Preparation method and application of novel dispersing agent for water-in-water polymerization

Abstract

The invention discloses a novel dispersing agent for water-in-water polymerization as well as a preparation method and application thereof. The dispersing agent is prepared from the following raw materials: a cationic monomer, a hydrophobic monomer, a chelating agent, an initiator and water. The dispersant provided by the invention is a hydrophobic associated polymer, has small molecular weight, has a hydrophobic alkyl chain as a branch chain, and has strong steric hindrance effect; the salt sensitivity is low, and the stability and flowability of the dispersion liquid can be improved. The dispersant is applied to a water-in-water polymerization process to prepare a cationic acrylamide copolymer dispersion liquid, after optimization, the molecular weight of the dispersion liquid is 8.75 * 10 < 6 > g / mol, the viscosity is about 297.6 mPa.s after the dispersion liquid is diluted by 10 times, the maximum solid content can reach about 15 wt%, the dispersion liquid can be almost completely dissolved within 1 min, and the dispersion liquid has good stability, fluidity and dissolvability. The basic requirements on the performance of the fracturing fluid are met. In addition, the preparation is simple, the cost is low, and the use of an organic solvent which seriously pollutes the environment is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of water-soluble polymer synthesis, and particularly relates to a preparation method and application of a novel dispersant for water-in-water polymerization. Background Art

[0002] The free radical polymerization methods for synthesizing cationic polymers mainly include aqueous solution polymerization, inverse emulsion polymerization, inverse suspension polymerization, etc. Although the aqueous solution polymerization method has the advantages of simple preparation, convenient operation, high monomer conversion rate and high molecular weight of the product, it has problems such as high viscosity of the polymerization system, difficult stirring and slow heat dissipation. To facilitate transportation, a large amount of heat needs to be consumed, and professional equipment is required for drying and making into powder. However, the powder is difficult to dissolve and disperse during use, and high-speed stirring and heating are required, which is time-consuming and laborious. Although the inverse emulsion polymerization method and the inverse suspension polymerization method have the advantages of fast reaction speed, high solid content and convenient use, they both use oil (hydrocarbons) as solvents. When used, they are likely to enter the water system, wasting precious hydrocarbon resources, causing water and environmental pollution, and the obtained products need to be demulsified, making the preparation process more complicated.

[0003] The aqueous dispersion polymerization method, also known as the water-in-water polymerization method, was first proposed by ICI Company in the United States in the 1970s and was not used for the preparation of polyacrylamide until the 1980s and 1990s. The aqueous dispersion polymerization method is to add components such as monomers, dispersants, and dispersion media into deionized water, stir and dissolve to form a homogeneous and clear solution. Subsequently, the temperature is adjusted, and an initiator is added to carry out the polymerization reaction, so that the synthesized polymer molecular chains gradually grow. When the critical point is reached, it will no longer dissolve in the medium, precipitate out in the shape of spherical particles, and suspend in the reaction medium to form a stable dispersion. This polymerization method not only overcomes the deficiencies of the above polymerization methods, but also has the advantages of high synthesis efficiency, green and environmental protection of the preparation process, strong solubility, high molecular weight and high solid content of the product, and has become the focus of research in various countries. At present, great breakthroughs have been made in the synthesis of cationic polymers. European Patent EP262945, US Patents US492955 and US5006590 all describe obtaining acrylamide copolymer dispersions by using acrylamide and cationic monomers in a solution containing polyvalent anion salts and stabilizers. However, the synthesized products have relatively low molecular weights, relatively poor solubility and stability, which are not conducive to storage.

[0004] The dispersant plays an important role in the water-in-water polymerization process and is also the main difference from precipitation polymerization. It is an important factor determining the success of the polymerization process. The dispersant is required to have excellent stability in the medium and affinity for particles. When dispersed particles are generated, they can be adsorbed on the surface of the particles, thereby protecting the stability of the particles. Currently, the published patents and literature all use linear anionic, cationic polymers or non-ionic polymers as dispersants, and achieve stability through the steric hindrance and electrostatic effects generated by the adsorption of the dispersant molecular chains on the particle surface, which requires the dispersant to have an appropriate molecular weight. However, the use of such dispersants brings a series of deficiencies. The water-in-water polymerization reaction is carried out in a high inorganic salt concentration. When the molecular weight of the dispersant is too high, it is difficult to dissolve quickly. Even after dissolution, the molecular structure is in a curled state due to the influence of the high inorganic salt concentration, which greatly reduces its adsorption rate and stabilizing effect. In addition, the viscosity of the dispersion system is relatively large at the initial stage of the reaction. Coupled with the entanglement and diffusion movement between molecular chains, the viscosity of the entire system often soars because it cannot be precipitated stably in time, ultimately leading to polymerization failure. Therefore, the cationic acrylamide copolymer dispersion prepared using the above linear dispersant has a low molecular weight, poor solubility, stability, and fluidity. Summary of the Invention

[0005] In view of the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a novel dispersant for water-in-water polymerization and its preparation method. Applying the dispersant of the present invention to water-in-water polymerization to synthesize a cationic acrylamide copolymer dispersion, so as to achieve the characteristics of high product molecular weight, high solid content, good solubility, good stability and fluidity, and excellent performance.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] In the first aspect, the present invention provides a novel dispersant for water-in-water polymerization, and the dispersant is a hydrophobically associating polymer.

