JP4462503B2 - Biaxially stretched laminated polypropylene film - Google Patents

Description

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

  Biaxially stretched 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, rigidity and the like. In general, various stabilizers are added to the OPP film, depending on the application, including an anti-blocking agent and an antistatic agent.

  On the other hand, an OPP film with excellent thickness accuracy has been developed. However, as the thickness accuracy of the OPP film is improved, the inner surface and the outer surface of the wound film adhere to each other and are difficult to peel off when the OPP film is wound. (So-called blocking is likely to occur). This tendency becomes stronger when corona treatment is applied to the film surface in order to improve printability and laminate characteristics. In order to improve blocking, an anti-blocking agent may be added to polypropylene, which is the base material of the OPP film. However, if a certain amount or more of the anti-blocking agent is added, the OPP film may become white depending on the stretching conditions, resulting in uneven thickness. In some cases, a good film could not be obtained.

  Therefore, as a result of various studies for the purpose of developing a biaxially stretched polypropylene film excellent in transparency, anti-blocking properties and excellent in thickness and thinness accuracy, the present invention has a propylene homopolymer and propylene. By using a propylene polymer composition comprising an ethylene random copolymer and laminating a layer containing an anti-blocking agent on at least one surface thereof, the biaxial superior in thickness accuracy and in transparency and anti-blocking properties A stretched laminated polypropylene film could be obtained.

  The present invention relates to 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 comprising a propylene polymer (C) layer containing an antiblocking agent laminated on at least one side of a base layer that can be obtained from the above.

    Since the biaxially stretched laminated polypropylene film of the present invention uses the propylene polymer composition for the base layer, uniform stretchability when biaxially stretched, stretchability such as wide temperature range stretchability is improved. The obtained biaxially stretched laminated polypropylene film is excellent in thickness and thinness accuracy, and when printing on the surface, it is difficult for printing omission to occur and the packaging suitability is also excellent. Furthermore, it has excellent blocking resistance, no solid, high rigidity, and excellent transparency.

Propylene homopolymer (A)
The propylene homopolymer (A) according to the present invention comprises a propylene homopolymer, and usually has an MFR (melt flow rate; ASTM D-1238 load of 2160 g, temperature of 230 ° C.) of usually 0.5 to 10 g / 10. Min, preferably in the range of 2-5 g / 10 min.

Propylene / α-olefin copolymer (B)
The propylene / α-olefin copolymer (B) according to the present invention has a random copolymer with propylene having an α-olefin content of 0.4 to 2.2 mol%, preferably 0.6 to 1.8 mol%. It is a polymer. If the α-olefin content is less than 0.4 mol%, the stretchability is not improved, while if it exceeds 2.2 mol%, the rigidity is poor. Examples of the α-olefin include ethylene, 1-butene, 1-hexene, 4-methyl / 1-pentene, 1-octene and the like. Of these, ethylene is preferred. The 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 usually 0.5 to 10 g / 10 min, preferably 2 to 5 g / It is in the range of 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 and usually 5 mol% or less of ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-octene. And a copolymer with an α-olefin such as The MFR (melt flow rate; ASTM D-1238 load 2160 g, temperature 230 ° C.) of the propylene polymer (C) is not particularly limited as long as it can be a stretched film, but usually 0.5 to 20 g / 10 minutes, preferably Is in the range of 2-15 g / 10 min. The propylene polymer (C) according to the present invention may be the same as the propylene polymer composition of the propylene homopolymer (A) and the propylene / α-olefin copolymer (B).

  An antiblocking agent is added to the propylene polymer (C) according to the present invention, and the amount is usually 0.01 to 3.0% by weight, preferably 0.05 to 1.0% by weight. Is in range. 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. When the amount of the antiblocking agent is less than 0.01% by weight, the resulting biaxially stretched laminated polypropylene film has insufficient blocking prevention effect, while when it exceeds 3.0% by weight, the resulting biaxially stretched laminated polypropylene film is obtained. Tends to be inferior in transparency. As such an antiblocking agent, various known compounds such as silica, talc, mica, zeolite, and further inorganic compound particles such as metal oxide obtained by firing metal alkoxide, polymethyl methacrylate, melamine formalin resin, Organic compound particles such as melamine urea resin and polyester resin can be used. Among these, silica and polymethyl methacrylate are particularly preferable in terms of antiblocking properties and transparency.

