JP5139011B2 - 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 into a sheet shape including a pair of parallel liner portions and a plurality of ribs perpendicular or oblique thereto has been used. This is a form in which two flat plates (liners) are bridged by ribs at regular intervals from the mouth of a die having a harmonica-shaped cross section. As shown in FIG. 4, the conventional manufacturing method of this hollow plastic sheet is obtained by extruding a molten plastic material from a die D and sizing it with a gap between upper and lower formers F, F facing each other with a gap. It is generally taken out and cut into a product plate (sheet) by a cutting machine with a predetermined size.
In other words, the melt-extruded high-temperature softened plate (sheet) has a structure in which a large number of holes are opened in the surface and is pulled by negative pressure, and passes between upper and lower fixed formers having a cooling function. In the state where the liner of the hollow plastic sheet is sucked to the former side, it is cooled and solidified by moving while being sized while sliding on the surface of the former.

This type of former is generally divided into a plurality of zones, and the cooling temperature and the degree of pressure reduction can be controlled for each zone former. Cooling piping and decompression piping are circulated in the former block. In addition, since a high processing cost is required, there is a problem that the former itself is expensive.
Further, when the take-up speed of the hollow plastic sheet is increased, the frictional resistance between the former and the hollow plastic sheet is increased, and it cannot be smoothly taken. Therefore, the thickness is set to 3 mm or less, and unit weight (hereinafter referred to as basis weight). However, the production speed 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 pressure-reducing molding method using the former former, the additive in the plastic of the sheet raw material bleeds out to the surface, and these are volatilized and sublimated. Since the holes were closed, regular cleaning of the former was necessary, 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 metal belt with a hole, and a shallow mesh mark of the cooling suction shaping means belt is formed on the liner surface. This makes it impossible to avoid the complexity and cost of the apparatus, such as the problem that the fluid path is complicated and the processing cost of the apparatus is increased, and a belt drive facility is required.

JP 2002-307534 A

  The present invention has been made in order to solve the above-mentioned conventional problems of the hollow plastic sheet, and the object thereof is sizing that can form a hollow plastic sheet having a relatively low basis weight at a higher speed than conventional ones. An object of the present invention is to provide a device and a method for producing a hollow plastic sheet using the device.

As a result of diligent research to solve the above-described problems of the prior art, the present inventors include a sizing plate having a water supply groove and a slit-like decompression suction hole, and a decompression box surrounding the take-up side of the sizing plate. It has been found that the above object can be achieved by using a sizing device for a hollow plastic sheet.
That is, the present invention
(1) A sizing device for a hollow plastic sheet comprising a metal sizing plate having a water supply groove and a slit-like decompression suction hole, and a decompression box surrounding the take-up side of the sizing plate , wherein the sizing plate comprises: A plurality of a pair of upper and lower plates formed of a kind of brass or aluminum selected from three brass, hexagonal brass, and free-cutting brass are connected, and the water supply groove is in contact with a melt-extruded hollow plastic sheet The vacuum suction hole is provided in the vicinity of the point in the form of a groove in the width direction of the hollow plastic sheet, and the vacuum suction hole is provided in the form of a slit in the width direction of the hollow plastic sheet on the take-off side. and spray nozzle has a reduced pressure and water suction port, and the sizing plate peripheral surface during the molding of hollow plastic sheet Hollow plastic sheet be made of a hollow plastic sheet sizing device, and (2) the upper and lower liner portions and a plurality of ribs perpendicular or oblique thereto parallel, characterized in capable of forming a water film between the hollow plastic molded sheet surface After melt-extruding the molded product, it is guided to a sizing plate, and a predetermined amount of cooling water is supplied to the upper and lower surfaces of the hollow plastic sheet molded product from a water supply groove provided near the contact point between the molded product and the sizing plate. A water film is formed between the inner surface of the sizing plate and the surface of the molded product of the hollow plastic sheet. On the sizing plate take-up side, negative pressure is applied to the suction slit, and the upper and lower liners are sucked into the upper and lower sizing plate under reduced pressure. While sliding in the sizing plate, spray the cooling water on the upper and lower sizing plates. Performed to promote the cooling and solidification of the hollow plastic molded sheet, and the vacuum and, by the draining of the supplied water and spray the cooling water from the water supply groove at the distal end of the sizing plate via vacuum and water suction opening at the same time A method for producing a hollow plastic sheet, characterized in that
Is to provide.

