VULCANIZATION APPARATUS AND PROCESS FOR VULCANIZING AND MOLDING TIRES AND PROCESS FOR TREATING A MEMBRANE FOR TIRE VULCANIZATION APPARATUS.

Abstract

A process for treating a membrane for tire vulcanizing and molding apparatus comprises: preparing the membrane (18) comprising an outer surface (20) and an inner surface (21) opposite the outer surface (20); applying at least one inner protective layer (27) onto the inner surface (21). The inner protective layer (27) is configured to facilitate sliding between the mutually contacting portions of the inner surface (21) of the membrane (18) and / or between portions of the inner surface (21) of the membrane (18) and elements of a vulcanizing apparatus (1) and / or to prevent direct contact with a fluid within the membrane (18).

Description

VULCANIZATION APPARATUS AND PROCESS FOR VULCANIZING AND MOLDING TIRES AND PROCESS FOR TREATING A MEMBRANE FOR APPARATUS TIRE VULCANIZATION Technical field of the invention The present invention relates to a vulcanizing apparatus and a process for vulcanizing and molding tires, and to a process for treating a membrane for tire vulcanizing apparatus. The present invention also relates to a membrane for vulcanizing apparatus for vulcanizing and molding tires and a method for extending the operational service life of a membrane for tire vulcanizing apparatus. The present invention falls within the field of processes and apparatus for producing vehicle tires. A vehicle tire generally comprises a casing structure consisting of at least one casing ply having end flanges coupled with respective anchoring rings. Radially outside the casing structure is an associated belt structure comprising one or more belt plies arranged radially over each other and over the casing ply, having textile or metal reinforcing cords with a cross orientation and / or orientation substantially parallel to the circumferential extension direction of the tire. Radially outside the belt structure is an applied tread, also made of elastomeric material, as a semi-finished product constituting the tire. The assembly of at least this belt structure and this tread forms the crown structure of the tire.They are also applied to the respective sidewalls made of elastomeric material on the lateral surfaces of the casing structure, each extending from one of the lateral edges of the tread to the respective anchoring ring structure on the beads. In tubeless tires, the casing layer is internally coated with a layer of elastomeric material, preferably butyl-based, commonly called a liner, with optimal airtight characteristics, extending from one bead to the other. Tire production cycles involve a manufacturing process in which the various structural components of the tire are manufactured and / or assembled on one or more drums. The assembled tires are then transferred to a molding and vulcanization line where a specific molding and vulcanization process is activated to define the tire's structure according to the desired geometry and tread pattern. State of the art Document WO2010 / 016073, filed by the same Applicant, illustrates a process and apparatus for molding and vulcanizing a tire, in which a green tire is introduced into a vulcanization mold. The mold comprises a first side plate and a second side plate, a ring with circumferential sectors that circumscribes a molding cavity, and an expansion chamber delimited by a membrane located within the molding cavity. The membrane is attached to a central telescopic body and expands during the molding and vulcanization process to bring it against a radially internal surface of the green tire, externally pressing that surface while heat is applied. At the end of the process, the membrane is deflated before the vulcanized tire is extracted. Document WO2015 / 166411, in the name of the same Applicant, illustrates a process for producing vehicle wheel tires in which the outer surface of an expandable chamber for tire molding and vulcanizing apparatus is provided to be coated with a crosslinkable polysiloxane composition, to facilitate the separation of the expandable chamber surface from the radially inner surface of the vulcanized tire. Ξ1 document KR20180084278 illustrates a process for vulcanizing a tire, in which a lubricating and releasing substance is applied between the tire and a vulcanizer's non-reliable membrane, to facilitate the separation of said non-reliable membrane from a radially inner surface of the tire at the end of the vulcanization process. Synthesis Notwithstanding the use of release agents placed on the outer surface of the membrane, the Applicant has observed that in some cases the membrane itself suffers such a break / deterioration that it must be replaced frequently to avoid such breakage / deterioration and to ensure the correct vulcanization and quality of the tires produced. Therefore, the Applicant has felt the need to improve the processes and equipment for vulcanizing and molding tires. In particular, the Applicant has felt the need to reduce the deterioration of the membrane's properties and increase its lifespan, in order to decrease the frequency with which the membrane is replaced in the apparatus, i.e., to increase the number of vulcanization cycles for each membrane. In this context, the Applicant has observed that at the end of each vulcanization process, in order to remove the vulcanized tire and insert a green tire for vulcanization into the vulcanization mold, the pressure in the chamber enclosed by the membrane is reduced below the external pressure, causing the membrane to collapse and be flattened, primarily by decreasing its radial volume. The internal surfaces of the membrane adhere to and / or come into contact with the heated parts of the vulcanization apparatus, such as the aforementioned central telescopic body. During this collapse and / or subsequent expansion, the Applicant has observed that these surfaces slide over one another and / or over the heated parts of the vulcanization apparatus. The Applicant has also noted that such slippage can lead to premature wear of the membrane. The Applicant has also noted that hot, pressurized fluids injected into the membrane to make it expand and adhere to the tire during vulcanization, and which contain chemical agents and / or dirt particles, can interact with the membrane material and corrode / wear it out. The Applicant has found that the action of sliding and / or the fluids mentioned above can cause a rapid deterioration of the membrane properties and / or its rupture. The Applicant has also found that the useful operational life of the membrane can be increased by protecting the inner surface of the membrane to prevent contact of