U.S. patent application number 12/479115 was filed with the patent office on 2009-09-24 for ortho-nitrosophenols as polymerization inhibitors.
Invention is credited to Qinggao MA, Paul E. Stott, Jay Wang, William A. Wortman.
Application Number | 20090240092 12/479115 |
Document ID | / |
Family ID | 37055092 |
Filed Date | 2009-09-24 |
United States Patent
Application |
20090240092 |
Kind Code |
A1 |
MA; Qinggao ; et
al. |
September 24, 2009 |
ORTHO-NITROSOPHENOLS AS POLYMERIZATION INHIBITORS
Abstract
Disclosed herein is a method for inhibiting the premature
polymerization of ethylenically unsaturated monomers comprising
adding to said monomers an effective amount of at least one nitroso
inhibitor of the structure: ##STR00001## wherein R.sub.1, R.sub.2,
R.sub.3, and R.sub.4 are independently selected from the group
consisting of hydrogen, nitro, nitroso, halogen, COOR wherein R is
hydrogen or alkyl, alkyl, and heteroatom-substituted alkyl; or
adjacent groups R.sub.1, R.sub.2, R.sub.3, and R.sub.4 can be taken
together to form a substituted or unsubstituted fused six-membered
ring. Also disclosed is a composition of matter comprising: A) an
ethylenically unsaturated monomer and B) at least one nitroso
compound of the above-described structure.
Inventors: |
MA; Qinggao; (Naugatuck,
CT) ; Wortman; William A.; (Harwinton, CT) ;
Wang; Jay; (Naperville, IL) ; Stott; Paul E.;
(Oxford, CT) |
Correspondence
Address: |
PATENT ADMINISTRATOR;CHEMTURA CORPORATION
199 Benson Road
Middlebury
CT
06749
US
|
Family ID: |
37055092 |
Appl. No.: |
12/479115 |
Filed: |
June 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11156214 |
Jun 17, 2005 |
7553896 |
|
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12479115 |
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Current U.S.
Class: |
585/5 |
Current CPC
Class: |
C08F 2/42 20130101; C07B
63/04 20130101; C07C 253/32 20130101; C07C 67/62 20130101; C07C
17/42 20130101; C07C 7/20 20130101; C08F 2/40 20130101; C07C 51/50
20130101; C07C 7/20 20130101; C07C 15/46 20130101; C07C 17/42
20130101; C07C 21/21 20130101; C07C 51/50 20130101; C07C 57/04
20130101; C07C 67/62 20130101; C07C 69/54 20130101; C07C 253/32
20130101; C07C 255/08 20130101 |
Class at
Publication: |
585/5 |
International
Class: |
C07C 7/20 20060101
C07C007/20 |
Claims
1-11. (canceled)
12. A composition of matter comprising: A) an ethylenically
unsaturated monomer and B) an effective inhibiting amount,
sufficient to prevent premature polymerization during distillation
or purification of said ethylenically unsaturated monomer, of at
least one nitroso compound of the structure: ##STR00015## wherein
R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently selected
from the group consisting of hydrogen, nitro, nitroso, halogen,
COOR wherein R is hydrogen or alkyl, alkyl, and
heteroatom-substituted alkyl; or adjacent groups R.sub.1, R.sub.2,
R.sub.3, and R.sub.4 can be taken together to form a substituted or
unsubstituted fused six-membered ring.
13. The composition of claim 12 further comprising at least one
additional compound selected from the group consisting of quinone
alkides, nitroxyl compounds, nitroaromatic compounds, hydroxylamine
compounds, phenylenediamine compounds, quinone compounds, and
hydroquinone compounds.
14. The composition of claim 12 further comprising oxygen.
15. The composition of claim 13 further comprising oxygen.
16. The composition of claim 12 wherein the nitroso inhibitor is
2-nitroso-naphthol.
17. The composition of claim 13 wherein the nitroso inhibitor is
2-nitroso-naphthol.
18. The composition of claim 12 wherein the nitroso inhibitor is
1-nitroso-2-naphthol.
19. The composition of claim 13 wherein the nitroso inhibitor is
1-nitroso-2-naphthol.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is directed to the use of at least one
o-nitrosophenol compound, alone or in combination with at least one
stable nitroxide free radical compound, and/or at least one
nitroaromatic compound, and/or at least one quinone alkide
compound, preferably a quinone methide, and/or at least one quinone
compound, and/or at least one hydroquinone compound, and/or at
least one hydroxylamine compound, and/or at least one
phenylenediamine compound, and/or air or oxygen to inhibit the
polymerization of ethylenically unsaturated monomers.
[0003] 2. Description of Related Art
[0004] Many ethylenically unsaturated monomers undesirably
polymerize at various stages of their manufacture, processing,
handling, storage, and use. A particularly troublesome problem is
equipment fouling caused by polymerization in the purification
stages of the production processes of such monomers.
Polymerization, such as thermal polymerization, during their
purification results in the loss of monomer and a loss in
production efficiency owing to the deposition of polymer in or on
the equipment being used in the purification, the deposits of which
must be removed from time to time. Additionally, the formation of
soluble polymer leads to loss of monomer, i.e., a lower yield, and
an increase in the viscosity of any tars that may be produced. The
processing of the tars then requires higher temperature and work
(energy cost) to remove residual monomer.
