JP2000052420A - Method and apparatus for molding inflation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method capable of molding an inflation film at a high speed and a molding apparatus used therein. SOLUTION: In a method for molding an inflation film by injecting air into the molten resin 2 extruded into a tubular form from an annular die 1 to expand the tubular resin and prescribing the outer diameter of the expanded resin while stretching the resin longitudinally and laterally to cool the same, cooling mist with a particle size of 10 μm or less is sprayed on the molten resin 2 from the inside and outside thereof to cool the resin 2. An inflation film molding apparatus is equipped with a mist spraying part generating mist in the chamber 6 provided to the central leading end part of a die in a protruded state to spray mist with a particle size of 10 μm or less on the inner surface of the film to cool the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a blown film made of a thermoplastic resin such as high-density polyethylene, low-density polyethylene, and polypropylene, and a molding apparatus used for the same.

[0002]

2. Description of the Related Art Inflation in which a thermoplastic resin is melted by an extruder, air is injected into a molten resin extruded into a tube shape from an annular die to inflate the resin, and the outer diameter is adjusted while being stretched in the vertical and horizontal directions and cooled. In the method of forming a film, air is blown from the inside and cooled, and natural cooling is performed from the outside, or the tubular molten resin is cooled by passing directly through a water tank and contacting with water to obtain an inflation film. Was.

[0003]

However, the molding technique described above has the following problems.

[0004] The thermoplastic resin is melted by an extruder and extruded into a tube from a die. However, in the case of cooling from inside and outside by air, the cooling time of the resin is prolonged. Problems arise.

When the outside is cooled with water, the cooling time of the resin is shorter than that of air, but there is a limit due to cooling by the sensible heat of water. In addition, when the folding diameter becomes large, the water tank becomes large.

[0006]

SUMMARY OF THE INVENTION The present invention has been intensively studied in order to solve the above-mentioned problems of the prior art, and has been made by extruding a resin blown film from a die. 10 from inside and outside of molten resin
The present invention provides a method for forming an inflation film and a molding apparatus used for the same, by spraying a cooling mist of μm or less to uniformly and quickly cool the inner and outer surfaces of the inflation film and enabling high-speed molding. It is.

A feature of the molding method according to claim 1 of the present invention that solves the above-mentioned problem is that, in the method of cooling and molding the molten resin extruded from the die, the inside is externally formed by a mist spraying part provided at the center of the die. Is 1 from the ring-shaped mist spray section
The cooling mist of 0 μm or less is sprayed to uniformly cool the inner and outer surfaces of the blown film.

According to the present invention, since the latent heat of vaporization by mist evaporation can be used to cool the inside and outside of the blown film together with ordinary external cooling, rapid forced cooling becomes possible and high-speed molding can be performed.

A blown film forming apparatus according to a second aspect of the present invention relates to an inflation film forming apparatus for inflation or deflation molding made of a thermoplastic resin, and includes an inside of a chamber protrudingly provided at a center end of a die. Mist is generated by 1
A mist spray unit capable of spraying a cooling mist of 0 μm or less onto the inner surface of the film is provided.

The blown film molding apparatus according to claim 3 of the present invention relates to an inflation film molding apparatus for inflation molding or deflation molding made of a thermoplastic resin, wherein the tubular molten resin extruded from an annular die. A ring provided so as to cover 10 μm with respect to the circumference of the tubular molten resin.
A mist spraying section capable of spraying mist of m or less is provided.

In the above method and apparatus, the spray
Any mist generated by any method can be used as the mist of μm or less, but water and air are separately sent through the die, and the two fluids are mixed in a chamber provided at the center end of the die. It is preferable to use those sprayed from the two nozzles and further atomized by reciprocal shearing by collision with each other.

The spray form of the mist is directly sprayed so as not to collide with the surface of the inflation film to form water droplets. However, since the latent heat of vaporization of water is used, the mist is sprayed until the resin temperature becomes 90 ° C. or lower. Preferably, it is sprayed.

In the present invention, it is preferable that the mist particle size is 10 μm or less, since an uneven surface is not formed on the surface of the molded product.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS This embodiment shows a typical embodiment of the method invention according to the first aspect and the apparatus invention according to the second and third aspects.

FIG. 1 shows a part of a blown film forming apparatus, in which a molten resin 2 extruded from a die 1 is provided so as to pass through a ring 3.

A mist spray unit 4 is attached to the ring 3.

