MXPA00008328A - Improved polymer composition and process for producing vulcanizates thereof - Google Patents

Abstract

A polymer composition useful to produce a vulcanizate having improved hot air aging properties is described. The polymer composition includes two components. The first component is a polymer having a main polymer chain derived from:(i) at least 30%by weight of a first monomer which introduces at least one of a secondary carbon and a tertiary carbon to the backbone, and (ii) from 0 to 70%by weight of at least one other monomer. The second component is a salt of a strong base and a weak acid, the salt comprising a metal selected from Group 1 of the Periodic Table of Elements (according to IUPAC 1985). The polymer compositions may further comprise optional ingredients such as one or more of:a vulcanization system, a polycarbodiimide and a filler.

Description

IMPROVED COMPOSITION OF POLYMERS AND PROCESS TO PRODUCE VULCANIZED THEMSELVES The present invention relates to an improved polymer composition and to a process for producing vulcanizates thereof. More particularly, in one of its aspects, the present invention relates to a rubber composition having improved characteristics of aging in hot air. In yet another of its aspects, the present invention relates to a method for improving the hot air aging characteristics of a polymer vulcanizate. The effects of oxidation conditions on vulcanizates obtained from polymers have been a problem for a long time, particularly in applications where vulcanizates are exposed to elevated temperatures for extended periods of time. A variety of methods have been developed in the art in an attempt to solve this problem. It is known that, in compositions comprising polymers based on a monomer that results in a polymer backbone having repeating units including at least one carbon-hydrogen bond (i.e., repeating units have a secondary or tertiary carbon), The thermo-oxidative attack initiated by a radical mechanism is very relevant in the deterioration of the useful properties of such compositions during oxidative aging. See, for example: 1. S. Bhattacharjee, A.K. Bhcwmick and B.N. Avasthi: "Degradation of Hydrogenated Nitrile Rubber"; Polymer Degradation and Stability, 31, 71-87 (1991); and 2. K.C. Smith and B.S. Tripathy: "HNBR and Long Term Serviceability in Modern Automotive Lubricants"; Rubber World, 217 (5), 28-45 (1998).

During the process of oxidative degradation located in such carbon-hydrogen bonds, among other substances, functionalities of hydroperoxide, alcohol, keto, aldehyde and carboxylic acid are introduced into the polymer backbone (also referred to as the "backbone of the polymer"). "). This often results in excision or cross-linking reactions of the polymer chain, which lead to changes and deterioration of the useful properties of the composition, such as tensile strength, hardness, static and dynamic stiffness, elongation at break, compression adjustment, etc.

The thermo-oxidative reactions, as described above, are autocatalytic chain reactions, where the reactive radicals are regenerated within the reaction cascade. It is known in the art to add substances (often referred to as antioxidants) to the polymer compositions to facilitate the destruction of radicals or reactive intermediates produced during the polymer oxidation process (such as hydroperoxides), thereby improving aging resistance in oxidative heat of the compositions. Non-limiting examples of useful antioxidants can be selected from the group comprising hindered phenols, p-phenylene diamine derivatives, qumoline derivatives and mixtures thereof. Phosphites, dithiophosphates, dithiocarbamates and mercarptoimidazole derivatives are also commonly used as antioxidants. These substances frequently wave both hydrogen atoms and other radicals and, during the polymer oxidation process: (i) are converted into non-reactive radicals themselves; (ii) block certain reactions that lead to the production of free radicals (eg, heavy metal capture) and / or (iii) favor the reactions of reactive intermediates that lead to the production of non-radical reaction products (eg, hydroperoxide decomposition agents).

