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Patent 2500372 Summary

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(12) Patent: (11) CA 2500372
(54) English Title: METHOD OF MODIFYING CROSSLINKED RUBBER
(54) French Title: METHODE DE MODIFICATION DE CAOUTCHOUC RETICULE
Status: Granted
Bibliographic Data
(51) International Patent Classification (IPC):
  • C08J 11/16 (2006.01)
  • C08J 11/20 (2006.01)
(72) Inventors :
  • TZOGANAKIS, COSTAS (Canada)
(73) Owners :
  • TZOGANAKIS, COSTAS (Canada)
(71) Applicants :
  • TZOGANAKIS, COSTAS (Canada)
(74) Agent: RIDOUT & MAYBEE LLP
(74) Associate agent:
(45) Issued: 2011-06-28
(86) PCT Filing Date: 2002-10-01
(87) Open to Public Inspection: 2003-04-10
Examination requested: 2007-09-25
Availability of licence: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): Yes
(86) PCT Filing Number: PCT/CA2002/001491
(87) International Publication Number: WO2003/029298
(85) National Entry: 2005-03-29

(30) Application Priority Data:
Application No. Country/Territory Date
2,358,143 Canada 2001-10-02

Abstracts

English Abstract




A method of modifying crooslinked rubber comprising subjecting the rubber to
mechanical elongational and shear forces in the presence of a supercritical
fluid that is normally gaseous. Controllable devulcanization of the rubber is
achieved.


French Abstract

Ce procédé de modification de caoutchouc réticulé consiste à soumettre le caoutchouc à des forces de cisaillement et d'allongement mécaniques en présence d'un fluide supercritique normalement gazeux. Ledit procédé permet d'obtenir une régénération de caoutchouc régulée.

Claims

Note: Claims are shown in the official language in which they were submitted.





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CLAIMS:


1. A method of modifying crosslinked rubber comprising
subjecting the rubber to mechanical elongational and shear
forces in the presence of a supercritical fluid that is
normally gaseous, wherein the ratio by weight of rubber to
said fluid is 100:1 to 20:1.


2. Method according to claim 1 wherein the supercritical
fluid is ethane, ethene, propane, propene, xenon, nitrogen,
ammonia, nitrous oxide, fluoroform or carbon dioxide.


3. Method according to claim 2 wherein the supercritical
fluid is carbon dioxide.


4. Method according to claim 1, 2 or 3 wherein said
supercritical fluid is at a pressure of from about 90% to
about 300% of its critical pressure.


5. Method according to any one of claims 1 to 4 wherein
said supercritical fluid is at a temperature expressed in
°K of about 90% to about 300% of its critical temperature.

6. Method according to any one of claims 1 to 5 wherein
the rubber is provided in finely divided form.


7. Method according to claim 6 wherein the rubber particle
size is 150 microns to 5 mm.


8. Method according to claim 7 wherein said particle size
is 160 to 1000 microns.




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9. Method according to claim 7 wherein said particle size
is 170 to 500 microns.


10. Method according to any one of claims 1 to 9 wherein
the rubber comprises a material selected from the group
consisting of natural rubber, styrene-butadiene rubber, EPDM
(ethylene-propylene diene rubbers), EPT (ethylene-propylene
terpolymer rubbers), TPU (thermoplastic urethane rubbers),
TPEs (thermoplastic elastomers), TPVs (thermoplastic
vulcanizates), butyl rubber, nitrile rubber, polysulfide
elastomes, polybutadiene, polyisoprene rubber,
polyisobutylene, polyester rubbers, isoprene-butadiene
copolymers, neoprene rubber, acrylic elastomers,
diisocyanate-linked condensation elastomers, silicone
rubbers, crosslinked polyethylene, ethylene-vinylacetate
polymers, and mixtures thereof.


11. Method according to claim 10 wherein the rubber
comprises styrene butadiene rubber.


12. Method according to claim 10 wherein the rubber
comprises EPDM rubber.


13. A method of modifying crosslinked rubber comprising
subjecting the rubber to mechanical elongational and shear
forces in the presence of a supercritical fluid that is
normally gaseous, wherein the weight content of
supercritical fluid, based on the weight of rubber, is 0.5
to 3%.


