JP2798103B2 - Multilayer parison forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer parison forming method, and more particularly to a multi-layer parison forming method effective for forming a volatile liquid container such as a fuel tank by blow molding.

[0002]

2. Description of the Related Art Conventionally, plastic fuel tanks, for example, gasoline tanks for vehicles, are formed by blow molding. In the case of a tank containing such a volatile liquid, gas permeation from the tank wall becomes a problem, and it is required to keep the gas permeability below a certain reference value,
Conventionally, the following method has been adopted.

(1) After molding by blow molding of a single layer, the inner surface of the tank is treated with fluorine or the like to prevent gas permeation.

(2) A tank is formed by so-called multilayer blow molding in which a multilayer parison composed of a nylon layer having low gasoline permeability and another resin layer such as high-density polyethylene is injected by a multilayer die.

(3) A single-layer blow molding machine uses pellets containing a mixture of nylon, and a nylon layer having a low gasoline permeability is mixed in the parison to suppress the gas permeability.

In the first method, a coating layer is separately formed on the inner surface of the tank after molding the resin tank, or in the second method, the multi-layer parison is directly injected, so that the tank wall has a multi-layer cross section, thereby effectively suppressing gas permeation. be able to. The third method is called a sealer method, and it is described that a gas transmission rate can be reduced by mixing a nylon layer with a tank resin wall.

[0007]

However, the above-mentioned conventional method has the following problems. That is, in the first method, a post-process of the fluorine treatment is required, and the number of processes is increased, and handling of the use of fluorine is difficult due to a problem of pollution. In the second method, large-scale equipment is required for the multi-layer, such as requiring a die having a complicated structure specially manufactured for the multi-layer to inject the multi-layer parison into the die, and there is a disadvantage in cost. Furthermore, in the third method, molding is relatively simple, but it is difficult to form a nylon layer on the entire surface, and it is difficult to reduce gas permeability.

The present invention focuses on the above-mentioned conventional problems, and forms a multi-layer parison in which a multi-layer parison can be ejected with a conventional single-layer die, whereby the gas permeability can be surely reduced. The aim is to provide a method.

[0009]

In order to achieve the above-mentioned object, a multilayer parison molding method according to the present invention comprises connecting an extruder for supplying a main material resin and an extruder for supplying a sub-material resin to a common accumulator. Then, the main resin and the sub-material resin are alternately and continuously supplied into the accumulator, so that the main resin and the sub-material resin are filled in a multi-layer state, which is pressed toward the parison injection die by the accumulator plunger. By supplying the multilayer parison, the main material and the sub-material are alternately stacked in the thickness direction.

[0010]

According to the above construction, when the main material and the sub material are alternately and continuously extruded from the main material extruder and the sub material extruder toward the accumulator, the main material layer and the sub material layer are formed in the accumulator. The plunger is filled alternately and pushes the plunger back to the pressure start position in a multilayer structure. When the plunger is driven to be pressurized during supply to the dies, the laminated resin material consisting of the main material and the sub-material, which are filled in multiple layers along the plunger driving direction, has a speed in the cross-sectional direction of the accumulator due to the frictional force due to the viscosity of the inner wall of the accumulator. A distribution occurs and increases parabolically from the accumulator wall to the center.
As a result, in the resin passage from the accumulator outlet to the supply port to the cylindrical passage in the die, the main material and the sub-material flow in a multilayer state in a cross-sectional direction orthogonal to the resin flow direction and are supplied into the die. The resin in this multilayer state is not always a beautiful multilayer in the die, but the parison extruded from the die is basically multilayered in the thickness direction, and the main material and the sub material are alternately laminated. It is injected at. Therefore, the container wall of the tank thus formed has a multi-layer structure of the main material and the sub-material. For example, high-density polyethylene is used as the main material and nylon with low gas permeability is used as the sub-material to greatly increase the gas permeability. It is possible to reduce to.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the method for forming a multilayer parison according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a main part device applied to a method for forming a multilayer parison according to an embodiment, and shows an extruder, an accumulator, and a parison injection die. First, the parison injection die 10 has a die housing 12 formed of a rectangular block, and a through-hole 14 having a substantially circular cross section is formed along a vertical center line thereof. In such a through-hole 14, the through-hole 1
A mandrel 16 having a diameter smaller than that of the mandrel 4 is inserted therethrough to form a cylindrical passage 18 between the outer peripheral surface of the mandrel 16 and the inner peripheral surface of the through hole 14. The parison control mandrel 2 is accessible at the lower end of the mandrel 16
A mandrel lip 24 that faces the opening of the through-hole 14 and forms a ring-shaped resin discharge port 22 with the opening of the through-hole 14 is integrally provided. A mandrel 16 is inserted in the upper part of the die housing 12. A passage 26 for supplying molding resin to the cylindrical passage 18 is formed on the upper side wall of the mandrel 16, and the resin is transferred from the resin introduction chamber 28 formed above the mandrel 16 to the cylindrical passage 18 through the passage 26. It is made to fill.