the hot fluid, and of possible physical-chemical agents, with the material that constitutes the membrane and / or to facilitate sliding, reducing friction, between portions of its inner surface and / or between its inner surface and the hot elements that constitute the vulcanization apparatus, particularly during the aforementioned collapse and crushing stage. According to a first aspect, the present invention relates to a process for treating a membrane for tire vulcanization and molding apparatus. Preferably, the apparatus comprises a vulcanization mold that internally delimits a vulcanization and molding cavity having a shape corresponding to an external shape to be given to a tire once molded and vulcanized. Preferably, the apparatus comprises devices operatively associated with the vulcanization and molding cavity and configured to administer heat to the tire contained in said vulcanization and molding cavity to vulcanize said tire. Preferably, the apparatus comprises a membrane disposed in the vulcanization and molding cavity. Preferably, the membrane can be moved at least between a contracted configuration and an expanded configuration. Preferably, in the contracted configuration, an external surface of the membrane is separated from a radially internal surface of the tire, and parts of the internal surface of the membrane, opposite the external surface, are in mutual contact and / or in contact with elements of said apparatus. Preferably, in the expanded configuration, the outer surface of the membrane is intended to engage and press against the radially inner surface of the tire. Preferably, the membrane is intended to comprise the outer surface and the inner surface opposite the outer surface. Preferably, the application of at least one internal protective layer on the internal surface is planned. The Applicant considers that at least said internal protective layer facilitates sliding between the mutually contacting portions of the inner surface of the membrane and / or between the portions of the inner surface of the membrane and the elements of said apparatus and / or prevents direct contact with a fluid inside the membrane. According to a second aspect, the present invention relates to a membrane for vulcanizing apparatus for vulcanizing and molding tires. Preferably, an external surface is provided configured to engage with a radially internal surface of a tire enclosed in a vulcanization and molding cavity of a vulcanization mold during a vulcanization and molding stage of said tire. Preferably, an internal surface is provided opposite the external surface and delimiting an expandable chamber. Preferably, at least one internal protective layer is provided, which is applied to the internal surface. Preferably, said membrane is movable under conditions of use at least between a contracted configuration and an expanded configuration, where, in the contracted configuration, portions of said internal surface of the membrane are in mutual contact and / or in contact with elements of said apparatus and where, in the expanded configuration, said external surface of the membrane is coupled and pressed against the radially internal surface of the tire during said molding and vulcanization stage. According to a third aspect, the present invention relates to an apparatus for vulcanizing and molding tires. Preferably, the vulcanization mold is provided which internally delimits a molding cavity that has a shape that corresponds to an external shape that will be given to a tire once molded and vulcanized. Preferably, devices are provided that are operatively associated with the vulcanization and molding cavity and configured to administer heat to the tire contained in said vulcanization and molding cavity to vulcanize said tire. Preferably, a membrane is provided in accordance with the second aspect. According to a fourth aspect, the present invention relates to a process for vulcanizing and molding tires. Preferably, a green tire is intended to be placed in a vulcanization and molding cavity of a vulcanization mold belonging to a vulcanizing apparatus, wherein the vulcanization and molding cavity has a shape corresponding to an external shape to be given to the tire once molded and vulcanized. Preferably, the inflation of a membrane arranged in the vulcanization and molding cavity is foreseen until an external surface of the membrane is coupled and pressed against a radially internal surface of the tire. Preferably, heat is provided to the tire in said vulcanization and molding cavity to vulcanize said tire. Preferably, the membrane is intended to contract to separate it from the internal surface of the tire and to bring portions of an internal surface of the membrane, opposite the external surface, into mutual contact and / or contact with elements of said apparatus. Preferably, the tire is expected to be removed from the vulcanization and molding cavity. Preferably, at least one internal protective layer is applied to the inner surface of the membrane. According to a fifth aspect, the present invention relates to a method for extending the operational life of a membrane for vulcanizing apparatus according to the third aspect. Preferably, it is intended to facilitate sliding between the mutually contacting portions of the inner surface of the membrane and / or between portions of the inner surface of the membrane and elements of said apparatus and / or to prevent direct contact with a fluid inside the membrane by applying at least one internal protective layer over the inner surface of said membrane. He The applicant believes that the present invention allows for a reduction in the wear of the membranes of the devices for vulcanizing and molding tires, delaying their deterioration and therefore increasing the operational lifespan of each individual membrane. In particular, the Applicant considers that the present invention allows for an increase in the number of tires that can be vulcanized and molded by means of each individual membrane compared to the use of a membrane that lacks the internal protective layer or layers. The Applicant considers that the present invention allows for a reduction in costs and times related to molding and vulcanization processes because it reduces the number of membranes used, since fewer machine stops and fewer labor hours are needed to replace worn membranes. The Applicant considers that the present invention also allows for increased reliability of the molding and vulcanization processes and reduces the probability of manufacturing defective tires (which would be discarded), since the membranes are less subject to wear and / or breakage. The present invention, in at least one