JPH11268209A - Polyolefin film, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the scratch-resistance and the drop-preventive property of anti-blocking agent grains from the surface of the film by a method wherein the substantially total surfaces of the anti-blocking agent grains protruding from the film surface on one face of the film, are coated with a polyolefin thin film. SOLUTION: This polyolefin film contains anti-blocking agent grains, and on the surface of the film, numerous anti-blocking agent grains protrude, and they impart an anti-blocking property to the film. In this case, the substantially total surfaces of the protruding anti-blocking agent grains are coated with a polyolefin thin film. Therefore, in spite of that the thin film is formed of polyolefin which is the same as the raw material resin of the film, a favorable anti-blocking property is kept, and the drop-preventive property of the anti- blocking agent grains, and the reduction of a scratch-resistance can be improved, and the slipperiness can be made a proper value by a thickness regulation of the coated polyolefin coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to scratch resistance,
The present invention relates to a polyolefin film having excellent slipperiness and preventing the anti-blocking agent particles from falling off during secondary processing.

[0002]

2. Description of the Related Art Resin films are widely used for packaging various articles. Among these, the polyolefin film is preferably used because the smoother the surface, the better the transparency and the better the appearance. However, since the polyolefin film is a relatively soft resin, there is a major problem that the films adhere to each other and are easily blocked. And the slipperiness also worsens, and the problem that the secondary workability such as slitting, printing, bag making and the like is deteriorated tends to occur.

In order to solve such problems, inorganic particles such as silica and zeolite are added to a polyolefin film.
Organic polymer particles such as silicone rubber and cross-linked polymethyl methacrylate have been added as antiblocking agents.

[0004]

However, the polyolefin film containing the anti-blocking agent particles has a problem that the anti-blocking agent particles fall off from the film surface during the secondary processing, and that the anti-blocking agent particles may not When the films are rubbed against each other because of the large number of exposed films, the problem of scratches on the soft film surface has been noticeable.

In particular, the printability of a polyolefin film,
When the surface is subjected to a corona discharge treatment to improve the antistatic property and the like, the scratch resistance of the film and the falling off of the anti-blocking agent particles were further deteriorated.
Further, the film subjected to the corona discharge treatment in this manner has a problem that the coefficient of friction is too small, and the product becomes excessively slippery, which causes load collapse.

In view of the above background, an object of the present invention is to provide a polyolefin film which is excellent in scratch resistance and anti-blocking agent particles from falling off from the film surface and has an appropriate sliding property. .

[0007]

Means for Solving the Problems The present inventors have intensively studied to solve the above-mentioned problems. As a result, they have found that the above-mentioned problems can be solved by coating the anti-blocking agent particles projecting from the film surface with a polyolefin thin film, and have completed the present invention.

[0008] That is, the present invention is a polyolefin film containing antiblocking agent particles, wherein at least one surface of the polyolefin film is substantially completely covered with the polyolefin thin film. It is.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin film of the present invention contains anti-blocking agent particles. Normal,
On the surface of such a polyolefin film, a large number of the antiblocking agent particles protrude, and this gives the film an antiblocking property. However, among the protruding anti-blocking agent particles, there are quite a few that penetrate the film surface to expose the particle surface, and this causes the film to have the problem of the anti-blocking agent particles falling off as described above, and has a scratch resistance. Causes the problem of a decrease in On the other hand, the present invention provides that even if the surface of substantially all of the protruding antiblocking agent particles is coated with a polyolefin thin film, the thin film is formed of the same polyolefin as the material resin of the film. Regardless, it has been found that good anti-blocking properties are maintained, and on the other hand, the problems of the anti-dropping property of the anti-blocking agent particles and the decrease in scratch resistance can be greatly improved. In the polyolefin film of the present invention, by adjusting the thickness of the polyolefin thin film to be coated, the slipperiness of the film can be controlled to an appropriate value.

