Patent Publication Number: US-9850032-B2

Title: Packaging bag

Description:
TECHNICAL FIELD 
     The present invention relates to a multifold packaging bag formed by stacking multiple films and, in particular, to a packaging bag colored with a colorant. 
     BACKGROUND ART 
     Packaging bags formed by forming, into a bag shape, a multifold film formed by stacking multiple films have been proposed as bags for packaging fluid, semifluid, powder, or the like. In such a packaging bag, the films forming the multifold film are unbonded over a wide range and can sideslip with respect to each other in the unbonded range. Thus, even if a pinhole occurs in one film, the other films can remain intact. Even if one film receives a bending stress, the other film can slide and escape. Therefore, such a packaging bag has advantageous effects, including improvements in mechanical properties such as pinhole resistance and impact resistance. 
     For example, Patent Literature 1 discloses a packaging bag and a manufacturing method thereof. This packaging bag is formed by bending a multifold film into a tubular shape and then sealing the edges and has containing space for containing an object to be packaged. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2004-43025 
     SUMMARY OF INVENTION 
     Technical Problem 
     Such packaging bags may be colored using a colorant such as a pigment or dye for the enhancement of design properties, the discovery of a foreign object, or other purposes. However, the colorant may move to and stain the packaged object. 
     As described above, the films forming the multifold film are unbonded over a wide range and thus the mechanical properties are improved. However, when the films forming the multifold film have high blocking properties, a pinhole penetrating through multiple films may occur, or the films may fail to slide and escape. This may result in problems such as the degradation of the mechanical properties. 
     Accordingly, an object of the present invention is to provide a packaging bag that can prevent a colorant contained in a multifold film from staining a packaged object and in which the films forming the multifold film have low blocking properties and thus high mechanical properties can be maintained. 
     Solution to Problem 
     In order to achieve the above object, in a packaging bag formed by forming a multifold film into a bag shape, the multifold film being formed by stacking a plurality of multilayer films, a colorant is contained in a layer of the multilayer films, the layer containing the colorant being not in contact with an object to be packaged. 
     In the packaging bag of the present invention, the colorant is contained in at least one layer except for the layer in contact with the containing space. Accordingly, the layer containing the colorant does not contact the packaged object, thereby preventing the colorant from moving to the packaged object. 
     In the packaging bag of the present invention, the colorant is preferably contained in at least a layer of one of adjacent two multilayer films forming the multifold film, the layer being in contact with the other multilayer film. 
     If the colorant is contained in at least a layer of one of adjacent two multilayer films of the multilayer films forming the multifold multilayer film in the packaging bag, the layer being in contact with the other multilayer film, the blocking properties of the one multilayer film and the other multilayer film can be reduced. 
     Effects of Invention 
     According to the present invention, the layer containing the colorant does not contact the packaged object, thereby preventing the colorant from moving to the packaged object. Thus, it is possible to provide a packaging bag that can prevent a packaged object from being stained by a colorant. Further, if the colorant is contained in a layer of one of adjacent two multilayer films, the layer being in contact with the other multilayer film, it is possible to provide a packaging bag in which the multilayer films have low blocking properties and thus high mechanical properties such as high impact resistance and high pinhole resistance can be maintained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  include diagrams schematically showing the configuration of a packaging bag of an embodiment of the present invention, in which  FIG. 1(A)  is a perspective view of a multifold multilayer film forming the packaging bag;  FIG. 1(B)  is a detailed perspective view of the multifold multilayer film;  FIG. 1(C)  is a perspective view showing an aspect in which the multifold multilayer film is bent into a tubular shape;  FIG. 1(D)  is a perspective view showing a state in which a longitudinal seal is attached to the stacked edge of the multifold multilayer film bent into the tubular shape; and  FIG. 1(E)  is a perspective view of a packaging bag formed by attaching transverse seals to the upper and lower edges of the multifold multilayer film. 
         FIG. 2  is an A-A sectional view of the multifold multilayer film of the embodiment. 
         FIG. 3  is a B-B sectional view of the packaging bag of the embodiment. 
         FIG. 4  is a diagram showing a method for manufacturing the packaging bag of the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Now, an embodiment of a packaging bag and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. 
