WO2018184797A1

WO2018184797A1 - Extrusion unit, device for extruding thermoplastic plastics, and use of the device

Info

Publication number: WO2018184797A1
Application number: PCT/EP2018/056321
Authority: WO
Inventors: Pablo Walter; Hendrik Lützen; Norman Friedrich; Lina GONZALEZ; Katrin Nisters; Thomas Härtig
Original assignee: Henkel Ag & Co. Kgaa
Priority date: 2017-04-04
Filing date: 2018-03-14
Publication date: 2018-10-11
Also published as: DE102017205673A1

Abstract

The invention relates to an extrusion unit (4) for a device (1) for extruding thermoplastic plastics, the extrusion unit (4) being designed as a separate component that can be connected to a metering unit (3) of the device (1) and the extrusion unit comprising the following: a hot channel system (10) having an inlet (13) and an outlet (14), the inlet (13) being connectable to an outlet (7) of the metering unit (3); at least one extrusion nozzle (11), which can be connected to the outlet (14) of the hot channel system (10). The invention further relates to an extrusion device (1) having such an extrusion unit (4) and to the use of the extrusion device (1) in particular for 3-D printing and/or for mixing and/or for strand extrusion.

Description

Extrusion unit, apparatus for the extrusion of thermoplastics and use of the device

description

The present invention relates to an extrusion unit for a device for the extrusion of thermoplastics. It further relates to a device for the extrusion of thermoplastics, which comprises a plasticizing unit, a metering unit and the extrusion unit. Furthermore, it relates to the use of such a device.

Extrusion devices are known with which thermoplastic plastics are pressed out under pressure continuously from a shaping nozzle. The force is applied to the thermoplastic material by means of one or more screw shafts. For ceramic materials also piston extruders are used. Typically, the processing temperatures set for the extrusion of thermoplastics are up to 300 ° C. At these relatively low temperatures, some thermoplastics can not be processed.

Thermoplastics are also processed by injection molding. In this case, the plasticized plastic is injected under pressure into an injection mold and removed from this after solidification again. Injection molding processes have numerous applications and are technically well developed.

It is an object of the present invention to provide a device for processing thermoplastics, with which a plurality of thermoplastics can be processed. In this case, the device should be usable in different processes, in particular for extrusion, for injection molding, for mixing and for three-dimensional printing (3D printing), in particular in an FDM (Fused Deposition Modeling) process.

This object is achieved by an extrusion unit according to claim 1, a device for the extrusion of thermoplastics according to claim 6 and by the use of the device according to claim 9 and 10.

Advantageous embodiments and modifications of the invention are the subject of the dependent claims. According to one aspect of the invention, there is provided an extrusion unit for an apparatus for extruding thermoplastics, wherein the extrusion unit is formed as a separate component connectable to a metering unit of the apparatus and comprises a hot runner system having an inlet and an outlet, the inlet having an outlet the dosing unit is connectable. Furthermore, the extrusion unit comprises at least one extrusion nozzle which can be connected to the outlet of the hot runner system.

The extrusion unit has the advantage that it can be used with standard plasticizing units for injection molding, instead of an injection molding tool, so that extrusion can be carried out instead of an injection molding process. This has the advantage that a large number of thermoplastics can be processed by means of extrusion, in particular also high-melting and / or highly filled plastics and highly viscous masses.

Furthermore, the extrusion unit has the advantage that the advantages of the highly developed and mass production suitable injection molding technology can be used.

According to one embodiment of the invention, the at least one extrusion die is exchangeable. This has the advantage that the cross section and / or shape of the extrusion nozzle can be changed in a simple manner, so that the extrusion can be adapted to the particular application. For example, the extrusion die can be screwed into the extrusion unit.

According to one embodiment, the at least one extrusion die has an extrusion opening with a diameter between 0, 1 mm and 4 mm. As has been found, can also be used with the extrusion unit described extrusion nozzles with very small diameter. This so-called micro-extrusion can be used, for example, for coating surfaces, for mixing materials, for extruding very small plastic strands and in 3D printing.

