Note: Descriptions are shown in the official language in which they were submitted.
:~2~37~1~
This invention relates to an improved process
for producing an acrylamide-type cationic polymeric
flocculant.
Acrylamide polymers find many applications, for
example as paper processing resins, fiber treating agents,
polymeric flocculants and oil recovery additives, because
of their good water-solubility and high molecular weights.
Particularly in Jap n, these polymers are extensively used
as paper processing resins and polymeric flocculants. For
use as paper processing resins, polymers which have a
relatively low molecular weight of, for example, several
hundred thousand can be used, but polymers used as polymeric
flocculants are usually required to have a molecular weight
of as high as several million or more. Recently, acrylamide
polymers having a super high molecular weight of more than
ten million have come into production.
Acrylamide-type polymeric flocculants are Toughly
classified into nonionic polymeric flocculants obtained by
using acrylamide alone as a monomer, anionic polymeric
flocculants obtained by partial hydrolysis of the amide
l33~
~,~
3 ~2237~
group of nonionic acrylamide polymers or by copolymerizing
acrylamide with an anionic monomer such as acrylic acid,
and cationic polymeric flocculants obtained by copolymeri-
zation of acrylamide with a cationic monomer such as
methacryloyloxyethyl trimethyl ammonium chloride.
The nonionic and anionic polymeric flocculants
are used mainly as sedimentation promoters in treating
general waste water, pulp spent liquors, mine waste water,
etc , whereas the principal use of the cationic polymeric
flocculants are as dehydrating aids in dehydrating organic
active sludge generate~ by sewage treatment, treatmellt oE
excre~cnt, treatment o waste water from disposal o~ :Eood
wastes, etc.
With the widespread practice of a high level of
waste water treatment and the widespread establishment of
sewerage, the amount of organic active sludge discharged
has increased year by year, and the amounts of acrylamlde-
type polymeric -floccula~nts, particularly cationic polymeric
-flocculants, used for the above purpose have greatly
increased. Since an increase in the ratio of dehydration
of organic active sludge permits a decrease in the amount
of heavy oil used in incinerating.the sludge and makes it
easy to handle the sludge in reclamation thereof, it has
been desired to develop cationic polymeric flocculants
having higher perormance.
Acrylamide a main raw material ~or acrylamide-
type polymer.ic flocculants has recently become producible
` ' ' ,
4 ~ ~37~
relatively easily by catalytic hydration of acrylonitrile
with water in the presence of a metallic copper catalyst
in a neutral region of pH 4 to 10, more generally 6 to 9
instead of the conventional sulfuric acid method which
involves hydration of acrylonitrile under strong acidity
with a pH of 1 or less.
The present inventors found that acrylamide
obtained by the catalytic hydrating method can be used with
good results as a raw material for nonionic or anionic
acrylamide polymers not only for production of relatively
low-molecular-weight polymers useful as paper processing
resins but also for production of nonionic or anionic
polymeric flocculants having super high molecular weights,
and that as a raw material for cationic polymers, the above
acrylamide may be-used satisfactorily for production of
polymers having such low molecular weights às to be suitable
for use~as paper processing resins, but when the above
acrylamide used to produce cationic polymeric floccuiants
having high molecular weights, the products have very poor
solubility in water and in an extreme case, they only become
swollen with water and dissolve hardly at all. Consequently,
the present inventors keenly recognized that this problem
sets a great restriction on the production of cationic
polymeric flocculants of high performance.
The present inventors assiduously investigated the
cause of the adverse effects of the above acrylamide on the
production of catiollic polymeric flocculants without any
5 ~ ~37~
deleterious effect on the production of nonionic and anionic
polymeric flocculants, and unexpectedly found that N-acryloyl
acrylamide present in acrylamide is a substance which causes
such adverse effects.
In U.S. Patent No. 3,130,~29~ formation o~ N-
acryloyl acrylamide during the hydration reaction of
acrylonitrile by the sulfuric acid method is presumed. In
this patent, however, the formation of N-acryloyl acrylamide
is merely presumed and not confirmed. The presence of an
acid and heat is considered to be essential for ~he formation
of N-acryloyl acrylamide. The N-acryloyl acrylamide in
acrylamide produced by this method, when considered from
its structure, is a difunctional crosslinkable impurity
like methylenebisacrylamide, and the present inventors
lS presume it to be one of the impurities which reduce the
water-solubility of nonionic polymeric flocculants having
a molecular weight of several million or more.
