JP6803618B2 - Inflation film manufacturing method and inflation molding equipment - Google Patents

Description

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

Among the film molding methods, the inflation molding method has been conventionally used because it has advantages such as simple equipment, low cost, and mass production of film.

However, while the inflation molding method has the above-mentioned advantages, 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 a bubble in the inflation molding method.

Japanese Unexamined Patent Publication No. 2002-240147

However, the inflation molding method as described in Patent Document 1 has room for improvement in that a uniform film can be easily obtained.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel method for producing an inflation film and an inflation molding apparatus capable of easily adjusting the uniformity of the thickness of the film.

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

(1) A method for manufacturing an inflation film.
The bubble forming process of forming bubbles from the raw material resin,
It has a step of forming the bubble into a sheet to obtain a film.
A method for producing an inflation film, which comprises an expansion suppressing step of suppressing the expansion of the bubble by contacting the bubble from the outside of the bubble and suppressing the 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 symmetrical with respect to the center of the bubble in the cross section in the width direction of the bubble.

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

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

(5) Inflation molding equipment
Bubble preparation means for preparing bubbles from raw resin,
An inflation molding apparatus comprising an expansion suppressing structure capable of contacting the bubble from the outside of the bubble and suppressing the expansion of the bubble.

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

(7) The apparatus according to (5) or (6), wherein the expansion suppression structure is configured so that the distance from the center of the bubble can be adjusted.

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

According to the present invention, it is possible to provide a novel method for producing an inflation film and an inflation molding apparatus capable of easily adjusting the uniformity of the thickness of the film.

It is a figure which shows the inflation molding apparatus 10 which concerns on one Embodiment of this invention. It is sectional drawing of the expansion suppression structure 11 which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not particularly limited thereto.

<Manufacturing method of inflation film>
The method for producing an inflation film of the present invention includes a bubble forming step of forming a bubble from a raw material resin and a step of forming a bubble into a sheet to obtain a film. In the bubble forming step, the bubble is formed from the outside of the bubble. It has an expansion suppression step that suppresses the expansion of the bubble by the expansion suppression structure that contacts and suppresses the expansion of the bubble. According to the present invention, the uniformity of the film thickness can be easily adjusted by such a configuration. The "inflation film" refers to a film obtained by the inflation method.

<Bubble formation process>
The bubble forming step is a step of forming bubbles from the raw material resin. "Bubble" refers to a cylindrical resin that is an intermediate in a film obtained by the inflation method.

The formation of 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 gas from the die to the extruded resin, and expanding the resin. Conditions for melting and extruding the raw material resin can be set according to a conventional method. The raw material resin can be melted, for example, at a temperature of 150 ° C. to 220 ° C. 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 described later, and is 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. Further, the raw material resin to be melted and extruded may be pellets that have been kneaded and extruded in advance, or the resin pellets may be directly added and kneaded at the same time as melting.

As the raw material resin, any resin used as a raw material for the conventional inflation film can be used. Typically, polyethylene (high density polyethylene, low density polyethylene), polypropylene, polyester, styrene resin and the like can be used. These may be used alone or in combination of two or more. Inorganic powder (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)
In the bubble forming step, the method for producing an inflation film of the present invention includes an expansion suppressing step of suppressing the expansion of a bubble by an expansion suppressing structure that contacts the bubble from the outside of the bubble and suppresses the expansion of the bubble. According to the present invention, the uniformity of the film thickness can be easily adjusted by such a step.

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

The position of the expansion suppression structure is arranged so as to come into contact with the bubble from the outside of the bubble, but with respect to the position in the traveling direction d of the bubble in FIG. 1 described later, the contact of the expansion suppression structure with the bubble is usually made. , It is performed at a place where the length of the outer circumference in the width direction of the bubble becomes the target stretching ratio. Since the contact is performed at this location, the expansion can be suppressed at the position at the target degree of expansion of the bubble, so that the expansion can be suppressed more accurately and a film having excellent thickness uniformity can be obtained. it can. The "length of the outer circumference in the width direction of the bubble" means the length of the outer circumference of the bubble that is the target for ending the expansion of the bubble in the width direction, and the "target stretching ratio" is , The length of the outer circumference in the width direction of the bubble with respect to the length of the outer circumference of the resin when the resin starts to expand from the outlet side of the die (that is, the length L1 of the inner circumference of the outlet side of the die in FIG. 1 described later). It means the percentage of the ratio (see L2 in FIG. 1 for details).