[0008] The raw materials for preparing the hydrophobically associating polymer include the following components in terms of mass percentage:

[0009]

[0010] The monomer is composed of a cationic monomer and a hydrophobic monomer.

[0011] Further, the content of the hydrophobic monomer is 0.05wt% - 0.11wt%, specifically such as 0.05wt%, 0.11wt%, 0.15wt%, 0.20wt%, 0.26wt%, etc.

[0012] Further, the content of the cationic monomer is 18wt% - 28wt%.

[0013] Furthermore, the cationic monomer is selected from one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and dimethyldiallyl ammonium chloride; preferably methacryloyloxyethyl trimethyl ammonium chloride (Formula 1);

[0014] Furthermore, the molecular structural formula of the hydrophobic monomer is as shown in (Formula 2).

[0015]

[0016] Furthermore, the total mass of the copolymer monomers (cationic monomer and hydrophobic monomer) accounts for 10.05 wt% - 40.26 wt% of the total mass of the reactants (including water) in the free radical polymerization reaction, and the molar ratio of the monomers shown in Formula (1) and Formula (2) is x:y, where x and y are the x and y in Formula (3).

[0017]

[0018] In Formula (3), x and y are the percentages of each structural unit, where x = 99.3% - 99.5%, y = 0.5% - 0.7%, and the molecular weight of the hydrophobic associative polymer is 1.39×10 5 ~3.88×10 5 g / mol.

[0019] Furthermore, the chelating agent used is selected from any one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, and disodium ethylenediaminetetraacetate dihydrate, preferably disodium ethylenediaminetetraacetate dihydrate. The dosage of the chelating agent is 0.09 wt% - 0.11 wt% of the total mass of the monomers. The chelating agent is used to complex metal ions, eliminate the interference of metal ions, control the decomposition rate of the initiator, and promote the stable progress of the polymerization reaction.

[0020] Furthermore, the initiator used in the aqueous solution polymerization method is selected from any one of ammonium persulfate, potassium persulfate, sodium persulfate, and hydrogen peroxide; the initiator accounts for 0.5 wt% - 1.2 wt% of the total mass of the added monomers. During the aqueous solution polymerization process, the molecular weight of the dispersant is adjusted by the dosage of the initiator and the dosage of the hydrophobic monomer.

[0021] In a second aspect, the present invention provides a preparation method of the novel water-in-water polymerization dispersant described in the first aspect.

[0022] The preparation method of the dispersant includes the following steps: in the presence of the chelating agent and the initiator, the cationic monomer and the hydrophobic monomer are used to obtain the hydrophobic associative polymer through an aqueous solution polymerization method.

[0023] Furthermore, the detailed preparation method of the dispersant includes the following steps:

[0024] S1. Place the cationic monomer, hydrophobic monomer, and water in a reactor in a certain proportion, stir and dissolve them to form a reaction solution.

[0025] S2. Place the reaction solution obtained in step S1 in a constant temperature water bath at 60°C to 70°C, introduce nitrogen, and add an initiator. The dosage of the initiator accounts for 0.5 wt% to 1.2 wt% of the total mass of the monomers.

[0026] S3. Keep the reaction solution obtained in step S2 in a constant temperature water bath at 60°C to 70°C. After reacting for 6 to 8 hours, cool it to room temperature to obtain a viscous, transparent, light yellow hydrophobic associative polymer.

[0027] The novel water-in-water polymerization dispersing hydrophobic associative polymer provided by the present invention has a relatively small molecular weight, and a hydrophobic monomer is introduced into its molecular structure. In a salt solution, the charges on the molecular chain of the dispersant are shielded, weakening the electrostatic repulsion between ions, making the molecular chain of the dispersant show a properly curled state. At this time, intramolecular association plays a dominant role. Therefore, it can maintain a relatively extended state of the molecular chain of the dispersant in a high inorganic salt concentration system, and the adsorption rate and diffusion rate of the dispersant are further improved. During the water-in-water polymerization reaction process, it can quickly stabilize the particles synthesized in the initial stage of the polymerization reaction; at the same time, because it has branched chains with large steric hindrance stabilization effects, its dispersion stability effect is further improved, which is beneficial to the stability of the dispersion system in the later stage of the polymerization reaction and improves the long-term storage stability of the dispersion liquid. In addition, the hydrophobic alkyl chain on the molecular structure of the dispersant can strengthen its stabilizing effect with the particles, which has a significant effect on improving the fluidity, stability, molecular weight, and solid content of the acrylamide copolymer dispersion.

[0028] In the third aspect, the present invention provides the application of the dispersant described in the first aspect in the water-in-water polymerization process.

