Environmentally friendly rubber additives based on corn cobs, their preparation methods and applications

Abstract

This invention provides an environmentally friendly rubber additive based on corn cobs, its preparation method, and its application, belonging to the field of rubber additive technology. The preparation method of this invention uses corn cobs as the sole core raw material. Corn cob powder is treated with an acidic solution to obtain filter residue A; filter residue A is treated with an alkaline solution to obtain lignin solution and cellulose; cellulose is enzymatically hydrolyzed to obtain glucose; glucose undergoes isomerization and dehydration reactions to obtain 5-hydroxymethylfurfural; the lignin solution is acid-precipitated and then subjected to amination or phenolation modification to obtain modified lignin; 5-hydroxymethylfurfural and modified lignin undergo a condensation reaction under the action of an acidic catalyst to obtain the environmentally friendly rubber additive. The preparation method of this invention achieves full resource utilization, producing a rubber additive with good environmental performance, high reactivity, and excellent adhesive properties, reducing dependence on petrochemical raw materials and reducing environmental pollutant emissions.

Description

Technical Field

[0001] This invention relates to the field of rubber additives technology, specifically to an environmentally friendly rubber additive based on corn cobs, its preparation method, and its application. Background Technology

[0002] Rubber additives are an indispensable component of the rubber industry, used to improve the processing performance, mechanical properties, and durability of rubber. Traditional rubber additives (such as carbon black, silica, and petroleum-based phenolic resins) largely rely on fossil resources, resulting in high energy consumption, heavy pollution, and non-renewable nature. With increasingly stringent environmental regulations and the advancement of "dual carbon" goals, the development of renewable, biodegradable, and low-cost bio-based rubber additives has become an important research direction in the industry.

[0003] Corn cobs are a major agricultural waste in my country, primarily composed of cellulose (approximately 35%-40%), hemicellulose (approximately 30%-35%), and lignin (approximately 20%-25%). Currently, corn cob utilization is mostly limited to low-value processing (such as fuel and feed), failing to achieve high-value utilization. While some studies have explored using lignin or cellulose derivatives as rubber fillers, these methods often suffer from poor dispersibility, insufficient adhesion, and poor compatibility with rubber, and rarely achieve efficient synergistic conversion of the three corn cob components (lignin, cellulose, and hemicellulose). Therefore, there is an urgent need to develop an innovative method that enables the high-value utilization of all corn cob components and the preparation of high-performance, environmentally friendly rubber additives.

[0004] Chinese patent document CN115745925A discloses a two-step hydrolysis catalytic conversion method for preparing 5-hydroxymethylfurfural from corn stalks. The method involves crushing and drying corn stalks, adding them to a hydrothermal reactor with an appropriate amount of water, and removing the hemicellulose component through a high-temperature liquid-phase hydrolysis reaction. The residue is then collected by filtration. This residue, along with lithium bromide molten salt solution, aluminum chloride, and acetone, is added to the reactor, and after sufficient reaction, 5-hydroxymethylfurfural is obtained. However, this method does not consider lignin recovery. If used for the preparation of bio-based phenolic resins, lignin needs to be sourced from other sources; corn stalks cannot be the sole bio-based source.

[0005] Chinese patent document CN114196039A discloses a method for extracting lignin, cellulose, and sugars from corn stalk lignocellulose. The method involves uniformly mixing corn stalk powder, an acid solution, and a catalyst, heating the mixture, acid washing, filtering, and separating the cellulose solid and the mixed solution. The separated mixed solution is then rotary evaporated, dissolved in water, and filtered to obtain lignin solid and a sugar solution. However, this method does not separate hemicellulose and cellulose. Hemicellulose, encapsulating cellulose, hinders contact between cellulase and cellulose, thus impeding subsequent enzymatic hydrolysis of cellulose into glucose. Summary of the Invention

[0006] In view of this, the present invention provides an environmentally friendly rubber additive based on corn cob, its preparation method and application. Using corn cob as the sole core raw material, lignin and cellulose are obtained. Through the directional conversion and synergistic synthesis of lignin and cellulose, the full utilization of resources is achieved, and a rubber additive with good environmental performance, high reactivity and excellent adhesion effect is prepared, reducing dependence on petrochemical raw materials and reducing the emission of environmental pollutants.

