Method for functionalizing elastomeric materials and their use in rubber compounds

Abstract

A method for functionalizing elastomeric materials, such as rubber particles, is provided. The method involves functionalizing the elastomeric materials through the use of an ionic liquid-based composition that includes a water-soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator, along with a zinc compound, sulfur, and an accelerator. Rubber particles functionalized according to the disclosed method, such as particles from recycled rubber products, can be successfully utilized in virgin rubber masterbatches at concentrations not previously possible.

Description

Introduction

[0001] The present invention relates to a method for functionalizing elastomeric materials. In particular, the present invention relates to a method for functionalizing elastomeric materials that includes using an ionic liquid-based composition together with a zinc compound, sulfur, and an accelerator.

[0002] Recycling of elastomeric materials, including pre-cured or vulcanized rubber products such as tires, hoses, belts, etc., remains a challenge for the industry despite already receiving a great deal of attention.

[0003] It is well known to those skilled in the art that one of the major problems in reprocessing or recycling precured materials is that during the vulcanization reaction, strong carbon-sulfur and sulfur-sulfur bonds are formed, which are extremely stable and therefore difficult to reverse. Thus, to date, these precured rubber products have only found applications where chemical reintegration of the material is not required, for example when utilized as a filler.

[0004] One strategy to increase the use of these recycled rubber materials is to devulcanize them to regain some of their original properties, so that they can be recompounded into new (virgin) rubber. Although there are several publications that address devulcanization processes, to date these processes have not produced materials that are commercially viable or capable of being used at high loads in industrial rubber applications.

[0005] Applicant's own International PCT patent application, WO 2019 / 145808, discloses a rubber vulcanization composition that is a water-soluble polymer-based solution that includes a cationic silicate component and a cationic additive component that is a salt of a vulcanization accelerator. The disclosure of WO 2019 / 145808 is incorporated herein by reference in its entirety.

[0006] The present inventors have surprisingly discovered that an ionic liquid-based composition comprising a water-soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator, along with a zinc compound, sulfur, and an accelerator, functionalizes elastomeric materials comprising rubber particles, thereby enabling the use of these functionalized particles in rubber masterbatches at levels heretofore unknown. It has further been found that new rubber products incorporating the functionalized rubber particles exhibit unexpected performance compared to similar rubber compounds not containing these functionalized rubber particles. Summary of the Invention

[0007] According to a first aspect of the invention, there is provided a method for functionalizing an elastomeric material, comprising the steps of: a) providing an elastomeric material having a surface to be functionalized; b) providing an ionic liquid-based composition comprising a water-soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator; c) providing a zinc compound, sulfur, and a vulcanization accelerator; d) producing a functionalized elastomeric material by contacting the ionic liquid-based composition of step b) and the components of step c) on a surface of the elastomeric material; A method is provided, comprising:

[0008] In one embodiment, the elastomeric material is an elastomeric particle.

[0009] In one embodiment, the elastomeric particles have a particle size ranging from about 10 to about 400 mesh.

[0010] In a preferred embodiment, the elastomeric material is selected from the group consisting of reclaimed elastomeric material, ground rubber, charred rubber, and micronized rubber powder.

[0011] In a particularly preferred embodiment, the elastomeric material is a vulcanized elastomeric material.

[0012] In one embodiment, the elastomeric material is recycled tire rubber.

[0013] In one embodiment, the ionic liquid-based composition further comprises one or more of a reinforcing filler and a thermoplastic elastomer.

[0014] In another embodiment, the method further comprises the step of mixing the elastomeric material of step a) with a reinforcing filler.

[0015] In one embodiment, the reinforcing filler is based on precipitated silica, optionally silanized amorphous precipitated silica.

[0016] In one embodiment, the vulcanization accelerator in the ionic liquid-based composition of step b) is selected from the group of accelerator classes comprising thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, and aldehyde amines.

[0017] In one embodiment, the salt of the vulcanization accelerator in the ionic liquid-based composition of step b) is a salt of 2-mercaptobenzothiazole (MBT), zinc dibenzyldithiocarbamate (ZBEC), zinc dialkyldithiophosphate (ZBOP), tetrabenzylthiuram disulfide (TBzTD), di-isopropylxanthogen disulfide (DIXD) or polysulfide (AS100), or a combination thereof, and the salt of the vulcanization accelerator is a sodium or potassium salt thereof.

[0018] In a preferred embodiment, the cation of the cationic silicate component is a sodium or potassium cation.

[0019] In a preferred embodiment, the water-soluble polymer is an ethylene oxide polymer or a polyvinyl alcohol polymer.

