Aqueous polyurethane emulsion and its preparation method and application

Abstract

The present invention relates to an aqueous polyurethane emulsion, its preparation method, and application. The preparation method of the aqueous polyurethane emulsion comprises the following steps: S1. Prepolymerization reaction: adding a diisocyanate and a catalyst to a polymer diol, and conducting a prepolymerization reaction at 60-85°C in an inert atmosphere for 45-150 minutes to obtain a prepolymer product; S2. Chain extension reaction: adding a first chain extender to the prepolymer product obtained in S1, conducting a chain extension reaction at 60-80°C for 60-180 minutes, and diluting with a diluent to obtain a chain extension product; S3. Emulsification, chain extension, and neutralization reaction: adding the chain extension product obtained in S2 to an aqueous solution containing an organosilicon wetting agent and a second chain extender, stirring for 60-240 minutes, and then adding a neutralizer to obtain the aqueous polyurethane emulsion. The aqueous polyurethane emulsion is used to prepare polyurethane / nitrile composite gloves, which have low demolding force and smooth demolding.

Description

Technical Field

[0001] The present invention relates to the field of polymer material synthesis and modification, and more particularly to an aqueous polyurethane emulsion and a preparation method and application thereof. Background Art

[0002] Coagulants are essential to the production of dipped gloves and play a crucial role in glove shaping, thickness control, and uniformity. Traditional coagulants primarily consist of flocculants, wetting agents, and internal release agents. The mechanism of action of flocculants is that the positively charged cations of the coagulant combine with anions adsorbed on the surface of rubber particles in the latex, quickly forming a non-dissociable substance, which causes the particles to lose their charge and coagulate. Flocculants typically include calcium chloride, calcium nitrate, barium chloride, magnesium nitrate, and calcium acetate. The wetting agent's primary function is to ensure that the coagulant is fully wetted and spread evenly across the mold surface, playing a crucial role in glove uniformity. Non-ionic surfactants such as Lutensol XL70 and Teric 320 are commonly used. Internal release agents are materials that can be evenly dispersed in the coagulant system, helping to reduce the adhesion of latex products to the mold after drying, making demolding easier without adversely affecting product quality. Internal release agents are important for demolding gloves after vulcanization and are also the main component for preventing adhesion of gloves after boxing. Internal release agents generally use aqueous stearate emulsions, light calcium carbonate dispersions, magnesium oxide powders, etc. For example, patent CN114773500A uses stearate as an internal release agent.

[0003] The traditional molding process for disposable dipped gloves includes: hand mold cleaning (acid wash - alkaline wash - disc brush - roller brush - wash) - hand mold drying - coagulant impregnation - drying - emulsion impregnation - latex drying - emulsion impregnation - latex drying - leaching - crimping - vulcanization - cooling - chlorine wash - leaching and cleaning - demolding - packaging. The primary function of hand mold cleaning is to remove residual release agent from the mold surface, preventing cosmetic issues such as uneven adhesive adhesion and powder stains during the secondary dipping process. Release agent concentration is a key control factor in glove production, significantly impacting both glove production and product quality. Excessively high release agent concentrations result in smooth demolding, but can easily accumulate on the mold, leading to the appearance of white powder spots on the product surface. Excessively low release agent concentrations can lead to poor demolding and a high tear rate.

[0004] It is necessary to solve the problem that the internal release agent in the coagulant in the current dipping glove molding process brings inconvenience to production and easily has a negative impact on the quality of the glove products. Summary of the Invention

[0005] The primary purpose of the present invention is to solve the problem that the internal release agent in the coagulant in the current dipping glove molding process brings inconvenience to production and easily has a negative impact on the quality of the glove products, and to provide a method for preparing an aqueous polyurethane emulsion.

[0006] A further object of the present invention is to provide an aqueous polyurethane emulsion.

[0007] A further object of the present invention is to provide use of the aqueous polyurethane emulsion in preparing polyurethane / nitrile composite gloves.

[0008] A further object of the present invention is to provide a method for preparing polyurethane / nitrile composite gloves.

