JPH1148335A - Biaxially oriented polypropylene film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resistance to blocking, transparency, appearance and the like by a method wherein the fibrous organization of a reticulated structure, in which arced projections are intersected, is provided on at least one side surface while the average value of surface roughness as well as the average size of the mesh of the organization are specified so as to be specified values. SOLUTION: A fibrous organization, constituted of a reticulated structure wherein arced projections are intersected, is provided on at least one side surface while the average value of surface roughness of the organization is specified so as to be 20-100 nm and the average size of mesh is specified so as to be 40-300 nm. Further, the diameter of the arced projection is preferable to be 5-100 nm and the degree of crystallization of a biaxially oriented polypropylene film is preferable to be 40-80%. On the other hand, it is preferable that a small amount of a blocking preventing agent is contained within a range of not deteriorating the appearance of the film in order to provide the film with more excellent resistance to blocking. The content of blocking the preventing agent is preferable to be 0.001-1 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel biaxially oriented polypropylene film. More specifically, biaxial stretching made of polypropylene having crystallinity, significantly improved blocking resistance, excellent transparency and excellent film appearance, and little adhesion of dirt to guide rolls during bag making. It relates to a polypropylene film.

[0002]

2. Description of the Related Art A polypropylene film, particularly a biaxially stretched polypropylene film, is widely used as a packaging material due to its excellent mechanical and optical properties. However, these biaxially stretched polypropylene films have a smooth surface and poor blocking resistance, and the wound films adhere to each other (hereinafter, referred to as blocking), or generate significant blocking under the pressure at the time of cutting the film. However, there is a disadvantage that workability in the packaging process is significantly reduced. Many studies have been made to improve such a defect of the blocking resistance. For example, a method of incorporating inorganic fine particles such as silica and talc as a blocking inhibitor (Japanese Patent Publication No. 52-16134)
Japanese Patent Application Laid-Open No. 50-36262), and a method for producing physical unevenness due to the above-mentioned anti-blocking agent on the film surface by a method of incorporating organic fine particles as an anti-blocking agent (Japanese Patent Publication No. 50-36262). I have.

However, when a large amount of the above-mentioned inorganic or organic fine particles are contained as an anti-blocking agent in order to improve the anti-blocking property, peeling occurs at the interface between the anti-blocking agent and the resin in the stretching process, and voids are formed. When the film travels on guide means such as a guide roll, a guide pin, and a triangular folding plate in a processing step such as bag making of the film or a problem that the transparency and appearance of the film are significantly deteriorated due to occurrence of the film, There is a problem that particles of the antiblocking agent protruding from the surface are scraped off, adhere to and accumulate on the guide means, and cause contamination.

Also, a method of adding a thermoplastic resin incompatible with polypropylene (Japanese Patent Laid-Open No. 4-122736),
A method of adding a β-crystal nucleating agent of polypropylene such as γ-quinacridone (JP-A-59-198122), a method of forming submicron granular projections of polypropylene on the film surface (JP-A-4-163442), etc. Although a method of roughening the film surface is known,
Films with irregularities formed on the surface by these methods have large surface roughness, decrease optical properties such as transparency and gloss, and during the bag making process, guide rolls and triangular folding plates of bag making machines In addition, there is a problem that stains due to white powder (resin shavings) occur due to friction, and it is impossible to obtain a film having the desired transparency and bag-making processability.

[0005]

As described above, attempts have been made in the past to improve the blocking resistance of a biaxially oriented polypropylene film by the above-described method. When added to the film, due to the occurrence of peeling voids due to the antiblocking agent, the transparency and appearance of the film are significantly deteriorated,
During the bag-making process, there is a problem that the anti-blocking agent falls off and the guide roll and the triangular folding plate of the bag-making machine are stained.

Accordingly, an object of the present invention is to provide a biaxially oriented polypropylene film having excellent blocking resistance, excellent transparency and appearance, and less adhesion of dirt to guide rolls and the like during bag making. To provide.

[0007]

From the above viewpoints, the present inventors have conducted intensive studies on a biaxially oriented polypropylene film which is excellent in blocking resistance, transparency and appearance and does not generate stain during bag making. By forming a specific fibrous structure having a network structure in which arc-shaped convex portions intersect on the surface of the film, blocking resistance is improved, and transparency and appearance are excellent, and no stain is generated during bag making processing. The inventors have found that a biaxially stretched polypropylene film can be obtained, and have completed the present invention.

