Method for modifying the surface polarity of a rubber substrate

Abstract

The present invention relates to a method for modifying the surface polarity of elastic rubber substrates to promote their cold bonding to other rubber substrates or non-elastic substrates of different materials by treating the rubber substrates with a chloride-containing composition and a permonosulfate-containing composition to chlorinate the surface of the rubber substrates. Other aspects relate to the surface-modified rubber substrates thus obtained, methods for bonding them to other substrates by using adhesives, and bonded substrates thus obtained.

Description

[0001] The present invention relates to a method for modifying the surface polarity of elastic rubber substrates to promote their cold bonding to other rubber substrates or non-elastic substrates of different materials by treating the rubber substrates with a chloride-containing composition and a permonosulfate-containing composition to chlorinate the surface of the rubber substrates. Other aspects relate to the surface-modified rubber substrates thus obtained, methods for bonding them to other substrates by using adhesives, and bonded substrates thus obtained.

[0002] For various applications, preformed parts made of elastomeric materials need to be bonded to another elastomeric material or to a different material such as glass, metal or plastic. Achieving sufficient bond strength between those materials is challenging because existing adhesives for non-elastic materials show no or insufficient adhesion to elastomers, while known adhesives for elastomers have insufficient water and steam resistance.

[0003] While some of the existing disadvantages can be overcome by using hot melt adhesives, low curing temperatures are required for most applications using epoxy adhesives. Low curing temperatures are desirable because they save energy and reduce thermal effects on the substrate. In addition, thermal stresses caused by differential heating rates or thermal elongation of the substrate can be minimized.

[0004] In recent years, photochemical and chemical techniques such as halogenation, etching, grafting, oxidation, crosslinking, and physical methods such as corona discharge, plasma treatment, electron or ion beam treatment, flame or laser treatment, have been widely used for the purpose of rubber surface modification, which is needed to improve the adhesion of ordinary cold-curing adhesives to the rubber substrate. The simplest mechanism is to mechanically roughen the surface, but this has limited effect.

[0005] Regarding halogenation techniques, different types of surface treatments based on organic solvents (e.g. trichloroisocyanuric acid in ethyl acetate or N-haloamides in solvents) or aqueous solutions (e.g. sodium hypochlorite) are known in the art. For example, US 4,500,685 A describes the use of N,N-dihalosulfonamides in a waxy matrix for the halogenation of vulcanized rubber surfaces. International Patent Publication WO 2000 / 05363A1 describes the halogenation of rubber surfaces with acidified hypochlorite solutions, chlorine and hydrochloric acid in organic solvents, chlorine- or fluorine-containing gases, and mixtures of two or more thereof. For example, M. Virtudes et al. The use of trichloroisocyanuric acid is described 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 the rubber chain, generating halogen-carbon atoms and thus increasing the surface polarity. The increased surface polarity leads to better compatibility with commonly used 2K adhesives.

[0006] Prior art techniques using organic solvents are undesirable due to high levels of toxic and flammable solvents and the resulting health and safety issues. Hypochlorite based techniques have been found to be disadvantageous due to stability issues and side reactions that generate free oxygen which reduces treatment performance.

[0007] Therefore, there is a need in the art for alternative processes that allow for the halogenation of rubber surfaces to promote their cold bonding without the disadvantages of prior methods.

[0008] The present invention meets this objective and provides a method for modifying the surface of an elastic rubber substrate using an aqueous solution of a chloride salt and an aqueous solution of a permonosulfate salt. The newly discovered method is based on the properties of persulfates as strong oxidants that readily react with chlorides to form sulfates and free chlorine. The free chlorine can then react with double bonds in the rubber surface and provide a chlorinated surface of the treated rubber substrate. As a result, the surface polarity of the rubber is increased and the adhesion of common adhesives on its surface is improved.

[0009] In a first aspect, the present invention therefore relates to a method for modifying the surface of an elastic rubber substrate, wherein the method comprises

[0010] (a) applying the first and second compositions to the surface of the elastic rubber substrate, wherein the first composition is a chloride (Cl - ), preferably sodium chloride, and the second composition is an aqueous composition comprising peroxymonosulfate (HSO5 - / SO5 2- ), preferably an aqueous composition of an alkali metal peroxymonosulfate, more preferably potassium peroxymonosulfate (KHSO5);

[0011] (b) optionally applying a third composition comprising activated carbon; and

[0012] (c) incubating the first, second and optionally third compositions with the rubber substrate for a period of time and under conditions that permit chlorination of the elastomeric rubber surface.

[0013] In a further aspect, the present invention relates to an elastomeric rubber substrate having a chlorinated surface area obtainable by the process according to the invention.

[0014] Yet another aspect relates to a method of forming a bond between a first and a second substrate, wherein the first substrate is an elastic rubber substrate according to the present invention or an elastic rubber substrate obtained according to the method of the present invention, and the second substrate is a rubber or metal substrate, wherein the method comprises:

[0015] (a) applying an adhesive composition to a surface to be bonded of a rubber or metal substrate, wherein the adhesive composition is preferably a 2K epoxy resin, polyurea, polyurethane or silicone adhesive comprising a resin formulation and a hardener formulation;

[0016] (b) contacting the chlorinated surface of the rubber substrate and the surface of the metal substrate with the applied adhesive under pressure to form a bond.

