Cationic aqueous polyurethane dispersions, methods of making and using the same

Abstract

The application discloses a kind of cationic water-based polyurethane dispersion and its preparation method and application, it is related to polyacrylamide water-based dispersion synthesis technical field, specifically related to a kind of preparation method of cationic water-based polyurethane dispersion;Including the following steps, 1) in the presence of catalyst, polyoxyethylene, polyether dihydric alcohol, alcohol amine, aliphatic and / or alicyclic diisocyanate are mixed, after reaction I, acrylamide compound and polymerization inhibitor are added, and reaction II is carried out, to obtain cationic water-based polyurethane prepolymer;2) after neutralization, dilution of the cationic water-based polyurethane prepolymer obtained in step 1), to obtain the cationic water-based polyurethane dispersion;The cationic water-based polyurethane dispersion prepared in the application is used as the stabilizer of polyacrylamide water-based dispersion, and can effectively stabilize polyacrylamide water-based dispersion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyacrylamide aqueous dispersion synthesis, in particular to a cationic water-based polyurethane dispersion and a preparation method and application thereof. BACKGROUND

[0002] Polyacrylamide (CPAM) has good water solubility, high efficiency of viscosity and unique adsorption, and is widely used in water treatment, oil extraction, papermaking, textile and many other fields. The aqueous dispersion polymerization method is an important method for preparing polyacrylamide aqueous dispersion. The polyacrylamide synthesized by this method is directly dispersed in the form of colloid in water or water / organic solvent, so that the polyacrylamide aqueous dispersion can be directly used, avoiding the complicated post-processing of the polymerization product. The biggest problem in preparing polyacrylamide aqueous dispersion by the aqueous dispersion polymerization method is that the molecular weight of polyacrylamide is high, the viscosity is high, and the stability of the dispersion is poor, so that the prepared polyacrylamide aqueous dispersion will be stratified after several weeks to several months of storage.

[0003] Improving the stability of polyacrylamide aqueous dispersion and establishing a simple and efficient method for synthesizing polyacrylamide aqueous dispersion are the problems to be solved in the synthesis of polyacrylamide aqueous dispersion at present. SUMMARY

[0004] The present application aims at the poor stability of the prior art polyacrylamide aqueous dispersion and the stratification problem during storage, and provides a cationic water-based polyurethane dispersion and a preparation method and application thereof. By synthesizing a cationic water-based polyurethane dispersion capped with acrylamide, polymerization is carried out in the cationic water-based polyurethane dispersion, and a polyacrylamide aqueous dispersion with good stability, flowability and high molecular weight is prepared.

[0005] To solve the above technical problems, the first aspect of the present application provides a preparation method of a cationic water-based polyurethane dispersion, comprising the following steps:

[0006] 1) In the presence of a catalyst, polyoxyethylene, polyether diol, alcohol amine, aliphatic and / or alicyclic diisocyanate are mixed and reacted to obtain a cationic water-based polyurethane prepolymer after reaction I, and then acrylamide compounds and a polymerization inhibitor are added to carry out reaction II;

[0007] 2) The cationic water-based polyurethane prepolymer obtained in step 1) is neutralized and diluted to obtain the cationic water-based polyurethane dispersion.

[0008] According to some embodiments of the present application, in step 1), the ratio of the amount of substance of the hydroxyl group in the polyoxyethylene, the amount of substance of the hydroxyl group in the polyether diol, the amount of substance of the hydroxyl group in the alcohol amine, the amount of substance of the isocyanate contained in the aliphatic and / or alicyclic diisocyanate, and the amount of substance of the hydroxyl group in the acrylamide compound is (0.1-0.4) : (0.1-0.4) : (0.1-0.3) : 1 : (0.2-0.4).

[0009] According to some embodiments of the present application, in step 1), the amount of the polymerization inhibitor added is 0.1% to 1.5% of the mass of the acrylamide compound.

[0010] According to some embodiments of the present application, in step 1), the amount of the catalyst added is 0.001% to 0.1% of the mass of the aliphatic and / or alicyclic diisocyanate.

[0011] According to some embodiments of the present application, in step 1), the molecular weight of the polyoxyethylene is 2000 Da to 20000 Da.

