JPH08175552A - Packaging bag that is easily torn up for opening - Google Patents

Abstract

PURPOSE: To provide a packaging that can be torn up, when opening is made, starting from a tear tip, in a straight line without giving consideration to ways of pulling the tear tip. CONSTITUTION: Biaxially oriented synthetic resin films 2 and 3 are stuck together with their orientation axes placed being opposite each other, and a laminated body 1 made up by laminating a heat-sealing material layer 5 to one side thereof is folded up with the heat-sealing material layer 5 facing the inside, and a packaging bag that is easily torn up for opening is formed by applying heat sealing to required edges thereof. A surface material layer may be provided at the side opposite to the heat-sealing material layer 5 of the above-mentioned laminated body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging bag made of a biaxially stretched synthetic resin film. In particular, the present invention relates to a packaging bag that can be easily torn linearly from a tear opening regardless of the pulling direction.

[0002]

2. Description of the Related Art It has been conventionally practiced to manufacture a packaging bag using a biaxially stretched synthetic resin film such as polyamide, polyester and polypropylene. The biaxially stretched film is produced by stretching a long synthetic resin film having a constant width formed by a T-die or casting method in a machine direction (longitudinal direction) and a width direction by a tenter method or the like. This biaxially stretched synthetic resin film is subjected to a large stretching force as it moves from the central portion in the width direction to both edge portions during stretching, and as a result, both side edge portions have a higher heat shrinkage ratio than the central portion. However, the difference in the heat shrinkage in two directions of 45 ° to the left and right to the mechanical direction at any point (heat shrinkage in the direction of 45 ° to the machine direction and heat shrinkage in the direction to the right of 45 ° to the machine direction) The difference in the rate (hereinafter, also simply referred to as the difference in the thermal contraction rate in two oblique directions) also shows a phenomenon (so-called bowing phenomenon) that increases as it moves from the central portion to both side edge portions.

The strain due to the molecular orientation of this biaxially stretched synthetic resin film is schematically shown in FIG. That is, the center portion in the width direction of the biaxially stretched synthetic resin film 6 is stretched uniformly in the machine direction and the width direction, but it is stretched unevenly at both side edges of the biaxially stretched synthetic resin film material 6. And the molecules are oriented obliquely to the machine direction. That is, on both side edges of the biaxially stretched synthetic resin film, the orientation axis of the molecular orientation is oblique to the machine direction. Therefore, both side edges have distortion, the difference in the heat shrinkage ratio in the two diagonal directions is large, and the heat shrinkability is non-uniform, so it takes many years to produce a packaging bag from a biaxially stretched synthetic resin film. , Only the central portion in the width direction was used.

The applicant of the present invention has previously used a portion having a large difference in heat shrinkage ratio between the two side edges of the biaxially stretched synthetic resin film in two oblique directions, that is, the orientation axis is oblique to the machine direction. We have developed a packaging bag with good tearability by using existing parts. This packaging bag is composed of a biaxially stretched polyamide film whose both sides of the front and back sides of the packaging bag have a difference in heat shrinkage in the two directions of 45 ° to the machine direction in both directions of 1.0% or more, and the front side. The biaxially stretched polyamide film and the biaxially stretched polyamide film on the back surface are oriented so that their orientation axes are opposite to each other. This packaging bag can be easily torn linearly from the tear opening by arranging the side having the larger difference in heat shrinkage so as to be inward with respect to the tearing direction (JP-A-63).
-96066). In addition, the distortion of the orientation axis of the front surface and the back surface of the packaging bag is opposite, that is, a packaging bag made of a stretched plastic film whose orientation axis is in the opposite direction, when the surface has a strain in the direction opposite to the "no" shape. Pull the right side to the front and the left side to the rear. It has been proposed to mark the tear opening (Japanese Patent Publication No. 4-319).
No. 41).

