Preparation of anionic and cationic polymers from 2-oxazolines

Anionic and cationic polymers are prepared by vinyl polymerizing a 2-alkenyloxazoline or 2-alkenyloxazine and reacting the resulting polymer which contains pendant oxazoline or oxazine moieties with a monobasic salt of sulfurous acid or a tertiary amine salt. Optionally, the 2-alkenyloxazoline or 2-alkenyloxazine can be polymerized with another ethylenically unsaturated monomer and/or a small amount of polyvinyl crosslinking monomer; and the resulting polymer is reacted with the desired salt to yield an anionic or cationic polymer.

BACKGROUND OF THE INVENTION 
This invention relates to a novel process for preparing anionic and 
cationic polymers. 
Cationic polymers are widely employed in water treatment, paper making, 
cosmetics, mineral processing and enhanced oil recovery. The polymers are 
generally prepared by the polymerization of quaternary ammonium monomers 
such as diallyldimethyl ammonium chloride, vinyl benzyl trimethyl ammonium 
chloride, methacryloylethyl trimethyl ammonium chloride, 
methacrylamidopropyl trimethyl ammonium chloride, and the like. 
Anionic polymers are widely employed as dispersants, friction reducers for 
aqueous fluids, flocculants, and in secondary oil recovery as viscosity 
modifiers. The polymers are generally prepared by the polymerization of 
monomers such as vinyl sulfonic acid, allyl sulfonic acid, 
2-acryloylamino-2,2-dimethylethane sulfonic acid, and the like, and the 
corresponding salts thereof. 
Cationic or anionic polymers are generally prepared using procedures such 
as aqueous phase polymerization as described by Schildknecht (II) in 
Polymer Process, Interscience, 191-194 (1956) or disperse aqueous phase 
polymerization as described by Vanderhoff et al. in U.S. Pat. No. 
3,284,393. The compositions of the polymers prepared by the aforementioned 
processes cannot be easily altered during the reaction process. For 
example, if one desires to employ various quaternary nitrogen substituents 
in a cationic polymer, it becomes necessary to copolymerize various 
monomers. 
In view of the deficiencies of the prior art, it would be highly desirable 
to provide a versatile and convenient process for producing anionic and 
cationic polymers. 
SUMMARY OF THE INVENTION 
In one aspect, the present invention is a process for preparing a polymer 
containing at least one pendant quaternary nitrogen atom wherein a 
2-alkenyloxazoline or a 2-alkenyloxazine is subjected to vinyl 
polymerization and the resulting polymer comprising a pendant 2-oxazoline 
or 2-oxazine functionality is reacted with at least one tertiary amine 
salt. 
In another aspect, the present invention is a process for preparing a 
polymer containing at least one pendant sulfonate moiety wherein a 
2-alkenyloxazoline or 2-alkenyloxazine is subjected to vinyl 
polymerization and the resulting polymer comprising a pendant 2-oxazoline 
or oxazine functionality is reacted with at least one monobasic salt of 
sulfurous acid. 
The process of this invention enables the skilled artisan to conveniently 
prepare a wide variety of anionic and cationic polymers. That is, this 
invention discloses a versatile process for preparing polymers having 
various anionic or cationic functionalities. The polymers prepared by the 
process disclosed herein are used in a wide variety of applications as is 
known in the art.

DETAILED DESCRIPTION OF THE INVENTION 
The 2-alkenyloxazoline or 2-alkenyloxazines of the present invention have 
the general formula: 
##STR1## 
wherein R is hydrogen or lower alkyl, and each of R.sup.1 -R.sup.4 is 
independently hydrogen, alkyl, aralkyl, phenyl or inertly substituted 
phenyl; and n is zero or one. Examples of suitable 2-alkenyloxazolines 
(i.e., oxazoline monomers) and 2-alkenyloxazines (i.e., oxazine monomers), 
and their methods of preparation are catalogued in U.S. Pat. Nos. 
3,505,297 and 4,144,211, which are incorporated herein by reference. 
Examples of preferred 2-alkenyloxazolines include 2-isopropenyloxazoline, 
2-vinyloxazoline, and 5-methyl-2-isopropenyloxazoline. 
Examples of monobasic salts of sulfurous acid include, for example, sodium 
bisulfite, potassium bisulfite, ammonium bisulfite, and the like. 
