JP5248252B2 - Sizing device for hollow plastic sheet and method for producing hollow plastic sheet using the same - Google Patents

Description

  The present invention relates to a sizing device for a hollow plastic sheet and a method for producing a hollow plastic sheet using the same.

A hollow plastic sheet formed between a pair of parallel liner (flat plate) portions and a plurality of ribs perpendicular to or oblique to the liner and used between the liners is used for packaging of articles. I came. This hollow plastic sheet has a form in which two liners are bridged by ribs at regular intervals by taking out a plastic material from a mouth of a die having a harmonica cross section.
As shown in FIG. 3, the conventional manufacturing method of the hollow plastic sheet is as follows. The molten plastic material is extruded from the die D and is sized in the gap between the upper and lower sizing plates F, F facing each other with a gap. In general, the sheet is taken out by a machine, and is cut into a product sheet by a cutting machine with a predetermined size.
That is, the melt-extruded high-temperature softened hollow plastic sheet has a function of applying a negative pressure by opening a large number of grooves on the surface and is passing through between the upper and lower fixed sizing plates having a cooling function. When the liner of the plastic sheet is sucked toward the sizing plate, the plastic sheet is cooled and solidified by moving while being sized while sliding on the surface of the sizing plate.

This type of sizing plate is generally divided into a plurality of zones, and the cooling temperature and the degree of pressure reduction can be controlled for each sizing plate in each zone. In each block including the sizing plate, cooling pipes and Since decompression piping is circulated and requires high processing costs, there is a problem that the apparatus itself is expensive.
Further, when the take-up speed of the hollow plastic sheet is increased, the frictional resistance between the sizing plate and the hollow plastic sheet is increased and cannot be taken out smoothly. Therefore, the thickness is 3 mm or less and the unit weight (hereinafter referred to as basis weight). However, the production rate was limited to about 8 m / min even in the production of about 400 g / m ² or less.
Furthermore, in the sizing of the conventional sizing plate with the sizing plate, the additive in the plastic of the sheet raw material bleeds out to the surface, and these are volatilized and sublimated. Since the grooves and the grooves were closed, it was necessary to periodically clean the sizing plate, and the work was difficult.

Patent Document 1 describes a synthetic resin hollow sheet forming system using a belt system in order to improve the production rate of a hollow plastic sheet having a low basis weight.
In this synthetic resin hollow body sheet forming system described in Patent Document 1, a plurality of fluid paths are formed in a plate made of a material having high thermal conductivity such as metal that forms a gap surface between upper and lower cooling tanks through which cooling water is circulated. In addition, an opening extending in the width direction for each fluid path is opened 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 sheet is pulled by driving the belt-type former, and negative pressure and / or cooling water is supplied to the plurality of fluid paths. Further, in order to enable high-speed production, an air cooling means is provided in front of the former to form a skin layer on the sheet surface.
However, since the belt needs air permeability and water permeability, it is necessary to use a fine mesh (mesh) or a grooved metal belt, etc., and a shallow mesh mark of the cooling suction shaping means belt is formed on the liner surface. In addition to the above problem, it is impossible to avoid an increase in the cost and complexity of the apparatus, such as a complicated fluid path and increased processing cost of the apparatus, and a belt drive facility.

The present applicant has previously proposed an invention obtained through intensive research in order to solve the above-described conventional problems (Japanese Patent Application No. 2007-236844).
This invention is an excellent invention capable of doubling the production speed and reducing the cost of the sizing plate and the hollow plastic sheet as compared with the conventional sizing device. However, the thickness of the hollow plastic sheet is relatively thin. , Which is intended for the production of relatively low basis weight hollow plastic sheets with a basis weight of about 250 to 400 g / m ² , and when the thickness and basis weight are larger, there are cases where it is not possible to respond due to insufficient cooling. found. That is, the cooling of the hollow plastic sheet can be performed by directly transferring heat from the surface of the liner by passing water, but particularly in the case of a product having a thickness of 3 mm or more, the rib cannot directly transfer heat from the cooling water. As a result, it was found that the ribs may stretch or bend. Therefore, it was developed to solve the problem of the prior application.

JP 2002-307534 A

  An object of the present invention is to provide a sizing device capable of forming a hollow plastic sheet having a relatively large thickness and a high weight per unit area at a higher speed than before, and a method for producing a hollow plastic sheet using the device. It is in.

