JPS61258723A - Manufacture of two-layer hollow film - Google Patents

Abstract

PURPOSE:To provide the film with excellent light beam transmittance as well as desired thin and flexible property, prevent the strain or buckling or leg between two layers of film and obtain a good temperature-keeping property by a method wherein the inner and outer two layers of tubular film are adhered to the side wall surfaces of inner and outer annular cooling-water tanks by the pressure of gas sent between annular slits and water is passed through both annular water tanks. CONSTITUTION:Molten thermoplastic resin 4, extruded through the delivery port 7 of an extruding dice 1, is formed into two-layer tube, connected by a multitude of legs between two layers, and the tube is inflated with a gas supplied from a pipe 37. The positions of height of a water depth regulating ring 21 for inside annular cooling-water tank and a water depth regulating hollow tubular nut 31 for the outside annular cooling-water tank are adjusted to equalize the depths of water, contacting with both inner and outer layers of the two-layer hollow film, and cool the inflated resin in the inside and outside annular cooling water tanks 2, 3 while the pressure of air, sent by pressure between both annular slits 8, 9 of the dice through an air sending port 11 formed between the same slits 8, 9, is adjusted to adhere both of the inner and outer films to the annular outside wall 12 and the annular inside wall 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a two-layer hollow film, particularly a two-layer hollow film, in which the two film layers are integrally connected by a number of separate legs, and a number of elongated segments are connected to each other. The present invention relates to a method for manufacturing a hollow film formed between

(Prior Art) The above-mentioned hollow film has been attracting attention in recent years as a covering material for greenhouses because it has superior heat retention properties compared to a single sheet film. However, due to the hollow structure between the two layers, the light transmittance is significantly lower than that of a single sheet film, and daytime solar heat is not stored sufficiently in the greenhouse, and the heat is not transferred between the upper and lower films. Unless the provided many legs firmly separate both films to maintain long and slender sectioned seedlings, the heat retention effect will be reduced and the film will not be able to function satisfactorily as a greenhouse covering material. In addition, this type of hollow film is required to be able to be rolled up, stored and transported like a conventional single-layer sheet film, and to have sufficient flexibility to ensure good workability. Ru.

In order to obtain the desired light transmittance, the upper and lower film layers as well as the legs are molded with transparent, thin, and flexible resin, and a two-layer hollow film that maintains a strong and elongated compartment is efficiently manufactured. It was considered difficult to do so.

One of the conventionally proposed methods for manufacturing a two-layer hollow film is to connect two large and small annular slits formed concentrically, as shown in JP-A-50-133263. An inflation extrusion molding method is known in which a molten thermoplastic resin is extruded and expanded through an annular extrusion die having a plurality of slits, and then cooled by an air cooling method.

(Problem to be solved by the invention) However, in this method, when the extruded molten thermoplastic resin is expanded and cooled, a relatively large amount of cooling air must be supplied in order to accelerate the cooling effect. . Also,
If you try to cool the resin surface discharged from the outer annular slit and the resin surface discharged from the inner annular slit under the same conditions, the air blown out from the cooling nozzle on the outer annular slit surface will absorb heat and return to the atmosphere. However, the blown air on the inner annular slit surface side is trapped inside the cylindrical film, and the pressure inside the film cylinder for expansion becomes abnormally high and cannot be adjusted. At the same time, the heat taken from the inner annular slit surface cannot be diffused, and the cooling effects of the outer annular slit surface and the inner annular slit surface differ, making it impossible to obtain a cooling effect under the same conditions.

To avoid this, if you try to dissipate the heat by providing an exhaust port for the cooling air that blows out on the inner annular slit surface,
Conversely, the pressure of the gas for expansion inside the film cylinder decreases, making it extremely difficult to balance the gas pressure.

In order to prevent the legs connecting the two layers of film from being irregularly distorted or buckled when simultaneously extruded molten thermoplastic resin is expanded, the pressure of the gas inside the film cylinder is supplied between the inner and outer annular slits. A balance with the gas pressure is required, but such adjustment is extremely difficult in the above-mentioned known inflation extrusion molding method in which cooling and solidification is performed by air cooling.

