Hydrogenation composition comprising a nitrile rubber

Abstract

The present invention relates to a hydrogenation composition, comprising (i) a polymer, wherein the polymer comprises a nitrile rubber; and at least the following components: (ii) at least one compound of general formula (I) wherein R1 means a saturated and unsubstituted linear C1-C17-alkyl, preferably a saturated and unsubstituted linear C2-C14-alkyl; and R2 are identical or different and mean straight chain or branched C1-C6 alkyl or C5-C6 cycloalkyl; and (iii) at least one compound of general formula (II) wherein R3 means straight chain or branched C1-C14 alkyl; and R4 means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio, and wherein the composition is free of dithiodipropionate tridecyl ester.

Description

[0001] Hydrogenation composition comprising a nitrile rubber

[0002] The present invention relates to a hydrogenation composition which is suitable for hydrogenating nitrile rubbers or which comes from a hydrogenation reaction. The present invention further relates to a method of hydrogenating a nitrile rubber in order to form a hydrogenated nitrile rubber.

[0003] Nitrile rubbers as well as hydrogenated nitrile rubbers are known in the art and suitable for a plurality of applications. There may be the need for stabilizing these polymers in order to ensure maintaining their properties, thereby withstanding for example high temperatures. Apart from that, it may be required that nitrile rubbers shall maintain their properties both as raw material as well as in its hydrogenated form, wherein it is important that the hydrogenation reaction is not deteriorated.

[0004] DE 10051 198 describes mixtures of different antioxidants. However, there is no hint if they are suitable for performing a hydrogenation reaction.

[0005] CN 103497376 A shows an antioxidant applied to acrylonitrile-butadiene rubber latex and carboxylic acrylonitrile butadiene rubber latex and a preparation method. The antioxidant comprises the following components: (a) component, i.e., one or a combination of two of 4,6-bis(octylsulfanyl methyl) orthocresol (a1) or 4,6-bis(n-dodecyl methyl sulfide) orthocresol (a2); (b) component, i.e., one or combination of two of 3,5-di-tert-butyl-4-isooctyl hydroxyphenyl propionate (b1) or 3,5-di-tert-butyl-4-hydroxybenzene propanoic acid C7-C9 mixed alcohol ester (b2), and (c) component, i.e., ditridecyl thiodipropionate. However, this document also does not give any hint to a suitability of the used components in a hydrogenation reaction.

[0006] US 5,116,534 describes storage-stable, non-sedimenting emulsions containing a) 10 to 40% by weight, based on the emulsion, of (A) phenolic antioxidants and antioxidants from the series comprising (B) thiodipropionic acid esters or / and (C) organic phosphites, b) 0.25 to 10% by weight, based on the emulsion, of a surfactant of the formula R-COOY, in which R is alkyl having 3 to 18 atoms, alkenyl having 3 to 18 C atoms or phenyl-C3-C18alkyl and Y is an alkali metal, 0.25 to 10% by weight, based on the emulsion, of an alcohol of the formula R'-OH, in which R' is alkyl having 4 to 19 C atoms, alkenyl having 4 to 19 C atoms or phenyl-C4C19alkyl, and water as the remainder to make 100% by weight.EP 3 102 631 A1 describes rubbers which are stabilized by a specific combination of at least three different anti ageing compounds. These three anti ageing compounds comprise inter alia Irganox 1076 having a C18 chain at an ester group and in general three different phenolic antioxidants.

[0007] However, the state of the art is silent about components which might be added specifically to nitrile rubbers both in non-hydrogenated and hydrogenated form and which on the one hand withstand hydrogenation reactions so that they are usable in the product before and after hydrogenation and that they further do not deteriorate the hydrogenation reaction and allow a high reaction throughput.

[0008] It is thus an object of the present invention to provide a measure for providing an improved hydrogenation composition which shows both good stabilizing properties as well as high catalytic activity in hydrogenation reactions.

[0009] Summary

[0010] In one aspect, the present invention provides a hydrogenation composition, comprising (i) a polymer, wherein the polymer comprises a nitrile rubber; and at least the following components:

[0011] (ii) at least one compound of general formula (I)

[0012]

[0013] wherein

[0014] R1means a saturated and unsubstituted linear Ci-Cn-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alky; and

[0015] R2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and

[0016] (iii) at least one compound of general formula (II)

[0017]

[0018] wherein

[0019] R3means straight chain or branched C1-C14 alkyl; and

[0020] R4may be the same or different and means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio and wherein

[0021] the composition is free of dithiodipropionate tridecyl ester.

[0022] According to a further aspect, the present invention provides a method of hydrogenating a polymer, wherein the polymer comprises a nitrile rubber and the method comprises the steps of

[0023] a) Providing a hydrogenation composition according to the present invention and a hydrogenation catalyst and thus a mixture of these compounds;

[0024] b) Arranging the mixture in a hydrogenation reactor; and

[0025] c) Performing a hydrogenation reaction in the hydrogenation reactor by setting defined hydrogenation conditions in said hydrogenation reactor.

[0026] According to a still further aspect, the present invention provides a hydrogenated polymer, wherein the hydrogenated polymer comprises a hydrogenated nitrile rubber, wherein the hydrogenated nitrile rubber is formed by a method according to the present invention.

[0027] According to a still further aspect, the present invention provides a composition comprising a hydrogenated nitrile rubber according to the invention and at least the following components:

[0028] (ii) at least one compound of general formula (I)

[0029]

[0030] wherein

[0031] R1means a saturated and unsubstituted linear Ci-Cn-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alky; and

[0032] R2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and

[0033] (iii) at least one compound of general formula (II)

[0034]

[0035] wherein

[0036] R3means straight chain or branched C1-C14 alkyl; and

[0037] R4means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio and wherein

[0038] the composition is free of dithiodipropionate tridecyl ester.

