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
1999-12-06
2002-07-09
Pezzuto, Helen L. (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...
C524S055000, C524S831000, C524S832000
Reexamination Certificate
active
06417268
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for making hydrophobically associative polymers (HAPs) using a brine dispersion method, and to compositions including these polymers.
2. Description of Background and Other Information
HAPs have been extensively studied in both academia and industry. The highly associative structure of a HAP in aqueous media results in its unique rheological properties, salt resistance and extremely high solution viscosity, which are very desirable in many applications, such as enhanced oil recovery, thickening and drug release applications.
U.S. Pat. Nos. 4,432,881 and 4,528,348 teach a micellar polymerization method for making polyacrylamide-based associative polymers by copolymerizing a hydrophobic comonomer with acrylamide or acrylic acid in aqueous solution in the presence of surfactants. The method has a severe disadvantage because the highly associative behavior of a HAP results in an extremely high bulk process viscosity, which causes difficulties in agitation and leads to incomplete monomer conversion. The high solution viscosity of HAP also leads to gel like final product appearance, and makes it very hard to transport and handle. Furthermore, the high process viscosity also limits the initial monomer concentration that could be used for the polymerization, which results in a final polymer having lower Molecular Weight (MW) and lower active content compared to the polymers made by emulsion and dispersion polymerization methods. Therefore, micellar polymerization is not a desirable method for large-scale production of HAP polymers.
U.S. Pat. Nos. 4,524,175 and 4,521,580 also teach, respectively, a HAP production method by water-in-oil emulsion and a HAP production method by microemulsion. However, the methods result in a product containing a significant amount of oil and surfactant which is undesirable for some applications and may cause increasing environmental concern as well as the inconvenience and expense associated with the make-down equipment for feeding the emulsions.
U.S. Pat. No. 5,707,533 teaches a brine dispersion polymerization method for preparing high molecular weight polyacrylamide copolymers comprising polymerizing a cationic monomer and an N-alkylacrylamide or an N,N-dialkylacrylamide in an aqueous salt solution. However, the associative properties of the polymers and the surfactant addition as described in the present invention is not disclosed in the '533 patent.
SUMMARY OF THE INVENTION
The present invention is directed to a method for producing HAPs by a brine dispersion polymerization method. Highly associative anionic HAP with its MW larger than 1,000,000 Dalton is synthesized in an aqueous salt solution. The HAP final product with a homogenous particle dispersion form has a bulk viscosity below 3000 cp.
The present invention relates to a method for producing a HAP which includes forming a monomer solution containing surfactant, at least one hydrophobic ethylenically unsaturated monomer, at least one hydrophilic monomer selected from nonionic ethylenically monomers, cationic ethylenically unsaturated monomers, anionic ethylenically unsaturated monomers or mixtures thereof, and water; forming a salt solution containing multivalent salt, stabilizer and water; mixing the monomer solution and the salt solution to form a mixed solution; and charging the mixed solution with an initiator, thereby polymerizing the monomers to form the HAP. The method may further include adding from about 0.01 to about 0.5 grams of free radical initiator per 100 grams of the total monomer.
The monomer solution may be formed by mixing the at least one hydrophilic monomer and water to form a monomer solution, adding the at least one hydrophobic ethylenically unsaturated monomer and surfactant to the monomer solution, and mixing until homogeneous.
The salt may be present in an amount of up to about 50% by weight, or preferably from about 10% to about 30% by weight, of the salt solution. The stabilizer may be present in an amount of up to 10% by weight of the salt solution, preferably in an amount from about 0.05% to about 2% by weight and more preferably in an amount from about 0.1% to about 0.5% by weight. A preferred stabilizer may be chemically modified quar gum.
The surfactant may be present in an amount up to about 10% by weight of the monomer solution, preferably in an amount from about 0.1% to about 2% by weight, and more preferably in an amount from about 0.25% to about 1% by weight. A preferred surfactant is sodium dodecyl sulfate.
The HAP is preferably a copolymer of acrylic acid, acrylamide, and lauryl acrylate.
The present invention also relates to a method for producing a HAP which includes: mixing at least one hydrophilic monomer selected from nonionic ethylenically monomers, cationic ethylenically unsaturated monomers, anionic ethylenically unsaturated monomers or mixtures thereof and water to form a monomer solution; adding at least one hydrophobic ethylenically unsaturated monomer and surfactant to the monomer solution and mixing until homogeneous; forming a salt solution comprising multivalent salt, stabilizer and water; mixing the monomer solution and the salt solution to form a mixed solution; and charging the mixed solution with an initiator to polymerize the monomers to form the HAP.
The present invention also relates to a method for producing a water soluble HAP containing acrylic acid, acrylamide, and lauryl acrylate, wherein the method includes forming a monomer solution of acrylic acid, acrylamide, lauryl acrylate, an anionic surfactant, and water; forming a salt solution comprising multivalent salt, stabilizer and water; mixing the monomer solution with the salt solution to form a mixed solution; and adding an initiator to the mixed solution, thereby polymerizing the acrylic acid, the acrylamide and the lauryl acrylate to produce a dispersion containing the water soluble HAP.
The present invention also relates to a method for producing a hydrophobically associative polymer which includes:
forming a monomer solution comprising up to about 10% by weight of surfactant, at least one hydrophobic ethylenically unsaturated monomer, at least one hydrophilic monomer selected from nonionic ethylenically monomers, cationic ethylenically unsaturated monomers, anionic ethylenically unsaturated monomers or mixtures thereof, and water;
forming a salt solution comprising up to about 50% by weight of multivalent salt, up to 10% by weight of stabilizer and water, the weight percent being based on the total weight of the salt solution;
mixing the monomer solution and the salt solution to form a mixed solution; and
charging the mixed solution with from about 0.01 to about 0.5 grams of free radical initiator per 100 grams of the total monomer content, thereby polymerizing the monomers to form the HAP.
The present invention also relates to an aqueous dispersion comprising the HAP made by any of the foregoing methods. The aqueous dispersions have many uses. The aqueous dispersion containing the HAP may be used as the one or more retention and drainage aids in a papermaking process from pulp furnish or as the one or more thickeners in a paint formulation containing pigment, polymer and a thickener.
The aqueous dispersion containing the HAP may be used as the one or more thickening agents in a mobility control fluid useful in enhanced oil recovery operations or as the one or more fluid loss control additives in a hydraulic cementious composition.
The aqueous dispersion containing the HAP may be used as the one or more viscosification agents either in an oil well drilling mud formulation for oil field production or in an oil well completion fluid.
The aqueous dispersion containing the HAP may also be used in a fracturing fluid formulation in oil recovery.
The aqueous dispersion containing the HAP may be used as the one or more flocculation aids in a waste water treatment system or in a dewatering sludge system.
The aqueous dispersion containing the HAP may be used as the one or more rheol
Chen Fu
Kawawa Baraka A.
Zhang Huashi T.
Hercules Incorporated
Pezzuto Helen L.
Sloan Martin F.
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