Antimicrobial adhesive and coating substance and method for the production thereof

Antimicrobial adhesive and coating material and method for producing the same

The invention relates to an antimicrobial adhesive and coating material, a use of the adhesive and coating material and a method for its production.

The invention relates to the field of adhesives and coating materials for medical, medical or hygienic applications in the broadest sense. In particular for the production of plasters, wound dressings, catheters, hygienic packaging, for coating the aforementioned materials and for coating components of medical devices, walls of rooms to be kept hygienic and the like. antimicrobial adhesives and coating materials are used. The use of such adhesives and coating materials is intended to prevent the settlement of microorganisms.

From DE 199 58 458 AI an antimicrobial wound dressing is known. The wound dressing is made of a synthetic polymer material which contains zeolites containing metal ions.

US 6,124,374 describes an antimicrobial adhesive cream for dentures. Divalent copper salts are added as an antimicrobial agent.

A pressure-sensitive adhesive is known from US Pat. No. 6,216,699 B1, to which diidomethyl-p-tolyl sulfone is added as an antimicrobial active ingredient.

The known antimicrobial additives are not particularly universal. They are specifically tailored to the respective matrix. The antimicrobial effectiveness of the materials added does not last very long.

A method for producing bactericidal or fungicidal plastic bodies is known from WO 95/20878. A thin layer of silver is first applied to a film using thin-film technology. The film is then shredded. The shredded film is melted and then shaped into the desired shape using conventional techniques. - The process is extremely time-consuming and costly. The production of a special intermediate product and its comminution is required.

From EP 0 190 504 an antimicrobial composition is known which contains 5 to 10% by weight of silver. To improve the antimicrobial properties, a hydratable or a hydrated oxide is also added.

DE 31 10 681 C2 describes a material for bone implants. The material is made from a polymer to which silver phosphate is added as an antimicrobial agent.

An antimicrobial surgical implant is known from WO 81/02667. Metallic silver is added to the implant as an antimicrobial agent.

The generic WO 82/01990 describes a bone cement based on polymethyl methacrylate as the main component, which contains 5 vol. As an antimicrobial agent. % of a silver salt is added.

No. 5,837,275 discloses an antimicrobial material which contains, among other things, silver particles with a grain size of less than 200 nm. The silver lattice has artificially created lattice defects and defects in order to facilitate the release of silver ions.

A material provided with silver sulfate or silver acetate is known from WO 84/01721. This material releases a concentration of more than 1 μM of silver ions in a surrounding liquid within 24 hours.

DE 32 288 849 AI describes a material with a silver coating. Elemental carbon or titanium is added to the material. The addition is said to facilitate an increased release of silver ions into the environment.

No. 4,849,233 discloses a bone cement to which approximately 10% by weight of elemental silver and titanium oxide or tantalum oxide have been added. The bone cement is characterized by a high rate of release of silver ions.

The antimicrobial effectiveness of the materials known according to the state of the art has been proven with the so-called inhibition zone measurement. The inhibition zone measurement is described, for example, in Raad I. et al. , J. Infec. Dis. 173 (1996). The material to be tested is embedded in a nutrient medium, eg agar. Due to the release of antimicrobial metal ions, an inhibitory zone is formed around the material. The

The design and size of such a zone of inhibition has been assessed according to the prior art as an indication of the antimicrobial effectiveness of the material.

The materials known from the prior art have the disadvantage that they initially release an excessively high concentration of silver ions. According to recent knowledge, materials that show an inhibition zone are not suitable for use in the medical field. Such materials release silver ions to the surrounding tissue in macroscopically visible amounts. However, such amounts of silver ions are cytotoxic. To the extent that such materials are approved by the regulatory authorities at all, approval is now only granted under pharmaceutical law. Such approval is extremely costly and time-consuming.

Seen overall, no antimicrobial adhesive and coating material is known according to the prior art which shows no inhibitory zone in the inhibitory test and is therefore not cytotoxic.

The object of the invention is to eliminate the disadvantages of the prior art. In particular, an adhesive and coating material that can be produced as simply and inexpensively as possible should be specified, which is not cytotoxic and whose antimicrobial activity lasts as long as possible. According to a further object of the invention, the adhesive and coating material should be as universal as possible and enable the production of thin coatings. Furthermore, a simple and inexpensive method for producing the adhesive and coating material is to be specified.

This object is solved by the features of claims 1, 22 and 23. Appropriate configurations result from the features of claims 2 to 21 and 24 to 35.

