JPH08290455A - Die for molding inflation film - Google Patents

Abstract

PURPOSE: To control to equalize the dimension of an outlet gap in the circumferential direction and to make a resin flow rate in each part uniform by elastically deforming the lower inside part of a thickness adjustment ring by pushing it inward in the radial direction and installing a means for adjusting the passage width in the radial direction in the lower part of an extrusion passage. CONSTITUTION: A thickness adjustment ring 35 which is formed from a ring- shaped main body part 35a having an inside diameter equal to that of a die main body 32 and a skirt part 35b and in which the third groove 35c which extends upward and has a cross section of an inverted U-shape is formed in a part near the inside part of the main body 35a has a role to allow the elastic deformation of the lower part of an inlet gap adjustment part 35d in the radial direction. In order to form a tubular film with even thickness, since it is necessary to equalize the flow rate in each part in the circumferential direction of a resin discharged from an extrusion passage 39, when the flow rates in the parts in the circumferential direction are different, the inlet gap GIN of each part in the circumferential direction of the passage 39 is adjusted so that the resin flow rate in each part is controlled to be uniform.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die used for extrusion molding a tubular film by an inflation molding method.

[0002]

2. Description of the Related Art When a tubular film is formed from a thermoplastic resin by an inflation molding method, molten resin is continuously extruded through a die to form a resin bubble, and air is blown into the bubble. By appropriately expanding, a tubular film having a desired inner diameter is obtained. The formed tubular film is
It is cut to an appropriate length and the bottom is welded to be used as a shopping bag or the like, or the ears are cut off to form a sheet and used as a laminated film original fabric.

Here, a ring-shaped outer peripheral member (often called an uneven thickness adjusting ring) is arranged on the upper part of the die.
An inner peripheral member having an outer diameter slightly smaller than the inner diameter of the outer peripheral member is arranged inside the outer peripheral member. Between the inner peripheral surface of the outer peripheral member and the outer peripheral surface of the inner peripheral member, a cylindrical extruding passage extending in the vertical direction is formed, and by passing the resin from the lower portion to the upper portion of the extruding passage, a tubular film (resin Bubbles) can be extruded.

In such a die, the resin collectively supplied to the lower portion of the die is distributed to each portion in the circumferential direction in the lower portion of the extrusion passage through the distribution passage inside the die. However, if the flow rate of the resin distributed through each distribution passage is not uniform, the flow rate of the resin discharged from the extrusion passage is circular even if the radial width of the extrusion passage (hereinafter referred to as a gap) is the same in each portion in the circumferential direction. The thickness is not uniform at each portion in the circumferential direction, and the thickness of the formed tubular film becomes uneven at each portion in the circumferential direction, resulting in a large so-called uneven thickness. Therefore, the shape of the distribution channel is devised like a spiral die to make the flow rate of the resin distributed to each part of the extrusion passage in the circumferential direction as uniform as possible. Can not.

Therefore, it is necessary to make the resin flow rate in each portion in the circumferential direction uniform by partially controlling the flow rate of the resin discharged from the extrusion passage in each portion in the circumferential direction. A method is conceivable in which the gap of the passage can be changed in each part in the circumferential direction. Then, as the method, the entire outer peripheral member is moved in the radial direction with respect to the inner peripheral member to narrow or widen the upper and lower portions of the gap at each portion in the circumferential direction, or the upper portion of the outer peripheral member is radially expanded. Method of pushing inward in the direction to elastically deform and narrowing or widening only the gap at the exit of the extrusion passage (for example, Japanese Patent Laid-Open No.
162182).

[0006]

However, since the size of the exit gap of the extrusion passage is almost determined by the relationship with the type of resin used, the adjustable range is narrow and the circular shape is effective. In many cases, it is not possible to control the flow rate in each part in the circumferential direction. In particular, if the outlet gap is originally wide depending on the type of resin, fine adjustment of the flow rate may not be possible unless the outlet gap is adjusted significantly, and the desired flow rate control cannot be performed.

