Polyacrylamide aqueous dispersion as well as synthesis method and application thereof

Abstract

The invention discloses a polyacrylamide aqueous dispersion as well as a synthesis method and application thereof, and relates to the technical field of polyacrylamide synthesis. The synthesis method of the polyacrylamide aqueous dispersion comprises the following steps: carrying out a reaction I on a reaction system of acrylamide I, a cationic monomer I, an inorganic salt, a stabilizer and an initiator I to obtain the polyacrylamide aqueous dispersion, wherein the stabilizer is a binary mixture of a cationic copolymer containing a polyacrylamide chain segment and polyoxyethylene; the prepared polyacrylamide aqueous dispersion has excellent stability, and destabilization does not occur after the polyacrylamide aqueous dispersion is placed at room temperature for more than one year; the paint can be stored in an environment of-10 DEG C or above, and when the temperature recovers to 2-40 DEG C, the paint can be continuously kept stable.

Description

Technical Field

[0001] The invention relates to the technical field of polyacrylamide synthesis, and in particular to a polyacrylamide aqueous dispersion and a synthesis method and application thereof. Background Art

[0002] Polyacrylamide has good water solubility, efficient viscosity increase and unique adsorption, so it is widely used in many fields such as water treatment, oil production, papermaking, textiles, etc. Aqueous phase dispersion polymerization is an important method for preparing aqueous dispersions of polyacrylamide.

[0003] At present, the biggest problem of preparing polyacrylamide aqueous dispersion by aqueous phase dispersion polymerization is that the stability of the aqueous dispersion is poor, and the prepared polyacrylamide aqueous dispersion will be stratified after being stored for several weeks to several months. For example, Chinese patent document CN 02627725A discloses a method for synthesizing a cationic polyacrylamide emulsion, and the preparation method described is as follows: using a mixed solution of tert-butyl alcohol, ammonium sulfate and water as a reaction medium, acrylamide, methacrylamide oxyethyl trimethyl ammonium chloride and N-vinyl pyrrolidone as reaction raw materials, ammonium persulfate and sodium bisulfite as reaction initiators, polyethylene glycol and polymethacrylamide oxyethyl trimethyl ammonium chloride as dispersion stabilizers, the prepared polyacrylamide aqueous dispersion has a relatively low molecular weight, resulting in a low viscosity of the polyacrylamide aqueous dispersion, and stratification occurs after being stored for up to two months, resulting in failure to be used normally.

[0004] In summary, improving the stability of aqueous polyacrylamide dispersions, especially the stability of high molecular weight aqueous polyacrylamide dispersions, is an urgent problem to be solved in the current synthesis of aqueous polyacrylamide dispersions. Summary of the invention

[0005] The present invention aims at the problems existing in the synthesis of polyacrylamide aqueous dispersion in the prior art, and prepares the polyacrylamide aqueous dispersion by dispersion polymerization, wherein the stabilizer of the dispersion polymerization is a binary mixture of a cationic copolymer containing polyacrylamide chain segments and polyoxyethylene. Different from other methods, the present invention uses the binary mixture of a cationic copolymer containing polyacrylamide chain segments and polyoxyethylene as a stabilizer, which can effectively solve the problem of poor stability of the polyacrylamide aqueous dispersion.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a method for synthesizing an aqueous polyacrylamide dispersion, comprising subjecting a reaction system of acrylamide I, a cationic monomer I, an inorganic salt, a stabilizer and an initiator I to a reaction I to obtain the aqueous polyacrylamide dispersion; wherein the stabilizer is a binary mixture of a cationic copolymer containing a polyacrylamide segment and polyethylene oxide.

[0007] According to some embodiments of the present invention, the mass ratio of the acrylamide I, the cationic monomer I, the inorganic salt and the stabilizer is 36: (4.32-5.76); 10: (270-275).

[0008] According to some embodiments of the present invention, the added amount of the initiator I is 0.1% to 0.5% of the mass of the acrylamide I.

[0009] According to some embodiments of the present invention, the cationic monomer I is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride.

[0010] According to some embodiments of the present invention, the inorganic salt is selected from ammonium salts; preferably, the ammonium salt is selected from at least one of ammonium sulfate and ammonium persulfate.

[0011] According to some embodiments of the present invention, the initiator I is selected from aqueous initiator I and / or thermal initiator I; preferably, the aqueous initiator I is selected from at least one of V-50 and VA-044; the thermal initiator I is selected from at least two of ammonium persulfate, sodium bisulfite, and potassium persulfate.