[0009] A further object of the present invention is to provide a polyurethane / nitrile composite glove.

[0010] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0011] A method for preparing an aqueous polyurethane emulsion comprises the following steps:

[0012] S1 prepolymerization: adding diisocyanate and a catalyst to the polymer diol, and carrying out a prepolymerization reaction at 60 to 85 ° C and an inert gas atmosphere for 45 to 150 minutes to obtain a prepolymerized product;

[0013] S2 chain extension reaction: adding a first chain extender to the prepolymer product obtained in S1, carrying out a chain extension reaction at 60 to 80 ° C for 60 to 180 minutes, adding a diluent to obtain a chain extension product;

[0014] S3 emulsification chain extension and neutralization reaction: to an aqueous solution containing a silicone wetting agent and a second chain extender was added the chain extension product obtained in S2, stirred for 60 to 240 minutes, and then a neutralizing agent was added to obtain the aqueous polyurethane emulsion;

[0015] The amount of the organosilicon wetting agent is 0.5 to 3% of the sum of the mass of the polymer diol and the diisocyanate;

[0016] The first chain extender is a chain extender containing a hydroxyl group or an amino group, and the second chain extender is a chain extender containing an amino group; and the first chain extender and / or the second chain extender contains at least one of a carboxyl group or a sulfonic acid group.

[0017] The aqueous polyurethane emulsion of the present invention undergoes a prepolymerization reaction in step S1, and a chain extension reaction occurs in step S2 to preliminarily form polyurethane latex particles; then, a method (step S3) of further chain extension in the emulsification process is adopted to improve the molecular weight and mechanical properties of the aqueous polyurethane; more importantly, chain extension and emulsification occur simultaneously in step S3 during the stirring process, and the organosilicon wetting agent and the polyurethane latex particles are closely combined together through the hydrophilic and hydrophobic self-assembly effect of the emulsification process. This, on the one hand, can improve the emulsification effect of the aqueous polyurethane; on the other hand, the organosilicon closely combined with the polyurethane latex particles has low surface energy performance, which can improve the demoulding performance of the gloves. The aqueous polyurethane emulsion is used to prepare polyurethane / nitrile composite gloves. During the preparation process of the polyurethane / nitrile composite gloves, no internal release agent needs to be added to the coagulant, and the gloves can still be smoothly demoulded, are not easy to adhere to each other, and can maintain good mechanical properties.

[0018] Optionally, the first chain extender is at least one of 1,3-propylene glycol, 1,4-butylene glycol, dimethylol propionic acid, dimethylol butyric acid or a sulfonate chain extender.

[0019] Optionally, the sulfonate chain extender is N-(2-aminoethyl)-2-aminoethanesulfonic acid sodium salt CA-95.

[0020] Preferably, the first chain extender is dimethylolpropionic acid.

[0021] Dimethylolpropionic acid is selected as the first chain extender, and the obtained aqueous polyurethane emulsion is used to prepare polyurethane / nitrile composite gloves, and the tensile strength of the gloves is higher.

[0022] Optionally, the second chain extender is at least one of propylenediamine, ethylenediamine or lysine.

[0023] Preferably, the second chain extender is at least one of propylene diamine or ethylene diamine.

[0024] The second chain extender is selected from propylene diamine or ethylene diamine, and the obtained aqueous polyurethane emulsion is used to prepare polyurethane / nitrile composite gloves, which can better balance the tensile strength and elongation at break of the gloves.

[0025] The polymer diols, diisocyanates, catalysts, diluents and silicone wetting agents commonly used in the art can be used in the present invention.

[0026] Optionally, the polymer diol is at least one of polytetramethylene glycol (PTMG), polypropylene glycol (PPG) or polycaprolactone glycol.

[0027] Optionally, the diisocyanate is at least one of isophorone diisocyanate, toluene diisocyanate, diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate or L-lysine diisocyanate.

[0028] Optionally, the catalyst is at least one of dibutyltin dilaurate, stannous octoate or organic bismuth.

[0029] Optionally, the diluent is at least one of acetone or butanone.

