Note: Descriptions are shown in the official language in which they were submitted.
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REACTIVE EXTRUSION OF TAILORED LIQUID POLYMERS (TLP'S)
The present invention relates to polyurethane polymers. The present invention
particularly relates to polyurethane polymers and to a process for preparing
same.
It is known to prepare polyurethane polymers from polyols, polyisocyanates and
other additives by combining an isocyanate "A-side" mixture with a polyol "B-
side"
mixture. Isocyanates and polyols are conventionally combined to make
polyurethanes
using what is known in the art of making polyurethane polymers as "A/B"
polyurethane
chemistry. Polyurethane polymers are useful as flexible foams, rigid foams,
elastomers, coating resins, adhesives, sealants, fibers, and films.
Conventional preparation of polyurethane polymer materials using traditional
"A/B" chemistry requires that a manufacturer of polyurethane polymer products
prepare the polymer on site. This can present problems for certain
manufacturers of
polyurethane products.
Extrusion of thermoplastic polymers such as polystyrene and acrylate polymers
such as poly(methyl methacrylate) is a well-known process. See, for example,
each of
the following, each with respect to the teachings on extrusion processes:
James M.
McKelvey, Plastics Processine, John Wiley & Sons, New York, 1962; A. S.
Haisser,
"Extrusion", in Modern Plastics Encyclopedia 1982-1983, Vol. 59, No. 10A,
McGraw-
Hill, New York, 1982; Paul N. Richardson, Introduction to Extrusion, John
Wiley &
Sons, New York, 1974. Extrusion is a fabrication process whereby polymeric
materials
are shaped or re-cast into useable, salable pieces of polymeric materials.
Typically, in
an extrusion process a polymer is pushed continuously along a screw while
being
melted and compacted in regions of high pressure and temperature. The polymer
is
finally forced through a die which gives the polymer its final shape. Polymers
having
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shapes which include tubing, hose, sheets, and films, for example, and can be
made in
an extrusion process.
It would be desirable in the art of preparing polyurethane polymers to prepare
such polymers from materials that have low viscosity and little chain
extension. It
would also be desirable in the art of preparing polyurethane polymers to
obtain foams,
films, gels, adhesives, and hard elastomers directly from an extruder by an
extrusion
process.
In one aspect, the present invention is a process for preparing, from
isocyanate-
terminated prepolymers, melt-processable elastomeric polymers comprising a
urethane
linkage, wherein the polymers are obtained by a reactive extrusion process
comprising
the steps: (a) feeding a liquid prepolymer to an extruder device; (b) passing
the
prepolymer of step (a) through the extruder while heating the prepolymer; and
(c)
extruding an elastomeric polymer.
In another aspect the present invention is a polyurethane polymer obtained by
preparing, from isocyanate-terminated prepolymers, melt-processable
elastomeric
polymers comprising a urethane linkage, wherein the polymers are obtained by a
reactive extrusion process comprising the steps: (a) feeding a liquid
prepolymer to an
extruder device; (b) passing the prepolymer of step (a) through the extruder
while
heating the prepolymer; and (c) extruding an elastomeric polymer.
Polyurethane polymers described herein can be prepared from tailored liquid
polymer (TLP) prepolymers in either the absence or presence of a polyurethane
catalyst. TLPs can be crosslinked in a reactive extrusion process wherein the
TLP is
fed to an extruder and processed as a liquid, is crosslinked to form the
polymer as it is
being forced through the screw cavity. Polymers of the present invention are
melt-
processable, that is polymers that can be processed above the Tg of the
polymer
material. For the purposes of the present application, melt-processable
polymers of the
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present invention can be formed from reactants, in the substantial absence of
a solvent,
at a temperature greater than the Tg of the product obtained, and the polymer
product
subsequently processed as a melt. Melt processable polymers can be heated
above the
Tg of the polymer and shaped, molded or otherwise physically altered as a
polymer
melt.
The term "polyurethane", as used herein, is not limited to those polymers
which
include only urethane or polyurethane linkages. It is well understood by those
of
ordinary skill in the art of preparing polyurethanes that the polyurethane
polymers also
include allophanate, biuret, carbodiimide, oxazolinyl, isocyanurate,
uretidinedione,
urea, and other linkages in addition to urethane linkages.
In one embodiment, melt processable polymers of the present invention can be
obtained by reactive extrusion of a TLP. A reactive extrusion process is
similar to a
1 S conventional extrusion process, except that the material fed into the
extruder is
chemically reacted and physically modified inside of the extruder. In a
conventional
extrusion process no chemical reaction is carried out in the extruder.
