JP5946440B2 - Sheet manufacturing method and sheet manufacturing apparatus - Google Patents

Description

The present invention relates to a process for producing a sheet to a sheet of molten resin is cooled with water, apparatus for producing contact and sheet.

As a method for producing a transparent polypropylene resin sheet, a method is known in which a molten resin extruded from a die is rapidly cooled and then heat-treated.
For example, as a cooling method, a method for producing a transparent polypropylene resin sheet by rapidly cooling a molten resin with water and heat-treating the front and back of the obtained sheet has been proposed (see Patent Documents 1, 2, and 3). Actually, according to such a water cooling method, a highly transparent sheet can be produced at a high speed of 30 m / min or more. However, if water droplets remain on the sheet surface in the heat treatment stage after water cooling, there is a problem that the appearance of the sheet surface is partially deteriorated and the commercial value is lowered. Therefore, in order to avoid the influence of residual water droplets, the operation at a sheet conveying speed of about 10 m / min is unavoidable in practice, and there is still room for improvement in terms of improving production efficiency.

On the other hand, various techniques for removing water droplets on a plastic sheet or film surface have been proposed. For example, a rubber draining roll or a liquid draining roll has been proposed (see Patent Documents 4 and 5). These are methods for draining sheets and films by pinching various rubber rolls.
It has also been proposed to use a water absorption roll for removing water droplets (see Patent Document 6). In this technique, molten resin extruded from a die is rapidly cooled by a metal belt. As a method for rapidly cooling the belt, water droplets are spray-cooled on the back surface of the belt, and a water absorption roll is used to remove the water. Specifically, after a fine non-woven pad is wound around the surface of a hollow metal roll provided with a large number of small holes, it is brought into contact with the back of the belt, and a vacuum pump is connected to the hollow portion to actively absorb water. Is.
Furthermore, as a method for producing an embossed sheet, it has been proposed to use a hollow water-absorbing roll having a permeation hole connected to a decompression device in order to remove water droplets attached to the backup roll (see Patent Document 7).

Japanese Patent Publication No. 7-64008 Japanese Patent Publication No.62-41457 WO05 / 092593 JP 2004-109698 A JP 2003-321235 A Japanese Patent Laid-Open No. 11-314264 JP 2003-025432 A

However, in the methods of Patent Documents 4 and 5, in a sheet having a large variation in absolute thickness in the TD direction (for example, a sheet thickness of 200 μm or more), water leakage occurs at a portion where the thickness difference is large, and water droplets are completely removed. In addition to being unable to do so, there are problems such as impurities in water and effluent from the sheet accumulating on the rolls, resulting in damage to the surface of the product and contamination with foreign substances. Moreover, in the water absorption rolls in Patent Documents 6 and 7, when the operation is performed for a long time, impurities contained in the absorbed water are accumulated in the fine nonwoven fabric or in a large number of small holes, and the water absorption capability is reduced, so that the continuous operation is performed. There is a disadvantage that it is unsuitable. Further, when the resin is directly water-cooled, the eluate from the resin is mixed in water, which may promote clogging and reduce the water absorption capacity.
In addition, hot air drying ovens, air nozzles, draining with contact polyurethane sponge rolls, etc. have also been proposed, but hot air drying ovens are large and expensive, and water nozzles cannot be removed sufficiently with air nozzles or sponge rolls. There is a problem.

The present invention aims to provide a manufacturing apparatus for carrying out a method of manufacturing a sheet which a water droplet comprising the step of efficiently removing water droplets from the sheet adhering, a method for manufacturing a contact and sheet.

The present invention relates to a method for producing a sheet by water-cooling an extruded sheet-shaped molten resin, wherein the contact surface with the sheet is elastically deformable with respect to the surface of the sheet after the water-cooling A step of biasing the porous water-absorbing roll, and a position downstream of the water-absorbing roll in the rotational direction from the position of the water-absorbing roll biased by the sheet, and the water-absorbing roll from above the water-absorbing roll A squeeze for squeezing out moisture contained in the water absorption roll, the step of continuously dripping water with respect to the water, and a position downstream from the position where the water is continuously dripped in the rotation direction of the water absorption roll And a step of urging the roll to the water absorbing roll .
According to the present invention, since the porous water-absorbing roll whose contact surface with the sheet can be elastically deformed is urged against the surface of the sheet after water cooling, water droplets attached to the sheet surface can be efficiently removed.
And in the invention of this configuration, the water held in the water absorption roll is discharged downward when the water absorption roll is urged against the sheet and elastically deformed, and the sheet is separated from the water absorption roll upward and deformed. When the shape of the water-absorbing roll returns, the holes in the water-absorbing roll are opened and the water-absorbing ability is restored to remove water drops on the sheet surface. Therefore, the sheet conveyance speed can be increased, which greatly contributes to an improvement in sheet productivity.
Furthermore, in the invention of this configuration, since the squeezing roll is biased by the water absorbing roll, the water absorbed by the water absorbing roll can be squeezed out. Therefore, it is possible to improve the ability of the water absorption roll to absorb water and to maintain the water absorption power at a certain level or higher. The squeeze roll is preferably rotatable, and may be a free roll, for example.
The water that cools the molten resin web contains impurities, and there are also substances that elute from the cooled sheet surface. Therefore, if the sheet is manufactured for a long time, contaminants gradually accumulate in the holes of the water absorption roll. Will come to do. When this happens, it is necessary to stop the production of the sheet and replace or clean the water absorption roll.
According to the invention of this configuration, since water is constantly dripped onto the water absorption roll, in the squeezing roll, water is always pushed out from the inside of the water absorption roll, and the water absorption roll is automatically cleaned. .

