U.S. patent application number 12/216958 was filed with the patent office on 2008-12-18 for elastomer mixtures for rubber manufacture.
This patent application is currently assigned to BUHLER AG. Invention is credited to Roland Halter, Federico Innerebner, Erhard Krumpholz, Christoph Naf, Bernhard Stalder, Achim-Philipp Sturm.
Application Number | 20080310251 12/216958 |
Document ID | / |
Family ID | 7699067 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080310251 |
Kind Code |
A1 |
Innerebner; Federico ; et
al. |
December 18, 2008 |
Elastomer mixtures for rubber manufacture
Abstract
A device is disclosed for producing elastomer compounds for use
in the production of rubbers. The device may include a mixing
extruder with at least one mixing area, and at least one charging
area for receiving an elastomer; and at least one dewatering area
disposed downstream from the at least one charging area for
receiving the elastomer.
Inventors: |
Innerebner; Federico;
(Zurich, CH) ; Krumpholz; Erhard; (Niederuzwil,
CH) ; Naf; Christoph; (Winterthur, CH) ;
Sturm; Achim-Philipp; (Niederuzwil, CH) ; Stalder;
Bernhard; (Niederuzwil, CH) ; Halter; Roland;
(St. Gallen, CH) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
BUHLER AG
Uzwil
CH
|
Family ID: |
7699067 |
Appl. No.: |
12/216958 |
Filed: |
July 14, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10798350 |
Mar 12, 2004 |
7407611 |
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12216958 |
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PCT/CH02/00477 |
Sep 2, 2002 |
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10798350 |
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Current U.S.
Class: |
366/75 |
Current CPC
Class: |
B29B 7/603 20130101;
B29B 7/86 20130101; C08J 2321/00 20130101; B29B 7/46 20130101; B29B
7/845 20130101; B29B 7/905 20130101; B29B 7/82 20130101; B29C 48/43
20190201; B29B 7/94 20130101; B29C 48/365 20190201; B29C 48/40
20190201; B29B 7/7495 20130101; C08J 3/215 20130101; B29K 2021/00
20130101 |
Class at
Publication: |
366/75 |
International
Class: |
B01F 7/08 20060101
B01F007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 14, 2001 |
DE |
101 45 392.2 |
Claims
1. A device for manufacturing and elastomer mixture for
manufacturing rubber, the device comprising: a mixing extruder with
at least one mixing area; at least one charging area for receiving
an elastomer; and at least one dewatering area disposed downstream
from the at least one charging area for receiving the
elastomer.
2. The device according to claim 1, wherein the mixing extruder is
a multi-screw extruder.
3. The device according to claim 2, wherein the mixing extruder is
a ring extruder.
4. The device according to claim 1, further comprising at least one
charging area for receiving reinforcing material.
5. The device according to claim 4, further comprising at least one
charging area for receiving additives and/or aids.
6. The device according to claim 5, further comprising at least one
area for degassing.
7. The device according to claim 6, further comprising at least one
charging area for receiving a vulcanizing agent.
8. The device according to claim 1, further comprising an
extraction pump and mold disposed downstream from the mixing
extruder, and wherein the at least one charging area for receiving
the elastomer is connected to a supply tank via a supply line, and
the elastomer is introduced into the at least one charging area via
a metering pump.
9. The device according to claim 4, further comprising a weigh
feeder in communication with the at least one charging area for
receiving the reinforcing material.
10. The device according to claim 5, further comprising a supply
tank for softeners connected by a line with the at least one
charging area for receiving the additives and/or aids.
11. The device according to claim 10, further comprising a metering
pump for introducing the softeners into the charging area for
receiving the additives and/or aids, and further comprising a heat
exchanger disposed downstream from the metering pump.
12. The device according to claim 6, further comprising a line in
communication with the at least one area for degassing, and a
vacuum chamber in communication with the line.
13. The device according to claim 7, further comprising a weigh
feeder in communication with the at least one charging area for
receiving the vulcanizing agent.
14. The device according to claim 1, further comprising a plurality
of dewatering areas distributed along the length of the mixing
extruder.
15. The device according to claim 1, further comprising a plurality
of charging areas distributed along the length of the mixing
extruder, and a plurality of dewatering areas distributed along the
length of the mixing extruder, wherein the dewatering areas and the
charging areas are distributed in alternate succession.
16. The device according to claim 1, further comprising a lateral
extruder in communication with the at least one dewatering
area.
17. The device according to claim 15, further comprising a lateral
extruder in communication with each of the dewatering areas.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of prior application Ser.
