U.S. patent application number 13/861710 was filed with the patent office on 2013-10-17 for new cationic polymers.
This patent application is currently assigned to BASF SE. The applicant listed for this patent is BASF SE. Invention is credited to Stefan Friedrich, Gregor Herth, Pierre-Eric MILLARD.
Application Number | 20130274369 13/861710 |
Document ID | / |
Family ID | 49325650 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130274369 |
Kind Code |
A1 |
MILLARD; Pierre-Eric ; et
al. |
October 17, 2013 |
NEW CATIONIC POLYMERS
Abstract
New water soluble cationic copolymers derived from N-vinyl amide
monomers and ethylenically unsaturated compounds bearing cationic
groups.
Inventors: |
MILLARD; Pierre-Eric;
(Altenmarkt, DE) ; Herth; Gregor; (Trostberg,
DE) ; Friedrich; Stefan; (Garching, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BASF SE |
Ludwigshafen |
|
DE |
|
|
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
49325650 |
Appl. No.: |
13/861710 |
Filed: |
April 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61623596 |
Apr 13, 2012 |
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Current U.S.
Class: |
522/175 ;
526/307.3 |
Current CPC
Class: |
C08F 226/04 20130101;
C08F 222/38 20130101; C08F 226/02 20130101; C08F 220/34
20130101 |
Class at
Publication: |
522/175 ;
526/307.3 |
International
Class: |
C08F 222/38 20060101
C08F222/38 |
Claims
1. A copolymer P comprising in polymerized form, a) at least one
compound of formula I ##STR00026## wherein R.sup.1 and R.sup.2 are
independently H or C.sub.1, C.sub.2 or C.sub.3 alkyl, and b) at
least one compound of formula II ##STR00027## wherein R.sup.3 is H
or C.sub.1, C.sub.2 or C.sub.3 alkyl, Y is ##STR00028## R.sup.4 is
an aliphatic or cycloaliphatic or aromatic group bearing a positive
charge, R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3
alkyl, and X.sup.- is an anion, wherein a molar ratio of components
a) to b) is 5:95 to 45:65.
2. A copolymer P comprising, in polymerized form, a) at least one
compound of formula I ##STR00029## wherein R.sup.1 and R.sup.2 are
independently H or C.sub.1, C.sub.2 or C.sub.3 alkyl, and b) at
least one compound of formula II ##STR00030## wherein R.sup.3 is H
or C.sub.1, C.sub.2 or C.sub.3 alkyl, Y is ##STR00031## R.sup.4 is
an aliphatic or cycloaliphatic or aromatic group bearing a positive
charge, R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3
alkyl, and X.sup.- is an anion, wherein a molar ratio of components
a) to b) is 5:95 to 80:20, and wherein the copolymer P has an
average molecular weight Mw of 5,000,000 to 100,000,000.
3. A copolymer P comprising, in polymerized form, a) at least one
compound of formula I ##STR00032## wherein R.sup.1 and R.sup.2 are
independently H or C.sub.1, C.sub.2 or C.sub.3 alkyl, and b) at
least one compound of formula II ##STR00033## wherein R.sup.3 is H
or C.sub.1, C.sub.2 or C.sub.3 alkyl, Y is ##STR00034## R.sup.4 is
an aliphatic or cycloaliphatic or aromatic group bearing a positive
charge, R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3
alkyl, and X.sup.- is an anion, wherein a molar ratio of components
a) to b) is 5:95 to 80:20, and wherein said copolymer P has an
intrinsic viscosity of 3 to 30 dl/g.
4. The copolymer according to claim 1, wherein component b)
comprises a quaternary ammonium group.
5. The copolymer according to claim 1, wherein component b) is an
ester or an amide of acrylic acid or methacrylic acid.
6. The copolymer according to claim 1, wherein component b) is
##STR00035## wherein R.sup.3 is H or C.sub.1, C.sub.2 or C.sub.3
alkyl, R.sup.5, R.sup.6 and R.sup.7 are independently C.sub.1 to
C.sub.3 alkyl, n is a number from 1 to 8, and X.sup.- is an
anion.
7. The copolymer according to claim 1, wherein component a) is
vinylformamide.
8. A process for manufacturing the copolymer P of claim 1,
comprising performing inverse emulsion polymerization, gel
polymerization or bead polymerization to obtain the copolymer
P.
9. The process of claim 8, wherein the polymerization is initiated
by at least one selected from the group consisting of a thermal
initiator, a redox initiator, UV irradiation and microwave
irradiation.
10. A copolymer HP comprising, in polymerized form: a) at least one
compound of formula I ##STR00036## wherein R.sup.1 and R.sup.2 are
independently H or C.sub.1, C.sub.2 or C.sub.3 alkyl, b) at least
one compound of formula II ##STR00037## wherein R.sup.3 is H or
C.sub.1, C.sub.2 or C.sub.3 alkyl, Y is ##STR00038## R.sup.4 is an
aliphatic or cycloaliphatic or aromatic group bearing a positive
charge, R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3
alkyl, X.sup.- is an anion, with the proviso that a total amount of
compounds in which Y is COOH does not exceed 80 molar % of a total
amount of compounds making up component b), and c) at least one
compound of formula III ##STR00039## wherein the copolymer has a
stoichiometric composition of A.sub.xB.sub.yC.sub.z, wherein A, B
and C represent components a), b) and c) in polymerized form, and
wherein a molar ratio of (x+z):y is from 5:95 to 45:65 and a molar
ratio of x:z is 0 to 100000.
11. A copolymer HP comprising in polymerized form: a) at least one
compound of formula I ##STR00040## wherein R.sup.1 and R.sup.2 are
independently H or C.sub.1, C.sub.2 or C.sub.3 alkyl, b) at least
one compound of formula II ##STR00041## wherein R.sup.3 is H or
C.sub.1, C.sub.2 or C.sub.3 alkyl, Y is ##STR00042## R.sup.4 is an
aliphatic or cycloaliphatic or aromatic group bearing a positive
charge, R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3
alkyl, X.sup.- is an anion, with the proviso that a total amount of
compounds in which Y is COOH does not exceed 80 molar % of a total
amount of compounds making up component b), and c) at least one
compound of formula III ##STR00043## wherein the copolymer has a
stoichiometric composition of A.sub.xB.sub.yC.sub.z, wherein A, B
and C represent components a), b) and c) in polymerized form, and
wherein a molar ratio of (x+z):y is from 5:95 to 80:20, a molar
ratio of x:z is 0 to 100000 and wherein the copolymer HP has an
average molecular weight of 5,000,000 to 100,000,000.
12. A process for manufacturing the copolymer HP of claim 10,
comprising partial or complete hydrolysis of a copolymer to obtain
the copolymer HP.
13. A flocculant comprising the copolymer of claim 1.
14. A drainage/retention aid or a flux enhancer comprising the
copolymer of claim 1.
15. The copolymer according to claim 2, wherein component b)
comprises a quaternary ammonium group.
16. The copolymer according to claim 3, wherein component b)
comprises a quaternary ammonium group.
17. The copolymer according to claim 2, wherein component b) is an
ester or an amide of acrylic acid or methacrylic acid.
18. The copolymer according to claim 3, wherein component b) is an
ester or an amide of acrylic acid or methacrylic acid.
19. The copolymer according to claim 2, wherein component b) is
##STR00044## wherein R.sup.3 is H or C.sub.1, C.sub.2 or C.sub.3
alkyl, R.sup.5, R.sup.6 and R.sup.7 are independently C.sub.1 to
C.sub.3 alkyl, n is a number from 1 to 8, and X.sup.- is an
anion.
20. The copolymer according to claim 3, wherein component b) is
##STR00045## wherein R.sup.3 is H or C.sub.1, C.sub.2 or C.sub.3
alkyl, R.sup.5, R.sup.6 and R.sup.7 are independently C.sub.1 to
C.sub.3 alkyl, n is a number from 1 to 8, and X.sup.- is an anion.
Description
[0001] This invention is related to new water soluble cationic
copolymers derived from N-vinyl amide monomers and ethylenically
unsaturated compounds bearing cationic groups. Another aspect of
the invention is a process for the preparation of such copolymers.
Another aspect of the invention relates to the use of such
copolymers as flocculants.
[0002] The flocculation of suspended matter in water to enhance the
clarification and purification of water is an important aspect of
industrial and municipal water treatment. Flocculation is the
agglomeration of coagulated colloidal and finely divided suspended
matter by physical mixing or chemical coagulant aids. Polymeric
organic coagulants such as cationic polyamines and high molecular
weight polyacrylamides have been used to aid flocculation and are
often used in combination with inorganic coagulants such as lime,
alum, ferric chloride, ferrous sulfate, ferric sulfate and sodium
aluminate.
[0003] Cationic copolymers are used in such applications as
flocculating agents. Conventionally known cationic polymers include
acrylamide-based copolymers ammonium salts of
dialkylaminoalkyl(meth)acrylates and Hofmann degradation or Mannich
reaction products of polyacrylamides.
[0004] A typical sewage treatment plant takes in raw sewage and
produces solids and clarified water. Typically the raw sewage is
treated in a primary sedimentation stage to form a primary sludge
and supernatant, the supernatant is subjected to biological
treatment and then a secondary sedimentation stage to form a
secondary sludge and clarified liquor, which is often subjected to
further treatment before discharge.
[0005] The sludges are usually combined to form a mixed sewage
sludge which is then dewatered to form a cake and a reject liquor.
