JP2525158B2 - Method for manufacturing easy-open bag - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an easily-openable bag that can be easily opened with the force of fingers.

[Prior Art] In recent years, a plastic film and a laminated film of a plastic and a metal such as aluminum foil, and other materials such as paper are lightweight, have excellent airtightness, high strength, are convenient to handle, and particularly when sealing. Since it does not require an adhesive and only needs to be heat-sealed, it is used as a sealed bag for various types and shapes of foods, chemicals, small items, etc., such as liquids, powders, pastes and solids.

These sealed bags pose the problem that the advantage of the material is resistance to tearing upon opening, which makes it difficult to tear. The film for the sealed bag is tough, but on the other hand, once scratches occur, the scratches tend to propagate, so if you scratch the edge of the bag in one place in advance and pull it as a breakage point, your fingers It can be opened only by force.

For this reason, it has been practiced to previously provide a cut (I notch) having a length of 2 mm or more in the transverse direction or a V-shaped scratch (V notch) at the edge of the film at the fused portion.

[Problems to be Solved by the Invention] However, some of the above-mentioned bags having I-notches and V-notches have many variations and can be easily torn, but those that are caught in the middle of tearing and require considerable force. , There was a problem that it exists in a considerable proportion.

[Means and Actions for Solving Problems] The present invention has been made in view of the above points,
An object of the present invention is to reliably manufacture an easily-openable bag that can be torn securely and easily without tearing during the tearing, regardless of the tearing method.

That is, the present invention has at least one base material layer formed of a thermoplastic resin harder than low density polyethylene and biaxially stretched 1.5 times or more, and at least one heat fusion layer. , A half-folded composite film having a scar penetrating at least the base material layer at an edge portion to be heat fusion bonded,
When making a bag by heat fusion bonding the edge part, when half-folding,
The composite film is selected such that the crossing angle of the orientation lines showing the orientation direction of the base material layer in the front and back composite films is 0 ° to 20 °, and the orientation direction of the base material layer in the front and back composite film is selected. The crossing angle of the orientation line shown is 0 ° to 20
Half-folded in the direction of 0 °, and the edge portion is heat fusion bonded to obtain a bag having the scar on the heat fusion bonded edge portion. Invention) and at least one base material layer formed of a thermoplastic resin harder than low-density polyethylene and biaxially stretched 1.5 times or more, and at least one heat fusion layer, When two composite films having a scratch penetrating at least the base material layer are superposed on the edges to be fusion-bonded, and when the edges are thermofusion-bonded to form a bag, the composite films on the front and back sides are overlapped. Select two composite films in which the crossing angle of the alignment lines showing the alignment direction of the base material layer is 0 ° to 20 °, and select the two composite films, and the alignment direction of the base material layer in the front and back composite films. Aligned with the orientation line crossing angle is 0 ° to 20 °, the edges are heat fused. To a method of manufacturing easily openable bag, characterized by a bag having the scar at the edge portion which is heat-crimped (second invention), there is provided a.

The present invention comprises at least one base layer and at least one base layer.
The easy-open bag is formed by folding a composite film having two layers of heat-sealing layers, or stacking the two composite films, and heat-sealing the edges thereof. The base material layer is formed of a thermoplastic resin that is harder than low density polyethylene.

Here, "harder than low density polyethylene" means that the Shore hardness (JIS Z 2246) is larger than that of low density polyethylene.

Specific examples of the thermoplastic resin that can be used as the base material layer include polyamides (nylons) such as 6-nylon and 66-nylon, polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), and biaxially oriented polypropylene. (OPP), hard vinyl chloride resin, polystyrene, polyacetal, polyvinyl alcohol and the like.

The base material layer is formed by biaxially stretching the thermoplastic resin film by 1.5 times or more in each of the vertical and horizontal directions.

Since such a base material layer is tough, it is naturally difficult to start breaking with the force of fingers.

The heat-sealing layer is formed of a material that is melted by the heat of fusion-sealing. Examples of such materials include low-density polyethylene [high-pressure polyethylene (LDPE), low-pressure linear low-density polyethylene (L-LDPE)], olefin resins such as unstretched polypropylene (unstretched PP), ethylene-acetic acid. Vinyl copolymer (EVA), ethylene-based ionomer (IR), etc. are used. Heat fusion temperature is pressing pressure, pressing time,
80 to 180, depending on the film thickness and type
C., usually 120 to 150.degree. C., and under these conditions, those which are in a molten state or at least a semi-molten state are preferable.

