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CN-122008515-A - Extrusion process for low-smoke halogen-free cable insulating layer

CN122008515ACN 122008515 ACN122008515 ACN 122008515ACN-122008515-A

Abstract

The invention discloses a low-smoke halogen-free cable insulating layer extrusion process, and belongs to the technical field of cable manufacturing. The process is carried out by integrated equipment and comprises the steps of premix preparation, supercritical CO 2 collaborative fluid preparation, melt plasticization and collaborative injection, gradient control extrusion molding and post-treatment rolling, and is realized through supercritical CO 2 collaborative fluid and micro-nano hydrotalcite modification, zonal and three-stage gradient temperature control, pressure-temperature linkage regulation and control and ultrasonic-ultraviolet post-treatment. The invention provides a scheme of coupling synergistic modification and integrated equipment, which not only fundamentally reduces melt viscosity and inhibits foaming, but also improves the flame retardance, mechanical strength and ageing resistance of the material, realizes double breakthrough of processing efficiency and product quality, and meets the industrial mass production requirement.

Inventors

  • Song Hanmeng
  • CAI YIFENG

Assignees

  • 兴胜山鹰线缆有限公司

Dates

Publication Date
20260512
Application Date
20260326

Claims (10)

  1. 1. The extrusion process of the low-smoke halogen-free cable insulating layer is characterized by being executed by an integrated equipment system, the system comprises a mixer (1), a supercritical fluid preparation unit, an extruder (2), a gradient anti-foaming forming unit (3), an ultrasonic-ultraviolet aftertreatment unit, a winding machine (4) and an intelligent control unit, the output ends of the mixer (1) and the supercritical fluid preparation unit are communicated with the extruder (2) through a double-channel precise injection unit, the ultrasonic-ultraviolet aftertreatment unit comprises an ultrasonic auxiliary cooling water tank (5) and an online ultraviolet pretreatment device (6), and the process comprises the following steps: S1, preparation of premix: adding a polyolefin substrate, a halogen-free flame retardant, modified micro-nano hydrotalcite and an antioxidant into a mixer (1) according to a proportion, stirring and pre-dispersing to form a premix; s2, preparation of supercritical CO 2 synergistic fluid: Pressurizing CO 2 to a supercritical state through a supercritical fluid preparation unit, introducing silane coupling agent steam into the supercritical fluid preparation unit, and stirring to form uniform supercritical CO 2 synergistic fluid; S3, plasticizing and co-injecting the melt: The pre-mixed material is fed into a charging barrel of an extruder (2) and is heated, plasticized and melted by partition to form a melt, and supercritical CO 2 synergistic fluid and a dispersing auxiliary agent are synchronously injected into the melt through an integrally equipped double-channel precise injection unit to form a mixed melt; S4, gradient control extrusion molding: after mixing, the melt flows through a gradient anti-foaming forming unit (3) to output an extrusion blank, and the pressure and the temperature of an outlet of the gradient anti-foaming forming unit (3) are monitored and controlled in real time through a pressure-temperature linkage control ring; s5, post-treatment and rolling: The extruded blank is sequentially sent into an ultrasonic auxiliary cooling water tank (5) and an on-line ultraviolet pretreatment device (6), and finally is pulled and rolled.
  2. 2. The extrusion process of the low-smoke halogen-free cable insulation layer according to claim 1, wherein the mass ratio of the polyolefin base material, the halogen-free flame retardant, the modified micro-nano hydrotalcite and the antioxidant in the S1 is 100:60-90:1-5:0.3-0.8.
  3. 3. The extrusion process of the low-smoke halogen-free cable insulation layer according to claim 1, wherein the preparation steps of the modified micro-nano hydrotalcite in the step S1 are as follows: Vacuum drying micro-nano hydrotalcite for 4-6h at 100-120 ℃, then placing the micro-nano hydrotalcite in a mixer (1), preheating to 90-110 ℃, adding silane coupling agent hydrolysate which is dissolved in ethanol-water solution and catalyzed to pH=4-5 by acetic acid in a spraying mode, continuously stirring and reacting for 20-40h, and finally drying and sieving to obtain the modified micro-nano hydrotalcite.
  4. 4. The extrusion process of the low-smoke halogen-free cable insulation layer according to claim 1, wherein the mass fraction of the silane coupling agent steam in the S2 is 0.5% -2%.
  5. 5. The extrusion process of a low smoke zero halogen cable insulation layer according to claim 1, wherein the temperature of each zone when heating in the step S3 is set as follows: One zone 110-130 ℃, two zones 130-150 ℃, three zones 150-170 ℃, four zones 160-180 ℃.
  6. 6. The extrusion process of the low-smoke halogen-free cable insulation layer according to claim 1, wherein in the step S3, the mass of supercritical CO 2 collaborative fluid injected into a melt accounts for 1.5% -6% of the mass of the melt, the dispersing aid is polyethylene glycol modified polyolefin wax, the addition amount is 0.1% -0.2% of the mass of the melt, two injection channels of the double-channel precise injection unit are distributed in a 45-60-DEG staggered mode, and a diversion mixing cavity of a spiral diversion structure is arranged in the double-channel precise injection unit.
  7. 7. The extrusion process for the insulation layer of the low-smoke halogen-free cable according to claim 1, wherein the temperature of the gradient anti-foaming molding unit (3) in the step S4 is set as follows: The temperatures of the inlet, the middle section and the outlet of the gradient anti-foaming molding unit (3) are respectively set to be 155-175 ℃, 145-165 ℃ and 135-155 ℃.
  8. 8. The extrusion process of the insulating layer of the low-smoke halogen-free cable according to claim 1, wherein the step of monitoring and controlling the outlet pressure and the temperature in real time in the step S4 is as follows: And monitoring the outlet pressure P in real time, comparing the outlet pressure P with the set pressure Ps and the pressure deviation threshold value delta P, and synchronously increasing the temperature of the outlet area and reducing the mechanical clearance when the P is smaller than Ps-delta P, wherein the temperature increase range is 2-5 ℃ each time until the outlet pressure P returns to the set pressure range, and the mechanical clearance reduction range is 0.01-0.03mm each time so as to inhibit the supercritical CO 2 synergistic fluid from vaporizing and foaming in advance.
  9. 9. The extrusion process of the low-smoke halogen-free cable insulation layer according to claim 1, wherein parameters of the ultrasonic auxiliary cooling water tank (5) in the step S5 are set to be 20-30 ℃ of cooling water temperature and 50-100W of ultrasonic power.
  10. 10. The extrusion process of the low-smoke halogen-free cable insulation layer according to claim 1, wherein the parameters of the online ultraviolet pretreatment device (6) in the step S5 are set to be ultraviolet intensity of 20-30mW/cm 2 and treatment time of 30-60S.

