A method for preparing oleophilic and hydrophobic corn stalk fibers for asphalt mixtures

Abstract

This invention discloses a method for preparing oleophilic and hydrophobic corn stalk fibers for asphalt mixtures, belonging to the technical field of asphalt mixtures. The preparation method first involves crushing and screening mature corn stalks, then softening and alkalizing the resulting corn stalk fragments under high temperature and pressure. The corn stalk fragments are then milled to obtain corn stalk fibers. Next, a plant fiber oleophilic and hydrophobic modifier is prepared using potassium hydroxide solution and carbon disulfide solution. The modifier and fibers are simultaneously added to a vacuum pressure impregnation device to impregnate and modify the resulting corn stalk fibers, obtaining the desired oleophilic and hydrophobic corn stalk fibers for asphalt mixtures. This invention can improve the oil absorption of corn stalk fibers while reducing their hydrophilicity. Adding the modified corn stalk fibers to asphalt mixtures can effectively improve the performance of asphalt mixtures, demonstrating significant practical value.

Description

Technical Field

[0001] This invention relates to the technical field of asphalt mixtures, and in particular to a method for preparing oleophilic and hydrophobic corn stalk fibers that can be used in asphalt mixtures. Background Technology

[0002] Asphalt pavement, due to its convenient construction and comfortable driving experience, has become a major road type in my country, applied across the country in various climates and traffic conditions. Asphalt mixtures, as the main component of asphalt pavement, play a crucial role in its performance. Asphalt mixtures are primarily composed of asphalt, coarse and fine aggregates, mineral powder, and fibers. The addition of fibers in asphalt mixtures serves to reinforce, connect, and absorb free asphalt. With increasing environmental awareness and in-depth research into the performance of asphalt mixtures, corn stalk fiber has gradually come into focus. The advantages of corn stalk fiber, such as good oil absorption, large specific surface area, and good environmental performance, have been proven and are widely used in practical engineering. However, because corn stalk fiber is made from corn stalks, its water absorption is better than its oil absorption. In asphalt mixtures, the intrusion of water reduces the adhesion between asphalt and aggregates, thus decreasing the pavement performance. Therefore, taking necessary measures to improve the oil absorption and water repellency of fibers is of significant practical importance. Patent CN109704649B discloses a method for preparing modified bamboo fiber asphalt mixture. The method involves first treating bamboo fiber with benzoic acid solution, then fully modifying the treated bamboo fiber in an oven, and finally adding the modified bamboo fiber to the asphalt mixture. While this modification method improves the road performance of the asphalt mixture to some extent, its effect on the fiber itself is not significant, especially regarding the crucial oil absorption and hydrophobicity properties of plant fibers. Furthermore, this method is applicable to bamboo fiber but not necessarily to corn stalk fiber because the two fibers have different compositions. Patent CN114150493A discloses a road-grade modified corn stalk fiber, its preparation method, and its application. The method involves first extracting corn stalk fiber, then treating the corn stalk fiber using microwave technology, and finally modifying the fiber with a silane coupling agent. Although this invention modifies corn stalk fiber and improves its performance, it does not address the modification of the corn stalk fiber's oil absorption and hydrophobicity properties.

[0003] In summary, existing methods for modifying and preparing corn stalk fibers lack specific techniques for improving their oil absorption and hydrophobicity. Furthermore, the preparation process for corn stalk fibers is relatively simple, and there is insufficient control over their size. Therefore, it is essential to propose a method for preparing oleophilic and hydrophobic corn stalk fibers for asphalt mixtures. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for preparing oleophilic and hydrophobic corn stalk fiber that can be used in asphalt mixtures, thereby improving the road performance of asphalt mixtures to a certain extent.

[0005] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:

[0006] A method for preparing oleophilic and hydrophobic corn stalk fiber for asphalt mixtures includes the following steps:

[0007] Step 1: After drying the mature corn stalks, crush and screen them to obtain corn stalk fragments with a diameter of less than 8 cm; soften and alkalize the obtained corn stalk fragments under high temperature and high pressure cooking environment to obtain corn stalk fragments with a pH value of 7-8.5; grind the alkalized corn stalk fibers into corn stalk fibers with a diameter of 50-80 μm and a length of 2-5 cm.

