JPH1029243A - Production of aromatic crystalline thermoplastic resin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a cylindrical film excellent in transparency from an aromatic crystalline thermoplastic resin in a descending air cooling system inflation molding method by using a small-sized apparatus reducing film molding cost and achieving easy molding. SOLUTION: In a descending air cooling inflation molding method wherein a resin is melted in an extruder cylinder 2 and a crosshead 3, the molten resin is downwardly extruded from a die 4 to form a bubble 8 which is, in turn, cooled by air and this bubble is flattened by stable plates 6 to be taken up by a pinch roll to form a cylindrical film, the set temp. of the die is set to about the m.p. of an aromatic crystalline thermoplastic resin or less to markedly shorten the interval between the die 4 and the pinch roll 7 as compared with a conventional interval and a cylindrical film excellent in transparency can be inexpensively produced from an aromatic crystalline thermoplastic resin with a melt flow rate of 3-8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aromatic crystalline thermoplastic resin film, and more particularly to a downward air-cooled inflation method.
The present invention relates to a method for producing a cylindrical film of an aromatic crystalline thermoplastic resin by a molding method.

[0002]

2. Description of the Related Art Conventionally, in the inflation molding method, a crystalline resin having a high degree of crystallinity, such as polypropylene, becomes opaque when gradually cooled by an air cooling method. In order to obtain a film, an inflation molding method using a water cooling method (for example, JP-B-36-2938, JP-A-47-20261, JP-B-44-30390, JP-B-54-18302, JP-B-2-61376) Issue).

However, in the case of the aromatic crystalline thermoplastic resin, firstly, when the water-cooling method is used, the surface of the bubble is not smoothed due to rapid cooling, so that the bubble becomes crater-like and wrinkles are easily generated. In addition, since a water tank and a drying device are required, there is a problem that the cost is higher than that of an air cooling system which does not require them. Secondly, it is extremely difficult to pull up the bubbles upward due to the insufficient viscosity of the molten resin when using the conventional upward air-cooled inflation molding method, while using the downward air-cooled inflation molding method. However, the conventional method of setting the temperature of the extruder has a problem that the viscosity of the molten resin is not sufficient, so that the film is liable to be cut, and it is also difficult to form bubbles. Third, the conventional air cooling system has a disadvantage that the distance from the tip of the die to the center axis of the pinch roll is as long as about 5 m, which increases the size of the apparatus and increases the cost of film forming.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention is directed to a downward air-cooled inflation molding method, which uses an aromatic crystalline thermoplastic resin to reduce the size and cost of the apparatus and facilitate film formation. It is another object of the present invention to provide a method for producing a cylindrical film having excellent transparency.

[0005]

Means for Solving the Problems In order to achieve the above object, as a result of intensive studies, the present invention has been completed. That is, in the invention of claim 1 of the present invention, after the resin is melted in the cylinder 2 of the extruder and the crosshead 3, the bubble 8 formed by extruding the molten resin downward from the die 4 is air-cooled, Further, in a downward air-cooled inflation molding method of a tubular film which is flattened by the stabilizing plate 6 and taken up by the pinch roll 7, an aromatic resin having a melt flow rate (MFR) of 3 to 8 as a resin. A method for producing an aromatic crystalline thermoplastic resin film, comprising using an aromatic crystalline thermoplastic resin and setting a temperature of a die 4 at a temperature close to or below the melting point of the aromatic crystalline thermoplastic resin. It is. Here, examples of the aromatic crystalline thermoplastic resin include polyethylene terephthalate, polybutylene terephthalate, and polycarbonate. MFR (measurement method is based on JIS K 6760)
Is an aromatic crystalline thermoplastic resin having 3 to 8
If the FR exceeds 8, the viscosity of the resin discharged from the die is too low, so that normal bubble formation becomes difficult. If the MFR is less than 3, it becomes difficult to feed the molten resin by the screw in the extrusion cylinder. is there.

The resin is cooled to a temperature within a viscosity range necessary for forming a normal bubble since the die portion is set at a temperature close to or lower than the melting point. Therefore, the resin discharged from the die blows up smoothly by the air blown out from the hole at the center of the die, and forms an appropriate inflation bubble. Furthermore, because the resin is sufficiently cooled in the die and the properties of the aromatic crystalline thermoplastic resin (high melting point, easy crystallization, etc.), the resin solidifies quickly when it exits the die, and the distance to the pinch roll is increased. Can be reduced to less than half of the conventional case. In this case, the vicinity of the melting point means including a range of 2 to 3 ° C. above and below the melting point, and the term equal to or lower than the melting point includes a range from the melting point to a set temperature before the molten resin is solidified in the die. This means that the set temperature of the die can be reduced to a temperature before the molten resin solidifies in the die. By adopting such a configuration, the distance from the die to the pinch roll can be significantly shortened compared to the conventional one, and the length of the bubble is also shortened. Therefore, the apparatus is small, the cost is low, the molding operation is easy, and the transparency is high. The effect of being able to produce a cylindrical film excellent in quality is obtained.

