JPH0360303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a blown film manufacturing apparatus that is capable of high discharge rate and high-speed molding without causing thickness unevenness, wrinkles, etc.

[Prior Art] As is well known, blown films have been widely used in the past, and a typical manufacturing device is one in which a cooling ring is mounted concentrically on an annular die as shown in FIG.

In addition, as an improved blown film manufacturing device capable of high discharge rate and high speed forming, a cooling ring having two cooling air outlets is attached to the annular die, and air is blown from the first cooling air outlet. By directing the ejected air radially outward with respect to the extrusion axis, the unexpanded tube-shaped molten resin extruded from the die is forced to expand radially outward due to the ventilate effect of the air, and the air flows along the outer surface of the tube to cool the surface, while a second cooling air outlet is provided between the first cooling air outlet and the die, and the air output amount is equal to the amount described above. There is a device which pre-cools the tube by lowering the air flow rate and also prevents the tube from sticking to a part of the air ring body between the two air outlets (Japanese Patent Publication No. 59-23269). be.

[Problems to be Solved by the Invention] Due to the cooling device used in conventional general blown film manufacturing equipment, it is difficult to achieve high discharge rates and high-speed molding, and even if molding is possible, high-quality products cannot be obtained.

In other words, when using conventional cooling equipment to increase the amount of cooling air to perform high discharge volume and high-speed molding, there is no way to stabilize the bubbles, so the valves are agitated by the cooling air and become unstable, resulting in so-called breathing problems. This causes uneven thickness, uneven width, and wrinkles in the product.

In addition, even if the above phenomenon does not occur, strong blowing of cooling air causes the valve to vibrate, resulting in uneven transparency on the bubble surface, so-called transverse waves, making it difficult to obtain high-quality products and making it difficult to produce high-output and high-speed molding. There was a limit.

In addition, high-output, high-speed molding blown film manufacturing equipment such as Japanese Patent Publication No. 59-23269 can improve molding speed compared to conventional general blown film manufacturing equipment; When molding a film using a molding inflation film manufacturing apparatus, unless the blow ratio (bubble diameter/annular die lip diameter) is large, a high-quality film with good balance in both vertical and horizontal directions cannot be obtained. In other words, in order to draw the tube-shaped molten resin extruded from the annular die lip outward in the radial direction by the Ventury effect, in other words, due to the mechanism that draws the tube in the molten state where molecular orientation does not occur to the outward radial direction by the Ventury effect, By the time the molten tube is cooled to an appropriate temperature and lateral molecular orientation begins, the tube has expanded, so that the previous expansion has not contributed to molecular orientation. Therefore, in order to obtain a strong, high-quality product with well-balanced molecular orientation in both the vertical and horizontal directions of the film, a higher blowing ratio is required.

In view of the current situation, the present invention has been completed after repeated studies on a blown film manufacturing device that can produce high-quality film with well-balanced molecular orientation in both vertical and horizontal directions even at a low blowing ratio with high discharge rate and high speed molding. It is.

[Means for Solving the Problems] In the device of the present invention, the expansion of the tube-shaped molten resin extruded from the annular die lip is suppressed by the pressure chamber formed by the cylindrical body provided on the cooling ring. The film is pulled up with a tube diameter that is almost the same as the tube diameter, and when it reaches a temperature that causes molecular orientation, it begins to expand and forms bubbles, so molecular orientation occurs in the lateral direction of the film in proportion to the expansion, and the strength in both the vertical and horizontal directions is balanced. improve well. Furthermore, since the cooling air is blown out in the same direction as the direction in which the tube-shaped molten resin is taken, the vibration of the tube-shaped molten resin is small, and the valve formed by the expansion of the tube-shaped molten resin has a ventilate effect. The excess cooling air is attracted to the inverted conical chamber, cylindrical body, etc. provided above the pressure chamber, and furthermore, the excess cooling air passes through the air volume adjustment port and the valve is stabilized, so that the bubble does not breathe and steer. It is possible to obtain a high-quality film with good thickness accuracy, without uneven width or wrinkles, by high discharge rate and high speed molding.

The resin that can be molded by the apparatus of the present invention may be any thermoplastic resin that is used in normal inflation molding. Various additives can be added to these resins, and various filler mixtures can also be used. Of course it is possible.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 1 is a vertical sectional view schematically showing an example of the device of the present invention.

