Modified stripping agent for papermaking and preparation method thereof

Abstract

The invention relates to the field of stripping agents, in particular to a preparation method of a modified stripping agent for papermaking, and the modified stripping agent for papermaking is prepared from the following raw materials in parts by mass: 45-55 parts of vinyl silicone oil, 2-4 parts of vinyl trimethylsilane, 2-4 parts of an OP-10 emulsifier, 10-15 parts of a modified polyurethane emulsion and 8-12 parts of butyl acrylate. According to the stripping agent, an environment-friendly material system is innovatively designed to achieve the synergistic effect with dynamic functional components, specific process regulation is combined, multi-dimensional optimization of the performance of the stripping agent is achieved, and compared with the prior art, a novel hydrophobic structure and an intelligent response network are adopted, so that the stability and safety of the product are remarkably improved; meanwhile, by strengthening the interface bonding capacity, it is ensured that the stripping force is accurate and controllable, the production and maintenance cost is reduced, and the adhesive is suitable for high-requirement scenes such as food packaging and high-speed paper machines and has wide market application prospects.

Description

Technical Field

[0001] The present invention relates to the field of release agents, and particularly to a modified release agent for papermaking and a preparation method thereof. Background Art

[0002] In the papermaking industry, a release agent is a key auxiliary agent to improve the production efficiency and finished product quality of paper. Its main function is to reduce the adhesion between the paper and the forming die, drying cylinder or pressure roller, thereby avoiding paper tearing, surface damage or production interruption. With the development of high-speed papermaking technology, the performance requirements for release agents are increasing day by day.

[0003] The main components of the release agent are silicone oil, emulsifier and polyurethane substances. Although the silicon-based release agent has good lubricity, it is prone to oxidative decomposition in high-temperature or high-humidity environments, resulting in unstable release effects. While the polyurethane-based release agent can improve the film-forming property, the residues may affect the subsequent printing or coating performance of the paper.

[0004] In the prior art, superhydrophobicity is achieved by adding perfluorinated compounds, resulting in environmental persistent pollution risks and biotoxicity problems of the materials. Although non-fluorinated superhydrophobic materials can increase the contact angle, due to the decrease in the flexibility of the molecular chain, the brittleness of the film increases, making it difficult to withstand the mechanical shear force of high-speed paper machines. Moreover, traditional release agents have poor wear resistance, affecting the continuous production of high-speed paper machines.

[0005] Therefore, according to the above related technologies, it is urgent to develop a modified release agent for papermaking and a preparation method thereof. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a modified release agent for papermaking and a preparation method thereof to solve the problems of poor environmental compliance, insufficient performance stability and poor wear resistance in the prior art.

[0007] Based on the above purpose, the present invention provides a modified release agent for papermaking and a preparation method thereof.

[0008] A modified release agent for papermaking is prepared from the following raw materials in parts by mass: 45-55 parts of vinyl silicone oil, 2-4 parts of vinyltrimethylsilane, 2-4 parts of OP-10 emulsifier, 10-15 parts of modified polyurethane emulsion, 8-12 parts of butyl acrylate, 6-8 parts of octadecyl acrylate, 1-3 parts of polyamide-amine dendrimer, 0.5-1 part of potassium persulfate, 1-1.5 parts of azobisisobutyronitrile, 1-3 parts of glycidyl methacrylate; The modified polyurethane emulsion is prepared from a modified polyisocyanate and a polyol containing a phosphate ester group.

[0009] A preparation method of a modified stripping agent for papermaking is as follows: Step S1: Under a nitrogen atmosphere, vinyl silicone oil, vinyltrimethylsilane, and OP-10 emulsifier are added to deionized water. The temperature is raised to 20 - 30 °C, and stirred for 20 - 40 min at a rotation speed of 1800 - 2200 rpm. Then the temperature is raised to 70 - 80 °C, potassium persulfate is added, and stirred and reacted for 2 - 3 h at a rotation speed of 400 - 600 rpm. After the reaction is completed, a silicone emulsion mixture is obtained; Step S2: The silicone emulsion mixture is added to a flask, the temperature is raised to 70 - 80 °C, and the rotation speed is 200 - 400 rpm. Modified polyurethane emulsion, butyl acrylate, polyamidoamine dendrimer, octadecyl acrylate, and azobisisobutyronitrile are added, and reacted for 3 - 5 h. After the reaction is completed, the temperature is lowered to 50 - 60 °C, glycidyl methacrylate is added, and stirred and reacted for 50 - 70 min at a rotation speed of 150 - 250 rpm. A 10 wt% citric acid solution is added to adjust the pH to 6.5 - 7, and filtered to obtain the modified stripping agent; Potassium persulfate and azobisisobutyronitrile are initiators, and glycidyl methacrylate is a crosslinking agent; By constructing a fluorine-free superhydrophobic silicone hybrid system, a micro-nano rough structure is formed synergistically by long-chain alkyl groups and polyamidoamine dendrimers to increase the contact angle and avoid the use of traditional perfluorinated compounds, thus avoiding the risk of environmental persistent pollution; By optimizing the formula, toxic components in traditional stripping agents are discarded, and biocompatible raw materials butyl acrylate and glycidyl methacrylate are introduced to reduce the toxicity of the paper and expand the application range of the paper.

