A bio-based cable material and a method for its preparation

Abstract

This invention proposes a bio-based cable material and its preparation method, comprising the following steps: pretreating a bio-based resin mixture and a compatibilizer, then adding the compatibilizer to the bio-based resin mixture for premixing to obtain a preform, wherein the bio-based resin mixture includes a continuous phase and a toughening phase; adding ammonium polyphosphate to the preform for mixing, then adding a synergist and an inorganic flame retardant for further mixing to obtain a flame-retardant intermediate material; pre-dispersing a nano-carbon mixture, then adding it to the flame-retardant intermediate material for mixing to obtain a molding compound; and granulating the molding compound to obtain the bio-based cable material. Through the stepwise introduction and combination of the continuous phase, toughening phase, compatibilizer, ammonium polyphosphate, synergist, inorganic flame retardant, and nano-carbon mixture, the resulting bio-based cable material can meet the multiple performance requirements of cable materials within the same material system.

Description

Technical Field

[0001] This invention belongs to the field of cable material technology, and in particular relates to a bio-based cable material and its preparation method. Background Technology

[0003] Bio-based resins belong to the polymer resin system and, like traditional petroleum-based resins, can be formulated into insulating or sheathing materials with continuous phase structures through molecular chain structure design, blending modification, cross-linking curing, or filler composites. Cable materials typically require good processability, mechanical strength, flexibility, electrical insulation, and certain heat resistance and environmental stability. Bio-based resins, after proper formulation design, can also meet these basic requirements, thus possessing a basis for application as cable matrix materials. Many bio-based resin molecules contain ester groups, ether bonds, long-chain aliphatic structures, aromatic structures, or reactive functional groups. These structures help impart certain flexibility, adhesion, and film-forming properties to the material, forming a stable coating on the conductor in the cable insulation or sheath layer.

[0004] However, cable materials not only need to be able to be molded and coated on the conductor surface, but also need to maintain stable structure and performance under long-term heat, bending, friction, and electric field effects. While single bio-based resins have the advantage of biological origin, if they are not combined with their molecular structure characteristics for blending modification, cross-linking curing, or filler composite, their structure, flexibility, mechanical support capacity, and environmental resistance are often insufficient, making it difficult to directly adapt to the usage requirements of cable insulation or sheath layers. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a bio-based cable material and its preparation method, which aims to solve the compatibility problem of bio-based resins in meeting the multi-performance synergy requirements of cable materials.

[0006] To solve the above-mentioned technical problems, the present invention is implemented as follows: The present invention proposes a method for preparing a bio-based cable material, the steps of which include: S1. After pretreating the bio-based resin mixture and the compatibilizer, the compatibilizer is added to the bio-based resin mixture for premixing to obtain a preform, wherein the bio-based resin mixture includes a continuous phase and a toughening phase; S2. Add ammonium polyphosphate to the preform and mix, then add synergist and inorganic flame retardant and continue mixing to obtain flame retardant intermediate material; S3. After pre-dispersing the nano-carbon mixture, it is added to the flame-retardant intermediate material for mixing to obtain the molding material. The molding material is then granulated to obtain the bio-based cable material.

[0007] In some embodiments of the present invention, step S1 includes: S1.1. The continuous phase and the toughening phase are added to the drying equipment for pretreatment. The continuous phase is dried at 55-70℃ for 4-8 hours, and the toughening phase is dried at 45-65℃ for 3-6 hours. S1.2. The compatibilizer is activated and pretreated by controlling the temperature at 50-80℃ and the time at 20-60 min, and stirring at 100-300 r / min to obtain the pretreated compatibilizer. S1.3. The pretreated continuous phase and toughening phase are added to the mixing equipment for premixing. The mixing temperature is controlled at 140-165℃, the rotation speed is 20-60 r / min, and the time is 3-8 min to obtain the initial two-phase mixture. S1.4 Add the pretreated compatibilizer to the initial two-phase mixture in stages and mix, controlling the mixing temperature at 145-170℃, the rotation speed at 25-70 r / min, and the time at 5-12 min to obtain the preform; S1.5. The preform is subjected to steady-state release treatment, with the treatment temperature controlled at 130-150℃ and the time at 1-3 min, to obtain the preform.

[0008] In some embodiments of the present invention, in step S1, the continuous phase includes at least one of polylactic acid, polybutylene succinate, and polyhydroxy fatty acid ester; the toughening phase includes at least one of poly-3-hydroxybutyrate-3-hydroxyhexanoate, polycaprolactone, and polyhydroxybutyrate valerate; and the compatibilizer includes at least one of maleic anhydride graft polymer compatibilizer, epoxy-reactive compatibilizer, and isocyanate reactive compatibilizer.

[0009] In some embodiments of the present invention, step S2 includes: S2.1 Surface compounding treatment of ammonium polyphosphate and synergist, controlling the treatment temperature at 85-110℃, the rotation speed at 200-500 r / min, and the time at 10-30 min, to obtain flame retardant precursor composite; S2.2 Add the inorganic flame retardant to the flame retardant precursor compound and perform low-speed coating treatment. Control the treatment temperature at 70-95℃, the rotation speed at 80-200r / min, and the time at 15-40min to obtain layered flame retardant composite particles. S2.3 Add the layered flame-retardant composite particles to the preform in batches for embedding treatment, control the embedding temperature to 145-165℃, the rotation speed to 25-55r / min, the interval between each batch addition to 30-120s, and the total time to 4-10min to obtain the flame-retardant embedding material. S2.4. The flame-retardant insert is subjected to low-shear bonding treatment, with the bonding temperature controlled at 130-150℃, the rotation speed at 10-25r / min, and the time at 2-6min, to obtain the flame-retardant intermediate material.

[0010] In some embodiments of the present invention, in step S2, the synergist includes at least one of pentaerythritol, melamine, phytic acid, lignin, starch, and chitosan, and the inorganic flame retardant includes at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, talc, and silicon dioxide.

[0011] In some embodiments of the present invention, step S2 includes: S2.1 Add ammonium polyphosphate to the dispersion medium and stir and disperse it at room temperature to 50°C for 20 to 60 minutes to obtain ammonium polyphosphate spray solution; S2.2. Apply ammonium polyphosphate spray solution to the surface of the preform and dry it at 50-90℃ for 5-30 minutes to obtain the main flame retardant layer preform. S2.3. Add the synergist to the dispersion medium and disperse it to obtain the synergistic treatment liquid. Contact the synergistic treatment liquid with the main flame retardant layer preform to obtain the synergistic composite preform. S2.4. Inorganic flame retardant is added to dispersion medium for dispersion to obtain inorganic flame retardant treatment liquid. Inorganic flame retardant treatment liquid is applied to the surface of synergistic composite preform and fixed to obtain flame retardant fixed body. S2.5. Melt and integrate the flame-retardant binder at 110-145℃ to obtain the flame-retardant intermediate material.

[0012] In some embodiments of the present invention, in step S2, the synergist includes at least one of pentaerythritol, melamine, phytic acid, lignin, starch, and chitosan; the inorganic flame retardant includes at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, talc, and silica; and the dispersion medium includes at least one of deionized water, anhydrous ethanol, and isopropanol.

