PROCESS FOR MODIFYING THE SURFACE POLARITY OF RUBBER SUBSTRATES

Abstract

The present invention relates to a process for modifying the surface polarity of elastomeric rubber substrates to facilitate their cold bonding to other rubber substrates or non-elastomeric substrates of a different material, preferably metal, by chlorinating the surface of the rubber substrate through treatment with a chloride-containing composition and a peroxymonosulfate-containing composition. Other aspects relate to the surface-modified rubber substrates thus obtained, to the processes of bonding them to other substrates using an adhesive, and to the bonded substrates thus obtained.

Description

PROCESS FOR MODIFYING THE SURFACE POLARITY OF RUBBER SUBSTRATES The present invention relates to a process for modifying the surface polarity of elastomeric rubber substrates to facilitate their cold bonding to other rubber substrates or to non-elastomeric substrates of a different material, preferably metallic, by chlorinating the surface of the rubber substrate through treatment with a chloride-containing composition and a peroxymonosulfate-containing composition. Other aspects relate to the surface-modified rubber substrates thus obtained, to the processes of bonding them to other substrates using an adhesive, and to the bonded substrates thus obtained. For various applications, preformed parts made of elastomeric materials need to be bonded to another elastomeric material or to different materials, such as glass, metals, or plastics. Achieving sufficient bond strength between these materials is challenging, as existing adhesives for non-elastomeric materials show little to no adhesion to elastomers, while known elastomeric adhesives have insufficient water and vapor resistance. While some drawbacks can be overcome by using hot-melt adhesives, low curing temperatures are preferable for most applications using epoxy adhesives. Low curing temperatures are advantageous because they save energy and reduce the thermal shock to the substrates. Furthermore, they minimize thermal stresses caused by different rates of heat transfer or thermal elongation of the substrates. In recent years, photochemical and chemical techniques, such as halogenation, etching, grafting, oxidation, and interlocking, as well as physical methods, such as corona discharge, plasma treatment, electron or ion beam treatment, flame treatment, and laser treatment, have been widely used to modify the rubber surface to promote the adhesion of common cold-curing adhesives to rubber substrates. The simplest mechanism is mechanical surface grinding, but its effectiveness is limited. Regarding halogenation techniques, there are different types of surface treatments based on organic solvents, for example, trichloroisocyanuric acid in ethyl acetate or N-haloamides in solvents, or aqueous solutions, for example, sodium hypochlorite, known in the art. For example, US patent 4,500,685 A describes the ML / d / ZUZI / UI i zoz use of N,N-dihalosulfonamides in a waxy matrix for the halogenation of vulcanized rubber surfaces. International patent publication WO 2000 / 05363 A1 describes the halogenation of rubber surfaces with solutions of acidified hypochlorite, chlorine and hydrochloric acid in an organic solvent, gases containing chlorine or fluorine and mixtures of two or more of them. The use of trichloroisocyanuric acid is described, for example, by M. Virtudes Navarro-Bahon in Water-based chlorination treatment of SBS rubber soles to improve their adhesion to waterborne polyurethane adhesives in the footwear industry (J. of Adhesion Science and Technology 2005, 19(11), pages 947-74). All these methods are based on the activation of double bonds in rubber chains, creating carbon-halogen atoms and thus increasing surface polarity.The increased surface polarity allows for better compatibility with commonly used 2K adhesives. Existing techniques using organic solvents are undesirable due to the high content of toxic and flammable solvents and the resulting health and safety problems. Hypochlorite-based techniques have proven disadvantageous due to stability issues and a side reaction that develops free oxygen, reducing treatment efficiency. IVIA / a / ^UZl / Ul 1 Therefore, in the technique there is a need for alternative methods that allow the halogenation of rubber surfaces to facilitate their cold bonding without having the drawbacks of existing methods. The present invention addresses this objective and provides a process for modifying the surface of an elastomeric rubber substrate using an aqueous solution of a chloride salt and an aqueous solution of a peroxymonosulfate salt. The newly discovered method is based on the property of persulfate to act as a strong oxidizing agent that readily reacts with chloride to generate sulfate and free chlorine. The free chlorine can then react with the double bonds on the rubber surface, providing a chlorinated surface of the treated rubber substrate. As a result, the polarity of the rubber surface increases, and the adhesion of commonly used adhesives to its surface is improved. In a first aspect, the present invention relates to a process for modifying the surface of an elastomeric rubber substrate, wherein the process comprises (a) applying a first and a second composition to the surface of the elastomeric rubber substrate, wherein the first composition is an aqueous composition comprising chloride (Cl~), preferably sodium chloride, and the second composition is an aqueous composition comprising peroxymonosulfate (HSO5- / SO52-), preferably an alkali metal peroxymonosulfate, more preferably potassium peroxymonosulfate (KHSO5); (b) optionally, apply a third composition comprising activated carbon; and (c) incubate the first, second and optionally third composition with the rubber substrate for a period of time and under conditions that allow chlorination of the elastomeric rubber surface. In another aspect, the invention relates to the elastomeric rubber substrate having a chlorinated surface that can be obtained according to the processes of the invention. An even further