The present inventors have found that the above object can be achieved by further increasing the cooling effect of the sizing plate.
That is, the gist of the present invention is as follows.
1. The first sizing plate that is in contact with the melt-extruded hollow plastic sheet and the first decompression section composed of the water supply / drainage block, and is connected to the first sizing plate to surround the second sizing plate provided on the take-up side. A sizing device for a hollow plastic sheet comprising a second decompression section composed of a decompression box, wherein the first sizing plate and the water supply / drainage block include a water supply groove and a drainage means connected to the water supply means in the width direction of the plate. The second sizing plate is provided with suction grooves in the width direction of the plate, and the decompression box is provided with a cooling water spray device, and for decompression and drainage. A sizing device for a hollow plastic sheet, comprising an opening.
2. The sizing device for a hollow plastic sheet according to the above 1, wherein the first and second sizing plates are formed by connecting a plurality of upper and lower pairs of plates.
3. The sizing device for a hollow plastic sheet according to the above 1 or 2, wherein the first and second sizing plates are formed of a metal plate having a wettability with a contact angle of 65 ° or less.
4). The sizing for a hollow plastic sheet according to 3 above, wherein the metal plate having a wettability of a contact angle of 65 ° or less is formed of brass, copper alloy, or aluminum whose surface is plated or anodized, or has a satin finish. apparatus.
5. The sizing device for a hollow plastic sheet according to any one of the above 1 to 4, wherein the decompression box is divided into a plurality of parts.
6). The thickness of the hollow plastic sheet, 1.5~6mm, and hollow plastic sheet sizing device according to any one of 1 to 5 unit weight are of 250~1500g / m ^2.
7. A method for producing a hollow plastic sheet using the sizing device for a hollow plastic sheet according to any one of the above 1 to 6, wherein a hollow plastic sheet comprising parallel liner portions and a plurality of ribs between the liners is melt-extruded. After that, the cooling water is led to the first sizing plate, provided on the first sizing plate, supplied to the upper and lower surfaces of the hollow plastic sheet from the water supply groove connected to the water supply means, and provided on the first sizing plate, A second sizing plate connected to the first sizing plate while draining a part of the cooling water from the drain groove connected to the means by a negative pressure and forming a water film between the sizing plate and the hollow plastic sheet The hollow plastic is removed by the negative pressure from the suction groove provided on the second sizing plate. With sliding the tick sheet above and below the sizing plate side, by spraying cooling water into the second sizing plate, hollow plastic sheet manufacturing method of which comprises carrying out the cooling solidification of the hollow plastic sheet.
8). 8. The method for producing a hollow plastic sheet according to 7 above, wherein supply and drainage of cooling water in the first sizing plate are repeated.
9. The hollow plastic sheet according to 7 or 8 above, wherein the negative pressure for sliding the hollow plastic sheet toward the upper and lower sizing plates is 3 to 9 kPa due to the negative pressure from the suction groove provided in the second sizing plate . Production method.
10. The method for producing a hollow plastic sheet according to any one of the above 7 to 9, wherein the hollow plastic sheet has a thickness of 1.5 to 6 mm and a unit weight of 250 to 1500 g / m ² .

  INDUSTRIAL APPLICABILITY The present invention can provide a sizing device that can form a hollow plastic sheet having a relatively large thickness and a high weight per unit area at a higher speed than the conventional one, and a method for producing a hollow plastic sheet using the device.

A sizing device for a hollow plastic sheet according to the present invention comprises a first sizing plate that is in contact with a melt-extruded hollow plastic sheet and a first decompression section composed of a water supply / drainage block, and is connected to the first sizing plate. A sizing device for a hollow plastic sheet comprising a second decompression section constituted by a decompression box surrounding the second sizing plate provided in the first sizing plate and the water supply / drainage block, in the width direction of the plate, The water supply groove connected to the water supply means and the water discharge groove connected to the drainage means are alternately arranged, the second sizing plate is provided with a suction groove in the width direction of the plate, and the decompression box is cooled. Hollow plus characterized by having water spray device and opening for decompression and drainage It is a Kkushito for sizing equipment.
As described above, when manufacturing a hollow plastic sheet having a relatively large thickness (about 3 to 6 mm) and a high basis weight (500 to 1500 g / m ² ), it is necessary to perform more efficient cooling. Therefore, in the present invention, a first sizing plate and a second sizing plate connected to the first sizing plate (hereinafter, both may be referred to as “metal sizing plate”) and hollow extrusion are used. In the vicinity of the contact point between the plastic sheet and the first sizing plate, water supply grooves and suction grooves are alternately arranged in the width direction of the sizing plate, and preferably a metal sizing plate exhibiting specific wettability is provided. Adopted.

