JP2002307534A - System for molding synthetic resin hollow body sheet by belt system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system for manufacturing a synthetic resin hollow body sheet by which a production rate of 7 m/min or more is realized and the mold ing of the synthetic resin hollow body sheet using new materials such as a reproduction material and further, a high-density polyethylene or a chain low- density polyethylene is achieved. SOLUTION: The system for manufacturing the synthetic resin hollow body sheet is of such a structure that a plurality of fluid flow paths are formed in a plate made of a material having a high heat conductivity such as a metal, which forms the gap faces of an upper and a lower cooling tank for cooling water to circulate through and openings extending in the widthwise direction per fluid flow path are formed in the gap faces of the plate. In addition, an air- and water-permeable belt runs on the gap faces of the upper and lower cooling tanks. Further, the sheet is taken up by driving a belt-system former and at the same time, a negative pressure and/or the cooling water are supplied to a plurality of the fluid flow paths. Besides, in order to achieve the high rate production, a skin layer is formed on the surface of the sheet by arranging an air cooling means at the first state of the former.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion molding system for producing a hollow synthetic resin sheet.

[0002]

2. Description of the Related Art In recent years, a sheet made of a hollow synthetic resin has been used as a sheet member. This is formed by extruding a plastic material from the mouth of a die having a cross-shaped cross section, and generally has a form in which two flat plates are bridged by ribs at regular intervals. An outline of a manufacturing system using a current fixed-type cooling suction shaping apparatus (this is referred to as a former in this specification) for forming a hollow sheet made of a synthetic resin will be described with reference to FIG. A molten plastic material fed by a screw (not shown) is extruded from the die 1 and taken up by a take-up machine 30 through a gap between upper and lower fixed formers 20 facing each other with a gap. And cut into a product sheet. The plastic material in a high temperature softened state is extruded from the opening of the die 1, and the plastic sheet material pulled by the downstream take-off device 30 is cooled and solidified in the process of passing through the gap of the fixed former 20 therebetween. Since the plastic sheet material at the time of being extruded from the die 1 is in a hennahenna soft state, it does not have a stable shape in which two flat plates are kept at a predetermined interval with the ribs standing. Fixed former 20 with the function of cooling and solidifying this softened plastic sheet material
Is basically composed of two upper and lower cooling tanks, and has a configuration in which a large number of holes are formed on both surfaces forming the gap so that a negative pressure is applied. With this configuration, it has a function of sucking the sheets on both sides at the time of passage and holding the ribs therebetween, and a function of cooling and solidifying the sheet material as the sheet passes between the upper and lower cooling tanks. FIG. 7 shows the state of the sheet temperature distribution when a synthetic resin hollow body sheet is formed on the line of the current fixed former system. This is an example of a case where a synthetic resin hollow sheet having a thickness of 3 mm and a basis weight of 500 g / m ² is taken out and molded at 5.6 m / min. In this case, when cooled by the fixed former, the surface portion reaches the softening point at a position of 50 mm, and the center portion is gradually cooled, and the center portion of the core (rib) reaches the softening point at 600 mm. The softening point indicates the temperature at which the solid plastic material starts to soften, not the temperature at which the molten plastic material completely solidifies. This figure shows that in this example, the cooling step is required about twice as long as the synthetic resin hollow body sheet is completely solidified, and a fixed former length of 1250 mm is required.

The conventional synthetic resin hollow sheet forming method using this fixed former employs a configuration in which the former itself is fixed and pulled out by a take-off machine on the downstream side. The suction force and the frictional force based on it are the feed resistance, and the production speed is 5.
It can only be raised to 6m / min. Further, only polypropylene (PP) and polycarbonate (PC) could be molded as plastic materials. In the production of this synthetic resin hollow body sheet, both side portions (ear portions) of the sheet are cut and discarded due to a problem in finishing. It is required to reuse this waste, and it has been attempted to pulverize this (repro material) into chips and mix the raw materials or use it alone, but the current fixed-former synthetic resin hollow body There is also a problem that it is difficult to actually use it in sheet manufacturing.

[0004]

An object of the present invention is to achieve a production speed of 7 m / min or more for conventional materials such as polypropylene and polycarbonate, and to repro-grade materials and various types of high-density polyethylene and chain low-density polyethylene. It is an object of the present invention to provide a manufacturing system which enables a synthetic resin hollow sheet to be formed from a thermoplastic material.