Further, the "target draw ratio" can be replaced with the "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, and for example, it can be selected in the range of 1.1 to 3.0 according to the purpose. The die diameter and the die lip width can be appropriately set according to the purpose. For example, a die diameter of 50 to 1000 mm can be used, and a die width of 0.5 to 1.5 mm can be used. Can be used. The "lip" refers to the portion where the film comes out of the die, and the "lip width" is the thickness of the film when it comes out of the die.

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

Further, the position of the expansion suppression structure in the width direction cross section of the bubble is preferably such that the expansion suppression structure is arranged at a position that is point-symmetric with respect to the center of the bubble in the width direction cross section of the bubble. As a result, the force for suppressing the expansion of the bubble is evenly applied to the outside of the bubble, so that the expansion of the bubble can be accurately suppressed. There may be one position or a plurality of positions that are point-symmetrical with respect to the center of the bubble. Further, the expansion suppression structure may be a continuous cyclic structure, and the expansion of the bubble may be suppressed from the entire outside of the bubble, whereby the expansion of the bubble can be suppressed more accurately. For this reason, the expansion suppressing structure is preferably a continuous cyclic structure.

Further, the suppression of the expansion of the bubble of the present invention may be further combined with the adjustment of 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. By adjusting the distance from the center of the bubble of the expansion suppression structure, the degree of suppression of bubble expansion can be arbitrarily adjusted.

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

For example, the above measurement may be continuously performed and the above adjustment step may be performed while always interlocking with the measurement result, or the above measurement may be performed intermittently and the above adjustment step may be performed each time. The target or intermittent measurement may be performed for a predetermined time, and the above adjustment step may be performed based on the amount of change or the average value of the measured value.

<Process to obtain film>
The method for producing an inflation film of the present invention includes a step of forming a bubble into a sheet to obtain a film.

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

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

<Measurement process>
The method for producing an inflation film of the present invention may further include a measuring step of measuring the bubble diameter or the film thickness on the downstream side of the expansion suppression structure. As described above, the present invention has a measuring step, and the film thickness can be made more uniform by performing the above adjusting step.

The “bubble diameter on the downstream side of the expansion suppression structure” refers to the bubble diameter on the side of the bubble traveling direction (d in FIG. 1 described later) from the position of the expansion suppression structure. The "film thickness" refers to the film thickness obtained by forming the above-mentioned bubbles 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 carried out by the inflation molding apparatus of the present invention described later.

<Inflation molding equipment>
The present invention provides an inflation molding apparatus, which comprises a bubble preparing means for preparing a bubble from a raw material resin and an expansion suppressing structure capable of contacting the bubble from the outside of the bubble and suppressing the expansion of the bubble. Include. Hereinafter, the 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 capable of suppressing the expansion of the bubble 20, a measuring unit 12 capable of measuring the bubble diameter, a control unit 13, a hopper 14, an extruder 15, and an extruder 15. A bubble preparing means composed of 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 capable of suppressing the expansion of the bubble 20.

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

The expansion suppression structure 11 is provided outside the bubble 20. The position on the traveling direction d side of the bubble 20 outside the bubble of the expansion suppression structure 11 is usually arranged at a position where the outer peripheral length L2 in the width direction of the bubble 20 becomes the target stretching 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 usually 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 placed at the target length of.

The expansion suppression structure 11 is arranged so as to occupy a position that is point-symmetric with respect to the center of the bubble 20 in the width direction cross section of the bubble 20. More specifically, in the present embodiment, as shown in FIG. 2, the expansion suppressing structure 11 has a continuous annular structure.

