JPH11254503A - Die for forming inflation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inner cooling hole at an axial center without considerably increasing an outer diameter by providing a step between a surface for forming a branch part of a melted resin and a surface for forming a dispersing part in a lengthwise direction of the axial center. SOLUTION: The die 11 for forming an inflation film for forming a tubular film by extruding a melted resin 12 from a die lip L has a step between a surface for forming a branch part 13 of the resin 12 and a surface for forming a dispersing part 14 in a lengthwise direction of an axial center. The die 11 comprises therein a mandrel 21 having a cooling passage 20, an upper body 22 having a gap around the mandrel 21, an intermediate body 23, a lower body 24 and a regulating ring 25. A supply port 15 connected to an outlet of an extruder is provided on an outer periphery of the body 24. Since the part 13 and the part 14 are formed in two-stage constitution, its outer diameter is reduced, and its weight can be decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a blown film forming die for forming a tubular film.

[0002]

2. Description of the Related Art Various methods for forming a blown film for forming a tubular film have been conventionally proposed. When extruding a tubular film from thermoplastic resin by inflation molding method,
The molten resin is continuously extruded through a die to form a resin bubble, and a certain amount of air is injected into the bubble and expanded as appropriate, or a cooling air is blown into the bubble to discharge air of a colleague. As a bubble having a desired size in a cooling system, it is cooled with cooling air from outside to form a tubular film.

FIG. 6 shows an example of an apparatus for producing a blown film. As shown in FIG. 6, the blown film device is connected to an extruder 101 that uniformly melts and extrudes the resin, and an outlet of the extruder 101,
An air ring 104 for cooling an inflation film 103 discharged from a die 102 for discharging a molten resin into a cylindrical shape, a take-off device 105 for drawing the inflation film 103 while flattening the same, and a winding for winding the flattened inflation film 103. It is constituted by a take-off machine 106. Then, the raw resin supplied from the hopper 107 of the extruder 101 is
1 and is discharged into the die 102 from the discharge port. This molten resin is discharged from the die 102 as an inflation film 103,
Cooled by the cooling air blown out from
It is guided while being flattened by the guide member 108 of the take-up device 105, taken up by the roller 109, and taken up by the take-up device 106.
Has been wound up.

FIGS. 7 and 8 show an example of a die used in the above apparatus. The die 01 shown in these drawings is:
The molten resin 03 is supplied to a resin supply port 02 provided at the axis of the diameter of the die lip L, and a branch portion 0 formed outward is formed.
4, the molten resin is guided to a plurality of resin conduits 05 formed in a spiral shape, dispersed outwardly, and discharged by a die lip L (Japanese Patent Laid-Open No. 57-173139). Gazette). Reference numeral 06 in the drawing indicates a cooling hole.

FIGS. 9 and 10 show an example of another die.
The die 07 shown in these drawings supplies a molten resin 02 to a resin supply port 08 provided on the outer side of the die, and branches into two, four, and eight branches 09 toward the axis. , And further dispersed at the dispersion portion 010 on the axial center side, so that the ink is discharged from the die lip L.

[0006]

However, in the prior art method shown in FIGS. 7 and 8, since the molten resin 02 is supplied to the supply port 01 provided at the shaft center, the inflation of the internal cooling system is performed. Since cooling holes required for molding cannot be provided in the shaft center portion, and cooling is performed by opening a plurality of small cooling holes 06 around the shaft,
There is a problem that the internal cooling device becomes complicated, the cross-sectional area of the cooling air passing therethrough is reduced, and only a small amount of cooling air can flow.

[0009] In other dies shown in FIGS. 9 and 10, although an internal cooling passage can be provided in the axial center portion, a branch portion 09 of the molten resin 02 supplied from a supply port 07 provided in the outer peripheral portion is provided. And the dispersion portion 010 are provided outside and inside the same plane, so that the die lip L
Is arranged. For this reason, there is a problem that the die has a very large outer shape with respect to the diameter of the die lip L, the volume ratio occupied by the device increases, and the device becomes large.

In view of the above problems, the present invention is intended for forming a single-layer or multilayer blown film in which the outer diameter does not become much larger than a desired die lip diameter and an internal cooling hole can be provided in the shaft center. The purpose is to provide a die.