Typically, a pre-
formed polymeric material is physically modified by softening and re-shaping a
polymer into a particular form.
TLPs are free flowing liquid oligomeric polyurethane materials prepared by
reaction of a polyisocyanate with a polyol. The reaction between the
polyisocyanate
and the polyol is carried out at low temperature and in the absence of
catalyst. The TLP
thus obtained has low viscosity and has very little chain extension. The
preparation of
TLPs is known and described in World Patent publication number W09634904-A1.
By
low temperature, it is meant that a TLP material can be prepared at a
temperature less
than about 150°C. Preferably a TLP is prepared at a temperature of from
20°C to
125°C. More preferably, a TLP is prepared at a temperature of from
25°C to 115°C,
and most preferably from a temperature of from 25°C to 100°C.
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A TLP of the present invention can have any molecular weight, so long as the
TLP is a free flowing liquid prepolymer material. A TLP suitable for use in
the
practice of the present invention can be a single TLP prepolymer or a mixture
of at least
two prepolymers. Whether a single component or a mixture, a TLP of the present
invention optionally has a functionality in the range of from 2 to 6. In a
preferred
embodiment, one prepolymer of a prepolymer mixture can have functionality of
about 2
with a molecular weight of less than about 10,000 and the other prepolymer can
have
mufti-functionality with molecular weight of less than about 12,000. More
preferred is
a prepolyrner mixture wherein at least one prepolymer has functionality about
2 and a
molecular weight of from 2000 to 10,000, and a second prepolymer of the
mixture has a
functionality of about six (6) and a molecular weight of from 3,000 to 12,000.
It is
preferred in the practice of the present invention that the TLP has
functionality and
molecular weight such that it is a free flowing liquid at less than about
50°C, and more
preferably, the TLP has a molecular weight and functionality such that it is a
free
flowing liquid at less than about 20°C. Prepolymer components used in
the mixture
herein can be combined in any ratio that will provide the average prepolymer
functionality suitable for the practice of the present invention. Prepolymers
having low
monomer content are preferred in the practice of the present invention.
Monomer
content of less than 20 percent, preferably less than 15 percent and more
preferably less
than 10 percent is desirable in the practice of the present invention.
A TLP can be reactively extruded, and an elastomeric polyurethane polymer
obtained, by feeding the TLP into an extruder and processing the TLP at a
screw speed
of from 10 to 200 rpm. The TLP can be processed in the extruder at a
temperature of
from 25°C to 250°C. Preferably the TLP is passed through the
extruder at a
temperature of from 50°C to 160°C, at a screw speed of from 50
rpm to 200 rpm. More
preferably, a TLP is passed through an extruder at a temperature of from
60°C to
140°C, at a screw speed of from 100 to 150 rpm.
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A polyisocyanate suitable for use in the practice of the present invention can
be
any polyisocyanate known to be useful in the preparation of polyurethane
foams. A
suitable polyisocyanate can be either aliphatic or aromatic. Aromatic
polyisocyanates
suitable for use herein include: phenyl diisocyanate; 2,4-toluene
diisocyanate; 2,6-
toluene diisocyanate; ditoluene diisocyanate; naphthalene 1,5-diisocyanate;
2,4'- and/or
4,4'-diphenylmethane diisocyanate (MDI); polymethylene
polyphenylenepolyisocyanates (polymeric MDI); like compounds, and mixtures
thereof. Suitable aliphatic polyisocyanates include: the hydrogenated
derivatives of
suitable aromatic polyisocyanates such as 1,6-hexamethylene diisocyanate;
isophorone
diisocyanate; 1,4-cyclohexyl diisocyanate; like compounds and mixtures
thereof. Also
suitable for use in the practice of the present invention are prepolymers
prepared from
polyisocyanates and polyols described herein, as is known in the art.
Preferred in the
practice of the present invention is TDI.
TLPs can be prepared by reaction of polyisocyanates with polyols, including
lower molecular weight diols, triols, and can also be prepared using
multivalent active
hydrogen compounds such as di- and tri-amines and di- and tri-thiols.
Individual
examples are aromatic polyisocyanates containing urethane groups, preferably
having
NCO contents of from 0 to 40 weight percent, more preferably 1 to 35 weight
percent,
obtained by reaction of diisocyanates and/or polyisocyanates with, for
example, lower
molecular weight diols, triols, oxyalkylene glycols, dioxyalkylene glycols or
polyoxyalkylene glycols.