[0017] In a further aspect, the invention relates to a bonded product obtainable according to the process described herein.

[0018] "At least one," as used herein, refers to at least one and includes 1, 2, 3, 4, 5, 6, 7, 8, 9 or more of the mentioned substances.

[0019] The present invention is based on the surprising discovery of the inventors that by using the method described herein, on the one hand, the problems associated with the use of organic solvents can be avoided, while on the other hand the method developed is more efficient than the known methods using hypochlorites, since oxygen is not formed during the reaction. In addition, since the persulfate used is much more reactive, the reaction time can be significantly shortened, from about 8 hours for hypochlorite treatment to only about 5 minutes to 60 minutes for persulfate-based modification reactions. Finally, it has been found that the method of the present invention allows the production of higher amounts of free chlorine due to the possibility of using higher chloride concentrations than hypochlorite concentrations, which have stability problems at high concentrations, which additionally improves the performance of the method. It has further been found that unreacted chlorine can be advantageously bound by using activated carbon. Thus, the release of free chlorine during the reaction can be minimized.

[0020] 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 chloride or sodium chloride, wherein sodium chloride is particularly preferred due to its ready availability, cost and high water solubility. The first composition is preferably 1M (mol / L) to 6M chloride, more preferably 4M to 6M (based on Cl -ions) contains chloride ions. The dosage is limited in principle only by the solubility of the salt.

[0021] In a preferred embodiment, the first composition is alkaline, preferably having a pH value of greater than 8, more preferably greater than 10, most preferably greater than 12. Preferably, the first composition comprises a hydroxide, which is preferably added as an alkali metal hydroxide. More preferably, the first composition contains sodium hydroxide and / or potassium hydroxide, most preferably sodium hydroxide. The benefit of the additional addition of hydroxide, especially sodium hydroxide and / or potassium hydroxide, is that it reduces the unreacted free chlorine released into the air. An additional effect is that if a hydroxide is added, the advantageous third component, activated carbon, is not required. Preferably, the first composition comprises 0.5M (mol / L) to 3M (based on OH). - ions), more preferably hydroxides in a concentration of 1M to 3M, especially sodium hydroxide and / or potassium hydroxide.

[0022] The second composition is preferably an aqueous composition comprising peroxymonosulfate, containing peroxymonosulfate ions (HSO5 - / SO5 2- ). Preferred are alkali metal salts, especially potassium permonosulfate (KHSO5). The permonosulfate concentration is preferably 10 M to 30 M persulfate, more preferably 18 to 22 M. The second composition may be a solution, but is preferably a paste of permonosulfate in water or a salt such as potassium permonosulfate moistened with water only.

[0023] In addition to the chloride and peroxymonosulfate, the first and second compositions may each contain additional components including, but not limited to, solvents, fillers, thickeners, etc. However, it is preferred that they contain no organic solvents, ie, contain those in a concentration of less than 1% by volume.

[0024] The composition containing chloride and peroxymonosulfate is used in an amount to maximize the production of free chlorine. Therefore, the actual amount used can be determined based on the respective concentrations of the solutions used. Generally, if the concentrations are within the ranges disclosed herein, the first and second compositions are used in a weight ratio of about 3:1 to 1:3, preferably about 2:1 to 1:2, and more preferably about 1.5:1 to 1:1.5.

[0025] In various embodiments, the amount of the first and / or second and / or third composition applied to the surface of the elastic rubber substrate is 500 to 900 g / m 2 , preferably 600 to 700 g / m 2 Again, this depends on the concentrations used, but the specified ranges are particularly preferred if the concentrations disclosed herein are used.

[0026] The activated carbon (third composition) is preferably used in solid form, such as powder or flakes. However, it can also be used in the form of an aqueous dispersion, and in such an embodiment, can also contain additional components as indicated above for other compositions.

[0027] The incubation step (c) of the composition and the rubber surface is carried out for a sufficient period of time 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 given herein, a reaction time of 5-60 minutes, preferably 15-30 minutes, is sufficient to produce the desired halogenated surface.

[0028] The application of the composition can be carried out by any suitable means known in the art. If the composition is liquid, application can be achieved by spraying, brushing, printing, dipping, casting, etc. Solid or substantially solid or pasty compositions, such as activated carbon or peroxymonosulfate moistened with water, can be applied by suitable solid material application techniques.

[0029] Prior to applying the compositions disclosed herein, the surface of the rubber substrate to be modified may be cleaned, degreased, etc.

[0030] In various embodiments of the inventive method, the rubber surface is first cleaned to remove oil, grease and dirt. After this optional step, the second composition is applied to the surface. The cloth is then placed on the surface on which the second composition is applied, and the third composition is preferably applied. Thereafter, the first composition is applied to the cloth. The surface is then covered with a foil, such as a plastic foil or similar covering, and the reaction is carried out for about 5-30 minutes. The foil and cloth are then removed, and the surface is washed with water and cleaned / dried with a cloth. Using the first composition with additional hydroxide, there is no need to use a plastic foil.

[0031] Therefore, in various embodiments of the present invention, the method further comprises the step of cleaning and optionally drying the substrate surface after the incubation step (c).

