NITRILE RUBBERS

• US 20080293869A1
• Filed: 02/28/2008
• Published: 11/27/2008
• Est. Priority Date: 05/22/2007
• Status: Active Grant

• Current Assignee: Arlanxeo Deutschland GmbH
• Original Assignee: Lanxess Deutschland GmbH (Lanxess AG)
• Inventors: Obrecht, Werner
• Granted Patent: US 8,664,340 B2
• Time in Patent Office: Days
• US Class Current: 524/439
• CPC Class Codes: C08C 1/14 Coagulation
• CPC Class Codes: C08C 1/15 characterised by the coagulants used
• CPC Class Codes: C08F 2/38 Polymerisation using regulators, e.g. chain terminating agents , e.g. telomerisation
• CPC Class Codes: C08F 236/12 with nitriles
• CPC Class Codes: C08L 9/02 Copolymers with acrylonitrile

Abstract

An improved polymerization and work-up process makes it possible to produce specific nitrile rubbers which have a particular ion index which is responsible for an excellent vulcanization rate and leads to vulcanizates having an advantageous property profile.

Claims

1. A nitrite rubber comprising repeating units of at least one α

,β

-unsaturated nitrite, at least one conjugated diene and optionally one or more further copolymerizable monomers and has an ion index (“

II”

) according to the general formula (I) in the range from 7 to 26 ppm×

g/mol,

$\begin{array}{cc}\mathrm{ion}<br><br><br><br>\mathrm{index}=\frac{3<br><br><br><br>c<br><br>\left({\mathrm{Ca}}^{2+}\right)}{40<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}-\left[\frac{c<br><br><br><br>\left({\mathrm{Na}}^{+}\right)}{23<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}+\frac{c<br><br><br><br>\left(K^{+}\right)}{39<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}\right]& \left(I\right)\end{array}$

where c(Ca²⁺), c(Na⁺) and c(K⁺) indicate the concentrations of the calcium, magnesium, sodium and potassium ions in the nitrile rubber in ppm.

2. The nitrile rubber according to claim 1 having an ion index in the range from 8 to 26 ppm×

mol/g and preferably in the range from 10 to 26 ppm×

mol/g.

3. The nitrile rubber according to claim 1 having repeating units of acrylonitrile, 1,3-butadiene and optionally one or more further copolymerizable monomers.

4. The nitrite rubber according to claim 3 having repeating units of one or more ad unsaturated monocarboxylic or dicarboxylic acids, their esters or amides.

5. The nitrile rubber according to claim 4 having repeating units of an alkyl ester of an α

,β

-unsaturated carboxylic acid, in particular 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 or lauryl(meth)acrylate.

6. The nitrite rubber according to claim 1 which has a Mooney viscosity (ML (1+4@100°

C.)) of from 10 to 150 Mooney units.

7. The nitrite rubber according to claim 6 which has a Mooney viscosity ML (1+4@100°

C.)) of from 20 to 100 Mooney units.

8. The nitrite rubber according to claim 1 having a glass transition temperature in the range from 70°

C. to +10°

C.

9. The nitrite rubber according to claim 8 having a glass transition temperature in the range from 60°

C. to 0°

C.

40. A vulcanizable mixture comprising at least one nitrile rubber according to claim 1 at least one crosslinker and optionally further additives.

42. A process for producing a vulcanizable mixture according to claim 40 by mixing at least one nitrite rubber comprising repeating units of at least one α

,β

-unsaturated nitrite, at least one conjugated diene and optionally one or more further copolymerizable monomers and has an ion index (“

II”

) according to the general formula (I) in the range from 7 to 26 ppm×

g/mol,

$\begin{array}{cc}\mathrm{ion}<br><br><br><br>\mathrm{index}=\frac{3<br><br><br><br>c<br><br>\left({\mathrm{Ca}}^{2+}\right)}{40<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}-\left[\frac{c<br><br><br><br>\left({\mathrm{Na}}^{+}\right)}{23<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}+\frac{c<br><br><br><br>\left(K^{+}\right)}{39<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}\right]& \left(I\right)\end{array}$

where c(Ca²⁺), c(Na⁺) and c(K⁺) indicate the concentrations of the calcium, magnesium, sodium and potassium ions in the nitrite rubber in ppm, at least one crosslinker and optionally further additives.

