JPH0696644B2 - Polyolefin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin film which has excellent blocking resistance and is less likely to be scratched or scratched on the surface.

[0002]

2. Description of the Related Art Improving the blocking resistance of a polyolefin film has hitherto been carried out by incorporating a small amount of silica into the polyolefin. Although the blocking resistance is improved by this method, when a polyolefin film containing this silica is used in an automatic packaging machine, there is a problem that packaging defects frequently occur due to insufficient sliding property of the polyolefin film. there were.

In order to solve the above problems, a silicone resin has recently been used in place of silica (Japanese Patent Laid-Open Nos. 62-215646 and 62-232448).
JP-A-62-233248). By blending the silicone resin, a slipperiness was improved, and a polyolefin film having blocking resistance as good as or better than silica was obtained.

[0004]

However, the polyolefin film containing a silicone resin is liable to be scratched on the surface due to the rubbing of the films, and the scratch on the surface deteriorates the transparency of the film, thus lowering the commercial value. There was a problem of doing.

An object of the present invention is to provide a polyolefin film which is excellent in blocking resistance and sliding property and which is resistant to scratches between the films.

[0006]

Means for Solving the Problems As a result of repeated experiments to achieve the above object, the present inventors have found that the silicone rubber particles having a specific particle size and elasticity are blended with a polyolefin film. The inventors have found that the object can be achieved and have proposed the present invention.

That is, in the present invention, the average particle size is 0.5 to 3
It is a polyolefin film containing 0.05 to 1% by weight of silicone rubber particles having a μm and a rubber hardness A of 30 to 80 degrees.

In the present invention, the silicone rubber particles dispersed and blended in the polyolefin film have an average particle diameter of 0.5 to 3 μm and a rubber hardness A of 30 to 80 degrees. The average particle diameter should be in the range of 0.5 to 3 μm, preferably in the range of 1 to 2 μm. When the average particle size of the silicone rubber particles is less than 0.5 μm, the effect of improving the blocking resistance and sliding property is poor, and when it exceeds 3 μm, the transparency of the film is deteriorated and the particles protrude from the film surface. Since the height of the protrusion due to the silicone rubber particles becomes high, the protrusion causes ink to escape during gravure printing or the like, which impairs aesthetics. Further, the rubber hardness A of the silicone rubber particles is 30 to 8
It must be 0 degrees, and preferably in the range of 35 to 75 degrees. When the rubber hardness A is less than 30 degrees, the effect of improving the blocking resistance and the sliding property is small, and when it exceeds 80 degrees, the transparency of the polyolefin film is lowered because scratches are likely to occur, which is not preferable. The rubber hardness A in the present invention is a value measured according to JISK6301.

The shape of the above-mentioned silicone rubber particles is not particularly limited, but it is preferably spherical in view of improvement of blocking resistance and sliding property. Since commercially available silicone rubber particles are usually spherical, commercially available products may be used as they are.

The content of the silicone rubber particles in the polyolefin film is 0.05 to 1% by weight.
It is preferably 0.5% by weight. When the compounding amount of the silicone rubber particles is less than 0.05% by weight, the effect of improving the blocking resistance and sliding property is poor, and when the compounding amount exceeds 1% by weight, the transparency deteriorates.

The polyolefin in the present invention is a homopolymer of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene, and the copolymerization of the α-olefins with each other. A combination, a copolymer of a monomer other than an α-olefin copolymerizable with the α-olefin and an α-olefin, a mixture thereof, and the like are adopted without any limitation. As the monomer other than the α-olefin copolymerizable with the α-olefin,
Examples thereof include vinyl acetate and maleic acid.

The present invention is particularly effective for the above-mentioned polyolefins whose surface is easily scratched.
Specific examples of such polyolefins include polyethylene, ethylene-propylene copolymer (ethylene content 2 to 5 mol%), ethylene-vinyl acetate copolymer, ethylene-1-butene copolymer, ethylene-propylene-.
Examples thereof include 1-butene copolymers, ethylene-propylene-butadiene copolymers, and blends containing these polyolefins as main components.

