Waterborne polyurethane (WPU) emulsion and preparation method therefor

Abstract

The present disclosure provides a waterborne polyurethane (WPU) emulsion and a preparation method therefor, and relates to the technical field of glove processing. The WPU emulsion of the present disclosure is prepared from polyol, isocyanate, a hydrophilic chain extender, a diluent, a neutralizer, a post chain extender, water, a catalyst, a cellulose thickener, a wetting agent, and a dispersant. The WPU emulsion of the present disclosure is used to dip knitted gloves, which can improve abrasion resistance and flexibility of the gloves, prolong service life of the gloves, and improve wearing comfort of the gloves.

Claims

1. A method of preparing a waterborne polyurethane (WPU) emulsion, the WPU emulsion comprising the following raw materials in part by weight: 230-250 parts of polyol, 50-60 parts of isocyanate, 5-10 parts of a hydrophilic chain extender, 60-80 parts of a diluent, 5-9 parts of a neutralizer, 500-600 parts of water, 15-20 parts of a post chain extender, 0.01-0.05 parts of a catalyst, 3-7 parts of a cellulose thickener, 0.5-1.5 parts of a wetting agent, and 3-5 parts of a dispersant; and the method comprising the following steps: step I: preparation of isocyanate terminated prepolymer adding the polyol and the hydrophilic chain extender into a reactor, adding the isocyanate while stirring at 150-200 r/min, adding the catalyst after a temperature rises to 75-85? C., introducing nitrogen, and conducting heat preservation for 3 h to obtain the isocyanate terminated prepolymer; step II: neutralization when the temperature in the reactor is reduced to be no more than 60? C., adding the diluent and the neutralizer to neutralize the isocyanate terminated prepolymer to obtain a neutralized prepolymer; step III: emulsification at 20? C., adding the neutralized prepolymer in step II into the water to obtain a mixture, and stirring the mixture at 3,000-3,500 r/min for 30 min to form a dispersion; step IV: post chain extension at 450-500 r/min, adding the post chain extender to the dispersion in step III, and stirring for 30 min to obtain a WPU dispersion, wherein a particle size is limited to 20-30 ?m during chain extension; and step V: preparation of emulsion adding the cellulose thickener, the wetting agent, and the dispersant into the WPU dispersion, and stirring for 30 min to obtain the WPU emulsion.

2. The method according to claim 1, wherein the polyol is one or more selected from the group consisting of polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, polysiloxane polyols, and polytetrahydrofuran (PTHF).

3. The method according to claim 1, wherein the isocyanate is one or two selected from the group consisting of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI).

4. The method according to claim 1, wherein the hydrophilic chain extender is 2,2-dimethylol propionic acid (DMPA).

5. The method according to claim 1, wherein the diluent is any one selected from the group consisting of dimethylacetamide (DMAC), acetone, N,N-dimethylformamide (DMF), and N-methylpyrrolidone (NMP).

6. The method according to claim 1, wherein the neutralizer is triethylamine (TEAM).

7. The method according to claim 1, wherein the post chain extender is one or two selected from the group consisting of diethylenetriamine, ethylenediamine, isophorone diamine, and hydrazine hydrate.

8. The method according to claim 1, wherein the catalyst is organic tin or organic bismuth; the cellulose thickener is carboxymethyl cellulose; the wetting agent is polyether modified organosiloxane; and the dispersant is aryl ethyl phenyl polyethylene glycol ether.

9. A method for dipping knitted gloves with a waterborne polyurethane (WPU) emulsion, the WPU emulsion comprising the following raw materials in part by weight: 230-250 parts of polyol, 50-60 parts of isocyanate, 5-10 parts of a hydrophilic chain extender, 60-80 parts of a diluent, 5-9 parts of a neutralizer, 500-600 parts of water, 15-20 parts of a post chain extender, 0.01-0.05 parts of a catalyst, 3-7 parts of a cellulose thickener, 0.5-1.5 parts of a wetting agent, and 3-5 parts of a dispersant; and the method comprising the following steps: a, slurry spraying: sleeving a knitted glove lining on an assembly line mold, heating to 30-60? C., spraying a first layer of the WPU emulsion on a surface of the knitted glove lining using a slurry spraying mode, initially curing for 10-20 min at 50-90? C., and fully curing for 10-20 min at 100-130? C. to obtain a layer of dipped gloves; b, dipping: cooling the layer of dipped gloves fully cured in step a to 30-60? C., coating a surface of the layer of dipped gloves with second to fourth layers of the WPU emulsion using a dipping mode, and fully curing for 10-20 min at 90-110? C. to obtain rough gloves; and c, demoulding: cooling the rough gloves obtained after dipping above to 30-60? C., coating a surface with the WPU emulsion by spraying or dipping, initially curing for 2-10 min at 50-90? C., fully curing for 10-20 min at 100-130? C., and cooling and demoulding.

