A microcapsule dispersion and temperature control strategy-based melt spinning process method and system

Abstract

The application discloses a kind of based on microcapsule dispersion and temperature control strategy melt spinning process method and system, it is related to the technical field of melt spinning, wherein the method includes preparation step, dosing step, control step, confluence step, spinning step and cooling forming step, system includes core layer injection module, skin layer conveying module, temperature control module, pressure control module, skin-core composite spinning assembly, spinneret, cooling module, feedback module, semiconductor refrigeration module, gradient temperature rising module.The present application utilizes core phase change material and temperature-sensitive wall material to make microcapsules, so that the microcapsules can form a heat buffer structure inside the fiber. When the temperature and pressure and other environmental factors fluctuate greatly, the hollow fiber can be further supported by the microcapsules and the suspension medium, reducing the probability of fiber structure collapse, thereby improving the fiber hollow degree.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of melt spinning, in particular to a melt spinning process method and system based on microcapsule dispersion and temperature control strategy. BACKGROUND

[0002] Fiber is an important basic material and is widely used in modern production and life. Generally, various functional materials are added in fiber production to endow fibers with various functions. Existing spinning methods are usually divided into wet spinning and melt spinning. The temperature of wet spinning is relatively low, and a large amount of solvent is required. The melt spinning method does not need to add a large amount of solvent when preparing fibers, but a high-temperature melting process is required, and functional materials are easily affected by high temperature. Microcapsules are usually composed of a core and a wall material, and the core is wrapped in the wall material. Microcapsules loaded with functional components or modified can have certain temperature sensitivity and are often used to prepare various composite materials with temperature sensitivity.

[0003] Hollow fiber is a chemical fiber with a tubular cavity and has certain elasticity and heat insulation properties, and has been widely used in clothing, environmental protection and medical fields. The existing preparation method of hollow fiber usually supplies melt and gas to the spinneret at the same time, so that the core component is distributed on the inner wall of the hollow structure after the core layer of the spinneret is spun and solidified, and then the hollow fiber is obtained.

[0004] At present, a Chinese patent with publication number CN102041562A proposes an antibacterial fiber product and a preparation method thereof. The preparation method uses a melt spinning process, and two screw machines are used to supply the core component to the skin-core spinneret assembly. At the same time, a controllable gas flow is injected into the core component by means of a gas flow meter, so that the core layer is made into a structure with one or more hollow holes.

[0005] For the above technical solution, the melt spinning method is prone to be affected by temperature, pressure and other process parameters in the actual production process because of large fluctuations in temperature and pressure. The hollow fiber only relies on the support of the gas flow to form a hollow structure, which is easily affected by temperature, pressure and other process parameters, resulting in irregular and uneven fiber channels, unstable fiber solidification process, increased probability of structure collapse, and reduced hollow degree of the fiber. SUMMARY

[0006] The present application aims to provide a melt spinning process method and system based on microcapsule dispersion and temperature control strategy to solve the problems raised in the background.

[0007] In a first aspect, the present application provides a melt spinning process method based on microcapsule dispersion and temperature control strategy, which realizes the purpose of the application by adopting the following technical solution:

[0008] A kind of melt spinning process method based on microcapsule dispersion and temperature control strategy, comprising the following steps:

[0009] Preparation step: with phase change material as core, coated temperature-sensitive polymer as wall material, form microcapsule, particle size 1-5 μm, core proportion 60-80 wt%, wall material temperature resistance >200 ℃;

[0010] Feeding step: disperse microcapsule in suspension medium as core layer gas, melt after fiber-forming polymer as skin layer melt, input core layer gas and skin layer melt into skin-core composite spinning assembly;

[0011] Control step: control the difference between core layer gas outlet temperature T and microcapsule phase transition temperature T1 less than or equal to 5 ℃, control core layer gas outlet pressure P and environmental pressure P0 satisfy the correction formula: (P × T0) / T=P0+Δ+δ, wherein T0 is ambient temperature, Δ is correction pressure, the value range is 0 < Δ ≤ 0.12 MPa, δ is the inward compensation pressure generated by microcapsule phase transition expansion, the value range is 0.02 MPa ≤ δ ≤ 0.08 MPa;

[0012] Confluence step: skin-core composite spinning assembly converges skin layer melt and core layer gas, screw shear rate ≥300 s -1 ;

[0013] Spinning step: the mixture after confluence enters spinneret, extruded to form filament by spinneret, to obtain nascent fiber;

[0014] Cooling forming step: nascent fiber is extruded into cooling zone, adopts ring blowing mode, wind speed range is 0.5 ~ 1.5 m / s, makes nascent fiber cooling solidification forming.

[0015] By adopting the above technical scheme, the core phase change material and the temperature-sensitive wall material are used to make the microcapsule, so that the microcapsule can form a heat buffer structure inside the fiber. When the temperature and pressure and other environmental factors fluctuate greatly, the hollow fiber can be further supported by the microcapsule and the suspension medium, so that the hollow cavity always maintains a positive pressure environment during the solidification process, instead of relying only on airflow to support the hollow structure, so that the fiber channel is more regular and uniform, and the wall material has a certain temperature resistance, which can effectively reduce the probability of microcapsule rupture failure in the high-temperature spinning process. At the same time, the microcapsules are dispersed in the suspension medium and then mixed with the skin layer melt. Compared with the traditional method of mixing the melt only by single airflow, the microcapsule can be prevented from early phase change and expansion. When the microcapsule carries functional components, such as phase change microcapsule variants containing conductive, magnetic or fluorescent modifications, the functional components are released after the hollow fiber is solidified by thermal / mechanical triggering, which can significantly improve the survival rate of the functional components in the microcapsule, the form stability during the fiber solidification process is higher, and the probability of fiber structure collapse is reduced, thereby improving the hollow degree of the fiber; The microcapsule expands after being sprayed, generating an inward expansion pressure, and the pressure loss caused by gas cooling. By controlling the temperature difference between the core layer and the phase change point, the microcapsule can be triggered to phase change accurately at the spinneret outlet, avoiding process failure caused by premature / late expansion. By introducing the modified pressure and the inward compensation pressure generated by the microcapsule phase change expansion, the modified pressure and the inward compensation pressure can be selected by historical data, which is beneficial to dynamically offset the gas contraction caused by sudden changes in temperature and pressure during the spinning process, effectively reducing the coefficient of variation of the hollow degree, reducing the irregular defects of the fiber cross section, improving the structural stability and practicality of the fiber, and better suitable for medical fiber drug delivery field, dialysis field or aerospace field.

[0016] Optionally, in the preparation step, the phase change material includes, but is not limited to, one or more combinations of alkanes, fatty acids, polyols, and salt hydrates, the temperature-sensitive polymer includes, but is not limited to, one or more combinations of single-layer organic matter, multi-layer organic polymer, organic-inorganic hybrid polymer, or bio-based material, and the minimum critical solution temperature of the wall material ranges from 32 to 40℃.

