Preparation method of a cationic polyacrylamide emulsion

Abstract

This application relates to the field of polymer technology, and specifically discloses a preparation method of a cationic polyacrylamide emulsion, which includes the following steps: mixing acrylamide, cationic monomers, modified nano-ferroferric oxide, dispersion stabilizer, ammonium sulfate and deionized water to obtain a premixed solution; heating the premixed solution to 45-65 °C under a nitrogen atmosphere, and then adding an initiator and reacting for 12-24 h to obtain a cationic polyacrylamide emulsion; wherein the modified nano-ferroferric oxide is obtained by modifying nano-ferroferric oxide with N-isopropylacrylamide and N,N ， -methylenebisacrylamide. The cationic polyacrylamide emulsion prepared by the preparation method provided in this application has excellent solubility, stability and flocculation effect, and the relative molecular weight can reach 500×10 4 g / mol or more.

Description

Technical Field

[0001] The present application relates to the field of polymer technology, and more specifically, it relates to a method for preparing a cationic polyacrylamide emulsion. Background Art

[0002] Cationic polyacrylamide can be divided into two forms: solid particles and emulsion according to different morphologies. As a flocculant, the emulsion form of cationic polyacrylamide has the advantages of economy, high efficiency, environmental protection and energy saving.

[0003] The preparation methods of cationic polyacrylamide mainly include aqueous solution polymerization method, inverse emulsion polymerization method, reverse microemulsion method, dispersion polymerization method, template polymerization method, etc. Among them, the dispersion polymerization method is a polymerization reaction carried out in an inorganic salt aqueous solution, and after the reaction, a water dispersion system similar to an emulsion can be obtained in appearance. The dispersion polymerization method has the characteristics of simple process, fast reaction speed and uniform heat dissipation. However, the cationic polyacrylamide emulsion prepared by the current dispersion polymerization method still has the defects of poor solubility, short stable storage time and poor flocculation effect, and the obtained polyacrylamide has a relatively low molecular weight.

[0004] Therefore, the present application provides a method for preparing a high molecular weight cationic polyacrylamide with excellent solubility, stability and flocculation effect to meet the market demand. Summary of the Invention

[0005] In order to obtain a high molecular weight cationic polyacrylamide emulsion with excellent solubility, stability and flocculation effect, the present application provides a method for preparing a cationic polyacrylamide emulsion, adopting the following technical scheme:

[0006] A method for preparing a cationic polyacrylamide emulsion, comprising the following steps:

[0007] Mix acrylamide, cationic monomer, modified nano-ferroferric oxide, dispersion stabilizer, ammonium sulfate and deionized water to obtain a premixed solution; heat the premixed solution to 45-65 °C under a nitrogen atmosphere, and then add an initiator and react for 12-24 h to obtain a cationic polyacrylamide emulsion;

[0008] Wherein the modified nano-ferroferric oxide is obtained by modifying nano-ferroferric oxide with N-isopropylacrylamide and N,N'-methylenebisacrylamide.

[0009] The relative molecular weight of the cationic polyacrylamide emulsion obtained in the above scheme can reach more than 500×10 4 g / mol, the dissolution time is within 10 min, it can be stably stored at room temperature for 9-12 months, and at the same time, the turbidity removal rate can reach more than 95%, and the comprehensive performance is relatively excellent.

[0010] Specifically, in the above solution, modified nano-ferroferric oxide was added to the acrylamide and cationic monomer polymerization system. Since the modified nano-ferroferric oxide is obtained by modifying nano-ferroferric oxide with N-isopropylacrylamide and N,N'-methylenebisacrylamide, a cross-linked structure is formed on the modified nano-ferroferric oxide, and both the dispersibility and storage stability are significantly improved. And both N-isopropylacrylamide and N,N'-methylenebisacrylamide can participate in the polymerization reaction as non-ionic monomers in the system. Furthermore, the modified nano-ferroferric oxide can be incorporated into the molecular chain in a bonded manner, and the stability is further improved.

