JPH11156916A - Annular die for extrusion molding of thermoplastic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an annular die for the extrusion molding of a thermoplastic resin capable of molding a tubular member high in strength even when a rubber elastomer is extruded. SOLUTION: In an annular die for the extrusion molding of a thermoplastic resin consisting of inside and outside dies 1, 2 and constituted so that the upstream resin flow path allowed to communicate from a resin supply part is provided between the base end parts of both of the inside and outside dies 1, 2 and an annular extrusion flow path is provided between the terminals of the inside and outside dies, the upstream resin path flow 13 is branched into a plurality of branched flow paths 15 toward the downstream side at an almost equal interval in a peripheral direction and the respective branched flow paths 15 are gradually expanded in the peripheral direction toward the downstream direction and parts 151 overlapped in a radius direction through a part of the mutually adjacent branched flow paths and partition walls 16 are provided to a part of the branched flow paths 15 so as to be extended thereto and the branched flow paths 15, 151 are allowed to meet and communicate with the annular flow path 18 at the terminals thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an annular die for thermoplastic resin extrusion molding, and more particularly to, for example,
It is suitable for use when the behavior of the resin flowing through the flow path of the annular die largely depends not only on the viscosity behavior of the resin but also on the elastic behavior as in the extrusion molding of rubber and elastomer.
Further, regarding the shape of the molded product to be molded, when applied to the molding of a molded product having a greater wall thickness than a thin-walled product such as a film, it is possible to prevent deformation due to elastic recovery of a weld line portion and the like. It is suitable.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Patent Publication No. 58-29209
As described in Japanese Patent Application Laid-Open Publication No. H10-163, a so-called spiral mandrel type annular die for thermoplastic resin extrusion molding is known.

[0003] Spiral mandrel type annular dies have the advantage that spider marks are not formed radially as in the case of using a spider type annular die, and therefore are particularly useful in the film forming field as an extrusion die for polyethylene, polypropylene or the like. Widely used for.

As shown in FIG. 10, a spiral mandrel type annular die has an annular flow path (d) between an inner die (b) provided with a spiral groove (a) and an outer die (c). Arrow a along the spiral groove (a)
The resin flow circling around the inner die (b) as shown by, and the axial leakage flow indicated by the arrow b along the annular flow path (d) between the inner die (b) and the outer die (c) And
At the location where the spiral groove ends, all of the resin becomes a leakage flow and is extruded in the axial direction.

[0005] When a normal thermoplastic resin is extruded using a spiral mandrel type annular die, the cross section of the formed tubular body is, as shown in FIG. 11, a resin formed by a leakage flow on the upstream side. A weld line (g) is formed at the boundary between the layer (e) and the resin layer (f) formed by the leakage flow on the downstream side. Generally speaking, it is preferable that the weld line be substantially equal to the angle around the mandrel starting from the beginning of the spiral groove cutting and reaching the end of the spiral groove.

The shape of the spiral groove has been designed on the basis of the conventional viscosity characteristic curve. Ideally, however, such a weld line (G) starts from the end (R) on the inner surface of the tubular body (H). (H) The angle α between the outer surface and the end (nu) is preferably equal to the angle from the beginning of the spiral groove cutting to the end of the spiral groove.
At this time, the uniformity of the thickness of the wall of the tubular body (h) is improved, and the strength of the tubular body (h) is increased.

[0007]

However, in the case of a conventional spiral mandrel type annular die, when it is used for extrusion molding of a rubber / elastomer which is frequently used in automobile parts or the like recently, a rubber / elastomer is used. Since the flow behavior in the above-mentioned annular die is completely different from that of a normal thermoplastic resin, there is a demand for an annular die suitable for molding a rubber / elastomer.

That is, when the rubber / elastomer is extruded by using the conventional spiral mandrel type annular die, the leakage flow rate in the axial direction is much smaller than that when the ordinary thermoplastic resin is extruded. When a rubber / elastomer is extruded using a conventional spiral mandrel type annular die, the flow in the direction transverse to the flow along the spiral groove due to the elasticity peculiar to the rubber / elastomer, that is, the leakage flow is usually It is considered that the number is much smaller than that of the thermoplastic resin.

As a result, as shown in FIG. 12, the length of the weld line (g) appearing in the cross section of the actually formed tubular body (lu) is short, and the length of the weld line (g) is set at the boundary of the weld line (g). Since the direction of freezing elastic stress is different inside and outside,
The relaxation of the freezing elastic stress causes a recovery of elastic strain in the past flow direction, that is, a different direction, and the tubular body (le) is peeled or deformed at the weld line (g), so that the strength is large. There was a problem that a tubular body or a tubular body having excellent roundness could not be formed.

