Preparation method of crosslinked cationic polyacrylamide retention and drainage aid

Abstract

The present invention discloses a preparation method of a crosslinked cationic polyacrylamide retention and drainage aid. By adopting a composite initiator system and a post-hydrolysis process, first, acrylamide, acryloyloxyethyl trimethyl ammonium chloride, a hydrophobic monomer cetyl dimethyl allyl ammonium chloride, and a crosslinking agent N,N-methylenebisacrylamide are formulated into an aqueous solution, and a composite initiator system is added to initiate a polymerization reaction to obtain a rubber block. Then, the rubber block is granulated and mixed with caustic soda for hydrolysis reaction. Finally, it is dried, pulverized, and sieved to obtain a finished product of a crosslinked cationic polyacrylamide retention and drainage aid. The crosslinked cationic polyacrylamide prepared by the present invention has the characteristics of high molecular weight, high viscosity, and low residual monomers, and at the same time has good solubility, salt resistance, and shear resistance. As a retention and drainage aid, it can be well used in the papermaking field to improve the retention rate of pulp and fillers and improve the water filtration performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of water-soluble polymer chemical polymerization reactions, and particularly relates to a preparation method of a crosslinked cationic polyacrylamide retention and drainage aid. Background Art

[0002] In recent years, with the rapid development of the paper-making industry, enterprises have been continuously expanding production to meet market demands. However, due to the shortage of domestic wood pulp fibers, a large amount of recycled waste paper pulp has to be used, resulting in an increasing amount of fine components in the pulp. Retention and drainage aids are important papermaking additives. Adding retention and drainage aids to the pulp can accelerate the water filtration rate of the pulp, improve the retention rate of fine fibers, and thus increase the utilization rate of wastewater. Polyacrylamide (PAM) is a linear high-molecular polymer with good solubility and high molecular weight. It is a commonly used additive in the paper-making industry to reduce fiber flocculation and improve the formation of paper stock. The application effect of polyacrylamide in the paper industry is mainly determined by the molecular weight, charge density, degree of ionization, and activity of functional groups. As a retention and drainage aid in the wet end of the paper machine, cationic polyacrylamide can improve the uniformity of the paper, enhance the dewatering performance of the pulp, and also increase the retention rate of fine fibers and fillers, reducing the consumption of raw materials and environmental pollution. Therefore, cationic polyacrylamide occupies a very important position in domestic papermaking chemicals.

[0003] In the preparation process of the existing cationic polyacrylamide retention and drainage aids, there are many residual monomers after the polymerization monomers are used, resulting in too low raw material utilization rate during the preparation process. The polyacrylamide prepared has low stability, and the prepared retention and drainage aids cannot effectively increase the pulp retention rate and improve the water filtration performance, resulting in a relatively high concentration of white water under the filter screen after pulp filtration, reducing the loss of fine fibers and fillers, and increasing the white water pollution load. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of a crosslinked cationic polyacrylamide retention and drainage aid. By using a composite initiator system and a post-hydrolysis process, first, acrylamide, acryloyloxyethyltrimethylammonium chloride, the hydrophobic monomer cetyl dimethyl allyl ammonium chloride, and the crosslinking agent N,N'-methylenebisacrylamide are formulated into an aqueous solution, and a composite initiator system is added to initiate the polymerization reaction to obtain a gel block. Then, the gel block is granulated and mixed with flake caustic soda for hydrolysis reaction. Finally, it is dried, pulverized, and sieved to obtain a finished product of a crosslinked cationic polyacrylamide retention and drainage aid.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of a crosslinked cationic polyacrylamide retention and drainage aid, comprising the following steps:

[0007] S1: Weigh acrylamide, acryloyloxyethyltrimethylammonium chloride, cetyl dimethyl allyl ammonium chloride, and N,N - methylenebisacrylamide and dissolve them in an appropriate amount of deionized water to prepare an aqueous monomer solution.

[0008] S2: Transfer the aqueous solution in S1 into a reaction vessel, add a complexing agent, a chain transfer agent, and a solubilizer. While continuously purging nitrogen, cool the temperature of the aqueous solution to 0 - 2 °C. After continuously purging nitrogen for 0.5 - 1 hour, add a composite initiator system to initiate the polymerization reaction. After polymerizing for 5 - 7 hours, a rubber block can be obtained. The composite initiator system includes the following components by weight percentage: (a) 0.2% - 25% persulfate; (b) 0.1% - 30% sulfite; (c) 0.2% - 20% azo compound; (d) 0.5% - 20% tertiary amine compound represented by NR1R2R3, where R1 - R3 are selected from C1 - C14 straight-chain or branched-chain alkyl or alkyl derivatives; (e) 0.5% - 20% aliphatic amine compound represented by NH2R4, where R4 is selected from C1 - C18 straight-chain or branched-chain alkyl or alkyl derivatives; the sum of the weight percentages of each component of the above composite initiator system is 100%;

[0009] S3: Cut the rubber block in S2 into pieces, add a certain mass of caustic soda, knead it evenly, and then carry out a hydrolysis reaction for 2 - 3 hours. After the hydrolysis reaction is completed, dry, crush, and sieve the rubber block to obtain the finished product of cross-linked cationic polyacrylamide.

