NO782507L - PROCEDURE FOR PREPARING A MEDICAL WOOD COMPOUND - Google Patents

Description

Method for producing a medical wound dressing.

The invention relates to a method for producing a medical wound dressing which is applicable for many types of injuries. However, it is particularly beneficial in the active treatment and for covering thermal, chemical, electrical and similar damage, which is usually treated as burns. The medical wound dressing is particularly suitable for covering the surface of untreated necrotic burns, for surgically treated burns and for other large-surface skin defects, thereby acting as a skin-like cover layer (temporary skin replacement) for protection and healing of wounds. Moreover, this medical wound dressing is applicable in the form of . compresses and as a connecting substance.

Dressing material for wound treatment must have different properties. In addition, the dressing material must be absorbent and remove the exudate emerging from the wound

and thereby it must at the same time protect and cover the wound so that the risk of infection from harmful bacteria is reduced. Furthermore, a connecting material must not contain toxic substances, which could be absorbed by the wound. Known dressing materials such as underlays of cotton-scharpie or cotton-rayon wool, covered with non-woven material, do indeed have good absorbent properties, however the fibers on their surface tend to cling to the wound or to absorb the exudate of the wound so that the fibers actually embedded in the crust, while this coagulates and becomes hard.

When such dressing material is removed to examine or treat the wound, the wound and/or the crust can thus be damaged, which delays the healing process and even opens the wound again.

Efforts have therefore already been made to produce connecting material from completely closed material, for example from polyethylene. Such dressing material does indeed provide a satisfactory environment for skin regeneration in the vicinity of the wound, but the exudate is not absorbed satisfactorily, so that fluid accumulations form in the wound, which is undesirable.

According to DOS 2,103,590, a medical wound dressing is known for local use to cover burns and the like, which consists of a pre-layer of a neutral thrombogenic, net-formed, open-pored foam material and a gas-permeable microporous backing attached to it extending in the same direction. The front side is formed by net-shaped polyurethane soft foam and the back side by a polyolefin or polypropylene foil, and both sides are connected to each other, e.g. using a gas permeable adhesive. This wound dressing has the disadvantage that its production using the starting materials required according to the invention and a three-layer construction is very expensive, in particular the use of a specially pre-treated polyurethane soft foam plays an important role. Furthermore, the back of the wound dressing does not have sufficient mechanical strength to prevent destruction of the surface during the medical application, so that local bacterial inhibition is not ensured. A further disadvantage of this wound dressing is the complete fluid permeability, whereby it is not possible to assess the wound with respect to its fluid secretion without removing the wound dressing. This fluid-tight backing of the wound dressing leads to uncontrolled fluid accumulations that hinder the optimal healing process.

Furthermore, according to DOS 248,813, a non-net-like polyurethane foam article is known for use as a connecting material, whose foam cells in the vicinity of at least one surface with respect to the foam cells removed from this surface are irreversibly partially collapsed.

When used as a dressing material, this polyurethane foam article has the disadvantage that it neither has a defined open-celled surface or no original cell structure of the starting material, or has a defined densified surface with reproducible properties. Furthermore, because of this unevenness, it is predominantly relatively stiff and thus not sufficiently compatible with wounds.

It does not guarantee any constancy in the gas and water vapor permeability over the entire surface and does not have a sufficient protective effect against infection of the wound from the outside. Furthermore, this medical wound dressing is not suitable as a temporary skin substitute for the treatment of 2nd and 3rd degree burns, ulcus cruris and other large surface skin defects, does not sufficiently favor the rapid formation of new capillaries and thus the formation of a wound bed suitable for transplantation with an even granulation lawn, as the original cell structure is missing.

The purpose of the invention is to provide an economical method for the production of a versatile,

cheap, medical wound dressing with good absorption, defined gas and water vapor permeability, sufficient protection against bacteria, necessary mechanical and good lyophilic properties, as the medical wound dressing is particularly suitable for the treatment of burns and similar wounds, and thereby acts as a skin-like covering layer (temporary skin replacement ) for protection and for healing.

The invention is based on the task of providing a method for the production of a versatile, inexpensive, medical wound dressing with good adaptability, defined gas and water vapor permeability, sufficient protection against bacteria, necessary mechanical and good lyophilic properties, especially for effective treatment of burns and similar wound, consisting of a front side defined to the original cell structure of the initial foam material and a defined, evenly densified with a uniform apparent pore volume equipped rear side of polyurethane soft foam material.

