JPH0931254A - Polyolefin-based film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyolefin-based film excellent in transparency and improved in sliding property, blocking resistance and winding characteristics. SOLUTION: This polyolefin-based film contains 100 pts.wt. polyolefin and >=0.01 pts.wt. and <=1.0 pts.wt. total amount of organic polymer fine particles and inert fine particles, and the organic polymer fine particles and the inert fine particles have >=0.1μm and <=7.0μm average particle diameter, respectively and the organic polymer fine particles have >=10sec water drop retention time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin film, and in particular, has excellent film transparency, slipperiness, and
The present invention relates to a polyolefin film having improved blocking resistance and winding properties.

[0002]

2. Description of the Related Art Conventionally, a method for improving the slipperiness and blocking resistance of a polyolefin film used for various packaging materials has been known.

For example, Japanese Patent Publication No. 52-16134 and Japanese Unexamined Patent Publication No. 3-9938 disclose a polyolefin film in which inorganic fine particles such as zeolite powder and spherical silica are added to polyolefin. These polyolefin-based films improve the slipperiness and blocking resistance of the film, but have a problem that the transparency and scratch resistance of the film are poor.

Japanese Patent Laid-Open Nos. 49-11945 and 5
7-64522 and JP-A-62-39219.
The publication discloses a polyolefin film in which a non-crosslinked acrylic polymer, polymer particles having a crosslinked structure, and fine organic polymer particles such as a condensation resin having a triazine ring are added to polyolefin. These polyolefin films have improved transparency and scratch resistance as compared with those containing the above-mentioned inorganic fine particles. However, these polyolefin films are
In order to obtain a film having excellent transparency, if the content of the fine particles is reduced, the slipperiness and blocking resistance of the film are reduced, and conversely, in order to improve the slipperiness and blocking resistance of the film, When the content is increased, there is a problem that the transparency of the film is lowered.
Therefore, the polyolefin-based film containing the above-mentioned organic polymer fine particles has an insufficient balance between the "transparency" of the film and the "sliding property and anti-blocking property", and reaches a level satisfying high market demand. I can't.

Further, in recent years, automation of processing devices such as film printing and laminating has rapidly progressed, and it has been desired to obtain a film having excellent winding characteristics. In order to improve the winding property of the film, it is easy to escape the air caught between the films when the film is wound, and to prevent wrinkling and misalignment of the film due to the caught air as much as possible. There is a need. Such a film having excellent winding properties can be achieved by increasing the particle size of the fine particles contained in the film, but on the contrary, there is a problem that the transparency is lowered.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and provides a polyolefin-based film having excellent film transparency and improved slipperiness, blocking resistance, and winding properties. The purpose is to provide.

[0007]

Means for Solving the Problems The polyolefin film of the present invention is
0.0 in total of organic polymer particles and inert particles
A polyolefin film containing 1 part by weight or more and 1.0 part by weight or less, wherein the organic polymer fine particles and the inert fine particles each have an average particle diameter of 0.1 μm or more and 7.0 μm or less, and The organic polymer particles are 1
It has a water drop holding time of 0 seconds or more.

In a preferred embodiment of the present invention, the organic polymer fine particles are formed from a monomer component containing a (meth) acrylic monomer and / or a styrene monomer.

In a preferred embodiment of the present invention, the inert fine particles are inorganic particles.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The polyolefin used in the present invention includes:
Mention may be made of homopolymers or copolymers of propylene, ethylene, butene and 4-methyl-pentene-1, or mixtures of these (co) polymers.

The organic polymer fine particles used in the polyolefin film of the present invention have a water droplet retention time of 10 seconds or longer, preferably 1 minute or longer, and more preferably 5 minutes or longer.

The term "water droplet holding time" used in the present specification represents the time until the water droplets are absorbed by the organic polymer fine particle layer and disappears, and is an index showing the degree of hydrophobicity of the organic polymer fine particles. . The water drop retention time was as follows: Organic polymer particles were sandwiched between two biaxially oriented polypropylene films on a horizontal table, and the upper film was lightly pressed to form a horizontal particle layer with a thickness of 2 mm. By gently removing the upper film, and measuring the time from the drop of a water droplet with a diameter of 3 mm from the position of 1 cm in height on the surface of the obtained fine particles until the water droplet is absorbed in the fine particle layer and disappears. can get. When the water droplet retention time of the organic polymer fine particles is less than 10 seconds, a film having improved transparency, slipperiness and blocking resistance cannot be obtained.

