RU2774650C1 - Method for manufacturing compounds for tyres and tyres containing said compounds - Google Patents

Abstract

FIELD: vehicles.

SUBSTANCE: group of inventions relates to a method for manufacturing a vulcanised elastomeric compound for tyres, to a vulcanised elastomeric compound, a tyre component containing the vulcanised compound, and a tyre for vehicle wheels. Claimed method for manufacturing a vulcanised elastomeric compound for tyres is characterised by the use of a vulcanisation-activating filler and the methods for adding additives, specifically a compatibilising agent, occuring only after the reaction between the zinc-containing activating filler and a fatty acid is complete.

EFFECT: production of compounds with a low content of zinc and, therefore, reduction in the amount of zinc released from tyres during operation at the level of the surroundings.

18 cl, 6 dwg, 12 tbl, 8 ex

Description

Technical field

The present invention relates to a process for the manufacture of elastomeric compounds for tires with reduced zinc content, characterized by the introduction of specific vulcanization-activating fillers and the exact sequence of addition of certain components of the compound.

State of the art

In the tire industry, vulcanization is a process commonly used to improve the mechanical properties of natural rubber or unsaturated polymers, a process that affects the hardness, elasticity, hysteresis of the material at different temperatures and therefore the behavior of the tire on wet surfaces, as well as friction and wear and tear during use.

Over the years, various additives have been proposed to improve the vulcanization process as vulcanization activators and accelerators.

In general, with these additives, it is desirable to increase the degree and uniformity of crosslinking while reducing the energy and time required to complete the reaction.

The main vulcanization activators that can increase the efficiency of the process are inorganic compounds such as metal oxides and hydroxides, for example, ZnO, MgO, Ca(OH) ₂ .

Among the various activators, zinc oxide ZnO is considered the most effective and is still used in many vulcanization processes. This activator is used in combination with weak inorganic acids (eg, stearic acid) which promote its activity in rubber.

In some studies (see, for example, Y. Ikeda et al., Dinuclear bridging bidentate zinc/stearate complex in sulfur cross-linking of rubber , Macromolecules 48 (2015) 462-475) it has been suggested that Zn ^{2+ ions} , generated by the interaction of ZnO with stearic acid, interact with the accelerator and sulfur molecules, forming an organometallic complex that could act as more effective sulphurizing agents. The hypothesis on the structure of such complexes is illustrated in FIG. 3 of this description.

The ability of Zn ²⁺ to form such complexes is a key element of the vulcanization process and is highly dependent on the dispersion of ZnO within the polymer matrix, which in turn is affected by both the particle size and the crystal structure of the zinc oxide.

As a rule, microcrystalline ZnO is used as an activator in the vulcanization process of rubbers for tires, which, however, is difficult to disperse in the polymer matrix and only partially reacts with other vulcanizing agents.

The poor dispersibility and reactivity of the microcrystalline zinc oxide in the elastomeric compound inevitably leads to its excessive dosage relative to the amount actually required for crosslinking.

When using the tire, especially due to tread wear on asphalt, the zinc in the compound is partially released.

Therefore, in view of environmental protection, attempts have been made over the years to reduce the amount of zinc in compounds.

For example, an attempt was made to use finely dispersed ZnO (nanosized particles), but dispersion was still difficult due to the formation of aggregates within the polymer matrix, which effectively eliminated the size advantage over microcrystalline zinc oxide.

On the other hand, the advantage of using products containing nanoparticles of zinc oxide directly bonded to nanoparticles of silicon dioxide, compounds that perform the dual function of a filler and vulcanization activators (hereinafter collectively called activating fillers or more specifically ZnO/SiO ₂ ) (see articles A. Susanna et al., ZnO nanoparticles anchored to silica filler, A curing accelerator for isoprene rubber composites , Chemical Engineering Journal 275 (2015) 245-252); A. Susanna et al., Catalytic effect of ZnO anchored silica nanoparticles on rubber vulcanization and cross-link formation , European Polymer Journal 93 (2017) 63-74).

According to the authors, compared to conventional microcrystalline ZnO, these activating fillers result in higher vulcanization efficiency, which includes a) faster reaction of ZnO with stearic acid and vulcanizing agents to form more reactive sulfur complexes, b) higher cross-linking in a compound with a more uniform the distribution of bonds and the predominant formation of mono- and disulfide bridges between polymer chains and, finally, c) a more uniform dispersion of nanoparticles in the absence of aggregates of unreacted ZnO inside the polymer matrix at the end of the vulcanization process.

All these aspects make the activating fillers described above promising substitutes for microcrystalline zinc oxide in the curing of tire compounds, which can reduce the use of zinc with important consequences for environmental stability.

The essence of the invention

Applicant has undertaken studies to further improve the performance of the activating fillers described above in the manufacture of tire compounds in order to further reduce the zinc content for vulcanization and hence contain environmental pollution by released zinc while maintaining or possibly improving process conditions, yield and all the properties of the final elastomeric compounds described above.

Surprisingly, it has been found that the desired goals can be achieved if during the production of the compound the order of adding some additives is set appropriately, for example, by introducing a compatibilizing agent (silane) only after the reaction between the activating filler (ZnO/SiO) ₂ ) and the fatty acid ( stearic acid).

The Applicant has confirmed that in addition to reducing the time and energy required for vulcanization, the resulting compounds with the same content of activating fillers and zinc show better crosslinking.

Moreover, the hysteresis properties exhibited by these compounds allow for generally lower rolling resistance and better abrasion resistance, and, if used in a tread band, better grip on wet surfaces is possible.

In addition, for the same performance or even better performance, the amount of activating filler and ultimately zinc in the compound can be reduced, resulting in lower environmental release of this metal.

The first aspect of the present invention is a method for the manufacture of a vulcanizable elastomeric tire compound, said method comprising at least:

- the step of mixing (1) at least one elastomeric polymer (A) and at least one additive for an elastomeric compound, excluding curing agents (B), to obtain a non-vulcanizable elastomeric compound;

- a step of mixing (2) a non-vulcanizable elastomeric compound and at least one curing agent (B) to obtain a curable elastomeric compound, and

- the stage of unloading the vulcanizable elastomeric compound,

where at the stages of mixing (1) and/or (2) add at least one fatty acid (C), at least one product (D) containing zinc directly associated with a light filler, and at least , one compatibilizing agent (E),

characterized in that said at least one compatibilizing agent (E) is added after completion of addition and processing of said at least one fatty acid (C) and at least one product (D) containing zinc directly associated with light filler.

The second aspect of the present invention is a vulcanizable elastomeric compound obtained in accordance with the method according to the first aspect of the present invention.

The third aspect of the present invention is a tire component containing the vulcanizable compound according to the second aspect of the invention or the vulcanized compound obtained by vulcanization thereof.

The fourth aspect of the present invention is a tire for vehicle wheels containing the component according to the third aspect of the invention.

Definitions

In relation to the present description and the following claims, the term "mass.h./100 mass.h. rubber" (mass parts per hundred mass parts of rubber) means the mass parts of a given component of the elastomeric composition per 100 mass parts of the diene elastomeric polymer.

Unless otherwise indicated, all percentages are expressed as weight percent.

As used herein, the term "elastomeric polymer" or "rubber" or "elastomer" means a natural or synthetic polymer that, after vulcanization at room temperature, can be stretched repeatedly to at least twice its original length, and which, after removal of the tensile load, is substantially returns immediately with force to approximately its original length (as defined by ASTM D1566-11 in standard rubber terminology).

In the present description, the term "reinforcing filler" refers to a reinforcing material generally used to improve the mechanical properties of tire rubbers, preferably selected from carbon black, conventional silica such as sand silica precipitated with strong acids, preferably amorphous, diatomaceous earth , calcium carbonate, silicon dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and mixtures thereof.

In the present description, the term "light filler" refers to a common reinforcing material used in this field, which is selected from conventional silica and silicates, such as sepiolite, palygorskite, also known as attapulgite, montmorillonite, alloisite, etc., optionally modified acid treated and/or derivatized. As a rule, light fillers have surface hydroxyl groups.

In the present description, the term "activating vulcanization" refers to a compound capable of facilitating vulcanization, making it flow in a shorter time and possibly at lower temperatures.

In the present description, the terms "activating filler" or "product (D) containing zinc directly bonded to a light filler" are used interchangeably and indicate a product capable of performing both the function of reinforcing the compound and the function of a vulcanization activator formed by a light filler and a zinc product. , in which zinc is directly bonded to the surface hydroxyl groups of the filler. In particular, as stated in A. Susanna et al., Chemical Engineering Journal 275 (2015) 245-252, zinc binds directly to the surface hydroxyl groups of a light-colored filler without the mediation of any group or space group using bonds of the Zn-O type -Si, determined for example, by analysis of Si ²⁹ -NMR. In the present description, such a direct connection is also called "fixing" zinc on a light filler.

In the present description, the term "zinc compound" means a compound selected from ZnO, Zn(OH) ₂ and organic or inorganic salts of Zn ²⁺ .

In the present description, the term "elastomer compound" refers to a product obtained by mixing and optionally heating at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tire compounds.

In the present description, the term "unvulcanizable elastomeric compound" means a product obtained by mixing at least one elastomeric polymer with at least one of the additives commonly used in the preparation of tire compounds, with the exception of vulcanizing agents. The non-vulcanizable elastomer compound may also be referred to as phase (1) of the elastomer compound.

As used herein, the term "vulcanizable elastomer compound" means a ready-to-vulcanize elastomer compound in which all additives, including vulcanization additives, have been incorporated. The vulcanizable elastomer compound may also be referred to as phase (2) of the elastomer compound.

In the present description, the term "vulcanized elastomeric compound" means a material obtained by vulcanizing a vulcanizable elastomeric compound.

In the present description, the term "conventional method" referring to a compounding method refers to a multi-stage production method in which a compatibilizing agent (silane) is supplied before the reaction between fatty acid and zinc has started or ended. In a conventional process, therefore, the compatibilizing agent is added at an earlier or concurrent step relative to the addition of the fatty acid and/or zinc.

In the present description, the term "method according to the invention", referring to a method for producing elastomeric compounds, indicates a multi-stage production method in which the compatibilizing agent (E) (silane) is introduced into the mixer only after the addition and processing of fatty acid (C) is completed and product (D) containing zinc directly associated with a light-colored filler.

In the process according to the invention, the processing of the fatty acid (C) and the product (D) containing zinc directly bound to the light-colored filler is continued for at least the time necessary to substantially complete the reaction between fatty acid and zinc.

In the present description, the term "mixing step (1)" refers to a step in the process for producing an elastomeric compound in which one or more additives may be added by mixing and possibly heating, with the exception of vulcanization additives, which are supplied in step (2).

This step may include a plurality of intermediate processes during which one or more additives, with the exception of curing additives, are introduced, followed by further processing.

This step may include a "grinding step", in this case also referred to as a "1-0 step", which is an initial step during which one or more diene elastomeric polymers (A) are mechanically processed, possibly hot and possibly with the addition of one or more additives, usually excluding the vulcanization additives and the compatibilizing agent (E), to form the elastomeric mass and make it more workable and homogeneous. At this stage, the polymer is usually treated, possibly with the help of plasticizers, to lower its viscosity and increase its exposed surface, which makes it easier to incorporate additives, in particular fillers.

As used herein, the term "mixing step (2)" includes a subsequent step in the process for producing an elastomeric compound, in which the vulcanizers and preferably vulcanization accelerators and/or retarders are added and mixed into the material at a controlled temperature, typically at a mixing temperature of less than 160°C. The mixing step (1) is also referred to as the "non-productive step", since the compound components are fed into the mixing device, with the exception of the components for crosslinking (for example, sulfur and accelerators).