The at least one extrusion die can be heated by means of a heating unit, wherein the heating unit can be designed, for example, as a heating cartridge. The heating of the extrusion nozzle has the advantage that cooling of the thermoplastic material prior to exiting the extrusion unit is prevented.

According to one embodiment, a housing of the extrusion unit has a cooling system. This may in particular be the housing surrounding the hot runner system. In order to avoid an undesirable release of heat to the environment, this housing can be cooled by means of a cooling system, wherein the cooling system can in particular have cooling channels for a cooling liquid, for example water. That has the advantage, that heat is introduced only selectively along the flow path of the thermoplastic material, which is partially thermally insulated from the environment.

According to one aspect of the invention, an apparatus for the extrusion of thermoplastics comprises a plasticizing unit for melting a thermoplastic, a metering unit with a metering piston for feeding the plastic to an extrusion unit and the extrusion unit for extrusion of plastic described. An inlet of the hot runner system communicates with an outlet of the dosing unit so that a flow path for plastic from the dosing unit is formed by the hot runner system and the extrusion die.

The device has the advantage that it allows the processing of thermoplastics with very high viscosities. In particular, the extrusion of the plastic can take place, wherein the plastic at 210 ° C and a shear rate of 1 s ^{~ has} a viscosity in the range of 100,000 mPas to 10,000,000 mPas. The viscosity has been measured in the present case with a Malvern Rheometer (cone plate 25 mm diameter). In particular, the device is suitable for the extrusion of thermoplastic materials with melt viscosities of 200,000-1,000,000 mPas.

According to one embodiment, the inlet of the hot runner system of the extrusion unit can be closed with a needle valve nozzle of the dosing unit. To terminate or interrupt an extrusion process, the inlet of the hot runner system can thus be closed by the needle valve nozzle. Needle valve systems are known from the injection molding of plastic parts and allow a clean closure of the outlet. This is advantageous because the extrusion unit formed as a separate part can be connected to the dosing unit in this way more easily. Preferably, the extrusion die alternatively or additionally has a needle closure. Another advantage of using a needle valve nozzle and / or an extrusion nozzle with a needle valve is the provision of a control option that allows a free choice of the timing of the operation of the needle valve nozzle and / or the needle valve (open and closed). The needle valve nozzle and / or the needle valve can be executed externally or self-actuated.

According to one embodiment, a mixing element is arranged after the outlet of the metering unit, in particular a passive element which promotes mixing of the plastic flowing past or through.

The device described can be used in particular for 3D printing. In this case, the component to be coated is guided for example in predetermined paths under the nozzle, wherein the extrusion device is fixed. This use has the advantage that it considerably increases the number of materials suitable for 3D printing, since virtually any thermoplastic material, including highly viscous materials and / or highly filled materials and / or refractory materials, can be processed by means of the extrusion device and the thermoplastics can be supplied as granules. The provision of the starting material in the form of filaments is therefore not necessary.

Furthermore, the device is also suitable for mixing materials, for providing molten material, for pressing parts and for injection molding, but also for the extrusion of filaments for 3D printing, for the extrusion of precise strands (preferably with a diameter in the Range from 0.1 mm to 3 mm) or thicker strands (preferably with a diameter in the range of 2.8 mm to 4 mm).

The extrusion device is thus very versatile.

In all the uses described, it is preferable to extrude the plastic with a viscosity of 100,000 to 10,000,000 mPas.