In many cases, to achieve their desired properties, the rubber compositions are hardened with a crosslinking system conventionally selected from the group comprising sulfur, compounds sulfur donors and / or a peroxide system. It is known in the art that the interference of antioxidants with hardening systems often presents a major problem. The reaction of the antioxidants with hardening systems can lead to a significant deterioration of the desired hardening state of the composition. The complete or partial exhaustion of the antioxidant in the composition during c.J hardening is likely to occur when the hardening system generates radicals during vulcanization. Therefore, a need remains in the art to improve antioxidant systems in a manner that offers protection against aging with desirable oxidative heat without harmful interference with hardening systems and, most importantly, without partial or complete loss of antioxidant activity due ai ^ chemical action in the vulcanization state. An object of the present invention is to avoid or mitigate one or less of the aforementioned drawbacks of the prior art. Another object of the present invention is to provide a novel polymer composition. Still another object of the present invention is to provide a novel process for producing a polymer vulcanizate. Still another object of the present invention is to provide a novel method for improving the hot-air aging characteristics of a polymer vulcanizate. Accordingly, in one of its aspects, the present invention provides a polymer composition comprising: a polymer having a polymer backbone derived from: (i) at least about 30% by weight of a first monomer that introduces at least one of a secondary carbon and a tertiary carbon to the polymer backbone, and (ii) from 0 to about 70% by weight of at least one other monomer; and a salt of a strong base and a weak acid, the salt comprising a metal selected from Group I of the Periodic table of elements. In another of its aspects, the present invention provides a method for improving the hot air aging characteristics of a polymer comprising 1 ts steps of: mixing (A) a polymer having a polymer backbone derived from: (i) at least about 30% by weight of a first monomer that introduces at least one of a (secondary arbon and a tertiary carbon in the polymer backbone, and (11) from 0 to about 0% by weight of at least one other monomer and (B) a salt of a strong base and a weak acid, the salt comprising a metal selected from Group I of the Periodic Table of the Elements: and vulcanizing the polymer composition. of a particular additive in a polymer composition results in a surprising and unexpected improvement in the resistance to oxidative heat aging of the composition thereby preventing or mitigating a harmful effect on the action of a vulcanization system used to harden the polymer composition. The particular additive is a salt of a strong base and a weak acid, the salt comprising a metal selected from Group I of the Periodic Table of the Elements. The present polymer composition is useful for producing a vulcanizate having improved physical properties. More specifically, the vulcanizates produced from the present polymer composition can be characterized by improvements (ie, compared to a vulcanizate produced without the additive) in a or more of the following properties: Aging in hot air: Aging in hot fluid Adjustment of aged compression: Aggressive dynamic elastic module (EN): Aggressive dynamic viscous module (EO): Static aged module; and Properties aged at low temperature. Even more specifically, the vulcanizates produced from the present polymer composition have improved aging in hot air. This results in a reduction of the deterioration of the polymer and may be accompanied by improvements in one or more of the other properties indicated above. Embodiments of the present invention will be described with reference to the accompanying Figure, which illustrates comparative characteristics of hot air aging between polymer vulcanizates of the invention and a conventional polymer vulcanizate. Therefore, the polymer composition present comprises two components. The first component of the present polymer composition is a polymer having a polymer backbone derived from: (i) at least about 30% by weight of a first monomer that introduces at least one of a secondary rarbono and a tertiary carbon in the polymer backbone, and (ii) from 0 to about 70% by weight of at least one other monomer. As used throughout this specification, the term "polymer" is intended to have a broad meaning and means that it encompasses any polymer having a polymer backbone comprising at least one secondary or tertiary carbon. Those skilled in the art will understand that a secondary carbon is a carbon atom that has two hydrogen atoms attached to it while a tertiary carbon is a carbon atom that has a hydrogen atom attached thereto. a homopolymer, a copolymer, a terpolymer and the like It is also possible to use a mixture of polymers, provided that at least one polymer in the Lenga mixture has the polymer backbone properties described above. elastomer (for example, a hydrocarbon rubber), a grafted polymer or block polymer of monomers having at least one ethylenically unsaturated bond and polymerizable through this unsaturation, and similar. The elastomers are well known to those skilled in the art. Non-limiting examples of suitable elastomers can be selected from the group comprising natural rubber (NR), cis-1 rubber, 4-polyisoprene (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), rubber acrylonitrile-butadiene (NBR), hydrogenated acrylonitrile-butadiene rubber (HNBR), other HNBR copolymers, HNBR terpolymers (including terpolymers of hydrogenated acrylonite, butadiene, msaturated carboxylic acid ester), ethylene-propylene monomer rubber (EPM) ), ethylene-propylene-diene monomer rubber (EPDM), ethylene-vinyl acetate rubber (EVM) and the like. However, subject to compatibility, mixtures of two or more of any of the foregoing polymers may be used herein. Preferably, the polymer used in the present polymer composition is an elastomer. More preferably, the elastomer is selected from the group comprising: Ethylene-propylene copolymer; Ethylene-propylene-non-conjugated diene terpolymer; Ethylene vinyl acetate copolymer; Unsaturated nitrile / conjugated diene copolymer; Hydrogenated unsaturated nitrile / diene copolymer with ugado; Unsaturated nitrile terpolymer / conjugated diene / ethylenically unsaturated monomer; Hydrogenated unsaturated nitrile / conjugated diene / ethylenically unsaturated monomer terpolymer; Styrene / conjugated diene copolymer; Hydrogenated styrene / conjugated diene copolymer; Polyisoprene Natural rubber; Polybutadiene; and mixtures thereof.