The mixing step (2) is instead referred to as the production step. At this stage, the elastomeric compound obtained from step (1) and curative additives capable of promoting and/or controlling crosslinking are added to the mixing device to obtain a curable elastomeric compound.

As used herein, the term "intermittent or batch mixer" refers to a mixing device adapted to batch feed components of an elastomeric composition in predetermined amounts (feeds) and mix them for a predetermined period of time to obtain an elastomeric composition. At the end of mixing, the resulting elastomeric composition is completely discharged from the mixing device in one solution.

Typically, a batch mixer includes a pair of tangential or interpenetrating rotors placed in the mixing chamber and rotating in opposite directions to mix the components introduced into the mixing chamber through its top.

To do this, the batch mixer can be equipped with a pneumatic or hydraulic cylinder located at the top of the mixing chamber and a piston that moves both upwards to open the mixing chamber, allowing the introduction of the ingredients of the composition using special hoppers, and downwards to apply pressure on the processed material in the mixing chamber and located above the pair of rotors.

A pneumatic or hydraulic system located at the bottom of the mixing chamber allows the elastomeric composition to be discharged at the end of the mixing cycle through a specially provided inlet end opening.

Specific examples of batch mixers that can be used in accordance with the present invention are closed (Banbury®, Intermix®, Tandem Mixer HF) or open (open mill or Z-blade mixer) type mixers.

As used herein, the term "continuous mixer" refers to a mixing device suitable for receiving the ingredients of an elastomeric composition as a continuous feed, mixing and/or processing them to produce and discharge the elastomeric composition in a continuous flow (with the exception of possible stops of the mixing device due to - for maintenance or reformulation of the elastomer composition) as opposed to batch loading/unloading in the case of a batch mixer.

The continuous mixer essentially allows the ingredients of the elastomeric composition to be mixed, especially under cold feeding/dispensing conditions, and to grind the elastomeric material, thereby raising its temperature, to make it processable and plastic to facilitate the incorporation and/or distribution of the ingredients within the polymer matrix. A continuous mixer is thus preferably provided with mixing sections capable of imparting high shear stress to the composition and any redistribution sections. The continuous mixer is additionally provided with transport sections capable of transferring the processed composition from one longitudinal end to the other end of the inner chamber. Examples of continuous mixers include twin screw or multi-screw (eg ring-type mixers), interpenetrating and co-rotating mixers, or planetary mixers.

The term "planetary mixer" means a continuous mixing device having a central rotor and a plurality of satellite mixers, each of which, driven by the central rotor, rotates simultaneously around its own axis and around the central rotor.

Both the batch mixer and the continuous mixer are able to impart enough energy to the elastomer composition to mix and disperse the filler in the elastomer polymer even when cold fed, unlike other devices for processing the elastomer composition, such as conveyor devices and devices for the manufacture of semi-finished product .

In the present description, the term "raw (green)" is usually used to indicate a material, compound, composition, component or tire that has not yet been vulcanized.

Detailed description of the invention

Below is illustrated in detail a process for the manufacture of a vulcanizable elastomeric tire compound in accordance with the invention.

This method is characterized by one or more of the following preferred aspects, taken alone or in combination with each other, in particular, characterized by the use of at least one activating filler (D) and the sequence of addition of some components.

The present process may be a continuous process, but preferably it is an intermittent process (batch).

The present process, when it is batchwise, can be carried out in one or more mixers, preferably in a single mixer.

The method according to the invention includes the step of mixing (step 1) at least one diene elastomeric polymer (A) and at least one elastomeric compound additive which is not a curing agent (B).

The at least one additive for elastomeric compounds which is mixed with at least one diene elastomeric polymer (A) in the mixing step (1) may be, for example, a fatty acid (C), a product (D) containing zinc , directly associated with a light-colored filler, possibly a compatibilizing agent (E), a reinforcing filler (H), an antioxidant (I), a wax (L), a plasticizer (M), etc.

Generally, no curing agent (B) is added in the mixing step (1), and preferably not even accelerating agents (F) or curing delay agents (G) are added.

In one embodiment, the process according to the invention comprises the step of mixing (step 1) at least one diene elastomeric polymer (A), at least one fatty acid (C), at least one product (D), containing zinc, directly associated with a light filler, and only after their addition and processing, at least one compatibilizing agent (E).

In one embodiment, the process according to the invention comprises the step of mixing (step 1) at least one diene elastomeric polymer (A), at least one fatty acid (C) and at least one product (D) , containing zinc, directly associated with a light filler. In this process variant, at least one product (D) containing zinc directly bound to the light filler and at least one fatty acid (C) is processed in step (1), wherein at least one compatibilizing agent (E) is fed into step (2).

In one embodiment, the process according to the invention comprises the step of mixing (step 1) at least one diene elastomeric polymer (A), at least one fatty acid (C), or at least one product (D ) containing zinc, directly associated with a light-colored filler. In this process variant, at least one product (D) containing zinc directly bound to the light filler, or at least one fatty acid (C), respectively, can be added and processed in step (2), followed by adding at least one compatibilizing agent (E).

The mixing stage (1) according to the present method may include several intermediate technological stages, here called stages 1-0, 1-1, 1-2, 1-3, etc., characterized by a short cessation of mixing and the addition of one or more ingredients, but without intermediate unloading of the compound.

Preferably, in the case of a batch process, in which the mixing step (1) includes several intermediate processing steps, the intermediate compounds are not discharged, but are processed in the same mixer with the addition of appropriate additives.

The mixing step (1) preferably includes an initial grinding step (step 1-0) during which at least one elastomeric polymer (A) is processed. At grinding, the polymer is subjected to mechanical and preferably heat treatment to reduce its viscosity, increase its open surface and processability, making it easier to incorporate additives. In addition, in the case of mixtures of several polymers (A), grinding provides a better homogeneity of the compound.

Optionally, at least one fatty acid (C) and/or at least one product (D) containing zinc directly associated with a light filler, or other additives of stage 1, but preferably a non-compatibilizing agent (E), can be introduced during grinding.

In the present method, at least one fatty acid (C) may be fed in whole or in part in the mixing step (1).

Preferably all of the fatty acid (C) is fed into the mixing step (1).

Optionally, the fatty acid (C) may be fed in whole or in part in the grinding step (step 1-0), if present.

On the other hand, the addition of the fatty acid (C) can also be divided into several intermediate steps in the mixing step (1), provided that they precede the step of adding the compatibilizing agent (E).

In the present method, in the mixing step (1), at least one product (D) containing zinc directly bound to the light-colored filler may be fed in whole or in part.

Preferably, all of the product (D) containing zinc directly bound to the light filler is fed to step (1).

Optionally, the product (D) containing zinc directly bound to the light filler may be fed in whole or in part to the grinding step (step 1-0) if present.

On the other hand, the addition of the product (D) containing zinc directly bound to the light-colored filler can also be divided into several intermediate steps in the mixing step (1), provided that they precede the step of adding the compatibilizing agent (E).

Preferably, the product (D) containing zinc directly bound to the light filler is not fed to the grinding step (step 1-0), if present.

In the present method, in the mixing step (1), if present, other additives besides at least one fatty acid (C), at least one product (D) containing zinc directly associated with light filler, and at least one compatibilizing agent (E), such as, for example, oils and waxes.

In the present process, the optional grinding step (step 1-0) can be carried out in a batch mixer or in a continuous mixer as described above, for a time period of, for example, 30 seconds to 2 minutes, at mixing temperatures typically from 70 to 155°C.

In the mixing step (1), at least one elastomeric polymer (A) and optionally at least one fatty acid (C) and/or at least one product (D) containing directly bonded zinc are mixed. with a light filler, and optionally, if both the fatty acid (C) and the product (D) containing zinc directly associated with the light filler are served at this stage, at least one compatibilizing agent (E), provided that that the compatibilizing agent (E), if present at this stage, is added after the supply and processing of the fatty acid (C) and the product (D) containing zinc directly associated with the light filler.

Preferably, at least one fatty acid (C), at least one product (D) containing zinc directly associated with a light filler, and at least one compatibilizing agent (E) are all served in stage (1 ), always in such a way that the compatibilizing agent (E) is added after the supply and processing of the fatty acid (C) and the product (D) containing zinc directly associated with the light filler.

The addition of at least one compatibilizing agent (E) may take place in one or more possible intermediate stages of the mixing stage (1), preferably not in the 1-0 grinding stage, or, on the other hand, in whole or in part, in the stage ( 2), always provided that the reaction between at least one fatty acid (C) and at least one product (D) containing zinc directly bound to the light filler is essentially complete before the addition of the compatibilizing agent ( e).

As a rule, the stage of processing at least one fatty acid (C) and at least one product (D) containing zinc directly associated with a light filler, during which a reaction between fatty acid and zinc occurs, continues, for at least 30 seconds or more at a mixing temperature preferably at least equal to, more preferably higher than, the melting point of the fatty acid, typically at a mixing temperature of at least 70°C. For example, processing may last for at least 90 seconds and at a mixing temperature of at least 100° C. before adding the compatibilizing agent (E). One skilled in the art can advantageously vary the processing time and temperature depending on, for example, the type of mixer, the mass being processed, the type of polymer, the type of fatty acid, and its melting point.

In step (1), the mixing is carried out at mixing temperatures typically between 70 and 160° C. and for a period of time typically from 2 to 20 minutes.

In the case of two or more intermediate steps, the person skilled in the art will be able to determine the optimal operating conditions for each of them, taking into account the type and intended use of the compound, the type of mixer, the components processed in each intermediate step, and the need to substantially end the reaction between the fatty acid (C) and product (D) containing zinc directly bound to the light filler before the subsequent addition of the compatibilizing agent (E).

As a guide, each intermediate step in step (1) typically lasts for a time in the range of 2 to 10 minutes, and is carried out at mixing temperatures in the range of 70 to 160°C.

In step (1) of the present process, the order in which the compounding components are added can always be changed, provided that any compatibilizing agent (E) is not added until the reaction between the fatty acid (C) and the product (D) containing zinc directly bound to light filler.

At the end of step (1), the elastomeric compound is fed into the same or a different mixer for the step of introducing vulcanizing agents (step 2).

Before starting step (2), it may be useful to carry out a step of unloading and/or resting the uncured elastomeric compound to ensure that any reactions are completed.

Preferably, the compound of step (1) is discharged before the start of step (2).

In the subsequent step (2), at least one curing agent (B) is added. Optionally, at least one vulcanization accelerating agent (F), at least one vulcanization retarding agent (G) can be added in step (2) and, if not already fully added in mixing step (1), at least , one fatty acid (C) and/or at least one zinc compound fixed on a light-colored filler (D), and after their addition and processing, at least one compatibilizing agent (E).

The mixing step (2) of the present process may include several intermediate processing steps, referred to as steps 2-0, 2-1, 2-2, etc., characterized by a short interruption of mixing to allow the addition of one or more ingredients, but without intermediate discharge compound.

In the process for producing elastomeric compounds according to the invention, if the compatibilizer (E) is supplied in more than one stage, the addition of at least one fatty acid (C) and at least one zinc-containing product (D) directly associated with a light filler, should occur in one or more stages preceding the first stage of supplying the compatibilizing agent (E).

In step (2) of the present method, the mixing temperature is usually maintained below 160°C, preferably at 140°C, more preferably at 120°C, in order to avoid the undesirable phenomenon of pre-crosslinking.

Typically, in step (2), the mixing can be carried out at mixing temperatures between 70 and 155° C. and for a period of 2 to 10 minutes.

At the end of step (2), the process in question includes the step of discharging the vulcanizable elastomeric compound, which will be destined for subsequent typical manufacturing steps in the production of tires and their components.

