JP2001521837A - Method for producing multilayer preform - Google Patents

Abstract

(57) Abstract The method for producing a multilayer preform of the present invention can produce very thin layers, especially thin surface layers and / or shielding layers. These thin layers represent up to 35% and 5% of the total volume, respectively. They are manufactured using multi-element injection molding means in which the plastic elements provided to create the thin layers are controlled to be fed through the innermost injection chamber. The plastic element is slightly hot and therefore slightly viscous. The preforms thus produced are characterized in that the surface layer is less than 35% by volume or the shielding layer is approximately 5% by volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a method according to the preamble of claim 1 and to a preform produced by this method.

[0002] Specifically, the present invention is a method suitable for producing a three-layer preform having a higher proportion of regenerated material, which comprises producing a preform having an improved barrier reaction to oxygen permeation. On how to make it possible.

BACKGROUND OF THE INVENTION Multilayer preforms have been known for some time. In particular, beverages in which the preforms are used to produce synthetic resin bottles (Kunststoff-Flaschen) and into which the respective beverages are bottled are described. Used in industry. Such beverage bottles are preferably made from PET, but could also be made from other thermoplastics such as PEN, polyamide or polycarbonate. Today, sequential injection molding in such a manufacturing facility can produce 48 three-layer preforms per process, resulting in an annual production capacity of approximately 500 million. In the case of producing such a preform, a new substance is first injected into the mold of the molding means, and then the recycled substance which has been washed and sorted is introduced, and the new substance is injected again in the third production step. This removes the reclaimed material at the injection molding nozzle. In this case, care is taken to minimize the tolerance in the distribution of the individual injection quantities. Such dispensing accuracy is assumed in the production of beverage bottles with a high proportion of regenerated material, as the regenerated material must not come into direct contact with the bottled beverage. This is set by legal provisions. Therefore, when manufacturing PET bottles by drawing blow molding the preform, it must be ensured that the inner layer made of recycled material is entirely covered by a layer made of new material, which results in injection molding. Means (Spritz
The demands for not only the structure of giess-Werkzeuge) but also the manufacturing facilities for preforms will increase. The injection molding equipment known today (Spritzgiessmaschinen) unfortunately does not have the high dispensing accuracy required for the production of PET preforms with a high proportion of recycled material. As disclosed in EP 0 655 306, the percentage of regenerated material in PET bottles used today for these reasons is basically at most about 25%.

[0004] However, in the beverage industry, the target is basically a higher ratio of regenerated substances in view of economic efficiency or economic stability. Specifically, today, returnable PET bottles containing 35% recycled material are very close to the economic balance ("break-even point") of disposable bottles. The higher the percentage of reclaimed material, the greater the economics of reusable PET bottles. This economy is largely driven by the price of new PET particles, which are very unstable. If these particles were cheaper than recycled material, it would be cheaper to produce a single-layer preform with 100% new material, but this price rose beyond the break-even point. In this case, a three-layer preform having a regenerated material ratio of 35% or more is less expensive. In the case of preformed bodies made of recycled PET, the large instability of the price of the new substance only partially affects the price, so that a higher proportion of recycled substance also improves price stability. . Thus, costs for manufacturers and bottling companies can be more easily estimated.

[0005] Therefore, a method that has already been proposed (“Modern Plastics International”, “Modern Plastics International”, February 1997, page 29) is a method of co-drawing when manufacturing a PET preform. Blow molding means (Co-Extrusions-Bla
Some parts are manufactured by using sform-Werkzeug) and are manufactured without being related to each other. This makes it possible to produce PET bottles containing up to 80% recycled material. However, such a method requires additional means and is therefore laborious and expensive.

DISCLOSURE OF THE INVENTION In the beverage industry, there is a need to produce legally shaped preforms that exhibit a high proportion of regenerated material without the use of laborious technical techniques.

[0007] The technical problem that arises is that preforms having an extremely thin layer of new material and not of a cumbersome structure are produced, and the proportion of recycled material in these preforms is determined. To improve.

[0008] Specifically, an easy method is used to form at least the thinnest layer or a three-layer preform having a regenerated substance ratio of 35% by volume or more, specifically 35 to 65% by volume. It is in.

