JP2009255414A - Method of manufacturing polypropylene-based film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a polypropylene-based film excellent in appearance and rigidity by preventing the film from winding around a temperature-controlling roller upon film formation. <P>SOLUTION: The method of manufacturing polypropylene-based film comprises processes of: cooling and solidifying a molten film made of a resin composition including a polypropylene-based resin with a cooling roller 1; and thereafter performing heat treatment by using at least three temperature controlling rollers, wherein, when temperature of a temperature controlling roller 2 arranged on the downstream of the cooling roller 1 is T2(°C), temperature of a temperature controlling roller 3 arranged on the downstream of the cooling roller 2 is T3(°C) and temperature of a temperature controlling roller 4 arranged on the downstream of the cooling roller 3 is T4(°C), the temperatures T2(°C), T3(°C) and T4(°C) satisfy the relation: T4(°C)> T2(°C)> T3(°C). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a polypropylene film having excellent film processability, appearance, and rigidity.

Polypropylene films made of polypropylene resins are widely used as food packaging films and industrial films because they are excellent in various performances such as transparency, rigidity, heat resistance, food hygiene, and heat seal suitability.
In recent years, these films have been desired to be improved in handling properties and dimensional changes during secondary processing, and various studies have been conducted to increase the rigidity in order to achieve these.
As a method of increasing the rigidity of a polypropylene resin, a method of performing a heat treatment is known. For example, Patent Document 1 describes a method of heat-treating a rapidly cooled polypropylene sheet at 40 ° C. or higher and below the melting point of polypropylene. Has been.

JP 58-142818

However, in the production of a thin film with a high film forming speed, if the heat treatment is performed so that sufficient rigidity is exhibited, the film surface melts and the roll surface state is transferred, and the appearance deteriorates or is severe. Is a problem because troubles such as film winding around a roll occur.
An object of the present invention is to obtain a polypropylene film excellent in appearance and rigidity without film being wound around a temperature control roll during film formation.

  That is, the present invention is a method for producing a polypropylene film in which a molten film made of a resin composition containing a polypropylene resin is cooled and solidified with a cooling roll (1) and then heat-treated with at least three temperature control rolls. The temperature T2 (° C), T3 (° C) and T4 (° C) of the temperature control rolls (2) to (4) are T4 (° C)> T2 (° C)> T3 (° C). The method for producing the polypropylene film (however, the temperature of the temperature control roll (2) disposed downstream of the cooling roll (1) is T2 (° C.) and is disposed downstream of the temperature control roll (2). The temperature of the temperature control roll (3) is T3 (° C.), and the temperature of the temperature control roll (4) disposed downstream of the temperature control roll (3) is T4 (° C.).

  According to the production method of the present invention, a polypropylene film excellent in appearance and rigidity can be obtained without the film being wound around a temperature control roll during film formation.

  The polypropylene resin used in the present invention is a polymer obtained by polymerizing a monomer mainly composed of propylene, a propylene-ethylene random copolymer, a propylene-ethylene-α-olefin terpolymer, and mainly composed of propylene. A copolymer component obtained by polymerizing a polymer component obtained by polymerizing the monomer, and one or more monomers selected from propylene and ethylene and / or an α-olefin having 4 to 12 carbon atoms. Examples thereof include a polypropylene copolymer (sometimes referred to as a block copolymer) obtained by producing in at least two or more stages. Preferred are a propylene homopolymer, a propylene-ethylene random copolymer, and a propylene-ethylene-α-olefin terpolymer. The aforementioned polymers may be used alone or in combination of two or more.

  Examples of the α-olefin include α-olefins having 4 to 12 carbon atoms, such as 1-butene, 2-methyl-1-propene, 1-pentene, 2-methyl-1-butene, and 3-methyl. -1-butene, 1-hexene, 2-ethyl-1-butene, 2,3-dimethyl-1-butene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene 3,3-dimethyl-1-butene, 1-heptene, methyl-1-hexene, dimethyl-1-pentene, ethyl-1-pentene, trimethyl-1-butene, methylethyl-1-butene, 1-octene, Methyl-1-pentene, ethyl-1-hexene, dimethyl-1-hexene, propyl-1-heptene, methylethyl-1-heptene, trimethyl-1-pentene, propyl-1-pen Ten, diethyl-1-butene, 1-nonene, 1-decene, 1-undecene, 1-dodecene and the like can be mentioned. 1-butene, 1-pentene, 1-hexene and 1-octene are preferable, and 1-butene and 1-hexene are more preferable from the viewpoints of copolymerization characteristics and economy.

  Content of the structural unit derived from ethylene and an alpha olefin in a copolymer is 0.1 to 40 weight% normally, Preferably it is 1 to 30 weight%.

