JPH0858041A - Polyolefin composite film - Google Patents

Abstract

PURPOSE: To provide a polyolefin composite film having excellent transparency, sliding property, and blocking resistance. CONSTITUTION: In a polyolefin composite film, at least on one face of a base layer of a composite film consisting of a polyolefin polymer, a polyolefin polymer film which contains 0.01-2wt.% of an organic polymer fine particle having an average particle size of 0.4-7.0μm and a water drop holding time of 10sec. or below based on 100wt.% of the polyolefin polymer is layered in multiple.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based composite film which is excellent in transparency, slipperiness and blocking resistance and is preferably used in the packaging field or other fields where high transparency is required. Is.

[0002]

2. Description of the Related Art As a method for improving the slipperiness and blocking resistance of a conventional polyolefin film, inorganic fine particles such as silica, calcium carbonate, clay, titanium white, and zeolite are added to change the surface properties of the film. A method for improving the blocking property by squeezing (JP-B-52-16134, JP-A-3-99).
No. 38). However, the fine particles of the inorganic substance are easily aggregated, the transparency of the polyolefin-based composite film is impaired due to the large difference in the refractive index with the polyolefin-based resin, and the inorganic material is less compatible with the polypropylene-based resin and the inorganic substance. Voids are generated around the substance and the transparency is reduced.

Therefore, it is impossible for the above reasons to add a sufficient amount of the finely divided inorganic substance to give a satisfactory slip property and anti-blocking property to a stretched film which requires transparency. A polypropylene-based composite film containing fine particles of an organic polymer is used as a polypropylene-based composite film in order to compensate for the drawbacks of the polyolefin film in which the inorganic material of these fine particles is added.
A fine polymer powder having a cross-linking structure of 0 μm and no melting point is uniformly mixed with 0.02 to 0.8% by weight of a polypropylene resin, melt-extruded, and then cooled. There is a stretched polypropylene resin film (Japanese Patent Application Laid-Open No. 57-64522) which is stretched in the above-mentioned manner, and an average particle diameter of 0.5 for the stretched polyolefin film.
Invention of a stretched polyolefin-based film containing a condensation-type resin having a spherical triazine ring of 10 μm in a proportion of 0.01 to 0.1% by weight with respect to a polyolefin and stretched at least 4 times in a uniaxial direction ( JP-A-62-3
9219).

However, according to the results of studies by the present inventors, the conventional polyolefin-based composite film using organic polymer fine particles is superior in transparency and scratch resistance as compared with the polyolefin-based composite film using inorganic fine particles. However, the balance of transparency, slipperiness, and blocking resistance is insufficient, and it has not reached the level that satisfies high-level market requirements.

[0005]

As described above, the conventional method of adding inorganic fine particles to a polyolefin-based composite film having excellent transparency, slipperiness, and blocking resistance is not limited to the conventional organic fine particles. The method of using polymer particles is also insufficient as described above, and in particular, it has not reached a level satisfying high market demands in the balance of transparency, slipperiness and blocking resistance of the polyolefin composite film. There was a problem. That is,
In order to achieve a high degree of transparency, when the amount of fine particles to be added to the polyolefin-based composite film is reduced, slipperiness and blocking resistance deteriorate, causing problems in workability in the film manufacturing process and processing process. On the contrary, when satisfying the characteristics of slipperiness and blocking resistance, the transparency is lowered, so that the polyolefin-based composite film that is excellent in both the contradictory characteristics of transparency and slipperiness and blocking resistance is still unclear. It has not been obtained. In view of the above, it is an object of the present invention to provide a polyolefin-based composite film having excellent transparency, slipperiness, and blocking resistance.

[0006]

The first aspect of the present invention is to provide a composite film formed of a polyolefin-based polymer having a mean particle size of 0.4 to 7.0 μm and a water drop retention time on at least one side of a base layer. The organic polymer fine particles having a duration of 10 seconds or more is 0.0 with respect to 100% by weight of the polyolefin-based polymer.
The present invention relates to a polyolefin-based composite film, which is formed by laminating a plurality of polyolefin-based polymer films containing 1 to 2 parts by weight.

Secondly, in the above-mentioned first invention, the organic polymer fine particles are acrylic monomer or methacrylic monomer [abbreviated as (meth) acrylic monomer] and / or styrene monomer. A polyolefin composite film characterized in that it is a polymer composed of a monomer component containing it.

