JP2678306B2 - 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 main resin layer and an auxiliary resin layer 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, Japanese Patent Publication No. 58-23212, a main material resin layer formed of a main material resin made of high-density polyethylene resin and a nylon resin capable of preventing permeation of gasoline and the like. An attempt has been made to form a multi-layer hollow molded container by blow molding using a multi-layer parison formed by laminating a sub-material resin layer formed of the sub-material resin made of.

(Problems to be Solved by the Invention) By using a nylon resin as a secondary material resin in this way, it is possible to prevent permeation of gasoline and the like, but since nylon resin is inferior in impact resistance, When it is used as an auxiliary material resin, the impact resistance of the blow-molded container is reduced accordingly.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a multilayer parison molding method capable of improving the impact resistance of a molded article blow-molded using a multilayer parison. Things.

(Means for Solving the Problems) In the multi-layer parison molding method according to the present invention, considering that the impact resistance is improved when the nylon resin is modified with an ionomer, at least a part of the auxiliary material resin layer is made of such an ionomer-modified nylon. The above object is achieved by forming the resin. That is,
In a multi-layer parison molding method for extruding a multi-layer parison formed by laminating a main resin layer and a sub resin layer, a polyethylene resin-based resin is used as a main resin for forming the main resin layer. It is characterized in that the extrusion molding is performed by using a resin whose base material is a nylon resin at least partially modified with an ionomer as a sub-material resin for forming the sub-material resin layer together with the use. is there.

The “resin having a polyethylene resin as a base material” may be a resin composed of only a polyethylene resin such as a high-density polyethylene resin or a resin obtained by modifying a part or all of the polyethylene resin. .

(Operation and Effect of the Invention) As shown in the above configuration, extrusion molding is performed using a resin having a nylon resin at least partially modified with an ionomer as a base material as a sub-material resin for forming the sub-material resin layer. Therefore, the impact resistance of the auxiliary material resin layer is significantly improved as compared with the case where the auxiliary material resin layer is simply formed of nylon resin. Therefore, a molded article blow-molded using a multi-layer parison in which such a sub-material resin layer and a main-material resin layer formed of a resin having a base material of a polyethylene resin having excellent impact resistance are laminated is also used. It is possible to improve impact resistance.

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

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

As shown in FIG. 5, the lower half portion of the accumulator head 1 is provided with a cylinder 2 and a ring piston 3 which slides vertically along the inner peripheral surface of the cylinder 2, and the central portion of the accumulator head 1 is provided. Is provided with a core 4 which 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 material 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 main resin is a resin having a polyethylene resin as a base material, that is, a modified polyethylene resin obtained by modifying a polyethylene resin with maleic anhydride (see FIG. 2) into a high-density polyethylene resin using a pelletizer or the like. Made of dispersed resin. 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, while an annular core support 9 is fixed to the lower end of the core 4, and the center of the core support 9 is fixed. The die 8 and the concentric core 10 are fitted in the above 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. The die slit 11 passes through an annular main material resin passage 12 formed between the cylinder 2 and the die 8 and the core 4 and the core support 9, and then passes through the resin storage chamber 5 described above.
Is in communication with

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, in the resin passage 12 of the main material, as shown in FIG. 6 and FIG.
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 first auxiliary material resin passage 20 located substantially at the center thereof and two annular second auxiliary material resin passages 21 located on both sides of the first auxiliary material resin passage 20. , 21 are formed, and these resin passages 20, 21, 21 pass through annular slits 22, 23, 23, respectively, and three concentric annular nozzles 24 formed on the lower surface of the ring member 17 are formed. , 25,25 are in communication.

The first auxiliary material resin passage 20 is provided outside the accumulator head 1 via the passage 26 formed in one support 18 between the ring member 17 and the cylinder 2.
It is in communication with the extruder 27. At the tip of the second extruder 27, the ionomer-modified nylon resin, which is the first auxiliary material resin continuously extruded in a molten state from the second extruder 27, is temporarily stored, and the piston 28a is operated, Accumulator that extrudes this ionomer-modified nylon resin
The accumulator 28 is provided with a temperature adjusting device (not shown) for adjusting the temperature of the stored ionomer-modified nylon resin. The ionomer-modified nylon resin is a resin obtained by modifying a nylon resin with an ionomer as shown in FIG. In the figure, the dotted line shows a weak hydrogen bond state, and the ionomer and the nylon resin maintain the bond state by this hydrogen bond and intermolecular force.

The second auxiliary material resin passages 21 and 21 pass through passages 29 and 29 formed in the other column 18 between the ring member 17 and the cylinder 2 and are provided outside the accumulator head 1 as a third extruder. It is connected to 30. An accumulator 31 equipped with a temperature adjusting device is also provided at the tip of the third extruder 30, and the accumulator 31 continuously modifies the second auxiliary material resin to be extruded from the third extruder 30 in a molten state. The modified nylon resin is extruded by once storing the nylon resin and operating the piston 31a. The modified nylon resin referred to here is
It means a resin in which a modified polyethylene resin (see FIG. 2) is highly dispersed microscopically in a nylon resin.

