Stock material or miscellaneous articles – Composite – Of quartz or glass
Reexamination Certificate
1999-03-30
2003-05-20
Berman, Susan W. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of quartz or glass
C428S442000, C428S476300, C428S483000, C428S507000, C428S511000, C428S516000, C522S086000, C525S903000, C525S919000, C526S930000
Reexamination Certificate
active
06565981
ABSTRACT:
TECHNICAL FIELD
The present invention relates, in general, to polymers that absorb aqueous liquids (such as water, blood, and urine) and especially, relates to superabsorbent polymers, which are those absorbent polymers that are capable of absorbing over 10 times their weight in water. More particularly, the present invention relates to pre-superabsorbent polymers that will, upon being subjected to radiation, such as heating, cross-link to form superabsorbent polymers.
DEFINITIONS OF ABBREVIATIONS
Definitions of Abbreviations
Abbreviations
Definitions
X-linking
cross-linking
SAP
superabsorbent polymer, a polymer which
absorbs over 10 times its weight in water
pre-SAP
a polymer which is not a SAP and which is
capable upon as heating, becoming a SAP
CAA
composite absorbency ability
CRC
centrifuge retention capacity
H
2
O
2
hydrogen peroxide
GAA
glacial acrylic acid
PA
polyacrylate
HPA
hydroxypropyl acrylate
N-MMA
N-methylol methacrylamide
NaOH
sodium hydroxide
2-ME
2-mercaptoethanol
DI
deionized
mg
milligram
ml
milliliter
g
gram
mm
millimeter
cm
centimeter
psi
pounds per square inch
ppm
parts per million
VOC
volatile organic compound
UV
ultraviolet
BACKGROUND OF THE INVENTION
General background on the manufacture of superabsorbent polymers can be seen in the journal article, “Keeping Dry with Superabsorbent Polymers”,
Chemtech,
(September 1994) by Buchholz. This article contains an excellent discussion of the conventional methods for making superabsorbent polymers, certain of which have sulfonate functional groups and certain of which have carboxylic acid functional groups. Also mentioned are various uses for superabsorbent polymers, such as in a disposable diaper, in a sealing composite between concrete blocks that make up the wall of underwater tunnels, and in tapes for water blocking in fiber optic cables and power transmission cables.
More general background with respect to various superabsorbent polymers and their methods of manufacture can be seen in U.S. Pat. No. 5,229,466 (issued Jul. 20, 1993) to Brehm and Mertens; U.S. Pat. No. 5,408,019 (issued Apr. 18, 1995) to Mertens, Dahmen and Brehm; and U.S. Pat. No. 5,610,220 (issued Mar. 11, 1997) to Klimmek and Brehm, all of which patents are assigned to Chemische Fabrik Stockhausen GmbH.
Another good background discussion of the methods for making superabsorbent polymers can be seen in U.S. Pat. No. 5,409,771 (issued Apr. 25, 1995) to Dahmen and Mertens, assignors to Chemische Fabrik Stockhausen GmbH. More specifically, this patent mentions that commercially available superabsorbent polymers are generally X-linked polyacrylic acids or X-linked starch-acrylic-acid-graft-polymers, the carboxyl groups of which are partially neutralized with sodium hydroxide or caustic potash. Also mentioned is that the superabsorbent polymers are made by two methods. One method is the solvent polymerization method and the other method is the inverse suspension or emulsion polymerization method.
In the solvent polymerization method, an aqueous solution of partially neutralized acrylic acid, for instance, and a multi-functional network X-linking agent is converted to a gel by radical polymerization, typically followed by a heat treatment. The resultant is dried, ground and screened to the desired particulate size.
In the inverse suspension or emulsion polymerization method, an aqueous solution of partially neutralized acrylic acid, for instance, is dispersed in a hydrophobic organic solvent by employing colloids or emulsifiers. Then, the polymerization is started by radical initiators. Water is azeotropically removed from the reaction mixture after completion of the polymerization, typically followed by a heat treatment. The resultant product is then filtered and dried. Network X-linking is typically achieved by dissolving a polyfunctional X-linking agent in the monomer solution.
