JPH02227210A - Formation of multilayer parison - Google Patents

Abstract

PURPOSE:To make it possible to recycle waste resin as it is without providing an extruder anew by a method wherein a first and a second resin layers consisting of two kinds of resins, which are adherent to each other, are respectively produced and, at the same time, a third resin layer made of the waste resin of multilayer parison, which is discharged in a process after extrusion, is produced between the first and the second resin layers. CONSTITUTION:Between the inner layer and the outer layer made of first resin, second resin and waste resins are extruded from annular nozzles 24, 25 and 25, which are provided on the rear surface of a ring member 17. The resins extruded from the annular nozzles 24, 25 and 25 form a tubular body consisting of the middle part made of a second resin layer and both the inner and the outer part made of third resin layers. The inner layer and the outer layer made of the first resin meet said tubular body from both the sides so as to form a laminated state. Molten resins laminated in a resin passage 12 is extruded downwards through a narrow die slit 11, resulting in closely joining the respective resin layers together and forming the tubular body having the predetermined wall thickness in order to obtain a multilayer parison having a three-kind five- layer structure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for molding a multilayer parison by extrusion molding a multilayer parison formed by laminating a plurality of resin layers.

(Prior art) As a molding method for hollow resin containers, blow molding is used. In other words, a parison formed by extrusion is placed in a mold cavity, and then pressurized gas is blown into the parison to perform molding. Molding methods are known. In recent years, fuel tanks for vehicles made of resin formed by blow molding have been proposed and are being put into practical use, and high-density polyethylene resin is generally adopted from the viewpoints of moldability, strength, cost, etc. has been done. However, since polyethylene has an affinity for gasoline, etc., if gasoline, etc. is left in a container made of high-density polyethylene resin for a long period of time, such as a fuel tank, etc.
There is a problem in that gasoline and the like gradually penetrate and permeate the peripheral wall of the container. For this reason, as disclosed in Japanese Patent Publication No. 58-23212 and Japanese Patent Application Laid-Open No. 62-138227, for example, a resin layer formed of high-density polyethylene resin and a resin layer that prevents the permeation of gasoline, etc. can be used. A multilayer blow molded container (fuel tank) is produced by blow molding using a multilayer parison made by laminating a resin layer made of nylon resin or the like in a sandwich shape with high density polyethylene resin layers located on both sides. Efforts have been made to form a

In this way, when blow molding is performed using a multilayer parison formed by laminating a plurality of resin layers, the waste resin such as paris formed together with the molded product by blow molding also overlaps with the plurality of resin layers. Since it contains a plurality of resins that were used to form the resin, if this waste resin is carelessly reused as recycled resin, the following problems will occur. In other words, each resin layer that makes up a multilayer parison is provided to obtain predetermined characteristics, so if waste resin is mixed into a specific resin layer, the characteristics that the resin layer should have will be degraded. It will be necessary to do so.

For example, in the above example, if waste resin is mixed into the high-density polyethylene resin layer, the nylon resin, etc. in the waste resin will come out on the outside or inside of the fuel tank, which is a blow-molded product. It is conceivable that the fuel tank may deteriorate due to chemicals (calcium chloride) or alcohol-containing gasoline. In addition, the waste resin has already been affected by heat and has inferior physical properties compared to new resin, so from this point of view as well, it is undesirable for the waste resin to come out on the outside or inside of the blow-molded product.

For this reason, conventional efforts have been made to avoid the above-mentioned disadvantages by forming a waste resin layer between the resin layers constituting the multilayer parison.

(Problem to be solved by the invention) However, since each resin layer constituting a multilayer parison is generally laminated via an adhesive resin layer, in order to form a new waste resin layer, it is necessary to It is necessary to perform a treatment to ensure adhesion with the resin layer on the side that is not the adhesive resin layer among the pair of resin layers located on the side. That is, it is necessary to form a new adhesive resin layer, or to subject the waste resin to a predetermined modification treatment in order to impart an adhesive function to it. Furthermore, in order to form the waste material resin layer, a dedicated extruder is required, and in the former method, an extruder is also required to form a new adhesive resin layer.

The present invention was made in view of these circumstances, and provides a multilayer parison that allows waste resin to be reused as is without the need to form a new adhesive resin layer or install a new extruder. The purpose of this invention is to provide a molding method.

