JPWO2017150307A1 - Inflation film manufacturing method and inflation molding apparatus - Google Patents

Abstract

A novel method for producing an inflation film and an inflation molding apparatus capable of easily adjusting the uniformity of film thickness are provided. The method for producing an inflation film includes a bubble forming step of forming bubbles from a raw material resin, and a step of obtaining a film by forming the bubbles into a sheet, and in the bubble forming step, the bubble is contacted from the outside of the bubble, An expansion suppressing process capable of suppressing the expansion of the bubble is provided by the expansion suppressing structure for suppressing the expansion of the bubble. The inflation molding apparatus includes a bubble preparation unit that prepares a bubble from a raw material resin, and an expansion suppression structure that contacts the bubble from the outside of the bubble and can suppress the expansion of the bubble.

Description

  The present invention relates to an inflation film manufacturing method and an inflation molding apparatus.

  Of the film molding methods, the inflation molding method has been conventionally used because it has advantages such as simple equipment, inexpensive production of large amounts of film, and the like.

  However, while the inflation molding method has the advantages as described above, there is a problem that the thickness of the obtained film tends to be non-uniform.

  Patent Document 1 discloses that a uniform film can be obtained by adjusting the amount of air introduced into bubbles in the inflation molding method.

JP 2002-240147 A

  However, the inflation molding method as described in Patent Document 1 has room for improvement in terms of easily obtaining a uniform film.

  This invention is made | formed in view of the above situation, and it aims at providing the manufacturing method and inflation shaping | molding apparatus of a novel inflation film which can adjust the uniformity of the thickness of a film simply.

  The present inventors have found that in the method for producing an inflation film, the bubble diameter can be easily adjusted by arranging an annular member so as to contact the outside of the bubble, and the present invention has been completed. More specifically, the present invention provides the following.

(1) A method for producing an inflation film,
A bubble forming step of forming bubbles from the raw resin;
Obtaining a film by forming the bubble into a sheet,
A method for producing an inflation film, comprising: an expansion suppressing step of suppressing expansion of the bubble by an expansion suppressing structure that contacts the bubble from outside the bubble and suppresses expansion of the bubble in the bubble forming step.

  (2) The method according to (1), wherein the expansion suppression structure is arranged at a position that is point-symmetric with respect to the center of the bubble in a cross section in the width direction of the bubble.

  (3) The method according to (1) or (2), wherein the expansion suppression step includes an adjustment step of adjusting a distance from a center of the bubble of the expansion suppression structure.

(4) It further has a measuring step of measuring the bubble diameter downstream from the expansion suppressing structure or the film thickness of the film,
The method according to (3), wherein the adjustment step is performed based on a measurement result in the measurement step.

(5) An inflation molding device,
Bubble preparation means for preparing bubbles from the raw material resin;
An inflation molding device comprising: an expansion suppression structure that contacts the bubble from the outside of the bubble and is capable of suppressing expansion of the bubble.

  (6) The device according to (5), wherein the expansion suppression structure is arranged so as to occupy positions that are point-symmetric with each other with respect to a center of the bubble in a cross-section in the width direction of the bubble.

  (7) The device according to (5) or (6), wherein the expansion suppression structure is configured such that a distance from a center of the bubble is adjustable.

(8) a measurement unit capable of measuring a bubble diameter downstream of the expansion suppressing structure or a film thickness of the film;
The apparatus according to (7), further comprising adjustment means for adjusting a distance from a center of the bubble of the expansion suppression structure based on a measurement result in the measurement unit.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and inflation shaping | molding apparatus of a novel inflation film which can adjust the thickness uniformity of a film simply can be provided.

1 is a diagram showing an inflation molding device 10 according to an embodiment of the present invention. It is sectional drawing of the expansion suppression structure 11 which concerns on one Embodiment of this invention.

  Hereinafter, although embodiment of this invention is described, this invention is not specifically limited to this.

