JP2512668B2 - Modular tubular extrusion head - Google Patents

Description

BACKGROUND OF THE INVENTION RELATED APPLICATION This application is filed on Sep. 20, 1990, entitled “MODULAR TUBULAR EXTRUSION”.
No. 535,452 to "HEAD)".

FIELD OF THE INVENTION The present invention relates to a resin extrusion device, in particular a parison,
An extrusion head for producing articles having one or more tube layers, such as wire coating coatings, blown films, pipes, pultruded rods, profiles, reinforced sheets, and the like.

DESCRIPTION OF THE PRIOR ART A parison, a tubular extrudate of plastic resin that is subsequently blow molded to form a bottle or other container, conventionally uses an extrusion head to extrude a continuous layer of plastic resin onto a mandrel. It is molded by various devices including. A typical multi-layer parison extrusion head has separate inlets to receive the heated and plasticized resin from the individual screw extruders, and separate dispensing and dispensing of each plastic resin onto the mandrel as a continuous layer. Have a channel. Each channel includes an annular homogenization and distribution chamber surrounding and surrounding the mandrel for receiving plastic resin from a corresponding inlet. From the homogenization chamber, the plastic resin is directed downwardly and inwardly through a frustoconical transfer path and fed into a tubular extrusion channel formed around a mandrel.
The annular extrusion channel exits through an annular die that opens inward or outward. The annular die includes a conical core member that is movable longitudinally relative to the outer member of the die,
The wall thickness of the extruded tubular article can vary.

One particularly useful and successful extrusion head for forming tubular articles such as parisons is US Pat.
No. 798,526. The head includes one or more annular extrusion modules each enclosing successive individual portions of a stepped or tapered mandrel, the annular extrusion receiving one or more plastic resin layers continuously extruded from the module. Forming an extrusion channel of Each module has a pair of members with mating surfaces in which a homogenization / distribution chamber and a frustoconical transfer path are formed. This head is made up of separate extrusion modules that are coaxially spaced apart, which makes assembly and disassembly easy and
The ability to assemble extrusion heads with varying numbers of modules allows one module to be used in one assembled head to extrude a single layer tubular article, or to differently assembled heads. It can be used to extrude any layer of a multilayer article. The modules forming the extrusion head can be arranged in any desired order. Further, the die modules are separated from each other by an annular air space. A concentric tubular neck or collar extends from each module and engages adjacent modules to define the separation distance or airspace width between the modules. These air spaces prevent heat transfer from the hot module to the adjacent cold module. Low temperature resins can deteriorate when heated to high temperatures. The patent further added that the polymer incident pressure at the extrusion head was 4,000 for polycarbonate.
0-6,000 psi (27,000-41,000 KPa), 2,500-4,000 psi (17,000-28,000 KPa) for polypropylene, 2,000-3,000 psi for binder and barrier resins
(13,000-21,000KPa) is disclosed.

U.S. Pat.Nos. 3,649,143, 4,111,630 and 4,18
No. 2,603 has a multilayer film blower having nested frustoconical, hemispherical and cylindrical die members that form a polycarbonate dispensing chamber with a spiral groove formed on the outer surface of the inner member. A tubular extrusion die for molding is disclosed. Because these grooves have a shallower depth from the point at or near the inlet to the outlet, the polymer flow is under progressive pressure, causing a frustoconical, hemispherical or tubular space between the groove and the die member. The polymer is evenly distributed throughout the chamber. These nested arrangements have some drawbacks, such as limited temperature differences between the various layers being extruded, larger heads required to extrude multiple layers, and one or more The conical passage from the tip of the groove to the annular outlet is long.

Prior art tubular extruders typically require a restricted frustoconical transfer passage from the dispensing chamber to the annular outlet through which the tubular article is extruded. With this restricted passage, the pressure drop will be relatively high in order to evenly distribute the polymer within the distribution chamber. That is, over 50% of the total pressure drop from the inlet of the extrusion head through the distribution region or chamber and the restricted passage to the outlet. Without this restrictive outlet passage with a relatively large pressure drop, the polymer would tend to flow at a faster rate along the shortest path from the inlet to the distribution chamber and along the closest region of the annular outlet, and the tubular There will be uneven thickness around the circumference of the article.