[0020] In a particularly preferred embodiment, the water soluble polymer is polyethylene glycol.

[0021] In one embodiment, the ionic liquid-based composition comprises polyethylene glycol, sodium metasilicate, and the promoter salt NaBEC.

[0022] In one embodiment, the accelerator in step c) is selected from the group of accelerator classes including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, and aldehyde amines.

[0023] According to a second aspect of the present invention there is provided the use of an ionic liquid based composition, a zinc compound, sulphur and an accelerator, for functionalising an elastomeric material, the ionic liquid based composition comprising a water soluble polymer, a cationic silicate component and a salt of a vulcanisation accelerator.

[0024] In one embodiment, the ionic liquid-based composition further comprises one or more of a reinforcing filler and a thermoplastic elastomer.

[0025] According to a third aspect of the present invention, there is provided a method for recycling rubber, comprising the steps of: a) providing an elastomeric material functionalized according to the method of the first aspect of the present invention; b) providing a synthetic or natural rubber masterbatch comprising virgin rubber; c) vulcanizing the mixture of the functionalized elastomeric material of step a) with the masterbatch of step b) to produce a final rubber product comprising reclaimed and virgin rubber; A method is provided, comprising:

[0026] In one embodiment, the final rubber product comprises reclaimed rubber in a concentration of about 1 to about 80 weight percent, based on the total weight of the final rubber product.

[0027] In one embodiment, the final rubber product is a product selected from the group consisting of tires, hoses, conveyor belts, and other industrial rubber products.

[0028] According to a further aspect of the present invention there is provided a rubber product obtainable by the process according to the third aspect of the present invention, the rubber product being a product selected from the group consisting of tyres, hoses, conveyor belts and other industrial rubber products.

[0029] In one embodiment, the product is a tire tread, the tread having improved performance compared to a tread that does not contain reclaimed rubber, the performance being selected from one or more of rolling resistance, abrasion resistance, wet grip, or a combination thereof. [Brief description of the drawings]

[0030] The invention will now be described in more detail with reference to the following non-limiting embodiments and figures. [Figure 1] 1 is a graph showing cure rate and torque response of various rubber compounds containing the functionalized elastomeric material of the present invention. [Diagram 2] 1 is a graph showing the stress strain response of a control batch and rubber compounds containing 40% and 100% of a rubber compound prepared with a functionalized elastomeric material of the present invention (Compound A). [Diagram 3] FIG. 1 is a graph showing the rheometry of NR coated rubber crumb with different coating ratios utilizing functionalized formulation S-. [Figure 4] FIG. 1 is a graph showing the rheometry of NR coated rubber crumb with different coating ratios utilizing functionalized formulation S+. [Diagram 5] 1 shows a rheometer trace of a control NR masterbatch with a standard curative package, a control NR masterbatch with unmodified rubber crumb, and a NR masterbatch with functionalized rubber crumb (PxActi8-based material) prepared according to the method of the present invention. [Figure 6] 1 shows the tan delta response of the NR masterbatches tested. [Figure 7] 1 is a graph showing the storage modulus (G') of the tested NRs masterbatches. [Figure 8] 1 is a graph showing the loss modulus (G") of the NR masterbatches tested. [Figure 9] 1 is a graph showing stress versus strain data for various NR masterbatch rubber compounds prepared using different rubber crumb materials. [Figure 10] FIG. 1 shows rheometer traces of a control SBR masterbatch with a standard curative package, a control SBR masterbatch with unmodified rubber crumb, and an SBR masterbatch with functionalized rubber crumb (PxActi8 based material) prepared according to the method of the present invention. [Figure 11] 1 is a graph showing the tan delta response of the SBR masterbatches tested. [Figure 12] 1 is a graph showing the loss modulus (G") of the SBR masterbatches tested. [Figure 13] 1 is a graph showing the storage modulus (G') of the SBR masterbatches tested. [Figure 14] 1 is a graph showing stress vs. strain data for the SBR masterbatches tested. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The invention will now be described in more detail with reference to the accompanying drawings, which show some non-limiting embodiments of the invention.

[0032] The invention described below should not be construed as limited to the specific embodiments disclosed, as slight modifications and other embodiments are intended to be included within the scope of the invention.

[0033] Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0034] As used herein, and throughout the specification and claims that follow, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise.

[0035] The terms and phrases used herein are for purposes of description and should not be considered as limiting. As used herein, the use of the terms "comprising," "containing," "having," "including," and variations thereof are meant to encompass the items listed thereafter, and equivalents thereof, as well as additional items.