A third aspect of the present invention relates to a polyolefin-based composite film according to the first and second aspects of the present invention, wherein the surface layer has a thickness of 0.03 to 4 μm. Here, the water droplet retention time means that the organic polymer fine particles are sandwiched between two biaxially oriented polypropylene films on a horizontal and smooth table, and the upper film is lightly pressed by a hand to obtain a smooth film having a thickness of 2 mm. After forming the organic polymer fine particle layer, the upper film is gently removed. It means the time until a water drop having a diameter of 2 mm is dropped from a height of 1 cm on the surface of the obtained organic polymer fine particle layer with a void and the water droplet is absorbed by the organic polymer fine particle layer and disappears.

As the polyolefin constituting the polyolefin composite film of the present invention, propylene, ethylene, butene and 4-methylpentene-1 are used for both the base layer and the surface layer.
And homopolymers thereof or a mixture of these copolymers. The type of the polyolefin constituting the base layer and the surface layer may be the same or different, and any of them may be used.

The organic polymer fine particles used in the present invention are not particularly limited as long as they are not melted at the melt molding temperature of the above polyolefin and have heat resistance to withstand the same temperature, and they are obtained by an addition polymerization method. It may be one obtained by a polycondensation or polyaddition reaction method. The polymer constituting the organic polymer fine particles may be a non-crosslinked type or a crosslinked type, but the crosslinked type is more preferable from the viewpoint of heat resistance.

The method of micronizing the polymer is not limited, but a method of directly micronizing during polymerization using a method such as emulsion polymerization or suspension polymerization is preferable. When these polymerization methods are adopted, a means for copolymerizing a small amount of a polar monomer having a special structure capable of imparting self-emulsifying property may be adopted. The shape of the polymer particles is not particularly limited, but a substantially spherical or rugby ball shape is preferable.

The organic polymer particles of the present invention include (meth) acrylic monomers and / or styrene monomers.
It is preferable to use fine particles of a polymer consisting of
That is, a homopolymer of a (meth) acryl-based monomer or a styrene-based monomer, a copolymer of a (meth) acrylic-based monomer (including a copolymer other than the above-mentioned terpolymers; the same applies hereinafter), a copolymer of a styrene-based monomer. Alternatively, a copolymer of a (meth) acrylic monomer and a styrene monomer
Etc. Among these, cross-linking type (meth) acrylic-styrene-based copolymers are preferable, and they are excellent in balance of transparency, slipperiness, heat resistance, water drop retention time and the like.

As the (meth) acrylic monomer component, acrylic acid, methyl acrylate, ethyl acrylate, acrylic acid such as acrylate, butyl acrylate, or the like, ester derivatives thereof, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylic acid are used. Methacrylic acid such as butyl or an ester derivative thereof can be mentioned. These monomers may be used alone or in combination of two or more.
In addition, 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 may be used as long as the amount is small.

Examples of the styrene-based monomer component include styrene such as styrene, methylstyrene, α-methylstyrene and β-methylstyrene, or a derivative thereof. If it is 20% by weight or less of the total monomer components, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile,
It does not matter if a polymerizable vinyl monomer such as methacrylonitrile is copolymerized. As the crosslinking method, a method such as copolymerizing a polyfunctional monomer such as diacrylic acid ester or dimethacrylic acid ester of divinylbenzene or ethylene glycol at the time of forming the fine particle polymer, or post-crosslinking after forming the polymer is used. However, the present invention is not limited to these.

The organic polymer fine particles used in the present invention must have a water droplet retention time of 10 seconds or more as measured by the above method. It is preferably at least 1 minute, more preferably at least 5 minutes. This water drop retention time defines the degree of hydrophobicity of the organic polymer fine particles. When the water drop retention time is less than 10 seconds, a highly transparent film having good slipperiness and blocking resistance can be obtained. I can't.

The means for keeping the water droplet holding time for 10 seconds or more is not particularly limited, but the following method is recommended. The structure of the polymer constituting the fine particles is optimized. The polymerization method and the preparation method of the fine particles are optimized so that the component having a hydrophobic group is unevenly distributed on the surface of the fine particles. When prepared by a method of directly forming fine particles by an emulsion polymerization method or a suspension polymerization method, the surfactant used during the polymerization and the monomer imparting the self-emulsifying property are optimized. When preparing by the method of directly forming fine particles by emulsion polymerization method or suspension polymerization method, wash thoroughly when separating fine particles from a solvent such as water, and then add hydrophilic additives such as surfactants and residual monomers. -Is removed. The surface of the fine particles is coated with a hydrophobic monomer or polymer. Surface treatment is performed with a surface treatment agent such as a silane coupling agent or a titanate coupling agent.

