A fluorine-free anti-oil agent for internal sizing, its preparation method and application method

Abstract

This invention discloses a fluorine-free oil-resistant agent for internal sizing, its preparation method, and its application method, belonging to the field of papermaking additives technology. Using agricultural waste as raw material, silicon carbide and silicon dioxide are mixed and pyrolyzed with nitrogen and dichloromethane. The pyrolysis products are condensed and allowed to stand to obtain an aqueous phase, a hydrophobic and oleophobic phase, and a dichloromethane phase. The hydrophobic and oleophobic phase is treated to generate chain-like siloxane compounds. These are then added to the dichloromethane phase and subjected to a halogenation reaction to generate halosiloxane compounds. The dehydrated aqueous phase is then added to the halosiloxane compounds to undergo an oxidation reaction, generating siloxane oxide compounds, i.e., the fluorine-free oil-resistant agent for internal sizing. The fluorine-free oil-resistant agent for internal sizing prepared by this method is used in the wet-end chemical stage of papermaking. It can be dispersed in water and adsorbed onto fibers. During the papermaking drying stage, it cross-links with the fibers through esterification, giving the paper good ring crush strength and oil-resistant effect.

Description

Technical Field

[0001] This invention relates to the field of papermaking additives technology, specifically to a fluorine-free anti-oil agent for internal sizing of pulp, its preparation method, and its application method. Background Technology

[0002] Paper, as a readily available, environmentally friendly, renewable, and biodegradable material, is widely used in packaging and food materials. However, the porous network structure formed by the interwoven fibers within paper products makes it prone to penetration and diffusion when in contact with liquids. This not only reduces the strength of the paper but also affects its packaging performance. Therefore, improving the water and oil resistance of paper has become an urgent problem to be solved in the industry.

[0003] Traditional solutions involve combining fluorinated compounds with fibers, utilizing the fluorocarbon chains to significantly reduce the surface tension of paper, thereby improving its water and oil repellency. For example, in the invention patent "A Waterborne Fluorinated Water and Oil Repellent Agent for Paper and Its Preparation and Application" (CN114773523A), soybean isoflavone aglycones are introduced into fluorinated copolymers to enhance the water and oil repellency of traditional waterborne fluorinated acrylate copolymers, resulting in increased paper strength after sizing. In the invention patent "A Preparation Method and Application of a Fluorinated Oil Repellent Agent" (CN113106779A), synthesized fluorocyanate synergists are applied to oil repellent agents, significantly improving the mechanical properties and heat and oil resistance of paper. However, during the production and use of fluorinated compounds, toxic perfluorinated and polyfluorinated compounds (PFAS) are released. These compounds accumulate in the ecological environment, such as soil and groundwater, and are difficult to degrade. Long-term exposure may also cause harm to the human body, such as leading to organ poisoning or impaired immune function.

[0004] Therefore, finding green and non-toxic methods and materials to prepare waterproof and oil-resistant cellulose composites to reduce dependence on harmful fluorine compounds is a current research hotspot. In the patent application "A fluorine-free oil-resistant agent for food packaging paper and its preparation method" (CN113931005A), paraffin wax is used as a raw material, and after emulsification, a non-toxic oil-resistant agent with excellent oil-resistant properties is obtained, and the oil-resistant coating exhibits high thermal stability. The fluorine-free oil-resistant agent prepared through this patent not only improves the mechanical properties and heat resistance of the paper but also reduces dependence on harmful fluorine compounds to a certain extent.

[0005] However, existing technologies for preparing food packaging paper using fluorine-free oil-resistant agents mostly involve applying the oil-resistant agent to the paper through surface impregnation coating. This method is prone to uneven sizing, resulting in poor sizing effect and low sizing efficiency, thus limiting its application in actual production.

[0006] To overcome these problems, researchers have begun exploring more environmentally friendly and efficient preparation methods. Among them, organosilicon materials have attracted much attention due to their unique properties. Organosilicon has low surface tension, good wettability and thermal stability, and easily forms a uniform film on the surface of materials, thereby achieving a protective effect. In particular, polysiloxane chains in siloxane compounds, due to their good hydrophobic properties, can form a siloxane film on the surface of objects, effectively preventing the adsorption and penetration of oil stains.

[0007] Therefore, how to utilize organosilicon materials to reduce dependence on harmful fluorine compounds and overcome the problem of poor surface sizing in traditional papermaking processes has become a technical challenge that urgently needs to be tackled by those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a fluorine-free oil-resistant agent for internal sizing, its preparation method, and its application method. Using agricultural and forestry biomass as raw material, it is mixed with silicon carbide and silicon dioxide to prepare a fluorine-free oil-resistant agent for internal sizing, thereby reducing dependence on harmful fluorine compounds through the use of organosilicon materials. Furthermore, the prepared fluorine-free oil-resistant agent is used in the wet-end chemical stage of papermaking, can be dispersed in water and adsorbed onto fibers, and cross-links with fibers through esterification during the papermaking drying stage, giving the paper good ring crush strength and oil-resistant effect, thus overcoming the problem of poor surface sizing effect in traditional papermaking processes.