(Means for Solving the Problems) The method for molding a multilayer parison according to the present invention includes forming two resin layers using two types of resins that have adhesive properties to each other, and forming a waste resin layer between these resin layers. This is intended to achieve the above objectives. That is, in a multilayer parison molding method in which a multilayer parison formed by laminating a plurality of resin layers is extrusion molded, the first and second resin layers are respectively formed of two types of resins that have mutually adhesive properties, and the extrusion The present invention is characterized in that a third resin layer is formed between the first and second resin layers using waste resin from the multilayer parison discharged in a process after molding.

The above-mentioned "multiple resin layers" are the first. It goes without saying that the structure may consist of only the second and third resin layers, but the waste resin may be used to form a third layer between the first and second resin layers.
When the third resin layer and the first and second resin layers are formed, the third resin layer and the first and second resin layers are formed.
It may also include other resin layers as long as a predetermined adhesiveness can be ensured between the resin layer and the other resin layer.

The "two types of resins" forming the first and second resin layers are not limited to a specific combination as long as they are "mutually adhesive".

(Operations and Effects of the Invention) As shown in the above configuration, the first and second resin layers are respectively formed using two types of resins that have adhesive properties, and the multilayer parison that is discharged in the process after extrusion molding is The third resin layer is formed between the first and second resin layers using the waste resin, but the waste resin contains the two types of resins mentioned above, and both resins have adhesive properties to each other. Therefore, the third resin layer has adhesive properties with both the first and second resin layers. Therefore, there is no need to form a new adhesive resin layer or to modify the waste resin in order to bond the waste resin layer with other resin layers, so there is no need to install a new extruder for this purpose, and the waste material The resin can be reused as is.

Moreover, since the adhesive resin layer that was conventionally provided for bonding the first and second resin layers is no longer required, the extruder used to form this adhesive resin layer can be used to It is possible to form a resin layer of.

(Examples) Examples of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a part of a multilayer parison (see FIG. 2) formed by an embodiment of the method for forming a multilayer parison according to the present invention.

The multilayer parison P includes a pair of first resin layers L1 located on the outer and inner sides thereof, a second resin layer L2 located between the pair of resin layers L1, and a second resin layer L2 located between the pair of resin layers L1. Layer L
2 and a third resin layer L3 located between the pair of first resin layers Ll are laminated.

The first resin layer L1 is a modified polyethylene resin obtained by modifying a polyethylene resin with maleic anhydride (see Fig. 3).
The second resin layer L2 is formed of a resin (hereinafter referred to as the first resin) that is highly dispersed microscopically in a high-density polyethylene resin using a pelletizer or the like, and the second resin layer L2 is formed by dispersing the modified polyethylene resin into a high-density polyethylene resin using a pelletizer or the like. It is formed from a resin (hereinafter referred to as the second resin) that is highly dispersed microscopically in a nylon resin. The third resin layer L3 forms a waste resin, that is, a part that should become waste material such as paris that is formed and discharged together with the blow molded product when blow molding is performed using the multilayer parison P. It is made of resin.

FIG. 5 is a side sectional view showing the overall configuration of a multilayer parison extrusion molding apparatus used to carry out an embodiment of the multilayer parison molding method according to the present invention.

As shown in FIG. 5, the lower half of the accumulator head 1 is provided with a cylinder 2 and a ring piston 3 that slides up and down along the inner peripheral surface of the cylinder 2. is provided with a core 4 that passes through the ring piston 3 and is fixed to the cylinder 2. A resin storage chamber (resin reservoir) 5 is formed inside the cylinder 2, which is partitioned by the ring piston 3 and surrounded by the cylinder 2 and the core 4. The first resin is continuously extruded in a molten state from the extruder 6 and is supplied through an annular communication path 7 connected to the first extruder 6. The temperature of the first resin stored in the resin storage chamber 5 is adjusted by a temperature adjustment device (not shown) provided in the cylinder 2, such as a heater.

Further, an annular die 8 is fixed concentrically to the lower end of the cylinder 2, and an annular core support 9 is fixed to the lower end of the core 4. A core IO concentric with the die 8 is fitted so as to be slidable in the vertical direction. The inner circumferential surface of the lower end of the die 8 and the outer circumferential surface of the lower end of the core 10 are each formed into a conical shape, and an annular guide slit 11 is formed therebetween. The die slit 11 communicates with the resin storage chamber 5 through an annular first resin passage 12 formed between the cylinder 2 and die 8 and the core 4 and core support 9.