[0010] Preferably, in step S1, the mass ratio of the vinyl silicone oil, vinyltrimethylsilane, OP-10 emulsifier, and potassium persulfate is 45 - 55:2 - 4:2 - 4:0.5 - 1.

[0011] Preferably, in step S2, the mass ratio of the silicone emulsion mixture, modified polyurethane emulsion, butyl acrylate, polyamidoamine dendrimer, octadecyl acrylate, azobisisobutyronitrile, and glycidyl methacrylate is 50 - 60:12 - 15:8 - 10:1 - 3:6 - 8:1 - 1.5:1 - 3.

[0012] Preferably, for the modified polyurethane emulsion, its preparation method is as follows: Add the modified polyisocyanate and the polyol containing phosphate groups into a three-necked flask, heat up to 80 - 90 °C, react for 2 - 4 h, cool down to 35 - 55 °C, add dimethylolpropionic acid and 1,4-butanediol, heat up to 70 - 90 °C, react for 60 - 90 min, cool down to 35 - 50 °C, add the catalyst dibutyltin dilaurate, then heat up to 60 - 80 °C, react for 3 - 5 h. After the reaction is completed, cool down to 30 - 50 °C, neutralize with triethylamine, emulsify with deionized water, and perform vacuum distillation to obtain the modified polyurethane emulsion.

[0013] Preferably, the mass ratio of the modified polyisocyanate, the polyol containing phosphate groups, dimethylolpropionic acid, 1,4-butanediol and the catalyst is 5.2 - 5.5:1:0.08 - 0.13:0.09 - 0.12:0.035 - 0.051.

[0014] Preferably, the preparation method of the modified polyisocyanate is as follows: Step A1: Add cyanuric chloride into the mixed solution of acetone and deionized water, add 4-(2-furyl)aniline, heat up to 10 - 20 °C, react for 20 - 40 min, then heat up to 50 - 70 °C, react for 2 - 3 h. After the reaction is completed, obtain Intermediate 1; The volume ratio of acetone to deionized water is 1:1.5.

[0015] Step A2: Add 4-maleimidophenol into the toluene solvent, stir evenly, heat up to 70 - 90 °C, add Intermediate 1, react for 5 - 7 h. After the reaction is completed, cool down to 20 - 30 °C, let stand for 50 - 70 min, filter, and dry to obtain Intermediate 2; Step A3: Add Intermediate 2 and 1,5-pentane diisocyanate into the toluene solvent, stir evenly, add the catalyst dibutyltin dilaurate, heat up to 70 - 90 °C, react for 2 - 4 h, cool down, and perform low-pressure distillation to obtain the modified polyisocyanate; Construct an intelligent response network through the furyl group and the maleimide group, reduce the shutdown maintenance frequency during the high-speed papermaking process, and improve the paper production efficiency; Through the triazine group and the phosphate group, the release agent can combine with Ca on the surface of the paper filler CaCO 3 Ca 2+ by electrostatic interaction and covalent bond, thereby enhancing the adhesion of the release agent to the substrate and ensuring the stability of continuous production of the high-speed paper machine.

[0016] Preferably, the mass ratio of cyanuric chloride to 4-(2-furyl)aniline in Step A1 is 1:2.4 - 2.6; The mass ratio of 4-maleimidophenol to Intermediate 1 in Step A2 is 0.6 - 0.7:1; In step A3, the mass ratio of intermediate 2, 1,5-pentane diisocyanate to dibutyltin dilaurate is 1:0.4 - 0.5:0.003 - 0.008.

[0017] Preferably, for the phosphoric acid ester group-containing polyol, its preparation method is as follows: Add polyether diol 400 into a beaker, heat up to 90 - 100 °C, dehydrate for 50 - 70 min, cool down to 20 - 40 °C, add toluene and triethylamine, stir evenly, then add phosphorus oxychloride, react for 3 - 5 h, separate the layers, and perform vacuum distillation to obtain the phosphoric acid ester group-containing polyol.

[0018] Preferably, the mass ratio of polyether diol 400, toluene, triethylamine to phosphorus oxychloride is 7 - 8:0.9 - 1.1:1.8 - 2:1.

