A process for the production of a pulp anti-deposition agent

Abstract

This invention relates to the field of pulp and paper additives, specifically a production process for a pulp anti-deposition agent. This invention overcomes the problem of easy deposition and clogging during pulp processing. By adding maleic anhydride and hydroxyethyl acrylate to waste pulp extract for a gradient temperature-controlled reaction, and introducing mercaptopropyltrimethoxysilane for high-temperature click modification, an amphiphilic emulsion with a solid content of 20% is prepared by controlling the conductivity mutation point through phase inversion emulsification; polyaluminum chloride and polydimethyldiallyl ammonium chloride are added in a stepwise manner. The final pulp anti-deposition agent emulsion has a particle size as low as 245 nm, a static deposition inhibition rate of 92.5%, a fine adhesive retention rate of 94.2%, and a drying cylinder peel force reduced to 18.5 N / m, significantly improving filtration and tensile strength.

Description

Technical Field

[0001] This invention relates to the field of pulp and paper additives technology, specifically to a production process for a pulp anti-deposition agent. Background Technology

[0002] In modern papermaking, with the increasing recycling rate of fiber resources, waste corrugated cardboard boxes and office waste paper have become core raw materials for packaging paper production. When using these waste paper pulps for high-speed papermaking, residual chemical impurities in the pulp, such as alkyd resin inks, ethylene-vinyl acetate hot melt adhesives, styrene-butadiene rubber pressure-sensitive adhesives, and natural resin acids, become key factors restricting paper quality and production efficiency. These fine adhesives exhibit extremely strong thermal adhesion during the papermaking process, easily depositing on the wire, felt, and drying cylinder surfaces of the paper machine. This not only leads to appearance defects such as blackheads and holes in the finished paper but also causes severe cylinder sticking in the drying section, resulting in frequent paper breaks and shortened doctor blade life. Furthermore, the large amount of anionic charge carried by these impurities interferes with the charge balance of the wet-end chemical system, leading to a significant decrease in the effectiveness of traditional reinforcing agents, retention agents, and other papermaking chemicals.

[0003] Existing technologies typically employ mechanical sieving and compounding with commercially available surfactants, dispersants, or talc for processing. However, conventional physical shielding additives often suffer from the following drawbacks when dealing with complex packaging pulp: First, traditional dispersants lack sufficient affinity for hydrophobic components such as hot melt adhesives and styrene-butadiene rubber, only producing temporary physical encapsulation. This encapsulation is easily detached under high shear stress or high-temperature drying conditions, leading to secondary aggregation of impurities. Second, existing anti-deposition additives are mostly general-purpose compound products, lacking the ability to chemically anchor specific components in waste paper pulp. This prevents fine adhesives from being effectively fixed to the fibers, resulting in a continuous increase in the anionic charge of waste materials in the white water recycling system. Furthermore, while some polymeric flocculants can improve retention, they often cause excessively large flocs, leading to deterioration of pulp filtration performance and severely limiting papermaking speed.

[0004] Therefore, developing a novel anti-deposition process that can accurately identify waste pulp impurities without affecting the system's filtration performance has become a pressing technical challenge in the field of pulp and paper chemicals. To address this, a production process for a pulp anti-deposition agent is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a production process for a pulp anti-deposition agent. This invention overcomes the problem of easy deposition and clogging during pulp processing. By adding maleic anhydride and hydroxyethyl acrylate to waste pulp extract for a gradient temperature-controlled reaction, and introducing mercaptopropyltrimethoxysilane for high-temperature click modification, an amphiphilic emulsion with a solid content of 20% is prepared by controlling the conductivity mutation point through phase inversion emulsification; polyaluminum chloride and polydimethyldiallyl ammonium chloride are added in a stepwise manner. The final pulp anti-deposition agent emulsion has a particle size as low as 245 nm, a static deposition inhibition rate of 92.5%, a micro-adhesive retention rate of 94.2%, and a drying cylinder peel force reduced to 18.5 N / m, significantly improving filtration and tensile strength.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a production process for a pulp anti-deposition agent, the production process being as follows: The pulp to be treated is enzymatically pulped, and after air flotation and centrifugal dewatering, coarse impurity blocks are obtained. These blocks are then recovered by ultrasonic-assisted solvent extraction and vacuum distillation to obtain a reaction substrate. The reaction substrate is then subjected to free radical grafting, and after cooling, a silane coupling agent is added dropwise to react and obtain an anti-deposition agent emulsion precursor. By controlling the conductivity, reverse emulsification is performed to obtain the pulp anti-deposition agent.

[0007] Preferably, the oven-dry solids components of the pulp to be treated are secondary coniferous long fibers, broad-leaved short fibers, adhesives, inks, natural resins, and ash fillers; wherein, secondary coniferous long fibers account for 60%-70% of the total fiber mass; and the concentration of the pulp to be treated is 10%-12%.