The core lO is moved up and down by a hydraulic cylinder (not shown) via a rod 13, thereby adjusting the width of the guide slit 11 formed between it and the die 8, that is, the thickness in the radial direction. It has become. Further, the ring piston 3 is lowered by the operation of a single-acting hydraulic cylinder 15 via a rod 14, and the first extrusion cylinder 15 and the ring piston 3 cause the first resin in the resin storage chamber 5 to be lowered. An accumulator 16 is configured to force-feed the resin to the first resin passage 12 or the die slit 11 side.

Further, in the first resin passage 12, as shown in FIGS. 6 and 7, a ring member 17 having a substantially vertically elongated hexagonal cross section is disposed concentrically with the resin passage 12. As shown in FIGS. The ring member 17 is supported at a predetermined distance from the inner peripheral surface of the cylinder 2 by four struts 18, 18, . ... and four pillars 19.19. provided at different positions in the circumferential direction. ... is supported at a predetermined distance from the outer peripheral surface of the core 4, and the first resin passage 12 is divided by the ring member 17 into an inner annular passage 12a and an outer annular passage 12b. There is. Inside the ring member 17, a second annular resin passage 20 located approximately at the center and two third annular resin passages 21, 21 located on both sides of the second resin passage 20 are formed. These resin passages 20, 21, 21 are formed by annular slits 22, 2, respectively.
3 formed on the lower surface of the ring member 17 through 3.23.
It communicates with the book's concentric annular nozzle 24.25.25.

The second resin passage 20 is a passage 28 formed in one pillar 18 between the ring member 17 and the cylinder 2.
The accumulator head 1 is connected to a second extruder 27 provided outside the accumulator head 1 through the accumulator head 1 . At the tip of the second extruder 27, an accumulator 28 temporarily stores the second resin continuously extruded in a molten state from the second extruder 27, and extrudes the second resin by operating the piston 28a. is provided, and this accumulator 28
is equipped with a temperature adjustment device (not shown) that adjusts the temperature of the stored second resin.

The third resin passage 21.21 is a passage 29.2 formed in the other support column 18 between the ring member 17 and the cylinder 2.
9, it is connected to a third extruder 30 provided outside the accumulator head 1. An accumulator 31 equipped with a temperature adjustment device is also provided at the tip of the third extruder 30, and the waste resin continuously extruded from the third extruder 30 in a molten state is temporarily stored by this accumulator 31, and This waste resin is pushed out by operating the piston 31a.

Next, the operation of this embodiment will be explained.

As shown in FIGS. 5.6 and 7, under normal conditions, the ring piston 3 of the accumulator head 1 and each piston 28a, 31a of the accumulator 28.31 outside thereof
Both are considered to be free.

As a result, in the accumulator head 1, the first
The first resin extruded from the extruder 6 and introduced into the resin storage chamber 5 is stored in the resin storage chamber 5 while pushing up the ring piston 3. Also, the second. Third extruder 27.
The second resin and waste resin extruded from 30 are
piston 28a of accumulator 28.31, respectively;
It is stored in the accumulators 2B and 3i while pushing up 31a.

When the stored amount of each resin reaches a predetermined amount, the ring piston 3 of the accumulator head 1 and each piston 28a, 31a of the accumulator 28.31 are simultaneously pushed down. As a result, the first resin in the resin storage chamber 5 is pumped toward the annular first resin passage 12, and the second resin and waste resin in the accumulator 28.31 are transferred to the resin passages 2B, 29.29, and 20, respectively. .21.21
through the slits 22, 23.23 and into each annular nozzle 24.25.25.

In this case, since the first resin passage 12 is divided by the ring member 17 into an inner annular passage 12a and an outer annular passage 12b, as shown in FIG.
The first resin passing through the resin passage 12 is divided into an inner layer and an outer layer by the ring member 17. A second resin and a waste resin are extruded between the inner layer and the outer layer of the first resin from the annular nozzles 24, 25, 25 provided on the lower surface of the ring member 17. These annular nozzles 24,
25. The resin extruded from 25 becomes a cylindrical body with the second resin layer at the center and third resin layers on both the inside and outside sides, and the inner and outer layers of the first resin that have passed through the ring member 17 form this cylindrical body. It merges with the body from both the inside and outside, forming a layered state.

