Continuous process for preparing a polyurethane latex

• US 6,087,440 A
• Filed: 02/16/1999
• Issued: 07/11/2000
• Est. Priority Date: 02/16/1999
• Status: Expired due to Term

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.)
• Original Assignee: The Dow Chemical Company (Dow, Inc.)
• Inventors: Skaggs, Kenneth W., Louks, Paul T., Willkomm, Wayne R., Tabor, Rick L.
• Primary Examiner(s): NILAND, PATRICK DENNIS
• Application Number:
  US09/250,640
• Time in Patent Office: 511 Days
• Field of Search: 524/591, 524/839, 524/840, 523/335, 523/315
• US Class Current: 524/839
• 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 18/3246 heterocyclic, the heteroatom being oxygen or nitrogen in the form of an amino group
• CPC Class Codes: C08J 2375/00 Characterised by the use of polyureas or polyurethanes; Derivatives of such polymers
• CPC Class Codes: C08J 3/03 in aqueous media

Abstract

A polyurethane/urea/thiourea latex having a narrow molecular weight polydispersity and sub-micron particle size can be prepared by first preparing a high solids (between about 65% and 74% solids) latex of a polyurethane/urea/thiourea prepolymer, then contacting the emulsion with a chain-extending reagent under such conditions to form the polymer latex.

Claims

1. A process for preparing a high solids content polyurethane/urea/thiourea latex comprising the steps of:

a) continuously merging in the presence of an emulsifying and stabilizing amount of a surfactant a first stream containing water flowing at a rate r₁, together with a second stream containing a polyurethane/urea/thiourea prepolymer flowing at a rate r₂, to form a polyurethane/urea/thiourea latex prepolymer; and

b) contacting the latex prepolymer with a chain-extending reagent under such conditions to form a polyurethane/urea/thiourea latex;

wherein the ratio of r₂ ;

r₁ is not less than 65;

35 and less than a ratio required to make a water-continuous HIPR emulsion.

2. The process of claim 1 wherein the polyurethane/urea/thiourea prepolymer is a polyurethane prepolymer or a polyurethane/urea prepolymer and wherein the prepolymer is prepared by contacting a high molecular weight organic compound having at least two active hydrogen atoms with sufficient polyisocyanate, and under such conditions to ensure that the prepolymer is terminated with at least two isocyanate groups.

3. The process of claim 2 wherein the polyurethane prepolymer is prepared by contacting a stoichiometric excess of a polyisocyanate with an amine-terminated polyol or a polyalkylene glycol ether or a polyester polyol, wherein the polyalkylene glycol is a polyethylene ether glycol, a poly-1,2-propylene ether glycol, a polytetramethylene ether glycol, a poly-1,2-dimethylethylene ether glycol, a poly-1,2-butylene ether glycol, or a polydecamethylene ether glycol, or a combination thereof, and wherein the polyester polyol is a polyethylene terephthalate or a polybutylene adipate.

4. The process of claim 3 wherein the polyisocyanate is 4,4'"'"'-diisocyanatodiphenylmethane, 2,4'"'"'-diisocyanatodiphenylmethane, p-phenylene diisocyanate, 2,6-toluene diisocyanate, polyphenyl polymethylene polyisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-diisocyanatocyclohexane, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3'"'"'-dimethyl-4,4'"'"'-biphenyl diisocyanate, 4,4'"'"'-diisocyanatodicyclohexylmethane, 2,4'"'"'-diisocyanatodicyclohexylmethane, isophorone diisocyanate, or 2,4-toluene diisocyanate, or a combination thereof.

5. The process of claim 4 wherein the surfactant is a sulfate of an ethoxylated phenol, an alkali metal alkylbenzene sulfonate, an amine alkylbenzene sulfonate, an alkali metal lauryl sulfate, an amine lauryl sulfate, a polyoxyalkylene, an alkylphenol ethoxylate, or a quaternary ammonium surfactant, or a combination thereof, and the diisocyanate is 4,4'"'"'-diisocyanatodicyclohexyl methane, 2,4'"'"'-diisocyanatodicyclohcxylmethane, or a mixture thereof.

6. The process of claim 1 wherein the chain-extending reagent contains water and the second stream contains a polyurethane/urea/thiourea prepolymer that is terminated with only one isocyanate group.

7. The process of claim 6 wherein the chain-extending reagent contains monoethanol amine, diethanol amine, hydrazine, aminoethylethanolamine, ethylene diamine, propylene-1,2-diamine, propylene-1,3-diamine, tetramethylenediamine, hexamethylenediamine, 4,4'"'"'-dimethylamino-3,3'"'"'-dimethyldiphenylmethane, 4,4'"'"'-diamino-diphenylmethane, 2,4-diaminotoluene, 2,6-diaminotoluene, or piperazine, or a combination thereof.

8. The process of claim 7 wherein the chain-extending reagent is an aqueous solution of piperazine.

9. A process for preparing a high solids content polyurethane/urea/thiourea latex comprising the steps of:

a) continuously merging in the presence of an emulsifying and stabilizing amount of a surfactant a first stream containing water flowing at a rate r₁, together with a second stream containing a polyurethane/urea/thiourea prepolymer flowing at a rate r₂, to form a polyurethane/urea/thiourea latex prepolymer; and

b) contacting the latex prepolymer with a chain-extending reagent under such conditions to form a polyurethane/urea/thiourea latex;

wherein the ratio of r₂ ;

r₁ is not less than 65;

35 and less than a ratio required to make a water-continuous HIPR emulsion, and wherein the prepolymer is prepared from an aromatic diisocyanate.

10. The process of claim 9 wherein the resultant polyurethane/urea/thiourea latex has volume average particle size of less than 1 micron.

11. The process of claim 9 wherein the ratio of r₂ :

r₁ is not less than 70;

30.