Method of producing a bioplastic granulate based on sunflower seed shells/sunflower seed hull material on the one hand and a plastic material on the other hand

Abstract

A method of producing a bioplastic granulate on the basis of sunflower seed shells or sunflower seed hulls. In the method, ground sunflower seed shells/sunflower seed hull material is provided, wherein the particle size is in the region of 3 mm or less, preferably in the region of 0.01 to 1 mm, preferably in the region of 0.1 to 0.3 mm. A plastic material is provided, which is compounded with the sunflower seed shells/sunflower seed hull material, wherein the compounding operation is preferably effected in an extruder, preferably a double-screw extruder. The compounded material is chopped at the end of the extruder section with a tool with the addition of water, wherein the water is at a temperature of preferably more than 50° C., preferably about 80 to 90° C., to cool down the compound material. During the compounding operation, the compounding material is subjected to atmospheric degassing and/or vacuum degassing.

Claims

1. A method of producing a bioplastic granulate on the basis of sunflower seed shells or sunflower seed hulls comprising the following steps: providing ground sunflower seed shell/hull material having a particle size of 3 mm or less; providing a plastic material; conducting a compounding operation in which the sunflower seed shell/hull material is compounded with the plastic material in an extruder to create a compounded material; and chopping the compounded material at the end of the extruder to create a compound granulate; wherein, during the compounding operation, the compounded material is subjected to atmospheric degassing, a vacuum degassing, or both; wherein the compound granulate is fed to a cooling and drying device in which a residence time of the compound granulate in the atmosphere is set for a predetermined period and the compound granulate is fed to the drying device at a temperature of more than 100° C. and the plastic granulate leaves the drying device at a temperature below 100° C.; wherein a first drying operation is carried out in which the sunflower seed shell/hull material is dried down a first amount prior to the compounding operation; wherein a second drying operation is carried out during the compounding operation in which the compounded material is dried down prior to chopping; and wherein a third drying operation is carried out in the cooling and drying device in which the compound granulate is dried down so that the produced bioplastic granulate has a residual moisture content of less than 1%.

2. The method according to claim 1; wherein a residence time of the compound granulate in the cooling and drying device is about 4 to 8 minutes.

3. The method according to claim 1; wherein, before being fed to the cooling and drying device, the compound granulate is fed to an additional drying device that is separate and distinct from the cooling and drying device, wherein the compound granulate leaves the additional drying device at a temperature of about 120-130° C. and with a relative moisture content of about 0.2% (±0.1%).

4. The method according to claim 3; wherein the additional drying device is a centrifugal dryer.

5. The method according to claim 1; wherein the compound granulate is fed to a classifying screen before it is fed to the cooling and drying device.

6. The method according to claim 1; wherein the extruder is subdivided into a plurality of zones.

7. The method according to claim 1; wherein the plastic material provided is a polypropylene (PP), polyethylene (PE), acrylonitrile butadiene styrene (ABS), or other known plastic material, which in the feed to the compounding process is in the form of a granulate or agglomerate.

8. The method according to claim 1; wherein the extruder is a double screw extruder.

9. The method according to claim 1; wherein the compounded material is chopped at the end of the extruder with a tool with the addition of water, wherein the water is at a temperature of more than 50° C.

10. The method according to claim 1; wherein the cooling and drying device is a spiral lift conveyor.

11. The method according to claim 1; wherein the sunflower seed shell/hull material is dried down a first amount prior to the compounding operation during grinding in a mill.

12. The method according to claim 1; wherein the second drying operation is carried out during the atmospheric degassing, the vacuum degassing, or both.

13. The method according to claim 1; wherein the third drying operation is carried out in the cooling and drying device so that the produced bioplastic granulate has a residual moisture content of less than 0.1%.

14. The method according to claim 1; wherein the third drying operation is carried out in the cooling and drying device so that the produced bioplastic granulate has a residual moisture content of less than about 0.05%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described hereinafter by means of embodiments by way of example illustrated in the Figures.

(2) FIG. 1 shows a first overview of the first part of a procedure or a structure for producing a bioplastic granulate according to the invention.

(3) FIG. 2 shows the second part as far as bagging of the bioplastic granulate produced.