Here, the surface condition of the protruding antiblocking agent particles on the film surface can be confirmed by observing the film surface with a scanning electron microscope or a reflection optical microscope. The polyolefin film of the present invention is most ideally free of any antiblocking agent particles that expose and protrude the particle surface on the target film surface, but the same effect as in this case is obtained. It is sufficient that the surface of substantially all of the protrusions is covered with a polyolefin thin film. Generally, it is preferred that 97% or more, preferably 98% or more, of the protruding anti-blocking agent particles are coated with a polyolefin thin film.

As the polyolefin, which is a material resin of the film used in the present invention, known polyolefins can be used without limitation.
Preferably, a homopolymer of an α-olefin having 2 to 10 carbon atoms such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene and 4-methyl-1-pentene,
-Olefin copolymers, copolymers of the above-mentioned α-olefin with other monomers copolymerizable therewith, and mixtures thereof. Other monomers copolymerizable with the α-olefin include vinyl acetate, maleic acid, vinyl alcohol, methacrylic acid, methyl methacrylate, ethyl methacrylate, and the like.

Specifically, polyethylene, polypropylene, propylene-ethylene copolymer, ethylene-1-butene copolymer, propylene-1-butene copolymer, ethylene-propylene-1-butene copolymer, ethylene- Propylene-butadiene copolymers and blends based on these polyolefins are included. Among them, propylene-based polymers such as polypropylene and propylene-ethylene copolymer are particularly preferred.

The anti-blocking agent particles used in the present invention do not melt or decompose at the film forming temperature.
Known particles can be used without limitation as long as they can form a protrusion on the film surface. Any material, shape, etc. may be used, but those having good dispersibility and affinity for the polyolefin to be used and having a near visible light refractive index are preferred. If the average particle size is too small, the antiblocking property tends to decrease, and if the average particle size is too large, the appearance and transparency tend to decrease.
It is preferably 0 μm, more preferably 0.8 to 3.0 μm. Further, the antiblocking agent particles preferably have excellent monodispersibility and have a spherical shape.

Specifically, inorganic particles such as silica, alumina, calcium carbonate, silica-alumina, silica-zirconia, and zeolite; silicone resin particles, silicone rubber particles, polyamide particles, cross-linked polymethyl methacrylate particles, cross-linked polystyrene particles, etc. Synthetic resin particles.

The amount of the anti-blocking agent particles is preferably 0.01 to 3% by weight, more preferably 0.05 to 0% by weight in the film, in consideration of the good anti-blocking property, sliding property and transparency. It is preferably 0.5% by weight.

In the present invention, the polyolefin thin film covering the surface of the protruding anti-blocking agent particles is:
This is a polyolefin thin film having a thickness equal to or less than the average particle diameter of the antiblocking agent particles. Here, if the thickness of the polyolefin film to be coated is larger than the average particle size of the anti-blocking agent particles, the anti-blocking agent particles projecting on the film surface are largely buried in the polyolefin film, and the film has slipperiness and anti-slipping property. Blocking properties cannot be sufficiently imparted. In particular, a thin film having a thickness of 1/2 or less of the average particle diameter of the antiblocking agent particles to be used is preferable. Also, if the thickness of the polyolefin thin film is too thin, it tends to be difficult to sufficiently coat the protruding antiblocking agent particles. For this reason, the polyolefin thin film preferably has a thickness of 0.1 μm or more.

Further, according to the present invention, by controlling the thickness of the polyolefin thin film within such a range,
The coefficient of friction of the film surface can be controlled, and a film having an appropriate slip property can be obtained.

In the present invention, as the polyolefin forming the above-mentioned polyolefin thin film, the same polyolefin as shown in the material resin of the film is used without limitation. The same type of polyolefin as the material resin of the film or a different type of polyolefin may be used.

In the present invention, the overall thickness of the polyolefin film may be appropriately set according to the material and the application. Usually, a thickness of 7 to 200 μm is selected.
For example, in the case of a biaxially stretched polypropylene film for fiber packaging, a film having a thickness of 25 to 50 μm can be suitably used.

