Note: Descriptions are shown in the official language in which they were submitted.
2S~7
Poly-2-pyrrolidone is produced by the alkaline-
catalyzed polymerization of 2-pyrrollione. The catalyst system
may comprise a partially carbonated pyrrolidonate sal-t made, for
example, by reacting an alkali metal hydroxide with 2-pyrrolidone,
or by reacting a quaternary ammonium hydroxide with 2-pyrrolidone,
dehydrating, and contacting the product with carbon dioxide
~United States 3,721,642). Japanese Patent 47-26195 discloses a
process for making a catalyst by reacting a non-water-forming
alkali metal compound with 2-pyrrolidone and contacting the pro-
lQ duct with a quaternary ammonium halide under anhydrous conditions.
In United States Patent 3,835,100, the catalyst obtained by react-
ing an alkali metal alkoxide with a quaternary ammonium halide and
contactingthe product, ammonium alkoxide, with 2-pyrrolidone, also
avoids the production of water. While both of the latter process-
es are anhydrous, they do not produce poly-2-pyrrolidone of very
high molecular weight in ordinary reaction times. For many
purposes, it is advantageous to be able to rapidly produce poly-2-
pyrrolidone having high molecular weight, e.g. in excess of
500,000, in good yield.
A catalyst capable o~ producing a high-molecular-
weight poly-2-pyrrolidone is made by contacting an alkali metal
pyrrolidonate, a quaternary ammonium salt and carbon dioxide, said
quaternary ammonium salt being a halide or a carboxylate.
While poly-2-pyrrolidone of 300,000 weigh-t average
molecular weight is producible over a polymerization period of
less than 2~ hours by using a partially carbonated potassium pyr-
rolidonate catalyst, the catalyst of the present invention is
capable of producing poly-2-pyrrolidone having a weight average
molecular weight in excess of 1,000,000 under the same conditions.
The present catalyst also achieves high yields and high conversion
rates without diminution of molecular weight. The catalyst does
2-
not require an anhydrous source of alkali metal pyrrolidonate. The pyr-
rolidonate may be made by contacting 2-pyrrolidone with the hydroxide,
rather than by contacting it with an alkali metal or alkali metal alkoxide.
Catalyst System
In the process of the present inven-tion a catalyst for the poly-
merization of 2-pyrrolidone is made by contacting an alkali metal pyrrol-
idonate, certain quaternary ammonium salts and carbon dioxide preferably in
mol ratio of about 1:0.1-2:0.1-0.5, more preferably in mol ratio of about
1:0.2-1.5:0.1-0.5, and most preferably in a mol ratio of about 1:1:0.3.
The reactants, i.e., the pyrrolidonate, the ammonium salt and
carbon dioxide, may be contacted in any order beginning ~ith the pyrrolid-
onate as one of the components. It is preferred, but not necessary, to add
the quaternary ammonium salt to the previously carbonated pyrrolidonate salt.
In a preferred embodiment, the catalyst of the present invention is formed in
a solution of 2-pyrrolidone. An alkali metal hydroxide is added to an ex-
cess of 2-pyrrolidone, with which it reacts to produce a solution of the
alkali metal pyrrolidonate and water in 2-pyrrolidone. The solution is de-
hydrated until it contains less than about 0.1-0.2 weight percent water.
Then carbon dioxide is added in the required mol ratio to the pyrrolidonate
in the solution at a temperature of about 20-50C, preferably 25-35 C. The
quabernary al~lonium salt is then added in the required mol ratio -to the pyr-
rolidonate at about the same temperature.
Another method for preparing the catalyst systems of this inven-
tion involves the in situ preparation of tetraalkyl ammonium halide by the
reaction of trialkylamine with an alkyl halide. A portion of the 2-pyrrol-
idone monomer may be used as a solvent in ~hich this reaction is carried out.
Tnis method involves dissolving the triaIkylamine in 2-pyrrolidone and then
adding the a~yl halide while at the same time maintaining the ternperature
within the range of about 10 to 50C. ~1hen the reaction is completed, the
resulting solution is reacted with alkali metal pyrrolidonate and carbon
~.~`
2587
dioxide as by addition to a pyrrolidone solution in which the carboxylated
alkali metal salt has been prepared by the usual procedures.