The present invention has been made in view of the above-mentioned problems in the conventional spiral mandrel type annular die, and an object thereof is to solve the problems in the conventional spiral mandrel type annular die. An object of the present invention is to provide an annular die for thermoplastic resin extrusion molding capable of molding a tubular body having high strength even when a rubber / elastomer is extruded.

[0011]

In order to achieve the above object, an annular die for thermoplastic resin extrusion molding according to the present invention comprises an inner die and an outer die. An upstream resin flow path communicated from the resin supply port is provided between the base ends, and a thermoplastic resin extrusion molding annular die in which an annular extrusion flow path is provided between the ends of the inner die and the outer die. The upstream resin flow path is branched into a plurality of branch flow paths at substantially equal intervals in the circumferential direction toward the downstream side, and each branch flow path is gradually expanded in the circumferential direction as going downstream, and each branch flow path is branched. A part of the path extends radially overlapping with a part of the adjacent branch flow path via a partition wall, and an annular extrusion is formed at each branch flow path and at the end of the radially overlapping part. It is characterized by being joined to the flow path.

The annular die for thermoplastic resin extrusion of the present invention according to the second aspect of the present invention is the annular die for thermoplastic resin extrusion of the first aspect, wherein a circumferential length of a portion overlapping in the radial direction is provided. Is 10 degrees to (360
(Degree / number of branch flow paths).

According to a third aspect of the present invention, there is provided an annular die for thermoplastic resin extrusion molding according to the first or second aspect of the present invention, wherein the outlet of a branch flow path extending from upstream to downstream is provided. Each of the numbers at the ends is a power of two.

In the present invention, the thermoplastic resins usable include olefin homopolymers such as polyethylene, polypropylene, polybutene and polybutylene, and olefins such as ethylene-propylene copolymer and ethylene-butene copolymer. In addition to ordinary thermoplastic resins such as polyolefin resins, vinyl chloride resins, and polyamides, which are copolymers with polymerizable monomers, or mixtures of these polymers and copolymers, the following rubber elastomers Can be used.

That is, thermoplastic special rubbers such as polyurethane and chloroprene rubber, polystyrene elastomers,
Thermoplastic elastomers such as polyolefin-based elastomer, polyvinyl chloride-based elastomer, polyurethane-based elastomer, polyester-based elastomer, polyamide-based elastomer, and fluorine-based elastomer.

In the annular die for thermoplastic resin extrusion molding according to the first aspect of the present invention, the upstream resin flow path is branched into a plurality of branch flow paths at substantially equal intervals in the circumferential direction on the downstream side. Each branch flow path is gradually expanded in the circumferential direction as it goes downstream, and a part of each branch flow path overlaps with a part of an adjacent branch flow path through a partition wall in a radial direction. Is provided, and is joined to the annular extrusion flow path at the end of the branch flow path and the radially overlapping portion, so that the circumferential length of the radially overlapping portion is increased to increase the weld line. Length can be increased,
Further, the resin flowing in the branch flow path and the resin flowing in the annular extrusion flow path flow in substantially the same direction, and the freezing residual stresses contained in both resins are in substantially the same direction, and the amount of the stress is also the same. It can be about the same. Therefore, there is no possibility that the two layers bounded by the weld line will be separated from each other after the merge.

Further, in the annular die for thermoplastic resin extrusion molding according to the second aspect of the present invention, the angle of the circumferential length of the overlapping portion in the radial direction with respect to the central axis is 10 degrees to (3 degrees).
(60 degrees / number of branch passages), the circumferential length of the portion overlapping in the radial direction can be increased, and the length of the weld line can be increased.

Further, in the annular die for thermoplastic resin extrusion molding according to the present invention, since the number of outlet ends of the branch passages from the upstream to the downstream is a power of 2 each, It is easy to make the amount of resin flowing on the road equal.

[0019]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of an annular die for thermoplastic resin extrusion molding of the present invention. In FIG. 1, reference numeral 1 denotes an inner die, 2 denotes an outer die provided outside the inner die 1, and a resin inflow pipe 3 is attached to a base end of the outer die 2 by screwing. The inflow hole 31 of the resin inflow pipe 3 communicates with the inflow path 21 of the outer die 2, and the inflow path 21 communicates with the inflow port 11 of the inner die 1.