In the blown film manufacturing apparatus of the present invention, a cooling ring 4 having an air outlet 3 that blows out cooling air in the same direction as the direction in which the tube-shaped molten resin 11 extruded from the annular die lip 2 is taken over the annular die 1. A cylindrical body 5 with a pressure adjustment port 12 provided below is attached on the cooling ring 4 to the outside of the air outlet 3 to form a pressure chamber 10. An inverted conical chamber 6 having an opening at the bottom through which the tube-shaped molten resin 11 passes is installed on top of the inverted conical chamber 6, and a chamber 6 is installed in the center of the inverted conical chamber 6 through which the tube-shaped molten resin 11 can pass. A disk 7 having an opening is provided concentrically, one or more cylinders 8 are provided on the disk 7 so that the upper end of the cylinder 8 and the bubble 9 maintain a constant distance, and the inverted conical shape An air amount adjustment port 14 is provided between the chamber 6 and the disc 7. More specifically, the tube-shaped molten resin 11 extruded from the annular die lip 2 does not shake because the cooling air blown out from the cooling air outlet 3 flows along the drawing direction of the tube-shaped molten resin 11. It can be pulled up stably and at high speed. Further, since the pressure adjustment port 12 is provided at the lower part of the cylindrical body 5, the pressure inside the tube-shaped molten resin 11 and the pressure inside the pressure chamber 10 are balanced, and the pressure inside the pressure chamber 10 of the tube-shaped molten resin 11 is balanced. Expansion is suppressed, and by the time it passes through the opening of the disk 7, it is cooled to a temperature at which molecular orientation occurs efficiently. Thereafter, the tube-shaped molten resin 11 is expanded by the air enclosed in the tube until it reaches a predetermined diameter, so that the molecular orientation occurs in a well-balanced manner both in the vertical and horizontal directions, and high film strength can be obtained. Furthermore, the bubble 9 is attracted to the cylindrical body 8 and the inverted conical chamber 6 due to the ventilly effect caused by the air passing through the air flow path 15, and the cross-sectional shape of the bubble is stably maintained in a state close to a perfect circle. A high quality film with less uneven thickness can be obtained. At this time, the stability of the bubble 9 depends on the amount of cooling air that passes through the gap 13 between the opening of the disk 7 and the bubble that has begun to expand. In other words, when the amount of cooling air is excessive, the bubbles 9 move violently up and down, or come into close contact with the disc 7 and the cylinder 8, causing the bubbles 9 to burst, making stable film production difficult. Moreover, when the amount of cooling air is small, the cooling effect of the film decreases, the bubble 9 rises, the air flow path 15 becomes wider, the ventilly effect ceases to work, and the cross-sectional shape of the bubble becomes close to a perfect circle. This makes it difficult to stabilize the film, making it more likely that the film will become uneven in thickness. Therefore, in the present invention, a large amount of cooling air is sent into the pressure chamber 10, and in order to stably produce a blown film with a high discharge rate and high speed molding, there is a gap between the inverted conical chamber 6 and the disc 7. By providing an air volume adjustment port 14 in the holder and appropriately setting the width of the air volume adjustment port 14 depending on the top and bottom of the disc 7,
Excess cooling air is passed through the air amount adjustment port 14 to keep the amount of air passing through the gap 13 constant, thereby maintaining the stability of the bubble 9. Note that the cooling air passing through the air amount adjustment port 14 is
4, it joins the cooling air passing through the gap 13 at the upper part of the inverted conical chamber, contributing to bubble cooling and bubble stabilization.

It is necessary that the upper end of the cylindrical body 8 follows the shape of the bubble 9 that begins to expand, so that the height increases toward the outside, and the number of cylindrical bodies 8 to be installed is preferably 1 to 4.

[Effects of the Invention] As described above, the blown film manufacturing apparatus of the present invention allows the tube-shaped molten resin to be appropriately cooled in the cylindrical body and then expanded, so that the molecular orientation in both the longitudinal and lateral directions is balanced even at a low blow ratio. By stabilizing the valve with a disc, cylinder, or inverted conical chamber and allowing excess cooling air to pass through the air volume adjustment port, a large amount of cooling air can be blown onto the bubble, resulting in high discharge volume and high speed molding. It is something that can be done.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view schematically showing an example of the blown film manufacturing apparatus of the present invention. FIG. 2 is a longitudinal sectional view of a conventional general blown film manufacturing apparatus. Symbols in the figure: 1...Annular die, 3...Air discharge port, 4...Cooling ring, 5...Cylindrical body, 6...Inverted conical chamber, 7...Disc, 8...Cylindrical body,
9...Bubble, 12...Pressure adjustment port, 13...Gap, 14...Air amount adjustment port.

Claims (1)

[Claims] 1 In a thermoplastic resin inflation film manufacturing device that blows cooling air onto the outer surface of a tube-shaped molten resin extruded from an annular die lip to form bubbles, the cooling air is blown in the same direction as the bubble take-up direction. A cooling ring 4 having an air outlet 3 to blow out is mounted concentrically on the annular die 1, and a cylindrical body 5 with a pressure adjustment port 12 provided below is placed on the cooling ring 4. It is attached to the outside to form a pressure chamber 10, and furthermore, an inverted conical chamber 6 having an opening at the bottom through which the tube-shaped molten resin 11 passes is attached above the pressure chamber 10, and the inside of the inverted conical chamber 6 is attached. A disk 7 having an opening in the center through which the tube-shaped molten resin 11 can pass is provided concentrically, and the cylinder is placed on the disk 7 so that the upper end of the cylinder 8 and the bubble 9 are kept at a constant distance. 8, and an air amount adjusting opening 14 is provided between the inverted conical chamber 6 and the disc 7.