An external cooling device for air-cooling the respective circumferential portions of the resin bubble extruded from the extrusion passage from the outside is attached above the die (peripheral member). It is also important to suppress uneven thickness by making the temperature of each part in the directional direction uniform and expanding each part in the circumferential direction uniformly. For this purpose, it is desirable that the upper end surface of the outer peripheral member and the lower end surface of the external cooling device are in close contact with each other so that outside air does not enter the inside of the external cooling device and heat does not escape from the inside of the device. . However, in the case of adjusting only the outlet gap, a heat bolt or the like that pushes and moves the outer peripheral member may be present above the upper end surface of the outer peripheral member.In this case, the external cooling device should be directly attached to the outer peripheral member. However, there is a problem that it is difficult to bring them into close contact with each other.

Furthermore, if the dimensions of the outlet gap are not the same in the circumferential direction, the discharge velocity (flow velocity) from the outlet will be different even if the resin flow rate discharged from each portion in the circumferential direction is uniform. Also, uniform cooling and uniform expansion of each portion of the resin bubble in the circumferential direction by the external cooling device is hindered.

The present invention has been made in view of these problems, and it is possible to control the resin flow rate at each portion in the circumferential direction to be uniform while keeping the dimensions of the outlet gap the same in the circumferential direction. Moreover, it is an object of the present invention to provide an inflation film molding die in which an external cooling device can be attached in close contact with the upper end surface of the die.

[0010]

In order to achieve the above object, in the present invention, a ring-shaped outer peripheral member disposed on the upper part of the die and an inner peripheral member disposed inside the outer peripheral member are provided. A cylindrical extruding passage extending vertically is formed between the inner peripheral surface of the outer peripheral member and the outer peripheral surface of the inner peripheral member, and a tubular film is extruded from the lower portion of the extruding passage to the upper portion of the resin through the resin. In the inflation film molding die, the lower inner peripheral portion of the outer peripheral member is formed so as to be elastically deformable inward in the radial direction, and the lower inner peripheral portion is pressed radially inward to elastically deform to radially expand in the lower portion of the extrusion passage. A passage width adjusting means for adjusting the width (gap) is provided. In addition,
In order to elastically deform the lower inner peripheral portion of the outer peripheral member inward in the radial direction, it is preferable to form a groove that opens at the lower end surface of the outer peripheral member and extends in the circumferential direction. Further, the passage width adjusting means,
It is desirable to install at a plurality of locations along the outer circumference of the extrusion passage.

[0011]

In such an inflation film forming die, only the gap below the extrusion passage (hereinafter referred to as the inlet gap) can be changed by the passage width adjusting means. Here, unlike the exit gap, the entrance gap is not affected by the type of resin and can be changed in a wider range than the exit gap. Therefore, by adjusting the inlet gap, it is possible to effectively control the flow rate of the resin in that portion. In particular, when the outlet gap is wide, the inlet gap can be set to be narrower than the outlet gap in advance, and good flow control can be performed by slightly adjusting the inlet gap. Then, by disposing a plurality of passage width adjusting means along the outer periphery of the extrusion passage and adjusting the inlet gap of each portion in the circumferential direction, the discharge flow rate from each portion in the circumferential direction in the extrusion passage can be easily made uniform. it can.

Moreover, even if the inlet gap is changed, the outlet gap does not change. Therefore, even if the inlet gaps in the respective circumferential portions of the extrusion passage become uneven, the outlet gaps can be kept the same in the circumferential direction. it can. Therefore, the flow velocity of the resin discharged from the extrusion passage can be made uniform in each part in the circumferential direction, and each part in the circumferential direction of the resin bubble can be uniformly expanded.

Further, since the passage width adjusting means pushes and moves the lower inner peripheral portion of the outer peripheral member, the passage width adjusting means can be attached to a relatively lower portion of the outer peripheral member. Therefore, the external cooling device can be attached in close contact with the upper end surface of the outer peripheral member without the passage width adjusting means interfering. And these can make the uneven thickness of a tubular film (resin bubble) extremely small.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. First, FIG. 5 shows an inflation molding apparatus for a tubular resin film using a die (spiral die) according to the present invention. This apparatus is equipped with a hopper 1 into which a resin material (for example, a polyolefin resin) to be inflation-molded is fed, and an extruder 2a which is connected to the hopper 1 and melts and kneads the resin material to push it out to the spiral die 3. 2 and.

