Elastomeric compositions and compounds comprising a new secondary crosslinking system and tires comprising them

Abstract

The present invention relates to elastomeric compositions and gums for tyres comprising a novel secondary crosslinking system comprising at least one methylene donor reagent (I) of formula (I) and at least one methylene acceptor reagent, and tyres for vehicle wheels comprising them. The new secondary crosslinking system of the invention allows to impart to the materials optimal stiffness, tensile strength and adhesion to reinforcing elements, improving the crosslinking kinetics and processability of the gums, while reducing or maintaining hysteresis. These materials are advantageously used in those tyre components which require a certain stiffness and resistance to breakage and / or high adhesion to textile or metal reinforcing elements and low rolling resistance.

Description

Technical Field

[0001] This invention relates to a novel secondary crosslinking system for elastomer compounds, wherein the secondary compound system includes, in addition to conventional methylene acceptor reagents, at least one methylene donor reagent having a bisoxazolidine structure. The invention also relates to tire elastomer compositions comprising the aforementioned secondary crosslinking system, elastomer compounds obtainable by crosslinking the compositions, tire components for vehicle wheels comprising the said elastomer compounds, and tires. Background Technology

[0002] In the tire industry, sulfur crosslinking (vulcanization or major crosslinking) is a common method used to improve the mechanical properties of rubber.

[0003] In particular, sulfur crosslinking occurs after heating in the so-called vulcanization step, forming sulfur-based bonds. Through vulcanization, a flexible material that is not very swollen is obtained.

[0004] Sulfur crosslinking affects the hardness, elasticity, and hysteresis of elastomer materials, and thus affects the performance and behavior of tires containing such elastomer materials.

[0005] Typically, using a conventional vulcanization system, vulcanizing agents and additives are introduced into the rubber compound downstream of the production process in a controlled temperature step (usually not exceeding 130°C) and mixed for a limited time.

[0006] However, the poor solubility of sulfur in elastomer compounds, coupled with the mild mixing conditions required for its introduction, means that its dispersion is not always ideal. The resulting material, due to the uneven distribution of sulfur, may not possess the desired properties; for example, it can be characterized by significant hysteresis, showing an increase in heat dissipation under dynamic conditions. Increased hysteresis in tire elastomer materials can be detrimental because it is associated with increased rolling resistance in road use and consequently increased vehicle fuel consumption, which contrasts sharply with the current trend in the automotive industry to minimize fuel consumption as much as possible.

[0007] Over the years, various additives have been proposed to improve the crosslinking process, such as vulcanization accelerators, promoters, and retarders. However, sulfur-based primary crosslinking systems do not always yield satisfactory results despite the use of additives. In fact, the primary lattice based on sulfur bonds formed during the vulcanization step does not always provide sufficient reinforcement to the rubber compound because these bonds are reversible and easily break (reverse) at high temperatures. As a result of this thermal instability, the mechanical properties of the tire, especially under stress, may deteriorate.

[0008] This problem is addressed by introducing thermally more stable secondary crosslinking systems into the elastomer compound. These secondary crosslinking systems compensate for the breaking of sulfur bonds in the primary lattice and impart stiffness and tear resistance to the material. The increased stiffness and tear resistance can be particularly beneficial for certain tire components that are typically subjected to heavy loads, such as the bead or sidewall inserts of self-supporting tires.

[0009] However, the use of secondary crosslinking systems can lead to processability problems in the rubber compound due to excessive viscosity increases. Too high a viscosity can make it difficult to mix the components of the compound and process the compound itself; furthermore, it can impair the uniform dispersion of additives and hinder complete crosslinking, resulting in defects in the final material, such as in mechanical properties, and increasing costs and production time.

[0010] A secondary crosslinking system commonly used for this purpose includes phenols (e.g., resorcinol) and methylene donor reagents (e.g., formaldehyde), which are capable of reacting with phenols to form crosslinks.

[0011] Crosslinking systems based on resorcinol and formaldehyde in latex are called RFL systems, and are also widely used as adhesives to adhere reinforcing elements present in the reinforcing structural elements of tires to the rubber.

[0012] In tires for vehicle wheels, reinforcing structural elements, including reinforcing components, perform various functions, which can be structural, containment, or protective. One characteristic to be examined to ensure the integrity of the reinforcing structural elements is that the reinforcing elements are firmly adhered to the elastomeric material that encloses them to prevent tearing and disintegration of the composite material.

[0013] Depending on the positioning, tire type, and application, the materials used for reinforcing elements in the carcass structure, belt layer structure, bead protection layer (bead wrapping), and reinforcing layer (outer bead wrapping) can generally be metallic or non-metallic textile materials.

[0014] Typically, metal reinforcing elements are made using one or more carbon steel wires. These wires and / or cords are usually coated with a brass layer to improve adhesion to the elastomer compound and protect the chords from corrosion.

[0015] Based on carbon content and breaking strength, the following types of metal wires can be distinguished: -NT (normal tension steel) wire, which has a tensile strength at break of 2800±200MPa, for example, at least 2700MPa for a wire diameter of 0.28mm. -HT (high-tensile steel) wire, which has a tensile strength at break of 3200±200MPa, for example, at least 3100MPa for a wire diameter of 0.28mm. -ST (ultra-high tensile steel) wire, which has a tensile strength at break of 3500±200MPa, for example, at least 3400MPa for a wire diameter of 0.28mm. -UT (Ultra-Tension Steel) wire, which has a tensile strength at break of 3900±200MPa, for example, at least 3800MPa for a wire diameter of 0.28mm.

[0016] The non-metallic materials most commonly used as components of tire reinforcement elements can be natural-derived polymer fibers such as rayon and lyocell, or synthetic fibers such as aliphatic polyamide (nylon), polyester, and aromatic polyamide (often called aramid). These materials are selected based on the component to which they will be included and the type of tire (for two-wheeled or four-wheeled vehicles, for heavy-duty vehicles) and the required performance such as HP (high performance), UHP (ultra-high performance), racing, road, or off-road.

[0017] RFL-based adhesive compositions are typically applied to textile cords by dip-in. These cords can then be incorporated into an elastomer matrix for subsequent assembly with other semi-finished products into the construction of a green tire, which is then molded, subjected to molding, and vulcanization. Typically, to further enhance adhesion between the reinforcing element and the rubber, adhesion-promoting additives can be introduced into the rubberized elastomer compound, which includes substantially the same or similar methylene donor and acceptor agents, such as hexamethylenetetramine and resorcinol. Crosslinking of these additives during the vulcanization step allows for higher adhesion, depending on the compound type, accelerator, fiber, and its treatment.

[0018] Resorcinol-formaldehyde (RF) systems are very common and effective secondary crosslinking systems and adhesives. However, at the industrial level, there is a desire to reduce the use of both resorcinol and formaldehyde to make tire component rubber compounds that include them more sustainable.

[0019] To substantially reduce the use of free resorcinol in every step of tire manufacturing, phenolic resins such as Alnovol are used as methylene acceptors, which are generally less harmful because the phenolic components are at least partially cross-linked.

[0020] In cases where the secondary crosslinking system includes these phenolic resins, the crosslinking that typically occurs during the vulcanization step of the compound still requires the introduction of at least one methylene donor, such as formaldehyde or, preferably, a less harmful donor selected from conventional formaldehyde precursors such as hexamethoxymethylmelamine (HMMM), hexamethylenetetramine (HMT), etc.

[0021] However, using these phenolic resins instead of resorcinol in secondary crosslinking systems can lead to slower crosslinking kinetics and, more importantly, higher material hysteresis.

[0022] Possible alternative methylene donors are known from the literature, such as oxazolidinyl reagents used alone or in combination with formaldehyde or conventional formaldehyde precursors such as HMMM or HMT.

[0023] In this regard, some literature, such as EP2316881A1, JP5448445B2, JP5317477B2, and JP2010150502A, generally mentions oxazolidines in combination with phenolic resins as secondary crosslinking systems in elastomer compounds for bead or sidewall inserts of self-supporting tires, among other methylene donors. However, these documents typically do not show any specific oxazolidines or provide experimental examples of them, but instead prefer conventional formaldehyde precursors such as HMT and HMMM.

[0024] US Patent 4361677 describes an elastomeric compound for tires, particularly for bead filling, which, in addition to conventional elastomers, includes specific thermosetting and vulcanized phenolic resins, thermosetting phenolic resins, and a hardener for curing these resins. The hardener may, among others, include, a bisoxazolidine reagent of formula (IA).

[0025] (IA)

[0026] It is mixed with other suitable methylene donors, preferably selected from HMT, polyfunctional derivatives of methylmelamine, oxazolidine and its derivatives, bis(1,3-oxazolidine) and its derivatives.

[0027] This literature does not recommend using those compounds as rubberized compounds for metal or textile reinforcing elements, nor does it show any data on the hysteresis of crosslinked elastomer materials, the trend of crosslinking kinetics, or the thermal stability of crosslinked compounds. In the illustrated compounds, a conventional methylene donor (HMMT) is always present, either alone or optionally mixed with compound (IA).

[0028] Other literature also mentions bisoxazolidine methylene donors, with particular emphasis on the same bisoxazolidine methylene donor (IA) mentioned above, replaced by CH2OH (hydroxymethyl).

[0029] For example, US3256137A relates to elastomeric compounds with improved adhesion to textile materials, comprising a secondary crosslinking system consisting of at least one bisoxazolidine methylene donor and at least one methylene acceptor. No crosslinking systems containing a mixture of methylene donors are illustrated in the experimental section. This literature reports the performance of some compounds in adhesion tests on rayon and nylon cords after crosslinking, but provides no indication of their crosslinking kinetics, processability, or network stability (reversal), nor evaluates their static and dynamic mechanical properties.

[0030] Document GB1112007A relates to the adhesion of polyester textile materials to rubber and generally describes elastomeric compounds comprising a secondary crosslinking system consisting of at least one methylene donor (including a bisoxazolidine structure) and at least one methylene acceptor. No crosslinking systems containing mixtures of methylene donors are illustrated in the experimental section. This document reports the performance of some compounds in adhesion tests on polyester ropes after crosslinking, but does not provide data on their crosslinking kinetics, processability, network stability (reversal), or hysteresis.

