JP3443966B2 - Biaxially oriented polypropylene film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polypropylene-based film which is excellent in film winding property in addition to transparency, slipperiness and blocking resistance.

[0002]

2. Description of the Related Art Biaxially oriented polypropylene film is
Since it is very excellent in 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 stick to each other, the opening property of the bag is deteriorated, and the workability of the packaging is deteriorated. Conventionally, inorganic fine particles have been added as a method for improving the slipperiness and blocking resistance of polyolefin-based films (for example, Japanese Patent Publication No.
52-16134, JP 3-9938) and organic polymer fine particles added (for example, JP 49-11945, JP 57-64522, JP 62-39219). Gazette) is known. Among them, the method using organic polymer fine particles is more useful than the method using inorganic fine particles because a film excellent in transparency and scratch resistance can be obtained, but transparency and slippage and blocking resistance The balance was insufficient, and there was a problem that it had not reached the level of satisfying high-level market demands. That is, when the amount of fine particles is reduced in order to achieve high transparency, slipperiness and blocking resistance deteriorate, and a problem occurs in workability in the manufacturing process and processing process of the film, and conversely,
If the properties of slipperiness and blocking resistance are satisfied, the transparency decreases, and there is no film that has both excellent properties of "transparency" and "slippery and blocking resistance" which are contradictory. The current situation. In addition, in recent years, automation of processing equipment such as film printing and laminating has rapidly advanced,
A film having excellent winding properties is required. In order to improve the winding characteristics of the film, it is important to easily escape the air that is caught between the films when winding the film, and to prevent wrinkles and winding deviations caused by the entrapped air as much as possible. Is. This can be achieved by increasing the particle size of the fine particles contained in the film,
There was a new problem of worsening transparency.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and its object is biaxial stretching which is excellent not only in transparency, slipperiness and blocking resistance but also in the winding property of the film. To provide a polypropylene film.

[0004]

The biaxially oriented polypropylene film of the present invention comprises 100 parts by weight of a crystalline propylene polymer and organic polymer fine particles having an average particle size of 0.1 to 1.5 μm.
(1) 0.02 to 0.5 parts by weight, with a particle size larger than the fine particles (1),
In addition, organic polymer fine particles with an average particle size of 1.5 to 4.0 μm
(2) 0.005-0.5 parts by weight and metal salt of oxycarboxylic acid 0.
Formed from 01 to 2 parts by weight of the composition. The organic polymer fine particles are preferably a polymer composed of a monomer component containing a (meth) acrylic monomer and / or a styrene monomer.

[0005]

The crystalline propylene polymer used in the biaxially oriented polypropylene film of the present invention includes propylene homopolymer, or propylene as a main component and ethylene, butene, hexene, 4-methylpentene or octene as a subordinate component. Another example is a copolymer consisting of the other α-olefin. Propylene homopolymer is the most preferable, but when it is a copolymer, it may be a random copolymer or a block copolymer, and a copolymer of propylene and 40% by weight or less of another α-olefin is preferable, and further 30% by weight. % Or less, particularly 20% by weight or less of a copolymer with ethylene or butene is preferable. The crystalline propylene-based polymer may be used alone or as a mixture of two or more. The crystalline propylene-based polymer has an isotactic index (II) of 40 or more, preferably 6
It is preferably 0 or more, particularly 80 or more. In the propylene homopolymer, those having II of 90 or more, particularly 95 or more are preferable. The melt index is 0.5-10g / 10 minutes,
Particularly, the one having 1 to 5 g / 10 minutes is preferable.

The molecular structures of the organic polymer fine particles (1) and (2) used in the present invention are such that they are non-melting at the melt molding temperature of the polypropylene polymer and have heat resistance to withstand the same temperature. There is no particular limitation so long as it is obtained by any one of addition polymerization method, polycondensation method and polyaddition reaction method. 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.

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

In the present invention, the organic polymer fine particles (1) and
As (2), it is preferable to use fine polymer particles composed of a monomer component containing a (meth) acrylic monomer and / or a styrene monomer, and a (meth) acrylic monomer or a homopolymer of a styrene monomer, or a (meth) acrylic monomer. Copolymers of monomers (including terpolymers other than copolymers; the same applies hereinafter), copolymers of styrene monomers, copolymers of (meth) acrylic monomers and styrene monomers, and the like. Among these, cross-linking type (meth) acrylic-ftylene-based copolymers are preferable, and they are excellent in balance of transparency, slipperiness, heat resistance, water drop retention time and the like. The polymer composition of the organic polymer particles (1) and (2) may be the same or different.