[0005]

According to the present invention, there is provided a synthetic resin hollow sheet manufacturing system comprising a fluid passage formed on a plate made of a material having high thermal conductivity, such as metal, which forms a gap between upper and lower cooling tanks through which cooling water is circulated. Are formed, and an opening extending in the width direction is opened for each fluid path in the gap surface of the plate, and a belt having air permeability and water permeability runs on the gap surface of the upper and lower cooling tanks. The belt-type former is driven to take out a sheet, and the plurality of fluid paths are supplied with negative pressure and / or cooling water.
Further, in order to enable high-speed production, an air cooling means is provided at a stage preceding the former to form a skin layer on the sheet surface.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is based on the fact that the force for suctioning a sheet material to a negative pressure by a fixed type former and the frictional force based on the force are feed resistances, and the production speed can be increased only to 5.6 m / min. In view of the above, it has been conceived that the former is not a fixed type but a belt type that runs with the sheet. Using a system in which a plastic sheet extruded from a die is directly sandwiched between former belts without using a take-off machine can significantly reduce the load on the sheet. It enables the production of materials that have been considered impossible, such as high density polyethylene and chain low density polyethylene. By using a belt drive system for the former, there is no feed resistance.However, since this former has the role of sucking the softened sheet from both sides and putting the ribs on it, use a breathable belt material. It can be vacuumed from the outside. Further, the former also has a role of cooling and solidifying the plastic sheet in a softened state. However, cooling the sheet in a cooling tank via the belt has a poor heat exchange efficiency. Therefore, a configuration in which cooling water is supplied to a plastic sheet and directly cooled using a water-permeable belt is adopted. In the present invention, the vacuum suction not only pulls the sheet from both sides to make the ribs hit, but also acts to forcibly drain the cooling water. The vacuum suction and cooling water supply form a plurality of fluid passages in a plate made of a material having high thermal conductivity such as metal which forms a gap surface between the upper and lower cooling tanks, and each fluid path is formed on the gap side surface of the plate. A plurality of openings are opened in the width direction for each path, a negative pressure or cooling water is supplied to each fluid path, and a belt-type former arranged to run on a gap between the upper and lower cooling tanks. Has a fine mesh (mesh) shape to ensure air permeability and water permeability. The belt does not necessarily have to be a net-shaped knitted material, and may be a metal belt or the like having a hole. In this specification, a belt having air permeability and water permeability is generally referred to as a mesh belt.

By the way, when the high-speed molding of a synthetic resin hollow body sheet was attempted by the above-mentioned belt type former,
About the appearance of the product A mesh pattern of the belt is formed on the surface of the product. The product is warped (warpage in the flow direction, S warp in the width direction). The product width varies depending on the discharge amount and the take-up speed. Incidentally, neck-in, which is a phenomenon in which the width dimension shrinks when pulled in the longitudinal direction, is large. The problem was seen. The reason for this is that the mesh form is adopted to give the belt air permeability and water permeability. This is not a problem especially when the product surface is required to be flat, such as when printing is required. The problem is considered to be caused by a temperature difference generated in the vertical direction or the width direction in the process of cooling the plastic. The problem with the present invention is that the present invention is a belt-type former, and since the end of the former has a roll structure, the distance (gap) between the opening of the die from which the plastic is extruded and the plastic is sandwiched by the former.
It is understood that this is due to the structural lengthening. As described above, the role of the former is to cool the plastic that is in a softened state at high temperature and to suck it from both sides to keep the ribs standing,
In the present invention, the distance from the mouth of the die to the former performing its function is structurally long. By the way, the gap, which was 50 mm in the conventional apparatus, was reduced to 150 mm by reducing the roll diameter as much as possible in the prototype of the present invention, but the gap (the distance until the sheet reaches the belt) was 115 mm.

In order to understand the temperature difference occurring in the vertical direction or the width direction in the plastic cooling process, which is the cause of the problem, the temperature distribution over the entire area of the former was measured. The cooling in the present invention employs a shower system in which cooling water is directly poured onto a sheet in addition to cooling the entire apparatus by a cooling tank, and it has been found that there is a difference in the supply amount of cooling water at the upper and lower surfaces due to gravity. . Therefore, in this case, a large number (48) of flow rate adjusting devices are arranged in the vertical width direction so that there is no difference in the actual flow rate. In order to balance the cooling and the negative pressure suction for securing the shape, the former is divided into a plurality of regions in the running longitudinal direction, and the fluid path for each region is connected to a vacuum source or a cooling water source as appropriate. It is divided into a vacuum zone and a cooling zone. The connection of each channel depends on the material, thickness, basis weight or molding speed of the synthetic resin hollow body sheet to be manufactured, and thus is specifically determined at the stage of designing the product. Will be. In short, it is set together with the flow rate value so as to minimize the temperature non-uniformity after securing a state where the ribs stand and solidify.