[0036] As used herein, the term "water-soluble polymer" should be understood to mean a polymer that dissolves, disperses, or swells in water, including polymers that contain hydroxyl groups, e.g., ethylene oxide type polymers or polyvinyl alcohol polymers.

[0037] As used herein, the term "elastomeric material" should be understood to mean a polymer that exhibits rubber-like elasticity. Elastomeric materials contain unsaturated double bonds (whether or not previously involved in crosslinking) that are capable of accepting new sulfur crosslinks when exposed to an ionic liquid-based composition and additional components according to the inventive methods disclosed herein.

[0038] The present invention provides a method for functionalizing an elastomeric material, comprising the steps of: a) providing an elastomeric material having a surface to be functionalized, b) providing an ionic liquid-based composition comprising a water-soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator, c) providing a zinc compound, sulfur, and an accelerator, and d) producing a functionalized elastomeric material by contacting the ionic liquid-based composition of step b) and the components of step c) with the elastomeric material surface.

[0039] The functionalization of elastomeric materials is achieved through the use of ionic liquid compositions in conjunction with a combination of additional ingredients including zinc compounds, sulfur, and accelerators.

[0040] Without wishing to be bound thereby by any particular theory, it is believed that the ionic liquid based composition allows for the formation of pendant groups (sulfur accelerator species derived from the composition of the accelerator). These pendant groups are activated by the interaction of the sulfur and the accelerator in the presence of the zinc compound (ZnO) in the ionic liquid based composition. Surprisingly, the above chemical reaction appears to occur at very low temperatures compared to those used in conventional vulcanization reactions. After only a few minutes of contact at a moderate temperature of about 80°C, these pendant groups are expected to form and react with available diene sites on the surface of the elastomeric material. This occurs even when the elastomeric material is not heated to its melting point (unvulcanized rubber) and occurs on the solid surface of the elastomeric material.

[0041] In one embodiment of the present invention, the elastomeric material to be functionalized is first contacted with the ionic liquid-based composition. Alternatively, in another embodiment of the present invention, the ionic liquid-based composition is mixed with a zinc compound, sulfur, and an accelerator to prepare a functionalization medium, which is then contacted and mixed with the elastomeric material. The surface treatment conditions are mild temperatures and can be performed either in situ during mixing or ex situ by preparing a pre-reaction medium prior to functionalization.

[0042] The vulcanization accelerator salt in the ionic liquid based composition may be selected from a group of accelerator classes including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, aldehyde amines, or combinations thereof.

[0043] The ionic liquid compositions used in the methods of the present invention are prepared according to the methods disclosed in the Applicant's earlier international patent application, WO 2019 / 145808, which is incorporated herein by reference in its entirety.

[0044] The ionic liquid compositions used to prepare the functionalized elastomeric materials are non-aqueous polymer-based composites that are linked to either oil or frozen wax materials. In rubber production, the compositions are suitable for direct addition to rubber-like materials in conventional mixing equipment in standard rubber manufacturing environments. The polymers are water-soluble polymers, such as ethylene oxide type polymers, polyvinyl alcohol polymers, or any other polymers that contain hydroxyl groups.

[0045] The ionic liquid compositions used in the methods of preparing functionalized elastomeric materials are themselves prepared by providing a suitable cationic silicate component solution, which is synthesized by dissolving silica powder in a basic solution, e.g., sodium hydroxide or potassium hydroxide.

[0046] The resulting cationic silicate component is added to a water soluble polymer, such as an ethylene oxide polymer including polyethylene glycol, and dried to produce a stable ionic liquid of the particular cationic silicate component.

[0047] Certain combinations of cationic silicate components and polymers, such as polyethylene glycol as a replacement for the aqueous environment, result in suitably stable ionic liquids.

[0048] These cationic silicate solutions and the resulting cationic silicate polymer compositions or complexes can be prepared by reacting different ratios of selected cations with silica, thereby modifying the surface chemistry and ionic nature of the ionic liquid. For example, a stoichiometric ratio of cation to silica can be used. Alternatively, the ratio can be altered depending on the requirements of the particular system being functionalized.

[0049] The cationic silicate polymer carrier composition is suitable for dissolving and stabilizing a number of ionic materials known to be useful or beneficial in rubber vulcanization, such as various salts or nanopowders of graphene oxide, zinc oxide, or any other suitable ionic material that can be dissolved or dispersed in the cationic silicate polymer composition.