[0019] Advantages of the present invention: The present invention provides a modified peeling agent for papermaking and its preparation method. Through innovative design of the environmentally friendly material system and the synergistic effect of dynamic functional components, combined with specific process regulation, multi-dimensional optimization of the performance of the peeling agent is achieved. Compared with the prior art, this solution abandons traditional harmful components, adopts a new hydrophobic structure and an intelligent response network, significantly improves the stability and safety of the product, and at the same time ensures precise control of the peeling force by strengthening the interfacial binding ability, and reduces the production and maintenance costs. It is applicable to high-demand scenarios such as food packaging and high-speed paper machines, and has broad market application prospects. Description of the drawings

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is the synthesis route diagram of the modified polyisocyanate in the present invention. Detailed implementation manners

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the following further details the present invention in combination with specific embodiments.

[0023] Example 1: A preparation method of a phosphoric acid ester group-containing polyol.

[0024] Add 700 g of polyether diol 400 into a beaker, heat up to 90 °C, dehydrate for 70 min, cool down to 20 °C, add 90 g of toluene and 180 g of triethylamine, stir evenly, then add 100 g of phosphorus oxychloride, react for 5 h, separate the layers, and perform vacuum distillation to obtain a polyol containing phosphate ester groups.

[0025] Example 2: A method for preparing a polyol containing phosphate ester groups.

[0026] Add 750 g of polyether diol 400 into a beaker, heat up to 95 °C, dehydrate for 60 min, cool down to 30 °C, add 95 g of toluene and 190 g of triethylamine, stir evenly, then add 100 g of phosphorus oxychloride, react for 4 h, separate the layers, and perform vacuum distillation to obtain a polyol containing phosphate ester groups.

[0027] Example 3: A method for preparing a polyol containing phosphate ester groups.

[0028] Add 800 g of polyether diol 400 into a beaker, heat up to 100 °C, dehydrate for 50 min, cool down to 40 °C, add 100 g of toluene and 200 g of triethylamine, stir evenly, then add 100 g of phosphorus oxychloride, react for 3 h, separate the layers, and perform vacuum distillation to obtain a polyol containing phosphate ester groups.

[0029] Example 4: A method for preparing a modified polyisocyanate S1: Add 100 g of cyanuric chloride into a mixed solution of 200 mL of acetone and 300 mL of deionized water, add 240 g of 4-(2-furyl)aniline, heat up to 10 °C, react for 40 min, then heat up to 50 °C, react for 3 h, after the reaction is completed, obtain intermediate 1; S2: Add 60 g of 4-maleimidophenol into 200 mL of toluene solvent, stir evenly, heat up to 70 °C, add 100 g of intermediate 1, react for 7 h, after the reaction is completed, cool down to 20 °C, stand for 70 min, filter, and dry to obtain intermediate 2; S3: Add 100 g of intermediate 2 and 40 g of 1,5-pentane diisocyanate into 150 mL of toluene solvent, stir evenly, add 0.3 g of catalyst dibutyltin dilaurate, heat up to 70 °C, react for 4 h, cool down, and perform low-pressure distillation to obtain a modified polyisocyanate.

[0030] Example 5: A method for preparing a modified polyisocyanate S1: Add 100 g of cyanuric chloride into a mixed solution of 200 mL of acetone and 300 mL of deionized water, add 250 g of 4-(2-furyl)aniline, heat up to 15 °C, react for 30 min, then heat up to 60 °C, react for 2.5 h, after the reaction is completed, obtain intermediate 1; S2: Add 65 g of 4-maleimidophenol to 200 mL of toluene solvent, stir evenly, heat up to 80 °C, add 100 g of Intermediate 1, react for 6 h. After the reaction is completed, cool down to 25 °C, let stand for 60 min, filter, and dry to obtain Intermediate 2; S3: Add 100 g of Intermediate 2 and 45 g of 1,5-pentanediisocyanate to 150 mL of toluene solvent, stir evenly, add 0.5 g of the catalyst dibutyltin dilaurate, heat up to 80 °C, react for 3 h, cool down, and perform low-pressure distillation to obtain the modified polyisocyanate.

[0031] Example 6: A preparation method of a modified polyisocyanate S1: Add 100 g of cyanuric chloride to a mixed solution of 200 mL of acetone and 300 mL of deionized water, add 260 g of 4-(2-furyl)aniline, heat up to 20 °C, react for 20 min, then heat up to 70 °C, react for 2 h. After the reaction is completed, obtain Intermediate 1; S2: Add 70 g of 4-maleimidophenol to 200 mL of toluene solvent, stir evenly, heat up to 90 °C, add 100 g of Intermediate 1, react for 5 h. After the reaction is completed, cool down to 30 °C, let stand for 50 min, filter, and dry to obtain Intermediate 2; S3: Add 100 g of Intermediate 2 and 50 g of 1,5-pentanediisocyanate to 150 mL of toluene solvent, stir evenly, add 0.8 g of the catalyst dibutyltin dilaurate, heat up to 90 °C, react for 2 h, cool down, and perform low-pressure distillation to obtain the modified polyisocyanate.

