Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
1998-08-28
2001-10-23
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
C528S50200C, C528S503000, C523S340000
Reexamination Certificate
active
06307012
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to processes for spray drying dispersions, emulsions and microemulsions containing water-soluble or water-swellable polymers to obtain substantially dry water-soluble or water-swellable polymer particles, compositions of substantially dry water-soluble or water-swellable polymer particles, and methods of using said polymer particles in water-treating, mining, paper, biotechnological, food processing, soil conditioning, solution thickening, and oil recovery applications.
BACKGROUND OF THE INVENTION
High molecular weight, water-soluble and water-swellable polymers produced from such monomers as acrylamide are commercially important materials. These polymers find use as flocculants for mining operations to recover ore from slurries, water treating to remove suspended impurities etc., in agriculture as soil conditioners, and also in paper making to aid paper formation and in oil recovery industries.
Water-soluble and water-swellable polymers are generally commercially available in solution, dry, dispersion, water-in-oil emulsion, and water-in-oil microemulsion forms. In many cases polymer solutions are convenient, but may be limited to low molecular weight polymers and/or low solids levels because of the problem of handling viscous solutions of high solids, high molecular weight polymers. At very high solids and/or molecular weights, the solutions form gels that can be comminuted to form fine polymer gel particles that may be dissolved into water by the end-user. Although these comminuted gels typically contain up to about 20% water, they are frequently called “dry” polymers to distinguish them from the other product forms, In many cases the dry polymers exhibit long dissolution times and poor handling characteristics e.g. dusting. Although some handling problems may be mitigated by agglomeration see e.g. EP 0 277 018 A2; U.S. Pat. Nos. 3,279,924; 3,275,449, 4,696,762; 5,171,781; both solutions and gels of water-soluble and water-swellable polymers may also suffer from the lack of a convenient method for post-reacting of functionalizing the polymer.
Another problem relates to blends of dry polymers, particularly when blending dry polymers having different particles sizes or particle size distributions. It is well known that dry polymer particles tend to stratify on handling and storage, with the larger particles tending to settle towards the bottom of the container, and the smaller particles tending to be concentrated towards the top. Stratification may be inconvenient because differences in handling characteristics are encountered as a function of container depth. The stratification problem may be exacerbated when two different dry polymers are blended together, because the particle size distributions of the two products are generally not identical. Stratification on storage may affect blend product performance as the top of the container tends to become enriched in the polymer having the smaller particle size. For obvious reasons, changes in product performance as a function of storage depth are to be avoided, and it is generally preferred that each polymer be of similar particle size, see e.g. EP 479 616 A1 and U.S. Pat. No. 5,213,693. However, when producing dry polymer by spray-drying, changes in production e.g. changes in dryer size, dryer temperature, bulk viscosity of the feed, atomizer type, etc. may affect particle size, and it may be difficult or impossible to achieve a desired particle size while simultaneously maintaining some other production parameter, so blends of spray-dried polymers may be adversely affected by stratification.
The advent of water-in-oil emulsion and water-in-oil microemulsion forms of water-soluble and water-swellable polymers solved some of these problems, e.g. blends of water-in-oil emulsions and water-in-oil microemulsions as disclosed in U.S. Pat. Nos. 5,883,181 and 5,763,530 do not tend to stratify, and high solids, high molecular weight, and relatively fast dissolution times may all be obtained simultaneously. In addition, unique functionalized polymers may be produced that cannot be practically manufactured by polymerization in solution. For instance, U.S. Pat. Nos. 4,956,399; 4,956,400; 5,037,881; and 5,132,023, teach that functionalization of a water-soluble polymer contained in a water-in-oil microemulsion can be carried out to produce high molecular weight charged polymers with advantageous flocculation performance. The use of microemulsions, as opposed to emulsions, in polymer production provides improved polymer performance properties among other benefits. Hydrolyzed polyacrylamides with uniquely high molecular weight are disclosed in U.S. Pat. No. 5,286,806. In U.S. Pat. No. 4,767,540, very high molecular weight hydroxamate-functionalized polyacrylamide is disclosed, and novel charged organic polymer microbeads are disclosed in U.S. Pat. Nos. 5,274,055, and 5,167,766. In addition, methods for esterifying (meth)acrylic acid polymer and, optionally, hydroxamating said polymers are disclosed in U.S. Pat. No. 5,842,056.
Despite the many benefits provided by emulsion and microemulsion polymers, transportation costs associated with such materials remain high and disposal of the oil and emulsifier in the emulsions may pose environmental concerns as secondary pollution. Moreover, many emulsion and microemulsion polymers tend to exhibit stability problems, e.g. detrimental changes in polymer properties and/or performance as a function of time. Although U.S. Pat. Nos. 5,883,181 and 5,763,530; and U.S. Pat. Nos. 4,956,399; 4,956,400; 5,037,881; 5,132,023; 5,274,055; and 5,167,766 mention non-solvent precipitation and stripping as methods of recovering dry polymer products from water-swellable or water-soluble polymer microemulsions or microemulsion-containing blends, these methods may produce a dry polymer with undesirable handling properties, poor dissolution times, low bulk density, etc. Practically, non-solvent precipitation and stripping may be inconvenient and expensive.
Water-soluble polymers may also be prepared in the form of suspensions or dispersions of polymer beads or droplets in a non-aqueous liquid e.g. oil. The reverse phase polymerization process described in U.S. Pat. No. 4,528,321 is said to form dispersions of water-soluble polymers. Water-soluble polymer dispersions, which may be azeotropically dried, are disclosed in U.S. Pat. No. 4,628,078. U.S. Pat. No. 4,506,062 discloses a reverse phase suspension polymerization process for the production of high molecular weight, water-soluble polymers and also reports that dry polymer beads may be obtained by azeotropic evaporation followed by filtration. However, a problem remains in that azeotropic distillation tends to be energy-intensive, and the filtering process may be hazardous or inconvenient.
Although dry polymers may be obtained from vinyl-addition polymer-containing water-in-oil emulsions, water-in-oil microemulsions or dispersions by such methods as precipitation in a non-solvent, stripping, etc., these methods may also be impractical for economic and environmental reasons because of difficulties in recovering, purifying and recycling the oil. Although the oil recovered from an emulsion or suspension polymerization may occasionally be recycled without further purification, as disclosed in U.S. Pat. No. 4,212,784 and JP 50-124979, in other cases e.g. S.I.R. H915 additional purification steps are necessary. The level of impurities in the oil is an important consideration, as certain polymerizations e.g. chain-growth polymelrzations, or polymerizations used to make very high molecular weight polymers, are especially sensitive to even trace amounts of polymerization-debilitating substances. Particular problems are also encountered where the polymer has been formed from monomers in the presence of the oil or the oil has been heated or subjected to processing steps, which may have a tendency to deposit polymerization-debilitating impurities in the oil.
Spray-drying is the transformation of feed from a fluid state to a dri
Davies William Bloor
Healy John Edward
Kozakiewicz Joseph J.
Miller Gary Kaui Lani
Cytec Technology Corp.
Mallon Joseph J.
Negron Liza
Teskin Fred
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