JPS62113530A - Method and device for manufacturing plastic film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and an apparatus for producing biaxially oriented synthetic thin plastic films by using the so-called blowing method.

BACKGROUND OF THE INVENTION In blowing methods, plastic material is extruded in the form of a molten tube through the nozzle of an extruder. This melt tube is pulled along a cooling mandrel that assimilates and crystallizes the plastic material. This produces a continuously moving, cooled and solidified tube which is pulled in one direction by a pair of pulling rolls. Above the tension rolls, the tubing is reheated in a heating furnace.

In this furnace, the tube reaches a certain drawing temperature.

Blank at this stretching temperature? The blank is blown biaxially by the blowing tube into a large-diameter, thin-walled bubble. The bubble is flattened smoothly by keeping the bubble circumference constant, and the bubble is sealed at one end by two pressure rollers, and the product is pulled between the pressure rollers.

Finally, the product is usually divided into two parts, subjected to heat treatment, and then wound onto rollers for storage for further processing.

In prior art methods, the blow tube is within a bubble;
Also, in order to create the above-described conditions due to being at the Buyoub drawing point, it is necessary to provide the pair of tension rolls with openings formed by annular grooves. Therefore, the surfaces of the pair of tension rolls contact the tube unevenly,
This uneven contact of the tension rolls then causes cooling defects within the tube. The tension roll is a working element (Para
Depending on the teater, the surface of the tube is cooled or warmed.

The cooling effect produced by the tension rolls leads to the production of thickness irregularities in the film at the points contacted by the tension rollers during stretching. Additionally, the pull rolls unevenly shape and squeeze the tube material as it leaves the cooling mandrel.

Non-uniform mechanical forming leads to the formation of defects that cause mottled areas and thickness variations, e.g. bows in the tube material, these defects are visible in the center of the final material wear, and Reduces film quality. The spots are caused by curling or wrinkling of the film at the edges.

Furthermore, the blowing tube inside the tube material creates *t*t, eg scratch marks, on the inner surface of the tube, and said friction marks are also visible in the finished tube. Fj! The rubbed spots must be directed towards the edges of the web and must be avoided as rubbed areas degrade the electrical properties.

The effect of said defects is visible in the final product and especially in 6-1
Increase the amount of defective products with thin films of 0t1m.

Cooling errors, temperature changes of more than 1-3° C., have a negative effect on quality due to the sensitivity of the cooling action.

[Problem to be Solved by the Invention] The object of the invention is to eliminate the drawbacks of the prior art and further avoid the defects caused by the prior art methods for heat-sensitive materials and to improve the quality of the product, in particular the uniformity. , and also to reduce m of defective products.

[Means for solving the problem] After cooling the tube material (4) extruded from the nozzle (2), it is pulled into an upper heating chamber by a pair of rolls,
Compressed air is blown into the heated tubing in the heating chamber to expand the tubing to working dimensions, and the expanded tubing is then drawn through an upper pair of tension rolls (9) to a storage roll (14). A method for producing a biaxially oriented synthetic plastic film by a blowing method, the method comprising: first and second pairs of lower tension rolls (1B) (18 ) and annular groove (1
The first pulling roll (16) with 5) blows compressed air into the tube material at the same time as it pulls the tube material to form an air bubble (18), and after the formation of said air bubble, it is smooth during the actual working time. A pair of second tension rolls (18) with surfaces feature a method of tensioning the tube material.

Apparatus comprising a pair of tension rolls (16) with annular grooves for tensioning the cooled tubing material and a blowing device for blowing compressed air into the tubing material to form a large diameter, ill bubble. 1 roll (16) alternately pulling the tube material - a pair of smooth second rolls (18)
It is characterized by having the following.

Prior to specifically explaining the present invention, a conventional method will be explained based on the drawings.

FIG. 3 shows the equipment conventionally used for the blowing process.

Raw materials are supplied to extruder 1, and the temperature is about 200-250℃
The heated material is passed from extrusion 11 through nozzle 2 over cooling mandrel 3. Upon reaching this cooling mandrel, the heated material has a thickness of approximately 300 to 70 mm.
It begins to crystallize into a tubular primary tube material 4 of 0 μm. This double-duped material is sent upwardly through a pair of first pulling rolls 5 which pull it at a constant speed V1. After passing through the first pair of tension rolls 5, the secondary tube material 4 is reheated by a suitable heater 6. Compressed air is blown through the blow tube 7 into the reheated tube material. A controlled bubble 8 is formed by this blowing. The thickness of the bubble 8 is approximately 5 to 30 μm. Said bubble 8 is flattened by a pair of upper tension rolls 9 whose speed V 1 is equal to vl at the beginning jlJ and becomes about five times Vl during actual operation. After the tube material has been flattened in a controlled manner, it is led to a splitting device 11, after which the product 12, 12' obtained is passed through a heat treatment device 13.
．． storage roll 14.13' for subsequent processing.
14'.

The bubbles 8 are injected through a blowing pipe 7 extending through the pair of first tension rolls 5 .

For this blowing pipe, the pair of first tension L41-rules 5 are provided with an annular groove 15 serving as a frontage in the remaining portion between the rolls as shown in FIG. FIGS. 5A and 5B illustrate the passing of the folded material 4 through a pair of pulling rolls 5 from different sides.

4 and 5 show irregular contact between the lower pair of tension rolls 5 and the tube material 4. FIG. FIG. 5B also shows defects 19 in the tube material 4 as a result of irregular contact between a pair of tension rolls 5.