According to the invention, an antimicrobial adhesive and coating material is proposed which contains metallic silver particles with a content of less than 5 ppm of silver, sodium and potassium ions as the antimicrobial component. - The proposed adhesive and coating material has a particularly long-lasting antimicrobial effect. It is not cytotoxic, ie no inhibitory zone is observed in the inhibitory test. This is attributed to the fact that a low rate of silver ions is continuously released from the silver particles and diffuses to the surface of the adhesive and coating material. According to current knowledge, the low release rate is attributed to the particularly low content of silver, sodium and potassium ions, which is less than 5 ppm overall. The materials known from the prior art predominantly contain silver particles, which initially release a high rate of silver ions. A high rate of release of silver ions is e.g. B. achieved by a disturbed lattice structure of the silver particles or by a high content of ions in the silver particles. This is precisely what is not given according to the subject matter of the present invention.

In the present case, the term adhesive and coating material is generally understood to mean a synthetically produced material on an organic basis. The material generally hardens after processing. It can be a paint, a lacquer, an adhesive, in particular also on a thermoset or thermoplastic basis.

According to a first embodiment, the average grain size of the particles is less than 100 nm, preferably in the range from 5 to 50 nm. Such silver particles are suitable for producing nanodispersed antimicrobial adhesives and coating materials.

According to a further embodiment, the silver particles are formed from aggregates of primary particles with an average grain size between 10 and 150 nm. Such silver particles are suitable for the production of so-called nanoporous antimicrobial adhesives and coating materials.

According to an advantageous embodiment, the primary particles have an average grain size in the range from 80 to 140 nm. Silver particles formed from such primary particles show a particularly good antimicrobial activity. They are not cytotoxic.

According to an advantageous embodiment, the aggregates have an average grain size of 1 to 20 μm, preferably 10 to 20 μm. The surface of the aggregates is advantageously 3 to 6 m²/G. They can have a porosity of up to 95%. The porosity is expediently between 70 and 95%. The abovementioned features contribute to the uniform and cytotoxically harmless release of silver ions on the surface of the material.

The antimicrobial adhesive and coating material is expediently produced from at least one liquid organic component. This can be hardened in the manner of a lacquer or a paint by the volatilization of a solvent. However, it is also possible to polymerize the organic component for curing, for example by means of UV light, heat or other physical influences. The antimicrobial adhesive and coating material can also be produced by mixing the organic component with at least one further liquid organic component. The further organic component can be, for example, a hardener which brings about polymerization. The silver particles can directly the liquid organic

Component or be added directly to a liquid intermediate product thereof. This makes it particularly easy to produce a particularly homogeneous dispersion of the silver particles. In particular, it is therefore not necessary to produce an intermediate product with great expenditure of time and money and then to further process it.

According to a further embodiment, 0.01 to 5.0% by weight of silver particles can be added. 0.01 to 2.0% by weight is preferably added. The silver particles used according to the invention have long-lasting antimicrobial activity even in a low concentration without causing a cytotoxic effect. They are expediently spherical, in particular spherical. This makes it easier to mix the silver particles into the liquid organic component. A homogeneous dispersion can be produced quickly. The aggregates are advantageously completely infiltrated with the organic component.

The organic component and / or the further organic component can contain an acrylate or a methacrylate as an essential constituent. They can also contain an essential component, an epoxy, urethane, silicone or cyanoacrylate.

In a further embodiment, the antimicrobial adhesive and coating material contains, as a further additive, cations at least one of the following metals: Au, Pt, Pd, Ir, Sn, Cu, Sb, Zn. The further additive increases and / or extends the antimicrobial activity. The cations are expediently bound in ion exchangers, in the form of a complex or added as a salt. The cations can diffuse from the adhesive and coating material on its surface and develop their antimicrobial effectiveness there. In this connection, it has also proven to be advantageous to use the salt of a, preferably polymeric, carboxylic acid as the salt.

The adhesive can be a pressure sensitive adhesive. The organic and / or the further organic component can contain one or more of the following additives: solvent, filler, pigment, binder, plasticizer, drying agent, fungicide. The coating material can be a lacquer, a paint or a curable dispersion. According to a further provision of the invention, the use of the adhesive and coating material according to the invention for the production and / or coating of wound dressings, dressings, incontinence products, for example diapers, medical devices, packaging materials, for coating walls of buildings, housings and / or components is more technical Devices provided. Eg The housing inner walls of air conditioning systems, the walls of operating theaters, containers for the production and storage of perishable foods, packaging for disposable medical devices, disposable medical devices, bandaging material, medical instruments etc. can be coated with the material according to the invention or produced therefrom.