[0008] Preferably, the production process of the reaction substrate is as follows: Enzymatic pulping and interfacial separation: Add 0.1-0.15% (by weight of oven-dry pulp) of a compound lipase, 0.3% of sodium hydroxide, and 0-0.15% of fatty alcohol polyoxyethylene ether or sodium dodecylbenzene sulfonate to a 10-12% concentration of untreated pulp. React at 55-60℃ for 30-40 minutes. The compound lipase directionally hydrolyzes the alkyd resin binder in the ink, and the surfactant reduces interfacial tension, promoting the peeling of adhesives such as ethylene-vinyl acetate and styrene-butadiene rubber from the fiber surface.

[0009] The complex lipase is a compound of triglyceride lipase EC3.1.1.3 and keratinase in a 4:1 ratio; its activity is ≥5000 U / g.

[0010] Air flotation enrichment and high-efficiency concentration: The slurry is diluted to 1.0%-1.2% and pumped into a multi-stage air flotation unit; 0.05% of the dry slurry mass of calcium chloride is added, and the calcium soap generated by the calcium ions and resin acid produces flocculation; the surface scum is collected by air flotation scraping, and the scum is dewatered by high-concentration centrifugation to a solid content of 40-45%, obtaining coarse impurity blocks containing organic polymers, pigments and resins.

[0011] Solvent ultrasonic purification and vacuum recovery: The coarse impurity block is added to d-limonene solvent at a mass ratio of 1:2.5-3.5, and 0.01-0.02% antioxidant is added. The mixture is ultrasonically treated at a frequency of 25-30kHz for 20-40 minutes. The cavitation effect of the ultrasound accelerates the dissolution of the polymer and the exfoliation of the pigment carbon black. The insoluble pigment is removed by filtration through a 5μm precision filter. The filtrate is then distilled under vacuum at 60-70℃ and a vacuum degree of 0.08-0.09MPa. The residue at the bottom of the column is the reaction substrate.

[0012] The apparent viscosity of the reactive substrate was measured using a Brookfield RV-DV II+Pro rotational viscometer in conjunction with a Thermo Fisher high-temperature system. A 12.0 g sample of the reactive substrate was placed in the sample container of an SC4-27 rotor and equilibrated for 30 min at a selected temperature. The rotation speed was set to 20 rpm, and three sets of data were continuously read and averaged. The apparent viscosity of the reactive substrate as a function of temperature is shown in the table below: Preferably, the antioxidant may be 2,6-di-tert-butyl-p-cresol or butylated hydroxyanisole.

[0013] The preferred production process for the anti-deposition agent emulsion precursor is as follows: The reaction substrate is heated to 130-165℃ to melt and obtain a hot-melt substrate. Under nitrogen protection, a mixture of maleic anhydride, hydroxyethyl acrylate, and initiator di-tert-butyl peroxide is added dropwise at a uniform rate over 2-3 hours; then the temperature is increased to 145-155℃ at a rate of 5℃ / min and held for 1.5-2.5 hours. Maleic anhydride provides carboxyl groups to enhance polarity, hydroxyethyl acrylate increases steric stability, and gradient temperature control ensures complete decomposition of the initiator, improves the grafting rate, and eliminates residual monomer odor. Subsequently, silane high-temperature anchoring modification is performed: the system is cooled to 85-110℃, 5-8 parts of silane coupling agent are added, and the reaction is carried out for 60-90 minutes.

[0014] Preferably, the silane coupling agent is one of mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane.

[0015] Preferably, the mass ratio of maleic anhydride, hydroxyethyl acrylate, di-tert-butyl peroxide, silane coupling agent and polyethylene oxide is 10-20:3-5:1-1.5:5-8:0.5-0.8; and the mass ratio of the reaction substrate to d-limonene is 1:2.5-3.5.

[0016] Preferably, the reverse emulsification process is as follows: Increase the rotation speed to 3000-4000 rpm, add sodium hydroxide solution to adjust the system to 35-50% of the original acid value of the pulp to be treated; add 70-85℃ deionized water dropwise at a rate of 2-3 L / min while monitoring the online conductivity; when the conductivity suddenly increases from less than 50 μS / cm to greater than 1200 μS / cm, maintain a high shear rate of 3000-4000 rpm for 2-5 min and add polyethylene oxide or nanocellulose; continue adding the remaining water until the solids content is diluted to 15%-25%. The reverse emulsification method transforms the amphiphilic polymer into a stable oil-in-water O / W microemulsion, ensuring its diffusion performance in the pulp.

[0017] The zeta potential of nanocellulose is -35mV to -50mV, the diameter is 5-20nm, the length is 500nm-2μm, and the aspect ratio is 50-200.

[0018] Preferably, pulp anti-settling agent, inorganic aluminum salt, cationic scavenger, cationic polyacrylamide and anionic polyacrylamide are sequentially added to the pulp to be treated, and recycled paper is obtained through charge destabilization and step-by-step scavenging and locking.