[0030] Preferably, the organosilicon wetting agent in step S3 is at least one of an acetylenic alcohol-modified organosilicon wetting agent, a polyether-modified organosilicon wetting agent, a polyester-modified organosilicon wetting agent or an aralkyl-modified polymethylsiloxane.

[0031] Preferably, the organosilicon wetting agent in step S3 is at least one of a polyether-modified organosilicon wetting agent or an aralkyl-modified polymethylsiloxane.

[0032] Polyether-modified silicone wetting agent or aralkyl-modified polymethylsiloxane is selected as the silicone wetting agent, and the obtained water-based polyurethane emulsion is used to prepare polyurethane / nitrile composite gloves, which has smaller demoulding force and smoother demoulding.

[0033] Preferably, the amounts of the polymer diol, diisocyanate, first chain extender, second chain extender and neutralizer are as follows: the molar ratio of isocyanate group of diisocyanate: hydroxyl group of polymer diol: hydroxyl group or amino group of the first chain extender: amino group of the second chain extender: neutralizer is (2.2-3.5):1.0:(0.8-2.0):(0.2-0.3):(0.6-1.8).

[0034] An aqueous polyurethane emulsion is prepared by the above preparation method.

[0035] Application of the above aqueous polyurethane emulsion in the preparation of polyurethane / nitrile composite gloves.

[0036] A method for preparing polyurethane / nitrile composite gloves comprises the following steps:

[0037] S4. The aqueous polyurethane emulsion is diluted and set aside; preparing an aqueous solution comprising a flocculant and a wetting agent and set aside;

[0038] S5. The polyurethane / nitrile composite gloves are obtained by soaking in diluted aqueous polyurethane emulsion - drying - soaking in aqueous solution - drying - soaking in nitrile emulsion - pre-vulcanization - soaking in nitrile emulsion - pre-vulcanization - leaching - vulcanization - chlorine water treatment - cleaning - demoulding.

[0039] Preferably, the solid content of the diluted aqueous polyurethane emulsion in step S4 is 0.5 to 3 wt%.

[0040] Preferably, the concentration of the flocculant in the aqueous solution in step S4 is 5-15 wt %, and the concentration of the wetting agent is 0.1-1 wt %.

[0041] The flocculants, wetting agents and nitrile emulsions commonly used in the art can be used in the present invention.

[0042] Optionally, the flocculant is at least one of calcium nitrate, calcium acetate or calcium chloride.

[0043] Optionally, the wetting agent is at least one of polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether or polyoxyethylene polyoxypropylene block copolymer.

[0044] A polyurethane / nitrile composite glove is prepared by the above preparation method.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The aqueous polyurethane emulsion of the present invention uses a method for further chain extension during the emulsification process to improve the molecular weight and mechanical properties of the aqueous polyurethane. More importantly, in step S3, chain extension and emulsification occur simultaneously during the stirring process. Through the hydrophilic and hydrophobic self-assembly effect of the emulsification process, the organosilicon wetting agent and the polyurethane latex particles are tightly combined together. This can improve the emulsification effect of the aqueous polyurethane. On the other hand, the organosilicon tightly combined with the polyurethane latex particles has low surface energy properties, which can improve the demoulding properties of the gloves. The aqueous polyurethane emulsion is used to prepare polyurethane / nitrile composite gloves. During the preparation process of the polyurethane / nitrile composite gloves, no internal release agent needs to be added to the coagulant, and the gloves can still be smoothly demoulded, are not easy to stick together, and can maintain good mechanical properties. DETAILED DESCRIPTION

[0047] In order to more clearly and completely describe the technical scheme of the present invention, the present invention is further described in detail below by specific examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the present invention. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0048] Polymer diol 1#: polytetramethylene glycol (PTMG) with a molecular weight of 1500, sourced from Dow Chemical;

[0049] Polymer diol 2#: polypropylene glycol PPG with a molecular weight of 1000, sourced from Dow Chemical;

[0050] Diisocyanate 1#: isophorone diisocyanate, sourced from BASF SE;

[0051] Diisocyanate 2#: hexamethylene diisocyanate, sourced from Adamas Ltd.;

[0052] Catalyst: dibutyltin dilaurate, commercially available;

[0053] Diluent: acetone, commercially available;

[0054] First chain extender 1#: dimethylol propionic acid, commercially available;

[0055] First chain extender 2#: N-(2-aminoethyl)-2-aminoethanesulfonic acid sodium salt, CA95, from Zhangjiagang Yarui Chemical Co., Ltd.

