Note: Descriptions are shown in the official language in which they were submitted.
CA 02670188 2009-06-25
RECIRCULATION LOOP REACTOR BULK POLYMERIZATION PROCESS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of U.S. App. Serial No.
11/845,807, filed
on August 28, 2007, which claims the benefit of U.S. Provisional Application
Ser. No.
60/841,079 filed on August 30, 2006 and U.S. Provisional Application Ser. No.
60/853,578
filed on October 23, 2006, the entire contents of which are hereby
incorporated by reference.
BACKGROUND OF INVENTION
100021 This application is directed to a continuous bulk polymerization
processes and
associated apparatuses for preparing polymeric compositions using a
recirculation tubular loop
reactor system and, more particularly, a continuous bulk polymerization
process and
associated apparatuses for preparing polymeric compositions, such as
adhesives, using a
recirculation tubular loop reactor including a planetary roller extruder
(PRE).
[0003] Conventional bulk polymerization processes for producing adhesives by
polymerization are known in the art. One such process includes a stirred tank
reactor having
a cooling jacket for removing heat from the vessel generated during the
exothermic reaction
therein. Such conventional processes have been somewhat effective at low
conversion rates.
However, at high conversion rates and associated high viscosities, the heat
transfer surfaces
often foul, thereby losing temperature control and facilitating runaway
reactions. Mandating
low conversion rates has not presented an economical solution to the problem
since the
excessive monomer used in low conversion operations must eventually be removed
from the
polymer by, for example, drying, de-volatilization or the like, thereby adding
an additional
processing step and associated costs.
SUMMARY OF INVENTION
[0004] In one aspect, a recirculation tubular loop reactor process for
polymerization may
include the steps of (a) preparing a feed stock by mixing at least one monomer
with at least
one initiator, the activation of which begins when the initiator is heated
above an activation
temperature, (b) heating the mixture to at least the activation temperature of
the initiator to
produce a partially polymerized intermediate, (c) recirculating a portion of
the partially
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polymerized intermediate in the loop reactor, (d) directing a remaining
portion of the
polymerized intermediate into a stream for removal from the loop reactor, (e)
cooling the
recirculating intermediate below the activation temperature of the initiator,
(f) mixing the
cooled recirculating intermediate with additional feed stock, (g) optionally
removing any
unreacted monomer from the remaining portion of the polymerized intermediate
through
drying, devolatilization, or the like and, (h) optionally applying the
remaining portion to a
web-form material. In a particular embodiment of the invention, the reaction
is carried out in
the presence of little or no solvent. More specifically the reaction is
carried out in the presence
of less than about 5% solvent and more specifically less than about 3% solvent
and still more
specifically no solvent.
[0005] In one embodiment of the invention, static mixers are used in the loop
reactor to mix
the feed stock and to mix the mixed feed stock with the recirculated partially
polymerized
intermediate. In another embodiment, a planetary roller extruder is used in
the loop reactor
for this purpose.
[00061 Static mixers can be advantageous for use in the loop reactor because
they can
accommodate comparatively large volumes of the reactants and thereby can
provide the
residence time that is required to obtain the degree of polymer conversion
that is desired at a
particular stage in the loop reactor. However, as the reactants polymerize in
the static mixer
their molecular weight and melt viscosity increase. This can make the
polymerized material
more difficult to circulate through the loop reactor. In one embodiment,
pressures in the
reactor may be greater than about 200 psi. In a still more particular
embodiment, pressures
may be greater than about 3,500 psi and up to about 10,000 psi. Pressure is
influenced by a
number of factors including tube diameter, linear velocity of the intermediate
product,
viscosity of the intermediate product, free volume, and static mixer
configuration. In
accordance with one embodiment, the reactor is operated under conditions that
yield a plug
flow. Plug flow reduces residence time distribution, resulting in a more
consistent molecular
weight, more consistent conversion rate, and the product that has reduced gel
content.
[00071 In one embodiment, it has been found desirable to replace one (or more)
of the static
mixers in the loop reactor with a dynamic mixer such as a twin screw extruder
or a planetary
roller extruder (PRE). While a dynamic mixer such as a PRE will often have a
smaller
residence volume than a static mixer, it imparts shear thinning to the
reaction mixture that
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reduces the melt viscosity of the reaction mixture thereby making it easier to
move the
polymerized material through the loop reactor. A dynamic mixer such as a PRE
is also
advantageous because it can efficiently mix the reactants and reduce localized
accumulations
of unreacted monomer in the reaction mass.
[0008] Accordingly, another process for preparing a polymeric material using a
loop reactor
may include the steps of (a) introducing a feed stock containing at least one
monomer and at
least one activatable initiator into a dynamic mixer such as an extruder and,
more particularly,
a planetary roller extruder located in a reaction loop, (b) introducing
partially polymerized
intermediate into the dynamic mixer to form a polymerizable mixture, (c)
heating the mixture
from step (b) to at least the activation temperature of the initiator to
polymerize the monomer
in the feed stock with the polymerized intermediate, (d) recirculating a first
portion of the
product of step (c) in the reactor, (e) directing the remaining portion of the
product of step (c)
into a stream for removal from the loop reactor, and (f) mixing the
recirculating portion of the
product from step (c) with additional feed stock.
