EP1885542A2

EP1885542A2 - Extrusion storage head, method for production of blow-moulded multi-layer plastic hollow bodies and corresponding plastic hollow bodies

Info

Publication number: EP1885542A2
Application number: EP06724730A
Authority: EP
Inventors: Peter Langos
Original assignee: Mauser Werke GmbH
Current assignee: Mauser Werke GmbH
Priority date: 2005-05-10
Filing date: 2006-05-05
Publication date: 2008-02-13
Also published as: US20080193582A1; WO2006119924A2; JP2008540174A; WO2006119924A3; DE112006000926A5; JP4996597B2

Abstract

The invention relates to an extrusion storage head (10) for a blow-moulding machine and a method for production of blow-moulded multi-layer plastic hollow bodies made from a two- or multi-layer pre-form, whereby two or more peripheral manifolds (16, 18) are arranged above a storage chamber (20), from which the peripherally-extruded plastic may be sequentially ejected as a tubular preform from a controlled annular nozzle (24) by means of an ejector piston (22). According to the invention, a further peripheral manifold (26) is arranged between the storage chamber (20) and the controlled annular nozzle (24) for application of a further plastic layer (outer functional layer) on the previously peripherally extruded plastic as support material, which is connected to a further separate extruder (32) by means of a supply line (28) from a further external storage element (30) for the molten plastic of the functional layer.

Description

Extrusion storage head and method for producing blow-molded multilayer plastic hollow bodies

The present invention relates to an extrusion storage head for a blow molding machine for the production of blow molded multilayer plastic hollow bodies, in which two or more peripheral manifolds are arranged above a storage space from which the circumferentially distributed plastic is ejected sequentially via a controllable annular nozzle by means of a displaceable ejection piston as a tubular preform.

The invention further relates to a process for the production of blow-molded multilayer plastic hollow bodies with this storage head and subsequently produced hollow plastic body.

Blow molding machines with extrusion storage head for the production of blow molded multilayer plastic hollow bodies are well known, for example from US-A-5,256,051. In such blow molding machines with extrusion storage head for producing multilayer plastic hollow body, it is desirable if the plastic layers from the various extruders in the respective circumference distributors are distributed under rheologically almost identical conditions. For this purpose, the peripheral manifolds are usually constructed concentric with each other. This results in several layers quickly to significant diameter dimensions of the storage head.

It is therefore an object of the present invention to avoid such disadvantages and to propose a slim design construction of a generic multilayer extrusion storage head on which in case of need by simple conversion measures various special designs of plastic hollow bodies can be produced.

This object is achieved by the device in that for applying a further plastic layer outside the previously circumferentially distributed plastic (substrate) between the storage space and the controllable annular nozzle, a further peripheral distributor is arranged, which via a delivery line to another external storage element for molten plastic (functional layer) connected with another separate extruder. This can be done in a simple manner by connecting a further peripheral distributor below the hollow cylinder Shaped storage space in which the already "finished" two-layer preform is stored, in addition to an external thin third layer on the ejected by means of ejection piston preform "smeared" or applied.

In an embodiment of the invention it is provided that the external storage element is also provided with a displaceable in a storage space discharge piston and arranged below the storage space closing valve. As a result, the plastic material of the additional layer (functional layer) can be conveyed parallel to or simultaneously with the ejection process of the main storage head or independently thereof.

In a preferred embodiment of the invention, it is provided that the annular ejection piston in the external storage element is designed to be displaceable within a likewise hollow-cylindrical storage space in which a central closing valve, preferably designed as a needle valve, is displaceably arranged. With this special construction can be produced in a reproducible manner different process variants for various embodiments of hollow plastic bodies with special properties.

A variety of blow molding machines in operation today for the production of blow molded packaging containers are designed as two-layer machines. Characterized in that the further, arranged between the storage space and the controllable annular nozzle of the extrusion storage head peripheral distributor is arranged with attached conveyor line in a replaceable ring kit, new or already in use two-layer blow molding machines in a simple and comparable cost-effective way to high-quality three-layer - Upgrade blow molding machines or multilayer machines for operation with a further additional plastic layer.

In order to keep the overall height of the extrusion storage head as low as possible, the further peripheral distributor is formed in a simple and cost-effective design with little design effort as a ring channel distributor. For a further particular application variant, the annular channel distributor is provided with at least one displaceable blocking element (blocking slide) which is arranged on its side opposite the conveying line so that the plastic material flowing into the annular channel distributor and circulating on both sides in the peripheral direction of the additional functional layer can not converge and thus become one Piece remains spaced apart. This makes it possible, for example, colored (black, blue) colored containers very easily and without great mechanical effort provided with a viewing strip. The inventive method for the production of blow molded multilayer plastic hollow bodies from a two- or multi-layer tubular preform in a blow molding machine with an extrusion storage head (battery head) with two or more peripheral manifolds above a storage space from which the circumferentially distributed plastic by means of a discharge piston sequentially via a controllable ring nozzle is extruded, characterized in that via another additional, arranged between the storage space and the controllable annular nozzle peripheral manifold, which is supplied sequentially or discontinuously via a feed line from a further external storage element with molten plastic, another thin plastic layer ( outer functional layer) is applied to the previously completely circumferentially distributed, at least two-layer plastic carrier material.

