HK1054558B - Process for hydrogenating carboxylated nitrile rubber, the hydrogenated rubber and its uses - Google Patents

Description

Hydrogenation method of carboxylated nitrile rubber, hydrogenated rubber and application thereof

The invention relates to a novel polymer, a method for producing the polymer and the use thereof.

Background

Polymers of conjugated dienes and unsaturated nitriles, i.e., nitrile rubbers, are well known. The hydrogenation of nitrile rubbers is also known. Hydrogenation improves the heat aging properties of the polymer. When hydrogenating, care is indeed taken to ensure that only carbon-carbon double bonds are hydrogenated. Hydrogenation of the nitrile moiety, for example, undesirable any reduction of the nitrile group, and deleterious effects on the properties of the nitrile rubber; in particular, it is undesirable to reduce the oil resistance of nitrile rubber.

It has been proposed to include various other copolymerizable monomers in the nitrile rubber. Mention may be made of α, β -unsaturated monocarboxylic and dicarboxylic acids. Although they can be incorporated into the backbone of the polymer, difficulties are encountered when hydrogenating polymers containing carboxyl groups. Particularly if the degree of hydrogenation is high, the carboxyl group will undergo reduction or other side reactions, failing to obtain a satisfactory product.

In order to avoid the problem of hydrogenation of the carboxyl groups, it has been proposed to prepare nitrile rubbers composed of conjugated dienes and unsaturated nitriles, to partially hydrogenate the nitrile rubbers and to add subsequently an α, β -unsaturated acid; see U.S. patent No. 5,157,083. This method has proven to be unsatisfactory. Since the acid moieties are neither randomly distributed nor alternately distributed along the main chain of the polymer when added after the formation of the nitrile rubber. The trimerization of conjugated dienes, unsaturated nitriles and unsaturated acids results in the formation of the predominant carbon backbone portion of the polymer at the alpha and beta carbon atoms of the acid in the polymer. In contrast, polymerization of unsaturated nitriles results in polymers having some carbon-carbon double bonds in the vinyl side chains due to 1, 2-polymerization of butadiene and conjugated dienes, and polymers having some carbon-carbon double bonds in the main polymer backbone due to 1, 4-polymerization of butadiene. These double bonds in the polymer backbone may be in either cis or trans configuration. When the polymer is hydrogenated, the vinyl group is hydrogenated first, and the double bond of the cis structure is hydrogenated subsequently. Thus, incompletely hydrogenated polymers incorporating α, β unsaturated acids contain most or all of the double bonds in the main polymer backbone and are in a trans-configuration. The reaction with the unsaturated acid results in the product having an acid with α, β carbon atoms that are not in the main carbon backbone of the polymer. Thus, the chemical structure of the polymer produced in the latter manner is different from that of a statistical (static) polymer formed by trimerization of a conjugated diene, an unsaturated nitrile and an unsaturated acid, in which the monomers are statistically or randomly distributed throughout the polymer chain.

European patent application No. 933381 relates to carboxylated nitrile group-containing highly saturated copolymer rubber, and three methods of adding maleic anhydride to nitrile group-containing highly saturated copolymer rubber are discussed in the background art. Although the European patent application refers to "highly saturated copolymer rubbers", it is believed that a certain degree of unsaturation is required in the rubber to serve as an addition reaction site with maleic anhydride. All three mentioned methods of adding maleic anhydride have the disadvantage that no satisfactory industrial process is found. In addition, the addition product, i.e., the polymer containing maleic anhydride-nitrile groups, is unsatisfactory in various properties including "abrasion resistance and tensile strength required for belts and hoses".

The preparation of carboxylated, hydrogenated nitrile rubbers by first preparing the nitrile rubber and then hydrogenating it, and thereafter adding an unsaturated acid, is an expensive production process. In addition, it is difficult to control the amount of acid added to the polymer, and thus the quality of the product is uncertain. Although the products produced in this way have already been introduced into industrial production, production has been stopped.

Summary of The Invention

It has been found that a process is provided for selectively hydrogenating polymers having a backbone of conjugated dienes, unsaturated nitriles and unsaturated carboxylic acids without causing any detectable hydrogenation of the nitrile or carboxylic acid moieties. The process allows the preparation of novel polymeric materials which are hydrogenated polymers of conjugated dienes, unsaturated nitriles and unsaturated acids. The novel polymeric materials have been found to have unexpected and useful properties.

Accordingly, in one aspect, the present invention provides a polymer of a conjugated diene, an unsaturated nitrile and an unsaturated carboxylic acid, which can be selectively hydrogenated to reduce a carbon-carbon double bond without hydrogenating a nitrile group and a carboxyl group.

In another aspect, the present invention provides a process for selectively hydrogenating a polymer of a conjugated diene, an unsaturated nitrile and an unsaturated carboxylic acid, which comprises hydrogenating the polymer in the presence of a rhodium-containing compound as a catalyst and a co-catalyst ligand, wherein the weight ratio of the rhodium-containing compound to the co-catalyst ligand is from 1:3 to 1: 55.

Description of the preferred embodiments

A wide variety of conjugated dienes for nitrile rubbers may all be used in the present invention. Mention may be made of 1, 3-butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, 1, 3-pentadiene and piperylene, 1, 3-butadiene being preferred.

The nitrile is usually acrylonitrile or methacrylonitrile or alpha-chloroacrylonitrile, of which acrylonitrile is preferred.

