Reactive polyurethane hotmelts with large PSA range
View Patent ↗Reactive polyurethane hotmelts comprising crystallizing polyesterpolyols based on fumaric acid and 1,6-hexanediol. These hotmelts exhibit good pressure-sensitive adhesive (PSA) properties over a very broad temperature range. The reactive polyurethane hotmelts are prepared by mixing a polyol mixture containing at least on crystallizing polyesterpolyol with an excess of polyisocyanates.
1. Reactive polyurethane hotmelts comprising the reaction product of
A a polyisocyanate component comprising at least one difunctional polyisocyanate having an isocyanate content of from 5 to 50% by weight (based on A) and
B a polyol mixture comprising at least one crystallizing polyesterpolyol (b1) which is the reaction product of fumaric acid and 1,6-hexanediol,
wherein the ratio of polyisocyanate component A to polyol component B is chosen so that the molar ratio of NOC to OH is from 1.2 to 4.0, and wherein the hotmelt has a storage modulus of 5×10 4 to 5×10 5 Pa in a temperature range of from 35° C. to 75° C.
2. Reactive polyurethane hotmelts according to claim 1 wherein the fraction of crystallizing polyesterpolyol (b1) in polyol component B amounts to from 15 to 55 weight fractions.
3. Reactive polyurethane hotmelts according to claim 1 , wherein the fraction of crystallizing polyesterpolyol (b1) in polyol component B amounts to from 15 to 30 weight fractions.
4. Reactive polyurethane hotmelts according to claim 1 , further comprising a fraction of at least difunctional crystallizing polyesterpolyols (b2) in polyol component B in amounts to up to 85 weight fractions.
5. Reactive polyurethane hotmelts according to claim 1 , further comprising a fraction of polyesterpolyols liquid at room temperature (b3) in polyol component B in amounts to up to 85 weight fractions.
6. Reactive polyurethane hotmelts according to claim 1 , further comprising a fraction of amorphous polyesterpolyols (b4) in polyol component B in amounts to up to 60 weight fractions.
7. Reactive polyurethane hotmelts according to claim 1 , further comprising a fraction of polyetherpolyols (b5) in polyol component B in amounts to up to 40 weight fractions.
8. Reactive polyurethane hotmelts according to claim 1 , wherein the ratio of polyisocyanate component A to polyol component B is chosen so that the molar ratio of NCO to OH is from 1.3 to 3.0.
9. Process for preparing the reactive polyurethane hotmelts according to claim 1 , comprising
a) mixing the liquid polyols B with an excess of the polyisocyanates A,
b) producing a homogeneous mixture of liquid polyols B and polyisocyanates A, and
c) discharging the homogeneous mixture.
10. Method for adhering a first substrate and a second substrate, comprising
a) applying reactive polyurethane hotmelts according to claim 1 to a first surface of a first substrate,
b) placing a second substrate in contact with the first surface of the first substrate.
11. The process of claim 9 , further comprising the additional step of stirring the mixture until a constant NCO level is obtained.
12. Reactive polyurethane hotmelts according to claim 1 wherein crystallizing polyesterpolyol (b1) has an OH number of 10 to 60 mg KOH/g.
13. Reactive polyurethane hotmelts according to claim 2 wherein crystallizing polyesterpolyol (b1) has an OH number of 10 to 60 mg KOH/g.
14. Reactive polyurethane hotmelts according to claim 3 wherein crystallizing polyesterpolyol (b1) has an OH number of 10 to 60 mg KOH/g.
15. Reactive polyurethane hotmelts according to claim 4 wherein crystallizing polyesterpolyol (b1) has an OH number of 10 to 60 mg KOH/g.
16. Reactive polyurethane hotmelts according to claim 1 wherein crystallizing polyesterpolyol (b1) has an OH number of 20 to 40 mg KOH/g.
17. Reactive polyurethane hotmelts according to claim 2 wherein crystallizing polyesterpolyol (b1) has an OH number of 20 to 40 mg KOH/g.
18. Reactive polyurethane hotmelts according to claim 3 wherein crystallizing polyesterpolyol (b1) has an OH number of 20 to 40 mg KOH/g.
19. Reactive polyurethane hotmelts according to claim 4 wherein crystallizing polyesterpolyol (b1) has an OH number of 20 to 40 mg KOH/g.