[0007] To achieve the above objectives, this invention provides a method for preparing an environmentally friendly rubber additive based on corn cob, comprising the following steps: (1) After corn cob powder is treated with an acidic solution, solid-liquid separation is performed to obtain filter residue A and filtrate A; after filter residue A is treated with an alkaline solution, solid-liquid separation is performed to obtain lignin solution and cellulose; (2) The cellulose obtained in step (1) is enzymatically hydrolyzed to obtain glucose; the glucose is isomerized and dehydrated to obtain 5-hydroxymethylfurfural; (3) After acid precipitation, the lignin solution obtained in step (1) is subjected to amination or phenolation modification to obtain modified lignin; (4) 5-hydroxymethylfurfural and modified lignin are subjected to a condensation reaction under the action of an acid catalyst to obtain an environmentally friendly rubber additive.

[0008] This invention first treats corn cob powder with an acidic solution, allowing hemicellulose to enter filtrate A, facilitating subsequent hemicellulose extraction and recovery. Then, the filter residue A is treated with an alkaline solution to separate lignin and cellulose. The obtained cellulose is used as a raw material to prepare 5-hydroxymethylfurfural; the obtained lignin is used as a raw material to obtain modified lignin. Therefore, all the raw materials for preparing environmentally friendly rubber additives come from corn cobs, achieving full utilization of corn cobs.

[0009] Hemicellulose interferes with the enzymatic hydrolysis of cellulose to produce glucose in the following ways: Hemicellulose wraps around the outside of cellulose, hindering the contact between cellulase and cellulose, reducing the rate and efficiency of cellulose degradation. Pre-treatment with acid to remove hemicellulose is beneficial for exposing cellulose for subsequent reactions.

[0010] Optionally, in step (1), the mass fraction of the acidic solution is 0.5-5%, the liquid-solid ratio of the acidic solution to corn cob powder is 8-12:1 (mL / g), and the treatment conditions are: stirring at 100-120℃ for 2-3 hours.

[0011] By using the parameters specified above, the hemicellulose component in the corn cob is fully dissolved and enters the solution, which facilitates the separation of the hemicellulose component through solid-liquid separation and avoids its interference with subsequent reactions.

[0012] Optionally, the acidic solution is an acidic aqueous solution, which is an aqueous solution of acetic acid or a dilute aqueous solution of sulfuric acid.

[0013] Optionally, in step (1), the mass fraction of the alkaline solution is 2-5%, the liquid-solid ratio of the alkaline solution and filter residue A is 8-12:1 (mL / g), and the treatment conditions are: stirring at 100-120℃ for 3-5 hours, solid-liquid separation, to obtain filter residue B and filtrate B. Filter residue B is washed and dried to obtain cellulose, and filtrate B is a lignin solution.

[0014] By setting the parameters above, the lignin component in filter residue A is fully dissolved and enters the solution, which facilitates the separation of lignin and cellulose through solid-liquid separation, thus facilitating subsequent directional conversion.

[0015] Optionally, the alkaline solution is an alkaline aqueous solution, which is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0016] Optionally, in step (2), the enzymatic hydrolysis method is as follows: add acetate-sodium acetate buffer and cellulase to cellulose, the amount of cellulase added is 3-5% of the mass of cellulose, and enzymatically hydrolyze for 48-72 hours at a pH of 4.8-5.2 and a temperature of 45-55℃ to obtain glucose.

[0017] The pH value was adjusted by using an acetate-sodium acetate buffer solution to make the pH value of the system 4.8-5.2, providing a suitable pH value for enzymatic hydrolysis.

[0018] Optionally, in step (2), glucose undergoes isomerization and dehydration reactions under the action of Lewis acid catalyst and Brønsted acid catalyst to obtain 5-hydroxymethylfurfural.

[0019] Glucose is first isomerized to fructose under the catalysis of Lewis acid, and then dehydrated from fructose to 5-hydroxymethylfurfural (HMF) under the catalysis of Brønsted acid.

[0020] Optionally, the amount of Lewis acid catalyst added is 2-4% of the glucose mass, the amount of Brønsted acid catalyst added is 2-4% of the glucose mass, and the mass ratio of Lewis acid catalyst to Brønsted acid catalyst is 1:1.

[0021] Optionally, the Lewis acid catalyst is chromium chloride, zinc chloride, or ferric chloride, and the Brønsted acid catalyst is H2SO4 or HCl.

