A glyoxal-modified polyacrylamide, and a preparation method and application thereof

Abstract

The application belongs to the technical field of microorganisms and particularly relates to a glyoxal modified polyacrylamide as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, seed liquids of Pseudomonas chlororaphis, Rhodococcus rhodochrous and Lactobacillus plantarum are mixed and inoculated into a fermentation medium to obtain a mixed seed liquid; secondly, acrylonitrile is gradiently added and continuously reacted to obtain acrylamide; thirdly, the acrylamide and diallyldimethylammonium chloride are dissolved in water to obtain a mixed liquid, an initiator is added, and the mixed liquid is reacted at a high temperature to obtain a cationic polyacrylamide aqueous solution; and finally, the cationic polyacrylamide aqueous solution is reacted with a glyoxal aqueous solution to obtain the glyoxal modified polyacrylamide. The glyoxal modified polyacrylamide is obtained by using a microbial fermentation synthesis method and through the synergistic effect of Pseudomonas chlororaphis, Rhodococcus rhodochrous and Lactobacillus plantarum, so that acrylamide monomers can be obtained by one-step fermentation, and the glyoxal modified polyacrylamide can be finally obtained, which can obviously improve the paper performance and improve the retention rate.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to a glyoxal-modified polyacrylamide, its preparation method, and its application. Background Technology

[0002] Polyacrylamide (PAM) is a linear polymer that is a hard, glassy solid at room temperature. Products include liquids, latexes, white powders, translucent beads, and flakes. Polyacrylamide is a general term for polymers obtained by homopolymerization of acrylamide or copolymerization with other monomers, and it is one of the most widely used water-soluble polymers. Due to the presence of amide groups in its structural units, polyacrylamide readily forms hydrogen bonds, giving it excellent water solubility and high chemical reactivity. It is easily modified through grafting or crosslinking to obtain various branched or network structures, and has wide applications in industries such as oil extraction, water treatment, textiles, papermaking, mineral processing, pharmaceuticals, and agriculture.

[0003] For example, Chinese invention patent publication number CN115558055A discloses an aldehyde-modified polyacrylamide reinforcing agent, its preparation method, and its application. The preparation method of the aldehyde-modified polyacrylamide reinforcing agent consists of the following steps: first, chain transfer agent, polymerization, and modification. When used in papermaking processes, the aldehyde-modified polyacrylamide reinforcing agent can effectively improve pulp single-pass retention, overcome the problem of frequent paper machine breaks, and further improve the folding endurance, bursting index, ring crush index, internal bond strength, and ash content of the paperboard.

[0004] Another Chinese invention patent publication number CN115612020A discloses a method for preparing bead-like micro-crosslinked polyacrylamide paper reinforcing agents and their applications, including S1: Aqueous phase preparation: acrylamide solid is dissolved in water, cationic ethylene monomers and crosslinking monomers are added, and mixed to obtain a monomer aqueous solution; an initiator is added to the above monomer aqueous solution and mixed evenly to prepare an aqueous phase; Oil phase preparation: in a reaction vessel, a surfactant and cyclohexane and / or methylcyclohexane with a volume of 1-3 times that of the aqueous phase are added to prepare an oil phase; S2: Polymerization reaction and S3: Post-treatment: after the reaction, the product is filtered dry using a Buchner funnel and dried in a hot air oven at 60-65℃ to obtain bead-like micro-crosslinked cationic polyacrylamide paper reinforcing agent.

[0005] However, the polyacrylamide prepared by the aforementioned invention patent is not ideal for improving paper strength, and the reagents used are complex and costly.

[0006] Currently, the mainstream process for preparing polyacrylamide in industry is the two-step method of “microbial preparation of acrylamide (AM) monomer - chemical polymerization to generate PAM”. This process has the following defects: (1) Step separation: acrylamide monomer needs to be separated and purified before chemical polymerization, which increases equipment investment and process complexity, leading to increased production costs; (2) Pollution risk: the chemical polymerization process requires the use of initiators (such as ammonium persulfate and azobisisobutyronitrile), which may not only remain in the product and affect application performance, but also generate nitrogen-containing wastewater, increasing the pressure of environmental protection treatment; (3) Poor controllability: the chemical polymerization reaction is highly exothermic and prone to local overheating, resulting in uneven molecular weight distribution of the product. It is necessary to accurately control the reaction conditions, which is difficult to operate.

