Note: Descriptions are shown in the official language in which they were submitted.
CA 02459191 2004-02-27
GROUND ELASTOMER OR PLASTIC OR COMPOSITE MATERIALS WITH
SUBSTANTIALLY HOMOGENOUS PROPERTIES
CROSS-REFERENCE TO RELATED APPLICATION
0001 The present application is related to U.S. Patent Nos. 6,333,373 filed on
February 10, 1999 entitled "Ground Elastomer and Method", 6,238,448 filed
August 16, 1999 entitled "Grinding Stones", 6,426,136 filed on January 30,
2000 entitled
"Method of Reducing Material Size" and U.S. Patent Application Nos. 60/331,537
filed
November 19, 2001; 60/334,097 filed November 30, 2001; 60/331,538 filed
November
19, 2001; 60/178,130 filed January 26, 2000; 10/164,426 filed June 10, 2002;
09/984,961
filed October 31, 2001; 10/294,897 filed November 15, 2002; 09/984,961 filed
October
31, 2001; 09/658,678 filed September 8, 2000; 10/177,161 filed June 24, 2002
and
09/768,497 filed January 25, 2001, the content of which is incorporated herein
by
reference in its entirety.
BACKGROUND OF THE INVENTION
Technical Field of the Invention
[0002] The present invention relates generally to elastomers and methods
involving at
least two different materials, and in particular, to methods and materials
that can be
employed with both virgin and recycled or scrap products.
Description of Related Art
[0003] In recycling and reusing rubber materials, it is generally known to
decrease the
size of such rubber materials to small ground rubber particles (i.e.,
particles of irregular
outline that pass through a minus 80 mesh or through a minus 50-mesh or
finer). Such
particles can be chemically more reactive and mechanically easier to dissolve
into various
mixes.
[0004] A variety of rubber products (e.g., natural rubber, synthetic rubber,
vulcanized
rubber, automotive tire scrap, etc.) may be reduced to ground rubber
particles. Known
methods for producing rubber of a decreased size include cryogenic cracking of
the
rubber. Other known methods include the milling of the rubber between
horizontal
la
CA 02459191 2004-02-27
Atty l7ocket No. 22132.00028
."
grinding stones in a horizontal grinding mill. Such milling techniques have
been
developed in the flour, paper pulp industry and the paint pigment compounding
industries. Such milling techniques include grinding the rubber between
opposed milling
wheels, such that one wheel is fixed and the other wheel rotates relative to
the fixed
wheel. Such known milling techniques include pressing the two wheels against a
rubber
slurry, such that the rubber is ground to a fme state (i.e., powder) in a
single pass.
However, such known milling methods have the disadvantage of creating friction
and
introducing energy to the slurry, which may increase the temperature of the
slurry.
Increased slurry temperatures may cause "flash over" in which the slurry
becomes a
largely dry rubber mass that inhibits grinding. Such known milling methods
further have
the disadvantage of not producing a uniformly fine rubber powder that passes
through a
minus 50-mesh.
[0005] Processes of reducing material size of elastomers are generally known
such as
described in U.S. Patent No. 6,133,373. However, it has been found that the
chemical
and physical properties of the final products produced thereby may not be
uniform
enough to be used in many industries. Such lack of uniformity would therefore
drive
down the market price for these materials and make them less desirable in
industries such
as the automotive industry where specifications and reproducible standards are
not only
encouraged, they are mandatory in almost every situation.
[0006] Accordingly, it would be advantageous to have methods and products
whereby
two or more different materials could be commingled together in an effort to
prepare a
single unitary product with common properties throughout. It would also be
desirable for
such common properties to be reproducible.
SLITyIMARY OF THE INVENTION
[0007] The present invention, therefore, is directed to ground elastomeric and
thermoplastic materials having substantially homogenous physical and chemical
properties as well as to related methods and their uses. Ground elastomeric
materials of
the present invention preferably include multiple materials from multiple
sources,
2
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CA 02459191 2004-02-27
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particularly recycled materials that are treated by grinding so that the
material becomes a
homogenous mixture with common properties throughout the entirety of the
material.
