JPH06320608A - Multi-layer blow molding method - Google Patents

Abstract

PURPOSE:To obtain a multi-layer blow molding method flexibly corresponding to the purpose of molding by a method wherein outer layer, intermediate layer, and inner layer resins are charged from outer layer, intermediate layer, and inner layer extruders to accumulators, respectively. CONSTITUTION:Outer layer, intermediate layer, and inner layer resins 13a, 13b, and 13c are extruded from outer layer, intermediate layer, and inner layer extruders 42, 52, and 62 to be charged into outer layer, intermediate layer, and inner layer accumulators 44, 54, and 64, respectively, while plungers 44a, 54a, and 64a are moved rearward. When the plungers 44a, 54a, and 64a are moved forward, the melting resins 13a, 13b, 13c flow from outer layer, intermediate layer, and inner layer resin inlets 71a, 71b, and 71c through nozzle paths 49, 59, 69 and resin introduction paths 48, 58, 68 into outer layer, intermediate layer, and inner layer manifolds 47, 57, and 67 and therein branch right and left to reach outer layer, intermediate layer, and inner layer resin confluent parts 72a, 72b, and 72c.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Hitherto, a parison has been multi-layered by an in-die accumulator system having a ring plunger.

[0003]

However, in the above-mentioned conventional method, since the internal structure of the die head is complicated, the resin stagnation portion is increased, and the resin (color, material) replacement is bad.
Alternatively, there is a problem in that workability such as disassembly cleaning for completely replacing the new and old resins is poor when changing the resin. Further, when the in-die accumulator type is used, the structure inside the head becomes complicated and it is not possible to sufficiently cope with the diversification of the number of layers (increase in the number of layers) according to the molded product.

It is an object of the present invention to provide a multi-layer blow molding method capable of flexibly meeting the molding purpose, focusing on the above-mentioned conventional problems.

[0005]

In order to achieve the above object, the multi-layer blow molding method according to the present invention is provided with an accumulator corresponding to an extruder for supplying the resin for each layer when the multi-layer parison is injected, An accumulator plunger inserts a multi-layered split mandrel coaxially into the die housing into the die with a resin passage formed under pressure, and supplies pressure from the accumulator side resin passage inlet to each surface of the divided mandrel. After branching to the left and right in the circumferential direction, the resin for each layer is laminated in the thickness direction through each manifold curved in the extrusion direction toward the anti-resin inlet of the mandrel.

[0006]

According to the above construction, the outer layer resin, the intermediate layer resin and the inner layer resin are filled from the outer layer extruder, the intermediate layer extruder and the inner layer extruder to the respective accumulators. When the plunger is driven under pressure, the resin for the outer layer, the resin for the intermediate layer, and the resin for the inner layer flow through the respective manifolds, and the resin flows evenly through each resin passage, and from the lower part of the die toward the parison thickness direction from the outer side to the inner side. A multi-layer parison having a three-layer structure of an outer layer resin, an intermediate layer resin, and an inner layer resin is molded.

[0007]

EXAMPLES Specific examples of the multilayer blow molding method according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a sectional view of a main part apparatus applied to the multilayer blow molding method according to the embodiment, and shows an extruder, an accumulator and a parison injection die. First, the die 10 has a die housing 12 made of a rectangular block, and a through-hole 14 having a substantially circular cross section is bored along the vertical center line. Such a through hole 14 is opened in the lower end surface of the die housing 12 in a state where the inner diameter is gradually reduced from the middle to the lower end surface of the die housing 12.

A mandrel 16 having a diameter smaller than that of the through hole 14 is inserted into the die housing 12. The mandrel 16 includes a circular main mandrel 16c located in the center of the die 10 and an inner ring mandrel 16b located on the outer periphery of the main mandrel 16c.
And the outer ring mandrel 16a located in the outermost layer,
It has a coaxial three-layer structure. That is, in the die housing 12, a cylindrical outer ring mandrel 16a having a diameter smaller than that of the through hole 14 is disposed, and between the outer peripheral surface of the outer ring mandrel 16a and the inner peripheral surface of the through hole 14. Internal ring mandrel 16
A resin passage 18 having a length reaching the lower end of b is formed.

Further, the outer peripheral surface from the middle of the main mandrel 16c to the lower end surface is engraved in a circular shape to form a resin passage 20 between the inner mandrel 16b and the inner peripheral surface. Further, the outer peripheral surface from the middle of the inner ring mandrel 16b to the lower end surface is carved in a circular shape to form a resin passage 21 between the inner ring mandrel 16b and the inner peripheral surface of the outer ring mandrel 16a. A mixed resin passage 22 having a length reaching the resin discharge port 28 is formed between the mandrel 16 and the reduced diameter portion 14a of the through hole 14 below the die housing 12.

