A polymer based on reversible addition-fragmentation chain transfer reaction and its preparation method and application

Abstract

The application belongs to the field of polymers, and discloses a preparation method of a polymer based on a reversible addition-fragmentation chain transfer reaction, which comprises the following steps: using a cationic monomer containing two unsaturated olefin bonds, methacryloyloxyethyl trimethyl ammonium chloride and / or acryloyloxyethyl trimethyl ammonium chloride, and a fluorine-containing hydrophobic monomer as comonomers, adopting a reversible addition-fragmentation chain transfer polymerization technology, and performing polymerization under the condition of photo initiation to obtain a block polymer. The method controls the block sequence by using the RAFT polymerization technology and introduces the hydrophobic monomer for modification through molecular structure design, and a high-efficiency decoloring, fast settling and highly adaptable block copolymer is prepared by combining the ultraviolet light initiation process. Meanwhile, the application also provides the polymer obtained based on the method and application thereof.

Description

Technical Field

[0001] This invention belongs to the field of polymers, and more specifically, relates to a polymer based on a reversible addition-fragmentation chain transfer reaction, its preparation method, and its application. Background Technology

[0002] Textile dyeing and printing wastewater is characterized by high color, high organic content, complex composition, and poor biodegradability.

[0003] Traditional treatment methods such as chemical precipitation and biodegradation have problems such as low decolorization efficiency, large sludge production, and poor removal effect on recalcitrant dyes.

[0004] Cationic polyelectrolytes such as polydimethyldiallylammonium chloride (PDMDAAC) are widely used for wastewater decolorization because they can remove dye anions through charge neutralization. However, single homopolymers or random copolymers have drawbacks such as simple molecular structure, difficulty in balancing charge density and floc strength, and poor removal efficiency for nonionic dyes such as disperse dyes.

[0005] Patents related to wastewater treatment, particularly dye-containing wastewater, based on cationic polyelectrolytes can be found in the following technologies:

[0006] The patent application with publication number CN114751499A, which is about a composite flocculant for treating dye wastewater and its preparation method and application, uses cationic polyacrylamide, chlorinated poly2-hydroxypropyl-1,1-N-dimethylammonium, hexadecyltrimethylammonium bromide, polydimethyldiallylammonium chloride, and polyethyleneimine.

[0007] The patent application with publication number CN110980912A, which is for a dyeing and printing wastewater treatment agent and its application, uses N,N-dimethyldiallylammonium chloride-acrylamide copolymer as one of the flocculants.

[0008] In existing technologies, although some polymers have a certain charge neutralization capacity, they lack the ability to adsorb hydrophobic dyes (such as disperse dyes), making it difficult for the color and COD of the treated effluent to consistently meet the standards.

[0009] Therefore, developing a novel cationic copolymer with controllable molecular structure and both high charge density and hydrophobic adsorption capacity is of great significance for solving the treatment of complex dyeing and printing wastewater. Summary of the Invention

[0010] The main objective of this invention is to provide a method for preparing polymers based on reversible addition-fragmentation chain transfer reaction (RAFT). This method uses molecular structure design and RAFT polymerization technology to control the block sequence, introduces hydrophobic monomers for modification, and combines ultraviolet photoinitiation process to prepare a block copolymer with high efficiency decolorization, rapid sedimentation and strong adaptability.

[0011] In addition, the present invention also provides polymers obtained based on this method and their applications.

[0012] The technical solution of the present invention is as follows:

[0013] A method for preparing a polymer based on a reversible addition-fragmentation chain transfer reaction, using a cationic monomer containing two unsaturated olefin bonds, methacryloyloxyethyltrimethylammonium chloride and / or acryloyloxyethyltrimethylammonium chloride, and a fluorinated hydrophobic monomer as comonomers, and employing reversible addition-fragmentation chain transfer polymerization technology under photoinitiated conditions to obtain a block polymer.

[0014] The molar ratio of the cationic monomer containing two unsaturated olefin bonds, methacryloyloxyethyltrimethylammonium chloride, and / or acryloyloxyethyltrimethylammonium chloride is 1:1 to 3:1.

[0015] The weight of the fluorinated hydrophobic monomer is 1 to 5 wt% of the total weight of the comonomer.