No. 10/798,350, filed Mar. 12, 2004, which claims priority under 35
U.S.C. .sctn.119 to German Application 101 45 392.2 filed in
Germany on 14 Sep. 2001, and is a continuation under 35 U.S.C.
.sctn.120 to PCT/CH02/00477 filed as an International Application
on 2 Sep. 2002 designating the U.S., the entire contents of which
are hereby incorporated by reference in their entireties.
BACKGROUND
[0002] The invention relates to a method and device for
manufacturing elastomer mixtures (elastomer compounds) to fabricate
rubber articles, in which at least one elastomer to be processed
for manufacturing the elastomer mixture is metered into a mixing
extruder, and mixed and plasticized and/or masticated ("melted
open") while passing through the mixing extruder.
[0003] Elastomer mixtures can include a continuous elastomer matrix
and a filler incorporated into the elastomer matrix, and are
starting products for rubber manufacture. For example, the
unprocessed elastomer can be natural rubber or synthetic rubber,
e.g., nitryl rubber. Soot particles or silicate particles can be
used as the filler, for example. The degree of distribution and
degree of dispersal (degree of dispersion) have been shown to
considerably influence the technical properties of the rubber. In
known methods for manufacturing such elastomer mixtures, closed
mixers are used for dispersive and distributive mixing along with
plasticizing and/or mastication of the filler or elastomer.
[0004] To simplify the manufacture of elastomer mixtures for the
rubber industry, an attempt was made to replace the traditional
forms of presentation of natural or synthetic rubber, e.g., ball
form, with liquid or powdery elastomer as the raw material. In
addition, the particle form of presentation is a precondition for
continuous rubber mixture manufacture.
[0005] The use of liquid elastomers has thus far only been
rudimentarily developed, since this would require a rethinking and
considerable investment on the part of the rubber industry.
However, it would seem that powdery elastomers are proving
themselves as a starting material for the manufacture of elastomer
mixtures in both discontinuous and continuous procedures. In turn,
this made it necessary to provide methods for manufacturing powdery
rubber. Methods were developed for spray-drying and freeze-drying
of nitryl rubber or natural rubber. The flash evaporation method or
milling procedures were also used to generate smaller particles.
However, one disadvantage to all of these methods lies in the
stickiness and creeping characteristic of the generated rubber
particles. Nonetheless, powder products were fabricated by dusting
the particles with very fine organic and inorganic powders to
deactivate the cohesive effects. Unfortunately, undesired
contaminants were introduced into the manufactured particles time
and again as a result of these measures.
[0006] As a consequence, a method was developed for manufacturing
rubber/filler mixtures in powder form. In this case, a stable
rubber/water emulsion is first formed independent of the type and
state of the rubber (e.g., solution or emulsion polymerizates,
natural rubber or nitryl rubber). This emulsion receives a filler
(soot or silicate) whose particle size distribution had previously
been precisely set, and which exists in an aqueous suspension along
with various additives. The latex emulsion and filler suspension
were homogenized in a mixing container via intensive blending. The
precipitation process is then concluded under continuous blending
in a reaction container, and the obtained precipitation product is
transferred to a homogenization container for further processing.
The bulk of the water is then removed in a centrifuge, whereupon
the finely distributed mixture is dried to a residual water content
of less than 1%. The resultant rubber/filler mixtures obtained in a
powder form are free-flowing after drying, and suitable for the
manufacture of rubber products in a continuous procedure.
[0007] To manufacture the rubber or rubber articles, the powdery
rubber/filler mixtures obtained in this way are then plasticized
and/or masticated ("melted open`) in a twin-shaft extruder along
with softeners and other admixtures, which yields a continuous,
liquid polymer matrix with filler particles suspended therein.
Adding a vulcanizing agent creates additional crosslinkages between
the elastomer molecules, so that the subsequently cooled "mass" has
the desired rubbery properties. This makes it possible to fabricate
tailor-made rubber mixtures depending on the type of used
elastomer, and on the type, size and content of filler particles.
Required to this end are at least two different powdery
rubber/filler mixtures, from which a wide range of rubber mixtures
can in turn be obtained by establishing a suitable mixture ratio
between them.
[0008] EP-1035155A1 discloses such a method for manufacturing
powdery, free-flowing rubber/filler mixtures (rubber/filler
batches). The rubber and soot are precipitated to "granulates"
(powdered rubber) via coagulation in a suspension with the
corresponding rubber and soot. The powdered rubber has a round
shape with a diameter of 1 to 3 mm, wherein the soot envelops the
polymer. The soot is already present in a pre-distributed form. The
soot enables easy handling, in particular simple storage and
metering.
