MXPA05013356A - Multistage process for the manufacture of peroxide-cured hxnbr-polyamide thermoplastic vulcanizates - Google Patents

Abstract

The present invention relates to a multistage process including at least two steps for making a heat and oil resistant peroxide-cured thermoplastic vulcanizate (TPV) based on hydrogenated carboxylated nitrite butadiene rubber (HXNBR) and at least one polyamide. TPV's according to the present invention have improved properties and morphology over known TPV's prepared in single-stage processes.

Description

PROCESS OF MULTIPLE STAGES FOR THE MANUFACTURE OF THERMOPLASTIC VULCANIZED HXNBR-POLYAMIDE CURED WITH PEROXIDE FIELD OF THE INVENTION The present invention relates to a multi-stage process that includes at least two steps to prepare a thermoplastic vulcanized cured with peroxide ("TPV" ) resistant to heat and oils based on hydrogenated carboxylated nitrile butadiene rubber ("HXNBR") and polyamides The TPV prepared according to the present multi-stage process of the invention has a better morphology and a smaller particle size of rubber compared to similar TPVs prepared in single-stage processes The TPV prepared according to the present invention can be easily formed by molding or extrusion, is recyclable and exhibits excellent properties of resistance to heat and oils that make it suitable for many industrial and automotive applications under the hood.

BACKGROUND OF THE INVENTION TPVs are biphasic systems in which the cured rubber particles are finely dispersed in a thermoplastic phase. The mixing temperature should be high enough to melt the thermoplastic and also cure the rubber. The curing of the rubber phase occurs under conditions of dynamic vulcanization (curing of the rubber during melt mixing), contrary to the static curing typically occurring in a rubber mold. Shear should continue to be applied to avoid agglomeration of the rubber particles, since the small size of the rubber particles is critical in obtaining a product with high performance. For TPVs to have high performance, the following properties are desired: (a) the surface energies of the two phases must be matched, (b) the molecular weight between the interlinking entanglements in the rubber must be low, (c) the thermoplastic must have crystallinity, (d) the rubber must cure at the mixing temperature and (e) both phases must be stable at the mixing temperature. TPVs are processed by techniques commonly used in the plastics industry, such as injection molding, which makes their manufacture more efficient and cost-effective than thermosetting. TPVs have non-Newtonian flow properties and their viscosity is very dependent on the cut. At lower cutting speeds, its viscosity increases, the flow decreases and there is a high retention of melt integrity and shape retention when cooled. By increasing the cutting speed, they become more fluid and can be more easily injected into a mold. Thermoplastic elastomers find many applications, for example, in coatings, adhesives and molded and extruded parts. The latter are valued in terms of their hardness and resistance to impact and find application in auto parts, mechanical parts, electrical parts and other uses. Specific applications include: seals, cable covers, fuel lines and hoses, cold air inlet pipes and CVJ boots, pedals, handles, cleaners, pipe seals, electrical molds, as well as wraps and sheet metal for electronic applications . Property improvements are constantly being sought and, often, polymeric materials are mixed or combined for this purpose. EP-A1-0,364,859 relates to vulcanizable rubber compositions containing a polyamide, partially hydrogenated nitrile rubber and curing agents in nitrile rubber. The partially hydrogenated nitrile rubber, mixed with a curing agent, was gradually added to molten polyamide with mixture. It is said that it is preferred to use a polyamide having a low melting point, such as nylon 12.