The organic polymer fine particles having the above water drop holding time are not particularly limited as long as they are fine particles made of an organic polymer which does not melt at the melt molding temperature of the above polyolefin and has heat resistance. Can be obtained by any method such as addition polymerization method, polycondensation method or polyaddition reaction method. Further, the polymer constituting the fine particles is preferably a crosslinked organic polymer fine particle, which may be either non-crosslinked type or crosslinked type, from the viewpoint of having heat resistance.

In the present invention, the organic polymer fine particles are preferably a polymer formed from a monomer component containing a (meth) acrylic monomer and / or a styrene monomer.

Examples of such polymers include homopolymers of (meth) acrylic monomers or styrene monomers, copolymers of (meth) acrylic monomers, copolymers of styrene monomers, (meth) acrylic monomers and styrene monomers. And the like. In particular, from the viewpoint of improving the balance among transparency, slipperiness, heat resistance, and water droplet retention time, it is preferable to use a cross-linking type (meth) acrylic-styrene copolymer. The polymer composition of the organic polymer fine particles may be the same or different.

Examples of the above-mentioned (meth) acrylic monomers include acrylic acid, methyl acrylate, ethyl acrylate, acrylic acid such as acrylate and butyl acrylate, or ester derivatives thereof, or methacrylic acid, methyl methacrylate, ethyl methacrylate, Methacrylic acid such as butyl methacrylate or its ester derivative can be mentioned. In particular, it is preferable to use (meth) acrylic acid ester. One or more of these monomers can be used. Further, a small amount of a metal salt of acrylic acid or methacrylic acid, an amide derivative, an ester derivative having a special structure such as hydroxylethyl ester or dimethylaminoethyl ester, and the like may be used.

Examples of the styrene-based monomer include styrene such as styrene, methylstyrene and α-methylstyrene, or a derivative thereof. Particularly, it is preferable to use styrene. Furthermore, if it is 20% by weight or less of the total monomer components, polymerizable vinyl monomers such as vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, and methacrylonitrile can be copolymerized.

For such a method of crosslinking the polymer, a polyfunctional monomer such as divinylbenzene, ethylene glycol diacrylate or dimethacrylate is mixed at the time of preparation of the organic polymer fine particles and copolymerized. Examples of the method include post-crosslinking after production, but the method is not particularly limited thereto.

A method of micronizing the above polymer is also
There is no particular limitation. However, from the viewpoint of economy, it is preferable to use a method of directly forming fine particles during polymerization by an emulsion polymerization method or a suspension polymerization method. When these polymerization methods are adopted, a means for copolymerizing a small amount of a polar monomer having a special structure, which can impart self-emulsifying property, can be adopted.

The shape of such organic polymer fine particles is not particularly limited, either, but a substantially spherical shape or a rugby ball shape is preferable.

Further, the means for keeping the water drop retention time of the organic polymer fine particles for 10 seconds or more is not particularly limited, but it is usually preferable to use the following method.

(1) A method of selecting the composition of the polymer constituting the fine particles so that the surfaces of the fine particles are hydrophobic.

(2) A method in which a component having a hydrophobic group such as a higher alkyl group is omnipresent on the surface of the fine particles by selecting a polymerization method or a fine particle preparation method.

(3) Surfactant used when the polymer is directly made into fine particles by the emulsion polymerization method or suspension polymerization method, or sodium p-vinylsulfonate which imparts self-emulsifying property, and 2 (dimethylamino). ) A method of selecting the type of monomer such as ethyl acrylate, N-vinylpyridone, a metal salt of acrylic acid or methacrylic acid.

