US2004012114

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as) United States

S 20040012114A1

a2) Patent Application Publication co) Pub. No.: US 2004/0012114 Al

Eyerer et al. (43) Pub. Date: Jan. 22, 2004
(54) METHOD FOR PRODUCING A (30) Foreign Application Priority Data
GRANULATED INTERMEDIATE PRODUCT
THAT IS TO BE SUBJECTED TO A Sep. 15,2000 (DE) .essecscssesneuneennnnene 100457940

SUBSEQUENT PROCESSING IN ODER TO
FORM PLASTIC SHAPED BODIES

(76) Inventors: Peter Eyerer, Karlsruhe (DE); Emilia
Inone, Pfinztal (DE); Helmut Nagele,
Beuernfeld (DE); Wilhelm Eckl,
Karlsruhe (DE); Norbert Eisenreich,
Pfinztal (DE); Jurgen Pfitzer,
Stockhausen (DE)

Correspondence Address:

Dr. Paul J Vincent

Lichti Lempert & Isch
Bergwaldstr 1

D-76227 Karlsruhe Germany (DE)

(21) Appl. No.: 10/363,218
(22) PCT Filed: Aug. 30, 2001
(86) PCT No.: PCT/EP01/10006

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Publication Classification

(51) Int. Cl”
(52) US. Cl

(57) ABSTRACT

For producing a granulated intermediate product which
consists of a fine-particle thermoplastic or thermoelastic
polymer and substantially inert fillers for further processing
into plastic shaped bodies through thermoplastic processing
methods it is proposed to mix the polymer in the form of
powder or particles with the fillers and compact the powder
mixture without plastification of the polymer exclusively
under mechanical pressure into pourable agglomerates with
larger grain size. Such an agglomerate can be processed into
shaped bodies in the same manner as a conventional plastic
granulated material, wherein thermal damage to the fillers
and the molecular structure of the polymer is reliably
prevented during production of the intermediate product and
extremely high fill fractions can be achieved.

. B28B 3/00
264/117; 264/319

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Patent Application Publication Jan. 22, 2004 US 2004/0012114 Al

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US 2004/0012114 Al

METHOD FOR PRODUCING A GRANULATED
INTERMEDIATE PRODUCT THAT IS TO BE
SUBJECTED TO A SUBSEQUENT PROCESSING IN
ODER TO FORM PLASTIC SHAPED BODIES

[0001] Translation of PCT/EP01/10006 as filed on Aug.
30, 2001

[0002] The invention concerns a method for producing a
granulated intermediate product from at least one substan-
tially powdery or particle-shaped thermoplastic and/or ther-
moelastic polymer and substantially inert fillers for further
processing into plastic shaped bodies through thermoplastic
processing methods by mixing the polymer and the fillers
and compacting the powder mixture into a granulated matter
of larger grain size.

[0003] Thermoplastic and thermoelastic polymers are usu-
ally processed, in the form of granulated matter, into shaped.
bodies through injection molding machines or extruders.
Towards this end, the raw material producer must first bring
the polymer into a pourable granulated form to ensure
reliable subsequent processing. Granulation can be effected
with extruders through melting-on the polymer and subse-
quent shaping and cooling of the produced granulated mat-
ter. This process requires energy and careful temperature
control to prevent damage to the molecular structure of the
polymer. During processing into the shaped body, the granu-
lated matter is again melted-on and heated. The same
happens when regenerated plastic materials are used.
Towards this end, the plastic particles are usually ground
into smaller fragments to produce granulated matter there-
from through remelting.

[0004] To influence the material properties of the final
product in the desired fashion, fiber materials which are
either cut short or in the form of powder are added either
during production of the raw granulated matter or during
melting-on thereof for producing the shaped body. For
conventional extrusion into raw granulated matter or extru-
sion of the raw granulated matter into a shaped body, fiber
fill fractions of up to a maximum of 65 mass % can be
obtained. In particular, natural fiber fillers may be thermally
damaged since the fibers are subjected to thermal stress
through granulation for plastification of the polymer as well
as during further processing of the granulated matter into the
shaped body.

[0005] DE 198 34 132 Al describes a device for producing,
a granulated intermediate product from thermoplastic poly-
mers and natural fibers in the form of a die press. The die
press comprises an annular space which can be loaded
axially with the powder mixture to be granulated which is
delimited at its periphery by a perforated die and in which
a revolving friction blade is disposed to press the charge
through the perforated die. The space formed between the
friction blade and the outer wall of the annular space serves.
as a plastification chamber for the fed polymer. The known
device ensures variation of the shearing forces acting on the
powder mixture and therefore permanent uniform distribu-
tion of the fibers in the plastificate. Moreover, exact tem-
perature control of the plastification chamber is expected
since it is relatively small and closed and thermal impair-
ment of the fibers is minimized. However, there is a risk of
thermal damage to the polymers and also, in particular, to the
admixed fibers due to the at least two-fold plastification of
the powder mixture, ic. during granulation and during
further processing into shaped bodies.