Here, the first embodiment of the spiral die 3 will be described in detail with reference to FIGS. The spiral die 3 includes a spiral nozzle 31 and a die body 3
2, an adjustment base member 33, an upper nozzle (“inner peripheral member” in the claims) 34, an uneven thickness adjusting ring (the same “outer peripheral member”) 35, a ring position adjusting bolt 36, and a heat bolt ( The same "passage width adjusting means").
The spiral nozzle 31 is composed of a body portion 31a formed in a truncated cone shape and a flange portion 31b projecting radially outward in the lower portion of the body portion 31a. A plurality of grooves (hereinafter referred to as spiral grooves) 31d spirally extending around the axis of the main body 31a are formed on the outer peripheral surface 31c of the main body 31a. These spiral grooves 31d are shown in FIG.
As shown in detail in FIG. 3, starting from a plurality of circumferential locations (10 locations in the figure) in the lower portion of the main body 31a, the main body 3
It extends to the upper part of 1a. Each spiral groove 31d has a U-shaped cross-sectional shape, and the depth thereof becomes shallower toward the upper portion of the main body 31a.

A resin inlet 31e having a required inner diameter is formed in the lower portion of the main body 31a at the center of the lower end surface, and the upper portion of the resin inlet 31e and the starting points of the spiral grooves 31d are formed. A plurality of distribution paths 31f connecting the parts are also formed. Further, the main body portion 31a is formed with a first air passage 31g which is open at the center of the upper end surface and the radial middle portion of the lower end surface and the outer peripheral surface of the flange portion 31b.

The die main body 32 is formed in a cylindrical shape having a required wall thickness (wall thickness), and is placed on the flange portion 31b of the spiral nozzle 31, and the flange portion 31b.
It is fixed to b with a plurality of bolts 41 at a plurality of circumferential positions. A spiral passage 38 is formed between the inner peripheral surface 32a of the die body 32 and the outer peripheral surface 31c of the spiral nozzle 31 facing the inner peripheral surface 32a. The spiral passage 38 has a distinct spiral shape in the lower portion because the outer peripheral surface 31c and the inner peripheral surface 32a are in close contact with each other, but the outer peripheral surface 31c becomes more distant from the inner peripheral surface 32a toward the upper portion. Get closer to the shape.

Further, as shown in detail in FIG. 3, the upper end surface of the die main body 32 has a first side from the outer side toward the inner side in the radial direction.
A horizontal plane 32b, a second horizontal plane 32c that is one step higher than the first horizontal plane, an inclined surface 32d that rises radially inward and upward at an angle of approximately 45 degrees from the second horizontal plane 32c, and an upper end of the inclined surface 32d. Third horizontal plane 32e extending horizontally
And the fourth horizontal plane 3 which is one step higher than the third horizontal plane 32e.
2f. At the top of the die body 32,
A first groove 32g having a U-shaped cross section, which is open at the inclined surface 32d and extends in a direction orthogonal to the inclination direction of the inclined surface 32d (extends radially inward and downward) is formed. The first groove 32g is formed in a ring shape extending in the circumferential direction of the die body 32.

Further, as shown in FIG. 4, the die main body 32
A plurality of second grooves 32h, which are open at the inclined surface 32d and the third horizontal surface 32e and are connected to the first groove 32g, are formed at a plurality of positions in the circumferential direction in the upper part of the. As a result, as shown in FIG. 3, the upper portion of the die body 32 is circumferentially provided at a plurality of positions in the circumferential direction, the upper portion of the inclined surface 32d, the third horizontal plane 32e, and the first horizontal plane 32e.
A portion (hereinafter, referred to as a pressure receiving portion) 32i surrounded by the upper inner surface of the groove 32g is formed. Further, at the upper part of the die body 32, through holes 32k obliquely extending so as to penetrate between the upper part of the outer peripheral surface of the die body 32 and the lower inner surface of the first groove 32g are provided at a plurality of positions in the circumferential direction (however, , At a position corresponding to the circumferential position of each pressure receiving portion 32i).

The adjustment base member 33 has a ring-shaped main body 33a and a lower end surface which is protruded radially outward from the vicinity of the outer periphery of the lower end of the main body 33a and is one step lower than the lower end surface 33c of the main body 33a. It is formed from the flange portion 33b. The lower portion on the inner peripheral side of the main body portion 33a is chamfered at an angle of 45 degrees.