As shown in the developed view of FIG.
A first branch flow path 13 communicating with the upstream end of the inflow path 12 and extending along the circumferential direction at the downstream end of the inflow path 12
And is branched into two branch flow paths. Further, the downstream end of the first branch flow path 13 is connected to the upstream end of the second branch flow path 14 along the circumferential direction, and is branched into two branch flow paths.

As shown in FIGS. 2 to 4, the second branch flow path 14 along the circumferential direction becomes a branch flow path 15 along the axial direction from the middle part, and the branch flow path 15 becomes circumferentially smaller in the downstream direction. The branch flow path 15 is gradually expanded in the direction, and a part of the branch flow path 15 is expanded in the radial direction, and a portion 151 that overlaps with the adjacent branch flow path 15 in the radial direction via a partition wall 16 is provided.
The angle θ with respect to the circumferential center axis of the radially overlapping portion 151 is about 80 degrees. Tip 1 of the partition wall 16
61 is in close contact with the inner surface of the outer die 1.

Each branch flow path 15 and a radially overlapping portion 151 are joined at an annular flow path 17 provided on the downstream side, and the annular flow path 17 passes through a narrow portion 171 to form an outlet annular flow path 18. Is communicated to.

In FIG. 1, reference numeral 181 denotes a core die attached to the tip of the inner die 1; 22 denotes a tip attached to the tip of the outer die 2; The size of the gap can be adjusted.

Since the annular die for thermoplastic resin extrusion molding of the present invention shown in FIGS. 1 to 4 has the above-described structure, the molten resin extruded from an extruder (not shown) is supplied to the inlet 31 of the resin inlet pipe 3. Through the inflow path 21 of the outer die 2 to the inlet 11 of the inner die 1. The molten resin flows through the inflow path 12 from the inflow port 11, and is branched at the end into a first branch flow path 13 along the circumferential direction. Further, the molten resin flows through the first branch flow path 13 and reaches the second branch flow path 14 along the circumferential direction at the end of the first branch flow path 13 to be branched.
In the illustrated embodiment, the first branch channel 13 is divided into two parts.
Although it is further divided into two by the second branch flow path 14, a third branch flow path and a fourth branch flow path are further provided.
The number of branch channels may be increased by a power of.

Further, the molten resin flows from the second branch flow path 14 in the axial branch flow path 15 and widens in the circumferential direction along the branch flow path 15. Part of the molten resin flowing through the branch flow path 15 flows through a portion 151 overlapping in the radial direction. Branch channel 1
5 and the molten resin flowing in the radially overlapping portion 151 join in the downstream in the annular flow path 17 to form a narrow portion 171.
Through the annular passage 18 at the outlet.

Here, the angle θ of the radially overlapping portion 151 with respect to the central axis in the circumferential direction is about 80 degrees, and the molten resin flowing in the radially overlapping portion 151 and the molten resin flowing in the branch flow path 15 inside it. The length of the weld line formed at the boundary with the molten resin is large.

Further, the molten resin flowing in the radially overlapping portion 151 and the branch flow path 15 flows in substantially the same direction as the molten resin flowing in the annular flow path 17 which is subsequently merged, and flows into both molten resins. The built-in freezing residual stresses have substantially the same direction as each other, and the amount of the stress can be made substantially the same.

Therefore, in the tubular body extruded in this way, there is no risk that the two layers bounded by the weld line will be delaminated and separated after merging. A high strength tubular body can be formed.

FIG. 5 is a sectional view showing a main part of another example of the annular die of the present invention. The annular die of the present invention shown in FIG.
The tip part 161 of the partition wall 16 present at the boundary between the branch flow path 15 of the annular die of the present invention shown in FIGS. The overlapping portion 151 exists continuously without interruption in the circumferential direction.

In the annular die of the present invention shown in FIG.
Since the radially overlapping portion 151 exists continuously without interruption in the circumferential direction, the radially overlapping portion 1
The molten resin flowing through 51 is not restricted, and the molten resin inside the partition wall 16 flows into the molten resin flow outside the partition wall 16 via the tip of the partition wall 16, or Conversely, a phenomenon in which the molten resin outside the partition wall 16 flows into the molten resin flow inside the partition wall 16 is observed.

Although the embodiments of the present invention have been described with reference to the drawings, the specific embodiments of the present invention are not limited to the illustrated embodiments, and modifications that do not depart from the gist of the present invention may be made. include.

For example, as shown in the illustrated embodiment, the first
Instead of branching from the branch flow path into a second branch flow path to make one flow path branch into four flow paths, or not branching into two or more flow paths, or Alternatively, the four flow paths may be further branched into eight or more flow paths.