[0010] Preferably, in S1, the addition amount of acrylamide is 70% - 80% of the total monomer amount; the addition amount of acryloyloxyethyltrimethylammonium chloride is 20% - 30% of the total monomer amount; the addition amount of cetyl dimethyl allyl ammonium chloride is 0.1% - 1% of the total monomer amount; the addition amount of N,N - methylenebisacrylamide is 0.1% - 1% of the total monomer amount; the sum of the weight percentages of each component of the above total monomer amount is 100%; the mass ratio of deionized water to acrylamide is (3 - 4):1.

[0011] Preferably, in S2, the complexing agent is selected from one or more of 2,2 - bipyridine, sodium ethylene diamine tetra(methylene phosphonate), or tris(2 - dimethylaminoethyl)amine, and the addition amount of the complexing agent is 0.005% - 0.01% of the mass of acrylamide.

[0012] Preferably, in S2, the chain transfer agent is selected from one or more of isopropanol, isobutanol, or pentaerythritol, and the addition amount of the chain transfer agent is 0.005% - 0.02% of the mass of acrylamide.

[0013] Preferably, in S2, the solubilizer is selected from one or more of urea or thiourea, and the addition amount of the solubilizer is 0.01%-0.5% of the mass of acrylamide.

[0014] Preferably, in S2, the persulfate is selected from one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0015] Preferably, in S2, the sulfite is selected from one of sodium sulfite, potassium sulfite, sodium bisulfite, and potassium bisulfite.

[0016] Preferably, in S2, the azo compound is selected from one of azobisisobutyronitrile, dimethyl azodicarboxylate, and azodiisobutylamidine hydrochloride.

[0017] Preferably, in S2, the tertiary amine compound is selected from one of β-dimethylaminopropionitrile and N,N-dimethylaminoethyl methacrylate.

[0018] Preferably, in S2, the aliphatic amine compound is selected from one of methylamine and ethylenediamine.

[0019] Preferably, in S2, the purity of the nitrogen gas introduced is ≧99.99%, and the flow rate is 60 m3 / h.

[0020] Preferably, in S3, the addition amount of the caustic soda is 10%-20% of the mass of the shredded rubber blocks; the temperature of the hydrolysis reaction is 80°C-90°C, and the temperature of drying after the hydrolysis reaction is 70°C-75°C.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. In the present invention, the monomer aqueous solution prepared from acrylamide, acryloyloxyethyltrimethylammonium chloride, the hydrophobic monomer cetyl dimethyl allyl ammonium chloride, and the cross-linking N,N-methylenebisacrylamide is used for the reaction. Since acryloyloxyethyltrimethylammonium chloride and the hydrophobic monomer cetyl dimethyl allyl ammonium chloride have good flocculation properties, the obtained cationic polyacrylamide retention and drainage aid has the characteristics of high molecular weight and high viscosity, improving the pulp retention rate and the drainage performance, significantly reducing the concentration of white water under the filter screen after pulp filtration, reducing the loss of fine fibers and fillers, and reducing the white water pollution load.

[0023] 2. In the composite initiator system used in the present invention, isopropanol, isobutanol, or pentaerythritol is used as a chain transfer agent. Through the alcohol solvent, the stable monomer aqueous solution is degraded into a series of cationic liquid-phase small molecules with different molecular weights and rich in multiple reactive groups, and then re-grafted and copolymerized into the acrylamide macromolecule to improve the retention and drainage performance of the cationic polyacrylamide retention and drainage aid for pulp, so that the retention rate of fine fibers and fillers increases.

[0024] 3. For the first time in the present invention, tertiary amine compounds and aliphatic amine compounds are applied to the composite initiator system for preparing polyacrylamide to promote the monomer polymerization reaction and increase the stability of cationic polyacrylamide, so that the prepared crosslinked cationic polyacrylamide has good shear resistance and reduces the content of residual monomers after the preparation. In addition, the obtained cationic polyacrylamide is hydrolyzed and dried with caustic soda, so that the prepared retention and drainage aid has good salt resistance and solubility, and improves the retention rate of pulp and filler and the drainage performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a process flow chart for preparing the crosslinked cationic polyacrylamide retention and drainage aid of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] Please refer to Figure 1 , the present invention provides a technical solution:

[0028] Example 1

[0029] Weigh 100 g of acrylamide, 35 g of acryloyloxyethyltrimethylammonium chloride, 0.5 g of cetyl dimethyl allyl ammonium chloride and 0.5 g of N,N - methylene bisacrylamide and dissolve them in 340 g of deionized water until fully dissolved. Transfer the dissolved aqueous solution into a reaction vessel, add 0.65 g of ethylenediamine tetra(methylene phosphonic acid) sodium, 1.05 g of isopropanol and 2.5 g of urea. While continuously passing nitrogen, lower the temperature of the aqueous solution to 1 °C. After continuing to pass nitrogen for 1 hour, add 1.6 g of 1% potassium persulfate aqueous solution, 3.5 g of 1% sodium sulfite aqueous solution, 1.1 g of 2% azobisisobutyronitrile aqueous solution, 4.8 g of 5% β - dimethylaminopropionitrile aqueous solution, 4.1 g of 1% ethylenediamine aqueous solution every two minutes. After 5.5 hours, a gel block is obtained. Cut the gel block into pieces, add 20 g of caustic soda, knead evenly and carry out hydrolysis reaction for 2.5 hours, then take it out and put it into a vacuum drying oven at 75 °C for drying. After drying, crush it with a pulverizer and sieve it through a 60 - mesh sieve to obtain the finished product of crosslinked cationic polyacrylamide.

[0030] Example 2

[0031] Same as Example 1, except that: 0.5 g of cetyl dimethyl allyl ammonium chloride is replaced with 0.25 g of cetyl dimethyl allyl ammonium chloride.

[0032] Example 3

[0033] Same as Example 1, except that: 0.5 g of cetyl dimethyl allyl ammonium chloride is replaced with 0.75 g of cetyl dimethyl allyl ammonium chloride.

[0034] Example 4

[0035] Weigh 95 g of acrylamide, 31.5 g of acryloyloxyethyl trimethyl ammonium chloride, 0.65 g of cetyl dimethyl allyl ammonium chloride, and 0.5 g of N,N'-methylenebisacrylamide, and dissolve them in 315 g of deionized water until completely dissolved. Transfer the dissolved aqueous solution into a reaction vessel, add 0.5 g of tris(2-dimethylaminoethyl)amine, 1.1 g of pentaerythritol, and 2.5 g of thiourea. While continuously purging with nitrogen, cool the aqueous solution to 1.5 °C. After continuously purging with nitrogen for 1 hour, add 1.6 g of 1% aqueous sodium persulfate solution, 3.5 g of 1% aqueous sodium sulfite solution, 1.1 g of 2% aqueous dimethyl 2,2'-azobis(2-methylpropionate) solution, 4.8 g of 5% aqueous N,N-dimethylaminoethyl methacrylate solution, and 4.1 g of 1% aqueous ethylenediamine solution every two minutes. After 6 hours, a gel block is obtained. Cut the gel block into pieces, add 20 g of flake soda, knead evenly, and carry out hydrolysis reaction for 2.5 hours. Then take it out and dry it in a vacuum drying oven at 75 °C. After drying, pulverize it with a pulverizer and sieve it through a 60-mesh sieve to obtain the finished product of crosslinked cationic polyacrylamide.

[0036] Example 5

[0037] Same as Example 4, except that: 0.5 g of N,N'-methylenebisacrylamide is replaced with 0.25 g of N,N'-methylenebisacrylamide.

[0038] Example 6

[0039] Same as Example 4, except that: 0.5 g of N,N'-methylenebisacrylamide is replaced with 0.75 g of N,N'-methylenebisacrylamide.

[0040] Comparative Example 1

[0041] Same as Example 1, except that: N,N'-methylenebisacrylamide is not added.

[0042] Comparative Example 2

[0043] Same as Example 1, except that: cetyl dimethyl allyl ammonium chloride is not added.

[0044] Comparative Example 3

[0045] Same as Example 1, with the only difference being that cetyl dimethyl allyl ammonium chloride and N,N-methylenebisacrylamide are not added.

[0046] The above examples were tested, and the results are shown in the following table:

[0047]

[0048] The test results in the table show that:

[0049] In Examples 1 to 6, an aqueous monomer solution was prepared from acrylamide, acryloyloxyethyl trimethyl ammonium chloride, the hydrophobic monomer cetyl dimethyl allyl ammonium chloride, and the crosslinking agent N,N-methylenebisacrylamide. Through the reaction with a composite initiator system, it forms characteristics of high molecular weight, high viscosity, and low residual monomers. At the same time, it also has good solubility, making it exhibit good flocculation performance during the papermaking process to improve the retention rate of pulp and fillers and improve the drainage performance.