[0012] According to some embodiments of the present application, in step 1), the polyether diol is selected from at least one of polypropylene glycol and polytetramethylene glycol; preferably, the polypropylene glycol has a molecular weight of 2000 Da to 4000 Da, preferably 2000 Da.

[0013] According to some embodiments of the present application, in step 1), the alcohol amine is selected from N-alkyl diethanolamine; preferably, the N-alkyl diethanolamine is selected from at least one of N-methyl diethanolamine, N-ethyl diethanolamine, and N-phenyl diethanolamine.

[0014] According to some embodiments of the present application, in step 1), the catalyst is an organometallic catalyst containing tin or bismuth; preferably, the catalyst is at least one of dibutyl tin dilaurate, stannous octoate, bismuth laurate, and bismuth iso-octoate.

[0015] According to some embodiments of the present application, in step 1), the aliphatic and / or alicyclic diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 2,4-toluene diisocyanate, methylcyclohexyl diisocyanate, and 2,2,4-trimethylhexane diisocyanate.

[0016] According to some embodiments of the present application, in step 1), the acrylamide compound is selected from hydroxy acrylamide; preferably, the hydroxy acrylamide is selected from at least one of N-hydroxyethyl acrylamide, N-(3-hydroxypropyl) acrylamide, and N-(4-hydroxybutyl) acrylamide.

[0017] According to some embodiments of the present application, in step 1), the polymerization inhibitor is selected from at least one of hydroquinone, tert-butyl hydroquinone, p-hydroxyanisole.

[0018] According to some embodiments of the present application, in step 1), the conditions of the reaction I include: temperature is 45℃-85℃, time is 1-4 hours.

[0019] And / or, the conditions of the reaction II include: temperature is 45℃-85℃, time is 2-4 hours.

[0020] According to some embodiments of the present application, in step 2), the conditions of the neutralization include: temperature is room temperature, time is 1-10 minutes; preferably, the neutralizing agent added in the neutralization process is selected from at least one of acetic acid, hydrochloric acid; further preferably, the amount of substance of the neutralizing agent is 40%-100% of the amount of substance of the alcohol amine.

[0021] According to some embodiments of the present application, in step 2), the conditions of the dilution include: temperature is room temperature, stirring for 60-80 minutes; preferably, the diluent added in the dilution process is water; further preferably, after the dilution, the solid content of the cationic waterborne polyurethane dispersion is 20%-30%.

[0022] The second aspect of the present application provides a cationic waterborne polyurethane dispersion prepared by the above preparation method, and the cationic waterborne polyurethane dispersion is an acrylamide-terminated cationic waterborne polyurethane dispersion.

[0023] The third aspect of the present application provides an application of the above cationic waterborne polyurethane dispersion as a stabilizer in the synthesis of a polyacrylamide aqueous dispersion.

[0024] The fourth aspect of the present application provides a method for preparing a polyacrylamide aqueous dispersion, which comprises adding acrylamide, methyl acryloyloxyethyl trimethyl ammonium chloride aqueous solution, water, and ammonium sulfate into a cationic waterborne polyurethane dispersion, and polymerizing to obtain the polyacrylamide aqueous dispersion under the conditions of a non-reactive atmosphere and the presence of an initiator; wherein the cationic waterborne polyurethane dispersion is the above cationic waterborne polyurethane dispersion.

[0025] Preferably, the mass concentration of the methyl acryloyloxyethyl trimethyl ammonium chloride aqueous solution is 80%.

[0026] According to some embodiments of the present application, the non-reactive atmosphere is selected from at least one of nitrogen and helium.

[0027] According to some embodiments of the present application, the mass ratio of the acrylamide, the aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride, the water, the ammonium sulfate and the cationic aqueous polyurethane dispersion is (150-450):(30-90):(1120-3360):(45-135):(100-300), preferably 300:60:2240:90:200.

[0028] According to some embodiments of the present application, the initiator is added in an amount of 0.01%-0.1% of the mass of the acrylamide; preferably, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite and VA-044 initiator.

[0029] According to some embodiments of the present application, the polymerization conditions include a temperature of 25-45℃ and a time of 2-6 hours.

[0030] Advantages:

[0031] The cationic aqueous polyurethane dispersion prepared in the present application is used as a stabilizer for the aqueous polyacrylamide dispersion, and can effectively stabilize the aqueous polyacrylamide dispersion by being connected to the polyacrylic acid molecular chain through a covalent bond.