aspect relates to a process for forming a bond between a first and a second substrate, wherein the first substrate is an elastomeric rubber substrate according to the invention or obtained according to the process of the invention, and the second substrate is a rubber or metal substrate, wherein the process comprises: (a) applying an adhesive composition to the surface to be bonded of the rubber or metal substrate, wherein the adhesive composition is preferably a 2K epoxy, polyurea, polyurethane or silicone adhesive comprising a resin formulation and a hardener formulation; (b) bringing the chlorinated surface of the rubber substrate and the surface of the metallic substrate into contact with the adhesive applied under pressure to form the bond. In an even more distant aspect, the present invention is directed to an adhered product obtainable according to the processes described herein. At least one, as used herein, refers to at least one and comprises 1, 2, 3, 4, 5, 6, 7, 8, 9 or more of the referred species. The present invention is based on the inventors' surprising discovery that, by using the processes described herein, the problems associated with the use of organic solvents can be avoided, and the developed process is more efficient than known processes using hypochlorite, since oxygen is not formed during the reaction. Furthermore, because the persulfate used is much more reactive, reaction times can be significantly shortened, from approximately 8 hours for hypochlorite treatments to only 5 to 60 minutes for persulfate-based modification reactions. Finally, it has been shown that the invented process allows for the generation of larger quantities of free chlorine due to the possibility of using higher chloride concentrations than those of hypochlorite, since the latter suffers from stability problems at high concentrations, thus increasing MA / d / ZUí l / UI 1 IOZ additionally the process yield. Furthermore, it has been discovered that unreacted chlorine can be advantageously bound using activated carbon. In this way, the release of free chlorine gas during the reaction can be minimized. The first composition used is preferably an aqueous solution of a chloride salt, containing chloride ions. The chloride salt is preferably an alkali metal chloride salt, such as potassium or sodium chloride, with sodium chloride being particularly preferred due to its easy availability, low cost, and high solubility in water. The first composition contains the chloride ions preferably at a concentration of 1 M (mol / L) to 6 M chloride, more preferably 4 M to 6 M (based on Cl⁻ ions). The amount used is, in principle, limited only by the solubility of the salt. In a preferred embodiment, the first composition is basic, preferably having a pH value greater than 8, more preferably greater than 10, and more preferably greater than 12. Preferably, the first composition contains a hydroxide, which is preferably added as an alkali metal hydroxide. More preferably, the first composition contains sodium and / or potassium hydroxide, more preferably sodium hydroxide. The advantage of an additionally added hydroxide, especially sodium and / or potassium hydroxide, is that it reduces the unreacted free chlorine released into the air. An additional effect is that, if a hydroxide has been added, the third advantageous component, activated carbon, is not required. Preferably, the first composition contains the hydroxide, especially sodium and / or potassium hydroxide, at a concentration of 0.5 M (mol / L) to 3 M (based on OH- ions), more preferably from 1 M to 3 M. The second composition is preferably an aqueous composition comprising a peroxymonosulfate salt, containing peroxymonosulfate ions (HSO5VSO52-). Alkali metal salts are preferred, particularly potassium peroxymonosulfate (KHSO5). The peroxymonosulfate concentration preferably ranges from 10M to 30M, more preferably from 18M to 22M. The second composition may be a solution, but preferably is a paste of the peroxymonosulfate in water, or the salt, such as potassium peroxymonosulfate, is simply wetted with water. The first and second compositions may, in addition to chloride and peroxymonosulfate, respectively, comprise additional components, including but not limited to solvents, fillers, thickeners, and the like. However, it is preferred that they not contain organic solvents, i.e., that they contain them in concentrations of less than 1% vol. Compositions containing chloride and peroxymonosulfate are used in quantities that maximize free chlorine generation. Therefore, the actual amount used can be determined based on the respective concentrations of the solutions employed. Typically, if the concentrations are within the ranges described herein, the first and second compositions are used in a weight ratio of approximately 3:1 to 1:3, preferably approximately 2:1 to 1:2, and more preferably approximately 1.5:1 to 1:1.5. In various configurations, the amount of the first and / or second and / or third composition applied to the surface of the elastomeric rubber substrate ranges from 500 to 900 g / m2, preferably between 600 and 700 g / m2. Again, this depends on the concentrations used, but the ranges indicated are particularly preferred if the concentrations described in this document are used. Activated carbon (third composition) is preferably used in solid form, as a powder or flakes. However, it can also be used as an aqueous dispersion and, in this form, may also contain additional components as indicated above for the other compositions. The incubation step (c) of the compositions and the rubber surface is carried out for a period of time sufficient to allow the desired degree of surface modification. Again, this depends on the reaction conditions; however, it has been found that under ambient conditions (20°C, 1013 mbar) and using the concentrations indicated herein, a reaction time of 5 to 60 minutes, preferably 15 to 30 minutes, is sufficient to obtain the desired halogenated surfaces. The compositions may be applied by any suitable means known in the art. If the compositions are liquid, application