WO2001056767A1

WO2001056767A1 - Method and device for producing multi-component plastic shaped parts

Info

Publication number: WO2001056767A1
Application number: PCT/DE2001/000180
Authority: WO
Inventors: Volker Reichert; Karl-Heinz Haberkorn
Original assignee: Reichert Gmbh
Priority date: 2000-02-05
Filing date: 2001-01-16
Publication date: 2001-08-09
Also published as: DE10005264C1

Abstract

The invention relates to the production of multi-component plastic shaped parts, which are comprised of a main constituent and of at least one minor constituent, on an injection molding machine. Said injection molding machine is equipped with a main aggregate, which is configured as a plasticizing and injecting unit and which is provided for preparing the main constituent, and is equipped with an auxiliary aggregate for preparing the minor constituent. According to the invention, the highly viscous minor constituent (19) is prepared by the auxiliary aggregate (17) and is fed to a storage space (10) of a melt reservoir (8) that is assigned to said auxiliary aggregate (17). The highly viscous main constituent (18) is prepared by the main aggregate (6) and is fed to a pressure space (11) of the melt reservoir (8). The minor constituent (19) and the main constituent (18) are dosed by a displacement measuring device of the main aggregate (6). The minor constituent (19) is stored in the storage space (10) and the main constituent (18) is stored in the pressure space (11) while being separated from one another by a sealing plunger (9) of the melt reservoir (8). The minor constituent (19) contained in the storage space (10) and the main constituent (18) contained in the pressure space (11) of the melt reservoir (8) are injected, optionally in succession or simultaneously, with the hydrostatic injection pressure of the main constituent (18) of the main aggregate (6) into a tool cavity (20; 21; 22).

Description

Method and device for producing multi-component molded parts made of plastic

The invention relates to a method for producing multicomponent molded parts made of plastic, consisting of a main component and at least one secondary component, on an injection molding machine with a main unit designed as a plasticizing and injection unit for providing the main component and at least one auxiliary unit for providing the Secondary component and an apparatus for performing this method.

The components to be processed are both plastic melts, including chemically reactive ones, and liquids that are injected together or at different times, in different orders, with which the plastic melt is injected into a tool and, if necessary, react chemically with the plastic melt. The components to be processed can differ in terms of their properties, such as viscosity, processing temperature and compatibility.

State of the art

DE 39 32 416 C2 discloses a method in which a plurality of plastic melts, which are produced separately for each injection cycle, are placed in front of at least one sprue channel or the inlet opening of a sprue channel system of a mold, initially in a suitable injection unit in the outlet area arranged collection space in a disc-like arrangement perpendicular to the longitudinal axis of the injection unit are deposited before they are injected into the mold with a single stroke of the injection unit through the sprue or the inlet opening of the sprue system after the build-up of the complete filling quantity for the molding tool. The disk-like arrangement of the plastic melts in the collecting space is produced by suitable selection and layering of the plastics used, which are let into the collecting space in the already melted state. The expert is thus given the information of how several different and already melted plastic melts can be deposited in layers in a collecting space in the end of an injection cylinder or an extruder unit facing an injection mold, in order then to be pressed into the injection mold without noticeable mixing with a stroke of the injection unit ,

The application of this method is, however, limited to selected plastics, the deposit of which in layers in the common collecting area does not indicate any mutual influences on the contact surfaces, for example temperature compensation, or chemical reactions. A certain mixing of the various components in the common collection room cannot be ruled out. The use of mechanical cutting disks cannot provide a thorough remedy, since due to the filling grooves and through openings through which the components are pressed, with vortex formation, mutual influences of the components cannot be prevented. All plastic components, regardless of their different properties, are injected under the same injection conditions, such as pressure, temperature and speed. Furthermore, the order in which the components are injected can only be selected to a limited extent, since the main component must always be injected last. Liquids that react chemically with one another or with the plastic melts cannot be processed. In the device for carrying out the method according to DE 39 32 416 C2, the plasticizing units are in any case connected to a common collecting space which is arranged in the exit area of a single selected injection unit. All plastic melt components flow through the movement of the screw piston, which reduces the volume of the common collecting space. The positioning of the collecting space is due to the forces necessary for the injection, which are transmitted by mechanical transmission elements and which require a correspondingly large dimensioning.

