Thermoplastic polyurethanes
A process for the preparation of thermoplastic polyurethane by reacting (a) isocyanates with (b) compounds reactive toward isocyanates and having a molecular weight (M w ) of from 500 to 10 000 g/mol and (c) chain extenders having a molecular weight of from 50 to 499 g/mol, if appropriate in the presence of (d) catalysts and/or (e) conventional additives, wherein the chain extender mixture consisting of a main chain extender (c1) and one or more co-chain extenders (c2) is used and the thermoplastic polyurethane prepared has a rigid phase fraction of greater than 0.40, the rigid phase fraction being defined by the following formula: rigid phase fraction = { ∑ x = 1 k [ ( m KVx / M KVx ) * M Iso + m KVx ] } / m ges with the following meanings: M KVx : molar mass of the chain extender x in g/mol m KVx : mass of the chain extender x in g M Iso : molar mass of the isocyanate used in g/mol m ges : total mass of all starting materials in g k: number of chain extenders.
1. A process for the preparation of thermoplastic polyurethane by reacting (a) the isocyanate diphenylmethane 4,4′-diisocyanate with (b) compounds reactive toward isocyanates and having a molecular weight (M w ) of from 500 to 10 000 g/mol and (c) chain extenders having a molecular weight of from 50 to 499 g/mol, optionally in the presence of (d) catalysts and/or (e) conventional additives, wherein the chain extender is a mixture consisting of a main chain extender 1,4-butanediol (c1) and a co-chain extender 1,3-propanediol (c2) and the thermoplastic polyurethane prepared has a rigid phase fraction of greater than 0.40, said rigid phase fraction being defined by the following formula:
Rigid
phase
fraction
=
{
∑
x
=
1
k
[
(
m
KVx
/
M
KVx
)
*
M
Iso
+
m
KVx
]
}
/
m
ges
wherein:
M KVx : molar mass of the chain extender x in g/mol
m KVx : mass of the chain extender x in g
M Iso : molar mass of the isocyanate used in g/mol
m ges : total mass of all starting materials in g
k: number of chain extenders wherein the proportion of n1 of the main chain extender (c1), based on the total amount of n of the chain extender (c) used, is from 0.80 to 0.999.
2. A thermoplastic polyurethane prepared by a process according to claim 1 .
3. A ski shoe based on thermoplastic polyurethane prepared by reacting (a) diphenylmethane 4,4′-diisocyanate with (b) compounds reactive toward isocyanates and having a molecular weight (M w ) of from 500 to 10 000 g/mol and (c) chain extenders having a molecular weight of from 50 to 499 g/mol, optionally in the presence of (d) catalysts and/or (e) conventional additives, wherein the chain extender (c) is a mixture consisting of a main chain extender 1,4-butanediol (c1) and a co-chain extender 1,3-propanediol (c2) wherein the proportion of n1 of the main chain extender (c1), based on the total amount of n of the chain extender (c) used, is from 0.80 to 0.999.
4. The ski shoe according to claim 3 , wherein the thermoplastic polyurethane is based on polytetramethylene glycol having a molecular weight (M n ) of from 600 to 2000 g/mol as (b) compounds reactive toward isocyanates and having a molecular weight (M n ) of from 500 to 10 000 g/mol.
5. The ski shoe according to claim 3 , wherein the thermoplastic polyurethane has a rigid phase fraction of greater than 0.4, said rigid phase fraction being defined by the following formula:
Rigid
phase
fraction
=
{
∑
x
=
1
k
[
(
m
KVx
/
M
KVx
)
*
M
Iso
+
m
KVx
]
}
/
m
ges
wherein:
M KVx : molar mass of the chain extender x in g/mol
m KVx : mass of the chain extender x in g
M Iso : molar mass of the isocyanate used in g/mol
m ges : total mass of all starting materials in g
k: number of chain extenders.
6. The ski shoe according to claim 3 , wherein the thermoplastic polyurethane has a transparency value T of less than or equal to 3.2, determined according to DIN 55988 (index 1 without correction), at a layer thickness H of 8.2 mm.
7. The ski shoe according to claim 3 , wherein the thermoplastic polyurethane has a Charpy notched impact strength of −30° C. according to DIN EN ISO 179-1/1eA of greater than 10 kJ/m 2 .
8. A process for the production of a ski shoe, wherein a thermoplastic polyurethane according to claim 2 is processed by means of injection molding to give the ski shoe.
9. The process for the production of thermoplastic polyurethane according to claim 1 wherein components (b) and (c) are used in a molar ratio of 10:1 to 1:10.
10. The process for the production of thermoplastic polyurethane according to claim 1 wherein components (b) and (c) are used in a molar ratio of 1:1 to 1:4.