On the other hand, the formation of N-acryloyl
acrylamide in a neutral region of a pH 4-10, more generally
6 to 9, as in the catalytic hydration of acrylonitrile with
water in the presence of a metallic copper catalyst
contemplated in the present invention, has not been known.
The process of the invention is able to produce
acrylamide-type cationic polymeric flocculants which have high
molecular weights and excellent solubility in water and are
useful as dehydrating agents.
In accordance with the present invention, there is
- 6
provided a process for producing an acrylamide-type cationic
polymeric flocculant comprising polymerizing acrylamide
obtained by the catalytic hydration of acrylonitrile
with water in the presence of a metallic copper catalyst
at a pH of from 4 to 10, a temperature of from 50 to
150C and a pressure of from atmospheric pressure to
an elevated pressure of up to about 10 kg/cm2, charac-
terized in that, a crude aqueous acrylamide solution
obtained by the catalytic hydration is purified by treating
with either a single or combined method selected from
physical adsorption, reactive adsorption, decomposition
by a chemical reaction and solvent extraction, so that
the concentration of N-acryloyl acrylamide contained
in the acrylamide solution is not more than 3 ppm based
on the acrylamide contained therein, and then the acrylamide
solution is subjected to copolymerization of acrylamide
and a cationic monomer selected from the group consisting
of amino alcohol esters of methacrylic or acrylic acid,
N-aminoalkyl substitution products of methacrylamide
or acrylamide and the salts or quaternary ammonium salts
thereof in a mole ratio of from 90:10 to 50:50.
In the following disclosure, reference is made
to the accompanying drawings, in which:
Figure 1 is a graph showing the effect o-E the
dissolving temperature on the water-solubility of a cationic
polymeric flocculant prepared by using9 as a starting
material, acrylamide purified by recrystallization to which
N-acryloyl acrylamide has been added; and
- ~;237~Q
Figure 2 is a graph showing the effect of the
dissolving temperature on the water-solubility of a cationic
polymeric flocculant prepared by using, as a starting
ma~erial, acrylamide purified by crystallization to which
methylenebisacrylamide , a typical crosslinkable compound,
has been added.
In these graphs, the ordinate shows the weight
percent of a water-insoluble portion of the flocculant,
and the abscissa, the content in ppm of N-acryloyl
acrylamide based on the weight of acrylamide. The numerals
1, 2, 3 and 4 refer respectively to a dissolving temperature
of 20C, 50C~ 60C, and 70C.
lhe present inventors ascertained that N-acryloyl
acrylamide is present as an impurity in the aqueous
acrylamide solution obtained by catalytic hydration of
acrylonitrile with water in the presence of a metallic
copper catalyst, and conducted an experiment in which
N-acryloyl acrylamide was added to acrylamide fully
purified by a recrystallization method and being free from
N-acryloyl acrylamide, and a comparative experiment in
which methylenebisacrylamide was added to the purified
acrylamide. The results are shown in Reference examples 1 an
2 below. ~hese results demonstrate that N-acryloyl
acrylamide, quite different from a typical crosslinkable
compound such as methylenebisacrylamide~ exerts no adverse
effects on the water-solubility of nonionic and anionic
polymeric flocculants, but that it exerts the same degree
of deleterious effects on the water-solubility of cationic
polymeric flocculants as does methylenebisacrylamide even
when its content is extremely small. It has also been
~Z~ 7~C~
- 8
ascertained that as shown in Examples given hereinbelow,
there is a very strong correlation between the degree of
poorness of the water-solubility of an acrylamide polymer
and the content of N-acryloyl acrylamide.
A comparison between Figu~,res 1 and 2 shows that
N-acryloyl acrylamide and methylenebisacrylamide behave
~uite differently toward the dissolving temperature. This
fact suggests that the mechanism of reduction of water
solubility by N-acryloyl acrylamide differs from that by
methylenebisacrylamide, a typical crosslinkable compound.
