Fireproof cable

Abstract

The invention relates to the technical field of cables, in particular to a fire-resistant cable which comprises a conductor formed by mutually winding a plurality of copper wire cores, an insulating layer used for wrapping the conductor is arranged on the conductor in the radial direction, and a shielding layer used for wrapping the insulating layer is arranged on the insulating layer in the radial direction. A flame-retardant layer used for wrapping the shielding layer is arranged in the radial direction of the shielding layer, and a sheath layer used for wrapping the flame-retardant layer is arranged in the radial direction of the flame-retardant layer; the insulating layer is made of thermoplastic resin containing magnesium oxide through an extrusion process. According to the fireproof cable provided by the invention, the insulating layer material in the fireproof cable can be produced at relatively low cost on the premise of ensuring the mechanical property and the electrical property which are equivalent to those of magnesium oxide serving as the insulating layer.

Description

Technical Field

[0001] The present invention relates to the technical field of cables, and more particularly to a fire-resistant cable. Background Art

[0002] Fire-resistant cable is a special cable that can maintain normal operation for a certain period of time when a fire occurs. Its structural components mainly include conductor, insulation layer, fire-resistant layer and sheath. The conductor is generally made of metal materials with good conductivity such as copper or aluminum, which is responsible for transmitting current. The insulation layer usually uses high-temperature resistant insulating materials, such as mica tape, ceramic silicone rubber, etc., to ensure the insulation between the conductors and the conductors from the outside world. The fire-resistant layer is the key part of the fire-resistant cable. It is mostly wrapped with fire-resistant mica tape outside the insulation layer, which can play a role of heat insulation and fire isolation at high temperatures, and protect the internal structure of the cable from damage. The sheath is generally made of flame-retardant and high-temperature resistant materials, such as polyvinyl chloride, low-smoke halogen-free flame-retardant polyolefin, etc., which can not only protect the cable from external mechanical damage, but also further improve the fire resistance of the cable. In the event of a fire, the fire-resistant cable can provide reliable power guarantee for personnel evacuation and fire rescue with its special structure.

[0003] Although fire-resistant cables have good fire-proof performance, they also have some shortcomings; (1) Relatively high material costs: Fire-resistant cables usually use special insulation materials, sheath materials, and fire-resistant mica tapes, etc., which are relatively expensive. For example, the magnesium oxide insulation material and copper sheath used in mineral insulated cables cost significantly more than the insulation and sheath materials of ordinary cables. (2) Complex production process: The production process of fire-resistant cables has high requirements and requires special equipment and technology. For example, when producing mineral insulated cables, a precision filling machine is required to fill and compact magnesium oxide, which increases production costs. Summary of the invention

[0004] The object of the present invention is to provide a fire-resistant cable, which is used to solve the technical problems that the existing fire-resistant cables use magnesium oxide as the insulation layer material, resulting in relatively high material costs and relatively complex production processes.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A fire-resistant cable comprises a conductor formed by winding a plurality of copper wire cores with each other, an insulating layer for wrapping the conductor itself is arranged radially on the conductor, a shielding layer for wrapping the insulating layer itself is arranged radially on the insulating layer, a flame retardant layer for wrapping the shielding layer itself is arranged radially on the shielding layer, and a sheath layer for wrapping the flame retardant layer itself is arranged radially on the flame retardant layer; the insulating layer is made of a thermoplastic resin containing magnesium oxide through an extrusion process.

[0007] Preferably, the insulating layer, based on a total mass percentage of 100%, includes 70-80% polyphenylene sulfide, 3-5% toughening agent, 5-10% lubricant, and 10-20% modified boron nitride / magnesium oxide composite filler.

