JPH02286219A - Multilayer blow molding device - Google Patents

Abstract

PURPOSE:To eliminate the need for the severe program control of a parison during extrusion therof and to form a thin film to the multilayer blow moldings having a thin-walled layer by providing an orifice part having proper length length to a flow path of resin provided between an extruder and an annular flow path for distributing resin to the circumferential direction. CONSTITUTION:An orifice part 14 having large resistance for a flow path is provided to the flow path 13 wherein the resin extruded through a pneumatic cylinder 9 from an extruder 1 reaches an annular flow path 5 for distributing resin to the circumferential direction in the inside of a head main body 4. The orifice part is not provided to a resin flow path 15 in an extruder 1' side of the left side shown in a figure. Different kind of resin is supplied to the left and right extruders 1, 1'. Thereby the multilayer blow moldings having two kinds and three-layer structure is obtained which has both a thin intermediate layer formed via the flow path 13 provided with the orifice part 14 and a thin- walled intermediate layer having the inner and outer layers thicker than the above-mentioned intermediate layer. The flow rate is stabilized and the multilayer blow thin film can be molded which is free from disturbance in the thick-wall distribution in the lengthwise direction.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a multilayer blow molding product used in blow molding blow molded products such as a gasoline tank or bumper made of brass for an automatic V; Regarding η. [Prior art] and [problems to be solved] Conventional layer blow molded products have been widely used as blow molded products, but recently, plastics have been used as containers for petroleum, solvents, gasoline, etc. Multi-layer blow-molded products with two or more layers are increasingly being marketed. For example, three-layer blow-molded products with nylon resin as the middle layer and high-density polyethylene as the inner and outer layers are becoming more popular. An example. In such multilayer blow molding, the parison is formed into multiple layers at the die location in the blow molding device, and blow molding is performed. FIG. 4 shows an example of a conventional multilayer blow molding apparatus. An example of multilayer blow molding using this apparatus extrudes resin from each extruder 1, and a parison head body comprising a ring plunger 2 and a partition wall 3 ( Hereinafter, IQ may also be referred to as head) 4, annular flow path (annular path) 5 and its lower part 7
A parison 8 having a three-layer structure is extruded from a diamond through a cumulator (ring camber) 6. The annular flow path 5
is a flow path for distributing molten resin in the circumferential direction within the head main body 4. Also, accumulator 6
This is to hold the resin extruded from the extruder 1 in a molten state and extrude the parison 8 at a time, and is intended to prevent the drawdown phenomenon that occurs when extruding the parison directly from the extruder. It is something. In FIG. 4, 9 indicates a hydraulic cylinder, and 10 indicates a core. When making a multilayer blow molded product using a die head type multilayer blow molding having such an accumulator 6; Sometimes I want something thin. For example, when the intermediate layer is an adhesive layer for bonding the inner and outer layers, you want to make the adhesive layer as thin as possible, or when the intermediate layer is a barrier layer and you want it to be thinner than the inner and outer layers. This is a case where it is sufficient. In such a case, in the conventional example, the wall thickness composition ratio of each layer is changed only by the pressure of each of the seven accumulators, and in order to meet such a request, it would be necessary to drastically change the die head structure or change the accumulator. This requires the installation of a precise control device, etc., which significantly increases the cost of the molding equipment and the multilayer blow-molded product. , Japanese Unexamined Patent Publication No. 57-75825 describes the prior art as a single-layer blowing crosshead in which a flow bin having a choke protruding from the resin flow path is provided. That is, the pressure distribution of the resin pushed into the head body by the extruder is high at the upper part of the resin flow path. The F section is blocked by the flow bin, resulting in low pressure, and the resin flow toward the gap between the die (nozzle) and mandrel (core) is uneven and turbulent. In order to correct this non-uniformity, a method has been described in which a flow bottle is provided with a choke to restrict the resin flow path. However, it has been stated that with this choke, there is no pressure uniformity such as the effect of ring-piston extrusion, and the parison becomes unstable as the temperature of the resin changes. Therefore, this publication proposes a blow molding machine as shown in FIG. 5 as an improvement over the above-mentioned conventional technology, and this blow molding machine is improved by providing a float 11 that can be raised and lowered. ing. In addition, in FIG. 7, 12 indicates a flow bin.
Further, in FIG. 7, an annular path 50 is further provided above the annular path 5. However, in any case, in the blow molding machine, the resin flow path after the annular path 5 (50) that distributes the resin in the circumferential direction has been improved, such as by providing a float in the resin flow path. In other words, this is to make the thickness distribution of the parison uniform in the circumferential direction after distributing the resin in the circumferential direction.