43. A process for producing a vulcanizable mixture according to claim 40 by mixing at least one hydrogenated nitrite rubber comprising repeating units of at least one α

,β

-unsaturated nitrite, at least one conjugated diene and optionally one or more further copolymerizable monomers and has an ion index (“

II”

) according to the general formula (I) in the range from 7 to 26 ppm×

g/mol,

$\begin{array}{cc}\mathrm{ion}<br><br><br><br>\mathrm{index}=\frac{3<br><br><br><br>c<br><br>\left({\mathrm{Ca}}^{2+}\right)}{40<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}-\left[\frac{c<br><br><br><br>\left({\mathrm{Na}}^{+}\right)}{23<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}+\frac{c<br><br><br><br>\left(K^{+}\right)}{39<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}\right]& \left(I\right)\end{array}$

where c(Ca²⁺), c(Na⁺) and c(K⁺) indicate the concentrations of the calcium, magnesium, sodium and potassium ions in the nitrite rubber in ppm, at least one crosslinker and optionally further additives, at least one crosslinker and optionally further additives.

10. A process for producing nitrite rubbers by emulsion polymerization of at least one α

,β

-unsaturated nitrile, at least one conjugated diene and optionally one or more further copolymerizable monomers, with the latex which is initially obtained in the polymerization and contains the nitrite rubber being subjected to coagulation and the coagulated nitrite rubber obtained subsequently being washed, wherein

(i) the emulsion polymerization is carried out in the presence of at least one alkyl thiol containing 12-16 carbon atoms and at least three tertiary carbon atoms, with the sulphur being bound to one of these tertiary carbon atoms, and

(ii) the pH of the latex obtained in the emulsion polymerization is set to at least 6 before coagulation and the latex is subsequently coagulated using at least one salt of a monovalent metal, with not more than 5% by weight of salts of a divalent metal, based on the total amount of all salts used for coagulation, being able to be present in the coagulation, and

(iii) a temperature of at least 50°

C. is set both during the coagulation of the latex and during subsequent washing.

11. The process according to claim 10, wherein the emulsion polymerization is carried out batchwise or continuously in a cascade of stirred vessels.

12. The process according to claim 10, wherein one or more ageing inhibitors are added to the latex containing the nitrile rubber before or during coagulation.

13. The process according to claim 10, wherein at least one salt of sodium or potassium is used for coagulation of the latex.

14. The process according to claim 10, wherein at least one halide of a monovalent metal is used for coagulation of the latex.

15. The process according to claim 14, where in at least one halide is sodium chloride or potassium chloride.

16. The process according to claim 10, wherein at least one nitrate of monovalent metal is used for coagulation of the latex.

17. The process according to claim 16, wherein at least one nitrate is sodium nitrate or potassium nitrate.

18. The process according to claim 10, wherein at least one sulphate of a monovalent metal is used for coagulation of the latex.

19. The process accordingly to claim 18, where in at least one sulphate is a sodium sulphate or potassium sulphate.

20. The process according to claim 10, wherein at least the salt of a monovalent metal cation and a monovalent anion is used for coagulation of the latex.

21. The process according to claim 10, wherein a mixture of two or more salts of a monovalent metal is used for coagulation of the latex, with the salts being able to be different salts of the same monovalent metal or various salts of various monovalent metals.

22. The process according to claim 10, wherein a maximum amount below 5% by weight and preferably a maximum amount below 3% by weight of salts of a divalent metal, based on the total amount of all salts used for coagulation, is present in the coagulation of the latex.

23. The process according to claim 10, wherein, in the coagulation of the latex, both sodium chloride and potassium chloride are used for coagulation of the nitrile rubber and the amount of potassium chloride is X % by weight, with the value of X % by weight being 40% by weight minus the % by weight of calcium chloride, if present.

24. The process according to claim 10, wherein the amount of the salt or salts of the monovalent metal used for coagulation of the latex is 1-200 parts by weight.

25. The process according to claim 24, wherein the amount of the salt or salts of the monovalent metal is 5-150 parts by weight.

26. The process according to claim 10, wherein the amount of the salt or salts of the monovalent metal used for coagulation of the latex is 10-100 pans by weight, per 100 parts by weight of nitrile rubber.

27. The process according to claim 10, wherein the latex used for the coagulation has a solids concentration in the range from 1% to 40% by weight.

28. The process according to claim 27, where in the latex used for the coagulation has a solids concentration in the range from 5% to 35% by weight.

