Inverse emulsion polymerization method of water-soluble monomer and emulsion polymer

Abstract

The invention relates to the field of polymer synthesis, and discloses an inverse emulsion polymerization method of a water-soluble monomer and an emulsion polymer. The invention relates to an inverse emulsion polymerization method of a water-soluble monomer, which comprises the following steps: (1) mixing a water solution containing the water-soluble monomer, a nonionic emulsifier and an oil phase to obtain a water-in-oil mixture, the nonionic emulsifier having an HLB value of 2-8; and (2) in the presence of an inorganic reducing agent, the water-in-oil type mixture in the step (1) is subjected to inverse emulsion polymerization reaction under the ultrasonic irradiation condition, and the inverse emulsion polymerization reaction in the step (2) does not use an initiator. According to the method, linear increase of the molecular weight of the polymer can be realized and narrower distribution of the molecular weight of the polymer can be maintained by using the nonionic emulsifier and the inorganic reducing agent under the condition of ultrasonic irradiation and under the relatively mild reaction condition, and the method does not need to use an initiator, so that the influence of a half-life period on the free radical concentration can be avoided; the polymerization activity of different monomers can be accurately researched.

Description

Technical Field

[0001] The present invention relates to the field of polymer synthesis, and in particular to an inverse emulsion polymerization method of a water-soluble monomer and an emulsion polymer. Background Art

[0002] Controlled radical polymerization is a hot topic in polymer research. The challenge lies in maintaining chain growth activity throughout the polymerization phase until the monomer is exhausted, meaning the polymerization reaction ends. Key characteristics include pseudo-first-order polymerization kinetics, a linear relationship between the polymer number-average molecular weight and monomer conversion, and a narrow molecular weight distribution. In recent years, key methods for achieving controlled radical polymerization include nitroxide-stabilized radical polymerization (NRMP) (in which nitroxides and monomer radicals undergo pseudo-death polymerization), atom transfer radical polymerization (ATRP) (metal-catalyzed atom transfer radical polymerization), and reversible addition-fragmentation chain transfer polymerization (RAFT). These methods share a similar underlying principle: establishing a reversible dynamic equilibrium between active and inert chains to control the polymerization reaction. The NRMP method uses a free radical scavenger, which couples with the growing chain to form a stable free radical that can be decomposed back into a free radical growing chain; the ATRP method uses organic halides and transition metal complexes to establish a dynamic equilibrium between active species and dormant species through redox reactions; the RAFT method uses a dithioester derivative SC(Z)S-R as a chain transfer agent to temporarily put the growing chain free radicals dormant, while the intermediates can be decomposed back into a free radical growing chain.

[0003] Emulsion polymerization is a method that uses emulsifiers and other agents to form an oil-in-water emulsion, initiating the polymerization of oil-soluble monomers such as styrene and acrylic acid. Because emulsion polymerization has unique nucleation and monomer migration mechanisms, it provides an ideal site for controlled polymerization. Foreign researchers have primarily used the RAFT (reversible addition-fragmentation chain transfer) method to conduct controlled emulsion polymerization research. Lansalot et al. studied RAFT emulsion polymerization of styrene and proposed that the leaving group of the RAFT agent enters the aqueous phase, reducing the concentration of chain-propagating free radicals and leading to retarded polymerization, significantly reducing the polymerization rate of the miniemulsion. Luo et al. demonstrated that the polymerization rate is determined by both the chain transfer constant and concentration of the RAFT agent. In contrast, inverse emulsion polymerization forms an oil-in-water emulsion to initiate the polymerization of water-soluble monomers such as acrylamide and acrylic acid. Qi et al. conducted RAFT inverse emulsion living polymerization of acrylamide, finding droplet nucleation as the primary nucleation mechanism. Ying et al. also concluded that in RAFT inverse emulsion living polymerization, the primary site of nucleation and polymerization remains the monomer droplets, with only a small portion of latex particles nucleated from the continuous phase.

[0004] Active polymerizations such as ATRP and RAFT are essentially reversible processes of continuous activation and deactivation of growing chains, which maintain the free radical concentration at an extremely low level and reduce the generation of dead chains caused by double radical termination. In emulsion polymerization and inverse emulsion polymerization, low free radical concentrations will lead to fewer reaction sites in the system, making it difficult to increase the monomer conversion rate, and ultimately affecting the stability of the polymerization and the product. In response to the late-stage runaway phenomenon of RAFT miniemulsion polymerization, Luo et al. proposed the superswelling theory. They believe that because the nucleation efficiency of miniemulsion polymerization cannot reach 100%, the chemical potential of the monomer in the nucleated droplets is lower than that of the unnucleated monomer droplets. The monomer will migrate from the latter to the former until the chemical potential of the two reaches equilibrium, resulting in the destruction of the emulsion stability. In addition, the RAFT agent is prone to failure during the migration process, making it difficult to maintain a low molecular weight distribution in the later stages of polymerization.

