JP2008144043A - Polypropylene resin composition, and film made therefrom - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene resin composition capable of producing a film excellent in all of appearance, transparency, blocking resistance and scratch resistance. <P>SOLUTION: The polypropylene resin composition comprises 100 pts.wt. of polypropylene resin particles 600-1,300 μm in average size with the proportion of microparticles 300 μm or less being 10 wt.% or less and 0.01-1 pt.wt. of silicon dioxide powder synthesized by sedimentation process, wherein the oil absorption and the pore volume of the silicon dioxide powder are 155-200 ml/100 g and 1.5-2.5 ml/g respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polypropylene resin composition containing a polypropylene resin and silicon dioxide powder synthesized by a precipitation method, and a film comprising the same.

  Polypropylene films are widely used in packaging applications such as food packaging and fiber packaging because of their excellent appearance, transparency, mechanical properties, packaging suitability, and the like. However, the polypropylene film has a drawback that it induces blocking in which the films are in close contact with each other, and deteriorates workability such as packaging. For this reason, in order to prevent blocking in a polypropylene film, an inorganic fine powder typified by silicon dioxide or an organic fine powder such as a crosslinked polymer is generally incorporated into the film as an antiblocking agent. Are known.

  As a method of blending an anti-blocking agent in polypropylene, industrially, an anti-blocking agent is added to polypropylene resin particles obtained by polymerization, and the mixture is mixed in advance at a temperature below the melting point of the polypropylene resin particles. Thereafter, a method of melt kneading at a temperature equal to or higher than the melting point of the polypropylene resin particles is generally used.

  Conventionally, polypropylene resin particles having a relatively small average particle size and a wide particle size distribution polymerized by a polymerization catalyst that has been used industrially have good dispersibility at a low concentration of 1 part by weight or less of an antiblocking agent. Met. However, in polypropylene resin particles having a relatively large average particle size and a small particle distribution with a small average particle size, polymerized with a recently developed highly active polymerization catalyst or a polymerization catalyst with improved particle properties by loading, etc., While there is an advantage that the danger of dust explosion is reduced and handling is easy, when an anti-blocking agent is blended, it is easy to produce aggregates, not only the blocking resistance deteriorates, but also the appearance is impaired. There was a problem.

As an attempt to solve such a problem, for example, methods described in JP-A-8-81591 and JP-A-2001-72812 are known. Japanese Patent Application Laid-Open No. 8-81591 discloses a polyolefin composition characterized in that fine particles of silicon dioxide having a specific property are blended and melt-kneaded with polyolefin fine particles having a specific property. Japanese Patent Application Laid-Open No. 2001-72812 discloses a polypropylene resin composition containing synthetic silica having a specific property in polypropylene resin particles having a specific property. However, the polyolefin composition described in Japanese Patent Application Laid-Open No. 8-81591 is not satisfactory in the balance between appearance and scratch resistance, and the polyolefin resin composition described in Japanese Patent Application Laid-Open No. 2001-72812 is not satisfactory. Synthetic silica having a pore volume of 1 ml / g or less was used, which was not satisfactory in terms of scratch resistance.
JP-A-8-81591 JP 2001-72812 A

  The objective of this invention is providing the polypropylene resin composition which can manufacture the film excellent in all of an external appearance, transparency, blocking resistance, and damage resistance.

As a result of intensive studies, the present inventors have found that the present invention can solve the above problems, and have completed the present invention.
That is, in the present invention, 100 parts by weight of polypropylene resin particles having an average particle diameter of 600 to 1300 μm and a ratio of fine particles of 300 μm or less of 10% by weight or less and silicon dioxide powder synthesized by a precipitation method 0.01 The present invention relates to a polypropylene resin composition containing ˜1 part by weight.

  According to the present invention, a film having excellent appearance, transparency, blocking resistance, and scratch resistance can be obtained.

  The polypropylene resin particles used in the present invention have an average particle size of 600 to 1300 μm, preferably 700 to 1300 μm, more preferably 700 to 1200 μm. In the polypropylene resin particles used in the present invention, the ratio of fine particles of 300 μm or less to the entire polypropylene resin particles is 10% by weight or less, preferably 5% by weight or less, more preferably 3% by weight or less. Dispersion of polypropylene resin particles having an average particle diameter exceeding 1300 μm or polypropylene resin particles having a proportion of fine particles of 300 μm or less exceeding 10% by weight may deteriorate even when silicon dioxide powder synthesized by a precipitation method is blended. is there.