[0050] Thus, it can be seen that the parameters such as molecular weight, apparent viscosity, insoluble matter, and AM residue of Examples 1 to 6 are superior to those of Comparative Examples 1 to 3. Therefore, a crosslinked cationic polyacrylamide retention and drainage aid prepared by the method of the present invention is reliable. At the same time, the significant differences in molecular weight and apparent viscosity between Example 1 and Comparative Examples 1 to 3 can prove the characteristics of high molecular weight, high viscosity, and low residual monomers of the crosslinked cationic polyacrylamide in the present invention.

[0051] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a cross-linked cationic polyacrylamide retention and drainage aid, characterized in that: It includes the following steps: S1: Weigh acrylamide, acryloyloxyethyltrimethylammonium chloride, cetyl dimethyl allyl ammonium chloride and N,N-methylenebisacrylamide, and dissolve them in deionized water to prepare a monomer aqueous solution; S2: Transfer the aqueous solution in S1 into a reaction vessel, add a complexing agent, a chain transfer agent and a solubilizer. While continuously introducing nitrogen, lower the temperature of the aqueous solution to 0-2°C. After continuously introducing nitrogen for 0.5-1 hour, add a composite initiator system to initiate the polymerization reaction. After polymerizing for 5-7 hours, a rubber block can be obtained. The composite initiator system includes the following components by weight percentage: (a) 0.2%-25% of persulfate; (b) 0.1%-30% of sulfite; (c) 0.2%-20% of azo compound; (d) 0.5%-20% of tertiary amine compounds represented by NR1R2R3, where R1-R3 are selected from C1-C14 straight-chain or branched-chain alkyl or alkyl derivatives; (e) 0.5%-20% of aliphatic amine compounds represented by NH2R4, where R4 is selected from C1-C18 straight-chain or branched-chain alkyl or alkyl derivatives; The tertiary amine compound is selected from one of β-dimethylaminopropionitrile and N,N-dimethylaminoethyl methacrylate; the aliphatic amine compound is selected from one of methylamine and ethylenediamine; S3: Cut the rubber block obtained in S2 into pieces, add caustic soda, knead evenly, and then carry out a hydrolysis reaction for 2-3 hours. After the hydrolysis reaction is completed, dry, crush and screen the rubber block to obtain the finished product of crosslinked cationic polyacrylamide.

2. The preparation method of a crosslinked cationic polyacrylamide retention and drainage aid according to claim 1, characterized in that: The addition amount of acrylamide is 70%-80% of the total monomer amount; the addition amount of acryloyloxyethyltrimethylammonium chloride is 20%-30% of the total monomer amount; the addition amount of cetyl dimethyl allyl ammonium chloride is 0.1%-1% of the total monomer amount; the addition amount of N,N-methylenebisacrylamide is 0.1%-1% of the total monomer amount; The mass ratio of deionized water to acrylamide is (3-4):

1.

3. The preparation method of a crosslinked cationic polyacrylamide retention and drainage aid according to claim 1, characterized in that: The complexing agent is selected from one or more of 2,2-bipyridine, sodium ethylene diamine tetra(methylene phosphonate) or tris(2-dimethylaminoethyl)amine, and the addition amount of the complexing agent is 0.005%-0.01% of the mass of acrylamide.

4. The preparation method of a crosslinked cationic polyacrylamide retention and drainage aid according to claim 1, characterized in that: The chain transfer agent is selected from one or more of isopropyl alcohol, isobutyl alcohol or pentaerythritol, and the addition amount of the chain transfer agent is 0.005%-0.02% of the mass of acrylamide.

5. The preparation method of a crosslinked cationic polyacrylamide retention and drainage aid according to claim 1, characterized in that: The solubilizer is selected from one or more of urea or thiourea, and the addition amount of the solubilizer is 0.01%-0.5% of the mass of acrylamide.

6. The preparation method of a cross-linked cationic polyacrylamide retention and drainage aid according to claim 1, characterized in that: The persulfate is selected from one of ammonium persulfate, potassium persulfate and sodium persulfate; the sulfite is selected from one of sodium sulfite, potassium sulfite, sodium bisulfite and potassium bisulfite.

7. The preparation method of a crosslinked cationic polyacrylamide retention and drainage aid according to claim 1, characterized in that: The azo compound is selected from one of azobisisobutyronitrile, dimethyl azobisisobutyrate and 2,2'-azobis(2-methylpropionamidine) dihydrochloride.

8. The preparation method of a crosslinked cationic polyacrylamide filter aid and retention aid according to claim 1, characterized in that: The addition amount of caustic soda is 10%-20% of the mass of the cut rubber block; the temperature of the hydrolysis reaction is 80°C-90°C, and the drying temperature after the hydrolysis reaction is 70°C-75°C.

9. The preparation method of a crosslinked cationic polyacrylamide filter aid and retention aid according to claim 1, characterized in that: The purity of the introduced nitrogen is ≥99.99%, and the flow rate is 60 m 3 / h.

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