In the outer functional layer various additives are mixed depending on the desired special property of the finished container. These additives are usually very expensive and it is therefore appropriate to form the functional layer as thin as possible in order to keep the required amount of expensive additives also low.

For this purpose, the invention provides that the outside of the ejected preform applied plastic layer (= functional layer) is applied very thin, so that they only between 1% and 10%, preferably about 2%, the wall thickness of the ejected preform or of the hollow body produced therefrom. This is z. B. then very advantageous if in the outside applied plastic layer (functional layer) additional color pigments are mixed and thereby the functional layer has a different color than the underlying plastic layer. Since additional color pigments or other additives to adjust certain properties are usually very expensive, this can achieve significant cost savings.

For special applications, it may be useful if the externally applied plastic layer (functional layer) - viewed in the circumferential direction - is not formed completely encircling or not continuous, but is provided with at least one interruption such that the two opposite edges of the functional layer at least slightly spaced apart and leaving a longitudinal interruption strip on the extruded preform. If, for example, blue or black colored plastic containers such as canisters, drums or inner containers for pallet containers with sight strips are to be produced, it is expedient if the interruption strip in the externally applied colored functional layer of the finished inflated container has a width of about 10 mm to 50 mm, depending on the volume of the container produced.

For other applications, it may also be expedient if the outside applied plastic layer is not applied in the longitudinal direction over the entire length of the ejected preform, but only over a predetermined length on the extruded preform. This particular variant of the method is very advantageous, for example, if special additives (such as, for example, nanoclay, metal fibers, conductive carbon black, antistatic masterbatch, polyamide copolymers or the like) are mixed into the plastic layer applied on the outside, the particular electrical or have electrostatic properties, whereby the inflated from the preform plastic hollow body can be provided with an electrically dissipative or an antistatic coating. In the area of Butzenstücke the container produced in the storage head according to the invention, the plastic material of the outer layer can be reduced in quantity or not applied, so that the relatively expensive plastic material (with special additives) is not wasted. It is considered that with each discontinuous hose discharge about 20% to 40% of the extruded hose length in the Butzenstücke go (= upper and lower squeezed tail on the finished blown end product). This Butzenstücke be used as regrind (= regranulate) mixed with virgin material in a middle layer of the produced plastic hollow body. On this Butzenstücke only a reduced or no functional layer is suitably applied.

In the machine concept according to the invention, the layer thickness of the outer functional layer is set via a controllably variable ejection speed of the ejection piston in the additional external memory element. As a result, the functional layer can be represented reproducibly in accordance with the velocity profile of the ejection piston in the additional memory element via the ejection length of the tube with a defined wall thickness profile. This basically offers the possibility of minimizing or completely switching off the functional layer in the slug area. On the other hand, a uniform wall thickness of the functional layer in the later blown part can be achieved even with very different inflation ratios or degrees of stretch such as in the lower and upper corner regions of a parallelepipedic inner container for a pallet container, wherein on the extruded preform a partially thicker functional layer for the container corner areas very high degrees of stretching is applied (partial wall thickness control of the outer layer). This will be an optimal Material utilization in the functional layer with cost minimization based on the blow part to be manufactured allows.

A blow molding machine with the extrusion storage head according to the invention has many advantages over a two-layer machine: the properties of the products produced can be improved by an electrically non-charging surface (permanent antistatic compounds), an electrically conductive surface (by mixed conductive carbon black), a optical layer (eg blue color pigments) and

Light protection and UV resistance for photosensitive products (eg white

Color pigments, UV stabilizers).

By a very thin design of the outer layer and by the achieved low color change times material costs are saved.

The extrusion storage head according to the invention with separate storage and ejection piston for the outer functional layer allows the use and processing of various types of plastics, such as HD-PE (High Density Polyethylene) and LD-PE (Low Density Polyethylene), where as low-viscosity and high-viscosity Polyethylene great differences in the viscosities and the flow properties of the respective plastic melts are present. In particular, the separate storage element with ejection piston offers excellent controllability and reaction speed, in particular. B. compared to a conventional pressure change in the melt stream by speed change of an extruder.

The invention will be explained and described in more detail with reference to an embodiment schematically illustrated in the drawing. FIG. 1 shows an extrusion storage head according to the invention,

Figure 2 shows a 1000 liter pallet container in side view and

Figure 3 is a 220 liter plastic L-ring barrel

In Figure 1, the reference numeral 10, an extrusion storage head (battery head) is shown, are connected to the two extruders 12, 14 for producing a two-layer tubular preform.