The adjusting base member 33 thus formed
Is placed on the die main body 32 with the lower end surface 33c abutting the second horizontal surface 32c of the die main body 32, and the flange portion 33
b is fixed to the die main body 32 at a plurality of positions in the circumferential direction by bolts 42 (see FIG. 1). As a result, the lower end surface of the flange portion 33b has the first horizontal plane 3 of the die body 32.
2b, and the chamfered portion of the body 33a faces the inclined surface 32d of the die body 32. The inner end of the chamfered portion in the radial direction (that is, the inner end of the main body portion 33a) is the first groove 32.
located above the opening of g. Further, the upper end surface of the main body portion 33a has substantially the same height as the third horizontal surface 32e of the die main body 32.

As shown in FIG. 1, the upper nozzle 34 is a cylindrical member having an outer diameter substantially equal to the outer diameter of the upper end of the main body 31a of the spiral nozzle 31, and is placed on the upper surface of the main body 31a. At the same time, the bolts 43 are fixed to the main body 31a at a plurality of circumferential positions. The outer peripheral surface 34a of the upper nozzle 34 is formed in a shape in which the upper portion is slightly outward in the radial direction from the lower portion. Also,
A second air passage 34b is formed in the center of the upper nozzle 34 so as to pass through the upper nozzle 34 in the vertical direction.

The uneven thickness adjusting ring 35 is formed of a ring-shaped main body portion 35a having an inner diameter equal to that of the die main body 32, and a skirt portion 35b extending downward from the lower end of the outer peripheral portion of the main body portion 35a in a cylindrical shape. Has been done. Skirt part 3
The inner diameter of 5b is somewhat larger than the outer diameter of the main body portion 33a of the adjustment base member 33. A third groove (a “groove” in the claims) 35c having an inverted U-shaped cross-section that is opened at the lower end surface of the body portion 35a and extends upward is formed in a portion near the inner periphery of the body portion 35a. There is. This third groove 35
c has a ring shape extending in the circumferential direction of the ring body 35a. Due to the formation of the third groove 35c, a portion of the main body portion 35a radially inward of the third groove 35c (hereinafter, this portion is referred to as an inlet gap adjusting portion) 35d has a lower portion inward in the radial direction. It becomes easy to elastically deform so as to project. That is, the third groove 35c has a role of allowing elastic deformation (that is, movement) of the lower portion of the inlet gap adjusting portion 35d inward in the radial direction.

As shown in FIG. 1, the main body portion 3a is provided at a plurality of circumferential positions in the vicinity of the outer periphery of the main body portion 35a.
A through hole 35e is formed to penetrate 5a in the vertical direction. Further, bolt holes 35f penetrating the skirt portion 35b in the radial direction are formed at a plurality of positions in the circumferential direction of the skirt portion 35b.

The uneven thickness adjusting ring 35 formed in this way
3, the lower end surface of the inlet gap adjusting portion 35d is brought into contact with the fourth horizontal surface 32f of the die body 32 and is placed above the die body 32 and the adjustment base member 33, as shown in FIG. As a result, between the upper part of the outer peripheral surface 34 a of the upper nozzle 34 and the inner peripheral surface 35 g of the uneven thickness adjusting ring 35, a push-out passage 39 that extends vertically in a cylindrical shape is formed. Further, the inner peripheral surface of the skirt portion 35b is positioned so as to face the outer peripheral surface of the main body portion 33a of the adjustment base member 33.

As shown in FIG. 1, the uneven thickness adjusting ring 35 is connected to the adjusting base member 33 by screwing the bolt 44 inserted into the through hole 35e into the main body portion 33a of the adjusting base member 33. Here, since the through hole 35e has an inner diameter somewhat larger than the diameter of the bolt 44,
The uneven thickness adjustment ring 35 can move to some extent in the radial direction with respect to the adjustment base member 33 and the die main body 32 (until the inner peripheral surface of the skirt portion 35b contacts the outer peripheral surface of the main body portion 33a of the adjustment base member 33). it can.

