U.S. patent application number 11/088454 was filed with the patent office on 2005-08-18 for continuous processes and apparatus for forming cyanoacetate and cyanoacrylate.
Invention is credited to Ayarza, Jaime, Badejo, Ibraheem T., Davis, Kenneth W., Hennenkamp, Jeffrey R..
Application Number | 20050182271 11/088454 |
Document ID | / |
Family ID | 24809632 |
Filed Date | 2005-08-18 |
United States Patent
Application |
20050182271 |
Kind Code |
A1 |
Badejo, Ibraheem T. ; et
al. |
August 18, 2005 |
Continuous processes and apparatus for forming cyanoacetate and
cyanoacrylate
Abstract
Continuous processes for forming cyanoacrylate from
polycyanoacrylate include stripping a solvent from a reaction mass;
cracking a polymer in the reaction mass to form a cracked
cyanoacrylate monomer and residue substances; and distilling the
cracked cyanoacrylate monomer to produce a cyanoacrylate monomer
product. These steps can be performed in short-path, wiped-film
evaporators. Polycyanoacrylate used in the processes can be formed
using cyanoacetate produced by processes for continuously producing
cyanoacetate by forming a higher homologue cyanoacetate from a
lower homologue cyanoacetate. The cyanoacetate can be formed in
short-path, wiped-film evaporators.
Inventors: |
Badejo, Ibraheem T.;
(Morrisville, NC) ; Ayarza, Jaime; (Raleigh,
NC) ; Davis, Kenneth W.; (Raleigh, NC) ;
Hennenkamp, Jeffrey R.; (Wake Forest, NC) |
Correspondence
Address: |
HUTCHISON & MASON PLLC
PO BOX 31686
RALEIGH
NC
27612
US
|
Family ID: |
24809632 |
Appl. No.: |
11/088454 |
Filed: |
March 24, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11088454 |
Mar 24, 2005 |
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10146061 |
May 16, 2002 |
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10146061 |
May 16, 2002 |
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09699508 |
Oct 31, 2000 |
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6420590 |
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Current U.S.
Class: |
558/441 |
Current CPC
Class: |
B01D 1/26 20130101; C07C
253/30 20130101; B01D 3/42 20130101; C07C 253/30 20130101; C07C
253/34 20130101; C07C 255/23 20130101; C07C 253/34 20130101; C07C
255/23 20130101 |
Class at
Publication: |
558/441 |
International
Class: |
C07C 253/30 |
Claims
What is claimed is:
1. A process for continuously producing cyanoacrylate monomer,
comprising the steps: (a) stripping solvent from a reaction mass
comprising polycyanoacrylate and solvent to produce stripped
polycyanoacrylate; (b) cracking the stripped polycyanoacrylate to
form a cracked cyanoacrylate monomer and residue substances in a
short-path, wiped-film evaporator; and (c) distilling the cracked
cyanoacrylate monomer to produce a purified cyanoacrylate
monomer.
2. A process for continuously making cyanoacetate, comprising:
converting a first cyanoacetate to a second cyanoacetate via a
transesterification reaction in a first wiped-film evaporator; and
purifying the second cyanoacetate in a second wiped-film
evaporator; wherein the first cyanoacetate is a lower homologue
cyanoacetate and the second cyanoacetate is a higher homologue
cyanoacetate as compared to each other.
3. The process of claim 2, wherein the first cyanoacetate is ethyl
cyanoacetate or methyl cyanoacetate, and the second cyanoacetate is
2-octyl cyanoacetate.
4. The process of claim 2, wherein the first wiped-film evaporator
and the second wiped-film evaporator are the same wiped-film
evaporator.
5. The process of claim 2, wherein the first wiped-film evaporator
and the second wiped-film evaporator are each a short-path
wiped-film evaporator.
6. The process of claim 2, wherein the first wiped-film evaporator
operates at a temperature of from about 100.degree. C. to about
250.degree. C. and at about atmospheric pressure during the
converting step.
7. The process of claim 2, wherein the second wiped-film evaporator
operates at a temperature of from about 75.degree. C. to about
105.degree. C. and a pressure of about 0.5 torr to about 10 torr
during the purifying step.
8. An apparatus for continuously producing cyanoacrylate monomer,
comprising: (a) means for stripping solvent from a reaction mass
comprising polycyanoacrylate and solvent to produce stripped
polycyanoacrylate; (b) means for cracking the stripped
polycyanoacrylate to form a cracked cyanoacrylate monomer and
residue substances; and (c) means for distilling the cracked
cyanoacrylate monomer to produce a purified cyanoacrylate
monomer.
9. An apparatus for continuously producing cyanoacrylate monomer,
comprising: (a) a first wiped-film evaporator for stripping solvent
from a reaction mass comprising polycyanoacrylate and solvent to
produce stripped polycyanoacrylate; (b) a separate second
wiped-film evaporator for cracking the stripped polycyanoacrylate
to form a cracked cyanoacrylate monomer and residue substances; and
(c) at least one separate evaporator for distilling the cracked
cyanoacrylate monomer to produce a purified cyanoacrylate
monomer.
10. The apparatus of claim 9, wherein the evaporator further
comprises a third wiped-film evaporator for distilling the cracked
cyanoacrylate monomer and the volatile substances to separate the
residue substances from the cracked cyanoacrylate monomer.
11. The apparatus of claim 10, wherein the evaporator further
comprises a fourth wiped-film evaporator for distilling the
distilled cracked cyanoacrylate monomer to produce a purified
cyanoacrylate monomer.
12. The apparatus of claim 11, wherein the third and fourth
wiped-film evaporators are short-path, wiped-film evaporators.
13. The apparatus of claim 9, wherein the second wiped-film
evaporator is a short-path, wiped film evaporator.
14. The apparatus of claim 9, wherein the first wiped-film
evaporator and the second wiped-film evaporator are each a
short-path, wiped-film evaporator.
15. The apparatus of claim 9, further comprising an apparatus for
continuously forming cyanoacetate.
16. The apparatus of claim 15, wherein the apparatus for
continuously forming cyanoacetate comprises: a fifth wiped-film
evaporator for synthesizing a second cyanoacetate via a reaction of
a first cyanoacetate; and a sixth wiped-film evaporator for
purifying the second cyanoacetate.
