Patent Publication Number: US-2005141788-A1

Title: Self-standing bag and method of manufacturing the bag

Description:
TECHNICAL FIELD  
      The present invention relates to a self-standing bag having a spout, and more particularly to a self-standing bag that is flexible and has good self-standing performance and high fixing strength of the spout, and also to a method of manufacturing the self standing bag.  
     BACKGROUND ART  
      Conventionally, self-standing bags for fluids in which a liquid is filled have been used mainly for refilling use, and little attention has been paid to the self-standing performance. Therefore, when the amount of the content has been decreased, the conventional self-standing bag loses its self-standing function because of bending at the upper portion of the bag. Particularly, a self-standing bag for a fluid may have a spout for pouring the content. In such a case, the upper portion of the bag becomes heavy and the self-standing performance may be considerably injured. In addition, the conventional self-standing bag having a spout has been formed by a method in which peripheral edges of a bag body are sealed by fusion bonding, the spout is separately molded, and the molded spout is manually inserted between sheets constituting the bag body to fusion bond to the inner surfaces of the sheets, thereby attaching the spout to the bag. Such a manual operation not only affects the mass-productivity, but also renders the fusion bonding between the spout and the sheets unsatisfactory, resulting in an insufficient strength of the bag body. On the other hand, molded vessels naturally have a sufficient self-standing performance, but they cannot be reduced in size by folding at the time of disposal.  
     DISCLOSURE OF INVENTION  
      It is an object of the present invention to provide a self-standing bag which maintains the self-standing performance until the content is used up, can be reduced in volume by folding in case of disposing of the bag, and has a high fixing strength of a spout, and a method of manufacturing such a self-standing bag.  
      According to the present invention, there is provided a self-standing bag comprising a bag body composed of two body films and a bottom film folded down in a reverse V-shape at the bottom portion, and a spout at an upper portion of the bag body, said bag body having fusion bonding parts at the lower edges and at least a part of each side edge to which the bottom film is present so that at least the bottom film is fixed with each body film, and a frame of a reverse-recessed shape integrally molded with the spout being attached from the upper edge to each side edge of the bag body. It is preferred that the frame is provided at each side edge to which the fusion bonding part is present so that a part or the whole of the fusion bonding part at each side edge is left, or provided so that the outer surface of each edge is covered with the frame.  
      The present invention also provides a method of manufacturing the above self-standing bag comprising the steps of joining by fusion bonding the lower edges and at least a part of each side edge to which the bottom film is present so that at least the bottom film is fixed with two body films, and then attaching the frame to the bag body so that the spout is integral with the frame, thereby preparing the self-standing bag having the spout.  
      The inventive self-standing bag comprises a bag body composed of two body films and a bottom film folded down in a reverse V-shape at the bottom portion, and a spout at an upper portion of the bag body, said bag body having fusion bonding parts at the lower edges and at least a part of each side edge to which the bottom film is present so that at least the bottom film is fixed with both the body films, and a frame of a reverse-recessed shape integrally molded with the spout being attached from the upper edge to each side edge of the bag body. Accordingly, the parts of the frame present at each side edge of the bag body constitute so-called ribs to the bag body and function as supports of the bag body, thereby improving the self-standing property of the bag body. Although the spout is provided at the upper portion of the bag body, the self-standing performance can be sufficiently maintained until the content is completely used up. In addition, since the spout is integrally molded with the frame, the bag is excellent in the attachment strength of the spout. Moreover, a variety of spouts can be easily attached securely.  
      The spout can be integrally molded simultaneously upon molding the frame. The spout may be preliminarily molded and the thus molded spout may be integrated with the frame by in-mold molding upon molding the frame. The fusion bonding parts can be formed at parts of the side edges to which the bottom film is not present, the lower edges, the lower corners (i.e., lower semi-arcuate fusion bonding parts, etc.) or the like in addition to parts of the side edges to which the bottom film is present.  
      The frame in the present invention may be attached to the bag body so as to extend over the entire length of the range from the upper edge to both side edges of the bag body, as will be described later. However, when the frame is attached to the bag body at a part of each side edge to which the fusion bonding parts is present so that a part or the whole of each fusion bonding is left, the self-standing performance can be assured by spreading the bottom film, and the amount of the resin used for molding the frame can be reduced, thereby leading to a lighter weight. In addition, the parts the bag body free of the frame become easier to fold, and the bag becomes easier to scrap. Therefore, such a configuration is preferable.  
      When the frame is attached so that the outer surface of each edge of the bag body is covered with the frame, the joint strength of the upper edge and both side edges of the bag body can be reinforced. This configuration is also preferable.  
