JPH1053675A - Polypropylene based resin composition for oriented film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene based resin composition and an oriented film of the same capable of giving an oriented polypropylene film excellent in antistatic properties. SOLUTION: This polypropylene based resin composition for oriented film contains following (a), (b) and (c) components. The oriented film is obtained by at least monoaxial stretching of the film. (a) 68-99.7wt.% of a crystalline polypropylene resin satisfying the following requirements, (1) having <=5.0wt.% of cold xylene(CXS) soluble parts, (2) having inherent viscosity ([η]) of 1.6-3.5dl/g. (b) 0.1-30wt.% of polyolefin based resin satisfying the following requirements, (1) having >=30wt.% of cold xylene(CXS) soluble parts, (2) having inherent viscosity ([η]) of 0.15-1.5dl/g. (c) 0.2-2.0wt.% of an antistatic agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin composition suitable for efficiently producing a stretched polypropylene resin film having excellent antistatic properties, and a stretched film using the same.

[0002]

2. Description of the Related Art Stretched polypropylene resin films, particularly biaxially stretched films, have optical properties such as transparency and gloss.
Because of its excellent mechanical properties such as tensile strength and rigidity, moisture resistance, etc., it is used in a wide range of applications such as food packaging, textile packaging, and the like. However, such excellent stretched polypropylene resin films are not without their disadvantages, but have the disadvantage that they tend to be charged with static electricity, which causes dust to adhere to the film surface and poor ink adhesion during printing. doing. For this reason, conventionally, in a stretched polypropylene resin film, antistatic properties are generally exhibited by incorporating a kneading type antistatic agent, but in a stretched film, unlike an unstretched film, highly oriented and crystallized. Since it is advanced, it is difficult for the antistatic agent to bleed uniformly on the film surface, and it is very difficult to obtain good antistatic properties. As described above, as a technique for causing an antistatic agent to bleed on a film surface in a biaxially stretched film, blending of a low molecular weight crystalline wax (Japanese Patent Laid-Open No.
However, in this method, a low molecular weight crystalline wax is incorporated into polypropylene crystals at the time of film formation, so that the antistatic agent does not easily bleed on the film surface, and a sufficient antistatic property is obtained. The effect of improving the properties cannot be obtained.

As a means for improving the antistatic property for all extrusion molding applications, use of a master batch in which an antistatic agent is kneaded at a high concentration in a low molecular weight amorphous polypropylene resin (Japanese Patent Laid-Open No. 5-98096). However, because the amorphous polypropylene resin exemplified in this has too small a molecular weight, the film itself bleeds on the film surface after film formation and the surface is sticky,
It is unsuitable for use in biaxially stretched films because of mutual adhesion between films.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polypropylene resin composition which gives a stretched polypropylene resin film having excellent antistatic properties, and a stretched film thereof.

[0005]