A "B"-side formulation of the present invention can include an active hydrogen
containing compound, capable of reacting with isocyanate functionality, in
addition to
other optional components. Active hydrogen containing compounds, as the term
is
used herein, are compounds having functionality that is reactive with
Zerewitinoff
reagent. Generally, active hydrogen-containing compounds include alcohols,
amines,
and mercaptans, for example. Polyols are active hydrogen containing compounds
suitable for use in the practice of the present invention. Representatives of
polyols
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suitable for use with the process of the present invention are generally known
and are
described in such publications as High Pol~, Vol. XVI, "Polyurethanes,
Chemistry
and Technology" by Saunders and Frisch, Interscience Publishers, New York,
Vol. I,
pp. 32-42, 44-54 (1962) and Vol. II, pp. 5-6,198-199 (1964); Or;~anic Polymer
Chemistry by K. J. Saunders, Chapman and Hall, London, pp. 323-325 {1973); and
Developments in Polvurethanes, Vol. I, J. M. Buist, ed., Applied Science
Publishers,
pp. 1-76 (1978). Examples of such materials include those selected from the
following
classes of compositions, alone or in admixture: (a) alkylene oxide adducts of
polyhydroxyalkanes; (b) alkylene oxide adducts of non-reducing sugars and
sugar
derivatives; (c) alkylene oxide adducts of polyphenols; and (d) polyester
polyols. Also
preferred are poly(oxypropylene) glycols, triols, tetrols and hexols and any
of these that
are capped with ethylene oxide. These polyols also include
poly(oxypropyleneoxyethylene)polyols.
Catalysts are optional in the practice of the present invention, but
preferably are
included. Catalysts suitable for use in the practice of the present invention
include any
trimerization catalysts known to those skilled in the art of preparing
polyurethane
polymers. A trimerization catalyst can be included in the formulation at from
0.01 to
1.0 percent by weight of the mixture (wt percent), preferably from 0.25 to 1.0
wt
percent, more preferably from 0.25 to 0.75 wt percent, and most preferably
from 0.25
to0.5 wt percent.
The present invention includes a chain extender. Chain extenders useful in the
practice of the present invention are preferably liquid at room temperature,
and can
have a molecular weight of less than or equal to about 8,000. Preferably the
chain
extender has a molecular weight of from 50 to 8,000. Most preferably, the
chain
extender has a molecular weight of from 50 to 600. Chain extenders useful in
the
practice of the present invention have hydroxyl functionality. More
preferably, chain
extenders useful herein are diols. Diol chain extenders useful herein most
preferably
have primary hydroxyl functionality. Preferred chain extenders include, but
are not
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limited to, ethylene glycol; diethylene glycol; diols derived from
polyethylene oxides of
molecular weight 200, 400, or 600; ethylene oxide-capped polypropylene oxide
diols
having a molecular weight of from 400 to 4000. A chain extender of the present
invention should be included such that the isocyanatelhydroxyl ratio is in the
range of
from 1.00 to 100; preferably in the range of from 1.00 to 10.0; and more
preferably in
the range of from 1.50 to 2.00.
TLPs can be blended with other components. For example TLPs can be
blended with other polymers and extruded to give a co-polymer product. TLPs
can be
blended with, for example, polyacrylates, polystyrenes, polyacrylonitriles.
TLPs can
also be blended with standard polyurethane prepolymers, MDI, or other polyols.
The present invention can include other optional components. For example, the
present invention optionally includes a filler material. Conventional fillers
such as
milled glass, calcium carbonate, ATH, talc, bentonite clays, antimony
trioxide, kaolin,
fly ash, or other known fillers can be used in the practice of the present
invention. A
polyurethane-forming composition of the present invention can optionally
include:
surfactants; fire retardants; pigments; anti-static agents; reinforcing
fibers; antioxidants;
preservatives; water scavengers; acid scavengers.
In another embodiment, the present invention is a process for obtaining a melt
processable polymer by reactive extrusion in a first stage, and in a second
stage or in
subsequent stages, melt-processing the polymer thus obtained to form a polymer
that
can be used in various applications. A polymer obtained from the first can be
repeatedly re-processed as in the second stage without detrimental effect on
the
polymer obtained from the first stage. In a second or subsequent re-processing
stage of
the present invention, a polymer can be passed thmugh an extruder at a
temperature of
from 100°C to 280°C, at a screw speed of from 5 to 50 rpm.