[0032] The cationic aqueous polyurethane dispersion prepared in the present application has an acrylamide end group, and can generate branched polyacrylamide by reacting with acrylamide, thereby increasing the molecular weight of the polyacrylamide. DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with examples. However, the present application is not limited by these examples.

[0034] The reaction kettle, three-necked flask and constant pressure funnel used in the examples of the present application are all ordinary commercially available products unless otherwise specified.

[0035] The polyoxyethylene used in the examples of the present application is purchased from Shanghai Dongda Chemical Co., Ltd., and has a model number of PEG2000 and a molecular weight of 2000 Da.

[0036] The polypropylene glycol used in the examples of the present application is purchased from Shandong Lansheng Dongda Co., Ltd., and has a model number of DL2000 and a molecular weight of 2000 Da.

[0037] The N-methyldiethanolamine, isophorone diisocyanate, N-hydroxyethyl acrylamide, N-(3-hydroxypropyl) acrylamide, p-hydroxyanisole and toluene diisocyanate used in the examples of the present application are all ordinary commercially available reagents unless otherwise specified.

[0038] In the present application, room temperature is 25℃ unless otherwise specified.

[0039] Example 1

[0040] The present embodiment provides a cationic waterborne polyurethane dispersion.

[0041] Into a reaction kettle, 3000 grams of dry polyethylene glycol (PEG 2000, molecular weight 2000 Da), 3000 grams of polypropylene glycol (DL 2000, molecular weight 2000 Da), 119 grams of N-methyldiethanolamine, 1112 grams of isophorone diisocyanate, and 0.10 gram of dibutyl tin dilaurate were added, stirred uniformly, warmed to 75°C, and reacted at 75°C for 3 hours, then 230 grams of N-hydroxyethyl acrylamide and 0.5 gram of p-hydroxyanisole were added, and the reaction was continued at 75°C for 3 hours, and then cooled to room temperature to obtain an acrylamide-terminated cationic waterborne polyurethane prepolymer;

[0042] At room temperature, 40 grams of acetic acid was added to the above-mentioned cationic waterborne polyurethane prepolymer, stirred for 5 minutes, then 17480 grams of pure water was added, and stirred for 1 hour to obtain an acrylamide-terminated cationic waterborne polyurethane dispersion A1 with a solid content of 30%.

[0043] In the above, the amount of substance of the acetic acid is 66.6% of the amount of substance of the N-methyldiethanolamine.

[0044] Example 2

[0045] The present embodiment provides a cationic waterborne polyurethane dispersion.

[0046] Into a reaction kettle, 4000 grams of dry polyethylene glycol (PEG 4000, molecular weight 4000 Da), 3000 grams of polypropylene glycol (DL 2000, molecular weight 2000 Da), 178 grams of N-methyldiethanolamine, 1112 grams of isophorone diisocyanate, and 0.10 gram of dibutyl tin dilaurate were added, stirred uniformly, warmed to 75°C, and reacted at 75°C for 3 hours, then 230 grams of N-hydroxyethyl acrylamide and 0.5 gram of p-hydroxyanisole were added, and the reaction was continued at 75°C for 3 hours, and then cooled to room temperature to obtain an acrylamide-terminated cationic waterborne polyurethane prepolymer;

[0047] At room temperature, 40 grams of acetic acid was added to the above-mentioned cationic waterborne polyurethane prepolymer, stirred for 5 minutes, then 19980 grams of pure water was added, and stirred for 1 hour to obtain an acrylamide-terminated cationic waterborne polyurethane dispersion A2 with a solid content of 30%.

[0048] In the above, the amount of substance of the acetic acid is 44.4% of the amount of substance of the N-methyldiethanolamine.

[0049] Example 3

[0050] This embodiment provides a cationic aqueous polyurethane dispersion.

[0051] 3000 g of dried polyethylene oxide (PEG2000, molecular weight 2000 Da), 3000 g of polypropylene glycol (DL2000, molecular weight 2000 Da), 119 g of N-methyldiethanolamine, 348 g of toluene diisocyanate, 669 g of isophorone diisocyanate and 0.10 g of dibutyltin dilaurate were added to a reaction vessel, stirred evenly, heated to 75°C, and reacted at 75°C for 3 hours. Then, 230 g of N-hydroxyethylacrylamide and 0.5 g of p-hydroxyanisole were added, and the reaction was continued at 75°C for 3 hours. The mixture was then cooled to room temperature to obtain an acrylamide-terminated cationic waterborne polyurethane prepolymer.

