JPH0430889B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an apparatus for extrusion molding a multilayer parison made of two or more different thermoplastic synthetic resins. Furthermore, the present invention relates to an apparatus for extrusion molding a multilayer parison for blow molding in which different types of thermoplastic synthetic resins are heat-sealed in multiple layers, and by performing blow molding using this multilayer parison, the material used can be It is possible to obtain a multilayered molded organism that takes advantage of each of the characteristics.

Traditionally, blow molded products have been widely used as containers for foods, pharmaceuticals, cosmetics, detergents, etc., but these are single-layer molded products, and the materials used include polyethylene, polypropylene, and polyvinyl chloride. It is being

These materials have insufficient gas permeability, chemical resistance, etc., depending on the content and intended use.

Therefore, nylon with excellent barrier properties and chemical resistance,
Various multilayer blow molded products laminated with saponified ethylene-vinyl acetate copolymers, polyester polymers, fluorine polymers, etc. have been studied and put into practical use.

〔the purpose〕

Taking these things into account, if you make a plastic container with two or three layers and use the appropriate material for each layer, you can achieve good quality with a smaller amount of material than conventional single-layer molded products. It is possible to make containers.

That is, an object of the present invention is to provide a novel multilayer parison molding apparatus for blow molding.

Another object of the present invention is to provide an apparatus for extrusion molding a multilayer parison, which allows obtaining a good blow molded product with uniform wall thickness.

Still another object of the present invention is to provide a multilayer parison forming apparatus that is simple in structure and reliable in operation.

Still another object of the present invention is to provide a novel die head for use in the multilayer parison forming apparatus.

[Means for solving problems]

The parison molding device of the present invention is used by being attached to the previous process of a conventional blow molding device,
One main extruder and one or more sub-extruders are attached radially to one die head. It is desirable that the radial arrangement angle between the main extruder and the sub-extruder is 25 to 90 degrees.

The die head of the present invention includes: a core holder having a core pin at the tip and movable up and down; a cylindrical mandrel surrounding the core holder except for the core pin; a cylindrical mandrel surrounding the mandrel at regular intervals; a plurality of sleeves arranged parallel to and in series with each other; an integral housing surrounding each of the sleeves and having a molten resin inlet connected to each extruder; surrounding the core pin to form a molten resin extrusion port; It consists of dice.

The three-layer parison is formed by forming an integral housing in which the die head is provided with an inner layer resin inlet, an intermediate layer resin inlet, and an outer layer resin inlet, and an inner layer sleeve, an intermediate layer sleeve, and an outer layer sleeve inside the housing. A three-layer parison is formed by sequentially arranging the sleeves around the periphery in series with each other and sequentially stacking them.

The details of the multilayer parison molding apparatus of the present invention will be further explained in detail with reference to the drawings.

The parison forming apparatus of the present invention comprises a die head 1, a main extruder 2 and a plurality of sub-extruders 3 attached radially to the die head 1. The apparatus shown in FIGS. 1 and 2 is an apparatus for extruding a three-layer parison using two sub-extruders and thus obtaining a three-layer blow-molded article.

The novelty of the multilayer parison forming apparatus of the present invention is that
It is located in a die head 1 which combines a plurality of extruders 2 and 3, and the extruder itself and the subsequent blow molding machine are the same as conventional ones.

In other words, hopper 4 is attached to extruders 2 and 3.
(The hopper of extruder 3 is omitted from the illustration). After feeding the thermoplastic resin materials and melting and pressurizing the materials with a heating screw, the die head 1 described below
Press the molten material into the Further, the multilayer parison extruded from the die head 1 of the apparatus of the present invention can be blow molded by a subsequent blow molding machine in a conventional manner to obtain a molded article.

Therefore, the die head 1 shown in FIG. 2 will be explained in detail below.

The die head 1 includes an innermost layer head portion 5 that forms a molten resin tube of the resin constituting the innermost layer of the molded product, an intermediate layer head portion 6 that forms a molten resin tube of the intermediate layer constituent resin, and a molten resin of the outer layer constituent resin. It consists of an outer layer head 7 that forms a tube and a die 8 that controls the extrusion state of the multilayer parison. These parts are sequentially assembled vertically around a mandrel 10 that surrounds a core holder 26 having a core pin 9 at its lower end, and each part is equipped with an independent temperature control device and wall thickness adjustment function. . This die head is of a so-called crosshead type connected at right angles to the extruder.

The resin constituting each layer is kneaded and melted under appropriate temperature conditions by separate extruders 2 and 3.
Press fit into each part of the die head. The innermost layer resin is
It is press-fitted from the main extruder 2 through the inlet 11 into the innermost layer head portion 5, and the inner layer sleeve 14
The inner layer sleeve 1
A molten resin pipe is formed within a flow path consisting of a concentric wall formed by the outer wall 4 and the inner wall 16 of the intermediate sleeve. The cross-sectional area of the flow path 15 gradually decreases, so that the pressure in the molten resin tube is throttled and increased as it decreases, and the resin flow becomes uniform and rectified. The wall thickness of this rectified molten resin tube is adjusted more precisely, but this is done in order to make the thickness uniform in the circumferential direction of the gap between the inner sleeve outer wall 14 and the middle layer sleeve 16 inner wall. In order to accurately maintain the accuracy of the gap, the housings 27 for fixing each sleeve are integrated to eliminate wobbling during assembly. Another feature is that the contact area in the circumferential direction is large in order to maintain precision when fixing the sleeve and housing. Further, in order to make the wall thickness uniform in the circumferential direction, this gap is characterized by widening and narrowing the gap several times in the flow direction of the resin to adjust the wall thickness.