[0056] Second chain extender 1#: propylene diamine, commercially available;

[0057] Second chain extender 2#: ethylenediamine, commercially available;

[0058] Second chain extender 3#: lysine, commercially available;

[0059] Silicone wetting agent 1#: Alkynol-modified silicone wetting agent, JC-7000, Wuhan Aoke Specialty Chemical Co., Ltd.

[0060] Silicone wetting agent 2#: polyether-modified polydimethylsiloxane, BYK307, BYK Chemical Co., Ltd.

[0061] Silicone wetting agent 3#: polyester-modified polydimethylsiloxane containing acrylic functional groups, BYK371, BYK Chemical Co., Ltd.

[0062] Silicone wetting agent 4#: Arylalkyl-modified polymethylsiloxane, BYK-346, BYK Chemical Co., Ltd.

[0063] Wetting agent 5#: polyoxyethylene alkylphenol ether, NP-6, Guangzhou Huayang Chemical Co., Ltd.;

[0064] Neutralizing agent: triethylamine, commercially available;

[0065] Flocculant: calcium nitrate, commercially available;

[0066] Nitrile emulsion: KNL830, Kumho Petrochemical Co., Ltd., South Korea.

[0067] Example 1

[0068] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, comprising the following steps:

[0069] 1.1 Preparation of waterborne polyurethane emulsion:

[0070] S1 prepolymerization: After dehydration, diisocyanate 1# and a catalyst were added to the polymer diol 1#, and the prepolymerization was carried out at 70°C and an inert gas atmosphere for 80 minutes to obtain a prepolymerized product;

[0071] S2 chain extension reaction: S1 obtained in the prepolymer product was added to the first chain extender 1 #, the chain extension reaction was carried out at 70 ° C for 60 minutes, diluted with a diluent to obtain a chain extension product;

[0072] S3 emulsification chain extension and neutralization reaction: to the aqueous solution containing a silicone wetting agent 1 # and a second chain extender 1 # was added S2 obtained by chain extension product, stirred for 100 minutes to carry out chain extension and emulsification, and then added a neutralizing agent to obtain an aqueous polyurethane emulsion;

[0073] The molar ratio of the components is: isocyanate group of diisocyanate 1#: hydroxyl group of polymer diol 1#: hydroxyl group of first chain extender 1#: amino group of second chain extender 1#: neutralizer = 2.8:1.0:1.0:0.5:1.0; the amount of organosilicon wetting agent 1# (the content of pure organosilicon wetting agent in the raw materials) is 2% of the sum of the masses of polymer diol 1# and diisocyanate 1#.

[0074] 1.2 Preparation of polyurethane / nitrile composite gloves

[0075] S4. The aqueous polyurethane emulsion was diluted to a solid content of 3% and set aside; preparing a flocculant concentration of 10%, a wetting agent 5 # 0.5% aqueous solution and set aside;

[0076] S5. Immerse the hand mold in the diluted aqueous polyurethane emulsion for 3 seconds and dry it at 80°C for 30 seconds; then immerse it in the aqueous solution for 5 seconds and dry it at 80°C for 30 seconds; then immerse the hand mold in a 15% solid content nitrile emulsion for 5 seconds and dry it at 100°C for 45 seconds; immerse the hand mold in a 15% solid content nitrile emulsion for 5 seconds and pre-vulcanize it at 100°C for 30 seconds; leach the hand mold in 60°C hot water for 10 seconds and vulcanize it in a 110°C oven for 30 minutes; finally, treat the hand mold with 500ppm chlorine water, clean it, and demould it to obtain the polyurethane / nitrile composite gloves.

[0077] Example 2

[0078] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, which is basically the same as Example 1, except that the first chain extender 1# is replaced with an equimolar amount of the first chain extender 2#.

[0079] Example 3

[0080] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, which is basically the same as Example 1, except that the second chain extender 1# is replaced by the second chain extender 2#.

[0081] Example 4

[0082] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, which is basically the same as that of Example 1, except that the second chain extender 1# is replaced by the second chain extender 3#.

[0083] Example 5

[0084] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, which is basically the same as Example 1, except that silicone wetting agent 1# is replaced with silicone wetting agent 2#.

[0085] Example 6

[0086] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, which is basically the same as Example 1, except that silicone wetting agent 1# is replaced with silicone wetting agent 3#.

[0087] Example 7

[0088] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, which is basically the same as Example 1, except that silicone wetting agent 1# is replaced with silicone wetting agent 4#.

[0089] Example 8

[0090] This embodiment provides a method for preparing a polyurethane / nitrile composite glove, which is substantially the same as that of Example 1, except that: in step 1.1, the molar ratio of the components used is: isocyanate group of diisocyanate 1#: hydroxyl group of polymer diol 1#: hydroxyl group of first chain extender 1#: amino group of second chain extender 1#: neutralizer is 2.2:1.0:0.8:0.2:0.6; and the amount of organosilicon wetting agent 1# used is 0.5% of the sum of the mass of polymer diol 1# and diisocyanate 1#.

[0091] Example 9

[0092] This embodiment provides a method for preparing a polyurethane / nitrile composite glove, which is substantially the same as that of Example 1, except that: in step 1.1, the molar ratio of the components used is: isocyanate group of diisocyanate 1#: hydroxyl group of polymer diol 1#: hydroxyl group of first chain extender 1#: amino group of second chain extender 1#: neutralizer is 3.5:1.0:2.0:0.3:1.8; and the amount of organosilicon wetting agent 1# used is 3% of the sum of the mass of polymer diol 1# and diisocyanate 1#.

[0093] Example 10

[0094] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, comprising the following steps:

[0095] 1.1 Preparation of waterborne polyurethane emulsion:

[0096] S1 prepolymerization: After dehydration, diisocyanate 2# and a catalyst were added to the polymer diol 2#, and the prepolymerization reaction was carried out at 85°C and an inert gas atmosphere for 45 minutes to obtain a prepolymerized product;

[0097] S2 chain extension reaction: S1 was added to the prepolymer product obtained first chain extender 1 #, the chain extension reaction was carried out at 60 ° C for 180 minutes, diluted with a diluent to obtain a chain extension product;

[0098] S3 emulsification chain extension and neutralization reaction: to the aqueous solution containing a silicone wetting agent 1 # and a second chain extender 1 # was added S2 obtained by chain extension product, stirred for 240 minutes to carry out chain extension and emulsification, and then added a neutralizing agent to obtain an aqueous polyurethane emulsion;

[0099] The molar ratio of the components is: isocyanate group of diisocyanate 2#: hydroxyl group of polymer diol 2#: hydroxyl group of first chain extender 1#: amino group of second chain extender 1#: neutralizer = 2.8:1.0:1.0:0.5:1.0; the amount of silicone wetting agent 1# (the content of pure silicone wetting agent in the raw materials) is 2% of the sum of the masses of polymer diol 2# and diisocyanate 2#.

[0100] 1.2 is the same as 1.2 of Example 1.

[0101] Example 11

[0102] This embodiment provides a method for preparing polyurethane / nitrile composite gloves, comprising the following steps:

[0103] 1.1 Preparation of waterborne polyurethane emulsion:

[0104] S1 prepolymerization: After dehydration, diisocyanate 2 # and a catalyst were added to the polymer diol 1 #, and the prepolymerization reaction was carried out at 60 ° C and an inert gas atmosphere for 150 minutes to obtain a prepolymerized product;

[0105] S2 chain extension reaction: S1 was added to the prepolymer product obtained first chain extender 1 #, the chain extension reaction was carried out at 80 ° C for 100 minutes, diluted with a diluent to obtain a chain extension product;

