JPS6327173B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to an internal stabilizing device used for molding a thermoplastic resin such as high-density polyethylene, low-density polyethylene, or polypropylene into a tubular film by an inflation method. Conventionally, when forming a tubular film using the inflation method, in order to prevent the tubular film from wobbling, especially in the case of high blowing ratios and high-speed take-off, it is connected to an annular die inside the film, has an air introduction hole in the core, and has an air inlet at the tip. An internal stabilizing device was used, which consisted of a fixed rod that opened at the end and a cylindrical or cylindrical stabilizer that was integrally attached to the fixed rod. However, perhaps because the contact length of the tubular film with the stabilizer is short and the contact pressure is weak, the tubular film has poor fixation after blow-up, making it susceptible to shaking and resulting in uneven cooling and stretching, resulting in uneven thickness and even wrinkles. It has been difficult to obtain a film with excellent flatness. The present invention was arrived at as a result of various studies to solve this problem, and its gist is to extrude it into a tubular shape from an annular die and then blow it up with gas discharged from a gas introduction hole provided through the die. During inflation film forming, a stabilizer is attached to the die, and the stabilizer is attached to the die, and the stabilizing body contacts the entire inner circumference of at least a portion of the tubular film before being blown up, and the gas introduction hole is formed in the core. In an internal stabilizing device for a tubular film that is concentrically integrated with a fixing rod that opens at the tip, the stabilizing body has a diameter larger than the inner diameter of the tubular film before being blown up, and has an opening. The internal stabilizing device of the tubular film is composed of a plurality of disc-like bodies with no space between each other, and the plurality of disc-like bodies are integrally provided on a fixing rod at desired intervals. The present invention will be explained below using the drawings. FIG. 1 is a vertical cross-sectional view showing a conventional internal stabilizing device for a tubular film and a forming process using an inflation method. is brought into contact with an internal stabilizing device consisting of a cylindrical stabilizer 4, and then penetrates the die 1 and the fixed rod 3 and is blown up by air introduced from the air inlet 3b that opens at the tip 3a of the fixed rod, and the frost line 5 is also blown up. Form. The contact length and contact pressure of the tubular film 2 with the cylindrical stabilizer 4 are influenced by the diameter of the annular die, blow-up ratio, take-up speed, resin viscosity, outer diameter of the stabilizer, etc., but the angular contact length is short. Perhaps because the contact pressure is so weak, the tubular film 2a after blow-up sways and becomes unevenly cooled and stretched.
Uneven thickness and wrinkles are likely to occur. FIG. 2 is a longitudinal sectional view showing the internal stabilizing device of the tubular film of the present invention and the forming process by the inflation method.
is melted and extruded via a fixing rod 3 into an internal stabilizing device comprising a plurality of disc-shaped bodies 6 without openings having a diameter larger than the inner diameter of the tubular film and arranged concentrically at predetermined intervals. After they are brought into contact with each other, the air blows up from air discharged from an air introduction hole which penetrates the die 1 and the fixed rod 3 and opens at the tip 3a thereof, thereby forming a frost line 5. When the tubular film 2 is taken up, some of the internal air moves with it, and the independent space 7 composed of the tubular film 2, the fixing rod 3, and the disc-shaped body 6 is depressurized, as shown in FIG. , the tubular film 2 exhibits a phenomenon in which it is curved and pulled together. Therefore, the plurality of disc-shaped bodies 6 without openings of the tubular film 2
The contact pressure against the tubular film 2 becomes stronger, the tubular film 2 becomes stable, cooling and stretching become uniform, and a film with excellent flatness without uneven thickness or wrinkles can be obtained. In this case, although the air pressure on the side where the fixed rod tip 3a is located is higher than the air pressure on the side of the independent space 7, since the contact pressure is high, almost no backflow of air toward the independent space side is observed. The disc-shaped stabilizer in the internal stabilizing device for a tubular film of the present invention has no openings other than holes for fitting into the fixing rod. The external shape is not only the disc-shaped body in Figure 3, but also the disc-shaped body in Figure 4, the abacus-bead shape in Figure 5, and the disc-shaped body in Figure 4.
Although it is not concentric in the strict sense of FIG. 6, various forms such as a spiral plate-like structure or an integrated structure as shown in FIGS. 7 and 8 can be adopted. Although the fixing rod does not necessarily need to be located at the center, a plurality of disc-like bodies should be provided concentrically at desired intervals, and one alone will not be sufficient. It is best to round the circumferential edge of each disk, with a vertical spacing of 0.3 to 15 cm, and the horizontal spacing between the circumferential edge of each disk and the fixing rod is not particularly limited, but the tubular film should be rounded to the fixing rod. It is preferable to provide a distance of 5 mm or more to prevent contact. 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; Shorex FX0190
(Density 0.950g/cm ³ , Melt index 0.08g/
Inflation films were formed under various conditions using a 10 min.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the internal stabilizing device of a conventional tubular film and the forming process by the inflation method, FIG. 2 is a vertical cross-sectional view of the same according to the present invention, and FIGS.
The figure is an example longitudinal cross-sectional view of a disc-shaped body in the device of the present invention. 1... Annular die, 2... Tubular film, 2a
...Tubular film after blow-up, 3...Fixing rod, 3b...Air introduction hole, 4...Cylindrical stable body,
5...Frost line, 6...Disk-shaped stable body, 7
...Independent space.

Claims (1)

[Claims] 1. When forming an inflation film in which the film is extruded into a tubular shape from an annular die and then blown up by gas discharged from a gas introduction hole provided through the die, at least a portion of the tubular film before being blown up is Internal stabilization of a tubular film, in which a stabilizer is attached to the die and is concentrically integrated with a fixing rod that is in contact with the entire inner circumference of the die, the gas introduction hole is formed in the core, and the hole opens at the tip. In the apparatus, the stable body is composed of a plurality of disc-shaped bodies having a diameter larger than the inner diameter of the tubular film before blowing up and having no opening, and the plurality of disc-shaped bodies are connected to a fixed rod. An internal stabilizing device for a tubular film, characterized in that the internal stabilizing device is integrally provided with a desired spacing between the tubular film.