The quaternary ammonium salts of this inven-tion are salts of the
formula (R)4N X , or RlR2R3R4N x wherein the R may be the same or different
lower alkyl, alkylaryl or aralkyl groups, preferably (Cl-C6) alkyl groups,
more preferably (Cl-C3) alkyl groups, most preferably methyl, and X is a
halide or carboxylate anion.
The preferred quaternary ammonium carboxylate of the present in-
vention is a lower alkyl tetraalkyl ammonium carboxylate of a lower alkanoic
acid. The tetraalkyl ammonium carboxylate may be produced by the neutraliza-
tion of the carboxylic acid with the tetraalkyl ammonium hydroxide. The
tetraalkyl ammonium carboxylate is preferably a tetra(C1-C6) alkyl ammonium
carboxylate, and more preferably a tetra(Cl-C3) alkyl ammonium carboxylate.
Representative alkyl groups include methyl, ethyl, propyl, isopropyl, butyl,
isobutyl, t-butyl, hexyl, etc. The carboxylate is preferably the alkanoate
of a Cl-C6 alkanoic acid, or preferably a Cl-C3 alkanoic acid and most pref-
erably the acetate. Representative alkyl ammonium carboxylates include
tetramethyl ammonium acetate, tetraethyl ammonium acetate, dimethyl diethyl
ammonium propionate, etc. The ammonium carboxylate may be used as a com-
bination of species, e.g., as a mixture of tetramethyl ammonium ace-tate and
tetraethyl ammonium acetate. However, the ammonium carboxylate should be
substantlally soluble under the alkaline conditions of catalyst system prep-
aration and 2-pyrrolidone polymerization in order to show an appreciable
effect on the polymerization reaction. In this regard, tetramethyl ammonium
acetate shows a considerable advantage overthe corresponding halide, tetra-
methyl ammonium chloride, since it is much more soluble in the polymerizate.
The quaternary ammonium halide of this invention is a lower alkyl,
alkylaryl or ara~kyl ammonium halide. The quaternary ammonium halide is
preferably a tetraalkyl ammonium halide. The tetraaIkyl ammonium halide is
3Q preferably a tetra(Cl-C6) alkyl ammonium halide, and most preferably a
~..
~ ~ ,
112ZS~37
tetra(Cl-C3) alkyl ammonium halide. Representative alkyl groups include
methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, hexyl, etc.
The ammonium halide is preferably a chloride, bromide or iodide or more pref-
erably a chloride or bromide, most preferably a chloride. The ammonium
halide may be used as a combination of species, e.g., as a mixture of tetra-
methyl ammonium chloride and tetraethyl ammonium bromide. The ammonium
halide should be substantially soluble under the alkaline conditions of cat-
alyst system preparation in order to show an appreciable effect on the poly
merization reaction.
Alkylaryl ammonium halides, such as phenyl trimethyl ammonium
halide and tolyl triethyl ammonium halide, are included within the scope of
the ammonium halides of this invention. The ammonium halides finding use
within the scope of this invention also include compounds such as R R R3
(~H2)NX wherein ~ represents a phenyl and Rl, R and R3 may be the same or
different lower alkyl groups or other lower aralkyl groups, and X is a
halide. Consequently, quaternary ammonium halide, as used herein encompasses
the aralkyl ammonium halides. These aralkyl groups will normally con-tain
7-12 carbon atoms e.g. benzyl, phenethyl etc.
The alkali metal pyrrolidonate is preferably sodium or potassium
pyrrolidona-te. For certain purposes, it may be ad~antageous to substitute
for pyrrolidonate in whole or in part an alkali metal caprolactamate or the
alkali metal salt of another low-molecular-weight lactam, but this is nor-
mally not preferred to the use of the pyrrolidonate. The alkali metal
pyrrolidonate is preferably made by contacting the alkali me-tal hydroxide
with excess 2-pyrrolidone, but other methods mæy be chosen, such as by re-
acting 2-pyrrolidone with an alkali metal or an alkali metal alkoxide. In
contrast to the production of quaternary ammonium pyrrolidonate from quater-
n ry ammonium hydroxide, the process of the present invention does not yield
as intense an amine odor. In fact, the process utilizing sodium pyrrol-
3Q idone (e.g. NaO~-derived) and quaternary ammonium halide, is substantially
~i
l~l;ZZS~37
odorless and sodium is preferred for this reason. While it is preferable
to contact the tetraalkyl a~monium halide, the pyrrolidonate and carbon
dioxide in a 2-pyrrolidone solution, inert solvents may be used in whole or
in part to replace the 2-pyrrolidone. Sulfur dioxide is believed to be a
partial substitute for carbon dioxide, and its use is not barred in the
practice of the present invention.
