JPS6059132B2 - Multilayer parison molding equipment for large blow molding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for extrusion molding a multilayer parison for large-scale blow molding made of two or more different types of thermoplastic synthetic resins.

Furthermore, the present invention relates to an apparatus for extrusion molding a multilayer parison for large-scale blow molding, which is made by heat-sealing different types of thermoplastic synthetic resins in multiple layers. It is possible to obtain large multilayer molded products that take advantage of each material's characteristics. [Conventional technology and its problems] Blow molded products have traditionally been widely used as containers for foods, medicines, cosmetics, detergents, etc., but these are single-layer molded products, and their materials include polyethylene and polypropylene. and polyvinyl chloride.

On the other hand, in recent years, there has been a demand for saving resources such as oil and electricity.
Issues have been raised regarding the disposal of waste materials such as plastics, and food hygiene issues related to polyvinyl chloride, and these containers should also meet usage requirements with a minimum amount of resin and be hygienic and prevent pollution. It is necessary that there are no problems.

However, none of the conventional single-layer molded products could satisfy all the conditions. Therefore, the present inventors
The present invention was completed as a result of focusing on the lamination that is used in film packaging materials and conducting various studies on applying this to blow-molded products.

That is, thermoplastic resins have superiority and inferiority in hardness, flexibility, etc. depending on their type. On the other hand, the outer surface of plastic containers is susceptible to external shocks, especially in large containers, and the resin used must have a high molecular weight and a type of resin with excellent mechanical strength. . Furthermore, the texture of the container is mainly influenced by the material of the outer surface. On the other hand, since the inner surface of a plastic container comes into direct contact with the product, it must not react with the contents or elute harmful substances. In addition, when molding a large blow-molded container as in the present invention, if a screw type extruder is used, the extrusion amount is not constant, so drawdown of the parison may occur, and the thickness of the molded parison may be constant. was not obtained. Considering the above, if a plastic container is made of two or three layers and the appropriate material is used for each layer, a container of good quality can be created using a smaller amount of material than a conventional single-layer molded product. It becomes possible to make.

[Purpose of the invention]

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

Another object of the present invention is to obtain a large-sized blow-molded product in which the thickness of the resin constituting each layer is uniform throughout, and to easily finely adjust the thickness of the resin in each layer. An object of the present invention is to provide an apparatus for extrusion molding a multilayer parison. Still another object of the present invention is to provide a new die head for use in the multilayer parison molding apparatus, particularly in which the length of the parison in the extrusion direction is made as short as possible.

[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, and one main extruder and one or more sub-extruders are installed in one die head in a radial manner. An accumulator is connected between the extruder and the die head.

The radial arrangement angle between the main extruder and the sub-extruder is preferably 25 to 90 degrees. 25
If the angle is smaller than the arrangement, the extruder bodies will interfere with each other and installation will be impossible, and if the extruder bodies are arranged more than 90 times, the installation area of the entire device will become large, which is disadvantageous.

However, it is not limited to this range. The die head has a core holder having a core pin at the tip, a cylindrical mandrel surrounding the core holder, and an adjustment screw for adjusting the relative position of the core pin and the die, and the die head surrounds the core pin and presses the molten resin. a die portion forming an outlet; a die portion formed between the base of the core holder and the die so as to form a flow path for molten resin along the mandrel between the die portion and the base of the core holder; a plurality of head parts disposed between the extruder and connected thereto; a pressure ring facing the flow path of the molten resin and rectifying the flow of the molten resin; each of the head parts includes a sleeve surrounding the mandrel; and a housing disposed coaxially with the sleeve, leaving a flow path for the molten resin between the sleeves, and the pressure ring is arranged on one side of the plurality of head parts adjacent to each other. Among the plurality of head parts, the head part that is interposed between the lower end of the housing of the head part of the sleeve and the upper end of the sleeve of the other head part and forms the outermost layer of the multilayer parison adjacent to the die part is the head part of the sleeve. It has a molten resin flow path communicating with the eluted resin extrusion port of the die part along both the inner and outer surfaces, and each head part except this head part and the pressure ring have the following configurations (a) to (c). Multilayer parison molding device for blow molding; (a) The outer surface of the sleeve includes a first surface parallel to the mandrel, a second surface inclined toward the center of the mandrel (from the downstream side of this second surface) (b) pressure facing the flow path of the molten resin, comprising a third surface parallel to the continuous mandrel and a fourth surface continuous from the third surface and inclined further downstream toward the center of the mandrel; The ring has an inner surface that faces a surface extending halfway from the second surface to the third surface of the sleeve at a distance, and the inner surface is such that the surface opposite to the second surface of the sleeve is located at the center of the mandrel. (c) the inner surface of the housing and the inner surface of the pressure ring connected thereto are inclined downstream toward the third surface of the sleeve, and the surface facing the third surface of the sleeve is parallel to the outer peripheral surface of the mandrel; The width of the molten resin flow path formed between the sleeve and the outer surface of the sleeve is gradually reduced.