The heat-sealing layer may be formed of the above-mentioned heat-sealable substance alone, and as an anchor coating agent for increasing the adhesive strength, isocyanate-based ones often have excellent properties.

The heat-sealing layer preferably has a tensile strength smaller than that of the base material layer. Further, the heat-sealing layer preferably has a tear resistance higher than that of the base material layer. Here, tear resistance is JIS
Tear resistance for a notched sample measured by the method according to P 8116.

Assuming that the base material layer and the heat-sealing layer are selected from materials having the above strength range, the substrate: heat-sealing layer thickness ratio is 5: 1 to 1:10.
Is preferred. More preferably, the thickness of the base material is 10 to 50 μm, the thickness of the heat-sealing layer is 10 to 100 μm, and the total thickness is 20 to 150 μm because the balance between easy-opening property and bag breaking resistance is good. That is, tearing from the part of the scratch penetrating the base material is facilitated, and due to the presence of the heat-sealing layer at the scratch part, careless and rapid propagation of the tear is suppressed, and care is taken during handling during transportation. It prevents the bag from being broken.

It is preferable to use a film of a resin having both Bayer property, strength and heat resistance such as polyester resin or polyamide resin for the base material layer, or a laminated film containing at least one of these, as a sealed bag applicable to high-level packaging. A laminate of an aluminum foil and a plastic layer or a film in which a metal thin film such as aluminum is formed on a plastic film by vapor deposition, sputtering, ion plating or the like is also preferable as the base material layer having a good barrier property. Also,
For example, a laminated film in which a vinylidene chloride-based barrier layer is further laminated on a plastic layer of polyester, polyamide, polypropylene or the like is also preferable.

The composite film forming the easily openable sealed bag can be manufactured by the following method.

A method of laminating a heat-sealing layer on a base material by a dry lamination method.

 A method of extruding a heat-sealing layer and laminating it on a substrate.

A method of sand laminating a heat-sealing layer on a substrate through an intermediate bonding layer such as polyethylene or unstretched polypropylene.

As the heat-sealing layer used in the dry lamination method (1), LDPE, non-stretched PP, L-LDPE and ethylene ionomer are preferable.

As the heat-sealing layer used in the extrusion lamination method of (1), LDPE film, L-LDPE film, non-stretched EVA film, ethylene ionomer film and the like are preferable.

As the heat fusion layer used in the sand lamination method, LDPE film, L-LDPE film, non-stretched EVA film, and non-stretched PP film are preferable.

The base material layer is 1.5 times or more in both vertical and horizontal directions,
It is preferably stretched 2 times or more, more preferably 3 times or more.

The orientation line showing the orientation direction is obtained by measuring the molecular orientation with a polarized fluorescence spectrophotometer, and defining the direction with the largest orientation and the direction perpendicular thereto as the vertical orientation line or the horizontal orientation line.

In general, the orientation direction does not exactly match the stretching direction in the film production stage. After the thermoplastic resin is melt extruded from the T-die, it is stretched in the MD (Machine Direction) direction and the TD (Transvers Direction) direction. First, looking at the state at the time of extrusion, a uniform thickness is obtained. To do this, the discharge port of the thermoplastic resin is not made uniform.
As shown in the figure, the shape is adjusted to be somewhat distorted. Therefore, although the film-like material discharged from the T-die has a substantially uniform thickness, the discharge speed when discharging the molten resin from the T-die is different in each part of the T-die, and therefore each part of the film is different. The temperature distribution in Fig. 2 is non-uniform, and this also affects the subsequent stretching, and the orientation direction of the stretched film is as shown in Fig. 2 and Fig. 3 in the stretching direction (XX direction, Y direction).
-Y direction).