[0050] The ionic liquid composition further comprises a salt of a vulcanization accelerator. The salt of the vulcanization accelerator is dissolved in the above-mentioned cationic silicate component and the water-soluble polymer carrier. The accelerator salt complex can be prepared in a caustic aqueous solution, for example, a solution of sodium hydroxide or potassium hydroxide. The accelerator salt complex can be prepared by dissolving sodium hydroxide or potassium hydroxide in water before reacting with the accelerator fragment. The accelerator salt complex can also be prepared in a suitable azeotropic mixture of water and alcohol. In a preferred method of the present invention, the accelerator salt complex is prepared in an azeotropic mixture of water and isopropyl alcohol.

[0051] The accelerator component may be selected from any one of the accelerators known in the art. In particular, the accelerator may be selected from the group of accelerator classes including thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, aldehyde amines, or combinations thereof.

[0052] The accelerator may be selected from the group of accelerator classes including thiazoles, dithiocarbamates, dithiophosphates, thiuram sulfides, or combinations thereof.Preferably, the salt of the vulcanization accelerator is sodium or potassium salt of 2-mercaptobenzothiazole (MBT), zinc dibenzyldithiocarbamate (ZBEC), zinc dialkyldithiophosphate (ZBOP), tetrabenzylthiuram disulfide (TBzTD), di-isopropylxanthogen disulfide (DIXD) or polysulfide (AS100), or combinations thereof.

[0053] The promoter salt solution is added to the cationic silicate solution to prepare a reaction mixture to which the water-based polymer is added. The resulting reaction mixture is then dried to remove the solution medium, in particular to remove all water from the system. In one embodiment, the mixture may be dried under vacuum, for example at 100 mbar or less, to remove the solution medium. The resulting composition is a non-aqueous composition based on a water-soluble polymer, for example, polyethylene glycol. The composition comprises a single phase without a separate layer (organic or aqueous).

[0054] In one embodiment, the promoter salt complex and the cationic silicate component can be selected so that the cationic portion of the additive component and the silicate component of the composition are the same, although different combinations can also be selected.

[0055] The accelerator salt complex and cationic silicate components may comprise about 50% of the total weight of the polymer-based composition, with the water-based polymer component making up the remainder of the composition.

[0056] The elastomeric material functionalized according to the present invention may in one embodiment be an elastomeric particle. Although it is envisioned that the functionalization methods described herein are equally applicable to all elastomeric surfaces and particles (having the appropriate diene group chemistry to allow for sulfur vulcanization), the elastomeric particles to be functionalized preferably have a particle size ranging from about 10 to about 400 mesh. The average particle size of the elastomeric particles depends on the source of the material to be functionalized and the method by which the material was processed. For example, elastomeric particles in the size range of about 10 to about 30 mesh are typically from ground tire rubber, while particles having a smaller particle size in the range of about 40 to about 300 mesh are generally considered to be micronized rubber powder.

[0057] In a preferred embodiment of the present invention, the elastomeric material to be functionalized for further processing is selected from the group consisting of reclaimed elastomeric material, ground rubber, burnt rubber, and pulverized rubber powder. As will be appreciated by those skilled in the art, in particularly desirable applications, the material to be functionalized is preferably a pre-vulcanized elastomeric material, including those listed above. However, the elastomeric material to be functionalized does not have to be a pre-vulcanized material.

[0058] In a particularly preferred embodiment of the present invention, the material to be functionalized is an elastomeric material or particle of any form originating from previously used or end-of-life tires, regardless of the preparation method of such particles. These particles are generally classified as rubber chips, rubber crumbs, ground tire rubber (GTR), or micronized rubber particles (MRP), depending on the preparation method and the average particle size obtained. These particles can be prepared according to any method known to those skilled in the art, including mechanical cutting and grinding, cryogenic freezing-based methods, and pyrolysis-based methods.

[0059] In some embodiments of the present invention, it may be beneficial for the ionic liquid-based composition to include a thermoplastic elastomer to facilitate product processing. The thermoplastic elastomer may be any elastomer having a melting point in the range of about 50°C to about 100°C. Preferably, the thermoplastic elastomer does not contain diene unsaturation. Preferably, the thermoplastic elastomer is selected from the group consisting of polyolefin-based elastomers and has an appropriate softening point and hardness to facilitate coating and blending at the required mixing conditions during the coating process. Additionally, the thermoplastic elastomer must also possess sufficient thermal stability not to degrade near the working temperatures of either the vulcanization and post-processing conditions of the final rubber composition.

[0060] Preferably, the thermoplastic elastomer is present in a concentration of from about 10 to about 60% by weight, more preferably from about 15 to about 55% by weight, more preferably from about 15 to about 50% by weight, even more preferably from about 15 to about 45% by weight, and most preferably from about 20 to about 40% by weight, based on the weight of the ionic liquid-based composition.

