Microencapsulated red phosphorus
View Patent ↗A method for preparing encapsulated red phosphorus is disclosed. The method entails obtaining a material system that contains dispersed particulate red phosphorus having a mean particle size of 0.1 to 100 μm in an aqueous phase that comprise urea, formaldehyde and a water-soluble silicon dioxide precursor, adding to the material system a sufficient amount of acid to lower the pH to 0 to 5 and maintaining the resulting acidic system at a temperature of 80 to 120° C. for a period longer than one hour. The encapsulated red phosphorus of the invention is suitable for using as a flame retarding agent for plastics molding compositions.
1. A material system comprising encapsulated red phosphorus having a core/shell structure wherein core contains red phosphorus in particulate form and wherein shell contains a combination of urea formaldehyde resin and silicon dioxide the combination produced in a one pot reaction, said urea formaldehyde resin being a water insoluble resin formed by the condensation of urea, formaldehyde, resorcinol and hexamethylenetetramine.
2. The material system of claim 1 wherein the weight of the shell is 1 to 50 wt.%, based on the total weight of the red phosphorus and encapsulating shell.
3. The material system of claim 1 wherein the weight ratio of urea formaldehyde resin to silicon dioxide is 95:5 to 5:95.
4. A method for preparing an encapsulated red phosphorus in a one pot reaction comprising
(i) obtaining a material system that contains dispersed particulate red phosphorus having a mean particle size of 0.1 to 100 μm in an aqueous phase that comprise urea, formaldehyde and a water-soluble silicon dioxide precursor, said phase having a pH of 6 to 13, and
(ii) adding to the material system a sufficient amount of acid to lower the pH to 0 to 5 and to obtains an acidic system,
(iii) maintaining the acidic system at a temperature of 80 to 120° C. for a period longer than one hour.
5. The encapsulated red phosphorus prepared by the method of claim 4 .
6. A method of using the red phosphorus of claim 5 comprising incorporating the red phosphorus as flame retardant in plastics materials.
7. A molding composition containing the encapsulated red phosphorus of claim 5 .
8. The molding composition of claim 7 further containing one or more members selected from the group consisting of glass fibers and talcum.
9. The molding composition of claim 7 further containing one or more members selected from the group consisting of inorganic and organic metal compound, metal salt and metal complex.
10. The molding composition of claim 7 further containing one or more additional flame retardant.
11. A molded article comprising the molding composition of claim 7 .