That is, the present invention has a network-like fibrous structure in which arc-shaped convex portions intersect on at least one surface, and the average value of the surface roughness is 20 to 100 nm. A biaxially stretched polypropylene film having an average diameter of 40 to 300 nm.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a biaxially stretched polypropylene film needs to have, on at least one surface thereof, a fibrous structure (fibril) having a network structure in which arc-shaped convex portions intersect. In the case of a film having no network structure on both surfaces formed of a fibrous structure, blocking resistance is poor and blocking occurs. The network structure formed by the fibrous structure on the film surface,
It can be measured by a commercially available atomic force microscope. As an atomic force microscope, manufactured by JEOL,
An atomic force microscope device manufactured by Seiko Electronics, Digital Instruments, Topometrics, or the like can be used. FIG. 1 is an atomic force microscope image of the surface of the biaxially stretched polypropylene film produced in Example 1, in which a network structure formed of a fibrous structure is recognized.

In the biaxially oriented polypropylene film of the present invention, the average value of the surface roughness of at least one surface of the film is required to be in the range of 20 to 100 nm.
８０80 nm, preferably 30-80 nm.
More preferably, it is in the range of 70 nm. If the average value of the surface roughness is less than 20 nm, the effect of improving the blocking resistance cannot be obtained. On the other hand, when the thickness exceeds 100 nm, a problem arises in that, during the bag making process, the guide roll of the bag making machine, the triangular folded plate, and the like are stained by white powder (resin shavings) due to friction. The average value of the surface roughness is a value obtained by analyzing the roughness of an atomic force microscope (irregularity) image obtained by measuring an area of 1 μm square using the above-described atomic force microscope. The average value of the heights (roughness values) of all the measurement points (512 × 512 points) of the area was calculated, and this was calculated for any one of the biaxially stretched polypropylene films.
The measurement was performed at five points, and the average value was defined as the average value of the surface roughness.

The fibrous structure formed on at least one surface of the biaxially stretched polypropylene film of the present invention has an average diameter of a network having a network structure in which arc-shaped convex portions intersect.
It needs to be in the range of 0 to 300 nm,
It is preferably in the range of 250 nm, more preferably 60 to
More preferably, it is in the range of 200 nm.

That is, when the average diameter of the network of the network structure is less than 40 nm, the effect of improving the blocking resistance cannot be obtained. Conversely, even when the thickness exceeds 300 nm, the effect of improving the blocking resistance cannot be obtained.

The average diameter (average pore diameter) of the network having the above-mentioned network structure is defined as the value obtained from the outermost surface (highest position) of the above-mentioned atomic force microscope (concavo-convex) image measuring an area of 1 μm square.
In a region having a depth of less than 0 nm, a mesh portion (fibrous tissue) and a portion surrounded by the mesh (inside of the mesh) are binarized,
This is a value obtained by obtaining the area ratio of the two and the number of meshes using an image analysis device, and approximating the shape of the meshes to a circle. This can be applied to any one of the biaxially oriented polypropylene films.
The measurement was performed at five points, and the average value was defined as the average diameter of the mesh.

The biaxially oriented polypropylene film of the present invention has the above-mentioned specific fibrous structure (fibril) on at least one surface thereof, and the average value of the surface roughness and the average diameter of the network structure are as described above. If it is within the range, the effects of the present invention can be sufficiently achieved, but furthermore, the biaxially oriented polypropylene film of the present invention takes into account the blocking resistance, transparency, appearance, and physical properties such as generation of stains during bag making. Then, it is preferable to satisfy the following requirements.

The diameter of the arc-shaped projections on the surface of the biaxially stretched polypropylene film of the present invention observed by an atomic force microscope is not particularly limited, but is preferably in the range of 5 to 100 nm, More preferably, it is in the range of 70 nm.

The surface crystallinity of the biaxially oriented polypropylene film of the present invention is not particularly limited, but is preferably in the range of 40 to 80%, and more preferably 50 to 80%.
More preferably, it is in the range of 70%. The term “surface crystallinity” as used herein refers to “R. Gee. Queen (R.G.Quyn
n) by the Journal of Applied Polymer Scienc
e), a value obtained in 2, 166 (reflection ATR method based on the degree of crystallinity calculation method according to the absorbance ratio of the methyl group of 974 cm ^-1 and 998 ^-1 in the infrared absorption spectrum published in 1959).

The biaxially oriented polypropylene film of the present invention exhibits good blocking resistance even without containing an anti-blocking agent, but a small amount of the anti-blocking agent is added to the film to give better blocking resistance. Is preferably contained within a range that does not reduce the amount of

In the present invention, the content of the antiblocking agent is preferably in the range of 0.001 to 1% by weight, more preferably in the range of 0.005 to 0.5% by weight, and more preferably 0 to 0.5% by weight. It is preferably in the range of 0.01 to 0.2% by weight. When the content of the antiblocking agent is 1.
If the content exceeds 0% by weight, the number of peeling voids caused by the antiblocking agent increases, and the transparency and appearance of the film deteriorate. Further, dirt adheres to the guide rolls and the triangular folding plate of the bag making machine due to the removal of the antiblocking agent during the bag making process.

