DE1417385A1 - Wound covering with improved healing properties and method for their manufacture - Google Patents

Description

Wound covering with improved healing properties and methods for their Manufacturing.

The invention relates to a wound covering m better Healing effect from a self-supporting, water-soluble, plasticizer-containing cellulose derivative film, the can be moistened and for cuts on the human or animal body, Wounds, infections and other external, pathological conditions to connect to the blood, to eoagulate the blood and stop an infection from spreading can be applied, as well as to a method for their production.

It was found that known wound dressings, e.g. support aids, Adhesives and non-porous coatings applied as liquids for protection or for the treatment of cuts, wounds and infections leave to be desired.

Non-porous protective films are due to the fact that they prevent access do not allow the wounds necessary for the healing process, very indelible. Bandage aids were designed to eliminate this disadvantage. However, they are undesirably unwieldy and constantly have to be replaced. since they do not allow adequate cleaning.

In the previous treatment of open wounds, such as burns, Injuries or the like. The bandages used on it often have a quick one Healing disturbed. When an ordinary dressing is applied to a damp wound becomes the scab or granulation tissue that is on the surface of the Wound has been formed, often incorporated into the bandage, so that the scab or the new skin that has formed during the healing process upon removal The dressing can be peeled off, causing secondary bleeding.

In addition, the previous associations were also involved in the treatment open wound with a drug, with a frequent change of dressing for Supplementation of the drug was necessary, disadvantageous, as it causes disturbances and Irritation the Ylunde were caused.

In order to avoid these disadvantages, non-fibrous films have been used. Such pilms, however, are so stiff and rough that they are not smooth on the surface adapt to the wound and exert an adverse irritant effect on it.

There are also known wound dressings that consist of a pre-formed self-supporting The main constituents of which are a water-soluble cellulose derivative, a film Contains plasticizers for the cellulose derivative and a sulfonamide.

It is also known to use water-soluble cellulose ethers, in particular cellulose glycolic acid balances as a liquid-absorbent dressing material, in particular to be used as a hemostatic cotton wool. As such cellulose ethers in particular Methyl cellulose or cellulose glycolate of a special fiber length is used.

When treating burns, a free formation is one sterile and uninfected scab of primary concern. There was one for this film-forming solution known to be sprayed onto a burn or wound can to form a scab. The proposed drug was previously on the combustion applied in a triethanolamine solution, with the formation of a Scab took three days to complete. According to these known processes, methyl cellulose was produced added, the time for scab formation being reduced to about one fljag became.

8 is also known to be used in surgical dressings with haemostatic property a free acid carboxymethyl cellulose or carboxyethyl cellulose, is used. The surface of a gauze bandage is covered with a hemostatic Agent impregnated with, in this case carboxymethyl cellulose or carboxyethyl cellulose or a salt thereof. Experiments showed that due to the hemostatic property the cellulosic compound reduces bleeding time without the need to apply pressure can be decreased from 5 minutes to 1 minute, 15 seconds.

It is known to use a polyol compound in such surgical dressings apply so that this acts as a stripping agent and an appropriate removal of the Bandage permitted.

In all cases, however, the cellulosic compound is treated with it free acid cellulose ether is obtained, for example by heating, e.g. to form the stable, free acid carboxymethyl cellulose. Implantation tea show that the free acid ciluloe ether is completely absorbable by the body was.

However, the known wound dressings described above were not yet completely satisfactory in all respects, although they are individually advantageous Had characteristics.

The object of the invention is therefore to create a wound covering with improved healing properties from a self-supporting water-soluble plasticizer containing Cellulose derivative film that does not need to be removed from the wound and wherein the cellulose derivative film drugs, antiseptics, bacteriostatic middle or the like. can wear and is suitable for the treatment of infections, The wound pad according to the invention should be soluble in blood plasma and weeping secretions, by its own hemostatic properties as a result of what is in the film cellulose glycolic acid ether contained in it with the blood and coagulate with it and have the physical property of arresting blood flow and xoagulation to promote.

In particular, one purpose of the invention is to create eSne wound dressing, which 1) coagulates the blood, 2) allows air to pass through, 3) a suitable one Provides protection against foreign objects, 4) if desired, medical substances, such as germicides, antiseptics and antibiotics, may contain ingested, 5) by Re-dissolution in water can be removed from skin and 6) in more beneficial Way promotes the healing process of the wound.