[0031] Document US3969568A claims protection for reinforced elastomer compositions and compounds containing a bisoxazolidine methylene donor, a methylene acceptor, and discontinuous aramid fibers. No crosslinking systems containing a mixture of methylene donors are illustrated in the experimental section. This document reports the mechanical properties of some compounds containing aramid, polyester, nylon, rayon, or glass flakes after crosslinking, but provides no indication of their crosslinking kinetics, processability, network stability (reversal), or their hysteresis. Summary of the Invention

[0032] Given the existing technology, the applicant felt a need to provide a more harmless secondary crosslinking system, namely, one with low or preferably no resorcinol and formaldehyde content, which, when incorporated into elastomer compounds, would exhibit sufficiently rapid crosslinking kinetics and provide a thermally stable network with less reversal, ease of processing, and the ability to impart suitable stiffness and high fracture strength to materials for use in particularly stressed tire components, while simultaneously not increasing or potentially decreasing hysteresis to control rolling resistance and thus wear. Furthermore, such a secondary crosslinking system should ideally also provide high adhesion between the elastomer compound and the reinforcing elements bonded therein. Meeting all these requirements and reconciling these sometimes contradictory properties in a single material appears extremely difficult.

[0033] The applicant conducted research to identify a thermally stable, more sustainable secondary crosslinking system that can impart stiffness, good processability, and high adhesion to reinforcing elements to the tire's elastomer compound, with the aim of producing higher-performance tires that exhibit structural resistance even under stress conditions and may curb wear.

[0034] The applicant has surprisingly discovered that the aforementioned objectives can be achieved through a novel secondary crosslinking system comprising a specific class of methylene donor reagents that can partially or completely replace formaldehyde and conventional formaldehyde precursor reagents (HMMM, HMT, etc.), as well as conventional methylene acceptor reagents, such as resorcinol or preferably phenolic resins. In its research, the applicant found that this novel system is particularly effective as a secondary crosslinking agent for elastomers. The crosslinked elastomer compounds can be used as constituent compounds for tire components requiring stiffness and fatigue resistance (e.g., bead, sidewall inserts, sidewalls, etc.) and / or high adhesion to reinforcing elements (e.g., carcass, belt layers, rubberized compounds for annular bead anchoring elements, bead protector-bead wrapping-or reinforcing layer-outer bead wrapping). The elastomer compounds of the present invention comprising the novel crosslinking system are also easier to process, have favorable crosslinking kinetics, higher initial crosslinking rates and comparable or reduced reversal, and ultimately exhibit hysteresis comparable to or even lower than known crosslinking systems.

[0035] Therefore, a first aspect of the present invention is a crosslinking composition for elastomeric compounds comprising at least one methylene donor agent of formula (I). (I) Where R 1 Represents H, linear or branched C1-C 20 Alkyl, straight-chain or branched C1-C 20 The alkenyl group, wherein the alkyl and alkenyl groups are optionally substituted with one or more oxygen atoms in the chain. And at least one methylene receptor reagent.

[0036] A further aspect of the invention is an elastomer composition comprising at least

[0037] At least one diene polymer with a phr of -100 phr - At least one reinforcing filler with a phr of at least 0.1 phr -0.1 to 20 phr of vulcanizing agent, and - At least 0.05 phr of the crosslinked composition according to the invention.

[0038] A further aspect of the invention is a crosslinked elastomer compound for vehicle wheel tires, which is obtained by mixing and vulcanizing an elastomer composition according to the invention.

[0039] A further aspect of the invention is a tire for a vehicle wheel comprising at least one tire component comprising a crosslinked elastomer compound according to the invention.

[0040] definition

[0041] The term "crosslinked system or composition" refers to a composition that enables natural or synthetic rubber to be transformed into an elastic and resistant material by forming a three-dimensional network of intermolecular and intramolecular bonds.

[0042] The term "crosslinking agent" refers to a crosslinking agent preferably selected from sulfur-based crosslinking agents such as elemental sulfur, polymeric sulfur, sulfur donor reagents such as bis[(trialkoxysilyl)propyl] polysulfides, thiuram, dithiodimorpholine and caprolactam-disulfides, peroxides such as dialkyl peroxide ROOR (where R is alkyl), alkyl-aryl peroxide ROO-R' (where R is alkyl and R' is aryl), diaryl peroxide R'-OO-R' (where R' is aryl), diacyl peroxide RC(O)-OO-(O)C-R' (where R and R' are aryl and / or alkyl), peroxyketal ROO(R)C(R')-OO-R' (where R and R' are aryl and / or alkyl), peroxy ester RC(O)-OO-R' (where R and R' are aryl and / or alkyl), metal oxides such as zinc oxide, quinones, resins and organic bases. The crosslinking agent is responsible for the main crosslinking or vulcanization of the elastomer compound.

[0043] The term "methylene donor" refers to an organic precursor of formaldehyde or formaldehyde that can decompose, at least partially, under normal sulfidation conditions, thereby releasing formaldehyde in situ. Methylene donors can react with methylene acceptors, typically forming a lattice in which they are wholly or partially incorporated.

[0044] The terms “conventional formaldehyde or methylene donor or conventional formaldehyde precursor reagent” and similar reagents herein refer to organic compounds that release formaldehyde in situ when heated, such as paraformaldehyde, hexamethylenetetramine (HMT), hexamethoxymethylmelamine (HMMM), hexahydroxymethylmelamine, N,N'-dimethoxyurea, N-hydroxymethyldicyandiamide, N-allyl dioxazine, N-phenyl dioxazine, N-hydroxymethylacetamide, N-hydroxymethylbutyramide, N-hydroxymethylacrylamide, N-hydroxymethylsuccinimide, dodecyloxymethylpyridinium chloride, ethoxymethylpyridinium chloride, trioxane hexamethoxymethylmelamine, hexahydroxymethylmelamine pentamethyl ether (HMPE), and known oxazolidinyl derivatives other than those of formula (I).

[0045] The term "methylene acceptor reagent" refers to an aromatic organic compound that can react with a methylene donor through aromatic electrophilic substitution reactions and lattice formation. Typical methylene acceptor reagents are phenols and phenolic resins.

[0046] The term "elastomer composition for tire rubber" means a composition comprising at least one diene polymer and one or more additives, which, by mixing and typically heating, provides an elastomer compound suitable for use in vehicle wheel tires and their components.

[0047] The components of the composition are typically added sequentially rather than simultaneously into the mixer. In particular, vulcanizing additives, such as vulcanizing agents and optional accelerators and retarders, are usually added in downstream steps relative to the incorporation and processing of all other components.

[0048] In elastomeric compounds, the components of the composition may be altered or no longer traceable individually due to complete or partial modification by interaction with other components and by thermal and / or mechanical processing.

[0049] The term "elastomer compound" refers to a composition that can be obtained by mixing at least one diene polymer with at least one additive commonly used in the preparation of tire compounds.

[0050] The term "vulcanizable elastomer compound" refers to a compound that can be obtained by mixing at least one diene polymer with at least one vulcanizing agent.

[0051] The term "vulcanized elastomer compound" refers to materials that can be obtained through the vulcanization of vulcanizable elastomer compounds.

[0052] The term "raw" refers to materials, rubber compounds, compositions, components, or tires that have not yet been vulcanized.

[0053] The term "crosslinking" refers to the reaction that forms a three-dimensional lattice between molecules and within molecules in natural or synthetic rubber.

[0054] The term "vulcanization" refers to the crosslinking reaction in natural or synthetic rubber induced by vulcanizing agents, typically based on sulfur.

[0055] The term "vulcanization accelerator" refers to compounds that can reduce the duration and / or operating temperature of the vulcanization process, such as TBBS, general sulfenamides, thiazoles, dithiophosphates, dithiocarbamates, guanidines, and sulfur donors such as thiuram.

[0056] The term "vulcanization activator" refers to a product that can further promote vulcanization, causing it to occur in a shorter time and possibly at a lower temperature. An example of an activator is the stearic acid-zinc oxide system.

[0057] The term "vulcanization retarder" refers to a substance that can delay the occurrence of the vulcanization reaction and / or inhibit undesirable secondary reaction products, such as N-(cyclohexylthio)phthalimide (CTP).

[0058] The term "vulcanizing package" refers to a vulcanizing agent and one or more vulcanizing additives selected from vulcanizing activators, accelerators and retarders.

[0059] The term "primary crosslinking system" or vulcanization system refers to a crosslinking system in which the vulcanizing agent is typically based on sulfur.

[0060] The term "secondary cross-linking system" refers to a cross-linking system other than the primary cross-linking system, which contains at least one methylene donor reagent and at least one methylene acceptor reagent.

[0061] The term "elastomeric polymer" refers to a natural or synthetic polymer that, after crosslinking, can be repeatedly stretched to at least twice its original length at room temperature and recovers to approximately its original length by force substantially immediately after the tensile load is removed (according to the definition of the term in the ASTM D1566-11 standard for rubber).

[0062] The term "diene polymer" refers to a polymer derived from the polymerization of one or more monomers, at least one of which is a conjugated diene. Diene polymers can be elastomeric polymers and acquire characteristic properties upon vulcanization.

[0063] The term "reinforcing filler" is intended to refer to reinforcing materials commonly used to improve the mechanical properties of tire rubber, preferably selected from carbon black, conventional silica such as silica from sand precipitated with strong acid, preferably amorphous silica, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicate, kaolin, silicate fibers, their derivatives and mixtures thereof.

[0064] The term "white filler" is intended to refer to reinforcing materials selected from conventional silica and silicates such as sepiolite, palygorskite (also known as attapulgite), montmorillonite, halloysite, etc., optionally modified by acid treatment and / or derivatization. Typically, white fillers have surface hydroxyl groups.

[0065] The term "mixing step (1)" refers to the step in the preparation of an elastomer compound in which one or more additives are incorporated through mixing and optional heating, in addition to the vulcanizing agent fed in step (2). Mixing step (1) is also referred to as a "non-productive step". There can be multiple "non-productive" mixing steps in the preparation of the compound, which can be represented by 1a, 1b, etc.

[0066] The term “mixing step (2)” refers to the next step in the preparation of the elastomer composition, in which a vulcanizing agent and, optionally, other additives of the vulcanizing package are introduced into the elastomer compound obtained from step (1) and mixed in the material at a controlled temperature, typically at a compound temperature greater than 120°C, thereby providing a vulcanizable elastomer compound. Mixing step (2) is also referred to as the “production step”.

[0067] For the purposes of this description and in the following claims, the term "phr" (abbreviation for parts per hundred parts of rubber) means the weight parts of a given elastomeric compound component per 100 parts by weight of polymer, excluding any plasticizing filler oil. Unless otherwise indicated, all percentages are expressed as weight percentages. Attached Figure Description

[0068] Please refer to the attached diagram: - Figure 1 A tire for a vehicle wheel is shown, the tire comprising at least one component comprising an elastomeric compound according to the invention.

[0069] - Figure 2 The trend of extraction force (Newtons, on the vertical axis) is shown as deformation (mm, on the horizontal axis) increases for reference carcass rubber compounds (Examples 1 and 2), according to the present invention (Example 3), and comparative example (Example 4).

