Cationic etherifying agent and method for its preparation

Abstract

This invention discloses a cationic etherifying agent and its preparation method, belonging to the field of cationic etherifying agent production technology. The preparation method includes: continuously feeding trimethylamine and hydrochloric acid into a raw material pretreatment unit, pre-cooling to -10~20℃; entering a first tubular reactor, reacting at -10℃~20℃ and 0.15MPa for 10~60 minutes to generate trimethylammonium chloride; trimethylammonium chloride and epichlorohydrin entering a static mixer, simultaneously adding a catalyst and an organic amine; entering a second tubular reactor, reacting at 10~50℃ and 0.2MPa for 1~3 hours; during the reaction, monitoring the chloride ion concentration and epichlorohydrin residue in real time, dynamically adjusting the reaction parameters; filtering the reaction product through a nanofiltration membrane to obtain a high-purity cationic etherifying agent. This invention employs a continuous tubular reaction process combined with automatic control and nanofiltration membrane separation, resulting in a short production cycle, low energy consumption, few by-products, and a high-purity, odorless product, showing good industrial application prospects.

Description

Technical Field

[0001] This invention belongs to the field of cationic etherifying agent production technology, specifically relating to a cationic etherifying agent and its preparation method. Background Technology

[0002] Cationic etherifying agents are multifunctional fine chemical products, commercially available in both solid and aqueous solutions. The aqueous solution is typically a colorless, transparent liquid with a concentration of 69%. Under alkaline conditions, this product rapidly transforms into a highly reactive epoxidized structure, readily reacting with compounds containing active hydrogen to generate quaternary ammonium-based multifunctional chemicals. It is widely used in papermaking, daily chemical products, petroleum, and water treatment, primarily in the preparation of cationic starch, cationic polyacrylamide, electroplating additives, and textile printing and dyeing auxiliaries.

[0003] In existing technologies, the preparation of cationic etherifying agents mainly employs a batch process as described in patents such as CN 107353213 A. This process uses hydrochloric acid, trimethylamine, and epichlorohydrin as raw materials, involving steps such as preparing trimethylamine hydrochloride, low-temperature dropwise addition of epichlorohydrin, room-temperature reaction, and product purification to synthesize the cationic etherifying agent. Although this process is relatively mature, the reaction is highly exothermic, requiring stringent temperature control, and produces numerous byproducts, necessitating complex post-treatment for impurity removal, resulting in high energy consumption and a long production cycle. Furthermore, the product and its use produce a strong ammonia odor, which not only deteriorates the operating environment but also limits the further expansion of its application range. Summary of the Invention

[0004] To overcome the aforementioned technical problems in the prior art, this invention provides a cationic etherifying agent and its preparation method. This invention achieves continuous production using a tubular reactor and employs nanofiltration membranes for post-treatment, shortening production time and reducing energy consumption. Furthermore, the addition of organic amines and alkylating agents promotes reaction conversion and reduces byproduct formation, simplifying the reaction process; simultaneously, automated control reduces the impact of human intervention on product quality.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In one aspect, the present invention provides a method for preparing a cationic etherifying agent, comprising the following steps:

[0007] (1) Trimethylamine and hydrochloric acid are mixed at a molar ratio of 1:0.95~1.05 and continuously fed into the raw material pretreatment unit at a total flow rate of 20~50 kg / h, and pre-cooled to -10~20℃;

[0008] (2) The pre-cooled mixture enters the first tubular reactor and reacts continuously at a temperature of -10℃ to 20℃ and a pressure of 0.15MPa. The material residence time is 10 to 60 minutes, and trimethylammonium chloride is generated.

[0009] (3) The trimethylammonium chloride and epichlorohydrin are introduced into a static mixer, and 0.2% to 2% of the total mass of the reaction system catalyst and 2% to 8% of the total mass of the organic amine are added at the same time and mixed evenly;

[0010] (4) The mixture is continuously fed into the second tubular reactor and reacted continuously at a temperature of 10~50℃ and a pressure of 0.2MPa, with a material residence time of 1~3h;

[0011] (5) During the reaction, the automatic control system monitors the chloride ion concentration and epichlorohydrin residue in the reactor in real time and dynamically adjusts the reaction parameters;

[0012] (6) The reaction product is filtered through a nanofiltration membrane at an operating pressure of 0.5~2MPa and a temperature of 20~25℃ to obtain a high-purity cationic etherifying agent.