[0022] Optionally, in step (2), the isomerization and dehydration reaction method includes: the reaction environment is water, the reaction is carried out at 120-140℃ and 0.3-0.5MPa for 3-6h, the reaction is cooled to room temperature after the reaction is completed, and 5-hydroxymethylfurfural is obtained by extraction-depressurized distillation combined purification.

[0023] Optionally, a combined extraction-vacuum distillation purification method can be used: HMF is extracted with ethyl acetate, followed by vacuum distillation at a vacuum of 0.085-0.09 MPa and 65-70°C. This combined extraction-vacuum distillation method is beneficial for improving purity.

[0024] Optionally, in step (3), the method for acid precipitation of lignin solution is as follows: adjust the pH value of lignin solution to 2-3, let it stand to precipitate, then separate the solid and liquid to obtain the residue, and wash and dry the residue to obtain solid lignin with a purity ≥90%.

[0025] Optionally, the pH of the lignin solution can be adjusted using a 20% hydrochloric acid aqueous solution or a 20% sulfuric acid aqueous solution.

[0026] Optionally, in step (3), the amination modification method is as follows: disperse the acid-precipitated lignin in an aqueous solution with a pH of 10-11, then add aliphatic amine, add formaldehyde solution dropwise at 60-90℃, keep warm and stir for 2-3 hours, and obtain amination-modified lignin after cooling.

[0027] Optionally, the formaldehyde solution is a 37% formaldehyde aqueous solution (abbreviated as: 37% formaldehyde solution), and the molar amount of formaldehyde is 80%-100% of the molar amount of aliphatic amines.

[0028] Optionally, the amount of aliphatic amine added is 80-120% of the lignin quality; the aliphatic amine is ethylenediamine or diethylenetriamine.

[0029] Optionally, in step (3), the phenolic modification method is as follows: phenol is added to lignin, sulfuric acid solution is used as a catalyst, and the mixture is kept warm and stirred at 90-110℃ for 3-4 hours. After cooling, phenolic modified lignin is obtained.

[0030] Optionally, in the phenolation modification, the amount of phenol added is 100-300% of the lignin content, the sulfuric acid solution is an aqueous sulfuric acid solution with a mass fraction of 98%, and the amount of sulfuric acid added is 2.5-8% of the lignin content.

[0031] Optionally, in step (4), the mass ratio of 5-hydroxymethylfurfural to modified lignin is 1:2.5-4; the amount of acid catalyst added is 2-7% of the mass of modified lignin. The acid catalyst is oxalic acid or p-toluenesulfonic acid.

[0032] Optionally, in step (4), the polycondensation reaction method includes: keeping the temperature at 90-110℃ and stirring for 4-6 hours; after the reaction is completed, raising the temperature to 150-160℃, dehydrating under reduced pressure, and then solidifying and granulating to obtain an environmentally friendly rubber additive.

[0033] Optionally, in the polycondensation reaction, the vacuum degree of dehydration under reduced pressure is 0.07-0.08 MPa.

[0034] Optionally, in step (1), the corn cob powder is prepared as follows: dry, mold-free corn cobs are crushed to 40-80 mesh, washed with deionized water, and dried in an oven at 60-80℃ to constant weight.

[0035] The environmentally friendly rubber additives are prepared by the aforementioned preparation method.

[0036] The application of environmentally friendly rubber additives as adhesives or reinforcing agents in rubber products.

[0037] Optionally, the rubber is prepared as a natural rubber product, a synthetic rubber product, or a rubber blend product.

[0038] The above-described technical solution of the present invention has at least the following beneficial effects: 1. Environmentally friendly raw materials and high resource utilization rate: Using corn cobs, agricultural waste, as the only bio-based raw material, it achieves the separation and high-value utilization of all components of hemicellulose, lignin and cellulose, with no raw material waste, reducing the pressure of agricultural waste treatment, and at the same time getting rid of dependence on petrochemical raw materials; 2. Green and environmentally friendly process: The production process uses an aqueous reaction system, the solvent can be recycled, pollutant emissions are low, and the product is biodegradable, so it has no burden on the environment after use; 3. Excellent product performance: glucose is converted into 5-hydroxymethylfurfural through Lewis acid and Brønsted acid catalysis, with a purity of ≥92%.