[0029] Further, the water-in-water polymerization is used to prepare a cationic acrylamide copolymer dispersion.

[0030] In the fourth aspect, the present invention provides a method for preparing a cationic acrylamide copolymer using the dispersant described in the first aspect of the present invention.

[0031] The method for preparing a cationic acrylamide copolymer provided by the present invention includes the following steps:

[0032] a. Place the non-ionic monomer, cationic monomer, dispersion medium, dispersant, and water in a reaction flask in a certain proportion to obtain a clear and transparent homogeneous solution, and adjust the pH value of the dispersion system to 7 to 8.

[0033] b. Heat the homogeneous solution obtained in step a to 50°C to 60°C, introduce nitrogen, and add an initiator.

[0034] c. React the solution obtained in step b at a constant temperature of 50 °C to 60 °C for 4 to 6 hours, and then cool it to room temperature to obtain a cationic acrylamide copolymer dispersion.

[0035] By mass percentage, the dosages of the above raw materials are as follows:

[0036]

[0037] The monomer consists of a non-ionic monomer and a cationic monomer;

[0038] The dispersant is the novel water-in-water polymerization dispersant described in the first aspect of the present invention.

[0039] Furthermore, by mass percentage, the dosages of the above raw materials are as follows:

[0040]

[0041] Furthermore, the content of the monomer can specifically be 10 wt%, 12 wt% or 15 wt%.

[0042] Furthermore, the non-ionic monomer is selected from one of acrylamide or methacrylamide, preferably acrylamide.

[0043] Furthermore, the non-ionic monomer accounts for 66.0 wt% to 75.5 wt% of the total mass of the entire monomer system.

[0044] In some preferred embodiments of preparing a cationic acrylamide copolymer dispersion by applying the dispersant of the present invention in the water-in-water polymerization process, the non-ionic monomer is acrylamide. Using acrylamide, it has high reaction activity, flexible molecular chains, good solubility, and is easy to form a molecular structure network; the main chain with C-C has good thermal stability.

[0045] Furthermore, the cationic monomer is selected from one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and dimethyldiallyl ammonium chloride, preferably methacryloyloxyethyl trimethyl ammonium chloride.

[0046] Furthermore, the cationic monomer accounts for 24.5 wt% to 34.0 wt% of the total mass of the entire monomer system.

[0047] In some preferred embodiments of preparing a cationic acrylamide copolymer dispersion by applying the dispersant of the present invention in the water-in-water polymerization process, the cationic monomer is methacryloyloxyethyl trimethyl ammonium chloride. The obtained cationic acrylamide copolymer dispersion has a higher molecular weight and better solubility.

[0048] Furthermore, the dispersion medium is selected from one of ammonium sulfate, sodium sulfate, and sodium chloride; ammonium sulfate is preferred.

[0049] In some preferred embodiments of preparing a cationic acrylamide copolymer dispersion by applying the dispersant of the present invention in the water-in-water polymerization process, the dispersion medium is ammonium sulfate. Using ammonium sulfate, the prepared cationic acrylamide copolymer dispersion has a lower viscosity, better stability, and faster dissolution rate.

[0050] Furthermore, the initiator is an azo initiator; when the initiator is an azo initiator, as long as the dosage requirement is met.

[0051] In some preferred embodiments of preparing a cationic acrylamide copolymer dispersion by applying the dispersant of the present invention in the water-in-water polymerization process, the azo initiator is 2,2'-azobis(2-methylpropionamidine) dihydrochloride.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The dispersant provided by the present invention has a relatively small molecular weight, low salt sensitivity, and can maintain a relatively stretched state of the dispersant molecular chain in a high inorganic salt concentration system. In addition, the dispersant of the present invention is a hydrophobic associating polymer with a low molecular weight, its side chains are hydrophobic alkyl chains, and the steric hindrance effect is strong; it can be quickly dissolved, has good salt tolerance, low viscosity, fast adsorption and diffusion, and high stability. When applied to the water-in-water polymerization system, it has strong encapsulation, effectively reduces the viscosity of the water-in-water polymerization system, and further improves the solid content, molecular weight, stability, and fluidity of the synthesized product.

[0054] The dispersant of the present invention is applied to the water-in-water polymerization process to prepare a cationic acrylamide copolymer dispersion. This dispersion has a high molecular weight, high solid content, good fluidity and stability, fast dissolution rate, simple preparation, convenient use, strong operability, low cost, and avoids using organic solvents that cause serious environmental pollution, meeting the requirements of the sustainable development strategy and "green chemistry". BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is the infrared spectrum of the novel water-in-water polymerization dispersant PDH-1 in Synthesis Example 1.

[0056] Figure 2 It is the fluidity and stability of the cationic acrylamide copolymer dispersion, where (a) is prepared with a common dispersant (i.e., the product prepared in the comparative example), and (b) is prepared with the novel water-in-water polymerization dispersant (i.e., the product prepared in Example 10).