[0009] The present invention solves the above-mentioned technical problems through the following technical solution:

[0010] A method for preparing a fluorine-free anti-oil agent for internal sizing includes the following steps:

[0011] Step 1: Mix silicon carbide, silicon dioxide and crushed agricultural waste, and carry out pyrolysis reaction under N2 and dichloromethane conditions. The products of the pyrolysis reaction are condensed to obtain an oil-water mixture. The oil-water mixture is allowed to stand and separate into layers, and each layer is extracted to obtain an aqueous phase, a dichloromethane phase and a hydrophobic and oleophobic phase.

[0012] Step 2: Dehydrate the aqueous phase described in Step 1 to obtain an organic mixture rich in aldehydes and carboxylic acids; filter and vacuum distill the hydrophobic and oleophobic phase described in Step 1 to obtain purified cyclosiloxane organic compounds.

[0013] Step 3: Dissolve the refined cyclosiloxane organic compounds described in Step 2 in toluene to obtain an organic solution. Perform a ring-opening reaction on the organic solution under alkaline conditions. Extract the organic solution after the ring-opening reaction multiple times with tetrahydrofuran. Perform vacuum distillation on the extracted organic solution to obtain chain-like siloxane organic compounds.

[0014] Step 4: Mix the chain-like siloxane organic compound described in Step 3 with the dichloromethane phase described in Step 1, add a halogenating agent and an initiator, and carry out a halogenation reaction to obtain a halosiloxane compound;

[0015] Step 5: Add the halosiloxane compound described in Step 4 to the organic mixture rich in aldehydes and carboxylic acids described in Step 2, add an oxidant, and carry out an oxidation reaction to obtain the oxidized siloxane compound, which is the fluorine-free anti-oil agent for sizing.

[0016] Furthermore, in step one, the agricultural waste is one or more of rice husks, straw, and wheat bran; the heating method used in the pyrolysis reaction is one of microwave heating, pulse heating, infrared heating, and plasma heating.

[0017] Further, step one specifically involves: pulverizing agricultural waste with a moisture content of 20%–50% to a particle size of 50–200 mesh, mixing it with silicon carbide and silicon dioxide with a particle size of 80–300 mesh, placing the mixture in a pyrolysis reactor, and continuously introducing N2 into the pyrolysis reactor. For 20–40 minutes, until all air is expelled, dichloromethane vapor is introduced into the pyrolysis reactor. The pyrolysis reactor is then turned on, and the temperature is rapidly increased to 700–1000℃ at a rate of 1000–5000℃ / min, and held at this temperature for 1–2 minutes to carry out the pyrolysis reaction, obtaining gaseous products. The gaseous products are collected at a condensation temperature of -35℃ to obtain an oil-water mixture. The oil-water mixture is allowed to stand to separate into upper, middle, and lower layers, wherein the upper layer is the aqueous phase, the middle layer is the dichloromethane phase, and the lower layer is the hydrophobic and oleophobic phase. Each layer is extracted separately to obtain the aqueous phase, the dichloromethane phase, and the hydrophobic and oleophobic phase.

[0018] Furthermore, the flow rate of N2 introduced is 1–5 mL / min per gram of agricultural waste; the flow rate of dichloromethane vapor introduced is 5–8 mL / min per gram of agricultural waste.

[0019] Further, step two specifically involves: adding a desiccant to the aqueous phase described in step one for dehydration treatment, stirring for 4–12 hours, and then filtering off the desiccant to obtain an organic mixture rich in aldehydes and carboxylic acids. The hydrophobic and oleophobic phase is then filtered through a microporous membrane of 0.22–0.45 μm. After filtration, the mixture is subjected to vacuum distillation at a temperature of 40–60 °C to remove low-boiling substances and obtain purified cyclosiloxane organic compounds.

[0020] The desiccant is one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate, and activated 4A molecular sieve; the mass ratio of aqueous phase to desiccant is 1:(0.01~0.1).

[0021] Further, step three specifically involves: dissolving the refined cyclosiloxane organic compound obtained in step two in toluene to obtain an organic solution; adding an alkaline catalyst to the organic solution to adjust the pH to 11-12; carrying out a ring-opening reaction at a reaction temperature of 80-140℃ for 4-8 hours; after the reaction, extracting the compound multiple times with tetrahydrofuran at a temperature of 25-40℃ to remove alkali metal ion impurities; and performing vacuum distillation at 50-65℃ to remove toluene and tetrahydrofuran to obtain a chain-like siloxane organic compound.

[0022] The alkaline catalyst is one or more of sodium hydroxide, potassium hydroxide, and iron hydroxide; the mass ratio of the purified cyclosiloxane organic compound to toluene in the organic solution is 1:(2-6).

[0023] Further, in step four, the mass ratio of the chain-like siloxane organic compound to dichloromethane is 1:(3-6); the temperature of the halogenation reaction is 20-60℃, and the reaction time is 6-8h; the halogenation reagent is one or more of N-chlorosuccinimide, N-bromosuccinimide, potassium bromide, and sodium bromide; the initiator is one or more of acetyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile; the mass ratio of the chain-like siloxane organic compound to the halogenation reagent and the initiator is 1:(0.5-1):(0.01-0.2).

