JP3384135B2 - Biaxially oriented polypropylene film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polypropylene film excellent in transparency, slipperiness and blocking resistance. 2. Description of the Related Art Biaxially oriented polypropylene-based films are:
Because of its excellent transparency and mechanical properties, it is widely used as a packaging material for various articles such as foods and textiles. However, it has a drawback that the blocking resistance is poor, the wound films adhere to each other, the opening property of the bag is deteriorated, and the workability of the packaging is reduced. Conventionally, as a method for improving the slipperiness and blocking resistance of a polyolefin-based film, a method in which inorganic fine particles are added (for example,
JP-A-52-16134, JP-A-3-9938) and those containing fine particles of an organic polymer (for example, JP-A-49-11945, JP-A-57-64522, JP-A-62-39219) Gazettes) are known. Among these, the method using organic polymer fine particles is useful because a film having excellent transparency and scratch resistance is obtained as compared with the method using inorganic fine particles. There was a problem that the balance was inadequate and did not reach a level that satisfies high market demands. That is, when the amount of fine particles is reduced to achieve a high degree of transparency, slipperiness and blocking resistance deteriorate, and problems arise in workability in a film manufacturing process and a processing process.
When satisfying the properties of slipperiness and blocking resistance, the transparency is reduced, and a film having both excellent properties of "transparency" and conflicting properties of "slipperiness and blocking resistance" has not been obtained. It is the current situation. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a biaxially stretched polypropylene film having excellent transparency, slipperiness and blocking resistance. Is to do. [0004] The biaxially stretched polypropylene film of the present invention comprises a crystalline propylene polymer 100
Parts by weight, fine organic polymer particles having an average particle diameter of 0.3 to 3 μm.
The gist lies in that the composition comprises from 0.01 to 1 part by weight and from 0.01 to 2 parts by weight of a metal salt of oxycarboxylic acid. The organic polymer fine particles are (meth) acrylic monomer and / or
Or, a preferred embodiment is a polymer comprising a monomer component containing a styrene monomer. The crystalline propylene polymer used in the biaxially oriented polypropylene film of the present invention may be a propylene homopolymer or propylene as a main component and ethylene, butene, hexene, and 4-methyl as subcomponents. Copolymers composed of other α-olefins such as pentene and octene can be mentioned. Most preferred is a propylene homopolymer, but as the copolymer, a random copolymer or a block copolymer may be used, and a copolymer of propylene and 40% by weight or less of another α-olefin is preferred,
Further, a copolymer with ethylene or butene of 30% by weight or less, particularly 20% by weight or less is preferable. In addition, the crystalline propylene-based polymer can be used alone or as a mixture of a plurality. The crystalline propylene polymer has an isotactic index (II) of 40 or more, preferably 60 or more, and particularly preferably 80 or more. In the propylene homopolymer, those having II of 90 or more, particularly 95 or more are suitable. The melt index is 0.5 ~
Those having 10 g / 10 min, especially 1 to 5 g / 10 min are preferred. [0006] The molecular structure of the organic polymer fine particles used in the present invention is not particularly limited as long as it is non-melting and has heat resistance to withstand the same temperature at the melting temperature of the polypropylene polymer. Those obtained by any of a polymerization method, a polycondensation method and a polyaddition reaction method may be used. The polymer constituting the fine particles may be a non-crosslinked type or a crosslinked type, but a crosslinked type is recommended from the viewpoint of heat resistance. In the present invention, the method of forming fine particles of the polymer is not limited, but a method of directly forming fine particles during polymerization using a method such as emulsion polymerization or suspension polymerization is preferred. When these polymerization methods are employed, means for copolymerizing a small amount of a polar monomer having a special structure capable of imparting self-emulsification may be employed. The shape of the polymer fine particles is not particularly limited, but is preferably substantially spherical or rugby ball-like. [0008] In the present invention, as the organic polymer fine particles,
It is preferable to use polymer fine particles comprising a monomer component containing a (meth) acrylic monomer and / or a styrene monomer, and a homopolymer of a (meth) acrylic monomer or a styrene monomer, a copolymer of a (meth) acrylic monomer (copolymer) The same applies to the following terpolymers, the same applies hereinafter), copolymers of styrene monomers, copolymers of (meth) acrylic monomers and styrene monomers, and the like. Among them, a cross-linked (meth) acrylic-butylene-based copolymer is preferable, and is excellent in balance of transparency, slipperiness, heat resistance and the like. The above-mentioned (meth) acrylic monomer component includes acrylic acid such as acrylic acid, methyl acrylate, ethyl acrylate and butyl acrylate, or ester derivatives thereof, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylic acid. Examples thereof include methacrylic acid such as butyl or an ester derivative thereof. These monomers may be used alone or in combination of two or more. If the amount is small, a metal salt of (meth) acrylic acid, an amide derivative, an ester derivative having a special structure such as hydroxylethyl ester or dimethylaminoethyl ester, or the like may be used. The styrene monomer component includes styrene such as styrene, methyl styrene and α-methyl styrene, or derivatives thereof. If the amount is 20% by weight or less of all the monomer components, a polymerizable vinyl monomer such as vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, and methacrylonitrile may be copolymerized. Examples of the cross-linking method include a method of copolymerizing a polyfunctional monomer such as divinylbenzene, diacrylate or dimethacrylate of ethylene glycol at the time of producing a fine particle polymer, or a method of post-crosslinking after producing the polymer. It is not limited to these. The organic polymer fine particles of the present invention have a water droplet retention time of 1 as measured by the following method.