Hereinafter, the sizing device for a hollow plastic sheet of the present invention will be described with reference to the drawings.
FIG. 1A is a side view showing an outline of a sizing device 1 for a hollow plastic sheet according to the present invention, which is composed of a first decompression section 10 and a second decompression section 11.
In each decompression section, the first sizing plate 2 and the second sizing plate 3 connected to each other are provided above and below with a gap therebetween, and the hollow plastic sheet is sized at the gap.
First, a hollow plastic material is discharged from a predetermined die D, and as shown in FIG. 1B, a sheet comprising a pair of parallel liners L and a plurality of vertical ribs R provided between the liners L. A hollow plastic sheet (hereinafter, simply referred to as a “molded body”) S formed into a shape, which is precooled by cold air, and then provided in the inlet section of the hollow plastic sheet sizing device 1 10 is sent.
The first decompression section 10 includes a first sizing plate 2 and a water supply / drainage block 20, and is fixed to a later-described decompression box 6 by a connecting bolt 21 provided on the water supply / drainage block 20. The molded body is supplied to the open first sizing plate 2 (in the present invention, the gap between the upper and lower sizing plates facing each other with a gap is simply referred to as a sizing plate. Sometimes).
In the present invention, the first sizing plate 2 and the water supply / drainage block 20 are integrated with the sizing plate 2 and the water supply / drainage block 20 in the plate width direction (direction perpendicular to the traveling direction) in order to perform heat exchange more efficiently. Thus, the water supply grooves 4 and the drainage suction grooves 5 are alternately arranged. Cooling water is supplied from the water supply groove 4 by means (not shown) such as a water supply pump with a flow meter. A part of the supplied cooling water is drained from the suction groove 5 by means (not shown) such as a vacuum pump.

In the present invention, a plurality of water supply grooves 4 and suction grooves 5 are provided. For example, when two water supply grooves 4 and two suction grooves 5 are provided as shown in FIG. 1A, water supply-drainage (suction) -water supply-drainage (suction) is provided. And each groove | channel is provided alternately so that water supply and drainage (suction) may be repeated.
That is, while supplying the cooling water in the vicinity of the inlet of the first sizing plate 2, a part of the cooling water is drained from the adjacent suction groove 5, and then the cooling water is supplied again, so that the adjacent suction groove 5, the cooling efficiency is enhanced by draining a part of the cooling water again.
This cooling water is supplied not only for cooling the molded body but also for forming a water film in the gap between the first sizing plate 2 and the second sizing plate 3 and the molded body S, and preferably supplied. Control is performed so that about 25 to 50 mass% of the cooling water is drained from the suction groove 5.
The degree of decompression of the first decompression sensation 10 composed of the first sizing plate 2 and the water supply / drainage block 20 is adjusted by a vacuum pump directly connected to the suction groove 5, but normally the vacuum pump is used in a fully opened state. In practice, the amount of cooling water discharged is controlled by setting the amount of cooling water supplied to the water supply groove 4 and the width dimension of the suction groove 5.

The width of the water supply groove 4 is preferably about 0.1 to 0.5 mm in order to uniformly supply cooling water to the entire groove. The water supply groove 4 is provided with water supply means such as a water supply pump with a water meter. It is connected. On the other hand, the width of the drainage suction groove 5 is preferably about three times the width of the water supply slit width, for example, about 0.3 to 1.5 mm, in order to ensure suction and drainage. As described above, the suction groove 5 is connected to a drainage means such as a vacuum pump to control the degree of decompression of the decompression section 10.
The thickness of the 1st sizing plate 2 shall be about 5-10 mm, and since the water supply groove | channel 4 and the suction groove 5 are provided with two or more in a longitudinal direction, it shall be about 50-80 mm.
The water supply / drainage block 20 is provided with a water supply groove and a suction groove, and piping connected to the water supply means and the suction means.
In implementation, the amount of supplied water and the widths of the water supply grooves 4 and the suction grooves 5 are adjusted so that the amount of the cooling water can realize the purpose of the cooling water.
With the above configuration, the cooling of the liner is made faster, so that the rib is also cooled more quickly.

Thus, in the process of passing the first sizing plate 2 of the first decompression section 10, the molded body S first comes into contact with the cooling water supplied from the water supply groove 4 in the vicinity of the inlet of the first sizing plate 2. Although water cooling is started and a part of the water supply is drained from the suction groove 5, a water film is formed between the molded body and the first sizing plate 2 by the remaining cooling water, and is provided in the second decompression section 11. The molded body is transferred to the second sizing plate 3 side. Due to the presence of this water film, the take-up resistance of the molded body can be significantly reduced as compared with the case of using a conventional sizing device, and thus the molding speed can be increased.
As described above, the hollow plastic sheet S and the water film, which have traveled through the gap between the upper and lower first sizing plates 2 and partially molded, cooled and solidified, are subsequently provided in a pair of upper and lower sides with a gap therebetween. It is taken into the gap between the plates 3 at a predetermined speed. This take-up is performed by a take-up machine 30 and a vacuum suction described later.

