CA2350760A1

CA2350760A1 - Granulate and method and device for the production thereof

Info

Publication number: CA2350760A1
Application number: CA002350760A
Authority: CA
Inventors: Gerhard Jakwerth
Original assignee: Individual
Current assignee: FLZ FASERLOGISTIKZENTRUM GmbH
Priority date: 1998-11-12
Filing date: 1999-11-12
Publication date: 2000-05-25
Also published as: EP1128941A1; CZ20011634A3; HUP0104341A2; PL348146A1; AU1975800A; DE29920772U1; BR9916604A; ID30227A; WO2000029183A1; SK6482001A3; WO2000029183A8; DE19956164A1

Abstract

The invention relates to a granulate and a method and a device for the production thereof. The aim of the invention is to provide a granulate on the basis of regenerative raw materials which is suitable as a material for injection molding and which is widely variable with respect to its mechanical and other physical properties due to the introduction of additives. The inventive method provides a means for producing the granulate without specifically pre-treating the plant parts used. A device is provided for carrying out the inventive method which device may consist of a pre-granulator and a final granulator or only of a pre-granulator. An especially clean-cut granulate can be obtained by the various configurations of the final granulator which can be equipped with counter-rotating matrices or with matrices that rotate one inside the other.

Description

A Granulate, a Method and a Plant for its Manufacture Description The invention concerns a granulate, a method and a plant to manufacture it according to the main terms of the claims 1, 11 and 21.
It is a well-known fact that the use of fibre composites in the manufacture of interior lining parts is widespread in the automobile construction industry. The use of natural plant fibres to reinforce plastics instead of traditional glass fibres is an economic and ecological alternative.
Until now, natural fibres accepted as suitable for the reinforcement of plastics and biopolymers are, in particular, bast, hard and leaf fibres such as flax, hemp, jute, sisal, ramie, yucca, wood, curano fibres and banana plant fibres. However, the use of these fibres involves various fibre pulping treatments., such as the mechanical processing of fibres in the rocker, during which the fibres are freed from wood content, or the pre-treatment of fibres in the oiler, rendering them suitable for mixing in further processing. It is common practice to introduce the natural fibres into the plastic in mat formation. The raw material for the composite consists of two different types of fibres: the polypropylene fibre serving as a die; the reinforcing fibre, e.g. flax fibres in the form of pressed bales, tapes or rovings.

_ It is also common knowledge that plastic processing technology is used to manufacture plastic fibre granulates, either for joining with textile mesh (DE
4412636 ) or for processing into a composite in the extruder together with the non-granulated natural fibre contents in the form of rovings or tapes.
The use of extruders for the plastification of plastic fibres generally has the disadvantage that the additional processing stage of extruding requires such high investment and electricity costs that products manufactured in this way are no longer economically viable. Furthermore, the fibres which are to be plastified must be subjected to an additional temperature load, at least equivalent to the melting point of the plastic content in question, resulting in greater odour emission and lower stress values. In the extruder, the fibres are shortened to very disparate lengths, which cannot be directly controlled, leading to a significant segregation of the fibre components, when injecting parts with different wall thicknesses. In large-scale production, the use of the extruder for natural fibres in common in-feed forms such as rovings, tapes and piles is very limited, owing to the tendency of some types of fibre to break in dry conditions. A
further disadvantage of processing natural fibre in the extruder is that, should a malfunction occur in the feeding-in area, the fibre content in the screw cannot be adjusted because of the first-in first out principle on which the extruder is based.
It is known from DE-A1 26 39 470 that granulates which contain natural, animal and/or mineral fibres and/or synthetic fibres can be processed into solid moulding bodies by drying in the presence of a binder and, if necessary, by additional application of pressure.