[0008] Additional objects, features and advantages of the invention will be
set forth in the
description which follows, and in part, will be obvious from the description,
or may be
learned by practice of the invention. The objects, features and advantages of
the
invention may be realized and obtained by means of the instrumentalities and
combination particularly pointed out in the appended claims.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0009] Preferably, the elastomers employed in connection with the present
invention are
originate from the same elastomeric "family." For example, fluoroelastomers
(such as
fluorosilicones), nitrites, SBR, silicones and so on. The size of an elastomer
(e.g., natural
rubber, synthetic rubber, recycled rubbers containing polyethylene and/or
polypropylene,
vulcanized rubber, carbon black, waste from tire production, various polymers,
various
plastics, thermoplastic elastomers, thermoplastic vulcanates, polyethylene
plastics, etc.)
may be decreased using a variety of mechanisms. According to an exemplary
embodiment, the elastomer is soaked in a fluid. According to a preferred
embodiment, the
fluid is soapy water and/or an aromatic oil. Soaking the elastomer, among
other things,
causes the elastomer to swell, removes oils a from the elastomer and dissolves
adhesives
in the elastomer.
[0010] According to an exemplary embodiment, a variety of water-soluble
additives may
be added to the soaking fluid. The additive, when used during soaking of the
elastomer,
decreases the swelling time of the elastomer as compared to elastomers soaked
in the
absence of the additive. According to an alternative embodiment, the additive
may be a
chemical that swells the rubber, but is not a tackifier, such as
tetrahydrofuran (THF) or
dimethyl formamide (DMF). According to other alternative embodiments, a
variety of
additives (as described below) may be used when soaking the elastomer.
According to a
preferred embodiment the additive used when soaking the elastamer is a fatty
amine, such
as DELAMINTM commercially available from Hercules, Inc. What is important is
that
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Atty Docket No. 22132.00028
whatever additive is employed; it is added in order to compatibilize the two
or more
elastomers that are desired to be homogenized.
[0011 J In fact, is is possible that even uncured elastomers (known as "spru"
in the
industry) can be cogound with at least one other elastomer of the same
elastomeric
family. It has unexpectedly been found that the uncured material when coground
with
other scrap material or other elastomers, will coat the other elastomer, i.e.,
especially with
silicone, and makes for better adhesive properties of the cured elastomer when
it is
utilized in downstream applications. Moreover, the spru coground with another
elastomer
(scrap or not scrap) can also be added to virgin materials for many
applications with a
huge degree of success. Since 10% of scrap material in many plants is the
uncured
material, the ability to reuse this material successfully amounts to an
unexpected
advantage of the present invention, particularly because the uncured material
can be
added in the degree desired to impart certain properties to the final coground
material
with homogenous properties. It is also possible to employ many thermoplastics
such as
polypropylenes, polyethylene, chlorinate PE, ultra high molecular weight PE,
polycarbonate can be reduced to plastic particles. Other materials such as
Nylon 6, Nylon
6.6, Nylon 12 and other composites can be reduced to particles in the present
invention.
This could also include carbon, vegetable matter, and biological materials.
[0012] In the present invention, at least two plastomers and/or elastomers
(designated at
"P") are employed wherein the final product may be Pl-~-PZ or P1+PZ+P3 or
P1+P3+P" and
so on. The number of elastomer (vulcanized and unvulcanized) can be any
desired
number and should be selected for the desired Tg and other physical properties
such as
TPA.
[0013) The size of the soaked elastomer may be decreased in a grinding
apparatus, such
as a set of milling stones. According to an alternative embodiment, the size
of the soaked
elastomer may be decreased by freezing the elastomer and cracking or hammering
or
extruding the elastomer into small sized particles. According to other
alternative
embodiments, the soaked elastomer is shredded by a series of blades or an
Archimedes
screw apparatus. According to still other alternative embodiments, the size of
a soaked or
non-soaked elastomer may be decreased by brute force (i.e., by two
counteracting
4
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Atty Docket No. 22132.00028
surfaces). According to a preferred embodiment, grinding of the soaked
elastomer
material is achieved using the grinding apparatus as disclosed in U.S. Pat.