In this invention, it is preferable that the said water absorption roll is a pair and each urges | biases the said water absorption roll with respect to the front side surface and back side surface of the said sheet | seat.
In the invention of this configuration, there are a pair of water-absorbing rolls, and each water-absorbing roll can be urged against the front side surface and the back side surface of the sheet.

In the present invention, it is preferable that the water-absorbing roll rotates at the same peripheral speed as the conveying speed of the sheet when urging the sheet.
When the sheet thickness is reduced, wrinkles and scratches are likely to occur due to slight tension applied to the sheet. However, in the invention of this configuration, the rotational peripheral speed of the water absorption roll is the same as the sheet conveyance speed, so the rotational load is Does not affect the tension of the sheet. Therefore, wrinkles and scratches are less likely to occur even with a thin sheet.

In this invention, it is preferable that the said water absorption roll consists of a porous elastic body comprised around the shaft center, and the said elastic body is a foam which has an open cell.
According to the invention of this configuration, since the water absorption roll is made of a predetermined foam, water droplets can be efficiently removed without damaging the sheet surface.

In this invention, it is preferable that the average diameter of the hole formed in the said porous elastic body is 130 micrometers or less, and the said hole is a continuous hole.
According to the invention of this configuration, since the average diameter of the holes formed in the porous elastic body is 130 μm or less, the sheet surface is hardly damaged. Further, the water droplets that remain slightly after passing through the water absorption roll are controlled to a level at which the water droplets are refined and immediately vaporized.

In the present invention, it is preferable that a pair of the water absorption rolls is provided so as to sandwich the water-cooled sheet.
In the invention with this configuration, a pair of water absorption rolls are provided so as to sandwich the water-cooled sheet, so that water droplets adhering to both surfaces of the sheet can be absorbed and removed simultaneously. Therefore, the removal process of adhering water can be made compact.

In this invention, it is preferable that the squeezing roll for squeezing out the water | moisture content contained in the said water absorbing roll is urged | biased by the lower part of the said water absorbing roll.
In the invention of this configuration, since the squeezing roll is biased to the lower part of the water absorbing roll, the water absorbed by the water absorbing roll can be squeezed out. Therefore, it is possible to improve the ability of the water absorption roll to absorb water and to maintain the water absorption power at a certain level or higher. The squeeze roll is preferably rotatable, and may be a free roll, for example.

In this invention, it is preferable that water is continuously dripped with respect to the said water absorption roll from the upper part of the said water absorption roll.
The water that cools the molten resin web contains impurities, and there are also substances that elute from the cooled sheet surface. Therefore, if the sheet is manufactured for a long time, contaminants gradually accumulate in the holes of the water absorption roll. become. When this happens, it is necessary to stop the production of the sheet and replace or clean the water absorption roll.
According to the invention of this configuration, since water is constantly dripped onto the water absorption roll, in the squeezing roll, water is always pushed out from the inside of the water absorption roll, and the water absorption roll is automatically cleaned. .

In the present invention, the relationship between the thickness (D1) of the elastic body portion in the water absorbing roll and the thickness (D2) of the elastic body portion when the water absorbing roll is urged to the surface of the sheet is expressed by the following formula (1). The value (compression rate) is preferably 1% or more and 50% or less.
((D1-D2) / D1) × 100% (1)
According to the invention of this configuration, the elastic body portion of the water absorbing roll is deformed so that the thickness of the elastic body portion when the water absorbing roll is urged to the sheet is a predetermined ratio with respect to the original thickness. Water droplets that are well attached to the sheet surface can be removed. If the value of the above formula is smaller than 1%, the water absorption effect may not be sufficiently exhibited. On the other hand, if the value of the above formula is larger than 50%, the elastic body of the water absorbing roll becomes hard and the sheet surface may be damaged, or the elastic recovery force of the elastic body may decrease and the water absorbing power may decrease.