The lower end of the mandrel 16 is formed so as to be narrowed in accordance with the reduced diameter portion of the through-hole 14, and a parison control core 16d is attached to the mandrel 16 so that the mandrel 16 can move in and out. A mandrel lip 29 is integrally provided at the tip of the parison control core 16d so as to face the opening of the through hole 14 and form a circular ring-shaped resin discharge port 28 between the opening of the through hole 14 and the parison control core 16d. There is. Therefore, by changing the amount of entry and exit of the parison control core 16d, the resin discharge port 28
The die gap of can be changed arbitrarily.

The die gap is changed by changing the die housing 1.
This is made possible by driving a control cylinder 30 fixed to a support plate 24 which is erected on the main mandrel 1. Therefore, the rod 32 connecting the control cylinder 30 and the parison control core 16d is connected to the main mandrel 1.
6c is penetrated.

On the other hand, the outer layer resin supply device 40 for supplying the outer layer resin 13a to the die 10 and the intermediate layer resin 13 are provided.
An intermediate layer resin supply device 50 for supplying b and an inner layer resin supply device 60 for supplying the inner layer resin 13c are attached. Since the resin supply devices 40, 50 and 60 have the same structure, only the structure of the outer layer resin supply device 40 will be described, and the description of the intermediate layer resin supply device 50 and the inner layer resin supply device 60 will be omitted.

The outer layer resin supply device 40 (50, 60) comprises an outer layer extruder 42 (52, 62) and an outer layer accumulator 44 (54, 64), and the die housing 12 has an outer layer accumulator 44 (54). , 64)
Is installed. This accumulator 44 (54,
64) is an insert of the plunger 44a (54a, 64a). The plunger 44a (54a, 64a) is driven by the outer layer injection cylinder 45 (55, 65) to drive the outer layer accumulator 44 (54, 64). Outer layer resin 13a supplied inside with variable inner volume
The injection pressure of the parison 70 is generated by pressurizing (13b, 13c) and feeding it into the die 10.

Outer layer accumulator 44 (54, 64)
To die 10 for outer layer resin 13a (13b, 13c)
The outer layer accumulator 44 (54, 54,
Nozzle portion 46 (56, 66) is provided at the tip of 64), and this is flange-connected to die housing 12, and outer ring mandrel 16 a (inner ring mandrel 16
b, the nozzle passages 49 (59, 69) are connected to the resin introduction passages 48 (58, 68) for the outer layer that reach the manifold 47 (57, 67) for the outer layer, which will be described later, formed on the main mandrel 16c). Further, the accumulator for outer layer 44 (5
An outer layer extruder 42 (52, 62) is connected to the outer layer resin 13a (13b, 13c) via an extrusion passage 45 (55, 66) for metering the outer layer resin 13a (13b, 13c). In the outer layer extruder 42 (52, 62), a screw 42a (52a, 62a) is provided so as to be rotatable and movable forward and backward in a loosely fitted state.

Further, from the nozzle passage 49 (59, 69) for connecting the outer layer accumulator 44 (54, 64) provided on the peripheral wall of the die housing 12 to the outer layer resin inlet 71.
outer layer resin 13a supplied to a (71b, 71c)
(13b, 13c) first, the outer ring mandrel 16
The outer layer manifold 47 (5) having a semicircular cross section, which is branched to the left and right in the circumferential direction of a (16b, 16c) and is gradually curved in the extrusion direction with a predetermined curvature while gradually reducing the passage cross-sectional area at a predetermined ratio.
7, 67) are formed. The outer layer manifold 47 (57, 67) is symmetrical with respect to the outer layer manifold 47 (57, 67) on the opposite surface side and the outer layer resin inlet 71a (71b, 71c) from the outer layer manifold 47 (57, 67).
It is formed so as to join each other at the positions of degrees.

The merging portion 72a (72b, 72c) is
The outer layer manifolds 47 (57, 67) having a confluent symmetry are joined together so as to come into contact with a line along the axis of the outer ring mandrel 16a (16b, 16c). As a result, the streamlines of the outer layer resin 13a (13b, 13c) flowing down the outer layer manifold 47 (57, 67) are parallel to each other at the merging portion 72a (72b, 72c). From the lower edge of the outer layer manifold 47 (57, 67) to the hybrid resin passage 22
To the outer layer resin passage 18 (20, 21) forming a passage that is shallower than the passage cross-sectional depth of the outer layer manifold 47 (57, 67) portion.
The outer ring mandrel 16a (16
(b, 16c) is formed by adjusting the shaving depth of the outer periphery of the outer peripheral surface of b), 16c) as described above.

The blow molding machine having such a structure is used to form a multi-layer parison having three layers in the thickness direction, which is performed as follows.