From the extruders 12, 14, the molten plastic material flows via two spiral channel distributors 16, 18 (circumferential distributors) into a storage space 20. The storage space 20 is defined by the wall thickness and the stroke of a hollow-cylindrical ejection piston 22. In the discontinuous mode of operation of the storage head, the circumferentially distributed plastic material is first accumulated in the storage space 20 and then sequentially by means of the discharge piston 22 discharged from the storage space 20 via a controllable annular nozzle 24 as a tubular preform. According to the present invention, a further peripheral distributor 26 is arranged between the storage space 20 and the controllable annular nozzle 24, which is connected via a delivery line 28 to a further storage element 30 for molten plastic (functional layer) with a separate extruder 32.

The further circumferential distributor 26 is formed in the present case as a simple annular channel distributor. The cylindrical storage element 30 has a storage space in which an ejection piston 34 is slidably disposed. In the ejection piston 34, which is designed as a hollow cylinder, a closing valve 36, which is likewise designed as a needle valve, is also centrally located in the center. The molten plastic material for the functional layer is continuously fed from the separate extruder 32 into the storage element 30, wherein the discharge piston 34 is raised until the storage space is filled. By means of the ejection piston 34, the plastic material of the functional layer is introduced via the delivery line 28 into the further peripheral distributor 26 of the extrusion storage head 10, from which it - in parallel to the ejection movement of the ejection piston 22 - in the, the tubular preform leading annular gap is so depressible that a thin plastic layer (outer functional layer) lays on the previously circumferentially distributed main plastic flow (carrier material). The further annular channel peripheral distributor 26 is equipped on the, the delivery line 28 opposite side with a designed as a simple locking slide blocking element 40, by means of which the annular channel 26 can be partially closed over a certain width predetermined (lockable annular slot). In the case of a hollow plastic body to be produced, at least one visible strip can be formed in the outer wall of the hollow body by the outer plastic layer (functional layer), which is not completely applied over the circumference, into which optionally electrically conductive additives and / or color pigments are mixed Is arranged offset to the mold parting plane.

The housing of the additional annular channel distributor is very advantageously designed as a modular component and is simply used as an interposed ring assembly 38 with delivery line 28, storage element 30 and separate extruder 32 in the usual construction of a two-layer storage head. The ring assembly 38 with the additional annular channel distributor can be used in newly built blow molding or retrofitting in existing two-layer blow molding. In Figure 2, a pallet container 42 for storage and transport of liquid or flowable products is shown as an application example. The pallet container 42 consists of a thin-walled plastic inner container 44, a plastic inner container 44 tightly enclosing grid frame 46 of welded together bars and a plastic bottom pallet 48 on which the inner container 44 rests and on which the grid frame 46 is attached. For use in potentially explosive atmospheres or for use in flammable products, the plastic inner container 44 is equipped with a thin, electrostatically non-chargeable surface (antistatic compounds). FIG. 3 shows, as a further example of application, a 220 liter plastic L-ring barrel 50 with an electrically dissipative barrel surface 52. In this case, the thin functional layer is dyed black by admixing conductive carbon black. A manufactured on the blow molding machine according to the invention three- or multi-layer plastic container, characterized in that the outer functional layer is very thin and only between 1% and 10%, preferably about 2%, the wall thickness of the tubular preform or the finished inflated Hollow body is, wherein the outer layer may have a different color than the middle and / or inner layer. The outer layer is in one embodiment - viewed in the circumferential direction - not formed completely encircling or closed, but provided with at least one strip-like interruption such that the two opposite edges of the cover layer are at least slightly spaced from each other, and / or the middle and inner layer is visible from the outside. The interruption in the outer colored functional layer should have a width of at least 10 mm in the finished inflated container so that at least one narrow, axially extending outer layer interruption strip is formed as a so-called visual strip. In the outer functional layer of the hollow plastic body any color pigments can be mixed. By using expensive color pigment additives only in the thin outer layer, colored or colored containers can be produced particularly cost-effectively.

In the field of industrial packaging, especially in the area of large-volume pallet containers with a capacity of approx. 1000 liters, so-called antistatic IBC Qntermediate BuIk Containers) with transparent, electrically non-rechargeable inner containers are among the latest developments. These plastic containers are provided with a special outer layer in which specially developed permanent antistatic compounds are incorporated. This one Materials (additives) are very expensive and the adjusted electrical surface resistance is a function of the concentration of these additives in the plastic material, a very thin outer cover layer was realized as a functional layer in the extrusion storage head. Due to the small thickness of the outer layer, the level of the liquid filling material in the container is still clearly visible and the otherwise complicated introduction of viewing strips is superfluous.