[0052] At room temperature, 40 g of acetic acid was added to the above cationic waterborne polyurethane prepolymer, and after stirring for 5 minutes, 16740 g of pure water was added and stirred for 1 hour to obtain a cationic waterborne polyurethane dispersion A3 with an acrylamide-terminated solid content of 30%.

[0053] In the above, the amount of acetic acid is 66.6% of the amount of N-methyldiethanolamine.

[0054] Example 4

[0055] This embodiment provides a cationic aqueous polyurethane dispersion.

[0056] 3000 g of dried polyoxyethylene (PEG2000, molecular weight 2000 Da), 3000 g of polypropylene glycol (DL2000, molecular weight 2000 Da), 119 g of N-methyldiethanolamine, 1112 g of isophorone diisocyanate and 0.10 g of dibutyltin dilaurate were added to a reaction vessel, stirred evenly, heated to 75°C, and reacted at 75°C for 3 hours. Then, 258 g of N-(3-hydroxypropyl)acrylamide and 0.5 g of p-hydroxyanisole were added, and the reaction was continued at 75°C for 3 hours. The mixture was then cooled to room temperature to obtain an acrylamide-terminated cationic waterborne polyurethane prepolymer.

[0057] At room temperature, 40 g of acetic acid was added to the above cationic waterborne polyurethane prepolymer, and after stirring for 5 minutes, 17570 g of pure water was added and stirred for 1 hour to obtain a cationic waterborne polyurethane dispersion A1 with an acrylamide end-capped solid content of 30%.

[0058] In the above, the amount of acetic acid is 66.6% of the amount of N-methyldiethanolamine.

[0059] Example 5

[0060] This embodiment provides a cationic aqueous polyurethane dispersion.

[0061] 4000 g of dried polyethylene oxide (PEG2000, molecular weight 2000 Da), 2000 g of polypropylene glycol (DL2000, molecular weight 2000 Da), 119 g of N-methyldiethanolamine, 1112 g of isophorone diisocyanate and 0.10 g of dibutyltin dilaurate were added to a reaction vessel, stirred evenly, heated to 75°C, and reacted at 75°C for 3 hours. Then, 230 g of N-hydroxyethylacrylamide and 0.5 g of p-hydroxyanisole were added, and the reaction was continued at 75°C for 3 hours. The mixture was then cooled to room temperature to obtain an acrylamide-terminated cationic waterborne polyurethane prepolymer.

[0062] At room temperature, 40 g of acetic acid was added to the above cationic waterborne polyurethane prepolymer, and after stirring for 5 minutes, 17480 g of pure water was added and stirred for 1 hour to obtain a cationic waterborne polyurethane dispersion A5 with an acrylamide-terminated solid content of 30%.

[0063] In the above, the amount of acetic acid is 66.6% of the amount of N-methyldiethanolamine.

[0064] Example 6

[0065] This embodiment provides a cationic aqueous polyurethane dispersion.

[0066] 5000 g of dried polyoxyethylene (PEG2000, molecular weight 2000 Da), 1000 g of polypropylene glycol (DL2000, molecular weight 2000 Da), 119 g of N-methyldiethanolamine, 1112 g of isophorone diisocyanate and 0.10 g of dibutyltin dilaurate were added to a reaction vessel, stirred evenly, heated to 75°C, and reacted at 75°C for 3 hours. Then, 230 g of N-hydroxyethylacrylamide and 0.5 g of p-hydroxyanisole were added, and the reaction was continued at 75°C for 3 hours. The mixture was then cooled to room temperature to obtain an acrylamide-terminated cationic waterborne polyurethane prepolymer.

[0067] At room temperature, 40 g of acetic acid was added to the above cationic waterborne polyurethane prepolymer, stirred for 5 minutes, then 17480 g of pure water was added and stirred for 1 hour to obtain a 30% acrylamide-terminated cationic waterborne polyurethane dispersion A6.

[0068] In the above, the amount of acetic acid is 66.6% of the amount of N-methyldiethanolamine.