14. Method according to claim 13 wherein the supercritical
fluid is ethane, ethene, propane, propene, xenon, nitrogen,
ammonia, nitrous oxide, fluoroform or carbon dioxide.




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15. Method according to claim 14 wherein the supercritical
fluid is carbon dioxide.


16. Method according to claim 13, 14 or 15 wherein said
supercritical fluid is at a pressure of from about 90% to
about 300% of its critical pressure.


17. Method according to any one of claims 13 to 16 wherein
said supercritical fluid is at a temperature expressed in °K
of about 90% to about 300% of its critical temperature.


18. Method according to any one of claims 13 to 17 wherein
the rubber is provided in finely divided form.


19. Method according to claim 18 wherein the rubber
particle size is 150 microns to 5 mm.


20. Method according to claim 19 wherein said particle size
is 160 to 1000 microns.


21. Method according to any one of claims 13 to 20 wherein
the rubber comprises a material selected from the group
consisting of natural rubber, styrene-butadiene rubber, EPDM
(ethylene-propylene diene rubbers), EPT (ethylene-propylene
terpolymer rubbers), TPU (thermoplastic urethane rubbers),
TPEs (thermoplastic elastomers), TPVs (thermoplastic
vulcanizates), butyl rubber, nitrile rubber, polysulfide
elastomes, polybutadiene, polyisoprene rubber,
polyisobutylene, polyester rubbers, isoprene-butadiene
copolymers, neoprene rubber, acrylic elastomers,
diisocyanate-linked condensation elastomers, silicone




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rubbers, crosslinked polyethylene, ethylene-vinylacetate
polymers, and mixtures thereof.


22. Method according to claim 21 wherein the rubber
comprises styrene butadiene rubber.


23. Method according to claim 21 wherein the rubber
comprises EPDM rubber.

Description

Note: Descriptions are shown in the official language in which they were submitted.




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METHOD OF MODIFYING CROSSLINKED RUBBER
TECHNICAL FIELD
The invention relates to modifying crosslinked rubbers
by mechanical treatment.
BACKGROUND OF THE ART
There are known procedures for devulcanizing
crosslinked polymers, but known procedures are not as
effective or as easily controllable as may be desired.
DISCLOSURE OF THE INVENTION
The present invention relates to a method of modifying
crosslinked rubber comprising subjecting the rubber to
mechanical elongational and shear forces in the presence of
a supercritical fluid that is normally gaseous.
It has been found that by application of the above
method modified rubber can be obtained. More particularly,
a devulcanized rubber can be obtained.
The term "supercritical" in the present specification
is used in its ordinary meaning as referring to a fluid
that is adjacent or above the critical temperature and
pressure. The fluid may be somewhat below the critical
temperature and pressure, for example at least, but not
limited to 90% the critical pressure and at least, but not
limited to 90o the critical temperature expressed in °K.
In the preferred form, the fluid is at a pressure from
about 90 to about 300% of its critical pressure and at a
temperature expressed in °K of about 90o to about 3000 of
its critical temperature.
By "normally gaseous" is meant a fluid that is a gas



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at standard temperature and pressure i.e. at 273°K and one
atmosphere (100 kPa or 14.7 psi).
While it is contemplated that various normally gaseous
fluids may be employed, such as ethane, ethene, propane,
propene, xenon, nitrogen, ammonia, nitrous oxide or
fluoroform, a preferred fluid is carbon dioxide.
In the preferred form, the ratio by weight of rubber
to the fluid constituting the supercritical fluid is in the
range of about 100:,1 to about 10:1, more preferably about
100:1 to about 20:1.
The content of the supercritical fluid in the mixture,
based on the weight of the rubber is preferably about 0.5
to about 10%. With contents of supercritical fluid
significantly less than about 0.5% by weight, the
plasticity and flowability of the rubber may be
insufficient with the result that application of
elongational and shear forces may be difficult or
impossible. Contents of supercritical fluid in excess of
about 10°s do not increase the plasticity and flowability of
the rubber significantly above those achievable at lower
contents, and merely increase the utilization of
supercritical fluid and the operating costs. More
preferably, the content of supercritical fluid is about 0.5
to about 5%, based on the weight of rubber, still more
preferably about 1.5 to about 3%.
Preferably, the rubber is provided in finely divided
form, for example at a particle size of 150 microns to
about 5 mm.
With larger particle sizes than about 5 mm, mechanical
processing difficulties may tend to arise as a result of
the persistence of unmasticated particles in the mix, while
the use of particles significantly smaller than about 150
microns does not facilitate processing substantially as