It goes without saying that the inner surface of the sleeve of the innermost layer forming head and the outer surface of the mandrel are in close contact to prevent the resin from flowing back.

When extruding a two-layer parison, one main extruder and one sub-extruder are used,
Furthermore, the sleeves, housings, accumulators, etc. may be combined in pairs.

In addition, when extruding a three-layer parison, two sub-extruders or an adapter for branching the molten resin to the sub-extruder can be installed on both sides of the main extruder to create a three-layer A-B-A molded product. You can also get When extruding a three-layer parison, three sleeves, housings, accumulators, etc. are sequentially arranged in series around a mandrel in the die head to form a resin passage for three layers.

That is, the novelty of the multilayer parison molding apparatus of the present invention lies in the fact that the plurality of extruders 2 and 3 and the die head 1 are connected by the accumulator 31, and in the die head 1. Regarding the extruder itself and the subsequent blow molding machine, It is the same as the conventional one. [Operation] First, a thermoplastic resin material is supplied to the extruders 2 and 3 from the hopper 4 (the hopper of the extruder 3 is not shown), and after melting and pressurizing the material with a heating screw, the material is press-fitted into the ram cylinder 32. , is accumulated, and the ram 33 presses the molten material into the die head 1, which will be described later.

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 has an innermost layer head section 5 that forms a molten resin tube for the resin constituting the innermost layer of the molded product, an intermediate head section 6 that forms a molten resin tube for the intermediate layer constituent resin, and a molten resin tube for the outer layer resin tube. It consists of an outer layer head section 7 for forming the outer layer, and a die section 8 for controlling the extrusion state of the multilayer parison. These parts are sequentially assembled in the vertical direction around a mandrel 10 surrounding a core holder 30 having a core pin 9 at the lower tip, and each part is equipped with an independent temperature control device and wall thickness adjustment device. ing. This die head is of a so-called crosshead type connected at right angles to the extruder and the cumulator. Separate extruder 2 for resin that makes up each layer
. The innermost layer resin is press-fitted from the main extruder 2 through the accumulator 31 and into the innermost layer head portion 5 via the inlet 11, divided into two parts facing the sleeve 14, and descending along the resin flow path 15 to both ends. are bonded and fused to form a molten resin tube within a flow path consisting of a concentric wall formed by the sleeve 14 and the housing 16. The width of this flow path 15 gradually becomes smaller, so as the pressure in the molten resin pipe decreases, it is constricted and increases, and the resin flow becomes uniform and rectified (
This also applies to the flow path 20). The thickness of the rectified molten resin pipe is further adjusted by slightly changing the position of the pressure ring 17 using an external adjustment bolt 18 to adjust the gap between the pressure ring 17 and the sleeve 14. The innermost layer resin pipe whose wall thickness has been adjusted then reaches the intermediate head portion 6.

In the intermediate head section 6, the molten resin for the intermediate layer is press-fitted from one sub-extruder 3 through the accumulator 31 and the inlet 12, and the molten resin for the intermediate layer is injected into the flow path 20 around the sleeve 19 in the same manner as described above. After the tube is formed and its thickness is adjusted using the pressure ring 21 and the adjustment bolt 22, it merges with the outside of the innermost layer molten resin tube at a merging point 23.

The two-layer flow descends through the flow path formed between the outer sleeve 24 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 7, the molten resin for the outer layer is press-injected from another sub-extruder 3 through the accumulator 31 and the inlet 13, and an outer layer molten resin pipe is formed in the flow path 25, and at the confluence point 26, the above-mentioned molten resin is injected. The two-layered molten resin pipe is joined to form a three-layered resin pipe.

This three-layer resin tube is fused by heat and pressure while flowing through a channel 27 formed between the die 8 and the core pin 9, and a parison is extruded through the opening 28 at the tip of the die 8. .

In this case, dice. Since the inner surface of the die 8 has a long inclined surface compared to the resin flow path for forming the inner layer and intermediate layer, the gap between the die 8 and the core pin 9 is finally controlled with the adjusting screw 29 to rectify the resin flow. Since the die 8 has the same effect as a pressure ring, there is no need to provide a pressure ring or its probe screw on the outer layer head 6 portion 7.
The parison formed in this manner is then fed to a well-known blow molding machine and processed into a three-layer molded product.

In addition, when molding a parison for a two-layer molded product, the intermediate head portion 6 is removed, and the flow path 15 of the inner layer head portion 5 is
The shape of the mandrel 10 may be deformed so that the end of the mandrel 10 merges with the end of the flow path 25 of the outer layer head portion 7.

Further, when the core holder 30 of the die head 1 is moved up and down, the core pin 9 at the tip moves, and the core pin 9 moves.
Since the thickness of the parison is adjusted by changing the slit between the die 8 and the die 8, an electronic parison programmer is connected to the core holder 30 to reduce the disturbance of the resin laminar flow inside the die head and adjust the thickness of the parison. Can be precisely adjusted.