The α, β unsaturated acid may be, for example, acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid (or in the form of its anhydride), fumaric acid or itaconic acid, with acrylic acid and methacrylic acid being preferred.

Generally, the polymer comprises from about 50% to 85% conjugated diene, from about 15% to 50% nitrile and from about 0.1% to 10% acid, preferably from 0.5% to 7%, these percentages being by weight. The polymer may also contain other copolymerizable monomers, for example, esters of unsaturated acids, such as ethyl, propyl or butyl acrylate or methacrylate, or vinyl compounds, for example styrene, alpha-methylstyrene or the corresponding compounds having an alkyl substitution in the benzene ring, for example para-alkylstyrenes such as para-methylstyrene, in amounts generally not exceeding about 10%. Preferably the polymer is a solid having a molecular weight in excess of about 60,000, more preferably in excess of about 100,000.

The statistical polymers to be hydrogenated can be obtained by emulsion or solution polymerization in a known manner. The polymer has a backbone composed entirely of carbon atoms. It has some vinyl side chains resulting from 1, 2-addition of the conjugated diene during the polymerization. It also has double bonds in the main chain due to 1, 4 addition of the diene. Some of these double bonds are in cis orientation and others are in trans orientation. These carbon-carbon double bonds are selectively hydrogenated by the process of the present invention without concomitant hydrogenation of the nitrile and carboxyl groups present in the polymer.

The selective hydrogenation can be carried out using a rhodium-containing catalyst. Preferred catalysts have the formula:

wherein each R is C₁-Alkyl (preferably C)₁-C₆Alkyl group), C₄-Cycloalkyl radical, C₆-C₁₅Aryl or C₇-C₁₅Aralkyl, B is phosphorus, arsenic, sulfur, or sulfoxide S-0, X is hydrogen or an anion, preferably a halide, and more preferably chloride and bromide, 1 is 2, 3 or 4, m is 2 or 3 and n is 1, 2 or 3, preferably 1 or 3. Preferred catalysts are tris (triphenylphosphine) -rhodium (I) -chloride, tris (triphenylphosphine) -rhodium (III) -chloride and tris (dimethyl sulphoxide) -rhodium (III) -chloride, and have the formula ((C)₆H₅)₃P)₄Tetrakis (triphenylphosphine) -rhodium hydride of RhH, and the corresponding compounds in which the triphenylphosphine moiety is replaced by a tricyclohexylphosphine moiety. The catalyst may be used in small amounts. Suitable amounts of catalyst range from 0.01% to 1.0%, preferably from 0.03% to 0.5%, more preferably from 0.06% to 0.12%, and especially about 0.08%, based on the weight of the polymer.

The catalyst and cocatalyst are used together, and the cocatalyst is of the formulaWherein R, m and B are as defined above, and preferably m is 3. Preferably, B is phosphorus and the R groups may be the same or different. Thus, triaryl, trialkyl, tricycloalkyl, diarylmonoalkyl, dialkylmonoaryl, diarylmonocycloalkyl, dialkylmonocycloalkyl, dicycloalkylmonoaryl or dicycloalkylmonoaryl cocatalysts may be used. In U.S. Pat. No. 4,631,315 is givenExamples of co-catalyst ligands are incorporated herein by reference for their disclosure. Preferably the cocatalyst ligand is triphenylphosphine. The preferred amount of co-catalyst ligand ranges from 0.3% to 5% by weight, more preferably from 0.5% to 4% by weight, based on the weight of the terpolymer. It is also preferred that the weight ratio of the rhodium-containing catalyst compound to the cocatalyst is in the range of from 1:3 to 1:55, more preferably in the range of from 1:5 to 1: 45. Suitable weight ranges for the co-catalyst are from 0.1 to 33, more suitable from 0.5 to 20, and preferably from 1 to 5, most preferably from greater than 2 to less than 5, based on 100 parts by weight of the rubber.

The promoter ligands are advantageous for selective hydrogenation reactions. However, since the ligand will be present in the hydrogenation product, no more than the necessary amount of co-catalyst should be used to obtain the beneficial effect. For example, separation of triphenylphosphine from the hydrogenation product is difficult, and if large amounts of triphenylphosphine are present, some difficulties arise in the processing of the product.

The hydrogenation reaction may be carried out in solution. The solvent must be of a type that will dissolve the carboxylated nitrile rubber. This limitation precludes the use of unsubstituted aliphatic hydrocarbons. Suitable organic solvents are aromatic compounds including halogenated aryl compounds of 6 to 12 carbon atoms. The preferred halogen is chlorine and the preferred solvent is chlorobenzene, especially monochlorobenzene. Other solvents which may be used include toluene, halogenated aliphatic compounds, especially chlorinated aliphatic compounds, ketones such as methyl ethyl ketone and methyl isobutyl ketone, tetrahydrofuran and dimethylformamide. The concentration of the polymer in the solvent is not particularly critical, but is suitably in the range of from 1 to 30% by weight, preferably 2.5 to 20% by weight, more preferably 10 to 15% by weight. The concentration of the solution depends on the molecular weight of the carboxylated nitrile rubber to be hydrogenated. Higher molecular weight rubbers are more difficult to dissolve, so lower concentration solutions are used.