[0008] Preferably, the preparation method of the modified boron nitride / magnesium oxide composite filler comprises the following steps:

[0009] S1: dispersing boron nitride and dopamine hydrochloride in a solvent consisting of tris(hydroxymethylaminomethane) buffer and ethanol, and then stirring at room temperature for 10-12 hours to obtain a polydopamine-modified boron nitride dispersion;

[0010] S2: adding γ-aminopropyltriethoxysilane to the polydopamine-modified boron nitride dispersion, stirring at 60-80° C. for 4-6 hours, filtering, and drying to obtain modified boron nitride;

[0011] S3: dispersing magnesium oxide and γ-glycidyloxypropyltrimethoxysilane in a solvent consisting of methanol and acetone, and then stirring at a stirring rate of 60-80° C. for 6-8 hours, and then filtering and drying to obtain modified magnesium oxide;

[0012] S4: Dispersing the modified boron nitride and modified magnesium oxide in a solvent, stirring at 60-80° C. for 6-8 hours, filtering, and drying to obtain a modified boron nitride / magnesium oxide composite filler.

[0013] Preferably, in step S1, the boron nitride is hexagonal boron nitride, cubic boron nitride or a mixture of the two.

[0014] Preferably, in step S3, the magnesium oxide is one or a mixture of two or more of amorphous magnesium oxide, spherical magnesium oxide, and magnesium oxide whiskers.

[0015] Preferably, in step S4, the mass ratio of modified boron nitride to modified magnesium oxide is 1:(1-4).

[0016] Preferably, the method for preparing the insulating layer comprises the following steps: mixing polyphenylene sulfide, a toughening agent and a lubricant, and kneading them at 280-320°C for 15-20 minutes to obtain a reaction mixture; kneading the modified boron nitride / magnesium oxide composite filler with the reaction mixture at 300-320°C for 5-10 minutes, and granulating after cooling to obtain an insulating material; and extruding the insulating material onto a conductor to form an insulating layer wrapping the conductor.

[0017] Preferably, the shielding layer is made of tinned annealed copper wire braid or aluminum wire braid.

[0018] Preferably, the flame retardant layer is made of polyvinyl chloride.

[0019] The above-mentioned embodiments of the present invention have the following beneficial effects: magnesium oxide and boron nitride are modified to prepare a special boron nitride / magnesium oxide composite filler, and then the prepared filler is mixed with polyphenylene sulfide, a toughening agent, and a lubricant into particles, and an insulating layer wrapped on the conductor is formed through an extrusion process. On the premise of ensuring the mechanical and electrical properties of the insulating layer, on the one hand, the amount of magnesium oxide added as an insulating material is reduced, thereby reducing the cost of the insulating material; on the other hand, magnesium oxide and boron nitride are filled into polyphenylene sulfide resin as thermally conductive insulating seasonings and wrapped on the conductor through an extrusion process, eliminating the filling and compacting processes, thereby reducing the cost of the production process of the fire-resistant cable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic cross-sectional view of the fire-resistant cable in the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. Several embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0022] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0023] Example 1

[0024] This embodiment provides a modified boron nitride / magnesium oxide composite filler, and the preparation steps are as follows:

[0025] S1: Dispersing 10 parts of hexagonal boron nitride and 1 part of dopamine hydrochloride in a solvent consisting of 100 parts of tris(hydroxymethyl)aminomethane buffer and 30 parts of ethanol, and then stirring at 600 rpm for 10 hours at room temperature to obtain a polydopamine-modified boron nitride dispersion;

[0026] S2: adding 1 part of γ-aminopropyltriethoxysilane to the polydopamine-modified boron nitride dispersion, and then stirring at 80° C. and 600 rpm for 5 h, and then filtering under negative pressure, and drying under vacuum at 80° C. for 12 h to obtain modified boron nitride;

[0027] S3: 15 parts of spherical magnesium oxide and 1 part of γ-glycidyloxypropyltrimethoxysilane are dispersed in a solvent consisting of 145 parts of methanol and 5 parts of acetone, and then stirred at 80°C at 600 rpm for 8 hours, and then filtered under negative pressure, and dried at 80°C under vacuum for 12 hours to obtain modified magnesium oxide;

[0028] S4: 15 parts of modified boron nitride and 15 parts of modified magnesium oxide were dispersed in 200 parts of ethanol solvent, and then stirred at 1000 rpm at 80°C for 8 hours, and then filtered under negative pressure, and dried under vacuum at 80°C for 12 hours to obtain a modified boron nitride / magnesium oxide composite filler.