The disadvantage caused by the long gap is that the plastic is extruded, but the plastic is in a high temperature state, so that the plastic deforms (mainly spreads) during that time. Moreover, since the present invention is started by increasing the molding speed, the plastic is extruded from the die at a higher speed than in the past, so that the cooling time is shortened and the temperature is increased. Since it is unavoidable that the gap becomes longer due to the adoption of the belt system, it is unavoidable from a structural point of view.Therefore, as a measure to make it difficult to cause shape deformation after molding, cooling is performed by the present invention. The inventor has conceived of providing an air cooling means in the space at the preceding stage. A cold gas is blown to both sides of the sheet extruded from the die opening to perform initial cooling. As a result, a solidified skin layer is formed on the surface of the plastic to suppress deformation. However, the position where this treatment is performed is a void and does not act to adjust the shape of the synthetic resin hollow sheet, so that the rib should not be solidified in a distorted state. It is necessary to ensure the flexibility that the rib is raised by the vacuum suction in the next-stage former. Therefore,
The air cooling here is suitably performed such that the surface portion is cooled and the sheet surface is solidified and formed as a skin layer.
Then, the problem of the formation of the skin layer on the sheet surface by the initial cooling and the trace of the mesh on the sheet surface is greatly improved. In addition, by performing the initial cooling (air cooling), the production speed, which is the initial purpose, is greatly improved, and it has become possible to form (thinner) a sheet having a low basis weight, which has been conventionally difficult. In addition, changes in the thickness of the ribs and the thickness of the liner accompanying the increase in the production speed shall basically correspond to this by changing the design of the die shape, but in general, the width of the ribs is narrow. It is covered with a die shape so that the rib part at the time of extrusion becomes thicker so as not to be formed.

[0010]

Embodiment 1 An embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of an embodiment employing a belt-type former system.
Reference numeral 1 denotes a die from which plastic is molded and extruded. 2 is a heat shield plate, a high-temperature die 1
This is to block heat from the air. Numeral 3 is an air cooling means for performing initial cooling by blowing cool air onto the plastic sheet 10 extruded from the die 1 in a high temperature softened state. 4 is a belt, 5 is a drive roller, and 6 is a tension roller. The belt 4 is stretched between two tension rollers 6 at the upstream end and a drive roller 5 on the downstream side, and driven by the power of the drive roller 5, The plastic sheet 10 is sandwiched between a pair of upper and lower belts 4 and 4 and is taken downstream. Therefore, the present invention does not require a conventional take-up machine. The space between the tension roller 6 and the drive roller 5 is divided into seven zones, and cooling tanks 7 separated for each zone are arranged. The belt 4, the driving roller 5, the two tension rollers 6, the seven cooling tanks 7, and a pair of these arranged vertically, constitute a belt-type former of the present invention. As a material for the belt, a polyester-based plastic having a fiber diameter of 1.4 mm was used. Cooling water is supplied to each cooling tank 7 to cool the apparatus as a whole, and a fluid path 8 (81 grooves, 82 holes, 83 pipes) is formed in each zone and connected to a vacuum source or a cooling water source. It is plumbed. Further, a cutting machine 9 for cutting the synthetic resin hollow body sheet manufactured to a predetermined size is disposed downstream of the belt-type former.