Injection molding devices are also known in which axially movable control pistons, torpedoes or sleeves, moved by the pressure of individual plastic components, selectively open and close flow paths in multi-component injection molding. These devices are used for the simultaneous and / or temporally successive merging of different melt streams. The movably arranged elements used for this purpose are moved partly by fluidic drives, partly by melt, namely through a pressure difference which results from the pressures acting on the respective end faces, which results in a force which triggers the movements in the pressure-controlled elements. The movements selectively release and block melt channels.

Three such devices are described below. In the injection molding apparatus according to EP 0 748 677 AI, in order to reduce the manufacturing and maintenance expenditure for the control unit in the nozzle head, a control piston with several control edges is mounted in a longitudinally displaceable manner within a control chamber formed in the nozzle head, with which, depending on the respective pressure of the skin, or core material, the supply of skin or core material can be controlled via the nozzle head and the supply of the plastic material (skin or core material) that is not being conveyed can be shut off.

From DE 197 57 411 Cl an injection molding tool is known which has, among other things, a controllable device which alternatively connects or decouples the first feed channel directly to the outlet opening by separating the second feed channel. The controllable device is formed by a tubular piston element which is displaceably arranged in the first feed channel and has a first piston surface which can be acted upon by the fluid pressure in the first feed channel and a second piston surface which can be acted on by the fluid pressure in the second feed channel. Depending on the stronger fluid pressure in the first or second feed channel, the piston element can be displaced into different switching positions for closing or opening the first and / or second feed channel. An axial passage opening of the tubular piston element is part of the first feed channel and is arranged coaxially to the shut-off needle. It can be opened and closed with the locking needle.

From DE OS 24 45 112 a spray nozzle arrangement can be seen which has a single feed channel. Which opens laterally from the mold and has at least three separate chambers, which are each separated from one another and arranged coaxially to one another. Each chamber is connected to an independent feed line for a material to be injected and has a unit for pressing. A disadvantage of the three devices described above is that they are severely restricted in their application. They are either part of the injection mold or the injection unit. A simple installation between the tool holder plate on the nozzle side and the tool half on the nozzle side is not possible. The provision of a defined melt volume for the skin component is not possible with these devices. They are therefore not suitable for storing and dosing. The movable elements of the devices mentioned only act as separating or control elements, but not to displace the melt in the sense of promoting it.

An increase in the injection pressure as a result of a pressure ratio cannot be achieved with these devices. In the three devices described above, for Injecting different melts requires one injection unit for each material.

The control and metering as well as the timing, for example for the simultaneous phase in which skin and core components are injected simultaneously, must be carried out by the injection molding machine.

Presentation of the invention

It is the object of the invention, while avoiding or minimizing the disadvantages described, to demonstrate a method and an apparatus for carrying out this method which enable the processing of a wide variety of materials and in a freely selectable order. Furthermore, the individual components should be able to be processed under processing conditions that are optimal for them.

The object is achieved by the method specified in claim 1 and the device described in claim 4. The method according to the invention enables a wide variety of materials to be processed with one injection unit. The main and secondary components are initially made available for injection in mechanically separate rooms. Plastic melts, including those that are chemically reactive, as well as liquids that are suitable for reacting chemically with the melts when they are touched, are injected simultaneously or in a selectable order with the hydrostatic pressure of the main component, with the components coming into contact with one another only when injecting, immediately before Tool cavity takes place. According to their different chemical and physical properties as well as the conditions of the process and the device, the individual components are provided and injected under the optimally adapted conditions. According to an advantageous embodiment of the method according to the invention, the hydrostatic injection pressure of the main component is transferred to the secondary component via a sealing piston, as a result of which any premature contact the components is excluded.

An advantageous embodiment of the method according to the invention can also be seen in the fact that, depending on requirements, several secondary components and only one main component are provided and injected in a process for producing multi-component molded parts.