These elastomers are well known in the art and are readily available or can be produced by a person skilled in the art. It is known in the art that elastomers, such as the preferred elastomers indicated above, may contain small amounts of antioxidants (typically less than 0.5 parts by weight), which are added during the manufacturing process of the polymers primarily to increase their Conservation life The second component is a salt of a strong base and a weak acid, the salt comprising a metal selected from the Group I of the Periodic Table of the Elements.

Non-limiting examples of the weak acids useful in the production of the salt mentioned above may be selected from the group comprising carboxylic acid, C? -C30 fatty acids; ethylene diamine tetra (acetic) acid, phosphoric acid and mixtures thereof. The preferred salt for use in the present polymer composition can be selected from the group comprising sodium carbonate, potassium carbonate, sodium stearate, potassium stearate and mixtures thereof. The most preferred salt for use in the present polymer composition is sodium carbonate. Preferably, the salt is present in the polymer composition in an amount in the range of from about 0.5 to about 50 parts by weight, preferably in the range from about 1 to about 20 parts by weight, more preferably in the range from about 2.5 to about 7.5 parts by weight. Optionally, the present polymer composition additionally comprises a carbodiimide, a polycarbodnmide or mixtures thereof. The carbodiimide is commercially available under the trade names Rhenogram ™ P50 and Stabaxol ™ P. This ingredient can be used in the present polymer composition in a range in the range from 0 to about 15 parts by weight, more preferably in the range from 0 to about 10 parts by weight, even more preferably in the range of from about 0 to about 2 parts by weight. Preferably, the present polymer composition further comprises a vulcanization system. The choice and quantity of the vulcanization system depends on a number of factors, including the choice of the polymer component, the intended application of the vulcanizate and the like. Preferably, the vulcanization system is selected from the group comprising sulfur, a sulfur donor hardening system and a peroxide compound. Non-limiting examples of useful sulfur donor hardening systems may be selected from the group comprising thiuram compounds (such as tetramethyl thiuramdisulfide, tetraethyl thiuramdisulfide, tetramethyl thiuram monosulfide, and the like), and morphol compounds (such as morpholine disulfide and Additionally, it is possible to use dithiobis (caprolactam) in a sulfur donor hardening system.The useful amount of sulfur or the sulfur donor compound is preferably in the range of about 0.1 to about 5 parts by weight. As is known in the art, when the vulcanizing agent is sulfur or a sulfur donor hardening system, it is conventional to include a vulcanization accelerator.Non-limiting examples of useful vulcanization accelerators can be selected from the group comprising tlazole compounds (such as 2-mercaptobenzothiazole [MBT], dithiobis mercaptoben zotiazole rMBTS] and the like), sulfenamide compounds (such as N-clohexyl-2-benzothiazyl sulfenamide and the like), dithiocarbamates (such as cmc-dibutyl dithiocarbamate) and mixtures thereof. Such vulcanization accelerators are preferably used in an amount in the range of 0.5 to 5 parts by weight. AdditionallyIt is known to use oxides of metals, such as zinc oxide, magnesium oxide and the like, as well as acids such as stearic acid, hardening activators in these vulcanization systems. As indicated above, the vulcanization system may comprise a peroxide compound, preferably an organic peroxide. Non-limiting examples of organic peroxide compounds can be selected from the group comprising dicumyl peroxide, benzoyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) -hexane, 2,2'-bis ( tert-butylperoxydiisopropyl benzene, t-butyl peroxybenzoate and the like Other useful peroxide compounds will be readily apparent to those skilled in the art The organic peroxide used is preferably in the range of about 0.5 to about 15 parts by weight, preferably The range of from about 2 to about 8 parts by weight When the vulcanization system comprises an organic peroxide, it is known to include a co-agent together with it.The coagent is indeed a polyfunctional monomer. such suitable coagents can be selected from the group comprising triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, and ethylene dimethacrylate, toluylene bismaleimide and the like. Preferably, the coagent is used in an amount in the range of from about 1 to about 10 parts by weight. Preferably, the present polymer composition comprises a filler. The nature of the filler is not particularly limited and the choice of suitable fillers is well within the skill of a person skilled in the art. Non-limiting examples of suitable fillers include carbon black (for example, FEF, MT, GPF and SRF), clays, titanium dioxide, silica fillers (with or without unsaturated silanes), calcium carbonate, talc ( magnesium silicate) and the like. The amount of filler is conventional. Preferably, the filler is present in an amount in the range of from about 20 to about 200 parts by weight per hundred parts by weight of the polymer. More preferably, the filler is present in an amount of from about 20 to about 100 parts by weight per hundred parts by weight of the polymer. More preferably, the filler is present in an amount ranging from about 40 to about 80 parts by weight per hundred parts by weight of the polymer. In the present process, the polymer, the czarga substance (as indicated above, the use of a filler is optional), the additive and the vulcanization system can be mixed in any conventional manner known in the art. For example, this polymer composition can be mixed in a two-roll rubber mill or an internal mixer. Therefore, the polymer composition is mixed in a conventional manner and the temperature thereof during mixing is maintained as is known in the art. In the present process, it is preferred to heat the polymer composition to form vulcanizates using conventional procedures well known in the art. Preferably, the polymer composition is heated at a temperature in the range of from about 130 ° to about 200 ° C, preferably from about 140 ° to about 190 ° C, more particularly from about 150 ° to about 180 ° C. Preferably, the heating is performed for a period of time from about 1 minute to about 15 hours, more preferably from about 5 minutes to about 30 minutes. Various methods of subsequent hardening, as is known in The technique, can be used to complete the vulcanization stage. In many cases, the present polymer composition will additionally comprise an antioxidant. Non-limiting examples of useful antioxidant compounds can be selected from the group comprising alkylated diphenylamines (such as styrene-diphenylamine and the like), quinoline-type stabilizers (such as polymer 2,2,4-trimethyl-1,2-dihydroquinoline and the like) ), m-decaptobenzimidazoles (such as zinc salts of methylmercaptobenzimide) and the like. With sulfur-containing vulcanization systems, phenylene diamine derivatives (such as N-phenyl-N'-i-sopropyl-p-phenylene diamine and the like) as well as spherically hindered phenols (such as butylated hydroxy toluene and the like) can also be used. The amount of antioxidant used is within the knowledge of a person skilled in the art. Other conventional compositional ingredients can also be included by mixing with the copolymer in the conventional manner. Other compositional ingredients of this type are used for their conventional purposes and include activators such as zinc oxide and magnesium oxide.; stearic acid; plasticizers; processing adjuvants; reinforcing agents; promoters and retarders in amounts well known in the art.