Jan. 22, 2004

[0006] DE 34 05 185 C2 discloses a further die press for
producing granulated matter from polymers mixed with
additives. The die is provided with a perforated plate which
can be temperature-controlled through which the initial
mixture is forced thereby plastifying at least a part thereof.
A heating and cooling device associated with the die heats
the perforated plate to an operating temperature of between
100° C. and 200° C. prior to operation of the die press and
discharges the frictional heat generated during continuing
operation to prevent overheating of the plate upper side
contacting the initial mixture to ensure perfect mixture of the
fine-particle polymer with powdery additives before the
actual agglomeration. Moreover, burned deposition and
melting of the plastic material onto the die plate should be
avoided. The danger of thermal damage to the initial mixture
is therefore reduced but not reliably eliminated.

[0007] It is the underlying purpose of the invention to
propose a cost-reducing method of the above-mentioned
type wherein higher fill fractions can be achieved while
reliably preventing thermal damage to the powder mixture.

[0008] This object is achieved in accordance with the
invention in a method of this type in that the powder mixture
is compacted into the granulated matter exclusively through
mechanical pressure without plastification of the polymer.

[0009] Many polymers are produced in the form of pow-
der or particles both in synthetic production as well as in
regeneration of plastic material. The situation is similar with
natural polymers, e.g. lignin, which is obtained in fine
particles from cellulose production through concentration of
cellulose waste water. The inventive method is based on
such a powder or particle shape of the polymer. The desired
fiber materials are added to this polymer powder in appro-
priately small particle sizes (ranging from cut short to
powdery) and uniformly mixed. The resulting homogeneous
power mixture is subsequently compacted without plastifi-
cation thereof exclusively under mechanical pressure into
agglomerates with grain sizes which are much larger than
those of the initial products.

[0010] Practical tests have surprisingly shown that
agglomerates produced in this fashion are inherently stable
and are non-abrasive and can be supplied, packed and dosed
as pourable intermediate products for processing into plastic
shaped bodies in the conventional fashion using any ther-
moplastic processing method such as extrusion, injection
molding or the like. The agglomerates can thereby be added
to unfilled polymers as a master batch or can be directly
processed into shaped bodies. Practical tests have also
shown that this pressing agglomeration produces consider-
ably higher filler fractions, in particular, for fibrous fillers
which can assume a mass portion of up to 95% relative to the
powder mixture used without significantly impairing bond-
ing in the polymer. In particular, the inventive method
permits filling of any synthetic thermoplastic or thermoelas-
tic polymers, such as polyethylene, polypropylene, etc, with
high portions of natural fibers which leads to considerable
cost reduction through substitution of a larger part of the
generally more expensive polymers with fibers. The con-
ventional method achieves fill fractions of a maximum of
only 65 mass %.

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US 2004/0012114 Al

[0011] The powder mixture is preferably compacted with
a linear force of between 5 kKN/cm and 30 kN/cm. Pressures
of this type can be easily realized in molding presses, screw
or roller presses to thereby obtain shaped agglomerates
without plastification thereof.

[0012] In continuous screw or roller pressing, the material
obtained can be disintegrated through simple disintegrating
processes into the desired particle size depending on the
consistency. The powder mixture may instead be compacted
through section rolling into shaped agglomerates. Another
possibility is to compact the powder mixture into an option-
ally profiled strand using a screw press and to disintegrate
the strand into the agglomerates of desired particle size.

[0013] Depending on the device used for mechanical
compacting, in particular the shearing stress of the powder
mixture may require cooling of the powder mixture during
compacting due to the produced frictional heat. This may be
effected e.g. by cooling the machine parts which are in
contact with the powder mixture. To safely and reliably
prevent even surface plastification of the used polymers, the
powder mixture should be kept at a maximum of 50° C.,
preferably a maximum of 40° C. In case of preferred use of
rollers or section rollers, cooling can be generally omitted,
in particular, when the arrangement is open. The use of
rollers made from a material having a relatively high heat
conducting coefficient, e.g. metals or metal alloys, is advan-
tageous since the frictional heat is permanently discharged.
This heat is much less than that generated in die presses due
to the smaller shearing forces.

[0014] The fiber material- added to the polymer powder
preferably has a particle size of between 10 wm and 10,000
wn.

[0015] The powder mixture is preferably compacted into
agglomerates having a particle size of between 1 mm and 10
mm.

[0016] The powder mixture is preferably substantially dry
processed into the agglomerates. If the fiber material is a
natural material, it may have a certain residual moisture and
be added in an amount of up to 95 mass %.