[0070] - Figure 3 The crosslinking kinetics trends (MDR analysis) of adhesives containing conventional resorcinol + HMMM systems (Sample 1, Example 1) or phenolic resin + HMMM (Sample 2, Example 2) are shown compared to the phenolic resin + oxazolidine (I) system (Sample 3, Example 3) according to the present invention. Detailed Implementation

[0071] The crosslinking composition according to the invention is characterized by one or more of the following preferred aspects, either alone or in combination with each other.

[0072] The crosslinking composition according to the present invention comprises at least one methylene donor reagent of formula (I). (I) Where R 1 Preferably, it represents a straight-chain or branched C1-C. 10 Alkyl, straight-chain or branched C1-C 10 Alkenyl, more preferably straight-chain or branched C1-C5 alkyl, straight-chain or branched C1-C5 alkenyl, even more preferably R 1 It represents the ethyl group.

[0073] The alkyl and alkenyl groups may optionally be substituted with one or more oxygen groups in the chain to produce alkoxy-alkyl or alkoxyalkenyl chains, including alkoxy-alkyl or alkoxyalkenyl chains containing one or more repeating units such as -O-CH2-CH2-(PEG), -O-CH2-CHOH-CH2-(PPG), etc.

[0074] The methylene donor reagent of formula (I) can be a commercial product, such as bicyclooxazolidine 5-ethyl-1-aza-3,7-dioxa-bicyclo[3.3.0]octane from Aldrich, or it can be synthesized from known reactants according to methods described in the literature, such as those described in US3256137 and the literature cited therein.

[0075] In one embodiment, in addition to at least one methylene donor reagent of formula (I), the crosslinking composition of the present invention may also contain at least one other conventional methylene donor reagent selected from, but not limited to, formaldehyde, paraformaldehyde, preferably selected from hexamethoxymethylmelamine (HMMM), hexamethylenetetramine (HMT), hexahydroxymethylmelamine, N,N'-dihydroxymethylurea, N-hydroxymethyldicyanamide, N-allyl dioxazine, N-phenyl dioxazine, N-hydroxymethylacetamide, N-hydroxymethylbutyramide, N-hydroxymethylacrylamide, N-hydroxymethylsuccinimide, dodecyloxymethylpyridinium chloride, ethoxymethylpyridinium chloride, trioxane hexamethoxymethylmelamine, as described in US3751331, hexahydroxymethylmelamine pentamethyl ether (HMPE), oxazolidine derivatives other than those of formula (I) and mixtures thereof, more preferably selected from hexamethylenetetramine (HMT), hexamethoxymethylmelamine (HMMM) and mixtures thereof.

[0076] In one embodiment, the crosslinking composition of the present invention comprises at least one compound of formula (I) as a methylene donor agent, preferably R. 1 A compound of formula (I) of ethyl form, in a mixture with hexamethylenetetramine (HMT) and / or hexamethoxymethylmelamine (HMMM).

[0077] Preferably, in the case of a methylene donor reagent comprising a donor mixture, the weight ratio between at least one reagent of formula (I) and at least one other conventional methylene donor reagent of a formula other than formula (I) is generally between 1:1 and 1:6, preferably between 1:1 and 1:3.

[0078] In a preferred embodiment, the crosslinking composition of the present invention comprises one or more reagents of formula (I) only as methylene donor reagents, preferably comprising only one reagent of formula (I) as a methylene donor reagent, and even more preferably only R 1 Represents straight or branched C1-C 10 Alkyl, saturated or unsaturated, preferably straight-chain or branched C1-C5 alkyl, saturated or unsaturated, more preferably ethyl of formula (I).

[0079] As highlighted in the experimental section of this paper, when incorporated into rubber compounds, the methylene donor of formula (I) of the crosslinking compositions of the present invention provides unexpected improvements compared to the oxazolidine compound of formula (IA) described in US4361677, for example in terms of better static properties, lower brittleness, higher tear resistance and better comfort in tire applications.

[0080] The crosslinking composition of the present invention contains at least one methylene acceptor reagent.

[0081] In this composition, the at least one methylene acceptor reagent can be any reagent capable of reacting with the methylene donor during vulcanization.

[0082] Specifically, the methylene acceptor reagent can be phenol, substituted phenol, phenolic resin obtained by partial crosslinking of phenol and / or at least one phenol substituted with formaldehyde or other methylene donors, and mixtures thereof, preferably phenolic resin. The phenol can be dihydroxyphenol or polyhydroxyphenol in addition to phenol itself; for example, it can be o-cresol, p-cresol, m-cresol, resorcinol, pyrocatechol, pyrogalactol, fluoroglucinol, and mixtures thereof, but resorcinol and other less sustainable dihydroxyphenols are preferred.

[0083] The phenolic resin in the crosslinking composition of the present invention is a non-self-crosslinking (non-thermosetting) phenolic resin. Unlike thermosetting phenolic resins that can be crosslinked by simple heating, non-self-crosslinking phenolic resins require at least one methylene donor in addition to heating for crosslinking.

[0084] The term "phenolic resin" refers to a series of polymers obtained by the reaction between phenol and formaldehyde or their precursors, which are classified as phenolic varnishes (novolacs) and soluble phenolic resins (resoles) depending on the ratio between the two reactants and the reaction conditions.

[0085] Typically, phenolic varnishes are prepared using an aldehyde:phenol ratio of less than 1 and acid catalysis, while soluble phenolic resins are prepared using an aldehyde:phenol ratio of greater than 1 and base catalysis.

[0086] Besides formaldehyde, other aldehydes can be used to replace formaldehyde or mixed with formaldehyde; among them, acetaldehyde and furfural.

[0087] Suitable phenolic resins as methylene acceptor reagents include, for example, phenolic varnish-type phenolic resins, phenolic varnish-type cresol resins, phenolic varnish-type xylenol resins, phenolic varnish-type resorcinol resins, or resins obtained by modifying these resins with oil. Preferably, the modified resin is modified with rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and / or linolenic acid.

[0088] Preferably, in this invention, a phenolic resin prepared by polymerization of phenol and formaldehyde is used as a methylene acceptor; more preferably, a phenolic varnish is used; and even more preferably, a phenolic varnish having a low content of free monomer (phenol) is used as a methylene acceptor.

[0089] Preferred methylene acceptors include resins sold under names such as Alnovol PN760, Durez 12686, and Elastobond A250.

[0090] In addition, natural products with polyphenolic structures, such as lignin and its derivatives, can also be suitable as methylene acceptors.

[0091] All other things being equal, more sustainable and harmless methylene donors and acceptors are particularly preferred.

[0092] Depending on the intended use of this crosslinking composition, the most suitable phenolic resin can also be selected based on its molecular weight.

[0093] For example, higher molecular weight phenolic resins are preferred in elastomer compositions designed to form the structure of tire components that require greater stiffness and tear resistance, such as bead fillers or sidewall inserts. Typically, these resins have a softening point of 90°C or higher.

[0094] Conversely, lower molecular weight phenolic resins are preferred for use in elastomer compositions intended to cover textiles or metal reinforcing elements, such as carcasses, belt layers, bead wraps, or outer bead wraps. Typically, these resins have a softening point not exceeding 95°C, and preferably even lower.

[0095] The methylene receptor phenolic resin of this crosslinking composition preferably does not include the formula claimed and described in US4361677.

[0096] Vulcanized thermosetting resins and vulcanized phenolic resins.

[0097] Preferably, the methylene acceptor does not contain free phenol, and in particular, it does not contain free resorcinol in significant amounts. Preferably, if it does contain it, it is present in the lowest possible amount, for example, less than 2%. More preferably, it consists only of one or more phenolic resins, which is advantageously less harmful and exhibits better processability in the compound, lower reversal (see MH and RET% in Table 7) and higher tear resistance (Table 15).

[0098] In a more sustainable preferred embodiment, the crosslinking composition according to the invention contains neither free phenols (resorcinol, etc.) nor formaldehyde.

[0099] In a preferred embodiment, the crosslinking composition according to the invention comprises one or more reagents of formula (I) as the sole methylene donor and one or more phenolic resins as the sole methylene acceptor.

[0100] In this embodiment, the weight ratio of the methylene donor of formula (I) to the total amount of one or more phenolic resins is preferably between 1:1 and 1:6, more preferably between 1:1.2 and 1:5.

[0101] In another embodiment, the crosslinking composition according to the invention comprises a reagent of formula (I) as a methylene donor and a mixture of one or more conventional formaldehyde donors (HMMM, HMT, etc.), and comprises one or more phenolic resins as the sole methylene acceptor reagent.

[0102] In this further embodiment, the weight ratio of the total methylene donor reagent to the total amount of one or more phenolic resins is preferably between 1:1.5 and 1:5, more preferably between 1:2 and 1:4.

[0103] In the secondary crosslinking composition according to the invention, at least one methylene donor agent of formula (I) is preferably present in an amount of at least 2 wt%, more preferably at least 3 wt%, based on the total weight of the crosslinking composition.

[0104] In the secondary crosslinking composition according to the invention, at least one methylene donor agent of formula (I) is preferably present in an amount not exceeding 70 wt%, more preferably not exceeding 60 wt%, based on the total weight of the crosslinking composition.

[0105] In the secondary crosslinking composition according to the invention, the methylene donor reagent preferably contains at least 15 wt%, more preferably at least 20 wt% of at least one methylene donor reagent of formula (I).

[0106] Another aspect of the present invention is represented by an elastomer composition comprising the crosslinking composition described above according to the present invention.

[0107] The preferred embodiments of the crosslinking compositions of the present invention, expressed above, are adapted as necessary to elastomer compositions comprising them and all subsequent aspects of the present invention.

[0108] The elastomeric composition according to the invention is characterized by one or more of the following preferred aspects, either individually or in combination with each other.

[0109] The elastomer composition according to the invention comprises at least one diene polymer of at least 100 phr.

[0110] The diene polymer (A) can be selected from those commonly used in sulfur-vulcanizable elastomer compositions, which are particularly suitable for the manufacture of tires, i.e., selected from solid elastomer polymers or copolymers having unsaturated chains, having a glass transition temperature (Tg) generally below 20°C, preferably in the range of 0°C to -110°C.

[0111] 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 dienes, optionally mixed with at least 60 wt% of a comonomer selected from monoolefins, monovinyl aromatic compounds and / or polar comonomers.

[0112] The conjugated diene typically contains 4 to 12, preferably 4 to 8, carbon atoms and is selected from, for example, 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. 1,3-butadiene and isoprene are particularly preferred.

[0113] Monoolefins can be selected from ethylene and α-olefins that typically contain 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or mixtures thereof.

