Transesterification method for making cyanoacrylates
Year:
Abstract:
An alpha-cyanoacrylate may be formed by first condensing a cyanoacetate with paraformaldehyde or formaldehyde; reacting the polymer formed with an alcohol to transesterify the polymer; and depolymerizing the polymer to form alpha-cyanoacrylate monomers.
Type of document:
Language:
US006245933B1
(12) United States Patent (10) Patent No.: US 6,245,933 B1
Malofsky et al. (45) Date of Patent: Jun. 12, 2001
(54) TRANSESTERIFICATION METHOD FOR 3,975,422 8/1976 Buck.
MAKING CYANOACRYLATES 4,012,402 3/1977 Buck-
4,321,180 3/1982 Kimura et al. .
(75) Inventors: Bernard Malofsky, Bloomfield, CT §iflII{1ure1etta11~ ~
, - ' ' , , 11111 C 8. . .
§JCS)’UI§raheem T‘ Bade” Momsvlue’ 5,359,101 10/1994 Woods et al. .
( ) 5,504,252 4/1996 Klemarczyk.
(73) Assignee: Closure Medical Corporation, E: 3:
Raleigh, NC (US) 5,637,752 6/1997 Nakamura et al. .
5,703,267 12/1997 Takahashi et al. .
(*) Notice: Subject to any disclaimer, the term of this 6,057,472 * 5/2000 Sailhan et al. ..................... .. 558/381
patent is extended or adjusted under 35
USC. 154(b) by 0 days. FOREIGN PATENT DOCUMENTS
726086 4/1980 (SU) .
(21) Appl. No.: 09/443,298 WO 95/33708 12/1995 (W0).
(22) Filed: Nov. 19, 1999 * cited by examiner
(51) Int. Cl.7 ...................... .. C07C 255/23; C07C 253/30 Primary Examiner_MiChae1 G. Ambrose
U.S. Cl. ................ .. . Assistant Examiner:EbeneZer Sacket
(58) Field of Search ................................... .. 558/443, 375, (74) Attorney, Agent, or Firm—Oliff & Berridge, PLC
558 381
/ (57) ABSTRACT
(56) References Cited
An 01-cyanoacrylate may be formed by first condensing a
Us. PATENT DOCUMENTS cyanoacetate with paraformaldehyde or formaldehyde;
reacting the polymer formed with an alcohol to transesterify
the polymer; and depolymerizing the polymer to form
01-cyanoacrylate monomers.
2,721,858 10/1955 Joyner et al. .
2,756,251 7/1956 Joyner et al. .
2,763,677 9/1956 Jeremias .
3,559,652 2/1971 Banitt et al. .
3,759,264 9/1973 Coover, Jr. et al. . 20 Claims, No Drawings
US 6,245,933 B1
1
TRANSESTERIFICATION METHOD FOR
MAKING CYANOACRYLATES
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a method for making cyanoacry-
lates.
2. Description of Related Art
Monomer and polymer adhesives are both used in indus-
trial (including household) and medical applications.
Included among these adhesives are 1,1-disubstituted eth-
ylene monomers and polymers, such as ot-cyanoacrylates.
Since the discovery of the adhesive properties of such
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 charac-
teristics have made ot-cyanoacrylate adhesives the primary
choice for numerous applications such as bonding plastics,
rubbers, glass, metals, wood, and, more recently, biological
tissues.
Medical applications of 1,1-disubstituted ethylene adhe-
sive compositions, such as ot-cyanoacrylate compositions,
include use as an alternate and an adjunct to surgical sutures
and staples in wound closure as well as for covering and
protecting surface wounds such as lacerations, abrasions,
burns, stomatitis, sores, and other surface wounds. When an
adhesive is applied, it is usually applied in its monomeric
form, and the resultant polymerization gives rise to the
desired adhesive bond.