[0009] In a further embodiment, step (d) additionally includes the step of (g)
cooling the
product of step (c) to below the activation temperature of the initiator. In a
further
embodiment, the process additionally includes the optional step of (h)
subjecting the
remaining portion of the partially polymerized material to an additional
reaction to further
polymerize the polymerized material prior to removal in step (e). In a further
embodiment,
the process additionally includes the step of (i) removing any unreacted
monomer from the
remaining portion through drying, devolatilization, or the like prior to
removal. In a further
embodiment, the process additionally includes the step of (j) applying the
polymerized
product to a web-form material.
[0010] In another aspect of the invention, a combination of a recirculation
loop reactor and
a dynamic mixer such as an extruder and, more particularly, a planetary roller
extruder is
used in a process for preparing polymeric material that may include the steps
of (a)
introducing a feed stock of at least one monomer and at least one initiator
into a loop reactor
having a partially polymerized intermediate recirculating there through to
form a
polymerizable mixture, (b) heating the mixture from step (a) to at least the
activation
temperature of the initiator to polymerize the monomer with the partially
polymerized
intermediate, (c) circulating the polymerized intermediate from step (b)
through the reactor
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while cooling it to a temperature below the activation temperature of the
initiator, (d) mixing
the cooled recirculating polymerized intermediate from step (c) with
additional feed stock to
further polymerize the monomer with the intermediate, (e) removing a portion
of the further
polymerized material from the loop reactor, and (f) subjecting the further
polymerized
polymeric material to an additional reaction in a planetary roller extruder to
reduce unreacted
monomer. In a further embodiment, the process additionally includes the step
of (g)
removing any unreacted monomer through drying, devolatilization, or the like.
In a further
embodiment, the process additionally includes the step of (h) applying the
polymerized
product to a web-form material.
[0011] In another aspect, a self-adhesive composition that is the reaction
product of at least
one alkyl acrylate monomer having at least one free radical polymerization
moiety and a
heat-activated initiator is manufactured according to the aforementioned
process. In a
particular embodiment of the invention the composition has a molecular weight
(Mw) of
about 1,500 and 1,000,000, and in a still more particular embodiment has a
molecular weight
of about 200,000 and 400,000 as measured by GPC.
[0012] In another aspect, the self-adhesive composition may be applied to a
web-formed
material using an application unit such as a slot-die applicator unit and
subsequently may be
crosslinked.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Fig. 1 is a schematic illustration of one aspect of the disclosed
recirculation tubular
reactor process.
[00141 Fig. 2 is a control diagram for the process of Fig. 1. A legend for
Fig. 2 is provided
below:
Index Description Index Description
ML Main line FIC Flow Indicator Control
AL Additive line PIC Pressure Indicator Control
AA Valve LIC Level Indicator Control
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AT Filter PSA Pressure Probe
CF Flow meter TSA Temperature Probe
SI Safety valve HTS N/A part number
SM Static mixer CT N/A part number
CP N/A part number HL Heated Line
FU Frequency converter M Motor
TCU Temperature control unit FT Flow Transmitter
TIC Temperature Indicator AP Pump
Control
[0015] Fig. 3 is a schematic illustration of one aspect of the disclosed
combined recirculation
tubular loop reactor and planetary roller extruder process.
[0016] Fig. 4 is a schematic illustration of another aspect of the disclosed
combined
recirculation tubular loop reactor and planetary roller extruder process.
DETAILED DESCRIPTION OF INVENTION
[0017] In one aspect, an adhesive product (e.g., an acrylate pressure
sensitive adhesive) may
be prepared according to the recirculation tubular reactor process 10 shown in
Fig. 1. The
primary raw materials may include a first monomer 12 (e.g., butyl acrylate or
"BA"), a second
monomer 13 (e.g., vinyl acetate or "VA"), a third monomer 14 (e.g., acrylic
acid or "AA") and
a thermal initiator 15 (e.g., azo-diisobutyronitrile or "AIBN"). Dosage of the
monomers 12, 13,
14 and the initiator 15 may be regulated with pumps 16, 17, 18, 19,
respectively, which may be
double diaphragm pumps or the like. The flowrate of each pump 16, 17, 18, 19
may be
controlled, for example, by controlling the frequency and/or the stroke-length
of the piston (not
shown) in each pump 16, 17, 18, 19.
[0018] Those skilled in the art will appreciate that the quantity, quality and
type of monomer
and initiator used is dependent upon the desired end product and that the
process of Fig. 1,
which illustrates the use of three monomers 12, 13, 14 and one initiator 15,
is only an example.
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Additional initiators may be used. One or more monomers may be used. It will
also be
apparent that the monomer(s) and initiator(s) do not need to be mixed off-loop
in the feed
stream 25 but they may be introduced to the loop as individual feeds and mixed
in a mixer in
the loop.
[0019] Monomers useful according to the disclosed process 10 may include, but
are not
limited to, alkyl acrylate monomers or mixtures of alkyl acrylate monomer
having, for
example, an alkyl group with from about 2 to about 20 and, preferably, 4 to 10
carbon atoms.