As the anti-blocking agent used in the biaxially oriented polypropylene film of the present invention, a known anti-blocking agent used for imparting blocking resistance to the film can be used without any particular limitation. For example,
Examples include inorganic blocking inhibitors such as silica, alumina, zeolite, kaolin, and calcium carbonate, and organic blocking inhibitors such as cross-linked polymethyl methacrylate, non-melting silicone resin powder, melamine resin powder, and polyamide resin powder. Among these, silica such as dry silica and wet silica, crosslinked polymethyl methacrylate powder, and non-melting type silicone resin powder are preferred.

The shape of the antiblocking agent used in the present invention is not particularly limited, but spherical particles having an excellent effect of improving the antiblocking property are preferred. Further, the average particle size of the antiblocking agent used in the present invention, 0.1-10 considering the anti-blocking effect of the biaxially stretched polypropylene film obtained, transparency and film appearance.
μm is preferable, and 0.5 to 3 μm is more preferable because a biaxially oriented polypropylene film having more excellent blocking resistance can be obtained.

As the material of the biaxially oriented polypropylene film of the present invention, a polypropylene having a known crystallinity is used without any particular limitation. In addition, as a component,
Examples include a homopolymer of propylene, a random copolymer of propylene and another α-olefin, or a mixture thereof. Examples of the α-olefin include ethylene, 1-butene, 1-pentene, 1
-Hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 4-methyl-1-pentene and the like can be mentioned. When the content of these α-olefins is 2 mol% or less, and more preferably 1 mol% or less, when the biaxially stretched polypropylene film is formed, the specific fibrous structure of the present invention is formed on the surface. It is preferable to obtain a biaxially stretched polypropylene film having good reproducibility.

In the present invention, the isotactic pentad fraction indicating the crystallinity of the polypropylene is not particularly limited, but is preferably in the range of 0.88 to 0.99, and more preferably 0.93 to 0.93. More preferably, it is in the range of 0.98 to 0.98.

The isotactic pentad fraction referred to here is defined as Macromolecules, 13 , 267 by A. Zambelli et al.
Propylene unit 5 quantified based on the peak assignment of the ¹³ C-NMR spectrum published in (1980)
This is the fraction in which the pieces take the same three-dimensional configuration continuously.

The melt flow of the above polypropylene
The latet is not particularly limited, but is usually 0.1 to 10 g in consideration of moldability to various stretched films.
/ 10 minutes is preferable, and 1 to 5 g /
More preferably, the range is 10 minutes. The range of the melt flow rate of the polypropylene of the present invention is expressed by a weight average molecular weight of 250,000 to 800,000, preferably 300,000 to 450,000.

The ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the polypropylene of the present invention.
The molecular weight distribution represented by is not particularly limited, but is preferably 2 to 20 in order to increase the melt tension and improve the processability in consideration of the ease of film formation, and more preferably 4 to 4. More preferably, it is in the range of 10 to 10. The molecular weight distribution was determined by gel permeation chromatography using o-dichlorobenzene as a solvent (hereinafter, referred to as “gel permeation chromatography”).
Also called GPC. ), The calibration curve used is calibrated with standard polystyrene.

The amount of the p-xylene soluble matter at room temperature of the polypropylene of the present invention is not particularly limited, but is preferably in the range of 6% by weight or less, more preferably 4% by weight or less. preferable.

Although the melting point of the polypropylene of the present invention is not particularly limited, it is preferably 150 ° C. or higher, more preferably 155 ° C. or higher, and further preferably 158 ° C. or higher. Here, the melting point of polypropylene is a peak temperature of a crystal melting curve at the time of temperature rise measured by a differential scanning calorimeter (hereinafter, also referred to as DSC).

The polypropylene of the present invention may contain, if necessary, an antioxidant, a chlorine scavenger, a heat stabilizer, an antistatic agent, an antifogging agent, an ultraviolet absorber, a lubricant, a nucleating agent, a pigment, a filler and the like. Additives, other polypropylenes, polyethylenes, elastomers, petroleum resins, and other thermoplastic resins may be blended as long as the effect is not impaired.

Although the thickness of the biaxially oriented polypropylene film of the present invention is not particularly limited, it is usually preferably from 3 to 200 μm.

The method for producing the biaxially oriented polypropylene film of the present invention is not particularly limited, but the following method may be mentioned as a typical production method.