[0032] The elastic rubber substrate can be made of rubber, for example, can be a rubber sheet, or have an elastic rubber surface. Rubber materials are well known in the art, and include but are not limited to natural rubber (NR), ethylene propylene diene rubber (EPDM), ethylene propylene rubber (EPM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber, styrene-butadiene rubber (SBR), styrene-butadiene-styrene rubber (SBS), butadiene rubber (BR), isoprene rubber (IR), styrene ethylene butylene styrene rubber (SEBS), and all other rubbers of copolymers of any two or more of styrene, butadiene, ethylene and isoprene. Particularly preferred are natural rubber and styrene-butadiene rubber.

[0033] The other substrate to be bonded can be made of any material. In various embodiments, it is made of the same rubber material or another rubber material or of metal. The metal substrate can be any metal. Usually, the metal is iron, steel and aluminum and their alloys. The metal substrate can be plated with other metals such as zinc, or can be surface treated such as through conversion treatment. The metal substrate can be composed of metal or can be surface coated with metal.

[0034] For bonding process, the adhesive used according to the method described herein can be any conventional adhesive used for rubber substrate bonding in the field, preferably 2K adhesive. Commonly used adhesives are those based on epoxides, polyureas, silicones or polyurethanes. This 2K adhesive usually comprises a resin and a hardener, which is usually in the form of a separate formulation directly merged before application. The formulation is designed so that once merged, polymerization reaction begins and proceeds until the composition is fully cured. Curing behavior and time depend on the resin and hardener used.

[0035] For the use of polyisocyanate-based adhesives (such as polyurea-based adhesives or polyurethane-based adhesives), the adhesive is crosslinked by components containing NCO groups and acidic H groups. Embodiments include known NCO-group-containing prepolymers or polyisocyanates as resin components, while known oligomers or polymers containing OH, NH, SH, COOH groups, preferably OH and / or NH, which can react with the NCO groups of other components can be used as hardener components. In order to obtain a network, it is convenient to include at least two NCO groups and at least two, in particular OH groups, in the crosslinking component. In addition, additives known per se can be included in the adhesive. These are components that can adjust and influence certain properties of the adhesive.

[0036] The resin component preferably comprises at least one polyisocyanate and / or at least one polyurethane prepolymer with at least two isocyanate groups or a mixture thereof. The PU prepolymer is obtainable, for example, by reacting a polyol component with a stoichiometric excess of at least difunctional isocyanate.

[0037] PU prepolymers within the meaning of the present invention are reaction products of compounds with OH groups or NH groups and excess polyisocyanates. They are polyols known for adhesive applications or corresponding compounds with secondary and / or primary amino groups. OH-containing starting compounds are preferred. Polyols with a molecular weight of up to 20,000 g / mol, in particular 200 to 10,000 g / mol (number average molecular weight, MN, can be determined by GPC) are particularly suitable for synthesizing the prepolymers. For example, they can be polyols based on polyethers, polyesters, polyolefins, polyacrylates, alkylene polyols. In another embodiment, such compounds with NH groups are used.

[0038] Polyisocyanates with two or more isocyanate groups known per se, such as aliphatic, alicyclic or aromatic isocyanates, can be used directly or as polyisocyanates in prepolymer synthesis. One embodiment uses monomers, oligomeric or polymeric isocyanates as resin components. A mixture of prepolymers and polyisocyanates is also possible. In principle, all known polyisocyanates can be used, in particular the following isomers: methylene diisocyanate (MDI) or toluene diisocyanate (TDI), tetramethylxylylene diisocyanate (TMXDI), 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (IPDI), naphthalene-1,5-diisocyanate (NDI), hexane-1,6-diisocyanate (HDI). At least trifunctional isocyanates can also be used, such as those obtained by trimerization or oligomerization of diisocyanates, such as isocyanurates, carbodiimide or biuret.

[0039] The hardener 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. These may be SH, COOH, NH or OH groups, for example. Polyols and amines are preferred.

[0040] A large number of polyols are suitable as polyol components for use as harder components of polyurethane-based adhesives. For example, they can be those having two to ten OH groups per molecule. They can be aliphatic compounds or aromatic compounds, and polymers with a sufficient number of OH groups can also be used. These can be primary or secondary OH groups, provided that they have sufficient reactivity with isocyanate groups. The molecular weight of such polyols can vary over a wide range, for example 500 to 10,000 g / mol. The polyols already described above can be included.

[0041] Examples of such polyols are low molecular weight aliphatic polyols, in particular C2 to C36 alcohols, preferably having two to ten OH groups. Another group of suitable polyols are, for example, polyethers. These are reaction products of alkylene oxides having 2 to 4 C atoms with low molecular weight di- or trifunctional alcohols. The polyether polyols should have a molecular weight of, in particular, 400 to 5000 g / mol. OH-containing poly(meth)acrylates or polyolefins are also suitable.

[0042] Polyester polyols are another group of suitable polyol compounds for component B. Polyester polyols known for adhesives can be used. They can be, for example, diols, particularly low molecular weight alkylene glycols or polyether glycols and dicarboxylic acid reaction products. These can be aliphatic or aromatic carboxylic acids or mixtures thereof. Such polyester polyols are known to those skilled in the art and are commercially available in various forms. These polyester polyols should have a molecular weight of, in particular, 200 to 3000 g / mol. These also include polymeric lactones or polyacetals, provided that they have at least two functional groups and a corresponding suitable molecular weight.

