Process for manufacturing, moulding and curing tyres for vehicle wheels

Abstract

A process for manufacturing, moulding, and curing a tire includes the steps of manufacturing a tire comprising a first elastomer material, providing an inner surface of the tire with a treatment to prevent permeation of a fluid under pressure through the treatment, closing the tire into a moulding cavity defined in a vulcanization mould, admitting a fluid under pressure into a space defined by the treatment in order to press an outer surface of the tire against the at least one wall of the moulding cavity, and applying heat to the tire to vulcanize the first elastomer material. A shape of the at least one wall of the moulding cavity matches a shape of the outer surface of the tire after vulcanization is complete. The treatment includes at least one layer of a second elastomer material having a sulfur-curable polymeric base and a vulcanizing system dissolved in an organic solvent.

1 . A process for manufacturing, moulding and curing tires for vehicle wheels, comprising the following steps: 
 manufacturing a green tire comprising a raw elastomer material;    closing the green tire into a moulding cavity defined in a vulcanization mould, said moulding cavity having walls the shape of which matches the shape of an outer surface of the tire when the vulcanization has been completed;    admitting a fluid under pressure to the space defined by an inner surface of the tire in order to press the outer surface of the green tire against the walls of the moulding cavity;    administering heat to the tire for producing the vulcanization of the raw elastomer material;    characterized in that said process, before the stage of admitting the fluid under pressure, further comprises a treatment stage of the inner surface of the green tire and adapted to prevent permeation of fluid under pressure into the inside of the tire itself.    
     
     
         2 . A process as in  claim 1 , wherein the stage of treating the inner surface of the tire is performed by associating at least one layer of prevulcanized elastomer material with the inner surface of the green tire.  
     
     
         3 . A process as in  claim 2 , wherein the stage of treating the inner surface of the green tire comprises the following steps: forming at least one layer of a raw elastomer material on an outer surface of a toroidal support the shape of which substantially matches the shape of the inner surface of the tire; manufacturing the green tire on the toroidal support carrying said layer of raw elastomer material; prevulcanizing the layer of raw elastomer material before introducing the green tire into the vulcanization mould.  
     
     
         4 . A process as in  claim 3 , wherein the prevulcanization of the elastomer layer is carried out, at least partly, during the manufacturing of the tire on the toroidal support.  
     
     
         5 . A process as in  claim 4 , wherein the prevulcanization of the elastomer layer takes place by heating the toroidal support.  
     
     
         6 . A process as in  claim 5 , wherein the heating of the toroidal support is at least partly achieved following to the use of the toroidal support in a previous moulding and vulcanization cycle of a tire.  
     
     
         7 . A process as in anyone of  claims 3  to  6 , wherein the formation of the layer of the raw elastomer material is put into practice by applying a vulcanizable liquid composition (primer) to the outer surface of the toroidal support.  
     
     
         8 . A process as in  claim 7 , wherein the primer comprises a polymeric base and a vulcanizing system capable of being active during the green-tire manufacturing step.  
     
     
         9 . A process as in  claim 8 , wherein the vulcanizing system which is present in the primer is complete and therefore active already at the moment the primer is applied to the toroidal support.  
     
     
         10 . A process as in  claim 8 , wherein the vulcanizing system which is contained in the primer can be activated only when it is brought into contact with the raw elastomer material constituting the innermost layer of the tire.  
     
     
         11 . A process as in anyone of  claims 7  to  10 , wherein the primer is in the form of a solution in a volatile organic solvent.  
     
     
         12 . A process as in anyone of  claims 7  to  10 , wherein the primer is in the form of an aqueous emulsion.  
     
     
         13 . A process as in anyone of  claims 7  to  12 , wherein the primer is applied by spraying onto the outer surface of the toroidal drum and subsequent evaporation of the solvent.  
     
     
         14 . A process as in anyone of  claims 7  to  12 , wherein the primer is applied by dipping of the toroidal support into the primer itself, by drawing out of the toroidal support and by subsequent evaporation of the solvent.  
     
     
         15 . A process as in anyone of  claims 3  to  14 , wherein a layer of elastomer material (liner) suitable for ensuring the retention of an inflating fluid of the tire is successively applied to the layer of raw elastomer material formed on the outer surface of the toroidal support.  
     
     
         16 . A process as in  claim 15 , wherein the application of at least one intermediate layer of the same composition as that of the liner is interposed between the primer application and the liner application.