DETAILED DESCRIPTION OF EMBODIMENTS

(4) It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, many other elements which are conventional in this art. Those of ordinary skill in the art will recognize that other elements are desirable for implementing the present invention. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein.

(5) The present invention will now be described in detail on the basis of exemplary embodiments.

(6) It will be seen from FIG. 1 that firstly sunflower pellets 1 are fed to the system. In that respect sunflower pellets are the shells of shelled sunflower kernels and those shells are pressed/compressed to form pellets.

(7) The moisture proportion contained in the sunflower shells in that case is still at about 10% but, as already mentioned, depending on the kind, harvesting conditions, degree of ripeness, storage conditions and so forth, can fluctuate, more specifically ±2 to 3%. The sunflower pellets are then fed to a mill 2 in which the sunflower shell material is ground to a desired particle size.

(8) During the grinding operation the shell material heats up (for example because of frictional heat) and in that case a large part of the moisture contained in the shells already escapes/evaporates so that the shell meal leaving the mill still has a moisture content of about 5% (±1%).

(9) The shell meal is thereafter passed to an extruder 3 which is subdivided into a plurality of zones, for example twelve zones in the example shown in FIG. 1.

(10) In the first zone a conventional plastic material granulate (or agglomerate) for example polypropylene (PP), of a predetermined particle size and with a predetermined (known) property, is fed to the extruder.

(11) In the extruder 3 which for example is in the form of a double screw extruder the actual compounding operation takes place, in which case the ratio of sunflower shells on the one hand and plastic material on the other hand is adjusted to a desired ratio of for example 50% to 50% or 35% shell material and 65% plastic (variations of 20%-70% shell material and 80-30% plastic material are possible) and thus the compound is homogenised and mixed in a desired ratio.

(12) During the compounding operation the temperature of the compound (that is to say the composite formed from sunflower shell meal and plastic) is about 180 to 220° C. (±10° C.). In that phase the compound is fluid. At those temperatures moisture further escapes from the shell material or compound and dehumidification or drying of the material is promoted in the extruder by for example atmospheric degassing 4 being carried out in one zone of the extruder and vacuum degassing 5 also being carried out if necessary in a further zone.

(13) By virtue of those steps, not only is the shell material further dehumidified but oil and fat constituents of the oil which under some circumstances are still present in the shell material are removed to a considerable extent from the shell material and conveyed out of the extruder by means of a blowing or suction device with exhaust air.

(14) At the end of the extruder the compounding material passes into underwater granulation 6. The water of the underwater granulation operation is in that case at a temperature of preferably more than 50° C., a temperature in the region of about 80 90° C. (±5° C.) is particularly suitable. In the hot pelletizing operation in the underwater granulation step the extrusion of the compound from the extruder is chopped (pelletized) by a rotating blade, that being effected under water. As already mentioned in that situation the water prevents the individual granulate bodies of the compound material, that are formed by the chopping operation, from sticking together, so that the compound material is ultimately present in the form of drops, balls, lenses, cylinders and so forth. At the same time the compound material is cooled down in the underwater granulation operation, but it is still at a temperature at the end of the underwater granulation step of about 130° (±10° C.).

(15) Finally the pelletized compound material is fed to a dryer, as shown in FIG. 1 a centrifugal dryer 7, and the material issuing from the dryer 7 is then a granulate which still has a residual moisture content of about 0.2% (+0.5%). Subsequently the material passes through a classifying screen 8 in which granulates which are too large or too small are removed from the flow of material. The material bodies which are separated off in that way are later recycled to the compounding process and can therefore be re-used.

(16) In the dryer, as shown in FIG. 1 the centrifugal dryer 7, the water clinging to the granulate bodies due to water pelletizing is removed by the granulate material being introduced into a centrifuge in which granulate bodies are separated from the outwardly passing water by means of a screen. If the removed water contains very small constituents of the bioplastic compound granulate material that can also be cleaned if required so that the water overall can be recycled to the circuit for renewed water pelletizing.

(17) It is to be emphasised at this juncture however that the centrifugal dryer 7 essentially involves the purpose of separating the bioplastic granulate from its surface water, that is to say the water which wets the granulate bodies on the outside due to the water pelletizing operation.

