Patent MX-PA05011805-A (MX)
Title: Process for manufacturing flexible solid monolithic inner tubes hermetically closed useful for tyres, and products obtained therewith.
Inventor: ESCALANTE IGNACIO ALVARADO
IPC: B29D30/00
Filed: 2005-11-03
Abstract: The invention relates to a method of producing solid semi-flexible monolithic inner tubes hermetically closed 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 80 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 subseque ntly joined, by emptying the mixture, which occupies 10 to 50% of the mould volume, into two moulds which have been prepared with a mould release agent and which have been pre-heated to a temperature of between 20 and 130 DEG C, each mould being made from a metal material or different suitable resins for manufacturing moulds useful for pouring plastic resins; the mould is placed into a mould carrier pertaining to a roto-moulding machine which has two different spins rotating in a perpendicular direction with respect to each other, each spin being performed at a speed of 10 to 200 revolutions per minute for about 15 to 90 minutes, the resin being adjusted at a temperature of 20 to 130 DEG C; 5) producing the inner tube in a single part by pouring an amount of mixture occupying from about 10 to 50% of the tyre inner volume into the pre-heated at a temperature of 20 to 130 DEG C, the side aperture of the tyre inner circle being closed with a cap made of any metallic material, wood or any plastic resin, then placing the tyre into the mould carrier of a roto-moulding machine which has two different spins rotating in a perpendicular direction with respect to each other, each spin being performed at a speed of 10 to 200 revolutions per minute for about 15 to 90 minutes, the resin being adjusted at a temperature of 20 to 130 DEG C; 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) attaching an air valve to the inner tube by means of a pipe or a hose. 9) 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 compresse d, 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.