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compared with the results obtained with larger particle
sizes, and increases the materials costs because of the
increased energy costs of comminution. More preferably,
the rubber particle size is about 160 to about 1000
microns, still more preferably about 170 to about 500
microns.
The term"rubber", designating the crosslinked
materials that may be modified and devulcanized in
accordance with the present method, should be interpreted
broadly, and as it would be understood by one skilled in
the art, to include natural rubber and natural or synthetic
polymers that have physical properties similar to natural
rubber, such as elastic recovery from deformation, and
mechanical strength. Examples of such materials include
natural rubber, styrene-butadiene rubber, EPDM (ethylene-
propylene diene rubbers), EPT (ethylene-propylene
terpolymer rubbers), TPU (thermoplastic urethane rubbers),
TPEs (thermoplastic elastomers), TPVs (thermoplastic
vulcanizates), butyl rubber, nitrile rubber, polysulfide
elastomers, polybutadiene, polyisoprene rubber,
polyisobutylene, polyester rubbers, isoprene-butadiene
copolymers, neoprene rubber, acrylic elastomers,
diisocyanate-linked condensation elastomers, silicone
rubbers, crosslinked polyethylene, ethylene-vinylacetate
polymers, and mixtures thereof.
Various forms of apparatus useable for applying
mechanical elongational and shear forces to crosslinked
rubber material are known to those skilled in the art and
may be modified to render them capable of pressurization by
a supercritical fluid.
In the preferred form, the present invention employs
an extruder, for example a twin screw extruder. Such
extruders are known to apply mechanical elongation and
shear forces to materials passing through them. The
invention is, however, by no means limited to the use of



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extruders, and other pressurized apparatus known to those
skilled in the art that apply mechanical elongation and
shear forces may be employed.
The invention will be described in more detail, by way
of example only, with reference to the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a schematic diagram of a twin screw
extrusion system.
Fig. 2 shows a schematic diagram of a wedge die.
Fig. 3 shows a schematic diagram of a screw
configuration .
Fig. 4 is a graph of viscosity against shear rate at
various extruder barrel pressures.
Fig. 5 is a graph of viscosity against shear rate at
different COZ concentrations.
Fig. 6 is a graph of tensile strength and elongation
at break for.recycled rubbers prepared at various
conditions.
Fig. 7 is a graph of tensile strength/density and
elongation at break for the recycled rubbers referred to in
Fig. 6.
BEST MODE FOR CARRYING OUT THE INVENTION
While the above description provides ample information
to enable one skilled in the art to carry out the
invention, Examples of preferred methods will be described
in detail without limitation of the scope of the invention.