[Example] Hereinafter, the present invention will be specifically explained based on the drawings.

Figures 1A, 1B and 7C show schematic portions of the apparatus of the present invention used to make biaxially oriented synthetic thin plastic films. When a product is being made in accordance with this invention, the warm raw material extruded from the extrusion nozzle 2 is passed over a conventional cooling mandrel 3. The generated primary tube material 4 is formed into an annular groove 1 for a blowing pipe.
5 is passed through an upper pair of tension rolls 16 provided with 5.

After passing through a pair of pulling rolls 16, -Next chew 1 material 4
The ink which is conveyed to the reheating device 6 is directed past a subsequent pair of tension rolls 9, which is shown in Figure 1Δ.

The primary tube material is approximately 130-150% in the reheating device 6.
When heated to the appropriate stretching temperature of 10°C, blowing is started with compressed air at room temperature or heated (about 100-300°C, preferably about 200°C) to create bubbles 8.

Compressed air is forced up the telescoping blow tube 11 of the present invention through openings in a pair of pull rolls 16 to the position shown in FIG. 1B. The blowing of compressed air continues until the bubble 8 has reached its proper working size. During blowing, the diameter of the tubing increases and the tubing expands by about 7 to 8 times more in the direction of travel of the garment.

When the bubble 8 reaches the proper size, the blowing is stopped and the blowing pipe 17 is lowered. Following this, the gap between the other pair of tension rolls 18 surrounding the tube material 4 is closed. See FIG. 1C for the fact that the gap between the pair of first pull rolls 16 provided with openings is opened so that the second pair of rolls 18 act as the lower pair of pull rolls. The lower pair of second tension rolls 18 include smooth and wide tension rolls (FIG. 2).

This pair of tension rolls 18 does not require an annular groove for the blow tube. The tubing material between the rolls therefore receives uniform contact. Regarding temperature J3 and tube surface,
The smooth, annular groove-free roll's operation is uniform and free of defects caused by annular grooves and temperature fluctuations. III caused by the blowpipe! ! ! The generation of marks is also eliminated when using the device of the invention.

Using the device of the invention J: elongation and normal [4]
Extreme thickness changes and pouch-like spots caused by concave roads during standing and driving can be eliminated. of tube material,
The flattening mark at the web end, caused by the bending or shrinkage of the flattening process, is easily directed towards the web end.

[Effects of the Invention] As described above, according to the present invention, a uniform product can be obtained without any scratches on the plastic film product, and the hanging of defective products can be drastically reduced, which is a remarkable effect. .

In the blowing method, the raw material is often polypropylene.
It is especially used in the production of electrically insulating films. but,
Other plastic materials can also be used as raw materials in the blowing process, such as L L'OP E or linear low density polyethylene, PB or propylene-butylene and PA or polyamide.

It is obvious that various changes can be made to the present invention without departing from its spirit.

[Brief explanation of drawings]

1A, 1B and 1C are diagrams showing each blowing process in an apparatus implementing the present invention, FIG. 2 is a plan view showing another pair of tension [calls] of the present invention, and FIG. 4 is a front view of a device conventionally used in the blowing method; FIG. 4 is a plan view of a pair of conventional tension Ll-rules;
Figure B is an iL view of a pair of prior art tension rolls, specifically illustrating the flaws caused in the tube material by the tension rolls. DESCRIPTION OF SYMBOLS 1... Extruder, 2... Nozzle, 3... Cooling mandrel, 4...-Next tube material, 5... Pull roll, 6... Reheating device, 7... Blowing pipe , 8...Bubble, 9...Upper tension roll, 11...Dividing device, 12.12゛...Product, 13.13'...Heat treater, 14.14'...Storage Roll, 15...
- Annular groove, 16... first tension roll, 17... nested blowing pipe, 18... second tension roll, 19...
·defect. Applicant Kosco Shiri 11-nen Agent Ashi 1) Nao Eicho Masayuki Kura

Claims (1)

[Claims] 1. After the tube material (4) extruded from the nozzle (2) is cooled, it is pulled into an upper heating chamber by a pair of rolls, and compressed air is blown into the tube material heated in the heating chamber. to expand the tubing material to working dimensions, and then pass the expanded tubing material over an upper pair of tension rolls (9).
) to a storage roll (14) by blowing the film into a storage roll (14); using a pair of lower tension rolls (16) (18);
The first pulling roll (16) with an annular groove (15) pulls the tube material and at the same time blows compressed air into the tube material to form an air bubble (8), and after the formation of said air bubble, the actual working time A method for producing plastic films, characterized in that a pair of second tension rolls (18) with a medium smooth surface tension the tube material. 2. A patent claim characterized in that during the blowing step of blowing compressed air into the heated tube material, the blowing is carried out by means of a telescoping blowing tube (17) which rises under the action of the compressed air and descends after blowing has ended. A method for producing a plastic film according to item 1. 3. An apparatus comprising a pair of tension rolls (16) with annular grooves for tensioning the cooled tubing material and a blowing device for blowing compressed air into the tubing material to form a large diameter, thin-walled bubble. a pair of smooth second rolls (18) for pulling the tubing material in alternation with the first roll (16);
A plastic film manufacturing device comprising: 4. The plastic film manufacturing apparatus according to claim 3, characterized in that the blowing device includes a nested blowing tube (17).