[0008] Step 2: Add potassium hydroxide solution and carbon disulfide to the ethanol solution, stir for the first time, then add potassium peroxide, dilute hydrochloric acid solution and ethyl acrylate, stir for the second time, and obtain the plant fiber oleophilic and hydrophobic modifier.

[0009] Step 3: After opening and preheating the vacuum pressure impregnation equipment, pour the plant fiber oleophilic and hydrophobic modifier obtained in Step 2 into the storage tank. Put the corn stalk fiber obtained in Step 1 into the impregnation container. Under high pressure, evacuate the impregnation container to a vacuum. Then, fill the impregnation container with liquid and pressurize it, so that the corn stalk fiber is impregnated and modified under high temperature and high pressure. Place the impregnated and modified corn stalk fiber in an oven and dry it at a constant temperature to obtain oleophilic and hydrophobic corn stalk fiber for asphalt mixture with an oil absorption rate of 8% to 12% and a water contact angle greater than 150°.

[0010] Preferably, the equipment used for crushing corn stalks in step 1 is a double-drum shaving machine with a cutter roller speed of 600 r / min, and the screening uses a 150-mesh screen.

[0011] Preferably, the equipment used in the high-temperature and high-pressure steaming environment in step 1 is a vertical steam sterilizer, with a steaming time of 1 hour, a steaming temperature of 121°C, and a steaming pressure of 0.14 MPa.

[0012] Preferably, the alkaline solution used in the alkalization treatment in step 1 is a 15% compound alkaline solution, and the liquid-to-material ratio of corn stalk fragments to the compound alkaline solution is 1:20.

[0013] Preferably, the equipment used for disc milling in step 1 is a high-concentration disc mill, with a spindle speed of 2400 r / min, a feed inlet screw speed of 150 r / min, a disc mill gap of 0.3 mm to 0.4 mm, and an accuracy controlled within 0.01 mm.

[0014] Preferably, in step 2, the concentration of potassium hydroxide solution is 15%–20%, and the concentration of dilute hydrochloric acid solution is 8%–10%.

[0015] Preferably, the first stirring conditions in step 2 are: stirring at 60°C for 30 minutes and stirring at room temperature for 1 hour; the second stirring conditions are: stirring at 40°C for 40 minutes and stirring at room temperature for 30 minutes.

[0016] Preferably, in step 3, the vacuum pressure impregnation equipment has a working pressure range of 0.6–2.5 MPa, a working temperature of 20–80°C, a leakage rate of 100 Pa·s, a preheating temperature of 55°C–65°C, a vacuum pressure of 300 Pa for the impregnation container, and a filling and pressurizing time of 45 min at a pressure of 2.0 MPa for the impregnation container.

[0017] As described in any of the above technical solutions, a method for using oleophilic and hydrophobic corn stalk fiber in asphalt mixtures involves adding the oleophilic and hydrophobic corn stalk fiber to the asphalt mixture at a ratio of 2% to 5% of the total mass of the asphalt mixture.

[0018] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0019] This invention proposes a preparation process that can effectively control the size of corn stalk fibers. The modification method mainly involves a chemical reaction to coat the surface of the corn stalk fibers with ethyl acrylate, thereby improving their oil absorption and hydrophobic properties. When the modified corn stalk fibers are added to asphalt mixtures, they can absorb more free asphalt than before modification, increasing the amount of structural asphalt and improving the adhesion between asphalt and aggregates, thus enhancing the high and low temperature performance of the asphalt mixture. Furthermore, the proposed modification method is specifically applicable to corn stalk fibers, demonstrating strong targeting and improving the utilization rate of corn stalk fibers in asphalt mixtures, which to some extent helps address the environmental pollution caused by corn stalks.