During the production of the vulcanizate from the polymer composition, the vulcanizate can be formed into a composite with, for example, polyester fiber, nylon fiber, aramid fiber, glass fiber, carbon fiber, fiber fabrics or cords. steel and the like, so that you have a desired rubber compound product. The embodiments of the present invention will be illustrated with reference to the following Examples which are provided for illustrative purposes and should not be used to limit the scope of the invention. Unless otherwise indicated, all parts in the Examples are parts by weight. Additionally, in the Examples, the materials used include the following: Therban ™ A3907: a hydrogenated nitrile butadiene polymer commercially available from Bayer Inc .; Therban ™ A3407: a hydrogenated nitrile butadiene polymer commercially available from Bayer Inc.; Therban ™ VPKA8798: a terpolymer of hydrogenated acrylonitrile, butadiene, unsaturated carboc acid ester, commercially available from Bayer Inc .; Buna ™ EP T2070: an ethylene-propylene copolymer commercially available from Bayer Inc .; Buna ™ EP T6850: a terpolymer of ethylene, propylene and 5-ethylidene-2-norbornene, commercially available from Bayer [nc.; Levapren ™ Lev 500HV: ethylene vinyl acetate commercially available from Bayer Inc .; Natural rubber (pale crepe); Dynamar ™ RC5251Q: commercially available sodium carbonate from Dyneon; Rhenogran ™ P50; polycarbodiimide commercially available from Rhein Chemie Corporation; Magl? Te ™ D: magnesium oxide, activator, commercially available from CP Hall; > Stearic acid, Emersol ™ 132NF: dispersing agent; Zinc oxide activator: Carbon black, N660 Sterling-V: filler; Armeen ™ 18D: 1-octadecanamine commercially available from Akzo Nobel Chemicals; ) Naugard ™ 445: antioxidant commercially available from UniRoyal Chemicals; Vulkanox ™ OCD / SG: antidegradant available commercially from Bayer Inc .; Vukanox ™ ZMB-2 / C5: antidegradant available commercially from Bayer Inc .; Sumpar ™ 2280: paraffinic oil available from Sun Refimng; Plasrhall TOTM: plasticizer available in the CP Hall trade; Diak # 7: triallyl isocyanate, crosslinking activator, commercially available from E.l. DuPont; and Vulcup ™ 40KE: 2, 2 '-bis (tert-butylperoxy diisopropyl benzene commercially available from Hercules; Sulfur: vulcanizing agent; Sulfasan DTDM: 4,4' -dithiodimorpholine commercially available from FLEXSYS America; and Vulkacit ™ Thiuram / C: tetramethyl zuramdifulfide vulcanization agent commercially available from Payer Inc.