The reject liquor is usually recycled to the head of the plant and
the start of the process, i.e., fed back to the primary
sedimentation stage or a preceding stage in the plant. Any water
which is required in the plant, for instance for dissolving
polymeric flocculant, is usually either potable water (from the
local drinking water supply) or is clarified water from the
secondary sedimentation stage, optionally after any subsequent
treatment procedures. It is standard practice to dewater the sludge
by mixing a dose of polymeric flocculant into that sludge at a
dosing point, and then substantially immediately subjecting the
sludge to the dewatering process and thereby forming a cake and a
reject liquor. The dewatering process may be centrifugation or may
be by processes such as filter pressing or belt pressing.
[0006] Another important application for cationic polymers is their
use as drainage and retention aids in the paper industry. Retention
is a term used in papermaking to denote the extent to which the
pulp fibers and other additives which are added to the furnish are
retained in the finished paper. The retention of pulp fibers,
fines, sizing agents, fillers and other additives in the paper
sheet during its formation in a paper making machine is an
important problem. A retention aid generally acts by increasing the
flocculating tendency of the pulp fibers and additives to inhibit
their loss during drainage through the paper machine wires or
screens.
[0007] Numerous factors affect the efficiency of retention aids
including 1) variables in the furnish such as pH, consistency,
temperature, type of pulp fiber (e.g., fiber length, degree of
refining, etc.), and white water recirculation (e.g. degree of
system closure), 2) conditions of the wire or screens such as wire
mesh size, machine speed, etc. and 3) factors relating to the
additives such as the dosage amount of additives, order of
additives, form, shape and density of particles and ionic
balance.
[0008] Drainage is another papermaking requirement that often
conflicts with retention, and requires a rapid reduction in water
content of an aqueous pulp suspension in the sheet forming areas of
a paper machine. Aqueous pulp suspensions contain more than 99%
water. To convert an agueous pulp suspension to a finished paper
sheet requires a rapid reduction in water content to a level of
about 6%. Drainage rates are dependent upon numerous factors
including the arrangement of the drainage elements in the paper
making machine, (e.g., arrangement of free drainage areas vis-a-vis
vacuum assistance area), characteristics of the wires, screens or
fabric, furnish characteristics (e.g. freeness, additives, etc.),
furnish thickness, temperature, furnish consistency and wire speed.
Suitable retention/drainage aids must not only inhibit the undue
loss of fibers and additives, but they must also promote rapid
drainage of water from the pulp suspension. Numerous
retention/drainage aids are known and are available to paper
makers.
[0009] EP 235 893 describes the use of a combination of organic,
substantially linear synthetic polyacrylamide copolymers and
bentonite to improve drainage/retention in papermaking.
[0010] U.S. Pat. No. 4,749,444 discloses a process for production
of paper and cardboard by adding to the paperstock a three
component mixture comprising an activated bentonite, a cationic
polyelectrolyte having a charge density not less than 4 mEq/g and a
high molecular weight acrylamide or methacrylamide copolymer having
an average molecular weight from 1 to 20 million.
[0011] U.S. Pat. No. 4,808,683 discloses copolymers containing
vinylamine, N-vinylformamide and N-monosubstituted or
N,N-disubstituted acrylamide for use as flocculating agents,
drainage aids and paper strength increasing agent.
[0012] U.S. Pat. No. 4,957,977 and U.S. Pat. No. 5,064,909 disclose
vinylamine containing copolymers by copolymerizing N-vinylformamide
and (meth)acrylonitrile and then hydrolyzing the resulting
copolymers with an acid. These copolymers are useful as
flocculating agents and paper strength increasing agents.
[0013] U.S. Pat. No. 5,037,927 discloses copolymers of
N-vinylformamide and alkyl(meth)acrylate and their hydrolyzed
products.
[0014] U.S. Pat. No. 7,084,205 discloses polymeric compositions for
dewatering sewage sludges.
[0015] WO 06/004745 discloses an inverse emulsion polymer having a
dispersed phase composed of an aqueous solution of an acrylic
polymer and a continuous phase composed of an ester of a fatty acid
and a water-soluble alcohol.
[0016] U.S. Pat. No. 5,225,088 discloses copolymers of
vinylformamide and N-substituted acrylamides or divinyldialkyl
ammonium salts, wherein vinylformamide is comprised in amounts
between 50 and 80 molar percent.
[0017] EP 821 704 discloses water soluble cationic copolymers
comprising a reaction product of N-vinylamides with diallyl
ammonium chloride derivatives or acrylic esters bearing an ammonium
groups or vinyl pyridine and their use as flocculants and drainage
retention aids.
[0018] Cationic polyacrylamide polymers used for waste water
treatment or in paper industry always contain some residual
monomeric acrylamide. While polymerized acrylamide is harmless,
N-unsubstituted acrylamide monomer (referred to as "acrylamide") is
highly toxic.
[0019] It was therefore an object of the invention to provide novel
copolymers that are free of acrylamide and that show good
performance as flocculating agents. In particular, it was an object
of the invention to provide copolymers that show improved
performance as flocculating agents for sludge dewatering in waste
water treatment.
[0020] It was another object of the invention to provide a method
for preparing novel copolymers described herein. Ideally such
processes should allow to make copolymers according to the
invention with high molecular weights and high intrinsic
viscosities.
[0021] To achieve the objectives of the invention, novel water
soluble cationic copolymers P have been found that comprise in the
form of polymerized units [0022] a) at least one vinylamide of the
general formula I
##STR00001##
[0022] wherein R.sup.1 and R.sup.2 are independently H, C.sub.1,
C.sub.2 or C.sub.3 alkyl, and [0023] b) at least one compound of
the general formula II
##STR00002##
[0023] wherein R.sup.3 is H or C.sub.1, C.sub.2 or C.sub.3 alkyl, Y
is
##STR00003##
[0024] R.sup.4 is an aliphatic, cycloaliphatic or aromatic rest
bearing a positive charge,
[0025] R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3
alkyl,
[0026] X.sup.- is an anion,
wherein the molar ratio of components a) to b) is 5:95 to
80:20.
[0027] Preferably, the molar ratio of components a) to b) is 5:95
to 45:65, more preferably 10:90 to 40:60 and particularly
preferably 15:85 to 30:70.
[0028] In a preferred embodiment, R.sup.1 is H.
[0029] In another preferred embodiment, R.sup.1 in CH.sub.3.
[0030] In another preferred embodiment, R.sup.2 is H or methyl.
[0031] Examples of preferred vinyl amides a) are N-vinyl formamide
(R.sup.1.dbd.R.sup.2.dbd.H) and N-vinyl acetic amide
(R.sup.1.dbd.H, R.sup.2.dbd.CH.sub.3).
[0032] Copolymer P may also comprise mixtures of different vinyl
amides a).
[0033] Compounds suitable as component b) carry a positive charge.
In a preferred embodiment, compounds suitable as component b) carry
a permanent positive charge. In a less preferred embodiment,
component b) is zwitterionic or are cationic only at low pH.
Normally, component b) comprises an anion X.sup.- that can for
example be selected from pseudo halides or halides like Cl.sup.-,
Br or I.sup.-; hydroxide, sulfates, carboxylates or alkylsulfonates
like C.sub.1-C.sub.3 alkyl sulfonates. In a preferred embodiment,
anions X.sup.- are selected from Cl.sup.-, OH.sup.- or
alkylsulfonates like CH.sub.3SO.sub.4.sup.-.
[0034] Preferably, component b) bears a quarternary ammonium group
or a pyridinium group. In a preferred embodiment, R.sup.3 is H or
CH.sub.3. More preferably, R.sup.3 is H.
[0035] Preferably, component b) is a derivative of (meth)acrylic
acid bearing cationic groups or a quaternized vinyl pyridine.
[0036] In a preferred embodiment, component b) is an ester or an
amide of acrylic acid or methacrylic acid or a vinylpyridinium
salt. In a particularly preferred embodiment, component b) is an
ester of acrylic acid or methacrylic acid or a vinylpyridinium
salt.
[0037] Preferably, R.sup.4 is selected from
[(CH.sub.2).sub.nNR.sup.5R.sup.6R.sup.7].sup.+X.sup.-. n is a
number from 1 to 8, preferably from 1 to 5, more preferably from 1
to 3.
[0038] In a preferred embodiment, component b) is selected from
##STR00004##
[0039] R.sup.5, R.sup.6 and R.sup.7 are independently substituted
or unsubstituted benzyl or C.sub.1 to C.sub.12 alkyl, and
preferably methyl or ethyl. In a particularly preferred embodiment,
R.sup.5, R.sup.6 and R.sup.7 are methyl.
[0040] Particularly preferred components b) are
N,N-dimethylaminoethyl acrylate methyl chloride,
Acryloyloxyethyltrimethyl ammonium chloride,
Acryloyloxyethyltrimethyl ammonium hydroxide,
Acryloyloxypropyltrimethyl ammonium chloride,
Methacryloyloxyethyltrimethyl ammonium chloride,
N,N-dimethylaminopropylacrylamide methyl chloride.
[0041] Copolymer P may also comprise mixtures of different cationic
monomers b).
[0042] When Y represents
##STR00005##
(also written as
--CH.sub.2N.sup.+(R.sup.5R.sup.6)CH.sub.2CH.dbd.CH.sub.2X.sup.-) in
forming the cationic quaternary amine monomer (CH2=CR.sup.3Y) which
is then a diallyl dialkylammonium salt monomer used to form the
copolymer P, it is understood that this Y group comprises an
ethylenic unsaturation which can further take part in the
copolymerization and thereby (i) form part of the same copolymer
chain on a head-to-head configuration, (ii) form part of the same
copolymer chain on a head-to-tail configuration, (iii) form part of
a different copolymer chain, or (iv) remain unreacted.
