JPH07171879A - Die for multilayer blow-molding - Google Patents

Abstract

PURPOSE:To obtain a molded form having high thickness accuracy by vertically movably providing an annular ring independent from inner and outer resin annular passages for connecting a resin annular passage between a mandrel at a center of a die head and an outer die to to an extruder, and providing a resin replacing passage communicating with the inner and outer passages. CONSTITUTION:An inner die 2 and an outer die 4 of a die 1 are coaxially provided, an outer mandrel 6 is provided in the die 4 to form an outer resin annular passage 10 communicating with an extruder 14, an inner mandrel 8 is provided in the die 2 to form an inner resin annular passage 12 communicating with an extruder 16. Both the passages 10, 12 are combined at a downstream side to a resin discharge port 20. An annular ring 30 is vertically movably provided between the mandrel 6 and the die 2, and a resin passage 9 between the die 4 and the mandrel 8 is branched to be guide at the passages 10, 12. Further, resin drain passages are formed from the passage 12 axially of the mandrel 8 and a reduced-diameter part 4b of the die 4, and plugs 43, 45 are provided.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a multilayer blow molding die.

[0002]

2. Description of the Related Art In a conventional die for a multi-layer parison, when the thickness of the inner and outer layers of the parison is adjusted, the extrusion amount or injection speed of the molten resin is changed in an extruder or an accumulator.

[0003]

However, in this method, the thickness of the multi-layer parison is controlled on the upstream side of the die lip for the final adjustment, so that the thickness of each layer constituting the multi-layer parison cannot be accurately adjusted. There was such a problem.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a multilayer blow molding die for obtaining a molded product having a precise wall thickness.

[0005]

In order to solve the above-mentioned problems, the present invention provides a resin annular passage formed between a mandrel at the center of a die head and a die main body at the outer periphery, wherein the resin annular passage is A ring-shaped ring that separates the inner and outer resin annular passages is provided so that it can move up and down, and the supply ports of the inner and outer resin annular passages merge downstream and communicate with a single annular parison outlet. At the same time, the upstream side is connected to the discharge port side of the extruder, and the mandrel and the die body are provided with resin material replacement passages for communicating the inner and outer resin annular passages.

[0006]

The multi-layer thick parison or the single-layer thick parison can be obtained by arranging the outer periphery of the mandrel and the die body so that they can be selectively brought into contact with and separated from each other while moving the annular ring up and down. Further, while the single-layer thick parison is being injected, the resin changing operation can be simultaneously performed on the other side.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the multilayer blow molding die according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a multilayer blow molding die according to the present invention, FIG. 2 is a sectional view of the multilayer blow molding die showing a state in which an annular ring is lowered, and FIG. 3 is an annular ring raised upward. FIG. 4 is a cross-sectional view of the multilayer blow molding die showing the state, FIG. 4 is an explanatory view showing a resin changing state of the external resin annular passage, and FIG. 5 is an explanatory view showing a multilayer molding state of the laminated resin.

First, the parison injection die 1 is composed of an inner die 2 and an outer die 4 which are circular blocks and are arranged coaxially. The inner die 2 and the outer die 4 are respectively formed with through through holes 2a, 4a having a substantially circular cross section along the vertical center line.

The through-hole 4a of the outer die 4 has a diameter-reduced portion 4b whose diameter is reduced in the middle of the through-hole 4a. It has an opening on the end face. Inside the outer die 4, an outer mandrel 6 having a diameter smaller than that of the through hole 4a is arranged. An outer resin annular passage 10 communicating with the first layer extruder 14 is formed between the outer die 4 and the outer mandrel 6.

On the other hand, an inner mandrel 8 having a diameter smaller than that of the through hole 2a of the inner die 2 disposed inside the outer die 4 is disposed, and a second portion between the inner die 2 and the inner mandrel 8 is disposed. An internal resin annular passage 12 communicating with the layer extruder 16 is formed.

The lower end of the inner mandrel 8 is formed so that its tip is narrowed according to the reduced diameter portion of the through hole 4a of the outer die 4. A parison control core 18 is attached to the lower end of the die 1 so as to be able to move in and out from the inner mandrel 8. A mandrel lip 22 is integrally provided at the tip of the parison control core 18 so as to face the opening of the through through hole 4a and form a circular ring-shaped resin discharge port 20 between the opening of the through through hole 4a. .