The present inventors ,selected acrylamides which
can be used without any problem in the production of
nonionic and anionic polymeric flocculants from those
acrylamides which were produced by the catalytic hydrating
method and had verious manufacturing histories, and
produced cationic polymeric flocculants from the selected
acrylamides. From the dissolving temperatures and water
solubility, they determined a correlation between thè
presumed content and analytical content of N-acryloyl
acrylamide using Figure 1. The results show that these
content values show a very good agreement, and the content
of N-acryloyl acrylamide greatly affects the water-solubility
o'f cationic polymeric flocculants.
It is presumed from the foregoing facts that N-
acryloyl acrylamide does not adversely affect the water
solubility of nonionic and anionic polymeric flocculants,
but causes a reduction in the water solubility of cationic
:3~2~23~
g
polymeric flocculants.
The present invention is described below in more
detail.
The aqueous crude acrylamide solution used in
this invention is obtained by catalytic hydration of
acrylonitrile with water in the presence of a metallic
copper catalyst at a pH in the range of from 4 to 10, more
generally from 6 to 9. Various metallic copper catalysts
have been proposed for use in the production of acrylamide,
and any of these can be used in the present invention.
They may, for example, be metallic copper or catalysts
containing metallic copper. Specific examples are given
below.
(1) A combination of a copper ion and copper
in the form of wire, powder, etc.
(2) Reduced copper obtained by reducing a copper
compound such as copper oxide, copper hydroxide or copper
salts with hydrogen, carbon monoxide, etc. at a high tem-
perature of, for example, 100 to 400C.
(3) Reduced copper obtained by reducing a copper
compound such as copper oxide, copper hydroxide or copper
salts in the liquid phase with a reducing agent such as
hydrazine, an alkali or alkaline earth metal borohydride
compound, or formaldehyde.
(4) Reduced copper obtained by treating a copper
compound such as copper oxide, copper hydroxide or copper
salts in the liquid phase with a metal having a greater
237~
- 10 -
ionizing tendency than copper, such as zinc, aluminum, iron
or tin.
(5) Raney copper obtained by leaching a Raney
alloy composed of copper and aluminum, zinc or magnesium.
(6) Metallic copper obtained by thermally
decompos-ing an organic copper compound such as copper
formate or copper oxalate at a temperature of~ for example,
100 to 400C.
(7) A thermal decomposition product of copper
hydride.
These copper-containing catalysts may contain
metals other than copper, such as chromiwn or molybdenum,
which are normally used, as well as usually employed
carriers.
The reaction between acrylonitrile and water in
the presence of the aforesaid copper-containing catalyst
is usually carried out in the liquid phase by using water
in an almost arbitrary amount, preferably at least 4 moles,
based on acrylonitrile at a temperature o:E 50 to 150C,
preferably 80 to 140C, under atmospheric pressure or an
elevated pressure which does not cause boiling of water
and acrylonitrile, for example up to about 10 kg/cm in a
suspended or fixed catalyst bed in accordance with a
continuous or batchwise reaction mode. The reaction is
carried out while avoiding contact of the reactants and
the copper-containing catalyst with oxygen or an oxygen-
containing gas.
:~Z~23~
- 11 -
The reaction is per-formed at a pH in the range
of from 4 to 10, more generally from 6 to 9. If the pH
is below 4, the rate of the reaction is slow~ and if the
pH is above 10, side-reactions such as hydrolysis of the
resulting acrylamide or the formation of nitrilo compounds
take place noticeably and the yield of the desired product
decreases. Hence, pH values outside the specified range
are undesirable.
The resul-ting aqueous solution of crude acrylamide
is then usually subjected to a distillation operation in
order to remove unreacted acrylonitrile from the solution
or concentrate the solution so as to obtain an aqueous
acrylamide solution having a concentration of, for example,
about 30 to 50% by weight. The aqueous solution of crude
acrylamide, optionally concentrated as above, is then
tTeated on an ion-exchange resin in order to remove
impurities normally present, such as copper ions, or acrylic
acid which is the hydrolysis product.