[0043] In one embodiment of the invention, copolymer P may comprise
up to 15% by weight, preferably up to 10% by weight, more
preferably up to 5% by weight and particularly preferably up to 2%
by weight of further monomers.
[0044] Further monomers can be cationic, anionic, hydrophobic or
neutral and can be any monomers that comprise an ethylenically
unsaturated double bond like (meth)acrylic acid, (meth)acrylic acid
derivatives like (meth)acrylic acid esters, (meth)acrylic amides,
styrene, substituted styrenes like alpha methyl styrene, acrylic
nitrile, vinyl esters like vinyl acetate, vinyl propionate.
unsaturated dicarboxylic acids like crotonic acid, itaconic acid,
maleic acid, maleic acid anhydride, olefins like ethylene.
[0045] In a particularly preferred embodiment, copolymer P is free
of acrylamide.
[0046] In a more preferred embodiment, copolymer P consists
essentially of components a) and b).
[0047] In a particularly preferred embodiment, copolymer P does not
comprise any further monomers but consists of components a) and
b).
[0048] Especially preferred are copolymers P consisting of
Vinylformamide and Acryloyloxyethyltrimethyl ammonium chloride.
[0049] In one preferred embodiment, copolymers P comprise 55 to 95
molar % methyl chloride quaternary ammonium salt of dimethyl amino
ethyl (meth)acrylate and 5 to 45% vinyl formamide.
[0050] Copolymers P normally have an average molecular weight Mw
(determined by light scattering) of 10,000 to 100,000,000,
preferably 100,000 to 70,000,000, more preferably 500,000 to
30,000,000. In a preferred embodiment, copolymers P have a
molecular weight above 1,000,000. In a particularly preferred
embodiment, copolymers P have a molecular weight above 4,500,000 or
5,000,000. In an especially preferred embodiment copolymers P have
an average molecular weight above 6,000,000, above 8,000,000 or
above 10,000,000. The term "average molecular weight" in the
context of this application means the weight average molecular
weight Mw.
[0051] The average molecular weight Mw can be determined by light
scattering using a field flow fractionation apparatus coupled with
a multi-angle Light scattering detector and a refractive index
detector.
[0052] In one embodiment of the invention, copolymer P comprises in
the form of polymerized units [0053] a) at least one compound of
the general formula I
[0053] ##STR00006## [0054] wherein R.sup.1 and R.sup.2 are
independently H, C.sub.1, C.sub.2 or C.sub.3 alkyl, and [0055] b)
at least one compound of the general formula II
[0055] ##STR00007## [0056] wherein R.sup.3 is H or C.sub.1, C.sub.2
or C.sub.3 alkyl,
[0057] Y is
##STR00008## [0058] R.sup.4 is an aliphatic or cycloaliphatic or
aromatic rest bearing a positive charge, [0059] R.sup.5 and R.sup.6
are independently C.sub.1 to C.sub.3 alkyl, [0060] X.sup.- is an
anion, [0061] wherein the molar ratio of components a) to b) is
5:95 to 80:20, [0062] and wherein said copolymer P has a number
average molecular weight of 5,000,000 to 100,000,000.
[0063] The molecular weight of the copolymers can for example be
controlled by the method of copolymerization, the copolymerization
temperature, the type and amount of initiator, the concentration of
monomers and the like. Generally, lower temperature and higher
monomer concentration produce a higher molecular weight copolymers
while higher temperature and lower monomer concentration produce
lower molecular weight copolymers. The monomer concentrations in
the reaction mixture are generally in the range of 5 to 70% by
weight, and are preferably between 10 to 60% by weight.
[0064] Normally copolymer P is a polymer that exhibits an intrinsic
viscosity of at least 0.5 dl/g. Typically, the intrinsic viscosity
will be the least 3 dl/g, preferably 5 dl/g and often it can be as
high as 20 or 30 dl/g. Preferably the intrinsic viscosity will be
from 5 to 20 dl/g.
[0065] Intrinsic viscosity is a parameter used to characterize the
molecular weight and the structure of the polymer. Longer polymers
have a higher intrinsic viscosity compared to shorter ones and
branched polymers have a lower intrinsic viscosity compared to
linear ones of same molecular weight.
[0066] The intrinsic viscosity of polymers may be determined as
described in WO 2005/095292 p. 8 , In 29 to p. 9, In 5 by preparing
an aqueous solution of the polymer (0.5-1% w/w) based on the active
content of the polymer. 4 g of this 0.5-1% polymer solution is
diluted to 100 ml in a volumetric flask with 50 ml of 2M sodium
chloride solution that is buffered to pH 7.0 (using 1.56 g sodium
dihydrogen phosphate and 32.26 g disodium hydrogen phosphate per
liter of deionized water) and the mixture is diluted to 100 mL with
deionized water. The intrinsic viscosity of the polymers is
measured using a "Number 1 suspended level viscometer" at
25.degree. C. in 1M sodium chloride solution that is buffered to pH
7.0.
[0067] In one embodiment of the invention, copolymer P comprises in
the form of polymerized units [0068] a) at least one compound of
the general formula I
[0068] ##STR00009## [0069] wherein R.sup.1 and R.sup.2 are
independently H, C.sub.1, C.sub.2 or C.sub.3 alkyl, and [0070] b)
at least one compound of the general formula II
[0070] ##STR00010## [0071] wherein R.sup.3 is H or C.sub.1, C.sub.2
or C.sub.3 alkyl, [0072] Y is
[0072] ##STR00011## [0073] R.sup.4 is an aliphatic or
cycloaliphatic or aromatic rest bearing a positive charge, [0074]
R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3 alkyl,
[0075] X.sup.- is an anion, [0076] wherein the molar ratio of
components a) to b) is 5:95 to 80:20, [0077] and wherein said
copolymer P has an intrinsic viscosity from 5 to 30 dl/g.
[0078] Copolymers P normally do not comprise more than 10,000 ppm
of unreacted monomer. Preferably, copolymers P do not comprise more
than 1000 ppm or 600 ppm. In a particularly preferred embodiment,
copolymers P do not comprise more than 400 or 200 ppm of unreacted
monomer.
[0079] Copolymers P and HP may be formed by any polymerization
process suitable for obtaining such copolymers and that is
preferably suitable for obtaining copolymers with a number average
molecular weight of 5,000,000 to 100,000,000.
[0080] For example, copolymers P may be prepared by gel
polymerization, water-in-oil suspension polymerization or by
water-in-oil emulsion polymerization or inverse emulsion
polymerization or by water-in-water dispersion polymerization.
These processes allow for a time and energy efficient process for
making copolymers according to the invention and enable the
manufacture of copolymers with a high average molecular weight.
[0081] When preparing gel polymers by solution polymerization, the
initiators are generally introduced into the monomer solution.
[0082] Gel polymers can for example be prepared using redox
initiation in an adiabatic process. Redox initiation systems are
generally composed of two parts, an oxidizing component and a
reducing component. Examples of oxidizing components which can be
used in the present invention are hydroperoxide and alkali metal or
ammonium salts of a per-acid, such as alkali metal and ammonium
peroxodisulfates (commonly known as persulfates) and alkali metal
and ammonium perborates.
[0083] Examples of reducing components which can be used in the
present invention are alkali metal and ammonium sulfites,
disulfites, hydrosulfites, thiosulfites and
formaldehydesulfoxylates, and salts of transition metals such as
iron (Fe.sup.2+), chromium (Cr.sup.2+), vanadium (V.sup.2+) and
titanium (Ti.sup.3+). In addition to the oxidizing and reducing
components certain other compounds may be present which help
solubilisation of one or more components of the system. Examples of
such compounds are complexing agents such as the disodium salt of
ethylenediamine tetraacetic acid or pentasodium salt of
diethylenetriaminepentaacetic acid. A particularly preferred redox
system comprises ammonium or potassium persulfate or tert-butyl
hydroperoxide or hydrogen peroxide and ferrous salts such as
ferrous sulfate or ferrous ammonium sulfate or sodium
metabisulfite. The amounts used are preferably in the ranges
0.00001 to 0.01% by weight relative to the monomer solution for the
oxidizing component and 0.00001 to 0.0045% by weight relative to
the monomer solution for the reducing agent.
[0084] Optionally a thermal initiator system may be included.
Typically a thermal initiator would include any suitable initiator
compound that releases radicals at an elevated temperature.
Suitable free-radical initiators include, but are not limited to,
azo initiators, peroxide initiators, persulfate initiators and free
radical redox systems. Especially preferred are water soluble azo
initiators such as azo-bis-isobutyronitrile,
2,2'-azobis(N,N'-dimethyleneisobutyramidine)dihydrocholoride,
2,2'-azobis(2-amidinopropane) dihydrochloride,
4,4'-azobis-(4-cyanopentanoic acid),
2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamid-
e}, and 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide). The
free-radical initiator is usually used in an amount of 0.0001 to 1%
by weight based on the weight of the total monomers.
[0085] The aqueous monomer phase is prepared by mixing
water-soluble monomers and polymerization additives such as
inorganic salts, chelants, pH buffers, transfer agents,
crosslinker, initiators and the like in water. Crosslinking agents
and transfer agents may be optionally be used to increase the
molecular weight and trigger the intrinsic viscosity of the
polymers obtained. The monomer solution is normally cooled to
-10.degree. C.-10.degree. C. and degassed to remove oxygen present.
The reaction can be carried out under an inert gas atmosphere. The
copolymerization reaction is usually initiated by introducing the
redox initiator solutions to the monomer solution at -5.degree. to
20.degree. C., preferably around 0.degree. C. Preferably, the
temperature during polymerization is let to rise to at least
70.degree. C. but preferably below 95.degree. C.