[0069] Preparation Example 1

[0070] This preparation example provides an aqueous dispersion of polyacrylamide.

[0071] 300 g of acrylamide, 60 g of 80% aqueous solution of methacryloyloxyethyltrimethylammonium chloride, 2240 g of water, 90 g of ammonium sulfate, and 200 g of the cationic aqueous polyurethane dispersion A1 obtained in Example 1 of this invention were added to a three-necked flask. 0.12 g of ammonium persulfate was dissolved in 3.0 g of water and placed in constant pressure funnel 1. 0.07 g of sodium bisulfite was dissolved in 3.0 g of water and placed in constant pressure funnel 2. The two constant pressure funnels were placed on the three-necked flask, and nitrogen gas was passed through the three-necked flask to remove oxygen under stirring.

[0072] When the three-necked flask is heated to 35°C, the initiator in the two constant pressure funnels is added to the three-necked flask. Under stirring conditions, the reaction is carried out for 5 hours to obtain polyacrylamide aqueous dispersion B1.

[0073] Preparation Example 2

[0074] This preparation example provides an aqueous dispersion of polyacrylamide.

[0075] 300 g of acrylamide, 60 g of methacryloyloxyethyltrimethylammonium chloride 80% aqueous solution, 2240 g of water, 90 g of ammonium sulfate, and 200 g of the cationic aqueous polyurethane dispersion A1 obtained in Example 1 of this invention were added to a three-necked flask; 0.12 g of VA-044 initiator was dissolved in 3.0 g of water and placed in a constant pressure funnel, which was then placed on the three-necked flask. Under stirring conditions, nitrogen gas was passed into the three-necked flask to remove oxygen.

[0076] When the three-necked flask is heated to 35°C, the initiator in the constant pressure funnel is added to the three-necked flask. Under stirring conditions, the reaction is carried out for 5 hours to obtain polyacrylamide aqueous dispersion B2.

[0077] Preparation Example 3

[0078] This preparation example provides an aqueous dispersion of polyacrylamide.

[0079] Add 300g of acrylamide, 60g of an 80% aqueous solution of methacryloyloxyethyltrimethylammonium chloride, 2240g of water, 90g of ammonium sulfate, and 200g of the cationic aqueous polyurethane dispersion A2 obtained in Example 2 of this invention to a three-necked flask; dissolve 0.12g of VA-044 initiator in 3.0g of water, place the solution in a constant pressure funnel, and place the constant pressure funnel on the three-necked flask. Under stirring conditions, purge the three-necked flask with nitrogen to remove oxygen.

[0080] When the three-necked flask is heated to 35°C, the initiator in the constant pressure funnel is added to the three-necked flask. Under stirring conditions, the reaction is carried out for 5 hours to obtain polyacrylamide aqueous dispersion B3.

[0081] Preparation Example 4

[0082] This preparation example provides an aqueous dispersion of polyacrylamide.

[0083] 300 g of acrylamide, 60 g of methacryloyloxyethyltrimethylammonium chloride 80% aqueous solution, 2240 g of water, 90 g of ammonium sulfate, and 200 g of the cationic aqueous polyurethane dispersion A5 obtained in Example 5 of this invention were added to a three-necked flask; 0.12 g of VA-044 initiator was dissolved in 3.0 g of water and placed in a constant pressure funnel, which was then placed on the three-necked flask. Under stirring conditions, nitrogen gas was passed into the three-necked flask to remove oxygen.

[0084] When the three-necked flask is heated to 35°C, the initiator in the constant pressure funnel is added to the three-necked flask. Under stirring conditions, the reaction is carried out for 5 hours to obtain polyacrylamide aqueous dispersion B4.

[0085] Preparation Example 5

[0086] This preparation example provides an aqueous dispersion of polyacrylamide.

[0087] 300 g of acrylamide, 60 g of methacryloyloxyethyltrimethylammonium chloride 80% aqueous solution, 2240 g of water, 90 g of ammonium sulfate, and 200 g of the cationic aqueous polyurethane dispersion A6 obtained in Example 6 of this invention were added to a three-necked flask; 0.12 g of VA-044 initiator was dissolved in 3.0 g of water and placed in a constant pressure funnel, which was then placed on the three-necked flask. Under stirring conditions, nitrogen gas was passed into the three-necked flask to remove oxygen.

