is
 folded in the form of the letter V between the front material (2) and the
 back material (3) in inverse direction to the bottom material (4) and
 provided from one side seal to the other side seal of the self-supporting
 film (1), the straw-thrusting film (6) being heat-welded to either one of
 the front material (2) and the back material (3).
 Furthermore, the present invention relates to a self-supporting package
 comprising said self-supporting bag (1) which is charged with a content
 and closed by sealing, wherein a seal part (7) is provided in the upper
 portion of the bag (1), said seal part (7) having an unsealed part (8)
 measuring 2 mm or more in longitudinal direction including therein the
 upper edge of the straw-thrusting film (6) and a width in lateral
 direction within the width of the self-supporting bag (1).
 Moreover, the present invention relates to a method for producing a
 self-supporting bag which comprises feeding a front material (2) and a
 back material (3) each consisting of a composite film having a seal layer
 and having flexibility so that the seal layers face each other, feeding a
 straw-thrusting film (6) consisting of said composite film between the
 front material (2) and the back material (3) with folding in half so that
 the seal layer faces outside, heat-welding the straw-thrusting film (6) to
 either one of the front material (2) and the back material (3) at a
 narrower than the width of the straw-thrusting film (6) folded in half,
 feeding a bottom material (4) consisting of said composite film between
 the front material (2) and the back material (3) with folding in half so
 that the seal layer faces outside, and carrying out bottom sealing and
 side sealing.
 In addition, the present invention relates to a method for producing a
 self-supporting package which comprises charging said self-supporting bag
 (1) with a content and closing the bag (1) by sealing at a seal part (7)
 provided in the upper portion of the bag (1), said seal part (7) having an
 unsealed part (8) measuring 2 mm or more in longitudinal direction
 including the upper edge of the straw-thrusting film (6) and a width in
 lateral direction within the width of the self-supporting bag (1).

The reference numerals in these figures have the following meanings.
 1: Self-supporting bag; 2: Front material; 3: Back material; 4: Bottom
 material; 5: Opening; 6: Straw-thrusting film; 7: Seal part; 8: Unsealed
 part; 9: Cutting off line; 11: Seal part of straw-thrusting film; 12:
 Bottom seal part; 13: Side seal portion; 14: Sealing hot platen; 15
 Sealing pad; 16: Sealing hot platen.
 DETAILED DESCRIPTION OF THE INVENTION
 The front material (2), the back material (3), the bottom material (4) and
 the straw-thrusting film (6) which constitute the self-supporting bag of
 the present invention each consist of a composite film having a seal layer
 and having flexibility. Preferably, the surface layer thereof consists of
 a polyamide film, a polyethylene terephthalate film or a laminated film of
 them, and the seal layer thereof consists of a polyolefin film, an
 ethylene-vinyl acetate copolymer film or a laminated film of them. When
 barrier property is needed, a film having barrier property such as an
 aluminum foil, an ethylene-vinyl alcohol copolymer film or a laminated
 film of them is provided as an intermediate layer, or aluminum, aluminum
 oxide, silicon oxide or the like is vapor-deposited on the surface layer,
 or polyvinylidene chloride or the like is coated on the surface layer,
 thereby to protect the content.
 Material of the straw-thrusting film of the present invention basically
 consists of the same material as that of the self-supporting bag per se,
 but for easy thrusting of a straw, thickness of the film may be made
 thinner within the range causing no problem in the performance of the bag
 or the surface layer may be omitted as far as no problem is caused in the
 performance. Furthermore, it may be made easier to thrust a straw through
 the straw-thrusting film by making innumerable fine holes through the
 surface layer.
 In the self-supporting bag of the present invention, the position of the
 straw-thrusting film to be inserted is such that the upper edge of the
 straw-thrusting film folded in half is positioned at a distance of 1-50
 mm, preferably 15-30 mm below the upper edge of the self-supporting bag.
 The width of the straw-thrusting film often being folded is 5-40 mm,
 preferably 10-20 mm. The position of the lower edge of the closing seal
 after charging of the content is 1 mm or more above the lower edge of the
 straw-thrusting film and not more than the height of the straw-thrusting
 film and preferably in the range of 3-10 mm. The size of the unsealed part
 in the seal part is such that the lower edge thereof is in the range of
 0-30 mm, preferably 0-3 mm, below the upper edge of the straw-thrusting
 film and the upper edge of the unsealed part is in the range of 2-40 mm,
 preferably 5-10 mm, above the upper edge of the straw-thrusting film.