[0013] In some embodiments of the present invention, step S3 includes: S3.1. Heat the nano-carbon mixture to 25-45℃, add the aggregation inducer and mix at a speed of 300-1200 r / min for 10-40 min to obtain primary aggregates; S3.2. Coating the primary aggregate with a portion of the flame-retardant intermediate material, controlling the processing temperature at 90–120℃, the rotation speed at 80–250 r / min, and the time at 5–20 min, to obtain the coated material; S3.3 Add the remaining flame-retardant intermediate material to the coating multiple times until it is completely added, controlling the temperature at 150-168℃, the rotation speed at 15-35 r / min, adding in 3-7 batches, and holding for 30-100 seconds after each addition to obtain a carbon mixture. S3.4. The carbon mixture is heat-insulated at a temperature of 118-136℃ for 6-18 minutes to obtain the molding material. S3.5. Add the molding material to the granulation equipment for extrusion granulation, control the barrel temperature to 145~170℃, the screw speed to 20~60r / min, and the die pressure fluctuation to no more than ±8%. Then cool and granulate to obtain bio-based cable material.

[0014] In some embodiments of the present invention, in step S3, the nano-carbon mixture includes at least one of a mixture of graphene and carbon nanotubes, a mixture of graphene and reduced graphene oxide, and a mixture of carbon nanotubes and carbon nanofibers, and the aggregation inducer includes at least one of 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate, 4-aminobenzoic acid, phytic acid, and tannic acid.

[0015] This invention provides a bio-based cable material, which is prepared by the method described above for preparing a bio-based cable material.

[0016] Compared with existing technologies, the bio-based cable material and its preparation method disclosed in this invention have the following advantages: The bio-based resin mixture and compatibilizer are pretreated first, and then the compatibilizer is introduced into the bio-based resin mixture, which consists of a continuous phase and a toughening phase, for premixing. Essentially, this pre-construction of the matrix phase structure is prioritized. The continuous phase primarily provides the molding skeleton, dimensional stability, and basic insulation load-bearing capacity. The toughening phase mainly serves as a stress buffer and crack passivation agent. The compatibilizer, through polar group action, reactive bonding, or interfacial wetting effects, reduces the interfacial tension between the continuous and toughening phases, promoting the formation of a more stable interfacial transition zone between the two phases. This mitigates phase coarsening, interfacial debonding, and localized stress concentration caused by insufficient compatibility between the two phases during subsequent processing. This pre-formation facilitates the establishment of a resin-based system with better continuity and interfacial stability.

[0017] Based on this, ammonium polyphosphate is added to the preform and mixed, followed by the addition of synergists and inorganic flame retardants for further mixing. Essentially, this process further establishes a flame-retardant functional phase within the pre-constructed resin phase structure. Ammonium polyphosphate primarily provides the acid source and promotes dehydration and char formation when the material is heated. The synergist provides the char source and / or gas source to enhance the expansion and char formation process. The inorganic flame retardant improves the integrity and thermal stability of the flame-retardant layer through endothermic decomposition, water release and cooling, thermal insulation, and residual skeleton support. Because the flame-retardant components are gradually introduced onto a relatively stable resin base, it is more conducive to the uniform distribution of the flame-retardant phase in the matrix and its effective bonding with the resin interface. This avoids the localized agglomeration, phase interface weakening, and processing fluctuations that can easily occur when a large amount of flame retardant is added at once, thus forming a flame-retardant intermediate material that combines matrix continuity and flame-retardant response capabilities.

[0018] Furthermore, the pre-dispersion of the nano-carbon mixture before its introduction into the flame-retardant intermediate material essentially constructs local reinforcement and interface control units based on the synergistic structure of the aforementioned resin and flame-retardant phases. The nano-carbon mixture possesses a high specific surface area and high interfacial activity. Pre-dispersion reduces the initial agglomeration tendency, facilitating the formation of a confined microscale structure within the system. Upon introduction, it can, on the one hand, locally reinforce the resin matrix and flame-retardant layer through lamellar, fibrous, or tubular structures, extending the thermal shielding path and hindering crack propagation; on the other hand, it can improve the density and integrity of the flame-retardant layer, enhancing the material's structural retention under thermal and mechanical effects. Subsequently, granulation molding stabilizes and solidifies the aforementioned resin, flame-retardant, and nano-carbon functional phases into the same material system.

[0019] Therefore, the above process is not a simple superposition of multiple components, but a hierarchical organizational path. By introducing components in a progressive manner according to their structural functions, the relationship between mechanical properties, toughness, thermal stability, flame retardancy, and insulation properties can be more effectively coordinated within the same bio-based cable material, making the resulting material more suitable for the comprehensive performance requirements of cable applications. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for preparing bio-based cable materials according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Please refer to Figure 1 This invention proposes a method for preparing a bio-based cable material, the steps of which include: S1. After pretreating the bio-based resin mixture and compatibilizer, the compatibilizer is added to the bio-based resin mixture for premixing to obtain a preform. The bio-based resin mixture includes a continuous phase and a toughening phase. The continuous phase includes at least one of polylactic acid, polybutylene succinate, and polyhydroxyalkanoate. The toughening phase includes at least one of poly-3-hydroxybutyrate-3-hydroxyhexanoate, polycaprolactone, and polyhydroxybutyrate valerate. The compatibilizer includes at least one of maleic anhydride grafted polymer compatibilizer, epoxy-reactive compatibilizer, and isocyanate-based reactive compatibilizer.

[0023] Step S1 includes: S1.1. The continuous phase and the toughening phase are added to the drying equipment for pretreatment. The continuous phase is dried at 55-70℃ for 4-8 hours, and the toughening phase is dried at 45-65℃ for 3-6 hours.

[0024] For polyester-type continuous phase materials such as polylactic acid, polybutylene succinate, and polyhydroxyalkanoates, and for toughening phase materials such as poly-3-hydroxybutyrate-3-hydroxyhexanoate, polycaprolactone, and polyhydroxybutyrate valerate, moisture will cause ester bond degradation under elevated temperatures, leading to shorter molecular chains. This results in problems such as decreased melt strength, brittleness, and reduced elongation at break during subsequent processing. Drying the continuous phase at 55–70°C for 4–8 hours and the toughening phase at 45–65°C for 3–6 hours can effectively remove moisture without excessively increasing the heat history, allowing the resin to maintain good molecular chain integrity during subsequent mixing.

[0025] S1.2. The compatibilizer is activated and pretreated by controlling the temperature at 50-80℃ and the time at 20-60min, and stirring at 100-300r / min to obtain the pretreated compatibilizer.

[0026] Maleic anhydride-grafted polymer compatibilizers inherently possess anhydride or polar grafted structures, epoxy-based reactive compatibilizers contain epoxy groups, and isocyanate-based reactive compatibilizers contain isocyanate groups. These groups can all act as bridges or reactive bonds at the resin phase interface. However, if the compatibilizer itself is poorly dispersed, lacks flowability, or is in a locally aggregated state, it is prone to remaining within a certain phase when subsequently added to the resin, and cannot be fully distributed in the interface region between the continuous phase and the toughening phase. By activating it at 50–80℃ for 20–60 min and stirring at 100–300 r / min, the compatibilizer can first reach a more uniform and active state, which is beneficial for its faster spread between the resin phases when added subsequently.

