JP2003191410A - Biaxially oriented laminated polypropylene film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide development of a biaxially oriented polypropylene film which is excellent in a transparent property and a blocking resistance and excellent in precision of a thickness. <P>SOLUTION: The biaxially oriented laminated polypropylene film is provided by stacking a propylene polymer (C) layer containing a blocking resistant agent on at least one side of a base layer capable of being obtained from propylene polymeric composition of a propylene monopolymer (A) and a propylene and α-olefin copolymer (B) of which an α-olefin content is within 0.1 to 1.8 mol%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biaxially stretched laminated polypropylene film excellent in transparency, antiblocking property and thickness accuracy.

[0002]

2. Description of the Related Art Biaxially oriented polypropylene films (hereinafter sometimes referred to as OPP films) are used in a wide range of fields including packaging materials by taking advantage of their excellent transparency, mechanical strength and rigidity. Further, various stabilizers such as an anti-blocking agent and an antistatic agent are usually added to the OPP film depending on the application.

On the other hand, although an OPP film having excellent thickness accuracy has been developed, as the thickness accuracy of the OPP film is improved, when the OPP film is wound, the inner surface and the outer surface of the wound film adhere to each other. It tends to be difficult to peel off (so-called blocking tends to occur). This tendency is to improve printability and laminating characteristics.
Corona treatment on the film surface makes it stronger. In order to improve blocking, an anti-blocking agent may be added to polypropylene, which is the base material of the OPP film, but if the anti-blocking agent is added in a certain amount or more, the OPP film becomes white depending on the stretching conditions and uneven thickness occurs. In some cases, a good film could not be obtained.

[0004]

Therefore, the present invention has conducted various studies for the purpose of developing a biaxially stretched polypropylene film which is excellent in transparency, antiblocking property, and excellent in thin-thickness precision, and as a result, the OPP film as a base layer has been investigated. Using a propylene polymer composition consisting of a propylene homopolymer and a propylene / ethylene random copolymer as a raw material,
By laminating a layer containing an anti-blocking agent on at least one side thereof, excellent in thickness accuracy, and transparency,
It was possible to obtain a biaxially stretched laminated polypropylene film having excellent antiblocking properties.

[0005]

[Means for Solving the Problems]

SUMMARY OF THE INVENTION The present invention has an α-olefin content of 0.
Antiblocking agent on at least one side of the base layer obtained from the propylene polymer composition of propylene homopolymer (A) and propylene / α-olefin copolymer (B) in the range of 1 to 1.8 mol%. A biaxially stretched laminated polypropylene film, comprising a propylene polymer (C) layer containing

[0006]

DETAILED DESCRIPTION OF THE INVENTION Propylene Homopolymer (A) The propylene homopolymer (A) according to the present invention comprises a propylene homopolymer and is usually MFR (melt flow rate; ASTM D-1238, load 2160 g,
The temperature (230 ° C.) is usually in the range of 0.5 to 10 g / 10 minutes, preferably 2 to 5 g / 10 minutes.

Propylene / α-olefin copolymer
(B) The propylene / α-olefin copolymer (B) according to the present invention contains propylene having an α-olefin content of 0.4 to 2.2 mol%, preferably 0.6 to 1.8 mol%. Is a random copolymer of. When the content of α-olefin is less than 0.4 mol%, the stretchability is not improved, while when it exceeds 2.2 mol%, the rigidity is poor. As α-olefin, ethylene, 1-butene, 1-hexene, 4
Examples include-methyl / 1-pentene and 1-octene. Of these, ethylene is preferred. Also, MFR
(Melt flow rate; ASTM D-1238 load 2160 g, temperature 230 ° C) is not particularly limited as long as it can be a stretched film, but is usually 0.5 to 10
g / 10 minutes, preferably 2 to 5 g / 10 minutes.

Propylene Polymer (C) The propylene polymer (C) according to the present invention is a homopolymer of propylene, or a small amount of propylene, usually 5 mol% or less of ethylene, 1-butene, 1-hexene, 4-. It is a copolymer with an α-olefin such as methyl-1-pentene or 1-octene. MFR of propylene polymer (C)
(Melt flow rate; ASTM D-1238 load 2160 g, temperature 230 ° C) is not particularly limited as long as it can be a stretched film, but is usually 0.5 to 20.
It is in the range of g / 10 minutes, preferably 2 to 15 g / 10 minutes. The propylene polymer (C) according to the present invention may be the same as the above-mentioned propylene polymer composition of the propylene homopolymer (A) and the propylene / α-olefin copolymer (B).

