JPH0615199B2 - Method for manufacturing multi-layer resin container - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a multi-layer resin container, and more particularly, to a multi-layer resin container having a thickness configuration according to a set thickness for any combination of resins. The present invention relates to a method of manufacturing the same without defects such as drawdown, uneven thickness, and defective fusion of the pinch-off portion.

(Prior Art) Multi-layer resin containers are used in various packaging fields for the purpose of utilizing the advantages of various resins and compensating for their drawbacks. For example, by utilizing the moisture resistance and hygienic properties of polyolefin resin as an inner / outer surface layer, on the other hand, in order to compensate for the poor oxygen gas barrier property of polyolefin resin, a gas barrier such as ethylene-vinyl alcohol copolymer is used. A container in which a transparent resin is used as an intermediate layer and these are laminated is widely used. In this case, the polyolefin layers provided on both sides of the ethylene-vinyl alcohol copolymer layer also have a complementary action of preventing a decrease in gas barrier property due to humidity.

Three-dimensional multilayer resin containers such as tube containers (extrusion containers) and bolt tanks are generally manufactured by a method called coextrusion blow molding method. To a ring-shaped multi-layer multiple die to extrude a multi-layer parison in which plural kinds of molten resins are laminated, and blow-mold this multi-layer parison.

However, when a large-capacity container is manufactured by this method, molding itself is difficult due to a property generally called drawdown property, that is, the upper part of the extruded parison is thinly stretched due to its own weight. However, even if molding is possible, it results in a significant uneven thickness in the axial direction of the container. In addition, since the part extruded first of the parison is cooled more than the part extruded later, poor adhesion of the pinch-off part at the bottom or perforation may occur, or poor expansion at the lower part of the parison. Some uneven thickness etc. become remarkable.

In order to improve this drawback, Japanese Patent Publication No. 52-37026 discloses that a cylindrical wall body having a temperature adjusting mechanism is arranged in layers inside a suction molding head to form a plurality of cylindrical resin reservoirs. ,
An extrusion molding apparatus for a multilayer tubular body is described, which comprises an extruder for extruding a resin into the resin reservoir and a ring piston for extruding the resin from the resin reservoir.

(Problems to be Solved by the Invention) In the extrusion molding apparatus of the above-mentioned prior art, an independent resin reservoir is formed in each molten resin passage of the die, and each resin reservoir is filled with molten resin, and then each resin reservoir is filled. It presses a plurality of ring pistons provided in the above to combine the resin flows and extrude them through the orifice.

However, this method has a problem that it is difficult to extrude the molten resin in each resin reservoir at a uniform pressure and at a uniform timing. That is, it is difficult to adjust the extrusion pressure of each resin by each piston ring to be constant,
If the extrusion pressure of the resin fluctuates, one resin tends to be extruded in preference to the other resin, or conversely, is extruded later than the other resin, and as a result, in the multilayer extrudate, It is recognized that each resin layer fluctuates more than the set thickness ratio, and the thickness distribution in the circumferential direction of each resin layer becomes remarkably irregular.

Such a tendency becomes particularly remarkable in a combination of a plurality of resins in which respective resins have considerably different melt flow characteristics.

Therefore, an object of the present invention is, regarding any combination of resins, a multilayer resin container having a thickness ratio according to a set thickness ratio and a uniform thickness distribution in the circumferential direction of each resin layer, drawdown, uneven thickness, It is an object of the present invention to provide a method capable of manufacturing without trouble such as defective fusion of the pinch-off portion.

(Means for Solving the Problems) According to the present invention, a plurality of types of molten resins are supplied from respective extruders into a ring-shaped multilayer multiple die, and a plurality of types of molten resins are laminated in a multilayer parison. In a molten resin passage from the final resin joining position of the multi-layer multi-die to the die orifice in the method for producing a multi-layer multi-layer container by blow molding the multi-layer parison. Then, a method for manufacturing a multi-layer resin container is provided, which comprises filling the multi-layer multi-molten resin in the reservoir and then rapidly extruding the multi-layer multi-molten resin through a die orifice.