DE-U 1 G 94 09 906 describes a cutter for the fine crushing of pre-crushed matter, such as plastic waste, wood or paper. The principle on which it works is based on a single-stage cutting system, in which the pre-crushed matter is fed into a cutting area between a fixed and a rotating knife edge, where it is then crushed purely through cutting processes. The matter to be crushed must be fed in in a dry condition. To avoid bonding when the plastic pieces are crushed, the cutter is cooled by an installed cooling facility.
The aim of the invention is therefore to produce a granulate based on renewable raw materials, suitable as an injection moulding material, whose versatility of mechanical and further physical properties is increased by the introduction of additional substances.
The invention further aims to create a method and the necessary equipment to produce a granulate whose plant components require no pre-treatment.

The solution for the problem is achieved by the features described in claims 1, 9 and 21.
Parts manufactured from the invented granulate offer special mechanical advantages, as the plant fibres attain a fibrillous consistency if the process is followed as prescribed.
Further advantageous developments are described in the sub-claims listed below.

As stated in claims 2 and 3, it is possible to produce granulates in which extremely diverse materials may be added to the plant fibres in particularly advantageous proportions, following the invented process S
The invented granulate described in claim 2 is particularly light, as it may consist of up to 98$ plant fibre. The fibrillous cohesion of the plant fibres is effected by contained binding agents and/or added substances.
Further developments as specified in claim 3 permit the addition of thermoplastic substances. It is particularly advantageous to employ thermoplastic polymers -especially polypropylenes and/or polyethylene, as described in claim 5 and 6.
Thermoplastic substances in the form of recycled synthetics may also form large proportions of the granulate composition.
As may be inferred from claim 10, it seems logical to structure the granulating process in two stages. It may be an advantage to mix in further additional substances between the first and second stages of granulation.
A further advantage of the invented process is, as described in claim 11, that plant components of raw material mixtures require no pre-treatment, but may be immediately introduced into the process, in a lightly pre-crushed or uncrushed state.

The choice of granulating parameter, according to claim 13, means that the plant and /or fibre parts may be most advantageously crushed with the addition of water, even to a fibrillous form.

Creating the optimal pressure level is achieved by following claims 14 to 17, combined with developing the pressing channel of the die according to claim 30.
Expanding on claim 17, the pressure level may be modified by changing the spacing between the counter-rotating die, i.e. adjusting the spacing between the die and the roller.
As described in claim 18, thermoplastic substances such as polypropylene and/or polyethylene may be added, as well as common additional substances such as colouring agents, bonding agents, flame-retardants, fillers and anti-biotic agents, so that the preserved granulates are immediately ready for application in processes such as injection-moulding. The finished products are hereby produced without additional post-processing.
A particular advantage of this process is that, using the device described in claim 21, all natural fibres and their mixtures can be utilised. The use of a pre granulation unit and final granulation unit makes further fibre-pulping treatments unnecessary, which means that all known natural fibres are suitable for processing.
Developing the claims of claim 22 in combination with claims 23. 24 and 30, the cost-efficient production of pre-granules with a high plant fibre content is possible.

A particularly clean granulate, suited to further processing in the injection moulding machine, is obtained by the especially advantageous output of the final granulation unit , as described in claims 25 and 28.
Further details regarding the minimum distance, the die diameter and clearing installations are described in claims 26, 27 and 29.
The granulate produced according to the invented process using the invented equipment, may be used to produce articles such as very light-weight composites, which satisfy mechanical requirements of tensile strength, bond strength, breaking and fissure strength and are extremely environmentally friendly as they can be recycled. Such products lend themselves to the manufacture of car parts made entirely from natural fibres, such as the complete interior including the roof lining, door panelling, interior and exterior side parts, seating components, dashboards, pillars etc.
Further advantages of the invention are the simple processing of the plant matter and the possibility of using all types of plant materials and their mixtures, while making essential steps in traditional production processes redundant and maintaining or expanding the areas of application of the granulate. The invented process means that the fibres mostly require no pre-treatment, irrespective of whether the fibres in question are long, short or simply straw.

