Chitin Silver Powder Biocidal Surface Treatment
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Solution Overview
Problem
The existing methods for preparing powders with contact biocidal properties, such as those containing silver, face challenges due to low solubility of preferred polymers like chitosan, leading to high liquor quantities and economic limitations, as well as environmental concerns with demineralization processes.
Innovation Solution
A method involving the use of polysaccharides like chitin or chitosan to interact with silver ions, followed by filtration, washing, and photochemical reduction to form a powder with atomic/metallic silver, which can be processed without demineralization, using natural bulking agents and reducing silver usage through surface deacetylation and adsorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chitosan is used as the polymer to prepare biocidal articles, then the contact biocidal property is achieved, but the liquor quantity becomes excessively large due to low solubility
Solution Approach 1:
The patent changes the physical state parameter of the polymer from soluble (chitosan solution) to insoluble (chitin powder), which fundamentally alters the processing method from solution-based to suspension-based, thereby reducing liquor quantity while maintaining biocidal efficacy
Solution Approach 2:
The patent uses inexpensive chitin powder as a disposable carrier that can be directly applied without requiring extensive processing or recovery, eliminating the need for large volumes of costly polymer solutions while achieving the same biocidal effect
2Ease of manufacture
If polymer solutions are transported for application, then the biocidal articles can be prepared, but transportation costs become excessively high
Solution Approach 1:
The patent extracts the active biocidal component (silver) and embeds it directly into the chitin powder carrier at the application site, eliminating the need to transport large volumes of polymer solution and reducing transportation costs and energy consumption
3Reliability
If demineralization treatment is applied to chitin, then the biocidal activity is enhanced, but environmental harm increases due to effluent disposal
Solution Approach 1:
The patent converts the naturally occurring mineral content in chitin, which would normally require harmful demineralization treatment, into a beneficial component that provides structural integrity and potential synergistic biocidal effects, thereby eliminating environmental harm while maintaining or enhancing biocidal activity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a more efficient and cost-effective production of powders with enhanced biocidal activity, requiring lower silver concentrations and minimizing environmental impact, as demonstrated by effective bactericidal performance against pathogens like MRSA.
Implementation Method 1
a polysaccharide, which is capable of interacting with silver ions
Implementation Method 2
reducing the silver ions which have interacted with the polysaccharide to atomic/metallic silver
Data Source
AI summary
Powders having contact biocidal properties comprise a polysaccharide carrying atomic/metallic silver. The preferred polysaccharide is chitin, although other polysaccharides including chitosan, carboxymethyl celluloses and carrageenans can be used. The chitin may be obtained from deproteinated crustacean shells without demineralisation, thus being admixed with calcium carbonate and other naturally occurring minerals present in the shells, and may be enzyme deacetylated. The powders of the invention can be used as biocidal dusting powders, formulated into pastes, gels, hydrogels, creams, foams and aerosol sprays for pharmaceutical applications, or dissolved to form solutions for coating substrates such as skin, fabrics, glass, leather and paper to give a bactericidal surface. A particular application of such a solution is as a protective, post-wash treatment for workwear in a laundering process. The powders of the invention may be prepared by slurrying a polysaccharide, which is capable of interacting with silver ions and which is in powder form, in a liquid in which the polymer is insoluble, which liquid contains silver ions, filtering off the powder, washing the powder, reducing the silver ions which have interacted with the polysaccharide to atomic/metallic silver, and drying the powder. According to the polysaccharide chosen, the liquid is suitably water or aqueous ethanol. The silver ions may derive from silver nitrate. The reduction of the silver ions which have interacted with the polysaccharide to atomic/metallic silver can be effected photochemically through exposure to light. To hasten the reduction, however, the washed powder is preferably slurried in a solution of an alkali metal halide, irradiated under stirring with natural or artificial light containing an ultraviolet component, and again filtered off and washed, before drying it.