According to the present invention, the core at the tip of the die, the shell provided coaxially with the core at the tip of the die, the die orifice formed between the core and the shell, the core supported at the tip and extending in the resin extruding direction. A core support shaft, a die block that supports a shell at the tip, is coaxial with the core support shaft, and has a hollow inside, and is entirely hollow, coaxial with the core support shaft, and radially spaced from the core support shaft. A hollow mandrel provided between the core support shaft and the die block, having an extension part fitted between the core support shaft and the mandrel and an extruding tip part, and reciprocating along the core support shaft. Movable ring piston, a plurality of independent resin passages arranged concentrically between the outer peripheral surface of the mandrel and the inner peripheral surface of the die block via one or a plurality of sleeves, and each of the independent resin passages Contact the rear end of Resin supply path, a multi-layered multiple resin path extending between at least the outer peripheral surface of the mandrel or ring piston and the inner peripheral surface of the die block and connected to the tips of the independent resin passages, the extrusion tip of the ring piston and the die orifice. Between the outer peripheral surface of the core support shaft and the inner peripheral surface of the die block, and a multi-layered resin reservoir connected to the rear end of the extension part of the ring piston and a multi-layered extruding tip part of the piston. Provided is a storage-type multi-layer multiple die, which comprises a driving mechanism for moving a multi-resin reservoir in a die orifice direction.

(Operation) In the present invention, it is possible to form a multilayer multiple molten resin flow having a layer structure corresponding to the final container in the die, store the multilayer multiple molten resin flow in the die, and rapidly extrude this to perform blow molding. It is a feature.

The multi-layered multi-die, the layered annular flow of the molten resin corresponding to the inner surface layer of the container is first formed, the layered annular flow of the intermediate layer resin, and then the layered annular flow of the outer surface layer resin are successively joined and laminated, A multi-layer multiple molten resin stream corresponding to the layer composition of the final container is formed. In the present invention, a reservoir for the multilayer multiplex molten resin is formed in the molten resin passage from the final resin joining position of the multilayer multiplex die to the die orifice.
By adopting this configuration, in the resin reservoir, the discharge amount from each extruder, that is, the thickness ratio corresponding to the set thickness ratio of the final container is maintained, and the thickness distribution in the circumferential direction of each resin layer is maintained. Accumulation of the multi-layer multiple resin is carried out in a state of being kept in a uniform manner.

By exerting a pressing force on the accumulated multi-layered molten resin in the resin reservoir, the multi-layered multiple molten resin passes through the die orifice of a predetermined size, and the thickness ratio of each resin layer and the circumferential thickness distribution It is rapidly extruded while maintaining uniformity, and the molten multilayer parison is smoothly formed.

In the present specification, rapidly extruding a multilayer multiple molten resin through a die orris means that the multilayer multiplex is performed at a speed as large as the accumulation rate of the multilayer multiple resin in the die and as large as possible within a range that does not cause a mettle fracture. This means extruding a molten resin. The effective volume in the resin reservoir, that is, the volume extruded in one extrusion cycle, corresponds to the total amount of the basis weight of the final container and the amount of by-product burr,
By setting the volume of the resin reservoir in the die to a predetermined volume, it is possible to freely manufacture large-capacity containers such as large-capacity bolts and tanks. Further, since a large amount of parison can be rapidly extruded, problems such as drawdown of the parison, uneven thickness, defective fusion of the pinch-off portion, etc. can be eliminated.

In the present invention, the multi-layered multiple molten resin reservoir is formed by moving an annular reciprocating member movably provided along the molten resin passage by the backward movement of the multi-layered multiple molten resin, and It is preferable to drive the reciprocating member to move forward to rapidly extrude the multi-layer multi-layer molten resin.