In the present invention, it is preferable that after removing water droplets by the water absorption roll, air is blown onto both surfaces of the sheet by a draining nozzle disposed on both surfaces of the sheet to remove water droplets remaining on both surfaces of the sheet.
According to the invention of this configuration, after the water droplets are removed by the water absorption roll, air is blown onto both surfaces of the sheet by the draining nozzles arranged toward both surfaces of the sheet. Can be removed.

In the present invention, it is preferable to heat-treat the sheet with an endless belt heated after removing water droplets adhering to the sheet surface.
According to the invention of this configuration, since the sheet is heat-treated by the heated endless belt after removing water droplets adhering to the sheet surface, a heat-treated sheet free from a defective phenomenon due to water droplets can be obtained.

The present invention is a sheet manufacturing apparatus that forms a sheet by water-cooling a molten resin web, the sheet after water cooling is conveyed from below to above, and the sheet after water cooling is brought into contact with the surface of the sheet. An elastically deformable porous water-absorbing roll that rotates and positioned downstream of the water-absorbing roll in the rotation direction of the water-absorbing roll, and the water-absorbing roll from above the water-absorbing roll. A water supply device that continuously drips water to the roll, and a position downstream of the water supply roll in the rotational direction from the position where water is dropped by the water supply device, and is urged by the water absorption roll to the water absorption roll. A water droplet removing device having a squeezing roll for squeezing out contained moisture is provided.
According to the sheet manufacturing apparatus of the present invention, water droplets attached to the sheet surface can be efficiently removed by the elastically deformable porous water-absorbing roll that rotates in contact with the surface of the sheet after water cooling.
And in the invention of this configuration, the water held in the water absorption roll is discharged downward when the water absorption roll is urged against the sheet and elastically deformed, and the sheet is separated from the water absorption roll upward and deformed. When the shape of the water-absorbing roll returns, the holes in the water-absorbing roll are opened and the water-absorbing ability is restored to remove water drops on the sheet surface. Therefore, the sheet conveyance speed can be increased, which greatly contributes to an improvement in sheet productivity.
Furthermore, in the invention of this configuration, since the squeezing roll is biased by the water absorbing roll, the water absorbed by the water absorbing roll can be squeezed out. Therefore, it is possible to improve the ability of the water absorption roll to absorb water and to maintain the water absorption power at a certain level or higher. The squeeze roll is preferably rotatable, and may be a free roll, for example.
Further, according to the invention of this configuration, since water is constantly dripped to the water absorption roll, water is always pushed out from the inside of the water absorption roll in the squeeze roll, and the water absorption roll is automatically cleaned. Done.

In this invention, it is preferable that the said water absorption roll is a pair and urges | biases with respect to the front side surface and back side surface of the said sheet | seat.
In the invention of this configuration, there are a pair of water-absorbing rolls, and each water-absorbing roll can be urged against the front side surface and the back side surface of the sheet.

In this invention, it is preferable that the said water droplet removal apparatus is equipped with the control apparatus which controls the circumferential speed of the said water absorption roll so that it may become the same as the conveyance speed of the said sheet | seat.
According to this invention, since the water droplet removing device includes the control device that controls the peripheral speed of the water absorbing roll so as to be the same as the sheet conveying speed, the load of rotation of the water absorbing roll on the sheet is reduced. Never give.

Schematic of the sheet manufacturing apparatus according to the present embodiment. The enlarged view of the water droplet removal apparatus in embodiment of FIG. The enlarged view of the water droplet removal apparatus in other embodiment.

  Below, embodiment of this invention is described as a manufacturing method and its manufacturing apparatus of a transparent polypropylene resin sheet. In addition, as a manufacture example of the transparent polypropylene resin sheet by a water cooling system, there is description in WO05 / 092593.

[Polypropylene resin]
The polypropylene resin is preferably a highly crystalline polypropylene resin having an isotactic fraction of 0.85 to 0.99, preferably 0.88 to 0.99. If the isotactic fraction is within such a range, it is possible to form a sheet having excellent crystallinity, excellent tensile properties and impact resistance, and a good balance with transparency. On the other hand, if the isotactic pentad fraction is less than 0.85, the tensile modulus may decrease, and if the isotactic pentad fraction exceeds 0.99, The internal haze deteriorates and it is not preferable because it may be difficult to use as a transparent polypropylene sheet.

[Production equipment for transparent polypropylene resin sheet]
In FIG. 1, the manufacturing apparatus 1 of the transparent polypropylene resin sheet which concerns on this embodiment is shown.
This manufacturing apparatus 1 includes an extrusion apparatus 11 that melts and kneads a resin composition that is a raw material and extrudes it as a sheet-shaped molten resin 20a, and a first cooling apparatus 12 that cools and solidifies the extruded sheet-shaped molten resin 20a with water. The water droplet removing device 16 that removes water droplets from the sheet-like material (sheet 20) to which the water droplets are attached, the preheating device 13 that reheats the sheet 20 after the water droplets are removed, and the sheet 20 is heat-treated to produce a transparent polypropylene resin. A heat treatment device 14 serving as a sheet 21 and a second cooling device 15 for cooling the sheet after the heat treatment are provided.