[0029] Example 2

[0030] This embodiment provides a modified boron nitride / magnesium oxide composite filler, and the preparation steps are as follows:

[0031] S1: Dispersing 10 parts of hexagonal boron nitride and 1 part of dopamine hydrochloride in a solvent consisting of 100 parts of tris(hydroxymethyl)aminomethane buffer and 30 parts of ethanol, and then stirring at 600 rpm for 10 hours at room temperature to obtain a polydopamine-modified boron nitride dispersion;

[0032] S2: adding 1 part of γ-aminopropyltriethoxysilane to the polydopamine-modified boron nitride dispersion, and then stirring at 80° C. and 600 rpm for 5 h, and then filtering under negative pressure, and drying under vacuum at 80° C. for 12 h to obtain modified boron nitride;

[0033] S3: 15 parts of spherical magnesium oxide and 1 part of γ-glycidyloxypropyltrimethoxysilane are dispersed in a solvent consisting of 145 parts of methanol and 5 parts of acetone, and then stirred at 80°C at 600 rpm for 8 hours, and then filtered under negative pressure, and dried at 80°C under vacuum for 12 hours to obtain modified magnesium oxide;

[0034] S4: 10 parts of modified boron nitride and 20 parts of modified magnesium oxide were dispersed in 200 parts of ethanol solvent, and then stirred at 1000 rpm at 80°C for 8 hours, and then filtered under negative pressure, and dried under vacuum at 80°C for 12 hours to obtain a modified boron nitride / magnesium oxide composite filler.

[0035] Example 3

[0036] This embodiment provides a modified boron nitride / magnesium oxide composite filler, and the preparation steps are as follows:

[0037] S1: Dispersing 10 parts of hexagonal boron nitride and 1 part of dopamine hydrochloride in a solvent consisting of 100 parts of tris(hydroxymethyl)aminomethane buffer and 30 parts of ethanol, and then stirring at 600 rpm for 10 hours at room temperature to obtain a polydopamine-modified boron nitride dispersion;

[0038] S2: adding 1 part of γ-aminopropyltriethoxysilane to the polydopamine-modified boron nitride dispersion, and then stirring at 80° C. and 600 rpm for 5 h, and then filtering under negative pressure, and drying under vacuum at 80° C. for 12 h to obtain modified boron nitride;

[0039] S3: 15 parts of spherical magnesium oxide and 1 part of γ-glycidyloxypropyltrimethoxysilane are dispersed in a solvent consisting of 145 parts of methanol and 5 parts of acetone, and then stirred at 80°C at 600 rpm for 8 hours, and then filtered under negative pressure, and dried at 80°C under vacuum for 12 hours to obtain modified magnesium oxide;

[0040] S4: 7.5 parts of modified boron nitride and 22.5 parts of modified magnesium oxide were dispersed in 200 parts of ethanol solvent, and then stirred at 1000 rpm at 80°C for 8 hours, and then filtered under negative pressure, and dried under vacuum at 80°C for 12 hours to obtain a modified boron nitride / magnesium oxide composite filler.

[0041] Example 4

[0042] This embodiment provides a modified boron nitride / magnesium oxide composite filler, and the preparation steps are as follows:

[0043] S1: Dispersing 10 parts of hexagonal boron nitride and 1 part of dopamine hydrochloride in a solvent consisting of 100 parts of tris(hydroxymethyl)aminomethane buffer and 30 parts of ethanol, and then stirring at 600 rpm for 10 hours at room temperature to obtain a polydopamine-modified boron nitride dispersion;

[0044] S2: adding 1 part of γ-aminopropyltriethoxysilane to the polydopamine-modified boron nitride dispersion, and then stirring at 80° C. and 600 rpm for 5 h, and then filtering under negative pressure, and drying under vacuum at 80° C. for 12 h to obtain modified boron nitride;

[0045] S3: 15 parts of spherical magnesium oxide and 1 part of γ-glycidyloxypropyltrimethoxysilane are dispersed in a solvent consisting of 145 parts of methanol and 5 parts of acetone, and then stirred at 80°C at 600 rpm for 8 hours, and then filtered under negative pressure, and dried at 80°C under vacuum for 12 hours to obtain modified magnesium oxide;

[0046] S4: 6 parts of modified boron nitride and 24 parts of modified magnesium oxide were dispersed in 200 parts of ethanol solvent, and then stirred at 1000 rpm at 80°C for 8 hours, and then filtered under negative pressure, and dried under vacuum at 80°C for 12 hours to obtain a modified boron nitride / magnesium oxide composite filler.