[0009]

According to a first aspect of the present invention, there is provided a blown film forming die for branching and dispersing a molten resin supplied from an extruder, and discharging the molten resin from a die lip. An inflation film forming die for forming an extruded tubular film, wherein the surface forming the branch portion of the molten resin and the surface forming the dispersion portion are provided with a step in the longitudinal direction of the axis. Features.

[0010] According to a second aspect of the present invention, in the blown film forming die according to the first aspect, the supply port of the molten resin supplied from the extruder is provided at a position other than the axis and is provided at the branch portion. It is characterized in that the resin hole is gradually branched into a plurality of holes from the side closer to the axis toward the outside.

The blown film forming die of claim 3 is characterized in that, in claim 1, spiral grooves are provided on both upper and lower surfaces of the dispersion portion, and a partition plate is provided between the spiral grooves. And

[0012] A fourth aspect of the present invention is directed to a blown film forming die, wherein the die of the first aspect is combined in a plurality of stages to form a multilayer film.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

<First Embodiment> FIGS. 1 to 3 show a blown film forming die according to the present embodiment. As shown in these drawings, the die 1 of the present embodiment is
1 is to branch and disperse the molten resin 12 supplied from the extruder 101 (see FIG. 6) in a plane substantially perpendicular to the axis of the diameter of the die lip L, and extrude the molten resin 12 from the die lip L into a tube. Film forming die for forming a film 103 (see FIG. 6), wherein the surface forming the branch portion 13 of the molten resin 12 and the surface forming the dispersing portion 14 extend in the longitudinal direction of the axis. And a step is provided. This die is used for the extruder 1
The supply port 15 for the molten resin 12 supplied from the cylinder 01 is provided at a position other than the axis.
Each time it branches into four, eight, and eight lines, it is a multiple and is branched.

As shown in FIG. 6, the die according to the present embodiment is connected to the outlet of an extruder 101 of a blown film device and is used as a die 102 for discharging a molten resin into a cylindrical shape. Details of the die according to the present embodiment will be described with reference to FIGS.
The die 11 according to the present embodiment includes a mandrel 21 having a cooling passage 20 therein, a cylindrical upper main body 22 provided with a gap therearound, an intermediate main body 23, a lower main body 24, and an adjustment ring 25. And is composed of
A supply port 15 connected to an outlet of the extruder is provided on an outer peripheral portion of the lower main body 24. In the present embodiment,
A resin hole 16 extends substantially horizontally in the axial direction from a supply port 15 provided in the outer peripheral portion of the lower main body 24, and further extends in a direction orthogonal to the horizontal direction toward the intermediate main body 23.
At the mating surface of the lower main body 24 and the intermediate main body 23, the resin holes 16
As shown in FIG. 2, while moving outward from the axis side,
Each time the branch is made, the branch is made in multiples of two, four, and eight, and the resin holes 16a to 16h are finally arranged near the outer periphery. Branched resin holes 16a-16
h communicates with the dispersing portion 14 of the mating surface of the book body 23 and the upper body 22. The dispersing part 14 has a spiral groove 1
7 and a gap G are formed, and the molten resin 12 is uniformly dispersed in the circumferential direction. As a result, the molten resin 12 supplied from the supply port 15 is once supplied in the axial direction, and then branched by the branch portion 13 provided in the intermediate main body 23, and the eight resin holes 16a to 16 arranged in the vicinity of the outer periphery. From 16h, it is introduced into the dispersion unit 14, where it is dispersed by the spiral groove 17 and the gap G, supplied to the die lip L, and discharged to the outside here. The spiral groove 17 may be formed in either the intermediate main body 23 or the upper main body 22.

In this embodiment, the branching unit 13 and the dispersion unit 1
4 has a two-stage configuration, so that the outer diameter can be reduced and the weight can be reduced.

In this embodiment, the branching section 13 and the dispersion section 14 are branched and dispersed in a substantially horizontal direction. However, the present invention is not limited to this. Oblique direction (for example, 4
(5 ° angle) and reducing the diameter of the apparatus main body can further reduce the weight.

<Second Embodiment> FIG. 4 shows a die according to a second embodiment. As shown in FIG. 4, a spiral groove 17 having an upper surface opening is formed in the intermediate body 23, and a spiral groove 18 having a lower surface opening is formed in the upper body 22. Spiral groove 1 of both
A separator plate 19 is interposed between 7 and 18. Incidentally, G ₁ and G ₂ illustrates a gap. In the present embodiment, since the opposed dispersion portions including the spiral grooves 17 and 18 with the separator plate 19 interposed therebetween are provided, the effect of dispersing the molten resin 12 in the circumferential direction on the axial center side is doubled.
The molten resin is more uniformly dispersed.

