Elastomeric composition comprising a novel secondary crosslinking system, elastomeric composite and tire comprising the elastomeric composite

Abstract

This invention relates to elastomer compositions, elastomer compounds for tires, and vehicle wheel tires comprising said elastomer compounds, said elastomer compositions comprising a novel secondary crosslinking system comprising at least one methylene donor reagent having general formula (I) and at least one phenolic resin as a methylene acceptor reagent, wherein R1 is ethyl. The novel secondary crosslinking system of this invention allows for the imparting of optimal stiffness, thermal stability, tensile strength, and adhesion to reinforcing elements to materials, thereby improving the crosslinking kinetics and processability of the compound, while reducing or maintaining hysteresis. These materials comprising such crosslinking systems are less harmful than conventional crosslinking systems because they do not contain resorcinol, formaldehyde, and similar substances, and are therefore advantageously suited for tire components requiring a certain stiffness and tensile strength and / or high adhesion to fabric or metal reinforcing elements and low rolling resistance. (I)

Description

Technical Field

[0001] This invention relates to a novel secondary crosslinking system for elastomer complexes, comprising, in addition to a resin acting as a methylene acceptor, at least one specific methylene donor having a bisoxazolidine structure. The invention also relates to elastomer compositions for tires comprising the said secondary crosslinking system, elastomer complexes obtained by crosslinking the elastomer compositions, and tire components comprising the said elastomer complexes and tires for vehicle wheels. Background Technology

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

[0003] Specifically, in the so-called vulcanization step, sulfur crosslinking occurs upon heating, and sulfur groups are formed. Through vulcanization, a material that is elastic and does not easily swell is obtained.

[0004] Sulfur crosslinking can affect the hardness, elasticity, and hysteresis of elastomer materials, thereby affecting the performance and behavior of tires incorporating such elastomer materials.

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

[0006] However, sulfur has poor solubility in elastomer composites, and the mild mixing conditions used for sulfur blending often result in suboptimal sulfur dispersion. Consequently, due to the uneven distribution of sulfur, the final material may not exhibit the desired properties; for example, it may be characterized by significant hysteresis, indicating increased heat dissipation under dynamic conditions. Increased hysteresis in tire elastomer materials can be detrimental because it is associated with increased rolling resistance during road use, thus increasing vehicle fuel consumption—a stark contrast to the current automotive industry trend of minimizing fuel consumption.

[0007] Over the years, various additives have been proposed to improve crosslinking processes, such as vulcanization activators, accelerators, and retarders. However, despite the use of additives, sulfur-based single-crosslinking systems often fail to yield satisfactory results. In fact, the main lattice based on the sulfur bonds formed during the vulcanization step does not always provide sufficient reinforcement for the composite because these bonds are reversible and break (reverse) at high temperatures. Due to this thermal instability, the mechanical properties of the tire, especially under stress, can deteriorate.

[0008] This problem has been solved by introducing secondary crosslinking systems with higher thermal stability into the elastomer composite. These secondary crosslinking systems can compensate for the breaking of sulfur bonds in the main lattice and impart rigidity and resistance to the material. The enhanced stiffness and tear resistance may be particularly beneficial for certain tire components that are typically subjected to loads, such as bead or sidewall inserts in self-supporting tires.

[0009] However, the excessive increase in viscosity can lead to processing problems in the composite due to the use of a secondary crosslinking system. Excessive viscosity can make the components of the composite difficult to mix and process; furthermore, it can impair the uniform dispersion of additives and hinder complete crosslinking, resulting in defects in the final material, such as mechanical property deficiencies, and increasing costs and production time.

[0010] One of the secondary crosslinking systems typically used for this purpose includes phenols (such as resorcinol) and methylene donors (such as formaldehyde), which can react with phenols to form crosslinks.

[0011] The cross-linking system based on resorcinol and formaldehyde in latex (called the RFL system) is also widely used as an adhesive to adhere reinforcing elements in the reinforcing structural elements of tires to the rubber.

[0012] In tires used for vehicle wheels, reinforcing structural elements, including reinforcing components, perform various functions, including structural, containment, and protective functions. To ensure the integrity of reinforcing structural components, one characteristic that needs to be checked is that the reinforcing elements are firmly adhered to the elastomeric material in which they are incorporated, 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 structural layers, belt layers, protective layers (bead wrapping), or reinforcing layers (such as bead wrapping) can typically be metallic or non-metallic fabric materials.

[0014] Typically, metal reinforcement elements are made using one or more carbon steel wires. The carbon steel wires and / or cords are usually coated with a layer of brass to increase adhesion to the elastomer composite and protect the rope from corrosion.

[0015] Based on carbon content and breaking strength, the following types of metal wires can be distinguished: -NT (ordinary tensile steel) wire has a tensile strength at break of 2800±200MPa. For example, for a wire diameter of 0.28mm, its tensile strength at break is at least 2700MPa. -HT (high tensile strength) steel wire has a tensile strength at break of 3200±200MPa. For example, for a steel wire diameter of 0.28mm, its tensile strength at break is at least 3100MPa. -ST (ultra-high tensile strength) steel wire has a tensile strength at break of 3500±200MPa; for example, for a steel wire with a diameter of 0.28mm, its tensile strength at break is at least 3400MPa. -UT (Extremely High Tensile Strength) steel wire has a tensile strength at break of 3900±200MPa; for example, for a wire diameter of 0.28mm, its tensile strength at break is at least 3800MPa.

[0016] The most commonly used non-metallic materials for tire reinforcement components can be naturally derived polymer fibers (such as rayon and lyocell) or synthetic fibers (such as aliphatic polyamides (nylon), polyesters, and aromatic polyamides (often called aramid)). The choice of these materials depends on the tire component in which they are blended, the tire type (for two-wheeled or four-wheeled vehicles, for heavy-duty vehicles), and the desired performance requirements (such as HP (high performance), UHP (ultra-high performance), racing, on-road, or off-road).

[0017] RFL-based adhesive compositions are typically applied to fabric cords via impregnation. The treated cords can then be incorporated into an elastomer matrix for subsequent assembly with other semi-finished products during the construction of green tires, which are subsequently shaped, molded, and vulcanized. Generally, to further enhance adhesion between the reinforcing element and the rubber, adhesion-promoting additives can be introduced into the rubberized elastomer compound. These additives comprise 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 strengths, which can vary depending on factors such as the type of compound used, the accelerator, the fiber, and its treatment.

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

[0019] In order to significantly reduce the use of free resorcinol in various steps of tire manufacturing, phenolic resins such as Alnovol have been used as methylene acceptors. Since the phenolic components are at least partially cross-linked, such resins are generally less harmful.

[0020] In the case of these phenolic resins included in the secondary crosslinking system, the crosslinking that usually occurs during the compound vulcanization step still requires the addition of at least one methylene donor (such as formaldehyde), or preferably a less harmful donor selected from conventional formaldehyde precursors, such as hexamethoxymethyl melamine (HMMM), hexamethylenetetramine (HMT), etc.

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

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

[0023] In this regard, some literature, such as EP2316881A1, JP5448445B2, JP5317477B2, and JP2010150502A, mentions in general terms, the use of oxazolidine in combination with phenolic resins in secondary crosslinking systems of elastomeric composites used for bead or sidewall inserts in self-supporting tires, in addition to other methylene donors. However, these documents typically do not show any specific oxazolidine or provide experimental examples of them; instead, they tend to use conventional formaldehyde precursor reagents such as HMT and HMMM.

[0024] US Patent 4361677 describes an elastomer compound for tires (particularly for bead fillers) comprising, in addition to conventional elastomers, specific thermosetting and vulcanized vulcanized phenolic resins, thermosetting phenolic resins, and a curing agent for curing these resins. The curing agent may, among other things, include a bisoxazolidine reagent of general formula (IA).

[0025] (IA)

[0026] It can be mixed with another suitable methylene donor, preferably selected from hexamethylenetetramine (HMT), polyfunctional derivatives of methyl melamine, oxazolidine and its derivatives, bis(1,3-oxazolidine and its derivatives).

[0027] This document does not recommend using these composites as rubberized compounds for use as metal or fabric reinforcing elements, nor does it provide any information regarding the hysteresis, crosslinking kinetics, or thermal stability of the crosslinked elastomer materials. In the exemplary compounds, a conventional methylene donor (HMMT) is always present, either alone or optionally mixed with the composite (IA). The document neither mentions nor exemplifies ethyl-substituted bisoxazolidine methylene donors.

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

[0029] For example, US3256137A relates to an elastomeric composite that improves adhesion to fabric materials, the elastomeric composite comprising a secondary crosslinking system consisting of at least one bisoxazolidine methylene donor and at least one methylene acceptor. This document does not exemplify composites comprising ethyl-substituted oxazolidine methylene donors combined with phenolic resins. This document reports the performance of certain composites in adhesive tests on rayon and nylon cords after crosslinking, but provides no indication of their crosslinking kinetics, processability, or network stability (reversal), nor does it evaluate their static and dynamic mechanical properties.

[0030] Document GB1112007A addresses the adhesion between polyester fabric materials and rubber, and generally describes elastomer composites comprising a secondary crosslinking system consisting of at least one methylene donor (including a bisoxazolidine structure) and at least one methylene acceptor. This document does not exemplify composites including ethyl-substituted bisoxazolidine methylene donors or phenolic resins, nor does it exemplify combinations of both. The document reports the performance of certain composites 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 a reinforced elastomer composition and composite comprising a bisoxazolidine methylene donor, a methylene acceptor, and discontinuous aramid fibers. This document does not exemplify composites comprising ethyl-substituted bisoxazolidine methylene donors or phenolic resins, nor does it exemplify combinations thereof. This document reports the mechanical properties of certain composites comprising aramid, polyester, nylon, rayon, or glass sheets after crosslinking, but provides no information regarding their crosslinking kinetics, processability, network stability (reversal), or hysteresis. Summary of the Invention

[0032] Given the existing technology, the applicant believes there is a need for a more harmless secondary crosslinking system, namely, one with low or preferably no resorcinol and formaldehyde content, exhibiting sufficiently rapid crosslinking kinetics when incorporated into an elastomer composite, producing a nearly irreversible thermally stable network, being easily processable, and providing the material with appropriate rigidity and high fracture resistance for use in tire components subjected to particularly high stresses. Simultaneously, this system should not increase or may decrease its hysteresis to curb rolling resistance and thus reduce consumption. Furthermore, ideally, the secondary crosslinking system should also provide high adhesion between the elastomer composite and the reinforcing elements incorporated therein. Meeting all these requirements and reconciling certain contradictory properties in a single material appears extremely difficult.