The effect of the present invention is more remarkably exhibited when a material having a high hydrophilicity of not more than minutes is used. [Water Drop Retention Time] Organic polymer fine particles are sandwiched between two biaxially stretched polypropylene-based films on a horizontal and smooth table, and are gently pressed by hand with an upper film to obtain a smooth organic polymer having a thickness of 2 mm. After forming the fine particle layer,
Gently remove the upper film. Drops of water having a diameter of 3 mm were applied to the surface of the obtained organic polymer fine particle layer with a spid at a height of 1 c
m, and the time until the water droplets absorbed by the organic polymer fine particle layer disappears is defined as the water droplet holding time. In the present invention, the average particle size of the organic polymer fine particles needs to be in the range of 0.3 to 3 μm. 0.
If the thickness is less than 3 μm, the effect of improving the slip property is undesirably reduced. Conversely, if it exceeds 3 μm, the effect of improving the slip property is saturated, and the transparency is undesirably deteriorated. 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 diameter of the organic polymer fine particles of the present invention is obtained by taking a photograph with a scanning electron microscope, measuring the Feret diameter in the horizontal direction using an image analyzer, and displaying the average value. In the present invention, the mixing ratio of the organic polymer fine particles in the film is 0.01 to 1 part by weight based on 100 parts by weight of the polypropylene polymer. Preferably 0.02
0.5 parts by weight. The amount of the organic polymer particles is 0.
When the amount is less than 01 parts by weight, it is impossible to impart slipperiness and blocking resistance to the film. On the other hand, when the amount is more than 1 part by weight, the slipperiness and blocking resistance are sufficiently provided, but the film is transparent. Is unfavorably inhibited. The optimum value of the average particle size and the blending ratio of the organic polymer fine particles described above varies depending on the type of the polyolefin, the thickness and the structure of the film, the presence or absence of stretching, and the like. It is good to set arbitrarily. In the present invention, the oxycarboxylic acid in the metal salt of oxycarboxylic acid is preferably oxystearic acid. As the metal salt of oxystearic acid, there is a metal acid of stearic acid having one hydroxyl group. 2-, 3-, 4-, 5-,
There are 7-, 9-, 11-, 12- and 18-isomers, but 12-oxystearic acid is recommended because it can be produced industrially at low cost by catalytic reduction of ricinol, the main resin acid of castor oil. Is one of the compounds to be used. Examples of the metal salt include alkali metal salts such as Li, Na, and K;
alkaline earth metal salts such as g, Ca, Sr, Ba, Z
Although there are n salts and the like, the use of Mg and Ca salts is particularly preferred. Further, as the above metal salt, a so-called basic metal salt containing a metal in excess of the theoretical value is preferable. In the polypropylene film of the present invention,
As long as the effects of the present invention are not impaired, organic or inorganic fine particles other than the organic polymer fine particles may be used in combination, or higher fatty acid amide, higher fatty acid ester, wax, lubricating metal soap other than metal oxystearate may be used. Although the lubricity is improved by using a combination of lubricants, it can be said that the use of a lubricant is rather preferable. Further, a known stabilizer, an antistatic agent, an ultraviolet absorber, a processing aid, a plasticizer and the like which are usually blended in the polyolefin film may be used at all. The method for mixing the organic polymer fine particles, the metal oxystearate, the additives, and the like with the polypropylene polymer is not particularly limited, and may be a V-type blender, a screw-type blender, a drive blender, a ribbon blender, a Henschel mixer. Generally, a method of uniformly kneading with a mixer such as a kneader and kneading into pellets is used. The above organic polymer fine particles and the metal oxystearate may be kneaded in an extrusion step at the time of film formation, but are preferably kneaded at a high concentration with respect to a polypropylene polymer in advance, and are preferably compounded by a so-called master batch method. It is an embodiment. Alternatively, the organic polymer fine particles and the metal oxystearate may be mixed in advance, a thin film of the metal oxystearate formed on the surface of the organic polymer fine particles, and blended with the polypropylene polymer. The biaxially oriented polypropylene-based film of the present invention can be produced from the above-mentioned polypropylene-based polymer composition by a conventional means such as a simultaneous or successive biaxial stretching method using a tenter or an inflation method. Further, it can be applied to both a single-layer configuration and a multilayer configuration of two or more layers,