Description

Extrusion process for low-smoke halogen-free cable insulating layer Technical Field The invention relates to the technical field of cable manufacture, in particular to a low-smoke halogen-free cable insulating layer extrusion process. Background The low-smoke halogen-free cable has become a core choice in the fields of safety and environmental protection of buildings, rail transit, ships and the like due to the characteristics of low smoke and halogen-free toxic gas release during combustion. At present, an insulating layer of the high-filling polymer system mainly comprises a polyolefin substrate and a halogen-free flame retardant, but the high filling amount leads to rapid rise of melt viscosity, poor fluidity, causes processing defects of rough extrusion surface, insufficient dimensional accuracy, internal air holes and the like, and simultaneously the mechanical strength and ageing resistance of the material are easily affected. The traditional solutions focus on process parameter adjustment or adding traditional plasticizers, wherein the former is difficult to fundamentally reduce the melt viscosity and the high-temperature processing is easy to cause material thermal ageing, and the latter has migration risk and damages the electrical and mechanical properties of the product for a long time. Although supercritical CO 2 is tried to be used for polymer viscosity adjustment, single viscosity reduction effect can be realized only by single application, the problem of agglomeration of nano particles in high-viscosity melt cannot be solved, and the technical bottlenecks such as foaming of an outlet of a gradient anti-foaming molding unit, limited product performance improvement and the like are caused due to lack of targeted process collaborative design, so that the dual requirements of industry on processing efficiency and product quality are difficult to meet. Therefore, a process method for effectively reducing melt viscosity and improving extrusion quality without affecting the comprehensive performance of the material is needed. Disclosure of Invention The invention aims to solve the defects in the prior art, and provides a low-smoke halogen-free cable insulating layer extrusion process. In order to achieve the above purpose, the present invention adopts the following technical scheme: The extrusion process of the low-smoke halogen-free cable insulating layer is executed by an integrated equipment system, the system comprises a mixer, a supercritical fluid preparation unit, an extruder, a gradient anti-foaming forming unit, an ultrasonic-ultraviolet post-treatment unit, a winding machine and an intelligent control unit, the output ends of the mixer and the supercritical fluid preparation unit are communicated with the extruder through a double-channel precise injection unit, the ultrasonic-ultraviolet post-treatment unit comprises an ultrasonic auxiliary cooling water tank and an online ultraviolet pretreatment device, and the process comprises the following steps: S1, preparation of premix: Adding a polyolefin substrate, a halogen-free flame retardant, modified micro-nano hydrotalcite and an antioxidant into a mixer according to a proportion, stirring and pre-dispersing to form a premix; s2, preparation of supercritical CO 2 synergistic fluid: Pressurizing CO 2 to a supercritical state through a supercritical fluid preparation unit, introducing silane coupling agent steam into the supercritical fluid preparation unit, and stirring to form uniform supercritical CO 2 synergistic fluid; S3, plasticizing and co-injecting the melt: The method comprises the steps of feeding premix into an extruder charging barrel, carrying out zonal heating, plasticizing and melting to form a melt, and synchronously injecting supercritical CO 2 synergistic fluid and a dispersing auxiliary into the melt through an integrally equipped double-channel precise injection unit to form a mixed melt; S4, gradient control extrusion molding: after mixing, the melt flows through a gradient anti-foaming forming unit to output an extrusion blank, and the outlet pressure and temperature are monitored and regulated in real time through a pressure-temperature linkage control ring at the outlet of the gradient anti-foaming forming unit; s5, post-treatment and rolling: the extruded blank is sequentially sent into an ultrasonic auxiliary cooling water tank and an on-line ultraviolet pretreatment device, and finally is pulled and rolled. Preferably, the mass ratio of the polyolefin base material, the halogen-free flame retardant, the modified micro-nano hydrotalcite and the antioxidant in the S1 is 100:60-90:1-5:0.3-0.8. Preferably, the preparation steps of the modified micro-nano hydrotalcite in the step S1 are as follows: Vacuum drying micro-nano hydrotalcite at 100-120 ℃ for 4-6 hours, then placing the micro-nano hydrotalcite in a mixer, preheating to 90-110 ℃, adding silane coupling agent hydrolysate which is dissolved in ethanol-water solu