In the catalyst system of the present invention, polymerization
initiators and polymerization accelerators may also be used. Unexpectedly
rapid polymerization to poly-2-pyrrolidone of satisfactorily high molecular
weight is achieved in this catalyst system by the addition of 0.05-1.5 mol
percent of acetic anhydride. Preferably 0.05-1.0 and most preferably about
0.05-0.5 mole percent of acetic anhydride is used. Suitable accelerators are
also described in United States 3,721,652 and include ~-acyl lactam, par-
ticularly the N-acyl pyrrolidones, preferably N-acetyl pyrrolidone. 1-(1-
pyrrolin-z-yl)-2-pyrrolidone is a particularly preferred activator~
Polymerization Conditions
~ he polymerization process of this invention is specifically ap-
plicable to the polymerization of 2-pyrrolidone to form a polymeric carbon-
amide of very high molecular weight in a reasonably short polymerization
time, for this reaction, of 4-2~ hours. Weight average molecular weights
ill excess of 1,000,000 have been attained. The high-molecular-weight polymer
is capable of being formed into filaments having substantial orientation
along the filamentary axis, high tensile strength and other properties suit-
able for making into textiles. It can be made into shaped articles and film
by melt-molding or extrusion.
In order to produce high-quality poly-2-pyrrolidone capable of
being formed into fibers, filaments and yarn of commercial textile quality,
it is necessary that the 2-pyrrolidone be of high purity. Depending upon
the process of manufacture, commercially available 2-pyrrolidone may contain
3Q appreciab~le amounts of various impurities, some of which are believed to
-- 6 --
~llZ2~
interfere deleteriously with polymeri~ation. Purification o~ the monomer to
polymerization grade is achieved by known purification techniques~ including
distillation.
The process of the present invention is applicable to the produc~
tion of polymers of C-alkyl-substituted pyrrolidone~ such as 4-methyl-2-
pyrrolidone and copolymers of 2-pyrrolidone, such as with caprolac-tam, as
~ell as to the production of poly-2-pyrrolidone. Consequently, in general,
and unless otherwise indicated, "monomer" denotes 2-pyrrolidone, substituted
2-pyrrolidone, and any compound capable of copolymerizing with 2-pyrrolidone
under the stated conditions of alkaline polymerization catalysis.
Preferably, the catalyst system comprises about 0.5-30 mol percent
or more of the 2-pyrrolidone-catalyst mixture, based on total 2-pyrrolidone,
more preferably about 5-20 mol percent, and most preferably about 10 mol per-
cent catalyst. Total 2-pyrrolidone consists of 2-pyrrolidonate catalyst,
including alkali metal pyrrolidonate and quaternary ammonium pyrrolidonate,
as well as carbonated alkali metal pyrrolidone and carbonated quaternary
ammonium pyrrolidonate, and 2-pyrrolidone provided as solvent to said cat-
alyst, and any additional monomer charged to the mixture for polymerization
reaction. The polymerization catalyst system is believed to principally
comprise quaternary ammonium pyrrolidonate and carbona-ked quaternary ammonium
pyrrolidonate, but substantial amounts of alkali metal pyrrolidonate and car-
bonated alkali metal pyrrolidonate (carboxypyrrolidonate) may also be present,
depending upon the mol ratios chosen. Alkali metal halide is thought to be
present, but it is believed to be inert towards the polymerization reaction.
In general, 2-pyrrolidone may be polymerized at a temperature from
about 15C to about 100C, preferably 25 C to 70C, and most preferably from
about 40 C to about 60C, under a pressure ranging from subatmospheric to
superatmospheric, in the presence of the catalyst system for a period from
about 4 to about 100 hours or longer, preferably for about 8 to about 72
hours, and most PreferablY from about 8 to about 48 hours. In continuous
~1225~7
operation, polymerization time refers to a~erage residence under polymer-
ization conditions. A small amount of water, not exceeding about 0.1-0.2
weight percent, based on total 2-pyrrolidone, is permissable in the reaction
mixture, but less than 0.1 weight percent is preferred.