17. The apparatus of claim 16, wherein the fifth wiped-film
evaporator and the sixth wiped-film evaporator are each a
short-path, wiped-film evaporator.
18. An apparatus for continuously producing cyanoacrylate monomer,
comprising: (a) means for stripping solvent from a reaction mass
comprising polycyanoacrylate and solvent in a first wiped-film
evaporator to produce stripped polycyanoacrylate; (b) means for
cracking the stripped polycyanoacrylate to form a cracked
cyanoacrylate monomer and residue substances in a second wiped-film
evaporator; and (c) means for distilling the cracked cyanoacrylate
monomer to produce a purified cyanoacrylate monomer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates to processes and apparatus for
forming cyanoacetate and cyanoacrylate.
[0003] 2. Description of Related Art
[0004] Monomer and polymer adhesives are used in both industrial
(including household) and medical applications. Included among
these adhesives are the 1,1-disubstituted ethylene monomers and
polymers, such as the .alpha.-cyanoacrylates. Since the discovery
of the adhesive properties of these monomers and polymers, they
have found wide use due to the speed with which they cure, the
strength of the resulting bond formed, and their relative ease of
use. These characteristics have made the .alpha.-cyanoacrylate
adhesives the primary choice for numerous applications such as
bonding plastics, rubbers, glass, metals, wood, and, more recently,
biological tissues.
[0005] It is known that monomeric forms of .alpha.-cyanoacrylates
are extremely reactive, polymerizing rapidly in the presence of
even minute amounts of an initiator, including moisture present in
the air or on moist surfaces such as animal (including human)
tissue. Monomers of .alpha.-cyanoacrylates are anionically
polymerizable or free radical polymerizable, or polymerizable by
zwitterions or ion pairs to form polymers. Once polymerization has
been initiated, the cure rate can be very rapid.
[0006] Cyanoacrylate monomers are generally produced by forming
polycyanoacrylate and then cracking the polycyanoacrylate polymer
to produce monomeric cyanoacrylate. Polycyanoacrylate is commonly
produced by first reacting cyanoacetate with formaldehyde, or a
functional equivalent such as the polymeric form paraformaldehyde,
in the presence of a base. The base acts as a catalyst for the
reaction between the cyanoacetate and paraformaldehyde. This
reaction in the presence of the catalyst produces formaldehyde and
polycyanoacrylate.
[0007] An exemplary known process for forming cyanoacetate is
described in Japanese Patent Appln. No. 10-267690. The disclosed
process synthesizes cyanoacetate in a wiped-film evaporator using
dibutyltin oxide. Titanium tetraisopropoxide can be used as a
catalyst. A continuous process is disclosed.
[0008] A method for preparing cyanoacetic acid higher ester is
described in U.S. Pat. No. 5,698,730 to Nakamura et al. This method
includes subjecting a cyanoacetic acid ester to a
transesterification reaction in the presence of a tin compound.
[0009] These known methods for producing cyanoacetate do not
convert a lower homologue cyanoacetate to a higher homologue
cyanoacetate in a continuous process.
[0010] Known processes for cracking polycyanoacrylate to produce
cyanoacrylate monomer have many disadvantages. One disadvantage of
the known processes is that they produce unwanted byproducts that
must be separated from the monomer product. Such byproducts
include, for example, alcohols and cyanoacetate. Often it is
difficult and/or costly to remove such byproducts from the monomer
product, resulting in impure product, increased production, cost
and time, and/or reduced yield. In addition, such impure product
may not be suitable for certain uses, such as, for example, animal
and human use.
[0011] Another disadvantage of known processes for cracking
polycyanoacrylate is that during the cracking process, the
temperature of the polycyanoacrylate is not sufficiently controlled
to avoid the formation of what is referred to as "hot monomer." If
the polymerization temperature is too high, monomer tends to
polymerize on surfaces of the reactor, causing a buildup in the
reactor. In addition, if the polycyanoacrylate polymer is cracked
at too high of a temperature, the resulting monomer may not be
stable. This problem again can result in an impure product,
increased production cost and time, and/or decreased yield.
[0012] Further, in known processes of cracking polycyanoacrylate,
the entire polymer is exposed to a high temperature for a long
period of time, typically for as long as about eight hours or more.
Consequently, side products are also formed during cracking. Hot
monomers can form, which are overly reactive and have a tendency to
polymerize. Consequently, such hot monomers have an insufficiently
short shelf life.
[0013] U.S. Pat. No. 3,728,373 to Imohel et al. discloses a method
for producing cyanoacrylic acid esters by depolymerizing
polycyanoacrylic acid esters in a continuous process. In this
process, polymer is admixed with an inert liquid having a high
boiling point and a polymerization inhibitor. Depolymerization is
conducted in a reaction zone at a temperature of 150-250.degree. C.
and a vacuum pressure of 0.540 mm Hg. Wiper blades in the reaction
zone distribute the mixture in the form of a thin film having a
thickness of up to 5 cm. Cyanoacrylic acid esters that are released
from the reaction zone are passed to a condenser and collected in
receivers. A dispersion of polycyanoacrylic acid esters and other
components is collected as a thin layer on the surface of Woods
metal filled in a vessel. The temperature of the metal surface is
180-240.degree. C. in the vessel. Vapors of the monomeric
cyanoacrylic acid ester are condensed in a cooled receiver.
[0014] U.S. Pat. No. 4,986,484 to Arlt et al. discloses a process
for the production of monomeric .alpha.-cyanoacrylates. The Arlt
process produces monomeric cyanoacrylates by pyrolyzing
poly-.alpha.-cyanoacrylates. The monomer is subsequently distilled
in a distillation column. The distillation is carried out in a
counter current apparatus at reduced pressure over a plurality of
separation stages. Polymerization inhibitors are fed continuously
to the counter current at an uppermost separation stage. Liquid
monomer is fed in at places where the condensation can collect in
the apparatus.