Further, a ring position adjusting bolt 36 is screwed into the bolt hole 35f, and its tip has a skirt portion 35.
body part 33a of the adjustment base member 33 protruding inside b
Abut the outer surface of the. Therefore, when the ring position adjustment bolt 36 is rotated, the entire thickness of the uneven thickness adjustment ring 35 is reduced by the force received from the bolt 36, which is prevented from moving in the radial direction due to the contact with the outer peripheral surface of the adjustment base member 33. This allows the radial width (hereinafter, referred to as an outlet gap) GOUT (see FIG. 3) of the upper end outlet of the extrusion passage 39 to be set to be the same in the circumferential direction.

Further, as shown in detail in FIG. 3, heat bolts 37 are inserted into the through holes 32k of the die body 32 from the outer peripheral side of the die body 32. This heat bolt 37
Has a built-in heater, and expands in the axial direction by heating by this heater. The expansion amount is controlled by the amount of electricity supplied to the heater. Then, the heat bolt 37 has its tip protruding from the through hole 32k into the first groove 32g and further in contact with the pressure receiving portion 32i (the inner surface of the upper side of the first groove 32g), with the base portion positioned below the through hole 32k. It is screwed in and fixed to the die body 32. For this reason,
When the heat bolt 37 expands, the tip end thereof receives the pressure receiving portion 32.
i is pushed inward in the radial direction (the direction of arrow F in the figure), and the pressure receiving portion 32i further pushes the lower portion of the inlet gap adjusting portion 35d to move it inward in the radial direction. As a result, the gap (hereinafter referred to as the inlet gap) GIN at the lower part of the extrusion passage 39 can be narrowed. Even if the lower portion of the inlet gap adjusting portion 35d moves inward in the radial direction, the upper portion does not move, so the outlet gap GOUT of the extrusion passage 39 does not change.

When a tubular film is produced by using the spiral die 3 thus constructed, the spiral die 3 is heated to a required temperature by the band heater 46 attached to the outer circumference. At this time, it is desirable to make the temperature distribution of each part of the die 3 in the circumferential direction uniform. Then, the molten resin P supplied from the die joint 2b of the extruder 2 to the resin inlet 31e enters the lower end inlet of the extrusion passage 39 through the distribution passage 31f and each spiral passage 38, and further inside the extrusion passage 39. And flows as a tubular resin bubble 50 from the upper end outlet.

Here, as shown in FIG. 1, an air ring (external cooling device) 45 is attached on the die 3 (uneven thickness adjusting ring 35). The air ring 45 has an inner peripheral portion disposed near the outside of the upper end outlet of the extrusion passage 39, and concentrically arranged air outlets 45a and 45b are formed in the inner peripheral portion. ing. Air A for cooling each portion of the resin bubble 50 in the circumferential direction blows out from the air outlets 45a and 45b. Here, if a bolt or the like is projected above the upper end surface of the uneven thickness adjustment ring 35, the air ring 45 must be disposed apart from the uneven thickness adjustment ring 35, and the lower surface of the air ring 45 cannot be offset. From the gap between the meat adjusting ring 35 and the upper surface, the air ring 4
Outside air enters inside 5 and heat escapes, making it difficult to uniformly cool each portion of the resin bubble 50 in the circumferential direction.

However, in the die 3 of this embodiment, the bolt 4
3 and 44 are respectively buried in the upper nozzle 34 and the uneven thickness adjusting ring 35, and the ring position adjusting bolt 36 and the heat bolt 37 are located slightly below the upper end of the uneven thickness adjusting ring 35. Therefore, the lower end surface of the air ring 45 can be attached to the upper surface of the uneven thickness adjusting ring 35 so as to be in close contact therewith. Therefore, the attachment itself of the air ring 45 to the uneven thickness adjusting ring 35 can be easily performed, and the upper end surface of the die 3 and the air ring 4 can be easily attached.
It is possible to prevent the outside air from being sucked into the inner peripheral space of the air ring 45 through the gap between the lower end surface of the air bubble 5 and the inner peripheral space of the air ring 45, and to uniformly cool the respective circumferential portions of the resin bubble 50.

Air is blown into the resin bubble 50 cooled to an appropriate temperature by the air ring 45 through the first and second air passages 31g and 34b formed in the die 3. As a result, as shown in FIG. 5, the resin bubble 50 has its circumferential portions stretched in the circumferential direction and expanded, and the expanded bubble 50 is cooled as it progresses upward, and the tubular film 50 'and Become.