USEFUL 1-4 The following procedure was used for each of Examples 1-4. The polymer composition used in Examples 1-4 are shown in Table 1. As will be apparent to those skilled in the art, the polymer composition of Examples 1 and 3 did not contain any special additive. Accordingly, Examples 1 and 3 were provided for comparison purposes and are outside the scope of the present invention. As will be further apparent to those skilled in the art, Examples 1 and 2 refer to a vulcanizate derivatized using a peroxide hardening system, while Examples 3 and 4 refer to a vulcanizate derivatized using a hardening system donor. sulfur. The components of the polymer composition were mixed in a Banbury mixer using conventional techniques. The polymer composition was vulcanized to 170 ° C for a period of 15, 12, 8 and 8 minutes, respectively, for each of Examples 1-4. The elongation at break of the vulcanizates was determined in accordance with ASTMD412-80. The hardness properties were determined using a Shore A type durometer in accordance with ASTM-D2240-81. The properties of the vulcanizates of Examples 1 and 2 are indicated in Table 2, while those of Examples 3 and 4 are indicated in Table 3. The properties of the vulcanizates indicated in Tables 2 and 3 clearly illustrate the superiority of hot air aging characteristics of the vulcanizates of Examples 2 and 4 (special additive used) when compared with the vulcanizate of Examples 1 and 3 (no special additive is used), respectively. This becomes significant practical advantages in many of the conventional applications (vulcanized ones).

EXAMPLES 5-8 The methodology used in Examples 1-4 was repeated in these Examples, using the polymer compositions indicated in Table 4. The polymer composition was vulcanized at 170 ° C for a period of 18, 25 and 26 minutes , respectively, for each of Examples 5-8. As will be apparent to those skilled in the art, the polymer composition of Examples 5 and 7 did not contain special additives. Accordingly, Examples 5 and 7 are provided for comparison purposes only and are outside the scope of the present invention. As will be further apparent to those skilled in the art, Examples 5 and 6 refer to a vulcanizate derived from EP copolymer rail, while Examples 7 and 8 are left to a vulcanizate derived from EPDM terpolymer. Various physical properties of the vulcanizates were determined, as described in Examples 1-4. These properties are indicated in Table 4 for Examples 5 and 6, and in Table 5 for Examples 7 and 8. The properties of the vulcanizates indicated in Tables 5 and 6 clearly illustrate the superiority of aging characteristics in air. of the vulcanizates of Examples 6 and 8 (special additive used) when compared with the vulcanizate of Examples 5 and 7 (no special additive is used), respectively. This translates into significant practical advantages in many of the conventional vulcanized applications.