Next, the polyolefin film of the present invention is usually produced by laminating a polyolefin thin film layer on at least one surface of a polyolefin base material layer containing antiblocking agent particles. In such a production method, when the material resins of the polyolefin base layer and the polyolefin thin film layer are different, the obtained polyolefin film becomes a multilayer film, while, when the material resins of these layers are the same, it is obtained. The polyolefin film becomes a uniform single-layer film as a resin component.

When the material resin of the polyolefin base layer and the material resin of the polyolefin thin film layer are different types, the resin of each layer may be selected in various combinations according to the performance required for the film. Specifically, for example, when obtaining a polyolefin film used for heat sealing applications, as the polyolefin base layer, polypropylene, propylene-ethylene copolymer, ethylene-
Polypropylene having excellent mechanical strength, such as a propylene-1-butene copolymer and a blend containing these polyolefins as main components, is used. On the other hand, as a polyolefin thin film layer, polyethylene, propylene-ethylene copolymer, ethylene- 1-butene copolymer, propylene-1
Polyolefins having excellent heat sealability such as -butene copolymer, ethylene-propylene-1-butene copolymer, ethylene-propylene-butadiene copolymer, and blends containing these polyolefins as main components may be used. .

The polyolefin substrate layer may have a multilayer structure of two or more layers. In this case, in the multilayer base material layer, as long as the outermost layer on which the polyolefin thin film layer is laminated contains an antiblocking agent, the other layers may not necessarily contain the antiblocking agent. If a specific example of such a multilayer base material layer is shown, a layer in which a layer using a polyolefin having excellent mechanical strength as a material resin and a layer using a polyolefin having excellent heat sealing properties as a material resin are laminated. Things. In this case, in the present invention, more sufficient heat can be obtained by laminating a thin film layer made of a polyolefin having excellent heat sealability on the layer made of polyolefin having excellent heat sealability of the multilayer base material layer. A film having a sealing property can be obtained.

In the present invention, the lamination of the polyolefin thin film layer on the polyolefin base material layer employs a method such as coextrusion and lamination. Specifically, as a production method by the casting method, after thoroughly mixing the polyolefin powder or pellets and the anti-blocking agent particles, which are the material resin of the base material layer, melt and film together with the material resin of the polyolefin thin film layer Coextrusion in the shape, if necessary, uniaxially or biaxially stretched, or laminating a polyolefin thin film layer on the surface of the uniaxially or biaxially stretched polyolefin base layer as necessary after melt extrusion into a film And the like. Alternatively, the co-extruded tubular raw material may be manufactured by inflation using a uniaxial machine, a uniaxial machine, a simultaneous biaxial machine, and no stretching. When the film is stretched, the stretching ratio is preferably 3 to 7 times in the casting method and 5 to 11 times in the horizontal direction in the casting method. In the inflation method, the vertical magnification is 3
-6 times and a lateral magnification of 1.1-5 times are preferred.

The polyolefin film of the present invention is preferably subjected to a corona discharge treatment on at least one surface, particularly on the surface on which the protruding antiblocking agent particles are coated with a polyolefin thin film. When a polyolefin thin film is formed on both surfaces of the film, the corona discharge treatment may be performed on both surfaces or only one surface. As described above, when the surface coated with the polyolefin thin film is subjected to corona discharge treatment, printability and antistatic property are improved on the surface, and the antiblocking agent particles are prevented from falling off and scratch resistance is improved. The effect of improving is particularly remarkably exhibited. Further, the slipperiness can be adjusted to an appropriate value, which is preferable. The treatment density in corona discharge may be appropriately set in consideration of the polyolefin used, stretching conditions, and the like. For example, a general processing density in a biaxially stretched polypropylene film is 3 to 60 W · m.
in / m ² .