U.S. Pat. No. 5,624,669 to Leung et al. describes a process
for making cyanoacrylates. In the method, ot-cyanoacrylates
are prepared by condensing a cyanoacetate and either form-
aldehyde or paraformaldehyde in the presence of a catalyst
at a molar ratio of 0.5—1.5:1 to obtain a condensate; depo-
lymerizing the condensation reaction mixture either directly
or after removal of the condensation catalyst to yield crude
cyanoacrylate; and distilling the crude cyanoacrylate to form
a high purity cyanoacrylate. In order to prepare a particular
ot-cyanoacrylate, the ’669 patent discloses making a corre-
sponding cyanoacetate by esterifying cyanoacetic acid with
the corresponding alcohol or by transesterifying an alkyl
cyanoacetate with the corresponding alcohol before the
cyanoacetate undergoes the condensation reaction with the
formaldehyde or paraformaldehyde.
U.S. Pat. No. 4,364,876 to Kimura et al. describes reac-
tion conditions for forming ot-cyanoacrylates by the method
described in the ’669 patent.
U.S. Pat. No. 2,721,858 to Joyner et al. and U.S. Pat. No.
2,763,677 to Jeremias et al. also describe reaction conditions
for forming ot-cyanoacrylates from the corresponding
cyanoacetate.
As used herein the terms “corresponding” or “corre-
sponds” with reference to a cyanoacetate and an
ot-cyanoacrylate means that the same R group is attached to
oxygen of the carboxyl group in the two compounds. Thus,
methylcyanoacetate corresponds to methyl ot-cyanoacrylate.
The term “corresponding alcohol,” as used herein, refers to
an alcohol having the same R group attached to the hydroxyl
group as the corresponding cyanoacetate or ot-cyanoacrylate
has attached to the oxygen of the carboxy group. Thus,
methyl alcohol corresponds to methylcyanoacetate and to
methyl ot-cyanoacrylate.
In all of the above mentioned references, the cyanoacetate
that undergoes the condensation reaction corresponds to the
ot-cyanoacrylate that is obtained.
10
15
20
25
30
35
40
45
50
55
60
65
2
U.S. Pat. No. 5,637,752 to Nakamura et al. describes
reaction conditions for the transesterification of a lower
alkyl cyanoacetate with an alcohol to form a higher alkyl
cyanoacetate.
SU 726,086 describes a process for producing
ot-cyanoacrylates by reacting ethyl ot-cyanoacrylate mono-
mer with excess alcohol in the presence of an acid or metal
chloride catalyst. The process is simplified and polymeriza-
tion of the final product is prevented by conducting the
transesterification reaction at 100—140° C. in the presence of
sulfuric or para-toluene sulfonic acid or zinc chloride cata-
lyst.
U.S. Pat. No. 2,756,251 to Joyner et al. describes a
method for depolymerizing polymeric ot-cyanoacrylates.
SUMMARY OF THE INVENTION
The parameters for conducting a condensation reaction of
methyl or ethyl cyanoacetate with formaldehyde or
paraformaldehyde to form methyl or ethyl ot-cyanoacrylate,
respectively, with maximum yield are well established.
However, the parameters for the condensation of other
cyanoacetates to form other ot-cyanoacrylates are not as well
established. In addition, due to steric considerations, it is
difficult to polymerize higher alkyl cyanoacetates and the
reaction generally results in smaller oligomers. When crack-
ing an oligomer, the last two monomers, which are joined as
cyanoglutarate, are generally difficult to crack. Thus, if a
greater number of smaller oligomers are formed, then more
of the starting material monomers may be lost. As a result,
the final yield of monomers from the overall process may not
be as ideal as with methyl or ethyl cyanoacetates. Therefore,
it is advantageous to form ot-cyanoacrylates other than
methyl and ethyl ot-cyanoacrylates using processes that do
not require the condensation of cyanoacetates other than
methyl and ethyl cyanoacetates.
The present invention provides a process for forming
ot-cyanoacrylates, particularly ot-cyanoacrylates of formula
(I) where R1 is a carbon containing organic group other than
a methyl or ethyl group:
(1)
CN 0
CH2=C—C—oR1 .