EXAMPLES 9-12 The methodology used in Examples 1-4 was repeated «MI these Examples, using the polymer compositions indicated in Table 7. The polymer composition was vulcanized at 180 ° C for a period of 12, 12, 13 and 13 minutes, respectively, for each of Examples 9-12. As will be apparent to those skilled in the art, the polymer composition of Examples 9 and 11 contained no special additive. Accordingly, Examples 9 and 11 are provided for comparison purposes only and are outside the scope of the present invention. As will be further apparent to those skilled in the art, Examples 9 and 10 relate to a vulcanizate derived from a hydrogenated nitrile butadiene polymer, while Examples 11 and 12 refer to a vulcanizate derived from a hydrogenated acrylonitrile terpolymer. , butadiene, unsaturated carboxylic acid ester. Various physical properties of the vulcanizates were determined, as described in Examples 1-4. These properties are indicated in Table 8 for Examples 9 and 10 and in Table 9 for Examples 11 and 12. The properties of the vulcanizates indicated in Tables 8 and 9 clearly illustrate the superiority of aging characteristics in hot air. of the vulcanizates of Examples 10 and 12 (special additive was used) when compared with the vulcanizate of Examples 9 and 11 (no special additive was used), respectively. This translates into significant practical advantages in many of the conventional vulcanized applications.

EXAMPLES 13-19 The methodology used in Examples 1-4 was repeated in these Examples, using the polymer compositions indicated in Table 10. As will be apparent to those skilled in the art, the polymer composition of Example 19 contained no additive (-special.) Therefore, Example 19 is provided for comparison purposes only and is outside the scope of the present invention.Some physical properties of the vulcanizates were determined, as described in Examples 1-4. in Tables 11 and 12, and are illustrated in the accompanying figure The properties of the vulcanizates indicated in Tables 8 and 9 clearly illustrate the superiority of hot air aging characteristics of the vulcanizates of Examples 13-18 (Special additive was used) when compared to the vulcanizate of Example J.9 (no special additive was used), respectively. The accompanying figure is particularly instructive to show significant relative improvement in the time necessary for the aged vulcanized to reach 100% elongation at break under the test conditions. Additionally, these results illustrate the pragmatic benefit of using a polycarbodiimide as an adjunct to the special additive. In this regard, reference may be made to a comparison of the properties of Example 13 with those of Examples 14 and 15, and a comparison of the properties of Example 16 with those of Examples 17 and 18, particularly in longer aging periods. . This translates into significant practical advantages in many of the conventional vulcanized applications.

EXAMPLES 20-21 The methodology used in Examples 1-4 was repeated in these Examples, using the polymer compositions indicated in Table 13. The polymer composition was vulcanized at 180 ° C for a period of 17 minutes in each Example. . As will be apparent to those skilled in the art, the polymer composition of Example 20 contained no special additive. Accordingly, Example 20 is provided for comparison purposes only and is outside the scope of the present invention. As will be further apparent to those skilled in the art, Examples 20 and 21 relate to a vulcanizate derived from an ethylene vinyl acetate copolymer. Various physical properties of the vulcanizates were determined, as described in Examples 1-4. These properties are indicated in Table 14. The properties of the vulcanizates indicated in Table 14 clearly illustrate the superiority of the hot air aging characteristics of the vulcanizates of Example 21 (special additive was used) when compared to the vulcanizate of the vulcanizate. Example 20 (no special additive was used). This translates into significant practical advantages in many of the conventional vulcanized applications.

Table 1 Table 2 Table 3 Table 4 Table 5 Table 6 Table 7 Hydrogenated acrylonitrile terpolymer, butadiene, unsaturated carboxylic acid ester. abla 8 Table 9 Table 10 F fifteen 2D Table 11 Table 12 Table 13 Table 14 The publications, patents and / or patent applications referred to in this specification are hereby incorporated by reference in their entirety to the same extent as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference in its integrity.

Claims (27)

Claims

1. A polymer composition comprising: a polymer having a polymer backbone derived from: (i) at least about 30% by weight of a first monomer that introduces at least one of a secondary carbon and a tertiary carbon into the polymer backbone, and (ii) from 0 to about 70% by weight of at least one other monomer; Y a salt of a strong base and a weak acid, the salt comprising a metal selected from Group I of the Periodic Table of the Elements.

2. The polymer composition defined in claim 1, further comprising a polycarbodiimide.

3. The polymer composition defined in claim 2, further comprising a filler.

4. The polymer composition defined in claim 3, wherein the filler is selected from the group comprising the black group of carbon, clay, titanium dioxide, silica fillers, talc and mixtures thereof.