[0009] This method can basically be used to manufacture all
important rubbers (natural or synthetic) as granulate. Various
additives and softeners can be incorporated into the granulate,
thereby simplifying the metering of components into the mixing
aggregate.
[0010] However, it has also been shown that there are disadvantages
to manufacturing rubber using powdery rubber/filler mixtures too.
Specifically, an examination of the entire energy balance from
natural rubber or artificial to the end product shows that this
type of rubber manufacture is energy-intensive. Sine the water is
already removed while manufacturing the powdered rubber
(rubber/filler mixture), and this powdered rubber is subsequently
"melted open" in a twin-shaft extruder along with a vulcanizing
agent and other admixtures, a very high level of energy must be
expended for melting open and incorporating the fillers. In
addition to the high energy costs, care must here always be taken
that the temperature of the product in the extruder does not exceed
a critical temperature, since the elastomer might otherwise become
damaged. The elastomer polymer chains are here broken down into
smaller fragments and/or chemically modified by the high
temperature, and/or additional organic constituents, in particular
softeners, are broken down, and/or premature crosslinkage can be
initiated in the presence of vulcanizing agent.
SUMMARY
[0011] A method for manufacturing elastomer mixtures for rubber
manufacture is disclosed, in which the aforementioned problems of
prior art can be eliminated, or at least ameliorated.
[0012] The elastomer is present in a uniformly distributed form in
a first fluid medium during the metering process in the method
mentioned at the outset for manufacturing elastomer mixture for
rubber manufacture.
[0013] The elastomer present in a uniformly distributed form in a
first fluid medium yields a lower viscosity as long as enough fluid
medium is contained in the product to be processed, and
simultaneously ensures a significantly better cooling than in a
"dry" method due to the presence of the fluid, such as water.
[0014] Depending on the type of elastomer (natural rubber,
synthetic rubber), etc., the first fluid medium can be a solvent in
which the elastomer has been dissolved, or the elastomer can be
present as an emulsion of an elastomer solution in a liquid not
miscible with the solvent. If needed, the elastomer can also be
present as a suspension of elastomer particles in a liquid, or as a
gelatinous bond in a solvent.
[0015] A tightly combing, equidirectionally rotating multi-screw
extruder, in particular a ring extruder, can be used as the mixing
extruder. Advantages to a ring extruder include its higher
degassing power, narrower retention spectrum, shorter structural
length and higher achievable degree of dispersion. This makes it
possible to achieve the same results as with a twin-shaft extruder
more efficiently.
[0016] In an exemplary embodiment, reinforcing materials, in
particular soot or silicates, are introduced to the elastomer
uniformly distributed in the first fluid medium before metering
into the mixing extruder. The additional components necessary for
rubber manufacture are hence incorporated at a point where the
product to be processed still has a relatively slight viscosity
given the still present first fluid medium. This also makes it
possible to set the necessary viscosity, since a certain shearing
energy is required for comminuting the components. This is
influenced by the viscosity, among other things. The idea is to set
the lowest possible viscosity still required to introduce enough
shearing energy. This makes it possible to utilize the low
viscosity set for the respective procedural step, so as to achieve
an ideal distribution and comminution of components in the product
even before dewatering and degassing.
[0017] As an alternative, the reinforcing materials, in particular
the soot or silicates, can also be introduced to the elastomer
uniformly distributed in the first liquid via direct metering into
the mixing extruder.
[0018] It is here particularly advantageous if the reinforcing
materials introduced to the elastomer are present as a suspension
in a second fluid medium. This second fluid medium then also helps
to diminish the viscosity or cool the product to be processed in
the mixing extruder.
[0019] The reinforcing materials introduced to the elastomer can be
prepared via wet milling in a device before being metered into the
mixing extruder. This can avoid cases where the energy that is used
for distributing and comminuting the reinforcing materials and
partially converted into heat does not become directly introduced
to the elastomer, thereby affording it thermal protection.
[0020] An agitating mill, in particular a conical agitating mill,
or a centrifugal mill, can be used as the device for wet milling.
Both the conical agitating ball mill and the centrifugal mill can
be designed as pin mills, which also contain additional collision
elements as required.
[0021] Additional components for the elastomer mixture used in
rubber manufacture can be at least partially metered into the
extruder. The additional components for the elastomer mixture can
be other reinforcing materials or fillers, additives, vulcanizing
agents, accelerators, softeners and aids.
[0022] In another embodiment, only filler is mixed in with the
elastomer, and crosslinking agents are not metered in.