First, an embodiment of the air cooling means will be described in detail with reference to the drawings. The air cooling means adopted here uses compressed air. In principle, a vortex effect, that is, a vortex (forced vortex) is generated in the vortex tube, and warm air is discharged from one end of the tube and cool air is discharged from the other end. This utilizes the phenomenon of discharging. FIG. 2 shows the positional relationship of the air cooling means 3 disposed between the die 1 and the belt-type former as a side view in the sheet take-off direction. Here, only the upper half of the apparatus is shown. As shown in the figure, a heat shield plate 2 for heat insulation is installed immediately in front of the die 1 except for the vicinity of its mouth, and the air cooling means 3 is integrally formed with the heat shield plate 2 and a spacer. It is attached. As shown in FIG. 3 as a front view in the width direction, five air cooling means 3 are arranged in the width direction, and a blow-off nozzle 31 is attached to a cool air discharge port of each air cooling means. A cylindrical space, a manifold 35, is formed in the width direction as shown by the broken line, and the cool air discharged from each air cooling means 3 is made uniform here and blows out from the slits 33 continuous in the width direction. ing. As shown in FIG.
It is installed at a position 45 mm in front of the mouth and 15 mm from the seat surface. The opening dimension of the blow-off nozzle 31 is width 0.
45mm and length of 600mm. The blow-off nozzle 31 is formed with a flow path 34 so as to surround the cool air flow path 32 as shown in a sectional view in FIG. Have been. This is because the nozzle 31 is cooled by the discharged cool air and heat is exchanged with a fluid such as normal-temperature air so that dew condensation does not occur in this portion. This portion corresponds to a region where a plastic sheet in a high-temperature softened state which has just been extruded from the die 1 exists, and if water droplets condensed adhere to this plastic sheet, the plastic sheet is deformed and a large defect is left. . The skin layer is formed on the surface of the plastic sheet by the action of the air cooling means, so that even when the belt is sandwiched by the belt 4 in the next stage, the trace of the mesh of the belt 4 is also reduced on the sheet surface,
Furthermore, even if it comes into direct contact with the cooling water, no damage is left on the surface. The temperature of the blown air is -3 ℃ ~ -8 ℃,
The flow rate is set at 3 to 5 m ³ / min according to the basis weight and the production speed.

Next, referring to FIG. 5, the fluid path 8 provided on the surface of the cooling tank 7 which comes into contact with the plastic sheet 10 via the belt 4 will be described in detail. This figure shows only the lower part of the devices arranged at the upper and lower target positions. In this example, as shown in the drawing, a groove 81 and holes 82 are drilled in the aluminum plate at key points in each zone divided in the sheet take-off direction, and the holes 82 are pipes 83 that are piped in the width direction. It is connected to communicate with. In the first zone, unlike the other zones, all the holes 82 communicating with the three pipes 83 are commonly connected by a groove 81. All three pipes 83 are connected to a vacuum source, and the plastic sheet 10 drawn into the belt-type former is first vacuum-suctioned from both sides in the first zone, and the shape is secured so that the ribs stand. Is made. This is because the preliminary cooling by the air cooling means was performed in the gap at the preceding stage to form the skin layer, and here, the shape securing is given priority over the cooling.
However, in this zone, the temperature of the equipment is expected to rise due to contact with the plastic that is still in a high temperature state. Therefore, as shown by the black circle in the figure, six pipes are installed near the surface to circulate the cooling water. And heat exchange was performed. The dimensions of the first zone are 720 mm wide × 310 mm long. In addition, in order to prevent the temperature of this portion in contact with the plastic which is still in a high temperature state near the high temperature die from being raised, and to lower the temperature of the belt 4 which first comes into contact with the plastic sheet, in the present embodiment, the tension roller 6 is provided inside the tension roller 6. Also, a cooling water circulation path is formed for cooling. The configuration of the subsequent second to seventh zones is the same, and these are provided with four pipelines 83, but are divided into two systems of two lines,
It is connected with 82 and is connected with groove 81. The dimensions of the second zone are 720 mm wide × 310 mm long. This is repeated in the subsequent zone, so that the temperature of the plastic sheet is gradually lowered from the surface to the center of the core, so that the plastic sheet is completely solidified and stable when passing through the seventh zone. The length of this belt-type former is 2500 mm in total including the roller. Further, a cooling water supply pipe (also indicated by a black circle) is provided in each cooling tank, and cooling water is circulated to prevent the tank itself from rising in temperature.