In the process of this invention, the amount of
N-acryloyl acrylamide contained in the aqueous solution of
acrylamide can always be controlled with good accuracy
depending upon the desired acrylamide polymer to be produced.
Methods avai]able for removing N-acryloyl acrylamide from
the aqueous solution of acrylamide include, for example,
physical adsorption by activated caTbon, activated clay,
etc.; reactive adsorption by a compound containing primary
and secondary amines such as polyamines, a weakly basic
~L~2~7~
- 12 -
anion exchange resin containing primary and secondary
amino groups, or a compound having a peptide linkage such
as a protein (e.g., silk) or its disintegration product;
decomposition by a chemical reaction such as alkaline
hydrolysis, or oxidation; extraction with a solvent such
as chloroform or carbon tetrachloride; and sublimation
which is normally employed in the art. Alternatively, it
is possible to add a compound capable of forming an adduct
with N-acryloyl acrylamide, thereby rendering the latter
non-deleterious.
These methods can be used either singly or in a
combination of two or more. Although some of these methods
are known as a method for purifying an aqueous solution of
acrylamide obtained by the catalytic hydrating method, the
content of N-acryloyl acrylamide cannot be reduced, under
the purifying conditions in the prior art, to below the
- - permissible amount specified in the process of this invention.
-Since the amount of N-acryloyl acrylamide contained in the
aqueous solution of crude acrylamide differs depending upon
the reaction conditions, the purifying conditions should
always be analy~ed, quantified and controlled in order to
adjust the content of N-acryloyl acrylamide in the purified
acrylamide to below ~he permissible value specified in the
process of the invention.
The present inventors have found that the amount
of N-acryloyl acrylamide in the aqueous solution of crude
acrylamide increases as the concentration of acrylonitrile
- 13 ~ 37~
in the reaction system and the reaction temperature increase,
and the use of such conditions can easily lead to the
formation of an aqueous solution of acrylamide unsuitable
for use as a raw material for cationic polymeric flocculants.
The amount of N-acryloyl acrylamide in the acrylamide which
is permissible in the production of cationic polymeric
flocculants is not more than 10 ppm, preferably not more
than 5 ppm, more preferably not more than 1 ppm. Accord-
ingly, in the present application, the "acrylamide sub-
stantially free from N-acryloyl acry~amide", denotes
acrylamide containing not more than 10 ppm of N-acryloyl
acrylamide.
The aqueous acrylamide solution so purified is
then polymerized in a customary manner to give acrylamide-
type cationic polymeric flocculants.
In the production of acrylamide polymers in
accordance with this invention, various known conventional
polymerization initiators can be used. Examples inciude
azo compounds such as azobisdimethylvaleronitrile, azobis
(sodium cyanovalerate), azobisisobutyronitrile and azobis-
aminopropane hydrochloride; organic peroxides such as
benzoyl peroxide, lauroyl peroxide and tertiary butyl
-hydroperoxide, and inorganic peroxides such as potassium
persulfate, sodium perbromate, ammonium persulfate and
hydrogen peroxide~
~ xamples of suitable reducing agents are inorganic
compounds such as ferrous sulfate, ferrous chloride, sodium
- 14
~2~3~
bisulfite, sodium metasulfite, sodium thiosulfate and
nitrite salts, and organic compounds such as dimethyl-
aniline, 3-dimethylaminopropionitrile and phenylhydrazine.
For production of a high-molecular-weight polymer
by the process of this invention, a mixture of acrylamide
and a cationic monomer copolymerizable with acrylamide is
used in a mole ratio of from 90:10 to 50:50. Examples
o~ the cationic comonomer are amino alcohol
esters of methacrylic or acrylic acid ~such as dimethyl-
aminoethyl methacrylate or diethylaminoethyl acrylate) and
the salts or quaternary ammonium salts thereof; and N-
aminoalkyl substitution products of methacrylamide or
acrylamide (such as N-methacryloyl-N', N'-dimethyl-1,3-
diaminopropane or N-acryloyl-N',N'-dimethyl-l,l-dimethyl-l,
lS 3-diaminopropane) and the salts or quaternary ammonium
salts thereof.
The following Referential Examples and Examples
illustrate the present invention further.