In the present invention, it is preferable that the set temperature difference between the crosshead of the extruder and the die is set to 20 ° C. to 50 ° C. By providing such a temperature difference, the molten resin is smoothly fed to the die portion, and the viscosity of the molten resin in the die is increased by the temperature drop, thereby facilitating bubble formation. . That is, according to the second aspect of the invention, an effect of facilitating bubble formation can be obtained in addition to the effect of the first aspect.

In the invention according to claim 3 of the present invention, the distance from the tip of the die to the center axis of the pinch roll is 0.5 m to 2 m.
A method for producing a tubular film of the crystalline thermoplastic resin described above. The distance between the tip of the die and the center axis of the pinch roll is 0.5 m to 1.5 m, which can be shorter than that of the conventional thermoplastic resin inflation molding method because the molten resin is sufficiently cooled in the die part. In addition, it is easier to crystallize than the properties of the aromatic crystalline thermoplastic resin, and the solidification is quicker. Moreover, even at a temperature higher than the glass transition point before crystallization, the bubble constituent film is soft but not viscous and has no viscosity. No blocking occurs even when folded. In this case, it is preferable to fold the bubble before it is cooled and completely crystallized. If the bubble is completely crystallized and then folded in two, the film is inflexible, so that the formed film may be creased, creased, or sagged. The invention described in claim 3 ensures the miniaturization of the device and the ease of molding. Further, the stabilizer and the pinch roll are arranged so that the distance from the tip of the die to the center axis of the pinch roll is adjusted according to the properties of the resin and the molding conditions.
It is convenient to be able to move integrally in the vertical direction as in the invention described. Thereby, the molding operation can be performed efficiently.

Further, in relation to the dice and the bubble,
The blow-up ratio is 1.0 to 2.0 when the film thickness is up to about 40μ and 1.0 to 1.5 when the film thickness exceeds 40μ. Is preferred. 2.0 in the former case and 1. in the latter case.
If it exceeds 5, the bubble becomes unstable, causing problems such as curl and uneven thickness, and a normal circular valve tends to be unable to be formed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG.
Is heated and melt-kneaded in the cylinder-2, and the pelletized aromatic crystalline thermoplastic resin supplied from the
(Not shown) in the crosshead 3 set several tens degrees higher than the melting point of the resin. Next, the resin is quenched in a die portion whose temperature is set near the melting point, and is extruded downward from an annular lip of the annular die while increasing the viscosity to form a bubble 8, and an air-ring provided near the tip of the die. 5 (the distance between the die and the air ring is 40mm-50m
m). At that time, the air was blown up to a predetermined size by air blown out from an air blowout port (not shown) at the center of the die, and then placed near the air ring 5. It is guided to the stabilizer 6 (the distance between the air ring and the upper end of the stabilizer is about 50 mm to 100 mm). Subsequently, the cylindrical bubble is flattened by the stabilizing plate 6 and taken up by the pinch roll 7 to produce a cylindrical film.

In this case, the heating in the cylinder section is performed by stepwise increasing or changing the set temperature by about 5 ° C. to 15 ° C. at the inlet, the middle, the outlet of the cylinder 2 and each part of the crosshead 3. Is preferred. Mode for screw
This is to reduce the tar load and to extrude the molten resin regularly. Further, it is preferable that the diameter of the air-ring lip is made larger than that of the die slip, and the interval between them is about 20 mm to 30 mm. This is because the cooling effect can be sufficiently exhibited while maintaining the bubble shape in a normal circular shape. This is because the resin does not completely crystallize and reaches the stabilizer in a flexible state, so that the bubble is not damaged. It is preferable to provide an enclosure around the stabilizer 6 and the pinch roll 7 in order to minimize the influence of the outside air temperature. For this purpose, for example, a cover member may be attached to the attachment frame 11 of the stabilizer shown in FIG. Further, if the stabilizer 6 and the pinch roll 7 are moved up and down as a unit, the distance between the die and the pinch roll can be changed according to the molding conditions, which is convenient. As such a configuration, as shown in FIG. 2, the mounting frame 11 of the stabilizer 6 and the pinch roll 7
The mounting frame 14 may be attached to the elevating plate 13 having a hole to be fitted to the shaft bar 12, and the elevating plate 13 may be moved in the vertical direction by rotation of the shaft bar 12 having a helical screw.

According to the above manufacturing method, the distance from the tip of the die to the center axis of the pinch roll is about 1 m.
Not only can the device be greatly reduced in size than conventional devices and the cost is reduced, but the handling of the bubble is short because the bubble length is short, and it is transparent and has a curl, blocking, ear wrinkle and the like. No, clean tubular film can be easily manufactured.

