WO2006069504A1 - A purification method for the cationic monomer of dimethyldiallylammonium chloride with high purity - Google Patents

Abstract

This invention relates to a purification method for the cationic monomer of dimethyldiallylammonium chloride with high purity, which comprise the steps: (a) determining the volatile and non­volatile components and their contents in the cationic monomer solution to be treated by chromatographic analysis; (b) charging the cationic monomer solution to a vessel and adding NaOH solution with stirring upon cooling to give free amines; (c) adding water to adjust the monomer content in the solution to be 35-55 %, and subjecting the resulting solution to vacuum distillation in two temperature ranges, the distillate is recycled after adsorption with water and the residue is treated by vacuum filtration or centrifugation to remove the precipitated NaCI; and (d) adding water into the filtrate to adjust the monomer content to be in specified range, and incorporating minor active carbon for decoloration to obtain the desired product with minimum impurities. Due to the accurate determination of the impurities and their contents, the inventive method can eliminate the use of indicators so as to avoid many problems, such as, the incorporation of new impurities and the excess addition of NaOH, which make the high purity product to be possible.

Description

 Method for purifying 髙purity cationic monomer dimethyldiallyl ammonium chloride

 The invention relates to a method for purifying a cationic quaternary ammonium salt monomer for polymer synthesis, in particular to a method for purifying a high-purity cationic monomer dimethyl diallyl ammonium chloride. Background technique

 Dimethyldiallylammonium chloride (DMDAAC) is a cationic quaternary ammonium monomer that can be used in polymerization. Its structural formula is as follows:

(Formula 1 )

 DMDAAC is a quaternary ammonium salt with excellent water solubility and containing two unsaturated double bonds. It is a white needle crystal with a melting point of 146-147 ° C. It is easy to absorb moisture in air as an aqueous solution. Therefore, the compound is mostly stored in the form of an aqueous solution. Due to its high charge density, good water solubility, acid and alkali resistance, non-toxicity, etc., it is itself in the field of petroleum exploitation, paper industry, textile printing and dyeing, sewage treatment, sludge dewatering and household chemicals. There are a wide range of applications. However, whether it is applied directly as a cationic quaternary ammonium salt or as a polymerization monomer, its purity or the content of impurities contained is critical, affecting its application range and application cost.

 The expression of the DMDAAC synthesis reaction is as follows:

 Tertiary amine reaction:

2(CH ₃ ) ₂ NH+CH ₂ =CHCH ₂ C1 (CH ₃ ) ₂ NCH ₂ CH=CH ₂ + (CH ₃ ) ₂ NH ⁺ ₂ Cr

 Dimethylamine chloropropene (dimethylallylamine) tertiary amine dimethylamine hydrochloride

Neutralization reaction, tertiary amination reaction: (; formula ₂₎

(CH ₃ ) ₂ NH2 Cl"+2NaOH + CH ₂ =CHCH ₂ Cl . ' (CH ₃ ) ₂ NCH ₂ CH=CH ₂ +2NaCl+2H ₂ 0

(Formula 3) Quaternization reaction:

(CH ₃ ) ₂ NCH ₂ CH=CH ₂ +CH ₂ =CHCH ₂ C1 . "(CH ₂ =CH-CH ₂ ) ₂ N ⁺ (CH ₃ ) ₂ C1—(Formula 4)

DMDAAC The main side reactions are:

 Salt formation reaction:

(CH ₃ ) ₂ NH+CH ₂ =CHCH ₂ C1 CH ₂ =CHCH ₂ N(CH ₃ ) ₂ H+C1—(Formula 5)

 Tertiary amine hydrochloride

 Hydrolysis reaction:

CH ₂ =CHCH ₂ C1 ^QH "> CH ₂ =CHCH ₂ OH+Cr (Formula 6)

 Allyl alcohol

 Oxidation reaction -

CH ₂ =CHCH ₂ OH ~~► CH ₂ =CH— C^^ (Equation 7)