[0032] Example 7: A preparation method of a modified polyurethane emulsion Add 52 g of the modified polyisocyanate and 10 g of the phosphate group-containing polyol to a three-necked flask, heat up to 80 °C, react for 4 h, cool down to 35 °C, add 0.8 g of dimethylolpropionic acid and 0.9 g of 1,4-butanediol, heat up to 90 °C, react for 60 min, cool down to 50 °C, add 0.35 g of the catalyst dibutyltin dilaurate, then heat up to 60 °C, react for 5 h. After the reaction is completed, cool down to 30 °C, neutralize with triethylamine, emulsify with deionized water, and perform reduced-pressure distillation to obtain the modified polyurethane emulsion.

[0033] Example 8: A preparation method of a modified polyurethane emulsion Add 53 g of modified polyisocyanate and 10 g of polyol containing phosphate ester groups into a three-necked flask, heat up to 85 °C, react for 3 h, cool down to 40 °C, add 1 g of dimethylolpropionic acid and 1 g of 1,4-butanediol, heat up to 80 °C, react for 75 min, cool down to 40 °C, add 0.4 g of the catalyst dibutyltin dilaurate, then heat up to 70 °C, react for 4 h. After the reaction is completed, cool down to 40 °C, neutralize with triethylamine, emulsify with deionized water, and perform vacuum distillation to obtain a modified polyurethane emulsion.

[0034] Example 9: A preparation method of a modified polyurethane emulsion Add 55 g of modified polyisocyanate and 10 g of polyol containing phosphate ester groups into a three-necked flask, heat up to 90 °C, react for 2 h, cool down to 55 °C, add 1.3 g of dimethylolpropionic acid and 1.2 g of 1,4-butanediol, heat up to 70 °C, react for 90 min, cool down to 35 °C, add 0.51 g of the catalyst dibutyltin dilaurate, then heat up to 60 °C, react for 5 h. After the reaction is completed, cool down to 30 °C, neutralize with triethylamine, emulsify with deionized water, and perform vacuum distillation to obtain a modified polyurethane emulsion.

[0035] Example 10: A preparation method of a modified peeling agent for papermaking S1: Under a nitrogen atmosphere, add 45 g of vinyl silicone oil, 2 g of vinyltrimethylsilane, and 2 g of OP-10 emulsifier into 100 g of deionized water, heat up to 20 °C, stir for 40 min at a rotation speed of 1800 rpm, then heat up to 80 °C, add 0.5 g of potassium persulfate, stir and react for 2 h at a rotation speed of 600 rpm. After the reaction is completed, obtain a silicone emulsion mixture. S2: Add 50 g of the silicone emulsion mixture into a flask, heat up to 70 °C, at a rotation speed of 400 rpm, add 12 g of the modified polyurethane emulsion, 8 g of butyl acrylate, 6 g of polyamide-amine dendrimer, 1 g of octadecyl acrylate, and 1 g of azobisisobutyronitrile, react for 5 h. After the reaction is completed, cool down to 50 °C, add glycidyl methacrylate, stir and react for 70 min at a rotation speed of 150 rpm, add 10 wt% citric acid solution, adjust the pH to 6.5 - 7, and filter to obtain a modified peeling agent.

[0036] Example 11: A preparation method of a modified peeling agent for papermaking S1: Under a nitrogen atmosphere, add 50 g of vinyl silicone oil, 3 g of vinyltrimethylsilane, and 3 g of OP-10 emulsifier into 100 g of deionized water, heat up to 25 °C, stir for 30 min at a rotation speed of 2000 rpm, then heat up to 75 °C, add 0.8 g of potassium persulfate, stir and react for 2.5 h at a rotation speed of 500 rpm. After the reaction is completed, obtain a silicone emulsion mixture. S2: Add 55 g of silicone emulsion mixture into a flask, heat up to 75 °C, with a rotation speed of 300 rpm, add 13 g of modified polyurethane emulsion, 9 g of butyl acrylate, 2 g of polyamidoamine dendrimer, 7 g of octadecyl acrylate and 1.2 g of azodiisobutyronitrile, react for 4 h. After the reaction is completed, cool down to 55 °C, add 2 g of glycidyl methacrylate, stir and react for 60 min, with a rotation speed of 200 rpm, add 10 wt% citric acid solution, adjust the pH to 6.5 - 7, filter to obtain the modified release agent.