An accumulator 30 is mounted on the die housing 12 to supply molding resin to the parison injection die 10. The accumulator 30 has a plunger 32 inserted therein. By driving the plunger 32 by an injection cylinder (not shown), the internal volume of the accumulator 30 is made variable, and the resin supplied inside is pressurized and sent to the die 10. It is designed to generate parison injection pressure.
In order to feed the resin from the accumulator 30 to the die 10, a nozzle portion 34 is provided at the tip of the accumulator 30.
This is flanged to the die housing 12 to connect the resin passage 36 in the die to the resin introduction chamber 28 formed in the die 10 with the nozzle passage 38.

An extruder is connected to the accumulator 30 for metering and supplying the molding resin. The extruder is connected to the limit position of the plunger 32. In this embodiment, in particular, a pair of extruders 40A, 40B are connected side by side. Each of the extruders 40A and 40B has the same configuration, in which a screw 42 is rotatably mounted inside, and resin supplied from a hopper (not shown) is extruded and supplied to the accumulator 30 by rotating the screw 42. In this embodiment, one extruder 40A extrudes a high-density polyethylene resin 44M as a main material of a molded product, and the other extruder 40B extrudes a nylon resin 44S as a sub-material.
Shut-off valves 46A and 46B are provided at the outlets of the extruders 40A and 40B so that resin extrusion from the extruders 40A and 40B can be performed alternately. A main shut-off valve 46M is also provided in the nozzle passage 38 of the accumulator 30, and the extruders 40A,
The nozzle passage 38 is shut off when the resin is supplied from 0B to the accumulator 30.

A multi-layer parison is formed by using the parison injection device having such a configuration, and this is performed as follows.

When a gasoline tank is to be molded, a high-density polyethylene resin 44 is used as the main material for the resin tank.
M is extruded from one extruder 40A to the accumulator 30, and nylon resin 44S having a small gas permeability as an auxiliary material is extruded from the other extruder 40B to the accumulator 30. Then, the nozzle passage 38 is shut off by the main shut-off valve 46M, and the main material 44M and the sub-material 44S are alternately formed while the extruders 40A and 40B are driven and the shut-off valves 46A and 46B attached thereto are alternately operated. The accumulator 30 is continuously filled. For this, the total supply amount to the accumulator 30 is calculated in advance, and the ratio of the amount of the main material 44M to the amount of the auxiliary material 44S is determined.
The ratio of the amounts of the main material 44M and the sub material 44S is, for example, 10: 1.
It may be set in the range of １1: 1. Then, when the main material 44M and the sub-material 44S are supplied to the accumulator 30, they are alternately extruded in a plurality of times so that the main material 44M and the sub-material 44S are inserted into the accumulator 30 as shown in FIG. The material 44S is filled in a state of being alternately stacked in the stroke direction of the plunger 32. The plunger 32 is retracted for each extrusion feed and moves to the injection start position. The ratio of the thickness of each layer in the accumulator 30 depends on the ratio of the amount of extrusion, and the actual thickness depends on the number of times of division extrusion. The number of each layer is not particularly limited, but is preferably as large as possible.