The extrusion apparatus 11 includes an existing extruder 111 such as a single-screw extruder or a multi-screw extruder, for example, and a T-die 112 for forming a sheet at the tip of the extruder 111.
The first cooling device 12 includes a large water tank 120, a first roll 121 and a second roll 122 that sandwich the melt-extruded sheet-like molten resin 20 a disposed in the large water tank 120, and these rolls 121. , 122, the third roll 123 installed closer to the bottom surface of the large water tank 120, the fourth roll 124 provided near the periphery of the large water tank 120 on the preheating device 13 side, and the upper side of the large water tank 120. And a small water tank 125.

  With such a configuration, the sheet-like molten resin 20a extruded by the extrusion device 11 flows down through the slit together with the cooling water constantly supplied to the small water tank 125, and then the rolls 121, 122, 123 Along with the rotation, it is introduced into the large water tank 120, cooled and solidified to form a sheet 20.

A large amount of water droplets adheres to both surfaces of the sheet 20 discharged through the roll 124, and if the heat treatment is performed as it is, various defective phenomena are caused. Therefore, the water droplet removing device 16 removes water droplets from both surfaces of the sheet 20. There is a need to.
In FIG. 2, the water droplet removing device 16 includes a pair of water absorbing rolls 163A and 163 that urge the sheet 20 that has passed through the rolls 161 and 162 to rotate from the front and back.
The water absorption rolls 163A, B are made of a porous elastic body that can be elastically deformed, and are provided with hollow shaft centers 163A1, B1 at the center of rotation. This porous elastic body is a sponge-like elastic body having a large number of continuous pores, and a PVF (polyvinyl formal) foam is particularly preferable in terms of having fine pores.
The water-absorbing rolls 163 </ b> A and 163 </ b> B are controlled to drive at the same peripheral speed as the conveying speed of the sheet 20. However, as long as there is not much load of the water absorption rolls 163A and B and the sheet can be rotated at the same peripheral speed as the conveyance speed of the sheet 20, a free roll may be used.
The pores formed in the porous elastic body are continuous pores, and the average diameter is preferably 130 μm or less, and more preferably 60 μm or less.

  Under the water absorbing rolls 163A, B, squeezing rolls 164A, B for squeezing out the water contained in the water absorbing roll are urged. The squeezing rolls 164A and B are preferably rotatable, and may be controlled to be the same peripheral speed in synchronization with the peripheral speeds of the water absorbing rolls 163A and B, but may be free rolls.

Further, above the water absorption rolls 163A, B, water supply devices 165A, B that can continuously drop water to the water absorption rolls are provided.
Under the water absorption rolls 163A, B, water receiving trays 166A, B for receiving the water pushed out by the squeezing rolls 164A, B are provided.
The sheet 20 from which the water droplets have been removed is discharged through a roll 167.

The preheating device 13 is disposed at a position sandwiched between the first and third preheating rolls 131 and 133 provided in parallel at substantially the same height, and the preheating rolls 131 and 133, and is slightly shifted downward. The preheating roll 132 and the pressure auxiliary roll 134 whose peripheral surface is pressed and rolled by the third preheating roll 133 and sandwiches the sheet 20 from above and below are configured.
Thus, the cooled and solidified sheet 20 is brought into close contact with the peripheral surfaces of the preheating rolls 131, 132, and 133 and is preheated.

  The heat treatment apparatus 14 includes first, second, and third heating rolls 141, 142, and 143, a cooling roll 144, an endless belt 145, a pressure-contact auxiliary roll 146, and a peeling roll 147. The first and second heating rolls 141 and 142 and the cooling roll 144 are provided in parallel at substantially the same height, and the third heating roll 143 is provided in parallel immediately below the heating roll 142.

  The peripheral surfaces of the first to third heating rolls 141, 142, and 143 can be heated below the melting point of the polypropylene resin (for example, from about 100 ° C. to 160 ° C.) by an electric heater or steam. Yes. On the other hand, the cooling roll 144 has a structure in which cooling water or the like circulates and is cooled to a desired temperature.

The endless belt 145 is wound around the first and third heating rolls 141 and 143 and the cooling roll 144 so as to be disposed inside. Thereby, the endless belt 145 is stretched in a state where it is pushed in from the outside to the inside by the second heating roll 142.
The pressure auxiliary roll 146 is pressed and rolled from the upper side of the first heating roll 141 to the circumferential surface. The peeling roll 147 peels the sheet 20 from the endless belt 145 and is provided in the vicinity of the cooling roll 144 with a predetermined interval.