[0024] Further, in step five, the oxidation reaction temperature is 50-100℃ and the reaction time is 8-24h; the oxidant is one or more of potassium dichromate, hydrogen peroxide, potassium permanganate and ammonium persulfate; the mass ratio of the halosiloxane compound to the organic mixture rich in aldehydes and carboxylic acids and the oxidant is 1:(3-6):(1-2.5).

[0025] A fluorine-free anti-oil agent for sizing is prepared by the above-mentioned method.

[0026] The above-mentioned method for using the fluorine-free anti-oil agent for internal sizing involves firstly adding the fluorine-free anti-oil agent for internal sizing before the oven-dry pulp enters the headbox during the wet end chemical stage; the fluorine-free anti-oil agent for internal sizing is 0.05% to 0.15% of the oven-dry pulp mass; secondly, the added fluorine-free anti-oil agent for internal sizing is adsorbed onto the fibers of the oven-dry pulp; finally, papermaking pressing and drying processes are carried out, wherein the pressing time is 3 to 4 minutes and the drying time is 5 to 7 minutes.

[0027] Compared with the prior art, the positive and progressive effects of the present invention are as follows:

[0028] The present invention provides a method for preparing a fluorine-free oil repellent for slurry sizing. This method utilizes agricultural waste such as rice husks and straw. During pyrolysis, it utilizes both silicon from the agricultural waste raw materials and a mixture of silicon carbide and silicon dioxide to provide a dual silicon source. Simultaneously, under the action of nitrogen and dichloromethane vapor, a cracking and silicon extraction reaction occurs, yielding an oil-water mixture containing cyclosiloxane organic compounds. After a series of treatments, a fluorine-free silicon-containing siloxane oil repellent is obtained, eliminating dependence on harmful fluorine compounds.

[0029] Furthermore, the preparation method of the present invention modifies the pyrolysis products of agricultural waste, makes full use of the moisture in the raw materials, eliminates the drying step of conventional agricultural and forestry waste collection and treatment, and reduces the energy consumption of raw material processing.

[0030] Furthermore, the preparation method of this invention fully utilizes the three-layer product obtained from the static settling of the oil-water mixture. The upper layer serves as a donor for the oxidation reaction of halosiloxane compounds; the organic mixture rich in aldehydes and carboxylic acids provides hydrophilic groups such as carboxyl groups for the oxidation of halosiloxane compounds. The dichloromethane phase in the middle layer can be used as a reaction solvent for the halogenation reaction of siloxane organic compounds. The cyclic siloxane organic compounds obtained in the lower layer are the main reaction phase, providing the main raw material for the synthesis of fluorine-free silicon-containing siloxane oil repellents, thus achieving complete utilization of the components. This layered, full-component utilization design improves the efficiency of product utilization and increases resource utilization.

[0031] Furthermore, in the preparation method of this invention, the siloxane compounds are cleverly modified by end-group hydrophilic modification, introducing carboxyl groups, which significantly enhances the hydrophilicity of the siloxane compounds, enabling them to disperse well in water and thus enhancing their adsorption capacity to fibers. This provides a strong support for the internal sizing of the oil repellent agent, ensuring that the oil repellent agent can act uniformly and effectively on the sizing fibers, thereby achieving the ideal oil repellent effect.

[0032] Furthermore, in the preparation method of the present invention, the temperature is increased at a rate of 1000-5000℃ / min in the pyrolysis reactor, which is beneficial to the silicon extraction and organosilicon synthesis reaction of silicon source and biomass organic carbon, thereby avoiding the problem that the silicon extraction reaction and the pyrolysis reaction of agricultural waste (cellulose, hemicellulose, lignin) cannot react synergistically due to the traditional low heating rate.

[0033] Furthermore, in the preparation method of the present invention, the pyrolysis reaction time is relatively short (reaction time is 1 to 2 minutes), which can effectively prevent the secondary reaction from causing further cracking of cyclosiloxane organic compounds.

[0034] The fluorine-free oil repellent for sizing prepared by the method of this invention makes full use of renewable resources, uses agricultural waste as raw material, gets rid of dependence on harmful fluorine compounds, effectively avoids the potential threat of fluorine compounds to human health, and overcomes the toxicity that fluorine-containing oil repellents may bring to the environment.

[0035] Furthermore, the siloxane compounds prepared by this invention overcome the shortcomings of traditional surface sizing with anti-oil agents, not only simplifying the sizing process but also significantly improving the applicability of siloxane compounds in the papermaking industry, providing a new, sustainable and efficient solution for the field of internal sizing.