      In the method of manufacturing the self-standing bag, the films constituting the bag body are formed as a self-standing shape. And the lower edges and at least a part of each side edge to which the bottom film is present are joined by fusion bonding so that at least the bottom film is fixed with the two body films, and thereafter the frame is attached to the bag body so that the spout is integral with the frame, thereby preparing a self-standing bag having the spout. Accordingly, even when the lower edges and only the lower parts of the side edges are fusion bonded so that only the bottom film is fixed to the body films of the bag body in the manufacture of the self-standing bag according to the present invention, the upper edge which is an unjoined edge and the unjoined parts of the side edges can be joined with the frame upon the attachment of the frame to the bag body, thereby obtaining a self-standing bag having the spout. Even when the bag body is formed in such a weak joining strength as that the parts except the lower parts of the side edges barely keep the bag shape, the attachment of the frame can reinforce the joining strength, thereby easily and surely joining the edges of the bag body. More specifically, the bag body may be formed completely or incompletely into a bag shape so long as the bottom film is fusion bonded. It is preferred as the method of manufacturing the self-standing bag according to the present invention to use the bag body completely formed into a bag shape, whereby the resulting self-standing bag becomes excellent in strength. The attachment of the spout and the frame is conducted more easily and surely.  
      The formation of the frame and the attachment and joining of the frame is preferably conducted by injection molding a resin. In this case, it is desirable to integrally mold the spout simultaneously with the frame or to integrally attach the previously molded spout with the frame.  
      The self-standing bag according to the present invention is flexible and has good self-standing performance, so that the bag functions as a self-standing packing bag and fulfills the self-standing performance until the contents are completely consumed upon use in spite that the spout is attached, and the bag can be disposed by rolling up the bag with a reduction in volume after the completion of use. Further, the self-standing bag is high in fixing strength of the spout to the bag. It is also possible to reinforce the joining strength. Therefore, the self-standing bag according to the present invention is easy to use, is excellent in strength as a packing bag, and is easy to reduce in volume in case of disposing the bag after the completion of use, which is suited to environmental protection. According to the method of manufacturing the self-standing bag of the present invention, the self-standing bag having the above-mentioned characteristics and particularly having an excellent seal strength of the bag body can be manufactured easily and securely. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       FIG. 1  is a schematic perspective view of a self-standing bag for illustrating an embodiment of configuration of the self-standing bag according to the present invention.  
       FIG. 2  is a schematic front view of the bag body obtained by the first step illustrating an embodiment of the method of manufacturing the self-standing bag according to the present invention.  
       FIG. 3  is a schematic front view of the self-standing bag obtained by the second step of the above manufacturing method. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      The present invention will be described more in detail below, referring to the drawings.  FIG. 1  illustrates one embodiment of configuration of the self-standing bag according to the present invention, and is a schematic perspective view showing the condition where the self-standing bag  1  is expanded. The self-standing bag  1  has a spout  3  at an upper edge of a bag body  2 . A frame  4  having a reverse-recessed shape which is integrally molded with the spout is attached ranging from one side edge  2   a  through the upper edge  2   b  to the other side edge  2   a  so as to clamp the edges  2   a,    2   b,    2   a  from the outer sides.  
      The bag body  2  is formed by folding an elongate film in four at the lower portion so as to provide two body films  2   c,    2   c  and a bottom film  2   d  folded down at the bottom portion in a reverse V-shape, then, as will be described later, joining by fusion bonding the side edges  2   a,    2   a  of the body films  2   c,    2   c,  and fusion bonding the folded portion parts in semi-arcuate shapes to form lower semi-arcuate fusion bonding parts  2   e,    2   e,  thereby forming a bottom portion. The bag body  2  is reinforced in strength of the bottom portion and in self-standing property by the lower semi-arcuate fusion bonding parts.  
      The film (the body films  2   c,    2   c  and the bottom film  2   d ) for forming the bag body  2  can be a monolayer or multilayer film. The film may be the conventional film, but may not necessarily have a fusion-bondability. It is preferable, however, that the film surface which is to become an outer surface of a bag has a good adhesion with a resin to be injected for forming the frame. The multilayer film is a co-extruded film, a laminate film, or the like. An oriented or unoriented polyolefin, nylon, polyester film, or a film for imparting required functions to the resin layer including a co-extrusion type film with a gas barrier layer (EVOH, saran, ceramic vapor deposition, etc.) or a laminate type film thereof is suitably used.  
      The thickness of the film is 20 to 900 μm. From the viewpoint of self-standing property, a thick film is suitable. From the viewpoint of flexibility and light-weightness, a thin film is preferably used. Even a thin film can secure the self-standing property by attaching the frame  4 . In view of moldability and handleability, the film thickness is preferably 60 to 200 μm. The film is not limited to those made of synthetic resin, and may be a monolayer or laminate film of paper or metal foil.  