[0114] The monovinyl aromatic compounds optionally used as comonomers typically contain 8 to 20, preferably 8 to 12, carbon atoms, and are selected from, for example: styrene; 1-vinylnaphthalene; 2-vinylnaphthalene; various alkyl, cycloalkyl, aryl, alkylaryl, or arylalkyl derivatives of styrene, such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolyl-styrene, 4-(4-phenylbutyl)styrene, and mixtures thereof. Styrene is particularly preferred.

[0115] The optional polar comonomers may be selected from, for example, vinylpyridine, vinylquinoline, acrylic acid and alkyl acrylates, acrylonitrile or mixtures thereof, such as methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, acrylonitrile and mixtures thereof.

[0116] Preferably, the diene polymer (A) may be selected, for example, from: cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (especially polybutadiene with a high 1,4-cis content), optionally halogenated isoprene / isobutene copolymer, 1,3-butadiene / acrylonitrile copolymer, styrene / 1,3-butadiene copolymer, styrene / isoprene / 1,3-butadiene copolymer, styrene / 1,3-butadiene / acrylonitrile copolymer, and mixtures thereof.

[0117] The compositions of the present invention may optionally comprise at least one polymer of one or more monoolefins and olefinic comonomers or derivatives thereof. Monoolefins may be selected from: ethylene and α-olefins generally containing 3-12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or mixtures thereof. Preferred are copolymers selected from ethylene and α-olefins, optionally with dienes; isobutene homopolymers or copolymers thereof with a small amount of dienes, optionally at least partially halogenated. The dienes optionally present generally contain 4-20 carbon atoms and are preferably selected from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethimide-2-norbornene, 5-methylene-2-norbornene, vinylnorbornene, or mixtures thereof. Among them, the following are particularly preferred: ethylene / propylene (EPR) copolymers or ethylene / propylene / diene (EPDM) copolymers; polyisobutylene; butyl rubber; halogenated butyl rubber, especially chlorobutyl rubber or brominated butyl rubber; and mixtures thereof.

[0118] The elastomer composition according to the invention comprises at least one reinforcing filler (B) of at least 0.1 phr, preferably at least 1 phr.

[0119] This composition may contain at least one reinforcing filler of 1 phr-170 phr, 5 phr-150 phr, or 10 phr-120 phr.

[0120] Preferably, the reinforcing filler is selected from carbon black, white filler, silicate fiber, their derivatives and mixtures thereof.

[0121] In one embodiment, the reinforcing filler comprises carbon black.

[0122] Preferably, carbon black as reinforcing filler (B) is present in the elastomer composition according to the invention in an amount of 1 phr-120 phr, preferably 5 phr-100 phr.

[0123] Preferably, the carbon black is selected from those with a particle size of not less than 20 μm. 2 / g, preferably at least about 40-50m 2 / g specific surface area of ​​carbon black (e.g., determined by STSA-Statistical Thickness Surface Area according to ISO 18852:2005).

[0124] Carbon black can be, for example, N375, N326, N339, N550 or N660 sold by Birla Group (India) or Cabot Corporation.

[0125] In one embodiment, the reinforcing filler is a white filler selected from metal hydroxides, oxides and hydrated oxides, salts and hydrated salts, silica, silicate fibers, their derivatives and mixtures thereof.

[0126] In one embodiment, the reinforcing filler may comprise silica, for example selected from fumed silica, precipitated amorphous silica, wet silica (hydrated silica), anhydrous silica (anhydrous silica), or mixtures thereof.

[0127] Preferably, the silica as a reinforcing filler is present in the elastomer composition according to the invention in an amount of 1 phr-100 phr, more preferably 5 phr-80 phr or 7 phr-50 phr.

[0128] The silica used in this invention may have a silica content of 10 μm. 2 / g-300m 2 / g, preferably 30m 2 / g-250m 2 / g, more preferably 40m 2 / g-190m 2 BET specific surface area within the range of / g (determined according to ISO standard 5794 / 1).

[0129] Commercially available examples of suitable silica include Zeosil 1165MP, Zeosil 1115MP, Zeosil 185GR, Efficium (from Solvay), Newsil HD90 and Newsil HD200 (from Wuxi), K160 and K195 (from Wilmar), H160AT and H180AT (from IQE), Zeopol 8755 and 8745 (from Huber), Perkasil TF100 (from Grace), Hi-Sil EZ 120G, EZ 160G, and EZ 200G (from PPG), and Ultrasil 7000GR and Ultrasil 9100GR (from Evonik). Another example of suitable silica is rice husk silica described in WO2019229692A1.

[0130] In one embodiment, the reinforcing filler comprises a mixture of silica with carbon black and / or silicate fibers.

[0131] The elastomer composition according to the invention comprises at least one vulcanizing agent in the form of 0.1-20 phr.

[0132] The vulcanizing agent is preferably selected from sulfur-based reagents, such as elemental sulfur, polymeric sulfur, sulfur donor reagents such as bis[(trialkoxysilyl)propyl] polysulfide, thiuram, dithiodimorpholine and caprolactam-disulfide, peroxides, such as dialkyl peroxide ROOR, where R is alkyl, alkyl-aryl peroxide ROO-R', where R is alkyl and R' is aryl, diaryl peroxide R'-OO-R', where R' is aryl, diacyl peroxide RC(O)-OO-(O)C-R', where R and R' are aryl and / or alkyl, peroxyketal ROO(R)C(R')-OO-R', where R and R' are aryl and / or alkyl, peroxyester RC(O)-OO-R', where R and R' are aryl and / or alkyl.

[0133] The at least one vulcanizing agent is preferably selected from sulfur, or alternatively, sulfur-based agents containing sulfur molecules (sulfur donors) such as bis(trialkoxysilyl)propyl polysulfides and mixtures thereof. Preferably, the vulcanizing agent is sulfur, and even more preferably selected from soluble sulfur (crystalline sulfur), insoluble sulfur (polymeric sulfur), (iii) oil-dispersible sulfur and mixtures thereof. A commercially available example of a vulcanizing agent suitable for use in the compositions of the present invention is Redball Superfine sulfur from Flexsys.

[0134] Preferably, the elastomer composition according to the invention comprises at least one vulcanizing agent of at least 0.5 phr, 0.8 phr or 1 phr, preferably a sulfur-based vulcanizing agent selected from those mentioned above.

[0135] Even more preferably, the composition contains at least one vulcanizing agent of 0.1-15 phr, 0.2-10 phr, 1-10 phr or 1.5-7 phr, preferably selected from those sulfur-based agents.

[0136] The elastomer composition according to the invention comprises at least 0.05 phr of the crosslinked composition according to the invention.

[0137] Preferably, the elastomer composition according to the invention comprises 0.1-30 phr, more preferably 3-20 phr, of the crosslinked composition according to the invention.

[0138] The methylene donor reagent of formula (I) may be present in the elastomer composition in an amount of 0.5-15 phr, preferably 0.5-8 phr.

[0139] If the methylene donor reagent includes at least one other methylene donor reagent in addition to component (I), it may be present in the elastomer composition in a total amount of preferably 0.5-15 phr or 0.5-8 phr.

[0140] The methylene receptor reagent is preferably present in the elastomer composition in an amount of 0.5-30 phr, more preferably 0.5-20 phr or 0.5-10 phr.

[0141] In a preferred embodiment, the elastomer composition comprises one or more reagents of formula (I) as the sole methylene donor reagent, and comprises one or more phenolic resins as described above as the sole methylene acceptor reagent.

[0142] In a preferred embodiment, the elastomer composition does not contain phenol, especially resorcinol, nor formaldehyde or conventional formaldehyde precursors having a formula other than (I), such as HMMM, HMT, etc.

[0143] The elastomer compositions according to the invention may further contain additives known to those skilled in the art, such as vulcanization activators, accelerators and / or retarders.

[0144] Sulfidation activators that may be included in this composition are zinc compounds, particularly ZnO, ZnCO3, zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms, preferably formed in situ in the composition by the reaction of ZnO with fatty acids, and Bi2O3, PbO, Pb3O4, PbO2, or mixtures thereof. For example, zinc stearate is used, preferably formed in situ in the composition by ZnO and fatty acids, or magnesium stearate formed from MgO, or mixtures thereof. Preferred activators are derived from the reaction of zinc oxide and stearic acid. An example of an activator is Aktiplast ST, a product sold by Rheinchemie.

[0145] In particular, the above-mentioned vulcanization activator may be present in the composition of the present invention in an amount preferably 0.2 phr-15 phr, more preferably 1 phr-5 phr.

[0146] The elastomer composition according to the invention may further contain at least one vulcanization accelerator.

[0147] Commonly used vulcanization accelerators can be selected, for example, from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenylimides, thiurams, amines, xanthates, or mixtures thereof. Preferably, the accelerator is selected from mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole-sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS), and mixtures thereof.

[0148] A commercial example of a suitable accelerator for use in this composition is N-cyclohexyl-2-benzothiazole-sulfenamide Vulkacit, sold by Lanxess. (CBS or CZ), and N-tert-butyl-2-benzothiazole-sulfenamide Vulkacit NZ / EGC.

[0149] In particular, the above-mentioned vulcanization accelerator can be used in this composition in an amount preferably 0.05 phr-10 phr, preferably 0.1 phr-7 phr, more preferably 0.5 phr-5 phr.

[0150] The elastomer composition according to the invention may further contain at least one vulcanization retarder.

[0151] The vulcanization retarder suitable for use in this composition is preferably selected from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthiophthalimide (CTP or PVI), and mixtures thereof. A commercial example of a suitable retarder is Lanxess's N-cyclohexylthiophthalimide VULKALENT G. The vulcanization retarder may be present in this composition in an amount preferably 0.05 phr to 2 phr.

[0152] In one embodiment, typically when silica is present as a reinforcing filler, the elastomer composition according to the invention may further contain at least 0.05 phr, preferably at least 0.1 phr or 0.5 phr, more preferably at least 1 phr or 2 phr of at least one silane coupling agent.

[0153] Preferably, the elastomer composition according to the invention comprises at least one silane coupling agent at a concentration of 0.5 phr to 10.0 phr, more preferably 1.0 phr to 8.0 phr, and even more preferably 3.0 to 8.0 phr.

[0154] Preferably, the silane coupling agent is selected from those having at least one hydrolyzable silane group, which can be identified, for example, by the following general formula (II): (R'')3Si-C n H 2n -X (II) The R'' groups, which may be the same as or different from each other, are selected from alkyl, alkoxy, or aryloxy groups, or from halogen atoms, provided that at least one of the R'' groups is alkoxy or aryloxy; n is an integer from 1 to 6; X is a group selected from the following: nitroso, 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 and the group R'' is as described above.