[0011] On this basis, due to the superparamagnetism of nano-ferroferric oxide, the prepared cationic polyacrylamide emulsion has the characteristics of magnetic separation, which can accelerate the floc sedimentation and improve the floc structure, and thus can effectively improve the flocculation effect. In addition, the electrostatic repulsion and steric hindrance of the nano-ferroferric oxide modified by N-isopropylacrylamide and N,N'-methylenebisacrylamide increase. During the polymerization process, when the chain length reaches the critical value, it tends to form primary particles with the modified nano-ferroferric oxide as the core and the molecular chains entangled with each other. At the same time, under the influence of the electrostatic repulsion and steric hindrance of the modified nano-ferroferric oxide, the aggregation between particles can be effectively reduced, thereby reducing the gel phenomenon caused by the increase in particle size and system viscosity, which is of positive significance for improving the relative molecular weight, stability and solubility of the obtained cationic polyacrylamide.

[0012] In a specific feasible embodiment, the preparation method of the modified nano-ferroferric oxide is as follows:

[0013] First, add nano-ferroferric oxide to deionized water, after ultrasonic dispersion, then add N-isopropylacrylamide and N,N'-methylenebisacrylamide, mix and carry out ultraviolet irradiation under a nitrogen atmosphere. After the reaction is completed, perform magnetic separation washing, and obtain the modified nano-ferroferric oxide after drying.

[0014] In a specific feasible embodiment, the mass ratio of nano-ferroferric oxide, N-isopropylacrylamide and N,N'-methylenebisacrylamide is 1:(3.5 - 5.8):(1.2 - 1.7).

[0015] In a specific feasible embodiment, the particle size of the nano-ferroferric oxide is 5 - 10 nm, and the particle size of the modified nano-ferroferric oxide is 20 - 40 nm.

[0016] In a specific feasible embodiment, in the preparation method, the mass parts of each raw material are as follows: 20 - 50 parts of acrylamide, 10 - 20 parts of cationic monomer, 5 - 20 parts of modified nano-ferroferric oxide, 10 - 30 parts of dispersion stabilizer, 30 - 55 parts of ammonium sulfate, 60 - 100 parts of deionized water, and 0.5 - 5 parts of initiator.

[0017] In a specific feasible embodiment, the cationic monomer includes at least one of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyldiallyl ammonium chloride, and acrylamidopropyl trimethyl ammonium chloride.

[0018] In a specific feasible embodiment, the dispersion stabilizer includes at least one of poly (methacryloyloxyethyl trimethyl ammonium chloride), poly (acryloyloxyethyl trimethyl ammonium chloride), and poly (diallyldimethyl ammonium chloride).

[0019] In a specific feasible embodiment, the relative molecular weight of the dispersion stabilizer is 80×10 4 -210×10 4 g / mol.

[0020] By using the dispersion stabilizer within the above relative molecular weight range, the viscosity of the system can be effectively reduced, and the solubility, stability, and relative molecular weight of the product can be improved.

[0021] In a specific feasible embodiment, the initiator is a redox system initiator, where the oxidant is persulfate and the reductant is sodium sulfite.

[0022] By adopting the above technical solution, with persulfate and sodium sulfite combined as the redox system initiator, since nano-ferroferric oxide can effectively activate persulfate to generate sulfate radicals and hydroxyl radicals, the polymerization initiation effect is relatively excellent.

[0023] In a specific feasible embodiment, the mass ratio of the persulfate to the sodium sulfite is 1:(1.5 - 3.2).

[0024] In summary, the present application has the following beneficial effects:

[0025] 1. In the present application, the modified nano-ferroferric oxide is bonded to the molecular chain of cationic polyacrylamide in the form of participating in the system monomer polymerization reaction, that is, the magnetic active substance can stably exist on the polymer chain; and nano-ferroferric oxide can endow cationic polyacrylamide with magnetic separation characteristics, so that the flocculation performance is significantly improved; at the same time, under the influence of the electrostatic repulsion and steric hindrance of the modified nano-ferroferric oxide, the aggregation between particles can be effectively reduced, thereby reducing the gel phenomenon caused by the increase in particle size and system viscosity, which is of positive significance for improving the relative molecular weight, stability, and solubility of the obtained cationic polyacrylamide.

[0026] 2. The relative molecular weight of the cationic acrylamide emulsion obtained by using the preparation method provided in the present application can reach 500×10 4Above g / mol, the dissolution time is within 10 min, it can be stably stored for 9 - 12 months at room temperature, and at the same time, the turbidity removal rate can reach more than 95%, with relatively excellent comprehensive performance.