     In the present embodiment, a packaging bag  1  sealed using envelope seaming will be described as an example. First, the configuration of the packaging bag  1  will be outlined.  FIG. 1  include drawings showing the configuration of the packaging bag  1  of the present embodiment. 
       FIG. 1(A)  is a perspective view of a multifold multilayer film  4 , and  FIG. 1(B)  is a detailed perspective view of the multifold multilayer film  4 . The multifold multilayer film  4  of the present embodiment is formed by flattening a tubular multilayer film formed using a known inflation method and acts as two multilayer films (inner multilayer film  2  and outer multilayer film  3 ) having edges  6  as the boundaries therebetween. More specifically, the multifold multilayer film  4  is formed by cutting off a predetermined-length region from a roll film  5  formed by flattening and winding up a tubular film. Thus, in the multifold multilayer film  4 , the inner multilayer film  2  and outer multilayer film  3  are stacked and connected together at edges  6  serving as the boundaries therebetween. The method for forming a multifold film acting as two multilayer films is not limited to the inflation method, and any other known technologies, including a method of pseudo-bonding two films together by roll press, may be used as appropriate. 
     Subsequently, as shown in  FIG. 1(C) , the multifold multilayer film  4  is bent into a tubular shape, and edge portions  7  and  8  thereof are stacked in such a manner that one edge portion,  7 , covers the other,  8 . Then, as shown in  FIGS. 1(D) and 1(E) , a longitudinal seal  9  is formed in the region in which the edges  7  and  8  are stacked, along the edges  6  in the length direction so that the edges  7  and  8  are bonded together. Further, transverse seals  10  and  11  are formed at upper and lower edges perpendicular to the longitudinal seal  9 , of the tubular multifold multilayer film  4  in such a manner that the transverse seals  10  and  11  cross the longitudinal seal  9 . In this way, the multifold multilayer film  4  is formed into a packaging bag  1  having containing space. An object to be packaged is filled into the containing space in the manufacturing process. While the packaging bag  1  is formed using envelope seaming in the present embodiment, any other methods, including butt seaming, in which edge portions of the inner multilayer film  2  are sealed longitudinally, may be used as appropriate. 
     In the packaging bag  1  thus configured, a colorant is contained in only at least one layer except for the layer in contact with the packaged object (containing space), that is, except for the outermost layer of the tubular multilayer film. Hereafter, the layer configuration of the packaging bag  1  will be described in detail.  FIG. 2  is a sectional view taken along line A-A of the multifold multilayer film  4  shown in  FIG. 1(B) . The multifold multilayer film  4  consists of the inner multilayer film  2  and outer multilayer film  3 , which are connected together and form a tubular shape. The multilayer films  2  and  3  have the connected edges as the boundaries therebetween and each consist of multiple layers. In the inner multilayer film  2 , a first layer  2   c , a second layer  2   b , and a third layer  2   a  are stacked on the unbonded surface S 1  thereof in this order. Similarly, in the outer multilayer film  3 , a first layer  3   c , a second layer  3   b , and a third layer  3   a  are stacked on the unbonded surface S 1  thereof in this order. The first layers  2   c  and  3   c  are formed of a resin having low blocking properties so that the multifold multilayer film  4  can act as two films. Preferred examples of such a resin include one containing an anti-blocking agent. The second layers  2   b  and  3   b  are formed of a base resin so that the multifold multilayer film  4  can exhibit good mechanical properties as a packaging bag. The third layers  2   a  and  3   a  are the outermost layer of the packaging bag and the layer to be contacted with the object to be packaged, respectively, and are formed of a resin which is suitably sealed. The first layers  2   c  and  3   c  and/or second layers  2   b  and  3   b  contain a colorant. Preferably, at least the first layers  2   c  and  3   c  contain a colorant. If the first layers  2   c  and  3   c  contain a colorant, it is possible to prevent the first layers  2   c  and  3   c  from blocking each other at the same time when the packaging bag is colored. Thus, the packaging bag  1  can maintain the good suitability as a multifold bag. Examples of the colorant include a pigment and a dye. As shown in  FIG. 1(C) , by bending the multifold multilayer film  4  into a tubular shape while positioning the inner multilayer film  2  in an inner position, the packaging bag  1  can be formed as a packaging bag which has high pinhole resistance and can avoid the colorant from moving to the packaged object. 