(4) When the polymer is directly made into fine particles by the emulsion polymerization method or the suspension polymerization method, sufficient washing is performed to separate the organic polymer fine particles from a solvent such as water, and a surfactant, etc. Of removing hydrophilic additives or residual monomers of.

(5) A method of forming fine particles of a polymer and then coating the surface of the fine particles with a hydrophobic monomer or polymer.

(6) A method of subjecting the fine polymer particles to surface treatment with a surface treating agent such as a silane coupling agent or a titanate coupling agent after the polymer has been finely divided.

In the present invention, it is preferable to use the above methods (1) to (4) as means for keeping the water drop retention time of the organic polymer fine particles for 10 seconds or more, particularly from the viewpoint of economy.

The polyolefin film of the present invention further contains inert fine particles.

The inert fine particles used in the present invention are not particularly limited as long as they are other than the above organic polymer fine particles.
From the viewpoint of balancing the transparency, slipperiness, blocking resistance, and economical efficiency of the film, inorganic fine particles are preferable.

Examples of such inorganic fine particles include silica,
Examples thereof include oxides such as alumina, complex oxides such as kaolin, zeolite, and talc, carbonates such as calcium carbonate, sulfates such as calcium sulfate and barium sulfate, and phosphates such as calcium phosphate. These mineral particles can be either natural or synthetic. The shape of the inert fine particles used in the present invention may be any shape such as an amorphous shape, a spherical shape, a square shape, a columnar shape, a needle shape, or a plate shape.

The average particle diameters of the organic polymer fine particles and the inert fine particles used in the present invention are both 0.1 μm.
m or more and 7.0 μm or less, preferably 0.2 μm or more 5.
It is required to be within the range of 0 μm or less. The average particle size of the organic polymer particles and the inert particles is 0.1
When it is less than μm, the slipperiness and blocking resistance of the film are deteriorated. On the other hand, even if the average particle diameter exceeds 7 μm, the slipperiness and blocking resistance of the film are not further improved, but rather the transparency of the film is lowered. Furthermore, the organic polymer fine particles and the inert fine particles used in the present invention preferably have a sharp particle size distribution in order to obtain both satisfactory film transparency, slipperiness and blocking resistance.

Furthermore, it is preferable that the organic polymer fine particles and the inert fine particles used in the present invention contain two or more kinds of fine particles having different particle diameters in a specific ratio. Among the fine particles having different particle diameters, the fine particle (a) having a small particle diameter mainly improves the slipperiness and the blocking resistance of the film, and the fine particle (b) having a large particle diameter has the winding property of the film. It is added for the purpose of improving.

The fine particles (a) having a small particle diameter and the fine particles (b) having a large particle diameter can be arbitrarily selected from the above organic polymer particles and inert particles. In particular, when using organic polymer particles as small particles (a), inert particles are selected as large particles (b), and the inert particles are small particles (a). When used as
It is preferable to select large particles (b) of organic polymer particles. Of course, the fine particles (a) and the fine particles (b) may be a mixture of organic polymer fine particles and inert fine particles.

The average particle size of such small particle (a) is 0.1 μm or more and 1.5 μm or less, and the average particle size of large particle (b) is 1.5 μm or more. 7.
0 μm or less.

The amount of the above-mentioned organic polymer fine particles and inert fine particles used in the present invention is such that the polyolefin 10
It is 0.01 part by weight or more and 1.0 part by weight or less, preferably 0.02 part by weight or more and 0.5 part by weight or less, relative to 0 part by weight. If the total content is less than 0.01 part by weight, the film may not be imparted with slipperiness and blocking resistance, and if the total content exceeds 1.0 part by weight, the transparency of the film is significantly lowered. .

When the above-mentioned fine particles used in the present invention are the fine particle (a) having a small particle diameter and the fine particle (b) having a large particle diameter, the compounding amount of the fine particle (a) having a small particle diameter is 100 parts by weight of polyolefin. 0.05 parts by weight or more and 0.9 parts by weight or less, preferably 0.01 parts by weight or more and 0.7 parts by weight or less, and the average particle diameter of the large particle (b) is 100 or less. The amount is 0.001 parts by weight or more and 0.5 parts by weight or less, preferably 0.003 parts by weight or more and 0.3 parts by weight or less with respect to parts by weight.