may be carried out by spraying, brushing, printing, dipping, pouring, and similar methods. Solid or essentially solid or pasty compositions, such as activated carbon or peroxymonosulfate moistened with water, may be applied using suitable solid material application techniques. Before applying the compositions described herein, the surface of the rubber substrate to be modified may be cleaned, degreased, and similarly. In several embodiments of the invention, the rubber surface is first cleaned to remove oil, grease, and dirt. After this optional step, the second composition is applied to the surface. A cloth is then placed over the surface with the second composition applied to it, and preferably, the third composition is applied. The first composition is then applied to the cloth. The surface is then covered with a sheet, such as a plastic sheet or similar covering, and the reaction is allowed to continue for approximately 5 to 30 minutes. The sheet and cloth are then removed, and the surface is washed with water and wiped / dried with a cloth. When using a first composition with an additional hydroxide, the use of the plastic sheet is not required. Therefore, in several embodiments of the invention, the process further comprises the step of cleaning and optionally drying the substrate surface after the incubation step (c). The elastomeric rubber substrate can be made of rubber, for example be a rubber sheet, or have an elastomeric rubber surface. Rubber materials are widely known in the art and include, without limitation, natural rubber (NR), ethylene propylene diene monomer (EPDM), ethylene propylene rubber (EPM), acrylonitrile butadiene rubber (NBR), polychloroprene, styrene butadiene rubber (SBR), styrene butadiene styrene (SBS), butadiene rubber (BR), isoprene rubber (IR), styrene ethylene styrene rubber (SEBS), and all other rubbers based on copolymers of two or more styrene, butadiene, ethylene, and isoprene. Natural rubbers and styrene butadiene rubber are especially preferred. The other substrate to be bonded can be made of any material. In various configurations, it is made of the same rubber material, another rubber material, or metal. The metallic substrate can be any metal. Typically, the metals are iron, steel, and aluminum, as well as their alloys. The metallic substrate may be plated with other metals, such as zinc, or it may have a surface treatment, such as a conversion treatment. The metallic substrate may consist of the metal itself or it may be surface-coated with a metal. For the bonding process, the adhesive used according to the procedures described herein may be any conventional adhesive, preferably a 2K adhesive, used for bonding rubber substrates in the field. Commonly used adhesives are those based on epoxies, polyurea, silicones, or polyurethanes. Such 2K adhesives typically comprise a resin and a hardener, usually in the form of separate formulations that are combined directly before application. MA / d / ZUí l / UI 1 ΙΌZ The formulations are designed so that, once combined, the polymerization reaction begins and continues until the composition is fully cured. The behavior and curing time depend on the resins and hardeners used. For the use of polyisocyanate-based adhesives, such as polyurea-based or polyurethane-based adhesives, the adhesive is crosslinked through components containing NCO groups and H groups. Examples include known prepolymers or polyisocyanates containing NCO groups as the resin component, while known oligomers or polymers containing OH, NH, SH, or COOH groups—preferably OH and / or NH—which can react with the NCO groups of the other component, can be used as the hardening component. To obtain a network, it is desirable that the crosslinking constituents contain at least two NCO groups and, in particular, at least two OH groups. In addition, known additives can be included in the adhesive. These are constituents that allow for the adjustment and influence of certain adhesive properties. The resin component preferably contains at least one polyisocyanate and / or at least one polyurethane prepolymer with at least two isocyanate groups, or a mixture thereof. PU prepolymers can be obtained, for example, by reacting a polyol component with at least a difunctional isocyanate in stoichiometric excess. PU prepolymers according to the present invention are reaction products of compounds with OH or NH groups with an excess of polyisocyanates. These are known polyols for adhesive applications or corresponding compounds having secondary and / or primary amino groups. Starting compounds containing OH are preferred. Polyols having a molecular weight up to 20,000 g / mol, particularly from 200 to 10,000 g / mol (number mean molecular weight, MN, as determined by GPC), are particularly suitable for synthesizing such prepolymers. They can be polyols based on polyethers, polyesters, polyolefins, polyacrylates, or alkylene polyols, for example. In another embodiment, such compounds having NH groups are used. Polyisocyanates known as polyisocyanates, which have two or more isocyanate groups, such as aliphatic, cycloaliphatic, or aromatic isocyanates, can be used directly or as polyisocyanates in the synthesis of the prepolymer. One approach uses monomeric, oligomeric, or polymeric isocyanates as a component of the resin. Blends of prepolymers and polyisocyanates are also possible. In principle, all known polyisocyanates can be used, in particular the isomers of methylene diisocyanate (MDI) or toluylene diisocyanate (TDI), tetramethylxylene diisocyanate (TMXDI), l-methyl-3-isocyanate 1,5,5-trimethylcyclohexane (IPDI), naphthalene-1,5-diisocyanate (NDI), hexane-1,6-diisocyanate (HDI).Trifunctional isocyanates, such as those obtained by trimerization or oligomerization of diisocyanates, such as isocyanurates, carbodiimides, or biurets, can also be used. The hardening component of a suitable two-component polyisocyanate-based adhesive must contain at least one compound having at least two groups that react with isocyanate groups. For example, these could be SH, COOH, NH, or OH groups. Polyols and amines are