10. The method for dipping knitted gloves with the WPU emulsion according to claim 9, wherein the polyol is one or more selected from the group consisting of polyester polyols, polyether polyols, polycaprolactone polyols, polycarbonate polyols, polysiloxane polyols, and polytetrahydrofuran (PTHF).

11. The method for dipping knitted gloves with the WPU emulsion according to claim 9, wherein the isocyanate is one or two selected from the group consisting of isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI).

12. The method for dipping knitted gloves with the WPU emulsion according to claim 9, wherein the hydrophilic chain extender is 2,2-dimethylol propionic acid (DMPA).

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The present disclosure is further described below with reference to examples.

Example 1

(2) A WPU emulsion included the following raw materials in part by weight: 270.74 parts of polyol, 50.56 parts of isocyanate, 7.82 parts of a hydrophilic chain extender, 36 parts of a diluent, 5.9 parts of a neutralizer, 541.66 parts of water, 17.21 parts of a post chain extender, 0.02 parts of a catalyst, 3.6 parts of a cellulose thickener, 2.2 parts of a wetting agent, and 1.8 parts of a dispersant.

(3) The polyol was PTHF 1000. The isocyanate consisted of 25.56 parts of IPDI and 25 parts of HDI. The hydrophilic chain extender was 2,2-dimethylol propionic acid DMPA. The diluent was acetone. The neutralizer was TEAM. The post chain extender was hydrazine hydrate. The catalyst was dibutyltin dilaurate. The cellulose thickener was carboxymethyl cellulose. The wetting agent was polyether modified organosiloxane. The dispersant was aryl ethyl phenyl polyethylene glycol ether.

(4) A preparation method for the WPU emulsion included the following steps.

(5) Step I: Preparation of Isocyanate Terminated Prepolymer

(6) The polyol and the hydrophilic chain extender were put into a reactor, The isocyanate was added while stirring at 150 r/min. The catalyst was added after a temperature rose to 80? C. Nitrogen was introduced. Heat preservation was conducted for 3 h to obtain the isocyanate terminated prepolymer.

(7) Step II: Neutralization

(8) When the temperature in the reactor was reduced to 60? C., the diluent and the neutralizer were added to neutralize the isocyanate terminated prepolymer to obtain a neutralized prepolymer.

(9) Step III: Emulsification

(10) At 20? C., the neutralized prepolymer in step II was added into the water to obtain a mixture, and the mixture was stirred at 3,200 r/min (high speed stirring) for 30 min to form a dispersion.

(11) Step IV: Post Chain Extension

(12) At 500 r/min (low speed stirring), the post chain extender was added to the dispersion in step III, and stirred for 30 min to obtain a WPU dispersion. A particle size was limited to 20-30 ?m during chain extension.

(13) Step V: Preparation of Emulsion

(14) The cellulose thickener, the wetting agent, and the dispersant were added into the WPU dispersion, and stirred for 30 min to obtain the WPU emulsion.

(15) A method for preparing dipped gloves with the above WPU emulsion included the following specific steps. a, Slurry spraying: a knitted glove lining was sleeved on an assembly line mold, and heated to 50? C. A first layer of the WPU emulsion was sprayed on a surface of the knitted glove lining using a slurry spraying mode, initially cured for 15 min at 80? C., and fully cured for 20 min at 120? C. to obtain a layer of dipped gloves. b, Dipping: the layer of dipped gloves fully cured in step a was cooled to 35? C. A surface of the layer of dipped gloves was coated with second to fourth layers of the WPU emulsion using a dipping mode. Each layer of the emulsion was fully cured for 20 min at 100? C. to obtain rough gloves. c, Demoulding: the rough gloves obtained after dipping above was cooled to 35? C. A surface was coated with the polyurethane particles by spraying or dipping, initially cured for 10 min at 60? C., fully cured for 20 min at 120? C., and cooled and demoulded.

(16) The above descriptions are merely preferred implementations of the present disclosure. It should be noted that those of ordinary skill in the art may further make several improvements and modifications without departing from the principle of the present disclosure, but such improvements and modifications should be deemed as falling within the protection scope of the present disclosure.