<Production method of blown film>
The method for producing an inflation film of the present invention includes a bubble forming step of forming bubbles from a raw material resin and a step of obtaining a film by forming bubbles into a sheet shape. There is an expansion suppressing step that suppresses the expansion of the bubble by the expansion suppressing structure that contacts and suppresses the expansion of the bubble. With this configuration, the present invention can easily adjust the uniformity of the film thickness. The “inflation film” refers to a film obtained by an inflation method.

<Bubble formation process>
A bubble formation process is a process of forming a bubble from raw material resin. “Bubble” refers to a cylindrical resin that is an intermediate of a film obtained by an inflation method.

  Formation of the bubbles from the raw material resin can be performed by a conventionally known method. For example, it can be obtained by melting and extruding the raw material resin, supplying a gas from the die to the extruded resin, and expanding it. Conditions for melting and extruding the raw material resin can be set according to a conventional method. Melting of the raw material resin can be performed at a temperature of 150 ° C. to 220 ° C., for example. The molten resin can be cooled, for example, by applying cooling air from above the die 16 to a bubble that expands in the width direction from the die 16 to be described later, and usually cooled to 80 ° C. to 120 ° C. Do. In the extrusion of the raw material resin, for example, the resin can be extruded to the outlet side of the die 16 by the force of the rotary screw in the extruder 15 described later. The raw material resin used for melting and extrusion may be pellets that have been once kneaded and extruded, or resin pellets may be directly charged and kneaded simultaneously with melting.

  Any material resin can be used as long as it is a resin used as a material for a conventional inflation film. Typically, polyethylene (high density polyethylene, low density polyethylene), polypropylene, polyester, styrene resin, or the like can be used. These may be used alone or in combination of two or more. In addition, inorganic powders (for example, calcium carbonate, calcium sulfate, barium sulfate, zinc oxide, kaolin, silica, talc, titanium dioxide, clay, silicon dioxide, bentonite, diatomaceous earth, etc.) may be added to the raw material resin.

(Expansion suppression process)
The method for producing an inflation film of the present invention includes an expansion suppressing step of suppressing bubble expansion by an expansion suppressing structure that contacts the bubble from the outside of the bubble and suppresses expansion of the bubble in the bubble forming step. In the present invention, the uniformity of the film thickness can be easily adjusted by this process.

  The expansion suppressing structure is configured to contact the bubble from the outside of the bubble and suppress the expansion of the bubble. As the expansion suppression structure, an expansion suppression structure in an inflation molding apparatus described later can be used.

  The position of the expansion suppressing structure is arranged so as to come into contact with the bubble from the outside of the bubble. Usually, with respect to the position in the bubble traveling direction d in FIG. It is carried out at a location where the length of the outer periphery in the width direction of the bubble becomes the target draw ratio. Since contact can be made at this point, expansion can be suppressed at a position corresponding to the target expansion degree of the bubble, so that expansion can be suppressed more accurately and a film having excellent thickness uniformity can be obtained. it can. In addition, “the length of the outer periphery in the width direction of the bubble” means the length of the outer periphery of the bubble that is the target for terminating the expansion in the width direction of the bubble, and “the target stretch ratio” The length of the outer periphery in the width direction of the bubble with respect to the length of the outer periphery of the resin when the resin starts to expand from the outlet side of the die (that is, the inner peripheral length L1 on the outlet side of the die in FIG. 1 described later) This means a percentage of the ratio (see L2 in FIG. 1 for details).

  Further, the “target draw ratio” can be replaced with “blow ratio”. The “blow ratio” is calculated by (bubble diameter) / (die diameter). As the blow ratio, the blow ratio used in the conventional inflation method can be used. For example, the blow ratio can be selected in the range of 1.1 to 3.0 according to the purpose. The diameter of the die and the lip width of the die can be appropriately set according to the purpose. For example, the diameter of the die can be 50 to 1000 mm, and the lip width is 0.5 to 1.5 mm. Can be used. The “lip” refers to a portion where the film comes out of the die, and the “lip width” is the thickness of the film as it comes out of the die.

