Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02350760 2001-05-11
1
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.
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_ 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.
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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.
30
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.
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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.
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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.
5
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.
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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.
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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
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_ 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.
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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.
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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
CA 02350760 2001-05-11
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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
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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.
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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.
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. 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.
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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
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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.
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1 Die
2 Die
3 Ball-bearings
4 Feed opening
5
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
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101 Ring die
102 Ring die
103
104
105
106
107 High-power belt
108 High-power belt pulley
10109
110
111 Swivel girder
112
113 Element to adjust height
15114
115
116
117
118 Electric drive for broaching screw
20119
120 Position of die 1 in lifted position
121
122 Housing hinge
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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
212
213 Pre-granulation discharge
214
215 Mixing chamber
216 Pr-granulation unit
217 Press canal
218 Relief slots
