JPH0571024B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method and apparatus for manufacturing a tube-shaped film, such as an inflation or deflation film, and a tube-shaped film. More specifically, the present invention relates to a method and apparatus for producing a film suitable for use in stationery without sagging or dripping, and a tubular film. [Prior Art] Tube-shaped film forming equipment is widely used because it is simpler and easier to operate than the T-shaped die method. This conventional process for manufacturing a tube-shaped film consists of the apparatus shown in FIG. 2, and as is well known, the molten resin extruded from a circular die is cooled, and the tube-shaped film is folded into a flat shape and taken up by a nip roll. [Problems to be Solved by the Invention] When a tube-shaped film is manufactured by the conventional method, the tube-shaped film is folded flat between the crease part (referred to as the ear part) and the center part between the two tube ears (abdominal part). In some cases, the length of the film in the direction of flow is longer at the abdomen than at the ears, resulting in sagging in the abdomen of the film called "middle sag," or, although the cause is unclear, a wave-like sag at the ears (ears). During secondary processing such as printing and bag making, there were problems such as misprinting, printing defects due to folding wrinkles, and sealing defects during bag making. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a tube-shaped film, a manufacturing apparatus, and a technology related to the film, in order to improve the above-mentioned problems and to obtain a film with low shrinkage at high temperatures. [Means for Solving the Problems] The present invention is a method for producing a tube-shaped film in which a molten resin extruded by a circular die is cooled and folded into a flat shape, and the speed of each film can be set individually after each film is folded. Roll A,
Roll B and roll C are provided, and the roll speed ratio B/
A, the roll speed ratio C/B is 1.0<B/A<1.2 0.8<C/B<1.0, and a heating device is installed between roll B and roll C, and the film temperature in front of roll B is T1, This is a method for producing a thermoplastic resin tubular film that satisfies the following conditions: T1<T2 5<T3<80°C, where T2 is the time immediately after passing through the heating device and T3 is the time before roll C. The present invention also provides a manufacturing apparatus for the above method and a tube-shaped film. An example of the apparatus used in the present invention is shown in FIG. 1, but the arrangement and shape of the inflation device of the apparatus are not limited to this. The present invention is a method for manufacturing a tube-shaped film, in which a heating device is provided after the film is folded, and rolls are provided in which the film speeds before and after the heating device can be individually set. The heating device of the present invention is used after the film is folded and stretched at a relatively low temperature. This heating device is often a heating tank, but may also be a roll heating device. The temperature setting of the heating device varies depending on the raw material of the film, and also varies depending on the film thickness, the line speed of the roll, and the line speed ratio. Further, in order to dry the moisture in the film, a drying tank can be placed in front of the heating device. With this drying tank, the heating process is more even than heating with a heating device alone, and the treatment effect is improved without requiring a large heating tank. For this reason, it is preferable to provide a drying tank, and drying can be accomplished by wiping off moisture from the film using relatively low-temperature hot air and a free roll covered with a cloth inside. The rolls of the present invention, roll A, roll B, and roll C, can be set individually. In conventional manufacturing equipment, the gear ratio is generally changed to increase the speed of roll C by 1 to 3% compared to roll A and take it off while applying tension, but it is not an independent drive system and does not change speed arbitrarily. The roll of the present invention,
Roll A, roll B, and roll C are often formed using pinch rolls that pinch from both sides. The line speed of roll A is often around 20 m/min, but is not limited to this. The roll speed ratio of the present invention is roll speed ratio B/
A, roll speed ratio C/B is 1.0<B/A<1.2 0.8<C/B<1.0. In Fig. 1, even if the temperature of the film by the heating device between the rolls A and B is within the conditions described, if the line speed ratio B/A of the rolls is 1.0 or less, the above-mentioned residual strain remains and, conversely, the line speed ratio B/A of the rolls is less than 1.0. If the speed ratio B/A is 1.2 or more, the tear strength of the film in the machine direction decreases, which is not preferable. Stress relaxation is performed between Nipprol B and C,
It is important to balance the heating conditions between the rolls and the line speed ratio. Even under predetermined temperature conditions, unless the line speed ratio is within the stated range, the objective cannot be achieved.
If the line speed ratio C/B is less than 0.8, the film will wind around the roll, and if it is more than 1.0, stress relaxation in the film will not be possible. In the manufacturing method of the present invention, one or more sets of cooling rolls and a pressure roll to the same rolls can be provided after the heating device. The cooling roll is a driving roll made of metal that controls the roll temperature (the temperature of the film in contact with it) by passing circulating water inside the roll.
A combination of two cooling rolls is suitable for this purpose, and more uniform cooling can be achieved by cooling the tube-shaped (double) film in two stages from the front and back. The pressure roll is a freely rotating roll made of rubber that presses (closely contacts) the film against the cooling roll to uniformly cool the film. The pressure force should be as small as possible in order to prevent scratches and the like on the film. The film temperature in the production method of the present invention is roll B
T1 is in front, T2 is immediately after passing through the heating tank, and T3 is in front of roll C.
Then, T1<T2, 5<T3<80°C. The film temperature T2 immediately after passing through the heating device is the temperature before the heating device.