Preferred alkyl acrylate monomers may include 2-ethylhexyl acrylate, butyl
acrylate (BA),
isooctyl acrylate, isodecyl acrylate and any other monomers or mixtures
thereof, known to
those skilled in the art. Di-vinyl monomers may be used to increase the
molecular weight
and the internal strength of the polymer backbone and may be employed in one
aspect of the
process 10. In one aspect, di-vinyl monomers may be used in amounts up to
about 11 percent
by weight of the acrylic polymer. Suitable vinylic monomers employed in the
practice of
certain embodiments include styrene, acrylic acid (AA), alpha methyl styrene,
tetraethylene
glycol diacrylate, hydroxyethyl methacrylate, methylmethacrylate,
ethylacrylate,
methylacrylate, propylacrylates, propylmethacrylates, hexylacrylates,
hexylmethacrylates and
vinyl acetate (VA).
100201 In one aspect, suitable polymerization initiators 15 useful according
to the disclosed
process 10 may be any compound or composition or combination of compounds
and/or
compositions that release free radicals when heated to an activation or
decomposition
temperature. For example, useful initiators 15 may include organic peroxides
and azo
compounds such as, but not limited to, lauroyl peroxide, tertiarybutyl
peroxy(2-
ethylhexanoate), benzoyl peroxide, 1, 1 -bis(tertiarybutylperoxy)-3,3,5-
trimethylcyclohexane,
azo-diisobutyronitrile and azobis-2-methylbutyronitrile. In another aspect,
the initiator 15 may
be any material or process that provides free radicals, such as light (e.g.,
UV light), radiation,
chemical interactions or the like.
[0021] In one aspect, the initiators 15 may be used in amounts varying from
about 0.002 to
about 2.0 percent by weight and, more particularly, between about 0.01 and
about 1.0 percent
by weight, based upon the total weight of the monomers.
[0022] Polymerization reaction temperatures may be selected based upon the
type of
monomer material used, the decomposition temperature of the initiator material
and/or the
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desired polymer product desired. For example, a polymerization reaction may be
carried out at
a temperature of about 100 to about 140 C when initiator 15 is AIBN.
[0023] In one embodiment, the process converts at least 50% of the monomer to
polymer
product and, still more particularly, the process converts at least 95%, even
more specifically,
the process converts more than 99% of the monomer to product. These high
conversions are
achieved with relatively short residence time in another embodiment of the
invention. For
example, the resident time may be about 15 to 600 minutes and more
particularly about 60 to
180 minutes.
[0024] Referring again to Fig. 1, the monomers 12, 13, 14 and the initiator 15
may be
thoroughly mixed in a first static mixer 28. In one aspect, the initiator 15
may be initially
mixed with the first monomer 12 to form a blended mixture 24 prior to entering
the bulk feed
stream 25 (also designated F in Fig. 1 and having units of weight per time)
and flowing into the
mixer 28. In one modification, the initiator 15 may be pre-mixed with the
monomer having the
highest through-put, thereby facilitating the distribution of the initiator.
100251 Static mixer 28 may be characterized as having sufficient residence
time il to
thoroughly mix the monomer 12, 13, 14 and initiator 15 and to generate an
output stream 30.
It should be noted that the static mixer 28 may be fitted with a jacket 26 or
other heat transfer
device to provide heating/cooling, should it be desired to raise or lower the
temperature of the
feed stock as it passes through mixer 28. The tubular reactor residence time,
generally
denoted i, may be defmed as the ratio of the reactor vessel free-volume to the
volumetric
feed rate. While static mixer 28 is shown in Fig. I as being off-loop, those
skilled in the art
will appreciate that the mixer 28 could be moved into the loop itself.
[0026] Based upon an overall material balance of the process 10 illustrated in
Fig. 1, the
polymer product output P may be equal to the flowrate F of the monomer(s) and
initiator(s).
Feed stock stream 30 has a flowrate F and may be combined with a recirculating
polymer
stream 48 having a flowrate R to form a polymer/monomer/initiator mixed stream
32. The
polymer/monomer/initiator mixed stream 32 may be fed to a static mixer 35,
which may be
characterized as having a sufficient residence time T2 to thoroughly mix the
stream 32. The
output of vessel 35 may be output stream 36. Static mixer 35 may be fitted
with a jacket 34
to provide heating and/or cooling if necessary.
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100271 The recirculation flowrate R may be defined as the volume of fluid
returned to the
reactor loop (i.e., the point where streams 30 and 48 merge). The recycle
ratio RR may be
defined as the ratio of R to P.
[0028) A gear pump 37 may be fluidly connected in the flow channel between the
stream
36 of static mixer 35 and the inlet stream 38 to a static mixer 40, which may
be characterized
as having sufficient residence time i3 to mix/react stream 38 to form stream
41. The
volumetric flowrate of gear pump 37 may be the sum of F and R.
[0029] In one aspect, the stream 38 may be heated in the mixer 40 to a
temperature above
the activation temperature of the initiator, thereby initiating a free-radical
polymerization
reaction, wherein the monomer is at least partially converted to a polymer
(i.e., stream 41
may have a conversion Xl). The mixer 40 may include a jacket 39 for providing
a
heating/cooling means for stream 38, 41.