[0086] Alternatively the gel polymerization may be carried out
under irradiation (ultra violet (UV) light, microwave energy, heat
etc.), preferably under UV light optionally also using suitable
radiation initiators.
[0087] In one embodiment, polymerization is effected by a
combination of redox and UV-polymerization processes. This implies
the presence of two different types of radical initiators, a redox
system as described earlier and a UV initiator. Preferred
UV-initiators are for example water-soluble azo initiators as
listed above. Suitable UV initiators are available under the trade
name Irgacure.RTM. from BASF SE. More details of suitable processes
are disclosed in WO 2001/025289 A1 p. 5, In 15 to p. 14, In 13.
[0088] Gel polymerization, inverse emulsion polymerization and
polymerizations induced by UV are particularly efficient with
respect to the reaction time and the energy efficiency.
[0089] Using polymerization techniques selected from gel
polymerization, inverse emulsion polymerization and polymerizations
induced by UV it is possible to vary the ratio of components a) to
b) over broad ranges and to obtain these products in high quality
(little side products, high purity, homogenous powder, easily
grindable powder). Furthermore, it is possible to make polymers
that comprise component a) in an amount from 5 to 80% by weight,
preferably between 10 to 45% by weight, more preferably from 15 to
45% by weight, 20 to 30% by weight.
[0090] Once the polymerization is complete, the gel can be
processed in a standard way by first comminuting the gel into
smaller pieces, drying to the substantially dehydrated polymer
followed by grinding to a powder.
[0091] The polymers may be produced as beads ("bead
polymerization") by suspension polymerization or as a water-in-oil
emulsion or dispersion by water-in-oil emulsion polymerization, for
example according to a process defined by EP-A-150933, EP-A-102760
or EP-A-126528. Alternatively the water soluble polymer may be
provided as a dispersion in an aqueous medium. This may for
instance be a dispersion of polymer particles of at least 20
microns in an aqueous medium containing an equilibrating agent as
given in EP-A-170394. This may for example also include aqueous
dispersions of polymer particles prepared by the polymerization of
aqueous monomers in the presence of an aqueous medium containing
dissolved low IV (intrinsic viscosity) polymers such as poly
diallyl dimethyl ammonium chloride and optionally other dissolved
materials for instance electrolyte and/or multi-hydroxy compounds
e.g. polyalkylene glycols, as given in WO-A-9831749 or
WO-A-9831748.
[0092] Aqueous solutions of water-soluble copolymers P are
typically obtained by dissolving the polymer in water. Generally
solid particulate polymer, for instance in the form of powder or
beads, is dispersed in water and allowed to dissolve with
agitation. This may be achieved using conventional make up
equipment. The polymer may be supplied in the form of a reverse
phase emulsion or dispersion which can then be inverted into
water.
[0093] The copolymers may be produced in a liquid form by inverse
emulsion polymerization. An inverse emulsion means a water-in-oil
polymer emulsion comprising the polymers according to this
invention in the aqueous phase, a hydrocarbon oil for the oil phase
and a water-in-oil emulsifying agent. Inverse emulsion polymers are
hydrocarbon continuous with the water-soluble polymers dispersed
within the hydrocarbon matrix. The inverse emulsion polymers are
then "inverted" or activated for use by releasing the polymer from
the particles using shear, dilution, and, generally, another
surfactant. See U.S. Pat. No. 5,137,641, incorporated herein by
reference. Representative preparations of high molecular weight
inverse emulsion polymers are described U.S. Pat. Nos. 6,605,674;
7,776,958; and 5,137,641.
[0094] The aqueous phase is prepared by mixing water-soluble
monomers, and any polymerization additives such as inorganic salts,
chelants, pH buffers, transfer agent, crosslinker, initiator and
the like in water.
[0095] The oil phase is prepared by mixing together an inert
hydrocarbon liquid with one or more oil soluble surfactants. The
surfactant mixture should have a low HLB, to ensure the formation
of an oil continuous emulsion. Appropriate surfactants for
water-in-oil emulsion polymerizations, which are commercially
available, are compiled in the North American Edition of
McCutcheon's Emulsifiers & Detergents, International Edition
Volume 1 (1994) p. 209 to p. 228. The oil phase may need to be
heated to ensure the formation of a homogenous oil solution.
[0096] The monomer phase is added to the oil phase and they are
vigorously mixed together using a mixing equipment to form an
emulsion. The media is then charged into a reactor equipped with a
stirrer, a thermocouple, a nitrogen purge tube, and a condenser.
The resulting emulsion is cooled or heated to the desired
temperature, purged with nitrogen, and a free-radical initiator is
added. The reaction mixture is stirred for several hours until the
reaction is completed under a nitrogen atmosphere at the desired
temperature. Upon completion of the reaction, the water-in-oil
emulsion polymer is cooled to room temperature, where any desired
post-polymerization additives, such as antioxidants, or a high HLB
surfactant (as described in U.S. Pat. No. 3,734,873, col 4, In 43
to col 6, In 44) may be added.
[0097] The resulting emulsion polymer is a free-flowing liquid. An
aqueous solution of the water-in-oil emulsion polymer can be
generated by adding a desired amount of the emulsion polymer to
water with vigorous mixing in the presence of a high-HLB surfactant
(as described in U.S. Pat. No. 3,734,873, col 4, In 43 to col 6, In
44).
[0098] A way of increasing the molecular weight and controlling the
intrinsic viscosity of the polymer is to introduce a structural
modifier in the formulation or during the polymerization process. A
structural modifier is an agent that is added to the aqueous
polymer solution to control the polymer structure and solubility
characteristics. The structural modifier is selected from the group
consisting of cross-linking agents and chain transfer agents.
[0099] Chain transfer agent means any molecule, used in
free-radical polymerization, which will react with a polymer
radical forming a dead polymer and a new radical. In particular,
adding a chain transfer agent to a polymerizing mixture results in
a chain-breaking and a concomitant decrease in the size of the
polymerizing chain. Thus, adding a chain transfer agent limits the
molecular weight of the polymer being prepared.
[0100] Suitable chain transfer agents include alcohols such as
methanol, ethanol, 1-propanol, 2-propanol, butyl alcohol, and
glycerol, and the like, sulfur compounds such as alkylthiols,
thio-ureas, sulfites, and disulfides, carboxylic acids such as
formic and malic acid, and their salts and phosphites such as
sodium hypophosphite, and combinations thereof. A preferred alcohol
is 2-propanol. Preferred sulfur compounds include ethanethiol,
thiourea, and sodium bisulfite. Preferred carboxylic acids include
formic acid and its salts. More preferred chain-transfer agents are
sodium hypophosphite and sodium formate.
[0101] Cross-linking agent or branching agent means a
multifunctional monomer that when added to polymerizing monomer or
monomers results in cross-linked polymers in which a branch or
branches from one polymer molecule become attached to other polymer
molecules. Preferred cross-linkers are polyethylenically
unsaturated monomers.
[0102] Preferred cross-linking agents include
N,N-methylenebisacrylamide, N,N-methylenebismethacrylamide,
triallylamine, triallyl ammonium salts, tetraallyl ammonium salts,
ethylene glycol dimethacrylate, diethylene glycol dimethacrylate,
polyethylene glycol diacrylate, triethylene glycol
dimethylacrylate, polyethylene glycol dimethacrylate,
N-vinylacrylamide, N-methylallylacrylamide, glycidylacrylate,
acrolein, glyoxal and vinyltrialkoxysilanes such as
vinyl-trimethoxysilane, vinyltriethoxysilane,
vinyltris(.beta.-methoxyethoxy)silane, vinyltriacetoxysilane,
allyltrimethoxysilane, allyltriacetoxysilane,
vinylmethyldimethoxysilane, vinyldimethoxyethoxysilane,
vinylmethyldiacetoxysilane, vinyldimethylacetoxysilane,
vinylisobutyldimethoxysilane, vinyltriisopropoxysilane,
vinyltri-n-butoxysilane, vinyltrisecbutoxysilane,
vinyltrihexyloxysilane, vinylmethoxydihexyloxysilane,
vinyldimethoxyoctyloxysilane, vinylmethoxydioctyloxysilane,
vinyltrioctyloxysilane, vinylmethoxydilauryloxysilane,
vinyldimethoxylauryloxysilane, vinylmethoxydioleyoxysilane, and
vinyldimethoxyoleyloxysilane. Especially preferred cross-linking
agents are N,N-methylenebisacrylamide, N,N
-methylenebismethacrylamide and tetraallyl ammonium salts.
[0103] The present invention is further directed to novel
copolymers HP comprising in the form of polymerized units: [0104]
a) at least one vinylamide of the general formula I
[0104] ##STR00012## [0105] wherein R.sup.1 and R.sup.2 are
independently H, C.sub.1, C.sub.2 or C.sub.3 alkyl, and [0106] b)
at least one compound of the general formula II
[0106] ##STR00013## [0107] wherein R.sup.3 is H or C.sub.1, C.sub.2
or C.sub.3 alkyl, [0108] Y is
[0108] ##STR00014## [0109] R.sup.4 is an aliphatic or
cycloaliphatic or aromatic rest bearing a positive charge, [0110]
R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3 alkyl,
[0111] X is an anion, [0112] with the proviso that the amount of
compounds where Y is COOH does not exceed 80 molar % of the amount
of compounds making up component b), [0113] c) at least one
compound of the general formula III
[0113] ##STR00015## [0114] wherein the stoichiometric composition
of said copolymer is reflected by the formula
A.sub.xB.sub.yC.sub.z, wherein A, B and C represent components a),
b) and c) in polymerized form, and wherein the molar ratio of
(x+z):y is from 5:95 to 80:20 and the molar ratio of x:z is 0 to
100000
[0115] Depending on the pH or the acidity of the medium, compounds
of the general formula III are present as amines or as ammonium
ions and a counterion. In the context of this application, ammonium
salts of amines according to formula III shall also be regarded as
compounds according to formula III.