[0009] This problem is solved by a surprisingly easy method for operating a multi-element injection molding means, as disclosed in claim 1, wherein the supply of elements A and B is of a conventional arrangement And in the process of the first cycle, the closing pin (
Verschlussnadel) is moved to a position where not only the inner injection chamber but also the outer injection chamber is in an open state. At that time, the feeding of the B element through the outer injection chamber is stopped, and only the A element is moved to the inner side. This is solved by operating the molding means so as to be injected into the molding cavity through the injection chamber.

[0010] In the case of producing a preform having a high proportion of the regenerated substance in this way, the element A (new substance) to be injected as the first element passes through the inner injection chamber to form a thin film layer. Element B (regenerated material) to be injected and then injected as the next element is introduced via the outer injection chamber to form a packed bed. In the case of injection molding such a three-layer preform, the closing pin is moved to position I in the first cycle step, in which case the outer injection chamber containing the B element and the inner injection chamber containing the A element. Are in the open state. In such a pin position, the feeding of the B element is interrupted, and the A element is injected into the molding cavity. In the second cycle step, the closing pin is moved to position I, in which case the inner injection chamber is closed and the outer injection chamber is open. At such a pin position, the feeding of the A element is interrupted and the B element is injected into the molding cavity. In the next so-called holding phase, the position of this closing pin remains unchanged in the cycle process in which the B element contracting on cooling is refilled (erganzt). At the end of the holding phase, the closing pin is moved to the closing position III, in which case both the inner and outer injection chambers are closed.

Unexpectedly, it is found that there is no unwanted B material at the first injection of the A element in the next injection cycle. This surprising effect can be explained by replacing the inlet tube. In particular, a particular reduction in the viscosity of element A (new material) is obtained by feeding each element in a specific manner, i.e. feeding the A element through a slightly warmer inner spray chamber. According to the method of the present invention, it is possible to form a preform having a thinner coating layer (A element) on a preform manufactured by a conventional injection molding method, and to perform a holding press phase (Haltendruckphase).
It is possible to increase the relative proportion of the filling substance by subsequently filling the molding cavity with the substance of the B element.

Furthermore, the method according to the invention makes it possible to produce a preform having a very thin barrier layer (eg consisting of nylon or the like). The role of such a barrier layer is to minimize the oxygen permeability of the molded article (bottle) and is relatively expensive. In order to produce a preform with a thin barrier layer according to the invention, the supply pipe is again turned over to the conventional arrangement and the barrier substance injected to produce the thin barrier layer is passed through the innermost spray chamber. The synthetic resin which is introduced and forms the coating layer is introduced via the outer spray chamber. When such a preform is injection-molded, the closing pin is again moved to the position I in the first cycle, and in this case, both the inner and outer injection chambers are in the open state. In this case, the element guided via the outer injection chamber is injected into the molding cavity, and at the same time the supply of the blocking substance guided via the inner injection chamber is interrupted. In the next cycle step, the closing pin remains in this position I, so that the blocking substance fed through the inner injection chamber and the filling substance fed through the outer or central injection chamber and in the molding cavity at the same time. Will be introduced. Thus, in this injection phase, both elements (filling and blocking substances) are fed simultaneously, i.e. by means of tubes located inside one another, in which case the proportion of the blocking substance fed is as small as possible, e.g. Care is taken to make up 5% of the total material content. In this case, the filling material and the material forming the coating layer can be the same. However, it is preferred to use inexpensive reclaimed materials as fillers. This can be obtained by controlling the supply of the melted synthetic resin by an easily known method. In the third cycle step, the supply of the blocking substance is stopped again and the filled molding cavity is filled with the required amount of filling substance to make up for the losses. By shifting the closing pin forward to position III, both injection chambers are closed and the molding process is completed. In the case of a preform manufactured in this way, a thin barrier layer is present in the central wall region of the preform.
It is clear that the preform or shaped body having such an ordered layer exhibits a barrier reaction to oxygen diffusing into the container as required.

Another embodiment of the method according to the invention is characterized by the features of the dependent claims. The preforms produced by the production method of the present invention exhibit a proportion of regenerated material of 35% by volume or more, and in some cases, a barrier layer proportion of 5% by volume or less.

Hereinafter, the present invention will be described in more detail based on examples.