The average particle size of the organic polymer fine particles in the present invention must be in the range of 0.4 to 7.0 μm. When it is less than 0.4 μm, the effect of improving the slipperiness is reduced, which is not preferable. On the other hand, if it exceeds 7.0 μm, the effect of improving the slipperiness is saturated, but the transparency is deteriorated, which is not preferable. The particle size distribution of the organic polymer fine particles is preferably sharp in order to satisfy transparency, slipperiness and blocking resistance. The average particle size of the organic polymer fine particles is a value obtained by taking a photograph with a scanning electron microscope, measuring the ferret diameter in the horizontal direction using an image analyzer, and displaying the average value. .

In the present invention, the blending ratio of the organic polymer fine particles in the film to the surface layer is determined by the polyolefin 10
Fine particles are 0.01 to 2 parts by weight with respect to 0 parts by weight.
It is preferably 0.02 to 0.5 part by weight. When the blending amount of the organic polymer fine particles is less than 0.01 part by weight, it is impossible to impart slipperiness and blocking resistance to the film, while when the blending amount exceeds 2 parts by weight, slipperiness,
Although sufficient blocking resistance is provided, the transparency of the film is significantly impaired, which is not preferable. The optimum value of the average particle diameter and the compounding ratio of the organic polymer fine particles described above varies depending on the type of polyolefin, the thickness and configuration of the film, the presence or absence of stretching, etc., so that it is within the range described above according to the desired film characteristics. It is preferable to set it arbitrarily.
The necessity of blending the above-mentioned organic polymer-fine particles into the polyolefin constituting the base layer is not particularly limited, but since the transparency of the film decreases when blended into the base layer, it is used in fields where transparency is highly required. In the case of a film, it is preferable that the blending of organic polymer fine particles is limited to only the surface layer.

In the polyolefin-based composite film of the present invention, organic or inorganic fine particles other than organic polymer fine particles may be used in combination, higher fatty acid amides, higher fatty acid esters, waxes, etc., as long as the effects of the present invention are not impaired. It is also possible to improve the slipperiness by using a lubricant such as metal soap. The combined use of lubricants is rather preferred. There is no limitation on the combined use of known stabilizers, antistatic agents, ultraviolet absorbers, processing aids, plasticizers, etc., which are usually incorporated in polyolefin films. The method for mixing the above-mentioned organic polymer fine particles, additives, etc. with the polyolefin is not particularly limited, but is uniformly mixed with a mixer such as a V-type blender, a screw-type blender, a dry blender, a ribbon blender, or a Henschel mixer. After that, a method of kneading and pelletizing may be used.

The method for laminating the polyolefin-based composite film of the present invention is not particularly limited and may be carried out by either a coextrusion method or a laminating method, but from the economical point of view, the coextrusion method is preferable. It is suitable. In the present invention, the thickness of the film of the surface layer needs to be 0.03 to 4 μm. Furthermore, 0.05-3 micrometers is more suitable. 0.03
If it is less than μm, the effect of improving slipperiness and blocking resistance is not sufficient, which is not preferable. On the other hand, when it exceeds 4 μm, the effect of improving the slipperiness and blocking resistance is saturated, and the transparency is lowered, which is not preferable. The total film thickness in the present invention is determined according to its application, but is usually 6 to 100.
μm, preferably 10 to 50 μm.

The composite film of the present invention may be an unstretched casting film which is simply extrusion-molded or a stretched film which is obtained by stretching the casting film in a uniaxial or biaxial direction. It is particularly preferable since it is expressed. Further, it is useful for application development to subject the film of the present invention to a surface treatment such as a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment or the like for improving the adhesiveness.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples, and modifications and implementations can be made without departing from the spirit described above or below. All are included in the technical scope of the present invention. The measuring method used in the examples is as follows. (1) Haze value According to JIS-K6714, Toyo Seiki Haze tester
Measured at J. (2) Narrow angle diffuse transmission value It was measured using a visual transparency tester manufactured by Toyo Seiki Seisakusho. The smaller the measured value, the higher the transparency. (3) Coefficient of friction Measured according to ASTM-D1894 at 20 ° C x 65% RH. (4) Blocking resistance The film is cut into 80 mm x 120 mm with a cutter, and two pieces of this cut piece are vertically shifted by 20 mm and overlapped to obtain a sample. Five sets of this type of sample are alternately stacked on each other, sandwiched between glass plates, and a weight of 2 kg is applied, and the sample is left at 50 ° C. for 48 hours. The sample was taken out, allowed to cool, and recut in the longitudinal direction with a width of 20 mm to give a test piece, and the shear stress was measured at a pulling speed of 220 mm / min.

