JPH06210698A - Method for producing polypropylene film - Google Patents

Abstract

(57) [Summary] [Purpose] A method for producing a polypropylene film having excellent impact strength with high productivity, which prevents occurrence of defective phenomena such as burning and uneven film thickness due to a decrease in molecular weight during film formation. I will provide a. [Structure] A propylene-based resin composition containing a predetermined amount of a predetermined antioxidant is formed into a film at a take-up speed of 50 m / min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suitable method for producing a polypropylene film used for packaging in the fields of foods, clothing and the like.

[0002]

2. Description of the Related Art Unstretched polypropylene films are widely used in the field of food packaging and the like because of their good transparency, heat resistance, mechanical properties and gloss. Unstretched polypropylene film is cast molding method (T-die method)
In order to prevent the occurrence of defective phenomena such as burning and film thickness unevenness due to a decrease in the molecular weight of the film during the molding process, an antioxidant is generally added to the resin. As the antioxidant, 2,6-di-t-
Butyl-p-cresol (BHT) is most often used, but it is unfavorable for safety and hygiene, and there is a problem that the film turns yellow. In recent years, antioxidants other than BHT have been used. Therefore, specifically, a hindered phenol-based antioxidant and a phosphorus-based antioxidant are used in combination.

[0003]

However, the use of such an antioxidant formulation has the following problems.
That is, when the take-up speed at the time of film formation is increased to improve productivity, in addition to the occurrence of defective phenomena such as burn and film thickness unevenness due to a decrease in molecular weight at the time of molding processing, the film due to orientation is further added. However, there was a problem that the impact strength of the product decreased. The present invention has been made in view of such problems, even when the take-up speed at the time of film formation is high, to prevent the occurrence of defective phenomena such as burn and film thickness unevenness due to a decrease in the molecular weight, and An object of the present invention is to provide a method for producing a polypropylene film having excellent impact strength with high productivity.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, by using a resin composition in which a specific antioxidant is combined, the take-up speed during film formation can be improved. The present invention has been completed by finding that the above problems can be solved even when the speed is increased.

That is, according to the present invention, a step of preparing a polypropylene resin composition containing an antioxidant,
And a method for producing a polypropylene-based film, which comprises a step of forming a film using the T-die method, wherein the polypropylene-based resin composition contains the following components (A), (B) and (C): A): Polypropylene resin 1
00 parts by weight, (B): octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate 0.05 to 0.30 parts by weight, (C): tris (2,4)
-Di-t-butylphenyl) phosphite 0.03 to
Provided is a method for producing a polypropylene-based film having 0.20 parts by weight and a take-up speed of 50 m / min or more in the film-forming step.

Further, the molding temperature in the film forming step is 2
30 to 280 ° C, and the thickness of the obtained film is 15
A method for producing a polypropylene film having a thickness of -60 μm is provided.

The present invention will be specifically described below. 1. Preparation Step of Resin Composition Constituent Components of Resin Composition The following components are used as the constituent components of the resin composition used in the present invention. (A): The type of polypropylene resin is not particularly limited, but homopolypropylene or a propylene-α-olefin copolymer having an α-olefin such as ethylene as a comonomer is preferable. The melt index (MI) is preferably 4 to 15 g / 10 minutes. This is because when the MI is less than 4 or the MI exceeds 15, the film forming property (cast film moldability) is deteriorated.

(B): Octadecyl-3- (3,5-di-t-butyl-4hydroxyphenyl) propionate The blending ratio of the component (B) is polypropylene resin 1
0.05 to 0.30 parts by weight with respect to 00 parts by weight,
It is preferably 0.07 to 0.20 parts by weight. 0.
This is because if the amount is less than 05 parts by weight, defective molding phenomena such as burning during film formation and film thickness unevenness will occur, and if the amount exceeds 0.30 parts by weight, reduction in impact strength of the film cannot be suppressed.

(C): Tris (2,4-di-t-butylphenyl) phosphite The blending ratio of the component (C) is polypropylene resin 1
0.03 to 0.20 parts by weight with respect to 00 parts by weight,
It is preferably 0.04 to 0.15 parts by weight. 0.
This is because if the amount is less than 01 parts by weight, a defective molding phenomenon such as burning at the time of film formation or film thickness unevenness will occur, and if the amount is more than 0.20 parts by weight, the reduction of the impact strength of the film cannot be suppressed.