[0057] Figure 3Solubility of the product prepared with the dispersant for novel water-in-water polymerization at a concentration of 5.00 wt% (i.e., the product prepared in Example 10)

[0058] Figure 4 Stability and fluidity of Examples 1 to 11 and Comparative Example on the fifth day of standing (in the order from left to right, from top to bottom) Detailed Description of the Invention

[0059] The present invention will be further described in detail below in conjunction with the specific embodiments. The provided embodiments are only for clarifying the present invention and not for limiting the scope of the present invention. The following provided embodiments can be used as a guide for those of ordinary skill in the art to make further improvements and do not limit the present invention in any way.

[0060] The experimental methods in the following examples are all conventional methods unless otherwise specified, and are carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. The materials, reagents, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0061] In the following embodiments, the raw materials involved in the preparation include:

[0062] 1. Methacryloyloxyethyltrimethylammonium chloride DMC: CAS No. 5039-78-1

[0063] 2. Hydrophobic monomer D (the monomer shown in Formula 2): Prepared with reference to the following literature: Tao Xianping, Zhang Yuejun, Li Xia, Jia Xu, Relationship between the structure and properties of diallylmethylalkylammonium bromide [J], Chinese Journal of Applied Chemistry, Vol. 32, No. 3, March 2015. DOI: 10.11944 / j.issn.1000-0518.2015.03.140227

[0064] 3. Acrylamide AM: CAS No. 79-06-1

[0065] 4. Ammonium persulfate: CAS No. 7727-54-0

[0066] 5. Disodium ethylenediaminetetraacetate dihydrate EDTA-2Na·2H2O: 6381-92-6

[0067] 6. Ammonium sulfate: CAS No. 7783-20-2

[0068] 7. 2,2'-Azobis(2-methylpropionamidine) dihydrochloride VA-044: CAS No. 27776-21-2

[0069] 8. Potassium bromide: CAS No. 7758-02-3

[0070] 9. Sodium chloride: CAS No. is 7647-14-5

[0071] 10. Absolute ethanol: CAS No. is 64-17-5

[0072] 11. Acetone: CAS No. is 67-64-1

[0073] The synthesis example is the synthesis method of the novel water-in-water polymerization dispersant provided by the present invention.

[0074] The example is the method for preparing a cationic acrylamide copolymer dispersion liquid with the dispersant prepared in the synthesis example of the present invention.

[0075]

Synthesis Example 1

[0076] S1. Place a beaker on a magnetic stirrer, add 25.64 g of an aqueous solution of methylacryloyloxyethyltrimethylammonium chloride (78 wt%), 0.06 g of a hydrophobic monomer D, 0.02 g of disodium ethylenediaminetetraacetate dihydrate, and 74.15 g of deionized water to the beaker, and stir until dissolved to form a monomer aqueous solution. Among them, the total mass fraction of the monomers is 20.06 wt%.

[0077] S2. Pour the reaction solution into a reaction vessel, place it in a constant temperature water bath, heat the water bath to 65°C, and at the same time introduce nitrogen. After introducing nitrogen for 30 minutes, add 0.14 g of the initiator ammonium persulfate.

[0078] S3. After 30 minutes, stop introducing nitrogen, seal the system, and under the protection of nitrogen and stirring conditions, carry out a constant temperature reaction for 6 hours, and cool to room temperature to obtain a light yellow, viscous novel water-in-water polymerization dispersant PDH-1 solution with a concentration of 20.06 wt%.

[0079] Add 100.00 g of deionized water to the above-synthesized novel water-in-water polymerization dispersant PDH-1 solution (20.06 wt%) to dilute its concentration to twice the original, and at this time the concentration is 10.03 wt% for standby.

[0080]

Example 1

[0081] a. In a glass reaction vessel equipped with a reflux condenser, a thermometer, a stirrer, and a nitrogen conduit, add 7.55 g of acrylamide, 3.14 g of an aqueous solution of methylacryloyloxyethyltrimethylammonium chloride (78 wt%), 28.00 g of ammonium sulfate, 15.00 g of the diluted dispersant PDH-1 solution (10.03 wt%), and 46.30 g of deionized water, and stir until dissolved. Adjust the pH value of the dispersion system to 7-8. Among them, the total mass fraction of the monomers is 10.00 wt%.

[0082] b. Place it in a constant temperature water bath, heat the water bath to 55 °C, and simultaneously introduce nitrogen for 30 min. After the water bath reaches 55 °C, add 0.01 g of initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride VA-044.

[0083] c. After 30 min, stop introducing nitrogen, seal the system, and under nitrogen protection and stirring conditions, carry out a constant temperature reaction for 4 hours, then cool to room temperature to obtain a milky white cationic acrylamide copolymer dispersion with a solid content of 10.00 wt%.

[0084] Synthesis Example 2 (Synthesis of Dispersant PDH-2 for Novel Water-in-Water Polymerization)

[0085] The method for preparing the dispersant in Synthesis Example 2 is basically the same as that in Synthesis Example 1, except that:

[0086] In step S1, add 0.11 g of hydrophobic monomer D and 74.10 g of deionized water, and the total mass fraction of the monomers is 20.11 wt%.