Examples of the (meth) acrylic monomer component include acrylic acid, methyl acrylate, ethyl acrylate, acrylic acid such as butyl acrylate, or ester derivatives thereof, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacrylic acid. 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. Further, as long as it is a small amount, a metal salt of (meth) acrylic acid, an amide derivative, an ester derivative having a special structure such as hydroxylethyl ester or dimethylaminoethyl ester may be used.

Examples of the styrene-based monomer component include styrene and its derivatives such as styrene, methylstyrene and α-methylstyrene. Further, a polymerizable vinyl monomer such as vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, methacrylonitrile or the like may be copolymerized as long as it is 20% by weight or less of the total monomer components. Examples of the cross-linking method include means such as copolymerizing a polyfunctional monomer such as diacrylic acid ester or dimethacrylic acid ester of ethylene glycol with a fine particle polymer, or post-crosslinking after forming the polymer. , But not limited to these. The effect of the present invention is more remarkably exhibited when the organic polymer fine particles of the present invention, which have a water drop retention time of 1 minute or less as measured by the following method and are highly hydrophilic.

[Water Drop Holding Time] Organic polymer particles are sandwiched between two biaxially oriented polypropylene films on a horizontal and smooth table, and the upper film is lightly pressed by hand to smooth organic polymer particles having a thickness of 2 mm. After forming the layers, gently remove the upper film. A drop of water with a diameter of 3 mm was placed on the surface of the obtained organic polymer fine particle layer with a height of 1 cm.
The water drop retention time is defined as the time until the water drops are absorbed from the organic polymer microparticle layer and disappear.

In the present invention, it is essential that the fine particles of organic polymer (1) and (2) having different average particle diameters are contained in the film composition in a specific amount. That is, the organic polymer fine particles (1) having a small particle diameter mainly improve the slipperiness and blocking resistance, and the fine particles (2) having a large particle diameter improve the winding property of the film. It is characterized by a combination of. At this time, the average particle size of the organic polymer fine particles (1) should be in the range of 0.1 to 1.5 μm.
The average particle size of (2) is larger than that of the fine particles (1) and is 1.5
~ 4.0 μm. In addition, the amount of the organic polymer fine particles (1) blended is 0 with respect to 100 parts by weight of the polypropylene polymer.
The amount of fine particles (2) should be 0.005
~ 0.5 parts by weight. When the average particle diameter or the blending amount is less than the above range, the effect of improving the slipperiness, blocking resistance and film winding property is not exhibited, and when it exceeds the above range, the transparency is deteriorated, which is not preferable.

The distribution of the particle size of the organic polymer fine particles (1) and (2) is preferably sharp in terms of satisfying the transparency, slipperiness, blocking resistance and winding property. In addition,
The average particle size of the organic polymer fine particles of the present invention is 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. The optimum value of the average particle diameter and the blending 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., and is appropriately set within the above range according to the desired film characteristics. It is good to set it arbitrarily.

As the oxycarboxylic acid of the metal salt of oxycarboxylic acid in the present invention, oxystearic acid is preferable, and as the metal salt of oxystearic acid, there is a metal acid of stearic acid having one hydroxyl group, 2-, 3-, 4-, 5-, 7-, 9-, 11 as the position of the hydroxyl group
There are isomers of-, 12- and 18-, but 12-oxystearic acid is one of the recommended compounds because it can be industrially produced at low cost by catalytic reduction of ricinol, which is the main resin acid of castor oil. is there. As the metal salt, Li, N
Alkali metal salts such as a, K, Mg, Ca, Sr, B
Alkaline earth metal salts such as a, Zn salts, etc., but M
The use of g and Ca salts is particularly preferred. Further, as the 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 effect of the present invention is not impaired, organic or inorganic fine particles other than organic polymer fine particles are used in combination, and higher fatty acid amides, higher fatty acid esters, waxes, lubrication of metal soaps other than metal oxystearate, etc. Although the lubricity is improved by, for example, using a lubricant together, it can be said that the use of a lubricant is a rather preferable embodiment. Further, known stabilizers, antistatic agents, ultraviolet absorbers, processing aids, plasticizers and the like which are usually blended in polyolefin films may be used in combination. The method of mixing the organic polymer fine particles, the metal salt of oxystearate, the additive, and the like with the polypropylene polymer is not particularly limited, and a V-type blender, a screw-type blender, a dry blender, a ribbon blender, a Henschel mixer. Generally, a method of uniformly mixing with a mixer such as the above and then kneading into pellets is used. The above-mentioned organic polymer fine particles and the metal salt of oxystearate may be kneaded in the extrusion step at the time of film formation, but they are preferably kneaded in a high concentration with respect to the polypropylene polymer in advance, and preferably blended by a so-called masterbatch method. It is an embodiment. Alternatively, the fine particles of the organic polymer and the metal salt of oxystearate may be mixed in advance to form a thin film of the metal salt of oxystearate on the surface of the fine particles of the polymer, and the fine particles may be blended with the polypropylene polymer.