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

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

  The organometallic compound catalyst component is preferably an organoaluminum compound, and specific examples include trialkylaluminum, dialkylaluminum halide, alkylaluminum sesquihalide, alkylaluminum dihalide, and the like. 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. Suitable specific examples include organic esters and organic ethers having these elements.

  Regarding the method for producing a polymer using a catalyst component with a carrier, for example, JP-A-50-108385, JP-A-50-126590, JP-A-51-20297, JP-A-51-28189, JP It is disclosed in various publications such as Sho 52-151691.

  The propylene homopolymer and propylene / α-olefin copolymer having high Iso according to the present invention can also be produced 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 comprising a metallocene transition metal compound, at least one compound selected from the group consisting of an organoaluminum compound and a compound that forms an ion pair by reacting with the metallocene transition metal compound, and an inorganic substance. It may be carried on.

  Examples of the metallocene-based transition metal compound include compounds described in JP-A-5-209014, JP-A-6-1005209, JP-A-1-301704, JP-A-3-193966, JP-A-5-148284, and the like. Etc.

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

  Examples of the compound that forms an ion pair by reacting with the metallocene transition metal compound include compounds described in JP-A-1-501950, JP-A-3-207704, and the like. Examples of the inorganic substance that supports the single-site catalyst include silica gel, zeolite, diatomaceous earth, and the like.

Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, gas phase polymerization and the like. These polymerizations may be batch processes or continuous processes. The polymerization conditions are usually a polymerization temperature: −100 to + 250 ° C., a polymerization time: 5 minutes to 10 hours, a reaction pressure; a normal pressure to 300 Kg / cm ² (gauge pressure).

Propylene Polymer Composition The propylene polymer composition according to the present invention is a composition that can be obtained from a propylene homopolymer (A) and a propylene / α-olefin copolymer (B), and has an α-olefin content. 0.1 to 1.8 mol%, preferably 0.2 to 1.5 mol%, preferably 95 to 10 wt% of propylene homopolymer (A), more preferably 90 to 20 wt% The propylene / α-olefin copolymer (B) is in the range of 5 to 90% by weight, 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 width may be small when obtaining a biaxially stretched film. Therefore, there is a possibility that a biaxially stretched film with excellent thickness accuracy will not be obtained, and when laminated with a propylene polymer (C) layer, the blocking property may not be improved. On the other hand, when it exceeds 90% by weight, the biaxially stretched film obtained may be deteriorated in 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, a propylene homopolymer (A) and a propylene / α-olefin copolymer (B) separately polymerized separately, a method of mechanically mixing, a method of mixing and then melt-kneading, Alternatively, after polymerizing with the propylene homopolymer (A) or the propylene / α-olefin copolymer (B), the propylene / α-olefin copolymer (B) or the propylene homopolymer (A) is subsequently polymerized. Or the like.

  In the propylene homopolymer (A), the propylene / α-olefin copolymer (B) or the propylene polymer composition of the present invention, either or any one of them, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, Various additives usually used for polyolefins such as lubricants, slip agents, nucleating agents, antistatic agents, antifogging agents, pigments, dyes, inorganic or organic fillers, and the like are added within a range not impairing the object of the present invention. Also good.

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. Usually, the propylene polymer composition layer is 10 to 100 μm, preferably 15 The propylene polymer (C) layer containing an antiblocking agent is in the range of ˜50 μm, and is in the range of 0.5˜15 μm, preferably 1˜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 as necessary. In addition, the biaxially stretched laminated polypropylene film of the present invention may further be subjected to high-pressure low-density polyethylene, linear low-density polyethylene, crystalline or low-crystalline ethylene and 3 carbon atoms in order to impart low-temperature heat sealability depending on applications. A random copolymer of 10 to α-olefin or a low-melting polymer such as a random copolymer of propylene and ethylene or an α-olefin having 4 or more carbon atoms, polybutene, ethylene / vinyl acetate copolymer, or the like Those compositions may be laminated on the propylene polymer (C) layer. In order to impart gas barrier properties, an ethylene / vinyl alcohol copolymer, polyamide, polyester, vinylidene chloride polymer, etc. may be laminated by extrusion coating or the like, or a metal or its oxide, silica, etc. Vapor deposition may be performed. Of course, in order to increase the adhesion to other substances, the surface of the stretched film may be anchored with an adhesive such as imine or urethane, or maleic anhydride-modified polyolefin may be laminated.