[0017] By adopting the above technical scheme, the temperature resistance of traditional wall materials such as pure PMMA is insufficient, usually below 200℃, and is easy to break and fail in high-temperature spinning. The composition boundary of the phase change material and the temperature-sensitive polymer is expanded to make the wall material temperature resistance > 200℃, so that the survival rate of the microcapsule in the melt blending stage is improved, and the defects of single application scene and insufficient temperature control precision of the original scheme are reduced. The conventional wall material releases functional components depending on passive diffusion, and the controlled release precision is low. By using the temperature-triggered switch effect of the temperature-sensitive polymer, when the fiber environment temperature exceeds the lower critical solution temperature, the wall material pore size can be quickly expanded, thereby realizing the on-demand release of functional components. The temperature-sensitive material can adapt to extreme spinning environments of-50℃ to 300℃, and can also be matched with a specific temperature range such as the human body temperature range to trigger the release function when the fiber contacts the skin, intelligently release active substances, greatly extend the function durability and stability, and the introduction of bio-based wall materials makes the fiber directly applicable to implanted medical devices, improves biocompatibility, and is applicable to the biomedical field.

[0018] Optionally, in the preparation step, the structure of the microcapsule is a multi-layer composite structure, and a middle layer is further arranged between the wall material and the core, the middle layer is filled with aerogel and nitrogen, the porosity of the aerogel is > 90%, and the aerogel includes but is not limited to one or a combination of oxide aerogel, organic carbon aerogel or multi-phase aerogel.

[0019] In the feeding step, the suspension medium includes but is not limited to a combination of one or more of supercritical , low-viscosity polysiloxane or anti-settling agent.

[0020] By adopting the above technical scheme, the aerogel intermediate layer can form a thermal insulation barrier, effectively reducing the influence of external heat conduction on the core phase change material, making the phase change behavior triggered by the design temperature, blocking the damage of heat conduction above 300℃ to the core, reducing the probability of high-temperature decomposition of functional components in melt spinning, and greatly improving the service life compared with single-layer wall materials. The nitrogen filling layer can reduce heat convection loss and buffer the volume stress of the phase change, and at the same time as a buffer, it can absorb a certain amount of spinning shear force, so that the survival rate of the microcapsule in the screw high shear zone, i.e. the region with a shear rate ≥ 300s -1 , is greatly improved, the probability of cavity deformation caused by microcapsule swelling and extrusion in the fiber solidification stage is reduced, and the structural stability and practicality of the fiber are improved. The low viscosity and high diffusion of supercritical have certain steric hindrance effect, which can effectively inhibit the agglomeration of microcapsules, facilitate the realization of zero sedimentation dispersion of microcapsules in the melt, reduce the melt flow resistance, reduce the probability of fiber surface cracking under high spinning speed, reduce the risk of spinneret blockage and fiber breakage caused by agglomeration in the original process, and the form stability of the fiber in the solidification process is higher, thereby reducing the probability of structural collapse of the fiber, and further improving the hollow degree of the fiber.

[0021] Optionally, in the control step, the value of the inward compensation pressure δ is also determined, and a specific value calculation model of the inward compensation pressure δ is δ=KV mi (ΔT / Δt), wherein K is a microcapsule expansion coefficient, V mi is a microcapsule volume fraction, and ΔT / Δt is a temperature change rate of a core material of the microcapsule per unit time.

[0022] By adopting the above technical solution, the value of Δ in the traditional method is adjusted or selected by manual operation or experience, and the influence of the inward compensation pressure is not considered, and the correlation between pressure compensation and physical parameters is not established. The value of δ is accurately calculated through the microcapsule expansion coefficient K, the volume fraction V mi , and the core temperature change rate ΔT / Δt, so as to realize the predictability and repeatability of the compensation pressure, and to make the pressure control from static to dynamic. The cooling rate change of the spinneret outlet is captured in real time through ΔT / Δt, the microcapsule phase change rate is obtained, when the ΔT / Δt abnormally rises, the compensation amount of δ can be automatically increased to reduce the probability of collapse of the hollow cavity caused by too fast cooling, and the risk of over-compensation or under-compensation caused by fixed Δ value. For example, when ΔT / Δt<1000℃ / s, the fiber is not cooled enough, at this time, δ can be increased to prevent the hollow from collapsing, and the probability of structural collapse of the fiber is reduced, thereby improving the hollow degree of the fiber. The model parameters K, V mi can be adapted to different types of microcapsules, and the tedious re-adjustment after replacing functional components is reduced, and the practicality and process compatibility are improved.

[0023] Optionally, in the spinning step, the temperature of the center area in the inside of the spinneret is set to T C , and the temperature of the edge area in the inside of the spinneret is set to T C -(10-20)℃.

[0024] In the converging step, the skin-core composite spinning assembly controls the gradient temperature rise during the converging process, and the converging process includes three sections, the first section is 190±5℃, the second section is 240±3℃, and a screw shear rate ≥500s -1 is applied, and the third section is 270±2℃.

[0025] By adopting the technical scheme, the temperature control of the spinneret partition is conducive to reducing the difference in solidification rate of the melt surface, compensating for heat loss, maintaining high temperature in the center area of the spinneret to improve the fluidity of the melt in the center area, reducing the probability of uneven fineness caused by extrusion swelling, actively cooling the edge area to inhibit the overheating and rupture of microcapsules, and inhibiting the oxidation and crosslinking of the melt skin, thereby reducing the quality fluctuation caused by uneven heating of the edge, reducing the waste heat, saving production cost, and reducing the probability of edge coking or center hole blocking compared with single-zone temperature control; the gradient temperature control can activate the surface groups of the microcapsules in stages, thereby enhancing the compatibility of the microcapsule particles with the melt and reducing the probability of microcapsule aggregation, and the specific process is as follows: the surface groups of the microcapsules are activated at 190 DEG C, the high shear (shear rate is greater than or equal to 500 s -1 -1) breaks the microcapsule aggregates and promotes the entanglement of the molecular chains of the wall material and the melt, the molecular entanglement is completed at 270 DEG C, the melt viscosity is sufficiently reduced, the microcapsules are molecularly dispersed in the melt, the probability of performance degradation of the functional additives caused by surface migration is effectively reduced, the gradient temperature mixing shortens the process time compared with the isothermal mixing, and the traditional one-step temperature rising method needs to realize dispersion and flow balance at high temperature, but high temperature accelerates the degradation of the microcapsules, the dispersion and flow gradient are controlled to different temperature zones through the gradient temperature rising, which is conducive to reducing the thermal damage to the minimum while improving the dispersion quality, and the fiber solidification process can stably maintain the shape, thereby improving the hollow degree of the fiber.

[0026] Optionally, in the cooling forming step, the cooling zone adopts three-layer gradient ring blowing quenching wind: the upper layer wind temperature is 40±2 DEG C, the middle layer wind temperature is 15±1 DEG C, and the lower layer wind temperature is 5±1 DEG C.

[0027] By adopting the technical scheme, the cooling zone adopts three-layer gradient ring blowing quenching wind, the upper layer wind delays the surface solidification to reduce the hard shell effect, reserves a time window for the phase change expansion of the microcapsules, the middle layer wind induces crystallization, and the lower layer wind locks the hollow shape and inhibits the deformation of the cavity, thereby synergistically improving the uniformity of fiber crystallization, compared with the traditional single-temperature blowing, the gradient ring blowing is more energy-saving, can reduce the temperature difference existing from the center of the spinneret hole to the edge of the melt, reduce the probability of fiber skin-core structure differentiation, inhibit the collapse caused by gas contraction, the fiber solidification process can stably maintain the shape, thereby improving the hollow degree of the fiber.

