JPH11239997A - Cutting method and polyolefin resin film obtained by it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance productivity by preventing film chips from being produced and by requiring no replacement of a blade for a long time. SOLUTION: This cutting device 1 consists of blades of a safety razor 4, 5 provided in a free pass part between carrying rolls 3a-3c to carry a film 2, winding shafts 8-11, and an ion spraying device 13 to remove static electricity. The film is formed by superimposing an inner surface of a single layer polyolefine resin film containing carbon molded in a tube shape on another inner surface by an inflation film forming method. The blade is heated to a temperature ranging from not less than 50 deg.C to not more than a melting point of the film, preferably to a temperature close to a softening point, and a decrease as to how sharp the film is cut is prevented by softening the film and making it easy to cut. A center part of the cut film is separated into two center parts 2b, 2c to make a product and is rolled around the winding shafts 8, 9, and both rim parts 2c, 2d to abandon are rolled around the winding shafts 10, 11 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutting method for continuously cutting a polyolefin resin film in a transport direction and a polyolefin resin film obtained by the cutting method.

[0002]

2. Description of the Related Art In general, there are the following methods for removing the ears of a film which is continuously conveyed or cutting the film into a desired width. (1) The film is cut by a fixed blade at a free path between the transport rolls. (2) The film is cut with a fixed blade and a rotary blade (for example, JP-A-64-58492). (3) Cutting with a grooved rotary roll and fixed blade. (4) Cutting with a rotating blade that moves while rotating along the fixed blade. (5) Cut by applying a laser beam.

[0003]

The cutting method of the above (1) is inexpensive and has good workability. However, the carbon-containing polyolefin resin film which is easy to elongate and increases the film conveying speed or is flexible and has high tear strength. When the film was cut, wrinkles were easily generated in the free path portion, and it was difficult to cut the film or a trouble occurred.
In particular, when the film to be cut is for a laminated film, if the cut edge is not good, the web may break during lamination. In addition, a linear low-density polyethylene containing carbon black that is flexible and has a large longitudinal tear strength and is easily stretched (hereinafter referred to as L-LDPE)
If the film made of resin is cut for a long time, only the portion of the fixed blade that contacts the film locally rises in temperature and the cutting sharpness is reduced, and the blade has to be replaced in about two days. Another problem is that a large amount of swarf is generated. In addition, dust and chips scattered in the air adhere to the film, which is caught in the film roll and pressed between the film layers, forming dents and projections on the film, or remaining stuck to the film. There was a problem of sticking to the product.

[0004] The cutting method (2) improves the cutting edge of a photographic film, a magnetic tape film or the like, and reduces the generation of cutting powder. However, the apparatus is expensive and the positioning of the upper blade and the lower blade is expensive. There is a disadvantage that it takes time. In particular, it is not suitable for cutting various films having different thicknesses and molecular orientations using inexpensive various resins like packaging films.
Furthermore, it is unsuitable for cutting a film which is flexible, has a large tear strength and is easily stretched like a carbon-containing polyolefin resin film.

In the cutting method (3), the film is cut while being stretched in the width direction on the surface of the grooved roll by the elasticity of the film, so that the use range is smaller than the cutting methods (1) and (2). Although widely preferred, the life of the blade is short as in (1), and it is necessary to stop the film forming line and replace the blade after about two days. Further, there is a disadvantage that chips are also generated, and a means for cleaning chips has been required.

The cutting method (4) can be used as a method for cutting or cutting a sheet or the like with a limited length, but it is difficult to put it into practical use as a method for cutting a long film to be conveyed.

The cutting method (5) can prevent the generation of chips, but limits the practical range in terms of production speed, cost, maintenance, safety and the like.

The present invention has been made in consideration of the above-mentioned problems of the prior art. For example, when cutting a film that is flexible and has a large tear strength and is easily stretched, such as a polyolefin resin containing carbon, almost no chips are generated. An object of the present invention is to provide a highly productive cutting method in which blade replacement is not required for a long time.

Another object of the present invention is to provide a polyolefin resin film which has a high cut edge and does not break even during lamination.

[0010]

According to the cutting method of the present invention, after the inner surfaces of a polyolefin resin film formed by an inflation film forming method are superimposed, the two polyolefin resin films thus superimposed are transferred to a transport roll. The sheet is cut into two pieces after being cut by a heating fixed blade heated to 50 ° C. or higher and lower than the melting point of the polyolefin resin film provided in a free path portion between the two. Also,
The polyolefin resin film contains carbon black. Further, the heated blade is a fixed blade heated by an electric resistance heater. Further, the heating fixed blade is a blade of a safety razor.