In a preferred embodiment, the composition includes maleic anhydride or succinic anhydride. The description says that the anhydride additive improves the mixture between the nylon and the rubber compound. Better results are obtained in an example in which maleic anhydride is used, but the properties of the product obtained are not particularly good and are not suitable for commercial use. U.S. Pat. No. 4,508,867 relates to vulcanizable rubbery compositions containing a crystalline polyamide, a synthetic rubbery polymer composed of acrylonitrile or methacrylonitrile, an α, β-unsaturated carboxylic acid and butadiene, an additive selected from lithium halides, magnesium , calcium and zinc and an additive selected from the oxides and hydroxides of magnesium, calcium, barium and zinc and the peroxides of calcium and zinc and which also contain active agents in the vulcanization of sulfur. Nylon 11 is the only polyamide whose use is exemplified. The descriptive portion of the memory suggests that the mixture of the polyamide and the synthetic rubbery polymer should have a temperature of about 50 to about 125 ° C. In Examples 1 and 2, the mixture of nylon 11 and carboxylated nitrile rubber and other ingredients took place at 50 ° C. In Example 3, the mixing took place at a temperature of 190 to 199 ° C and Example 4 does not specify the mixing temperature. It is believed that the compositions of US Pat. No. 4,508,867 does not exhibit adequate properties of heat resistance. WO 03/020820A1 describes the preparation of mixtures of heat-resistant polymers and oils of polyamides and hydrogenated carboxylated nitrile rubber prepared according to a single-stage process. The TPNs of HNBR-Polyamide prepared according to WO 03/020820 Al do not give the morphology and the particle size of rubber of the TPV prepared according to the present invention.