[0015] U.S. Pat. No. 5,436,363 to Wang et al. discloses a method
for making cyanoacrylate by the depolymerization of
poly(alkyl-.alpha.-cyanoa- crylate). In the Wang process, a
reaction mixture containing poly(alkyl-.alpha.-cyanoacrylate), a
polymerization inhibitor and a solvent is fed into a film
evaporator to depolymerize the feed material. The film evaporator
is operated at a pressure of 10 mm Hg vacuum and a temperature of
about 200.degree.-260.degree. C. A first gas stream and a first
residual liquid stream are produced from the film evaporator. The
first residual liquid stream is passed to a collector. The first
gas stream is fed to an intermediate heat exchanger having a very
high temperature of about 150.degree. C. to produce a second gas
stream and a second residual stream of high-boiling residue. The
second gas stream is fed from a liquid collector to a second heat
exchanger (condenser) to form alkyl-.alpha.-cyanoacrylate
monomer.
[0016] Wang utilizes classical wiped-film evaporator technology.
However, such wiped-film devices cannot operate at low pressure
levels, such as at micron pressure levels, i.e., pressures as low
as about 10.sup.-3 mbar. Consequently, wiped-film evaporators heat
the polymer to a relatively high temperature. As explained above,
however, heating the polymer to high temperatures is
disadvantageous, as it produces hot monomers and unwanted
byproducts.
[0017] Thus, there is a need for a process that can produce
cyanoacrylate monomer from polycyanoacrylate without incurring the
above-described disadvantages of known processes. There is also a
need for a continuous process for preparing cyanoacetate that
converts a lower homologue cyanoacetate to a higher homologue
cyanoacetate.
SUMMARY OF THE INVENTION
[0018] This invention provides processes and apparatus for the
production of cyanoacrylate from polycyanoacrylate that satisfy one
or more of the above-described needs.
[0019] Processes and apparatus for producing cyanoacrylate
according to this invention can produce cyanoacrylate in a
continuous manner. The cyanoacrylates that can be produced include
alkyl cyanoacrylates, as well as other types of cyanoacrylates.
[0020] In addition, processes and apparatus for producing
cyanoacrylate according to this invention can reduce exposure of
polycyanoacrylate to high temperatures. Consequently, the
above-described problems associated with exposing polycyanoacrylate
to high temperatures, that occur in known processes and apparatus
for forming cyanoacrylate, can be avoided.
[0021] Embodiments of this invention can produce cyanoacrylate with
reduced waste, increased efficiency and at reduced cost.
[0022] This invention also provides processes and apparatus for the
continuous production of cyanoacetate. Embodiments of the processes
can convert a lower homologue cyanoacetate to a higher homologue
cyanoacetate. The cyanoacetate produced by these processes can
subsequently be used in embodiments of the above-described
processes for continuously producing cyanoacrylate according to
this invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Preferred embodiments of this invention will be described in
detail, with reference to the following figures, in which:
[0024] FIG. 1 illustrates a short-path, wiped film evaporator,
[0025] FIG. 2 illustrates a classical wiped-film evaporator,
[0026] FIG. 3 illustrates an exemplary embodiment of an apparatus
for continuously producing cyanoacrylate according to this
invention;
[0027] FIG. 4 illustrates another exemplary embodiment of an
apparatus for producing cyanoacrylate according to this invention;
and
[0028] FIG. 5 illustrates an exemplary embodiment of an apparatus
for producing cyanoacetate according to this invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0029] This invention provides processes and apparatus for
producing cyanoacrylate from polycyanoacrylate. Embodiments of the
invention produce cyanoacrylate in a continuous manner. Embodiments
of processes and apparatus for producing cyanoacrylate according to
this invention use one or more wiped-film evaporators such as those
shown in FIGS. 1 and 2 and, preferably, one or more short-path,
wiped-film evaporators, such as that shown in FIG. 1.
[0030] This invention further provides processes for continuously
producing cyanoacetate. The cyanoacetate produced in processes
according to this invention can be utilized in processes of the
invention for producing cyanoacrylate. Thus, for example, the
cyanoacetate produced according to processes of this invention can
be fed directly into a cyanoacrylate production process, including
embodiments of the processes of producing cyanoacrylate according
to this invention, to provide a combined continuous process of
producing both cyanoacetate and cyanoacrylate. Alternatively,
cyanoacetates produced by processes according to this invention can
be stored for later use and/or used in other processes.
[0031] Embodiments of processes for forming cyanoacetate according
to this invention can utilize one or more wiped-film evaporators
and, preferably, one or more short-pass, wiped-film
evaporators.
[0032] Embodiments of processes for continuously producing
cyanoacrylate from polycyanoacrylate according to this invention
comprise stripping a solvent from a reaction mass produced from a
synthesis step and cracking polymer contained in the reaction mass
to form a distillate comprising cracked cyanoacrylate monomer and
residue substances. The cracked cyanoacrylate monomer is distilled
to produce a purified cyanoacrylate monomer.
[0033] In embodiments of processes according to this invention, the
cracked cyanoacrylate monomer can be distilled twice. Particularly,
the distillate can be distilled a first time to separate the
volatile substances from the cracked cyanoacrylate monomer. The
cracked cyanoacrylate monomer can then be distilled a second time
to produce purified cyanoacrylate monomer product.
[0034] In embodiments of processes for continuously producing
cyanoacrylate from polycyanoacrylate according to this invention,
one or more wiped-film evaporators are used to perform different
process steps. Particularly, a wiped-film evaporator is preferably
used for stripping solvent from the reaction mass. The same or a
different wiped-film evaporator is also used to crack the polymer
in the reaction mass to form a cracked cyanoacrylate monomer and
residue substances.
[0035] In embodiments, wiped-film evaporators are also used for
distilling the cracked cyanoacrylate monomer. For example, a
wiped-film evaporator can be used to separate the volatile
substances from the cracked cyanoacrylate monomer. The same or a
different wiped-film evaporator as used in the first distillation
step can then be used to distill the cracked cyanoacrylate monomer
again to produce purified cyanoacrylate monomer product.