The sizing device for a hollow plastic sheet of the present invention has a water supply groove provided in the vicinity of a contact point with a hollow extruded plastic sheet molded product, and the hollow extruded plastic sheet molded product is brought into direct contact with cooling water to start cooling and form a water film. Therefore, the water film acts as a lubricant, and the frictional resistance between the sizing device and the hollow plastic sheet can be reduced, and the production rate can be improved by about twice as compared with the conventional case.
Further, the sizing device for a hollow plastic sheet of the present invention has a slit-like shape for providing a required number of water supply grooves in the vicinity of the entrance, cooling water supply piping to the water supply grooves, and vacuum suction to the sizing plate. Since the sizing plate body can be configured by machining that provides the through holes, the cost of the sizing plate can be reduced.
Further, since the melt-extruded hollow plastic sheet is cooled by spraying the cooling water from the water supply groove and the cooling water directly onto the sizing plate from the nozzle, the cooling efficiency is high and the cooling cost can be reduced.
In the method for producing a hollow plastic sheet according to the present invention, since the hollow plastic sheet is molded using the sizing apparatus according to the present invention, the speed can be increased by a factor of about 2 compared with the case of using a conventional apparatus. Yes, the production cost of the hollow plastic sheet can be reduced.

A sizing device for a hollow plastic sheet according to the present invention is a sizing device for a hollow plastic sheet comprising a metal sizing plate having a water supply groove and a slit-like decompression suction hole, and a decompression box surrounding the take-up side of the sizing plate. The water supply groove is provided in the width direction of the molded product in the vicinity of the contact point with the hollow extruded plastic sheet molded product, and the vacuum suction hole is formed in a through hole shape in the width direction of the plastic sheet molded product on the take-up side. The decompression box has a cooling water spray nozzle and a suction port for decompression and drainage.
Further, the water supply groove cooling water and the spray cooling water are respectively supplied by a predetermined amount using a fixed amount supply means, and the degree of decompression of the decompression box is controlled to a predetermined degree of decompression by the decompression degree control means.

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 schematic explanatory view of a sizing device for a hollow plastic sheet according to the present invention, and a hollow plastic sheet molded body (hereinafter simply referred to as “molded body”) discharged from a predetermined die D. ) S ′ is precooled by cold air, then travels through the gap of the sizing plate 2 opened at the inlet of the sizing device 1, and is molded, cooled and solidified to form a hollow plastic sheet S as a take-up side take-up machine Is taken out at a predetermined speed. In the process of passing through the sizing plate, the molded body S ′ first comes into contact with the cooling water supplied to the water supply groove 3 in the vicinity of the inlet of the sizing plate, and water cooling is started. A water film is formed on the inner surface. 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. In order to promote cooling of the molded body, the sizing plate 2 is sprayed with cooling water, and the inside of the apparatus has a structure in which the piping opening 15 can be depressurized by a vacuum pump. The liner L is pulled toward the sizing plate, so that the thickness of the molded body can be ensured and the smoothness of the surface of the liner L can be obtained.

Fig.2 (a) is a perspective view which shows the one aspect | mode of a structure of the sizing apparatus for hollow plastic sheets of this invention. The sizing device 1 shown in the figure has a box shape including a bottom plate 8, four side plates 9, and a lid body 13, and has an inlet portion 12 and an outlet portion 16. Upper and lower sizing plates 2a and 2b are fixed to the entrance with a predetermined gap. Cooling water spray nozzles 14a and 14b are provided above and below the upper and lower sizing plates 2a and 2b to cool the sizing plates. By sucking the hose side connected to the decompression / water absorption suction port 15 which also serves as decompression suction and drainage, the upper and lower liners of the hollow plastic sheet are pulled to the sizing plate side from the slit-like holes, and the thickness of the hollow sheet Is ensured with a predetermined dimension, and the water supplied from the water supply groove and the sprayed water are drained on the tip side of the sizing plate.
The water temperature of the water supplied to the water supply groove and the cooling water spray 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. For example, in the case of polycarbonate, the hot water temperature Sometimes.