This makes it possible to produce molded parts with very different properties, which significantly increases the scope of the method. The inventive device according to claim 4 enables the production of multi-component molded parts by the method according to claim 1 with the advantages shown. According to an advantageous embodiment of the device according to the invention, there are a number of auxiliary units and just as many melt stores assigned to them. As a result, the range of use of the device for the production of multi-component molded parts consisting of different components can be increased. Not all existing auxiliary units and associated melt stores have to be used in the manufacture of the multi-component molded parts. This makes it possible to accelerate the need to convert the device to the manufacture of other products. An advantageous embodiment can also be seen in this that the melt accumulators do not have to be arranged in the injection axis, but can also be arranged in parallel or at any angle to them, because the injection pressure is not transmitted hydrostatically via mechanical links but via appropriately dimensioned connecting lines and melt accumulators. This results in advantages with regard to the control of the occurring forces, but also with regard to the user-friendly accessibility of the melt storage in the event that parameter changes or product changes become necessary.

Furthermore, one embodiment of the device according to the invention is that the backflow of the secondary component into the auxiliary unit is prevented by a check valve. According to a further embodiment, connection channels are provided in the melt reservoir, which allow the main component to flow over to the tool. This makes it possible to introduce the main component into the tool before the secondary component or before the secondary components. It is also possible to finally inject the main component.

The connecting channels are expediently opened or closed by the piston in order to control the main component. The main component and the secondary component can be injected into a common tool cavity as well as into separate tool cavities, so that both after the sandwich and after the overmoulding Procedure can be worked. An embodiment of the invention can also be seen in the fact that the piston has a control piston with which the overflow can be controlled. A melt reservoir designed in this way is particularly expedient if a pressure transmission is to be achieved via the piston. Finally, an embodiment of the invention can also be seen in the fact that the piston is designed as a stepped piston, as a result of which a simple adjustment of the pressure conditions can be achieved.

Brief description of the drawings

Fig.l: Device for producing multi-component molded parts, in a schematic representation, Fig.2: melt storage, in longitudinal section, Fig.3: other melt storage, in longitudinal section, Fig.4: further melt storage, in longitudinal section.

Best way to carry out the invention

1 comprises a main unit 6 for the provision of the main component 18, three secondary units 7 for the provision of three secondary components 19, three melt stores 8 individually assigned to the secondary units 7, Control devices 12 and check valves 13 in the connecting lines from the melt accumulators 7 to the tool cavity 23 of the tool consisting of the nozzle-side tool half 3 and the ejector-side tool half 4 in the connecting lines from the auxiliary units 7 to the melt accumulators 8.

The main unit 6 is designed as a plasticizing and injection unit. The plasticized main component 18 located in the screw antechamber 25 is, after actuation of the injection piston 17 in the injection cylinder by the screw piston 15, with the non-return valve 16, first in the middle melt reservoir 8, according to FIG. 1, and then, for example, in succession the upper melt memory 8 and the lower melt memory 8 pressed. From Fig. 2 it can be seen that the main component 18 reaches the pressure chamber 11 via the connecting channel 27 in the base body 22. In the storage space 10 there is the secondary component 19, which was metered by the auxiliary unit 7, for example as a plasticizing unit, as a low-viscosity plastic component, with the aid of a displacement measuring device (not shown) on the screw piston 15 of the main unit 6. When metering the secondary component 19 into the storage space 10, the piston 9 has moved from its left end position into the position shown in FIG. 2, whereby it has pushed the main component 18 back out of the pressure space 11 into the screw antechamber 25 and pushed the screw piston 15 to the right ,

When a predetermined path is reached, the path measuring device of the main assembly 6 gives a signal to end the filling process of the secondary component 19. The main assembly 6 then plastifies the main component 18 up to a predetermined plasticizing stroke. If a plurality of melt stores 8 are present, the filling processes of the storage rooms 10 take place one after the other, so that precisely defined quantities of the individual secondary components 19 are available. As already explained, in the injection process, after actuation of the control 12, the main component 18 is pressed into the pressure chamber 11, where it acts on the piston 9. This displaces the secondary component 19 the storage space 10 into the tool cavity 23. In the position of the piston 9 shown in FIG. 2, the main component 18, without coming into contact with the secondary component 19, can be moved into the tool cavity 23 as the first component via the connecting channel 28 after actuation of the control device 12 be injected.