[0005] A wide variety of compounds has been proposed and used for
inhibiting uncontrolled and undesired polymerization of
ethylenically unsaturated monomers. There remains a need, however,
for an inhibitor that not only provides highly effective inhibition
of polymerization during normal operation of a continuous
manufacturing or purification process, but also provides
satisfactory protection in the event of a loss of continuous
inhibitor feed. While many inhibitors are known to provide
sufficient protection in one of these scenarios, they have not been
fully satisfactory under both normal and upset operating
conditions. Accordingly, a substantial need continues in the art
for improved compositions for inhibiting the polymerization of such
monomers during their production and during the distillation
process for purifying or separating them from impurities, as well
as during transport and storage.
[0006] N-nitroso compounds and C-nitrosophenols are known as
polymerization inhibitors, especially under the conditions for
monomer production and processing.
[0007] Aromatic nitroso and di-nitroso compounds are also known to
be useful as chemical agents capable of promoting the formation of
filler-elastomer linkages. The aromatic nitroso compounds may be
aromatic amines, including polyamines or phenolic compounds. They
are also known to be useful intermediates in the production of
other chemicals, such as p-aminodiphenylamine.
[0008] U.S. Pat. No. 3,163,677 discloses N,N,O-trisubstituted
hydroxylamines and N,N-disubstituted nitroxides of the
formulas:
##STR00002##
wherein R.sub.1, R.sub.2, and R.sub.3 are each an alkyl radical
having 1 to 15 carbon atoms. (As used herein, the designation N--O*
denotes a stable free radical wherein the asterisk is an unpaired
electron.) The N,N,O-trisubstituted hydroxylamines can be used to
make the N,N-disubstituted nitroxides, which are stable free
radicals and are said to be useful as polymerization
inhibitors.
[0009] U.S. Pat. No. 3,267,132 discloses that the polymerization of
unsaturated nitrites can be greatly inhibited by incorporating
therein a minor amount of a nitroso compound selected from the
group consisting of p-nitrosodiarylamines and
N-nitrosoarylamines.
[0010] U.S. Pat. Nos. 3,988,212 and 4,341,600 disclose the use of
N-nitrosodiphenylamine combined with dinitro-cresol derivatives for
inhibiting the polymerization of vinyl aromatic compounds under
vacuum distillation conditions.
[0011] U.S. Pat. Nos. 4,003,800 and 4,040,911 disclose the use of
quinone alkides in a styrene purification process.
[0012] U.S. Pat. No. 4,086,147 discloses a process using
2-nitro-p-cresol as a polymerization inhibitor.
[0013] U.S. Pat. Nos. 4,105,506 and 4,252,615 disclose a process
using 2,6-dinitro-p-cresol as a polymerization inhibitor.
[0014] U.S. Pat. Nos. 4,132,602 and 4,132,603 disclose the use of a
halogenated aromatic nitro compound as a polymerization inhibitor
for use during the distillation of vinyl aromatic compounds.
[0015] U.S. Pat. No. 4,182,658 discloses a method for preventing
the polymerization of a readily polymerizable vinyl aromatic
compound during distillation at elevated temperatures within a
distillation apparatus that is subject to an emergency condition,
such as a power outage. This method comprises force-feeding a
supplemental polymerization inhibitor having a high solubility in
the vinyl aromatic compound and a long duration of efficiency into
each of the distillation vessels of a conventional distillation
apparatus in an amount sufficient to prevent polymerization
therein.
[0016] U.S. Pat. No. 4,252,615 discloses a process for the
distillation of readily polymerizable vinyl aromatic compounds and
a polymerization inhibitor therefor. The process comprises
subjecting a vinyl aromatic compound to elevated temperatures in a
distillation system in the presence of a polymerization inhibitor
comprising 2,6-dinitro-p-cresol.
[0017] U.S. Pat. No. 4,341,600 discloses a process for distilling
vinyltoluene comprising subjecting vinyltoluene to distillation
conditions in the presence of a synergistic polymerization
inhibiting mixture of N-nitrosodiphenylamine (NDPA) and
dinitro-para-cresol (DNPC). Preferably from about 100 to about 300
ppm by weight NDPA and about 300 to about 700 ppm by weight DNPC
are dissolved in the crude vinyltoluene and the resulting solution
is vacuum distilled.
[0018] U.S. Pat. No. 4,466,904 discloses the use of phenothiazine,
4-tert-butylcatechol and 2,6-dinitro-p-cresol as a polymerization
inhibitor system in the presence of oxygen during heating of vinyl
aromatic compounds.
[0019] U.S. Pat. No. 4,468,343 discloses a composition and a
process for utilizing 2,6-dinitro-p-cresol and either a
phenylenediamine or 4-tert-butylcatechol in the presence of oxygen
to prevent the polymerization of vinyl aromatic compounds during
heating.
[0020] U.S. Pat. No. 5,254,760 teaches that the polymerization of a
vinyl aromatic compound, such as styrene, is very effectively
inhibited during distillation or purification by the presence of at
least one stable nitroxyl compound together with at least one
aromatic nitro compound.
[0021] U.S. Pat. No. 5,504,243 discloses a method for inhibiting
polymerizable (meth)acrylic acid and esters thereof from
polymerizing during their production, transportation and storage by
using as the inhibitor N-oxyl compound and more than one compound
selected from the group consisting of manganese salt compound,
copper salt compound, 2,2,6,6,-tetramethylpiperidine compound and
nitroso compound. The N-oxyl compound is one or more kinds selected
from 2,2,6,6,-tetramethylpiperidinooxyl,
4-hydroxy-2,2,6,6,-tetramethylpiperidinooxyl and
4,4',4''-tris-(2,2,6,6,-tetramethylpiperidinooxyl)phosphite. The
combined use of the inhibitors is said to provide a superior
inhibiting effect to use alone.