The biaxially stretched polypropylene film of the present invention can be produced from the above polypropylene-based polymer composition by a conventional means such as simultaneous or sequential biaxial stretching method using a tenter and inflation method. Further, it can be applied to both a single layer structure and a laminated structure of two or more layers,
In the case of a laminated structure, it is preferable to add the organic polymer fine particles and the metal salt of oxystearic acid to the surface layer, but it is 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 effect 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 application, but is usually 5 to 100 μm, preferably
It is in the range of 10 to 50 μm.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification and implementation within the scope of the present invention is within the technical scope of the present invention. Included. The measuring method used in the examples is as follows. (1) Haze tester J manufactured by Toyo Seiki Seisakusho according to JIS-K6714
It was measured at. (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) Friction coefficient Measured according to ASTM-D1894 at 20 ° C x 65% RH. (4) A blocking resistant film is cut into 80 mm × 120 mm by a cutter, and two cut pieces are vertically shifted by 20 mm and overlapped to obtain a sample. Five sets of this sample and type paper are alternately stacked, sandwiched between glass plates, and a weight of 2 kg is applied, and the sample is left to stand in an environment of 50 ° C. for 48 hours. The sample was taken out, allowed to cool, and re-cut in the longitudinal direction with a width of 20 mm to give a test piece. The test piece was measured for shear stress at a pulling speed of 200 mm / min using a tensile tester. (5) Air bleeding speed First, after placing the film 4 on the base 1 shown in FIG. 1 with the B side (flat surface) facing upward, place the film presser 2 on the base 4 onto the base 1. The film 4 is placed and fixed while applying tension. Then, the film 5 is placed on the film retainer 2 with the A side (easy sliding surface) facing downward, the film retainer 8 is placed on the film 5, and the film retainers 8 and 2 are attached using the screws 3 and the base 1 To fix. Here, when the vacuum pump 6 connected through the pores 2c and the pipe 7 is driven and sucked from the cavity 2a provided in the film retainer 2, the film 5 is attracted to the cavity 2a, so that the tension is increased. Add. Further, at that time, the overlapping portion X of the film 4 and the film 5 is also circumferentially provided on the film retainer 2 and is decompressed through the pores 2d, and the film 4 and the film 5 are overlapped from the outer peripheral portion at the overlapping portion X. Start to stick together. Since the close contact state can be grasped by observing the interference fringes from the upper part of the X section, the interference fringes spread from the outer circumference of the X section to the entire X section until the movement of the interference fringes stops. The time (second) was measured, and this time (second) was defined as the "air escape rate". The shorter the deflation time, the better the winding properties of the film.

[0018]

Example 1 (1) Production of masterbatch Polypropylene powder 9 with melt index 2.5 g / 10 min
1.4 parts by weight, cross-linked acrylic with water drop retention time within 2 seconds-
Styrene-based copolymer particles [methyl methacrylate / n-
Butyl acrylate / styrene / divinylbenzene = 36
/ 27/36/1 (weight ratio)], the average particle size is 1.1 μm
5.0 parts by weight of [fine particles (1)] and 2.1 μm [fine particles]
(2)] 1.0 part by weight (all were spherical fine particles exhibiting a substantially monodisperse particle size distribution), and basic magnesium 12-hydroxystearate 2.6 parts by weight were uniformly mixed using a Henschel mixer. The product was melt-extruded at 200 ° C. using a twin-screw kneading extruder to obtain a masterbatch. (2) Production of film For 100 parts by weight of polypropylene having a melt index of 2.5 g / 10 min, the masterbatch produced by the above method 3.1
Using a composition in which 0.3 part by weight of glycerin resin acid ester and 0.3 part by weight of erucic acid amide are mixed, melt extrusion is performed at a resin temperature of 270 ° C, and the mixture is rapidly cooled with a cooling roller at 20 ° C to give a thickness of 0.90 mm. To obtain an unstretched sheet. This unstretched sheet was stretched 4.5 times in the machine direction at a stretching temperature of 120 ° C. by utilizing the roll peripheral speed difference of the machine, and was subsequently stretched 8 times in the transverse direction at a stretching temperature of 155 ° C. by a tenter type stretching machine. . Then, heat treatment was carried out at 160 ° C. to obtain a biaxially stretched film having a thickness of about 25 μm, and then one side was subjected to corona treatment. Table 1 shows the compounding recipes of Examples and Comparative Examples, and Table 2 shows the characteristic values of the obtained films.