In the case of a laminated structure, the organic polymer fine particles and the metal salt of oxystearic acid are preferably added to the surface layer, but are not particularly limited. With a laminated structure of two or more layers, and
The method of adding the organic polymer fine particles and the metal salt of oxystearic acid to the surface layer is a particularly recommended embodiment because the effects of the present invention can be more remarkably exhibited. Further, the film of the present invention may be subjected to a surface treatment such as a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment or the like to improve the adhesiveness, if necessary. The thickness of the biaxially stretched film of the present invention is determined according to its use, but is usually 5 to 100 μm, preferably
It is in the range of 10 to 50 μm. Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples do not limit the present invention, and all modifications and alterations that do not depart from the gist of the present invention fall within the technical scope of the present invention. Included. In addition, the measuring method used in an Example is as follows. (1) Haze tester J manufactured by Toyo Seiki Seisakusho in accordance with JIS-K6714
Was measured. (2) Narrow angle diffuse transmission value Measured using a visual transparency tester manufactured by Toyo Seiki Seisaku-sho. The smaller the measured value, the higher the transparency. (3) Coefficient of friction was measured at 20 ° C. × 65% RH according to ASTM-D1894. (4) The blocking-resistant film is cut into a piece of 80 mm x 120 mm with a cutter, and two pieces of the cut pieces are overlapped with each other by being shifted vertically by 20 mm in the longitudinal direction. Five sets of this sample are alternately superimposed on a type sheet, sandwiched between glass plates, and then subjected to a load of 2 kg and left in an environment of 50 ° C. for 48 hours. The sample was taken out, allowed to cool, recut in the longitudinal direction with a width of 20 mm to obtain a test piece, and the test piece was measured for shear stress at a pulling speed of 200 mm / min using a tensile tester. Example 1 (1) Production of Masterbatch Polypropylene powder 9 having a melt index of 2.5 g / 10 minutes
2.5 parts by weight, water droplet holding time within 2 seconds, average particle size 1.1
Spherical crosslinked acryl-styrene copolymer particles having a substantially monodisperse particle size distribution of [mu] m [methyl methacrylate / n
-Butyl acrylate / styrene / divinylbenzene =
36/27/36/1 (weight ratio)] A mixture obtained by uniformly mixing 5 parts by weight and 2.5 parts by weight of basic magnesium 12-hydroxystearate with a Hensiel mixer at 200 ° C. using a twin-screw kneading extruder. To obtain a melt-extruded master batch. (2) Production of film For 100 parts by weight of polypropylene having a melt index of 2.5 g / 10 min.
Using a composition in which 0.3 parts by weight of glycerin resin acid ester and 0.3 part by weight of erucamide were mixed, the mixture was melt-extruded at a resin temperature of 270 ° C., quenched with a cooling roll at 20 ° C., and was 0.90 mm thick To obtain a stretched sheet. The stretched sheet was stretched 4.5 times in the longitudinal direction at a stretching temperature of 120 ° C. by utilizing the difference in roll peripheral speed of the longitudinal stretching machine, and subsequently stretched 8 times in the transverse direction at a stretching temperature of 155 ° C. by a tenter type stretching machine. . Next, a heat treatment was performed at 160 ° C. to form a biaxially stretched film having a thickness of about 25 μm, and then one surface was subjected to corona treatment. Table 1 below shows the formulations of Examples and Comparative Examples, and Table 2 shows the characteristic values of the obtained films. Comparative Example 1 The procedure of Example 1 was repeated except that the mixing of the basic magnesium 12-hydroxystearate was stopped and the amount of the polypropylene powder was changed to 95 parts by weight. Masterbatches and films were produced in the same manner. Comparative Example 2 A masterbatch and a film were produced in the same manner as in Example 1 except that calcium stearate was used instead of basic magnesium 12-hydroxystearate in the production of the masterbatch of Example 1. . Table 1 shows the characteristic values of the obtained film. Comparative Examples 3 and 4 The same procedure as in Example 1 was carried out except that the average particle system of the crosslinked acrylic-styrene copolymer particles was changed to 0.1 μm and 5.0 μm, respectively, in the production of the masterbatch of Example 1. To obtain a film. Comparative Examples 5 and 6 In the production of the masterbatch of Example 1, the addition amount of the crosslinked acryl-styrene copolymer particles was 0.05 parts by weight and 1.2 parts by weight, respectively, and the weight loss of the polymer particles was A film was obtained in the same manner as in Example 1, except that the film was offset with polypropylene powder. Example 2 In the method of Example 1, a crosslinked acrylic