[0036] Wiped-film evaporators used in processes for continuously
producing cyanoacrylate from polycyanoacrylate according to this
invention are preferably short-path, wiped-film evaporators. A
suitable short-path, wiped-film evaporator for use in processes of
this invention includes, but is not limited to, the Model KDTA-4
evaporator, available from UIC Incorporated of Joliet, Illinois.
Other short-path, wiped-film evaporators, including wiped-film
evaporators of different sizes and/or configurations, can also be
used in embodiments of this invention.
[0037] Embodiments of the processes and apparatus utilize
short-path, wiped-film evaporators. Short-path, wiped-film
evaporators provide important advantages as compared to classical
wiped-film evaporators (referred to hereinafter as "wiped-film
evaporators") that have been used in known processes. FIG. 1
illustrates an exemplary short-path, wiped-film evaporator 10. The
short-path, wiped-film evaporator 10 includes a heating surface 12,
a wiper system 14 and an internal condenser 16. FIG. 2 illustrates
an exemplary wiped-film evaporator 20. The wiped-film evaporator 20
includes an evaporator 22 including wiper blades 24, a condenser 26
and a conduit connecting the evaporator 22 and condenser 26. In
contrast to the short-pass, wiped-film evaporator 10, in the
wiped-film evaporator 20, the condenser 26 is external to the
evaporator system.
[0038] The difference in location of the internal condenser 16 in
the short-pass, wiped-film evaporator 10 as compared to the
external condenser 26 in the wiped-film evaporator 20 significantly
affects the operation of these two evaporators. That is, in
evaporators generally, the distance between the condensation
surface, which is a cold surface, and the evaporation surface,
which is a hot surface, significantly affects the efficiency of the
evaporator. The short-path, wiped-film evaporator 10 has a
decreased distance between the evaporation surface and the
condensation surface due to the internal condenser 16, as compared
to wiped-film evaporator 20 having an external condenser 26 that is
separated from the evaporation surface by a greater distance.
Consequently, short-path, wiped-film evaporator 10 can operate at
lower pressures than wiped-film evaporator 20, due to the shorter
vapor path in short-path, wiped-film evaporators. For example,
short-path, wiped-film evaporators can operate at pressures as low
as about 0.001 mbar. This low pressure is not achievable in the
wiped-film evaporator 20. By achieving lower pressures, lower
process temperatures can also be achieved in short-path, wiped-film
evaporators. For example, for many organic materials, each order of
magnitude decrease in pressure results in a 25.degree. C. lowering
of the boiling temperature.
[0039] Accordingly, the higher pressures in wiped-filmed
evaporators require that polymers, such as polycyanoacrylate, be
heated to higher temperatures than those used in short-path, wiped
film evaporators. As stated above, heating polymers to high
temperatures is undesirable, because it can produce hot monomers
and unwanted byproducts. By operating at lower pressures and
temperatures, short-path, wiped-film evaporators at least
significantly reduce production of hot monomers and/or undesired
byproducts.
[0040] In addition, in short-path, wiped-film evaporators, there is
a short residence time on heated evaporator surfaces. In addition,
the product film is agitated to enhance heat transfer and eliminate
hot spots in the evaporator. Consequently, only small amounts of
material are exposed to high temperature at any one time. Also, the
travel time of substances between the hot surface and the cold
surface is reduced in short-path, wiped-film evaporators as
compared to wiped-film evaporators, thereby providing a higher
process efficiency.
[0041] FIG. 3 illustrates an exemplary embodiment of an apparatus
30 that can be used in processes for continuously forming
cyanoacrylate from polycyanoacrylate according to this invention.
Polycyanoacrylate polymer is produced in a reactor 32. The
polycyanoacrylate polymer is typically produced by reacting
cyanoacetate with a substance such as paraformaldehyde in the
presence of a base. The base acts as a catalyst for the reaction
between the cyanoacetate and paraformaldehyde. This reaction
produces polycyanoacrylate. A solvent such as toluene is used
during synthesis to remove water.
[0042] The polycyanoacrylate formed in the reactor 32 may be stored
in a suitable vessel, such as feed tank 34. As shown, the feed tank
34 is typically in communication with the reactor 32, so that the
polycyanoacrylate can be transported directly from the reactor 32
to the feed tank 34.
[0043] The reaction mass including the polycyanoacrylate and
solvent is fed from the feed tank 34 to a first evaporator 36. The
first evaporator 36 is preferably a wiped-film evaporator and, more
preferably, a short-path, wiped-film evaporator. The first
evaporator 36 is used to perform a stripping step, which removes
the solvent from the polycyanoacrylate contained in the reaction
mass by evaporating and condensing the solvent.
[0044] The first evaporator 36 is operated at an appropriate
temperature range, such as from about 40.degree. C. to about
120.degree. C., preferably from about 95.degree. C. to about
115.degree. C., and more preferably from about 100.degree. C. to
about 110.degree. C. during the stripping step. The first
evaporator 36 is operated at a vacuum pressure of from about 10
torr to about 100 torr, preferably from about 25 torr to about 85
torr, and more preferably from about 40 torr to about 70 torr
during the stripping step. Of course, in embodiments, temperatures
and pressures outside of these temperature and pressure ranges can
alternatively be used, if desired, depending, for example, on the
specific polycyanoacrylate and solvent involved.
[0045] It is also possible to conduct this process in the presence
of an acid gas, such as, for example, SO.sub.2.
[0046] The solvent is stripped from the reaction mass in the first
evaporator 36, preferably in the presence of a suitable radical
inhibitor and a dehydrating agent. Preferred radical inhibitors
include, but are not limited to, hydroquinone (HQ), butylated
hydroxy anisole (BHA), CuCl.sub.2 and butylated hydroxy toluene
CBHT). Preferred dehydrating agents include, but are not limited
to, polyphosphoric acid (PPA), P.sub.2O.sub.5, boric acid and
mixtures thereof The solvent stripping preferably removes at least
about 99% of the solvent from the reaction mass.
[0047] Polycyanoacrylate separated from the reaction mass in the
first evaporator 36 is fed to a second evaporator 38 located
downstream of the first evaporator 36. The second evaporator 38 is
preferably a wiped-film evaporator and, more preferably, a
short-path, wiped-film evaporator. The second evaporator 38 cracks
the polycyanoacrylate to form crude monomer. Volatiles and cracking
bottoms are also formed during cracking.