[0039] 4. The reactivity of lignin is significantly enhanced after amination or phenolation modification. When bio-based phenolic resin synthesized with 5-hydroxymethylfurfural is used as a rubber additive, it has good compatibility with the rubber matrix and can significantly improve the tensile strength, tear strength and abrasion resistance of rubber products. The bonding effect is comparable to that of traditional petroleum-based phenolic resin additives, and it can partially or completely replace traditional petroleum-based phenolic resin additives. 5. The preparation process is simple and controllable: the reaction steps are mild, the equipment requirements are low, it is easy to scale up industrial production, and the production cost is lower than that of traditional petroleum-based rubber additives, which has significant economic and social benefits. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0041] Example 1 The preparation method of environmentally friendly rubber additives based on corn cobs includes the following steps: (1) Corn cob pretreatment: Select dry corn cobs, crush them to 60 mesh, wash them 3 times with deionized water, and dry them in an oven at 70℃ to constant weight to obtain pretreated corn cob powder; Three-element separation: 100g of corn cob powder was added to the reactor, and 1200mL of 5% acetic acid aqueous solution was added. The mixture was kept at 100℃ and stirred for 2h. The mixture was filtered to obtain filter residue A and filtrate A. Filter residue A was washed with water once until neutral and dried at 60℃ to constant weight to obtain 67.2g of filter residue A. Add 800 mL of 2% sodium hydroxide aqueous solution to 67.2 g of filter residue A, keep warm and stir at 110 °C for 4 h, filter residue B and filtrate B are obtained by filtration. Filter residue B is washed with hot water until neutral and dried at 60 °C to constant weight to obtain 38.9 g of cellulose. Filtrate B is an aqueous solution of lignin. (2) Preparation of 5-hydroxymethylfurfural by directional conversion of cellulose: 310 ml of acetate-sodium acetate buffer (solid-liquid ratio 1:8) and 1.55 g of cellulase (4% of the mass of cellulose) were added to cellulose. The mixture was enzymatically hydrolyzed at pH 5.0 and 50 °C for 60 h to obtain a glucose aqueous solution. The mass of glucose was approximately 30.1 g as determined by HPLC.

[0042] 0.9 g of chromium chloride (3% of the glucose mass) and 0.9 g of H2SO4 were added to a glucose aqueous solution. The reaction was carried out at 130 °C and 0.4 MPa for 4.5 h. After the reaction was completed, the mixture was cooled to room temperature, and HMF was extracted with ethyl acetate. The mixture was then purified by vacuum distillation (0.085-0.09 MPa, 65-70 °C) to obtain 18.7 g of 5-hydroxymethylfurfural with a purity of 92.5%. (3) Lignin precipitation: Slowly add 20% hydrochloric acid aqueous solution to filtrate B until the pH value is 2-3, with a dropping rate of 2 ml / min. Let it stand for acid precipitation for 2 hours. Wash the filter residue with hot water until neutral and dry it at 60℃ to constant weight to obtain 23.8 g of lignin. Amination modification: 23.8g of lignin was added to the modification reactor and dispersed in an aqueous solution with a pH of 10-11 (the pH was adjusted with NaOH aqueous solution). Then, 23.8g of ethylenediamine and 28.9g of 37% formaldehyde solution were added (the formaldehyde solution was added dropwise at a rate of 2ml / min). The mixture was stirred at 75℃ for 2.5h and cooled to obtain 54.7g of amination-modified lignin. (4) Synthesis of bio-based phenolic resin: 18.7g of 5-hydroxymethylfurfural was mixed with the amination-modified lignin obtained in step (3), 1.1g of p-toluenesulfonic acid was added, and the mixture was kept at 110℃ and stirred for 5h. The temperature was raised to 150℃, and the mixture was dehydrated under reduced pressure (vacuum degree 0.08MPa) and then cooled to room temperature to obtain 65.5g of environmentally friendly rubber additive.

