Use of ruthenium and osmium catalysts for the metathesis of nitrile rubber

Abstract

The present invention relates to the use of Ru and Os carbene complexes with a hydroxamic acid (ester) function for the metathesis degradation of nitrile rubber (NBR). The invention further relates to a method for producing hydrogenated nitrile rubbers, by subjecting a nitrile rubber to a metathesis degradation in the presence of the said catalyst, and the degraded nitrile rubber obtained subsequently undergoes a hydrogenation, preferably in situ.

Claims

1. A method for the metathesis of nitrile rubber comprising carrying out a metathesis reaction of the nitrile rubber in the presence of a catalyst of formula (I) or (III): ##STR00028##

2. The method according to claim 1, wherein: the catalyst is present at 0.001 to 1 phr, based on the nitrile rubber.

3. The method according to claim 1, wherein the metathesis reaction is carried out without the presence of a co-olefin.

4. The method according to claim 1, wherein copolymers or terpolymers which comprise repeat units of at least one conjugated diene, at least one α,β-unsaturated nitrile, and optionally one or more further copolymerizable monomers are present in the metathesis reaction as nitrile rubbers.

5. The method according to claim 4, wherein copolymerizable monomers of α,β-unsaturated monocarboxylic or dicarboxylic acids, the esters or amides thereof, the alkoxyalkyl esters thereof, or a PEG acrylate of formula (X): ##STR00029## wherein: R is hydrogen or a branched or unbranched C.sub.1-C.sub.20 alkyl, n is 1 to 8, and R.sup.1 is hydrogen or CH.sub.3—, are present in the metathesis reaction.

6. The method according to claim 1, wherein: the nitrile rubbers have a Mooney viscosity (ML 1+4 at 100° C.) in the range of from 30 to 70.

7. The method according to claim 1, wherein: the concentration of the nitrile rubber is in the range of from 1 to 20 wt %, based on the total weight of the reaction mixture.

8. The method according to claim 1, wherein the metathesis reaction is carried out in a solvent.

9. The method according to claim 1, wherein the metathesis reaction is carried out at a temperature in the range of from 10° C. to 150° C.

10. The method according to claim 1, wherein the metathesis reaction is carried out in the presence of a co-olefin.

11. The method according to claim 5, wherein mixtures of the copolymerizable monomers are present in the metathesis reaction.

12. A method for producing hydrogenated nitrile rubbers comprising subjecting a nitrile rubber to a metathesis degradation in the presence of a catalyst of the formula (I) or (III): ##STR00030## thereby obtaining a degraded nitrile rubber, wherein the degraded nitrile rubber subsequently undergoes a hydrogenation.

13. The method according to claim 12, wherein the hydrogenation of the degraded nitrile rubber is performed in situ.

Description

EXAMPLES

(1) Metathesis degradation of nitrile rubber in the presence of different catalysts

(2) The following examples show that, in each case at the same dosage, the catalysts of the formula (I) has metathesis activity in the metathesis degradation of nitrile rubber.

(3) The following catalysts were used:

(4) “Grubbs II catalyst” (comparative example 1): [1,3-bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(phenylmethylene)(tricyclohexylphosphine)ruthenium (CAS number: 246047-72-3), C.sub.46H.sub.65Cl.sub.2N.sub.2PRu weight: 848.97 g/mol; the Grubbs II catalyst was obtained from the company Materia Inc.

(5) ##STR00024##

(6) “Hoveyda-Grubbs II catalyst” (comparative example 2): [1,3-Bis-(2,4,6-trimethylphenyl)-2-imidazolidinylidene]dichloro(o-isopropoxyphenylmethylene)ruthenium (CAS number: 301224-40-8); C.sub.31H.sub.38Cl.sub.2N.sub.2ORu, weight: 626.62 g/mol; the Hoveyda-Grubbs II catalyst was obtained from the company Materia Inc.

(7) ##STR00025##

(8) “Nitro-Grela catalyst AS2032” (comparative example 3): [1,3-Bis(2,4,6-trimethylphenylimidazolidine-2-ylidene)]-(2-i-propoxy-5-nitrobenzylidene)ruthenium(II) dichloride (CAS number: 502964-52-5); C.sub.31H.sub.37Cl.sub.2N.sub.3O.sub.3Ru; weight: 671.62 g/mol; green powder. The catalyst is commercially available from Apeiron or Strem. The production of the catalyst is known to those skilled in the art from WO-A-2004/035596 and also K. Grela, S. Harutyunyan, A. Michrowska “A New Highly Efficient Ruthenium Catalyst for Metathesis Reaction” Angew. Chem. Int. Ed., 41, 4038-4040, (2002) or J. Org. Chem. 2004, 69, 6894-6896.

