Aramid pulp pre-dispersion and method of making same
By employing a phased processing and interface layer formation method, the problem of uneven dispersion of aramid pulp in rubber was solved, achieving efficient reinforcement and stable bonding, and improving the overall performance of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAANXI PAROD NEW MATERIAL TECH CO LTD
- Filing Date
- 2026-04-07
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are insufficient to effectively disperse the three-dimensional fiber entanglement structure of aramid pulp in rubber, which leads to its easy agglomeration during processing, affecting the reinforcing effect and interfacial bonding stability.
A staged paraffin oil-stearic acid-silane coupling agent system is adopted. Through vacuum drying and stepwise heating treatment, it gradually penetrates the internal pores of the fiber and forms a stable interface layer on the fiber surface to achieve the pre-dispersion of aramid pulp.
Stable dispersion of aramid pulp in rubber matrix was achieved, which improved the modulus, fatigue resistance and thermal aging stability of the material, reduced the risk of agglomeration, and improved fiber utilization and interfacial bonding strength.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of polymer material processing technology, specifically to an aramid pulp predispersant and its preparation method. Background Technology
[0002] The long-term service stability of rubber products under high-temperature environments and high-frequency dynamic loads is crucial. To improve the modulus, fatigue resistance, and thermal aging stability of rubber materials, industrial manufacturers typically introduce reinforcing phases such as carbon black, silica, and short fibers to construct multiphase composite systems, thereby improving stress transmission paths and inhibiting crack propagation.
[0003] Aramid pulp, as a highly fibrous microfiber reinforced material, possesses excellent heat resistance and high specific surface area. Its microfiber size ranges from submicron to micron, enabling it to form a spatial reinforcing network within the rubber matrix, significantly improving rubber modulus and fatigue resistance. However, unlike conventional particulate fillers, aramid pulp exhibits a distinct three-dimensional fiber entanglement structure. Its interior is composed of numerous interwoven microfibers forming multi-level network units. Stable bonding nodes are formed between fibers through hydrogen bonding and mechanical entanglement. Furthermore, the presence of micropores and capillary channels within the fiber bundles, while requiring high specific surface area and reinforcing capacity, also makes it highly prone to agglomeration during actual processing.
[0004] To address the dispersion problem of aramid pulp in rubber, existing technologies have proposed various pretreatment schemes. For example, patent CN201710069877.X discloses a method for preparing highly active, finely pre-dispersed aramid pulp masterbatch, which uses a pretreatment composition (in-situ modifying agent, coupling agent, and penetration isolating agent) to pre-disperse the aramid pulp. However, this technology uses a one-time addition method, making it difficult for the oil phase to penetrate the internal pores of the fiber bundles, thus limiting the dispersion effect. Patent CN202311316575.X discloses a method for modifying aramid pulp, which uses dopamine and silane coupling agent for surface modification in an aqueous solution, followed by the application of a lubricant. Although this method can improve interfacial bonding, the aqueous phase treatment process is complex, and the lubricant is applied by mist spraying, making it difficult to achieve deep wetting inside the fibers. In addition, some technical solutions involve mixing aramid pulp with dispersing solvents, release agents, coupling agents, and dispersion carriers such as coumarone resin to prepare dispersions (e.g., CN201110424390.4). However, the introduction of resin carriers may affect the compatibility with the rubber matrix. For another example, patent CN110885461A discloses an aramid pulp dispersion and its preparation method, which uses release agents (such as calcium carbonate, carbon black, or silica) to modify the aramid pulp. Although this improves the dispersibility of aramid pulp in rubber to some extent, the binding ability of the release agent with the aramid pulp is poor, resulting in limited improvement.
[0005] During the rubber mixing or open milling stage, due to the high viscosity of the rubber matrix and the limited shear space, the entangled network inside the aramid pulp is difficult to be completely disintegrated. Some fiber agglomerates remain in the matrix at the micron scale, which not only reduces the effective utilization rate of the fiber, but also forms a stress concentration source under dynamic stress, inducing interfacial debonding or microcrack propagation, thereby weakening the overall reinforcement effect.