[0048] The second evaporator 38 is typically operated at a suitable
pressure, such as from about 0.001 torr to about 5 torr, preferably
from about 0.001 torr to about 2 torr, and more preferably from
about 0.001 torr to about 0.5 torr during the cracking step. The
reduced pressure used to crack the polycyanoacrylate allows a
corresponding lower temperature also to be used during cracking.
For example, the temperature in the second evaporator 38 during the
cracking step may be from about 160.degree. C. to about 250.degree.
C., preferably from about 175.degree. C. to about 240.degree. C.,
and more preferably from about 190.degree. C. to about 240.degree.
C. Of course, in embodiments, temperatures and pressures outside of
these temperature and pressure ranges can alternatively be used, if
desired, depending on the polycyanoacrylate being cracked.
[0049] The reduced pressure used to crack the polycyanoacrylate in
the second evaporator 38 is further advantageous in that it reduces
the cracking time during the cracking step as compared to
conventional polycyanoacrylate cracking processes that utilize
evaporators that operate at higher pressures.
[0050] By using reduced cracking pressures, temperatures and times
in the second evaporator 38, as compared to the cracking pressures,
temperatures and times that are used in known cracking processes
that utilize wiped-film evaporators, as well as other types of
evaporators, the formation of hot monomer and undesired reaction
byproducts can be avoided in the cracking step in the second
evaporator 38. Consequently, in embodiments of this invention, it
is not necessary to separate such undesired reaction byproducts
from the crude monomer that results from cracking the
polycyanoacrylate in the second evaporator 38. As a result,
processes and apparatus according to this invention can reduce
process times and costs, as compared to known processes that
utilize other types of evaporators.
[0051] Furthermore, the crude monomer that is produced by cracking
the polycyanoacrylate in the second evaporator 38 at the reduced
cracking temperatures and pressures has enhanced stability.
[0052] Cracking bottoms, including uncracked polycyanoacrylate,
resulting from the cracking step are preferably removed from the
second evaporator 38.
[0053] The crude monomer produced by cracking is then distilled to
purify the crude monomer. The crude monomer can be distilled using
one or more suitable evaporators, to purify the monomer to a
desired purity level.
[0054] In embodiments, crude monomer is fed from the second
evaporator 38 to a third evaporator 40 located downstream of the
second evaporator 38. The third evaporator 40 is preferably a
wiped-film evaporator and, more preferably, a short-path, wiped
film evaporator. In such preferred embodiments, the wiped-film, or
short-path, wiped-film, third evaporator 40 can be operated at
reduced pressures and temperatures.
[0055] In the third evaporator 40, the crude monomer is distilled
to extract volatiles from the crude monomer. In this distillation
step, in embodiments that utilize a wiped-film evaporator, or a
short-path, wiped film evaporator, for the third evaporator 40, the
third evaporator 40 may operate at a suitable temperature, such as
from about 45.degree. C. to about 110.degree. C., preferably from
about 70.degree. C. to about 100.degree. C., and more preferably
from about 70.degree. C. to about 90.degree. C. In such
embodiments, the third evaporator 40 may be operated at a suitable
pressure, such as a vacuum pressure from about 0.1 torr to about
1.6 torr, preferably from about 0.2 torr to about 1.0 torr, and
more preferably from about 0.2 torr to about 0.8 torr. Of course,
in embodiments, temperatures and pressures outside of these
temperature and pressure ranges can alternatively be used, if
desired.
[0056] Depending on the size of the evaporator, different
production rates of the once-distilled monomer can be achieved.
[0057] In embodiments of processes according to this invention,
distilled crude monomer that has been distilled in the third
evaporator 40 is preferably subjected to a second distilling step
to further purify the cyanoacrylate monomer. The second distilling
step can be performed in the third evaporator 40 or in a fourth
evaporator 42. In embodiments, distilled crude monomer is fed from
the third evaporator 40 to the fourth evaporator 42 located
downstream of the third evaporator 40. The fourth evaporator 42 is
preferably a wiped-film evaporator and, more preferably, a
short-path, wiped-film evaporator. In such embodiments, the
wiped-film, or short-path, wiped-film, fourth evaporator 42 may
operate at reduced pressures and temperatures. The fourth
evaporator 42 distills the cracked cyanoacrylate monomer a second
time to remove undesired substances, such as uncracked polymer and
cyanoglutarate, to form a purified monomer product.
[0058] In embodiments that utilize a wiped-film evaporator, or a
short-path, wiped film, evaporator for the fourth evaporator 42,
the fourth evaporator 42 may be operated at a suitable temperature,
such as from about 70.degree. C. to about 100.degree. C.,
preferably from about 75.degree. C. to about 95.degree. C., and
more preferably from about 75.degree. C. to about 90.degree. C. The
fourth evaporator 42 may be operated at a suitable pressure, such
as a vacuum pressure of from about 0.01 torr to about 1.0 torr,
preferably from about 0.1 torr to about 0.85 torr, and more
preferably from about 0.1 to about 0.5 torr.
[0059] Of course, in embodiments, temperatures and pressures
outside of these temperature and pressure ranges can alternatively
be used, if desired. Low temperatures used in the second
distillation step of the cyanoacrylate monomer reduce the heat
exposure of the monomer, which thus improves the stability of the
purified monomer product. Consequently, the shelf life of the
purified monomer is enhanced.
[0060] As shown in FIG. 3, the apparatus can optionally include a
controller 44 that automatically controls the operating conditions
of one or more of the reactor 32, feed tank 34 and first, second,
third and fourth evaporators 36, 38, 40 and 42, respectively.
Preferably, the controller 44 controls at least the first, second,
third and fourth evaporators 36, 38, 40 and 42, respectively. The
controller 44 can enable processes according to this invention to
be fully automated.