The second decompression section 11 includes a decompression box 6 surrounding the second sizing plate 3 provided with a plurality of suction grooves 13. The thickness of the second sizing plate 3 is about 5 to 15 mm. The decompression box 6 is determined according to the raw material resin, the melt extrusion temperature of the molded body S, the traveling speed, and the like, and may be divided into a plurality of parts depending on cooling conditions and the like.
FIG. 1A shows an example in which the decompression box 6 is divided into two parts. In the front decompression box 7 and the rear decompression box 8, the molded body S taken from the first decompression section 10 is cooled and In order to promote solidification and molding, cooling water is sprayed from a plurality of spray nozzles 14 which are cooling water spray devices toward the second sizing plate 3 provided with a plurality of suction grooves 13 , and the second sizing plate 3. The molded body S is cooled via the. The decompression boxes 7 and 8 can be adjusted in degree of decompression by pressure regulating means 16 with a solenoid valve and decompression means 15 including a vacuum pump connected via a decompression tank (not shown). Yes. When the decompression box 6 is depressurized, air in the gap between the second sizing plates 3 is sucked by applying negative pressure from the plurality of suction grooves 13 provided in the second sizing plate 3, and from the take-up machine 30. Since it is taken up, the liner L of the molded body S is pulled toward the upper and lower second sizing plates 3 to ensure the thickness of the molded body S and to obtain the smoothness of the surface of the liner.

  In FIG. 1A, the pre-stage decompression box 7 and the post-stage decompression box 8 are decompressed by a common decompression means 15. Each chamber is provided with a pressure adjusting means 16 with a solenoid valve, and is controlled so that the internal pressures of the decompression boxes 7 and 8 become predetermined values. When the pressure in each of the decompression boxes 7 and 8 is lower than a predetermined value, the pressure is adjusted by introducing outside air with an electromagnetic valve attached to the pressure adjusting means 16. The pressure reducing boxes 7 and 8 may be the same pressure or different pressures, but usually, the latter pressure reducing box 8 has a slightly lower negative pressure than the preceding pressure reducing box 7 so as not to suck the water film as much as possible. Take over effectively.

The second sizing plate 3 surrounded by the decompression box 6 is provided with a plurality of suction grooves 13 in the width direction of the plate. At this time, the second sizing plate 3 surrounded by the front-stage decompression box 7 is relatively dense, while the second sizing plate 3 surrounded by the rear-stage decompression box 8 is relatively sparse, respectively. 13 is preferably provided.
The width of the suction groove 13 is preferably about 0.1 to 0.5 mm so as not to suck the water film as much as possible and suck the air in the gap.
By comprising in this way, the water film reduced by the suction | attraction | suction for improving smoothness by the front | former pressure reduction box 7 side can be maintained to the exit vicinity of the back | latter stage pressure_reduction | reduced_pressure box 8, and the taking-out effect is exhibited efficiently In addition, it is possible to finish the molding by cooling and solidification, which is preferable.
In addition, the drainage level | step difference 17 is provided in the terminal part of the 2nd sizing plate 3, and the water film sent accompanying from the molded object S is isolate | separated.
The water temperature of the cooling water supplied to the water supply groove 4 varies depending on the cooling and solidification characteristics of the raw material resin of the plastic sheet to be molded, and is not necessarily a water temperature below room temperature or the like. is there.
This is because the polycarbonate is an amorphous thermoplastic resin, so the cooling rate and the solidification rate are proportional to each other, and the shape of the molded body is rapidly fixed due to a rapid temperature change. It is preferable to mold by slowly cooling with hot water temperature.
The water in the front and rear decompression boxes 7 and 8 is discharged from the opening 22 by a drainage means (not shown) such as a drainage pump.