In view of the above circumstances, the present inventors have made various studies to improve the antistatic property of a stretched polypropylene resin film, and as a result, have found that a polyolefin resin having a specific structure in a crystalline polypropylene resin. The present inventors have found that a blend of a resin and an antistatic agent can provide a polypropylene-based resin composition for a stretched film and a stretched film thereof suitable for the above purpose, and have reached the present invention. That is, the present invention is as follows. [1] A polypropylene-based resin composition for a stretched film, comprising the following components (a), (b) and (c): (A) Crystalline polypropylene resin satisfying the following conditions: 68 to 99.7% by weight Cold xylene soluble part 5.0% by weight or less Intrinsic viscosity ([η]) 1.6 to 3.5 dl / g (b 1.) Polyolefin resin satisfying the following conditions
1 to 30% by weight Cold xylene soluble part 30% by weight or more Intrinsic viscosity ([η]) 0.15 to 1.5 dl / g (c) Antistatic agent 0.2 to 2.0% by weight [2] The above A stretched film obtained by stretching the polypropylene resin composition for a stretched film of at least one direction.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. The crystalline polypropylene resin as the component (a) in the present invention is a known crystalline polymer mainly composed of propylene, and is a crystalline homopolymer or an α-olefin such as ethylene and butene-1 in an amount of 2% by weight. It is a crystalline propylene polymer contained below. Further, two or more types of α-olefins contained in the crystalline polypropylene polymer may be used. These polypropylenes may be supplied, for example, using a highly active catalyst described in Japanese Patent Publication Nos. 64-6211 and 4-37084, supplying propylene alone to the polymerization system, or supplying propylene and a small amount of propylene. The polymerization is carried out by supplying an α-olefin to the polymerization system,
Obtainable. The weight ratio of the component (a) to the entire polypropylene resin composition for a stretched film of the present invention is as follows:
It must be in the range of 68 to 99.7% by weight.
If the amount is less than 68% by weight, the rigidity of the film decreases. On the other hand, if it is more than 99.7% by weight, the effect of improving the antistatic property cannot be obtained. The crystalline polypropylene-based resin of the component (a) of the present invention comprises a cold xylene-soluble portion (a ratio (% by weight) of a soluble portion to xylene at 20 ° C. in all resins, hereinafter referred to as “CXS”).
Must be 5.0% by weight or less,
It is preferably at most 4.0% by weight, particularly preferably at most 3.0% by weight. If the amount of CXS is too large, the rigidity of the film decreases. The component (a) has an intrinsic viscosity (intrinsic viscosity measured using an Ubbelohde viscometer, hereinafter referred to as “[η]” ”).
Is required to be 1.6 to 3.5 dl / g, and preferably 1.8 to 2.8 dl / g.
If [η] is too small or too large, the processability during film formation decreases. Further, the molecular weight distribution of the component (a) of the present invention (gel permeation chromatography (GP
Ratio of the weight average molecular weight and the number average molecular weight of the resin measured by C) (Mw / Mn), hereinafter referred to as “Mw / Mn”)
Is Mw / as obtained with the high activity catalyst system described above.
Mn is 6.0 or less, preferably 5.0 or less, particularly preferably 4.5 or less.

The polyolefin resin as the component (b) in the present invention may be, for example, a single polymer such as propylene, ethylene, butene-1, hexene-1, 4-methylpentene-1 or the like polymerized by a known Ziegler-Natta catalyst. It is a coalesced or copolymer or a mixture of these polymers. Among them, propylene homopolymer, ethylene-propylene copolymer, propylene-butene-1 copolymer, ethylene-propylene-butene-1 copolymer, propylene-hexene-1 copolymer, propylene-4-methylpentene -1 copolymer is preferably used. Among them, a propylene copolymer obtained by copolymerizing ethylene, butene-1, hexene-1, and 4-methylpentene-1 in an amount of 0.5% by weight or more, preferably 1.5% by weight or more is particularly preferably used. The weight ratio of the component (b) to the entire polypropylene resin composition for a stretched film of the present invention is 0.1 to 30.
% By weight, and preferably
It is 0.2 to 20% by weight, particularly preferably 0.3 to 10% by weight. If the amount is less than 0.1% by weight, the effect of improving the antistatic property cannot be obtained, and if it is more than 30% by weight, the rigidity of the film decreases. The component (b) of the present invention has a CXS of 30.
It is necessary to be at least 50% by weight, preferably at least 50% by weight, particularly preferably at least 70% by weight. CX
If S is small, the effect of improving the antistatic property cannot be obtained. The component (b) has [η] of 0.15 to 1.5 dl / g.
And preferably from 0.20 to 1.2
dl / g, particularly preferably 0.30 to 1.0 dl / g. If [η] is too small, the film itself bleeds on the film surface after the film is formed, and the surface becomes sticky, which tends to cause mutual adhesion of the films. On the other hand, if [η] is too large, the dispersibility in the crystalline polypropylene resin (component (a)) deteriorates. The component (b) has a temperature of 18
The melt viscosity at 0 ° C. is 6,000 to 20,000 cps, preferably 8,000 to 15,000. If the melt viscosity is too low, the film itself bleeds on the film surface after the film is formed, and the surface becomes sticky, which tends to cause mutual adhesion of the films. On the other hand, if it is too large, the dispersibility in the crystalline polypropylene resin (component (a)) deteriorates. The component (b) in the present invention comprises (1). It can be obtained as a by-product when the component (a) is polymerized,
(2). It can also be obtained by polymerizing only the component (b) alone. In the case of (1), the resin obtained by polymerization of the component (a) can be used as it is as a resin composition containing the component (b), or the component (b) once isolated from the component (a) can be used. It can also be used by blending it with the component (a) by the method described below. In the case of (2),
The obtained component (b) can be blended with the separately prepared component (a) by a method described later and used. Among them, the method of (2), in which the component (b) obtained by polymerizing alone is blended with the separately prepared component (a) by a method described later and used, is preferable.

