U.S. patent application number 09/924475 was filed with the patent office on 2002-03-28 for purification of alkenyl compounds.
Invention is credited to Bottcher, Arnd, Lorenz, Rudolf Erich, Pinkos, Rolf.
Application Number | 20020038059 09/924475 |
Document ID | / |
Family ID | 7651768 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020038059 |
Kind Code |
A1 |
Lorenz, Rudolf Erich ; et
al. |
March 28, 2002 |
PURIFICATION OF ALKENYL COMPOUNDS
Abstract
A process for purifying alkenyl compounds having a divalent or
trivalent heteroatom in the .alpha.-position relative to the double
bond by distillation comprises carrying out at least two
distillations in which the purified alkenyl compounds are obtained
from the gas phase by condensation, where the time between the
first distillation after the synthesis of the alkenyl compounds and
at least one further distillation is at least one day and the
purified alkenyl compounds have an APHA color number of <30.
Inventors: |
Lorenz, Rudolf Erich;
(Ludwigshafen, DE) ; Bottcher, Arnd; (Frankenthal,
DE) ; Pinkos, Rolf; (Bad Durkheim, DE) |
Correspondence
Address: |
HERBERT B. KEIL
KEIL & WEINKAUF
1101 CONNECTICUT AVE., N.W.
WASHINGTON
DC
20036
|
Family ID: |
7651768 |
Appl. No.: |
09/924475 |
Filed: |
August 9, 2001 |
Current U.S.
Class: |
568/687 ; 203/71;
564/498 |
Current CPC
Class: |
C07D 249/08 20130101;
C07C 209/84 20130101; C07D 223/10 20130101; C07C 41/42 20130101;
C07D 233/56 20130101; C07C 211/21 20130101; C07C 43/16 20130101;
C07D 231/12 20130101; C07B 63/00 20130101; C07C 41/42 20130101;
C07C 209/84 20130101 |
Class at
Publication: |
568/687 ;
564/498; 203/71 |
International
Class: |
B01D 003/00; C07C 29/84;
C07C 041/42 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 9, 2000 |
DE |
10038747.0 |
Claims
We claim:
1. A process for purifying alkenyl compounds having a divalent or
trivalent heteroatom in the a position relative to the double bond
by distillation, which comprises carrying out at least two
distillations in which the purified alkenyl compounds are obtained
from the gas phase by condensation, where the time between the
first distillation after the synthesis of the alkenyl compounds and
at least one further distillation is at least one day and the
purified alkenyl compounds have an APHA color number of <30.
2. A process as claimed in claim 1, wherein the time between the
first distillation after the synthesis of the alkenyl compounds and
at least one further distillation is at least five days.
3. A process as claimed in claim 1, wherein the purified alkenyl
compounds have an APHA color number of .ltoreq.10.
4. A process as claimed in claim 1, wherein the alkenyl compounds
are compounds of the formula (Ia) or (Ib) 3where X is a divalent
heteroatom, R.sup.1, R.sup.2 and R.sup.3 are each, independently of
one another, a carbon-containing organic radical, where R.sup.2 and
R.sup.3 may also be joined to one another, and R.sup.4, R.sup.5,
R.sup.6 and R.sup.7 are each, independently of one another,
hydrogen or a hydrocarbon radical.
5. A process as claimed in claim 1, wherein the alkenyl compounds
are vinyl compounds.
6. A process for purifying alkenyl compounds (Ia) as claimed in
claim 4 by distillation, wherein X is oxygen.
7. A process as claimed in claim 6, wherein the alkenyl compounds
(Ia) are vinyl ethers.
8. A process as claimed in claim 4, wherein the alkenyl compounds
(Ib) are N-vinyl amides or N-vinyl heterocycles.
9. A process as claimed in claim 8, wherein the alkenyl compound
(Ib) is N-vinylimidazole or N-vinyl-.epsilon.-caprolactam.
Description
[0001] The present invention relates to a process for purifying
alkenyl compounds having a divalent or trivalent heteroatom in the
a position relative to the double bond, in particular alkenyl
compounds of the formula (Ia) or (Ib) 1
[0002] where X is a divalent heteroatom, R.sup.1, R.sup.2 and
R.sup.3 are each, independently of one another, a carbon-containing
organic radical, where R.sup.2 and R.sup.3 may also be joined to
one another, and R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are each,
independently of one another, hydrogen or a hydrocarbon radical, by
distillation.