[0116] Preferably, the molar ratio of components a) and c) to b)
(the molar ratio (x+z):y) in copolymer HP is 5:95 to 45:65, more
preferably 10:90 to 40:60 and particularly preferably 15:85 to
30:70.
[0117] In one embodiment of the invention, the molar ratio x:z is
from 0 to 10, preferably from 0.1 to 8, more preferably from 0.5 to
5.
[0118] In another embodiment of the invention, the molar ratio x:z
is from 10 to 100,000, preferably from 100 to 10,000. In a
preferred embodiment, the molar ratio x:z is above 1000.
[0119] In a preferred embodiment, R.sup.1 is H.
[0120] In another preferred embodiment, R.sup.1 is CH.sub.3.
[0121] In another preferred embodiment, R.sup.2 is H or methyl.
[0122] Examples of preferred vinyl amides a) are N-vinyl formamide
(R.sup.1.dbd.R.sup.2.dbd.H) and N-vinyl acetic amide
(R.sup.1.dbd.H, R.sup.2.dbd.CH.sub.3).
[0123] Compounds suitable as component b) carry a positive charge.
In a preferred embodiment, compounds suitable as component b) carry
a permanent positive charge. In a less preferred embodiment,
component b) is zwitterionic or are cationic only at low pH.
Normally, component b) comprises an anion X.sup.- that can for
example be selected from pseudo halides or halides like Cl.sup.-,
Br.sup.- or I.sup.-; hydroxide, sulfates, carboxylates or
alkylsulfonates like C.sub.1-C.sub.3 alkyl sulfonates. In a
preferred embodiment, anions X are selected from Cl.sup.-, OH.sup.-
or alkylsulfonates like CH.sub.3SO.sub.4.sup.-.
[0124] Preferably, component b) bears a quarternary ammonium group
or a pyridinium group.
[0125] In a preferred embodiment, R.sup.3 is H or CH.sub.3. More
preferably, R.sup.3 is H.
[0126] Preferably, component b) is a derivative of (meth)acrylic
acid bearing cationic groups or a quaternized vinyl pyridine.
[0127] In a particularly preferred embodiment, component b) is an
ester or an amide of acrylic acid or methacrylic acid. In a
particularly preferred embodiment, component b) is an ester or
amide of acrylic acid.
[0128] In another embodiment of the invention, when copolymer HP is
prepared by hydrolysis of co-polymers P, component b) is preferably
not an ester, because esters tend to by hydrolyzed more easily that
amides.
[0129] Preferably, R.sup.4 is selected from
[(CH.sub.2).sub.nNR.sup.5R.sup.6R.sup.7].sup.+X.sup.-. n is a
number from 1 to 8, preferably from 1 to 5, more preferably from 1
to 3.
[0130] In a preferred embodiment, component b) is selected from
##STR00016##
[0131] R.sup.5, R.sup.6 and R.sup.7 are independently C.sub.1 to
C.sub.3 alkyl, and preferably methyl or ethyl. In a particularly
preferred embodiment, R.sup.5, R.sup.6 and R.sup.7 are methyl.
[0132] Preferred components b) are for example
N,N-dimethylaminoethyl acrylate methyl chloride,
Acryloyloxyethyltrimethyl ammonium chloride,
Acryloyloxyethyltrimethyl ammonium hydroxide,
Acryloyloxypropyltrimethyl ammonium chloride,
Methacryloyloxyethyltrimethyl ammonium chloride,
N,N-dimethylaminopropylacrylamide methyl chloride.
[0133] Particularly preferred compounds b) for copolymers HP are
N,N-dimethylaminopropyl acrylamide methyl chloride
[0134] It is possible that during hydrolysis of copolymer P, ester
or amide groups originating from component b) can also be partially
hydrolyzed. Thus, in copolymers HP, Y can also be COOH, provided
that the molar ratio compounds b) bearing a COOH group (Y.dbd.COOH)
does not exceed 80 molar %, preferably 50, more preferably 30 and
especially preferably 10 molar % relative to the amount of
component b) originally included in the polymer.
[0135] Copolymer HP may also comprise mixtures of different
cationic monomers b).
[0136] When Y represents
##STR00017##
(also written as
--CH.sub.2N.sup.+(R.sup.5R.sup.6)CH.sub.2CH.dbd.CH.sub.2X.sup.-) in
forming the cationic quaternary amine monomer
(CH.sub.2.dbd.CR.sup.3Y) which is then a diallyl dialkylammonium
salt monomer used to form the copolymer HP, it is understood that
this Y group comprises an ethylenic unsaturation which can further
take part in the copolymerization and thereby (i) form part of the
same copolymer chain on a head-to-head configuration, (ii) form
part of the same copolymer chain on a head-to-tail configuration,
(iii) form part of a different copolymer chain, or (iv) remain
unreacted.
[0137] In one embodiment of the invention, copolymer HP may
comprise up to 15% by weight, preferably up to 10% by weight, more
preferably up to 5% by weight and particularly preferably up to 2%
by weight of further monomers.
[0138] Further monomers can be cationic, anionic, hydrophobic or
neutral and can be any monomers that comprise an ethylenically
unsaturated double bond like (meth)acrylic acid, (meth)acrylic acid
derivatives like (meth)acrylic acid esters, (meth)acrylic amides,
styrene, substituted styrenes like alpha methyl styrene, acrylic
nitrile, vinyl esters like vinyl acetate, vinyl propionate,
unsaturated dicarboxylic acids like crotonic acid, itaconic acid,
maleic acid, maleic acid anhydride, olefins like ethylene.
[0139] In a particularly preferred embodiment, copolymer HP is free
of acrylamide.
[0140] Copolymers HP normally have an average molecular weight Mw
(determined by light scattering of at 10,000 to 100,000,000,
preferably 100,000 to 70,000,000, more preferably 500,000 to
30,000,000. In a preferred embodiment, copolymers P have a
molecular weight above 1,000,000. In a particularly preferred
embodiment, copolymers P have a molecular weight above 4,500,000 or
5,000,000. In an especially preferred embodiment copolymers P have
a molecular weight above 6,000,000, above 8,000,000 or above
10,000,000.
[0141] In one embodiment, copolymer HP comprises in the form of
polymerized units: [0142] a) at least one compound of the general
formula I
[0142] ##STR00018## [0143] wherein R.sup.1 and R.sup.2 are
independently H, C.sub.1, C.sub.2 or C.sub.3 alkyl, and [0144] b)
at least one compound of the general formula II
[0144] ##STR00019## [0145] wherein R.sup.3 is H or C.sub.1, C.sub.2
or C.sub.3 alkyl, [0146] Y is
[0146] ##STR00020## [0147] R.sup.4 is an aliphatic or
cycloaliphatic or aromatic rest bearing a positive charge, [0148]
R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3 alkyl,
[0149] X.sup.- is an anion, [0150] with the proviso that the amount
of compounds where Y is COOH does not exceed 80 molar % of the
amount of compounds making up component b), [0151] c) at least one
compound of the general formula III
[0151] ##STR00021## [0152] wherein the stoichiometric composition
of said copolymer is reflected by the formula
A.sub.xB.sub.yC.sub.z, wherein A, B and C represent components a),
b) and c) in polymerized form, and wherein the molar ratio of
(x+z):y is from 5:95 to 80:20 and the molar ratio of x:z is 0 to
100000 and wherein said copolymer HP has an average molecular
weight of 5,000,000 to 100,000,000.
[0153] In one embodiment, copolymer HP comprises in the form of
polymerized units: [0154] a) at least one compound of the general
formula I
[0154] ##STR00022## [0155] wherein R.sup.1 and R.sup.2 are
independently H, C.sub.1, C.sub.2 or C.sub.3 alkyl, and [0156] b)
at least one compound of the general formula II
[0156] ##STR00023## [0157] wherein R.sup.3 is H or C.sub.1, C.sub.2
or C.sub.3 alkyl, [0158] Y is
[0158] ##STR00024## [0159] R.sup.4 is an aliphatic or
cycloaliphatic or aromatic rest bearing a positive charge, [0160]
R.sup.5 and R.sup.6 are independently C.sub.1 to C.sub.3 alkyl,
[0161] X.sup.- is an anion, [0162] with the proviso that the amount
of compounds where Y is COOH does not exceed 80 molar % of the
amount of compounds making up component b), [0163] c) at least one
compound of the general formula III
[0163] ##STR00025## [0164] wherein the stoichiometric composition
of said copolymer is reflected by the formula
A.sub.xB.sub.yC.sub.z, wherein A, B and C represent components a),
b) and c) in polymerized form, and wherein the molar ratio of
(x+z):y is from 5:95 to 80:20 and the molar ratio of x:z is 0 to
100000 and wherein said copolymer HP has an intrinsic viscosity
from 5 to 30 dl/g.
[0165] Copolymers HP are obtainable through partial or complete
hydrolysis of copolymers P using an inorganic or organic acid or
base.
[0166] In a preferred embodiment, copolymers HP are obtained
through partial or complete hydrolysis of copolymers P using an
inorganic base.