[0039] Further, the present invention provides a use of a mixture as an additive in a hydrogenation composition in a hydrogenation of a nitrile rubber to form an at least partly hydrogenated nitrile rubber, wherein the mixture comprises at least the following components:

[0040] (ii) at least one compound of general formula (I)

[0041]

[0042] wherein

[0043] R1means a saturated and unsubstituted linear Ci-Cn-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alky; and

[0044] R2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and

[0045] (iii) at least one compound of general formula (II)

[0046]

[0047] wherein

[0048] R3means straight chain or branched C1-C14 alkyl; and

[0049] R4means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio and wherein

[0050] The composition is free of dithiodipropionate tridecyl ester.

[0051] The present invention shows very good results regarding the stability of nitrile rubber, both in non-hydrogenated and in hydrogenated form, as well as regarding the use of respective additives in a hydrogenation reaction. Examples of applications of respective nitrile rubbers comprise inter alia applications in batteries, such as binders or dispersant aids.

[0052] Detailed Description

[0053] In the following description norms may be used. If not indicated otherwise, the norms areused in the version that was in force on January 1 , 2025. If no version was in force at that date because, for example, the norm has expired, then the version is referred to that was in force at a date that is closest to January 1 , 2025.

[0054] In the following description the amounts of ingredients of a composition or polymer may be indicated interchangeably by “weight percent”, “wt. %” or “% by weight”. The terms “weight percent”, “wt. %” or “% by weight” are used interchangeably and are based on the total weight of the composition or polymer, respectively, which is 100 % unless indicated otherwise.

[0055] The term “phr” means parts per hundred parts of rubber, i.e. , the weight percentage based on the total amount of rubber which is set to 100%.

[0056] Ranges identified in this disclosure include and disclose all values between the endpoints of the range and also include the end points unless stated otherwise.

[0057] The present invention provides inter alia a composition comprising a nitrile rubber and additionally a combination of two compounds suitable as additives, in particular for avoiding heat aging, wherein a hydrogenation reaction is not negatively influenced.

[0058] The used compounds and their effects are as follows.

[0059] Nitrile rubber:

[0060] In a preferred embodiment the invention is directed to a nitrile rubber being present in combination with a mixture of at least two additives and thus being stabilized, the nitrile rubber having repeating units derived from of at least one a,p-unsaturated nitrile, at least one conjugated diene and none, one or more further copolymerizable monomers.

[0061] Generally, the term nitrile relates to its non-hydrogenated or to its hydrogenated species.

[0062] As a,p-unsaturated nitrile, it is possible to use any known a,p-unsaturated nitrile, preferably a (C3-C5) a,p-unsaturated nitrile such as acrylonitrile, methacrylonitrile, ethacrylonitrile or mixtures thereof. Particular preference is given to acrylonitrile.

[0063] The conjugated diene can be of any nature. Preference is given to using (C4-C6) conjugated dienes. Particular preference is given to 1,3-butadiene, isoprene, 2,3-dimethylbutadiene, piperylene or mixtures thereof. Very particular preference is given to 1,3-butadiene and isoprene or mixtures thereof. Especial preference is given to 1,3-butadiene.

[0064] A particularly preferred nitrile rubber used in the process of this invention is thus a copolymer having repeating units derived from acrylonitrile and 1,3-butadiene.

[0065] It may be preferred that the nitrile rubber has repeating units solely derived from an a,p-unsaturated nitrile and a conjugated diene, such as only derived from acrylonitrile and 1,3-butadiene.

[0066] Apart from the conjugated diene and the a,p-unsaturated nitrile, the hydrogenated nitrile rubber may comprise repeating units of one or more further copolymerizable monomers known in the art, e.g. a,p-unsaturated (preferably mono-unsaturated) monocarboxylic acids, their esters and amides, a,p-unsaturated (preferably mono-unsaturated) dicarboxylic acids, their mono- or diesters, as well as the respective anhydrides or amides of said a,p-unsaturated dicarboxylic acids.

[0067] As a,p-unsaturated monocarboxylic acids acrylic acid and methacrylic acid are preferably used.

[0068] Esters of a,p-unsaturated monocarboxylic acids may also be used, in particular alkyl esters, alkoxyalkyl esters, aryl esters, cycloalkylesters, cyanoalkyl esters, hydroxyalkyl esters, and fluoroalkyl esters.

[0069] As alkyl esters C1-C18 alkyl esters of the a,p-unsaturated monocarboxylic acids are preferably used, more preferably C1-C18 alkyl esters of acrylic acid or methacrylic acid, such as methylacrylate, ethylacrylate, propylacrylate, n-butylacrylate, tert.-butylacrylate, 2-ethyl-hexylacrylate, n-dodecylacrylate, methylmethacrylate, ethylmethacrylate, propylmethacrylate, n-butylmethacrylate, tert.-butylmethacrylate and 2-ethylhexyl-methacrylate.

[0070] As alkoxyalkyl esters C2-C18 alkoxyalkyl esters of a, - unsaturated monocarboxylic acids are preferably used, more preferably alkoxyalkylester of acrylic acid or methacrylic acid such as methoxy methyl(meth)acrylate, methoxy ethyl(meth)acrylate, ethoxyethyl(meth)acrylate and methoxyethyl(meth)acrylate.It is also possible to use aryl esters, preferably Ce-C -aryl-, more preferably Ce-C -aryl esters and most preferably the aforementioned aryl esters of acrylates and methacrylates.

[0071] In another emodiment cycloalkyl esters, preferably C5-C12-, more preferably C6-Ci2-cyclo-alkyl and most preferably the aforementioned cycloalkyl acrylates and methacrylates are used.