[0003] Alkenyl compounds are used, inter alia, as monomeric
building blocks for oligomers, polymers and copolymers. Thus,
alkenyl compounds are employed, for example, in the production of
paper coatings, adhesives, printing inks, laundry detergents, motor
oil additives, textile assistants, radiation-curing surface
coatings, cosmetics, pharmaceuticals, auxiliaries for crude oil
recovery or chemicals for photographic applications.
[0004] Alkenyl compounds are obtained industrially by means of
various processes, for example by addition of alkynes
(alkenylation), transfer of alkenyl groups, elimination to form the
double bond or oxidative addition of alkenes. An overview of the
preparation of vinyl ethers and vinyl esters is given in Ullmann's
Encyclopedia of Industrial Chemistry, 6.sup.th edition, 1999
Electronic Release, Chapter "VINYL ETHERS" and Chapter "VINYL
ESTERS".
[0005] W. Reppe et al., Justus Liebigs Ann. Chem., Vol. 601, 1956,
pages 81 to 138, describe the preparation of vinyl ethers, vinyl
esters, vinyl amines, vinyl-N-heterocycles and vinyl amides by
reaction of ethyne with the corresponding alcohols, carboxylic
acids, amines, NH-heterocycles and amides in the presence of basic
catalysts.
[0006] As indicated in the documents cited, the actual synthesis
step is usually followed by purification by distillation, in which
the desired products can be obtained in high purity by condensation
from the gas phase. In this way, purities of significantly above
99% can be achieved without problems for very many alkenyl
compounds, which is completely satisfactory for many
applications.
[0007] However, in applications in which the products should have
as little color as possible, for example in the cosmetic or
photographic areas or in the case of paper coatings, it is not only
a high chemical purity of the alkenyl compounds but also a very
high purity in respect of color-imparting impurities which is
demanded. Amounts of only a few ppm by weight of color-imparting
impurities are generally sufficient to cause significant
discoloration of the product.
[0008] As a measure of the color of transparent compounds, it is
usual to report the APHA color number which is defined in DIN EN
1557 (March 1997). The lower the APHA color number, the more
colorless is the product.
[0009] In the industrially customary distillation of alkenyl
compounds immediately after their preparation, it is, depending on
the type of alkenyl compounds and the color-imparting impurities
present therein, impossible or possible only with great difficulty
(e.g. large number of theoretical plates, high reflux ratio,
additional purification steps such as adsorptive processes) to
bring the APHA color number to below 40.
[0010] It is an object of the present invention to find a process
for purifying alkenyl compounds which no longer has the
abovementioned disadvantages and leads, without incurring high
costs, to purified alkenyl compounds having a very low color
number.
[0011] We have found that this object is achieved by a process for
purifying alkenyl compounds having a divalent or trivalent
heteroatom in the a-position relative to the double bond by
distillation, which comprises carrying out at least two
distillations in which the purified alkenyl compounds are obtained
from the gas phase by condensation, where the time between the
first distillation after the synthesis of the alkenyl compounds and
at least one further distillation is at least one day and the
purified alkenyl compounds have an APHA color number of <30.
[0012] For the purposes of the present invention, the term
distillation encompasses quite generally all processes in which the
alkenyl compounds are obtained from the gas phase by condensation.
In general, the distillation is carried out in a distillation
column having distillation packing and/or distillation trays as
column internals. Examples of suitable column internals are ordered
packing, random packing elements, valve trays, sieve trays and
bubble cap trays. Preference is given to column internals which
lead to a low pressure drop, for instance ordered packing and
random packing elements. The second distillation and any further
distillations are very particularly preferably carried out without
column internals. The vaporization of the alkenyl compounds to be
purified can in principle be achieved by a variety of
constructions. Preference is given to using falling film and thin
film evaporators, since these make particularly gentle vaporization
possible. The purified alkenyl compounds are preferably isolated at
the top.
[0013] The distillations in the process of the present invention
can be carried out with or without reflux.