The process comprises reacting a particular cyanoacetate,
particularly methyl or ethyl cyanoacetate, with paraformal-
dehyde or any other convenient form of formaldehyde to
prepare an ot-cyanoacrylate oligomer or polymer. The
cyanoacrylate oligomer or polymer condensation product is
then transesterified with an alcohol to form a different
cyanoacrylate oligomer or polymer before undergoing a
depolymerization to form the target ot-cyanoacrylate. The
process may be demonstrated in the following reaction
scheme:
CN 0
l formaldehyde condensation
1) nCH2—C—OR2 + or
paraformaldehyde
(|ZN
—('CH2‘(|35T
o=C—oR2
US 6,245,933 B1
3
-continued
CN
2) _(_CH2_Cfi7+ nR1OH
o=C—oR2
CN
—(-CH2—Cj7+ nR2OH
o=c—oR1
CN CN 0
l deploymerization I
3) —(-CH2—Cfi,,— nCH2=C—C—oR1
o=C—oR1
In this reaction scheme, R1 and R2 both represent any carbon
containing organic group as long as they are different from
one another. Preferably, n is from 2 to 100.
Although an embodiment of the invention is directed to a
process in which R2 is a methyl or ethyl group and R1 is a
group other than a methyl or ethyl group, the present
invention is not limited to such an embodiment. Thus, R2
may be a group other than a methyl or ethyl group and/or R1
may be a methyl or ethyl group.
By conducting the transesterification reaction after the
condensation reaction, better yield can be obtained. In
particular, by using lower alkyl cyanoacetates, longer oli-
gomers or polymers may be obtained, which results in
higher yield during the cracking reaction. In addition,
because it is not necessary to use the corresponding
cyanoacetate to form particular ot-cyanoacrylate monomers,
a different cyanoacetate for which optimal condensation
conditions are more well established and/or more readily
available may be effectively used to produce the particular
ot-cyanoacrylate monomers at relatively high yield.
DETAILED DESCRIPTION OF PREFERRED
EMBODIMENTS
The process of the present invention comprises reacting a
particular cyanoacetate, particularly methyl or ethyl
cyanoacetate, with paraformaldehyde or any other conve-
nient form of formaldehyde to prepare an ot-cyanoacrylate
oligomer or polymer. Conditions for achieving this conden-
sation reaction are known in the art. In particular, U.S. Pat.
No. 5,624,669 to Leung et al., U.S. Pat. No. 4,364,876 to
Kimura et al., U.S. Pat. No. 2,721,858 to Joyner et al. and/or
U.S. Pat. No. 2,763,677 to Jeremias et al., each of which is
hereby incorporated herein by reference, describe conditions
for the condensation reaction.
As used herein the term “formaldehyde” is intended to
include any source of formaldehyde that may be used to
achieve the condensation reaction of the present invention
including formaldehyde itself, as well as polymers thereof,
such as paraformaldehyde or the like, and aqueous solutions
of formaldehyde, such as formalin.
The cyanoacrylate oligomer or polymer formed generally
contains from about 2 to 100 cyanoacrylate monomer units.
However polymers having a larger number of cyanoacrylate
monomers may also be formed. Preferably, the cyanoacry-
late oligomer or polymer contains from 3 to 75, more
preferably from 5 to 50, and even more preferably from 10
to 50, cyanoacrylate monomers.
The condensation may be conducted in an organic sol-
vent. Preferably, the solvent forms an azeotropic mixture
with water. Exemplary solvents include toluene, hexane,
pentane, benzene, cyclohexane, heptane, octane, nonane,
10
15
20
25
30
35
40
45
50
55
60
65
4
xylenes, carbon tetrachloride and ethylbenzene. During the
condensation reaction, the solution may be heated to the
azeotropic point. By such heating, the water may be selec-
tively removed from the reaction medium.
In an embodiment of the present invention, the conden-
sation reaction is conducted in the presence of one or more
basic condensation catalysts. However, one or more acidic
condensation catalysts may alternatively be used. Basic
catalysts that may be used include, but are not limited to,
pyridine; alkali metal or alkaline earth hydroxide, carbonate
or bicarbonates, such as sodium hydroxide, potassium
hydroxide, sodium carbonate, sodium bicarbonate; metal
alcoholates, such as sodium methoxide and potassium
t-butoxide; trialkylamines, such as triethylamine;
dialkylamines, such as dimethylamine; alkylamines, such as
methylamine; and primary and secondary amines, such as
piperidine, as well as salts of the various amines. Acidic
catalysts that may be used include, but are not limited to,
acetic acid, piperidine hydrochloride and Lewis acids, such
as zinc chloride or titanium tetrachloride. In addition to more
traditional acid and basic catalysts, the condensation reac-
tion can be conducted in the presence of an acidic or basic
ion-exchange resin, such as an acidic or basic DOWEX
ion-exchange resin manufactured and sold by Dow
Chemical, Midland, Mich.
