JP2646129B2 - Multi-layer parison molding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a multilayer parison molding method for extruding a multilayer parison in which a plurality of resin layers are laminated.

(Prior Art) As a method of molding a hollow container made of resin, after forming a parison formed by blow molding, that is, extrusion molding in a cavity of a molding die, molding is performed by blowing a pressurized gas into the parison. Molding methods are known. recent years,
For fuel tanks for vehicles, etc., those made of resin formed by blow molding have been proposed and put into practical use. As the material, high-density polyethylene resin is generally adopted from the viewpoint of moldability, strength, cost, and the like. I have. However, since polyethylene has an affinity for gasoline and the like, if the gasoline and the like are stored in a container such as a fuel tank made of a high-density polyethylene resin for a long period of time, the gasoline and the like gradually increase. There is a problem that it penetrates and penetrates the peripheral wall of the container. Therefore, as disclosed in, for example, JP-B-58-23212 and JP-A-62-138227, it is possible to prevent the permeation of gasoline and the like with a resin layer formed of a high-density polyethylene resin. There has been devised a method of forming a multilayer hollow molded container by blow molding using a multilayer parison formed by laminating a resin layer formed of a nylon resin or the like.

(Problems to be Solved by the Invention) By providing a resin layer formed of a nylon resin or the like as described above, it is possible to prevent gasoline or the like from being permeated. In order to use this as a resin for forming a resin layer, it is necessary to form an adhesive resin layer between both resin layers, as described in the above publications. Since an extra extruder is required, the molding cost is high.

On the other hand, it is possible to provide an adhesive property between both resin layers by performing an appropriate modification treatment on a nylon resin or the like or a polyethylene resin, but even in this case, extrusion for forming both the resin layers is still required. Each machine is required.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a multilayer parison forming method capable of forming a multilayer parison with an extruder having a minimum number of members.

(Means for Solving the Problems) In the multilayer parison molding method according to the present invention, generally, when a fluid having a difference in viscosity flows inside a pipe, a portion having a high viscosity flows through the center, and a portion having a low viscosity flows into a peripheral wall. Focusing on the fact that there is a property of flowing in the vicinity, by pressure-feeding the two kinds of resins in the resin passage with a viscosity difference between the two resins, while stratifying both resins in the resin passage,
These are extruded in a state where two types of resin layers are formed from the open ends of the resin passages, thereby enabling two types of resin layers to be formed by one extruder, thereby achieving the above object. It was made. That is, in a multi-layer parison molding method for extruding a multi-layer parison formed by laminating a plurality of resin layers, a first resin for forming a first resin layer and a second resin for forming a second resin layer. And mixing the first resin and the second resin into a predetermined resin passage under pressure with a viscosity difference between the two resins, and extruding the resin from the open end of the resin passage. It is a feature.

The "viscosity difference" may be any size that is large enough to cause two-layer separation in the resin that is pressure-fed in the resin passage and extruded from the open end thereof. Although not limited, for example, it is possible to generate a difference in viscosity by appropriately setting the resin melting temperature, or by appropriately setting the water absorption of the resin.

When the multilayer parison is composed of only the first and second resin layers, the “open end of the resin passage” corresponds to an open end of a die slit or the like from which the completed multilayer parison is extruded. In the case where a resin layer other than the first and second resin layers is also laminated, the opening end of the resin passage through which only the first resin and the second resin are fed, that is, the first resin and the second resin This corresponds to an open end where the other end is joined with another resin that is pressure-fed in another resin passage.

(Operation and Effect of the Invention) As shown in the above configuration, after the first resin and the second resin are mixed, these two resins are pressure-fed in a predetermined resin passage with a viscosity difference therebetween. Since the first resin and the second resin are extruded from the open end of the resin passage, the first resin and the second resin are stratified by the difference in viscosity when being fed through the resin passage, and two types of resin layers are formed from the open end. Will be extruded in a state where is formed. Therefore, two types of resin layers can be formed by one extruder. That is, molding of the multilayer parison can be performed by an extruder with a minimum number of members, and the molding cost can be reduced.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 7 is a side sectional view showing the overall configuration of a multilayer parison extrusion molding apparatus used for carrying out one embodiment of the multilayer parison molding method according to the present invention.

