DE1933570A1 - Multicoloured plastic moulded parts - Google Patents

Abstract

Plastic parts of marble-like appearance are produced by a worm-screw plasticiser to which at least two different types of material are fed. The two streams are joined just before the worm-screw.

Description

Process for the production of multicolored molded parts from plastic Masses by means of machines with screw plasticization and device for implementation of the method The invention relates to a method for producing multicolored Molded parts from plastic masses by means of piasehines with screw plasticization, whereby at least two different colored material streams are fed to the plasticizing screw will.

These can be shaped bodies or strand-shaped parts, those with mold filling machines, e.g. B, injection molding machines, injection blow molding machines, Injection molding machines or with injection molding machines, e.g. B. extruders will.

One has already dealt with the production of multi-colored plastic parts deals and develops mold filling machines and extrusion machines for this purpose, where to achieve mass tion effects in the molded part or in the injected Line 2 or more plasticizing units with plasticizing screws connected to one another in this way that the different colored material stt ime during the plasticizing process are separated, but before entering the actual mold through merging material guide channels are merged. The merging during the plasticizing process takes place continuously or intermittently. Spray heads for multi-colored profiles and connections for two or more are known Have plasticizing units and the supply of various materials takes place through a distribution member, which the different colored material flows subdivided several times into a round nozzle, in which it turns into a round rod unite. This allows sector-shaped longitudinal markings or, if that Distributor link is set in rotation, coiled markings are achieved, With the conventional piston injection molding machines you can get good grain effects thereby enable the granules of different or different colored materials is entered in the mixed state together into the mass collector. Due to the lack of rotational movement and the relatively low mixing effect Such piston injection molding machines can achieve a good grain effect. However, the use of the piston injection molding machine brings the known disadvantages of Piston plasticization compared to the snail plasticization with it. These disadvantages mainly exist in the fact that there are significant temperature differences within the spray material are that a much greater effort is required for the mold filling process than with screw injection molding machines. That also has an unfavorable effect thermally sensitive materials are difficult to process and that a.

Color change of the material only after cleaning the piston and the injection cylinder is possible.

The invention is based on the problem of grain or marbling effects in the case of multi-colored molded parts, this can be achieved by means of machines with screw molding. It has been shown that there are considerable difficulties to overcome here.

The amalgamation of multi-colored ones known from Ivolbenspritzgiessmasshinen Materials to achieve such grain effects brinat in screw injection molding machines or with extrusion machines therefore no success because of the rotational movement the screw an intensive mixing of the supplied material takes place and thereby a uniform mixed color instead of a grain is achieved.

The known method of working with two or more plasticizing units, which initially work separately from each other and their material flows to the inlet in the injection mold the injection mold are brought together, result in Relation to the achievable color mixing and An Relation to the strength of the produced Parts major disadvantages. Naturally, there are only grain stripes that are sharply separated from one another and achievable at most in a number per unit area that corresponds to the intermittent Operation of the plasticizing units or the relative movement of the merging organs is equivalent to. Due to the separate plasticization of the material flows z. B. Temperature differences between the individual material flows are unavoidable.

There is also the relatively long separate leadership of the Material flows run the risk of external cooling. Both phenomena lead to insufficient mixing of the material flows, which has an adverse effect on the strength of the manufactured parts, The use of separately working plasticizing units, how to B. knows about extruders that are arranged at an angle to each other and together a spray head with rotating material feed channels loading, represents a considerable construction effort.

The invention is therefore also based on the object of a device to carry out the process for the production of multicolored molded parts, which is simple in structure and subject to little wear and tear.

According to the invention, this object is achieved in a method solved that the unification of the different colored material flows can only be achieved in the The working area of the plasticizing screw. It has been shown that in one such a case in further course of the plasticizing or spraying process the material mixing is sufficiently low so that there is an intimate mixing the merged streams of material, which would cause a mixed color, avoided will. It is thus possible to have a recognizable grain or marbling structure in the molded part to obtain. In the case of mold-filling machines, when using the inventive Procedure in the collecting space in front of the screw tip the thrust screw the different colored Material collected and sprayed out in only partially mixed condition.

Due to the well-known movement of material in the screw flights there is a fine, but not too intimate mixing of the individual material flows, which allows the grain structure to be preserved. Because both materials are still one going through a common stretch of the plasticizing cylinder, there is no risk of that Temperature differences occur. Rather, these are balanced out, however only a partial intermingling of the grain strands takes place.

With the procedure it is possible to determine the intensity of the grain structure, d, h. the proportions of the different colors per unit area, in a simple manner to influence, This can be done, for example, that the feed the different colored material flows into the injection cylinder continuously or occurs intermittently, with the throughput rates, the inflow times or, for example the variables characteristic of the spraying process or the mixing effect, such as Material temperature, speed or derg ##, by means of known control devices can be changed.