[0013]

[Table 1] The operation setting in this embodiment will be described with reference to Table 1. As shown in Table 1, circulating cooling water of 5 ° C. is supplied to the tension roll 6 to cool this portion and the belt 4. After entering the first zone, a vacuum source is connected to the three pipes, and cooling water is not blown out.
Pour circulating cooling water. In the second zone, 10 ° C. cooling water is supplied to the front system (tubes 5 and 6) of the two systems of the flow path 8, and a vacuum source is connected to the rear system (tubes 7 and 8). These pipes are opened on both sides (operating side and driving side) of this device, and cooling water is supplied from both sides and vacuum suction is performed. This is to ensure homogenization of the product. The cooling water was supplied at a rate of 60 liters / hour from both pipes. The plastic sheet 10 sucked from both sides so that the ribs stand in the first zone is cooled by directly immersing the sheet with cooling water in the front stage of the second zone, and the ribs stand by sucking both surfaces in the rear stage. At the same time, the cooling water is suctioned and discharged. In the second zone, the cooling water at 5 ° C. is circulated in the cooling tank to prevent the temperature of the device in this portion from rising. From the third zone to the seventh zone, the front system (tubes 9, 10,
13,14,17,18,21,22,25,26) is supplied with 10 ° C cooling water and the rear system (tubes 11,12,15,16,19,20,23,24,27,2)
8) Connect a vacuum source. The only difference is that the temperature of the cooling water circulated through the cooling tank is changed from 5 ° C. to 10 ° C.

Next, a test result of a trial production of a hollow sheet of synthetic resin made of polypropylene using the apparatus of this embodiment at different basis weights and production rates is shown in comparison with that of a conventional apparatus (fixed former). It is shown in FIG. However, since a production speed of 15 m / min was the limit as the mechanical capability of the apparatus of this example, no further test was possible.

[Table 2]Basis weight 200g / m²The following cannot be molded with conventional equipment
There was, but the basis weight was 100 g / m²Up to production speed
Molding was confirmed at 15 m / min. In addition, basis weight 250g / m²of
From thing 350g / m²Up to 6m / min production speed,
Basis weight 300g / m ²Production speed 5.5m / min, basis weight 350
g / m²The limit of the production speed was 5 m / min.
In addition, the conventional equipment has a basis weight of 500 g / m²Production speed 4
m / min was the limit, but the production speed was 11
It was confirmed that molding was possible at m / min. In addition,
630 g / m basis weight²Production speed of 4m / min
Although it was at the limit, in the device of this embodiment, the production speed was 10 m / min.
It was confirmed that molding was possible. These are at 15m / min
High speed molding is not possible because the discharge amount from the die cannot catch up
Extrusion molding technology such as improvement of dies that can withstand high pressure
Further improvement in production speed is possible by improving the technique.

The present invention employs a belt-type former to increase the production speed. In this case, as described above, a structurally long gap is formed between the die and the former. Therefore, in order to solve the problem, in the present invention, the air cooling means is arranged in the gap to perform the initial cooling. Next, Table 3 shows the results of confirming the effect of the cold air spraying by comparing the data when the cold air spraying was performed and the data when the cold air spraying was not performed in the present embodiment.

[Table 3] Plastic material is polypropylene, discharge rate is 80kg /
At this time, data was obtained by setting the sheet thickness to 4 mm, changing the basis weight and the molding speed. However, when there is no air cooling means, the distance from the tip of the die opening to the position where the sheet contacts the tip of the belt-type former (roller apex) is 113 mm. The distance to the position where the roller contacts the belt (the top of the roller) is 158 mm, which is slightly longer by the installation of the air cooling means, and the position of the cool air blowing slit is 65 mm from the tip of the die opening. As can be seen from this table, take-up speed 2m / min
When the grammage was 800 g / m ² , the molding of the product could be confirmed without blowing out cold air, but when the grammage was 600 g / m ² at a take-up speed of 3 m / min, the take-up speed was 4 m / min. And the grammage is
In the case of 400 g / m ² , irregular growth occurs in the voids,
Not a decent sheet. This production speed is in the range realized by the conventional apparatus, and it can be seen that the length of this gap greatly affects the quality of the product. On the other hand, when the cooling air is blown by installing the air cooling means, the basis weight is 600 g / m ² at the take-up speed of 3 m / min, and the basis weight is 400 g / m ² at the take-up speed of 4 m / min. In the case of, the take-up speed is 8 m / m even when the take-up speed is 6 m / min and the basis weight is 300 g / m ^2.
In the case of high-speed molding when the basis weight is 200 g / m ^{2 and} the stable molding has been confirmed. The performance of the synthetic resin hollow sheet manufactured by the shaping system of the belt former type according to the present invention is not inferior to the conventional products in physical properties and shaping state although the production speed is improved.
However, it is different from the conventional product in that the mark of the mesh of the shallow belt remains on the surface (outer surface of the liner). This mesh mark may be difficult to capture fine characters when printing on the surface, but it has a matte flavor and the surface is rough, so it does not stick to a flat surface It has advantages such as good sliding.