  The second cooling device 15 is provided in parallel at substantially the same height and cooled by the first, second, and third cooling rolls 151, 152, and 153, and the third cooling roll 153. It is comprised with the press-contact auxiliary | assistant roll 154 which is moved and pinches | interposes the sheet | seat 20. As shown in FIG.

[Method for producing transparent polypropylene resin sheet]
(Melting extrusion process)
The transparent polypropylene resin sheet 21 is manufactured by the manufacturing apparatus 1 described above. First, the raw material resin composition is melt-extruded into a sheet form from the T die 112 by the extrusion apparatus 11 to obtain a sheet-shaped molten resin 20a.

(First cooling step)
Next, the sheet-like molten resin 20a is introduced into the first cooling device 12 and cooled and solidified. That is, the melt-extruded sheet-shaped resin composition 20a flows down together with the cooling water that is constantly supplied to the small water tank 125, and is then guided into the large water tank 120, where the first roll 121 and the second roll 122 are introduced. And is sent to the third roll 123, and is led out of the large-sized water tank 120 by the fourth roll 124 to become a sheet (sheet 20).

(Water drop removal process)
Next, the sheet 20 is introduced into the water droplet removing device 16 (see FIG. 2). That is, the sheet 20 passes through the rolls 161 and 162 and is sandwiched (biased) between the pair of water absorption rolls 163A and 163B having the same peripheral speed as the conveyance speed, and the water droplets W present on both surfaces of the sheet 20 are removed. The Further, the water absorbed in the water absorbing rolls 163A, B is pushed out by the squeezing rolls 164A, B urged to the lower part of the water absorbing rolls 163A, B, and drops onto the water receiving trays 166A, B.
At this time, the relationship between the thickness (D1) of the elastic body portion in the water absorbing rolls 163A and B and the thickness (D2) of the elastic body portion when the water absorbing rolls 163A and B are biased to the surface of the sheet 20 is as follows. When represented by the formula (1), water droplet removal is performed under an urging condition such that the value (compression ratio) is 1% or more and 50% or less, preferably 5% or more and 30% or less.
((D1-D2) / D1) × 100% (1)
Moreover, water is continuously dripped at the water absorption rolls 163A and B from the water supply apparatuses 165A and B provided above the water absorption rolls 163A and B.
The sheet 20 from which the water droplets W on both surfaces have been removed by the water absorption rolls 163A and 163B is discharged through the roll 167.
Furthermore, the sheet 20 from which the water droplets have been removed is blown with air on both sides by a draining nozzle (air nozzle) (not shown), and the remaining water droplets are removed.

(Preheating process)
Next, the sheet 20 from which the water droplets have been removed is introduced into the preheating device 13 and preheated to a predetermined temperature. That is, the sheet 20 is guided from the fourth roll 124 to the upper peripheral surface of the first preheating roll 131, and above the third preheating roll 133 via the lower peripheral surface of the second preheating roll 132. It is sent to the peripheral surface and is sent out while being sandwiched by the pressure welding auxiliary roll 134.

(Heat treatment process).
Next, the preheated sheet 20 is introduced into the heat treatment apparatus 14 and heat treated, and the surface becomes smooth. That is, the sheet 20 is guided from the preheating roll 133 to the upper peripheral surface of the first heating roll 141, and is sandwiched and pressed together with the endless belt 145 by the pressing auxiliary roll 146, and is in close contact with the endless belt 145. The sheet 20 is guided to the lower peripheral surface of the second heating roll 142 together with the endless belt 145, and is pressed against the endless belt 145 again by the second heating roll 142.

  Subsequently, the sheet 20 is sent together with the endless belt 145 above the cooling roll 144, cooled by the cooling roll 144, guided to the peeling roll 147, and peeled from the endless belt 145. By these means, the sheet 20 is sufficiently pressed against the endless belt 145 and the roll 142 which are mirror-finished while being heated below the melting point of the polypropylene resin, and the pressed surface is mirror-transferred and smoothed. Become.

(Second cooling step)
Next, the heat-treated sheet 20 is introduced into the second cooling device 15 and cooled to a predetermined temperature. That is, the sheet 20 is guided from the peeling roll 147 to the upper peripheral surface of the first cooling roll 151 and is sent to the third cooling roll 153 via the lower peripheral surface of the second cooling roll 152. And press-contacted by the press-contact auxiliary roll 154.
The transparent polypropylene resin sheet 21 of this embodiment will be obtained by the above process.

