JPH11222257A - Thin packaging plastic leaf and packaging sheet and packaging bag using the leaf - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a thin plastic leaf of good air permeability and hard to be broken, and also provide a packaging sheet and a packaging bag using the thin plastic leaf. SOLUTION: The number of openings 2a on opening lines 2 on a thin packaging plastic leaf with at least one opening line 2 on a biaxially oriented polypropylene film 1 or an non-oriented polypropylene film or a high density polyethylene film is 4-37 per unit length (cm) of the opening line 2. The air permeation amount of a section including the opening line 2 is 300-1300 mL/ min.cm<2> .100 mmAq.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic thin sheet for packaging and a packaging sheet and a packaging bag using the same.
More specifically, the present invention relates to a plastic thin leaf body which has a large mechanical strength despite having a large number of openings formed on its surface and is useful as a material for packaging bags for various raw foods such as fruits and vegetables and noodles.

[0002]

2. Description of the Related Art Raw foods such as vegetables, root vegetables, fruits, fruits and vegetables such as mushrooms, noodles, breads, and cakes such as cream puffs are generally packaged with a flexible plastic film. It is distributed, stored and sold over-the-counter in a sealed state in a bag, and its packaging bag is formed with an opening that penetrates inside and outside to ensure the freshness of the sealed raw food. .

[0003] Such a packaging bag is conventionally usually manufactured by the following mechanical opening method. One method is to press a roll, on the surface of which a plurality of needles project in a predetermined pattern, against one surface of a continuously running plastic film, thereby forming a plurality of openings of a predetermined diameter in the plastic film. This is a method in which the film is formed, and then the perforated film is formed into a desired packaging bag.

[0004] As other methods, a packaging bag is first manufactured from a non-open plastic film, and then a punching process is performed on one side of the bag to open holes on both sides of the bag. There is a method of performing a punching process on the plastic film before manufacturing the bag, and then manufacturing a packaging bag. In those cases, a relatively large hole, for example, 4 to 10 mm, is usually formed on one side of 4 to 1 mm.
Two are formed.

[0005] However, the packaging bag manufactured by the former method has the following problems. That is, the aperture of the aperture film used as a material is mechanically formed with a needle, but in that case, burrs are generated in the formed aperture. In addition, the needle may be opened by heating, but in this case, the shape of the opening may be distorted and uneven, and the surrounding area may become dirty, and further, melting residue (stringing) may be observed. In some cases, the periphery of the opening is melted and becomes a burr-like projection.

[0006] Therefore, when relatively heavy raw food or the like is enclosed in a packaging bag made of such an apertured film, cracks are generated in the film from the apertures due to the burrs described above, and the film breaks. May happen. Such problems are less likely to occur if the number of apertures is reduced,
In this case, the ventilation amount of the packaging bag is also reduced, and it is difficult to ensure freshness of raw foods and the like.

When a packaging bag is manufactured such that a burr-like portion is on the inside, the burr of the packaging bag may peel off during the transportation process and adhere to raw foods or the like. The problem arises also in the point. On the other hand, in the case of the packaging bag manufactured by the latter method, since about 4 to 12 holes perforated on one side thereof are relatively large, the mechanical strength thereof is significantly larger than that of the non-perforated state. To
When a heavy object is enclosed, the film may break from the opening. If the number of openings is small, the enclosed raw food or the like may block these openings from the inside, so that the ventilation inside and outside the bag is blocked.
If the diameter of the opening is large, insect invasion and scattering of the epidermis of the product may occur.

It is to be noted that, unlike the above-mentioned mechanical opening method, it has been proposed to irradiate a plastic film with a laser to form an opening and to use the hole to produce a packaging material (Japanese Patent Application Laid-Open No. 9-1989). 98658). The packaging material disclosed herein requires strict quality control and is for lightweight Enokitake. The number of openings is one per packing unit (see the above-described prior art example), and is not a packaging material in which a large number of openings are formed by laser irradiation.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a problem in a packaging bag made of a perforated film produced by the above-mentioned mechanical perforation method, that is, a method for encapsulating heavy raw foods having low mechanical strength. It solves the problem of easy breakage and food hygiene when transported, and has high mechanical strength and heavy raw food despite having many holes and good air permeability. It is an object of the present invention to provide a plastic thin body which is a material of a packaging bag which is hard to be broken even if it is enclosed, and a packaging sheet or a packaging bag using the same.

[0010]

In order to achieve the above-mentioned object, in the present invention, a biaxially oriented polypropylene film, a non-oriented polypropylene film, or a high-density polyethylene film is provided with at least one row of holes by laser irradiation. The air permeability of the plastic thin sheet for packaging in which the rows are formed, in particular, the portion including the aperture row is 30
A plastic leaf for packaging having a volume of 0 to 1300 mL / min · cm ² · 100 mmAq is provided.