It must be higher than T1, which is the temperature at which the film will not melt. If the film temperature T2 is lower than T1, the residual strain of the film will not be relaxed, and if it is higher than T1, the film will be fused. Furthermore, the film temperature T3 before roll C is 5 to 80°C, preferably 5 to 40°C; if it exceeds 80°C, wrinkles will appear in the film when wound. This is not desirable as the investment will be large. The tube-shaped film of the present invention is often an inflation film in which the circumference of the obtained film is smaller than the circumference of a die (lip), but it may also be a deflation film that is the opposite. . The resin used in the present invention is a thermoplastic resin, and may be soft vinyl chloride resin, expanded polystyrene, or polyamide, but most are polyolefins, such as low-density polyethylene (LD-PE), linear low-density polyethylene (LLD), etc. -PE), high-density polyethylene (HD-PE), polypropylene (PP), etc. Among them, PP is the most transparent and relatively rigid resin suitable for use in stationery film bags. [Effects of the Invention] The manufacturing method and manufacturing device of the present invention are a film manufacturing method and manufacturing device in which the film speed can be set individually and a heating device is provided at a specific position.
For this reason, the tube-shaped film manufactured by the manufacturing method and manufacturing apparatus of the present invention is made by stretching out the residual strain that causes "sag in the middle and runny ears" caused by flat folding at a relatively low temperature, and then uniformly by heat treatment at a high temperature. Because it is relaxed and then cooled and solidified,
I was able to improve my ``sagging middle and ear discharge.'' The tubular film produced by the manufacturing method and manufacturing apparatus of the present invention not only has improved sagging and ear dripping, but also has a film that looks like it has been ironed.
The film is taut and has a beautiful appearance. The tube-shaped film obtained by the manufacturing method and manufacturing apparatus of the present invention has improved film quality in terms of rigidity and gloss, and also has improved heat resistance. The tubular film produced by the production method and production apparatus of the present invention has low shrinkage at high temperatures;
It was a film with little thermal change. Furthermore, even when an embossing device was incorporated into the manufacturing apparatus and manufacturing method of the present invention, the effects of improving sagging and ear dripping were still good. [Examples and Comparative Examples] The present invention will be specifically explained below using Examples and Comparative Examples, but the scope of the present invention is not limited thereby. The following method was used to evaluate the performance of the films used in Examples and Comparative Examples. (1) Sagging in the middle: The film was folded in half in the flow direction, stacked, and cut out at a right angle of 3 m along the selvage, and the length of the abdomen relative to this was measured, and the degree of sagging in the middle was judged according to the following criteria. ○; 0 to less than 5 mm △; 5 to less than 10 mm The degree of ear discharge was determined by counting according to the following criteria. ○; 0 to 2 pieces/1m △; 3 to 5 pieces/1m ×; 6 or more pieces/1m (3) Heat resistance: Cut the film 500mm in the flow direction and 300mm in the width direction and heat it with hot air at 60℃ for 8 hours. The shrinkage rate was calculated before and after the treatment, and the degree of heat resistance was determined according to the following criteria. ○; 0 to less than 0.3% △; 0.3 to less than 0.6% The reflectance was measured as follows. The higher the reflectance, the better the gloss. (5) Rigidity: The rigidity of the film was determined from the tensile modulus of the rising slope of the film by determining the load and elongation curve (stress-strain curve) of the film in accordance with ASTM D882. The larger the value, the higher the rigidity. Examples 1 to 3, Comparative Examples 1 to 9 MFR = 9 g/10 min, ethylene content 3% by weight,
A crystalline ethylene-propylene random copolymer resin with a crystalline melting point of 150°C as measured by the DSC method was used, and a film was formed by a water-cooling method using an inflation manufacturing device as shown in Figure 1. . In addition, the processing conditions are: die temperature 200℃, water temperature 25℃.
C. and a line speed of Nipprol A of 18 m/min, etc., were fixed, and films with a thickness of 60 μm and a fold width of 470 mm were formed under the processing conditions of Examples and Comparative Examples shown in Table 1. In Examples 1 to 3 shown in Table 1, the roll speed ratio B/A/C/B of each nip roll, the film temperature T1/T2 immediately after passing through each heating tank, and the film temperature T3 immediately after passing through the cooling roll were determined. The film was formed within the conditions shown in Table 1. Comparative Examples 1 to 8 have roll speed ratios B/A, C/
B, T1, T2, T3, etc. were formed under conditions outside the conditions of the present invention. In Comparative Example 1, the roll speed ratio B/A<
1.0, Comparative Example 2: B/A>1.2, Comparative Example 3:
C/B<0.8, Comparative Example 4 is C/B>1.2, Comparative Example 5 is T1>T2, Comparative Example 6 is extremely high T2, Comparative Example 7 is T3>80℃, etc. except,
Films were formed under the conditions shown in Examples. Also, comparative example 8
was carried out under the conditions of Example 3 without using the pressure roll on the cooling roll. Comparative Example 9 was carried out using a conventional manufacturing method with a roll speed ratio C/A of 1.03. Using the films obtained in the above-mentioned Examples and Comparative Examples, the performance of the films was evaluated by the evaluation method described above. The results are shown in Table 1. In Comparative Examples 1, 3, and 6, the film was wound around the roll, making it difficult to form the film. Comparative examples 2 and 4 are
Stretching unevenness occurred in the film machine direction, the film was easily torn, and its aesthetic appearance was degraded. Comparative example 5 is
No improvement in ear laxity, ear discharge, etc. was observed. In Comparative Example 7, the strength of the film decreased, and in Comparative Example 8, the entire surface of the film was uneven, which was not preferable. In Examples 1, 2, and 3, the film sagging, runny ears, etc. were improved, and the heat resistance, rigidity, and gloss were improved, and the film had a good appearance. Examples 4 to 5, Comparative Examples 10 to 11 Table 2 shows Examples and Comparative Examples of LD-PE and HD-PE. LD-PE has MI=1, density 0.920, HD-PE has MI
= 0.8, density 0.950. The manufacturing equipment is the same as in the example, and the die temperature is
160℃, Nitzprol A line speed 18m/min,
A film was formed using the air cooling method in accordance with Example 1 except that the film thickness was 25 μm and the fold width was 250 mm. Comparative Examples 10 and 11 were carried out using a conventional manufacturing method with a roll speed ratio C/A of 1.03. In all of the Examples, the problems such as center sagging and runny ears were improved, proving that the thermoplastic resin inflation film manufacturing apparatus and manufacturing method of the present invention are effective.