Plastification of the fibres using the extruder method is also made unnecessary. The highly concentrated granulates produced may be recycled in combination with other substances, such as plastics in injection moulding processes, to form other products The diagrams below illustrate the invention in greater detail.
Fig. 1 A combination of pre-granulation unit and final granulation unit in a schematic sectional view.
Fig. 2 Diagram of pressure distribution in various roller-profiles Fig. 3 Pressing channel structure a) for compressable raw material b) for highly compressable raw material c) for highly concentrated fibre granulate Fig. 4 Diagram showing the principle of the final granulation unit with its co-rotating die Fig. 5 Detail of co-rotating die with drive Fig. 6 Sectional view of co-rotating die with drive Fig. 7 Structure of a final granulation unit with co-rotating die Fig. 8 Detail of co-rotating die with openings and pressing channels g _ Fig. 9 Structure of a final granulation unit with parallel die Fig. 10 Sectional view of counter-rotating die Fig. 11 Schematic diagram of final granulation unit with counter-rotating die and Fig. 12 Detail of counter-rotating die with opening and pressing channels The invented device shown in Figure 1 is composed of a crushing unit 216 and a final granulation unit unit 211. The crushing unit 216 has in-feeds 201, 202 and 203, through which the raw materials, which must be pourable, are directed to mixing chamber 215. All soft raw materials such as mixtures of various plant components, individual types of plant fibre and foil granulates from recycled materials are directed through feed 203. Feeds 201 and 202 are used for hard raw materials such as colouring agents, bonding agents and fillers, e.g. titanium dioxide and other metals and their alloys. High-pressure nozzles 204 and 205 line the circumference of the pre-granulation unit.. 216 so that they project into the mixing chamber where the introduction of water or water steam is possible. The introduced water may contain various additives, such as agents to counter the formation of mould, odour and bacterial infestation, or flame-retardants. For structural reasons, the high-pressure nozzle 205 is an angular nozzle.

The fed in raw materials collect on a baffle plate 206, shaped as a sharp cone. The resulting vorticity means that the fed-in raw materials are more thoroughly mixed.
Underneath the baffle plate 206 is a common flat bed die press, which consists of a perforating die 209 on which the roller 208 rolls off, which is, in turn, secured with a clasp nut 207. The material in the mixing chamber 215 is pressed through the pressing channel 217 of the perforated die 217 by the Roller 208. The pressing channel 217 and the surface of the Roller 208 display a newly invented structure. The surface of the roller 208 has a sawtooth profile. The higher the proportion of plant fibre in the raw material, the steeper and deeper are the flanks of the sawtooth profile. The sawtooth profile means that the material is cut with far greater force and therefore mixed and crushed more intensively.
The build-up and distribution of pressure effected by a sawtooth profile is compared to that effected by the common symmetrical profile in Figure 2. This clearly shows that far less pressure is built up by a weakly defined, symmetrical profile. (Figure 2, pressure chart la) Pressure increases with a more clearly defined symmetrical profile (Figure 2, pressure chart 2a) and is highest with a sawtooth profile (Figure 2, pressure chart 3a).
The Roller 208 rolls on the perforated die 209, which is equipped with pressing channels 217, whose number and diameter play a significant part in determining the specific quality of the innovative granulate.
The geometrical form of the pressing channels 217 influences the development of heat and thereby also the temperature and thickness of the granulate produced.