Here, for example, when a composite film having a film as shown in FIG. 2 as a base layer is made into a bag, a conventional commercially available bag making machine for a three-way seal bag is folded in half to form a heat-sealing layer. Since the stretched film on the front surface side of the bag and the stretched film on the back surface side are in a state where the orientation lines do not coincide with each other, because they are overlapped and sealed on the three sides. Further, such a phenomenon also occurs when a seal bag is manufactured by cutting a composite film original sheet into a separate body without half-folding. That is, since it is necessary to seal the heat-sealing layers inside each other, the film on one side is always inverted and sealed. Therefore, the film on the upper surface of the bag and the film on the lower surface do not have the same orientation direction.

Then, when the orientation direction of the base material layer is different between the upper surface and the lower surface of the bag, the other base material layer interferes with the attempt to tear the base material layer on one side, and the interference effect is The layers are most prominent in the heat fusion portion where the layers are laminated via the heat fusion layer. Therefore, even if an I notch or a V notch is put in the heat-sealed edge of such a bag, the bag will be stuck at the heat-sealed portion, and it will take a larger force to tear it further, and it will not be possible with a large force. When the film is torn, the film on the upper surface and the film on the lower surface are torn in different directions along the respective alignment lines as shown in FIG. 5 in FIG. 5 is a tear part.

The present invention has a great feature in locating the above-mentioned cause of variation in tearability and preventing the occurrence thereof. In the first invention, particularly when half-folded, the base in the front and back composite films is Select a composite film whose crossing angle of the orientation line showing the orientation direction of the material layer is 0 ° to 20 °,
A major feature is that the composite film is half-folded in the direction in which the crossing angle of the alignment lines showing the alignment direction of the base material layers in the front and back composite films is 0 ° to 20 ° C. In the second invention, two composite films are selected such that when they are stacked, the crossing angle of the alignment lines showing the alignment directions of the base material layers in the front and back composite films is 0 ° to 20 °.
A great feature is that the composite films are superposed in such a manner that the crossing angles of the alignment lines showing the alignment directions of the substrate layers in the front and back composite films are 0 ° to 20 °.
In both the first and second inventions, the intersection angle θ0 ° to 15 ° is preferable, and 0 ° to 5 ° is more preferable,
It is more preferably 0 ° to 2 ° or less, and most preferably 0 °, that is, the orientation directions are perfectly matched.

In the present invention, the crossing angle of the alignment line simply means the crossing angle between the straight lines when the alignment line is a straight line, and when the alignment line is a curve (for example, see FIG. 8), at the intersection of the curves. The intersection angle of each tangent line.

When the composite film forming the bag has two or more base layers, it is necessary to arrange so that the orientation lines of all the base layers intersect at an angle of 0 ° to 20 °.

In the second invention, since the crossing angle of the alignment lines can be changed depending on the superposition method of the two composite films, the two composite films are selected in consideration of the superposition method. The following methods are available for superimposing the orientation lines to reduce the crossing angle.

After being biaxially stretched and oriented as shown in FIG. 6, the stretched film is run in the machine direction (machine direction = MD).
Each L is cut so that it can be overlapped with a ₁ and b ₁ and a ₂ and b ₂ in FIG. A method of forming a composite film from the stretched film of 1 above and stacking the composite film.

After being biaxially stretched and oriented as shown in FIG. 7, the stretched film is stretched in the width direction (transverse direction = TD).
To a suitable width so that the crossing angle of the alignment lines becomes the smallest value and can be moved in parallel, or inverted as shown in FIG. A method of forming and stacking films.

In the above method, when the production of the stretched film is in a steady state, the same orientation state appears continuously in the running direction of the stretched film, so that the cutting length can be kept constant and the layers can be superposed. If a composite film is formed and overlapped as possible, the crossing angle can be made approximately 0 °.

In the above method, the orientation direction of the stretched film is checked by a polarized fluorescence spectrophotometer, and the composite film is stretched from each stretched film so that parallel movement or inversion can be performed so that the crossing angle of the orientation line becomes a small value. It is formed and overlaid. When applying the method of (1), when the alignment line is in a constant oblique direction as shown in FIG. 7, for example, the stretched film is cut in half in the width direction, and one stretched film A is transversely cut. Translate to
When laminated as a composite film that can be superposed such that the back surface of B and the front surface of B coincide with each other, the crossing angle between the orientation line of A and the orientation line of B, which are the base material layers of the front and back composite films, is very large. It can be a small value (close to 0 °). Further, in order to apply the method in the case of being oriented substantially symmetrically as shown in FIG. 8, it is possible to cut at the center shown by the broken line and superimpose them with their front surfaces or back surfaces facing each other. When the composite films are formed and overlapped with each other, the crossing angle can be reduced. In the case of the orientation state shown in FIG. 8, the same applies when the first invention is applied and half folding is performed at the center shown by the broken line. Furthermore, in the case of cutting into four or more equal parts in the width direction in the orientation state shown in FIG. 8, it is possible to overlap the front and back surfaces of the stretched films at the symmetrical positions with the center shown by the broken line as a boundary. The crossing angle can be reduced by forming a composite film and stacking it as possible.