The present invention may be a monolayer film of polyolefin, and further comprises the above-mentioned layer of polyolefin (A) which is easily scratched and polyolefin (B) having a melting point higher than that of the polyolefin (A). It may be an easily heat-sealable polyolefin film in which layers are laminated. In the case of the above laminated film, the silicone rubber particles are blended in the layer of the polyolefin (A). The polyolefin (A) is as described above, but as the polyolefin (B), one having a melting point higher than that of the polyolefin (A) by 20 to 70 ° C. is generally used. Specifically, propylene homopolymer, propylene-ethylene random copolymer (ethylene content 3 mol% or less)
Etc. can be mentioned.

To obtain a laminated polyolefin film having a good heat-sealing property, 60-90 parts by weight of a propylene-ethylene random copolymer (ethylene content 2-5 mol%) and 1-butene are used as the polyolefin (A). It is preferable to use a mixture of 10 to 40 polymerized parts of a homopolymer and use a propylene homopolymer or a propylene-ethylene random copolymer (ethylene content of 0.5 mol% or less) as the polyolefin (B).

The layer of the polyolefin (A) preferably has a thickness approximately equal to the diameter of the silicone rubber particles in order to prevent the surface from being scratched, and usually 0.5.
Is selected from the range of 3 μm. The polyolefin (B) layer is generally 10 to 6 from the viewpoint of film strength.
It is selected from the range of 0 μm.

Further, it is optional to laminate a layer of polyolefin (A) on the layer of polyolefin (B) of the laminated polyolefin film to form a sandwich structure, or to laminate another polyolefin layer. Can be done.

The polyolefin film of the present invention can be produced by sufficiently mixing the polyolefin powder or pellets with the silicone rubber particles, and then melt-extruding or further uniaxially or biaxially stretching. Also, in the case of a laminated film, co-extrusion of the polyolefin constituting each layer, and then uniaxially or biaxially stretched if necessary, or one layer of polyolefin melt-extruded and uniaxially stretched, other layers of it. A method of melt extruding a polyolefin and stretching it in a direction substantially perpendicular to the uniaxial stretching direction is used.

[0018]

[Effect] The polyolefin film of the present invention has excellent blocking resistance and sliding property, and therefore can be used for packaging by an automatic packaging machine. Furthermore, since the film is hardly scratched by rubbing, transparency is improved. Can be suppressed. Therefore, the polyolefin film of the present invention can be suitably used as various packaging materials for foods, cigarettes, cassette tapes, video tapes, floppy disks and the like.

[0019]

EXAMPLES Examples and comparative examples are given below to specifically describe the present invention, but the present invention is not limited to these examples. The film properties in the following examples and comparative examples were measured by the following methods.

(1) Scratch resistance Two films were prepared and one film (20 × 3
0 cm) as the lower film, the other film as the upper film, a weight of 4.6 kg is placed on the upper film, and the lower film is brought into contact with an area of 10 × 10 cm, and the upper film is moved horizontally.
Rubbing was repeated twice between cm. The haze before and after the above operation was measured according to JIS K 6714.

(2) Slip property After the film is manufactured, it is cured at 40 ° C. for 3 days, and then ASTM-D.
It was measured according to the static friction coefficient measuring method of -1894.

(3) Blocking property Two films (120 × 120 mm) are superposed,
40 × 40m after leaving for 24 hours in an atmosphere of load 10kg (69.4g / cm ² ), temperature 40 ° C, humidity 90% RH
Cut the sample into m and pull tester (speed: 100
The shear peel strength was measured in (mm / min).

(4) Heat-sealability 15 mm from a sample sealed under the conditions of a heat-sealing pressure of 1 kg / cm ² and a heat-sealing time of 1.0 second using a heat-sealing bar of 5 × 200 mm at each set temperature.
A sample of width was cut out and measured at a pulling speed of 100 mm / min using a tensile tester. The result was an average value of 5 samples.

In addition, in the above (1) to (4), various measurements were carried out by facing layers containing silicone rubber particles in Examples and layers containing various particles in Comparative Examples. Further, the surface of the layer containing the above silicone rubber particles or various particles was subjected to corona discharge treatment (treatment density 30 W / m ² · min) and was not performed, respectively, and exhibited slipping property and blocking property, respectively.

