Modification method of aramid pulp fiber, aramid pulp fiber and rubber material

Abstract

The invention discloses a modification method of aramid pulp fibers, which comprises the following steps: putting the aramid pulp fibers into a modification solution for modification treatment, and grafting isocyanate groups on the surfaces of the aramid pulp fibers, the modified liquid contains an isocyanate-based silane coupling agent. The invention also provides an aramid pulp fiber and a rubber material. According to the modification method disclosed by the invention, the isocyanate group is grafted on the surface of the aramid pulp fiber through the isocyanate-based silane coupling agent, and the isocyanate group has relatively high reaction activity and can react with double bonds in a rubber matrix during sulfuration, so that the cross-linking density among natural rubber molecules is increased, and the natural rubber is more stable in performance. The mechanical property and the wear resistance of the rubber are improved.

Description

Technical Field

[0001] The present invention belongs to the field of polymer composites, and particularly relates to a modification method of a rubber reinforcing material, a rubber reinforcing material, and a rubber material. Background Art

[0002] Aramid is a synthetic fiber with high tensile strength, high tensile modulus, good fatigue resistance, chemical corrosion resistance, and dimensional stability. In addition, aramid also has excellent properties such as high heat resistance, low expansion, low thermal conductivity, non-combustibility, and insolubility, making it an ideal reinforcing material for rubber composites.

[0003] However, due to the steric hindrance effect of the benzene ring of aramid fibers and the high crystallinity of the molecular chain, it is difficult for the amide groups on the surface of aramid fibers to interact with other groups, seriously affecting the exertion of the excellent mechanical properties of aramid fibers. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies and defects in the background art, and provide a modification method of aramid pulp fibers, aramid pulp fibers, and a rubber material. The aramid pulp fibers obtained by this modification method can enhance the crosslinking density between rubber molecules during vulcanization, and improve the mechanical properties and wear resistance of aramid fiber / rubber composites.

[0005] To solve the above technical problem, the technical solution proposed by the present invention is as follows: A modification method of aramid pulp fibers, comprising the following steps: putting aramid pulp fibers into a modification liquid for modification treatment (the modification liquid is kept sufficient), and grafting isocyanate groups on the surface of the aramid pulp fibers; the modification liquid contains an isocyanate group silane coupling agent.

[0006] In the above modification method, preferably, the modification liquid is an ethanol solution, which contains an isocyanate group silane coupling agent and a dispersant. The mass content of the isocyanate group silane coupling agent is 2-10%, and the mass content of the dispersant is 0.5-1%. The presence of the dispersant is beneficial to the uniform dispersion of aramid pulp fibers and facilitates their uniform grafting. If the amount of the isocyanate group silane coupling agent is too small, the modification effect is not obvious, and it is difficult to play a crosslinking role with the rubber matrix, resulting in poor modification effect of aramid pulp fibers. In addition, considering economy and the limit of organic reactions, the amount of the isocyanate group silane coupling agent should not be too much, as excessive use does not significantly improve the effect.

[0007] In the above modification method, preferably, the isocyanate group-containing silane coupling agent includes one or more of 3-isocyanatopropyltriethoxysilane (KH-907), 3-isocyanatopropyltrimethoxysilane (KH-901), and 3-isocyanatopropylmethyldimethoxysilane (KH-9011). The above isocyanate group-containing silane coupling agent can react and graft with the surface groups of aramid pulp fibers, improving the effect of aramid pulp fibers.

[0008] In the above modification method, preferably, the dispersant includes one or more of nonylphenol-polyethylene glycol ether, sodium dodecyl diphenyl ether disulfonate, and sodium lauryl polyoxyethylene ether sulfate. Adding a dispersant to the modification solution can improve the dispersibility of aramid pulp fibers, which is beneficial to the efficiency of the silanization grafting reaction.

[0009] In the above modification method, preferably, the reaction time during the modification treatment is 2 - 10 h, and the reaction temperature is 40 - 100 °C. Controlling the minimum reaction time and the lowest reaction temperature enables the smooth progress of this modification treatment. If the time is too long or the temperature is too high, the improvement of the reaction effect is not obvious, and the energy consumption increases.

[0010] In the above modification method, preferably, first soak the aramid pulp fibers in acetone, dry them after ultrasonic cleaning, and then etch the surface of the aramid pulp fibers by the ultraviolet irradiation method, irradiating with an ultraviolet lamp for 5 - 10 min. The above treatment process can activate the surface of the aramid pulp fibers, facilitating the subsequent grafting of isocyanate groups.