The method for producing the polypropylene resin particles used in the present invention is produced by a known polymerization method using a known catalyst.
Known catalysts include, for example, a Ti-Mg catalyst composed of a solid catalyst component in which a Ti compound is compounded with a magnesium compound, an organoaluminum compound and, if necessary, an electron donating compound, etc. Examples include a catalyst system in which a third component is combined, or a metallocene catalyst, preferably a catalyst system composed of a solid catalyst component containing magnesium, titanium and halogen as essential components, an organoaluminum compound, and an electron donating compound. JP-A-61-218606, JP-A-61-287904, JP-A-7-216017 and the like.

  Known polymerization methods include, for example, a slurry polymerization method using an inert hydrocarbon solvent, a solvent polymerization method, a liquid phase polymerization method without a solvent, a gas phase polymerization method, or a liquid phase-gas phase polymerization method in which they are continuously performed. The gas phase polymerization method is preferred.

  In the production of the polypropylene resin particles used in the present invention, if necessary, drying is performed at a temperature equal to or lower than the temperature at which the polypropylene melts in order to remove the residual solvent of the polypropylene and the ultra-low molecular weight oligomer by-produced during the production. You may go. Examples of the drying method include the methods described in JP-A Nos. 55-75410 and 2565753.

Examples of the polypropylene resin of the polypropylene resin particles used in the present invention include a propylene homopolymer, a copolymer of propylene and ethylene, a copolymer of propylene and an α-olefin having 4 to 20 carbon atoms, propylene and ethylene. And an α-olefin having 4 to 20 carbon atoms, or a mixture thereof. From the viewpoint of excellent transparency, a copolymer of propylene and ethylene, a copolymer of propylene and an α-olefin having 4 to 20 carbon atoms, propylene, ethylene and an α-olefin having 4 to 20 carbon atoms and These copolymers are preferred.
Examples of the α-olefin having 4 to 20 carbon atoms include butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, decene-1, and the like. Preferred are butene-1, hexene-1 and octene-1, and these α-olefins may be used alone or in combination of two or more.

  As a copolymer of propylene and ethylene, a copolymer of propylene and an α-olefin having 4 to 20 carbon atoms, a copolymer of propylene, ethylene and an α-olefin having 4 to 20 carbon atoms, for example, , Propylene-ethylene copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, propylene-hexene-1 copolymer, propylene-ethylene-hexene-1 copolymer, etc. Preferred are propylene-ethylene copolymer, propylene-butene-1 copolymer, and propylene-ethylene-butene-1 copolymer.

  Ethylene in a copolymer of propylene and ethylene, a copolymer of propylene and an α-olefin having 4 to 20 carbon atoms, and a copolymer of propylene, ethylene and an α-olefin having 4 to 20 carbon atoms The content of the α-olefin having 4 to 20 carbon atoms is not particularly limited, but is usually 0.5 to 15% by weight and preferably 0.5 to 10% from the viewpoint of excellent rigidity. % By weight.

  The silicon dioxide powder used in the present invention is a silicon dioxide powder synthesized by a precipitation method. As a synthesis method of silicon dioxide powder, a dry method and a wet method are known. The dry method is a method of synthesizing silicon dioxide by a high-temperature gas phase reaction, and the wet method is a method of synthesizing silicon dioxide by reacting sodium silicate with an acid. The wet method includes a gelation method and a sedimentation method. In the gelation method, the reaction between sodium silicate and an acid such as sulfuric acid proceeds in an acidic region to suppress the growth of primary particles. In this method, gelation is carried out by a three-dimensional network structure. The precipitation method is a method in which the reaction between sodium silicate and an acid such as sulfuric acid proceeds in a relatively high temperature and alkaline region, and the primary particles grow rapidly. It is a production method that aggregates and settles.

  The average particle diameter of the silicon dioxide powder used in the present invention is 1.0 to 3.0 μm, preferably 1.0 to 2.9 μm, from the viewpoint of good transparency and blocking resistance of the film. More preferably, it is 1.2-2.5 micrometers. In addition, the average particle system referred to in the present specification is a value measured by a Coulter counter method.

  The apparent specific gravity of the silicon dioxide powder used in the present invention is 0.15 to 0.30 g / ml, preferably 0.18 to 0.30 g / ml, from the viewpoint of excellent film appearance and scratch resistance. More preferably, it is 0.20 to 0.28 g / ml. In addition, the apparent specific gravity as used in this specification is the value measured based on JIS-K6220.

  The oil absorption of the silicon dioxide powder used in the present invention is 100 to 300 ml / 100 g, preferably 150 to 210 ml / 100 g, more preferably 155 to 200 ml / 100 g, from the viewpoint of excellent film appearance and scratch resistance. It is. The oil absorption amount in the present specification is a value measured according to JIS K5101.