[0072] It is also possible to use cyanoalkyl esters, in particular cyanoalkyl acrylates or cyanoalkyl methacrylates, with 2 to 12 C atoms in the cyanoalkyl group, preferably a-cyanoethyl acrylate, p-cyanoethyl acrylate or cyanobutyl methacrylate.

[0073] In another emodiment hydroxyalkyl esters are used, in particular hydroxyalkyl acrylates and hydroxyalkyl methacrylates with 1 to 12 C-atoms in the hydroxylalkyl group, preferably 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate or 3-hydroxypropyl acrylate.

[0074] It is also possible to use fluorobenzyl esters, in particular fluorobenzyl acrylates or fluorobenzyl methacrylates, preferably trifluoroethyl acrylate and tetrafluoropropyl methacrylate. Substituted amino group containing acrylates and methacrylates may also be used like dimethylaminomethyl acrylate and diethylaminoethylacrylate.

[0075] Various other esters of the a,p-unsaturated carboxylic acids may also be used, like e.g. poly-ethyleneglycol(meth)acrylate, polypropyleneglycole(meth)acrylate, glycidyl(meth)acrylate, epoxy(meth)acrylate, N-(2-hydroxyethyl)acrylamide, N-(2-hydroxymethyl)acrylamide or urethane(meth)acrylate.

[0076] It is also possible to use mixture of all aforementioned esters of a,p-unsaturated carboxylic acids.

[0077] Further on a,p-unsaturated dicarboxylic acids may be used, preferably maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid and mesaconic acid.

[0078] In another embodiment anhydrides of a,p-unsaturated dicarboxylic acids are used, preferably maleic anhydride, itaconic anhydride, itaconic anhydride, citraconic anhydride and mesaconic anhydride.In a further embodiment mono- or diesters of a,p-unsaturated dicarboxylic acids can be used. Suitable alkyl esters are e.g. Ci-C -alkyl, preferably ethyl-, n-propyl-, iso-propyl, n-butyl-, tert.-butyl, n-pentyl- Oder n-hexyl mono- or diesters. Suitable alkoxyalkyl esters are e.g. C2-C12 alkoxyalkyl-, preferably Cs-Cs-alkoxyalkyl mono- or diesters. Suitable hydroxyalkyl esters are e.g. C1-C12 hydroxyalkyl-, preferably C2-C8-hydroxyalkyl mono- or diesters. Suitable cycloalkyl esters are e.g. Cs-Ci2-cycloalkyl-, preferably C6-Ci2-cycloalkyl mono- or diesters. Suitable alkylcycloalkyl esters are e.g. C6-Ci2-alkylcycloalkyl-, preferably Cy-Cw-alkylcycloalkyl mono- or diesters. Suitable aryl esters are e.g. Ce-Cu-aryl, preferably Ce-C -aryl mono- or diesters.

[0079] Explicit examples of the a,p-ethylenically unsaturated dicarboxylic acid monoester monomers include

[0080] • maleic acid monoalkyl esters, preferably monomethyl maleate, monoethyl maleate, monopropyl maleate, and mono n-butyl maleate;

[0081] • maleic acid monocycloalkyl esters, preferably monocyclopentyl maleate, monocyclohexyl maleate, and monocycloheptyl maleate;

[0082] • maleic acid monoalkylcycloalkyl esters, preferably monomethylcyclopentyl maleate, and monoethylcyclohexyl maleate;

[0083] • maleic acid monoaryl ester, preferably monophenyl maleate;

[0084] • maleic acid mono benzyl ester, preferably monobenzyl maleate;

[0085] • fumaric acid monoalkyl esters, preferably monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, and mono n-butyl fumarate;

[0086] • fumaric acid monocycloalkyl esters, preferably monocyclopentyl fumarate, monocyclohexyl fumarate, and monocycloheptyl fumarate;

[0087] • fumaric acid monoalkylcycloalkyl esters, preferably monomethylcyclopentyl fumarate, and monoethylcyclohexyl fumarate;

[0088] • fumaric acid monoaryl ester, preferably monophenyl fumarate;

[0089] • fumaric acid mono benzyl ester, preferably monobenzyl fumarate;

[0090] • citraconic acid monoalkyl esters, preferably monomethyl citraconate, monoethyl citraconate, monopropyl citraconate, and mono n-butyl citraconate;

[0091] • citraconic acid monocycloalkyl esters, preferably monocyclopentyl citraconate, monocyclohexyl citraconate, and monocycloheptyl citraconate;

[0092] • citraconic acid monoalkylcycloalkyl esters, preferably monomethylcyclopentyl citraconate, and monoethylcyclohexyl citraconate;

[0093] • citraconic acid mono aryl ester, preferably monophenyl citraconate;

[0094] • citraconic acid mono benzyl ester, preferably monobenzyl citraconate;• itaconic acid mono alkyl esters, preferably monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, and mono n-butyl itaconate;

[0095] • itaconic acid monocycloalkyl esters, preferably monocyclopentyl itaconate, monocyclohexyl itaconate, and monocycloheptyl itaconate;

[0096] • itaconic acid monoalkylcycloalkyl esters, preferably monomethylcyclopentyl itaconate, and monoethylcyclohexyl itaconate;

[0097] • itaconic acid mono aryl ester, preferably monophenyl itaconate;

[0098] • itaconic acid mono benzyl ester, preferably monobenzyl itaconate.

[0099] As a,p-ethylenically unsaturated dicarboxylic acid diester monomers the analogues diesters based on the above explicitly mentioned mono ester monomers may be used, wherein, however, the two organic groups linked to the C=O group via the oxygen atom may be identical or different.

[0100] As further termonomers vinyl aromatic monomers like styrene, a-methyl styrene and vinylpyridine, as well as non-conjugated dienes like 4-cyanocyclohexene and 4-vinylcyclohexene, as well as alkines like 1- or 2-butine may be used.