[0011] As a general technical concept, the present invention also provides aramid pulp fibers prepared by the above modification method.

[0012] As a general technical concept, the present invention also provides a rubber material obtained by vulcanizing the above aramid pulp fibers and a rubber matrix. The above rubber matrix can be natural rubber or synthetic rubbers such as styrene-butadiene rubber, cis-1,4-polybutadiene rubber, nitrile rubber, and chloroprene rubber. During vulcanization, the vulcanization temperature is 140 - 160 °C, and the vulcanization time is 10 - 20 min.

[0013] Among the above-mentioned rubber materials, preferably, before vulcanization, a crosslinking synergist is first added to the aramid pulp fiber, mixed evenly, and then kneaded with the rubber matrix to mix the rubber matrix and the aramid pulp fiber; the crosslinking synergist includes one or more of aluminum distearoyl isopropylate, isopropyl tris(isostearoyl) phthalate, isopropyl tris(dodecylbenzenesulfonyl) phthalate, and tetraisopropyl bis(dilauryl phosphite) phthalate. In the present invention, a crosslinking synergist is added before vulcanization, and the crosslinking synergist and the modified aramid pulp fiber act synergistically, which is beneficial to promoting the crosslinking reaction between the aramid pulp fiber and the rubber matrix, and is beneficial to improving the mechanical properties and wear resistance of the final rubber material. More preferably, the crosslinking synergist is isopropyl tris(isostearoyl) phthalate, and the rubber matrix is natural rubber. In this case, the matching relationship between the crosslinking synergist, the rubber matrix, and the modified aramid pulp fiber is better.

[0014] Among the above-mentioned rubber materials, preferably, the addition amount of the crosslinking synergist is 1-2% of the mass of the aramid pulp fiber. If the amount of the crosslinking synergist is too small, the promoting effect on the crosslinking reaction between the modified aramid pulp fiber and the rubber matrix is limited. If the amount of the crosslinking synergist is too large, it will affect the performance of the rubber material. Therefore, the amount of the crosslinking synergist needs to be reasonably controlled. More preferably, the addition amount of the crosslinking synergist is 1% of the mass of the aramid pulp fiber.

[0015] More preferably, the preparation method of the above-mentioned rubber material includes the following steps: soaking the aramid pulp fiber in acetone, cleaning and drying it, and irradiating it with an ultraviolet lamp for 10 min; placing the ultraviolet-irradiated aramid pulp fiber in a silane coupling agent solution for sealing, where the silane coupling agent is KH-907, with a mass fraction of 8%, and the dispersant is sodium lauryl polyoxyethylene ether sulfate, with a mass fraction of 1%. Set the reaction time to 8 h and the reaction temperature to 80 °C; mix isopropyl tris(isostearoyl) phthalate (with a mass of 1% of the aramid pulp fiber) into the modified aramid pulp fiber and then knead it with the rubber; then cut the kneaded rubber into strips with a length of 5 mm and an appropriate thickness, put them into a mold, vulcanize them using a flat vulcanizer, and cut off the overflowing rubber after taking them out of the mold to obtain H-shaped strips.

[0016] Compared with the prior art, the advantages of the present invention are as follows: The modification method of the present invention grafts isocyanate groups on the surface of the aramid pulp fiber through an isocyanate group-containing silane coupling agent. The isocyanate group itself has strong reactivity and can react with the double bonds in the rubber matrix during sub-vulcanization, increasing the crosslinking density between natural rubber molecules and improving the mechanical properties and wear resistance of the rubber.

[0017] The method of the present invention directly modifies and grafts the surface of aramid pulp fibers and then uses them in a rubber matrix. It has the advantages of simple operation, high efficiency, easy control of the modification process of aramid pulp fibers, easy control of the modification process of the rubber matrix, high safety and less environmental pollution, etc., and has broad prospects in the application field of aramid fibers. Detailed Embodiments

[0018] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0019] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0020] Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0021] Comparative Example 1: A rubber material, and its preparation method includes the following steps: Step 1: Immerse the aramid pulp fibers in acetone, then wash and dry them, and irradiate them with an ultraviolet lamp for 10 min.

[0022] Step 2: Prepare a modification solution, wherein the silane coupling agent is an amino coupling agent (KH-550) with a mass fraction of 4%, and the dispersant is nonylphenol-polyethylene glycol ether with a mass fraction of 1%.

[0023] Step 3: Place the ultraviolet-irradiated aramid pulp fibers in the modification solution and seal them. Set the reaction time to 2 h and the reaction temperature to 40 °C.