The cyanoacrylate oligomer or polymer condensation
product is then transesterified with an alcohol to form a
different cyanoacrylate oligomer or polymer. The solvent
used for the condensation reaction may or may not be
removed from the reaction medium before the transesteri-
fication reaction. The alcohol is generally added in molar
excess, such as in an amount of from 1.5 to 2.0 moles per
cyanoacrylate monomer unit in the oligomer or polymer to
drive the transesterification reaction. To transesterify the
oligomer or polymer, the reaction medium is generally
heated. It may be heated to a temperature above the boiling
point of the alcohol produced in the reaction to concurrently
remove the alcohol being produced. Alternatively or in
addition, it is possible to add a molecular sieve to remove the
alcohol produced and help drive the reaction.
The transesterification reaction may be conducted in the
presence of a strong acid (Bronsted acid) catalyst or an
organometallic catalyst. Acidic catalysts that may be used
include, but are not limited to, p-toluenesulfonic acid,
hydrochloric acid, trifluoroacetic acid and Lewis acids, such
as boron trifluoride and zinc chloride. Organometallic cata-
lysts that may be used include, but are not limited to,
titanium tetraisopropoxide, such as the product sold under
the trademark TYZOR TPT by DuPont, aluminum
isopropoxide, tributyltin oxide and sumarium isopropoxide.
The transesterification reaction may also be conducted in
the presence of metal alcoholate (alkali metal alcoholate or
alkaline earth alcoholate), such as potassium 2-octoxide or
sodium 2-octoxide. The type of metal alkoxide to be used
depends on the alcohol used in the reaction. For example, the
transesterification of ethylcyanoacrylate oligomer or poly-
mer to 2-octylcynoacrylate oligomer or polymer may be
conducted with sodium 2-octoxide. It is also possible to use
sodium ethoxide for the transesterification of ethylcy-
anoacrylate oligomer or polymer to 2-octylcynoacrylate
oligomer or polymer. In addition, the transesterification may
be conducted in the presence of an acidic or basic ion-
exchange resin, such as an acidic or basic DOWEX ion-
exchange resin manufactured and sold by Dow Chemical,
Midland, Mich.
In a particular embodiment, a methyl or ethyl
ot-cyanoacrylate oligomer or polymer is transesterified with
US 6,245,933 B1
5
an alcohol other than methyl or ethyl alcohol to form an
ot-cyanoacrylate oligomer or polymer other than methyl or
ethyl ot-cyanoacrylate oligomer or polymer. Preferably the
alcohol transesterified with the oligomer or polymer has four
or more carbons.
Since the alcohol is generally added in molar excess, it is
generally necessary to remove the excess alcohol after the
transesterification process. In addition, since the second
stage of the reaction may be conducted in a solvent in
addition to the alcohol, it may also be necessary to remove
other solvent after the transesterification. Thus, after com-
pleting the transesterification, in embodiments of the
invention, the solvent and/or excess alcohol are removed,
such as by stripping the polymer under a vacuum.
The transesterified cyanoacrylate oligomer or polymer
then undergoes a depolymerization to form the
ot-cyanoacrylate. The depolymerization may be conducted
by processes known in the art, such as by the processes
described in U.S. Pat. No. 5,624,669 to Leung et al., U.S.
Pat. No. 4,364,876 to Kimura et al. and/or U.S. Pat. No.
2,756,251 to Joyner et al., each of which is incorporated
herein by reference. In particular, the polymer may be heated
to a sufficiently high temperature, such as a temperature of
from 100° C. to 200° C., to crack the oligomer or polymer.
The cracking process should be conducted in an anhy-
drous environment. The cracking process may be conducted
in the presence of a dehydrant, such as polyphosphoric acid
or phosphorus pentoxide (P205), to keep the environment
anhydrous. In addition, the cracking process may be con-
ducted in the presence of a radical scavenger, such as copper
chloride, hydroquinone or any hindered phenolic radical
scavenger.
In the above-mentioned reaction scheme, R2 may be any
carbon containing organic group, such as an alkyl group
having 1-16 carbon atoms, but is preferably a methyl or
ethyl group, more preferably an ethyl group.