[0087] Example 2

[0088] The preparation method in Example 2 is basically the same as that in Example 1, except that:

[0089] In step a, add dispersant PDH-2 for novel water-in-water polymerization.

[0090] Synthesis Example 3 (Synthesis of Dispersant PDH-3 for Novel Water-in-Water Polymerization)

[0091] The method for preparing the dispersant in Synthesis Example 3 is basically the same as that in Synthesis Example 1, except that:

[0092] In step S1, add 0.15 g of hydrophobic monomer D and 74.06 g of deionized water, and the total mass fraction of the monomers is 20.15 wt%.

[0093] Example 3

[0094] The preparation method in Example 3 is basically the same as that in Example 1, except that:

[0095] In step a, add dispersant PDH-3 for novel water-in-water polymerization.

[0096] Synthesis Example 4 (Synthesis of Dispersant PDH-4 for Novel Water-in-Water Polymerization)

[0097] The method for preparing the dispersant in Synthesis Example 4 is basically the same as that in Synthesis Example 1, except that:

[0098] In step S1, add 0.20 g of hydrophobic monomer and 74.01 g of deionized water, and the total mass fraction of the monomers is 20.20 wt%.

[0099]

Example 4

[0100] The preparation method of Example 4 is basically the same as that of Example 1, with the only difference being that:

[0101] In step a, a novel water-in-water polymerization dispersant PDH-4 is added.

[0102]

Synthesis Example 5

[0103] The method for preparing the dispersant in Synthesis Example 5 is basically the same as that in Synthesis Example 1, with the only difference being that:

[0104] In step S1, 0.26 g of a hydrophobic monomer and 73.95 g of deionized water are added, and the total mass fraction of the monomers is 20.26 wt%.

[0105]

Example 5

[0106] The preparation method of Example 5 is basically the same as that of Example 1, with the only difference being that:

[0107] In step a, a novel water-in-water polymerization dispersant PDH-5 is added.

[0108]

Synthesis Example 6

[0109] The method for preparing the dispersant in Synthesis Example 6 is basically the same as that in Synthesis Example 1, with the only difference being that:

[0110] In step S1, 0.15 g of hydrophobic monomer D and 74.10 g of deionized water are added, and the total mass fraction of the monomers is 20.15 wt%. In step S2, 0.10 g of initiator ammonium persulfate is added for initiation polymerization.

[0111]

Example 6

[0112] The preparation method of Example 6 is basically the same as that of Example 1, with the only difference being that:

[0113] In step S1, a novel water-in-water polymerization dispersant PDH-6 is added.

[0114]

Synthesis Example 7

[0115] The method for preparing the dispersant in Synthesis Example 7 is basically the same as that in Synthesis Example 1, with the only difference being that:

[0116] In step S1, 0.15 g of hydrophobic monomer D and 74.02 g of deionized water were added, and the total mass fraction of the monomers was 20.15 wt%. In step S2, 0.18 g of initiator ammonium persulfate was added for initiation polymerization.

[0117]

Example 7

[0118] The preparation method of Example 7 was basically the same as that of Example 1, except that:

[0119] In step S1, a novel water-in-water polymerization dispersant PDH-7 was added.

[0120]

Synthesis Example 8

[0121] The method for preparing the dispersant in Synthesis Example 8 was basically the same as that in Synthesis Example 1, except that:

[0122] In step S1, 0.15 g of hydrophobic monomer D and 74.00 g of deionized water were added, and the total mass fraction of the monomers was 20.15 wt%.

[0123] In step S2, 0.20 g of initiator ammonium persulfate was added for initiation polymerization.

[0124]

Example 8

[0125] The preparation method of Example 8 was basically the same as that of Example 1, except that:

[0126] In step S1, a novel water-in-water polymerization dispersant PDH-8 was added.

[0127]

Synthesis Example 9

[0128] The method for preparing the dispersant in Synthesis Example 9 was basically the same as that in Synthesis Example 1, except that:

[0129] In step S1, 0.15 g of hydrophobic monomer D and 73.96 g of deionized water were added, and the total mass fraction of the monomers was 20.15 wt%.

[0130] In step S2, 0.24 g of initiator ammonium persulfate was added for initiation polymerization.

[0131]

Example 9

[0132] The preparation method of Example 9 was basically the same as that of Example 1, except that:

[0133] In step a, a novel water-in-water polymerization dispersant PDH-9 was added.

[0134]

Example 10

[0135] Example 10 has basically the same preparation method as Example 1, except that:

[0136] In step a, a novel water-in-water polymerization dispersant PDH-2 was added, and the total mass fraction of the monomers was 12.00 wt%.

[0137] For the finally formed water-in-water polymerization system, the amounts of each substance were as follows: 9.06 g of acrylamide, 3.77 g of methacryloyloxyethyltrimethylammonium chloride solution (78 wt%), 22.80 g of diluted dispersant PDH-2 solution (10.06 wt%), 28.00 g of ammonium sulfate, 36.37 g of deionized water, and 0.0048 g of initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride VA-044 to obtain a cationic acrylamide copolymer dispersion.