[0007] Therefore, there is an urgent need in the field to provide an environmentally friendly, stable, convenient modified polyacrylamide that can significantly improve paper strength. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art by providing a glyoxal-modified polyacrylamide, its preparation method, and its application.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing glyoxal-modified polyacrylamide includes the following steps:

[0011] (1) First, mix the seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum, inoculate them into the fermentation medium, and culture them to obtain a mixed seed culture; then add acrylonitrile in a gradient flow to continue the reaction and obtain acrylamide;

[0012] (2) Then, acrylamide and diallyl dimethyl ammonium chloride are dissolved in water to obtain a mixture. An initiator is added and the mixture is heated to react, resulting in an aqueous solution of cationic polyacrylamide.

[0013] (3) Finally, the cationic polyacrylamide aqueous solution is reacted with the glyoxal aqueous solution to obtain the product;

[0014] In step (1), the preservation number of the *Pseudomonas aeruginosa* is ATCC 13985, the preservation number of the *Rhodococcus rosea* is CGMCC 1.2348, and the preservation number of the *Lactobacillus plantarum* is CCTCC NO: M 20242630.

[0015] Preferably, the preparation process of the seed liquid of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum in step (1) includes: inoculating Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum into activation medium, activating them, and obtaining the corresponding seed liquid.

[0016] Preferably, the activation medium is LB medium or MRS medium.

[0017] Preferably, the activation conditions are: incubation at 50-200 rpm and 35-37℃ until OD500 = 0.8-1.2.

[0018] Preferably, the volume ratio of the seed liquid of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum in step (1) is 2-3:1-2:1.

[0019] More preferably, the volume ratio of the seed liquid of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum in step (1) is 3:2:1.

[0020] Preferably, in step (1), the fermentation medium comprises: 20-25 g / L glucose, 10-12 g / L sucrose, 12-15 g / L soybean meal hydrolysate, 6-8 g / L yeast extract, 3-4 g / L dipotassium hydrogen phosphate, 1.2-1.5 g / L magnesium sulfate heptahydrate, and 2-3 g / L sodium citrate; the pH of the fermentation medium is 7.2-7.5.

[0021] Preferably, in step (1), the inoculation amount is 10-12%.

[0022] Preferably, in step (1), the culture conditions are: cultured at 200-300 rpm and 25-35℃ for 12-14 h.

[0023] Preferably, in step (1), the gradient flow acrylonitrile addition procedure is as follows:

[0024] 0-12 h: 0.5-0.8 g / (L·h);

[0025] 12-30 h: 0.8-1 g / (L·h).

[0026] Preferably, in step (1), the final concentration of acrylonitrile in the fermentation medium is 4.5-5%; the temperature for continuing the reaction is 35-38℃, and the reaction time is 30-35 h; after the reaction is completed, filtration and vacuum drying are also performed.

[0027] Preferably, in step (2), the mass concentration of the mixture is 12-28%; the initiator includes a mixed aqueous solution of ammonium persulfate and sodium bisulfite, and the total mass concentration of ammonium persulfate and sodium bisulfite in the mixed aqueous solution is 0.06-0.18%.

[0028] Preferably, in step (2), the mass ratio of acrylamide, diallyl dimethyl ammonium chloride, ammonium persulfate and sodium bisulfite is 100:10-30:0.01-0.1:0.01-0.1.

[0029] Preferably, in step (2), the heating reaction is carried out in a nitrogen atmosphere, the temperature of the heating reaction is 30-42℃, and the heating reaction time is 4-6 h.

[0030] Preferably, in step (2), the cationic polyacrylamide has a weight-average molecular weight of 0.5 × 10⁻⁶. 5 -10×10 5 g / mol.