[0030] The fractional conversion of liquid monomer into adhesive polymer,
generally
denoted Xo, may be calculated as follows:
Xn=1- (C./Co)
wherein X. has a numerical value between 0 and 1, inclusive. For example, Xl
may be
calculated as follows:
X1=1-(Cl/Co)
wherein C. is the concentration of reactant monomer in stream 32 and Cl is the
concentration
of reactant monomer in stream 41. In a similar manner X2 may be calculated as
follows:
X2=1-(C2/Co)
wherein C2 is the concentration of reactant monomer in stream 44. Likewise, X3
may be
calculated as follows:
X3 =1-(C3/Co)
where C3 is the concentration of reactant monomer in stream 50.
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[0031] For example, when the process 10 is used to react BA, VA and AA with
AIBN to
form an acrylate PSA, conversion X, may be about 0.8, conversion X2 may be
0.95 and
conversion X3 may be 0.99, though those skilled in the art will appreciate
that the actual
conversions may be dependent upon the flowrates F, R, P and the sizes of the
vessels 28, 35,
40, 42, 50, 60, among other factors.
[0032] The stream 41 from static mixer 40 may flow into static mixer 42 which
may be
characterized as having sufficient residence time i4 to continue converting
monomer into
polymer to obtain a conversion X2. Vessel 42 may include a jacket 43 to
provide
heating/cooling means to stream 41. Stream 44 may be characterized by a
flowrate
consisting of the sum of F and R and may be split into stream 45 having a
flowrate P and
stream 46 having a flowrate R. The volumetric split may be regulated by a gear
pump 51,
which may be fluidly connected in the flow channel between streams 50 and 52.
The
volumetric flowrate of gear pump 51 may be characterized as P. Alternatively,
or in
combination with pump 51, a three-way valve (not shown) may be located at the
point where
stream 45 diverges from stream 46 to regulate the recirculation flowrate R.
Stream 45 may
enter a static mixer 60 to further react the monomer to a conversion X3.
Vesse160 may be
characterized as having a sufficient residence time z6 and heating/cooling
capabilities (e.g.,
jacket 58) to convert stream 45 having a flowrate P at a conversion X2 into
stream 50 having
a flowrate P at a conversion X3.
[0033] The tubular reactor loop process cycle may be completed by stream 46
entering
static mixer 50 at a flowrate R, which may be characterized as having
sufficient residence
time T5 to cool the mass below the initiation temperature. Exit stream 48 may
exit the vessel
50 while generally retaining the conversion X2. Static mixer/cooler 50 may
include a jacket
54 to facilitate the cooling of stream 46.
100341 In one aspect, the total loop residence time may be the sum of i2, i3,
T4 and T. For
example, the total loop residence time may be about 20 minutes such that the
polymer mixture
recirculates in the loop about 3 times per hour. In another aspect, gear pumps
37, 51 may be
adjusted such that the total loop residence time provides about 1 to about 4
recirculations per
hour. At this point, those skilled in the art will appreciate that the total
residence time may be
selected to obtain the desired product depending upon the type of end polymer
desired and the
monomers and initiators used.
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[0035] In one aspect, the product stream 52 (i.e., the final product) may be
applied to a
web-formed material using an application unit such as a slot-die applicator.
However, those
skilled in the art will appreciate that the recirculation tubular reactor
process 10 described
herein may be used to produce a wide variety of polymeric materials for a
variety of different
uses. For example, the process 10 described herein may be used to produce
release coatings,
primer coatings, non-PSA adhesives, sealants, caulks, acrylic hybrid PSAs and
non-PSA
coatings, such as urethane acrylics, epoxy acrylics, styrene acrylics and the
like.
[0036] Static mixers, such as continuous tubular reactors, may be
characterized as having
reactants introduced and products withdrawn simultaneously in a continuous
manner. The
reactants may enter at one end of the reactor and the products may exit at the
other end, with
a continuous variation in the composition of the reacting mixture in between.
Heat transfer to
and/or from the tubular reactor may be accomplished with jackets or a shell
and tube design.
Fluid media may be forced to mix themselves through a progression of divisions
and
recombinations within a static mixer. As a static mixer has no moving parts,
the maintenance
and operating costs may be significantly reduced. The energy for mixing may be
delivered
by the pumps 37, 51 that facilitate flow through the vessels. Tubular reactors
may be
characterized by the fact that the flow of fluid through the reactor is
orderly with no element
of fluid overtaking or mixing with any other element ahead or behind.
[0037] The gear pumps 37, 51 discussed herein may include a housing defining a
pump
cavity (not shown), a pair of intermeshing toothed gears (not shown) rotatably
disposed
within the pump cavity, each gear having a mounting shaft (not shown)
extending axially
therefrom, and a bearing means (not shown) for rotatably supporting the gear
shafts. The
bearing means may include a radial face disposed in facing relation to the
gears and a pair of
axial openings for rotatably receiving the gear shafts. The gear pumps 37,51
may be driven
externally by rotating the drive shaft of the pumps 37, 51 with a motor (not
shown). As
materials passes through the gear pumps 37, 51, the rotation imparted by or on
the gears may
be in direct proportion to the amount of material passing through the gears.
Thus, the gears
may act as precise devices to meter the quantity of intermediate product
flowing in the
channel. The volume of the gear mechanisms may be varied either by varying the
size of the
gears or the axial thickness of the gears.
