JPS598340B2 - Thermoplastic resin stretching air injection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air injection method and apparatus for producing a film by heating a thermoplastic resin tube (hereinafter referred to as a raw tube) and stretching it by a tubular method.

Generally, film production involves passing a raw tube between nip rolls placed at an appropriate distance, installing a heating device on the upstream nip roll side to heat the tube to a predetermined temperature, and injecting air. This is done by forming bubbles, passing through a cooling ring and a deflator, and drawing them off to downstream nip rolls.

Conventionally, as a method for injecting air when producing a stretched film in this manner, a method using an air gun has generally been used.

That is, grasp the tube wall of the raw material tube with one hand, hold the air gun with the other hand, and push it into the tube wall.
While injecting air, move along with the flow of the tube, pull out the air gun near the downstream nip roll, and at the same time release your grip on the tube wall to allow the insertion port to pass through the downstream nip roll and maintain the bubble diameter. By repeating this process several times, bubbles of a predetermined size are formed into a film. however,
Disadvantages include that the operation is complicated, there is a high risk of getting caught in nip rolls, it is difficult to apply at high speeds, and batch operations must be repeated many times to form large bubbles. . There is also a method of injecting air by incorporating an air injection device as shown in FIG. 1 further downstream of the downstream nip roll. In this device, an air injection nozzle 2 is passed between constricted nip rolls 3 and 4 having a constricted portion on the circumference, and a cutter is cut in accordance with the intersection of the air injection nozzle 2 and a film 1 that passes while covering the air injection nozzle 2. A blade 5 is arranged, and air is injected in the following manner. That is, the two downstream rolls and the constricted nip rolls 3 and 4 are opened, and the tube 1 is passed between the constricted nip rolls 3 and 4 so as to cover the air injection nozzle 2, and the tube is removed while being cut with a single knife blade 5. , air is injected by nipping the constricted rolls 3 and 4. When the bubble reaches a predetermined size, the air injection is stopped at the same time as the downstream nip roll is nipped, and the film is cut on the outlet side of the downstream nip roll to prevent stretching. After removing enough film, it is taken out to the winder. This method is suitable for forming large-capacity bubbles, but it still requires many injection devices such as constricted nip rolls. There are disadvantages such as complicated operations such as cutting and pulling out the film and changing the film flow path after injection. In view of such conventional shortcomings, the present inventors completed the present invention after various studies.

That is, generally when air is injected into the raw fabric tube to form bubbles, the part immediately after coming out of the heating device (
It swells at the neck (hereinafter referred to as the neck), is then cooled and fixed in shape, and is taken downstream to the nip roll to obtain a film. The film that has been cooled and retains its shape will not shrink due to punctures even if you cut it in the flow direction of the tube with a razor etc. just above the Nitzprol on the downstream side. Not enough. The inventors of the present invention have focused on this point and have completed the present invention. That is, in the present invention, a slit is made on one side of the tube flowing between two nip rolls while maintaining the diameter of the original fabric tube near the nip roll on the downstream side, and an air injection nozzle is inserted into this slit. , a thermoplastic synthetic resin stretching air injection method in which a larger bubble is formed by injecting a larger amount of air than the air escaping from the tearing part, and a method for injecting air into a thermoplastic synthetic resin to form a large bubble by injecting a larger amount of air than the air escaping from the tearing part, and a method for injecting air into the back of the cutter so that it does not protrude from at least the cutting edge of the cutter blade. This is an air injection device for stretching thermoplastic synthetic resin in which an air injection nozzle is positioned so that both can be pushed into and pulled out from a tube. In the method of the present invention, it is preferable that the distance between the tearing start part and the air injection nozzle is short because less air escapes. Therefore, the air injection pipe itself can be made into a single blade. In addition, various shapes can be considered that allow for smooth cutting of the tube wall and prevent air from escaping. On the other hand, it is preferable that the downstream side of the air injection nozzle is also designed to prevent air from escaping from the tube cut portion as much as possible. Possible methods for this include, for example, providing a backing plate, or making a slit in the tube as close as possible to the downstream nip roll and injecting air.
Also, as the air is injected, the diameter of the bubble changes and the tube wall may escape from the cutter blade, so the position of the cutter blade and pourer nozzle must be adjusted while carefully monitoring. No.

Instead of making this adjustment, if you insert a cutter blade or an air injection nozzle into the raw fabric tube through the deflator 1, the tube wall will not escape beyond the deflator 1 even if the bubble diameter changes, making it convenient. Air can be injected. The deflator in this case may or may not be integrated with the cutter knife. Furthermore, it goes without saying that the single cutter blade and the air injection nozzle may be integrated. FIG. 2 shows an example of an apparatus for carrying out the method of the invention.