[0031] Preferably, in step (3), the mass fraction of the glyoxal aqueous solution is 35-45%; the mass ratio of the dry matter in the glyoxal aqueous solution to that in the cationic polyacrylamide aqueous solution is 0.9-1.1:2-3.

[0032] Preferably, in step (3), the reaction temperature is 10-35℃, the reaction time is 1-4 h, and the pH is adjusted to 2.5-3.5 after the reaction is completed.

[0033] The present invention also provides glyoxal-modified polyacrylamide prepared by the above preparation method.

[0034] The present invention also provides the application of the above-mentioned glyoxal-modified polyacrylamide as a reinforcing agent, synergist or water retention filter aid in the papermaking field.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The present invention adopts a microbial fermentation synthesis method. By utilizing the synergistic effect of Pseudomonas aeruginosa, Rhodococcus roseus and Lactobacillus plantarum, acrylamide monomer can be obtained by one-step fermentation, and cationic polyacrylamide is finally obtained. Then, it is mixed and reacted with glyoxal online to finally obtain glyoxal-modified polyacrylamide.

[0037] (2) Experiments show that the glyoxal-modified polyacrylamide provided by the present invention has a high retention rate when used as a paper strengthening agent in papermaking, which can significantly improve paper performance and increase retention rate. Detailed Implementation

[0038] It is worth noting that all raw materials used in this invention are commercially available products. Specifically, LB medium was purchased from Beijing Solarbio Science & Technology Co., Ltd.; MRS medium was purchased from Qingdao Haibo Biotechnology Co., Ltd.; soybean meal hydrolysate was purchased from Shandong Yubao Biotechnology Co., Ltd.; and yeast extract was purchased from Beijing Hongrun Baoshun Technology Co., Ltd.

[0039] Example 1

[0040] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0041] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rosacea CGMCC 1.2348 were inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2 to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rosacea seed culture. Then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 0.8 to obtain Lactobacillus plantarum seed culture.

[0042] (2) The seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum were mixed in a volume ratio of 3:2:1 and inoculated into the fermentation medium (containing 22 g / L glucose, 12 g / L sucrose, 14 g / L soybean meal hydrolysate, 7 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 2 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0043] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0044] (3) Dissolve 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride in water to obtain a mixture with a mass concentration of 28%. Add an initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) at a dropping rate of 0.3 mL / min. Under a nitrogen atmosphere, react at 30℃ for 6 h to obtain a solid content of 28% and a weight average molecular weight of 9×10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0045] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0046] Example 2

[0047] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0048] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rosacea CGMCC 1.2348 were inoculated into LB medium and cultured at 200 rpm and 35℃ until the OD500 was 1 to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rosacea seed culture. Then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 1.2 to obtain Lactobacillus plantarum seed culture.

[0049] (2) The seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum were mixed in a volume ratio of 2:2:1 and inoculated into the fermentation medium (containing 20 g / L glucose, 10 g / L sucrose, 15 g / L soybean meal hydrolysate, 8 g / L yeast extract, 3 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 2 g / L sodium citrate; pH=7.5) at 250 rpm and 25℃ for 14 h to obtain the mixed seed culture.

[0050] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.5 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 35 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0051] (3) Dissolve 200 g of acrylamide and 57 g of diallyl dimethyl ammonium chloride in water to obtain a mixture with a mass concentration of 22%. Add an initiator aqueous solution with a mass concentration of 0.06% (0.08 g each of ammonium persulfate and sodium bisulfite in the initiator) at a dropping rate of 0.3 mL / min. Under a nitrogen atmosphere, the mixture is heated to 36℃ for 5 h to obtain a solid content of 22% and a weight average molecular weight of 5×10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0052] (4) Prepare the materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1.1:2 and react online at 10°C for 4 hours. After the reaction is completed, adjust the pH of the reaction solution to 3.5 to obtain glyoxal-modified polyacrylamide.