[0028] In the second aspect, the present application provides a melt spinning process system based on the microcapsule dispersion and temperature control strategy, which applies the melt spinning process method based on the microcapsule dispersion and temperature control strategy as described in the first aspect, and adopts the following technical scheme to achieve the purpose of the application:

[0029] A melt spinning process system based on the microcapsule dispersion and temperature control strategy, comprising the following modules:

[0030] Core layer injection module: used for dispersing and mixing microcapsules in a suspension medium to form a core layer gas, and inputting the core layer gas into a core-sheath composite spinning assembly;

[0031] Sheath layer conveying module: used for inputting a molten fiber-forming polymer as a sheath layer melt into the core-sheath composite spinning assembly;

[0032] Temperature control module: used for controlling the difference between the core layer gas outlet temperature T and the microcapsule phase change temperature T1 to be less than or equal to 5℃;

[0033] Pressure control module: used for controlling the core layer gas outlet pressure P and the ambient pressure P0 to satisfy the correction formula: (P×T0) / T=P0+Δ+δ, wherein T0 is the ambient temperature, Δ is the correction pressure, the value range is 0<Δ≤0.12 MPa, δ is the inward compensation pressure generated by the microcapsule phase change expansion, the value range is 0.02 MPa≤δ≤0.08 MPa;

[0034] Core-sheath composite spinning assembly: used for converging the sheath layer melt and the core layer gas, and conveying the converged mixture to a spinneret;

[0035] Spinneret: used for extruding a filament through the spinneret to obtain a primary fiber;

[0036] Cooling module: after the primary fiber is extruded, it enters a cooling zone, and an air ring blowing mode is adopted to cool and solidify the primary fiber into a formed product.

[0037] By adopting the technical scheme, the microcapsules are made of the core phase change material and the temperature-sensitive wall material, the core layer injection module disperses the microcapsules into the suspension medium, the skin layer conveying module inputs the skin layer melt into the skin-core composite spinning assembly to mix with the core layer gas, the skin-core composite spinning assembly conveys the mixed flow to the spinneret, extrudes the primary fiber, and adopts the ring blowing method to cool and solidify the primary fiber into a fiber, compared with the method of mixing the melt by a single airflow in the traditional method, the microcapsules can be prevented from early phase change and expansion, when the functional components are carried in the microcapsules, the functional components are released by thermal / mechanical triggering after the hollow fiber is solidified, the survival rate of the functional components in the microcapsules can be significantly improved, the morphological stability in the fiber solidification process is higher, and the probability of fiber structure collapse is reduced, and the hollow degree of the fiber is improved; the microcapsules are heated and expanded after being sprayed, the inward expansion pressure is generated, the pressure loss is caused by gas cooling, the temperature of the core layer gas outlet is controlled by the temperature control module, the temperature difference between the core layer temperature and the phase change point is controlled, the microcapsules are accurately triggered to phase change at the spinneret outlet, the process failure caused by early / late expansion is avoided, the pressure of the core layer gas outlet is controlled by the pressure control module, the inward compensation pressure generated by the introduction of the correction pressure and the microcapsule phase change expansion is introduced, the correction pressure and the inward compensation pressure can be selected by historical data, which is beneficial to dynamically offset the gas contraction caused by the sudden change of temperature and pressure in the spinning process, effectively reduces the variation coefficient of the hollow degree, reduces the irregular defects of the fiber section, and improves the structural stability and practicality of the fiber.

[0038] Optionally, the feedback module is further included: for calculating the temperature change rate ΔT / Δt of the microcapsule core material per unit time according to the high-speed infrared thermal imager, and generating a pressure compensation instruction according to δ=K·V mi ·(ΔT / Δt), wherein K is the expansion coefficient of the microcapsule, V mi is the volume fraction of the microcapsule, and the value of the inward compensation pressure δ is updated.

[0039] By adopting the technical scheme, the value of Δ in the traditional method is adjusted by manual adjustment or experience selection, and the influence of the inward compensation pressure is not considered, and the association between the pressure compensation and the physical parameters is not established, the feedback module calculates the temperature change rate ΔT / Δt of the microcapsule core material per unit time by using the high-speed infrared thermal imager, and generates a pressure compensation instruction according to δ=K·V miThe core temperature change rate ΔT / Δt is accurately calculated to obtain the δ value, so as to realize the predictability and repeatability of the compensation pressure, and to control the pressure from static to dynamic. The cooling rate change of the spinneret outlet is captured in real time through ΔT / Δt, and the phase change rate of the microcapsule is obtained. When the ΔT / Δt abnormally rises, the probability of the hollow cavity collapse caused by too fast cooling can be reduced by automatically increasing the δ compensation amount, and the overcompensation or undercompensation risk caused by the fixed Δ value can be reduced. For example, when ΔT / Δt<1000℃ / s, the fiber cooling is insufficient, and at this time, the hollow collapse can be prevented by increasing δ, and the probability of fiber structure collapse is reduced, thereby improving the hollow degree of the fiber. The model parameters K, V mi The model parameters K, V mi can be adapted to different types of microcapsules, reducing the tediousness of re-adjustment after replacing functional components, and improving the practicality and process compatibility.

[0040] Optionally, it also includes a semiconductor refrigeration module and a gradient temperature rising module.

[0041] The semiconductor refrigeration module is used for refrigeration of the edge area inside the spinneret, the temperature of the center area inside the spinneret is set to T C , and the temperature of the edge area inside the spinneret is controlled to T C - (10-20)℃.

[0042] The gradient temperature rising module is used for gradient temperature rising control of the confluence area inside the sheath-core composite spinning assembly. The confluence area includes three sections, the first section is 190±5℃, the second section is 240±3℃, and the screw shear rate is ≥500s -1 , and the third section is 270±2℃.

[0043] By adopting the technical scheme, the semiconductor refrigeration module controls the temperature of the spinneret in sections, which is beneficial to reduce the difference in solidification rate of the melt surface, compensate for heat loss, maintain high temperature in the center area of the spinneret, improve the fluidity of the melt in the center area, reduce the probability of uneven fiber diameter caused by extrusion swelling, actively cool the edge area, inhibit the overheating and rupture of microcapsules, and inhibit the oxidation and crosslinking of the melt surface skin, thereby reducing the quality fluctuation caused by uneven edge overheating and cooling, reducing invalid heat consumption, saving production cost, and reducing the probability of edge coking or center hole blocking compared with single-zone temperature control.

[0044] Optionally, the cooling module is updated as follows: the nascent fiber is extruded into a cooling zone, the cooling zone is provided with an upper ring-shaped air hood, a middle ring-shaped air hood and a lower ring-shaped air hood which are independently controlled in temperature, the upper ring-shaped air hood is 5-10 cm away from the spinneret, the upper air temperature is 40±2℃, the middle ring-shaped air hood is 10-20 cm away from the spinneret, the middle air temperature is 15±1℃, the lower ring-shaped air hood is 20-30 cm away from the spinneret, and the lower air temperature is 5±1℃, so that the ring blowing method is adopted to cool and solidify the nascent fiber.