[0037] Example 12: A preparation method of a modified release agent for papermaking S1: Under a nitrogen atmosphere, add 55 g of vinyl silicone oil, 4 g of vinyltrimethylsilane and 4 g of OP-10 emulsifier into 100 g of deionized water, heat up to 30 °C, stir for 20 min, with a rotation speed of 2200 rpm, then heat up to 70 °C, add potassium persulfate, stir and react for 3 h, with a rotation speed of 400 rpm. After the reaction is completed, obtain the silicone emulsion mixture. S2: Add 60 g of silicone emulsion mixture into a flask, heat up to 80 °C, with a rotation speed of 200 rpm, add 15 g of modified polyurethane emulsion, 10 g of butyl acrylate, 3 g of polyamidoamine dendrimer, 8 g of octadecyl acrylate and 1.5 g of azodiisobutyronitrile, react for 5 h. After the reaction is completed, cool down to 50 °C, add 3 g of glycidyl methacrylate, stir and react for 70 min, with a rotation speed of 150 rpm, add 10 wt% citric acid solution, adjust the pH to 6.5 - 7, filter to obtain the modified release agent.

[0038] Comparative Example 1: In this comparative example, compared with Example 10, polyamidoamine dendrimer was not added during the preparation process of the modified release agent, and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified release agent was obtained.

[0039] Comparative Example 2: In this comparative example, compared with Example 10, only "vinyl silicone oil and vinyltrimethylsilane" was replaced with "equal mass of perfluorooctanoic acid", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified release agent was obtained.

[0040] Comparative Example 3: In this comparative example, compared with Example 10, only "phosphate group-containing polyol" was replaced with "polyether diol 400", and the remaining steps and parameters were the same. This comparative example will not be repeated here, and finally the modified release agent was obtained.

[0041] Comparative Example 4: This comparative example is the same as Example 10 except that "potassium persulfate" is replaced with "ammonium persulfate". The remaining steps and parameters are the same, so this comparative example will not be repeated here. Finally, a modified stripping agent is obtained.

[0042] Comparative Example 5: This comparative example is the same as Example 10 except that "4-maleimidophenol" is replaced with "4-aminophenol". The remaining steps and parameters are the same, so this comparative example will not be repeated here. Finally, a modified stripping agent is obtained.

[0043] Comparative Example 6: This comparative example is the same as Example 10 except that the amount of butyl acrylate is increased to 15 g during the preparation of the modified stripping agent. The remaining steps and parameters are the same, so this comparative example will not be repeated here. Finally, a modified stripping agent is obtained.

[0044] Preparation of experimental samples Add 100 g of ethanol and 50 g of propylene glycol monomethyl ether to 700 g of deionized water, stir evenly, and add the modified stripping agents prepared in Examples 10 - 12 and Comparative Examples 1 - 6 respectively. Stir at a speed of 800 - 1000 rpm, and adjust the pH to 6.5 - 7.0 with 10% wt citric acid solution to obtain experimental samples.

[0045] Performance testing: Stripping force test Refer to the test standard of GB / T2792 - 2014 and use an MTS - Criterion universal material testing machine; 1. Take the experimental samples of Examples 10 - 12 and Comparative Examples 1 - 6 respectively, and evenly coat them on copperplate paper with a basis weight of 80 g / m 2 and paper filled with CaCO 3 . Place them in a thermostatic and humidistatic chamber at a temperature of 25°C ± 1°C and a humidity of 50% RH ± 5% for 24 h of curing; 2. Take them out, fix them on a stripping fixture, with a stripping angle of 180°, a tensile speed of 300 mm / min, and take the average stripping force in the stable section, unit: N / m.

[0046] Abrasion resistance test Refer to the test standard of ASTM D4060 - 19 and use a Taber - 5135 abrasion tester; Take the experimental samples of Examples 10 - 12 and Comparative Examples 1 - 6 respectively and coat them on paper. Cut the paper into circular pieces with a diameter of 100 mm, fix them on the abrasion tester turntable, with a load of 500 g / rotation, and conduct 100 abrasion cycles. Record the mass loss of the sample after abrasion and the visual surface wear grade, and calculate the abrasion resistance index: Contact angle test Refer to the test standard of ISO 19403-2:2017, and use a DSA25 contact angle measuring instrument; Respectively take the experimental samples of Examples 10-12 and Comparative Examples 1-6 and coat them on the paper. The paper is cut into 20mm×20mm, 3 μL of deionized water is added dropwise, and a high-speed camera is used to record the droplet morphology. The software automatically calculates the contact angle, unit: °. Five different positions of each sample are measured, and the average value is taken.