Examples of tertiary nitrogen compounds include, for example, acid salts of 
tributylamine, triethylamine, triethanolamine, pyridine, dimethyl aniline, 
and trimethylamine. These tertiary amine salts are readily prepared by 
mixing stoichiometric amounts of the tertiary amine with protonic acids 
such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, 
and the like. 
Optionally, at least one other ethylenically unsaturated monomer can be 
copolymerized with the oxazine or oxazoline monomers. For example, 
ethylenically unsaturated, water-soluble monomers can be copolymerized 
with the oxazine or oxazoline monomers. Suitable such monomers for use in 
the invention are those which are sufficiently water-soluble when 
dissolved in water and which readily undergo additional polymerization to 
form polymers which are at least inherently water-dispersible and 
preferably water-soluble. By "inherently water-dispersible" is meant that 
the polymer, when contacted with an aqueous medium, will disperse therein 
without the aid of surfactant to form a colloid dispersion of polymer in 
the aqueous medium. 
Examplary water-soluble monomers preferably include the nonionic monomers 
and those suitably employed in the practice of this invention are those 
ethylenically unsaturated monomers that are sufficiently water-soluble to 
form at least a 5 weight percent solution when dissolved in water and 
readily undergo addition polymerization to form polymers that are 
water-soluble. Examples of such nonionic monomers include ethylenically 
unsaturated amides such as acrylamide, methacrylamide and fumaramide; 
their water-soluble N-substituted nonionic derivatives such as the 
N-methylol derivatives of acrylamide and methacrylamide as well as the 
N-methyl and N,N-dimethyl derivatives of acrylamide and methacrylamide; 
hydroxyalkyl esters of unsaturated carboxylic acids such as hydroxyethyl 
acrylate and hydroxypropyl acrylate; and the like. Of the foregoing 
nonionic monomers, the ethylenically unsaturated amides are preferred, 
with acrylamide being especially preferred. The acrylamide can also 
undergo small amounts of hydrolysis after polymerization. 
Ethylenically unsaturated water-insoluble monomers can also be 
copolymerized with the oxazine or oxazoline monomers and with the 
aforementioned water-soluble monomers. These monomers are well known in 
the art and, hence, are illustrated below only by representative examples. 
The nonionic ethylenically unsaturated monomers are represented by, but 
not restricted to, hydrocarbon monomers such as the styrene compounds; the 
unsaturated alcohol esters such as vinyl acetate and vinyl propionate; the 
nonionic derivatives of ethylenically unsaturated carboxylic acids such as 
acrylic esters which include methyl acrylate, ethyl acrylate, butyl 
acrylate, hexyl acrylate, 2-ethylhexyl acrylate and lauryl acrylate; 
methacrylic esters, such as methyl methacrylate and ethyl methacrylate; 
the maleic esters; and the nitriles, such as acrylonitrile and 
methacrylonitrile. Nonionic monomers containing halogens which are not 
activated such as monochlorostyrene, dichlorostyrene, vinyl fluoride, 
chloroprene, vinyl chloride, vinylidene chloride, and the like, can be 
employed. 
It is also possible to polymerize an oxazine or oxazoline monomer, and/or 
the aforementioned water-soluble monomers, the water-insoluble monomers 
and a small amount (i.e., less than about 5 weight percent based on the 
weight of all monomers) of a polyvinyl crosslinking monomer. 
The amounts of water-soluble monomers, water-insoluble monomers and/or 
polyvinyl crosslinking monomers which are polymerized with the 
aforementioned oxazoline and oxazine monomers can vary, depending upon the 
polymer desired. 
The aforementioned oxazoline and oxazine polymers, copolymers and 
terpolymers are readily prepared by conventional procedures such as 
aqueous phase polymerization as described by Schildknecht (II) in Polymer 
Process, Interscience, 191-194 (1956) or disperse aqueous phase 
polymerization as described in U.S. Pat. Nos. 3,284,393 and 4,376,850. 
Normally, such polymerization is carried out in the presence of a 
polymerization initiator capable of generating free radicals. Preferably, 
this free radical initiator is employed in amounts from about 0.0001 to 
about 3 weight percent of initiator based on the monomers and depending on 
the type of initiator. Exemplary polymerization initiators include the 
inorganic persulfates such as potassium persulfate, ammonium persulfate 
and sodium persulfate, azo catalyst such as azobisisobutyronitrile and 
dimethyl azoisobutyrate; organic peroxygen compounds such as benzyl 
peroxide, t-butyl peroxide, diisopropylbenzene hydroperoxide and t-butyl 
hydroperoxide. Of these initiators, the azo catalyst is preferred. In 
addition to the aforementioned ingredients, the polymerization recipe 
optionally includes chain transfer agents such as isopropyl alcohol, 
chelating agents, buffers, salts and the like. 
