Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Web – sheet or filament bases; compositions of bandages; or...
Reexamination Certificate
2000-03-17
2003-05-20
Page, Thurman K. (Department: 1615)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Web, sheet or filament bases; compositions of bandages; or...
C424S424000, C424S449000
Reexamination Certificate
active
06565878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for preparing a non-fibrous porous material being swellable but not soluble in water essentially consisting of one or more hydrophilic polymers and/or pharmaceutical water-soluble medicaments, an absorbing article containing such material and the use of such material for the preparation of an absorbing article.
2. Description of the Related Art
Non-fibrous porous materials essentially consisting of one or more hydrophilic polymers and/or pharmaceutical water-soluble medicaments and methods for preparing such materials are disclosed in WO 95/05204 and in JP 01-011141.
One method for preparing such products using a hydrous solution of a hydrophilic polymer such as casein, gelatine, collagen, albumin, fibroin, cellulose, starch, agar, sodium carboxyl methyl cellulose, methyl cellulose, polyvinyl alcohol, polyacrylic acid, or polyacrylamide is disclosed in JP 01-011141. According to JP 01-011141, a surfactant of non-ionic, cationic, anionic or amphoteric type is added to the hydrous solution and then freeze-drying is carried out. The polymer is dispersed in water at a concentration of 0.05 to 50%, and the surfactant is used in amounts of from 0.5-100%.
Another method or preparing such products using a hydrous solution of a hydrophilic polymer such as a synthetic hydrophilic polymer, a polysaccharide or a biological hydrophilic polymer is disclosed in WO 95/05204. According to WO 95/05204, one or more pharmaceutical medicaments and/or hydrophilic polymers are dissolved in water to provide a solution or a sol, a freeze plate is pre-nucleated by passive condensation or by evaporating or atomising water or the aqueous solution of the pharmaceutical medicaments and/or hydrophilic polymers and/or salts, the solution of one or more pharmaceutical medicaments and/or hydrophilic polymers is provided on the pre-nucleated freeze plate, the temperature of which is kept below the freezing point of the atomised water or solution, the solution is frozen to provide an ice sheet comprising the pre-nucleated frozen material, the sheet is freeze dried, and the resulting sheet is optionally cut into pieces of suitable sizes.
WO 96/20015 discloses chitosan salts and a process for the preparation thereof. The chitosan salt may be recovered in a desired form depending on the use for which it is intended, and for use in absorbent personal care products such as a wound dressing it is generally in the form of a discrete particle, fibre or flake. There is no indication of production of a cohesive gel and the content of cross-linker is below 10 weight percent.
GB 2 296 250 discloses a method for-preparing water-swellable, water-insoluble chitin/chitosan salts having improved absorption properties by forming a mixture of a chitosan, water, an acid, and, optionally, a crosslinking agent, recovering the formed chitosan salt from the mixture and, optionally, treating said recovered chitosan salt with heat under humid conditions. Freeze drying of these hydrogels results in stiff and brittle xerogels which are unpleasant in contact with human skin or wounds.
A water absorbing porous material can be prepared from cross-linked CMC powders by the freeze drying technique disclosed in WO 95/05204. However, xerogels produced in this manner have no cohesion after rehydration due to the formation of a sol gel.
These properties render such materials less suitable for use if they are not fully enclosed as they tend to disintegrate when absorbing water. Such disintegration render such materials less suitable for use in wound dressings as it is highly desirable that the absorbing material has a sufficient cohesion to be removed as an integrate piece without leaving residues on the skin or in the wound.
WO 94/04724 discloses a method of producing a fibre or film by extruding an aqueous solution of a water-soluble polymer into a gaseous medium to form fibre or film. The extruded fibre or film is dried and cross-linked at a temperature in the range of 125 to 250° C. to a degree sufficient that the crosslinked fibre or film is water-insoluble. The resulting fibres or film are intended for use in preparing webs for use in absorbing articles.
EP 0 269 393 discloses preparation of fibre or film by dry extrusion of a solution of a linear polymer formed from a water soluble blend of mono ethylenically unsaturated monomers comprising plasticizing monomer.
EP 0 268 498 discloses a water absorbent water insoluble polymeric element such as a fibre, film, coating, bonding layer or foam made by forming a substantially linear polymer by polymerization of water soluble ethylenically unsaturated monomer blends and then crosslinking the same.
DE 26 27 708 discloses water swellable fibres made from water-insoluble acrylic acid polymerization.
The above references are silent with respect to preparation of an absorbing material having a very high absorbing capacity and having, at the same time, a very high degree of cohesion rendering the material suitable for use in an article being in direct contact with the skin or the surface of a wound
Thus, there is still a need for an absorbing material having a very high absorbing capacity and having, at the same time, having a very high degree of cohesion rendering the same suitable for use in an article being in direct contact with the skin or the surface of a wound. Examples of absorbing articles are, e.g., disposable diapers, incontinence articles, sanitary napkins or the like having an absorbing core or an absorbing wound dressing.
It has surprisingly been found that the novel porous materials prepared according to the present invention are swellable but not soluble in water and are very suitable for use as absorbing components in, e.g., wound dressings.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a method for preparing a non-fibrous porous material being swellable but not soluble in water essentially consisting of one or more hydrophilic polymers and/or pharmaceutical water-soluble medicaments; a non-fibrous material which may be produced by the method; a dressing comprising a non-fibrous porous material essentially consisting of one or more hydrophilic polymers and/or pharmaceutical medicaments; and the use of such a material for the preparation of a dressing or an absorbent article.
DETAILED DESCRIPTION OF THE INVENTION
In a first aspect, the invention relates to a method for preparing a non-fibrous porous material being swellable but not soluble in water, the material essentially consisting of one or more natural or semi-synthetic hydrophilic polymers or one or more hydrophilic polymeric component(s) and one or more pharmaceutical medicaments, the method comprising forming an aqueous solution or sol gel comprising one or more hydrophilic polymers or one or more hydrophilic polymeric component(s) and one or more pharmaceutical medicaments, forming an object of the solution or sol gel having a desired shape and dehydrating the same leaving a non-fibrous porous material in a solid, porous form, and subjecting the resulting porous material to a dry heat treatment.
A material produced in this manner shows superior absorbing capacity and does not disintegrate upon absorbing water. It is believed that the dry heat treatment causes formation of cross-links in the non-fibrous porous material being responsible for the superior properties with respect to absorbing capacity combined with a cohesion ensuring non-disintegration upon swelling.
In a preferred embodiment of the method of the invention, one or more hydrophilic polymeric component(s) or one or more hydrophilic polymeric materials component(s) and one or more pharmaceutical medicaments are dissolved or solubilized in water to provide a sol gel, the gel sol is placed on a surface, the temperature of which is to be kept below the freezing point of water or the gel sol, freezing the solution or sol gel to provide an ice structure comprising the frozen material and removing the water selectively leaving the solid materials of the solution
Ayzma Josef
Nielsen Brian
Schoenfeldt Lars
Coloplast A/S
Ghali Isis
Jacobson & Holman PLLC
Page Thurman K.
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