Fig. 3a, b and c show different innovative geometrical shapes of the pressing channels 217. A reproducible high quality with different raw materials is achieved by the pressing channels 217 which, alongside their extension on the entry side, have additional relief slots 218 on the exit side. As the invention reveals, these relief slots 218 have regular and symmetrical shapes, as shown in Fig. 3a, b or c. To create the relief slots 208, the pressing channel 217 is squeezed open on the exit side using a tool steel ram. The longer relief slots 218 shown in Fig. 3 c are used when there is a larger proportion of plant fibres in the raw material.
Underneath the perforated die 209, there is a clearing device 210 to strip the treaded granulate, which can be adjusted to the position of the roller 208. This granulate can now be taken out for further processing.
However, if the proportion of plant contents of the raw material mixture is greater than 60~, the quality of the granulate produced by the pre-granulation unit 216 can be significantly improved by the follow-on final granulation unit 211. The pre-granulate is therefore immediately, or, if necessary, after minimal further mixing, fed into a mixing chamber (not shown separately here) together with other additives over a pre-granulate discharge 213 into the final granulation unit 211.
As shown in Fig. 1, the final granulation unit 211 contains an arrangement of cylindrical counter-rotating dies 1 and 2, as shown in Fig. 9, 10, 11 and 12, which are set side by side on a machine table 15. Die 1 is turned by drive 6, whose movement is transferred onto receiving part 4 via belt 7 and a belt drive wheel. The receiving part rests on a bearing which supports die 1.
By mounting engine 25, belt 7, which is protected by an _ 11 appropriate casing, can be tightened. Die 2 is placed on a dovetail 28 so that it can be radially shifted. With an adjustable hydraulic compression cylinder 10, fixed above a joint on a rest block of adaptable height 13, die 2 can be moved towards die 1. This movement is limited by an end stop 23. When dies 1 and 2 have been sufficiently approximated, die 2 is rotated by the rotating die 1 via an end face ebonite part 11.
Adaptable broaching combs on the inside of dies 1 and 2 cut the pressed through materials which are then conveyed towards a granulate discharge casing 16 by the electronic drive 18 of screw conveyor 19. The casing 24 is attached to a fixed shaft 27 with an overarm 26 at the other end. Dies 1 and 2 are cased with housing 22, upon which tilting guards are mounted on hinges. On top of housing 22 is the granulate in-feed housing 21. The rotational direction of dies 1 and 2 are marked with arrows. If die 2 is in a lifted position, distanced from die 1, it takes up position 20. Machine table 15 contains a power pack 14 to control the lateral movements of die 2.
Figures 4, 5, 6 and 7 show a further model of the final granulation unit 211, which, as described below, are innovatively equipped with co-rotating ring dies. The centre of the final granulation unit 211 is formed by the co-rotating cylindrical ring dies 101 and 102 (Fig.

8). The width of the ring dies 101 and 102 control the throughput volume of the raw material. There is also an outer, bigger, driven ring die 101 whose receiving part 4 rests on bearing 3 and is powered by drive 6, either electrically or hydraulically, by a high-performance belt 107, i.e. a high-performance belt wheel 108. On the inside of the outer ring die 101, the small inside rotating ring die 102 is rotably mounted onto the swivel girder 111. The sense of rotation of the ring dies 101 and 102 is indicated with arrows. The chosen diameter of the smaller die 102 depends on the fibre content of the material to be granulated or the pre-granulate.
The diametrical proportion of the ring dies 101 and 102 determines the pressure area. A large ring die 101 and a small ring die 102 will, for example, generate a smaller pressure area with higher pressure. Generally, the diameter of the smaller ring die 102 can vary between one third to two-thirds of the diameter of the large ring die 101.
In the invention, the size of the diameter can be changed easily and this is necessary to produce granulate with different fibre contents and additives.
The back of the swivel girder 111 of the ring die 102 is fastened to element 113 with joint 112, which depending on the condition, i.e. wear and tear of the ring die 102, serves as the centre point of the joint for different heights and directions. The adjustable hydraulic compression cylinder 10 generates the contact pressure of the engaging ring die 102, which moves the ring die 102 into the waiting or assembly position. The mobility of the swivel girder 111 is limited by the fixed stop 23, which ensures that the minimum distance between ring dies 101 and 102 is maintained and prevents the metallic grinding together of ring dies 101 and 102.
The hydraulics ensure that in case of overload or the presence of solids in the pre-granulate, the ring die 102 can spring back into position 120, thereby preventing the system from getting damaged.

