MXPA99002191A - Improved vulcanization of nitrile polymer and procedure for your producc - Google Patents

Abstract

The present invention relates to a vulcanizate of nitrile polymer that has better characteristics of aging in hot air. The vulcanizate of nitrile polymer can be reduced by mixing a composition consisting of: (i) a nitrile polymer, (ii) a filler, (iii) an additive selected from the group consisting of a strong base, a salt of a strong base and a weak acid, a weak acid salt, a carbodiimide, a polycarbodiimide and mixtures thereof, and (iv) a vulcanization system. Also disclosed is a vulcanizable composition useful for producing said vulcanizate and a method for improving the aging characteristics in hot air of a nitrate polymer.

Description

IMPROVED VULCANIZATION OF NITRILE POLYMER AND PROCEDURE FOR ITS PRODUCTION TECHNICAL FIELD The present invention relates to an improved vulcanization of nitrile polymer and to a process for its production. More specifically, in one of its aspects, the present invention relates to vulcanizates of nitrile polymers that have better characteristics of aging in hot air. In another of its aspects, the present invention relates to a vulcanizable composition useful for producing said vulcanizates. In still another of its aspects, the present invention relates to a method for improving the characteristics of aging in hot air of a vulcanizate of nitrile polymer.

PREVIOUS TECHNIQUE The effects of oxidizing conditions on vulcanizates obtained from polymers having unsaturation of carbon-carbon double bonds have been a problem for a long time, particularly in applications where vulcanizates are exposed to high temperatures for prolonged periods of time. A variety of approaches in the technique have been developed in an attempt to solve this problem. It is known that the carbon-carbon double bonds of said polymers activate the vulcanized against attack oxidative A solution to the problem of oxidative attack is to use polymers with few or no double bonds. Examples of such polymers include butyl rubber (copolymers of isobutylene and isoprene), typically containing from about 0.5 to about 3.0 mole percent unsaturation of carbon-carbon double bonds, and ethylene copolymers. -propylene, which do not contain said unsaturation. Certain applications, such as the various hoses and joints in the engine compartment of automobiles, require vulcanized polymers with a combination of oil resistance and resistance to oxidative attack in air at elevated temperatures for extended periods of time. The vulcanizates of conjugated diene copolymers and α, β-unsaturated nitriles, such as the acrylonitrile-butadiene copolymer, commonly known as nitrile rubber or NBR, are well known for their resistance to oil. However, they contain unsaturation of carbon-carbon double bonds and, therefore, are susceptible to oxidative attack, unless subjected to special procedures for the formation of compounds for the production of vulcanizates resistant to oxidation. In order to reduce the amount of unsaturation of carbon-carbon double bonds in the NBR and still preserve the oil resistance of the copolymer, which is thought to be facilitated by the nitrile-functional groups in the copolymer, methods have been developed to selectively hydrogenate the unsaturation of carbon-carbon double bonds of NBR without hydrogenating the nitrile groups to produce hydrogenated NBR or HNBR. See, for example, the British patent 1,558,491, whose contents are here incorporated as reference. Although the development of the HNBR has constituted a significant advance in the technique, there is still room for further improvement. Specifically, there is a continuing need to develop vulcanizates of nitrile polymers that are characterized by better physical properties, such as aging in hot air and the like.