[0006] To address the aforementioned issues, existing technologies enhance mechanical dispersion by increasing the shear strength of the mixing process or by pre-wetting the aramid pulp in the oil phase before mixing, aiming to improve its dispersion in rubber. Additionally, some technologies directly introduce silane coupling agents into the rubber system to strengthen the interfacial bonding between the fiber and rubber molecular chains. However, in practical applications, these measures still fall short of fundamentally solving the problems of deep dispersion and interfacial structural stability of aramid pulp.
[0007] On the one hand, relying solely on mechanical shearing is insufficient to effectively disrupt the stable three-dimensional entangled network structure within aramid pulp. This is because insufficient shear strength makes it difficult for agglomerates to dissociate, while excessive shear strength can lead to decreased fiber length or even structural damage, thus hindering efficiency improvement. On the other hand, traditional oil-phase prewetting often involves a one-time addition of processing oil for surface impregnation. However, due to the inherent viscosity of rubber processing oils, they struggle to penetrate the internal pore structure of the fiber bundles through capillary action within a short time. The oil phase remains largely on the outer surface, leaving the internal regions relatively dry, making them prone to secondary agglomeration during subsequent mixing. Simultaneously, if silane coupling agents are directly added to high-viscosity rubber compounding systems, their diffusion process is limited, making it difficult to preferentially form a uniform and continuous reaction layer on the aramid fiber surface. Some coupling agents may undergo self-condensation or compete with other fillers for reaction, thereby reducing interfacial chemical anchoring efficiency. Summary of the Invention
[0008] To address the problems of complex rubber processing and unstable product performance in existing technologies, this invention provides an aramid pulp pre-dispersion and its preparation method, which can achieve substantial penetration into the internal pore structure of aramid pulp and overcome the limitations of traditional surface wetting.
[0009] This invention is achieved through the following technical solution: A method for preparing aramid pulp predispersant includes: Step 1: Dry the aramid pulp under vacuum conditions to obtain oven-dry aramid pulp; Paraffin oil, stearic acid and silane coupling agent are mixed in proportion and stirred and heated for the first time to form a homogeneous modified oil phase, which is then divided into part A and part B. Step 2: Add the oven-dry aramid pulp to the modified oil phase A, and stir and heat for the second time until an oil phase coating layer is formed on the fiber surface; then add the modified oil phase B, and stir and heat for the third time to form a paste-like mixture. Step 3: Stir and heat the paste-like mixture for the fourth time to obtain aramid pulp predispersant.
[0010] Preferably, in step 1, the temperature during vacuum drying is 80~100℃, the vacuum degree is 0.08~0.10 MPa, and the drying time is 12~15h.
[0011] Preferably, in step 1, the paraffin oil is a paraffin-based rubber processing oil with an aromatic content of 25.3%, a viscosity of 481 cst, and a density of 0.896 g / L; The silane coupling agent is an aminosilane coupling agent, preferably γ-aminopropyltriethoxysilane (KH-550).
[0012] Preferably, in step 1, the proportions of paraffin oil, stearic acid, and silane coupling agent, by mass parts, are 40-60 parts paraffin oil, 4-6 parts stearic acid, and 1-3 parts silane coupling agent.
[0013] Preferably, in step 1, the temperature during the first stirring and heating is 75~85℃, the stirring speed is 200~300 RPM, and the time is 10~15 min.
[0014] Preferably, in step 2, the mass ratio of oven-dried aramid pulp, modified oil phase A, and modified oil phase B is (2~3):(10~15):(8~12).
[0015] Preferably, in step 2, the conditions for the second and third stirring and heating are the same: the temperature is 100~110℃, the stirring rate is 400~500 RPM, and the stirring time is 20~30 min.
[0016] Preferably, in step 3, during the fourth stirring and heating, the temperature is 120~130℃, the stirring rate is 600~800RPM, and the stirring time is 40~60 min.
[0017] An aramid pulp predispersant prepared by a method is disclosed. The predispersant contains an oil phase layer containing paraffin oil and stearic acid on the surface of the aramid pulp fibers, and a silane coupling agent is grafted onto the surface of the aramid fibers by chemical bonding. The predispersant is solid or paste-like at room temperature and can melt and flow at temperatures above 80°C.