In both the first invention and the second invention, a composite film having a scar penetrating at least a base material layer is used for an edge portion to be heat fusion bonded, and the edge portion is subjected to half-folding or superposition as described above. By carrying out the heat fusion bonding of (1), a bag having the scar on the edge portion of the heat fusion bonded which becomes the tear start end is obtained.

The shape and size of the scratch are not limited, but it is preferable that a part of the scratch has an acute-angled (notched) portion so that a notch effect is generated. Further, as shown in FIGS. 9-C and 10-A, it is preferable that the composite film be elongated in a direction perpendicular to the longitudinal direction. 10-A to 10-E are plan views for illustrating the shape of the scar, and FIG. 10-A is a short line having an elongated shape in a direction perpendicular to the longitudinal direction of the composite film. Fig. 10-B shows a triangular scar,
Figure 10-C shows a diamond-shaped (diamond-shaped) scar.
Figure D shows a star-shaped scar, and Figure 10-E shows a dot-shaped scar.

Further, even if the scratches are not punched, they can be provided by pressing, rubbing, tapping with a blade or a grater-shaped tool as shown in FIG.

The tool shown in FIG. 11 and a projection 11 having an elongated cutting edge are provided, and this projection 11 is, as shown in FIG.
It is manufactured by inserting a pseudo-triangular cut 13 into the metal surface 12 and using the base of the pseudo-triangular shape as a central axis to erect a metal portion that is cut and separated from the metal surface 12 and project the protrusion 11. . The cut portion of the metal surface 12 has a recess 14
Remains as. 16 is a ridgeline and 17 is a raised surface.

It is preferable that the surface of the protrusion 11 on the recessed side, that is, the angle of the standing surface 15 with respect to the metal surface is 60 ° or more and 90 ° or less. One or more rows of such protrusions are linearly arranged, and the metal is quenched and used. FIG. 13 is a perspective view of a processing roll 18 having such a protrusion on its circumferential surface.

When the composite film 2 is pressed by the protrusions 11 as shown in FIG. 11, the edge portion of the upright surface 15 acts as a cutting edge, and the upright surface 15
On the side of, the edge portion of the composite film is straightly inserted into the composite film, and the composite film on the side of the raised surface 17 is expanded by the raised surface 17, and as shown in FIG. Straightly, the portion where the raised surface 17 is pushed in is deformed obliquely downward and becomes distorted, and at the same time, has distortion. That is, there will be a part with and without a distortion at the boundary of the cut, and the part with a distortion will remain as internal distortion even when it returns to the almost common state after there is no difference in that step. The strength is reduced by the internal strain, and it has the important effect that it can be easily torn from the boundary between the distorted part and the distorted part with fingers. Moreover, unlike the case of cutting with a normal blade, cracks are formed at both ends of the scar, and this crack gives a large cutting start effect. The process of imparting a scratch with the tool of FIG. 11 as described above is hereinafter referred to as MC process.

FIG. 14 is an explanatory view showing an example of processing the composite film 2 using the processing roll shown in FIG. Processing roll 18
While holding the press roll 19, the press roll 19 rotates in the opposite direction at the same peripheral speed. The composite film 2 passes through the contact portions of both rolls. At this time, the composite film 2 is pressed by the projections 11 of the processing roll 18, and the scratches 6 as shown in FIGS. 9-A, 9-B, and 9-C are arranged. 20 is the original film of the composite film.

The tool for imparting scars is preferably made of a hard material, and in addition to quenched steel, ceramics such as silicon carbide, titanium carbide and silicon nitride can also be used.
Also, after finishing the tool shape with metal material, CVD method, PVD
Those obtained by coating with a thin film of silicon carbide, titanium carbide, or the like by the method are also preferable because they have excellent wear resistance and do not deteriorate in sharpness.