[0005] Ultrasonic irradiation emulsion polymerization uses the acoustic cavitation effect to produce extremely small bubble nuclei in the liquid. When the cavitation bubbles collapse, high temperatures and pressures exceeding 5000K and 108Pa are generated, initiating chemical reactions that cannot occur under normal conditions. Stoffer et al. used sodium dodecyl sulfate (SDS) as an emulsifier and prepared polymethyl methacrylate by ultrasonic irradiation without adding an initiator, but the yield was low. Stoffer confirmed through capture experiments that free radicals originated from the decomposition of the ionic emulsifier SDS. Biggs et al. prepared polystyrene by ultrasonic irradiation emulsion polymerization without adding a chemical initiator, with a yield of approximately 30%. The above studies are difficult to commercialize due to low molecular weight and low yield.

[0006] Inverse emulsion polymerization typically uses water-soluble initiators such as persulfates (such as ammonium persulfate, potassium persulfate, and sodium persulfate), hydrogen peroxide, and azo hydrochlorides (such as V044 and V050). Chemical initiators have a short half-life, making it difficult to maintain a stable polymerization rate. However, using ultrasonic irradiation to controllable inverse emulsion polymerization of water-soluble monomers can achieve a dynamic balance between chain growth and termination through "acoustic cavitation" and "chain scission" effects. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of the inverse emulsion polymerization system and the ultrasonic irradiation emulsion polymerization system in the prior art, and to provide an inverse emulsion polymerization method of a water-soluble monomer and an emulsion polymer. The method uses a non-ionic emulsifier and an inorganic reducing agent under relatively mild reaction conditions under ultrasonic irradiation conditions to achieve linear growth of the polymer molecular weight and maintain a narrow distribution of the polymer molecular weight. Moreover, the method does not require the use of an initiator, and can avoid the influence of the half-life on the free radical concentration, so as to accurately study the polymerization activity of different monomers.

[0008] In order to achieve the above object, the first aspect of the present invention provides a method for inverse emulsion polymerization of a water-soluble monomer, wherein the method comprises the following steps:

[0009] (1) mixing an aqueous solution containing a water-soluble monomer, a nonionic emulsifier, and an oil phase to obtain a water-in-oil mixture, wherein the nonionic emulsifier has an HLB value of 2-8;

[0010] (2) In the presence of an inorganic reducing agent, the water-in-oil mixture of step (1) is subjected to an inverse emulsion polymerization reaction under ultrasonic irradiation conditions, and the inverse emulsion polymerization reaction of step (2) does not use an initiator.

[0011] The second aspect of the present invention provides an emulsion polymer prepared by the inverse emulsion polymerization method of the water-soluble monomers described in the first aspect.

[0012] The method provided by the present invention can achieve linear growth of molecular weight under relatively mild conditions by using a non-ionic emulsifier in the presence of an inorganic reducing agent through ultrasonic irradiation, and can maintain a narrow distribution of molecular weight of the emulsion polymer at a conversion rate of over 90%.

[0013] The method provided by the present invention does not use a chemical initiator, can avoid the influence of half-life on free radical concentration, and can accurately study the polymerization activity of different monomers.

[0014] The method provided by the present invention selects an inorganic reducing agent, and by virtue of the efficient reducing property of the inorganic reducing agent under mild conditions, the polymerization reaction process is easily controlled to obtain an emulsion polymer with a narrow molecular weight distribution.

[0015] The method provided by the present invention has low difficulty in industrial production and has broad application prospects in the fields of fine polymer synthesis, coatings, oilfield chemistry, etc. DETAILED DESCRIPTION

[0016] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0017] A first aspect of the present invention provides a method for inverse emulsion polymerization of a water-soluble monomer, wherein the method comprises the following steps:

[0018] (1) mixing an aqueous solution containing a water-soluble monomer, a nonionic emulsifier, and an oil phase to obtain a water-in-oil mixture, wherein the nonionic emulsifier has an HLB value of 2-8;

[0019] (2) In the presence of an inorganic reducing agent, the water-in-oil mixture of step (1) is subjected to an inverse emulsion polymerization reaction under ultrasonic irradiation conditions, and the inverse emulsion polymerization reaction of step (2) does not use an initiator.

[0020] The method provided by the present invention can achieve linear growth of molecular weight under relatively mild conditions by using a non-ionic emulsifier in the presence of an inorganic reducing agent through ultrasonic irradiation, and can maintain a narrow distribution of molecular weight of the emulsion polymer at a conversion rate of over 90%.

[0021] The method provided by the present invention does not use a chemical initiator, can avoid the influence of half-life on free radical concentration, and can accurately study the polymerization activity of different monomers.

[0022] The method provided by the present invention selects an inorganic reducing agent, and by virtue of the efficient reducing property of the inorganic reducing agent under mild conditions, the polymerization reaction process is easily controlled to obtain an emulsion polymer with a narrow molecular weight distribution.

[0023] The method provided by the present invention has low difficulty in industrial production and has broad application prospects in the fields of fine polymer synthesis, coatings, oilfield chemistry, etc.

