JPS5818226A - Manufacture of tubular film and apparatus therefor - Google Patents

Abstract

PURPOSE:To prevent a film from oscillating so as to exclude the occurring of uneven thickness and wrinkling of the film, by providing air holes through a plurality of spaced and secured disc-like bodies, and permitting the inner circumferential surface of a melted resin bulb before it is expanded to be in contact with the disc-like bodies. CONSTITUTION:A thermoplastic resin such as polyethylene and polypropylene is melt-extruded from an annular die 1 to be formed into the bulb 2, the inner circumferential surface of the bulb is caused to be in contact with a stable body comprising a fixed rod 3 and the plurality of the disc-like bodies 6 each having the air hole 8, and the bulb is blown up. With the movement of the bulb, the amount of air that moves to the direction of nip rolls is compensated by the air holes 8, and the degree of the negative pressure in the spaces defined by the bulbs 2 and the discs 6. By adjusting the size of the air holes 8, even a large diameter tubular film can be taken off at high speed, with the flatness of the product better. It is preferable that the configuration of the disc-like body has, for example, a shape 6, 6a or 6b, and the number of the disc-like bodies is 2-6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for manufacturing a tubular film of thermoplastic resin such as high-density polyethylene, low-density polyethylene, polypropylene, etc. by an inflation method.

Conventionally, in the production of thermoplastic resin tubular films using the inflation method, in order to prevent the tubular film from swaying, especially in the case of high blowing ratios and high-speed take-off, an annular die is connected to the inside of the molten resin bubble before expansion. cylindrical,
The bubbles were brought into contact and stabilized using a stabilizer such as a truncated cone. This stability is affected by the diameter of the annular die, blow-up ratio, take-up speed, resin viscosity, outer diameter of the stabilizer, etc., but it may be because the contact distance of the bubble with the stabilizer is still short and the contact pressure is insufficient. It was difficult to obtain a film with excellent flatness due to vibration, uneven cooling and stretching, uneven thickness, and even wrinkles.

The present inventors had previously invented a stabilizer in which a plurality of disk-like bodies were provided at intervals, but when the diameter of the tubular film was made larger or when it was taken up at a higher speed, bubble bubbles were needed. On the other hand, when the contact with the disc-shaped stabilizer is strong, the resistance becomes too large, and vibration (squeezing phenomenon) of the tubular film occurs, making it difficult to produce a film with excellent flatness without uneven thickness or wrinkles. It became difficult to obtain the film, and in the worst case, the film was cut.

The present invention was arrived at as a result of studies to solve these problems, and its main points are (1) The inner circumferential surface of the molten resin bubble before expansion is made up of a plurality of vent holes provided at intervals. A tubular film of thermoplastic resin produced by an inflation process, characterized in that a heated body made by the inflation process is connected to a die at intervals, and the heated body is brought into contact with a fixed disc-shaped body. manufacturing equipment.

The present invention will be explained below using the drawings.

FIG. 1 is a longitudinal cross-sectional view showing the method for producing tubular fubulum of the present invention using the apparatus of the present invention.

The resin is melted and extruded from an annular die 1 connected to an extruder (not shown) to form bubbles 2, which are then molded into a stable body consisting of a fixed rod 3 and a plurality of fixed disc-shaped bodies 6 having ventilation holes 8. Contact, then blow up, frost line 5
Through this process, a tubular ficum 4 is obtained. The vent hole 8 adjusts the degree of negative pressure in the space 7 formed by the body 6 as the bubble 2 moves. If the size of the ventilation hole 8 is too large, the degree of negative pressure will be small, and the degree of contact of the bubble 2 with the disc-shaped body 6 will be weak, as in the case of conventional cylindrical or truncated conical stabilizers, resulting in a good film. Hard to get caught. On the other hand, if the size of the vent hole 8 is too small, the degree of negative pressure will become large, causing the bubble 2 to curve strongly toward the center line, and the degree of contact between the bubble 2 and the disk-like body 6 will increase. This makes it difficult to manufacture tubular films with larger diameters and to take them off at higher speeds. Therefore, it is preferable that the size of the vent hole 8 is adjusted as appropriate depending on the die diameter, take-up speed, disk diameter, film diameter (folding diameter), film thickness, etc.