[0138]

Example 11

[0139] Example 11 has basically the same preparation method as Example 1, except that:

[0140] In step a, a novel water-in-water polymerization dispersant PDH-2 was added, and the total mass fraction of the monomers was 15 wt%.

[0141] For the finally formed water-in-water polymerization system, the amounts of each substance were as follows: 11.32 g of acrylamide, 4.72 g of methacryloyloxyethyltrimethylammonium chloride solution (78 wt%), 24.00 g of diluted dispersant PDH-2 solution (10.06 wt%), 28.00 g of ammonium sulfate, 31.96 g of deionized water, and 0.0030 g of initiator 2,2'-azobis(2-methylpropionamidine) dihydrochloride VA-044 to obtain a cationic acrylamide copolymer dispersion.

[0142]

Comparative Synthesis Example

[0143] S1. Place the beaker on a magnetic stirrer, add 25.64 g of methacryloyloxyethyltrimethylammonium chloride aqueous solution (78 wt%), 0.02 g of disodium ethylenediaminetetraacetate dihydrate, and 74.21 g of deionized water to the beaker, and stir until dissolved to form a monomer aqueous solution. Among them, the total mass fraction of the monomers was 20.00 wt%.

[0144] S2. Pour the reaction solution into a reaction vessel, place it in a constant temperature water bath, heat the water bath to 65 °C, and at the same time introduce nitrogen. After introducing nitrogen for 30 min, add 0.14 g of initiator ammonium persulfate.

[0145] S3. After 30 min, stop introducing nitrogen, seal the system, and under the protection of nitrogen and stirring, carry out a constant temperature reaction for 6 hours, and cool to room temperature to obtain a light yellow, viscous dispersant PDMC with a concentration of 20.00 wt%.

[0146] 100.00 g of deionized water was added to the above-synthesized novel water-in-water polymerization dispersant PDH-1 solution (20.00 wt%), and its concentration was diluted to half of the original, and the concentration was 10.00 wt% at this time for standby.

[0147]

Comparative Example

[0148] a. In a glass reaction vessel equipped with a reflux condenser, thermometer, stirrer, and nitrogen conduit, 7.55 g of acrylamide, 3.14 g of methacryloyloxyethyltrimethylammonium chloride aqueous solution (78 wt%), 28.00 g of ammonium sulfate, 15.00 g of the diluted dispersant PDMC solution (10.00 wt%) in the comparative synthesis example, and 46.30 g of deionized water were stirred until dissolved, and the pH value of the dispersion system was adjusted to 7 - 8.

[0149] b. It was placed in a constant temperature water bath, and the water bath was heated to 55 °C. At the same time, nitrogen was introduced for 30 min. After the water bath reached 55 °C, 0.01 g of the initiator azobisisobutyramidine hydrochloride VA-044 was added.

[0150] c. After 30 min, the nitrogen introduction was stopped, and the system was sealed. Under nitrogen protection and stirring conditions, the reaction was carried out at a constant temperature for 4 hours, and then cooled to room temperature to obtain a milky white cationic acrylamide copolymer dispersion.

[0151] The product in Synthesis Example 1 was tested by Fourier transform infrared spectroscopy (FT-IR).

[0152] 1) Purification and drying: A certain amount of the dispersant was repeatedly washed and precipitated 2 - 3 times with anhydrous ethanol solution and acetone to remove the residual inorganic salts and unreacted monomers in the product. Then it was dried at a constant temperature of 60 °C to constant weight, and then ground to obtain a white powdery sample.

[0153] 2) Fourier transform infrared spectroscopy (FT-IR) test

[0154] A small amount of the purified and dried white powdery sample was mixed with potassium bromide and pressed into a tablet, and then tested using a Fourier transform infrared spectrometer.

[0155] Figure 1 It is the infrared spectrum of the product in the synthesis example. It can be seen from the infrared spectrum that at a wavelength of 3141.7 cm -1 is the asymmetric absorption peak of methyl and methylene, and at a wavelength of 1666.0 cm -1 is the characteristic absorption peak of C=O in the cationic monomer DMC, and at a wavelength of 1110.3 cm -1 is the stretching vibration absorption peak of the C-O bond on the ester group in the cationic monomer DMC, and at a wavelength of 1613.5 cm-1 and 2850.9 cm -1 、3029.7 cm -1 They are respectively the symmetric absorption node and bending vibration absorption peak of the C-H bond in the cationic hydrophobic monomers -CH2- and -CH3, with a wavelength of 1401.3 cm -1 is the methylene bending vibration absorption peak of -CH2-N- in the cationic monomer DMC and the hydrophobic monomer, with a wavelength of 984.1 cm -1 is for -CH2-N in the cationic monomer DMC + -(CH3)3 absorption peak of the methyl group. The characteristic absorption peaks of the main groups in the cationic monomer methacryloyloxyethyltrimethylammonium chloride (DMC) and the hydrophobic monomer are all reflected in the infrared spectrogram, thus proving that the expected new water-in-water polymerization dispersant PDH has been synthesized. Its molecular weight is shown in Table 1.