  The pore volume of the silicon dioxide powder used in the present invention is 1.0 to 3.0 ml / g, preferably 1.2 to 2.7 ml / g, from the viewpoint of excellent film appearance and scratch resistance. More preferably, it is 1.5-2.5 ml / g. In addition, the pore volume as used in this specification is the value measured by the mercury adsorption method.

  The compounding quantity of the silicon dioxide powder used by this invention is 0.01-1 weight part with respect to 100 weight part of polypropylene resin particles from a viewpoint that the blocking resistance of a film, transparency, and an external appearance are excellent, Preferably 0.05 to 0.5 parts by weight, more preferably 0.05 to 0.3 parts by weight

  In the polypropylene resin composition of the present invention, if necessary, a polyolefin polymer such as polyethylene, polybutene-1, styrene resin, ethylene / α-olefin copolymer rubber, ethylene-propylene-diene copolymer rubber, etc. Can be added.

  In the polypropylene resin composition of the present invention, other additives such as a neutralizing agent, an antioxidant, an antifungal agent, a flame retardant, an antistatic agent, a plasticizer, a lubricant, a copper damage preventing agent, etc., if necessary. Can be added.

  Examples of the method for producing a film comprising the polypropylene resin composition of the present invention include, for example, polypropylene resin particles, silicon dioxide powder, and various additives that are added as necessary, such as a tumbler mixer, a Henschel mixer, and a ribbon blender. After mixing using a mixer such as the above, it is obtained by melt-kneading with a single-screw extruder, twin-screw extruder, Banbury mixer, etc., and melt extrusion. Examples of the film of the present invention include an unstretched film obtained by melt extrusion by a T-die method or a tubular method, and a stretched film stretched at least uniaxially after melt extrusion by the above method.

  The film of the present invention may be a single layer film or a multilayer film composed of two or more layers, but the multilayer film is formed on at least one surface of a base material layer that is not a layer composed of the polypropylene resin composition of the present invention. It is preferable that the surface layer has a layer made of the polypropylene resin composition of the present invention.

  The thickness of the film of this invention can be suitably selected according to a use, and is 5-100 micrometers, Preferably, it is 10-60 micrometers. The film of the present invention is widely used for packaging applications such as food packaging, fiber packaging, and miscellaneous goods packaging.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
The physical properties of each item in Examples and Comparative Examples were measured according to the following methods.

(1) Average particle diameter of polypropylene resin particles and ratio of fine particles of 300 μm or less Measurement was performed with GRADIS (dry dropping method) using a HELOS & RODOS laser diffraction particle size distribution analyzer manufactured by Sympatec.

(2) Ethylene content and 1-butene content of polypropylene resin (unit:% by weight)
The ethylene content was determined by IR spectrum measurement and according to the method relating to (i) random copolymers described on page 616 of the polymer handbook (1995, published by Kinokuniya).
The 1-butene content was determined according to the method described in page 619 of the polymer handbook (1995, published by Kinokuniya Shoten) by performing IR spectrum measurement.

(3) Average particle diameter of silicon dioxide powder The average particle diameter of the silicon dioxide powder was measured according to the Coulter counter method (AP · 30 μm).

(4) Apparent specific gravity of silicon dioxide powder Measured according to JIS K6220.

(5) Oil absorption of silicon dioxide powder Measured according to JIS K5101.

(6) The pore volume mercury adsorption method of silicon dioxide powder was measured.

(7) Melt flow rate (MFR, unit: g / 10 minutes)
According to JIS K7210, the measurement was performed at a temperature of 230 ° C. and a load of 21.18 N.

(8) Haze (Unit:%)
It measured according to JIS K7150.

(9) Blocking resistance (unit: kg / 12cm ² )
Two films with a width of 30 mm and a length of 150 mm were overlapped in a range of 40 mm × 30 mm, and the condition was adjusted at 60 ° C. for 3 hours under a load of 42 g / cm ² . Thereafter, the film was left in an atmosphere of 23 ° C. and 50% humidity for 30 minutes or more, and the peel strength was measured at a tensile rate of 200 mm / min with a Toyo Seiki shopper type tensile tester (C type).

(10) Δhaze (scratch resistance) (unit:%)
After fixing the film with the measurement surface facing up on the silicon sheet of the measurement table in which the silicon sheet is laminated on the flat plate, the measurement surface overlaps another film with a load of 2 kg on the measurement film. And slide the film 10 times. The haze of the film fixed on the silicone is measured, and the haze difference before and after the test is calculated. The smaller the value, the better the scratch resistance.