Examples 1 to 3 Melt index 2.0 g / 10 minutes, crystallinity 98.
To 100 parts by weight of 4% polypropylene (melting point 159 ° C.), 0.5 parts by weight of glycerin monostearate and N, N′-bis (2-hydroxyethyl) alkylamine as antistatic agents, and 0.5 parts of erucic acid amide were added. 03 parts by weight and 0.04 parts by weight of calcium stearate were added and melt-kneaded, and this was used as a resin composition for a base material layer.
On the other hand, a resin (melting point: 115 ° C.) obtained by mixing 30 parts by weight of polybutene-1 with 100 parts by weight of a propylene-ethylene random copolymer having an ethylene content of 3 mol% had an average particle size of 1.
Silicone rubber sphere particles having a rubber hardness A of 8 degrees and a rubber hardness A of 8 degrees were added at a compounding ratio shown in Table 1 to obtain a resin composition for a surface layer.

Using the above resin composition for the base layer and the surface layer, a tenter biaxial stretching machine was used to obtain a three-layer laminated film in which the surface layers were laminated on both sides of the base layer.
The thickness of each layer was 1.5 μm / 22 μm / 1.5 μm.

The scratch resistance, slip resistance, blocking resistance and heat sealability of these films were measured, and the results are shown in Table 1.

Example 4 100 parts by weight of a propylene-ethylene copolymer having an ethylene content of 3.5 mol% (melting point: 125 ° C.) had an average particle diameter of 1.
A laminated film (thickness: thickness: 5 μm, 0.2 parts by weight of silicone rubber spherical particles having a rubber hardness A of 70 degrees) was added to form a resin composition for the surface layer, and the surface layer was laminated on one surface of the base material layer. The same procedure as in Examples 1 to 3 was carried out except that the surface layer was 1.5 μm / base material layer 23.5 μm). First result
Shown in the table.

Comparative Examples 1 to 3 In place of the silicone rubber spherical particles added to the surface layer of Example 1, melamine resin spherical particles having an average particle diameter of 1.5 μm, non-melting type silicone resin spherical particles having an average particle diameter of 2 μm, and The same procedure as in Example 1 was carried out except that pulverized silica particles having an average particle size of 1.5 μm were used. The results are shown in Table 1.

[0030]

[Table 1]

Examples 5 to 7 Resin having 5 parts by weight of polybutene-1 mixed with 100 parts by weight of propylene-ethylene random copolymer having a melt index of 7.5 g / 10 min and an ethylene content of 2.5 mol% (melting point 122 ° C. ), 0.5 parts by weight of glycerin monostearate and N, N'-bis (2-hydroxyethyl) alkylamine as antistatic agents, 0.03 parts by weight of erucic acid amide, and 0.04 parts by weight of calcium stearate. Were mixed. Further, silicone rubber sphere particles having an average particle diameter of 2.5 μm and a rubber hardness A of 40 degrees were added at a compounding ratio shown in Table 2. A single layer film was obtained from this using a cast film forming machine. The thickness was 25 μm.

The scratch resistance, slip resistance and blocking resistance of these films were measured, and the results are shown in Table 2.

Comparative Examples 4 to 5 Instead of the silicone rubber spherical particles of Example 5, melamine resin spherical particles having an average particle diameter of 1.5 μm and average particle diameter 2
The same procedure as in Example 5 was carried out except that the non-melt type silicone resin spherical particles having a size of μm were used, and the results are shown in Table 2.

[0034]

[Table 2]

Claims (2)

[Claims] 1. A silicone rubber particle having an average particle diameter of 0.5 to 3 μm and a rubber hardness A of 30 to 80 degrees is 0.05.
A polyolefin film containing 1% by weight. 2. A silicone rubber particle having an average particle diameter of 0.5 to 3 μm and a rubber hardness A of 30 to 80 degrees is 0.05.
A polyolefin film obtained by laminating a layer of polyolefin (A) containing 1 to 1% by weight and a layer of polyolefin (B) having a melting point higher than that of the polyolefin (A).