That is, as a method for producing a stretched film by a sequential biaxial stretching method by a tenter method, the above polypropylene composition is formed into a sheet or film by a T-die method, an inflation method or the like, and then supplied to a longitudinal stretching apparatus. 3 to 10 at heating roll temperature of 100 to 170 ° C
Times, preferably 4 to 8 times lengthwise (in the direction of film flow)
The film is stretched, and then the tenter temperature is set to 110 using a tenter.
The film is stretched transversely (in the direction perpendicular to the film flow direction) at 4 to 15 times, preferably 6 to 13 times at 180 ° C., and in the above stretching, the area stretch ratio which is the product of the longitudinal stretch ratio and the transverse stretch ratio. Is 30 to 100 times, preferably 35 to 90 times
There is a method of adjusting so as to be doubled.

In the above longitudinal stretching, the c-axis orientation coefficient in the stretching direction of the stretched film or sheet is preferably in the range of 0.55 to 1.0, more preferably 0.65.
The longitudinal stretching ratio and the stretching temperature so that the range of ~ 0.9,
It is preferable to appropriately adjust the above-mentioned physical properties of the polypropylene in order to form the fibrous structure of the present invention on the surface of the obtained biaxially stretched polypropylene film.

In order to obtain a longitudinally stretched sheet or film having a c-axis orientation coefficient in the above range, the unstretched sheet or film before longitudinal stretching is heated at 100 ° C. to a temperature lower than the melting point of the unstretched sheet or film by at least 10 ° C. A method in which the crystallinity is increased by heating and heat treatment at a temperature of preferably 110 ° C. to 15 ° C. or lower than the melting point of the unstretched sheet or film, and then longitudinally stretching 4 to 8 times, preferably 5 to 7.5 times. Is preferably adopted.

The c-axis orientation coefficient is a value quantitatively representing the degree of uniaxial orientation of the c-axis (molecular chain axis) of the polypropylene crystal in the stretching direction of the film or sheet determined by the X-ray diffraction method. . See Zet. Wu. ZWWilchinsky [Journal of Appli Physics
ed Physcis), 31 , 1969 (1960)] from the orientation distribution curve (crystal plane density distribution curve) of the (110) plane and the (040) plane. Root mean square <cos ² φ _{110, Z} >, <cos ² φ
_{040, Z} >, the mean square of the direction cosine of the crystal c-axis and the Z-axis can be calculated by the following equation.

<Cos ² φ _{c, Z} > = 1-1.099 <cos
_{^{2 φ 110, Z> -0.901 <}} cos 2 φ 040, Z> from the value of <cos ² φ _{c, Z>} can be calculated c-axis orientation coefficient by the following equation.

[C-axis orientation coefficient] = (3 <cos ² φ _{c, Z} > −1) / 2 Then, the transverse stretching of the longitudinally stretched film or sheet obtained by the above method is performed on the surface of the film after the transverse stretching. The orientation index is preferably in the range of 0.7 to 1.6, more preferably 0.8.
It is preferable to appropriately adjust the transverse stretching ratio, the stretching temperature, and the like so as to be in the range of 1.5 to 1.5 in order to form the fibrous structure of the present invention on the surface of the obtained biaxially stretched polypropylene film.

A method for obtaining a biaxially stretched film having a plane orientation index in the above range may be, for example, a method in which a longitudinally stretched sheet or film before transverse stretching is heated at a temperature of 110 ° C. to 5 ° C. or lower than the melting point of the longitudinally stretched sheet or film. , Preferably 1
10 ° C-1 point higher than the melting point of longitudinally stretched sheet or film
A method in which the crystallinity of a vertically stretched sheet or film is increased by heating and heat treatment at a temperature of 0 ° C. or lower, and then 6 to 13 times, preferably 7 to 12 times, and particularly the above-described longitudinal stretching ratio and transverse stretching. A method of performing biaxial stretching at an area stretch ratio of 35 times or more, preferably 40 times or more, expressed as a product of the ratios (longitudinal stretch ratio × lateral stretch ratio).

The above-mentioned plane orientation index is an index indicating the degree of plane orientation of the polypropylene crystal (010) plane to a plane parallel to the film plane, which is determined by an X-ray diffraction method. Specifically, while rotating the biaxially oriented polypropylene film at a high speed around an axis perpendicular to the film surface, X-rays are incident from a direction perpendicular to the film surface to measure the diffraction intensity,
The obtained X-ray diffraction intensity curve was subjected to peak separation into an amorphous peak and each crystalline peak to obtain a polypropylene crystal (α
From the (111) plane reflection (2θ = about 21.4 °) and the peak intensity of the (040) plane reflection (2θ = about 17.1 °).