The wound covering according to the invention with improved healing properties made of a self-supporting, water-soluble, plasticizer-containing cellulose derivative film is characterized in that the film is ventilated and porous. According to the invention In particular, a wound dressing of the type specified above is created at which is the film of carboxyalkyl cellulose, its alkali salts or oxyalkyl cellulose consists.

The film preferably contains glycerol as a plasticizer. As a treatment agent can g, if desired, iodine, sulfanilamide and / or sulfathiazole used will.

According to a particular embodiment of the invention, the film can in addition an emulsifier, especially sodium laurel -yl sulfate, contain.

Furthermore, in the wound covering according to the invention, the pilm Contains 30 biq 40 vol .-% air in the form of very small bubbles.

The wound covering according to the invention is suitable for use on the skin a pre-formed scab in the form of a water-soluble, transparent, porous To apply film that can be handled like a bandage, 'is antiseptic and is partially dissolved by exuding wounds, so that an adhesive contact formed and drug treatment released. One educated in this way Scab has a porosity similar to that of natural scab and healing proceeds rapidly moving forward. On the other hand, the film can be treated with water without any disturbance the wound can be removed in some way, using the materials applied act as a natural coagulant for blood.

When applying the self-supporting, soluble film as healing Coating over an exuding wound, the flow of plasma is halted and the formation Avoided by bubbles.

The wound covering according to the invention is expediently in the form of a water soluble, flexible, self-supporting thin sheet or equivalent Sheet of substantially uniform thickness of a water solution of a cellulosic compound and a plasticizer.

The wound dressing can be produced in an expedient and advantageous manner by pointing the solution to the Surface of a moving Tape of polytetrafluoroethylene conducts and on it during a to form a dried film is heated for a sufficient period of time and then a film of the Tape removed.

For making the ventilated, porous film according to the invention a device for aerating a water solution is particularly suitable, which a container, a positive displacement pump, which is connected to the container for drawing off liquid from it and for returning part of it is connected to snakes to Cooling of that part that is returned to the container, a high-speed one Wiper to which the liquid not returned to the container is fed, and it comprises partially returning the output from the mixer to the container with the remainder available for flow to a device through a demand valve is to make films out of it.

The invention is illustrated below with reference to the drawing.

Fig. 1 is a greatly enlarged sectional view of a reinforced Film according to the invention.

Fig. 2 is an enlarged plan view of a piece of a reinforced Film according to the invention.

Figure 3 is a perspective view of a non-adhesive film according to the invention which is shaped to fit a human hand.

Fig. 4 shows an elevation of an apparatus for silm making according to the invention.

Fig. 5 is a perspective view of a different type of device, which is used with that of FIG. 4 for the practice of the invention can be.

The aerated and porous cellulose derivative film according to the invention should have a very good tensile strength in the dry state and sufficient be flexible so that it can be handled easily and without damage. Also must the film represent a pure product free from toxicity and the same Protection like a clot of blood guaranteed with equivalent air passage, i.e. is a protective material equivalent to the natural method of protecting wounds is. This is achieved through the use of the water-soluble cellulose derivatives indicated above ensured, of which sodium carboxymethyl cellulose is particularly preferred.

This product is in such a pure state (for example from Hercules Powder Co.) that it is edible.

A preferred quality 7L is easily soluble in water and can, if it is mixed with a plasticizer, for example glycerine, to form a film of great elasticity and excellent tensile strength. Other plasticizers are sorbitol, "Corpolin" (Heyden Chemical Corp.) and ethylene glycol. After deforming is such a film lciciit soluble in water and can be obtained in different degrees of thickness from a water solution using a Ventilation as described below, for example on a heated drum or a corresponding tape. i> checks on simple cuts showed that the film not only coagulates the blood, but also deals with it connects, whereby an artificial scab is formed, which underneath the healing allowed. Repeated washes only reduced the thickness of the film around the wound and removed it as healing progressed.

For special purposes can be antiseptic, medicinal, germicide and / or antibiotic materials are incorporated into the film to prevent infection minimize or heal one after it has occurred is. For example, there is currently no completely satisfactory method of Distribution of iodine. Iodine is usually found in low-alcohol solutions put on the market; the original percentage of a fresh cookie however, it will not be sustained as repeated use will result in evaporation of the Alcohol itself, thereby concentrating iodine levels to a point where at which he can become dangerous. According to the invention, iodine can be in the film be incorporated so that this in a defined salary is present, making the film in a small book form or in loose form Sheets can be distributed in a container.

