Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2000-08-10
2001-05-22
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S033000, C521S053000, C521S056000, C521S038000, C521S146000, C525S332200, C525S344000
Reexamination Certificate
active
06235802
ABSTRACT:
BACKGROUND
This invention relates to the postcrosslinking of pendant vinyl groups of crosslinked macroporous copolymers to produce macroporous adsorbents with improved properties. In particular the present invention relates to the use of organic sulfonic acids to provide the postcrosslinking of the macroporous copolymers.
High surface area adsorbents can be prepared by the “macronetting” of divinylbenzene copolymers or by the suspension polymerization of divinylbenzene (DVB) in the presence of a nonsolvent. These high surface area adsorbents are useful for the removal of organics from non-organic streams and have found use in a wide variety of applications including the removal of organic wastes from water and the recovery of pharmaceutical products from fermentation broths.
“Macronetted” or “hyper-crosslinked” adsorbents represent one class of adsorbents and can be produced by postcrosslinking involving the introduction of alkylene-bridge crosslinks into a swollen copolymer subsequent to initial polymerization, as described in U.S. Pat. Nos. 4,191,813, 4,263,407, 5,416,124 and D. A. Davankov et al.,
Reactive Polymers,
Elsevier Science Publishers, Vol. 13, pages 27-42 (1990). The process disclosed in U.S. Pat. No. 4,191,813 involves first swelling a crosslinked vinylbenzylchloride-containing copolymer with an organic solvent followed by treatment with a Lewis-acid catalyst. The process described in U.S. Pat. No. 4,263,407 involves first swelling a crosslinked polystyrene copolymer with an organic solvent followed by treatment with a Lewis-acid catalyst in the presence of a polyfunctional Friedel-Crafts-reactive crosslinker. In both cases, upon heating the reactants, the substrate copolymer aromatic rings are further crosslinked (macronetted) with methylene or alkylene-type “bridges” derived from the chloromethyl group or reactive polyfunctional crosslinker. Another well-known approach to prepare macronetted adsorbents is first to chloromethylate a styrene/DVB copolymer with chloromethyl ether and then form methylene bridge crosslinks by adding a Friedel-Crafts/Lewis-acid catalyst in the presence of a swelling solvent (see U.S. Pat. No. 5,416,124 and Davankov et al.).
Macronetted adsorbents produced as described above swell in organic solvents and have been found to be less structurally stable than conventional “non-macronet” polydivinylbenzene adsorbents, the latter, for example, being represented by highly crosslinked polymers prepared by suspension polymerization in the presence of a nonsolvent. Additionally, the production of these macronetted adsorbents requires the use of organic swelling solvents and Friedel-Crafts/Lewis-acid catalysts that are difficult to remove from the final product.
Macroporous copolymers produced from the suspension polymerization of DVB-containing monomer mixtures in the presence of a nonsolvent represent another class of adsorbents with a particular pore size distribution and surface area (conventional macroporous adsorbents). These conventional macroporous copolymers often contain a significant amount of pendant vinyl groups resulting from the incomplete crosslinking of DVB (R. V. Law et al.,
Macromolecules,
Vol. 30, pages 2868-2875 (1997); K. Lise Hubbard et al.,
React. Funct. Polym,
Vol. 36 (1), pages 17-30 (1998)). The incomplete crosslinking of these vinyl groups leads to a material with undesirable swelling properties in organic solvents, such as solvents used during adsorption/regeneration operations. Additionally the unreacted vinyl groups represent a potential site of undesirable chemical reactivity.
The enhancement of surface area and porosity of crosslinked macroporous copolymers by postcrosslinking the pendant vinyl groups has been disclosed in U.S. Pat. No. 5,218,004, where enhanced surface area was achieved by reacting the residual vinyl groups of a crosslinked copolymer (preconditioned with swelling solvent) with a Lewis-acid catalyst in the presence of water or other nonswelling liquid at elevated temperature. U.S. Pat. No. 4,543,365 discloses the use of a Lewis-acid catalyst to increase the surface area of a copolymer containing 8 to 80 percent crosslinker by postcrosslinking in the presence of an organic swelling agent.