[0088] When the three-necked flask is heated to 35°C, the initiator in the constant pressure funnel is added to the three-necked flask. Under stirring conditions, the reaction is carried out for 5 hours to obtain polyacrylamide aqueous dispersion B5.

[0089] Comparative Example 1

[0090] This comparative example prepares an acrylamide-terminated anionic aqueous polyurethane dispersion.

[0091] The procedure was carried out according to the method described in Example 1, except that 134 g of 2,2-dimethylolpropionic acid was used instead of 119 g of N-methyldiethanolamine.

[0092] Comparative Example 2

[0093] This comparative example prepares a cationic aqueous polyurethane dispersion without acrylamide end groups.

[0094] The procedure was carried out according to the method described in Example 1, except that 92 grams of ethanol was used instead of 230 grams of N-hydroxyethylacrylamide.

[0095] Comparative Preparation Example 1

[0096] This preparation example provides an aqueous dispersion of polyacrylamide.

[0097] The preparation was carried out according to the method described in Preparation Example 1, except that the acrylamide-terminated anionic aqueous polyurethane dispersion obtained in Comparative Example 1 was used instead of the cationic aqueous polyurethane dispersion A1 obtained in Example 1 of this invention.

[0098] Comparative Preparation Example 2

[0099] This preparation example provides an aqueous dispersion of polyacrylamide.

[0100] The preparation was carried out according to the method described in Preparation Example 1, except that the cationic aqueous polyurethane dispersion A1 obtained in Example 1 of the present invention was replaced with the acrylamide-free cationic aqueous polyurethane dispersion obtained in Comparative Example 2.

[0101] Test case

[0102] The basic parameters of the cationic aqueous polyurethane dispersions prepared in Examples 1-6 and the aqueous polyurethane dispersions prepared in Comparative Examples 1-2 are shown in Table 1.

[0103] In Examples 1-6, the amounts and molecular weights of polyoxyethylene and polypropylene glycol used were different, as were the aliphatic and / or alicyclic diisocyanates, but all yielded acrylamide-terminated cationic aqueous polyurethane dispersions. Due to the large number of hydrophilic groups in the polyurethane molecular chains, the hydrodynamic radius of the aqueous polyurethane dispersions was small. Comparative Example 1 prepared an acrylamide-terminated anionic aqueous polyurethane dispersion, which had the opposite charge to that of Examples 1-6. Comparative Example 2 prepared a cationic aqueous polyurethane dispersion without acrylamide end groups.

[0104] The appearance, solid content, viscosity, freeze-thaw stability and centrifugal stability of the aqueous polyurethane dispersions prepared in Examples 1-6 and Comparative Examples 1-2 of this invention were tested in accordance with GB / T 11175-2002.

[0105] Freeze-thaw stability: 50 mL of waterborne polyurethane dispersion was placed in a low-temperature chamber at -5±2℃. After 18 hours, it was taken out and placed at 23±2℃ for 6 hours. The operation was repeated to observe whether there was any precipitation.

[0106] Centrifugal stability: 30 mL of waterborne polyurethane dispersion was placed in a centrifuge and centrifuged for 30 min at a speed of 3000 r / min to test the centrifugal stability of the waterborne polyurethane dispersion.

[0107] The viscosity testing instrument was a Brookfield DV1 viscometer, and the viscosity measurement method was direct testing at a temperature of 25°C.

[0108] The method for determining the hydrodynamic diameter is as follows: dilute the cationic aqueous polyurethane dispersion with water to a solid content (mass concentration) of 1%, and then use Malvern Nano-ZS90 to measure the hydrodynamic diameter of the cationic aqueous polyurethane dispersion with a mass concentration of 1%.

[0109] The concentration of acrylamide end groups in the cationic aqueous polyurethane dispersion was measured by nuclear magnetic resonance spectroscopy.

[0110] Table 1. Basic parameters of the cationic aqueous polyurethane dispersions prepared in Examples 1-6 and the aqueous polyurethane dispersions prepared in Comparative Examples 1-2 of this invention.