[0018] Application of an aramid pulp predispersant in rubber.
[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a method for preparing a predispersed aramid pulp. This method utilizes the reversible solid-liquid phase transition characteristics of the paraffin oil-stearic acid system, and through the synergistic effect of staged oil phase wetting and in-situ silane coupling reaction, achieves a stable predispersed modification treatment of aramid pulp in a rubber matrix. The specific details are as follows:
[0020] First, a modified oil phase is introduced in stages, allowing it to gradually penetrate the capillary pores and microchannels within the aramid pulp fiber bundles under controlled temperature and viscosity conditions. Compared to existing technologies where processing oil is added only once and forms a coating layer on the surface, the oil phase of this invention forms a continuous wetting layer at fiber interlacing nodes and internal pores. This weakens the stable three-dimensional network formed between fibers by hydrogen bonds and mechanical interlocking, transforming the aggregate structure from a dense, overall structure to a loose, separable one. This avoids the defect of the oil phase remaining only on the surface in traditional processes, fundamentally solving the potential for secondary agglomeration of aramid pulp due to internal dry areas.
[0021] Secondly, this invention achieves a stepwise temperature control through a second and third heating process, ensuring that the fiber is fully wetted and the three-dimensional network structure is sufficiently relaxed before triggering the condensation reaction of the silane coupling agent by raising the temperature further. Specifically, during the second heating (100~110℃), the physical wetting stage is underway, primarily involving oil phase penetration and fiber untangling. The viscosity of the paraffin oil decreases, stearic acid melts, and the mixed oil phase enters the micropores and interlacing nodes within the fiber bundle through capillary action. Simultaneously, the heat energy causes some intermolecular hydrogen bonds to break, transforming the tightly entangled fiber three-dimensional network into a loose and accessible state. At this stage, the silane coupling agent merely migrates with the oil phase to the fiber surface and interior without triggering chemical bonding.
[0022] When the temperature is raised to the chemical bonding stage of the third heating (120~130℃), the silane coupling agent reaches the activation energy threshold. Its alkoxy groups undergo condensation reactions with the active groups such as hydroxyl and carboxyl groups on the surface of the aramid fiber, forming covalent bonds, thereby constructing a stable interface layer in situ on the fiber surface. Compared with the prior art where the coupling agent is directly added to the high viscosity rubber system or reacts prematurely in the aqueous phase, this invention avoids the coupling agent from failing due to intermolecular self-condensation forming oligomers before sufficient wetting by controlling the temperature in stages. It also prevents the coupling agent from reacting too early and locking and hardening the surface of the undissociated fiber aggregates, ensuring that the fiber network is fully opened before chemical anchoring, thus achieving a sequence of dispersion followed by fixation.
[0023] The aramid pulp predispersant prepared by the present invention exhibits a reversible solid-liquid phase transition characteristic. At room temperature, it is solid or paste-like, facilitating storage, transportation, and metering. At rubber processing temperatures, the melting of stearic acid reduces the system viscosity, causing the predispersant to transition from a solid to a liquid state. This facilitates solid-liquid feeding and in-situ dynamic dispersion of the aramid pulp within a rubber matrix. Furthermore, the reversible solid-liquid phase transition characteristic of the predispersant is not reported in existing aramid pulp predispersant technologies. Attached Figure Description
[0024] Figure 1 This is a flowchart illustrating the preparation process of an aramid pulp predispersant according to the present invention.
[0025] Figure 2 This is a schematic diagram of the wetting mechanism of the aramid pulp predispersant by the dispersing oil according to the present invention.
[0026] Figure 3 This is a scanning electron microscope (SEM) image of an existing pulp.
[0027] Figure 4 This is a scanning electron microscope (SEM) image of a portion of the aramid pulp from Example 1 after processing according to the present invention.
[0028] Figure 5 This is a scanning electron microscope (SEM) image of another part of the aramid pulp of Example 1 after processing according to the present invention. Detailed Implementation
[0029] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.
[0030] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.