No. 5,238,194
issued Aug. 24, 1993 to Rouse et al. for "METHOD OF PRODUCING FINE
ELASTOMERIC PARTICLES" and incorporated herein by reference. The grinding
apparatus expediently includes a horizontal grinding machine providing a fixed
stator and
a rotating rotor, on which disc-shaped grinding stones having hollow centers
can be
mounted. The grinding stones provide flat, opposing abrasive surfaces (i.e.,
flat annulus
surface), and each grinding stone is opposed to the other. The abrasive
surfaces provide
periodically spaced openings in the annulus for introducing the elastomers to
be ground
between the closed, cooperating abrading surfaces.
[0014] Impurities (e.g., metals, cords, reinforcing materials; etc.) may be
removed from
the ground elastomer. According to an alternative embodiment, a magnet may be
used to
remove certain metallic impurities from the ground elastomer. According to a
preferred
embodiment, the impurities can be removed by passing the ground elastomer
through a
screen that allows 1/4-inch to 518-inch particles to pass through.
[0015] An elastorner slurry may be formed by adding a carrier to the ground
elastorner.
According to an alternative embodiment, the carrier may be a gas (e.g., air)
that may
carry a wet or dry stream of elastomer particles. According to other
alternative
embodiments, the carrier is a fluid (e.g., water). According to other
alternative
embodiments, the carrier may be provided through the grinding apparatus before
the
slurry is provided through the grinding apparatus. According to any
alternative or
preferred embodiment, a uniform set point fluid flow rate through a properly
spaced set of
grinding stones is determined as disclosed in U.S. Pat. No. 5,238,194 issued
Aug. 24,
1993 to Rouse et al. for "METHOD OF PRODUCING FINE ELASTOMERIC
PARTICLES" and incorporated herein by reference.
[0016] According to an exemplary embodiment of the present invention, the
additive may
be added to the slurry. The additive provides for faster grinding of the
slurry as compared
to a slurry in which the additive is absent. According to an alternative
embodiment the
additive is a water miscible dispersing agent for carbon black, such as
DAXADTM
commercially available form R. T. Vanderbilt Company, Incorporated of Norwalk,
Conn.
CA 02459191 2004-02-27
Atty Docket No. 22132.00028
According to a particularly preferred embodiment about 25% DAXADTM is added to
an
elastomer slurry of 15% to 60% solids. According to an alternative embodiment,
the
additive is a surfactant, such as TRITON-XTM commercially available from Rohm
&
Haas Company. According to a particularly preferred embodiment, the additive
is added
to the slurry in the amount of about 1% to 20% based on the amount of
elastomer in the
slurry, and about 10% to 15% by total weight of the elastomer in the slurry.
[0017] The additive provides a higher yield at the first pass of grinding of
the slurry as
compared to a slurry in which the additive is absent. Use of the additive
produces a higher
quantity (i.e., more uniformly fine ground and having less shear) particle as
compared to
a the particles produced from a slurry in which the additive is absent. A
slurry having an
additive yields a significant increase in throughput of ground particles of
the desired
smaller size, and a smaller percentage of particles passed through the mill
without
adequate reduction in size. This alone is beneficial, as the economic losses
occasioned by
the necessity of screening out insufficiently reduced particles and re-
grinding them can be
reduced. Further, use of the additive provides decreased grinding times of the
slurry as
compared to a slurry in which the additive is absent. Generally, optimizing
the proper
additive will affect the desired properties and/or consistency of the slurry.
Decreased
grinding times may reduce wear and damage to the wheels of the grinding
apparatus.
[0018] The additives provide a lower temperature to the slurry as compared to
a slurry in
which the additive is absent. A slurry in which the additive is absent reaches
high
temperatures, whereas the slurry having the additive may have lower maximum
tempertatures. Decreased temperature of the slurry is beneficial, in part,
because high
temperatures may destroy some polymers, less insulation is required in the
grinding
apparatus, heat damage to the grinding apparatus is decreased and the
temperature of the
grinding operation is better controlled to achieve the desired viscoelastic
effects in milling
the elastomer.