[0005]

As described above, in a packaging bag made of a biaxially stretched synthetic resin film having a conventional orientation axis as described above, it is necessary to pinch the tear opening and tear the bag. It could not be torn well without consideration. Therefore, the tearing method of the packaging bag is marked. The present invention, for a packaging bag composed of a biaxially stretched synthetic resin film having an orientation axis, when tearing from the tear opening, without considering the way of pulling, i.e. when tearing by gripping the tear opening with the hand, the right side is the front direction. To pull the left side backward,
Another object of the present invention is to provide a packaging bag which can always be easily torn linearly from the tear opening regardless of how the user pulls the left side toward the front and the right side toward the rear.

[0006]

Means for Solving the Problems That is, according to the present invention, two biaxially stretched synthetic resin films are laminated so that their orientation axes are in mutually opposite directions, and a thermal adhesive layer is laminated on one surface thereof. It is a packaging bag with good tearability, which is obtained by folding a body so that the heat-adhesive layer is on the inside and heat-bonding the required edges to form a bag. In addition, the above-mentioned laminated body is a laminated bag having a surface material layer on the surface opposite to the heat-adhesive material layer, which is a packaging bag having good tearability.

The present invention will be described in detail. First, the laminate used for manufacturing the packaging bag of the present invention will be described.
FIG. 1 shows a cross-sectional view of a laminate according to the present invention. 1 is a laminated body used for manufacturing the packaging bag of the present invention, 2 is a biaxially stretched synthetic resin film layer (A), 3 is a biaxially stretched synthetic resin film layer (B), 4 is an adhesive layer, and 5 is heat bonding. It is a material layer (sealant layer). The above-mentioned biaxially stretched synthetic resin film is obtained by forming a film of polyamide, polyester, polypropylene or the like and then stretching it in the biaxial direction. This biaxial stretching is performed using a tenter or the like in the machine direction (longitudinal direction) and the width direction. The biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. FIG. 2 schematically shows the state of strain due to the molecular orientation of the biaxially stretched synthetic resin film material 6. Due to the bowing phenomenon described above, the central portion in the width direction of the biaxially stretched synthetic resin film material 6 has a uniform molecular orientation in the machine direction and the width direction and has little distortion, but the side edge portion of the biaxially stretched synthetic resin film material 6 is mechanical. The molecules are oriented obliquely with respect to the direction and the strain is large.

The two biaxially stretched synthetic resin films used in the present invention are, for example, films on both side edges of the biaxially stretched synthetic resin film material 6 shown in FIG. In FIG. 2, the orientation axis of the left side edge is diagonally right with respect to the machine direction, and the orientation axis of the right side edge is diagonally left with respect to the machine direction. In the present invention, 2 having this orientation axis is used.
A sheet of biaxially stretched synthetic resin film is laminated so that the respective orientation axes are in mutually opposite directions. For example, the left side edge portion (A) of the biaxially stretched synthetic resin film in FIG. 2 is cut off, and the right side edge portion (B) of the biaxially stretched synthetic resin film is cut.
Is cut off, the right side edge (B) of the biaxially stretched synthetic resin film is superposed on the left side edge (A) in a state where the right side edge (B) is moved to the left, and bonded with an adhesive. In FIG. 1, 2 is a left side edge portion (A) of the biaxially stretched synthetic resin film, and 3 is a right side edge portion (B) of the biaxially stretched synthetic resin film. 4 is an adhesive. Of course, these 2 and 3 may be reversed.

FIG. 3 is a plan view schematically showing the direction of the orientation axis of each of the cut films described above by a solid line. FIG.
Is a solid line schematically showing the direction of the orientation axis of each film when both films are laminated and adhesively laminated. An isocyanate adhesive is used as the adhesive 4 when laminating the biaxially stretched synthetic resin films 2 and 3. It is preferable that the two layers of the biaxially stretched synthetic resin film are directly adhered to each other via an adhesive, but the two layers of the biaxially stretched synthetic resin film may have another laminated material interposed therebetween. Good. Also, in the above, two films were cut and laminated, but for example, one film of a predetermined size is cut from the left edge portion (A) of the biaxially stretched synthetic resin film, and this is folded in two, The inner sides may be laminated with an adhesive agent.

