Hybrid systems consisting of foamed thermoplastic elastomers and polyurethanes
The present invention relates to a hybrid material comprising a matrix of polyurethane and foamed particles of thermoplastic polyurethane comprised therein and also a process for producing such hybrid materials and the use of these hybrid materials as bicycle saddles, upholstery and shoe soles.
1. A process, comprising:
(1) mixing the following components:
a) a polyisocyanate,
b) a compound having hydrogen atoms which are reactive toward isocyanates, and
c) foamed particles having a closed skin, which are expanded particles (c″) of thermoplastic polyurethane,
and optionally,
d) a chain extender and/or a crosslinker,
e) a catalyst,
f) an additional blowing agent, and
g) a further additive,
to obtain a mixture;
(2) reacting the mixture, to form a hybrid material comprising a matrix of polyurethane having the foamed particles distributed therein, wherein components a), b), and, if present, d) to g) form the matrix; wherein the matrix has a density of from 0.1 to 0.8 g/cm 3 ; and
(3) preparing a shoe sole comprising said hybrid material.
2. The process according to claim 1 , wherein the reaction is carried out at a temperature of the reaction mixture of from 100 to 140° C.
3. The process according to claim 1 , wherein the expanded particles (c″) have a diameter of from 0.1 mm to 10 cm.
4. The process according to claim 1 , wherein the expanded particles (c″) have a density of from 0.005 to 0.50 g/cm 3 .
5. The process according to claim 1 , wherein an isocyanate prepolymer having an NCO content of from 1 to 20% by weight is firstly prepared from components a) and b) and, optionally, components d), e) and g), and the isocyanate prepolymer is subsequently mixed with the expanded particles (c″) of thermoplastic polyurethane and the composite is allowed to cure by action of water.
6. The process according to claim 5 , wherein the weight ratio of the components a), b) and d) g) to component (c″) is from 1:1 to 1:20.
7. The process according to claim 1 , wherein the thermoplastic polyurethane of the expanded particles (c″) is formed from polytetrahydrofuran having a number average molecular weight of from 600 to 2500 g/mol.
8. The process according to claim 1 , wherein component a) comprises 4,4′-MDI.
9. The process according to claim 1 , wherein the reacting is carried out at an index of 60 to 120.
10. The process according to claim 1 , wherein the hybrid material has an elasticity of greater than 40% in accordance with DIN 53512.
11. The process according to claim 1 , wherein the weight ratio of matrix to foamed particles is from 1:1 to 1:20.
12. The process according to claim 1 , wherein a tear propagation resistance is greater than 2.5 N/mm at an average density of the hybrid material of from 0.4 to 0.5 g/cm 3 , greater than 2.2 N/mm at an average density of the hybrid material of from 0.3 to <0.4 g/cm 3 , greater than 2.0 N/mm at an average density of the hybrid material of from 0.2 to <0.3 g/cm 3 and greater than 1.0 N/mm at an average density of the hybrid material of from 0.1 to <0.2 g/cm 3 .
13. The process according to claim 1 , wherein
the thermoplastic polyurethane of the expanded particles (c″) is formed from polytetrahydrofuran having a number average molecular weight of from 600 to 2500 g/mol;
component a) comprises 4,4′-MDI; and
the reacting is carried out at an index of 60 to 120.
14. The process according to claim 1 , wherein the expanded particles (c″) have a compact outer skin.
15. A process, comprising:
(1) mixing the following components:
a) a polyisocyanate,
b) a compound having hydrogen atoms which are reactive toward isocyanates, and
c) foamed particles having a closed skin, which are expanded particles (c″) of thermoplastic polyurethane,
and optionally,
d) a chain extender and/or a crosslinker,
e) a catalyst,
f) an additional blowing agent, and
g) a further additive,
to obtain a mixture;
(2) reacting the mixture, to form a hybrid material comprising a matrix of polyurethane having the foamed particles distributed therein, wherein components a), b), and, if present, d) to g) form the matrix; wherein the matrix has a density of from 0.1 to 0.8 g/cm 3 ; and
(2) preparing an article comprising said hybrid material, wherein said article is upholstery, a bicycle saddle, or a surfacing for a playground, an athletic track, a playing field, or a sports hall.
16. The process according to claim 1 , wherein the expanded particles (c″) are spherical or ellipsoidal.
17. The process according to claim 1 , wherein the matrix has a density of from 0.3 to 0.6 g/cm 3 .