SUMMARY OF THE INVENTION The present invention relates to a multi-stage process that includes at least two steps to produce a thermoplastic thermoplastic vulcanizate (TPV) cured with heat and oil resistant peroxide based on hydrogenated carboxylated nitrile butadiene rubber (HXNBR). and Polyamides. Accordingly, the present invention provides a multi-stage process that includes at least two steps for preparing a thermoplastic vulcanizate (TPV) cured with heat and oil resistant peroxide based on nitrile rubber and carboxylated hydrogenated butadiene (HXNBR) and polyamides. The multi-stage process according to the present invention involves two or more stages. The first step of the present invention includes the intimate mixture of HXNBR and polyamide in such a way that the compatibilization in itself between the carboxylic groups of the HXNBR and the amine groups of the polyamide results in a lower interfacial tension and a better mixture. The second stage according to the present invention includes the dynamic vulcanization of the mixture of HXNBR / polyamide with a peroxide, in such a way that the rubber particles cure during the melt mixing, giving rise to a TPV of finely cured finely dispersed HXNBR particles. in a polyamide matrix. The result is a TPV with smaller rubber particles, with a finer dispersion and a better morphology than a similar TPV mixed in a single-mix process. The process according to the present invention provides a better morphology, partly due to the multistage mixing process, which allows a better dispersion of the peroxide and a better control of the rates of curing and mixing compared to the mixing procedures in a single one. stage. In addition, the process according to the present invention can be carried out in three stages. The first stage includes the preparation of a rubber masterbatch, stabilizers, fillers, plasticizers and other necessary additives. The second stage includes the intimate mixture of the masterbatch of the first stage with a polyamide. The third includes the dynamic vulcanization of the second stage mixture to obtain a TPV composed of cured HXNBR particles dispersed in a polyamide matrix. The present invention also provides a peroxide cured TPV based on HNBR / Polyamide, where the HXNBR is mixed with HNBR or used as a compatibilizer between the HNBR and the polyamide. Moreover, the HXNBR can also be used as compatibilizer for other TPV rubber-polyamide.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 and 2 illustrate the Transmission Electron Microscopy (MET) images of comparative TPVs and TPVs prepared according to the present invention, where the light color is rubber, the dark color is polyamide, the colors between light and dark correspond to the interfacial regions and the black points correspond to the filler or the peroxide support. DESCRIPTION OF THE PREFERRED EMBODIMENTS The polyamides useful in the present invention include homopolymers and copolymers having repeated amide linkages along a polymer chain. The polyamides are preferably of high molecular weight and are crystalline or vitreous polymers. Examples include polycaprolactam (nylon 6), polylaurolactam (nylon 12), polyhexamethylene adipamide (nylon 6,6), polyhexamethylene azide amide (nylon 6,9), polyhexamethylene sebacamide (nylon 6,10), polyhexamethylene isophthalamide (nylon 6, IP), acid po-liaminoundecanoico (nylon 11), polytetramethyleneadipamide (nylon) 4.6) and copolymers of caprolactam, hexamethylenediamine and adipic acid (nylon 6.66), and also aramides, such as polypariefe-nilenterephthalamide. Most polyamides have softening points and melting points of 160 to 250 ° C. Hydrogenated carboxylated nitrile rubbers (HXNBR) useful in the present invention and processes for products are not known in the art and are the subject of our co-pending Canadian Patent Application 2,304,501, whose description is incorporated as reference in order that the Jurisdictions accept this characteristic. Said rubbers are formed by copolymerization of at least one diene monomer, preferably a conjugated diene, at least one nitrile monomer, at least one unsaturated acid monomer and optionally also copolymerizable monomers, to form a copolymer with a random or statistical distribution of repeating units derived from the diene, the nitrile, the acid and, if appropriate, the other comonomers, followed by hydrogenation. When the diene is polymerized, preferably conjugated, the product contains some carbon-carbon double bonds. In the past, attempts to hydrogenate these carbon-carbon double bonds also led to the reduction of the nitrile and carboxyl groups, which is not de-seable. CA Application 2,304,501 allows the hydrogenation of carbon-carbon double bonds of carboxylated nitrile rubber without concomitant reduction of the nitrile and carboxyl groups, giving new and valuable polymers. These are currently marketed by Lanxess Deutschland GmbH under the trademark Therban XT. Many dienes, preferably conjugates, can be used in the hydrogenated carboxylated nitrile rubber. Mention is made of 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and piperylene, of which 1,3-butadiene is preferred. The nitrile monomer is usually acrylonitrile, methacrylonitrile or alpha-chloroacrylonitrile, of which acrylonitrile is preferred. The unsaturated acid is preferably α, β-unsaturated and may be, for example, acrylic, methacrylic, ethacrylic, crotonic, maleic (possibly in the form of its anhydride), fumaric or itaconic acid, of which acrylic and methacrylic The