WO2004073400A2

WO2004073400A2 - Material, in particular to be introduced into binder systems

Info

Publication number: WO2004073400A2
Application number: PCT/DE2004/000251
Authority: WO
Inventors: Lisa Aberle; Erwin Born; Andreas Hartwig; Malte Kleemeier
Original assignee: Fraunhofer Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2003-02-19
Filing date: 2004-02-12
Publication date: 2004-09-02
Also published as: WO2004073400A3

Abstract

The invention relates to a material, in particular material which is to be introduced into binder systems, a method for producing said material and to formulations produced therewith. Materials and the formulations containing them exhibit biocidic properties. Said formulations are used, in particular for field of applications where bactericide, antifouling and bacteriostatic properties are essential.

Description

Material, especially for incorporation in binder systems

• The invention relates to a material, in particular for incorporation into binder systems, processes for its production and its use.

Silver is known for its extremely hygienic surfaces. Accordingly, there has been no lack of attempts in the past to incorporate silver into materials which are said to have a bacteriocidal (killing effect on microorganisms), bacteriostatic (preventing the growth of microorganisms) or antifouling (preventing colonization by microorganisms and other organisms) surface , It is very important to provide organic materials with a hygienic surface. Usually organic biocides are incorporated into the materials e.g. Binder systems, i.e. Monomers, thermoplastic polymers and reactive resins as well as the thermosets made from them and the components and components made from them, incorporated in order to colonize with bacteria, the growth of mussels etc. to prevent. The disadvantage of these fabrics is that they are washed out of the materials. As a result, the equipment of the materials is lost and at the same time the biologically active substances are distributed in the environment. This has obvious toxicological consequences and should therefore be avoided. Alternatively, silver can be used as a biocidal substance. However, all methods developed to date to provide the required silver ions on the surfaces have considerable disadvantages. The direct addition of soluble silver salts has the same disadvantages as the incorporation of the relevant organic biocides, namely the slow washing out, with the result that they are distributed in the environment and the biocidal action on the material surface diminishes. With the commercially available silver powders, such as e.g. available for the production of conductive adhesives, on the other hand, the effective surface is so small that the silver ion concentration on the material surfaces is not sufficient for a biocidal effect. In addition, a high amount of silver is required, which is uneconomical.

DE 199 58 458 AI describes a process for the inclusion of silver ions in zeolites. This makes a fine one Distribution possible in the organic material. But here too there is the disadvantage of the silver ions being washed out of the material too quickly.

Other developments deal with the biocidal treatment of materials with silver nanoparticles in the form of the solid material. The particles are produced either by precipitation from an aqueous solution or by vacuum evaporation into an organic matrix. These processes and the formulations produced with them have the disadvantages that only the silver located on the surface of the nanoparticles can have an effect, the silver located inside the particles is therefore ineffective, and the silver particles tend to agglomerate and sediment, which is too low Processing time of the formulations produced results.

The object of the present invention is to provide material, in particular for incorporation in binder systems for the production of sedimentation-stable formulations, such as a production process. The formulations should have bacteriocidal, bacteriostatic and antifouling surfaces and the lowest possible silver content.

This object is achieved by the features specified in claims 1, 14 and 19. The subclaims represent advantageous developments.

According to this, materials in which an inorganic carrier material is coated with a silver-containing layer are suitable for the production of formulations which are stable to sedimentation and have biocidal properties. These materials are completely dispersible in liquid media.

The silver-containing layer can contain from 1% by weight to 100% by weight silver. For some applications it is advantageous if the silver-containing layer contains 100% by weight of silver so that it forms a silver coating. In the case of a closed coating with silver, the material according to the invention is electrically conductive and has biocidal properties.

It is advantageous if the coated inorganic carrier materials are in the form of nanoparticles. The coating of these particles can have a closed, a non-closed or even an in-soap structure. Suitable inorganic materials for the production of such particles are, in particular, oxides and in this case very particularly silicon dioxide, for example in the form of silicas, glass and, as porous materials, pyrogenic silicas with an aggregate structure or pyrogenic silicas with largely degraded aggregates. However, materials can also be used which only contain oxides. Pyrogenically produced oxides are very particularly preferred as carriers for the silver-containing coating.

The method for producing the material according to the invention essentially consists of the step of applying the coating of silver-containing material to the inorganic carrier material, which is explained in more detail in the examples.