The reaction can be carried out under a wide range of pressures, from 10 to 250 atmospheres, preferably from 50 to 100 atmospheres. The temperature range of the reaction can also be wide. Suitable reaction temperatures are from 60 ℃ to 160 ℃, preferably from 100 ℃ to 160 ℃, more preferably from 110 ℃ to 140 ℃. Under these conditions, the hydrogenation reaction is generally completed in about 3 to 7 hours. The reaction is preferably carried out in an autoclave with stirring.

Hydrogenation of the carbon-carbon double bonds improves various properties of the polymer, particularly oxidation resistance. Preferably, at least 80% of the carbon-carbon double bonds present are hydrogenated. To achieve some of these objectives, it is desirable to eliminate all carbon-carbon double bonds and the hydrogenation is carried out until all double bonds are eliminated, or at least 99% of the double bonds are eliminated. However, for some other purposes some residual carbon-carbon double bonds are required and the hydrogenation reaction can be carried out only to hydrogenate 90% or 95% of the bonds. By infrared spectroscopy or¹The degree of hydrogenation can be determined by H-NMR analysis of the polymer.

In some cases, the degree of hydrogenation can be determined by measuring the iodine value. This is not a particularly accurate method and cannot be used in the presence of triphenylphosphine, so a method using an iodine value is not preferred.

The degree of hydrogenation can be determined by routine experimentation using conditions and reaction durations to obtain a particular degree of hydrogenation. This experiment enables the hydrogenation reaction to be stopped at any preselected degree of hydrogenation. The degree of hydrogenation can be determined by ASTM D5670-95. See also Dieter Brueck, Kautschuk + Gummi Kunststoffe, Vol 42, No 2/3(1989), the disclosure of which is incorporated herein by reference. The process of the present invention allows control of the degree of hydrogenation, which is of great advantage in optimizing various properties of the hydrogenated polymer for specific applications.

As mentioned above, hydrogenation of the carbon-carbon double bond is not accompanied by reduction of the carboxyl group. As illustrated in the examples below, the carboxylated nitrile rubber was found to have 95% of the carbon-carbon double bonds reduced by infrared analysis, but no detectable reduction of the carboxyl and nitrile groups. However, there may be a negligible range of reduction of carboxyl and nitrile groups and the present invention is considered to extend to include any process and product in which negligible reduction of carboxyl groups occurs. Negligible means that less than 0.5%, preferably less than 0.1%, of the originally present carboxyl or nitrile groups have undergone a reduction reaction.

To extract the polymer from the hydrogenated mixture, the mixture may be treated by any suitable method. One method is to distill off the solvent. Another method is to inject steam followed by drying the polymer. Yet another method is to add an alcohol which will coagulate the polymer.

The catalyst may be recovered using a resin column that adsorbs the rhodium, as described in U.S. Pat. No. 4,985,540, the disclosure of which is incorporated herein by reference.

The hydrogenated carboxylated nitrile rubber (HXNBR) of the present invention may be crosslinked. Thus, it can be vulcanized with sulfur or a sulfur-containing vulcanizing agent using a known method. Vulcanization requires the presence of some unsaturated carbon-carbon double bonds in the polymer to serve as reaction sites for the addition of sulfur atoms to effect crosslinking. If the polymer is to be vulcanized, the degree of hydrogenation is controlled to give a product having the desired amount of residual double bonds. In most cases, it is suitable that the degree of hydrogenation results in about 3% or 4% Residual Double Bonds (RDB) based on the number of double bonds initially present. As described above, the method of the present invention can accurately control the degree of hydrogenation.

The HXNBR can also be crosslinked in a known manner using a peroxide crosslinking agent. Peroxide crosslinking does not require the presence of double bonds in the polymer and results in carbon-containing crosslinks rather than sulfur-containing crosslinks. As the peroxide crosslinking agent, dicumyl peroxide, di-t-butyl peroxide, benzoyl peroxide, 2, 5-dimethyl-2, 5-di (t-butylperoxy) -hexyne-3, 2, 5-dimethyl-2, 5-di (benzoylperoxy) hexane and the like can be mentioned. Peroxide crosslinking agents are suitably used in amounts of about 0.2 to 20 parts by weight, preferably 1 to 10 parts by weight, per 100 parts by weight of rubber.

The HXNBR can also be crosslinked by carboxyl groups with polyvalent ions, in particular metal ions, which are ionically bonded to the carboxyl groups on two different polymer chains. For example, zinc, magnesium, calcium or aluminum salts may be used for bonding. The carboxyl groups can also be crosslinked with amines, in particular diamines, which react with the carboxyl groups. Mention may be made of alpha, omega-alkylenediamines such as 1, 2-ethylenediamine, 1, 3-propylenediamine and 1, 4-butylenediamine, and also 1, 2-propylenediamine.

The HXNBR of the invention can be mixed with any of the usual compounding agents (compounding agents), for example, fillers such as carbon black or silica, heat stabilizers, antioxidants, activators such as zinc oxide or zinc peroxide, curing agents, adjuvants, processing oils and extenders. Such compounds and adjuvants are well known to those of ordinary skill in the art.

The hydrogenated carboxylated nitrile rubber of the present invention exhibits excellent adhesion, and in particular its excellent hot tear strength is much better than that of the unhydrogenated carboxylated nitrile rubber. The rubbers according to the invention also exhibit better resistance to thermal ageing and better flexibility at low temperatures compared with unhydrogenated carboxylated nitrile rubbers. The rubbers of the invention also exhibit excellent abrasion resistance and also good adhesion both at low and high temperatures. These properties render them useful for many specialized applications, but particular mention is made of the use as sealants, high-hardness automotive (belt) belts, roller covers and (hoses) which encounter strong stress points.