[0019] The additives chemically react with the elastomer to produce a more
desirable
uniform homogenous elastomer particle. The glass transition temperature (Tg)
of the
elastomer-additive product is more uniform as compared to elastomer particle
product in
which the mixtures and optional additives are not employed. A uniform Tg value
over
6
CA 02459191 2004-02-27
Atty Dacket No. 22132.00028
the entirety of the product produced is beneficial in producing downstream
materials from
the elastomer-additive product because uniformity of glass transition
temperature is
necessary for down stream applications. That is, the Tg should not vary more
than 15%
over the entire "batch" produced, preferably not more than 10%, most
preferably no more
than 5%. A lower temperature is often required for the elastomer-additive
product to
change from a brittle state to a plastic state, which reduces energy costs.
Uniformity is
often difficult to achieve, even when an additive is used. Further, the
additives
chemically react with the elastomer to produce a more tacky elastomer-additive
particle
product as compared to the elastomer particle product in which the additive is
absent.
Thus, the Tg can vary widely with many additives.
[0020] According to an alternative embodiment, the additive is a resin
(natural or
synthetic). According to other alternative embodiments, the additive is a
rosin (i.e., a
mixture of monocarboxylic acids having a hydrophenanthrene nucleus) such as
gum rosin
or wood rosin. Rosins are of particular interest because they tend to act as
dispersing
agents in the elastomer slurry and affect the tackiness of the elastomer-
additive product.
According to a preferred embodiment of the present invention, the rosin is
tall oil rosin
(i.e., a by-product of the paper manufacturing process). According to a
particularly
preferred embodiment, the tall oil rosin has a low acid number, such as XP56TM
commercially available from Arizona Chemical Company.
[0021 ] According to an alternative embodiment, the additive is a resin acid
(i.e., abietic-
type acids that contain an isopropyl group pendent from carbon 13 as numbered
using the
Chemical Abstracts system, or pimaric-type acids that include a methyl and
vinyl group
pendent from the same carbon atom). According to other alternative
embodiments, the
resin acid is abietic acid or rosin soap (i.e., rosin leached with sodium
hydroxide). The
rosin is made water-soluble by neutralizing the rosin with a suitable base,
such as
ammonia, ammonium hydroxide, an amine (i.e., a Frisch amine). Other additives
of
interest include any rosin acid, polymerized rosin acid, esters of rosin acid,
dispersions of
rosin acid, dispersions of esters of rosin acid, copolymers of rosin acid,
disproportionated
rosin acid, hydrogenated rosin acid, 9-anthracene carboxylic acid, 2-
ethylhexanoic acid,
acetal R-type acids, or any organic acid that could be soluble in water by
neutralizing the
acid.
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CA 02459191 2004-02-27
Atty Docket No. 22132.00028
[0022] According to an alternative embodiment, the additive is oleic acid
(i.e., (CH3
(CH2)~ CH:CH(CH2)~ COOH derived from animal tallow or vegetable oils). Oleic
acid
may not substantially modify the tackiness of the elastomer-additive product.
[0023] According to an alternative embodiment, the additive is an oligimer
(i.e., a low
molecular weight polymer molecule consisting of only a few monomer units
(e.g., dimer,
trimer, tetramer)). According to a preferred embodiment, the oligimer has a
viscosity of
about 100,000 CP and tends to act as a dispersing agent in the elastomer
slurry.
According to a preferred embodiment the oligimer is short chain copolymers of
styrene
and malefic anhydride that offer typical anhydride functionality in a
polymeric material
such as SMA~ resin commercially available from Sinclair Petrochemicals,
Incorporated.
According to a preferred embodiment, the oligimer is ethylene-malefic
anhydride
copolymers such as EMA~~'i resin commercially available from Monsanto
Industrial
Chemicals Co.
[0024] According to an alternative embodiment, the additive is an ester, such
as di(2-
ethylhexyl) adipate (also known as dioctyl adipate or DOA), DOS, DOD or
plasticizers in
PVC.