The task is solved according to the invention in that an open-cell polyurethane soft foam fabric film with a thickness of 0.5 to 10 mm, preferably 1.2 to 2 mm, softens on a surface without thermal splitting until sticky and is bonded with a from 2-

to 30-fold, preferably 10- to 20-fold, irreversibly densified polyurethane soft foam film, with a thickness of from 0.1 to 2.0 mm, preferably 0.3 to 0.6 mm, gas and water vapor permeable and'optionally thereafter cleaned physically and/or chemically.

Achieving stickiness of the surface of the open-cell polyurethane soft foam film takes place, for example, with the help of flame, radiation or a heat wedge. When heating the surface of the open-cell polyurethane soft foam film to sticky heat with a flame, work is preferably done in a temperature range from 500 to 700°C and at a residence time of 0.05 to 0.06 seconds. The irreversibly densified polyurethane soft foam film compresses both sides irreversibly throughout, preferably of polyurethane soft foam with a thickness from 1 to 80 mm, preferably 50 mm, continuously between two steel bands at a temperature from 200 to 280°C, preferably 230° C, a residence time of from 2 to 10 minutes, preferably 3 minutes, and a compression ratio of from 2:1 to 30:1, preferably 10:1 to 20:1, and then cleaved into foils with a thickness of from 0.1 to 2, 0mm, preferably 0.3 to 0.6 mm, continuous in widths up to 2500 mm. The upper and lower cover layer of the continuous irreversibly compressed polyurethane soft foam material is preferably separated with a thickness of 0.2 to 0.6 mm and added to a different application purpose so that any soiling and crusting cannot affect the quality of the foil.

The polyurethane soft foam film that can be used according to the invention can be a polyurethane soft foam on a polyester or polyether basis, preferably using a polyurethane soft foam with a high amount of residual cell walls. The room weight is 15 to 100 kg/m<3>.

As a polyester-based polyurethane soft foam material, a foam material with the following composition is preferred: 100.0 parts polyester alcohol based on adipic acid,

diol, triol

4.0" water

1.5 " tert. amine

44.0 toluylene diisocyanate

The unsealed open-cell original polyurethane soft foam foil forms the front side and the continuous irreversibly compressed polyurethane soft foam foil forms the back side of the wound dressing produced according to the invention.

The water vapor permeability of the wound dressing produced according to the invention preferably amounts to approx. 120 g/m<2> for 24 hours and the air permeability is preferably approx.

-1 -2 -1

0.2. mm water column, m . pp

The wound dressing produced according to the invention is immunologically inactive, ideally sterilizable both with β-rays and ethylene oxide as well as in an autoclave under discolouration without reducing the properties.

The front side of the wound dressing produced according to the invention covers the wound surface with the open-celled original structure, and the continuous irreversibly densified layer causes, in the presence of a sufficiently high amount of residual cell walls, a labyrinth effect, which with an apparent average pore size of 3 x 10 -4 mm to 8 x 10<-4>mm,

-4 -4

preferably 4 x 10 mm to 6 x 10 mm a sufficient barrier against an external bacterial invasion, guarantees a gas and water vapor permeability conducive to the healing process, regulates the fluid balance and in particular allows localizing a strong secretion and exudate accumulation without loosening the wound dressing according to the invention.

Overcoming unevenness in gas and water vapor permeability was primarily the main problem for the confirmation of such materials as medical wound dressing in the practical application. Surprisingly, it was now found that, in contrast to the material compressed only from one side, which does not guarantee evenness of the parameters, the method according to the invention can provide continuous irreversible densification of normal original polyurethane soft foam webs into a continuous irreversible densified polyurethane soft foam web followed by splitting in thin, hitherto unproducible porous foils are produced with precisely adjustable gas and water permeability dependent on the degree of thickening, volume of the starting foam material and foil thickness, which after dressing with an uncompressed open-cell original polyurethane soft foam film according to the invention produced medical wound dressings with the in relation to previously known dressings, the stated advantages.

Moreover, it was unexpected that despite thermal stress on the unsealed open-celled original polyurethane soft foam film when treated with a flame to achieve adhesiveness, no negative impact on the therapeutic effect is produced and thus this highly effective method can be used in contrast to unproductive bonding with physiologically unacceptable adhesives. There are thus no toxic side effects. In contrast, the method according to the invention provides a medical wound dressing with better therapeutic properties than the previously known products.