The HXNBR of the present invention exhibits good adhesion to other materials including textiles, woven and nonwoven fabrics, metals and plastics, especially plastics having polar groups. The HXNBR will bind to textiles of natural fibers such as wood, cotton, hemp, silk, and also to textiles of synthetic fibers such as polyamides, polyesters, polyolefins such as polyethylene and polypropylene, poly (meth) acrylonitrile, and aramid fibers. It also bonds well to glass fibers and steel cords. The HXNBR exhibits particularly good adhesion when the substrate to which it is applied also has polar groups. A particularly surprising and useful property of HXNBR is the ability to maintain good adhesion at high temperatures, where both hydrogenated nitrile rubber (HNBR) and carboxylated nitrile rubber (XNBR) exhibit good adhesion at room temperature, but have poor adhesion at high temperatures. These properties render the HXNBR particularly beneficial for various applications, such as for tapes, where the polymeric coating material is adhered as impregnant and covering of the textile material, especially for any application where (leather) tapes may be subjected to heat.

Hydrogenated nitrile rubbers are used in many specific applications under severe conditions. The hydrogenated carboxylated nitrile rubber of the present invention has various physical properties superior to those of commercially available hydrogenated nitrile rubbers, and thus, the hydrogenated carboxylated nitrile rubber can be applied to many application fields using hydrogenated nitrile rubbers. Mention may be made of sealants (seals), in particular those used in automotive systems and heavy equipment, and any other environment where high or low temperatures, oils and greases may be encountered. Examples thereof include wheel bearing sealants, damper sealants, camshaft sealants, power steering gear assembly sealants, O-ring seals, water pump seals, gear box shaft sealants and air conditioning system sealants. Mention may be made of oil well professional applications such as packers, drill pipe protectors and rubber stators in hole making applications. Various belts, pipes and fittings that meet environmental requirements, and the HXNBR nature of the present invention renders it suitable for use in air conditioner hoses, camshaft drive belts, oil cooler pipes, crowned (poly-V) belts, torsional vibration humidifiers, feed and bellows pipes, chain tensioners, overflow valves and power steering apparatus hoses. The high modulus and high wear resistance of the HXNBR render it suitable for use in high hardness rolls such as metal working rolls, paper industry rolls, printing rolls, elastomeric compositions for use in loom and textile rolls, and the good wear resistance and good adhesion of the HXNBR to metal render it suitable for use as a support pad for attachment to the track of tracked vehicles such as bulldozers and other large scale earth and stone machinery, military tanks, and the like.

The material to which the polymer of the invention is to be adhered may be treated to enhance adhesion before it is contacted with the polymer. For example, cotton, rayon or nylon may be dipped in a mixture of an aqueous solution of resorcinol and formaldehyde initial condensate (referred to as RF) and a rubber latex, referred to as RFL. The rubber latex is not particularly limited, but may be an acrylonitrile/butadiene copolymer latex, and an acrylonitrile/butadiene/methacrylic acid copolymer latex, an acrylonitrile/butadiene/acrylic acid copolymer emulsion or an acrylonitrile/butadiene/vinylpyridine copolymer latex. To form the rubber latex, the HXNBR rubber of the invention can be used in the form of a latex.

The polyester and aramid fibers may be treated with an impregnating solution containing isocyanate, ethylene thiourea or epoxy, heat treated and then treated with RFL.

As mentioned above, the HXNBR rubber of the present invention can be used in the form of a latex. The HXNBR rubber is ground in water with a suitable emulsifier until the desired rubber latex is formed. Suitable emulsifiers for this purpose include amino emulsifiers such as fatty acid soaps, i.e. sodium and potassium salts of fatty acids, abietic acid salts, alkyl and aryl sulfonates and the like. Oleic acid salts may be mentioned as examples. The rubber latex may be a solution in an organic solvent, or a mixture with an organic solvent, which when added to water forms an oil-in-water emulsion. The organic solvent is then removed from the emulsion to obtain the desired latex. Organic solvents that can be used include those that can be used in hydrogenation reactions.

The invention is further illustrated by the following examples and figures. The drawings illustrate the following:

FIG. 1 shows an infrared spectrum of a polymer before undergoing a hydrogenation reaction and an infrared spectrum of a polymer after undergoing a hydrogenation reaction; and

FIG. 2 shows the degree of hydrogenation of a polymer as a function of the amount of ligand cocatalyst employed.

FIG. 3 shows the degree of hydrogenation of a polymer as a function of time using various amounts of catalyst loading;

FIG. 4 is a bar graph showing die (die) B tear strength for HNBR, XNBR and HXNBR compounds at various temperatures;

FIG. 5 is a bar graph showing die C tear strength for HNBR, XNBR and HXNBR compounds at various temperatures;

FIG. 6 is a bar graph showing the adhesion of HNBR, XNBR and HXNBR compounds to nylon at room temperature and 125 ℃;

FIG. 7 is a bar graph showing the results of Pico abrasion resistance tests using HNBR, XNBR and HXNBR; and

FIG. 8 shows the storage tensile modulus (E') of HNBR, XNBR and HXNBR as a function of temperature.