[0111]

[0112]

[0113] The results in Table 1 show that the cationic aqueous polyurethane dispersions prepared in Examples 1-4 are all water-white and transparent dispersions with hydrodynamic diameters ranging from 18 to 23 nm. The concentration of acrylamide end groups in the cationic aqueous polyurethane dispersions is close to or slightly lower than the theoretical value (calculated based on the feed amount), indicating good stability. The hydrodynamic diameters of the aqueous polyurethane dispersions prepared in Comparative Examples 1-2 are similar. Among them, Comparative Example 1 is an anionic aqueous polyurethane dispersion, and Comparative Example 2 is a cationic aqueous polyurethane dispersion without acrylamide end groups. The particle size and stability are similar to those of the aqueous polyurethane dispersion prepared in Example 1.

[0114] The basic parameters of the polyacrylamide aqueous dispersions prepared in Examples 1-5 and Comparative Examples 1-2 of this invention are shown in Table 2.

[0115] The polymer concentration measurement method is as follows: dilute the polyacrylamide aqueous dispersion of weight C1 with water to a mass concentration of 1%, then put it into a dialysis bag (molecular weight cutoff: 1000 Da) and dialyze it in water for three days. After that, freeze-dry the sample to obtain the weight C2 of the dried sample. The polymer concentration is the percentage of the ratio of C2 to CI.

[0116] The apparent viscosity is the viscosity of the polyacrylamide aqueous dispersion tested directly without dilution with water; the viscosity of the polymer solution with a mass concentration of 1% refers to the viscosity of the solution when the polyacrylamide aqueous dispersion is diluted with water to a mass concentration of 1% for polyacrylamide and its copolymers.

[0117] Among them, the stability of the polyacrylamide aqueous dispersions prepared in Examples 1 to 5 of the present invention is determined by visual observation at room temperature. If the dispersion does not separate into layers, it is considered stable; if it separates into layers, it is considered unstable.

[0118] Table 2. Parameters of the polyacrylamide aqueous dispersions prepared in Examples 1-5 of this invention.

[0119]

[0120] The results in Table 2 show that the aqueous polyacrylamide dispersions prepared in Examples 1-5 have high viscosity at a mass concentration of 1% and stability exceeding 3 months. This indicates that the cationic aqueous polyurethane dispersions prepared in Examples 1-6 of this invention are effective stabilizers for preparing aqueous polyacrylamide dispersions. In contrast, the acrylamide-terminated anionic aqueous polyurethane dispersion in Comparative Example 1, used as a stabilizer, resulted in an unstable aqueous polyacrylamide dispersion exhibiting stratification and high viscosity at a mass concentration of 1%, but with extremely poor stability. Furthermore, using the cationic aqueous polyurethane dispersion without acrylamide end groups in Comparative Example 2 as a stabilizer resulted in a slightly lower viscosity and slightly lower stability at a mass concentration of 1% for the polymer solution.

[0121] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a cationic aqueous polyurethane dispersion, characterized in that, Includes the following steps, 1) In the presence of a catalyst, polyoxyethylene, polyether diol, alkanolamine, aliphatic and / or alicyclic diisocyanate are mixed and reacted in reaction I. Acrylamide compounds and polymerization inhibitors are then added and reacted in reaction II to obtain cationic waterborne polyurethane prepolymer. 2) After neutralizing and diluting the cationic aqueous polyurethane prepolymer obtained in step 1), the cationic aqueous polyurethane dispersion is obtained; In step 1), the ratio of the amount of hydroxyl groups in polyoxyethylene, the amount of hydroxyl groups in polyether diol, the amount of hydroxyl groups in alkanolamine, the amount of isocyanate contained in aliphatic and / or alicyclic diisocyanates, and the amount of hydroxyl groups in acrylamide compounds is (0.1–0.4): (0.1–0.4): (0.1–0.3): 1: (0.2–0.4). The amount of the polymerization inhibitor added is 0.1% to 1.5% of the mass of the acrylamide compound; The molecular weight of the polyoxyethylene is 2000 Da to 20000 Da; The polyether diol is selected from polypropylene glycol; The alcohol amine is selected from N-alkyldiethanolamine; The aliphatic and / or alicyclic diisocyanate is selected from at least one of toluene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 2,4-phenyl diisocyanate, methylcyclohexyl diisocyanate, and 2,2,4-trimethylhexane diisocyanate. The acrylamide compounds are selected from hydroxyacrylamide.

2. The preparation method according to claim 1, characterized in that, In step 1), the amount of catalyst added is 0.001% to 0.1% of the mass of aliphatic and / or alicyclic diisocyanate.