【table】

【table】 [Brief explanation of drawings]

FIG. 1 is a process diagram showing the manufacturing method of the present invention. Figure 2 is a schematic diagram of a conventional process. 1...Nitsprol A, 2...Nitsprol B, 3...Nitsprol C, 4...Cooling roll,
5...Crimping roll, 6...Drying tank, 7...Heating tank, 8...Inflation film, 9...Guide plate, 10...Dice, 11...Nippro roll, 12...Water tank, 13... Air ring.

Claims (1)

[Claims] 1. In a method for producing a tube-shaped film in which a molten resin extruded by a circular die is cooled and folded into a flat shape, roll A, roll B, and roll are capable of individually setting the film speed after folding. C, the roll speed ratio B/A and the roll speed ratio C/B are 1.0<B/A<1.2 0.8<C/B<1.0, and a heating device is provided between the rolls B and C, A method for producing a thermoplastic resin tubular film that satisfies the following conditions: T1<T2 5<T3<80°C, where the film temperature before roll B is T1, immediately after passing through a heating device is T2, and before roll C is T3. 2. Manufacture of a tube-shaped film according to claim 1, wherein the heating device is a heating tank, the roll is Nipprol, and the thermoplastic resin is polyolefin, and after the heating tank, one or more sets of cooling rolls and a pressure roll to the same roll are provided. Device. 3. A tubular polyolefin film produced by the apparatus according to claim 2.