[0020] Specific implementation measures

[0021] The present invention proposes a method for preparing oleophilic and hydrophobic corn stalk fiber for asphalt mixtures, comprising the following steps:

[0022] Step 1: After drying the mature corn stalks, crush and screen them to obtain corn stalk fragments with a diameter of less than 8 cm; soften and alkalize the obtained corn stalk fragments under high temperature and high pressure cooking environment to obtain corn stalk fragments with a pH value of 7-8.5; grind the alkalized corn stalk fibers into corn stalk fibers with a diameter of 50-80 μm and a length of 2-5 cm.

[0023] Step 2: Add potassium hydroxide solution and carbon disulfide to the ethanol solution, stir for the first time, then add potassium peroxide, dilute hydrochloric acid solution and ethyl acrylate, stir for the second time, and obtain the plant fiber oleophilic and hydrophobic modifier.

[0024] Step 3: After opening and preheating the vacuum pressure impregnation equipment, pour the plant fiber oleophilic and hydrophobic modifier obtained in Step 2 into the storage tank. Put the corn stalk fiber obtained in Step 1 into the impregnation container. Under high pressure, evacuate the impregnation container to a vacuum. Then, fill the impregnation container with liquid and pressurize it, so that the corn stalk fiber is impregnated and modified under high temperature and high pressure. Place the impregnated and modified corn stalk fiber in an oven and dry it at a constant temperature to obtain oleophilic and hydrophobic corn stalk fiber for asphalt mixture with an oil absorption rate of 8% to 12% and a water contact angle greater than 150°.

[0025] Preferably, the equipment used for crushing corn stalks in step 1 is a double-drum shaving machine with a cutter roller speed of 600 r / min, and the screening uses a 150-mesh screen.

[0026] Preferably, the equipment used in the high-temperature and high-pressure steaming environment in step 1 is a vertical steam sterilizer, with a steaming time of 1 hour, a steaming temperature of 121°C, and a steaming pressure of 0.14 MPa.

[0027] Preferably, the alkaline solution used in the alkalization treatment in step 1 is a 15% compound alkaline solution, and the liquid-to-material ratio of corn stalk fragments to the compound alkaline solution is 1:20.

[0028] Preferably, the equipment used for disc milling in step 1 is a high-concentration disc mill, with a spindle speed of 2400 r / min, a feed inlet screw speed of 150 r / min, a disc mill gap of 0.3 mm to 0.4 mm, and an accuracy controlled within 0.01 mm.

[0029] Preferably, in step 2, the concentration of potassium hydroxide solution is 15%–20%, and the concentration of dilute hydrochloric acid solution is 8%–10%.

[0030] Preferably, the first stirring conditions in step 2 are: stirring at 60°C for 30 minutes and stirring at room temperature for 1 hour; the second stirring conditions are: stirring at 40°C for 40 minutes and stirring at room temperature for 30 minutes.

[0031] Preferably, in step 3, the vacuum pressure impregnation equipment has a working pressure range of 0.6–2.5 MPa, a working temperature of 20–80°C, a leakage rate of 100 Pa·s, a preheating temperature of 55°C–65°C, a vacuum pressure of 300 Pa for the impregnation container, and a filling and pressurizing time of 45 min at a pressure of 2.0 MPa for the impregnation container.

[0032] As described in any of the above technical solutions, a method for using oleophilic and hydrophobic corn stalk fiber in asphalt mixtures involves adding the oleophilic and hydrophobic corn stalk fiber to the asphalt mixture at a ratio of 2% to 5% of the total mass of the asphalt mixture.

[0033] Example 1:

[0034] (1) After drying mature corn stalks, they are crushed using a double-drum chipper at a speed of 600 r / min. Then, they are sieved using a 150-mesh screen to remove impurities remaining during chipping, resulting in corn stalk fragments with a diameter of less than 8 cm. The obtained corn stalk fragments are then placed into a cooking bag and put into a vertical steam sterilizer. A 15% compound alkaline solution is added to the vertical steam sterilizer, and the mixture is cooked at 121°C for 1 hour at a pressure of 0.14 MPa, resulting in corn stalk fragments with a pH of 7.2. The cooked corn stalk fragments are then fed into a high-concentration disc mill for grinding, with the disc mill gap controlled at 0.35 mm, to obtain corn stalk fibers with a diameter of 50–60 μm and an average length of 2.5 cm.