When the piston 9 has reached its left end position again, the main component 18 can flow into the tool cavity 23 via the connection channel 26 that has now been released. The connecting channel 28 is not available in this case. In sandwich injection molding, the main component 18 forms the core material and the secondary component 19 the skin material. If, however, the main component 18 is to form the skin material, it is first brought into the tool cavity via the connecting channel 28 then, when the piston 9 is in the position shown in FIG. 2, without coming into contact with the secondary component 19, after actuation of the control device 12 23 injected. The control device 12 is designed, for example, as a hydraulically or pneumatically operated 2-way valve or rotary slide. The check valves 13 prevent the back flow of the main component 18 and the secondary component 19 both during injection and during plasticizing. When using a plurality of melt stores 8, for example three as shown in FIG. 1, the individual secondary components 19 and the main component 18 can be injected into the tool cavity 23 in the desired order by corresponding actuation of the respective control devices 12. Fig. 3 shows another melt storage 8. In an axial bore, the piston 9 receives a control piston 24, which also has an axial bore. During injection, the main component 18 acts on the piston 9, which displaces the secondary component 19 from the storage space 10. The axial bore in the control piston 24 is blocked. When the piston 9 reaches the left end position, it blocks the connection between the storage space 10 and the tool cavity 23.

At the same time, the control piston 24 is actuated and the main component 18 can flow from the pressure chamber 11 through the axial bore in the control piston 24 into the tool cavity 23. Connecting channels 26; 28 are not required. The length and the diameter of the piston 9, the storage space 10 and the pressure space 11 can be well adapted to the structural installation conditions. In particular, the piston 9 can be designed as a stepped piston with which a pressure transmission can be effected. Basically, there is a possibility of adaptation to the respective properties of the individual components and the processing conditions. The associated melt stores 8 are then designed differently accordingly. Since the melt storage 8 can be easily replaced, a simple adaptation to changed component properties or processing conditions is also possible. For example, an increase in the pressure of the secondary component 19 is achieved in order to overcome greater flow resistances during injection, such as occur with long flow paths or very thin wall thicknesses of the molded part. It is also possible in this way to compensate for unavoidable pressure losses when the highly viscous main component 18 flows from the main unit 6 to the melt reservoir 7.

FIG. 4 shows a further melt store 8, which is used in over-molding multi-component injection molding. The tool with the tool cavities 20; 21 is designed in rotary, transfer or slide technology. The melt storage device 8 is heated by means of a heating device 14. In principle, all melt stores 8 and connecting lines can be heated. This is another easy-to-implement option for optimal adaptation to the respective component properties and processing conditions.

During the injection process, the tool cavity 20 is first filled with the secondary component 19 of the auxiliary unit 7 from the storage space 10 by the pressure of the piston 9. After the reprint time, both control devices 12 are switched over and the tool cavity 21 is connected via the connecting channels 26; 27 filled with the main component 18 from the main unit 6. In this process sequence, the injection and hold pressure times for the secondary component 19 and the main component nente 18, for example, one after the other. However, parallel injection is also possible if the pressure conditions during the injection process result in a defined filling process. It is also possible to use the bi-injection method, in which the main component 18 and the secondary component 19 simultaneously in a common tool cavity 20; 21 are injected and the flow fronts collide at a specific point on the molded part.

Industrial applicability

The invention is used in the production of multi-component molded parts made of plastic, consisting of a main component and at least one secondary component, on an injection molding machine with a main assembly designed as a plasticizing and injection unit for the provision of the main component and at least one auxiliary assembly for the provision of the minor component.