[0047] Table 1 Detection data of Examples 10-12 and Comparative Examples 1-6 Thermal stability test Refer to the test standard of GB / T 1735-2009, and use a UF110 high-temperature oven and a Q500 thermogravimetric analyzer; 1. Static thermal aging: Respectively take the experimental samples of Examples 10-12 and Comparative Examples 1-6 and coat them on the samples, place them in the oven, heat up to 100°C ± 2°C, and keep for 24 h, and observe whether the coating cracks, peels off or discolors 2. Dynamic thermal analysis: Respectively take 10 mg of the dry experimental samples of Examples 10-12 and Comparative Examples 1-6, put them into the crucible, under the nitrogen atmosphere, with a heating rate of 10°C / min and a temperature range of 30-600°C, record the thermal decomposition temperature (Td, the temperature corresponding to a 5% weight loss) and the char residue rate.

[0048] Table 2 Thermal stability data of Examples 10-12 and Comparative Examples 1-6 Environmental protection test Refer to the test standard of GB18582-2020, and use a UNITY2 thermal desorption instrument and an Agilent -7890B gas chromatograph. Chromatographic column: DB-5 capillary column, 30m×0.25mm×0.25μm, inlet temperature: 250°C, detector temperature: 280°C; 1. Respectively take 5 g of the experimental samples of Examples 10-12 and Comparative Examples 1-6, put them into a clean aluminum foil weighing dish, under the nitrogen atmosphere with a flow rate of 50 mL / min, put them into the oven, heat up to 105°C, bake for 1 h, and carry the volatile substances into the adsorption tube; 2. Connect the adsorption tube to the thermal desorption instrument, set the desorption temperature at 280°C and the desorption time at 10 min. The desorbed gas is directly introduced into the GC injection port, initially maintained at 50°C for 2 min, heated to 250°C at a rate of 10°C / min, and maintained for 5 min; 3. VOC content formula: Where: m 0: Mass of the blank adsorption tube (g); m 2 : Total mass of the adsorption tube and volatile substances (g); m 1 : Initial mass of the sample (g).