[0061] This invention also provides processes and apparatus for
producing cyanoacrylate in fewer evaporators. For example, two or
more of the first, second, third and fourth evaporators discussed
above can be the same evaporator. Referring to FIG. 4, in exemplary
embodiments of such processes and apparatus 50, two or more, or
even all, of the steps of solvent stripping, polymer cracking and
monomer distilling are performed in the same evaporator 52. In such
embodiments, the evaporator 52 is preferably a wiped-film
evaporator and, more preferably, a short-path, wiped-film
evaporator. Process conditions utilized in each of the steps in the
single wiped-film evaporator, or short-path, wiped-film evaporator,
can be the same as the above-described process conditions that are
utilized in processes and apparatus according to this invention
that utilize multiple wiped-film evaporators, or multiple
short-path, wiped-film evaporators.
[0062] In the apparatus 50, a feed tank 54 contains a supply of a
reaction mass comprising polycyanoacrylate and solvent that has
been produced in a reactor. The reaction mass is subjected to the
steps of solvent stripping, polymer cracking and monomer distilling
in the evaporator 52. The apparatus preferably also includes a
holding container 56 downstream of the evaporator 52 to temporarily
hold material that has been formed in the evaporator 52 before this
material is re-introduced into the evaporator 52 for subsequent
processing.
[0063] In embodiments, solvent is stripped from polycyanoacrylate
in the evaporator 52 and the stripped polycyanoacrylate is then fed
from the evaporator 52 to the holding tank 56. Stripped solvent is
removed from the evaporator 52 as indicated at 58 in FIG. 4.
[0064] The stripped polycyanoacrylate is then returned to the
evaporator 52 via the return passage 60. The stripped
polycyanoacrylate is then subjected to cracking in the evaporator
52 to form cracked cyanoacrylate monomer, bottoms and volatile
substances. The cracked cyanoacrylate monomer and volatiles are fed
to the holding tank 56. The bottoms are removed from the evaporator
as indicated at 59.
[0065] Next, cracked cyanoacrylate monomer is returned from the
holding tank 56 to the evaporator 52 via the return passage 60. The
cracked cyanoacrylate monomer is then subjected to one or more
distilling step(s), to remove the volatile substances as at 58 and
purify the cyanoacrylate monomer. In embodiments in which the
cyanoacrylate is distilled more than once, the cyanoacrylate
monomer is fed from the evaporator 52 to the holding tank 56 and
then returned to the evaporator 52 for subsequent distilling of the
distilled cyanoacrylate monomer. As stated above, cyanoacrylate
monomer can be distilled twice in the evaporator 52 to produce
purified cyanoacrylate monomer.
[0066] Processes according to this invention that utilize a single
wiped-film evaporator, or a short-path, wiped-film evaporator, are
advantageous, for example, when only a single wiped-film or
short-path, wiped film evaporator is available for performing the
cyanoacrylate production process, or where process space is
limited. In addition, these processes are also advantageous for
making small amounts of cyanoacrylate.
[0067] Processes for producing cyanoacrylates according to this
invention can produce alkyl .alpha.-cyanoacrylates. Such monomers
are known in the art and have the formula: 1
[0068] wherein R.sup.1 is hydrogen and R.sup.2 is a hydrocarbyl or
substituted hydrocarbyl group; a group having the formula
--R.sup.3--O--R.sup.4--O--R.sup.5 or the formula
--R.sup.4--O--R.sup.5, wherein R.sup.3 is a 1,2-alkylene group
having 2-4 carbon atoms, R.sup.4 is an alkylene group having 2-4
carbon atoms, and R.sup.5 is an alkyl group having 1-6 carbon
atoms; or a group of the formula: 2
[0069] wherein R.sup.6 is --(CH.sub.2).sub.n--, 3
[0070] or --C(CH.sub.3).sub.2--, wherein n is 1-10, preferably 1-5
carbon atoms, and R.sup.7 is an organic radical.
[0071] Examples of suitable hydrocarbyl and substituted hydrocarbyl
groups include straight chain or branched chain alkyl groups having
1-16 carbon atoms; straight chain or branched chain
C.sub.1-C.sub.16 alkyl groups substituted with an acyloxy group, a
haloalkyl group, an alkoxy group, a halogen atom, a cyano group, or
a haloalkyl group; straight chain or branched chain alkenyl groups
having 2 to 16 carbon atoms; straight chain or branched chain
alkynyl groups having 2 to 12 carbon atoms; cycloalkyl groups;
aralkyl groups; alkylaryl groups; and aryl groups.
[0072] The organic moiety R.sup.7 may be substituted or
unsubstituted and may be straight chain, branched or cyclic,
saturated, unsaturated or aromatic. Examples of such organic
moieties include C.sub.1-C.sub.8 alkyl moieties, C.sub.2-C.sub.8
alkenyl moieties, C.sub.2-C.sub.8 alkynyl moieties,
C.sub.3-C.sub.12 cycloaliphatic moieties, aryl moieties such as
phenyl and substituted phenyl and aralkyl moieties such as benzyl,
methylbenzyl and phenylethyl. Other organic moieties include
substituted hydrocarbon moieties, such as halo (e.g., chloro-,
fluoro- and bromo-substituted hydrocarbons) and oxy- (e.g., alkoxy
substituted hydrocarbons) substituted hydrocarbon moieties.
Preferred organic radicals are alkyl, alkenyl and alkynyl moieties
having from 1 to about 8 carbon atoms, and halo-substituted
derivatives thereof. Particularly preferred are alkyl moieties of 4
to 6 carbon atoms.
[0073] In the cyanoacrylate monomer of formula (I), R.sup.2 is
preferably an alkyl group having 1-10 carbon atoms or a group
having the formula --AOR.sup.8, wherein A is a divalent straight or
branched chain alkylene or oxyalkylene moiety having 2-8 carbon
atoms, and R.sup.8 is a straight or branched alkyl moiety having
1-8 carbon atoms.
[0074] Examples of groups represented by the formula --AOR.sup.8
include 1-methoxy-2-propyl, 2-butoxy ethyl, isopropoxy ethyl,
2-methoxy ethyl, and 2-ethoxy ethyl.