[0012] According to some embodiments of the present invention, the conditions of reaction I include: temperature of 25° C. to 45° C., and time of 1 hour to 6 hours.

[0013] According to some embodiments of the present invention, the preparation of the stabilizer includes: in the presence of an initiator II and an inactive atmosphere, mixing a cationic monomer II, acrylamide II, and polyethylene oxide in water to obtain a mixed solution, and performing a reaction II to obtain the stabilizer.

[0014] In the present invention, polyoxyethylene does not participate in the polymerization reaction during the preparation of the stabilizer, that is, the cationic copolymer containing polyacrylamide segments and polyoxyethylene in the binary mixture do not react with the polyoxyethylene, and the role of polyoxyethylene is to stabilize the cationic copolymer.

[0015] According to some embodiments of the present invention, the mass ratio of the cationic monomer II, acrylamide II, polyethylene oxide and water is 72:60:(30-100):(160-260).

[0016] According to some embodiments of the present invention, the added amount of the initiator II is 0.1% to 0.5% of the mass of the cationic monomer II.

[0017] According to some embodiments of the present invention, the cationic monomer II is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride.

[0018] According to some embodiments of the present invention, the polyoxyethylene is selected from polyoxyethylene with or without end capping; preferably, the molecular weight of the polyoxyethylene is 2000Da to 200000Da; further preferably, the polyoxyethylene with end capping includes single-end capped polyoxyethylene and double-end capped polyoxyethylene; further preferably, the single-end capped polyoxyethylene is selected from polyoxyethylene monomethyl ether; the double-end capped polyoxyethylene is selected from polyoxyethylene dimethyl ether; the polyoxyethylene without end capping is polyethylene glycol.

[0019] According to some embodiments of the present invention, the initiator II is selected from aqueous initiator II and / or thermal initiator II; preferably, the aqueous initiator II is selected from at least one of V-50 and VA-044; the thermal initiator II is selected from at least two of ammonium persulfate, sodium bisulfite, and potassium persulfate.

[0020] According to some embodiments of the present invention, the inactive atmosphere is selected from at least one of nitrogen and argon.

[0021] According to some embodiments of the present invention, the conditions of reaction II include: temperature of 30° C. to 80° C., and reaction time of 5 hours to 10 hours.

[0022] According to some embodiments of the present invention, the reaction II further includes dilution; preferably, the stabilizer is cooled to room temperature, and then a certain amount of water is added to dilute the stabilizer to a mass concentration of 5wt% to 10wt%, to obtain an aqueous solution of a binary mixture of a cationic copolymer containing polyacrylamide segments and polyethylene oxide.

[0023] The second aspect of the present invention provides an aqueous polyacrylamide dispersion obtained by using the above method for synthesizing an aqueous polyacrylamide dispersion.

[0024] A third aspect of the present invention provides a use of the above-mentioned aqueous dispersion of polyacrylamide as a flocculant in sewage and / or wastewater treatment.

[0025] Beneficial effects:

[0026] The polyacrylamide aqueous dispersion prepared by the present invention has high viscosity and excellent stability, and no destabilization occurs when it is placed at room temperature for more than one year.

[0027] The polyacrylamide aqueous dispersion prepared by the present invention can be stored in an environment above -10°C, and can continue to remain stable when the temperature returns to 2-40°C.

[0028] The polyacrylamide aqueous dispersion prepared by the invention can be used as a flocculant and can be widely used in environmental protection fields such as sewage and wastewater treatment in industries such as petrochemical industry, printing, steelmaking and papermaking. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the embodiments, but the present invention is not limited by these embodiments.

[0030] The three-necked flask and three-necked bottle used in the examples of the present invention are common commercially available products unless otherwise specified.

[0031] In the present invention, methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, acrylamide, polyethylene glycol, VA-044 initiator, ammonium sulfate, ammonium persulfate, and sodium bisulfite are all common commercially available reagents unless otherwise specified.

[0032] Unless otherwise specified, the room temperature in the embodiments of the present invention is 25°C.

[0033] Example 1

[0034] This embodiment provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0035] In a three-necked flask, 60 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, 30 g of an aqueous solution of acryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 30 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature. 2900 g of water was added to dilute the mixture into an aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration of 5%, i.e., stabilizer A1.

[0036] This embodiment further provides an aqueous dispersion of polyacrylamide.