[0043] As the hardener component of the polyurea-based adhesive, the amine used is preferably a sterically hindered amine. Suitable sterically hindered amines having two or more amine groups, preferably two amine groups, are aspartic acid ester amines or aromatic diamines. Examples of aromatic diamines are those that are sterically hindered to reduce reactivity when combined with the polymeric isocyanate of the resin component. Such aromatic amines include, but are not limited to, toluenediamine, 1-methyl-3,5-diethyl-2,4-diaminobenzene, 1-methyl-3,5-diethyl-2,6-diaminobenzene (also known as DETDA or diethyltoluenediamine), di(methylthio)toluenediamine, 1,3,5-triethyl-2,6-diaminobenzene, toluenediamine derivatives containing halogen groups, cyano groups, alkoxy groups, alkylthio groups, alkenyl groups, or carbonyl moieties, m-phenylenediamine, p-phenylenediamine, 4',4'-methylenedianiline, 4,4'-diaminodiphenyl sulfone, 2,6-diamino-pyridine, 4,4'-methylene-bis-(3-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline), 4,4-methylene-bis-(3-chloro-2,5-diethylaniline), aniline), 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 4,4'-bis-(sec-butylamino)diphenylmethane (SBMDA), 3,5,3',5'-tetraethyl-4,4'-diaminodiphenylmethane, propylene-di-4-aminobenzoate, 4-chloro-3,5-diaminobenzoic acid isobutyl ester, bis-(2-aminophenyl) disulfide, bis-(4-aminophenyl) disulfide, 3,3'-carbomethoxy-4,4'-diaminodiphenylmethane, 1,2-bis(2-aminophenylthio)ethane, dimethylthiotoluenediamine (DMTDA), 0,1,8-diamino-p-menthane, α,α,α',α'-tetramethylxylenediamine, N,N'-di-tert-butylethylenediamine, and mixtures thereof.

[0044] In the case of silicone-based adhesives, known one-component and two-component silicone adhesives can be used. Preferably, two-component silicone adhesives. Silicon adhesives include one or more poly(diorganosiloxanes). These poly(diorganosiloxanes) are crosslinkable. Crosslinking can be carried out through reactive end groups or through the end groups of poly(diorganosiloxanes) that can be converted into reactive groups. All conventional poly(diorganosiloxanes) can be used. For example, such poly(diorganosiloxanes) are well known for producing adhesives or sealants and are commercially available.

[0045] The poly(diorganosiloxane) may preferably be a poly(diorganosiloxane) having hydroxyl end groups and / or may be a poly(diorganosiloxane) having alkoxysilyl end groups. Hydroxy-terminated poly(diorganosiloxane)s and alkoxysilyl-terminated poly(diorganosiloxane)s are known and commercially available. The poly(diorganosiloxane) is preferably a poly(dialkylsiloxane), wherein the alkyl group preferably has 1 to 5, more preferably 1 to 3, carbon atoms, and particularly preferably a methyl group. Most preferred are hydroxy-terminated poly(dimethylsiloxane)s and methoxysilyl-terminated poly(dimethylsiloxane), which are preferably used in combination, each of which is included in one component of the 2K silicone-based adhesive.

[0046] The silicone adhesive further comprises one or more crosslinkers for the poly(diorganosiloxane), which may be all crosslinkers known in the art for this purpose. For example, the crosslinker is preferably selected from tetraalkoxysilanes, organotrialkoxysilanes, diorganodialkoxysilanes and / or oligo(organoalkoxysilanes), tetraketoximesilanes (ketoximosilane), organotriketoximesilanes, diorganodiketoneoximesilanes and / or oligo(organoketoneoximesilanes), which are optionally functionalized with one or more heteroatoms in the organic radical, or mixtures thereof. Suitable examples are methyltrimethoxysilane, chloromethyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, phenyltriethoxysilane, methyltripropoxysilane, phenyltripropoxysilane, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, methyltri(methyl-ethylketoximino)silane, phenyltri(methyl-ethylketoximino)silane, vinyltri(methyl-ethylketoximino)silane, methyltri(isobutylketoximino)silane or tetra(methyl-ethylketoximino)silane. Methyltrimethoxysilane, vinyltrimethoxysilane, tetraethoxysilane, methyltri(methyl-ethylketoximino)silane, vinyltri(methyl-ethylketoximino)silane and methyltri(isobutylketoximino)silane.

[0047] As an optional component, the silicone adhesive (more particularly the two-component silicone formulation) may further comprise one or more condensation catalysts. This serves as a catalyst for crosslinking the polydiorganosiloxane. Preferred condensation catalysts are organic compounds and / or metal or metalloid complexes, in particular from Groups Ia, IIa, IIIa, IVa, IVb or IIb of the Periodic Table of the Elements, such as Sn compounds, Ti compounds, such as titanates and borates or mixtures thereof. Preferred organotin compounds are dialkyltin compounds, for example selected from dimethyltin di-2-ethylhexanoate, dimethyltin dilaurate, di-n-butyltin diacetate, di-n-butyltin di-2-ethylhexanoate, di-n-butyltin dioctoate, di-n-butyltin di-2,2-dimethyloctoate, di-n-butyltin dilaurate, di-n-butyltin distearate, di-n-butyltin dimaleate, di-n-butyltin dioleate, di-n-butyltin diacetate, di-n-octyltin di-2-ethylhexanoate, di-n-octyltin di-2,2-dimethyloctoate, di-n-octyltin dimaleate and di-n-octyltin dilaurate.