[0019]

[Comparative Example 1] The same method as in Example 1 except that in the production method of the masterbatch of Example 1, the basic magnesium 12-hydroxystearate was stopped and the amount of polypropylene powder was changed to 94 parts by weight. Masterbatches and films were produced.

[0020]

Comparative Example 2 A masterbatch and a film were produced in the same manner as in Example 1 except that calcium stearate was changed in place of basic magnesium 12-hydroxystearate in the method for producing the masterbatch of Example 1. .

[0021]

[Comparative Example 3] The same as Example 1 except that the fine particles (2) having an average particle size of 2.1 μm were not mixed in the production of the masterbatch of Example 1 and the amount of polypropylene powder was changed to 92.4 parts by weight. A film was obtained by the method.

[0022]

[Comparative Example 4] In the production of the masterbatch of Example 1, the same method as in Example 1 was used, except that the fine particles (1) having an average particle size of 1.1 μm were not compounded and the compounding amount of polypropylene powder was changed to 96.4 parts by weight. I got a film with.

[0023]

[Comparative Example 5] In the production of the masterbatch of Example 1, except that the compounding amount of the fine particles (1) having an average particle size of 1.1 μm was changed to 1 part by weight and the compounding amount of the polypropylene powder was changed to 95.4 parts by weight, A film was obtained in the same manner as in 1.

[0024]

Comparative Example 6 In the production of the film of Example 1, 1.05 parts by weight of fine particles (1) having an average particle size of 1.1 μm and 0.5 parts by weight of basic 12-magnesium oxystearate were added to 100 parts by weight of polypropylene. A film was obtained in the same manner as in Example 1 except that the above was performed.

[0025]

Comparative Example 7 The procedure of Example 1 was repeated except that the amount of the fine particles (2) having an average particle size of 2.1 μm was changed to 0.16 parts by weight and the amount of polypropylene powder was changed to 92.24 parts by weight. A film was obtained in the same manner as in Example 1.

[0026]

Comparative Example 8 In the production of the film of Example 1, 0.57 part by weight of fine particles (2) having an average particle size of 2.1 μm and 0.3 part by weight of basic 12-magnesium oxystearate were added to 100 parts by weight of polypropylene. A film was obtained in the same manner as in Example 1 except that the above was performed.

[0027]

Example 2 In the production of the masterbatch of Example 1, the crosslinked acrylic-styrene copolymer particles were replaced by
Spherical cross-linked acrylic particles having a monodisperse particle size distribution of 0.95 μm [fine particles (1)] and 2.5 μm [fine particles (2)] having a water drop retention time of 2 seconds or less [composition; methyl methacrylate] / Trimethylolpropene trimethacrylate = 98/2 (weight ratio)], and the compounding amounts thereof are 6.67 parts by weight, 0.83 parts by weight, polypropylene powder and basic magnesium 12-oxystearate in the compounding amounts of 89.0, respectively. A film was obtained in the same manner as in Example 1 except that the amount was 3.5 parts by weight.

[0028]

Comparative Example 9 Same as Example 2 except that in the preparation of the masterbatch of Example 2, the basic magnesium 12-oxystearate was stopped and the polypropylene powder was changed to 92.5 parts by weight. A film was obtained by the method.

[0029]

[Comparative Example 10] In the production of the masterbatch of Example 2, the same as Example 2 except that the compounding of the fine particles (2) having an average particle size of 2.5 μm was stopped and the compounding amount of the polypropylene powder was changed to 89.83 parts by weight. A film was obtained in the same way.