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EXAMPLE 1
In the present example, a twin-screw compounding
extruder 10 as illustrated in Fig. 1 was used for the
production of recycled rubber using a high pressure
supercritical carbon dioxide injection system.
Two types of materials, fine powders (40-60 mesh) (250
microns to 420 micron particle size) and granules (4-8
mesh) (2.38 mm to 4.76 mm particle size), were obtained (ex
Huronco, Huron Park, Ontario, Canada). They were processed
at various temperatures and feed rates in the extruder 10
equipped with a gas injection port 11. The extruder used
is a Leistritz LSM 30.34, intermeshing and co-rotating
twin-screw machine having a 34 mm screw diameter operating
in a barrel 12 and driven through a gear box 13. Rubber
particles were fed by a K-Tron feeder 14 (LWFD 50200), and
COZ was injected into the extruder along a line 16 through
the injection port 11 on the barrel 12 using a positive
displacement syringe pump 17 connected to a COz cylinder
18. The pressure at the barrel injection port 11 was
monitored by a pressure transducer 19 (Dynisco PT462-5M-
6/18) connected to a data acquisition system 21. In order
to measure the flowability (viscosity) of rubber/COZ
mixtures, a wedge die 22 equipped with three other pressure
transducers 23 (one Dynisco PT462-10M-6/18, two Dynisco
PT462-7.5M-6/18) also connected to the system 21 was
attached to the extruder 10. The pressures in the barrel
12 and in the wedge die 22 were manipulated by controlling
the opening area of a secondary die 24 attached to the end
of the wedge die 22. The temperature of the rubber/C02
mixtures was measured using a fiber optic melt temperature
transducer 26 (Dynisco MTS 92206/24) at the end of the
wedge die 22 and connected to a control panel 28. As is
conventional, the barrel 12 is equipped with heating
devices connected to and controlled from the control panel
28, to maintain the barrel at a desired temperature. The
temperatures at various points along the length of the



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barrel 12 could be measured by thermocouples indicated by
broken lines 29 in Fig. 1, also connected to the control
panel 28. In this Example, the rubber feed rate was varied
from 20 to 70 g/min. and a relatively low screw speed of 50
rpm was used in order to maintain the high pressure
required and to minimize the heat generation in the barrel
12. A cross-section of the wedge die 22 is shown in Figure
2.
Flowability (Viscosity) Measurements
The flowability (viscosity) of rubber and rubber/COZ
mixtures was measured on the wedge die attached to
extruder.
Tensile Tests
In order to investigate the tensile properties of the
rubber, dumbbell specimens were prepared using a hot press
at different pressurizing forces and temperatures. The
pressurizing force was varied from 25000 psi to 35000 psi,
and the temperature was changed from 150°C to 250°C. The
thickness of the specimens was varied due to the
differences in elasticity. During the tensile test, the
crosshead speed was controlled at 10 mm/min.
SCREW CONFIGURATION
In order to produce foamed rubber materials, the
dissolution of COZ into the rubber in a twin-screw extruder
was performed. For that purpose, an optimum screw
configuration was determined based on several design
concepts:
(a) At the injection point of CO2, pressure fluctuations
inside the barrel are desirably minimized for a stable
injection. Use of conveying screw elements is
therefore preferable rather than that of kneading



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discs.
(b) Injected C02 is desirably to be prevented from leaking
upstream. This may be achieved by a melt seal
generated using a reverse conveying screw elements,
for example.
(c) The pressure downstream of the COZ injection point is
desirably maintained sufficiently high, to ensure that
COZ remains dissolved in the polymer phase. The
barrel pressure may be manipulated through the die
resistance, for example.
(d) Although the mixing capability of a twin-screw
extruder is much higher than that of a single-screw
extruder, an array of kneading discs is desirably used
to ensure complete dissolution of CO2.
One form of screw configuration 31 meeting these design
requirements is shown in Figure 3. The points of injection
of the crosslinked polymer and of COZ are indicated at 32
and 33, respectively.
EXTRUSION CHARACTERISTICS
Without COZ Injection
In the absence of CO2, when the barrel temperature was
varied from 200°C to 280°C in the range of feed rates from
20 to 70 g/min., regardless of screw speed, extrusion was
impossible due to the overload of the motor. At the early
stage of extrusion, the rubber particles fill the empty
space between the screw and barrel. Motor amperage
gradually increases continuously during this filling stage
and it reaches the maximum safe operating value. The
reasons for this overload appear to come mainly from the
high viscosity and the crosslinked nature of the recycled
rubber. In other words, extrusion of the recycled rubber



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was impossible under the conditions listed earlier.
With COZInjection
The extrusion of rubber was successfully performed by
injecting the supercritical CO2. The designed screw
configuration shown in Figure 3 generates high pressure in
the barrel in order to dissolve the injected CO2. In this
example, the injection of supercritical fluid greatly
increases the flowability of rubber during extrusion.
Operating conditions are shown in Table 1.
Table 1. Operating conditions in a twin screw extruder
Operating Conditions Values