of the above aspects, may have one or more of the preferred features described below. Preferably, the membrane comprises or is intended to apply at least two overlapping inner layers of protection. Preferably, the membrane comprises or is intended to have at least three overlapping internal protective layers. Preferably, the membrane comprises or is intended to apply four internal layers of protection overlapping each other. Preferably, at least one internal protective layer is applied over the internal surface of the surface or covering the entire internal surface. Preferably, the entire internal surface is intended to be covered with at least this internal protective layer. Preferably, at least said internal protective layer has a thickness greater than or equal to 0.02 mm, more preferably greater than or equal to 0.025 mm. Preferably, at least said internal protective layer has a thickness less than or equal to 0.10 mm, more preferably less than or equal to 0.04 mm. Preferably, each inner protective layer has a thickness greater than or equal to 0.02 mm, and less than or equal to 0.10 mm. Preferably, each inner protective layer has a thickness greater than or equal to 0.025 mm, and less than or equal to 0.04 mm. Preferably, at least this internal protective layer adheres to the membrane and follows its movements and deformations. Preferably, at least this inner protective layer is flexible. Preferably, at least said internal protective layer elastic. Preferably, at least the internal protective layer is non-stick, in the sense that one part of it does not stick to the other (when parts of the internal surface of the membrane are in mutual contact) or to the elements of said device. Preferably, at least said internal protective layer is anti-abrasive, in the sense that one part of it tends to slide over the other (when parts of the internal surface of the membrane are in mutual contact) or over the elements of said apparatus. Preferably, at least said inner protective layer comprises polysiloxane. Preferably, at least said inner protective layer comprises substantially crosslinked polysiloxane. 10 Preferably, applying at least such an internal protective layer comprises: preparing a substantially crosslinkable composition. Preferably, applying at least this internal protective layer comprises: a) cover the internal surface with said substantially crosslinkable composition; b) cross-link said substantially cross-linkable composition on the internal surface. Preferably, apply at least the internal protective layer 25 comprising: Preferably, operation a) comprises: applying the substantially crosslinkable composition to the internal surface by means of a sponge or a brush. Preferably, operation a) comprises: pulverizing the substantially crosslinkable composition onto the internal surface. Preferably, during application, the substantially crosslinkable composition is in liquid or semi-solid form or is substantially gaseous. Preferably, operation a) comprises: applying an amount of substantially crosslinkable composition greater than or equal to 5 g, more preferably greater than or equal to 10 g. Preferably, operation a) comprises: applying an amount of substantially crosslinkable composition less than or equal to 30 g, more preferably less than or equal to 20 g. Preferably, operation a) comprises: applying an amount of substantially crosslinkable composition greater than or equal to 5 g and less than or equal to 30 g. Preferably, operation a) comprises: applying an amount of substantially crosslinkable composition greater than or equal to 10 g and less than or equal to 20 g. Preferably, operation b) comprises: heating the membrane, more preferably in an oven or stove. Preferably, the membrane is placed in the oven at a temperature greater than or equal to 140°C, more preferably greater than or equal to 160°C. Preferably, the membrane is placed in the oven at a temperature less than or equal to 180°C, more preferably less than or equal to 170°C. Preferably, the membrane is placed in the oven at a temperature greater than or equal to 140°C and less than or equal to 180°C. Preferably, the membrane is placed in the oven at a temperature greater than or equal to 160°C and less than or equal to 170°C. Preferably, the membrane is placed in the oven for a heating time greater than or equal to 50 minutes, more preferably greater than or equal to 60 minutes. Preferably, the membrane is placed in the oven for a heating time of less than or equal to 70 minutes, more preferably less than or equal to 65 minutes. Preferably, the membrane is placed in the oven for a heating time greater than or equal to 50 minutes and less than or equal to 70 minutes. Preferably, the membrane is placed in the oven for a heating time greater than or equal to 60 minutes and less than or equal to 65 minutes. Preferably, the membrane should be removed from the oven and allowed to cool. Preferably, the membrane is allowed to cool to room temperature. Preferably, the membrane is allowed to cool for a cooling time greater than or equal to 2 hours, more preferably greater than or equal to 3 hours. Preferably, the membrane is allowed to cool for a time less than or equal to 4.5 hours, more preferably less than or equal to 4 hours. Preferably, the membrane is allowed to cool for a cooling time greater than or equal to 2 hours and less than or equal to 4.5 hours. Preferably, the membrane is allowed to cool for a cooling time greater than or equal to 3 hours and less than or equal to 4 hours. Preferably, the membrane comprises at least one external protective layer applied over the outer surface, to facilitate separation of the membrane from the radially internal surface of the vulcanized and molded tire. Preferably, the application of at least one external protective layer on the outer surface of the membrane is planned. Preferably, at least the inner protective layer and at least the outer protective layer are made of the same substance / material. Preferably, the same substantially crosslinkable composition is intended to be applied to both the inner and outer surfaces. Preferably, the outer protective layer is intended to be applied using substantially the same application methods as the inner protective layer. Preferably, the application of the outer protective layer is planned at least partially at the same time as the inner protective layer. Preferably, the following is planned for: d) cover the internal and external surfaces with said substantially crosslinkable composition; e) reticulate said substantially reticulable composition on the internal surface and on the external surface. Preferably, the following is planned for: f) repeat operations d) and