JPS6058011B2 - Multilayer parison molding equipment for 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 blow molding 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. It is possible to obtain 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 resource conservation in oil and electricity,
Problems with waste disposal such as plastics and food hygiene issues with polyvinyl chloride have been raised, and these containers should also meet usage requirements with a minimum amount of resin.
It is also necessary that the material poses no problems in terms of hygiene and pollution prevention.

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

In other words, thermoplastic resins have different hardness, flexibility, and
There are differences in tensile strength, gas permeability, printing suitability, etc.
On the other hand, the outer surface of a plastic container is susceptible to external shocks, and the texture of the container is mainly determined by the material of the outer surface. Furthermore, when printing on containers, it is desirable to use a material that has an affinity for printing ink. On the other hand, the inner surface of a plastic container is directly fused with the product. It must not react with the contents or elute harmful substances. Taking these things into consideration, if you make a plastic container into two or three layers and use the appropriate material for each layer, you can achieve better quality with a smaller amount of material than conventional single-layer molded products. It is possible to make containers.

[Purpose of the invention]

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 obtain a good blow-molded product in which the thickness of the resin constituting each layer is uniform over the whole,
Another object of the present invention is to provide an apparatus for extrusion molding a multilayer parison in which fine adjustment of the resin thickness of each layer can be easily performed. 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 apparatus of the present invention is used in the pre-process of the blow molding process, and has one main extruder and one or more sub-extruders radially provided in one die head. It is something that

The radial arrangement angle between the main extruder and the sub-extruder is preferably 25 to 900 degrees. 2
If the angle is smaller than a pentagonal angle, the extruder bodies will interfere with each other, making installation impossible.If the angle is greater than 90°, 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 arranged between the mandrels and connected to the extruder; 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 parts surrounds the mandrel. It is comprised of a sleeve and a housing disposed coaxially with the outer side of the sleeve leaving a flow path for molten resin between the sleeve, and the pressure ring is arranged adjacent to each other in the plurality of head parts. A head part, which is interposed between the lower end of the housing of one head part 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 among the plurality of head parts, The sleeve has a molten resin flow path communicating with the molten resin extrusion port of the die part along both the inner and outer surfaces of the sleeve, and each head part except this head part and the pressure ring have the following configurations (a) to (c). (a) The outer surface of the sleeve has a first surface parallel to the mandrel, a second surface inclined in the downstream direction toward the center of the mandrel, and this second surface.
a third surface parallel to the mandrel that is continuous from the downstream side of the surface, and a fourth surface that is continuous from the third surface and slopes further downstream toward the center of the mandrel, (b)
The pressure ring facing the flow path of the molten resin 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 this inner surface (c) the inner surface of the housing and the surface connected thereto; The inner surface of the pressure ring is formed so as to gradually reduce the width of a flow path for molten resin formed between the inner surface and the outer surface of the sleeve.

Note that the inner surface of the sleeve of the head for forming the innermost layer 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, 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, etc. are sequentially arranged in series around the mandrel in the die head to form a resin passage for the three layers.

[Effect]

First, thermoplastic resin materials are supplied to extruders 2 and 3 from hoppers 4 (the hopper of extruder 3 is not shown), and after melting and pressurizing the materials with a heating screw, the molten materials are press-fitted into 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. The resins constituting each layer are kneaded and melted under appropriate temperature conditions by separate extruders 2 and 3, and then press-fitted into each part of the die head 1.
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, and is divided into two parts facing the sleeve 14, forming the resin flow path 1.
While descending along the pipe 5, both ends thereof are joined and fused to form a molten resin pipe within a flow path consisting of a concentric wall formed by the sleeve 14 and the housing 16. The width of the flow path 15 gradually decreases, and as the pressure in the molten resin pipe decreases, it is constricted and rises, and the resin flow becomes uniform and rectified. The same is true). The wall thickness of this rectified molten resin pipe is further adjusted, but this is due to pressure reduction. The gap between the ring 17 and the sleeve 14 is adjusted using an external adjustment bolt 18.
This is done by slightly changing the position of the pressure ring 17. The innermost layer resin pipe whose wall thickness has been adjusted then reaches the intermediate head portion 6.

One sub-extruder 3 in the intermediate head section 6
The molten resin for the intermediate layer is press-fitted from the tube through the inlet 12, and an intermediate layer molten resin tube is formed in the flow path 20 around the sleeve 19 in the same manner as described above, and the wall thickness is adjusted using the pressure ring 21 and the adjustment bolt 22. After that, it merges with the outside of the innermost layer molten resin pipe 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-fitted from another sub-extruder 3 through the inlet 13.
An outer layer molten resin tube is formed within the flow path 25, and merges with the aforementioned two-layer molten resin tube at a confluence point 26 to form a three-layer resin tube.