In addition, with this type of air cooling method, cooling takes a relatively long time, so the resin is stretched thin, which not only causes the legs between the two layers to become distorted and buckled, but also reduces the transparency of the resin due to slow cooling. Then, the practicality is mentioned.

It is conceivable to adopt a conventional water cooling method instead of the air cooling method described above, but since the conventional water cooling method was used to cool a single layer film, this water cooling method cools a film consisting of two layers. It is not possible to cool them simultaneously and uniformly without changing their hollow shapes, and the same defects as in the case of air cooling occur.

Therefore, the present invention improves the conventionally proposed method for manufacturing a two-layer hollow film using the inflation extrusion molding/air cooling method, and provides excellent light transmittance and desired thinness and flexibility, while preventing distortion of the legs between the two-layer films. An object of the present invention is to provide a method for efficiently producing a two-layer hollow film with good heat retention properties that does not buckle or buckle.

(Means for Solving the Problems) According to the method for producing a two-layer hollow film of the present invention, a die consisting of a pair of closely arranged concentric annular slits and a large number of leg slits extending between them. Extrude the molten thermoplastic resin into a two-layer cylindrical film from the outlet of the
Gas is inserted into the inside of the extruded two-layer cylindrical film to cause it to expand, and gas is also introduced between the pair of annular slits to maintain the two-layer spacing so that the film has a desired apparent thickness. The expanded two-layer cylindrical film is passed between the inner and outer walls of an outer annular cooling water tank and an inner annular cooling water tank disposed below the die, and the water in the cooling water tanks is kept at the same level. The upper parts of the inner and outer walls are overflowed to the same depth and brought into contact with the thermoplastic resin immediately after being extruded from the die, and the inner and outer two-layer cylindrical films are respectively separated by the pressure of the gas introduced between the pair of annular slits. The cooling water tank is passed between the inner and outer annular cooling water tanks in close contact with the side walls of the inner and outer annular cooling water tanks.

(Embodiments) Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

In Fig. 1, reference numeral 1 indicates an extrusion die for extruding molten thermoplastic resin, and an inner annular cooling water tank 2 and an outer annular cooling water tank 3 are arranged directly below this die. The extruded and expanded thermoplastic resin 4 is immediately cooled and solidified in both cooling water tanks 2.3, folded from a cylindrical shape into a sheet shape by a pair of pinch rolls 5.6, and then one side is cut open to separate the two layers. The hollow sheet film is appropriately wound on a winding machine or the like.

As shown in detail in FIG. 2, the discharge lower of the extrusion die 1 includes a pair of closely spaced concentric annular slits 8.9 and a number of legs extending between these slits 8.9. An air blowing hole 11 is formed in each unit area defined by the annular slit 8.9 and two adjacent leg slits 10-10. Due to the shape of the discharge lower of the extrusion die 1, the molten thermoplastic resin 4 to be extruded has a two-layer cylindrical shape in which the two layers are connected by a large number of legs.

A gas feed pipe 37 protrudes into the interior of the extrusion die 1 on the center side of the annular slit 8°9, and the molten thermoplastic resin extruded from the die is expanded by the gas supplied from this pipe. . At this time, the pressure of the gas fed from the pipe 37 and the air pressure of the air vent 11 between the annular slits 8 and 9 are adjusted, and the air pressure of the air vent 11 between the annular slits 8 and 9 is adjusted.
The air supplied from 1 is not at a pressure that would cause the thermoplastic resin between the two layers to expand, and the air supplied from the gas supply pipe 37
The air pressure inside the film cylinder supplied from the air hole 11 expands the two-layer cylindrical film while being slightly lower than the air pressure supplied from the air hole 11.

The two-layer cylindrical film expanded in this way is then led to a cooling water bath 2.3. The cooling water tank 2 includes a support column 32 and a large diameter pipe 20, as shown in detail in FIG.
The cooling water tank 3 is supported by a support column 33.