FIG. 1 shows part of the structure of an injection and molding means having a hot runner nozzle 34 and a pin closure 36 for two different types of elements A and B. The plasticized material in the extruder reaches the hot runner and distribution block (Heisskanal-Verteiler-block) 15 via the separated tubes, where it is branched and fed to the respective hot runner nozzles 34. Each hot runner nozzle 34 has a removable nozzle holder 33 and is constituted by a plurality of mutually positioned nozzle nests, between which the inner jet chamber 3 and at least one outer jet chamber 5 Are formed through which various synthetic resin elements (Kunststoffkomponente
n) is supplied to the nozzle tip. A heating element keeps both the hot runner and distribution block 15 and the nozzle holder 33 as well as the hot runner nozzle 34 at a desired temperature. A hydraulically controlled pin closure 36 controls a movable pin 37 in the nozzle tip region of the hot runner nozzle 34 to release or shut off the respective element A or B and / or C.

In the conventional operating method, the closing pin 37 is moved to four positions in one injection cycle to fill the cavity with, for example, three layers. Pin in the first position
37 is drawn backward only through the injection chamber 5 outside the cavity to the extent that the first element, specifically Original PET or raw material, is filled. In the second position, the pin 37 is pulled further rearward, so that the second element is returned until the pin 37 is returned to the first position again in the holding phase and finally pushed forward to close the nozzle 34. Alternatively, the regenerated PET is also pressed into the molding cavity via the inner injection chamber 3. Thus, in each injection cycle, the closing pin is moved to four predetermined positions: A) opening of the outer injection chamber 5, B) opening of the inner injection chamber 3, C) closing of the inner injection chamber 3, d) Blockage of the outer injection chamber 3.

As shown in FIG. 1, the pin closing part 36 is a pneumatic cylinder (pheumatischer Zyli).
nder) is contained within the space in the cover plate 13 that functions as
, And a second plunger is movably provided thereon. A cylinder lid 40 that hermetically closes this space hermetically. Appropriately provided pressure tubes 41, 43 and 44 allow the individual plungers and thus the pins 37 to be moved to the desired position. Each individual pressure tube presents the pressure required for the movement of the pin. Thus, a pressure of typically 20 bar is applied to the outer pressure tube 44, 10 bar to the central pressure tube 43 and 5 bar to the inner pressure tube 41. The alignment of the individual plungers 38 and 39 shown in FIG. 1 is obtained when the individual pressure tubes are under the aforementioned pressure. If the pin 37 is pulled backwards to the first position to open the first plastic element in a conventional manner, it is only necessary to reduce or offset the pressure in the central pressure tube 43. Thus, the first plunger 38 is moved by the pressure of the inner pressure pipe 41 until it comes into contact with the second plunger 39. The pin 37 is used to release the supply via the injection chamber inside the second plastic element.
, The pressure in the outer pressure tube 44 is reduced or canceled in the same manner. This causes both plungers 38, 39 to move to the cylinder lid 40 together. To stop the supply of material again, first the outer pressure tube 44 is put under pressure, whereby both plungers 38, 39 are both moved in the closing direction. Similarly, movement of the first plunger 38 may interrupt the outer injection chamber only after the central pressure tube 43 is again under pressure. Each plunger is provided with an airtight packing 51, 52 and a cylinder lid so that the pneumatic pin closing means can operate satisfactorily.
40 is provided with a packing 53. In addition, the nozzle holder 33 is provided with a shaft packing 55, by means of which a pressure adjustment is made between the plunger means 38, 39 and the nozzle means 33, 34 so that the individual hot plastic elements under pressure are The vapor enters the nozzle holder 33 along the nozzle pin 37 and further sinks at the plunger wall or the nozzle pin to close the pin closing portion.
Any loss or obstruction of the mobility of the individual components at 36 is prevented. This can be achieved in a well-known manner by means of an airtight shaft packing 55 made of a heat-resistant synthetic resin.