Prior art devices are generally effective and successful in extruding tubular articles such as multilayer parisons, blown films, wire coatings, etc., but also have room for improvement. In addition to the pressure difference problem described above, it is necessary to reduce the stress caused by the temperature difference. For example,
In prior art extrusion heads, the polymer melt flows from the inlet side of the homogenization and distribution chamber to the opposite side. As a result, the resin processed in the prior art extrusion head experiences a temperature differential in the resin and the aforementioned pressure differential during processing through the inlet, distribution means and outlet. As a result of these process differences, the extruded parison is subjected to a non-uniform distribution of the extruded resin, resulting in actual and latent internal stresses in the extruded parison. When this parison is then formed into a final shaped bottle or similar container, the internal stresses are carried over to the final product, and possibly worse. For example, if such an article such as a bolt is reused, subjected to high temperature cleaning, etc., and filled with a carbonated beverage under pressure, for example, the article may explode as a result of the internal stress. Conventional extrusion equipment does not appear to be able to relieve these stresses, and further improvements in extrusion heads are needed. This is especially the case from the point of view of environmental requirements that it is required to reuse the container instead of discarding it such as landfill.

Accordingly, it is an object of the present invention to provide a more uniform distribution of extruded polymer by minimizing the processing variations that occur in prior art extrusion heads and processes. To establish a new and improved polymer extrusion head and process for use.

It is also an object of the present invention to provide a container having excellent properties as a result of the improved polymer distribution described above, and thereby having sufficient properties to be effectively and safely reused or regenerated. Provide the container.

SUMMARY OF THE INVENTION The present invention provides a method of extruding a container that achieves the above objectives. In this method, one or a plurality of extrusion modules are arranged and fixed along an axis [However, each of the one or a plurality of extrusion modules has a resin inlet and a bore having a cylindrical inner surface. And an annular extrusion outlet opening into the inner surface of the cylinder, each of the one or more modules receiving and distributing a resin extending from the inlet to the outlet and a polymer. Is an annular extrusion outlet from the inlet (through which the polymer is extruded in an annular form)
A channel means defining a flow path for flowing up to, said channel means extending symmetrically about an axis of said one or more extrusion modules, and therefore from said inlet All of the polymer flowing to the outlet is subjected to substantially the same process conditions throughout the flow path, whereby the polymer distributed at the annular outlet is distributed to all the resin distributed through this outlet. On the other hand, it has a property of being substantially symmetrical around the axis], a polymer material is introduced into the inlet, the extruded flow is introduced from the inlet through the flow path through one or a plurality of modules. Flow the polymer to the outlet (as a result,
The flowing polymeric material substantially surrounds the shaft, 1
Reaching the extrusion outlet with substantially symmetrical properties about the axis for all the polymer flowing through the module or modules), extruding the polymeric material through the extrusion channel, and extruding the polymeric material A parison is then formed as it exits the channel, and a container is formed from the parison thus formed, which causes the otherwise different properties of the extruded polymer to differ near the periphery of the parison. It is formed with virtually no resulting internal stress).

In one aspect, the method comprises: one or more annular extrusion modules arranged along the axis of one or more modules; and one or more annular extrusion modules along the axis. One or more extrusion modules, each of which comprises a polymer inlet, a bore having a cylindrical inner surface, and an annular opening into the cylindrical inner surface. And one or more modules each of which receives and distributes a polymer extending from the inlet to the outlet, and the polymer has an annular extrusion outlet from the inlet. Through which there is flow in a circular configuration) to define a flow path, the channel means defining the axis of rotation of said one or more extrusion modules. Symmetrically extending so that all of the polymer flowing from the inlet to the extrusion outlet is subjected to substantially the same process conditions throughout the flow path, whereby the annular extrusion outlet By the way, the polymer to be dispensed has the property of being substantially symmetrical about said axis with respect to all the resin dispensed through this outlet, using a polymer resin extrusion head for extruding tubular articles. It can be carried out.

In another aspect, the invention provides: one or more annular extrusion modules arranged along the axis of one or more modules; and holding one or more annular extrusion modules along the axis. And a means for securing the pair of mating annular members, each of the one or more extruding modules having a pair of coaxial annular members, the pair of mating annular members on the periphery of the module. It defines a resin inlet, a coaxial bore with a cylindrical inner surface, and an annular extrusion outlet opening into the cylindrical surface, each pair of mating annular members A channel means formed on the mating surfaces for receiving and distributing the resin from the inlet to the annular extrusion outlet, and the polymer from the inlet to the annular extrusion outlet (where the polymer passes through A channel means defining a flow path for flowing up to (extruded in an annular form), said channel means extending symmetrically about the axis of said one or more extrusion modules, and , All of the polymer flowing from the inlet to the extrusion outlet is subjected to substantially the same process conditions throughout the flow path, whereby the polymer distributed at the annular extrusion outlet is Having a property of being substantially symmetrical about said axis with respect to all of the resin dispensed therethrough, each pair of mating members having an inner and an outer nesting frustoconical section, respectively. The outlet is defined by an annular space between, and the angle of the inner surface of the inner frustoconical portion from the axis is greater than the angle of the outer surface of the outer frustoconical portion. Are summarized tubular article by the polymeric resin extrusion head for extruding.