[0031] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that commonly used dictionary-defined terms should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.
[0032] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.
[0033] This invention discloses a method for preparing aramid pulp predispersant, referring to... Figure 1 ,include: Step 1: Dry the aramid pulp at a vacuum of 0.08~0.10 MPa and a temperature of 80~100℃ for 12~15 hours to obtain oven-dried aramid pulp.
[0034] Paraffin oil, stearic acid, and silane coupling agent were mixed in proportion and stirred and heated for the first time to form a homogeneous modified oil phase, which was then divided into part A and part B.
[0035] The paraffin oil is a paraffin-based rubber processing oil with an aromatic hydrocarbon content of 25.3%, a viscosity of 481 cst, and a density of 0.896 g / L. The silane coupling agent is an aminosilane coupling agent, preferably γ-aminopropyltriethoxysilane (KH-550).
[0036] The proportions of paraffin oil, stearic acid, and silane coupling agent, by mass, are 40-60 parts paraffin oil, 4-6 parts stearic acid, and 1-3 parts silane coupling agent.
[0037] During the first stirring and heating, the temperature should be 75~85℃, the stirring speed should be 200~300 RPM, and the time should be 10~15 min.
[0038] Step 2: Add the oven-dried aramid pulp to the modified oil phase A and stir and heat for a second time until an oil phase coating layer is formed on the fiber surface; then add the modified oil phase B and stir and heat for a third time to form a paste-like mixture.
[0039] The mass ratio of oven-dried aramid pulp, modified oil phase A, and modified oil phase B is (2~3):(10~15):(8~12).
[0040] During the third stirring and heating, the temperature is 100~110℃, the stirring rate is 400~500 RPM, and the stirring time is 20~30 min.
[0041] Step 3: Stir and heat the paste-like mixture for the fourth time to allow the silane coupling agent to undergo a chemical bonding reaction on the surface of the aramid fiber, complete the condensation reaction of the silane coupling agent and form a stable interface layer, and obtain the aramid pulp pre-dispersion.
[0042] During the fourth stirring and heating, the temperature was 120~130℃, the stirring rate was 600~800 RPM, and the stirring time was 40~60 min.
[0043] The present invention discloses a method for preparing aramid pulp predispersant by mixing paraffin oil, stearic acid and silane coupling agent in a certain proportion and dividing them evenly into two parts. These parts are then stirred and heated together with oven-dried aramid pulp in sequence. By pre-completing internal lubrication and structural relaxation treatment, the stability of the agglomeration structure is reduced, and the friction coefficient between fibers and the bonding strength of nodes are significantly reduced, forming an oil phase coating layer on the fiber surface. Subsequently, the silane coupling agent undergoes a chemical bonding reaction on the surface of the aramid fiber, thereby obtaining the aramid pulp predispersant.
[0044] This invention also discloses an aramid pulp predispersant obtained by a method for preparing aramid pulp predispersant, referring to... Figure 2 The aramid pulp fiber surface in this pre-dispersion is coated with an oil phase layer containing paraffin oil and stearic acid. The oil phase can gradually penetrate into the fiber network to form a uniform isolation layer, which can reduce the proportion of dry areas inside the fiber bundle. At the same time, under controlled conditions, it can promote the coupling agent to react in a directional manner on the fiber surface to form a stable interface structure, thereby maintaining the dispersion stability and interfacial bonding strength of fiber units in the subsequent rubber compounding process. This has important engineering significance for achieving high-efficiency reinforcement, reducing the risk of agglomeration, and improving the batch consistency of materials, and is conducive to industrial promotion and application.
[0045] Silane coupling agents are grafted onto the surface of aramid fibers via chemical bonding. Their alkoxy groups undergo condensation reactions with active groups such as hydroxyl and carboxyl groups on the surface of aramid fibers to form covalent bonds, thereby constructing a stable interface layer in situ on the fiber surface.
[0046] The pre-dispersion is solid or paste-like at room temperature, but can melt and flow at temperatures above 80°C.
[0047] The present invention also discloses the application of an aramid pulp predispersant in rubber.