Underneath the outer ring die 101, there is an alignable and adjustable broaching comb 17 to dislodge the granulate. The granulate coming out of the inside of the ring die 102 passes the electric drive 118 which activates the screw conveyor and is transported to the granulate output housing 16. The filler, e.g. the pre-granulate, reaches the area above the ring die 102 via the granulate input housing 21 with housing hinge 122.
The outer rotating ring die 101 and drive are protected by housing coating 9, whose front guards are adjustably designed.
The method of the invention is described in greater detail below:
Raw materials used are flax straw, jute straw, hemp straw as well as flax, jute, hemp and sisal fibres and other plant components and mixtures thereof. As is common practice, these plant components are cut, riffled and dried as well as processed into bale shapes. It is also possible to use fine, medium and coarse shavings as well as rovings or tapes consisting of mixtures of the fibres listed above. If the straw is stored in a dry condition with plenty of ventilation, it may be stored for at least three years.
In one example, the base material used are short fibres or plant components pressed into bales. In this case, a remaining wood content of up to 10~ of the weight is possible. These impurities are not a nuisance, but rather work as fillers. With this method, small stones, which would damage the extruder in the traditional method, are not a problem.

. The plant parts are then fed into a common bale opener.
When different fibres are used, e.g. flax, sisal and jute, each sort is processed in a separate bale opener with an integrated scale, so that the fibre mixture can be produced according to pre-set weight proportions.
All proportions are possible and are only determined in the following fields of application. Although the plant components, depending on intended use, can theoretically be further processed without being crushed. However, usually, the plant matter is shortened to a maximum length of 50 mm with two cutters or, alternatively, with an opening roll shortening plant matter to the required fibre length of up to SOmm. In a further method, the raw material is fed in by a heavy-parts separator and a metal separator to eliminates big impurities. In the multi-mixer, the fed-in plant components are put through several phases of powerful mixing. A mixture of, e.g.
30~ flax, 30~ sisal and 32~ jute fibres is pneumatically driven into a pre-granulation unit 216, to be pre-granulated to a diameter of 5mm with a pressure level determined by a ratio of 1:6 between the length and the diameter of the pressing channel 217, at 120°C to 130°C.
At the same time, the fibre mixture is sprayed with water mist, containing agents to prevent the formation of odour, mould and bacterial infestation.
Depending on the intended use of the granulate, it is further possible to mix it with thermoplastic material such as polypropylenes, to obtain granulates for a most diverse range of applications. Thermoplastic materials may be added in the form of powder, fibre or granulate.