[0045] By adopting the technical scheme, the cooling module adopts three-layer gradient air blowing, the upper ring-shaped air hood blows air to delay surface solidification, thereby reducing the hard shell effect and reserving a time window for microcapsule phase change expansion, the middle ring-shaped air hood blows air to induce crystallization, and the lower ring-shaped air hood blows air to inhibit cavity deformation, thereby improving the uniformity of fiber crystallization, compared with the traditional single-temperature blowing, the gradient ring blowing is more energy-saving, can reduce the temperature difference existing in the melt from the center of the spinneret to the edge, reduce the probability of fiber skin-core structure differentiation, the fiber solidification process can stably maintain the shape, and the hollow degree of the fiber is improved.

[0046] Compared with the prior art, the beneficial effects of the present application are:

[0047] 1. By utilizing core phase change materials and temperature-sensitive wall materials to create microcapsules, the microcapsules can form a thermal buffer structure within the fiber. When environmental factors such as temperature and pressure fluctuate significantly, the hollow fiber can be further supported by the microcapsules and the suspension medium, maintaining a positive pressure environment in the hollow chamber during the curing process, rather than relying solely on airflow to support the hollow structure. This results in more regular and uniform fiber channels. The wall material has a certain degree of temperature resistance, effectively reducing the probability of microcapsule rupture and failure during high-temperature spinning. Furthermore, dispersing the microcapsules in the suspension medium and then mixing them with the skin melt, compared to traditional methods that only use a single airflow to mix the melt, avoids premature phase change expansion of the microcapsules. When the microcapsules contain functional components... When the functional components are released through thermal / mechanical triggering after the hollow fiber is cured, the survival rate of the functional components in the microcapsule can be significantly improved, the probability of structural collapse of the fiber is reduced, and thus the hollowness of the fiber is improved. After being ejected, the microcapsule expands due to heat, generating inward expansion pressure. The gas cooling causes pressure loss. By controlling the temperature difference between the core layer and the phase change point, the microcapsule can be precisely triggered to trigger the phase change at the spinneret outlet, avoiding process failure caused by premature / late expansion. By introducing the correction pressure and the inward compensation pressure generated by the phase change expansion of the microcapsule, the gas contraction caused by the sudden change in temperature and pressure during spinning is dynamically offset, the coefficient of variation of hollowness is reduced, the irregular defects of the fiber cross section are reduced, and the structural stability and practicality of the fiber are improved.

[0048] 2. Traditional wall materials have insufficient temperature resistance and are prone to breakage and failure during high-temperature spinning. By expanding the compositional boundary between phase change materials and temperature-sensitive polymers, the temperature resistance of the wall material is improved, resulting in a higher survival rate of microcapsules during the melt blending stage. This reduces the shortcomings of the original solution, such as limited applicability and insufficient temperature control precision. Conventional wall materials rely on passive diffusion to release functional components, resulting in low controlled release precision. By utilizing the temperature-triggered switching effect of temperature-sensitive polymers, the pore size of the wall material can rapidly expand when the fiber ambient temperature exceeds the minimum critical dissolution temperature, thereby achieving on-demand release of functional components. The temperature-sensitive material can be adapted to extreme spinning environments and can also be matched with specific temperature ranges such as the human body temperature range, enabling the release function to be triggered when the fiber comes into contact with the skin, intelligently releasing active substances, and significantly extending the functional durability and stability.

[0049] 3. The aerogel interlayer forms a thermal insulation barrier, effectively reducing the impact of external heat conduction on the core phase change material. This allows the phase change behavior to be triggered by the design temperature, reducing heat conduction damage to the core and lowering the probability of high-temperature decomposition of functional components during melt spinning. The lifespan is significantly improved compared to single-layer wall materials. The nitrogen-filled layer reduces heat convection loss and buffers phase change volume stress. Simultaneously, it acts as a buffer, absorbing a certain amount of spinning shear force, significantly increasing the survival rate of microcapsules in the high-shear zone of the screw. This reduces the probability of chamber deformation caused by microcapsule expansion and compression during fiber curing, improving the structural stability and practicality of the fiber. (Supercritical) The low viscosity and high diffusivity of the microcapsules have certain steric hindrance effect, which can effectively inhibit the agglomeration of the microcapsules, facilitate the zero sedimentation dispersion of the microcapsules in the melt, reduce the risk of spinneret blockage and fiber breakage caused by agglomeration in the original process, and improve the morphological stability of the fiber during the solidification process, thereby reducing the probability of structural collapse of the fiber and improving the hollow degree of the fiber.

[0050] 4. The traditional method relies on manual adjustment or experience to select the value of Δ, and does not consider the influence of inward compensation pressure. The correlation between pressure compensation and physical parameters is not established. The value of δ is accurately calculated by the microcapsule expansion coefficient K, the volume fraction V mi , and the core temperature change rate ΔT / Δt, so as to realize the predictability and repeatability of the compensation pressure, and to make the pressure control from static to dynamic. The cooling rate change at the spinneret outlet is captured in real time by ΔT / Δt, and the phase change rate of the microcapsule is obtained. When the ΔT / Δt abnormally rises, the δ compensation amount can be automatically increased to reduce the probability of hollow cavity collapse caused by too fast cooling, and to reduce the risk of overcompensation or undercompensation caused by fixed Δ value. When ΔT / Δt<1000℃ / s, the fiber is not cooled enough. At this time, the hollow collapse can be prevented by increasing δ, which reduces the probability of structural collapse of the fiber and improves the hollow degree of the fiber. The model parameters K, V mi can be adapted to different types of microcapsules, reducing the complexity of re-adjustment after replacing functional components, and improving the practicality and process compatibility.

[0051] 5. The temperature control of the spinneret partition is beneficial to reduce the difference in solidification rate of the melt surface, compensate for the heat loss, maintain high temperature in the center area of the spinneret to improve the fluidity of the melt in the center area, reduce the probability of uneven fineness caused by extrusion swelling, actively cool the edge area to inhibit the overheating and rupture of the microcapsules, and inhibit the oxidation and crosslinking of the melt skin. The quality fluctuation caused by uneven cooling and overheating of the edge is reduced, which is beneficial to reduce the probability of edge scorching or center blockage. The gradient temperature control can activate the surface groups of the microcapsules in stages, which can enhance the compatibility of the microcapsule particles and the melt, reduce the probability of microcapsule agglomeration, and effectively reduce the probability of performance degradation of the functional additives caused by surface migration. The traditional one-step heating method needs to achieve dispersion and flow balance at high temperature, but high temperature accelerates the degradation of the microcapsules. By gradient heating, the dispersion and flow gradient are controlled to different temperature zones, which can improve the dispersion quality while minimizing thermal damage. The fiber solidification process can stably maintain the morphology, thereby improving the hollow degree of the fiber. BRIEF DESCRIPTION OF DRAWINGS

[0052] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. It will be appreciated that the drawings are merely schematic and are not intended to represent the actual size or shape of the application, but are intended to conceptually convey the principles of the application. It will be understood by those skilled in the art that various modifications can be made to the implementations described in the specification without departing from the scope of the application. In some instances, certain features, functions, aspects, and / or

[0053] Figure 1 A flow chart of a melt spinning process method based on microcapsule dispersion and temperature control strategy for an embodiment of the application;

[0054] Figure 2 A system block diagram of a melt spinning process system based on microcapsule dispersion and temperature control strategy for an embodiment of the application. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings of the embodiments of the application. Figure 1 and Figure 2 The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings of the embodiments of the application.

[0056] The application provides a melt spinning process method based on microcapsule dispersion and temperature control strategy, which comprises a preparation step S1, a feeding step S2, a control step S3, a confluence step S4, a spinning step S5 and a cooling forming step S6.