In order to produce a multi-layered preform having an increased proportion of regenerated material or having a very thin layer by using such a multi-element injection molding means, the present invention requires a conventional method. In contrast to the above measures, the feed of the elements A and B is converted so that the element A containing a substance (new substance or shielding substance) introduced only to form a thin layer is formed by the injection chamber 3 inside the hot runner nozzle 34. , While the element B containing the regenerated material to be introduced is operated by the injection chamber 5 outside or in the center of the hot runner nozzle 34. In the case of producing a molded body with a thin coating layer of a new material and a thin shielding layer, the new material is determined by the outermost one of the three spray chambers and the shielding layer material is determined by the innermost one. Is supplied in such a way that the shielding layer material is injected simultaneously with the filling material (Fullmaterial) from the central injection chamber. In the case of producing a molded body made of a single carrier material and having a thin shielding layer, a first part of the carrier material is applied in a first step to the molding cavity via the outer one of the two injection chambers. In a second step, the carrier substance and the shielding substance are simultaneously injected into the molding cavity, i.e. through the hoses located within one another. In this case the pin 37 is moved to a position as described in detail below with reference to FIGS.

FIGS. 2 a-2 d show the hot runner nozzle 34 and the pin closure used with it.
A partial cross-sectional view of 36 is shown. As shown in FIG. 2a, the inner injection chamber 3
In order to introduce the original element A supplied by the engine, the pin 37 is pulled backwards until the inner injection chamber 3 is opened. By interrupting the feeding of element B and feeding element A, the required amount of original element A can be introduced into the molding cavity. Since this original element A has a lower viscosity inside the hot runner nozzle 34 than the element B in the outer injection chamber 5, only a very small part of the original substance has to be introduced into the molding cavity. This pin position I reduces the pressure of the first plunger 38 while reducing the pressure in the pressure tubes 44 and 43 at the top of the second plunger 39 or between the first plunger 38 and the second plunger 39, for example to 0 bar. The pressure of the lower pressure pipe 41 is set to, for example, 6
Obtained by being barred. This pressure distribution places both plungers in their respective highest positions, so that the inner injection chamber 3 can be opened by means of the pins 37.

In the second cycle step shown in FIG. 2b, the pins 37 are connected to the inner injection chamber 3
Is moved to a position II such that the outer injection chamber 5 remains open while being closed. This means that in the pressure tube 41, for example, while maintaining a pressure of 6 bar,
It is obtained by raising the pressure tube 44 at the top of the second plunger 39 slightly higher, for example to 10 bar. With this position, the element B (filling substance) is supplied through the outer injection chamber 5 into the molding cavity. This material is the inner spray chamber 3
In order to exhibit a higher viscosity than in, the previously injected element A is pressed in the form of a thin layer against the outer surface of the molding cavity without breaking this layer. This difference in viscosity makes it possible to produce a preform having a thin coating layer.
The molding cavities filled in the third cycle step are subsequently held under pressure by the filling substance B for a certain period of time, the so-called holding phase, in order to make up for the volume loss in the substance which occurs in the shrinking step.

FIG. 2c shows the hot runner nozzle 34 and its pin closure 36 in position III, in which not only the inner injection chamber 3 but also the outer injection chamber 5 are closed. This means that the pressure in the pressure tube 41 below the first plunger 38 is reduced to, for example, 0 bar, while the pressure in the pressure tube 43 between both plungers is increased to, for example, 6 bar, and the second This is achieved by maintaining the pressure in the pressure tube 44 at the top of the plunger 39 at, for example, 10 bar.

As before, the injection cycle is started at the pin position as shown in FIG. 2b without changing the supply pipes of the elements A and B, and the element A (new substance) is introduced into the molding cavity. Thereafter, the closing pin 37 is moved to position I to fill the mold cavity with the element B (filling substance). In the holding phase, the pins are moved to position II again as shown in FIG. 2d, the material contracted by cooling is replenished by using element A, and in the next injection cycle the element B (regenerated material) is replaced with the initial material. Assure that it does not reach the cavity. To end the injection cycle, the pins are moved to position III as shown in FIG. 2c.

This allows the contracted filling material to be identical in the actuation step (Betriebsverfahren), whereas the contracted material volume is conventionally supplemented by the element to be injected as the first material in the next injection cycle. It becomes clear that the injection cycle ends by being refilled by the element. Thus, a greater amount of the B component (regenerated material) can be introduced into the molding cavity by the method, surprisingly by the fact that the A component supplied in the inner injection chamber exhibits a lower viscosity, and also by the subsequent injection Strict demands in the beverage industry are met by blow molded articles having a complete outer or inner membrane so that only the A element reaches the molding cavity by interrupting the supply of the B element when starting the cycle What you get.