DESCRIPTION OF THE INVENTION It is an object of the present invention to obviate or mitigate at least one of the aforementioned drawbacks of the prior art. It is another object of the present invention to obtain a new vulcanizate of nitrile polymer. It is yet another object of the present invention to obtain a new process for producing a nitrile polymer vulcanizate. It is still another object of the present invention to obtain a new vulcanizable composition for producing a nitrile polymer vulcanizate. It is yet another object of the present invention to obtain a new method for improving the hot air aging characteristics of a nitrile polymer vulcanizate. Accordingly, in one of its aspects, the present invention provides a vulcanizate of nitrile polymer produced by vulcanization of a composition consisting of: (i) a nitrile polymer; (ii) a filler; (iii) an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and mixtures thereof, and (iv) a system of vulcanization. In another of its aspects, the present invention provides a process for producing a nitrile polymer vulcanizate, consisting of the step of mixing a polymer composition consisting of: (i) a nitrile polymer; (ii) a filler; (iii) an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and mixtures thereof, and (iv) a vulcanization system. In another of its aspects, the present invention provides a vulcanizable composition consisting of: (i) a nitrile polymer; (ii) a filler; (iii) an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and mixtures thereof, and (iv) a system of vulcanization. In yet another of its aspects, the present invention provides a method for improving the characteristics of aging in hot air of a nitrile polymer, consisting of the step of mixing a nitrile polymer with an additive selected from the group consisting of: a strong base, a salt of a strong base and an acid weak, a salt of a weak acid, a carbodiimide, a polycarbodiimide and their mixtures. In yet another aspect, the present invention provides a vulcanizate of hydrogenated nitrile polymer having an aging time in hot air to achieve a 100% elongation at break of at least about 200 hours when measured according to ASTM-D573 -88 to 150 ° C, deriving the vulcanizate from a vulcanization system based on sulfur. Therefore, it has been discovered that the incorporation of a particular additive in a nitrile polymer vulcanizate results in a surprising and unexpected improvement in the hot air aging characteristics of the vulcanized (i.e., an improvement in the resistance to attack). oxidative in aging in air at high temperature under oxidizing conditions). The improvement in the hot air aging characteristics of the vulcanized can manifest itself in a number of ways, including (by way of example only) an increase in: (i) the period of time necessary for the vulcanized to reach 100 % elongation at break at 150 ° C and (ii) the maximum service temperature at which the vulcanizate can be exposed for a specified period of time before reaching 100% elongation at break, when compared to a vulcanized made without additive. The vulcanized present may also be characterized by refinement (i.e., compared to a vulcanizate produced without the additive) in one or more of the following properties: hot fluid aging at rest, compression set at rest, dynamic elastic coefficient at rest (E1), dynamic viscous coefficient at rest (E "), static coefficient at rest, properties of low temperature at rest and hardness at rest.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will be described with reference to the accompanying drawings, wherein: Figures 1-5 illustrate the comparative characteristics of hot air aging between the vulcanizates of nitrile polymers of the invention and vulcanizates of conventional nitrile polymers.

BEST WAY TO CARRY OUT THE INVENTION Therefore, the various aspects of the present application relate to a composition consisting of: (i) a nitrile polymer; (ii) a filler; (iii) an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and its mixtures, and (iv) a vulcanization system. The components (i), (ii), (iii) and (iv) can be added independently of one another or in one or more subcombinations thereof. As used throughout this description, the term "nitrile polymer" is intended to have a broad meaning and is intended to ine a copolymer of a conjugated diene and an unsaturated nitrile.