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[0038] The vessels 28, 35, 40, 42, 50, 60 described herein may have dual
purposes, namely
(1) elevating and/or decreasing the temperature and (2) mixing the fluid
passing therethrough.
The vessels 28, 35, 40, 42, 50, 60 may be "residence time reactors" because
they may provide
the reactants with additional time to reach the activation temperature and may
provide
additional mixing.
[0039] At this point, those skilled in the art will appreciate that more or
less vessels 28, 35,
40, 42, 50, 60 may be used according to the process 10. For example, vessels
40, 42 may be
separate vessels or may be combined as a single vessel.
[0040] For exemplary purposes only, the bulk feed stream 25 may include a BA
monomer
stream 12 at a flowrate of 6.83 kg/hr, a VA monomer stream 13 at a flowrate of
0.6 kg/hr, an
AA monomer stream at a flowrate of 68 grams/hr and an AIBN initiator 15 at a
flowrate of 2
grams/hr. The product stream 52 may be an acrylate PSA at a flowrate P of 7.5
kg/hr.
[0041] The static mixer/heater 35 may mix the low viscosity monomers/initiator
with the
high viscosity polymer. At 70 C, the initiator (AIBN) and monomers are
present together but
they do not react. Recirculation stream 48 may be 0.042 m3/hr, 900 kg/m3, 700
Pas; Stream 30
may be 0.00833 m3/hr, 900 kg/m3, 0.01 Pas; Stream 32 may be 0.05 m3/hr, 900
kg/m3, 583 Pas.
Static mixer/heater 35 may be CSE-X/8, DN 49.5, 18 elements, Ap = ca. 21 bar,
shear rate 10.5
s residence time 104 s, length approximately 900 mm, as shown in Fig. 2.
[0042] In one aspect, the gear pump 37 may be capable of pumping about 50
kg/hr of
polymer with about 1,000 Pas viscosity against a pressure of about 50 bar. The
flow may be
controlled by the accuracy of the pump 37 (a flow meter may be optional). In
one aspect, the
recirculation rate R may be about 1 to about 5 times the feed-rate F.
[0043] The homogenized mixture 38 of monomer/polymer/initiator may be heated
in the
mixer/heat exchanger 40. By increasing the temperature from about 70 C to
about 120 C the
polymerization reaction may be induced. The exothermic heat generated may be
partly
absorbed by the bulk polymer and the temperature rise due to the reaction may,
for example, be
about 20 to about 40 C. Heating may be performed with Marlotherm L heat
transfer fluid
supplied to the reactor jacket 39 (e.g., at about 120 C). Once the reaction
starts the reactor
jacket 39 may operate as a cooler, thereby keeping the temperature under
control. Mixture data
(stream 41) may be 0.005 m3/hr, 900 kg/m3, 700 Pas, Cp (heat capacity) of
2,300 J/kg/ K, k
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(latent heat) of 0.15 W/m/ K. Mixer/heat exchanger 40 may be a CSE-XR, DN 80,
8 elements,
Ap = ca. 5 bar, shear rate 4 s-1, residence time 170 s, length approximately
750-1,100 mm as
shown in Fig. 2.
[0044] Marlotherm LH is a high-performance synthetic, organic heat-transfer
medium for
use in the liquid phase in closed forced circulation unpressurized heat
transfer systems at
working temperatures from about 0 to about 280 C. The Marlotherm heat
transfer fluid is
supplied by Sasol Olefins & Surfactants (Marl, Germany). A reaction
temperature of about 120
C may be suitably selected for the AIBN initiator, although alternatively,
different thermal
initiators or mixtures of thermal initiators may require a different reaction
temperature.
[0045] Vessel 42 may be a double jacketed mixer and may be capable of
providing additional
residence time and mixing performance in order to increase the yield and the
product quality.
The polymer streams 41, 44 may be kept at a constant temperature (e.g., 120
C). Mixture data
(stream 44) may be characterized as 0.05 m3/hr, 900 kg/m3, 700 Pas. Mixer/heat
exchanger 42
may be characterized as CSE-X/4, DN 80, 15 elements, Z~p = ca. 3 bar, shear
rate 1.6 s-~,
residence time 390 s, length approximately 1,200 mm, as illustrated in Fig. 2.
[0046] The monomer/polymer/initiator mixture may be cooled in the
recirculation loop by
vessel 50 from about 120 C down to about 70 C, thereby reducing or
preventing further
polymerization. The cooling of vessel 50 may be performed with Marlotherm L
supplied to
the jacket 54 of the vessel 50 (e.g., at about 60 C). Mixture data (stream
48) may be 0.005
m3/hr, 900 kg/m3, 700 Pas, Cp of 2,300 J/kg/ K, X of 0.15 W/m/ K. Mixer/heat
exchanger 50
may be a CSE-XR, DN 80, 18 elements, Lp = ca. 11 bar, shear rate 4 s-1,
residence time 390 s,
length approximately 1,600 mm, as illustrated in Fig. 2.
[0047] Vessel 60 may be a double jacketed static mixer and may provide
additional residence
time and mixing, thereby increasing the conversion from X2 to X3. The 7.5
kg/hr flow-rate P
may be regulated by the gear pump 51. Mixture data (stream 52) may be
characterized as
0.00833 m3/hr, 900 kg/m3, 700 Pas. Mixer/heat exchanger 60 may be
characterized as, CSE-
X/4, DN 40, 15 elements, Op = ca. 6 bar, shear rate 2.7 s-1, residence time
265 s, length
approximately 700 mm, as shown in Fig. 2.