Sulfa drugs can also be incorporated into the film.

As a result of their antiseptic properties for superficial infections An easy method of application for the general public considers the danger more serious Infection in very many cases. Research showed that sulfa drugs that are not soluble in the film or are incompatible with it, dispersed therein t can be and in the dried film in a uniform surface area can be sustained, with regard to the concentration of the drug in there is no limit to the movie. Other remedies can be used in a similar manner come to use with the film according to the invention.

If desired, the film can be coated by cotton or Tissues are reinforced with the film-forming solution with or without the various drugs and dried to produce a smooth film coating. In the places where tape is currently used, due to the difficulty of its Removal has serious drawbacks, no such problem occurs cellulose-coated fabric according to the invention. It is only necessary Soak this tape or bandage in water for easy removal.

The wound covering according to the invention is of great help in this Medicine when performing operations. A film of this type can be applied to stop the flow of blood and no removal is required because it is gradually absorbed and removed from the system. Such a film Lann can also be used to make cuts while avoiding the use of stitches conclude. It should be noted that in infections such as fungal disease, Fungal growth, poison oak or the like. Can be used. Such infections are spread unintentionally by individuals. A protective film localized over the wound the infection, being. at the same time the correct form of drug treatment is created. Given the transparency, observation of the wound is essential made possible without removal.

The film is usually made up of e @@@@ @@@ chung from around 70 to 85 Parts by weight of a carboxy or oxyal @ yl cellulose, e.g. oxyethyl cellulose, or one soluble alkali salt of carboxymethyl cellulose, together with 15 to 30 parts by weight a suitable plasticizer, for example glycerine, prepared.

In the practical implementation of the invention are oxyethylcellulose, a water-soluble alkali salt of carboxymethyl cellulose (e.g. the alkaline earth salts or the ammonium, @ atrium or potassium salts thereof) and preferably sodium carboxymethyl cellulose applicable, especially that welce a substitution of at least 0.3 to 1,2 and usually from 0.65 to 0.95; the substitution refers to the mean number of sodium carboxymethyl groups 1e. Anhydroglucose unit the cellulosic structure, each unit having three reactive hydroxyl groups (i.e. if complete substitution of the sodium could be achieved, the substitution number would be 3.0).

These cellulose derivatives are said to be in addition to their ready water solubility have a maximum concentration and minimum viscosity; expedient should their Viscosity does not exceed 1000 cps, and especially in the range of lo cs up to 750 cps. The term "viscosity" used here is called the logarithm the viscosity in centipoise at 2500 of a 2% aqueous solution of the applied Expressed carboxy or oxyalkyl cellulose.

The bleaching agent for the purposes of the invention normally consists from a liquid, saturated, acyclic, optionally substituted alcohol with usually no more than 6 hydroxy groups. Examples are glycerine, diglycerine, Glycerin - # - monomethyl ether, glycerin monochlorohydrin, 1,2,6-hexanetriol, ethylene glycol, Propylene glycol, 2,3-butylene glycol, 2-nitro-2-methyl-1,3-propanediol and ethanolamines, such as 2,2 1-dioxydiethylamine or 2-oxyethylamine.

The film according to the invention is usually made with air in the following described tracks ventilated, so that its air content is preferably about 30 to 40% by volume, the air being present in the form of very small bubbles.

In the drawing, in detail in Figures 1 and 2, a reinforced Illustrates film 5 made by deposition on a gauze strip 6 can be. Such a strip can be from a moving belt of the device Enjoyment Fig. 4 are worn on the operation of a solution according to the invention can be applied. After drying and stripping off the tape, the cheesecloth is embedded in the lower surface of the film. The film can then be removed and wound up or cut into strips. En such a reinforced film than surgical Bandage is applied, forms the area in which the gauze is embedded, the outer surface of the dressing.

On this dish, the gauze of the bundle is through the soluble film separated, which prevents unwanted sticking of the gauze.

The film-forming mixture according to the invention can be applied to the outer, smooth surface of a mold are applied, which is designed so that they adapts to a part of the human body, for example a hand. the Coated form can then be put in a drying cabinet to dry on a suitable one Temperature. After drying, the mold is covered with a film, which can be pulled off and resembles a glove, as shown in FIG. 3 is illustrated. A film produced in this way can be used as a glove for Covering one hand can be used to make a very effective, surgical dressing for part of the body with the usual surgical Dressings cannot be easily covered represents.