FIG. 2 is a plan view showing a mounting state of the lower first sizing plate 2 and the second sizing plate 3 connected thereto in the first decompression section 10 and the second decompression section 11 of the sizing apparatus of the present invention. FIG.
The first sizing plate 2 attached to the water supply / drainage block 20 fixed to the decompression box 6 by the connecting bolt 21 opens to the side of the molded body (upper side in FIG. 2) that travels across the entire width direction of the plate. Water supply grooves 4 and suction grooves 5 having a predetermined width and depth are provided alternately on the plate plate and the water supply / drainage block 20. The width dimensions and the number of grooves of the water supply grooves 4 and the suction grooves 5 are determined according to the melt extrusion temperature of the molded body S and the traveling speed, and FIG. 2 shows a total of four cases.
The second sizing plate 3 on the take-up side is provided with a plurality of slit-like suction grooves 13 at appropriate intervals. The suction groove 13 is a through-groove extending over the entire thickness of the plate, and by applying a negative pressure to the gap, a molded body that is running from the upper and lower surfaces of the first and second sizing plates 2 and 3. A tensile force is applied to the upper and lower liners of S.
The number of suction grooves 13 , installation locations, and the like are appropriately determined according to the type of resin of the hollow plastic sheet to be molded, the basis weight, and the molding speed.
The above metal sizing plate is fixed to the base plate 23 by fixing means such as bolts both in the upper and lower sides.
Below the second sizing plate 3 on the lower side, a plurality of spray nozzles 14 are provided as cooling water spray devices for cooling the second sizing plate 3, and the amount of water supplied is a metering pump (not shown). ) Etc.

As described above, the first and second sizing plates 2 and 3 on the lower side have been described. However, the upper sizing plate is also provided with a water supply groove and a drainage groove at vertically symmetrical positions. However, the lower first and second sizing plates 2 and 3 are provided with a travel groove having a depth of about 1.5 mm and a width of about 100 mm. When the upper and lower sizing plates are assembled, the hollow plastic molded body is taken along the gap formed by the groove.
Note that the travel groove with a depth of about 1.5 mm is provided only on the lower sizing plate. If the travel grooves are provided on the upper and lower sizing plates, a groove with a depth of about 0.75 mm is required for each. Therefore, more man-hours are required than in the case where a groove of about 1.5 mm is formed on one side, and the processing cost is prevented from increasing.

Since the first and second sizing plates 2 and 3 are intended for forming, cooling and solidifying the hollow plastic sheet S, it is desirable that the first and second sizing plates 2 and 3 are made of metal and have a high thermal conductivity. In particular, in the present invention, the object is to produce a hollow plastic sheet having a large thickness (about 3 to 6 mm) and a high basis weight (500 to 1500 g / m ² ). The thickness is thinner or the basis weight is low. The length of the second sizing plate 3 is longer than that of manufacturing a hollow plastic sheet.
When the length of the second sizing plate 3 is increased, it is indispensable that the water film rides more uniformly. By obtaining such a water film, the moldability of the molded body is improved. In the present application, in order to make the water film more uniform, the wettability of the metal surface is set to 65 ° or less in terms of contact angle, thereby realizing the above.
Conventional brass used for sizing plates has a contact angle of 66 °, and as shown in a comparative example described later, when the second sizing plate 3 becomes longer, the water film becomes uneven, and the contact with the metal is uneven. Therefore, cooling spots are generated, causing resin clogging.
Examples of such a metal having a surface wettability of 65 ° or less in contact angle include chrome plating, kanzen plating, anodized brass, copper alloy, aluminum, etc., especially workability, mechanical strength, plate From the viewpoint of rigidity, thermal conductivity, and rust prevention, copper alloy or aluminum is preferable.
Of these, brass (brass) is preferable as the copper alloy, and in particular, seven-three brasses represented as material symbol C2600 and sixty-four brasses represented as material symbol C2801 (copper is about 60% by mass, zinc is about 40% by mass). %) And free-cutting brass expressed as C3604 (copper is 57 to 61 mass%, lead is 1.8 to 3.7 mass%, iron is 0.5 mass% or less, and zinc is the balance).

  As described above, the sizing device for a hollow plastic sheet of the present application has been described with reference to FIGS. 1 and 2. In the above description, the rib R provided between the liners L is described as being perpendicular to the liner L. However, the present invention is not limited to this, and the ribs R may be oblique to the liner L. Moreover, although the decompression means and the drainage means of the decompression boxes 7 and 8 are provided separately, the decompression means may be connected to the opening 22 and the drainage and decompression may be performed simultaneously. Furthermore, although the description has been made using a common vacuum pump as the decompression means for the decompression boxes 7 and 8 divided into two, the decompression box 7 and the rear decompression box 8 may be provided independently of each other.