R1 is preferably any carbon containing organic group
other than a methyl or ethyl group. For example, R1 may be
a hydrocarbyl or substituted hydrocarbyl group; a group
having the formula —R4—O—R5—O—R6 or the formula
—R5—O—R6, where R4 is a 1,2-alkylene group having 2-4
carbon atoms, R5 is an alkylene group having 2-4 carbon
atoms, and R6 is an alkyl group having 1-6 carbon atoms;
or a group having formula
jR7_fi:O_R8 ,
0
wherein R7 is
TH3
:(CH2),, , —CH— , or C(CH3)2— ,
wherein n is 1-10, preferably 1-5, and R8 is an organic
moiety.
Examples of suitable hydrocarbyl and substituted hydro-
carbyl groups include straight chain or branched chain alkyl
groups having 1-16 carbon atoms; straight chain or
branched chain C1-C16 alkyl groups substituted with an
acyloxy group, a haloalkyl group, an alkoxy group, a halo-
gen 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.
10
15
20
25
30
35
40
45
50
55
60
65
6
The organic moiety R8 may be substituted or unsubsti-
tuted and may be straight chain, branched or cyclic,
saturated, unsaturated or aromatic. Examples of such
organic moieties include C1-C8 alkyl moieties, C2-C8 alk-
enyl moieties, C2-C8 alkynyl moieties, C3-C12
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-substituted hydrocarbon (e.g., alkoxy substituted
hydrocarbons) moieties. Preferred organic radicals are alkyl,
alkenyl, and alkynyl moieties having from 1 to about 8
carbon atoms, and halo-substituted derivatives thereof. Par-
ticularly preferred are alkyl moieties of 4 to 6 carbon atoms.
In embodiments of the invention, R1 is preferably an alkyl
group having 1-10 carbon atoms or a group having the
formula —AOR9, wherein A is a divalent straight or
branched chain alkylene or oxyalkylene moiety having 2-8
carbon atoms, and R9 is a straight or branched alkyl moiety
having 1-8 carbon atoms.
Examples of groups represented by the formula —AOR9
include 1-methoxy-2-propyl, 2-butoxy ethyl, isopropoxy
ethyl, 2-methoxy ethyl, and 2-ethoxy ethyl.
Preferred ot-cyanoacrylates produced by the method of
the present invention are alkyl ot-cyanoacrylates other than
methyl and ethyl ot-cyanoacrylates, including octyl
cyanoacrylate, such as 2-octyl cyanoacrylate; dodecyl
cyanoacrylate; 2-ethylhexyl cyanoacrylate; butyl
cyanoacrylate such as n-butyl, iso-butyl or t-butyl
cyanoacrylate; 3-methoxybutyl cyanoacrylate;
2-butoxyethyl cyanoacrylate; 2-isopropoxyethyl cyanoacry-
late; and 1-methoxy-2-propyl cyanoacrylate. More preferred
monomers are n-butyl and 2-octyl ot-cyanoacrylate. Mono-
mers used for medical purposes in the present application
should be very pure and contain few impurities (e.g., sur-
gical grade). Monomers utilized for industrial purposes need
not be as pure.
The following examples illustrate specific embodiments
of the present invention. One skilled in the art will recognize
that the appropriate reagent, component ratio/concentrations
may be adjusted as necessary to achieve specific product
characteristics.
EXAMPLE I
A reaction flask fitted with a stirrer, a thermocouple, a
Dean-Stark trap and a condenser is charged with 100 mL of
toluene, 113.1 g of ethylcyanoacetate, 1.3 mL of acetic acid,
31.9 g of paraformaldehyde (96—98%) and 0.79 g of pip-
eridine hydrochloride. The reaction medium is heated to 90°
C. over 38 minutes and held at this temperature for two
hours to condense the ethylcyanoacetate. During the
reaction, 15 mL of water is collected. Then, the reaction
medium is cooled to room temperature and maintained at
room temperature overnight.
Thereafter, 300 mL of toluene, 19.02 g of
p-toluenesulfonic acid and 261 g of 2-octanol are added. The
reaction medium is heated to reflux to transesterify the
polymer. During the reflux reaction, ethanol generated from
the transesterification is allowed to boil off and is thus
removed. Because toluene is boiled off with the ethanol,
2000 mL of toluene is added over the course of the reflux
reaction. After the reflux reaction, the reaction medium is
cooled to room temperature.