[0024] In the present invention, the HLB value of the nonionic emulsifier is calculated by weighting the mass fraction of each emulsifier component in the total amount of emulsifier used. It should be noted that when the reaction system contains only one water-soluble monomer, the HLB value is the HLB value of the water-soluble monomer; when the reaction system contains two or more water-soluble monomers, the HLB value is calculated according to the above method. For example, when two nonionic emulsifiers are selected, the HLB value of the nonionic emulsifier is calculated as follows: HLB value = x*A+(1-x)*B, where A and B are the HLB values ​​of the two nonionic emulsifiers, respectively, and x and 1-x are the mass fractions of the two nonionic emulsifiers, respectively.

[0025] According to a preferred embodiment of the present invention, step (1) comprises:

[0026] dissolving a water-soluble monomer in water to obtain an aqueous solution containing the water-soluble monomer;

[0027] Mixing a nonionic emulsifier and an oil phase to obtain a mixture I containing a nonionic emulsifier and an oil phase, wherein the HLB value of the nonionic emulsifier is 2-8;

[0028] The aqueous solution containing the water-soluble monomer is added dropwise to the mixture I containing the nonionic emulsifier and the oil phase to obtain a water-in-oil mixture. In the present invention, there is no particular limitation on the rate of addition. Preferably, the rate of addition is 1-10 drops / s.

[0029] Compared with the prior art method of mixing water-soluble monomers, nonionic emulsifiers, water and oil phases together, the method provided by the present invention has the advantage of adopting this mixing order to make the dispersed phase particle size more uniform, avoid premature Ostwald ripening effect, and maintain system stability.

[0030] In the present invention, there is no particular limitation on the specific operation mode of mixing in each step of step (1). Preferably, the mixing in step (1) is independently carried out under stirring conditions, and preferably the stirring conditions include: a stirring rate of 200-1200 rad / min and a temperature of room temperature. In the present invention, the room temperature refers to 25±5°C. In the present invention, the stirring rates in each mixing process of step (1) can be the same or different, preferably the same, and those skilled in the art can adjust according to actual needs.

[0031] In the present invention, an aqueous solution containing a water-soluble monomer is used as the dispersed phase, and an oil phase is used as the continuous phase to synthesize an emulsion polymer by inverse emulsion polymerization. The source of the aqueous solution containing the water-soluble monomer is not particularly limited in the present invention, as long as an aqueous solution containing the water-soluble monomer can be obtained. Preferably, in step (1), the aqueous solution of the water-soluble monomer is prepared by dissolving the water-soluble monomer in water.

[0032] In the present invention, different water-soluble monomers have different solubilities. The present invention does not particularly limit the amounts of water-soluble monomers and water. Those skilled in the art can make adaptive adjustments according to actual needs. Preferably, the mass ratio of the water-soluble monomer to water is 0.01-2:1.

[0033] In the present invention, there is no particular limitation on the type of water-soluble monomer. Any water-soluble monomer conventionally defined in the art as suitable for inverse emulsion polymerization is applicable to the present invention. Preferably, the water-soluble monomer is selected from nonionic monomers and / or anionic monomers. More preferably, the water-soluble monomer is a nonionic monomer or anionic monomer.

[0034] In the present invention, there is no particular limitation on the type of water-soluble nonionic monomer. Any water-soluble nonionic monomer conventionally defined in the art as suitable for inverse emulsion polymerization can be used in the present invention. Preferably, the nonionic monomer is selected from at least one of acrylamide, methacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, and N-vinyl-2-pyrrolidone, and more preferably at least one of acrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, and N,N-dimethylacrylamide.

[0035] In the present invention, there is no particular limitation on the type of water-soluble anionic monomer. Any water-soluble anionic monomer conventionally defined in the art as suitable for inverse emulsion polymerization can be used in the present invention. Preferably, the anionic monomer is selected from at least one of acrylic acid, sodium acrylate, itaconic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-acryloyloxy-2-methylpropanesulfonic acid, sodium methacrylic acid, and sodium p-styrenesulfonate, and more preferably at least one of acrylic acid, sodium acrylate, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, and sodium methacrylic acid.

[0036] The advantages of adopting the above preferred embodiment are that the use of a single monomer avoids the competitive polymerization of different monomers, is easy to control the polymerization process, and obtains an emulsion polymer with a narrow molecular weight distribution.

[0037] In the present invention, the inverse emulsion polymerization system is a water-in-oil reaction system, and the inverse emulsion polymerization of water-soluble monomers is achieved by controlling the amounts of water-soluble monomers and oil phase. Preferably, the mass ratio of the water-soluble monomers to the oil phase is 0.01-2:1, more preferably 0.5-1.5:1, and more preferably 0.5-1:1.

[0038] In the present invention, preferably, the mass ratio of the water phase to the oil phase is 0.1-2.5:1, more preferably 0.5-1.7:1.

[0039] In the present invention, the inverse emulsion polymerization reaction is controlled by controlling the pH value of the aqueous solution containing the water-soluble monomer. Preferably, step (1) further comprises optionally introducing an acid-base regulator into the aqueous solution containing the water-soluble monomer.

[0040] In the present invention, there is no particular limitation on the type of acid-base regulator, as long as it meets the pH value requirement, and those skilled in the art can select it according to actual needs. Preferably, the acid-base regulator is a basic compound and / or an acidic compound.