That is, according to this preferred embodiment of the present invention, the multi-layer multi-layer molten resin is stored in the reservoir formed by the retracting of the annular reciprocating member without substantially disturbing the multi-layer multi-layer structure. This annular reciprocating member can be retracted by the resin pressure itself which is forcibly supplied into the multi-layer multiple die by a plurality of extruders, and the pressure from the outside at a speed commensurate with the amount of resin supplied, For example, hydraulic pressure, water pressure, compressed air pressure or the like can be used for retreating. After a predetermined amount of the multi-layer resin is stored in the reservoir, the annular reciprocating member is forcibly driven to move forward by the hydraulic pressure or the like, so that the molten resin maintains the multi-layer structure, and the draw-down and deviation are caused. Co-pressing is performed at a high speed so that meat and the like can be prevented, and a blow molding ballison is formed.

(Example) In FIGS. 1 and 2 showing an example of an apparatus used for carrying out the method of the present invention, FIG. 1 shows a state in which a multi-layer multiple molten resin is filled in the reservoir, and FIG. 2 shows a reservoir. The state where the multilayer multiple molten resin in the part is extruded is shown.

The multilayer multi-layer die shown in FIGS. 1 and 2 has a core 1 at the tip of the die, a shell 2 coaxially provided with the core 1 at the tip of the die, a die orifice 3 formed between the core 1 and the shell 2, and at the tip. A core support shaft 4 that supports the core 1 and extends in the resin extruding direction, a die block 5 that supports the shell 2 at the tip and is coaxial with the core support shaft 4, and has a hollow inside, the whole of which is hollow. Is provided coaxially with the core support shaft 4 and at a distance from the core support shaft 4 in the radial direction, and is composed of a small diameter portion 6, a large diameter portion 7 and a tapered connecting portion 8 between them, and the tip of the large diameter portion. The hollow mandrel 10 located between the core support shaft 4 and the die block 5 and the small diameter extension 9 fitted between the core support shaft 4 and the mandrel small diameter portion 6 in a positional relationship in which 9 is retracted from the die orifice 3 by a predetermined distance. Part 11, core support shaft 4 and mandrel A ring piston 13 having a large-diameter tip portion 12 fitted between the large-diameter portion 7 and reciprocating along the core support shaft 4, an outer peripheral surface of the mandrel 10, and an inner peripheral surface of the die block 5. And a plurality of independent resin passages 15a, 15b, 15c arranged concentrically with one or a plurality of sleeves 14a, 14b between them and the independent resin passages and the rear end portions thereof, respectively. Resin supply path 16a,
16b, 16c, a multi-layered resin passage 17 connected to the tip of each independent resin passage and extending at least between the outer peripheral surface of the mandrel 1 diameter portion and the inner peripheral surface of the die block, the mandrel large diameter portion tip 9 and the die orifice 3. Between the core support shaft outer peripheral shaft 18 and the die block inner peripheral surface 19, and a multi-layered resin reservoir 20 and a rear end 21 of the small-diameter extension 11 of the ring piston, which is connected to the large diameter of the piston. The driving mechanism 22 is provided for moving the tip portion 12 in the multi-layered resin reservoir 20 toward the die orifice.

In the embodiment shown in the accompanying drawings, the first resin passage 15a
Is for forming the inner layer of a multi-layer plastic container,
The second resin passage 15b is for forming an intermediate layer of the container, and the third resin passage 15c is for forming an outer layer of the container. These resin passages are fed from the extruder (not shown) corresponding to each resin to the supply ports 16a, 16b, 16
Molten resin is supplied through c. When the inner and outer layers of the multi-layer plastic container are made of the same plastic, it is preferable that the molten resin supplied from a single extruder is supplied to the supply ports 16a and 16c through branch channels (not shown). Of course, the multilayer resin passage is not limited to the above three layers, and the number of sleeves can be increased to have a structure of five layers, six layers, seven layers or the like. For example, when there is no thermal adhesiveness between the intermediate layer resin and the inner / outer layer resin described above,
An adhesive resin layer can be provided in these resin layers.

First, the inner resin flow of emotion is formed by the first resin passage 15a, and the resin flow of the intermediate layer is superposed thereon in an annular shape,
Further, a multilayer and multiple molten resin flow having a stable and set thickness ratio is formed in the passage 17 in such a manner that the outer layer resin flow is superposed thereon in an annular shape.