FIG. 3A shows an attached state of the lower sizing plate 2b in the sizing device. Under sizing plate 2b, as shown in FIG. 3 (b), is constituted by the inlet side of the sizing plate 2b-1 and the outlet sizing plate 2b-2 of the two plates, and are. The sizing plate 2b-1 on the entrance side has a water supply groove 3 having a predetermined width and depth opened on the traveling plastic molded product side (upper side in FIG. 3B) over the entire width direction of the plate. Yes. In addition, the width dimension and the number of grooves of the water supply groove are determined according to the melt extrusion temperature of the plastic molded product and the traveling speed, and FIG. On the take-up side following the water supply groove, slit-like decompression suction holes 4 are provided at appropriate intervals. The vacuum suction hole is a through-hole extending over the entire thickness of the sizing plate, and applies a tensile force to the upper and lower liners of the molded product that is running from the upper and lower surfaces of the upper and lower sizing plates 2a and 2b. The number of slit-like vacuum suction holes 4, installation locations, and the like are appropriately determined according to the type of resin, basis weight, and molding speed of the hollow plastic sheet to be molded. A predetermined amount of water is supplied by a metering pump (not shown), and the degree of pressure reduction in the decompression box is controlled by the degree of vacuum of a vacuum pump connected via an opening / closing valve and a pressure reduction tank (not shown).

As shown in FIG. 3C, the sizing plate 2 is configured by connecting a plurality of upper and lower pairs of plates.
The sizing plates 2a-1 and 2b-1 on the entrance side are formed with flanges including bolt holes for attachment to the sizing box and water supply pipe screw holes 3a and 3b.
The upper and lower sizing plates 2 a and 2 b are fixed to the base plate 7 by bolts 6.

Since the sizing plate is intended for forming, cooling and solidifying a hollow plastic sheet molded article, it is desirable that the sizing plate is made of metal and has a high thermal conductivity. From the viewpoint of workability, mechanical strength, plate rigidity, thermal conductivity, and rust prevention, it is preferable to use a copper alloy or aluminum.
As the copper alloy, brass (brass) is preferable. In particular, seven three brasses represented as material symbol C2600, sixty-four brasses represented as material symbol C2801 (copper is about 60%, zinc is about 40%), C3604 Is preferred as free-cutting brass (57-61% copper, 1.8-3.7% lead, 0.5% iron or less, zinc balance).

A method for producing a hollow plastic sheet of the present invention is a production method using the above sizing device for a hollow plastic sheet, and a hollow plastic sheet molded article comprising a pair of parallel liner portions and a plurality of ribs perpendicular or oblique thereto, After melt extrusion, it is guided to a sizing plate, and a predetermined amount of cooling water is supplied to both the upper and lower surfaces of the hollow plastic sheet molded product from a water supply groove provided near the contact point between the hollow plastic sheet molded product and the sizing plate. A water film is formed between the inner peripheral surface of the plate and the surface of the hollow plastic sheet molding, and on the take-up side of the sizing plate, negative pressure is applied to the suction slit, and the upper and lower liners are sucked under reduced pressure to the upper and lower sizing plate side. While sliding in the sizing plate, cooling to the upper and lower sizing plates Spray and promote cooling and solidification of the hollow plastic molded sheet, and a method for producing hollow plastic sheet characterized by performing the decompression and spray cooling water discharge at the same time.
After melt extrusion as a hollow plastic sheet molded product, immediately before being guided to the sizing plate, it is precooled with a gas such as air to lower the surface temperature of the melt extruded product, from the viewpoint of molding stability. Is more preferable.

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.
The method for producing a hollow plastic sheet of the present invention can be suitably used particularly for producing a hollow plastic sheet made of polypropylene resin.
For the purpose of enhancing the color pigment and rigidity, 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. Increasing the amount of filler added leads to high costs and specific gravity. Therefore, considering these balances, the amount added is 5 to 30% by mass in the case of talc and 20% in the case of calcium carbonate. It is preferable to be about% or less.
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.

  In addition, 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 sides of the upper and lower liners. A plastic sheet body may be coextruded into a plurality of layers.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention, this invention is not limited to these Examples at all.

As a plastic resin material, a polypropylene block copolymer [Grade name: E601, MI = 0.8 (g / 10 min)] containing 4% by mass of ethylene manufactured by Prime Polymer Co., Ltd., having a thickness of 1.5 mm and a basis weight of 250 g / The goal was to form a hollow plastic sheet with m ² and a 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 product width of about 100 mm by neck-in. This led to a sizing device which will be described in detail below.