conjugated diene usually constitutes from 50 to 85% of the polymer, the nitrile usually constitutes from 15 to 50% of the polymer and the acid from 0.1 to 10%, preferably from 0.5 to 7%, these percentages being by weight. The polymer may also contain an amount, usually not greater than 10% by weight, of another copolymerizable monomer, for example an ester of an unsaturated acid, say acrylate or ethyl methacrylate, propyl or butyl, or a vinyl compound, for example -styrene, alpha-methylstyrene or a corresponding compound bearing an alkyl substituent on the phenyl ring, for example a p-alkylstyrene, such as p-methylstyrene. It is trivial that the values of the repetitive units given above have to be adjusted accordingly to give a total of 100% by weight. The polymer is preferably a solid having a molecular weight greater than 60,000, more preferably greater than 100,000 g / mol. The degree of hydrogenation can be expressed in terms of residual double bonds (DER), which is the number of carbon-carbon double bonds remaining after hydrogenation, expressed as a percentage of the carbon-carbon double bonds before hydrogenation. HXNBR with less than 6 DER are preferred, in particular, HXNBR with 0.9 to 5.5 DER. The preferred contents in acrylonitrile are 32%, 33%, 34%, 36%, 39% and 43% (all by weight). Preferably, according to the multi-step process of the present invention, the first step involves mixing a polyamide with HXNBR under high cut with the necessary additives. The suitable mixing temperature can vary between 100 ° C and 300 ° C, preferably between 150 and 240 ° C, depending on the degree of polyamide. In a second stage according to the present invention, the curing agent is added to carry out the dynamic vulcanization and cure the rubber particles under high cut conditions. It is important to add the spent curing agent at temperatures to which it can be incorporated in such a way that curing and mixing rates are controlled. Preferably, the curing agent is added at a temperature below the melting point of the polyamide incorporated in step 1, more preferably at a temperature of 150 to 240 ° C, more preferably 180 to 220 ° C. After the addition and dispersion of the curing agent, the mixing conditions are adjusted to cause a rapid increase in temperature in order to achieve dynamic vulcanization. This requires careful selection of the peroxide and control of mixing temperatures and cutting conditions. Also according to the present invention, the process can be carried out in three stages. The first stage includes the preparation of a rubber masterbatch, stabilizers, fillers, plasticizers and other necessary additives. The second stage includes the intimate mixture of the masterbatch of the first stage with a polyamide. The third includes the dynamic vulcanization of the second stage mixture to obtain a TPV composed of cured HXNBR particles dispersed in a polyamide matrix. An antioxidant can be used in the mixing process according to the present invention. Examples of suitable antioxidants include p-dicumildiphenylamine (Naugard® 445), Vulkanox® DDA (a diphenylamine derivative), Vulkanox® ZMB2 (zinc salt of methyl t-butylbenzimidazole), Vulkanox® HS (1, 2- polymerized dihydro-2, 2, 4-trimethylquinoline) and Irganox® 1035 (thiodiethylene bis (3,5-di-tert-butyl-4-hydroxy) hydrocinnamate or bis (3- (3,5-di-tert. thioethylene propyl-4-hydroxyphenyl) propionate, supplied by Ciba-Geigy.) Suitable peroxide curing agents useful in the present invention include dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, 2, 2'-bis (tert-butylperoxy) diisopropylbenzene (Vulcup® 40KE), 2,5-dimethyl-2,5-di (tert-butylperoxy) hexyne-3,5,5-dimethyl-2,5-di (benzoylperoxy) hexane, 2, 5-bis (tert-butyl-peroxy) -2,5-dimethylhexane and the like The high temperature of the polyamide melt influences, however, the selection. s suitable by means of several preliminary experiments. A preferred peroxide curing agent is commercially under the trademark Vulcup® 40KE. The peroxide curing agent is suitably used in an amount of 0.2 to 7 parts per hundred parts of rubber ("phr"), preferably 1 to 3 phr. Too much peroxide can lead to an undesirably violent reaction. Sulfur-curing agents, sulfur-containing compounds and resins can also be used as curing agents. Vulcanizing coagents can also be used. Mention may be made of the triallyl isocyanurate ("TAIC"), marketed under the trademark DIAK 7 of DuPont Or, of the N, N'-tn-phenylenedimaleimide known as HVA-2 (DuPont Dow), of the cyanide-to trially ("TAC") or the liquid polybutadiene known as Ricon D 153 (supplied by Ricon Resins). The amounts may be equivalent to the peroxide curing agent or lower, preferably the same. The density of the crosslinker can be increased further by adding an activator, such as zinc peroxide, (50% on an inert support) using Struktol ZP 1014 in combination with the peroxide. The amounts can be between 0.2 and 7 phr, preferably from 1 to 3 phr. It is possible to achieve greater crosslinking by using curing agents used in carboxylated polymers, such as: amines, epoxies, isocyanates, carbodiimides, aziridines or any other additive which can form a derivative of a carboxylic group. The ratio of polyamide to hydrogenated carboxylated nitrile rubber can vary within wide limits, preferably from 90 parts to 10 parts by weight with respect to 10 parts to 90 parts by weight. The properties of the conjugate vary depending on the ratio of polyamide to elastomer. The reason for optimizing particular properties can of