The form of the bag obtained in the first invention is a three-way seal type as shown in FIG. 15, and the form of the bag obtained in the second invention is the sixteenth form.
It is a four-way seal type as shown in the figure. Reference numeral 21 is a vertical thermal fusion bonding portion, and 22 is a horizontal thermal fusion bonding portion.

The position of the scar when the bag is formed may be an end portion that is thermo-compression-bonded, and may be located on the end edge or slightly inward from the end edge. The thermal fusion bonding may be performed up to the edge of the composite film, or may be performed with some unfused portion left on the outer edge side of the thermal fusion bonding portion.

When used as a bag, the composite film used in the present invention has scars on both the front and back edges to be heat fusion bonded over the entire length or locally. When using a mass-production type automatic bag-making filling machine that simultaneously cuts two or more bags while cutting the composite film in the vertical direction, a plurality of rows of scratches are provided in the vertical direction. As shown in FIG. 17, when a group of square-shaped scratches 6 are provided in the vertical and horizontal directions and manufactured by the second invention, it is possible to obtain a four-side sealed bag that can be broken from any of the four sides. it can.

In the bag of the present invention, the position of the scar is within about 5 mm from the edge of the heat-sealed portion of the bag, and the gap between the scars is 1 to 5 mm, and may be arranged in two or more rows.

The site where the scars are to be provided is the site that serves as the edge of the fusion-bonded part, and is preferably 0.5-3 mm inside the edge line.

The scratch group may be one row or a plurality of rows of two or more rows as long as they are substantially on the edge line. When the plurality of rows are provided, the width of the scratch group is preferably within 5 mm, more preferably within 3.5 mm.

Even if the pitch l of the scar as shown in FIG. 9-C is long, the tearing property is exhibited, and the length l can be made long, for example, to about 5 mm.

EXAMPLES Next, the present invention will be described with reference to examples.

Example 1 A polyamide film having a width of 720 mm (Unitika 6 nylon film: emblem thickness 15 μm) obtained by biaxially stretching by a tenter method after extruding from a T-die was stretched and oriented using a polarized fluorescence spectrophotometer for the original fabric. 6 was obtained by investigating the direction of and connecting them with a line. As can be seen from FIG. 6, the same stretch orientation pattern was continuously and repeatedly produced.

The above polyamide film original fabric was cut at a position of 2000 m and a position of 4000 m, and the first half was film A and the latter half was B. Then, the L-LDPE film (Tocello TUX-FC, thickness 25 μm) is formed on the upper surface of A and the lower surface of B by a dry lamination method.
Was laminated to obtain a composite film capable of being heat fusion bonded, and A and B were wound on separate rolls.

Next, roll out A and B from each roll,
The upper surface (L-LDPE surface) of B was overlaid with the lower surface (L-LDPE surface) of B, and an automatic bag-making machine was used to obtain a 3-sided sealed bag with a length of 300 mm, a width of 200 mm, and a seal width of 8 mm (about 2000 bags ).

800 g of tomato ketchup was put into the obtained bag, and the opening was made into a four-side sealed bag under the conditions of 160 ° C. × 1 sec × 2.1 kg / cm ² using a sentinel heat sealer.

MC processing, V notches, and I notches were placed in both side seals to check the tear openability.

There was no difference between those with MC processing, V notch, and I notch, and all could be opened easily without resistance. In addition, it was easy to open without any resistance when tearing from either side.

Comparative Example 1 Polyamide film raw material (Unitika 6 nylon film: emblem thickness 15 μm) with a width of 720 mm obtained by extruding from a T-die and then biaxially stretching by a tenter method was stretched and oriented using a polarized fluorescence spectrophotometer. 6 was obtained by investigating the direction of and connecting them with a line. As can be seen from FIG. 6, the same stretch orientation pattern was continuously and repeatedly produced.

L-LDPE film (Tohcello TUX-FC,
A thickness of 25 μm) was continuously laminated to obtain a composite film capable of being heat fusion bonded.

Divide the obtained composite film 4000 m into half in the longitudinal direction 2000
m rolls A and B were obtained, and two rolls were obtained.