[0022] U.S. Pat. Nos. 5,545,782 and 5,545,786 disclose that
nitroxyl inhibitors in combination with some oxygen reduce the
premature polymerization of vinyl aromatic monomers during the
manufacturing processes for such monomers. Even small quantities of
air used in combination with the nitroxyl inhibitors are said to
result in vastly prolonged inhibition times for the monomers.
[0023] U.S. Pat. Nos. 5,583,247, 5,670,692, and 5,750,765 disclose
the protection of ethylenically unsaturated monomers from premature
polymerization during manufacture and storage by the incorporation
therein of an effective stabilizing amount of a quinone methide
compound having an electron withdrawing substituent at the
7-methylene group.
[0024] U.S. Pat. No. 5,616,774 discloses the protection of
ethylenically unsaturated monomers from premature polymerization
during manufacture and storage by the incorporation therein of an
effective stabilizing amount of a 7-aryl quinone methide compound
wherein the 7-aryl substituent is 2-, 3-, or 4-pyridyl, 2- or
3-thienyl, 2- or 3-pyrryl, 2- or 3-furyl, aryl of six to 10 carbon
atoms, or said aryl substituted by one to three alkyl of one to
eight carbon atoms, alkoxy of one to eight carbon atoms, alkylthio
of one to eight carbon atoms, alkylamino of one to eight carbon
atoms, dialkylamino of two to eight carbon atoms, alkoxycarbonyl of
two to eight carbon atoms, hydroxy, nitro, amino, cyano, carboxy,
aminocarbonyl, chloro, or mixtures of said substituents. The
combination of these quinone methides with at least one stable
nitroxyl compound is also disclosed.
[0025] U.S. Pat. No. 5,888,356 discloses inhibiting the
polymerization of a vinylaromatic or vinylaliphatic compound at
elevated temperature in the absence of air by processing the
vinylaromatic or vinylaliphatic compound in the presence of
4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl or
4-acetylamino-2,2,6,6-tetramethylpiperidine-N-oxylalone or in
admixture with p-nitrosophenol or 2-methyl-4-nitrosophenol.
[0026] U.S. Pat. No. 5,910,232 teaches that inhibition performance
in styrene processing is improved through the addition of a stable
nitroxide free radical compound to the styrene feed and to the
reflux of at least one column. A nontoxic retarder, such as
phenylenediamine, may also optionally be added to the styrene feed
and to the reflux.
[0027] U.S. Pat. No. 6,342,647 discloses that the polymerization of
vinyl aromatic compounds, such as styrene, may be inhibited by the
addition of a composition that contains a hindered hydroxylamine,
and, optionally, a synergist together with the hindered
hydroxylamine. In one embodiment of the invention, the hindered
N,N-disubstituted hydroxylamine has the formula: [(R.sup.1 R.sup.2
R.sup.3)C].sub.2 N--OH where R.sup.1, R.sup.2, and R.sup.3 are
independently selected from the group consisting of hydrogen,
straight, branched or cyclic alkyl, aryl, aralkyl, and alkaryl
moieties; where no more than two of R.sup.1, R.sup.2, and R.sup.3
on each C can be hydrogen at a time; where one or more of R.sup.1,
R.sup.2, and R.sup.3 on one C may be joined to an R.sup.1, R.sup.2,
and R.sup.3 on the other C to form a cyclic moiety selected from
the group consisting of alkylene, and aralkylene moieties; where
any two of the R.sup.1, R.sup.2, and R.sup.3 on any one C may be
joined together to form a cycloalkyl; where any of the above
definitions of R.sup.1, R.sup.2, and R.sup.3 may contain one or
more heteroatoms selected from the group consisting of N, O and S;
and where the total number of carbon atoms in the hindered
N,N-disubstituted hydroxylamine ranges from 6 to 70. Optional
synergists may include alkyl-substituted hydroxyarenes such as
2,5-di-tert-butylhydroquinone, and hydrogen transfer agents such as
1,2,3,4-tetrahydronaphthalene; and the like, and mixtures
thereof.
[0028] U.S. Pat. No. 6,395,943 discloses a process for inhibiting
the polymerization of vinyl aromatic compounds, such as styrene,
during its distillation. The process involves adding a mixture of
at least two inhibitors to the vinyl aromatic compound. One such
combination is N,N'-di-2-butyl-N,N',4-dinitroso-1,4-diaminobenzene
and dinitrocresol. A stabilizer such as
N,N'-di-2-butyl-1,4-diaminobenzene can also be added.
[0029] U.S. Pat. No. 6,685,823 discloses a method for inhibiting
the premature polymerization of ethylenically unsaturated monomers
comprising adding to said monomers an effective amount of at least
one inhibitor selected from the group consisting of
C-nitrosoaniline and quinone imine oxime compounds. Also disclosed
is a composition of matter comprising: A) an ethylenically
unsaturated monomer and B) an effective inhibiting amount,
sufficient to prevent premature polymerization during distillation
or purification of said ethylenically unsaturated monomer, of at
least one inhibitor selected from the group consisting of
C-nitrosoaniline and quinone imine oxime compounds used together
with an effective amount of oxygen or air to enhance the inhibiting
activity of said inhibitor.
[0030] European Patent Application 0 178 168 A2 discloses a method
for inhibiting the polymerization of an
.alpha.,.beta.-ethylenically unsaturated monocarboxylic acid during
its recovery by distillation by using a nitroxide free radical.
[0031] European patent application 240,297 A1 teaches the use of a
substituted hydroxylamine and a dinitrophenol to inhibit the
polymerization of a vinyl aromatic compound at elevated
temperatures in a distillation process.