The resin flow path up to point 0) has a structure that minimizes the flow path resistance as much as possible, and in addition, the parison is uniform in the length direction in multilayer blow molding that has a thin resin layer and in the multilayer blow molding.・Gender preservation is not considered. The purpose of the present invention is to provide a technology that can eliminate the drawbacks of the conventional technology. When you want to make the thickness of a layer as thin as possible compared to the inner and outer layers, for example, when the middle layer is an adhesive layer for bonding the inner and outer layers, you want to make the adhesive layer as thin as possible. or when the intermediate layer is a barrier layer and it is sufficient to be thinner than the inner and outer layers, it is possible to obtain a parison with a multilayer structure including thin layers while maintaining uniformity in the length direction. , we provide a technology that can meet these demands without requiring major changes to the die head structure or setting precise values for the accumulator control device, and therefore without increasing the cost of the molding equipment or multilayer blow molded product. Particularly, one object of the present invention is to provide a multilayer blow molding apparatus suitable for obtaining a multilayer blow molded product including multiple thin layers of various types using various types of resins. [Means for Solving the Problems 1 What is the present invention for achieving this object? A multilayer blower that extrudes resin from I number of extruders, distributes the extruded molten resin in the circumferential direction within the parison head body, merges the distributed resins, and extrudes it outside the goo as a multilayered parison. In the molding apparatus, the multilayer blow molding apparatus is equipped with an accumulator for accumulating the extruded molten resin in the parison head body, wherein at least one of the layers of the multilayer parison is compared to the other layers. In the resin flow path between the extruder for obtaining a thin layer and the annular flow path where the resin extruded from the extruder is distributed in the circumferential direction and has increased flow path resistance, The present invention resides in a multilayer blow molding apparatus for obtaining a parison having a multilayer structure including thin layers characterized by having an orifice portion that increases the flow resistance of the resin. If so, as mentioned above,
A float is installed and moved up and down to restrict the flow of resin, or a choke is installed in the flow bin to restrict the flow of resin, but the resin flow path from the extruder to the annular flow path is controlled as much as possible. It has a structure that reduces flow path resistance. In contrast, in the present invention, in the resin flow path between the extruder and the annular flow path (passage) that distributes the resin in the circumferential direction,
An orifice portion of an appropriate length is provided. In this case, when the resin flow path includes a flow path that branches the resin into each layer, the orifice section is provided in each of the branched flow paths. The effects of this invention are as follows. Although the desired results of the present invention can be obtained to some extent by changing the pressure in the accumulator during extrusion of the parison, strict program control of the parison is required. - On the other hand, the resin flow path between the extruder and the annular flow path as described above should be kept in a structure that minimizes the flow resistance as much as possible, and the resin flow path between the extruder and the annular flow path as described above should be kept as low as possible. If only a part with high flow resistance is installed, such as
Maintaining the uniformity of the wall thickness distribution in the length direction of the parison It is difficult to maintain uniformity, especially in multilayer blow thin film molding, which has thin film layers with significantly different thicknesses, as described above, and the flow rate at the confluence section fluctuates. cannot be stabilized. In contrast, by adopting the above means of the present invention,
Since the waterfall at the confluence becomes smaller and stabilized, it becomes possible to form multilayer blow-molded products with thin layers, and the thickness distribution in the length direction of the parison can be made even. Moreover, in the present invention, it is only necessary to provide an orifice section in the resin flow path after exiting the extruder, so strict control of the head body is not required, and there is no need for major structural changes to the die head. [Example] Next, an example of the present invention will be described with reference to the drawings. Fig. 1 shows one example of the present invention. An example is shown in which the molding device is applied to a multilayer blow molded product having two types and three layers.As shown in FIG. An annular channel for distributing the resin in the circumferential direction (
In the resin flow path 13 up to 5 (hereinafter also referred to as lip portion), an orifice portion 14 with increased flow path resistance
will be established. The resin flow path 15 on the extruder 1' side on the left side in the figure is not provided with the orifice section.
1' is provided with a different class I4 resin. As a result, 1, for example, a multilayer blow molding having a two-type, three-layer structure having a thin intermediate layer layered through a resin flow path 13 provided with an orifice portion 14, and a thin intermediate layer having inner and outer layers thicker than the intermediate layer. This enables multilayer blow thin film molding with a stable flow M and no disturbance in the wall thickness distribution in the length direction. Figure 2 shows an example in which the present invention is applied to a multilayer blow molding apparatus for obtaining a parison with a three-layer five-layer structure, where the third layer is thin and the other two layers are thicker. The resin flow path 13 from the extruder 1 on the right side of the figure to the annular path (lip portion) 5 has an orifice portion 1 with high flow path resistance.