Other additives commonly used in the production of tire compounds may be added at one or more stages of the present process, which are selected based on the particular application for which the composition is intended. For example, the following components can be added: antioxidants, plasticizers, adhesives, antiozonants, modifying resins, or mixtures thereof.

In the present method, at least one diene elastomeric polymer (A) may be selected from polymers commonly used in sulfur curable elastomeric compositions that are particularly suitable for tire production, i.e., from among elastomeric polymers or unsaturated chain copolymers, having a glass transition temperature (T _article ) usually below 20°C, preferably in the range from 0 to -110°C.

Preferably, the diene elastomeric polymer has a weight average molecular weight (Mw) greater than 80,000 g/mol.

These polymers or copolymers may be of natural origin or may be obtained by solution polymerization, emulsion polymerization or gas phase polymerization of one or more conjugated diolefins, optionally mixed with at least one comonomer selected from monovinylarenes and/or polar comonomers, in an amount not exceeding 60% of the mass.

Conjugated diolefins generally contain 4 to 12, preferably 4 to 8 carbon atoms and may be selected, for example, from the group consisting of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3 -pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene and mixtures thereof.

Especially preferred are 1,3-butadiene and isoprene.

Monovinylarenes, which may optionally be used as comonomers, generally contain from 8 to 20, preferably from 8 to 12 carbon atoms and may be selected, for example, from styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, various alkyl, cycloalkyl, aryl , alkylaryl or arylalkyl derivatives of styrene, such as, for example, α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4- (4-phenylbutyl)styrene and mixtures thereof. Styrene is especially preferred.

Polar comonomers, which may optionally be used, may be selected, for example, from vinyl pyridine, vinyl quinoline, acrylic acid and alkyl-acrylic acid esters, nitriles or mixtures thereof, such as, for example, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.

Preferably, the diene elastomeric polymer (A) which can be used in the present invention may be selected from, for example, cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (in in particular polybutadiene with a high 1,4-cis content), optionally halogenated isoprene/isobutene copolymers, 1,3-butadiene/acrylonitrile copolymers, styrene/1,3-butadiene copolymers, styrene/isoprene/1,3-butadiene copolymers, styrene/ 1,3-butadiene/acrylonitrile copolymers and mixtures thereof.

The vulcanizable elastomeric compound described above may conceivably comprise an elastomeric polymer of one or more monoolefins with an olefin comonomer or derivatives thereof (A'). The mono-olefins may be selected from ethylene and α-olefins, typically having 3 to 12 carbon atoms, such as, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and mixtures thereof. The following are preferred: ethylene-α-olefin copolymers, optionally with a diene; isobutene homopolymers or copolymers thereof with small amounts of a diene, which are optionally at least partially halogenated. The potentially present diene typically contains 4 to 20 carbon atoms and is preferably selected from 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-methylidene-2-norbornene , vinylnorbornene and mixtures thereof. Of these, the following copolymers are particularly preferred: ethylene/propylene (EPR) copolymers or ethylene/propylene/diene (EPDM) copolymers; polyisobutene; butyl rubber; halogenated butyl rubbers, especially chlorobutyl or bromobutyl rubbers; or mixtures thereof.

Diene elastomeric polymer (A) or elastomeric polymer (A') functionalized by reaction with suitable chain terminators or coupling agents can also be used. In particular, diene elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator (especially an organolithium initiator) can be functionalized by reacting residual organometallic groups derived from the initiator with suitable chain terminators or coupling agents, such as, for example, imines, carbodiimides , alkyltin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

In the present method for obtaining a vulcanizable elastomeric compound, at least one elastomeric polymer (A) may contain one or more diene elastomeric polymers (A) as defined above in a mixture that can be successfully subjected to a grinding step (step 1-0) for better mixing.

In the present method, the amount of at least one elastomeric polymer (A) or a mixture of two or more elastomeric polymers (A) as defined above to be used is 100 parts by mass/100 parts by mass. rubber.

In the present process, the at least one curing agent (B) is preferably selected from sulfur or, on the other hand, sulfur-containing molecules (sulfur donors) such as, for example, caprolactam disulfide (CLD), bis(trialkoxysilyl)-propyl]polysulfides , dithiophosphates, phosphoryl polysulfide (SDT) and mixtures thereof.

Preferably, the vulcanizing agent (B) is sulfur, preferably selected from soluble sulfur (crystalline sulfur), insoluble sulfur (polymeric sulfur), oil-dispersed sulfur, and mixtures thereof.

Commercial examples of suitable vulcanizing agents (B) are 65% sulfur known under the trade name Rhenogran from Lanxess, 67% sulfur known under the trade name Crystex OT33 from Eastman, 95% sulfur known under the trade name name Solvay SchwefelKC, rhombic crystalline sulfur, known under the trade name Sulfur (1% oil and 0.3% silica) from the company Zolfindustria.

The curing agent (B) may be present in the curable elastomeric compound in a total amount of typically 0.1 to 15 parts by weight/100 parts by weight. rubber, preferably from 0.5 to 10 wt.h./100 wt.h. rubber, even more preferably from 1 to 7 wt.h./100 wt.h. rubber.

The elastomeric compound in question may contain, in a mixture, one or more of the curing agents (B) described above.

In the present method, the vulcanizing agent (B) is preferably used together with adjuvants such as vulcanization accelerators and/or retarders, which are known to the person skilled in the art.

In the present method, preferably the fatty acid (C) is selected from saturated or unsaturated fatty acids having from 8 to 26 carbon atoms, their esters, their salts and mixtures thereof.

Preferred fatty acids are lauric acid (C12), myristic acid (C14), palmitic acid (C16), stearic acid (C18), behenic acid (C22), lignoceric acid (C24).

Examples of fatty acid mixtures are C18/C16 (stearic acid and palmitic acid), C12/C14 (lauric acid and myristic acid), C22/C24 (behenic acid and lignoceric acid) mixture.

Preferably the fatty acid (C) is stearic acid or an ester or salt thereof, more preferably stearic acid.

In the present process for preparing a vulcanizable elastomeric compound, the total amount of fatty acid (C) is usually in the range between 0.05 and 20 mass/100 mass. rubber, preferably in the range between 0.1 and 15 wt.h./100 wt.h. rubber, more preferably in the range between 0.5 and 5 wt.h./100 wt.h. rubber.

Product (D) containing zinc directly bonded to the light-colored filler or activating filler (D) is preferably an inorganic compound containing a zinc product, preferably zinc oxide or zinc hydroxide, in which zinc is bonded directly to the surface of the light-colored filler.

The zinc present in product (D) is in the form of, for example, zinc oxide, zinc hydroxide, a divalent zinc salt such as zinc acetate or zinc silicate, or mixtures thereof, but not as zinc metal (Zn ⁰ ). Preferably the zinc is present in the form of zinc oxide.

Preferably, the product (D) containing zinc directly bonded to the light-colored filler contains zinc oxide fixed on silica.

Preferably, the zinc oxide fixed on the light-colored filler is zinc oxide in the form of medium particle sizes between 3 and 100 nm, preferably between 4 and 10 nm (nanoparticles).

Zinc oxide nanoparticles can be amorphous or crystalline, and with different morphologies, such as spherical, tetragonal, orthorhombic, monoclinic or triclinic. Preferably, the zinc oxide nanoparticles are amorphous.

The zinc content of the product (D) containing zinc directly bound to the light filler can generally be in the range of 0.5 to 50% by mass, preferably 1 to 25%, more preferably 7 to 14% by mass. relative to the total weight of the product (D).

The zinc content can be determined, for example, using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry, ICP-AE) analysis, as described in the experimental part.

The product (D) containing zinc directly bonded to the light filler preferably has a zinc oxide content of 1 to 65%, preferably 5 to 30%, more preferably 7 to 15% by mass. relative to the total weight of the product (D).

The light-colored filler to which the zinc is attached can be any conventional light-colored reinforcing filler that has hydroxyl groups on the surface.

The light filler is preferably selected from silica and silicates in the form of fibers, flakes or granules, such as bentonite, nontronite, beidellite, wolkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, palygorskite, also known as attapulgite, montmorillonite, alloisite and the like, optionally acid-treated and/or derivatized, and mixtures thereof, more preferably the filler is silica.

The silica on which the zinc compound is attached can vary in shape, specific surface area and size.

Examples of silica are pyrogenic silica, precipitated amorphous silica, wet silica (hydrated silicic acid), or mixtures thereof.

Examples of suitable industrial silicas are precipitated silica Rhodia Zeosil MP1165 (BET specific surface area 160 m ² /g), Ultrasil VN3 GR (BET specific surface area 180 m ² /g) and Zeosil 1115 MP (BET specific surface area 95-120 m ² /g).

Preferably the silica has a specific surface area (BET) of at least 120 m ² /g, more preferably at least 140 m ² /g.

Preferably the silica has a specific surface area (BET) of less than 220 m ² /g, more preferably less than or equal to 180 m ² /g.

FIG. 2 is a TEM image (TEM) taken from the Chemical Engineering Journal article 275 (2015) 245-252 of an activating excipient suitable for use in the present process, which contains zinc oxide nanoparticles supported on silica.

The product (D) containing zinc directly bound to the light-colored filler can be obtained and characterized according to known methods, for example, those described in Chem. Eng. 275 (2015), 245-252 or Solid State Phenom. 151 (2009) 264-268, or which are given in this experimental part.

In the present process for preparing a vulcanizable elastomer compound, the total amount of product (D) containing zinc directly bonded to a light-colored filler in the elastomer compound is between 1 and 100 parts by mass/100 parts by mass. rubber, preferably between 5 and 80 wt.h./100 wt.h. rubber, more preferably between 10 and 30 wt.h./100 wt.h. rubber.

In the present method, at least one compatibilizing agent (E) is added.

The term "compatibilizing agent (E)" generally means a compound capable of reacting with a reinforcing filler, in particular a light-colored filler such as silica, and bonding it to the diene elastomeric polymer during vulcanization.

In the present method, the compatibilizing agent (E) is usually a silane selected from silanes having at least one hydrolyzable group, which can be described, for example, by the following general formula (I):

(R) ₃ Si-C _n H _2n -X (I),

where the R groups, which may be the same or different, are selected from alkyl, alkoxy or aryloxy groups or from halogen atoms, provided that at least one of the R groups is an alkoxy or aryloxy group or a halogen atom ; n is an integer from 1 to 6 inclusive; X is a group selected from nitrogen, mercapto, amino, epoxy, vinyl, imide, chlorine, -(S) _m C _n H _2n -Si-(R) ₃ and -S-COR, where m and n are integers from 1 to 6 inclusive, and the R groups are as defined above.

Preferred compatibilizing agents (E) are bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) and bis(3-triethoxysilylpropyl)disulfide (TESPD).

A commercial example of a suitable compatibilizing agent (E) is TESPT or bis(3-triethoxysilylpropyl)tetrasulfide Si69 marketed by Evonik.

Preferably, the compatibilizing agent (E) is incorporated into the elastomeric compound in a total amount between 0.1 and 20 parts by mass/100 parts by mass. rubber, preferably between 0.5 and 10 wt.h./100 wt.h. rubber.

The elastomeric compound in question may contain in admixture one or more compatibilizing agents (E) as defined above.

In the present process, the vulcanization accelerator (F) is preferably selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates and mixtures thereof.

Preferably the accelerator (F) is selected from N-cyclohexyl-2-benzothiazolesulfenamide (CBS), N-tert-butyl-2-benzothiazolesulfenamide (TBBS) and mixtures thereof.

A commercial example of a suitable accelerator (F) is N-cyclohexyl-2-benzothiazolesulfenamide Vulkacit® (CBS or CZ) marketed by Lanxess.

The accelerator (F) may be present in the vulcanizable elastomer compound in a total amount typically between 0.05 and 10 wt/100 wt. rubber, preferably between 0.1 and 5 wt.h./100 wt.h. rubber.

