JPH0827329A - Polypropylene film - Google Patents

Abstract

PURPOSE:To obtain a polypropylene film excellent in clarity, antiblocking properties, slip properties, and scratch resistance. CONSTITUTION:This film is produced from a compsn. comprising 100 pts.wt. crystalline propylene copolymer and 0.01-1 pt.wt. fine spherical magnesium silicate particles having an average particle size of 0. 5-7mum, a magnesium oxide content of 40wt.% or lower. a sphericity (Fx) of 0.7 or higher, a specific surface area by the BET method of 500m<2>/g or higher, and an oil absorption of 150ml/100g or lower. Pref., the copolymer is a crystalline propylene-alpha-olefin copolymer having a propylene unit content of 80wt.% or higher and a crystalline m.p. of 150 deg.C or lower.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to polypropylene films. More specifically, the present invention relates to a polypropylene film which is excellent in slipping property and blocking preventing property at the time of forming a polypropylene film, and is excellent in transparency and scratch property.

[0002]

2. Description of the Related Art A polypropylene film using a crystalline propylene copolymer is most widely used as various packaging materials. However, a polypropylene film using such a crystalline propylene copolymer has a drawback that it is apt to cause blocking due to its adhesiveness and thus impairs workability during film forming and high-order processing, and further, the film. When, for example, packing or wrapping is performed, problems such as defective opening of the film are likely to occur. In order to solve such a drawback, a method of adding anhydrous activated silicic acid (silica) to the crystalline propylene copolymer has been disclosed in JP-B-39-16908 and finely pulverized zeolite powder. Is added to the crystalline propylene copolymer as disclosed in JP-B-52-16134.
It has been proposed in the publication. However, although these methods show some improvement effect in terms of blocking resistance, they do not satisfy other recently required performance requirements. That is, recently, the transparency of the film is emphasized from the viewpoint of aesthetics. Further, in order to enhance the blocking resistance of the film, a large amount of an antiblocking agent may be blended, but if the blending amount of the antiblocking agent is increased, the amount of the antiblocking agent is increased accordingly in the crystalline propylene copolymer. Dispersion becomes poor, resulting in poor transparency.

Further, since the film forming apparatus in recent years has been designed to operate at high speed, winding workability during film forming has become very important. If the slipperiness (especially the initial slipperiness) at the time of winding the film is not good, the film cannot be taken up well, so that many defective products are produced. However, the slipperiness at the time of winding the film is obtained by mixing various lubricants. The reality is that it cannot be improved easily.

Further, when an extremely hard substance such as synthetic zeolite is added to the crystalline propylene copolymer in order to improve the blocking resistance and the sliding property, the film surface is scratched due to the rubbing of the films, There is a defect that the appearance of the obtained film is significantly deteriorated.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies to solve the above-mentioned problems of a polypropylene film using a conventional crystalline propylene copolymer. As a result, when a crystalline propylene copolymer is formed into a film by using a composition containing a specific amount of spherical fine particles of magnesium silicate, the resulting film has transparency, blocking resistance, slipperiness and scratchability. It was found that the film would be a significantly improved film, and the present invention was completed based on this finding. As is clear from the above description, an object of the present invention is to provide a polypropylene film having excellent transparency, blocking resistance, slipperiness and scratch resistance.

[0006]

Means for Solving the Problems The present invention includes the following (1):
It has the configuration of (2). (1) 100 parts by weight of crystalline propylene copolymer, average particle diameter of 0.5 to 7 μm, magnesium oxide content of 40% by weight or less, sphericity (Fx) of 0.7 or more, specific surface area by BET method Is 500 m ² / g or more and the oil absorption is 15
A polypropylene film comprising a composition containing 0.01 to 1 part by weight of spherical fine particles of magnesium silicate of 0 ml / 100 g or less. (2) The crystalline propylene copolymer has a propylene component of 80.
The polypropylene film according to the above item 1, which is a crystalline propylene-α-olefin copolymer having a crystal melting point of 150 ° C. or less in an amount of not less than wt%.

Hereinafter, the present invention will be described in detail. The polypropylene film of the present invention is a crystalline propylene-α-olefin copolymer having a propylene component copolymerization ratio of 80% by weight or more, preferably a crystalline propylene-α-olefin copolymer having a crystal melting point of 150 ° C. or less, 100 In the parts by weight, the average particle size is 0.5 to 7 μm, the magnesium oxide content is 40% by weight or less, the sphericity (Fx) is 0.7 or more, and the non-surface area by the BET method is 500 m ² / g or more,
In addition, a film is formed by using a composition in which 0.01 to 1 part by weight of spherical fine particles of magnesium silicate having an oil absorption of 150 ml / 100 g or less is blended.