Implementation examples

Example 1

Made of an open-cell polyurethane soft foam material block on a polyester basis with a room weight of 42 kg/m . and a width of 1,500 mm is peeled off in a known manner each time a foam material web with a thickness of 50 mm and a thickness of 2 mm.

The foam web with -50 mm thickness is continuously compacted between heated steel bands, irreversibly throughout. The temperature of the steel bands is 251°C, the residence time 4 min. and the compression ratio 17:1. The thus densified foam web is then split into foils with a thickness of 0.3 mm. The upper and lower cover layers are separated with a thickness of 0.4 mm each time and added to a different application purpose, so that any soiling and crusting cannot adversely affect the quality of the irreversible compacted polyurethane soft foam film.

Next, the undensified open-celled polyurethane soft foam sheet with a thickness of 2 mm together with the continuous irreversibly densified polyurethane soft foam sheet is passed through two rollers and 'connected', the surface of the undensified open-celled polyurethane soft foam sheet on the to the continuous irreversibly pressed polyurethane soft foam film facing side without thermal cleavage by means of a flame in the temperature range from 500 to 700° C until tackiness. The roller is arranged so that the undensified open cell polyurethane soft foam film presses against the continuous irreversibly densified polyurethane soft foam foil as the foils run at the same speed. The resulting composition is then wound up. The finished material is divided using known methods into individual pieces, prepackaged in a known manner and sterilized.

The examination of the following Ex. 1 produced material took place with an apparatus, which consisted of a gas burette (150 ml), a separatory funnel (250 ml) and two tubes. The two tubes are identical to the tubes C and D of the one under "Prufung auf Arsen-Ionen"

in 2. AB-GDR mentioned apparatus. The level difference between the upper liquid mirror in the separating funnel and the zero point in the gas burette was 650 mm. The material to be examined was with the help of a

screwing fixed between the two planar ends of the pipes C and D.

Under these conditions, the following results emerged: The blank value corresponded to the passage time of the liquid without material application = 7 sec.

The first comparison value corresponded to a millipore filter with a pore diameter of 2 x 10 —4mm = 32 sec.

Another comparison value corresponded to a millipore filter with a pore diameter of 4.5 x 10 -4 mm = 22 sec.

Third comparison value corresponded to millipore filter with pore diameter of 6 x 20<-4>mm = 15 sec.

Under these conditions, 20 sec was measured for the medical wound dressing produced according to the invention.

The mean, apparent pore diameter was therefore at approx.

-4

4.9 x 10 mm. This average, apparent pore diameter has a sufficiently bactericidal effect, so the wound dressing produced according to the invention is particularly suitable for covering typical wound patterns such as - 2nd and 3rd degree burns with or without surgical pretreatment

- ulcus cruris

- large-scale skin defects and scrapings or after surgical procedures.

Example 2

From an open-cell polyurethane soft foam block on a polyester basis with a bulk density of 28 kg/m 3 , a foam web with a thickness of 40 mm and 2 mm is peeled off in a known manner each time. The foam web with a thickness of 40 mm is compacted irreversibly continuously between heated steel bands. The temperature of the steel bands is 258°C, the residence time 3% minutes and the densification ratio. 10:1. The irreversibly compacted polyurethane soft foam fabric web is then split into foils with a thickness of 0.5 mm. The upper and lower cover layers are separated with a thickness of 0.3 mm and added to a different application purpose, so that possible soiling and crusting do not negatively affect the quality of the irreversibly compacted polyurethane soft foam film.

The continuous irreversibly densified polyurethane soft foam film and the non-densified open-cell polyurethane soft foam film are then connected according to Ex. 1 with each other, rolled up, divided into individual pieces, packed and sterilized.

The investigation•of that according to Ex. 2 produced material was similar to that under Ex. 1 specified test device while maintaining the blank value and the three comparison values, and gave a passage time of the liquid of 14 sec. The average overseer--4

The average pore diameter is therefore 6 x 10 mm and is a sufficient barrier against bacterial invasion.