[0061] In some further embodiments of the invention, especially when no thermoplastic elastomer is present in the ionic liquid based composition, it is desirable for the method to include the further step of providing a reinforcing filler and mixing the reinforcing filler with the ionic liquid based composition and the further components (zinc compound, sulfur, and accelerator) in a heated environment under shear conditions. The mixture should completely coat the elastomeric material while being exposed to a temperature sufficient to initiate the vulcanization initiation reaction. In one embodiment of the invention, the reinforcing filler is based on precipitated silica, preferably a silane-treated amorphous precipitated silica.

[0062] The ionic liquid-based composition used in the method of the present invention comprises a water-soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator. In addition, a component or mixture of components comprising a zinc compound, sulfur, and an additional accelerator is used in the method (step (c) of the method). The accelerator in the mixture of components used in step (c) of the method does not have to be the same as the accelerator fragment of the accelerator salt in the ionic liquid-based composition. The accelerator in step c) can be selected from any known accelerator, but is preferably selected from the group of accelerator classes comprising thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, and aldehyde amines.

[0063] Preferably, the amount of ionic liquid-based composition comprises from about 0.5 to about 2% by weight, based on the total weight of the components in steps (a) to (c) of the method of the present invention.

[0064] Preferably, the amount of elastomeric material comprises from about 40 to about 95 weight percent, based on the total weight of the components in steps (a)-(c) of the method of the present invention.

[0065] Preferably, the amount of zinc compound comprises from about 0.2 to about 1 weight percent, based on the total weight of the components in steps (a) to (c) of the method of the present invention.

[0066] Preferably, the amount of sulfur comprises from about 0.2 to about 1 weight percent, based on the total weight of the components in steps (a) to (c) of the method of the present invention.

[0067] Preferably, the amount of promoter in step (c) comprises from about 0.2 to about 1 weight percent, based on the total weight of the components in steps (a)-(c) of the method of the present invention.

[0068] Preferably, the amount of reinforcing filler comprises from about 20 to about 50 weight percent, based on the total weight of the components in steps (a)-(c) of the method of the present invention.

[0069] The present invention further provides a method for recycling rubber comprising the steps of: a) providing a functionalized elastomeric material prepared according to the methods disclosed herein; b) providing a masterbatch of synthetic or natural rubber comprising virgin rubber; and c) vulcanizing the mixture of the functionalized elastomeric material of step a) with the masterbatch of step b) to produce a final rubber product comprising reclaimed and virgin rubber.

[0070] The present invention further provides a rubber product comprising reclaimed elastomeric material functionalized according to the methods disclosed herein. The final rubber product may comprise such reclaimed elastomeric material in a concentration of about 1 to about 80% by weight, preferably about 3 to about 70% by weight, preferably about 5 to about 60% by weight, and most preferably about 10 to about 50% by weight, based on the total weight of the final rubber product.

[0071] Those skilled in the art will appreciate that the functionalized elastomeric materials prepared according to the methods of the present invention find application in any rubber product, however, particularly preferred examples of such rubber products incorporating the functionalized materials of the present invention include tires, hoses, conveyor belts, and other industrial rubber products. EXAMPLES

[0072] The invention will now be described in more detail with reference to the following non-limiting examples and experimental results.

[0073] Example 1: Preparation of Compound A using MRP40 mesh, PxActi8, sulfur, TBBS, and ZnO Rubber crumb elastomer material, mesh 40, was obtained from SN Rubber, South Africa, as shown in Table 1. The rubber crumb material was prepared by conventional mechanical grinding and contained 50%±10% natural rubber ("NR"). The rubber crumb (241 g) was mixed with 2.5 g of an ionic liquid-based composition, referred to as "PxActi8" in Table 1 below, comprising (1) polyethylene glycol, (2) sodium metasilicate, (3) sodium dibenzyldithiocarbamate (NaBEC), (4) silica, and (5) thermoplastic elastomer ("TPE") in a ratio of (1+2+3):4:5 of 50:30:20, 2 g sulfur, 1 g ZnO, and N-tert-butyl-benzothiazole sulfonamide (TBBS) accelerator, as well as other standard rubber compounds.

[0074] These ingredients were mixed in an internal mixer for 10 minutes at about 80°C. The combined materials and ingredients appeared to melt on the surface of the rubber crumb. This mixture was then further processed by adding virgin NR to the material until it behaved like a normal rubber and could be discharged from the internal mixer and rolled in a calendar mill without issue. Thus, this material is a combination of recycled functionalized rubber crumb and NR. The formulation details of Compound A are shown in Table 1 below.