[0033] The applicant has conducted research to identify thermally stable and more sustainable secondary crosslinking systems that can impart stiffness, good processability, and high adhesion to reinforcing elements to the tire's elastomer compound, with the aim of producing tires with better performance, structural resistance even under stress conditions, and potentially controlled consumption.

[0034] The applicant has surprisingly discovered that the aforementioned objectives can be achieved through a novel secondary crosslinking system comprising a specific methylene donor reagent and a phenolic resin as a methylene acceptor reagent, wherein the methylene donor reagent can partially or completely replace formaldehyde and conventional formaldehyde precursor reagents (HMMM, HMT, etc.). In its research, the applicant has found that this novel system is particularly effective as a secondary crosslinking agent for elastomers. Crosslinked elastomer composites can be advantageously used as constituent composites for tire components requiring stiffness and fatigue resistance (e.g., beads, sidewall inserts, sidewalls, etc.) and / or requiring high adhesion to reinforcing elements (e.g., carcass, belts, rubberized composites of annular bead anchoring elements, bead protector-bead wrapping, or reinforcing layer-steel wire bead wrapping). Compared to known crosslinkers, the elastomer composites of the present invention, including the novel crosslinking system, also exhibit better processability, favorable crosslinking kinetics, higher initial crosslinking rates and comparable or reduced reversibility, and ultimately, comparable or even lower hysteresis.

[0035] Therefore, a first aspect of the present invention is a crosslinking composition for an elastomer complex, said crosslinking composition comprising at least one methylene donor reagent having general formula (I).

[0036] (I)

[0037] Among them, R 1 Represents ethyl, And at least one phenolic resin obtained by partially crosslinking phenol and / or at least one substituted phenol with formaldehyde and / or other methylene donors and mixtures thereof, as a methylene acceptor reagent.

[0038] Another aspect of the present invention is 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; Vulcanizing agents ranging from -0.1 phr to 20 phr; and - At least 0.05 phr of the crosslinked composition according to the invention.

[0039] Another aspect of the present invention is a vulcanized elastomer compound for tires used in vehicle wheels, said vulcanized elastomer compound being obtained by mixing and vulcanizing the elastomer composition of the present invention.

[0040] Another aspect of the invention is a tire for a vehicle wheel, the tire comprising at least one tire component comprising a vulcanized elastomer compound according to the invention.

[0041] definition

[0042] The term "crosslinked system or composition" refers to a composition that can transform natural or synthetic rubber into an elastic and resistant material by forming a three-dimensional network of intermolecular and intramolecular bonds.

[0043] The term "vulcanizing 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 RC(O)-OO-(O)C-R', where R and R' are aryl and / or alkyl; peroxyketal R–O–O–(R)C(R')–O–O–R', where R and R' are aryl and / or alkyl; peroxide ester R–C(O)–O–O–R', where R and R' are aryl and / or alkyl), metal oxides (such as zinc oxide), quinones, resins and organic bases. The vulcanizing agent is responsible for the primary crosslinking or vulcanization of the elastomer composite.

[0044] The term "methylene donor reagent" refers to an organic complex precursor of formaldehyde or formaldehyde that may at least partially decompose under normal sulfidation conditions, releasing formaldehyde in situ. Methylene donor reagents are capable of reacting with methylene acceptor reagents, typically forming a lattice and becoming wholly or partially bound within it.

[0045] The terms “conventional formaldehyde or methylene donor or conventional formaldehyde precursor reagent” and similar reagents are intended herein to refer to an organic complex that releases formaldehyde in situ upon heating, such as: paraformaldehyde, hexamethylenetetramine (HMT), hexamethoxymethylmelamine (HMMM), hexahydroxymethylmelamine, N,N'-dihydroxymethylurea, N-hydroxymethyldicyandiamide, N-allyl dioxazine, N-phenyl dioxazine, N-hydroxymethylacetamide, N-hydroxymethylbutyramide, N-hydroxymethylacrylamide, N-hydroxymethylsuccinimide, chlorolaurooxymethylpyridine, chloroethoxymethylpyridine, trioxane hexamethyl etherified melamine, hexahydroxymethylmelamine pentamethyl ether (HMPE), and known oxazolidinyl derivatives other than the complex shown in formula (I).

[0046] The term "methylene acceptor reagent" refers to an aromatic organic complex that can react with a methylene donor reagent via an aromatic electrophilic substitution reaction to form a crystal lattice. Typical methylene acceptor reagents are phenols and phenolic resins.

[0047] The term "elastomer composition for tires" refers to a composition comprising at least one diene polymer and one or more additives, which, through mixing and generally heating, provides an elastomeric compound suitable for vehicle wheel tires and their components.

[0048] The components of the composition are typically not introduced into the mixer simultaneously, but rather added sequentially. In particular, vulcanizing additives (such as vulcanizing agents) and optional accelerators and retarders are typically added in downstream steps of blending and processing of all other components.

[0049] In the final composite, due to interactions with other components (thermal and / or mechanical processing), the individual components of the elastomer composition may be altered or no longer individually traceable due to complete or partial modification.

[0050] The term "elastomer complex" refers to a complex that can be obtained by mixing at least one diene polymer with at least one of the additives commonly used in the preparation of tire complexes.

[0051] The term "vulcanizable elastomer complex" refers to a complex obtained by mixing at least one diene polymer with at least one vulcanizing agent.

[0052] The term "vulcanized elastomer compound" refers to materials that can be obtained by vulcanizing vulcanizable elastomer compounds.

[0053] The term "raw tire" refers to materials, compounds, compositions, parts, or tires that have not yet been vulcanized.

[0054] The term "crosslinking" refers to the reaction that forms a three-dimensional lattice of intermolecular and intramolecular bonds in natural or synthetic rubber.

[0055] The term "vulcanization" refers to the cross-linking reaction in natural or synthetic rubber caused by typical sulfur-based vulcanizing agents.

[0056] The term "vulcanization accelerator" refers to a complex that can shorten the duration of the vulcanization process and / or reduce the operating temperature, such as TBBS, general sulfonamides, thiazoles, dithiophosphates, dithiocarbamates, guanidines, and sulfur donors such as thiuram.

[0057] The term "vulcanization activator" refers to a product that can further promote vulcanization, enabling it to be completed in a shorter time and possibly at a lower temperature. An example of an activator is the stearic acid-zinc oxide system.

[0058] The term "vulcanization retardant" refers to a product that can delay the onset of vulcanization and / or inhibit undesirable secondary reactions, such as N-(cyclohexylthio)phthalimide (CTP).

[0059] The term "vulcanizing package" refers to a vulcanizing agent and one or more vulcanizing additives selected from vulcanizing activators, accelerators and retarders.

[0060] The term "single crosslinking system" or vulcanization system refers to a crosslinking system in which the vulcanizing agent is usually sulfur-based.

[0061] The term "secondary cross-linking system" refers to a cross-linking system that includes at least one methylene donor reagent and at least one methylene acceptor reagent in addition to a primary cross-linking system.

[0062] The term "elastomer 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, upon removal of the tensile load, substantially immediately returns to approximately its original length under force (as defined in the standard terminology relating to rubber in ASTM D1566-11).

[0063] The term "diene polymer" refers to a polymer formed by polymerizing one or more monomers (at least one of which is a conjugated diene). This diene polymer can be converted into an elastomer polymer and acquires its characteristic properties upon vulcanization.

[0064] The term "reinforcing filler" refers to reinforcing materials commonly used to improve the mechanical properties of tire rubber, preferably selected from carbon black, conventional silica (such as silica derived from sand precipitated with strong acid, preferably amorphous silica), diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and their derivatives and mixtures.

[0065] The term "white filler" refers to reinforcing materials selected from conventional silica and silicates, such as sepiolite, palygorskite (also known as attapulgite), montmorillonite, halloysite, and the like, which may be modified by acid treatment and / or derivatization. Typically, white fillers have surface hydroxyl groups.

[0066] The term "mixing step (1)" refers to a step in the preparation process of an elastomer composite in which one or more additives other than the vulcanizing agent supplied in step (2) are incorporated by mixing and optionally heating. Mixing step (1) is also referred to as a "non-productive step". In the preparation of the composite, there may be several "non-productive" mixing steps, which can be represented by 1a, 1b, etc.

[0067] The term “mixing step (2)” refers to the next step in the preparation process of the elastomer compound, in which a vulcanizing agent, along with optionally other additives from the vulcanizing package, is introduced into the elastomer compound obtained in step (1) and mixed in the material at a controlled temperature (typically at a compound temperature below 120°C) to provide a vulcanizable elastomer compound. Mixing step (2) is also referred to as the “production step”.

[0068] For the purposes of this specification and the following claims, the term "phr" (abbreviation for parts per hundred parts of rubber) means the number of weight parts of a given elastomeric compound component in 100 parts by weight of polymer, excluding any plasticizing extension oil. Unless otherwise stated, all percentages are expressed as weight percentages. Attached Figure Description

[0069] Please refer to the attached diagram: - Figure 1 A tire for a vehicle wheel is shown, the tire comprising at least one component containing an elastomeric compound according to the invention.

[0070] - Figure 2 The trend of tensile force (Newtons, ordinate) as deformation (mm, abscissa) increases is shown in the case of reference carcass rubberized compounds (Example 1 and Example 2) according to the present invention (Example 3) and comparative examples (Example 4).

[0071] - Figure 3 The crosslinking kinetics trends (MDR analysis) of complexes including conventional resorcinol + HMMM system (sample 1, example 1) or phenolic resin + HMMM system (sample 2, example 2) are shown compared with the phenolic resin + oxazolidine (I) system (sample 3, example 3) according to the present invention. Detailed Implementation

[0072] The crosslinking composition according to the invention is characterized by having one or more of the following preferred aspects, either individually or in combination thereof.

[0073] The crosslinking composition according to the invention comprises at least one methylene donor having the general formula (I).

