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
1999-09-03
2002-03-26
Lipman, Bernard (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, C525S292000, C525S328200, C525S359300, C525S385000
Reexamination Certificate
active
06362266
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for producing a polyallylamine polymer gel having reduced cohesiveness during drying and to cross-linked polyallylamine polymer gel compositions produced thereby.
BACKGROUND OF THE INVENTION
Cross-linked polyallylamine polymers have found many therapeutic applications. See for example, WO 98/57652, JP 07309766-A and U.S. Pat. Nos. 5,618,530, 5,679,717, 5,693,675 and 5,607,669 for reducing blood cholesterol levels by reducing reabsorption of bile acids, U.S. Pat. No. 5,702,696 for decreasing the absorption of dietary iron from the gastrointestinal track, and WO 96/21454 and U.S. Pat. No. 5,496,545 for removing phosphate from the gastrointestinal track. Further, JP 05244915 discloses the use of cross-linked polyamine polymers as food preservatives.
Methods to produce cross-linked polyamine polymers are known. See for example, the references cited above and U.S. Pat. No. 4,605,701, DE 4227019 A1 and EP 732352 A1, the disclosures of which are incorporated herein by reference. These references disclose cross-linking the polyallylamine polymer by reacting the polymer with a suitable cross-linking agent in aqueous caustic solution or an aqueous caustic solution and immiscible solvent mixture.
The existing methods to produce cross-linked polyamine polymers create difficult and costly handling and cleanup procedures, especially in an industrial. production process. In all cases, once the polymer gel is dried to a certain volatile content (dependent on temperature), it becomes extremely cohesive and sticks to itself. This cohesive phase results in a significantly increased power requirement to agitate the polymer and a decreased heat transfer efficiency from the heated dryer shell. The present invention addresses these problems and gives a more practical solution to them.
SUMMARY OF THE INVENTION
The present invention is directed to a process for producing a cross-linked polyallylamine polymer gel having reduced cohesiveness during drying comprising the steps of reacting an aqueous solution of a polyallylamine polymer with a multifunctional cross-linking agent, preferably epichlorohydrin, to give a cross-linked polyallylamine polymer.
One embodiment of the present invention comprises the step of washing the cross-linked polyallylamine polymer with an alcohol or alcohol/water solution.
In a further embodiment, the present invention comprises the step of drying the cross-linked polyallylamine polymer.
In yet a further embodiment, the present invention involves the use of a reactor designed for high viscosity processing, preferably a LIST reactor, in the cross-linking and/or drying steps.
In yet a further embodiment, the present invention involves compositions of cross-linked polyallylamine polymers produced by the foregoing process.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The present invention provides a process for producing a cross-linked, water-insoluble but swellable polyallylamine polymer that has decreased cohesiveness during drying. The process comprises subjecting a portion of the amino groups present in an aqueous solution of polyallylamine polymer to a cross-linking reaction with a compound having, in its molecule, at least two functional groups reactive with primary amino groups, as well as providing said cross-linked polyallylamine polymers.
The polyallylamine acid salt polymer used in the present invention is well known from references cited above and U.S. Pat. No. 4,528,347, the disclosure of which is incorporated herein by reference. Generally, monoallylamine is polymerized as a monomer inorganic acid salt (e.g., hydrochloride, sulfate, etc.) of monoallylamine in the presence of an azo type radical initiator. The polyallylamine acid salt polymer used in the invention typically has a weight average molecular weight (“MW
w
”) greater than about 2,000 daltons and more preferably greater than about 20,000 daltons. The polyallylamine polymer used in the invention typically has a MW
w
less than or equal to about 200,000 daltons and more preferably less than or equal to about 100,000 daltons. Polyallylamine hydrochloride polymer, the polymerization product from the hydrochloric acid salt of monoallylamine, is a preferred polyallylamine acid salt polymer.
Preferably, the polyallylamine acid salt polymer is neutralized prior to cross-linking. The neutralized polyallylamine polymer is sometimes referred to as polyallylamine polymer. The aqueous solution of polyallylamine polymer used in the invention is prepared by dissolving a polyallylamine acid salt polymer (obtained by the process described above) into water or other suitable solvent. Neutralization can be accomplished with any suitable base such as ammonium hydroxide, preferably sodium hydroxide, by ion exchange, electrodeionization or by other suitable methods.
Neutralization of an aqueous solution of polyallylamine hydrochloride polymer by a suitable base (e.g., lithium hydroxide, potassium hydroxide, sodium hydroxide, etc.) provides an aqueous solution of polyallylamine polymer with high levels of salt (e.g., sodium chloride). However, means to remove salt, for example, ion exchange, dialysis, nanofiltration or ultrafiltration may be used to provide the aqueous solution of polyallylamine polymer of the present invention.
Preferably, reducing the level of salt in polyallylamine polymer to provide a reduced salt polyallylamine polymer is done by ultrafiltration. Ultrafiltration is a pressure driven filtration separation occurring on a molecular scale and is well known in the art. Typically, a process fluid containing dissolved and/or suspended material contacts one side of a porous membrane. A pressure gradient is applied across the membrane. The liquid, including small dissolved molecules (e.g., unreacted allylamine and low molecular weight polyallylamine polymer) and ions (e.g., the salt) are forced through the pores. Sieving retains colloids, suspended solids, and large dissolved molecules (e.g., the polyallylamine polymer). A good discussion of ultrafiltration is contained in
Encyclopedia of Polymer Science and Engineering,
1988, Volume 17, pp. 75-107, the entire disclosure of which is incorporated herein by reference.
A complete neutralization of the polyallylamine acid salt polymer prior to cross-linking is not always necessary. Depending on its intended use, a partial neutralization is also allowable and often desirable to give the desired level of cross-linking, pH, properties and efficacy for the cross-linked polyallylamine polymer. Preferably, the polyallylamine acid salt polymer is neutralized to a point where at least about 50 percent, more preferably at least about 60 percent, even more preferably at least about 65 percent, even more preferably at least about 70 percent, and most preferably at least about 71 percent of the amino groups in the polyallylamine acid salt polymer are neutralized. Preferably, the polyallylamine acid salt polymer is neutralized whereby about 100 percent, more preferably no more than about 90 percent, more preferably no more than about 80 percent, even more preferably no more than about 75 percent, even more preferably no more than about 73 percent, and most preferably about 72 percent of the amino groups in the polyallylamine acid salt polymer are neutralized.
Preferably, the aqueous solution of polyallylamine polymer is concentrated following neutralization and prior to cross-linking by any known means in the art such as concentrative ultrafiltration or flash evaporation under vacuum at elevated temperatures. Preferably the reduced salt, aqueous solution contains at least about 1.5 milliequivalents polyallylamine polymer per gram of solution (“meq/g”), more preferably at least about 2.0 meq/g, even more preferably at least about 2.5 meq/g, even more preferably at least about 3.0 meq/g, even more preferably at least about 3.5 meq/g, even more preferably at least about 4.0 meq/g, even most preferably at least about 4.5 meq/g polyallylamine polymer. Preferably the reduced salt, aqueous solution contains less than or equal to abo
Buchholz Fredric L.
Chappelow Christopher M.
Staples Thomas L.
Lipman Bernard
The Dow Chemical Company
LandOfFree
Process for reducing cohesiveness of polyallylamine polymer... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for reducing cohesiveness of polyallylamine polymer..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for reducing cohesiveness of polyallylamine polymer... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2838029