Low NMP aqueous polyurethane composition with reactive diluent

1. An aqueous composition with a sediment content ≦5% comprising a polyurethane vinyl hybrid dispersion and containing ≦0.5 wt % of 1-methyl-2-pyrrolidinone by weight of the composition; wherein the polyurethane has an acid value in the range of from 25 to 65 mgKOH/g and is obtained by the reaction of:

A) an isocyanate-terminated prepolymer formed from components comprising:

(i) 36 to 60 wt % of at least one aromatic organic polyisocyanate;

(ii) 0 to 30 wt % of at least one aliphatic organic polyisocyanate;

(iii) 0 to 15 wt % of at least one isocyanate-reactive polyol bearing ionic and/or potentially ionic water-dispersing groups with a weight average molecular weight ≦500 g/mol;

(iv) 0 to 10 wt % of at least one isocyanate-reactive polyol bearing non-ionic water-dispersing groups;

(v) 0 to 15 wt % of at least one isocyanate-reactive polyol with a weight average molecular weight ≦500 g/mol not comprised by (iii) or (iv);

(vi) 20 to 58 wt % of at least one isocyanate-reactive polyol not comprised by (iii), (iv) or (v);

where (i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %;

where the NCO/OH ratio is in the range of from 1.2:1 to 2.5:1; and

B) at least one active-hydrogen chain extending compound;

where the active-hydrogen/NCO ratio is in the range of from 0.4:1 to 1.3:1; in the presence of (a) ≦5 wt % of 1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at least one reactive diluent.

2. An aqueous composition according to claim 1 wherein the ratio of polyurethane to vinyl polymer in the polyurethane vinyl hybrid is in the range of from 95:5 to 30:70.

3. An aqueous composition according to claim 1 wherein the calculated Tg of the vinyl polymer in the polyurethane vinyl hybrid is in the range of from 20 to 120° C.

4. An aqueous composition according to claim 1 wherein at least 20 to 80 wt % of component (i) consists of methylenebis(phenyl isocyanate) (MDI).

5. An aqueous composition according to claim 1 where components (i)+(ii)+(iii)+(v) add up to ≧42 wt %.

6. An aqueous composition according to claim 1 wherein the reactive diluent comprises between 5 and 40% by weight of both the isocyanate-terminated prepolymer and the reactive diluent together.

7. An aqueous composition according to claim 1 wherein the reactive diluent comprises vinyl monomers.

8. An aqueous composition according to claim 7 wherein the reactive diluent comprises 40 to 100 wt % of vinyl monomer selected from the group consisting of methyl methacrylate and ethylmethacrylate.

9. An aqueous composition according to claim 7 wherein the reactive diluent comprises <45 wt % of styrene and styrene based vinyl monomers.

10. An aqueous composition according to claim 1 wherein the ionic water-dispersing groups in the isocyanate-terminated prepolymer are neutralised with a neutralising agent in the range of from 0.5:1 to 1.4:1.

11. An aqueous composition according to claim 1 wherein the ionic-water-dispersing groups are anionic water-dispersing groups and ≧60 wt % of the anionic water-dispersing groups in the isocyanate-terminated prepolymer are neutralised with an oxygen containing amine.

12. An aqueous composition according to claim 11 where the oxygen containing amine is selected from the group consisting of N-ethyl morpholine; N-methyl morpholine; and R 1 (R 2 )NR 3 OH with a Mn in the range of from 88 to 118, where R 1 , R 2 and R 3 are independently C 1 to C 4 alky.

13. An aqueous composition according to claim 1 which when in the form of film has a König Hardness ≦120s.

14. An aqueous composition according to claim 1 which when in the form of a film has an elongation at break ≧50% and a König Hardness ≧120s.

15. An aqueous composition according to claim 1 with a minimum film forming temperature≦500 C.

16. An aqueous composition according to claim 1 , containing ≦2 wt % of a co-solvent by weight of the composition with a minimum film forming temperature ≦23° C. and which when in the form of a film has a König Hardness 120s.

17. An aqueous composition according to claim 1 with a solids content in the range of from 20 to 55 wt %.

18. An aqueous composition according to claim 1 with a weight average particle size less than 500 nm.

19. A substrate having a coating obtained from an aqueous composition according to claim 1 .

20. A substrate according to claim 19 selected from the group consisting of wood, metal, concrete, plastic and glass.

21. A floor having a coating obtained from an aqueous composition according to claim 1 .

22. An aqueous composition according to claim 1 , wherein all of the isocyanate groups are directly bonded to an aromatic group, irrespective of whether aliphatic groups are also present.

23. A process for making an aqueous composition with a sediment content ≦5% comprising a polyurethane vinyl hybrid dispersion and containing ≦0.5 wt % of 1-methyl-2-pyrrolidinone by weight of the composition, wherein the polyurethane has an acid value in the range of from 25 to 65 mgKOH/g, and where the process is carried out in steps comprising:

I: reacting in the presence of (a) ≦5 wt % of 1-methyl-2-pyrrolidinone by weight of polyurethane and (b) at least one reactive diluent;

(i) 36 to 60 wt % of at least one aromatic polyisocyanate;

(ii) 0 to 30 wt % of at least one aliphatic polyisocyanate;

(iii)0 to 15 wt % of at least one isocyanate-reactive polyol bearing ionic and/or potentially ionic water-dispersing groups with a weight average molecular weight ≦500 g/mol;

(iv) 0 to 10 wt % of at least one isocyanate-reactive polyol bearing non -ionic water-dispersing groups;

(v) 0 to 15 wt % of at least one isocyanate-reactive polyol with a weight average molecular weight ≦500 g/mol not comprised by (iii) or (iv);

(vi) 20 to 58 wt % of at least one isocyanate-reactive polyol not comprised by (iii), (iv) or (v);

where (i)+(ii)+(iii)+(iv)+(v)+(vi) add up to 100 wt %;

where the NCO/OH ratio is in the range of from 1.2:1 to 2.5:1 to form an isocyanate-terminated prepolymer;

II: neutralising the isocyanate-terminated prepolymer with a neutralising agent;

III: forming an aqueous dispersion of the isocyanate-terminated prepolymer in water;

IV: reacting the isocyanate-terminated prepolymer with at least one active hydrogen chain-extending compound to form the polyurethane; where the active hydrogen/NCO ratio is in the range of from 0.4:1 to 1:3:1;

V: optionally adding additional vinyl monomer; VI: polymerising the reactive diluent and vinyl monomer added in step V.

24. A process according to claim 23 where step II is carried out by means of at least an in-line mixer.

25. A process according to claim 23 where the time between step III and step IV is less than 40 minutes.

26. A process according to claim 23 where at least 50 wt % of the active-hydrogen chain extending compound is present in the water before completion of step III.

27. A method of coating a substrate using an aqueous composition according to claim 1 comprising applying the composition to a substrate.