That is, the cutter blade 1 extending from the tip of the air injection nozzle 8 to the deflator 19 is mounted so that the cutting edge faces upstream of the film and the air injection nozzle 8 does not protrude from the cutting edge of the cutter blade 7. Further, the deflator 19 has an appropriate opening angle in the direction of the cutting edge of the cutter blade 7. When compressed air is connected to this injection device through a valve for adjusting air with a flexible pipe such as a rubber hose, and a thermoplastic resin tube is heated to produce a stretched film by the tubular method, a tube is placed immediately upstream of the downstream nip roll. With the tip of the cutter facing upstream, insert it into the tube and inject air. The front side wall of the tube is torn, and the torn part straddles the air injection nozzle and is taken to the downstream Nitsuprol. After adjusting the air adjustment valve and injecting air to inflate the bubble to a predetermined size, pull out the air injection device to complete the air injection. As described above, according to the present invention, air can be injected simply by putting in and taking out the air injector.

Therefore, if the loading and unloading of the air injection device is carried out by incorporating it into an air cylinder or the like, it can be easily automated and can be used very effectively industrially. Example polyethylene (specific gravity 0.920, M11.0) with a diameter of 5
0Vf1, slit width 2u0) Extruded from an annular die under normal conditions, cooled with water and then taken off with a take-off machine, folding width 76u, wall thickness 5
A 00μ original fabric tube was prepared.

In addition, two sets of Nippro rolls with a diameter of 120 u were assembled one above the other with a distance of 2.5 m, and a 300 watt Infrastein 24
Assemble a tube heating furnace with an inner diameter of 150 Vt and a height of 600 Vt with a diameter of 400 mm, a slit width of 5 U, and a blowing angle of 6 mm.
A 0 degree air ring is placed at 200T1Jt from the heating furnace, and a roll 10 with a length of 600U1 and a diameter of 40Vft is placed.
A pair of deflators assembled with a book at an opening angle of 60 degrees, separated by 500 degrees from the air ring, and fitted with the lower two rolls was used as a stretching device. While feeding the raw fabric tube into this stretching device at a speed of 3 m/min, the surface temperature of the raw fabric tube at the outlet of the heating furnace reached 11
Heat it to 0℃, and heat it to 12m/
Pick up at a speed of 1 minute. 20 m3/min of air is sent to the air ring to cool the tube. The original fabric tube has a fold width of 76 and a wall thickness of 125 μm, and flows while being stretched only in the vertical direction. The lower roll on one side of the deflator is discontinuous in the center and has a width of 3 to allow the injection device to take in and out.
A notch with a height of 0U1 and a height of 50u is provided.

With the injection device shown in Figure 2, without a debulator, the length of each cutter blade is 100mm, the diameter of the injection pipe is 10U, and the nozzle rise time is 30TI! Connect the Jl injection device to a 3Kf/Cd pressure air container via a valve with a rubber hose, and inject air from the notch in the deflator by adjusting the plunge depth so that it does not reach the tube wall on the opposite side. did. The raw fabric tube swelled from about 50 u below the heating furnace, forming a bubble. Ball diameter is 250TI1Jt
When the air became dry, the air injection device was pulled out and air injection was completed. Maharatantube was able to complete the operation very smoothly without getting a puncture. The resulting film had an average wall thickness of 20 μm.

[Brief explanation of the drawing]

FIG. 1 shows a conventional air injection device having a constricted nip roll, and FIG. 2 shows an embodiment of the device of the present invention. 1 is a thermoplastic resin tube, 2 is an air injection nozzle, 3
, 4 is a narrowed nip roll, 5 is a katsuta single blade, 6 is a turn roller, 7 is a katsuta single blade, 8 is an air pourer pipe,
9 is the first deflator.

Claims (1)

[Scope of Claims] 1. When a thermoplastic resin tube is passed between two sets of nip rolls installed at a distance and heated to be stretched to produce a film, the flow of the tube between the two sets of nip rolls is A thermoplastic resin stretching air injection method characterized by making a slit in one side wall near a nip roll on the downstream side and injecting air from the slit. 2. An air injection device for stretching thermoplastic resin, characterized in that an air injection nozzle is positioned on the back side of the cutter so as not to protrude from at least the cutting edge of the cutter blade. 3. The thermoplastic resin stretching air injection device according to claim 2, wherein the cutter and the air injection nozzle are integrally constructed. 4. The thermoplastic resin stretching air injection device according to claim 2 or 3, characterized in that a deflator having an appropriate opening angle in the direction of the cutting edge is attached near the base of the cutter blade.