[Plane orientation index] = log {1.508 × I ₍₁₁₁₎ / I ₍₀₄₀₎ } where I ₍₁₁₁₎ : peak intensity of (111) plane reflection (co
unts) I ₍₀₄₀₎ : peak intensity of (040) plane reflection (count
s) where the coefficient 1.508 in the above equation is The Journal of Macromolecular Science, Physics by Z. Mencik
romoleculer Science, Physics) B6 , 101 (19
72), the intensity ratio I ₍₀₄₀₎ / I ₍₁₁₁₎ calculated from theoretical intensity I ₍₀₄₀₎ and I ₍₁₁₁₎ when the polypropylene crystal is completely randomly oriented, 116.9 / 77. 5
= 1.508 (reciprocal of the value of I ₍₁₁₁₎ / I ₍₀₄₀₎₎ .
For example, (0)
10) If the plane is completely randomly oriented with respect to the film plane, the value of [plane orientation index] becomes 0, and (01)
The value of the [plane orientation index] increases as the 0) plane is oriented parallel to the film plane.

Further, in the above-mentioned production method, a method of performing heat treatment at 80 to 180 ° C. after biaxial stretching while allowing 0 to 15% relaxation in the longitudinal and transverse directions as necessary may be used. Of course, after these stretchings, if necessary, the film may be stretched in the vertical and horizontal directions again. In the longitudinal stretching, a stretching method such as multi-stage stretching or rolling may be combined.

One or both surfaces of the biaxially oriented polypropylene film of the present invention may be subjected to a surface treatment such as a corona discharge treatment if necessary. Further, for the purpose of imparting a function such as heat sealing properties, a layer made of another resin having a lower melting point than the polypropylene used in the present invention on one side so as to have a surface having the fibrous structure of the present invention on the surface. May be laminated. The method of laminating other resins is not particularly limited, but a co-extrusion method, a laminating method and the like are preferable.

The biaxially oriented polypropylene film of the present invention can be used as a laminated film by laminating it on at least one side of another base film. The production method of the laminated film is not particularly limited,
As a preferred method, the biaxially stretched polypropylene film of the present invention, a method of laminating other films, for example, a film of polyethylene, polypropylene, polyethylene terephthalate, nylon, polyvinyl alcohol, vinylon, cellophane, etc. via an adhesive layer, A method of directly extruding and laminating a thermoplastic resin having a lower melting point than the biaxially oriented polypropylene film of the present invention on one side of the biaxially oriented polypropylene film of the present invention, and using the polypropylene film of the present invention as one or both outermost surface layers of another polyolefin. After co-extrusion with a thermoplastic resin such as the above, biaxial stretching by the above-described method can be used.

[0043]

According to the present invention, the blocking resistance, transparency and appearance of the biaxially stretched polypropylene film are improved, and dirt adheres to the guide rolls and triangular folding plates of the bag making machine during bag making. And a biaxially oriented polypropylene film having a small number of particles can be obtained. In the present invention,
By forming a specific fibrous structure on the surface of the biaxially stretched polypropylene film, the reason why the blocking resistance and bag making processability are improved is not yet clear, but the present inventors have determined the following from the following analysis results. Think like.

The fibrous texture (shape, size, thickness of fibrous texture, etc.) of the film surface observed with an atomic force microscope is determined by the longitudinal and transverse stretching under specific stretching conditions during film production. It turned out that it changes depending on magnification, temperature, and the like. From this, it is presumed that the fibrous structure is a highly crystalline fibril formed when the polypropylene crystals are stretched in the film stretching step. Therefore, a highly rigid crystalline fibril (fibrous structure) is formed on the surface of the biaxially oriented polypropylene film.
It is considered that the formation of such a mesh reduces the contact area when the films are stacked, and the blocking resistance is exhibited due to the high rigidity of the surface. Further, it is considered that this structure reduces the friction between the guide roll and the film surface during the bag making process and increases the strength of the film surface, thereby reducing the generation of dirt (resin shavings). .

As is apparent from the above description, the biaxially oriented polypropylene film of the present invention has improved blocking resistance, excellent transparency and appearance, and a guide roll or a triangle of a bag making machine at the time of bag making. It has an excellent property that dirt does not adhere to a folding plate or the like, which cannot be achieved by a conventionally known biaxially oriented polypropylene film.

Therefore, it can be suitably used for applications requiring transparency, appearance, bag making characteristics, etc., as well as blocking resistance, for example, applications as packaging materials.

[0047]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited to these examples. In addition, evaluation of the biaxially stretched polypropylene film and polypropylene obtained in the following Examples and Comparative Examples was performed by the following method.

(1) Average value of surface roughness of film, observation of morphology, average diameter of mesh, diameter of fibrous structure, using scanning probe microscope JSTM-4200D manufactured by JEOL Ltd.
An atomic force microscope image of an area of 1 μm square was measured in the contact mode. In the measurement, a cantilever having no abrasion or dirt was used, and a measurement location was a location where no protrusion was caused by a lubricant, an antistatic agent or an antiblocking agent in the film. Further, the average value of the surface roughness of 1 μm square is obtained by calculating the average value of the heights (roughness values) of all 512 × 512 measurement points of 1 μm square at arbitrary 15 points of the film.
The average value was used.