[0023] The product temperature in the mixing extruder can be kept
under the vulcanizing temperature at least on the side opposite the
conveying direction from the metering a point when metering a
vulcanizing agent into the product. This can prevent the elastomer
mixture from vulcanizing already while fabricating its mixture.
[0024] While incorporating and/or comminuting and/or distributing
the components and reinforcing materials into the elastomer in the
mixing extruder, the product in the mixing extruder can be
gradually degassed.
[0025] In this case, the first and/or second fluid medium can be at
least partially removed from the product as it passes through the
mixing extruder in at least one dewatering step. This ensures a low
viscosity at the beginning of the mixing process, when many
components are still incorporated into the elastomer mixture. The
dewatering and degassing can cause a rise in viscosity toward the
end of the mixing process, but this rise is still acceptable at
this point in time.
[0026] It can be particularly advantageous if the first and/or
second fluid medium is removed via degassing or dewatering before
metering in the vulcanizing agent. The presence of water often
influences the reactivity of the vulcanizing agent. In addition,
the mixture can be anhydrous at the end. Temperatures clearly
exceeding 100.degree. C. are typically used for vulcanization
(introduced after the respective shaping). If water is still
present, it causes the rubber mass to foam.
[0027] In another embodiment, the first and/or second fluid medium
is removed in several dewatering steps as the product passes
through the mixing extruder, wherein the filler is also
incorporated in several incorporation steps as the product passes
through the mixing extruder.
[0028] It can be particularly expedient if the incorporation steps
and dewatering steps alternate in succession, wherein only as much
is removed from the product during a dewatering step involving the
first and/or second fluid medium as required ensuring optimal
incorporation for the respectively ensuing incorporation step.
[0029] In a particularly advantageous embodiment of the method, the
one or more dewatering steps take place at one or more lateral
openings in the direction of product passage along the mixing
extruder, wherein another lateral extruder is arranged on the at
least one lateral opening of the mixing extruder, conveying toward
and emptying into this opening. This lateral extruder allows the
released water to escape from the product against the conveying
direction of the lateral extruder, while the lateral extruder
always causes the elastomer material to be retained in the mixing
extruder.
[0030] If necessary, a coagulant can be added to the product. This
is particularly expedient if the product is shaped when exiting the
mixing extruder, e.g., for subsequent granulation. Under suitable
conditions, this yields a formable and as yet unvulcanized initial
product, which can be vulcanized in a final step after formed. This
makes it possible to bring about an analogy between elastomer
processing and thermoplastic processing that has been desired for
many years.
[0031] When manufacturing long rubber articles, it is particularly
advantageous to heat the product exiting the mixing extruder along
a vulcanization path in such a way that the polymers are
continuously crosslinked. In the special case of long rubber
articles, e.g., profiles, this provides a complete, continuous
process proceeding from the raw materials latex and filler with
initially abundant water and solvent to the completely formed,
dewatered and finally crosslinked long rubber article end
product.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Additional advantageous, features and applications can be
gleaned from the following description of exemplary embodiments,
wherein:
[0033] FIG. 1 shows a diagrammatic view of a device according to a
first exemplary embodiment, and
[0034] FIG. 2 shows a diagrammatic view of a device according to a
second exemplary embodiment.
DETAILED DESCRIPTION
[0035] FIG. 1 shows a system for executing a procedure based on a
first exemplary embodiment. A mixing extruder 1, such as a
multi-screw extruder, (for example, a ring extruder) has several
areas 1a, 1b, 1d and 1e in the direction of product passage that
each correspond to different procedural steps. Reinforcing
materials are charged in area 1a, additives and aids are charged in
area 1b, product degassing takes place in area 1d, and vulcanizing
agent is charged in area 1e. An extraction pump 3 and mold 4 are
placed downstream from the mixing extruder. A supply tank 7 for
latex emulsion or latex suspension is connected by line 7a with
area 1a of mixing extruder 1, in which both elastomer and
reinforcing materials are charged. The elastomer and latex emulsion
or latex suspension are charged via a metering pump 5, while the
reinforcing materials are supplied to the mixing extruder 1 in its
area 1a by way of a weigh feeder 9. As with the reinforcing
materials, further aids and additives are supplied to the mixing
extruder in its area 1b by means of a weigh feeder 10. A supply
tank 8 for softeners is connected by a line 8a with area 1d of
mixing extruder 1. Therefore, area 1d is the site where the product
is degassed on the one hand, and softener is added on the other.