[0101] Particularly preferred are termonomers or their respective di- or triester chosen from the below depicted formulae:

[0102]

[0103]

[0104] where

[0105] R1is hydrogen or methyl group, and

[0106] R2, R3, R4, R5are identical or different and may represent H, C1-C12 alkyl, cycloalkyl, alkoxyalkyl, hydroxyalkyl, expoxyalkyl, aryl, heteroaryl.

[0107] In one embodiment of the present invention the rubber is NBR, preferably having repeating units derived from of at least one a, p-unsaturated nitrile, more preferably acrylonitrile, at least one conjugated diene, more preferably butadiene, and none, one or more further copolymerizable monomers, more preferably none or one copolymerizable monomer selected from acrylic acid and methacrylic acid. In a further preferred embodiment, the nitrile rubber is the hydrogenated species, i.e. hydrogenated nitrile rubber which may be derived from the repeating units as described before so that the features relating to NBR may also apply to H NBR if not indicated otherwise.

[0108] The proportions of conjugated diene and a, p-unsaturated nitrile in the NBR or HNBR to be used can vary within wide ranges. The proportion of the conjugated diene or the sum of conjugated dienes is usually in the range from 20 to 95% by weight, preferably in the range from 40 to 90% by weight, more preferably 50 to 85% by weight, based on the total polymer. The proportion of a, p-unsaturated nitrile or the sum of a, p-unsaturated nitriles is usually from 5 to 80% by weight, preferably from 10 to 60, more preferably 15 to 50% by weight, based on the total polymer. The proportions of the monomers in each case add up to 100% by weight. The additional monomers can be present in amounts of from 0 to 40% by weight, preferably from 0.1 to 40% by weight, particularly preferably from 1 to 30% by weight, based on the total polymer. In this case, corresponding proportions of the conjugated diene or dienes and / or the a, p-unsaturated nitrile or nitriles are replaced by proportions of the additional monomers, with the proportions of all monomers in each case adding up to 100% by weight.The preparation of the nitrile rubbers by polymerization of the abovementioned monomers is adequately known to those skilled in the art and is comprehensively described in the literature. The hydrogenated form may be produced from the non-hydrogenated nitrile rubbers by a hydrogenation reaction. Such hydrogenation reaction may be performed by a rhodium catalyst, a ruthenium catalyst or a palladium catalyst and may further be performed as generally known in the art to the skilled artisan.

[0109] The non-hydrogenated nitrile rubbers have Mooney values (ML (1+4 @100°C)) of from 10 to 150, preferably from 20 to 140, Mooney units, particularly preferably from 25 to 120 Mooney units, such as from 30 to 45 Mooney units, for example from 33 to 37 Mooney units.

[0110] The glass transition temperatures of the non-hydrogenated nitrile rubbers are in the range from -80°C to +20°C, preferably in the range from -70°C to +10°C and most preferably in the range from -60°C to +5°C.

[0111] Preference is given to nitrile rubbers according to the invention which comprise repeating units of acrylonitrile, 1,3-butadiene and none, one or more further copolymerizable monomers. Preference is likewise given to nitrile rubbers having repeating units of acrylonitrile, 1 ,3-butadiene and one or more a,p-unsaturated monocarboxylic or dicarboxylic acids, their esters or amides, and in particular repeating units of an alkylester of an a,p-unsaturated carboxylic acid, very particularly preferably of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate or fumaric acid.

[0112] It might be preferred that the nitrile rubber is coagulated by using an acid. This may be done as generally known in the art. Examples for acids for coagulation comprise sulfuric acid.

[0113] It might also be preferred that the nitrile rubber is coagulated by using a salt, such as a divalent salt. Preferred examples comprise salts, such as chloride or sulfate salts, of calcium, aluminium, sodium or magnesium.

[0114] Additives of the composition

[0115] The composition comprises, next to the nitrile rubber either in non-hydrogenated or hydrogenated form, a mixture of at least two additives, which are as follows:(ii) at least one compound of general formula (I)

[0116]

[0117] wherein

[0118] R1means a saturated and unsubstituted linear Ci-Ci?-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alkyl; and

[0119] R2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and

[0120] (iii) at least one compound of general formula (II)

[0121]

[0122] wherein

[0123] R3means straight chain or branched C1-C14 alkyl; and

[0124] R4means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio and wherein

[0125] the composition is free of dithiodipropionate tridecyl ester.

[0126] These compounds, or additives, respectively, may act as stabilizing agents which counteract heat aging, or hot air aging, respectively. Further, these compounds may withstand the conditions in a hydrogenation reaction and may further be essentially inert, i.e. do not or at least not significantly deteriorate a hydrogenation reaction. The respective hydrogenation reaction is particularly the hydrogenation of the non-hydrogenated nitrile rubber to form the hydrogenated rubber.With regard to compounds according to general formula (I), it may be preferred that R2means terf-butyl.

[0127] It may be especially preferred if compound according to general formula (I) has the following chemical structure (1-1),

[0128]

[0129] With regard to compounds according to general formula (II), it may be preferred that R3means straight chain or branched C1-C4 alkyl. It may further be preferred that R4are identical and mean straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted Ce-C alkyl, in particular Cs alkyl.

[0130] A compound according to general formula (II) may preferably comprise a compound according to structure (11-1),

[0131]

[0132] The hydrogenation composition according to the invention thus comprises the nitrile rubber and the additives as described before. Therefore, the use of the described mixture as an additive in a hydrogenation composition is described.It may be preferred that the hydrogenation composition comprises compounds of general formula (I) and of general formula (II) in an amount of at least 60 wt.-% relating to all present antioxidant components in the hydrogenation composition. Thus, a further antioxidant component is generally possible. However, it may also be preferred that the hydrogenation composition comprises compounds of general formula (I) and of general formula (II) in an amount of at least 99.5 wt.-% relating to all present antioxidant components in the hydrogenation composition. It may be preferred that the hydrogenation composition comprises compounds of general formula (I) and of general formula (II) as sole stabilizing, such as antioxidant, compounds. It may thus be preferred that the hydrogenation composition is free of any phenolic and sulfur containing antioxidants additionally to the compounds of general formulae (I) and (II), or that the hydrogenation composition is free of any antioxidants additionally to the compounds of general formulae (I) and (II). In particular, it is provided that the composition is free of dithiodipropionate tridecyl ester, which may allow reducing the required copmpounds and making the composition less complex and more cost sensitive.