Therefore, the die gap of the resin discharge port 20 can be arbitrarily changed by changing the amount of entry and exit of the parison control core 18.
The die gap can be changed by the column 24 standing on the die 1.
This is made possible by driving a Parison cylinder 26 fixed to the upper support plate 25. Therefore, a Parison rod 27 connecting the Parison cylinder 26 and the parison control core 18 is passed through the inner mandrel 8.

In the present embodiment, as shown in FIG. 1, a resin passage 9 formed between the outer mandrel 6 and the inner mandrel 8 is slidably held between the outer mandrel 6 and the inner mandrel 2 so as to have a reduced diameter portion. An annular ring 30 for branching and guiding the outer resin annular passage 10 and the inner resin annular passage 12 is arranged above 4b. The annular ring 30 can be moved up and down by an annular ring actuating hydraulic cylinder 32 arranged above the inner die 2.

First layer extruder 14 and second layer extruder 16
An outer layer heater 34 is provided on the outer surface of the outer die 4, and an inner mandrel 34 is provided on the outer surface of the outer die 4, in order to heat and maintain the molten resin supplied to the outer resin annular passage 10 and the inner resin annular passage 12 from the die 1 at a predetermined temperature. Inner heaters 36 for the inner layer are arranged in each of the shafts 8 along the axial direction.

Further, with respect to the manifold 38 (39), since the outer die 4 and the inner die 2 have almost the same structure,
The outer die 4 will be described. First, the molten resin supplied from the outer resin annular passage 10 (12) connected to the first layer extruder 14 (16) provided on the peripheral wall of the outer die 4 (2) to the resin inlet 11 (13) is From the surface of the outer mandrel 6 (8) on the resin inlet 11 (13) side, branch in the left and right in the circumferential direction,
Manifold 38 (39) having a semicircular cross section that curves in the extrusion direction with a predetermined curvature while gradually decreasing the passage cross-sectional area toward the resin inlet 11 (13) side of the outer mandrel 6 (8) at a predetermined rate. Is formed. The end of the manifold 38 (39) is joined with the symmetrical manifold 38 (39) at the position approximately 180 degrees from the resin inlet 11 (13).

In the present invention, with the above structure as a basic structure, as shown in FIG. 2 and FIG. 3, in order to replace old resin and new resin, which have stayed in the die 1 without being moved, quickly, completely, in order. A resin drain hole 40 is provided in each of the inner mandrel 8 communicating with the inner resin annular passage 12 and the outer die 4 communicating with the outer resin annular passage 10.

An inner layer resin drain passage 42 is provided along the axial direction of the inner mandrel 8 from the inner resin annular passage 12 to the outside, and the inner layer resin drain passage inlet 42 is used when replacing old and new resin.
An inner layer resin removal plug 43 for completely opening a is provided.

On the other hand, the reduced diameter portion 4b of the outer die 4 is provided with an outer layer resin drain passage 44 communicating with the outside, and an outer layer resin drain plug 45 for completely opening the outer layer resin drain passage inlet 44a at the time of changing old and new resin is arranged. It is set up.

The multi-layer blow molding die having such a structure is used to form the multi-layer parison, which is performed as follows.

For example, when a gasoline tank is to be molded, a high-density polyethylene resin 46 is used as a main material for a resin tank, and this is extruded from one first layer extruder 14. A polyamide resin 48 having a small gas permeability is extruded from the other second layer extruder as a barrier material.

In this case, the annular ring 30 is moved to a desired position by the annular ring actuating hydraulic cylinder 32. The passage speed of the resin passing through the outer and inner resin annular passages 10 and 12 is determined at the position of the determined movement of the annular ring 30.