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

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this invention is not restrict | limited to these Examples, unless the summary is exceeded.

The physical property values and the like in Examples and Comparative Examples were obtained by the following evaluation methods.
(Evaluation methods)
1) Elastic modulus: measured in accordance with JIS K 7127.
2) Film thickness unevenness: Standard deviation of specified width was measured.
3) Blocking strength: The film was cut into 20 mm widths and stacked in 20 mm increments, left under a load of 0.25 kg / cm ² at 40 ° C. for 48 hours, and then pulled at a tensile speed of 30 mm / min with a tensile tester (manufactured by Toyo Seiki Co., Ltd.). The shear strength was measured.

Example 1
<Base layer: propylene polymer composition layer>
Polypropylene blended with 60% by weight of propylene / ethylene random copolymer (ethylene content 1.3 mol% MFR = 3.0g / 10min) to 40% by weight of propylene homopolymer (MFR = 3.0g / 10min) A plain resin composition was prepared. Tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane (product name: Irganox 1010) manufactured by Nippon Ciba Gaiky Co., Ltd. as an antioxidant was added to the resin composition. 1000 ppm of calcium stearate (manufactured by Nippon Oil & Fats), 6000 ppm of stearic acid monoglyceride (manufactured by Riken Vitamin) as antistatic agents, and 2000 ppm of stearyl diethanolamine (manufactured by Toho Chemical) were blended.
<Anti-blocking layer (coating layer): Propylene polymer layer>
The propylene homopolymer (melting point 160 ° C. MFR: 2.5 g / 10 min) was mixed with 1000 ppm of silica as the antioxidant and the anti-blocking agent described above.
<Manufacture of biaxially stretched laminated film>
The propylene polymer composition shown above and the propylene polymer are each melt extruded using a screw extruder so as to have an extrusion ratio (1/10/1), and shaped using a multi-manifold type T-die, cooling roll The sheet was rapidly cooled above to obtain an original 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 is heated to 155 ° C. and then stretched 10 times in the direction perpendicular to the flow direction (lateral direction). The thickness of the base layer: 26 μm and the thickness of the antiblocking layer: 2.5 μm (total) A biaxially stretched laminated polypropylene film having a thickness of 30 μm was obtained. The physical properties of the biaxially stretched multilayer polypropylene film were measured by the method described above. The results are shown in Table 1.

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

  As is apparent from the results in Table 1, biaxially stretched laminates based on a propylene polymer composition obtainable from the propylene homopolymer (A) of the present invention and the propylene / α-olefin copolymer (B). It can be seen that the polypropylene film has reduced thickness unevenness and blocking force compared to the biaxially stretched film shown in the comparative example.

  The biaxially stretched laminated polypropylene film of the present invention can be used for all uses where an OPP film has been conventionally used, for example, general printing, laminating, part coating and the like.

Claims (2)

  The biaxially stretched α-olefin content is in the range of 0.2 to 1.5 mol%, the propylene homopolymer (A) is 90 to 20% by weight, and the α-olefin content is 0.6 to 1. Propylene homopolymer or antiblocking containing an antiblocking agent on at least one side of the base layer which can be obtained from a propylene polymer composition containing 8 to 8 mol% of propylene / α-olefin copolymer (B) in an amount of 10 to 80% by weight A biaxially stretched laminated polypropylene film, wherein the propylene polymer composition layer containing an agent is laminated.   The biaxially stretched laminated polypropylene film according to claim 1, wherein the propylene polymer composition layer and a propylene homopolymer containing an antiblocking agent or the propylene polymer composition layer containing an antiblocking agent can be obtained by coextrusion molding. .