[0017] As mentioned above, the polymers may be syn-
thetic and/or natural polymers or also mixtures thereof. The
inventive method can be used with particular advantage with
a powder mixture of lignin powder produced in cellulose
production and fillers of natural fibers.

[0018] The invention is described below with reference to
a system for carrying out the method which is schematically
shown in the drawing.

[0019] A powdery polymer or a powdery polymer mixture
and fillers of powdery to fibrous consistency are fed into and
uniformly mixed in a mixer 1 indicated with directional
arrow 2. The mixer 1 can be a continuous or a batch mixer.
The mixture leaving the mixer is fed at 3 into a funnel 4 or
the Ike from which the powder mixture is metered and
discharged or removed. In the embodiment shown it reaches
the roller gap between two press rollers 5 and is compacted
there purely mechanically into a strand or band-shaped
material (scab) which is subsequently disintegrated into
pourable agglomerates 7 in a disintegrating apparatus 6
comprising ¢.g. revolving beaters or knifes. During com-
pacting of the powder mixture in the roller gap, it is heated

Jan. 22, 2004

only minimally through friction to approximately 25° to 40°
in dependence on the initial temperature of the powder
mixture such that any thermal damage to the material and in
particular plastification of the polymers used is reliably
prevented.

[0020] The pourable agglomerates 7 can be processed into
a plastic shaped part 10 using any conventional thermoplas-
tic processing methods, e.g. feeding into an extruder 8 with
feeding funnel 9 or a conventional injection molding
machine and melting of the polymer.

[0021] Embodiments:

[0022] 1. 10 mass % polyethylene powder and 90 mass
% wood dust or short-cut wood fibers are uniformly
mixed. The powder mixture is agglomerated into a
profiled strand in a strand or roller press with a linear
force of between 5 kKN/cm and 30 kN/cm. The strand is
subsequently disintegrated into individual agglomer-
ates with a particle size of between 1 mm and 15 mm.

[0023] 2. 70 mass % lignin powder from cellulose
production is uniformly mixed with 30 mass % short-
cut hemp fibers. The powder mixture is compacted
between two rollers with a linear force of between 5
kN/em and 30 kN/em and the produced material is
disintegrated into pourable agglomerates.

1. Method for producing a granulated intermediate prod-
uct from at least one substantially powdery or particle-
shaped thermoplastic and/or thermoelastic polymer and sub-
stantially inert fillers for further processing into plastic
shaped bodies through thermoplastic processing methods by
mixing the polymer and the fillers and compacting the
powder mixture into a granulate with larger grain size,
characterized in that the powder mixture is compacted into
the granulate exclusively under mechanical pressure without
plastifying the polymer and is kept at a maximum of 40° C.
during compacting

2. Method according to claim 1, characterized in that the
powder mixture is compacted with a linear force of more
than 5 kN/em.

3. Method according to claim 1 or 2, characterized in that
the powder mixture is compacted with a linear force of less
than 30 kN/em.

4. Method according to any one of the claims 1 through
3, characterized in that the powder mixture is compacted
into shaped agglomerates in a press.

5. Method according to any one of the claims 1 through
3, characterized in that the powder mixture is compacted
using rollers.

6. Method according to claim 5, characterized in that the
powder mixture is compacted into shaped agglomerates
through section rolling.

7. Method according to claim 5 or 6, characterized in that
the powder mixture is compacted through rollers into a
planar material which is then disintegrated into the agglom-
erates.

8. Method according to any one of the claims 1 through
3, characterized in that the powder mixture is compacted
through a screw press into an optionally profiled strand and
the strand is disintegrated into the agglomerates.

9. Method according to any one of the claims 1 through
8, characterized in that the powdery or particle-shaped
polymer is mixed with disintegrated fiber material as filler.

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US 2004/0012114 Al

10. Method according to claim 9, characterized in that the
fiber material is a natural material.

11. Method according to claim 10 or 11, characterized in
that fiber material of a particle size of between 10 sam and
10,000 um is used.

12. Method according to any one of the claims 1 through
11, characterized in that the powder mixture is compacted
into agglomerates having a particle size of between 1 mm
and 10 mm.

13. Method according to any one of the claims 1 through
12, characterized in that the powdery or particle-shaped
polymer is processed with up to 95 mass % of fillers relative
to the powder mixture.

Jan. 22, 2004

14. Method according to any one of the claims 1 through
13, characterized in that the powder mixture is substantially
dry processed into the agglomerates.

15. Method according to any one of the claims 1 through
14, characterized in that synthetic and/or natural polymers or
mixtures thereof are used.

16. Method according to any one of the claims 1 through

15, characterized in that lignin powder from cellulose pro-
duction is used.