[0025] A filler may optionally be added to the slurry. The filler may be added
to the
slurry (i.e., elastomer slurry or elastomer-additive slurry) to combine with
the slurry to
form an elastomer-additive product or an elastomer product having reinforcing
properties,
temperature modifying properties, increased high surface area, and/or
increased tensile
strength. A filler (e.g., nylon) combines with the final elastomer product to
give the final
product reinforcing properties, temperature modifying properties, increased
high surface
area, and/or increased tensile strength. According to a particularly preferred
embodiment
of the present invention, the filler is a nylon material. Also silica, Talc or
any other
desired partition agents can be used.
[0026] The slurry (i.e., elastomer-additive slurry or elastomer slurry) is
provided within a
grinding apparatus and the elastomer and the additive can be co-ground (or the
elastomer
is ground) to decrease the elastomer particles to a decreased size. According
to an
alternative embodiment, the slurry is provided between the two wheels of the
grinding
apparatus as disclosed in U.S. Pat. No. 5,238,194 issued Aug. 24, 1993 to
Rouse et aI. for
8
CA 02459191 2004-02-27
Atty Docket No. 22132.00028
"METHOD OF PRODUCING FINE ELASTOMERIC PARTICLES" and incorporated
herein by reference. The grinding stones can be brought into contact with (or
spaced a
distance apart from) each other. Choosing or maintaining the fixed position of
the
grinding stones with respect to each other is known in the art of colloid
mills. Persons of
skill in the art will readily understand how the slurry is input, at a feed
pressure, to such
grinding stones and how the spacing between the stones is to be adjusted and
set. The
grinding action generates heat, which may be controlled, modified or reduced
by the
particular additive in the slurry.
[0027] The earner and the slurry (i.e., elastomer-additive slurry or elastomer
slurry) can
be separated. According to an alternative embodiment, the liquid from the
slurry is
removed to a capture region positioned outside the outer perimeter of the
opposed
grinding stones. According to a preferred embodiment, the carrier is removed
by a
centrifuge action, such that the carrier is driven off from the slurry and the
elastomer-
additive particles or the elastomer particles remain. Floatation methods can
also be
employed if desired as known in the industry.
[0028] The grinding of the slurry (i.e., elastomer-additive slurry or
elastomer slurry) may
be conducted in a single pass or a multiple pass operation. According to an
alternative
embodiment, the grinding operation may be conducted in a single pass where the
coarse
particles that do not pass a screening operation can be feed to a slurry
(i.e., elastomer-
additive slurry or elastomer slurry) for re-grinding. According to any
alternative or
preferred embodiment, the grinding operation may be conducted in a multiple
pass where
two interconnected grinding mills sequentially grind the slurry to a final
fine grind state
as disclosed in U.S. Pat. No. 5,411,215 issued May 2, 1995 to Rouse for "TWO
STAGE
GRINDING" and incorporated herein by reference. According to the multiple pass
grinding operation, a first grinding mill produces an intermediate feedstock
of decreased
size. The feedstock is re-wet with water or another carrier to form a feed
slurry that is
then sequentially fed into a second mill. The multiple pass grinding
operation, by
selecting optimum size of the grinding stones for production of the
intermediate feedstock
and then for the production of the final minus 80-mesh to 200-mesh product,
requires less
energy than, for example, the single pass grinding operation.
9
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[0029] The elastomer mixture plus optional additive if needed or desired which
can
optionally form a composite may be dried by heat or air.
[0030] According to an alternative embodiment, the earner "flashes off' when
the ground
particles in slurry exit from between the grinding stones to a decreased
pressure (i.e.,
atmospheric pressure). The flash avoids the necessity of having a separate
processing step
of drying the ground particles, which saves energy costs of running a
separator. The
elastomer product is recovered.
[0031] The elastomer or plastomer, which preferably chemically bonds with the
additive
to form the mufti-elastomer-additive and/or plastomer product, has certain
functional
characteristics. According to an exemplary embodiment, the elastomer-additive
product is
a very fme powder having a consistency similar to cooking flour. According to
an
alternative embodiment, the elastomer-additive product is in the original
vulcanized state.
The top and bottom variation of the softening point of the rosin-modified
elastomer-
additive product varies by about 1°Celsius. This range of softening
variation is
advantageous compared to the elastomer product that is not rosin-modified,
which has a
top and bottom softening point that various by about 10°Celsius.