  The melt flow rate (MFR) measured at 230 ° C. of the polypropylene resin used in the present invention is preferably 1 to 50 g / 10 minutes, more preferably 2 to 15 g / 10, from the viewpoints of fluidity and film forming properties. Minutes.

  The polypropylene resin used in the present invention is, for example, a Ti-Mg catalyst comprising a solid catalyst component in which a Ti compound is combined with a magnesium compound, etc., an organoaluminum compound and, if necessary, an electron donating compound For example, JP-A-61-2218606, JP-A-61-287904, JP-A-7- This is a catalyst system described in Japanese Patent No. 216017.

  Examples of the polymerization method of the polypropylene resin used in the present invention 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 for continuously performing them. A phase-gas phase polymerization method and the like can be mentioned. From the viewpoint of productivity, a gas phase polymerization method, a liquid phase-gas phase polymerization method and the like are preferable.

It is preferable to mix | blend antioxidant with the polypropylene resin used for this invention, for example, a phenolic antioxidant, a phosphorus antioxidant, etc. are mentioned as antioxidant.
A preferable blending amount of the antioxidant is, for example, 0.01 to 0.2% by weight with respect to 100 parts by weight of the polypropylene polymer in the case of a phenolic antioxidant, and a polypropylene type in the case of a phosphorus antioxidant. It is 0.01 to 0.2 weight% with respect to 100 weight part of polymers.

  Examples of the phenolic antioxidant include 2,6-di-t-butyl-4-methylphenol and tetrakis [methylene-3 (3 ′, 5′-di-t-butyl-4-hydroxyphenyl) propionate. ] Methane, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 3,9-bis [2- {3- (3-tert-butyl-4-hydroxy-5-methyl) Phenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5 · 5] undecane, tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanate Nurate, triethylene glycol-N-bis-3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate, 1,6-hexanediol Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propylate], 2,2-thiobis-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate], α-tocophenols represented by vitamin E, and the like.

  Examples of the phosphorus antioxidant include tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) phosphite, distearyl pentaerythritol diphosphite, and bis (2,4-di-). t-butylphenyl) pentaerythritol diphosphite, bis (2,4-di-t-butyl-6-methylphenyl) pentaerythritol diphosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite Bis (2,4-dicumylphenyl) pentaerythritol diphosphite, tetrakis (2,4-di-t-butylphenyl) -4,4′-diphenylenediphosnite, 2,2′-methylenebis (4,6 -Di-t-butylphenyl) 2-ethylhexylphosphine 2,2'-ethylidenebis (4,6-di-t-butylphenyl) fluorophosphite, bis (2,4-di-t-butyl-6-methylphenyl) ethyl phosphite, 2- (2 , 4,6-tri-t-butylphenyl) -5-ethyl-5-butyl-1,3,2-oxaphosphorinane, 2,2 ′, 2 ″ -nitrilo [triethyl-tris (3,3 ′ , 5,5′-tetra-t-butyl-1,1′-biphenyl-2,2′-diyl) phosphite and the like.

  In addition to the polypropylene resin, other additives and other polymers may be added to the polypropylene resin composition used in the present invention, as long as the purpose and effect of the present invention are not impaired. Also good. Examples of other additives include lubricants typified by higher fatty acid amides and higher fatty acid esters, anti-blocking agents typified by silica, glycerin esters and sorbitan acid esters of fatty acids having 8 to 22 carbon atoms, polyethylene glycol esters, etc. In addition to these antistatic agents, nucleating agents, pressure-sensitive adhesives, antifogging agents, ultraviolet absorbers and the like can be mentioned.

  Other polymers include low density polyethylene, high density polyethylene, ethylene-α-olefin copolymers, olefin polymers such as polybutene, and vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymers. A fluorine-type polymer is mentioned. These may be produced with a heterogeneous catalyst or a homogeneous catalyst typified by a metallocene catalyst. Also included are styrene copolymer rubbers obtained by hydrogenating styrene-butadiene-styrene copolymers, styrene isoprene-styrene copolymers, and other elastomers.

  As a method for producing the polypropylene resin composition used in the present invention, a known method may be mentioned. For example, after blending a polypropylene resin powder and various additives using a mixing device such as a Henschel mixer, directly pelletize, or a relatively high concentration additive masterbatch such as a twin screw granulator Examples thereof include a method of blending into a polypropylene polymer after pelletizing using a high kneading extruder, a method of adding an additive to a melted polypropylene resin, and the like.

The apparatus for manufacturing the polypropylene film used in the present invention is a T-die film manufacturing apparatus including an extruder, a T-die, a cooling roll, and at least three temperature control rolls. FIG. 1 shows a schematic diagram of a T-die film manufacturing apparatus as an example. The extruder may be provided with a hopper, a filter, or an air chamber. Moreover, as a film take-up device, a plurality of take-up rolls and film winders different from the temperature control roll can be provided.
Especially for the above temperature control roll, it is necessary to greatly improve the rigidity without deteriorating the film appearance and film processing suitability, so at least three temperature control rolls (2) installed downstream of the cooling roll (2), The temperatures of (3) and (4) need to be controlled in the order of T4>T2> T3.