The width of the branch channels 15, 151 in the circumferential direction is increased as shown in FIG.
Instead of widening both in the direction of arrow c (right direction in FIG. 2), the branch flow paths 15 and 151 may also be widened in direction d (left direction in FIG. 6). Alternatively, as shown in FIG. 7, the branch channel 15 may be widened in the direction of arrow d, and the branch channel 151 may be widened in the direction of arrow c.

Further, as for the branch of the inflow path 12, instead of branching at the joining surface between the inner die 1 and the outer die 2 as in the illustrated embodiment, as shown in FIGS. Using the joining surface between the annular portion 4 provided in the middle of the outer die 1 and the outer die 2 and the inner die 1, a branch is made from the branch start point 121 at the end of the inflow path 12 to two branch end points 122. It may be.

As for the positional relationship between the branch flow path 15 and the portion 151 overlapping in the radial direction via the partition wall 16, as shown in the illustrated embodiment, the portion 151 overlapping in the radial direction is a partition. Instead of being provided outside the branch flow path 15 via the wall 16, it may be provided inside.

[0036]

According to the first aspect of the present invention, the length of the weld line is increased by increasing the circumferential length of the portion overlapping in the radial direction. In addition, the resin flowing in the branch flow path and the resin flowing in the annular extrusion flow path flow in substantially the same direction, and the freezing residual stress built in both resins is substantially the same direction. The amount of stress can be substantially the same. Therefore, there is no fear that the two layers bounded by the weld line will be separated from each other after the merge from the branch flow path, and a strong tubular body can be formed even when rubber or elastomer is used as the thermoplastic resin.

In the annular die for thermoplastic resin extrusion molding according to the present invention, the length of the weld line can be increased, so that the rubber / elastomer can be used as the thermoplastic resin. A strong tubular body can be formed.

Further, in the annular die for thermoplastic resin extrusion molding according to the third aspect of the present invention, it is easy to equalize the amount of resin flowing through each branch flow path, so that a tubular body having high strength can be formed. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of an annular die for thermoplastic resin extrusion molding of the present invention.

FIG. 2 is a development view of a branch flow path of the annular die for thermoplastic resin extrusion molding of the present invention shown in FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 1;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 1;

FIG. 5 is a sectional view showing a main part of another example of the annular die for thermoplastic resin extrusion of the present invention.

FIG. 6 is a developed view of another example of a branch flow path of the annular die for thermoplastic resin extrusion molding of the present invention.

FIG. 7 is a developed view of another example of the branch flow path of the annular die for thermoplastic resin extrusion molding of the present invention.

FIG. 8 is a cross-sectional view showing a main part of still another different example of the annular die for thermoplastic resin extrusion of the present invention.

FIG. 9 is a sectional view taken along line IX-IX in FIG. 8;

FIG. 10 is an explanatory view showing a conventional spiral mandrel type annular die.

FIG. 11 is an explanatory view of a tubular body when a usual thermoplastic resin is extruded using a conventional spiral mandrel type annular die.

FIG. 12 is an explanatory view of a tubular body when rubber and elastomer are extruded using a conventional spiral mandrel type annular die.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 inner die 11 inflow port 12 inflow path 13 first branch flow path 14 second branch flow path 15 branch flow path 151 part overlapping in radial direction 16 middle partition wall 17 annular flow path 171 narrow part 18 annular flow at outlet Road 2 Outer die 21 Inflow path 3 Resin inflow pipe 4 Annular part

Claims (3)

[Claims] An upstream resin flow path communicated from a resin supply port is provided between a base end portion of an inner die and an outer die, and a distal end of the inner die and the outer die. In a thermoplastic resin extrusion molding annular die in which an annular extrusion flow path is provided, the upstream resin flow path is branched into a plurality of branch flow paths at substantially equal intervals in the circumferential direction toward the downstream side, and The branch flow path is gradually expanded in the circumferential direction as it goes downstream, and a part of each branch flow path extends in a radial direction with a part of an adjacent branch flow path through a partition wall. An annular die for thermoplastic resin extrusion molding, wherein the annular die is provided and joined to an annular extrusion channel at an end of each branch channel and a portion overlapping in a radial direction. 2. The thermoplastic resin according to claim 1, wherein the angle of the circumferential length of the portion overlapping in the radial direction with respect to the center axis is 10 degrees to (360 degrees / number of branch passages). Annular die for extrusion molding. 3. The annular die for thermoplastic resin extrusion molding according to claim 1, wherein the number of outlet ends of the branch flow paths from the upstream to the downstream is a power of two.