Further, the polyolefin resin film of the present invention is obtained by cutting the polyolefin resin film by the above-mentioned method for cutting the polyolefin resin film, and making the cut end thicker than before cutting.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A cutting apparatus 1 embodying the present invention comprises:
As shown in FIG. 1, a transport roll 3 for transporting a film 2
a, 3b, 3c, the transport roll 3a, the transport roll 3b,
3c, a cutting blade 4 provided in a free path portion between
5, winding shafts 8, 9, 10, 11 for winding each part of the film cut in the transport direction by the blades 4, 5;
It comprises a static eliminator for removing static electricity generated at the contact portion between the film 2 and the blades 4 and 5, for example, an ion sprayer 13.

The film 2 is a single-layer carbon-containing polyolefin resin film formed into a tube by an inflation film forming method, and the inner surfaces thereof are overlapped to form a two-layered film. The blades 4 and 5 are heated by, for example, a heater 6 of an electric resistance type, and the temperature is maintained in a range of 50 ° C. or higher and lower than the melting point of the film 2, preferably at a substantially constant value before and after the softening point of the film 2. Used. As a result, the film 2 is softened and easily cut, thereby preventing the sharpness of the cut. If the temperature is 50 ° C. or lower, the temperature difference between the contact portion and the contact portion between the film and the blade becomes large due to the local temperature rise due to friction, and the film does not soften. Therefore, the durability of the blade cannot be improved.

The central portion of the cut film 2 is separated into two central portions 2a and 2b as products, and the winding shaft 8,
9 are wound in a roll shape. The edges 2c, 2d on both sides of the film 2 are wound around the winding shafts 10, 11, respectively, and then discarded. In addition,
The blades 4 and 5 are easy to obtain, inexpensive and easy to handle, and are excellent in various necessary characteristics such as suitability for film cutting, large electric resistance and easy heat generation. I have.

[0015]

EXAMPLE 1 The cutting device 1 was used, and the film 2 had a melt index (MI) of 1.1.
g / 10 minutes, 5% by weight of a homopolyethylene resin having a density of 0.954 g / cm ³ . I. Is ethylene g-4-methylpentene having a density of 2.1 g / 10 min and a density of 0.920 g / cm ^3.
87% by weight of a copolymer resin, 3% by weight of furnace carbon black having an average particle diameter of 21 mμ, I. Is 2.4g
/ 10 minutes, 4.5% by weight of high-pressure low-density homopolyethylene resin having a density of 0.923 g / cm ³ , and erucamide of 0.1%.
A 50 μm thick carbon-containing polyolefin resin inflation film was formed from a resin composition having a softening point of 102 ° C. and a weight of 0.05% by weight and an antioxidant of 0.1% by weight, and the resulting film was folded by a nip roll.

The film 2 is wound around a winding shaft 8-11.
At a winding speed of 30 m / min.
And cut with heated blades 4 and 5. Since the entire blades 4 and 5 are heated, a local temperature rise due to friction with the film 2 is suppressed, and a decrease in cutting sharpness is prevented by softening the film 2 to facilitate cutting. You. As a result, the cutting sharpness was good even after continuous cutting for 240 hours, and the film 2 could be used continuously even after switching to another type of film.

Further, as shown in FIG.
5a, 15b, 16a, 16b, 17a, 17b, 18
The a and 18b are melted by the heat of the blades 4 and 5, and the swarf and the carbon powder of the film 2 adhere thereto, so that the swarf and the carbon powder hardly scatter. Also, the cutting cut 15a,
15b, 16a, 16b, 17a, 17b, 18a, 1
Since the thickness D ₁ of the 8b thickens slightly raised from the original thickness D ₀ of the film 2, tear strength is the machine direction 80
7 g, and 1040 g in the horizontal direction, no breakage occurred in the film forming step or the laminating step of laminating with another flexible sheet. On the other hand, in Comparative Example 1 in which the blades 4 and 5 were used without heating at room temperature, for example, at 25 ° C., the cutting sharpness of the blades 4 and 5 deteriorated after continuous cutting for 38 hours. Created a need.

[0018]

[Embodiment 2] The cutting device 1 is used, and a film 2 is used as a film 2. I. Is 3.2 g / 10 minutes and the density is 0.
922 g / cm ³ high pressure method low density homopolyethylene resin 9
6.8% by weight, 3% by weight of furnace carbon black having an average particle size of 21 mμ, phenolic antioxidant 0.0
A resin composition having a softening point of 92 ° C. and a thickness of 100 μm comprising 5% by weight, 0.05% by weight of oleamide, 0.05% by weight of zinc stearate and 0.05% by weight of synthetic silica.
A m-carbon polyolefin resin inflation film was molded and folded with a nip roll.