[0027] S1.3. The pretreated continuous phase and toughening phase are added to the mixing equipment for premixing. The mixing temperature is controlled at 140-165℃, the rotation speed is 20-60 r / min, and the time is 3-8 min to obtain the initial two-phase mixture.

[0028] Continuous phases, such as polylactic acid, polybutylene succinate, and polyhydroxyalkanoates, typically provide the main structural support; toughening phases, such as poly-3-hydroxybutyrate-3-hydroxyhexanoate, polycaprolactone, and polyhydroxybutyrate valerate, are more focused on compensating for flexibility and toughness. The flowability, polarity, and crystallization behavior of the two phases in the molten state are not entirely the same. If all components are added simultaneously from the beginning, localized accumulation and interfacial disorder can easily occur. By premixing at 140–165℃, 20–60 r / min, and 3–8 min, the continuous phase can first form a basic molten framework, and then the toughening phase can be gradually dispersed into this framework, resulting in a two-phase mixture with the initial phase structure.

[0029] S1.4. The pretreatment compatibilizer is added to the initial two-phase mixture in stages for mixing. The mixing temperature is controlled at 145-170℃, the rotation speed is 25-70 r / min, and the time is 5-12 min to obtain the preform.

[0030] The anhydride structure in maleic anhydride-grafted polymer compatibilizers enhances the interaction with polar resin segments. The epoxy groups in epoxy-based reactive compatibilizers can interact with resin end groups or interfacial polar groups, while the isocyanate groups in isocyanate-based reactive compatibilizers more readily form bonds with active hydrogen or polar end groups. Adding the compatibilizer in stages, rather than all at once, allows it to first cover the already formed main phase interface before gradually supplementing other interfacial regions, thus reducing the problem of compatibilizer concentration in a localized area. Mixing at 145–170 °C, 25–70 r / min, and 5–12 min balances the needs of compatibilizer dispersion and two-phase interface construction.

[0031] S1.5. The preform is subjected to steady-state release treatment, with the treatment temperature controlled at 130-150℃ and the time at 1-3 min, to obtain the preform.

[0032] During processes S1.3 and S1.4, the continuous phase, toughening phase, and compatibilizer undergo high temperatures and certain shearing, often resulting in localized stress accumulation, differences in melt flow orientation, and incomplete stabilization of some phase interfaces within the system. Directly proceeding to subsequent steps can amplify these unstable factors during further processing, leading to uneven dispersion of flame-retardant components, decreased surface quality, or localized performance deviations. A steady-state release treatment at 130–150°C for 1–3 minutes allows the preform to undergo short-term finishing at a temperature lower than the main mixing temperature, stabilizing the interface between the continuous and toughening phases and resulting in a more uniform distribution of the compatibilizer at the interface.

[0033] S2. Add ammonium polyphosphate to the preform and mix, then add synergist and inorganic flame retardant and continue mixing to obtain flame retardant intermediate material; In one embodiment, step S2 includes: S2.1 Surface compounding treatment of ammonium polyphosphate and synergist is carried out, with the treatment temperature controlled at 85-110℃, the rotation speed at 200-500 r / min, and the time at 10-30 min, to obtain flame retardant precursor composite.

[0034] Ammonium polyphosphate is the main phosphorus-based flame retardant component, but if it is directly introduced into the preform as independent particles, it is prone to uneven distribution with the resin phase. By first surface-compounding it with a synergist, components containing more hydroxyl groups or organic frameworks, such as pentaerythritol, lignin, starch, and chitosan, can be distributed onto the surface of the ammonium polyphosphate. Melamine can provide assistance for subsequent expansion under heat, while phytic acid can enhance the polarity and activation sites on the precursor surface. The resulting flame-retardant precursor complex is no longer a simple ammonium polyphosphate particle, but a composite particle with a synergistic layer on its surface.

[0035] S2.2 Add the inorganic flame retardant to the flame retardant precursor compound and perform low-speed coating treatment. Control the treatment temperature at 70-95℃, the rotation speed at 80-200 r / min, and the time at 15-40 min to obtain layered flame retardant composite particles.

[0036] Aluminum hydroxide and magnesium hydroxide absorb heat and release moisture when heated, thus reducing local temperature rise; zinc borate helps improve the density and stability of the char layer; talc and silica enhance the supporting effect of the char layer or inorganic residue layer. If these inorganic components are directly mixed with the preform under high shear, they tend to exist as independent particles, making it difficult to form an effective synergy around ammonium polyphosphate and the synergist. By first performing a low-speed coating treatment, the inorganic flame retardant can be preferentially distributed on the outer surface of the flame-retardant precursor complex, forming a clearer layered relationship from the inside out.

[0037] S2.3 Add the layered flame-retardant composite particles to the preform in batches for embedding treatment, control the embedding temperature to 145-165℃, the rotation speed to 25-55r / min, the interval between each batch to 30-120s, and the total time to 4-10min to obtain the flame-retardant embedding material.

[0038] Since the preform has already formed a relatively stable basic structure consisting of a continuous phase, a toughening phase, and a compatibilizer in S1, adding the layered flame-retardant composite particles in batches allows each batch of particles to undergo initial dispersion and positional adjustment within the preform before adding the next batch. This helps reduce mutual compression and secondary agglomeration between the layered flame-retardant composite particles. The principle is that the outer layer of the flame-retardant composite particles already contains inorganic flame retardants, the middle layer contains synergists, and the inner layer is mainly composed of ammonium polyphosphate. Such particles are inherently more complex than single flame retardant particles when entering the resin system. If added too quickly or mixed too vigorously, their layered structure can be easily destroyed. By controlling the embedding temperature, rotation speed, and addition interval, these particles can be introduced into the preform in a gentler manner.

[0039] S2.4. The flame-retardant insert is subjected to low-shear bonding treatment, with the bonding temperature controlled at 130-150℃, the rotation speed at 10-25r / min, and the time at 2-6min, to obtain the flame-retardant intermediate material.

[0040] Because even after S2.3, although the flame-retardant composite particles are embedded in the preform, their distribution and orientation may still vary in local areas. Continuing to use higher rotation speeds or stronger shear can easily disrupt the established hierarchical relationship between ammonium polyphosphate, synergists, and inorganic flame retardants, and may even cause the outer inorganic flame retardant layer to separate from the inner structure. By performing low-shear integration at 130–150℃, 10–25 r / min, and 2–6 min, the resin phase, compatibilizer interface, and flame-retardant particles can be further bonded together, while simultaneously achieving a more homogeneous state suitable for subsequent processing steps.

[0041] Synergists include at least one of pentaerythritol, melamine, phytic acid, lignin, starch, and chitosan, while inorganic flame retardants include at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, talc, and silica.

[0042] In one embodiment, step S2 includes: S2.1 Add ammonium polyphosphate to the dispersion medium and stir and disperse it for 20 to 60 minutes at room temperature to 50°C to obtain ammonium polyphosphate spray solution.