The conjugated diene may be a C4-C6 conjugated diene. Non-limiting examples of said suitable conjugated dienes can be selected from the group consisting of butadiene, isoprene, piperylene, 2,3-dimethylbutadiene and mixtures thereof. The preferred C4-CG conjugated diene may be selected from the group consisting of butadiene, isoprene and mixtures thereof. The most preferred C4-C6 conjugated diene is butadiene. The unsaturated nitrile may be an α, β-unsaturated nitrile C3-C3. Non-limiting examples of said suitable C3-C3-n-unsaturated nitriles can be selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile and mixtures thereof. The most preferred α3, β-unsaturated nitrile C3-C5 is acrylonitrile. Preferably, the copolymer consists of about 40 to about 85 weight percent of the bound conjugated diene copolymer and about 15 to about 60 weight percent of the bound unsaturated nitrile copolymer. More preferably, the copolymer consists of about 60 to about 75 weight percent of the bound conjugated diene copolymer and about 25 to about 40 weight percent of the bound unsaturated nitrile copolymer. More preferably, the copolymer consists of about 60 to about 70 weight percent of the bound conjugated diene copolymer and about 30 to about 40 weight percent of the bound unsaturated nitrile copolymer. Optionally, the copolymer can also consist of a bound unsaturated carboxylic acid. The examples do not Limitations of said suitable bound unsaturated carboxylic acids can be selected from the group consisting of fumaric acid, maleic acid, acrylic acid, methacrylic acid and mixtures thereof. The bound unsaturated carboxylic acid may be present in an amount of about 1 to about 10 weight percent of the copolymer, displacing this amount to a corresponding amount of the conjugated diolefin. In addition, a third manomer can be used in the production of the nitrile polymer. Preferably, the third monomer is an unsaturated mono- or dicarboxylic acid or derivative thereof (e.g., esters, amides and the like). Although the invention can be used with fully or partially unsaturated nitrile polymers, a particularly preferred group of nitrile polymers useful in the production of the present vulcanized are hydrogenated or partially hydrogenated nitrile polymers (also known in the art as HNBR). Preferably, the copolymer is hydrogenated and contains a residual carbon-carbon double bond unsaturation of less than about 30, more preferably from about 30 to about 0.05 mole percent, even more preferably from about 15 to about 0.05 mole percent, even more preferably from about 10.0 to about 0.05 mole percent, even more preferably from about 7.0 to about 0.05 mole percent, more preferably about a 5.5 to about 0.05 mole percent. The vulcanizable polymer composition also contains preferably a filler. The nature of the filler is not particularly restricted and the choice of suitable fillers is within the scope of a person skilled in the art. Non-limiting examples of suitable fillers include carbon black (eg, FBF, MT, GPF and SRF), clays, titanium dioxide, silica fillers (with or without unsaturated silanes) and the like. The amount of filler is conventional. Preferably, the filler is present in an amount in the range of about 20 to about 130 parts by weight per hundred parts by weight of the nitrile polymer. More preferably, the filler is present in an amount in the range of about 20 to about 100 parts by weight per hundred parts by weight of nitrile polymer. More preferably, the filler is present in an amount in the range of about 40 to about 80 parts by weight per hundred parts by weight of the nitrile polymer. The vulcanizable composition further contains an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a polycarbodiimide, a carbodiimide and mixtures thereof. Non-limiting examples of strong bases useful in the vulcanized present may be the inorganic bases selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium oxide and the like.

Preferably, the salt has a p at of at least about 9.0, more preferably at least 10.0, more preferably in the range of about 10.0 to about 14.0. A preferred group of additives consists of a salt of a Group I metal (e.g. sodium, potassium, etc.) of a weak acid (for example, carbonic acid, phosphonic acid, boric acid, C-C30 fatty acids and the like). Non-limiting examples of salts useful in the present vulcanizate can be selected from the group consisting of sodium carbonate, sodium acetate, sodium phosphate, potassium carbonate, sodium stearate, sodium EDTA and mixtures thereof. The most preferred salt is sodium carbonate. The additive is present in an amount of from about 0.5 to about 30 parts by weight per hundred parts by weight of nitrile polymer, more preferably from about 1.0 to about 10.0 parts by weight per hundred parts by weight of polymer of nitrile, more preferably from about 2.0 to about 8.0 parts by weight per hundred parts by weight of nitrile polymer. The vulcanization system used in the production of the present vulcanized nitrile polymer is conventional and its choice is within the reach of a person skilled in the art. In one embodiment, the vulcanization system used in the present invention consists of an organic peroxide (eg, dicumyl peroxide, 2,2'-bis (tert-butylperoxy) diisopropylbenzene and the like). In another embodiment, the vulcanization system used in the present invention consists of sulfur or a conventional sulfur-containing vulcanization product, such as Vulkacit ™ DM / C (benzothiazyl disulfide), Vulkacit ™ Thiuram MS / C (tetramethylthiuram monosulfide), Vulkacit ™ Thiuram / C (tetramethylthiuram disulfide), mixtures of these and similar. Preferably, said sulfur-based vulcanization systems further contain a peroxide, such as zinc peroxide. In yet another embodiment, the vulcanization system used in the present invention contains a reactive phenol-formaldehyde resin and a Lewis acid activator. It is known to those skilled in the art that a reactive phenol-formaldehyde resin can be prepared by reaction of a para-substituted phenol with a molar excess of formaldehyde - see, for example, U.S. Patent 2,726,224, the contents of which are herein incorporated as reference. The use of said phenol-formaldehyde resins in vulcanization systems for butyl rubber is well known. The vulcanization system used in the present process preferably contains at least about 3 parts by weight of reactive phenol-formaldehyde resin per one hundred parts by weight of nitrile polymer. It is especially preferred to use from about 8 to about 16 parts by weight of the phenol-formaldehyde reactive resin per hundred parts by weight of polymer. If more than about 16 parts by weight of the resin are used per one hundred parts of nitrile polymer, the entire composition tends to become resinous and, therefore, such high resin levels are generally undesirable.