  The position in the cross-section in the width direction of the bubble can be arranged based on the length from the center of the bubble at the position of the expansion suppression structure in the direction of bubble movement, but the position of the expansion suppression structure in the direction of bubble movement The position of the bubble in the cross-section in the width direction is closer to the target length of the bubble, the expansion of the bubble is suppressed, and the film is more excellent in uniformity of thickness by bringing the bubble closer to the target diameter more accurately Can be obtained. Therefore, it is preferable that the position in the cross-section in the width direction of the bubble at the position of the expansion suppressing structure in the bubble traveling direction is arranged at a target length from the center of the bubble.

  Moreover, it is preferable that the position in the width direction cross section of the bubble of an expansion suppression structure arrange | positions an expansion suppression structure in the position which is mutually point symmetrical with respect to the center of a bubble in the width direction cross section of a bubble. Thereby, since the force which suppresses expansion | swelling of a bubble applies to the outer side of a bubble equally, expansion | swelling of a bubble can be suppressed correctly. There may be one or a plurality of positions that are point-symmetric with respect to the center of the bubble. In addition, the expansion suppression structure may be a continuous annular structure, and the expansion of the bubble may be suppressed from the entire outside of the bubble, thereby suppressing the expansion of the bubble more accurately. From this, it is preferable that the expansion suppressing structure is a continuous annular structure.

  Further, the suppression of the expansion of the bubble of the present invention may be performed by further adjusting the pressure.

  The method for producing an inflation film of the present invention preferably includes an adjustment step of adjusting the distance from the center of the bubble of the expansion suppression structure in the expansion suppression step. The degree of suppression of bubble expansion can be arbitrarily adjusted by adjusting the distance from the center of the bubble of the expansion suppression structure.

  The adjustment in the adjustment step is preferably performed based on a measurement result in a measurement step for measuring a bubble diameter downstream of the expansion suppressing structure or a film thickness of the film, which will be described later. By measuring the bubble diameter downstream of the expansion suppression structure or the film thickness of the film, it is possible to know how uniform the thickness is, and based on the result, adjust the distance from the center of the expansion suppression bubble Thus, the thickness can be made more uniform. In addition, a bubble diameter refers to the diameter in the cross section of the width direction of a bubble.

  For example, the above measurement step may be performed continuously while always interlocking with the measurement result, the above adjustment step may be performed intermittently, and the above adjustment step may be performed each time, continuously. Alternatively, the adjustment step may be performed based on a change amount or an average value of the measurement value.

<Step of obtaining a film>
The manufacturing method of the inflation film of this invention has the process of making a bubble into a sheet form and obtaining a film.

  The method for forming the bubble into a sheet can be performed according to a conventional method, but it can be usually formed into a sheet by folding the bubble while winding it with a winder.

  The film thickness of produced films is often about 10 to 150 μm.

<Measurement process>
The manufacturing method of the inflation film of this invention may further have the measurement process which measures the bubble diameter downstream from an expansion | swelling suppression structure, or the film thickness of a film. As described above, the present invention includes a measurement process, and the film thickness can be made more uniform by performing the adjustment process.

  “The bubble diameter on the downstream side of the expansion suppression structure” refers to the bubble diameter on the side of the bubble progression direction (d in FIG. 1 described later) from the position of the expansion suppression structure. “Film thickness” refers to the thickness of a film obtained by forming the above-mentioned bubble into a sheet.

  The above measurement may be performed continuously or intermittently.

  The method for producing an inflation film of the present invention can be performed by an inflation molding apparatus of the present invention described later.