[0027] 3. In this application, a redox initiator system is used to initiate polymerization, and the effect is good; moreover, there is a coordination relationship between nano-ferroferric oxide and persulfate oxidant, which can further improve the comprehensive performance of the obtained polymerization product. Detailed implementation manners

[0028] The following further elaborates on this application with reference to examples and comparative examples. All raw materials involved in this application can be obtained commercially.

[0029] Example 1

[0030] The masses of each raw material in this example are as follows: acrylamide 40 g, cationic monomer 17 g, modified nano-ferroferric oxide 10 g, dispersion stabilizer 23 g, ammonium sulfate 48 g, deionized water 82 g, initiator 2 g; the cationic monomer is methacryloyloxyethyl trimethyl ammonium chloride; the dispersion stabilizer is poly-methacryloyloxyethyl trimethyl ammonium chloride with a relative molecular weight of 150×10 4 g / mol; the initiator is a redox initiator system, where the oxidant is ammonium persulfate and the reductant is sodium sulfite, and the mass ratio of ammonium persulfate to sodium sulfite is 1:2.5;

[0031] The preparation method of the modified nano-ferroferric oxide is as follows:

[0032] First, add 20 g of nano-ferroferric oxide with a particle size of 5 - 10 nm to 500 ml of deionized water. After ultrasonic dispersion for 5 min, add 90 g of N-isopropylacrylamide and 30 g of N,N'-methylenebisacrylamide. After mixing, irradiate with ultraviolet light for 3 h at room temperature under a nitrogen atmosphere to obtain a crude product; magnetically separate and wash the crude product, and then dry it in an oven at 60 °C to constant weight to obtain modified nano-ferroferric oxide with a particle size of 20 - 40 nm.

[0033] A preparation method of a cationic polyacrylamide emulsion includes the following steps:

[0034] Mix acrylamide, cationic monomer, modified nano-ferroferric oxide, dispersion stabilizer, ammonium sulfate and deionized water to obtain a premixed solution; heat the premixed solution to 50 °C in a nitrogen atmosphere in a water bath, and then add the initiator and react for 12 h to obtain a cationic polyacrylamide emulsion.

[0035] The differences between Examples 2 - 5 and Example 1 lie in the different raw material ratios for preparing cationic polyacrylamide, as shown in the following table.

[0036] Table 1 Raw material ratio table

[0037]

[0038] Example 6

[0039] The difference between this example and Example 1 is that in the preparation process of the cationic polyacrylamide emulsion, after adding the initiator, the reaction is carried out for 24 h to obtain the cationic polyacrylamide emulsion.

[0040] Example 7

[0041] The difference between this example and Example 1 is that in the preparation process of the modified nano-ferroferric oxide, the masses of nano-ferroferric oxide, N-isopropylacrylamide and N,N'-methylenebisacrylamide are 20 g, 70 g and 24 g respectively.

[0042] Example 8

[0043] The difference between this example and Example 1 is that in the preparation process of the modified nano-ferroferric oxide, the masses of nano-ferroferric oxide, N-isopropylacrylamide and N,N'-methylenebisacrylamide are 20 g, 116 g and 34 g respectively.

[0044] Example 9

[0045] The difference between this example and Example 1 is that the cationic monomer is acryloyloxyethyltrimethylammonium chloride.

[0046] Example 10

[0047] The difference between this example and Example 1 is that the dispersion stabilizer is acryloyloxyethyltrimethylammonium chloride, and the relative molecular weight is 146×10 4 g / mol.

[0048] Example 11

[0049] The difference between this example and Example 1 is that the relative molecular weight of the dispersion stabilizer is 80×10 4 g / mol.

[0050] Example 12

[0051] The difference between this example and Example 1 is that the relative molecular weight of the dispersion stabilizer is 210×10 4 g / mol.

[0052] Example 13

[0053] The difference between this example and Example 1 is that the relative molecular weight of the dispersion stabilizer is 70×10 4 g / mol.

[0054] Example 14

[0055] The difference between this example and Example 1 is that the relative molecular weight of the dispersion stabilizer is 250×10 4 g / mol.

[0056] Example 15

[0057] The difference between this example and Example 1 is that the mass ratio of persulfate to sodium sulfite is 1:1.5.