[0057] S1, the preparation step: taking a phase change material as a core and a temperature-sensitive polymer as a wall material to form a microcapsule, the particle size is 1-5 μm, the core accounts for 60-80 wt%, and the wall material has a temperature resistance > 200℃.

[0058] The phase change material includes but is not limited to one or more combinations of alkanes, fatty acids, polyols and salt hydrates, such as n-eicosane, polyethylene glycol 6000 or The temperature-sensitive polymer includes but is not limited to one or more combinations of single-layer organic matter, multi-layer organic polymer, organic-inorganic hybrid polymer or bio-based material, such as polymethyl methacrylate-silica hybrid wall material, poly(N-isopropyl acrylamide-co-acrylamide) temperature-sensitive polymer or chitosan / sodium alginate bio-based wall material, and the minimum critical solution temperature of the wall material ranges from 32 to 40℃.

[0059] The microcapsule has a multi-layer composite structure, and a middle layer is arranged between the wall material and the core, the middle layer is filled with aerogel and nitrogen, the porosity of the aerogel is > 90%, and the aerogel includes but is not limited to one or a combination of oxide aerogel, organic carbon aerogel or multiphase aerogel.

[0060] S2, a feeding step: dispersing the microcapsule in a suspension medium as a core layer gas, melting the fiber-forming polymer as a skin layer melt, and inputting the core layer gas and the skin layer melt into a skin-core composite spinning assembly.

[0061] The suspension medium includes but is not limited to a combination of one or more of supercritical , low-viscosity polysiloxane or anti-settling agent.

[0062] S3, a control step: controlling the difference between the core layer gas outlet temperature T and the microcapsule phase change temperature T1 to be less than or equal to 5℃, and controlling the core layer gas outlet pressure P and the ambient pressure P0 to satisfy the correction formula: (P×T0) / T=P0+Δ+δ, wherein T0 is the ambient temperature, Δ is the correction pressure, the value range is 0<Δ≤0.12MPa, δ is the inward compensation pressure generated by the phase change expansion of the microcapsule, and the value range is 0.02MPa≤δ≤0.08MPa.

[0063] The specific value calculation model of the inward compensation pressure δ is: δ=KV mi (ΔT / Δt), wherein K is the expansion coefficient of the microcapsule, V mi is the volume fraction of the microcapsule, and ΔT / Δt is the temperature change rate of the core material of the microcapsule per unit time.

[0064] S4, a confluence step: the skin-core composite spinning assembly converges the skin layer melt and the core layer gas, and the screw shear rate during the convergence process is ≥300s -1 .

[0065] The skin-core composite spinning assembly controls the convergence process by gradient heating, and the convergence process includes three sections, the first section is 190±5℃, the second section is 240±3℃, and a screw shear rate ≥500s -1 is applied, and the third section is 270±2℃.

[0066] S5, a spinning step: the mixture after convergence enters the spinneret, is extruded through the spinneret to form a yarn, and the primary fiber is obtained.

[0067] The spinneret is internally controlled by temperature zoning, the center zone temperature inside the spinneret is set to T C , and the edge zone temperature inside the spinneret is set to T C -(10-20)℃.

[0068] S6, cooling forming step: after the nascent fiber is extruded, it enters a cooling zone, an annular blowing method is adopted, the wind speed ranges from 0.5 to 1.5 m / s, and the nascent fiber is cooled and solidified.

[0069] The cooling zone adopts three layers of gradient annular blowing quenching wind: the upper layer wind temperature is 40±2℃, the middle layer wind temperature is 15±1℃, and the lower layer wind temperature is 5±1℃.

[0070] Example one: the embodiment discloses a melt spinning process method based on microcapsule dispersion and temperature control strategy, referring to Figure 1 , comprising the following steps:

[0071] S1, preparation step: using n-eicosane as a core phase change material, a poly (methyl methacrylate) -silica hybrid wall material is coated to form a microcapsule, the microcapsule is a multi-layer composite structure, including a wall material, a middle layer and a core, the microcapsule particle size is 2.5 μm, the core accounts for 60 wt%, the wall material accounts for 40 wt%, the wall material temperature resistance is > 300℃, the minimum critical solution temperature of the wall material is 33℃, the wall material thickness is 30 nm, the core thickness is 80 nm, the middle layer is a silica aerogel network, the thickness is 25 nm, the porosity is 92%, the phase change temperature of the phase change material n-eicosane is 36-38℃, the phase change enthalpy is 240-260 J / g, and the survival rate of the microcapsule under the condition of 300℃ / 30min is ≥95%.

[0072] S2, feeding step: dispersing the microcapsule in a supercritical suspension medium as a core layer gas, the concentration is 15 wt%, the melted fiber-forming polymer is used as a skin layer melt, and the core layer gas and the skin layer melt are input into a skin-core composite spinning assembly.

[0073] S3, control step: controlling the difference between the core layer gas outlet temperature T and the microcapsule phase change temperature T1 to be less than or equal to 5℃, and controlling the core layer gas outlet pressure P and the environmental pressure P0 to satisfy the correction formula: (P×T0) / T=P0+Δ+δ, real-time calculating and updating the inward compensation pressure: δ=KV mi (ΔT / Δt).

[0074] S4, confluence step: the skin-core composite spinning assembly conducts confluence of the skin layer melt and the core layer gas, the screw shear rate is ≥300 s -1， , the confluence process is controlled by gradient temperature rise, the first section is 190±5℃, the second section is 240±3℃, and the screw shear rate is ≥500 s -1 , and the third section is 270±2℃.

[0075] S5, spinning step: the mixture after confluence enters a spinneret, is extruded through the spinneret to form a filament, and nascent fiber is obtained, the spinneret is internally controlled by partition temperature, the center zone temperature is T C, the edge zone temperature is T C - (10-20) ℃, the core layer channel is provided with a semiconductor refrigeration ring to make the inlet temperature ≤ 50℃.

[0076] S6, cooling forming step: after the nascent fiber is extruded, it enters a cooling zone, three-layer gradient ring blowing quenching wind is adopted, the upper layer wind temperature is 40±2℃, the middle layer wind temperature is 15±1℃, and the lower layer wind temperature is 5±1℃. The wind speed range is 0.5-1.5 m / s, so that the nascent fiber is cooled and solidified.

[0077] The implementation principle of the melt spinning process method based on the microcapsule dispersion and temperature control strategy in the embodiment is as follows:

[0078] The microcapsule is made of core phase change material and temperature-sensitive wall material, so that the microcapsule can form a heat buffer structure inside the fiber. When the temperature and pressure and other environmental factors fluctuate greatly, the hollow fiber can be further supported by the microcapsule and the suspension medium, so that the hollow cavity always maintains a positive pressure environment during the solidification process, instead of relying only on air flow to support the hollow structure, so that the fiber pore is more regular and uniform, and the wall material has a certain temperature resistance, which can effectively reduce the probability of microcapsule rupture failure in the high-temperature spinning process.

[0079] The microcapsule is dispersed into the suspension medium and then mixed with the skin layer melt. Compared with the method of mixing the melt only by single air flow in the traditional method, the microcapsule can be prevented from swelling in advance. When the microcapsule carries functional components, such as phase change microcapsule variants containing conductive, magnetic or fluorescent modifications, the functional components can be released after the hollow fiber is solidified through thermal / mechanical triggering, which can significantly improve the survival rate of functional components in the microcapsule, the form stability during the fiber solidification process is higher, and the probability of fiber structure collapse is reduced, thereby improving the hollow degree of the fiber.