[0048] The interior of the aramid pulp predispersant exhibits a gradient structure consisting of a high-modulus fiber skeleton and an exterior flexible transition layer composed of an oil phase and a coupling interface layer. During the process of rubber being subjected to stress, this structure can buffer local stress concentration, allowing the load to be transferred from the rubber matrix to the fiber skeleton step by step, rather than abruptly concentrating at the interface. This improves the material modulus and tensile strength while maintaining good elongation at break and fatigue performance.
[0049] Adding aramid pulp pre-dispersion during rubber internal mixing allows for dispersion under conventional shear conditions without increasing rotation speed or extending mixing time, nor does it require modifying the production line or altering the vulcanization system formulation. This demonstrates excellent process compatibility and feasibility for large-scale production. Furthermore, due to substantial improvements in dispersion uniformity and interfacial bonding quality, the aramid pulp of this invention can effectively enhance performance even at lower addition levels, reducing the problems of increased processing viscosity and energy consumption caused by high filler content. Example 1
[0050] Step 1: Dry the aramid pulp at 80℃ and 0.08 MPa for 12 h to obtain oven-dried aramid pulp; Take 50 parts by mass of paraffin oil, 5 parts of stearic acid and 1.0 part of γ-aminopropyltriethoxysilane (KH-550) and mix them. Heat to 80°C and heat at a stirring rate of 250 RPM for 10 min to completely dissolve the stearic acid and form a homogeneous modified oil phase. Divide the modified oil phase into part A and part B by mass ratio of 12:10. Step 2: By weight, take 2.0 parts of oven-dried aramid pulp and add it to part A of modified oil phase. Heat to 105°C and stir at a stirring rate of 450 RPM for 25 min for initial impregnation to form an oil phase coating layer on the fiber surface. Then add part B of modified oil phase, maintain the temperature at 105°C, and continue stirring for 12 min to fully wet the aramid pulp and form a paste-like mixture. Step 3: Continue heating the paste-like mixture to 125°C and stir at a stirring rate of 700 RPM for 50 min to obtain the aramid pulp predispersant. Example 2
[0051] Step 1: Dry the aramid pulp at 80℃ and 0.08 MPa for 12 h to obtain oven-dried aramid pulp; Take 50 parts by mass of paraffin oil, 5 parts of stearic acid and 1.5 parts of γ-aminopropyltriethoxysilane (KH-550) and mix them. Heat to 80°C and heat at a stirring rate of 250 RPM for 10 min to completely dissolve the stearic acid and form a homogeneous modified oil phase. Divide the modified oil phase into part A and part B by mass ratio of 10:8. Step 2: By weight, take 2.2 parts of oven-dried aramid pulp and add it to part A of modified oil phase. Heat to 105°C and stir at a stirring rate of 450 RPM for 25 min for initial impregnation to form an oil phase coating layer on the fiber surface. Then add part B of modified oil phase, maintain the temperature at 105°C, and continue stirring for 12 min to fully wet the aramid pulp and form a paste-like mixture. Step 3: Continue heating the paste-like mixture to 120°C and stir at a stirring rate of 600 RPM for 60 min to obtain the aramid pulp predispersant. Example 3
[0052] Step 1: Dry the aramid pulp at 80℃ and 0.08 MPa for 12 h to obtain oven-dried aramid pulp; Take 50 parts by mass of paraffin oil, 5 parts of stearic acid and 2 parts of γ-aminopropyltriethoxysilane (KH-550) and mix them. Heat to 85°C and heat at a stirring rate of 300 RPM for 10 min to completely dissolve the stearic acid and form a homogeneous modified oil phase. Divide the modified oil phase into part A and part B by mass ratio of 15:12. Step 2: By weight, take 2.5 parts of oven-dry aramid pulp and add it to part A of modified oil phase. Heat to 110°C and stir at a stirring rate of 500 RPM for 20 min for initial impregnation to form an oil phase coating layer on the fiber surface. Then add part B of modified oil phase, maintain the temperature at 110°C, and continue stirring for 15 min to fully wet the aramid pulp and form a paste-like mixture. Step 3: Continue heating the paste-like mixture to 130°C and stir at a stirring rate of 800 RPM for 40 min to obtain the aramid pulp predispersant. Example 4