The tubular film 50 'is sandwiched between a pair of stabilizers 8 which are arranged in a V shape so as to face each other on the left and right and have a narrower space toward the upper part, and are folded into a sheet shape. It is pulled up by the take-up pinch roll 5 located above the stabilizers 8, 8.
Then, the tubular film (sheet) 50 'pulled up by the pinch roll 5 has a plurality of guide rolls 6a.
The winding shaft 7a of the winding device 7 while being guided by 6d.
It is rolled up.

Although inflation molding of the tubular film is performed in this manner, in order to mold the tubular film without uneven thickness, the flow rate of the resin discharged from the extrusion passage 39 in each portion in the circumferential direction is made uniform. There is a need. Therefore, when the flow rate in each part in the circumferential direction is different (when the formed film has uneven thickness), the amount of electricity supplied to each heat bolt 37 is controlled to control the inlet gap GIN of each part in the circumferential direction of the extrusion passage 39. Is adjusted so that the resin flow rate at each portion in the circumferential direction is controlled to be uniform. Here, the inlet gap GIN can be adjusted in a wide range regardless of the type of resin. Therefore, compared with the case of adjusting the outlet gap GOUT where the size is almost determined by the type of resin and the adjustable width is not so large, the resin flow rate at that portion can be controlled more effectively and easily. The resin flow rate in each part in the circumferential direction can be made uniform.

The outlet gap GOUT may be set wide depending on the type of resin. In this case,
As shown in FIG. 6, the inner peripheral surface 35 g of the uneven thickness adjusting ring 35
It is advisable that the lower part of the is pushed inward in the radial direction so that the inlet gap GIN becomes narrower than the outlet gap GOUT in advance. According to this, a good flow rate control effect can be obtained by only slightly adjusting the inlet gap GIN.

Further, as described above, if the outlet gap GOUT of the extrusion passage 39 is made to be the same in the circumferential direction by the ring position adjusting bolt 36, the resin whose flow rate is made uniform by adjusting the inlet gap GIN has a uniform flow velocity. Can be discharged. Therefore, the air ring 45 does not hinder the uniform cooling of each portion of the resin bubble 50 in the circumferential direction,
It is possible to uniformly stretch (expand) the respective parts in the circumferential direction, and it is possible to form a tubular film with less uneven thickness.

By the way, in the above embodiment, the die body 32 is
And the lower end surface of the uneven thickness adjusting ring 35 (the inlet gap adjusting portion 35d) are brought into contact with each other to push out the extrusion passage 39.
However, in addition to this, the extrusion passage 39 may be sealed by the method shown in FIG. In FIG. 3A, a surface 32f 'corresponding to the fourth horizontal surface 32f of the above embodiment is formed into a curved surface which is convex outward in the radial direction and upward, and this surface 32f' is formed in the inlet gap adjusting portion 3a.
It is in contact with the lower end surface of 5d. Further, in FIG. 7B, the surface 32 corresponding to the third horizontal surface 32e of the first embodiment.
Ring-shaped grooves facing each other are formed on the lower surfaces of e'and the gap adjusting portion 35d ', and O-rings 61 are fitted in both grooves. The point that the fourth horizontal surface 32f is brought into contact with the lower end surface of the gap adjusting portion 35d 'is the same as in the first embodiment.

Further, in FIG. 6C, the ring-shaped projection 62 having an inverted U-shaped cross section is formed on the surface 32e "corresponding to the third horizontal surface 32e of the first embodiment, while the gap adjusting portion 35d" is formed. A ring-shaped groove having an inverted U-shaped cross section is formed on the lower surface of, and the projection 62 is fitted into this groove. An escape groove 62a is formed in the lower portion of the outer periphery of the ring-shaped protrusion 62 to avoid interference with the outer peripheral side lower end of the ring-shaped groove. Also in this case, the fourth horizontal surface 32f is brought into contact with the gap adjusting portion 35d ″.

In the first embodiment, the heat bolt 37 is attached to the die body 32 of the spiral die 3, but the heat bolt 77 is attached to the uneven thickness adjusting ring 75 as shown in FIG. May be. Less than,
This will be described as a second embodiment. The die 70 shown in this embodiment has a spiral nozzle 71, a die body 72, and an upper nozzle 74, similar to the die 3 of the first embodiment. However, the adjustment base member used in the first embodiment is not provided, and the die main body 72 also serves as this. In addition,
Detailed description of the spiral nozzle 71, the die main body 72, and the upper nozzle 74 is omitted.

