Block-resistant, radiation-curable coating systems based on high molecular mass, aqueous polyurethane dispersions

• US 8,231,976 B2
• Filed: 04/24/2009
• Issued: 07/31/2012
• Est. Priority Date: 04/28/2008
• Status: Active Grant

• Current Assignee: Covestro Deutschland AG
• Original Assignee: Bayer Materialscience AG (Covestro AG)
• Inventors: Sommer, Stefan, Weikard, Jan, Luehmann, Erhard
• Primary Examiner(s): Tran, Thao T.
• Application Number:
  US12/429,398
• Publication Number:
  US 20090269589A1
• Time in Patent Office: 1,194 Days
• Field of Search: 428/423.1, 428/425.1, 525/123
• US Class Current: 428/425.1
• 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 18/423 containing cycloaliphatic groups
• CPC Class Codes: C08G 18/6659 with compounds of group C08G18/34
• CPC Class Codes: C08G 18/673 containing two or more acrylate or alkylacrylate ester groups
• CPC Class Codes: C08G 18/722 Combination of two or more aliphatic and/or cycloaliphatic polyisocyanates
• CPC Class Codes: C08G 18/758 containing two or more cycloaliphatic rings
• CPC Class Codes: C09D 175/16 having terminal carbon-to-carbon unsaturated bonds
• CPC Class Codes: Y10T 428/31591 Next to cellulosic

Abstract

The present invention describes block-resistant, radiation-curable coating systems based on high molecular mass, aqueous polyurethane dispersions, a process for preparing them, the use of the coating systems as paints and/or adhesives, and also articles and substrates provided with these paints and/or adhesives.

Claims

1. Coating systems based on radiation-curing, aqueous polyurethane dispersions comprising

I) polyurethanes obtained from

A) 40% to 80% by weight of a hydroxyl-containing component comprising

A1) 10% to 80% by weight, based on the sum of components (A) to (F) and (II), of one or more hydroxyl-containing prepolymers selected from the group consisting of polyester (meth)acrylates or polyether (meth)acrylates having an OH number of from 5 to 300 mg KOH/g solids and comprising groups which, on exposure to high-energy radiation, undergo polymerization reaction with ethylenically unsaturated double bonds,

A2) 0% to 50% by weight, based on the sum of components (A) to (F) and (II), of one or more monomeric alcohols containing (meth)acrylate groups and having an OH number of from 35 to 1000 mg KOH/g solids,

B) 0.1% to 20% by weight of one or more compounds which are reactive towards isocyanate groups and contain groups which are non-ionic, ionic or capable of forming ionic groups and have a dispersing action for the polyurethane dispersion,

C) 0.1% to 30% by weight of a hydroxyl- and/or amine-containing component comprising

C1) 0.1% to 10% by weight, based on the sum of components (A) to (F) and (II), of hydroxyl- and/or amine-functional monomeric compounds having a functionality of 3 to 6 and a molecular weight of from 92 to 254 g/mol

and/or

C2) 0.1% to 20% by weight, based on the sum of components (A) to (F) and (II), of hydroxy- and/or amine-functional polyesters, C2, C3 and/or C4 polyethers and polyetheresters having a functionality of 2.3 to 4.0 and a molecular weight of from 238 to 4000 g/mol,

D) 0% to 30% by weight, based on the sum of components (A) to (F) and (II), of hydroxyl-functional compounds selected from the group of monoalcohols and/or diols, each with a molecular weight in the range from 32 to 118 g/mol, polyesters, polycarbonates, C2, C3, and/or C4 polyethers, polyetheresters and polycarbonate polyesters having a functionality of 1.0 to 2.0, in each case with a molecular weight in the range from 300 to 4000 g/mol,

E) 0.1% to 10% by weight, based on the sum of components (A) to (F) and (II), of monoamines, diamines and/or difunctional amino alcohols, with

F) 10% to 50% by weight, based on the sum of components (A) to (F) and (II), of one or more polyisocyanates,

with the proviso that the use of polyepoxy(meth)acrylates in the synthesis of (I) is excluded, and

II) 0% to 40% by weight of oligo(meth)acrylates selected from the group of component (A1) with a double bond density of more than 2.0 mol of double bonds/kg of solids and, on exposure to high-energy radiation, undergoing polymerization reaction with ethylenically unsaturated compounds,

the fractions of components (A) to (F) and of component (II) adding up to 100% by weight, and the mixture of (I) and (II) that is present in the coating system having a weight-average molar mass MW of 50,000 to 3,000,000 g/mol.

2. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 1, wherein component (C1) comprises aliphatic or cycloaliphatic triols, tetrols, hexols, triamines and/or tetraamines containing 3 to 10 carbon atoms.

3. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 1, wherein component (C1) comprises glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, glucose, fructose, diethylenetriamine and/or triethylenetetraamine.

4. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 1, wherein component (C2) comprises polyester alcohols selected from the group of the reaction products of adipic acid, isophthalic acid and phthalic anhydride with trimethylolpropane, glycerol, pentaerythritol, hexanediol, butanediol, diethylene glycol, monoethylene glycol or neopentyl glycol or mixtures of the stated diols.

5. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 4, wherein the polyester alcohols have a molecular weight of 300 to 4000 g/mol.

6. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 1, component (C2) comprises polyethylene glycols, polypropylene glycols and/or polytetrahydrofurans.

7. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 1, wherein the mixture of (I) and (II) that is present therein has a weight-average molar mass MW of 100 000 to 2 000 000 g/mol.

8. Coating systems based on radiation-curing, aqueous polyurethane dispersions according to claim 1, wherein there are at least initiator and, if desired, further auxiliaries and additives present that allow curing with high-energy radiation.

9. Process for preparing the coating systems according to claim 1, comprising the following steps:

i) reacting components A) to D) with component F) to give polyurethane prepolymers,

ii) admixing component II with the reaction product of step i), and

iii) dispersing the mixture obtained after step ii) in water to give an aqueous polyurethane dispersion,

the (potentially) ionic groups introduced, if appropriate, with component B) being at least partly neutralized before, during or after the admixing of component II, or before, during or after the dispersing, and

the polyurethane prepolymers being reacted with component E at any point in time after step i) that is possible.

10. Process according to claim 9, wherein the reaction of the remaining free isocyanate groups of the polyurethane prepolymers with component (E) takes place to an extent of 80% to 110%.

11. Process according to claim 9, wherein the difference between the NCO content at the end of step i) and the theoretically attainable NCO content is 2.0% to −

1.0% by weight.

12. Adhesives or paints comprising a coating system according to claim 1.

13. Substrates coated with a paint according to claim 12.

14. Substrates according to claim 13, the substrate being selected from the group consisting of mineral underbases, wood, wood-based materials, furniture, wood block flooring, doors, window frames, metallic articles, plastics, paper, paperboard, cork, mineral substrates, textiles and leather.

15. Dual-cure-systems comprising a coating system according to claim 1.