[0041] In the present invention, there is no particular limitation on the type of the alkaline compound. Preferably, the alkaline compound is at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and potassium carbonate.

[0042] In the present invention, there is no particular limitation on the type of the acidic compound. Preferably, the acidic compound is at least one selected from hydrochloric acid, sulfuric acid, and phosphoric acid.

[0043] In the present invention, there is no particular limitation on the amount of the acid-base regulator, as long as it can meet the pH requirement. Preferably, the amount of the acid-base regulator is such that the pH value of the water-soluble monomer aqueous solution is 4-10.

[0044] In the present invention, there is no particular limitation on the type of nonionic emulsifier, and all nonionic emulsifiers conventionally defined in the art are applicable to the present invention. Preferably, in step (1), the nonionic emulsifier is a lipophilic emulsifier and optionally a hydrophilic emulsifier.

[0045] In the present invention, there is no particular limitation on the type of lipophilic emulsifier, and any nonionic emulsifier conventionally defined in the art is applicable to the present invention. Preferably, the lipophilic emulsifier is selected from the Span series emulsifiers and / or amphiphilic block copolymer emulsifiers, such as Span 40, Span 60, Span 80, Span 83, and Span 85.

[0046] In the present invention, there is no particular limitation on the type of hydrophilic emulsifier, and any nonionic emulsifier conventionally defined in the art is applicable to the present invention. Preferably, the hydrophilic emulsifier is a Tween series emulsifier and / or an OP series emulsifier. For example, the Tween series emulsifier may be Tween 40, Tween 60, or Tween 80, and the OP series emulsifier may be OP-4, OP-5, OP-6, OP-7, OP-8, OP-10, or OP-15.

[0047] In the present invention, there is no particular limitation on the amount of the nonionic emulsifier used. Preferably, the mass ratio of the nonionic emulsifier to the oil phase is 0.05-0.5:1, more preferably 0.15-0.4:1.

[0048] In the present invention, there is no particular limitation on the amount of the lipophilic emulsifier and the hydrophilic emulsifier, as long as the HLB value of the nonionic emulsifier is within the aforementioned range. Preferably, the mass ratio of the lipophilic emulsifier to the hydrophilic emulsifier is 1:0.03-0.5.

[0049] In the present invention, the oil phase serves as the continuous phase in the inverse emulsion polymerization system, and the type of the oil phase is not particularly limited. Preferably, in step (1), the oil phase comprises at least one of alkanes, liquid paraffin, α-olefin synthetic base oil, mineral oil, and aromatic hydrocarbons, and more preferably at least one of liquid paraffin, mineral oil, and aromatic hydrocarbons. The advantages of using the above preferred types of oil phase as the continuous phase are that it has a suitable boiling point, is not easily volatilized during the process, maintains a stable oil-to-water ratio, is easy to obtain, has a stable system, and has a high monomer conversion rate.

[0050] In the present invention, there is no particular limitation on the specific type of alkane. Preferably, the alkane is selected from C5-C12 alkanes, and more preferably is selected from at least one of pentane, hexane, cyclohexane and heptane.

[0051] In the present invention, there is no particular limitation on the specific type of α-olefin. The α-olefin synthetic base oil is a C4-C24 α-olefin synthetic base oil, more preferably a C12-C18 α-olefin synthetic base oil.

[0052] In the present invention, there is no particular limitation on the specific type of mineral oil. For example, the mineral oil may be at least one of No. 3 mineral white oil, No. 5 mineral white oil, No. 7 mineral white oil, No. 10 mineral white oil, No. 15 mineral white oil, No. 26 mineral white oil, and No. 32 mineral white oil.

[0053] In the present invention, there is no particular limitation on the specific type of aromatic hydrocarbons. Preferably, the aromatic hydrocarbons are selected from C5-C10 aromatic hydrocarbons, more preferably toluene and / or xylene.

[0054] In the present invention, an inorganic reducing agent is used to cooperate with other components in the inverse emulsion polymerization system to achieve the polymerization of the water-in-oil type inverse emulsion polymerization system. The reducing property of the inorganic reducing agent is mild, and it is easy to control the reaction to obtain an emulsion polymer with a narrow molecular weight distribution. Preferably, in step (2), the inorganic reducing agent is selected from at least one of ammonium bisulfite, ammonium sulfite, potassium bisulfite, potassium sulfite, sodium bisulfite, sodium sulfite, sodium thiosulfate, sodium metabisulfite, potassium iodide, copper powder, iron powder, cuprous chloride, ferrous chloride and ammonium ferrous sulfate, and is further preferably selected from at least one of ammonium sulfite, potassium bisulfite, potassium sulfite, sodium bisulfite and sodium sulfite. The advantage of using this preferred embodiment is that the reducing property is strong, and a higher conversion rate can be obtained at a smaller dosage.

[0055] In the present invention, preferably, the inorganic reducing agent is provided by an aqueous solution containing the inorganic reducing agent, and preferably the mass concentration of the aqueous solution containing the inorganic reducing agent is 2-10%.