[0019] Preferably, in the gradient papermaking process of the pulp, an anti-deposition emulsion is first added. The hydrophobic end of the agent spontaneously adsorbs onto the residual adhesives and resin surface in the pulp, while the hydrophilic end faces outward, causing it to change from a viscous state to a hydrophilic non-viscous state. 0.1-0.2% polyaluminum chloride is added for preliminary charge destabilization, 0.04-0.12% polydimethyldiallylammonium chloride is added to capture dissolved organic waste, 0.01-0.015% cationic polyacrylamide is added to form coarse flocs, which are chemically anchored to the fibers through silane groups, and 0.002-0.008% anionic polyacrylamide is added to achieve final network locking, ensuring that impurities migrate out with the paper sheet.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By constructing a polymeric emulsion with an amphiphilic structure, in-situ encapsulation of hydrophobic adhesives such as ethylene-vinyl acetate copolymer and styrene-butadiene rubber in pulp was achieved. The emulsion particle size was controlled between 245 nm and 485 nm, and its extremely strong diffusion and penetration power reduced the anionic waste load of the pulp system. The system's cation requirement was reduced from 310.0 μeq / L in the blank pulp to 125.8 μeq / L, eliminating impurity interference and significantly improving the efficiency and stability of subsequent papermaking chemical addition.

[0021] 2. By introducing active siloxane groups at the ends of the anti-deposition agent molecules, a stable bond is established between the modified adhesive particles and the surface of secondary coniferous wood fibers. Combined with a polyelectrolyte step-interception system, the retention rate of fine adhesives is improved, and fine impurities are resource-based and fixed inside the paper sheet, preventing the accumulation of harmful components in the white water circulation system and forming wire, and reducing the wastewater treatment load in the papermaking process.

[0022] 3. By using surface-active components to modify the interfacial energy of adhesives, a hydrophilic protective film is formed on the surface of polyacrylate pressure-sensitive adhesive and ink binder, which changes the thermal adhesion characteristics of impurities. Under simulated papermaking conditions, the peel force of wet paper sheets on the surface of a 105℃ hot plate decreases from 72.5 N / m in the blank pulp to 18.5 N / m. This performance improvement significantly reduces the frequency of paper defects and paper breaks caused by impurities sticking to the cylinder during production, and extends the equipment maintenance cycle.

[0023] 4. The bridging effect of modified polymers enhances the bonding strength between fibers within the paper sheet, increasing the tensile index of hand-made sheets from 28.2 N·m / g in blank pulp to 36.5 N·m / g. Simultaneously, the uniform distribution and charge neutralization of the emulsion prevent excessive flocculation of the pulp, maintaining the water content within a favorable range of 28 to 33°SR. While improving the physical properties of the finished paper, the dewatering rate is optimized, reducing energy consumption in the drying section and achieving simultaneous optimization of strength and production capacity. Attached Figure Description

[0024] Figure 1 This is a flow chart of the production process of the pulp anti-deposition agent of the present invention; Figure 2 The results are the test results of the filtration rate and the retention rate of fine adhesives in the pulp anti-deposition agents produced in Examples 1-3 and Comparative Example 1 of this invention in specific applications. Detailed Implementation

[0025] The initial raw material was untreated pulp, which was a mixture of waste packaging pulp. The pulp concentration was a fixed 10.0%, i.e., the moisture content was 90.0%. The main raw material composition and content were as follows: the total material moisture content was 900.0 kg, and the total weight of oven-dry solids was 100.0 kg. Of the 78.0 kg of oven-dry solids fiber, the secondary coniferous long fiber accounted for 50.7 kg, or 65% of the total fiber; the broadleaf short fiber accounted for 27.3 kg, or 35% of the total fiber; it contained 6.5 kg of residual lignin, 14.0 kg of hemicellulose, and an acid value of 2.42 KOH / g.

[0026] Of the 4.0 kg of oven-dry solid adhesive: 2.2 kg of ethylene-vinyl acetate copolymer; 1.0 kg of styrene-butadiene rubber; and 0.8 kg of polyacrylate pressure-sensitive adhesive.

[0027] In 3.0 kg of oven-dry solid ink: alkyd resin binder is 1.8 kg; carbon black pigment with 97% carbon content is 1.08 kg, accounting for 36% of the total ink; and phthalocyanine blue pigment is 0.12 kg, accounting for 4% of the total ink.

[0028] In 1.5 kg of oven-dry solid natural resin: free fatty acids and resin acids account for 1.0 kg; neutral triglycerides account for 0.5 kg.

[0029] Of the 13.5 kg of oven-dry solid ash filler, 13.5 kg consists of inorganic components such as talc and calcium carbonate.

[0030] Example 1 Based on 10% concentration pulp to be treated, the following production process is carried out: S101, high-concentration pulping and compound enzymatic desorption Add 0.1% of compound lipase, 0.3% of sodium hydroxide, and 0.15% of fatty alcohol polyoxyethylene ether AEO-9 by weight of oven-dried pulp to 10% concentration pulp. React at 55℃ for 40 min to degrade the ink binder using the enzyme preparation, while the surfactant prevents the 4.0 kg of detached adhesive from re-adhesion.

[0031] S102, Multi-stage air flotation and condensation concentration The slurry was diluted to 1.2% and pumped into the flotation unit. 0.05% calcium chloride by weight of the oven-dry slurry was added to generate calcium soap for filtration. The flotation slag was collected and centrifuged to a solids content of 40%, yielding coarse impurity blocks containing ethylene-vinyl acetate, styrene-butadiene rubber, ink resin, and calcified resin acid.