[0058] Example 16

[0059] The difference between this example and Example 1 is that the mass ratio of persulfate to sodium sulfite is 1:3.2.

[0060] Example 17

[0061] The difference between this example and Example 1 is that the initiator is a 5wt% aqueous solution of azodiisobutyramidine hydrochloride.

[0062] Example 18

[0063] The difference between this example and Example 1 is that an equal amount of hydrogen peroxide is used to replace persulfate.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that modified nano-ferroferric oxide is not added.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 1 is that an equal amount of nano-ferroferric oxide is used to replace modified nano-ferroferric oxide.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 1 is that the preparation method of modified nano-ferroferric oxide is as follows:

[0070] First, nano-ferroferric oxide is added to deionized water, ultrasonically dispersed, then N,N'-methylenebisacrylamide is added, and after mixing, ultraviolet light irradiation is carried out under a nitrogen atmosphere. After the reaction is completed, magnetic separation and washing are carried out, and after drying, modified nano-ferroferric oxide is obtained.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 1 is that the preparation method of modified nano-ferroferric oxide is as follows:

[0073] First, add nano-ferroferric oxide to deionized water. After ultrasonic dispersion, add N-isopropylacrylamide. After mixing, conduct ultraviolet irradiation under a nitrogen atmosphere. After the reaction ends, perform magnetic separation and washing, and obtain modified nano-ferroferric oxide after drying.

[0074] Comparative Example 5

[0075] The difference between this comparative example and Example 1 is that a composition of N,N'-methylenebisacrylamide and N-isopropylacrylamide is used to replace the modified nano-ferroferric oxide, and the dosage ratio of the two remains unchanged.

[0076] Performance detection test method

[0077] Relative molecular weight test: The powders obtained by drying the cationic polyacrylamide emulsions obtained in Examples 1-18 and Comparative Examples 1-5 are used as test samples. Referring to the method for determining the relative molecular weight in GB / T 31246-2014 "Technical Conditions and Test Methods for Water Treatment Agent Cationic Polyacrylamide", take a quantitative test sample in a 100 ml volumetric flask. First, completely dissolve the powder with a small amount of 1 mol / L sodium chloride solution, and then continue to calibrate to 100 ml in a constant temperature glass water bath at (30±0.1)°C to prepare a sample solution. Using the "one-point method", in a constant temperature glass water bath at (30±0.1)°C, use an Ubbelohde viscometer to measure the flow-through times of 1 mol / L sodium chloride solution and the sample solution respectively, and calculate the relative molecular weight of cationic polyacrylamide according to the following formula.

[0078] ηr = t / t0;

[0079]

[0080] Among them, t is the flow-through time (s) of the sample solution, t0 is the flow-through time (s) of the sodium chloride solution, η r is the relative viscosity of the sample solution, c is the concentration (g / mL) of the sample solution, [η] is the intrinsic viscosity (mL / g) of the sample solution, M v is the relative molecular weight (g / mol) of cationic polyacrylamide.

[0081] Stability performance test: Transfer 100 mL of the cationic polyacrylamide emulsions prepared in Examples 1-18 and Comparative Examples 1-5 to transparent sample storage bottles and store them at a constant temperature of 25°C, and observe the time required for the emulsion to completely gel or show stratification.

[0082] Dissolution performance test: Place a beaker containing a magnetic stir bar and 100 ml of water in an electromagnetic stirring constant temperature water bath at (30 ± 1) °C. Then insert a conductivity meter into the beaker. After the temperature is constant, add (0.10 ± 0.002) g of cationic polyacrylamide emulsion to the beaker at a certain stirring speed, and record the time it takes for the conductivity meter value to become constant from the start, which is recorded as the dissolution time.

[0083] Flocculation performance test: (1) Accurately weigh 0.1 g of cationic polyacrylamide into a beaker, add an appropriate amount of deionized water for dissolution. After complete dissolution, transfer it to a volumetric flask with a specification of 100 ml, and then make up the volume to the calibration line with deionized water to prepare a flocculant solution with a concentration of 1 g / L. After mixing and shaking well, pour it into a sample bottle for storage and standby.

[0084] (2) Accurately weigh 1 g of kaolin into a beaker with a magnetic stir bar, add 99 ml of deionized water to it, and then stir at a speed of 400 r / min on a magnetic stirrer for 20 min to obtain a kaolin suspension with a mass fraction of 1%. Prepare it immediately before use.

