Patent MX-PA05010181-A (MX)
Title: Method of producing solid flexible inner tubes for tyres and resulting products.
Inventor: ESCALANTE IGNACIO ALVARADO
IPC: B29D30/32
Filed: 2005-09-23
Abstract: The invention relates to a method of producing solid flexible inner tubes for tyres, which are made from polyurethane elastomer material and which are characterised in that they can recover the original shape thereof, with the self-sealing of punctures, and to inner tubes thus obtained. The inventive method comprises the following steps consisting in: 1) heating a polymer resin having a viscosity varying between 1000 and 25000 centipoises to a temperature varying between 25 and 120 DEG C; 2) placing the hot resin in a vacuum chamber with a vacuum of between 1 and 32 inches of mercury for between 5 and 390 minutes; 3) mixing the hot resin with another mixture of isocyanate- and amine-type catalysts at a concentration of between 10 and 60 wt.- % of any mixture selected from said type of catalysts for between 5 and 20 minutes at a velocity of between 60 and 6500 revolutions per minute; 4) producing the inner tube in two separate parts which are subsequently joined, by emptying the mixtur e into two moulds which have been prepared with a mould release agent and which have been pre-heated to a temperature of between 25 and 120 DEG C, each mould being made from a metal material or different suitable resins, with a counter mould which is made from the same material or a similar material to that of the mould, the thickness of the walls of the inner tube varying between 4 and 25 millimetres; 5) producing the inner tube in a single part, using polystyrene foam as a counter mould which is fixed to the mould using strips of polypropylene, cotton or any synthetic fibre with a width of between 1 and 4 centimetres; 6) leaving the part to cure at ambient temperature or heating same to a maximum temperature of 120 DEG C for a period of 6 to 24 hours; 7) following said period, stripping the part and leaving same to rest for 24 hours; 8) joining the two halves using the same resin or any epoxide- or cyanacrylate-type adhesive; 9) removing the polystyrene foam from the finished part u sing any suitable solvent, such as methyl ethyl ketone, toluene, methylene chloride, etc., which is poured into the part through holes which are formed by the fixing of the above-mentioned strips; 10) sealing the perforations in the finished part that are provided to support the polypropylene strips, using pieces of the same material or any other elastomer material, which are inserted and affixed using the urethane elastomer material or the epoxide- or cyanacrylate-type adhesive; 11) inserting the inner tube into a normal vehicle tyre and, subsequently, inserting the tyre into the rim of the vehicle and filling same with pressurised air in accordance with that specified for the tyre of the vehicle. The tyre inner tubes thus produced have the following properties: any section of the inner tubes can be repeatedly extended or compressed, such as to return to the original shape and dimensions thereof, with the self-sealing of perforations caused by impacts from bullets, sharp metal parts or sharp rigid parts, thereby preventing air from being released from the tyre and enabling the continued use of said tyre.