[0032] S103, Solvent Extraction and Solid-Liquid Separation The coarse impurity block was added to 3 times its mass of d-limonene solvent, along with 0.01% of the antioxidant BHT. Extraction was performed using ultrasound-assisted extraction at 28 kHz for 30 min. Carbon black and phthalocyanine blue were removed by filtering through a 5 μm precision filter to ensure the purity of the reaction substrate.

[0033] S104, Vacuum-reduced pressure distillation recovery The solvent was recovered at 65℃ and 0.085MPa vacuum. The residue at the bottom of the column was the No. 1 substrate for modification, with an acid value of 11.5 mg KOH / g, which served as the core raw material for subsequent synthesis.

[0034] S201, Gradient-temperature controlled free radical grafting reaction 100 kg of reaction substrate was heated to 130 °C to melt it. Under nitrogen protection, a monomer mixture consisting of 15 kg of maleic anhydride, 5 kg of hydroxyethyl acrylate and 1.2 kg of di-tert-butyl peroxide was added dropwise. The dropwise addition time was controlled at 2 h. After the dropwise addition was completed, the temperature was raised to 150 °C and held for 2 h to completely decompose the initiator by using high temperature, thereby improving the grafting rate and reducing the residual monomer content.

[0035] S202, silane coupling agent high-temperature anchoring modification Adjust the reactor temperature to 105℃, add 5kg mercaptopropyltrimethoxysilane, and supplement with 0.05kg triethylamine as a base catalyst. Stir the reaction at 800rpm for 60min.

[0036] S203, Conversely, the quantitative control of transemulsification of fatty alcohol polyoxyethylene ether AEO-9 The material temperature is reduced to 90℃ by cooling water in the vessel jacket, and the rotation speed is increased to 3500 rpm to start the reverse emulsification process. The key quantitative indicators are as follows: Pre-neutralize, add 8% sodium hydroxide solution, and calculate the acid value in real time until the system reaches 40% of the original acid value. At this time, the system is still in a high viscosity W / O state.

[0037] Instead, add deionized water at 75°C dropwise at a rate of 2.5 L / min.

[0038] Conductivity monitoring and close observation of the online conductivity meter showed that when the amount of water added reached about 40% of the total mass of the system, the conductivity suddenly increased from 48 μS / cm to 1550 μS / cm.

[0039] Phase transition point treatment: maintain high shear for 3 minutes at the instant of conductivity jump, then add 0.5% of 4.5 million molecular weight polyethylene oxide, and continue to add the remaining water until the solid content is diluted to 20%.

[0040] Example 2 S101, High-Concentration Pulping and Anionic Surfactant-Assisted Treatment Add 0.1% of the total dry mass of compound lipase, 0.3% of sodium hydroxide, and 0.15% of anionic sodium dodecylbenzenesulfonate to a 10% concentration pulp, and react at 60℃ for 30 min.

[0041] S102, Multi-stage air flotation enrichment and mechanophysical concentration The slurry was diluted to a concentration of 1.2% and then pumped into the flotation unit. 0.05% (by weight of oven-dried slurry) of calcium chloride was added. The slag was collected and dewatered by centrifuge to a solids content of 40%, yielding coarse impurity lumps.

[0042] S103, Solvent extraction and solid-liquid separation purification The coarse impurity block was added to 3 times its mass of d-limonene solvent, and 0.02% of the antioxidant di-tert-butyl-p-cresol was added. Ultrasonic extraction was performed at 28 kHz for 30 min. The solid pigment was filtered out through a 5 µm filter to obtain a clear filtrate.

[0043] S104, Vacuum Distillation and Substrate Recovery The solvent was recovered at 65℃ and 0.085MPa vacuum to obtain reaction substrate No. 2, with an acid value of 17.5 mgKOH / g.

[0044] Synthesis of S201 through isothermal grafting reaction of highly polar monomers 100 kg of reaction substrate No. 2 was heated to 140°C, and a mixture consisting of 20 kg of maleic anhydride, 3 kg of hydroxyethyl acrylate and 1.5 kg of initiator di-tert-butyl peroxide was added dropwise at a uniform rate under nitrogen protection. The dropwise addition time was 3 h, and the reaction was maintained at 140°C for 2 h.

[0045] S202, medium-temperature silanization modification Cool the reactor to 85°C, add 5 kg of 3-aminopropyltrimethoxysilane, and add 0.1 kg of triethylamine as a base catalyst. Stir the reaction at 1200 rpm for 90 min. Before reverse emulsification, ensure that the pH of the system is adjusted to 7-8 to prevent premature self-condensation of aminosilane.

[0046] S203, high steric hindrance space-stabilized emulsification process Under high shear force of 3500 rpm, 8% sodium hydroxide solution was added to adjust the acid value to 50% of the original value, and 70℃ deionized water was added dropwise at a rate of 2.5 L / min. The online conductivity was monitored in real time until the abrupt change point reached 1200 μS / cm, and 0.8% polyethylene oxide with a molecular weight of 2 million was added to dilute the emulsion to a solid content of 20%.