[0056] In the present invention, there is no particular limitation on the amount of the inorganic reducing agent used. Preferably, in step (2), the mass ratio of the inorganic reducing agent to the oil phase is 0.000001-0.55:1, more preferably 0.00001-0.001:1. It should be noted that the mass of the inorganic reducing agent herein refers to the mass of the inorganic reducing agent in the aqueous solution containing the inorganic reducing agent.

[0057] In the present invention, there is no particular limitation on the type of inert gas. Preferably, in step (2), the inert gas is selected from at least one of nitrogen, argon, helium and neon.

[0058] In the present invention, inverse emulsion polymerization is achieved by ultrasonic irradiation of a water-in-oil polymerization system. The present invention does not particularly limit the conditions for ultrasonic irradiation. Preferably, in step (2), the conditions for ultrasonic irradiation include: an ultrasonic frequency of 20-33 kHz, an ultrasonic power of 10-50 W, and a reaction temperature of 10-60°C; further preferably, in step (2), the conditions for ultrasonic irradiation include: an ultrasonic frequency of 20-30 kHz, an ultrasonic power of 20-40 W, and a reaction temperature of 30-50°C. The advantage of adopting this preferred embodiment is that the frequency and power are suitable for the cavitation effect of ultrasound, and an emulsion polymer with a narrow molecular weight distribution can be obtained.

[0059] In the present invention, preferably, the method further comprises: introducing an inert gas in step (2) and performing the emulsion inverse emulsion polymerization reaction in the presence of the inert gas.

[0060] In the present invention, there is no particular limitation on the type of inert gas. Preferably, in step (2), the inert gas is selected from at least one of nitrogen, argon, helium and neon.

[0061] In the present invention, there is no particular limitation on the rate of introduction of the inert gas, and those skilled in the art can adjust it according to actual needs.

[0062] According to a specific embodiment of the present invention, the inverse emulsion polymerization method comprises the following steps:

[0063] (1) dissolving a water-soluble monomer in water to obtain an aqueous solution containing the water-soluble monomer, and then optionally introducing an acid-base regulator into the aqueous solution containing the water-soluble monomer to adjust the pH to 4-10;

[0064] Mixing a nonionic emulsifier and an oil phase to obtain a mixture I containing a nonionic emulsifier and an oil phase, wherein the nonionic emulsifier has an HLB value of 2-8;

[0065] The aqueous solution containing the water-soluble monomer is added dropwise to the mixture I containing the nonionic emulsifier and the oil phase at a rate of 1-10 drops / s under stirring at a speed of 200-1200 rad / min and room temperature to obtain a water-in-oil mixture;

[0066] (2) introducing an inert gas into the water-in-oil mixture of step (1), maintaining the inert gas atmosphere and heating to the ultrasonic irradiation reaction temperature, then adding an organic reducing agent to carry out an inverse emulsion polymerization reaction under ultrasonic irradiation conditions, wherein the inverse emulsion polymerization reaction does not use an initiator, and the ultrasonic irradiation conditions include: an ultrasonic frequency of 20-30 kHz, an ultrasonic power of 20-40 W, and a reaction temperature of 30-50°C.

[0067] The second aspect of the present invention provides an emulsion polymer prepared by the inverse emulsion polymerization method of the water-soluble monomers described in the first aspect.

[0068] In the present invention, preferably, the molecular weight distribution index of the emulsion polymer is 1.05-1.8, more preferably 1.05-1.4.

[0069] In the present invention, the weight average molecular weight and number average molecular weight of the emulsion polymer were measured using an Agilent 1260mct GPC. The chromatographic column used was PL1149-6800, and the mobile phase was aqueous. The molecular weight distribution index was calculated according to the following formula:

[0070] Molecular weight distribution index = weight average molecular weight / number average molecular weight.

[0071] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, all raw materials used are commercially available.

[0072] The HLB value of span80 is 4.3, and the HLB value of Tween60 is 14.9.

[0073] The HLB value of Tween80 is 15.0, and the HLB value of span60 is 4.7.

[0074] The HLB value of OP-10 is 14.5, and the HLB value of span85 is 1.8.

[0075] The HLB value of Tween40 is 15.6, and the HLB value of span40 is 6.7.

[0076] The HLB value of OP-4 is 8.3, and the HLB value of span83 is 3.7.

[0077] The HLB value of OP-15 is 15, and the HLB value of OP-7 is 12.

[0078] In the present invention, the monomer conversion rate is determined by the following method: the total mass fraction of all added monomers in the reaction system is recorded as Z. Two drops of hydroquinone (inhibitor) are first added to ethanol, and then the mass of the emulsion polymer product is recorded as m0. After magnetic stirring for 6 hours, it is allowed to settle for 24 hours. The filter paper is dried in an oven at 105°C to constant weight, and the mass of the precipitate is recorded as m1. After the precipitate is filtered with filter paper, it is washed three times with a mixed solvent prepared by ethanol and acetone in a mass ratio of 1:1, and vacuum dried at 60°C to constant weight. The mass is recorded as m2. The conversion rate Y is calculated according to the following formula:

[0079] Conversion rate Y = (m2-m1) / (m0×Z)×100%.