A mist spraying section 5 is provided at the center of the die 1 so as to protrude. The mist spraying section 5 is provided with a chamber 6 for mixing water and air, which is a mist source for generating mist, and spraying. Consisting of chips 7. The two chips 7 face each other. The mist spraying section 4 has the same structure as the mist spraying section 5.

The operation of this embodiment will be described in conjunction with a typical embodiment of the method invention of claim 1 and the apparatus invention of claims 2 and 3.

The molten resin 2 is extruded from the die 1 and is sent upward through the ring 3 while being expanded by air.

Next, water and air, which are mist sources, are separately sent through the die 1 and mixed in the chamber 6 of the mist spraying section 5 projecting to the center of the die 1 to generate mist from the chips 7. The pressure of the water and air to be sent is adjusted so that the mist particle size at this time is 20 μm or less. Then, the mist generated from the chips 7 facing each other collides with each other, and is further atomized and sprayed down to 10 μm or less. The mist is brought into direct contact with the inner surface of the molten resin 2 and rapidly cooled by the latent heat of vaporization by evaporation.

Simultaneously with the above operation, a mist of 10 μm or less is directly applied to the outer surface of the tubular molten resin 2 from the mist spraying section 4 of the ring 3 provided so as to cover the tubular molten resin 2 by the same operation as described above. The inside and the outside are quenched uniformly by the latent heat action of vaporization by evaporation, and the blown film is wound by a winder.

[0022]

EXAMPLES Inflation molded articles made of resin were molded in Example 1 and Comparative Examples 1 to 3 using the apparatus described in the embodiment under the following conditions. The outer surface temperature at a position 2 m away from the die in the vertical direction was measured.
It was shown to.

Target material: linear low-density polyethylene SP2520 (manufactured by Mitsui Petrochemical Industries, Ltd.) (melt index MI = 1.8 g / 10 min, density
d = 0.925 g / cm ³ ) Inflation molded product: Folded diameter: 350 mm, film thickness: 20 μm Molding conditions: Molding temperature: 180 ° C. Temperature measurement method of the inflation molded product outer surface: Thermography is used to measure the temperature of the molded product outer surface when it comes out of a die by 2 m. (Manufacturer: Japan Avionics Co., Ltd., model TVS
-2100MKIIST).

Method for observing the state of the molded article: The surface of the molded article was observed, and the trace of water droplets and residual water due to mist spraying were observed.

Example 1 The inner and outer surfaces of a molded product were cooled with a mist of 10 μm or less.

At a take-off speed of 120 m / min, 2 m from the die
The temperature at the pick-up location was measured.

Comparative Example 1 The molded product was cooled only with air.

At a take-off speed of 120 m / min, 2 m from the die
The temperature at the pick-up location was measured.

Comparative Example 2 The molded article was cooled only with air.

At a take-up speed of 30 m / min, the temperature at a place where 2 m was taken from the die was measured.

Comparative Example 3 The inner and outer surfaces of the molded article were cooled with a mist of about 200 μm.

At a take-off speed of 120 m / min, 2 m from the die
The temperature at the pick-up location was measured.

[0033]

[Table 1]

[0034]

According to the method for forming an inflation film of the present invention and the forming apparatus used in the method, a mist of 10 μm or less comes into contact with the inner and outer surfaces of the heated inflation film and is cooled by the latent heat of vaporization due to evaporation. Thus, the inner and outer surfaces can be forcibly cooled uniformly and quickly. Thereby, the take-up speed can be increased, and the productivity can be improved.

By using a mist of 10 μm or less, the mist evaporates instantaneously when it comes into contact with the surface of the molded product,
No large water marks are left on the surface of the cooled molded product, and no water remains.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a blown film forming apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 annular die 2 molten resin 3 ring 4 mist spray section 5 mist spray section 6 chamber 7 chip

Claims (3)

[Claims] In a method for forming an inflation film, air is injected into a molten resin extruded into a tube shape from an annular die, expanded, stretched in the vertical and horizontal directions, and the outer diameter is adjusted and cooled. 10 μm from inside and outside
A method for forming an inflation film, comprising spraying and cooling the following cooling mist. 2. A mist spraying section capable of generating mist in a chamber protruding from the center of the die and spraying mist of 10 μm or less on the inner surface of the film and cooling the mist. Characteristic blown film forming equipment. 3. A ring provided so as to cover the molten resin extruded from the annular die into a tube and provided with a mist spraying section capable of spraying a mist of 10 μm or less on the circumference of the molten resin. An inflation film forming apparatus characterized by the following: