2K polyurethane systems with a high glass-transition temperature

Abstract

A two-component polyurethane composition with a viscosity of 20 to 3000 mPa.Math.s (EN ISO 2555, 25 C.), containing i) 10 to 80 wt. % of at least one polyol with a number-average molecular weight of 200 g/mol to 3000 g/mol, ii) 5 to 70 wt. % of at least one polyisocyanate, iii) 0 to 10 wt. % of a catalyst, wherein the composition has an NCO:OH ratio of 2:1 to 1:2 and polyisocyanates are used, wherein 3 to 25 mol % of the NCO groups of the polyisocyanate are converted into carbodiimide and/or uretonimine. The two-component polyurethane compositions are used as matrix binders for fiber composite moldings.

Claims

1. A two-component polyurethane composition consisting of a polyol component and a polyisocyanate component, containing 10 to 80 wt. % based on weight of the composition of the polyol component comprising at least one polyol with a number-average molecular weight of 200 g/mol to 3000 g/mol, 5 to 70 wt. % based on weight of the composition of the polyisocyanate component comprising at least one polyisocyanate, wherein 3 to 25 mol % of the NCO groups of the polyisocyanate are converted into carbodiimides and/or uretonimine, 0 to 10 wt. % based on weight of the composition of additives, the additives being present in the polyol component, the polyisocyanate component or both the polyol component and the polyisocyanate component, wherein the composition is free of polyester polyols and a mixture of the polyol component and the polyisocyanate component has an NCO:OH ratio of 2:1 to 1:2, a viscosity of 20 mPa.Math.s to 3000 mPa.Math.s (EN ISO 2555, 25 C.) immediately after mixing, and crosslinked products of the mixture have a glass transition temperature T.sub.g above 60 C.

2. The two-component polyurethane composition according to claim 1, wherein the mixture has a viscosity of below 1000 mPa.Math.s (25 C.).

3. The two-component polyurethane composition according to claim 1, wherein MDI and the carbodiimide and/or uretonimine derivatives thereof are present as the polyisocyanate.

4. The two-component polyurethane composition according to claim 1, wherein polyether polyols with an average functionality of greater than 2.5 are used as polyols.

5. The two-component polyurethane composition according to claim 1, wherein the crosslinked products of the mixture have a glass transition temperature T.sub.g above 100 C.

6. The two-component polyurethane composition according to claim 1, wherein the additives are selected from the group consisting of stabilizer, catalyst, release agent, solvent, plasticizer, pigment, leveling agent, wetting agent, antioxidant, dye, resin and combinations thereof.

7. The two-component polyurethane composition according to claim 6, wherein the catalyst is a tertiary amine or a Sn, Ti, or Bi compound.

8. The two-component polyurethane composition according to claim 6, wherein the catalyst is a Sn catalyst with a cyclic complexing agent selected from cyclic -hydroxyketone or 1-alkyl-2,3,4-triphenol derivative or cyclic tertiary amine.

9. The two-component polyurethane composition according to claim 1, characterized in that the composition is free of catalysts.

10. The two-component polyurethane composition according to claim 1, wherein the composition is free of solvents, plasticizers, carboxylic acids and pigments.

11. A method for producing fiber composite materials, wherein an external mold is filled with fiber materials and the two-component polyurethane composition according to claim 1 is introduced under pressure into said mold.

12. A method for producing fiber composite materials, wherein an external mold filled with fiber materials is provided and the two-component polyurethane composition according to claim 1 is introduced with application of a vacuum.

13. The method according to claim 11, wherein the fiber content amounts to greater than or equal to 60 volume-%, relative to the fiber composite material.

14. The method according to claim 13, wherein the mixture is crosslinked at a temperature of up to 120 C.

Description

EXAMPLES

(1) The following examples illustrate the invention.

Example 1

(2) Component A

(3) Polyether triol (amine-free, M.sub.n approximately 350)
Component B 4,4-MDI (13% of the NCO groups as uretonimine) NCO:OH ratio 1.2:1

(4) Method: the components are mixed together with 0.05% Sn catalyst with exclusion of moisture in a vessel with a high-speed stirrer, the mixture thereafter being degassed under a vacuum with stirring. Viscosity (2 minutes): approximately 200 mPa.Math.s

(5) Test specimens (4 mm) were cast from the mixtures and crosslinked for 45 minutes at 95 C. and 60 minutes at 150 C. Modulus of elasticity <2200 MPa.

Example 2

(6) Mixtures of the MDI with a fixed carbodiimide/uretonimine content are stored at different temperatures for a period of 3 or 6 months and checked for stability.

(7) TABLE-US-00001 Carbodiimide/ 2,4-/4,4-MDI uretonimine 6 months 3 months 6 months mixtures content at 12 C. at 23 C. at 23 C. 50% 2,4-MDI 0% sediment turbid turbid 10% OK OK OK 35% 2,4-MDI 0% turbid turbid turbid 5% OK OK OK 10% OK OK OK

(8) The tests reveal improved storage stability of the isocyanate component in the presence of carbodiimide/uretonimine.