[0133] Preferably, the compounds of general formula (I) and the compound of general formula (II) together are present in the hydrogenation composition in an amount of > 0,15 phr. Exemplarily, the compounds of general formula (I) and the compound of general formula (II) together are present in the hydrogenation composition in an amount of > 0,2 phr, such as > 0,15 to < 2 phr, for examples 0,2 phr to < 1 phr. In case further stabilizing agents, such as antioxidants, are present, the above values are valid for all stabilizing components.

[0134] The hydrogenation composition may further comprise a hydrogenation catalyst. Such hydrogenation catalyst may comprise at least one of a Rhodium-based catalyst, a Ruthenium-based catalyst and a Palladium-based catalyst. Exemplarily, the hydrogenation catalyst may comprise the generally known Wilkinson catalyst, or a Grubbs catalyst (e.g. Grubbs-Hoveyda I or Grubbs-Hoveyda II).

[0135] It thus becomes clear that the hydrogenation composition may be suitable for performing a hydrogenation reaction even though not necessarily comprising a catalyst, or it may be derived from a hydrogenation reaction. In the latter case, it may be provided that the hydrogenation composition comprises residues of respective hydrogenation catalysts.Method of hvdrooenatino a oolvmer

[0136] The present invention further relates to a method of hydrogenating a polymer, wherein the polymer comprises a nitrile rubber and wherein the method comprises the steps of a) Providing a mixture of a hydrogenation composition according to the present invention and a hydrogenation catalyst;

[0137] b) Arranging the hydrogenation composition in a hydrogenation reactor; and

[0138] c) Performing a hydrogenation reaction in the hydrogenation reactor by setting defined hydrogenation conditions in said hydrogenation reactor.

[0139] Thus, the hydrogenation composition according to the present invention may be used for performing a hydrogenation reaction with the nitrile rubber in order to form a hydrogenated nitrile rubber.

[0140] The hydrogenation reaction may be arranged in a hydrogenation reactor and suitable reaction conditions may be set. Thus, especially a respective temperature and hydrogen pressure is set, wherein the specific values may be chosen in dependance of the used catalyst, for example. The used catalyst may for example be a Ruthenium-based catalyst or a Rhodium-based catalyst or a Palladium-based catalyst.

[0141] Such a hydrogenation reaction is generally known in the art for the skilled artisan and the parameters to be set are also well known. It produces the hydrogenated nitrile rubber which is defined in detail above.

[0142] Advantages of the hydrogenation composition:

[0143] The stabilized rubbers of the present invention surprisingly show the desired very good heat aging stability while at the same time withstanding the conditions during a hydrogenation reaction and further not deteriorating the catalytic activity or at least not significantly.

[0144] For the purposes of the present invention, the heat aging stability of a rubber is given if the Mooney viscosity is as stable as possible over a heat influence, especially for a rather long period of time.

[0145] The heat aging stability is usually determined by storing the unvulcanized rubber for a defined period of time at elevated temperature (also referred to as hot air storage) and determining the difference between the Mooney viscosities before and after this storage at elevated temperature. Since the Mooney viscosity of rubber usually increases during hot airstorage, the storage stability is characterized by the difference of Mooney viscosity after storage minus Mooney viscosity before storage. This will be shown in the examples of stabilized nitrile rubbers in the following.

[0146] The high storage stability has positive effects even during drying of the nitrile rubber, since some unintended ageing of the rubber otherwise takes place during this drying. The high storage stability aids the setting of a prescribed target Mooney viscosity. The amount of out-of-specification nitrile rubber is reduced as a result. Furthermore, the high storage stability results in a reduction in complaints due to a change in the Mooney viscosity during long storage or transport times. The rubbers of the invention are suitable for the reproducible production of vulcanizable mixtures. The mouldings obtained therefrom by vulcanization thus also have a reproducible mechanical and physical property profile.

[0147] Further, the heat aging stability should be present both for nitrile rubber and hydrogenated nitrile rubber. This indicates that the additives withstand the hydrogenation reaction and maintain their stabilizing properties.

[0148] With regard to the hydrogenation reaction, it is important that the additives do not reduce the catalytic activity in a significant amount. The catalytic activity might be determined by the TOF (turn over frequency) which is explained in more detail in the experimental part. According to the invention, it was shown that the TOF is not reduced in a significant amount in case the additives of the composition according to the present invention are present.

[0149] Definition of well performing system for use in NBR hydrogenation feedstock according to the inveniton

[0150] Limits for NBR hot air aging behaviour, hydrogenation performance and HNBR hot air aging behaviour were defined to assess the additive system used in the NBR feedstock.

[0151] A well performing system for NBR feedstock matched all of the following parameters:

[0152] NBR aging behaviour: Delta Mooney Viscosity of prior and after to the hot air aging for 14 days at 70°C is < 7 MU

[0153] - TOF > 2, 1 s-1

[0154] HNBR aging behaviour: Delta Mooney Viscosity of prior and after to the hot air aging is < 30 MU for 4 days at 140°C.General Conditions

[0155] NBR latex was obtained by emulsion polymerization, either in a batch process in a stirred tank reactor, or in continuous process in a CSTR cascade (continuous stirred-tank reactor (CSTR)).