[0035] (2) Add 20% potassium hydroxide solution and carbon disulfide to the ethanol solution, stir at 60°C for 30 min, stir at room temperature for 45 min, then add potassium peroxide, 10% dilute hydrochloric acid solution and ethyl acrylate, stir at 40°C for 30 min, stir at room temperature for 30 min to obtain fiber oleophilic and hydrophobic modifier.

[0036] (3) Turn on the vacuum pressure impregnation equipment switch, start the heating system, set the temperature to 65℃, pour the fiber oleophilic and hydrophobic modifier into the storage tank, put the corn stalk fiber into the impregnation container, draw a vacuum at 300pa, then fill the impregnation container with liquid, pressurize the impregnation container after the liquid filling is completed, pressurize for 45 minutes, and pressurize at 2.0Mpa. After impregnation is completed, start the pressure relief system, take out the impregnated corn stalk fiber, place it in a 60℃ constant temperature oven, and dry it until completely dry to obtain oleophilic and hydrophobic corn stalk fiber for asphalt pavement.

[0037] Example 2:

[0038] (1) After drying mature corn stalks, they are crushed using a double-drum chipper at a speed of 550 r / min. Then, they are sieved using a 150-mesh screen to remove impurities remaining during chipping, resulting in corn stalk fragments with a diameter of less than 7 cm. The obtained corn stalk fragments are then placed into a cooking bag and put into a vertical steam sterilizer. A 15% compound alkaline solution is added to the vertical steam sterilizer, and the mixture is cooked at 121°C for 1.2 h at a pressure of 0.13 MPa, resulting in corn stalk fragments with a pH of 7.1. The cooked corn stalk fragments are then fed into a high-concentration disc mill for grinding, with the disc mill gap controlled at 0.37 mm, to obtain corn stalk fibers with a diameter of 50–65 μm and an average length of 3.5 cm.

[0039] (2) Add 15% potassium hydroxide solution and carbon disulfide to the ethanol solution, stir at 60°C for 40 min, stir at room temperature for 55 min, then add potassium peroxide, 9% dilute hydrochloric acid solution and ethyl acrylate, stir at 40°C for 40 min, stir at room temperature for 40 min to obtain fiber oleophilic and hydrophobic modifier.

[0040] (3) Turn on the vacuum pressure impregnation equipment switch, start the heating system, set the temperature to 65℃, pour the fiber oleophilic and hydrophobic modifier into the storage tank, put the corn stalk fiber into the impregnation container, draw a vacuum at 300pa, then fill the impregnation container with liquid, pressurize the impregnation container after filling, pressurize for 50 minutes, and pressurize at 2.1MPa. After impregnation, start the pressure relief system, take out the impregnated corn stalk fiber, place it in a 55℃ constant temperature oven, and dry it until completely dry to obtain oleophilic and hydrophobic corn stalk fiber for asphalt pavement.

[0041] Example 3:

[0042] (1) After drying mature corn stalks, they are crushed using a double-drum shredder with a blade roller speed of 650 r / min. Then, they are sieved with a 150-mesh sieve to remove impurities remaining during shredding, resulting in corn stalk fragments with a diameter of less than 9 cm. The obtained corn stalk fragments are then placed into a cooking bag and put into a vertical steam sterilizer. A 15% compound alkaline solution is added to the vertical steam sterilizer, and the mixture is cooked at 121°C for 1.5 h at a pressure of 0.1 MPa, resulting in corn stalk fragments with a pH of 7.8. The cooked corn stalk fragments are then fed into a high-concentration disc mill for grinding, with the disc mill gap controlled at 0.4 mm, to obtain corn stalk fibers with a diameter of 40–70 μm and an average length of 4.5 cm.