The device according to FIG. 4 for producing a film according to FIG Invention comprises a container 7 from which a film of an approximate thickness can be pulled out by the moving belt 8 of o.20 mm. The ribbon then passes through a heating zone which is provided below the heating element 9, wherein the excess water evaporates and a dry film is obtained on the and will. Such a film lo is then removed as soon as the tape is around a drum 11 runs around, which can be belt-driven by a suitable electric motor 12. The film can be wound up on a roll 13. Giving a dry film of the tape is only using a tape with a non-stick surface, for example a "Teflon" tape. Such a surface is necessary so that the Film can be self-releasing.

Polytetrafluoroethylene or "Teflon" is used as a drying surface for the film solutions according to the invention are particularly desirable. A Teflon-coated one Glass fiber fabric, e.g. Armalon, a coated metal plate or a coated Ketal tape or a heat bonded film that attaches to the surface of a material that is connected to the for the protective film applicable working temperatures, e.g. around 149N, which is heat-resistant and chemically inert, can also be used for this Purpose to be used. Particularly preferred is a polytetrafluoroethylene with a Density from 0.030 to 0.040, in particular 0.035, and a softening point of about 327N due to the non-stick surface, which makes it easy to peel off the allows dried film.

The device according to FIG. 5 for aeration of film-forming solutions according to the invention comprises a container 14 from which a solution with high Viscosity is pumped by a positive displacement pump 15, part being added to the container is returned by cooling snakes 16 and another part by don high-speed mixer 17 goes. This mixer is if desired at a Speed of about 3450 RPM in a counterclockwise direction operated if the connections are made in the manner shown in the drawing, so that the solution flows onto the approaching edges of the rotor blades of the mixer. The solution of lower viscosity is extracted from the mixer through the extraction line 18 passed, and the entire portion is regulated by the needle valve 20, through the line 19 is returned to the container, with that part being withdrawn which is fed to the application device according to FIG. 4 through the demand valve 21.

The device described above is the desired Solution of atriumcarboxymethylcelluloae in connection with an emulsifying agent, for example Sodium lauryl sulfate, and a suitable medicinal or antibiotic aterial, a plasticizer and water for continuous coating, drying and subsequent Remove the "Tefion" -3and oã. like. the device according to FIG. 4 produced.

In addition to the desired ventilation, the device 3 other purposes achieved; It reduces the viscosity of the solution by one @ert from about 100,000 oentipoise to about 2,000 centipoise, whereby the metering of the Solution to the "Teflon" tape of uniform thickness is facilitated.

2) It reduces the density of the solution, for example by emulsification, by introducing and dispersing xu2> in the form of each small and microscopic vesicles: thereby removing the solution from the Allowing tape to be in continuous form after drying.

3) As a result of a homogeneous film of low density, it becomes Solubility in water greatly increased after completion. This is so far from of essential importance than the usability of the finished product is affected. The physical changes in the solution and in that of it manufactured film after completion as it is by moving at high speed are brought about within narrow limits are essential for successful manufacture a film that is quickly soluble in water is very essential.

The drying of the liquid film is continued until its water content is about 5 to 15 wt. of the film. A much smaller proportion of water than 5% leads to films which are too brittle for the stated purpose. An essential greater than 15% of water results in a film that is too soft and not can be handled easily.

Dried films about 0.025mm to 0.15mm thick suitable for use as medical or sterile protective films. If the Thickness substantially less than 0.025 nm, the film is brittle and it is absent strength so that it breaks easily. The desired thickness above the bottom gates Limit depends on the purpose of use. When the movie too is fat the rate of dissolution in water becomes undesirably slow. Preferred thicknesses are in the range from 0.076 to 0.100 mm.

The foregoing shows that according to the invention a self-supporting film is created, which is made from aqueous solution, by placing them on a moving belt with a surface made of polytetrafluoroethylene or Teflon conducts and the solution for a sufficient period of time to form of a dried film and then removed the film in question from the tape.

The invention is explained in more detail below with the aid of examples.

Example 1 As a typical solution for the production of a film according to of the invention are 8.73 g of sodium carboxymethyl cellulose together with 0.87 g of glycerol dissolved in 90 g of water. If desired, a certain antiseptic, for example 0.2 g of iodine and 0.2 g of potassium iodide are added. The solution is dark green Coloring. When processing into a film, its final composition is the water content is not taken into account, 87.2746 sodium carboxymethyl cellulose, 8.73% glycerin, 2% iodine and 2% potassium iodide. One such film is clear and 6,452 cm2 of it dissolves in water in 15 minutes and 15 seconds. He owns good flexibility and moderate plasticity and although orbits or Sheets of the film show very little tendency to stick together under pressure, they can be separated easily. Although only a very small amount of free Iodine was present in the film, there was a correspondingly large amount of iodine in the Film bound state before. This bound iodine was easily removed and it was quantitatively obtained free iodine with a reagent such as chlorine gas.