For image analysis of the atomic force microscope image, an image analyzer LA-555 manufactured by Pierce was used.

(2) Surface Crystallinity Fourier Transform Infrared Spectrophotometer 1 manufactured by PerkinElmer
Using a 600 type FTIR, a horizontal ATR manufactured by ST Japan and a ZnSe flat plate (45 °) were mounted, and the measurement was performed under the following conditions.

Resolution: 4.0 cm ^-1 apodization function: weak veil-Norton apodization Scanning range: 4000-400 cm ^-1 scanning mode: single luminous flux ratio Number of integrations: 64 times (3) Isotactic pentad fraction (mmmm) ),
α-Olefin content It was measured under the following conditions using JNM-GSX-270 ( ¹³ C-nuclear resonance frequency 67.8 MHz) manufactured by JEOL Ltd.

Measurement mode: ¹ H-complete decoupling Pulse width: 7.0 microseconds (C45 degrees) Pulse repetition time: 3 seconds Integration count: 10,000 times Solvent: Mixed solvent of ortho-dichlorobenzene / deuterated benzene (90 / Sample concentration: 120 mg / 2.5 ml Solvent measurement temperature: 120 ° C. In this case, the isotactic pentad fraction is ¹³ C—N
It was determined by measuring the splitting peak in the methyl group region of the MR spectrum. The peak of the methyl group region was assigned to A.I. Zambelli et al [Macromol
ecules, 13 , 267 (1980)].

(4) Melt flow rate (MFR) Measured according to ASTM D-790.

(5) Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) High-temperature GPC apparatus SSC-7100 manufactured by Senshu Kagaku
Was measured under the following conditions.

Solvent: ortho-dichlorobenzene Flow rate: 1.0 ml / min Column temperature: 145 ° C. Detector: high-temperature differential refraction detector Column: “SHODEX UT” manufactured by Showa Denko 8
07, 806M, 806M, 802.5 are connected in series and used.

Sample concentration: 0.1% by weight Injection amount: 0.50 ml (6) Soluble amount of p-xylene at room temperature [p-Xy.sol.] 1 g of polymer was added to 100 ml of p-xylene, and stirred at 120 ° C. After the temperature was increased, stirring was further continued for 30 minutes to completely dissolve the polymer to prepare a uniform solution.
The p-xylene solution was allowed to cool to room temperature (23 ° C.) and then left at room temperature (23 ° C.) for 24 hours. Thereafter, the precipitated gel was separated from the gel, and the amount of soluble matter was determined by completely concentrating the p-xylene solution.

Room temperature p-xylene solubles [p-Xy.sol.]
Is determined by the following equation.

[P-Xy.sol.] = {P-xylene solubles (g) / polymer 1 (g)} × 100 (% by weight) (7) Melting point Using a DSC 6200 DSC device manufactured by Seiko Instruments Inc.
The measurement was performed under the following conditions.

Sample amount: about 5 mg Atmospheric gas: nitrogen (flow rate: 20 ml / min) Temperature condition: After maintaining at 230 ° C. for 10 minutes, 10 ° C./min.
The temperature was lowered to 30 ° C. per minute, and the endothermic behavior of melting when the temperature was subsequently raised at 10 ° C./min was measured.

(8) c-axis orientation coefficient A fiber sample device was attached to an X-ray diffractometer JDX-3500 manufactured by JEOL Ltd. and measured under the following conditions.

Target: copper (Cu-Kα ray) Tube voltage-tube current: 40 kV-400 mA X-ray incidence method: vertical beam transmission method Monochromatization: graphite monochromator Collimator: 1 mmφ pinhole Light receiving slit: 2 mmφ pinhole Detector: Scintillation counter 1) 2θ scanning (Bragg angle) measurement Measurement angle range (2θ): 8 to 32 ° Step angle: 0.1 ° Counting time: 2.0 seconds 2) In-plane rotation (β rotation) measurement Measurement angle range ( β): -20 to 110 ° Step angle: 0.5 ° Counting time: 2.0 seconds 15 m of a vertically stretched film or sheet in the stretching direction
A strip sample cut to mx 5 mm width was mounted on a fiber sample device, and X-rays were vertically incident on the film surface and 2θ scanning was performed by a vertical transmission method. Bragg angle of (040) plane (2
θ °). Next, the counter was fixed to the Bragg angle of the (110) plane, the sample was rotated in plane (β rotation), and the intensity distribution was measured for the (110) plane. Similarly, the intensity distribution of the (040) plane was measured. The background intensity due to air scattering or the like at the (110) plane and (040) plane reflection positions of the X-ray diffraction profile measured by 2θ scanning was determined, and the (110) plane and (04) plane were obtained, respectively.
The orientation distribution curves (crystal plane density distribution curves) of the (110) and (040) planes are subtracted from the diffraction intensity distribution of the 0) plane.
I got From these orientation distribution curves, the c-axis orientation coefficient was determined by the method described above.