Selective hydrogenation of XNBR

Example 1

Laboratory tests were conducted by charging 6% polymer in 2.7kg chlorobenzene, 184g of a methacrylic acid-acrylonitrile-butadiene statistical trimer containing 28% by weight acrylonitrile, 7% methacrylic acid, 65% butadiene, ML 1+4/100 ℃ ═ 40(Krynac X7.40, available from Bayer) into a 2US gallon Parr high pressure reactor. With thorough stirring, pure H₂The reactor was degassed three times (100-. The temperature of the reactor was raised to 130 ℃ and a solution of 0.139g (0.076phr) tris (triphenylphosphine) -rhodium (I) chloride catalyst and 2.32g of the cocatalyst Triphenylphosphine (TPP) in 60ml of monochlorobenzene having an oxygen content of less than 5ppm was added to the reactor under a hydrogen atmosphere. The temperature of the reactor was raised to 138 ℃ and the pressure of the reactor was set at 1200psi (83 atm). The reactor temperature and hydrogen pressure were kept constant throughout the reaction. After a certain time of reaction, a sample was taken and analyzed by fourier transform infrared spectroscopy (FTIR) to detect the degree of hydrogenation. The reaction was allowed to proceed at 138 ℃ for 140 minutes under a hydrogen pressure of 83 atm. Thereafter, the chlorobenzene was removed by injecting steam and the polymer was dried in an oven at 80 ℃. The degree of hydrogenation is 95% (by IR spectrum and¹H-NMR measurement). The results of FTIR (fig. 1) show that the nitrile and carboxyl groups of the polymer remain intact after hydrogenation, indicating that hydrogenation is only a selection for the C ═ C bondAnd (4) performing sexual hydrogenation reaction.

As can be seen, the peak of carbon-carbon double bonds almost completely disappeared after the hydrogenation reaction, and 5% of the double bonds remained. Peaks for nitrile groups and carboxyl groups still remained, indicating that there was no detectable reduction of nitrile groups and carboxyl groups.

The results of the hydrogenation reaction, and the results of example 2 are shown in Table 1 below.

Example 2

The hydrogenation reaction was carried out as in example 1 using Krynac X7.40 polymer in the presence of varying amounts of the cocatalyst Triphenylphosphine (TPP), i.e. 0-4% by weight (based on solid rubber), or a co-catalyst/catalyst ratio of 0-53, and a catalyst concentration of 0.076% by weight based on the weight of the terpolymer in the polymer solution. The results of the hydrogenation reaction are given in FIG. 2 and Table 1 below. It is clear that the presence of a cocatalyst can significantly promote the hydrogenation reaction of the polymer. Those runs without cocatalyst and those without the process according to the invention are comparative tests.

Table 1 XNBR (7.0% acid) was hydrogenated using different ratios of Triphenylphosphine (TPP) to catalyst.

TABLE 1

Parts per 100 parts by weight of rubber

Example 3

Additional methacrylic acid-acrylonitrile-butadiene copolymer (7% acid, 28% ACN, 65% butadiene) was hydrogenated following the procedure of example 1, except that the amount of catalyst was different from that of example 1. The degree of hydrogenation obtained is in the range 93-99.5%. The results of these experiments are shown in table 2 and fig. 3.

TABLE 2 hydrogenation of XNBR (7.0% acid).

TABLE 2

Example 4

Methacrylic acid acrylonitrile butadiene terpolymer (3% acid, and 3.5% acid monomer) was hydrogenated according to the procedure of example 1. The details and results are shown in Table 3. It can be seen that 99 +% hydrogenation can be achieved in less than 2 hours with a 12% polymer solution, 0.076phr catalyst and cocatalyst ligand, at a catalyst to cocatalyst ratio of 1: 16.7.

TABLE 3 hydrogenation results for XNBR A and B (32% ACN, 3% and 3.5% acid).

TABLE 3

Example 5

The fumaric acid-butadiene-acrylonitrile terpolymer (< 1% acid) was hydrogenated according to the procedure of example 1. Without the use of a cocatalyst, a degree of hydrogenation of 86% was obtained in 4 hours. When the ratio of cocatalyst to catalyst was 4:1, a degree of hydrogenation of 99% was obtained in 3 hours. The results are shown in Table 4.

Table 4 hydrogenation of fumaric acid-butadiene-nitrile terpolymer (6% polymer, 0.076phr catalyst).

TABLE 4

Physical Properties of HXNBR

The various properties of the HXNBR of the present invention are investigated in the following examples. All of the non-copolymer starting materials used in the examples are commercially available. The preparations of examples 1 to 5 described above were carried out in the laboratory. The process was then converted to a pilot plant. The HXNBR tested for physical properties was produced in a pilot plant production plant, but was typically produced according to the conditions used in the laboratory. In particular, the amount of catalyst used was 0.076phr, the weight ratio of triphenylphosphine cocatalyst to rhodium-containing catalyst was 16.7:1, the XNBR subjected to the hydrogenation reaction was Krynac X7.40, the solvent was monochlorobenzene, and the solution had a concentration of 6% or 12%.

HXNBR has a Mooney value (Mooney) of 114(ML 1+ 4100 ℃). The XNBR is commercially available as Krynac X7.40. For comparison purposes, Hydrogenated Nitrile Butadiene Rubber (HNBR) available from Bayer under the trade name Therban C3446, consisting of 34% acrylonitrile, 66% butadiene, hydrogenated to about 3.5-4.5% RDB, may also be used. Therban C3446 has a Mooney value of 58(ML 1+ 4100 ℃ C.).