[0013] As a further aspect of the present invention: in step (1), the molar ratio of trimethylamine to hydrochloric acid is 1:1 to 1.05.

[0014] As a further aspect of the present invention: in step (2), the pH value of the material at the outlet of the first tubular reactor is collected in real time by an automatic control system and the pH is maintained at 3~6. If the pH is lower than 3.0, the hydrochloric acid delivery rate is automatically reduced.

[0015] And / or, in step (2), the inner diameter of the first tubular reactor is 50 mm and the tube length is 8 m, and the interior is provided with spiral guiding ribs;

[0016] And / or, in step (2), samples are taken for analysis every 10 minutes to ensure that the purity of trimethylammonium chloride is ≥99% and the free amine content is ≤0.5%;

[0017] And / or, in step (2), the temperature is -5℃ to 10℃ and the material residence time is 20 to 50 minutes.

[0018] As a further aspect of the present invention: in step (2), the pH is maintained at 4 to 5.

[0019] As a further aspect of the present invention: in step (3), the molar ratio of epichlorohydrin to trimethylamine is 1.0~1.2:1;

[0020] And / or, in step (3), the organic amine is a tertiary amine, preferably trimethylamine;

[0021] And / or, in step (3), the catalyst is at least one of 10% to 20% dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid.

[0022] As a further embodiment of the present invention: in step (3), the catalyst is 10%~20% dilute hydrochloric acid and / or dilute sulfuric acid.

[0023] As a further embodiment of the present invention: in step (4), the inner diameter of the second tubular reactor is 60 mm and the tube length is 12 m, and the temperature is controlled by jacketed hot water circulation;

[0024] And / or, in step (4), the temperature is 10~40℃.

[0025] As a further aspect of the present invention: in step (5), the automatic control system monitors the chloride ion concentration in the reactor in real time. If the concentration is ≥1.2%, the reaction temperature is reduced. At the same time, the epichlorohydrin residue is monitored by online chromatography to ensure that it is ≤0.3%.

[0026] As a further aspect of the present invention: in step (6), the nanofiltration membrane is selected from NF270 or NF90.

[0027] In another aspect, the present invention provides a cationic etherifying agent, which is prepared by the above-described method for preparing a cationic etherifying agent.

[0028] The beneficial effects of this invention are as follows:

[0029] This invention achieves continuous production using a tubular reactor, shortening production time and reducing energy consumption. The reaction process is simplified by adjusting reaction parameters and introducing nanofiltration membranes for purification and impurity removal. The addition of organic amines and alkylating agents promotes reaction conversion, reduces byproduct formation, and yields an odorless etherifying agent. Furthermore, automated control reduces the impact of human intervention on product quality, expands product application, enhances product competitiveness, and improves production efficiency. Detailed Implementation

[0030] The present invention is further illustrated below by way of examples, but these examples do not limit the invention to the scope of the embodiments described. Experimental methods in the following examples, unless otherwise specified, were performed according to conventional methods and conditions, or as selected in the product instructions. Furthermore, all reagents and raw materials used in this invention are commercially available.

[0031] Example 1

[0032] A method for preparing a cationic etherifying agent specifically includes the following steps:

[0033] (1) Clean the tubular reactor. Ensure the equipment meets production requirements.

[0034] (2) Through the metering module, 118 kg of trimethylamine and 248 kg of industrial hydrochloric acid (31 wt%) are continuously fed into the raw material pretreatment unit at a total flow rate of 50 kg / h and pre-cooled to 20°C.

[0035] (3) The pre-cooled mixture enters the first tubular reactor (inner diameter 50mm, tube length 8m), and the reaction parameters are set as follows: temperature -10℃, pressure 0.15MPa. The mixing is enhanced by spiral guide convex ridges, and the material residence time is 60 minutes.

[0036] (4) The automatic control system collects the pH value (maintained at 3~6) and temperature of the material at the reactor outlet in real time. If the pH is lower than 3.0, the hydrochloric acid delivery rate is automatically reduced.

[0037] (5) Samples are taken every 10 minutes for analysis to ensure that the purity of trimethylammonium chloride is ≥99% and the free amine content is ≤0.5%. After passing the test, the sample is sent to the static mixer.