[0053] Example 3

[0054] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0055] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rosacea CGMCC 1.2348 were inoculated into LB medium and cultured at 150 rpm and 35℃ until the OD500 was 1.2 to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rosacea seed culture. Then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 1 to obtain Lactobacillus plantarum seed culture.

[0056] (2) The seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum were mixed in a volume ratio of 3:1:1 and inoculated into the fermentation medium (containing 25 g / L glucose, 12 g / L sucrose, 12 g / L soybean meal hydrolysate, 6 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.5 g / L magnesium sulfate heptahydrate and 3 g / L sodium citrate; pH=7) at 200 rpm and 35℃ for 12 h to obtain the mixed seed culture.

[0057] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 5% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.8 g / (L·h); 12-30 h: 1 g / (L·h)). After fermentation at 38℃ for 30 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0058] (3) Dissolve 110 g of acrylamide and 10 g of diallyl dimethyl ammonium chloride in water to obtain a 12% (w / w) mixture. Add an initiator aqueous solution with a 0.18% (w / w) concentration (0.11 g each of ammonium persulfate and sodium bisulfite in the initiator) at a dropping rate of 0.3 mL / min. React at 42℃ for 4 h under a nitrogen atmosphere to obtain a solid content of 12% and a weight-average molecular weight of 5 × 10⁻⁶. 4 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0059] (4) Prepare the materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 0.9:3 and react them online at 35°C for 1 h. After the reaction is completed, adjust the pH of the reaction solution to 2.5 to obtain glyoxal-modified polyacrylamide.

[0060] Comparative Example 1

[0061] Compared with Example 1, the only difference is that it does not contain *Lactobacillus plantarum*, and the seed liquid volume ratio of *Pseudomonas aeruginosa* and *Rhodococcus roseum* in step (2) is 3:2. Specifically:

[0062] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0063] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rubra CGMCC 1.2348 were inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2, to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rubra seed culture.

[0064] (2) The seed cultures of Pseudomonas aeruginosa and Rhodococcus roseum were mixed at a volume ratio of 3:2 and inoculated into the fermentation medium (containing 22 g / L glucose, 12 g / L sucrose, 14 g / L soybean meal hydrolysate, 7 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 2 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0065] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0066] (3) Then, 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride were dissolved in water to obtain a mixed solution with a mass concentration of 28%. An initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) was added at a dropping rate of 0.3 mL / min. The mixture was heated to 30 °C for 6 h under a nitrogen atmosphere to obtain a solid content of 18% and a weight average molecular weight of 6.4 × 10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0067] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0068] Comparative Example 2

[0069] Compared with Example 1, the only difference is that it does not contain Rhodococcus roseum, and the seed liquid volume ratio of Pseudomonas aeruginosa and Lactobacillus plantarum in step (2) is 3:1. Specifically:

[0070] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0071] (1) First, Pseudomonas aeruginosa ATCC 13985 was inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2 to obtain Pseudomonas aeruginosa seed culture; then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 0.8 to obtain Lactobacillus plantarum seed culture.

[0072] (2) The seed cultures of Pseudomonas aeruginosa and Lactobacillus plantarum were mixed at a volume ratio of 3:1 and inoculated into the fermentation medium (containing 22 g / L glucose, 12 g / L sucrose, 14 g / L soybean meal hydrolysate, 7 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 2 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0073] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0074] (3) Then, 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride were dissolved in water to obtain a mixed solution with a mass concentration of 28%. An initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) was added at a dropping rate of 0.3 mL / min. The mixture was heated to 30 °C for 6 h under a nitrogen atmosphere to obtain a solid content of 16% and a weight average molecular weight of 4.1 × 10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0075] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0076] Comparative Example 3

[0077] Compared with Example 1, the only difference is that it does not contain *Pseudomonas aeruginosa*, and the seed liquid volume ratio of *Rhodococcus roseum* and *Lactobacillus plantarum* in step (2) is 2:1. Specifically:

[0078] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0079] (1) First, Rhodococcus roseus CGMCC 1.2348 was inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2 to obtain Rhodococcus roseus seed culture; then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 0.8 to obtain Lactobacillus plantarum seed culture.