preferred. A large number of polyols are suitable as polyol components for use as the hardening component of a polyurethane-based adhesive. For example, they can be those with two to ten OH groups per molecule. They can be aliphatic or aromatic compounds, and polymers with a suitable number of OH groups can also be used. These can be primary or secondary OH groups, provided they have suitable reactivity with isocyanate groups. The molecular weight of these polyols can vary widely, for example, from 500 to 10,000 g / mol. The polyols already described above can be included. Examples of such polyols are low molecular weight aliphatic polyols, preferably those with two to ten OH groups, particularly C2 to C36 alcohols. Another suitable group of polyols is, for example, polyethers. These are the reaction products of alkylene oxides with two to four carbon atoms with low molecular weight di- or trifunctional alcohols. Polyethers should have a molecular weight between 400 and 5000 g / mol. Poly(meth)acrylates containing OH groups or polyolefins are also suitable. Polyester polyols are another suitable group of polyol compounds for use in component B. Polyester polyols commonly used in adhesives can be employed. These may be, for example, the reaction products of diols, particularly low molecular weight alkylene diols or polyether diols, with dicarboxylic acids. These may be aliphatic or aromatic carboxylic acids, or mixtures thereof. Such polyester polyols are known to those skilled in the art in many forms and are commercially available. These polyester polyols should, in particular, have a molecular weight between 200 and 3000 g / mol. Polymeric lactones or polyacetals are also included among them, provided they have at least two functional groups and a correspondingly suitable molecular weight. As a hardening component for polyurea-based adhesives, the amine used is preferably a spherically hindered amine. Suitable spherically hindered amines having two or more amino groups, preferably two amino groups, are aspartic ester amines or aromatic diamines. Examples of aromatic diamines are those spherically hindered to reduce reactivity when combined with the polymeric isocyanate of the resin component.Such aromatic amines include, but are not limited to, toluene diamine, l-methyl-3,5-diethyl-2,4-diaminobenzene, l-methyl-3,5-diethyl-2,6-diaminobenzene (also known as DETDA or diethyltoluene diamine), di(methylthio)toluene diamine, 1,3,5-triethyl-2,6-diaminobenzene, toluene diamine derivatives containing halogen, cyano, alkoxy, alkylthio, alkenyl or carbonyl groups, m-phenylene diamine, p-phenylenediamine, 4',4'-methylenedianiline, 4,4'-diaminodiphenyl sulfone, 2,6-diaminopyridine, 4,4'-methylene-bis-(3-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline), 4,4-methylene-bis(3-chloro-2. 5-diethylaniline, 3,3'-di-isopropyl-4,4'diaminodi phenylmethane, 4,4'-bis-(sec-butylamino)di phenylmethane (SBMDA), 3,5,3',5'-tetraethyl-4,4'-diaminodiphenylmethane, propylene-di-4-aminobenzoate, isobutyl. 4-chloro-3,518 diaminobenzoate, bis-(2-aminophenyl) disulfide, bis-(4-aminophenyl)disulfide, 3,3'-carbomethoxy-4,4'-diamino diphenylmethane, 1,2-bis(2-aminophenylthio)ethane, dimethylthiotoluenediamine (DMTDA), 0,1,8-diamino-p-menthane, a,a,a',a'-tetramethyl xylenediamine, N,N'-ditertiary-butylenediamine, and mixtures thereof. In the case of silicone-based adhesives, both well-known one-component and two-component silicone adhesives can be used. Two-component silicone adhesives are preferred. The silicone adhesive comprises one or more poly(diorganosiloxanes). These poly(diorganosiloxanes) are crosslinkable. The crosslinking can be achieved through reactive end groups or through end groups of the poly(diorganosiloxanes) that can be converted into reactive groups. All common poly(diorganosiloxanes) can be used. For example, such poly(diorganosiloxanes) are well-known for the production of adhesives or sealants and are commercially available. The poly(diorganosiloxane) may preferably be a poly(diorganosiloxane) with hydroxyl-terminating groups and / or a poly(diorganosiloxane) with alkoxysilyl-terminating groups. Hydroxyl-terminated and alkoxy-terminated poly(diorganosiloxanes) are known and commercially available. The poly(diorganosiloxane is preferably IVIA / a / ZUZl / Ul I / 04 a poly(dialkylsiloxane), wherein the alkyl radicals preferably have from 1 to 5, and more preferably from 1 to 3, carbon atoms, and particularly preferably are methyl groups. The most preferred are the hydroxyl-terminated poly(dimethylsiloxanes) and the methoxy-terminated poly(dimethylsiloxanes), which are preferably used in combination, each containing one of these in a component of a 2K silicone-based adhesive. The silicone adhesive further includes one or more crosslinking agents for the poly(diorganosiloxanes), which can be any crosslinking agent known in the technology for this purpose. For example, the crosslinking agent is preferably selected from a tetraalkoxysilane, an organotrialkoxysilane, a diorganodialkoxysilane and / or an oligo(organoalkoxysilane), a tetrakis ketoxymosilane, an organotris ketoxymosilane, a diorganobis ketoxymosilane and / or an oligo(organoketoxymosilane), which are optionally functionalized with one or more heteroatoms in the organyl group, or mixtures thereof.Suitable examples include methyltrimethoxysilane, chloromethyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, methyltripropoxysilane, phenyltripropoxysilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, methyltris(methyl-ketoximo)silane, phenyltris(methyl-ketoximo)silane, vinyltris(methylketoximo)silane, methyltris(isobutyl-ketoximo)silane, or tetra(methyl-ketoximo)silane. Methyltrimethoxysilane, vinyltrimethoxysilane, tetraethoxysilane, methyltris(methylketoximo)silane, vinyltris(methylketoximo)silane and methyltris(isobutylketoximo)silane. As an optional component, the silicone adhesive, and more specifically the two-component silicone formulation, may also include one or more condensation catalysts. These catalysts facilitate the crosslinking of the polydiorganosiloxanes. Preferred