WO1991011316A1

WO1991011316A1 - Process and device for continuous manufacture of panels from a hot plastic moulding material

Info

Publication number: WO1991011316A1
Application number: PCT/EP1990/001840
Authority: WO
Inventors: Wilfried Ensinger
Original assignee: Wilfried Ensinger
Priority date: 1990-01-26
Filing date: 1990-11-02
Publication date: 1991-08-08
Also published as: DE4002214A1

Abstract

In a process for continuous manufacture of panels from a hot plastic moulding material, the moulding material is continuously extruded under pressure into a mould, where it solidifies. The plastic moulding material is extruded into a pressure-tight mould in the form of a multiple-strip press with advancing pressed strips, where it solidifies under pressure. A device for carrying out the process comprises a multiple strip press with two facing continuously circulating main strips, with an inlet and an outlet side, lateral strips of runners, which tightly seal the space between the main strips at the sides, and an extruder nozzle arranged at the inlet side and connected in a pressure-tight manner to the pressed strips or runners.

Description

Process and device for the endless production of sheets from a warm, plastic plastic molding compound

The invention relates to a process for the endless manufacture of sheets from a warm, plastic molding compound by continuous extrusion of the molding compound into a mold, the inner profile of which corresponds to the plate profile, and solidification of the molding compound in the mold. The invention further relates to a device for performing such a method.

During continuous casting in - possibly cooled - sliding molds, the plastic molding compound used must be kept under pressure and conveyed because of the contraction in volume of the gradually solidifying zones of the melt, so that in particular no voids are formed in the core of the finished product. The effect of the pressure creates a frictional force between the extruded profile and the sliding form, which can easily lead to cracks and other surface damage to the finished product, as well as internal stresses. In order to avoid these deficiencies, the continuous casting process has hitherto only been carried out at relatively low ejection speeds and the finished products have been subsequently tempered if necessary. It is an object of the invention to improve a generic continuous casting process for the continuous production of plates in such a way that the end product has no surface damage and is stress-free, and yet it is possible to work with relatively high ejection speeds.

The object is achieved in that the plastic molding compound is extruded continuously and under pressure into a pressure-tight mold-forming multiband press with leading press belts and solidified there under pressure.

A device for carrying out this method comprises a multi-belt press consisting of at least two opposing, endlessly rotating main belts with an inlet and outlet side, lateral belts or skids which seal the space between the main belts laterally and one arranged on the inlet side, extrusion nozzle connected pressure-tight to the belts or skids.

The following description of preferred embodiments of the invention, together with the accompanying schematic drawing, serves for further explanation. It shows:

FIG. 1 shows a sectional side view of a multi-belt press with an extrusion nozzle connected pressure-tight on the inlet side; FIG. 2 shows a sectional top view of the arrangement from FIG. 1;

Figure 3 is a sectional view taken along line 3-3 in Figure 1;

Figure 4 is a sectional view taken along line 4-4 in Figure 1;

FIG. 5-6 solidification lines of a plastic molding compound conveyed in the multi-belt press;

Figure 7 shows a modified from Figure 1

Arrangement with an extrusion nozzle and having several outlet openings

FIG. 8 schematically shows a modified implementation of the method according to the invention.

Figure 1 shows schematically in section a double or multi-belt press 1 with two upper rollers 2, 3 and two lower rollers 4, 5 around which endless press belts 6 and 7 are guided. At least one of the rollers 2, 3 and 4, 5 is driven and heated by a motor, so that the press belts 6, 7 are heated and circulate continuously. A reaction space 8 is formed between the lower run of the upper press belt 6 and the upper run of the lower press belt 7.

In the area of the rollers 2 and 4 forming the inlet side of the arrangement, the leading press belts 6, 7 are connected an extrusion nozzle 9 is connected in a pressure-tight manner and is connected downstream of an extruder (ram extruder, screw extruder), for example. A warm, plastic molding compound, for example a thermoplastic, a thermoset, an elastomeric plastic or a mixture of such plastics, is introduced into a nozzle space 12 via an inlet opening 11 of the extrusion die 9. The molding compound 9 leaves the extrusion die via an outlet opening 13 which lies between the rollers 2 and 4.