As shown in FIG. 7, a cylinder 2 and a ring piston 3 that slides up and down along the inner peripheral surface of the cylinder 2 are provided in the lower half of the accumulator head 1, and a central portion of the accumulator head 1 is provided. Is provided with a core 4 that penetrates the ring piston 3 and is fixed to the cylinder 2. A resin storage chamber (resin storage) 5 is formed inside the cylinder 2 and defined by a ring piston 3 and surrounded by the cylinder 2 and the core 4. The main resin composed of a high-density polyethylene resin continuously extruded in a molten state from the extruder 6 is supplied through an annular communication path 7 connected to the first extruder 6. The temperature of the main resin stored in the resin storage chamber 5 is adjusted by a temperature adjusting device (not shown) including a heater and the like provided in the cylinder 2.

An annular die 8 is concentrically fixed 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 10 concentric with the die 8 is fitted so as to be slidable in the vertical direction. The inner peripheral surface at the lower end of the die 8 and the outer peripheral surface at the lower end of the core 10 are each formed into a conical surface, and an annular die slit 11 is formed therebetween. This die slit 11 is
And, it communicates with the resin storage chamber 5 through an annular main resin passage 12 formed between the die 8 and the core 4 and the core support 9.

The core 10 is moved up and down by a hydraulic cylinder (not shown) via a rod 13, whereby the width of the die slit 11 formed between the core 8 and the die 8, that is, the thickness in the radial direction is adjusted. It has become. The ring piston 3 is connected to a single-acting hydraulic cylinder 15 via a rod 14.
The first pushing cylinder 15 and the ring piston 3 allow the resin storage chamber 5 to move downward.
An accumulator 16 is configured to feed the main resin in the container to the main resin passage 12 or the die slit 11 side.

Further, as shown in FIG. 8 and FIG. 9, a ring member having a substantially
17 is provided concentrically with the resin passage 12. The ring member 17 is supported at predetermined intervals from the inner peripheral surface of the cylinder 2 by four columns 18, 18,... And is provided at a position different from the columns 18, 18,. Are supported at a predetermined distance from the outer peripheral surface of the core 4, and the main material resin passage 12 is connected to the inner annular passage 12 a and the outer annular passage 12 a by the ring member 17. Annular passage 12b
And is divided into: Inside the ring member 17, an annular sub-material resin passage 20 located substantially at the center thereof is formed, and the resin passage 20 passes through a ring-shaped slit-shaped resin passage 21 to form a ring member. It communicates with an annular nozzle 22 which is an open end formed on the lower surface of 17.

The secondary material resin passage 20 is provided outside the accumulator head 1 through a resin passage 23 formed on one support 18 between the ring member 17 and the cylinder 2.
It is connected to the extruder 24. At the tip of the second extruder 24, an auxiliary material resin that is continuously extruded in a molten state from the second extruder 24 is temporarily stored, and by operating a piston 25a, an accumulator 25 that extrudes the auxiliary material resin is stored. The accumulator 25 includes a temperature adjusting device (not shown) for adjusting the temperature of the stored auxiliary material resin.

The secondary resin is a resin (first resin) in which a modified polyethylene resin obtained by modifying a polyethylene resin with maleic anhydride (see FIG. 4) is highly dispersed microscopically in a high-density polyethylene resin using a pelletizer or the like. And a resin (second resin) in which the above modified polyethylene resin is microscopically highly dispersed in a nylon resin using a pelletizer or the like.
Then, these first resin and second resin, as shown in Figure 5, is turned from the first resin pellets R ₁ and the second resin pellets R ₂ as hoppers 24a respectively in the second extruder 24 by screw 24b Heat generated by rotation of screw and screw 2
It is heated and melted by the heat generated by a heater 24c disposed around 4b.