[0043] Example 2 The preparation method of environmentally friendly rubber additives based on corn cobs includes the following steps: (1) Corn cob pretreatment: Select dry corn cobs, crush them to 40 mesh, wash them twice with deionized water, and dry them in an oven at 80℃ to constant weight to obtain pretreated corn cob powder; Separation of three elements: 100g of pretreated corn cob powder was added to a reactor, and 1000mL of 2.4% sulfuric acid aqueous solution was added. The mixture was stirred at 110℃ for 3h, and filtered to obtain filter residue A and filtrate A. Filter residue A was washed once with water until neutral and dried at 60℃ to constant weight to obtain 66.7g of filter residue A. 800mL of 5% potassium hydroxide aqueous solution was added to 66.7g of filter residue A, and the mixture was stirred at 100℃ for 5h. The mixture was filtered to obtain filter residue B and filtrate B. Filter residue B was washed with hot water until neutral and dried at 60℃ to constant weight to obtain 39.2g of cellulose. Filtrate B was an aqueous solution of lignin. (2) Preparation of 5-hydroxymethylfurfural by directional conversion of cellulose: 315 ml of acetate-sodium acetate buffer (solid-liquid ratio 1:8) and 1.18 g of cellulase (3% of cellulose mass) were added to cellulose. The mixture was enzymatically hydrolyzed at pH 4.8 and 45℃ for 72 h to obtain a glucose aqueous solution. The glucose mass was determined by HPLC to be approximately 29.88 g. 0.75 g of zinc chloride (2.5% of glucose mass) and 0.75 g of H2SO4 were added to the glucose aqueous solution. The mixture was reacted at 120℃ and 0.3 MPa for 6 h. After cooling, HMF was extracted with ethyl acetate and then purified by vacuum distillation (vacuum degree 0.085-0.09 MPa, 65-70℃) to obtain 18.52 g of 5-hydroxymethylfurfural with a purity of 92.1%. (3) Lignin precipitation: Slowly add 20% sulfuric acid aqueous solution to filtrate B until the pH value is 2-3, with a dropping rate of 2 ml / min. Let it stand for acid precipitation for 2 hours. Wash the filter residue with hot water until neutral and dry it at 60℃ to constant weight to obtain 22.5 g of lignin.

[0044] Phenolic modification: 22.5g of lignin was added to the modification reactor, along with 56.2g of phenol and 0.9g of 98% sulfuric acid aqueous solution. The mixture was stirred at 90℃ for 4h and then cooled to obtain 68.5g of phenolic modified lignin. (4) Synthesis of bio-based phenolic resin: 18.52g of 5-hydroxymethylfurfural was mixed with the phenolic modified lignin obtained in step (3), 1.37g of p-toluenesulfonic acid was added, and the mixture was kept at 110℃ and stirred for 6h. The temperature was raised to 150℃, and the mixture was dehydrated under reduced pressure (vacuum degree 0.07MPa) and then cooled to room temperature to obtain 78.7g of environmentally friendly rubber additive.

[0045] Example 3 The preparation method of environmentally friendly rubber additives based on corn cobs includes the following steps: (1) Corn cob pretreatment: Select dry corn cobs, crush them to 80 mesh, wash them twice with deionized water, and dry them in an oven at 70℃ to constant weight to obtain pretreated corn cob powder; Separation of three elements: 100g of pretreated corn cob powder was added to a reactor, and 1000mL of 4% acetic acid aqueous solution was added. The mixture was stirred at 100℃ for 2h. After the reaction was completed, the mixture was filtered to obtain residue A and filtrate A. Residue A was washed once with water until neutral and dried at 60℃ to constant weight to obtain residue A, which weighed approximately 66.4g. 535mL of 3% sodium hydroxide aqueous solution was added to 66.4g of residue A and the mixture was stirred at 120℃ for 3h. After the reaction was completed, the mixture was filtered to obtain residue B and filtrate B. Residue B was washed with hot water until neutral and dried at 60℃ to constant weight to obtain 38.7g of cellulose. Filtrate B was an aqueous solution of lignin. (2) Preparation of 5-hydroxymethylfurfural by directional conversion of cellulose: 310 ml of acetate-sodium acetate buffer (solid-liquid ratio 1:8) and 1.94 g of cellulase (5% of cellulose mass) were added to cellulose. The mixture was enzymatically hydrolyzed at pH 5.2 and 55℃ for 48 h to obtain a glucose aqueous solution. The glucose mass was determined by HPLC to be approximately 29.8 g. 1.2 g of ferric chloride (4% of glucose mass) and 1.2 g of HCl were added to the glucose aqueous solution. The mixture was reacted at 140℃ and 0.5 MPa for 3 h. After cooling, HMF was extracted with ethyl acetate and then purified by vacuum distillation (vacuum degree 0.085-0.09 MPa, 65-70℃) to obtain 18.48 g of 5-hydroxymethylfurfural. (3) Lignin precipitation: Slowly add 20% sulfuric acid aqueous solution to filtrate B until the pH value is 2-3, with a dropping rate of 2 ml / min. Let it stand for acid precipitation for 2 hours. Wash the filter residue with hot water until neutral and dry it at 60℃ to constant weight to obtain 23.1 g of lignin. Phenolic modification: 23.1g of lignin was added to the modification reactor, along with 46.2g of phenol and 1.73g of 98% sulfuric acid aqueous solution. The mixture was stirred at 110℃ for 3h and then cooled to obtain 60.3g of phenolic modified lignin. (4) Synthesis of bio-based phenolic resin: 18.48g of 5-hydroxymethylfurfural was mixed with the phenolic modified lignin obtained in step (3), 3.62g of oxalic acid was added, and the mixture was kept at 100℃ and stirred for 6h. The temperature was raised to 160℃, and the mixture was dehydrated under reduced pressure (vacuum degree 0.07MPa) and then cooled to room temperature to obtain 75.1g of environmentally friendly rubber additive.