The Lewis acid activator may be present as a separate component, such as stannous chloride (SnCl2) or poly (chlorobutadiene). Alternatively, the Lewis acid activator may be present in the structure of the resin itself-for example, alkylphenol-bromomethylated formaldehyde resin (which may be prepared by substitution of some of the hydroxyl groups of the methylol group of the resin discussed above by bromine). The use of said halogenated resins in vulcanization systems for butyl rubber is well known to those skilled in the art. In the present process, the nitrile polymer, the filler, 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. The preferred hydrogenated nitrile copolymer used in the present process tends to be quite stiff and has a predisposition to swell when mixed in a two-roll rubber mill. The addition of a reactive phenol-formaldehyde resin improves the mixture of the hydrogenated copolymer reducing the swelling problem. Therefore, the polymer composition is mixed in a conventional manner and its temperature 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, this polymer composition is heated to a temperature in the range of about 130 ° to about 200 ° C, preferably about 140 ° to about 190 ° C, more preferably about 150 ° to about 180 ° C. Preferably, the heating is carried out for a period of from about 1 minute to about 15 hours, more preferably from about 5 minutes to about 30 minutes.

Other conventional compound forming ingredients can also be included, by blending with the copolymer in the conventional manner. Said other compounding ingredients are used for their conventional purposes and include activators, such as zinc oxide and magnesium oxide; antioxidants, such as diphenylamines and the like; stearic acid; plasticizers; processing aids; reinforcing agents; fillers; promoters, and retarders, in amounts well known in the art. Embodiments of the present invention will be illustrated with reference to the following Examples, which are provided for illustrative purposes and are not to be employed to limit the scope of the invention. In addition, in the Examples, the following materials were used: Therban ™ XN532A / A4307, a hydrogenated nitrile and butadiene polymer marketed by Bayer, Inc .; Therban ™ A4555, a hydrogenated nitrile and butadiene polymer marketed by Bayer Inc .; Therban ™ A3407, a hydrogenated nitrile and butadiene polymer marketed by Bayer, Inc .; Therban ™ XN533A (A3907), a hydrogenated nitrile and butadiene polymer marketed by Bayer, Inc .; Therban ™ XN541C, a nitrile and butadiene polymer having a residual content in double bonds of 2-4% and marketed by Bayer, Inc.; Therban ™ X0543C / C3467, a nitrile-butadiene polymer having a residual content in double bonds of 5.5% and marketed by Bayer, Inc .; HNBR # 1, a hydrogenated nitrile and butadiene polymer having a residual content in double bonds of 4%; HNBR # 2, a hydrogenated nitrile and butadiene polymer having a residual content in double bonds of 10%; Rhenogran ™ P-50, a polycarbodiimide marketed by Rhein Chemie; Dynamar ™ L 13890, a sodium carbonate marketed by Dyacon; Suprapur ™ 6395, sodium carbonate (soda ash) marketed by EM Industries; Sodium stearate, additive; Stearic acid NBS, dispersing agent; Vulkanox ™ OCD / SG, antidegradant marketed by Bayer, Inc.; Vulkanox ™ ZMB-2 / C5, antidegradant marketed by Bayer, Inc.; Vulkacit ™ DMC, benzothiazyl disulfide vulcanizing agent sold by Bayer, Inc .; Vulkacit ™ Thiuram MS / C, vulcanizing agent of tetramethylthiuram monosulfide marketed by Bayer, Inc.; Vulkacit ™ Thiuram / C, tetramethylthiuram disulfide vulcanizing agent sold by Bayer, Inc .; Maglite ™ D, magnesium oxide, activator, marketed by CP Hall; Zinc oxide, activator; Carbon black N660, filling; Carbon black IRB # 6, activator; Plasthall ™ TOTM, plasticizer marketed by CP Hall; Crosslinked sulfur, vulcanizing agent; DIAK ™ # 7: triallyl isocyanate, crosslinking activator, marketed by E.I. DuPont, and Vulcup ™ 40KE, 2, 2'-bis (tert-butylperoxy) diisopropylbenzene marketed by Hercules. EXAMPLES 1-4 The following procedure was used for each of Examples 1-4. The polymer composition used in Examples 1-4 is shown in Table 1. As will be apparent to those skilled in the art, the polymer composition of Example 1 does not contain any special additives. Accordingly, the Example is provided for comparative purposes only and is beyond the scope of the present invention. The components of the polymer composition were mixed in a Banbury mixer using conventional techniques. The polymer composition was vulcanized at 180 ° C for a period of 12 minutes. The tensile stress until the break was determined ("tensile strength") of vulcanizates according to ASTM D412-80. The hot air aging properties of the vulcanizates were determined according to ASTM-D573-88.