First, the multilayer resin 13a (13b, 13
Using the c), the outer layer extruder 42 (52, 62) is turned to the outer layer accumulator 44 (54, 64) by the plunger 44.
A (54a, 64a) is pushed back while being retracted. Next, the accumulator for outer layer 44 (54, 64)
When the plunger 44a (54a, 64a) of No. 1 is advanced, the melted outer layer resin 13a (13b, 13c) flows from the nozzle passage 49 (59, 69) to the resin introduction passage 48 (58, 6).
8) via the outer layer resin inflow port 71a (71b, 71)
c), and the outer layer resin 13a (13b, 13c)
Is branched left and right at the outer layer manifold 47 (57, 67) and reaches the outer layer resin merging portion 72a (72b, 72c).

At this time, the branch portion is flowed down, and from the lower edge of the outer layer manifold 47 (57, 67) to the land portion 75 (7
6, 77) and the outer layer resin 13a flows uniformly over the entire circumference of the resin passage. Further, since the groove cross-sectional area of the outer layer manifold 47 (57, 67) is set to be gradually reduced, the pressure distribution in the circumferential direction becomes uniform and the resin passage 18 (20, 21) is allowed to flow down and mixed. The resin passage 22 is reached. In this hybrid resin passage 22, the outer layer resin 13a flowing down the resin passage 18 flows down on the reduced diameter portion 14a side of the through hole 14, and then the resin discharge port 2
The intermediate layer resin 13b flowing down from the resin passage 21 on the way to 8 flows down on the outer layer resin 13a. Further, the inner layer resin 13c flowing down from the resin passage 20 near the resin discharge port 28 flows down on the intermediate layer resin 13b, whereby the outer layer resin 13a, the intermediate layer resin 13b, and the inner layer resin 1
3c, a multi-layer parison with the so-called three-layer structure 7
It is injected from the resin discharge port 28 as 0. Although the parison 70 has a three-layer structure in this embodiment, it may have a single-layer structure, a two-layer structure, or a four-layer structure or more if the number of divisions of the mandrel 16 is increased.

[0021]

As is apparent from the above description, in the multi-layer blow molding method according to the present invention, an accumulator is provided corresponding to the extruder that supplies the resin for each layer when the multi-layer parison is injected, and the accumulator is provided. A multi-layered mandrel that is coaxially divided into multiple layers is inserted from the plunger into the die housing to supply pressure to the die with resin passages, and the circumference of each surface of the divided mandrel from the resin passage inlet on each accumulator side. After branching to the left and right in the direction, the resin for each layer is laminated in the wall thickness direction through each manifold curved in the extrusion direction toward the anti-resin inlet of the mandrel. There is no resin retention area in the flow path, which improves color changeability and resin changeability. Degradation, incorporation is facilitated, effective cleaning during color changing or resin replacement, it is possible to flexibly cope with diversification of the number of layers of the molded article.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a blow molding machine showing an embodiment according to the present invention.

FIG. 2 is an enlarged sectional view of a lower part of the die.

[Explanation of symbols]

10 dies 12 dies housing 13a outer layer resin 13b intermediate layer resin 13c inner layer resin 16 mandrel 16a outer ring mandrel 16b inner ring mandrel 16c main mandrel 18, 20, 21 resin passage 22 mixed resin passage 28 resin discharge port 40 (50, 50, 60) Outer layer resin supply device (intermediate layer resin supply device, inner layer resin supply device) 42 (52, 62) Outer layer extruder (intermediate layer extruder,
Inner layer extruder) 44 (54, 64) Outer layer accumulator (intermediate layer accumulator, inner layer accumulator) 44a, 54a, 64a Plunger 45, 55, 65 Extrusion passage 47 (57, 67) Outer layer manifold (intermediate layer) Manifold, inner layer manifold) 48, 58, 68 Resin introduction passage 49, 59, 69 Nozzle passage 70 Parison 71a (71b, 71c) Outer layer resin inlet (intermediate layer resin inlet, inner layer resin inlet) 72a ( 72b, 72c) Resin joining portion for outer layer (resin joining portion for intermediate layer, resin joining portion for inner layer) 75 (76, 77) Land portion

Claims (1)

[Claims] 1. When a multi-layer parison is injected, an accumulator is provided corresponding to an extruder that supplies the resin for each layer, and a resin mandrel is coaxially inserted into a die housing from a accumulator plunger to form a resin passage. The pressure is supplied toward the formed die, and after branching from the resin passage inlet of each accumulator side to the left and right in the circumferential direction of each surface of the split mandrel, it is curved in the extrusion direction toward the anti-resin inlet of the mandrel. The multilayer blow molding method, characterized in that the resin for each layer is laminated in the thickness direction through each of the manifolds.