In the described uses of the thermoplastic material is preferably to a temperature in a range between 30 ° C and 420 ° C, in particular 180 ° C to 300 ° C, melted. Thus, the extrusion device has suitable means to heat the thermoplastic material accordingly. These means may in particular be a heating cartridge. Conceivable is a use in particular for the following thermoplastic materials with the appropriate melt temperatures: polyamide 6 (PA 6) with a melt temperature in the range of 240 ° C and 290 ° C; Polyamide 66 (PA 66) with a melt temperature in the range of 260 ° C and 300 ° C; Polycarbonate (PC) having a melt temperature in the range of 270 ° C and 320 ° C; Polymethyl methacrylate (PMMA) having a melt temperature in the range of 200 ° C and 290 ° C; Polypropylene (PP) having a melt temperature in the range of 200 ° C and 300 ° C; Polyethylene (PE) having a melt temperature in the range of 180 ° C and 300 ° C; Polystyrene (PS) having a melt temperature in the range of 180 ° C and 280 ° C; Styrene-acrylonitrile copolymer (SAN) having a melt temperature in the range of 200 ° C and 260 ° C; Acrylonitrile-butadiene-styrene copolymer (ABS) having a melt temperature in the range of 200 ° C and 300 ° C; Acrylonitrile-styrene-acrylate copolymer (ASA) with a melt temperature in the range of 200 ° C and 250 ° C or polyoxymethylene (POM) with a melt temperature in the range of 180 ° C and 230 ° C.

The melting can be carried out in particular in the plasticizing unit by heat conduction and convection, wherein the plasticizing unit as a piston-in-piston plasticizing unit is formed, so that only small shear forces act on the plastic and this is particularly gently melted.

According to one embodiment, the extrusion is carried out discontinuously by means of a hydraulically or pneumatically operated piston of the metering unit. A hydraulically or pneumatically operated piston has the advantage that the pressure of 1000 to 1500 bar necessary for the processing of highly viscous materials and the use of very small extrusion nozzles can be provided in the region of the extrusion die.

When using a metering, the extrusion is carried out discontinuously, with the described device, for example, between 0.001 and 36 cm ³ material can be extruded. The use of small extrusion nozzles and a material volume of 36 cm ³ thus results in a quasi-continuous extrusion for many applications.

In the following the invention will be explained in more detail by means of embodiments with reference to the accompanying drawings. Show it:

Figure 1: a schematic sectional view through an extrusion device with a

Extrusion unit according to an embodiment of the invention and

Figure 2: the extrusion unit according to Figure 1 in detail.

The extrusion apparatus 1 according to FIG. 1 is suitable for the extrusion of thermoplastics. It has a plasticizing unit 2, a metering unit 3 and an extrusion unit 4.

The plasticizing unit 2 comprises a reservoir 5 in which thermoplastic plastic material, in particular in the form of a granulate, is kept. In a manner known per se, this material slides into a plasticizing region 16 in the plasticizing unit 2, where it is melted by convection heat and conveyed by means of a plasticizing piston 6 in the direction of the outlet 7 of the plasticizing unit 2. The melting of the plastic takes place in a particularly short time (for example, 36 g in 4 seconds) and thus very gently. The minimization of shear forces by the use of a plasticizing 6 instead of a screw conveyor contributes to a gentle processing of the plastic.

The metering unit 3 has a metering piston 8, which allows a precise metering of the extruded material. The outlet 7 of the plasticizing unit 2 can be closed by means of a needle valve nozzle 9. In front of the outlet 7, a mixing element not shown in FIG. 1 can be arranged. In front of the outlet 7, the extrusion unit 4 is arranged, which is shown in more detail in FIG. The extrusion unit 4 comprises a housing 12 in which a hot runner 10 is arranged. In operation, the hot runner 10 is in communication with the outlet 7 of the plasticizing 2. Thermoplastic plastic thus passes from the outlet 7 in the hot runner 10 and from there through the extrusion die 1 1 to the extrusion opening 15. The extrusion die 1 1 is thus with an outlet 14 of the hot runner 10 connected.

The extrusion die 1 1 is interchangeable. The extrusion unit 4 can thus be used with different extrusion dies 1 1, which have different diameters of the extrusion openings 15. For example, the extrusion unit 4 can be used with an extrusion die 11 having a diameter of 2 to 4 mm. But it can also be used with an extrusion die 1 1, which has a diameter of 0, 1 to 4 mm, in particular 0.2 to 1 mm and can be extruded with the smallest strands.