It is desirable that the independent resin passages 15a, 15b, 15c be provided on the outer circumference of the mandrel small-diameter portion 6.

In FIG. 2 showing the state in which the ring piston 13 is at the lowermost position, that is, the extrusion end position, the multilayer multiple molten resin is
The piston passes through the multi-layer multiple passage 17 formed between the outer peripheral surface of the mandrel large-diameter portion 7 and the die block 5 and the multi-layer multiple passage 23 formed between the ring piston large-diameter portion 12 and the die block 5. Tip surface 24 and orifice 3
Enters the small space 25 formed between and. In this case, the resin pressure applied to the multilayer multiple molten resin causes the ring piston 13 to move backward. That is, the cross-sectional area of the orifice 3 is quite small, and if the resistance of the ring piston 13 moving backward (moving upward) is made smaller than the resistance of the molten resin passing through the orifice 3, the orifice 3
While the molten resin is not extruded through the ring piston 13, the ring piston 13 moves backward and is formed thereby.
That is, the multi-layer multiple resin is stored in 0. Of course, it does not matter that the ring piston 13 is driven backward by the external pressure at a speed corresponding to the resin supply speed.

The property that the molten resin spreads due to its viscoelastic property is well known by a phenomenon generally called die swell.
Also in the present invention, due to the same characteristics as the die swell,
Despite the dimensional difference between the multilayer resin passage 17 and the reservoir 204, the molten resin is stored in the reservoir 20 while maintaining the multilayer structure.

The state where the multi-layered multiple resin is filled in the reservoir 20 (Fig. 1)
When the ring piston 13 is driven forward (moved downward), the resin in the reservoir 20 is pressed from the die orifice 3 in the form of a cylindrical parison while maintaining the multi-layer structure, and the parison is clamped by a pair of split molds. Then, by blowing a fluid into the enclosed parison, a multilayer plastic hollow container such as a bottle or a tank is manufactured. When the ring piston 13 is driven forward, it is desirable to stop the extruder.

The operation of each mechanism in the present invention is preferably performed according to the system diagram shown in FIG. In this case, as shown in FIG. 1, the limit switch Ls-1 for detecting the raised position (retracted position) of the ring piston 13 and the lowered position (forward position).
A limit switch Ls-2 for detecting is provided. A hydraulic cylinder is used as the drive mechanism 22 for the ring piston, and a hydraulic circuit switching valve S is attached.

(I) Preparation of parison extrusion In the state shown in FIG. 1, the reservoir 20 is filled with the multi-layer multiple resin, the ring piston 13 is in the raised position, and the limit switch Ls-1 is turned on. When Ls-1ON, the extruder is stopped and the hydraulic circuit switching valve S operates.

(Ii) Extrusion of parison Due to this, the hydraulic cylinder 22 is driven forward, the ring piston 13 descends, and the multi-layer multiple resin is extruded in the form of a parison. Limit switch Ls-2 at the lowest position
Turns on. When Ls-2 is turned on, the switching valve S is turned off and the hydraulic cylinder 22 is set in a free state, or a light hydraulic pressure is applied to the ring piston retract side. (Ii
i) Resin Storage With Ls-2ON, the extruder is driven again, resin extrusion is started, and the ring piston 13 is retracted (raised) to advance the storage of resin in the reservoir.

(IV) Blow Molding With Ls-2ON, the blow mold is clamped, the fluid is blown into the parison in the mold, the blow molded product is cooled, exhausted,
A series of steps for taking out the product by opening the mold is performed.

In FIGS. 4 and 5 showing a device that can be used in the present invention, a core 1 and a core support shaft 4 supporting the core 1 are provided slidably in the resin extruding direction. That is, the pin 30 is provided in the retracted portion of the core support shaft 4, and the support shaft 4 is rotated by swinging the lever 31 engaging with the pin 30.
And the core 1 can move. The core 1 has a flange portion 32 at its tip, and in the resin storage state shown in FIG.
The flange portion 32 engages with the inner peripheral surface of the shell 1, and the die orifice 3 is closed. Therefore, the ring piston 13 is moved backward (moved upward) by the resin pressure.