The melting temperature of the secondary resin in the second extruder 24 is:
The temperature can be adjusted by controlling the amount of heat generated by the heater 24c. In this embodiment, the temperature is set to about 220 ° C.
The melt viscosities of the polyethylene resin and the nylon resin with respect to the melting temperature show different characteristic curves as shown in FIG. 1, and the viscosity is higher at about 190 ° C. and above, and below about 190 ° C. Nylon resin has higher viscosity. Therefore, when the melting temperature in the second extruder 24 is set to about 220 ° C., a large difference in viscosity between the first resin based on polyethylene resin and the second resin based on nylon resin. Will occur. The accumulator 25 also maintains the melting temperature of the stored auxiliary material resin at about 220 ° C.

 Next, the operation of the present embodiment will be described.

As shown in FIGS. 7, 8, and 9, at normal times, the ring piston 3 of the accumulator head 1 and the piston 25a of the external accumulator 25 are all in a free state. As a result, in the accumulator head 1, the main resin extruded from the first extruder 6 and guided to the resin storage chamber 5 is stored in the resin storage chamber 5 while pushing up the ring piston 3. Also, the second
The secondary resin extruded from the extruder 24 is stored in the accumulator
The piston 25 is stored in the accumulator 25 while pushing up the piston 25a.

When the storage amount of each resin reaches a predetermined amount, the ring piston 3 of the accumulator head 1 and the piston 25a of the accumulator 25 are simultaneously pushed down. Thereby, the main material resin in the resin storage chamber 5 is pumped toward the annular main material resin passage 12, and the sub material resin in the accumulator 25 passes through the resin passages 23 and 20 and further through the slit-like resin passage 21. The pressure is sent to the annular nozzle 22.

The sub-resin fed by pressure to the annular nozzle 22 has a melting temperature of about 220 ° C. in the second extruder 24 and the accumulator 25.
The resin passages 23, 20
Also, when flowing through the first and second resins, a state in which the first resin and the second resin constituting the sub-material resin have a viscosity difference is maintained. In general, when a fluid having a viscosity difference flows inside the pipe, a portion having a high viscosity flows in the center and a portion having a low viscosity flows in the vicinity of the peripheral wall. The flowing secondary material resin is
As shown in the figure, the second resin having a high viscosity flows in the center of the resin passage 21, and the first resin having a low viscosity flows on both wall sides of the resin passage 21. The second resin layer formed of the second resin forms two or three sub-material resin layers sandwiched from both sides by the first resin layer formed of the first resin.

On the other hand, the main material resin passage 12 is, as shown in FIG.
The main member resin passage 12 is divided into an inner annular passage 12a and an outer annular passage 12b by the ring member 17.
Is divided into an inner layer and an outer layer by the ring member 17. Then, between the inner layer and the outer layer of the main material resin, the sub-material resin is extruded from an annular nozzle 22 provided on the lower surface of the ring member 17. This annular nozzle 22
The sub-material resin extruded from the resin becomes a cylindrical body, and the inner layer and the outer layer of the main material resin which have passed through the ring member 17 are joined to the cylindrical body from both the inner and outer surfaces thereof to form a laminated state.

Thus, the molten resin laminated in the resin passage 12 is extruded downward through the narrow die slit 11, and the two resin layers are tightly adhered to each other and formed into a cylindrical body having a predetermined thickness. , Thus, as shown in FIG. 3, the first located in the second resin layer L ₂ and the both sides of the center
And secondary wood resin layer L _S made of a resin layer L _1, the multilayer parison P of the three 5-layer structure in which the main resin layer L _M are stacked, located on both sides of the Fukuzai resin layer L _S is obtained.