When the first layer extruder 14 and the second layer extruder 16 are driven, the high density polyethylene resin 46 extruded from the first layer extruder 14 flows through the outer resin annular passage 10 through the outer manifold 38. While flowing down toward the resin discharge port 20. On the other hand, the polyamide resin 48 extruded from the second layer extruder 16 flows down through the inner manifold 39 to the resin discharge port 20 while flowing through the inner resin annular passage 12, and at the lower end of the annular ring 30, both molten resins are melted. Four
Reference numerals 6 and 48 serve as inner and outer resin layers forming the parison 50 and are ejected as the parison 50 from the resin discharge port 20.

When a resin tank is formed by the multi-layered parison thus obtained, a high density polyethylene resin 46 forming an outer layer and a polyamide resin forming an inner layer in the thickness direction of the tank as shown in FIG. 48 is a multi-layer, and the polyamide resin 48 of the inner layer blocks the permeation of gasoline, and a tank having extremely little gasoline permeation can be obtained as a molded product.

After the gasoline tank is molded as a blow-molded product repeatedly in this way, and when the old resin and the new resin are changed in accordance with the material change and the color change, for example, the annular ring 30 is moved downward as shown in FIG. The outer resin annular passage 10 is closed halfway by being brought into contact with the reduced diameter portion 4b. Then remove the outer layer resin removal plug 45 with a wrench, etc.
While rotating the screw of the first layer extruder 14 to feed the new resin, the inner layer resin removal passage 4 is formed so that the old resin is washed out with the new resin.
2 can be discharged.

On the other hand, when the old resin annular passage 10 is completely replaced with the new resin, the annular resin ring 30 is moved upward and brought into contact with the inner mandrel as shown in FIG. 3, but the inner resin annular passage 12 is closed. The single layer parison 50 can be discharged from the first layer extruder 14 through the outer manifold 38 and the outer resin annular passage 10 through the resin discharge port 20.

[0027]

As is apparent from the above description, according to the present invention, the resin annular passage is provided in the resin annular passage formed between the mandrel at the center of the die head and the die main body at the outer periphery. The inner and outer resin annular passages are provided with independent annular rings so as to be movable up and down, and the supply ports of the inner and outer resin annular passages are formed on the downstream side so as to join and communicate with a single annular parison outlet. At the same time, by connecting to the discharge port side of the extruder on the upstream side, and further arranging a resin material replacement passage that connects the inner and outer resin annular passages to the mandrel and the die body, the annular ring is moved up and down. Since it is possible to adjust the wall thickness of the inner and outer layer resin only by adjusting the resin passage by using the resin passage, it is possible to easily control the multi-layer thickness with high accuracy. Further, since the single-layer parison can be injected at the same time while changing the resin, the productivity is remarkably improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a blow molding die according to the present invention.

FIG. 2 is a cross-sectional view of a multilayer blow molding die showing a state where an annular ring is lowered.

FIG. 3 is a cross-sectional view of a multilayer blow molding die showing a state where an annular ring is lifted up.

FIG. 4 is an explanatory diagram showing a resin change state of an external resin annular passage.

FIG. 5 is an explanatory view showing a multi-layer molding state of a laminated resin.

[Explanation of symbols]

 1 Die 2 Inner Die 2a, 4a Through Through Hole 4 Outer Die 4b Reduced Diameter Part 6 Outer Mandrel 8 Inner Mandrel 9 Resin Passage 10 External Resin Annular Passage 11, 13 Resin Inlet 12 Internal Resin Annular Passage 14 First Layer Extruder 16 Second layer extruder 20 Resin discharge port 22 Mandrel lip 26 Paricon cylinder 30 Annular ring 38 Outer manifold 39 Inner manifold 40 Resin drain hole 42 Inner resin drain passage 42a Inner resin drain passage inlet 43 Inner resin drain plug 44 Outer resin drain passage 44a Outer layer resin removal passage inlet 45 Outer layer resin removal plug 50 Parison

Claims (1)

[Claims] 1. A resin ring passage formed between a mandrel at the center of the die head and an outer periphery of the die body, and an annular ring for separating the resin ring passage from the inner and outer resin ring passages, respectively. The inner and outer resin annular passages are formed so as to be joined to each other on the downstream side so as to communicate with a single annular parison outlet, and are connected to the outlets of the extruders on the upstream side. A multi-layer blow molding die, further comprising a resin material replacement passage that connects the inner and outer resin annular passages to the mandrel and the die body.