In a device for performing the method described the plasticizing cylinder of the plasticizing unit has bores for receiving a or several different colored material streams in plasticized or unplasticized State immediately in the working area of the plasticizing screw. In this can Another plasticizing screw open out at an angle to the main plasticizing screw is arranged. If more than two material streams are used, corresponding several plasticizing screws are used. The plasticizing screws involved can do this with regard to the axial drive may be of different types, e.g. Axially displaceable thrust screw with an axially fixed extrusion screw or vice versa.

With a particularly simple design of the injection unit for implementation of the method described is the bore of the plasticizing cylinder with at least two material containers in connection, each of which can be operated from the outside, useful automatically controllable locking devices are assigned.

In this case, the locking devices expediently consist of slides, which by means of control devices the openings of the mass container alternately or release periodically. Such an execution is characterized by particularly small ones Construction costs, since a screw injection molding machine, for example, is more normal here Design can be used, with only the funnel and the associated Slide and control elements are specially designed, ~ emass one advantageous embodiment, the slide can simultaneously receiving elements Receipt of a dosed amount of material from the corresponding material containers exhibit.

In such an arrangement, it is advantageous if in an alternating Addition of the material flows in the feed device leading to the plasticizing cylinder Pless sensors, e.g. photocells, are attached to the filling chute of the plasticizing unit monitor their filling level and the opening of the next material flow depend on a suitable signal from the sensor.

It can also be advantageous if the plasticizing unit in on is equipped in a known manner with a pressureless zone and at this point dosing with the help of a feed chute or other known conveying elements, e.g. a screw conveyor.

Further advantages and features of the invention are evident from the following 3 description can be seen in connection with the attached drawing. Show in it: 1 shows a plasticizing unit of a screw injection molding machine in section, FIG. 2 shows a detail from FIG. 1 with a modification of the feed hopper and the associated one Plasticizing unit with control device.

Fig. 3 shows a section of a modification of the material supply to the main plasticizing unit, FIG. 4 shows a further modification to FIG. 3.

11 with the injection cylinder is referred to, in which a screw 12 longitudinally displaceable -is and plastic material in the direction of the nozzle opening 10 promotes and squirts out through this.

For the sake of clarity, heating units and the like have been omitted, The feed chute 14a of a feed hopper is located in a bore 13 of the injection cylinder 14 arranged, above which there are material storage containers 15, 16, their outlet openings 15a and 16a can be closed and opened by means of slides 17 and 18, respectively. For this purpose, piston-cylinder units 17a and 18a are provided, which by means of pneumatic or hydraulic control units 19 and 20 are controlled. the Slides 17 and 18 are connected to the control units 19 by means of control lines 21, 22 and 20, a pump 30 and connected to a transducer 23 electrical Pulse lines 24 and 25 included, connected.

In the filling shaft 14a of the filling funnel 14 measuring probes 28 are attached, which give a signal as soon as there is no material in the feed chute at the measuring point more is located. These measuring probes are connected to the transducer via signal lines 26 and 27 23 connected.

The plasticizing screw is designated by a total of 32 Drive unit driven, which includes an electric motor 33, a spur gear 34 and a spline shaft 35. The axial displacement of the screw is accomplished by a piston-cylinder unit 40. With the end part of the snail 12, a switching cam 36 is firmly connected, which interacts with two limit switches 37 and 38. These limit switches are also connected to the transducer by means of electrical lines 41, 42 23 electrically connected.

The mode of operation of the arrangement according to FIG. 1 is as follows: In the The position of the slide valve 17,18 shown is the supply of material to Auger 12 from container 15. The material contained therein is different Color as the plastic material stored in the container 16. The material supply to the screw cylinder 11 through the hopper 14 takes place until the slide 17 closes the opening 15a, this process is activated by one of the limit switches 37,38 or triggered, for example, by a switching timer, not shown.

That which is still in the funnel 14 after the opening has been closed Material is drawn into the injection cylinder 11 during the further plasticizing. As soon as the material level in the funnel shaft 14a is below that by the measuring probes 28 has fallen, a signal is triggered via lines 26, 27, that after a time delay in the transducer 23 a shift of the slide 18 causes and thereby exposes the opening 16a of the material storage container 16, Thus, the differently colored material located in the funnel 16 can now pass through the funnel 14 flow into the injection cylinder 11.

Here it only partially mixes with the material that has previously flowed in, so that a grain effect can come about in the molded part.

In the structural modification of the slide shown in FIG the same parts are provided with the same reference numerals as in Fig. 1. Instead of the two slides 17 and 18 is a single one here, the two openings 15a and 16a alternating closing or opening slide 50 is provided. The slider 50 has two through holes 51 and 52. In the position shown is the Bore 52 in front of the opening l5a of the material storage container 15 and is in this Position filled with material. In the event of a subsequent movement of the slide 50, this bore 52 reaches the filling shaft 14a, so that the one located therein Material enters the injection cylinder 11.