[0048] Flowrate, temperature, pressure, vessel level, melt viscosity and
electrical power
sensor readouts and various control systems may be provided to assist the
process operator
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with process control, as illustrated in Fig. 2. Other process control features
may include
pressure-resistant piping, pressure-resistant valving, process start-up
features, process shut-
down features, 3-way valves, polymer content monitoring and residual monomer
monitoring
and the like.
100491 In one aspect, a polymeric product (e.g., an acrylate pressure
sensitive adhesive
(PSA)) may be prepared according to the process 110 shown in Fig. 3 using a
planetary
roller extruder. While a PRE is illustrated in this figure, other dynamic
mixers or extruders
could be substituted for or used in combination with the PRE. The primary raw
materials
may include a first monomer 120 (e.g., butyl acrylate or "BA"), a second
monomer 130 (e.g.,
vinyl acetate or "VA"), a third monomer 140 (e.g., acrylic acid or "AA") and a
thermal
initiator 150 (e.g., azo-diisobutyronitrile or "AIBN"). Dosage of the monomers
120, 130,
140 and a liquid initiator or solid initiator in solution 150, may be
performed and controlled
with pumps 160, 170, 180, 190, respectively, which may be double diaphragm
pumps or the
like. The flowrate of each pump 160, 170, 180, 190 may be controlled, for
example, by
controlling the frequency and/or the stroke-length in each pump 160, 170, 180,
190.
[0050] Those skilled in the art will appreciate that the quantity, quality and
type of
monomer and initiator used is dependent upon the desired end product and that
the process of
Fig. 3, which illustrates the use of three monomers 120, 130, 140 and one
initiator 150, is
only an example. More or fewer monomers and initiators may be used depending
on the final
product desired.
[0051] Monomers 120, 130, 140 and polymerization initiators 150 useful
according to the
disclosed process 110 may include those listed previously for disclosed
process 10.
[0052] In one aspect, the initiators 150 may be used in amounts varying from
about 0.002
to about 2.0 percent by weight and, more particularly, between about 0.01 and
about 1.0
percent by weight, based upon the total weight of the monomer feed stock.
[0053] Referring to Fig. 3, a reactor loop, generally designated 110, is used
in one aspect to
prepare an acrylate polymeric product. The monomers 120, 130, 140 and a liquid
initiator or
solid initiator in solution 150, are provided by pumps 160, 170, 180 and 190,
respectively to
form a bulk feed stream 200 (having a flow rate F in Fig. 3).
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CA 02670188 2009-06-25
[0054] The feed stream 200 is carried into the first planetary roller barrel
270 and combined
with a recycled polymer stream 370 (having a recirculation flowrate R in Fig.
3), and heated
to about 25 to about 240 C to initiate the free-radical reaction process. In
this embodiment,
the mixture 300 is fed into a second planetary roller extruder barrel 280 and
a third planetary
roller barre1290, where a preset residence time is provided to minimize the
residual monomer
content of the finished polymer stream 300. Individual monomers 120, 130, 140
as well as
the feed stream 200 can be injected into the PRE anywhere along the length but
most
preferably using injection valves inserted into a spray ring before the first
PRE barrel.
Alternatively, it could also be injection valves inserted into any dispersion
rings before and
after any PRE barrels or a side port directly into a barrel or other internal
and external
delivery mechanisms. The recycle polymer stream 370 can be introduced into the
PRE
anywhere along its length but most preferably using a recirculation port in
the side of a PRE
barrel. Alternatively, it could also be introduced at any injection valves
specially designed to
handle such viscosity material at the same rings as monomer additions or other
internal or
external delivery mechanisms. To those skilled in the art, it is understood
that the use of a
three barrel PRE is only an example and barrels may be added or subtracted
depending on the
product desired. Temperature control is maintained within zones 270, 280, 290
for example
by heating/cooling medium through the barrel walls 220, 230, 240 as well as
through a
central bore 250 in the central spindle 260. In one embodiment, the polymer
process
temperature is maintained below 240 C (e.g., the minimum degradation
temperature for
acrylic polymers and copolymers).
[0055] The fractional conversion of liquid monomer into adhesive polymer,
generally
denoted Y,,, in process 110 may be calculated as follows:
Y.= 1- (Cx'o)
wherein Yõ has a numerical value between 0 and 1, inclusive. For example, Yl
may be
calculated as follows:
YJ=1-(C 1/C~o)
wherein C o is the concentration of reactant monomer in combined streams 200
and 370 and
C1 is the concentration of reactant monomer in stream 300. In a similar manner
Y2 may be
calculated as follows:
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CA 02670188 2009-06-25
Y2=1-(C 2/Co)
wherein C'2 is the concentration of reactant monomer in stream 350. Likewise,
Y3 may be
calculated as follows:
Y3 =1-(C3/Co)
where C3 is the concentration of reactant monomer in stream 400.