[0038] (6) In a static mixer, trimethylammonium chloride and 222 kg epichlorohydrin are added simultaneously with 2% dilute hydrochloric acid (10 wt%) and 8% trimethylamine by mass of the total reaction system.

[0039] (7) The mixture is continuously fed into the second tubular reactor (60 mm inner diameter, 12 m tube length). The reaction parameters are set as follows: temperature 10℃, pressure 0.2 MPa, temperature is controlled by hot water circulation in the jacket, and material residence time is 3 h.

[0040] (8) The automatic control system monitors the chloride ion concentration in the reactor in real time. If the concentration is ≥1.2%, the reaction temperature is appropriately reduced (2℃ each time). At the same time, the epichlorohydrin residue is monitored by online chromatography to ensure that it is ≤0.3%.

[0041] (9) The material is filtered through a nanofiltration membrane (NF270) (pressure 0.5MPa, temperature 25℃) to remove impurities and obtain a high-purity, odorless cationic etherifying agent.

[0042] Example 2

[0043] A method for preparing a cationic etherifying agent specifically includes the following steps:

[0044] (1) Clean the tubular reactor. Ensure the equipment meets production requirements.

[0045] (2) Through the metering module, 118 kg of trimethylamine and 224 kg of industrial hydrochloric acid (31 wt%) are continuously fed into the raw material pretreatment unit at a total flow rate of 20 kg / h and pre-cooled to -10°C.

[0046] (3) The pre-cooled mixture enters the first tubular reactor (inner diameter 50mm, tube length 8m), and the reaction parameters are set as follows: temperature 20℃, pressure 0.15MPa. Mixing is enhanced by spiral guide convex ridges, and the material residence time is 10 minutes.

[0047] (4) The automatic control system collects the pH value (maintained at 3~6) and temperature of the material at the reactor outlet in real time. If the pH is lower than 3.0, the hydrochloric acid delivery rate is automatically reduced.

[0048] (5) Samples are taken every 10 minutes for analysis to ensure that the purity of trimethylammonium chloride is ≥99% and the free amine content is ≤0.5%. After passing the test, the sample is sent to the static mixer.

[0049] (6) In a static mixer, trimethylammonium chloride and 186 kg epichlorohydrin are added simultaneously with 0.2% dilute sulfuric acid (15 wt%) and 2% trimethylamine by mass of the total reaction system.

[0050] (7) The mixture is continuously fed into the second tubular reactor (60 mm inner diameter, 12 m tube length). The reaction parameters are set as follows: temperature 50℃, pressure 0.2 MPa, temperature is controlled by hot water circulation in the jacket, and material residence time is 1 h.

[0051] (8) The automatic control system monitors the chloride ion concentration in the reactor in real time. If the concentration is ≥1.2%, the reaction temperature is appropriately reduced (2℃ each time). At the same time, the epichlorohydrin residue is monitored by online chromatography to ensure that it is ≤0.3%.

[0052] (9) The material is filtered through a nanofiltration membrane (NF90) (pressure 1.5MPa, temperature 20℃) to remove impurities and obtain a high-purity, odorless cationic etherifying agent.

[0053] Example 3

[0054] A method for preparing a cationic etherifying agent specifically includes the following steps:

[0055] (1) Clean the tubular reactor. Ensure the equipment meets production requirements.

[0056] (2) 118 kg of trimethylamine and 242 kg of industrial hydrochloric acid (31 wt%) were continuously fed into the raw material pretreatment unit at a total flow rate of 40 kg / h through the metering module and pre-cooled to 10°C.

[0057] (3) The pre-cooled mixture enters the first tubular reactor (inner diameter 50mm, tube length 8m), and the reaction parameters are set as follows: temperature 10℃, pressure 0.15MPa. Mixing is enhanced by spiral guide convex ridges, and the material residence time is 30 minutes.

[0058] (4) The automatic control system collects the pH value (maintained at 3~6) and temperature of the material at the reactor outlet in real time. If the pH is lower than 3.0, the hydrochloric acid delivery rate is automatically reduced.

[0059] (5) Samples are taken every 10 minutes for analysis to ensure that the purity of trimethylammonium chloride is ≥99% and the free amine content is ≤0.5%. After passing the test, the sample is sent to the static mixer.