[0167] The amount of acid or base used to hydrolyze the copolymers
in solution can vary widely and is generally added in a molar ratio
of from 0.05:1 to 3:1, preferably from 0.1:1 to 1:1 based on the
N-vinylamide monomer content of the initially formed polymeric
material. Generally, partial hydrolysis is preferably achieved with
a suitable acid such as inorganic acids as, for example,
hydrochloric acid, hydrobromic acid, hydrofluoric acid, sulfuric
acid, nitric acid, phosphoric acid and the like, although suitable
bases, such as inorganic bases as, for example, sodium hydroxide,
ammonia, ammonium hydroxide, potassium hydroxide, and the like may
also be used. The degree of hydrolysis can be controlled by
controlling the amount of acid or base, the reaction temperature
and/or the reaction time. In general, greater amounts of acid or
base, higher reaction temperatures and longer reaction times result
in higher degrees of hydrolysis.
[0168] It is possible that during hydrolysis of copolymer P, ester
or amide groups originating from component b) can also be partially
hydrolyzed. Thus, in copolymers HP, Y can also be COOH, provided
that the molar ratio compounds b) bearing a COOH group (Y.dbd.COOH)
does not exceed 80 molar %, preferably 50, more preferably 30 and
especially preferably 10 molar % relative to the amount of
component b) originally included in the polymer.
[0169] The copolymers P and HP of this invention have been found to
be useful as flocculating agents to agglomerate coagulated
colloidal and/or finely divided suspended matter in aqueous or
non-aqueous systems such as aqueous solutions, dispersions or
suspensions. Thus, another embodiment of this invention is directed
to the use of copolymer P and/or HP as flocculants and to
flocculants comprising copolymers P and/or HP.
[0170] Copolymers P and HP can be used alone, as mixtures of
different copolymer P and/or HP or in combination with other
organic polymers.
[0171] The copolymers may be added directly to the solutions
containing the suspended matter, or may be pre-dissolved in a
suitable miscible solvent and then added to the solution. The
dosage amount of copolymer is not, per se, critical to the
invention, and is generally in an amount effective to flocculate
the suspended matter. Those of ordinary skill in the art can
readily determine suitable dosage amounts by conventional means.
Thus, while the exact dosage amount for a particular system can
vary widely depending on the nature of the system and the amount of
suspended matter, in general the dosage amount can range from 0.005
to 1 weight percent, preferably from 0.01 to 0.5 weight percent on
the basis of the dry weight of the suspended matter.
[0172] Copolymers P and HP are particularly suitable as flocculants
for any suitable suspensions in which it is desirable to
concentrate the suspended solids. This includes waste waters,
sludge, textile industry effluents, mineral suspensions such as red
mud from Bayer Alumina Process or coal tailings, in paper mill
wastes such as cellulosic sludges. Copolymers P and HP and
flocculants according to the invention are particularly suitable
for waste water or sludge treatment for municipal or industrial
water treatment and particularly for the dewatering of sewage
sludge.
[0173] The copolymers P and HP of this invention have also been
found to be useful as drainage/retention aids in pulp and
papermaking systems.
[0174] For the use as retention/free drainage aids, copolymers P
and/or HP can for example be used in combination with
microparticles. The combination of a polymeric flocculating agent
with organic and/or inorganic microparticles is often referred to
as a "microparticle system".
[0175] Suitable microparticles for use in this embodiment of the
present invention generally include organic polymeric particles
and/or inorganic colloidal particles having cationic anionic or
amphoteric charged surfaces. Inorganic microparticles include, but
are not limited to particulate siliceous materials, china clay,
alumina, titanium, zirconium, tin, borium compounds, and the like,
and mixtures thereof. The particulate siliceous materials can be
selected from water swellable clay materials, colloidal silica
solutions, or water dispersible siliceous materials. The water
swellable clay materials are primarily smectite or vermiculite
type, and are preferably the bentonite type materials. The term
"bentonite" generally embraces the sheet silicates that are
swellable in water.
[0176] Suitable microparticles for use in this invention also
include "modified" inorganic particles wherein the ionicity of the
inorganic particles is modified by contacting the particles with a
low molecular weight (e.g. below 100,000), high charge density
(e.g. at least 4 mEq/g) anionic co-polymer such as acrylic or
methacrylic polymers.
[0177] Suitable organic polymeric microparticles for use in the
invention include organic polymeric microparticles which are either
water dispersible or water soluble, and have an ionic surface.
Organic polymeric microparticles having the above properties
include, but are not limited to, various latex particles. The
particle size of the microparticles of this invention is not, per
se, critical to the invention provided of course that these
particles can disperse or be readily dispersed into an aqueous pulp
suspension in a paper making process and which do not negatively
affect the surface characteristics of the final paper product.
These particles, in general, will have an average dry particle size
in the range 1 nm to 50 microns, and more typically from 2 nm to 10
microns.
[0178] In a preferred embodiment, the drainage/retention aids of
this invention comprise a combination of an inorganic bentonite
microparticle and a copolymer having a molecular weight of at least
100,000 and which has been hydrolyzed to provide a charge density
between 4 and 22 mEq/g.
[0179] As flocculant for sludge dewatering, copolymers P and/or HP
can be used in combination with inorganic or polymeric coagulants.
Suitable inorganic coagulants are for example lime, alum, ferric
chloride, ferrous sulfate, ferric sulfate and sodium aluminate.
[0180] Copolymers P and/or HP are very effective and efficient
flocculants, particularly for sludge de-watering. In particular,
copolymers P and/or HP are very effective flocculants for sewage
suspensions such as any type of sludge derived from a sewage
treatment plant including digested sludge, activated sludge, raw or
primary sludge or mixtures thereof.
[0181] Flocculants comprising copolymers P and/or HP show high
clarification rates when used to flocculate suspended matter in
water.
[0182] The dosage of copolymers H and HP required for dewatering of
sludge is very low.
[0183] The cake obtained comprises only little water. The cake
obtained has a high cake solid.
[0184] In particular, they allow efficient flocculation and free
water separation from the sludge at low as well as at high polymer
dosages.
[0185] Also, floc strengths of flocs obtained when using P or HP as
flocculants are very good.
[0186] Furthermore, copolymers P and HP show only little
degradation in sludge conditioning (free drainage) when the polymer
is placed under mechanical pressure.
[0187] Also, copolymer P and HP help to form flocs very quickly, so
that only little mixing of the sludge-polymer mixture is required
for free water separation.
[0188] Copolymers P and HP can also be used as flux enhancers for
membrane bioreactor application.
EXAMPLES
[0189] The following examples are provided to illustrate the
present invention in accordance with the principles of this
invention, but are not to be construed as limiting the invention in
any way.
[0190] All parts and percentages are by weight unless otherwise
indicated.
[0191] VFA: Vinyl formamide
[0192] AM: Acrylamide
[0193] DMA3Q: Acryloyloxyethyltrimethyl ammonium chloride
[0194] TAAC: Tetraallylammonium chloride
[0195] Trilon C: Diethylenetriaminepentaacetic acid
[0196] V50: 2,2'-Azobis(2-methylpropionamidine)dihydrochloride
[0197] Lutensol TO89: ethoxylated saturated iso-C13 alcohol
[0198] Span 80: Sorbitan monooleate
[0199] Exxsol D 100: Dearomatised hydrocarbon
[0200] Zetag 8185: cationic poly(acrylamide) powder flocculant
based on acrylamide and DMA3Q having DMA3Q mol. % of ca. 60%
[0201] Zetag 8190: cationic poly(acrylamide) powder flocculant
based on acrylamide and DMA3Q having DMA3Q mol. % of ca. 77%
[0202] Zetag 9048 FS:
Example 1
Preparation of 60 mol % Cationic Copolymer P1 by Gel
Polymerization
[0203] In a flask, 184.9 g of water, 0.4 g of a 50% by weight
Trilon C solution, 36 g of vinyl formamide and 179.1 g of a 80% by
weight dimethylaminoethyl acrylate methyl chloride solution in
water were introduced. The pH was corrected to be between 6-6.5 and
the flask was put in a cryostate to be cooled until the temperature
reached 0.degree. C. Then, the monomer solution was degassed by
bubbling through of nitrogen for 30 min. 16 mL of a 1% by weight
aqueous solution of
2,2'-Azobis(2-methylpropionamidine)dihydrochloride and 6 mL of
tert-butyl hydroperoxide (0.1% by weight) were added. The solution
was warmed to 10.degree. C. In a second flask, 0.8 mL of sodium
bisulfite (1% by weight) followed by the monomer solution were
introduced. The second flask was directly placed under 4 UV Lamp
(Phillips 40W-R) with an intensity of 2300 mow. The polymerization
started directly and reached a temperature of 80.degree. C. within
10 minutes. After an additional 15 minutes, UV irradiation was
stopped and the polymer was cooled slowly until reaching room
temperature. The gel was then cut using a meat chopper and the
pieces were dried at 80.degree. C. for two hours. Afterwards, the
solid product was ground to generate a powder having an average
particle size of approximately 0.5-1 mm.
[0204] The polymer obtained was fully water soluble and no
insoluble particles were observed.
[0205] The polymer obtained was suitable for use as flocculant for
sludge dewatering.
Example 2
Preparation of 60 mol % Cationic Copolymer P2 by Gel
Polymerization
[0206] In a flask, 150.3 g of water, 0.4 g of a 50% by weight
Trilon C solution, 36 g of vinyl formamide, 179.1 g of a 80% by
weight dimethylaminoethyl acrylate methyl chloride solution in
water and 12 g of a 0.1% by weight tetraallylammonium chloride
solution in water were introduced. The pH was adjusted to be
between 6-6.5 and the flask was put in a cryostate to be cooled
until the temperature reached 0.degree. C. Then, the monomer
solution was degassed by bubbling through of nitrogen for 30 min.