The upper surface of the large-diameter pipe 20 is sealed with a gasket 38, a hakama 39 is attached to the outer cylinder, and the hakama 39 is installed under the water surface of the inner annular chamber 14 to block the flow of gas between the inside of the die 36 and the inside of the water collection container 22. ing. Further, a gasket 35 is provided in the gap 34 between the support column 32 and the die 1 to prevent air from flowing between the outside air and the inside 36 of the die.

A gas feed pipe 37 that applies pressure of gas to expand the two-layer cylindrical film inside the die 36 is inserted without any gap between it and the die 1.

In this way, the cooling water tank is arranged directly below the die, and the distance between the discharge port and the water surface (W) in the cooling water tank is made as narrow as possible, in this example, about 100 mm to 150 mm.
Therefore, the two-layer cylindrical resin extruded from the die is expanded by the pressure of the gas supplied from the gas feed pipe 37 while balancing the pressure between the inner and outer annular slits, and is immediately cooled.

Inner annular cooling water 4f! The vertical outer wall 12 of the outer annular cooling water tank 3 is disposed on the same level as the vertical inner wall 13 of the outer annular cooling water tank 3 and is slightly separated from the vertical outer wall 12 of the die. After the two-layer film gap of the two-layer cylindrical resin 4 extruded from the die and expanded is slightly narrowed by the draft applied by the pinch rollers 5 and 6, the two-layer film surface is The supplied blowing air pressure causes the tube to be vertically guided while closely adhering to the outer and inner walls 12,13. The inner annular cooling water tank 2 has an inner annular chamber 1.
4 and an outer annular chamber 15 are formed separately, and a water supply pipe 16 is connected to the bottom of the outer annular chamber 15, from which cooling water is supplied. A baffle plate 18 is fixed to the upper end of the inner wall 17 of the outer annular chamber 15, and guides the cooling water supplied to the outer annular chamber 15 to flow upward to the outer wall thereof, that is, the vertical outer wall 12. . The inner wall 19 of the inner annular chamber 14 defines a central opening of the cooling water tank 2, and a large-diameter vibrator 20 that supports the inner cooling water tank 2 is inserted through the central opening with a gap from the inner wall 19. Further, a ring 21 for water depth adjustment is screwed onto this inner wall 19.

With this structure, the water supply vibrator 16 is connected to the outer annular chamber 1.
The cooling water supplied to 5 overflows to the upper part of the vertical outer wall 12, contacts and cools the molten two-layer cylindrical resin inner layer film, and passes through the upper surface of the baffle plate 18 to the inner annular chamber. 14, and further flows down through the gap between the inner wall 19 and the vibrator 20 over the upper surface of the water depth adjustment ring 21.

This flowing water temporarily accumulates in a water collecting container 22 provided below the inner cooling water tank 2. This water is detected by the discharge liquid level detection device 23.
Drainage vibrator 2 that is detected by and penetrates the large diameter pipe 20
4 is discharged to the outside.

As understood from the above description, water depth adjustment ring 2
1 by moving and adjusting the vertical outer wall 12 up and down.
The depth of the water that overflows to the top of the tank can be adjusted.

The outer annular cooling water tank 3 is also divided into an inner annular chamber 25 and an outer annular chamber 26, a water supply vibrator 27 is coupled to the bottom surface of the inner annular chamber 25, and a baffle plate 28 is attached to the upper end surface of the partition wall of the inner annular chamber 25.26. is attached so that the cooling water supplied to the inner annular chamber 25 flows upwardly of the vertical inner wall 13. A drainage vibrator 29 is attached to the bottom surface of the outer annular chamber 26, and a hollow cylindrical nut 31 for water depth adjustment is screwed into an upper drainage hole 30 of the drainage vibrator 29 so as to be movable up and down. With this structure, the cooling water supplied from the water supply vibrator 27 to the inner annular chamber 25 flows inward by the deflector plate 28 and overflows to the upper part of the vertical inner wall 13 to form a melted two-layer cylindrical outer layer of resin. Water that contacts the film and cools it, enters the outer annular chamber 26 through the upper surface of the baffle plate 28, and water that exceeds the height of the hollow cylindrical nut 31 for water depth adjustment is discharged to the outside by the drain vibrator 29. Ru.