Referential Example 1
A 70~ aqueous solution of acrylamide was prepared
under heating from commercially available acrylamide
crystals and distilled water. The solution was cooled at
5C to precipitate acrylamide crystals. This recrylstal-
?5 lization procedure was repeated to obtain purified acrylamide.
To the purified acrylamide was added N-acryloyl acrylamide
in an amount of 1, 3, 6, 10, 20, 30, and 50 ppm respectively
based on the weight of the acrylamide. In accordance with
l~
~iL2~37a:~
- 15 -
the polymerization recipes shown below, high-molecular-
weight nonionic, anionic and cationic polymeric flocculants
were respectively produced, and tested for water solubility.
The results are shown in Table 1.
Non-ionic polymeric flocculants:
(A) Acrylamide was dissolved in distilled water
to a concentration of 20% by weight. Then, 500 g of the
aqueous solution was taken, and nitrogen gas was blown
therein to remove any dissolved oxygen present. At 30C,
~.8 mg of ammonium persulfate and 2.2 mg of sodiunl bisulfite
were added thereto, and the reaction was carried out while
allowing the temperature to rise by the heat of polymerization
and the polymerization to proceed by the effect of the tem-
perature rise. After arise in temperature was no longer
noted, the reaction mixture was allowed to stand further
for 1 hour to terminate the polymerization. Thus~ an agar-
like mass consisting of an acrylamide polymer and water was
obtained.
The agar-like mass was then coarsely crushed by
a mincer, dried in hot air at 1~0C for 1 hour, and pulver-
ized to form a powdery nonionic polymeric flocculant which
was found to have a molecular weight, calculated from its
intrinsic viscosity, of about 7 million.
(~) A nonionic polymeric flocculant having a
molecular weight of about 10 million was prepared by
operating in the same way as in (A) above except that the
~2~3'7~
- 16 -
amounts of ammonium persulfate and sodium bisulfite were
changed to 6.0 mg and 1.5 mg, respectively.
(C) A nonionic polymeric flocculant having a
molecular weight of about 13 million was prepared by
operating in the same way as in (A) above except that the
amounts of ammonium persulfate and sodium bisulfite were
changed to 3.5 mg and l.0 mg, respectively.
Anionic polymeric flocculant:
An aqueous solution of a mixkure of acrylamide
and sodium acrylate in a mole ratio of 80:20 in a monomer
concentration of 20% by weight was prepared by using
acrylamide, sodium acrylate and distilled water. Then,
500 g of the aqueous solution was taken, and nitrogen gas
was blown therein to remove any dissolved oxygen present.
At 30C, 60 mg of sodium 4,4'-azobis-4-cyanovalerate,
4.0 mg of ammonium persulfate and 2 mg of sodium bisulfite
were added. The mixture was then worked up in the same
way as in the preparation of the nonionic polymeric
flocculants to give an anionic polymeric flocculant having
a molecular weight of about 12 million.
Cationic polymeric flocculants:
(A) An aqueous solution of a mixture of acrylamide
and N-methacryloyl-N',N',N'-trimethyl-1,3-diaminopropane
chloride in a mole ratio of 90:10 in distilled water in a
monomer concentration of 20% by weight was prepared. The
pH of the solution was adju~ted to 5 0. Then, 500 g of the
~L~23~
- 17 -
aqueous solution was taken, and nitrogen gas was blown
therein to remove any dissolved oxygen present. At 30C,
100 mg of sodium 4,4'-azobis-4-cyanovalerate, 7.2 mg o-f
ammonium persulfate and 3.6 mg of sodium bisulfite were
added. The mixture was worked up in the same way as in
the preparation of the nonionic polymeric flocculants to
give a cationic polymeric flocculant A containing 0.11
cation equivalent/100 g.
(B) A solution of a mixture of acrylamide and
methacryloyloxyethyl trimethyl ammonium chloride in a mole
ratio o-f 50:50 or 85:15 in distilled water in a monomer
concentration of 20% by weight was prepared. The pH of
the solution was àdjusted to 5Ø Then, 500 g of the
aqueous solution was taken, and nitrogen gas was blown into
it to remove any dissolved oxygen present. At 30C, 100 mg
of sodium 4,4'-azobis-4-cyanovalerate, 7.2 mg o-f ammonium
persulfate and 3.6 mg of sodium bisulfate were added. The
mixture was worked up in the same way as in the preparation
of the nonionic polymeric flocculants. Thus, cationic
polymeric flocculants B ~ B' containing 0.36 cation
equivalent/100 g and 0.16 cation equivalent/lOOg, respectively,
were obtained.