According to the embodiment described above, the following effects can be obtained.
(1) Since the sheet 20 to which water droplets are attached is conveyed from below to above, and the water absorbing rolls 163A and 163B having the same peripheral speed as the conveying speed of the sheet 20 are further urged against the surface of the sheet 20, the sheet 20 Water droplets adhering to the surface can be efficiently removed. That is, the water held in the water absorption rolls 163A and B is discharged downward when the water absorption rolls 163A and B are urged and elastically deformed with respect to the sheet 20, and the sheet 20 is moved upward from the water absorption rolls 163A and B. When the deformed water-absorbing rolls 163A and 163 return to their shapes, the holes in the water-absorbing rolls 163A and B are opened, the water-absorbing ability is restored, and water droplets on the surface of the sheet 20 are removed. Therefore, the conveyance speed of the sheet 20 can be increased, and as a result, the productivity of the transparent polypropylene resin sheet 21 is greatly improved. In particular, when the sheet thickness is reduced, wrinkles are likely to occur due to adhesion of water droplets. However, in this embodiment, the rotational peripheral speed of the water absorption rolls 163A, B is controlled to be the same as the conveyance speed of the sheet 20, so Does not affect the tension of the sheet. Therefore, even if the sheet 20 is thin, wrinkles are unlikely to occur and long-term continuous operation is possible. And since the sheet | seat 20 is heat-processed with the heated endless belt 145 after removing the water drop adhering to the sheet | seat 20 surface, the transparent polypropylene resin sheet 21 without the defect phenomenon resulting from a water drop is obtained.

(2) Further, the thickness (D1) of the elastic body portion in the water absorbing rolls 163A, B and the thickness (D2) of the elastic body portion when the water absorbing roll is urged to the surface of the sheet are within a predetermined range. As a result, water droplets attached to the surface of the sheet 20 can be efficiently removed. When the value of the above formula is smaller than 1%, there is a possibility that the water absorption port cannot be sufficiently exhibited. On the other hand, if the value of the above formula is larger than 50%, the elastic body of the water absorbing roll becomes hard and the sheet surface may be damaged, or the elastic recovery force of the elastic body may decrease and the water absorbing power may decrease.

(3) Since the water absorption rolls 163A and B are made of an open cell foam of hydrophilic PVF, water droplets can be efficiently removed without damaging the surface of the sheet 20. In addition, since the average diameter of the holes formed in the foam is 130 μm or less, there is an effect that the surface of the sheet 20 is more difficult to be damaged.

(4) Since the water absorption rolls 163A and 163B are provided in a pair so as to sandwich the sheet 20 after water cooling, water droplets adhering to both surfaces of the sheet 20 can be simultaneously absorbed and removed. Therefore, the removal process of adhering water can be made compact.

(5) Since the squeezing rolls 164A and B are biased to the lower portions of the water absorbing rolls 163A and B, the water absorbed by the water absorbing rolls 163A and B can be squeezed out. Therefore, it is possible to improve the ability of the water absorption rolls 163A, B to absorb water, and to maintain the water absorption power at a certain level or higher. The squeezing rolls 164A, B are preferably rotatable, and may be free rolls, for example.

(6) The water that cools the molten resin sheet 20a contains impurities, and there are substances that elute from the surface of the cooled sheet 20. Therefore, if the production of the sheet is continued for a long time, the holes of the water absorption rolls 163A, B Contaminants gradually accumulate inside. In that case, it is necessary to stop the production of the sheet and replace or clean the water absorption rolls 163A and 163B. In the present embodiment, water is constantly dripped onto the water absorption rolls 163A, B by the water supply devices 165A, B, so that the water is always pushed out of the water absorption roll by the squeezing rolls 164A, B. The water absorption rolls 163A and 163B are automatically cleaned.

(7) In the present embodiment, after the water droplet removing device 16, air is blown onto both surfaces of the sheet 20 by a pair of draining nozzles provided on both surfaces of the sheet 20. It can be removed even better.

It should be noted that the present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the water droplet removing device 16 in the above embodiment, the pair of water absorbing rolls 163A and 163B are used. However, it is not always necessary to simultaneously remove the water droplets at the same location with the pair of rolls on the water-cooled sheet. For example, as shown in FIG. 3, the sheet 20 may be sandwiched by providing a water absorbing roll 163C on one surface side of the sheet 20 and providing metal or rubber guide rolls 167A, B, and C on the opposite side. There are no particular restrictions on the shape and number of guide rolls. By providing a similar process in which the positions of the water absorption roll and the guide roll are reversed after this process, the same effects as those of the above-described embodiment can be obtained.
The material of the water absorbing rolls 163A, B, and C is not limited to the crosslinked PVA foam, and may be a foamed material such as a thermoplastic resin or a thermoplastic elastomer as long as the water absorbing performance is high and the pores are fine.
In the present embodiment, a pair of draining nozzles is provided on both sides of the sheet 20 after the water droplet removing device 16, but it is not always necessary to provide sufficient water droplet removal. Further, a sponge roll such as PU (polyurethane) may be provided after the water droplet removing device 16 in order to further improve the draining ability.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by this. Specifically, a polypropylene resin sheet was produced under each condition using the production apparatus 1 shown in FIG. 1, and various evaluations were performed. In addition, the part except the water droplet removal apparatus 16 among the manufacturing apparatuses 1 in a present Example is based on the manufacturing apparatus of the polypropylene resin sheet described in WO05 / 092593.