[0043] After spraying, ammonium polyphosphate preferentially adheres to the surface of the preform and the easily accessible phase interface areas. As the dispersion medium evaporates, the ammonium polyphosphate remains relatively evenly in these areas. The practical effect of this is that when subsequent materials are heated, the outermost layer undergoes a phosphorus-based flame-retardant response first, exhibiting earlier dehydration and charring tendencies, thus delaying further heat transfer to the interior. Compared to directly mixing all the ammonium polyphosphate into the resin, spraying to form the main flame-retardant layer first more easily improves the surface flame-retardant efficiency and better aligns with the actual heating process of cable materials, which typically proceeds from the outside in. Simultaneously, controlling drying at 50–90°C allows the dispersion medium to evaporate quickly without significantly compromising the structural stability of the preform itself.

[0044] S2.2. Apply ammonium polyphosphate spray solution to the surface of the preform and dry it at 50-90℃ for 5-30 minutes to obtain the main flame retardant layer preform.

[0045] After spraying, ammonium polyphosphate preferentially adheres to the surface of the preform and the easily accessible phase interface areas. As the dispersion medium evaporates, the ammonium polyphosphate remains relatively evenly in these areas. The practical effect of this is that when subsequent materials are heated, the outermost layer undergoes a phosphorus-based flame-retardant response first, exhibiting earlier dehydration and charring tendencies, thus delaying further heat transfer to the interior. Compared to directly mixing all the ammonium polyphosphate into the resin, spraying to form the main flame-retardant layer first more easily improves the surface flame-retardant efficiency and better aligns with the actual heating process of cable materials, which typically proceeds from the outside in. Simultaneously, controlling drying at 50–90°C allows the dispersion medium to evaporate quickly without significantly compromising the structural stability of the preform itself.

[0046] S2.3. The synergist is added to the dispersion medium and dispersed to obtain a synergistic treatment solution. This solution is then contacted with the main flame-retardant layer preform to obtain a synergistic composite preform. The pentaerythritol, lignin, starch, and chitosan components in the synergist provide good organic char sources, melamine provides expansion assistance upon heating, and phytic acid possesses both phosphorus-containing characteristics and multi-site interaction capabilities. Preparing these components into a synergistic treatment solution before contacting it with the main flame-retardant layer preform allows the synergist to preferentially adhere to or penetrate around the ammonium polyphosphate layer, thereby increasing the proximity between the acid source, char source, and gas source. This makes it easier to form an expanded and more continuous char layer upon subsequent heating, rather than the acid source, char source, and gas source being dispersed and having a fragmented effect. The technical effect is to improve the flame-retardant synergistic efficiency, enhance the integrity and stability of the subsequent char layer formation, and reduce the potential underutilization of the synergist when added alone.

[0047] S2.4. Inorganic flame retardant is added to a dispersion medium for dispersion to obtain inorganic flame retardant treatment liquid. The inorganic flame retardant treatment liquid is applied to the surface of the synergistic composite preform and fixed to obtain flame retardant fixed body.

[0048] Aluminum hydroxide and magnesium hydroxide can endothermally decompose and release moisture when heated, thereby reducing the surface temperature rise of the material and diluting flammable decomposition products; zinc borate helps to improve the density and stability of the char layer; talc and silica help to enhance the supporting effect of the outer residual structure. Preparing these inorganic flame retardants into a treatment liquid and then applying it to the surface of the synergistic composite preform can improve its coverage uniformity and allow it to remain more in the outer layer area. Subsequent fixation treatment ensures that the inorganic flame retardants do not simply adhere, but form a more stable composite structure with the underlying ammonium polyphosphate layer and synergistic layer.

[0049] S2.5. Melt and integrate the flame-retardant binder at 110-145℃ to obtain the flame-retardant intermediate material.

[0050] After steps S2.2 to S2.4, ammonium polyphosphate, synergist, and inorganic flame retardant have been sequentially distributed on the surface and near-surface area of ​​the preform. However, there may still be issues with insufficient contact or weak adhesion between these components and between them and the preform. By performing melt integration at 110–145°C, the surface of the preform can be moderately softened, allowing the outer flame retardant components to partially embed into the surface resin, while maintaining the previously formed layered distribution without being completely disrupted.

[0051] The dispersion medium includes at least one of deionized water, anhydrous ethanol, and isopropanol.

[0052] S3. After pre-dispersing the nano-carbon mixture, it is added to the flame-retardant intermediate material for mixing to obtain the molding material. The molding material is then granulated to obtain the bio-based cable material.

[0053] Step S3 includes: S3.1 Heat the nano-carbon mixture to 25-45℃, add the aggregation inducer and mix at a speed of 300-1200 r / min for 10-40 min to obtain the primary aggregate.

[0054] Introducing at least one of 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate, 4-aminobenzoic acid, phytic acid, and tannic acid can form adsorption, bridging, or multi-site interactions on the surface of carbon nanoparticles. For example, tannic acid and phytic acid, with their numerous polar groups, readily adsorb onto the surface of carbon nanoparticles and alter their surface state; 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate, and 4-aminobenzoic acid can constitute structural units with multiple interaction sites, enabling limited connections between carbon nanoparticles. Controlling the treatment temperature to 25–45 °C can improve the uniformity of these aggregation inducers on the surface of carbon nanoparticles without prematurely triggering thermal history accumulation in subsequent systems.

[0055] S3.2. Coating the primary aggregate with a portion of the flame-retardant intermediate material, controlling the processing temperature at 90–120℃, the rotation speed at 80–250 r / min, and the time at 5–20 min, to obtain the coated material.

[0056] Since the flame-retardant intermediate material already contains the resin phase, flame-retardant layer, and relatively stable interface structure formed in the previous steps, using a portion of it to first coat the primary aggregates is equivalent to adding a transition layer to the outside of the nano-carbon local structure that is more easily accepted by the main system. Treatment at 90–120℃, 80–250 r / min, and 5–20 min allows the surface of the flame-retardant intermediate material to soften moderately and coat the outside of the primary aggregates, while preventing the complete disintegration of the nano-carbon local structure.

[0057] S3.3 Add the remaining flame-retardant intermediate material to the coating multiple times until it is completely added, controlling the temperature at 150-168℃ and the rotation speed at 15-35 r / min. Add the material in 3-7 batches, and hold it for 30-100 seconds after each addition to obtain a carbon mixture.

[0058] If all the remaining flame-retardant intermediate material is added at once, the local structure of the nano-carbon in the coating is more easily disrupted under the shearing action of the large system, or the instantaneous concentration change in local areas is too large, leading to a new round of uneven distribution. Adding it in 3-7 batches, with a 30-100s interval after each addition, allows each batch of remaining flame-retardant intermediate material to first achieve local fusion with the existing coating before adding the next batch, thus allowing the local structure of the nano-carbon to expand into the entire system under a relatively stable environment. Controlling the process at 150-168℃ and 15-35 r / min also helps to balance the flowability of the flame-retardant intermediate material with the preservation of the nano-carbon structure.

[0059] S3.4. The carbon mixture is heat-insulated at a temperature of 118-136℃ for 6-18 minutes to obtain the molding material.