[0075] [Table 1]

[0076] Compound A has a recycled content of 61.8% recycled rubber. Compound A was designed to be blended with Compound B (see below) to produce a formulation with an increased concentration of recycled content (Compound A) for further testing.

[0077] Example 2: Preparation of Compound B (no recycled content) This experiment simply prepared a standard NR rubber compound that was used for further testing of blends with Compound A to determine the performance of rubber compounds containing various levels of recycled content, as shown in Table 2 below.

[0078] [Table 2]

[0079] Compound B's formulation contains no recycled content.

[0080] This material was mixed in an internal mixer using standard mix times and standard operating procedures. This material was prepared with the addition of Si69 so that further additions of silica filler (a design requirement for this compound) could be tested. These formulations are not shown, but it is suggested that the goal is to then use additions of recycled and filler contents to achieve a wide range of properties for this parent compound.

[0081] Example 3: Testing of various formulations including Compound A / Compound B After intimate mixing, compounds A and B are obtained, which are then calendered to prepare thick sheets of NR rubber compound.

[0082] Compound A contains small cure packages on the surface of the recycled material, which can crosslink. Compound B does not have a cure package and requires a cure package to vulcanize.

[0083] Compound A and Compound B were milled together in different weight ratios as can be seen in Table 3 below. These ratios started with 0% recycled material containing Compound A and the trend ended with the testing of pure Compound A.

[0084] [Table 3]

[0085] Table 3 above shows the formulations and how the standard cure package (shown as 0% Compound A content, i.e. pure Compound B) is adjusted to match the actual pure rubber content of each of these mixes in order to retain the actual cure package associated with the actual virgin rubber that can be cured.

[0086] [Table 4]

[0087] As can be seen from the results shown in Figure 1 and Table 4 above, the addition of recycled rubber increases the cure rate and affects the compound's modulus (Smax and Smin). There is a slight change in the scorch time of this compound, which is related to the uncured rubber used to stabilize the recycled material in Compound A. Figure 2 shows the stress strain response of formulations containing 0% Compound A (S' Control), 40% Compound A (40RA8), and 100% Compound A (S'100RA8), respectively.

[0088] Example 4: Preparation of ionic liquid-based functionalized formulations Different formulations of the ionic liquid-based functionalized additive according to the present invention were prepared and are referred to herein as Formulation S+ and Formulation S- to indicate whether the amount of sulfur or accelerator is higher (relating to the usual vulcanization terminology between efficient vulcanization (EV) and conventional vulcanization (CV), with CV indicating a higher sulfur concentration).

[0089] [Table 5]

[0090] [Table 6]

[0091] Compounds S+ and S- were used as functionalizing additives in different ratios to measure and determine the effect on the vulcanization of the resulting reactivated rubber material.

[0092] The functionalization procedure followed in these experiments was the same as that followed in Example 1. This pretreatment process can be modified (i.e., higher temperatures for shorter times) to achieve the same kinetic results in the prevulcanization reaction of the rubber surface.

[0093] Functionalization tendency tests were performed on formulations S+ and S- at 0.1, 0.5, 1, and 3 g per 100 g of rubber crumb. These experiments showed that using 3 g per 100 g of rubber crumb allowed the functionalized formulation to bind and facilitate further processing.

[0094] The rheometry of functionalized rubber crumb with functionalized formulation S- in the masterbatch without additional cure package is shown in Figure 3. As can be seen from Figure 3, some crosslinking between the rubber crumb and the NR virgin material appears to become evident around 3 phr of coating of the crumb. Coating rates above 3 phr are expected to impart additional vulcanizing properties to the final vulcanizate.

[0095] The rheometry of the functionalized rubber crumb with functionalized compound S+ in the masterbatch without additional cure package is shown in Figure 4. Higher coating ratios of the functionalized compound may also be considered, especially if very high crumb ratios are required for vulcanization of the final rubber product.

[0096] As can be seen from Figure 4, a rheometric response (seen by a rise in torque) occurs in the mix as the coating reaches a certain limit on the surface of the crumb. As is evident, the rheometer begins to level off at about 1 phr of coating, after which evidence that the remaining rubber (unvulcanized) has indeed been vulcanized is evident from the torque rise at the 3% coating trace. This is used to determine at what coating rate a cure interaction between the crumb and unvulcanized rubber can be achieved. This is used to tailor the properties of the final vulcanizate and to determine the stability of the mix if long term storage is required.

[0097] Example 5: Testing of Functionalized Rubber Crumb Containing NR Masterbatch The differences between the functionalized rubber crumb versus the control rubber crumb were evaluated with the baseline NR masterbatch material while using the standard cure package of the virgin rubber masterbatch.