More specifically with regard to use of heat to effect X-linking, EP Patent Application Publication No. 0 397 410 A2 (published Nov. 14, 1990) to Allen, assignor to Allied Colloids Limited, describes a water soluble, substantially linear, polymer made by co-polymerization of a water soluble blend of monoethylenically unsaturated monomers comprising carboxylic acid monomers such as acrylic acid and a hydroxylic monomer of the formula CHR
1
═CR
2
—Y—M
a
—OH, where R
1
is hydrogen or carboxy; R
2
is hydrogen, carboxy, or methyl; Y is oxygen, CH
2
O, or COO; M is alkyleneoxy; and a is at least 5. After the polymer is shaped by extrusion or other shaping of an aqueous solution of the polymer, the polymer is X-linked, such as by heating above 150° C., typically at 220° C., to form X-linkages between the carboxyl and hydroxyl groups. The shaped resultant is described as being useful for diapers, catamenial appliances (i.e., sanitary napkins), incontinence pads, and bandages. EP Patent Application Publication No.0 397 410 A2 has priority to GB 8910788, which is one of several GB applications to which U.S. Pat. No. 5,147,956 (issued Sep. 15, 1992) and U.S. Pat. No. 5,280,079 (issued Jan. 18, 1994), both assigned to Allied Colloids Limited, have priority.
Moreover, EP Patent Application Publication No. 0 397 410 A2 states that achieved are higher and more reproducible absorption characteristics than in EP Patent Application Publication No.0 268 498 A2 (published May 5, 1988) to Allen, Farrar, and Flecher, assignors to Allied Colloids Limited. EP No. 0 268 498 A2 is a counterpart of U.S. Pat. No. 4,962,172 (issued Oct. 9, 1990), assigned to Allied Colloids Limited. Each of U.S. Pat. Nos. 5,147,956 and 5,280,079 is a Continuation-in-Part leading back to the U.S. application that matured into U.S. Pat. No. 4,962,172.
Additionally, U.S. Pat. No. 4,057,521 (issued Nov. 8, 1977) to Gross, assignor to The Dow Chemical Company, shows water swellable absorbent articles, made from copolymers having a copolymerized crosslinker, together with methods for their preparation, and a composition containing a copolymerized crosslinker useful to make said articles. The articles are crosslinked by heating and/or removing substantially all of the water from the precursor composition. The absorbent articles are useful as surgical sponges, diapers, tampons, meat trays, bath mats, and the like.
Furthermore, U.S. Pat. No. 5,534,304 to Geursen and Willemsen, assignors to Akzo Nobel NV, shows a process for treating a substrate, namely a fibre or a fibrous product, with a superabsorbent material, in which process there is applied to the surface of the substrate, which is not an aramide fibre, a layer of a water-in-oil emulsion which contains a superabsorbent material in its aqueous phase, so that there is applied to the substrate, calculated on its dry weight, 0.3 to 40 wt. % of the superabsorbent material, after which the liquid constituents of the emulsion are wholly or partially removed from the substrate.
Also of interest are U.S. Pat. No. 4,812,491 (issued Mar. 14, 1989) to Hahn, assignor to the Glidden Company, and EP Published Patent Application No. 0 021 618 A1 (published Jan. 7, 1981) to Backhouse and Palluel, assignors to Imperial Chemical Industries Limited, both of which describe suspension polymers useful as paint coatings. More particularly, the U.S. patent involves a process for producing a self-curing paint coating composition that requires co-polymerizing ethylenically unsaturated monomers, such as carboxyl or hydroxyl functional monomers and also alkylol acrylamide monomer (but excluding amine monomers), followed by treating the resultant with an ion exchange resin to remove cations from the emulsion polymer and produce a pH of less than 2.5 in order to produce a thermoset paint coating film. The European publication involves a process for the production of X-linked addition polymer microparticles made from the dispersion polymerization of ethylenically unsaturated monomers in an aliphatic hydrocarbon liquid in the presence of a specific stabilizer. The process requires that at least one of the monomers contains hydroxymethylamino or alkoxymethylamino and at least one other monome
Agne Robert
Hsu Whei-Neen
Messner Bernfried
Berman Susan W.
Smith Moore LLP
Stockhausen GmbH & Co. KG
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