According to another aspect of the invention, a method for producing the adhesive and coating material according to the invention is provided, with the following steps:

Generating a silver vapor by means of sputtering or by evaporation in a vacuum recipient,

Condensing the silver vapor so that silver particles with less than 5 ppm of silver, sodium and potassium ions are formed,

Adding a liquid organic component with the silver particles and

at least partial curing of the organic components.

The proposed method is simple and inexpensive to carry out. An antimicrobial adhesive and coating material can thus be provided, the antimicrobial effect of which is particularly long-lasting and which at the same time has no cytotoxic effect on tissue in contact with it. The process can be used to produce solid adhesives and coatings, and partially curing pressure-sensitive adhesives. The method is also generally suitable for the production of plastics, preferably plastics produced from at least one liquid component. From such plastics, for example, medical devices such as catheters and the like. getting produced.

In a first process variant, the silver vapor is condensed in the gas phase, so that aggregates consisting of primary particles with an average particle size of 10 to 150 nm are formed, which have an average particle size of 1 to 20 μm.

In this variant of the method, the primary particles initially form from the vapor phase. The primary particles formed have an extremely high surface energy. When the primary particles are stacked together, the given activation energy leads to diffusion processes which result in the formation of sintered necks. Aggregates are formed in which the primary particles are connected to one another by sintered necks. In this way, highly porous aggregates can be formed.

According to a further process variant, the silver vapor is condensed on the surface of a liquid, so that the silver particles have an average grain size in the range from 10 to 100 nm. In this variant of the process, the formation of agglomerates is prevented by the activation energy required for the formation of sintered necks being removed from the silver particles by condensation on a liquid surface. In this way, nanodisperse antimicrobial adhesives and coating materials can be produced.

The liquid can be a preliminary product of the organic component or the organic component. The proposed method is particularly easy to carry out. A homogeneous dispersion of the silver particles in the organic component or its precursor can be produced in a single device. The adhesive and coating material can be cured by curing the organic component, for example by adding another organic component.

For further advantageous configurations, reference is made to the features already described for the antimicrobial adhesive and coating material, which can also be used in connection with the method.

Exemplary embodiments of the invention are explained below with reference to the drawing. Show it:

1 silver particles dispersed in polytetrahydrofuran,

2 silver particles dispersed in diethylhexyl phthalate,

3 silver particles dispersed in dimethylsiloxane,

4 the proof of the antimicrobial effect of an epoxy resin adhesive mixed with silver particles,

5 shows a scanning electron micrograph of a silver aggregate and FIG. 6 shows an inhibition test of a coating material according to the invention.

Production of the metallic silver particles: Silver (99.95 silver wire from Heraeus) is evaporated by magnetron sputtering in a vacuum recipient at a temperature of 20 ° C. and a pressure of 0.01 to 0.1 mbar in an argon atmosphere. The evaporation can also be thermal, e.g. B. in a crucible. The silver vapor is then deposited on the surface of a liquid or condensed together with the vaporized liquid on a cooled surface. The liquid can e.g. B. silicone oil, polytetrahydrofuran, diethylhexyl phthalate or dimethylsiloxane. The liquid is continuously mixed so that the deposited or condensed metallic silver particles are homogeneously dispersed in the liquid. The organic component or a precursor of the organic component of the adhesive and coating material to be produced is preferably used as the liquid.

Fig.l shows spherical silver particles dispersed in polytetrahydrofuran by the aforementioned method. It is a preliminary product of an epoxy resin. It can be seen from FIG. 1 that the silver particles have an average grain size of less than 10 nm.

2 shows spherical silver particles which have been dispersed in diethylhexyl phthalate by the aforementioned process. It is a component for a polyvinyl chloride (PVC) paint. Here too there is a homogeneous dispersion of the silver particles in the component. The silver particles have an average grain size of less than 10 nm. 3 shows a dispersion of spherical silver particles in a dimethylsiloxane. It is a component of a silicone adhesive. The silver particles here again have an average grain size of less than 10 nm.

The above-described dispersions can then be cured, for example by adding another liquid component. They can also be mixed with functional groups, for example acrylic or methacrylate groups, or copolymerized, for example in the case of polytetrahydrofuran.