[Examples 1 to 5]
Raw material: Polypropylene resin (Homotype, E103WA) made by Prime Polymer Co., Ltd.
Target sheet thickness: 300 μm
Water absorption roll (pair):
Roll diameter: 130mmφ
Material: PVF (polyvinyl formal) foam (open cell)
Foam thickness: 20mm
Average pore diameter of foam: 60 μm
Compression rate (%): 3, 5, 15, 30, 50
Water supply: Continuously supply water to the water absorption roll Squeeze roll (free roll): Energized against the water absorption roll PU (polyurethane) sponge roll: Installed after the water absorption roll Draining air (draining nozzle): Installed after the PU sponge roll Sheet conveyance speed (m / min): 18, 20, 20 or more, 20 or more, 16

Example 6
In Example 3, it implemented similarly except not providing a squeeze roll and driving a water absorption roll.

Example 7
In Example 3, it implemented similarly except not supplying water to a water absorption roll.

Example 8
In Example 3, it implemented similarly except having set the average hole diameter of the foam of the water absorption roll to 130 micrometers.

Example 9
In Example 3, it was carried out in the same manner except that the PU sponge roll was not provided and the average pore diameter of the foam of the water absorbing roll was 130 μm.

[Comparative Example 1]
In Example 1, it implemented similarly except not providing a water absorption roll, draining air, and PU sponge roll, and having made the sheet | seat conveyance speed into 10 m / min.

[Comparative Example 2]
In Comparative Example 1, the same procedure was carried out except that drained air and a PU sponge roll were provided.

[Comparative Example 3]
In Comparative Example 2, the same procedure was performed except that the sheet conveyance speed was set to 13 m / min.

[Comparative Example 4]
In Comparative Example 2, the same procedure was performed except that the sheet conveyance speed was set to 15 m / min.

[Comparative Example 5]
In Example 3, the same operation was performed except that the water absorption roll was not driven (free roll) and the sheet conveyance speed was 15 m / min. In this case, the squeeze roll became a load, and the peripheral speed of the water absorption roll was lower than the sheet conveyance speed.

[Evaluation Item / Evaluation Method]
The following items were evaluated, and the results are shown in Tables 1 to 3.

(1) Appearance of sheet About the sheet finally obtained, the appearance defect caused by water droplets remaining on the sheet was visually measured.
The evaluation criteria are as follows. However, the table shows the number of appearance defects actually observed.
Sheet 1m ² per 0.5mm ² less than the number of poor appearance 5 following: OK
6 or more: NG
-Number of appearance defects with a size of 0.5 mm ² or more per 1 m ^{2 of} sheet
0: OK
1 or more: NG

(2) Scratches on sheet surface For the finally obtained sheet, the number of scratches (pieces / m ² ) on the surface was visually measured and evaluated according to the following criteria.
A: None.
B: Several very thin fine scratches are observed.
C: 5 or less scratches of 0.5 mm ² or less are observed.
D: Six or more scratches of 0.5 mm ² or less, or scratches exceeding 0.5 mm ² are observed.
(3) Wrinkles at the time of sheet manufacture Evaluation was made according to the following criteria.
A: None.
B: There is some tarmi.
C: Although there is tarmi, it can be manufactured.
D: Wrinkles occur and cannot be manufactured.
(4) Days of continuous operation The number of days in which the above-mentioned “sheet appearance” is “OK” as the evaluation standard can be produced continuously and stably. When the continuous operation days were less than one day, it was determined as NG.

〔Evaluation results〕
From the results of Table 1, in the manufacturing method (manufacturing apparatus) of each example, each of which includes a predetermined water-absorbing roll, and the drive of the water-absorbing roll is controlled so as to have the same peripheral speed as the sheet conveyance speed. It can be seen that problems after the water droplet removal process do not occur and continuous operation for a long time is possible. In particular, continuous operation for 90 days or more is possible by supplying water droplets to the upper part of the water absorption roll.
On the other hand, in Comparative Example 1, no water-absorbing roll is used, and no draining air or PU sponge roll is installed, so the appearance of the sheet is poor and continuous operation is almost impossible. In Comparative Example 2, it is possible to operate for a long time only by installing draining air and a PU sponge roll and setting the sheet conveying speed to a low speed of 10 m / min. High speed operation as in the embodiment is impossible. In Comparative Examples 3 and 4 in which the sheet conveyance speed is increased as compared with Comparative Example 2, the continuous operation performance and the appearance of the sheet are deteriorated. Comparative Example 5 is a case where the driving of the water absorbing roll was stopped in Example 3, but the squeezing roll became a rotational load of the water absorbing roll and wrinkles were generated on the sheet. Also, continuous operation was almost impossible.