course be varied and POS tests of different proportions can be performed routinely by those skilled in the art. It is possible to include processing oils and extenders or plasticizers in the POS according to the present invention. As suitable plasticizers, those known for use with nitrile polymers are included, such as the phthalate compounds, the phosphate compounds, the adipate compounds, the alkylcarbitolformal compounds, the coumarona-indene resins and the like. An example is the plasticizer marketed under the trademark Plasthall 810 or Plasthall TOTM (trioctyl trimellitate) or TP-95 (di (butoxyethoxyethyl) adipate, supplied by Morton International.) The plasticizer should be a stable material at high temperature and will not exude of the conjugate If a plasticizer is to be used, it is preferred to melt the polyamide, add a first portion of the hydrogenated carboxylated nitrile rubber, say about half, mix, then add the plasticizer, mix and then add the rest of the HXNBR and continue The amount of plasticizer used will depend on the proposed end use of the conjugate, but it can be between 1 and 40 phr, preferably between 5 and 20 phr It is also possible to use a mixture of polyamides It is also possible to use a mixture of HXNBR or a mixture of HXNBR and another elastomer, for example a carboxylated nitrile rubber (XNBR), a hydrogenated nitrile rubber (HNBR) or a rubber of nitrile (NBR), a vinyl acetate rubber (EVM) or an ethylene / acrylate rubber (AEM). • Suitable XNBRs are marketed by Lanxess Deutsch-land GmbH under the trademark Krynac and suitable HNBRs are marketed by Lanxess Deutschland GmbH under the trademark Therban and suitable NBRs are marketed by Lanxess Deutschland GmbH under the trademark Perbunan. EVM is marketed by Lanxess Deutschland GmbH under the registered trademark Levapren. Vamac® D, an ethylene acrylic elastomer, is marketed by DuPont. The POS of the present invention may also include at least one filler. The filler may be an active or inactive filler or a mixture of these. The filler can be, in particular: highly dispersed silicas, prepared, e.g. , by precipitation of silicate solutions or flame hydrolysis of silicon halides, with specific surface areas of 5 to 1. 000 m2 / g and with primary particle sizes from 10 to 400 nm: the silicas can also possibly be present as mixed oxides with other metal oxides, such as those of Al, Mg, Ca, Ba, Zn, Zr and Ti; - synthetic silicates, such as aluminum silicate and alkaline earth metal silicate, such as magnesium silicate or calcium silicate, with BET specific surface areas of 20 to 400 m2 / g and primary particle diameters of 10 to 400 nm; - natural silicates, such as kaolin and other natural silicas; - glass fibers and glass fiber products (mats, extruded) or glass microspheres; - carbon blacks; the carbon blacks for use here are prepared by the process of carbon black, furnace black or carbon black by carbonization of natural gas and preferably have BET specific surface areas (DIN 66 131) of 20 to 200. m2 / g / vg, carbon blacks SAF, ISAF, HAF, FEF or GPF; - rubber gels, especially those based on polybutadiene, butadiene / styrene copolymers, butadiene-no / acrylonitrile copolymers and polychloroprene; or its mixtures. Examples of preferred mineral fillers include silica, silicates, clay, such as bentonite, gypsum, alumina, titanium dioxide, talc, mixtures thereof and the like. These mineral particles have hydroxyl groups on their surface, making them hydrophilic and oleophobic. This exacerbates the difficulty of achieving good interaction between the filler particles and the rubber. For many purposes, the preferred mineral is silica, especially silica produced by precipitation with sodium silicate carbon dioxide. The dried amorphous silica particles suitable for use according to the invention can have an agglomerated average particle size of 1 to 100 microns, preferably 10 to 50 microns and more preferably 10 to 25 microns. It is preferred that less than 10 volume percent of the agglomerate particles are below 5 microns or above 50 microns in size. Moreover, a suitable dry amorphous silica normally has a BET surface area, measured according to DIN (Deutsche Industrie Norm) 66131, of 50 to 450 square meters per gram and an absorption of DBP, measured according to DIN 53601, of 150 to 400 grams per 100 grams of silica, and a loss of desiccation, measured according to DIN ISO 787/11, from 0 to 10 percent by weight. Suitable silica fillers are available under the trademarks HiSil® 210, HiSil® 233 and HiSil® 243, from PPG Industries, Inc. Also suitable are Vulkasil® S and Vulkasil® N, from Lanxess AG. The POS according to the present invention may contain other rubber auxiliaries, such as reaction accelerators, vulcanization accelerators, vulcanization acceleration aids, antioxidants, foaming agents, anti-aging agents, thermal stabilizers, light stabilizers. , stabilizers against ozone, processing aids, plasticizers, adherents, blowing agents, dyes, pigments, waxes, extenders, organic acids, inhibitors, metal oxides and activators, such as triethanolamine, polyethylene glycol, hexanotriol, etc., which are known in the rubber industry. The processing aids are used in conventional quantities, which depend, among others, on the intended use. Conventional amounts are, for example, 0.1 to 50% by weight based on rubber. Preferably, the TPV contains from 0.1 to 20 phr of an organic fatty acid, such as an auxiliary product, preferably an unsaturated fatty acid having one, two or more