Water solubility test:
One gram of the powdery polymer sample was added
to 1,000 g of distilled water, and the mixture was stirred
for 1 hour by a magnetic stirrer. The solution was then
~23~
- 18 -
filtered through a 200-mesh wire screen to separate and
collect a water-insoluble portion from the solution. The
water-insoluble portion was dried at 120C, and its amount
was measured.
Table 1
Amount of N-acryloyl acrylamide _
added ~ppm based on acrylamide) l l
1 1 3 l6 10 20 l30 50
Type of acrylamide polymeric ~ I ~
flocculant \ I l _ _
Nonionic polymeric flocculant l l l l l
l~molecular weight about IO~O IO O O i O O
,7 million) , I I ~ !
Ditto (molecular weight about O O O ~ O O O _
.itto (molecular weight about ~O ¦O ¦ O ¦
Anionic polymeric flocculant r i
~molecular weight about O O O O O I O O
12 million)
Cationic polymeric flocculant A _
(cation equivalent: O O! O Q X I X X
0.11 eq./100 g) ~ 1, , `
iDitto B ~cation equivalent: i l _
0.36 eq./100 g) ,O I O, a I x I x x I x
~Ditto B' ~cation equivalent: io I a I x x x x I x
1 0.16 eq./100 g) ~
.
In the above table, the evaluation of water
solubility is as follows:
o : the amount of the water-insoluble portion is less
than 0.2%
a the amount of the water-insoluble portion is 0.2-2.0%.
X : the amount of the water-insoluble portion is more
than 2.0%.
- 1 9 ~ 37
Referential ~xample _
Methylenebisacrylamide was added in a weight of
1, 1.5, 3, 6, and 10 ppm respectively based on acrylamide
to pure acrylamide obtained in the same way as in Referential
Example 1. Using the resulting polymeric flocculant, the
same water-solubility test as in Referential Example 1 was
conducted. The results are shown in Table 2.
Table 2
Amount of methylenebis acrylamide
added (ppm based on acrylamide)
~ 0.6 1.5 3 6 10
Type of acrylamide polymeric \
flocculant \ !
Nonionic polymeric flocculant
(molecular weight aboutO O ~ IX X
7 million)
. _ _ j .
Ditto ~molecular weight about O O I a x I x
10 million) l
Ditto ~molecular weight about O I ~ X IX X
13 million)
_
Anionic polymeric flocculant . I
~molecular weight about . O O X 'IX X .
12 million)
.
Cationic polymeric flocculant A l
~cation equivalent: O O X X X
0.11 eq./100 g) l
. Ditto B ~cation equivalent: ¦I o l~ X i X
¦ 0.36 eq./100 g) ¦ O l ~ I
0.16 eq./100 g) ¦ O O ~ X ¦ X
-
The evaluation of the water-solubility was done
in accordance with the same standards as given in the
footnote to Table 1.
- 20 - ~2
Example 1
Production of an aqueous solution of crude acrylamide:
A reactor was charged with 70 parts by weight of
Raney copper and 1,000 parts of an aqueous solution of
acrylonitrile in a concentration of 25% by weight, and
the reaction was carried out at 135C for 4 hours at a pH
of 7 to 9. The catalyst was removed from the resulting
reaction solution by filtration, and the residue was passed
through a vacuum-distillation device to remove the unreacted
acrylonitrile and a part of water to give a 50% by weight
aqueous solution of acrylamide. The crude aqueous
acrylamide solution contained less than 300 ppm of acrylo-
nitrile and less than 80 ppm of copper.
Purification of the aqueous acrylamide solution:
Glass columns A, B and C each having an inside
diameter of 20 mm and a lèn~th of 50 cm were provided,
and the aqueous acrylamide solution was purified by ~he
following method.