[0014] In the first distillation after the synthesis of the alkenyl
compound, the alkenyl compound is separated from the by-products
formed. To enable the separation task to be achieved reliably, it
is preferably carried out with reflux. In this way, a purity of the
alkenyl compound of over 99% can generally be achieved in the first
distillation after the synthesis of the alkenyl compound.
[0015] Since the alkenyl compounds to be purified generally have a
purity of significantly above 99% before the second distillation
and any further distillations and the traces of color-imparting
impurities to be removed preferably remain in the bottoms, the
second distillation and any further distillations are preferably
carried out without reflux. The absence of reflux brings with it a
series of economic advantages, for example simpler construction of
the apparatus, a lower instrumentation requirement and a lower
energy and time requirement.
[0016] The distillations in the process of the present invention
can be carried out batchwise, semicontinuously or continuously. In
the case of batchwise distillation, the alkenyl compound to be
purified is generally introduced all at once into the still pot and
is vaporized by heating and/or lowering the pressure. The
distilled, purified alkenyl compound is taken off continuously or
passed to a receiver. A semicontinuous distillation is generally
commenced in a manner similar to the batchwise distillation, but
the still pot is refilled during the distillation process. In the
case of a continuous distillation, the alkenyl compound to be
purified is fed continuously into the distillation apparatus and
the distilled, purified product is taken off continuously.
[0017] The distillations in the process of the present invention
can in principle be carried out at atmospheric pressure, at
subatmospheric pressure (e.g. as a vacuum distillation) or at
superatmospheric pressure. The choice of the pressure and thus the
distillation temperature generally depends on the product to be
distilled and the impurities present therein. Preference is given
to carrying out both the first distillation after the synthesis of
the alkenyl compounds and the second and any further distillations
under a pressure lower than or equal to atmospheric pressure,
particularly preferably at subatmospheric pressure.
[0018] An essential aspect of the process of the present invention
is that the time between the first distillation after the synthesis
of the alkenyl compounds and at least one further distillation is
at least one day. In each case, the distillation is considered to
be complete at the time at which the alkenyl compounds have been
condensed from the gas phase and isolated. In general, the
condensed, purified alkenyl compounds are isolated by being passed
to a receiver.
[0019] In general, a total of two distillations are sufficient for
achieving the desired APHA color number of <30 in the process of
the present invention. The first distillation is generally carried
out immediately after the synthesis of the alkenyl compounds and
the second distillation is carried out after expiry of the
specified time, namely at least one day. However, it is also
possible to carry out further distillations.
[0020] Furthermore, it has surprisingly been found that the
purified alkenyl compounds obtainable by means of the process of
the present invention have a lower color number the greater the
time between the first distillation after the synthesis and at
least one further distillation. In the process of the present
invention, this time is at least one day. It is preferably at least
2 days, particularly preferably at least 5 days and very
particularly preferably at least 10 days.
[0021] It may be advantageous to add a stabilizer before or during
storage. The type and amount of stabilizer generally depends on the
type of alkenyl compound and is known by or can routinely be
determined by a person skilled in the art. A widely applicable and
very frequently used stabilizer is, for example,
N,N'-bis(1-methylpropyl)-1,4-phenylenediamine- , which is marketed
by BASF AG under the tradename Kerobit.RTM. BPD. A further
frequently used stabilizer is, for example, potassium
hydroxide.
[0022] The storage conditions are generally not critical, i.e. the
storage can in principle be carried out under various conditions.
Since the alkenyl compounds are generally reactive compounds, it is
advantageous to choose gentle conditions. Storage is therefore
advantageously carried out at below 40.degree. C., preferably below
30.degree. C., possibly under a protective gas atmosphere. Alkenyl
compounds which are solid under these conditions are generally
stored in the solid state and are melted prior to the distillation.
For the present purposes, the term storage encompasses transport
such as pumping through a pipe or transportation in a
container.
[0023] After the process of the present invention has been carried
out, the purified alkenyl compounds have an APHA color number of
<30. The definition and determination of the APHA color number
are described in DIN EN 1557 (March 1997). The purified alkenyl
compounds obtained after carrying out the process of the present
invention preferably have an APHA color number of .ltoreq.20,
particularly preferably 10. Thus, alkenyl compounds having an APHA
color number of significantly below 10 can generally be obtained
without problems after a storage time of only a few days.