[0155] Particularly preferred silane coupling agents are bis(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide. These coupling agents can be added as is or mixed with an inert filler (e.g., carbon black) to facilitate their introduction into the elastomer composition.

[0156] An example of a silane coupling agent is TESPT: bis(3-triethoxysilylpropyl)tetrasulfide Si69, sold by Evonik.

[0157] The elastomer composition according to the invention preferably does not contain the formula claimed and described in US4361677.

[0158] Thermosetting and vulcanized phenolic resins.

[0159] Another aspect of the present invention is a vulcanized elastomer composition for vehicle wheel tires, obtained by mixing and vulcanizing the above-described elastomer composition.

[0160] The above-described preferred embodiments of the crosslinking compositions and elastomer compositions of the present invention, with necessary modifications, are applicable to vulcanized elastomer compositions and all subsequent aspects of the present invention.

[0161] The elastomer compound according to the invention can typically be strengthened by reacting a secondary crosslinking system according to the invention during vulcanization, i.e., simultaneously with a conventional primary crosslinking system, the secondary crosslinking system comprising at least one methylene donor reagent and at least one methylene acceptor reagent of formula (I) as defined above, the primary crosslinking system comprising a sulfur-based vulcanizing agent.

[0162] Advantageously, the crosslinking of the adhesive according to the invention is based on, as in Figure 3 The dynamics shown proceed, where a rapid initial step is followed by a plateau with network stabilization and minimal reversal.

[0163] The elastomeric compound according to the invention can be prepared by a method that typically includes one or more mixing steps in one or more suitable mixers, particularly at least one mixing step 1 (non-productive) and mixing step 2 (productive), as described above.

[0164] Each mixing step may include several intermediate processing steps or sub-steps, characterized by a temporary interruption of mixing to allow the addition of one or more components without intermediate discharge of the adhesive.

[0165] For example, an open mixer of the open mill type or a closed mixer of the tangential rotor (Banbury®) or the intermix type (Intermix) can be used, or in Ko-KneaderTM Mixing is performed in a continuous mixer of type (Buss®) or twin-screw or multi-screw type.

[0166] Therefore, after one or more thermomechanical treatment steps (non-productive step 1), the rubber is typically processed with some additives (including methylene acceptor reagents), which, in addition to vulcanizing agents, vulcanization accelerators and retarders, and methylene donor reagents, are introduced into the rubber compound in the next step. In the final treatment step (productive step 2), the temperature is typically maintained below 120°C and preferably below 100°C to prevent any undesirable pre-vulcanization. The rubber compound is then incorporated into one or more components of the tire and subjected to vulcanization, according to known techniques. Advantageously, the elastomeric rubber compound of the present invention is even more processable than similar known compositions.

[0167] Vehicle wheel tire components comprising or substantially composed of vulcanized elastomer compounds according to the invention are selected from the following: tread, underlayer, anti-wear layer, sidewall, sidewall insert, mini sidewall, inner liner, lower inner liner, carcass structure rubberized layer and / or belt layer and / or zero-degree belt layer, annular bead anchoring structure, bead filler, bead reinforcement layer (outer bead wrapping), bead protection layer (bead wrapping), and sheet.

[0168] In one embodiment, the elastomeric compound according to the invention is a compound reinforced by incorporating reinforcing elements of various properties, such as metals or textiles, also known as rubberized compounds.

[0169] Preferably, the elastomeric compound of the present invention is found to be used in reinforced tire components such as belt layer structures, carcass structures, rubber layers, annular bead anchoring structures, bead reinforcement layers (outer bead wrapping), and bead protection layers (bead wrapping).

[0170] Preferably, the reinforcing element is made of one or more textile materials.

[0171] The reinforcing element may be composed of aliphatic polyamide fibers (e.g., nylon 6, nylon 6.6, nylon 4.6, nylon 4.10, nylon 10.10, nylon 11, nylon 12, nylon 6.10, nylon 6.12) or aramid fibers (e.g., aramid), polyester fibers (e.g., polybutylene terephthalate, polyethylene terephthalate, polyethylene isophthalate), polyaryletherketone fibers (e.g., polyetheretherketone), or mixtures thereof. More preferably, the polyester fiber is polyethylene terephthalate (PET) fiber. The reinforcing element may be made of cellulose derivatives such as rayon or lyocell.

[0172] In a preferred embodiment, the reinforcing element is composed of aliphatic polyamide, PET, or a mixture thereof.

[0173] Advantageously, this crosslinking composition gives the elastomer compound of the present invention excellent adhesion to reinforcing elements, as highlighted in Tables 15 to 18.

[0174] In another embodiment, the elastomeric compound according to the invention is used as a constituent compound for tire components that typically bear loads and require a certain stiffness and, in particular, fatigue resistance, for example, as a filler compound for bead or sidewall inserts in self-supporting tires.

[0175] Advantageously, compared to compounds containing only conventional formaldehyde precursor reagents such as HMT or HMMM, the elastomer compounds according to the invention exhibit faster vulcanization kinetics, accompanied by better processability and comparable or superior thermal stability, such as T90, MH, and %RET values ​​(see Tables 6 to 9). Figure 3 As shown in the graph.

[0176] Furthermore, under equivalent static performance, the elastomer compounds of the present invention exhibit comparable or lower hysteresis (see, for example, the Tanδ values ​​in Tables 10 and 12), which predicts comparable or lower rolling resistance in tires and therefore similar or lower consumption.

[0177] Another aspect of the invention is represented by a tire for a vehicle wheel, which includes at least one tire component comprising an elastomeric compound according to the invention or preferably substantially composed of an elastomeric compound according to the invention.

[0178] The term "consistent essentially of elastomer rubber" means that tire components may contain other elements such as textile or metal reinforcement elements in addition to the elastomer rubber according to the invention, but not other elastomer rubbers besides those according to the invention.

[0179] In one embodiment, the tire includes at least one reinforcing tire component comprising an elastomeric compound according to the invention or preferably substantially composed of an elastomeric compound according to the invention, preferably selected from rubberized compounds used for carcass structures, belt layer structures, zero-degree belt layer structures, bead protection (bead wrapping) or reinforcement (outer bead wrapping) layers.

[0180] In one embodiment, the tire includes at least one tire component that is unreinforced (i.e., without reinforcing elements) and generally subjected to fatigue, comprising or preferably substantially composed of an elastomeric compound according to the invention, preferably selected from bead fillers and sidewall inserts.

[0181] The tire according to the invention may include more of the components mentioned above, comprising or preferably consisting essentially of the elastomeric compound according to the invention, for example, it may comprise a combination of one or more components selected from: rubberized compound for the carcass structure, belt layer structure, zero-degree belt layer structure, protective layer (bead wrapping) or reinforcing layer (outer bead wrapping), bead filler and / or sidewall inserts.

[0182] Based on the predictive data shown in the experimental section, tires according to the invention can exhibit lower rolling resistance, better comfort and fatigue resistance, and a longer overall lifespan.

[0183] The tires according to the invention can be tires for two-wheeled, three-wheeled or four-wheeled vehicles, and can be used in summer or winter or in all seasons.

[0184] In one embodiment, the tire according to the invention is a tire for a motorcycle wheel, wherein at least one component comprises or is substantially composed of an elastomeric compound according to the invention. Typically, tires for motorcycle wheels are tires with a straight section, characterized by a high lateral curvature.

[0185] In a preferred embodiment, the tire according to the invention is a tire for the wheels of a sports or racing motorcycle.

[0186] In one embodiment, the tire according to the invention is a tire for automobile wheels.

[0187] In one embodiment, the tire according to the invention is a tire for high-performance vehicles (HP, SUV and UHP), wherein at least one component comprises or is substantially composed of an elastomeric compound according to the invention.

[0188] In one embodiment, the tire according to the invention is a tire for a bicycle wheel. A tire for a bicycle wheel typically comprises a carcass structure surrounding a pair of bead cores at the bead and a crown positioned radially outward relative to the carcass structure.

[0189] The tire according to the present invention can be prepared according to a method comprising the following steps: - A component for manufacturing raw tires on at least one forming drum; - The tire is formed, molded, and vulcanized; At least one component used in manufacturing raw tires includes: - To manufacture at least one raw component comprising or substantially composed of an elastomeric compound according to the invention.

[0190] Proofread to page 26, line 23

[0191] Description of tires according to the present invention

[0192] exist Figure 1 The image shows a radial half-section of a tire for a vehicle wheel according to the invention, which includes at least one component containing the elastomer compound.

[0193] exist Figure 1 In this context, "a" indicates the axial direction, "X" indicates the radial direction, and specifically, XX represents the outline of the equatorial plane. For simplicity, Figure 1 Only a portion of the tire is shown; the remaining portion, not shown, is identical and arranged symmetrically with respect to the equatorial plane “XX”.

[0194] The tire (100) for a four-wheeled vehicle includes at least one carcass structure comprising at least one carcass layer (101) having opposing end flaps that engage with a corresponding annular anchoring structure (102), referred to as a bead core, which is optionally associated with a bead filler (104).

[0195] The tire region containing the bead core (102) and filler (104) forms a bead structure (103) for anchoring the tire to the corresponding mounting rim, not shown.

[0196] The carcass structure is typically radial, meaning that the reinforcing element of at least one carcass ply 101 is located in a plane including the axis of rotation of the tire and substantially perpendicular to the equatorial plane of the tire. The reinforcing element is typically made of textile cords, such as rayon, nylon, or polyester (e.g., polyethylene terephthalate PET or polyethylene naphthalate PEN). Each bead structure is associated with the carcass structure by folding back the opposite sides of at least one carcass ply (101) around the annular anchoring structure (102), thereby forming so-called carcass flaps (101a), as shown below. Figure 1 As shown.

[0197] In one embodiment, a second carcass layer (applied at an axially lateral position relative to the first carcass layer) can be used. Figure 1 (Not shown in the image) to provide the connection between the carcass structure and the bead structure.

[0198] An anti-wear strip (105) optionally made of an elastomeric material is arranged at the outer position of each bead structure (103).

[0199] The carcass structure is associated with a belt layer structure (106), which includes one or more belt layers (106a), (106b) arranged radially overlapping each other and relative to the carcass layer, typically having textile and / or metal reinforcing cords introduced within the elastomeric material layer.

[0200] Such reinforcing cords can have a cross orientation relative to the circumferential direction of the tire (100). The term "circumferential" direction refers to the direction generally facing the direction of tire rotation.

[0201] At least one zero-degree reinforcing layer (106c), commonly referred to as the “0° belt layer”, can be applied at the outermost radial position of the belt layers (106a) and (106b). This layer typically incorporates multiple elongated reinforcing elements, usually metal or textile cords, oriented in a substantially circumferential direction, thus forming an angle of a few degrees (e.g., between about 0° and 6°) with the direction parallel to the tire equatorial plane, and is coated with an elastomeric material.