[0036] The fluorine-free oil-resistant agent for internal sizing prepared in this invention is simple and efficient to use, eliminating concerns about uneven sizing leading to poor sizing effect and low sizing efficiency. In the wet end stage of the papermaking process, this fluorine-free oil-resistant agent can be used directly. The siloxane compounds are added before the pulp enters the headbox, allowing the compounds to be rapidly and uniformly adsorbed onto the pulp fibers, thus achieving the effect of internal sizing. When the pulp enters the press and dryer sections, the modified siloxane compounds undergo esterification with the fibers, forming stable covalent bonds. This not only enhances the bonding force between fibers but also imparts excellent oil-resistant properties to the paper. Furthermore, the internal sizing method not only reduces production costs but also improves sizing effect and efficiency, and enhances the ring crush strength and oil-resistant properties of the paper, broadening its applicability. Attached Figure Description

[0037] The accompanying drawings are provided to further understand the invention and constitute a part of this invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0038] Figure 1 This is a schematic flowchart of the preparation method of the present invention;

[0039] Figure 2 The images show the physical product and oil-resistant grade test results of the fluorine-free oil-resistant agent for sizing in the embodiments of the present invention.

[0040] Among them, (a) is a physical picture of Example 1 and a picture of the oil resistance test results; (b) is a physical picture of Example 2 and a picture of the oil resistance test results; (c) is a physical picture of Example 3 and a picture of the oil resistance test results; and (d) is a physical picture of Example 4 and a picture of the oil resistance test results. Detailed Implementation

[0041] This invention proposes a fluorine-free anti-oil agent for sizing and its preparation method, comprising the following steps:

[0042] 1. Agricultural waste with a moisture content of 20%–50% is pulverized to a particle size of 50–200 mesh. This mixture is then combined with silicon carbide (80–300 mesh) and silicon dioxide (80–300 mesh) and placed in a pyrolysis reactor. N2 atmosphere is continuously introduced into the reactor for 20–40 minutes to purge the air. Then, while maintaining a constant N2 flow rate, dichloromethane vapor is introduced. The pyrolysis reactor is then turned on, and the temperature is rapidly increased to 700–1000°C at a rate of 1000–5000°C / min, and held at this temperature for 1–2 minutes. The gaseous products generated during pyrolysis are collected at a condensation temperature of -35°C to obtain an oil-water mixture. The agricultural waste is one of rice husks, straw, or wheat bran. The heating method of the pyrolysis reactor can be microwave heating, pulse heating, infrared heating, plasma heating, or other heating methods that can achieve rapid temperature increases. The flow rate of N2 introduced per gram of agricultural waste is 1-5 mL / min, and the flow rate of dichloromethane vapor introduced per gram of agricultural waste is 5-8 mL / min.

[0043] 2. After the oil-water mixture obtained in step 1 is allowed to stand for 24 hours, it separates into three layers: an upper aqueous phase, a middle dichloromethane phase, and a lower hydrophobic and oleophobic phase. Each of the three layers is extracted separately. The upper aqueous phase is dehydrated by adding a desiccant at a mass ratio of 1:(0.01–0.1). After stirring for 4–12 hours, the desiccant is filtered off to obtain an organic mixture rich in aldehydes and carboxylic acids. The lower hydrophobic and oleophobic phase is a crude extract of cyclosiloxane organic compounds. This crude extract is filtered through a 0.22–0.45 μm microporous membrane and subjected to vacuum distillation at 40–60 °C to remove low-boiling-point substances, yielding purified cyclosiloxane organic compounds. The desiccant is anhydrous sodium sulfate, anhydrous magnesium sulfate, or activated 4A molecular sieve.

[0044] 3. The purified cyclosiloxane organic compound obtained in step 2 is dissolved in toluene, and then an alkaline catalyst is added to adjust the pH to 11-12. A ring-opening reaction is carried out at a reaction temperature of 80-140℃ for 4-8 hours. The solution is then extracted three times with tetrahydrofuran at 25-40℃ to remove alkali metal ion impurities. Toluene and tetrahydrofuran are removed by vacuum distillation at 50-65℃ to obtain the chain-like siloxane organic compound. The alkaline catalyst is one of sodium hydroxide, potassium hydroxide, and iron hydroxide. The mass ratio of the purified cyclosiloxane organic compound to toluene is 1:(2-6).

[0045] 4. The chain-like siloxane organic compound obtained in step 3 is mixed with the middle layer dichloromethane phase in step 2 at a mass ratio of 1:(3-6), and then a halogenating reagent and an initiator are added. The reaction temperature is 20-60℃, and the reaction time is 6-8h to generate a halosiloxane compound. The halogenating reagent is one of N-chlorosuccinimide, N-bromosuccinimide, potassium bromide, and sodium bromide. The initiator is one of acetyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile. The mass ratio of the chain-like siloxane organic compound to the halogenating reagent and the initiator is 1:(0.5-1):(0.01-0.2).

[0046] 5. Add the above-mentioned halosiloxane compound to the organic mixture rich in aldehydes and carboxylic acids obtained in step 2, then add an oxidant, and allow oxidation to occur at a reaction temperature of 50–100°C for 8–24 hours to obtain oxidized siloxane compounds. The oxidant is one of potassium dichromate, hydrogen peroxide, potassium permanganate, and ammonium persulfate. The mass ratio of the halosiloxane compound to the organic mixture rich in aldehydes and carboxylic acids and the oxidant is 1:(3–6):(1–2.5).