[0032] European Patent Application 0 765 856 A1 discloses a
stabilized acrylic acid composition in which the polymerization of
the acrylic acid is inhibited during the distillation process for
purifying or separating the acrylic acid as well as during
transport and storage. The compositions comprise three components:
(a) acrylic acid, (b) a stable nitroxyl radical, and (c) a
dihetero-substituted benzene compound having at least one
transferable hydrogen (e.g., a quinone derivative such as the
monomethyl ether of hydroquinone (MEHQ)). During the distillation
process, transport, and storage, components (b) and (c) are present
in a polymerization-inhibiting amount. During the distillation
process, oxygen (d) is preferably added with components (b) and
(c).
[0033] FR 2,761,060 relates to the prevention of premature
polymerization of styrene during its production by dehydrogenation
of ethylbenzene by injecting into the process effluent a radical
inhibitor based on an oxyl-tetramethylpiperidine derivative.
[0034] Hung. 150,550 discloses that free radical polymerization was
inhibited with organic nitroso compounds, e.g.,
p-H.sub.2C.sub.6H.sub.4NO (I), .alpha.-nitroso-.beta.-naphthol, or
.beta.-nitroso-.alpha.-naphthol. For example, addition of 0.3 grams
of (I) to one liter of styrene is said to have resulted in the
stability of the latter for months. Also, (I) could be removed with
azodiisobutyronitrile.
[0035] JP2003277302 discloses that 5 ppm of a4-hydroxyl TEMPO/95
ppm DBSA blend can inhibit styrene polymerization for ten minutes
under certain laboratory test conditions.
[0036] JP2003277423 discloses that 5 ppm DBSA/100 ppm DNBP showed a
good inhibiting effect.
[0037] SU-478838 is directed to the inhibition of the radical
polymerization of oligoester acrylates and the prevention of
oligomeric peroxides using a binary polymerization inhibitor
comprising quinone.
[0038] WO 98/14416 discloses that the polymerization of vinyl
aromatic monomers such as styrene is inhibited by the addition of a
composition of a stable hindered nitroxyl radical and an oxime
compound.
[0039] WO 98/25872 concerns substance mixtures containing: (A)
compounds containing vinyl groups; (B) an active amount of a
mixture which inhibits premature polymerization of the compounds
containing vinyl groups and contains: (i) at least one N-oxyl
compound of a secondary amine which does not carry any hydrogen
atoms on the .alpha.-carbon atoms; and (ii) at least one iron
compound; (C) optionally nitro compounds; and (D) optionally
co-stabilizers. The publication also discloses a process for
inhibiting the premature polymerization of compounds (A) containing
vinyl groups, and the use of (B) optionally mixed with nitro
compounds (C) and/or co-stabilizers (D) for inhibiting the
premature polymerization of radically polymerizable compounds and
stabilizing organic materials against the harmful effect of
radicals.
[0040] WO 99/20584 discloses that polymerization can be inhibited
during the anaerobic production of styrene through the addition of
a combination of a stable nitroxide free radical compound and a
nontoxic phenylenediamine compound.
[0041] Georgieff, K. K., J. Appl. Polymer Sci. 9(6):2009-18 (1965)
measured the inhibitory effect of the following compounds on the
bulk polymerization of methyl methacrylate: hydroquinone,
p-tert-butylcatechol, p-methoxyphenol, 2,4-dichloro-6-nitrophenol,
n-propyl gallate, di-tert-butyl-p-cresol,
2,2'-methylenebis(4-methyl-6-tert-butylphenol), 1-amino-7-naphthol,
p-benzoquinone, 2,6-dichloro-p-benzoquinone,
2-amino-1,4-naphthoquinone, three aminoanthraquinones,
diphenylamine, p-nitrosodimethylaniline, .alpha.- and
.beta.-naphthylamine, phenothiazine, N-nitroso-dimethylamine,
hexamethylphosphoramide, n-dodecyl mercaptan, benzenethiol,
2,2-diphenyl-1-picrylhydrazyl, phenyl hydrazine, divinylacetylene,
and various antimony and copper salts. Polymerization was carried
out in a test tube in a bath at 101.2.degree. C., benzoyl peroxide
being used as initiator. Generally, phenols and naphthols were the
strongest inhibitors, followed by quinones, aromatic amines,
2,2-diphenyl-1-picrylhydrazyl, antimony pentachloride, phenyl
hydrazine, divinylacetylene, and the thiols.
[0042] Harth, E. et al., Chem. Commun. 9:823-824 (2001) reported
that intramolecular H-bonding is a powerful tool in increasing the
performance of alkoxylamine initiators for nitroxide mediated
living free radical polymerizations.
[0043] The foregoing are incorporated herein by reference in their
entirety.
SUMMARY OF THE INVENTION
[0044] It is well known that vinyl compounds, such as styrene and
acrylates, have a strong tendency to polymerize under elevated
temperatures. This polymerization is undesirable during their
manufacture, processing, handling, storage, and use. A particular
problem during the monomer purification process, usually through
continuous vacuum distillation, the formation of soluble polymer
leads to loss of monomer, i.e., a lower yield, and an increase in
the viscosity of any tars that may be produced, and a loss in
production efficiency owing to the deposition of polymer in or on
the equipment being used in the purification, the deposits of which
must be removed from time to time, and an exothermic and
uncontrollable polymerization during a plant upset when no fresh
inhibitor could be added may lead to disastrous results.
[0045] A wide variety of compounds has been proposed and used for
inhibiting uncontrolled and undesired polymerization of
ethylenically unsaturated monomers under different conditions. Many
compounds that are effective for inhibiting the polymerization of
vinyl aromatic compounds under storage conditions, such as
alkylphenol or hydroquinones, are not suitable for a vacuum
distillation process, since they are effective only in the presence
of oxygen. The partial pressure of oxygen in a vacuum distillation
column is accordingly too low for these storage inhibitors to be
effective.