[0056] Stream 300 may have a conversion Yl, and a flowrate characterized as
the sum of
F, the flow from the feed materials, and R, the recycled feed. A gear pump 310
is fluidly
connected in the flow channel between the stream 300 and the stream 320 to a
static mixer
340. The volumetric flowrate of pump 310 may be but is not necessarily the sum
of F and R.
Those skilled in the art will recognize that as a result of the shear thinning
that occurs in the
PRE and other volumetric changes that can accompany the mixing of reactants,
as will as
compressive effects that can be accommodated within the loop reactor, the
flowrate of pump
310 can vary. In general, the purpose of the pump 310 is to minimize
pulsations in flowrate.
The static mixer 340 may include a jacket 330 and/or other heat exchange
device for
providing a heating/cooling means for stream 320.
[0057] Stream 350 may have a conversion Y2 and may be split into stream 360
having a
flowrate P and stream 370 having a flowrate R. The volumetric split may be
regulated by a
pump 410, which may be fluidly connected in the flow channel between streams
400 and
420. The volumetric flowrate of pump 410 may be characterized as P. Stream 360
may enter
a static mixer 390 to further react the monomer to a conversion Y3. Static
mixer 390 may
have heating/cooling capabilities (e.g., jacket 380) to convert stream 360
having a flowrate P
at a conversion Y2 into stream 400 having a flowrate P at a conversion Y3.
[0058] Thus by incorporating at least one PRE in the loop reactor, the reactor
and process
defined earlier is made more versatile. If the only mixers are static mixers,
then mixing is
dependent upon a threshold linear velocity of the polymeric material, above
which is required
to impart sufficient shear for effective mixing. With a dynamic mixer, mixing
efficiency is
largely independent of linear velocity of the polymeric material. Thus the
option of using a
PRE in the loop reactor increases mixing and heat exchange versatility of the
overall reactor
system.
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CA 02670188 2009-06-25
[0059] Referring to Fig. 4, an alternative process, generally designated 120,
is used in one
aspect to prepare an acrylate polymeric product. The monomers 500, 510, 520
and a liquid
initiator or solid initiator in solution 530, are provided by pumps 540, 550,
560 and 570,
respectively to form a bulk feed stream 580 (also designated F in Fig. 4).
[0060] In one embodiment, the stream 580 may have a flowrate F and may be
combined
with a recirculation polymer stream 740 having a flowrate R to form a
polymer/monomer/initiator mixture stream 590. The polymer/monomer/initiator
mixture
stream 590 may be fed to a static mixer 600, which is designed to thoroughly
mix the stream
590. The output of static mixer 600 may be output stream 620. Static mixer 600
may be
fitted with a jacket 610 to provide heating and/or cooling if necessary. A
gear pump 630 may
be fluidly connected in the flow channel between the stream 620 of static
mixer 600 and the
inlet stream 640 to a static mixer 650, which is designed to mix/react stream
640 to form
stream 670. The volumetric flowrate of pump 37 may approximate the sum of F
and R, but
as mentioned earlier, the system will accommodate variations in flow.
[0061] The fractional conversion of liquid monomer into adhesive polymer,
generally
denoted Z., in process 120 may be calculated as follows:
Zn= 1- (Cn/Co)
wherein Zõ has a numerical value between 0 and 1, inclusive. For example, Zl
may be
calculated as follows:
Z1=1-(C1/C
wherein C"o is the concentration of reactant monomer in stream 590 and C"I is
the
concentration of reactant monomer in stream 670. In a similar manner Z2 may be
calculated
as follows:
Z2=1-(C 2/C o)
wherein C"2 is the concentration of reactant monomer in stream 700. Likewise,
Z3 may be
calculated as follows:
Z3 =1-(Cit 3/Cft o)
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CA 02670188 2009-06-25
[00621 where C"3 is the concentration of reactant monomer in stream 840.
[0063] Analogous to the earlier description, the inlet stream 640 may be
heated in the static
mixer 650 to a temperature above the activation temperature of the initiator,
thereby initiating
a free-radical polymerization reaction, wherein the monomer is at least
partially converted to
a polymer (i.e., stream 670 may have a conversion Z1). The static mixer 650
may include a
jacket 660 and/or other heat exchange device for providing a heating/cooling
means for
slream 640, 670.
[0064] The exiting stream 670 from static mixer 650 may flow into static mixer
680 which
may be characterized as having sufficient residence time to continue
converting monomer
into polymer to obtain a conversion Z2 in stream 700. Static mixer 680 may
include a jacket
690 and/or other heat exchange device to provide heating/cooling means to
streams 670, 700.
Stream 700 may be split into stream 750 having a product flowrate P and
recirculated stream
710 having a flowrate R. The amount of product removed from the reactor loop
120 may be
regulated by a pump 850, which may be fluidly connected in the flow channel
between
streams 840 and 860. The volumetric flowrate of pump 850 may be characterized
as P.
Stream 710 may enter a static mixer 720 to further react the monomer. Static
mixer 720 may
be characterized as having a sufficient residence time and cooling
capabilities (e.g., jacket
730) to convert stream 710 having a flowrate R into stream 740 at a
temperature below the
activation temperature and possible additional conversion Z4 (i.e., where C"4
is the
concentration of reactant monomer in stream 740).