Further, the present invention provides a packaging sheet and a packaging bag using the above-mentioned plastic thin leaf.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The thin leaf of the present invention comprises a biaxially oriented polypropylene film, a non-oriented polypropylene film,
Alternatively, a plurality of openings are formed by irradiating a high-density polyethylene film with a laser beam from a laser opening device. The biaxially stretched polypropylene film, unstretched polypropylene film, or high-density polyethylene film to be used is not particularly limited, and has an appropriate tensile strength while taking into consideration the weight of the raw food to be enclosed in the packaging sheet or packaging bag for manufacturing purposes. One having a thickness and thickness is selected.

Among the above films, a biaxially stretched polypropylene film is preferable because of its relatively high tensile strength as compared with other films. Note that the thickness is required to be a thickness capable of being opened by a laser beam from a laser opening device. Depending on the power of the laser beam, if the thickness is too large, it becomes difficult to form an opening, and the thickness is too small. And the strength characteristics also deteriorate. Although the thickness varies depending on the type of film used, it is usually preferably about 10 to 50 μm.

With respect to the laser aperture apparatus used for forming apertures in these films and the operation mode thereof, for example, the apparatus disclosed in JP-A-1-46236 and the operation mode thereof are employed. Can be. 1 shows an example of the thin leaf of the present invention when the film of the starting material is a biaxially stretched polypropylene film.

In FIG. 1, the biaxially oriented polypropylene film 1 has a plurality of openings 2a penetrating from the front surface 1a to the back surface 1b. These openings 2
a is formed by using the laser opening apparatus as described above. Therefore, when the positions of the apertures 2a in the film 1 are indicated by an XY orthogonal coordinate system as shown in the figure, these apertures 2a
Are formed in a single row at predetermined intervals in the X-axis direction in the figure, for example, and form a single row 2 of apertures. A plurality of openings 2 are formed at a predetermined pitch in the Y-axis direction in the drawing, so that a plurality of openings are formed in the biaxially stretched polypropylene film 1.

Here, the aperture row 2 in the thin leaf body of the present invention
FIGS. 2 and 3 show an example of a single opening 2a forming a hole, which will be described. FIG. 2 is a plan view showing the state of the opening 2a and its vicinity, and FIG. 3 is a cross-sectional view along the line III-III in FIG. In the figure, an opening 2a formed through the front surface 1a to the back surface 1b of the biaxially stretched polypropylene film 1 has a substantially perfect circular shape, and the periphery thereof has a thickness greater than the thickness of the film 1. A thick donut-shaped body 3 is formed.

In the donut-shaped body 3, the polypropylene at the irradiation point is once melted by the heat of the laser beam applied to the film 1, and then contracts to the non-melted film side in the course of cooling, and is integrated with the film 1. It is formed in a transformed state. Therefore, the donut-shaped body 3 is solid, is smooth without even minute projections on the surface, and has a higher density and higher strength than the peripheral film 1. .

Although the opening 2a shown in FIG. 2 has a substantially perfect circular shape, an ellipse having a desired shape can be obtained by changing the operating conditions of the laser opening device. In any case, in the thin leaf of the present invention, a donut-shaped body 3 having a solid, smooth surface and higher strength than the film 1 is provided around the periphery of the opening 2 a formed in the film 1. Are formed. As described above, since there is no portion that causes stress concentration at the periphery of the opening, the situation where the opening of the opening 1 serves as a starting point and the breakage of the film 1 proceeds is greatly suppressed.

In the thin leaf of the present invention, a plurality of openings as described above are formed in the film 1. In this case, the size of the aperture can be appropriately changed depending on the operating conditions of the laser aperture device. However, if the aperture is too small, the air permeability when used as a packaging sheet or a packaging bag deteriorates, and the aperture by the laser beam is reduced. Therefore, its size is limited, and usually, when the opening is a substantially perfect circle, the diameter is 0.01 to 0.90 mm.
And, if the opening is elliptical, the major axis 0.10
It has a diameter of 0.90 mm and a minor diameter of 0.05 to 0.25 mm.

Here, an opening 2a formed in the film 1
Is set to 4 to 37 per unit length (cm) in the X-axis direction of the aperture row 2 described above. If the number of apertures in one aperture row 2 is less than 4 / cm,
This is because if the air permeability is poor, and if it is more than 37 pieces / cm, the strength becomes low and the material becomes unsuitable as a material for a relatively heavy raw food packaging bag.