[0060] After S3.3, although the carbon mixture has been largely mixed, some local orientation differences and temporarily unstable distributions may still exist due to processing shear. Holding it at 118–136℃ for 6–18 minutes can maintain the resin phase and flame-retardant phase in a certain adjustable state, while allowing the local structure of nano-carbon to re-adhere to a more stable position without being disturbed by strong shear. This avoids breaking up the initially formed local carbon units as would happen with repeated high shear, and also prevents them from developing into an excessively long continuous network.

[0061] S3.5. Add the molding material to the granulation equipment for extrusion granulation, control the barrel temperature to 145~170℃, the screw speed to 20~60r / min, and the die pressure fluctuation to no more than ±8%. Then cool and granulate to obtain bio-based cable material.

[0062] Controlling the barrel temperature to 145–170℃ ensures sufficient fluidity of the extruded material without significantly accelerating the degradation of the bio-based resin due to excessive temperature. Controlling the screw speed to 20–60 r / min helps mitigate the damage to local carbon units and flame-retardant layers caused by excessive shearing. Maintaining die pressure fluctuations within ±8% ensures a smooth extrusion process and reduces structural rearrangement caused by excessive pressure fluctuations. Subsequent cooling and pelletizing fixes the relatively stable internal structure within the pellets.

[0063] The nano-carbon mixture includes at least one of the following: a mixture of graphene and carbon nanotubes, a mixture of graphene and reduced graphene oxide, and a mixture of carbon nanotubes and carbon nanofibers. The aggregation inducer includes at least one of 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate, 4-aminobenzoic acid, phytic acid, and tannic acid.

[0064] This invention proposes a bio-based cable material, which is prepared by the method described above for preparing a bio-based cable material.

[0065] Example 1.

[0066] In this embodiment, the bio-based resin mixture uses a combination of a continuous phase and a toughening phase. The continuous phase consists of 70 parts by mass of polylactic acid (PLA), and the toughening phase consists of 30 parts by mass of poly-3-hydroxybutyrate-3-hydroxyhexanoate (POH3-H ... Subsequently, pretreated polylactic acid and poly-3-hydroxybutyrate-3-hydroxyhexanoate were added to a mixer and premixed for 5 minutes at 150°C and 40 r / min to obtain an initial two-phase mixture. The pretreated compatibilizer was then added in two portions and mixed for 8 minutes at 155°C and 45 r / min to obtain a preform. Finally, the preform was transferred to a two-roll mill and subjected to steady-state release treatment at 140°C for 2 minutes to obtain the product of step S1.

[0067] Step S2 of this embodiment follows the route described in claim 4. Specifically, 18 parts by mass of ammonium polyphosphate and 10 parts by mass of synergist, including 5 parts by mass of pentaerythritol, 3 parts by mass of melamine, and 2 parts by mass of phytic acid; 14 parts by mass of inorganic flame retardant, including 8 parts by mass of magnesium hydroxide, 3 parts by mass of zinc borate, and 3 parts by mass of silica. The total mass ratio of ammonium polyphosphate to synergist is 18:10, and the mass ratio of inorganic flame retardant to the total amount of ammonium polyphosphate and synergist is 14:28. First, ammonium polyphosphate and synergist are added to a high-speed hot mixer and subjected to surface compounding treatment at 95°C and 320 r / min for 20 min to obtain a flame retardant precursor composite; then, magnesium hydroxide, zinc borate, and silica are added to the flame retardant precursor composite and subjected to low-speed coating treatment at 85°C and 120 r / min for 25 min to obtain layered flame retardant composite particles. The obtained layered flame-retardant composite particles were then added to the preform obtained in step S1 in four batches and embedded at 155°C and 35 r / min. Each batch was added 60 seconds apart, and the total time was controlled to be 6 minutes to obtain flame-retardant embedding material. The flame-retardant embedding material was then subjected to low-shear integration at 138°C and 15 r / min for 4 minutes to obtain flame-retardant intermediate material.

[0068] In step S3 of this embodiment, 3.0 parts by mass of the nano-carbon mixture are used, which is a mixture of graphene and carbon nanotubes, wherein 2.0 parts by mass of graphene and 1.0 parts by mass of carbon nanotubes, with a mass ratio of 2:1; 1.5 parts by mass of the aggregation inducer are used, wherein 0.3 parts by mass of 2-amino-4-hydroxy-6-methylpyrimidine, 0.4 parts by mass of hexamethylene diisocyanate, 0.4 parts by mass of 4-aminobenzoic acid, and 0.4 parts by mass of tannic acid. First, the graphene and carbon nanotubes are added to a high-speed dispersion device and heated to 35°C, then the aggregation inducer is added, and the mixture is mixed at 800 r / min for 25 min to obtain the primary aggregate. Then, 15% of the total amount of flame-retardant intermediate material and primary aggregate were treated in a small coating machine at 105℃ and 150r / min for 10min to obtain the coating material. The remaining 85% of the flame-retardant intermediate material was added to the coating material in 4 batches and mixed at 158℃ and 22r / min, with each batch held for 60s after addition. After all the materials were added, a carbon mixture was obtained. The carbon mixture was then kept at 126℃ for 10min to obtain the molding material. Finally, the molding material was added to a twin-screw extruder and granulated at a barrel temperature of 160℃, a screw speed of 35r / min, and a die pressure fluctuation controlled within ±5%. After air cooling, the material was granulated to obtain the bio-based cable material.

[0069] Example 2: In this embodiment, the continuous phase consists of 55 parts by mass of polylactic acid and 15 parts by mass of polybutylene succinate, totaling 70 parts by mass; the toughening phase consists of 30 parts by mass of polycaprolactone; and the compatibilizer consists of 7 parts by mass of an epoxy-reactive compatibilizer. The mass ratio of the continuous phase to the toughening phase is 70:30, and the mass ratio of the compatibilizer to the total amount of the bio-based resin mixture is 7:100. In step S1, the polylactic acid is dried at 60°C for 6 hours, the polybutylene succinate is dried at 60°C for 5 hours, and the polycaprolactone is dried at 50°C for 4 hours; the epoxy-reactive compatibilizer is activated at 70°C for 35 minutes, and the stirring speed is 180 r / min. The continuous phase and toughening phase were then added to the front section of the twin-screw extruder and premixed for 6 minutes at 148–158°C to obtain an initial two-phase mixture. The compatibilizer was then added in stages from the side feed port and mixed for 7 minutes at 160°C and 50 r / min. The mixture was then released steadily for 2 minutes at 138°C to obtain the preform.

