GB1583367A

GB1583367A - Wound coverings

Info

Publication number: GB1583367A
Application number: GB41538/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-05-19
Filing date: 1978-05-19
Publication date: 1981-01-28

Description

(54) WOUND COVERINGS (71) I, BRUCE SAMWAYS, a British subject of Wonderstone House, Bleadon, Avon BS24 ONX, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a process for the production of wound coverings, and to wound coverings made according to the process described. It further relates to processes for converting bulk wound covering material into discrete wound covers peelably adhered to protective backings. There is described in BP 1384537 wound coverings capable of adhering to moistened mucosal or skin surfaces comprising a water-soluble film forming material characterised in that there is present on one major surface of the film a water-insoluble metal salt of the filmforming material and a process for their manufacture comprising the forming of a film from a solution of a water-soluble material removing part of the solvent and applying to one surface of the film a solution of a metal salt to form the water-insoluble metal salt on that surface, and then further drying of the film. According to the present invention there is provided an improved method for the manufacture of improved coverings of the above type characterised in that a layer of an aqueous solution, containing a wetting agent, of a suitable metal salt is first deposited on to a patterned surface having a design in intaglio or relief, followed by doctoring of that layer, followed by the superposition thereon of a layer of controlled thickness of a solution of the water-soluble film forming material followed by drying of the whole in one operation to the desired residual moisture content.

In a preferred form of the invention the patterned surface comprises that of an endless belt of butyl rubber of sufficient thickness and rigidity to prevent shrinkage of the wound covering material during drying, and bearing a patterned surface of raised or intaglio dots, lines or other pattern including lettering, characterised in that all unpatterned portions of the surface shall have at least one dimension in any direction less than 0.1 inches and preferably less than 0.05 inches. Unpatterned areas which do not meet this criterion can result in either insufficient dose of precipitant or else in splitting of the wound covering material during drying.

In the preferred form the process is carried out as follows. The belt is caused to move in a substantially horizontal plane under a feed means supplying an excess of - an aqueous solution of a suitable metal salt containing a wetting agent and the fully wet belt is passed under an inclined doctor blade to remove excess solution.

The blade preferably comprises a rubber strip inclined at an angle of from 20 to 80 degrees, preferably 45 degrees and loaded so that it exerts a force of from 20 to 100, preferably 50 grams per linear centimetre, on the wetted belt surface. This permits the required dose of precipitant to remain in the intaglio portions of the design whilst leaving a sufficiently wet surface on the raised portions of the design to ensure that the insolubilised surface of the finished wound covering is continuous.

There is then deposited on to the precipitant-wet patterned surface by extrusion or other controlling means well known in the art of film manufacture a layer of controlled thickness of an aqueous solution of the film-forming material, and the laden belt is caused to pass under drying means of conventional type, preferably comprising a series of hot air blowers to remove the aqueous solvent down to the desired final residual moisture content.

The wound covering material produced by this process is found to have desirably different surfaces on its two opposed faces in that the insolubilised under surface bears an image of the pattern and is substantially non-tacky, whereas the upper surface will adhere lightly to any smooth surface.

In the preferred form of the process this facility is exploited by laying on to the upper surface of the wound covering material a continuous backing sheet of a suitable film material, preferably white opaque polythene 0.002 to 0.010 inches thick and ideally 0.005 inches thick whilst the wound covering material is still supported on the butyl rubber belt. The backing film and the wound covering material adhering together are then removed continuously from the belt and may be wound up together for subsequent handling. It will be noted that the tacky surface is that which will be applied ultimately to the wound, and that this surface is fully protected from dust and contamination by the application of the backing film.

The composite of a backing film as above described bearing a wound covering material as described in BP 1384537 prepared according to the process of this invention may be further processed advantageously as follows. The backing film is passed under rotary or reciprocating cutters of known type so that the wound covering material only is cut or punched into desired shapes such as discs whilst the backing is left súbstantially uncut.