[0048] If an epoxy adhesive is used, the epoxy resin may include any known and used epoxy resin in the epoxy resin formulation of the 2K epoxy adhesive. Suitable epoxy resins preferably include epoxy resins having 1 to 10 epoxy groups per molecule. These epoxy groups may be 1,2-epoxy groups. Epoxy resins may in principle be saturated, unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic polyepoxide compounds. Examples of suitable epoxy resins include polyglycidyl ethers prepared by reacting epichlorohydrin or epibromohydrin with polyphenols in the presence of a base, and polyglycidyl ethers of the following resins: phenol-formaldehyde novolac resins, alkyl-substituted phenol-formaldehyde resins (epoxy novolac resins), phenol-hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins, and dicyclopentadiene-substituted phenol resins. Polyphenols suitable for this purpose include, for example, resorcinol, catechol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), bisphenol F (bis(4-hydroxy-phenyl)methane), 1,1-bis(4-hydroxyphenyl)isobutane, 4,4′-dihydroxybenzophenone, 1,1-bis(4-hydroxyphenyl)-ethane, 1,5-hydroxynaphthalene. Also suitable are diglycidyl ethers of ethoxylated resorcinol (DGER), for example from Indspec Chemical Corporation, and diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (1,1-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol F, bisphenol K, bisphenol M, bisphenol S, tetramethylbisphenol; diglycidyl ethers of alkylene glycols having 2 to 20 carbon atoms and poly(ethylene oxide) or poly(propylene oxide) glycols.

[0049] Further suitable epoxy resins are polyglycidyl ethers of polyols or diamines. These polyglycidyl ethers are derived from polyols, for example ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butanediol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol or trimethylolpropane.

[0050] Other suitable epoxy resins are polyglycidyl esters of polycarboxylic acids, examples being reaction products of glycidol or epichlorohydrin with aliphatic or aromatic polycarboxylic acids, such as oxalic acid, succinic acid, glutaric acid, terephthalic acid or dimerized fatty acids.

[0051] Other suitable epoxy resins are derived from the epoxidation products of ethylenically unsaturated cycloaliphatic compounds or from natural oils and fats.

[0052] In a preferred embodiment, the epoxy resin has 1 to 10 epoxy groups and is selected from the diglycidyl ethers of resorcinol, catechol, hydroquinone, bisphenol, bisphenol A, bisphenol AP (1,1-bis(4-hydroxyphenyl)-1-phenylethane), bisphenol F, bisphenol K, bisphenol M, bisphenol S, tetramethylbisphenol; diglycidyl ethers of alkylene glycols having 2 to 20 carbon atoms and poly(ethylene oxide) or poly(propylene oxide); polyglycidyl ethers of phenol-formaldehyde novolac resins, alkyl-substituted phenol-formaldehyde resins (epoxy novolac resins), phenol-hydroxybenzaldehyde resins, cresol-hydroxybenzaldehyde resins, dicyclopentadiene-phenol resins and dicyclopentadiene-substituted phenol resins; and any combination thereof, preferably the diglycidyl ether of bisphenol F and the diglycidyl ether of bisphenol A and any combination thereof.

[0053] Particularly preferred are epoxy resins derived from the reaction of bisphenol A or bisphenol F with epichlorohydrin. It may be advantageous to use a liquid epoxy resin, preferably based on bisphenol A and having a sufficiently low molecular weight. Epoxy resins that are liquid at room temperature generally have an epoxy equivalent weight of 150 to about 220. Such epoxy resins are available from Dow under the trade name DER TM Commercially available.

[0054] The resin formulation may include many other components, all of which are well known to those skilled in the art, including but not limited to conventional adjuvants and additives, such as fillers, plasticizers, tougheners, reactive and / or non-reactive diluents, flow aids, coupling agents (e.g., silanes), adhesion promoters, wetting agents, tackifiers, flame retardants, wetting agents, thixotropic agents and / or rheological agents (e.g., fumed silica), aging and / or corrosion inhibitors, stabilizers and / or colorants. Based on the requirements of the adhesive and its application, and taking into account production, flexibility, strength, and adhesion to the substrate, the adjuvants and additives are incorporated into the composition in different amounts. In various embodiments, the resin formulation includes fillers and / or colorants, but generally in an amount not exceeding 10% by weight relative to the resin formulation.

[0055] In various embodiments, the hardener formulation comprises a compound capable of crosslinking with epoxy groups on the epoxy resin. Any hardener suitable for use with 2K epoxy resins may be used. Preferred hardeners include thiols, polymeric amines (polyamines) and polymeric amides (polyamides) (including, for example, polyamidoamines), low molecular weight amines, and combinations thereof. Also preferred are adducts of the above hardeners with epoxy resins such as those described above.

[0056] In various embodiments, preferred polyamines include polyetheramine-epoxy adducts, i.e., the reaction product of a stoichiometric excess of an amine prepolymer and an epoxy resin. Polyamine hardeners tend to react more slowly than low molecular weight amines, but can increase the flexibility of the cured adhesive. The amine prepolymer used for adduct formation can be any amine prepolymer having at least two amine groups to allow crosslinking to occur. The amine prepolymer contains primary amine groups and / or secondary amine groups, and preferably contains primary amine groups. Suitable amine prepolymers include polyetherdiamines and polyethertriamines, and mixtures thereof. Polyetherdiamines are preferred. Polyetheramines can be linear, branched, or mixtures. Branched polyetheramines are preferred. Polyetheramines of any molecular weight can be used, and molecular weights in the range of 200-6000 or more are suitable. The molecular weight can be higher than 1000, or more preferably higher than 3000. Molecular weights of 3000 or 5000 are preferred.

