POLYURETHANE DISPERSIONS AND COATINGS PRODUCED THEREFROM

• US 20100273939A1
• Filed: 12/09/2008
• Published: 10/28/2010
• Est. Priority Date: 12/26/2007
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Inventors: Stollmaier, Friederike, Roser, Jean-Luc, Grassini, Stefano Carlo E, Skaggs, Kenneth W., Radhakrishnan, Bindushree
• Granted Patent: US 8,362,142 B2
• Time in Patent Office: Days
• US Class Current: 524/590
• CPC Class Codes: C08G 18/0866 the dispersing or dispersed phase being an aqueous medium
• CPC Class Codes: C08G 18/12 using two or more compounds having active hydrogen in the first polymerisation step
• CPC Class Codes: C08G 18/283 Compounds containing ether groups, e.g. oxyalkylated monohydroxy compounds
• CPC Class Codes: C08G 18/3212 containing cycloaliphatic groups
• CPC Class Codes: C08G 18/3218 containing cyclic groups having at least one oxygen atom in the ring
• CPC Class Codes: C08G 18/3228 acyclic
• CPC Class Codes: C08G 18/3231 Hydrazine or derivatives thereof
• CPC Class Codes: C08G 18/4808 Mixtures of two or more polyetherdiols
• CPC Class Codes: C08G 18/4812 Mixtures of polyetherdiols with polyetherpolyols having at least three hydroxy groups
• CPC Class Codes: C08G 18/4845 containing oxypropylene or higher oxyalkylene end groups
• CPC Class Codes: C08G 18/4883 containing cyclic groups having at least one oxygen atom in the ring
• CPC Class Codes: C08G 18/6677 having at least three hydroxy groups
• CPC Class Codes: C08G 18/755 and at least one isocyanate or isothiocyanate group linked to a secondary carbon atom of the cycloaliphatic ring, e.g. isophorone diisocyanate
• CPC Class Codes: Y10T 428/31551 Of polyamidoester [polyurethane, polyisocyanate, polycarbamate, etc.]

Abstract

The present invention discloses polyurethane dispersions based on aliphatic isocyanates which form hard coatings wherein the coatings also have good solvent resistant properties. The enhanced properties of the coatings are achieved by including from 1 to 8 weight percent of a high functional polyol in the polyol formulation for producing the dispersions.

Claims

1. An aqueous polyurethane dispersion containing polyurethane solids and a non-aqueous, organic solvent content of less than 5 weight percent wherein the polyurethane solids are obtained from a polyurethane prepolymer prepared by reacting

a) a polyol comprising

ai) from 92 to 99 wt % of a polyol or polyol blend having a mean average equivalent weight of 150 to 600 and a nominal average functionality of from 1.5 to 2.9 and

aii) from 1 to 8 wt % of at least one polyol having a nominal functionality of 4 to 8;

and an equivalent weight of 100 to 170;

(b) at least one aliphatic polyisocyanate;

(c) optionally additional stabilizers; and

(d) optionally chain extenders

wherein the prepolymer has an isocyanate (NCO) content of from 2 to 20 wt %, or wherein the solids content of the dispersion is from 30 to 60 weight percent, or wherein the solids content of the dispersion is from 40 to 60 weight percent.

4. The dispersion of claim 1 wherein the isocyanate is, 6-hexamethylene-diisocyanate (HDI);

isophorone diisocyanate (IPDI);

2,4- and 2,6-hexahydrotoluene-diisocyanate;

4,4′

-, 2,2′

- and 2,4′

-dicyclohexylmethanediisocyanate (H12MDI);

tetramethyl xylene diisocyanate, norbornane diisocyanate;

1,3- and 1,4-(bisisocyanatomethyl)cyclohexane (including cis- or trans-isomers thereof);

tetramethylene-1,4-diisocyanate (TMXDI);

cyclohexane 1,4-diisocyanate;

4,4′

-dicyclohexylmethane diisocyanate;

xylene diisocyanate;

1,12-dodecane diisocyanate;

2,2,4-trimethylhexamethaylene diisocyanate;

or a mixture thereof.

6. The dispersion of claim 1 wherein polyol ai) has an average nominal functionality from 1.8 to 2.4, or wherein polyol ai) has a mean average equivalent weight of 75 to 500, or wherein polyol ai) is one or more polyether diols, or wherein polyol aii) comprises from 2 to 6 weight percent of the total polyol a), or wherein the polyol aii) has a mean average equivalent weight of 105 to 160, or wherein the dispersion contains less than 2.5 weight percent of an organic solvent, or wherein the prepolymer is made in the presence of a solvent and the solvent is substantially removed prior to dispersion of the prepolymer in water, or wherein the isocyanate content of the prepolymer is from 4 to 18 weight percent, or wherein the isocyanate content of the prepolymer is from 6 to 12 weight percent, or wherein the dispersion is stabilized by the use of an external surfactant.

18. The dispersion of claim 1 wherein the dispersion is made in a continuous process.

20. The use of the polyurethane dispersion of claim 1 to make a hard coating on a surface.

2. (canceled)

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21. An isocyanate terminated prepolymer comprising

a) a polyol having

ai) from 92 to 99 wt % of a polyol or polyol blend having a mean average equivalent weight of 150 to 600 and a nominal average functionality of from 1.5 to 2.9;

and

aii) from 1 to 8 wt % of at least one polyol having a nominal functionality of 4 to 8; and

an equivalent weight of 100 to 170; and

(b) at least one aliphatic polyisocyanate;

wherein the prepolymer has a free isocyanate content of from 2 to 20 wt %.