The expansion suppression structure 11 is configured so that the distance from the center of the bubble 20 of the expansion suppression structure 11 can be adjusted. Specifically, the distance of the portion 111 in contact with the bubble 20 from the center of the bubble 20 can be adjusted. An example of the expansion suppression structure 11 is shown in FIG. As shown in FIG. 2, the distance of the expansion suppression structure 11 from the center of the bubble 20 may be such that the expansion suppression structure 11 is composed of a plurality of vanes 115. In the expansion suppression structure 11, the distance of the portion 111 in contact with the bubble 20 from the center of the bubble 20 can be adjusted by using the pin 113 and the fulcrum 114 by a mechanism similar to the aperture mechanism of the lens of the camera. Further, the expansion suppression structure 11 may use a belt structure capable of forming an annular structure (that is, a structure having a variable circumference as in the case of a belt used for body tightening).

The length of the expansion suppression structure 11 in the vertical direction (the length on the d side of the bubble 20 in the traveling direction) is not particularly limited, but the longer the length, the more the bubble can be suppressed from being excessively expanded. Is the length to a position close to the frost line of bubble 20 (for example, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more of the distance from the outlet of the die to the frost line of bubble 20. It is preferable to have a length such as 100%).

The material of the expansion suppression structure 11 is not particularly limited and may be appropriately selected depending on the purpose and the type of the diameter adjusting mechanism of the expansion suppression structure 11, but for example, synthetic resin, metal or the like can be used.

(Measuring unit 12)
The measuring unit 12 is configured to be capable of measuring the bubble diameter or the film thickness on the downstream side (advancing direction d of the bubble 20) of the expansion suppressing structure 11. Further, in the present embodiment, as shown in FIG. 1, the measuring unit 12 and the control unit 13 are configured so that signals can be exchanged with each other, and the measurement result of the bubble diameter is transmitted from the measuring unit 12 to the control unit 13. It is output.

The measuring unit 12 may be configured in any way as long as the bubble diameter on the downstream side of the expansion suppression structure 11 can be measured, but in the present embodiment, as shown in FIG. 1, the laser beam emitting port 121 And, it is configured to have a laser beam receiving port 122 facing the laser beam receiving port 122. The laser beam outlet 121 and the laser beam light receiving port 122 are arranged so as to face 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 light.

(Control unit 13)
The control unit 13 is configured to be controllable so as to adjust the distance of the expansion suppression structure 11 from the center of the bubble 20 based on the measurement result of 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.

The control unit 13 can use, for example, a personal computer or the like.

(Hopper 14)
The hopper 14 is a portion where the raw material resin of 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. As the raw material resin, the same one used in the above-mentioned method for producing an inflation film of the present invention can be used.

(Extruder 15)
The extruder 15 is a portion for melt-extruding the raw material 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 one used in the conventional inflation method can be used, but for example, the resin may be configured to be able to be transferred to the outlet side of the die 16 by two rotary screws.

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

In the present embodiment, the bubble preparation means is composed of the above-mentioned hopper 14, extruder 15, and 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 guide conventionally used in the inflation method can be used.

(Nip roll 18)
The nip roll 18 is provided on the upper part of the guide 17 to take up the inflated bubble 20 as shown in FIG. The rotation speed of the nip roll 18 can be controlled to make the inside of the film airtight.

(Other parts)
Although not shown in FIG. 1, the inflation molding apparatus 10 may further include members used in the conventional inflation molding apparatus. For example, a cooling device for bubbles extruded from the die 16 or a winder for winding the film may be provided.

(How to use the inflation molding apparatus 10)
The inflation molding apparatus 10 of the present invention can be used according to a normal method of using the inflation molding apparatus, but the measuring unit 12 measures the bubble diameter with respect to the bubble 20, and the measurement result is the control unit 13. Is output to. 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 the optimum length according to the output measurement result, and the bubble of the expansion suppression structure 11 according to the output. The distance from the center of 20 is adjusted.

