Aqueous polyurethane emulsion for ultra-thin polyurethane condom with low modulus and high strength, and preparation method therefor

1 . A waterborne polyurethane emulsion, comprising:

15 to 18 parts by mass of a macromolecular diol selected from the group consisting of polypropylene glycol (PPG), polytetrahydrofuran ether glycol (PTMEG), poly(neopentyl glycol adipate) (PNA), and combinations thereof,

4 to 6 parts by mass of a diisocyanate,

0.6 to 0.9 parts by mass of a hydrophilic chain extender,

0.4 to 0.8 parts by mass of a small-molecule chain extender selected from the group consisting of cyclohexanedimethanol (CHDM), 1,4-butanediol (BD), methylpropanediol (MPD), and combinations thereof,

0.5 to 0.68 parts by mass of a salt-forming agent,

0.3 to 0.5 parts by mass of a cross-linking agent,

0.1 to 2.0 parts by mass of a modifying agent,

50 to 55 parts by mass of an ice-water mixture, and

21 to 23 parts by mass of acetone;

wherein said modifying agent is a polyether substance that causes the terminal groups of the chain of the waterborne polyurethane molecule to form a cross-linked structure.

2 . The waterborne polyurethane emulsion according to claim 1 , wherein said modifying agent is a polyetheramine.

3 . The waterborne polyurethane emulsion according to claim 1 , wherein said cross-linking agent is a latent isocyanate-based cross-linking agent.

4 . The waterborne polyurethane emulsion according to claim 1 , wherein said macromolecular diol is one of or a combination of more of polypropylene glycol, polytetrahydrofuran ether glycol, and poly(neopentyl glycol adipate).

5 . The waterborne polyurethane emulsion according to claim 1 , wherein said diisocyanate is selected from the group consisting of isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, and combinations thereof.

6 . The waterborne polyurethane emulsion according to claim 1 , wherein said hydrophilic chain extender is dihydroxymethyl propionic acid and/or dihydroxymethyl butyric acid.

7 . A method for preparing a waterborne polyurethane emulsion, comprising at least the following steps:

providing a reactor;

adding to said reactor 15 to 18 parts by mass of a macromolecular diol selected from the group consisting of polypropylene glycol (PPG), polytetrahydrofuran ether glycol (PTMEG), poly(neopentyl glycol adipate) (PNA), and combinations thereof, 4 to 6 parts by mass of a diisocyanate, 0.6 to 0.9 parts by mass of a hydrophilic chain extender, 0.4 to 0.8 parts by mass of a small-molecule chain extender, 0.5 to 0.68 parts by mass of a salt-forming agent, and 4 to 23 parts by mass of acetone to obtain a prepolymer, and wherein the small-molecule chain extender is selected from the group consisting of cyclohexanedimethanol (CHDM), 1,4-butanediol (BD), methylpropanediol (MPD), and combinations thereof;

mixing said prepolymer, 0.3 to 0.5 parts by mass of a cross-linking agent, and 50 to 55 parts by mass of an ice-water mixture to obtain an open-chain prepolymer; and

adding 0.1 to 2.0 parts by mass of a modifying agent to said open-chain prepolymer, so that the terminal groups of said open-chain prepolymer form a cross-linked structure to obtain said waterborne polyurethane emulsion, and wherein the modifying agent is a polyether substance.

8 . The waterborne polyurethane emulsion according to claim 7 , wherein said modifying agent is added dropwise to said open-chain prepolymer over a period of 25 to 35 minutes.

9 . A method of using the waterborne polyurethane emulsion according to claim 1 to manufacture polyurethane condoms, the method comprising:

treating a mold by immersing the mold in an emulsion of nanoscale waterborne polyurethane cross-linked particles;

drying the treated mold;

immersing the treated mold in the waterborne polyurethane emulsion;

drying the mold to produce a waterborne polyurethane film formed on the surface of the mold;

rolling an open end of the waterborne polyurethane film;

immersing the mold in water at 50±5° C.;

soaking and drying the mold;

dipping the mold into a mold release agent; and

demolding the waterborne polyurethane film.

10 . The method according to claim 7 , wherein said modifying agent is a polyetheramine.

11 . The method according to claim 7 , wherein said cross-linking agent is a latent isocyanate-based cross-linking agent.

12 . The method according to claim 7 , wherein said diisocyanate is selected from the group consisting of isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, and combinations thereof.

13 . The method according to claim 7 , wherein said hydrophilic chain extender is dihydroxymethyl propionic acid and/or dihydroxymethyl butyric acid.

14 . The method according to claim 9 , wherein said modifying agent is a polyetheramine.

15 . The method according to claim 9 , wherein said cross-linking agent is a latent isocyanate-based cross-linking agent.

16 . The method according to claim 9 , wherein said diisocyanate is selected from the group consisting of isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, and combinations thereof.

17 . The method according to claim 9 , wherein said hydrophilic chain extender is dihydroxymethyl propionic acid and/or dihydroxymethyl butyric acid.