A blocking inhibitor is added to the propylene polymer (C) according to the present invention, and the amount thereof is usually 0.01 to 3.0% by weight, preferably 0.05 to
It is in the range of 1.0% by weight. By setting the amount of the antiblocking agent in such a range, a biaxially stretched laminated polypropylene film having excellent transparency and antiblocking properties can be obtained. If the amount of the antiblocking agent is less than 0.01% by weight, the resulting biaxially stretched laminated polypropylene film is insufficient in the antiblocking effect, while if it exceeds 3.0% by weight, the obtained biaxially stretched laminated polypropylene film is obtained. Transparency tends to be inferior. As such an anti-blocking agent, various publicly known ones, for example, silica, talc, mica, inorganic compound particles such as metal oxides obtained by firing zeolite or further metal alkoxide, polymethyl methacrylate, melamine formalin resin, Organic compound particles such as melamine urea resin and polyester resin can be used. Among these, silica,
Polymethylmethacrylate is particularly preferable from the viewpoint of antiblocking property and transparency.

Method for Producing Polymer The propylene homopolymer (A), propylene / α-olefin copolymer (B) and propylene polymer (C) according to the present invention are variously known methods, for example, typically. It can be produced using a catalyst formed from a solid titanium catalyst component and an organometallic compound catalyst component, or a catalyst formed from both components and an electron donor.

As the solid titanium catalyst component, titanium trichloride or a titanium trichloride composition produced by various methods,
Alternatively, a carrier-supported titanium catalyst component having a specific surface area of preferably 100 m ² / g or more, which contains magnesium, halogen, an electron donor, preferably an aromatic carboxylic acid ester or an alkyl group-containing ether and titanium as essential components, can be mentioned. In particular, a polymer produced by using the latter catalyst component with a carrier is suitable.

The organometallic compound catalyst component is preferably an organoaluminum compound, specifically, trialkylaluminum, dialkylaluminum halide,
Examples thereof include alkyl aluminum sesquihalide and alkyl aluminum dihalide. Among these compounds, a suitable organometallic compound catalyst component varies depending on the type of the titanium catalyst component used.

The electron donor is an organic compound containing nitrogen, phosphorus, sulfur, oxygen, silicon, boron and the like, and preferable specific examples thereof include organic esters and organic ethers having these elements. .

The method for producing a polymer using a catalyst component with a carrier is described in, for example, JP-A-50-108385 and JP-A-50-108385.
No. 126590, JP-A-51-20297, JP-A-51-28189, JP-A-52-151691 and the like.

The propylene homopolymer and propylene / α-olefin copolymer having high Iso according to the present invention can also be produced by using a single site catalyst. The single-site catalyst is a catalyst having a uniform active site (single site), and examples thereof include a metallocene catalyst (so-called Kaminsky catalyst) and a Brookhart catalyst. For example, a metallocene catalyst is a catalyst composed of a metallocene-based transition metal compound and at least one compound selected from the group consisting of an organoaluminum compound and a compound that reacts with the metallocene-based transition metal compound to form an ion pair, and an inorganic substance It may be supported on.

The metallocene-based transition metal compound is, for example, JP-A-5-209014 and JP-A-6-10.
0579, JP-A-1-301704, JP-A3-1
Examples thereof include the compounds described in JP-A No. 93796, JP-A No. 5-148284 and the like.

Examples of the organoaluminum compound include alkylaluminum, chain or cyclic aluminoxane, and the like. The chain or cyclic aluminoxane is produced by contacting alkylaluminum and water. For example, it can be obtained by adding alkylaluminum at the time of polymerization and then adding water, or by reacting water of crystallization of a complex salt or adsorbed water of an organic or inorganic compound with alkylaluminum.

The compound which reacts with the metallocene-based transition metal compound to form an ion pair is, for example, JP-A-1-50.
Examples thereof include compounds described in 1950, JP-A-3-207704 and the like. Examples of the inorganic material supporting the single-site catalyst include silica gel, zeolite, diatomaceous earth and the like.

Polymerization methods include bulk polymerization, solution polymerization,
Examples include suspension polymerization and gas phase polymerization. These polymerizations may be a batch method or a continuous method. The polymerization conditions are usually polymerization temperature: -100 to + 250 ° C, polymerization time: 5 minutes to 10 hours, reaction pressure: normal pressure to 300 Kg / cm2 (gauge pressure).