3. The preparation method according to claim 1, characterized in that, In step 1), the molecular weight of the polypropylene glycol is 2000 Da to 4000 Da; And / or, the N-alkyldiethanolamine is selected from at least one of N-methyldiethanolamine, N-ethyldiethanolamine, and N-phenyldiethanolamine; And / or, the hydroxyacrylamide is selected from at least one of N-hydroxyethylacrylamide, N-(3-hydroxypropyl)acrylamide, and N-(4-hydroxybutyl)acrylamide; And / or, the catalyst is an organometallic catalyst containing tin or bismuth; And / or, the polymerization inhibitor is selected from at least one of hydroquinone, tert-butylcatechol, and p-hydroxyanisole.

4. The preparation method according to claim 3, characterized in that, In step 1), the molecular weight of the polypropylene glycol is 2000 Da; And / or, the catalyst is at least one of dibutyltin dilaurate, stannous octoate, bismuth laurate, and bismuth isooctanoate.

5. The preparation method according to any one of claims 1-4, characterized in that, In step 1), the conditions for reaction I include: a temperature of 45°C to 85°C and a time of 1 hour to 4 hours; And / or, the conditions for reaction II include: a temperature of 45°C to 85°C and a time of 2 to 4 hours.

6. The preparation method according to any one of claims 1-4, characterized in that, In step 2), the conditions for neutralization include: room temperature and time of 1 to 10 minutes.

7. The preparation method according to any one of claims 1-4, characterized in that, The neutralizing agent added during the neutralization process is selected from at least one of acetic acid and hydrochloric acid.

8. The preparation method according to claim 7, characterized in that, The amount of the neutralizing agent is 40% to 100% of the amount of the alcohol amine.

9. The preparation method according to any one of claims 1-4, characterized in that, In step 2), the dilution conditions include: room temperature and stirring for 60 to 80 minutes.

10. The preparation method according to any one of claims 1-4, characterized in that, The diluent added during the dilution process is water.

11. The preparation method according to claim 10, characterized in that, After dilution, the solid content of the cationic aqueous polyurethane dispersion is 20% to 30%.

12. A cationic aqueous polyurethane dispersion prepared by the preparation method according to any one of claims 1-11, characterized in that, The cationic aqueous polyurethane dispersion is an acrylamide-terminated cationic aqueous polyurethane dispersion.

13. The use of a cationic aqueous polyurethane dispersion prepared by any one of claims 1-11 or the cationic aqueous polyurethane dispersion of claim 12 as a stabilizer in the synthesis of an aqueous polyacrylamide dispersion.

14. A method for preparing an aqueous dispersion of polyacrylamide, characterized in that, The method includes adding acrylamide, an aqueous solution of methacryloyloxyethyltrimethylammonium chloride, water, and ammonium sulfate to a cationic aqueous polyurethane dispersion, and polymerizing the dispersion under an inactive atmosphere and in the presence of an initiator to obtain the aqueous polyacrylamide dispersion; wherein the cationic aqueous polyurethane dispersion is the cationic aqueous polyurethane dispersion prepared by any one of claims 1-11 or the cationic aqueous polyurethane dispersion of claim 12.

15. The method according to claim 14, characterized in that, The mass concentration of the aqueous solution of methacryloyloxyethyltrimethylammonium chloride is 80%.

16. The method according to claim 14, characterized in that, The non-active atmosphere is selected from at least one of nitrogen and argon; And / or, the mass ratio of the acrylamide, methacryloyloxyethyltrimethylammonium chloride aqueous solution, water, ammonium sulfate and cationic aqueous polyurethane dispersion is (150-450):(30-90):(1120-3360):(45-135):(100-300); And / or, the amount of the initiator added is 0.01% to 0.1% of the mass of acrylamide; And / or, the polymerization conditions include: a temperature of 25°C to 45°C and a time of 2 hours to 6 hours.

17. The method according to claim 14, characterized in that, The mass ratio of the acrylamide, the aqueous solution of methacryloyloxyethyltrimethylammonium chloride, water, ammonium sulfate and the cationic aqueous polyurethane dispersion is 300:60:2240:90:200; And / or, the initiator is selected from at least one of ammonium persulfate, sodium bisulfite, and VA-044 initiator.

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