double carbon bonds in the molecule and most preferably including a carbon atom. % by weight or more of a conjugated diene acid with at least one carbon-carbon double bond conjugated to its molecule. Preferably, these fatty acids have from 8 to 22 carbon atoms, more preferably from 12 to 18. As examples, stearic acid is included, palmitic acid and oleic acid and its salts of calcium, zinc, magnesium, potassium and ammonium. Preferably, the TPV includes from 5 to 50 phr of an acrylate as an auxiliary product. Suitable acrylates are known thanks to EP-A1-0,319,320 and US Pat. Nos. 5,208,294 and 4,983,678. Reference is made to zinc acrylate, zinc diacrylate or zinc dimethacrylate or a liquid acrylate, such as trimethylolpropane trimethacrylate ("TRIM"), butanediol dimethacrylate ("BDMA") and dimethacrylate of ethylene glycol ("EDMA"). It may be advantageous to use a combination of different acrylates and / or their metal salts. It is particularly advantageous to use metal acrylates in combination with scorch retarder, such as sterically blocked phenols (e.g., methyl-substituted aminoalkylphenols, in particular 2,6-di-tert-butyl-4-dimethylaminomethylphenol). It is possible to incorporate other known additives or mixing agents in the POS according to the present invention. The TPV of the present invention can be formed into free flowing pellets, remelting and resolidifying without any significant deterioration or deleterious effect on their properties. In this regard, it differs from elastomers such as pure HXNBR, XNBR, HNBR and the like; after crosslinking, they can not be melted and resolidified. The POS of the present invention is also recyclable. EXAMPLES General procedure A Plasticorder Brabender was fitted with roller mixing blades and a 369 g capacity container. The temperature of the mixing vessel, the filling factor, the mixing time and the speed of the rolls were varied. In the first stage of the multi-stage mixing process, the rubber and the additives used were mixed with molten nylon. In a second step, the peroxide was added and the dynamic vulcanization occurred. The compound was then passed through a mill at 70 ° C once to produce a flat sheet. A Preco Press was used to compress the mold test pieces. The compound was added to a preheated mold and placed in the press at 0 psi and at 240 ° C for 10 minutes. The mold was then maintained at 20,000 psi for 20 minutes, after which the molded sample was transferred to a cold press and maintained at 10,000 psi for 5 min. The polyamide used was polyamide 6 Durethan® C 38 F (mp 210 ° C), supplied by Bayer AG. The HXNBR used was a Therban® XT having carboxylic moieties, based on methacrylic acid, at approximately 5.0% and an acrylonitrile content of 33%, the balance being 1,3-butadiene, a Mooney viscosity of 77. and a DER of 3.5%. The HNBR used in this example is Therban® A3907, with an acrylonitrile content of 39% and a% DER not higher than 0.9. Example 1 In the first stage, 70 phr of Therban® XT rubber and 30 phr of polyamide 6 (Durethan® C 38 F) were mixed in the presence of Naugard® 445 antioxidant, Armeen 18D and Vanfre Vam processing aids, Plasthall TOTM plasticizer and Carbon Black N762. The nylon was melted and the mixture mixed well. In the second step, the peroxide was added, namely 3.5 phr of Vulcup 40KE and 2.2 phr of Struktol ZP 1014, at a temperature of between 150 and 220 ° C to the mixture prepared in step 1 and got dynamic vulcanization under high cut conditions. 1 phr of anti-oxidant Irganox 1035 (thiodiethylene bis (3, 5-di-t-butyl-4-hydroxy) hydrocinnamate or bis (3- (3,5-di-t-butyl-4-hydroxyphenyl)) was added. thiodiethylene propionate), supplied by Ciba-Geigy, before stopping the mixing.The final temperatures in both stages were around 240 ° C. The Brabender mixing conditions for the two stages were as follows: filling factor 75 % mixing blade speed 95 RPM, temperature range 150-240 ° C, total mixing time (step 1 + 2) 20 minutes Tables 1 and 2 show the formulations and stress strain data TPV, Example 2 Prepared according to Example 1, except for the use of 35 phr of Therban® XT and 35 phr of Therban® A3907 instead of 70 phr of Therban® XT Comparative example 1 The formulation of the POS was used prepared according to Example 2, but the mixture was made in a single step process.The Brabender mixing conditions were as follows. entities: filling factor of 75%; mixing blade speed 95 RPM; temperature range 210-220 ° C; Total mixing time 20 minutes. 70 phr of Therban® XT rubber and 30 phr of polyamide 6 (Durethan® C 38 F) were mixed in the presence of Naugard® 445 antioxidant, Armeen 18D and Vanfre Vam processing aids, Plasthall TOTM plasticizer and N762 Carbon Black. Vulcup 40KE and Struktol ZP 1014 were added at a temperature of 180 to 220 ° C. Iroganox 1035 was added before stopping the mixture. The total mixing time was 20 minutes. Comparative Example 2 The TPV was prepared in a single-stage process according to WO 03/020820A1. Durethan® C 38 F was melted first at 240 ° C and then Therban® XT and Naugard 445 were added. After mixing for 3 to 5 minutes, Vulcup 40KE and Struktol ZP1014 were added at a temperature above 225 ° C. Irganox 1035 was added 1 minute before the end and the total mixing time was 8 to 10 minutes. Table 1. POS formulation of HXNBR / HNBR-Polyamide Therban ™ XT ™ 8889 is HXNBR and Therban ™ A3907 HNBR, from Lanxess Deutschland GmbH. Durethan® C 38 F is a polyamide from Lanxess Deutschland GmbH. Durethan® B31 SK is a polyamide from Lanxess Deutschland GmbH.