Temperature (C) 240-260


Feed Rate (g/min) 50-70


Screw Speed (rpm) 50


CO2 Concentration (wt%) 2-3


The operation with fine powders (40-60 mesh) was found
to be better than that with granules (4-8 mesh) for the die
used in this Example. In the latter case, the die was
blocked frequently by large unmasticated granules. Also,
it should be noted that the extruded material could ignite
under certain conditions (high temperatures) possibly due
to partial devulcanization and ignition of plasticizers in
the recycled rubber.
VISCOSITY MEASUREMENTS
The viscosities of rubber/COZ mixtures were measured
in the wedge die while the viscosity of the pure recycled
rubber could not be measured due to its crosslinked nature.
The dissolution of COZ was achieved by generating high
pressure in the barrel and the wedge die, and the pressures
were controlled by adjusting the opening area of the



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secondary die. The viscosity of rubber/2wt% C02 mixture
(weight ratio rubber: COZ of 50:1) at various barrel
pressures at 242°C is shown in Figure 4, where curves 51,
52 and 54 are for barrel pressures of 970, 1130 and 2170
psi, respectively. As indicated, the viscosity of the
mixture decreases with increasing the barrel pressure. It
should be noted that increasing the pressure leads to
increased dissolution of COZ which results in increasing
the plasticization effect.
The effect of COZ concentration on the viscosity at
242°C was also investigated as shown in Figure 5, where
curve 56 shows the viscosity for 2 wto COZ at PB = 2170 psi
and curve 57 shows the viscosity for 3 wt% COZ at PB = 1920
psi. The viscosity of the 3wts C02 mixture (weight ratio
of rubber: COZ of 33.3:1) is slightly less than that of
the 2wt% COZ mixture. It should be noted, that the
pressure levels are different for the two curves in Figure
5. If the barrel pressure of 3wtoC02 mixture is increased
up to 2170 psi or over the solubility pressure, the
viscosity of the 3wt% COz mixture would be less than that
shown in Figure 5, in the same manner shown in Figure 4.
Consequently, the viscosity or flowability of rubber/COz is
affected strongly by the concentration of COZ as well as
the barrel pressure, and the required pressure level should
be maintained to achieve increased flowability of the
rubber/COZ mixture.
TENSILE TEST RESULTS
Tensile tests were performed for the extruded rubber
as well as unextruded (40-60 mesh powder)rubber. The
tensile strength versus elongation curve is shown in Figure
6.
The curves are for materials prepared under conditions
as follows:



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Table 2
Curve No. Material
58 unextruded, 200°C, 25000 lbs
59 unextruded, 200°C, 35000 lbs
61 unextruded, 250°C, 35000 lbs
62 extruded, 200°C, 25000 lbs
63 extruded, 200°C, 35000 lbs
64 extruded, 250°C, 35000 lbs
As clearly indicated in Figure 6, the conditions for
the specimen preparation greatly affected the tensile
properties of unextruded rubber rather than of extruded
rubber. It was noted that high temperature leads to
decrease in the tensile modulus. The decrease in the
modulus can be explained by devulcanization of rubber at
high temperature. It appears that the extruded rubber in
Figure 6 has experienced some devulcanization at high
temperature (about 260°C) during extrusion. The tensile
moduli of various specimens are listed in Table 3. In
order to compare the tensile strength at the same level of
material density, density measurements were performed for
the specimens. The density was calculated by measuring the
volume and weight of samples. As shown in Table 3, the
densities of extruded specimens were only slightly lower
than those of unextruded specimens. It would be expected
that the specimens extruded in the presence of COZ would
have a foamed structure. The density of foamed plastics is
usually much lower than that of unfoamed plastics. In this
study, however, the foamed structure was collapsed during
the hot press treatment. The tensile strength divided by
the density versus elongation curves for the same materials
designated by the same curve numbers as in Fig. 6 are shown
in Figure 7. This graph is not different than Figure 6,
from which it can be concluded that the lower values
obtained for the extruded rubber are due to partial
devulcanization taking place during extrusion.