The sizing plate of the sizing plate sizing device was made of brass (copper 70%, zinc 30%).
The sizing plate was composed of a first sizing plate (length 220 mm) on the entrance side and a second sizing plate (length 280 mm) on the take-up side.
The first sizing plate has a flange portion having a thickness of 40 mm and a length of 40 mm on the front end side, as shown as a lower plate in FIG. 3 (b), and from a water supply hole 3 b provided at the side end of the flange portion. A predetermined amount of cooling water is supplied to the four water supply grooves 3 through the water supply passages. The water supply grooves 3 are formed at a pitch of 5 mm from a position 15 mm from the entrance side end and a groove width of 1 mm over the width of 100 mm of the molded article running portion of the sizing plate. Further, the thickness of the rear plate is 5 mm, and four vacuum suction slits having a width of 1 mm and penetrating the entire thickness are provided at positions of 60 mm, 80 mm, 150 mm, and 210 mm from the entrance side.

The second sizing plate disposed downstream has a thickness of 5 mm, and slits having a width of 1 mm penetrating the entire thickness for vacuum suction were provided at positions of 80 mm, 140 mm, and 270 mm from the tip of the second sizing plate. The lower first and second plates are provided with a groove (passage) having a depth of 1.5 mm and a width of 100 mm through which the molded article travels.
The first and second sizing plates on the lower side have been described above. However, the upper sizing plate is also provided with a water supply groove and a vacuum suction slit at positions that are vertically symmetrical. However, the upper sizing plate is not provided with a groove (passage) having a depth of 1.5 mm and a width of 100 mm, on which the molded article travels, and has a flat surface, as shown in FIG. With the plate assembled, a 1.5 mm gap through which the molded article travels was formed. It should be noted that the travel groove having a depth of 1.5 mm is provided only in the lower sizing plate. If the travel grooves are provided in the upper and lower sizing plates, the groove is processed to a depth of 0.75 mm in each, so that 1 is provided on one side. This is because more man-hours are required than in the case of machining a 5 mm groove, and the machining cost is avoided.

Decompression Box The hollow plastic sheet sizing device of the present invention forms the depressurization box 20 as shown in the perspective view of FIG. 2 (a) when the hollow plastic sheet is continuously formed. In the embodiment of the present invention, the height (depth) is 350 mm, the width is 370 mm, the length (running direction of the molded product) is 980 mm, and the internal volume is about 127 liters. In the molding of the hollow plastic sheet, the molded product extruded from the die is supplied to the water supply groove through the open part of the molded product running passage of the decompression box, while being brought into contact with the lower sizing plate. It is led to the take-up device located at the rear, and is continuously run while taking it. Thereafter, the upper sizing plate is stacked on the lower sizing plate while supplying water to the water supply groove, and the sizing plate is assembled as shown in FIG.
Thereafter, the outlet shutter 16 is attached to the rear side plate, and the lid 13 is closed and fixed to form a sealed space as the decompression box 20. Although not shown, the side plate of the decompression box is provided with a window through which the inside can be seen with thick glass.
The width of the inlet 12 and the width of the outlet 16 do not necessarily coincide completely with the width of the molded product, and are slightly wider. Therefore, the gap is closed with a Teflon (registered trademark) sheet or the like, and pressure reduction is possible.
The decompression operation is configured such that the decompression / water suction port 15 is connected to a decompression tank (not shown), a vacuum pump is connected to the discharge side, and decompression and cooling water in the decompression box are performed.

Cooling water spray nozzles (manufactured by Miri no Ikeuchi: Part No. SSXPO40 1 / 4M) Cooling water spray devices 14a and 14b each having five nozzles are arranged above and below the sizing plate, and a predetermined amount of water can be supplied from a water pump not shown. It was.
In addition, the water supply grooves of the upper and lower sizing plates are configured so that a fixed amount of water can be supplied independently.
The cooling water temperature was 18 ° C. for the water supply groove and 18 ° C. for the cooling water spray device.

Examples 1 and 2
In the state where the molded product width was about 91 mm, the molded product 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, dimensions, and the like of the hollow plastic sheet. Since there is a gap of 70 to 80 mm between the die outlet and the sizing plate inlet, air at room temperature with an air volume of 462 L / min is directed from the slit-shaped outlet at a position of 50 mm above and below the extruded product to the molded product. After pre-cooling by spraying, it led to the sizing plate.
In addition, as for the fabric weight, 20 things of the magnitude | size of 5 cm x 5 cm were measured continuously, and the deviation R of the average and the maximum value and the minimum value was calculated | required.