 Allyl aldehyde

 One method is a method for directly preparing DMDAAC by integrating a multi-step reaction in an aqueous solution of dimethylamine, chloropropene and sodium hydroxide. The reaction solution is filtered to remove precipitated sodium chloride, and then purified by distillation to obtain a DMDAAC aqueous solution or a crystal product thereof. The one-step process has the advantages of simple and safe process, high yield, and no need to use organic solvent and less "three wastes" in the production and purification process. However, since the multi-step reaction proceeds at the same time, the side reaction in the process is increased (formula 2, formula 5 to formula 7), and the amount of impurities in the product is large, so that the reactivity as a polymer monomer is low. The main components of impurities are generally considered to be unreacted starting materials, intermediates and by-products. For example, dimethylamine (or a salt thereof), a tertiary amine (or a salt thereof), chloropropene, allyl alcohol, allyl aldehyde, sodium chloride or the like.

In the prior art, two methods are generally used to solve the problem: one is to control the synthesis process conditions, make the reaction process more reasonable, and reduce the formation of impurities such as by-products in the preparation process; the second is the crude product obtained by synthesis. Purification, such as distillation under reduced pressure, removal of volatile impurities, decolorization of activated carbon to remove less volatile impurities. For example: Document 1 (Jeery E. Boothe, Synthesis of Dimethyldially lammonium Chloride, US 3 461 163, 1969), by reducing the reaction temperature to 10 ° C in the one-step preparation of DMDAAC, and noting that high purity DMDAAC is required. In aqueous solution, the reaction process should be kept neutral. It is necessary to control the competitive reaction of sodium hydroxide with dimethylamine for chloropropene to reduce the formation of impurities such as by-product allyl alcohol. For this reason, a reaction of adding chloropropene and dimethylamine at a low temperature ratio in the first place is employed, and a method of alternately adding 50% sodium hydroxide and chloropropene is employed. After the last addition of the residual chloropropene, the temperature is raised to 45 ° C, the reaction is 6.5 h, the system is near neutral, and the quaternization reaction is completed at a lower temperature, which prevents the high temperature from being too high. The product is broken down. Result The product was subjected to vacuum distillation and decolorization with activated carbon to obtain a finished DMDAAC aqueous solution. Document 2 (Jeery E. Boothe, Process for Parifying Dialkyl Diallylammonium Chloride and Diallyl Dimethally lammonium Chloride, US 3 472 740, 1969) further proposes that the cationic monomer DMDAAC solution decolorized by vacuum distillation and activated carbon is added to the total amount of 0.04. After the % phenolphthalein indicator, adjust the pH = 10.5 to 11.5 with 5% aqueous NaOH solution, and extract (distill) at 110 ° C with water vapor under pressure or atmospheric pressure to remove impurities until the distillate precipitation index remains unchanged. A pink liquid was obtained, and after cooling, 300 g of an activated carbon column was filled, and then the activated carbon was removed by filtration. The monomeric DMDAAC aqueous solution treated by the above method 2 has a purity which is significantly higher than that of the original literature 1 method. Taking the polymerization performance of the monomer as an example: a solution of 60%, 231 g (about 0.5 mol) of monomeric DMDAAC, adjusted to a pH of 6.5, and heated to 80 °C. Under a nitrogen atmosphere, a certain amount of (NH4) ₂ S _{2 8} initiator was used to initiate the reaction for 100 min, and then reacted at 80 ° C for 0.5 h to obtain a homopolymer. The viscosity of the 5% and 10% aqueous solutions of the homopolymer was 6.0 cps (centipoise) and 390 cps, respectively, and the viscosity of the homopolymerized product of the cationic monomer DMDAAC obtained under the same conditions of the literature 1 was only 3.2 cps. And 20cps. Chromatographic analysis showed that the phosgene of an unknown substance in the original cationic monomer DMDAAC solution was significantly removed by the method of literature 2 purification. Document 3 (Nippon Kayaku Co., Ltd., Japan, Diallyldimethylammonium Chloride and its Polymer. JP 5601 6448, 1981), 820 g of chloropropene was added to 900 g of a 50% aqueous solution of dimethylamine (in which the content of methylamine was less than 240 mg/kg). The feed was carried out at 0 ° C. After adding about 1/3 of the chloropropene for a period of 1 h, a 50% aqueous NaOH solution (10.7 mol) was added in parallel, and the addition was completed in 2 h. After reacting at 36-45 ° C for 16 h, the obtained product was extracted with water vapor for 1 h, and decolorized with activated carbon to obtain an aqueous solution having a cationic monomer DMDAAC content of 70% and 2188 g. The monomer product was initiated with tert-butyl peroxide at 40 ° C to give its homopolymerized product. When the homopolymerized product was at 20 ° C, the viscosity of the 0.5% aqueous solution reached 180 cps, and its characteristic viscosity was 2.8 dg (30 ° C, measured in a 5% NaCl aqueous solution).