Examples for the production of the antimicrobial adhesives and coating materials are described below.

example 1

Preparation of bactericidal silicone materials:

A component, for example a binder, of an addition-crosslinking two-component silicone rubber based on polydimethylphenylsiloxane (RTV-S691; Wacker) is doped with silver particles produced by the process described above. The component is then mixed in a ratio of 9: 1 with another component, for example a hardener. Curing takes place at T = 25 ° C. The resulting concentration of silver in the hardened material is 0.01 to 5% by weight, preferably 0.05-1% by weight, of silver. The curable material can be used directly as an adhesive, varnish or, after adding suitable pigments or dyes, as a printing ink. Example 2

Preparation of bactericidal epoxy resin adhesives: A hardener (HV 998, Ciba) of a pasty two-component adhesive based on epoxy resin (Araldit AV138M, Ciba) is doped with silver nanoparticles using the process described above. The doped hardener is stirred into the epoxy resin and cured at room temperature. The concentration of silver is 0.01 to 5% by weight, preferably 0.1 to 1% by weight, of silver in the cured two-component adhesive. The curable material can be used directly as an adhesive, lacquer or, after adding suitable pigments or dyes, for example as a printing ink.

Example 3

Preparation of bactericidal and bacteriostatic epoxy resin adhesives: adhesives based on cationically curing cycloaliphatic epoxy resins are prepared. The epoxy resin ERL 4221

(Union Carbide) is copolymerized with polytetrahydrofuran (PTHF) of Molasses 1000 (PTHF 1000, BASF). PTHF is used for flexibility or as a plasticizer. The PTHF contains 5% by weight of silver introduced via the process described above (designation: PTHF-VERL-Ag). This results in a silver content of 1% by weight of the samples according to the invention. No silver is included in the comparative examples. The thermal cationic curing takes place with the addition of an initiator. For example, the iodonium salt Rhodorsil 2074 (Rhodia) with ascorbic acid 6-hexadecanate (ASHD) as an accelerator and on the other hand with α, α-dimethyl-benzylpyridinium hexafluoroantimonate (S. Nakano, T. Endo, J. Polym. Sei .: Part A, 34 (1996) 475) can be used. Hardening takes place with the following temperature program: 90 min 80 ° C, 60 min 100 ° C and 60 min 120 ° C. The composition of the individual mixtures in% by weight and the microbiological effect on staphylococcus epidermidis is summarized in the following table.

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The results shown in FIG. 4 have been determined by the method known from DE 197 51 581 AI. This method is further described in Bechert, Thorsten et al. , Nature Medicine, Vol. 6, No. 8 (09/2000). The disclosure content of the two aforementioned documents is hereby included.

First 8 parallel samples of the same batch of epoxy resin adhesive are made. The samples are usually cylindrical. They have a length of about 1 cm and a diameter of 2 to 5 mm. Then 200 μl of the bacteria-containing solution is filled into each well of the microtiter plate. The samples are incubated at 37 ° C for one hour. The samples are then removed and washed three times with physiological buffers. The samples are then placed in the wells of a microtiter plate, which are filled with a minimal medium. 200 μl of minimal medium are filled into each well. The samples are incubated for 24 hours at 37 ° C. The samples are then removed and discarded. 50 μl of one are added to each well of the microtiter plate

Full medium (Trypcasesoj a) added. The turbidity or absorption of the solution is then measured at intervals of 30 minutes over a period of 48 hours. The solution is kept at a temperature of 37 ° C. The turbidity measurement is carried out using light with a wavelength of 578 nm using a suitable reading device. A turbidity indicates that bacteria have been released into the environment from the surface of the sample.

The results shown in FIG. 4 show that the bactericidal action of the adhesives can be controlled by a suitable choice of the initiator. The curable material can be used directly as an adhesive, lacquer or, after adding suitable pigments or dyes, for example as a printing ink.

5 shows a scanning electron micrograph of the silver aggregate according to the invention. The silver aggregate essentially consists of spherical primary particles with an average grain size of approximately 20 nm. The primary particles are essentially connected to one another via sintered necks. They form a highly porous framework. The silver aggregate shown here has a size of approximately 10 μm. Such silver aggregates can also be added to the adhesive and coating material instead of the fine silver particles described in the previous examples. Comparable results are achieved with regard to the antimicrobial effect and in the inhibitory test.

6 shows an inhibition test of an adhesive and coating material according to the invention. It is a polyurethane varnish to which 0.1% by weight of silver particles have been added. The silver particles are agglomerates as shown in FIG. 5. The samples are used in TSB agar as a nutrient medium, to which Staphylococcus epidermidis is added as a test organism. The samples have been incubated for 48 hours. As from Fig. 6 the samples show no inhibitory zone. In this respect, they are not considered to be cytotoxic.