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, since the inner surface of the die 8 has a longer sloped surface than 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 by the adjusting screw 29. Since the resin flow can be rectified by using the die 8 and the die 8 has the same effect as a pressure ring, there is no need to provide a pressure ring or a screw for investigating the pressure ring in the outer layer head portion 7. The parison formed in this manner is fed to a well-known blow molding machine and processed into a three-layer molding.

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.

Furthermore, 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 slit between the core pin 9 and the die 8 changes to adjust the thickness of the parison. An electronic parison programmer is connected to the core holder 30 to reduce disturbances in the resin laminar flow within the die head and to precisely adjust the thickness of the parison.

Examples of the present invention are shown below.

Example 1 A blow molding machine having a 50φ main extruder was connected to the inner layer head of the single-head two-layer die head of the present invention, and a 30φ sub was attached to the main extruder at an angle of 9 horizontal steps using this die head as a fulcrum. An extruder was attached and connected to the outer layer head of the die head.

The main extruder is made of maleic acid-modified polypyrene (
MIL. On the other hand, the sub-extruder was loaded with nylon and the maximum cylinder temperature was set at 250℃, and the die head temperature was set at 240℃.
When a 500cc outer layer nylon/inner layer polypropylene two-layer container was continuously molded using the following settings, a two-layer container that took advantage of the characteristics of each resin was obtained. It was confirmed that the thickness is approximately proportional to the thickness ratio of each layer of the product. The properties of the molded two-layer container (nylon 22Wt% total pressure 600μ) are: oxygen permeability 0.39y/I・24Hr30μ, haze 35% (JI
SK67l4), interlayer adhesion degree 450/15Tnf! It was t width and 90% peeling. Example 2 A blow molding machine having an 80φ main extruder and the two-layer dual die head of the present invention were connected by an adapter that evenly branches the molten resin extruded from the main extruder and supplies it to the inner layer head portions of the two die heads. Furthermore, separate 30φ sub-extruders were attached and connected to the outer layer head portions of the two die heads at an angle of 30 degrees with respect to the main extruder.

Furthermore, an electronic parison programmer (manufactured by Hunker◆Carporate Incorporated, 20 point type) is connected to the core holder of the die head, and while adjusting the wall thickness of the parison, a relatively A two-layer container with a nylon outer layer and a colored polypropylene inner layer was molded in which the flow ratio of each part of the bottle varied greatly. The height of the bottle is approximately 12 cm, and the maximum diameter is 8 d. Load colored maleic acid-modified polypropylene into the main extruder,
The two sub-extruders are loaded with 6 nylon,
Molding was carried out at the same set temperature as in Example 1, but no disturbance of the laminar flow in the die head due to parison control was observed, and a good molded product with well-adjusted wall thickness was obtained. This product was compared with a product without parison wall thickness adjustment. FIG. 5 shows the wall thicknesses at the position A of the bottle shown in FIG. 4. Example 3 A blow molding machine having a 60φ main extruder and the two-layer dual die head of the present invention were connected using the same adapter as in Example 2, and two 25φ sub-extruders were connected in the same manner as in Example 2. Connected main extruder.

- colored maleic acid-modified low-density polyethylene (12
．． Density, 0.920) was loaded, and the cylinder maximum temperature was set to 190℃, while the sub-extruder was loaded with nylon 6, the cylinder maximum temperature was set to 240℃, and the die head temperature was set to 220℃. When a 30φ tube-shaped blow container was molded, the total thickness was 600μ (15% nylon), and the interlayer adhesion strength was 500y/1 with little uneven thickness.
A molded article with good peeling of 900 mm in normal width was obtained. Example 4
Another layer head portion was inserted between the inner and outer layer head portions of the two layer double die head used in Example 3, and the mandrel was changed to a three layer die head to create a three layer double die head.