 According to the self-supporting package of the present invention, since it
 is in the form of self-supporting bag consisting of a composite film, it
 is superior in suitability for the content such as preservation and heat
 resistance and has self-supporting property and variety of the shapes, and
 besides, in some case, the content can be seen. Furthermore, since the
 content can be drunk through a straw, the container per se is not
 complicated and the container can be supplied cheaply.
 Moreover, since sterilization at high temperatures is possible, the
 contents are not limited to only those which are sterilized at about
 85.degree. C. and charged in the soft packaging containers with spouts and
 can be more freely selected, and development of beverages in the new field
 can be expected.
 EXAMPLE
 The present invention will be illustrated below referring to the
 accompanying drawings.
 FIG. 1 and FIG. 2 show one example of the self-supporting bag of the
 present invention. The front material 2, the back material 3 and the
 bottom material 4 formed in the form of the letter V between the front and
 back materials in the self-supporting bag 1 each consist of a polyethylene
 terephthalate film of 12 .mu.m, an aluminum foil of 7 .mu.m, a nylon film
 of 15 .mu.m and a polyethylene film of 60 .mu.m in succession from the
 surface layer toward the seal layer. First, the straw-thrusting film 6
 consisting of a polyethylene terephthalate film of 12 .mu.m, an aluminum
 foil of 7 .mu.m, and a polyethylene film of 40 .mu.m in succession from
 the surface layer toward the seal layer is folded with the seal layer
 facing outside between the front material 2 and the back material 3 in
 such a manner that the film 6 folded in half in the form of the letter V
 just in inverse direction to the bottom material 4 has a height of 15 mm
 and the upper edge thereof is positioned at 20 mm below the opening 5 of
 the upper edge of the self-supporting bag. Then, as shown in FIG. 3, the
 front material 2 and the straw-thrusting film 6 are sealed to give the
 seal 11 which is in the range of from 2 mm below the upper edge of the
 straw-thrusting film 6 to 5 mm above the lower edge of the straw-thrusting
 film 6. Thereafter, between the front material 2 and the back material 3,
 the bottom material 4 is folded with the seal layer facing outside in the
 form of the letter V, and the bottom sealing 12 and side sealing 13 are
 performed to produce the self-supporting bag 1.
 In the self-supporting bag 1 mentioned above, the content is charged from
 the opening 5 formed between the straw-thrusting film 6 and the back
 material 3 which is not sealed to the film 6, and sealing is performed
 using a sealing plate 16 as shown in FIG. 4 to form a self-supporting
 package. As shown in FIG. 5, FIG. 6 or FIG. 7, the seal part 7 has a seal
 height ranging from the upper edge of the self-supporting bag 1 to 5 mm
 above the lower edge of the straw-thrusting film 6. An unsealed part 8 is
 provided in the seal part 7, and the lower edge of the unsealed part 8 is
 positioned at 2 mm below the upper edge of the straw-thrusting film 6 and
 the upper edge of the unsealed part 8 is positioned at 10 mm above the
 upper edge of the straw-thrusting film 6.
 Furthermore, in the self-supporting package, when the bag 1 is sealed for
 closing, a cutting off line 9 which passes through the unsealed part 8 is
 provided at the position of 5 mm above the upper edge of the
 straw-thrusting film 6 in correspondence to the seal part 7.
 In order to make easier to thrust a straw through the straw-thrusting film
 6, thickness of the film 6 can be made thinner so far as no problem is
 caused in the properties of the container, or fine holes can be formed
 through only the surface layer constituting the straw-thrusting film 6.
 Moreover, the film 6 can be composed only of the barrier layer and the
 seal layer by omitting the surface layer.
 The content contained in the self-supporting package of the present
 invention as shown in FIG. 7 can be drunk by cutting off the upper seal
 part at the cutting off line 9, inserting a straw from the unsealed part 8
 and thrusting the straw through the straw-thrusting film 6.