<Third Embodiment> FIG. 5 shows a die according to a third embodiment. As shown in FIG. 5, the die 31 according to the third embodiment has a two-stage structure including a branch portion 13 formed in the lower main body 24 and a dispersion portion 14 formed in the intermediate main body 23 as shown in FIG. A plurality of stages (three stages in the present embodiment) I, II, and III are provided and joined immediately before the lip L to form a die for a multilayer film. What is necessary is just to make it overlap according to the number of laminations suitably.
Also in this case, the diameter of the device can be reduced by dispersing the diagonal portion and the dispersing portion not in the horizontal direction but in the oblique direction, and the weight can be further reduced.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below.
The present invention is not limited to this.

(First Embodiment) A die having a lip diameter of 200 mm as shown in FIGS. 1 to 3 was used. As a comparison, a blown film was formed at a throughput of 120 kg / Hr using a conventional die as shown in FIGS. 9 and 10, a weight, a length of a branch passage, and LLDPE (linear low density polyethylene) as raw materials. The resin pressure loss at the branch portion and the thickness accuracy of the film were compared. The results are shown in Table 1 below.

(Second Embodiment) Using a die having opposed dispersion portions as shown in FIG. 4, the same operation as in the first embodiment was performed, and the resin pressure loss at the branch portion and the film thickness accuracy were compared. did. The results are shown in Table 1 below.

[0023]

[Table 1]

(Third Embodiment) As shown in FIG. 1, the branch and dispersion paths of the die are inclined at 45 degrees, and the same operation as in the first embodiment is performed. The resin pressure loss and the film thickness accuracy were compared. The results are shown in Table 1 below.

From the results shown in Table 1, according to the first embodiment, the outer diameter was reduced and the weight was significantly reduced. Further, the length of the branch passage is greatly reduced, and the pressure loss is reduced by about 2
/ 3. In addition, according to the second example, it was found that the dispersion efficiency was improved, so that the thickness accuracy of the molded film was improved. Further, according to the third embodiment, it was found that the outer diameter can be further reduced, which contributes to reduction of the weight and pressure loss of the device.

[0026]

As described above, according to the die of the present invention, the outer diameter is reduced and the weight is reduced even if the die has an internal cooling hole in the axis of the lip diameter. be able to. Further, dispersing portions are opposed to each other, so that the dispersion efficiency is improved, and a die having good thickness accuracy of a molded product can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a blown film forming die according to the present invention.

FIG. 2 is a sectional view taken along the line II-II of FIG.

FIG. 3 is a sectional view taken on line III-III of FIG. 1;

FIG. 4 is a sectional view of a main part of a die according to a second embodiment.

FIG. 5 is a sectional view of a main part of a die according to a third embodiment.

FIG. 6 is a schematic diagram of a blown film manufacturing apparatus.

FIG. 7 is a schematic view of a blown film forming die according to the prior art.

FIG. 8 is a sectional view taken along the line VIII-VIII in FIG. 7;

FIG. 9 is a schematic view of another blown film forming die according to the prior art.

FIG. 10 is a sectional view taken along the line XX of FIG. 9;

[Explanation of symbols]

11 die 12 the molten resin 13 branch portion 14 distribution unit 15 supply port 16a~16h resin hole 17 spiral groove 20 passageway 21 mandrel 22 upper body 23 intermediate the body 24 lower body 25 adjusting ring G, G _1, G ₂ gap L lip

Claims (4)

[Claims] 1. An inflation film forming die for branching and dispersing a molten resin supplied from an extruder and extruding the molten resin from a die lip to form a tube-shaped film, wherein the branched portion of the molten resin is formed. A die for forming an inflation film, wherein a surface to be formed and a surface to form a dispersion portion are provided with a step in the longitudinal direction of the axis. 2. The method according to claim 1, wherein the supply port of the molten resin supplied from the extruder is provided at a position other than the axis, and the resin hole provided at the branch portion is arranged outward from a side closer to the axis. A blown film forming die characterized by gradually branching into a plurality of pieces. 3. The blown film forming die according to claim 1, wherein spiral grooves are provided on the upper and lower surfaces of the dispersion portion, and a partition plate is provided between the spiral grooves. 4. A blown film forming die, wherein the die according to claim 1 is combined in a plurality of stages to form a multilayer film.