At the time of extruding the parison shown in FIG. 5, the core 1 advances (falls) from the position shown in FIG.
The die orifice 3 is released by releasing the engagement with the inner peripheral surface.
Opens. The resin in the reservoir 20 is extruded by lowering the ring piston 13 in this state.

According to the present invention, blow-molded products having an internal volume of 1 to 100, particularly 3 to 50 and a basis weight of 30 to 90 g / can be produced. Extrusion of the parison generally varies from 0.5 to 5 depending on its length.
It is preferable to carry out in seconds, especially in 1 to 3 seconds. According to the present invention, it is a remarkable feature that a large amount of parison can be extruded at a relatively high speed even when an extruder having a relatively small discharge capacity is used.

The type and combination of multilayer multi-layer resins can vary widely. For example, as the resin, low-density polyethylene and (acid-modified), medium-density polyethylene (〃), linear-polyethylene (〃), polypropylene (〃), ethylene-propylene copolymer (acid-modified), ethylene -Vinyl acetate copolymer (modified with acid), ionomer, polystyrene polyvinyl chloride, vinylidene chloride-vinyl chloride copolymer, high nitrile, acrylonitrile, polycarbonate, polyethylene terephthalate, polyethylene isophthalate, 6-nylon, 6-66 Use any combination of two or more of copolymerized nylon, polybutylene terephthalate, poly-4-methyl-pentene-I, polytetrafluoroethylene, saponified ethylene-vinyl acetate copolymer, and xylene group-containing polyamide. It can be. A suitable example of the multi-layer structure is a combination of a high gas barrier resin intermediate layer and an inner / outer layer of a moisture-resistant thermoplastic resin, and in particular, as the inner / outer layer, polyethylene, a die swell large olefin resin such as polystyrene is used, The multilayer multi-layer structure is very well maintained in the parison. In this case, the thickness ratio of the intermediate layer to the inner and outer layers is generally 1: 1 to 1:60,
In particular, it is desirable to set it within the range of 1: 3 to 1:20.

Example of Molded Container A polypropylene resin having a melt index of 1.5 g / 10 min and a density of 0.90 g / cc of ethylene content of 3 wt% was used as the inner and outer layers, and the middle layer had an ethylene content of 30 mol% and a vinyl alcohol content of 70 mol%. Made from ethylene vinyl alcohol copolymer, and used as adhesive layer resin, melt index 2.g / 10min density 0.91g / cc carbonyl group concentration 30mmol / 100g polymer polypropylene modified with maleic anhydride. Outer layer / adhesive layer /
In forming a 20-poly multilayer tank with a 5-layer structure consisting of an intermediate layer / adhesive layer / inner layer, the diameter was 65φ and the effective length was
1430m / m, 2 melt channels (for inner and outer layers), diameter 40φ, effective length 880m / m, 1 melt channel
Channel (for intermediate layer), diameter 40φ, effective length 880m / m
, The melt channel has two dimensions of each channel (for adhesive layer), through the small-diameter part to the large-diameter part of the storage-type multi-layer multiplex die, and the storage part is filled with 1500 g of 5-layer resin, and the hydraulic pressure The ring piston was operated all at once by the pump to form the multilayer parison.

The thickness ratio of each layer of the parison is 1: 1/10: 1/10: 1/10: 1 for outer layer: adhesive layer: intermediate layer: adhesive layer: inner layer, and the total thickness is about 5 m / It was m.

The parison was sandwiched between 20 blow molds mounted on a molding machine having a mold clamping force of 15 t, and the lower part was 7 kg / cm ²
Air was blown into the parison at a pressure of 1 to expand the parison, and blow molding was performed to obtain 20 blow bottles (tanks) having a five-layer structure.

The blow bottle obtained had good appearance with no uneven thickness of each layer, no melt fracture, and good fusion at the pinch-off portion, internal volume of about 20, vertical 330 m / m, width 17
Square type with 0 m / m and height of 340 m / m, average body thickness of 1.2 m / m
m and basis weight (weight) were 1150 g.

