Flexible fireproof cable and preparation method of thermal insulation layer thereof

Abstract

The invention discloses a flexible fireproof cable and a preparation method of a thermal insulation layer thereof, and relates to the technical field of fireproof cables, and the flexible fireproof cable comprises a conductor, an insulating layer, a filling layer, a wrapping layer and a thermal insulation layer which are sequentially arranged from inside to outside; a closed cavity is pre-formed in the heat insulation layer, and the cavity is filled with a thermal expansion foaming material; when the cable is on fire, the thermal expansion foaming material is heated to expand and open the closed cavity, and a porous heat insulation foaming layer is formed on the outer side of the cable. According to the flexible fireproof cable and the preparation method of the thermal insulation layer thereof, when the cable is on fire, the foaming material rapidly expands to form a complete porous thermal insulation foaming layer on the outer side of the cable. The foaming layer is low in heat conductivity coefficient, can effectively prevent flame and heat from being transmitted to the interior of the cable, delays aging damage of the conductor and the insulating layer, ensures that the cable continuously works for a certain time in a fire disaster environment, and provides guarantee for emergency rescue and personnel evacuation. Meanwhile, the heat insulation layer can be integrally formed, multi-step machining is not needed, and the production efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of fire-resistant cable technology, specifically to a flexible fire-resistant cable and a method for preparing its insulation layer. Background Technology

[0002] Fire-resistant cables are the lifeline for ensuring the continuous operation of emergency power supply and control systems in critical fields such as modern buildings, rail transportation, and energy and power during fires. Their core performance requirement is to maintain circuit integrity for a specified time under open flame or high-temperature environments, providing valuable power support for personnel evacuation, fire rescue, and emergency braking of critical equipment.

[0003] Currently, the mainstream flexible fire-resistant cables on the market mainly utilize passive protection technology with mica tape wrapping: this is the most widely used solution. It involves wrapping multiple layers of synthetic mica tape around the conductor or insulation layer, using the mica sheets to sinter into a hard, ceramic-like shell at high temperatures to achieve heat insulation and electrical insulation. However, its complex multi-layer wrapping process leads to a lengthy, inefficient, and costly production process. Secondly, the large amount of rigid inorganic material wrapped around the cable severely affects its inherent flexibility, making laying and installation difficult. Furthermore, after long-term bending and vibration, the mica sheets are prone to detachment, leading to a risk of reduced fire resistance or even failure.

[0004] Therefore, it is necessary to propose a method for preparing flexible fire-resistant cables and their insulation layers to solve the above problems. Summary of the Invention

[0005] (a) Technical problems to be solved The purpose of this invention is to provide a method for preparing a flexible fireproof cable and its insulation layer, so as to solve the problems mentioned in the background art.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a flexible fireproof cable, comprising a conductor, an insulation layer, a filling layer, a wrapping layer, and a heat insulation layer arranged sequentially from the inside to the outside; the heat insulation layer has a pre-set closed cavity, which is filled with a heat-expanding foam material; when exposed to fire, the heat-expanding foam material expands and breaks through the closed cavity, forming a porous heat-insulating foam layer on the outside of the cable.

[0007] Preferably, the cavity extends along the cable axis, and one side of the cavity is provided with axially distributed guide grooves to guide the rupture from that point when heated.

[0008] Preferably, the heat-expanding foaming material includes thermally expanding microspheres, a charring agent, and an acid source.

[0009] Preferably, the material of the insulation layer is polyvinyl chloride, polyethylene, polyurethane, or thermoplastic elastomer.

[0010] The method for preparing the heat insulation layer of the above-mentioned flexible fire-resistant cable includes the following steps: S1: Prepare sheathing material and heat-expanding foaming material; S2: After melting the sheath material, it is extruded through a mold to form an axially extending cavity inside the sheath; S3: After the cavity is formed, the heated expansion foam material is directly injected into the cavity; S4: Then it is extruded through the mold outlet and cooled and shaped to form a heat insulation layer with foam material inside.

[0011] Preferably, the heat-expanding foaming material is in powder or paste form.

[0012] Preferably, the mold includes a core mold for forming a cavity, the core mold having an injection channel in the middle and a protrusion for forming a guide groove on one side of the core mold.

[0013] (III) Beneficial Effects Compared with the prior art, the present invention provides a method for preparing a flexible fire-resistant cable and its heat insulation layer, which has the following beneficial effects: 1. The method for preparing the flexible fire-resistant cable and its insulation layer involves pre-setting a closed cavity inside the insulation layer and filling it with a heat-expanding foam material. When exposed to fire, the foam material rapidly expands and breaks through the outer sheath along the weakest point, forming a complete porous insulation foam layer on the outside of the cable. This foam layer has a low thermal conductivity, effectively blocking the transfer of flames and heat into the cable, delaying the aging and damage of the conductor and insulation layer, ensuring the cable can continue to operate for a certain period in a fire environment, and providing protection for emergency rescue and personnel evacuation.

[0014] 2. The preparation method of this flexible fireproof cable and its heat insulation layer adopts an integrated extrusion molding process. While the sheath material is extruded to form a cavity, foaming material is injected. After cooling and shaping, a composite sheath can be formed. No multi-step processing is required, resulting in high production efficiency. Attached Figure Description

[0015] Figure 1 This is a three-dimensional cross-sectional view of the structure of the present invention; Figure 2 This is a cross-sectional schematic diagram of the structure of the present invention.