[0070] Step S2 of this embodiment adopts the spraying route described in claim 6. 20 parts by weight of ammonium polyphosphate are used; 9 parts by weight of synergist are used, including 4 parts by weight of pentaerythritol, 3 parts by weight of lignin, and 2 parts by weight of chitosan; 13 parts by weight of inorganic flame retardant are used, including 7 parts by weight of aluminum hydroxide, 3 parts by weight of talc, and 3 parts by weight of silica. The dispersion medium is a mixture of deionized water and anhydrous ethanol, with a volume ratio of 3:2. First, ammonium polyphosphate is added to the dispersion medium and stirred and dispersed at 35°C for 30 minutes to obtain an ammonium polyphosphate spray solution; then, it is sprayed onto the surface of the preform and dried at 70°C for 15 minutes to obtain the main flame-retardant layer preform. Subsequently, pentaerythritol, lignin, and chitosan are added to the dispersion medium for dispersion to obtain a synergistic treatment solution, which is then sprayed onto the surface of the main flame-retardant layer preform to obtain a synergistic composite preform. Aluminum hydroxide, talc, and silica are then added to a dispersion medium for dispersion to obtain an inorganic flame retardant treatment liquid. This liquid is applied to the surface of the synergistic composite preform and fixed at 85°C for 20 minutes to obtain a flame retardant solid. Finally, it is melt-integrated at 125°C for 5 minutes to obtain a flame retardant intermediate material.

[0071] In step S3 of this embodiment, 2.8 parts by mass of the nano-carbon mixture are used, which is a mixture of graphene and reduced graphene oxide, wherein 1.8 parts by mass of graphene and 1.0 parts by mass of reduced graphene oxide are used; 1.2 parts by mass of the aggregation inducer are used, wherein 0.6 parts by mass of phytic acid and 0.6 parts by mass of tannic acid are used. The nano-carbon mixture is first heated to 32°C, and then phytic acid and tannic acid are added. The mixture is mixed at 700 r / min for 20 min to obtain the primary aggregate. Then, 20% of the total amount of flame-retardant intermediate material was coated with the primary aggregate at 100℃ and 120r / min for 8 minutes to obtain the coated material. The remaining flame-retardant intermediate material was added in 5 batches and mixed at 155℃ and 20r / min, with each batch held for 50 seconds to obtain the carbon mixture. The mixture was then kept at 124℃ for 12 minutes to obtain the molding material. Finally, the mixture was extruded and granulated at a barrel temperature of 155℃ and a screw speed of 30r / min, with the die pressure fluctuation controlled within ±6%. After cooling and pelletizing, the bio-based cable material was obtained.

[0072] Example 3: In this embodiment, the continuous phase consists of 60 parts by mass of polyhydroxyalkanoate and 10 parts by mass of polylactic acid, totaling 70 parts by mass; the toughening phase consists of 20 parts by mass of polyhydroxybutyrate valerate and 10 parts by mass of poly-3-hydroxybutyrate-3-hydroxyhexanoate, totaling 30 parts by mass; and the compatibilizer consists of 5 parts by mass of isocyanate-based reactive compatibilizer. In step S1, the polyhydroxyalkanoate is dried at 58°C for 5 hours, the polylactic acid is dried at 60°C for 6 hours, the polyhydroxybutyrate valerate is dried at 50°C for 4 hours, and the poly-3-hydroxybutyrate-3-hydroxyhexanoate is dried at 52°C for 4 hours; the isocyanate-based reactive compatibilizer is activated at 60°C and 150 r / min for 25 minutes. The continuous phase and toughening phase were then premixed at 145℃ and 30r / min for 6 min to obtain an initial two-phase mixture. The compatibilizer was then added in stages, mixed at 150℃ and 40r / min for 9 min, and then released steadily at 135℃ for 2 min to obtain the preform.

[0073] Step S2 of this embodiment adopts the layered particle route described in claim 4. Ammonium polyphosphate is used in proportion to 16 parts by weight; the synergist is used in proportion to 11 parts by weight, comprising 4 parts by weight of melamine, 3 parts by weight of phytic acid, 2 parts by weight of starch, and 2 parts by weight of chitosan; the inorganic flame retardant is used in proportion to 15 parts by weight, comprising 6 parts by weight of magnesium hydroxide, 5 parts by weight of aluminum hydroxide, and 4 parts by weight of silica. First, the ammonium polyphosphate and the synergist are surface-compounded at 100°C and 350 r / min for 18 min to obtain a flame-retardant precursor composite; then, the inorganic flame retardant is added, and the mixture is slowly coated at 90°C and 150 r / min for 20 min to obtain layered flame-retardant composite particles. Subsequently, the layered flame-retardant composite particles were added to the preform in 5 batches and embedded for 8 minutes at 150℃ and 30r / min, with a 50s interval between each batch, to obtain the flame-retardant embedding material; then, it was low-shear integrated for 5 minutes at 136℃ and 18r / min to obtain the flame-retardant intermediate material.

[0074] In step S3 of this embodiment, 3.2 parts by mass of the nano-carbon mixture are used, which is a mixture of carbon nanotubes and carbon nanofibers, wherein 1.7 parts by mass of carbon nanotubes and 1.5 parts by mass of carbon nanofibers are used; 1.6 parts by mass of the aggregation inducer are used, wherein 0.4 parts by mass of 2-amino-4-hydroxy-6-methylpyrimidine, 0.5 parts by mass of hexamethylene diisocyanate, 0.5 parts by mass of 4-aminobenzoic acid, and 0.2 parts by mass of phytic acid are used. The nano-carbon mixture is first heated to 40°C, and then the aggregation inducer is added. The mixture is mixed at 900 r / min for 30 min to obtain the primary aggregate. Next, 18% of the total amount of primary aggregate and flame-retardant intermediate material were coated at 110℃ and 180r / min for 12min to obtain a coated material. The remaining flame-retardant intermediate material was then added in 6 batches and mixed at 160℃ and 25r / min, with each batch held for 45s to obtain a carbon mixture. After holding at 130℃ for 10min, a molding material was obtained. Finally, the material was extruded and granulated at a barrel temperature of 162℃ and a screw speed of 40r / min, with the die pressure fluctuation controlled within ±4%. After cooling and pelletizing, the bio-based cable material was obtained.

[0075] Comparative Example 1: The only difference between this comparative example and Example 1 is that step S2 does not use the layered flame-retardant composite particle route. Instead, 18 parts by weight of ammonium polyphosphate, 5 parts by weight of pentaerythritol, 3 parts by weight of melamine, 2 parts by weight of phytic acid, 8 parts by weight of magnesium hydroxide, 3 parts by weight of zinc borate, and 3 parts by weight of silica are directly added to the preform obtained in Example 1 in one go and mixed at 155°C and 45 r / min for 10 min. Then, the flame-retardant intermediate material is obtained directly. The remaining steps and the compounds, amounts, and proportions used are the same as in Example 1.

[0076] Comparative Example 2: The only difference between this comparative example and Example 1 is that: in step S3, no aggregation inducer is added, that is, the mixture of graphene and carbon nanotubes is still 3.0 parts by mass, but 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate, 4-aminobenzoic acid and tannic acid are not added. Instead, the graphene and carbon nanotubes are directly mixed with all the flame-retardant intermediate materials at 160°C and 30 r / min for 8 min and then granulated; the remaining steps and the compounds, amounts and ratios used are the same as in Example 1.

