Concentrated aqueous dispersions of water-soluble polymers

Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...

Reexamination Certificate

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C252S180000, C516S162000, C516S180000, C524S458000, C525S327600, C526S932000

Reexamination Certificate

active

06174950

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to water-in-water dispersions and more especially, to highly concentrated aqueous dispersions comprising water-soluble polymers and having low viscosity.
2. Description of the Prior Art
Aqueous dispersions of water-soluble polymers are used in various applications and, in particular, as flocculants for the treatment of industrial and municipal waters, the dewatering of sludges, as thickeners and agents for the treatment of soils.
It is known to this art that aqueous water-soluble polymer systems having a high solids content are in the form of a gel and exhibit very high viscosities, which renders them difficult to handle and store. Need exists in this art for such aqueous systems, but which simultaneously have a high solids content and a low viscosity. It is also necessary for such systems to be stable on storage.
U.S. Pat. No. 5,403,883 describes the polymerization, in water, of a mixture of monomers comprising one or more hydrophilic monomers or one or more hydrophobic monomers and, optionally, one or more amphiphilic monomers. The polymerization results in a water-soluble polymer having a high molecular weight. The operation is carried out in the presence of a dispersing polymer incompatible with the water-soluble polymer prepared. The dispersant has a weight-average molecular weight of less than 500,000. A typical dispersant is poly(diallyldimethylammonium chloride), hereinafter denoted as “poly DADMAC.”
However, this system of aqueous dispersions exists in the form of a transparent gel having a relatively high viscosity.
SUMMARY OF THE INVENTION
It has now surprisingly been determined that, by using certain other hydrophilic monomers or certain other dispersants, aqueous water-soluble polymer dispersions are prepared which are of low viscosity and which are not gels. These dispersions can also be formulated as opaque emulsions.
DETAILED DESCRIPTION OF BEST MODE AND SPECIFIC/PREFERRED EMBODIMENTS OF THE INVENTION
More particularly according to the present invention, in a first embodiment thereof, a water-soluble polymer comprising recurring structural units (a) of at least one hydrophilic monomer A1, (b) optionally, of at least one amphiphilic monomer B, and, (c) also optionally, of at least one hydrophobic monomer C, is prepared in the presence of a polymeric dispersing agent, incompatible with the water-soluble polymer synthesized, said dispersant comprising vinylaromatic recurring structural units and unsaturated dicarboxylic acid anhydride recurring structural units. The dispersant is imidized and then salified or quaternized. A representative dispersant according to the invention is a styrene/maleic anhydride copolymer imidized and then salified by means of acetic acid, hereinafter denoted by SMA+.
In a second embodiment of the invention, a water-soluble polymer comprising (a′) at least one hydrophilic monomer A selected from among at least one hydrophilic monomer A2 and, optionally, at least one hydrophilic monomer A1, (b′) optionally, at least one amphiphilic monomer B, and (c′) also optionally, at least one hydrophobic monomer C, is prepared in the presence of a dispersing polymer D incompatible with the water-soluble polymer.
The water-soluble monomer Al must include at least one ionic group. It is advantageously a monomer having the following general formula:
in which R
1
is H or methyl, and Q is a positive charged metal ion, such as Na+ or K+, or an ammonium ion NH+, or a monomer having the following general formula:
in which R
2
is H or methyl, and R
3
and R
4
, which may be identical or different, are each H or a C
1-6
alkyl or hydroxyalkyl or C
5-12
cycloalkyl radical, or a monomer having the following general formula:
in which R
5
is H or CH
3
, Z
1
is 0, NH or NR
6
, wherein R
6
is a C
1-6
alkyl or hydroxyalkyl radical, and:
