Patent Application
20070259196
The sheets of two test series 1 and 2 described below were prepared and tested as follows:
Various silver loads were applied by a magnetron sputtering process to sheets, which consisted of carrier media of a nonwoven material that has a areal weight between 50 and 500 mg/m2.
The nonwoven material consists of polymer fibers. Additionally, it contains natural fibers, namely cellulose fibers. Specifically, nonwovens that contain viscose, polypropylene and polyethylene terephthalate fibers in a blend were used.
Sample 2 has a silver load of 10.5 mg/m2. Samples 3 to 6 have silver loads of 29.4, 56.7, 115.5 and 231 mg/m2, respectively. Sample 1 does not have a silver load and is a control sample.
As the antimicrobially active substance, the carrier material contains silver, which is in colloidal and/or nanoscale form. This is brought about by the generation of essentially rectangular nanoparticle island structures of silver with an edge length in the range of 5 nm.
The island structures that result on the carrier material have a specific surface that is greater than the surface of a closed nanolayer with a thickness of 5 nm.
This is why the delivery rate of a carrier medium that has rectangular island structures with edge length 5 nm is clearly greater than that of a completely coated carrier medium.
The rectangular island structures were detected by SIMS. Specifically, it was found that the nanoscale and/or colloidal silver structures are preferably deposited on the polyolefin fibers of the nonwoven that is used. The viscose fibers are largely free of silver. In this way it is possible to deposit silver selectively on a particular fiber type in a nonwoven that consists of a fiber blend.
By appropriate variation of the process parameters and the load, the size of the islands and the range of their size distribution can be controlled. In this way the specific surface and thus the delivery profile of the antimicrobially active silver can be adjusted. Specifically, polymodally distributed nanostructures can be generated by controlled adjustment of the process parameters. These structures will each have a variously high number of unsaturated surface atoms. Through this they have a variously high reactivity or microbiological activity.
Samples 1 to 6 were subjected to a test for antimicrobial finish according to the generally known AATCC Method 100, which is used for textile materials.
The results of this test are shown in Table 1. Table 1 shows the eradication rate of Escherichia coli cells as a function of the silver load. In Table 1, the silver load is given in mg/m2 in the first column. The second column shows the microbial count in units CFU/mL (colony-forming units/mL) after 24 h, and the third column shows the eradication rate after 24 h in percent. The fourth and fifth columns are similarly organized.
Table 2 shows the results of a microbiological test conducted with spores of type Aspergillus niger on Samples 1 to 6. The samples 1 to 6 functioned as patterns for dishtowels (dishtowel master).
Because of its dark spores, Aspergillus niger is also called black mold. Aspergillus niger is very common food spoilage agent and destroyer of materials. It occurs in soil world wide. This mold fungus can destroy paper and packaging materials as well as leather and paints, even plastics and optical glasses. Diseases caused by Aspergillus niger include, in addition to allergic reactions, infections of the outer ear, pulmonary aspergillosis, inflammations of the peritoneum, inflammations of the endocardium, diseases of the nails as well as skin infections
The first column in Table 2 shows the silver load in mg/m2. Quantity B in the second column qualitatively indicates if the relevant sample has been overgrown with spores after two days. The third column analogously indicates if the sample is overgrown after four days. (B) expresses, only qualitatively, that the growth is somewhat weaker. The (−) qualitatively indicates that there is no growth present.
Samples 1 to 6 in Test Series 1 was additionally subjected to an odor test.
For this, the samples set up as towels were stored for 48 h at 32° C. in 100 mL 10% milk solutions. Then the samples were removed and dried. The milk solutions and the samples, rewetted with 100 μL water after they have been dried, were olfactometrically evaluated. The samples were subjected to a blind test by 10 testers. The testers were requested to evaluate the solution or the samples on a scale based on the following qualitative evaluations:
Table 3 shows the results of the evaluation.
Moreover, the rapid mobilizability of the silver ions was confirmed in rinse-out experiments.
Samples 1 to 6, 2.5×5 cm in size, were each stored in 100 mL water with pH values 3, 7 and 11, and the silver concentrations were determined. It was found that the delivery rate is the greatest in the first hour of storage. The antibacterial activity therefore is effective very rapidly, so that complete eradication of bacteria can be achieved after only 24 h. Nevertheless, after the end of the first hour, a moderate release rate is observed, which also guarantees a medium to long term effect.
In another test a reference sample with a silver load of 55 mg/m2 was subjected to two complete standard wash cycles in a commercial washing machine with a commercial washing powder. After the first wash cycle, about 30% of the silver was still present on the towel. After the second wash cycle, eradication rates of up to 91.17% for bacteria of type Escherichia coli and 99.33% for bacteria of type Staphylococcus aureus could be detected on the towel.
Table 4 shows the results of a test in which glass panes were treated with different samples.
Samples of type A were used for this: Sheets with a carrier medium of nonwoven [material] or impregnated with a nanosilver dispersion. These sheets served as wiping towels for disinfection of glass panes In these sheets, the silver is colloidally dispersed on the carrier medium. The silver is homogenously distributed in the carrier medium.
To prepare these sheets, first a standard floor cleaner was provided with a silver concentration of 500 ppm silver.
This standard floor cleaner was applied to 10×10 cm samples, which were put into a beaker and left covered for about 17 h overnight at room temperature. After 17 h, each sample was cut in half. One half was directly pressed out gently between two hand towels, while the other half was gently rinsed for about 30 seconds with tap water and then gently pressed out.
All the samples of type A were then dried for 3 h at 100° C. in a circulating air oven.
Moreover, glass panes were wiped with samples of type B (towel) that had been wetted with 120 mg/m2 silver.
Class panes were specifically and reproducibly wiped a number of times with samples of type A and B. Then microbiological tests were carried out with the samples and the eradication rates were determined. This was done as follows:
2.5×5 cm samples of types A and B were stamped out and loaded with 20 mL water. The samples were moved back and forth with 50 N normal force on 20 cm long and 5 cm wide glass panes in 50 oscillation cycles.
For bacteria of type Escherichia coli an eradication rate of 95.7% was obtained when using the wetted samples (towels). An eradication rate of 99.83% resulted when using samples that had been impregnated with the standard floor cleaner with a silver concentration of 500 ppm.
An eradication of >99.89% was obtained for bacteria of type Staphylococcus aureus when using the wetted samples. An eradication of 99.93% was seen when using the impregnated samples.
Glass panes that were not wiped did not show any eradication, i.e., on these glass panes the bacteria were present in the initial concentrations.
Finally, it should expressly be pointed out that said embodiment examples merely serve for discussion of the claimed teaching, but do not limit it to these embodiment examples.
Escherichia coli
Aspergillus niger
Escherichia
Staphylococcus
coli
aureus
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 020 791.2 | May 2006 | DE | national |