Preparation of polymers of 2-pyrrolidone, according to the normal
process of this invention, can be carried out with various amoun-ts of mon-
omers, catalyst, inert nonsolvent liquids, initiators and other additives --
the amount of each being properly coordinated to produce the most effective
polymerization -- with or without stirred reactors, by bulk polymerization,
solution polymerization, or otherwise, continuously or batchwise. Al-though
the preferred conditions and amounts of the components in the reaction have
been given, it is understood that these are not intended to be limitations
to polymerization, since it may be possible to achieve substantial polymer-
ization outside the preferred ranges.
EXE~LIFICATION
Example 1
100 g of 2-pyrrolidone (1.175 M) was mixed with 1.55 g of 85.5%
KOH pellets (0.0236M) to make a 2 mol percent potassium pyrrolidonate solu-
tion which was dehydra-ted by heating to incipient distillation at 2 mm
pressure for 11 minutes. To the dehydrated solu-tion was added sufficient
carbon dioxide to make a polymerizate containing 30mQl ~ C02 based on potas-
sium. The carbonated pyrrolidonate solution was poured into 2 bo-ttles, one
of which (a) was held at 50 C for 8 hours,the other (b) held at 50C for 22
hours. After these time intervals the contents of the bottles were chopped,
washed with water, dried, weighed and subjected to viscosity measurement for
molecular weight determination as described. The results are presented in
Table I. Examples 2-3 are performed substantially as Example 1.
Example 4
Same as Example 1 except for the addition of 2.59 g (0.0236M) of
3~ tetra ~ethyl ammonium chloride after carbonation by welghing the dried onium
-- 8 --
~ ~ 2~5~7
salt in a dry box and adding same under N2 at room temperature to the poly-
merizate with stirring for 5 minutes. The remaining procedure was as in
~xample 1. Examples 5-9 are performed substantially as Example 4.
xamples 10-12
A 3-liter flask equipped with stirrer, thermometer, and distilla-
tion head, was charged with 1000 ml of benzene and 108 g (2 mols) of sodium
methoxide. The mixture was heated to the boiling point and 100 ml of ben-
zene was distilled overhead. Then, while maintaining distillation~ 187.24 g
(2.2 mols) of pyrrolidone was added over 38 minutes. Distillation was con-
tinued until no more methanol came over. During this time, 1200 ml of ben-
zene was added, and the total overhead was 998 ml. After cooling to 21 C,
24.5 g of C02 was bubbled into the slurry for 40 minutes. The precipitate
was removed by filtration, washed with benzene and then pentane, and finally
dried under a nitrogen atmosphere to give 238.67 g of a white solid. Anal-
ysis showed this to be a 7:3 (molar) ratio of sodium pyrrolidonate and a C02-
sodium pyrrolidonate mixture. Three flasks were charged with 24.26 grains
(0.285 mols) of 2-pyrrolidone and 1.8 g (0.015 mols) of the above-described
solid. The resulting mixture was heated at 100 C for 10 minutes to dissolve
the solid. It was then cooled to room temperature before addin~ 1.64 g of
tetramethyl a~monium chloride to the flask of Example 11; and 2.1~8 g of
tetraethyl ammonium chloride to the flask of Example 12. Nothing was added
to the flask of Example 10. The contents of the flasks were polymerized at
50 C for 22 hours. The results are given in Table III.
Example 13
100 g (1.175M) of 2-pyrrolidone was mixed with 3.85 g of 85.5% KOX
pellets (o.o588M) to form a 5 mol percent potassium pyrrolidonate solution
which was dehydrated by heating to incipient distillation at 2 mm pressure
for 10 minutes. To the dehydrated solution was added 30 mol % carbon dioxide
based on potassium. Then 0.12 g of acetic anhydride (0.1 mol percent based
3Q on total monomer) was added dropwise to the stirred polymeriza-te which was
_ g _
then polymerized for 8 hours at 50C. The product was chopped, washed,
dried, weighed and subjected to molecular weight determination. The results
are given in Table IV.
Example 14
Same as Example 13 but 6.~ g (o.o588M) of tetramethyl ammonium
chloride was added after carbonation to make a 5 mol ~ solution based on
total monomer. Then 0.12 g of acetic anhyaride was added. The remaining
procedure was as in Example 13.