The medical wound dressing produced according to the invention is suitable for those in Ex. 1 indicated wound images. The medical wound dressing according to the invention has no total liquid barrier, but enables increased exudate and secretion uptake by capillary action of the through-and-through irreversibly thickened backside and enables, without removing the wound dressing, an assessment of the covered wound surface from the outside with regard to local accumulation or increased formation of wound secretions and exudate, as well as allowing for faster partial dressing changes for optimal wound treatment.

Example 3

From an open-cell polyurethane soft foam block on a polyester basis with a bulk density of 15 kg/m 3 , a foam web with a thickness of 60 mm and 2 mm is peeled off in a known manner each time.

The foam web with a thickness of 60 mm is compacted irreversibly continuously between heated steel bands. The temperature is 237°C, the residence time 4.3 minutes and the densification ratio 30:1. The thus densified foam web is then split into foils with a thickness of 0.2 mm. The upper and lower cover layers are separated with a thickness of 0.3 mm each time and added to a different application purpose, so that any soiling and crusting cannot negatively affect the quality of the throughout irreversibly compacted polyurethane soft foam foil.

Next, the continuous irreversibly densified polyurethane soft foam material film is connected with the non-densified open-celled polyurethane soft foam material film according to Ex. 1 with each other, rolled up, divided into individual pieces, packed and sterilized.

The examination of it according to Ex. 3 material produced was similar to that under Ex. 1 specified test device and gave an average, apparent pore diameter of 5.8 x 10 mm, and is likewise suitable for those under Ex. 1 indicated wound images.

Example 4

From an open-celled polyurethane soft foam block on a polyester basis with a bulk density of -100 kg/m 3 , two foam sheets with a thickness of 2 mm each are peeled off in a known manner.

One of the two polyurethane soft foam webs is solidified throughout continuously between heated corrosion-resistant steel bands. Steel rail's temperature is 248 oC, the residence time 6 min. and the densification ratio 2:1.

Then, the through-through irreversibly densified polyurethane soft foam fabric film with a thickness of 1 mm and the non-densified open-celled polyurethane soft foam fabric film according to Ex. 1 with each other. The resulting composition is then wound up and cut using known methods into strips of a freely selectable width.

The connection material according to the invention can be used in desirable lengths as elastic bandages and is particularly suitable as a bandage and for varicose symptom complex.

Example 5

From an open-cell polyurethane soft foam material block on a polyester basis with a room weight of 30 kg/m 3 , two foam material webs with a thickness of 10 mm and 30 mm are peeled off in a known manner.

The polyurethane soft foam web with a thickness of 30 mm is densified - irreversibly throughout continuously between heated steel bands. The temperature of the steel bands is 254°C, the residence time 4k minutes and the densification ratio 15:1.

The continuous irreversibly densified polyurethane soft foam web of 2 mm thickness is then split into two equally thick foils of 1 mm thickness. The 1 mm thick continuous irreversibly densified polyurethane soft foam foil is connected to the surface not produced by cleavage with the 10 mm thick, non-densified open cell polyurethane soft foam sheet according to Ex. 1. The formed material is then wound up and cut using known methods into strips of a freely selectable width.

The connection material according to the invention can be used in the desired length as elastic bandages and is particularly suitable for varicose symptom complex, as the kidney function is ideally supported.

The material according to the invention can also be used with results, in the form of compresses.

Example 6

Foils in thicknesses of 10 mm and 1.5 mm are peeled off in a known manner from an open-cell polyurethane soft foam block on a polyester basis with a bulk density of 20 kg/m 3 .

The polyurethane soft foam film with a thickness of 10 mm is thickened throughout irreversibly continuously between two heated corrosion-resistant steel bands. The temperature of the steel bands is 257°C, the residence time 4.6 min. and densification ratio 5:1. Then, the continuous irreversibly densified polyurethane soft foam foil in a thickness of 2 mm is passed without any treatment of the upper and lower cover surface with the non-densified open cell polyurethane soft foam foil in a thickness of 1.2 mm through bo rollers and connected, proceeding according to Ex. . 1.

The composite fabric formed according to the invention is cut using known methods into strips of freely selectable width and laid down corresponding to its use as elastic bandages with high slip resistance.