[0049] Table 3 Thermal stability data of Examples 10 - 12 and Comparative Examples 1 - 6 Dynamic response ability detection Take 5 mL each of Examples 10 - 12 and Comparative Examples 1 - 6 respectively, evenly coat the samples on the lower plate, slowly close the clamp until the gap is 1 mm, start the DHR - 3 rotational rheometer, the initial temperature is 25°C, keep constant temperature for 5 min, heat up to 80°C at a rate of 2°C / min, keep for 5 min, cool down to 25°C at a rate of 2°C / min, and keep for 5 minutes; the shear rate is constant at 100 s -1 , and the data acquisition frequency is 1 Hz; By integrating the viscosity difference region of the heating and cooling curves, calculate the area (unit: Pa·s·°C), and the viscosity recovery rate calculation formula: (η 峰值 is the maximum viscosity at 80°C) Table 4 Dynamic response ability detection data of Examples 10 - 12 and Comparative Examples 1 - 6 Data analysis: As can be seen from Tables 1 - 4, the modified release agent prepared by the present invention has better interfacial binding force, abrasion resistance, hydrophobicity, thermal stability, environmental protection and dynamic response ability; In Comparative Example 1, due to the absence of polyamidoamine dendrimer, the surface structure is loose, the abrasion resistance decreases, and it cannot effectively bind to the paper filler, resulting in weakened adhesion. The thermal stability and dynamic response ability also decrease due to the lack of cross - linked network. The reason is that polyamidoamine dendrimer can have a synergistic effect with long - chain alkyls, and by constructing a rough structure, the hydrophobicity and interfacial binding force of the release agent can be improved; In Comparative Example 2, due to replacing vinyl silicone oil and vinyltrimethylsilane with perfluorooctanoic acid of equal mass, the contact angle increases, but its VOC content increases sharply. The reason is that perfluorooctanoic acid contains a large number of C - F bonds, and C - F bonds have superhydrophobicity. Although the contact angle is increased through the superhydrophobicity of C - F bonds, at high temperatures, the carboxylic acid groups in perfluorooctanoic acid will undergo decarboxylation reaction, releasing CO 2and fluorine-containing fragments, resulting in a sharp increase in the VOC content. At the same time, perfluorooctanoic acid itself has been listed as a persistent organic pollutant. In addition, its self-healing mechanism declines because the bond energy of the C-F bond in perfluorooctanoic acid is high. Although it endows certain chemical inertness, it also enhances the rigidity of the molecular chain. Moreover, the electronegativity of fluorine atoms is extremely high, making the C-F bond highly polar. However, the intermolecular force is mainly van der Waals force, resulting in the difficulty of perfluorinated compounds to form effective compatibility with other polar components, destroying the flexibility of the dynamic network. And the rigid molecular chain is difficult to undergo conformational changes when stressed, limiting the deformation ability of the material under mechanical stress and leading to a decrease in the dynamic response recovery rate; In Comparative Example 3, since the polyol containing a phosphate ester group was replaced by polyether diol 400, the adhesion of its release agent to the substrate was lost, the release force increased, and the coating was prone to peeling. At the same time, an effective hydrophobic structure could not be formed because the negative charge of the phosphate ester group could directly attract Ca 2+ , forming an ion pair, thereby providing initial interfacial binding force and enabling the release agent to be quickly adsorbed on the surface of the filler. At the same time, the long-chain structure of the polyol can form multiple anchor points of the phosphate ester group on the surface of the filler, further enhancing the binding stability. In addition, the stable bonding can prevent the release agent from falling off under mechanical stress and maintain the integrity of the coating, thereby optimizing the wear resistance index. And the bond energy of the Ca-O-P bond formed by the phosphate ester group and Ca 2+ is relatively high and is not easily broken at high temperatures, resulting in a higher thermal decomposition temperature of the release agent containing a phosphate ester group; In Comparative Example 4, since potassium persulfate was replaced by ammonium persulfate, the crosslinking density was insufficient, affecting the thermal stability and dynamic response ability. At the same time, the residual by-products increased the VOC emissions because the decomposition temperature of potassium persulfate is higher than that of ammonium persulfate, and the free radical release rate of potassium persulfate as an initiator is moderate, which is conducive to controlling the polymerization reaction process, avoiding local over-reaction, and ensuring the uniformity of the crosslinked network. Moreover, the high crosslinking degree network can improve its thermal stability and mechanical strength. In addition, the decomposition product of potassium persulfate is a water-soluble inorganic salt, which is easy to clean and has a small residue, so the VOC emissions are low. However, the decomposition product of ammonium persulfate contains NH + 4 , which will react with carboxylic acid groups to generate ammonia, resulting in an increase in the VOC content; In Comparative Example 5, replacing 4-maleimide aniline with 4-aminophenol led to the absence of a dynamic network, resulting in a decrease in interfacial binding force, poor thermal stability, and the inability to respond to mechanical stress. The reason is that the maleimide group and the furan group form a six-membered ring structure through the Diels-Alder reaction. When the temperature is below 100 °C, a stable cyclic structure is formed. When the temperature is above 120 °C, the cyclic structure dissociates and reverts to the maleimide and furan groups. This reversibility endows the material with dynamic bonding ability, enabling self-healing under mechanical damage or thermal stimulation. Moreover, the dynamic bonds form a three-dimensional network through chemical cross-linking, which can enhance the bonding strength between the release agent and the paper filler. Additionally, at high temperatures, the dynamic bonds decompose to absorb energy, delaying the decomposition of the material, thereby reducing the pyrolysis of the release agent and improving its utilization rate; In Comparative Example 6, due to the excessive amount of butyl acrylate, the cross-linking density was uneven, the surface roughness decreased, and at the same time, the flexibility and rigidity were unbalanced, affecting the wear resistance and the control of the release force. The reason is that butyl acrylate, as a flexible monomer, participates in the formation of the cross-linking network through free radical polymerization. Its long alkyl chain endows the material with flexibility and adhesiveness. In the formulation, butyl acrylate is balanced with octadecyl acrylate and the cross-linking agent glycidyl methacrylate to form a uniform three-dimensional network. Although the flexible chain segments of butyl acrylate increase the fluidity of the material, during the curing process, they cause the surface to tend to be smooth, reducing the construction of a rough structure by polyamidoamine dendrimers on the surface. Moreover, the excessive butyl acrylate interferes with the aggregation of octadecyl acrylate, hindering the formation of a rough structure and further reducing the surface roughness. In addition, the -COO- bond of the excessive butyl acrylate forms hydrogen bonds with the CaCO 3 paper filler, enhancing the release resistance. At the same time, the use of excessive butyl acrylate leads to uneven cross-linking, resulting in a decrease in the cohesive strength of the material, and thus causing cohesive failure in some areas during peeling, further increasing the actual release force. Therefore, its release force increases.

[0050] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail.

[0051] The present invention aims to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A modified stripping agent for papermaking, characterized in that: The invention is prepared from the following raw materials in parts by weight: 45-55 parts of vinyl silicone oil, 2-4 parts of vinyl trimethylsilane, 2-4 parts of OP-10 emulsifier, 10-15 parts of modified polyurethane emulsion, 8-12 parts of butyl acrylate, 6-8 parts of octadecyl acrylate, 1-3 parts of polyamide-amine dendrimer, 0.5-1 parts of potassium persulfate, 1-1.5 parts of azobisisobutyronitrile and 1-3 parts of glycidyl methacrylate; The modified polyurethane emulsion is prepared from modified polyisocyanate and polyol containing phosphate groups.