[0074] (I)

[0075] R1 represents ethyl.

[0076] The methylene donor reagent having general formula (I) can be a commercially available product, such as 5-ethyl-1-aza-3,7-dioxabicyclo[3.3.0]octane purchased from Aldrich, or it can be synthesized from known reagents according to the methods described in the literature (e.g., US3256137 and the literature cited therein).

[0077] In one embodiment, the crosslinking composition of the present invention, in addition to including a methylene donor reagent having general formula (I), may also include at least one other conventional methylene donor reagent, said conventional methylene donor reagent being selected from, but not limited to: formaldehyde, paraformaldehyde, preferably hexamethoxymethyl melamine (HMMM), hexamethylenetetramine (HMT), hexahydroxymethyl melamine, N,N'-dihydroxymethylurea, N-hydroxymethyl dicyandiamide, N-allyl dioxazine, N-phenyl dioxazine, N-hydroxymethyl ... Methylacetamide, N-hydroxymethylbutyramide, N-hydroxymethylacrylamide, N-hydroxymethylsuccinimide, chlorolaurooxymethylpyridine, chloroethoxymethylpyridine, trioxymethylene, hexamethoxymethylmelamine (as described in US3751331), hexamethoxymethylmelamine pentamethyl ether (HMPE), oxazolidine derivatives other than those having general formula (I) and mixtures thereof, more preferably selected from hexamethylenetetramine (HMT), hexamethoxymethylmelamine (HMMM) and mixtures thereof.

[0078] In one embodiment, the crosslinking composition of the present invention comprises a reagent having general formula (1) as a methylene donor reagent, wherein R1 is an ethyl group, which is mixed with hexamethylenetetramine (HMT) and / or hexamethoxymethyl melamine (HMMM).

[0079] Preferably, in the case where the methylene donor reagent comprises a mixture of donors, the weight ratio between at least one reagent having general formula (I) and at least one other conventional methylene donor reagent having a general formula different from general formula (1) is generally between 1:1 and 1:6, preferably between 1:1 and 1:3.

[0080] In a preferred embodiment, the crosslinking composition of the present invention comprises a reagent having only the general formula (I) as a methylene donor reagent, wherein R1 represents an ethyl group.

[0081] As highlighted in this experimental section, the methylene donor of the crosslinking composition of the present invention, having general formula (I), provides unexpected improvements when incorporated into the composite compared to the oxazolidine compounds having general formula (IA) described in US4361677. For example, in tire applications, it exhibits better static properties, lower brittleness, higher tear resistance, and better comfort. Furthermore, unexpectedly, the combination of the methylene donor of general formula (I) with phenolic resin imparts excellent fracture properties to the composite while reducing hysteresis, resulting in improved materials compared to known materials (e.g., as shown in Table 12 herein).

[0082] The crosslinking compositions of the present invention comprise at least one phenolic resin and mixtures thereof as methylene acceptor reagents, said phenolic resin being obtained by a partial crosslinking reaction of phenol and / or at least one substituted phenol with formaldehyde and / or other methylene donors. In addition to phenol itself, phenol may also be dihydroxyphenol or polyhydroxyphenol, for example, it may be o-cresol, p-cresol, m-cresol, resorcinol, catechol, pyrogallol, phlorogallol, etc., and mixtures thereof, but preferably phenol, rather than resorcinol or other less sustainable dihydroxyphenols.

[0083] The phenolic resin in the crosslinking composition of this invention is a non-self-crosslinking (non-thermosetting) phenolic resin. Unlike thermosetting phenolic resins that crosslink solely through heating, non-self-crosslinking phenolic resins require not only heating for crosslinking but also the presence of at least one methylene donor. The term "phenolic resin" refers to a family of polymers obtained through the reaction of phenol with formaldehyde or a formaldehyde precursor. Depending on the ratio of these two reagents and the reaction conditions, this family of polymers is classified into linear phenolic resins (Novolacs) and thermosetting phenolic resins (Resoles).

[0084] Typically, linear phenolic resins (Novolacs) are prepared by acid catalysis when the aldehyde:phenol ratio is less than 1, while thermosetting phenolic resins (Resoles) are prepared by alkali catalysis when the aldehyde:phenol ratio is greater than 1.

[0085] In addition to formaldehyde, other aldehydes can be used as substitutes for formaldehyde or mixed with formaldehyde; these include acetaldehyde and furfural.

[0086] Suitable phenolic resins as methylene acceptor reagents include, for example, linear phenolic resins, linear cresol resins, linear xylenol resins, linear resorcinol resins, or resins obtained by modifying the above resins with oils. Preferably, the modified resin is modified with rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and / or linolenic acid.

[0087] Preferably, in this invention, a phenolic resin prepared by polymerization of phenol and formaldehyde is used as the methylene acceptor; more preferably, a linear phenolic resin (Novolacs) is used; and even more preferably, a linear phenolic resin having a low content of free monomer (phenol) is used.

[0088] Preferred methylene acceptors include resins marketed under names such as Alnovol PN760, Durez 12686, and Elastobond A250.

[0089] In addition, natural products with polyphenol structures (such as lignin and its derivatives) can also be suitable as methylene acceptors.

[0090] All other things being equal, more sustainable and harmless methylene donors and acceptors are particularly preferred.

[0091] Depending on the intended use of this crosslinking composition, the most suitable phenolic resin can also be selected based on the molecular weight of the phenolic resin.

[0092] For example, higher molecular weight phenolic resins are preferred for use in elastomer compositions designed to form structures for tire components requiring greater stiffness and tear resistance (such as bead fillers or sidewall inserts). Typically, these resins have a softening point of 90°C or higher.

[0093] Conversely, lower molecular weight phenolic resins are preferred for elastomer compositions intended to cover fabrics or metal reinforcing elements (such as elastomer compositions for carcasses, belts, bead wraps, or wire loop wraps). Typically, these resins have a softening point not exceeding 95°C, preferably lower.

[0094] The phenolic resin of the methylene acceptor in this crosslinking composition preferably does not include the vulcanized thermosetting vulcanized phenolic resin having the general formula claimed and described in US Patent 4361677.

[0095]

[0096] Preferably, the methylene acceptor reagent does not contain a large amount of free phenol, particularly free resorcinol, and preferably, if it does contain a large amount of free phenol, its content is as low as possible, for example, less than 2%. More preferably, the methylene acceptor reagent consists of only one or more phenolic resins, which is advantageously less harmful and exhibits better processability, lower reversibility (see MH and RET% in Table 7) and higher tear resistance (Table 15).

[0097] In a more sustainable preferred embodiment, the crosslinking composition according to the invention contains neither free phenols (such as resorcinol) nor formaldehyde.

[0098] In a preferred embodiment, the crosslinking composition according to the invention comprises a reagent having general formula (I) as the sole methylene donor reagent, and one or more phenolic resins comprising a sole methylene acceptor reagent.

[0099] In this embodiment, the weight ratio of the total amount of the methylene donor reagent having general formula (I) to one or more phenolic resins is preferably between 1:1 and 1:6, more preferably between 1:1.2 and 1:5.

[0100] In another embodiment, the crosslinking composition according to the invention comprises: a complex having general formula (I) as a methylene donor reagent mixed with one or more conventional formaldehyde donors (e.g., HMMM, HMT, etc.), and one or more phenolic resins as the sole methylene acceptor reagent.

[0101] In this further embodiment, the weight ratio of the total amount of 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. In the secondary crosslinking composition according to the invention, the amount of at least one methylene donor reagent having general formula (I) is preferably at least 2% by weight relative to the total weight of the crosslinking composition, more preferably at least 3%.

[0102] In the secondary crosslinking composition according to the invention, the amount of at least one methylene donor reagent having general formula (I) is preferably no more than 70% by weight of the total weight of the crosslinking composition, more preferably no more than 60% by weight of the total weight of the crosslinking composition.

[0103] In the secondary crosslinking composition according to the invention, the methylene donor preferably comprises at least 15 wt.% of at least one methylene donor having general formula (I), more preferably at least 20 wt.%.

[0104] Another aspect of the present invention is represented by an elastomer composition comprising the crosslinked composition according to the present invention.

[0105] With necessary modifications, the preferred embodiments of the crosslinking compositions of the present invention described above also apply to elastomer compositions including the crosslinking compositions and all subsequent aspects of the present invention.

[0106] The elastomer composition according to the invention is characterized by one or more of the following preferred aspects, either individually or in combination with each other.

[0107] The elastomeric composition according to the invention comprises at least one diene polymer of at least 100 phr.

[0108] The diene polymer (A) may be selected from polymers commonly used in sulfur-vulcanizable elastomer compositions that are particularly suitable for the production of tires, i.e., may be selected from solid elastomer polymers or copolymers having unsaturated chains, whose glass transition temperature (Tg) is generally below 20°C, preferably in the range of 0°C to -110°C.

[0109] 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, and may optionally be mixed with at least one comonomer selected from monoolefins, monoethylene aromatics and / or polar comonomers in an amount not exceeding 60% by weight.

[0110] Conjugated dienes typically contain 4 to 12 carbon atoms, preferably 4 to 8 carbon atoms, and can be 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. Of these, 1,3-butadiene and isoprene are particularly preferred.

[0111] Monoolefins can be selected from ethylene and α-enes that typically contain 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or mixtures thereof.

[0112] The monovinyl aromatic hydrocarbons optionally used as comonomers typically contain 8 to 20 carbon atoms, preferably 8 to 12 carbon atoms, and are selected from, for example, styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, various alkyl, cycloalkyl, aryl, alkyl or aralkyl derivatives of styrene, such as α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-methylstyrene, 4-(4-phenylbutyl)styrene, and mixtures thereof. Styrene is particularly preferred.

[0113] The polar comonomers that may be used 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.

[0114] Preferably, the diene polymer (A) may be selected from, for example: cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene (especially polybutadiene with a high content of 1,4-cis), optionally halogenated isoprene / isobutene copolymers, 1,3-butadiene / acrylonitrile copolymers, styrene / 1,3-butadiene copolymers, styrene / isoprene / 1,3-butadiene copolymers, styrene / 1,3-butadiene / acrylonitrile copolymers, and mixtures thereof.