The differences between the present invention and the conventional method are evident from the longitudinal sectional views shown in FIGS. FIG. 3 is a longitudinal sectional view of a preform manufactured by a conventional method, which has a screw portion 61 and a container portion 62, and has a nozzle tap 63
Are provided in the bottom 64. It can also be seen from this longitudinal section that not only the inner membrane 65 but also the outer membrane 66 (except for the nozzle tap) has not been breached at any point by the filling substance B. A particularly dangerous point is the formation of the screw portion 61 in the preform. The figure further illustrates the effect of the filling of the new substance A on the volume of the filling substance contracted during the holding phase. In particular, the new material introduced into the bottom 64 substantially reduces the percentage of regenerated material.

On the other hand, FIG. 4 shows a longitudinal sectional view of a preform manufactured according to the present invention. This is distinguished in the configuration of the bottom 64, which essentially exhibits only three layers: the inner membrane, the filling material and the outer membrane. Moreover, the essential difference lies in the strength of the individual layers. The strength of the outer membrane in a conventional preform with a weight of 48.0 g and a total wall thickness of 4.37 mm suitable for a 1.5 liter bottle is 1.3 to 1.5 mm. Therefore, the volume ratio of the filling substance B existing inside is 25 to 3
It becomes 3% by volume. The weight as shown in FIG.
In a preform weighing 8.0 g, the outer materials 65, 66 exhibit a strength of 1.2 to 0.6 mm, and the percentage of filling material can be increased to 37 to 63% by volume by this special production method.

It is also possible to produce a preform having a shielding layer (for example made of nylon, EVH, etc.) that exhibits an improved shielding effect against oxygen by replacing the supply pipe. This will be described in detail with reference to FIGS. In the present invention, when producing a preform with a shielding layer, the pin 37 is moved to position II in the first cycle step (FIG. 2b) and the material used to form the coating layer in the cavity is Will be filled. In the second cycle step, the closing pin 37 is used.
Is moved to the position I (FIG. 2a) and the shielding material supplied via the inner nozzle 3 (
(For example nylon) are injected into the molding cavity with the element guided through the outer nozzle 5. This allows the shielding material to be along the inner wall region of the preform and allows for the provision of a very thin shielding layer of approximately 5% by volume or less of the preform.

In a preferred embodiment, the shielding material is supplied via the innermost spray chamber, and the method according to the invention is such that in the first cycle step the pin 37 is moved to position I, in which case not only the inner spray chamber, Although the outer injection chamber is also in the open state, only the substance guided through the outer injection chamber 5 is fed into the molding cavity, and the supply of the substance guided through the inner injection chamber 3 is stopped. It is provided as is. In the second cycle step, the pins 37 remain in this position I and are simultaneously supplied with the substance via the outer ejection chamber 5 and the shielding layer material via the inner ejection chamber 3 so that the shielding against all the ejected substances is achieved. The proportion of the substance is about 5% or less. In order to replenish the contraction of the substance in the holding phase, the closing pin remains in position I and the supply of the shielding substance supplied via the inner injection chamber 3 is stopped. After the supply is complete, the pins are moved to position III (FIG. 2c) to close the inner and outer injection chambers. The preform thus obtained has a thin shielding layer located on the central wall of the preform.

The advantages of the method according to the invention and of the preforms produced using this method can be easily understood by a person skilled in the art. Specifically, four consecutive pin positions are required for each injection cycle in the conventional method, whereas only two or three pin positions are required in the operating method of the present invention. This facilitates control of the pin closing portion. Furthermore, according to the invention, the contracted B element is replenished with the same substance, thus increasing the percentage of this element (regenerated substance) or guided through the innermost injection chamber (Dusenkammer). It is possible to reduce the percentage rate. There is no need to provide new and expensive machines or means to carry out the method according to the invention.

Further developments, in particular those affecting the viscosity of the individual elements and the operation of the injection cycle, are within the abilities of those skilled in the art. PE in this way
It can be understood that not only T materials but also synthetic resins that can be used in the injection molding technique, specifically nylon, etc., can be processed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a hot runner nozzle and a pin closing portion thereof.

FIGS. 2a to 2d show the position of the closing pin and its operation.

FIG. 3 is a longitudinal sectional view of a preform manufactured by a conventional method.