DESCRIPTION OF SYMBOLS 1 Manufacturing apparatus 11 Extrusion apparatus 12 1st cooling apparatus 13 Preheating apparatus 14 Heat processing apparatus 15 2nd cooling apparatus 16 Water drop removal apparatus 20 Sheet 20a Sheet-like molten resin 21 Transparent polypropylene resin sheet 111 Extruder 112 Die 120 Large water tank 121, 122, 123, 124 Roll 125 Small water tank 131, 132, 133 Preheating roll 134 Pressure auxiliary roll 141, 142, 143 Heating roll 144 Cooling roll 145 Endless belt 146 Pressure auxiliary roll 147 Peeling roll 151, 152, 153 Cooling roll 154 Pressure welding Auxiliary rolls 161, 162, 167 Rolls 163A, B, C Water absorbing rolls 163A1, B1, C1 Hollow shaft centers 164A, B, C Squeezing rolls 165A, B, C Water supply devices 166A, B, C Water receiving tray W Water droplets

Claims (12)

A method for producing a sheet by cooling the extruded sheet-shaped molten resin with water,
The sheet after water cooling is
Conveyed from below to above,
Urging a porous water-absorbing roll whose contact surface with the sheet is elastically deformable with respect to the surface of the sheet ;
From the position urged by the sheet in the water-absorbing roll, located downstream in the rotation direction of the water-absorbing roll, continuously dropping water from the upper part of the water-absorbing roll to the water-absorbing roll;
Biasing the squeezing roll for squeezing out the water contained in the water-absorbing roll from the position where the water is continuously dripped from the rotational direction of the water-absorbing roll; and The manufacturing method of the sheet | seat characterized by implementing . In the manufacturing method of the sheet | seat of Claim 1,
The water absorbing roll is a pair, and the water absorbing roll is biased against the front side surface and the back side surface of the sheet. In the manufacturing method of the sheet | seat of Claim 1 or Claim 2 ,
The water absorbing roll rotates at the same peripheral speed as the conveying speed of the sheet when biased to the sheet. In the manufacturing method of the sheet | seat of any one of Claim 1- Claim 3 ,
The water absorption roll is made of a porous elastic body formed around an axis,
The method for producing a sheet, wherein the elastic body is a foam having open cells. In the manufacturing method of the sheet | seat of Claim 4 ,
The average diameter of the hole formed in the said porous elastic body is 130 micrometers or less, The said hole is a continuous hole. The manufacturing method of the sheet | seat characterized by the above-mentioned. In the manufacturing method of the sheet | seat of any one of Claim 1- Claim 5 ,
A pair of the water-absorbing rolls is provided so as to sandwich the water-cooled sheet. In the manufacturing method of the sheet | seat of any one of Claim 1- Claim 6 ,
When the relationship between the thickness (D1) of the elastic body portion in the water-absorbing roll and the thickness (D2) of the elastic body portion when the water-absorbing roll is biased to the surface of the sheet is expressed by the following formula (1) Further, the value is 1% or more and 50% or less ((D1-D2) / D1) × 100% (1)
A method for producing a sheet characterized by the above. In the manufacturing method of the sheet | seat of any one of Claim 1- Claim 7 ,
After the removal of water droplets by the water absorbing roll, air is blown onto both surfaces of the sheet by a draining nozzle disposed toward both surfaces of the sheet, and water droplets remaining on both surfaces of the sheet are removed. Method. In the manufacturing method of the sheet | seat of any one of Claim 1- Claim 8 ,
A method for producing a sheet, comprising: heat-treating the sheet with a heated endless belt after removing water droplets adhering to the surface of the sheet. A sheet manufacturing apparatus for cooling a molten resin web to form a sheet,
The water-cooled sheet is conveyed from below to above,
An elastically deformable porous water-absorbing roll rotating in contact with the surface of the sheet after water cooling, and a position downstream of the water-absorbing roll in the rotational direction from a position of the water-absorbing roll biased by the sheet A water supply device that is positioned on the side and continuously drops water from the upper portion of the water absorption roll to the water absorption roll, and a position downstream of the water absorption roll in the rotation direction from the position where water is dropped by the water supply device. And a squeeze roll having a squeezing roll that urges the water-absorbing roll and squeezes out water contained in the water-absorbing roll . In the sheet manufacturing apparatus according to claim 10 ,
The sheet producing apparatus according to claim 1, wherein the water absorbing roll is a pair and urges the front side surface and the back side surface of the sheet. In the sheet manufacturing apparatus according to claim 10 or 11 ,
The water droplet removal device comprises:
A sheet manufacturing apparatus comprising: a control device that controls a peripheral speed of the water absorption roll so as to be equal to a conveying speed of the sheet.

Images