Literature 4 (Quan Yanmei et al., Synthesis and identification of dimethyldiallylammonium chloride, Xi'an Petroleum Journal, 1992, 7 (1): 58-60) developed a one-step method for one-time feeding. The DMDAAC was prepared by a method of sealing, inert gas protection and pressurization, less than 60 ° C, and reacting for 30 h. After the completion of the reaction, the NaCl was removed by filtration, and a small amount of water was added thereto, and the mixture was distilled under reduced pressure until the distilled water was obtained as a solvent, or a pH of 7 was obtained in pure water, and the precipitated NaCl was removed by filtration, and decolorized with activated carbon to obtain a cationic monomer product DMDAAC solution. Document 5 (Zheng Yan, a method for preparing a cationic polymerization monomer, CN 1243 88A, 1999), developed a method of adding an equal amount of chloropropene and the like in a reaction vessel. After dimethylamine, the reaction was carried out by alternately adding chloropropene and sodium hydroxide at 65 to 85 ° C under a pressure of 0.2 MPa for 4 to 5 hours. The obtained product was subjected to vacuum distillation under reduced pressure of 0.08 MPa at 55 to 65 ° C to remove NaCl, and a product DMDAAC aqueous solution was obtained. Literature 6 (Zhao Huazhang et al., Synthesis and Analysis of Cationic Polymer Flocculants PDMDAAC and P (DMDAAC-A), Fine Chemicals, 2001, 18 (11): 645) Control pH 9.5 at less than 20 °C ~10.5, chloropropene and sodium hydroxide were added dropwise to an aqueous solution of dimethylamine, and then the reaction was refluxed to complete the reaction. After the obtained reaction liquid is separated from NaCl, impurities are removed by distillation under reduced pressure (vacuum), and precipitated NaCl or the like is filtered off, and the obtained DMDAAC product monomer solution is polymerized at 40 ° C with an initiator of 1% by mass of the monomer or The nonionic monomer acrylamide was copolymerized for 8 h to obtain the homopolymer PDMDAAC and the copolymer P (DMDAAC-AM) having a cationic degree of 10%, respectively, and the characteristic viscosity values were 1.96 dL/g (recrystallized with hexanol and acetone). Remove small molecules) and 9.26 dL/g (measured in aqueous solution of lM NaCl at 30 ° C).

 In the cationic monomer DMDAAC prepared by the one-step method, impurities such as by-products are formed. Therefore, not only the parameters such as the feed ratio, the feeding mode, the reaction temperature and the pH of the medium are controlled in the preparation process to reduce the formation of by-products, but also the vacuum distillation of the crude cationic monomer solution, decolorization of the activated carbon, or The base is adjusted to pH value and then purified by high-temperature steam to purify the monomer, and the purity of the cationic monomer DMDAAC solution is increased by removing impurities. However, various refinement methods proposed so far to reduce impurities in the monomeric DMDAAC product are empirical methods, lacking proper theoretical guidance and reasonable analytical methods. Therefore, the main drawbacks of these purification methods are:

1 For the cationic monomer DMDAAC solution prepared by one-step method, some volatile impurities can be removed by simple vacuum distillation, some NaCl is removed by dehydration filtration, most of the colored substances are removed by decolorization by activated carbon, but most unreacted is difficult to volatilize. And excellent water-soluble impurities. Such as: salt substances, aqueous solutions of good tertiary amines, allyl alcohol can not be effectively removed, such as literature 1, literature 4, literature 5 and literature 6; 2 although after the pressure is taken up with atmospheric pressure and pressurized high temperature steam retention It can remove some unknown impurities in the ionic monomer DMDAAC solution prepared by the one-step method, and improve the polymerization performance of the cationic monomer DMDAAC, but the overbased medium condition with pH value of 10.5~11.5 and 11CTC high temperature water vapor Stripping may lead to new side reactions: decomposition of monomeric quaternary ammonium salts or the occurrence of self-polymerization, as in literature 2, document 3; 3 in addition to removing a certain amount of precipitated NaCl by filtration and decolorization by activated carbon to reduce chromaticity, now Some various purification methods can not explain the changes of various impurities in the aqueous solution of cationic monomer DMDAAC before and after refining and guide the improvement of refining process, such as literature 1~6, etc., but only by participating in the reaction of monomeric DMDAAC before and after purification to obtain the relative molecular mass or degree of polymerization of homopolymers and copolymers, and characterizing the viscosity and characteristic viscosity at a certain temperature to compare the effects of the purification method. . For example, Document 2, Document 3, and Document 6. The above various defects have resulted in the difficulty in obtaining high purity and quality stable cationic monomer DMDAAC products by various existing one-step preparation processes.

Summary of the invention

 The object of the present invention is to provide a high-purity cationic monomer dimethyl diallyl ammonium chloride with simple process, low operation cost, basically no "three wastes", high purity of products, clear quality index and stable quality. Refined method.

 A technical solution for achieving the object of the present invention is: A method for purifying a high-purity cationic monomer dimethyldiallylammonium chloride, characterized in that the process flow and operating conditions are carried out as follows:

 1. Using chromatographic analysis method, analyzing the composition and content of various impurities in the cationic monomer DMDAAC solution prepared by one-step method, and measuring various volatile and difficult-to-volatile impurity components and contents;

 2. Add a cationic monomer DMDAAC solution to the steaming or falling film evaporator. According to the measured content of the amine hydrochloride, the ratio of the amine hydrochloride: sodium hydroxide is 1.00: 0.90. ~1.00, adding an industrial alkali sodium hydroxide solution under cooling and stirring to release the amine substance freely;

 3. Add 1/6~1/2 of the monomer mass to make the monomer content in the solution 35%~55%, and under the pressure of less than 0.090MPa, 40±5°C and 60±5 respectively. °C two temperature ranges are subjected to vacuum distillation for 0.5~3.5h, and each enthalpy is distilled under reduced pressure until no significant distillate is obtained. The vapor evaporated under reduced pressure is absorbed by water and reused;

 4. The reaction solution is filtered under reduced pressure or centrifugally to remove precipitated crystal NaCl;

 5. Water is added to the filtrate to adjust the content of monomer DMDAAC in the monomer solution to 60±5%, and a small amount of activated carbon is added for decolorization treatment, and the activated carbon is removed by filtration to obtain a cationic monomer DMDAAC product solution with low impurity content and high purity.

Compared with the prior art, the invention has the significant advantages of: 1. Using a chromatographic method, various possible volatile impurities, dimethylamine, tertiary amine, allyl alcohol, chloropropene, in the cationic monomer DMDAAC product solution. Quantitative analysis of allyl aldehyde and difficult-to-volatile impurities NaCl, tertiary amine hydrochloride, dimethylamine hydrochloride, etc., as a basis for purification and refining, overcomes the defects in the prior art that the impurity object and its content are inaccurate; The amount of the amine hydrochloride which is obtained by the analysis, the amount of the industrial alkali sodium hydroxide to be added is designed, and the amine hydrochloride is freed from the amine to become a volatile Quality, making it easy to quantitatively remove by vacuum distillation, avoiding the introduction of new impurities and the addition of alkali by the addition of phenolphthalein indicator and pH indicating the end of alkali addition; 3. By adding water, adding dilute alkali, Step-by-step temperature-programmed vacuum distillation and vacuum distillation at relatively low temperature to remove various volatile impurities and volatile amines dimethylamine and tertiary amine freed by alkali treatment, avoiding alkaline Under the conditions, local over-alkali occurs in the monomer solution during high-temperature distillation, and side reactions caused by excessive temperature occur - decomposition of the cationic quaternary ammonium salt monomer DMDAAC and inactivation of self-polymerization; 4. NaCl formed by alkali addition, The mixture was concentrated by precipitation under reduced pressure and filtered. The filtrate is decolorized by activated carbon to remove the non-volatile impurities which may be formed during the purification process, and further purified; 5. The impurity type and content of the cationic monomer DMDAAC product solution obtained by the purification method of the invention can be characterized by chromatographic analysis results, and can be compared with the pre-refining condition. For comparison; the polymerization activity of the purified monomer solution can be initiated by the same conditions (mass fraction of 65% monomer solution, initiated by 50% C (NH ₄ ) ₂ S _{2 8} initiator of 0.5% by mass of monomer) Reaction 9h) Comparison of the relative molecular mass (expressed by the intrinsic viscosity value) of the polydimethyldiallylammonium chloride (Poly-DMDAAC, PDMDAAC), a polymerization product of the cationic monomer DMDAAC. See Table 1 for details. Table 1 Impurity content and polymerization activity before and after cationic monomer purification