As is clear from the above description, by adjusting the height of the hollow cylindrical nut 31, the depth of water that contacts the outer layer film of the two-layer cylindrical hollow film can be adjusted.

In the present invention, the inner and outer annular cooling water tanks 2.3 are provided to not only simply cool the expanded resin extruded into a two-layer cylinder, but also the water depth adjustment ring 21 of the inner annular cooling water tank and the outer annular The height position of the hollow cylindrical nut 31 for adjusting the water depth of the cooling water tank is adjusted to equalize the depth of water that contacts both the inner and outer layers of the two-layer cylindrical hollow film, and at the same time, the water pressure at both water depths causes the hollow film to In order to prevent both the inner and outer layers from bending inward or the leg between the two film layers from buckling, air is forced to be blown through the air ventilation hole 11 formed between the inner annular slits 8 and 9 of the die. The inner and outer films are adjusted so that they are in close contact with the annular outer wall 12 and the annular inner wall 13 of the inner and outer cooling water tanks 2.3, respectively, so that cooling water does not drip downward from between these side walls 12.13 and the inner and outer films. Cool it in this way.

Examples of the present invention will be described below.

Example 1: The center diameter of the discharge lower of die 1 shown in Fig. 2 is 770 m.
m extrusion die is connected to 90m+ extruder, 190
Film grade ethylene vinyl acetate resin with a MI2 vinyl acetate content of 15% melted at a temperature of
Form into a two-layered cylinder at a ratio of 2 and extrude downward.

The distance between the inner annular slit 8 and the outer annular slit 9 of this discharge lower is 6.21 m, and the leg slit 10-1
The interval between zeros was also 4.0 mm. The resin extruded into a two-layer cylinder expands under the pressure of the gas supplied from the gas feed vibrator 37, and forms the outer wall 12 of the inner annular cooling water tank 2 separated by an interval of 2nun, which is arranged directly below the die. It passes between the outer annular cooling water Pa3 and the inner wall 13. At this time, the distance between the upper end surfaces of the inner and outer walls 12° 13 and the die discharge lower was approximately 130 mm. Further, the center circle diameter of the slits in the inner and outer walls 12 and 13 was 880 mm.

The air pressure fed from the air blowing hole 11 formed between the inner annular slits 8 and 9 of the die is approximately 29.7 mm in water column pressure.
The air pressure to inflate the two-layer cylindrical film supplied from the gas feed vibrator 37 is approximately 12f in water column pressure.
flI11, and the depth of the cooling water beyond the upper end surfaces of the inner and outer walls 12°13 was changed in stages.

When the water depth was set to 20111 m, the two-layer films were bent in a direction toward each other, the legs between the two-layer films partially buckled, and cooling water dripped between the inner and outer walls 12, 13 and the films. Conversely, when the water depth was set to 5 a + m, the outer film expanded outward due to the air pressure being pumped between the two-layer films, and the cooling efficiency decreased, making it difficult to obtain products of stable quality. there were. As a result, it was learned that the appropriate value of water depth was within the range of 5II1m to 20g1I11. Therefore, when we set the water depth to 17 mm and finely adjusted the air pressure pumped between both annular slits of the die to around the above value, the inner and outer cylindrical film layers were in close contact with the inner and outer wall surfaces, and the upper cooling water was There was no need to drip water, and the pressure inside the film cylinder for expansion was also balanced with the water pressure of the cooling water, so both film layers were not distorted and the legs between them were not buckled. The cooling water appears to be stationary, and the surface of the water is as smooth as a mirror, making the cooling conditions extremely stable. 880s+
It was expanded to a size of m and then cooled and solidified at a rate of 5+a/rmin. Cooling water! The two-layer cylindrical film that has descended through 2.3 is folded into a sheet by a pair of pinch rolls, one side is cut with a knife-like cutter, and then a wide two-layer film with a width of about 2.7 m is formed. It was then wound on a regular winder.

