Antimicrobial plastics product and process for production thereof
Inventors
Cichos, Christoph • Cichos, Irmgard
Assignees
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
Publication Number
US-8673441-B2
Publication Date
2014-03-18
Expiration Date
Abstract
The invention relates to antimicrobial plastics products which comprise, as the antimicrobially active component, silver orthophosphate or particles of partly reduced silver orthophosphate. The plastics products have a very good antimicrobial efficacy. The production process achieves the effect that the plastics products, in spite of their content of silver orthophosphate or partly reduced silver orthophosphate, are not discolored under the action of light.
Core Innovation
The invention relates to antimicrobial plastics products containing plastic and partly reduced silver orthophosphate particles distributed therein. Each partly reduced silver orthophosphate particle consists of silver orthophosphate and metallic silver, where there is direct contact between the silver orthophosphate and the metallic silver within each particle, and the particle surface consists partly of silver phosphate and partly of metallic silver.
The invention addresses the production of antimicrobially effective plastics products characterized by improved photostability, including no discoloration under light. The process avoids using inorganic oxide supports described in the document, including titanium dioxide and other listed oxides and minerals.
The process includes provision of a solution of a silver salt in aqueous ammonia, precipitation of silver orthophosphate by addition of phosphoric acid while maintaining a suspension pH between 6.0 and 8.0, and separation of the solid. The solid is suspended in deionized water, treated with aqueous ammonia and heated to a temperature in the range from 40–90 °C, followed by addition of a reductant sufficient to reduce silver ions to metallic silver, forming partly reduced silver orthophosphate particles as a solid. After separation, the solid is repeatedly washed with deionized water until the specific conductivity of the last wash portion at 25 °C is below the specified limit, then dried, incorporated into a plastics intermediate product not treated with colloidal metal or not containing same, and shaped.
Claims Coverage
The document provides multiple independent claims covering both processes for producing an antimicrobially effective plastics product and the resulting plastics product composition/structure. There are four independent claims: three process claims and one product claim. Across the independent claims, five inventive features are defined.
Partly reduced silver orthophosphate particles with direct contact and mixed-phase surface
The antimicrobially effective plastics product contains plastic and partly reduced silver orthophosphate particles distributed therein, wherein each partly reduced silver orthophosphate particle consists of silver orthophosphate and metallic silver with direct contact, and the surface of each partly reduced silver orthophosphate particle consists partly of said silver phosphate and partly of said metallic silver.
Silver salt in aqueous ammonia and phosphoric acid precipitation at suspension pH 6.0 to 8.0
The process comprises provision of a solution of a silver salt in aqueous ammonia and addition of phosphoric acid accompanied by precipitation of silver orthophosphate particles as a solid contained in suspension until the pH of the suspension lies between 6.0 and 8.0.
Ammonia heating and reductant addition to form partly reduced particles
The process comprises suspension of the solid in deionized water, addition of aqueous ammonia to the suspension and heating to a temperature in the range from 40-90 °C, and addition of a reductant at the chosen temperature in a quantity sufficient to reduce the silver ions in solution to metallic silver, forming partly reduced silver orthophosphate particles as a solid.
Repeated washing with deionized water to specific conductivity at 25 °C
The process comprises repeated washing of the solid with portions of deionized water until the specific conductivity at 25 °C of the last portion of wash water after separation of the solid has a value below 20 µS/cm, or below 50 µS/cm followed by a further washing sequence until below 20 µS/cm.
Incorporation into plastics intermediate product not treated with colloidal metal and shaping
The process comprises incorporation of the dried solid into a plastics intermediate product which has not been treated with a colloidal metal or does not contain same, and shaping of the plastics product.
Overall, the independent claims define antimicrobially effective plastics products containing partly reduced silver orthophosphate particles made of silver orthophosphate and metallic silver in direct contact with a mixed-phase particle surface. For the process claims, the document further specifies silver orthophosphate precipitation under a suspension pH of 6.0 to 8.0, formation of the partly reduced particles by ammonia and reductant treatment within 40–90 °C conditions, repeated washing to conductivity-defined limits at 25 °C, and incorporation into a plastics intermediate product not treated with colloidal metal followed by shaping.
Stated Advantages
Improved photostability, including no discoloration under light.
Antimicrobial efficacy in antimicrobially effective plastics products containing the specified partly reduced silver orthophosphate particles.
Documented Applications
Medical products including catheters using the plastics product containing partly reduced silver orthophosphate particles.
Plastics product applications are exemplified in both medical and non-medical example product forms in the document.
Interested in licensing this patent?