[0098] [Table 7]

[0099] The rubber masterbatch above contains a standard cure package including CBS 1.2, ZnO2, and Sulfur 1.6.

[0100] The different rubber crumb materials were introduced at 30 g per 70 g of control rubber.

[0101] Three compounds were prepared: 1) a control masterbatch containing a standard curative package, 2) a control masterbatch containing unmodified rubber crumb, and 3) a masterbatch containing functionalized rubber crumb prepared according to the method of the present invention (PxActi8 based material). As can be seen in Figure 5 and demonstrated by the rheometer traces, there is a significant difference in the functionalized rubber crumb material versus regular crumb in this NR system.

[0102] Various dynamic and physical properties of NR masterbatches containing functionalized rubber crumb were investigated.

[0103] As can be seen from Figure 6, the tan delta response of the NR system without rubber crumb is lower than the system containing rubber crumb. However, the samples containing functionalized rubber crumb have improved dynamic response as measured by tan delta. This is an indication of a cure interaction between the crumb and the bulk rubber. The purpose of this is to maximize the dynamic response of the functionalized crumb and create a rubber vulcanizate with better dynamic response than is currently achieved using other crumb sources.

[0104] In Figures 7 and 8, the storage modulus is represented by G' and the loss modulus is represented by G". As evident in the log(G') curve, it is clear that the introduction of crumbs to this rubber increases the storage modulus. The reactivated rubber containing functionalized rubber crumbs has a slightly higher storage modulus at higher elongation. This is evidence of a different interaction between the modified rubber crumbs and the new rubber phase. Similarly, for the log(G") trace, the loss modulus is slightly lower, indicating a slightly lower loss modulus for the reactivated rubber crumbs, which is a desired property change.

[0105] Figure 9 shows the stress-strain data of the prepared examples. From Figure 9, it can be seen that the stress-strain response of the control sample is higher than that of the modified rubber crumb containing vulcanizate. This is a normal result. The stress-strain response of the reactivated rubber containing functionalized rubber crumb is higher at lower elongation, which is evidence of improved vulcanization and interaction between the rubber crumb and the virgin rubber phase. This is a desirable result, which means that the processing strength in the useful range of the rubber is higher, i.e., the stress-strain response in the normal use elongation range of the rubber is higher.

[0106] Example 6: Testing of Functionalized Rubber Crumb Containing SBR Masterbatch The differences between the functionalized rubber crumb versus the control rubber crumb were evaluated with a baseline SBR masterbatch material while using a standard cure package with a virgin rubber masterbatch.

[0107] [Table 8]

[0108] The standard cure package included in the above rubber masterbatch contains CBS 1.2, ZnO2, and sulfur 1.6.

[0109] Again, the different rubber crumb materials were introduced at 30 g per 70 g of control rubber.

[0110] As can be seen in Figure 10, for this SBR vulcanizate, it is clear that the functionalized rubber crumb reduces the rheometer modulus response (torque). There is also a slight reduction in the torque of the vulcanizate at the early stages (during the scorch period). This is a desirable property as it means that the molten rubber is less viscous and easier to mold and extrude into the required shape before curing.

[0111] Various dynamic and physical properties of SBR masterbatches containing functionalized rubber crumb were investigated.

[0112] As can be seen in Figure 11, for the SBR vulcanizate, the tan delta response of the reactivated rubber containing functionalized rubber crumb is significantly reduced at elongations up to 1 radian. This is a desirable result as it means that this compound has a lower rolling resistance (important for dynamic applications). What is also clear is that at higher strains (>1.5 radians), the reactivated rubber appears to behave very similarly to the normal crumb-filled material in its dynamic response. This is likely due to the stronger crosslinking interactions at low strains, which are irrelevant at higher elongations, and the simple physical presence of the crumbs influencing its dynamics.

[0113] As can be seen from Figures 12 and 13, these figures support the tan delta conclusions showing how the behavior of the reactivated rubber containing functionalized rubber crumb is more favorable than the control and the control with crumb at lower strains (a desirable property), and at higher strains showing a trend toward the normal physical presence of crumb.

[0114] The effect of the reactivated crumb on the dynamic properties is clear: at low elongation (strain) it does not behave like a normal crumb.

[0115] Figure 14 shows the stress vs. strain data for the SBR examples prepared, showing that the SBR masterbatch containing the functionalized rubber crumb is slightly stronger.

[0116] As can be seen from the experiments detailed above, the masterbatches containing functionalized rubber crumb are more tightly crosslinked, as seen in their behavior, especially in the lower range of elongation (strain), in both dynamic and physical tests. This means that the homogenization of the rubber vulcanizate is very good, which is expected to translate into good processing properties.