Four head parts of the innermost layer and the outer layer of this three-layer double die head were connected to a 60φ main extruder using adapters that evenly divided the molten resin extruded from the main extruder into four parts. Furthermore, 2 of the middle layer head part
A 25φ sub-extruder was separately connected to each of these locations as in Example 2. The main extruder was loaded with maleic acid-modified low-density polyethylene (LDPE) and the maximum cylinder temperature was set at 190°C, while the two sub-extruders were loaded with saponified ethylene/vinine acetate copolymer (containing 30 mol of ethylene). %, degree of saponification 99.5%
), the cylinder maximum temperature was set at 240°C, and the die head temperature was set at 230°C to mold a three-layer flexible container composed of LDPE/ethylene-modified PVA/LDPE.
A molded product having a diameter of 90μ) with good content protection properties was stably obtained. The characteristics of this container are oxygen permeability 0.04y/d・2
4Hr・30μ・Atml moisture permeability 8y/d・24Hr・
30p1 interlayer adhesion 4009/15 width 90, peeling. Example 5 An adapter that evenly branches the molten resin extruded from the extruder was used at two locations in the innermost layer head part of the three-layer double die head used in Example 4, and was connected to a 25% sub-extruder, and similarly 2 layer head parts and 60φ
The main extruder and two outermost layer heads were connected to the other 25% sub-extruder.

The two sub-extruders are equipped with high-density polyethylene (
MIO. 3. Density 0.945) was loaded and the cylinder maximum temperature was set at 200℃, while the main extruder was loaded with polyethylene-based high filler resin containing 50% clay and the cylinder maximum temperature was set at 180℃, and the die head temperature was set at 180℃. When the temperature was set at 190'C and a flat container was molded at 200°C, a stable molded product was obtained. This is a drawback of high filler resin because the inside and outside of high filler resin are covered with polyethylene. Surface quality, appearance, pinch-off strength and extraction into contents were significantly improved. Total thickness is 800μ
The polyethylene layer had a thickness of 60μ both inside and outside. [Effects of the Invention] Since the present invention is configured 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 portion of the inner surface of the pressure ring and the outer surface of the sleeve is Since it is formed of a part that is flat with respect to the mandrel and a part that is sloped toward the mandrel, it is easy to finely adjust the thickness of the resin in each layer, and the resin flow path is formed in the part where the pressure ring is provided. 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 opposing parts of the inner surface of the pressure ring and the outer surface of the sleeve have a shape that is flat with respect to the mandrel and a part that is sloped downward toward the mandrel. In order to obtain the same rectification effect, the length of the device in the parison extrusion direction can be made shorter than in the case of a straight and inclined shape, 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 device for blow molding of the present invention; Fig. 2 is a vertical cross-sectional view of a die head for forming a three-layer parison used in the device; A vertical cross-sectional view of a die head for forming a parison; FIG. 4 is a side view showing an example of a container manufactured by blow molding from a parison formed using the parison forming apparatus of the present invention;
The figure is a graph showing the results of measuring the wall thickness of a molded container. 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, 1
0... Mandrel, 11, 12, 13...
...Resin inlet, 14, 19, 24...Sleeve, 1
7, 21... Pressure ring, 18, 22.
...Pressure ring adjustment screw, 29.Dice adjustment screw.

Claims (1)

[Claims] 1. A multilayer parison molding device for blow molding in which one main extruder and one or more sub-extruders are radially attached to one die head, and the die head includes a core holder having a core pin at the tip, and a core holder having a core pin at the tip; a die portion comprising a cylindrical mandrel surrounding a core holder, and a die having an adjustment screw for adjusting the relative position of the core pin and the die, and surrounding the core pin to form a molten resin extrusion port; a plurality of heads disposed between the base of the core holder and the die and connected to the extruder so as to form a flow path for molten resin along the mandrel between the core holder and the base of the core holder; 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 parts includes a sleeve surrounding the mandrel and a pressure ring that rectifies the flow of the molten resin between the sleeve and the sleeve. The pressure ring includes a housing disposed coaxially with the outer side of the sleeve, and the pressure ring connects the lower end of the housing of one of the plurality of head parts adjacent to each other and the sleeve of the other head part. A head part, which is interposed between the upper ends and forms the outermost layer of the multilayer parison adjacent to the die part among the plurality of head parts, extends along both the inner and outer surfaces of the sleeve and the molten resin extrusion opening of the die part. A multilayer parison molding device for blow molding, which has a molten resin flow path communicating with the sleeve, and each head section except this head section and the pressure ring have the following configurations (a) to (c); (a) a sleeve The outer surface is the first 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 fourth surface continuous from the third surface and inclined further downstream toward the center of the mandrel. (b) The pressure ring facing the flow path of the molten resin 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 this inner surface has:
A surface of the sleeve opposite to the second surface is inclined downstream toward the center of the mandrel, and a surface of the sleeve opposite to the third surface is parallel to 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 flow path for molten resin formed between the inner surface of the housing and the outer surface of the sleeve.