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Table 3. Tensile Modulus for recycled
rubber at various preparation conditions
Molding Molding Tensile Density


Temper- Force Modulus (g/cm3)


ature (C) (lbs) (MPa)


Unextruded 200 25000 1.216 1.080


Unextruded 200 35000 1.209 1.081


Unextruded 250 35000 0.803 1.089


Extruded 200 25000 0.474 1.039


Extruded 200 35000 0.412 . 1.032


Extruded 250 35000 0.406 1.015


In the following Examples, devulcanization procedures
were carried out using a co-rotating twin-screw extruder
modified as described above with reference to Figs. 1 to 3.
The crumb rubber materials used in the following
Examples consisted of three different sizes of rubber
powder of 40, 60 and 80 mesh. Table 4 shows the
correspondence between mesh size and particle diameter.
Table 4. Mesh Size to Particle Diameter
Approximate Relation
Mesh Size Microns Millimeters Inches


40 425 0.425 0.0165


60 250 0.250 0.0098


80 180 0.180 0.0070


In the following Examples, soxhlet extraction was used
to evaluate the degree of devulcanization by separating the
soluble fraction from the gel in the rubber samples.
First, acetone was used to remove low molecular weight
substances. 20 g of extrudate was placed in a thimble in



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the extraction tube. 250 ml acetone was heated to boiling
point (about 56°C). The vapor was condensed down to the
tube by the condenser with cold water circulation. The
extraction was run for 5 hours. After the sample, now free
of low molecular weight substances, was dried by
distillation in a fume hood and weighed, 250 ml toluene was
used as solvent to separate the sol from the gel in the
residue by following the same procedure for 8 hours. The
residue swelled in toluene and from the dried and weighed
residue, the weights of sol and gel were obtained.
Example 2
80 mesh SBR rubber was devulcanized at 250°C using
rubber feed rates, as supplied by the feeder 14, of 15
g/min and 30 g/min. The COz concentrations were varied.
The contents of low m.w. substances, sol, and total soluble
(low m.w. plus sol) were obtained for the starting material
SBR rubber and for the devulcanized products, and are shown
in Table 4 in weight percent based on the total weight of
the sample.
Table 4
Starting Feed Feed
rate rate
15 30
g/min g/min


material COZ C02
concentration concentration


SBR 1s 2% 3% 1% 20 30


Low m.w.6 9 8 9 9 9 8


Sol 2 17 16 17 17 14 18


Total 8 26 24 26 26 23 26
solubles


It will be noted that extrusion with supercritical COZ
resulted in an increase of the soluble fraction from 8o in
the starting powder to about 26% in the devulcanized
material. Also, it can be seen that changes in feed rate



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and COZ concentration did not have an effect on the soluble
fraction in the rubber. Furthermore, it will be noted that
the soluble part consists mainly of sol resulting from
devulcanization (about 17%) and that the low molecular
weight fraction (about 9%) is not considerably different
from that of the starting material.
Example 3
Example 2 was repeated at barrel temperatures of 200°C
and 250°C, with screw speeds of 25 and 50 rpm and 2 wt%
CO2. The results are shown in Table 5.
Table 5
Temp. 200C 250C


Screw speed (rpm) 25 50 25 50


Low m.w. 8 9 8 9


Sol 9 11 14 18


Total solubles 17 20 22 27


The results show that increasing screw speed leads to
increased shearing and therefore increased devulcanization.
In order to study the changes in properties after
devulcanization through extrusion, products were
revulcanized with curing agents. Two samples were prepared
using devulcanized SBR 40 mesh obtained following the
procedure as described in the Examples above with 2.1 wto
COZ and 4.6 wt% COZ concentration at 250°C, 50 rpm. These
samples were compounded according to the following recipe:



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Table 6
Ingredient Parts by weight
Devulcanized Rubber 100