However, the softener can be already charged beforehand, e.g., in
area 1b. This is because, as soon as the fluid medium has been
degassed, viscosity can increase dramatically, and can be lowered
with the softener. The evaporating point of the softener can
clearly exceed 100.degree. C. A metering pump 6 pumps the softener
through line 8a, which also accommodates a heat exchanger 13
downstream from metering pump 6. The degassing also ongoing in area
1d takes place via a line 12a, which connects area 1d of mixing
extruder 1 with a vacuum chamber 12. Finally, vulcanizing agent can
be charged in area 1e of mixing extruder 1 by means of a weigh
feeder 11.
[0036] Proceeding from the latex emulsion or latex suspension kept
in storage tank 7 as well as the reinforcing materials, additives,
aids, softeners and, finally, vulcanizing agent gradually charged
in mixing extruder 1, a product resembling a web or strand can be
obtained at the end of the extruder, comprised of a continuous
elastomer matrix in which the reinforcing materials have been
incorporated in a uniformly distributed manner. In addition to the
reinforcing materials, this product 14 can also contain uniformly
distributed vulcanizing agent.
[0037] When processing the product as it passes through mixing
extruder 1, care can always be taken to keep the product
temperature below a critical temperature of the product starting at
which the polymer chains of the elastomer material are damaged and
broken down. After charging the vulcanizing agent, i.e., behind
area 1e of mixing extruder 1, care can also be taken to always keep
the temperature below the vulcanizing point for the respective
elastomer and vulcanizing agent. This ensures that the product web
or strand exiting at the extruder end has polymer chains that are
sufficiently long, but not yet crosslinked by the vulcanizing
agent. This initial product 14 for manufacturing rubber articles
can be granulated with the mold 4, if necessary. The granulated
product 14 obtained in this way can then be melted open and
processed further into various rubber articles, e.g., via injection
molding, stretch blow molding or continuous profile molding and
similar molding procedures, yielding end products made out of
rubber. During this last further processing of the initial product
14 for manufacturing rubber, initial product 14 can then be heated
to its vulcanization point, so that vulcanization can take place
after molding. After molding, the elastomers can be calibrated and
crosslinked according to the various known procedures for
manufacturing rubber articles (profiles, etc.) via a vulcanization
path.
[0038] As an initial product for rubber manufacture, the elastomer
mixture 14 obtained forms a basis on which any rubber articles can
be similarly fabricated, as already common practice today during
the processing of thermoplastics.
[0039] One special advantage to the method is that the product
containing, for example, high quantities of water or solvent, is
not immediately, but only gradually dewatered as the product passes
through mixing extruder 1. In this way, the product to be processed
has an optimal viscosity, making it possible to keep the mechanical
energy to be introduced for processing the product within optimal
limits, which in turn yields a less intensive heating of the
product. In addition, the presence of larger quantities of water or
solvent in the product also moderates the temperature of the
product to be processed in mixing extruder 1 due to the high
heating capacity of the water. The dewatering areas of mixing
extruder 1 (not shown) can be distributed over its entire
length.
[0040] FIG. 2 shows a system for executing the method based on a
second exemplary embodiment. The system on FIG. 2 differs from the
system on FIG. 1 in that an area 1c is provided in mixing extruder
1 for dewatering the product to be processed in mixing extruder 1.
Dewatering in area 1c takes place with a dewatering device.
Degassing can also take place repeatedly.
[0041] Before the reinforcing materials are charged via weigh
feeder 9, the reinforcing materials, e.g., comprised of soot or
silicates, can be subjected to wet milling. In this case, a liquid
weigh feeder can be used in place of the shown solid weigh feeder.
The use of a conical agitating ball mill or centrifugal mill (not
shown) is here particularly advantageous. A lateral extruder (not
shown) that ends in area 1c of mixing extruder 1 intended for
dewatering and conveys toward mixing extruder 1 can be used instead
of the dewatering device 2 for product dewatering shown on FIG. 2.
In this way, any elastomer material that exited in the lateral
extruder (not shown) is immediately returned to mixing extruder 1,
while water exiting in the lateral extruder along with the
elastomer material can pass between the screw elements of the
lateral extruder and casing of the lateral extruder against the
conveying direction of the lateral extruder oriented toward mixing
extruder 1. This produces a clean separation of water in area 1c of
mixing extruder 1. All dewatering areas distributed over the entire
length of mixing extruder 1 can be equipped with such a lateral
extruder.
[0042] It will be appreciated by those skilled in the art that the
present invention can be embodied in other specific forms without
departing from the spirit or essential characteristics thereof. The
presently disclosed embodiments are therefore considered in all
respects to be illustrative and not restricted. The scope of the
invention is indicated by the appended claims rather than the
foregoing description and all changes that come within the meaning
and range and equivalence thereof are intended to be embraced
therein.
* * * * *