e) at least once. Preferably, it is planned to repeat operations d) and e) at least twice. Preferably, operations d) and e) are expected to be repeated at least three times. Preferably, the membrane is flexible and more preferably elastic. Preferably, the membrane comprises at least one crosslinkable rubber selected from natural or synthetic rubbers, more preferably comprising a mixture with a butyl rubber base. Preferably, the membrane has a thickness greater than or equal to 3 mm, more preferably greater than or equal to 4 mm. 6 mm. Preferably, the membrane has a thickness less than or equal to 5 mm. Preferably, the membrane has a thickness greater than or equal to 3 mm and less than or equal to 6 mm. Preferably, the membrane has a thickness greater than or equal to 4 mm and less than or equal to 5 mm. Preferably, in a resting configuration, i.e., when not under load, the membrane has a tubular or substantially tubular or toroidal shape and is similar to the shape of a tire. Preferably, the membrane has circumferential edges with anchoring appendages anchored or anchorable to parts of the apparatus. Preferably, at least in the expanded or inflated configuration, the membrane has a substantially toroidal shape that mimics the radially inward shape of a tire. Preferably, at least in the contracted configuration, the membrane is gathered towards a central axis of the apparatus and at least partly in contact with elements of said apparatus. Preferably, at least in the contracted configuration, a portion of the membrane is gathered in the vicinity of an axial symmetry plane of the same towards a central axis of the apparatus and at least partly in contact with elements of said apparatus. Preferably, in a resting configuration, the pressure inside the expandable chamber is equal to an external pressure and, more preferably, the membrane is barrel-shaped. Preferably, a part of the apparatus comprises anchoring zones for the membrane anchoring appendages; wherein said anchoring zones are located, at least when the vulcanization mold is closed, on the parts of the apparatus configured to receive the tire beads. Preferably, the vulcanization mold comprises a lower part and an upper part that can be coupled together in an axial symmetry plane and configured to internally delimit a vulcanization and molding cavity. Preferably, the vulcanization mold comprises a working surface arranged to operate on the heels and sides of the green tire to be vulcanized and a circumferential surface arranged to operate against a tread of the green tire to be vulcanized. Preferably, the vulcanization mold comprises a pair of axially opposed half-shells. Preferably, each of the covered half-sheets comprises a working surface arranged to act on the heels and on the sides of the green tire to be vulcanized. Preferably, the vulcanization mold comprises a plurality of circumferential sectors, where said mutually adjacent circumferential sectors define a circumferential surface arranged to operate against a tread of the green tire to be vulcanized. Preferably, a portion of the apparatus comprises a central stem coupled to a pair of flanges that are separated from each other; wherein each of the flanges carries one of the anchoring zones of the membrane anchoring appendages. Preferably, at least in the contracted configuration, a portion of the membrane close to a symmetrical axial plane of the same comes into contact with the central stem. Preferably, inflating the membrane comprises: introducing a hot, pressurized fluid into the expandable chamber. Preferably, the (relative) pressure of the fluids and / or gases used to vulcanize the tire in the expansion chamber is greater than or equal to 0.15 bar, more preferably greater than or equal to 0.2 bar. Preferably, the (relative) pressure of the fluids and / or gases used to vulcanize the tire in the expandable chamber is less than or equal to 30 bar, more preferably less than or equal to 25 bar. Preferably, the (relative) pressure of the fluids and / or gases used to vulcanize the tire in the expandable chamber is greater than or equal to 0.15 bar and less than or equal to 30 bar r . Preferably, the (relative) pressure of the fluids and / or gases used to vulcanize the tire in the expandable chamber is greater than or equal to 0.2 bar and less than or equal to 25 bar. Preferably, the apparatus comprises a generator and / or a tank of a hot, pressurized fluid operatively connected to the expansion chamber. Preferably, the hot, pressurized fluid is gas, more preferably nitrogen. Preferably, the hot, pressurized fluid is water vapor. Preferably, the contraction of the membrane comprises: extract the hot fluid and any air until the pressure inside the expandable chamber is reduced so that it falls below the pressure outside the expandable chamber. Preferably, the apparatus comprises a vacuum pump operatively connected or connectable to the expandable chamber to reduce the pressure inside the expandable chamber so that it falls below the pressure outside said expandable chamber. Preferably, the membrane of an apparatus is intended to be replaced by a number of vulcanized and molded tires greater than or equal to 300, preferably greater than or equal to 350. Preferably, the membrane of an apparatus is intended to be replaced by a number of vulcanized and molded tires less than or equal to 600, preferably less than or equal to 500. Preferably, the membrane of said apparatus is to be replaced by a number of vulcanized and molded tires greater than or equal to 300 and less than or equal to 600. Preferably, the membrane of said apparatus is to be replaced by a number of vulcanized and molded tires greater than or equal to 350 and less than or equal to 500. Other features and advantages will become clearer from the detailed description of preferred but not exclusive embodiments of a membrane for vulcanizing apparatus for vulcanizing and molding tires and of a process for treating a membrane for tire vulcanizing apparatus according to the present invention. Description of the drawings The following description will be made with reference to the attached drawings, provided only as a non-limiting example, in which: Figure 1 shows, in a diameter section, a part of a vulcanizing apparatus for vulcanizing and molding tires at an initial stage of a process for vulcanizing and molding tires; Figures 2, 3, 4 and 5 schematically illustrate the vulcanization apparatus in the respective operating steps; Figure 6 illustrates a membrane for vulcanizing apparatus in an undeformed configuration during a treatment operation; - Figure Ί illustrates an enlarged half section of the membrane in Figure 6; -Figure 8 illustrates