[0156] All manipulations with air and moisture sensitive compounds were performed under nitrogen atmosphere using standard Schlenk techniques.. As organic solvent, recycled and purified MCB was used. Additionally needed MCB was commercially purchased and used without further purification. The NBR material was produced as described below. The hydrogenation catalyst system Wilkinson I TPP was prepared as MCB solution.

[0157] Stabilization of NBR Latex

[0158] Prior to stabilization, the solids content of the NBR latex was determined using an Ohaus MB120 moisture analyzer. Based on the solids content, the necessary amount of an aqueous dispersion of the stabilizer(s) was added to the latex. The latex was shaken for 10 minutes, to obtain stabilized NBR latex.

[0159] of NBR Latex

[0160] The stabilized NBR latex was added slowly and under vigorous stirring to an aqueous solution of calcium chloride having a concentration of 0.34 % by weight, containing 0,5 phr Superfloc C567 (Kemira) (poly(dimethylamine-co-epichlorohydrin) at 60°C. The stabilized rubber coagulates, is washed with water at 80 °C, and dried for 16 hours at 60°C in a vacuum oven. Subsequently the Mooney-viscosity is determined as described below.

[0161] Alternatively, the rubber was coagulated by using sulfuric acid in an acid-based coagulation according to the method described in EP1369436B1.

[0162] NBR Hydrogenation

[0163] A solution of NBR in MCB (13 wt.%, 3984,6 g) was transferred from a pressure drum into a 10 L autoclave. Afterwards, the solution was stirred at 600 rpm under 0,5 - 1 bar nitrogen pressure and heated to 110°C. The catalyst system which comprises Wilkinson catalyst (0,50 wt.%; 207 mg; 0,224 mmol, 0,040 phr) and TPP (1,5 wt.%; 0,621 g; 2,368 mmol, 0,12 phr) in MCB (41,4 g) as well as an additional TPP (30,0 wt.%; 4,56 g; 17,386 mmol, 0,88 phr) MCB (15,2 g) solution was dosed to the NBR starting solution. Hydrogen pressure was stepwise increased to 85 bars. After the hydrogenation reaction started, the reactiontemperature was increased to 138°C. In case the temperature exceeded 145°C, the cooling system ensured desired temperature control. After 3 h reaction time, the hydrogenation has been re-activated via an additionally catalyst boost of MCB solution (25,9 g) of Wilkinson catalyst (0,50 wt.%; 129,5 mg; 0,140 mmol, 0,025 phr) and TPP (1,5 wt.%; 0,389 g; 1,481 mmol, 0,075 phr). Reaction progress was monitored by hourly RDB measurements of reaction samples.121Reaching an RDB of < 0,9 %, the hydrogenation was stopped by degassing and cooling to < 50°C. Finally, the HNBR solution was transferred into a plastic can and analyzed. To synthesize partially hydrogenated HNBR samples no additional catalyst boost was added and the reaction was stopped after a reduced reaction time.

[0164] Besides, a 10 L reactor, also a 12 and 40 L reactor were used for hydrogenation reactions. The used amounts of the NBR solution and the Rh catalyst system were adjusted correspondingly. The hydrogenation performance was comparable for all kinds of reactors.

[0165] For the HNBR finishing, a 10 L glass vessel was filled with 4 L H2O and heated to 110°C via jacket heating. Afterwards steam was injected (5 bar) and the diluted HNBR reaction mixture (7 wt.%) was added dropwise. As processing aids an aqueous CaCl2 solution (2,5 wt.%) and an aqueous polycarboxylate solution (1,0 wt.%) was used to adjust the HNBR crumb size. By a distillation bridge the MCB was removed in parallel. The whole HNBR finishing process was performed at a pH value of 7 which is adjusted with treatment of NaOH solution (0,5 wt.%) or HCI solution (0,5 wt.%), respectively. After the HNBR was completely precipitated, the mixture was cooled down, the rubber crumbs were isolated and dried in the vacuum oven at 55°C.

[0166] Analytical Methods

[0167] IR spectroscopy

[0168] IR spectra were measured on NaCI crystals using the Nicolet IS10 FTIR or the Nicolet IS50 FTIR / ART spectrometer. This analytical method is used the determination of residual double bonds in the HNBR. Therefore, several drops of a 5 wt.% HNBR solution in MCB are placed on a NaCI crystal. After several minutes of drying in the vacuum oven, the crystal is put into the IR spectrometer and the measurement is started. The RDB is calculated according to an internal calibration and is given in %.

[0169] ACN content

[0170] The nitrogen content to determine the bound acrylonitrile content (“ACN content”) of thenitrile rubbers is determined by the Dumas method in accordance with ISO 24698-1: 2018.

[0171]

[0172] The Mooney viscosity was determined on the rotational viscometer MV2000 from Alpha Technologies. As the measurement was performed via unmassed ML1+4 at 100°C in accordance with. ASTM D 1646 at 100°C.

[0173] NBR hot air aging - raw polymer

[0174] A sufficient amount of NBR crumbs was pressed, like for unmassed Mooney viscosity. The samples were then stored in an oven at at a temperature and for a period of time as outlined in the examples section. After cooling down the sample to room temperature, the Mooney viscosity was measured, and the aging behaviour evaluated via the delta of Mooney points prior to and after the aging process.

[0175] HNBR hot air aging - raw polymer

[0176] After cooling down the sample to room temperature, the Mooney viscosity was measured, and the aging behaviour evaluated via the delta of Mooney points prior to and after the aging process. Again, the samples (~ 50 g) were stored in an oven at a temperature and for a period of time as outlined in the examples section.

[0177] Quantification of stabilizer content

[0178] The stabilizer amount within NBR or HNBR material was determined by HPLC method.