Next, the manufacturing method of the hollow plastic sheet of this invention is demonstrated.
The object of the method of the present invention is to produce a hollow plastic sheet having a relatively large thickness (about 3 to 6 mm) and a high basis weight (500 to 1500 g / m ² ).
A method for producing a hollow plastic sheet according to the present invention is a method for producing a hollow plastic sheet using the above sizing device for a hollow plastic sheet, wherein the hollow plastic sheet comprises parallel liner portions and a plurality of ribs between the liners. After being melt extruded, it is led to the first sizing plate, provided on the first sizing plate, supplied with cooling water to the upper and lower surfaces of the hollow plastic sheet from the water supply groove connected to the water supply means, and provided on the first sizing plate The cooling water is drained by a negative pressure from the drainage groove connected to the drainage means, and a water film is formed between the sizing plate and the hollow plastic sheet, and the first sizing plate is connected to the first sizing plate. Lead to the second sizing plate and from the suction groove provided on the second sizing plate A hollow plastic sheet is produced by sliding the hollow plastic sheet toward the upper and lower sizing plates by negative pressure and spraying cooling water on the second sizing plate to cool and solidify the hollow plastic sheet. It is.

In the method of the present invention, immediately after being melt-extruded as a hollow plastic sheet S and immediately before being led to the first sizing plate 2, the temperature of the surface of the melt-extruded molded body is lowered by precooling with a gas such as air. Is preferable from the viewpoint of molding stability.
As described above, in the first sizing plate 2, the supply and drainage of the cooling water are repeated, and about 50 to 75 mass% of the supplied cooling water is transferred to the second sizing plate 3 side as a water film. .
The negative pressure of the decompression box 6 is controlled to about 3 to 9 kPa. When the decompression box is divided into two as in the above example, it is preferable that the negative pressure in the rear-stage decompression box 8 is slightly lower than that in the front-stage decompression box 7.

The thermoplastic resin to which the method for producing a hollow plastic sheet of the present invention can be applied is a high density, of course, these crystalline thermoplastic resins conventionally used as hollow plastic plates such as polyolefin resins such as polypropylene and polycarbonate resins. Hollow plastic sheets of various thermoplastic resins such as polyethylene and linear low-density polyethylene can be produced, and in particular, it can be suitably used for the production of polypropylene resin hollow plastic sheets.
For the purpose of improving the color pigment and moldability, the raw material resin for the hollow plastic sheet may be blended with a filler as an auxiliary material.
The auxiliary material is not particularly limited, but talc, calcium carbonate, and the like are preferable in consideration of the balance with cost, formability, handleability, and the like.
Further, in addition to the filler, an antioxidant, an ultraviolet absorber, an antistatic agent, an antibacterial agent, a flame retardant, a light stabilizer, a lubricant such as calcium stearate, etc., in any amount, any kind, and combination as necessary. May be.

  Further, the hollow plastic sheet that can be produced by the production method of the present invention is not limited to a simple extruded raw material, and an antistatic layer is provided on one or both surfaces of the upper and lower liners. The sheet body may be coextruded into multiple layers.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention, this invention is not limited to these Examples at all.
Examples 1 and 2
As a plastic resin material, a polypropylene block copolymer containing 4% by mass of ethylene (grade name: E601, MI = 0.8 (g / 10 min)) manufactured by Prime Polymer Co., Ltd., having a thickness of 3.0 mm and a basis weight of 500 g / The goal was to form a hollow plastic sheet with m ² , target leg spacing of 3.8 mm, thickness of 5.0 mm, basis weight of 1000 g / m ² and target leg spacing of 3.8 mm. A resin flow path with a core bar (core) that can blow out air to form a hollow chamber is shaped like a harmonica, extruded from a 165 mm wide die, and a molded body width of about 100 mm by neck-in. In the state, it led to the sizing apparatus shown in FIG.

First and second sizing plates The first sizing plate (length: 75 mm) and second sizing plate (length: 990 mm) of the sizing device are aluminum with anodized aluminum surface (wetability is contact angle 54.0 °). Consists of.
The first sizing plate was attached to a water supply / drainage block having a thickness of 50 mm and a length of 75 mm at the top, and connected to the inlet side of the decompression box. The first sizing plate had slits at 10 mm, 30 mm, 50 mm, and 70 mm from the entrance, which were water supply / drainage (suction) / water supply / drainage (suction), respectively. The width of the water supply groove was set to 0.3 mm for uniform discharge, and the width of the suction groove was set to 1.0 mm for stable drainage.
A flow meter was installed in the water supply means (pump) to the water supply channel. The thickness of the first sizing plate is 5 mm, the thickness of the second sizing plate is 5 mm, the width from the connecting portion is 1 mm, and suction grooves penetrating the entire thickness are 6 rows at 25 mm intervals, 3 rows at 50 mm intervals, and 2 at 70 mm intervals. After providing two rows at 90 mm intervals and three rows at 120 mm intervals, 5 mm drainage steps were attached to the remaining 40 mm end to the outlet of the vacuum box.
That is, by providing this step, water brought to the vicinity of the second sanding plate outlet was removed.