[0016] In the diagram: 1. Conductor; 2. Insulating layer; 3. Filling layer; 4. Wrapping layer; 5. Heat insulation layer; 6. Cavity; 7. Guide groove. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Please see Figure 1 and 2 As shown, a flexible fire-resistant cable comprises, from the inside out, a conductor 1, an insulation layer 2, a filling layer 3, a wrapping layer 4, and a heat insulation layer 5. The heat insulation layer 5 has a pre-set cavity 6 extending axially along the cable. This cavity 6 is a sealed space filled with a powdered or paste-like heat-expanding foaming material. An axially extending guide groove 7 is designed on the outer wall of the cavity 6 facing the cable. This guide groove 7 is a structural weakness formed by locally thinning the sheath material during the manufacturing process. Its function is to precisely guide and control the rupture location and shape of the heat insulation layer 5 during heat expansion, ensuring that the foaming material can expand outwards in an orderly and concentrated manner, forming a regular fire-resistant layer.

[0019] The preferred thermally expandable foam material is a composite system composed of thermally expandable microspheres, a charring agent, and an acid source. The thermally expandable microspheres, acting as a physical foaming agent, expand tens to hundreds of times their original volume upon heating, forming a foam skeleton. The charring agent (such as pentaerythritol) and the acid source (such as ammonium polyphosphate) undergo a chemical reaction upon heating, catalyzing the formation of a dense char layer that adheres to the skeleton, together forming a fluffy yet robust fire-resistant and heat-insulating barrier.

[0020] The base material of the insulation layer 5 is a common cable sheath material, such as polyvinyl chloride, polyethylene, polyurethane, or thermoplastic elastomer. These materials themselves have good processability, flexibility, and a certain degree of flame retardancy.

[0021] The specific steps of the method for preparing the heat insulation layer of the present invention are as follows: Material preparation: Input the selected sheath material into the main hopper of the extruder. Load the proportioned heat-expanding foaming material into the powder injection unit.

[0022] Melt extrusion and cavity forming: The sheath material is heated and melted in the extruder and pushed to the forming die. The die has multiple hollow cores, the outer contour of which determines the inner diameter and shape of the cavity 6.

[0023] Foam material injection: After cavity 6 is formed, foam material is continuously injected into the newly formed cavity at a constant pressure through the injection channel set inside the core mold. The injection process is strictly synchronized with the extrusion speed to ensure that the cavity is fully and uniformly filled.

[0024] Shaping and Sealing: The tubular preform filled with foamed material continues to move forward and is cooled and shaped in a water-cooling tank, thus obtaining the heat insulation layer 5 with heat-expanding foamed material embedded inside. The core mold has a protrusion at the position corresponding to the guide groove 7. During the extrusion process, the protrusion will form a thinned groove on the inner wall of the sheath at the corresponding position, which becomes the preset guide groove 7 after cooling.

[0025] Thermally expandable microspheres are core-shell structured functional microspheres. Their core material is stable at room temperature and can be controlled to vaporize upon heating. Specifically, the outer shell is a high-strength thermoplastic polymer with excellent gas barrier properties; the core is a hydrocarbon compound with a specific boiling point. When the temperature rises to the shell's softening temperature, the shell's mechanical strength decreases while its flexibility increases. Simultaneously, the material encapsulated in the core vaporizes upon heating, generating internal pressure that drives the shell to expand. The selection of thermally expandable microspheres must ensure that the initial expansion temperature is higher than the extrusion temperature to prevent premature foaming within the extrusion temperature range of the sheath material (150-200℃), initiating expansion only in fire environments (above 200℃). Furthermore, their expansion temperature overlaps with the temperature range of the charring agent and acid source decomposition to form a carbon layer, ensuring their synergistic formation of an effective thermally insulating carbonized foam layer.

[0026] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A flexible fire-resistant cable, characterized in that: It includes a conductor (1), an insulation layer (2), a filling layer (3), a wrapping layer (4), and a heat insulation layer (5) arranged sequentially from the inside to the outside; the heat insulation layer (5) has a pre-set closed cavity (6), which is filled with a heat-expanding foam material; when exposed to fire, the heat-expanding foam material expands and breaks through the closed cavity (6), forming a porous heat insulation foam layer on the outside of the cable.

2. The flexible fire-resistant cable according to claim 1, characterized in that, The cavity (6) extends along the cable axis, and a guide groove (7) is provided on one side of the cavity (6) to guide the cable to break from there when heated.

3. The flexible fire-resistant cable according to claim 1, characterized in that, The heat-expanding foaming material includes thermally expanding microspheres, a charring agent, and an acid source.

4. The flexible fire-resistant cable according to claim 1, characterized in that, The insulation layer (5) is made of polyvinyl chloride, polyethylene, polyurethane or thermoplastic elastomer.

5. A method for preparing the heat insulation layer (5) of a flexible fireproof cable as described in any one of claims 1-4, characterized in that, Includes the following steps: S1: Prepare sheathing material and heat-expanding foaming material; S2: After melting the sheath material, it is extruded through a mold to form an axially extending cavity inside the sheath (6). S3: After the cavity (6) is formed, the heated expansion foam material is directly injected into the cavity (6); S4: Then it is extruded through the mold outlet and cooled and shaped to form a heat insulation layer (5) with foam material inside.

6. The preparation method according to claim 5, characterized in that, The heat-expanding foaming material is in powder or paste form.

7. The preparation method according to claim 5, characterized in that, The mold includes a core mold for forming a cavity (6), the core mold having an injection channel in the middle and a protrusion for forming a guide groove (7) on one side of the core mold.

Images