[0202] A crown (109) is applied at a radially outer position of the belt layer structure (106).

[0203] In addition, the respective sidewalls (108) of the elastomeric material are applied at an axially lateral position on the side surface of the carcass structure, each extending from one side of the tread (109) at the corresponding bead structure (103).

[0204] At a radially outer position, the tread (109) has a rolling surface (109a) designed to contact the ground. A circumferential groove is typically formed on this surface (109a), the circumferential groove being formed by a lateral cut ( Figure 1 (Not shown) are connected to define multiple blocks of various shapes and sizes distributed on the rolling surface (109a), for simplicity. Figure 1 The middle part indicates smoothness.

[0205] A lower layer (111) made of an elastomeric material may be arranged between the belt layer structure (106) and the crown (109), the lower layer preferably extending beyond a surface that substantially corresponds to the extended surface of the belt layer structure.

[0206] Optionally, a strip (110) of elastomeric material, commonly referred to as a "mini sidewall," may be provided in the connection area between the sidewall (108) and the crown (109). This mini sidewall is typically obtained by co-extrusion with the crown (109) and allows for improved mechanical interaction between the crown (109) and the sidewall (108). Preferably, the end portion of the sidewall (108) directly covers the side of the crown (109).

[0207] In the case of tubeless tires, a rubber layer 112, commonly referred to as a "liner", can be provided at a position radially inside the tire carcass layer 101 to provide the airtightness required for tire inflation.

[0208] The stiffness of the tire sidewall 108 can be improved by providing a reinforcing layer 120 (commonly referred to as "outer bead wrap" or additional strip insert) to the bead structure 103.

[0209] The outer bead wrap 120 is a reinforcing layer that is wound around the respective bead core 102 and bead filler 104 to at least partially surround them, the reinforcing layer being disposed between at least one carcass layer 101 and the bead structure 103. Typically, the outer bead wrap is in contact with the at least one carcass layer (101) and the bead structure (103).

[0210] The outer sheath fabric 120 typically comprises multiple textile cords incorporated within an elastomer material layer.

[0211] The reinforcing ring structure or bead (103) of the tire may include a further protective layer, usually known by the term “bead wrap” (121) or protective strip, which has the function of increasing the stiffness and integrity of the bead structure (103).

[0212] The bead wrap (121) typically comprises multiple cords incorporated into a rubber layer of an elastomeric material. Such cords are typically made of textile materials (e.g., aramid or rayon) or metallic materials (e.g., steel cords).

[0213] A layer or sheet of elastomeric material (not shown) can be arranged between the belt layer structure and the carcass structure. This layer can have a uniform thickness. Alternatively, the layer can have a variable thickness in the axial direction. For example, the layer can have a greater thickness near its outer axial edge than in the central (crown) region.

[0214] Advantageously, the layer or sheet can extend on a surface that substantially corresponds to the extended surface of the belt layer structure.

[0215] The elastomeric composition according to the invention can be advantageously incorporated into one or more of the above-described tire components, preferably selected from the carcass (101), bead core (102), bead (104), belt layer (106), outer bead wrap (120), and bead wrap (121).

[0216] The tire according to the invention can be constructed by assembling corresponding semi-finished products of components suitable for forming a tire on a forming drum using at least one assembly device.

[0217] At least a portion of the components for forming the tire carcass structure can be built and / or assembled on the forming drum. More specifically, the forming drum is designed to first receive a possible inner liner, and then the carcass structure. Subsequently, suitable means coaxially engage one of the annular anchoring structures around each end flap, positioning the outer sleeve, which includes the belt layer structure and the tire crown, in a coaxially centered position around the cylindrical carcass sleeve, and shaping the carcass sleeve according to an annular configuration by radial expansion of the carcass structure so that it is applied against the radially inner surface of the outer sleeve.

[0218] After the raw tire is constructed, molding and vulcanization processes are typically performed to determine the structural stabilization of the tire through crosslinking of the vulcanizable elastomer composition, and to impart the desired tread pattern on the tread crown and any distinguishing graphic markings on the sidewall.

[0219] Experimental Section

[0220] Analytical methods

[0221] Rheological analysis (MDR) (according to ISO 6502)

[0222] For this analysis, an Alpha Technologies MDR2000 rheometer was used. Tests were conducted for 30 minutes at 170°C with an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ±0.5°. This measured the time required to achieve an increase of one or two rheological units (TS1, TS2), as well as the time required to achieve 5%, 30%, 60%, 90%, 95%, and 100% (T05, T30, T60, T90, T95, and T100) of the final torque value (Mf). The maximum torque value MH, minimum torque value ML, and reversal (RET%) were also measured.

[0223] Figure 3 The article reports the vulcanization curves of elastomer compositions containing different secondary crosslinking systems.

[0224] According to UNI 6065:2001 standard, static mechanical properties (load at 50% elongation, load at 100% elongation, load at 300% elongation, CR breaking load, AR breaking elongation, and breaking energy) of cyclic elastomer materials vulcanized at 170°C for 10 minutes were measured at 23°C.

[0225] The compressive dynamic mechanical properties E', E'', and Tanδ were measured using an Instron Model 1341 dynamic apparatus in the tension-compression mode described herein. Cylindrical specimens (length = 25 mm; diameter = 14 mm) of vulcanized material were preloaded under compression to a longitudinal deformation of up to 10% relative to their initial length and held at pre-set temperatures of 23 °C, 70 °C, or 100 °C for the entire test duration, subjected to a dynamic sinusoidal stress with an amplitude of ±3.33% relative to the preloaded length and a frequency of 10 Hz. The dynamic mechanical properties are expressed as the dynamic elastic modulus (E'), dynamic viscous modulus (E''), and Tanδ (loss factor). The Tanδ value was calculated as the ratio of the viscous dynamic modulus (E'') to the dynamic elastic modulus (E').

[0226] Peel test: Peel tests are performed by measuring the force (N) required to separate two elastomer samples with identical compositions and co-vulcanized to form an interface region. This test predicts the tear resistance of the finished product. The test is also performed after the samples have undergone a thermal oxidative aging process at 70°C for 48 hours in an oven.

[0227] Tables 15 to 17 show the average detachment force values, expressed in Newtons, involved in tear tests (3 samples for each material).

[0228] Adhesion test (H-test, ASTM D4776): This test measures the force required to pull the cord away from the elastomeric material block of the sample after vulcanization and evaluates the coverage remaining on the cord after traction.

[0229] The sample, vulcanized at 150°C for 30 minutes, contained PET textile cords. The textile cords were previously treated by immersion in an adhesive RFL composition comprising a latex of a styrene-butadiene-vinylpyridine polymer, resorcinol, and formaldehyde, and subsequently heated to approximately 200-250°C for fixation.

[0230] The cords treated in this way are rubberized with a reference or invented rubber compound, the detailed composition of which is described in Table 3 to provide representative samples of the reinforcing structural elements of the tire. Adhesion evaluation was performed on the samples prepared in this way as described herein.

[0231] Table 18 shows the average pull-out force in N and the evaluation of the coating (3 samples for each compound).

[0232] Example

[0233] According to the present invention, elastomer compounds for use in tire carcasses, belt layers, or bead fillers are prepared from the elastomer compositions described in Tables 1 to 5 below for reference or comparison. The reactivity and properties of these compounds are investigated by varying the secondary crosslinking system. Specifically, the properties of elastomer compounds comprising the crosslinking composition (Inv.) according to the present invention, characterized by the presence of a methylene donor agent of formula (I) alone or in combination with a conventional formaldehyde donor, are compared with the properties of known crosslinking systems corresponding to those used in commercial tires or reported in the literature, which contain resorcinol or phenolic resins and conventional formaldehyde donors (HMMM, HMT, etc.), and finally with resorcinol and a methylene donor agent of formula (I) (wherein R...). 1 = Ethyl (as shown in US3256137) or phenolic resin and oxazolidinyl methylene donor reagent of formula (IA) (wherein R 1 =CH2OH, as described in US4361677) (Compare) the crosslinking system.

[0234] Table 1: Elastomer compositions used in tire carcass rubber compounds

[0235] in

[0236] -Resor represents resorcinol, resin represents phenolic resin, and oxaz-inv represents the bisoxazolidine (formula (I)) according to the present invention, wherein R 1 =CH2CH3) and oxaz-comp represents bisoxazolidine (formula (IA)) according to US4361677, where R 1 =CH2OH); - The natural rubber is of type NRP91 (cis-1,4-polyisoprene) SIR 20 (Indonesia); -CB N326 is carbon black from Birla Carbon (300% modulus ASTM D3192 IRB8-ASTM D412 Method B is -3.9±1.8MPa; CTAB: 83m). 2 / g); - Zinc oxide is zinc oxide obtained from metallic zinc through an indirect process from Zincoloxides; - Stearic acid is supplied by Oleon; -6PPD is Santoflex N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine from Flexsys, an anti-ozone agent and antioxidant; -ALNOVOL PN 760 is a modified phenolic resin varnish containing 1% free phenol and 0.1% free formaldehyde, with a softening point between 80-95℃, supplied by Allnex (Germany). -RESORCINOL 80 is a polymer of 80% resorcinol and 20% binder and dispersant, supplied by RDC; -HMMM is 65% hexamethoxymethyl melamine on a large amorphous silica carrier, supplied by Brenntag; -Oxaz-inv is 5-ethyl-1-aza-3,7-dioxabicyclo[3.3.0]octane (CAS No. 7747-35-5) (Formula (I), R 1 =CH2CH3), supplied by Sigma Aldrich; -Oxaz-comp(R 1 =CH2OH) Formula (IA) is prepared as described in US8466294B2.

[0237] -TBBS 80 is an N-tert-butyl-benzothiazolyl sulfenamide (accelerator) from RDC; -Sulfur for Redball Superfine amorphous sulfur, insoluble in carbon disulfide and toluene, is a 33% processed heavy cycloalkane fraction (petroleum) from Flexsys (Germany).

[0238] The composition of Example 1 provides information on the effect of the combination of HMMM and resorcinol, while the composition of Example 2 provides information on the combination of HMMM and Alnovol phenolic resin. These compositions correspond to those used in commercial tires. The composition of Ex.2 represents a reference composition for the compositions of Ex.3 (Inv.) and Ex.4 (Comp.) having the same components, in the same amounts, except for the methylene donor reagent (HMMM relative to bisoxazolidine).

[0239] The composition of Example 3 according to the present invention, on the contrary, relates to a bisoxazolidine of formula (I) (wherein R 1 =Ethyl) combined with phenolic resin Alnovol.