Further, the anti-blocking agent particles contained in the film are easily exposed to the surface when the anti-blocking agent particles are stretched, and the problems of falling off and lowering the scratch resistance tend to occur. Therefore, the polyolefin film of the present invention exerts a particularly remarkable effect when it is uniaxially or biaxially stretched.

The polyolefin film of the present invention may contain an antistatic agent and a lubricant. As the antistatic agent, alkyldiethanolamine, alkyldiethanolamine monofatty acid ester, glycerin monofatty acid ester, and the like, and a mixture of two or more thereof are preferable. As the lubricant, fatty acid metal salts and the like are preferable.
Further, the polyolefin film of the present invention may be blended with other known additives such as an antioxidant, an antifogging agent, a weathering agent and the like, if necessary.

[0027]

The polyolefin film of the present invention has good anti-blocking properties, excellent scratch resistance and anti-fall properties of anti-blocking agent particles. By controlling the thickness of the polyolefin thin film, the coefficient of friction of the film surface can be adjusted, and a film having a desired slip property can be obtained. In particular, those having a dynamic friction coefficient measured in accordance with ASTM-D-1894 in the range of 0.2 to 0.4 and a static friction coefficient in the range of 0.25 to 0.6 have a film opening property and Excellent in preventing collapse of load, etc., and is preferable.

Therefore, the polyolefin film of the present invention having the above properties can be suitably used as a packaging material for foods, fibers, miscellaneous goods and the like. Further, it can be suitably used in applications such as multicolor printing in which anti-dropping property of anti-blocking agent particles is strongly required.

[0029]

The present invention will be described in more detail with reference to the following Examples, which by no means limit the scope of the present invention. In the following Examples and Comparative Examples, the physical properties of the film were measured at 40 ° C. after film production.
After curing for one day, the following method was used.

(1) Surface coverage of protruding anti-blocking agent particles Observing 0.1 mm ² of the film surface with a reflection type optical microscope, the entire surface of the anti-blocking agent particles protruding from the film surface is observed. The ratio of those covered with the polyolefin thin film was determined.

(2) Transparency The haze of the film was measured according to JIS-K-6714.

(3) Slip property The coefficient of static friction and the coefficient of dynamic friction were measured according to ASTM-D-1894.

(4) Scratch resistance Two films cut to 20 cm × 30 cm were overlapped, one was fixed downward, and one was used as an upper film. A 4.6 kg weight was placed on the upper film, brought into contact with the lower film in an area of 10 cm × 10 cm, and rubbed back and forth twice between 20 cm by moving the upper film horizontally. Haze is measured before and after operation and the difference is 0%
◎ to less than 1.5%, 、 to 1.5% to less than 3%, 3% to
Less than 6% was rated as Δ, and 6% or more was rated as x.

(5) Blocking property A film of 4 cm × 30 cm was cut out and laminated so as to have a thickness of 3 mm. Film sample at temperature 30
After leaving for 24 hours in an atmosphere of 70 ° C. and 70% RH, a pressure of 20 kg / cm ² was applied to the film sample for 30 seconds using a press machine. Thereafter, both ends of the film sample were fixed with jigs, and the bending strength was measured using an autograph (manufactured by Shimadzu Corporation).

(6) Drop-off property of antiblocking agent particles Fusing seal bag making machine (manufactured by Kyoei Printing Machine Materials Co., Ltd .; PP
500 type) at a speed of 25 m / min.
(00 mm) and bag making. At this time, the contact portion with the film is 5c above the folded portion of the film.
A black cloth was wound so as to be mx 60 cm, and bag making was performed until the unwinding length of the film reached 2000 m. The weight change of the black cloth after bag making was measured and evaluated according to the following.
◎: 0 mg or more and less than 2 mg, ○: 2 mg or more and less than 6 mg, Δ: 6 mg or more and less than 10 mg
g or more was evaluated as x.