The laminated body 1 of the material for making the packaging bag of the present invention is provided with a thermal adhesive layer 5 for making a bag. This thermal adhesive layer 5 is made of low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, polypropylene, ethylene-propylene copolymer. Such as coalescing. The thermal adhesive layer 5 may be formed by forming a film of these polymers and adhering them to a laminate with an adhesive such as an isocyanate, or by melt-extruding these polymers on the laminate. It may be formed directly. Moreover, you may provide a surface material layer in the laminated body on the surface opposite to a thermal-adhesive material layer as needed. Polyvinylidene chloride, cellophane, aluminum, etc. are used for the surface material layer.

The packaging bag of the present invention is manufactured by folding the above-mentioned laminated body with the heat-adhesive material layer inside, for example, folding it in two along the dotted line in FIG. To do. Further, the above-mentioned laminated body may be folded in three so that an overlapping portion may be formed, and the overlapping portion and the bottom portion may be heat-bonded to manufacture a packaging bag. Further, a so-called notch may be provided in the tear opening, and a mark indicating that there is a tear opening may be provided to facilitate the tearing operation.

[0012]

[Function] Conventionally, the front and back sides of a packaging bag are made of biaxially stretched synthetic resin films having an orientation axis oblique to the machine direction, and the orientation axes of the front and back biaxially stretched synthetic resin films are opposite to each other. 3B, that is, the biaxially stretched synthetic resin film (A) in the molecular orientation state of (A) in FIG. 3 is on the front side, and the biaxially stretched synthetic resin film (B) in the molecular orientation state ( A packaging bag is known in which B) is laminated on the back side and the necessary edges are heat-bonded. In this conventional packaging bag, when the tear opening is pinched with both hands and pulled, depending on the direction of the orientation axis of the biaxially stretched synthetic resin film (A) on the front side, the pinched right hand is pulled forward or the pinched left hand is pulled. If you don't pull it either way, either way, you cannot tear it straight. This is because the orientation axis of the film on the front side is opposite to the orientation axis of the film on the back side.

The packaging bag of the present invention comprises two biaxially stretched synthetic resin films laminated so that their orientation axes are in mutually opposite directions, and a thermal adhesive layer is laminated on one side of the laminated body. Alternatively, since it is made into three folds and the necessary edges are heat-bonded to form a bag, when the packaging bag of the present invention is torn by pinching the tear opening, a biaxially stretched synthetic resin film having different orientation axes. Therefore, the influence of the orientation axis of each film on the tearing direction is mitigated, the orientation of the orientation axis of the biaxially stretched synthetic resin film on the front and back sides is eliminated, and the tear opening is When pinching and tearing with, it is not necessary to decide the tearing method by considering the direction of the orientation axis of the biaxially stretched synthetic resin film on the front side as in the case of tearing the conventional packaging bag described above, and the right side is the front side. Countercurrent, be pulled to the left in the rear direction, or the left side toward the front side, even by pulling the right side to the rear direction, it is possible to linearly easily torn from always tear opening. As described above, the present invention is useful for a packaging bag using a biaxially stretched synthetic resin film having an orientation axis, for example, films on both side edges in the width direction of a biaxially stretched film material as a raw material. Since the film near the widthwise central part of the biaxially stretched film fabric is almost uniformly oriented and has no orientation distortion,
When manufacturing a packaging bag using the film in the vicinity of the central portion in the width direction, particularly without applying the technique of the present invention,
A packaging bag is obtained which can be easily torn straight from the tear opening.