FIG. 4 is a longitudinal sectional view of a preform having a high proportion of a regenerated substance manufactured according to the present invention.

FIG. 5 is a longitudinal sectional view of a preform having a barrier layer manufactured according to the present invention.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] December 27, 1999 (December 27, 1999)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

2. In the second cycle step, the closing pin (37) is moved to a position II in which the innermost injection chamber (3) is shielded and at least one outer injection chamber (5) is open. The method according to claim 1 .

3. A method for operating a multi-element injection molding means for producing a multilayer molded article , said multi-element injection molding means comprising an injection chamber ( 34 ) inside an injection body (34 ). A hot runner nozzle with a pin closure (36) for opening or closing the 3) and the outer injection chamber (5) , said pin closure (36) comprising a movable pin (37) and a cylinder at least one of the first plug Nja provided movably and (38) and a second plunger (39) is provided in the chamber, these plungers (38, 39) is connected to the plunger (38, 39) The pin (37) being moved can be selectively displaced by the pressure medium such that it is moved to the respective open or shut-off position (I, II, III, IV) , whereby a thin surface layer of new material is removed. The A element that is injection molded to form Side of the injection chamber (3) is supplied through the, B elements are injection-molded is supplied via the outside of the injection chamber (5) as a fill material, it more, closing pin in a first cycle step (37) there is moved to position (I) as in the injection chamber (5) Hiraku Toga state of the outer containing innermost injection Ishitsu (3) and B elements including C-element, whereby the first cycle step only C elements innermost jet chamber (3) feed by the feeding of the other elements through to a method outside of the injection chamber (5) thus being stopped in the shielding layer made of C material when producing a three So予備成features having, C elements in the second cycle step, the proportion of C elements in particular to the total volume of about 5%
Or are respectively fed B element also via the outer side of the injection chamber (5) with the feed through the innermost jet chamber (3) such that below, in the third cycle steps , The feeding step of the C elements is interrupted so that only the B elements are fed from the outer injection chamber (5) into the molding cavity, and in the fourth cycle step the substances which shrink during cooling are replenished by these B elements. The closing pin (37) is moved to a position III in which not only the innermost injection chamber (3) but also at least one outer injection chamber (5) is closed in order to end the injection cycle. who shall be the method.

4. A method according to claim 3, wherein the closing pin in the second and third cycle process (37) is held in position I.

5. An outer (66) and inner (65) film made of substance A, a shielding layer made of substance C which is nylon, and a filler material B which is regenerated material. In the production of a five-layer preform, the closing pin (37) is used in the first cycle step with the innermost injection chamber (3) containing the C element and the outer injection chamber (A) containing the A element, and between them. Is moved to the position I in which the injection chamber containing the B element (regenerated substance) is in the open state, and in this first cycle step, the supply of the B and C elements is stopped, and only the A element is located outside. It is supplied through the injection chamber, the supply of the element A is stopped in the second cycle step, the B and C elements are supplied simultaneously, that is, in a tubular form, and the supply of the element C is stopped in the third cycle step. The synthetic resin base that shrinks during cooling The method of claim 1 or 2 wherein is supplemented by the element.

6. A proportion of the C-element is approximately 5 volume% in the second cycle step method of claim 5, wherein the ratio of B element against the total volume is 30% or more is fed.

7. A preform made by the method of claim 1 or 3, preforms percentage of the B component is 35 volume% or more.

8. A preform manufactured by the method according to claim 3 or 5, wherein a shielding layer made of a C element is located in a central wall region of the preform.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Unexpectedly, it is found that there is no unwanted B material at the first injection of the A element in the next injection cycle. As described by the examples of EP 0 768 163 or EP 0 380 215 , all methods known today use the A element at the time of filling, i.e. Replenish material that contracts on cooling. This surprising effect is even was not expected to those skilled in the art, it may be explained by the replacement of the inlet tube. In particular, a specific reduction in the viscosity of the element A (new substance) is obtained by feeding each element in a specific manner, i.e. feeding the A element through a slightly warmer inner spray chamber. According to the method of the present invention, it is possible to form a preform having a thinner coating layer (A element) with respect to a preform produced by a conventional injection molding method, and to form the preform in a holding and pressing phase (Haltendruckphase). By subsequently filling the cavity with the substance of element B, it is possible to increase the relative proportion of the filling substance.