In an advantageous embodiment it is provided that before the inorganic carrier material is coated with silver-containing material, a silver-free coating is first applied, which is then e.g. serves as an adhesion promoter layer for the silver-containing layer. This intermediate layer can e.g. selectively set the zeta potential of the inorganic particles, which has a direct influence on the coating process and the morphology of the deposited layer. These coatings are e.g. around silanes, which are used according to the prior art as modifiers for inorganic particles. However, it is also possible to use polymers or to produce polymers on the particles from monomers. Furthermore, organic particles can also be used as a substrate for the silver-containing layers, both alone and with an additional adhesion promoter layer. The organic particles are preferably polymers which e.g. were prepared by emulsion or suspension polymerization. With the methods mentioned, it is also possible to produce core-shell dispersions which are preferred substrates for the silver-containing coatings. The organic materials are materials known to the person skilled in the art.

The silver-containing coating on the particles can be closed or not closed. The dark color of the closed or almost closed silver-containing coatings can be disadvantageous, in particular in applications with cosmetic aspects, such as, for example, tooth fillings. In such applications, a non-closed coating is included preferred so many imperfections that the coated areas are so small that the dark metallic color is not yet formed.

The material produced according to the invention is in the form of a powder. The particles have a diameter of approx. 5nm to 20μm. The particles produced from porous materials with an aggregate structure preferably have a diameter which is <1 μm.

It is advantageous that the size of the particles can be adjusted in the manufacturing process so that it can be adapted for later use.

The dispersions produced using these particles as a filler which is dispersed in a liquid medium are stable to sedimentation. They can also have thixotropic properties. It is advantageous if the density of the particles and the density of the liquid binder are largely approximated. This further reduces the tendency of the dispersions to sediment. Since particles of different sizes can be produced according to the invention, an optimized particle size distribution, i.e. the rheological properties of the dispersions to be produced with these particles, e.g. Thixotropy, adapted particle size possible.

It has been shown that formulations made from an organic matrix and the materials according to the invention have a bacteriocidal, bacteriostatic and antifouling surface. In order to achieve this effect, an addition of at least 0.05% by weight of the particles provided with a silver-containing coating is required. A content of greater than 0.5% by weight is preferred and particularly preferably between 1 and 50% by weight. It has been found that electrically conductive particles with a silver coating also have biocidal properties, so that dispersions produced with these particles are not only electrically conductive but also biocidal.

All organic or organically modified inorganic binders known to the person skilled in the art can be used as binders. In a preferred embodiment, the organic matrix is a reactive resin.

These reactive resins can be an epoxy, silicone, polyurethane, acrylate or a thermoplastic or reactive hot melt adhesive be fabric. Pressure sensitive adhesives are also suitable binders. In the media containing the components mentioned, preferably binders, the fillers are added to the medium which is liquid at the incorporation temperature and stirred in so that they are uniformly distributed in the medium to produce the dispersion. The particles introduced into the medium do not sediment and agglomerate, they remain completely dispersed.

Such dispersions can e.g. used as paints or adhesives in the manufacture of articles with a hygienic surface from the field of medical technology. The pressure sensitive adhesives comprising the material according to the invention can be applied in the form of plasters or other dressing materials. The materials can also be used as varnishes for tank interior coatings. This solves the problems with bacterial growth on aircraft tanks and process boilers. Another technically important problem that is solved with the formulations according to the invention is the exterior painting of ships with antifouling properties, i.e. the prevention of overgrowth with mussels, barnacles and other living things without releasing toxic substances into the environment. In this application in particular, the use of a soft, silicone-based organic matrix in combination with the silver-coated fillers is particularly preferred.

The formulations according to the invention can also preferably be used in the field of dentistry. Here the silver-coated fillers in the organic matrix serving as tooth filling material prevent the growth of bacteria in the area of the filling and in particular in the space between the tooth and the filling. In this application in particular, the particles according to the invention are also outstandingly suitable for providing materials with a ceramic matrix with biologically active properties.

With suitable binders as the liquid phase, it is particularly advantageous that the dispersions can be crosslinked within a short time, for example by UV radiation. Formulations of epoxides or acrylates or methacrylates with the silver-coated fillers are particularly suitable for this, the mean diameter of the filler particles being less than 100 nm. Due to the small diameter of the filler particles, the UV radiation can, in contrast to comparison materials, also convince the material penetrate well with silver fillers. Fillers with a non-closed silver-containing coating in which the silver-containing areas are so small that the metallic color is not yet available are also particularly suitable.

The use of the silver-coated particles as filler for the production of dispersions also has the effect that the metal content required to achieve the biocidal action is reduced to a minimum.

It is also possible to use the dispersions which have been prepared using coated pyrogenic silica to produce printing inks with a low viscosity. These dispersions are particularly suitable for inkjet printers with which markings, e.g. Barcodes with a hygienic surface on medical items etc. can be printed. Due to the black color of the contained silver, there is even no need for additional pigmentation.