16 mL of a 1% by weight aqueous solution of
2,2'-Azobis(2-methylpropionamidine)dihydrochloride and 6 mL of
tert-butyl hydroperoxide (0.1% by weight) were added. The solution
was warmed to 10.degree. C. In a second flask, 0.8 mL of sodium
bisulfite (1% by weight) followed by the monomer solution were
introduced. The second flask was directly placed under 4 UV Lamp
(Phillips 40W-R) with an intensity of 2300 mW. The polymerization
started directly and reached a temperature of 80.degree. C. within
10 minutes. After an additional 15 minutes, UV irradiation was
stopped and the polymer was cooled slowly until reaching room
temperature. The gel was then cut using a meat chopper and the
pieces were dried at 80.degree. C. for two hours. Afterwards, the
solid product was ground to generate a powder having an average
particle size of approximately 0.5-1 mm.
[0207] The polymer obtained was fully water soluble and no
insoluble particles were observed.
[0208] The polymer obtained was suitable for use as flocculant for
sludge dewatering.
Example 3
Preparation of 60 mol % Cationic Copolymer P3 by Gel
Polymerization
[0209] In a flask, 146.3 g of water, 0.4 g of a 50% by weight
Trilon C solution, 36 g of vinyl formamide, 179.1 g of a 80% by
weight dimethylaminoethyl acrylate methyl chloride solution in
water and 16 g of a 0.1% by weight tetraallylammonium chloride
solution in water were introduced. The pH was adjusted to be
between 6-6.5 and the flask was put in a cryostat to be cooled
until the temperature reached 0.degree. C. Then, the monomer
solution was degassed by bubbling through of nitrogen for 30 min.
16 mL of a 1% by weight aqueous solution of
2,2'-Azobis(2-methylpropionamidine)dihydrochloride and 6 mL of
tert-butyl hydroperoxide (0.1% by weight) were added. The solution
was warmed to 10.degree. C. In a second flask, 0.8 mL of sodium
bisulfite (1% by weight) followed by the monomer solution were
introduced. The second flask was directly placed under 4 UV Lamp
(Phillips 40W-R) with an intensity of 2300 mW. The polymerization
started directly and reached a temperature of 80.degree. C. within
10 minutes. After an additional 15 minutes, UV irradiation was
stopped and the polymer was cooled slowly until reaching room
temperature. The gel was then cut using a meat chopper and the
pieces were dried at 80.degree. C. for two hours. Afterwards, the
solid product was ground to generate a powder having an average
particle size of approximately 0.5-1 mm.
[0210] The polymer obtained was fully water soluble and no
insoluble particles were observed.
[0211] The polymer obtained was suitable for use as flocculant for
sludge dewatering.
Example 4
Polymer Evaluation of ca. 60 mol % Cationic VFA Copolymer Powders
and Comparison to a Commercially Available 60 mol % Cationic
Polyacrylamide Powder
TABLE-US-00001 [0212] TABLE 1 A B C D E F G H I J K P1 VFA 36 40.5
DMA3Q 179.1 59.5 TAAC 0 0 13.7 P2 VFA 36 40.5 DMA3Q 179.1 59.5 TAAC
12 30 10.5 P3 VFA 36 40.5 DMA3Q 179.1 59.5 TAAC 16 40 10.1 Zetag AM
40.5 DMA3Q 59.5 14 8185 Composition of Copolymers of Examples 1 to
3 and commercial Zetag 8185 powder based on acrylamide technology
and having similar cationic composition; columns A to G of table 1:
A: experiment No. or commercial product reference; B: name of first
monomer, C: mass of first monomer used in grams, D: molar % age of
first monomer relative to the copolymer, E: name of second monomer,
F: mass of second monomer solution in grams, G: molar % age of
second monomer relative to the copolymer, H: name of crosslinker,
I: mass of 0.1% by weight crosslinker solution in grams, H: parts
per million of crosslinker calculated over the overall monomer
solution. K: Intrinsic viscosity in dL/g
[0213] Cationic copolymer of vinyl formamide and dimethylaminoethyl
acrylate methyl chloride P1 exhibits similar intrinsic viscosity
compared to very high molecular weight and high performance
commercial cationic poly(acrylamide) Zetag 8185 powder. It
demonstrates that the gel polymerization process allows to reach
high molecular weight polymer P1 powder. The introduction of
tetraallylammonium chloride crosslinker has an impact on the
polymer structure by generating a polymer more branched. Moreover
the molecular weight of the polymer increases. Up to 40 ppm of
crosslinker no insoluble particle was found when the powder was
dissolved in water. The effect of the crosslinker can be observed
on the intrinsic viscosity values which decreased from 13.5 dL/g to
10 dL/g
Example 5
Preparation of 77 mol % Cationic Copolymer P5 by Gel
Polymerization
[0214] In a flask, 131.2 g of water, 0.4 g of a 50% by weight
Trilon C solution, 20 g of vinyl formamide, 221.7 g of an 80% by
weight dimethylaminoethyl acrylate methyl chloride solution in
water and 4.5 g of a 0.1% by weight tetraallylammonium chloride
solution in water were introduced. The pH was corrected to be
between 6-6.5 and the flask was put in a cryostate to be cooled
until the temperature reached 0.degree. C. Then, the monomer
solution was degassed by bubbling through of nitrogen for 30 min.
16 mL of a 1% by weight aqueous solution of
2,2'-Azobis(2-methylpropionamidine)dihydrochloride and 6 mL of
tert-butyl hydroperoxide (0.1% by weight) were added. The solution
was warmed to 10.degree. C. In a second flask, 0.8 mL of sodium
bisulfite (1% by weight) followed by the monomer solution were
introduced. The second flask was directly placed under 4 UV Lamp
(Phillips 40W-R) with an intensity of 2300 mW. The polymerization
started directly and reached a temperature of 80.degree. C. within
10 minutes. After an additional 15 minutes, UV irradiation was
stopped and the polymer was cooled slowly until reaching room
temperature. The gel was then cut using a meat chopper and the
pieces were dried at 80.degree. C. for two hours. Afterwards, the
solid product was ground to generate a powder having an average
particle size of approximately 0.5-1 mm.
[0215] The polymer obtained was fully water soluble and no
insoluble particle was observed when the powder was dissolved in
water.
[0216] The polymer obtained was suitable for use as flocculant for
sludge dewatering.
Example 6
Preparation of 77 mol % Cationic Copolymer P6 by Gel
Polymerization
[0217] In a flask, 122.4 g of water, 20 g of vinyl formamide, 221.7
g of an 80% by weight dimethylaminoethyl acrylate methyl chloride
solution in water and 13.4 g of a 0.1% by weight tetraallylammonium
chloride solution in water were introduced. The pH was corrected to
be between 6-6.5 and the flask was put in a cryostate to be cooled
until the temperature reached 0.degree. C. Then, the monomer
solution was degassed by bubbling through of nitrogen for 30 min.
16 mL of a 1% by weight aqueous solution of
2,2'-Azobis(2-methylpropionamidine)dihydrochloride and 6 mL of
tert-butyl hydroperoxide (0.1% by weight) were added. The solution
was warmed to 10.degree. C. In a second flask, 0.8 mL of sodium
bisulfite (1% by weight) followed by the monomer solution were
introduced. The second flask was directly placed under 4 UV Lamp
(Phillips 40W-R) with an intensity of 2300 mW. The polymerization
started directly and reached a temperature of 80.degree. C. within
10 minutes. After an additional 15 minutes, UV irradiation was
stopped and the polymer was cooled slowly until reaching room
temperature. The gel was then cut using a meat chopper and the
pieces were dried at 80.degree. C. for two hours. Afterwards, the
solid product was ground to generate a powder having an average
particle size of approximately 0.5-1 mm.
[0218] The polymer obtained was fully water soluble and no
insoluble particle was observed when the powder was dissolved in
water.
[0219] The polymer obtained was suitable for use as flocculant for
sludge dewatering.
Example 7
Preparation of 77 mol % Cationic Copolymer P5 by Gel
Polymerization
[0220] In a flask, 118 g of water, 20 g of vinyl formamide, 221.7 g
of an 80% by weight dimethylaminoethyl acrylate methyl chloride
solution in water and 17.8 g of a 0.1% by weight tetraallylammonium
chloride solution in water were introduced. The pH was corrected to
be between 6-6.5 and the flask was put in a cryostate to be cooled
until the temperature reached 0.degree. C. Then, the monomer
solution was degassed by bubbling through of nitrogen for 30 min.
16 mL of a 1% by weight aqueous solution of
2,2'-Azobis(2-methylpropionamidine)dihydrochloride and 6 mL of
tert-butyl hydroperoxide (0.1% by weight) were added. The solution
was warmed to 10.degree. C. In a second flask, 0.8 mL of sodium
bisulfite (1% by weight) followed by the monomer solution were
introduced. The second flask was directly placed under 4 UV Lamp
(Phillips 40W-R) with an intensity of 2300 mW. The polymerization
started directly and reached a temperature of 80.degree. C. within
10 minutes. After an additional 15 minutes, UV irradiation was
stopped and the polymer was cooled slowly until reaching room
temperature. The gel was then cut using a meat chopper and the
pieces were dried at 80.degree. C. for two hours. Afterwards, the
solid product was ground to generate a powder having an average
particle size of approximately 0.5-1 mm.
[0221] The polymer obtained was fully water soluble and no
insoluble particle was observed when the powder was dissolved in
water.
[0222] The polymer obtained was suitable for use as flocculant for
sludge dewatering.