[0240] The composition of Example 4 is a combination of (IA) bisoxazolidine (wherein R 1 A comparative composition of CH2OH (as shown in US4361677) and the phenolic resin Alnovol.

[0241] Table 2: Elastomer compositions used in bead filler compounds

[0242] in

[0243] -CB N375 is 300% modulus carbon black (according to ASTM D3192 IRB8-ASTM D412 Method B) 0.4±1.8MPa, from Birla Carbon; - Zinc salts of fatty acid mixtures (CAS No. 67701-12-6) from Eigemann and Veronelli; -MES oil is a mineral base oil that has been solvent refined and / or hydrotreated (CAS No. 64742-65-0 or 64742-54-7); - tert-butylphenol resin is OFF APM SL1410 resin, which is a resin obtained by condensing p-tert-butylphenol with formaldehyde, from Sino Legend Company; - Phenolic varnish uses DUREZ 12686 phenolic resin, modified with cashew nut shell oil, from Sumitomo Bakelite Europe, and has a softening point between 90°C and 105°C. -HMT 80 is hexamethylenetetramine, 80% methylene donor reagent with 20% polymer binder and RDC dispersant; - The silanizing agent (silane coupling agent) is a 1:1 mixture of bis[3-(triethoxysilyl)propyl]tetrasulfide (CAS No. 40372-72-3) from EVONIK and carbon black N330 (CAS No. 1333-86-4); - The silica is ZEOSIL 1115 MP, precipitated amorphous silica, from Solvay RhodiaOperations; -TBBS is N-tert-butyl-2-benzothiazolyl sulfenamide from Lanxess (CAS No. 95-31-8); -PVI is N-cyclohexylthiophthalimide (CAS No. 17796-82-6) from Shandong Derek New Materials; Furthermore, the natural rubber, stearic acid, zinc oxide, 6PPD, HMMM, and sulfur are the same as those used in Table 1.

[0244] The composition of Example 5 provides information on the effectiveness of combining phenolic resin with HMMM and HMT.

[0245] The elastomer composition according to Example 6 of the invention, instead of having a bisoxazolidine of formula (I), wherein R 1 =Ethyl, replacing HMMM, used in combination with HMT and phenolic resins.

[0246] The comparative composition of Example 7 is the same as that of Example 6 of the present invention, except that it uses bisoxazolidine of formula (IA), wherein R 1 =CH2OH, as shown in US4361677, replacing the bisoxazolidine of formula (I) of the invention, wherein R 1 =Ethyl.

[0247] Table 3: Elastomer compositions used in tire carcass rubber compounds

[0248] The components are the same as those in Table 1.

[0249] In these embodiments, in addition to the reference compositions (Ex. 8 and Ex. 10), in which HMMMM is respectively bound to resorcinol or Alnovol phenolic resin, two compositions according to the invention (Ex. 9 and Ex. 11) were also prepared and compared, in which HMMM is respectively bound to bisoxazolidine (formula (I), R) according to the invention. 1 =CH2CH3) can be used as a substitute, in combination with resorcinol or with the phenolic resin Alnovol.

[0250] Table 4: Elastomer compositions for belt layer rubberized compounds

[0251] in

[0252] - The natural rubber is natural rubber STR 20 (Thailand); -MANOBOND 680 C Rubber-Metal Adhesion Promoter, cobalt / boron salt from Shepherd Ltd; -DCBS is N,N-dicyclohexyl-2-benzothiazole sulfenamide from Huatai Chemicals; and Other components are the same as those reported in Tables 1, 2 or 3.

[0253] In these embodiments, the reference composition of Ex.12 replaces resorcinol with the phenolic resin Alnovol and HMMM. The elastomer composition of Ex.13 according to the invention comprises bisoxazolidine (R) of formula (I). 1 =CH2CH3) was combined with the phenolic resin Alnovol as the sole methylene donor.

[0254] Table 5: Elastomer compositions used in bead filler compounds

[0255] The ingredients are those listed in Table 2.

[0256] In these examples, the reference composition of Ex.14 is similar to the composition in Table 2 above and the composition according to Ex.15 of the present invention (which contains bisoxazolidine of formula (I)). 1 =CH2CH3) replaces HMMM, and is the same as HMT and phenolic resin combination.

[0257] The composition of Ex.16 is an elastomer composition according to the invention, comprising a bisoxazolidine (R) of formula (I). 1 =CH2CH3) replaces HMT, and is combined with HMMM and phenolic resin.

[0258] The compositions of Ex.17 and Ex.18 are compositions according to the invention, wherein conventional crosslinking agents HMMM and HMT (present in Ex.14) are increased in amount of bisoxazolidine of formula (I) (R 1 =CH2CH3) completely substituted, combined with phenolic resin.

[0259] Preparation of elastomer compounds

[0260] Starting with the elastomer compositions shown in Tables 1-5, prepare the corresponding elastomer compounds according to the following process.

[0261] Use an internal mixer (Banbury, Intermix, or Brabender) to mix the components in two steps.

[0262] In the first step (1), all components except the vulcanizing agent, accelerator, and methylene donor reagent are introduced. Mixing continues for a maximum of 5 minutes, reaching a temperature of approximately 145°C. Subsequently, in the second step (2), the vulcanizing agent, accelerator, and methylene donor reagent are added again using an internal mixer, and mixing continues for approximately 4 minutes, maintaining a temperature below 100°C. The raw rubber compound is then discharged. After cooling and at least 12 hours from preparation time, some samples of the rubber compound are vulcanized in a press at 170°C for 10 minutes to obtain specimens for mechanical characterization.

[0263] Characterization of rubber compounds

[0264] MDR rheological analysis

[0265] Some raw elastomer compounds obtained from the elastomer compositions reported in Tables 1 to 5 were subjected to MDR rheological analysis as described above.

[0266] Figure 3The trends in crosslinking kinetics of adhesives comprising conventional resorcinol + HMMM systems (Sample 1, Ex. 1) or phenolic resin + HMMM (Sample 2, Ex. 2) compared to the phenolic resin + oxazolidine (I) system according to the invention (Sample 3, Ex. 3) are shown. As can be seen from the figures, the crosslinking of Sample 3 according to the invention comprises a very steep initial phase like Sample 1, followed by an equilibrium period with a stabilized network and minimal reversal, comparable to Sample 2.

[0267] Tables 6 to 9 below contain the results of rheological analyses performed on various samples: Table 6: MDR Analysis Elastomer compositions for rubberized tire carcass compounds (according to Table 1)

[0268] As demonstrated by the data reported in Table 6, the compound of the present invention in Ex.3 exhibits faster crosslinking kinetics compared to the reference compound in Ex.2 and the comparative compound in Ex.4, with a lower maximum MH torque than both, indicating better processability, and a reduced reversal compared to the conventionally produced compound in Ex.2.

[0269] Table 7: MDR Analysis

[0270] Elastomer compositions for rubberized tire carcass compounds (according to Table 3)

[0271] As demonstrated by the data reported in Table 7, the present invention compound of Ex.9 exhibits faster crosslinking kinetics (approximately -20% at T90) and lower maximum MH torque (approximately -10%) compared to the reference compound of Ex.8, predicting better processability of the compound, as well as minimal reversal increase (approximately +10%) within fully acceptable limits.

[0272] Similar results were obtained for the present invention compound Ex.11 compared to the reference compound Ex.10 (faster kinetics of about -20% on T90 and lower maximum torque of about -5% on MH), and with comparable reversal of about 3%. Both compounds include phenolic resin instead of resorcinol.

[0273] Table 8: MDR Analysis

[0274] Elastomer compositions for use in belt layer rubberized compounds (according to Table 4)

[0275] The data reported in Table 8 demonstrate that, compared with the reference compound of Ex.12, the compound of Ex.13 of the present invention exhibits faster crosslinking kinetics at all T points (approximately -20% at T30, -30% at T60 and -40% at T90) and has a lower maximum MH torque (approximately -20%), predicting better processability of the compound.

[0276] Table 9: MDR Analysis

[0277] Elastomer compositions for use in bead filler compounds (according to Table 5)

[0278] The data reported in Table 9 demonstrate that the compound of the present invention, Ex.15, comprising a combination of phenolic resin, HMT, and oxaz-inv, exhibits similar crosslinking kinetics to the reference compound of Ex.14 at the lowest values ​​of T30 and T60, while an increase in rate is noted for values ​​above T60 (approximately +5% at T90). Furthermore, a slightly higher maximum MH torque (approximately +7%) is observed for the compound of the present invention, which remains acceptable.

[0279] In summary, the MDR analysis data reported in Tables 6 to 9 highlight that the crosslinking kinetics of the rubber compound in which the reagent of formula (I) of the present invention is used are generally faster than those of the reference rubber compound, which is easier to process and has lower or comparable reversal.

[0280] Static and dynamic mechanical properties of the compound

[0281] Tables 10 to 14 below show the analytical results of the mechanical properties of the elastomer compounds prepared from the compositions shown in Tables 1 to 5 according to the above method: Table 10: Static and Dynamic Mechanical Properties of Rubber Compounds Elastomer compositions for tire carcass rubberization (according to Table 1)

[0282] From the static performance data reported in Table 10, it was observed that the elastomeric composition according to the invention in Ex.3 has substantially the same or only slightly worse static performance than the reference in Ex.2.

[0283] Conversely, the comparative composition of Ex.4, containing the bisoxazolidine as described in US4361677, exhibited higher static stiffness and poorer fracture performance compared to the composition of the present invention in Ex.3. Specifically, the lower values ​​of CR, AR% and energy, and the higher value of CA3, indicate that the comparative composition of Ex.4 was worse, more brittle, and had a greater tendency to tear, which was associated with lower fatigue resistance.

[0284] Regarding dynamic performance, the elastomer composition of the present invention in Ex.3 was observed to have a lower dynamic modulus E' than both Ex.2 and Ex.4, indicating greater comfort in tire applications. Furthermore, the hysteresis of the elastomer composition of the present invention in Ex.3 at all temperatures is lower than or approximately comparable to that of Reference Ex.2 and Comparative Ex.4.

[0285] Conversely, the comparative composition of Ex.4 exhibits a higher dynamic modulus at all temperatures compared to the composition of the present invention in Ex.3 and compared to the references in Ex.2 and Ex.1, which foreshadows lower comfort in specific tire applications due to excessive stiffness and poor damping.

[0286] Table 11: Static and Dynamic Mechanical Properties

[0287] Elastomer compositions for use in bead filler compounds (according to Table 2)

[0288] Generally, higher static and dynamic stiffness is desired for bead filler compounds; however, it is important to avoid deterioration of fracture properties and possible crack propagation in the bead.