The antistatic agent as the component (c) in the present invention is not particularly limited as long as it is generally used as an antistatic agent for polyolefin films (particularly, polypropylene films). Specific examples of the antistatic agent (c) include cationic amines such as primary amine salts, tertiary amines, and quaternary ammonium compounds, sulfated oils, sulfated amide oils, and sulfated ester oils. , Fatty alcohol sulfates, alkyl sulfates, fatty acid ethyl sulfonates, alkyl sulfonates, alkyl benzene sulfonates, phosphoric acid ester salts and the like, partial fatty acid esters of polyhydric alcohols, fatty alcohols Ethylene oxide adducts of fatty amines or fatty acid amides, ethylene oxide adducts of alkyl phenols, ethylene oxide adducts of alkyl naphthols, polyethylene glycols, fatty acid esters of alkyl diethanolamine, alkyl diethanol amides, etc. Those on system, the carboxylic acid derivatives include those amphoteric such imidazoline derivatives. Among them, partial fatty acid esters of polyhydric alcohols, fatty acid esters of alkyldiethanolamine, nonionic ones of alkyldiethanolamide are preferably used,
Glycerin stearate and stearyl diethanolamine monostearate are particularly preferably used. These antistatic agents can be used not only alone but also in combination of two or more.
The weight ratio of the component (c) to the whole polypropylene resin composition for a stretched film of the present invention needs to be in the range of 0.2 to 2.0% by weight, and preferably 0.3 to 2.0% by weight.
It is 1.7% by weight, particularly preferably 0.5 to 1.5% by weight. If it is less than 0.2% by weight, sufficient antistatic properties cannot be obtained, and if it is more than 2.0% by weight, problems such as smoke generation and roll contamination will occur during film formation.

In the present invention, as a method for blending the polyolefin resin as the component (b) or the antistatic agent as the component (c) with the crystalline polypropylene resin as the component (a), There is no limitation on the method of dispersing, and examples thereof include a method of mixing with a ribbon blender, a Henschel mixer, a tumbler mixer or the like, and melting and kneading the mixture with an extruder. At this time, known antioxidants, neutralizing agents, lubricants, drip-free agents, anti-blocking agents, and the like can be appropriately compounded as necessary. Further, a masterbatch containing the component (a) and the component (b) or (c) in an amount of about 1 to 100 parts by weight may be prepared in advance, and may be appropriately blended and used at a predetermined concentration. The polypropylene-based resin composition for a stretched film of the present invention thus obtained is usually formed into a film and stretched by the methods described below to form a biaxially stretched film. That is, the composition is melted by an extruder, extruded from a T-die, and cooled and solidified into a sheet by a cooling roll. Next, the obtained sheet is preheated and stretched in the longitudinal direction by a number of heating rolls, and then stretched in the transverse direction in a heating furnace comprising a preheating section, a stretching section, and a heat treatment section, and if necessary, corona treatment or the like. And winding. The melting temperature of the composition depends on the molecular weight, but usually is 23.
The reaction is carried out at a temperature of 0 to 290C, preferably 240 to 280C. The longitudinal stretching temperature is usually 120 to 150 ° C, preferably 130 to 145 ° C, the longitudinal stretching ratio is usually 3 to 8 times, preferably 4 to 6 times, and the transverse stretching temperature is usually 150 to 150 times.
170 ° C., preferably 155 ° C. to 165 ° C., and the transverse stretching ratio is usually 6 to 12 times, preferably 8 to 10 times.
The thickness of the film of the present invention is not particularly limited, but is usually 200 μm or less, preferably 5 to 100 μm, and particularly preferably 8 to 80 μm. Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not particularly limited by the following Examples.