[0115] The compositions according to the invention may optionally comprise at least one polymer of one or more monoolefins and olefinic comonomers or derivatives thereof. The monoolefin may be selected from: ethylene and α-olefins typically containing 3 to 12 carbon atoms, such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, or mixtures thereof. Among these copolymers, ethylene / propylene (ERR) or ethylene / propylene / diene (EPDM) copolymers are preferred. Preferred copolymers are those selected from: copolymers of ethylene and α-olefins (optionally containing a diene), isobutylene homopolymers or copolymers thereof containing a small amount of diene, which are optionally at least partially halogenated. The optionally present diene typically contains 4 to 20 carbon atoms and is preferably selected from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5-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 bromobutyl rubber; and mixtures thereof.

[0116] 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.

[0117] This composition may include at least one reinforcing filler of 1 phr to 170 phr, 5 phr to 150 phr, or 10 phr to 120 phr.

[0118] Preferably, the reinforcing filler is selected from carbon black, white filler, silicate fiber, its derivatives and mixtures thereof.

[0119] In one embodiment, the reinforcing filler comprises carbon black.

[0120] Preferably, the amount of carbon black as reinforcing filler (B) in the elastomer composition according to the invention is between 1 phr and 120 phr, and more preferably between 5 phr and 100 phr.

[0121] Preferably, the carbon black is selected from materials with a surface area of ​​not less than 20m². 2 / g, preferably at least about 40m 2 / g-50m 2 / g carbon black (determined by STSA-statistical thickness surface area according to ISO 18852:2005).

[0122] Carbon black, for example, can be N375, N326, N339, N550 or N660 sold by Birla Group (India) or Cabot.

[0123] In one embodiment, the reinforcing filler is a white filler selected from metal hydroxides, oxides and hydrated oxides, salts and hydrated salts; silicon dioxide; silicate fibers; derivatives thereof and mixtures thereof.

[0124] In one embodiment, the reinforcing filler may include silica, for example selected from pyrolytic silica, precipitated amorphous silica, wet silica (hydrated silica), anhydrous silica (anhydrous silica), or mixtures thereof.

[0125] Preferably, the amount of silica as a reinforcing filler in the elastomer composition according to the invention is between 1 phr and 100 phr, more preferably between 5 phr and 80 phr or 7 phr and 50 phr.

[0126] The silica that can be used in this invention can have a 10m 2 / g to 300m 2 / g, preferably 30m 2 / g to 250m 2 / g, more preferably 40m 2 / g to 190m 2 / g BET surface area (measured according to ISO standard 5794 / 1).

[0127] Commercial examples of suitable silica include Zeosil 1165MP, Zeosil 1115MP, Zeosil 185GR, and 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 120 G, EZ 160 G, and EZ 200 G from PPG; and Ultrasil 7000 GR and Ultrasil 9100 GR from Evonik. Another example of suitable silica is rice husk silica as described in WO2019229692A1.

[0128] In one embodiment, the reinforcing filler comprises silica mixed with carbon black and / or silicate fibers.

[0129] The elastomer composition according to the invention comprises at least one vulcanizing agent in the form of 0.1 to 20 phr.

[0130] The vulcanizing agent is preferably selected from sulfur-based reagents, such as elemental sulfur, polymeric sulfur, sulfur donor reagents (e.g., 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), peroxy ketal R–O–O–(R)C(R')–O–O–R' (where R and R' are aryl and / or alkyl), and peroxy ester R–C(O)–O–O–R' (where R and R' are aryl and / or alkyl)).

[0131] The at least one vulcanizing agent is preferably a sulfur-based reagent selected from sulfur or alternatively from sulfur-containing 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-dispersed sulfur, and mixtures thereof. A commercial example of a vulcanizing agent suitable for the compositions of the present invention is Redball ultrafine sulfur from Flexsys.

[0132] 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, wherein the vulcanizing agent is preferably a sulfur-based agent selected from those listed above.

[0133] More preferably, the composition includes at least one vulcanizing agent in the range of 0.1 phr to 15 phr, 0.2 phr to 10 phr, 1 phr to 10 phr, or 1.5 phr to 7 phr, preferably selected from sulfur-based vulcanizing agents mentioned above.

[0134] The elastomer composition according to the invention comprises at least 0.05 phr of the crosslinked composition according to the invention.

[0135] Preferably, the elastomer composition according to the invention comprises 0.1 phr to 30 phr, more preferably 3 phr to 20 phr of the crosslinked composition according to the invention.

[0136] The amount of the methylene donor reagent (D1) in the complex is preferably between 0.5 phr and 15 phr, more preferably between 0.5 phr and 8 phr.

[0137] If the methylene donor reagent includes at least one other methylene donor reagent in addition to reagent (I), its total presence in the elastomer composition is preferably between 0.5 phr and 15 phr or between 0.5 phr and 8 phr.

[0138] The amount of the methylene receptor reagent in the elastomer composition is preferably between 0.5 phr and 30 phr, more preferably between 0.5 phr and 20 phr or between 0.5 phr and 10 phr.

[0139] In a preferred embodiment, the elastomer composition includes a reagent of general formula (I) as the sole methylene donor and one or more phenolic resins as defined above as the sole methylene acceptor.

[0140] In a preferred embodiment, the elastomer composition does not include phenolic compounds (especially resorcinol), nor does it include formaldehyde or conventional formaldehyde precursor reagents (such as HMMM, HMT, etc., having a general formula other than general formula (I)).

[0141] The elastomer compositions according to the invention may further include adjuvants known to those skilled in the art, such as vulcanization activators, accelerators and / or retarders.

[0142] Sulfidation activators that can be used in this composition include zinc compounds, particularly ZnO, ZnCO3, and zinc salts of saturated or unsaturated fatty acids containing 8 to 18 carbon atoms (preferably formed in situ in the composition via the reaction of ZnO with fatty acids), as well as Bi2O3, PbO, Pb3O4, PbO2, or mixtures thereof. For example, zinc stearate (preferably formed in situ in the composition via the reaction of ZnO with fatty acids), magnesium stearate (formed via MgO), or mixtures thereof can be used. Preferred activators are derived from the reaction of zinc oxide with stearic acid. An example of an activator is Aktiplast ST product sold by Rheinchemie.

[0143] In particular, the amount of the above-mentioned vulcanization activator in the composition of the present invention is preferably between 0.2 phr and 15 phr, more preferably between 1 phr and 5 phr.

[0144] The elastomer composition according to the invention may further include at least one vulcanization accelerator.

[0145] Commonly used vulcanization accelerators can be selected, for example, from dithiocarbamates, guanidines, thioureas, thiazoles, sulfonamides, sulfonylimides, thiurams, amines, xanthates, or mixtures thereof. Preferably, the accelerator is selected from mercaptobenzothiazole (MBT), N-cyclohexyl-2-benzothiazole sulfonamide (CBS), N-tert-butyl-2-benzothiazole sulfonamide (TBBS), and mixtures thereof.

[0146] Commercial examples of accelerators suitable for use in the compositions of the present invention include N-cyclohexyl-2-benzothiazole sulfonamide Vulkacit. ® (CBS or CZ) and N-tert-butyl-2-benzothiazole sulfonamide (Vulkacit) sold by Lanxess ® NZ / EGC).

[0147] In particular, the amount of the above-mentioned vulcanization accelerator in the composition of the present invention is preferably between 0.05 phr and 10 phr, preferably between 0.1 phr and 7 phr, and more preferably between 0.5 phr and 5 phr.

[0148] The elastomer composition according to the invention may further include at least one vulcanization inhibitor.

[0149] Suitable sulfidation inhibitors for use in the compositions of the present invention are preferably selected from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthioimide (CTP or PVI), and mixtures thereof. A commercial example of a suitable inhibitor is N-cyclohexylthioimide VULKALENTG manufactured by Lanxess. The amount of the sulfidation inhibitor present in the compositions of the present invention may preferably be between 0.05 phr and 2 phr.

[0150] In one embodiment, typically in the presence of silica as a reinforcing filler, the elastomer composition according to the invention may further include 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 silane coupling agent.

[0151] Preferably, the elastomer composition according to the invention comprises at least one silane coupling agent in an amount between 0.5 phr and 10.0 phr, more preferably between 1.0 phr and 8.0 phr, and even more preferably between 3.0 phr and 8.0 phr.

[0152] Preferably, the silane coupling agent is selected from silane coupling agents having at least one hydrolyzable silane group, which can be identified by the following general formula (II): (R)3Si-C n H 2n-X (II) Wherein, the R' groups may be the same or different from each other, and are selected from alkyl, alkoxy, or aryloxy groups or from halogen atoms, provided that at least one of the R' groups is an alkoxy or aryloxy group; n is an integer from 1 to 6; X is selected from nitroso, mercapto, amino, epoxy, vinyl, imide, chloro, -(S) m C n H 2n The groups in -Si-(R')3 and -S-COR'', where m and n are integers from 1 to 6, and the group R' is defined as above.

[0153] Particularly preferred silane coupling agents are bis(3-triethoxysilylpropyl)tetrasulfide and bis(3-triethoxysilylpropyl)disulfide. These coupling agents can be added as is or in the form of a mixture with inert fillers (such as carbon black) to facilitate their incorporation into the elastomer composition.

[0154] An example of a silane coupling agent is TESPT, which is bis(3-triethoxysilylpropyl)tetrasulfide (Si69) sold by Evonik.

[0155] The elastomer compositions according to the invention preferably do not include thermosetting phenolic resins having the following general formula as claimed and described in U.S. Patent US4361677.

[0156]

[0157] Another aspect of the present invention is a vulcanized elastomer compound for tires used in vehicle wheels, which is obtained by mixing and vulcanizing the above-mentioned elastomer composition.

[0158] The preferred embodiments of the crosslinking compositions and elastomer compositions of the present invention described above, with necessary modifications, are applicable to vulcanized elastomer complexes and all subsequent aspects of the present invention.

[0159] The elastomer composite according to the invention can generally be formed by simultaneously reacting and solidifying a secondary crosslinking composition according to the invention, which includes at least a methylene donor reagent having general formula (I) and at least one phenolic resin as described above, with a conventional primary crosslinking system including a sulfur-based vulcanizing agent during vulcanization.