~ 1~ One hundred milliliters of a strongly acidic
cation exchange resin (Amberlite IR-120B, a tradename for
a product of Rohm ~ Haas Co.) was filled in the column A
and maintained in H form. The column B was filled with
100 ml of a strongly basic anion exchange resin ~Diaion
PA316, a tradename for a~product of Mitsubishi Chemical
Industries, Ltd.), and the resin was maintained in carbonate
salt form. The two columns were connected in series in the
- 21 - ~ ~Z37~0
order A-B. The aqueous crude acrylamide solution was
passed through the columns ~t room temperature and an SV
of 2 (200 ml/hr), and f~actions formed during 3 to 7 hours
~l-a), 12 to 16 hours (l-b) and 26 to 30 hours ~l-c) after
the starting of passing the solution were collected and
offered for use in the production of polymers and the
analysis of the N-acryloyl acrylamide content.
~ 2) One hundred milliliters of a strongly acidic
cation exchange resin (Amberlite IR-120B) was filled in the
column A and maintained in H form. One hundred milliliters
of a weakly basic anion exchange resin (Lewatit MP-62, a
tradename for a product of Bayer AG) was filled in the
column B and maintained in free form. The two columns were
connected in series in the order A-B. The above aqueous
solution of crude acrylamide was aerated by blowing air
into it at room temperature, and then the acrylamide
solution was passed through the columns A and B. Fractions
formed during 3 to 7 hours ~2-a), 21 to 25 hours (2-b) and
31 to 35 hours ~2-c) after the starting of passing the
.
solution were collected and used for the production of
polymers and the analysis of the N-acryloyl acrylamide
content.
(3) The column C was fil~ed with 100 ml of
-activated carbon (Filtrasoap F~00, a tradename for a product
of Calgon, Inc.), and fully washed with water. The columns
A and B were filled with the same ion exchange resins as
in (2) above. The three columns A, B and C were connected
37~13
- 22 -
in series in the order A-B-C. The aforesaid aqueous solution
of acrylamide was passed through the columns A, B, and C
at room temperature and an SV of 2 (200 ml/hr), and
fractions formed during 4 to 8 hours (3-a), 15 to 19 hours
(3-b) and 24 to 28 hours (3-c~ after the starting of passing
the solution were collected and used for the production of
polymers and the analysis of the N-acryloyl acrylamide
content.
(4) An aqueous solution of acrylamide obtained
by the same treatment as in (2) above was heated to 40C,
and an aqueous solution of sodium hydroxide was added while
blowing air into it to adjust the pH of the solution to 12.8.
Subsequently, the solution was allowed to stand at 40C
while blowing air therein for 10 minutes (4-a). Then, dilute
sulfuric acid was added to adjust the pH of the solution to
7Ø The resulting acrylamide solution was used for the
production of polymers and the analysis of the N-acryloyl
acrylamide content.
(5) One hundred milliliters of a weakly basic
.
anion exchange resin having secondary amino groups ~Diaion
WA-20, a tradename for a product of Mitsubishi Chemical
Industries, Ltd.) was charged in column C and the anion
exchange resin was formed in free form. An aqueous solution
of acrylamide obtained by the same treatment as in (2) was
passed through the column C at room temperature and an S~
of 2 (200 ml/hour). Fractions formed during 1 to 5 hours
(5-a), 11 to 15 hours (5-b) and 26 to 30 hours (5-c) after
~223~
- 23 -
the starting of passing the solution were collected and
offered for use in the production of polymers and the
analysis of the N-acryloyl acrylamide content.
(6) Five hundred parts by weight of an aqueous
solution of acrylamide obtained by the same treatment as
in (2) above was washed with 100 parts of chloroform (6-a)
or 100 parts of carbon tetrachloride (6-b), and then
offered for use in the production of polymers and the
analysis of the N-acryloyl acrylamide content.