The The inter multilayer parison main resin layer L _M and Fukuzai resin layer during the extrusion of the P L _S is closely adhered is of two kinds of resin layers constituting the Fukuzai resin layer L _S, the first resin layer L ₁ in contact with the main resin layer L _M is a high-density polyethylene resin is a resin for forming the main resin layer L _M because is formed of a resin as a base material. As for the two types of resin layers constituting the Fukuzai resin layer L _S, and a modified polyethylene resin of the first resin layer L ₁ of the nylon resin of the second resin layer L ₂ is as shown in Figure 6 chemically bonded Te, and, for the first high-density polyethylene resin or modified polyethylene resin of the resin layer L ₁ and the modified polyethylene resin of the second resin layer L ₂ is good inherently adhesive, both closely It will be glued.

After the multilayer parison P is placed in a cavity of a molding die (not shown), pressurized gas is blown into the inside and blow molding is performed. The molded product thus formed is formed. Since the (fuel tank) includes a resin layer formed using a nylon resin as a base material, permeation of gasoline and the like can be prevented.

As described above in detail, according to the present embodiment, three types and five layers of a multi-layer parison can be formed by two extruders, and the molding cost can be reduced. Further, since resins having good adhesion to each other are employed as the resin forming each resin layer, an adhesive resin layer can be eliminated.

In the present embodiment has been described extrusion of multilayer parisons three 5-layer, multi-layer parison of two 3-layer is omitted main resin layer L _M in the present embodiment (see FIG. 10) In the case of molding, the first extruder 6 becomes unnecessary,
Molding by one extruder becomes possible.

Further, in the above embodiment, although have a function to reduce the permeation prevention such as gasoline (barrier function) in the second resin layer L ₂ of Fukuzai resin layer L _S, it is desired to further enhance the barrier function In this case, if the melting temperature of the auxiliary material resin at the time of extrusion molding is set to a predetermined temperature of 190 ° C. or less (for example, 180 ° C.), the melt viscosity of the nylon resin and the polyethylene resin becomes as shown in FIG. To reverse the case of the above embodiment,
As for the secondary material resin layer L _S, the first resin layer L ₁ and the second resin layer L ₂ are exchanged to obtain a multilayer parison having two second resin layers L ₂ as shown in FIG. The barrier function can be improved. In this case, to enhance the adhesion between the second resin layer L ₂ and the main resin layer L _M, modified polyethylene resin (see FIG. 4) to a micro high-density polyethylene resin as the main resin It is preferable to use a highly dispersed one.

[Brief description of the drawings]

FIG. 1 is a graph showing the operation of one embodiment of the multilayer parison molding method according to the present invention, FIG. 2 is an enlarged view of part II of FIG. 9, showing the operation of the above embodiment, and FIG. FIG. 4 is a sectional view showing a part of a molded multi-layer parison. FIG. 4 is a structural formula of a modified polyethylene resin used in the above embodiment. FIG. 5 is a side sectional view showing a second extruder used in the above embodiment. FIG. 6, FIG. 6 is a structural formula showing a bonding state of the modified polyethylene resin and the nylon resin used in the above embodiment, and FIG. 7 is a side showing an entire configuration of a multilayer parison extrusion molding apparatus used in the above embodiment. FIG. 8 is a sectional view taken along line VIII-VIII of FIG. 7, FIG. 9 is a sectional view taken along line IX-IX of FIG. 8, and FIGS. 10 and 11 are sectional views of a multilayer parison formed according to another embodiment. It is sectional drawing which shows a part. P: multilayer parison L ₁ ... first resin layer L ₂ ... second resin layer R ₁ ... first resin pellet R ₂ ... second resin pellet 20, 21, 23 ... resin passage 22 ... annular Nozzle (open end) 24 ... second extruder 25 ... accumulator

Claims (1)

(57) [Claims] 1. A multi-layer parison molding method for extruding a multi-layer parison formed by laminating a plurality of resin layers, comprising: a first resin for forming a first resin layer and a second resin layer for forming a second resin layer; After mixing the second resin with the second resin, the mixed first resin and the second resin are pressure-fed in a predetermined resin passage in a state where a viscosity difference is provided between the two resins, and the mixed resin is fed from the opening end of the resin passage. A multilayer parison molding method characterized by extruding.