[0024] The alkenyl compounds to be purified in the process of the
present invention have, for example, the formula (Ia) or (Ib) 2
[0025] where X is a divalent heteroatom, R.sup.1, R.sup.2 and
R.sup.3 are each, independently of one another, a carbon-containing
organic radical, where R.sup.2 and R.sup.3 may also be joined to
one another, and R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are each,
independently of one another, hydrogen or a hydrocarbon
radical.
[0026] For the purposes of the present invention, a
carbon-containing organic radical is an unsubstituted or
substituted, aliphatic, aromatic or araliphatic radical having from
1 to 22 carbon atoms. This radical may contain one or more
heteroatoms such as oxygen nitrogen or sulfur, for example --O--,
--S--, --NR--, --CO-- and/or --N.dbd. in aliphatic or aromatic
systems, and/or may be substituted by one or more functional groups
containing, for example, oxygen, nitrogen, sulfur and/or halogen,
for example by fluorine, chlorine, bromine, iodine and/or a cyano
group. If the carbon-containing organic radical contains one or
more heteroatoms, it can also be bound via a heteroatom or a
heteroatom-bearing carbon atom. Thus, for example, radicals which
are bound via a nitrogen atom or a carbon group are also
included.
[0027] Preferred monovalent, i.e. terminal, carbon-containing
organic radicals R.sup.1, R.sup.2 or R.sup.3 are:
[0028] unbranched or branched, acyclic or cyclic alkyl having from
1 to 22 aliphatic carbon atoms, in which one or more of the
--CH.sub.2-- groups may also be replaced by heteroatoms such as
--O--, or by heteroatom-containing groups such as --CO-- or --NR--
and in which one or more of the hydrogen atoms may be replaced by
substituents, for example aryl groups,
[0029] unbranched or branched, acyclic or cyclic alkenyl having
from 2 to 22 aliphatic carbon atoms and one or more double bonds in
any positions, in which one or more of the --CH.sub.2-- groups may
also be replaced by heteroatoms such as --O--, or by
heteroatom-containing groups such as --CO-- or --NR-- and in which
one or more of the hydrogen atoms may be replaced by substituents,
for example aryl groups,
[0030] aryl having up to 10 aromatic carbon atoms, in which one or
more of the .dbd.CH-- groups may be replaced by heteroatoms such as
.dbd.N-- and in which one or more of the hydrogen atoms may be
replaced by substituents, for example alkyl groups,
[0031] and radicals as mentioned above in which one or more of the
hydrogen atoms are replaced by a X--CR4.dbd.CHR5 or
>Y--CR6.dbd.CHR7-- group.
[0032] Preferred divalent organic radicals formed by
R.sup.2-R.sup.3 are:
[0033] unbranched or branched alkylene having from 3 to 20
aliphatic carbon atoms, in which one or more of the --CH.sub.2--
groups may also be replaced by heteroatoms such as --O--, or by
heteroatom-containing groups such as --CO-- or --NR-- and in which
one or more of the hydrogen atoms may be replaced by substituents,
for example aryl groups,
[0034] unbranched or branched alkenylene having from 3 to 20 carbon
atoms and one or more double bonds, in which one or more of the
--CH.sub.2-- groups may also be replaced by heteroatoms such as
--O-- or by heteroatom-containing groups such as --CO-- or --NR--
in which one or more of the .dbd.CH-- groups may also be replaced
by heteroatoms such as .dbd.N-- and in which one or more of the
hydrogen atoms may be replaced by substituents, for example aryl
groups.
[0035] The divalent heteroatom X in the alkenyl compounds (Ia) can
be an oxygen atom or a sulfur atom. Examples of alkenyl compounds
(Ia) are alkenyl ethers, alkenyl esters and alkenyl sulfides. The
process of the present invention is preferably carried out using
alkenyl compounds (Ia) in which X is oxygen.