The extrusion die 1 1 can thus be replaced as needed and is therefore detachably connectable to the housing 12 of the extrusion unit 4. For example, it can be screwed into the housing 12. The extrusion die 1 1 is heated in the embodiment shown by means of a heating cartridge, not shown in the figures.

A typical cycle time for the extrusion by means of the described extrusion device is in a range between 3 and 120 seconds, in particular in a range between 3 and 20 seconds. At a processing temperature between 30 and 420 ° C, in particular between 180 and 300 ° C, while quantities of 0.001 to 36 g, in particular 1 to 8 g, plasticized and having a melt viscosity between 100,000 and 10,000,000 mPas, in particular between 200,000 and 1,000,000 mPas, extruded with a strand diameter in a range between 0.1 mm and 4 mm, in particular in a range between 0.2 mm and 1 mm. Due to the gentle processing and the high possible melt temperatures, many different, even filled thermoplastics can be processed. When using hydraulically operated pistons, the processing of very high-viscosity thermoplastics is possible.

Typically, the entire plasticizing and dosing unit is stationary. A component to be coated can be robotically guided under the extrusion die. Alternatively or additionally, the entire device can be moved. For example, it is conceivable to move the extrusion die relative to a stationary component to be coated. In one variant, both the device and the component to be coated are moved. So it is particularly conceivable to move the component to be coated in the axes x and y, while the entire device or the extrusion nozzle is moved in the z-axis. LIST OF REFERENCE NUMBERS

1 extrusion device

2 plasticizing unit

3 dosing unit

4 extrusion unit

5 reservoir

6 plasticizing pistons

7 outlet

8 metering pistons

9 needle valve nozzle

10 hot runner

1 1 extrusion nozzle

12 housing

13 inlet

14 outlet

15 extrusion opening

16 plasticizing area

Claims

claims

1 . Extrusion unit (4) for a device (1) for the extrusion of thermoplastics, wherein the extrusion unit (4) is formed as a separate component which can be connected to a metering unit (3) of the device (1) and comprises:

a hot runner system (10) having an inlet (13) and an outlet (14), the inlet (13) being connectable to an outlet (7) of the dosing unit (3);

at least one with the outlet (14) of the hot runner system (10) connectable extrusion nozzle (1 1).

2. Extrusion unit (4) according to claim 1,

wherein the at least one extrusion die (1 1) is exchangeable.

3. extrusion unit (4) according to claim 1 or 2,

wherein the at least one extrusion die (1 1) has an extrusion opening (15) with a diameter between 0.1 mm and 4 mm.

4. extrusion unit (4) according to one of claims 1 to 3,

wherein the at least one extrusion die (1 1) can be heated by means of a heating unit.

5. Extrusion unit (4) according to one of claims 1 to 4,

wherein a housing of the extrusion unit (4) comprises a cooling system.

6. Apparatus (1) for the extrusion of thermoplastics, comprising:

a plasticizing unit (2) for melting a thermoplastic resin;

a metering unit (3) with a metering piston (8) for feeding the plastic to an extrusion unit (4);

an extrusion unit (4) for extruding the plastic according to any one of claims 1 to 5,

wherein an inlet (13) of the hot runner system (10) communicates with an outlet (7) of the dosing unit (3) so that a flow path for plastic from the dosing unit (3) through the hot runner system (10) and the extrusion die (11 ) is formed.

7. Device (1) according to claim 6, wherein the inlet (13) of the hot runner system (10) of the extrusion unit (4) with a needle valve nozzle (9) of the metering unit (3) is closable.

8. Device (1) according to claim 6 or 7,

wherein after the outlet (7) of the dosing unit (3) a mixing element is arranged.

9. Use of the device (1) according to any one of claims 6 to 8 for mixing thermoplastic materials.

10. Use of the device (1) according to any one of claims 6 to 8 for 3D printing.