Safety tires, methods and equipment therefor

A method for completely filling a tire casing with a thermosetting, three component, closed-cell polyurethane foam comprising:

• mixing a first component non-reactive liquid frothing agent with a second component comprising a liquid mixture of (1) a hydrogen donor comprising (a) a diol selected from the group consisting of polyoxypropylene glycol and hydroxyl terminated polybutadiene (b) optionally at least one glycerine based triol and (c) at least one polyol selected from the group consisting of aliphatic amine based polyols, castor oil, and piperazine based polyols;
• (2) an organo-silicone block copolymer surfactant;
• and (3) a tall oil fatty acid to form a first liquid mixture;
• mixing said first liquid mixture with a third component comprising an NCO-terminated prepolymer, said prepolymer being selected from the group consisting of polyoxypropylene glycol and hydroxyl terminated polybutadiene to form a second liquid mixture wherein (1) the ratio of the equivalent weight of the hydrogen donor of the second component to the equivalent weight of the NCO-terminated prepolymer of the third component, is from about 1:1.04 to about 1:1.06;
• (2) the equivalent weight ratio of the diol, triol, and polyol which constitute the hydrogen donor is from about 1:1.2:3.3 to about 1:0:2.0 respectively;
• (3) the surfactant and tall oil fatty acid are present in an amount sufficient to impart a non-shrinking characteristic to said closed cell foam;
• and (4) the frothing agent is present in an amount sufficient to control the density of the foam to the extent necessary to impart the required load bearing characteristics to the tire casing;
• reacting the second and third components of the second liquid mixture to form a polyurethane while maintaining the frothing agent liquid;
• and
• introducing said second reacting liquid mixture into a tire casing under pressure conditions whereby said frothing agent vaporizes and foams the polyurethane within the tire casing to achieve a substantially uniform density throughout.