_ 15 A further advantage of the invention is that a proportion of the natural fibre can be replaced by treated recycled material, such as the produce of used binding agents.
Pre-granulation works according to the common principle of compression agglomeration, so that the pre-crushed mixture is conveyed onto the perforated die 209 which is fitted with the pressing channel 217. As the roller 208 rolls over, the fibre material is pressed through the pressing channel 217 of the perforated die 209.
Depending on the special feed-in of the mixture to the perforated die 209 and the structure of the pressing channel 217, the granulating process is stabilised after 15 minutes and an easily dosable dry granulate is produced. The pre-granulate, which is pressed through the pressing channel 217 of the perforated die 209, is gravimetrically and continually mixed again in a further mixing chamber with a colour master batch and is discharged in doses in the final granulation unit 211.
The essence of the invention is that the diameter, shape and length of the pressing channel 217 on the perforated die 209 in the crushing unit 216 or the final granulation unit 211, determine the differences in the granulate produced. The pressure ratio created by a 4mm pressing channel diameter is 1:8; a 3mm diameter, in case of 92~ pre-granulate and 8$ colour master batch, is 1:10. An increase in throughput is achieved with the profile of the surface of roller 208 and the number of pressing channels 217 on the perforated die 217.
The ability to determine the proportion of closed surface to open surface on the perforated die 209 and the distance between the surface of the roller 208 and the perforated die 209, enables the most varied fibre mixtures to be processed.
Granulate leaving the final granulation unit 211, is cooled and vacuum packed, and then handed over to the user. It can now, for example, be combined in the desired proportion with a pure plastic granulate, using a gravimetrical dosing device and introduced directly into the injection machine.
In a further example, straw cut to 3 and 5 mm in the pre-granulation unit 216 is sprayed with water mist spray containing dissolved additives to prevent the formation of mould, biological infestation and odour emission is pre-granulated at a pressure ratio of 1:6 at a temperature of 120°C to 130°C as described above. The pre-granulated material has a pellet diameter of 6°mm.
Subsequently, 35~ in weight of the pre-granulate are mixed with 35$ in weight of the first plastic granulate and 30~ in weight of a second plastic granulate. The thickness of the dies 1 and 2 of the final granulation unit 211 is 30°mm in the area of the pressing channel 217, the diameter of dies 1 and 2 is 440°mm and is fitted with a pressing channel 217 with a diameter of 3°mm, whereby the pressing channel 217 has a relief notch 218 and a compression proportion of 1:8 has to be upheld.

1 Die 2 Die 3 Ball-bearings 4 Feed opening 6 Drive, electrical or hydraulic 7 Belt 8 Belt pulley 9 Housing cover 10 Adjustable hydraulic compression cylinder 11 Ebonite-covered surface 12 Joint 13 Height-variable steady 14 Power pack 15 Machine table 16 Granulate discharge housing 17 Broaching comb 18 Electric drive 19 Screw conveyor 20 Position 21 Granulate infeed housing 22 Housing 23 Positive stop 24 Inner die housing 25 ~ Motor mounting 26 Overarm 27 Fixed shaft 28 Dovetail 101 Ring die 102 Ring die 107 High-power belt 108 High-power belt pulley 111 Swivel girder 113 Element to adjust height 118 Electric drive for broaching screw 120 Position of die 1 in lifted position 122 Housing hinge 201 Feed 202 Feed 203 Feed 204 High-pressure nozzles 205 High-pressure nozzles 206 Baffle plate 207 Clasp nut 208 Roller 209 Perforated die 210 Clearing device 211 Final granulation unit 213 Pre-granulation discharge 215 Mixing chamber 216 Pr-granulation unit 217 Press canal 218 Relief slots

Claims

1. A granulate that consists of fibres, binding agents and/or plant components and/or additives, whereby additives are understood to be coupling agents and/or flame-retardants, and/or fillers, and/or colouring agents and/or antibiotic agents, characterised in that the granulate contains plant fibres in a fibrillious condition.

2. Granulate as in claim 1, characterised in that it contains 92 to 98% plant fibres and 2 to 8% additives.

3. Granulate as in claim 1 or 2 characterised by in that it contains thermoplastics.

4. Granulate as in claim 1 or 2 and 3, characterised in that it contains 1 to 80% thermoplastics, 2 to 8% additives and 12% to 97% plant fibres.

5. Granulate as in one of the claims 1 to 4, characterised in that it contains thermoplastic polymers.

6. Granulate as in one of the claims 1 to 5, characterised by in that it contains polypropylene and/or polyethylene.

7. Granulate as in one of the claims 1 to 6, characterised in that it contains plant fibre mixtures of different plants.

8. Granulate as in one of the claims 1 to 7, characterised in that it contains flax, sisal and/or jute fibres.

9. A method for the production of granulate as described in claim 1 through press agglomeration, characterised in that it contains plant fibres and/or plant fibre mixtures and/or plant components and thermoplastic material and/or thermoplastic polymers and/or binding agents and/or additives, whereby the additives - coupling agents and/or flame-retardants and/or filler and/or colouring agents and/or antibiotic agents - are mixed in presence of water and under higher temperature within 2 to 60 seconds and this mixture is pressed under mechanical pressure through a perforated die for purpose of granulation, and then a crunching of the mass which is pressed through the perforated die follows.