[0053] Step 1: Dry the aramid pulp at 80℃ and 0.08 MPa for 12 h to obtain oven-dried aramid pulp; Take 50 parts by mass of paraffin oil, 5 parts of stearic acid and 2.5 parts of γ-aminopropyltriethoxysilane (KH-550) and mix them. Heat to 80°C and heat at a stirring rate of 250 RPM for 12 min to completely dissolve the stearic acid and form a homogeneous modified oil phase. Divide the modified oil phase into part A and part B by mass ratio of 13:9. Step 2: By weight, take 2.8 parts of oven-dried aramid pulp and add it to part A of modified oil phase. Heat to 105°C and stir at a stirring rate of 450 RPM for 25 min for initial impregnation to form an oil phase coating layer on the fiber surface. Then add part B of modified oil phase, maintain the temperature at 105°C, and continue stirring for 12 min to fully wet the aramid pulp and form a paste-like mixture. Step 3: Continue heating the paste-like mixture to 125°C and stir at a stirring rate of 700 RPM for 50 min to obtain the aramid pulp predispersant. Example 5
[0054] Step 1: Dry the aramid pulp at 80℃ and 0.08 MPa for 12 h to obtain oven-dried aramid pulp; Take 50 parts by mass of paraffin oil, 5 parts of stearic acid and 3.0 parts of γ-aminopropyltriethoxysilane (KH-550) and mix them. Heat to 80°C and heat at a stirring rate of 250 RPM for 10 min to completely dissolve the stearic acid and form a homogeneous modified oil phase. Divide the modified oil phase into part A and part B by mass ratio of 14:11. Step 2: Take 3.0 parts by weight of oven-dried aramid pulp and add it to part A of modified oil phase. Heat to 105°C and stir at a stirring rate of 450 RPM for 25 min for initial impregnation to form an oil phase coating layer on the fiber surface. Then add part B of modified oil phase, maintain the temperature at 105°C, and continue stirring for 12 min to fully wet the aramid pulp and form a paste-like mixture. Step 3: Continue heating the paste-like mixture to 125°C and stir at a stirring rate of 700 RPM for 50 min to obtain the aramid pulp predispersant.
[0055] The aramid pulp pre-dispersions prepared in Examples 1-5 above were mixed and vulcanized according to the same basic formula (100 parts natural rubber, the pre-dispersions obtained in the examples, 5 parts zinc oxide, 2 parts stearic acid, 1.5 parts accelerator CZ, and 2.5 parts sulfur). Their mechanical properties and dispersion state were tested, and the results are shown in Table 1.
[0056] Table 1. Relevant data on the dispersion of the products obtained in Examples 1-5 into rubber. Example Dispersion Tensile strength (MPa) Tear strength (kN / m) Elongation at break (%) Storage stability 1 The fibers are evenly dispersed and there are no visible agglomerates. 14.9 24.4 646 No change after 30 days, solid-state stable 2 The fibers are evenly dispersed and there are no visible agglomerates. 17.6 29.2 585 No change after 30 days, solid-state stable 3 The fibers are evenly dispersed and there are no visible agglomerates. 21.3 35.8 541 No change after 30 days, solid-state stable 4 The fibers are evenly dispersed and there are no visible agglomerates. 23.7 40.4 503 No change after 30 days, solid-state stable 5 The fibers are evenly dispersed and there are no visible agglomerates. 26.5 45.7 478 No change after 30 days, solid-state stable Referring to Table 1, the aramid pulp predispersants prepared in Examples 1-5 all exhibited excellent dispersion in the rubber matrix. With a consistent increase in the amount of aramid pulp and silane coupling agent, the mechanical properties of the composite material showed a significant gradient improvement trend, fully demonstrating the advanced nature and controllability of the technical solution of this invention. Furthermore, all examples remained stable in a solid state and showed no change in dispersion after 30 days at room temperature, further indicating that the predispersants have a stable structure, are easy to store and transport industrially, and have good engineering application prospects.
