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
1999-08-18
2002-07-02
Wu, David W. (Department: 1713)
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...
C524S555000, C524S547000, C524S609000, C524S812000, C524S814000, C524S817000, C524S728000, C526S288000, C526S287000, C526S307100
Reexamination Certificate
active
06414080
ABSTRACT:
FIELD OF INVENTION
The present invention relates to inverse emulsion polymers that are useful in delivering a high molecular weight, high solids concentration of a water-soluble polymer. The present invention further relates to these compositions for use in water treatment as a coagulant/flocculent, paper processes as a drainage and retention aid, in the oil field as a fluid loss additive, and in personal care as a keratin conditioner for hair and skin.
BACKGROUND OF THE INVENTION
Many polymerization processes and compositions are well known in many different fields. Aqueous solution polymerization techniques are known, but use low monomer concentrations and require that the resulting solution polymer be dried to prepare powder polymers, as disclosed in U.S. Pat. Nos. 4,555,269 and 4,515,635, the disclosures of which are incorporated herein by reference in their entirety. Should these dry polymers then be required to be formed into a flowable liquid phase, the powdered polymer must then be dispersed in a hydrocarbon carrier phase to be used in the resulting application. Copolymers of N,N,-dimethylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid are known and disclosed in these patents. However, these dispersions have a high viscosity and are, therefore, difficult to handle and process. Particularly, these dispersions are hard to pump and generally have high Brookfield viscosities, greater than 30,000 Cps (mPa). These dispersions also have poor storage stability and tend to phase separate over time, sometimes as short as in a matter of days, particularly at the extremes of temperature. At both high and low temperatures, these dispersions phase separate fairly quickly. These dispersions also tend to have a poor pour point at low temperatures (i.e. they are difficult to pour).
It would be very desirable to produce a stable high molecular weight, soluble, easily handleable polymer composition and system that has a low viscosity, good storage stability, and a good low temperature pour point. With these properties, the composition could be directly applied and easily handleable. The product could be poured directly into the system needing the polymer, without special procedures. The product could be pumped with any commercially available pump. Should the polymer have these characteristics it would be useful in many more applications.
SUMMARY OF THE INVENTION
The present invention is an inverse emulsion composition that comprises a copolymer or copolymer salt of N,N,-dimethylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid or acid salts thereof having a Brookfield viscosity of less than 20,000 centipoise (Cps) at 25° C., a polymer reduced viscosity at 0.05 gm/dl active in one Normal (1N) NaCl at 30° C. of about 3 to about 10 dl/gm, having an active polymer concentration of about 25 to about 75 weight percent, in about 0 to about 50 weight percent water, about 10 to about 50 weight percent hydrocarbon, and about 1 to about 10 weight percent primary surfactant at a pH of about 1 to about 8.
The present invention also comprises an inverse emulsion polymerization process comprising;
(1) forming a water-in-oil emulsion of an aqueous solution of the monomers N,N,-dimethylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid or acid salts thereof in an inert hydrocarbon liquid organic dispersion medium and
(2) polymerizing said monomers in said dispersion medium to form a polymer emulsion, using a free radical generating catalyst to initiate the reaction, and controlling the temperature of the reaction mix to between about 5° and 105° C.,
wherein the composition contains an emulsifier/primary surfactant at a concentration of about 0.5 to about 10%, by weight, of the total emulsion.
A further improvement comprises producing the polymer in the process above in the presence of an effective chain transfer agent, such as 2-mercaptoethanol and a crosslinker, such as methylene bis-acrylamide.
DETAILED DESCRIPTION OF THE INVENTION
The inventors have unexpectedly discovered an improved inverse emulsion polymer composition and process of forming such emulsion of a copolymer of N,N,-dimethylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid, or salts thereof.
This composition is unexpectedly stable at low viscosity, has a low freeze point, has good storage stability, and has a good low temperature pour point, while having a high solid concentration of active polymer.
The composition contains at least the two named monomers (N,N,-dimethylacrylamide and 2-acrylamido-2-methylpropane sulfonic acid or acid salts thereof) but can have others present as well and thus can be a terpolymer or higher. Suitable examples preferred monomers include acrylamide, acrylic acid, and sodium vinyl sulfonate.
The ratio of the monomer N,N,-dimethylacrylamide to the monomer 2-acrylamido,-2-methyl propane sulfonic acid or acid salts thereof in the copolymer is preferably about 1:4 to about 4:1, more preferably about 1:2 to about 2:1, with a monomer ratio of N,N,-dimethylacrylamide to 2-acrylamido-2-methylpropane sulfonic acid of about 1:1.5 being most preferred. At ratios much greater than 1:4 there is not sufficient N,N,-dimethylacrylamide to provide the preferred nonionic character, whereas at ratios much greater than 4:1, concentrations of 2-acrylamido-2-methylpropane sulfonic acid or acid salts thereof are too low to provide the preferred anionic character.
The inverse emulsion polymer composition of the present invention has a Brookfield viscosity of less than 20,000 centipoise (Cps) at 25° C., preferably about 500 to about 10,000, with a Brookfield viscosity about 1,000 to about 5,000 being most preferred. Emulsions with a Brookfield viscosity of over 20,000 centipoise is an indication of undesirable particle size, generally resulting in poor emulsion stability. However, extremely low Brookfield viscosities, say of less than 100 centipoise are not practical due to the requirement of adding an extreamly high amount of surfactant.
The inverse emulsion polymer composition of the present invention has a polymer reduced viscosity at 0.05 gm/dl active in one Normal (1N) NaCl at 30° C. of about 3 to about 10 dl/gm, preferably about 3.5 to about 7 dl/gm. At a polymer reduced viscosity much higher than 10 dl/gm, the emulsion may have poor mixability in water. Whereas at reduced viscosities much below 3 dl/gm the emulsion has poor performance properties.
The inverse emulsion polymer composition of the present invention has an active polymer concentration of about 25 to about 75 weight percent, preferably about 30 to about 60 weight percent, with an active polymer concentration of about 35 to about 45 being most preferred. At a polymer concentration less than 25 weight percent it is not generally cost effective. However, concentrations of as low as 20, 15, 10, and even 5 weight percent could still be effective in the present invention. Whereas polymer concentrations over 75 weight percent are not practically possible. At concentrations much over about 50 weight percent the polymer produced in the emulsion is in a less desirable concentration and should be concentrated by removing at least a portion of the water, as is disclosed in U.S. Pat. No. 5,480,921, the disclosure of which is incorporated herein by reference in its entirety.
The inverse emulsion polymer composition of the present invention optionally has water. The polymer is produced in water but the water can be partially or totally removed as stated above. Thus the inverse emulsion composition of the present invention preferably contains about 0 to about 50 weight percent water. Water is preferably present in the composition of the present invention and that amount of water present in the emulsion of the present invention is preferred to be that amount that remains after emulsion polymerization, generally over 20 weight percent, more preferably about 20 to about 40 weight percent. This amount of water is generally limited by the amount of water present in the monomer solution.
The inverse emulsion polymer composition of the present invention
Chen Shih-Ruey T.
Frederick Kevin W.
Loeffler Randy J.
Rak James E.
Breininger Thomas M.
Calgon Corporation
Egwim Kelechi
Martin Michael B.
Wu David W.
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