[0043] (2) Add 25% potassium hydroxide solution and carbon disulfide to the ethanol solution, stir at 60°C for 35 min, stir at room temperature for 50 min, then add potassium peroxide, 10% dilute hydrochloric acid solution and ethyl acrylate, stir at 40°C for 30 min, stir at room temperature for 50 min to obtain fiber oleophilic and hydrophobic modifier.

[0044] (3) Turn on the vacuum pressure impregnation equipment switch, start the heating system, set the temperature to 65℃, pour the fiber oleophilic and hydrophobic modifier into the storage tank, put the corn stalk fiber into the impregnation container, draw a vacuum at 300pa, then fill the impregnation container with liquid, pressurize the impregnation container after the liquid filling is completed, pressurize for 55 minutes, and pressurize at 2.2Mpa. After impregnation is completed, start the pressure relief system, take out the impregnated corn stalk fiber, place it in a 65℃ constant temperature oven, and dry it until completely dry to obtain oleophilic and hydrophobic corn stalk fiber for asphalt pavement.

[0045] Example 4:

[0046] (1) After drying mature corn stalks, they are crushed using a double-drum shredder at a speed of 700 r / min. Then, they are sieved using a 150-mesh screen to remove impurities remaining during shredding, resulting in corn stalk fragments with a diameter of less than 8.5 cm. The obtained corn stalk fragments are then placed into a cooking bag and put into a vertical steam sterilizer. A 20% compound alkaline solution is added to the vertical steam sterilizer, and the mixture is cooked at 121°C for 2 hours at a pressure of 0.13 MPa, resulting in corn stalk fragments with a pH of 7.7. The cooked corn stalk fragments are then fed into a high-concentration disc mill for grinding, with the disc mill gap controlled at 0.38 mm, to obtain corn stalk fibers with a diameter of 55–70 μm and an average length of 4 cm.

[0047] (2) Add 23% potassium hydroxide solution and carbon disulfide to the ethanol solution, stir at 60°C for 40 min, stir at room temperature for 1 h, then add potassium peroxide, 8% dilute hydrochloric acid solution and ethyl acrylate, stir at 40°C for 55 min, stir at room temperature for 40 min to obtain fiber oleophilic and hydrophobic modifier.

[0048] (3) Turn on the vacuum pressure impregnation equipment switch, start the heating system, set the temperature to 65℃, pour the fiber oleophilic and hydrophobic modifier into the storage tank, put the corn stalk fiber into the impregnation container, draw a vacuum at 300pa, then fill the impregnation container with liquid, pressurize the impregnation container after filling, pressurize for 1 hour, and pressurize at 2.3MPa. After impregnation, start the pressure relief system, take out the impregnated corn stalk fiber, place it in a 70℃ constant temperature oven, and dry it until completely dry to obtain oleophilic and hydrophobic corn stalk fiber for asphalt pavement.

[0049] The oil absorption rate and water contact angle of the oleophilic and hydrophobic corn stalk fibers in Examples 1 to 4 are shown in Table 1.

[0050] Oil absorption rate and water contact angle of oleophilic and hydrophobic corn stalk fibers in Examples 1-4

[0051]

[0052] The oleophilic and hydrophobic corn stalk fiber of this invention can be used to improve the performance of asphalt mixtures at an addition rate of 2% to 5%. To verify the performance improvement effect of this invention on asphalt mixtures, the oleophilic and hydrophobic corn stalk fiber prepared in Examples 1 to 4 was added to asphalt mixtures at a dosage of 3%, and its Marshall stability was tested. The test results are shown in Table 2.

[0053] Table 2: Marshall stability of asphalt mixtures in Examples 1-4

[0054]

[0055]

[0056] Table 1 shows that the present invention can effectively improve the oil absorption rate of fibers and increase the contact angle with water. Table 2 shows that the Marshall stability of asphalt mixtures is significantly improved after adding oleophilic and hydrophobic corn stalk fibers. In summary, the present invention can effectively improve the performance of asphalt mixtures.