Mixing step

The respective compounds HXNBR, HNBR and XNBR were mixed in a 1.6 liter model BR 82, Farrel Banbury mixer at 53 rpm. For better mixing, 80% of the filler was used when sorting the batch. The carbon black filler was first added to the polymer and mixed for 1 minute, followed by all other dry fillers, stearic acid, zinc free antioxidants and plasticizers. The batch was poured at 6 minutes of mixing and the temperature at pouring was recorded. The typical pouring temperature range for HXNBR-based compounds is 140-155 ℃. For the other two polymer-based compounds, the pour temperature was below 140 ℃. Standard laboratory mill mixing procedures were used to incorporate each curative and zinc-containing ingredient in separate mixing procedures.

Example 6

In this example, each compound was peroxide cured. The formulations of the respective compounds HXNBR, HNBR and XNBR are shown in Table 5.

TABLE 5

Operation (numbering)	A	B	C	D	E	F
							Carbon black, N660	50	50	50	50	50	50
HXNBR(5％ RDB)					100	100
							KRYNAC X7.40			100	100
THERBAN C 3466	100	100
							NAUGARD 445 antioxidant	1	1	1	1	1	1
PLASTHALL TOTM plasticizer oil	5	5	5	5	5	5
							Stearic acid activator	1	1	1	1	1	1
DIAK #7 (Co) adjuvant	1.5	1.5	1.5	1.5	1.5	1.5
							STRUKTOL ZP 1014 Zinc peroxide		7		7		7
VULCUP 40KE organic peroxides	7.5	7.5	7.5	7.5	7.5	7.5
							Vulkanox ZMB-2/C5 (ZMBI) antioxidant	0.4	0.4	0.4	0.4	0.4	0.4
Zinc oxide (KADOX 920) activator	3		3		3
							Total of	169.4	173.4	169.4	173.4	169.4	173.4

The three compounds were tested for tensile strength (tensile strength), elongation at break and modulus at different strains at 23, 100, 125, 150 and 170 ℃. Table 6 shows the tensile strength and elongation at break of each of the HNBR, XNBR and HXNBR compounds with ZnO activators. It is clear that the HXNBR-based compounds show physical properties that are very different from those of XNBR and HNBR.

When the samples were tested at room temperature, both the XNBR and HXNBR showed higher modulus and higher tensile strength compared to HNBR. However, the HXNBR-based compound is much better than the XNBR-based compound in elongation at break. The HXNBR-based compound also showed the best tensile strength and ultimate elongation at high test temperatures.

Table 6 summary of the results of tensile strength and elongation at break

TABLE 6

Compound number	A(HNBR)	C(XNBR)	E(HXNBR)
				Test temperature (. degree. C.)	23	23	23
Hardness Shore (Shore) A2 Inst. (pts.)	67	84	81
				Ultimate tensile strength (Mpa)	23.63	25.66	29.3
Ultimate elongation (%)	223	138	231
				Test temperature (. degree. C.)	100	100	100
Hardness shore a2 Inst. (pts.)	65	74	67
				Ultimate tensile strength (Mpa)	8.47	15.32	17.96
Ultimate elongation (%)	109	116	329
				Test temperature (. degree. C.)	125	125	125
Hardness shore a2 Inst. (pts.)	65	76	66
				Ultimate tensile strength (Mpa)	6.73	11.36	15.32
Ultimate elongation (%)	95	100	288
				Test temperature (. degree. C.)	150	150	150
Hardness shore a2 Inst. (pts.)	65	66	67
				Ultimate tensile strength (Mpa)	6.46	10.03	13.21
Ultimate elongation (%)	87	89	257
				Test temperature (. degree. C.)	170	170	170
Hardness shore a2 Inst. (pts.)	67	72	72
				Ultimate tensile strength (Mpa)	4.64	7.54	10.51
Ultimate elongation (%)	71	74	228

Hot tear Strength (Hot tear Strength)

Table 7 and FIGS. 4 and 5 compare the tear strength of HXNBR with the tear strength of XNBR and HNBR at different test temperatures. At all temperatures, the HXNBR showed excellent tear strength in the tear tests for die (die) B and die C. For example, when tested at 100 ℃ and 170 ℃, the die B tear strength of the HXNBR is still between 30 and 40kN/m, while the die B tear strength of the XNBR and HNBR is only between 10 and 20kN/m (FIG. 4 and Table 7). In the case of the die C tear test, the HXNBR showed the same tear strength as HNBR at room temperature, but at the higher test temperature it showed twice or three times the tear strength as HNBR. The HXNBR-based compound also has a much higher die C tear strength than the XNBR-based compound at a temperature of 23-170 ℃.