<Inflation molding device>
The present invention relates to an inflation molding apparatus comprising a bubble preparation unit that prepares a bubble from a raw material resin, and an expansion suppression structure that contacts the bubble from the outside of the bubble and can suppress expansion of the bubble. Include. Hereinafter, an inflation molding apparatus 10 which is one of the preferred embodiments of the present invention will be described.

  As shown in FIG. 1, the inflation molding apparatus 10 includes an expansion suppression structure 11 that can suppress expansion of the bubble 20, a measurement unit 12 that can measure the bubble diameter, a control unit 13, a hopper 14, an extruder 15, A bubble preparing means including a die 16, a guide 17, and a nip roll 18 are provided.

(Expansion suppression structure 11)
The expansion suppression structure 11 is configured to be able to suppress expansion of the bubble 20.

  The expansion suppressing structure 11 may be configured in any way as long as it is configured to be able to suppress the expansion of the bubble 20, but in the present embodiment, the control unit 13 expands based on the measurement result in the measuring unit 12. By adjusting the distance from the center of the bubble of the suppression structure 11, the expansion of the bubble 20 can be more accurately suppressed.

  The expansion suppressing structure 11 is provided outside the bubble 20. The position of the bubble 20 in the direction of travel d on the outside of the bubble of the expansion suppressing structure 11 is usually arranged at a position where the outer peripheral length L2 in the width direction of the bubble 20 is the target draw ratio.

  Regarding the position of the expansion suppression structure 11 in the width direction cross section of the bubble 20, the expansion suppression structure 11 is normally from the center of the bubble 20 in the width direction cross section of the bubble 20 at the position of the expansion suppression structure 11 in the traveling direction d of the bubble 20. It is arranged at the location of the target length.

  The expansion suppressing structure 11 is disposed so as to occupy positions that are point-symmetric with respect to the center of the bubble 20 in the cross-section in the width direction of the bubble 20. More specifically, in this embodiment, the expansion suppressing structure 11 has a continuous annular structure as shown in FIG.

  The expansion suppression structure 11 is configured such that the distance from the center of the bubble 20 of the expansion suppression structure 11 can be adjusted. Specifically, the distance from the center of the bubble 20 of the part 111 which contacts the bubble 20 is comprised so that adjustment is possible. An example of the expansion suppressing structure 11 is shown in FIG. The distance from the center of the bubble 20 of the expansion suppression structure 11 may comprise the expansion suppression structure 11 by a plurality of wings 115 as shown in FIG. In the expansion suppression structure 11, the distance from the center of the bubble 20 of the portion 111 that contacts the bubble 20 can be adjusted by a mechanism similar to the diaphragm mechanism of the lens of the camera using the pin 113 and the fulcrum 114. Further, the expansion suppressing structure 11 may use a belt structure capable of forming an annular structure (that is, a structure having a variable circumferential length similar to a belt used for body fastening).

  The length in the vertical direction of the expansion suppressing structure 11 (the length on the traveling direction d side of the bubble 20) is not particularly limited. However, the longer the length, the more preferable it is because it is possible to suppress excessive expansion of the bubble. Is the length to the position near the frost line of the bubble 20 (for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more of the distance from the die outlet to the frost line of the bubble 20; It is preferable to have a length such as 100%.

  The material of the expansion suppressing structure 11 is not particularly limited and can be appropriately selected according to the purpose and the type of the diameter adjusting mechanism of the expansion suppressing structure 11. For example, synthetic resin, metal, or the like can be used.

(Measurement unit 12)
The measurement unit 12 is configured to be able to measure the bubble diameter or the film thickness of the film on the downstream side (in the traveling direction d of the bubble 20) from the expansion suppressing structure 11. In the present embodiment, as shown in FIG. 1, the measurement unit 12 and the control unit 13 are configured to exchange signals with each other, and the measurement result of the bubble diameter is transferred from the measurement unit 12 to the control unit 13. Is output.