      The spout  3  is not particularly limited as to shape and size thereof. The spout  3  can have arbitrary shape and size according to the purpose of use of the packing bag. Generally, the self-standing bag with the spout is manufactured by inserting the spout into the upper edge of the self-standing bag by a separate operation using hands or an automatic inserting machine, followed by fusion bonding. Therefore, when the thickness of the spout is large, it is difficult to bond tightly the spout to a spout inserting gate at the upper edge of the self-standing bag body, and the fusion operation involves difficulties in many cases. On the other hand, in the present invention, such difficulties are obviated because the spout  3  is integrally molded with the frame  4 , as will be described later.  
      The frame  4  is integrally molded simultaneously with the spout  3  by, for example, injection molding, or is integrally molded with a previously molded spout  3  in a mold. The resin for forming the spout is not particularly limited, so long as the resin can be injection molded and can be joined to the edges of the bag body  2 . Examples of the resin which can be utilized include not only general-purpose resins such as polyethylene and polypropylene resins but also injectable plastics, e.g., nylon, polyester, etc., a variety of engineering resins, and blends and copolymer resins of these resins with elastomers or the like.  
      The frame  4  is shaped along the portion ranging from one side edge  2   a  through the upper edge  2   b  to the other side edge  2   a  of the bag body  2  composed of a resin film preliminarily molded in a predetermined self-standing bag shape. The frame in the self-standing bag according to the present invention may be a frame  4 ′ shown in  FIG. 3 , in which the frame part along each side edge has such a length as to extend over the whole length of each side edge. Alternatively, the frame may be a frame  4  shown in  FIG. 1 , in which the frame part along each side edge has such a length as to leave the lower portion of each side edge. In this case, the self-standing property and the strength as a bag, which are aimed at in the present invention, can be obtained because the bottom strength and the self-standing property are reinforced by the lower semi-arcuate fusion bonding parts  2   e,    2   e  where the folded portion parts of the film of the bag body  2  are fusion bonded in semi-arcuate shapes, and also by the fusion bonding portions of the side edges.  
      When the length of the frame parts corresponding to the side edges  2   a,    2   a  is so set as to leave the lower portions of the side edges  2   a,    2   a,  the length of each corresponding part of the frame  4  is desirably not less than 60%, particularly not less than 80%, based on the whole length of each side edge. If the corresponding parts of the frame  4  are too short, the effects of the present invention may be insufficient. It should be noted that when only the lower portions of the side edges  2   a,    2   a  are fusion bonded so that the undersurface  2   f  is formed as will be described later, it is favorable that the frame has such a length that the tip ends of the frame reach at least the upper portions of the fusion bonding parts and the lower portions thereof are left.  
      The frame  4  is not particularly limited in width or thickness. For example, when the frame is so shaped that the parts corresponding to the side edges  2   a,    2   a  are tapered on the tip ends (on the lower portions in the figure) as in the case of the frame  4  shown in  FIG. 1 , the frame  4  is preferably so shaped that, at the parts having a uniform width, the width is 1 to 20 mm, particularly 5 to 10 mm, and the thickness is 1 to 10 mm, particularly 2 to 5 mm. When the frame is generally uniform over the entire part thereof as in the case of the frame  4 ′ shown in  FIG. 3 , it is preferable that its average width and average thickness are in the above-mentioned ranges, respectively. When the width is too small or the thickness is too small, it may be difficult to obtain a sufficient strength of the attachment of the frame to the bag body  2 . When the thickness is too large, the amount of the resin to be used is increased, which is unfavorable from the viewpoint of scrapping property. When the width is too large, it may be difficult for the self-standing bag to have a sufficient inside volume.  
      Next, one embodiment of the method of manufacturing the self-standing bag according to the present invention will be described referring to  FIGS. 2 and 3 .  FIG. 2  is a front view of a self-standing bag formed by a first step, before the attachment of the frame, and  FIG. 3  is a front view of another configuration of the self-standing bag according to the present invention obtained by a second step.  
      In the first step, by the use of an ordinary self-standing bag manufacturing machine, an elongate film for constituting a bag body  2  is folded to have a four-folded part on the lower side into the shape of a self-standing bag having body films  2   c,    2   c  and a bottom film  2   d  folded down to the bottom portion in a reverse V-shape, then the lower edge, one side edge  2   a  and the other side edge  2   a  are joined by fusion bonding such as heat sealing or ultrasonic sealing, and the folded portion parts  2   e,    2   e  of the film are joined by a means such as fusion bonding in semi-arcuate shapes, whereby body films  2   c,    2   c  and the bottom film  2   d  are fixed to manufacture a top-open bag body  2  as shown in  FIG. 2 . In this step, a part of the upper edge  2   b  of the bag body  2  may be fusion bonded, as long as the attachability of the spout is not spoiled, as will be described later.  