[0047] Example 3 S101, high-concentration pulping and high-ratio bio-enzyme pretreatment Add 0.15% of the total dry mass of compound lipase and 0.3% of sodium hydroxide to a 10% concentration pulp, and react at 55°C for 40 minutes without adding any additional chemical surfactants.

[0048] S102, Multi-stage air flotation enrichment and high-concentration centrifugal concentration After diluting the slurry to a concentration of 1.2%, it is pumped into the flotation unit. 0.05% of the dry slurry mass of calcium chloride is added, the slag is collected and discharged, and then dewatered by centrifuge to a solid content of 45%, thus obtaining coarse impurity blocks.

[0049] S103, Solvent extraction and solid-liquid separation purification The coarse impurity block was added to 3 times its mass of d-limonene solvent without the addition of antioxidants, and ultrasonic-assisted extraction was performed at a frequency of 28 kHz for 30 min. The solid pigment was then filtered through a 5 µm filter to obtain a clear filtrate.

[0050] S104, Vacuum Distillation and Substrate Recovery The solvent was recovered at 65℃ and 0.085MPa vacuum to obtain reaction substrate No. 3, with an acid value of 16.0 mg KOH / g.

[0051] S201, high-temperature short-time grafting reaction synthesis 100 kg of reaction substrate No. 3 was heated to 165 °C, and 10 kg of maleic anhydride was added at once. Then, 5 kg of glycidyl methacrylate and 1.0 kg of initiator di-tert-butyl peroxide were added dropwise at a uniform rate over 2 hours. The reaction was maintained at 165 °C for 1 hour.

[0052] S202, high-temperature rapid silanization modification The system was cooled at a rate of 5℃ / min to maintain the temperature at 115℃. 8 kg of mercaptopropyltrimethoxysilane was added, and 0.1 kg of tetrabutylammonium bromide was added as a base catalyst. The mixture was stirred at 800 rpm for 30 min.

[0053] S203, nanocellulose physical stabilization emulsification process Under high shear at 3500 rpm, 8% sodium hydroxide solution was added to adjust the neutralization degree to 35%, and hot water at 85°C was added dropwise at a rate of 2.5 L / min. The conductivity mutation point was monitored in real time until it reached 1800 μS / cm. 0.5% nanocellulose was added, and finally diluted to a solid content of 20%.

[0054] Comparative Example 1 S101-S104, the production steps and methods are the same as in Example 1; S201-S202, Physical compounding process: 20 kg of commercially available rosin emulsion and 10 kg of nonylphenol polyoxyethylene ether emulsifier are directly added to the above melt, and stirred at 100°C for 30 min; this process does not involve chemical initiators, does not involve grafting reactions, and does not involve the addition of silane coupling agents.

[0055] S203, Direct dilution emulsification process: Start mechanical stirring and directly spray in room temperature tap water for physical dilution. Do not observe the conductivity abrupt change point, and do not control the acid value of the system. Directly dilute to a mixture with a solid content of 20%.

[0056] Test Example 1 The pulp anti-settling agents produced in the examples and comparative examples were subjected to the following specific performance tests: Take 10.0 mL of the finished emulsion into a centrifuge tube, place it in a centrifuge, and centrifuge continuously at 3000 rpm for 30 minutes. Observe whether there is sediment at the bottom of the tube, whether there is floating oil or layering on the surface, and conduct the emulsion centrifugation stability test according to GB / T 6753.3-1986. Particle size distribution was tested according to GB / T 29022-2012, using a laser particle size analyzer with dynamic optical dispersion method. The 20% solids content emulsion was diluted to 0.01% with deionized water before measurement, and the average particle size D50 and polydispersity index PDI were recorded.

[0057] Take 100 mL of mixed pulp with a concentration of 1.0% and test it using a charge titrator. Titrate with 0.001 N polydimethyldiallylammonium chloride standard solution and measure the amount of titrant consumed when the fluid potential reaches 0 mV. Refer to the relevant procedures for charge titration analysis in the industry standard TAPPI T 449.

[0058] The static deposition inhibition rate test was conducted using the circulating stirring method. A 316L stainless steel probe, precisely weighed to the nearest 0.1 mg, was suspended in a slurry container at a constant temperature of 50°C. After stirring for 4 hours, the probe was removed, gently rinsed with distilled water, dried, and reweighed. The deposition inhibition rate was calculated as [1 - (increase in deposition after chemical addition / deposition amount in blank control)] × 100%. The test was conducted in accordance with the enterprise standards for chemical evaluation in the paper industry and the relevant resin control and evaluation methods in QB / T. The test results are recorded in Table 1.

[0059] Table 1 The results in Table 1 show that Example 1 exhibited the finest particle size and the highest deposition inhibition rate, attributed to the precise control of the conductivity abrupt change point in the S203 process and the steric hindrance effect of polyethylene oxide. The fine particle size ensured that the agent possessed extremely strong diffusion and penetration power in the high-viscosity pulp to be treated, enabling efficient encapsulation of hot melt adhesive and styrene-butadiene rubber. The overall performance of Examples 2 and 3 was lower than that of Example 1.