10. Method as in claim 9, characterised in that the granulating process occurs in two stages wherein in the first stage a pre-granulation occurs in the presence of water steam and with the addition of additives, this pre-granulate is then fed into a mixer, where additional additives can be mixed in and then the mixture is put through a final granulation.

11. Method as in claim 9 and 10, characterised in that the plant components used in a not pre-treated, not crushed and/or crushed form.

12. Method as in claim 9, 10 and 11 characterised in that the plant fibres are put in a fibrillious condition.

13. Method as in claim 9 to 12, characterised in that, granulation is carried out at a pressure from 15 to 200 bar and at a temperature from 0 to 150°C.

14. Method as in claim 9 to 12, characterised in that the pressure is generated by the rolling movement of the roller on the die surface.

15. Method as in claim 9 to 12, characterised in that the pressure is generated by the counter movements of at least two dies.

16. Method as in claim 9 to 12, characterised in that, the pressure is generated by an extrusion screw.

17. Method as in claim 9 to 12, characterised in that the pressure is controlled by varying the distance between the counter-moving dies.

18. Method as in claim 9 to 17, characterised in that in the first stage of granulation and/or the second stage of granulation, thermoplastics such as polypropylene and/or polyethylene are added.

19. Method as in claim 9 to 18, characterised in that 92 to 98% plant fibres and 2 to 8% additives are used.

20. Method as in claim 9 to 18, characterised in that, 1 to 80% thermoplastics 2 to 8% additives and 12 to 97% plant fibres are used.

21. A plant for the production of granulates from plant components, consisting of a pre-granulating unit (216) and a final granulating unit (211).

22. Plant as in claim 21, characterised in that the pre-granulating unit (216) consists of a known flatbed die press with a mixing chamber above it (215), whereby water outlet nozzles (204, 205) and feeds (201, 202, 203) lead into the mixing chamber (215), a baffle plate (206) is fixed above a roller (208) in the mixing chamber (215) with a clearing device (10) and the pre-granulation discharge (13) beneath the perforated die (209).

23. Plant as in claim 21, characterised in that there is a further mixing chamber in between pre-granulation unit (216) and final granulation unit (211).

24. Plant as in claim 21 to 23, characterised in that the surface of the roller (8) has a sawtooth profile.

25. Plant as in claim 21, characterised in that the final granulation unit (211) consists of a known ring die press where, instead of a inner-rotating roller, there is a cylindrical ring die (102) rotably mounted inside an outer cylindrical ring die (101) in such a way that the inner ring die (102) presses against the outer ring die (101).

26. Plant as in claim 21 and 25, characterised in that the diameter of the ring die (102) is one third to two thirds the size of the diameter of ring die (101).

27. Plant as in claim 21, 25 and 26, characterised in that there is a changeable and adjustable broaching comb (17) underneath ring die (101) and a screw conveyor inside die (102).

28. Plant as in claim 21, characterised in that the final granulation unit (211) has two counter-rotating cylindrical dies (1) and (2), whereby die (1) is connected to the drive (6) and the mobile die (2) is mounted at a minimum distance from die (1).

29. Plant as in claim 21, 24 and 28, characterised in that a fixed stop (23) can set a minimum distance between the dies (1, 101) and the dies (2, 102).

30. Plant as in claim 21 to 29, characterised in that the perforated die (9) and/or the ring dies (101, 102) and/or the dies (1, 2) are equipped with press .canals (217) whereby it is planned to add regular, symmetrically-shaped relief slots (218) to the press canal (217) on the entrance side and/or on the exit side.

31. Plant as in claim 21, characterised in that the plant only consists of a pre-granulation unit (16).