Note: 1 "one" means not detected, the detection limit is lmg/kg (the same below);

 2 The characteristic viscosity of the product was calculated by single point method in 30±0.rC, lM NaCl (the same below). DRAWINGS

 BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are a process flow diagram of a process for purifying a high purity cationic monomer dimethyl diallyl ammonium chloride of the present invention.

detailed description The present invention will be described in detail below with reference to the accompanying drawings.

 Example 1.

 Referring to the drawings, a specific embodiment of the method for purifying a high-purity cationic monomer dimethyl diallylammonium chloride of the present invention is as follows:

 In the first step, the chromatographic method is used to systematically analyze the cationic monomer to be purified obtained by the one-step process.

The composition and content of various impurities in the aqueous solution of DMDAAC, which contain volatile and hard-to-volatile impurities such as dimethylamine, chloropropene, allyl alcohol, allylaldehyde and sodium chloride, dimethylamine hydrochloride, and uncle The corresponding content of amine hydrochloride is shown in Table 2.

 Secondly, a 50% one-step monomer DMDAAC solution A 50 kg to be purified is added to a 120 L distillation still or a 200 L falling film evaporator, and the amine hydrochloride (dimethylamine hydrochloride) is analyzed according to the chromatographic method. The total amount of salt, tertiary amine hydrochloride) is 0,87 (7.66 tnol), and the ratio of the amount of amine hydrochloride: sodium hydroxide is 1.00: 1.00-0.99, and the content is added under cooling and stirring. A 8.0% aqueous solution of NaOH was 3.79 kg (7.98 mol).

 In the third step, 15.0kg of water is added and distilled under reduced pressure of 0.5±5°C and 60±5°C for 1.5~2.5h under a pressure of 0.098MPa, and each step is steamed until no significant distillate is obtained. until. The tail gas distilled under reduced pressure is recovered by water absorption.

 The fourth step: the monomer solution is subjected to vacuum filtration or centrifugal filtration to remove precipitated crystal NaCl.

 Step 5: The solution is added with water to adjust the monomer content to (60 ± 5)%, and the activated carbon is less than 1% by mass. The treatment temperature is 45~65°C, and the time is 0.5~1.5h. The activated carbon was removed by filtration under reduced pressure to obtain a high purity cationic monomer DMDAAC product solution, and the impurities contained in Table 2 are shown in Table 2.

 Change of impurity content in monomer DMDAAC solution before and after refining

 Example 2.

 Referring to the drawings, a specific embodiment of the method for purifying the high purity cationic monomer dimethyl diallylammonium chloride of the present invention is as follows:

In the first step, the chromatographic analysis method is used to systematically analyze various impurity components and contents of the cationic monomer DMDAAC aqueous solution B prepared by the one-step process, and the volatile and hard-to-volatile impurities contained therein are: Dimethylamine, chloropropene, allyl alcohol, allylaldehyde and sodium chloride, dimethylamine hydrochloride, and tertiary amine hydrochloride are shown in Table 3 below.