(9) ##STR00026##

Example (I)

(10) “GreenCat AS2034”: [1,3-Bis(2,6-di-i-propylphenyl)imidazolidin-2-ylidene]{2-[[1-(methoxy(methypamino)-1-oxopropan-2-yl]oxy]benzylidene}ruthenium(II) dichloride (CAS number: 1448663-06-6); C.sub.39H.sub.53Cl.sub.2N.sub.3O.sub.3Ru; molecular weight: 783.33 g/mol. The catalyst is commercially available from Apeiron or Strem.

(11) ##STR00027##

(12) The degradation reactions described below were carried out using a nitrile rubber from ARLANXEO Deutschland GmbH with 34 wt % acrylonitrile content; a Mooney viscosity (ML 1+4 @100° C.) of 34 MU and a residual double bond content (RDB) of 100. This nitrile rubber is abbreviated to NBR below.

(13) General description of the metathesis reactions carried out:

(14) In each case 425 g of chlorobenzene (MCB; Aldrich) were used for the metathesis degradation. 75 g of NBR were dissolved therein at room temperature over a period of 24 h.

(15) TABLE-US-00002 TABLE 1 Analytical data of the NBR solution before the metathesis reaction Analytical data NBR solution Mw [g/mol] 292 406 Mn [g/mol]  74 461 PDI 3.9

(16) In each case 3.1 g (4 phr) of 1-hexene were added to the NBR solution and mixed thoroughly to homogenize for 120 min on an agitator.

(17) The 0.0049 g of ruthenium-containing catalysts were each dissolved in 5 ml of MCB at room temperature. The catalyst solutions were added to the NBR solutions immediately after the catalyst solutions had been prepared.

(18) After 24 hours the metathesis reaction came to an end, and in each case 5 ml of the reaction solution were used for the GPC.

(19) The molecular weight was determined by gel permeation chromatography (GPC) to DIN-55672-1 version 2007. A modular system comprising a Shodex RI-71 differential refractometer, S 5200 autosampler (from SFD), column oven (ERC-125), Shimadzu LC 10 AT pump and a column combination of 3 PLgel 10 μm Mixed B 300×7.5 mm columns from Agilent was used.

(20) The solvent used was tetrahydrofuran; the molecular weights present are based on polystyrene standards from PSS (Mainz). The finished THF sample solutions are filtered through syringe filters having 0.45 μm PTFE membranes and diameter 25 mm. The measurements were conducted at 40° C. and a flow rate of 1 ml/min in tetrahydrofuran.

(21) The molecular parameters such as number-average molecular weight Mn, mass-average molecular weight Mw and the resulting polydispersity index PDI are determined from the RI signal by means of the “Empower 2 data base” software from Waters.

(22) The following characteristic indices were determined by means of GPC analysis both for the original NBR rubber (before degradation) and for the degraded nitrile rubbers:

(23) Mw [g/mol]: weight-average molecular weight

(24) Mn [g/mol]: number-average molecular weight

(25) PDI: Width of the molecular weight distribution (Mw/Mn)

(26) Activity comparison of the “Grubbs II catalyst”, the “Hoveyda-Grubbs II catalyst” and the “nitro-Grela catalyst” with the catalyst of formula (I) in the presence of 4 phr of 1-hexene

(27) The activity of the “Grubbs II catalyst”, the “Hoveyda-Grubbs II catalyst” and the “nitro-Grela catalyst” with the catalyst of formula (I) were carried out with the inventive catalyst of the formula (I) at a catalyst concentration of 0.0065 phr (0.0049 g) and a dosage of 4.0 phr (3.1 g) of the co-catalyst 1-hexene.

(28) TABLE-US-00003 TABLE 2 Molecular weight and PDI of the nitrile rubbers after 24 h of metathesis in the presence of the comparative catalysts V1 to V3 and also the inventive catalysts (I)* and (II)* in comparison to the starting values at the start Start V1 V2 V3 (I)* Analytical data 0 h 24 h 24 h 24 h 24 h Mw [g/mol] 292 406 107 336 72 957 97 137 52 237 Mn [g/mol]  74 461  45 657 31 327 39 288 24 079 PDI 3.9 2.4 2.3 2.5 2.2 *Inventive examples

(29) The use of the catalyst (I)* leads to a metathesis degradation of nitrile rubber without perceptible gel formation.

(30) The comparison of the reduction in the weight-average molecular weight Mw of the nitrile rubber in the inventive example (I)* shows that the activity of the catalyst (I) (GreenCat AS2034) is significantly higher than the comparative catalysts used in the comparative examples V1 to V3, Grubbs II catalyst, Hoveyda-Grubbs II catalyst and nitro-Grela catalyst. In each case with the same reaction time, with the catalyst (I) (GreenCat AS2034) lower molecular weights than with the comparative catalysts V1 to V3 are achieved. The inventive catalyst (lis thus suitable for use in a method for the metathesis of nitrile rubber.