The film 2 is wound around a winding shaft 8-11.
At a winding speed of 25 m / min.
And cut with heated blades 4 and 5. As a result, the sharpness was good even after continuous cutting for 240 hours. Further, since the cut edge is melted by the heat of the blades 4 and 5, as in the first embodiment, there is no generation of swarf, and the cut edge slightly rises and becomes thick. The tear strength is 211 g in the vertical direction and 895 g in the horizontal direction. As a result, no break occurred in the film forming step or the laminating step. In contrast, blades 4, 5
In Comparative Example 2 in which was used at room temperature, for example, at 25 ° C. without heating, the sharpness of the blades 4 and 5 deteriorated after continuous cutting for 68 hours, so that it was necessary to replace them.

Although the blades 4 and 5 are of a safety razor, the present invention is not limited to this.
In addition, a corona discharge device may be used instead of the ion spraying device 13, or a film may be formed by bringing a knitted or woven fabric made of a conductive material such as a metal molding, a conductive film, a metal fiber or a carbon fiber into contact with the film. The static electricity generated at this point may be released from here.

[0021]

As described above, according to the cutting method of the present invention, after the inner surfaces of a polyolefin resin film formed by an inflation film forming method are overlapped, the two polyolefin resin films thus stacked are conveyed. After cutting with a heated fixed blade heated to 50 ° C. or higher and lower than the melting point of the polyolefin resin film provided in the free pass section between the rolls, it is separated into two pieces, so use an inexpensive blade that is easy to obtain, easy to handle, and easy to use. However, the polyolefin resin film can be continuously cut for a long time, and two polyolefin resin films can be cut at once, which contributes to an improvement in production efficiency.
Further, since the cut edge of the polyolefin resin film is melted by the heat of the blade, the generation of cutting powder can be prevented.

When carbon black is contained in the polyolefin resin film, the polyolefin resin film is flexible and the tear strength is greatly increased, but according to the cutting method of the present invention, the cut end of the polyolefin resin film is melted. It is possible to prevent the generation of cutting powder and carbon powder, and to prevent the occurrence of wrinkles in the free path portion, difficulty in cutting the film, and breakage of the film.

When a fixed blade heated by an electric resistance heater is used as the heated blade, the temperature of the blade is in the range of 50.degree. C. or more and the melting point of the polyolefin resin film, preferably the polyolefin resin film. It can be easily maintained at a substantially constant value before and after the softening point, and a decrease in cutting sharpness can be prevented.

When a safety razor blade is used as the heating fixed blade, many advantages such as easy availability, low cost and easy handling, suitability for film cutting, high electric resistance and easy heat generation are obtained. Can be.

Further, the polyolefin resin film of the present invention is cut by the above-mentioned cutting method, and the thickness of the cut end is increased as compared with that before cutting, so that the strength of the cut end is increased, and the film forming step and other flexible processes are performed. In the laminating step of laminating the sheet and the bag making step, breakage from the cut edge can be prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a cutting device embodying the present invention.

FIG. 2 is a sectional view of a film cut by the cutting device shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cutting device 2 Film 3a-3c Transport roll 4,5 Blade 6 Heater 13 Ion spraying device 15a, 15b, 16a, 16b, 17a, 17b, 1
8a, 18b cutting edge

Claims (5)

[Claims] After the inner surfaces of a polyolefin resin film formed by an inflation film forming method are overlapped with each other, the two stacked polyolefin resin films are provided in a free path portion between transport rolls.
A method for cutting a polyolefin resin film, wherein the film is cut into two pieces after being cut with a heated fixed blade heated to a temperature of not lower than the melting point of the polyolefin resin film. 2. The method for cutting a polyolefin resin film according to claim 1, wherein the polyolefin resin film contains carbon black. 3. The method for cutting a polyolefin resin film according to claim 1, wherein the heated blade is a fixed blade heated by an electric resistance heater. 4. The method for cutting a polyolefin resin film according to claim 3, wherein said heated fixed blade is a blade of a safety razor. 5. A polyolefin resin film, wherein the polyolefin resin film is cut by the method for cutting a polyolefin resin film according to any one of claims 1 to 4, and the thickness of the cut edge is larger than before cutting.