(9) Plane orientation index Using an X-ray diffractometer JDX-3500 manufactured by JEOL Ltd.,
The measurement was performed under the following conditions.

Target: copper (Cu-Kα ray) Tube voltage-tube current: 40 kV-400 mA X-ray incidence method: vertical beam transmission method Monochromatization: graphite monochromator Divergence slit: 0.2 mm Light receiving slit: 0.4 mm Detector : Scintillation counter Measurement angle range: 9.0 to 31.0 ゜ Step angle: 0.04 ゜ Counting time: 4.0 seconds Sample rotation speed: 120 rotations / min In this case, the sample film is cut out into a circular shape of 27mmφ.
This was stacked so as to have a thickness of about 3 mm, and the measurement was carried out by mounting the sample on a rotary sample stand of a transmission method attached to a wide-angle goniometer. The peak separation was performed using a general peak separation program, which is software attached to the instrument.
After removing the background due to air scattering or the like in the range of 31 °, it was separated into an amorphous peak and each crystalline peak by a general peak separation method using a Gaussian function and a Lorentz function. The plane orientation index was calculated from the peak intensities of the (040) plane reflection and the (111) plane reflection by the method described above.

(10) Haze Measured according to JIS K 7105.

(11) Blocking resistance (blocking value) A film was cut into strips having a length of 300 mm in the longitudinal stretching direction and 40 mm in the transverse stretching direction, and superimposed so as to have a thickness of 3 mm, at a temperature of 30 ° C. and a humidity of 70% RH. 24 under the atmosphere of
After leaving for a period of time, 2
A pressure of 0 kg / cm ² was applied for 30 seconds. Thereafter, both ends of the film bundle sample were fixed with jigs, and the bending strength was measured using an autograph (manufactured by Shimadzu Corporation). The magnitude of the bending strength at that time was used as an index of the degree of blocking of the film.

(12) Film Appearance The film was cut into a size of 200 mm × 200 mm, sandwiched between crossed polarizing films, and the number of peeling voids (fish eyes) having a major axis of 300 μm or more caused by an antiblocking agent was visually observed on a light box. evaluated. This was performed 15 times, and the film appearance was evaluated as follows from the average value of the number of peel voids per 1 m ² .

[0067] ◎: less peeling void number 20 / m ² ○: Peeling void number 20 / m ² or more and less than 50 / m ² △: Peeling void number 100 / m ² to 500 pieces / m ² less ×: The number of peeling voids is 500 / m ² or more. (13) Situation of dirt Using a fusing seal bag making machine equipped with a Kyoeisha PP-500 type fusing blade for OPP film, fusing seal temperature 40
250 mm bag size at 0 ° C and 100 bags / min.
× 300 mm bags were continuously made for 2 hours. Two hours later, the adhesion of dirt (white powder) to the guide rolls and the sides of the triangular folded plate was visually evaluated by the following method.

X: One hour after the start of bag making, the adherence of dirt is directly visually confirmed.

Δ: Two hours after the start of bag making, the adherence of dirt is directly visually confirmed.

：: Two hours later, although it cannot be directly confirmed by visual observation, a small amount of dirt is confirmed on the cloth by wiping the guide roll and the triangular folded plate with a black felt cloth.

A: No dirt is confirmed by the above method.

Example 1 (Granulation) 0.1 part by weight of 2,6-di-t-butylhydroxytoluene as an antioxidant, 100 parts by weight of a powder of homopolypropylene A shown in Table 1, and a chlorine scavenger 0.1 part by weight of calcium stearate, and 0.3% by weight of stearyl diethanolamide as an antistatic agent
And an average particle size of 0.1 shown in Table 2 as a blocking inhibitor.
8 μm of fused spherical silica (“Admafine SO-C3” manufactured by Admatech, abbreviated as silica in the table) is 0.1
% By weight and mixed with a Henschel mixer for 5 minutes.
The mixture was extruded at 0 ° C., and the pellets were granulated to obtain raw material pellets.