Preferably the screw
speed is from 10 to 50 rpm, and the temperature of the extruder is from 1
SO°C to
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280°C. Most preferably, the extruder screw speed is from 20 to 40 rpm,
and the
temperature of the extruder heated zone is in the range of from 180°C
to 270°C.
Polyurethane elastomeric polymers obtained in the practice of the present
invention can be useful in a variety of applications, including use as foams,
films, gels,
adhesives, non-woven fibers and hard elastomers. Elastomeric polymers obtained
according to the practice of the present invention can demonstrate elongation
of from
50 percent to 1000 percent.
EXAMPLES
The following examples were merely illustrative of the present invention. They
were
not intended to - nor do they - represent the entire scope of the invention
claimed
herein.
Example 1
A 2000 equivalent weight polyol prepared from sorbitol and a 60:40 mixture of
ethylene oxide and propylene oxide and toluene diisocyanate were combined to
prepare
a TLP. The TLP was fed to an extruder and extruded at zone temperature
settings of
150, 165, 245, and 245°C and at a rate of 35 rpm to yield a polymeric
material.
Example 2
A blend prepared by combining 100 parts of the TLP of Example 1 and 25 parts
of a
HEMA modified TLP was fed to an extruder and extruded at zone temperature
settings
of 150, 165, 195, and 225°C at a rate of 35 rpm to yield a polymeric
material.
Example 3
The TLP of Example 1 was fed into an extruder and extruded with extruder
heating
zone temperatures of 150, 165, 225, and 225°C at 35 rpm to give a
sticky gelled
polymer.
Example 4
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The TLP of Example 1 was fed into an extruder and extruded with extruder
heating
zone temperatures of 150, 165, 225, and 225°C at 35 rpm into a
container of stirred
water. The extruded material formed a foamed soft polymer which separated from
the
water.
Example 5
A blend of nominally 2 and nominally 6 functional TLP prepolymers, wherein the
weight average functionality of the blend was greater than 2 but less than 3,
incorporating 0.5 percent by weight trimerization catalyst was fed into the
extruder and
extruded at zone temperatures of 80, 110, 80 and 70 °C respectively at
a screw speed of
150 rpm and yielded an elastomeric polymer material.
Example 6
A blend of nominally 2 and nominally 3 functional TLP prepolymers, wherein the
weight average functionality of the blend was greater than 2 but less than 3,
incorporating 0.75 percent by weight trimerization catalyst was fed into the
extruder
and extruded at zone temperatures of 80, 110, 80 and 70 °C respectively
at a screw
speed of 100 rpm and yielded an elastomeric polymer material.
Example 7
A blend of nominally 2 and nominally 6 functional TLP prepolymers, wherein the
weight average functionality of the blend was greater than 2 but less than 3,
incorporating 1.0 percent by weight of diethylene glycol and 0.5 percent by
weight
trimerization catalyst was fed into the extruder and extruded at zone
temperatures of 80,
110, 80 and 70 °C respectively at a screw speed of 150 rpm and yielded
an elastomeric
polymer material.
Example 8
A blend containing a nominally 2 functional TLP prepolymer, 1.0 percent by
weight of
diethylene glycol and 0.5 percent by weight trimerization catalyst was fed
into the
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extruder and extruded at zone temperatures of 80, 110, 80 and 70 °C
respectively at a
screw speed of 150 rpm and yielded an elastomeric polymer material.
Example 9
A blend of nominally 2 and nominally 6 functional TLP prepolymers, wherein the
weight average functionality of the blend was greater than 2 but less than 3,
incorporating 2.0 percent by weight trimerization catalyst was fed into the
extruder and
extruded at zone temperatures of 90, 110, 110, 140 and 120 °C
respectively at a screw
speed of 20-40 rpm and yielded an elastomeric polymer material.
Example 10
The polymer derived from example 7 was fed into the extruder hopper in the
form of
granules/chips/pellets and extruded at zone temperatures of 240, 260, 260, 250
°C at a
screw speed of 20-40 rpm and yielded elastomeric polymer.
Example 11
The polymer derived from example 8 was fed into the extruder hopper in the
form of
granules/chips/pellets and extruded at zone temperatures of 240, 240, 240, 200
°C at a
screw speed of 20-40 rpm and yielded elastomeric polymer.
Example 12
The polymer derived from example 9 was fed into the extruder hopper in the
form of
granules/chips/pellets and extruded at zone temperatures of 80, 110, 120, 140
and
120°C at a screw speed of 20-40 rpm and yielded elastomeric polymer.
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