[0080] The microcapsule expands after being heated, generating an inward swelling pressure. The pressure loss is caused by gas cooling. By controlling the temperature difference between the core layer and the phase change point, the microcapsule can be triggered to change phase accurately at the spinneret outlet, avoiding premature / late swelling caused by process failure. By introducing the modified pressure and the inward compensating pressure generated by the swelling of the microcapsule, the modified pressure and the inward compensating pressure can be selected through historical data, which is beneficial to dynamically offset the gas contraction caused by sudden changes in temperature and pressure during spinning, effectively reducing the coefficient of variation of the hollow degree, reducing the irregular defects of the fiber cross section, improving the structural stability and practicality of the fiber, and better suitable for medical fiber drug delivery field, dialysis field or aerospace field, etc.

[0081] The temperature resistance of traditional wall materials such as pure PMMA is insufficient, usually below 200℃, and is easy to break and fail in high-temperature spinning. By expanding the composition boundary of phase change materials and temperature-sensitive polymers, the temperature resistance of the wall material is >200℃, which improves the survival rate of microcapsules in the melt blending stage, reduces the defects of single application scene and insufficient temperature control precision of the original scheme, and realizes on-demand release of functional components. The conventional wall material releases functional components by passive diffusion, and the control release precision is low. By using the temperature-triggered switch effect of temperature-sensitive polymers, when the fiber environment temperature exceeds the lower critical solution temperature, the wall material pore size can be quickly expanded, thereby realizing on-demand release of functional components. The temperature-sensitive material can adapt to extreme spinning environments of-50℃ to 300℃, and can also be matched with a specific temperature range such as the human body temperature range to trigger the release function when the fiber contacts the skin, intelligently release active substances, greatly extend the function durability and stability, and the introduction of bio-based wall materials enables the fiber to be directly used in implantable medical devices, improving biocompatibility and being applicable to the biomedical field.

[0082] The aerogel intermediate layer can form a thermal insulation barrier, effectively reducing the influence of external heat conduction on the core phase change material, triggering the phase change behavior at the designed temperature, blocking the damage of heat conduction above 300℃ to the core, reducing the probability of high-temperature decomposition of functional components in melt spinning, and greatly improving the service life compared with single-layer wall materials. The nitrogen-filled layer can reduce heat convection loss and buffer the volume stress of the phase change material, and at the same time as a buffer, it can absorb a certain amount of spinning shear force, so that the survival rate of microcapsules in the high shear region of the screw, i.e., ≥300s -1 , is greatly improved, reducing the probability of cavity deformation caused by microcapsule swelling and extrusion during the fiber solidification stage, and improving the structural stability and practicality of the fiber.

[0083] The low viscosity and high diffusivity of supercritical carbon dioxide have certain steric hindrance effect, which can effectively inhibit the agglomeration of microcapsules, is conducive to realizing zero sedimentation dispersion of microcapsules in the melt, reducing the melt flow resistance, reducing the probability of fiber surface cracking at high spinning speed, reducing the risk of spinneret blockage and fiber breakage caused by agglomeration in the original process, and the form stability is higher during the fiber solidification process, thereby reducing the probability of structural collapse of the fiber, and further improving the hollow degree of the fiber.

[0084] In the traditional method, the value of Δ is manually adjusted or selected by experience, and the influence of inward compensation pressure is not considered, and the correlation between pressure compensation and physical parameters is not established. By accurately calculating the δ value from the microcapsule swelling coefficient K, volume fraction V mi , and core temperature change rate ΔT / Δt, the predictability and repeatability of the compensation pressure are realized, and the pressure control is from static to dynamic.

[0085] The cooling rate change of the spinneret outlet is captured in real time by ΔT / Δt, the phase change rate of the microcapsule is obtained, when the abnormal rise of ΔT / Δt is detected, the probability of the collapse of the hollow cavity caused by the too fast cooling can be reduced by automatically increasing the δ compensation, and the risk of overcompensation or undercompensation caused by the fixed Δ value can be reduced, such as the sudden change of the high-speed spinning working condition, when ΔT / Δt < 1000℃ / s, the fiber is not cooled enough, at this time, the hollow collapse can be prevented by increasing δ, the probability of the structural collapse of the fiber is reduced, and the hollow degree of the fiber is improved, which is suitable for the transient working condition of high-speed spinning, the model parameters K, V mi Different types of microcapsules can be adapted, the tedious re-adjustment after replacing functional components is reduced, and the practicality and process compatibility are improved.

[0086] The temperature control of the spinneret partition is beneficial to reduce the difference in solidification rate of the melt surface, compensate for the heat loss, maintain high temperature in the center area of the spinneret to improve the fluidity of the melt in the center area, reduce the probability of uneven fiber caused by extrusion swelling, actively cool the edge area to inhibit the overheating and rupture of the microcapsule, and at the same time, inhibit the oxidation and crosslinking of the melt skin, reduce the quality fluctuation caused by the overheating and uneven cooling of the edge, reduce the invalid heat consumption, and save the production cost. Compared with single-zone temperature control, it is beneficial to reduce the probability of edge coking or center hole blocking.

[0087] The gradient temperature control can activate the microcapsule surface groups in stages, which can enhance the compatibility of the microcapsule particles and the melt, and reduce the probability of microcapsule aggregation. The specific process is as follows: at 190℃, the microcapsule surface groups are activated, at 240℃, the shear rate is ≥500s -1 , the microcapsule aggregation is broken, and the molecular chain entanglement of the wall material and the melt is promoted, at 270℃, the molecular entanglement is completed, the melt viscosity is sufficiently reduced, the microcapsule reaches molecular level dispersion in the melt, the probability of performance degradation of the functional additive caused by surface migration is effectively reduced, and the gradient temperature mixing shortens the process time compared with the isothermal mixing.

[0088] The traditional one-step temperature rising method needs to realize dispersion and flow balance at high temperature, but high temperature accelerates the degradation of the microcapsule. By gradient temperature rising, the dispersion and flow gradient are controlled to different temperature zones, which is beneficial to reduce the heat damage to the minimum while improving the dispersion quality, and the fiber solidification process can stably maintain the morphology, thereby improving the hollow degree of the fiber.

[0089] The cooling zone adopts three-layer gradient air blowing, the upper layer air delays surface solidification to reduce the hard shell effect, reserves time window for microcapsule phase change expansion, the middle layer air induces crystallization, the lower layer air locks the hollow form and inhibits the deformation of the cavity, thereby synergistically improving the uniformity of fiber crystallization. Compared with the traditional single-temperature air blowing, the gradient ring air blowing is more energy-saving, can reduce the temperature difference existing from the center to the edge of the spinneret, reduce the probability of fiber skin-core structure differentiation, inhibit the collapse caused by gas contraction, and stabilize the form during the fiber solidification process, thereby improving the hollow degree of the fiber.