Sulphur POLYBOUNDT"" 80%* 1.2


MBTS 301 POLYBOUNDT~~ 80%* 0.6


TMTD 304 POLYBOUNDTM 80s* 0.6


*ex Poly One Canada Inc., Mississauga, Ontario, Canada
The samples were milled on a Farrel Laboratory mill
with size 28 cm length and 15 cm. diameter for 2-3 minutes.
The nip size was 6 mm and the mill rolls start-up
temperatures was 20°C. The curing agents were added and
blended for another 3-4 minutes. When the compound was
running, the temperature increased to 25°C gradually and
the compound became sticky and not easily removed from the
mill rolls. After mixing, the matrix was molded on a 15T
vantage Press with 2 cavities for 15 minutes at 330° F for
test specimen preparation. The molded specimens had a good
rubbery appearance.
After compounding, the following properties were
determined based on ASTM D412 method. The properties,
including Mooney viscosity, tensile strength, elongation at
break, modulus, and tear strength and are summarized in the
Table 7.
Compared to typical rubber compounds, the physical
properties of devulcanized rubber are apparently reduced.
This suggests that severe devulcanization has occurred at
the used extrusion conditions. However, the processing can
easily be controlled and optimized, for example by reducing
shear rates, to reduce the degree of devulcanization. The
devulcanized rubber product obtained in accordance with the
invention may be used in blends with virgin rubber as well
as other thermoplastic polymers.



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Table 7 Processing and Physical Properties
of Devulcanized SBR
Compound Parameter Dewlcanized SBR withDevulcanized SBR
4.6 wt% COZ with
2.1 wto COz


Mooney(1+4, 125C)min32.1 34.7


T5 (121C) min 8.79 8.58


T90 (169.8C) min 0.60 0.59


MLS1 1.35 1.49


MHS1 7.24 7.98


Tensile MPa 3.3 3.7


Tensile set at break0.50 1.50


Tensile set 1.1% 5.2%


Elongation s 172's 1800


Hardness Shore A 47 48


Modulus 100% MPa 1.7 1.8


Modulus 2000 MPa 3.0 2.6


Modulus 300% MPa 0.8


Tear KN/m 10.0 10.1


While the above Examples have described use of carbon
dioxide as the supercritical fluid, it will be appreciated
that other normally gaseous fluids that can be rendered
supercritical in the apparatus may be employed. Such
normally gaseous fluids include but are not limited to
ethane, ethene, propane, propene, xenon, nitrogen, ammonia,
nitrous oxide and fluoroform.
Using procedures similar to those described above in
Examples 1 to 3, other crosslinked rubber materials can be
devulcanized. Such other materials include natural rubber,
EPDM (ethylene-propylene dime rubbers), EPT (ethylene-
propylene terpolymer rubbers), TPU (thermoplastic urethane
rubbers), TPEs (thermoplastic elastomers), TPVs
(thermoplastic vulcanizates), butyl rubber, nitrile rubber,



CA 02500372 2005-03-29
WO 03/029298 PCT/CA02/01491
- 16 -
polysulfide elastomers, polybutadiene, polyisoprene rubber,
polyisobutylene, polyester rubbers, isoprene-butadiene
copolymers, neoprene rubber, acrylic elastomers,
diisocyanate-linked condensation elastomers, silicone
rubbers, crosslinked polyethylene, ethylene-vinylacetate
polymers, and mixtures thereof.
Example 4
EPDM rubber 60 mesh was processed as described in the
preceding Examples at barrel temperatures of 250°C and
300°C and at screw speeds of 25 and 50 rpm, with a feed
rate of 15 g/min and 2 wt% COZ concentration. The analysis
of the starting materials and of the products is shown in
Table 8.
Table 8
Starting 250C 300C


material
EPDM 25 rpm 50 rpm 25 rpm 50 rpm


Low m.w. 15 15 18 9 14


Sol 9 14 16 17 14


Total 24 29 34 26 28
solubles


The effect of temperature on the devulcanization may
be seen. While SBR is temperature sensitive, EPDM has very
good heat resistance and displays quite different
devulcanization behavior at 250°C and 300°C. The raw EPDM
powder could not be devulcanized at 200°C. Increasing
temperature resulted in decreased soluble fraction and low
molecular weight fraction. For instance, the soluble part
at 50 rpm changed from approximately 34a at 250°C to 28s at
300°C. Nevertheless, at 25 rpm, the sol content increased
from about 14o at 250°C to about 17% at 300°C compared to



CA 02500372 2005-03-29
WO 03/029298 PCT/CA02/01491
- 17 -
the decrease of sol content at 50 rpm from about 16% at
250°C to about 14% at 300°C. Therefore, excessively high
temperature is unsuitable for devulcanization process of
EPDM at higher screw speed, and the devulcanization can be
controlled by controlling shear rates and temperature.