[0047] Example 5

[0048] The present embodiment provides an insulating layer material, and the preparation steps are as follows: based on the total mass of 100%, 80% of polyphenylene sulfide, 3% of toughening agent, and 5% of lubricant are mixed, and kneaded at 300°C for 20 minutes to obtain a reaction mixture; 12% of the modified boron nitride / magnesium oxide composite filler prepared in Example 1 is mixed with the reaction mixture at 300°C for 10 minutes, and granulated after cooling to obtain an insulating layer material.

[0049] Example 6

[0050] The present embodiment provides an insulating layer material, and the preparation steps are as follows: based on the total mass of 100%, 70% of polyphenylene sulfide, 3% of toughening agent, and 7% of lubricant are mixed, and kneaded at 300°C for 20 minutes to obtain a reaction mixture; 20% of the modified boron nitride / magnesium oxide composite filler prepared in Example 2 is mixed with the reaction mixture at 300°C for 10 minutes, and granulated after cooling to obtain an insulating layer material.

[0051] Example 7

[0052] The present embodiment provides an insulating layer material, and the preparation steps are as follows: based on the total mass of 100%, 75% of polyphenylene sulfide, 5% of toughening agent, and 5% of lubricant are mixed, and kneaded at 300°C for 20 minutes to obtain a reaction mixture; 15% of the modified boron nitride / magnesium oxide composite filler prepared in Example 3 is mixed with the reaction mixture at 300°C for 10 minutes, and granulated after cooling to obtain an insulating layer material.

[0053] Example 8

[0054] The present embodiment provides an insulating layer material, and the preparation steps are as follows: based on the total mass of 100%, 75% of polyphenylene sulfide, 5% of toughening agent, and 10% of lubricant are mixed, and kneaded at 300°C for 20 minutes to obtain a reaction mixture; 10% of the modified boron nitride / magnesium oxide composite filler prepared in Example 4 is mixed with the reaction mixture at 300°C for 10 minutes, and granulated after cooling to obtain an insulating layer material.

[0055] Comparative Example 1

[0056] Spherical magnesium oxide is commercially available as the insulating layer material, and its size is 10-20 μm.

[0057] The mechanical and electrical properties of the insulating layer materials in the above Examples 5-8 and Comparative Example 1 were tested respectively. For mechanical properties, tensile strength and tensile modulus were tested according to the ASTM D638 method, and bending tests were performed according to the ASTM D790 method. For electrical properties, the breakdown strength test was performed according to the GB1408.1-2016 insulation material electrical strength test method. The following data were obtained:

[0058] Table 1 Performance test data of each insulation layer material

[0059]

[0060] It can be seen from Table 1 that the tensile strength, tensile modulus, flexural modulus and breakdown strength of the insulating layer materials prepared in Examples 5-8 of the present invention are all higher than those in Comparative Example 1, and they have better mechanical properties and better insulation properties, and can be used as excellent insulating layer materials in fire-resistant cables.

[0061] Application Examples 1-4

[0062] A fire-resistant cable, such as Figure 1 As shown, it includes a conductor 1 formed by winding a plurality of copper wire cores, an insulating layer 2 for wrapping the conductor 1 itself is arranged radially on the conductor 1, a shielding layer 3 for wrapping the insulating layer 2 itself is arranged radially on the insulating layer 2, a flame retardant layer 4 for wrapping the shielding layer 3 itself is arranged radially on the shielding layer 3, and a sheath layer 5 for wrapping the flame retardant layer 4 itself is arranged radially on the flame retardant layer 4. The insulating layer 2 is formed by extrusion process using the insulating layer materials prepared in Examples 5-8.