[0046] For the compounds that are effective for a continuous
distillation process, the ideal inhibitor should work both with air
and without air. Currently, these inhibitors are categorized into
two classes: "true inhibitors" and "retarders". The so-called "true
inhibitors" ensure the low production of undesirable polymers under
normal operation conditions; however, during a plant upset, when no
fresh "true inhibitors" can be added, the leftover inhibitors are
quickly consumed and the polymerization may go out of control.
These "true inhibitors" include nitroxides, aromatic nitroso
compound, (non ortho) nitrosophenols, N-nitroso aromatics, and the
like. "Retarders" on the other hand, allow more polymer to form
during normal operation, which leads to relatively low monomer
production, but during plant upsets, "retarders" are thought to be
able to protect the column for a long period of time. Aromatic
nitrophenols are considered to be such compounds. Previously known
distillation inhibitors do not have both the characters of "true
inhibitor" and "retarder" and are not fully satisfactory.
[0047] Physical blends of "true inhibitors" and "retarders"
seemingly solved the problem. For example, commercially available
blends of 100 ppm nitroxide and 150 ppm DNBP blends are commonly
used, but, in fact, they do not offer long enough protection during
a serious plant upset. The "true inhibitor" gets consumed quickly
during a plant upset and the amount of DNBP "retarder" left in the
physical blend, which in this case is significantly less than when
retarder itself is used alone, is not enough to handle the
situation. Therefore, the polymerization can run out of control
much more quickly, since the blend can not provide a sufficiently
long protection time for the plant.
[0048] The present invention is directed to the use of at least one
compound having both true inhibitor and retarder characteristics,
alone or in combination with at least one additional inhibitor, in
the presence or absence of air or oxygen, to prevent or retard the
polymerization of ethylenically unsaturated monomers.
[0049] More particularly, the present invention is directed to a
method for inhibiting the premature polymerization of ethylenically
unsaturated monomers comprising adding to said monomers an
effective amount of at least one nitroso inhibitor of the
structure:
##STR00003##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently
selected from the group consisting of hydrogen, nitro, nitroso,
halogen, COOR wherein R is hydrogen or alkyl, alkyl, and
heteroatom-substituted alkyl; or adjacent groups R.sub.1, R.sub.2,
R.sub.3, and R.sub.4, i.e., R.sub.1 and R.sub.2, or R.sub.2 and
R.sub.3, or R.sub.3 and R.sub.4, can be taken together to form a
substituted or unsubstituted fused six-membered ring. For
convenience, compounds having this structure are referred to herein
simply as ortho-nitrosophenols.
[0050] In another aspect, the present invention is directed to a
composition of matter comprising:
[0051] A) an ethylenically unsaturated monomer and
[0052] B) an effective inhibiting amount, sufficient to prevent
premature polymerization during distillation or purification of
said ethylenically unsaturated monomer, of at least one nitroso
compound of the structure:
##STR00004##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently
selected from the group consisting of hydrogen, nitro, nitroso,
halogen, COOR wherein R is hydrogen or alkyl, alkyl, and
heteroatom-substituted alkyl; or adjacent groups R.sub.1, R.sub.2,
R.sub.3, and R.sub.4 can be taken together to form a substituted or
unsubstituted fused six-membered ring.
[0053] Preferably, the nitroso compound is a substituted or
unsubstituted ortho-nitrosophenol or a substituted or unsubstituted
ortho-nitrosonaphthol.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0054] The nitroso compounds of the present invention, which are
commercially available, can be used alone or in combination with at
least one nitroxyl compound, at least one nitroaromatic compound,
at least one quinone alkide, at least one quinone derivative, at
least one hydroquinone derivative, at least one hydroxylamine
compound, at least one phenylenediamine compound, air or oxygen, or
a mixture of the foregoing.
[0055] These compounds are suitable for use over a wide range of
temperatures, but distillation temperatures employed with the
ethylenically unsaturated monomers that are stabilized by the
process of the present invention typically range from about
60.degree. C. to about 180.degree. C., preferably from about
70.degree. C. to about 165.degree. C. and, more preferably, from
about 80.degree. C. to about 150.degree. C. Such distillations are
generally performed at an absolute pressure in the range of about
10 to about 1,200 mm of Hg.
[0056] As noted above, the nitroso compounds employed in the
practice of the present invention are of the structure:
##STR00005##
wherein R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are independently
selected from the group consisting of hydrogen, nitro, nitroso,
halogen, alkyl, heteroatom-substituted alkyl, and COOR wherein R is
hydrogen or alkyl; or adjacent groups R.sub.1, R.sub.2, R.sub.3,
and R.sub.4, i.e., R.sub.1 and R.sub.2, or R.sub.2 and R.sub.3, or
R.sub.3 and R.sub.4, can be taken together to form a substituted or
unsubstituted fused six-membered ring.
[0057] Where any of R, R.sub.1, R.sub.2, R.sub.3, or R.sub.4 are
alkyl, they are preferably alkyl of from 1 to about 15 carbon
atoms, e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,
octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl,
pentadecyl, isomers of the foregoing, and mixtures thereof.
Similarly, where any of R.sub.1, R.sub.2, R.sub.3, or R.sub.4 are
heteroatom-substituted alkyl, the alkyl moiety thereof preferably
comprises from 1 to about 15 carbon atoms. Preferably the
heteroatom(s) of such heteroatom-substituted alkyls will be
selected from the group consisting of oxygen, sulfur, nitrogen, and
combinations thereof.