A Dean-Stark trap is then removed, and the reaction flask
is set-up for vacuum distillation. By vacuum distillation, the
toluene is stripped from the reaction medium. Then, 20.8 g
US 6,245,933 B1
7
of polyphosphoric acid and 1.0 g of copper chloride are
added and the reaction medium is heated to 185° C. to crack
the polymer to give 45.6 g of crude 2-octyl ot-cyanoacrylate
monomer.
EXAMPLE II
A reaction flask fitted with a stirrer, a thermocouple, a
Dean-Stark trap and a condenser is charged with 100 mL of
toluene, 114.0 g of ethylcyanoacetate, 1.3 mL of acetic acid,
32.0 g of paraformaldehyde (96—98%) and 0.79 g of pip-
eridine hydrochloride. The reaction medium is heated to 90°
C. over 18 minutes and held at this temperature for two
hours to condense the ethylcyanoacetate. During the
reaction, 15 mL of water is collected. Then, the reaction
medium is cooled to room temperature and maintained at
room temperature overnight.
Thereafter, 300 mL of toluene, 14.82 g of
p-toluenesulfonic acid and 261.4 g of 2-octanol are added.
The reaction medium is heated to reflux and the reflux is
maintained for 5 hours and 30 minutes to transesterify the
polymer. During the reflux reaction, ethanol generated from
the transesterification is allowed to boil off and is thus
removed. Because toluene is boiled off with the ethanol,
2000 mL of toluene is added over the course of the reflux
reaction. After the reflux reaction, the reaction medium is
cooled to room temperature.
ADean-Stark trap is then removed, and the reaction flask
is set-up for vacuum distillation with a vigreux column. By
vacuum distillation at a temperature of from 20.3 to 126.4°
C. (2.02—8.44 mmHg of pressure), the toluene is stripped
from the reaction medium. Then, 23.6 g of polyphosphoric
acid and 1.0 g of copper chloride are added and the reaction
medium is heated to 227.3° C. to crack the polymer to give
72.3 g of crude 2-octyl ot-cyanoacrylate monomer.
EXAMPLE III
A reaction flask fitted with a stirrer, a thermocouple, a
Dean-Stark trap and a condenser is charged with 100 mL of
toluene, 113.1 g of ethylcyanoacetate, 1.3 mL of acetic acid,
31.9 g of paraformaldehyde (96—98%) and 0.79 g of pip-
eridine hydrochloride. The reaction medium is heated to
91.6° C. over 31 minutes and held at a temperature between
89.9 and 93.3° C. for two hours to condense the ethylcy-
anoacetate. During the reaction, 15 mL of water is collected.
Then, 300 mL of xylene is added and the reaction tempera-
ture is increased to 130° C. and held at this temperature for
three hours to remove an additional 3 mL of water.
Thereafter, 261.4 g of octanol is added to the reaction
medium. Then the Dean-Stark trap is replaced with a con-
denser for distillation and the reaction medium is heated to
150° C. to distill off toluene and xylene. Then, the reaction
medium is cooled to 90° C. Thereafter, 28 g of titanium
tetraisopropoxide (TYZOR TPTTM) is added. The reaction
medium is heated to 200° C. When the system reaches a
reaction temperature of 120° C., ethanol is distilled off. Once
the temperature of the reaction medium reaches 200° C., it
is maintained at this temperature for two hours to transes-
terify the oligomer. Then the reaction medium is cooled to
room temperature.
The reaction flask is set-up for vacuum distillation. By
vacuum distillation at 88° C. (1.40-2.55mmHg), the unre-
acted octanol is stripped from the reaction medium. Then,
32.0 g of polyphosphoric acid and 1.0 g of copper chloride
are added and the reaction medium is heated between 138.7
and 176.6° C. (1.14—400 mmHg) to crack the polymer to
give 75.6 g of crude 2-octyl ot-cyanoacrylate monomer.
