# US 5,705,110 A · Process for reducing cross link vapors from rotomolded products made of cross link polyethlylene > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,705,110 A - Document ID: US5705110A - Status: Granted - Kind: A - Application number: 08/709,989 - Filed: 1996-09-09 - Granted: 1998-01-06 - Earliest claimed: 1996-09-09 - Assignees: Centro Corporation - Inventors: Brian M. Weber - Web page: https://patentgrep.com/patent/US5705110A ## CPC - B29C 41/04: Rotational or centrifugal casting, i.e. coating the inside of a mould by rotating the mould - B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00) ## Abstract A method to reduce cross link vapors trapped in hollow cross link polyethylene products produced by rotomolding is disclosed. Ozone is introduced into the hollow product after the polymer has cross linked. Compressed air is delivered with the ozone to circulate the ozone effectively. Use of the ozone oxidizes the cross link vapors and permits reduction in stored inventory of units awaiting dissipation of the cross link polyethylene vapors. A system for batch treatment of the products is also disclosed. ## Claims ### Claim 1 In a rotomolding system operated in accordance with the method comprising the steps of introducing a powdered mixture of polyethylene and free radical generator into a hollow mold, biaxially rotating the mold in an oven, heating the mold sufficiently to cross link the polyethylene, curing and solidifying the cross linked polyethylene into a hollow body, removing the mold from the oven to a cooling station, cooling the mold, opening the mold to withdraw the hollow body from the mold, the improvement comprising the steps of introducing ozone into the hollow body after tho polyethylene begins to cure whereby the cross link vapors generated arc reduced. ### Claim 2 (depends on 1) The rotomolding process of claim 1 wherein said ozone is introduced into the hollow body after the mold is removed from the oven. ### Claim 3 (depends on 1) The rotomolding process of claim 1 wherein said ozone is introduced into the hollow body after the body is removed from the mold. ### Claim 4 (depends on 1) The rotomolding process of claim 1 wherein said ozone is introduced at the rate of between 2 and 6 grams per hour. ### Claim 5 (depends on 1) The rotomolding process of claim 1 wherein a stream of compressed air is introduced into said hollow body coincident with introduction of said ozone. ### Claim 6 (depends on 5) The rotomolding process of claim 5 wherein said ozone is injected at the rate of between 2 and 6 grams per hour. ### Claim 7 (depends on 1) The rotomolding process of claim 1 wherein said ozone is injected at the rate of approximately 2.8 grams per hour per one hundred gallon volume within the hollow body. ### Claim 8 (depends on 7) The rotomolding process of claim 7 wherein a stream of compressed air is introduced into said hollow body coincident with introduction of said ozone. ### Claim 9 (depends on 8) The rotomolding process of claim 8 wherein said stream of compressed air is delivered at a pressure of approximately 90 p.s.i. ### Claim 10 (depends on 8) The rotomolding process of claim 8 wherein said stream of compressed air is introduced into said body by a nozzle affixed to a hose, said ozone is drawn into said stream of compressed air at said nozzle. ### Claim 11 (depends on 10) The rotomolding process of claim 10 wherein said stream of compressed air and said ozone are controlled by an automated controller. ### Claim 12 (depends on 11) The rotomolding process of claim 11 wherein said automated controller first activates an ozone generator and then activates an air compressor, said automated controller opens a valve in said air stream at a predetermined delay interval, said automated controller closes a valve in said air stream after a predetermined time interval. ### Claim 13 A method to produce a molded form from cross link polyethylene comprising the steps of introducing a mixture of powdered polyethylene resin and a cross linking agent into a hollow mold, biaxially rotating the mold in an oven, heating the mold sufficiently to cause the resin to be cross linked, curing and solidifying the cross linked polyethylene into a form, exposing the form to ozone for a predetermined time whereby the vapors generated by cross linking are reduced. ### Claim 14 (depends on 13) The method of claim 13 wherein the ozone is introduced into the form at a rate of from one to three grams per hour per one hundred gallons of space within the form. ### Claim 15 (depends on 13) The method of claim 13 wherein the ozone is introduced into the form at a rate of approximately 2.8 grams per hour per one hundred gallons of space within the form. ### Claim 16 (depends on 13) The method of claim 13 wherein said mold is removed from the oven before said form is exposed to ozone. ### Claim 17 (depends on 13) The method of claim 13 wherein a stream of compressed air is introduced into the form while the form is exposed to the ozone. ### Claim 18 (depends on 17) The method of claim 17 wherein the ozone is introduced into the form at a rate of two to six grams per hour per one hundred gallon volume within the form. ### Claim 19 (depends on 17) The method of claim 17 wherein the stream of compressed air is pressurized to approximately 90 psi. ### Claim 20 (depends on 17) The method of claim 17 wherein the ozone is introduced into the stream of compressed air before the compressed air is introduced into the form. ### Claim 21 A method of reducing malodorous oxidizable gaseous byproducts generated in the forming of a hollow workpiece from a powdered mixture of polyethylene and free radical generator in molds carried in a rotomolding apparatus, the workpiece having an interior space, comprising introducing ozone into said interior space of said workpiece. ### Claim 22 (depends on 21) The method of reducing malodorous oxidizable gaseous byproducts of claim 21 wherein said ozone is introduced into said interior space of said workpiece after said workpiece is removed from said rotomolding apparatus. ### Claim 23 (depends on 21) The method of reducing malodorous oxidizable gaseous byproducts of claim 21 wherein said ozone is introduced at the rate of between 1 and 6 grams per hour per one hundred gallon volume within said workpiece. ### Claim 24 (depends on 21) The method of reducing malodorous oxidizable gaseous byproducts of claim 21 wherein compressed air is introduced into said hollow workpiece coincident with introduction of said ozone.