DE3024229A1 - Reconstituted thermoplastic sheets prodn. - in which assorted film waste is reduced, mixed, hot-pressed between cauls and cooled to release - Google Patents

Abstract

Thermoplastic materials, and partic. waste, is reconstituted into sheets by measuring out, distributing over an area, and densifying hot. The material is reduced and laid between two metal cauls at over 120 deg.C (pref. over 200 deg.C); it heats up and is pressed at 6 kp/cm2, air is removed, and the controlled-dimension sheet is cooled under pressure to permit release from the cauls. Various polymers can be used without binder, prods. are dense, rigid, physiologically neutral sheets suitable for use in drainage/soil improvement, process can use e.g. bag scrap. In the plant a conveyor passes to and through a hot and a cold press, both working at over 6 kp/cm2. Different kinds of scrap thermoplastic materials are reduced and mixed together beforehand, fed on to a bottom caul, and distributed evenly. A second press caul is laid on top. The conveyor moves this press load stepwise into the hot press, occluded air in the material escapes from between its (e.g.) strips. The cauls adhere to the densified sheet produced, and a subsequent cooling station is therefore necessary for their release.

Description

Process and device for the production of plastic

plates The invention relates to a method for producing plastic plates made of thermoplastics, in particular plastic waste, the thermoplastic The starting material is dosed, distributed over the area and compacted with the use of heat will. The invention also shows an apparatus for carrying out the method with a conveyor for the starting material and the resulting plastic sheets, from a feed station for the starting material through a heatable press station leads.

Such a method is known from DE-OS 2,128,899.

There, thermoplastic plastic waste in particular Heat- and sound-insulating, vibration-damping and room-delimiting profiles are produced. For this purpose, the thermoplastic plastic waste, i.e. the starting material, placed one on top of the other, dosed and distributed over a wide area. The material is up compressed to some extent and pierced by heated needles so that tubular melts of the plastic around the heated needles and arise transversely to the direction of extension of the porous plate. After interrupting the supply of heat to the heated needles and the occurrence of cooling and solidification of the thermoplastic material, the compression is ended and the insulation mat taken out of the device. The individual plastic waste is only there connected to each other by the tubular welds. It creates a light, porous mat with limited uses. Is advantageous with this Process that an adhesive or a binder is not required because the thermoplastic plastics are melted locally.

When panels of comparatively greater strength are produced should, the number of tubular melts is increased, but always a considerable part of the mat remains unconnected.

The strength properties of such a mat-shaped plate are very limited. In addition, the mat is both air and water permeable, see above that they are not used for purposes in which the tightness plays a role is useful.

It is also known, dense plastic sheets with greater strength made of low-pressure polyethylene.

These panels are flexible depending on their thickness. You will be spread out Flat nozzles extruded, whereby new material is used in granulate form. These Production is comparatively complex and expensive. It is the same with production known from Plexiglas to pour this between two glass plates or also to extrude through nozzles. Here, too, new material is used.

The invention is based on the object of a method and a device to show the type described above, with the plates or molded body thermoplastic plastic, in particular plastic waste, using also different types of plastics and types of plastics without the use of binders to produce efficiently, in such a way that dense, relatively stiff panels with good mechanical strength arise, which on the one hand physiologically neutral and on the other hand Should be machinable, so that they are particularly suitable for use in hydraulic engineering and dyke construction and can be used for soil improvement.

The inventive method is characterized in that the thermoplastic raw material crushed between two metal ones Press plates are used, over the entire surface to a temperature of more than 1200C, preferably above 2000C, heated and under pressure of more than 6 kp / cm2 Removal of the air is compressed and that the heated calibrated plastic plate is cooled with the adhering press plates under pressure, so that the plastic plate detached from the press plates. It is essential that the thermoplastic starting material crushed and distributed over a large area, i.e. dosed on a first metal press plate is applied and covered with a second metal press plate. Through the Applying an appropriate temperature and a relatively high pressure will do that Starting material heated over the entire surface and compressed so that the air between the shredded starting material escapes. The cooling then takes place at which it is essential to apply pressure here too in order to prevent the plates from warping to avoid. As a result of cooling, the melted thermoplastic solidifies Plastic mass instead. At the same time, these shrinking processes result in loosening and causing the metal press plates to be lifted off the plastic plate thus obtained. The plastic plate is airtight and watertight, can be mechanically, for example machining and processing by sawing, drilling, filing, etc. The mechanical strength and flexibility results depending on the panel thickness.

In the case of continuous, cyclical production, the heating takes place and the cooling of the plastic plate immediately one after the other in different Stations so that one station is warrry and the other station is kept cold can.

This is the only way to ensure efficient production.

When using different types and types of plastic, the Dwell time and heating adjusted accordingly. For example, polyethylene melts depending on the type at 130 to 1400C. Polypropylene also has different melting temperatures in the range between 166 and 2000C. It goes without saying that melting temperature and residence time be coordinated.

The thermoplastic starting material is preferably made gradually heated, the temperature being increased in stages.

The starting material of the plastic plate is also matched to this compacted in stages until the final wall thickness of the Plastic plate. This special process step makes the necessary Plasticization is also achieved inside the plate and the plastic material becomes in this plastic state, in which individual parts more or less plasticized are pressed together and pressed, so that an intimate connection is also different Types and types of plastic among each other.

When the plastic plate cools down, it is essential that this cool down to be done so far until the tension-free state is reached, thus just Plates result.