The uneven thickness adjusting ring 75 is formed of a ring-shaped main body portion 75a having an inner diameter equal to the inner diameter of the die main body 72, and a skirt portion 75b extending downward from the lower end of the outer peripheral portion of the main body portion 75a in a cylindrical shape. Has been done. Skirt part 7
The inner diameter of 5b is somewhat larger than the outer diameter of the uppermost portion of the die main body 72 (the portion having an outer diameter slightly smaller than the lower portion) 72a. In the vicinity of the inner circumference of the main body portion 75a, a groove having an inverted U-shaped cross section that opens at the lower end surface of the main body portion 35a and extends upward 7
5c is formed. This groove 75c is formed in the main body 75a.
Is formed in a ring shape extending in the circumferential direction of the main body 75a, and allows a lower portion of a portion (inlet gap adjusting portion) 75d radially inward of the groove 75c in the main body portion 75a to move radially inward by elastic deformation. Have a role.

A plurality of pressure receiving portions 75e are formed inwardly of the groove 75c at a plurality of circumferential positions on the radially outer side surface of the inlet gap adjusting portion 75d (the radially inner surface of the groove 75c). In addition, the lower end surface 75f of the inlet gap adjusting portion 75d including the pressure receiving portion 75e is formed in a curved surface shape protruding downward in the radial direction. Further, through holes 75k extending in the radial direction and opening at the outer peripheral surface of the main body 75a and the inner side surface of the groove 75c on the outer side in the radial direction are formed at a plurality of positions in the circumferential direction of the main body 75a.
Further, bolt holes 75f are formed at a plurality of positions in the circumferential direction of the skirt portion 75b so as to penetrate the skirt portion 75b in the radial direction.

The uneven thickness adjusting ring 75 formed in this way
Is placed above the die body 72 with the lower end surface 75f of the inlet gap adjusting portion 75d abutting on the upper end surface of the uppermost portion 72a of the die body 72. As a result, between the upper portion of the outer peripheral surface 74a of the upper nozzle 74 and the inner peripheral surface 75g of the uneven thickness adjusting ring 75, a cylindrical extrusion passage 79 extending in the vertical direction is formed. The inner peripheral surface of the skirt portion 75b faces the outer peripheral surface of the uppermost portion 32a of the die body 32.
The uneven thickness adjusting ring 75 is attached to the die main body 72 by a bolt 84 shown by a chain line in the figure in a state where the radial deviation is allowed.

Then, the ring position adjusting bolt 76 is screwed into the bolt hole 75f, and its tip comes into contact with the outer peripheral surface of the uppermost portion 32a of the die body 32. Therefore, if the ring position adjusting bolt 76 is rotated, the uneven thickness adjusting ring 75
Can be moved in the radial direction.

A heat bolt 77 is inserted from the outer peripheral side into each through hole 75k. This heat bolt 77
Has its tip protruding into the groove 75c, and the pressure receiving portion 75
While being in contact with the side surface of e, the base is screwed into the through hole 75k and fixed to the uneven thickness adjusting ring 75. Therefore, when the heat bolt 77 expands, the tip of the heat bolt 77 pushes the lower portion of the inlet gap adjusting portion 75d to move it inward in the radial direction (direction indicated by arrow F in the figure). As a result, the inlet gap GIN of the extrusion passage 79 can be narrowed. Even if the lower portion of the inlet gap adjusting portion 75d moves inward in the radial direction, the upper portion does not move, so the outlet gap GOUT does not change.

Also in the die 7 configured as described above,
Similar to the die 3 of the first embodiment, the ring position adjusting bolt 7
6, the radial position of the uneven thickness adjusting ring 75 can be adjusted so that the outlet gap GOUT of the extrusion passage 79 becomes the same in the circumferential direction. Also, optional heat bolt 77
By heating and expanding the resin, only the inlet gap GIN of the extrusion passage 79 can be changed to make the flow rate (and further the flow rate) of the resin uniform in the circumferential direction. Moreover, also in this embodiment, since the ring position adjusting bolt 76 and the heat bolt 77 are located below the upper end surface of the uneven thickness adjusting ring 75, the air ring 45 is brought into close contact with the upper end surface of the uneven thickness adjusting ring 75. Can be installed.