The optimum values of the average particle size and the blending amount of the organic polymer fine particles and the inert fine particles are as follows:
Since it changes depending on whether or not the film is stretched, it can be appropriately set within the above range according to the desired film characteristics. In the present invention, it is particularly preferable to use organic polymer particles as the small particle (a) and inert particles as the large particle (b).

From the viewpoint of improving the slipperiness of the film, the polyolefin film of the present invention may be used in combination with additives within a range that does not impair both the transparency of the film and the blocking resistance and winding properties. Such additives include organic or inorganic fine particles other than the above organic polymer fine particles and inert fine particles, higher fatty acid amides, higher fatty acid esters, waxes, lubricants such as metal soaps,
In addition, known stabilizers, antistatic agents, ultraviolet absorbers, processing aids, plasticizers, etc., which are commonly added to polyolefin films are included. In the present invention, it is rather preferable to use the above lubricant together.

The polyolefin-based film of the present invention can be obtained by mixing the above-mentioned polyolefin, organic polymer fine particles, inert fine particles and, if necessary, additives and forming them by a conventional method. For example, the above materials are usually uniformly mixed in a mixer such as a V-type blender, a screw-type blender, a dry blender, a ribbon blender, or a Henschel mixer, and then kneaded into pellets. Then, the above mixture kneaded and pelletized is made into an unstretched film by extrusion molding or casting, or this unstretched film is uniaxially or biaxially stretched by a usual method.
It can be manufactured by stretching in the axial direction. In particular, it is preferable to use a biaxially stretched film from the viewpoint of improving both transparency of the film, slipperiness and blocking resistance, and winding characteristics. Furthermore, the polyolefin-based film of the present invention may have either a single layer structure or a laminated structure of two or more layers. Here, when the polyolefin film of the present invention has a laminated structure, it is preferable that the organic polymer fine particles and the inert fine particles are mixed in the surface layer.

Further, the above-mentioned film may be subjected to a usual surface treatment such as corona discharge treatment, plasma treatment and ultraviolet irradiation treatment in order to enhance the adhesiveness of the film.

In this way, the polyolefin film of the present invention can be obtained.

[0044]

EXAMPLES The present invention will be described in more detail with reference to the following examples, which are not intended to limit the present invention and all modifications within the scope of the present invention are included in the technical scope of the present invention. .

The measuring methods used in the examples and comparative examples are as follows.

(1) The average particle diameters of the organic polymer fine particles and the inert fine particles were measured by the Coulter Coulter method.

(2) Haze Value To evaluate the transparency of the polyolefin film,
According to JIS-K6714, the haze value of the polyolefin film was measured by a haze tester J manufactured by Toyo Seiki Seisakusho.

(3) Narrow-angle diffuse transmission value In order to evaluate the transparency of the polyolefin film,
The narrow-angle diffuse transmission value of the polyolefin film was measured by a visual transparency tester manufactured by Toyo Seiki Seisakusho. The smaller the measured value, the higher the transparency.

(4) Friction coefficient In order to evaluate the slipperiness of the polyolefin film,
The friction coefficient of the polyolefin film at 20 ° C. and RH of 65% was measured according to ASTM-D1894.

(5) Blocking resistance A polyolefin film is 80 mm × 12 with a cutter.
The sample is cut into 0 mm, and the two cut pieces are vertically overlapped with each other by shifting by 20 mm in the longitudinal direction. 5 sets of this sample are piled up alternately with type paper, and then sandwiched between glass plates, and a weight of 2 kg is applied.
Leave at 0 ° C. for 48 hours. Then, the sample is taken out, allowed to cool, and cut in the longitudinal direction to a width of 20 mm to obtain a sample piece. The sample pieces were placed in a tensile tester and the shear stress was measured at a pull rate of 200 mm / min.

(6) Air Venting Speed In order to evaluate the winding characteristics of the polyolefin film, the air venting speed of the film was measured.