Propylene Polymer Composition The propylene polymer composition according to the present invention is a composition obtainable from a propylene homopolymer (A) and a propylene / α-olefin copolymer (B). The content is 0.1 to 1.8 mol%, preferably 0.2 to 1.
It is in the range of 5 mol%, preferably 95 to 10% by weight of the propylene homopolymer (A), and more preferably 90 to 2%.
0% by weight, the propylene / α-olefin copolymer (B) is 5 to 90% by weight, and more preferably 10 to 80% by weight. If the α-olefin content is less than 0.1 mol% and further the propylene / α-olefin copolymer (B) is less than 5% by weight, the effect of improving the stretching temperature range in obtaining a biaxially stretched film may be small. Therefore, there is a possibility that it will not be a biaxially stretched film with excellent thin and thin precision,
Further, when laminated with the propylene polymer (C) layer, the blocking property may not be improved. On the other hand, if it exceeds 90% by weight, the resulting biaxially stretched film may have reduced rigidity, mechanical strength and the like.

The propylene polymer composition according to the present invention can be obtained by mixing the propylene homopolymer (A) and the propylene / α-olefin copolymer (B) by various known methods. For example, propylene homopolymer (A) and propylene / α-olefin copolymer (B) are previously prepared.
And the propylene homopolymer (A) or the propylene / α-olefin copolymer (B). After the polymerization, the propylene / α-olefin copolymer (B) or the propylene homopolymer (A) may be subsequently polymerized.

In the propylene homopolymer (A), propylene / α-olefin copolymer (B) or propylene polymer composition of the present invention, a heat resistance stabilizer, a weather resistance stabilizer, an ultraviolet light stabilizer, an ultraviolet light stabilizer, or an ultraviolet light stabilizer may be used. Absorbents, lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, dyes, various additives usually used for polyolefins such as inorganic or organic fillers are added within a range not impairing the object of the present invention. You may keep it.

Biaxially Stretched Laminated Polypropylene Film The thickness of the biaxially stretched laminated polypropylene film of the present invention is variously determined depending on the application and is not particularly limited, but usually 10 to 10 parts by weight of the propylene polymer composition layer.
0 μm, preferably 15 to 50 μm, 0.5 to 1 for the propylene polymer (C) layer containing an antiblocking agent.
It is in the range of 5 μm, preferably 1 to 10 μm.

The biaxially stretched laminated polypropylene film of the present invention may be subjected to surface treatment such as corona treatment or flame treatment on one side or both sides, if necessary. In addition, the biaxially stretched laminated polypropylene film of the present invention may further have a low-temperature heat-sealing property depending on the application, in order to impart low-temperature heat-sealing property, high-pressure process low-density polyethylene, linear low-density polyethylene, crystalline or low-crystalline ethylene and C3 A low-melting polymer such as a random copolymer of 10 to α-olefin or a random copolymer of propylene and ethylene or α-olefin having 4 or more carbon atoms, polybutene, ethylene-vinyl acetate copolymer Those compositions may be laminated on the propylene polymer (C) layer. Further, in order to impart a gas barrier property, ethylene / vinyl alcohol copolymer, polyamide, polyester, vinylidene chloride polymer or the like may be laminated by extrusion coating or the like, or a metal or its oxide, silica or the like may be laminated. You may vapor-deposit. Of course, the surface of the stretched film may be subjected to anchor treatment with an adhesive such as imine or urethane, or a maleic anhydride-modified polyolefin may be laminated in order to increase the adhesion with other substances.

To the biaxially stretched laminated polypropylene film of the present invention, a propylene polymer composition obtainable from a propylene polymer (A) and a propylene / α-olefin copolymer (B) and a predetermined amount of an antiblocking agent are added. The multilayer sheet obtained by co-extrusion molding with the above-mentioned propylene polymer (C) can be obtained by a known biaxially stretched film manufacturing method such as a simultaneous biaxial stretching method or a sequential biaxial stretching method. In particular, the propylene polymer composition according to the present invention is capable of widening the transverse stretching temperature range to 7 ° C. as compared with the conventional method in the sequential biaxially stretched film production method, resulting in easy transverse stretching operation. The accuracy of thickness of biaxially stretched film, and the variation of thickness with respect to the standard thickness of ordinary OPP film (2
σ) can be improved by 20 to 50% compared to the current level.

[0026]

EFFECTS OF THE INVENTION The biaxially stretched laminated polypropylene film of the present invention uses the propylene polymer composition as a base layer, so that the biaxially stretched polypropylene film has improved stretchability such as uniform stretchability and wide temperature range stretchability. As a result, the obtained biaxially stretched laminated polypropylene film is excellent in thickness accuracy,
When printing on the surface, printing omission is unlikely to occur and packaging suitability is excellent. Furthermore, it has excellent blocking resistance, is not sticky, has high rigidity, and has excellent transparency. Therefore, it can be used for all the applications in which the OPP film has been conventionally used, for example, general printing, laminating, part coating, and the like.