[0023]

Example 1 As a resin for a base layer, a composition prepared by mixing 0.3 part by weight of glycerin resin acid ester and 0.3 part by weight of erucic acid amide with 100 parts by weight of polypropylene having a melt index of 2.5 g / 10 min. As a resin for the surface layer, 100 parts by weight of polypropylene having a melt index of 2.5 g / 10 min was used, and a water drop retention time was 10 minutes or more, and an average particle size was 1.1 μm. Cross-linked acrylic-styrene copolymer particles [Methyl methacrylate / n-butyl acrylate / styrene / divinylbenzene = 36/27/36/1 (weight ratio)] Then
When separating the copolymer particles from the emulsion, washing with water is repeated 5 times to sufficiently remove the surfactant adhering to the surface of the particles. ] Using a composition in which 0.15 parts by weight, glycerin resin acid ester 0.3 parts by weight, and erucic acid amide 0.3 parts by weight are mixed, the above base layer resin and surface layer resin are respectively prepared by separate extruders. The melt was melted, and the melt was joined between the dies, and the melt having a three-layer structure in which the surface layers were laminated on both sides of the base layer was rapidly cooled with a cooling roll at 20 ° C., and the total thickness was 0.90 mm unstretched. I got a seat. [(Surface layer / Base layer /
Thickness ratio of surface layer = 1/23/1]. This unstretched sheet was stretched at a stretching temperature of 40 by utilizing the roll peripheral speed difference of the longitudinal stretching machine.
It was stretched 4.5 times in the machine direction at 0 ° C., and subsequently stretched 8 times in the cross direction at a stretching temperature of 155 ° C. by a tenter type stretching machine. Next, heat treatment was performed at 160 ° C. to obtain a biaxially stretched film having a thickness of about 25 μm, and then one surface was subjected to corona discharge treatment. The characteristic values of the obtained film are shown in [Table 1].

[0024]

[Table 1]

[0025]

[Comparative Example 1] In Example 1, crosslinked acrylic-styrene copolymer particles having a water droplet retention time of 2 seconds or less obtained by separating the copolymer particles from the emulsion by washing only once (average) A film was obtained by the same method as in Example 1 except that the particle size, particle size distribution, particle shape, and particle composition were the same as in Example 1. The characteristic values are shown in [Table 1].

[0026]

Comparative Example 2 Spherical cross-linked acrylic-styrene-based copolymer having substantially monodisperse particle size distribution having an average particle size of 0.6 μm, which was washed with water in the same manner as in Example 1 and had a water droplet retention time of 10 minutes or more. A film was obtained in the same manner as in Example 1 except that fine particles (the composition of which is the same as in Example 1) were used. The characteristic values are shown in [Table 1].

[0027]

Comparative Example 3 Spherical crosslinked acryl-styrene copolymer fine particles (composition: water-washed by the same method as in Example 1) having a water drop retention time of 10 minutes or more and having an average particle size of 8 μm and exhibiting a substantially monodispersed particle size distribution. Is the same as in Example 1)
I got a film in the same way. The characteristic values are shown in [Table 1].

[0028]

Comparative Example 4 A film was obtained in the same manner as in Example 1 except that the amount of the crosslinked acrylic-styrene copolymer fine particles added was 0.05 parts by weight. The characteristic values are shown in [Table 1].

[0029]

[Comparative Example 5] [Table 1] shows the characteristic values of the film obtained by the same method as in Example 1 except that the amount of the crosslinked acrylic-styrene copolymer fine particles added was 1.2 parts by weight.

[0030]

[Comparative Example 6] In the method of Example 1, the same crosslinked acrylic resin as that compounded in the surface layer resin was used for the base layer resin.
A film was obtained in the same manner as in Example 1 except that 0.15 part by weight of styrene-based copolymer fine particles was added to 100 parts by weight of polypropylene. The characteristic values are shown in [Table 1].

[0031]

Example 2 In the method of Example 1, a crosslinked acrylic-
Water droplet retention time is 8 instead of styrene copolymer fine particles.
Minute cross-linked acrylic fine particles having an average particle size of 1.7 μm and exhibiting a substantially monodispersed particle size distribution [composition: methyl methacrylate / trimethylol propane trimethacrylate =
98/2 (weight ratio)] and the addition amount thereof is 0.
A film was obtained in the same manner as in Example 1 except that the amount was 10 parts by weight. The characteristic values are shown in [Table 1].

