Nitrile rubbers which optionally contain alkylthio terminal groups and which are optionally hydrogenated
View Patent ↗An improved polymerization and processing method allows the production of special nitrile rubbers which are characterized by a specific cation content which leads to an excellent storage stability and particularly good vulcanization rate and moreover results in vulcanized materials that have advantageous properties.
1. Nitrile rubber comprising:
repeating units of at least one α,β-unsaturated nitrile, at least one conjugated diene and optionally one or more further copolymerizable monomers; and
further comprising calcium, magnesium, sodium and/or potassium ions, and
wherein the nitrile rubber further comprises magnesium ions in a concentration in the range from 100-180 ppm and calcium ions in a concentration in the range from 50-145 ppm, in each case based on the nitrile rubber.
2. The nitrile rubber according to claim 1 having an ion index (“II”) according to the general formula (I) in the range from 5 to 30 ppm×mol/g,
II
=
3
[
c
(
Ca
2
+
)
40
g
/
mol
+
c
(
Mg
2
+
)
24
g
/
mol
]
-
[
c
(
Na
+
)
23
g
/
mol
+
c
(
K
+
)
39
g
/
mol
]
(
I
)
where c(Ca 2+ ), c(Mg 2+ ), c(Na + ) and c(K + ) indicate the concentrations of the calcium, magnesium, sodium and potassium ions in the nitrile rubber in units of ppm.
3. The nitrile rubber according to claim 1 , wherein said nitrile rubber contains repeating units of acrylonitrile and 1,3-butadiene and optionally one or more further copolymerizable monomers.
4. The nitrile rubber according to claim 3 , wherein said nitrile rubber further comprises repeating units of one or more α,β-unsaturated monocarboxylic or dicarboxylic acids, their esters or amides.
5. Nitrile rubber according to claim 3 , wherein said nitrile rubber further comprises repeating units of an alkyl ester of an α,β-unsaturated carboxylic acid.
6. Nitrile rubber according to claim 3 , wherein said nitrile rubber further comprises repeating units 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 and/or lauryl(meth)acrylate.
7. Nitrile rubber according to claim 1 having a Mooney viscosity (ML (1+4 @ 100° C.)) of from 10 to 150 Mooney units.
8. The nitrile rubber according to claim 1 having a glass transition temperature in the range from −70° C. to +10° C.
9. The nitrile rubber according to claim 1 , wherein said nitrile rubber comprises 2,2,4,6,6-pentamethylheptane-4-thiol and/or 2,4,4,6,6-pentamethylheptane-2-thiol, 2,3,4,6,6-pentamethylheptane-2-thiol, and 2,3,4,6,6-pentamethylheptane-3-thiol.
10. Nitrile rubber according to claim 1 wherein the II is in the range of from 10 to 25 ppm×mol/g.
11. Nitrile rubber according to claim 1 having a Mooney viscosity (ML (1+4 @ 100° C.)) of from 20 to 100 Mooney units.
12. Nitrile rubber according to claim 1 having a glass transition temperature in the range from −60° C. to 0° C.