Excess wound covering material is then peeled off and discarded, leaving a series of discs or other desired shapes spaced on the backing film, which is then cut into suitable units each bearing one or more shaped wound covers. It is found that the coverings prepared by this process may be conveniently peeled by hand or forceps from the backing film at the time of use, and it will be noted that this feature avoids any ambiguity as to the correct face of the covering to apply to the wound.

The pattern may be used to define medi cation to other data applicable to the product.

The following example illustrates the invention: Butyl rubber plates 0.1 inches thick were prepared according to the art practiced in flexographic printing, each plate having one surface covered with a regular relief pattern of circular dots, each dot having a diameter of 0.05 inches and with its centre at a distance of 0.1 inches from that of its nearest neighbouring dot. The plates were trimmed to the same rectangular shape and were butt joined to form an endless belt. An aqueous solution of 5 w/w calcium chloride expressed as the anhydrous salt containing also 5 w/w glycerol and sufficient surface active agent to ensure wetting of the butyl rubber sur face was applied to the patterned face, and the flooded belt was passed horizontally under a transversely disposed doctor blade comprising a 0.1 inch thick strip of rubber 10 inches wide inclined at 45 degrees to the belt with a force of 0.9 kilograms. All of the recessed part of the pattern remained full of the solution and the surfaces of the raised dots were also wet therewith. The wet belt was then passed at a speed of 6 inches per minute under a hopper 9 inches wide disposed to feed a constant thickness of 0.055 inches of a solution in water containing 10 w/w sodium alginate, 8 w/w glycerol and 0.2 w/w lignocaine hydrochloride. The belt bearing the two superposed layers of solutions was then passed at the same speed under a series of air jets discharging air at 80 C sufficient to dry the wound covering material to a residual moisture content of 12%. A layer of white opaque polythene film 0;003 inches thick was unwound and applied continuously to the upper smooth surface of the wound covering material, and the polythene film bearing the lightly adherent .wound covering material was stripped from the belt and wound up into a roll as alternating layers of polythene and wound covering material. The patterned surface of the wound covering material did not adhere to the obverse side of the polythene, thus enabling the composite web to be unwound to give a continuous sheet of poly thene bearing a continuous sheet of wound covering material. This composite sheet was cut into pieces of convenient size which were fed separately into a platen press arranged to cut through the wound covering material layer only into a set of discs each 1 centimetre in diameter with a minimum space of 1 millimetre between each such disc. The spare wound covering material was stripped easily in one piece from the polythene, leaving the polythene bearing a series of discrete discs of wound covering material. These discs remain adhered to the polythene through a storage period of one year and were then easily peelable from the backing to give clean surfaces which were found to be suitable for adhering directly to a moistened mucosal or skin surface.

WHAT I CLAIM IS: 1. A process for producing wound cover ings of the type described in BP 1384537 characterised in that a layer of an aqueous solution, containing a wetting agent, of a suitable metal salt is first deposited onto a patterned surface having a design in intaglio or relief, followed by doctoring of that layer, followed by the super position thereon of a layer of controlled thickness of a solution of the water soluble film forming material followed by drying of the whole in one operation to the desired residual moisture content.

2. A process in which a layer of wound covering material as claimed in claim 1 is adherently covered with a smooth filmic