[0080] (2) The seed cultures of Rhodococcus roseus and Lactobacillus plantarum were mixed at a volume ratio of 2:1 and inoculated into the fermentation medium (containing 22 g / L glucose, 12 g / L sucrose, 14 g / L soybean meal hydrolysate, 7 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 2 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0081] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0082] (3) Dissolve 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride in water to obtain a mixture with a mass concentration of 28%. Add an initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) at a dropping rate of 0.3 mL / min. Under a nitrogen atmosphere, react at 30 °C for 6 h to obtain a solid content of 20% and a weight average molecular weight of 5.3 × 10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0083] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0084] Comparative Example 4

[0085] Compared with Example 1, the only difference is that in step (2), the seed cultures of *Pseudomonas aeruginosa*, *Rhodococcus roseum*, and *Lactobacillus plantarum* are mixed in a volume ratio of 1:1:1. Specifically:

[0086] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0087] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rosacea CGMCC 1.2348 were inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2 to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rosacea seed culture. Then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 0.8 to obtain Lactobacillus plantarum seed culture.

[0088] (2) The seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum were mixed in a volume ratio of 1:1:1 and inoculated into the fermentation medium (containing 22 g / L glucose, 12 g / L sucrose, 14 g / L soybean meal hydrolysate, 7 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 2 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0089] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0090] (3) Then, 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride were dissolved in water to obtain a mixed solution with a mass concentration of 28%. An initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) was added at a dropping rate of 0.3 mL / min. The mixture was then heated to 30 °C for 6 h under a nitrogen atmosphere to obtain a solid content of 21% and a weight average molecular weight of 8.4 × 10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0091] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0092] Comparative Example 5

[0093] Compared with Example 1, the only difference is the component ratio of the fermentation medium in step (2). Specifically:

[0094] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0095] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rosacea CGMCC 1.2348 were inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2 to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rosacea seed culture. Then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 0.8 to obtain Lactobacillus plantarum seed culture.

[0096] (2) The seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum were mixed in a volume ratio of 3:2:1 and inoculated into the fermentation medium (containing 15 g / L glucose, 18 g / L sucrose, 18 g / L soybean meal hydrolysate, 4 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 1 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0097] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0098] (3) Dissolve 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride in water to obtain a mixture with a mass concentration of 28%. Add an initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) at a dropping rate of 0.3 mL / min. Under a nitrogen atmosphere, react at 30℃ for 6 h to obtain a solid content of 22% and a weight average molecular weight of 8.2 × 10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0099] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0100] Comparative Example 6

[0101] Compared with Example 1, the only difference is the component ratio of the fermentation medium in step (2). Specifically:

[0102] A method for preparing glyoxal-modified polyacrylamide, comprising the following steps:

[0103] (1) First, Pseudomonas aeruginosa ATCC 13985 and Rhodotorula rosacea CGMCC 1.2348 were inoculated into LB medium and cultured at 180 rpm and 37℃ until the OD500 was 1.2 to obtain Pseudomonas aeruginosa seed culture and Rhodotorula rosacea seed culture. Then, Lactobacillus plantarum CCTCC NO: M20242630 was inoculated into MRS medium and cultured at 50 rpm and 37℃ until the OD500 was 0.8 to obtain Lactobacillus plantarum seed culture.

[0104] (2) The seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum were mixed in a volume ratio of 3:2:1 and inoculated into the fermentation medium (containing 30 g / L glucose, 8 g / L sucrose, 10 g / L soybean meal hydrolysate, 10 g / L yeast extract, 4 g / L dipotassium hydrogen phosphate, 1.2 g / L magnesium sulfate heptahydrate and 4 g / L sodium citrate; pH=7.2) at 200 rpm and 30℃ for 13 h to obtain the mixed seed culture.