The hardness properties were determined using a Type A Shore Durometer according to ASTM-D2240-81. The properties of the vulcanizates are given in Table 2. The hot-air aging properties of the vulcanizates are also illustrated in FIG. The properties of the vulcanizates given in Table 2 and illustrated in Figure 1 clearly illustrate the superiority of hot air aging characteristics of the vulcanizates of Examples 2-4 (use of special additive) in comparison with the vulcanizate of Example 1 (use of conventional MgO additive). Figure 1 is particularly instructive in showing the significant refinement in the time necessary for the aged vulcanized to reach 100% elongation at break under the test conditions. This translates into significant practical advantages in many of the conventional vulcanized applications. EXAMPLES 5-9 The methodology used in Examples 1-4 was repeated in these Examples, using the polymer compositions shown in Table 3. As will be apparent to those skilled in the art, the polymer composition of the Example 5 does not contain any special additives and the polymer compositions of Examples 6 and 7 contain a conventional additive (MgO). Accordingly, Examples 5-7 are provided for comparative purposes only and are beyond the scope of the present invention. Several of the physical properties of the vulcanizates were determined as described in Examples 1-4. These properties appear in Table 4. Also illustrated in Figure 2 are the hot air aging properties of the vulcanizates. The properties of the vulcanizates given in Table 4 and illustrated in Figure 2 clearly illustrate the superiority of the hot air aging characteristics of the vulcanizates of Examples 8 and 9 (use of special additive) in comparison with the vulcanized from Example 5 (without use of additive) and from Examples 6 and 7 (use of conventional MgO additive). Figure 2 is particularly instructive in showing the significant refinement in the time necessary for the aged vulcanized to reach 100% elongation at break under the test conditions. Again, this translates into significant practical advantages in many of the conventional vulcanized applications. Figure 2 is also instructive in terms of showing that the advantages obtained from the use of sodium carbonate as a special additive: (i) can not be achieved simply by increasing the amount of conventional additive (MgO) and (ii) are apparent at lower and higher levels of the special additive. EXAMPLES 10-14 The methodology used in Examples 5-9 was repeated in these Examples, using the polymeric compositions indicated in Table 5. As will be apparent to those skilled in the art, the polymer composition of Example 10 contains no special additive and the polymer compositions of Examples 11 and 12 contain a conventional additive (MgO). Accordingly, Examples 10-12 are provided for comparative purposes only and are outside the scope of the present invention. Several physical properties of the vulcanizates were determined as described in Examples 1-4. These properties are indicated in Table 5. Figure 3 also illustrates the hot-air aging properties of vulcanizates. The properties of the vulcanizates given in Table 5 and illustrated in Figure 3 clearly illustrate the superiority of hot air aging characteristics of the vulcanizates of Examples 13 and 14 (use of special additive) compared to the vulcanizate of Example 10 (without the use of additive) and of Examples 11 and 12 (use of conventional additive) of MgO). Figure 3 is particularly instructive in showing the significant refinement in the time necessary for the aged vulcanizate of Examples 13 and 14 to reach 100% elongation at break under the test conditions. Again, this translates into a significant practical advantage in many of the conventional vulcanized applications. Figure 3 is also instructive in showing that the trends and advantages discussed above in relation to Examples 1-9 are maintained even when a different nitrile rubber is used. EXAMPLES 15-22 The methodology used in Examples 5-9 was repeated in these Examples using the polymeric compositions indicated in Table 7. As will be apparent to those skilled in the art, the polymeric compositions of the Examples 15, 17, 19 and 21 contain a conventional additive (MgO). Accordingly, Examples 15, 17, 19 and 21 are provided for comparative purposes only and are beyond the scope of the present invention. Several physical properties of the vulcanizates were determined as described in Examples 1-4. These properties are indicated in Table 7. The hot air aging properties of the vulcanizates of Examples 15-18 are illustrated in Figure 4 and those of the vulcanizates of Examples 19-22 are illustrated in Figure 5. Figures 4 and 5 are particularly instructive in showing the significant refinement in the time necessary for the aged vulcanizate of Examples 16, 18, 20 and 22 to reach 100% elongation at break under the conditions of test in comparison with the aged vulcanizate of Examples 15, 17, 19 and 21, respectively. Once again, this translates into a significant practical advantage in many of the conventional vulcanized applications. Figures 4 and 5 are also instructive in showing that the trends and advantages discussed above in relation to Examples 1-9 are maintained even when using a nitrile rubber with a high residual content in double bonds. EXAMPLES 23-30 The methodology used in Examples 5-9 in these Examples was repeated using the polymer compositions indicated in Table 9. As will be apparent to those skilled in the art, the polymer compositions of Examples 23 and 26 do not contain any special additive. Examples 24, 27 and 29 contain a conventional additive (MgO). Accordingly, Examples 23, 24, 26, 27 and 29 are provided for comparative purposes only and are beyond the scope of the present invention. Several physical properties of the vulcanizates were determined as described in Examples 1-4. These properties are indicated in Table 10. The results in Table 10 clearly demonstrate the significant improvements in the properties of aging in hot air (time necessary for the vulcanized to reach 100% elongation at break in the test conditions) of the vulcanizates prepared with the sodium carbonate (Examples 25, 28 and 30) compared to the vulcanizates prepared using a conventional additive (Examples 24, 27 and 29) or without special additive (Examples 23 and 26). Once again, this translates into significant practical advantages in many industrial applications of vulcanizates.