The oxazoline or oxazine polymer, copolymer or terpolymer so prepared is 
dispersed in water or a water-miscible cosolvent and mixed with the 
tertiary amine salt or monobasic salt of sulfurous acid. It is understood 
that all of the oxazoline or oxazine portion of the polymer can be 
converted to the desired anionic (i.e., sulfonate) or cationic (i.e., 
quaternary ammonium salt) unit by mixing the polymer with an equivalent 
amount or a slight excess of the desired tertiary amine salt or monobasic 
salt of sulfurous acid, based on the amount of axazine or oxazoline units 
in the polymer. It is also understood that a portion of the oxazoline or 
oxazine units of the polymer can remain unreacted by reacting the 
resulting polymer with less than an equivalent amount of the desired 
tertiary amine salt or monobasic salt of sulfurous acid. The reactants can 
also be mixed in an organic solvent in which all of the reactants are 
soluble. Most advantageously, the temperature of the mixture is raised 
from about 75.degree. C. to about 120.degree. C. and heating is continued 
for about 1 to 50 hours, most preferably for about 20 to about 30 hours. 
The resulting product is then isolated using conventional means. 
The molecular weight of the polymers so prepared is not particularly 
critical and is dependent upon the method of preparation employed. Typical 
molecular weights can range from about 10,000 to several million. 
The following examples are given for the purpose of illustrating the 
present invention and are not to be construed as limiting its scope. 
Unless otherwise indicated, all parts and percentages are by weight. 
EXAMPLE 1 
A homopolymer of 2-acrylamido-ethane-1-sulfonic acid is prepared as 
follows. A homopolymer of 2-isopropenyloxazoline is prepared by a 
conventional free radical polymerization technique. An aqueous mixture of 
the polymer weighing 75 g (25 percent solids, 0.17 meq. of oxazoline) and 
16 g (84 mmoles) of sodium bisulfite is prepared in 50 ml of water. The 
mixture is heated on a steam bath for 2 hours and cooled to room 
temperature. The polymer is isolated by precipitation from methanol and 
dried in a vacuum oven at 50.degree.-60.degree. C. The recovered polymer 
weighs about 22 g. 
EXAMPLE 2 
A copolymer of acrylamide and 2-acrylamido-ethane-1-sulfonic acid is 
prepared as follows. A copolymer gel of acrylamide and 
isopropenyloxazoline is prepared by solution polymerization. The polymer 
is 83 percent acrylamide and 17 percent isopropenyloxazoline. An aqueous 
solution of copolymer (15 percent solids, 23 meq. of oxazoline) and 5.2 g 
(27 mmoles) of sodium bisulfite weighing 99 g is prepared in 10 ml of 
water. The final product is reacted and isolated as described in Example 
1. 
EXAMPLE 3 
A homopolymer of methacryloylethyl trimethyl ammonium chloride is prepared 
as follows. A homopolymer of 2-isopropenyloxazoline is prepared by a free 
radical polymerization technique. A 2.7 g aqueous mixture of the 
polyisopropenyloxazoline (25 percent solids, 6 meq. oxazoline) and 0.7 g 
(7 mmoles) of trimethylamine hydrochloride is mixed. The mixture is heated 
for 24 hours at 100.degree. C. in a sealed vial. The mixture is cooled to 
room temperature and the polymer is isolated by precipitation from 
acetonitrile. 
EXAMPLE 4 
A homopolymer of 2-isopropenyloxazoline is prepared by a conventional free 
radical polymerization technique. An aqueous mixture of the polymer 
weighing 5 g (25 percent solids, 10 meq. of oxazoline) and 1.5 g (0.01 
mol) of pyridine hydrochloride is mixed at room temperature. The mixture 
is heated for 17 hours at 100.degree. C. in a sealed vial, cooled to room 
temperature and the polymer is isolated by precipitation from 
acetonitrile. The polymer is dissolved in methanol, reprecipitated from 
tetrahydrofuran, and dried. The recovered polymer weighs about 0.8 g.