[0024] Step 4: Knead the modified aramid pulp fibers with natural rubber.

[0025] Step 5: Cut the kneaded rubber into strips with a length of 5 mm and an appropriate thickness, put them into a mold, and vulcanize them using a flat vulcanizer (150 °C, 20 min). After taking them out of the mold, cut off the overflowing rubber to obtain H-shaped strips.

[0026] Example 1: A rubber material, and its preparation method includes the following steps: Step 1: Immerse the aramid pulp fibers in acetone, then wash and dry them, and irradiate them with an ultraviolet lamp for 10 min.

[0027] Step 2: Prepare the modified liquid, where the silane coupling agent is KH-901 with a mass fraction of 4%, and the dispersant is nonylphenol-polyethylene glycol ether with a mass fraction of 1%.

[0028] Step 3: Place the ultraviolet-irradiated aramid pulp fibers in the modified liquid and seal it. Set the reaction time to 2 h and the reaction temperature to 40 °C.

[0029] Step 4: Knead the modified aramid pulp fibers with natural rubber.

[0030] Step 5: Cut the kneaded rubber into strips with a length of 5 mm and an appropriate thickness, put them into a mold, and vulcanize them using a flat vulcanizer (150 °C, 20 min). After taking them out of the mold, cut off the overflowing rubber to obtain H-shaped strips.

[0031] Example 2: A rubber material, and its preparation method includes the following steps: Step 1: Immerse the aramid pulp fibers in acetone, then wash and dry them, and irradiate them with an ultraviolet lamp for 10 min.

[0032] Step 2: Prepare the modified liquid, where the silane coupling agent is KH-901 with a mass fraction of 4%, and the dispersant is sodium dodecyl diphenyl ether disulfonate with a mass fraction of 1%.

[0033] Step 3: Place the ultraviolet-irradiated aramid pulp fibers in the modified liquid and seal it. Set the reaction time to 2 h and the reaction temperature to 40 °C.

[0034] Step 4: Mix in aluminum isostearoyl aluminate as a crosslinking synergist with a mass of 1% of the aramid pulp fibers in the modified aramid pulp fibers, and then knead them with natural rubber.

[0035] Step 5: Cut the kneaded natural rubber into strips with a length of 5 mm and an appropriate thickness, put them into a mold, and vulcanize them using a flat vulcanizer (150 °C, 20 min). After taking them out of the mold, cut off the overflowing rubber to obtain H-shaped strips.

[0036] Example 3: A rubber material, and its preparation method includes the following steps: Step 1: Immerse the aramid pulp fibers in acetone, then wash and dry them, and irradiate them with an ultraviolet lamp for 10 min.

[0037] Step 2: Prepare the modified liquid, where the silane coupling agent is KH-907 with a mass fraction of 8%, and the dispersant is sodium lauryl ether sulfate with a mass fraction of 1%.

[0038] Step 3: Place the ultraviolet-irradiated aramid pulp fibers in the modified liquid and seal it. Set the reaction time to 8 h and the reaction temperature to 80 °C.

[0039] Step 4: Mix isopropyltriisostearoyl titanate, a crosslinking synergist, into the modified aramid pulp fiber, with a mass of 1% of the aramid pulp fiber, and then knead it with natural rubber.

[0040] Step 5: Cut the kneaded natural rubber into splines with a length of 5 mm and an appropriate thickness, put them into a mold, and vulcanize them using a flat vulcanizer (150 °C, 20 min). After taking them out of the mold, cut off the overflowing rubber material to obtain H-shaped splines.

[0041] Example 4: A rubber material, and its preparation method includes the following steps: Step 1: Immerse the aramid pulp fiber in acetone, wash and dry it, and irradiate it with an ultraviolet lamp for 10 min.

[0042] Step 2: Prepare a modification solution, where the silane coupling agent is KH-907 with a mass fraction of 8%, and the dispersant is sodium lauryl polyoxyethylene ether sulfate with a mass fraction of 1%.

[0043] Step 3: Place the ultraviolet-irradiated aramid pulp fiber in the modification solution and seal it. Set the reaction time to 8 h and the reaction temperature to 80 °C.

[0044] Step 4: Mix tetraisopropyl bis(dilauryl phosphite) titanate, a crosslinking synergist, into the modified aramid pulp fiber, with a mass of 2% of the aramid pulp fiber, and then knead it with natural rubber.

