JPH0246993Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an auxiliary stabilizer useful when molding a tubular film of thermoplastic synthetic resin, particularly polyolefin resin, by an inflation method. Currently, polyolefin resin films, among others,
As a method for stably inflation-molding an extremely thin film of high-density polyethylene produced by a medium-low pressure method, a bubble stabilizer having a diameter smaller than the diameter of the die is protruded from the die surface, and a molten tubular film ( A widely used method is to bring the constrictions of bubbles into contact with each other, then expand the bubbles, take them out, and use them as a product (Special Publications Act, 1973).
2180 etc.). According to this method, the stability is greatly improved because the stabilizer can prevent lateral shaking, but the stability in the vertical direction (vertical direction) is insufficient, and the film is in surface contact with the stabilizer, so the film is There were problems such as the physical properties of the product film being oriented in the warp direction, resulting in a large difference in the physical properties between the warp and the width. The present invention has been made with the aim of solving these problems. That is, the present invention provides a tubular film forming apparatus using an inflation method, in which a thin tube is provided that stands upright in the extrusion direction from the center of the die surface and has ventilation holes near its upper end and base. On the thin tube, a disk-shaped first stable body is installed at a position 3 to 6 times the die diameter from the die surface, and the diameter is approximately the same as the die diameter, and the edge portion has a curved surface with R = 25 mm or less. Yes,
Furthermore, a second stable body in the shape of an inverted cone, trapezoid of inverted cone, or funnel having a maximum diameter of 1.5 to 2 times the die diameter is provided at a position 5 to 12 times the die diameter from the die surface on the thin tube. This is an auxiliary device for forming a tubular film. The present invention will be explained in more detail below based on the drawings. FIG. 1 is a vertical cross-sectional view schematically showing the structure of an apparatus according to the present invention, and the structure will be explained while describing the process of forming a film by this apparatus. The molten resin 3 extruded from the circular die opening 2 is pulled up while being cooled by the air blown out from the air ring 4 from the outside, and is first drawn up from the die surface.
It comes into contact with the edge of the disk-shaped first stable body 5 set at a position (l ₁ ) 3 to 6 times the diameter of the die. This first stable body is not simply cylindrical, but its edges are rounded in longitudinal section so that the contact area with the resin is minimized.
= It has a curved surface of 25 mm or less. A thin tube 6 extending upright from the center of the die surface passes through the center of the first stable body, and the first stable body can be moved up and down on the thin tube and fixed at any position. This first
The stabilizer prevents the tubular molten resin (bubble) from swaying. The bubble that comes into contact with the first stable body becomes slightly thinner and then passes through an inverted cone-shaped or funnel-shaped tube set on the capillary at a position (l ₁ + l ₂ ) 5 to 12 times the die diameter from the die surface. 2 At the stable body 7,
While in contact with it, it is blown up by air exiting from the air hole at the top of the tube. This second stable body may be an inverted trapezoidal cone as shown in Figure 2A, in which case,
The diameter of the bottom surface is at least the same as or smaller than the diameter of the die, and the diameter _D2 of the maximum diameter portion of the top surface is 1.5 to 2 times the diameter of the die. Further, the angle α between the conical surface (tapered surface) and the center line is preferably about 20 to 50 degrees. Further, the conical surface may not be a right circular conical surface but may have a bulged conical surface as shown in FIG. 2B. Like the first stable body, this second stable body is also movable on the central thin tube and can be fixed at any position. As mentioned above, the fixing position is 5 to 12 times from the die surface, but specifically, it is installed at a position that presses the constriction of the bubble in the direction of the die. This second stable body restricts the vertical fluctuation (vertical fluctuation) of the bubble, and eliminates the vertical fluctuation that has been unresolved in the past. The bubbles are further blown up and stretched, cooled and solidified, and wound up into a product. The materials of the first and second stabilizers are not particularly limited, but in general, materials with lower thermal conductivity are easier to handle at the start of operation. Further, the second stable body may be hollow as long as the outer shape is maintained. Next, the effect of actually manufacturing a tubular film using the apparatus of the present invention will be shown by comparing it with a case where the apparatus of the present invention is not used. Resin used: High-density polyethylene (manufactured by Chitsuso Co., Ltd.)
MI0.05g/10 minutes, specific gravity 0.950g/cm ³ die diameter: 40mm Die temperature: 200℃ 1st stable body Outer diameter (maximum diameter): 40mm Edge radius: 20mm Thickness: 15mm, material: Wood position: 120mm from the die surface (3 times the die diameter) 2nd stable body Maximum diameter (D ₂ ): 80mm Minimum diameter: 15mm (outer diameter of central tubule) Length: 57mm Center angle of conical surface: 30° position :300mm from the die surface (of the die diameter)
7.5 times) Using the above equipment and resin, a blown film with a thickness of 10 μm and a fold width of 200 mm can be taken at a speed of
When manufactured at 60 m/min, the bubble running was stable (the position of the film inflating was stable).
Stable operation was possible, and the uniformity of the obtained film was excellent as shown in Table 1. Instead of the first and second stabilizers mentioned above, films with the same thickness and width can be produced under almost the same conditions using a device that has an aluminum stabilizer with a diameter of 35 to 37 mm and a length of 200 mm, which is conventionally used. As a result, the bubble traveling was particularly unstable in the vertical direction, and the physical properties of the obtained film, especially the vertical and horizontal balance, were as shown in Table 1, compared to those obtained with the apparatus of the present invention. It was inferior.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing the outline of the configuration of the present invention;
FIGS. 2A and 2B are longitudinal cross-sectional views showing other embodiments of the second stable body. 1...Dice, 2...Dice mouth, 3...Synthetic resin (bubble), 4...Earring, 5...First stable body, 6...Thin tube, 7...Second stable body.

Claims (1)

[Scope of utility model registration request] A thin tube is provided that stands upright in the extrusion direction from the center of the die surface and has ventilation holes near its upper end and base.
At the 6 times position, a first stable body in the form of a disk is provided, which has approximately the same diameter as the die diameter, and whose edge portion has a curved surface of R = 25 mm or less, and furthermore, the die surface on the thin tube. A second stable body having a maximum diameter of 1.5 to 2 times the die diameter and having an inverted conical shape, an inverted trapezoidal trapezoid shape, or a funnel shape is provided at a position 5 to 12 times the die diameter. An auxiliary device for forming tubular films using the inflation method.