[0016] The inventive point of this invention is:

[0017] 1. The present invention contains a cationic monomer with two unsaturated olefin bonds, methacryloyloxyethyltrimethylammonium chloride and / or acryloyloxyethyltrimethylammonium chloride as the main monomer. Both of these monomers provide positive charge, which provides a basis for the adsorption of anionic dyes;

[0018] 2. This invention uses a long-chain fluorinated monomer as a comonomer. The content of this monomer is relatively small, which avoids diluting the positive charge density and provides affinity for hydrophobic dyes. Compared with non-fluorinated hydrophobic monomers, it has a stronger ability to adsorb hydrophobic dyes. At the same time, the binding ability of the fluorinated monomer with a chain length of 12 carbon atoms is also significantly stronger than that of the fluorinated monomer with a chain length of 6 carbon atoms.

[0019] 3. This invention employs a reversible addition-fragmentation chain transfer reaction to form block copolymers. Compared to traditional random copolymers, it significantly improves the adsorption capacity for both anionic and hydrophobic dyes, with particularly excellent adsorption for hydrophobic dyes. This is because the block copolymers spontaneously form nanomicelles in aqueous solution, with fluorinated hydrophobic segments as the core and cationic segments as the shell. The high-density fluorinated alkyl chains within the hydrophobic core provide abundant partitioning sites for hydrophobic dyes, achieving efficient adsorption. Meanwhile, the cationic shell simultaneously provides electrostatic neutralization. In contrast, in random copolymers, hydrophobic monomers are randomly isolated by hydrophilic segments, making it difficult to form stable hydrophobic microregions and significantly reducing the affinity for nonpolar dyes. Therefore, the microphase separation and synergistic effect brought about by the block structure are key to performance improvement.

[0020] This invention utilizes reversible addition-fragmentation chain transfer polymerization (RAFT) technology, eliminating the need for conventional emulsifiers. The RAFT chain transfer agent used in this technology, such as 2-cyano-2-propylbenzimidazole-2-ylthiocarbamate, functions as a "self-emulsifier." In this system, the hydrophilic RAFT agent first plays a dual role in chain transfer and surface activity, stabilizing the formation of microdroplets from hydrophobic monomers in aqueous solution. As the polymerization reaction proceeds, the growing hydrophobic segments reach a critical degree of polymerization, spontaneously forming a micelle structure with a fluorinated segment core and a water-soluble cationic polymer chain shell, thereby achieving stable dispersion of the block copolymer in the aqueous phase.

[0021] In the above preparation method, the method specifically involves adding the comonomer, RAFT chain transfer agent, and photoinitiator to deionized water, and carrying out a photoinitiated polymerization reaction at room temperature for 1-3 hours.

[0022] In the above preparation method, the weight of the RAFT chain transfer agent is equivalent to 0.5~2wt% of the total weight of the comonomer; the weight of the photoinitiator is equivalent to 0.2~1wt% of the total weight of the comonomer; and the deionized water is equivalent to 0.8~1.2 times the total weight of the comonomer.

[0023] In the above preparation method, the RAFT chain transfer agent is one or more of the following: 2-cyano-2-propylbenzimidazole-2-ylthiocarbamate, 2-(dodecyltrithiocarbonate)-2-methylpropionic acid, and benzyl dithiobenzoate; the photoinitiator is one or more of the following: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and ethyl 2,4,6-trimethylbenzoyl-phenylphosphonite; the photoinitiation conditions are: the light source is ultraviolet light, the light intensity is 50~200 mW / cm², and the wavelength is 365 nm.

[0024] In the above preparation method, the cationic monomer containing two unsaturated olefin bonds is dimethyl diallyl ammonium chloride; the fluorinated hydrophobic monomer is hexafluorobutyl acrylate, hexafluorobutyl methacrylate, dodecylfluoroheptyl acrylate or dodecylfluoroheptyl methacrylate.

[0025] In the above preparation method, the molecular weight of the block polymer is greater than 3500 Da.

[0026] In addition, the present invention also discloses a polymer prepared by any of the methods described above.

[0027] Furthermore, the present invention also discloses the use of the polymer described above in the preparation of wastewater flocculants or complexing agents.

[0028] Finally, the present invention also discloses a wastewater treatment method, comprising the following steps:

[0029] Step 1: Add the polymer as described above to the wastewater to carry out a flocculation and complexation reaction;

[0030] Step 2: Add hydrogen peroxide to the water from Step 1 to break down the flocculated complex products;

[0031] Step 3: Adjust the pH of the water from Step 2 to 6-8, and add polyaluminum chloride to neutralize the charge of the polymer;

[0032] Step 4: Separate the water from Step 3 to obtain supernatant and sediment.