[0106] S3 emulsification chain extension and neutralization reaction: to the aqueous solution containing a silicone wetting agent 1 # and a second chain extender 1 # was added S2 obtained by chain extension product, stirred for 60 minutes to carry out chain extension and emulsification, and then added a neutralizing agent to obtain an aqueous polyurethane emulsion;

[0107] The molar ratio of the components is: isocyanate group of diisocyanate 2#: hydroxyl group of polymer diol 1#: hydroxyl group of first chain extender 1#: amino group of second chain extender 1#: neutralizer = 2.8:1.0:1.0:0.5:1.0; the amount of silicone wetting agent 1# (the content of pure silicone wetting agent in the raw materials) is 2% of the sum of the masses of polymer diol 1# and diisocyanate 2#.

[0108] 1.2 is the same as 1.2 of Example 1.

[0109] Comparative Example 1

[0110] This comparative example provides a method for preparing polyurethane / nitrile composite gloves, which differs from Example 1 in that no silicone wetting agent 1# is added.

[0111] Comparative Example 2

[0112] This comparative example provides a method for preparing polyurethane / nitrile composite gloves, which differs from Example 1 in that silicone wetting agent 1# is replaced with wetting agent 5#.

[0113] Comparative Example 3

[0114] This comparative example provides a method for preparing polyurethane / nitrile composite gloves, which differs from Example 1 in that the organosilicon wetting agent 1# is added in S2 but not in S3.

[0115] Comparative Example 4

[0116] This comparative example provides a method for preparing polyurethane / nitrile composite gloves, which differs from Example 1 in that the second chain extender 1# is not added.

[0117] Comparative Example 5

[0118] This comparative example provides a method for preparing polyurethane / nitrile composite gloves. The selection and dosage of each raw material are the same as those in Example 1. The difference from Example 1 is that:

[0119] S3. Chain extension and neutralization reaction: The chain extension product obtained in S2 was added to an aqueous solution containing a second chain extender 1#, stirred for 100 minutes to extend the chain, and then a neutralizing agent was added, and then a silicone wetting agent 1# was added and stirred to obtain the aqueous polyurethane emulsion.

[0120] Performance Testing

[0121] Demolding force test: 1. Prepare a pointer-type push-pull force gauge and calibrate the equipment. 2. Manually demold the vulcanized, molded, and dried polyurethane / nitrile composite gloves to the four-finger area (just after the thumb is removed). 3. Use a pointer-type push-pull force gauge to test the maximum force required to release the glove from the four fingers.

[0122] Tensile strength and elongation at break test: refer to ASTM D412-2006a tensile test method for vulcanized rubber and thermoplastic elastomers.

[0123] Adhesion test: 25 gloves are neatly stacked and a 1.5kg weight is placed flat on top. After 2 hours, the weight is removed and the gloves are turned over. The number of gloves lifted when the gloves are turned over is used to measure adhesion. (Severe adhesion - all gloves lifted; moderate adhesion - 5-6 gloves lifted; slight adhesion - 1-2 gloves lifted; no adhesion - each glove can be opened independently).

[0124] The polyurethane / nitrile composite gloves prepared in the examples and comparative examples were tested for performance according to the above test methods. The results are shown in Table 1.

[0125] Table 1 Performance test results of polyurethane / nitrile composite gloves prepared in various embodiments and comparative examples

[0126]

[0127]

[0128] From Table 1 we can see that:

[0129] The polyurethane / nitrile composite gloves of Examples 1-11 all had demolding forces less than 13N, and the gloves did not stick together. This demonstrates that the aqueous polyurethane emulsion of the present invention can be used to prepare polyurethane / nitrile composite gloves. Without the use of an internal release agent, the gloves can be smoothly demolded and are not prone to sticking together. Furthermore, the polyurethane / nitrile composite gloves of Examples 1-11 all had tensile strengths greater than 17 MPa and elongations at break greater than 665%, maintaining excellent mechanical properties.