Representative Drawing
A single figure which represents the drawing illustrating the invention.
Administrative Status

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Administrative Status

Title Date
Forecasted Issue Date 2011-06-28
(86) PCT Filing Date 2002-10-01
(87) PCT Publication Date 2003-04-10
(85) National Entry 2005-03-29
Examination Requested 2007-09-25
(45) Issued 2011-06-28

Abandonment History

Abandonment Date Reason Reinstatement Date
2008-10-01 FAILURE TO PAY APPLICATION MAINTENANCE FEE 2009-09-16

Payment History

Fee Type Anniversary Year Due Date Amount Paid Paid Date
Reinstatement of rights $200.00 2005-03-29
Application Fee $400.00 2005-03-29
Maintenance Fee - Application - New Act 2 2004-10-01 $100.00 2005-03-29
Maintenance Fee - Application - New Act 3 2005-10-03 $100.00 2005-07-29
Maintenance Fee - Application - New Act 4 2006-10-02 $100.00 2006-09-21
Request for Examination $800.00 2007-09-25
Maintenance Fee - Application - New Act 5 2007-10-01 $200.00 2007-09-25
Reinstatement: Failure to Pay Application Maintenance Fees $200.00 2009-09-16
Maintenance Fee - Application - New Act 6 2008-10-01 $200.00 2009-09-16
Maintenance Fee - Application - New Act 7 2009-10-01 $200.00 2009-09-16
Maintenance Fee - Application - New Act 8 2010-10-01 $200.00 2010-06-25
Final Fee $300.00 2011-04-13
Maintenance Fee - Patent - New Act 9 2011-10-03 $200.00 2011-07-13
Maintenance Fee - Patent - New Act 10 2012-10-01 $250.00 2012-05-03
Maintenance Fee - Patent - New Act 11 2013-10-01 $250.00 2013-04-05
Maintenance Fee - Patent - New Act 12 2014-10-01 $250.00 2014-04-04
Maintenance Fee - Patent - New Act 13 2015-10-01 $250.00 2015-04-14
Maintenance Fee - Patent - New Act 14 2016-10-03 $250.00 2016-04-15
Maintenance Fee - Patent - New Act 15 2017-10-02 $450.00 2017-09-05
Maintenance Fee - Patent - New Act 16 2018-10-01 $450.00 2018-09-11
Maintenance Fee - Patent - New Act 17 2019-10-01 $450.00 2019-07-02
Maintenance Fee - Patent - New Act 18 2020-10-01 $450.00 2020-09-02
Maintenance Fee - Patent - New Act 19 2021-10-01 $459.00 2021-08-18
Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
TZOGANAKIS, COSTAS
Past Owners on Record
None
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Cover Page 2005-06-20 1 25
Claims 2005-03-29 2 57
Abstract 2005-03-29 1 45
Claims 2010-05-18 4 125
Drawings 2005-03-29 6 83
Description 2005-03-29 17 628
Cover Page 2011-06-17 1 26
Prosecution-Amendment 2009-12-22 2 53
PCT 2005-03-29 3 104
Assignment 2005-03-29 3 86
Fees 2005-07-29 1 26
Fees 2006-09-21 1 28
Prosecution-Amendment 2007-09-25 1 27
Fees 2007-09-25 1 29
Fees 2009-09-16 2 68
Prosecution-Amendment 2010-05-18 7 212
Fees 2010-06-25 1 35
Correspondence 2010-10-15 1 30
Correspondence 2011-04-13 1 36