  The temperature control roll (2) is disposed downstream of the cooling roll (1), and the temperature T2 is preferably 60 to 60% from the viewpoint of improving rigidity in a range that does not deteriorate the film appearance and film processing suitability. It is Tm-40 degreeC, More preferably, it is 80-Tm-60 degreeC.

  The temperature control roll (3) is disposed downstream of the temperature control roll (2), and the temperature T3 is preferably 5 to 5 from the viewpoint of imparting film heat resistance at the temperature control roll (4). It is Tc-40 degreeC, More preferably, it is 20-50 degreeC.

  Furthermore, the temperature control roll (4) is disposed downstream of the temperature control roll (3), and the temperature T4 is preferable from the viewpoint of improving the rigidity of the film in terms of the appearance of the film and the suitability for film processing. Is T2 to Tm ° C, more preferably T2 + 20 to Tm-20 ° C.

In the method for producing a polypropylene film of the present invention, a temperature control roll can be further installed on the downstream side of the temperature control roll (4). If the n-th temperature control roll temperature downstream of the temperature control roll (4) is Tn, conditions satisfying the following (1) and (2) are preferable from the viewpoint of film processing suitability, appearance, and rigidity.
(1) When n is an even number, Tn is T4 to Tm ° C.
(2) When n is an odd number, Tn is 5 ° C to Tc-40 ° C.

  In the method for producing a polypropylene film of the present invention, the temperature T1 of the cooling roll (1) is preferably 5 ° C to 100 ° C, and more preferably 10 to 40 ° C from the viewpoint of transparency.

  The preferred thickness of the polypropylene film produced in the present invention is 10 to 150 μm, more preferably 20 to 100 μm. From the viewpoint of productivity, the molding speed is preferably in the range of 30 to 300 m / min, more preferably 100 to 300 m / min. Other manufacturing conditions such as the die lip gap and the resin temperature at the tip of the extruder can be known conditions. For example, the gap between the die lip and the resin temperature at the tip of the extruder is 0.3 to 3.0 mm. 180 ° C to 300 ° C.

  The polypropylene film produced in the present invention may be a single layer film or a laminated film including at least one layer made of polypropylene resin. In the case of a laminated film, the layer made of the polypropylene resin is preferably formed on the outermost surface of the film.

The invention is illustrated by examples and specific examples.
The measured value of each item of an Example and a comparative example was measured with the following method.

(2) Appropriate film processing (visual)
At the time of film formation, the film was wound around the temperature control roll and visually evaluated.
○ ... The film peels off smoothly from the roll, and there is no appearance of any wrapping.
Δ: The film is sticking to the roll, and sometimes it appears that it is likely to wind.
X: The film was wound around the roll.

(3) Rigidity (Young's modulus) (kg / cm2)
A test piece having a width of 20 mm was taken from the machine direction (MD direction), an SS curve was taken with a tensile tester at a chuck interval of 60 mm and a tensile speed of 5 m / min, and the initial elastic modulus was measured.

(4) Film appearance (visual)
The transfer state of the temperature control roll surface shape was visually evaluated.
5 points: No transfer of the temperature control roll surface shape is observed on the film surface.
4 points: Transfer of the surface shape of the temperature control roll is observed locally, but no cloudiness is observed.
3 points: Transfer of the surface shape of the temperature control roll is observed locally, and the film becomes cloudy.
2 points: The surface shape of the temperature control roll is transferred over the entire surface, and the film becomes cloudy.
1 point: The film winds around the roll and breaks.

The polymers used in the examples and comparative examples were as follows.
[Polypropylene resin (1)]
A propylene homopolymer (trade name: FLX80E4, Tm = 164 ° C., Tc = 119 ° C.) manufactured by Sumitomo Chemical Co., Ltd. was used.

Example 1
A feed block type in which a polypropylene resin (1) is melt-kneaded at 240 ° C. with a 90 mmφ extruder using a sintered metal filter with a filtration accuracy of 60 μm and two 65 mmφ extruders, and these extruders are joined. Were introduced into a T die (die width 1250 mm, lip opening 0.8 mm), and a molten film was extruded from the T die. The temperature of the T die was 240 ° C.
The molten film is wound around a cooling roll (1) having a cooling water temperature T1 = 30 ° C. rotating at 40 m / min, and air is blown out from an air chamber provided in the vicinity of the cooling roll to thereby remove the molten film. While being pressed against a cooling roll, it was cooled and solidified to obtain an unstretched film having a thickness of 40 μm.
The temperature T2 of the temperature control roll (2) was controlled at 100 ° C, the temperature of the temperature control roll (3) was 30 ° C, and the temperature of the temperature control roll (4) was controlled at 120 ° C.