Further, a portion including the above-described aperture row 2 is set in a vent having an area of 1 cm ² , and a pressure difference between before and after the vent, that is, a pressure difference between both surfaces of the thin leaf body in the portion is 100
When set to mmAq and the air flow per minute in that part was measured, the value was 300 to 1300 mL / min · cm ² ·
It is preferably 100 mmAq. 400mL of this ventilation
If it is less than / mm · cm ² · 100 mmAq, the air permeability when used as a packaging sheet or packaging bag will be poor.
If the amount is more than 0 mL / min · cm ² · 100 mmAq, the strength is reduced.

Further, a plurality of aperture rows 2 may be formed in the Y-axis direction with the number of apertures in one aperture row 2 being defined as described above. However, if the number of rows is too large, the strength of the packaging bag is reduced. Therefore, it is usually preferable that one packaging bag has 1 to 40 rows. The packaging bag of the present invention is manufactured using the above-mentioned thin leaf. An example is shown in FIG.

The packaging bag shown in FIG. 4 is obtained by adding the thin leaf shown in FIG.
It is folded in two in the axial direction, and both sides thereof are heat-sealed, for example, to form a seal portion 1c. Therefore, in this packaging bag, when the opening 2a is elliptical, its long axis direction matches the direction in which the packaging bag is weighted (vertical direction) when actually used. When the bag is manufactured in such a manner, the strength of the obtained packaging bag in the vertical direction is increased.

Further, as shown in FIG. 5, even in a packaging bag in which the opening row 2 and the opening of the packaging bag are parallel,
It has sufficient strength compared to bags made of mechanically perforated films. FIG. 6 is an exploded perspective view of another packaging bag using the thin leaf body 1 of the present invention. In the case of this packaging bag, the thin thin body 1 and the non-open film 4 are overlapped, and the three edges of the two are heat-sealed, for example, to form a seal portion 1c. This packaging bag is suitable for, for example, enclosing an elongated vegetable such as burdock. Further, since one surface is a non-opening film, its strength characteristics are also excellent.

FIG. 7 is a perspective view showing an example when the thin leaf 1 of the present invention is used as a packaging sheet. That is,
For example, a vegetable 5 such as a lettuce is wrapped with a thin leaf 1 from the outside, and the top is sealed with a sealing material 6. Also in this case, the freshness of the vegetables 5 is suitably ensured by the good air permeability of the thin leaf body 1.

[0026]

EXAMPLES Examples 1 to 3 A biaxially stretched polypropylene film (FOB manufactured by Nimura Chemical Co., Ltd.) having a thickness of 25 μm and a width of 600 mm was irradiated with a laser beam using a laser opening apparatus. With such a pattern, various aperture films were manufactured by forming an aperture row 2 comprising elliptical apertures 2a having a long axis in the X-axis direction and a short axis in the Y-axis direction.

Table 1 shows, for each apertured film, the distance between the apertures 2a constituting the aperture row 2, the length of the major axis and the length of the minor axis, and the number of apertures in the aperture row 2. Was. JIS
In accordance with K6301, a test piece for measuring the characteristics in the X-axis direction and a test piece for measuring the characteristics in the Y-axis direction, with each film including one row of apertures in the film. And for each specimen,
Temperature 2 according to the test method specified in JISZ1702
The tensile strength and elongation at 3 ° C. were measured. The results are shown in Table 1.

The air permeability of each film was measured according to the following specifications. That is, the opening row portion was set in a vent having an area of 1 cm ² , the differential pressure before and after the vent was set to 100 mmAq, and the amount of ventilation per minute (mL / min · cm ² ·
100 mmAq). Further, for comparison, an aperture row having the same pattern as in each example was formed by a mechanical aperture method using a needle,
The results are shown in Table 1 as comparative examples corresponding to the examples. Further, the characteristics were measured in the same manner for the biaxially stretched polypropylene film as a starting material, and the results were shown as reference examples.

The test piece (A1) of Example 1, the test piece (A2) of Example 3, the test piece (B1) of Comparative Example 1, the test piece (B2) of Comparative Example 3, and the test piece of Reference Example FIG. 8 shows the relationship between tensile strength and elongation in (C). In the figure, the solid lines represent the results in the X-axis direction for the test pieces A1, A2, B1, B2, and C, and the broken lines represent the results in the Y-axis direction.