[0057] Suitable commercially available polyetheramines that can be used in adduct formation or as such include those sold by Huntsman under the trade name Suitable polyether diamines include those sold in the D, ED and DR series of Jeffamine. These include Jeffamine 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 Jeffamine in the T series. These include Jeffamine T-403, T-3000 and T-5000. Polyether diamines are preferred, and polyether diamines with a molecular weight of about 400 (e.g., Jeffamine D-400) are most preferred. Any of the above equivalents may also be used for partial or complete replacement.

[0058] When polyamides are included, any polyamide hardener may be used. Some preferred polyamides include the reaction product of dimerized fatty acids and polyamines. Examples of such polyamides include those sold under the trade names Those that are available.

[0059] Suitable thiols include difunctional thiols, such as 1,8-dimercapto-3,6-dioxooctane (DMDO), as a monomer or as an epoxy adduct, ie, the reaction product of a stoichiometric excess of thiol with an epoxy resin. Particularly preferred are difunctional thiol-epoxy resin adducts.

[0060] The hardener composition may include a low molecular weight (non-polymeric) amine hardener. Preferred compounds include primary and / or secondary amines having a molecular weight of up to 300 g / mol, 250 g / mol or 200 g / mol. Aliphatic amine hardeners include those sold by Evonik under the trade name Those that are sold.

[0061] In all of the above adducts, the epoxy resin may be any of the above epoxy resins, but is preferably a bisphenol diglycidyl ether, such as the reaction product of bisphenol A and epichlorohydrin.

[0062] Any amount of the hardener may be used in the present invention.

[0063] In the hardener composition, one or more curing accelerators (catalysts) are preferably used to accelerate the curing of the adhesive. The curing accelerator preferably acts by catalyzing the reaction between the polyamine / polyamide / thiol hardener on the one hand and the epoxy resin on the other hand. The curing accelerator preferably comprises a tertiary amine. A preferred example is 2,4,6-tris(dimethylaminomethyl)phenol, which is available from Cognis under the name Other suitable polyamines are described in US Pat. No. 4,659,779 (and its family members US Pat. Nos. 4,713,432 and 4,734,332; and EP-A-0 197 892).

[0064] The curing accelerator may be present in any amount suitable to accelerate the curing of the epoxy adhesive. Preferably, the curing accelerator may be present in an amount less than 5 wt %, more preferably between 0.5 and 2 wt %, based on the weight of the hardener composition.

[0065] The curing temperature is preferably less than 60° C., or 50° C., or 40° C. The epoxy adhesive composition is preferably cured at ambient temperature, for example, about 20° C. or 25° C. Therefore, the method of the present invention is preferably carried out at ambient temperature, that is, in the temperature range of about 15 to 40° C. Heating the epoxy adhesive of the present invention is permissible but not preferred, for example to further reduce the curing time or to obtain a more complete cure.

[0066] As used herein, "about" in connection with a numerical value refers to the reference value of the numerical value ± 10%.

[0067] In various embodiments, the hardener may include any of the additives and adjuvants disclosed above in connection with the resin composition, such as a filler, such as calcium carbonate or silica.

[0068] In the bonding method, step (b) may be performed at a temperature of 15 to 30° C. and a relative humidity of 85% or less.

[0069] Prior to steps (a) and / or (b) of the bonding process, the rubber and / or metal substrate surfaces may be cleaned to remove dirt, oil, grease, etc., all of which may interfere with the bonding process. Suitable cleaning agents are well known in the art and include those from Henkel. SF-7063.

[0070] Mixing, applying and / or dispensing of the adhesive can be accomplished using simple manual equipment or fully automated systems, all of which are known and readily available to those skilled in the art.

[0071] The step of contacting the two substrates under pressure to form a bond can be performed using known equipment, such as rollers, plates or other suitable equipment. In a preferred embodiment, step (b) is performed by rolling.

[0072] In various embodiments, the entire process can be automated.

[0073] As mentioned above, the present invention also includes the product obtained by bonding two substrates in the method described.

[0074] All embodiments disclosed herein in relation to the described methods and formulations are equally applicable to the claimed products and vice versa.All documents cited herein are hereby incorporated by reference in their entirety.

[0075] The present invention is further illustrated by the following examples, but is not limited thereto. Example

[0076] Example 1

[0077] First composition

[0078] 27 wt% sodium chloride, 73 wt% deionized water.

[0079] Second composition

[0080] 70 wt% potassium persulfate (KHSO5), 30 wt% deionized water.

[0081] The mixing ratio of the first and second compositions by weight is 1:1

[0082] The third composition

[0083] 100 wt% activated carbon (flakes)

[0084] 2K Polyurea Adhesive

[0085] Hardener preparations:

[0086] 100 wt% Ethacure 420 (hindered secondary amine curing agent; Albemarle (US))

[0087] Resin preparation:

[0088] 100 wt% Desmodur N3900 (aliphatic polyisocyanate; Covestro, DE)

[0089] The hardener and resin are mixed in a weight ratio of 1:1.3.