[0010]

EXAMPLES The detailed description of the present invention and each item in the examples were measured by the following methods. (1) Cold xylene soluble part (CXS) (unit: wt%) After completely dissolving 5 g of a sample in 500 ml of boiling xylene, the temperature is lowered to 20 ° C and left for 4 hours. Thereafter, this was separated by filtration into a precipitate and a solution, and the filtrate was dried to 70 ° C. under reduced pressure.
And dried. The weight was measured to determine the content (% by weight). (2) Intrinsic viscosity ([η]) (unit: dl / g) Reduced viscosities were measured at three points of concentration 0.1, 0.2 and 0.5 g / dl using an Ubbelohde viscometer.
The limiting viscosity is “polymer solution, polymer experimental science 11” (19
1982, published by Kyoritsu Shuppan Co., Ltd., page 491, that is, an extrapolation method in which the reduced viscosity is plotted against the concentration and the concentration is extrapolated to zero. The measurement was performed at a temperature of 135 ° C. using tetralin as a solvent. (3) Molecular weight distribution (Mw / Mn) It was measured by gel permeation chromatography (GPC) under the following conditions. The calibration curve was prepared using standard polystyrene. Model: 150CV type manufactured by Millipore Waters Co., Ltd. Column: Shodex M / S 80 Measurement temperature: 145 ° C Solvent: orthodichlorobenzene Sample concentration: 5 mg / 8 ml NBS (National Bureau oo) under these conditions
f Standards) Standard Ref
erence Material 706 (Mw / Mn
= 2.1) and a molecular weight distribution (Mw / Mn) of 2.1 was obtained. (4) Ethylene content, butene-1 content (unit:
Ethylene content: Polymer Analysis Handbook (1985)
, Published by Asakura Shoten Co., Ltd.), page 256, "(i) Random copolymer". Butene-1 content: determined from the following equation by IR spectroscopy. Butene-1 content (% by weight) = 1.208 K ′ where K ′ is the absorbance at 767 cm ⁻¹ . (5) Melt viscosity (unit: cps) Temperature of 180 ° C. was measured using a BL viscometer manufactured by Tokyo Keiki Co., Ltd.
Was measured. (6) Antistatic property (unit: second) In a constant temperature / humidity room (temperature 23 ° C, humidity 50%), a static honest meter (Static Honestme) was used.
ter, manufactured by Shishido Shokai Co., Ltd.)
After charging an m-size sample piece for 1 minute at an applied voltage of 10 kV, the number of seconds until the charged voltage was reduced to half was defined as an antistatic value. It can be said that the smaller the value is, the better the antistatic property is.
The measurement was performed on the surface side of the film aged at 40 ° C. for 3 days, on which the corona discharge treatment was performed. The measurement was performed three times for each sample, and the average value was obtained.