As can be seen from FIG. 2, the reaction space 8 located between the main belts 6, 7 is laterally closed by two further endless belts 15, 16 which run around rollers 17, 18 and 19, 20, respectively. At least one of the rollers 17, 18 and 19, 20 is driven by a motor and optionally heated. The arrangement is such that the lateral bands 15, 16 bear against the main bands 6, 7 in a pressure-tight manner and thus close the reaction space 8 laterally in a pressure-tight manner.

As FIGS. 1 and 2 show, the extrusion nozzle is designed in a projecting manner at its outlet opening 13 in such a way that the lateral outer boundary of the extrusion nozzle 9 closely conforms to the rollers provided on the inlet side of the multi-belt press 1 or the press belts lying on these rollers. The edge edges of the extrusion die 9 protruding between the rollers on the inlet side of the multi-belt press can be formed elastically, for example using suitable thermoresistant plastics, so that they close to the plastic molding compound under the pressure of the extrusion die 9 Put on press belts 6, 7, 15, 16. The axes of rotation of the (large) rollers 2, 3, 4 and 5 are usually horizontal, while the axes of the (small) rollers 17, 18, 19, 20 are usually aligned vertically.

As can further be seen from FIGS. 1 and 2, known pressure plates 21 are provided on the rear sides of the press belt sections delimiting the reaction chamber 8, which hold the belts in mutual sealing and exert the necessary pressing pressure on the molding compound leading in the reaction chamber 8. The pressure plates 21 can be heated or cooled in a manner known per se. Normally, the printing plates adjacent to rollers 2, 4 and 17, 19 are heated, while the printing plates provided on the outlet side of the multi-belt press (rollers 3, 5, 18, 20) can be cooled. However, it is also possible to provide heated printing plates again in the area of the outlet side in order to anneal the finished product after cooling.

FIG. 3 shows a sectional view along the line 3-3 in FIG. 1. In this figure, one can also see in particular the plastic molding compound 22 enclosed and pushed forward in the reaction space 8, which is a plate-shaped strand with relatively large, upper and lower broad sides 23 or 24 and relatively small narrow sides 25 or 26 forms. After leaving the multi-belt press 1, this plate-like strand can be divided into individual plates or sheets.

FIG. 4 shows in a view along line 4-4 in FIG. 1 the mouth of the extrusion nozzle 9 between the Rollers 2, 4, 17, 19 and the adaptation of the outer nozzle shape to the roller contour.

In the described embodiment of a multi-belt press, the main belts 6, 7 are closed laterally by the belts 15, 16 in a pressure-tight manner. It is possible to replace these lateral bands 15, 16 with stationary skids. In this case, undesirable friction per se arises on the narrow sides of the extruded and advanced sheet-like strand, but since the narrow sides of the strand are considerably smaller than its broad sides, this relatively small friction can be accepted under certain circumstances become.

In extrusion and thus also in the method according to the invention, the solidification process of the plastic molding compound in the mold (multi-belt press) proceeds only slowly from the outside inwards, the boundary between the solidified region and the melt taking on a conical shape 10 (FIG. 1). FIG. 5 schematically shows the reaction space 8 formed by the belts 6, 7, 15 and 16 and the self-contained curves 27 which represent the conical shape of the interface between the solidified area on the outside and the melt located on the inside. The solidification progresses through uniform cooling from the outside inwards and leads to undesirable residual compressive stresses occurring in the outer region of the extruded profile and undesirable tensile residual stresses in the inner region of the extruded profile.

According to FIG. 6, these internal stresses can be applied to the heated pressure plates 21 Avoid side straps 15, 16. In this case, the plastic molding compound remains in the melt state in the region of the lateral bands 15, 16 and only solidifies in layers from the top or bottom to the inside. It has been found that internal stresses on the heated side areas of the molding compound 22 largely compensate. In this way, a very low internal stress, plate-like extrudate solidified from the broad sides in layers.