The gist of the invention in yet another aspect comprises a plurality of coaxial annular extrusion modules arranged along an axis and means for holding the modules longitudinally spaced along the axis of the module. And each module has a pair of coaxial annular members that mate with each other,
And a means for fixing the mating annular member pair to each other, the mating annular member pair comprising a resin inlet on the periphery of the module, a coaxial bore having a cylindrical inner surface, and a cylindrical surface. An open annular extrusion outlet is defined, wherein the one or more modules each receive and distribute a polymer extending from the inlet to the outlet and the polymer is annularly extruded from the inlet. Has channel means defining a flow path for flow to an outlet (through which the polymer is extruded in annular form), said channel means around the axis of said one or more extrusion modules All polymers flowing symmetrically, so that they flow from the inlet to the extrusion outlet, are subjected to substantially the same process conditions throughout the flow path, whereby The polymer dispensed at the extrusion outlet has a property that is substantially symmetrical about said axis with respect to any resin dispensed through this outlet, each module further having a frustoconical central portion. , The axial dimension of the frustoconical central portion in the central bore is greater than the axial dimension of the outer portion of each module, so that the top of each preceding module engages the adjacent succeeding module, resulting in an adjacent It is a polymer resin extrusion head for extruding multi-layered tubular articles that forms an air space including a frustoconical air space portion between the modules to enhance the thermal insulation effect between the modules.

The invention in another aspect provides an elongated mandrel and a continuous, longitudinally spaced apart mandrel extending around successive sections of the mandrel, between the module and the mandrel, extruded by the module. An annular die having a plurality of concentric annular extrusion modules defining tubular extrusion channels for receiving the formed layers into the tubular extrusion channels and three successive sections disposed downstream of the extrusion modules. An annular die for receiving and shaping the multi-layer tubular extrudate from the channel (the diameter of the first section is tapered from the diameter of the annular extrusion channel, the diameter of the second section is its length) Is constant throughout and equal to the exit diameter of the first section, and the third section The diameter of Deployment is composed of a second is flared progressively increasing diameter section to the desired diameter), a polymer resin extrusion head for extruding multilayer tubular articles.

Other objects, advantages and features of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an extrusion head for extruding a multilayer parison according to the present invention.

2 is a bottom view of the top member of one extrusion module within the head of FIG.

3 is a cross-sectional view of the extrusion module taken out of the head of FIG. 1, taken along line 3-3 of FIG.

FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2 of a part cut out from the module of FIG.

FIG. 5 is an elevation view of a part cut out from the upper member of the module of FIG. 3, taken along the line 5, 6-5, 6 in FIG.

FIG. 6 is a sectional elevation view of a part cut out from the lower member of the module of FIG. 3, taken along line 5, 6-5, 6 of FIG.

7 is a diagrammatic view of a parison extrusion device including the extrusion head of FIG.

FIG. 8 is a view similar to FIG. 2 showing a variation of the spiral channel of the upper member of the extrusion module.

FIG. 9 is a view similar to FIGS. 2 and 6, showing another variation of the spiral channel of the upper member of the extrusion module.

FIG. 10 illustrates an example of a container blow molding process and apparatus that can incorporate the extrusion head of the present invention.

 FIG. 11 is a sectional view of a part of the annular die of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 7, one embodiment of the present invention, an extrusion head (generally designated by 10), is 14, 16, 1
It includes one or more extrusion modules, such as the plurality of extrusion modules shown at 8 and 20. These modules are standard screw extruders 24, 26, 2
A variety of different polymeric material streams from 8 and 30 are received to form the multi-layer parison 32. This parison is then extruded into the blow mold of the container, as shown in FIG. As shown in FIG. 1, the modules 14, 16, 18, 20 are mounted coaxially in a spaced relationship along an axis 22 of these modules, which allows each module in the head to be heated. An extruding temperature control of each extruded layer can be improved by forming an air space 88 including an electrically insulating frustoconical air space 90.

In the case of the illustrated parison head, modules 14, 16,
18, 20 are coaxially over the spaced sections of the mandrel to extrude each layer into a tubular extrusion channel 36 defined between the inner surface of the module and the outer surface of the tapered stepped mandrel 34. It is growing.