29. The process according to claim 28, wherein the latex used for the coagulation has a solids concentration in the range from 15 to 30% by weight.

30. The process according to claim 10, wherein the coagulation of the latex is carried out at a temperature in the range from 50 to 100°

C.

31. The process according to claim 30, wherein the coagulation of the latex is carried out at a temperature range from 55 to 90°

C.

32. The process according to claim 31, wherein the coagulation of the latex is carried out at a temperature range from 60 to 90°

C.

33. The process according to claim 10, wherein the latex and the solution of at least one salt of a monovalent metal are firstly combined at a temperature of <

50°

C. and the temperature of the latex/salt mixture is subsequently increased to a temperature above 50°

C.

34. The process according to claim 10, wherein deionized water (“

DW”

) or water which has not been deionized (“

BW”

) is used for washing of the coagulated nitrile rubber.

35. The process according to claim 10, wherein water which has not been deionized if no calcium salt is present in the possible amounts of up to 5% by weight of all salts used in the coagulation of the latex using at least one salt of a monovalent metal.

36. The process according to claim 10, wherein the washing of the coagulated nitrile rubber is carried out at a temperature in the range from 50 to 90°

C.

37. The process according to claim 36, where in the washing of the coagulated nitrile rubber is carried out at a temperature in the range from 55 to 90°

C.

38. The process according to claim 10, wherein the obtained nitrile rubber is subsequently subjected either (i) to a metathetic degradation reaction, (ii) a metathetic degradation reaction and a subsequent hydrogenation, or (iii) only a hydrogenation reaction.

39. An optionally hydrogenated nitrile rubber prepared by the process according to claim 38.

41. A vulcanizable mixture comprising at least one nitrite rubber according to claim 39, at least one crosslinker and optionally further additives.

45. A process for producing mouldings comprising vulcanizing a hydrogenated nitrite rubber comprising repeating units of at least one α

,β

-unsaturated nitrite, at least one conjugated diene and optionally one or more further copolymerizable monomers and has an ion index (“

II”

) according to the general formula (I) in the range from 7 to 26 ppm×

g/mol,

$\begin{array}{cc}\mathrm{ion}<br><br><br><br>\mathrm{index}=\frac{3<br><br><br><br>c<br><br>\left({\mathrm{Ca}}^{2+}\right)}{40<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}-\left[\frac{c<br><br><br><br>\left({\mathrm{Na}}^{+}\right)}{23<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}+\frac{c<br><br><br><br>\left(K^{+}\right)}{39<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}\right]& \left(I\right)\end{array}$

where c(Ca²⁺), c(Na⁺) and c(K⁺) indicate the concentrations of the calcium, magnesium, sodium and potassium ions in the nitrite rubber in ppm based on a nitrite rubber according to claim 28, where in a vulcanizable mixture according to claim 32 is vulcanized in a shaping process.

46. A moulding obtainable by the process according to claim 36.

47. The moulding according to claim 45, characterized in that it is a seal, a cap, a hose or a diaphragm, in particular an O-ring seal, a flat seal, a corrugated sealing ring, a sealing sleeve, a sealing cap, a dust protection cap, a plug seal, a thermal insulation hose (with or without addition of PVC), an oil cooler hose, an air intake hose, a servo control hose or a pump diaphragm.

44. A process for producing mouldings comprising vulcanizing nitrile rubber comprising repeating units of at least one α

,β

-unsaturated nitrite, at least one conjugated diene and optionally one or more further copolymerizable monomers and has an ion index (“

II”

) according to the general formula (I) in the range from 7 to 26 ppm×

g/mol,

$\begin{array}{cc}\mathrm{ion}<br><br><br><br>\mathrm{index}=\frac{3<br><br><br><br>c<br><br>\left({\mathrm{Ca}}^{2+}\right)}{40<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}-\left[\frac{c<br><br><br><br>\left({\mathrm{Na}}^{+}\right)}{23<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}+\frac{c<br><br><br><br>\left(K^{+}\right)}{39<br><br><br><br>g<br><br>\text{/}<br><br>\mathrm{mol}}\right]& \left(I\right)\end{array}$

where c(Ca²⁺), c(Na⁺) and c(K⁺) indicate the concentrations of the calcium, magnesium, sodium and potassium ions in the nitrite rubber in ppm in a shaping process.