(11) Defect (unit: piece / m ² )
Defects of 0.05 mm or more were measured using a film defect inspection apparatus GX-40K (manufactured by Mitsubishi Kasei Corporation).

Example 1
Propylene-ethylene-1-butene random copolymer particles having an average particle size of 930 μm and a proportion of fine particles of 300 μm or less of 0.55 wt% (ethylene content: 2.4 wt%, butene content: 6.8 wt%) 100 0.10 parts by weight of fine seal G70 (manufactured by Tokuyama Co., Ltd.), 0.01 parts by weight of hydrotalcite DHT4C (manufactured by Kyowa Chemical Co., Ltd.), Irganox 1010 (manufactured by Ciba Specialty Chemicals) 10 parts by weight, Irgafos 168 (manufactured by Ciba Specialty Chemicals) 0.05 part by weight, 0.05 part by weight of erucic acid amide, mixed for 1 minute with a tumbler, L / D = 18 30 mm diameter biaxial Using an extruder, pellets were obtained by melt-kneading at a set temperature of 230 ° C. The MFR of the obtained pellet was 6.5 g / 10 minutes.
(Create unstretched film)
The obtained pellets were extruded using a φ50 mm extruder equipped with a coat hanger type T die having a width of 400 mm, with a resin temperature of 250 ° C. and a discharge rate of 12 kg / hr, a chill roll temperature of 30 ° C., a line speed of 10 m / min, and air chamber cooling. It cooled by the system and the film with a thickness of 30 micrometers was created.
(Evaluation of biaxially stretched film)
Using the pellets obtained for the surface layer, using Sumitomo Nobrene FS2011DG3 (melting point 159 ° C., MFR = 2.5 g / 10 min) for the base material layer, melting in a separate extruder at a resin temperature of 230 ° C. and 260 ° C., respectively. Extruded and fed into a single coextrusion T die. The resin extruded from the T die in a two-layer configuration with two layers was cooled with a cooling roll at 30 ° C. to obtain a cast sheet having a thickness of about 1 mm.
The obtained cast sheet was stretched 5 times by a roll peripheral speed difference with a longitudinal stretching machine at a stretching temperature of 115 ° C., and subsequently stretched 8 times in the transverse direction at a stretching temperature of 157 ° C. in a heating furnace, to 165 ° C. And a biaxially stretched film having a thickness of 21 μm (thickness structure: surface layer / base material layer = 1/20) was prepared.

Example 2
Example 1 was the same as Example 1 except that the fine seal G70 used in Example 1 was changed to a fine seal G71.

Example 3
Example 1 was the same as Example 1 except that the fine seal G70 used in Example 1 was changed to a fine seal G80.

Example 4
The same procedure as in Example 1 was performed except that the addition amount of the fine seal G70 used in Example 1 was changed to 0.20 parts by weight.

Example 5
Example 2 was the same as Example 2 except that the amount of fine seal G71 used in Example 2 was changed to 0.20 parts by weight.

Comparative Example 1
The same procedure as in Example 1 was performed except that the fine seal G70 used in Example 1 was changed to Silicia 420 (manufactured by Fuji Silysia). However, as a result of measuring the defects of the unstretched film, the dispersibility of the silicon dioxide powder was 48 / m ² , so the evaluation of the biaxially stretched film was stopped.

Comparative Example 2
The same operation as in Example 1 was performed except that the fine seal G70 used in Example 1 was changed to Siricia 530 (manufactured by Fuji Silysia).

  Table 1 shows the properties of the silicon dioxide powder used in Examples and Comparative Examples.

The evaluation results of the films obtained in Examples and Comparative Examples are shown in Table 2.

Examples 1 to 5 that satisfy the requirements of the present invention were films excellent in appearance, transparency, blocking resistance, and scratch resistance.
On the other hand, Comparative Example 1 using silicon dioxide synthesized by the gelation method has many disadvantages and is poor in dispersion of silicon dioxide powder, and Comparative Example 2 is inferior in scratch resistance. .

Claims (4)

  100 parts by weight of polypropylene resin particles having an average particle size of 600 to 1300 μm and a proportion of fine particles of 300 μm or less of 10% by weight or less, and 0.01 to 1 part by weight of silicon dioxide powder synthesized by a precipitation method Contains polypropylene resin composition.   The polypropylene resin composition according to claim 1, wherein the silicon dioxide powder has an oil absorption of 155 to 200 ml / 100 g and the silicon dioxide powder has a pore volume of 1.5 to 2.5 ml / g.   A film comprising the polypropylene resin composition according to claim 1.   A stretched film obtained by melt-extruding the polypropylene resin composition according to claim 1 or 2 and stretching it at least uniaxially.