[0117] This above description of some of the exemplary embodiments of the present invention shows how the present invention can be made and practiced. Those skilled in the art will appreciate that various details can be modified to arrive at further embodiments, many of which remain within the scope of the present invention.

Claims

1. 1. A method for functionalizing a vulcanized elastomeric material, comprising: a) providing a vulcanized elastomeric material having a surface to be functionalized; b) providing an ionic liquid-based composition comprising a water-soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator; c) providing a zinc compound, sulfur, and an accelerator; d) producing a functionalized elastomeric material by contacting the ionic liquid-based composition of step b) and the components of step c) with a vulcanized elastomeric material surface; A method comprising:

2. The method of claim 1 , wherein the vulcanized elastomeric material is vulcanized elastomeric particles.

3. The method of claim 2, wherein the vulcanized elastomer particles have a particle size range of 10 to 400 mesh.

4. The method according to any one of claims 1 to 3, wherein the vulcanized elastomeric material is selected from the group consisting of ground rubber, charred rubber, and micronized rubber powder.

5. The method of any one of claims 1 to 3, wherein the vulcanized elastomeric material is recycled tire rubber.

6. The method of any one of claims 1 to 3, wherein the ionic liquid-based composition further comprises one or more of a reinforcing filler and a thermoplastic elastomer.

7. The method according to any one of claims 1 to 3, wherein the method further comprises mixing the vulcanized elastomeric material of step a) with a reinforcing filler.

8. The method of claim 6, wherein the reinforcing filler is based on precipitated silica.

9. 4. The method according to any one of claims 1 to 3, wherein the vulcanisation accelerator in the ionic liquid-based composition of step b) is selected from the group of accelerator classes comprising thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines and aldehyde amines.

10. 4. The method according to any one of claims 1 to 3, wherein the salt of a vulcanization accelerator in the ionic liquid-based composition of step b) is a salt of 2-mercaptobenzothiazole (MBT), zinc dibenzyldithiocarbamate (ZBEC), zinc dialkyldithiophosphate (ZBOP), tetrabenzylthiuram disulfide (TBzTD), di-isopropylxanthogen disulfide (DIXD) or polysulfide (AS100), or a combination thereof, and the salt of the vulcanization accelerator is a sodium or potassium salt thereof.

11. 4. The method according to any one of claims 1 to 3, wherein the cation of the cationic silicate component is a sodium cation or a potassium cation.

12. The method according to any one of claims 1 to 3, wherein the water-soluble polymer is an ethylene oxide polymer or a polyvinyl alcohol polymer.

13. The method of claim 12 , wherein the water soluble polymer is polyethylene glycol.

14. The method of any one of claims 1 to 3, wherein the ionic liquid-based composition comprises polyethylene glycol, sodium metasilicate, and the promoter salt NaBEC.

15. 4. The method of any one of claims 1 to 3, wherein the accelerator of step c) is selected from the group of accelerator classes comprising thiazoles, dithiocarbamates, dithiophosphates, sulfenamides, thiuram sulfides, xanthates, guanidines, and aldehyde amines.

16. 1. Use of an ionic liquid based composition, a zinc compound, sulfur, and an accelerator for functionalizing a vulcanized elastomeric material, the ionic liquid based composition comprising a water soluble polymer, a cationic silicate component, and a salt of a vulcanization accelerator.

17. 17. The use according to claim 16, wherein the ionic liquid-based composition further comprises one or more of a reinforcing filler and a thermoplastic elastomer.

18. 1. A method for recycling rubber, comprising the steps of: a) providing an elastomeric material functionalized according to the method of claim 4; b) providing a masterbatch of synthetic or natural virgin rubber; c) vulcanizing the mixture of the functionalized elastomeric material of step a) with the masterbatch of step b) to produce a final rubber product comprising reclaimed and virgin rubber; A method comprising:

19. The method of claim 18, wherein the final rubber product comprises reclaimed rubber in a concentration of 1 to 80% by weight, based on the total weight of the final rubber product.

20. 20. The method of claim 19, wherein the final rubber product is a product selected from the group consisting of tires, hoses, conveyor belts, and other industrial rubber products.

21. 20. A rubber product obtainable by the process of claim 18, the product being selected from the group consisting of tires, hoses, conveyor belts, and other industrial rubber products.

22. 22. The rubber article of claim 21, wherein the article is a tire tread, and the tread has improved performance compared to a tread that does not contain reclaimed rubber, the performance being selected from one or more of: rolling resistance, abrasion resistance, wet grip, or a combination thereof.

Images