[0057] As the amount of aramid pulp added increased from 2.0 parts to 3.0 parts, and the amount of silane coupling agent increased simultaneously from 1.0 parts to 3.0 parts, the tensile strength of the composite material gradually increased from 14.9 MPa to 26.5 MPa, the tear strength increased from 24.4 kN / m to 45.7 kN / m, and the elongation at break decreased regularly from 646% to 478%. This indicates that, under the premise of ensuring good dispersion, increasing the content of the reinforcing phase and the interfacial bonding strength can linearly improve the mechanical properties of the material, and can achieve wide-range adjustable performance to meet the needs of different application scenarios.
[0058] Figure 3 The image in the middle is a scanning electron microscope (SEM) image of untreated aramid pulp, showing the structural features of tightly entangled fibers forming a stable three-dimensional network. Figure 4 and Figure 5 The image shows a scanning electron microscope (SEM) image of the aramid pulp processed according to the present invention. It can be seen that the paraffin oil-stearic acid mixed oil phase is uniformly attached to the surface of the aramid fiber, encapsulating the entanglement network inside the aramid pulp, and the fibers change from a tightly entangled state to a loose state.
[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.
Claims
1. A method for preparing aramid pulp predispersant, characterized in that, include: Step 1: Dry the aramid pulp under vacuum conditions to obtain oven-dry aramid pulp; Paraffin oil, stearic acid and silane coupling agent are mixed in proportion and stirred and heated for the first time to form a homogeneous modified oil phase, which is then divided into part A and part B. Step 2: Add the oven-dry aramid pulp to the modified oil phase A, and stir and heat for the second time until an oil phase coating layer is formed on the fiber surface; then add the modified oil phase B, and stir and heat for the third time to form a paste-like mixture. Step 3: Stir and heat the paste-like mixture for the fourth time to obtain aramid pulp predispersant.
2. The method for preparing aramid pulp predispersion according to claim 1, characterized in that, In step 1, during vacuum drying, the temperature is 80~100℃, the vacuum degree is 0.08~0.10 MPa, and the drying time is 12~15h.
3. The method for preparing aramid pulp predispersion according to claim 1, characterized in that, In step 1, the paraffin oil is a paraffin-based rubber processing oil with an aromatic content of 25.3%, a viscosity of 481 cst, and a density of 0.896 g / L. The silane coupling agent is an aminosilane coupling agent, preferably γ-aminopropyltriethoxysilane (KH-550).
4. The method for preparing aramid pulp predispersion according to claim 1, characterized in that, In step 1, the proportions of paraffin oil, stearic acid, and silane coupling agent, by mass, are 40-60 parts paraffin oil, 4-6 parts stearic acid, and 1-3 parts silane coupling agent.
5. The method for preparing aramid pulp predispersant according to claim 1, characterized in that, In step 1, during the first stirring and heating, the temperature is 75~85℃, the stirring speed is 200~300 RPM, and the time is 10~15 min.
6. The method for preparing aramid pulp predispersion according to claim 1, characterized in that, In step 2, the mass ratio of oven-dried aramid pulp, modified oil phase A, and modified oil phase B is (2~3):(10~15):(8~12).
7. The method for preparing aramid pulp predispersion according to claim 1, characterized in that, In step 2, the conditions for the second and third stirring and heating are the same: the temperature is 100~110℃, the stirring rate is 400~500 RPM, and the stirring time is 20~30 min.
8. The method for preparing aramid pulp predispersion according to claim 1, characterized in that, In step 3, during the fourth stirring and heating, the temperature is 120~130℃, the stirring rate is 600~800 RPM, and the stirring time is 40~60 min.
9. An aramid pulp predispersant obtained by the method for preparing aramid pulp predispersant as described in claims 1-8, characterized in that, The aramid pulp fiber surface in this pre-dispersion is coated with an oil phase layer containing paraffin oil and stearic acid, and a silane coupling agent is grafted onto the aramid fiber surface through chemical bonding; it is solid or paste-like at room temperature and can melt and flow above 80°C.
10. The application of the aramid pulp predispersant as described in claim 9 in rubber.