[0058] Where a nitroso compound of the present invention comprises
a substituted fused six-membered ring, the substituent(s) on such
ring can be any that will not adversely affect the true inhibitor
and retarder characteristics of the compound as a whole in a
significant way.
[0059] Most preferably, the nitroso compound employed in the
practice of the present invention is selected from the group
consisting of 2-nitroso-naphthol, 1-nitroso-2-naphthol, and
mixtures thereof.
[0060] The nitroxyl compounds that can be employed in combination
with the nitroso compounds employed in the practice of the present
invention are preferably of the structure:
##STR00006##
wherein R.sub.5 and R.sub.8 are independently selected from the
group consisting of hydrogen, alkyl, and heteroatom-substituted
alkyl and R.sub.6 and R.sub.7 are (1) independently selected from
the group consisting of alkyl and heteroatom-substituted alkyl, or
(2) taken together, form a ring structure with the nitrogen; and
X.sub.1 and X.sub.2 (1) are independently selected from the group
consisting of halogen, phosphorus (in any of its oxidation states),
cyano, COOR.sub.9, --S--COR.sub.9, --OCOR.sub.9, (wherein R.sub.9
is alkyl or aryl), amido, --S--C.sub.6H.sub.5, carbonyl, alkenyl,
or alkyl of 1 to 15 carbon atoms, or (2) taken together, form a
ring structure with the nitrogen.
[0061] In a particularly preferred embodiment, the nitroxyl
compound has the structural formula:
##STR00007##
wherein R.sub.5 and R.sub.8 are independently selected from the
group consisting of hydrogen, alkyl, and heteroatom-substituted
alkyl and R.sub.6 and R.sub.7 are independently selected from the
group consisting of alkyl and heteroatom-substituted alkyl, and
the
##STR00008##
portion represents the atoms necessary to form a five-, six-, or
seven-membered heterocyclic ring.
[0062] The quinone alkide compounds that can be employed in
combination with the nitroso compounds in the practice of the
present invention are preferably of the structure:
##STR00009##
wherein
[0063] X is oxygen;
[0064] Y is CR.sub.124R.sub.125;
[0065] R.sub.120, R.sub.121, R.sub.122, and R.sub.123 are
independently selected from the group consisting of hydrogen,
alkyl, aryl, cycloalkyl, sulfonyl, heterocyclic, substituted alkyl,
substituted aryl, OR.sub.110, NR.sub.110R.sub.111, SR.sub.110, NO,
NO.sub.2, CN, COR.sub.112, and halogen, or R.sub.120 and R.sub.121,
can be taken together and/or R.sub.122 and R.sub.123 can be taken
together to form one or two ring structures, respectively, either
of which can be of five to seven members;
[0066] R.sub.124 and R.sub.125 are independently selected from the
group consisting of hydrogen, alkyl, aryl, cycloalkyl,
heterocyclic, substituted alkyl, substituted aryl, OR.sub.110,
NR.sub.110R.sub.111, SR.sub.110, NO.sub.2, NO, CN, COR.sub.112,
halogen, and/or can be taken together to form a ring structure of
five to seven members;
[0067] R.sub.110 and R.sub.111 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, benzyl, cyclic,
heterocyclic, substituted alkyl or aryl where the substituents are
C, O, N, S, or P, and COR.sub.102, or R.sub.110 and R.sub.111 can
be taken together to form a ring structure of five to seven
members;
[0068] R.sub.112 is R.sub.102, OR.sub.102, or NR.sub.102R.sub.103;
and
[0069] R.sub.102 and R.sub.103 are independently selected from the
group consisting of hydrogen, alkyl, aryl, benzyl, cyclic,
heterocyclic, and substituted alkyl or aryl where the substituents
are C, O, N, S, or P, or R.sub.102 and R.sub.103 can be taken
together to form a ring structure of five to seven members.
[0070] The nitroaromatic compounds that can be employed in
combination with the nitroso compounds in the practice of the
present invention are preferably of the structure:
##STR00010##
wherein
[0071] R.sub.3 through R.sub.7 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, hydroxyl, alkoxy,
acyloxy, N R.sub.8(R.sub.9), nitro, nitroso, halogen, and sulfonyl,
or any two adjacent R's can form a cyclic ring that is aryl,
cycloalkyl, polyaryl, or heterocyclic; and
[0072] R.sub.8 and R.sub.9 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, and nitroso.
Preferably R.sub.8 is hydrogen and R.sub.9 is alkyl. Preferably,
R.sub.3 is hydroxyl, R.sub.6 is nitro, and R.sub.4 is alkyl.
[0073] The hydroxylamine compounds that can be employed in
combination with the nitroso compounds in the practice of the
present invention are preferably of the structure:
##STR00011##
wherein
[0074] R.sub.100 and R.sub.101 are independently selected from the
group consisting of hydrogen, alkyl, alkylidene, benzylidene, aryl,
benzyl, COR.sub.102, COOR.sub.102, CONR.sub.102R.sub.103, cyclic,
heterocyclic, hydroxyalkyl, and substituted alkyl or aryl where the
substituents are C, O, N, S, or P, or R.sub.100 and R.sub.101 can
be taken together to form a ring structure of five to seven
members.
[0075] The phenylenediamine compounds that can be employed in
combination with the nitroso compounds in the practice of the
present invention are preferably of the structure:
##STR00012##
wherein
[0076] R.sub.1 and R.sub.2 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, hydroxyl, alkoxy,
nitroso, and sulfonyl, or R.sub.1 and R.sub.2 can form a cyclic
ring that is aryl, cycloalkyl, polyaryl, or heterocyclic;
[0077] R.sub.3 through R.sub.7 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, hydroxyl, alkoxy,
acyloxy, NR.sub.8(R.sub.9), nitro, nitroso, halogen, and sulfonyl,
or any two adjacent R's can form a cyclic ring that is aryl,
cycloalkyl, polyaryl, or heterocyclic, provided that at least one
of R.sub.3 through R.sub.7 must be an NR.sub.8(R.sub.9) group;
and
[0078] R.sub.8 and R.sub.9 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, and nitroso.