  The first and second sizing plates described above are provided with a water supply groove and a suction groove at vertically symmetrical positions, and a depth of 1.5 mm and a width that the molded body travels only on the lower first and second sizing plates. A 100 mm groove was provided. The upper side was flat without any grooves. Thus, when the upper and lower sizing plates are assembled, a 1.5 mm gap in which the molded body travels is formed.

Decompression box A decompression box having a height (depth) of 350 mm, a width of 370 mm, and a length (running direction of the molded body) of 1030 mm and an internal volume of about 133 liters was manufactured and divided into a front stage and a rear stage. The decompression operation is configured such that decompression means connected to a decompression tank and a vacuum pump is connected to the discharge side of each decompression box and decompression in the decompression box and cooling water are conducted simultaneously. The vacuum pressure was controlled to 5 kPa with the electromagnetic valve of the pressure adjusting means. The inlet width and outlet width of the sizing plate were as close as possible to the width of the molded body, but the gap was closed with a Teflon (registered trademark) sheet or the like to enable decompression.

A cooling water spray device having a plurality of cooling water spray nozzles (manufactured by Miri no Ikeuchi Co., Ltd .: product number SSXPO40 1 / 4M) was arranged above and below the second sizing plate, and a predetermined amount of water could be supplied from the water supply pump. In addition, the upper and lower water supply grooves of the first sizing plate are configured to be capable of supplying quantitative water independently. The cooling water temperature was 15 ° C. for the water supply groove and 15 ° C. for the cooling water spray device.

  In the state of the molded body width of about 91 mm, the molded body was guided to the sizing apparatus 1 and molded. Table 1 shows the temperature conditions of the melt extruder (screw diameter: 65 mm) from the screw inlet to the outlet (C1 to C4), the pipe part (H, N) from the extruder to the die, and the dies (D1 to D5). .

Table 2 summarizes the molding conditions, cooling conditions, sizing conditions, basis weight of the obtained sheet, dimensions, etc. of the hollow plastic sheet. Since there is a gap of 40 to 70 mm between the die outlet and the sizing plate inlet, air at room temperature at an air volume of 240 L / min is directed from the slit-shaped outlet at a position of 50 mm above and below the extruded body to the molded body. After pre-cooling by spraying, it led to the sizing plate. In addition, as for the fabric weight, 5 things of a magnitude | size of 5 cm x 5 cm were measured continuously, and the average was calculated | required.
As shown in Table 2, the molded bodies in Examples 1 and 2 were 6.5 m / min, which is the upper limit of the speed in molding a hollow plastic sheet having a basis weight of 500 g / m ² with a thickness of 3.0 mm in the conventional method. The result was inferior. In the conventional molding method, there is no water supply groove or drainage groove, and a water film is not interposed between the molded body and the sizing plate, and it is inserted into an aluminum sizing plate having a total length of about 1.5 m. The molded body is molded, cooled and solidified only by contact with the reduced pressure (5 kPa) from the sizing plate side and the sizing plate having a water-cooling pipe inside.

Example 3
The contact angle when hard chrome plating was applied to brass for the cooling plate was 60 ° and the carry-in rate was reduced to 54%. However, the moldability was good under the same production conditions as in Example 1. It was.

Comparative Example 1
When the cooling plate is made of aluminum and brass plate, the contact angle exceeds 65 °, the wettability is deteriorated, the carry-in rate is further reduced to 45%, and the moldability is reduced under the same production conditions as in Example 1. Resin clogging occurred in Bocks, making moldability unstable.
Table 3 shows the results of water supply, drainage conditions, and moldability of Example 3 and Comparative Examples 2 and 3.