[0160] Advantageously, the crosslinking of the composite according to the invention is based on, for example, Figure 3 The kinetics shown occur when there is a rapid initial step followed by a plateau period in which the crosslinked network is stable and has minimal reversibility.

[0161] This elastomer composite can be prepared according to a process that typically includes one or more mixing steps performed in at least one suitable mixer, particularly including at least one mixing step 1 (non-productive mixing) and mixing step 2 (productive mixing) as defined above.

[0162] Each mixing step may include several intermediate processing steps or sub-steps, characterized by momentary interruption of mixing to allow the addition of one or more components, but without intermediate discharge of the complex.

[0163] For example, mixing can be performed using the following mixers: open-type mixers with open mills, internal mixers with tangential rotors (Banbury®) or intermix rotors (Intermix), or in Ko-Kneader™ type (Buss®) continuous mixers or twin-screw or multi-screw type continuous mixers.

[0164] For this purpose, after one or more thermomechanical treatment steps (non-productive step 1), the rubber is typically treated with some of the additives (including methylene acceptor reagents), except for vulcanizing agents, vulcanization accelerators, retarders, and methylene donor reagents that will be incorporated into the compound in the next step. In the final treatment step (productive step 2), the temperature is typically maintained below 120°C, preferably below 100°C, to prevent any undesirable pre-vulcanization. Subsequently, the compound is incorporated into one or more parts of the tire and vulcanized according to known techniques. Advantageously, the elastomer compositions of the present invention are even easier to process than similar known compositions comprising, for example, a secondary crosslinking system based on resin and HMMM or resin and bisoxazolidine (IA) (as shown by the MH values ​​in Table 6); or a secondary crosslinking system based on resorcinol and bisoxazolidine (I), wherein R1 is ethyl (as shown in Table 7). Vehicle tire components comprising, or preferably primarily composed of, the vulcanized elastomer compound according to the invention, are selected from: tread belts, underlayers, wear-resistant layers, sidewalls, sidewall inserts, mini sidewalls, liners, underlayer liners, rubberized carcass structures and / or belt layers and / or zero-degree belts, annular bead anchoring structures, bead fillers, bead reinforcement layers (bead wrapping), bead protection layers (bead wrapping), and sheets.

[0165] In one embodiment, the elastomeric composite according to the invention is a composite reinforced by incorporating reinforcing elements of various properties (metals or fabrics), also known as a rubberized composite.

[0166] Preferably, the elastomeric composite of the present invention is applied to reinforced tire components, such as belt structures, carcass structures, rubber layers, annular bead anchoring structures, bead reinforcement layers (bead wrapping), and bead protection layers (bead wrapping).

[0167] Preferably, the reinforcing element is made of one or more fabric materials.

[0168] 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), aromatic polyamides (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 (e.g., rayon or lyocell fibers).

[0169] In a preferred embodiment, the reinforcing element is composed of aliphatic polyamide, PET, or a mixture thereof.

[0170] Advantageously, this crosslinking composition imparts excellent adhesion of the elastomeric composite of the present invention to reinforcing elements, as highlighted in Tables 15 to 18 herein.

[0171] In another embodiment, the elastomeric compound according to the invention is used as a constituent compound of tire components that typically bear loads, the tire components needing to have a certain stiffness and, more importantly, fatigue resistance, for example, as a filler compound for bead or sidewall inserts of a self-supporting tire.

[0172] Advantageously, the elastomer composites according to the invention exhibit faster vulcanization kinetics than composites comprising only conventional formaldehyde precursor reagents (such as HMT or HMMM), while also possessing better processability and comparable or superior thermal stability, as determined by T90, MH, and %RET values ​​(see Tables 6 to 9). Figure 3 This is confirmed by the graph in the image.

[0173] Furthermore, under the same static performance, the elastomeric composites of the present invention exhibit comparable or lower hysteresis (see, for example, the Tan Delta values ​​in Tables 10 and 12), which indicates that the tires will have equal or lower rolling resistance and therefore equal or lower energy consumption.

[0174] Another aspect of the invention is represented by a tire for a vehicle wheel, the tire comprising 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.

[0175] The term "consistent essentially of an elastomeric compound" indicates that, in addition to the elastomeric compound according to the invention, the tire component may include other elements, such as fabric or metal reinforcement elements, but not any other elastomeric compound besides the elastomeric compound according to the invention.

[0176] In one embodiment, the tire includes at least one reinforced tire component comprising an elastomeric compound according to the invention or preferably substantially composed of an elastomeric compound according to the invention, wherein the reinforced tire component is preferably selected from rubberized compounds used for carcass structures, belt structures, zero-degree belt structures, bead protection layers (bead wraps) or reinforcement layers (bead wraps).

[0177] In one embodiment, the tire includes at least one unreinforced tire component (i.e., without reinforcing elements) that is generally susceptible to fatigue, comprising or preferably substantially composed of an elastomeric compound according to the invention, wherein the unreinforced tire component is preferably selected from bead fillers and sidewall inserts.

[0178] The tire according to the invention may include a plurality of the components described above, and the plurality of components include an elastomeric compound according to the invention or preferably substantially composed of an elastomeric compound according to the invention. For example, it may include a combination of one or more components of a rubberized compound selected from the following: carcass structure, belt structure, zero-degree belt structure, protective layer (bead wrapping) or reinforcing layer (bead wrapping), bead filler and / or sidewall insert.

[0179] Based on the predicted data shown in the experimental section, the tires according to the present invention can exhibit lower rolling resistance, better comfort and fatigue resistance, and overall longer service life.

[0180] The tires according to the present invention can be tires for two-wheeled, three-wheeled or four-wheeled vehicles, and can be tires for summer or winter or all-season use.

[0181] 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. Generally, a tire for a motorcycle wheel refers to a tire having straight sections characterized by high lateral curvature.

[0182] In a preferred embodiment, the tire according to the invention is a tire for the wheels of a sports or racing motorcycle.

[0183] In one embodiment, the tire according to the invention is a tire for automobile wheels.

[0184] 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 an elastomeric compound according to the invention or is substantially composed of an elastomeric compound according to the invention.

[0185] In one embodiment, the tire according to the invention is a tire for a bicycle wheel. A tire for a bicycle wheel typically includes a carcass structure that is turned up around a pair of bead cores at the bead and a tread strip arranged radially outward relative to the carcass structure.

[0186] The tires according to the present invention can be manufactured according to a process comprising: - A component for constructing a green tire on at least one forming drum; - The tires are formed, molded, and vulcanized; At least one of the components used to construct a raw tire includes: - To manufacture at least one green component, the green component comprising or substantially composed of an elastomeric compound according to the invention.

[0187] Description of the tire according to the invention

[0188] Figure 1 A tire for a vehicle wheel according to the invention is shown in a radial half-sectional view, the tire comprising at least one component comprising the elastomeric compound of the invention.

[0189] 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 rest, not shown, is identical and arranged symmetrically with respect to the equatorial plane “XX”.

[0190] The tire (100) for a four-wheeled vehicle includes at least one carcass structure, the carcass structure including at least one carcass layer (101) having correspondingly opposite end flaps that engage with a corresponding annular anchoring structure (102) referred to as a bead core, the bead core optionally associated with a bead filler (104).

[0191] The tire region, including the bead core (102) and filler (104), forms a bead structure (103) designed for anchoring the tire to a corresponding mounting rim (not shown).

[0192] The carcass structure is typically radial, meaning that a reinforcing element in at least one carcass ply (101) lies on 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 composed of fabric cords, such as rayon, nylon, or polyester (e.g., polyethylene terephthalate PET or polyethylene naphthalate PEN). Each bead structure is formed by folding back at least one opposing lateral edge of the carcass ply (101) around the annular anchoring structure (102) to create a shape resembling... Figure 1 The so-called fetal body folds (101a) shown are connected to the fetal body structure.

[0193] In one embodiment, the connection between the carcass structure and the bead structure may be provided by a second carcass layer applied at an axially lateral position relative to the first carcass layer. Figure 1 (Not shown in the image) is provided.

[0194] Optionally, wear-resistant strips (105) made of elastomeric material are arranged in the outer position of each bead structure (103).

[0195] The carcass structure is associated with a belt structure (106), which includes one or more belt layers (106a), (106b) arranged radially stacked relative to each other and relative to the carcass layers, and typically has fabric and / or metal reinforcing cords bonded to an elastomeric material layer.

[0196] Such reinforcing cords may have a cross orientation relative to the circumferential extension direction of the tire (100). The “circumferential” direction refers to the direction that is generally oriented toward the direction of tire rotation.

[0197] At least one zero-degree reinforcement layer (106c), typically referred to as a “0° belt”, may be applied at the radially outermost position of the belt layers (106a) and (106b), which typically incorporates a plurality of elongated reinforcement elements, which are typically metal or fabric cords, oriented in a substantially circumferential direction to form an angle of a few degrees (such as an angle between about 0° and 6°) relative to a direction parallel to the equatorial plane of the tire, and coated with an elastomeric material.

[0198] The tread band (109) is applied at the radially outer position of the belt structure (106).

[0199] Furthermore, corresponding sidewalls (108) of the elastomeric material are applied at axially outer positions on the lateral surface of the carcass structure, each sidewall extending from one of the lateral edges of the tread (109) at the corresponding bead structure (103).

[0200] In the radially outer position, the tread band (109) has a rolling surface (109a) designed to contact the ground. Typically, circumferential grooves are formed on this rolling surface (109a), the circumferential grooves consisting of lateral notches ( Figure 1 (Not shown) are connected to define a plurality of blocks of different shapes and sizes distributed on a rolling surface (109a). For simplicity, the rolling surface is... Figure 1 It is shown as smooth.

[0201] A base layer (111) made of an elastomeric material may be arranged between the belt structure (106) and the tread belt (109), the base layer preferably extending on a surface substantially corresponding to the extended surface of the belt structure.

[0202] A strip (110) of elastomeric material, often referred to as a “mini sidewall,” may optionally be disposed in the connection region between the sidewall (108) and the tread band (109). This mini sidewall is typically obtained by co-extrusion with the tread band (109), and allows for improved mechanical interaction between the tread band (109) and the sidewall (108). Preferably, the end portion of the sidewall (108) directly covers the lateral edge of the tread band (109).