The elastomeric compound in question may contain one or more accelerators (F) as defined above in the mixture.

In the present process, the vulcanization retardant (G) may be selected from, for example, urea, phthalic anhydride, N-nitroso-diphenylamine, N-cyclohexylthiophthalimide (CTP or PVI) and mixtures thereof.

A commercial example of a suitable moderator (G) is N-cyclohexylthiophthalimide VULKALENT G from Lanxess.

The retarder (G) may be present in the vulcanizable elastomer compound in an amount typically in the range between 0.05 and 2 parts by weight/100 parts by weight. rubber.

The elastomeric compound in question may contain in the mixture one or more retarders (G) as defined above.

Preferably, in the present process, one or more optional additives, such as, for example, at least one reinforcing filler (H), at least one antioxidant (I), at least one wax (L) and at least one plasticizer (M).

In the present method, a reinforcing filler is understood to mean a conventional filler in which there is no zinc compound attached to its surface.

In the present method, the reinforcing filler (H) is selected from carbon black, conventional silica such as sand silica precipitated with strong acids, preferably amorphous, hydrotalcite, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin , silicate fibers and mixtures thereof.

Preferably, the additional reinforcing filler (H) is selected from carbon black, conventional silica, silicate fibers and mixtures thereof, preferably silica.

The carbon black may be selected from standard tire grade carbon black or having a specific surface area of not less than 20 m ² /g, more preferably greater than 50 m ² /g (measured in accordance with ASTM D6556-16).

A commercial example of a suitable reinforcing filler (H) is Zeosil 1165MP silica from Solvay Rhodia.

Commercial examples of carbon black are N375 or N234 marketed by Birla Group (India) or Cabot Corporation.

The reinforcing filler (H) may be present in the vulcanizable elastomeric compound in an amount typically in the range between 0 and 120 wt/100 wt. rubber, preferably between 3 and 80 wt.h./100 wt.h. rubber.

In one embodiment, the reinforcing filler (H) may be absent, in which case the reinforcing function is performed by the product (D).

In some applications, the elastomeric compound obtained in accordance with the present method may contain at least 1 wt.h./100 wt.h. rubber, more preferably at least 2 mass/100 mass. rubber, more preferably at least 3 or 4 wt.h./100 wt.h. carbon black rubber, which successfully protects the elastomer from aging caused by ultraviolet radiation.

The elastomeric compound in question may contain one or more reinforcing fillers (H) as defined above in a mixture.

In the present method, phenylenediamine, diphenylamine, dihydroquinoline, phenol, benzimidazole, hydroquinone and their derivatives, possibly in mixture, can be used as antioxidant (I).

In the present method, the antioxidant (I) is preferably selected from N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N, N'-bis-(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N, N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine (DOPD), N, N'-bis( 1,4-dimethyl-pentyl)-p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine (DPPD), N, N'-ditolyl-p-phenylenediamine (DTPD), N, N'-di-beta- naphthyl-p-phenylenediamine (DNPD), N,N'-bis(1-methylpentyl)-p-phenylenediamine, N,N'-di-sec-butyl-p-phenylenediamine (44PD), N-phenyl-N-cyclohexyl -p-phenylenediamine, N-phenyl-N'-1-methylpentyl-p-phenylenediamine and the like, and mixtures thereof, preferably the antioxidant is N-(1,3-dimethylbutyl)-N'-phenyl-p- phenylenediamine (6PPD).

A commercial example of a suitable antioxidant (I) is 6PPD from Solutia/Eastman.

The antioxidant (I) may be present in the vulcanizable elastomeric compound in a total amount usually in the range of 0 and 20 wt/100 wt. rubber, preferably between 0.5 and 10 wt.h./100 wt.h. rubber.

In the present method, the wax (L) may be, for example, a petroleum wax or a mixture of paraffins.

Commercial examples of suitable waxes are Repsol N paraffin blend and Antilux® 654 microcrystalline wax from Rhein Chemie.

Wax (L) may be present in the vulcanizable elastomeric compound in a total amount usually in the range between 0 and 20 wt/100 wt. rubber, preferably between 0.5 and 5 wt.h./100 wt.h. rubber.

In the present process, to improve processability, the elastomeric compound may be mixed with at least one plasticizing agent (M), typically selected from mineral oils, vegetable oils, synthetic oils, low molecular weight polymers, and mixtures thereof, such as, for example, aromatic oil, naphthenic oil, phthalates, soybean oil and mixtures thereof. The amount of plasticizer usually lies in the range from 0 and 70 wt.h./100 wt.h. rubber, preferably from 5 to 30 wt.h./100 wt.h. rubber. Preferably, the plasticizing agent (M) is added during the 1-0 polymer milling step, if present.

As a non-limiting example, some embodiments of the considered method are presented below.

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A);

step 1-1: fatty acid (C);

stage 1-2: activating filler (D);

step 1-3: compatibilizing agent (E);

stage 2: vulcanizing agent (B).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A);

step 1-1: fatty acid (C);

stage 1-2: activating filler (D);

step 1-3: compatibilizing agent (E);

step 2: curing agent (B) and compatibilizing agent (E).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A) and fatty acid (C);

step 1-1: fatty acid (C) and activating excipient (D);

step 1-2: compatibilizing agent (E);

stage 2: vulcanizing agent (B).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A) and fatty acid (C);

step 1-1: activating filler (D);

step 1-2: compatibilizing agent (E);

stage 2: vulcanizing agent (B).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A);

stage 1-1: filler (H), fatty acid (C) and antioxidant (I);

stage 1-2: activating filler (D);

step 1-3: compatibilizing agent (E);

stage 2: vulcanizing agent (B) and accelerator (F).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A);

stage 1-1: filler (H), fatty acid (C) and antioxidant (I);

stage 1-2: activating filler (D);

step 1-3: compatibilizing agent (E);

stage 2: vulcanizing agent (B), accelerator (F) and compatibilizing agent (E).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A) and fatty acid (C);

stage 1-1: filler (H), fatty acid (C) and activating filler (D);

step 1-2: antioxidant (I), wax (L) and compatibilizing agent (E);

stage 2: vulcanizing agent (B), accelerator (F) and retarder (G).

In one embodiment of the present method, the order in which the compound components are added is as follows:

step 1-0: polymer (A) and fatty acid (C);

stage 1-1: filler (H) and activating filler (D);

step 1-2: antioxidant (I), wax (L) and compatibilizing agent (E);

stage 2: vulcanizing agent (B), accelerator (F) and retarder (G).

The second aspect of the present invention is a vulcanizable elastomeric compound obtained in accordance with the method described above.

Preferably, the vulcanizable elastomeric compound according to the invention contains zinc in an amount of less than 4 parts by weight/100 parts by weight. rubber, more preferably less than 3 wt.h./100 wt.h. rubber, even more preferably less than 2 wt.h./100 wt.h. rubber with the consequent environmental benefit of lower rubber release compared to traditional elastomer compounds.

Preferably, the vulcanized elastomeric compound according to the invention contains zinc in an amount of less than 4 parts by mass/100 parts by mass. rubber, more preferably less than 3 wt.h./100 wt.h. rubber, even more preferably less than 2 wt.h./100 wt.h. rubber.

In the elastomeric compound according to the invention, zinc is usually present in various forms, for example in ionic form such as Zn ²⁺ , covalently bound and/or complexed, but not in the form of metallic zinc (Zn ⁰ ).

The amount of zinc in the compound can be determined, for example, using X-ray fluorescence (XRF), as described in the experimental part.

The vulcanizable elastomeric compound in question may be incorporated into one or several tire components.

Due to the presence of at least one vulcanizing agent (B), the vulcanizable compound can be vulcanized according to known techniques.

By using the product (D) containing zinc directly bound to the light-colored filler as an activator and the delayed addition of the compatibilizing agent (E), according to the present method, a complete and homogeneous dispersion of zinc is obtained with undoubted advantages in the subsequent vulcanization reaction of the elastomeric compound, such as higher and more uniform crosslinking, no aggregates of unreacted zinc oxide, and properties of the vulcanized compound in terms of improved load and elongation at break.

This particular reactivity is confirmed by the increase in mono- and disulphide bridges in the vulcanized compound, as measured in this experimental part in example 6 (table 8), and the reduction in crosslinking time (see, for example, the T-MH values in tables 6, 10 or T90 in table 12) and is also reflected in the graph of the normalized curves of the torque values presented in FIG. 5 and 6.

Moreover, the experiments presented herein prove that the elastomeric tire compound produced according to the method of the invention is characterized, at the same zinc content, by a significant reduction in hot hysteresis (70 and 100°C), which makes it possible to predict a decrease in rolling resistance at useful for increasing tire mileage and/or increasing cold hysteresis (10 and 23°C) which is associated with better tire performance on wet surfaces.

With the present process, it is possible to reduce the amount of zinc added to the compounds, with important environmental benefits, without compromising or even improving their performance compared to comparable conventional compounds.

According to a third aspect of the invention, the subject elastomeric compound is applicable to tire components such as tread band, liner, anti-abrasion elongate, sidewall, sidewall insert, mini-sidewall, liner, rubber plies, filler cord and bead wing web, more preferably in the tread band. , interlayer and sidewall.

Preferably, the tire component according to the invention consists of the vulcanizable compound according to the invention (green component) or the vulcanized compound obtained by vulcanizing it (vulcanized component).

A fourth aspect of the present invention is a tire for vehicle wheels comprising at least one of the components identified above.

Preferably, a tire for vehicle wheels according to the invention comprises at least one tire component which consists of a vulcanizable elastomeric compound (green component) according to the second aspect of the invention or a vulcanized elastomeric compound obtained by vulcanization thereof.

In one embodiment, a tire for vehicle wheels according to the present invention comprises at least

a carcass structure comprising at least a carcass ply having opposite side edges associated with a respective bead structure;

- possibly a pair of sidewalls superimposed on the side surfaces of the frame structure, respectively, in an axially outward position;

possibly a belt structure superimposed in a radially outward position relative to the frame structure;

- a tread band applied in a radially outward position to said carcass structure or, if present, a belt structure,

possibly a layer of elastomeric material, called interlayer, applied in a radially inward position relative to said tread band,

wherein at least one component selected from said pair of sidewalls, said interlayer and said tread band comprises or preferably consists of an elastomeric compound according to the invention.

An embodiment in accordance with the present invention relates to a tire for high performance vehicles (HP, SUV and UHP) in which at least one component, preferably selected from the ply, sidewalls and tread band, contains an elastomeric compound or preferably consists of an elastomeric compound in accordance with the invention.

An embodiment in accordance with the present invention relates to a tire for heavy vehicles, in which at least one component, preferably selected from the ply, sidewall and tread band, contains or preferably consists of an elastomeric compound in accordance with the invention.

The tire according to the invention may be a tire for two or four wheeled vehicles.

In one embodiment, the tire according to the invention is a bicycle tire.

A bicycle tire typically comprises a carcass structure wrapped around a pair of tire bead cores on the beads and a tread band placed at a radially outward position relative to the carcass structure.

The frame structure is designed to withstand inflation pressure and support the weight of the bike and rider. It includes one or more carcass plies, each containing a plurality of suitably oriented reinforcing cords. In the case of several carcass layers, they are inclined relative to each other to form a closed structure.

The tire bead cores ensure that the tire is securely attached to the wheel rim.

In the radially inward position of the frame structure, an air chamber may be provided into which compressed air is introduced.

The tire according to the invention may be intended for use in summer or winter or all seasons.

A tire according to the present invention may be produced by a process which includes:

- assembly of raw tire components on at least one molding drum;

- shaping, molding and vulcanization of the tire;

where the assembly of at least one of the components of the green tire includes:

- production of at least one raw component containing or preferably consisting of a vulcanizable elastomeric compound according to the invention.