condensation catalysts are organotin compounds and / or metal or metalloid complexes, particularly from groups Ia, Ia, IIIa, IVa, IVb, or Ilb of the periodic table, such as Sn compounds, Ti compounds (e.g., titanates), and borates, or mixtures thereof.The preferred organotin compounds are dialkyltin compounds, for example, those selected from dimethyltin 2-ethylhexanoate, dimethyltin dilaurate, di-n-butyltin, di-n-butyltin 2-ethylhexanoate, di-n-butyltin dicaprylate, di-n-butyltin di-2,2-dimethyloctanoate, di-n-butyltin dilaurate, di-n-butyltin distearate, di-n-butyltin dimaleinate, di-n-butyltin dioleate, di-n-butyltin diacetate, di-2-ethylhexanoate di-n-octyltin, di-2,2-dimethyloctanoate of di-n-octyltin, di-n-octyltin dimaleinate and di-n-octyltin dilaurate. If epoxy-based adhesives are used in the epoxy resin formulation of the 2K epoxy adhesive, the epoxy resins can include any commonly known and used epoxy resin. Suitable epoxy resins preferably include epoxy resins with 1 to 10 epoxy groups per molecule. These epoxy groups can be 1,2-epoxy groups. The epoxy resin can, in principle, be a saturated, unsaturated, cyclic, or acyclic polyepoxide compound, aliphatic, alicyclic, aromatic, or heterocyclic.Examples of suitable epoxy resins include polyglycidyl ethers, commonly prepared by reacting epichlorohydrin or epibromohydrin with a polyphenol in the presence of alkali, as well as polyglycidyl ethers of novolac phenol-formaldehyde resins, alkyl-substituted phenol-formaldehyde resins (novalac epoxy resins), phenol-hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins, and dicyclopentadiene-substituted phenol resins. Suitable polyphenols for this purpose include, for example, resorcinol, pyrocatechol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol F. IVIA / a / 4U4 l / UII / 04 (bis(4-hydroxyphenyl)methane), 1,1-bis(4-hydroxyphenyl)isobutane, 4,4'-dihydroxybenzophenone, l,l-bis(4-hydroxyphenyl)ethane, 1,5-hydroxynaphthalene. Also suitable are ethoxylated resorcinol diglycidyl ethers (DGER), for example from Indspec Chemical Corporation, and diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (l,l-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol F, bisphenol K, bisphenol M, bisphenol S, tetramethylbiphenol; diglycidyl ethers of alkylene glycols with 2 to 20 carbon atoms and polyethylene oxide glycols (or polypropylene oxide). Other suitable epoxy resins are polyglycidyl ethers of polyalcohols or diamines. These polyglycidyl ethers are derived from polyalcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, or trimethylolpropane. Other suitable epoxy resins are polyglycidic esters of polycarboxylic acids, examples of which are the reaction products of glycidol or epichlorohydrin with aliphatic or aromatic polycarboxylic acids such as oxalic acid, succinic acid, glutaric acid, terephthalic acid or dimeric fatty acid. Other suitable epoxy resins are derived from the epoxidation products of olefinically unsaturated cycloaliphatic compounds or from natural oils and fats. In preferred embodiments, epoxy resins have from 1 to 10 epoxy groups and are selected from the group consisting of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (1,1-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol F, bisphenol K, bisphenol M, bisphenol S, tetramethylbiphenol, alkylene glycol diglycidyl ethers with 2 to 20 carbon atoms and polyethylene oxide) or polypropylene oxide); polyglycidyl ethers of novolac phenol-formaldehyde resins, alkyl-substituted phenol-formaldehyde resins (novalac epoxy resins), phenol-hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins and substituted dicyclopentadiene-phenol resins, and any combination thereof, preferably bisphenol F diglycidyl ethers and bisphenol A diglycidyl ethers and any combination thereof. Epoxy resins derived from the reaction of bisphenol A or bisphenol F and epichlorohydrin are given special preference. It can be advantageous to use liquid epoxy resins, preferably bisphenol A-based and having a sufficiently low molecular weight. Epoxy resins that are liquid at room temperature generally have an epoxy equivalent weight of 150 to approximately 220. Such epoxy resins are commercially available under the trade name DER™ from Dow. Resin formulations may comprise numerous other components, all well known to those skilled in the art, including, but not limited to, commonly used adjuvants and additives such as fillers, plasticizers, hardeners, reactive and / or non-reactive thinners, flow agents, coupling agents (e.g., silanes), adhesion promoters, wetting agents, adhesives, flame retardants, thixotropic and / or rheological agents (e.g., fumed silica), aging and / or corrosion inhibitors, stabilizers, and / or colorants. Depending on the adhesive requirements and its application, and considering the production, flexibility, strength, and bonding properties of the adhesive to the substrate, these adjuvants and additives are incorporated into the composition in varying quantities.In various forms, the resin formulation includes fillers and / or coloring agents, but typically in quantities not exceeding 10% by weight in relation to the resin formulation. The hardener formulation, in its various forms, comprises compounds capable of crosslinking with epoxy groups in the epoxy resin. Any hardener suitable for a 2K epoxy may be used. Preferred hardeners include mercaptans, polymeric amines (polyamines) and polymeric amides (polyamides) (including, for example, polyamidoamines), low molecular weight amines, and combinations thereof. Admixtures of the aforementioned hardeners with epoxy resins as described above are also preferred. In several embodiments, the preferred polyamines include a polyetheramine-epoxy adduct, that is, a reaction product of a stoichiometric excess of an amine prepolymer with an epoxy resin. Polyamine hardeners tend to react more slowly than low-molecular-weight amines but can add flexibility to the cured adhesive. The amine prepolymer used for adduct formation can be any amine prepolymer that has at least two amine groups to allow crosslinking. The amine prepolymer