TABLE 1 Employ TABLE 2 Example TABLE 3 Example Vulcanized not aged TABLE 4 (cont.) Example Example AJBL _6. Example TABLE 6 (cont.) TABLE 7 Example TABLE 8 Example Vulcanized not aged Hardness, Shore 73 73 71 71 71 72 71 72 A (pts.) At the rgamiento 535 470 730 655 455 400 510 455 final (%) Vulcanized aging for 72 hours ® 150 ° C Hardness, Shore 78 78 77 76 76 76 76 77 A (pts.) Elongation 470 520 545 640 315 445 305 510 final (%) Vulcanised aged for 216 hours @ 150 ° C Hardness, Shore 82 80 82 80 83 82 86 82 A (pts.) Elongation 260 480 385 580 125 385 75 275 Example TABLE 1Q Vulcanized not aged Hardness, Shore 73 73 72 73 75 73 73 73 A (pts.) Elongation 255 195 210 275 235 240 235 245 final (%) Vulcanized aged for 168 hours @ 150 ° C Hardness, Shore 82 81 81 84 84 85 83 83 A (pts.) Elongation 180 190 250 150 160 240 185 260 final (%) Vulcanized aged for 504 hours ® 150 ° C Hardness, Shore 86 84 81 89 85 86 86 84 A (pts.) Elongation 55 85 220 35 70 180 70 260 final (%) TABLE 10 ícont. ) Example Vulcanized aged for 1008 hours ® 150 ° C Hardness, Shore 90 92 83 88 94 89 85 87 A (pts.) Elongation 15 35 155 5 15 135 25 210 final (%) Vulcanized aged for 1512 hours @ 150 ° C Hardness , Shore 93 96 89 96 95 90 97 90 A (pts.) Elongation 0 5 140 0 0 85 5 150 final (%)

Claims (30)

Claims

1. A vulcanizable composition consisting of: (i) a nitrile polymer; (ii) a filler; (iii) an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and mixtures thereof, and (iv) a system of vulcanization.

2. The vulcanizable composition defined in claim 1, wherein the nitrile polymer consists of a copolymer of a conjugated diene and an unsaturated nitrile.