another operation for treating the membrane of Figure 6; Figures 9, 10 and 11 illustrate respective enlarged portions of the membrane from Figure 6; -Figure 12 is a radial half-section of a vehicle tire. Detailed description Figure 1 illustrates a part of a vulcanization apparatus for vulcanizing and molding tires 2. The tire 2, illustrated in Figure 12, essentially comprises a casing structure 3 having one / two casing layers 4a / 4a, 4b. A layer of the elastomeric waterproof material or so-called lining 5 is applied within the casing layer(s) 4a / 4a, 4b. Two annular anchoring structures 6, each comprising a so-called bead core 6a carrying an elastomeric filler 6b in a radially external position, with the respective end flanges of the casing layer(s) 4a / 4a, 4b. The annular anchoring structures 6 are integrated in the vicinity of areas normally identified as beads 7, where coupling between the tire 2 and the respective mounting rim is normally present.The belt structure 8, comprising, for example, layers of belts 8a, 8b, is applied circumferentially around the casing layer(s) 4a / 4a, 4b, and a tread 9 is circumferentially juxtaposed over the belt structure 8. The belt structure 8 may be associated with so-called underbelt inserts 10, each positioned between the casing layer(s) 4a / 4a, 4b and one of the axially opposite end edges of the belt structure 8. Two sidewalls 11, each extending from the corresponding heel 7 to a corresponding side edge of the tread 9, are applied in laterally opposite positions over the casing layer(s) 4a / 4a, 4b. The portion of each sidewall 11 near the lateral edge of the tread 9 is known as the shoulder of tire 2. Tire 2 has an axial symmetry plane M equidistant from the respective heels 7 and perpendicular to their rotation axis XX. As can be seen in Figures 1 to 5, the vulcanizing apparatus 1 for vulcanizing and molding tires 2 comprises a vulcanizing mold comprising a lower part 12 and an upper part 13 coupled together in an axial symmetry plane P. Each of said lower part 12 and upper part 13 comprises the respective half-shell 14. The two half-shells 14 are axially opposed. Each of the half-shells 14 comprises a working surface 15 arranged to operate on the beads 7 and on the sidewalls 11 of a green tire 2. The lower part 12 and the upper part 13 can be moved axially between a first position, in which they are separated from each other, and a second position, in which they are adjacent to each other. The vulcanization mold comprises a plurality of circumferential sectors 16 all arranged around a central axis γ-γ of the apparatus 1. The circumferential sectors 16 are movable between a first position, in which they are circumferentially separated from each other and farther from the central axis YY, and a second position, in which they are circumferentially adjacent to each other and closer to the central axis YY. The mutually adjacent circumferential sectors 16 define a circumferential surface 17 arranged to operate against the tread of the green tire 2 to be vulcanized. When the circumferential sectors 16 are in the second position and the lower part 12 and the upper part 13 are mutually coupled in the axial symmetry plane P, the working surfaces 15 and the circumferential surface 17 delimit a vulcanization and molding cavity configured to receive a green tire 2 and having a shape corresponding to an external shape that will be given to the tire 2 once molded and vulcanized. A flexible and elastic membrane 18, for example made of a butyl rubber-based mixture, is installed in apparatus 1. The membrane 18 has, for example, an average thickness of 4.5 mm. When at rest, i.e., not subjected to any load, for example, simply resting against a surface, the membrane 18 has a shape similar to that of a tire, i.e., a radially external part of a toroid, and therefore has the corresponding central axis ZZ. The membrane 18 has a pair of radially internal circumferential edges 19 provided with anchoring appendages configured for attachment to a portion of the apparatus 1. The membrane 18 has an external surface 20 and an internal surface 21, opposite the external surface 20. The internal surface 21 is directed primarily towards the central axis ZZ thereof. The external surface 20 is directed primarily radially and externally with respect to the central axis ZZ thereof. For anchoring the membrane 18 to a portion of the apparatus 1, said portion of the apparatus 1 comprises a central stem 23 coupled to a first and second flange 24, 25 separated from each other and coaxial with the central stem 23. The central stem 23 extends upward from the half-shell 14 of the lower portion 12 and along the central axis YY of the apparatus 1. The first flange 24 is positioned in the half-shell 14 of the lower portion 12.The second tab 25 is carried by means of an upper end of the central stem 23. Each of said first and second flanges 24, 25 has a circumferential anchoring zone or seat which is configured to accommodate one of the radially internal circumferential edges 19 of the membrane 18. The stem 23 can be moved between a raised position and a lowered position. When the membrane 18 is installed on a part of the apparatus 1 with the circumferential edges 19 fitted into the circumferential anchor seats, it is located around the central stem 23 and radially inwards with respect to the circumferential sectors 16. In addition, the membrane 18 internally delimits an expandable chamber 26. The devices known per se, not illustrated, are configured to move the aforementioned parts of apparatus 1 between the indicated positions. The apparatus 1 also comprises a generator and / or a tank of a hot, pressurized fluid (up to 30 bar), not illustrated as it is of a known type, operatively connected to the expandable chamber 26 to inflate the membrane 18. This fluid may be, for example, nitrogen or water vapor. The apparatus 1 also comprises a vacuum pump, not illustrated as it is of a known type, operatively connected or connectable to the expandable chamber 26, to reduce the pressure inside the expandable chamber below a pressure outside said expandable chamber and collapse / contract the membrane 18. The apparatus 1 also comprises devices operatively associated with the vulcanization and molding cavity and configured to administer heat, also via the hot fluid, to the tire 2 contained in said vulcanization and molding cavity to vulcanize said tire 2. The membrane in 18 is movable between a contracted configuration and an expanded configuration, where, in the contracted configuration, portions of said internal surface 21 of the membrane 18 are in mutual contact and / or in contact with the central stem 23, and where, in