In another preferred embodiment, the particles with a silver-containing coating are incorporated into thermoplastics. This is done either by mixing the particles with the silver-containing coating with the monomers and subsequent polymerization, or by incorporating them into a melt of the thermoplastic. The latter is preferably done in a twin-screw extruder. Furthermore, the incorporation into a solution or dispersion of the thermoplastic polymer can take place. The formulations thus produced with a hygienic surface are preferred for the production of disposable articles for medicine and other plastic articles with special hygiene requirements, e.g. Toys used in areas with bacterial contamination. Furthermore, the use for the production of plastic articles for use in a marine environment is preferred.

If the polymers are in the form of dispersions or solutions, the silver-coated particles are preferably incorporated directly into these preparations. Mixtures of this type are used in particular to provide wall paints or pressure-sensitive adhesives with a hygienic surface. Pressure sensitive adhesives equipped in this way are used in particular for the production of bandage plasters and other bandaging articles. Polymers particularly preferred for this purpose are based on acrylates, methacrylates, polyisoprene and natural latex. In all cases, the biocidal action of the silver can be enhanced by ions having a synergistic effect, particularly preferably zinc ions. As a result, the silver content in the formulations according to the invention can be further reduced. The zinc ions are preferably provided in the form of salts with monomeric or polymeric carboxylic acids or bound to ion exchangers. A zinc content in the formulations of 0.01% by weight to 20% by weight is preferred here. The bioactive effect of the particles with a silver-containing coating is primarily attributed to the released silver ions. In order to adjust the release rate of the silver ions, nobler or less noble metals are added in the form of the elements or as ions. The addition can take place both to the formulation containing the particles with a silver-containing coating, as well as directly into the silver-containing coating or as a component of the coated particles. For example, the addition of more noble elements than silver accelerates the formation of silver ions. As a result, the same biological effect can be achieved with a lower addition of particles with a silver-containing coating. On the other hand, the duration of action is shortened. If, on the other hand, less noble metals are added, the formation of the silver ions is slowed down, which increases the duration of action.

The invention is explained in more detail by means of examples.

example 1

6 g of iron (II) sulfate-7-hydrate are dissolved in about 50 ml of water at room temperature. A solution of 12 g of trisodium citrate-2-dihydrate in 30 ml of water is added. A dark green-brown clear mixture is obtained, into which 1.8 g of pyrogenic silica / Aerosil 200 are worked in with intensive stirring in an ultrasonic bath. 20 ml of 10% silver nitrate solution are then added at room temperature and with vigorous stirring, the mixture immediately turning brown-black. The separated, silver-coated Aerosil particles are centrifuged off and washed twice with 50 ml of 10% ammonium nitrate solution (made from 18.7 ml ammonium hydroxide 25%, 17.3 ml nitric acid 65% and 164 ml water). Finally, it is washed twice with technical ethanol. After drying in a vacuum drying cabinet at around 30 ° C, a black, slightly greenish, iridescent powder is obtained. Example 2

6 g of iron (II) sulfate-7-hydrate are dissolved in about 50 ml of water. A solution of 12 g of trisodium citrate-2-dihydrate in 30 ml of water is added. A dark green-brown clear mixture is obtained, into which 3.5 g of glass spheres with a particle size of at most 4 μ are dispersed with intensive stirring in an ultrasonic bath. After the glass particles have been dispersed, 20 ml of 10% silver nitrate solution are added at room temperature and with vigorous stirring, the mixture immediately turning gray-black. The separated glass-coated glass particles are centrifuged off and washed twice with 50 ml of 10% ammonium nitrate solution (made from 18.7 ml ammonium hydroxide 25%, 17.3 ml nitric acid 65% and 164 ml water). Finally, it is washed twice with technical ethanol. After drying in a vacuum drying cabinet at approx. 30 ° C, a dark gray, free-flowing powder is obtained.

Example 3

Preparation of bacteriocidal and bacteriostatic epoxy resin adhesives:

Adhesives based on cationically curing cycloaliphatic epoxy resins are prepared. For flexibility, the epoxy resin ERL 4221 (Union Carbide) is copolymerized with polytetrahydrofuran with a molecular weight of 1000 (PTHF, Terathane 1000, BASF). In the examples according to the invention, the polytetrahydrofuran contains 3% by weight of the silver-coated pyrogenic silica prepared according to Example 1. This was worked into the PTHF with a disk disperser at a speed of 1000 rpm at 60 ° C. in 60 min. The intermediate is in the table with PTHF-Ag-coat. designated. No silver is included in the comparative examples. The thermal cationic curing takes place on the one hand with the iodonium salt Rhodorsil 2074 (Rhodia) with ascorbic acid 6-hexadecanate (ASHD) as an accelerator and on the other hand with α, α-dimethylbenzylpyridinium hexafluoroantimonate (S. Nakano, T. Endo, J. Polym Be: Part A, 34 (1996) 475). The curing 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 mi percentages by weight and the microbiological effect on staphylococcus epidermidis is summarized in the table.