The distance from the center of the bubble 20 of the expansion suppression structure 11 may be adjusted by continuously measuring the bubble diameter and interlocking with the measurement, or by measuring the bubble diameter for a certain period of time. The bubble diameter may be adjusted periodically 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 preparing means for preparing the bubble 20 from the raw material resin, and an expansion suppressing structure 11 capable of contacting the bubble 20 from the outside of the bubble 20 and suppressing the expansion of the bubble 20. .. Thereby, in the production of the inflation film, the uniformity of the film thickness can be easily adjusted.

The inflation molding apparatus 10 was arranged so as to occupy a position symmetrical with respect to the center of the bubble 20 in the width direction cross section of the bubble 20. As a result, the force for suppressing the expansion of the bubble is evenly applied to the outside of the bubble, so that the expansion of the bubble can be accurately suppressed. Further, more specifically, in the present embodiment, since the expansion suppressing structure 11 has a continuous annular structure, the expansion of the bubble can be accurately suppressed.

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

A measuring unit 12 capable of measuring the bubble diameter or the film thickness on the downstream side of the expansion suppressing structure 11, and an adjusting means for adjusting the distance of the expansion suppressing structure 11 from the center of the bubble 20 based on the measurement result in the measuring unit 12. And, it was configured with further. As a result, the degree of uniformity of the bubble diameter on the downstream side of the expansion suppression structure 11 or the film thickness of the film can be found, and the film thickness can be adjusted by adjusting the diameter from the center of the bubble of the expansion suppression structure based on the result. Can be made more uniform.

(Modification example)
The present embodiment described above is a preferred embodiment, but can be appropriately modified as necessary.

The inflation molding apparatus 10 is configured to include the control unit 13, but is not limited to this, and the bubble diameter can be adjusted by other means based on the measurement result in the measurement unit. For example, from the measurement result, the diameter of the expansion suppression structure 11 may be adjusted to be changed directly (manually) without going through the control unit. Further, the diameter of the expansion suppression structure 11 from the center of the bubble does not have to be adjustable.

In the inflation molding apparatus 10, the measuring unit 12 is configured to measure the bubble diameter using a laser beam, but the present invention is not limited to this.

10 Inflation molding device 11 Circular part 111 Contact part 113 Pin 114 Support point 115 Blade 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 Length of inner circumference on the exit side of the die L2 Length of outer circumference in the width direction of the bubble

Claims (8)

Inflation film manufacturing method
The bubble forming process of forming bubbles from the raw material resin,
It has a step of forming the bubble into a sheet to obtain a film.
In the bubble forming step, there is an expansion suppressing step of suppressing the expansion of the bubble by the expansion suppressing structure that contacts the bubble from the outside of the bubble and suppresses the expansion of the bubble.
A method for producing an inflation film, wherein the expansion suppressing structure has an annular structure that continuously surrounds the outer periphery of the bubble, and the annular structure has a belt structure having a variable circumference and a cylindrical shape . The method according to claim 1, wherein the expansion suppression structure is arranged at a position symmetrical with respect to the center of the bubble in the cross section in the width direction of the bubble. The method according to claim 1 or 2, wherein the expansion suppressing step includes an adjusting step for adjusting the distance of the expansion suppressing structure from the center of the bubble. It further has a measuring step of measuring the bubble diameter on the downstream side 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 the measurement result in the measurement step. Inflation molding equipment
Bubble preparation means for preparing bubbles from raw resin,
It is provided with an expansion suppression structure capable of contacting the bubble from the outside of the bubble and suppressing the expansion of the bubble.
An inflation molding apparatus in which the expansion suppressing structure has an annular structure that continuously surrounds the outer periphery of the bubble, and the annular structure has a belt structure having a variable peripheral length and a cylindrical shape . The device according to claim 5, wherein the expansion suppression structure is arranged so as to occupy a position symmetrical with respect to the center of the bubble in the cross section in the width direction of the bubble. The device according to claim 5 or 6, wherein the expansion suppression structure is configured so that the distance from the center of the bubble can be adjusted. A measuring unit capable of measuring the bubble diameter or the film thickness on the downstream side of the expansion suppression structure,
The apparatus according to claim 7, further comprising an adjusting means for adjusting the distance from the center of the bubble of the expansion suppressing structure based on the measurement result in the measuring unit.

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