The sizing apparatus for hollow plastic sheets of the present invention is an apparatus capable of sizing a hollow plastic sheet having a thickness of 3 to 5 mm and a unit weight of 500 to 1500 g / m ^2. It can be used as a sizing device that can greatly improve speed.
The sizing device for a hollow plastic sheet according to the present invention has a process for providing a required number of water supply grooves and drainage grooves in the vicinity of the entrance, a cooling water supply piping process for the water supply grooves, and a suction groove in the sizing plate. Since the sizing plate body can be constructed by machining to the extent of processing, the manufacturing cost of the sizing plate can be greatly reduced, and it can be used as an extremely practical hollow plastic sheet sizing device.
Furthermore, the sizing device for hollow plastic sheets of the present invention cools the melt-extruded hollow plastic sheet by spraying the cooling water from the water supply groove and the cooling water directly onto the sizing plate, so that the cooling efficiency is high, It can be used as a sizing device for hollow plastic sheets that can reduce cooling costs.
In addition, the method for producing a hollow plastic sheet according to the present invention forms the hollow plastic sheet using the sizing device according to the present invention, so that the thickness is larger and higher than when using a conventional device. Sizing is possible even with a fabric weight, and the speed can be increased by a factor of about 2 with a conventional fabric having a high thickness. In particular, it can be used as a highly productive method for producing a high-weight hollow plastic sheet suitable as a protective material or cushioning material.

(A) Cross-sectional view of the sizing apparatus of the present invention, (b) A cross-sectional view of the hollow plastic sheet at section A-A ′ of (a). It is a top view of the lower sizing plate of the sizing device of the present invention. It is explanatory drawing of the conventional manufacturing method.

Explanation of symbols

D dice S hollow plastic sheet L liner R rib 1 sizing device for hollow plastic sheet 2 first sizing plate 3 second sizing plate 4 water supply groove 5 drainage groove 6 decompression box 7 front decompression box 8 rear decompression box 10 first decompression section 11 Second pressure reducing section 13 Suction groove 14 Cooling water spray device 15 Pressure reducing means 16 Pressure adjusting means with solenoid valve 20 Water supply / drainage block 21 Connecting bolt 22 Opening 23 Cooling panel 30 Take-up machine 51 Pressure reducing line 52 Cooling piping

Claims (10)

  The first sizing plate that is in contact with the melt-extruded hollow plastic sheet and the first decompression section composed of the water supply / drainage block, and is connected to the first sizing plate to surround the second sizing plate provided on the take-up side. A sizing device for a hollow plastic sheet comprising a second decompression section composed of a decompression box, wherein the first sizing plate and the water supply / drainage block include a water supply groove and a drainage means connected to the water supply means in the width direction of the plate. The second sizing plate is provided with suction grooves in the width direction of the plate, and the decompression box is provided with a cooling water spray device, and for decompression and drainage. A sizing device for a hollow plastic sheet, comprising an opening.   The sizing device for a hollow plastic sheet according to claim 1, wherein the first and second sizing plates are formed by connecting a plurality of upper and lower pairs of plates.   The sizing device for a hollow plastic sheet according to claim 1 or 2, wherein the first and second sizing plates are formed of a metal plate having a wettability with a contact angle of 65 ° or less. Metal plate having a contact angle of 65 ° or less of the wettability, or plated or anodized surface, or textured and brass, hollow plastic sheet according to the copper alloy or claim 3 comprising formed of aluminum, Sizing device.   The sizing device for a hollow plastic sheet according to any one of claims 1 to 4, wherein the decompression box is divided into a plurality of parts. The thickness of the hollow plastic sheet, 1.5~6mm, and hollow plastic sheet sizing device according to any one of claims 1 to 5 unit weight are of 250~1500g / m ^2.   A method for producing a hollow plastic sheet using the sizing device for a hollow plastic sheet according to any one of claims 1 to 6, wherein a hollow plastic sheet comprising a parallel liner portion and a plurality of ribs between the liners is melted. After extrusion, led to the first sizing plate, provided on the first sizing plate, supplying cooling water to the upper and lower surfaces of the hollow plastic sheet from the water supply groove connected to the water supply means, and provided on the first sizing plate, A second sizing connected to the first sizing plate in a state where a part of the cooling water is drained from the drain groove connected to the drain means by negative pressure and a water film is formed between the sizing plate and the hollow plastic sheet. The hollow plate is guided by the negative pressure from the suction groove provided on the second sizing plate. With sliding the stick sheets above and below the sizing plate side, by spraying cooling water into the second sizing plate, method for producing hollow plastic sheet characterized by performing the cooling and solidification of the hollow plastic sheet.   The manufacturing method of the hollow plastic sheet of Claim 7 which repeats supply and drainage of the cooling water in a 1st sizing plate. The hollow plastic sheet according to claim 7 or 8, wherein the negative pressure for sliding the hollow plastic sheet toward the upper and lower sizing plates by the negative pressure from the suction groove provided on the second sizing plate is 3 to 9 kPa. Manufacturing method. The thickness of the hollow plastic sheet, 1.5~6mm, and hollow plastic sheet manufacturing method according to any one of the things which claims 7-9 unit weight 250~1500g / m ^2.

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