comprises primary and / or secondary amino groups, and preferably comprises primary amino groups. Suitable amine prepolymers include diamine polyethers and triamine polyethers, and mixtures thereof. Polyetherdiamines are preferred. Polyetheramines can be linear, branched, or a mixture. Branched polyetheramines are preferred.Any polyetheramine of molecular weight may be used, with molecular weights in the range of 200-6000 or higher being suitable. Molecular weights may be greater than 1000, or more preferably greater than 3000. Molecular weights of 3000 or 5000 are preferred. Suitable commercially available polyetheramines that can be used for adduct formation or on their own include those sold by Huntsman under the trade name Jeffamine®. Suitable polyetherdiamines include the D, ED, and DR series Jeffamines. These include Jeffamines D-230, D-400, D-2000, D-4000, HK-511, ED-600, ED-900, ED-2003, EDR-148, and EDR-176. Suitable polyether triamines include the T series Jeffamines. These include Jeffamine T-403, T-3000, and T-5000. Polyetherdiamines are preferred, with polyetherdiamines of approximately 400 molecular weight (e.g., Jeffamine D-400) being the most preferred. Equivalents of any of the above may also be used as partial or full replacements. When a polyamide is included, any polyamide hardener may be used. Some preferred polyamides include reaction products of a dimerized fatty acid and a polyamine. Examples of such polyamides include those available under the trade names Versamid®. Suitable mercaptans include difunctional mercaptans, such as 1,8-dimercapto-3,6-dioxaoctane (DMDO), either as monomers or as epoxy adducts—that is, reaction products of a stoichiometric excess of the mercaptan with an epoxy resin. Difunctional adducts of mercaptan and epoxy resin are particularly preferred. The hardening composition may comprise a low molecular weight (non-polymeric) amine hardener. Preferred compounds include primary and / or secondary amines with molecular weights up to 300 g / mol, 250 g / mol, or 200 g / mol. Aliphatic amine hardeners include those sold under the trade name Ancamine® by Evonik. In all the adducts described above, the epoxy resin can be any of the epoxy resins described above, but preferably it is a bisphenol diglycidyl ether, such as the reaction products of bisphenol A with epichlorohydrin. Any quantity of the hardeners described may be used in the present invention. In the hardener composition, one or more curing accelerators (catalysts) are preferably used to accelerate the setting of the adhesive. The curing accelerator preferably acts by catalyzing the reaction between the polyamine / polyamide / mercaptan hardeners, on the one hand, and the epoxy resin, on the other. The curing accelerator preferably includes a tertiary amine. A preferred example is ML / d / ZUZI / UI i zoz the 2,4,6-tris(dimethylaminomethyl)phenol, available from Cognis under the name Versamine® EH30. Other suitable polyamines are described in U.S. Patent No. 4,659,779 (and its family members, U.S. Patent Nos. 4,713,432 and 4,734,332; and EP-A-0 197 892). The curing accelerator may be present in any amount that adequately accelerates the curing of the epoxy adhesive. Preferably, the curing accelerator may be present in amounts less than 5% by weight, more preferably between 0.5% and 2% by weight based on the weight of the hardening composition. The curing temperature is preferably below 60°C, or 50°C, or 40°C. Epoxy adhesive compositions preferably cure at room temperature, for example, around 20°C or 25°C. Therefore, the inventive processes are preferably carried out at room temperature, i.e., within a temperature range of about 15 to 40°C. Heating the inventive epoxy adhesive is permissible, but not preferred, for example, to further reduce the curing time or to achieve more complete curing. Approximately, as used herein in relation to a numerical value, refers to the referenced value ±10% of that numerical value. In various forms, the hardener may comprise any of the additives and auxiliaries described. IVIA / a / 4U41 / Ul I / 04 previously in relation to the resin composition, such as fillers such as calcium carbonate or silica. In adhesion processes, step (b) can be carried out at a temperature of 15 to 30°C and a relative humidity of 85% or less. Before steps (a) and / or (b) of the described bonding processes, the rubber and / or metal substrate surfaces may be cleaned to remove dirt, oil, grease, etc., which may interfere with the bonding process. Suitable cleaning agents are well known in the art and include Henkel's Loctite® SE 7063. The mixing, application and / or dispensing of adhesives can be done with simple manual equipment or with fully automated systems, all of which are known to experts in the field and readily available. The contact step between the two substrates to form the bond under pressure can be carried out using known equipment, such as rollers, plates, or other suitable equipment. In preferred embodiments, step (b) is carried out by means of rollers. In various forms, the entire process can be automated. As described above, the present invention also covers the products obtained by joining the two substrates in the processes described. IVIA / a / ZUZl / Ul1 All the methods described herein in relation to the processes and formulations described are equally applicable to the claimed products and vice versa. All documents cited herein are incorporated by reference in their entirety. The invention is further illustrated by, but not limited to, the following examples. EXAMPLES Example 1 First composition % by weight of sodium chloride, 73% by weight of deionized water. Second composition % by weight of potassium peroxymonosulfate (KHSOs) , 30% by weight of deionized water. Mixing ratio of the first and second composition 1:1 by weight Third composition 100% activated carbon (flakes) 2K polyurea adhesive Hardener formulation: 100% by weight of Ethacure 420 (hindered secondary amine curing agent; Alheñarle (USA)) Resin formulation: 100% by weight of Desmodur N3900 (aliphatic polyisocyanate; Covestro, DE) The hardener and