Claims

1. A method for preparing oleophilic-hydrophobic type corn stalk fiber for asphalt mixture, characterized by The method comprises the following steps: Step 1: drying and crushing mature corn stalks to obtain corn stalk fragments with a diameter less than 8 cm; softening and alkali treatment of the obtained corn stalk fragments in a high-temperature and high-pressure cooking environment to obtain corn stalk fragments with a pH value of 7-8.5; and disc milling of the alkali-treated corn stalk fibers to obtain corn stalk fibers with a diameter of 50-80 μm and a length of 2-5 cm; Step 2: adding potassium hydroxide solution and carbon disulfide to an ethanol solution, stirring for the first time, then adding potassium peroxide, dilute hydrochloric acid solution and ethyl acrylate, stirring for the second time, and obtaining a plant fiber lipophilic hydrophobic modifier; Step 3: opening and preheating a vacuum pressure impregnation device, pouring the plant fiber lipophilic hydrophobic modifier obtained in Step 2 into a liquid storage tank, loading the corn stalk fibers obtained in Step 1 into an impregnation container, vacuumizing the impregnation container under high pressure, then liquid-filling and pressurizing the impregnation container, so that the corn stalk fibers are impregnated and modified in a high-temperature and high-pressure environment, and the impregnated and modified corn stalk fibers are placed in an oven for constant temperature drying to obtain lipophilic hydrophobic corn stalk fibers for asphalt mixture with an oil absorption rate of 8%-12% and a contact angle with water of greater than 150°.

2. A method of preparing oleophilic hydrophobic corn stalk fiber for asphalt mixture as claimed in claim 1, wherein, The corn stalk crushing device in Step 1 is a double-drum flaker with a knife roller rotating at a speed of 600 r / min, and the screening is performed by using a 150-mesh screen.

3. A method of preparing oleophilic hydrophobic corn stalk fiber for asphalt mixture as claimed in claim 1, wherein, The high-temperature and high-pressure cooking environment in Step 1 is a vertical steam sterilizer, the cooking time is 1 h, the cooking temperature is 121°C, and the cooking pressure is 0.14 Mpa.

4. The method of claim 1, wherein the oleophilic hydrophobic corn stover fiber for asphalt mixtures is characterized by, The alkali solution used in the alkali treatment in Step 1 is a composite alkali solution with a concentration of 15%, and the liquid-to-material ratio of the corn stalk fragments to the composite alkali solution is 1:

20.

5. The method of claim 1, wherein the oleophilic hydrophobic corn stover fiber for asphalt mixtures is characterized by, The disc milling device in Step 1 is a high-concentration disc mill, the main shaft rotates at a speed of 2400 r / min, the screw at the feeding port rotates at a speed of 150 r / min, the disc milling gap is 0.3-0.4 mm, and the precision is controlled to be 0.01 mm.

6. The method of claim 1, wherein the oleophilic hydrophobic corn stover fiber for asphalt mixtures is characterized by, The concentration of the potassium hydroxide solution in Step 2 is 15%-20%, and the concentration of the dilute hydrochloric acid solution is 8-10%.

7. A method of preparing oleophilic hydrophobic corn stalk fiber for asphalt mixture as claimed in claim 1, wherein, The first stirring condition in Step 2 is stirring at 60°C for 30 min and stirring at room temperature for 1 h, and the second stirring condition is stirring at 40°C for 40 min and stirring at room temperature for 30 min.

8. A method of preparing oleophilic hydrophobic corn stalk fiber for asphalt mixture as claimed in claim 1, wherein, The vacuum pressure impregnation device in Step 3 has a working pressure range of 0.6-2.5 Mpa, a working temperature of 20-80°C, a leakage rate of 100 pa.1 / s, a preheating temperature of 55-65°C, a vacuum pressure of 300 pa for the impregnation container, and a liquid-filling and pressurizing time of 45 min and a pressure of 2.0 Mpa for the impregnation container.

9. A method of using oleophilic hydrophobic corn stover fiber for asphalt mixtures, characterized by, The lipophilic-hydrophobic type corn stalk fiber is prepared by the method for preparing the lipophilic-hydrophobic type corn stalk fiber for asphalt mixture according to any one of claims 1-8.

Images