Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-08-17
2002-10-29
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
active
06472479
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to the sulfonation products of bead copolymers prepared from styrene, vinylpyridines, and crosslinkers, to a process for preparing them, and to their use as cation exchangers.
Cation exchangers are described in “Ion Exchange”,
Kirk-Othmer Ency. Chem. Tech
., 3rd edition, Vol. 13, pages 678-705.
A problem of sulfonic acid functional cationic exchangers is the oxidative degradation experienced during use under typical conditions. This degradation results in a reduction in the degree of crosslinking, instances of contamination of the water to be deionized, and corrosion problems. In particular, the conductivity of the eluted water is raised by the decomposition products.
The associated problems, and attempted solutions, are described in U.S. Pat. No. 5,302,623 and in EP-A 366,258.
U.S. Pat. No. 5,302,623 describes copolymers containing para-substituted styrenes instead of styrene. An unsatisfactory aspect of this method is that some or all of the styrene, which is very readily available industrially, must be replaced by p-alkyl-styrenes.
In EP-A 366,258, phenolic antioxidants are added to the cation exchangers. This addition brings with it the disadvantage that such antioxidants are themselves elutable with the passage of time.
The object, therefore, was to prepare oxidatively stable ion exchangers that consist essentially of styrene and contain no low molecular mass additions.
It has surprisingly been found that the sulfonation products of bead polymers prepared from styrene, vinylpyridines, acrylonitrile, and divinylbenzene result in a considerably reduced conductivity of the eluted water relative to the sulfonation products of vinylpyridine-free bead polymers.
SUMMARY OF THE INVENTION
The invention provides a process for preparing bead copolymers comprising
(i) forming a suspension of seed polymer and a monomer mixture in a continuous aqueous phase while the seed polymer itself will be obtained by jetting the monomer mixture of components (A) and (B) or (A) and (B) and (C) in an aqueous and adjacent polymerization or the seed polymer is obtained in a heterodisperse or homodisperse suspension of the monomer mixture by stirring or jetting in a continuous aqueous phase using a monomer mixture comprising
(A) from 67 to 99.45% by weight (preferably from 79 to 95.9% by weight) of styrene,
(B) from 0.5 to 20% by weight (preferably from 2 to 12% by weight) of crosslinkers (preferably divinylbenzene), which optionally are present as an isomer mixture and can contain up to 50% by weight of isomers of ethylstyrenes and up to 10% by weight of isomers of diethyl-benzenes,
(C) from 0.5 to 8% by weight (preferably from 1 to 5% by weight) of vinylpyridines, especially vinylpyridines having the general formula (I)
wherein
R
1
represents hydrogen or methyl (preferably hydrogen),
R
2
and R
3
independently of one another represent hydrogen or a C
1
-C
4
-alkyl radical (preferably hydrogen) or if R
2
and R
3
are positioned ortho to one another, together also represent members of a 5- to 7-membered ring, and
(D) from 0.1 to 1.1 parts by weight, based on 100 parts by weight of the mixture of components (A)+(B) or (A)+(B)+(C) of a poly-merization initiator,
(ii) polymerizing the monomer mixture in the seed polymer or in a heterodisperse or homodisperse suspension to form a copolymerisate and
(iii) functionalizing the resulting copolymer by sulfonation.
if desired, after process step (i), the seed polymer can be swollen in a monomer mixture comprising vinylpyridine, crosslinker, and free-radical initiator.
The invention further provides the products prepared by sulfonating the polymers of the invention.
The invention further provides for the use of the sulfonation products of the invention as cation exchangers.
DETAILED DESCRIPTION OF THE INVENTION
The bead polymers are prepared in aqueous suspension by single-stage or multistage processes as are described in Helfferich,
Ion Exchange
, McGraw-Hill Book Co., Inc., pages 26-47 (1962), in
Polymer Processes
, Interscience Publishers, Inc., New York, pages 69 to 109, in EP-B 98,130, in EP-B 101,943, in DE-A 198 52 667.9, and in DE-A 198 20 049.0.
Processes for sulfonation are described in Helfferich,
Ion Exchange
, McGraw-Hill Book Co., Inc., pages 26 to 47 (1962), in EP-A 826,704, and in DE-A 198 52 667.9.
Components (B) for the purposes of the invention are di- or trialkenylbenzenes, such as, for example, all isomers of divinylbenzenes, of trivinylbenzenes, of diisopro-penylbenzenes, and of triisopropenylbenzenes.
Examples of component (C) are 2-vinylpyridine, 4-vinylpyridine, and vinylquin-olines, preferably 2-vinylpyridine or 4-vinylpyridine.
Component (C) can be added homogeneously in the whole bead polymer or, for seed feed processes, can be added in the seed and/or in the feed.
In addition to components (A), (B), and (C) it is possible, if desired, to use further monomers. Further monomers for the purposes of the invention are vinylnaphthalene, ethylstyrene, alpha-methylstyrene, chlorostyrenes, acrylic acid, methacrylic acid, acrylic acid C
1
-C
8
-alkyl esters, methacrylic acid C
1
-C
8
-alkyl esters, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, vinylidene chloride, or vinyl acetate. These further monomers are used in concentrations of from 0 to 15% by weight, preferably from 2 to 8% by weight. In one particularly preferred embodiment, 4% by weight of acrylonitrile is used.
Polymerization initiators for the purposes of the invention are the initiators customarily used in free-radical addition polymerization. Preference is given to initiators having low solubility in water. Suitable initiators are azo compounds such as azobisisobutyronitrile, peresters, or percarbonates.
The copolymers of the invention from process step (iii) are suitable as starting materials for preparing ion exchangers, preferably cation exchangers, by sulfonating them. The sulfonation products of the invention are suitable as cation exchangers and are superior to prior art products in having a marked superiority in terms of oxidative degradation relative to cation exchangers prepared in accordance with the prior art EP-A 366,258 or U.S. Pat. No. 5,302,623.
REFERENCES:
patent: 4365023 (1982-12-01), Fujimoto et al.
patent: 4419245 (1983-12-01), Barrett et al.
patent: 5248435 (1993-09-01), Morita et al.
Journal of Membrane Science, NL, Elsevier Scientific Publ. Company, Amsterdam, vol. 71, NR.
1/02, pp. 129-137, XP000453664, ISSN: 0376-7388, L. Liang et al, “Charge-Mosaic Membrane From Gamma-Irradiated Poly(Styrene-Butadiene-4-Vinylpyridine) Triblock Copolymer II Preliminary Dialysis Test” Database Compendex Online! engineering Information, Inc., /New York, NY, US; Database.
Accession No. EIX94021779969, XP002155281, Zusammenfassung, & React Polym; Reactive Polymers Oct. 1993, Bd. 21, Nr. 1-2, Oct. 1993, Seiten 77-88, M. Chanda et al, “Selective Chromate Recovery With Quaternized Poly(4-Vinylpyridine)”.
Halle Olaf
Köhler Burkhard
Seidel Rüdiger
Wenz Eckhard
Bayer Aktiengesellschaft
Gil Joseph C.
Henderson Richard E. L.
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