[0179] Turnover Freguency Calculation

[0180] The turnover freguency (TOF) is an indicator for catalyst activity or hydrogenation rate. As higher this value, as higher is the reaction performance. The TOF was calculated according to the following formula, which considered all reaction parameters (for a good comparison of the reaction performances.

[0181] TOF = dbhyd I (cat * time) [s’1],

[0182] wherein dbhyd is the molar amount of hydrogenated double bonds, cat is the molar amount of catalyst and time is the hydrogenation time in seconds.

[0183] All TOF values were calculated after a reaction time of 180 minutes and with the Wilkinson catalyst starting loading of 0,04 phr.1 : Reference evaluation

[0184] In the scope of the present invention, the short chain phenolic ester 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate having following chemical structure (1-1) was used as material in-line with general formula (I):

[0185]

[0186] and phenolic thioether 4, 6-bis(octylthiomethyl)-o-cresol having following chemical structure (11-1) was used as material in-line with general formula (II):

[0187]

[0188] Using these substances as additives in a hydrogenation composition according to the present invention resulted in an extraordinary and surprisingly well performing additive system in NBR feedstock and the resulting HNBR and further worked well in hydrogenation reactions. The performance was investigated by NBR hot air aging behavior, NBR hydrogenation activity and HNBR hot air aging behavior.

[0189] Generally the additives according to structure (1-1) and (11-1) are used in a 1:1 ratio with regard to wt.-% if not indicated otherwise.

[0190] Further, all experiments were performed with a nitrile rubber having an ACN-content of 34 wt.-% if not indicated otherwise.

[0191] Table 1 shows results of the basic evaluation achieving the advantages of the present invention.

[0192]

[0193] Table 1: inventive reference examples

[0194] It was clearly shown that using the additives as described for forming a hydrogenation composition according to the present invention allows all of superior heat aging behavior of NBR as well as of H NBR and additionally allows a highly active hydrogenation reaction. This could not be foreseen as it is generally known that compounds such as the used phenolic thioether contains a sulfuric functional group which is categorized as catalyst poison for the Wilkinson catalyst in hydrogenation reactions. Therefore, the object of the present invention is in asurprising manner clearly achieved according to the present invention even in combination with Rhodium based catalysts.

[0195] However, example 1-5 shows that the present invention also works with further catalyst systems, such as with the Grubbs Hoveyda II catalyst (GH II). This is important as in case a catalyst change has to be done, no change in the polymer together with its additives is required, so that the present invention works independently of the used catalyst.

[0196] Example 2: Influence of the length of the ester chain of structure (III)

[0197] The influence of the length of the ester chain in structure (III) was evaluated by adapting the carbon numbers n in chemical formula (III):

[0198]

[0199] The respective compound according to structure (III) was used together with the compound according to structure (11-1) in a 1:1 ratio.

[0200] The following results could be achieved as shown in table 2, wherein examples marked with * are comparative examples not forming part of the invention:

[0201]

[0202] Table 2: influence of chain length of R1

[0203] According to the examples as shown in table 2, a blend comprising a short chain phenolic ester with 1 < n < 17, preferably with 2 < n < 14 led to well performing results for NBR and HNBR hot air aging behavior and efficiency of NBR hydrogenations with TOF >2,1 s-1. In contrast, using a phenolic ester with n = 0 or n > 18, the resulting additive system showed negative impact on the NBR hot air aging behavior (experiments 2-1, 2-5), which might result in gel formation during HNBR-forming process, and / or HNBR hot air aging behavior (experiment 2-5).Example 3: Impact of stabilizer concentration

[0204] A blend of compounds according to chemical structures (1-1) and (11-1) was used in different concentrations to form the hydrogenation composition. Thus, a different total additive load in the hydrogenation composition was used, wherein the additive refers to compounds having chemical structures (1-1) and (11-1). Examples 3-1 and 3-2 correspond to examples 1-1 and 1-3, respectively. The respective results are shown in table 3, wherein examples marked with * are comparative examples not forming part of the invention:

[0205]

[0206] Table 3: Impact of stabilizer concentration (compound loading)

[0207] It was shown that the standardized tests for NBR and HNBR hot air aging behavior and hydrogenation reaction screening showed that the additive concentration should at best be > 0,15 phr (referred to NBR amount).

[0208]

[0209] of additive mixture to si

[0210]

[0211] The performance of several additives alone was investigated using them as pure compounds in NBR feedstock.

[0212] In example 4-3, solely Irganox 1135 was used as antioxidant.

[0213] In example 4-4, solely Irganox 1076 was used as antioxidant.

[0214] In example 4-5, solely Irganox 1520 was used as antioxidant.

[0215] In example 4-6, solely Anox 1315 was used as antioxidant.

[0216] In example 4-7, solely 3-(3,5-Di-tert-butyl-4-hydroxyphenyl)propionic acid was used as antioxidant.

[0217] In example 4-8, solely Irganox 565 was used as antioxidant.

[0218] Examples 4-1 and 4-2 correspond to examples 1-1 and 1-2, respectively. The respective results are shown in table 4, wherein examples marked with * are comparative examples not forming part of the invention:

[0219]

[0220] Table 4: results of antioxidants

[0221] The experiments 4-3 and 4-8 resulted to low impact on NBR hot air aging but the TOF values were <2,1 s-1which indicated decreased NBR hydrogenation activities. The experiments 4-4 to 4-7 showed a high Mooney increase after hot air aging. Gel formation during HNBR process is one of the consequences. Using the pure acid derived from the phenolic ester antioxidant, 3-(3,5-di-tert.-butyl-4-hydroxyphenyl)propanoic acid, as stabilizer for NBR (example 4-7), led to gelled NBR feedstock unusable for further HNBR process.As conclusion, the performance is significantly lower using the pure stabilizer compounds in NBR feedstock compared to the additive system in a hydrogenation composition according to the present invention.