Embodiment 1 (I). Pelletization of crystalline polypropylene resin as component (a) CXS is 1.9% by weight, [η] is 2.1 dl / g, Mw
0.1 part by weight of calcium stearate, 0.2 part by weight of BHT (2,6-di-tert-butylhydroxytoluene) and 100 parts by weight of a propylene homopolymer powder having an Mn / Mn of 3.8 and a trade name Ir
ganox1010 (Antioxidant manufactured by Ciba-Geigy)
After mixing 0.05 parts by weight with a Henschel mixer, 6
Granulation and pelletization were performed with a 5 mmφ extruder. (II). Preparation of Masterbatch of Polyolefin Resin of Component (b) To 80 parts by weight of the propylene homopolymer powder described in (I), CX was used as the polyolefin resin of the component (b).
Ethylene-propylene copolymer 2 having S of 71% by weight, [η] of 0.43 dl / g and an ethylene content of 2.4% by weight
0 parts by weight, calcium stearate 0.1 as a stabilizer
Parts by weight, 0.2 parts by weight of BHT (2,6-di-tert-butylhydroxytoluene), and Irgan (trade name)
ox1010 (Antioxidant manufactured by Ciba-Geigy) 0.05
After mixing the parts by weight with a Henschel mixer,
The mixture was granulated and pelletized by an extruder to obtain a master batch of the component (b). (III). (C) Preparation of Masterbatch of Component Antistatic Agent For 90 parts by weight of the propylene homopolymer powder described in (I), 10% by weight of glycerin stearate and stearyl diethanolamine monostearate as an antistatic agent was added. Parts, 0.1 parts by weight of calcium stearate as a stabilizer, 0.2 parts by weight of BHT (2,6-di-tert-butylhydroxytoluene), and 0.05 parts by weight of Irganox 1010 (antioxidant manufactured by Ciba-Geigy) in Henschel After mixing with a mixer, granulating and pelletizing with a 65 mmφ extruder (c)
A masterbatch of the components was obtained. (IV). Production of Stretched Film For 80 parts by weight of the polypropylene pellets obtained in (I), 10 parts by weight of the masterbatch pellets of the component (b) obtained in (II) and 10 parts by weight of the component (c) obtained in (III) After adding 10 parts by weight of the master batch pellets and mixing with a pellet blender, the mixture is melt-extruded at a resin temperature of 260 ° C., rapidly cooled by a cooling roll at 30 ° C., and solidified by cooling into a sheet having a thickness of 1.0 mm. Subsequently, after preheating, the film is stretched 5 times in the longitudinal direction at a stretching temperature of 145 ° C. due to a difference in roll peripheral speed of the longitudinal stretching machine. And a stretched film having a thickness of 25 μm (weight ratio of each component: component (a): 96.7% by weight, component (b): 2.0
% By weight, component (c): 1.0% by weight), and the surface wetting tension of one surface of the film was 42 dy using a corona discharge treatment machine.
Ne was processed. The obtained stretched film was aged at 40 ° C. for 3 days, and the antistatic property was evaluated. Table 1 shows the evaluation results.

Example 2 87.5 polypropylene pellets described in Example 1 (I)
2.5 parts by weight of the masterbatch pellets of the component (b) described in Example 1 (II),
A stretched film was prepared in the same manner as in Example 1 (IV) except that 10 parts by weight of the master batch pellet of the component (c) described in I) was added and mixed with a pellet blender (weight ratio of each component (a)). Component: 98.2% by weight, Component (b): 0.5% by weight, Component (c): 1.0% by weight), and the antistatic property was evaluated. Table 1 shows the evaluation results.

Example 3 20 parts by weight of the masterbatch pellet of the component (b) described in Example 1 (II) and 70 parts by weight of the polypropylene pellet described in Example 1 (I), and 70 parts by weight of the polypropylene pellet described in Example 1 (I) Example 1 except that 10 parts by weight of the master batch pellets of the component (c) were added and mixed with a pellet blender.
A stretched film was prepared in the same manner as in (IV) (weight ratio of each component (a): 94.7% by weight, component (b):
4.0% by weight, component (c): 1.0% by weight), and the antistatic property was evaluated. Table 1 shows the evaluation results.

Example 4 In Example 1 (II), as the polyolefin resin of the component (b), CXS was 79% by weight and [η] was 0.4%.
1 dl / g, ethylene having an ethylene content of 6.5% by weight.
Example 1 (II) except that a propylene copolymer was used
In the same manner as in (1), a master batch pellet of the component (b) was obtained. Further, a stretched film was prepared in the same manner as in Example 1 (IV) (weight ratio of each component: (a) component: 96.7% by weight, (b) component: 2.0% by weight, (c) component: 1). 0.0% by weight), and the antistatic property was evaluated. Table 1 shows the evaluation results.