[0037] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the above-mentioned stabilizer A1 (an aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration of 5%) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B1.

[0038] Example 2

[0039] This embodiment provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0040] In a three-necked flask, 60 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 30 g of an aqueous solution of acryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 30 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 2900 g of water was added to dilute it into an aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration of 5%, i.e., stabilizer A1.

[0041] This embodiment further provides an aqueous dispersion of polyacrylamide.

[0042] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, the above-mentioned 270 g of stabilizer A1 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed and deoxygenated aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B2.

[0043] Example 3

[0044] This embodiment provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0045] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 100 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 4130 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A2.

[0046] This embodiment further provides an aqueous dispersion of polyacrylamide.

[0047] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the stabilizer A2 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B3.

[0048] Example 4

[0049] This embodiment provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0050] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 100 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 4130 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A2.

[0051] This embodiment further provides an aqueous dispersion of polyacrylamide.

[0052] At room temperature, 36 g of acrylamide, 7.2 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, the above-mentioned 275 g of stabilizer A2 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B4.

[0053] Example 5

[0054] This embodiment provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0055] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 200 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 6362 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A3.

[0056] This embodiment further provides an aqueous dispersion of polyacrylamide.

[0057] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the stabilizer A3 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B5.

[0058] Example 6

[0059] This embodiment provides a binary mixture containing a cationic copolymer and polyoxyethylene.

[0060] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 200 g of polyethylene glycol (PEG20000, molecular weight 20000 Da), 0.10 g of VA-044 initiator and 260 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 6362 g of water was added to dilute it to a mass concentration of 5% aqueous solution containing a binary mixture of cationic copolymer and polyethylene oxide, i.e., stabilizer A3.

[0061] This embodiment further provides an aqueous dispersion of polyacrylamide.

[0062] At room temperature, 36 g of acrylamide, 7.2 g of an aqueous solution of methacryloyloxyethyl trimethyl ammonium chloride with a mass concentration of 80%, the above-mentioned 275 g of stabilizer A3 (a 5% aqueous solution containing a cationic copolymer and a binary mixture of polyoxyethylene with a mass concentration) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B6.

[0063] Comparative Example 1

[0064] This comparative example provides a cationic copolymer.

[0065] The method described in Example 2 was followed, except that PEG20000 was not added to the raw materials; the details are as follows:

[0066] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at a temperature of 45° C. for 7 hours, and then cooled to room temperature, and 2330 g of water was added to dilute it to an aqueous solution of a cationic copolymer with a mass concentration of 5%, i.e., stabilizer A4.

[0067] This comparative example further provides an aqueous dispersion of polyacrylamide.

[0068] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 270 g of the above-mentioned stabilizer A4 (an aqueous solution of a cationic copolymer with a mass concentration of 5%) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was introduced after degassing and deoxygenation, the temperature was raised to 45°C, 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, the reaction was continued for 6 hours, the heating source was removed, the reaction was stopped, and a polyacrylamide aqueous dispersion B7 was obtained.

[0069] Comparative Example 2

[0070] This comparative example provides a cationic copolymer.

[0071] The method described in Example 2 was followed, except that PEG20000 was not added to the raw materials; the details are as follows:

[0072] In a three-necked flask, 90 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, 60 g of acrylamide, 0.10 g of VA-044 initiator and 160 g of water were added in sequence, and nitrogen was introduced after degassing and deoxygenation. The mixture was reacted at 45° C. for 7 hours, and then cooled to room temperature, and 2330 g of water was added to dilute it to a cationic copolymer aqueous solution with a mass concentration of 5%, i.e., stabilizer A4.

[0073] This comparative example further provides an aqueous dispersion of polyacrylamide.

[0074] At room temperature, 36 g of acrylamide, 7.2 g of an aqueous solution of methacryloyloxyethyltrimethylammonium chloride with a mass concentration of 80%, the above-mentioned 280 g of stabilizer A4 (aqueous solution of a cationic copolymer with a mass concentration of 5%) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. Then, nitrogen was charged after degassing and deoxygenation, and the temperature was raised to 30° C., and 0.60 mL of a degassed and deoxygenated aqueous solution of ammonium persulfate (the concentration of the aqueous solution of ammonium persulfate was 40 mg / mL) and 0.40 mL of an aqueous solution of sodium bisulfite (the concentration of the aqueous solution of sodium bisulfite was 40 mg / mL) were added respectively, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B8.