[0065] Stream 750 having a conversion Z2 is carried into the first planetary
roller barre1760
and heated to about 25 to about 240 C to continue the free-radical reaction
process. The
mixture is carried into a second planetary roller barrel 770 and a third
planetary roller barrel
780, where a preset residence time is provided to minimize the residual
monomer content of
the finished polymer stream 840. Accurate temperature control can be
maintained within
barrels 760, 770, 780 by conducting heating/cooling medium through the barrel
walls 790,
800, 810, respectively and close to the intermeshing surfaces, as well as
through a central
bore 830 in the central spindle 820. The polymer process temperature is
maintained below
the polymeric materials degradation temperature (i.e., 240 C for butyl acrylic
polymers).
Planetary roller barrels 760, 770, 780 convert stream 750 having a flowrate P
at a conversion
Z2 into stream 840 having a flowrate P at a conversion Z3.
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CA 02670188 2009-06-25
(0066] In one aspect, the product streams 52, 420 and 860 from the processes
10, 110, 120,
respectively, may be applied to a web-formed material using an application
unit such as a
slot-die applicator or other application and doctoring methods.
[0067] Those skilled in the art will appreciate that the processes 10, 110,
120 described
herein may be used to produce a wide variety of polymeric materials for a
variety of different
uses, for example release coatings, primer coatings, adhesives, PSA and non-
PSA, sealants,
caulks, and architectural coatings. Moreover, these adhesives and coatings can
be
polymerized with a wide variety of chemistries. Specifically chemistries such
as, but not
limited to, acrylic monomers, polyols, isocyanates, vinyl materials, epoxies
and the like.
[0068] In one embodiment, the polymeric composition produced according to
processes 10,
110, 120 may be crosslinked with the aid of electron beams or UV energy in a
manner known
in the art. For example, crosslinking the polymeric material using UV energy
may require
the addition of appropriate UV promoters (e.g., photoinitiators, such as
peroxides). If
desired, the UV promoters or actinic radiation promoters may be added by way
of the
recirculated tubular reactor process without departing from the scope of this
disclosure.
[0069] In the event that additional tack and/or adhesion is required, resins,
oils and/or other
additives may be added to the reactants and/or the final product. In the event
that color or
other properties need to be modified; pigments, dyes, fillers, anti-degradants
and/or other
additives may be added to the reactants and/or the final product.
[0070] Typical tackifying resins may include, but are not limited to partially
or fully
hydrogenated wood, gum or tall oil rosins, esterified wood, gum or tall oil
rosins, alpha and
beta pinene resins and polyterpene resins. The resins may be introduced in
solid, liquid, i.e.
including, but not limited to solutions and dispersions and/or molten form.
Typical anti-
degradents include antioxidants, ultraviolet absorbers and ultraviolet
stabilizers. Typical
crosslinking agents may include peroxides, ionic, thermally-activated resins,
isocyanates,
UV, and/or EB activated curing agents. Typical colorants may include titanium
dioxide and
other various metal pigments. In the event that the use of solvents is
desired, typical solvents
may include liquid carboxylates such as ethyl acetate and n-butyl acetate,
ketones such as
acetone, dimethyl ketone and cyclohexanones, aromatic hydrocarbons such as
benzene,
toluene, and the xylenes, liquid aliphatic and cyclo-aliphatic hydrocarbons
such as petroleum
fractions having boiling points of about 50 and 150 C and in particular about
60 and 100 C,
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CA 02670188 2009-06-25
cyclohexane, and others such as dioxane, tetrahydrofuran and di-t-butyl ethers
or mixtures
thereof. Particularly useful solvents for the polymeric composition of this
disclosure may
include ethyl acetate, cyclohexane, and mixtures of acetone with petroleum
ether (e.g.,
having a boiling point of about 60 to about 95 C).
[0071] The use of a slot-die for coating polymeric materials onto web-form
material may
have particular advantages over the traditional coating processes, e.g., roll-
over-roll, reverse-
roll, knife-over-roll, and the like. Web-form coating speeds, when employing
traditional
coating processes may be limited to polymeric materials with viscosities of
40,000 cPs or less
and are not conducive to high solids polymeric materials. However, the use of
slot-die
coating technology, particularly when employed in conjunction with high-solids
polymeric
materials produced by the recirculated tubular reactor process may be of
particular interest as
application speeds approach and exceed 1,000 meters per minute.
[0072] Depending upon the intended use of the web-form product incorporating
the
polymers produced according to the disclosed process, suitable web-form
carrier materials
may include any known carriers, with or without appropriate chemical or
physical surface
pretreatment of the coating side, and with or without appropriate anti-
adhesive physical
treatment or coating of the reverse side. Representative examples include
creped, non-creped
and release papers, polyethylene, polypropylene, mono- or biaxially oriented
polypropylene
films, polyester, polyamide, PVC, release and other films, as well as foamed
materials,
wovens, knits and nonwovens in web form made from polyolefins.
[0073] Although the disclosed polymerization processes have been shown and
described
with respect to certain aspect and embodiments, modifications will occur to
those skilled in
the art upon reading and understanding the specification. The disclosed
polymerization
process includes all such modifications. In particular, while the discussion
herein focuses on
a particular embodiment for manufacturing an adhesive, those skilled in the
art will recognize
that the invention has application to the manufacture of polymeric material in
general.
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