10
15
20
25
30
35
40
45
50
55
60
65
8
What is claimed is:
1. A method for making ot-cyanoacrylates, comprising:
reacting a cyanoacetate with paraformaldehyde or form-
aldehyde to form a cyanoacrylate oligomer or polymer;
reacting the cyanoacrylate oligomer or polymer with an
alcohol to transesterify the cyanoacrylate oligomer or
polymer; and
depolymerizing the transesterified cyanoacrylate oligo-
mer or polymer to form ot-cyanoacrylates.
2. The method of claim 1, wherein said cyanoacetate is
methyl or ethyl cyanoacetate.
3. The method of claim 2, wherein said cyanoacetate is
ethyl cyanoacetate.
4. The method of claim 1, wherein the cyanoacrylate
formed is an ot-cyanoacrylate other than methyl or ethyl
cyanoacrylate.
5. The method of claim 1, wherein said alcohol has the
formula R1—OH, wherein R1 is selected from the group
consisting of a hydrocarbyl group; a substituted hydrocarbyl
group; a group having the formula —R4—O—R5—O—R°
or the formula —R5—O—R°, where R4 is a 1,2-alkylene
group having 2-4 carbon atoms, R5 is an alkylene group
having 2-4 carbon atoms, and R° is an alkyl group having
1-6 carbon atoms; and a group having formula
—R7—C—o—R3 ,
0
wherein R7 is
CH3
, —cH— , or
:(CH2)n C(CH3)2‘ ,
wherein n is 1-10, and R8 is an organic moiety.
6. The method of claim 5, wherein said hydrocarbyl and
substituted hydrocarbyl groups are selected from the group
consisting of straight chain or branched chain alkyl groups
having 1-16 carbon atoms; straight chain or branched chain
C1-C16 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.
7. The method of claim 1, wherein said alcohol has the
formula R1—OH, wherein R1 is selected from the group
consisting of an alkyl group having 1-10 carbon atoms and
a group having the formula —AOR°, wherein Ais a divalent
straight or branched chain alkylene or oxyalkylene moiety
having 2-8 carbon atoms, and R9 is a straight or branched
alkyl moiety having 1-8 carbon atoms.
8. The method of claim 7, wherein said group having the
formula —AOR° is selected from the group consisting of
1-methoxy-2-propyl, 2-butoxy ethyl, isopropoxy ethyl,
2-methoxy ethyl and 2-ethoxy ethyl.
9. The method of claim 1, wherein said cyanoacrylate
formed is selected from the group consisting of octyl
cyanoacrylate; dodecyl cyanoacrylate; 2-ethylhexyl
cyanoacrylate; butyl cyanoacrylate; 3-methoxybutyl
cyanoacrylate; 2-butoxyethyl cyanoacrylate;
2-isopropoxyethyl cyanoacrylate; and 1-methoxy-2-propyl
cyanoacrylate.
10. The method of claim 9, wherein said cyanoacrylate
formed is n-butyl ot-cyanoacrylate or 2-octyl
ot-cyanoacrylate.
US 6,245,933 B1
9
11. The method of claim 1, wherein said cyanoacrylate
oligomer or polymer comprises 2 to 100 monomer units.
12. The method of claim 11, wherein said cyanoacrylate
oligomer or polymer comprises 3 to 75 monomer units.
13. The method of claim 11, wherein said cyanoacrylate
oligomer or polymer comprises 10 to 50 monomer units.
14. The method of claim 1, wherein the transesterification
is conducted in the presence of an organometallic catalyst.
15. The method of claim 14, wherein said organometallic
catalyst is selected from the group consisting of titanium
tetraisopropoxide, aluminum isopropoxide, tributyltin oxide
and sumarium isopropoxide.
16. The method of claim 1, wherein the transesterification
is conducted in the presence of an acidic catalyst.
10
10
17. The method of claim 16, wherein said acidic catalyst
is selected from the group consisting of p-toluenesulfonic
acid, hydrochloric acid, trifluoroacetic acid and Lewis acids.
18. The method of claim 1, wherein the transesterification
is conducted in the presence of an alkali metal or alkaline
earth metal alcoholate.
19. The method of claim 1, wherein the transesterification
is conducted in the presence or an acidic or basic ion-
exchange resin.
20. The method of claim 2, wherein the cyanoacrylate
formed is an ot-cyanoacrylate other than methyl or ethyl
cyanoacrylate.
Coments go here:
- Log in to post comments