[0036] Examples of alkenyl compounds (Ib) are alkenylamines,
N-alkenylamides and N-alkenylheterocycles. The term N-alkenylamides
also encompasses cyclic N-alkenylamides, which are also known as
N-alkenyllactams.
[0037] For the purposes of the present invention a hydrocarbon
radical is an aliphatic, aromatic or araliphatic radical having
from 1 to 12 carbon atoms. Preferred hydrocarbon radicals R.sup.4,
R.sup.5, R.sup.6 and R.sup.7 are C.sub.1-C.sub.4-alkyl, for example
methyl, ethyl, 1-propyl, 2-propyl, 1-butyl, 2-butyl,
2-methyl-1-propyl and 2-methyl-2-propyl, in particular methyl,
C.sub.6-aryl, specifically phenyl, C.sub.7-C.sub.8-aralkyl, for
example phenylmethyl and phenylethyl, and C.sub.7-C.sub.8-alkaryl,
for example 2-methylphenyl, 3-methylphenyl and 4-methylphenyl.
[0038] Particular preference is given to alkenyl compounds (Ia) and
(Ib), in which the radicals R.sup.4, R.sup.5, R.sup.6 and R.sup.7
are each, independently of one another, hydrogen or methyl. Very
particular preference is given to alkenyl compounds (Ia) and (Ib)
in which the radicals R.sup.4, R.sup.5, R.sup.6 and R.sup.7 are
hydrogen, i.e. the vinyl compounds.
[0039] Examples of alkenyl sulfides of the formula (Ia) with
X=sulfur which can be used in the process of the present invention
are vinyl methyl sulfide, vinyl ethyl sulfide, vinyl 1-propyl
sulfide, vinyl 2-propyl sulfide (vinyl isopropyl sulfide), vinyl
1-butyl sulfide, vinyl 2-butyl sulfide (vinyl sec-butyl sulfide),
vinyl (2-methyl-2-propyl) sulfide (vinyl tert-butyl sulfide), vinyl
pentyl sulfide and its isomers and vinyl hexyl sulfide and its
isomers.
[0040] The alkenyl compounds (Ia) used in the process of the
present invention are particularly preferably vinyl ethers.
Examples of preferred vinyl ethers are vinyl methyl ether, vinyl
ethyl ether, vinyl 1-propyl ether, vinyl 2-propyl ether (vinyl
isopropyl ether), vinyl 1-butyl ether, vinyl 2-butyl ether (vinyl
sec-butyl ether), vinyl 2-methyl-2-propyl ether (vinyl tert-butyl
ether), vinyl pentyl ether and its isomers, vinyl hexyl ether and
its isomers, vinyl heptyl ether and its isomers, vinyl octyl ether
and its isomers, vinyl nonyl ether and its isomers, vinyl decyl
ether and its isomers, vinyl undecyl ether and its isomers, vinyl
dodecyl ether and its isomers, vinyl tridecyl ether and its
isomers, vinyl tetradecyl ether and its isomers, vinyl pentadecyl
ether and its isomers, vinyl hexadecyl ether and its isomers, vinyl
heptadecyl ether and its isomers, vinyl octadecyl ether and its
isomers, vinyl nonadecyl ether and its isomers, vinyl eicosyl ether
and its isomers, vinyl henicosyl ether and its isomers, vinyl
docosyl ether and its isomers, vinyl cyclopentyl ether, vinyl
cyclohexyl ether, vinyl cycloheptyl ether, vinyl cyclooctyl ether,
vinyl cyclododecyl ether, vinyl phenyl ether, vinyl 2-methylphenyl
ether, vinyl 3-methyl-phenyl ether, vinyl 4-methylphenyl ether,
vinyl phenylmethyl ether, vinyl 2-phenylethyl ether, 2-hydroxyethyl
vinyl ether (3-oxapent-4-en-1-ol), ethylene glycol divinyl ether
(3,6-dioxaocta-1,7-diene), diethylene glycol monovinyl ether
(3,6-dioxaocta-7-en-1-ol), diethylene glycol divinyl ether
(3,6,9-trioxaundeca-1,10-diene), triethylene glycol monovinyl ether
(3,6,9-trioxaundeca-10-en-1-ol), triethylene glycol divinyl ether
(3,6,9,12-tetraoxatetradeca-1,13-diene), tetraethylene glycol
monovinyl ether (3,6,9,12-tetraoxatetradeca-13-en-1-ol),
tetraethylene glycol divinyl ether