[0075] Comparative Example 3

[0076] In this comparative example, a polyoxyethylene (PEG20000) aqueous solution with a mass concentration of 5% was used as stabilizer A5.

[0077] This comparative example further provides an aqueous dispersion of polyacrylamide.

[0078] At room temperature, 36 g of acrylamide, 5.4 g of an aqueous solution of 80% methacryloyloxyethyltrimethylammonium chloride, 270 g of the above-mentioned stabilizer A5 (aqueous solution of 5% polyoxyethylene) and 10 g of ammonium sulfate were added to a three-necked flask equipped with a stirring paddle, and the mixture was stirred until all the added materials were completely dissolved. The mixture was then degassed and deoxygenated and filled with nitrogen. The temperature was raised to 45° C., 1 mL of a degassed and deoxygenated VA-044 aqueous solution (the concentration of the VA-044 aqueous solution was 40 mg / mL) was added, and the reaction was continued for 6 hours. The heating source was removed to stop the reaction to obtain an aqueous polyacrylamide dispersion B9.

[0079] Test Case

[0080] (I) Stabilizer parameters

[0081] The basic parameters of stabilizers A1-A3 prepared in Examples 1-6 of the present invention are shown in Table 1.

[0082] Among them, the binary mixture containing cationic copolymer and polyoxyethylene prepared and used in Examples 1-6, namely stabilizers A1, A2 and A3, have different weight ratios of cationic copolymer to polyoxyethylene. The ratio in A1 is 4.4 / 1 ((mass of cationic monomer II in the raw material + mass of acrylamide) / mass of PEG20000), that is, cationic copolymer is the main component; in A2, the content of polyoxyethylene is increased, and the ratio is 1.3 / 1; in A3, the content of polyoxyethylene is further increased, and the ratio is 0.66 / 1, that is, PEG20000 is the main component;

[0083] Comparative Examples 1-3 prepared and used a single cationic copolymer aqueous solution or a PEG20000 aqueous solution as a stabilizer.

[0084] In Table 1, the appearance, solid content, and viscosity of stabilizers A1-A3 were tested with reference to GB / T 11175-2002;

[0085] The viscosity test instrument is Brookfield viscometer DV1, and the viscosity determination method is: direct testing at a temperature of 25°C.

[0086] Table 1 Comparison of basic parameters of the stabilizers prepared in Examples 1-6 and the stabilizers described in Comparative Examples 1-2

[0087]

[0088]

[0089] In Table 1, PEG content (taking Example 1 as an example): 30g / (60g+30g+60g+30g+160g+2900g)×100%=0.92%.

[0090] The results in Table 1 show that the stabilizers A1, A2 and A3 prepared in Examples 1-6 have slightly lower viscosities than the cationic copolymer stabilizer A4 prepared in Comparative Example 1-2 due to the presence of nonionic polymer PEG. The viscosities of the stabilizers A1, A2 and A3 prepared in Examples 1-6 decrease as the content of PEG20000 increases.

[0091] (II) Parameters of polyacrylamide aqueous dispersion

[0092] The basic parameters of the aqueous polyacrylamide dispersions prepared in Examples 1-6 of the present invention and Comparative Examples 1-3 are shown in Table 2.

[0093] The polymer concentration is measured by diluting a polyacrylamide aqueous dispersion of weight C1 with water to a concentration of 1% of the polyacrylamide aqueous dispersion, placing it in a dialysis bag (molecular weight cutoff size: 1000 Da) and dialyzing it in water for three days, and then freeze-drying the sample to obtain a dry sample weight C2, and the polymer concentration is the percentage of the ratio of C2 to CI;

[0094] Among them, the apparent viscosity is the viscosity of the aqueous polyacrylamide dispersion prepared in Examples 1-6 and Comparative Examples 1-3 directly tested 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 aqueous polyacrylamide dispersion is diluted with water to a mass concentration of polyacrylamide and its copolymer of 1%;

[0095] The stability of the aqueous polyacrylamide dispersions prepared in Examples 1-6 and Comparative Examples 1-3 at room temperature is visually observed. If the dispersions are not stratified, they are stable, and if they are stratified, they are unstable.

[0096] Among them, freeze-thaw stability: take 50mL of polyacrylamide dispersion and place it in a low-temperature box with a temperature of -5±2℃, take it out after 18 hours, and place it at a temperature of 23±2℃ for 6 hours. Repeat the operation to observe whether there is precipitation.

