Aqueous, highly cross-linked two-component polyurethane coating system, method for the production and use thereof

• US 20050027092A1
• Filed: 04/23/2004
• Published: 02/03/2005
• Est. Priority Date: 10/25/2001
• Status: Active Grant

• Current Assignee: Construction Research & Technology GmbH (BASF SE)
• Original Assignee: Degussa Construction Chemicals GmbH (Compagnie De Saint-Gobain S.A.)
• Inventors: Maier, Alois, Wolfertstetter, Franz, Steidl, Norbert
• Granted Patent: US 7,825,210 B2
• Time in Patent Office: Days
• US Class Current: 528/44
• CPC Class Codes: C08G 18/0823 containing carboxylate salt groups or groups forming them
• CPC Class Codes: C08G 18/12 using two or more compounds having active hydrogen in the first polymerisation step
• CPC Class Codes: C08G 18/3206 aliphatic
• CPC Class Codes: C08G 18/3275 containing two hydroxy groups
• CPC Class Codes: C08G 18/348 Hydroxycarboxylic acids
• CPC Class Codes: C08G 18/4277 Caprolactone and/or substituted caprolactone
• CPC Class Codes: C08G 18/44 Polycarbonates
• CPC Class Codes: C08G 18/6659 with compounds of group C08G18/34
• CPC Class Codes: C08G 18/792 formed by oligomerisation of aliphatic and/or cycloaliphatic isocyanates or isothiocyanates
• CPC Class Codes: C09D 175/04 Polyurethanes

Abstract

An aqueous highly cross-linked two-component polyurethane coating system is described with reduced hydrophilicity and improved resistance to chemicals which can be obtained by a) producing a binder component based on an aqueous solution or dispersion of low-molecular hydroxyfunctional and/or aminofunctional oligourethanes or polyurethanes and b) by subsequently reacting the binder component a) with a cross-linking component (H) in a ratio of 3:1 to 5:1, wherein water-dispersible polyisocyanates are used as the cross-linking component (H).

Claims

1. An aqueous highly cross-linked two-component polyurethane coating system formed by a process comprising:

a) producing a binder component based on an aqueous solution or dispersion of low-molecular hydroxyfunctional and/or aminofunctional oligourenthanes or polyurethanes, wherein

a₁) forming polyurethane preadduct by reacting 10 to 50 parts by weight of a higher-molecular polyol component (A)(i) containing two or more hydroxyl groups that are reactive with polyisocyanates and having a molecular mass of 500 to 5000 Daltons and 0 to 5 parts by weight of a low-molecular polyol component (A)(ii) containing two or more hydroxyl groups that are reactive with polyisocyanates and having a molecular mass of 50 to 499 Daltons with 2 to 20 parts by weight of a polyisocyanate component (B) consisting of at least one polyisocyanate, polyisocyanate derivative or polysocyanate homologue containing two or more aliphatic or aromatic isocyanate groups with addition of 0 to 6 parts by weight of a solvent component (C);

a₂) forming free isocyanate groups of polyurethane prepolymer by reacting the polyurethane preadduct from step a₁) with 0.1 to 1.5 parts by weight of a low-molecular and anionically modifiable polyol component (A)(iii) containing one or more hydroxyl groups that are reactive with polyisocyanates and one or more inert carboxylic acid and/or sulfonic acid group(s) which can be partially or completely converted into carboxylate or sulfonate groups in the presence of bases or are already present in the form of carboxylate and/or sulfonate groups, having a molecular mass of 100 to 499 Daltons and/or with 0 to 8 parts by weight of a polymeric diol component (A)(iv) containing two or more hydroxyl groups that are reactive with polyisocyanates and other hydrophilic groups that are inert towards polyisocyanates having a molecular mass of 500 to 5000 Daltons;

a₃) forming a multifunctional polyurethane oligomer or polymer by reacting the free isocyanate groups of the polyurethane prepolymer from step a₂) with 0.1 to 15 parts by weight of a multifunctional chain stopping component (D) containing three or more hydroxyl groups and/or primary and/or secondary amino groups that are reactive with isocyanate groups and having a molecular mass of 50 to 500 Daltons, one of which reacts with the polyurethane preadduct;

a₄) reacting the multifunctional polyurethane oligomer or polymer from step a₃)with 0.1 to 1 parts by weight of a neutralization component (E) to partially or completely neutralize the acidic groups and to form neutralized polyurethane oligomer or polymer; and

a₅) dispersing the neutralized polyurethane oligomer or polymer from step a₄) in 40 to 60 parts by weight of water which also contains 0 to 50 parts by weight of a formulation component (F) to form a binder component; and

b) reacting the binder component from step a₅) with a cross-linking component (H) in a ratio of 3;

1 to 5;

1, wherein the cross-linking component (H) comprises water-dispersible polyisocyanates containing aliphatically and/or cycloaliphatically and/or aromatically bound isocyanate groups which can contain 0 to 20 parts by weight of an organic solvent.

2. The polyurethane coating system as claimed in claim 1, comprising:

a₆) reacting the partially chain-terminated polyurethane oligomer or polymer from step a₅) with 0 to 15 parts by weight of a chain extending component (G) containing two or more primary and/or secondary amino groups that are reactive with isocyanate groups and having a molecular mass of 50 to 500 Daltons.

3. The polyurethane coating system as claimed in claim 1, wherein the highermolecular polyol component (A)(I) comprises polyalkylene glycols, aliphatic or aromatic polyesters, polycarprolactones, polycarbonates, α

, ω

-polymethacrylatedioles, α

, ω

-dihydroxyalkylpolydimethylsiloxanes, hydroxyfunctional macro-monomers, hydroxyfunctional telechels, hydroxyfunctional epoxide resins having a molecular mass of 1000 to 3000 Dalton or suitable mixtures thereof.

4. The polyurethane coating system as claimed claim 1 wherein the component (A)(i) is linear or difunctional hydrophobically modified polyether polyols consisting of saponification-resistant block copolymers having an ABA, BAB or (AB)_n structure in which A represents a polymer segment with hydrophobizing properties and B represents a polymer segment based on polypropylene oxide having an average molecular mass or 1000 to 3000 Daltons.

5. The polyurethane coating system as claimed in claim 1, wherein the component (A)(ii) is 1,4-butanediol.

6. The polyurethane coating system as claimed in claim 1, wherein the component (A)(iii) comprises a bishydroxyalkanecarboxylic acid and/or bishydroxysulfonic acid or alkali salts thereof having a molecular mass of 100 to 499 Daltons.

7. The polyurethane coating system as claimed in claim 6, wherein the bishydroxyalkanecarboxylic acid comprises 2-hydroxymethyl-2-methyl-3-hydroxypropionic acid or dimethylol-propionic acid.

8. The polyurethane coating system as claimed in claim 1, wherein the component (A)(iv) comprises reaction products of poly(ethylene oxide[-co/block/ran-propylene oxide])-monoalkyl ethers, a diisocyanate and diethanolamine.

9. The polyurethane coating system as claimed in claim 1, wherein the multifunctional chain-stopper component (D) comprises aliphatic of cycloaliphatic polyols and/or polyamines and/or amino-alcohols.

10. The polyurethane coating system as claimed in claim 9, wherein the multifunctional chain-stopper component (D) comprises diethanalamine and/or trimethylopropane.

11. The polyurethane coating system as claimed in claim 1, wherein the formulation component (F) comprises antifoaming agents, deaerators, lubricating and flow-control additives, radiation hardening additives, dispersing additives, substrate wetting additives, hydrophobizing agents, rheology additives such as polyurethane thickeners, coalescing agents, dulling agents, bonding agents, antifreeze agents, antioxidants, UV stabilizers, bactericides, fungicides, other polymers and/or polymer dispersions as well as fillers, pigments, dulling agents or suitable combinations thereof.

12. The polyurethane coating system as claimed in claim 1, wherein the cross-linking component (H) comprises water-dispersible polyisocyanates containing aliphatically and/or cycloaliphatically and/or aromatically bound isocyanate groups which contain 0 to 20 parts by weight of an organic solvent.

13. The polyurethane coating system as claimed in claim 1, wherein the NCO/OH equivalent ratio of components (A) and (B) is adjusted to a value of 1.25 to 2.5.

14. The polyurethane coating system as claimed in claim 13, wherein the NCO/OH equivalent ratio of components (A) and (B) is adjusted to a value of 1.5 to 2.25.

15. The polyurethane coating system as claimed in claim 1, wherein the reactions of steps a₁) and a₂) are carried out in the presence of 0.01 to 1 weight % based on the components (A) and (B) of a conventional catalyst for polyaddition reactions on polyisocyanates.

16. The polyurethane coating system as claimed in claim 1, wherein the chainstopper component (D) is added in such an amount that the degree of chain termination based on the free isocyanate groups of the polyurethane prepolymer comprising components (A) and (B) is 80 to 100 equivalent %.

17. The polyurethane coating system as claimed in claim 1, wherein the neutralization component (E) is added in such an amount that the degree of neutralization based on the free carboxylic acid and/or sulfonic acid groups of the polyurethane oligomer or polymer consisting of components (A), (B) and (D) is 70 to 100 equivalent %.