2. A method for preparing a modified stripping agent for papermaking, characterized in that: The preparation method is as follows: Step S1: under nitrogen atmosphere, vinyl silicone oil, vinyl trimethylsilane and OP-10 emulsifier are added to deionized water, heated to 20-30°C, stirred for 20-40min, rotating at 1800-2200rpm, then heated to 70-80°C, potassium persulfate is added, stirred for reaction for 2-3h, rotating at 400-600rpm, and the reaction is completed to obtain a silicone emulsion mixture; Step S2: Add the silicone emulsion mixture into a flask, heat it to 70-80°C, rotate at 200-400rpm, add modified polyurethane emulsion, butyl acrylate, polyamide-amine dendrimer, octadecyl acrylate and azobisisobutyronitrile, react for 3-5h, and after the reaction is completed, cool it to 50-60°C, add glycidyl methacrylate, stir and react for 50-70min, rotate at 150-250rpm, adjust the pH to 6.5-7, filter, and obtain a modified stripping agent.

3. The method for preparing a modified stripping agent for papermaking according to claim 2, characterized in that: The mass ratio of the vinyl silicone oil, vinyl trimethylsilane, OP-10 emulsifier and potassium persulfate in step S1 is 45-55:2-4:2-4:0.5-1.

4. The method for preparing a modified stripping agent for papermaking according to claim 2, characterized in that: The mass ratio of the silicone emulsion mixture, modified polyurethane emulsion, butyl acrylate, polyamide-amine dendrimer, octadecyl acrylate, azobisisobutyronitrile and glycidyl methacrylate in step S2 is 50-60:12-15:8-10:1-3:6-8:1-1.5:1-3.

5. The method for preparing a modified stripping agent for papermaking according to claim 2, characterized in that: The modified polyurethane emulsion is prepared by the following method: Add modified polyisocyanate and polyol containing phosphate group into a three-necked flask, heat to 80-90℃, react for 2-4h, cool to 35-55℃, add dimethylol propionic acid and 1,4-butanediol, heat to 70-90℃, react for 60-90min, cool to 35-50℃, add catalyst dibutyltin dilaurate, heat to 60-80℃, react for 3-5h, after the reaction is completed, cool to 30-50℃, neutralize with triethylamine, emulsify with deionized water, and distill under reduced pressure to obtain modified polyurethane emulsion.

6. The method for preparing a modified stripping agent for papermaking according to claim 5, characterized in that: The mass ratio of the modified polyisocyanate, the polyol containing a phosphate group, the dimethylol propionic acid, the 1,4-butanediol and the catalyst is 5.2-5.5:1:0.08-0.13:0.09-0.12:0.035-0.

051.

7. The method for preparing a modified stripping agent for papermaking according to claim 5, characterized in that: The modified polyisocyanate is prepared as follows: Step A1: add cyanuric chloride to a mixed solution of acetone and deionized water, add 4-(2-furyl)aniline, raise the temperature to 10-20°C, react for 20-40 minutes, then raise the temperature to 50-70°C, react for 2-3 hours, and the reaction is completed to obtain intermediate 1; Step A2: Add 4-maleimidephenol to toluene solvent, stir evenly, heat to 70-90°C, add intermediate 1, react for 5-7h, and after the reaction is complete, cool to 20-30°C, stand for 50-70min, filter, and dry to obtain intermediate 2; Step A3: Add intermediate 2 and 1,5-pentane diisocyanate to toluene solvent, stir evenly, add catalyst dibutyltin dilaurate, heat to 70-90°C, react for 2-4h, cool, and distill at low pressure to obtain modified polyisocyanate.

8. The method for preparing a modified stripping agent for papermaking according to claim 7, characterized in that: The mass ratio of cyanuric chloride to 4-(2-furyl)aniline in step A1 is 1:2.4-2.6; The mass ratio of 4-maleimide phenol to intermediate 1 in step A2 is 0.6-0.7:1; The mass ratio of the intermediate 2, 1,5-pentane diisocyanate and dibutyltin dilaurate in step A3 is 1:0.4-0.5:0.003-0.

008.

9. The method for preparing a modified stripping agent for papermaking according to claim 5, characterized in that: The preparation method of the polyol containing phosphate groups is as follows: Add polyether diol 400 into a beaker, heat to 90-100°C, dehydrate for 50-70 minutes, cool to 20-40°C, add toluene and triethylamine, stir evenly, then add phosphorus oxychloride, react for 3-5 hours, separate into layers, and distill under reduced pressure to obtain a polyol containing a phosphate group.

10. The method for preparing a modified stripping agent for papermaking according to claim 9, characterized in that: The mass ratio of the polyether diol 400, toluene, triethylamine and phosphorus oxychloride is 7-8: 0.9-1.1:1.8-2:1。

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