[0060] Comparative Example 1 performed the worst across all indicators. It did not undergo the S201 free radical grafting reaction, and the large amounts of ethylene-vinyl acetate and styrene-butadiene rubber in the reaction substrate retained their original hydrophobic properties. The physically compounded surfactant, nonylphenol polyoxyethylene ether, only bound to impurities through intermolecular forces. After melting and mixing at 100°C, macroscopic phase separation occurred during cooling due to the hydrophilic-hydrophobic imbalance, resulting in significant stratification and oil floating during centrifugation. Simultaneously, due to the lack of shear control and conductivity monitoring from the S203 phase-conversion emulsification process, the system could not form a microemulsion, instead forming an irregular coarse dispersion. Large particles could not penetrate into the fine adhesive, only producing localized adhesion. Furthermore, without the addition of maleic anhydride and hydroxyethyl acrylate for grafting, the molecular chain lacked carboxyl plasma functional groups, failing to produce a chemical synergistic effect with the anions in the slurry. Its cation requirement was almost close to the blank value of the original slurry, indicating that the reagent contributed almost nothing to improving the system's charge. Due to the lack of chemical anchoring by silane coupling agents, the reagent cannot form a durable protective film on the surface of the metal probe. Under stirring shear force, the physical coating layer is easily detached, resulting in the rapid deposition of impurities on the probe surface and a significant decrease in the inhibition rate.

[0061] Application Example 1 For application treatment of slurry systems with a charge level of -280 μeq / L.

[0062] S301, Anti-deposition agent added The emulsion prepared by Example 1 S203 was added to the slurry tank at a dosage of 0.15% of the oven-dry slurry mass. The mixture was stirred at 800 rpm for 5 minutes. The hydrophobic skeleton of the agent was combined with 4.0 kg of adhesive, and the hydrophilic groups were turned outward, thus achieving polarity reversal.

[0063] S302, Inorganic Aluminum Salt Charge Destabilization Add 0.1% polyaluminum chloride by weight of the oven-dried slurry and stir for 5 minutes. The high positive charge reduces the zeta potential on the particle surface, promoting the flocculation of fine ink residue and resin.

[0064] S303, electrolyte trapping and Add 0.06% polydimethyldiallylammonium chloride (molecular weight 800,000) by weight of oven-dried slurry as a cationic trap to further neutralize dissolved organic waste.

[0065] S304, flocculant bridging Add 0.012% cationic polyacrylamide by weight of oven-dried pulp. The molecular weight is 12 million. The long chain spans the fiber and impurities, and it is firmly fixed on the 50.7 kg long fiber skeleton of coniferous wood.

[0066] Construction of S305 and anionic micropolymer system Before printing, 0.005% anionic polyacrylamide (molecular weight 15 million) by weight of oven-dried pulp is added to construct a micro-cluster locking network, ensuring that all modified impurities and pigments migrate out with the paper sheet, maintaining cleanliness.

[0067] Application Example 2 For application treatment of slurry systems with a charge level of -280 μeq / L.

[0068] S301, Anti-deposition agent added The emulsion prepared in Example 2 S203 was added to the slurry tank at a dosage of 0.20% of the oven-dry slurry mass, and stirred at 800 rpm for 5 minutes. The hydrophobic framework of the agent bonded with 4.0 kg of adhesive, with the hydrophilic groups facing outward, achieving a polarity reversal.

[0069] S302, Inorganic Aluminum Salt Charge Destabilization Add 0.1% polyaluminum chloride by weight of oven-dried slurry and stir for 5 minutes. The high positive charge reduces the zeta potential on the particle surface, promoting the flocculation of fine ink residue and resin.

[0070] S303, electrolyte trapping and Add 0.04% polydimethyldiallyl ammonium chloride (molecular weight 800,000) by weight of the oven-dried slurry. This acts as a cationic trap to further neutralize dissolved organic waste.

[0071] S304, flocculant bridging Add 0.012% cationic polyacrylamide by weight of oven-dried pulp. The molecular weight is 12 million. The long chain spans the fiber and impurities, and it is firmly fixed on the 50.7 kg long fiber skeleton of coniferous wood.

[0072] Construction of S305 and anionic micropolymer system Before printing, 0.005% anionic polyacrylamide (molecular weight 15 million) by weight of oven-dried pulp is added to construct a micro-cluster locking network, ensuring that all modified impurities and pigments migrate out with the paper sheet, maintaining cleanliness.

[0073] Application Example 3 For application treatment of slurry systems with a charge level of -280 μeq / L.

[0074] S301, Anti-deposition agent added The emulsion prepared in Example 3 S203 was added to the slurry tank at a dosage of 0.12% of the oven-dry slurry mass, and stirred at 800 rpm for 5 minutes. The hydrophobic framework of the agent bonded with 4.0 kg of adhesive, with the hydrophilic groups facing outward, achieving a polarity reversal.