[0033] In the above-mentioned wastewater treatment method, the wastewater is dyeing and printing wastewater; the weight ratio of the polymer to hydrogen peroxide is 1:0.5~1:2; the concentration of the hydrogen peroxide is (5)~(30) wt%

[0034] The weight ratio of the polymer to polyaluminum chloride is 1:1 to 2:1.

[0035] One of the above-described technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0036] 1. By combining RAFT polymerization with ultraviolet light initiation, well-defined block copolymers with controllable molecular weight and narrow distribution were prepared in the aqueous phase, overcoming the defect of uncontrollable structure of random copolymers.

[0037] 2. Fluorine-containing hydrophobic monomer modified cationic polymer, block copolymer self-assembles into core-shell nanomicelles, which have both high positive charge and hydrophobic microdomains. They can simultaneously electrostatically neutralize anionic dyes and hydrophobically adsorb disperse dyes, with decolorization rate and COD removal rate both reaching over 90%.

[0038] 3. The polymerization does not require the addition of external emulsifiers or organic solvents. It is photo-initiated at room temperature, with low energy consumption, simple operation, and low RAFT reagent usage, making it suitable for industrial scale-up.

[0039] 4. The three-step process of "flocculation and complexation - hydrogen peroxide complex breaking - PAC neutralization" solves the problem of "colloidal restabilization" caused by flocculants, resulting in rapid floc settling and clear effluent.

[0040] 5. This product has excellent removal effects on a variety of dyes, including reactive, disperse, and acidic dyes. In particular, its adsorption capacity for hydrophobic dyes is significantly better than that of random copolymers, providing a new approach for the deep treatment of dyeing and printing wastewater. Detailed Implementation

[0041] The embodiments of the present invention are described in detail below.

[0042] Examples and Comparative Examples

[0043] Preparation of block copolymers

[0044] The monomers (types and proportions are shown in Table 1) were dissolved in 100g of deionized water and transferred to a quartz reactor equipped with a stirrer and a nitrogen inlet. Nitrogen gas was introduced for protection for 30 minutes. The reactor was then placed in a 365 nm ultraviolet light reactor, with the light intensity controlled at 100mW / cm², the reaction temperature at 25℃, and the polymerization reaction carried out for 2 hours.

[0045] After the reaction was complete, the product was placed in a dialysis bag (molecular weight cutoff 3500 Da) and dialyzed in deionized water for 48 hours, with the water changed every 6 hours. After dialysis, the solution was freeze-dried to obtain a white powdery block copolymer A.

[0046] Table 1 Formulation Table

[0047]

[0048] In Example 10 above, hexafluorobutyl methacrylate was used instead of dodecafluoroheptyl methacrylate;

[0049] In Comparative Example 6, acrylamide was used instead of methacryloyloxyethyltrimethylammonium chloride;

[0050] In Comparative Example 7, n-heptyl methacrylate was used instead of dodecafluoroheptyl methacrylate;

[0051] In Comparative Example 8, lauryl methacrylate was used instead of dodecafluoroheptyl methacrylate.

[0052] Preparation of random copolymers

[0053] The monomer formulations required for the preparation of random copolymers are shown in Table 2.

[0054] Its preparation method is as follows:

[0055] 1. Material preparation

[0056] Weigh out the required amount of methacryloyloxyethyltrimethylammonium chloride and place it in a dropping device for later use.

[0057] 2. Feeding and mixing

[0058] Add dimethyl diallyl ammonium chloride, pure water (100g), and long-chain alkyl methacrylate or dodecafluoroheptyl methacrylate to the reaction vessel in sequence, start stirring, and mix evenly.

[0059] 3. Heating and Reaction

[0060] Heat the system to 47-48°C and stabilize it for 10 minutes. Then, start to add sodium metabisulfite solution (net content 0.2g), ammonium persulfate solution (net content 0.2g), and the methacryloyloxyethyltrimethylammonium chloride prepared in step 1 dropwise simultaneously.

[0061] Control the dropping rate, maintain the reaction temperature at 47-50℃ throughout the process, and control the dropping time to 8 hours.

[0062] 4. Insulation and Discharge

[0063] After the addition is complete, heat the system to 70-75°C and maintain the temperature for 2 hours. After the temperature maintenance is complete, cool down and discharge the material.