Example 7

From an open-cell polyurethane soft foam block on a polyester basis with a room weight of 30 kg/m, a foam web with a thickness of 50 mm is peeled off in a known manner, densified throughout irreversibly continuously between heated steel bands. The temperature of the steel bands is 252°C, the residence time 3% minutes and the densification ratio 8:1. Then, after removal of the upper and lower cover layers, the continuous irreversibly densified polyurethane soft foam sheet is split to a thickness of 0.4 mm each time into continuous irreversibly densified polyurethane soft foam foils of 0.8 mm thickness.

From another open-cell polyurethane soft foam material block on a polyester basis with a room weight of 50 kg/m 3, a polyurethane soft foam film of 4 mm thickness is peeled off. The 0.8 mm thick continuous irreversibly densified polyurethane soft foam foil is connected to the non-densified open cell polyurethane soft foam foil of 4 mm thickness according to Ex. 1.

The resulting composition is cut using known methods into strips of a freely selectable width.

The composite material according to the invention can be cut into desired lengths corresponding to the particular application and used as elastic bandages with a good healing effect.

Example 8

From an open-cell polyurethane soft foam block on a polyester basis with a room weight of 22 kg/m, a foam web with a thickness of 36 mm is peeled off in a known manner, irreversibly densified throughout continuously between heated steel bands. The temperature of the steel bands is 262°C, the residence time 4% minutes and the densification ratio 12:1.

Then, after removal of the upper and lower cover layers, the continuous irreversibly densified polyurethane soft foam web is split on a polyester basis to a thickness of 0.3 mm each time into continuous irreversibly densified polyurethane soft foam foils of 0.8 mm thickness. From another open-cell polyester-based polyurethane foam block with a bulk density of o 80 kg/m 3 , a polyurethane foam film with a thickness of 1.5 mm is peeled off and connected to the continuous irreversibly densified polyurethane foam film with a thickness of 0.8 mm according to Ex. 1.

The material formed according to the invention is cut using known methods into strips with freely selectable widths. This dressing material can be manufactured in desired lengths corresponding to the special application purposes and is particularly suitable as elastic bandages, as the very thin unsealed open-celled soft foam layers prevent the individual wrapping layers from sliding relative to each other.

Claims (7)

1. Process for the production of a versatile, usable stretchable, medical wound dressing with sufficient protection against bacteria, necessary mechanical and good lyophilic properties, especially for effective treatment of burns and similar injuries, consisting of polyurethane soft foam material, characterized in that an undensified, open-cell original polyurethane soft foam fabric film with a thickness of 0.5 to 10 mm, preferably from 1.2 to 2 mm, on a surface without thermal cleavage is softened to tackiness and connected with one to 2 to 30 times, preferably 10 to 20 times throughout irreversibly densified polyurethane soft foam material film with a thickness of from 0.1 to 2 mm, preferably 0.3 to 0.6 mm, gas and water vapor permeable and then possibly cleaned by physical and/or chemical means, and that the medical wound dressing consists of a defined to the original cell structure of the starting material corresponding advantage and a defined, uniformly condensed with a uniform apparent po revolum equipped with polyurethane soft foam backing and has a defined gas and water vapor permeability. 2. Method according to claim 1, characterized in that the unsealed, open-celled original polyurethane soft foam fabric film is softened on a surface by means of flame in a temperature range from 500 to 700°C and a residence time from 0.05 to 0.6 seconds until tackiness. 3. Method according to claim 1, characterized in that the through irreversibly densified polyurethane soft foam fabric is produced by continuous splitting of the through irreversibly densified polyurethane soft foam fabric f in widths of up to 2.500 mm. 4. Method according to claim 1, characterized in that the densification degree of the throughout irreversibly densified polyurethane soft foam fabric film is set so that "preferably a medium apparent -4 -4 -4 pore size from 3 x 10 mm to 8 x 10 mm, especially 4 x 10 mm -4 to 6 x 10 mm. 5. Method according to claim 1, characterized in that the throughout irreversibly densified polyurethane soft foam fabric film is produced from foamed, open-cell original polyurethane on a polyester or polyether basis. 6. Method according to claim 1, characterized in that the throughout irreversibly densified polyurethane soft foam film is preferably produced from polyurethane soft foam f with a high amount of residual cell walls. 7. Method according to claim 1, characterized in that the undensified, open-celled original polyurethane soft foam fabric foil and the through-through irreversibly densified polyurethane soft foam fabric foil are produced from polyurethane soft foam fabrics with bulk weights from 15 to 100 kg/m .