A method for measuring the air bleeding speed of a polyolefin film will be described using the apparatus shown in FIG. That is, the polyolefin film 4 is attached to the ring-shaped base 1
After the film is placed on the base 4, the ring-shaped film presser 2 is placed on the base 1 from above the film 4, and the film 4 is fixed in a tensioned state. Next, another polyolefin film 5 is placed on the film retainer 2, another ring-shaped film retainer 8 is placed on the film retainer 2, and the film retainers 8 and 2 and the base 1 are fixed by using the screw 3. To do.
Here, the film retainer 2 has a circular slot 2a on the upper surface,
A hole 2c is formed in which a part of the groove 2a communicates with an outer portion of the film retainer 2, and a hole 2d in which a part of the groove 2a communicates with an inner portion of the film retainer 2.

In the measurement of the air bleeding speed, by operating the vacuum pump 6 connected to the pore 2c through the pipe 7, the film 5 is sucked by the groove 2a and a tension is applied. . Further, since the film overlapping portion X where the films 4 and 5 are overlapped with each other is also depressurized through the pores 2d in the film presser 2,
Film 4 and film 5 are the overlapping part X
In between, it starts to adhere from the outer periphery. The close contact state can be grasped by observing the interference fringes from above the film overlapping portion X. Therefore, the time (seconds) from the occurrence of the interference fringes on the outer periphery of the film overlapping portion X until the interference fringes spread over the entire surface of the film overlapping portion X and the movement of the interference fringes is measured, and this time (second) is measured. It was defined as "air bleeding speed." The shorter the air bleeding time, the better the winding characteristics of the film.

(Example 1) Methyl methacrylate / n-
Butyl acrylate / styrene / divinylbenzene = 3
Spherical crosslinked acrylic-styrene copolymer fine particles were polymerized and prepared from a monomer component composed of 6/27/36/1 (weight ratio) by a known emulsion polymerization method. The copolymer particles were separated from the emulsion and washed 5 times with water to remove the surfactant adhering to the surface of the copolymer fine particles. This copolymer fine particle has a water droplet retention time of 10 minutes or longer and an average particle diameter of 1.
It showed an almost monodisperse particle size distribution of 1 μm.

Next, the melt index is 2.5 g /
To 100 parts by weight of polypropylene for 10 minutes, 0.15 parts by weight of the above copolymer fine particles, 0.01 parts by weight of amorphous silica having an average particle size of 2.8 μm, glycerin fatty acid ester of 0.1.
3 parts by weight and 0.3 part by weight of erucic acid amide were added and mixed. This mixture was melt extruded at a resin temperature of 270 ° C. and then rapidly cooled by a 90 ° C. cooling roll to obtain an unstretched sheet having a thickness of 0.90 mm. This unstretched sheet was stretched 4.5 times in the machine direction at a stretching temperature of 145 ° C. by a longitudinal stretching machine using the roll peripheral speed difference, and then transversely stretched at a stretching temperature of 155 ° C. by a tenter type stretching machine. It was stretched 8.0 times in the direction. Then, heat treatment at 160 ° C.
After forming a biaxially stretched film having a thickness of about 25 μm, one side was subjected to corona treatment. Table 1 shows the evaluation results of the obtained films.
Shown in

(Comparative Example 1) A crosslinked acrylic-styrene-based polymer having a water drop retention time of 2 seconds or less, which was obtained by washing only once when separating the crosslinked acrylic-styrene-based copolymer particles from the emulsion. A film was obtained in the same manner as in Example 1 except that the copolymer particles were used. Table 1 shows the evaluation results of the obtained films.

Comparative Example 2 A film was obtained in the same manner as in Example 1 except that the amorphous silica was not added. Table 1 shows the evaluation results of the obtained films.

Comparative Example 3 A film was obtained in the same manner as in Example 1 except that the crosslinked acryl-styrene copolymer particles were not added. Table 1 shows the evaluation results of the obtained films.

(Comparative Example 4) A film was obtained in the same manner as in Example 1 except that the compounding amount of the crosslinked acryl-styrene copolymer particles was 0.03 part by weight. Table 1 shows the evaluation results of the obtained films.