Example 2
A feed block type in which a polypropylene resin (1) is melt-kneaded at 240 ° C. with a 90 mmφ extruder using a sintered metal filter with a filtration accuracy of 60 μm and two 65 mmφ extruders, and these extruders are joined. Were introduced into a T die (die width 1250 mm, lip opening 0.8 mm), and a molten film was extruded from the T die. The temperature of the T die was 240 ° C.
The molten film is wound around a cooling roll (1) having a cooling water temperature T1 = 30 ° C. rotating at 40 m / min, and air is blown out from an air chamber provided in the vicinity of the cooling roll to thereby remove the molten film. While being pressed against a cooling roll, it was cooled and solidified to obtain an unstretched film having a thickness of 40 μm.
The temperature T2 of the temperature control roll (2) was controlled at 80 ° C., the temperature of the temperature control roll (3) was controlled at 30 ° C., and the temperature of the temperature control roll (4) was controlled at 120 ° C.

Comparative Example 1
A feed block type in which a polypropylene resin (1) is melt-kneaded at 240 ° C. with a 90 mmφ extruder using a sintered metal filter with a filtration accuracy of 60 μm and two 65 mmφ extruders, and these extruders are joined. Were introduced into a T die (die width 1250 mm, lip opening 0.8 mm), and a molten film was extruded from the T die. The temperature of the T die was 240 ° C.
The molten film is wound around a cooling roll (1) having a cooling water temperature T1 = 30 ° C. rotating at 40 m / min, and air is blown out from an air chamber provided in the vicinity of the cooling roll to thereby remove the molten film. While being pressed against a cooling roll, it was cooled and solidified to obtain an unstretched film having a thickness of 40 μm.
The temperature T2 of the temperature control roll (2) was controlled at 100 ° C, the temperature of the temperature control roll (3) was 120 ° C, and the temperature of the temperature control roll (4) was controlled at 30 ° C.

Comparative Example 2
A feed block type in which a polypropylene resin (1) is melt-kneaded at 240 ° C. with a 90 mmφ extruder using a sintered metal filter with a filtration accuracy of 60 μm and two 65 mmφ extruders, and these extruders are joined. Were introduced into a T die (die width 1250 mm, lip opening 0.8 mm), and a molten film was extruded from the T die. The temperature of the T die was 240 ° C.
The molten film is wound around a cooling roll (1) having a cooling water temperature T1 = 30 ° C. rotating at 40 m / min, and air is blown out from an air chamber provided in the vicinity of the cooling roll to thereby remove the molten film. While being pressed against a cooling roll, it was cooled and solidified to obtain an unstretched film having a thickness of 40 μm.
The temperature T2 of the temperature control roll (2) was controlled at 30 ° C, the temperature of the temperature control roll (3) was controlled at 30 ° C, and the temperature of the temperature control roll (4) was controlled at 30 ° C.

Table 1

It turns out that Examples 1-2 which satisfy the requirements of this invention are the manufacturing methods of the polypropylene-type film excellent in film processability, a film external appearance, and rigidity.
In contrast, Comparative Examples 1 and 2 that do not satisfy the requirements of the present invention are found to be insufficient in the effect of improving the film appearance or rigidity.

It is the schematic of a T-die film manufacturing apparatus.

Explanation of symbols

1: Cooling roll (1)
2: Temperature control roll (2)
3: Temperature control roll (3)
4: Temperature control roll (4)

Claims (3)

A molten film made of a resin composition containing a polypropylene resin is cooled and solidified with a cooling roll (1), and then subjected to heat treatment with at least three temperature control rolls. The polypropylene-based film, wherein the temperatures T2 (° C), T3 (° C), and T4 (° C) of 2) to (4) are T4 (° C)> T2 (° C)> T3 (° C) Manufacturing method (however, the temperature of the temperature control roll (2) disposed downstream of the cooling roll (1) is T2 (° C.), and the temperature control roll (3) disposed downstream of the temperature control roll (2) Is T3 (° C.), and the temperature of the temperature control roll (4) disposed downstream of the temperature control roll (3) is T4 (° C.). The T2 (° C) is 60 to Tm-40 (° C), the temperature T3 (° C) is 5 to Tc-40 (° C), and the temperature T4 (° C) is T2 to Tm (° C). 1. A method for producing a polypropylene film according to 1, wherein Tm (° C. indicates a melting point of the polypropylene resin and Tc (° C.) indicates a crystallization temperature of the polypropylene resin).   The manufacturing method of the polypropylene-type film of Claim 1 or 2 whose temperature T1 of a cooling roll (1) is 5-40 degreeC.

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