Modules 14, 16, 18, and 20 have similar structures. Each module includes an upper member 40 and a lower member 42, as shown in FIG. These members are mated with each other and a plastic material inlet 46 opening on the periphery of the module, an annular outlet 48 opening on the inner surface of the module, and
Outlet 48 from bifurcated inlet channels 52 and 53
And includes one or more spiral channels, such as a pair of spiral channels 50 and 51 (FIGS. 2 and 3) extending to positions adjacent to. The inlet 46 is formed by machining the mating surface of the member or boring along the parting line between the outer portions of the member. Alternatively, the inlet 46
Can be formed by boring into one of the members 40 or 42 similar to that shown in U.S. Pat. No. 4,798,526. Bifurcated introduction channel
52 and 53 are 90 at the mating surface of the outer flange portion of members 40 and 42.
It is machined in the opposite direction by the arc of the angle of °. Element
The flat mating planes of the flange portions of 40 and 42 sealingly engage each other to close channels 52 and 53.

The central portions 54 and 56 of members 40 and 42 are generally frustoconical with the top facing down. As shown in Figure 6, the central part
The inner surface of 56 has a cylindrical ring portion 58 and three conical frusto-conical portions 60, 61, 62. These frustoconical sections extend inwardly from the ring portion 58 to the cylindrical surface 63 of the bore. The cylindrical surface of this bore has a tubular extrusion channel 36
Defines a portion of the outer wall of the (Fig. 1). Tilt angle of face 61,
That is, the angle of surface 61 with respect to axis 22 is less than the angle of inclination of surfaces 60 and 62 so that the thickness of the annular frustoconical space or passage 64 (FIG. 4) between portions 54 and 56 is the same as spiral channel 50. Increasingly over 51 areas. This is indicated by the dash-dotted line 70 at the same angle as faces 60 and 62. As shown in FIG. 5, the outer surface of the inner frustoconical portion 54 has a cylindrical ring portion 65 that sealingly engages the surface 58.
And a first frustoconical portion extending inwardly from the ring portion 65 to the first spiral of the spiral channels 50 and 51.
66 and a second frustoconical surface portion 67 extending inwardly from the outermost spiral vortex formed by channels 50 and 51 to the top of frustoconical portion 54. At the top of the truncated cone portion 54, a cylindrical surface 68 (FIG. 4) defines a portion of the outer wall of the tubular extrusion channel 36. The bores defining the cylindrical surfaces 63 and 68 are coaxial. The first and second frustoconical surfaces 66
An edge 71 (FIG. 2) between 67 is formed in the planar area between the spiral channels 50 and 51 and the first spiral. The first frustoconical surface portion 66 has an inclined surface equal to the surface 60 so that the surface portion 66 sealingly engages the surface portion 60. The second frustoconical surface portion 67 also has the same tilt angle as the surfaces 60 and 66, but has a smaller diameter as indicated by the dash-dotted line 69 extending from the surface 66, thus allowing the helical channels 50 and 51 to be formed. An initial frustoconical space or thickness is introduced between the separating planar area and the surface 61 to initiate the frustoconical passage 64. The frustoconical passage 64 defines an outlet 48 at its inner end.

Referring to FIG. 2, the inlet channels 52 and 53 have extensions 72 and 73 machined into faces 65 and 66 of the inner central portion 54, leading to the origin of the respective helical channels 50 and 51. These origins are 180 ° apart on the opposite side.
The spiral channels 50 and 51 are frustoconical surfaces of the inner frustoconical portion 54.
Formed by machining to 67, each extending clockwise and forming a spiral of approximately one and a half revolutions about the truncated cone portion 54. Since the cross-sectional area of each of channels 50 and 51 gradually decreases from its origin to its end,
The polymer forced into each channel at its origin is gradually distributed within the increasing width of the frustoconical passage 64 and is evenly distributed about the frustoconical portion 54. The pitch of the spiral channels, ie the spacing between adjacent vortices, is constant and the depth of the spiral channels relative to surface 67 varies linearly to facilitate machining of the channels.

The length of the spiral channel, when taken together, must surround or be symmetrical about the axis of one or more modules, ie forming the extrusion channel 36. Since the mating inner and outer portions extend approximately 360 ° around the axis of the bore formed, all of the polymer flowing from the inlet to the outlet will be subject to substantially the same process conditions.
As used herein, "surrounding" is meant to include both circular and non-circular passages. Such channels ensure that the polymer is distributed at the annular extrusion outlet with a property that is substantially symmetrical about the axis of the extrusion module (s) with respect to all the resin being distributed through the outlet. Means are provided.