[0203] In the case of tubeless tires, a rubber layer (112), commonly referred to as a “liner”, may also be provided in a radially inner position relative to the carcass layer (101), which provides the necessary impermeability for the tire’s inflation air.

[0204] The stiffness of the tire sidewall (108) can be improved by providing a reinforcing layer (120) for the bead structure 103, which is commonly referred to as “bead wrapping” or additional strip insert.

[0205] The 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 bead wrap is in contact with the at least one carcass layer (101) and the bead structure (103).

[0206] The wire loop outer covering 120 typically comprises multiple fabric cords bonded within an elastomer material layer.

[0207] The tire's reinforcing ring structure or bead (103) may include an additional protective layer or strip, commonly referred to as "bead wrap" (121), and has the function of increasing the stiffness and integrity of the bead structure (103).

[0208] The bead wrap (121) typically comprises multiple cords bonded to a rubber layer of elastomeric material. These cords are typically made of woven materials (e.g., aramid or rayon) or metallic materials (e.g., steel cords).

[0209] An elastomeric material layer or sheet (not shown) may be disposed between the belt structure and the carcass structure. This layer may have a uniform thickness. Alternatively, the layer may have a varying thickness in the axial direction. For example, the layer may have a greater thickness near its axial outer edge relative to the central (crown) region.

[0210] Advantageously, the layer or sheet can extend on a surface that substantially corresponds to the extended surface of the belt structure.

[0211] The elastomeric compound according to the invention can be advantageously incorporated into one or more of the tire components described above, which are preferably selected from the tire carcass (101), bead core (102), bead (104), belt (106), bead wrapping fabric (120), and bead wrapping fabric (121).

[0212] The construction of the tire according to the present invention can be performed by assembling corresponding semi-finished products suitable for forming tire components on a forming drum by at least one assembly device.

[0213] At least a portion of the components intended to form the tire carcass structure can be constructed and / or assembled on the forming drum. More specifically, the forming drum is designed to first receive any liner that may be present, followed by the tire carcass structure. Subsequently, suitable means coaxially engage one of the annular anchoring structures around each of the end flaps, positioning the outer sleeve, including the belt structure and tread belt, in a coaxially centered position around the cylindrical tire carcass sleeve, and causing the tire carcass sleeve to be shaped according to the annular configuration by radial expansion of the tire carcass structure, so that it is applied to abut against the radially inner surface of the outer sleeve.

[0214] After the raw tire is constructed, it is typically molded and vulcanized to determine the structural stability of the tire through the crosslinking of the vulcanizable elastomer composition, to impart the desired tread pattern on the tread belt, and to impart any distinguishing graphic markings on the sidewall.

[0215] Experimental Section

[0216] Analytical methods

[0217] Rheological analysis MDR (According to ISO 6502)

[0218] This analysis used an Alpha Technologies MDR2000 rheometer. 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°. The time required to achieve an increase of one or two rheological units (TS1, TS2) and the time required to achieve an increase of 5%, 30%, 60%, 90%, 95%, and 100% (T05, T30, T60, T90, T95, and T100) in the final torque value (Mf) were also measured. The maximum torque value MH, the minimum torque value ML, and the reversibility (RET%) were also measured.

[0219] Figure 3 The report presents vulcanization curves of elastomer composites including different secondary crosslinking systems.

[0220] Static mechanical properties: According to UNI 6065:2001 standard, the static mechanical properties (load CA05 at 50% elongation, load CA1 at 100% elongation, load CA3 at 300% elongation, breaking load CR, elongation at break AR%, and breaking energy) of cyclic elastomer material samples were measured for 10 minutes at 23℃.

[0221] Compression dynamic mechanical properties E', E”, and Tan delta were measured in tensile-compression mode using an Instron Model 1341 dynamic device as described herein. Vulcanized specimens (length = 25 mm; diameter = 14 mm) were subjected to dynamic sinusoidal strain (at 170 °C for 10 minutes) with an amplitude of ±3.33% of their preloaded length at a frequency of 10 Hz. The cylindrical specimens were subjected to compressive preload until longitudinal deformation reached up to 10% of their initial length and maintained at predetermined temperatures of 23 °C, 70 °C, or 100 °C throughout the test. The dynamic mechanical properties were expressed as dynamic elastic modulus (E'), dynamic viscous modulus (E''), and Tan delta (loss factor). The Tan delta value was calculated as the ratio between the dynamic viscous modulus (E'') and the dynamic elastic modulus (E').

[0222] Peel test : Peel tests are performed by measuring the force (N) required to separate two elastomer composite samples with the same composition, which were co-vulcanized to create an interfacial region. This test can predict the tear resistance of the finished product. Peel tests were also performed after the samples were subjected to a thermal oxidative aging treatment at 70°C for 48 hours in an oven.

[0223] Tables 15 to 17 show the average separation force values ​​(in Newtons) associated with the tear test (three samples were taken for each material).

[0224] Adhesion test (H-type test, ASTM D4776): This test measures the force required to pull the cords out of the elastomeric material block of the sample after vulcanization and evaluates the remaining coverage of the cords after stretching.

[0225] The samples vulcanized at 150°C for 30 minutes included PET fabric cords. The fabric cords were pretreated by immersing them in an adhesive REL composition comprising a latex of styrene-butadiene-vinylpyridine polymer, resorcinol, and formaldehyde, and then the fabric cords were heated to approximately 200°C to 250°C for fixation.

[0226] The treated cords were rubberized using reference or inventive composites, the detailed composition of which is listed in Table 3, to provide representative samples of the reinforcing structural elements of the tire. As described herein, the samples thus prepared underwent an adhesion evaluation.

[0227] Table 18 shows the average pull-out force in Newtons and the coverage assessment (3 samples for each compound).

[0228] Example

[0229] The elastomer composites according to the invention for rubberizing tire carcasses, belts, or bead fillers, used as reference examples or comparative examples, were prepared from the elastomer compositions reported in Tables 1 to 5 below. The reactivity and properties of these composites were investigated by varying the secondary crosslinking systems. In particular, the properties of elastomer composites (of the invention) comprising crosslinked compositions according to the invention (characterized by the presence of a methylene donor reagent of general formula (I), alone or in mixture with a conventional formaldehyde donor) were compared with the following known crosslinking systems corresponding to those used in commercially available tires or reported in the literature, and which include resorcinol or phenolic resins and conventional formaldehyde donors (HMMM, HMT, etc.); finally, crosslinking systems comprising resorcinol with a methylene donor reagent of general formula (I) (wherein R1 = ethyl, as shown in US3256137) or phenolic resin with an oxazolidine methylene donor reagent of general formula (IA) (wherein R1 = CH2OH, as described in US4361677) (as comparative examples).

[0230] Table 1: Elastomer compositions used in carcass rubberization compounds

[0231] -Resor refers to resorcinol; Resin refers to phenolic resin; oxaz-Et refers to a bisoxazolidine methylene donor reagent having the general formula (I); where R1 = CH2CH3; and oxaz-CH2OH refers to a bisoxazolidine having the general formula (IA) according to US4361677, where R1 = CH2OH; - The natural rubber is NRP91 (cis-1,4-polyisoprene) type SIR20 (Indonesia). -CB N326 is carbon black from Birla Carbon (300% modulus of 3.9 + / - 1.8 MPa, ASTM D3192IRB8 - ASTM D412 Method B); CTAB: 83m 2 / g); - Zinc oxide is derived from zinc oxide obtained from metallic zinc via an indirect method from Zincolossidi; - Stearic acid is supplied by Oleon; -6PPD is Santoflex N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine from Flexsys, which is an anti-ozone agent and antioxidant. -ALNOVOL PN 760 is a modified phenolic linear resin supplied by Allnex (Germany), containing 1% free phenol and 0.1% free formaldehyde, with a softening point between 80°C and 95°C. -RESORCINOL 80 is 80% resorcinol and 20% adhesive polymer and dispersant supplied by RDC; -HMMM is a 65% hexamethoxymethyl melamine on an amorphous silica carrier supplied by Brenntag; -Oxaz-Et is 5-ethyl-1-aza-3,7-dioxabicyclo[3.3.0]octane (CAS No. 7747-35-5) (general formula (I), R1=CH2CH3) supplied by Sigma Aldrich. -Oxaz-CH2OH (R1=CH2OH) of general formula (IA), which is prepared as described in US8466294B2.

[0232] -TBBS 80 is N-tert-butylbenzothiazole sulfonamide (accelerator) from RDC; - The sulfur is selected from Redball® ultrafine amorphous sulfur from Flexsys (Germany), which is insoluble in carbon disulfide and toluene, and is treated with 33% hydrogenation of the heavy cycloalkane fraction (petroleum).

[0233] 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 effect of the combination of HMMM and Alnovol phenolic resin. These compositions correspond to those used in commercially available tires. The composition of Example 2 represents a reference composition for use in the compositions of Example 3 (the present invention) and Example 4 (comparative examples), with all components and amounts identical except for the methylene donor reagents (HMMM and bisoxazolidine).

[0234] The composition according to Example 3 of the present invention relates to a combination of bisoxazolidine having the general formula (I) and the phenolic resin Alnovol (wherein R1 = ethyl).

[0235] The composition of Example 4 is a comparative composition that combines a bisoxazolidine having the general formula (IA) (where R1 = CH2OH, as shown in US4361677) with the phenolic resin Alnovol.

[0236] Table 2: Elastomer compositions for bead filler compounds

[0237] in: -CB N375 is 0.4 ± 1.8 MPa of 300% modulus carbon black from Birla Carbon (ASTM D3192 IRB8 - ASTM D412 Method B); - 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). -The tert-butylphenol resin is OFF APM SL1410 resin from Sino Legend, which is made by the condensation reaction of tert-butylphenol and formaldehyde; - The linear phenolic resin is DUREZ 12686 phenolic resin from Sumitomo Bakelite Europe, which is modified with cashew nut shell oil and has a softening point between 90°C and 105°C. -HMT 80 is hexamethylenetetramine, containing 80% methylene donor reagent and 20% polymer binder and RDC dispersant; - The silanizing agent (silane coupling agent) is a 1:1 mixture of bis[3-(triethoxysilane)propyl]tetrasulfide (CAS No.: 40372-72-3) from EVONIK and carbon black N330 (CAS No.: 1333-86-4); -The silica is precipitated amorphous silica from Solvay Rhodia's ZEOSIL 1115MP; -TBBS is Nt-butyl-2-benzothiazolium sulfonamide from Lanxess (CAS No.: 95-31-8). -PVI is N-cyclohexylthiophthalimide (CAS No.: 17796-82-6), purchased from Shandong Derek New Materials Co., Ltd.; Natural rubber, stearic acid, zinc oxide, 6PPD, HMMM, and sulfur are the same as those used in Table 1.

