Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
1995-01-10
2001-08-07
Bawa, Raj (Department: 1619)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S443000, C424S078060, C424SDIG001
Reexamination Certificate
active
06270794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an improved wound filler. More particularly, this invention relates to a wound filler having high moisture absorption capacity.
2. Description of the Prior Art
It is well known that the removal of wound exudates is important to the process of healing of wounds. Commonly used wound dressings utilize gauze, foams, sponges, cotton wads or other fibrous materials. Gauze and other fibrous materials absorb fluids by capillary action. However, gauze and other fibrous materials have the disadvantage in that when new tissue is formed, in the process of healing, it engulfs the fibers of these materials and it is torn when the material is removed causing wound injury on removal.
Various other materials have been used, such as gels, hydrogels, granules and pastes to remove exudates from wounds. These materials have the disadvantage of being difficult to remove from the wound after hydration.
U.S. Pat. No. 4,551,490 describes an adhesive composition useful with ostomy and incontinent appliances and which has also been used in adhesive bandages. The composition consists of a homogeneous mixture of polyisobutylene, styrene radial or block-type copolymer, mineral oil, soluble hydrocolloid gum, water swellable cohesive strengthening agent and a tackifier. This composition has limited exudate absorption capacity and requires a tackifier for its intended use as an adhesive composition.
SUMMARY OF THE INVENTION
The present invention provides wound filler having high exudate absorbing capacity. The wound filler comprises from about 25% to 75% by weight of a polymeric matrix and 25% to 75% by weight of absorbing powders. The polymeric matrix contains from about 15% to 75% by weight of one or more styrene radial or block type copolymers, from about 5% to 40% by weight of one or more polyisobutylenes and from about 5% to 40% of mineral oil. The absorbing powders contain from about 10% to 100% by weight of sodium calcium alginates, from about 0% to 80% by weight of cross-linked sodium carboxymethylcellulose, from about 0% to 80% by weight of absorbent polyacrylates and from about 0% to 20% by weight of water soluble hydrocolloids.
This invention is also directed to a method of wound healing which comprises placing the absorbent wound filler into the wound to absorb the exudate.
The absorbent wound filler of this invention can absorb 500% to 1000% its original weight, can be removed from the wound in one piece and does not cause wound injury on removal. The wound filler keeps the wound bed moist and produces in a wound an environment suitable for healing. The filler absorbs exudate without desiccating or dehydrating the wound bed, freshly generated tissue does not grow into it causing injury on removal. The absorbent wound filler of this invention is particularly useful for chronic heavily exudating wounds with large cavities.
DETAILED DESCRIPTION OF THE INVENTION
The absorbent wound filler of the present invention contains a polymeric matrix and absorbing powers dispersed within the matrix.
The wound filler contains from about 25% to 75% by weight of polymeric matrix and 25% to 75% by weight of absorbing powders. Preferably, the wound filler contains 35% to 50% matrix and 50% to 65% absorbing powders.
The polymeric matrix is the structural component of the wound filler of this invention. It is sponge-like or a network of polymeric stretchable fibers or lamellas, within which the absorbing powders are entrapped. The polymeric matrix is a stretchable, elastic, sponge-like network of long chain molecules which form a mat-like structure. Embedded within this three-dimensional network are absorbing powders, powders capable of hydrating and swelling when exposed to exudate. The polymeric stretchable network allows the hydrating powders to swell and retains the powders in an integral structure but does not disintegrate under the forces of expansion. In addition, the polymeric matrix retains its physical properties when irradiated.
The polymeric matrix contains from about 15% to 75% by weight of styrene radial or block type copolymers and from about 5% to 40% by weight of mineral oil and from about 5% to 40% by weight of polyisobutylene. The preferred polymeric matrix composition contains 40% to 60% styrene radial or block type copolymers and 20% to 30% mineral oil and 20% to 30% polyisobutylenes.
The styrene radial or block copolymer component of the wound filler provides structure and elasticity. The material permits swelling of the absorbent powders and does not break down when exposed to gamma radiation. These materials are described in U.S. Pat. No. 4,551,490. Particularly suitable styrene copolymers include styrene-butadiene-styrene (S-B-S) and styrene-isoprene-styrene (S-I-S) block type copolymers both of which are commercially available, for example, from Shell Chemical Co. under the trademark Kraton, as Kraton 1100, 1101, 1102, 1107, etc. The most preferred material is the styrene-isoprene-stryrene copolymer Kraton 1107. One or more styrene-isoprene-styrene (S-I-S) block type copolymers may be employed.
The polyisobutylene component of the wound filler helps to bind the absorbing powders in the styrene radial or block copolymers network. It is a very viscous semi-solid material. Suitable polyisobutylene materials are described in U.S. Pat. No. 4,551,490. The preferred polyisobutylenes are more low molecular weight polyisobutylenes having a viscosity average molecular weight of from about 36,000 to about 58,000 (Florey). Such polyisobutylenes are commercially available under the trademark Vistanex from Exxon as grades LMMS and LMMH. Preferably, polyisobutylene Vistanex LMMH is used in the wound filler of this invention. If desired, 25% to 75% of the polyisobutylene can be substituted with butyl rubber.
The mineral oil functions as a plasticizer for the styrene radial or block copolymer component. It is also functions to increase the stretchability of the wound filler matrix.
The absorbing powders of the wound filler of the present invention constitute 25% to 75% by weight of the composition. In the preferred compositions, the absorbing powders are present in about 50% to 65%. The powders for use in this invention absorb at least 300% by weight of the wound filler and preferably 500%. The absorbing powders useful in the invention have large water absorbing capacity, i.e., 1000% to 4000% by weight and are capable of being irradiated without substantial loss of water absorbing capacity. Additionally, they must not be easily leached out of the matrix when in contact with water.
The absorbing powders contain from about 10% to 100% by weight of sodium-calcium alginates such as those available under the tradename KELSET from Kelco Co., or mixtures of sodium alginate and calcium alginate commercially available under the tradename SOBALG Na Alginate and SOBALG Ca Alginate and commercially available from Grinsted of Denmark or mixtures of Na Alginate and Ca Alginate available under the tradenames PROTANAL Na Alginate and PROTANAL Ca Alginate from Protan of Norway. Preferably, the absorbing powders contain 10% to 75% by weight of sodium-calcium alginates.
In addition to the alginates, the absorbing powders contain from 0% to 80% and preferably 0% to 60% by weight of cross-linked sodium carboxymethylcellulose such as that commercially available under the tradename AcDiSol from FMC and under the tradename AKUCELL SWX 177 from Akzo Co. of Holland and 0% to 80% and preferably 0% to 60% of finely divided substantially water insoluble highly absorbent polyacrylates representative of the highly absorbent polyacrylates are starch-graft copolymer such as that described in U.S. Pat. No. 3,661,815 and commercially available from Grain Processing Corp. under the tradename WATER LOCK A100 [a starch-graft-poly (sodium acrylate-co-acrylamide)], salt of cross-linked polyacrylic acid/polyalcohol grafted copolymer commercially available under the tradename FAVOR SAB800 from Stockhausen, Inc., Greensboro, N.C., polyacrylate available under t
Bolton Laura Lee
Cilento Rodolfo D.
Pirone Louis A.
Bawa Raj
Bristol--Myers Squibb Company
Furman, Jr. Theodore R.
Kilcoyne John M.
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