[0156] The molecular weights of Synthesis Examples 1-9, Examples 1-11 and Comparative Examples were tested. Among them, the Examples are expressed by viscosity, and viscosity is also a way of expressing molecular weight. Observe the stability of the cationic acrylamide copolymer dispersion prepared in Examples 1-11 and Comparative Examples.

[0157] 1) Dispersant molecular weight test: Prepare a 1 mol / L NaCl standard solution. Weigh a certain amount of the synthesized dispersant and place it in a 100 mL volumetric flask. Add a small amount of 1 mol / L NaCl standard solution to completely dissolve the dispersant. Then fix the volumetric flask in a water bath pot and make up to 100 mL in a water bath at about 30 °C to form a sample to be tested. Then use a Ubbelohde viscometer with an inner diameter of 0.8 mm and vertically fix it in a constant temperature water bath. Control the temperature within the range of 30 °C. Respectively measure the flow times of the 1 mol / L NaCl standard solution and the sample to be tested between two scales of the Ubbelohde viscometer, and repeat the measurement 2-3 times and take the average value. Calculate its molecular weight according to formulas (1), (2), and (3) by the "one-point method".

[0158]

[0159] t0 is the flow time of the NaCl solvent (s), t is the flow time of the sample solution (s)

[0160]

[0161] c is the actual mass concentration of the sample (g / mL), [η] is the intrinsic viscosity (mL / g)

[0162]

[0163] M v is the viscosity-average molecular weight (g / mL)

[0164] 2) Viscosity test of the dispersion: Using a six-speed viscometer, measure the viscosity of the diluted (10 times) different cationic acrylamide copolymer dispersions at 100 r / min under room temperature conditions.

[0165] 3) Stability test of the dispersion: Transfer the synthesized dispersion into a transparent sample bottle, store it statically at 25 °C under normal temperature conditions, and record the time required for complete gelation.

[0166] 4) Solubility test of the dispersion: Add the synthesized dispersion into a beaker containing 200 mL of deionized water, stir to dissolve, use a six-speed viscometer to test its viscosity, and record the time required for almost complete dissolution.

[0167] The test results of the molecular weight of the dispersant PDH for novel water-in-water polymerization and the viscosity of the dispersion after being diluted 10 times are shown in Table 1.

[0168] Table 1 Evaluation results of the molecular weight of the dispersant for novel water-in-water polymerization, the viscosity and stability of the prepared cationic acrylamide copolymer dispersion after being diluted 10 times

[0169] Example Dispersant Name <![CDATA[Dispersant molecular weight / ×10 5 > Viscosity of Dispersion Liquid / mPa·s Stability Example 1 PDH-1 1.4629 144.0 Good Example 2 PDH-2 3.5133 138.9 Good Example 3 PDH-3 0.8053 114.9 Good Example 4 PDH-4 1.3262 129.0 Good Example 5 PDH-5 2.2797 110.4 Good Example 6 PDH-6 3.8807 107.4 Good Example 7 PDH-7 2.7937 117.0 Good Example 8 PDH-8 1.3908 93.6 Good Example 9 PDH-9 1.1307 90.3 Good Example 10 PDH-2 3.5133 297.6 Good Example 11 PDH-2 3.5133 355.5 Good Comparative Example PDMC 4.5264 123.9 Poor

[0170] As can be seen from Table 1, Figure 2 and Figure 4 the molecular weight of the dispersant synthesized using the hydrophobic monomer D and the cationic monomer methacryloyloxyethyl trimethyl ammonium chloride is smaller than that of the common dispersant. When it is applied to the water-in-water polymerization process, the synthesized cationic acrylamide copolymer dispersion has higher stability and fluidity than the conventional acrylamide copolymer dispersion. After optimization, the viscosity of the dispersion (the product in Example 10) after being diluted 10 times is 297.6 mPa·s, and the molecular weight is 8.75×10 6 g / mol, which is higher than the molecular weight (7.31×10 6 g / mol) of the product in the comparative example, and it can be almost completely dissolved within 1 min (as Figure 3 shown). Compared with the comparative example, the dispersions synthesized in Examples 1-11 have good fluidity, stability and solubility, and Examples 1-2, 6-7 and 10 are particularly excellent. It shows that the cationic acrylamide copolymer dispersion prepared using the novel dispersant for water-in-water polymerization of the present invention has good stability, fluidity and solubility. From the data in Table 1, it can be obtained that the molecular weight of the novel dispersant for water-in-water polymerization first increases, then decreases, then increases again and then decreases with the increase of the concentration of the hydrophobic monomer; and it gradually decreases with the increase of the initiator dosage. Considering the influence on the cationic acrylamide copolymer dispersion, the concentration of the hydrophobic monomer is preferably 0.05 wt% - 0.11 wt%.