[0238] The composition of Example 5 provides information about the effects of combining phenolic resin with HMMM and HMT.

[0239] The elastomer composition of Example 6 according to the invention replaces HMMM with bisoxazolidine of general formula (I) (where R1 is ethyl) and is combined with HMT and phenolic resin.

[0240] The comparative composition of Example 7 is substantially the same as the composition of the present invention in Example 6, except that the bisoxazolidine having general formula (IA) shown in US4361677 (where R1 is CH2OH) is replaced by the bisoxazolidine having general formula (I) of the present invention (where R1 is ethyl).

[0241] Table 3: Elastomer compositions used in carcass rubberization compounds

[0242] The ingredients are the same as those listed in Table 1.

[0243] In these examples, in addition to the reference compositions (Examples 8 and 10, wherein HMMMM is combined with resorcinol or Alnovol phenolic resin, respectively), two other compositions were prepared and compared: one is a comparative composition (Example 9), and the other is the composition of the present invention (Example 11), in which HMMM is replaced by a bisoxazolidine having the general formula (I) (where R1 = CH2CH3) and combined with resorcinol (as described in US3256137) or Alnovol phenolic resin, respectively.

[0244] Table 4: Elastomer compositions for belt rubberization compounds

[0245] in: -The natural rubber is STR20 (Thailand); -MANOBOND 680 C rubber-metal adhesion accelerator (cobalt / boron salt) from Shepherd Ltd.; -DCBS is N,N-dicyclohexyl-2-benzothiazole sulfonamide from Huatai Chemicals; Furthermore, the remaining components are the same as those listed in Table 1, Table 2, or Table 3.

[0246] In these examples, instead of resorcinol, the reference composition of Example 12 includes the phenolic resin Alnovol and HMMM. The elastomer composition of Example 13 according to the invention includes a bisoxazolidine (R1=CH2CH3) having the general formula (I) as the sole methylene donor and combined with the phenolic resin Alnovol.

[0247] Table 5: Elastomer compositions for bead filler compounds

[0248] The ingredients are those listed in Table 2.

[0249] In these examples, the reference composition of Example 14 is the same as the composition in Table 2 above; while the composition of Example 15 according to the invention, instead of HMMM, comprises a bisoxazolidine having the general formula (I) (R1 = CH2CH3) and is combined with HMT and phenolic resin.

[0250] The composition of Example 16 is an elastomer composition according to the invention, which, instead of HMT (Example 14), comprises a bisoxazolidine having the general formula (I) (R1=CH2CH3) and is combined with HMMM and a phenolic resin.

[0251] The compositions of Examples 17 and 18 are compositions according to the invention, wherein conventional crosslinking agents HMMM and HMT (present in Example 14) are completely replaced with bisoxazolidine (R1=CH2CH3) having general formula (I) in increasing amounts, and are combined with phenolic resin.

[0252] Preparation of elastomer composites

[0253] Starting with the elastomer compositions shown in Tables 1 to 5, the corresponding elastomer complexes are prepared according to the following treatment.

[0254] Use an internal mixer (Banbury, Intermix, or Brabender) to mix the components in two steps.

[0255] In the first step (1), all components except the vulcanizing agent, accelerator, and methylene donor are introduced. Mixing is continued for a maximum of 5 minutes until a temperature of approximately 145°C is reached. Subsequently, in the second step (2), mixing is performed again using an internal mixer, adding the vulcanizing agent, accelerator, and one or more methylene donors, and mixing continues for approximately 4 minutes while maintaining a temperature below 100°C. The original composite is then discharged. After cooling and at least 12 hours from the start of preparation, some samples of the composite are vulcanized in a press at 170°C for 10 minutes to provide samples with useful mechanical characteristics.

[0256] Characteristics of the complex

[0257] MDR rheological analysis

[0258] The original elastomeric composites obtained from the elastomeric compositions reported in Tables 1 to 5 were subjected to MDR rheological analysis as described above.

[0259] Figure 3 The trends in crosslinking kinetics of complexes including conventional resorcinol + HMMM systems (sample 1, example 1) or phenolic resin + HMMM systems (sample 2, example 2) compared to the phenolic resin + oxazolidine (I) system (sample 3, example 3) according to the invention are shown. As can be seen from the graphs, the crosslinking of sample 3 according to the invention includes a very steep initial phase like sample 1, followed by a plateau phase, wherein the network stability and minimum reversal are comparable to sample 2. Tables 6 to 9 below contain the results of rheological analysis for various samples: Table 6: MDR Analysis Elastomer compositions for use in tire carcass rubberization compounds (see Table 1)

[0260] As confirmed by the data reported in Table 6, the composite of the present invention in Example 3 exhibits faster crosslinking kinetics compared to the reference composite of Example 2 and the comparative composite of Example 4, with a lower maximum MH torque value, indicating better processability, and also shows reduced reversal compared to the conventionally produced composite of Example 2.

[0261] Table 7: MDR Analysis

[0262] Elastomer compositions for use in tire carcass rubberization compounds (see Table 3)

[0263] As confirmed by the data reported in Table 7, the compound of the present invention in Example 11 exhibits the best combination of performance compared to all other compounds, namely, faster kinetics (T90 of approximately -20% compared to the classic resin + HMMM system of Example 10), the lowest maximum MH torque indicating better processability, and very low reversibility, which foreshadows the significant thermal stability of the network.

[0264] Table 8: MDR Analysis

[0265] Elastomer compositions for belt rubberization compounds (see Table 4)

[0266] As confirmed by the data reported in Table 8, compared with the reference composite of Example 12, the composite of the present invention in Example 13 exhibits faster crosslinking kinetics at all T points (approximately -20% at T30, approximately -30% at T60, and approximately -40% at T90) and lower maximum MH torque (approximately -20%), which indicates that the composite has better processability.

[0267] Table 9: MDR Analysis

[0268] Elastomer compositions for use in bead filler compounds (see Table 5)

[0269] As confirmed by the data reported in Table 9, the composition of the present invention, including Example 15 which is composed of phenolic resin, HMT, and oxaz-Et, exhibits similar crosslinking kinetics to the reference composite of Example 14 at the lowest values ​​of T30 and T60, while the rate increases at values ​​above T60 (approximately +5% at T90). Furthermore, for the composite of the present invention, the maximum torque MH was observed to be substantially equivalent to the maximum torque MH of the reference composite in use.

[0270] In summary, based on the MDR analysis data reported in Tables 6 to 9, it can be emphasized that the crosslinking kinetics of the complexes using the reagents of the present invention having general formula (I) are generally faster than those of the reference complexes, and such complexes are easier to process and have lower or comparable reversibility.

[0271] Static and dynamic mechanical properties of the composite

[0272] Tables 10 to 14 below show the results of mechanical property analysis of the elastomer composites prepared from the compositions shown in Tables 1 to 5 according to the methods described above: Table 10: Static and Dynamic Mechanical Properties Elastomer compositions for use in tire carcass rubberization compounds (see Table 1)

[0273] Based on the static performance data reported in Table 10, it can be observed that the static performance of the elastomer composition according to the invention in Example 3 is substantially the same or only slightly worse than that of the reference example in Example 2.

[0274] Conversely, compared to the composition of the present invention in Example 3, the comparative composition of Example 4 containing bisoxazolidine as described in US4361677 exhibits higher static stiffness and poorer fracture performance. In particular, the comparative composition of Example 4 is worse, more brittle, and has a greater tendency to tear, which is associated with lower fatigue resistance, as evidenced by lower CR, AR% and energy values, and higher CA3 values.

[0275] Regarding dynamic performance, it was observed that the elastomer composition of Example 3 according to the invention has a lower dynamic modulus E' compared to Examples 2 and 4, indicating greater comfort in tire applications. Furthermore, the elastomer composition of Example 3 according to the invention is characterized by hysteresis at all temperatures below or substantially equivalent to those of Reference Example 2 and Comparative Example 4.

[0276] Compared to the composition of the present invention in Example 3 and the reference examples in Examples 2 and 1, the comparative composition in Example 4 exhibits a higher dynamic modulus at all temperatures, which suggests lower comfort in certain tire applications due to excessive stiffness and poor damping.

[0277] Table 11: Static and Dynamic Mechanical Properties

[0278] Elastomer compositions for use in tire bead fillers (see Table 2)

[0279] Generally, for bead filler compounds, higher static and dynamic stiffness is desirable; however, it is equally important to avoid deterioration of their fracture properties and the potential propagation of cracks in the bead.

[0280] As can be observed from the static performance data reported in Table 11, with reference to the composition of Example 5, the elastomer composition according to the invention in Figure 6 has higher CR, AR and energy, indicating high tear resistance.

[0281] Conversely, the comparative composition of Example 7 exhibits significantly worse fracture properties compared to the elastomer composition according to the invention in Example 6, indicating poor fatigue resistance.

[0282] Regarding dynamic performance, it is evident that, compared to the elastomer composition according to the invention in Example 6, the comparative composition in Example 7 exhibits a higher E' value at all temperatures, which foreshadows lower tire comfort.

[0283] Table 12: Static and Dynamic Mechanical Properties

[0284] Elastomer compositions for use in tire carcass rubberization compounds (Table 3)

[0285] As can be observed from the static performance data given in Table 12, the comparative composition of Example 9, which is similar to that shown in US3256137A and contains resorcinol and the oxazolidine reagent of the present invention having general formula (I), exhibits similar static stiffness but lower fracture performance compared to the reference composition of Comparative Example 8, and is therefore less suitable for structural carcass composites subjected to heavy stress in use.