[0090] preparation

[0091] Shake the sodium chloride and water until the sodium chloride is completely dissolved. Mix the potassium peroxymonosulfate and water until the potassium peroxymonosulfate is thoroughly wetted.

[0092] method

[0093] 1) Clean the substrates to be bonded (mild steel, SBR, NR) to remove dirt, oil and grease by using Loctite 7063 (Henkel, DE)

[0094] 2) Sandblast the metal substrate and clean it again with Loctite 7063

[0095] 3) Apply the second composition containing peroxymonosulfate to the rubber surface using a plastic scraper

[0096] 4) Cover the rubber with a cloth, apply activated carbon on it, followed by the first composition, cover the surface with a plastic foil and react for 15 minutes

[0097] 5) Remove the cloth and foil, wash the surface with water and clean with a cloth

[0098] 6) Mix the resin and hardener components of the adhesive by hand and apply as a single coat to the metal surface of the roller peel specimen or the rubber surface of the T peel specimen

[0099] 7) Roller peeling specimens (rubber to metal substrate) and T peeling specimens (rubber to rubber substrate) were assembled by rolling (20°C, relative humidity <85%)

[0100] After 3 days at room temperature, peeled with SBR roller (ASTM D 3167-03) 18N / mm After 3 days at room temperature, peeled with NR roller (ASTM D 3167-03) 14N / mm T-peel test with SBR after 3 days at room temperature (ASTM D1876) 10N / mm T peeling of NR after 3 days at room temperature (ASTM D1876) 13N / mm

[0101] Example 2

[0102] First composition

[0103] 27 wt% sodium chloride, 73 wt% deionized water.

[0104] Second composition

[0105] 70 wt% potassium persulfate (KHSO5), 30 wt% deionized water.

[0106] The mixing ratio of the first and second compositions by weight is 1:1

[0107] The third composition

[0108] 100 wt% activated carbon (flakes)

[0109] 2K Epoxy Adhesive

[0110] Resin preparation :

[0111] 99 wt% DER 356P (bisphenol A / F based epoxy resin, Dow), 0.01 wt% defoamer 1244 (defoamer, Solutia); 0.99 wt% silane A187 (epoxy silane, Momentive)

[0112] Hardener preparations :

[0113] 95.99 wt% Ancamine 1922A (Evonik), 3.00 wt% fumed silica, 1.00 wt% tris(dimethylaminomethyl)phenol, 0.01 wt% (defoaming agent, Solutia)

[0114] The hardener and resin are mixed in a weight ratio of 31:100.

[0115] preparation

[0116] Shake the sodium chloride and water until the sodium chloride is completely dissolved. Mix the potassium persulfate and water until the potassium persulfate is fully wetted. Disperse DER356, defoamer, and epoxy silane with a high-speed dispenser under a powered vacuum until a uniform mixture is obtained. Disperse Ancamine 1922A, fumed silica, tris(dimethylaminomethyl)phenol, and defoamer with a high-speed dispenser under a powered vacuum until a uniform mixture is obtained.

[0117] method

[0118] 1) Clean the substrates to be bonded (mild steel, SBR, NR) to remove dirt, oil and grease by using Loctite 7063 (Henkel, DE)

[0119] 2) Sandblast the metal substrate and clean it again with Loctite 7063

[0120] 3) Apply the second composition containing peroxymonosulfate to the rubber surface using a plastic scraper

[0121] 4) Cover the rubber with a cloth, apply activated carbon on it, followed by the first composition, cover the surface with a plastic foil and react for 15 minutes

[0122] 5) Remove the cloth and foil, wash the surface with water and clean with a cloth

[0123] 6) Mix the resin and hardener components of the adhesive by hand and apply as a single coat to the metal surface of the roller peel specimen or the rubber surface of the T peel specimen

[0124] 7) Roller peeling specimens (rubber to metal substrate) and T peeling specimens (rubber to rubber substrate) were assembled by rolling (20°C, relative humidity <85%)

[0125] After 3 days at room temperature, peeled with SBR roller (ASTM D 3167-03) 19N / mm After 3 days at room temperature, peeled with NR roller (ASTM D 3167-03) 10N / mm T-peel test with SBR after 3 days at room temperature (ASTM D1876) 13N / mm T peeling of NR after 3 days at room temperature (ASTM D1876) 14N / mm

[0126] Example 3

[0127] First composition

[0128] 21 wt% sodium chloride, 8 wt% sodium hydroxide, 71 wt% deionized water.

[0129] Second composition

[0130] 70 wt% potassium persulfate (KHSO5), 30 wt% deionized water.

[0131] The mixing ratio of the first and second compositions by weight is 1:1

[0132] 2K Silicone Adhesive

[0133] Hardener preparations:

[0134] LOCTITE SI 5610B

[0135] Resin preparation:

[0136] LOCTITE SI 5610A

[0137] Mix the hardener and resin in a volume ratio of 1:2

[0138] preparation

[0139] Shake the sodium chloride, sodium hydroxide and water until the sodium chloride is completely dissolved. Mix the potassium peroxymonosulfate and water until the potassium peroxymonosulfate is thoroughly wetted.