Description of drawings

FIG. 1 shows a radial half-section of a tire for vehicle wheels containing at least one component formed by an elastomeric compound obtained in accordance with the method of the invention.

FIG. 1 shows a radial half-section of a tire for vehicle wheels according to the invention.

FIG. 1 "a" indicates the axial direction and "X" indicates the radial direction, in particular X-X defines the equatorial plane. For simplicity, FIG. 1 shows only part of the tire, the rest, which is not shown, is identical and is located symmetrically with respect to the equatorial plane "X-X".

The tire 100 for four-wheeled vehicles comprises at least one carcass structure including at least one carcass ply 101 having respectively opposite end rim bands engaged with respective annular fastening structures 102, called bead cores, optionally connected with side filler cord 104.

The carcass layer 101 is optionally made with an elastomeric compound.

The region of the tire containing the bead core 102 and filler cord 104 forms a bead structure 103 for attaching the tire to a corresponding mounting rim, which is not shown.

The carcass structure is typically of the radial type, that is, the reinforcing elements of at least one carcass ply 101 lie on planes including the axis of rotation of the tire and substantially perpendicular to the equatorial plane of the tire. These reinforcing elements usually consist of textile cords such as viscose, nylon, polyester (for example, polyethylene naphthalate, PEN (PEN)). Each bead structure is connected to the carcass structure by wrapping opposite side edges of at least one carcass ply 101 around an annular fastening structure 102 in such a way that so-called carcass rim bands 101a are formed, as shown in FIG. one.

In one embodiment, the connection between the carcass structure and the bead structure can be provided with a second carcass ply (not shown in FIG. 1) superimposed at an axially outward position relative to the first carcass ply.

An anti-abrasive tape 105, optionally made of an elastomeric compound, is located at the outer position of each bead structure 103.

The carcass structure is associated with a belt structure 106 comprising one or more belt layers 106a, 106b located in a radial superimposition with respect to each other and relative to the carcass layer, having, as a rule, textile and/or metal reinforcing cords embedded inside the layer of vulcanized elastomeric compound .

Such reinforcing cords may have a cross orientation with respect to the direction of circumferential development of the tire 100. By "circumferential" is meant a direction generally facing the direction of rotation of the tire.

At least one zero angle reinforcement ply 106c, commonly known as a "0° breaker", may be applied at a radially extreme position to the breaker plies 106a, 106b, which typically includes a plurality of elongated reinforcements, typically metal or textile cords. , oriented in a substantially circumferential direction, resulting in an angle of several degrees (eg, an angle between approximately 0° and 6°) relative to a direction parallel to the equatorial plane of the tire, and coated with a vulcanized elastomeric compound.

The vulcanized elastomer compound tread band 109 is applied at a position radially outward from the belt structure 106.

Moreover, respective sidewalls 108 of vulcanized elastomer compound are applied in an axially outward position to the side surfaces of the carcass structure, each projecting from one of the side edges of the tread 109 at the respective bead structure 103.

In the radially outward position, the tread band 109 has a rolling surface 109a designed to contact the ground. Annular grooves, which are connected by transverse recesses (not shown in FIG. 1) so that they define a plurality of blocks of different shapes and sizes distributed over the entire rolling surface 109a, are usually made on this surface 109a, which for simplicity is represented by smooth in FIG. one.

A layer 111 of vulcanized elastomeric compound may be placed between the belt structure 106 and the tread band 109.

A strip 110 consisting of an elastomeric compound, commonly known as a "mini-sidewall", of vulcanized elastomeric compound may optionally be provided in the bonding area between the sidewalls 108 and the tread band 109, and this mini-sidewall is typically produced by co-extrusion with the tread band 109 and provides improved mechanical performance. interaction between the tread band 109 and the sidewalls 108. Preferably, the end portion of the sidewall 108 directly covers the side edge of the tread band 109.

In the case of tubeless tyres, the rubber layer 112, commonly known as the "seal layer", which provides the necessary impermeability to the tire's inflation air, may also be provided at a radially inward position relative to the carcass layer 101.

The rigidity of the tire sidewall 108 can be improved by providing a bead structure 103 with a reinforcement layer 120 commonly known as a "flipper" or additional strip insert.

The flipper 120 is a reinforcing layer that is wound around the respective bead core 102 and the bead filling cord 104 in such a way that it at least partially surrounds them, said reinforcing layer being located between at least one carcass ply 101 and the bead structure. 103. Typically, the flipper is in contact with said at least one carcass ply 101 and said bead structure 103.

Flipper 120 typically contains a plurality of textile cords embedded in a layer of vulcanized elastomeric compound.

The tire bead structure 103 may include an additional protective layer, which is commonly known as "bead tape" 121 or protective strip, and which has the function of increasing the rigidity and integrity of the bead structure 103.

The bead tape 121 typically comprises a plurality of cords embedded in a rubber layer of vulcanized elastomer compound. Such cords are usually made of textile materials (eg aramid or viscose) or metallic materials (eg steel cords).

A layer or sheet of elastomeric compound may be placed between the belt structure and the carcass structure. The layer may have a uniform thickness. On the other hand, the layer may have a variable thickness. For example, the layer may have a greater thickness closer to the axially outer edge relative to the central zone (crown).

Preferably, the layer or sheet may extend over a surface substantially corresponding to the raised surface of said belt structure.

In a preferred embodiment, a layer of elastomeric compound as described above, referred to as an interlayer, may be placed between said belt structure and said tread band, said interlayer preferably extending over a surface substantially corresponding to the raised surface of said belt structure.

The elastomeric compound of the present invention may preferably be incorporated into one or more tire components selected from belt structure, carcass structure, tread band, ply, sidewall, mini-sidewall, sidewall insert, bead, flipper, bead tape, sheet, and anti-abrasion tape, preferably inserted at least in the sidewalls and/or in the interlayer.

According to an embodiment not shown, the tire may be a motorcycle tire, which is typically a tire having a straight portion characterized by a high tread curve.

According to an embodiment not shown, the tire may be a bicycle tire.

In accordance with an embodiment not shown, the tire may be a tire for wheels of heavy vehicles such as trucks, buses, trailers, vans, and in general for vehicles in which the tire is subjected to a high load. Preferably, such a tire is adapted to be mounted on rims having a diameter equal to or greater than 17.5 inches (44.5 cm) for steering or trailer wheels.

FIG. 2 is a high resolution electron microscope image of the ZnO/SiO ₂ (D) activating filler (HRTEM) showing that the zinc oxide particles are attached to the silica surface.

FIG. 3 shows schematically a possible structure of the complex that forms between stearic acid and ZnO nanoparticles anchored on SiO ₂ , where Y is a counterion such as an OH group or an acetate.

FIG. 4 is a spectroscopic image in attenuated total internal reflection Fourier transform IR (ATR-FTIR) showing the formation of the complex shown in FIG. 2, the reaction between stearic acid and ZnO nanoparticles anchored on SiO ₂ (plot a) compared to a standard system of ZnO and stearic acid (plot b) that were heated at 120° C. for 5 min in a simplified vulcanization model. This model uses low molecular weight molecules that mimic a reactive polymer, such as 2,3-dimethyl-2-butene, used in modeling isoprene rubbers.

FIG. 5 shows a normalized curve of torque values [(S _x -S _min )/(S _max -S _min )×100] measured over time (min) during vulcanization of a vulcanizable compound according to the invention and a comparative compound (examples 7.2 and 7.1).

FIG. 6 shows a normalized curve of torque values [(S _x -S _min )/(S _max -S _min )×100] measured over time (min) during vulcanization of two comparative vulcanizable compounds (Examples 8.1 and 8.2) and a compound in according to the invention (example 8.3).

Below is a description of some preliminary examples in accordance with the invention and comparative examples, which are given only to illustrate and not to limit the scope of the invention.

experimental part

Analysis Methods

ATR-FTIR (Fourier Transform Attenuated Total Reflectance IR) analysis was performed using a Perkin Elmer Spectrum 100 instrument (4 cm ⁻¹ resolution spectra, 650 to 400 cm ⁻¹ region, 32 scans) (see FIG. . four).

High resolution transmission electron microscopy (HRTEM) was performed using a 300 KV Jeol 3010 high resolution polar pole microscope (0.17 nm point-to-point resolution) and equipped with a Gatan CCD 792 slow scan camera. isopropanol and a drop of 5 μl of this suspension is applied to a perforated carbon film supported on a 3 mm copper grid for TEM analysis (see FIG. 2)

Determination of the zinc content in the activating filler (D)

The content of zinc oxide fixed on a light-colored filler (D) can be determined using ICP-AE spectroscopy (ICP-AES) (Inductively Coupled Plasma Atomic Emission Spectrometry) with a simultaneous plasma IRS spectrometer (model TJA IRIS II; source excitation: RF generator with a frequency of 27.12 MHz and variable output power up to 1750 W).

Determination of the content of zinc in the compound using X-ray fluorescence (XRF)

X-ray fluorescence analysis is based on the radiation effect created by a primary x-ray beam of high intensity and corresponding energy incident on a sample.

The sample is prepared by passing approximately 2 g of the vulcanized compound between the cylinders of a cold laboratory mixer until a uniform and compact sheet is obtained between 0.5 and 0.7 mm thick.

Then, a round test piece with a diameter of approximately 4 cm is cut from the sheet and inserted into the sample holder of the instrument (Wavelength Dispersion X-ray Fluorescence Spectrometer Model ARL-XRF 8420+).

Rheometric MDR analysis (according to ISO 6502)

An Alpha Technologies type MDR2000 rheometer was used. The test is carried out at 170°C for 20 min at an oscillation frequency of 1.66 Hz (100 oscillations per minute) and at an oscillation amplitude of ±0.5°, measuring the time required to achieve an increase of two rheometric units (TS2), and the time required to achieve 30% (T30), 60% (T60), 90% (T90) and 100% (T-MH), respectively, of the maximum torque (MH). The maximum torque value MH and the minimum torque value ML are measured and their difference (MH-ML) is calculated.

Properties of vulcanized materials

The elastomeric materials prepared in the previous examples are vulcanized to obtain test specimens on which analytical studies and evaluation of static and dynamic mechanical properties are carried out.

Unless otherwise stated, vulcanization is carried out in a mold, in a hydraulic press at 170° C. and 200 bar pressure for approximately 10 minutes.

Hardness in units of IRHD (23°C) (the degree of hardness of rubber on the international scale) is measured in accordance with ISO 48:2007 on samples of elastomeric materials vulcanized under the conditions presented in the experimental part.

Determination of the total degree of cross-linking and mono- and disulfide bonds (% wt.)

The measurement of the total number of bonds or the degree of overall crosslinking (total number of bonds expressed as moles per gram of compound, mol/g) is carried out using the effect of swelling of toluene on the compound. A highly crosslinked compound will have a lower tendency to absorb solvent than a compound that is less crosslinked. In accordance with this principle, an inverse relationship has been established between the amount of absorbed solvent and crosslinking. The amount of absorbed solvent is determined gravimetrically by calculating the difference in mass between a sample swollen in equilibrium with the solvent and the same sample after complete removal of the absorbed solvent by vacuum drying.

The toluene swelling technique is also used to quantify mono- and disulfide bonds, but is preceded by treatment with suitable reagents capable of selectively separating polysulfide bonds. A mixture of piperidine and propane-2-thiol is used to cleave all polysulfide bonds (containing 3 or more sulfur atoms). Therefore, during subsequent swelling, only the contribution of the remaining mono- and di-sulfur bonds is measured.

The measurement of the total number of bonds and the determination of mono- and disulfide bonds are carried out in parallel on two different portions of the same sample in two different reaction containers in accordance with the following procedure.