resin were mixed in a weight ratio of 1:1.3 Preparation The sodium chloride and water were stirred until the sodium chloride was completely dissolved. The potassium peroxymonosulfate and water were mixed until the potassium peroxymonosulfate was thoroughly moistened. Process 1) The substrates (mild steel, SBR, NR) to be bonded were thoroughly cleaned to remove dirt, oil and grease using Loctite 7063 (Henkel, DE), 2) The metal substrates were cleaned by sandblasting and again with Loctite 7063, 3) The second composition containing peroxymonosulfate was applied to the rubber surface with a plastic spatula, 4) The rubber was covered with a cloth, activated carbon was applied to it, followed by the first composition, the surface was covered with a plastic sheet and left to act for 15 minutes, 5) The cloth and film were removed, the surface was washed with water and wiped with a cloth, 6) The resin and the hardening component of the adhesive were mixed by hand and applied in a single layer onto the metal surface for the roll peel samples or onto the rubber surface for the T-shaped peel samples, 7) Roll peel samples (rubber to metal substrates) and T-shaped peel samples (rubber to rubber substrates) were mounted on rolls (20°C, relative humidity <85%). SBR roll peel after 3 days at room temperature (ASTM D 3167-03) 18 N / mm NR roll peel after 3 days at room temperature (ASTM D 3167-03) 14 N / mm SBR T-section peel after 3 days at room temperature (ASTM D1876) 10 N / mm T-shaped detachment with NR after 3 days N / mm ινΐΛ / a / zuz ι / υ ii zoz at room temperature (ASTM D1876) Example 2 First composition % by weight of sodium chloride, 73% by weight of deionized water. Second composition % by weight of potassium peroxymonosulfate (KHSO), 30% by weight of deionized water. Mixing ratio of the first and second composition 1:1 by weight Third composition 100% activated carbon (flakes) 2K epoxy adhesive Resin formulation: % by weight of DER 356 P (bisphenol-A / F based epoxy resin, Dow), 0.01% by weight of Antifoam 1244 (antifoaming agent, Solutia); 0.99% by weight of Silane A187 (epoxy silane, Momentive) Hardener formulation: 95.99% by weight of Ancamine 1922A (Evonik), 3.00% by weight of pyrogenic silica, 1.00% by weight of tris(dimethylaminomethyl)phenol, 0.01% by weight (antifoaming agent, Solutia) The hardener and resin were mixed in a weight ratio of 31:100 Preparation The sodium chloride and water were stirred until the sodium chloride was completely dissolved. The potassium peroxymonosulfate and water were mixed until the potassium peroxymonosulfate was thoroughly moistened. DER356, Antifoam and silane epoxy were dispersed under dynamic vacuum until a homogeneous mixture was achieved using a high-speed dispenser. Ancamine 1922A, pyrogenic silica, tris(dimethylaminomethyl)phenol, and antifoam were dispersed under dynamic vacuum until a homogeneous mixture was achieved using a high-speed dispenser. Process 1) The substrates (mild steel, SBR, NR) to be bonded were thoroughly cleaned to remove dirt, oil and grease using Loctite 7063 (Henkel, DE), 2) The metal substrates were cleaned by sandblasting and again with Loctite 7063, 3) The second composition containing peroxymonosulfate was applied to the rubber surface with a plastic spatula, 4) The rubber was covered with a cloth, activated carbon was applied to it, followed by the first composition, the surface was covered with a plastic sheet and left to act for 15 minutes, 5) The cloth and film were removed, the surface was washed with water and wiped with a cloth, 6) The resin and the hardening component of the adhesive were mixed by hand and applied in a single layer onto the metal surface for the roll peel samples or onto the rubber surface for the T-shaped peel samples. 7) Roll peel samples (rubber substrates to metal substrates) and T peel samples (rubber substrates to rubber substrates) were assembled in roll form (20°C, relative humidity <85%). IVIA / a / ZUZ l / UI Ί ΙΌZ Roll peel strength with SBR after 3 days at room temperature (ASTM D 3167-03) 19 N / mm Roll peel strength with NR after 3 days at room temperature (ASTM D 3167-03) 10 N / mm T-shaped peel strength with SBR after 3 days at room temperature (ASTM D1876) 13 N / mm T-shaped peel strength with NR after 3 days at room temperature (ASTM D1876) 14 N / mm iviA / a / zuzi / ui 1 zoz Example 3 First composition % by weight of sodium chloride, 8% by weight of sodium hydroxide, 71% by weight of deionized water. Second composition % by weight of potassium peroxymonosulfate (KHSO5), % by weight of deionized water. Mixing ratio of the first and second composition 1:1 by weight 2K Silicone Adhesive Hardener formulation: LOCTITE SI 5610 B Resin formulation: LOCTITE SI 5610 A The hardener and resin were mixed in a volume ratio of 1:2 iviA / a / zuz ι / υ i1 Preparation The sodium chloride, sodium hydroxide, and water were stirred until the sodium chloride was completely dissolved. The potassium peroxymonosulfate and water were mixed until the potassium peroxymonosulfate was thoroughly wetted. Process 1) The substrates (mild steel, SBR, NR) to be bonded were thoroughly cleaned to remove dirt, oil and grease using Loctite 7063 (Henkel, DE), 2) The metal substrates were cleaned by sandblasting and again with Loctite 7063, 3) The second composition containing peroxymonosulfate was applied to the rubber surface with a plastic spatula, 4) The rubber was covered with a cloth, the first composition was applied and left to act for 15 minutes, 5) The cloth was removed, the surface was washed with water and wiped with a cloth, 6) The resin and the hardening component of the adhesive were applied with a pneumatic gun in a single layer onto the metal surface for the roll peel samples or the rubber surface for the T-shaped peel samples, 7) Roll peel samples (rubber substrates to metal substrates) and T-peel peel samples (rubber substrates to rubber substrates) were assembled by lamination (20°C, relative humidity <85%). SBR roll peel after 3 days at room temperature (ASTM D 3167-03) 4 N / mm SBR T peel after 3 days at room temperature (ASTM D1876) 5 N / mm