In place of the styrene copolymer particles, spherical crosslinked acrylic polymer particles exhibiting a substantially monodispersed particle size distribution having an average particle size of 1.7 μm and having a water droplet retention time of 2 seconds or less [composition: methyl methacrylate / trimethylolpropane triane] Methacrylate = 98/2 (weight ratio)], and the amount of the master batch was changed to 2.05 parts by weight, to obtain a film in the same manner as in Example 1. Comparative Example 7 The same procedure as in Example 2 was carried out except that in the preparation of the masterbatch in Example 2, the mixing of the basic magnesium magnesium 12-hydroxystearate was stopped and the amount of the polypropylene powder was changed to 95 parts by weight. Masterbatches and films were produced by the method. Example 3 In the preparation of the masterbatch of Example 1, substantially monodisperse particles having a water droplet holding time of 2 seconds or less and an average particle size of 1.3 μm were used instead of the crosslinked acrylic-styrene copolymer particles. Spherical crosslinked polystyrene-based particles exhibiting a diameter distribution [prepared by suspension polymerization: composition; styrene / divinylbenzene = 98
/ 2 (weight ratio)], and a film was obtained in the same manner as in Example 1. Comparative Example 8 The procedure of Example 3 was repeated, except that the mixing of the basic magnesium 12-hydroxystearate was stopped and the amount of the polypropylene powder was changed to 95 parts by weight in the production of the master batch of Example 3. Masterbatches and films were produced by the method. Example 4 As a resin for the base layer, a melt index was used.
0.3 parts by weight of glycerin resin acid ester and 0.3 parts by weight of erucamide to 100 parts by weight of polypropylene 2.5 g / 10 min
Using the same composition as that used in Example 1 as the surface layer resin, the composition obtained by mixing parts by weight was melted with a separate extruder for the base layer lysine, and the melt was joined between dies to form a base layer resin. The melt having a three-layer structure in which a surface layer was laminated on both sides of the sample was quenched by a cooling roll at 20 ° C. to obtain a stretched sheet having a total thickness of 0.90 mm (thickness ratio of surface layer / base layer / surface layer =
1/23/1). This unstretched sheet was biaxially stretched in the same manner as in Example 1 to obtain a film. Comparative Example 9 A film was produced in the same manner as in Example 4 except that the blending of the basic magnesium 12-hydroxystearate was stopped. The films of the present invention obtained in Examples 1 to 3 each show excellent transparency, and show good sliding properties and blocking resistance,
Very high quality. On the other hand, the films obtained in Comparative Examples 1 and 2 were inferior in transparency and blocking resistance and were of low quality. In the “haze value”, which is generally used as a method for evaluating transparency, the films of Comparative Examples 1 and 2 do not have much difference from those of Examples, but have a high correlation with transparency by visual observation. It can be seen that the narrow-angle diffuse transmission value is significantly inferior. The films obtained in Comparative Examples 3 and 5 have good transparency, but have extremely poor slipperiness and blocking resistance. The films obtained in Comparative Examples 4 and 6 have good slipperiness and blocking resistance. However, the transparency was inferior, and all were of low quality. Further, the films obtained in Comparative Examples 7 and 8 had good slipperiness, but were inferior in transparency and blocking resistance. The film of the present invention obtained in Example 4 shows excellent transparency and good slipperiness and anti-blocking properties, is particularly excellent in transparency, and has a remarkable effect as a laminated film. , Very high quality. On the other hand, the film of Comparative Example 9 had good transparency and slipperiness, but was inferior in blocking resistance and of low quality. [Table 1] [Table 2] Since the polyolefin film of the present invention has a constitution in which the organic polymer fine particles and the metal salt of oxystearic acid are blended in a specific amount, the polyolefin film is excellent not only in transparency but also in slipperiness and blocking resistance. For example, it can be widely used as various packaging materials.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI B29K 23:00 B29K 23:00 (72) Inventor Tsutomu Isaka 2-8-2 Dojimahama, Kita-ku, Osaka-shi, Osaka Toyobo Co., Ltd. (56) References JP-A-1-129050 (JP, A) JP-A-8-59915 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 5/00-5 / 24 C08L 1/00-101/16

Claims (1)

(57) [Claim 1] 100 parts by weight of a crystalline propylene polymer,
(Meth) acrylic monomer with an average particle size of 0.3 to 3 µm
And / or from monomer components containing styrene monomers
Organic polymeric microparticles 0.0 consisting of polymerized polymer
1 to 1 part by weight and a metal salt of oxycarboxylic acid 0.01 to
A biaxially stretched polypropylene-based film, comprising 2 parts by weight of a composition.