[0045] Step 5: Cut the kneaded natural rubber into splines with a length of 5 mm and an appropriate thickness, put them into a mold, and vulcanize them using a flat vulcanizer (150 °C, 20 min). After taking them out of the mold, cut off the overflowing rubber material to obtain H-shaped splines.

[0046] Example 5: A rubber material, and its preparation method includes the following steps: Step 1: Immerse the aramid pulp fiber in acetone, wash and dry it, and irradiate it with an ultraviolet lamp for 10 min.

[0047] Step 2: Prepare a modification solution, where the silane coupling agent is KH-9011 with a mass fraction of 6%, and the dispersant is sodium lauryl polyoxyethylene ether sulfate with a mass fraction of 0.5%.

[0048] Step 3: Place the ultraviolet-irradiated aramid pulp fiber in the modification solution and seal it. Set the reaction time to 6 h and the reaction temperature to 60 °C.

[0049] Step 4: Mix the modified pulp fiber with crosslinking synergist isopropyl tris (dodecylbenzenesulfonyl) phthalate, with a mass of 2% of the aramid pulp fiber, and then mix it with natural rubber.

[0050] Step 5: Cut the mixed natural rubber into splines with a length of 5 mm and an appropriate thickness and put them into a mold, and vulcanize them using a flat vulcanizer (150 °C, 20 min). After taking them out of the mold, cut off the overflowing rubber material to obtain H-shaped splines.

[0051] The mechanical properties and abrasion properties of the modified aramid pulp fiber-reinforced natural rubber composites prepared in the above examples and comparative examples are shown in Table 1 below, where the mechanical properties are tested in accordance with GB / T 529-2008, and the abrasion volume is tested in accordance with GB / T 1689-2014.

[0052] Table 1: Mechanical properties and abrasion properties of rubber composites prepared in examples and comparative examples

[0053] As can be seen from the above table, the modified aramid pulp fiber in this example can enhance the crosslinking density between natural rubber molecules and improve the mechanical properties and wear resistance of the aramid pulp fiber / natural rubber composite. Especially after the synergistic effect of the modified aramid pulp fiber and the crosslinking synergist, there is an obvious improvement in the mechanical properties and wear resistance of the rubber material.

Claims

1. A method for modifying aramid pulp fibers, characterized in that, It includes the following steps: Put the aramid pulp fiber into a modification liquid for modification treatment to graft isocyanate groups on the surface of the aramid pulp fiber; The modification liquid contains an isocyanate group silane coupling agent.

2. The modification method according to claim 1, characterized in that, The modification liquid is an ethanol solution, which contains an isocyanate group silane coupling agent and a dispersant. The mass content of the isocyanate group silane coupling agent is 2-10%, and the mass content of the dispersant is 0.5-1%.

3. The modification method according to claim 2, characterized in that, The isocyanate group silane coupling agent includes one or more of 3-isocyanatopropyltriethoxysilane, 3-isocyanatopropyltrimethoxysilane, and 3-isocyanatopropylmethyldimethoxysilane.

4. The modification method according to claim 2, wherein, The dispersant includes one or more of nonylphenol-polyethylene glycol ether, sodium dodecyl diphenyl ether disulfonate, and sodium lauryl polyoxyethylene ether sulfate.

5. The modification method according to claim 1, wherein The reaction time during the modification treatment is 2-10 h, and the reaction temperature is 40-100 °C.

6. The modification method according to any one of claims 1-5, characterized in that, First, soak the aramid pulp fiber in acetone, dry it after ultrasonic cleaning, and then etch the surface of the aramid pulp fiber by the ultraviolet irradiation method, and irradiate it with an ultraviolet lamp for 5-10 min.

7. An aramid pulp fiber prepared by the modification method according to any one of claims 1-6.

8. A rubber material, characterized in that, It is obtained by vulcanizing the aramid pulp fiber according to claim 7 and a rubber matrix.

9. The rubber material according to claim 8, characterized in that, Before vulcanization, first add a crosslinking synergist to the aramid pulp fiber, mix it evenly, and then mix it with the rubber matrix to mix the rubber matrix and the aramid pulp fiber; the crosslinking synergist includes one or several of aluminum di(stearoyl isopropoxide), isopropyl tris(isostearoyl) phthalate, isopropyl tris(dodecylbenzenesulfonyl) phthalate, and tetra-isopropyl di(dilauryl phosphite) phthalate.

10. The rubber material according to claim 9, characterized in that, The addition amount of the crosslinking synergist is 1-2% of the mass of the aramid pulp fiber.

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