[0030]

Comparative Example 11 The same as Example 2 except that in the production of the masterbatch of Example 2, the fine particles (1) having an average particle size of 0.9 μm were stopped and the polypropylene powder was mixed in an amount of 95.67 parts by weight. A film was obtained by the method.

[0031]

Example 3 In the method for producing a masterbatch of Example 2, the crosslinked polystyrene type particles having a spherical and substantially monodisperse particle size distribution in place of the crosslinked acrylic particles and having a water drop retention time of 2 seconds or less [composition; styrene / Divinylbenzene = 98
/ 2] (the fine particles (1) and (2) had the same average particle size and compounding amount as in Example 2), and a film was obtained in the same manner as in Example 2.

[0032]

[Comparative Example 12] The same as Example 3 except that the compounding of basic magnesium 12-oxystearate was stopped and the compounding amount of polypropylene powder was changed to 92.5 parts by weight in the method for producing the masterbatch of Example 3. A film was obtained in the same way.

[0033]

Example 4 As a resin for the base layer, a melt index
0.3 part by weight of glycerin resin acid ester and 0.3 part of erucic acid amide for 100 parts by weight of polypropylene 2.5 g / 10 min
Using the same composition as used in Example 1 as the resin for the surface layer, the lysine for the base layer was melted by a separate extruder, and the melt was merged between the dies to form a base layer. The three-layered melt having surface layers laminated on both sides was rapidly cooled with a chill roll at 20 ° C. to obtain an unstretched sheet with a total thickness of 0.90 mm (surface layer / base layer / surface layer thickness ratio =
1/23/1). This unstretched sheet was biaxially stretched in the same manner as in Example 1 to obtain a film.

[0034]

Comparative Example 13 A film was produced in the same manner as in Example 4, except that the basic magnesium 12-hydroxystearate was stopped in the method of Example 4.

The films of the present invention obtained in Examples 1 to 3 have excellent transparency, good slipperiness and blocking resistance, and excellent film winding characteristics.
It was of very high quality. On the other hand, Comparative Examples 1, 2, 9, 12
The film obtained in 1. was inferior in transparency, blocking resistance, and air bleeding speed, and was of low quality. Comparative Example 3,
The films obtained in Nos. 7 and 10 have good transparency, but have poor air bleeding speed and poor winding characteristics. Comparative Example 4,
The films obtained in Nos. 5 and 11 are inferior in slipperiness, blocking resistance and air bleeding speed. The films obtained in Comparative Examples 6 and 8 had good film winding characteristics but poor transparency. The film of the present invention obtained in Example 4 has excellent transparency, good slipperiness and blocking resistance, and also has good film winding characteristics. In particular, the transparency is extremely excellent, the effect of forming a laminated film is remarkably exhibited, and the quality is extremely high. On the other hand, the film of Comparative Example 9 has good transparency and slidability,
The blocking resistance and the winding property were poor and the quality was low.

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

The polyolefin film of the present invention is
Since it is composed of a specific amount of organic polymer fine particles and a metal salt of oxystearic acid, it has excellent transparency, slipperiness and blocking resistance, and film winding characteristics. For example, it is widely used as various packaging materials. can do.

[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 platform 2,8 film holder 2a cavity 2c, 2d pores 3 screws 4,5 film 6 vacuum pipe 7 pipes X film overlap

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Isaka 2-8 Dojimahama, Kita-ku, Osaka City, Osaka Prefecture Toyobo Co., Ltd. (56) Reference JP-A-5-214120 (JP, A) JP JP-A-47-34542 (JP, A) JP-A-3-188139 (JP, A) JP-A-6-73202 (JP, A) JP-A-63-25024 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) C08L 23/02-23/24 C08J 5/18 CES

Claims (2)

(57) [Claims] 1. A crystalline propylene polymer 100 parts by weight,
Organic polymer particles with an average particle size of 0.1 to 1.5 μm (1) 0.02
~ 0.5 parts by weight, finer particles of organic polymer (2) having a larger particle size than the fine particles (1) and an average particle size of 1.5 to 4.0 μm (0.005 to 0.
A biaxially oriented polypropylene film, comprising 5 parts by weight and 0.01 to 2 parts by weight of a metal salt of oxycarboxylic acid. 2. The biaxially oriented polypropylene according to claim 1, wherein the polymer of the organic polymer fine particles is a polymer polymerized from a monomer component containing a (meth) acrylic monomer and / or a styrene monomer. Series film.