Patent ID: 6938480

Claim:
A method of encapsulating a float for liquid level sensing with a protective skin comprising: A first step, to a Banbury mill mixer or the like mix by weight about 30.0% to 55.0% acrylonitrile rubber 0.5% to 4.2% zinc oxide 1.0% to 15.0% stearic acid 0.1% to 2.0% retarder SAX salicylic acid (O-hydroxybenzoic acid) C 6 H 4 (OH) (COOH) 3.0% to 22% mistron vapor Mg 3 Si 4 O 10 (OH) 2 0.3% to 2.75% coumarone Indene resin absorbed on synthetic calcium Silicate (72% cumar P-25) and 8.0% to 15.0% sulfur mix said components for between about 60 to 80 minutes while maintaining the temperature of the mixture to below about 250° F., a second step comprising taking the mixture of the first step transferring it to a suitably sized roller mill or the like and adding by weight about 12.0% to 40.0% phenolic resin (C 6 H 6 O.CH 20 )X 2.5% to 10.0% carbon black 0.25% to 1.5% Altax C 14 H 8 N 2 S 4 1.75% to 15% epoxy-resin and 1.0% to 5.0% blowing agent mixing said components for about 15 to 50 minutes while maintaining the temperature of the mixture to below about 200° F.; a third step comprising transferring the mixture of th second step to a compression tool where the mixture is subjected to a pressure of about 20-900 lbs. per cubic inch for between about 5 to 45 minutes at a temperature of between about 200° F. to 350° F., removing the mixture from th compression tool and cooling a fourth step, placing a sufficient amount of the material of the third step to fill a plastic container of the desired shape and size; a fifth step of placing the plastic container into the desired finish mold tool and heating to between about 250° F. and 550° F. for between about 20 to 180 minutes to allow the acrylonitrile rubber to expand into intimate contact with the interior surface of the plastic container, whereby a rubber based float with a protective coating is produced.