Vanfre Vam ™ is a phosphate processing aid from R.T. Vanderbilt Armeen ™ 18D is an octadecylamine from AkzoNobel and is used to reduce the adhesion of the compound to the metal. Naugard ™ 445 (p-dicumildiphenylamine) is a Uni-al al stabilizer. Carbon black N672 from Cabot. Plasthall TOTM ™ (trioctyl trimellitate) is a plasticizer of C.P. Hall. DIAK # 7 (triallyl isocyanurate) is a co-agent of DuPont Dow Elastomers. Struktol ™ ZP 1014 (50% zinc peroxide on inert support).

Vulcup 40 KE (a, β-bis (t-butylperoxy) diisopropylbenzene), 40% peroxide. Irganox 1035 is a stabilizer (thiodiethylene bis (3,5-di-t-butyl-4-hydroxyhydrocinnamate) Table 2. Stress-strain and aging data * ASTM D2240, ** ASTM D412. The METs of the compounds discussed in Table 1 are shown in Figures 1 and 2. The light color is rubber, the dark color is polyamide, the colors between light and dark correspond to the interfacial regions and black dots. correspond to the filler or the peroxide support. METs illustrate that Examples 1 (only Therban XT) and 2 (Therban® XT / Therban® A3907), which are prepared in a multi-stage process according to the present invention, have better morphology and dispersion of the rubber particles than the Comp. 1, which was mixed during the same period, but in a single stage. Examples 1 and 2 also have a better morphology and a smaller size of the rubber particle when compared to the Comp. 2 (MET scale is 5 microns) of WO 03/020820A1, which is also prepared in a one-step mixing process. Although the Comp. 1 and 2 have some small rubber particles, they have fewer small particles than Examples 1 and 2. The best morphology of the present multi-stage mixing process of the invention resides in the preparation of an uncured rubber-plastic mixture in a stage, followed by a second stage in which the curing agent is added to a certain temperature range that allows a better control of the mixing conditions (curing and mixing speeds) to achieve the best morphology .. It is evident that the The multi-stage mixing process of this invention gives a better morphology, a finer dispersion and a greater number of smaller rubber particles compared to compounds prepared in a single mixing process. This better morphology exhibited by Examples 1 and 2 is demonstrated in its higher tensile strength and its higher Eb, since it is known to those skilled in the art that a smaller particle size of the rubber and a finer dispersion result in to better mechanical properties. Although the invention has been described in detail in the foregoing for purposes of illustration, it is to be understood that such detail has only that purpose and that those skilled in the art can make variations therein without departing from the spirit and scope of the invention, except in what may be limited by the claims.