Next, let out A and B from each roll, and L-
LDPE film surfaces are overlaid and length is 30 by automatic bag making machine.
A 3-sided bag with a width of 0 mm, a width of 200 mm, and a seal width of 8 mm was obtained (about 2000
bag).

800 g of tomato ketchup was put into the obtained bag, and the opening was made into a four-side sealed bag under the conditions of 160 ° C. × 1 sec × 2.1 kg / cm ² using a sentinel heat sealer.

MC processing, V notch, and I notch were put on both sides, and tear openability was checked. In both cases, tear resistance is strong and opening is not easy, and the heat and pressure bonding films on the back and front are as shown in FIG.
Each was asymmetrically torn and could not be opened smoothly and easily.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a shape of an opening of a thermoplastic resin discharge port for forming a film, FIGS. 2 and 3 are explanatory views showing a deviation between an orientation direction and a stretching direction of a stretched film, and FIG. The figure is an explanatory view showing the state where the orientation lines of the film on the upper and lower surfaces of the bag do not match when the film is made into a bag, and FIG. 5 shows the tearing state when the orientation lines on the upper surface and the lower surface of the bag do not match. 6A, 6B, 7A, and 8B are explanatory views of a method of reducing the intersection angle of the alignment lines, FIGS. 9 and 10 are explanatory diagrams of a scratch, and FIG. 11 is a tool for giving a scratch. FIG. 12 is an enlarged perspective view of the surface portion of FIG. 12, FIG. 12 is an explanatory view showing the manufacturing process of the tool of FIG. 11, FIG. 13 is a schematic perspective view showing a tool having air as shown in FIG. 11, and FIG. FIG. 15 is an explanatory view showing a state in which scratches are formed by using the tool shown in FIG. 15, FIG. 15 is a perspective view showing a three-way seal bag, and FIG. 16 is a four-way seal bag. Perspective view illustrating, FIG. 17 is a plan view showing a film marked with scar. 1 ... Stretched film, 2 ... Composite film, 3 ... Alignment line, 4 ... I notch, 5 ... Tear part, 6 ... Scratch, 7 ... Composite film width, 8 ... Cutting line, 9 ... … Substrate layer, 10 …… Heat fusion layer, 11 …… Protrusions, 12 …… Metal surface, 13 …… Incisions, 14 …… Dimples, 15 …… Upright surface, 16 …… Ridge line, 17 …… Raised surface , 18 …… Processing roll, 19 …… Pressing roll, 20 …… Composite film web, 21 …… Vertical heat fusion bonding section, 22 …… Horizontal heat fusion bonding section, 23 …… Discharge port.

Claims (2)

(57) [Claims] 1. At least one base material layer formed of a thermoplastic resin harder than low-density polyethylene and biaxially stretched 1.5 times or more, and at least one heat-sealing layer, When the composite film having a scar that penetrates at least the base material layer is half-folded at the edge portion to be heat-melt-bonded, and when the edge portion is heat-melt-bonded to form a bag, the half-folded composite film is used. In the composite film of which the crossing angle of the orientation line showing the orientation direction of the base material layer in the above is 0 ° to 20 °, the composite film is treated with an alignment line showing the orientation direction of the base material layer in the front and back composite films. Easy-opening, characterized in that the bag is half-folded in the direction in which the crossing angle becomes 0 ° to 20 °, and the end edges are heat fusion bonded to form a bag having the scratches on the heat fusion bonded end edges. Bag manufacturing method. 2. At least one base material layer formed of a thermoplastic resin harder than low density polyethylene and biaxially stretched 1.5 times or more, and at least one heat fusion layer, When two composite films having a scratch penetrating at least the base material layer are superposed on the edge portions to be heat fusion bonded, and the edge portions are heat fusion bonded to form a bag, the composite films on the front and back sides are overlapped. Select two composite films whose crossing angle of the alignment line showing the alignment direction of the base material layer in 0 ° to 20 °,
In the two composite films, the crossing angle of the alignment lines showing the alignment direction of the base material layers in the front and back composite films was 0 ° to.
A method for producing an easily-openable bag, characterized in that the bag is piled up in a direction of 20 °, and the end edge portion is subjected to heat fusion bonding to obtain a bag having the scar on the heat fusion bonded edge portion.