(Effects of the Invention) According to the present invention, for any combination of resins, a drawdown of a multilayer resin container having a thickness ratio according to a set thickness ratio and a uniform thickness distribution in the circumferential direction of each resin layer, Uneven thickness,
There is an advantage that it can be manufactured without trouble such as defective fusion of the pinch-off portion, and that a large-capacity container can be easily manufactured by using an extruder having a relatively small discharge amount.

[Brief description of drawings]

1 and 2 are side sectional views showing an embodiment of the apparatus used in the present invention. FIG. 1 shows a state in which the ring piston is in an extrusion start position and FIG. 2 is a state in which the ring piston is in an extrusion end position. FIG. 3 is a systematic diagram of the steps of the method of the present invention, and FIGS. 4 and 5 are side sectional views of the essential parts showing another embodiment of the apparatus used in the present invention. Shows a resin storage state and FIG. 5 shows a resin extrusion state. 1 ... core, 2 ... shell, 3 ... die orifice, 4 ... core support shaft, 5 ... die block, 6 ... small diameter part, 7 ... large diameter part, 8 ... tapered connection part, 9 ... Large diameter tip, 10 ... Hollow mandrel, 11 ... Small diameter extension, 12 ... Large diameter tip (extrusion tip), 13 ... Ring piston, 14a, 14b ... Sleeve, 15a, 15b, 15c ... Resin passage, 16a, 16b, 16c ... Resin supply passage, 17 ... Multi-layer multiple resin passage, 18 ... Core support shaft outer peripheral surface, 19 ... Die block inner peripheral surface, 20 ... Reservoir , 21 ... rear end, 22 ... drive mechanism.

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Claims (3)

[Claims] 1. A method of supplying a plurality of kinds of molten resin from respective extruders into a ring-shaped multi-layer multiple die to extrude a multilayer parison in which a plurality of kinds of molten resin are laminated, and blow molding the multilayer parison. In the method for producing a multi-layered resin container, the multi-layered multi-melted resin reservoir is formed in the molten resin passage from the resin final merging position of the multi-layered multiple die to the die orifice, and the multi-layer multiple molten resin is stored in the reservoir. After charging,
A method for producing a multi-layer resin container, which comprises rapidly extruding a multi-layer multiple molten resin through a die orifice. 2. An annular reciprocating member provided movably along the molten resin passage in the multi-layered multiple molten resin reservoir,
Claims: A multi-layer multi-molten resin is extruded backward by the pressure of the multi-layer multi-molten resin or an external pressure, and the multi-layer multi-molten resin is rapidly extruded by driving the annular reciprocating member to move forward. The manufacturing method according to item 1. 3. A core at the tip of a die, a shell provided coaxially with the core at the tip of the die, a die orifice formed between the core and the shell, and supporting the core at the tip and extending in the resin extruding direction. A core support shaft, a die block that supports a shell at the tip, is provided coaxially with the core support shaft, and has a hollow inside, and is entirely hollow, coaxial with the core support shaft, and radially spaced from the core support shaft. A hollow mandrel provided between the core support shaft and the die block, an extension part fitted between the core support shaft and the mandrel, and a tip for extrusion, and reciprocating along the core support shaft. Possible ring pistons, a plurality of independent resin passages concentrically arranged between the outer peripheral surface of the mandrel and the inner peripheral surface of the die block via one or a plurality of sleeves, and each of the independent resin passages. Touches the rear end A continuous resin supply path, a multi-layered resin passage extending at least between the outer peripheral surface of the mandrel or ring piston and the inner peripheral surface of the die block, which is connected to the tip of each independent resin passage, the extruding tip of the ring piston, and the die. It is connected to the reservoir of the multi-layered multi-layered resin formed between the orifice and the outer peripheral surface of the core support shaft and the inner peripheral surface of the die block, and the rear end of the extension part of the ring piston, and the piston extruding tip part is connected. A storage-type multi-layered die comprising a drive mechanism for moving a multi-layered resin reservoir in a die orifice direction.