The molten resin laminated in the resin passage 12 is forced downward through the narrow die slit 11, and the resin layers are tightly bonded and formed into a cylindrical body with a predetermined wall thickness. As a result, a multilayer parison P having a five-layer structure of three types as shown in FIG. 1 is obtained.

During extrusion molding of this multilayer parison P, the resin layers are tightly adhered to each other because the first resin forming the first resin layer L1 and the second resin forming the second resin layer L2 are bonded to each other. This is because the waste resin, which is made of adhesive resin and forms the third resin layer L3, is made of these first and second resins. That is, the modified polyethylene resin in the first resin and the nylon resin in the second resin are chemically bonded together as shown in FIG. Because the modified polyethylene resin in the second resin has good adhesive properties,
The first resin and the second resin have a strong adhesive relationship with each other. Since the waste resin is made up of the first and second resins, it has sufficient adhesion to the first resin and the second resin, although it has already been affected by heat. Therefore, multilayer Parisan P
The resin layers are tightly bonded to each other.

The above-mentioned multilayer parison P is then placed in a cavity of a mold (not shown), and then pressurized gas is blown into the cavity to perform blow molding. The product (fuel tank) is equipped with a second resin layer L2 formed of a second resin whose base material is nylon resin, so it can prevent penetration of gasoline, etc.; Since the third resin layer L3 is sealed inside the layer by the first resin layer L1 formed of the first resin whose base material is high-density polyethylene resin, the blow molded product deteriorates early. There is no fear. Of course, even after the multilayer parison P is made into a blow-molded product, the resin layers are maintained in a tightly bonded state.

On the other hand, the waste resin such as paris, which is formed and discharged together with the blow molded product during the blow molding, is supplied as it is to the second extruder 27 without being subjected to any modification treatment, and is extruded into the multilayer parison P. be reused for.

As described in detail above, according to this embodiment, the first and second resin layers L are made of two types of resins that have adhesive properties to each other.
1 and Lz respectively, and the first and second resin layers L1. Third resin layer L3 between L2
However, the waste resin is
The third resin layer L3
are the first and second resin layers L1. Lz also has adhesive properties. Therefore, there is no need to form a new adhesive resin layer or to modify the waste resin in order to bond the waste resin layer with other resin layers, so there is no need to install a new extruder for this purpose, and the waste material The resin can be reused as is. Moreover, since the adhesive resin layer that was conventionally provided for bonding the first and second resin layers is no longer required, the extruder used to form this adhesive resin layer can be used to The resin layer L3 can be formed.

In the above embodiment, a resin having a nylon resin as a base material was used as the second resin for forming the second resin layer L2, but instead of this nylon resin, EVOH
(ethylene vinyl alcohol) resin, PVA (polyvinyl alcohol) resin, PTFE (polytetrafluoroethylene) resin, etc. can also be used to obtain the same effects as in the above embodiments.

[Brief explanation of the drawing]

FIG. 1 is a partially detailed side view of FIG. 2 showing a part of a multilayer parison formed by an embodiment of the method for molding a multilayer parison according to the present invention; FIG. 2 is a perspective view showing the multilayer parison; , Figure 3 is the structural formula of the modified polyethylene resin used in the above example, Figure 4 is the structural formula showing the bonding state of the modified polyethylene resin and nylon resin used in the above example, and Figure 5 is the above formula. A side sectional view showing the overall structure of the multilayer parison extrusion molding apparatus used in the examples, FIG.
-Vl line sectional view, and FIG. 7 is a sectional view taken along ■--■ line in FIG. P...Multilayer parison Ll...First resin layer L2...Second resin layer L3...Third resin layer

Claims (1)

[Claims] In a method for molding a multilayer parison by extrusion molding a multilayer parison formed by laminating a plurality of resin layers, the first and second resin layers are each formed from two types of resins that have adhesive properties to each other, and after the extrusion molding, A method for molding a multilayer parison, characterized in that a third resin layer is formed between the first and second resin layers using waste resin from the multilayer parison discharged in the step of step .