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
1999-09-08
2001-07-24
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...
C524S401000, C524S555000, C524S825000, C524S831000, C526S201000, C526S303100, C526S307600
Reexamination Certificate
active
06265477
ABSTRACT:
TECHNICAL FIELD
This invention relates to a high molecular weight anionic and nonionic dispersion polymers and to a process for their preparation.
BACKGROUND OF THE INVENTION
One of the problems that has confronted industry in the use of water soluble polymer flocculants is how to dissolve the polymer into water so that it can be utilized for its intended purpose. Early water soluble polymers were provided as dilute aqueous solutions. As the technology improved, and the molecular weights of the polymers were improved, it becomes increasingly difficult for manufacturers to ship these polymers in solution form because of the high viscosity of even one-half to one percent solutions of the polymers. Manufacturers accordingly started shipping the polymers in the form of commutated solids which could be dissolved into water using various mechanical means. While solving shipment problems, some mechanical means degraded the polymers through shear, and, incomplete dissolution of water soluble polymers, the formation of swollen translucent particles, was common. This led to a waste of polymer, and in some cases, detrimental results such as in the case of so called “fish-eye” particles which caused defects in the manufacture of paper. In the early 1970's water-in-oil emulsions of water soluble polymers were introduced. Using the water-in-oil technology, high molecular weight polymers that rapidly dissolved could be produced, and this technology achieved great acceptance in the water soluble polymer industry. A disadvantage of the water-in-oil emulsion polymer technology however is that the emulsions contain substantial quantities of hydrocarbon liquid. The introduction of hydrocarbon liquids into the systems where these water soluble polymers are used is not always beneficial.
U.S. Pat. No. 4,929,655 and U.S. Pat. No. 5,006,590 issued to Kyoritsu Yuki Co. Ltd. describe and claim a method for the production of dispersions of water soluble cationic polymers. These polymers were manufactured in an aqueous salt or brine solution in which the polymer was insoluble. The disclosure of these two patents is hereinafter incorporated by reference into this specification. The process yielded dispersions of high molecular weight polymers which when added to water would completely dissolve over a relatively short period of time. While an advance to the art, the invention was practical only for dispersions of cationically charged water soluble polymers containing at least a portion of a hydrophobically modified cationic monomer. Anionically charged water soluble polymers, those typically useful as flocculants and as drainage and retention aids in the manufacture of paper, although disclosed, could not be successfully made utilizing the Kyoritsu Yuki method which relies upon the inclusion of a cationic monomers having hydrophobic quaternary ammonium groups. Anionic polymers of course can not be prepared which include such functionality without detracting from the performance of the resultant polymer which is based on the anionic character of the polymer.
U.S. Pat. No. 5,605,970 discloses a method for the manufacture of a particular anionic water soluble polymer in dispersion form. This disclosure teaches that certain anionic polymers, incorporating hydrophobically modified monomers, can be prepared using dispersion polymer methods. The application specifically teaches the manufacture of acrylic acid-ethylhexylacrylate polymers. The ethylhexylacrylate monomer adds a hydrophobic character to the polymer, causing the polymer to become insoluble in certain brine solutions. While these polymers, and the methods for their manufacture are useful, the incorporation of a hydrophobic monomer into a water soluble polymer, where water solubility is desirable is not always advantageous in the final use of the polymer. Moreover, the useful stabilizer disclosed therein is described as having low levels of some hydrophobic monomer along with NaAMPS and or NaAc.
A process for the production of a water-soluble polymer dispersion in the presence of a dispersant, wherein the dispersant may be a poly(2-acrylamido-2-methyl propane sulfonic acid (AMPS)) or a copolymer having 30 or more mole percent of AMPS is disclosed in EP 0 183 466.
U.S. Pat. No. 5,837,776 discloses a composition and a method of making a dispersion in the presence of a stabilizer copolymer, wherein the stabilizer copolymer contains at least 20 mole percent acrylamidomethyl propane sulfonic acid. The dispersion polymers prepared as described in this patent are prepared at a pH of from 2 to 5. However, a need still exists for stable, high molecular weight dispersion polymers which do not incorporate hydrophobic monomers and which can be prepared over a wide pH range.
SUMMARY OF THE INVENTION
The polymer of this invention is a high molecular weight, nonionic or anionic water soluble vinyl addition polymer in aqueous dispersion form. The polymer is prepared over a wide pH range and without the inclusion of any monomers having hydrophobic character. The polymers are useful as flocculants and especially as retention and drainage aids in the manufacture of paper.
Accordingly, in its principle aspect, this invention is directed to a high molecular weight water-soluble dispersion polymer having a bulk Brookfield viscosity of from about 10 to about 25,000 cps at 25° C. comprising from about 5 to about 50 weight percent of a water soluble polymer prepared by polymerizing under free radical forming conditions in an aqueous solution of a water-soluble salt in the presence of a stabilizer at a pH greater than 5:
i. 0-30 mole percent of at least one anionic monomer, and,
ii. 100-70 mole percent of at least one non-ionic vinyl monomer; wherein the stabilizer is an anionic water soluble polymer having an intrinsic viscosity in 1M NaNO
3
of from about 0.1-10 and comprises from about 0.1 to about 5 weight percent based on the total weight of the dispersion, and the water soluble salt is selected from the group consisting of ammonium, alkali metal and alkaline earth metal halides, sulfates, and phosphates and comprises from about 5 to about 40 weight percent based on the weight of the dispersion.
In another aspect, this invention is directed to a method of preparing a high molecular weight dispersion polymer having a bulk Brookfield viscosity of from about 10 to about 25,000 cps at 25° C. comprising
a) adding a free-radical initiator to an aqueous mixture comprising:
i. from about 5 to about 50 weight percent of a mixture comprising 0-30 mole percent of at least one anionic monomer and 100-70 mole percent of at least one non-ionic vinyl monomer;
ii. from about 0.1 to about 5 weight percent based on the total weight of the dispersion of a stabilizer, wherein the stabilizer is an anionic water soluble polymer having an intrinsic viscosity in 1M NaNO
3
of from about 0.1-10 and
iii. from about 5 to about 40 weight percent based on the weight of the dispersion of a water soluble salt selected from the group consisting of ammonium, alkali metal and alkaline earth metal halides, sulfates, and phosphates; and
b) polymerizing the monomers.
DETAILED DESCRIPTION OF THE INVENTION
“Monomer” means a polymerizable allylic, vinylic or acrylic compound.
“Anionic monomer” means a monomer as defined herein which possesses a net negative charge. Representative anionic monomers include acrylic acid, methacrylic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, acrylamidomethylbutanoic acid, maleic acid, fumaric acid, itaconic acid, vinyl sulfonic acid, styrene sulfonic acid, vinyl phosphonic acid, allyl sulfonic acid, allyl phosphonic acid, sulfomethylated acrylamide, phosphonomethylated acrylamide and the water soluble alkali metal, alkaline earth metal, and ammonium salts thereof. The choice of anionic monomer is based upon several factors including the ability of the monomer to polymerize with the desired comonomer, the use of the produced polymer, and cost. A preferred anionic monomer is acrylic acid.
In certain instances, it may be possible to chemically modify a non-ionic monomer
Breininger Thomas M.
Egwim K. C.
Martin Michael B.
Nalco Chemical Company
Wu David W.
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