The innermost layer molten resin tube whose wall thickness has been adjusted then reaches the intermediate layer head section 6.

In the intermediate layer head 6, the molten resin for the intermediate layer is press-injected from one sub-extruder 3 through the inlet 12, and an intermediate layer molten resin tube is formed in the flow path 17 around the sleeve 16 in the same manner as described above. After the wall thickness is adjusted using the same function as the flow, it merges with the outside of the innermost layer molten resin pipe at the merging point 19. The two-layer flow descends through the flow path formed between the outer layer sleeve 18 and the mandrel 10, and is fused by heat and pressure while maintaining the two-layer state.

On the other hand, in the outer layer head section 7, the molten resin for the outer layer is press-injected from another sub-extruder 3 through the inlet 13, and an outer layer molten resin tube is formed in the flow path 21 with the same function as described above, and at the confluence point 22, the molten resin for the outer layer is formed. The two-layered molten resin pipe is merged to the outside to form a three-layered molten resin pipe. This three-layer resin tube has a flow path 23 formed between the die 8 and the core pin 9.
While flowing, they are fused by heat and pressure, and a parison is extruded from the opening 24 at the tip of the die 8. In this case, since the gap between the die 8 and the core pin 9 is ultimately controlled by the adjustment screw 25, there is no need to provide the outer layer head 7 with a pressure ring or its adjustment screw.

Examples of the present invention are shown below.

〔Example〕

A blow molding machine with a 60φ main extruder is connected to the inner layer head of the single-head three-layer die head of the present invention, and with this die head as a fulcrum, 30φ subs are placed on the left and right sides of the main extruder at an angle of 45 degrees in the horizontal direction. An extruder was attached and connected to the outer layer head and the middle layer head of the die head, respectively. The main extruder was filled with polypropylene (MI1.5 density 0.91), the outer layer sub-extruder was filled with 6 nylon, the middle layer sub-extruder was filled with modified polypropylene, and the maximum cylinder temperature was set at 250℃. When a three-layer container of 500c.c. outer layer nylon/middle layer modified polypropylene/inner layer polypropylene was continuously molded with the die head temperature set at 240℃, a three-layer container that took advantage of the characteristics of each resin was obtained, and the moldability was stable. It was confirmed that the extrusion ratio of each extruder was approximately proportional to the thickness ratio of each layer of the molded product. Molded three-layer container (nylon 22wt% total thickness
600μ) has an oxygen permeability of 0.39g/ ^m2・24Hr・
30μ・atm, moisture permeability 9g/m ²・24Hr・30μ, haze 35% (JISK6714), interlayer adhesion strength 450g/15mm
There was peeling in the width and 90 degrees.

〔Effect of the invention〕

The parison molded in this manner is then fed to a well-known blow molding machine and processed into a three-layer molding.

Furthermore, by replacing the adapter connecting the die head and extruder of the parison molding apparatus of the present invention, a three-layer resin parison or a two-layer resin three-layer parison (layer configuration: A-B-A) can be formed.
It is also possible to form any of the following.

Furthermore, the core holder 2 of the die head 1
When 6 is moved up and down, the core pin 9 at the tip moves,
Since the thickness of the parison is adjusted by changing the slit between the core pin 9 and the die 8, an electronic parison programmer is connected to the core holder 26 to reduce the disturbance of the resin laminar flow in the die head and to increase the thickness of the parison. can be precisely adjusted.

[Brief explanation of drawings]

FIG. 1 is a plan view schematically showing an apparatus for forming a multilayer parison for blow molding according to the present invention, and FIG. 2 is a longitudinal cross-sectional view of a die head for forming a three-layer parison used in the apparatus. 1...Die head, 2...Main extruder, 3...Sub extruder, 4...Hopper, 5...Innermost layer head, 6...Middle layer head, 7...Outer layer head, 8... Dice, 9...
...Core pin, 10...Mandrel, 11,1
2, 13... Resin inlet, 14, 16, 24... Sleeve, 25... Die adjustment screw, 26... Core holder, 27... Housing.

Claims (1)

[Claims] 1. One main extruder and one or more sub-extruders are attached radially to one die head, and the die head is composed of the following members: Multilayer parison molding equipment for blow molding. (b) A cylindrical mandrel that surrounds the core holder except for the core pin portion; (c) A cylindrical mandrel that surrounds the mandrel at regular intervals and that is parallel to the mandrel and mutually a plurality of sleeves arranged in series; d) an integral housing surrounding each of the sleeves and having a molten resin inlet connected to each extruder; e) a die surrounding the core pin to form a molten resin extrusion port; .