The slide 50 is actuated via a piston-cylinder unit 50a, the electrically or pneumatically via control lines 59,60 with a total with 53 designated control unit are connected. The electric or electromagnetic Part of this control unit 53 is connected to a switch 57 via a line 54, which is part of a control unit designated as a whole with 55. This The unit contains a camshaft 56 which is in operative connection with the switch 57 stands.

The bores 51 and 52 in the slide 50 are arranged so that at that position in which the bore 52 of the slide 50 is above the filling chute 14a, the bore 51 is located immediately below the outlet opening 16a of the material storage container 16 and is filled with this differently colored material. at a return of the slide into the position shown, the bore 51 passes above of the feed chute 14a, so that the material of the other color from the material storage 16 reaches the closing cylinder 11. With this device, it is therefore easier Way possible an alternating and simultaneously metered addition of different colored material in the plasticizing cylinder 12 to accomplish.

In the embodiment shown in Fig. 3 is on the plasticizing cylinder 11 another cylinder 72 connected at right angles, which has a bore 73 opens into the cylinder 11.

The screw 71 located in the cylinder 72 can rotate in it, however, it is not arranged to be longitudinally displaceable.

The material conveyed by the screw 71 is fed through a hopper 70 filled. This has a different color than that caused by the plasticizing cylinder 11 funded material.

The bore 73 is attached to the cylinder 11 so that the through this entering material reaches a region of the plasticizing cylinder 11 in which the screw 12 also has a circulating effect on the material conveyed therein is exercised.

Instead of the rotary screw 71 according to the embodiment shown a pusher screw corresponding to the plasticizing screw 12 can also be selected. Furthermore, instead of the thrust screw 12, a rotary screw can be used for extruder operation Find use, while then the secondary cylinder 72 with a weft or rotary screw 71 can be equipped.

In the Ausfüiirungsbeispiel shown in Fig. 4 is a screw feeder 80 combined with a rotary screw 81, with both cylinders 72 and 11 connecting bore 83 a rotary valve O2 is arranged. The through hole 82a of the rotary valve 82 is shown here in the closed position.

It can be introduced by means of control elements not shown in detail of the differently colored material located in the cylinder 8p is brought into the open position be, whereby this material is located in the plasticizing cylinder mix different colored material.

The invention can be applied with the same advantage to an axially fixed Rotary screw instead of the plasticizing screw 12 shown, with grained Strand parts are produced in an extruder.

Claims (13)

Claims 1 Process for the production of multicolored molded parts from plastic Masses by means of machines with screw plasticizing, whereby the plasticizing screw at least two different colored material streams are fed, characterized in that that the unification of the separate material flows can only be achieved in the working area of the Plasticizing screw makes. 2. The method according to claim 1, characterized in that the throughput quantities the different colored material flows according to the desired grain effect can be changed by known control devices. 3. The method according to claim 1 and 2, characterized in that the Alternating feeding of the different colored material streams into the plasticizing cylinder he follows, 4. The method according to claim 3, characterized in that the times for the alternating supply of the different colored material streams kept adjustable are. 5. The method according to claim 4, characterized in that between The waiting times that can be set for the feed times of the individual material flows are observed will, 6. The method according to claim 1, characterized in that the different colored Material flows with regard to those characteristic for the plasticizing and injection molding process Sizes, z, B. in terms of material temperature, speed or the like, held differently or influenced, 7. Device for Implementation of the method according to claim 1 or one of the preceding claims, characterized by a plasticizing cylinder (11> and plasticizing screw (12) existing plasticizing unit, with the plasticizing cylinder bores (13; 73, 83) for receiving one or more different colored material streams in plasticized or unplasticized state directly in the working area of the plasticizing screw (12). 8. Apparatus according to claim 7, characterized in that for Feeding a further material flow to the plasticizing cylinder at least one further Plasticizing screw (71; 80) is provided, which is at an angle to the main plasticizing screw (12) is arranged and opens into this. 9. The device according to claim 8, characterized in that the Plasticizing screws are different in terms of their axial drive by E.g. an axially displaceable pusher screw with an axially fixed extrusion screw or vice versa. 10. The device according to claim 7, characterized in that the Plasticizing unit 111, 12) with at least two material containers (15, 16> in connection stands, each of which can be operated from the outside, appropriately automatically controllable Locking devices (1.7,18) are assigned. 11. The device according to claim 10, characterized in that the Closure devices consist of slides that are controlled by means of control devices the openings (15a, 16a) of the mass container alternately or periodically open. 12. The device according to claim 11, characterized in that the Slider receiving elements (51,52) for receiving a metered amount of material having a corresponding material container. 13. The device according to claim 8, characterized in that in the Bore (83) a controllable rotary valve (82) is arranged.