Example 2 In another example of a film according to the invention 8.2 g of sodium carboxymethyl cellulose together with 0.8 g of glycerine in 90 g Dissolved in water. If desired, a particular antiseptic, for example 1 g of sulfanilamide are mixed in. The composition of that formed from this solution The film was, without taking into account the water content, 81.82 s of sodium carboxymethylc @ llulose, 8.18% glycerin and lo 5 'sulfanilamide. Such a film is clear, easily soluble and has good flexibility although it has low elasticity, and its Sheets or webs do not stick together under pressure. Such films can be im When dry, it can be separated from the skin in one piece. That way produced film was filled with white spots.

Example 3 For the production of films according to the invention 9.6 g sodium carboxymethyl cellulose and 2 g glycerin dissolved in 85 g water. If so desired 1.3 g of sulfathiazole can be mixed in. Although a smaller percentage here Proportion of water than in the above examples is present in order to To achieve an increase in thickness, it has been found that the decrease in water the thickness did not increase significantly. The film came off the device easily remove, and it contained about 10% medicament in the final form.

Example 4 Composition of the solution: sulfanilamide 0.1 g sodium carboxymethyl cellulose 9.0 g glycerine 0.9 g water 90.0 g composition of a film after casting in the device: sulfanilamide 1, o% sodium carboxymethyl cellulose 9o, o .glycerin 9.0% solubility: 6.452 cm2 of the film dissolved in water at 28 ° C in 1 minute and lo seconds.

Example 5 A solution was prepared from the following ingredients: Sulphanilamide 0.1 g sodium carboxymethyl cellulose 9.0 g sodium lauryl sulphate 4 o g glycerin 0.9 g water 90.0 g This solution was after mixing for complete Dissolution passed through a homogenizing mixer (see. Fig. 5) to the viscosity reduce and aerate the solution, and then on a "Teflon" tape (see. Fig. 4) applied.

Instead of the sulfanilamide used in this example, also the desired amounts of z. B. iodine, sulfathiazole or the like. be used.

Example 6 Composition of the solution: sodium carboxymethyl cellulose 9.6 g glycerol 1.7 g sulfathiazole 0.6 g water 86.0 ml The sulfathiazole was good Compatibility with the above solution and there were concentrations increased from 0.6 g to 2.9 g.

Example 7 Water-soluble sulfadiazine (alkali salicylate, as in the U.S. Patent 2,510,993) 0.1 g sodium carboxymethyl cellulose 9.0 g glycerin 0.9 g water 90.0 g The above solution was used to prepare of a ventilated film passed through the apparatus shown in Fig. 5 and then cast into a film, whereby they are cast by a "Teflon" tape device (cf. Fig. 4) was directed.

Example 8 In this example, films according to the invention as well as Control films or comparison films produced and these with regard to their properties compared.

(1) Manufacture of ventilated films The ventilated films were made prepared as in Example 1, using the components indicated below became.

(2) Manufacture of non-ventilated films Here, the became the film component containing solution directly using the device shown in FIG cast into a film material without prior ventilation.

The film compositions are given below.

Film no. Composition 1 sodium carboxymethyl cellulose (ventilated) - 0.325 mm additives: glycerine, sodium lauryl sulfate 2 methyl cellulose (dense) - 0.125 mm additives: glycerine 3 methyl cellulose (ventilated) - 0.08 mm additives: sodium lauryl sulfate 4 Sodium carboxymethyl cellulose (dense) - o, 11 rain additives: none During the evaluation the effect of the above films on coagulation time was the Classic method by Lee and White (see e.g. Hematology for the Medical Technologist, Charles E. Seiverd, 2nd edition, 1958, page 137) as indicated below is: Jlc blood samples were from oral, healthy, male and female dogs been received. Using a sterile needle and syringe 8 to 10 cm3 of blood were drawn from each animal by venipuncture.