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

As shown in FIGS. 5, 6 and 7, normally, the ring piston 3 of the accumulator head 1 and the pistons 28a, 31a of the accumulators 28, 31 outside thereof are both free. 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. The ionomer-modified nylon resin and the modified nylon resin extruded from the second and third extruders 27 and 30 are stored in the accumulators 28 and 31 while pushing up the pistons 28a and 31a of the accumulators 28 and 31, respectively. It

When the storage amount of each resin reaches a predetermined amount, the ring piston 3 of the accumulator head 1 and the pistons 28a, 31a of the accumulators 28, 31 are simultaneously pushed down. As a result, the main material resin in the resin storage chamber 5 is pressure-fed toward the annular main material resin passage 12, and the accumulators 28, 3
The ionomer modified nylon resin and modified nylon resin in 1 are passed through the resin passages 26, 29, 29 and 20, 21, 21 respectively, and further through the slits 22, 23, 23 to the annular nozzles 2 respectively.
Pumped to 4,25,25.

In this case, since the main material resin passage 12 is divided into the inner annular passage 12a and the outer annular passage 12b by the ring member 17, as shown in FIG.
The main resin passing through 12 is divided into an inner layer and an outer layer by the ring member 17. Then, the ionomer-modified nylon resin and the modified nylon resin are extruded from the annular nozzles 24, 25, 25 provided on the lower surface of the ring member 17 between the inner layer and the outer layer of the main material resin. These annular nozzles 2
The resin extruded from 4,25,25 is a cylindrical body with an ionomer modified nylon resin layer at the center and modified nylon resin layers on both inner and outer sides, and the inner and outer layers of the main resin that have passed through the ring member 17 are The inner and outer surfaces of the sheet are joined to form a laminated state.

Then, the molten resin laminated in the resin passage 12 is extruded downward through the narrow die slit 11 to tightly bond the resin layers, and is molded into a tubular body having a predetermined wall thickness. As a result, as shown in FIG. 1, the auxiliary material resin layer L _S including the central ionomer-modified nylon resin layer L _IMN and the modified nylon resin layers L _MN located on both sides thereof, and this auxiliary material resin layer L _S A multi-layered parison P having a three-kind five-layer structure in which the main material resin layers L _M located on both sides of the is laminated is obtained.

The reason why the resin layers are tightly adhered to each other during the extrusion molding of the multi-layer parison P is as follows. That is, since the ionomer-modified nylon resin layer L _IMN and the modified nylon resin layer L _MN forming the sub-material resin layer L _S are both formed of a resin having a nylon resin as a base material, there is originally no adhesiveness between them. Good. In addition, the modified nylon resin layer of the auxiliary material resin layer L _S
Between the L _MN and the main material resin layer L _M , the nylon resin in the modified nylon resin layer L _MN and the modified polyethylene resin in the main material resin layer L _M chemically react as shown in FIG. bound, and modified nylon resin layer L _MN in the modified polyethylene resin and high density polyethylene resin or modified polyethylene resin of the main resin layer L _M good inherently adhesive, and thus modified nylon resin layer L _MN and the main The material resin layer L _M is closely adhered to each other.

The multi-layer parison P is then placed in a cavity of a molding die (not shown), and then pressurized gas is blown into the cavity to perform blow molding. A molded product formed in this manner. In the (fuel tank), since a part of the auxiliary material resin layer L _S for preventing the permeation of gasoline and the like is formed of the ionomer-modified nylon resin layer L _IMN , as shown in Table 1, The impact resistance can be significantly improved as compared with the case where the auxiliary material resin layer L _S is formed of only nylon resin or modified nylon resin.

In this example, the auxiliary material resin layer L _S is the ionomer modified nylon resin layer L _IMN and the modified nylon resin layer L _MN.
It has a side-itch structure in which it is sandwiched from both sides, but this is because when the auxiliary material resin layer L _S is formed using a resin obtained by modifying a nylon resin with a large amount of ionomer, the impact resistance is significantly improved. Since it was found by experiments that the barrier function for preventing permeation of gasoline and the like is somewhat deteriorated, in order to prevent this, a protective film is formed by a modified nylon resin having excellent barrier properties. This makes it possible to obtain the auxiliary material resin layer L _S having excellent impact resistance and barrier properties.

The ionomer modified nylon resin layer L _IMN and modified nylon resin layer L _MN that compose the auxiliary material resin layer L _S may be set to a thickness of about 100 μm when the molded product is a fuel tank, etc. Of course, the value may be changed according to the shape of the product, the purpose, and the like. For example, the ionomer modified nylon resin layer L _IMN may be thickened and the modified nylon resin layer L _MN may be thinned for the purpose of further improving the impact resistance.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of a multi-layer parison molded by an embodiment of the multi-layer parison molding method according to the present invention, FIG. 2 is a structural formula of a modified polyethylene resin used in the above-mentioned embodiment, and FIG. Is a structural formula of the ionomer-modified nylon resin used in the above examples, FIG. 4 is a structural formula showing the bonding state of the modified polyethylene resin and nylon resin used in the above examples, and FIG. FIG. 6 is a sectional view taken along the line VI-VI of FIG. 5, and FIG. 7 is a sectional view taken along the line VII-VII of FIG. 6, showing a general configuration of the multilayer parison extrusion molding apparatus used. P ...... multilayer parison L _M ...... main resin layer L _S ...... Fukuzai resin layer L _IMN ...... ionomer modified nylon resin layer L _MN ...... modified nylon resin layer

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Claims (1)

(57) [Claims] 1. A multi-layer parison molding method for extruding a multi-layer parison formed by laminating a main resin layer and a sub resin layer, wherein a polyethylene resin is used as a main resin for forming the main resin layer. It is possible to perform the extrusion molding using a resin as a base material and a resin having a nylon resin at least partially modified with an ionomer as a base material as a sub-material resin for forming the sub-material resin layer. Characteristic multi-layer parison molding method.