As shown in Table 2, in Examples 1 and 2, the basis weight deviation R of the molded product is as small as 14 g / m ² and 16 g / m ^2, and the basis weight at a thickness of 1.5 mm in the conventional method is 250 g / m ^2. The result was inferior to the case of 8 m / min, which is the upper limit of the speed in the molding of the hollow plastic sheet. In the conventional molding method, the sizing plate is inserted through an aluminum sizing plate having a total length of about 1.5 m without a water supply groove or the like and without a water film interposed between the molded product and the sizing plate. The molded product is molded, cooled and solidified only by contact with a reduced pressure (300 mmH ₂ O) from the side and a sizing plate having a water-cooling pipe inside.

The sizing device for a hollow plastic sheet of the present invention is provided with a water supply groove in the vicinity of a contact point with a hollow extruded product, and the hollow extruded product is brought into direct contact with cooling water to start cooling and form a water film. Therefore, the water film acts as a lubricant and reduces the frictional resistance between the sizing device and the hollow plastic sheet. Therefore, the water film can be used as a sizing device that can greatly improve the production speed as compared with the prior art.
The sizing device for a hollow plastic sheet according to the present invention includes a process for providing a required number of water supply grooves in the vicinity of the inlet, a process for piping for supplying cooling water to the water supply grooves, and a slit-shaped transparent for vacuum suction to the sizing plate. Since the sizing plate body can be configured by machining that is equivalent to the process of providing holes, 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 sheet 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. It can be used as a sizing device for hollow plastic sheets that can reduce costs.
In addition, the method for producing a hollow plastic sheet of the present invention forms the hollow plastic sheet using the sizing device of the present invention, so that compared with the case of using a conventional device,
The speed can be increased by a factor of about 2, and it can be used as a highly productive method for producing a low-weight hollow plastic sheet suitable as a protective material or cushioning material.

(A) Explanatory drawing of the sizing apparatus of this invention, and a manufacturing method, (b) It is a cross-sectional view of the hollow plastic sheet obtained by the manufacturing method of this invention. (A) Front perspective drawing which shows the one aspect | mode of the sizing apparatus of this invention, (b) The entrance side side view. (A) The top view which shows the one aspect | mode of the sizing apparatus of this invention, (b) The top view of a lower sizing plate, (c) The assembly condition explanatory drawing of an up-and-down sizing plate. It is explanatory drawing of the conventional manufacturing method.

Explanation of symbols

D dice S hollow plastic sheet L liner R rib F former 1 sizing device 2 sizing plate 3 water supply groove 4 vacuum suction hole (slit)
12 Sizing Device Inlet 14 Cooling Water Spray Nozzle 15 Depressurization / Water Suction Inlet 16 Sizing Device Exit (Shutter)
20 Decompression box 50 Sizing block 51 Decompression line 52 Cooling piping

Claims (2)

A sizing device for a hollow plastic sheet comprising a metal sizing plate having a water supply groove and a slit-like decompression suction hole, and a decompression box surrounding the take-up side of the sizing plate,
The sizing plate is formed by connecting a plurality of upper and lower pairs of plates formed of a kind of brass or aluminum selected from seven-three brass, six-four brass, and free-cutting brass,
The water supply groove has a groove shape in the width direction of the hollow plastic sheet in the vicinity of the contact point with the melt-extruded hollow plastic sheet,
Said vacuum suction holes, the width direction of the hollow plastic sheet into a slit-shaped through holes like the receipt side, provided,
The vacuum box has a cooling water spray nozzle and a vacuum / water suction port ,
A sizing device for a hollow plastic sheet , wherein a water film can be formed between the inner peripheral surface of the sizing plate and the surface of the molded product of the hollow plastic sheet when the hollow plastic sheet is molded . A hollow plastic sheet molded product composed of parallel upper and lower liner parts and a plurality of ribs perpendicular or oblique thereto is melt extruded and then guided to a sizing plate, and provided in the vicinity of a contact point between the molded product and the sizing plate A predetermined amount of cooling water is supplied to the upper and lower surfaces of the hollow plastic sheet molded product to form a water film between the inner peripheral surface of the sizing plate and the surface of the hollow plastic sheet molded product. A negative pressure is applied to the slit and the upper and lower liners are slid in the sizing plate while sucking the upper and lower sizing plates under reduced pressure, while cooling water is sprayed on the upper and lower sizing plates to cool and solidify the hollow plastic sheet molded product. promote, and said reduced pressure is supplied from the water supply groove at the distal end of the sizing plate water Hollow plastic sheet manufacturing method of which is characterized in that the drainage of the fine spray cooling water at the same time through the vacuum and water suction port.

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