the expanded configuration, said external surface 20 of the membrane 18 is coupled and pressed against the radially internal surface of the tire 2 during said molding and vulcanization stage. An internal protective layer 27, illustrated in Figures 7, 9, 10, and 11, is present on the internal surface 21 of the membrane 18 and is configured to facilitate sliding between the mutually contacting parts of the internal surface 21 of the membrane 18 and / or between portions of the internal surface 21 of the membrane 18 and the elements or parts constituting the apparatus 1 and to prevent direct contact with the hot fluid being introduced into the expandable chamber 26. The membrane 18 comprises an outer protective layer applied to the outer surface 20 to facilitate separation of the membrane 18 from the radially inner surface of the vulcanized and molded tire 2. The outer protective layer is not shown in the accompanying drawings as it is already known. In the non-limiting embodiment described herein, once the butyl rubber membrane 18 has been constructed, the inner protective layer 27 and, optionally, the outer protective layer are applied before mounting the membrane 18 onto the parts constituting the apparatus 1. For this purpose, and in accordance with the process of treating a membrane for tire molding and vulcanizing apparatus according to the present invention, a substantially crosslinkable polysiloxane composition is prepared and this composition is spread by means of a sponge or brush or sprayed onto the inner surface 21 and possibly also onto the outer surface 20 to completely and uniformly cover it (as illustrated schematically in Figure 6). During application, the substantially crosslinkable composition is in liquid, semi-solid, or substantially gaseous form. For example, the substantially crosslinkable polysiloxane composition comprises at least one reactive polysiloxane oil and at least one crosslinking agent configured to react with the reactive polysiloxane oil. For example, the substantially crosslinkable polysiloxane composition is of the type described in the aforementioned WO 2015 / 166411, which is incorporated herein by reference. The amount of substantially crosslinkable polysiloxane composition that you apply to the inner surface 21 depends on the dimensions of the tire 2. For example, this amount is between about 5 g and about 30 g. Once the composition has been applied, any excess product and / or liquids are removed, and the membrane 18 is placed in an oven 100 or stove (Figure 8) for a sufficient time to crosslink the composition. For example, the membrane 18 is held at a temperature between approximately 140°C and approximately 180°C for a heating time of between approximately 50 minutes and approximately 70 minutes. Once the residence time in oven 100 is complete, the membrane 18 is removed and allowed to cool to room temperature for a cooling time of between 2 and 4.5 hours in a clean, well-ventilated area. At the end of the process described above, the membrane 18 has a single inner protective layer 27, as illustrated in Figure 9. The inner protective layer 27 adheres to the membrane 18 and follows its movements and deformations; that is, it is flexible and preferably also elastic, substantially like the butyl rubber of the membrane 18. The inner protective layer 27 has a thickness s, for example, between approximately 0.025 mm and approximately 0.10 mm. The inner protective layer 27 is non-stick, in the sense that one part of it does not stick to the other (when parts of the inner surface 21 of the membrane 18 are in mutual contact) or to the elements of said apparatus 1. The inner protective layer 27 is anti-abrasive, in the sense that one part of it tends to slide over the other (when parts of the inner surface 21 of the membrane are in mutual contact) or over the elements that constitute the apparatus 1. According to a method for extending the service life of a membrane for tire vulcanization and molding apparatus according to the present invention, it is therefore provided to facilitate sliding between the mutually contacting portions of the inner surface of the membrane 18 and / or between the portions of the inner surface of the membrane 18 and the elements of said apparatus 1 and / or to prevent direct contact with a fluid inside the membrane 18 by applying at least one internal protective layer 27 on the inner surface 21 of said membrane 18. There may also be more than one internal protective layer 27 and possibly more than one external protective layer. Depending on the specific application, two (Figure 10), three (Figure 11), or even four overlapping internal protective layers 27 may be applied. The total thickness s of the overlapping internal protective layers 27 (from one to four) ranges, for example, from approximately 0.02 mm to approximately 0.4 mm. In these specific applications, the operations described above (application, oven curing, and cooling) may be repeated multiple times for each internal protective layer 27. In the example described above, the same substantially crosslinkable composition is applied to the inner surface 21 and the outer surface 20. The outer protective layer can be applied using the same application methods as the inner protective layer 27 or using different methods. For example, the outer protective layer can be applied before, after, or simultaneously with the inner protective layer. Once the composition has been applied to both the inner surface 21 and the outer surface 20, the membrane 18 is placed in oven 100 and then allowed to cool to achieve simultaneous crosslinking of both the inner and outer protective layers. Once the membrane 18 is mounted on the parts that constitute the apparatus 1, the apparatus 1 is ready to activate a process for vulcanizing and molding tires 2, which is also part of the present invention, i.e., for molding and vulcanizing one batch of tires 2 after another. With reference to Figures 1 to 5, while the lower part 12 and the upper part 13 are in their first position, where they are separated from each other, the circumferential sectors 16 are in their first position, where they are circumferentially separated from each other and further from the central YY axis, and the stem 23 is in the raised position (Figure 2), the vacuum pump maintains a pressure inside the expandable chamber 26 that is below the pressure outside said expandable chamber 26. In this way, the diaphragm 18 is kept in a contracted configuration and a portion of it in the vicinity of an axial symmetry plane is bunched / pressed against the stem 23.Parts of the inner surface 21 of the membrane 18, more precisely of the inner protective layer 