The resin filled in the accumulator 30 is extruded to the die 10 by the plunger 32, and the internal resin is removed by the plunger pushing movement as shown in FIG.
It behaves as shown in (2) to (3). That is, although it depends on the type of resin, when the plunger 32 is extruded, the resin flow velocity distribution in the accumulator 30 as shown in FIG. A parabolic flow velocity distribution is obtained in which the resin is extruded earlier and becomes slower as it reaches the inner wall surface side (FIG. 2B). When the plunger 32 is further extruded, FIG.
As shown in the above, the center of the resin flows more in advance, and the inclination of the lamination surface of the main material 44M and the sub-material 44S increases. Finally, while the layers of the main material 44M and the sub-material 44S pass through the nozzle passage 38, as shown in FIG. It is supplied to the die 10 in a so-called parallel grain shape. At this time, the resin layer is pressure-supplied into the die 10 in a state of completely intersecting the extrusion direction.

While the resin flows through the die 10, the multilayer resin flow is deformed and does not form a beautiful multilayer surface, but the parison 50 injected from the die 10 basically has a thickness direction. It becomes multilayer.

When a resin tank is formed from the multi-layer parison 50 thus obtained, the main material 44M and the sub material 44S are multi-layered in the thickness direction of the tank, and the nylon of the sub material 44S is made of gasoline. A tank with very low gasoline permeation is obtained as a molded article.

According to this embodiment, it is not necessary to use a single-layer parison injection die 10 as it is, and it is not necessary to use a special die for multi-layer parison injection. Therefore, the parison 50 having a multilayer cross section can be easily injected. Since the parison 50 has a nylon layer having a small gas permeability built in as an intermediate layer between the 44M layers of the main material, the gasoline permeability can be significantly reduced as compared with the case where nylon is mixed, and the fuel tank Has the effect of being good for use in

FIG. 3 is a cross-sectional view of a main part showing another example of the configuration of a parison injection device for performing the method of forming a multilayer parison. This sets the position of connecting the pair of extruders 40A and 40B to the accumulator 30 in the apparatus shown in FIG.
The resin filled first from the extruders 40A and 40B is
The difference is that the pre-extrusion is performed at 0. It is a so-called first-in first-out method of resin. A bush 52 is inserted into the accumulator 30, and the plunger 32 slides along the inner wall of the bush 52. The other configuration is the same as that of the apparatus shown in FIG. 1, and the same components are denoted by the same reference numerals and description thereof will be omitted.

By extruding the main material 44M and the sub-material 44S from the pair of extruders 40A and 40B alternately into the accumulator 30, the main material 4
4M and the sub material 44S are alternately laminated. Therefore, by extruding this from the accumulator 30 with the plunger 32, the resin in the multilayer state inside exhibits the same behavior as shown in FIG. 2, and the multilayer parison 50 can be injected.

FIG. 4 shows an injection apparatus according to another configuration applied to the embodiment of the method for forming a multilayer parison. This in particular places the accumulator 30 vertically,
A pair of extruders 40A and 40B are connected to the retreat limit position of the plunger 32, and the extruders 40A and 40B are operated alternately so that the main material 44M and the sub-material 44S are flow-down laminated in the accumulator 30. is there. For this reason, the air intake port 54 is formed at the lower end of the barrel of the accumulator 30 and the air passage 56 is opened at the upper end of the barrel. The air passage 56 is branched, one of which is a vacuum suction port 60 connected to a vacuum suction pump 58,
The other is an atmosphere opening port 62. These air inlets 5
4. An opening / closing valve 64 is attached to each of the vacuum suction port 60 and the atmosphere opening port 62 so that the valve can be arbitrarily opened and closed.

A method of forming a multilayer parison by using such an injection apparatus is performed as follows. That is, first, the plunger 32 is moved upward, which is the retreat limit position, and is kept on standby. The extruders 40A and 40B are alternately driven to extrude the main material 44M and the sub-material 44S in a molten state so that the main material 44M and the sub-material 44S are alternately stacked in the accumulator 30 sequentially from the lower layer. Let it flow down. After the resin is filled in the accumulator 30, the internal air is vacuum-suctioned from the vacuum suction port 60 above the barrel, and the air entrained when the resin flows down into the accumulator 30 is deaerated. After the completion of the deaeration, the valve 64 is switched to close the vacuum suction port 60 and open the atmosphere opening port 62, and the plunger 3
2 is driven downward. The plunger 32 extrudes the internal resin into the die 10. At this time, the internal resin laminated in multiple layers behaves as shown in FIG. 2, and the multilayer parison 50 is injected from the die 10. When the injection is completed, the air intake port 54 at the lower part of the barrel is opened, the plunger 32 is raised to the rearmost position, and then the air intake port 54 is closed.
Thereafter, this operation is repeated, and the multilayer parison 50 can be continuously ejected.