The results show that the bacteriocidal effect of the adhesives can be controlled by the amount of the silver-coated filler added. Example 4

Preparation of a silicone coating with antifouling properties:

5 g of iodonium salt Rhodorsil 2074 (Rhodia) and 5 g of ascorbic acid 6-hexadecanate (ASHD) as an accelerator are added to 500 g of the silicone SB-1972 (Goldschmidt, test product) functionalized with epoxy groups and stirred until a clear mixture is obtained. 210 g of the mixture are removed for the comparison test. 27 g of the silver-coated glass spheres produced according to Example 2 are added to the remaining 300 g and dispersed therein. Steel sheets made of St37, each 30x30 cm in size, are coated with 100 μm thick coatings and hardened at 120 ° C in 30 minutes. The plates are hung in a cultivation basin with Mytilus edulis. On the comparative sample without the silver-coated particles, a dense mussel population developed after only one week, while even after three weeks, individual mussels settled on the plate with the coating according to the invention, which in addition can easily be removed again.

Claims

claims

1. Material, in particular for incorporation into binder systems, characterized in that an inorganic carrier material is coated with a silver-containing layer.

2. Material according to claim 1, characterized in that the

Layer is a silver layer.

3. Material according to claim 1 or 2, characterized in that the inorganic material consists of nanoparticles.

4. Material according to any one of claims 1 to 3, characterized in that the inorganic carrier material is an oxide.

5. Material according to claim 4, characterized in that the

Oxide is a fumed oxide.

6. Material according to claim 4 or 5, characterized in that the inorganic carrier material is silicon dioxide.

7. Material according to claim 6, characterized in that the

Silicon dioxide is fumed silica.

8. Material according to claim 7, characterized in that the fumed silica has an aggregate structure.

9. Material according to any one of claims 1 to 6, characterized in that the inorganic carrier material has silica.

10. Material according to claim 8, characterized in that the silver-containing layer has a closed structure.

11. Material according to claim β, characterized in that the inorganic carrier material is glass.

12. Material according to any one of the preceding claims, characterized in that it has a biologically active effect.

13. Material according to claim 11, characterized in that it has bacteriocidal, bacteriostatic or biocidal properties.

14. A method for producing the material according to one of the preceding claims, characterized in that silver-containing material is deposited on particles of inorganic material.

15. The method according to claim 14, characterized in that before the coating with the silver-containing material, a silver-free coating is first applied to the particles.

16. The method according to claim 15, characterized in that the silver-free coating serves as an adhesion promoter layer for the silver-containing coating.

17. The method according to claim 14, characterized in that the particle size is adjustable.

18. The method according to claim 17, characterized in that the particle size is adjustable in the nanometer and micrometer range.

19. Material according to one of the preceding claims 1 to 13 contained in formulations.

20. Material according to any one of the preceding claims 1 to 13 contained in formulations which have a biologically active effect.

21. Material according to one of the preceding claims 1 to 13 contained in formulations which are an organic binder system.

22. Material according to claim 21, characterized in that the organic binder is a thermoplastic polymer.

23. Material according to claim 21, characterized in that the organic binder is a reaction resin.

24. Material according to one of the preceding claims 1 to 13 contained in formulations for use as a biocidal material.

25. Material according to any one of the preceding claims 1 to 13 contained in formulations which are used for the production of moldings with a bacteriocidal or bacteriostatic surface.

26. Material according to one of the preceding claims 1 to 13 contained in formulations for the production of adhesives and pressure-sensitive adhesives with a bacteriocidal or bacteriostatic bottle.

27. Material according to one of the preceding claims 1 to 13 contained in formulations for the production of dental filling materials.

28. Material according to one of the preceding claims 1 to 13 contained in formulations for the production of lacquers with a bacteriocidal or bacteriostatic surface.

29. Material according to one of claims 1 to 13 contained in formulations for the production of coatings with anti-fouling properties.

30. Material according to claim 29, characterized in that the coatings are used as inner tank coatings and in shipbuilding.

31. Material according to one of claims 1 to 13 contained in formulations for the production of films for food packaging.

32. Material according to one of the preceding claims 1 to 13 contained in formulations with a biologically active effect in which synergistic ions are present.

33. Material according to claim 32, characterized in that zinc ions are present as synergistic ions.

34. Material according to claim 33, characterized in that the zinc ions are contained in the form of low molecular weight or polymeric carboxylic acid salts or bound as ion exchangers.