[0032]

Comparative Example 7 A film was obtained in the same manner as in Example 2 except that crosslinked acrylic particles having a water drop holding time of 2 seconds or less were used. The characteristic values are shown in [Table 1].

[0033]

[Comparative Example 8] In the same manner as in Example 2, except that the same crosslinked acrylic particles as the base layer resin and the surface layer resin were blended in an amount of 0.10 parts by weight per 100 parts by weight of polypropylene. A film was obtained in the same manner as in Example 1. The characteristic values are shown in [Table 1].

[0034]

[Comparative Example 9] In the same manner as in Comparative Example 7, except that 0.10 parts by weight of the same crosslinked acrylic particles as the base layer resin and the surface layer resin are blended with 100 parts by weight of polypropylene. Was obtained in the same manner as in Comparative Example 7. The characteristic values are shown in [Table 1].

[0035]

Example 3 In the method of Example 1, a crosslinked acrylic resin was used.
Instead of the styrene-based copolymer particles, the water droplet retention time obtained by surface-treating with a polymer-type silane coupling agent was 10
Spherical cross-linked polystyrene particles having an average particle diameter of 1.3 μm and an almost monodispersed particle diameter distribution [prepared by suspension polymerization, composition: styrene / divinylbenzene = 98/2 (weight ratio)] are used. A film was obtained in the same manner as in Example 1 except for the above. The characteristic values are shown in [Table 1].

[0036]

Comparative Example 10 A film was obtained in the same manner as in Example 3 except that the surface treatment of the crosslinked polystyrene-based particles was not carried out and particles having a water drop retention time of 2 seconds or less were used. The characteristic values are shown in [Table 1].

[0037]

[Comparative Example 11] In the method of Example 3, except that 0.15 parts by weight of the same crosslinked styrene-based particles as those blended in the resin for the base layer and the resin for the surface layer are blended with 100 parts by weight of polypropylene. Was obtained in the same manner as in Example 1. The characteristic values are shown in [Table 1].

[0038]

COMPARATIVE EXAMPLE 12 In the method of Comparative Example 11, except that 0.15 parts by weight of the same crosslinked styrenic particles that are blended with the base layer resin and the surface layer resin are blended with 100 parts by weight of polypropylene. Was obtained in the same manner as in Comparative Example 11. The characteristic values are shown in [Table 1].

The films of the present invention obtained in Examples 1 to 3 all showed excellent transparency, good slipperiness and blocking resistance, and were of extremely high quality. On the other hand, the film obtained in Comparative Example 1 was inferior in transparency and blocking resistance and had low quality. In the "cloudiness value" which is generally used as a method for evaluating transparency, the film of Comparative Example 1 does not differ much from the film of Example, but the narrow angle having a high correlation with the transparency by visual observation. It can be seen that the diffuse transmission value is significantly inferior.

The film obtained in Comparative Example 2 has good transparency, but has poor blocking resistance.
The films obtained in Nos. 7, 9, 10, and 12 were poor in transparency and blocking resistance, and the film obtained in Comparative Example 4 was poor in slipperiness and blocking resistance.
The films obtained from Nos. 6, 8 and 11 were inferior in transparency and were all of low quality.

[0041]

The polyolefin film of the present invention is
Since it is a multi-layered structure and has a composition in which a specific amount of organic polymer fine particles having a specific surface characteristic of long water drop retention time is blended, the composition is excellent in transparency, and also in slipperiness and blocking resistance. It can be widely used as a packaging material. In particular, since it is excellent in transparency, it can be suitably used in the field of packaging where high transparency is required.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Yasushi, Inuyama City, Aichi Prefecture 334 Kizu character, Maebata, Toyo Boseki Co., Ltd. No. 8 Toyobo Co., Ltd. Head Office

Claims (3)

[Claims] 1. An average particle size of 0.4 on at least one side of a base layer of a composite film formed of a polyolefin polymer.
A polyolefin polymer film containing 0.01 to 2% by weight of organic polymer fine particles having a water droplet retention time of 10 seconds or more and 0.01 to 2% by weight is laminated in a plurality of layers. A polyolefin film-based composite film characterized in that 2. The polyolefin composite film according to claim 1, wherein the organic polymer fine particles are a polymer composed of a monomer component containing a (meth) acrylic monomer and / or a styrene monomer. Here, the (meth) acrylic monomer is an abbreviation for an acrylic monomer or a methacrylic monomer. 3. The thickness of the surface layer film is from 0.03 to
3. The polyolefin-based composite film according to claim 1, which has a thickness of 4.0 μm.