In FIG. 7, parts which correspond to one another are designated by the same reference numerals as in FIG. 1. The difference between the embodiments according to FIGS. 1 and 7 is that the extrusion nozzle 29 has not only one but two outlet openings 31 and 32 which are located one above the other, so that in particular different plastic molding compositions in two. Layers were placed one above the other in the reaction space 8 between the belts 6, 7 and thus laminated plates or sheets can be produced. Instead of two outlet openings, it is also possible to provide more than two such openings on the nozzle 29.

When the method according to the invention is carried out with the aid of the devices described, the warm and plastic plastic molding compound (melt) emerging from the extrusion die 9, 29 is introduced continuously and under pressure between the leading belts 6, 7, 15, 16 by taken along and specifically cooled via the plates 21, so that practically no friction occurs at the lateral boundaries of the extruded profile strand, which could lead to undesired surface defects of the extrudate and internal stresses thereof. The multiple belt press is so long that the extrudate solidifies in it to the desired profile and exits at the outlet side of the press. The consolidation can be accelerated by cooled pressure plates 21. The solidification can also be accelerated by spray or water bath cooling downstream of the multiple belt presses.

The amount of molding compound introduced per unit of time from the nozzle 9, 29 between the press belts 6, 7, 15, 16 and the advance speed of these belts are matched to one another in such a way that there is practically no relative movement between the molding compound and the belts .

Plastic compositions suitable for carrying out the process according to the invention can consist, for example, of: polyamide, polyethylene, polypropylene, polycarbonate, polymethacrylate, polyamideimide, polyether ketone, polysulfone, polyurethane, saturated and unsaturated polyester, epoxy resin, phenolic resin, melamine resin, polyimide and polytetrafluoroethylene and Mixtures of these.

Reinforcing materials, for example glass, carbon, aramid, metal and natural textile fibers, chalk, silicate, mica, graphite, molybdenum disulfide, can be introduced into the plastic molding composition.

Furthermore, it is possible to allow a film, a mat or the like to flow into the reaction space 8 in a pressure-tight manner on the inlet side of the multi-belt press between the belts 6, 7 wrapping around the rollers 2, 4 there and the outer boundary of the nozzle 9 , so that an end product coated on the broad side surfaces results. Such a mat can, for example, consist of glass fibers.

When using press strips 6, 7 structured on the outside (plastically patterned), according to the invention it is also possible to produce plates with a correspondingly structured surface.

Structured surfaces on the plate profile produced according to the invention can also be produced by applying correspondingly superficial profiled sheets to the press belts, which are taken along by the press belts and between which the plastic molding compound is introduced.

By adjusting the distance between the rollers 2, 3 on the one hand and the rollers 4, 5 on the other hand and thus between the press belts 6 and 7, plates of different thicknesses can be produced. In this case, the extrusion dies 9, 29 are formed in a manner known per se from a plurality of parts which are adjustable relative to one another and which allow adaptation to the changed distance between the press belts 6 and 7. In particular, the extrusion die 9, 29 can be designed such that the cross section of the die outlet opening can also be adjusted in height as a function of the set spacing of the main belts.

The same applies to the adjustability of the outlet cross section of the extrusion nozzle in the transverse direction, that is to say in width, this adjustment taking place as a function of the set spacing of the lateral belts (or skids) if these are arranged between the main press belts 6, 7 and lie with their side edges sealed against these belts.

By appropriately designing the extrusion die 9, 29 in a manner known per se, the pressure under which the molding compound is solidified in the reaction chamber 8 can also be set.

It is advantageous if the surfaces of the extrusion die 9, 29 and the press belts 6, 7, 15, 16 that come into contact with the plastic molding compound are designed such that the molding compound does not adhere to them. For example, these surfaces can be coated with polytetrafluoroethylene. A lubricating mist can be applied to the outside of the press belts.