In the variant shown in FIG. 8, the channels 93 and 94 extend in opposite directions, each extending at least 180 ° along the spiral passage, so that the channels 93 and 94, taken together, have an inner frustoconical portion. Extends completely around. The number of spiral channels and their directions can be varied. The variation of FIG. 9 shows a single spiral channel 96 forming three or more spirals around the inner frustoconical portion.

Returning to FIG. 3, the outer surface 76 of the lower portion of the lower frustoconical portion 56 has an inclination angle that is less than the inclination angle of the inner surface 78 of the upper frustoconical portion 54, so that the axis 22 of the inner surface of the module 18 is
The width 82 along is greater than the width 86 of the outer portion of this module 18. The difference between the widths 82 and 86 is selected to provide the desired spacing 88 (FIG. 1) between adjacent modules. The lower edge of each higher module 14, 16, 18 engages the upper side of the next lower module 16, 18, 20 to define a spacing 88 between the modules. Spacers 84 formed on the bottom of the flanges of the lower member 42 help abut adjacent modules to maintain a uniform spacing between the module flanges or outer portions near the module circumference. There are various holes in these spacers 84 leading to the flange, so this space 88
Air can enter and leave the room. The frustoconical air space portion 90 of the space 88 extends to the point of engagement between the modules.

The upper member 40 and lower member 42 of the extrusion modules 14, 16, 18, 20 are secured together by bolts 98 (FIGS. 1 and 2). When assembled, the members 40 and 42 are guide pins 99
(Figures 2 and 4) allow proper alignment. Screw hole 101 in member 42 (FIG. 6) and recess 103 in member 40 (FIGS. 2 and 5)
Since they are aligned with each other, when disassembling, a conventional jacking bolt (not shown) can be screwed into the hole 101 to engage the recess to separate the members 40 and 42.

As shown in FIG. 1, modules 14, 16, 18,
20 is held in the extrusion head 10 by upper and lower clamp members 100 and 102 and bolts 104 (see also FIG. 2) extending through holes in the clamp and extrusion modules. The lower surface 106 of the upper clamp member 100 has a convex frustoconical shape similar to the lower surface of the extrusion modules 14, 16, 18, 20 and the upper surface 108 of the lower clamp member 102 has a concave frustoconical shape similar to the upper surface of the extrusion module. I have This allows the extrusion modules to be repositioned and clamp members to be used to hold a single extrusion module or any number of modules.

The mandrel 34 is tubular and extends through the clamp member and a mounting plate 110 secured to the upper clamp member 100 by bolts 112. The mounting plate 110 is secured to a conventional blow molding and support structure (not shown) by bolts 113. The upper end of the mandrel which is tapered and fits into the clamp member 100 is fixed by a threaded nut. The mandrel 34 tapers downwardly with a plurality of successive steps 118, 120, 122, 124. Each of these stages begins at the outlet of the corresponding module 14, 16, 18, 20 and extrudes a continuous polymer layer onto the mandrel. The diameter of each step is selected according to the desired thickness of the corresponding layer to be extruded. Generally, different arrangements of extrusion modules require different mandrels.

Alternatively, the mandrel can have a constant diameter throughout the extrusion module and the inner diameter of the extrusion module can be stepped. This limits the replacement of modules, but allows blank modules to be manufactured whose inner diameter is machined after the extrusion head configuration has been determined.

An annular upper die 128 and lower die 130 are attached to the bottom of the module clamp member 102 by die clamps 132 and bolts 136 and 138. The lower die 130 is screwed into the upper die 128. Inside the die is a die core 140, which is screwed onto the lower end of a shaft 142 which extends slidably through the lumen of the mandrel 34. The die opening of this die 128 is reduced in diameter or stepped at 144 corresponding to the tapered end of the mandrel 34 so that a constant cross-sectional area of the extrusion passageway is maintained. This reduced diameter is a constant diameter section
Along 146, through the top of the lower die 130, the bottom 148 of the lower die extends to the desired diameter of the article or parison. The bottom 150 of the die core 140 diverges outward at an angle that is slightly greater than the angle of the die portion 148, so that the outlet size of the tubular extrusion channel is smaller than the top of the extrusion channel and the layer of plastic polymer is It is ensured that they adhere firmly to one another and that the cross-sectional area of the extrusion channel is maintained.

To ensure that the polymer layer is slightly radially compressed as it is extruded from the die, to ensure this, the cross-sectional area of the annular channel as it exits the bottom of the die sections 148 and 150 depends on the introduction of this channel. Make it slightly smaller than the cross-sectional area of the part. In other words, the extruded multi-layer polymer structure has a reduced cross-sectional area of the flow path formed by the channels formed by the elements 148 and 150.
It is preferably slightly compressed in the outflow direction. This allows
Its compression is ensured when the multilayer structure exits the die, the film adheres tightly and the structural integrity of the extruded multilayer parison is enhanced.