The problem addressed by the present invention is to overcome the deficiencies of prior methods used to prepare high surface area adsorbents, such as requiring the use of swelling solvents and Lewis-acid/Friedel-Crafts catalysts, and to provide high surface area macroporous adsorbents having improved swelling properties, that is, a reduced tendency to swell in solvents during the adsorption/regeneration cycles of typical end use applications.
STATEMENT OF INVENTION
The present invention provides a macroporous polymeric adsorbent comprising monomer units of (a) from 50 to 100 percent by weight of one or more polyvinylaromatic monomer, and (b) from zero to 50 percent by weight of one or more monounsaturated vinylaromatic monomer; wherein the adsorbent contains less than 0.5 millimole vinyl groups per gram, has a surface area of greater than 700 square meters per gram, has a mesoporosity of greater than 0.7 cubic centimeter per gram, and has a swelling ratio in organic solvent of less than 10 percent by volume.
The present invention further provides a method for preparing a high surface area, low-swelling macroporous polymeric adsorbent comprising (a) contacting one or more macroporous copolymer comprising from 50 to 100 weight percent polyvinylaromatic monomer units, and having at least 1.0 millimole residual vinyl groups per gram copolymer, with at least 5 weight percent of one or more organic sulfonic acid, based on total weight of the macroporous copolymer, to form a copolymer-acid mixture; (b) maintaining temperature of the copolymer-acid mixture between 20 and 140° C. for at least 30 minutes; and (c) removing the organic sulfonic acid from the copolymer-acid mixture and isolating the macroporous adsorbent.
DETAILED DESCRIPTION
We have discovered a process for preparing a macroporous adsorbent that does not require the use of organic swelling solvents and provides a macroporous adsorbent having good physical stability, little or no swelling in organic solvents, and with few or no residual pendant vinyl groups.
As used herein, the term “superlink (SL) macroporous adsorbent” refers to macroporous polymers having the following properties:
(a) contain no or few residual vinyl groups, that is, less than 0.5, preferably from zero to 0.3, more preferably from zero to 0.2 and most preferably from zero to 0.1 millimole vinyl groups per gram polymer (mmol/g); and
(b) exhibit little or no swelling in organic solvents (such as methanol, acetone or isopropanol), that is, less than 10%, preferably less than 5% and more preferably less than 3%, based on volume.
In a preferred embodiment, the SL macroporous adsorbents comprise at least 1.0, preferably from 1 to 7 and more preferably from 2 to 7 millimole of (C
2
-C
4
)alkylene bridging groups per gram of polymer (mmol/g); most preferably, the SL macroporous adsorbent will contain between 2 and 5 mmol/g of (C
2
-C
4
)alkylene bridging groups.
The SL macroporous adsorbents comprise at least 50% polyvinylaromatic monomer units, have surface areas of greater than 700, preferably greater than 800 and more preferably greater than 1000 square meters per gram (m
2
/g); and mesoporosity values of greater than 0.3, preferably greater than 0.7 and more preferably greater than 0.9 cubic centimeter mesopores per gram polymer (cm
3
/g).
Particularly preferred SL macroporous adsorbents of the present invention contain from zero to 0.1 mmol/g vinyl groups, have surface areas of greater than 800 m
2
/g, mesoporosities of greater than 0.8 cm
3
/g and swelling ratios in organic solvent of less than 5% by volume.
As used herein, the term “crosslinked macroporous copolymer” indicates a polymer or copolymer polymerized from a monomer or mixture of monomers containing at least 50 weight percent (%), based on the total monomer weight, of polyvinyl unsaturated monomer. The crosslinked macroporo
Langenmayr Eric Jon
Lundquist Eric Gustave
Foelak Morton
Howell Thomas J.
Rohm and Haas Company
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