Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Patent
1993-11-04
1998-04-28
Weber, Thomas R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
5263497, C08F 232
Patent
active
057445648
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to absorbents formed of water insoluble, typically gel-forming, polymeric materials that are capable of, for example, absorbing many times their own weight upon contact with aqueous fluids. More particularly, the present invention focuses upon polymeric materials that absorb substantial volumes of such fluids at a high rate of absorption, processes for making them, uses thereof in absorbent articles, and absorbent articles incorporating such polymeric materials.
Many water insoluble gel-forming polymers are known for their usefulness as absorbents because of their ability to imbibe and bind or immobilize aqueous fluids. These polymeric materials find employment in industry for various dewatering and fluid immobilization uses, such as water retaining agents in agricultural/horticultural fields, dehydration of oil, and like purposes. In recent years absorbent polymers having large capacities for absorbing aqueous fluids have been developed and have found use in personal care products for absorbing aqueous biological fluids. In a typical personal care product, such as a diaper, the aqueous fluid absorbent polymer is utilized in powder form, and is often mixed with cellulosic fibers that help initially absorb and distribute the fluid load. The polymeric materials of interest in such products are based upon a variety of polymers including those derived from water soluble ethylenically unsaturated monomers or graff polymers in which unsaturated monomers are graff polymerized onto a polysaccharide (such as starch or cellulose) or other polymeric backbone.
A preferred absorbent material is derived from a water insoluble gel formed by copolymerizing an ethylenically unsaturated carboxylic acid with a multifunctional crosslinking monomer. The acid monomer or polymer is substantially neutralized with an alkali metal hydroxide, dried and pulverized into a powder form before use in a personal care product. A preferred polymer gel is a copolymer of acrylic acid/sodium acrylate and any of a variety of crosslinkers.
Achieving desired polymeric characteristics that provide superior performance in a personal care product has long been a challenging goal of researchers. The product must perform for the user but also must be capable of being economically and safely made. At the customer/user level, a diaper, for example, most desirably must keep the user substantially dry, even in response to repeated wettings. Thus, a key desired characteristic of an aqueous fluid absorbent polymer, at least for diaper use, is that it have high fluid capacity, e.g., a centrifuge capacity greater than 10 grams/gram. In addition, a most desired characteristic of the aqueous fluid absorbent polymer is that it has a fast rate of absorption, adequate to imbibe and hold the fluid during absorption without leakage of fluid from the device in which it is employed. It is adequate fast rate, while maintaining all of the other desired qualities of the aqueous absorbent, that has eluded prior researchers.
It is well-known in the prior art that the rate of fluid absorbency is substantially determined by the surface area of the particles. Thus, extremely fine particles of aqueous fluid absorbent, those less than 100 mesh (149 micrometers), would be expected to absorb liquids at a rapid rate. However, the individual particles at the surface of the polymeric mass of such fines initially contacted by the fluid rapidly swell and adhere together, drastically reducing the rate of absorption as the fluid is "gel blocked" from access to particles of absorbent in the mass that are more remote from the surface. Lumps or "fish eyes" often form such that overall performance of the absorbent material is unsatisfactory.
An additional difficulty with fine materials is that such fines create dusting problems in manufacturing and forming into finished articles. Fines or dusts may be a source of industrial hygiene risks for workers as well as pose difficult materials handling problems. At the product level it may be difficult to immobilize fin
REFERENCES:
patent: 4037040 (1977-07-01), Trapasso
patent: 4340706 (1982-07-01), Obayashi
patent: 4446261 (1984-05-01), Yamasaki
patent: 4578068 (1986-03-01), Kramer
patent: 4600458 (1986-07-01), Kramer
patent: 4666983 (1987-05-01), Tsubakimoto
patent: 4683274 (1987-07-01), Nakamura
patent: 4739008 (1988-04-01), Robinson
patent: 4742086 (1988-05-01), Masamizu
patent: 4757091 (1988-07-01), Hawrylko
Lamphere Jack C.
Stanley, Jr., deceased Frederick W.
Wilson Larry R.
The Dow Chemical Company
Weber Thomas R.
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