[0060] (6) In a static mixer, trimethylammonium chloride and 195 kg epichlorohydrin are added simultaneously with 1% dilute hydrochloric acid (20 wt%) and 6% trimethylamine by mass of the total reaction system.

[0061] (7) The mixture is continuously fed into the second tubular reactor (60 mm inner diameter, 12 m tube length). The reaction parameters are set as follows: temperature 30℃, pressure 0.2 MPa, temperature is controlled by hot water circulation in the jacket, and material residence time is 2 h.

[0062] (8) The automatic control system monitors the chloride ion concentration in the reactor in real time. If the concentration is ≥1.2%, the reaction temperature is appropriately reduced (2℃ each time). At the same time, the epichlorohydrin residue is monitored by online chromatography to ensure that it is ≤0.3%.

[0063] (9) The material is filtered through a nanofiltration membrane (NF270) (pressure 2MPa, temperature 22℃) to remove impurities and obtain a high-purity, odorless cationic etherifying agent.

[0064] Comparative Example 1

[0065] A method for preparing a cationic etherifying agent specifically includes the following steps:

[0066] (1) Pump 350g of 31wt% hydrochloric acid into the reactor, start stirring, and slowly introduce 180g of trimethylamine over 3 hours, keeping the temperature at 40℃ during the reaction. After all the trimethylamine has been added to the reactor, continue the reaction at room temperature for 60 minutes.

[0067] (2) Keep the material at 15°C, turn on the metering pump, and add 280g of epichlorohydrin dropwise into the reactor within 4 hours. Two hours after the drop begins, add 1.2% (10wt%) of dilute hydrochloric acid (based on the total mass of the raw materials) to adjust the pH to 9, so that the material always maintains a rapid reaction environment.

[0068] (3) After the epichlorohydrin is added, raise the temperature to 40°C and maintain this temperature for 2 hours to continue the reaction.

[0069] (4) The crude cationic etherifying agent is introduced into the adjustment device and citric acid is added to eliminate free trimethylamine while adjusting the pH to 6.5. The product is then purified by stripping and the effective content is adjusted by adjusting the stripping temperature or the amount of deionized water added to obtain the cationic etherifying agent product.

[0070] Comparative Example 2

[0071] The only difference from Example 1 is that the automatic control system is removed, and the pH value, chloride ion concentration and epichlorohydrin residue are not monitored in real time. The reaction parameters are kept constant and are not dynamically adjusted.

[0072] Comparative Example 3

[0073] The only difference from Example 1 is that trimethylamine is not added in step (6).

[0074] Comparative Example 4

[0075] The only difference from Example 1 is that the temperature of the first tubular reactor is set to 30°C and the temperature of the second tubular reactor is set to 60°C.

[0076] Comparative Example 5

[0077] The only difference from Example 1 is that the material residence time in the first tubular reactor is set to 5 minutes, and the material residence time in the second tubular reactor is set to 0.5 hours.

[0078] Comparative Example 6

[0079] The only difference from Example 1 is that trimethylamine, hydrochloric acid, epichlorohydrin, catalyst and organic amine are mixed at one time and continuously fed into the first tubular reactor. No staged reaction is set. The reaction temperature is 20°C, the pressure is 0.15 MPa and the total residence time of the material is 3.5 h.

[0080] Comparative Example 7

[0081] Commercially available products: cationic etherifying agents produced by Yanzhou Tiancheng Chemical Co., Ltd.

[0082] Effect Example

[0083] The performance of samples from Examples 1-3 and Comparative Examples 1-7 was tested using the following methods or standards:

[0084] I. Effective content detection: Detected by hydrochloric acid back titration method.

[0085] 1. Instruments

[0086] Electronic balance with a strength of 0.01 g; acid-base burette, 25 mL; iodine flask, 250 mL.

[0087] 2. Reagents

[0088] Sodium hydroxide standard solution: c(NaOH=0.5 mol / L), prepared according to GB / T601 "Preparation of Chemical Reagents and Standard Titration Solutions"; Sodium hydroxide standard solution: c(NaOH=0.1 mol / L), prepared according to GB / T601 "Preparation of Chemical Reagents and Standard Titration Solutions"; Hydrochloric acid standard solution: c(HCl)=0.1 mol / L, prepared according to GB / T603 "Chemical Reagents, Preparations Used in Test Methods and Preparation of Preparations"; Phenolphthalein indicator: 10 g / L, prepared according to GB / T603 "Chemical Reagents, Preparations Used in Test Methods and Preparation of Preparations".