Alternatively, as shown in FIG. 11, the bottom portion 150 of the die core 140 can open inwardly at an angle greater than the angle of the die portion 148. as a result,
The die tapers inward, but the annular extrusion channel widens. In the embodiment of FIG. 11, it is preferred that the cross-sectional area of the annular channel be similarly reduced to compress the more or less extruded structure as it exits the die.

A central longitudinal bore 152 is formed through die core 140 and shaft 142 to prevent gas from passing through the extruded parison and causing the parison to collapse.

The extrudate exits the die described above and enters a container blow (molding) mold according to conventional methods. As shown in FIG. 10, parison 32 emerges in container blow mold 200. The container blow mold 200 may be a conventional split mold which is divided along its longitudinal axis into mold halves 200a and 200b having the shape selected for the particular container desired. . The extruded parison 32 is then processed according to conventional blow molding techniques. See, for example, "Blow Molding", pages 222-224, Modern Plastics, October 1991.

For example, after the parison 32 emerges in the container blow mold 200, the mold halves 200a and 200b are combined, and the bottom of the parison 32 is cut off and sealed. The closed bottom of the parison becomes the bottom of the final container. Immediately after scoring the bottom of the parison, a conventional cutting blade (not shown) is used to cut the parison from the extrudate exiting the annular die 130. The container blow mold 200 is then removed from below the annular die 130 and replaced with another mold 300 and the above process is repeated. This particular process is known as the single station shuttle process.

After taking out the container blow mold from below the extrusion head 10, the container blow mold 200 is transferred to the calibration station 310. Next, a blow pin 311 is inserted into the container blow mold 200 and the parison 32 to inflate the parison into the container shown as 312 in FIG.
The container blow mold 200 is not shown in the calibration station 310 for clarity of the container 312. The blow molded container 312 is then removed from the mold 200 and trimmed using standard methods.

As shown in FIG. 7, the illustrated parison extrusion device includes a conventional control 160 that adjusts the vertical position of the shaft 142 within the mandrel 34. Extruded parisons often vary in thickness from bottom to top. That is, the bottom of the bottle with the inside out is
The bottom wall must be thickened to prevent bottom bulging due to pressure in bottle contents such as carbonated drinks. In addition, the control 160 uses the extruder 24, 2 in the conventional manner.
The extrusion pressure of 6, 28, 30 can be varied to change the thickness of each layer extruded relative to the other layers. For example,
The thickness of the barrier layer can be kept constant over the height of the bottle, while the thickness of the structural layer is reduced at the top of the bottle.

Returning to FIG. 1, the extrusion modules 14, 16, 18,
20, the clamp members 100, 102, and the lower die member 130, the corresponding members are first heated to the desired operating temperature,
And, electric heater coils 164, 166, 168, 170, 172, 174, 175, 176 for maintaining an appropriate temperature during operation are mounted respectively. Thermocouple sensing elements 180, 182,
184, 186, 188, 190 allow extrusion modules 14, 16,
The temperature signals of 18, 20, bottom clamp 102, and die member 130 are fed to a conventional control circuit (not shown) that activates the heater coils.

In one example of a parison suitable for blow molding to form a bottle, the parison is formed by extruding an outer layer of an inner layer of polycarbonate and an intermediate layer of amorphous polyamide through a multiple extrusion module. But,
A single material may have properties that meet all the requirements of a particular container application. In such cases, a parison with only one layer is needed. Therefore, according to the invention, it is also possible to produce a single-layer container from a single-layer parison using only one extrusion module.

The described embodiment has several advantages over prior art extrusion equipment. As a result of the use of one or more spiral channels which together form at least one complete spiral and gradually open into the frustoconical passage 64, The pressure difference is
It is offset by the pressure difference in the upper, thinner portion of the frustoconical passage 64. This eliminates the need for the annular pressure equalization and distribution chamber normally required in prior art tubular article extrusion equipment. There is still some non-uniform pressure in such a homogenization and distribution chamber. That is, there must be a pressure differential to cause the plastic polymer to flow from one side of the annular chamber to the other. Non-uniform pressure around the annular outlet causes non-uniform thickness of the layers formed in the parison. Thus, the concrete examples of FIGS. 1 to 9 are excellent in the uniformity of the layer thickness on the circumference.