(18) At the issue from the centrifugal dryer the bioplastic granulate has an (internal) residual moisture of about 0.2% (±0.1%) and is substantially completely freed from the water supplied by the water pelletizing operation.

(19) Subsequently to the centrifugal dryer 7, as already described above, the bioplastic granulate passes through a classifying screen 8 in which the granulates which are too large or too small are removed from the flow of material. The granulates (material bodies) which are separated off in that way are later recycled to the compounding process and can therefore be re-used. Upon recycling the supplied material then forms fresh granulates, with the newly formed material, and thus is of dimensions corresponding to the dimensions desired for the granulates.

(20) Finally downstream of the classifying screen step the granulate material is transferred into a spiral lift conveyor—FIG. 2—in which granulate material which is still hot at over 100° C. is exposed to the atmosphere and therein on the one hand cooling of the material and on the other hand further drying of the granulate is then effected so that finally at the end of the spiral lift conveyor section there is still a residual moisture content of 0.05% relative moisture in the granulate.

(21) At the end of the spiral lift conveyor section the material temperature is still at about 50 to 70° C. and the bioplastic granulate according to the invention produced in that way can then be packaged in air-tightly welded bags. The packaging material, therefore for example the air-tightly welded bags, for the bioplastic according to the invention, is in that respect so designed that it represents a barrier to prevent the ingress of air moisture from the exterior so that even after storage of the bioplastic according to the invention in the bags air moisture cannot diffuse from the exterior into the granulates.

(22) It should be emphasised that the conveyor section between underwater granulation and the centrifugal dryer is as short as possible so that the material is resident there only for a few seconds, for example 5 to 15 seconds, which has the advantage that the material is fed from the underwater granulator to the centrifugal dryer as quickly as possible.

(23) That is particularly important when there are still relevant moisture components contained in the granulate and thus also in the shell material, for, when the temperature there is 120° C., it is also necessary according to the invention to afford the option of carrying out the residual drying operation within a short time, and the water clinging to the outside of the granulates is not to penetrate into the granulate and excessively greatly cool down the granulates.

(24) As already described at least one degassing step is carried out in the extruder, either atmospheric degassing or vacuum degassing. As already described in that case oil or fat constituents which under some circumstances are still present in the shell material are removed from the shell material and thus from the compound which is being formed. That removal is extremely advantageous in terms of the overall quality of the bioplastic granulate which is produced at the end, and in a first experiment it was already possible to provide that substantial oil constituents still present in the shell material could be removed in the extruder from the shell material and thus from the compound by the degassing operation. Substantial signifies at least 5 to 10%, with an increase in the time in the extruder, and in particular in the case of vacuum degassing it was also possible for the proportion of oil removed in the shell material to be increased to 30 to 50% so that as a result the bioplastic granulate produced according to the invention not only has an extremely low moisture content, as mentioned about 0.05%, but also a lower oil/fat content by virtue of the removal of oil/fat in the extruder.

(25) It should be emphasised that the oil and fat proportion in the sunflower shell material depends on many factors, for example also the choice of type of sunflower shell material, degree of crop ripening, and so forth. The method according to the invention ensures that, in spite of different oil and fat constituents at the outcome in the shell material finally a desired quality of the bioplastic material according to the invention is also achieved in regard to its oil and fat content without costly additional measures having to be undertaken for that purpose.

(26) The method according to the invention provides a bioplastic granulate which can be superbly implemented in an injection moulding tool in order to produce therefrom a plastic product of the desired dimensions. In that respect by virtue of the extremely low residual moisture content the injection moulding tools are treated gently and carefully and in particular are scarcely exposed to relevant oxidation.

(27) Finally the plastic product produced is also of first-rate uniform quality which is markedly better than plastic products which were hitherto produced from a bioplastic granulate. In particular the bioplastic granulate according to the invention can be used to manufacture plastic products which are of first-rate quality in regard to typical plastic parameters, in particular in regard to the modulus of elasticity, notch impact strength, surface smoothness and so forth.

(28) While this invention has been described in conjunction with the specific embodiments outlined above, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the inventions as defined in the following claims.