In each of the first and second embodiments, the case where the heat bolt is used as the passage width adjusting means has been described so that the inlet gap of the extrusion passage can be automatically controlled. Instead of the bolt, a bolt that is manually turned may be used. Further, in each of the above embodiments, the case where the spiral die is used has been described, but the present invention can also be applied to a circular die or a T die other than the spiral die.

[0047]

As described above, in the inflation film molding die of the present invention, only the lower gap (inlet gap) of the extrusion passage can be changed by the passage width adjusting means. Since the inlet gap is not so sensitive to the type of resin, it can be adjusted in a wider range than the outlet gap. Therefore, by using the present blown film molding die, the resin flow rate in that portion can be controlled more effectively than in the conventional die that adjusts the exit gap. By arranging a plurality of passage width adjusting means along the outer periphery of the extrusion passage, the discharge flow rate at each portion in the extrusion passage in the circumferential direction can be easily made uniform. Moreover, since the outlet gap does not change even if the inlet gap is changed, the outlet gap can be kept the same in the circumferential direction. Therefore, the flow velocity of the resin discharged from the extrusion passage can be made uniform, which is extremely effective in forming a film having less uneven thickness.

Further, the passage width adjusting means is attached to a relatively lower part of the outer peripheral member so that the lower inner peripheral part of the outer peripheral member can be pushed. Therefore, the external cooling device can be attached in close contact with the upper end surface of the outer peripheral member without the passage width adjusting means interfering. Therefore, the external cooling device can be easily attached to the die. Moreover, since such an attachment method prevents outside air from entering the inside of the external cooling device from between the external cooling device and the die, the resin by the external cooling device is coupled with the uniformity of the discharge flow rate / flow velocity. It is possible to reliably perform uniform cooling of each portion of the bubble in the circumferential direction, and it is possible to suppress the occurrence of uneven thickness of the film.

[Brief description of drawings]

FIG. 1 is a front sectional view of an inflation film molding die according to the present invention.

FIG. 2 is a plan view and a bottom view of the die.

FIG. 3 is a partially enlarged view of the die.

FIG. 4 is a partial plan view of a die body that constitutes the die.

FIG. 5 is a configuration diagram of an inflation molding device using the die.

FIG. 6 is a modified example of the uneven thickness adjusting ring forming the die.

7A to 7C are various examples of a contact seal portion between a die body and an uneven thickness adjusting ring that form the die.

FIG. 8 is a partial cross-sectional view of a second embodiment of a blown film molding die according to the present invention.

[Explanation of symbols]

3,70 Spiral die 31,71 Spiral nozzle 32,72 Die body 33 Adjustment base member 34,74 Upper nozzle (inner peripheral member) 35,75 Uneven thickness adjusting ring (outer peripheral member) 35c, 75c Groove 35d, 75d Inlet gap adjustment Part (lower inner peripheral portion of outer peripheral member) 36,76 Ring position adjusting bolt 37,77 Heat bolt 39,79 Extrusion passage

Claims (3)

[Claims] 1. A ring-shaped outer peripheral member disposed on an upper portion of a die, and an inner peripheral member disposed inside the outer peripheral member, wherein an inner peripheral surface of the outer peripheral member and an inner peripheral member of the outer peripheral member. An inflation film molding die for forming a cylindrical extrusion passage extending vertically with an outer peripheral surface, and extruding a tubular film through a resin from a lower portion to an upper portion of the extrusion passage, the lower portion of the outer peripheral member. The inner peripheral portion is formed so as to be elastically deformable radially inward, and the lower inner peripheral portion is pressed radially inward to elastically deform,
An inflation film forming die, characterized in that it is provided with a passage width adjusting means for adjusting a radial width in a lower portion of the extrusion passage. 2. A groove is formed in the outer peripheral member, the groove being open at the lower end surface of the outer peripheral member and extending in the circumferential direction to allow elastic deformation of the lower inner peripheral portion inward in the radial direction. The inflation film molding die according to claim 1, wherein 3. The inflation film molding die according to claim 1, wherein the passage width adjusting means is attached at a plurality of circumferential positions along the outer periphery of the extrusion passage.