      In the joining of one side edge  2   a  and the other side edge  2   a,  only the lower edges and on the lower-end portions of one side edge  2   a  and the other side edge  2   a  may be fusion bonded as long as the body films  2   c,    2   c  and the bottom film  2   d  can be fixed and an undersurface  2   f  can be formed. It is preferable that, as shown in  FIG. 2 , the fusion bonding parts include the intersections of one side edge  2   a  and the other side edge  2   a  with the line indicating the undersurface  2   f  (the joint parts of the bottom film), in view of an excellent strength obtained upon completion of the self-standing bag according to the present invention. In this case, only the parts ranging from about 2/5 times the whole length of each side edge on the upper portion to the lower end of each of the side edges  2   a,    2   a  (arrows  2   g,    2   g  in  FIG. 2 ) may be fusion bonded. Particularly, when the frame is not attached over the whole length of both side edges, as in the case of the self-standing bag shown in  FIG. 1 , the parts of both side edges where the frame is not to be attached must be fusion bonded in advance. It is desirable that the lower semi-arcuate fusion bonding parts  2   e,    2   e  formed for enhancing the self-standing property are also fusion bonded in advance, taking workability into account.  
      In addition, even when one side edge  2   a  and the other side edge  2   a  are preliminarily joined over the entire length thereof, a joint strength comparable to that in the conventional self-standing bag is not specially required; for example, such a joint strength as to maintain a bag shape for the time being may suffice. In this case, however, since the presence of only the frame may not provide a sufficient bond strength of the bottom portion (in the self-standing bag, stress is exerted most heavily on the joint parts of the bottom film); it is preferable that at least the part for forming the bottom face  2   f  is fusion bonded in advance with a sufficient joint strength. When the frame does not extend over the whole length of both side edges as above-mentioned, it is preferable that the parts of both side edges where the frame is not attached are fusion bonded in advance with a sufficient joint strength.  
      In case of the present invention, at least parts of the side edges and the lower edges of the film folded so as to form at least the undersurface as mentioned above are fusion bonded, so that the alignment of the back and face films is facilitated, and the spout and the frame can be integrally molded at accurate positions. In addition, even when a separately-molded spout is used, the spout can be integrally molded with the frame at an accurate position by such a technique as insert molding.  
      In the second step, the film constituting the bag body  2  obtained in the first step is set in an ordinary injection molding machine, the spout  3  is injection molded at a position to be a predetermined upper portion of the film constituting the bag body  2 , simultaneously when the frame  4 ′ is injection molded from a thermoplastic resin extending from the spout so as to cover the outer surfaces (back and face surfaces) of the upper edge  2   b  and both side edges  2   a,    2   a  of the film constituting the bag body  2 , and the frame  4  is joined to the upper edge  2   b  and both side edges  2   a,    2   a  of the bag body  2 , to thereby manufacture the self-standing bag  1 ′ shown in  FIG. 3 .  
      The self-standing bag is filled with contents (not shown) via the spout, whereby it is set into a self-standing shape with the undersurface spread, then the spout is stoppered, and the self-standing bag with the contents therein is stored or transported. Upon use, the contents can be discharged through the spout. The kind of the contents is not particularly limited, and, by appropriately selecting the kinds of materials of the film constituting the bag body and of the spout, it is possible to cope with a wide range of products as the contents. Among the various contents, those having fluidity are preferred. Examples of the fluid contents include liquids, consistency materials, powders, small-diameter solids, etc. The self-standing bag can maintain the self-standing performance until the contents therein are completely used up, because the frame parts along both side edges function as ribs, and can be reduced in volume by folding or crumpling at the time of scrapping. Therefore, according to the self-standing bag of the present invention, there is obtained a flexible container which is compatible with a bottle, a can or the like and which can be fitted into or over a variety of spout.  
      The present invention is not limited to the above-described embodiments. For example, instead of providing the lower semi-arcuate fusion bonding parts, a simple rectilinear lower end fusion bonding parts may be provided. In place of the lower semi-arcuate fusion bonding parts, skew 45° rectilinear fusion bonding parts extending from the joint parts of the bottom film may be provided in addition to the rectilinear lower end fusion bonding parts. Further, a bottom film different from the body films may be used. Thus, various modifications are possible within the scope of the gist of the present invention.  
      As for the spout, a variety of selections can be made. For example, a cap of a screw sealing type or a cap capable of being opened and closed at a hinge may be added, and a spout having a nozzle for taking out the contents by suction may be used.  
      Furthermore, as to the shape of the bag body, variously designed irregularly shaped bags may be adopted, as long as the self-standing function through spreading of the bottom is not spoiled.