[0047] 6. The siloxane compounds obtained in step 5, due to the introduction of certain hydrophilic carboxyl groups, can be used directly in the wet end of papermaking. In the papermaking section, the siloxane compounds are added before the pulp enters the headbox, at a ratio of 0.05% to 0.15% of the oven-dry pulp mass. The added siloxane compounds can adsorb onto the pulp fibers. Then, when entering the press and drying sections, the siloxane compounds undergo esterification with the hydroxyl groups of the fibers to form covalent bonds, grafting onto the fiber surface. The resulting fiber / paper exhibits excellent oil resistance, with an oil resistance rating of up to level 11.

[0048] The present invention will be further described in detail below with reference to the accompanying drawings. These descriptions are for illustrative purposes only and are not intended to limit the scope of the invention.

[0049] Example 1:

[0050] See Figure 1The schematic diagram of the preparation method shows that 40g of straw with a moisture content of 25% is crushed to a particle size of 50-100 mesh, then mixed with silicon carbide and silica with a particle size of 80-200 mesh, and placed in a pyrolysis reactor. N2 atmosphere is continuously introduced into the pyrolysis reactor for 40 minutes to purge the air from the reactor. The N2 flow rate is 1 mL / min. Then, while maintaining a constant N2 flow rate, dichloromethane vapor is introduced at a flow rate of 5 mL / min. The pyrolysis reactor is then turned on, and microwave heating is used to rapidly raise the temperature to 700℃ at a rate of 1000℃ / min, and held for 2 minutes. The resulting gaseous products are collected at a condensation temperature of -35℃ to obtain an oil-water mixture. The obtained oil-water mixture is allowed to stand for 24 hours to separate into three layers: an upper aqueous phase, a middle dichloromethane phase, and a lower hydrophobic and oleophobic phase. 7g of the upper aqueous phase was extracted and 0.07g of anhydrous magnesium sulfate was added. After stirring for 4 hours, the anhydrous magnesium sulfate was removed by filtration, yielding a mixed solution rich in aldehydes and carboxylic acids. The lower hydrophobic and oleophobic phase was filtered through a 0.22μm microporous membrane and distilled under reduced pressure at 40℃ to obtain purified cyclosiloxane organic compounds. 5g of the purified cyclosiloxane organic compounds were added to 10g of toluene, and sodium hydroxide was added to adjust the pH to 11. The mixture was stirred at 80℃ for 8 hours, then extracted three times with tetrahydrofuran at 25℃ to remove sodium hydroxide. The mixture was then distilled under reduced pressure at 50℃ to obtain chain-like siloxane organic compounds. 4g of the chain-like siloxane organic compounds were mixed with 12g of the middle dichloromethane phase, and 2g of N-chlorosuccinimide and 0.04g of acetyl peroxide were added. The mixture was stirred at 20℃ for 8 hours to obtain halosiloxane compounds. 2g of a halosiloxane compound was added to 6g of an organic mixture rich in aldehydes and carboxylic acids, along with 2g of potassium dichromate. The mixture was stirred and reacted at 50℃ for 24 hours to obtain a siloxane oxide compound, which is a fluorine-free anti-oil agent for internal sizing. Because the siloxane oxide compound introduces certain hydrophilic carboxyl groups, it can be used directly in the wet end of papermaking. 0.02g of the siloxane compound was added to 40g of oven-dry pulp, pressed for 3 minutes, and then dried for 5 minutes to prepare a product with a basis weight of 475.5g / m³. 2 Oil-resistant paper. Its internal bond strength was tested to be 550.4 J / m. 2 The ring crush strength is 44.15 N·m / g, and the bursting strength index is 3.23 kPa·m. 2 / g, with an oil resistance rating of 9. See the attached image for a picture of the prepared oil-resistant paper and the oil resistance rating test results. Figure 2 (a) in the middle.

[0051] Example 2:

[0052] See Figure 1The schematic diagram of the preparation method shows that 50g of rice husks with a moisture content of 20% are crushed to a particle size of 100-150 mesh, then mixed with silicon carbide and silica with a particle size of 80-200 mesh, and placed in a pyrolysis reactor. N2 atmosphere is continuously introduced into the pyrolysis reactor for 30 minutes to purge the air from the reactor. The N2 flow rate is 3 mL / min. Then, while maintaining a constant N2 flow rate, dichloromethane vapor is introduced at a flow rate of 7 mL / min. The pyrolysis reactor is then turned on, and pulse heating is used to rapidly raise the temperature to 800℃ at a rate of 1500℃ / min, and held for 2 minutes. The resulting gaseous products are collected at a condensation temperature of -35℃ to obtain an oil-water mixture. The obtained oil-water mixture is allowed to stand for 24 hours to separate into three layers: an upper aqueous phase, a middle dichloromethane phase, and a lower hydrophobic and oleophobic phase. 8g of the upper aqueous phase was extracted and 0.3g of anhydrous sodium sulfate was added. After stirring for 6 hours, the anhydrous sodium sulfate was removed by filtration, yielding a mixed solution rich in aldehydes and carboxylic acids. The lower hydrophobic and oleophobic phase was filtered through a 0.22μm microporous membrane and distilled under reduced pressure at 45℃ to obtain purified cyclosiloxane organic compounds. 4g of the purified cyclosiloxane organic compounds were added to 12g of toluene, and potassium hydroxide was added to adjust the pH to 11. The mixture was stirred at 100℃ for 7 hours, then extracted three times with tetrahydrofuran at 30℃ to remove potassium hydroxide. The mixture was then distilled under reduced pressure at 55℃ to obtain chain-like siloxane organic compounds. 2g of the chain-like siloxane organic compounds were mixed with 8g of the middle dichloromethane phase, and 1.5g of N-bromosuccinimide and 0.1g of azobisisobutyronitrile were added. The mixture was stirred at 30℃ for 7 hours to obtain halosiloxane compounds. 2g of a halosiloxane compound was added to 7g of an organic mixture rich in aldehydes and carboxylic acids, along with 4g of hydrogen peroxide. The mixture was stirred and reacted at 70℃ for 18 hours to obtain a siloxane compound, which is a fluorine-free oil-resistant agent for internal sizing. Because the siloxane compound introduces certain hydrophilic carboxyl groups, it can be used directly in the wet end of papermaking. 0.03g of the siloxane compound was added to 30g of oven-dry pulp, pressed for 4 minutes, and then dried for 5 minutes to prepare an oil-resistant paper with a basis weight of 486.5g / m². The tested internal bond strength was 555.2J / m², ring crush strength was 44.61N·m / g, bursting index was 3.45kPa·m² / g, and oil resistance grade was 10. See the attached image of the prepared oil-resistant paper and the oil resistance grade test results. Figure 2 (b) in the middle.

[0053] Example 3:

[0054] See Figure 1The schematic diagram of the preparation method shows that 60g of wheat bran with a moisture content of 35% is crushed to a particle size of 100-150 mesh, then mixed with silicon carbide and silica with a particle size of 100-300 mesh, and placed in a pyrolysis reactor. N2 atmosphere is continuously introduced into the pyrolysis reactor for 25 minutes to purge the air from the reactor. The N2 flow rate is 3 mL / min. Then, while maintaining a constant N2 flow rate, dichloromethane vapor is introduced at a flow rate of 7 mL / min. The pyrolysis reactor is then turned on, and infrared heating is used to rapidly raise the temperature to 900℃ at a rate of 3000℃ / min, and held at this temperature for 1 minute. The resulting gaseous products are collected at a condensation temperature of -35℃ to obtain an oil-water mixture. The obtained oil-water mixture is allowed to stand for 24 hours, separating into three layers: an upper aqueous phase, a middle dichloromethane phase, and a lower hydrophobic and oleophobic phase. 15g of the upper aqueous phase was extracted and 1.2g of activated 4A molecular sieve was added. After stirring for 8 hours, the activated 4A molecular sieve was filtered off to obtain a mixed solution rich in aldehydes and carboxylic acids. The lower hydrophobic and oleophobic phase was filtered through a 0.45μm microporous membrane and distilled under reduced pressure at 52℃ to obtain purified cyclosiloxane organic compounds. 5g of the purified cyclosiloxane organic compounds were added to 25g of toluene, and ferric hydroxide was added to adjust the pH to 12. The mixture was stirred at 120℃ for 6 hours, then extracted three times with tetrahydrofuran at 35℃ to remove ferric hydroxide. The mixture was then distilled under reduced pressure at 60℃ to obtain chain-like siloxane organic compounds. 4g of the chain-like siloxane organic compounds were mixed with 16g of the middle dichloromethane phase, and 2.5g of potassium bromide and 0.45g of azobisisobutyronitrile were added. The mixture was stirred at 47℃ for 7 hours to obtain halosiloxane compounds. 2.5g of a halosiloxane compound was added to 10g of an organic mixture rich in aldehydes and carboxylic acids, along with 5g of potassium permanganate. The mixture was stirred and reacted at 85℃ for 12 hours to obtain a siloxane compound, which is a fluorine-free anti-oil agent for internal sizing. Because the siloxane compound introduces certain hydrophilic carboxyl groups, it can be used directly in the wet end of papermaking. 0.045g of the siloxane compound was added to 35g of oven-dry pulp, pressed for 3 minutes, and then dried for 7 minutes to prepare a product with a basis weight of 472.4g / m³. 2 Oil-resistant paper. Its internal bond strength was tested to be 665.1 J / m. 2 The ring crush strength is 44.48 N·m / g, and the bursting strength index is 3.68 kPa·m. 2 / g, with an oil resistance rating of 10. See the attached image for a picture of the prepared oil-resistant paper and the oil resistance rating test results. Figure 2 (c) in the middle.