[0046] Example 4 This embodiment is basically the same as that of embodiment 1, except that: (3) Amination modification of lignin: 23.8g of lignin was added to the modification reactor and dispersed in an aqueous solution with a pH of 10-11 (the pH was adjusted with NaOH aqueous solution), and then 28.56g of diethylenetriamine and 20.2g of 37% formaldehyde solution were added (the formaldehyde solution was added dropwise at a rate of 2ml / min), and the mixture was kept warm and stirred at 90°C for 2h. After cooling, 53.2g of amination-modified lignin was obtained.

[0047] Table 1. Formulation of the rubber compound

[0048] Table 2 Adhesive Resins for Compounds 1#-5#

[0049] The preparation of the rubber compound consists of a single-stage mixing process and a two-stage mixing process. The single-stage mixing process is as follows: Raw materials are weighed according to the formula proportions in Table 1. Natural rubber NR, carbon black N326, ZnO-80, cobalt borate, antioxidant 4020, antioxidant RD, and adhesive resin are added to an internal mixer. The rotor speed is 70 rpm, the pressure is 0.6 MPa, the heating rate is 10 ℃ / min, the temperature is raised to 115 ℃, held for 0.5 minutes, and then further heated to 160 ℃. The rubber is then discharged to obtain the primary compound. The two-stage mixing process is as follows: The primary compound is added to the internal mixer, along with adhesion accelerator HMMM-55, rubber accelerator DZ, and vulcanizing agent OT20-80. The mixture is mixed for 3 minutes at a pressure of 0.5 MPa and a temperature of 95 ℃, with a rotation speed of 50 rpm. After completion, the rubber compound is obtained.

[0050] Test methods for various performance parameters of rubber compounds Processing performance test: A scorch test was conducted using a Mooney viscometer in accordance with the national standard GB / T 1233-92.

[0051] Vulcanization characteristics: The test was conducted using a rotorless vulcanization analyzer MDR 2000 according to GB / T 9869-1997, with a test temperature of 150℃ and a test time of 35min.

[0052] Mechanical properties: The tensile properties of the rubber compound were determined according to GB / T 528-2009; the compression set was determined according to GB / T 7759-1996 using cylindrical specimens of 29.0 mm × 12.5 mm, and the aging conditions were: compression set was determined at 100 ℃ for 48 h, with a pre-compression rate of 25%.

[0053] Adhesion performance test: Tested according to GB / T 16586-2014.

[0054] Table 31#-5# Rubber Compound Scorch Time

[0055] As shown in Table 3, the scorch times of 1#-4# are relatively close, while the scorch times of 4# and 5# are greater than those of 1#, 2# and 3#. Extending the scorch time improves processing safety, makes early vulcanization less likely during mixing, extrusion, calendering and storage, and allows the rubber compound to maintain its flow time after being heated, resulting in good mold filling and strong adhesion.

[0056] Table 41-5# Rubber Compound Vulcanization Properties

[0057] As shown in Table 4, compared with rubber compounds 1#-3#, the vulcanization rates Tc90-Tc10 and Ts2 (min) of rubber compounds 4#-5# are slightly increased, which avoids premature vulcanization during the rubber compound processing due to excessively short vulcanization time.