[0105] Acrylonitrile was added to the mixed seed culture in a gradient flow until the final concentration of acrylonitrile was 4.8% (the gradient flow program for adding acrylonitrile was: 0-12 h: 0.6 g / (L·h); 12-30 h: 0.8 g / (L·h)). After fermentation at 35°C for 32 h, the mixture was filtered and dried under vacuum to obtain acrylamide.

[0106] (3) Dissolve 210 g of acrylamide and 60 g of diallyl dimethyl ammonium chloride in water to obtain a mixture with a mass concentration of 28%. Add an initiator aqueous solution with a mass concentration of 0.015% (0.024 g each of ammonium persulfate and sodium bisulfite in the initiator) at a dropping rate of 0.3 mL / min. Under a nitrogen atmosphere, the mixture is heated to 30℃ for 6 h to obtain a solid content of 24% and a weight average molecular weight of 7.8 × 10⁻⁶. 5 A cationic polyacrylamide aqueous solution at a concentration of g / mol.

[0107] (4) Prepare materials and store them separately. When using, mix the 40% glyoxal aqueous solution with the dry matter in the cationic polyacrylamide aqueous solution at a mass ratio of 1:2 and react them online at 20°C for 2 hours. After the reaction is completed, adjust the pH of the reaction solution to 3 to obtain glyoxal-modified polyacrylamide.

[0108] Test Example 1

[0109] Based on a basis weight of 80 g / m² per sheet 3Weigh the milled bleached wood pulp (the mass ratio of softwood pulp to hardwood pulp is 15:85), add deionized water, and dilute to a bleached wood pulp mass concentration of 1%. Then add the glyoxal-modified polyacrylamide obtained in Examples 1-3 and Comparative Examples 1-6 (the amount of glyoxal-modified polyacrylamide added is 1.0 wt% of the oven-dry weight of the softwood pulp). Place the above pulp into a decanter for dispersing. After dispersing is complete, add it into a paper forming machine and dry it in an oven at 100°C for 10 min to obtain household paper. Use the polyacrylamide without glyoxal modification as a control group.

[0110] (1) Dry tensile strength index: Using a tensile strength tester, the paper to be tested was cut into a rectangle of 250 mm × 15 mm according to the method of GB / T12914-2018. Each paper was measured 3 times and the average value was taken.

[0111] (2) Paper retention rate: Refer to the test standard TAPPI T261 CM-94.

[0112] The experimental results are shown in Table 1. As can be seen from Table 1, compared with Comparative Examples 1-6, the tissue paper prepared by Examples 1-3 has better dry tensile strength index and pulp retention. This indicates that the present invention, by utilizing the synergistic effect of *Pseudomonas aeruginosa*, *Rhodococcus roseum*, and *Lactobacillus plantarum*, can obtain acrylamide monomer through a one-step fermentation method, and then react it with glyoxal online to finally obtain glyoxal-modified polyacrylamide, which can significantly improve paper strength and increase retention.

[0113] Table 1 Performance parameters of household paper

[0114]

[0115] Test Example 2

[0116] The glyoxal-modified polyacrylamide obtained in Examples 1-3 and Comparative Examples 1-6 was applied to the preparation of white cardboard. The core pulp of the white cardboard (without any reinforcing agent added) was taken from a paper mill. The amount of glyoxal-modified polyacrylamide added was 1.0 wt% of the oven-dry pulp weight. The laboratory preparation yielded a basis weight of 210 g / m³. 2 White cardboard was used as a control group, with polyacrylamide without glyoxal modification added.

[0117] (1) Interlayer bonding strength: Refer to GB / T26203-2010, measure each sheet of paper 3 times and take the average value.

[0118] (2) 10 s filtration: Weigh out 2 g of dry white cardboard core pulp, put it into a fiber dissociator for dissociation, add deionized water to obtain a white cardboard pulp suspension with a mass concentration of 0.2% (pH=7.0), assemble the Buchner funnel filtration device, quickly pour in 1000 mL of pulp suspension, accurately record the volume of the filtered liquid in the first 10 s, perform three parallel tests and take the average value.

[0119] The specific test results are shown in Table 2.