The polymerization process of this invention produces a high mo-
lecular weight poly-2-pyrrolidone at a high rate of conversion without pro-
ducing the unpleasant odors which are sometimes associated with the dehydra-
tion of quaternary = onium hyaroxide-2-pyrrolidone mixtures. The combina-
tion of carbon dioxide polymeriza-tion activation and quaternary ammonium
halide as a source of polymerization catalyst produces extremely high mo-
lecular weight polypyrrolidone. The addition of about one mol percent acetic
anhydride has the additional effect of greatly accelerating the rate of
polymerization.
Table I shows several polymerizations in the presence of potassium
pyrrolidonate and carbon dioxide (Py-K/C02) with and without -tetramethyl am-
monium chloride. The tetramethyl or tetraethyl ammonium chloride in com-
blnation with carbon dioxide and potassium pyrrolidonate are found to be
capable of producing polypyrrolidone of an extremely high weight average
molecular weignt in excess of one million. All molecular weights are re-
ported as the weight average molecular weight determined from the specific
viscosity of 0.1 g of polymer/100 cc of m-cresol solution at 25 C. All
reported percentages are mol percent unless otherwise indicated.
-- 10 --
13L2:~87
TABLE I
8 hours % Py-K/CO~_ % (CH3)4NC1 % Conversion Mw x 10 3
Example la2 8.5 117
Example 2a5 0 16.3 2~5
Example 3a10 0 14.4 305
Example 4a2 2 15.0 210
Example 5a5 5 40.0 575
Example 6a10 10 53.9 g80
22 hours
Example lb2 0 20.1 220
Example 2b5 0 45.2 380
Example 3b10 0 48.3 500
Example 4b2 2 37.7 330
Example 5b5 5 69.1 1050
Example 6b10 10 59.4 820
50C 230 mol % C02 based on K-
TABLE II
Mol Ratio
% (CH3~ NCl (CH3~ NCl/K % Conversion M~ x 10 3
Example 2b 0 -- 45.2 380
Example 7 1.5 0.3 62.9 555
Example 8 3 o.6 68.7 635
Example 5b 5 1.0 69.1 1050
Example 9 7.7 1.5 69.2 605
22 hours, 50C, 5 mol % Py-K/C02 (30 mol% C02 based on K)
TABLE III
Carbonated Ammonium
Pyrrolidonate. 5% Halide, 5% % Con~ersion Mw x 10 3
Example 2b Py-K/C021 L~5.2 380
Example 5b 2 tCH3)4NC1 69.1 1050
Example 10 Py-Na/C02 o 34.8 2g5
Example 11 n ( CH ) NCl 48.5 380
Example 12 " ( ~ L~ 67.4 385
2From KOH, 50C, 22 hours, 30 mol % C02 based on K
From Na-alkoxide, 50 C, 22 hours, 30 mol % C02 based on Na
TABLE IV
%(CH3~ ~Cl ~oAC201 % Convers _n
Example 2a 0 0 16
Example 13 0 0.1 47
Example 5a 5 0 40
Example 14 5 0.1 76
Acetic anhydride, mol%
8 hours at 50C, 5 mol% Py-K/C02 (30 mol % C02 based on K)
~L~ZZS~7
The examples of Table I show the remarkably high weight average
molecular weights obtainable from the catalyst system of the present inven-
tion with good conversions of monomer to poly-2-pyrrolidone in remarkably
short times for these molecular weights in this reaction. Percent conver-
sion is calculated as lOO x (weight of polymer)/(weight of total 2-pyyrol-
idone) and total 2-pyrrolidone has been defined heretofore.
The examples of Table ~I show the effect of mol ratio of alkali
metal, e.g., potassium hydroxide, to tetra~yl ammonium halide. The highest
molecular weights are believed to be achieved at about equimolar amounts
(equivalent amounts) of the alkali metal pyrrolidonate and the tetraalkyl
ammonium halide.
Table III shows the effect of an anhydrous source of alkali me-tal
vs. a water-forming source, i.e., alkali metal hydroxide which reacts with
2-pyrrolidone to produce water, with and without 5 mol percent of the spec-
ified halide. In general~ the hydroxide is a very satisfactory source of
alkali metal for this catalyst system.
Table IV shows the remarkable effect produced on the rate of poly-
merization by the addition of a small amount of acetic anhydride to this
catalyst system. 76% conversion is achievable after only 8 hours at 50 C,
giving a product having a molecular weight of 175,000.