[0080] In the present invention, the weight average molecular weight and number average molecular weight of the emulsion polymer were measured using an Agilent 1260mct GPC. The chromatographic column used was PL1149-6800, and the mobile phase was aqueous. The molecular weight distribution index was calculated according to the following formula:

[0081] Molecular weight distribution index = weight average molecular weight / number average molecular weight.

[0082] Example 1

[0083] To a four-necked flask, add 100.0g of No. 3 mineral white oil (Jingmen Petrochemical), 30.0g of Span 80, and 5.0g of Tween 80 (HLB value of 5.8) and stir thoroughly to form the oil phase. Weigh 100.0g of 2-acrylamido-2-methylpropanesulfonic acid and dissolve it in 100.0g of deionized water. Adjust the pH to 8 with potassium hydroxide. Add the oil phase dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature with mechanical stirring at 650 rad / min. After the addition is complete, high-purity nitrogen is introduced for 20 minutes and maintained under a nitrogen atmosphere. The system is heated to 30°C and maintained under reflux. Then, 1.0g of a 10% sodium metabisulfite aqueous solution is added. After stirring for 2 minutes, the mixture is irradiated using an ultrasonic cleaner at a frequency of 25kHz and a power of 20W, maintaining the reaction at 30°C for a specified period of time.

[0084] Example 2

[0085] To a four-necked flask, add 100.0g of liquid paraffin (McLean, reagent, analytical grade), 18.0g of Span 80, and 2.0g of OP-10 (HLB value of 5.3) and stir thoroughly to form the oil phase. Weigh 50.0g of itaconic acid and dissolve it in 100.0g of deionized water. Adjust the pH to 6.5 with sodium hydroxide. Add the oil phase dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature with mechanical stirring at 500 rad / min. After the addition is complete, introduce high-purity argon for 20 minutes and maintain the argon atmosphere. Raise the temperature to 50°C, maintain reflux, and add 0.5g of potassium bisulfite (solution mass concentration of 2.0%). After stirring for 2 minutes, irradiate the solution using an ultrasonic cleaner at a frequency of 20kHz and a power of 40W, maintaining the temperature at 50°C for a desired reaction time.

[0086] Example 3

[0087] To a four-necked flask, add 100.0g of toluene (Aladdin, reagent, analytical grade), 26.0g of Span 60, and 1.0g of OP-10 (HLB value of 5.1) and stir thoroughly to form the oil phase. Weigh 10.0g of acrylamide and dissolve it in 150.0g of deionized water to an initial pH of 7. Under mechanical stirring at 450 rad / min, the oil phase is added dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature. After the addition is complete, high-purity nitrogen is introduced for 20 minutes and maintained. The system is heated to 45°C, and 0.1g of sodium sulfite (0.01% solution mass concentration) is added. After stirring for 2 minutes, the mixture is refluxed and irradiated using an ultrasonic cell disruptor at a frequency of 30kHz and a power of 30W. The reaction is maintained at 45°C for a specified period of time.

[0088] Example 4

[0089] To a four-necked flask, add 100.0g of hexane (Aladdin, reagent, analytical grade) and 35.0g of Span 80 (HLB value 4.3) and stir thoroughly to form the oil phase. Weigh 2.0g of N-vinyl-2-pyrrolidone and dissolve it in 200.0g of deionized water. With mechanical stirring at 700 rad / min, add the oil phase dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature. After the addition is complete, introduce high-purity argon gas for 20 minutes and maintain the argon atmosphere. The system is heated to 40°C, and 0.1g of ammonium sulfite (solution mass concentration 0.001%) is added. After stirring for 2 minutes, the mixture is irradiated using an ultrasonic cleaner at a frequency of 55kHz and a power of 40W, maintaining the reaction at 40°C for a specified period of time.

[0090] Example 5

[0091] To a four-necked flask, add 100.0g of cyclohexane (Aladdin, reagent, analytical grade), 13.0g of Span 85, and 12.0g of OP-7 (HLB value of 6.7) and stir thoroughly to form the oil phase. Weigh 40.0g of sodium p-styrene sulfonate and dissolve it in 80.0g of deionized water. Adjust the pH to 4 with hydrochloric acid. Add the oil phase dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature with mechanical stirring at 600 rad / min. After the addition is complete, introduce high-purity helium for 20 minutes and maintain the helium atmosphere. The system is temperature-controlled to 10°C, and 1.0g of potassium iodide and 1g of an aqueous solution of ferrous ammonium sulfate (both at a 5% mass concentration) are added. After stirring for 2 minutes, the mixture is irradiated using an ultrasonic cell disruptor at a frequency of 35kHz and a power of 50W, maintaining the reaction at 60°C for a specified period.