The following is a trial production data of a synthetic resin hollow body sheet made of high-density polyethylene or chain-like low-density polyethylene, which has been considered impossible according to the present invention. At this time, the cooling condition in the former is as follows: Air cooling means: The number of tubes used is three for both upper and lower sides, and the original pressure is 0.3
MPa. Cooling water supplied to the tension roll, the first and second zone cooling blocks: temperature 5 ° C., supply amount 40 l / min. Cooling water supplied to the third to seventh zone cooling blocks: temperature 10
Supply to maintain ° C. Blowing cooling water in the second to seventh zones: the temperature was set at 10 ° C., and the supply amount was set to 20 l / h for both upper and lower sides, and production of a synthetic resin hollow body sheet appropriate for each material and basis weight was confirmed. The following table shows the settings at that time. (1) Low density polyethylene (LF-542H)

[Table 4] Here, the φ65 EX condition is a condition in extrusion molding, and φ65 is the diameter of a screw for extruding a material.
65 mm. The extruded portion is formed from the screw inlet to the screw outlet (C1 to C
4) The extruder and the dies up to the die (SC to FB2),
The die is formed from the die entrance to the exit (D1 to D5), and the set temperature of the heater in each part is shown in the above table. The extruder temperature setting was 190 ° C., indicating that the temperature was set slightly lower on both sides. In the table below,
`` Motor '' indicates the current value of the motor that drives the screw, and `` core air '' indicates the pressure value of the air blown out from the opening provided in the center of the core of the die. ing. In addition, the jet air has a function of expanding the space between the ribs forming the hollow body. As can be seen from this table, low density polyethylene having a basis weight of 150 g / m ² , 250 g / m ² , or 340 g / m ² has a belt peripheral speed of 6 m / mi (this corresponds to the production speed).
With n, an appropriate synthetic resin hollow body sheet could be formed.

(2) High density polyethylene

[Table 5] From this table, it is found that the high-density polyethylene has a basis weight of 150 g /
Those having m ² , 200 g / m ² , 250 g / m ² , and 350 g / m ² could be formed as appropriate synthetic resin hollow body sheets at a belt peripheral speed of 6 m / min. (3) Chain low density polyethylene

[Table 6] As can be seen from this table, the basis weight of linear low-density polyethylene is
Samples of 150 g / m ² , 250 g / m ² and 350 g / m ² could be formed as appropriate synthetic resin hollow sheets at a belt peripheral speed of 6 m / min. (4) Ethylene vinyl acetate copolymer From the same Table 6, the ethylene vinyl acetate copolymer having a basis weight of 400 g / m ² could be formed as an appropriate synthetic resin hollow sheet at a belt peripheral speed of 6 m / min. It has been shown. As described above, in the conventional fixed-former method in which the plastic sheet extruded by the downstream take-off machine is taken out, the load on the sheet is large,
It has been shown that it is possible to form a synthetic resin hollow body sheet even for a material that was considered impossible. Although the data for the repro material is not shown here, it can be understood that the repro material is easier to mold than PE or the like because the repro material is originally a recycling of appropriate materials such as PP and PC.

[0018]

According to the synthetic resin hollow sheet forming system of the present invention, a plurality of fluid passages are formed on a plate made of a material having high thermal conductivity such as metal which forms a gap between upper and lower cooling tanks through which cooling water is circulated. At the same time, an opening extending in the width direction is opened for each fluid path in the gap surface of the plate, and a belt having air permeability and water permeability runs on the gap surface of the upper and lower cooling tanks. Since the sheet is pulled by driving the belt-type former and negative pressure and / or cooling water is supplied to the plurality of fluid paths,
Vacuum suction for making the rib stand does not become a feed resistance of the take-up machine, so that the production speed can be improved. In addition, since the extruded plastic sheet is sandwiched between belts and pulled directly by the former without using a take-off machine, the load on the sheet is small, and materials such as repro materials and polyethylene, which were not possible before, can be used. Manufacture of a synthetic resin hollow body sheet becomes possible.

In the present invention, a large number of flow control devices are arranged in the vertical direction in the plurality of fluid paths of the plate so as to uniformly supply the cooling water, so that the temperature is not uneven in the width direction of the former. In addition, even when the production speed was increased, the sheet could be prevented from warping. Further, in the present invention, the upper and lower cooling tanks are divided into a plurality of zones in the sheet take-off direction, and a plurality of fluid paths extending in the width direction are arranged on the gap surface of each zone. Since the pressure or cooling water can be selectively supplied, stable molding can be achieved according to the specifications of the synthetic resin hollow body sheet to be manufactured.