TABEE V
~AC20 ~o(CH~MCl % Conversion4 Mw x 10 3
Example 152 o O 4.1 35
Example 163 0 5 35-4 165
Example 173 o.6 5 48.2 150
Example 18 1.11 5 75.7 56
2Mol percent acetic anhydride
10 mol percent KOH (K-pyrrolidonate), no CO2
45 mol percentO KOH (K-pyrrolidonate), no CO2
22 hours, 5O C
Table V shows the effect of omitting CO2 from -the catalyst system.
~olecular weights are found to be lowered. While the addi-tion of acetic an-
hydride gives high conversion at 22 hours the average molecular weight in the
- 12 -
:1~2ZS~37
absence of carbon dioxide is still lowered.
TABLE VI
Ammonium Salt % Conversion Mw x 10 3
_ _ _ 32.9 39
(CH3)4~C1 69.1 1050
(CH3)4NBr 35.0 4ZO
(CH ) NI 33 380
(C ~ 5~4~C1 73.2 1025
(C2H )~Br 51.6 610
(C2H5)~NI 33 390
(C2H5) (~CH2)NC1 63.9 880
(C2H )3~CH2)~Br l~9.1 510
(C~H5) ~I 23.9 l~10
(CH3~ ~CH CH20H)NC1 17.9 95
(CH )33H~C~
H ~ ~1
In mol ratio ammonium salt/K = 1-0.77,
5 mol% KOH (K-pyrrolidonate), 1.5 mol % C02,
2based on total 2-pyrrolidone.
22 hours at 50C
Table VI shows the results obtained with a variety of ammonium
halides used in combination with potassium pyrrolidonate and carbon dioxide
to form the catalyst of the present invention. The results include remark-
ably high molecular weights for poly-2-pyrrolidone.
Example 19
200 g o~ purified 2-pyrrolidone (2.3 mols) was contacted with 7.7
g of KOH pellets (0.117 mol, 85.5% KOH) in a stirred reactor vessel and the
mixture heated to incipient distillation ~mder reduced pressure at a temper-
ature of about 115 C. The mixture was cooled and a calibrated amount of car-
bon dioxide was introduced to produce a polymerizate containing 30 mol per-
cent carbon dioxide based on potassiu~. About 10 g of the polymerizate was
poured into each of several successive polyethylene bottles, 3 of w~ich con-
tained 6 millimols of the dried onium salts shown in Table VII. The bottles
were shaken well and held at 50 C for 22 hours. The polymer was then re-
moved, washed, dried and weighed. The molecular weight was determined as
described elsewhere. The results are given in Table VII.
- 13 -
~ 25~37
Example 20
The process of the present invention was tested in another example
otherwise duplicative of Example 19. 50 g of purified 2-pyrrolidone was
contacted with 1.93 g of KOH pelle-ts (85.5% KOH) in a stirred reaction ves-
sel and the mixture was heated to incipient distillation under reduced pres~
sure at a temperature of about 110C. The mixture was cooled and a calibrat-
ed amount of carbon dioxide was introduced to produce a polymerizate com-
prising 30 mol percent carbon dioxide based on potassium. 1.5 millimols of
the previously dried tetrame-thylammonium acetate was weighed into a poly-
ethylene bottle and 10 g of polymerizate was added to it. The bottle wasshaken well and polymerized at 50 C for 22 hours. The product was worked up
a~ described in Example 19. The results are given in Table VII.
TABLE VII
Comparative Polymeriz~tion Results
Mol Ratio % Con~
Example Onium Salt K/Onium Salt version Mw x 10 3
19 ~one --- L~o5
(CH ) ~+OCOCH ~ 1.2 56 720
19 ( 3)4 Cl 4 1 31 400
19 (CH3)4~ BF4 1.1 35 ~15
19 ~ 3)L~ 6 1 33 405
5 mol percent potassium pyrrolidonate from KOH.
30 mol percent C02 based onO K.
Polymerized 22 hours at 50 C.
Table VII shows comparative polymerizations in the presence of
potassium pyrrolidonate and carbon dioxide with and without tetramethyl
ammonium acetate. The tetraalkyl ammonium carboxylate in combination with
carbon dioxide and potassium pyrrolidonate is found to be capable of produc-
ing polypyrrolidone of extremely high weight average molecular weight.
- 14 -