[0090] Embodiment two: the embodiment discloses a melt spinning process system based on microcapsule dispersion and temperature control strategy, referring to Figure 2 , comprising the following modules:

[0091] Core injection module: for dispersing and mixing microcapsules in a suspension medium to form a core gas, and inputting the core gas into a skin-core composite spinning assembly;

[0092] Skin delivery module: for inputting the melted fiber-forming polymer as a skin melt into the skin-core composite spinning assembly;

[0093] Temperature control module: for controlling the difference between the core gas outlet temperature T and the microcapsule phase change temperature T1 to be less than or equal to 5℃;

[0094] Pressure control module: for controlling the core gas outlet pressure P and the environmental pressure P0 to satisfy the correction formula: (P×T0) / T=P0+Δ+δ, wherein T0 is the environmental temperature, Δ is the correction pressure, the value range is 0<Δ≤0.12MPa, δ is the inward compensation pressure generated by the microcapsule phase change expansion, the value range is 0.02MPa≤δ≤0.08MPa;

[0095] Skin-core composite spinning assembly: for converging the skin melt and the core gas, and delivering the converged mixture to a spinneret;

[0096] Gradient temperature rising module: for gradient temperature rising control of the converging area inside the skin-core composite spinning assembly, the converging area includes three sections, the first section is 190±5℃, the second section is 240±3℃, and the screw shear rate is ≥500s -1 , and the third section is 270±2℃.

[0097] Spinneret: for extruding a filament through the spinneret to obtain a primary fiber;

[0098] Semiconductor refrigeration module: for refrigerating the edge area inside the spinneret, setting the temperature of the central area inside the spinneret as T C , and controlling the temperature of the edge area inside the spinneret as T C -(10-20)℃.

[0099] The feedback module is configured to calculate the temperature change rate ΔT / Δt of the microcapsule core material per unit time according to the high-speed infrared thermal imager, and generate a pressure compensation instruction according to δ=K·V mi wherein K is the expansion coefficient of the microcapsule, V mi is the volume fraction of the microcapsule, and the value of the inward compensation pressure δ is updated.

[0100] The cooling module is configured to cool and solidify the nascent fiber into a shape after the nascent fiber is extruded into a cooling area. The cooling area is provided with an upper ring-shaped air cover, a middle ring-shaped air cover and a lower ring-shaped air cover which are independently controlled in temperature. The upper ring-shaped air cover is 5-10 cm away from the spinneret, the temperature of the upper air is 40±2℃, the middle ring-shaped air cover is 10-20 cm away from the spinneret, the temperature of the middle air is 15±1℃, the lower ring-shaped air cover is 20-30 cm away from the spinneret, and the temperature of the lower air is 5±1℃. Thus, the nascent fiber is cooled and solidified into a shape by adopting a ring air blowing mode.

[0101] The implementation principle of the melt spinning process system based on the microcapsule dispersion and temperature control strategy in the embodiment is as follows:

[0102] The microcapsule is made of core phase change material and temperature-sensitive wall material. The core layer injection module disperses the microcapsule into the suspension medium, the skin layer conveying module inputs the skin layer melt into the skin-core composite spinning assembly and the core layer gas for mixing, the skin-core composite spinning assembly conveys the mixed material to the spinneret, and the nascent fiber is extruded. The nascent fiber is cooled and solidified into a shape by adopting a ring air blowing mode. Compared with the method of mixing the melt by a single air flow in the traditional method, the microcapsule can be prevented from early phase change and expansion. When the functional component is carried in the microcapsule, the functional component is released after the hollow fiber is solidified by thermal / mechanical triggering, which can significantly improve the survival rate of the functional component in the microcapsule, the form stability during the fiber solidification process is higher, and the probability of fiber structure collapse is reduced, thereby improving the hollow degree of the fiber.

[0103] The microcapsule is heated and expanded after being sprayed, generating an inward expansion pressure. The pressure loss is caused by gas cooling. The core layer gas outlet temperature is controlled by the temperature control module. By controlling the temperature difference between the core layer temperature and the phase change point, the microcapsule can be accurately triggered to phase change at the spinneret outlet, which can avoid process failure caused by early / late expansion. The core layer gas outlet pressure is controlled by the pressure control module. By introducing the correction pressure and the inward compensation pressure generated by the microcapsule phase change and expansion, the correction pressure and the inward compensation pressure can be selected by historical data, which is beneficial to dynamically offset the gas contraction caused by sudden changes in temperature and pressure during spinning, effectively reduces the variation coefficient of the hollow degree, reduces the irregular defects of the fiber cross section, and improves the structural stability and practicality of the fiber.

[0104] In the traditional method, the value of Δ is adjusted manually or selected by experience, and the influence of internal compensation pressure is not considered, the correlation between pressure compensation and physical parameters is not established, and the feedback module calculates the temperature change rate ΔT / Δt of the microcapsule core material per unit time by using a high-speed infrared thermal imager, and the microcapsule expansion coefficient K, volume fraction V mi , core temperature change rate ΔT / Δt accurately calculates the δ value, so as to realize the predictability and repeatability of the compensation pressure, and make the pressure control from static to dynamic.

[0105] By ΔT / Δt, the cooling rate change of the spinneret outlet is captured in real time, and the microcapsule phase change rate is obtained. When an abnormal increase in ΔT / Δt is detected, the δ compensation amount can be automatically increased to reduce the probability of hollow cavity collapse caused by too fast cooling, and the risk of over-compensation or under-compensation caused by fixed Δ value. For example, when ΔT / Δt < 1000℃ / s, the fiber is not cooled enough, at this time, δ can be increased to prevent the hollow from collapsing, thereby reducing the probability of structural collapse of the fiber, and thus improving the hollow degree of the fiber. It is suitable for transient conditions of high-speed spinning. Model parameters K, V mi can adapt to different types of microcapsules, reducing the complexity of re-adjustment after replacing functional components, and improving practicality and process compatibility.

[0106] The semiconductor refrigeration module controls the temperature of the spinneret partition, which is beneficial to reduce the difference in solidification rate of the melt surface, compensate for heat loss, maintain high temperature in the center area of the spinneret to improve the fluidity of the melt in the center area, and reduce the probability of uneven fiber caused by extrusion swelling. The edge area is actively cooled to prevent microcapsule overheating and rupture, while inhibiting the oxidation and crosslinking of the melt skin, reducing the quality fluctuations caused by uneven cooling and overheating of the edge, reducing waste heat, and saving production costs. Compared with single-zone temperature control, it is beneficial to reduce the probability of edge coking or center blockage.

[0107] The gradient temperature rising module controls the activation of microcapsule surface groups in stages through gradient temperature rising, which can enhance the compatibility of microcapsule particles and melt, and reduce the probability of microcapsule aggregation. The specific process is as follows: in the 190℃ stage, the microcapsule surface groups are activated, in the 240℃ stage, the microcapsule aggregates are broken by high shear, and at the same time, the molecular chains of the wall material and the melt are entangled, in the 270℃ stage, the microcapsule reaches molecular level dispersion in the melt, effectively reducing the probability of performance degradation of functional additives caused by surface migration. The traditional one-step heating method needs to achieve dispersion and flow balance at high temperature, but high temperature accelerates the degradation of microcapsules. By gradient temperature rising, the dispersion and flow gradient are controlled in different temperature zones, which helps to minimize thermal damage while improving dispersion quality. The fiber solidification process can maintain its shape stably, thereby improving the hollow degree of the fiber.