Method and device for producing multi-component molded parts made of plastic

LIST OF REFERENCE NUMBERS

2 tool clamping plate on the ejector side

3 tool halves on the nozzle side

4 tool half on the ejector side

6 main unit

7 auxiliary unit

8 melt stores

9 pistons

10 Storage space for secondary components

11 pressure chamber for main component

12 control device

13 check valve

14 heating device

15 screw pistons

16 non-return valve

17 injection pistons

18 main component

19 secondary component

20 tool cavity

21 Tool cavity

22 basic body

23 Tool cavity

24 control pistons

25 snail vestibule 26 ... connecting channel 27 ... connecting channel 28 ... connecting channel

Claims

Method and device for producing multi-component molded parts from plastic claims

1. A method for producing multi-component molded parts made of plastic, consisting of a main component and at least one secondary component, on an injection molding machine with a main unit designed as a plasticizing and injection unit for the provision of the main component and at least one secondary unit for the provision of the secondary component, the highly viscous secondary component is provided by the auxiliary unit and is fed to a storage space of a melt store assigned to the auxiliary unit and the high-viscosity main component is provided by the main unit and is fed to a pressure chamber of the melt store, characterized in that ß - the dosage of the secondary component (19) and the main component ( 18) by means of a displacement measuring device of the main unit (6), the secondary component (19) in the storage space (10) and the main component (18) in the pressure space (11), by a sealing piston (9) of the melt storage

(8) is separated, stored, controlled by control devices (12), in selectable sequence or simultaneously, the secondary component te (19) from the storage space (10) and the main component (18) from the pressure space (11) of the melt reservoir (8) with the hydrostatic injection pressure of the main component (18) of the main assembly (6) into a tool cavity (20; 21; 23 ) between a nozzle-side tool half (3) and an ejector-side tool half (4) of a tool.

2. The method according to claim 1, characterized in that the secondary component (19) is injected into the mold by the hydrostatic injection pressure of the main component (18) of the main unit (6) through the sealing piston (9) in the melt reservoir ( 8) is transferred to the secondary component (19).

3. The method of claim 1 or 2, d a d u r c h g e k e n n z e i c h n e t, d a ß for an injection cycle two or more secondary components (19) of the same number of auxiliary units (7), each with its own melt storage (8) are assigned.

4. Apparatus for carrying out the method according to claim 1, wherein the auxiliary unit is assigned a melt reservoir which comprises a storage space for storing the secondary component provided by the auxiliary unit and a pressure space for accommodating the main component provided by the main unit, so that the main component is provided

- Between the storage space (10) and the pressure space (11), controlled by the hydraulic pressures when metering the secondary component (19) and the main component (18), axially displaceable, the volume ratios between the storage space (10) and the pressure space (11) changing, sealing piston (9) is arranged,

- In the connecting line from the melt reservoir (8) the tool cavity (23) a control device (12) is arranged, - a path measuring device for controlling the metering of the main component (18) by the main unit (6) and the secondary component (19) by the secondary unit (7) on

Main unit (6) is present.

5. The device according to claim 4, characterized in that the sealing piston (9) for the transmission of the hydrostatic injection pressure of the main component (18) of the main unit (6) in the pressure chamber (11) on the secondary component (19) in the storage space (10) of the Melt storage (8) is suitably designed.

6. Apparatus according to claim 4 or 5, d a d u r c h g e k e n n z e i c h n e t, d a ß a number of auxiliary units (7) and just as much melt storage (8) assigned to them are available.

7. The device according to claim 6, d a d u r c h g e k e n n z e i c h n e t, that the melt stores (8) are arranged in, or parallel to or at any angle to the injection axis.

8. Device according to one of claims 4 to 7, d a d u r c h g e k e n n e e c h e d, that a check valve (13) is arranged in a connecting line between the auxiliary unit (7) and the melt reservoir (8).

9. Device according to one of claims 4 to 8, characterized in that ß in the melt memory (8) connecting channels (26; 28) for the overflow of the main component (18) from the pressure chamber (11) are arranged in the connecting line to the tool.

10. The apparatus of claim 9, d a d u r c h g e k e n n z e i c h n e t, that the opening and closing of the connecting channels (26; 27; 28) by the piston (9) is controllable.

11. Device according to one of claims 4 to 10, characterized in that the piston (9) has an axially displaceable control piston (24) with end sealing surfaces and an axial overflow channel for the main component (18) from the pressure chamber (11) into the connecting line owns the tool.

12. Device according to one of claims 4 to 11, d a d u r c h g e k e n n z e i c h n e t, that the piston (9) is designed as a stepped piston.