[0064] Table 2 Formulation Table

[0065]

[0066] In Comparative Example 11 above, hexafluorobutyl methacrylate was used instead of dodecafluoroheptyl methacrylate.

[0067] In Comparative Example 12 above, n-heptyl methacrylate was used instead of dodecafluoroheptyl methacrylate;

[0068] In Comparative Example 13 above, lauryl methacrylate was used instead of dodecafluoroheptyl methacrylate.

[0069] Textile dyeing and printing wastewater treatment

[0070] Case 1

[0071] The wastewater sample used for the treatment of textile printing and dyeing wastewater 1 is: a mixed wastewater from a printing and dyeing factory, with a color of 1500 times and a COD of 800 mg / L. This mixed wastewater contains approximately 80~150 mg / L of anionic dyes and 40~80 mg / L of hydrophobic dyes.

[0072] Processing technology:

[0073] Add copolymer: Add copolymer at a rate of 100 mg / L per liter of wastewater and stir rapidly for 5 minutes;

[0074] Add oxidant: Add 50 mg / L of H2O2 and let it stand for 30 minutes to react (construct a "complex-oxidation" system);

[0075] Compound coagulation: Adjust the pH to 7.0, add 50 mg / L of PAC (polyaluminum chloride) per liter of wastewater, set the Zeta potential to (-5~0) mV, and stir for 10 minutes;

[0076] Precipitation: Let stand for 60 minutes to precipitate, then take the supernatant for testing.

[0077] At the same time, a blank group is set up, and the processing technology for the blank group is as follows:

[0078] Add oxidant: Add 50 mg / L of H2O2 and let it stand for 30 minutes to react;

[0079] Compound coagulation: Adjust the pH to 7.0, add 50 mg / L of PAC (polyaluminum chloride) per liter of wastewater, set the Zeta potential to -12~8mV, and stir for 10 minutes;

[0080] Precipitation: Let stand for 60 minutes to precipitate, then take the supernatant for testing.

[0081] The test results are shown in Table 3 below;

[0082] Table 3 Test Results

[0083]

[0084] Case 2

[0085] Similar to Case 1, the difference is that the amount of PAC was increased to 150 mg / L, and the Zeta potential was +2.5 mV, close to 0 mV, which can be considered as complete charge neutralization.

[0086] Textile dyeing and printing wastewater treatment

[0087] Textile dyeing wastewater 2 is a simulated wastewater artificially prepared in the laboratory, containing only Disperse Red 3B (100 mg / L), COD: 550; color: 900.

[0088] Processing technology:

[0089] Add copolymer: Add copolymer at a rate of 100 mg / L per liter of wastewater and stir rapidly for 5 minutes;

[0090] Add oxidant: Add 50 mg / L of H2O2 and let it stand for 30 minutes to react (construct a "complex-oxidation" system);

[0091] Compound coagulation: Adjust the pH to 7.0, add 50 mg / L of PAC (polyaluminum chloride) per liter of wastewater, set the zeta potential to -2 to +2 mV, and stir for 10 minutes;

[0092] Precipitation: Let stand for 60 minutes to precipitate, then take the supernatant for testing.

[0093] The test results are shown in Table 4 below;

[0094] Table 4 Test Results

[0095]

[0096] Results analysis:

[0097] Based on the results in Tables 1 and 2 above, the effects of the examples are generally better than those of the comparative examples. A comparison between the blank group and the examples shows that the blank group, using only polyaluminum chloride, has only moderate effects on decolorization and COD removal. Considering the test results of each example, it can be found that the effects of Examples 4, 6, and 10 are slightly worse. Specifically, the amount of fluorine monomer used in Example 4 is too small, resulting in poor affinity for hydrophobic dyes and reduced adsorption effect. The amount of initiator used in Example 6 is too small, theoretically leading to a significant increase in the molecular weight and chain length of the system, resulting in poor dispersibility in water and hindering the chelation adsorption effect. Example 10 uses a fluorine monomer with a slightly shorter chain segment, which has relatively poor hydrophobic effect, resulting in poor affinity for hydrophobic dyes and reduced adsorption effect.