In addition, a generally frustoconical transfer path extends from the homogenization and distribution chamber to the annular outlet to minimize pressure differentials within the prior art homogenization and distribution chamber. This prior art restrictive transfer path requires a much higher melt pressure than the present embodiment. In this example, at least one spiral formed by a channel of decreasing cross-sectional area that opens into a gradually thickening frustoconical passage 64 or by the combined length of two or more channels. Is used to minimize the circumferential pressure differential at outlet 48. The size of the one or more spiral channels and the thickness of the passage 64 are selected so that the pressure drop between the inlet 46 and the outlet 48 is substantially smaller than in the prior art.

Furthermore, the omission of prior art homogenization chambers that open into the restricted frustoconical transfer path reduces the shear forces on the plastic polymer caused by such openings. The substantially reduced shear force is a result of the use of one or more helical channels that are gradually open in the frustoconical passage 64 through one or more spirals in this example. As a result, the strength of the produced article is increased.

Circumferential polymer extrusion temperatures tend to be more uniform in extrusion heads according to the invention, and are substantially even more uniform in embodiments having more than one spiral distribution channel spiral. As discussed above, prior art polymer melts flow from the inlet side to the opposite side of the homogenization and distribution chamber, which can result in a temperature difference that the introduced polymer melt temperature and the average temperature of the distribution module are different. As a result, the above-mentioned actual internal stress and latent internal stress occur. However, in the extrusion head of the present invention, all portions of the polymeric material flowing from the inlet to the annular extrusion channel have substantially the same process conditions (e.g., temperature, pressure, Shearing force, etc.). Therefore, all polymers reaching the annular extrusion channel have approximately the same process history. That is, the polymers have all been exposed to about the same process conditions by then, and thus are nearly uniform in their properties near the perimeter of the extrusion channel as it is extruded. That is, the tendency of temperature difference on the circumference and the occurrence of non-uniformity are reduced.

The reduction in the occurrence of non-uniformities makes it possible to produce parisons and bottles that appear superior to conventional products. As already mentioned, reducing the non-uniform distribution of the resin caused by pressure and temperature differences as well as other processing conditions differences results in a parison made from the resin,
The number of real and potential internal stresses in bottles or similar articles is reduced. Thus, the resulting bottle or similar article has an excellent ability to remain in place under external stress.

The term "property" as used herein refers to a property that is a result of process conditions that are applied to the resin while flowing from the inlet to the outlet. These include parameters such as process temperature, pressure, shear conditions, and other process conditions to which the polymer is exposed along the path of flow from the inlet to the annular extrusion outlet. The flow paths are symmetrically arranged around the axis of the module (s), so that the polymer is subject to approximately the same process conditions while all of it flows from the inlet to the extrusion outlet. As a result, when it reaches the extrusion outlet, it has a substantially symmetrical and uniform property over the entire periphery of the extrusion outlet.

In this specific example, it is possible to further improve the temperature shutoff between the adjacent modules with a relatively simple and inexpensive structure. The prior art used abutting collars to separate the modules, but the collars were thick enough to transfer heat between the modules. In this example, the frustoconical air space 90 is employed to improve the temperature isolation between the extrusion modules.

Still further, the die outlet structure is such that in section 144 the diameter of the annular extrusion channel is reduced, followed by a constant diameter section 146, and then in section 148 the diameter is increased to the diameter of the desired container or parison. The result is an improved product by eliminating the tendency of the multilayers not to adhere uniformly found in the prior art.

Although the embodiments described relate to the manufacture of parisons for use in blow molding bottles, the disclosed modular extrusion head is suitable for the manufacture of many other tubular articles. For example, a film formed by slitting in a tube form with or without blow molding a tube form, bubbles may or may not be filled with air, such as through a bore 152. Elongated profiled articles, glass head reinforced sheets that extrude polymers onto glass fiber mats using one or more annular extrusion heads with rectangular central bores, pultruded sheets, rods or profiled articles, and wire coating coatings. is there. For some applications, such as forming wire coating coatings or extruding coatings on other elongated materials, the extrusion head does not have a mandrel. Rather, the object whose coating is to be applied by extrusion is used instead of the mandrel. The term "container" is used inclusive of all of the above items.

The container of the present invention has less residual internal stress carried over from the parison in the prior art due to the fact that in the prior art the polymer of the material forming the parison was subjected to non-uniform process conditions in the extrusion head. It is far superior to those molded by prior art methods in that it does not have any. These non-uniform conditions were based on the fact that the flow path from the inlet to the annular extrusion channel of the prior art extruder was asymmetric in its flow pattern. In the apparatus and method of the present invention, such channels extend symmetrically around the axis of each module so that all of the polymer flowing from the inlet to the extrusion channel is subject to substantially the same process conditions, and , The properties of the polymer are approximately the same and uniform throughout the circumference of the annular extrusion channel at the point of extrusion from the channel.