[0120] Table 2 Performance parameters of white cardboard

[0121]

[0122] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing glyoxal-modified polyacrylamide, characterized in that, Includes the following steps: (1) First, mix the seed cultures of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum, inoculate them into the fermentation medium, and culture them to obtain a mixed seed culture; then add acrylonitrile in a gradient flow to continue the reaction and obtain acrylamide; (2) Then, acrylamide and diallyl dimethyl ammonium chloride are dissolved in water to obtain a mixture. An initiator is added and the mixture is heated to react, resulting in an aqueous solution of cationic polyacrylamide. (3) Finally, the cationic polyacrylamide aqueous solution is reacted with the glyoxal aqueous solution to obtain the product; In step (1), the preservation number of *Pseudomonas aeruginosa* is ATCC 13985, the preservation number of *Rhodococcus roseus* is CGMCC 1.2348, and the preservation number of *Lactobacillus plantarum* is CCTCC NO: M 20242630; the volume ratio of the seed culture of *Pseudomonas aeruginosa*, *Rhodococcus roseus*, and *Lactobacillus plantarum* is 2-3:1-2:1; the components of the fermentation medium include: glucose 20-25 g / L, sucrose 10-12 g / L, soybean meal hydrolysate 12-15 g / L, yeast extract 6-8 g / L, dipotassium hydrogen phosphate 3-4 g / L, magnesium sulfate heptahydrate 1.2-1.5 g / L, and sodium citrate 2-3 g / L; the pH of the fermentation medium is 7.2-7.

5.

2. The preparation method according to claim 1, characterized in that, The preparation process of seed liquids of Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum in step (1) includes: inoculating Pseudomonas aeruginosa, Rhodococcus roseum and Lactobacillus plantarum into activation medium, activating them, and obtaining the corresponding seed liquids.

3. The preparation method according to claim 2, characterized in that, The activation medium is LB medium or MRS medium; the activation conditions are: culture at 50-200 rpm and 35-37℃ until OD500 = 0.8-1.

2.

4. The preparation method according to claim 1, characterized in that, In step (1), the inoculation amount is 10-12%; the culture conditions are: culture at 200-300 rpm and 25-35℃ for 12-14 h.

5. The preparation method according to claim 1, characterized in that, In step (1), the gradient addition of acrylonitrile is performed as follows: 0-12 h: 0.5-0.8 g / (L·h), 12-30 h: 0.8-1 g / (L·h); the final concentration of acrylonitrile in the fermentation medium is 4.5-5%; the temperature for the continued reaction is 35-38℃, and the reaction time is 30-35 h; after the reaction is completed, filtration and vacuum drying are also performed.

6. The preparation method according to claim 1, characterized in that, In step (2), the mass concentration of the mixture is 12-28%; the initiator comprises a mixed aqueous solution of ammonium persulfate and sodium bisulfite, with a total mass concentration of 0.06-0.18%; the mass ratio of acrylamide, diallyl dimethyl ammonium chloride, ammonium persulfate, and sodium bisulfite is 100:10-30:0.01-0.1:0.01-0.1; the heating reaction is carried out in a nitrogen atmosphere at a temperature of 30-42°C for 4-6 hours; and the weight-average molecular weight of the cationic polyacrylamide is 0.5 × 10⁻⁶. 5 -10×10 5 g / mol.

7. The preparation method according to claim 6, characterized in that, In step (3), the mass fraction of the glyoxal aqueous solution is 35-45%; the mass ratio of the dry matter in the glyoxal aqueous solution to the cationic polyacrylamide aqueous solution is 0.9-1.1:2-3; the reaction temperature is 10-35℃, the reaction time is 1-4 h, and the pH is adjusted to 2.5-3.5 after the reaction is completed.

8. A glyoxal-modified polyacrylamide prepared by the preparation method according to any one of claims 1-7.

9. The application of glyoxal-modified polyacrylamide as described in claim 8 as a reinforcing agent, synergist, or water retention filtration aid in the papermaking industry.

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