[0092] Example 6

[0093] To a four-necked flask, add 100.0g of Saraline 185 (Shell's alpha-olefin synthetic base oil), 14.0g of Span 40, and 1.0g of Tween 40 (HLB value 7.3) and stir thoroughly to form the oil phase. Weigh 30.0g of sodium methyl propylene sulfonate and dissolve it in 60.0g of deionized water. Adjust the pH to 8 with sodium carbonate. Add the oil phase dropwise at a rate of 1-2 drops / s using a dropping funnel with mechanical stirring at 750 rad / min at room temperature. After the addition is complete, introduce high-purity neon gas for 20 minutes and maintain the neon atmosphere. The system is heated to 60°C, and 0.95g of copper powder and 0.5g of a 10% cuprous chloride aqueous solution are added. After stirring for 2 minutes, the mixture is refluxed and irradiated using an ultrasonic cleaner at a frequency of 35kHz and a power of 10W. The reaction is maintained at 10°C for a specified period of time.

[0094] Example 7

[0095] To a four-necked flask, 100.0g of No. 5 mineral white oil (Jingmen Petrochemical), 18.0g of Span 60, and 6.0g of OP-4 (HLB value of 5.6) were added and stirred uniformly to form the oil phase. 40.0g of N-hydroxyethyl acrylamide was weighed and dissolved in 100.0g of deionized water. The pH was adjusted to 5 with phosphoric acid. The oil phase was added dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature with mechanical stirring at 600 rad / min. After the addition was complete, high-purity nitrogen was introduced for 20 minutes and maintained. The system was temperature-controlled to 20°C, and 0.5g of iron powder and 2.5g of an aqueous ferrous chloride solution (20% by mass) were added. After stirring for 2 minutes, the mixture was irradiated using an ultrasonic cell disruptor at a frequency of 25kHz and a power of 20W. The reaction was maintained at 20°C for a predetermined period of time.

[0096] Example 8

[0097] The method of Example 1 was followed, except that sodium metabisulfite was replaced with an equal mass of potassium iodide.

[0098] Comparative Example 1

[0099] In a four-necked flask, 100.0g of No. 3 mineral white oil (Jingmen Petrochemical), 30.0g of Span 80, and 5.0g of Tween 80 (HLB value of 5.8) were added and stirred evenly to form the oil phase. 100.0g of 2-acrylamido-2-methylpropanesulfonic acid was weighed and dissolved in 100.0g of deionized water. The pH was adjusted to 8 with potassium hydroxide. Under mechanical stirring at 650 rad / min, the oil phase was added dropwise using a dropping funnel at a rate of 1-2 drops / s at room temperature. After the addition was complete, high-purity nitrogen was introduced for 20 minutes, and the nitrogen atmosphere was maintained. The system was heated to 30°C, maintained under reflux, and irradiated using an ultrasonic cleaner with a frequency of 25kHz and a power of 20W. The reaction was maintained at 30°C for a certain period of time.

[0100] Comparative Example 2

[0101] To a four-necked flask, add 100.0g of liquid paraffin (McLean, reagent, analytical grade), 18.0g of Span 80, and 2.0g of OP-10 (HLB value of 5.3) and stir thoroughly to form the oil phase. Weigh 50.0g of itaconic acid and dissolve it in 100.0g of deionized water. Adjust the pH to 6.5 with sodium hydroxide. Add the oil phase dropwise using a dropping funnel at a rate of 1-2 drops / s at room temperature with mechanical stirring at 500 rad / min. After the addition is complete, introduce high-purity argon gas for 20 minutes and maintain the argon atmosphere. Raise the system to 50°C, maintain reflux, and irradiate with an ultrasonic cleaner at a frequency of 20kHz and a power of 40W. Maintain the reaction at 50°C for a specified period.

[0102] Comparative Example 3

[0103] To a four-necked flask, add 100.0g of toluene (Aladdin, reagent, analytical grade), 26.0g of Span 60, and 1.0g of OP-10 (HLB value of 5.1) and stir thoroughly to form the oil phase. Weigh 10.0g of acrylamide and dissolve it in 150.0g of deionized water to an initial pH of 7. With mechanical stirring at 450 rad / min, the oil phase is added dropwise at a rate of 1-2 drops / s using a dropping funnel at room temperature. After the addition is complete, high-purity nitrogen is introduced for 20 minutes and maintained under a nitrogen atmosphere. The system is heated to 45°C, maintained under reflux, and irradiated with an ultrasonic cell disruptor at a frequency of 30 kHz and a power of 30 W. The reaction is then maintained at 45°C for a specified period of time.

[0104] Comparative Example 4

[0105] In a four-necked flask, 100.0 g of No. 3 mineral white oil (Jingmen Petrochemical), 30.0 g of span80 and 5.0 g of Tween80 (HLB value of 5.8), 2.0 g of N-vinyl-2-pyrrolidone and 100.0 g of deionized water were added. Mechanical stirring was maintained at 650 rad / min, and high-purity nitrogen was introduced for 20 minutes. The system was heated to 30°C and reflux was maintained. 1.0 g of sodium metabisulfite aqueous solution (solution mass concentration of 10%) was added and stirred for 2 minutes. The mixture was irradiated with an ultrasonic cleaner with a frequency of 25 kHz and a power of 20 W, and the reaction was maintained at 30°C for a certain period of time.

[0106] The monomer conversion rates during the reaction of the above examples and comparative examples and the molecular weight distribution index of the prepared emulsion polymers are listed in Table 1.