18. The polyurethane coating system as claimed in claim 17, wherein the degree of neutralization 80 to 90 equivalent %.

19. The polyurethane coating system as claimed in claim 2, wherein the chain extending component (G) is added in such an amount that the degree of chain extension based on the free isocyanate groups of the polyurethane oligomer or polymer consisting of components (A), (B), (D) and (E) is 0 to 20 equivalent %.

20. The polyurethane coating system as claimed in claim 19, wherein the solids content of polyurethane oligomer or polymer consisting of components (A), (B), (D), (E) and (G) is adjusted to 35 to 70 weight %, based on the total amount of the aqueous binder component consisting of components (A) to (E) and (G).

21. The polyurethane coating system as claimed in claim 20, wherein the solids content is adjusted to 45 to 55 weight %.

22. The polyurethane coating system as claimed in claim 20, wherein an average particle size of micelles of the aqueous binder component consisting of components (A) to (E) and (G) is 10 to 300 nm.

23. The polyurethane coating system as claimed in claim 2, wherein the polyurethane oligomer or polymer consisting of the components (A), (B), (D), (E) and (G) has an average molecular mass of 1000 to 20,000 Daltons.

24. The polyurethane coating system as claimed in claim 1, wherein the NCO/(OH+NH₍₂₎)-equivalent ratio of the isocyanate groups of the cross-linking component and the hydroxyl and/or amino groups of the binder component is adjusted to 1.1 to 1.6.

25. The polyurethane coating system as claimed in claim 24, wherein the NCO/(OH+NH₍₂₎)-equivalent ratio is 1.2 to 1.4.

26. Method of producing the aqueous two-component polyurethane coating system of claim 1, comprising

a₁) reacting the components (A)(i), (A)(ii), (B) and (C) to form a polyurethane preadduct during which reacting the hydroxyl groups of components (A)(i) and (A)(ii) with the isocyanate groups of component (B);

a₂) reacting the polyurethane preadduct from reaction step a₁) with components (A)(iii) and (A)(iv) to form an anionically modifiable polyurethane prepolymer;

a₃) reacting the anionically modifiable polyurethane prepolymer from reaction step a₂) with component (D) so that in each case only one reactive group of component (D) reacts with one isocyanate group of the polyurethane preadduct;

a₄) reacting the functionalized and anionically modifiable polyurethane oligomer and polyurethane polymer from reaction step a₃) which has two or more reactive groups per chain end and a total functionality of 4 with component (E) for partial or complete neutralization;

a₅) dispersing the functionalized and anionically modifiable polyurethane oligomer or polyurethane polymer from reaction step a₄) in water; and

b) reacting the binder component from reaction step a₅) with the hydrophillicatlly modified cross-linking component (H), the cross-linking component (H) being added to the binder component, and obtaining a highly cross-linked polyurethane coating system with reduced hydrophilicity and improved chemical resistance.

27. The method of claim 26, wherein in step a₅) the water also contains the component (F).

28. The method of claim 26, comprising:

a₆) reacting the only partially chain-stopped, functionalized and anionically modified polyurethane oligomer or polyurethane polymer from step a₅) with component (G).

29. The method of claim 26, wherein steps a₄) and a₅) are combined in such a manner that component (E) is added to the water before dispersion.

30. The method of claim 26, wherein steps a₄) and a₅) are combined in such a manner that component (G) is added to the water before dispersion.

31. The method of claim 26, wherein steps a₁) and a₃) are carried out at a temperature of 60 to 120°

C.

32. The method of claim 31, wherein steps a₁) and a₃) are carried out at a temperature of 80 to 100°

C.

33. The method of claim 26, wherein step a₄) is carried out at a temperature of 40 to 65°

C.

34. The method of claim 33, wherein step a₄) is carried out at 50°

C.

35. The method of claim 26, wherein step b) is carried out at a temperature of 20 to 40°

C.

36. The method of claim 35, wherein step b) is carried out at a temperature of 20°

C.

37. A coating for surfaces, comprising the aqueous two-component polyurethane coating system of claim 1, wherein the coating is used as formulated or unformulated chemical-resistant and lightfast paint for surfaces of mineral building materials, such as concrete, plaster, ceramics, clay, cement, as well as for surfaces of glass, rubber, wood and derived timber products, plastic, metal, paper, composite materials, leather, and as a binder for hardening hydraulic binders.

38. Construction coating material comprising the aqueous two-component polyurethane coating system of claim 1, individually or in combination, wherein the material is used for coating indoor floors, balconies, parking decks and multi-store parking garages.