Example 5 In Example 1 (II), as the polyolefin resin of the component (b), CXS was 84% by weight and [η] was 0.4%.
Example 1 (I) except that an ethylene-propylene copolymer having 2 dl / g and an ethylene content of 12.2% by weight was used.
A masterbatch pellet of the component (b) was obtained in the same manner as in I). Further, a stretched film was produced in the same manner as in Example 1 (IV) (weight ratio of each component (a) component: 96.7).
% By weight, component (b): 2.0% by weight, component (c): 1.
0% by weight), and the antistatic property was evaluated. Table 1 shows the evaluation results.

Example 6 In Example 1 (II), as the polyolefin resin of the component (b), CXS was 91% by weight and [η] was 0.4%.
Example 1 (I) except that 3 dl / g and a propylene-butene-1 copolymer having a butene content of 45.2% by weight were used.
A masterbatch pellet of the component (b) was obtained in the same manner as in I). Further, a stretched film was produced in the same manner as in Example 1 (IV) (weight ratio of each component (a) component: 96.7).
% By weight, component (b): 2.0% by weight, component (c): 1.
0% by weight), and the antistatic property was evaluated. Table 1 shows the evaluation results.

Comparative Example 1 A pellet blender was added to 90 parts by weight of the polypropylene pellets described in Example 1 (I) and 10 parts by weight of a master batch pellet of the antistatic agent of the component (c) described in Example 1 (III). , And a stretched film was prepared in the same manner as in Example 1 (IV) except that the masterbatch pellet of the component (b) described in Example 1 (II) was not mixed (weight ratio of each component ( Component (a): 98.7% by weight, component (b): not added, component (c): 1.0% by weight), and antistatic properties were evaluated. Table 1 shows the evaluation results.

Comparative Example 2 In Example 1 (II), as the polyolefin resin of the component (b), CXS was 21% by weight and [η] was 0.1%.
1 dl / g, ethylene having an ethylene content of 3.2% by weight
Example 1 (II) except that a propylene copolymer was used
In the same manner as in (1), a master batch pellet of the component (b) was obtained. Further, a stretched film was prepared in the same manner as in Example 2 (weight ratio of each component (a) component: 98.2% by weight,
(Component (b): 0.5% by weight, component (c): 1.0% by weight), and antistatic properties were evaluated. Table 1 shows the evaluation results.

Comparative Example 3 With respect to 75 parts by weight of the polypropylene pellets described in Example 1 (I), 15 parts by weight of the masterbatch pellets of the component (b) obtained in Comparative Example 2 were used. Example 1 (I) except that 10 parts by weight of the master batch pellets of component c) were added and mixed in a pellet blender.
A stretched film was prepared in the same manner as in V) (weight ratio of each component: component (a): 95.7% by weight, component (b): 3.0)
% By weight, component (c): 1.0% by weight), and the antistatic property was evaluated. Table 1 shows the evaluation results. From the above Examples and Comparative Examples, the film stretched with the resin composition obtained according to the present invention clearly shows the effect of improving the antistatic property.

[0020]

[Table 1]

[0021]

The polypropylene resin composition for a stretched film of the present invention gives a stretched film having excellent antistatic properties. The stretched film provided by the present invention can be used for a wide range of uses such as food packaging and fiber packaging by utilizing the excellent antistatic property.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29L 7:00

Claims (2)

[Claims] 1. A polypropylene resin composition for a stretched film, comprising the following components (a), (b) and (c): (A) Crystalline polypropylene resin satisfying the following conditions: 68 to 99.7% by weight Cold xylene soluble part 5.0% by weight or less Intrinsic viscosity ([η]) 1.6 to 3.5 dl / g (b 1.) Polyolefin resin satisfying the following conditions
1 to 30% by weight Cold xylene-soluble portion 30% by weight or more Intrinsic viscosity ([η]) 0.15 to 1.5 dl / g (c) Antistatic agent 0.2 to 2.0% by weight 2. A stretched film obtained by stretching the polypropylene resin composition for a stretched film according to claim 1 in at least one axial direction.