[0030]

[Table 1]

The following is clear from Table 1 and FIG. (1) As is clear from the comparison between each example and the corresponding comparative example, both have the same number of holes (number / cm) as the pattern of the hole rows formed on the film. However, the thin leaf of the present invention is significantly superior in tensile strength to the comparative example. In particular, the tensile strength in the long axis direction of the opening is twice or more. This is because, in the case of the comparative example, burrs are generated because the mechanical opening method is applied. However, in the case of the present invention, since laser irradiation is applied, the periphery of the opening has high strength.

(2) As is clear from the comparison between Example 1 and Reference Example, the thin leaf of Example 1 has significantly reduced tensile strength and elongation in the Y-axis direction (the short axis direction of the aperture). However, in the X-axis direction, the tensile strength is the same and the elongation is only slightly reduced.

(3) As is clear from FIG. 8, the test pieces A1 and A2 of the present invention have strength characteristics in the Y-axis direction (the short axis direction of the opened ellipse) whose test pieces have no holes. Although it is inferior to C, its tensile strength in the X-axis direction (the major axis direction of the ellipse) shows an excellent value as compared with the test piece C. This is because, as described above, a donut-shaped body having higher density and higher strength than the film main body is formed on the periphery of the opening.

Examples 4 and 5 An unstretched polypropylene film having a thickness of 25 μm and a width of 600 mm (manufactured by Nimura Chemical Industry Co., Ltd.).
Examples 1 to 3 except that a high-density polyethylene film having a width of 600 mm and a width of 600 mm (manufactured by Hokuetsu Kasei Co., Ltd.) was used.
In the same manner as in the above, an apertured film was produced. The former is Example 4 and the latter is Example 5. For comparison, an aperture row having the same pattern as in each example was formed by a mechanical aperture method, and used as comparative examples.

With respect to these apertured films, Examples 1 to
Various characteristics were measured in the same manner as in the case of No. 3. Table 2 shows the results.

[0036]

[Table 2]

As is clear from Table 2, even when the starting material film is an unstretched polypropylene film or a high-density polyethylene film, the film is superior to the apertured film of the comparative example manufactured by the mechanical aperture method. Can be manufactured.

[0038]

As is apparent from the above description, the plastic thin leaf of the present invention has a large number of holes formed by laser irradiation on biaxially oriented polypropylene, non-oriented polypropylene film, and high-density polyethylene film. In addition, the periphery of the formed hole has high strength, and it is hard to break greatly as compared with the case where a conventional mechanical hole method is applied. Therefore, the packaging sheet or packaging bag manufactured from this plastic thin body has good breathability, while ensuring freshness of the encapsulated raw food, etc., even if the raw food is heavy, It is useful without being broken in the course of transportation as compared with a packaging bag by a conventional mechanical opening method.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view showing an example of a thin leaf of the present invention.

FIG. 2 is a plan view showing an example of an aperture formed in the thin leaf body of the present invention.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a perspective view showing an example of a packaging bag manufactured from the thin leaf of the present invention.

FIG. 5 is a perspective view showing another packaging bag manufactured from the thin leaf body of the present invention.

FIG. 6 is an exploded perspective view showing another packaging bag of the present invention.

FIG. 7 is a perspective view showing an example of using the thin leaf of the present invention as a packaging sheet.

FIG. 8 is a graph showing the relationship between tensile strength and elongation of various films.

[Explanation of symbols]

 Reference Signs List 1 biaxially oriented polypropylene film 1a surface of biaxially oriented polypropylene film 1 1b back surface of biaxially oriented polypropylene film 1

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seigo Nishida 212-1 Kuse Tsukiyamacho, Minami-ku, Kyoto-shi, Kyoto, Japan Inside the Kyoto Tobacco Inc. Kyoto Printing Plant (72) Inventor Akihiko Gunji Minami, Kyoto-shi, Kyoto 212-1 Kuze Tsukiyamacho, Ward Japan Tobacco Inc. Kyoto Printing Plant

Claims (6)

[Claims] 1. A packaging plastic thin body comprising a biaxially stretched polypropylene film, a non-stretched polypropylene film, or a high-density polyethylene film having at least one row of apertures formed by laser irradiation,
A plastic thin leaf for packaging, wherein the number of apertures in the aperture row is 4 to 37 per unit length (cm) of the aperture row. 2. The plastic thin leaf for packaging according to claim 1, wherein the opening has a circular or elliptical shape. 3. The air flow rate in a portion including the row of apertures is 30.
0-1300mL / min.cm ^Two-The package according to claim 1, which is 100 mmAq.
Wearable plastic thin body. 4. A packaging bag using the plastic thin leaf for packaging according to claim 1. 5. The packaging bag according to claim 4, wherein one side is formed of the plastic thin leaf for packaging according to claim 1. 6. A packaging sheet using the plastic thin leaf for packaging according to claim 1.