[0075] Preferred .alpha.-cyanoacrylate monomers used in this
invention include 2-octyl cyanoacrylate, dodecyl cyanoacrylate,
2-ethylhexyl cyanoacrylate, butyl cyanoacrylate, methyl
cyanoacrylate, 3-methoxybutyl cyanoacrylate, 2-butoxyethyl
cyanoacrylate, 2-isopropoxyethyl cyanoacrylate, or
1-methoxy-2-propyl cyanoacrylate.
[0076] In addition, processes and apparatus according to this
invention can also produce other types of cyanoacrylates, such as
those described in the patents and patent applications incorporated
herein by reference.
[0077] Processes according to this invention can produce
cyanoacrylate monomers that have high purity and contain few
impurities. These monomers can be utilieed for medical purposes.
Monomers utilized for industrial purposes need not always be as
pure as those for medical purposes, but can also be produced by
processes and apparatus of the invention.
[0078] The purified cyanoacrylate monomers produced by processes
according to this invention can be applied to substrates in any
suitable manner. For example, polymerizable 1,1-disubstituted
ethylene monomers, and adhesive compositions comprising such
monomers, can be applied to substrates, and particularly in medical
applications, as described, for example, in U.S. Pat. Nos.
5,624,669 and 5,928,611 to Leung et al. and 5,981,621 to Clark et
al., and U.S. patent application Ser. Nos. 08/714,288 to Clark et
al. and 09/471,392 to Narang et al., each of which is incorporated
herein by reference in its entirety.
[0079] As stated above, this invention also provides processes and
apparatus for continuously producing cyanoacetate. The cyanoacetate
produced by these processes can then be used to produce
polycyanoacrylate, which is cracked to form cyanoacrylate monomer
by the above-described exemplary embodiments, or alternatively can
be stored, shipped and/or used in other processes.
[0080] Embodiments of processes for producing cyanoacetate
according to this invention comprise synthesizing cyanoacetate and
then purifying the cyanoacetate. The synthesizing and purifying
steps are preferably both performed in one or more wiped-film
evaporators, and preferably in one or more short-path, wiped-film
evaporators, so that reduced synthesizing and purifying
temperatures and pressures can be used. These steps can be
performed in either the same wiped-film evaporator, or
alternatively in different wiped-film evaporators.
[0081] In embodiments of processes for producing cyanoacetate
according to this invention, a first cyanoacetate is reacted with a
suitable compound by transesterification, or ester interchange, to
form a second cyanoacetate. This reaction is conducted in a
wiped-film evaporator. The second cyanoacetate is then purified,
preferably in a wiped-film evaporator. Processes for forming
cyanoacetate by transesterification are discussed in incorporated
U.S. Pat. No. 5,624,669 to Leung et al.
[0082] In exemplary embodiments, the first cyanoacetate can be a
lower homologue cyanoacetate and the second cyanoacetate can be a
higher homologue cyanoacetate. For example, the first cyanoacetate
can be ethyl or methyl cyanoacetate and the second cyanoacetate can
be 2-octyl cyanoacetate.
[0083] Referring to FIG. 5, an exemplary embodiment of an apparatus
70 for producing cyanoacetate in a continuous process comprises a
first evaporator 72 and a second evaporator 74 downstream of the
first evaporator 72. A reactor 76 for forming polycyanoacrylate is
shown downstream of the second evaporator 74. A controller 78 can
optionally be used to control cyanoacetate production.
[0084] The first evaporator 72 used for transesterification can
have a suitable operating temperature, such as from about
100.degree. C. to about 250.degree. C. during the synthesizing
step, preferably a temperature of from about 120.degree. C. to
about 210.degree. C., and more preferably a temperature of from
about 140.degree. C. to about 175.degree. C. The operating pressure
of the first evaporator 72 during the synthesizing step is
preferably about atmospheric pressure. Of course, in embodiments,
temperatures and pressures outside of these temperature and
pressure ranges can alternatively be selected by those of ordinary
skill in the art in light of this disclosure.
[0085] The second evaporator 74 used in embodiments for the
purifying step can have a suitable operating temperature, such as
from about 75.degree. C. to about 105.degree. C., preferably from
about 80.degree. C. to about 100.degree. C., and more preferably
from about 85.degree. C. to about 95.degree. C. The second
evaporator 74 can have a suitable operating pressure, such as from
about 0.5 torr to about 10 torr during the step of purifying the
first cyanoacetate. Of course, in embodiments, temperatures and
pressures outside of these temperature and pressure ranges can be
selected by those of ordinary skill in the art in light of this
disclosure.
[0086] In embodiments of processes for producing cyanoacetate
according to this invention, cyanoacetate can be produced by the
esterification of cyanoacetic acid. For example, cyanoacetic acid
can be mixed with an excess amount of alcohol, such a 2-octanol, in
the presence of a strong acid, such as sulfuric acid,
p-toluenesulfonic acid, methanesulfonic acid and trifluoroacetic
acid, and fed into a wiped-film evaporator set to a temperature
below the boiling point of the alcohol. An ester is produced in the
wiped-film evaporator. Preferably, the ester has a high boiling
point.
[0087] In embodiments of this invention, purified cyanoacetate
product that is formed by the continuous cyanoacetate processes can
be used to form polycyanoacrylate in the reactor 76 in a continuous
process. As stated, the polycyanoacrylate that is continuously
produced by these processes can be used in the above-described
continuous processes for forming cyanoacrylate according to this
invention.
[0088] Particularly, the purified cyanoacetate can be reacted with
a suitable substance in the presence of a suitable catalyst in
reactor 76 to form polycyanoacrylate. For example, the cyanoacetate
can be reacted with formaldehyde or a functional equivalent, such
as the polymeric form paraformaldehyde or formaline, to form
polycyanoacrylate. Processes for forming polycyanoacrylate by
reacting cyanoacetate with a substance, such as paraformaldehyde,
are discussed in U.S. patent application Ser. No. 09/443,298 to
Malofsky et al., which is incorporated herein by reference in its
entirety.
[0089] The catalyst can be any suitable basic material. Suitable
basic substances for use as the catalyst include, for example,
piperidine, piperidine hydrogen chloride, sodium bicarbonate and
triethylamine.
[0090] The catalyst is dissolved in any suitable solvent. For
example, a suitable solvent is toluene.