[0107] Table 1

[0108]

[0109] As can be seen from the data in the table above, the emulsion polymers produced in the methods of the present invention all maintained stable polymerization without gel formation. The induction period was approximately 10 minutes, and the monomer conversion increased linearly over time within 190 minutes. Compared with the comparative examples, the corresponding examples significantly improved monomer conversion and had a narrower molecular weight distribution index, demonstrating clear controllable polymerization characteristics.

[0110] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for inverse emulsion polymerization of a water-soluble monomer, wherein: The method comprises the following steps: (1) mixing an aqueous solution containing a water-soluble monomer, a nonionic emulsifier, and an oil phase to obtain a water-in-oil mixture, wherein the nonionic emulsifier has an HLB value of 2-8; (2) In the presence of an inorganic reducing agent, the water-in-oil mixture of step (1) is subjected to an inverse emulsion polymerization reaction under ultrasonic irradiation conditions, and the inverse emulsion polymerization reaction of step (2) does not use an initiator.

2. The method according to claim 1, wherein The water-soluble monomer is a nonionic monomer and / or an anionic monomer, preferably a nonionic monomer or an anionic monomer; Preferably, the nonionic monomer is selected from at least one of acrylamide, methacrylamide, N-isopropylacrylamide, N-hydroxyethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide and N-vinyl-2-pyrrolidone; Preferably, the anionic monomer is at least one selected from acrylic acid, sodium acrylate, itaconic acid, methacrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-acryloyloxy-2-methylpropanesulfonic acid, sodium methacrylic acid and sodium p-styrenesulfonate.

3. The method according to claim 2, wherein: The mass ratio of the water-soluble monomer to the oil phase is 0.01-2:1, preferably 0.5-1.5:1; Preferably, the mass ratio of the water phase to the oil phase is 0.1-2.5:1, more preferably 0.5-1.7:

1.

4. The method according to any one of claims 1 to 3, wherein: Step (1) further comprises optionally introducing an acid-base modifier into the aqueous solution of the water-soluble monomer; Preferably, the acid-base regulator is a basic compound and / or an acidic compound; Preferably, the alkaline compound is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate and potassium carbonate; Preferably, the acidic compound is selected from at least one of hydrochloric acid, sulfuric acid and phosphoric acid; Preferably, the amount of the acid-base regulator is such that the pH value of the water-soluble monomer aqueous solution is 4-10.

5. The method according to any one of claims 1 to 4, wherein: In step (1), the nonionic emulsifier is a lipophilic emulsifier and optionally a hydrophilic emulsifier; Preferably, the lipophilic emulsifier is selected from the group consisting of Span series emulsifiers and / or amphiphilic block copolymer emulsifiers; Preferably, the hydrophilic emulsifier is a Tween series emulsifier and / or an OP series emulsifier, more preferably a Tween series emulsifier and an OP series emulsifier; Preferably, the mass ratio of the nonionic emulsifier to the oil phase is 0.05-0.5:1, more preferably 0.15-0.4:

1.

6. The method according to any one of claims 1 to 5, wherein: In step (1), the oil phase comprises at least one of alkanes, liquid paraffin, α-olefin synthetic base oil, mineral oil and aromatic hydrocarbons, and more preferably at least one of liquid paraffin, mineral oil and aromatic hydrocarbons; Preferably, the alkane is selected from C5-C12 alkanes, and further preferably is selected from at least one of pentane, hexane, cyclohexane and heptane; Preferably, the α-olefin synthetic base oil is a C4-C24 α-olefin synthetic base oil, more preferably a C12-C18 α-olefin synthetic base oil; Preferably, the aromatic hydrocarbon is selected from C5-C8 aromatic hydrocarbons, more preferably benzene and / or toluene.

7. The method according to any one of claims 1 to 6, wherein: In step (2), the inorganic reducing agent is selected from at least one of ammonium bisulfite, ammonium sulfite, potassium bisulfite, potassium sulfite, sodium bisulfite, sodium sulfite, sodium thiosulfate, sodium metabisulfite, potassium iodide, copper powder, iron powder, cuprous chloride, ferrous chloride and ammonium ferrous sulfate, preferably selected from at least one of ammonium sulfite, potassium bisulfite, potassium sulfite, sodium bisulfite, sodium sulfite, sodium thiosulfate and sodium metabisulfite; Preferably, in step (2), the mass ratio of the inorganic reducing agent to the oil phase is 0.000001-0.55:1, more preferably 0.00001-0.001:

1.

8. The method according to any one of claims 1 to 7, wherein: In step (2), the conditions of the ultrasonic irradiation include: ultrasonic frequency of 20-33 kHz, ultrasonic power of 10-50 W, and reaction temperature of 10-60° C.; Preferably, in step (2), the conditions of the ultrasonic irradiation include: ultrasonic frequency of 20-30 kHz, ultrasonic power of 20-40 W, and reaction temperature of 30-50°C.

9. An emulsion polymer obtained by the inverse emulsion polymerization method of a water-soluble monomer according to any one of claims 1 to 8.

10. The emulsion polymer according to claim 9, wherein The molecular weight distribution index of the emulsion polymer is 1.05-1.8, preferably 1.05-1.4.

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