The present invention eliminates the adverse effect of the long gap between the die opening and the tip of the belt former based on the adoption of the belt-type former system, that is, the adverse effect that the plastic sheet is deformed during this period. For this reason, an air cooling means for injecting cool air toward the sheet surface is provided, so that a stable and solidified skin layer is formed on the surface of the plastic sheet, thereby improving the production speed and realizing a sheet having a low basis weight. Further, the formation of the skin layer reduced the trace of the mesh-like belt shape remaining on the sheet surface, and enabled printing on the surface. In addition, the mark of the shallow mesh belt shape gives the sheet surface a matte flavor,
This has the effect of eliminating suction on a flat surface and improving slippage.
Also, in the present invention, a ventilation path is formed so that the nozzle portion of the air cooling means surrounds the cool air injection flow path, and a fluid such as a normal temperature gas is circulated in the ventilation path, thereby preventing the dew condensation phenomenon at the nozzle portion. There is no flaw caused by the adhesion of water droplets on the plastic sheet surface in the softened state at high temperature.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a basic configuration of a belt-type former of the present invention.

FIG. 2 is a side view showing a position of an air cooling unit.

FIG. 3 is a front view showing an arrangement state of air cooling means.

FIG. 4 is a side sectional view of a blow-off nozzle.

FIG. 5 is a diagram showing piping of a belt former.

FIG. 6 is a schematic diagram showing a basic configuration of a fixed former.

FIG. 7 is a diagram showing a state of a temperature distribution when a synthetic resin hollow body sheet is manufactured by a fixed former.

[Description of Signs] 1 Dice 7 Cooler 2 Heat shield plate 8 Fluid passage 3 Air cooling means 81 Groove 31 Blow-off nozzle 82 Hole 32 Cold air passage 83 Pipe line 33 Slit 9 Cutting machine 34 Flow passage 10 Plastic sheet 35 Manifold 20 Fixed former 4 Belt 30 Take-up machine 6 Tension roller

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) B29L 31:60 B29L 31:60 F term (Reference) 4F033 AA05 BA01 DA01 EA01 HA03 4F207 AA05 AA07 AA08 AA10 AF16 AG01 AG06 AG18 AJ02 AJ12 AK02 KA01 KK64 KK74

Claims (7)

[Claims] A plurality of fluid passages are formed in a plate made of a material having high thermal conductivity such as a metal which forms a gap between upper and lower cooling tanks to which cooling water is supplied, and each fluid passage is formed in a gap between the plates. An opening extending in the width direction is opened every time, and a belt having air permeability and water permeability is configured to run on a gap surface between the upper and lower cooling baths, and a sheet extruded by driving the belt is formed. A synthetic resin hollow sheet molding system configured to form a cooling suction shaping device for cooling and solidifying the sheet by supplying negative pressure and / or cooling water to the plurality of fluid paths while taking off. 2. A plurality of flow control devices are arranged in a plurality of fluid passages of the plate in a vertical direction to supply cooling water uniformly.
The synthetic resin hollow sheet forming system according to claim 1, wherein temperature unevenness is prevented in the width direction of the former. 3. The upper and lower cooling tanks are divided into a plurality of zones in the sheet take-off direction, and a plurality of fluid passages extending in the width direction are arranged on a gap surface of each zone. A synthetic resin hollow sheet forming system capable of selectively supplying negative pressure or cooling water according to the specifications of the synthetic resin hollow sheet. 4. The synthetic resin according to claim 1, wherein an air cooling means for injecting cool air toward the sheet surface is provided in a gap between the die opening and a tip of the belt-type cooling suction shaping means. Hollow body sheet forming system. 5. The synthetic resin according to claim 4, wherein a flow path is formed in the nozzle portion of the air cooling means so as to surround the cool air injection flow path, and a fluid is supplied to the flow path to prevent dew condensation. Hollow body sheet forming system. 6. A synthetic resin hollow sheet having a liner surface with shallow mesh marks of a belt of a cooling suction shaping means. 7. A synthetic resin hollow sheet made of high-density polyethylene, low-density polyethylene, chain low-density polyethylene or ethylene-vinyl acetate copolymer.