Crystalline propylene-α used in the present invention
The -olefin copolymer is a crystalline diolefin obtained by copolymerizing 1 or 2 or more of these α-olefin components with ethylene or butene-1, hexene or the like having 4 or more carbon atoms, and propylene. The copolymer is a terpolymer or a terpolymer or more terpolymer, preferably a crystalline propylene-α-olefin copolymer having a crystal melting point of 150 ° C. or less. The crystal melting point (hereinafter referred to as Tm)
Is 150 ° C. or less, the polypropylene film obtained has not only good slipperiness and blocking resistance, but also good transparency. Here, the crystal melting point (Tm)
Means the peak temperature of the endothermic curve accompanying the melting of crystals obtained by heating a 10 mg sample at a rate of 10 ° C./min in a nitrogen atmosphere using a scanning differential calorimeter. In the case of a crystalline copolymer containing propylene as a main component, Tm increases as the content of ethylene or α-olefin as a comonomer component increases.
Will fall. For example, in the case of a crystalline ethylene-propylene random copolymer, it will be 150 ° C. or lower when the ethylene content exceeds approximately 2.5% by weight, although it varies slightly depending on the randomness of the copolymer. It is possible to obtain a polymer having a plurality of Tm's by carrying out copolymerization in two or more stages by multistage polymerization under different polymerization conditions. In this case, a polymer having a main peak of 150 ° C. or lower is desirable.

The spherical fine particles of magnesium silicate used in the present invention have a content of magnesium oxide (MgO) of 40% by weight or less and a sphericity (Fx) of 0.7 or more.
The specific surface area by the T method is 500 m ² / g or more and the oil absorption amount is 150 ml / 100 g or less. The composition formula thereof is (SiO ₂ ) x. (MgO) y. (Na ₂ O) z. (H ₂
O) n, where the component ratio of each component is x = 30 to 99% by weight y = 0.5 to 40% by weight z = 0 to 2% by weight n = 1 to 25% by weight, and x + y + z + n = It is 100% by weight. Such magnesium silicate is obtained by reacting silicon dioxide (SiO ₂ ) prepared by the gel method with magnesium hydroxide (Mg (OH) ₂ ), and a commercially available product is a trade name of Mizusawa Chemical Industry Co., Ltd.・ Mizpearl M is mentioned. The average particle size of the spherical fine particles of magnesium silicate is 0.5 to 7 μm, and the average particle size is 7 μm.
When it is more than 0.5, the transparency of the obtained film is deteriorated, and when it is less than 0.5 μ, the slipperiness and blocking resistance at the time of winding the film during molding are poor.

The compounding amount of the spherical particles of magnesium silicate is 100% by weight of crystalline propylene-α-olefin copolymer.
It is 0.01 to 1 part by weight, and particularly preferably 0.03 to 0.3 part by weight, based on parts by weight. If the amount is less than 0.01 part by weight, the effect of improving the slipperiness and blocking resistance of the resulting film is insufficient, and if it exceeds 1 part by weight, fish eyes are generated and transparency is deteriorated, which is not preferable. The magnesium oxide content of the magnesium silicate spherical fine particles used in the present invention is 40% by weight or less. If the magnesium oxide content exceeds 40% by weight, the scratch resistance of the obtained film is deteriorated.

The sphericity (Fx) of the magnesium silicate spherical fine particles used in the present invention is 0.7 or more,
When the sphericity (Fx) of less than 0.7 is used, the slipperiness of the obtained film is poor. Further, the specific surface area of the magnesium silicate spherical fine particles used in the present invention by the BET method is 500 m ² / g or more, and the oil absorption is 150 ml.
/ 100 g or less. The specific surface area is 500 m ²
/ G and oil absorption of more than 150 ml / 100 g, the resulting film has good blocking properties but poor slipperiness. The average particle diameter, specific surface area and oil absorption of the spherical magnesium silicate particles in the present invention are measured by the following methods. Average particle size: According to the Coulter counter method. Sphericity (Fx): Fx = A / (π / 4) Dmax Here, A is the cross-sectional area (mm ² ) of the powder, and Dmax is the longest diameter (mm) of the cross-section. A and Dmax are obtained by adding an epoxy resin to spherical fine particles of magnesium silicate to solidify, cutting with a microtome, and analyzing the cross section of the fine particles with an image analyzer. Specific surface area: By BET method by N ₂ adsorption at liquid nitrogen temperature. Oil absorption: In accordance with JIS K-5101 19.