[0171] Based on the data in Table 1 andFigure 2 , Figure 3 , Figure 4 The displayed fluidity, stability and solubility indicate that the novel water-in-water polymerization dispersant synthesized by the present invention is of great help in improving the molecular weight, stability and fluidity of the dispersion liquid, meets the requirements of the performance of the slick water fracturing fluid, and is expected to be widely applied in the fields of enhanced oil recovery, oil and gas field development, etc.

[0172] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to the typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as stipulated, and the present invention can 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 dispersant for water-in-water polymerization, wherein the dispersant is a hydrophobically associating polymer; For the hydrophobically associating polymer, its raw materials for preparation, calculated by mass percentage, include the following components: The monomer is composed of a cationic monomer and a hydrophobic monomer.

2. The dispersant for water-in-water polymerization according to claim 1, characterized in that: The content of the cationic monomer is 18 wt% - 28 wt%; And / or, the content of the hydrophobic monomer is 0.05 wt% - 0.11 wt%.

3. The dispersant for water-in-water polymerization according to claim 1 or 2, characterized in that: The cationic monomer is selected from one of methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and dimethyldiallyl ammonium chloride; preferably methacryloyloxyethyl trimethyl ammonium chloride, and its structural formula is as shown in Formula 1: And / or, for the hydrophobic monomer, its molecular structure is as shown in Formula 2:

4. The dispersant for water-in-water polymerization according to any one of claims 1 - 3, characterized in that: The chelating agent is selected from any one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, and disodium ethylenediaminetetraacetate dihydrate, preferably disodium ethylenediaminetetraacetate dihydrate; And / or, the initiator is selected from any one of ammonium persulfate, potassium persulfate, sodium persulfate, and hydrogen peroxide.

5. The preparation method of the dispersant for water-in-water polymerization according to any one of claims 1 - 4, including the following steps: in the presence of the chelating agent and the initiator, the cationic monomer and the hydrophobic monomer are obtained through aqueous solution polymerization to obtain the hydrophobically associating polymer.

6. The preparation method according to claim 5, wherein: The specific preparation method of the dispersant includes the following steps: S1. Place the cationic monomer, hydrophobic monomer, and water in a reactor in a certain proportion, stir and dissolve to form a reaction solution; S2. Place the reaction solution obtained in step S1 in a constant temperature water bath at 60°C - 70°C, introduce nitrogen, add an initiator, and the dosage of the initiator accounts for 0.5 wt% - 1.2 wt% of the total mass of the monomers; S3. React the reaction solution obtained in step S2 in a constant temperature water bath at 60°C - 70°C for 6 - 8 hours, and cool to room temperature to obtain the hydrophobically associating polymer.

7. A hydrophobically associating polymer with a structural formula as shown in Formula 3: In formula (3), x and y are respectively the percentages of each structural unit, where x = 99.3% - 99.5%, y = 0.5% - 0.7%, and the molecular weight of the hydrophobic associating polymer is 1.39×10 5 ~3.88×10 5 g / mol.

8. The application of the dispersant for water-in-water polymerization according to any one of claims 1 - 3 or the hydrophobically associating polymer according to claim 7 in the process of water-in-water polymerization; Furthermore, the water-in-water polymerization is used to prepare a cationic acrylamide copolymer.

9. A preparation method of a cationic acrylamide copolymer, including the following steps: a. Place the non-ionic monomer, cationic monomer, dispersion medium, dispersant, and water in a reaction flask in a certain proportion, stir and dissolve to obtain a clear and transparent homogeneous solution, and adjust the pH value of the dispersion system to 7 - 8; b. Heat the homogeneous solution obtained in step a to 50°C - 60°C, introduce nitrogen, and add an initiator; c. React the solution obtained in step b at a constant temperature of 50°C - 60°C for 4 - 6 hours, and cool to room temperature to obtain a cationic acrylamide copolymer dispersion; The dosages of the above raw materials are as follows by mass percentage: The monomer consists of a non-ionic monomer and a cationic monomer; The dispersant is the water-in-water polymerization dispersant described in any one of claims 1-3 or the hydrophobically associating polymer described in claim 7.

10. The preparation method according to claim 9, characterized in that: The dosages of the above raw materials are as follows by mass percentage: And / or, the non-ionic monomer is selected from one of acrylamide or methacrylamide, preferably acrylamide; And / or, the non-ionic monomer accounts for 66.0 wt% to 75.5 wt% of the total mass of the entire monomer system; And / or, the cationic monomer is selected from one of methylacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride, and dimethyldiallyl ammonium chloride, preferably methylacryloyloxyethyl trimethyl ammonium chloride; And / or, the cationic monomer accounts for 24.5 wt% to 34.0 wt% of the total mass of the entire monomer system; And / or, the dispersion medium is selected from one of ammonium sulfate, sodium sulfate, and sodium chloride; preferably ammonium sulfate; And / or, the initiator is an azo initiator.

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