       FIG. 3  is a B-B sectional view of the packaging bag  1  and is a partial sectional view showing a region including the transverse seal  10 , of the packaging bag  1 . Containing space S 2  for containing an object to be packaged is formed between the side of the packaging bag  1  on which the longitudinal seal  9  is formed (hereafter referred to as “the front side”) and the side opposite to the front side (hereafter referred to as “the back side”). 
     The front side consists of the inner multilayer film  2  ( 21 ) and outer multilayer film  3  ( 31 ), and the back side consists of the inner multilayer film  2  ( 22 ) and outer multilayer film  3  ( 32 ). In the regions other than the longitudinal seal  9  and transverse seals  10  and  11 , the inner multilayer film  2  and outer multilayer film  3  are not bonded together and can move (sideslip or contact/separate) with respect to each other. Note that in  FIG. 3 , the unbonded surface S 1  between the inner multilayer film  2  and outer multilayer film  3  is illustrative of the unbonded state. The multilayer films  2  and  3  may be in contact with each other in some or all regions. 
     In the inner multilayer film  2 , the third layer  2   a , the second layer  2   b , and the first layer  2   c  are disposed in this order from the side thereof adjacent to the containing space S 2 . That is, the colorant is contained in the layer (first layer  2   c ) which is not the third layer  2   a , which is in contact with the containing space S 2 . Since the colorant contained in the first layer  2   c  does not move to the packaged object contained in the containing space S 2 , it is possible to prevent the colorant from staining the packaged object. 
     In the outer multilayer film  3 , the first layer  3   c , the second layer  3   b , and the third layer  3   a  are disposed in this order from the side thereof adjacent to the inner multilayer film  2 . That is, the first layer  3   c  adjacent to the inner multilayer film  2 , of the outer multilayer film  3  and the first layer  2   c  adjacent to the outer multilayer film  3 , of the inner multilayer film  2  contain the colorant. For the above reasons, the embodiment of the present invention can reduce the blocking properties of the outer multilayer film  3  and inner multilayer film  2 . Thus, advantageous effects can be obtained, including the maintenance of the high mechanical strengths, such as the high impact resistance and high pinhole resistance, of the packaging bag  1 . While known materials such as an organic synthetic dye (tar dye), natural dye, and inorganic pigment may be used as the colorant as appropriate, an inorganic pigment is preferred in terms of the blocking properties. 
     As shown in  FIG. 2 , the multifold multilayer film  4  comprises two stacked multilayer film formed by flattening the tubular multilayer film whose innermost layers are the first layers  2   c  and  3   c  containing the colorant. Thus, the multifold multilayer film  4  can prevent the colorant from staining the packaged object, as well as can reduce the blocking properties. 
     Next, a method for manufacturing the packaging bag  1  will be described using a case in which it is manufactured using a pillow packaging machine  100  as shown in  FIG. 4 . The following steps are sequentially performed: a first step in which a multifold multilayer film  4  is formed into a tubular shape; a second step in which a longitudinal seal  9  is formed; a third step in which a lower transverse seal  10  is formed; a fourth step in which an object to be packaged W is filled; a fifth step in which an upper transverse seal  11  is formed; and a sixth step in which the boundaries between connected bags are cut. The respective steps will be described below. 
     The first step in which a multifold multilayer film is formed into a tubular shape: a multifold multilayer film  4  obtained from a roll film  5  travels around feed rolls  120  and  121  and is led to a former  112 . A sensor  119  is disposed on the path from the roll film  5  to the former  112 . The sensor  119  detects register marks printed on the multifold multilayer films  4  at predetermined intervals in the length direction so that the multifold multilayer films  4  each having a predetermined length can be fed onto the path in the packaging machine  100  at predetermined time intervals. During the passage through the former  112 , each multifold multilayer film  4  is bent into a tubular body in which the edges  7  and  8  of the bent multifold multilayer film overlap each other. More specifically, the multifold multilayer film  4  in which the first layers  2   c  and  3   c , second layers  2   b  and  3   b , and third layers  2   a  and  3   a  are stacked in this order from the inside, as shown in  FIG. 2 , is bent into a tubular body. Thus, the third layer  2   a  of the inner multilayer film  2  forms the inner surface of the tubular body. The tubular body has a multifold structure in which the outer multilayer film  3  is stacked on the outside of the inner multilayer film  2 , and the first layer  2   c  containing the colorant, of the inner multilayer film  2  and the first layer  3   c  containing the colorant, of the outer multilayer film  3  are in contact with each other. 