Claims (12)

[Claims] 1. A method for operating a multi-element injection molding means for producing a multilayer molded body, said multi-element injection molding means comprising an injection chamber (3) inside an injection body (34). A hot runner nozzle having a pin closure (36) for opening or shutting off the at least one outer injection chamber (5).
For this purpose, a movable pin (37) and at least one first plunger (38) and a second plunger (39) movably provided in the cylinder chamber are provided, and these plungers (38, 39) are In which the pins (37) connected to the plungers (38, 39) can be selectively displaced by a pressure medium so as to be moved to the respective open or shut-off positions (I, II, III, IV). The plastic molding compound (new or shielding material) injected to form a thin layer, in particular a coating or shielding layer (element A or C), is supplied via the innermost injection chamber (3). The plastic molding compound to be injected as a filling substance (regenerated substance B or fresh substance A) is supplied via at least one outer injection chamber (5). 2. In a first cycle step, the closing pin (37) has an innermost injection chamber (3) containing an A or C element and at least one outer injection chamber (5) containing a B or A element. It is moved to the position (I) such that it is in the open state, and in this first cycle step only the A or C elements are fed through the innermost injection chamber (3) and the feed of the other elements is at least 2. The method according to claim 1, wherein the outer injection chamber is stopped by one. 3. In the case of producing a three-layer preform in which the proportion of element B (regenerated material) is at least 35%, in a second cycle step the element B comprises at least one outer injection chamber (5). The material which is fed in through the third cycle step and contracts on cooling in the third cycle step is replenished by the B-element and the closing pin (37) is used to terminate the injection cycle, as well as the innermost injection chamber (3). 3. The method according to claim 1, wherein the at least one outer injection chamber is also moved to the closed position III. 4. In the second cycle step, the closing pin (37) is moved to a position II in which the innermost injection chamber (3) is shielded and at least one outer injection chamber (5) is open. 4. The method of claim 3, wherein 5. In the case of producing a three- or five-layer preform having a shielding layer made of a C substance, the C element in the second cycle step, specifically, the ratio of the C element to the total volume is reduced. It is fed through the innermost injection chamber (3) so that it is approximately 5% or less and also has a B element in at least one outer injection chamber (
5), and in this third cycle step, the step of feeding the C element is interrupted so that only the B element is fed from the outer injection chamber (5) into the molding cavity, In the cycle step 4, the material contracted upon cooling is replenished by these B elements, and in order to end the injection cycle, the closing pin (37) is provided not only with the innermost injection chamber (3) but also with at least one outer injection chamber (3). 3. The method according to claim 1, wherein 5) is also moved to the position III where it is closed. 6. The method according to claim 5, wherein the closing pin (37) is held in position I during the second and third cycle steps. 7. An outer (66) and inner (65) film made of the substance A, a shielding layer made of the substance C which is nylon, and a filler material B which is a regenerated substance. In the production of a five-layer preform, the closing pin (37) is used in the first cycle step with the innermost injection chamber (3) containing the C element and the outer injection chamber (A) containing the A element, and between them. Is moved to the position I in which the injection chamber containing the B element (regenerated substance) is in the open state, and in this first cycle step, the supply of the B and C elements is stopped, and only the A element is located outside. It is supplied through the injection chamber, the supply of the element A is stopped in the second cycle step, the B and C elements are supplied simultaneously, that is, in a tubular form, and the supply of the element C is stopped in the third cycle step. The base of the synthetic resin shrunk during cooling 3. The method according to claim 1 or 2, wherein the method is supplemented by an element. 8. The method according to claim 7, wherein in the second cycle step, a proportion of the C element which is approximately 5% by volume and a proportion of the B element which is not less than 30% of the total volume are fed.
The described method. 9. A preform manufactured by the method according to claim 3, wherein the ratio of the B element (regenerated substance) is 35% by volume or more. 10. A preform manufactured by the method according to claim 5, wherein the shielding layer comprising the C element is located in a central wall region of the preform. 11. A preform manufactured by the method according to claim 7, wherein a ratio of a shielding layer composed of about 5 element% or less of a C element and the B element (regenerated substance) is 35% by volume or more. Is a preform. 12. A preform manufactured by the method according to claim 7, wherein the A element and the B element are made of the same substance.