  The measurement unit 12 may be configured in any manner as long as it can measure the bubble diameter downstream from the expansion suppressing structure 11. In the present embodiment, as shown in FIG. 1, as shown in FIG. And a laser beam receiving opening 122 opposite to this. The laser beam emitting port 121 and the laser beam receiving port 122 are arranged opposite to each other so that the laser beam blocks the bubble 20, and the bubble diameter can be calculated by measuring the intensity of the blocked laser beam.

(Control unit 13)
The control unit 13 is configured to be controllable so as to adjust the distance from the center of the bubble 20 of the expansion suppression structure 11 based on the measurement result in the measurement unit 12. In the present embodiment, the control unit 13 is configured to exchange signals with the measurement unit 12 and the expansion suppression structure 11.

  As the control unit 13, for example, a personal computer or the like can be used.

(Hopper 14)
The hopper 14 is a portion into which the raw material resin for the bubble 20 is charged. As shown in FIG. 1, the hopper 14 is provided above the extruder. As the hopper 14, any one used in the conventional inflation method can be used. The same raw material resin as that used in the above-described method for producing an inflation film of the present invention can be used.

(Extruder 15)
The extruder 15 is a part that melts and extrudes the raw resin charged from the hopper 14. As shown in FIG. 1, the extruder 15 is provided below the hopper 14. As the extruder 15, any of those used in the conventional inflation method can be used. For example, the resin may be transferred to the outlet side of the die 16 by two rotating screws.

(Die 16)
As shown in FIG. 1, the die 16 is a part that is provided on the outlet side of the extruder 15 and expands the resin extruded from the extruder 15 by supplying gas. As the die 16, any of those conventionally used in the inflation method can be used. Further, in FIG. 1, the length of the inner periphery on the outlet side of the die 16 is L1.

  In the present embodiment, the bubble preparation means includes the hopper 14, the extruder 15, and the die 16.

(Guide 17)
The guide 17 is provided above the bubble 20 as shown in FIG. The guide 17 is used for the bubble to travel in the traveling direction d. As the guide 17, any of those conventionally used in the inflation method can be used.

(Nip roll 18)
The nip roll 18 is provided in the upper part of the guide 17 in order to take out the bubble 20 which expanded as shown in FIG. By controlling the rotational speed of the nip roll 18, the inside of the film can be made airtight.

(Other parts)
Although not shown in FIG. 1, the inflation molding apparatus 10 may further include a member used in a conventional inflation molding apparatus. For example, you may provide the cooling device of the bubble extruded from the die | dye 16, the winder for winding a film, etc.

(Usage method of the inflation molding apparatus 10)
The inflation molding apparatus 10 of the present invention can be used in accordance with a normal method of using an inflation molding apparatus. For the bubble 20, the measurement unit 12 measures the bubble diameter, and the measurement result is the control unit 13. Is output. The control unit 13 outputs a signal to the expansion suppression structure 11 so that the distance from the center of the bubble 20 becomes an optimum length according to the output measurement result, and the bubble of the expansion suppression structure 11 is output according to the output. The distance from the center of 20 is adjusted.

  The adjustment of the distance from the center of the bubble 20 of the expansion suppressing structure 11 may be performed by continuously measuring the bubble diameter and interlocking with the measurement. Alternatively, the measurement of the bubble diameter may be performed for a certain period of time. The bubble diameter may be periodically adjusted based on the change in the measured value of the bubble diameter, the average value, and the like.

(effect)
The inflation molding apparatus 10 as described above has the following effects.

  The inflation molding apparatus 10 includes a bubble preparation unit that prepares a bubble 20 from a raw material resin, and an expansion suppression structure 11 that contacts the bubble 20 from the outside of the bubble 20 and can suppress expansion of the bubble 20. . Thereby, in manufacture of an inflation film, the uniformity of the thickness of a film can be adjusted easily.