In this embodiment, when the main material 44M and the sub-material 44S are alternately laminated in the accumulator 30, the subsequent resin is reliably prevented from being mixed into the preceding resin layer. Since the alternate lamination of the main material 44M and the sub-material 44S is easily generated, the thickness cross section of the injection parison 50 also has a multilayer structure, so that the gas permeability can be further reduced.

FIG. 5 shows the construction of still another embodiment of the injection apparatus applied to the embodiment. This provides a common extrusion passage 70 for the accumulator 30, branches this common extrusion passage 70, and connects the extruder 40 </ b> A for the main material 44 </ b> M to one and the extruder 40 </ b> B for the sub-material 44 </ b> S to the other. The main material 44M and the sub-material 44S are alternately filled in the accumulator 30 through the common passage 70. In this case, FIG. 1A shows a first-in first-out method, and FIG. 2B shows a first-in, last-out method. Only the connection points of the common passage 70 to the accumulator 30 are different.

In this embodiment, the configuration of the single-layer parison injection die is utilized almost as it is, and the extrusion passage 70 to the accumulator 30 is branched to form a plurality of extruders 40.
Since A and 40B are connected, there is an advantage that an apparatus for forming a multi-layer parison can be configured more easily.

[0028]

As described above, in the method for forming a multilayer parison according to the present invention, the extruder for supplying the main resin and the extruder for supplying the sub-material resin are connected to a common accumulator, and the main accumulator is provided in the accumulator. The main resin and the sub-material resin are filled in a multi-layer state by alternately and continuously supplying the material resin and the sub-material resin, and the thickness is increased by pressurizing and supplying the resin and the sub-material resin toward the parison injection die with an accumulator plunger. Since the multi-layer parison in which the main material and the sub-material are alternately laminated in the direction is configured to be injected, the multi-layer parison can be injected with the conventional single-layer die, thereby reliably lowering the gas permeability. The excellent effect that can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a parison injection device for performing a multilayer parison forming method according to the present invention.

FIG. 2 is an explanatory diagram of a behavior of a resin in an accumulator.

FIG. 3 is a cross-sectional view of a parison injection device according to another configuration for performing the multilayer parison forming method according to the present invention.

FIG. 4 is a cross-sectional view showing another example of the structure of the parison injection device for performing the multilayer parison forming method.

FIG. 5 is a cross-sectional view of a parison injection device according to still another structural example applicable to the implementation of the multilayer parison forming method.

[Explanation of symbols]

REFERENCE SIGNS LIST 10 parison injection die 12 die housing 16 mandrel 18 cylindrical passage 22 resin discharge port 30 accumulator 32 plunger 34 nozzle portion 36 resin passage in die 38 nozzle passage 40A, 40B extruder 42 screw 44M main resin (high-density polyethylene) 44S sub Material resin (nylon) 46A, 46B, 46M Shut-off valve 50 Multi-layer parison

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁶ Identification code FI B29C 49/42 B29C 49/42 (72) Inventor Yoshiaki Kano 1980 No. Yama, Kogushi-ji, Oji, Ube City, Yamaguchi Prefecture Ube Industries Ube Co., Ltd. (56) References JP-A-2-249623 (JP, A) JP-A-2-121824 (JP, A) JP-A-3-132329 (JP, A) Jpn. (JP, U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B29B 11/10 B29C 45/16 B29C 47 / 56,57 / 58 B29C 49 / 04,49 / 22,49 / 42

Claims (1)

(57) [Claims] An extruder for supplying a main material resin and an extruder for supplying a sub material resin are connected to a common accumulator, and the main resin and the sub material resin are alternately and continuously supplied into the accumulator. Akyu the main resin and Fukuzai resin by
The multi-layer parison in which the main material and the sub-material are alternately stacked in the thickness direction is injected by filling the multi-layer parison in a multi-layer state along the driving direction of the mulrator plunger and supplying the pressure to the parison injection die by the accumulator plunger. A method for forming a multilayer parison.