[0055] Example 4:

[0056] See Figure 1The schematic diagram of the preparation method shows that 80g of rice husks with a moisture content of 50% are crushed to a particle size of 100-200 mesh, then mixed with silicon carbide and silica with a particle size of 150-300 mesh, and placed in a pyrolysis reactor. N2 atmosphere is continuously introduced into the pyrolysis reactor for 20 minutes to purge the air from the reactor. The N2 flow rate is 5 mL / min. Then, while maintaining a constant N2 flow rate, dichloromethane vapor is introduced at a flow rate of 8 mL / min. The pyrolysis reactor is then turned on, and plasma heating is used to rapidly raise the temperature to 1000℃ at a rate of 5000℃ / min, and hold for 1 minute. The resulting gaseous products are collected at a condensation temperature of -35℃ to obtain an oil-water mixture. The obtained oil-water mixture is allowed to stand for 24 hours to separate into three layers: an upper aqueous phase, a middle dichloromethane phase, and a lower hydrophobic and oleophobic phase. 25g of the upper aqueous phase was extracted and 2.5g of anhydrous magnesium sulfate was added. After stirring for 12h, the anhydrous magnesium sulfate was removed by filtration, yielding a mixed solution rich in aldehydes and carboxylic acids. The lower hydrophobic and oleophobic phase was filtered through a 0.45μm microporous membrane and distilled under reduced pressure at 60℃ to obtain purified cyclosiloxane organic compounds. 6g of the purified cyclosiloxane organic compounds were added to 36g of toluene, and sodium hydroxide was added to adjust the pH to 12. The mixture was stirred at 140℃ for 4h, then extracted three times with tetrahydrofuran at 40℃ to remove sodium hydroxide. The mixture was then distilled under reduced pressure at 65℃ to obtain chain-like siloxane organic compounds. 3g of the chain-like siloxane organic compounds were mixed with 18g of the middle dichloromethane phase, and 3g of sodium bromide and 0.6g of acetyl peroxide were added. The mixture was stirred at 60℃ for 6h to obtain halosiloxane compounds. 2g of a halosiloxane compound was added to 12g of an organic mixture rich in aldehydes and carboxylic acids, along with 5g of ammonium persulfate. The mixture was stirred at 100℃ for 8 hours to obtain a siloxane compound, which is a fluorine-free anti-oil agent for pulp sizing. Because the siloxane compound introduces certain hydrophilic carboxyl groups, it can be used directly in the wet end of papermaking. 0.0675g of the siloxane compound was added to 45g of oven-dry pulp, pressed for 4 minutes, and then dried for 6 minutes to prepare a product with a basis weight of 473.4g / m³. 2 Oil-resistant paper. Its internal bond strength was tested to be 721.6 J / m. 2 The ring crush strength is 45.17 N·m / g, and the bursting strength index is 3.71 kPa·m. 2 / g, with an oil resistance rating of 11. See the attached image for the prepared oil-resistant paper and the oil resistance rating test results. Figure 2 (d) in the middle.

[0057] The performance of the fluorine-free oil-resistant paper prepared by internal sizing in Examples 1-4 was tested. The main test items included internal bond strength, ring crush index, bursting strength index, and oil resistance. Internal bond strength was tested according to GB / T26203-2010 "Determination of Internal Bond Strength of Paper and Paperboard"; ring crush index was tested according to GB / T2679.8-2016 "Determination of Ring Crush Strength of Paper and Paperboard"; bursting strength index was tested according to GB / T454-2002 "Determination of Bursting Strength of Paper"; and oil resistance was tested according to GB / T22805.2-2008 "Determination of Grease Resistance of Paper and Paperboard Part 2: Surface Repulsion Method". The test results are shown in Table 1.

[0058] Table 1

[0059] Sample Indicators Example 1 Example 2 Example 3 Example 4 <![CDATA[Quantitative (g / m 2 )]]> 475.5 486.5 472.4 473.4 Moisture (%) 6.29 6.41 6.09 6.26 <![CDATA[Internal bond strength (J / m 2 )]]> 550.4 555.2 665.1 721.6 Ring pressure index (N·m / g) 44.15 44.61 44.48 45.17 <![CDATA[Bursting index (kPa·m 2 / g)]]> 3.23 3.45 3.68 3.71 Oil resistance Level 9 Level 10 Level 10 Level 11

[0060] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a fluorine-free anti-oil agent for internal sizing, characterized in that, Includes the following steps: Step 1: Mix silicon carbide, silicon dioxide and crushed agricultural waste, and carry out pyrolysis reaction under N2 and dichloromethane conditions. The products of the pyrolysis reaction are condensed to obtain an oil-water mixture. The oil-water mixture is allowed to stand and separate into layers, and each layer is extracted to obtain an aqueous phase, a dichloromethane phase and a hydrophobic and oleophobic phase. Step one specifically involves: pulverizing agricultural waste with a moisture content of 20%–50% to a particle size of 50–200 mesh, mixing it with silicon carbide and silicon dioxide (80–300 mesh particles), placing the mixture in a pyrolysis reactor, continuously introducing N2 into the reactor for 20–40 minutes until all air is expelled, then introducing dichloromethane vapor into the reactor; turning on the pyrolysis reactor and rapidly heating it to 700–1000 °C at a rate of 1000–5000 °C / min, holding it at this temperature for 1–2 minutes to carry out the pyrolysis reaction, obtaining gaseous products, and then storing the gaseous products at -35 °C. The mixture was collected at a condensation temperature of ℃ to obtain an oil-water mixture. The mixture was allowed to stand to separate into three layers: an upper layer of aqueous phase, a middle layer of dichloromethane phase, and a lower layer of hydrophobic and oleophobic phase. Each layer was extracted to obtain the aqueous phase, the dichloromethane phase, and the hydrophobic and oleophobic phase. Step 2: Dehydrate the aqueous phase described in Step 1 to obtain an organic mixture rich in aldehydes and carboxylic acids; filter and vacuum distill the hydrophobic and oleophobic phase described in Step 1 to obtain purified cyclosiloxane organic compounds. Step 3: Dissolve the refined cyclosiloxane organic compounds described in Step 2 in toluene to obtain an organic solution. Perform a ring-opening reaction on the organic solution under alkaline conditions. Extract the organic solution after the ring-opening reaction multiple times with tetrahydrofuran. Perform vacuum distillation on the extracted organic solution to obtain chain-like siloxane organic compounds. Step 4: Mix the chain-like siloxane organic compound described in Step 3 with the dichloromethane phase described in Step 1, add a halogenating agent and an initiator, and carry out a halogenation reaction to obtain a halosiloxane compound; Step 5: Add the halosiloxane compound described in Step 4 to the organic mixture rich in aldehydes and carboxylic acids described in Step 2, add an oxidizing agent, and carry out an oxidation reaction to obtain the oxidized siloxane compound, which is the fluorine-free anti-oil agent for sizing. The mass ratio of the halosiloxane compound to the organic mixture rich in aldehydes and carboxylic acids and the oxidant is 1:(3~6):(1~2.5).