Example 8
Polymer Evaluation of ca. 77 mol % Cationic VFA Copolymer Powders
and Comparison to a Commercially Available 77 mol % Cationic
Polyacrylamide Powder
TABLE-US-00002 [0223] TABLE 2 A B C D E F G H I J K P5 VFA 20 23.2
DMA3Q 221.7 76.8 TAAC 4.5 11 8.6 P6 VFA 20 23.2 DMA3Q 221.7 76.8
TAAC 13.4 33 8.5 P7 VFA 20 23.2 DMA3Q 221.7 76.8 TAAC 17.8 44 7.2
Zetag AM 23.2 DMA3Q 76.8 9 8190 Composition of Copolymers of
Examples 5 to 7 and commercial Zetag 8190 powder based on
acrylamide technology and having similar cationic composition;
columns A to G of table 2: A: experiment No. or commercial product
reference; B: name of first monomer, C: mass of first monomer used
in grams, D: molar % age of first monomer relative to the
copolymer, E: name of second monomer, F: mass of second monomer
solution in grams, G: molar % age of second monomer relative to the
copolymer, H: name of crosslinker, I: mass of 0.1% by weight
crosslinker solution in grams, H: parts per million of crosslinker
calculated over the overall monomer solution. K: Intrinsic
viscosity in dL/g
[0224] Cationic copolymer of vinyl formamide and dimethylaminoethyl
acrylate methyl chloride P5 exhibits similar intrinsic viscosity
compared to very high molecular weight and high performance
commercial cationic poly(acrylamide) Zetag 8190 powder. It
demonstrates that the gel polymerization process allows to reach
high molecular weight polymer P5 powder. The introduction of
tetraallylammonium chloride crosslinker has an impact on the
polymer structure by generating a polymer more branched. Moreover
the molecular weight of the polymer increases. Up to 44 ppm of
crosslinker no insoluble particle was found when the powder was
dissolved in water. The effect of the crosslinker can be observed
on the intrinsic viscosity values which decreased from 8.6 dL/g to
7.2 dL/g
Example 9
Preparation of a 60 mol % Cationic Copolymer P9 by Inverse Emulsion
Polymerization
[0225] Oil Phase
[0226] In a beaker, 182.0 g of Exxsol D 100 and 16.1 g of Span 80
were mixed to a homogenous solution.
[0227] Water Phase
[0228] In a flask, 77.80 g of water, 69.92 g of vinyl formamide,
343.51 g of an 80% by weight dimethylaminoethyl acrylate methyl
chloride solution in water and 0.128 g of a 40% by weight tetra
allylammonium chloride solution in water were introduced.
[0229] Preparation of the Emulsion
[0230] The oil phase was in put in a beaker and stirred slowly with
a Silverson homogenizer and the water phase was added. The emulsion
was then stirred for 3 min at 8000 rpm.
[0231] Polymerization
[0232] The emulsion was transferred to a 2 L reactor was stirred at
300 rpm. Nitrogen was sparged through the emulsion for one hour and
cooled to 10.degree. C. Then the polymerization was started by
parallel dosage of two solutions A and B. The solution A was
composed of 9.0 g of a 1% by weight aqueous solution of sodium
sulfite and 0.05 g of a 1.0% by weight aqueous solution of ferrous
ammonium sulfate. The solution B was 5 g a 1% by weight aqueous
solution tert-butyl hydroperoxide. The dosage was done by a
peristaltic pump. The dosage speed was adjusted so that the
temperature rose from 10.degree. C. to 40.degree. C. within 30 min.
After that the dosage was completed over one hour and the
temperature was kept at 40.degree. C.
[0233] After cooling to room temperature 15.0 g of Lutensol TO89
was added to invert the emulsion. The polymer obtained was suitable
for use as flocculant for sludge dewatering.
Example 10
Polymer Evaluation of an Inverse Emulsion ca. 60 mol % Cationic VFA
Copolymer and Comparison to a Commercially Available 60 mol %
Cationic Polyacrylamide Inverse Emulsion
TABLE-US-00003 [0234] TABLE 3 A B C D E F G H I J K P9 VFA 36 40.5
DMA3Q 179.1 59.5 TAAC 0.13 150 6.1 Zetag 9048 AM 40.5 DMA3Q 59.5 7
Composition of Copolymers of Examples 10 and commercial Zetag 9048
FS inverse emulsion based on acrylamide technology and having
similar cationic composition; columns A to G of table 3: A:
experiment No. or commercial product reference; B: name of first
monomer, C: mass of first monomer used in grams, D: molar % age of
first monomer relative to the copolymer, E: name of second monomer,
F: mass of second monomer solution in grams, G: molar % age of
second monomer relative to the copolymer, H: name of crosslinker,
I: mass of 40% by weight crosslinker solution in grams, H: parts
per million of crosslinker calculated over the overall monomer
solution. K: Intrinsic viscosity in dL/g
[0235] Cationic copolymer of vinyl formamide and dimethylaminoethyl
acrylate methyl chloride P9 exhibits similar intrinsic viscosity
compared to very high molecular weight and high performance
commercial cationic poly(acrylamide) Zetag 9048 FS inverse
emulsion. It demonstrates that the inverse emulsion polymerization
process developed allows to reach high molecular weight and
structured polymer P9.
Example 11
Dewatering of Aqueous Suspensions Via Direct Addition of Organic
Polymer Flocculant
[0236] Polymer Solutions Preparation
[0237] Polymer solutions for samples in a solid form (powder and
bead) were prepared at a concentration of 0.4% using the following
procedure. To generate 1000 g of polymer solution, 4 g of powder
were accurately weighed and put in a flask with screw cap. 5 mL of
acetone were added. The flask was sealed and shaken gently for a
complete wetting of the polymer with acetone. 991 g of
demineralized water were introduced and the flask was sealed. The
dispersion was shaken until all polymeric particulates were
completely dispersed in the media. Then the flask was put on a
tumbler with a rotation speed of 30 rpm for at least 2 hours and
typically overnight until complete dissolution of the material.
Polymer solutions were used fresh within 24 hours.
[0238] Polymer solutions for samples in a liquid form (inverse
emulsion) were prepared at a concentration of 0.4% by weight based
on active polymer content using the following procedure. For
instance, to obtain 500 g of polymer solution for an inverse
emulsion having an active polymer content of 50%, 496 g of
demineralized water were introduced in a beaker glass and stirred
at 500 rpm using a mechanical stirrer. 4 g of activated inverse
emulsion were introduced to the water drop by drop using a syringe
under stirring. After complete addition, the solution was stirred
for another 2 H at the same speed and then introduced in a flask
with a screw cap. Then the flask was put on a tumbler with a
rotation speed of 30 rpm for at least 2 H and typically overnight
until complete dissolution of the material. Polymer solutions were
used fresh within 24 hours.
[0239] Experimental Procedure
[0240] The sludge used for the experiments was a digested sludge
taken in a municipal water-treatment plant on the river Inn in
Germany.
[0241] Free drainage curve determination. In a plastic beaker were
introduced 250 mL of sludge, X g of polymer solution and (250-X) g
of water, with X being a weight between 20 and 50 g. The sludge was
flocculated by stirring at 6000 rpm for 10 s using a mixer and
mixing paddle. The suspension was poured into a filtration cell,
which had a filter membrane, comprising a belt-press filter cloth
and the filtrate collected in a measuring cylinder. Filtrate
volumes were recorded after 5 s using a data recording program
Sarto Connect from Sartorius which monitored on-line the weight
difference of the balance.
[0242] This test was performed at least 8 times at different
polymer solution dosages to elaborate a reliable dosage curve. The
maximum filtrate volume is defined as the optimum of the dosage
curve. The optimum polymer dosage is defined as the polymer dose
necessary to reach the maximum filtrate volume.
[0243] Cake solid determination. From the free drainage curve, the
optimum polymer dosage was obtained for a specific polymer. The
Flocculation test was reproduced twice at the optimum polymer
dosage to get two samples for the cake solid determination. After 1
minute of dewatering in the filtration cell, all the thickened
sludge was transferred into the piston press device and subjected
to a compression dewatering stage. A pressure of 7 bar was applied
for 15 minutes when the pressure was constant. Then the wet cake
was removed and the cake solids content was determined by
gravimetric measurement in an oven overnight at 110.degree. C. The
cake solid value is defined as the average of the two gravimetric
measurements.
TABLE-US-00004 TABLE 4 Flocculation performance of Copolymers of
Examples 6 and 10 compared to copolymers based on AM; columns A to
D of table 4: A: experiment No. or commercial product reference; B:
Maximum filtrate volume in milliliters, C: optimum dosage in
kilogram per ton of dried matter suspended in the sludge, D: cake
solid in percent A B C D P6 18 135 19.1 Zetag 8190 17.5 140 17.7
P10 24 150 18 Zetag 9048 26 140 17.2
[0244] High molecular weight 90% by weight cationic poly(vinyl
formamide) powder P6 exhibited similar dosage and maximum filtrate
volume compared to commercial high performance 90% by weight
cationic poly(acrylamide) powder Zetag 8190. However, the cake
solid of the vinyl formamide copolymer had an improved cake solid
which is highly desired to reduce the volume of waste in the water
treatment plant. The inverse emulsion 80% by weight cationic
poly(vinyl formamide) P10 exhibited a better and faster water
released (maximum filtrate volume) compared to Zetag 9048 FS at a
lower dosage which is more economical for the user. Moreover, the
waste generated was found to have a lower moisture content which
has a positive impact on the volume generated.
[0245] Determination of molecular weight by light scattering was
done using a field flow fractionation apparatus from Eclipse
coupled with a multi-angle Light scattering detector from Dawn EOS
and a refractive index detector optilab DSP from Wyatt. A 0.5 M
NaNO3 solution is used to dilute the polymer at a concentration of
0.3 g/L. Then 30 to 50 .mu.L of polymer solution was injected. A
do/dc of 0.150 mL/g was taken for all the samples to allow the
molecular weight determination.
* * * * *