[0073]

[Table 1]

(Production of Biaxially Stretched Film) Using the obtained polypropylene raw material pellets, a biaxially stretched film production experiment was carried out by the following method. The polypropylene raw material pellets were heated and melted at 280 ° C. using a T-die sheet extruder having a screw diameter of 90 mmφ, extruded, and formed into a sheet having a thickness of about 2 mm with a cooling roll at 30 ° C. Next, a biaxially-stretched polypropylene film was produced from the raw sheet using a tenter-type sequential biaxially-stretching apparatus as follows. First, the raw sheet was longitudinally stretched 6.8 times in the longitudinal direction by a heated roll stretching machine. The longitudinally stretched sheet was sampled, and the c-axis orientation coefficient at the center was measured. The results are shown in Table 2. Subsequently, the film was transversely stretched 10 times in the transverse direction with a mechanical magnification by a tenter transverse stretching machine, relaxed by 8%, and heat-treated to form a biaxially stretched polypropylene film having a thickness of 50 µm. In addition, the thickness of the film was adjusted by the extrusion amount (thickness of the raw sheet) of the T-die sheet extruder. One side of the film was subjected to a corona discharge treatment of 30 W min / m ² according to a conventional method, and after winding, the obtained film was aged at 35 ° C. for 3 days. Table 2 shows the plane orientation index of the film after aging. The surface of the obtained biaxially stretched film that had not been subjected to corona discharge treatment was subjected to atomic force microscope measurement. The presence or absence of a network structure on the surface of the obtained biaxially stretched polypropylene film, the average value of the surface roughness, the average diameter of the mesh of the network structure, the diameter of the arc-shaped convex portion (the fiber structure diameter), the degree of surface crystallization, the haze, The blocking value (blocking resistance), the appearance (the number of peeling voids), and the occurrence of contamination on the bag making machine were measured.

The results are shown in Table 3. FIG. 1 shows an atomic force microscope image. In FIG. 1, a network structure formed of a fibrous structure is observed.

Examples 2 to 5 The same procedures as in Example 1 were carried out except that the polypropylene A of Example 1 and the antiblocking agent were used and the stretching ratio was as shown in Table 2. The results are shown in Tables 2 and 3.

Comparative Examples 1 and 2 The same procedures as in Example 1 were carried out except that the polypropylene A of Example 1 and the antiblocking agent were used and the stretching ratios were as shown in Table 2. The results are shown in Tables 2 and 3.

Examples 6 to 8 Homopolypropylene B shown in Table 1 and crosslinked polymethyl methacrylate spherical particles having an average particle size of 2.0 μm shown in Table 2 ("Eposter MA1002" manufactured by Nippon Shokubai Co., Ltd., Table 1 is abbreviated as PMMA), and the same procedure was performed as in Example 1 except that the draw ratio in Table 2 was used.
The results are shown in Tables 2 and 3.

Comparative Examples 3 and 4 The same procedures as in Example 6 were carried out except that the draw ratios shown in Table 2 were used. The results are shown in Tables 2 and 3.

Examples 9 and 10 Polypropylene C in Table 1 (ethylene content 0.5 mol%)
Propylene-ethylene random copolymer) and the draw ratios in Table 2 were used in the same manner as in Example 1.
The results are shown in Tables 2 and 3.

Comparative Examples 5 to 7 The same procedures as in Example 9 were carried out except that the draw ratios shown in Table 2 were used. The results are shown in Tables 2 and 3.

Comparative Examples 8 and 9 Polypropylene D in Table 1 (ethylene content 3.2 mol%
Propylene-ethylene random copolymer) and the draw ratios in Table 2 were used in the same manner as in Example 1.
The results are shown in Tables 2 and 3.

An atomic force microscope image of the biaxially stretched polypropylene film obtained in Comparative Example 8 is shown in FIG. In FIG.
No network structure as seen in FIG. 1 (the surface of the biaxially stretched polypropylene film obtained in Example 1) was observed.

Examples 11 and 12 Example 1 was repeated except that polypropylene E shown in Table 1 (a propylene-butene-1 random copolymer having a butene-1 content of 0.6 mol%) was used and the stretching ratio was as shown in Table 2. Was performed in the same manner as described above. The results are shown in Tables 2 and 3.

Comparative Example 10 The same procedures as in Example 11 were carried out except that the stretching ratio was as shown in Table 2. The results are shown in Tables 2 and 3.

Example 13 The same procedure as in Example 1 was carried out without adding an antiblocking agent, and the results are shown in Tables 2 and 3.

Examples 14 to 17 The same procedures as in Example 1 were carried out except that the amount of the antiblocking agent of Example 1 was changed as shown in Table 2. The results are shown in Tables 2 and 3.

[0088]

[Table 2]

[0089]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an atomic force microscope image of the surface of the biaxially stretched polypropylene film obtained in Example 1.

FIG. 2 is an atomic force microscope image of the surface of the biaxially stretched polypropylene film obtained in Comparative Example 8.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B29K 105: 16 B29L 7:00

Claims (2)

[Claims] At least one surface has a fibrous structure having a network structure in which arc-shaped convex portions intersect, the average value of the surface roughness is 20 to 100 nm, and the average diameter of the network of the network structure is 40. A biaxially stretched polypropylene film having a thickness of from 300 to 300 nm. 2. The biaxially oriented polypropylene film according to claim 1, wherein the film contains 0.001 to 1% by weight of an antiblocking agent.