[0077] Experimental procedures for tensile strength and elongation at break: First, the sample particles were made into sheets of standard thickness by hot pressing or extrusion, and then cut into standard dumbbell-shaped specimens using a cutter. All specimens were placed in an environment of approximately 23℃ and 50% relative humidity for 24 hours to allow them to reach a uniform state. During testing, an electronic universal testing machine was used. The specimens were clamped between upper and lower clamps and stretched at a constant tensile speed until the specimens broke. The maximum tensile load and the change in gauge length at fracture were recorded. The tensile strength was calculated based on the original cross-sectional area of ​​the specimens, and the elongation at break was calculated based on the elongation at fracture. Each group of samples was tested in parallel at least 5 times, and the average value was used as the data in the table.

[0078] Experimental procedure for air oven thermal aging and performance change rate after aging: First, the initial tensile strength and elongation at break of each group of samples were prepared and measured according to the tensile property test requirements. Then, another group of samples of the same specifications were placed in an air oven and continuously aged at 110±2℃ for 240 hours. After aging, the samples were removed and left at room temperature for at least 4 hours before undergoing tensile testing again (4 hours, 5 hours, 6 hours, etc.) to obtain the tensile strength and elongation at break after aging. The maximum change rate of tensile strength and the maximum change rate of elongation at break were then calculated by dividing the difference between the aging value and the initial value by the initial value. This test is used to evaluate the material's ability to retain performance under long-term thermal conditions.

[0079] The experimental procedure for heat deformation at 90℃ / 1h is as follows: Each sample is prepared into a strip or sheet specimen of uniform size, with a reference length marked on the specimen. The specimen is then placed in a constant temperature environment of 90℃ for 1 hour. During the test, the specimens are in a free state or a specified light load state to simulate the dimensional stability of the material under heated conditions. After the test, the specimens are removed and cooled to room temperature, and their deformed dimensions are measured and compared with the initial dimensions to calculate the percentage of heat deformation. This project primarily reflects the material's ability to resist softening and deformation at higher temperatures.

[0080] The dielectric strength test procedure is as follows: The dielectric strength test is conducted at an ambient temperature of (20±2)℃, using symmetrical electrodes with a diameter of 25mm and an edge radius of 2.5mm. The test piece thickness is (1.0±0.1)mm, and the dielectric constant of the insulating oil used in the test should be close to 2.3 with sufficient dielectric strength. The initial test voltage is zero, and the voltage ramp-up rate should be 2kV / s.

[0081] Impact embrittlement temperature (-25℃) – Experimental procedure for fracture count / failure count: Each sample is prepared as a low-temperature impact specimen of specified size and placed in a low-temperature test chamber. The specimen is kept at -25℃ for a sufficient time to ensure uniform internal and external temperatures. Subsequently, each specimen is removed and subjected to an impact test at a specified energy under low-temperature conditions. The specimen is observed for fracture, cracking, or significant failure. Each group consists of 30 specimens tested, and the number of fractures or failures is recorded, expressed as fracture count / failure count. This test is primarily used to evaluate the material's resistance to embrittlement in low-temperature environments.

[0082] The experimental procedure for the oxygen index is as follows: Each sample is processed into a strip specimen of specified size and placed under constant temperature and humidity conditions for 24 hours. During testing, the specimen is vertically mounted in the oxygen index analyzer. By adjusting the mixing ratio of oxygen and nitrogen, the specimen is allowed to maintain a sustained combustion after ignition. The lowest oxygen concentration in the mixed gas at this point is recorded and used as the oxygen index. Each group of samples is tested at least three times, and the average value is taken. A higher oxygen index indicates that the material is less flammable and has better flame-retardant properties.

[0083] Experimental procedure for determining the pH value of acidic gases released during combustion: Each sample was prepared according to standard requirements and placed in a combustion boat, then placed in the heating zone within a quartz glass tube for combustion in a tube furnace. During combustion, an air stream was introduced, and the combustion-released gases entered a gas washing bottle via a gas guiding system and were absorbed by the absorbent liquid. The height of the absorbent liquid column in the gas washing bottle was controlled at 100 mm ± 2 mm, and a magnetic stirrer was used to maintain the absorbent liquid in a homogeneous state during the test. After combustion, the absorbent liquid was measured at room temperature using a pH meter, and its pH value was recorded. This test is used to evaluate the acidity of the gases released during material combustion; a higher pH value indicates a weaker acidity in the combustion-released gases.

[0084] Experimental procedure for determining the conductivity of combustion-released gases in acidic solutions: After absorbing the combustion-released gases, the same absorbent solution as used in the pH test is employed, maintaining consistency in the source, volume, and gas delivery conditions. The conductivity of the absorbent solution is then measured using a conductivity meter, and the results are recorded. Since the acidic or ionic gases released during combustion increase the ion concentration in the absorbent solution, conductivity reflects the degree of release of acidic and ionic components after combustion. Lower conductivity indicates weaker corrosiveness of the combustion-released gases and a relatively lower risk of corrosion to the environment and equipment.

[0085] Experimental procedure for volume resistivity at 20℃: The sample thickness is (1.0±0.1) mm, and the test voltage is 1000 V. To test the volume resistivity at 20℃, the sample should be immersed in distilled water at (20±2)℃ for 24 hours, dried, and tested immediately. For testing the volume resistivity at the working temperature, the electrodes should be preheated to 20℃ in an oven and kept constant for at least 1 hour. During the test, a high-resistivity meter and volume resistivity testing electrodes are used. The sample is clamped between the electrodes and held under a specified DC voltage for a certain period. After the current stabilizes, the current value is recorded. The volume resistivity is then calculated based on the sample thickness and electrode area, with units of Ω·m. This test is used to evaluate the volume insulation performance of materials under room temperature conditions.

[0086] The experimental data from the above experiment are shown in Table 1.

[0087] Table 1:

[0088] The data in the table show that the tensile strength and elongation at break of Examples 1-3 are higher than those of Comparative Examples 1 and 2. This indicates that the present invention, through the premixing of the continuous phase, toughening phase, and compatibilizer in step S1, and the orderly introduction of the flame-retardant component and nano-carbon mixture in steps S2 and S3, can more effectively improve the interfacial bonding state of the material, enabling the material to maintain good flexibility while retaining a certain strength. The change rates of tensile strength and elongation at break after thermal aging of Examples 1-3 are both lower than those of Comparative Examples 1 and 2, and the heat deformation values ​​are also lower, indicating that the structures in the embodiments of the present invention are more stable and less prone to significant performance degradation and dimensional changes under long-term high-temperature conditions. This suggests that the flame-retardant intermediate material formed in step S2 and the local nano-carbon structure formed in step S3 are beneficial to improving the heat resistance stability of the material. The dielectric strength and volume resistivity at 20°C of Examples 1-3 are superior to those of Comparative Examples 1 and 2, indicating that the introduction of the nano-carbon mixture in this invention does not significantly damage the main insulating properties of the material. Instead, through aggregation induction, coating, and batch re-addition in step S3, the nano-carbon mixture is distributed in a more restricted state, thus achieving both reinforcement and insulation performance. The impact embrittlement temperature test results of Examples 1-3 are superior to those of Comparative Examples 1 and 2, indicating that the material of this invention can still maintain good toughness and anti-brittleness under low-temperature conditions. This shows that the regulation of the resin phase structure and functional component distribution in this invention helps to reduce the risk of cracking under low-temperature conditions. The oxygen index of Examples 1-3 is higher than that of Comparative Examples 1 and 2, and the pH value and conductivity of the combustion-released gases are higher, indicating that the flame-retardant system formed by this invention has a better synergistic flame-retardant effect and can reduce the release of acidic and ionic gases during combustion. Therefore, compared with the comparative examples, this invention achieves a better comprehensive balance among mechanical properties, heat resistance, flame retardancy, low-temperature performance, and insulation performance.