The withdrawal time was recorded and 1 cc samples were in with silicone treated test tubes transferred. A 1.25 x 0.6 cm sample of the sample film was made then added to each test tube, with at least one test tube, however, as a control was kept without film addition. After 4 minutes have passed since the withdrawal time the glasses became soft jeae panned for half a minute until a lump was formed and no more blood flowed from the test tube. The duration of coagulation is the elapsed time between the withdrawal time and complete coagulation in the test tubes.

In the experiments given above, those in the following Results listed in the table were obtained.

Determination of the influence of different dense and ventilated films on the coagulation time Coagulation time (min) Dog- Control 1 2 3 4 male @ AL 2 A 10 5 15 female A 15 6 19 HG 30 B 15 6 22 male A 15 5 19 W 8 B 16.5 5 19 female A 16 5 24.5 53 B 18 7 28 male A 17 5.5 21 FB 71 B 19 5.5 25 female A 15.5 6 25 114 B 21 6 26 16.2 5.6 22.1 average -65% + 36%% change Dog congulation time (min.) No. Control 1 2 3 4 female A 11.5 11 8 53 B 11.5 11 10 female A 18.5 12.5 12 HG 30 B 22 18 14 male A 18 12 6 FB 71 B 19 12 6 By- 16.8 12.8 9.3 cut -24% -45% %Modification *) "A" and "B" refer to parallel experiments on the same blood samples. Within the limits of the experiments described above, the following facts are readily apparent: (1) The non-aerated (dense) methylcellulose film (film no. 2) did not fail only in reducing the blood coagulation time, but showed a considerable increase in the coagulation time.

(2) Ventilation of the methyl cellulose film (cf. film no. 3) resulted a reversal of the above result, as if by a significant one Reduction of the coagulation time in comparison with the non-ventilated film (cf. Film Tr. 2) can be seen.

(3) The non-aerated (dense) sodium carboxymethyl cellulose film (Film No. 4) gives a significant one in contrast to the dense methyl cellulose film Decrease in the coagulation time compared with the control blood.

(4) Aeration of the sodium carboxyme / ethyl cellulose film resulted in a further considerable reduction in the coagulation time (cf. film no. 1).

Since the xoagulation speed is a direct factor for the hemostatic Properties of the examined film materials is from the experiments above It is clear that ventilated films are compared with the corresponding non-ventilated films Films have significantly increased hemostatic properties, and that is very surprising Non-aerated sodium carboxymethyl cellulose had a significant hemostatic effect Has a deteriorating effect, while for non-ventilated: ethylcellulose Effect on hemostasis observed vitirde.

The films made according to the invention are clear, easily soluble and have good flexibility. Sheets or strips of film stick under Pressure not together.

Such films can in the dry state in one piece of the ; can be separated from. From the above it can be seen that according to the invention a ventilated film, optionally medicated is and ger, if necessary also reinforce: - can be, is created. Preferably these films are made from sodium carboxymethyl cellulose and glycerin and an emulsifier educated. The aerated film has almost instantaneous solubility in water and body fluids.

The films according to the invention accordingly have remarkable haemostatic properties and properties such as drug delivery properties.

Claims (9)

Claims 1) wound covering with improved healing properties a self-supporting, water-soluble, plasticizer-containing cellulose derivative film, characterized in that the film is vented and porous. 2) wound covering according to claim 1, characterized in that the Carboxyalkyl cellulose film composed of alkali salts or oxyalkyl cellulose. 3) wound covering according to claim 1 or 2, characterized in that that the film contains glycerine as a plasticizer. 4) wound covering according to one of claims 1 to 3, characterized in that that the film additionally contains an emulsifying agent, in particular sodium lauryl sulfate. 5) wound covering according to one of claims 1 to 4, characterized in that that the film contains 30-40% by volume of air in the form of very small bubbles. 6) wound covering according to one of claims 1 to 5, characterized in that that it contains a drug, germicide, antiseptic, or antibiotic. 7) experienced in making a wound covering with improved sealing effect, which may contain medicaments, characterized in that one aqueous solution of a cellulose derivative containing a plasticizer on a polytetrafluoroethylene surface a moving one Tape conducts the solution during a period sufficient to form a dried film Heated time and then removed the film from the tape. 8) Method according to claim 7, characterized in that the Viscosity of the solution by positive displacement pumping applied to the solution and the density is decreased by treating the solution with air. 9) method according to claim 7 or 8, characterized in that the solution as a cellulose derivative is a carboxyalkyl cellulose or an alkali derivative contains the same or an oxyalkyl cellulose. Read more e