In the composition according to the present invention, various antioxidants, neutralizing agents, lubricants, antiblocking agents, antistatic agents, olefinic rubbers, etc., which are usually compounded with polyolefins, are included in the composition of the present invention. It may be added or used in combination within a range that does not impair the effect of. As a method of adding the above-mentioned additive to the composition of the present invention, any method may be used as long as it is a method of uniformly dispersing the mixture, and the mixture is mixed with a ribbon blender, a Hensell mixer (trade name) or the like, and the mixture is mixed. It is preferable to melt-knead the above with an extruder or the like and pelletize. The polypropylene film of the present invention can be obtained from the above composition in the form of a uniaxially or biaxially stretched film or an unstretched film by a usual film extrusion molding method such as a T-die method or an inflation method. Further, in the present invention, in addition to the above single-layer plastic film, the single-layer film may be laminated on one or both surface layers of another substrate film to form a laminated composite film. The case of a single-layer film will be described below, but the same applies to the case of a composite film.

[0013]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The methods for measuring the physical properties shown in Examples and Comparative Examples and the criteria for evaluation are as follows. (1) Haze: A value (unit:%) measured according to ASTM D 1003 is shown as haze.
The smaller this value is, the better the transparency and the film appearance are, and the haze value of 4.0% or less is defined as good. (2) Slip property (initial / dynamic friction coefficient): 30 minutes after the film is formed, the slip property is determined by the dynamic friction coefficient between the corona-treated surface and the non-treated surface of the base film measured by the method specified in ASTM D523. Indicated. The smaller this value is, the better the slip property is, and the coefficient of dynamic friction of 0.80 or less is considered good. (3) Blocking degree 2 cm (width) x 7 cm (length) corona-treated film and non-corona-treated film of the same size are length 2
over 50 cm under a load of 500 g / cm ₂ ,
After standing for 24 hours, the force required for breaking and peeling the sample was measured using a tensile tester. The smaller this value is, the better the blocking resistance is. 0.70 kgf / 4 cm ²
The following were considered good. (4) Scratchability (Scratchability) The compositions of Examples and Comparative Examples were extruded at a melting temperature of 220 ° C. using a 65-dia.
It is rapidly cooled with an air chamber and a cooling roll with a surface temperature of 30 ° C to form a film, and immediately subjected to corona discharge treatment so that the wetting index on one side of the film is 400 dyne / cm, and a film with a thickness of 25 μm and a width of 60 cm is obtained. I wound up. This film was cut into a width of 50 cm using a slitter and set as a base film in a continuous vacuum vapor deposition apparatus. While continuously feeding the base film into the vapor deposition chamber, aluminum vapor deposition was performed on the corona-treated surface under a vacuum of 10 ^-5 Torr. Then, the film was wound up to obtain an aluminum vapor-deposited film having a vapor-deposited film thickness of about 500 Å and a length of 1000 m and having aluminum vapor-deposited on one surface.

The glossiness of the vapor deposition surface of the aluminum vapor deposition film obtained above is measured according to the method defined in ASTM D 523, and the value is designated as G1. Next, A
According to the method specified in STM D1894, the vapor deposition surface of the aluminum vapor deposition film is set on the table side and the non-vapor deposition surface is set on the sled side, and the sled is slid. (At this time, the sled weighs 2200 g.) The glossiness of the portion of the aluminum vapor-deposited film on the table side through which the sled has passed is measured and designated as G2. Further, ΔG was obtained from the following formula, and the scratch resistance was shown by the value. ΔG = G1−G2 The smaller this value, the less likely scratches are and the better the scratchability is. (5) Melt flow rate of polypropylene resin (M
FR) According to JIS K 6758 (test conditions: 230 ° C, 2.16kgf).