(3,6,9,12,15-pentaoxaheptadeca-1,16-diene), 1,2-propylene glycol
monovinyl ether (4-oxahexa-5-en-2-ol and 2-methyl-3-oxapent-4-en-1-
-ol), 1,2-propylene glycol divinyl ether
(4-methyl-3,6-dioxaocta-1,7-diene- ), 3-hydroxypropyl vinyl ether
(5-oxa-hept-6-en-1-ol), 1,3-propylene glycol divinyl ether
(3,7-dioxanona-1,8-diene), 4-hydroxybutyl vinyl ether
(5-oxahept-6-en-1-ol), 1,4-butylene glycol divinyl ether
(3,8-dioxadeca-1,9-diene), 5-hydroxypentyl vinyl ether
(6-oxaoct-7-en-1-ol), 1,5-pentylene glycol divinyl ether
(3,9-dioxaundeca-1,10-diene), 6-hydroxyhexyl vinyl ether
(7-oxanon-8-en-1-ol), 1,6-hexylene glycol divinyl ether
(3,10-dioxadodeca-1,11-diene), 8-hydroxyoctyl vinyl ether
(9-oxaundec-10-en-1-ol), 1,8-octylene glycol divinyl ether
(3,12-dioxatetradeca-1,13-diene), 12-hydroxydodecyl vinylether
(13-oxapentadec-14-en-1-ol), 1,12-dodecylene glycol divinyl ether
(3,16-dioxaoctadeca-1,17-diene), 4-hydroxycyclohexyl vinyl ether,
1,4-cyclohexylene divinyl ether (1,4-bis(vinyloxy)cyclohexane),
4-vinyloxyphenol and bis(vinyloxy)-1,4-phenylene.
[0041] Vinyl ethers which are very particularly preferred in the
process of the present invention are ethylene glycol divinyl ether
(3,6-dioxaocta-1,7-diene), diethylene glycol divinyl ether
(3,6,9-trioxaundeca-1,10-diene), triethylene glycol divinyl ether
(3,6,9,12-tetraoxatetradeca-1,13-diene) and 4-hydroxybutyl vinyl
ether (5-oxahept-6-en-1-ol).
[0042] Alkenyl compounds (Ib) used in the process of the present
invention are particularly preferably acyclic and cyclic N-vinyl
amines, acyclic and cyclic N-vinyl amides and N-vinyl heterocycles,
in particular N-vinyl amides and N-vinyl heterocycles.
[0043] Examples of preferred acyclic and cyclic N-vinyl amines
are
[0044] N-vinyldimethylamine, N-vinyldiethylamine,
[0045] N-vinyldi(1-propyl)amine, N-vinyldi(2-propyl)amine
[0046] (N-vinyldiisopropylamine), N-vinyldi(1-butyl)amine,
[0047] N-vinyldi(2-butyl)amine (N-vinyldi-sec-butylamine),
[0048] N-vinyldi(2-methyl-2-propyl)amine
(N-vinyldi-tert-butylamine),
[0049] N-vinylmethylethylamine, N-vinylmethyl(1-propyl)amine,
[0050] N-vinylmethyl(2-propyl)amine
(N-vinylmethylisopropylamine),
[0051] N-vinylmethyl(1-butyl)amine, N-vinylmethyl(2-butyl)amine
[0052] (N-vinylmethylsec-butylamine),
[0053] N-vinylmethyl(2-methyl-2-propyl)amine
[0054] (N-vinylmethyl-tert-butylamine), N-vinylmethylpentylamine
and its isomers, N-vinylmethylhexylamine and its isomers,
[0055] N-vinylmethylheptylamine and its isomers,
N-vinylmethyloctylamine and its isomers, N-vinylmethylnonylamine
and its isomers,
[0056] N-vinylmethyldecylamine and its isomers,
[0057] N-vinylmethylundecylamine and its isomers,
[0058] N-vinylmethyldodecylamine and its isomers,
[0059] N-vinylmethyltridecylamine and its isomers,
[0060] N-vinylmethyltetradecylamine and its isomers,
[0061] N-vinylmethylpentadecylamine and its isomers,
[0062] N-vinylmethylhexadecylamine and its isomers,
[0063] N-vinylmethylheptadecylamine and its isomers,
[0064] N-vinylmethyloctadecylamine and its isomers,
[0065] N-vinylmethylnonadecylamine and its isomers,
[0066] N-vinylmethyleicosylamine and its isomers,
[0067] N-vinylmethylhenicosylamine and its isomers,
[0068] N-vinylmethyldocosylamine and its isomers,
[0069] N-vinylmethylcyclopentylamine,
N-vinylmethylcyclohexylamine,
[0070] N-vinylmethylcycloheptylamine,
N-vinylmethylcyclooctylamine,
[0071] N-vinylmethylcyclododecylamine,
N-vinylmethylphenylamine,
[0072] N-vinyldiphenylamine,