[0075] S302, Inorganic Aluminum Salt Charge Destabilization Add 0.15% polyaluminum chloride by weight of oven-dried slurry, stir for 5 minutes, and use the high positive charge to reduce the zeta potential on the particle surface, promoting the flocculation of fine ink residue and resin.

[0076] S303, electrolyte trapping and Stop adding polydimethyldiallylammonium chloride.

[0077] S304, flocculant bridging Adding 0.015% cationic polyacrylamide by weight of oven-dried pulp, with a molecular weight of 12 million and long chains spanning the fibers and impurities, firmly fixes it onto the 50.7kg long fiber skeleton of coniferous wood.

[0078] Construction of S305 and anionic micropolymer system Anionic polyacrylamide (molecular weight 15 million) at 0.005% of the oven-dry pulp mass is added before paper printing. This constructs a micro-cluster locking network, ensuring that all modified impurities and pigments migrate out with the paper sheet, maintaining cleanliness.

[0079] Application Comparative Example 1 For application treatment of slurry systems with a charge level of -280 μeq / L.

[0080] S301, Anti-deposition agent added The emulsion prepared by Comparative Example 1 S203 was added to the slurry tank at a dosage of 0.30% of the oven-dry slurry mass. The mixture was stirred at 800 rpm for 5 minutes. The hydrophobic skeleton of the agent was combined with 4.0 kg of adhesive, and the hydrophilic groups were turned outward, thus achieving polarity reversal.

[0081] S302, Inorganic Aluminum Salt Charge Destabilization Add 0.2% polyaluminum chloride by weight of the oven-dried slurry and stir for 5 minutes. The high positive charge reduces the zeta potential on the particle surface, promoting the flocculation of fine ink residue and resin.

[0082] For S303 to S305, no subsequent polymeric polyelectrolyte step-by-step treatment process is performed.

[0083] Test Example 2 The above-mentioned agents were added to the pulp according to the methods in Application Examples 1-3, and the papermaking process and paper performance were evaluated. The results are shown in Table 2 and... Figure 2 As shown: The filtration performance test is conducted in accordance with GB / T 3332-2004. Weigh 2.0g of the diluted slurry with an oven-dry weight, adjust the temperature to 20℃, inject it into the Shore beating tester, and measure the amount of water discharged through the copper mesh in 1000mL of slurry. The result is expressed as beating degree °SR. The higher the value, the worse the filtration performance.

[0084] The retention rate of fine adhesives was tested according to GB / T 24324-2009. White water from the hand-making process was collected, filtered using a fiber grade classifier with a pore size of 100μm, and the organic carbon content of suspended solids in the white water was measured by a total organic carbon analyzer and compared with the original pulp. Retention rate = [1-(organic carbon content in white water / total organic carbon content in original pulp)]×100%.

[0085] The method for testing the peel force on the surface of the drying cylinder is as follows: The wet paper is applied to the surface of the 105℃ stainless steel hot plate of the simulated drying cylinder, and after drying to a moisture content of 5%, the paper is peeled off in a 180° direction using a tensile testing machine, and the average peel force per unit width (N / m) is recorded.

[0086] The tensile index test of handmade sheet is conducted in accordance with GB / T 12914-2018. Under constant temperature and humidity conditions, the handmade sheet is cut into 15mm wide samples, and its breaking tensile force is measured using an electronic tensile tester. Tensile index = breaking length / basis weight (N·m / g).

[0087] Table 2 Application Examples 1-3 showed good results after treatment in the pulping system, preventing sedimentation and clogging during the treatment process. In Application Example 1, the filtration efficiency increased slightly from 26°SR of the original pulp to 28°SR, the smallest increase, indicating that the formed floc structure was uniform and did not clog the filter screen. Due to its finest emulsion particle size and high degree of silanization, under the synergistic effect of the polyelectrolytes S304 and S305, the fine adhesives were efficiently locked onto the fiber surface, achieving a retention rate of 94.2%. Simultaneously, because the adhesives were completely encapsulated and their polarity reversed, the drying cylinder peel force decreased to 18.5 N / m, significantly improving the cylinder adhesion phenomenon. The tensile index increased because the silane coupling agent enhanced the chemical bonding between impurities and fibers, compensating for the interference of impurities on hydrogen bonds. In Application Example 2, due to the grafting of more acrylic acid monomers, the increased charge on the molecular chains led to a slight increase in filtration efficiency. However, the excessive polarity resulted in some reagent residue remaining in the aqueous phase, resulting in a slightly lower retention rate of fine adhesives compared to Application Example 1. Its peel strength was 22.4 N / m, which, while better than the blank, was slightly higher than Application Example 1. This was mainly due to the slightly weaker stability of its surface-active components during high-temperature drying. Although Application Example 3 discontinued the use of a cationic scavenger in step S303, its fine adhesive retention rate remained at a relatively high level of 90.8%, and its tensile index was better than Application Example 2. This was primarily because the nanocellulose played a supporting role in the system's strength.