It is also useful, the comminuted starting material before Mix the dosage so that there is approximately a homogeneous distribution in the plate. If the raw material currently being used changes, the temperature will also change and the length of stay adjusted.

The device for carrying out the method is identified in that immediately after the heatable press station, a second cooled one Press station is provided. This makes it possible to work in cycles, whereby it goes without saying that both press stations are synchronized with one another in cycles, such that a just heated and compacted plate in the first press station can be moved into the open second press station, where it is pressurized and cooled in the process, so that the plastic plate the required straightness and distortions are avoided.

The feed station can expediently have a shredding machine for the thermoplastic starting material must be connected upstream.

This has the advantage that a more uniform and a more homogeneous Distribution of the starting material over the plate length and width is achievable. As a rule, the starting material changes, i.e. waste from different types of plastic and types are used, it is even better if between of the shredding machine and the feeding station is equipped with a mixer Storage for the crushed starting material is provided, so that the straight required starting material can be withdrawn from this memory. To this In this way, the transitions between the individual types of plastic are evened out, what a relief in terms of production and also a homogenization with regard to the manufactured product.

The metal press plates used within the device exist especially made of aluminum. Aluminum has sufficient strength and on the other hand a favorable high thermal conductivity. Between the metal press plates and mediating this the starting material is fed through the two pressing stations.

The invention is illustrated by means of an exemplary embodiment in the drawings and further described in the following.

1 shows a schematic side view of the device for carrying out the method, FIG. 2 is a schematic plan view of the device, Fig. 3 is a cross section through the starting material between the press plates and Fig. 4 shows a cross section through the plastic plate between the press plates, for example in the cooled press station.

The device shown in FIGS. 1 and 2 has a conveyor 1, which can consist of several, also differently designed sections and which leads to or through the two pressing stations 2 and 3. The press station 2 is heated. With it there are temperatures of more than 1200C in the starting material, preferably above 2000C, can be generated.

The press station 3 is cooled. Both press stations are for one print of preferably more than 6 kp / cm2.

Upstream of the device are a shredding machine, not shown here, a storage tank equipped with a mixer and a feeding and metering device, which connects to the conveyor 1.

During the manufacture of the plastic sheets, thermoplastic material comes into play Plastic material, in particular plastic waste, preferably in the form of plastic bags and bags are used. This is shredded in the shredder and transferred to memory. The memory is equipped with a mixer to make plastics Mix different types and types and thus the starting material, consisting made of film-like strips and tears, to be able to even out. This raw material 4 is dosed and distributed area-wise according to FIG. 3 on a lower press plate 5 given up. The press plate 5 is located at the beginning of the conveyor 1. The Starting material 4 is then covered with an upper press plate 6. The press plates 5, 6 are made of metal, preferably aluminum. It goes without saying that the size the press plates 5, 6 corresponds to the size of the press station 2, 3. Prepared in this way Sandwich packets from the two press plates 5, 6 and the starting material 4 arrive according to arrow 7 in cyclical movement of the conveyor 1 into the first pressing station 2. The heating takes place here and the compression, with the air escapes between the individual chips of the starting material 4. It arises a dense plastic plate 8, as can be seen from FIG. The Press plates 5, 6 firmly on this plate. During the next bar a newly prepared Sandwich package enters the press station 2, the previously located in this Package transferred to the second press station 3 and also put there under pressure. The cooling now takes place here, the plastic plate 8 solidifying and becoming the press plates 5 and 6 by cooling from the surface of the plastic plate 8 so that the next cycle after leaving the press station 3, the two Press plates 5, 6 released from the plastic plate 8 and this can be removed. Depending on the intended use of the plastic plate 8, mechanical division, for example a sawing process.

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Claims (10)

Method and device for the production of plastic sheets Patent claims: Process for the production of plastic sheets from thermoplastics, in particular plastic waste, where the thermoplastic raw material is dosed, is distributed over an area and compacted with the use of heat, characterized in that, that the thermoplastic starting material is crushed between two metal press plates is used, over the entire area to a temperature of more than 1200C, preferably over 2000C, heated and under a pressure of more than 6 kp / cm2 with removal the air is compressed and that the heated calibrated plastic plate with the adhering press plates is cooled under pressure, so that the plastic plate detached from the press plates. 2. The method according to claim 1, characterized in that at continuous cycle-wise production, the heating and cooling of the plastic plate immediately takes place one after the other in different stations. 3. The method according to claim 1 and 2, characterized in that the Dwell time and heating up when using different types of plastic and types can be adapted to this. 4. The method according to claim 3, characterized in that the thermoplastic The starting material is gradually heated and gradually up to the final wall thickness the plastic plate is compressed. 5. The method according to claim 2, characterized in that the cooling the plastic plate takes place until the tension-free state. 6. The method according to claim 1, characterized in that the crushed Raw material is mixed before dosing. 7. Apparatus for performing the method according to claim 1 to 4, with a conveyor for the starting material and the plastic sheets from a feed station for the starting material through a heatable press station leads, characterized in that immediately behind the heatable pressing station (2) a second cooled press station (3) is provided. 8. Apparatus according to claim 7, characterized in that the feed station a shredding machine for the thermoplastic raw material is connected upstream is. 9. Apparatus according to claim 7 and 8, characterized in that Between the shredding machine and the feeding station there is a mixer equipped with a mixer Storage for the shredded starting material is provided. 10. Apparatus according to claim 7, characterized in that metallic Press plates (5, 6), in particular made of aluminum, are provided between which and by means of which the starting material (4) through the two pressing stations (2, 3) to be led.