[0013]

【Example】

Example 1 Using an extruder of 50 mmφ, L / D = 26,
Crystalline polyethylene terephthalate resin (MFR: 5,
Cylinder-2, crosshead 3 with a melting point of 241 ° C), an inlet temperature of 260 ° C, an intermediate temperature of 265 ° C, an outlet temperature of 270 ° C, and a crosshead temperature of 275 ° C.
Is supplied from the hopper 1 and is sent to a die set at a temperature of 240 ° C. while melting and kneading with a screw.
The die has a slit diameter of 150 mmφ and a lip interval of 1.
Using a 0 mm spiral die, the molten resin is extruded downward from the lip to form a cylindrical bubble, which is guided to a slit type air ring device having an inner diameter of 400 mm (the distance between the die and the air ring is 40 mm). Air cool. At this time, air is blown out from the air outlet at the center of the die to blow up bubbles 1.5 times. In this case, the bubbles are drawn by a pinch roll while forming a frost line in the air ring and guided and folded by a nearby stabilizer (the distance between the air ring and the upper end of the stabilizer is 50 mm). In this case, the distance from the tip of the die to the center axis of the pinch roll is 1 m. The obtained polyethylene terephthalate film was excellent in transparency, and was clean without creases, folds, curls, uneven thickness, adhesion, and the like.

Example 2 Using an extruder having a diameter of 50 mmφ and L / D = 26, a crystalline polycarbonate resin (MFR:
3, melting point 253 ° C.), a cylinder-2 having an inlet temperature of 285 ° C., an intermediate temperature of 290 ° C., an outlet temperature of 290 ° C., and a crosshead temperature of 285 ° C .; 1 and fed to a die set at a temperature of 250 ° C. while melting and kneading with a screw. As the die, a spiral die having a slit diameter of 150 mmφ and a lip interval of 1.0 mm is used. The molten resin is extruded downward from the lip to form a cylindrical bubble, which is then slit into a 400 mm inner diameter slit type air ring device (die and air). -The distance from the ring is 40 mm) and air-cooled. At this time, air is blown out from the air outlet at the center of the die to blow up bubbles 1.5 times. In this case, the bubbles are drawn by a pinch roll while forming a frost line in the air ring, guided near a stabilizer (the distance between the air ring and the upper end of the stabilizer is 60 mm) and folded. . In this case, the distance from the tip of the die to the center axis of the pinch roll is 0.8 m. The resulting polycarbonate film was excellent in transparency and free of creases, folds, curls, and uneven thickness.

[0015]

As described above, the method for producing an aromatic crystalline thermoplastic resin film according to the present invention provides a downsized air-cooled inflation system that is small in size and inexpensive and easy to form. The present invention can provide a cylindrical film of an aromatic crystalline thermoplastic resin which is a molding method and has excellent transparency.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an example of a method for producing an aromatic crystalline thermoplastic resin film according to the present invention.

FIG. 2 is an explanatory view of another embodiment of the method for producing an aromatic crystalline thermoplastic resin film according to the present invention.

[Explanation of symbols]

1; Hopper, 2; Cylinder, 3; Crosshead,
4; die, 5; air ring, 6; stabilizer, 7; pinch roll, 8; valve. 11; mounting frame for stabilizer 6
12: shaft rod with helical screw cut; 13; elevating plate with hole fitted to shaft core 12; 14; mounting frame for pinch roll 7, 15; outer frame.

Claims (5)

[Claims] 1. Cylinder-2, crosshead 3 of an extruder
After the resin is melted inside, the bubble 8 formed by extruding the molten resin downward from the die 4 is air-cooled, and further flattened by the stabilizing plate 6 and taken down by the pinch roll 7, and downward air-cooling of the cylindrical film. In the inflation molding method, an aromatic crystalline thermoplastic resin having a melt flow rate of 3 to 8 is used as the resin, and the set temperature of the die 4 is set to a value close to the melting point of the aromatic crystalline thermoplastic resin. A method for producing an aromatic crystalline thermoplastic resin film, characterized in that: 2. The method for producing an aromatic crystalline thermoplastic resin film according to claim 1, wherein the difference between the set temperatures of the crosshead 3 and the die 4 is 20 ° C. to 50 ° C. 3. The aromatic crystalline thermoplastic resin according to claim 1, wherein the distance from the tip of the die 4 to the center axis of the pinch roll 7 is 0.5 to 1.5 m. Film manufacturing method. 4. The device according to claim 1, wherein the stabilizer plate and the pinch roll are integrally movable in the vertical direction.
4. The method for producing an aromatic crystalline thermoplastic resin film according to 2 or 3. 5. A blow-up ratio in a relation between a die and a bubble is set to 1.0 to 1.0 when the film thickness is about 40 μm.
2.0, and 1.0 to 1.5 when the film thickness exceeds about 40 μm.
5. The method for producing an aromatic crystalline thermoplastic resin film according to 3 or 4.