Preferably, R.sub.1 is hydrogen, R.sub.2 is alkyl or aryl, R.sub.8
is hydrogen, and R.sub.9 is alkyl.
[0079] The quinone compounds that can be employed in combination
with the nitroso compounds in the practice of the present invention
are preferably of the structure:
##STR00013##
wherein
[0080] R.sub.120, R.sub.121, R.sub.122, and R.sub.123 are
independently selected from the group consisting of hydrogen,
alkyl, aryl, cycloalkyl, sulfonyl, heterocyclic, substituted alkyl,
substituted aryl, OR.sub.110, NR.sub.110R.sub.111, SR.sub.110, NO,
NO.sub.2, CN, COR.sub.112, and halogen, or R.sub.120 and R.sub.121
can be taken together and/or R.sub.122 and R.sub.123 can be taken
together to form one or two ring structures, respectively, either
of which can be of five to seven members;
[0081] R.sub.110 and R.sub.111 are independently selected from the
group consisting of hydrogen, alkyl, aryl, benzyl, cyclic,
heterocyclic, substituted alkyl or aryl where the substituents are
C, O, N, S, or P, and COR.sub.102, or R.sub.110 and R.sub.111 can
be taken together to form a ring structure of five to seven
members;
[0082] R.sub.112 is R.sub.102, OR.sub.102, or NR.sub.102R.sub.103;
and
[0083] R.sub.102 and R.sub.103 are independently selected from the
group consisting of hydrogen, alkyl, aryl, benzyl, cyclic,
heterocyclic, and substituted alkyl or aryl where the substituents
are C, O, N, S, or P, or R.sub.102 and R.sub.103 can be taken
together to form a ring structure of five to seven members.
[0084] The hydroquinone compounds that can be employed in
combination with the nitroso compounds in the practice of the
present invention are preferably of the structure:
##STR00014##
wherein
[0085] R.sub.3 through R.sub.7 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, hydroxyl, alkoxy,
acyloxy, N R.sub.8(R.sub.9), nitro, nitroso, halogen, and sulfonyl,
or any two adjacent R's can form a cyclic ring that is aryl,
cycloalkyl, polyaryl, or heterocyclic, provided that at least one
of R.sub.3 through R.sub.7 must be an OH group; and
[0086] R.sub.8 and R.sub.9 are independently selected from the
group consisting of hydrogen, alkyl, aryl, acyl, and nitroso.
Preferably, either R.sub.5 is OH and R.sub.3 and R.sub.6 are alkyl
or R.sub.3 is OH and R.sub.5 is alkyl.
[0087] In the foregoing, alkyl (or substituted alkyl) groups, or
the alkyl moieties of alkoxy groups, preferably contain one to 15
carbon atoms, e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl,
heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,
tetradecyl, pentadecyl, and the like, and isomers thereof, e.g.,
t-butyl, 2-ethylhexyl, and the like. It is more preferred that the
alkyl (or substituted alkyl) groups be of one to five carbon atoms
(e.g., methyl, ethyl, propyl, butyl, pentyl, and isomers thereof).
Substituents on the substituted alkyl groups can be any moiety that
will not interfere with the functions of the compounds. Aryl groups
are preferably of from six to 10 carbon atoms, e.g., phenyl or
naphthyl, which, in addition, may be substituted with
non-interfering substituents, e.g., lower alkyl groups, halogens,
and the like.
[0088] The effective amount of nitroso compound(s), alone or in
combination with a nitroxyl, and/or nitroaromatic, and/or quinone
alkide, and/or quinone, and/or hydroquinone, and/or hydroxylamine,
and/or phenylenediamine compound(s), is typically about 1 to 2,000
ppm, based on the weight of the ethylenically unsaturated monomer,
although amounts outside this range may be appropriate depending
upon the conditions of use. The amount is preferably in the range
of from about 5 to about 1,000 ppm, based on the weight of the
ethylenically unsaturated monomer.
[0089] The air or oxygen used in the practice of the present
invention the amount is typically about 1 to 2,000 ppm, based on
the weight of the ethylenically unsaturated monomer, although
amounts outside this range may be appropriate depending upon the
conditions of use. The amount is preferably in the range of from
about 1 to about 1,000 ppm, based on the weight of the
ethylenically unsaturated monomer.
[0090] Preferred embodiments of the instant invention comprise a
process wherein a mixture is used that is from 1 to 99 percent by
weight of at least one nitroso compound and 99 to 1 percent by
weight of at least one additional compound. A more preferred
mixture comprises from 5 to 75 percent by weight of at least one
nitroso compound and 95 to 25 percent by weight of at least one
additional compound. A still more preferred mixture comprises from
5 to 50 percent by weight of at least one nitroso compound and 95
to 50 percent by weight of at least one additional compound.
[0091] The ethylenically unsaturated monomer, the premature
polymerization of which is an object of the present invention, can
be any such monomer for which unintended polymerization during its
manufacture, storage, and/or distribution is a problem. Among those
monomers that will benefit from the practice of the present
invention are: styrene, .alpha.-methylstyrene, styrene sulfonic
acid, vinyltoluene, divinylbenzenes, polyvinylbenzenes, alkylated
styrene, 2-vinylpyridine, acrylonitrile, methacrylonitrile, methyl
acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate,
acrylic acid, methacrylic acid, butadiene, chloroprene, isoprene,
and the like.