[0085] (3) Place the beaker containing the kaolin suspension and the magnetic stir bar on a magnetic stirrer, adjust the pH value of the kaolin suspension to 7 with a hydrochloric acid solution and a sodium hydroxide solution with a concentration of 0.1 mol / L. Then use a pipette to measure 1 ml of the flocculant solution and add it to the suspension. First, stir rapidly at a speed of 400 r / min for 3 min, then stir slowly at a speed of 50 r / min for 5 min. Finally, after standing and sedimenting for a period of time, take the supernatant about 1 cm below the liquid surface, and measure the transmittance with a UV2400 type ultraviolet spectrophotometer. Calculate the turbidity removal rate according to the following formula.

[0086] Turbidity = (1 - T) × 100%;

[0087] Turbidity removal rate = [(N0 - N) / N0] × 100%;

[0088] Where, T is the transmittance of the supernatant; N0 is the turbidity of the kaolin suspension before flocculation; N is the turbidity of the kaolin suspension after flocculation.

[0089] Table 2 Detection data table

[0090]

[0091]

[0092] By analyzing the detection data in Table 2, it can be seen that the cationic polyacrylamide emulsions prepared in each example of this application have excellent comprehensive performance and strong practicability. Specifically, the relative molecular weight of the obtained cationic polyacrylamide emulsion can reach 500 × 10 4Above g / mol, the dissolution time is within 10 min, the stabilization time is 9 - 12 months, and the turbidity removal rate can reach over 95% when actually applied to flocculation.

[0093] Specifically, in combination with the test results of Example 1 and Examples 17 - 18, the comprehensive properties of the cationic polyacrylamide emulsions obtained in Examples 17 and 18 are significantly worse than those of Example 1. It is analyzed that in Example 17, an azo initiator is used to replace the redox initiator in Example 1, and the actual initiation effect is not good, resulting in a decrease in the product performance. In Example 18, the redox initiator is still used. By comparing the product properties of Examples 17 and 18, it can be seen that in the preparation method of the present application, the initiation effect of the redox initiator is better than that of the azo initiator.

[0094] In addition, in Example 18, hydrogen peroxide is used to replace persulfate as the oxidant, but the actual results show that the product performance is not as good as that of Example 1. It is analyzed that there is a coordination relationship between nano - Fe₃O₄ and persulfate, that is, the activation effect of nano - Fe₃O₄ on persulfate is of positive significance for improving the comprehensive properties of the product.

[0095] Specifically, in combination with the test results of Example 1 and Comparative Examples 1 - 2, in Comparative Example 1, modified nano - Fe₃O₄ is not added, and the comprehensive properties of the obtained cationic polyacrylamide emulsion are significantly decreased compared with those of Example 1. This is because during the polymerization of the system monomers, modified nano - Fe₃O₄ can not only provide some non - ionic monomers to participate in the polymerization, but also act as a core to provide better electrostatic repulsion and steric hindrance, thereby reducing the viscosity of the system and the adverse phenomenon of particle aggregation, which has an obvious positive effect.

[0096] In Comparative Example 2, although nano - Fe₃O₄ is added, it is not modified. It is difficult to combine with the molecular chain and participate in the polymerization reaction in the polymerization system. Therefore, it mainly exists in the system in the form of nanoparticles, and its own agglomeration and other negative effects may cause the normal reaction in the system to be blocked. Therefore, from the results, adding unmodified nano - Fe₃O₄ to the system makes the comprehensive properties of the obtained cationic polyacrylamide emulsion worse than when not adding it.