[0098] In the comparative examples of this invention, the excessive amounts of methacryloyloxyethyltrimethylammonium chloride in Comparative Examples 1 and 4, and the excessive amount of dimethyl diallyl ammonium chloride in Comparative Example 2, significantly reduced their adsorption effect on dyes. When constructing the isolation region of the hydrophilic segments, the mixing ratio of different hydrophilic segments has a significant impact on performance. Comparative Example 3 uses nonionic acrylamide, which reduces the content of positive charge and decreases the adsorption capacity for anionic and hydrophobic dyes. In Comparative Example 5, no fluorinated monomer is used, resulting in reduced hydrophobicity and decreased adsorption capacity for hydrophobic dyes. In Comparative Examples 7 and 8, unsaturated long-chain fatty acid monomers are used, which are far inferior to fluorinated monomers in terms of color and COD control.

[0099] To further verify the importance of the block copolymers formed by the reversible addition-fragmentation chain transfer reaction for the products of the present invention, the present invention also carried out random copolymerization of the above-mentioned embodiments and comparative examples. As can be seen from the comparison of Comparative Examples 9 to 10, fluorinated monomers are still quite important in both reversible addition-fragmentation chain transfer reactions and random copolymerization, and fluorinated methacrylates play a more significant role in reversible addition-fragmentation chain transfer reactions.

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing a polymer based on a reversible addition-fragmentation chain transfer reaction, characterized in that, Using cationic monomers containing two unsaturated olefin bonds, methacryloyloxyethyltrimethylammonium chloride and / or acryloyloxyethyltrimethylammonium chloride, and fluorinated hydrophobic monomers as comonomers, block polymers were obtained by reversible addition-fragmentation chain transfer polymerization under photoinitiated conditions. The molar ratio of the cationic monomer containing two unsaturated olefin bonds, methacryloyloxyethyltrimethylammonium chloride, and / or acryloyloxyethyltrimethylammonium chloride is 1:1 to 3:

1. The weight of the fluorinated hydrophobic monomer is 1 to 5 wt% of the total weight of the comonomer.

2. The preparation method according to claim 1, characterized in that, The method specifically involves adding the comonomer, RAFT chain transfer agent, and photoinitiator to deionized water and carrying out a photoinitiated polymerization reaction at room temperature for 1-3 hours.

3. The preparation method according to claim 2, characterized in that, The weight of the RAFT chain transfer agent is equivalent to 0.5~2wt% of the total weight of the comonomer; the weight of the photoinitiator is equivalent to 0.2~1wt% of the total weight of the comonomer; and the deionized water is equivalent to 0.8~1.2 times the total weight of the comonomer.

4. The preparation method according to claim 2, characterized in that, The RAFT chain transfer agent is one or more combinations of 2-cyano-2-propylbenzimidazole-2-ylthiocarbamate, 2-cyano-2-propylbenzodisulfide, and 2-cyano-2-propyldithiobenzoate; the photoinitiator is one or more combinations of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2,4,6-trimethylbenzoyl-xylylphosphine oxide; the photoinitiation conditions are: the light source is ultraviolet light, the light intensity is 50~200 mW / cm², and the wavelength is 365 nm.

5. The preparation method according to claim 1, characterized in that, The cationic monomer containing two unsaturated olefin bonds is dimethyl diallyl ammonium chloride; the fluorinated hydrophobic monomer is dodecylfluoroheptyl acrylate or dodecylfluoroheptyl methacrylate.

6. The preparation method according to claim 1, characterized in that, The molecular weight of the block polymer is greater than 3500 Da.

7. A polymer, characterized in that, Prepared by the method described in any one of claims 1 to 6.

8. Use of the polymer as described in claim 7 to prepare wastewater flocculants or complexing agents.

9. A wastewater treatment method, characterized in that, Includes the following steps: Step 1: Add the polymer as described in claim 7 to the wastewater to carry out a flocculation and complexation reaction; Step 2: Add hydrogen peroxide to the water from Step 1 to break down the flocculated complex products; Step 3: Adjust the pH of the water from Step 2 to 6-8, and add polyaluminum chloride to neutralize the charge of the polymer; Step 4: Separate the water from Step 3 to obtain supernatant and sediment.

10. The wastewater treatment method according to claim 9, characterized in that, The wastewater is dyeing and printing wastewater; the weight ratio of the polymer to hydrogen peroxide is 1:0.5 to 1:2; the concentration of the hydrogen peroxide is 5 to 30 wt%. The weight ratio of the polymer to polyaluminum chloride is 1:1 to 2:1.

Images