 In the second step, 50 kg of a ruthenium monomer DMDAAC solution B to be purified is added to a 120 L distillation still or a 200 L falling film evaporator, and the hydrochloride salt of the amine (dimethylamine salt) is analyzed according to the chromatographic method. The total amount of the acid salt and the tertiary amine hydrochloride is 1.35 kg (11.81 mol), and the ratio of the amine hydrochloride to sodium hydroxide is 1.00: 1.00. Under cooling, the content is 6.0. The aqueous solution of % NaOH was 7.87 kg (11.81 mol).

 The third step is to add 12.0kg of water and distill it under reduced pressure of 2.5±5°C and 60±5°C for 2.5~3.5h in two steps at a pressure of 0.099MPa, and distill each step to no significant distillation. Immediately before the liquid, the exhaust gas distilled under reduced pressure is absorbed by water for synthesis reaction.

 In the fourth step, the monomer solution is subjected to vacuum filtration or centrifugal filtration to remove precipitated crystal NaCl.

 In the fifth step, the filtrate is adjusted with water to a monomer content of (60±5)%, and decolorization treatment of activated carbon less than 1% by mass is added, the treatment temperature is 60±5° C., the time is 0.5 to 1.5 h, and the pressure is reduced. The activated carbon was removed by suction filtration or centrifugation to obtain a high-purity cationic monomer DMDAAC product solution, and the impurity content thereof is shown in Table 3. Change of impurity content in monomer DMDAAC solution before and after refining

Impurity content / (mg - kg ¹ )

 Serial number

 Chloropropene dimethylamine allyl alcohol allylaldehyde tertiary amine NaCl tertiary amine salt dimethylamine salt

1 Before refining ― ― ― ― 600 2000 23500 3500

2 After refining ― ― ― ― ― 2000 20 ―

Claims

Claim A method for refining a high-purity cationic monomer dimethyl diallylammonium chloride, characterized in that the process flow and operating conditions are as follows:  1. Using chromatographic analysis method, the composition and content of various impurities in the cationic monomer DMDAAC solution prepared by one-step method are analyzed, and various volatile and difficult-to-volatile impurity components and contents are measured;  1. 2 Add a cationic monomer DMDAAC solution to the steamer or falling film evaporator. According to the measured content of amine hydrochloride, the ratio of the amine hydrochloride: sodium hydroxide is 1.00: 0.90-1.00, adding an industrial alkali sodium hydroxide solution under cooling and stirring to release the amine substance freely;  1. 3 Add 1/6~1/2 of the monomer mass to make the monomer content in the solution 35%~55%, and under the pressure of less than 0.090MPa, respectively, at 40±5°C and 60± The two temperature ranges of 5 ° C are subjected to vacuum distillation for 0.5 to 3.5 hours, and each step is distilled under reduced pressure until no significant decanting liquid is obtained, and the vapor distilled out under reduced pressure is absorbed by water;  1. 4 reaction solution is removed by vacuum or centrifugal filtration to remove precipitated crystal NaCl;  1. The water in the filtrate is adjusted to a monomer solution having a DMDAAC content of 60±5%, and a small amount of activated carbon is added for decolorization treatment, and the activated carbon is removed by filtration to obtain a cationic monomer DMDAAC product solution having a small impurity content and high purity.  2. The method for purifying a high-purity cationic monomer dimethyl diallyl ammonium chloride according to claim 1, wherein: the industrial alkali sodium hydroxide is added in an amount of 4% to 32% under cooling and stirring. The solution releases the amine species freely.  The method for purifying a high-purity cationic monomer dimethyldiallylammonium chloride according to claim 1 or 2, which is characterized in that it is at 40 ± 5 ° C under a pressure of less than 0.090 MPa. And under the temperature range of 60±5°C, steam distillation under reduced pressure for 0.5~3.5h.  The method for purifying a high-purity cationic monomer dimethyl diallyl ammonium chloride according to claim 1 or 2, characterized in that the activated carbon is added to an activated carbon having a mass of less than 1% by mass of the monomer solution, and the treatment temperature is 45 ° C ~ 65 ° C, the time is 0.5 ~ 1.5h, the activated carbon is removed by filtration to obtain a cationic monomer DMDAAC product solution with low impurity content and high purity.