A 10×10×1 mm sample of the vulcanized compound (0.10±0.05 g) is immersed in toluene at 25°C in a laboratory flask and kept in the dark for seven days. The toluene is replaced with fresh toluene after three days. On the seventh day, the bulk of the swollen solid is weighed, then dried under vacuum at 70° C. for 12 hours and reweighed.

The volume fraction of swollen rubber is calculated using the equation:

,

,

where m ₀ is the mass of the compound before swelling; m _sw means the mass of the swollen compound; m _d is the weight of the compound dried after swelling; m _so is the mass of solvent within the swollen mass, given as m _sw -m _d ; ρ _p =0.94 g/cm ³ means the density of the polymer; ρs=0.87 g/cm ³ means the density of toluene; f means the fraction of the filler, determined by TGA (TGA). Crosslink density (ν), that is, the number of linked chains per gram on two different polymer chains, is estimated according to the Flory-Rehner equation [Thermodynamics of high polymer solutions, J. Chem. Phys. 10 (1942) 51-61].

,

,

where Vs=105.91 is the molar volume of toluene and χ is the Flory parameter of the solvent-polymer interaction, which is 0.43 for the toluene-(isoprene rubber) (IR) system.

Static mechanical properties are measured at 23°C in accordance with ISO 37:2005.

Specifically, on the samples of elastomeric materials mentioned above, the load at 100% elongation referred to as CA1, the load at break CR and the elongation at break AR% are measured.

Tensile tests are carried out on straight dumbbell-type specimens (ISO37-2011, T=23°C) or ring specimens (ISO37-2011, T=23°C).

Dynamic mechanical properties are measured according to the following methods.

Dynamic moduli E (tension/compression): measured using an Instron dynamic device in compression-tension mode using the following procedure.

A sample of the investigated vulcanized elastomeric compounds, having a cylindrical shape (length 25 mm, diameter 18 mm), subjected to compression before loading up to 25% longitudinal deformation relative to the initial length and maintained at a given temperature (equal to +23°C or 70°C) in during the entire duration of the test, is subjected to a dynamic sinusoidal deformation having an amplitude of ± 3,5% relative to the length under preload, with a frequency of 100 Hz. Dynamic elastic properties are expressed in terms of dynamic tensile/compressive modulus of elasticity (E'), viscous modulus (E") and Tan delta (loss tangent E"/E').

The Tan delta value is calculated as the ratio between the dynamic modulus of viscosity (E") and the dynamic modulus of elasticity (E'), which are both determined using the dynamic measurements described above.

Dynamic modulus G (at shear) : measured using a Monsanto RPA 2000 rheometer by the following method. Cylindrical test specimens weighing between 4.5 and 5.5 g are prepared by stamping specimens of the curable elastomer composition and curing them in an RPA machine (at 170° C. for 10 minutes). On the vulcanized samples, the dynamic shear modulus (G') is measured at 70° C., 10 Hz, 0.1% and 10% strain.

Dynamic elastic properties are expressed in terms of shear modulus (G'), viscosity (G") and Tan delta (loss angle E"/E').

Example 1

Preparation of activating fillers (ZnO/SiO ₂ ) in accordance with the prior art

ZnO/SiO ₂ activating fillers are prepared following the procedure described in Chemical Engineering Journal 275 (2015) 245-252.

Powdered silica (0.426 mol, precipitated silica Rhodia Zeosil MP1165, BET specific surface area 160 m ² /g) was dispersed in 0.90 L of anhydrous ethanol by sonication for 10 min (1 sec pulses; 20 kHz). Zn(CH ₃ COO) ₂ is then added to the silica slurry with stirring at 65°C ^. 2H ₂ O (amount in table 1) and NaOH (0.10 mol).

Table 1

Sample Zn acetate, 2H ₂ O (mol) ZnO content (wt. %) 1A 0.205 14.2 1B 0.081 7.7 0.015 4.0

ZnO nanoparticles formed as a result of hydrolysis condense on the surface of silicon dioxide, forming samples with different amounts of zinc. After 20 min, particles of solid ZnO/SiO2 are filtered off, then washed four times with ethanol and dried in air at room temperature.

Example 2

Preparation of vulcanization-activating fillers (ZnO/SiO ₂ )

In a 3-liter flask, 1.2 liters of ethanol, 4.7 g of NaOH and 8.9 g of zinc acetate dihydrate are added with stirring until complete dissolution. The solution thus obtained is heated to 65° C. until it becomes milky due to the possible formation of a zinc compound of the [Zn(OH)n] ⁿ⁺ type. Then, 17.06 g of silica (Rhodia Zeosil MP1165, BET specific surface area 160 m ² /g) was added, maintaining the temperature at 65° C., for 20 minutes with stirring. The suspension is then filtered through a filter, the solid is washed with 200 ml of ethanol three times and finally the product is dried in air at room temperature.

Get 19.4 g of a solid substance containing nanoparticles of silicon dioxide, loading ZnO approximately 12.3% of the mass.

Example 3

Preparation of vulcanization-activating fillers (ZnO/Sepiolite)

Dissolve 1 g of sepiolite in 50 ml of 0.01 M NaOH and leave under stirring at room temperature for 24 hours. The dispersion is centrifuged at 9000 rpm for 30 minutes. The precipitate is dispersed several times in deionized water to ensure optimal washing, and again recovered by centrifugation until pH neutral. The solid is dried by lyophilization. To another flask, add 140 ml of ethanol and 0.56 g of NaOH (conc. 0.1 M NaOH) and stir at 65°C for 10 minutes. After dissolution, add soda, zinc acetate dihydrate (0.39 g) and leave under stirring until the solution becomes cloudy. Finally, 1 g of the previously treated sepiolite is added and left under stirring for 20 minutes.

The product is filtered off on a Buchner funnel, washed 3 times with fresh ethanol and dried in an oven overnight at 80°C.

Description of vulcanization-activating fillers (D)

On samples of activating fillers obtained in example 2, conduct the following studies.

table 2

Analytical method Result Property X-ray diffraction
(XRD) No signal Amorphous state of ZnO Absorption UV visible area
(UV Vis) 3.29-3.47 eV Absorption energy of ZnO particles
(micro versus nano) Total attenuated internal reflection (ATR-FTIR) 963-965 cm ^-1 No signal related to silanols
(Si-OH) Mass spectroscopy with inductively coupled plasma
(ICP) 9-13% wt. Amount of ZnO fixed on silicon dioxide

Example 4

Preparation of elastomeric compounds based on isoprene for interlayer

In this example, a comparison is made between a conventional interlayer compound containing a traditional filler (silica) and an activating agent (microcrystalline ZnO) (comparative example 4.1), a compound containing an activating filler (ZnO/SiO ₂ ), but prepared according to a standard method with the simultaneous addition of silane (comparative example 4.2), a compound containing an activating filler (ZnO/SiO2) obtained by adding silane together with the indicated filler and only after stearic acid (comparative example 4.3, as described in Chem. Eng, 2015, 245 , p. 247, par. 2.4), and a compound according to the invention (example 4.4), in which the silane is added at the last stage, when the stearic acid has completely reacted with the zinc of the activating filler.

The elastomeric compounds of examples 4.1-4.4 below are prepared in accordance with the methods described here. The amounts of the various components are given in parts by weight/100 parts by weight. rubber and are shown in table 3.

Table 3

Stage Ingredients Ref. pr. 4.1 Ref. pr. 4.2 Ref. pr. 4.3 Appl. Ex 4.4 ZnO content 1-0 IR 100 100 100 100 1-1 Silica 40 26.9 26.9 26.9 1-1 Stearic acid 2 2 - 2 1-1 6PPD 2 2 2 2 1-1 Silane - - 3.2 - 1-1 ZnO/SiO ₂ Ex. 2 (12.3%) - - 14.9 - 1.84 1-2 ZnO/SiO ₂ Ex. 2 (12.3%) - 14.9 - 14.9 1.84 1-2 Stearic acid - - 2 - 1-2 ZnO (80%) 2.3 - - - 1.84 1-2 Silane - 3.2 - - 1-3 Silane 3.2 - - 3.2 2-0 CBS 1.6 1.6 1.6 1.6 2-0 Sulfur (67%) 3 3 3 3

In the table:

IR: Synthetic polyisoprene with a high cis content (min. 96%) obtained by solution polymerization with a Ziegler-Natta catalyst. Supplier NIZHNEKAMSKNEFTECHIM EXPORT;

Silica: ZEOSIL 1115 MP (BET specific surface area 95-120 m ² /g, white microbeads obtained by precipitation from sodium silicate solutions with sulfuric acid. Does not contain crystalline silica. Supplied by SOLVAY RHODIA OPERATIONS;

Stearic acid: Supplier TEMIX OLEO SRL;

6PPD: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine. Supplier: SOLUTIA/EASTMAN;

ZnO (80): 80% zinc oxide, 20% polymeric binder and dispersing agent. Supplier LANXESS ADD;

Silane: TESPD, bis(3-triethoxysilylpropyl)disulfide. Supplier JINGZHOU JIANGHAN FINE CHEM;

CBS: N-cyclohexyl-2-benzothiazylsulfenamide, cyclohexylamine content <1%. Supplier DUSLO;

Sulfur: Crystex OT33, amorphous sulfur, insoluble in CS ₂ and toluene. Treated with 33% hydrotreated heavy naphthenic distillate (petroleum). EASTMAN Supplier.

Mixing is carried out in several stages using an internal laboratory mixer Thermo Haake Reomix with a tangential rotor (mixing chamber 250 ml).

In the first step (1-0), elastomeric polymers are added and triturated for 30 seconds at 60°C (set temperature).

In the next step (1.1) the traditional filler, the antioxidant and possibly the stearic acid, the activating filler, the silane, are added.

Stirring is continued for 2 min until reaching 120±5°C.

After 12-24 hours, in the next step (1.2) carried out using the same mixer, ZnO (comparative example 4.1) or an activating filler ZnO/SiO ₂ (comparative example 4.2, comparative example 4.3 and claimed example 4.4) are introduced, for a comparative example 4.2 silane and for comparative example 4.3 stearic acid. Stirring is continued for approximately 2 minutes until the reaction between stearic acid and zinc is completed, reaching 125±5°C. In the next step 1.3, in the case of some examples, silane is added and mixing is extended for another 2-3 minutes, after which the compounds are discharged.

After 12-24 hours, in step (2) carried out in the same mixer, the vulcanizing agent (sulphur) and accelerator are added and mixing is continued for about 2 minutes until 95±5°C is reached when the compounds are discharged.

The elastomeric compounds 4.1-4.4 prepared above are evaluated for their vulcanization behavior (170° C., 10 min) and then for static and dynamic mechanical properties according to the methods described here. The results of these tests, recalculated as per 100 values obtained with Comparative Example 4.1, are summarized in Table 4.

Table 4

Measured parameter Units Ref. pr. 4.1 Ref. pr. 4.2 Ref. pr. 4.3 Appl. Ex 4.4 When vulcanized MH dnm 100 93 (-7%) 93 (-7%) 97 (-3%) MH-ML dnm 100 84 (-16%) 102(+2%) 99 (-1%) T-MH min 100 65 (-35%) 77(-23%) 100.6(+0.6%) After vulcanization Tan D at 70°C, 10 Hz, 9% - 100 69 (-31%) 113(+13%) 54 (-46%) G' at 70°C, 10 Hz, 9% kPa 100 88 (-12%) 95(-5%) 86 (-14%) G'' at 70°C, 10 Hz, 9% kPa 100 61 (-39%) 107(+7%) 47(-53%) CR MPa 100 n.a. 82(-18%) 110 (+10%) CA1 MPa 100 n.a. 65(-35%) 107 (+7%)

In the table:

MH (maximum torque): torque measured when the stitching can be considered finished;

MH-ML: difference between maximum torque MH and minimum torque ML;

T-MH: time required to achieve complete crosslinking of the sample;

Tan D (hysteresis) is calculated as the modulus ratio G”/G’ (strain 9% at 70°C);

G' (9%): shear modulus measured at 70°C with a strain amplitude of 9%;

G” (9%): shear modulus measured at 70°C with a strain amplitude of 9%;

CR: indicates stress at elongation at break (MPa);

CA1: indicates the stress measured at 100% strain (MPa);

n.d.: no data.