27, are therefore in mutual contact and / or in contact with elements that constitute the apparatus 1, in particular with the stem 23 and with the first and second tabs 24, 25. A green tire 2 is positioned between the circumferential sectors 16 and rests against the lower half-shell 14 of part 12, passing the second flange 25, the stem 23 and the membrane 18 through the central opening of the tire 2 delimited by the heels 7. In this configuration, the outer surface 20 of the membrane 18 is separated from a radially internal surface of the green tire 2, i.e., from the lining 5. After the green tire 2 has been placed, the stem 23 and the second tab 25 are taken to the lowered position (Figure 3) in which the membrane 18 is further grouped / crushed and parts of the inner protective layer 27 are slid over each other, over the stem 23 and on the first and second flanges 24, 25. At this point, the vulcanization mold is closed, bringing the lower part 12 and the upper part 13 to their second position, where they are side by side, and radially contracting the circumferential sectors 16 to their second position, where they are circumferentially adjacent to each other and closer to the central axis YY. When the vulcanization mold is closed, the anchoring zones or seats are positioned on the parts of the vulcanization mold configured to receive the beads 7 of the tire 2. The hot, pressurized fluid is introduced into the expandable chamber 26 to inflate the membrane 18 to its expanded configuration, in which the outer surface 20 engages and presses against the radially internal surface of the tire 2 (Figure 4). In this expanded or inflated configuration, the membrane has a substantially toroidal shape that mimics the radially internal shape of a tire 2.Then, heat is applied to tire 2, which is placed in the vulcanization and molding cavity to vulcanize said tire 2. After the required time has elapsed, the vulcanization mold is opened and the membrane 18 is re-contracted to separate it from the radially inner surface of the tire 2. To do this, the hot fluid is extracted and the pressure inside the expandable chamber 26 is brought below an external pressure. The molded and vulcanized tire 2 is then removed from the vulcanization mold and another green tire 2 can be loaded into the mold. When apparatus 1 is stopped and in the rest configuration, the vulcanization mold is open, the stem 23 is in the raised position, and the pressure inside the expandable chamber 26 is equal to the external pressure, i.e., equal to atmospheric pressure. The membrane 18 adopts a barrel configuration (Figure 5). COMPARATIVE TESTS As can be seen from the tests presented here, the presence of one or more internal protective layers 27 allows a series of molding and vulcanizing steps to be carried out before replacing the membrane 18 because it is worn or broken, i.e., up to 300% more than the number of cycles performed when using the membrane 18 that lacks the internal protective layer or layers 27 mentioned above. Table 1 below reports the results of the comparative tests performed on devices A, B, C and 0. Apparatus A is provided with a membrane 18 without any internal protective layer 27. In contrast, apparatuses B, C, and D are provided with membranes provided with internal protective layers 27. Each internal protective layer 27 comprises at least one reactive polysiloxane oil and at least one crosslinking agent configured to react with the reactive polysiloxane oil. The number of molding and vulcanizing cycles (equal to the number of vulcanized and molded tires) is the number at which wear and / or rupture of the membrane becomes evident. This number was normalized to 100 for the membrane lacking the internal protective layer(s). Table 1 Test No. 1 Apparatus A Test duration 7 days N9 standardized molding and vulcanization cycles (%) 100 N9 internal protective layers applied N? external protective layers applied 3 2 B 13 days 261 2 3 3 B 8 days 211 2 3 4 B 9 days 288 2 3 5 C 10 days 371 3 4 6 D 10 days 381 3 4 7 C 9 days 332 3 4 8 D 8 days 308 3 4 As can be observed, the number of molding and vulcanization cycles, i.e., the number of vulcanized and molded tires, of apparatuses B, C and D, provided with membrane 18 with internal protective layers 27, is considerably greater than the number of molds and vulcanization cycles of apparatus A, even with the same external protective layers. Tables 2 and 3 below show the results of further comparative tests between membranes according to the invention provided with a single internal protective layer and membranes according to the invention provided with three internal protective layers. In these tables, the number of molding and vulcanization cycles (equal to the number of vulcanized and molded tires) is the number at which membrane wear and / or rupture is evident. This number was also normalized to 100 for the membrane lacking the internal protective layer or layers. Table 2 Test No. N? standardized molding and vulcanization cycles (%) N? internal protective layers applied 1 100 - 2 204 1 3 178 1 4 214 1 5 201 1 Table 3 Test No. N? standardized molding and vulcanization cycles (%) N? internal protective layers applied 1 100 - 2 279 3 3 248 3 4 474 3 5 302 3 6 171 3 7 348 3 8 403 3 9 313 3 10 366 3 11 393 3 As can be seen, on average, membranes with three internal protective layers perform significantly better than those with only one. The applicant believes that the substantially crosslinkable composition adheres better to the inner surface and covers it more evenly when applied multiple times. Regarding the membranes 18 used in the aforementioned tests, these were treated on 100% of their outer surface with the substantially crosslinkable polysiloxane composition Mono-Lube® 1100 (Chem-Tendence® Corporation). These membranes 18 had a diameter of 540 mm and were obtained by injection molding and crosslinking butyl rubber and phenolic resins with a non-smooth outer surface, to improve air leakage during tire vulcanization. Prior to coating, impurities were removed from the membranes, and the membranes were prepared for the coating using a hydrocarbon solvent. The coating was applied with a sponge, and approximately 20 g of the composition were applied per coating. After each coating, each membrane was left at room temperature for approximately 30 minutes, then placed in an oven at 160°C for 1 hour to achieve crosslinking of the polysiloxane film, and cooled to room temperature (approximately 25°C), allowing it to air dry for at least 4 hours. The membrane treatment, comprising coating a substantially crosslinkable polysiloxane composition and crosslinking the same, was carried out from one to four times.