  The inflation molding device 10 is configured so as to occupy positions that are point-symmetric with respect to the center of the bubble 20 in the cross-section in the width direction of the bubble 20. Thereby, since the force which suppresses expansion | swelling of a bubble applies to the outer side of a bubble equally, expansion | swelling of a bubble can be suppressed correctly. More specifically, in the present embodiment, since the expansion suppressing structure 11 is a continuous annular structure, it is possible to accurately suppress bubble expansion.

  The expansion suppressing structure 11 is configured so that the distance from the center of the bubble 20 can be adjusted. Thereby, the degree of suppression of bubble expansion can be arbitrarily adjusted.

  Measuring unit 12 capable of measuring the bubble diameter or film thickness downstream of the expansion suppressing structure 11 and adjusting means for adjusting the distance from the center of the bubble 20 of the expansion suppressing structure 11 based on the measurement result in the measuring unit 12 And further comprising. Thereby, it is understood how much the bubble diameter downstream of the expansion suppressing structure 11 or the film thickness uniformity is, and the film thickness is adjusted by adjusting the diameter from the center of the bubble of the expansion suppressing structure based on the result. Can be made more uniform.

(Modification)
Although this embodiment described above is a preferable form, it can be suitably changed as needed.

  The inflation molding apparatus 10 includes the control unit 13, but is not limited thereto, and the bubble diameter can be adjusted based on the measurement result in the measurement unit by other means. For example, the measurement result may be adjusted so as to change the diameter of the expansion suppression structure 11 directly (manually) without using the control unit. Moreover, the diameter from the center of the bubble of the expansion suppression structure 11 may not be configured to be adjustable.

  In the inflation molding apparatus 10, the measurement unit 12 is configured to measure the bubble diameter using a laser beam, but is not limited thereto.

DESCRIPTION OF SYMBOLS 10 Inflation shaping | molding apparatus 11 Annular part 111 Contact part 113 Pin 114 Pedestal 115 Blade | wing part 12 Measuring part 121 Laser beam emitting port 122 Laser beam receiving port 13 Control part 14 Hopper 15 Extruder 16 Die 17 Guide 18 Nip roll 20 Bubble d Bubble progress Direction L1 Inner peripheral length L2 on the die outlet side Outer peripheral length in the width direction of the bubble

Claims (8)

A method for producing an inflation film,
A bubble forming step of forming bubbles from the raw resin;
Obtaining a film by forming the bubble into a sheet,
A method for producing an inflation film, comprising: an expansion suppressing step of suppressing expansion of the bubble by an expansion suppressing structure that contacts the bubble from outside the bubble and suppresses expansion of the bubble in the bubble forming step.   The method according to claim 1, wherein the expansion suppressing structure is disposed at a position that is point-symmetric with respect to a center of the bubble in a cross section in the width direction of the bubble.   The method according to claim 1, wherein the expansion suppression step includes an adjustment step of adjusting a distance from a center of the bubble of the expansion suppression structure. It further has a measurement step of measuring the bubble diameter downstream of the expansion suppression structure or the film thickness of the film,
The method according to claim 3, wherein the adjustment step is performed based on a measurement result in the measurement step. An inflation molding device,
Bubble preparation means for preparing bubbles from the raw material resin;
An inflation molding device comprising: an expansion suppression structure that contacts the bubble from the outside of the bubble and is capable of suppressing expansion of the bubble.   The apparatus according to claim 5, wherein the expansion suppressing structure is arranged to occupy positions that are point-symmetric with respect to a center of the bubble in a cross section in the width direction of the bubble.   The device according to claim 5 or 6, wherein the expansion suppressing structure is configured such that a distance from a center of the bubble is adjustable. A measurement unit capable of measuring a bubble diameter downstream of the expansion suppressing structure or a film thickness of the film;
The apparatus according to claim 7, further comprising: an adjusting unit that adjusts a distance from a center of the bubble of the expansion suppression structure based on a measurement result in the measurement unit.

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