[0091] The reaction of cyanoacetate with paraformaldehyde in the
presence of the catalyst produces polycyanoacrylate, formaldehyde
and solvent. In order to produce cyanoacrylate monomer, the solvent
is stripped off, and polycyanoacrylate polymer is cracked,
preferably as described above. Conventional processes for forming
polycyanoacrylate from cyanoacetate are described, for example, in
U.S. Pat. Nos. 2,467,927 and 2,721,858, which are each incorporated
herein by reference in their entirety.
[0092] The following examples illustrate specific embodiments of
the present invention. One skilled in the art will recognize that
process conditions may be adjusted to achieve specific process
results.
EXAMPLES
[0093] The following examples are performed in an apparatus as
shown in FIG. 4. In Example 1, a reaction mass of polycyanoacrylate
and toluene produced during synthesis in a reactor are fed into a
short-path wiped-film evaporator operated at the process conditions
shown in TABLE 1 below. The wiped-film evaporator separates the
toluene (distillate) from the reaction mass, producing a
polycyanoacrylate residue.
[0094] The polycyanoacrylate residue is then subjected to the
process conditions shown in TABLE 1 in the same wiped-film
evaporator to crack the polycyanoacrylate and form a distillate
comprising crude cracked cyanoacrylate monomer and uncracked
polycyanoacrylate residue.
[0095] Next, the crude cyanoacrylate monomer is subjected to two
distilling steps in the wiped-film evaporator, in order to purify
the crude cyanoacrylate monomer and produce a purified
cyanoacrylate monomer. The process conditions for the first and
second distillation steps are shown in TABLE 1. The first
distilling step distills the crude cyanoacrylate monomer to remove
low boiling point substances, such as one or more of octane,
octanol, propionate and acetate, to form a more concentrated
cyanoacrylate monomer and typically also other substances, such as
dicyanoglutarate.
[0096] The once-distilled cyanoacrylate monomer and high boilers
are then subjected to the second distillation step. In this step,
the twice distilled pure cyanoacrylate monomer is separated from
the residue.
1 TABLE 1 Example No. 1 Solvent Stripping Feed Rate .about.170
gm/hr Feed Temp. .about.70.degree. C. Evaporator Temp. 100.degree.
C. Wiper Speed 450 rpm Pressure (mmHg) 20 Condenser Temp.
-20.degree. C. Residue Temp. 90.degree. C. Residue (%) .about.82
Distillate (%) .about.17 Trap (%) .about.1 Polymer Cracking Feed
Rate .about.90 gm/hr Feed Temp. 120.degree. C. Wiper Speed 450 rpm
Evaporator Temp. 238.degree. C. Pressure (mmHg) 0.041 Condenser
Temp. -20.degree. C. Residue (%) 38.1 Distillate (%) 56.3 Trap (%)
5.6 First Distillation Crude Source Feed Rate .about.145 gm/hr
Evaporator Temp. 75.degree. C. Wiper Speed 400 rpm Pressure (mmHg)
0.314 Condenser Temp. 5.degree. C. Residue (%) 80.4 Distillate (%)
19.6 Trap (%) 0 Second Distillation Feed Rate .about.160 gm/hr
Evaporator Temp. 90.degree. C. Wiper Speed 400 rpm Pressure (mmHg)
0.18 Condenser Temp. 5.degree. C. Residue (%) 86.3 Distillate (%)
13.7 Trap (%) 0.0
[0097] Examples 2-7 are conducted to further demonstrate the
formation of crude cyanoacrylate monomer by the performance of a
solvent stripping step and a polymer cracking step, in accordance
with this invention. The process conditions used for the solvent
stripping step and the polymer cracking step are shown in TABLE 2
below. The distillate is then analyzed for Example Nos. 1-4, 6 and
7.
2 TABLE 2 Example No. 2 3 4 5 6 7 Solvent Stripping Feed Rate
(gm/hr) .about.140 .about.250 .about.250 .about.330 .about.350
.about.250 Feed Temp. ambient ambient ambient ambient ambient
.about.70.degree. C. Evaporator Temp. 100 100 100 100 100 100
(.degree. C.) Wiper Speed (rpm) 400 400 400-500 500 450 450
Pressure (mmHg) 10 10-12 10-14 10 12 15-20 Condenser Temp. 5 5 5
-10 -10 -20 (.degree. C.) Residue Temp. 90 90 90 90 90 90 (.degree.
C.) Residue (%) .about.81 .about.81 .about.85 .about.82 .about.80
.about.82 Distillate (%) .about.3 .about.2 .about.4 .about.11
.about.18 .about.12 Trap (%) .about.16 .about.17 .about.11 .about.7
.about.2 .about.5 Polymer Cracking Feed Rate (gm/hr) .about.60
.about.80 .about.40 .about.100 .about.125 .about.80 Feed Temp.
(.degree. C.) 90 110 110 120 120 120 Wiper Speed (rpm) 400 400-500
500 500 500 450 Evaporator Temp. 240 220-230 235-238 238 235
235-237 (.degree. C.) Pressure (mmHg) 0.1* 0.07* 0.061 0.051 0.065
0.2-0.3 Condenser Temp. 5 5 5 -10 -20 -20 (.degree. C.) Residue (%)
NA** 68.6 19.7 1.1 4.8 65.3 Distillate (%) 86.3 27.6 73.7 93.8 92.0
30.0 Trap (%) NA 3.8 6.6 5.1 3.2 4.7 Distillate Data Octene (ppm)
2,503 7,994 7,095 NA 6,026 4,485 Octanol (ppm) 13,375 24,148 17,334
NA 15,290 21,383 Propionate (%) NA 0.61 0.7 NA None 0.92 Acetate
(%) NA 7.58 9.42 NA 7.18 13.32 Acrylate Purity (%) NA 85.42 81.75
NA 90.36 76.45 *Used pirani vacuum gauge for pressure measurement
**NA = Not Analyzed.
[0098] While the invention has been described in conjunction with
the specific embodiments described above, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, preferred embodiments of the
invention as set forth above are intended to be illustrative and
not limiting. Various changes can be made without departing from
the spirit and scope of the invention.
* * * * *