N-vinylmethyl(2-methylphenyl)amine,
[0073] N-vinylmethyl(3-methylphenyl)amine,
[0074] N-vinylmethyl(4-methylphenyl)amine,
[0075] N-vinylmethyl(phenylmethyl)amine,
[0076] N-vinylmethyl(2-phenylethyl)amine, N-vinylpyrrolidine,
[0077] N-vinylpiperidine, N-vinylmorpholine.
[0078] Examples of preferred acyclic and cyclic N-vinyl amides are
N-vinyl-N-methylacetamide, N-vinylpyrrolidone, N-vinyl-2-piperidone
(N-vinyl-.delta.-valerolactam), N-vinyl-.epsilon.-caprolactam
(N-vinyl lactam of 6-aminohexanoic acid), the N-vinyl lactam of
7-aminoheptanoic acid, the N-vinyl lactam of 8-aminooctanoic acid,
the N-vinyl lactam of 9-aminononanoic acid, the N-vinyl lactam of
10-aminodecanoic acid, the N-vinyl lactam of 12-aminododecanoic
acid (N-vinyllaurolactam).
[0079] N-vinyl amides which are very particularly preferred in the
process of the present invention are N-vinyl-2-piperidone
(N-vinyl-.delta.-valero- lactam) and N-vinyl-.epsilon.-caprolactam
(N-vinyl lactam of 6-aminohexanoic acid).
[0080] Examples of preferred N-vinyl heterocycles are
N-vinylpyrrole, N-vinylpyrazole, N-vinylimidazole,
N-vinyl-1,2,3-triazole, N-vinyl-1,2,4-triazole,
N-vinyl-1,3,4-triazole and N-vinyl-2-methylimidazole.
[0081] The very particularly preferred N-vinyl heterocycle in the
process of the present invention is N-vinylimidazole.
[0082] In a preferred embodiment of the process of the present
invention, the alkenyl compound originating from the preceding
synthetic step, including work-up of the crude product by
distillation, is stored for at least one day at below 40.degree. C.
and is subsequently subjected to a further distillation to achieve
the desired APHA color number.
[0083] This storage can be carried out in many ways. In a preferred
variant, the alkenyl compound which has been distilled after the
synthesis is stored in an intermediate vessel (e.g. a drum, a
container or a tank), taken out after one day at the earliest and
redistilled as described to achieve the desired APHA color
number.
[0084] In another preferred variant, the alkenyl compound distilled
after synthesis is firstly, if desired, stored in an intermediate
vessel (e.g. a drum, a container or a tank), subsequently
transported in a suitable vessel (e.g. a drum, a container or a
tank), subsequently, if desired, stored again in an intermediate
vessel (e.g. a drum, a container or a tank) and subsequently, but
at the earliest after one day calculated from the first
distillation after the synthesis, taken out and distilled as
described to achieve the desired APHA color number.
[0085] The purification process of the present invention for
purifying alkenyl compounds by distillation leads to a purified
product having a very low color number. The process of the present
invention can be carried out very efficiently and economically at
low cost. As a result of the second and possibly further
distillations which are simple to carry out industrially and can
preferably even be carried out without reflux, the process of the
present invention has a low energy consumption and low demands in
terms of materials. The yield of the purified alkenyl compounds is
very high, frequently even almost quantitative. The process of the
present invention is successful in the case of both unstabilized
and stabilized alkenyl compounds. Alkenyl compounds having an APHA
color number of significantly below 10 can be obtained without
problems by means of the process of the present invention.