From the values of MH, CR and CA1 presented in the table, it can be seen that the activating filler ZnO/SiO ₂ guarantees at least the same mechanical and kinetic characteristics of the vulcanization of a system of standard microcrystalline ZnO with the same amount of Zn and filler (claimed example 4.4 with respect to comparative example 4.1).

In addition, by modifying the order of addition of the ingredients of the present method, i.e., with the early addition of stearic acid in step 1.1 and especially the delayed introduction of silane in step 1.3, it is noted that the vulcanized compound of the claimed example (4.4) shows a significant decrease in tan D and viscosity modulus at shear (G”) at 70°C (10 Hz and 9%) by 46% and 53%, respectively. Such properties suggest a reduction in rolling resistance during operation, resulting in increased tire mileage and therefore greater environmental sustainability.

When, on the other hand, silane is added simultaneously with ZnO/SiO ₂ in step 1.2 as a mixture in comparative example 4.2, the reduction in tan D and modulus G” at 70°C is only 31% and 39%.

Comparative example 4.3 shows the negative effect of adding ZnO/SiO ₂ together with silane, especially on the G” values at 70°C, where a 7% increase can be seen compared to a significant decrease (-53%) for the sample according to the invention (4.4).

Example 5

Preparation of elastomeric compounds based on synthetic isoprene and polybutadiene for tire sidewalls

In this example, for the same method according to the invention, the effect of introducing a Zn/SiO ₂ filler relative to traditional ZnO on the vulcanization parameters and on the mechanical properties of a compound based on synthetic isoprene (40%) and polybutadiene with a high cis content (60%) was evaluated. .

The elastomeric compounds of examples 5.1 and 5.2 are prepared in accordance with the methods described in the invention. The amounts of the various components are given in parts by weight/100 parts by weight. rubber and are presented in the following table 5.

Table 5

Stage Ingredients Comparative example 5.1 Claimed Example 5.2 ZnO content 1-0 IR 40 40 1-0 BR 60 60 1-1 Silica 40 26.9 1-1 Stearic acid 2 2 1-1 6PPD 2 2 1-2 ZnO/SiO ₂ Ex. 2 (12.3%) -- 14.9 1.84 1-2 ZnO(80) 2.3 -- 1.84 1-3 Silane 3.2 3.2 2-0 CBS 1.6 1.6 2-0 Sulfur (67%) 3 3

In the table:

BR: high cis butadiene (97.5%) polymerized with neodymium. Supplier ARLANXEO; and

the other ingredients are the same as in the previous example 4.

Mixing is carried out in several steps as described in example 4 by adding the ingredients in the quantities, steps and in the order indicated in table 5, in particular by adding stearic acid (1.1) before and silane (1.3) later.

The resulting elastomeric compounds 5.1 and 5.2 are evaluated for their vulcanization behavior (170° C., 10 min) and then for static and dynamic mechanical properties in accordance with the methods described in the invention. The results, recalculated to 100 values obtained with Comparative Example 5.1, are summarized in the following Table 6.

Table 6

Measured parameter Units Comparative example 5.1 Claimed Example 5.2 When vulcanized ML 100 84.6 (-15.4%) MH dnm 100 110.7 (+10.7%) MH-ML dnm 100 116.5 (+16.5%) T-MH min 100 87.8 (-12.2%) After vulcanization Tan D at 70°C, 10 Hz, 9% - 100 79 (-21%) G' at 70°C, 10 Hz, 9% kPa 100 95 (-5%) G'' at 70°C, 10 Hz, 9% kPa 100 75 (-25%) DG' at 70°C, 10 Hz, 9% and 3% kPa 100 94 (-6%)

In the table:

DG' at 70°C, 10 Hz, 9% and 3% means the difference in shear modulus measured at 70°C with a strain amplitude of 9% or 3% respectively (predicting rolling resistance), and the other parameters have the meanings discussed above.

From the values of MH, G' and DG' presented in table 6, it can be noted that with the same production method and with the same elastomeric polymers, the ZnO/SiO ₂ activating filler provides good mechanical properties and a significant reduction in hot tan Delta, which makes it possible to predict a decrease in rolling resistance tire during operation.

In the method according to the invention (claimed example 5.2), a significant reduction in the T-MH crosslinking time was also noted.

Example 6

Preparation of elastomeric compounds based on synthetic isoprene and polybutadiene for tire sidewalls

In this example, for the same method according to the invention, the effect of introducing a Zn/SiO ₂ filler relative to traditional ZnO on the vulcanization parameters and on the mechanical properties of a compound based on synthetic isoprene (40%) and polybutadiene with a high cis content (60%) was evaluated. in the presence of a vulcanization system different from the previous system.

The elastomeric compounds of examples 6.1 and 6.2 were prepared according to the methods described in the invention. The amounts of the various components are given in parts by weight/100 parts by weight. rubber and are presented in the following table 7.

Table 7

Stage Ingredients Comparative example 6.1 Claimed Example 6.2 ZnO content 1-0 IR 40 40 1-0 BR 60 60 1-1 Carbon black CB 17 17 1-1 Wax one one 1-1 Silica twenty 6.88 1-1 Stearic acid 2 2 1-1 6PPD 1.5 1.5 1-2 ZnO/SiO ₂ Ex. 2 (12.3%) -- 14.95 1.84 1-2 ZnO(80) 2.3 -- 1.84 1-3 Silane one one 2-0 TBBS 1.87 1.87 2-0 Sulfur (67%) 2 2 2-0 50% TESPT on CB 330 2.4 2.4

In the table:

Carbon black CB: produced by kiln process. ORION ENGINEERED CARBONS supplier;

Wax: mixture of normal and iso-paraffins with bimodal distribution (may contain at most 1% polyethylene (PE)). REPSOL LUBRICANTES Y ESPECIAL supplier;

TBBS: N-tert-butyl-2-benzothiazylsulfenamide. Supplier LANXESS; and

the other ingredients are the same as in the previous examples.

Mixing is carried out in several steps as described in example 4 by adding the ingredients in the quantities, steps and in the order shown in table 7, in particular by adding stearic acid (step 1.1) before and silane (step 1.3) later.

The resulting elastomeric compounds 6.1 and 6.2 are evaluated in terms of the type of crosslinking after vulcanization (170°C, 10 min) and then in terms of static and dynamic mechanical properties in accordance with the methods described in the invention. The results, recalculated to 100 values obtained with Comparative Example 6.1, are summarized in the following Table 8.

Table 8

Measured parameter Units Comparative example 6.1 Claimed Example 6.2 When vulcanized MH dnm 100 94.8 (-5.2%) MH-ML dnm 100 98.3 (-1.7%) After vulcanization Mono- and disulfides % w/w 100 111 (+11%) Tan D at 70°C, 10 Hz, 9% - 100 91 (-9%) G' at 70°C, 10 Hz, 9% kPa 100 97 (-3%) DG' at 70°C, 10 Hz, 9% and 3% kPa 100 75 (-25%)

It can be seen from the values presented in Table 8 that, with all variables being equal, including the curing system, the ZnO/SiO ₂ activating filler and addition methods in the method of the invention guarantee a reduction in hot tan D along with an increase in mono- and disulfides with less hysteresis behavior. compound, which makes it possible to predict a lower rolling resistance of the tire during operation.

Example 7

Preparation of elastomeric compounds based on natural rubber for interlayer

In this example, the effect of the addition of a ZnO/SiO ₂ filler according to the method according to the invention relative to traditional ZnO at the same filler and zinc content on the vulcanization parameters and on the mechanical properties of a natural rubber compound was evaluated.

The elastomeric compounds of examples 7.1 and 7.2 were prepared in accordance with the methods described in the invention. The amounts of the various components are given in parts by weight/100 parts by weight. rubber and are presented in the following table 9.

Table 9

Stage Ingredients Comparative example 7.1 Claimed Example 7.2 ZnO content 1-0 NR 100 100 1-0 Stearic acid 2.0 2.0 1-1 Carbon black CB 23.0 23.0 1-1 Silica 22.8 - 1-1 Stearic acid 2.0 2.0 1-1 ZnO 3.3 - 3.3 1-1 ZnO/SiO ₂ Ex. 2 (12.3%) - 26.0 3.2 1-2 TMQ 1.3 1.3 1-2 6PPD 3.0 3.0 1-2 Wax 1.0 1.0 1-2 TESPD (silane) 2.2 2.2 2-0 TBBS 1.3 1.3 2-0 PVI 0.3 0.3 2-0 Sulfur (67%) 4.5 4.5

In the table:

NR: natural rubber (cis-1,4-polyisoprene), SIR 20. Supplier PT. KIRANA MUSI PERSADA, SFN;

ZnO: microcrystalline, white powder. Supplier ZINCOL OSSIDI;

TMQ: polymerized 2,2,4-trimethyl-1,2-dihydroquinoline. Supplier LANXESS;

PVI: N-cyclohexylthiophthalimide Supplier SHANDONG YANGGU HUATAI CHEM, and

the other ingredients are the same as in the previous examples.

The mixing is carried out in several stages as described in example 4 by adding the ingredients in the quantities, stages and in the order indicated in table 9, in particular by adding stearic acid (stage -0) even earlier and silane (stage 1.2) later.

The resulting elastomeric compounds 7.1 and 7.2 are evaluated for vulcanization parameters and then for static and dynamic mechanical properties in accordance with the methods described in the invention. The results, recalculated to 100 values obtained with Comparative Example 7.1, are summarized in the following Table 10.

Table 10

Measured parameter Units Comparative example 7.1 Claimed Example 7.2 Vulcanizing (170°C, 10 min) T30 min 100 59 (-41%) T60 min 100 57 (-43%) T90 min 100 57 (-43%) T-MH min 100 60 (-40%) After vulcanization (30 min at 151°C) E’’ 10°C, 10Hz, 7.5%-20% MPa 100 105 (+5%) Tan Delta 10°C, 10Hz, 7.5%-20% - 100 111 (+11%) E’’ 23°C, 10Hz, 7.5%-20% MPa 100 105 (+5%) Tan Delta 23°C, 10Hz, 7.5%-20% - 100 111 (+11%) E’’ 100°C 10Hz 7.5% -20% MPa 100 95 (-5%) Tan Delta 100°C, 10Hz, 7.5% -20% - 100 100 (0%) (170°C, 10 min)
Tension on ring specimens CR MPa 100 114 (+14%) AR % 100 117 (+17%)

In the table:

T30, T60, T90 and T-MH: time required to reach respectively 30% (T30), 60% (T60), 90% (T90) and 100% (T-MH) of the maximum torque value (MH);

E”: tensile/compressive modulus of viscosity;

E': tensile/compressive modulus of elasticity;

Tan delta: ratio between the dynamic modulus of viscosity (E”) and the dynamic modulus of elasticity (E’);

AR: elongation at break.

From the values presented in Table 10, it can be seen that, with all other variables being equal, the ZnO/SiO ₂ activating filler gives the compound according to the invention of Example 7.2 with better static mechanical properties (CR and AR increased by 14% and 17% respectively) and faster vulcanization kinetics relative to the compound of comparative example 7.1 containing conventional microcrystalline ZnO (compare the values of T30, T60, T90 and T-MH). The difference in vulcanization kinetics can be estimated from the pattern of the graphical curves shown in FIG. 5.