[0108] The cooling module adopts three-layer gradient air blowing, the upper ring-shaped air cover blows air to delay surface solidification, so as to reduce the hard shell effect, reserve a time window for microcapsule phase change expansion, the middle ring-shaped air cover blows air to induce crystallization, and the lower ring-shaped air cover blows air to suppress cavity deformation, so that the uniformity of fiber crystallization is synergistically improved, compared with the traditional single-temperature air blowing, the gradient ring air blowing is more energy-saving, can reduce the temperature difference existing from the center to the edge of the melt in the spinneret hole, reduces the probability of fiber skin-core structure differentiation, the fiber solidification process can stably maintain the form, and then the hollow degree of the fiber is improved.

[0109] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application shall be covered within the protection scope of the present application.

Claims

1. A melt spinning process based on microcapsule dispersion and temperature control strategies, characterized in that, Includes the following steps: Preparation steps: Using a phase change material as the core and a thermosensitive polymer as the wall material, microcapsules are formed with a particle size of 1-5 μm and a core content of 60-80 wt%. The wall material has a temperature resistance of >200℃. The microcapsules have a multi-layer composite structure, with a middle layer between the wall material and the core. The middle layer is filled with aerogel and nitrogen. The porosity of the aerogel is >90%. The aerogel includes one or more of oxide aerogel, organic carbon aerogel, or multiphase aerogel. Feeding step: The microcapsules are dispersed in a suspension medium as the core gas, and the molten fiber-forming polymer is used as the skin melt. The core gas and skin melt are fed into the core-skin composite spinning assembly. The suspension medium includes one or more of supercritical CO2, low-viscosity polysiloxane, or anti-settling agent. Control steps: The difference between the core gas outlet temperature T and the microcapsule phase change temperature T1 is less than or equal to 5℃. The core gas outlet pressure P and the ambient pressure P0 are controlled to satisfy the correction formula: (P×T0) / T=P0+Δ+δ, where T0 is the ambient temperature, Δ is the correction pressure with a value range of 0<Δ≤0.12MPa, and δ is the inward compensation pressure generated by the phase change expansion of the microcapsule with a value range of 0.02MPa≤δ≤0.08MPa. Combination Step: The core-sheath composite spinning assembly combines the sheath melt and core gas, with a screw shear rate ≥300s. -1 ; Spinning steps: The confluenced mixture enters the spinneret and is extruded through the spinneret to form filaments, thus obtaining nascent fibers; Cooling and molding step: After the nascent fibers are extruded, they enter the cooling zone and are cooled and solidified by a ring-blowing method with a wind speed range of 0.5 to 1.5 m / s.

2. The melt spinning process method based on microcapsule dispersion and temperature control strategy according to claim 1, characterized in that: In the preparation steps, the phase change material includes one or more of alkanes, fatty acids, polyols and salt hydrates, the temperature-sensitive polymer includes one or more of monolayer organic materials, multilayer organic polymers, organic-inorganic hybrid polymers or bio-based materials, and the minimum critical dissolution temperature range of the wall material is 32-40°C.

3. The melt spinning process method based on microcapsule dispersion and temperature control strategy according to claim 1, characterized in that: In the control steps, the value of the inward compensation pressure δ is also determined. The specific calculation model for the inward compensation pressure δ is: δ=KV mi (ΔT / Δt), where K is the microcapsule expansion coefficient, V mi ΔT / Δt represents the volume fraction of the microcapsule, and ΔT / Δt represents the rate of temperature change of the microcapsule core material per unit time.

4. The melt spinning process method based on microcapsule dispersion and temperature control strategy according to claim 1, characterized in that: In the spinning step, the spinneret is internally temperature-controlled in zones, and the temperature of the central zone inside the spinneret is set to T. C The temperature of the edge region inside the spinneret is set to T. C -(10~20)℃; In the merging step, the core-sheath composite spinning assembly performs gradient temperature control on the merging process, which includes three regions: the first region is 190±5℃, the second region is 240±3℃, and a screw shear rate of ≥500s is applied. -1 The third region is 270±2℃.

5. The melt spinning process method based on microcapsule dispersion and temperature control strategy according to claim 1, characterized in that: In the cooling and forming step, the cooling zone uses a three-layer gradient circulating cooling airflow: the upper layer air temperature is 40±2℃, the middle layer air temperature is 15±1℃, and the lower layer air temperature is 5±1℃.

6. A melt spinning process system based on a microcapsule dispersion and temperature control strategy, employing a melt spinning process method based on a microcapsule dispersion and temperature control strategy as described in any one of claims 1-5, characterized in that, Includes the following modules: Core layer injection module: used to disperse and mix microcapsules in a suspension medium to form core layer gas, and to input the core layer gas into the core-sheath composite spinning assembly; Sheet delivery module: used to input the molten fiber-forming polymer as the sheet melt into the core-sheet composite spinning assembly; Temperature control module: used to ensure that the difference between the core gas outlet temperature T and the microcapsule phase change temperature T1 is less than or equal to 5℃; Pressure control module: Used to control the core gas outlet pressure P to satisfy the correction formula: (P×T0) / T=P0+Δ+δ, where T0 is the ambient temperature, Δ is the correction pressure with a value range of 0<Δ≤0.12MPa, and δ is the inward compensation pressure generated by the phase change expansion of the microcapsules with a value range of 0.02MPa≤δ≤0.08MPa; Sheath-core composite spinning assembly: used to combine the sheath melt and core gas, and to transport the combined mixture to the spinneret; Spinneret: Used to extrude filaments to obtain nascent fibers; Cooling module: After the nascent fibers are extruded, they enter the cooling zone and are cooled and solidified by a ring-blowing method.

7. The melt spinning process system based on microcapsule dispersion and temperature control strategy according to claim 6, characterized in that: It also includes a feedback module: used to calculate the temperature change rate ΔT / Δt of the microcapsule core material per unit time based on the high-speed infrared thermal imager, and according to δ=K·V mi • (ΔT / Δt) generates pressure compensation command, where K is the microcapsule expansion coefficient, V mi The value of the inward compensating pressure δ is updated to represent the volume fraction of the microcapsules.

8. The melt spinning process system based on microcapsule dispersion and temperature control strategy according to claim 6, characterized in that: It also includes a semiconductor cooling module and a gradient temperature rise module; Semiconductor cooling module: Used to cool the edge area inside the spinneret, setting the temperature of the central area inside the spinneret to T. C Control the temperature of the edge area inside the spinneret to T C -(10~20)℃; Gradient heating module: Used to control the gradient temperature of the confluence region inside the core-sheath composite spinning assembly. The confluence region consists of three sections: the first section is 190±5℃, the second section is 240±3℃, and a screw shear rate of ≥500s is applied. -1 The third region is 270±2℃.

9. The melt spinning process system based on microcapsule dispersion and temperature control strategy according to claim 6, characterized in that: The cooling module has been updated as follows: after the nascent fibers are extruded, they enter the cooling zone, which is equipped with an upper annular hood, a middle annular hood, and a lower annular hood with independent temperature control. The upper annular hood is 5-10 cm away from the spinneret and the upper air temperature is 40±2℃. The middle annular hood is 10-20 cm away from the spinneret and the middle air temperature is 15±1℃. The lower annular hood is 20-30 cm away from the spinneret and the lower air temperature is 5±1℃. Thus, the nascent fibers are cooled, solidified, and formed by the ring-blowing method.

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