3. The vulcanizable composition defined in claim 2, wherein the conjugated diene is a C4-C6 conjugated diene.

4. The vulcanizable composition defined in claim 3, wherein the C4-C6 conjugated diene is butadiene.

5. The vulcanizable composition defined in claim 2, wherein the unsaturated nitrile is an α, β-unsaturated C3-C5 nitrile selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile and mixtures thereof.

The vulcanizable composition defined in claim 2, wherein the copolymer consists of about 40 to about 85 weight percent of the conjugated diene copolymer bound and about 15 to about 60 weight percent of the unsaturated nitrile copolymer United.

7. The vulcanizable composition defined in Claim 2, wherein the nitrile polymer is a copolymer of butadiene and acrylonitrile.

8. The vulcanizable composition defined in claim 7, wherein the copolymer consists of about 55 to about 75 weight percent of the bound butadiene copolymer and about 25 to about 45 weight percent of the acrylonitrile copolymer. United.

9. The vulcanizable composition defined in claim 2, wherein the copolymer is hydrogenated.

The vulcanizable composition defined in claim 9, wherein the copolymer contains a residual unsaturation of carbon-carbon double bonds of less than about 30 mole percent.

11. The vulcanizable composition defined in claim 1, wherein the salt of a strong base and a weak acid has a pE ^ of at least about 9.0.

12. The vulcanizable composition defined in claim 1, wherein the salt of a strong base and a weak acid consists of a salt of a Group I metal and a carbonate.

The vulcanizable composition defined in claim 1, wherein the additive is selected from the group consisting of a salt of a Group I metal and a weak acid, optionally in combination with a carbodiimide, a polycarbodiimide and mixtures thereof.

14. The vulcanizable composition defined in claim 1, wherein the metal of Group I is selected from sodium and potassium and the weak acid is selected from carbonic acid and fatty acids ^ -030.

15. The vulcanizable composition defined in claim 1, wherein the additive is present in an amount of about 0.5 to about 30 parts by weight per hundred parts by weight of nitrile polymer.

16. A process for the production of a nitrile polymer vulcanizate consisting of the vulcanization step of the vulcanizable composition defined in claim 1.

17. A polymeric vulcanizate produced by the process defined in claim 16.

18. A method for improving the characteristics of aging in hot air of a nitrile polymer, consisting of the step of mixing a nitrile polymer with an additive selected from the group consisting of: a strong base, a salt of a strong base and a weak acid, a salt of a weak acid, a carbodiimide, a polycarbodiimide and mixtures thereof.

19. The method defined in claim 18, wherein the nitrile polymer consists of a copolymer of a conjugated diene and an unsaturated nitrile.

20. The method defined in claim 18, wherein the nitrile polymer is a copolymer of butadiene and acrylonitrile.

21. The method defined in claim 12, wherein the nitrile polymer is hydrogenated.

22. The method defined in claim 21, wherein the nitrile polymer contains a residual unsaturation of carbon-carbon double bonds of less than 30 mole percent.

23. The method defined in claim 18, wherein the salt of a strong base and a weak acid has a pKa of at least about 9.0.

24. The method defined in claim 18, wherein the additive is selected from the group consisting of a metal salt of Group I and a weak acid, optionally in combination with a carbodiimide, a polycarbodiimide and mixtures thereof.

25. The method defined in claim 18, wherein the metal of Group I is selected from sodium and potassium and the weak acid is selected from carbonic acid and C ^ C ^ fatty acids.

26. The method defined in claim 18, wherein the additive is present in an amount of about 0.5 to about 30 parts by weight per hundred parts by weight of nitrile polymer.

27. The method defined in claim 18, further including mixing a vulcanization system with the nitrile polymer and the additive.

28. The method defined in claim 18, further including mixing a filler with the nitrile polymer and the additive.

29. The method defined in claim 18, further including mixing a vulcanization system and a filler with the nitrile polymer and the additive.

30. A vulcanizate of hydrogenated nitrile polymer having an aging time in hot air to reach 100% elongation at break of at least about 200 hours when measured according to ASTM-D573-88 at 150 ° C, deriving the vulcanization of a sulfur-based vulcanization system.