[0058] Table 5 Mechanical properties of 1-5# rubber compounds

[0059] As shown in Table 5, the mechanical properties of rubber compounds #4 and #5 after aging are better than those of rubber compounds #1-#3.

[0060] Table 61#-5# Adhesive properties

[0061] As shown in Table 6, the initial adhesive strength of compounds #4-#5 is greater than that of compounds #1 and #2, but less than that of compound #3, although the difference is not significant. Therefore, it can be concluded that the adhesive properties of the compounds prepared using the rubber additives of this invention are comparable to those of existing bonding resins.

Claims

1. A method for preparing an environmentally friendly rubber additive based on corn cob, characterized in that, Includes the following steps: (1) After corn cob powder is treated with an acidic solution, solid-liquid separation is performed to obtain filter residue A and filtrate A; After being treated with an alkaline solution, filter residue A underwent solid-liquid separation to obtain a lignin solution and cellulose. (2) The cellulose obtained in step (1) is enzymatically hydrolyzed to obtain glucose; the glucose is isomerized and dehydrated to obtain 5-hydroxymethylfurfural; (3) After acid precipitation of the lignin solution obtained in step (1), it is subjected to amination modification or phenolation modification to obtain modified lignin; (4) 5-hydroxymethylfurfural and modified lignin are subjected to a condensation reaction under the action of an acid catalyst to obtain an environmentally friendly rubber additive.

2. The method for preparing the environmentally friendly rubber additive based on corn cob according to claim 1, characterized in that, In step (1), the mass fraction of the acidic solution is 0.5-5%, the liquid-solid ratio of the acidic solution and corn cob powder is 8-12 mL:1 g, and the treatment conditions include: stirring at 100-120℃ for 2-3 hours.

3. The method for preparing the environmentally friendly rubber additive based on corn cob according to claim 1 or 2, characterized in that, In step (1), the mass fraction of the alkaline solution is 2-5%; the liquid-solid ratio of the alkaline solution and filter residue A is 8-12 mL: 1 g; the treatment conditions include: stirring at 100-120℃ for 3-5 h, solid-liquid separation, obtaining filter residue B and filtrate B, filter residue B is washed and dried to obtain cellulose, and filtrate B is a lignin solution.

4. The preparation method according to claim 1, characterized in that, In step (2), glucose undergoes isomerization and dehydration reactions under the action of Lewis acid catalyst and Brønsted acid catalyst to obtain 5-hydroxymethylfurfural.

5. The method for preparing the environmentally friendly rubber additive based on corn cob according to claim 4, characterized in that, The amount of Lewis acid catalyst added is 2-4% of the glucose mass, the amount of Brønsted acid catalyst added is 2-4% of the glucose mass, and the mass ratio of Lewis acid catalyst to Brønsted acid catalyst is 1:

1.

6. The method for preparing the environmentally friendly rubber additive based on corn cob according to claim 1, 4 or 5, characterized in that, In step (2), the isomerization and dehydration reaction methods include: the reaction environment is water, and the reaction is carried out at 120-140℃ and 0.3-0.5MPa for 3-6 hours. After the reaction is completed, 5-hydroxymethylfurfural is obtained by extraction-depressurized distillation combined purification.

7. The method for preparing the environmentally friendly rubber additive based on corn cob according to claim 1 or 2, characterized in that, In step (3), the amination modification method includes: dispersing the acid-precipitated lignin in an aqueous solution with a pH of 10-11, then adding aliphatic amine, adding formaldehyde solution dropwise at 60-90℃, keeping warm and stirring for 2-3 hours, and then cooling to obtain amination-modified lignin.

8. The method for preparing the environmentally friendly rubber additive based on corn cob according to claim 1 or 2, characterized in that, In step (3), the phenolic modification method includes: adding phenol to the acid-precipitated lignin, using sulfuric acid solution as a catalyst, keeping it heated and stirred at 90-110℃ for 3-4 hours, and then cooling to obtain phenolic modified lignin.

9. An environmentally friendly rubber additive, characterized in that: Prepared using the preparation method described in any one of claims 1-8.

10. The application of the environmentally friendly rubber additive of claim 9 as an adhesive or reinforcing agent in rubber products.

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