5. The polymer composition of claim 4, wherein the polymer comprises an elastomer.

6. The polymer composition defined in claim 5, wherein the elastomer is selected from the group comprising ethylene-propylene copolymer, > ethylene-propylene-non-conjugated diene terpolymer, ethylene vinyl acetate copolymer, unsaturated nitrile / conjugated diene copolymer, hydrogenated unsaturated nitrile / conjugated diene copolymer, unsaturated nitrile terpolymer / conjugated diene / ethylenically unsaturated monomer, unsaturated nitrile terpolymer hydrogenated / conjugated diene / ethylenically unsaturated monomer, styrene / conjugated diene copolymer, hydrogenated styrene / conjugated diene copolymer; polyisoprene, natural rubber, polybutadiene; and mixtures thereof.

7. The polymer composition defined in claim 6, wherein the salt is selected from the group comprising potassium carbonate, sodium carbonate, sodium or potassium salts of mono-, di- or polycarboxylic acids of C-, -C30, sodium phosphate, potassium phosphate and mixtures thereof.

8. The polymer composition defined in claim 7, wherein the salt is selected from the group comprising sodium carbonate, sodium stearate and mixtures thereof.

9. The polymer composition defined in claim 8, wherein the salt is present in an amount in the range of from about 0.5 to about 50 parts by weight.

10. The polymer composition defined in claim 9, wherein the salt is present in an amount in the range of from about 1 to about 20 parts by weight.

11. The polymer composition defined in claim 10, further comprising a vulcanization system.

12. The polymer composition defined in claim 11, wherein the vulcanization system is selected from the group comprising sulfur, a sulfur donor hardening system and a peroxide compound.

13. A process for producing a polymer vulcanizate, comprising the steps of: (i) mixing the polymer composition defined in any one of claims 1-10 with a vulcanization system to produce a hardened composition; Y (n) vulcanizing the curable composition to produce the polymer vulcanizate.

14. The process defined in claim 13, further comprising a vulcanization system.

15. The process defined in claim 14, wherein the vulcanization system is selected from the group comprising sulfur, sulfur donor hardening system and a peroxide compound.

16. A method for improving the hot air aging characteristics of a polymer, comprising the steps of: mixing: (A) a polymer having a polymer backbone derived from: (i) at least about 30% by weight of a first monomer that introduces at least one of a secondary carbon and a tertiary carbon into the polymer backbone , and (ii) from 0 to about 70% by weight of at least one other monomer: and (B) a salt of a strong base and a weak acid, the salt comprising a metal selected from Group I of the Periodic Table of the Elements : and vulcanize the polymer composition.

17. The method defined in claim 16, wherein the polymer composition additionally comprises a polycarbodnmide.

18. The method defined in claim 17, further comprising a filler.

19. The method defined in claim 18, wherein the filler is selected from the group comprising the black group of carbon, clay, titanium dioxide, silica fillers, talc and mixtures thereof.

20. The polymer composition of claim 19, wherein the polymer comprises an elastomer.

The method defined in claim 20, wherein the elastomer is selected from the group comprising ethylene-propylene copolymer, ethylene-propylene-non-conjugated diene terpolymer, ethylene vmyl acetate copolymer, unsaturated nitrile / conjugated diene copolymer, hydrogenated unsaturated nitrile / conjugated diene copolymer, unsaturated nitrile terpolymer / conjugated diene / ethylenically unsaturated monomer, hydrogenated unsaturated nitrile terpolymer / conjugated diene / ethylenically unsaturated monomer, styrene / conjugated diene copolymer, hydrogenated styrene / conjugated diene copolymer; polnsoprene, natural rubber, polybutadiene; and mixtures thereof.

22. The method defined in claim 21, wherein the salt is selected from the group comprising potassium carbonate, sodium carbonate, sodium or potassium salts of mono, di or polycarboxylic acids of Ci-C30, sodium phosphate, potassium phosphate and mixtures thereof.

23. The method defined in claim 22, wherein the salt is selected from the group comprising sodium carbonate, sodium stearate and mixtures thereof.

24. The method defined in claim 23, wherein the salt is present in an amount in the range of from about 0.5 to about 50 parts by weight.

25. The method defined in claim 24, wherein the salt is present in an amount in the range of from about 1 to about 20 parts by weight.

26. The method defined in claim 25, further comprising a vulcanization system.

27. The method defined in claim 26, wherein the vulcanization system is selected from the group comprising sulfur, a sulfur donor hardening system and a peroxide compound.