[0089] 3. Operating Steps

[0090] 3.1 Blank Titration: Accurately weigh 2.6-3.4 g (accurate to 0.0002 g) of the sample into a dry iodine flask, then add 60 mL of distilled water and 3 drops of phenolphthalein indicator, and titrate with 0.1 mol / L sodium hydroxide standard solution until a faint red endpoint is reached.

[0091] 3.2 Titration of Active Ingredient Content

[0092] Accurately weigh 1.0-1.1 g (accurate to 0.0002 g) of the sample into a dry iodine flask. Then, add 10.0 mL of 0.5 mol / L sodium hydroxide standard solution to the iodine flask using a burette. Add 10 mL of distilled water, stopper the flask tightly, and shake well. After 10 min, add 3 drops of phenolphthalein indicator and titrate with 0.1 mol / L hydrochloric acid standard solution until the red color disappears as the endpoint.

[0093] 4. Calculation

[0094] The content of active ingredients in the sample is calculated according to formulas (1) and (2):

[0095] (1)

[0096] (2)

[0097] In the formula:

[0098] X — Content of active ingredient in the sample;

[0099] c1 — Concentration of the sodium hydroxide standard solution, NaOH = 0.5 mol / L;

[0100] V1—The volume of sodium hydroxide standard solution consumed by the sample, in mL;

[0101] c2 — Concentration of the hydrochloric acid standard solution, 0.1 mol / L;

[0102] V2—The volume of 0.1 mol / L hydrochloric acid standard solution consumed by the sample, in mL;

[0103] m—mass of the sample, in grams;

[0104] C3 – Concentration of sodium hydroxide standard solution, 0.1 mol / L;

[0105] V3 — Volume of sodium hydroxide standard solution consumed in the blank, in mL;

[0106] A – Blank test value;

[0107] 0.1881 — The mass of etherifying agent, expressed in grams, equivalent to 1 mL of standard hydrochloric acid titration solution [c(HCl) = 1.000 mol / L].

[0108] II. Yield Measurement: Yield = (Actual Yield / Theoretical Yield) * 100%

[0109] III. pH value measurement: A Leici PHS-2F pH meter was used;

[0110] IV. Determination of Inorganic Impurities (Trimethylamine Hydrochloride and Bisquaternary Ammonium Salts): An Agilent 1260 Infinity II high-performance liquid chromatograph with a UV detector was used for detection via the external standard method. The chromatographic column was a Polaris 5 C18A (250 × 4.6 mm). The mobile phase consisted of 3.98 g sodium 1-octanesulfonate, 96 g sodium perchlorate, 112 g methanol, and 1750 g high-purity water. The flow rate was 0.5 mL / min, the detector temperature was 40℃, the equilibration time was 1 h, the column temperature was 40℃, and the injection volume was 20 μL. The sample was dissolved and diluted to an appropriate concentration in the mobile phase before injection and determination. The total content of inorganic impurities was calculated based on the peak areas of each impurity and the reference standard.

[0111] V. Appearance: Visual inspection (Q / 0882YTC008-20241)

[0112] VI. Odor: Instrumental and sensory evaluation are combined. Instrumental detection mainly reflects the content of inorganic salt impurities indirectly. Sensory evaluation involves adding 10 mL of liquid alkali (effective content 32%) to 100 mL of the stock solution, gently stirring it by hand, and smelling it. Evaluation is based on the following standards:

[0113] Odorless: No noticeable odor;

[0114] Slight amine odor: detectable but not very irritating;

[0115] Distinct amine odor: A clearly identifiable amine smell;

[0116] Strong amine odor: a strong, pungent amine smell

[0117] The samples from Examples 1-3 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0118] Table 1

[0119]

[0120] As shown in Table 1, the cationic etherifying agent prepared by this invention has a high yield (≥99%), low inorganic impurity content (≤0.8%), and is colorless, transparent, and odorless, exhibiting excellent overall performance. In contrast, the comparative products all showed varying degrees of deficiencies in terms of inorganic impurity content, appearance, or odor. Among them, Example 3 showed the highest yield (99.4%), the lowest inorganic impurity content (0.5%), and achieved optimal appearance and odor, making it the best example in terms of overall performance.