4 is provided. An orifice portion is not provided in the resin flow path 15 in the extruder 1'' at the upper left in the figure. The resin flow path 16 from the extrusion lll'' at the upper left in the figure to the annular path 5 branches in the middle as shown in the figure. An orifice portion 14 is provided in front of the branched flow paths 160 and 161 of the hI4 fat flow path 16. FIG. 3 shows an example in which the present invention has been applied to blow molding 6 to obtain a parison of three types and five layers, similar to that shown in FIG. 2, and is different from that shown in FIG. In the L resin flow path 16, an orifice portion 14.14 is provided in each of the first flow path 160 and 161 after branching into eight layers. Next, an example of implementation of the present invention will be shown. The results of an example test in which a multilayer blow molded product was produced using the multilayer blow molding apparatus shown in FIG. 1 are shown below. The dimensions of the lip portion 5 of the molding device used in the test were 2 seconds in width.
- x Length 30 m 5 x Diameter (φ) 200 mm, die exit diameter is φ200 am, accumulator 6 has 8 jets on the side forming one layer of the multilayer blow molded product
, the capacitance on the side forming the intermediate layer was set to 4β. Also, the orifice portion 14 in the resin flow path 13 is set to φ1
(diameter) x loomm (length) and φl x low-. For comparison, the resin flow path 13 is
A test was also conducted with 0 binding. As the resin used, high-density polyethylene (M+ (melt index) 0.1 g / 10 minutes) was placed on the l side of the extruder (
II D P E ) and Mr'RO on the extruder 1 side.
,4g/l 01n, (235℃) polyamide (
Nylon 6) was used, the die temperature was 230°C, and the total parison wall thickness was 5Il11. Blow molding was performed at a parison discharge speed of 0.3 m/sec. As a result, in the case of the present invention in which the orifice portion I4 is provided in the resin flow path 13 and the orifice portion 14 is set to φ1XloO+++m, the lower limit of the thickness is 13 μm, and
In the case of XlO+am, a multilayer blow-molded product with a two- or three-layer structure having an extremely thin film layer (intermediate layer as a barrier layer) with a uniform wall thickness distribution in the length direction, which is at the lower limit of Jou@, is 1- I was able to do it. On the other hand, the resin flow path 13 has a diameter of φI OX 400 mm.
In the conventional example in which the orifice portion according to the present invention is not provided,
Only 41 # of multilayer blow molded products having layers with a maximum thickness of 100 μm were made. [Effects of the Invention] According to the present invention, an orifice portion of an appropriate length is provided in the resin flow path between the extruder and the annular flow path (passage) that distributes the resin in the circumferential direction. This requires strict program control of the parison during its extrusion. The resin flow path between the extruder and the annular flow path as described above is kept in a structure that minimizes flow path resistance as much as possible, and only within the head body, the flow path resistance such as the conventional annular flow path is reduced. Merely providing a large portion of the parison will not maintain the uniformity of the wall thickness distribution in the longitudinal direction of the parison. Especially, multilayer blowing i? It is difficult to maintain uniformity in ll1Q molding, and the flow rate at the merging section fluctuates and cannot be stabilized, whereas according to the present invention, the cascade of the merging product becomes smaller, and
It was possible to obtain a parison that was stable and had a uniform wall thickness distribution in the length direction, and it became possible to perform thin film molding of multilayer blow molded products having thin layers. In addition, in the present invention, since it is sufficient to provide an orifice section in the resin flow path after exiting the extruder, not only does strict control of the head body not be required, but also a major structural change of the die head is not required. This made it possible to reduce the cost of multilayer blow molding equipment and multilayer blow molded products.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the invention, FIG. 2 is a sectional view showing another embodiment of the invention, FIG. 3 is a sectional view showing still another embodiment of the invention, and FIG. 4 is a sectional view showing another embodiment of the invention. is a sectional view showing a conventional example,
FIG. 5 is a sectional view showing a conventional example. 1', 1... Extruder 4... Parison head Fig. 1 - Annular flow path, accumulator, die, parison, hydraulic cylinder, core, resin flow path, orifice section, resin flow path, resin flow path, branch flow path

Claims (1)

[Claims] 1. Extrude resin from a plurality of extruders, distribute the extruded molten resin in the circumferential direction within the parison head body, merge the distributed resins, and create a multilayer structure outside the die. A multilayer blow molding apparatus for extruding a parison, the multilayer blow molding apparatus comprising an accumulator for temporarily accumulating the extruded molten resin in a parison head body, wherein at least one of the layers of the multilayer parison is between the extruder for obtaining a layer whose thickness is thinner than other layers and the resin extruded from the extruder before reaching the annular flow path where the resin is distributed in the circumferential direction and has increased flow path resistance. A multilayer blow molding device for obtaining a parison having a multilayer structure including thin layers, characterized in that a resin flow path is provided with an orifice portion that increases the flow path resistance of the resin. 2. When the resin flow path according to claim 1 includes a flow path that branches the resin into each layer, each of the branched flow paths is provided with an orifice portion that increases the flow path resistance of the resin. A multilayer blow molding apparatus for obtaining a parison having a multilayer structure including thin layers.