TABLE 7 tear Strength (kN/m) of HXNBR, XNBR and HNBR at different temperatures

TABLE 7

Die head B	HNBR+ZnO	HNBR+ZnO	XNBR+ZnO	XNBR+ZnO	HXNBR+ZnO	HXNBR+ZnO
							23℃	46.95	40.69	50.73	43.74	85.45	62.18
100℃	16.26	15.09	23.51	21.41	39.76	31.65
							125℃	18.08	12.2	20.18	18.3	31.63	25.01
150℃	9.25	17.49	19.25	18.1	38.56	27.52
							170℃	11.02	10.54	16.43	14.44	30.61	27.34
Die head C	HNBR+ZnO	HNBR+ZnO	XNBR+ZnO	XNBR+ZnO	HXNBR+ZnO	HXNBR+ZnO
							23℃	32.46	34.45	23.51	20.42	32.28	28.09
100℃	11.25	11.03	10.77	7.23	21.74	20.37
							125℃	8.85	7.9	9.18	6.44	19.77	16.86
150℃	4.57	5.5	6.79	5.12	16.22	14.11
							170℃	4.23	4.56	6.69	4.62	12.97	13.04

Adhesion of HXNBR to Nylon textiles

One particular property of HXNBR is improved adhesion to textiles used in the belt industry. The polymer exhibits excellent tear strength at high temperatures and better adhesion at high temperatures. The adhesion of the HXNBR, XNBR and HNBR compounds to nylon textiles (nylon textiles typically used for automotive timing belts) was tested at both 23 ℃ and 125 ℃. The results of this test on the three classes of compounds using ZnO as activator are shown in table 8 and figure 6.

It is clear that at room temperature, XNBR and HXNBR have better adhesion than HNBR. However, at 125 ℃, only HXNBR showed the same good adhesion as at room temperature. The adhesive strength of both the XNBR-based compound and the HNBR-based compound decreased significantly when the test temperature was varied from 23 ℃ to 125 ℃.

TABLE 8 results of adhesion test at different temperatures

TABLE 8

Compound (I)	A(HNBR)	C(XNBR)	E(HXNBR)
				Curing time (minutes)	40	40	40
Curing temperature (. degree.C.)	160	160	160
				Test temperature (. degree. C.)	23	23	23
Objects to be bonded	Nylon	Nylon	Nylon
				Adhesive Strength (kNm)	2.92	3.62	4.97
Curing time (minutes)	40	40	40
				Curing temperature (. degree.C.)	160	160	160
Test temperature (. degree. C.)	125	125	125
				Objects to be bonded	Nylon	Nylon	Nylon
Adhesive Strength (kNm)	1.15	0.74	4.91

Wear resistance

It is well known to improve the abrasion resistance of nitrile rubber (NBR) by introducing carboxylic acid groups into the polymer. This effect is shown in the Pico abrasion test (see FIG. 7). Although both HXNBR and XNBR exhibit better abrasion resistance than HNBR-based compounds, the HXNBR-based compounds have much better abrasion resistance than XNBR. This unique property of the HXNBR indicates that the polymer has a very important potential in various applications such as rubber roll and shaft seals.

In the DIN abrasion test as shown in Table 9, no excellent abrasion resistance of the HXNBR was observed. This is probably due to the fact that the wear mechanism is somewhat different from that of the Pico wear test. In the tests, HNBR and HXNBR both showed better abrasion resistance than XNBR based compounds.

TABLE 9 DIN abrasion test results

TABLE 9

	A	B	C	D	E	F
								HNBR	HNBR	XNBR	XNBR	HXNBR	HXNBR
Curing time (minutes)	25	25	25	25	25	25
							Curing temperature (. degree.C.)	170	170	170	170	170	170
Specific gravity of	1.16	1.165	1.2	1.21	1.165	1.165
							Loss of wear volume (mm))	93	104	160	181	92	96

Flexibility at low temperature

In the Gehman and TR tests, the low temperature flexibility of the HXNBR-based compound was compared to the low temperature flexibility of HNBR and XNBR-based compounds. The results of these tests are shown in tables 10 and 11. Due to the presence of 7% carboxylic acid groups, the HXNBR polymer did not have as good low temperature flexibility as HNBR, as shown by Gehman and TR tests. The lower temperature performance of the HXNBR compound is better than that of the XNBR compound.

TABLE 10 Gehman Low temperature toughness

Watch 10

Compound number	A	B	C	D	E	F
								HNBR	HNBR	XNBR	XNBR	HXNBR	HXNBR
Curing time (minutes)	20	20	20	20	20	20
							Curing temperature (. degree.C.)	170	170	170	170	170	170
Starting temperature (. degree.C.)	-70	-70	-70	-70	-70	-70
							Temperature @ T2 (. degree. C.)	-19	-19	-2	-2	-3	-3
Temperature @ T5 (. degree. C.)	-24	-25	-11	-9	-15	-15
							Temperature @ T10 (. degree. C.)	-26	-26	-14	-13	-18	-19
Temperature @ T100 (. degree. C.)	-30	-31	-24	-25	-28	-28

TABLE 11 temperature recovery (recovery) comparison

TABLE 11

Compound number	A	B	C	D	E	F
								HNBR	HNBR	XNBR	XNBR	HXNBR	HXNBR
Curing time (minutes)	20	20	20	20	20	20
							Curing temperature (. degree.C.)	170	170	170	170	170	170
Initial elongation (%)	50％	50％	50％	50％	50％	50％
							TR 10(℃)	-22	-22	-16	-14	-14	-14
TR 30(℃)	-19	-19	-9	-8	-7	-8
							TR 50(℃)	-16	-16	-3	-1	-2	-2
TR 70(℃)	-13	-13	3	5	3	3
							Temperature recovery TR10-TR 70	9	9	19	19	17	17

Example 7

Three peroxide-cured compounds were produced from HXNBR, XNBR and conventional HNBR using the formulations shown in Table 12 below.