[0032] By using one or more additives with the ground elastomer as described
herein, a
finely ground product is obtained that is unexpectedly superior in terms of
many of its
properties, particularly when used in many products such as roofing, paving,
building
materials, sealants, automotive products, plastic skins, etc. The final
product obtained
when using one or more additives as described herein will generally have a
bulk density
of 26-28 lbs./sq. ft., have a specific gravity of from 1.13 +.backslash.-0.02;
have 100% of
the particles finer than 17S microns or minus 80 mesh. Ground elastomer, or
thermoplastic, products prepared as described herein will typically resist
phase separation,
are storage stable, provide superior low temperature properties and have
excellent high
temperature stiffness. When the ground elastomer is mixed at a ratio of from
10-1S%
with asphalt such as WY Sour AC-20, AC-10, Venezu. AC-20, Saudi AC-20 and the
like,
by any known method, the storage stability of the asphalt product per ASTM
DS892
(incorporated herein by reference) also known as the "Cigar Tube" storage
stability test
will typically range for the top (SP, top, °F.) from 133-144 and at the
bottom (SP, bottom,
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Atty Docket No. 22132.00028
°F.) from 134-156. The change in storage stability between the top and
bottom sections
generally remains substantially unchanged, that is, the ~1F. from top to
bottom will
preferably be from 0-2 degrees. This is beneficial, inter alia, because the
small change in
storage stability of the asphalt will minimize cracking due to temperature
changes since
the layers of asphalt applied for example on a road, will generally age at the
same rate.
Asphalt including a ground elastomer with one or more of the instantly
described
additives will also be easier to store and ship. However, asphalt is but one
possible use;
many others are envisioned and are highly adventageous.
[0033] The additive can be added in any desired amount. Preferably the
additive is added
in an amount from 0.5% to 95%, more preferably from 5% to 40% advantageously
from
5% to 20% but in a preferred embodiment is added in an amount of about 10% or
10%, in
each case being based on the total weight of the elastomer.
(0034] In accordance with the present invention, the final material produced
by the
process involves a situation whereby the at least two elastomers are ground
for a time
sufficient to commingle the polymeric backbone of both materials to form a new
polymeric material that is chemically uniform throughout the whole of the
material. If
necessary, an additive can be provided that causes the polymeric backbones of
the
materials to breakdown when being ground in at such a force to impart a new
polymeric
material with substantially uniform glass transition temperature, and a
substantially
uniform particle gradation TPA when subjected to a gravonometric analysis as
well as a
uniform melt flow index, when any part of the final material is tested.
EXAMPLES
[0035] In a two roll mill as disclosed in US Patent No. 5,411,215, and
5,238,194, the
contents of which is incorporated herein by reference, two different silicone
materials
(one prepared by peroxide oxide or and one by catalysis system) are coground
according
to the method disclosed therein to -40 mesh and the Tg (glass transition
temperature) and
particle gradation (TPA) are analyzed. It was found throughout the entirety of
the ground
material, the Tg, and TPA and melt flow index varied by as much as 45%. This
was used
as a baseline comparison.
11
CA 02459191 2004-02-27
Atty Docket No. 22132.00028
[0036] In the same two roll mill, the same two silicone materials peroxide and
catalysis
q made polymers were coground with uncured silicone. During the mixing and
cogrinding,
the mixture was monitored to ensure that the polymeric backbones of the two
silicones
were broken down. The materials were ground to the same -40 mesh size.
However,
when the Tg, TPA and melt flow index were measured of this inventive material,
it wsa
found that these physical properties did not vary more than 5% throughout the
entirety of
the material.
[0037] Additional advantages, features and modifications will readily occur to
those
skilled in the art. Therefore, the invention in its broader aspects is not
limited to the
specific details, and representative devices, shown and described herein.
Accordingly,
various modifications may be made without departing from the spirit or scope
of the
general inventive concept as defined by the appended claims and their
equivalents.
[0038] All documents referred to herein are specifically incorporated herein
by reference
in their entireties.
[0039] As used herein and in the following claims, articles such as "the", "a"
and "an"
can connote the singular or plural.
12