References list

10 storage head 12 extruder I

14 extruders Il 16 spiral channel distributor I

18 spiral channel distributor Il 20 storage space

22 ejection piston 24 annular nozzle

26 Circumferential distributor (annular channel) 28 Delivery line

30 storage element 32 extruder IM

34 discharge piston Il 36 closing valve (needle valve)

38 ring kit 40 blocking element (slider)

42 pallet containers 44 plastic inner container

46 Lattice frame 48 Plastic floor pallet

50 plastic L-ring barrel 52 barrel surface

Claims

claims

1.) extrusion storage head (10) for a blow molding machine for the production of blow molded multilayer plastic hollow bodies, in which two or more circumferential distributors (16, 18) above a storage space (20) are arranged, from which the circumferentially distributed plastic by means of a displaceable annular ejection piston ( 22) as a two- or multi-layer tubular preform sequentially via a controllable annular nozzle (24) is ejected, characterized in that for applying a further additional plastic layer (outer functional layer) on the previously circumferentially distributed, at least two-layer plastic carrier material below the storage space ( 20) and above the controllable annular nozzle (24) a further peripheral distributor (26) is arranged, which via a feed line (28) to another external memory element (30) for molten plastic (functional layer) connected to a further separate extruder (32) i st.

2.) storage head according to claim 1, characterized in that the external storage element (30) is also provided with a displaceable in a storage space discharge piston (34) and arranged below the storage space closing valve (36).

3.) storage head according to claim 1 or 2, characterized in that the closing valve (36) is designed as a needle valve.

4.) storage head according to claim 1, 2 or 3, characterized in that the annular ejection piston (34) in the external storage element (30) within a likewise hollow cylindrical storage space is slidably formed, in which center-centrally designed as a needle valve closing valve (36) also slidably arranged.

5.) storage head according to claim 1, 2, 3 or 4, characterized in that the further, below the storage space (20) and above the controllable annular nozzle (24) arranged circumferential distributor (26) with attached delivery line (28) in a replaceable ring kit (38) is arranged.

6.) storage head according to claim 1, 2, 3, 4 or 5, characterized in that the further circumferential distributor (26) is designed as a ring channel distributor.

7.) storage head according to one of the preceding claims 1 to 6, characterized in that the annular channel distributor on its delivery line (28) opposite side with a displaceable blocking element (40) (locking slide) is provided.

8.) A process for the production of blow molded multilayer plastic hollow bodies from a two- or multi-layer tubular preform in a blow molding machine with an extrusion storage head according to at least one of the preceding claims 1 to 7 with two or more Umfangsverteilem above a storage space from which the circumferentially distributed plastic means an ejection piston is extruded sequentially via a controllable ring die, characterized in that via another additional, arranged between the storage space and the controllable annular nozzle peripheral manifold, which is supplied sequentially or discontinuously via a delivery line from a further external storage element with molten plastic, another thin plastic layer (outer functional layer) is applied to the previously circumferentially distributed, at least two-layer plastic carrier material.

9.) Process according to claim 8, characterized in that the layer thickness of the outer functional layer is controlled on the extruded tubular preform during the ejection process via a variable ejection speed of the ejection piston in the additional external memory element.

10.) The method of claim 8 or 9, characterized in that by time-delayed opening and closing of the valve in the supply line of Plastic stream for the functional layer during the ejection process of the tubular preform the Lände the functional layer is set on the tubular preform such that the removed from the blow mold, finished blown plastic hollow body is covered with a uniformly thin functional layer, while the two above and below-hanging Butzenstücke only partially slightly or not at all covered by the functional layer.

11.) Plastic hollow body, produced by the blow molding process according to claim 8, 9 or 10 in a blow molding machine with an extrusion storage head according to at least one of the preceding claims 1 to 7, of an at least three-layer tubular preform, characterized in that the inner with the contents Coming layer is formed comparatively thin and made of virgin material, that the middle layer is formed comparatively thick and consists essentially of regranulate, and that the outer functional layer is formed comparatively thin and made of virgin material with special additives (such B. color pigments, UV stabilizers, plasticizers, antistatic compounds, Leitruß o. Ä.) Is.).

12.) Plastic hollow body according to claim 11, characterized in that the inner layer of virgin material (virgin material) existing layer has a layer thickness of about 5% to 30%, the average, consisting of regranulate layer has a layer thickness of about 50% to 93% and the outer functional layer has a layer thickness of about 2

% to 20% of the mean total wall thickness of the plastic hollow body.

13.) plastic hollow body according to claim 11 or 12, characterized in that the outer functional layer is not closed over the entire circumference, but at least at one point is formed interrupted in the longitudinal direction, so that the

Ranges of the interrupted functional layer are spaced apart and in

Lengthwise at least one narrow longitudinal strip with a width of about 10 mm to 40 mm remains free and the underlying plastic layer is visible.