[0097] Specifically, in view of the test results of Example 1 and Comparative Examples 3-5, in Comparative Examples 3-4, N-isopropylacrylamide and N,N'-methylenebisacrylamide were not added during the modification process of nano-ferroferric oxide. The comprehensive performance of the obtained cationic polyacrylamide emulsion was significantly lower than that of Example 1. The analysis is that during the modification process, N-isopropylacrylamide mainly forms a cross-linked structure on the surface of nano-ferroferric oxide under the cross-linking action of N,N'-methylenebisacrylamide, enabling nano-ferroferric oxide to be stably grafted onto the polyacrylamide molecular chain. Therefore, in the absence of either of them, the cross-linked structure is difficult to form or has poor stability, resulting in nano-ferroferric oxide being difficult to play a role in the subsequent monomer polymerization reaction. The test data of Comparative Example 3 is better than that of Comparative Example 4, and the reasons may be as follows: When N,N'-methylenebisacrylamide is used alone, a certain degree of cross-linked structure can still be formed, enabling nano-ferroferric oxide to play a certain positive role in the reaction system; while when N-isopropylacrylamide is used alone, it is difficult to form a cross-linked structure on the surface of nano-ferroferric oxide, and nano-ferroferric oxide basically exists independently in the reaction system and basically does not play a positive role.

[0098] In addition, from the test data, in Comparative Example 5, under the condition of not adding nano-ferroferric oxide, N-isopropylacrylamide and N,N'-methylenebisacrylamide were directly added to the reaction system, which could only act as non-ionic monomers and could not replace the positive role played by nano-ferroferric oxide.

[0099] This specific embodiment is only an interpretation of the present application and does not limit the present application. Those skilled in the art can make modifications without creative contributions to this embodiment as needed after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A preparation method of a cationic polyacrylamide emulsion, characterized in that, The preparation method comprises the following steps: Mix acrylamide, cationic monomer, modified nano-ferroferric oxide, dispersion stabilizer, ammonium sulfate and deionized water to obtain a premixed solution; heat the premixed solution to 45 - 65 °C under a nitrogen atmosphere, and then add an initiator and react for 12 - 24 h to obtain a cationic polyacrylamide emulsion; Among them, the modified nano-ferroferric oxide is obtained by modifying nano-ferroferric oxide with N-isopropylacrylamide and N,N ， -methylenebisacrylamide; The preparation method of the modified nano-ferroferric oxide is as follows: First, add nano-ferroferric oxide into deionized water. After ultrasonic dispersion, add N-isopropylacrylamide and N,N ， -methylenebisacrylamide. After mixing, carry out ultraviolet irradiation under a nitrogen atmosphere. After the reaction is completed, perform magnetic separation and washing, and obtain modified nano-ferroferric oxide after drying.

2. The preparation method of a cationic polyacrylamide emulsion according to claim 1, characterized in that, The mass ratio of nano-ferroferric oxide, N-isopropylacrylamide and N,N ， -methylenebisacrylamide is 1:(3.5 - 5.8):(1.2 - 1.7).

3. The preparation method of a cationic polyacrylamide emulsion according to claim 1, characterized in that, The particle size of the nano-ferroferric oxide is 5 - 10 nm, and the particle size of the modified nano-ferroferric oxide is 20 - 40 nm.

4. The preparation method of a cationic polyacrylamide emulsion according to claim 1, characterized in that, In the described preparation method, the mass parts of each raw material are as follows: 20 - 50 parts of acrylamide, 10 - 20 parts of cationic monomer, 5 - 12 parts of modified nano-ferroferric oxide, 10 - 30 parts of dispersion stabilizer, 30 - 55 parts of ammonium sulfate, 60 - 100 parts of deionized water, and 0.5 - 5 parts of initiator.

5. The preparation method of a cationic polyacrylamide emulsion according to claim 1, characterized in that The cationic monomer includes at least one of acryloyloxyethyl trimethyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, dimethyldiallyl ammonium chloride, and acrylamidopropyl trimethyl ammonium chloride.

6. The preparation method of a cationic polyacrylamide emulsion according to claim 1, characterized in that, The dispersion stabilizer includes at least one of polyacryloyloxyethyl trimethyl ammonium chloride, polyacryloyloxyethyl trimethyl ammonium chloride, and polydiallyldimethyl ammonium chloride.

7. The preparation method of a cationic polyacrylamide emulsion according to claim 6, wherein The relative molecular weight of the dispersion stabilizer is 80×10 4 -210×10 4 g / mol.

8. The preparation method of a cationic polyacrylamide emulsion according to claim 1, characterized in that, The initiator is a redox system initiator, wherein the oxidant is persulfate and the reductant is sodium sulfite.

9. The preparation method of a cationic polyacrylamide emulsion according to claim 8, characterized in that, The mass ratio of the persulfate to the sodium sulfite is 1:(1.5 - 3.2).

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