(7) One hundred milliliters of a strongly acidic
cation exchange resin, Amberlite IR-120B, maintained in
H form, and 100 ml of a strongly basic anion exchange resin
Diaion PA316 maintained in a carbonate salt form were well
mixed, and the mixture was equally divided and filled in
the columns A and B. The columns were connected in series
in the order A-B. The aforesaid aqueous solution of crude
acrylamide was passed through the columns A and B at room
temperature and an SV of 2 (200 ml/hr). Fractions formed
during 3 to 7 hours (7-a), 12 to 16 hours (7-b) and 26 to
30 hours (7-c) after the starting of passing the solution
were collected, and offered for use in the production of
polymers and the analysis of the N-acryloyl acrylamide
content.
24 ~Z;~3~
Process for producing polymers and method for testing
water-solubility:
By the method described in Referential Example 1,
a polymer was prepared and the water-solubility of the
resulting polymer was tested.
Method for analysis of N-acryloyl acrylamide:
The acrylamide prepared in Referential Example 1
which contained a known amount of N-acryloyl acrylamide was
extracted with chloroform containing a predetermined amount
of dimethyl phthalate used as an internal standard. The
chloroform layer was separated and concentrated and a
calibration curve of N-acryloyl acrylamide was made using
gas chromatography. Using the calibration curve, the
content of N-acryloyl acrylamide in the above aqueous
solution of purified acrylamide was determined.
Table 3 summarizes the relation between the
content of N-acryloyl acrylamide in a polymer-and the water
solubility of the polymer.
- 2 5 - ~ 2~7~
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- 26 - ~2~3~
Referential Example 3
An attempt was made to produce nonionic, anionic
and cationic polymers using an aqueous solution of acrylamide
which was treated in the same way as in Example 1, (4)
except that the time during which the solution was allowed
to stand while blowing air at 40C was changed to 1 hour
(4-b) and 4 hours (4-c), respectively. But the rate of the
polymerization was so slow that the polymerization was not
completed.
Example 2
The same glass columns A, B and C as in Bxample 1
were pTovided. Column A was filled with 100 ml of a strongly
acidic cation exchange resin, Amberlite IR-120B, in an H
-form; column B, with 100 ml of a s~rongly basic anion
exchange resin, Diaion PA316, in an OH form, and column C,
with 100 ml of a weakly acidic cation exchange resin
(~ewatic CNP-80, a tradename for a product of Bayer AG) in
an H form. The three columns were connected in series in
the order A-B-C. The same aqueous solution of crude
acrylamide as used in Example 1 was passed through the
columns A, B and C at 18C and an SV of 2 (200 ml/hr).
Fractions formed during 3 to 7 hours (8-a), 21 to 25 hours
(8-b) and 41 to 45 hours (8-c) after starting the passing
of the solution were collected and analyzed for their content
of N-acryloyl acrylamide. The content of ~-acryloyl acryl-
amide was less than 0.5 ppm in all of these fractions.
- 27 ~237~
Seven types of polymers were produced from these
fractions in the same way as in Referential Example 1 and
were tested for water solubility. All of these polymers
were found to contain less than 0.2% of a water-insoluble
portion.
Example 3
The same glass columns A, B and C as used in
Example 1 and a glass column D having an inside diameter
of 23 mm and a length of 2 m were provided. The columns
A and B were each filled with 100 ml of a strongly acidic
cation exchange resin IR-120 B in an H form, and the column
C was filled with 100 ml o-f a weakly basic anion exchange
resin, Lewatit MP-62, in a -free form. The column D was
packed with strainless steel Raschig- rings. The four
columns were connected in series in the order A-D-B-C.
The same aqueous solution of crude acrylamide as used in
Example 1 was passed through the columns A, D, B and C at
20C and a~l SV of 200 ml/hr-. A small amount of sodium
hydroxide was continuously introduced from the inlet of
column D to maintain the aqueous acrylamide solution at
the inlet of column D at a pH of 12.5 to 12.8. Fractions
formed during 8 to 12 hours (9-a), 28 to 32 hours (9-b) and
48 to 52 hours (9-c) after the starting of the passing of
the solution were collected and analyzed for their content
of N-acryloyl acrylamide. In all of these frac-tions, the
content of N-acryloyl acrylamide was less than 0.5 ppm.
- 28 ~ 370~
Seven types of polymers were produced from the fractions
in the same way as in Referential Example 1, and tested
for water solubility. All of these polymers were found
to contain less than 0.2~ of a water-insoluble portion.