Examples of the present invention are shown below.

〔Example〕

A three-layer triple die head was created according to the present invention.

An adapter was used for the innermost layer head of this three-layer triple die head, and an accumulator was used to connect the 40φ main extruder and the inlet. Furthermore, the intermediate layer head part, the sub-extruder outer layer head part of 40φ, and the 10
The 0φ sub-extruders were each connected to the main extruder at an angle of 30° by an accumulator. The main extruder is loaded with 6-nylon, the 40φ sub-extruder is loaded with maleic acid-modified low-density polyethylene, and the 100φ sub-extruder is loaded with ultra-high molecular polyethylene (Shorex manufactured by Showa Yuka Co., Ltd.). Spar 555/H) was loaded and extruded under the following temperature conditions to form a three-layer parison of 6-nylon/maleic acid-modified low-density polyethylene/ultra-high molecular weight polyethylene. A blow container was obtained. Temperature Conditions As each layer is extruded by the Akiyum Regotor in this way, even large containers can be extruded at high speed, resulting in the formation of large multi-layer parisons with less drawdown and uneven thickness of the parison, with excellent aesthetics and reduced thickness. A uniform large container was obtained.

The adhesive strength was 20 kg/15 Trfm or more, which was sufficient. [Effects of the Invention] Since the present invention is constructed as described above, it has the following excellent practical effects.

(a) A pressure ring is interposed between the lower end of the housing of one of the adjacent head parts and the upper end of the sleeve of the other head part, and the shape of the opposing part of the inner surface of the pressure ring and the outer surface of the sleeve is Since it is formed of a part parallel to the mandrel and a part inclined toward the mandrel, it is easy to finely adjust the thickness of the resin in each layer. The result is the same effect as providing a long one, and the resin can be rectified reliably.

(B) In the head parts other than the head part for forming the outermost layer, the shape of the opposing part of the inner surface of the pressure ring and the outer surface of the sleeve is divided into a part parallel to the mandrel and a part inclined downward toward the mandrel. Because of this shape, the length of the device in the parison extrusion direction can be made shorter than in the case of a straight and inclined shape in order to obtain the same rectifying effect, and the entire device can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a plan view schematically showing the multilayer parison molding apparatus for large-scale blow molding of the present invention, and FIG.
FIG. 2 is a longitudinal cross-sectional view of a die head for forming a layer parison. 1...Die head, 2...Main extruder, 3...Sub extruder, 4
...Hopper, 5 ...Inner layer head section, 6
...Middle layer head part, 7...Outer layer head part, 8...Dice, 9...Core pin, 10
・・・・・・Mandrel, 11, 12, 13...
・Resin inlet, 14, 19, 24...Sleeve, 1
7,21... Pre, Tushiaring, 18,22
...Pressure ring adjustment screw, 29...Dice adjustment screw, 30...Core holder, 31
...accumulator, 32...ram cylinder, 33...ram.

Claims (1)

[Claims] 1. A multilayer parison molding device for blow molding in which one main extruder and one or more sub-extruders are attached radially to one die head, and an accumulator is provided between the extruder and the die head. , the die head has a core holder having a core pin at the tip, a cylindrical mandrel surrounding the core holder, and an adjustment screw for adjusting the relative position of the core pin and the die, and the die head surrounds and melts the core pin. a die portion that forms a resin extrusion port; a die portion comprising a die portion that forms a resin extrusion port; and a pressure ring that faces the flow path of the molten resin and rectifies the flow of the molten resin, and each of the head portions includes:
The pressure ring is composed of a sleeve surrounding the mandrel and a housing coaxially disposed outside the sleeve with a flow path for molten resin remaining between the sleeve and the plurality of heads. interposed between the lower end of the housing of one of the head parts and the upper end of the sleeve of the other head part adjacent to each other, and forms the outermost layer of the multilayer parison adjacent to the die part of the plurality of head parts. The head portion has a molten resin flow path that communicates with the molten resin extrusion port of the die portion along both the inner and outer surfaces of the sleeve,
A multilayer parison molding device for blow molding in which each head section except this head section and the pressure ring have the following configurations (a) to (c); (a) the outer surface of the sleeve is a first surface parallel to the mandrel; , a second surface inclined downstream toward the center of the mandrel, a third surface parallel to the mandrel continuous from the downstream side of the second surface, and a third surface continuous from the third surface and oriented toward the center of the mandrel. (b) A pressure ring facing the flow path of the molten resin is spaced apart from a surface halfway from the second surface to the third surface of the sleeve. the inner surface has opposing inner surfaces, the surface facing the second surface of the sleeve being inclined downstream toward the center of the mandrel, and the surface facing the third surface of the sleeve being facing the outer circumferential surface of the mandrel. (c) The inner surface of the housing and the inner surface of the pressure ring connected thereto are formed so as to gradually reduce the width of the molten resin flow path formed between the inner surface of the housing and the outer surface of the sleeve. There is.