Claims (14)

Claims

1. A multi-stage process consisting of at least two steps for the preparation of a cured thermoplastic vulcanizate resistant to heat and oils based on a rubber and a polyamide, where the process consists of: a. mix the rubber and the polyamide at a temperature of 100 to 300 ° C and then b. vulcanizing the rubber / polyamide mixture in the presence of a curing agent, where the peroxide curing agent is added at a temperature of 150 to 240 ° C.

2. A process according to claim 1, wherein the polyamide is selected from the group of polycaprolactam, poly-laurolactam, polyhexamethylene adipamide, polyhexamethylene azelamide, polyhexamethylene sebacamide, polyhexamethylene isophthalamide, polyaminoundecanoic acid, polytetramethylene adipamide, copolymers of caprolactam, hexamethylenediamine and adipic acid, aramides or its mixtures

3. A process according to Claim 1, wherein the rubber is a hydrogenated carboxylated nitrile rubber.

4. A process according to Claim 3, wherein the hydrogenated carboxylated nitrile rubber is a copolymer of acrylonitrile, butadiene and acrylic acid having a residual carbon-carbon double bond content of 6% or less.

5. A process according to Claim 1, wherein the rubber is a mixture of an HXNBR and an HNBR.

6. A process according to Claim 1, wherein the rubber is a mixture of HXNBR and an elastomer selected from carboxylated nitrile rubber (XNBR), nitrile rubber (NBR), vinyl acetate rubber (EVM) or ethylene rubber / acrylate (AEM).

7. A process according to Claim 1, wherein the curing agent is a peroxide.

8. A process according to Claim 7, wherein the peroxide is selected from dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, 2,2'-bis (tert-butylperoxy) diisopropylbenzene (Vulcup® 40KE), , 5-dimethyl-2, 5-di (tert-butylperoxy) hexy-3, 2, 5-dimethyl-2, 5-di (benzoylperoxy) hexane, 2,5-bis (tert-butyl-peroxy) -2, 5-dimethylhexane or its mixtures.

9. A process according to Claim 1, wherein the curing agent consists of zinc peroxide.

10. A process according to Claim 1, wherein the multi-stage process is carried out in an extruder or in an internal mixer.

11. A method according to claim 1, further comprising the step of forming the TPV in free flow pellets.

12. A POS prepared according to claim 1.

13. A POS according to claim 12 in the form of a molded or extruded part.

14. A multi-stage process consisting of at least three stages for the preparation of a cured thermoplastic vulcanizate resistant to heat and oils based on a rubber and a polyamide, where the process consists of: a. mix the rubber, at least one plasticizer and at least one filler to form a rubber masterbatch, b. then mix the rubber masterbatch and a polyamide at a temperature of 100 to 300 ° C and b. then vulcanizing the rubber / polyamide mixture in the presence of a curing agent, where the peroxide curing agent is added at a temperature of 150 to 240 ° C.