The ZnO/SiO ₂ activating filler and preparation method according to the invention lead to an increase in hysteresis at 23°C and 10°C of the cured compounds with a corresponding increase in the E'modulus, thus predicting better wet surface performance. Otherwise, at 100°C, there is a hysteresis similar to the reference, which makes it possible to predict comparable rolling resistance and wear resistance of the tire in operation.

Example 8

Preparation of elastomeric compounds based on natural rubber for interlayer

In this example, a comparison is made between conventional comparative interlayer compounds comprising conventional silica and activating microcrystalline ZnO (Comparative Examples 8.1 and 8.2), which were first prepared according to the present method with early addition of ZnO and silica and subsequent addition of silane (step 1.2) and second by another method in which silane and silica are introduced initially in step 1.1 and ZnO and stearic acid subsequently in step 2.0, with a compound according to the invention containing alternatively an activating filler ZnO/SiO ₂ (D) and obtained with late addition of silane (stage 1.2) (claimed example 8.3). The elastomeric compounds of examples 8.1-8.3 were prepared in accordance with the methods described in the invention. The amounts of the various components are given in parts by weight/100 parts by weight. rubber and are presented in the following table 11.

Table 11

Stage Ingredients Ref. example 8.1 Ref. example 8.2 Claimed Example 8.3 ZnO content 1-0 NR 100 100 100 1-0 Stearic acid 2.0 - 2.0 1-1 ZnO 2.6 - - 2.6 1-1 Carbon black CB 23.0 23.0 23.0 1-1 Silica 18.2 18.2 - 1-1 TESPD - 1.4 - 1-1 ZnO/SiO ₂ Ex. 2 (12.3%) - - 20.7 2.6 1-2 TMQ 1.3 1.3 1.3 1-2 6PPD 3.0 3.0 3.0 1-2 Wax 1.0 1.0 1.0 1-2 TESPD 1.4 - 1.4 2-0 ZnO - 2.6 - 2.6 2-0 Stearic acid - 2.0 - 2-0 TBBS 1.3 1.3 1.3 2-0 PVI 0.3 0.3 0.3 2-0 Sulfur (67%) 4.5 4.5 4.5

In the table, all ingredients are the same as in the previous examples.

Mixing is carried out in several stages, as described in example 4, by adding the ingredients in the amounts, at the stage and in the order indicated in table 11.

The resulting elastomeric compounds 8.1-8.3 are evaluated in terms of vulcanization parameters and then in terms of static and dynamic mechanical properties in accordance with the methods described in the invention. The results, recalculated to 100 values obtained with Comparative Example 8.1, are summarized in the following Table 12.

Table 12

Measured parameter Units Comparative example 8.1 Comparative example 8.2 Claimed Example 8.3 When vulcanized
(170°C, 10 min) ML (23°C) dnm 100 100 83 (-17%) T30 min 100 89 (-11%) 67 (-33%) T60 min 100 87 (-13%) 65 (-35%) T90 min 100 86 (-14%) 67 (-33%) After vulcanization
(30 min at 151°C) E’’ 10°C, 10Hz, 7.5%-20% MPa 100 100 (0%) 109 (+9%) Tan Delta 10°C, 10Hz, 7.5%-20% - 100 98 (-2%) 112(+12%) E’’ 23°C, 10Hz, 7.5%-20% MPa 100 99 (-1%) 109 (+9%) Tan Delta 23°C, 10Hz, 7.5%-20% - 100 96 (-4%) 112(+12%) E’’ 100°C 10Hz 7.5% -20% MPa 100 95 (-5%) 87 (-13%) Tan Delta 100°C, 10Hz 7.5%-20% - 100 91 (-9%) 91 (-9%) Tension on ring specimens CR MPa 100 98 (-2%) 99 (-1%) AR % 100 94 (-6%) 106 (+6%)

From the values presented in Table 12, it can be seen that, all variables being equal, the compound according to the invention (example 8.3, method according to the invention, activating filler ZnO/SiO ₂ ) relative to the comparative compounds of example 8.1 (method according to the invention, but with standard microcrystalline ZnO) and example 8.2 (standard method and standard microcrystalline ZnO) shows an increase in hysteresis at 10°C and 23°C with increasing modulus E”, which predicts good tire behavior on wet surfaces, and a significant decrease at high temperatures (100°C) mainly way due to the decrease in the modulus E', which allows, on the contrary, to predict improved rolling and abrasion resistance of the tire during operation.

Moreover, the inventive compound example 8.3 shows a significant reduction in curing time (see T30-T90 values).

When considering the vulcanization times shown in Table 12 (T30-T90), an increase is observed when going from the standard compound (comparative example 8.2, standard method and zinc compound) to the compound of comparative example 8.1 (standard method according to the invention and zinc compound), so that, as the late addition of a compatibilizing agent, which characterizes the present method, does not in itself lead to an increase in the crosslinking rate, but is observed, surprisingly, only in the specific case of using zinc in the form of an activating filler ZnO/SiO ₂ .

The difference in vulcanization kinetics can be seen from the shape of the graphical curves shown in FIG. 6.

FIG. 6 shows a normalized curve of torque values [(S _x -S _min )/(S _max -S _min )×100] measured over time (min) while vulcanizing at 170°C for 10 minutes for a curable compound according to with the invention of example 8.3 relative to the comparative compounds of example 8.1 and 8.2. As can be seen, the sample of the claimed example 8.3 shows faster vulcanization kinetics compared to both comparative examples 8.2 and 8.1.

Moreover, it is noted that microcrystalline zinc introduced in step 1.1 of example 8.1 results in slower kinetics.

Claims (30)

1. A method of making a vulcanizable elastomeric tire compound, said method comprising at least: - the stage of mixing (1) at least one elastomeric polymer (A) and at least one additive for elastomeric compounds, with the exception of vulcanizing agents (B), to obtain a non-vulcanizable elastomeric compound; - a step of mixing (2) a non-vulcanizable elastomeric compound and at least one curing agent (B) to obtain a curable elastomeric compound, and - the stage of unloading the vulcanizable elastomeric compound, moreover, at the mixing stages (1) and/or (2), at least one fatty acid (C), at least one product (D) containing zinc directly associated with a light filler, and at least one compatibilizing agent ( E), characterized in that said at least one compatibilizing agent (E) is added after completion of the addition and processing of said at least one fatty acid (C) and at least one product (D) containing zinc directly bound to the light filler, when this compatibilizing agent (E) is a silane selected from silanes having at least one hydrolysable group, with the general formula (I): (R) ₃ Si-C _n H _2n -X (I), where the R groups, which may be the same or different, are selected from alkyl, alkoxy or aryloxy groups or from halogen atoms, provided that at least one of the R groups is an alkoxy or aryloxy group or halogen; n is an integer from 1 to 6 inclusive; X is a group selected from nitrogen, mercapto, amino, epoxy, vinyl, imide, chlorine, -(S) _m C _n H _2n -Si-(R) ₃ and -S-COR, where m and n are integers from 1 to 6 inclusive, and the groups R are the groups defined above. 2. The method according to p. 1, in which both the specified at least one fatty acid (C), and at least one product (D) containing zinc directly associated with a light filler, and at least one compatibilizing agent ( E) is added at the mixing stage (1). 3. The method according to claim 1, in which said at least one fatty acid (C) and at least one product (D) containing zinc directly associated with a light filler are added at the mixing stage (1), and said at least one compatibilizing agent (E) is added in the mixing step (2). 4. The method according to any one of the preceding claims, in which the processing of said at least one fatty acid (C) and at least one product (D) containing zinc directly associated with a light filler is carried out at a compound temperature of at least equal to the melting point of said fatty acid (C), or higher. 5. Process according to any one of the preceding claims, wherein the mixing step (2) is carried out at a compound temperature of less than 160°C, preferably less than 140°C, more preferably less than 120°C. 6. A method according to any one of the preceding claims, wherein: said diene elastomeric polymer (A) is selected from 1,4-polyisoprene, 3,4-polyisoprene, polybutadiene, optionally halogenated isoprene/isobutene copolymers, 1,3-butadiene/acrylonitrile copolymers, styrene/1,3-butadiene copolymers, styrene /isoprene/1,3-butadiene copolymers, styrene/1,3-butadiene/acrylonitrile copolymers and mixtures thereof; and/or said curing agent (B) is selected from sulfur and sulfur donors selected from caprolactam disulfide (CLD), bis[(trialkoxysilyl)propyl]polysulfides, dithiophosphates, phosphoryl polysulfide (SDT) and mixtures thereof. 7. Process according to any of the preceding claims, wherein said fatty acid (C) is selected from saturated or unsaturated fatty acids having from 8 to 26 carbon atoms, their esters, their salts and mixtures thereof, preferably selected from lauric acid (C12) , myristic acid (C14), palmitic acid (C16), stearic acid (C18), behenic acid (C22), lignoceric acid (C24) and mixtures thereof, more preferably the acid is stearic acid. 8. Process according to any one of the preceding claims, wherein the zinc in said product (D) is present in the form of zinc oxide, preferably in the form of zinc oxide in particles with an average particle size in the range of 3 to 100 nm, more preferably 4 to 10 nm. 9. The method according to any one of the preceding claims, wherein the light filler of the product (D) is selected from silica and silicates selected from bentonite, nontronite, beidellite, wolkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, palygorskite or attapulgite, montmorillonite, halloysite, optionally acid-treated and/or derivatized, and mixtures thereof, more preferably the filler is silica. 10. The method according to any one of the preceding claims, wherein the zinc-containing product (D) directly bonded to the light-colored filler is zinc oxide on silica. 11. The method according to any one of the preceding claims, wherein the compatibilizing agent is selected from bis(3-triethoxysilylpropyl)tetrasulfide (TESPT) and bis(3-triethoxysilylpropyl)disulfide (TESPD). 12. The method according to any one of the previous paragraphs, in which: - fatty acid (C) is added in a total amount in the range from 0.05 to 20 wt./100 wt.h. rubber, preferably from 0.1 to 15 wt.h./100 wt.h. rubber, more preferably from 0.5 to 5 wt.h./100 wt.h. rubber - product (D) containing zinc, directly associated with a light filler, is added in a total amount in the range from 1 to 100 wt.h./100 wt.h. rubber, preferably from 5 to 80 wt.h./100 wt.h. rubber, more preferably from 10 to 30 wt.h./100 wt.h. rubber and - compatibilizing agent (E) is added in a total amount in the range from 0.1 to 20 wt.h./100 wt.h. rubber, preferably from 0.5 to 10 wt.h./100 wt.h. rubber. 13. The method according to any one of the preceding claims, wherein one or more additional additives are added selected from vulcanization accelerators (F), vulcanization retarders (G), reinforcing fillers (H), antioxidants (I), waxes (L) and plasticizers ( M). 14. Vulcanizable elastomeric compound obtained by the method according to any one of the previous paragraphs. 15. Vulcanizable elastomeric compound according to claim 14, containing zinc in an amount of less than 4 wt.h./100 wt.h. rubber, preferably less than 3 wt.h./100 wt.h. rubber, more preferably less than 2 wt.h./100 wt.h. rubber. 16. A tire component containing a vulcanizable compound according to claim 14 or 15 or a vulcanized compound obtained by vulcanizing it. 17. The tire component of claim 16, selected from a tread band, interlayer, anti-abrasion elongate, sidewall, sidewall insert, mini-sidewall, liner, rubber plies, filler cord, and bead wing web, preferably of interlayer and sidewall. 18. Tire for vehicle wheels, comprising at least one tire component according to claim 16 or 17.

Images