[0130] In the preparation process of the polyurethane / nitrile composite gloves of Comparative Example 1, no organosilicon wetting agent was added. The demolding force of the gloves was large, the gloves showed moderate adhesion, and demolding was not smooth. In the preparation process of the polyurethane / nitrile composite gloves of Comparative Example 2, the organosilicon wetting agent was replaced with a polyoxyethylene alkylphenol ether containing no silicon component. The demolding force of the gloves was large, the gloves showed moderate adhesion, and demolding was not smooth. If the organosilicon wetting agent was added in step S2 of the preparation process (Comparative Example 3), the demolding force of the gloves was also large, the gloves showed slight adhesion, and demolding was still not smooth. If the second chain extension was not performed (Comparative Example 4), the demolding force of the gloves was large, the gloves showed moderate adhesion, demolding was not smooth, and the tensile strength of the gloves was low. If the organosilicon wetting agent was added after the second chain extension was completed (such as in Comparative Example 5), the demolding force of the gloves was also large, the gloves showed slight adhesion, and demolding was still not smooth.

[0131] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an aqueous polyurethane emulsion, characterized in that: The steps include: S1 prepolymerization: adding diisocyanate and a catalyst to the polymer diol, and carrying out a prepolymerization reaction at 60 to 85 ° C and an inert gas atmosphere for 45 to 150 minutes to obtain a prepolymerized product; S2 chain extension reaction: adding a first chain extender to the prepolymer product obtained in S1, carrying out a chain extension reaction at 60 to 80 ° C for 60 to 180 minutes, adding a diluent to obtain a chain extension product; S3 emulsification chain extension and neutralization reaction: to an aqueous solution containing a silicone wetting agent and a second chain extender was added the chain extension product obtained in S2, stirred for 60 to 240 minutes, and then a neutralizing agent was added to obtain the aqueous polyurethane emulsion; The amount of the organosilicon wetting agent is 0.5 to 3% of the sum of the mass of the polymer diol and the diisocyanate; The first chain extender is a chain extender containing a hydroxyl group or an amino group, and the second chain extender is a chain extender containing an amino group; and the first chain extender and / or the second chain extender contains at least one of a carboxyl group or a sulfonic acid group.

2. The preparation method according to claim 1, characterized in that The first chain extender is dimethylol propionic acid.

3. The preparation method according to claim 1, characterized in that The organosilicon wetting agent in step S3 is at least one of an acetylenic alcohol-modified organosilicon wetting agent, a polyether-modified organosilicon wetting agent, a polyester-modified organosilicon wetting agent, or an aralkyl-modified polymethylsiloxane.

4. The preparation method according to claim 3, characterized in that The organosilicon wetting agent in step S3 is at least one of a polyether-modified organosilicon wetting agent or an aralkyl-modified polymethylsiloxane.

5. The preparation method according to claim 1, characterized in that: In step S3, the second chain extender is at least one of propylene diamine or ethylene diamine.

6. The preparation method according to claim 1, characterized in that: The amounts of the polymer diol, diisocyanate, first chain extender, second chain extender and neutralizer are as follows: the molar ratio of isocyanate group of diisocyanate: hydroxyl group of polymer diol: hydroxyl group or amino group of the first chain extender: amino group of the second chain extender: neutralizer is (2.2-3.5):1.0:(0.8-2.0):(0.2-0.5):(0.6-1.8).

7. An aqueous polyurethane emulsion, characterized in that It is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the aqueous polyurethane emulsion according to claim 7 in the preparation of polyurethane / nitrile composite gloves.

9. A method for preparing polyurethane / nitrile composite gloves, characterized in that: The steps include: S4. The aqueous polyurethane emulsion according to claim 7 is diluted and set aside; preparing an aqueous solution comprising a flocculant and a wetting agent and set aside; S5. The polyurethane / nitrile composite gloves are obtained by soaking in diluted aqueous polyurethane emulsion - drying - soaking in aqueous solution - drying - soaking in nitrile emulsion - pre-vulcanization - soaking in nitrile emulsion - pre-vulcanization - leaching - vulcanization - chlorine water treatment - cleaning - demoulding.

10. A polyurethane / nitrile composite glove, characterized in that: It is prepared by the preparation method according to claim 9.

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