2. The method for preparing a fluorine-free anti-oil agent for sizing according to claim 1, characterized in that, In step one, the agricultural waste is one or more of rice husks, straw, and wheat bran; the heating method used in the pyrolysis reaction is one of microwave heating, pulse heating, infrared heating, and plasma heating.

3. The method for preparing a fluorine-free anti-oil agent for sizing according to claim 1, characterized in that, The flow rate of N2 introduced is 1~5 mL / min / gram of agricultural waste; the flow rate of dichloromethane vapor introduced is 5~8 mL / min / gram of agricultural waste.

4. A method for preparing a fluorine-free anti-oil agent for sizing according to claim 1, characterized in that, The second step specifically involves: adding a desiccant to the aqueous phase described in the first step for dehydration treatment, stirring for 4-12 h, and then filtering off the desiccant to obtain an organic mixture rich in aldehydes and carboxylic acids. The hydrophobic and oleophobic phase is then filtered through a microporous membrane of 0.22-0.45 μm. After filtration, the mixture is subjected to vacuum distillation at a temperature of 40-60 °C to remove low-boiling substances and obtain refined cyclosiloxane organic compounds. The desiccant is one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate, and activated 4A molecular sieve; the mass ratio of aqueous phase to desiccant is 1:(0.01~0.1).

5. A method for preparing a fluorine-free anti-oil agent for sizing according to claim 1, characterized in that, Step three specifically involves: dissolving the refined cyclosiloxane organic compounds obtained in step two in toluene to obtain an organic solution; adding an alkaline catalyst to the organic solution and adjusting the pH to 11-12; carrying out a ring-opening reaction at a reaction temperature of 80-140 °C for 4-8 h; after the reaction, extracting the solution multiple times with tetrahydrofuran at a temperature of 25-40 °C to remove alkali metal ion impurities; and then performing vacuum distillation at 50-65 °C to remove toluene and tetrahydrofuran to obtain chain-like siloxane organic compounds. The alkaline catalyst is one or more of sodium hydroxide, potassium hydroxide, and iron hydroxide; the mass ratio of the purified cyclosiloxane organic compound to toluene in the organic solution is 1:(2~6).

6. A method for preparing a fluorine-free anti-oil agent for sizing according to claim 1, characterized in that, In step four, the mass ratio of the chain siloxane organic compound to dichloromethane is 1:(3~6); the temperature of the halogenation reaction is 20~60 °C, and the reaction time is 6~8 h; the halogenation reagent is one or more of N-chlorosuccinimide, N-bromosuccinimide, potassium bromide, and sodium bromide; the initiator is one or more of acetyl peroxide, azobisisobutyronitrile, and azobisisoheptanenitrile; the mass ratio of the chain siloxane organic compound to the halogenation reagent and the initiator is 1:(0.5~1):(0.01~0.2).

7. A method for preparing a fluorine-free anti-oil agent for sizing according to claim 1, characterized in that, In step five, the oxidation reaction is carried out at a temperature of 50-100 °C for 8-24 h; the oxidant is one or more of potassium dichromate, hydrogen peroxide, potassium permanganate, and ammonium persulfate.

8. A fluorine-free anti-oil agent for internal sizing, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The method of using a fluorine-free anti-oil agent for slurry application according to claim 8, characterized in that, First, before the oven-dry pulp enters the headbox during the wet-end chemical stage, a fluorine-free anti-oil agent for internal sizing is added; the fluorine-free anti-oil agent for internal sizing is 0.05%~0.15% of the oven-dry pulp mass. Second, the added fluorine-free anti-oil agent for internal sizing is adsorbed onto the fibers of the oven-dry pulp. Finally, papermaking pressing and drying processes are carried out, wherein the pressing time is 3~4 minutes and the drying time is 5~7 minutes.

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