Thus, the parison thus formed has little residual internal stress that would otherwise occur as a result of the inhomogeneities and inhomogeneities described above. The same effect is achieved whether the container is molded from a single layer or multiple layers according to the present invention. In each case, the final container has little residual internal stress that would otherwise be present from the formation of the parison. Therefore, the final container of the present invention can be reused or recycled effectively and safely.

The embodiments described above are merely illustrative of the disclosed aspects, and in many respects many other embodiments, variations, modifications and variations without departing from the scope and spirit of the invention as defined in the following claims. You can make changes.

Claims (10)

(57) [Claims] 1. A polymer resin extrusion head for extruding a multi-layer container for holding a plurality of coaxial annular extrusion modules and modules longitudinally spaced along the axes of the plurality of modules. Each module having a pair of mating coaxial annular members and means for securing the mating annular member pairs to each other, the mating annular member pairs being on a periphery of the module. It defines a resin inlet, a coaxial bore having a cylindrical inner surface, and an annular extrusion outlet opening into the cylindrical surface, wherein each of the one or more modules is A flow for receiving and distributing the polymer extending to the outlet and for flowing the polymer from the inlet to the annular extrusion outlet through which the polymer is extruded in annular form. A channel means defining an annular extrusion by subjecting all of the polymer flowing from the inlet to the extrusion outlet to substantially the same process conditions along the flow path. Around the axis of the one or more extrusion modules so that the polymer is distributed at the outlet with a property that is substantially symmetrical about the axis with respect to all resin dispensed through the outlet. Symmetrically extending, each module further having a frustoconical central portion, the axial bore of the frustoconical central portion in the central bore being greater than the axial dimension of the outer portion of each module, and each preceding The top of a module engages an adjacent subsequent module to form an air space that includes a frustoconical air space portion between adjacent modules. And increasing the temperature insulation effect between modules, polymeric resin extrusion head. 2. The channel means includes one or more spiral flow passages within one or more annular extrusion modules, the one or more flow passages substantially surrounding the shaft, A polymeric resin extrusion head according to claim 1 and which gradually opens into an annular frustoconical space to distribute the resin into the outlet. 3. The channel means includes two spiral channels, each passage starting from the inlet, each passage extending at least 180 ° in opposite directions about the axis, the axes being The polymer resin extrusion head of claim 1, wherein the polymer resin extrusion head is substantially surrounded by two passages. 4. The two helical passages each substantially encircle the shaft of one or more extrusion modules such that one passage and the other passage are substantially concentric. 3. The polymer resin extrusion head according to item 3. 5. The extrusion head of claim 1, wherein the channel means surrounds the shaft along more than one spiral passage. 6. The channel means has a decreasing cross section from the inlet to the outlet, and the channel means gradually opens into an annular frustoconical space opening into the outlet. The polymer resin extrusion head according to any one of 1 to 5. 7. The polymer resin extrusion head of claim 6 wherein the thickness of the annular frustoconical space increases as the space opens into the outlet. 8. A polymeric resin extrusion head, wherein each pair of mating members has an inner and an outer telescopic truncated cone portion, the annular space between the truncated cone portions defining an annular extrusion outlet. 7. The polymer resin extrusion head according to claim 6, wherein an angle of an inner surface of the inner truncated cone portion with respect to the axis is larger than an angle of an outer surface of the outer truncated cone portion. 9. A frustoconical space between frustoconical portions is initially determined by reducing the diameter of the inner frustoconical portion downstream of the first spiral of the spiral channel, with a frustoconical space of increasing thickness. 9. Formed by a frustoconical surface portion inside the outer frustoconical portion having an inclination angle less than the inclination angle of the surface of the inner frustoconical portion over the entire area of the spiral passage. Polymer resin extrusion head. 10. A polymer resin extrusion head for extruding a multi-layer container, comprising: an elongated mandrel, longitudinally spaced along the mandrel, extending around a continuous section of the mandrel; Between the mandrel and the mandrel, a plurality of coaxial annular extrusion modules defining a tubular extrusion channel for receiving the continuous layers extruded by the module into the tubular extrusion channel, and mounted in series downstream of the extrusion module. An annular die having three sections, the annular die for receiving and forming the multi-layer tubular extrudate from the extrusion channel means (the first section being a tapered diameter that decreases from the diameter of the annular extrusion channel). The second section spans its entire length. With a constant diameter equal to the outlet diameter of the first section and the third section has a flared diameter that gradually increases from the diameter of the second section to the desired diameter). head.