(Comparative Example 5) Except that the compounding amount of the crosslinked acrylic-styrene copolymer particles was 1.2 parts by weight.
A film was obtained in the same manner as in Example 1. Table 1 shows the evaluation results of the obtained films.

(Example 2) Methyl methacrylate / trimethylolpropane trimethacrylate = 98/2
Using the monomer component consisting of (weight ratio) in the same manner as in Example 1, spherical crosslinked acrylic fine particles having a water droplet retention time of 8 minutes and an average particle diameter of 2.5 μm were obtained.

Then, 100 parts by weight of polypropylene as in Example 1, 0.04 parts by weight of the above crosslinked acrylic fine particles, and a silane coupling treatment showing an almost monodispersed particle size distribution with an average particle size of 0.9 μm. A polyolefin film was obtained in the same manner as in Example 1 by using 0.10% by weight of the spherical synthetic zeolite subjected to the above. Table 1 shows the evaluation results of the obtained films.

(Comparative Example 6) When separating the crosslinked acrylic fine particles from the emulsion, the crosslinked acrylic fine particles obtained by washing only once with water and having a water drop retention time of 2 seconds or less were used. A film was obtained in the same manner as in Example 2.
The evaluation results of the obtained film are shown in Table 1.

Comparative Example 7 A film was obtained in the same manner as in Example 2 except that the synthetic zeolite was not added. Table 1 shows the evaluation results of the obtained films.

Comparative Example 8 A film was obtained in the same manner as in Example 2 except that the crosslinked acrylic fine particles were not added. Table 1 shows the evaluation results of the obtained films.

Example 3 A monomer component composed of styrene / divinylbenzene = 98/2 (weight) was added to Example 1
By using the same method as above, and then subjecting the surface to a polymer type silane coupling agent,
Cross-linked polystyrene fine particles having a spherical shape with an average particle diameter of 0. 2 minutes or more and 1.2 μm and having a monodispersed particle diameter distribution were obtained.

The crosslinked polystyrene-based fine particles were mixed with 0.12
A film was obtained in the same manner as in Example 1 except that the compounding was by weight. Table 1 shows the evaluation results of the obtained films.

(Comparative Example 9) The water droplet retention time obtained without surface treatment with a polymer type silane coupling agent was 2
A film was obtained in the same manner as in Example 3 except that crosslinked polystyrene-based fine particles within a second were used. Table 1 shows the evaluation results of the obtained films.

(Comparative Example 10) A film was obtained in the same manner as in Example 3 except that the amorphous silica was not added to the resin composition. Table 1 shows the evaluation results of the obtained films.

[0070]

[Table 1]

As shown in Table 1, the polyolefin films obtained in Examples 1 to 3 are superior in transparency, slipperiness, blocking resistance, and And the film winding characteristics were both excellent.

[0072]

Industrial Applicability According to the present invention, there is provided a polyolefin film which is excellent in transparency and has improved slipperiness, blocking resistance and winding property. These films can be widely used, for example, as various packaging materials.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view of an apparatus for measuring “air bleeding speed” representing film winding characteristics.

[Explanation of symbols]

 1 Base 2,8 Film holder 2a Groove hole 2c Hole 2d Pore 3 Screw 4,5 Polyolefin film 6 Vacuum pump 7 Pipe X Film overlapping part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Isaka 2-2-8 Dojimahama, Kita-ku, Osaka City, Osaka Toyobo Co., Ltd.

Claims (3)

[Claims] 1. With respect to 100 parts by weight of polyolefin,
0.0 in total of organic polymer particles and inert particles
A polyolefin-based film containing 1 part by weight or more and 1.0 part by weight or less, wherein the organic polymer fine particles and the inert fine particles each have a content of 0.
A polyolefin-based film having an average particle size of 1 μm or more and 7.0 μm or less, and the organic polymer fine particles having a water droplet retention time of 10 seconds or more. 2. The polyolefin-based film according to claim 1, wherein the organic polymer fine particles are formed from a monomer component containing a (meth) acrylic-based monomer and / or a styrene-based monomer. 3. The inactive fine particles are inorganic particles.
The polyolefin film according to claim 1 or 2.