[0289] As observed from the static performance data reported in Table 11, with reference to the composition of Ex.5, the elastomer composition of the present invention of Ex.6 has higher CR, AR and energy, indicating higher tear resistance.

[0290] Conversely, the comparative composition of Ex.7 exhibits significantly worse fracture properties compared to the elastomer composition of the present invention in Ex.6, indicating poor fatigue resistance.

[0291] Regarding dynamic performance, it is evident that the comparative composition of Ex.7 has a higher E' value at all temperatures compared to the elastomer composition of the present invention in Ex.6, which foreshadows lower tire comfort.

[0292] Table 12: Static and Dynamic Mechanical Properties

[0293] Elastomer compositions used in tire carcass rubber compounds (Table 3)

[0294] As observed from the static performance data given in Table 12, the composition of the present invention containing resorcinol in Ex.9 exhibits similar static stiffness and slightly lower fracture properties compared to the reference material in Ex.8.

[0295] Conversely, the elastomer composition of Ex.11 according to the invention exhibits similar static stiffness and comparable fracture properties when compared with the reference composition of Ex.10, which also contains phenolic resin.

[0296] Regarding dynamic performance, compared with the reference composition of Ex.8, the composition of Ex.9 according to the invention has slightly higher dynamic stiffness (about +5%) at all temperatures and significantly reduced hysteresis (about -20% at 23°C and 70°C, and about -13% at 100°C).

[0297] In contrast, the elastomer composition according to the invention in Ex.11 shows similar dynamic stiffness and low hysteresis (about -12% at 23°C and 70°C, and about -9% at 100°C) at all temperatures compared to the reference composition in Ex.10.

[0298] Table 13: Static and Dynamic Mechanical Properties

[0299] Elastomer compositions for use in belt layer rubberized compounds (according to Table 4)

[0300] From the static performance data given in Table 13, it was observed that the composition according to the invention in Ex.13 exhibits lower static stiffness (Ca3 about -20%) and similar fracture properties compared to the reference composition in Ex.12. Regarding dynamic performance, the composition according to the invention in Ex.13 exhibits lower dynamic modulus and significantly reduced hysteresis compared to the reference composition in Ex.12, resulting in improved fatigue resistance and reduced rolling resistance.

[0301] Table 14: Static and Dynamic Mechanical Properties

[0302] Elastomer compositions for use in bead filler compounds (according to Table 5)

[0303] From the static performance data given in Table 14, it is observed that the composition according to the invention in Ex.15 exhibits similar static stiffness and comparable fracture properties compared to the reference in Ex.14.

[0304] Similarly, regarding dynamic performance, the composition of Ex.15 according to the invention exhibits similar dynamic modulus and hysteresis compared to the reference composition of Ex.14.

[0305] Peel test

[0306] The elastomer compounds reported above underwent the aforementioned peel test, and the results are shown in Tables 15 to 17 below: Table 15: Peel test at 100℃ Rubberized compound for tire carcass (according to Table 1)

[0307] The data reported in Table 15 show that the rubberized compound of Ex.3 according to the invention, which contains phenolic resin and oxa-inv, exhibits a peel force value that is only slightly lower than that of the reference compound of Ex.2, and much higher than that of the reference composition of Ex.1 used in production, indicating high material properties, in terms of tear resistance and reduced crack propagation.

[0308] Conversely, the comparative composition Ex.4, containing bisoxazolidine (IA) as described in US4361677, exhibited significantly lower peel force values ​​than all other samples, effectively offsetting the improved adhesion gained by replacing resorcinol with the phenolic resin Alnovol (see Increase in peel force by changing from the resorcinol-containing composition of Ex.1 to the Alnovol-containing composition of Ex.2). Such low peel forces as Ex.4 suggest that the compound is more prone to tearing and has less resistance to crack propagation.

[0309] As from Figure 2 The graph shows the trend of peel force (N) of various samples as deformation increases (mm on the horizontal axis). The curve of the adhesive (Ex.3) according to the invention is consistent with the curve of the reference composition of Ex.2, which contains a conventional methylene donor in addition to phenolic resin. The curve of the composition of Ex.4, which contains oxazolidine (IA) as a donor, has a similar trend to the reference in Ex.1, and has much worse adhesion properties.

[0310] Table 16: Peel test at 100°C

[0311] Rubberized compound for tire carcass (according to Table 3)

[0312] The data reported in Table 16 appear to suggest that both resorcinol and formaldehyde in the secondary crosslinking composition can be successfully replaced with more sustainable products while maintaining performance. Indeed, the peel strength value of the compound according to the invention in Ex.11, although lower than that of the composition in Ex.10, is still acceptable and consistent with the performance of the reference production compound in Ex.8.

[0313] Table 17: Peel test at 100°C

[0314] Layered rubberized composition (according to Table 4)

[0315] The data reported in Table 17 show that the ex-13 compound according to the invention unexpectedly exhibits an increase in peel strength compared to the reference ex-12 compound which includes phenolic resin and HMMM.

[0316] In summary, comparative experimental data between the secondary crosslinking system of the present invention, comprising an oxazolidinyl agent of formula (I), and a comparative crosslinking system suggested by document US4361677, which in turn comprises an oxazolidinyl agent of formula (IA), demonstrates the obvious and unexpected advantages of the material of the present invention, for example, in terms of better static properties and lower brittleness (lower CA3, Table 10; higher CR and AR, Tables 10 and 11), higher tear resistance (Table 15), higher comfort (lower dynamic modulus, Table 10), and lower hysteresis (Table 10).

[0317] Adhesion test of textile reinforcement materials

[0318] The rubberized carcass compounds of the present invention and the reference carcass prepared from the compositions shown in Table 3 were subjected to the adhesion tests described above using PET fiber textile materials.

[0319] Table 18 below shows the results of the experiment.

[0320] Table 18: Adhesion Test (T = 23℃)

[0321] Tire carcass rubberization composition (according to Table 3)

[0322] in

[0323] PET is PET 1672 F105 polyethylene terephthalate fiber from HYOSUNG VN; Coverage refers to the visual assessment of the amount of rubber material that still covers the stringer after it has been pulled.

[0324] The data reported in Table 18 show that the adhesive compound of Ex.11 according to the invention exhibits better adhesion to PET cords compared to the reference compound of Ex.10.

[0325] In summary, the experimental data reported above demonstrate that the crosslinking composition according to the present invention, which contains at least one methylene acceptor agent such as resorcinol, or preferably at least one phenolic resin and at least one methylene donor agent of formula (I), when incorporated into tire elastomer compositions, can impart optimal stiffness, tensile strength and adhesion to reinforcing elements to the material, improve crosslinking kinetics and processability, while maintaining or even reducing hysteresis compared to known secondary crosslinking systems.

[0326] The elastomeric material according to the invention comprises the crosslinking system of the invention, which is less harmful than conventional ones and characterized by the aforementioned properties, and is advantageously used in tire components that require a certain degree of stiffness and fracture resistance (e.g., bead fillers, sidewall inserts) and / or high adhesion to textiles or reinforcing elements (e.g., carcass, belt layer, bead protection (bead wrapping) or reinforcement (outer bead wrapping) layer).

Claims

1. A crosslinking composition for use in elastomer compounds, comprising at least one methylene donor agent of formula (I). (I) Where R 1 Represents H, linear or branched C1-C 20 Alkyl, straight-chain or branched C1-C 20 The alkenyl group, wherein the alkyl and alkenyl groups are optionally substituted with one or more oxygen atoms in the chain. And at least one methylene receptor reagent.

2. The crosslinking composition according to claim 1, wherein R 1 Represents straight or branched C1-C 10 Alkyl, straight-chain or branched C1-C 10 Alkenyl, preferably straight-chain or branched C1-C5 alkyl, straight-chain or branched C1-C5 alkenyl, more preferably R 1 It represents the ethyl group.

3. The crosslinking composition according to claim 1 or 2 further comprises at least one other methylene donor agent selected from hexamethoxymethylmelamine (HMM), hexamethylenetetramine (HMT), hexahydroxymethylmelamine, N,N'-dimethylurea, N-hydroxymethyldicyandiamide, N-allyl dioxazine, N-phenyl dioxazine, N-hydroxymethylacetamide, N-hydroxymethylbutyramide, N-hydroxymethylacrylamide, N-hydroxymethylsuccinimide, dodecyloxymethylpyridinium chloride, ethoxymethylpyridinium chloride, trioxane hexamethoxymethylmelamine, hexahydroxymethylmelamine pentamethyl ether (HMPE), oxazolidine derivatives of formula (I), and mixtures thereof.

4. The crosslinking composition according to any one of the preceding claims, wherein the methylene acceptor reagent is selected from phenols, substituted phenols, phenolic resins obtained by partially crosslinking phenols and / or at least one substituted phenol with formaldehyde and / or other methylene donor reagents, and mixtures thereof.

5. The crosslinking composition according to claim 1 or 2, comprising one or more reagents of formula (I) as the sole methylene donor reagent and comprising one or more phenolic resins as the sole methylene acceptor reagent.

6. An elastomer composition comprising at least: At least one diene polymer with a phr of -100 phr - At least one reinforcing filler with a phr of at least 0.1 phr A vulcanizing agent of -0.1 to 20 phr, and - At least 0.05 phr of the crosslinked composition according to any one of claims 1 to 5.

7. The elastomer composition according to claim 6, wherein: - The reinforcing filler is present in an amount of at least 1 phr. - The vulcanizing agent is a sulfur-based reagent and is present in an amount of at least 0.5 phr. - The crosslinking composition is present in an amount of 0.1 phr to 30 phr.

8. A vulcanized elastomer compound for use in vehicle wheels and tires, obtained by mixing and vulcanizing the elastomer composition according to claim 6 or 7.

9. A vehicle wheel tire comprising at least one tire component comprising the vulcanized elastomer compound according to claim 8.

10. The tire according to claim 9, wherein the tire component is selected from the tread, underlayer, anti-wear layer, sidewall, sidewall insert, mini sidewall, inner liner, lower inner liner, carcass structure rubberized layer, belt layer, zero-degree belt layer, annular bead anchoring structure, bead filler, bead reinforcement layer (outer bead wrapping), bead protection layer (bead wrapping), and sheet material.

11. The tire according to claim 9 or 10, wherein the tire component comprises a reinforcing element, preferably made of aliphatic polyamide, polyethylene terephthalate, or a mixture thereof.

12. The self-supporting tire of claim 9, comprising the vulcanized elastomer compound at least in the sidewall insert.

13. Tires for use in high-performance passenger vehicles (HP, SUV and UHP) according to any one of claims 9 to 12.

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