[0014]

EXAMPLES The present invention will be described below with reference to examples. Example Using a normal T-die, the formed polyamide film was biaxially stretched 2.5 times in the longitudinal direction and 3 times in the transverse direction to give a width of 4
A film having a thickness of 000 mm and a thickness of 15 μm was used. With respect to this polyamide film, the heat shrinkage in the direction of 45 ° to the left and right with respect to the machine direction was measured while shifting from the center in the width direction to the left side surface. 1200 mm to the left of the film center
The heat shrinkage in the direction of 45 ° to the right and 4.5% in the direction of the machine direction, and the heat shrinkage in the direction of 45 ° to the left were 1.2%, and the difference was 3.3%. Met. At this site, the molecules are oriented to the right 45 ° to the machine direction,
It means that there is an orientation axis in that direction. Further, the heat shrinkage rate in the direction of 45 ° to the left in the machine direction is 4.4% at a position 1200 mm to the right from the center of the film.
The heat shrinkage in the right 45 ° direction was 1.2%, and the difference was 3.2%. At this site, it means that the molecules are oriented in the direction of 45 ° to the left with respect to the machine direction, and the orientation axis is in that direction. Then, a film having a size of 170 mm in the width direction and 120 mm in the machine direction was cut around a part distant by 1200 mm on the left side from the center part in the width direction, which is a measurement part on the left side of the film. Similarly, a film having a size of 170 mm in the width direction and 120 mm in the machine direction was cut around a part 1200 mm left from the center in the width direction, which is the measurement part on the right side.

The two cut films were arranged so that their orientation axes were in opposite directions, and bonded and laminated using a polyurethane adhesive composed of diisocyanate and polyol. Then, an aluminum foil of 9μ and a polyester film of 12μ were laminated on the surface thereof. Further, an unstretched polypropylene film having a thickness of 50 μ was laminated on the back surface as a thermal adhesive layer. This laminated body was folded in two along the machine direction with the unstretched polypropylene film layer inside, and three peripheral portions were heat-bonded to produce a packaging bag. This packaging bag can be torn in a straight line regardless of which way you tear it, whether you pull the pinched right hand toward you or pull your pinched left hand toward you when you tear it by pinching the tear opening. It was The heat shrinkage ratio is a heat shrinkage ratio measured by boiling a polyamide film at 100 ° C. for 30 minutes.

[0016]

EFFECTS OF THE INVENTION A packaging bag made of a conventional biaxially stretched synthetic resin film having an orientation axis has a tearing direction depending on the orientation axis of the biaxially stretched synthetic resin film on the front side of the packaging bag when the tear opening is pinched and torn. When I made a mistake in the tearing direction, I could not tear it straight from the tear opening. A packaging bag made of a biaxially stretched synthetic resin film having an orientation axis of the present invention is a biaxially stretched synthetic resin on the front side, as in the case of tearing the conventional packaging bag described above, when tearing by gripping the tear opening with both hands. It is not necessary to decide the tearing method by considering the orientation axis of the film.Tearing is always performed even if the right side is pulled forward and the left side is pulled backward, or the left side is pulled forward and the right side is pulled backward. It has the special effect that it can be easily torn straight from the mouth.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a laminate constituting a packaging bag of the present invention.

FIG. 2 is a schematic diagram showing orientation distortion of a biaxially stretched synthetic resin film.

FIG. 3 is a schematic diagram showing orientation distortion of a biaxially stretched synthetic resin film used for the packaging bag of the present invention.

FIG. 4 is a schematic diagram showing the orientation strain of two laminated biaxially stretched synthetic resin films used in the packaging bag of the present invention.

[Explanation of symbols]

1 laminated body which comprises the packaging bag of this invention, 2 biaxially stretched synthetic resin film, 3 biaxially stretched synthetic resin film, 4
Adhesive, 5 heat adhesive, 6 biaxially stretched synthetic resin film cloth

Claims (2)

[Claims] 1. A laminated body in which two biaxially stretched synthetic resin films are laminated so that their orientation axes are in mutually opposite directions, and a thermal adhesive layer is laminated on one surface of the laminated film. A wrapping bag with good tearability that is folded so that the required edges are heat-bonded. 2. The packaging bag with good tearability according to claim 1, wherein the laminated body is a laminated body having a surface material layer provided on the surface opposite to the thermal adhesive material layer.