[0027]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

Physical properties and the like in the examples and comparative examples were determined by the following evaluation methods. (Evaluation Method) 1) Elastic Modulus: Measured according to JIS K 7127. 2) Film thickness unevenness: standard deviation of a specified width was measured. 3) Blocking strength: Films were cut into a width of 20 mm and stacked by 20 mm, and under a 0.25 kg / cm ² load, 4
After standing at 0 ° C. for 48 hours, the shear strength was measured with a tensile tester (manufactured by Toyo Seiki Co., Ltd.) at a tensile speed of 30 mm / min.

Example 1 <Base layer: propylene polymer composition layer> 40% by weight of a propylene homopolymer (MFR = 3.0 g / 10 minutes) was added to a propylene / ethylene random copolymer (ethylene content: 1.
A polypropylene resin composition containing 60% by weight of 3 mol% MFR = 3.0 g / 10 min) was prepared. This resin composition contains tetrakis [methylene-3-
(3 ', 5'-di-t-butyl-4'hydroxyphenyl) propionate] methane (product name Irganox 1010, product of Ciba-Gaiki, Japan) 1000 ppm, calcium stearate (Nippon Yushi) 1000 ppm,
As an antistatic agent, 6000 ppm of stearic acid monoglyceride (manufactured by Riken Vitamin) and 2000 ppm of stearyldiethanolamine (manufactured by Toho Kagaku) were added. <Anti-blocking Layer (Coating Layer): Propylene Polymer Layer> Propylene homopolymer (melting point 160 ° C. MFR: 2.
To 5 g / 10 min), 1000 ppm of silica was blended as an antioxidant and an antiblocking agent described above. <Manufacture of Biaxially Stretched Laminated Film> The propylene polymer composition and the propylene polymer shown above are extruded at an extrusion ratio (1/10).
/ 1), each is melt-extruded using a screw extruder and shaped using a multi-manifold type T-die,
It was rapidly cooled on a cooling roll to obtain a raw sheet having a thickness of about 1.5 mm. This sheet was heated to about 125 ° C. and stretched 5 times in the film flow direction (longitudinal direction). The sheet stretched 5 times was heated to 155 ° C., and then stretched 10 times in the direction (transverse direction) orthogonal to the flow direction, and the thickness of the base layer was 26 μm.
m, the thickness of the anti-blocking layer: 2.5 μm (total thickness: 30 μm), to obtain a biaxially stretched laminated polypropylene film. The physical properties of the biaxially stretched multilayer polypropylene film were measured by the methods described above. The results are shown in Table 1.

Comparative Example 1 Example 1 except that the propylene homopolymer was used as the base layer resin.
A biaxially stretched laminated polypropylene film was obtained in the same manner as above. The physical properties of the biaxially stretched multilayer polypropylene film were measured by the methods described above. The results are shown in Table 1.

[0031]

[Table 1]

As is clear from the results shown in Table 1, a propylene polymer composition obtained from the propylene homopolymer (A) and the propylene / α-olefin copolymer (B) of the present invention was used as the base layer. It can be seen that the axially stretched laminated polypropylene film has reduced film thickness unevenness and blocking force as compared with the biaxially stretched film shown in the comparative example.

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Claims (5)

[Claims] 1. A propylene polymer composition of a propylene homopolymer (A) and a propylene / α-olefin copolymer (B) having an α-olefin content in the range of 0.1 to 1.8 mol%. A biaxially stretched laminated polypropylene film, characterized in that a propylene polymer (C) layer containing an antiblocking agent is laminated on at least one surface of a base layer obtainable from the product. 2. The propylene homopolymer (A) is 10 to 95.
The biaxially stretched laminated polypropylene film according to claim 1, wherein the biaxially stretched laminated polypropylene film is a propylene polymer composition which can be obtained by containing the propylene / α-olefin copolymer (B) in an amount of 90% by weight to 90% by weight. 3. The propylene / α-olefin copolymer (B) has an α-olefin content of 0.4 to 2.2 mol%.
The biaxially stretched laminated polypropylene film according to claim 2. 4. The biaxially stretched laminated polypropylene film according to claim 1, wherein a propylene polymer (C) layer containing an antiblocking agent is laminated on both layers. 5. The biaxially stretched laminated polypropylene film according to claim 1, wherein the propylene polymer composition layer and the propylene polymer (C) layer can be obtained by coextrusion molding.