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. this facility is exploited by laying on to the upper surface of the wound covering material a continuous backing sheet of a suitable film material, preferably white opaque polythene 0.002 to 0.010 inches thick and ideally 0.005 inches thick whilst the wound covering material is still supported on the butyl rubber belt. The backing film and the wound covering material adhering together are then removed continuously from the belt and may be wound up together for subsequent handling. It will be noted that the tacky surface is that which will be applied ultimately to the wound, and that this surface is fully protected from dust and contamination by the application of the backing film. The composite of a backing film as above described bearing a wound covering material as described in BP 1384537 prepared according to the process of this invention may be further processed advantageously as follows. The backing film is passed under rotary or reciprocating cutters of known type so that the wound covering material only is cut or punched into desired shapes such as discs whilst the backing is left súbstantially uncut. Excess wound covering material is then peeled off and discarded, leaving a series of discs or other desired shapes spaced on the backing film, which is then cut into suitable units each bearing one or more shaped wound covers. It is found that the coverings prepared by this process may be conveniently peeled by hand or forceps from the backing film at the time of use, and it will be noted that this feature avoids any ambiguity as to the correct face of the covering to apply to the wound. The pattern may be used to define medi cation to other data applicable to the product. The following example illustrates the invention: Butyl rubber plates 0.1 inches thick were prepared according to the art practiced in flexographic printing, each plate having one surface covered with a regular relief pattern of circular dots, each dot having a diameter of 0.05 inches and with its centre at a distance of 0.1 inches from that of its nearest neighbouring dot. The plates were trimmed to the same rectangular shape and were butt joined to form an endless belt. An aqueous solution of 5 w/w calcium chloride expressed as the anhydrous salt containing also 5 w/w glycerol and sufficient surface active agent to ensure wetting of the butyl rubber sur face was applied to the patterned face, and the flooded belt was passed horizontally under a transversely disposed doctor blade comprising a 0.1 inch thick strip of rubber 10 inches wide inclined at 45 degrees to the belt with a force of 0.9 kilograms. All of the recessed part of the pattern remained full of the solution and the surfaces of the raised dots were also wet therewith. The wet belt was then passed at a speed of 6 inches per minute under a hopper 9 inches wide disposed to feed a constant thickness of 0.055 inches of a solution in water containing 10 w/w sodium alginate, 8 w/w glycerol and 0.2 w/w lignocaine hydrochloride. The belt bearing the two superposed layers of solutions was then passed at the same speed under a series of air jets discharging air at 80 C sufficient to dry the wound covering material to a residual moisture content of 12%. A layer of white opaque polythene film 0;003 inches thick was unwound and applied continuously to the upper smooth surface of the wound covering material, and the polythene film bearing the lightly adherent .wound covering material was stripped from the belt and wound up into a roll as alternating layers of polythene and wound covering material. The patterned surface of the wound covering material did not adhere to the obverse side of the polythene, thus enabling the composite web to be unwound to give a continuous sheet of poly thene bearing a continuous sheet of wound covering material. This composite sheet was cut into pieces of convenient size which were fed separately into a platen press arranged to cut through the wound covering material layer only into a set of discs each

1 centimetre in diameter with a minimum space of 1 millimetre between each such disc. The spare wound covering material was stripped easily in one piece from the polythene, leaving the polythene bearing a series of discrete discs of wound covering material. These discs remain adhered to the polythene through a storage period of one year and were then easily peelable from the backing to give clean surfaces which were found to be suitable for adhering directly to a moistened mucosal or skin surface.

backing followed by the removal of the backing and wound covering material together for subsequent processing.

3. A process as in claims 1 and 3 wherein the patterned surface is in intaglio or relief characterised in that all portions of the unpatterned area have at least one dimension in any direction less than 0.1 inches.

4. A process as in claim 3 wherein all portions of the unpatterned area have at least one dimension in any direction less than 0.05 inches.

5. A process as in any one of the claims 1 to 4 wherein the surface is that of a butyl rubber plate.

6. A process as in any one of the claims 1 to 5 wherein the plate is joined singly or in multiples to produce an endless belt.

7. A process as in any one of the claims I to 6 wherein the doctoring is performed by a rubber blade inclined at from 20 degrees to 80 degrees to the patterned surface and is loaded to give a pressure of from 20 to 100 grams/centimetre of length.

8. A process as in claim 7 wherein the blade is inclined at 45 degrees and is loaded to give a pressure of 50 grams/centimetre of length.

9. A process wherein wound covering material prepared according to any one of the claims 2 to 8 is cut or punched to shape whilst still in contact with the filmic backing followed by stripping of the discarded portion of the wound covering material to leave discrete wound covers tackily adhered in spaced relationship one to another on the filmic backing.

10. A process as claimed in claim 1 substantially as described in the Example.

11. Wound coverings when prepared by a process as claimed in any of the claims 1 to 10.