In addition to the above components, additives such as weathering agents, colorants, fillers, antiblocking agents, lubricants, chlorine scavengers, nucleating agents, antistatic agents, antifogging agents and the like are appropriately blended as necessary. You can also

Preparation Method There is no particular limitation on the method of preparing the above-mentioned constituents to form a resin composition, and examples thereof include a method of kneading and granulating with a single-screw extruder.

2. Film-forming step T-die method The T-die method used in the present invention is a type of melt extrusion method, in which a resin is heated and melted and extruded from a T die (flat film die) attached to the tip of an extruder, and then cooled. , A method of producing a film by solidifying. The film forming conditions and film forming method are not particularly limited, but the molding temperature is 230 to 2 from the viewpoint of resin film forming characteristics and practicability.
80 ° C. is preferable, and the thickness of the obtained film is 15 to 6
0 μm is preferable. For cooling, known methods such as roll cooling and water cooling can be appropriately used.

Take-up speed The take-up speed in the present invention means the speed at which the film extruded from the extruder is taken out. 50m in the present invention
It is characterized in that it is collected at a speed of not less than / minute. 50m /
This is because the conventional formulation of the antioxidant is sufficient when the speed of more than a minute is not required. In addition, the measurement can be performed using a tachometer (rev counter).

[0014]

EXAMPLES The present invention will be described in more detail below with reference to examples. In the examples and comparative examples of the present invention, as the polypropylene resin composition, the following constituent components were used at the compounding ratios shown in Table 1. (1) Polypropylene resin P1: Homopolypropylene, MI = 7.0 g / 10 minutes (trade name “Idemitsu Polypropylene H-700)”) P2: Propylene-ethylene random copolymer (ethylene content 3.5%) MI = 7.0 g / 10 min (trade name "Idemitsu Polypropylene R-740)" (2) Antioxidant A1: Octadecyl-3- (3,5-di-t-butyl-)
4-hydroxyphenyl) propionate A2: tris (2,4-di-t-butylphenyl) phosphite A3: pentaerythrityl-tetrakis [3- (3,5
-Di-t-butyl-4-hydroxyphenyl) propionate] A4: tetrakis 2 (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphonite That is, the polypropylene resin shown in Table 1. 100 parts by weight of calcium stearate as a chlorine scavenger.
05 parts by weight, synthetic silica 0.
06 parts by weight, 0.08 parts by weight of erucic acid amide as a lubricant and the antioxidant shown in Table 1 were added at the compounding ratio shown in Table 1 and melt-kneaded to form pellets. Next, the obtained pellets were formed into a film by using a 65 mmφ cast molding machine at a molding temperature of 250 ° C., a film thickness of 30 μm, and a take-up speed of 60 m / min. The obtained film was aged under the condition of 40 ° C. for 1 day and then evaluated. The results are shown in Table 1.

[0015]

[Table 1]

The evaluation was carried out by the following method. (1) Film Impact Strength Using a film impact tester manufactured by Toyo Seiki Seisaku-sho, Ltd., the film impact strength of each film was measured under the conditions of a capacity of 15 kgf · cm and an impact head of 1/2 inch. (2) Appearance of film The occurrence of defective phenomena such as burning and unevenness of film thickness was visually confirmed. ◯: Good x: Burns and unevenness of flume thickness are observed.

[0017]

According to the present invention, the take-up speed is 5 at the time of film formation.
Even at a high speed of 0 m / min or more, it is possible to prevent the occurrence of defective phenomena such as burning and uneven film thickness due to a decrease in molecular weight, and it is possible to produce a film having excellent impact strength with high productivity. .

Claims (2)

[Claims] 1. A method for producing a polypropylene-based film, comprising: a step of preparing a polypropylene-based resin composition containing an antioxidant; and a step of forming a film using a T-die method, wherein the polypropylene-based resin composition is (A), (B)
And (C), and (A): polypropylene resin 10
0 parts by weight (B): octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate
0.05 to 0.30 parts by weight (C): tris (2,4-di-t-butylphenyl) phosphite 0.03 to 0.20 parts by weight and the take-up speed in the film forming step is 50 m / A method for producing a polypropylene-based film, characterized in that it is at least a minute. 2. The molding temperature in the film forming step is 230.
~ 280 [deg.] C. and the resulting film has a thickness of 15-6.
It is 0 micrometer, The manufacturing method of the polypropylene film of Claim 1 characterized by the above-mentioned.