[0089] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a bio-based cable material, characterized in that the steps include... include: S1. After pretreating the bio-based resin mixture and the compatibilizer, the compatibilizer is added to the bio-based resin mixture for premixing to obtain a preform, wherein the bio-based resin mixture includes a continuous phase and a toughening phase; S2. Add ammonium polyphosphate to the preform and mix, then add synergist and inorganic flame retardant and continue mixing to obtain flame retardant intermediate material; S3. After pre-dispersing the nano-carbon mixture, it is added to the flame-retardant intermediate material for mixing to obtain the molding material. The molding material is then granulated to obtain the bio-based cable material.

2. The method for preparing a bio-based cable material according to claim 1, characterized in that, Step S1 includes: S1.

1. The continuous phase and the toughening phase are added to the drying equipment for pretreatment. The continuous phase is dried at 55-70℃ for 4-8 hours, and the toughening phase is dried at 45-65℃ for 3-6 hours. S1.

2. The compatibilizer is activated and pretreated by controlling the temperature at 50-80℃ and the time at 20-60 min, and stirring at 100-300 r / min to obtain the pretreated compatibilizer. S1.

3. The pretreated continuous phase and toughening phase are added to the mixing equipment for premixing. The mixing temperature is controlled at 140-165℃, the rotation speed is 20-60 r / min, and the time is 3-8 min to obtain the initial two-phase mixture. S1.4 Add the pretreated compatibilizer to the initial two-phase mixture in stages and mix, controlling the mixing temperature at 145-170℃, the rotation speed at 25-70 r / min, and the time at 5-12 min to obtain the preform; S1.

5. The preform is subjected to steady-state release treatment, with the treatment temperature controlled at 130-150℃ and the time at 1-3 min, to obtain the preform.

3. A method for preparing a bio-based cable material according to claim 1 or 2, characterized in that, In step S1, the continuous phase includes at least one of polylactic acid, polybutylene succinate, and polyhydroxy fatty acid ester; the toughening phase includes at least one of poly-3-hydroxybutyrate-3-hydroxyhexanoate, polycaprolactone, and polyhydroxybutyrate valerate; and the compatibilizer includes at least one of maleic anhydride grafted polymer compatibilizer, epoxy-reactive compatibilizer, and isocyanate reactive compatibilizer.

4. The method for preparing a bio-based cable material according to claim 1, characterized in that, Step S2 includes: S2.1 Surface compounding treatment of ammonium polyphosphate and synergist, controlling the treatment temperature at 85-110℃, the rotation speed at 200-500 r / min, and the time at 10-30 min, to obtain flame retardant precursor composite; S2.2 Add the inorganic flame retardant to the flame retardant precursor compound and perform low-speed coating treatment. Control the treatment temperature at 70-95℃, the rotation speed at 80-200r / min, and the time at 15-40min to obtain layered flame retardant composite particles. S2.3 Add the layered flame-retardant composite particles to the preform in batches for embedding treatment, control the embedding temperature to 145-165℃, the rotation speed to 25-55r / min, the interval between each batch addition to 30-120s, and the total time to 4-10min to obtain the flame-retardant embedding material. S2.

4. The flame-retardant insert is subjected to low-shear bonding treatment, with the bonding temperature controlled at 130-150℃, the rotation speed at 10-25r / min, and the time at 2-6min, to obtain the flame-retardant intermediate material.

5. A method for preparing a bio-based cable material according to claim 1 or 4, characterized in that, In step S2, the synergist includes at least one of pentaerythritol, melamine, phytic acid, lignin, starch, and chitosan, and the inorganic flame retardant includes at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, talc, and silica.

6. The method for preparing a bio-based cable material according to claim 1, characterized in that, Step S2 includes: S2.1 Add ammonium polyphosphate to the dispersion medium and stir and disperse it at room temperature to 50°C for 20 to 60 minutes to obtain ammonium polyphosphate spray solution; S2.

2. Apply ammonium polyphosphate spray solution to the surface of the preform and dry it at 50-90℃ for 5-30 minutes to obtain the main flame retardant layer preform. S2.

3. Add the synergist to the dispersion medium and disperse it to obtain the synergistic treatment liquid. Contact the synergistic treatment liquid with the main flame retardant layer preform to obtain the synergistic composite preform. S2.

4. Inorganic flame retardant is added to dispersion medium for dispersion to obtain inorganic flame retardant treatment liquid. Inorganic flame retardant treatment liquid is applied to the surface of synergistic composite preform and fixed to obtain flame retardant fixed body. S2.

5. Melt and integrate the flame-retardant binder at 110-145℃ to obtain the flame-retardant intermediate material.

7. The method for preparing a bio-based cable material according to claim 6, characterized in that, In step S2, the synergist includes at least one of pentaerythritol, melamine, phytic acid, lignin, starch, and chitosan; the inorganic flame retardant includes at least one of aluminum hydroxide, magnesium hydroxide, zinc borate, talc, and silica; and the dispersion medium includes at least one of deionized water, anhydrous ethanol, and isopropanol.

8. The method for preparing a bio-based cable material according to claim 1, characterized in that, Step S3 includes: S3.

1. Heat the nano-carbon mixture to 25-45℃, add the aggregation inducer and mix at a speed of 300-1200 r / min for 10-40 min to obtain primary aggregates; S3.

2. Coating the primary aggregate with a portion of the flame-retardant intermediate material, controlling the processing temperature at 90–120℃, the rotation speed at 80–250 r / min, and the time at 5–20 min, to obtain the coated material; S3.3 Add the remaining flame-retardant intermediate material to the coating multiple times until it is completely added, controlling the temperature at 150-168℃, the rotation speed at 15-35 r / min, adding in 3-7 batches, and holding for 30-100 seconds after each addition to obtain a carbon mixture. S3.

4. The carbon mixture is heat-insulated at a temperature of 118-136℃ for 6-18 minutes to obtain the molding material. S3.

5. Add the molding material to the granulation equipment for extrusion granulation, control the barrel temperature to 145~170℃, the screw speed to 20~60r / min, and the die pressure fluctuation to no more than ±8%. Then cool and granulate to obtain bio-based cable material.

9. The method for preparing a bio-based cable material according to claim 6, characterized in that, In step S3, the nano-carbon mixture includes at least one of the following: a mixture of graphene and carbon nanotubes, a mixture of graphene and reduced graphene oxide, and a mixture of carbon nanotubes and carbon nanofibers. The aggregation inducer includes at least one of 2-amino-4-hydroxy-6-methylpyrimidine, hexamethylene diisocyanate, 4-aminobenzoic acid, phytic acid, and tannic acid.

10. A bio-based cable material, characterized in that, It is prepared by the method of preparing a bio-based cable material as described in any one of claims 1-9.

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