[0088] Comparative Example 1 exhibited significant difficulties in filtration, high adhesion, and low strength. Without grafting, the polyacrylate pressure-sensitive adhesive and natural resin were in a free or coarse emulsified state. Unmodified hydrophobic substances agglomerated randomly after the addition of polyaluminum chloride in S302. These coarse hydrophobic aggregates filled the tiny pores between fibers during paper forming, causing a significant increase in freeness to 45°SR, severely impacting production efficiency. Due to the lack of effective affinity between the chemically encapsulated adhesive and fibers, and without the stepwise polymer trapping in steps S303-S305, the charge neutralization of polyaluminum chloride alone was insufficient to fix the fine adhesives. A large amount of impurities were lost with the white water, resulting in low retention. The high peel force on the drying cylinder surface was mainly due to… Because the agent lacks silane coupling agents and grafted functional groups, it cannot form a protective layer on the surface of impurities. Since the ink binder and hot melt adhesive have extremely high surface adhesion at 105℃, they directly adhere physically when in contact with the hot plate of the simulated drying cylinder, with a peel force of 65.8 N / m, which means that paper breakage is very likely to occur in actual production. Unmodified hydrophobic impurities, as a physical isolation layer, cover the surface of coniferous and hardwood fibers, hindering the approach of hydroxyl groups between fibers and the formation of hydrogen bonds. The tensile index of Comparative Example 1, 25.5 N·m / g, is even lower than the blank value of 28.2 N·m / g of the original pulp, indicating that the physically compounded additives actually worsen the bonding quality between fibers.

[0089] In summary, Application Example 1 achieves the optimal balance in terms of particle size control, charge neutralization, deposition suppression, and paper strength improvement. While Application Example 2 has a high grafting rate, its excessive polarity leads to slightly inferior stability during high-temperature drying. Application Example 3, influenced by the introduction of nanocellulose, exhibits good retention, but its water absorption burden and distribution uniformity are slightly lacking. Comparative Application Example 1 verifies that purely physical methods cannot solve the problem of fouling in complex waste paper pulp and may even worsen the papermaking environment.

[0090] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A production process for a pulp anti-settling agent, characterized in that, The production process is as follows: Lipase and fatty alcohol polyoxyethylene ether were used to enzymatically break down the pulp to be treated. After adding calcium chloride for air flotation and centrifugal dewatering, coarse impurity blocks were obtained. The reaction substrate was obtained by ultrasonic-assisted solvent extraction and vacuum distillation of d-limonene. The reaction substrate is melted to obtain a hot-melt substrate; a monomer mixture is added dropwise to the hot-melt substrate to carry out a free radical grafting reaction; after cooling, a silane coupling agent is added dropwise to react and obtain an anti-deposition agent emulsion precursor; the conductivity is controlled to carry out reverse emulsification to obtain the pulp anti-deposition agent.

2. The production process of the pulp anti-settling agent according to claim 1, characterized in that, The oven-dry solids components of the pulp to be treated are secondary coniferous long fibers, broad-leaved short fibers, adhesives, inks, natural resins, and ash fillers; wherein, the secondary coniferous long fibers account for 60%-70% of the total fiber mass; and the concentration of the pulp to be treated is 10%-12%.

3. The production process of the pulp anti-settling agent according to claim 1, characterized in that, The production process of the reaction substrate is as follows: the crude impurity block is added to the d-limonene, and the antioxidant is added, followed by ultrasonic-assisted extraction; The filter element removes solid pigments and carbon black to obtain a clear filtrate; the filtrate is then subjected to vacuum distillation to recover the solvent, and the residue at the bottom of the distillation column is the reaction substrate.

4. The production process of the pulp anti-settling agent according to claim 1, characterized in that, The production process of the anti-deposition agent emulsion precursor is as follows: the reaction substrate is heated to 130-140℃ to melt, and the monomer mixture composed of maleic anhydride, hydroxyethyl acrylate and di-tert-butyl peroxide is added dropwise under nitrogen protection for 2-3 hours; after the addition is completed, the temperature is raised to 145-155℃ and kept at that temperature for 1.5-2.5 hours; after cooling to 85-110℃, the silane coupling agent is added to react, and polyethylene oxide is added to obtain the anti-deposition agent emulsion precursor.

5. The production process of the pulp anti-settling agent according to claim 4, characterized in that, The mass ratio of maleic anhydride, hydroxyethyl acrylate, di-tert-butyl peroxide, silane coupling agent, and polyethylene oxide is 10-20:3-5:1-1.5:5-8:0.5-0.8; the mass ratio of the reaction substrate to d-limonene is 1:2.5-3.

5. The silane coupling agent is one of mercaptopropyltrimethoxysilane and 3-aminopropyltrimethoxysilane.

6. The production process of the pulp anti-settling agent according to claim 1, characterized in that, The reverse emulsification process is as follows: add sodium hydroxide solution to adjust the system to 35%-50% of the original acid value; add deionized water at 70-85℃ at a rate of 2-3L / min and monitor the online conductivity; shear and add stabilizer, and continue to add the remaining water to dilute the solids; The stabilizer is one of polyethylene oxide and nanocellulose.

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