The two-layer film thus obtained has an apparent thickness of 2.0IllI11° between the upper and lower two layers, a unit weight of about tsog, and a total light transmittance of about 85%. It had excellent transparency, no buckling of the legs between the two-layer film, and was highly flexible.
,.

Example 2: In the same manner as in Example 1 above, an extrusion die with a center diameter of the discharge lower of die 1 of 880 mm was connected to a 90 mm extruder, and MI2 vinyl acetate content 15% was melted at a temperature of 190°C. Ethylene vinyl acetate resin for film is formed into a two-layer cylinder and extruded downward at a rate of 110 Jl/hour.

The interval between the slits of the die outlet is 6.
The distance between the leg slit and the leg slit is 4. It was set to On+m.

The distance between the die outlet and the top surface of the annular cooling water tank is approximately 150 mm.
mIg, the center diameter of the 2III slit in the annular cooling water tank is 975 mm, the air pressure fed between the two-layer film is approximately 2811I11 in water column pressure, and the air pressure inside the film cylinder for expansion is approximately 1011 in water column pressure. The water depth of the cooling water was set to 1511III, and the air pressure pumped between the two-layer films was finely adjusted to bring the inner and outer cylindrical films into close contact with the inner and outer walls of the inner and outer cooling water tanks. The film was cooled and solidified at a rate of 5 t/min, and wound up into a two-layer film with a width of approximately 3.0 m.

(Effects) As described above, in the method for producing a two-layer hollow film according to the present invention, the two-layer cylindrical film extruded from a die and expanded is immediately brought into contact with the cooling water in the inner and outer cooling water tanks, and also brought into contact with this cooling water. Since the degree of cooling is the same between the inner and outer films, the inner and outer films are cooled equally, resulting in good transparency and no distortion due to differential shrinkage.

In addition, the inner and outer double-layer cylindrical films are passed between the dotted water tanks in close contact with the side walls of the inner and outer annular cooling water tanks due to the pressure of the gas introduced between them, so that the legs of the two-layer film are There is no distortion or buckling, and it is possible to prevent wrinkles due to cooling spots that occur when cooling water drips between the film and the side wall surface of the cooling water tank.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an apparatus for carrying out the method for producing a two-layer hollow film according to the present invention, FIG. 2 is a partially enlarged plan view showing the discharge port of an extrusion die, and FIG. FIG. 4 is a partially cutaway perspective view showing the molded two-layer cylindrical hollow film in a state before it is cut into sheets. 1...Extrusion die 2...Inner annular cooling water tank 3...
... Outer annular cooling water tank 7 ... Extrusion die outlet 8.9 ... Concentric annular slit 10 ... Leg slit 11 ... Air ventilation hole 12... Outer wall 13 of the inner annular cooling water tank...
... Inner wall 21 of outer annular cooling water tank ... Water depth adjustment ring 31 ... Hollow cylindrical nut 37 for water depth adjustment ...
...Gas feeding vibe 40 for expansion...
...Air communication pipe patent applicant Ube Nitto Kasei Co., Ltd. Representative Patent attorney - Kensuke Shiro Figure 1

Claims (1)

[Claims] The molten thermoplastic resin is extruded into a two-layer cylindrical film from the outlet of a die consisting of a pair of concentric annular slits arranged close to each other and a number of leg slits placed between them, and the extruded two-layer The expanded two-layer cylindrical film is produced by inserting gas into the inside of the cylindrical film to cause it to expand, and by feeding the gas between the pair of annular slits to maintain the two-layer spacing so that the film has a desired apparent thickness. The water is passed between the inner and outer walls of the outer annular cooling water tank and the inner annular cooling water tank disposed below the die, and the water in the inner and outer cooling water tanks is set at the same level, and the water is placed at the same depth on the upper part of the inner and outer walls. The water overflows into the thermoplastic resin immediately after being extruded from the die, and the inner and outer two-layer cylindrical films are cooled by the pressure of the gas introduced between the pair of annular slits. A method for producing a two-layer interlayer hollow film, characterized in that the film is passed between the annular water tanks in close contact with the side wall surface of the water tank.