EXAMPLES
Examples 1 and 2
[0086] N-Vinyl-.epsilon.-caprolactam was obtained by base-catalyzed
reaction of .epsilon.-caprolactam with ethyne and the crude product
was subsequently distilled. The N-vinyl-.epsilon.-caprolactam
obtained comprised 99.7 GC-% by area of
N-vinyl-.epsilon.-caprolactam and 0.25 GC-% by area of unreacted
.epsilon.-caprolactam. The APHA color number was 55.
[0087] In Example 1 (comparative example), the
N-vinyl-.epsilon.-caprolact- am obtained was immediately, i.e.
without intermediate storage, redistilled in a downstream column at
a pressure of about 0.6 kPa abs at the top and a temperature at the
bottom of about 130.degree. C. The distillation column was provided
with a random packing and was operated at a reflux ratio of 1. The
purified N-vinyl-.epsilon.-caprolactam obtained via the top had an
APHA color number of 30.
[0088] In Example 2 (according to the present invention), the
N-vinyl-.epsilon.-caprolactam obtained from the distillation of the
crude product in Example 1 was stored without addition of a
stabilizer for 5 days at about 25.degree. C. The APHA color number
rose to 100. It was subsequently redistilled from a still pot, i.e.
without a column, at about 0.7 kPa abs and a liquid-phase
temperature of about 126.degree. C. The purified
N-vinyl-.epsilon.-caprolactam obtained via the top had an APHA
color number of only 5.
Example 3
(According to the Present Invention)
[0089] N-vinylimidazole was obtained by base-catalyzed reaction of
imidazole with ethyne and distilled. The N-vinylimidazole obtained
had an APHA color number of 50. After storage for 2 days at
25.degree. C., the unstabilized N-vinylimidazole was redistilled
from the still pot of the same apparatus as in Example 2 at about
0.5 kPa abs. The purified N-vinylimidazole obtained via the top had
an APHA color number of only 3.
Example 4
(According to the Present Invention)
[0090] Diethylene glycol divinyl ether was obtained by
base-catalyzed reaction of diethylene glycol with ethyne and
distilled. The diethylene glycol divinyl ether obtained was
stabilized with 100 ppm by weight of potassium hydroxide and had an
APHA color number of 45. After storage for 5 days at 25.degree. C.,
the diethylene glycol divinyl ether was redistilled from the still
pot of the same apparatus as in Example 2 at about 0.5 kPa abs. The
purified diethylene glycol divinyl ether obtained via the top had
an APHA color number of only 3.
Example 5
(According to the Present Invention)
[0091] Triethylene glycol divinyl ether was obtained by
base-catalyzed reaction of triethylene glycol with ethyne and
distilled. The triethylene glycol divinyl ether obtained was
stabilized with 100 ppm by weight of potassium hydroxide and had an
APHA color number of 105. After storage for 30 days at 25.degree.
C., the triethylene glycol divinyl ether was redistilled from the
still pot of the same apparatus as in Example 2 at about 0.5 kPa
abs. The purified triethylene glycol divinyl ether obtained via the
top had an APHA color number of only 5.
[0092] Table 1 gives a summary of the results.
1 Storage APHA color number Exam- time before after ple Product
[days] distillation distillation 1* N-vlnyl-.epsilon.-caprolactam
none 55 30 2 N-vinyl-.epsilon.-caprolactam 5 55 5 3
N-vinylimidazole 2 50 3 4 Diethylene glycol divinyl 5 45 3 ether 5
Triethylene glycol divinyl 30 105 5 ether * Comparative
experiment
[0093] The examples show that APHA color numbers of significantly
below 30 can be obtained without problems and in a simple way for
the various vinyl compounds by means of the process of the present
invention.
[0094] As comparative example 1 and Example 2 according to the
present invention show, this is made possible only by an
appropriate storage time between the first distillation after the
synthesis of the alkenyl compound and the second or possibly
further distillation.
* * * * *