     The second step in which a longitudinal seal is formed: at the timing when a multifold multilayer film  4  moves at a predetermined time interval, a longitudinal sealer  113  heat-seals the overlapping edges  7  and  8  of the multifold multilayer film  4  by contacting the contact surfaces thereof with each other or separate them from each other, thereby forming a longitudinal seal  9 . 
     The third step in which a lower transverse seal is formed: after the longitudinal sealer  113  completes the heat-sealing, a squeezing roll  115  is closed to squeeze the tubular body formed from the multifold multilayer film  4 . Then, transversely sealing machines  116  and  117  are closed to form a lower transverse seal  10  in a predetermined position of the flattened tubular body. 
     The fourth step in which an object to be packaged is filled: a predetermined amount of an object W to be packaged is introduced into a hopper  111  and thus filled into the tubular body. 
     The fifth step in which an upper transverse seal is formed: a predetermined length of a yet-to-be-separated packaging bag  1   a , the tubular body and the multifold multilayer film  4  following the tubular body are fed by opening the squeezing roll  115  and transversely sealing machines  116  and  117  and then rotating the feed roll  114 . Then, the transversely sealing machines  116  and  117  are closed to heat-seal a predetermined position, thereby forming an upper transverse seal  11 , as well as forming a lower transverse seal  10  connected to the upper transverse seal  11 , of a subsequent packaging bag located upstream of the path. 
     The sixth step in which the boundary between connected bags are cut: a press/cutter  118  is closed to press the lower transverse seal  10  of the yet-to-be-separated packaging bag  1   a  and the upper transverse seal  11  connected to the transverse seal  10 , then cuts the boundary between both the upper transverse seal  11  and the transverse seal  10 , and drops a packaging bag  1  onto a conveyor  130 . 
     In this way, the packaging bag  1  shown in  FIG. 1(E)  is manufactured. The packaging bag  1  can prevent the colorant from moving to and staining the packaged object W. The packaging bag  1  also has advantageous effects, including the reductions in the blocking properties of the inner multilayer film  2  and outer multilayer film  3  and the maintenance of the high mechanical strengths. 
     While the embodiment of the present invention has been described, the invention is not limited thereto, as a matter of course. Various changes or modifications can be made thereto without departing from the spirit and scope of the invention. 
     For example, the multifold multilayer film does not have to be tubular and may be formed by stacking multiple separate multilayer films. 
     The multifold multilayer film may be a twofold multilayer film, in which two multilayer films are stacked, or may be any other multifold multilayer film, in which three or more multilayer films are stacked. 
     The colorant may be contained in only one multilayer film of the multifold multilayer film, or may be contained in the multiple multilayer films thereof. The colorant may also be contained in only one layer of each multilayer film, or may be contained in two or more of the multiple films. 
     Each multilayer film may consist of two layers or three or more layers. The colorant may be contained in an intermediate layer of a multilayer film. However, in terms of the blocking properties, the colorant is preferably contained in a layer of one of adjacent two multilayer films, the layer being in contact with the other multilayer film. 
     The stacked part of the packaging bag may be formed using butt seaming. The number of seals or the positions of the seals is not particularly limited. For example, three-side sealing or four-side sealing may be used. 
     DESCRIPTION OF NUMERALS 
     
         
           1  packaging bag 
           2  inner multilayer film 
           2   a  third layer 
           2   b  second layer 
           2   c  first layer containing colorant 
           3  outer multilayer film 
           3   a  third layer 
           3   b  second layer 
           3   c  first layer containing colorant 
           4  multifold multilayer film 
           41  front surface of multifold multilayer film 
           42  back surface of multifold multilayer film 
           5  multifold multilayer roll film 
           6  side edge of multifold multilayer film 
           7  overlapping one edge of multifold multilayer film 
           8  overlapping other edge of multifold multilayer film 
           9  longitudinal seal 
           10  lower transverse seal 
           11  upper transverse seal 
           12  tubular body 
           100  packaging machine 
           112  former