[0092] The ethylenically unsaturated monomers will not necessarily
be stabilized indefinitely by the presence of the inhibitor blend,
especially when the monomers are heated as in distillation, but
they can be considered to be stabilized as long as there is a
measurable increase in the time for which they can be heated before
the onset of polymerization in a static system and/or the amount of
polymer made at constant temperature remains constant over time in
a dynamic system.
[0093] Those skilled in the art will understand that, if desired,
additional free radical scavengers can be included in the
stabilized compositions. For example, air or O.sub.2, as disclosed
in U.S. Pat. Nos. 5,545,782 and 5,545,786, can be added, as can the
dihetero-substituted benzene compounds having at least one
transferable hydrogen, e.g., a quinone derivative such as the
mono-methyl-ether of hydroquinone disclosed in European Patent
Application 0 765 856 A1, and other inhibitors well-known to those
skilled in the art.
[0094] The disclosures of the foregoing are incorporated herein by
reference in their entirety.
[0095] The composition(s) employed in the practice of the present
invention can be introduced into the monomer to be protected by any
conventional method. It can be added as a concentrated solution in
suitable solvents just upstream from the point of desired
application by any suitable means. For example, the individual
components can be injected separately or in combination to the
monomer feed tank prior to injection into a distillation train. The
individual components can also be injected separately into the
distillation train along with the incoming feed or through separate
entry points, provided there is an efficient distribution of the
compounds. Since the compounds are gradually depleted during the
distillation operation, it is generally advantageous to maintain
the appropriate amount thereof in the distillation apparatus by
replenishing them during the course of the distillation process.
Additions can be done either on a generally continuous basis or
intermittently, in order to maintain the concentration of the
various components above a minimum required level.
[0096] The advantages and the important features of the present
invention will be more apparent from the following examples.
EXAMPLES
Preparation of Inhibitor Solution
[0097] T-Butylcatechol (TBC) is removed from commercially available
styrene by distillation from CaH.sub.2. The desired amount of
inhibitor(s) is added to the TBC-free styrene directly, together
with inert polystyrene standard (Mn from 2,000,000, 500 ppm wt %),
as internal standard.
[0098] Procedure for GPC Schlenk Test Under Nitrogen
[0099] To a 100 mL Schlenk flask with magnetic stirbar and septum,
was added 20 mL of styrene solution with the desired amount of
inhibitors. The flask was connected to a double manifold and
degassed by three freeze-pump-thaw cycles to remove all oxygen and
allow warming to room temperature before being placed in a
pre-heated oil bath (116.degree. C.) to heat under N.sub.2. At
various time intervals, 0.2 mL of solution was taken via a
gas-tight syringe for Gel Permeation Chromatography (GPC) analysis.
The reaction was typically stopped when the solution became too
viscous to take samples via syringe and the last sample was taken
directly from the flask after the flask was cooled down to room
temperature and opened to air.
[0100] The above procedure is carried out to provide the following
data.
TABLE-US-00001 TABLE Inhibitor system Appearance, Polymer Make (wt
%), and M.sub.w 500 ppm 3 hr 8 hr 16 hr 24 hr 48 hr 72 hr 2NNP Oily
Oily Oily Oily Oily 22.1% Viscous 0.3% 2.2% 6.1% 10.1% 36,000 29.4%
5,000 26,000 35,000 36,000 37,000 DNBP Oily Oily Very Viscous Gummy
n.a. n.a. 0.7% 2.7% 23.8% n.a. 16,000 26,000 162,000 SFR Oily Oily
Very Viscous Gummy n.a. n.a. 1.6% 6.3% 21.7% 62.5% 22,600 42,000
76,000 123,000 QE Oily Viscous Gummy n.a. n.a. n.a. 0.31% 9.2% 40%
6,800 224,000 413,000 XTR Oily Very viscous n.a. n.a. n.a. n.a.
1.4% 18.5% 172,000 247,000 2,6-di-tertbutyl-4- Very Viscous n.a.
n.a. n.a. n.a. n.a. nitrosophenol 7.5% (75% oxime form) 140,000
2,5-di-tert-butyl Viscous n.a. n.a. n.a. n.a. n.a. quinone 4.5%
186,000 Cyclohexanone oxime Gummy n.a. n.a. n.a. n.a. n.a. 11.0%
540,000 BHEB Gummy n.a. n.a. n.a. n.a. n.a. 12.2% 550,000 Pure
Styrene Gummy n.a. n.a. n.a. n.a. n.a. 12.5% 550,000
[0101] The abbreviations stand for:
2NNP (2-nitroso-1-naphthol) DNBP (2-sec-butyl-4,6-dinitrophenol) QE
(1,5-di-tert-butyl-3-ethylidene-6-methylenecyclohexa-1,4-diene) SFR
(4-oxo-2,2,6,6-tetramethyl-1-piperidinyloxy) XTR
(N-(1,4-dimethylpentyl)-N-(4-nitrosophenyl)amine) BHEB
(butylatedhydroxylethylbenzene)
[0102] The above data show that 2-nitroso-1-naphthol is superior to
its para-nitrosophenol counter part and other inhibitors in
preventing polymer from formation. The polymer formed has very low
molecular weight (can avoid crosslinking problem), low viscosity
(easy to be removed) thus can offer long-term protection for the
reboiler.
[0103] In view of the many changes and modifications that can be
made without departing from principles underlying the invention,
reference should be made to the appended claims for an
understanding of the scope of the protection to be afforded the
invention.
* * * * *