Claims

1. A process for modifying the surface of an elastomeric rubber substrate, wherein the process comprises: (a) applying a first and a second composition to the surface of the elastomeric rubber substrate, wherein the first composition is an aqueous composition comprising chloride (Cl₂), preferably sodium chloride, and the second composition is an aqueous composition comprising peroxymonosulfate (HSO₅ / SO₅²⁻), preferably an alkali metal peroxymonosulfate, more preferably potassium peroxymonosulfate (KHSO₅); (b) optionally applying a third composition comprising activated carbon; and (c) incubating the first, second, and optionally the third composition with the rubber substrate for a period of time and under conditions that allow chlorination of the elastomeric rubber surface.

2. The process according to claim 1, wherein the first composition is an aqueous solution of sodium chloride, preferably with a concentration of 1M to 6M of sodium chloride, more preferably 4M to 6M.

3. The process according to claim 1 or 2, wherein the second composition is an aqueous solution of a persulfate, preferably potassium monopersulfate, preferably with a concentration of 10M to 30M persulfate, more preferably 18 to 22M.

4. The process according to any one of claims 1 to 3, wherein the first and second compositions are used in a weight ratio of approximately 3:1 to 1:3, preferably approximately 2:1 to 1:2, more preferably approximately 1.5:1 to 1:1.

5. 5 - The process according to any of claims 1 to 4, wherein the amount of the first and / or second and / or third composition applied to the surface of the elastomeric rubber substrate ranges from 500 to 900 g / m2, preferably from 600 to 700 g / m2.

6. The process according to any one of claims 1 to 5, wherein step (c) is carried out for 5 to 60 minutes, preferably 15 to 30 minutes.

7. The process according to any one of claims 1 to 6, wherein the process further comprises the step of cleaning the substrate surface after step (c).

8. The process according to any one of claims 1 to 7, wherein the first composition additionally contains a hydroxide, preferably sodium and / or potassium hydroxide. 9.- The process according to claim 8, wherein the first composition contains the hydroxide in a concentration of 0.5 M (mol / L) to 3 M (based on OH- ions). 10.- An elastomeric rubber substrate having a chlorinated surface obtainable according to the process of any one of claims 1 to 9.

11. A process for forming a bond between a first and a second substrate, wherein the first substrate is an elastomeric rubber substrate according to claim 8 or obtained according to the process of any one of claims 1 to 9 and the second substrate is a rubber or metal substrate, wherein the process comprises: (a) applying an adhesive composition to the bonded surface of the rubber or metal substrate, wherein the adhesive composition is preferably a 2K epoxy, polyurea, silicone or polyurethane adhesive comprising a resin formulation and a hardener formulation; (b) contacting the chlorinated surface of the rubber substrate and the surface of the metal substrate with the adhesive applied under pressure to form the bond.

12. The process according to claim 11, wherein the process further comprises a step of cleaning the surfaces of the rubber and / or metal substrate before steps (a) and / or (b).

13. The process according to any one of claims 11 to 12, wherein step (b) is carried out at a temperature of 15 to 30°C and a relative humidity of 85% or less. 5 14.- The process according to any one of claims 11 to 13, wherein step (b) is carried out by rolling. 15.- An agglomerated product obtained according to the process of any one of claims 9 to 10 13.