[0121] Finally, it should be noted that in this invention, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0122] Although this disclosure has been described above through specific embodiments, it should be understood that those skilled in the art can devise various modifications, improvements, or equivalents to this disclosure within the spirit and scope of the appended solutions. Such modifications, improvements, or equivalents should also be considered to be included within the scope of protection claimed in this disclosure.

Claims

1. A method for preparing a cationic etherifying agent, characterized in that, Includes the following steps: (1) Trimethylamine and hydrochloric acid are mixed at a molar ratio of 1:0.95~1.05 and continuously fed into the raw material pretreatment unit at a total flow rate of 20~50 kg / h, and pre-cooled to -10~20℃; (2) The pre-cooled mixture enters the first tubular reactor and reacts continuously at a temperature of -10℃ to 20℃ and a pressure of 0.15MPa. The material residence time is 10 to 60 minutes, and trimethylammonium chloride is generated. (3) The trimethylammonium chloride and epichlorohydrin are introduced into a static mixer, and 0.2% to 2% of the total mass of the reaction system catalyst and 2% to 8% of the total mass of the organic amine are added at the same time and mixed evenly; (4) The mixture is continuously fed into the second tubular reactor and reacted continuously at a temperature of 10~50℃ and a pressure of 0.2MPa, with a material residence time of 1~3h; (5) During the reaction, the automatic control system monitors the chloride ion concentration and epichlorohydrin residue in the reactor in real time and dynamically adjusts the reaction parameters; (6) The reaction product is filtered through a nanofiltration membrane at an operating pressure of 0.5~2MPa and a temperature of 20~25℃ to obtain a high-purity cationic etherifying agent.

2. The method for preparing the cationic etherifying agent according to claim 1, characterized in that, In step (1), the molar ratio of trimethylamine to hydrochloric acid is 1:1 to 1.

05.

3. The method for preparing the cationic etherifying agent according to claim 1, characterized in that, In step (2), the pH value of the material at the outlet of the first tubular reactor is collected in real time by the automatic control system and the pH is maintained at 3~6. If the pH is lower than 3.0, the hydrochloric acid delivery rate is automatically reduced. And / or, in step (2), the inner diameter of the first tubular reactor is 50 mm and the tube length is 8 m, and the interior is provided with spiral guiding ribs; And / or, in step (2), samples are taken for analysis every 10 minutes to ensure that the purity of trimethylammonium chloride is ≥99% and the free amine content is ≤0.5%; And / or, in step (2), the temperature is -5℃ to 10℃ and the material residence time is 20 to 50 minutes.

4. The method for preparing the cationic etherifying agent according to claim 3, characterized in that, In step (2), the pH is maintained at 4 to 5.

5. The method for preparing the cationic etherifying agent according to claim 1, characterized in that, In step (3), the molar ratio of epichlorohydrin to trimethylamine is 1.0~1.2:1; And / or, in step (3), the organic amine is a tertiary amine, preferably trimethylamine; And / or, in step (3), the catalyst is at least one of 10% to 20% dilute hydrochloric acid, dilute sulfuric acid or dilute nitric acid.

6. The method for preparing the cationic etherifying agent according to claim 5, characterized in that, In step (3), the catalyst is 10%~20% dilute hydrochloric acid and / or dilute sulfuric acid.

7. The method for preparing the cationic etherifying agent according to claim 1, characterized in that, In step (4), the inner diameter of the second tubular reactor is 60 mm and the tube length is 12 m, and the temperature is controlled by jacketed hot water circulation; And / or, in step (4), the temperature is 10~40℃.

8. The method for preparing the cationic etherifying agent according to claim 1, characterized in that, In step (5), the automatic control system monitors the chloride ion concentration in the reactor in real time. If the concentration is ≥1.2%, the reaction temperature is reduced. At the same time, the residual amount of epichlorohydrin is monitored by online chromatography to ensure that it is ≤0.3%.

9. The method for preparing the cationic etherifying agent according to claim 1, characterized in that, In step (6), the nanofiltration membrane is selected from NF270 or NF90.

10. A cationic etherifying agent, which is prepared by the method for preparing the cationic etherifying agent according to any one of claims 1 to 9.

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