Examples 1 to 6 Polyolefin for a base material layer shown in Table 1 and antiblocking agent particles were added in the mixing ratio shown in Table 1, and glycerin monostearate 0.3% by weight was further used as an antistatic agent. 0.1% by weight of stearyl diethanolamine, 0.2% by weight of stearyl monostearate, 0.05% by weight of calcium stearate as a lubricant
And melt-kneaded. After stretching, the resin composition and the polyolefin for a thin film layer shown in Table 1 were co-extruded with a T-die after stretching so that each layer had the thickness shown in Table 1, and then a biaxial stretching device with a tenter method was used. After stretching 5 times in the machine direction, it was stretched 10 times in the transverse direction. Physical properties of the obtained polyolefin film were measured, and the results are shown in Table 2.

Example 7 Polyolefins for a base material layer and antiblocking agent particles shown in Table 1 were added in the proportions shown in Table 1, and the same antistatic agent and lubricant as in Example 1 were added and melt-kneaded. The resin composition was extruded from a T-die, stretched 5 times in the machine direction by a biaxial stretching machine successively by a tenter method, and then stretched 10 times in the transverse direction.
The film was stretched twice to obtain a stretched film. Further, a polyolefin for a thin film layer having a thickness shown in Table 1 was laminated on the surface of the stretched film. Physical properties of the obtained polyolefin film were measured, and the results are shown in Table 2.

Comparative Examples 1 to 5 Polyolefin films of the type shown in Table 1 were used in the same manner as in Example 1 except that the polyolefin thin film layer was not laminated under the conditions shown in Table 1 using particles of the antiblocking agent. I got Measure the anti-blocking physical properties of the obtained polyolefin film,
The results are shown in Table 2.

[0039]

[Table 1]

[0040]

[Table 2]

Examples 8 to 12 Polyolefin films of the type shown in Table 3 and antiblocking agent particles were used to obtain polyolefin films under the conditions shown in Table 3 and under the same conditions as in Example 1. Next, 30 W · on one side of the obtained polyolefin film
Corona discharge treatment was performed at a treatment density of min / m ² . The physical properties of the corona discharge treated surface of the obtained polyolefin film were measured, and the results are shown in Table 4.

Example 13 A polyolefin film was obtained using a polyolefin of the type shown in Table 3 and antiblocking agent particles under the conditions shown in Table 3 and under the same other conditions as in Example 7. Next, corona discharge treatment was performed on the polyolefin thin film layer surface of the obtained polyolefin film at a treatment density of 30 W · min / m ² . The physical properties of the corona discharge treated surface of the obtained polyolefin film were measured, and the results are shown in Table 4.

Comparative Examples 6, 7 Polyolefin films of the type shown in Table 3 were used in the same manner as in Example 1 except that the polyolefin thin film layer was not laminated under the conditions shown in Table 1 using particles of the antiblocking agent. I got Next, 30 W · min / m ² was applied on one side of the obtained polyolefin film.
Corona discharge treatment was performed at a treatment density of. The physical properties of the corona discharge treated surface of the obtained polyolefin film were measured, and the results are shown in Table 4.

[0044]

[Table 3]

[0045]

[Table 4]

Claims (4)

[Claims] 1. A polyolefin film containing anti-blocking agent particles, wherein at least one surface thereof
A polyolefin film in which substantially all of the antiblocking agent particles protruding from the film surface are coated on the surface with a polyolefin thin film. 2. The polyolefin film according to claim 1, wherein the surface of the protruding anti-blocking agent particles is coated with a polyolefin thin film, and then subjected to a corona discharge treatment. 3. The anti-blocking agent according to claim 1, wherein the thickness of the polyolefin thin film is not more than 1/2 of the average particle diameter of the anti-blocking agent particles.
The polyolefin film according to the above. 4. The method for producing a polyolefin film according to claim 1, wherein a polyolefin thin film layer is laminated on at least one surface of the polyolefin base material layer containing the antiblocking agent particles.