Thus, the present invention provides a method that enables high-speed take-up of a tubular film with a large diameter and excellent flatness, as well as an apparatus for achieving the same.

The diameter of the disc-shaped body of the present invention is 0.5 to 1.5 of the die diameter.
times, preferably in the range of 0.8 to 1.2 times.

If it is too small, the contact with the bubbles will be weak, and if it is too large, the obtained tubular film will easily break into rings, probably because it is strongly oriented in the lateral direction. The shape of the disc-shaped body includes the disc shown in Fig. 2,
Figure 3 Disk, Figure 4 Abacus beads, Figure 5 (a), (b)
A variety of composites of these can be employed. Also, this number is 2
Although any number greater than or equal to 1 can be selected, the objective can be achieved within the range of 2 to 6. Even if more than this is provided, the effect will not change much.

The disc-shaped body may have not only one ventilation hole but also a plurality of small ventilation holes, and its shape is arbitrary.

In short, it is sufficient to have an area large enough to adjust the degree of negative pressure in the space 7, but the degree of opening can be adjusted by providing larger or more ventilation holes, pasting adhesive tape, or using a throttle valve, shutter, etc. It is convenient to do so. If the degree of opening can be adjusted by centrifugal melting, it is possible to adjust the degree of negative pressure according to changes in operating conditions during film forming.

It is preferable that the ends of each disc-shaped body be rounded. The vertical distance between the ends of each disc is 0.3 to 5 (lffl), and the horizontal distance between each disc end and the fixing rod 3 is 5Ia1 to prevent the resin bubble from touching the fixing rod. It is preferable to provide the above.The material of the disc-shaped body is not limited to any heat-resistant material such as metal, as long as it is not deformed by the heat of bubbles or the like.

Note that the fixed rod does not necessarily need to be located at the center or be one, but the plurality of disc-like bodies may be connected to the annular die with their center substantially centered on the center line of the annular die. establish.

The present invention will be explained in more detail by giving Examples and Comparative Examples below.

Examples 1 to 5, Comparative Examples 1 to 3 High-density polyethylene; Showa Denko K.K. Showa Rex (registered trademark) FX 0132 H-5 (density 0.95
09 / Crn 1 Melt index 0.06y
/10 m) under various conditions, and after winding up the film, the film was pulled out and uneven thickness was formed at intervals of 2 crn in the circumferential direction. The results are shown in Table 1. Note that under the conditions of Comparative Example 1, the folding diameter is 1so
o%'s take-up speed is 451L/Il! If it exceeds II+, the film will break, and in Comparative Example 2, the take-up speed was set to 60
While keeping WL/11IiR, the fold diameter was set to 1. It was not possible to increase the percentage to more than ooo%.

The following can be understood from the above Examples and Comparative Examples.

(1) When using a conventional cylindrical stabilizer, it is possible to take off a film with a large diameter (large fold diameter) at high speed, but uneven thickness and wrinkles occur, making it difficult to take a film with excellent flatness. can't get it.

(2) Using multiple disc-shaped bodies without ventilation holes as a stabilizer will help to stabilize films with excellent flatness when picking up a certain diameter at high speed or when producing a film with a large diameter at a constant drawing speed. You can't get it.

(3) With the method and apparatus of the present invention, a film with a large diameter and excellent flatness can be taken at high speed, while a film with excellent flatness can be obtained even when a film with a small diameter is taken at low speed.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing the method for producing a tubular film of the present invention using the apparatus of the present invention. FIGS. 2 to 5(a) and 5(b) are side views of examples of disc-shaped bodies according to the apparatus of the present invention. 1... Annular die, 2... Molten resin bubble, 3
...Fixing rod, 4...Tubular film, 5...Frost line, 6...Disc-shaped body, 7...Space,
8...Vent hole. Patent applicant Showa Denko Co., Ltd. agent Patent attorney Sei Kikuchi

Claims (2)

[Claims] (1) Thermoplasticity by an inflation method characterized by bringing the inner circumferential surface of a portion of a molten resin bubble before expansion into contact with a plurality of fixed disc-shaped bodies provided at intervals and having ventilation holes. A method for manufacturing a resin tubular film. (2) An apparatus for manufacturing a thermoplastic resin tubular film by an inflation method, characterized in that a plurality of disc-shaped bodies having ventilation holes are connected to a die at intervals as internal stabilizers.