FIG. 8 schematically shows a device for carrying out a modified method according to the invention. As shown, the molding compound 22 is applied to the lower main belt 7 without pressure on the inlet side of the multi-belt press 51, that is to say in the region of the rollers 2 and 4, without using a pressure-tightly connected nozzle. The multi-belt press 51 is otherwise designed as shown in FIG. 6, that is to say heatable pressure plates 21 are provided on the rear sides of the side press belts 15 and 16, so that the molding compound 22, as explained above, is layered in the region of the melting cone 10 stiffens. As FIG. 8 shows, in the foremost area, that is to say at the tip of the melting cone 10, there are those provided pressure plates 21 arranged obliquely, so that the main bands 6, 7 then initially wedge-shaped and then again parallel to each other, but with a smaller distance. In this way, molding compound applied freely and without pressure is first put under pressure only at the end of the melting cone 10. There, the viscosity of the molding compound has already increased so much by cooling that pressures applied there can no longer propagate toward the inlet side of the multi-belt press 51. As a result, the molding compound solidifies from the tip of the melting cone 10 under further advance under pressure and shows essentially the same properties in the finished state as if it had been introduced under pressure into the multi-band press with the aid of a pressure-tightly connected eccentric nozzle. The embodiment of the method according to the invention on which FIG. 8 is based is that the molding compound is first introduced without pressure, but is heated and selectively cooled laterally, as shown in FIG. 6. The main belts 6, 7 and the pressure plates 21 are first arranged in a wedge shape in the foremost region, that is to say at the end of the melting cone 10, so that the molding compound then solidifies under pressure as a result of the constriction formed thereby.

Claims

Patent claims

1. Process for the endless production of sheets from a warm, plastic plastic molding compound by continuous extrusion of the molding compound into a mold under pressure, the inner profile of which corresponds to the plate profile and solidification of the molding compound in the mold, characterized in that the plastic Molding compound is continuously extruded and under pressure into a multiband press forming a pressure-tight mold with leading press belts and solidified there under pressure.

2. The method according to claim 1, characterized in that one uses a molding compound made of thermoplastic, thermosetting elastomeric plastics or mixtures of such plastics.

3. The method according to claim 1, characterized in that one uses a plastic molding compound reinforced by reinforcing and / or fillers.

4. The method according to claim 1, characterized in that one can run together with the plastic molding compound endless reinforcing elements into the multi-belt press.

5. The method according to claim 1, characterized in that by using structured press belts plates manufactures according to structured surface.

6. The method according to claim 1, characterized in that for the production of largely stress-free plates, the plastic molding compound is heated on the narrow sides of the multi-belt press in such a way that the solidification of the molding compound takes place from the surfaces of the broad plate sides to the plate center The molding compound on the narrow sides of the board initially remains plastic and tensions in this area can even out.

7. The method according to claim 1, characterized in that for the production of plates with a profiled surface, the plastic molding compound is applied to sheets taken from the multiple belt press, which are profiled accordingly.

8. The method according to claim 1, characterized in that the plastic molding compound is first introduced without pressure into the multi-band press and pressure is only applied at the end of the melting cone forming in the mass.

9. Device for performing the method according to one of claims 1 to 7, characterized by an at least two opposite, endlessly circulating Haupt¬ belts (6, 7) comprising multi-belt press (1) with inlet and outlet side, by side belts (15, 16) or skids, which close the reaction space (8) between the main belts (6, 7) laterally, and are connected by a pressure-tight arrangement on the inlet side to the press belts (6, 7, 15, 16) or the skids Extrusion nozzle (9, 29).

10. The device according to claim 9, characterized in that the main belts (6, 7) and the lateral belts (15, 16) and skids by heating and cooling devices (21) can be heated or cooled in some areas.

11. The device according to claim 9, characterized in that the outlet cross section of the extrusion nozzle (9, 29) is adjustable in height depending on the set distance of the main belts (6, 7).

12. The apparatus according to claim 9, characterized in that the outlet cross section of the extrusion nozzle (9, 29) is adjustable in width depending on the set distance of the side bands (15, 16) or skids.

13. The apparatus according to claim 9, characterized in that the extrusion nozzle (29) for the production of multilayer plates has a plurality of separate outlet openings (31, 32) for plastic molding compounds or reinforcing materials.

14. An apparatus for performing the method according to claim 8, characterized by on the rear sides of the main belts (6, 7) arranged pressure plates (21) in the forward direction of the molding compound (22) only from the end of the melting cone forming in the compound (10) are effective, and by means of heatable pressure plates (21) arranged on the rear sides of the side bands (15, 16).