TABLE 12

Compound (I)	4	5	6
				Carbon black, N660	50	50	50
HXNBR C(J-11341)			100
				KRYNAC X7.40		100
THERBAN C 3466	100
				NAUGARD 445	1	1	1
PLASTHALL TOTM	5	5	5
				Stearic acid	1	1	1
DIAX # 7	1.5	1.5	1.5
				STRUKTOL ZP 1014	7	7	7
VULCUP 40KE	7.5	7.5	7.5
				VULKANOX ZMB-2/C5(ZMMBI)	0.4	0.4	0.4

The low temperature flexibility of these three classes of compounds was determined using a Rheometrics Solid analyzer (RSA-II). In this test, a small sinusoidal tensile deformation is imposed on the sample at a given frequency. At various temperatures, the force generated, and the phase difference between the applied deformation and the response (stress) were measured. Based on the principle of linear viscoelasticity, the storage tensile modulus (E'), the loss tensile modulus (E ") and tan δ can be calculated. Generally, as the temperature is reduced, the rubber becomes harder and E' increases. Near the glass transition temperature, E' increases rapidly. FIG. 8 shows the E' -temperature profiles of the three compounds. The HXNBR has been shown to have a higher glass transition temperature than HNBR. It has surprisingly been found that the HXNBR has a lower glass transition temperature than the XNBR.

Claims (19)

1. A process for selectively hydrogenating a polymer of a conjugated diene, an unsaturated nitrile and an unsaturated carboxylic acid, which comprises hydrogenating the polymer in the presence of a rhodium-containing compound as a catalyst and a co-catalyst ligand, wherein the weight ratio of the rhodium-containing compound to the co-catalyst ligand is from 1:3 to 1:55,

wherein the rhodium-containing compound is a compound of the formula:

(R_mB)₁R_hX_n

wherein each R is C₁-C₆Alkyl radical, C₄-C₈Cycloalkyl radical, C₆-C₁₅Aryl or C₇-c₁₅Aralkyl, B is a phosphorus, arsenic or sulfur atom, or a sulfoxide group S ═ 0, X is a halide ion, 1 is 2, 3 or 4, m is 2 or 3 and n is 1, 2 or 3,

wherein the cocatalyst ligand has the formula:

R_mB

wherein R, m and B are as defined above.

2. The process of claim 1 wherein X is chloride or bromide.

3. The method of claim 1, wherein B is phosphorus.

4. The process of claim 1, wherein the rhodium-containing compound is tris (triphenylphosphine) -rhodium (I) -chloro, tris (triphenylphosphine) -rhodium (III) -chloro or tris (dimethyl sulfoxide) -rhodium (III) -chloro.

5. The process of claim 1 wherein the amount of rhodium-containing compound is from 0.03% to 0.5% by weight of the polymer to be hydrogenated.

6. The process of claim 1 wherein the cocatalyst ligand is triphenylphosphine.

7. The process of claim 1, 2, 3, 4, 5, or 6 wherein the weight ratio of rhodium-containing catalyst compound to promoter ligand is in the range of from 1:3 to 1: 45.

8. The process of claim 1, 2, 3, 4, 5, or 6 wherein the cocatalyst is present in an amount ranging from 0.1 to 20 percent based on the weight of the polymer to be hydrogenated.

9. The process of claim 1, 2, 3, 4, 5, or 6 wherein the cocatalyst is present in an amount ranging from 0.5 to 20 percent based on the weight of the polymer to be hydrogenated.

10. The process of claim 1, 2, 3, 4, 5, or 6 wherein the amount of cocatalyst is in the range of from 1 to less than 5% by weight of the polymer to be hydrogenated.

11. The process of claim 1, 2, 3, 4, 5, or 6 wherein the amount of cocatalyst is in the range of from 2% to 5% by weight of the polymer to be hydrogenated.

12. The process of claim 1, 2, 3, 4, 5, or 6 wherein the polymer subjected to selective hydrogenation has a molecular weight greater than 60,000.

13. The process of claim 1, 2, 3, 4, 5, or 6 wherein the polymer subjected to selective hydrogenation has a molecular weight greater than 100,000.

14. The process of claim 1, 2, 3, 4, 5, or 6 wherein the process is conducted at a temperature of 60 to 160 ℃ and a pressure of 10.13 x 10⁵To 253.31 x 10⁵Pa, and the like.

15. The process of claim 1, 2, 3, 4, 5, or 6 wherein the selective hydrogenation is carried out until at least 80% of the carbon-carbon double bonds have been hydrogenated.

16. The process of claim 1, 2, 3, 4, 5, or 6 wherein the selective hydrogenation is carried out until at least 90% of the carbon-carbon double bonds have been hydrogenated.

17. The process of claim 1, 2, 3, 4, 5, or 6 wherein the selective hydrogenation is carried out until at least 95% of the carbon-carbon double bonds have been hydrogenated.

18. The process of claim 1, 2, 3, 4, 5, or 6 wherein the selective hydrogenation is carried out until at least 99% of the carbon-carbon double bonds have been hydrogenated.

19. The process of claim 1, 2, 3, 4, 5, or 6 wherein the polymer comprises from 85% to 50% by weight conjugated diene-based monomer units, from 0.1% to 10% by weight α, β -unsaturated carboxylic acid-based monomer units, and from 15% to 50% by weight acrylonitrile or methacrylonitrile-based monomer units, wherein the sum of all components is 100%.