[0097] Table 2 Parameters of aqueous polyacrylamide dispersions prepared in Examples 1-6 of the present invention and Comparative Examples 1-3

[0098]

[0099]

[0100] The results in Table 2 show that the polyacrylamide aqueous dispersions prepared in Examples 1-6 have suitable apparent viscosity and a relatively high viscosity of a polymer solution with a mass concentration of 1%, and a stability of more than 6 months, or even 1 year; while the viscosity of the polyacrylamide aqueous dispersions prepared in Comparative Examples 1-3 with a mass concentration of 1% polymer solution is significantly reduced, and the stability is less than 1 month; this shows that the present invention is an effective method for preparing a highly stable and highly viscous polyacrylamide aqueous dispersion using a cationic copolymer and a polyoxyethylene binary as a stabilizer for dispersion polymerization.

[0101] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for synthesizing an aqueous dispersion of polyacrylamide, characterized in that: The method comprises the following steps: reacting a reaction system of acrylamide I, a cationic monomer I, an inorganic salt, a stabilizer and an initiator I to obtain the polyacrylamide aqueous dispersion; wherein the stabilizer is a binary mixture of a cationic copolymer containing polyacrylamide segments and polyethylene oxide.

2. The synthesis method according to claim 1, characterized in that The mass ratio of the acrylamide I, the cationic monomer I, the inorganic salt and the stabilizer is 36: (4.32-5.76); 10：(270～275)； And / or, the added amount of the initiator I is 0.1% to 0.5% of the mass of the acrylamide I.

3. The synthesis method according to claim 2, characterized in that The cationic monomer I is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride; And / or, the inorganic salt is selected from ammonium salt; preferably, the ammonium salt is selected from at least one of ammonium sulfate and ammonium persulfate; And / or, the initiator I is selected from aqueous initiator I and / or thermal initiator I; preferably, the aqueous initiator I is selected from at least one of V-50 and VA-044; the thermal initiator I is selected from at least two of ammonium persulfate, sodium bisulfite, and potassium persulfate.

4. The synthesis method according to any one of claims 1 to 3, characterized in that The conditions of the reaction I include: a temperature of 25° C. to 45° C. and a time of 1 hour to 6 hours.

5. The synthesis method according to any one of claims 1 to 4, characterized in that The preparation of the stabilizer comprises: mixing cationic monomer II, acrylamide II and polyethylene oxide in water under the conditions of initiator II and inactive atmosphere, and carrying out reaction II to obtain the stabilizer.

6. The synthesis method according to claim 5, characterized in that The mass ratio of the cationic monomer II, acrylamide II, polyethylene oxide and water is 72:60:(30-100):(160-260); And / or, the added amount of the initiator II is 0.1% to 0.5% of the mass of the cationic monomer II.

7. The synthesis method according to claim 5 or 6, characterized in that: The cationic monomer II is selected from one or more of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyl diallyl ammonium chloride, acryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl dimethyl benzyl ammonium chloride, and 2-acrylamido-2-methylpropyl trimethyl ammonium chloride; And / or, the polyoxyethylene is selected from polyoxyethylene with or without end-capping; preferably, the molecular weight of the polyoxyethylene is 2000Da to 200000Da; further preferably, the polyoxyethylene with end-capping includes single-end-capped polyoxyethylene and double-end-capped polyoxyethylene; further preferably, the single-end-capped polyoxyethylene is selected from polyoxyethylene monomethyl ether; the double-end-capped polyoxyethylene is selected from polyoxyethylene dimethyl ether; And / or, the initiator II is selected from aqueous initiator II and / or thermal initiator II; preferably, the aqueous initiator II is selected from at least one of V-50 and VA-044; the thermal initiator II is selected from at least two of ammonium persulfate, sodium bisulfite and potassium persulfate; And / or, the inactive atmosphere is selected from at least one of nitrogen and argon.

8. The synthesis method according to any one of claims 5 to 7, characterized in that The conditions of the reaction II include: a temperature of 30°C to 80°C, and a reaction time of 5 hours to 10 hours; And / or, the reaction II further comprises dilution.

9. An aqueous dispersion of polyacrylamide obtained by the synthesis method according to any one of claims 1 to 8.

10. Use of the aqueous polyacrylamide dispersion obtained by the synthesis method according to any one of claims 1 to 8 or the aqueous polyacrylamide dispersion according to any one of claim 9 as a flocculant in sewage and / or wastewater treatment.

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