wherein R
7
is a C
1-6
alkylene or hydroxyalkylene radical and L
1
, L
2
and L
3
, which may be identical or different, are each H or a C
1-6
alkyl or hydroxyalkyl or C
5-12
cycloalkyl or C
6-12
arylalkyl radical.
The preferred monomer Al according to the invention is acrylamide.
The water-soluble monomers A2 advantageously have the following general formula:
in which R
8
is H or methyl, Z
2
is 0, NH or NR
10
, wherein R
10
is a C
1-6
alkyl or hydroxyalkyl or C
5-12
cycloalkyl radical, R
9
is a C
1-6
alkylene or hydroxyalkylene radical, L
4
and L
5
, which may be identical or different, are each a C
1-12
alkyl or hydroxyalkyl or C
5-12
cycloalkyl or C
6-12
aryl radical, and X is an ion, such as Cl, SCN, or the like.
The preferred monomer A2 according to the invention is acryloyloxyethyldimethylbenzylammonium chloride.
The amphiphilic comonomers are advantageously selected from among:
(i) compounds having the following general formula:
in which R
12
and R
15
, which may be identical or different, are each a C
1-6
alkylene or hydroxyalkylene or C
5-12
cycloalkylene radical, Z
3
is 0, NH or NR
17
, wherein R
17
is a C
1-4
alkyl or cycloalkyl radical, R
11
is H or methyl, R
13
, R
14
and R
16
, which may be identical or different, are each a C
1-6
alkyl or hydroxyalkyl or C
5-12
cycloalkyl radical, and X is an ion, such as Cl, SCN, or the like;
(ii) compounds having the following general formula:
in which R
18
is H or methyl, R
19
is H or methyl, Z
4
is 0, NH or NR
20
, wherein R
20
is a C
1-6
alkyl or hydroxyalkyl radical, y is a C
1-4
alkylene radical, and n is a whole number ranging from 1 to 8.
The following are also considered amphiphilic monomers:
(iii) compounds A2 in which R
11
has from 7 to 12 carbon atoms, and L
4
and L
5
, which may be identical or different, are each a C
1-12
alkyl or hydroxyalkyl or C
6-18
cycloalkyl or aryl radical;
(iv) compounds having the general formula:
in which R
5
is H or CH
3
, Z
1
is 0, NH or NR
6
, wherein R
6
is a C
1
-C
16
alkyl or hydroxyalkyl radical, and
wherein R
7
is a C
6
-C
18
alkylene radical and L
1
, L
2
and L
3
, which may be identical or different, are each a C
6
-C
18
alkyl, C
6
-C
18
cycloalkylene or C
9
-C
18
arylalkylene radical.
The hydrophobic comonomers are advantageously selected from among:
(1) compounds having the following general formula:
in which R
21
is H or a C
1-9
alkyl radical, and R
22
is a C
1-4
alkyl, C
5-12
cycloalkyl or C
6-12
radical;
(2) compounds having the following general formula:
in which R
23
is H or CH
3
, Z
5
is O, NH or NR
25
, wherein R
25
is a C
1-4
alkyl radical, and R
24
is a C
1-9
alkyl, C
5-12
cycloalkyl or C
6-12
aryl radical.
In another embodiment, the dispersions of the invention are based on water-soluble polymers prepared by polymerizing:
from 70% to 100% by weight of at least one water-soluble monomer A1,
from 0% to 30% by weight of at least one amphiphilic comonomer B, and
from 0% to 30% by weight of at least one hydrophobic comonomer C,
in the presence of a polymeric dispersant comprising maleic anhydride recurring structural units which is imidized and then salified.
In another embodiment, the dispersions are based on water-soluble polymers prepared by polymerizing:
from 70% to 100% by weight of at least one monomer A2,
from 0% to 30% by weight of at least one comonomer A1,
from 0% to 30% by weight of at least one comonomer B, and
from 0% to 30% by weight of at least one comonomer C,
dispersed in a polymeric dispersant D, such as polymers which comprise imidized and then neutralized or salified maleic anhydride, or poly(diallyldimethylammonium chloride).
The dispersing polymer D and the water-soluble polymer are incompatible. They must not form a blend when they are mixed together. The weight-average molecular weight of the dispersing polymer advantageously ranges from 500 to 500,000 and preferably from 1,000 to 400,000. The dispersing polymer D must have at least one functional group selected from among the following: ether, hydroxyl, carboxyl, amine, quaternary ammonium, imine, and the like. The dispersant can also be any copol

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