[0222] Example 5: Influence of Further Stabilizer Compounds

[0223] The compound Irganox® 565 or Irganox 1076 are also generally known as stabilizer.

[0224] To evaluate the impact of a further compound in the inventive mixture, the following examples were evaluated:

[0225] In example 5-3, a 1 : 1 mixture of compounds of general structure (1-1) and of Irganox 565 is used..

[0226] In example 5-4, a 1:1:1 mixture of compounds of general structure (1-1), of general structure (II- 1) and of Irganox 565 is used; and

[0227] In example 5-5 a 1:1:1 mixture of general structure (11-1), of Irganox 565 and of Irganox 1076 is used..

[0228] Examples 5-1 and 5-2 correspond to examples 1-1 and 1-2, respectively. The respective results are shown in table 5, wherein examples marked with * are comparative examples not forming part of the invention:.

[0229]

[0230] The results of experiment 5-4 showed that - even though not required - generally a third component did not reduce the stabilizing performance and all defined criteria were fulfilled (example 5-4). In contrast, the hydrogenation performance is reduced by replacing additives according to the invention by non-inventive additive mixtures (example 5-3 and 5-5). However, it was shown that due to cost and efficiency, a third antioxidant material may be omitted.

[0231] Example 6: Influence of NBR feedstock

[0232] In example 6, different NBR feedstocks were used.

[0233] In examples 6-3 and 6-4, an NBR feedstock with an ACN content of 40 wt.-% was used, wherein the coagulation method was changed as outlined in table 6. Examples 6-1 and 6-2 correspond to examples 1-1 and 1-3, respectively. The respective results are shown in table 6.

[0234]

[0235] It can be seen that the inventive effects were achieved independently from the NBR feedstock. This shows the high application range of the present invention.

Claims

Claims1. A hydrogenation composition, comprising(i) a polymer, wherein the polymer comprises a nitrile rubber; and at least the following components:(ii) at least one compound of general formula (I)whereinR1means a saturated and unsubstituted linear Ci-Ci?-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alkyl; andR2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and(iii) at least one compound of general formula (II)whereinR3means straight chain or branched C1-C14 alkyl; andR4means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio, and whereinThe composition is free of dithiodipropionate tridecyl ester.

2. The hydrogenation composition according to claim 1, wherein the hydrogenation composition contains the compounds of general formulae (I) and (II) in an amount of > 99.5 wt.-%, relating to all present antioxidants.

3. The hydrogenation composition according to any of claims 1 or 2, wherein the hydrogenation composition is free of any phenolic and sulfur containing antioxidants additionally to the compounds of general formulae (I) and (II).

4. The hydrogenation composition according to any of the preceding claims, wherein the hydrogenation composition further comprises a hydrogenation catalyst or residues thereof.

5. The hydrogenation composition according to claim 1, wherein R2means terf-butyl.

6. The hydrogenation composition according to any of the preceding claims, wherein R3means straight chain or branched C1-C4 alkyl; and wherein R4are identical and mean straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted Ce-C alkyl.

7. The hydrogenation composition according to any of the preceding claims, wherein the compound of general formula (I) and the compound of general formula (II) together are present in the hydrogenation composition in an amount of > 0,15 phr.

8. The hydrogenation composition according to any of the preceding claims, wherein the nitrile rubber is produced by using a salt as coagulating reagent.

9. The hydrogenation composition according to any of the preceding claims, wherein the nitrile rubber is produced by using an acid as coagulating reagent.

10. The hydrogenation composition according to any of the preceding claims, wherein the nitrile rubber is a copolymer of acrylonitrile and butadiene.

11. Method of hydrogenating a polymer, wherein the polymer comprises a nitrile rubber and wherein the method comprises the steps ofa) Providing a mixture of a hydrogenation composition according to any of the preceding claims and a hydrogenation catalyst;b) Arranging the mixture in a hydrogenation reactor; andc) Performing a hydrogenation reaction in the hydrogenation reactor by setting defined hydrogenation conditions in said hydrogenation reactor.

12. The method according to claim 11, wherein a hydrogenation catalyst is used which is a Ruthenium-based catalyst or a Rhodium-based catalyst or a Palladium-based catalyst.

13. A hydrogenated nitrile rubber, wherein the hydrogenated nitrile rubber comprises a hydrogenated nitrile rubber, wherein the hydrogenated nitrile rubber is formed by a method according to any of claims 11 or 12.

14. A composition comprising a hydrogenated nitrile rubber according to claim 13 and at least the following components:(ii) at least one compound of general formula (I)whereinR1means a saturated and unsubstituted linear Ci-Ci?-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alky; andR2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and(iii) at least one compound of general formula (II)whereinR3means straight chain or branched C1-C14 alkyl; andR4means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio and whereinThe composition is free of dithiodipropionate tridecyl ester.

15. Use of a mixture as an additive in a hydrogenation composition in a hydrogenation of a nitrile rubber to form an at least partly hydrogenated nitrile rubber, wherein the mixture comprises at least the following components:(ii) at least one compound of general formula (I)whereinR1means a saturated and unsubstituted linear Ci-Cn-alkyl, preferably a saturated and unsubstituted linear C2-Ci4-alky; andR2are identical or different and mean straight chain or branched Ci-Ce alkyl or Cs-Ce cycloalkyl; and(iii) at least one compound of general formula (II)whereinR3means straight chain or branched C1-C14 alkyl; andR4means hydrogen, straight chain or branched, saturated or one or more times unsaturated, unsubstituted or substituted alkyl; saturated or one or more times unsaturated carbocyclyl or hetercyclyl; aryl; heteroaryl, arylalkyl, heteroarylalkyl, alkoxy, aryloxy, heteroaryloxy, alkylthio or arylthio and whereinThe composition is free of dithiodipropionate tridecyl ester.

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