Example 1 100 parts by weight of a crystalline ethylene-propylene binary random copolymer having a crystal melting point (Tm) of 147 ° C., an ethylene copolymerization ratio of 2.5% by weight, and an MFR of 7.0 g / 10 min. To
0.20 parts by weight of a specific magnesium silicate spherical fine powder shown in Table 1 below was blended, and tetrakis- was used as an antioxidant.
[Methylene-3- (3 ', 5'-di-t-butyl-4'
-Hydroxyphenyl) propionate] methane 0.10 part by weight, calcium stearate 0.10 part by weight as a neutralizing agent, erucic acid amide 0.10 part by weight as a lubricant,
After stirring and mixing for 3 minutes with a Henschel mixer, pellets were formed using an extruder. The obtained pellets were kneaded and extruded at a melting kneading temperature of 220 ° C using a 65 mmφ extruder with a T-die, and rapidly cooled with an air chamber and a cooling roll having a surface temperature of 30 ° C to obtain a polypropylene film, which was immediately coated on one side of the film. A film having a thickness of 25 μ and a width of 60 cm was wound while performing corona discharge treatment so that the wetting index was 40 dyn / cm. The characteristics of the obtained film are shown in Table 2 below. As is clear from Table 2, haze, slip property, blocking property, and scratch property were all good.

Examples 2 to 7 and Comparative Examples 1 to 3 In Examples 2 to 7, the crystalline melting point (Tm) was 137 ° C., the ethylene copolymerization ratio was 3.0% by weight, and the butene-1 copolymerization ratio was 100 parts by weight of a crystalline ethylene-propylene-butene-1 ternary random copolymer having 1.2% by weight and an MFR of 7.0 g / 10 min was blended with a specific amount of a specific magnesium silicate shown in Table 1 below. A film was produced in accordance with Example 1 except that the above was performed. Further, as Comparative Examples 1 to 3, Comparative Example 1 has an average particle size of 9.0 μm, and Comparative Example 2 has a sphericity (F
x) is 0.55, Comparative Example 3 is a film based on Example 1 except that magnesium silicate fine particles having a magnesium oxide content of 50% by weight and outside the range of the magnesium silicate spherical fine particles used in the present invention are used. It was created. Table 2 shows the characteristics of the films obtained in the examples and comparative examples. As is clear from Table 2, the haze of the film obtained in Comparative Example 1 in which the average particle diameter of the magnesium silicate fine particles used is outside the range of the present invention is poor, and the slip of the film obtained in Comparative Example 2 in which the sphericity is out of range. It can be seen that the scratch resistance of the film obtained in Comparative Example 3 in which the property deteriorates and the magnesium oxide content deviates, deteriorates.

Example 8 A crystalline ethylene-propylene binary random copolymer having a crystalline melting point (Tm) of 157 ° C., an ethylene copolymerization ratio of 0.5% by weight, and an MFR of 7.0 g / 10 min was used. A film was prepared according to Example 1. The characteristics of the obtained film are shown in Table 2. As is clear from Table 2, the obtained film has good slip properties, blocking properties, and scratch properties.

Comparative Examples 4 to 8 Crystal melting point (Tm) 137 ° C., ethylene copolymerization ratio 3.0% by weight, butene-1 copolymerization ratio 1.2% by weight, MFR 7.0 g / 10 min. Example 1 except that 100 parts by weight of the crystalline ethylene-propylene-butene-1 terpolymer of Example 1 was blended with additives as described in Table 1 below.
A film was prepared according to the above (however, Comparative Example 4 was not added). The characteristics of the films obtained in each comparative example are shown in Table 2. As is clear from Table 2, the obtained film is inferior in slip properties, blocking properties or scratch properties.

[0019]

EFFECT OF THE INVENTION Since the polypropylene film of the present invention uses a specific amount of specific spherical particles of magnesium silicate, it has excellent properties of transparency, slip property (slip property), blocking resistance and scratch property. There is. Also,
Compared with the conventionally used anti-blocking agent silica and the film using synthetic zeolite, it is excellent in all properties such as slip property (slip property), blocking resistance and scratch property.

[0020]

[Table 1]

[0021]

[Table 2]

Claims (2)

[Claims] 1. 100 parts by weight of crystalline propylene copolymer, average particle size 0.5 to 7 μm, magnesium oxide content 40% by weight or less, sphericity (Fx) 0.7 or more, BE
A polypropylene film comprising a composition in which 0.01 to 1 part by weight of spherical fine particles of magnesium silicate having a specific surface area of 500 m ² / g or more and an oil absorption of 150 ml / 100 g or less according to the T method are blended. 2. The polypropylene film according to claim 1, wherein the crystalline propylene copolymer is a crystalline propylene-α-olefin copolymer having a propylene component of 80% by weight or more and a crystal melting point of 150 ° C. or less.