Claims

1. A process for treating a membrane for vulcanizing apparatus (1) for vulcanizing and molding tires, wherein the apparatus (1) comprises: a vulcanizing mold internally delimiting a molding and vulcanizing cavity having a shape corresponding to an external shape to be imparted to a tire (2) once molded and vulcanized; a device operatively associated with the vulcanizing and molding cavity and configured to administer heat to the tire (2) contained in said vulcanizing and molding cavity to vulcanize said tire (2); a membrane (18) disposed in the vulcanizing and molding cavity; wherein the membrane (18) can be moved at least between a contracted configuration and an expanded configuration;wherein in the contracted configuration, the outer surface (20) of the membrane (18) is separated from a radially internal surface (5) of the tire (2) and wherein portions of an internal surface (21) of the membrane (18) are in mutual contact with the outer surface (20) and / or with elements of said apparatus (1); wherein in the expanded configuration, the outer surface (20) of the membrane (18) is coupled and pressed against the radially internal surface (5) of the tire (2); wherein the process comprises: preparing the membrane (18) comprising the outer surface (20) and the inner surface (21) opposite the outer surface (20); applying at least one internal protective layer (27) on the inner surface (21).

2. The process according to claim 1, comprising: applying at least two internal protective layers (27) superimposed on each other.

3. Process according to claim 1 or 2, comprising: covering the entire internal surface (21) with at least one internal protective layer (27).

4. The process according to claim 1 or 2 or 3, wherein applying at least one internal protective layer (27) comprises: preparing a substantially crosslinkable composition and: a) coating the internal surface (21) with said substantially crosslinkable composition; b) crosslinking said substantially crosslinkable composition onto the internal surface (21); c) repeating operations a) and b) at least once.

5. The process according to claim 4, wherein operations a) and b) are repeated at least twice.

6. The process according to claim 4, wherein operations a) and b) are repeated at least three times.

7. The process according to any of claims 4 to 6, wherein operation a) comprises: applying the substantially crosslinkable composition to the inner surface (21) by means of a sponge or a brush; or spraying the substantially crosslinkable composition onto the inner surface (21).

8. The process according to any of claims 4 to 7, wherein operation a) comprises: applying a quantity of substantially crosslinkable composition between 5 g and 30 g.

9. The process according to any of claims 4 to 8, wherein B) comprises: heating the membrane (18) in an oven (100). 10 10. The process according to claim 9, wherein the membrane (18) is placed in the oven at a temperature between 140°C and 180°C for a heating time between 50 minutes and 70 minutes. 15 11. The process according to claim 9 or 10, comprising: removing the membrane (18) from the oven (100) and allowing it to cool to ambient temperature for a cooling time of between 2 hours and 4.5 hours. 20 12. The process, according to any one of claims 4 to 11, wherein the substantially crosslinkable composition is polysoxylane and comprises: at least one reactive polysiloxane oil, at least one crosslinking agent configured to react with the reactive polysiloxane oil.

13. The process of vulcanizing and molding tires, comprising: placing a green tire (2) in a vulcanizing and molding cavity of a vulcanizing mold belonging to a vulcanizing apparatus (1), wherein the vulcanizing and molding cavity has a shape corresponding to an external shape to be imparted to the tire (2) once molded and vulcanized; inflating a membrane (18) disposed in the vulcanizing and molding cavity until an external surface (20) of the membrane (18) is coupled and pressed against a radially internal surface (5) of the tire (2); applying heat to the tire (2) in the vulcanizing and molding cavity to vulcanize said tire (2);contracting the membrane (18) to separate it from the radially internal surface (5) of the tire (2) and until portions of an internal surface (21) of the membrane (18), opposite the external surface (20), are in mutual contact and / or in contact with elements of said apparatus (1); -extracting the tire (2) from the vulcanization and molding cavity; where at least one internal protective layer (27) is applied over the internal surface (21) of the membrane (18).; 14. The process according to claim 13, wherein the membrane (18) comprises applying at least two internal protective layers (27) superimposed upon each other.

15. The process according to claim 13 or 14, wherein at least one internal protective layer (27) is applied over the entire internal surface (21).

16. The process according to any of claims 13 to 15, wherein at least one internal protective layer (27) has a thickness greater than 0.02 mm.

17. The process according to any of claims 13 to 16, wherein at least one internal protective layer (27) has a thickness of less than 0.1 mm.

18. The process according to any of claims 13 to 17, wherein at least one internal protective layer (27) is elastic. 5 19. The process according to one of claims 13 to 18, wherein at least one internal protective layer (27) comprises polysiloxane.

20. Membrane for vulcanizing apparatus (1) for vulcanizing and molding tires, comprising: an outer surface (20) configured to engage with a radially inner surface (5) of a tire (2) enclosed in a vulcanizing and molding cavity of a vulcanizing mold during a vulcanizing and molding stage of said tire (2); an inner surface (21) opposite the outer surface (20) and delimiting an expansion chamber (26); at least one inner protective layer (27) applied over the inner surface (21);said membrane (18) is movable under the conditions of use at least between a contracted configuration and an expanded configuration, wherein, in the contracted configuration, portions of said internal surface (21) of the membrane (18) are in mutual contact and / or in contact with elements of said apparatus (1), and wherein, in the expanded configuration, said external surface (20) of the membrane (18) is coupled and pressed against the radially internal surface (5) of the tire (2) during said molding and vulcanization stage.

21. The membrane according to claim 20, comprising at least two internal protective layers (27) overlapping each other.

22. The membrane according to claim 20 or 21, wherein at least one internal protective layer (27) is applied over the entire internal surface (21).

23. The membrane according to any of claims 20 or 21 or 22, wherein at least one internal protective layer (27) has a thickness greater than 0.02 mm.

24. The membrane according to any of claims 20 to 23, wherein at least one internal protective layer (27) has a thickness of less than 0.10 mm.

25. The membrane according to any of claims 20 to 24, wherein at least one internal protective layer (27) is elastic.

26. The membrane according to any of claims 20 to 25, wherein at least one internal protective layer (27) comprises polysiloxane.

27. The membrane according to any of claims 20 to 26, comprising at least one external protective layer applied over the external surface (20), to facilitate separation of the membrane (18) from the radially internal surface (5) of the vulcanized and molded tire (2); wherein at least one internal protective layer (27) and at least one external protective layer are made of the same substance.

28. The vulcanizing apparatus (1) for vulcanizing and molding tires comprises: a molding and vulcanizing cavity having a shape corresponding to an external shape to be imparted to a tire (2) once molded and vulcanized; a device operatively associated with the vulcanizing and molding cavity and configured to administer heat to the

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