[0140] method

[0141] 1) Clean the substrates to be bonded (mild steel, SBR, NR) to remove dirt, oil and grease by using Loctite 7063 (Henkel, DE)

[0142] 2) Sandblast the metal substrate and clean it again with Loctite 7063

[0143] 3) Apply the second composition containing peroxymonosulfate to the rubber surface using a plastic scraper

[0144] 4) Cover the rubber with a cloth, apply the first composition and react for 15 minutes

[0145] 5) Remove the cloth, wash the surface with water and clean with a cloth

[0146] 6) Apply the resin and hardener components of the adhesive as a single coat by means of an air gun to the metal surface of the roller peel specimen or the rubber surface of the T peel specimen

[0147] 7) Roller peeling specimens (rubber to metal substrate) and T peeling specimens (rubber to rubber substrate) were assembled by rolling (20°C, relative humidity <85%)

[0148] After 3 days at room temperature, peeled with SBR roller (ASTM D 3167-03) 4N / mm T-peel test with SBR after 3 days at room temperature (ASTM D1876) 5N / mm

Claims

1. A method for modifying the surface of an elastic rubber substrate, wherein the method comprises (a) applying a first composition and a second composition to the surface of the elastic rubber substrate, wherein the first composition is an aqueous composition comprising an alkali metal chloride salt, and the second composition is an aqueous composition comprising an alkali metal permonosulfate salt; (b) optionally applying a third composition comprising activated carbon; and (c) incubating the first composition, the second composition, and optionally the third composition with the rubber substrate for a period of time and under conditions that permit chlorination of the elastomeric rubber surface.

2. The method of claim 1, wherein the alkali metal chloride salt is sodium chloride.

3. The method of claim 1, wherein the alkali metal peroxymonosulfate is potassium peroxymonosulfate.

4. The method of claim 1, wherein the first composition is an aqueous solution of sodium chloride.

5. The method according to claim 4, wherein the aqueous solution of sodium chloride has a concentration of 1M to 6M sodium chloride.

6. The method of claim 4, wherein the aqueous solution of sodium chloride has a concentration of 4M to 6M sodium chloride.

7. The method of claim 1, wherein the second composition is an aqueous solution of an alkali metal permonosulfate salt.

8. The method according to claim 7, wherein the aqueous solution of alkali metal permonosulfate is an aqueous solution of potassium permonosulfate.

9. The method of claim 7, wherein the aqueous solution of alkali metal permonosulfate has a concentration of 10 M to 30 M permonosulfate.

10. The method according to claim 9, wherein the aqueous solution of alkali metal permonosulfate has a concentration of 18 M to 22 M alkali metal permonosulfate.

11. The method according to any one of claims 1 to 10, wherein the first composition and the second composition are used in a weight ratio of 3:1 to 1:

3.

12. The method according to any one of claims 1 to 10, wherein the first composition and the second composition are used in a weight ratio of 2:1 to 1:

2.

13. The method according to any one of claims 1 to 10, wherein the first composition and the second composition are used in a weight ratio of 1.5:1 to 1:1.

5.

14. The method according to any one of claims 1 to 10, wherein the amount of the first composition and / or the second composition and / or the third composition applied to the surface of the elastic rubber substrate is 500 g / m 2 Up to 900g / m 2 .

15. The method according to claim 14, wherein the amount of the first composition and / or the second composition and / or the third composition applied to the surface of the elastic rubber substrate is 600 g / m 2 Up to 700g / m 2 .

16. The method according to any one of claims 1 to 10, wherein step (c) is performed for 5 to 60 minutes.

17. The method of claim 16, wherein step (c) is performed for 15 to 30 minutes.

18. The method according to any one of claims 1 to 10, wherein the method further comprises a step of cleaning the surface of the substrate after step (c).

19. The method according to any one of claims 1 to 10, wherein the first composition further comprises a hydroxide in a concentration of 0.5 mol / L to 3 mol / L, based on OH - ion.

20. The method of claim 19, wherein the hydroxide is sodium hydroxide and / or potassium hydroxide.

21. A method of forming a bond between a first substrate and a second substrate, wherein the first substrate is an elastic rubber substrate and the second substrate is a rubber or metal substrate, wherein the method comprises: (a) applying a first composition and a second composition to the surface of the elastic rubber substrate, wherein the first composition is an aqueous composition comprising an alkali metal chloride salt, and the second composition is an aqueous composition comprising an alkali metal permonosulfate salt; (b) optionally applying a third composition comprising activated carbon; and (c) incubating the first composition, the second composition, and optionally the third composition with the elastomeric rubber substrate for a period of time under conditions that allow chlorination of the elastomeric rubber surface, (e) applying the adhesive composition to the surface to be bonded of the second substrate; (f) contacting the chlorinated surface of the elastomeric rubber substrate and the surface of the second substrate with the applied adhesive under pressure to form a bond.

22. The method according to claim 21, wherein the method further comprises the step of cleaning the surface of the rubber and / or metal substrate before steps (e) and / or (f).

23. The method according to claim 21 or 22, wherein step (f) is performed at a temperature of 15°C to 30°C and a relative humidity of 85% or less.

24. The method according to claim 21 or 22, wherein step (f) is performed by rolling.

25. The method of claim 21, wherein the adhesive composition is a 2K epoxy, polyurea, silicone, or polyurethane adhesive comprising a resin formulation and a hardener formulation.