[0286] Conversely, compared to the comparative composition of Example 9, which included the same oxazolidine and resorcinol instead of resin, the elastomer composition of Example 11 according to the invention exhibits significantly improved, superior fracture properties. Furthermore, compared to the reference composition of Example 10, which also contained phenolic resin, the composition of the present invention (Example 11) has similar static stiffness and comparable fracture properties. In fact, it is possible to successfully replace resorcinol and formaldehyde in secondary crosslinked compositions with more sustainable products, i.e., while simultaneously maintaining or improving performance.

[0287] Regarding the dynamic properties in the presence of classic donors such as HMMM and the switch from resorcinol to phenolic resin, a sharp and undesirable increase in hysteresis was observed at all temperatures (Example 8 compared to Example 10).

[0288] Surprisingly, using the oxazolidine reagent of the present invention with general formula (I) instead of HMMM, the hysteresis was greatly reduced (see Examples 9 and 8 and Examples 11 and 10), and only in the case of Example 11 was the fracture performance unexpectedly maintained, while in Example 9 the fracture performance deteriorated instead.

[0289] In other words, starting with a less eco-sustainable composition containing resorcinol and HMMM (Example 8), and replacing resorcinol with a less harmful phenolic resin (Example 10), a significant increase in hysteresis was observed. However, quite unexpectedly, using the oxazolidine reagent of the present invention, having general formula (I), instead of HMMM, it was possible to restore the hysteresis to a value suitable for the application while maintaining excellent fracture properties (Example 11).

[0290] Table 13: Static and Dynamic Mechanical Properties

[0291] Elastomer compositions for use in belt rubberized compounds (see Table 4)

[0292] As can be observed from the static performance data given in Table 13, the composition of the present invention in Example 13 exhibits lower static stiffness (approximately -20% Ca3) compared to the reference composition of Example 12, while having similar fracture properties. Regarding dynamic performance, the composition of the present invention according to Example 13 exhibits a lower dynamic modulus and significantly reduced hysteresis compared to the reference composition of Example 12, resulting in improved fatigue resistance and reduced rolling resistance.

[0293] Table 14: Static and Dynamic Mechanical Properties

[0294] Elastomer compositions for use in bead filler compounds (see Table 5)

[0295] As can be observed from the static performance data given in Table 14, the composition of Example 15 according to the invention exhibits similar static stiffness and comparable fracture performance compared to the reference composition of Example 14.

[0296] Regarding dynamic performance, the composition of the present invention according to Example 15 exhibits a lower dynamic modulus compared to the reference composition of Example 14, which foreshadows better comfort, and has similar hysteresis.

[0297] Peel test

[0298] Some of the elastomer compounds reported above underwent the peel test described above, and the results are shown in Tables 15 to 17 below: Table 15: Peel test at 100℃ Tire carcass rubberization compound (see Table 1)

[0299] As can be observed from the data reported in Table 15, the rubberized compound according to the invention of Example 3, containing phenolic resin and oxa-Et, exhibits a peel force value in production that is only slightly lower than the excellent value of Reference Example 2 and much higher than the excellent value of the reference composition of Example 1, indicating high material properties in terms of tear resistance and reduction of crack propagation.

[0300] Conversely, the comparative composition of Example 4, containing bisoxazolidine (IA) as described in US4361677, exhibited a significantly lower peel force value than all other samples, effectively offsetting the improved adhesion obtained by using the phenolic resin Alnovol instead of resorcinol (see the increase in peel force when switching from the resorcinol-containing composition of Example 1 to the Alnovol-containing composition of Example 2). Peel forces as low as those of Example 4 suggest a greater tendency for the composite to tear and lower resistance to crack propagation.

[0301] from Figure 2 As can be seen from the graph, the graph shows the trend of tensile force (N on the vertical axis) of various samples as deformation increases (mm on the horizontal axis). The curve of the composite according to the present invention (Example 3) is consistent with the curve of the reference composition of Example 2, which contains conventional methylene donors in addition to phenolic resin. The trend of the composition of Example 4, which contains oxazolidine (IA) as a donor, is similar to that of the reference composition in Example 1, but the adhesion performance is significantly worse.

[0302] Table 16: Peel test at 100℃

[0303] Tire carcass rubberization compound (see Table 3)

[0304] The data reported in Table 16 clearly demonstrate that resorcinol and formaldehyde in the secondary crosslinking composition can be successfully replaced with more sustainable products (i.e., while maintaining performance). Indeed, the peel force value of the composite according to the invention in Example 11, while lower than that of the composition in Example 10, is still acceptable and consistent with the performance of the reference production composite in Example 8.

[0305] Table 17: Peel test at 100℃

[0306] Belt rubberized composite (see Table 4)

[0307] As can be observed from the data reported in Table 17, the composite of Example 13 according to the invention unexpectedly exhibits increased peel strength compared to the reference composite of Example 12, which includes phenolic resin and HMMM.

[0308] In summary, comparative experimental data between the secondary crosslinking system of the present invention, comprising an oxazolidine reagent of general formula (I) and a phenolic resin, and a comparative crosslinking system suggested in document US4361677, which comprises an oxazolidine reagent of the aforementioned general formula (IA), demonstrate that the material according to the present invention has significant and unexpected advantages, 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), better comfort (lower dynamic modulus - Table 10), and lower hysteresis (Table 10). Furthermore, as shown in Tables 7 and 12 (Example 11 of the present invention and Comparative Example 9), the secondary crosslinking system of the present invention also outperforms the comparative system shown in US3256137 in terms of processability, lower reversibility, higher tear resistance, and fatigue resistance, which comprises the same methylene donor (I) (where R1 = Et) and resorcinol instead of a phenolic resin.

[0309] Adhesion test of fabric reinforcement materials

[0310] The adhesion tests described above were conducted on the carcass rubberized composites of the present invention and reference examples prepared from the compositions shown in Table 3 with PET fiber fabric materials.

[0311] Table 18 below shows the results of this test.

[0312] Table 18: Adhesion test (T = 23℃)

[0313] Tire carcass rubberization compound (see Table 3)

[0314] in: PET is PET 1672 F105 polyethylene terephthalate fiber from HYOSUNG VN; Coverage refers to the visual assessment of the amount of compound that remains on the line after being pulled.

[0315] The data reported in Table 18 show that the composite of Example 11 according to the invention exhibits better adhesion to PET cords compared to the reference composite of Example 10.

[0316] In summary, the above experimental data emphasize that, compared with known secondary crosslinking systems, the crosslinking composition according to the invention, including at least one phenolic resin as a methylene acceptor reagent and at least one methylene donor reagent having general formula (I), when incorporated into elastomer composites for tires, can impart optimal stiffness, tensile strength and adhesion to reinforcing elements to improve crosslinking kinetics and processability, while maintaining or even reducing hysteresis.

[0317] The elastomeric material according to the invention comprises a crosslinking system that is less harmful than conventional crosslinking systems and is characterized by having the aforementioned properties. It is advantageously used in tire components that require a certain stiffness and fracture resistance (e.g., bead fillers, sidewall inserts) and / or have high adhesion to fabric or metal reinforcement elements (e.g., carcass, belts, bead protection (bead wrapping) or reinforcement (bead wrapping) layers).

Claims

1. A crosslinking composition for an elastomer complex, said crosslinking composition comprising at least one methylene donor having general formula (I): （I） Where R1 represents ethyl; And at least one phenolic resin as a methylene acceptor reagent, said phenolic resin being obtained by partially crosslinking phenol and / or at least one substituted phenol with formaldehyde and / or other methylene donors and mixtures thereof.

2. The crosslinking composition according to claim 1, further comprising at least one other methylene donor reagent selected from the group consisting of: hexamethoxymethyl melamine (HMM), hexamethylenetetramine (HMT), hexahydroxymethyl melamine, N,N'-dihydroxymethylurea, N-hydroxymethyldicyandiamide, N-allyl dioxazine, N-phenyl dioxazine, N-hydroxymethylacetamide, N-hydroxymethylbutyramide, N-hydroxymethylacrylamide, N-hydroxymethylsuccinimide, chlorolaurooxymethylpyridine, chloroethoxymethylpyridine, trioxane hexamethyl etherified melamine, hexahydroxymethyl melamine pentamethyl ether (HMPE), oxazolidine derivatives other than those shown in general formula (I), and mixtures thereof.

3. The crosslinking composition according to claim 1, comprising a reagent having the general formula (I) as the sole methylene donor reagent and one or more phenolic resins as the sole methylene acceptor reagent.

4. The crosslinking composition according to claim 3, wherein, The weight ratio of the methylene donor reagent having general formula (I) to the total amount of the one or more phenolic resins is between 1:1 and 1:6, preferably between 1:1.2 and 1:

5.

5. An elastomer composition, said elastomer composition comprising at least: At least one diene polymer with a phr of -100 phr; - At least one reinforcing filler with a strength of at least 0.1 phr; Vulcanizing agents ranging from -0.1 phr to 20 phr; as well as - At least 0.05 phr of the crosslinked composition according to any one of claims 1 to 4.

6. The elastomer composition according to claim 5, wherein: -The amount of the reinforcing filler present is at least 1 phr; - The vulcanizing agent is a sulfur-based reagent, and its presence amount is at least 0.5 phr; - The crosslinking composition is present in an amount of 0.1 phr to 30 phr.

7. A vulcanized elastomer compound for vehicle wheel tires, said vulcanized elastomer compound being obtained by mixing and vulcanizing the elastomer composition according to claim 5 or 6.

8. A tire for a vehicle wheel, the tire comprising at least one tire component, the tire component comprising the vulcanized elastomer compound according to claim 7.

9. The tire according to claim 8, wherein, The tire components are selected from the following: tread belt, underlayer, wear-resistant layer, sidewall, sidewall insert, mini sidewall, liner, underlayer liner, rubberized carcass structure layer, belt bundle, zero-degree belt bundle, annular bead anchoring structure, bead filler, bead reinforcement layer (steel wire bead wrapped with cloth), bead protection layer (bead wrapped with cloth), and sheet materials.

10. The tire according to claim 8 or 9, wherein, The tire component includes a reinforcing element, which is preferably made of aliphatic polyamide, polyethylene terephthalate, or a mixture thereof.

11. The tire of claim 8, wherein the tire is a self-supporting tire, and the self-supporting tire includes the vulcanized elastomer compound at least in the sidewall insert.

12. The tire according to any one of claims 8 to 10, wherein the tire is used in high-performance passenger vehicles (HP, SUV and UHP).

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