[0063] Application Example 5

[0064] A fire-resistant cable, such as Figure 1 As shown, it comprises a conductor 1 formed by winding a plurality of copper wire cores, an insulating layer 2 for wrapping the conductor 1 itself is arranged radially on the conductor 1, a shielding layer 3 for wrapping the insulating layer 2 itself is arranged radially on the insulating layer 2, a flame retardant layer 4 for wrapping the shielding layer 3 itself is arranged radially on the shielding layer 3, and a sheath layer 5 for wrapping the flame retardant layer 4 itself is arranged radially on the flame retardant layer 4. The insulating layer 2 is obtained by filling and compacting the magnesium oxide of Comparative Example 1.

[0065] The shielding layer 3 of the fire-resistant cable in Application Examples 1-5 is made of tinned annealed aluminum wire braid, the flame retardant layer 4 is made of polyvinyl chloride, and the sheath layer 5 is made of fluoroplastic. The conductor 1 has a diameter of 1 cm, the thickness of the insulating layer 2 is 1.0 mm, the thickness of the shielding layer 3 is 0.2 mm, the thickness of the flame retardant layer 4 is 1.0 mm, and the thickness of the sheath layer 5 is 1.5 mm.

[0066] The fire-resistant cables in the above application examples 1-5 were subjected to thermal shock test and linear withstand voltage test according to UL2353 / IEC62368 standard. The following data were obtained:

[0067] Table 2 Performance test data of various fire-resistant cables

[0068]

[0069] As can be seen from Table 2, the maximum continuous use temperature of the fire-resistant cables prepared in Application Examples 1-4 of the present invention can reach 165-174°C, there is no cracking on the surface after thermal shock at 275 degrees / 30 minutes, and there is no breakdown in the voltage test up to 30KV / 60S, which is equivalent to the performance of the fire-resistant cable prepared in Application Example 5.

[0070] The fire-resistant cable provided by the present invention can produce the insulation layer material in the fire-resistant cable at a relatively low cost under the premise of ensuring the mechanical properties and electrical properties equivalent to those of magnesium oxide as the insulation layer.

[0071] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A fire-resistant cable, characterized in that: The invention comprises a conductor formed by winding a plurality of copper wire cores with each other, wherein an insulating layer for wrapping the conductor itself is arranged radially on the conductor, a shielding layer for wrapping the insulating layer itself is arranged radially on the insulating layer, a flame retardant layer for wrapping the shielding layer itself is arranged radially on the shielding layer, and a sheath layer for wrapping the flame retardant layer itself is arranged radially on the flame retardant layer; the insulating layer is made of a thermoplastic resin containing magnesium oxide by an extrusion process.

2. The fire-resistant cable according to claim 1, characterized in that: The insulating layer comprises 70-80% of polyphenylene sulfide, 3-5% of toughening agent, 5-10% of lubricant and 10-20% of modified boron nitride / magnesium oxide composite filler based on the total mass percentage of 100%.

3. The fire-resistant cable according to claim 2, characterized in that: The preparation method of the modified boron nitride / magnesium oxide composite filler comprises the following steps: S1: dispersing boron nitride and dopamine hydrochloride in a solvent consisting of tris(hydroxymethylaminomethane) buffer and ethanol, and then stirring at room temperature for 10-12 hours to obtain a polydopamine-modified boron nitride dispersion; S2: adding γ-aminopropyltriethoxysilane to the polydopamine-modified boron nitride dispersion, stirring at 60-80° C. for 4-6 hours, filtering, and drying to obtain modified boron nitride; S3: dispersing magnesium oxide and γ-glycidyloxypropyltrimethoxysilane in a solvent consisting of methanol and acetone, and then stirring at a stirring rate of 60-80° C. for 6-8 hours, and then filtering and drying to obtain modified magnesium oxide; S4: Dispersing the modified boron nitride and modified magnesium oxide in a solvent, stirring at 60-80° C. for 6-8 hours, filtering, and drying to obtain a modified boron nitride / magnesium oxide composite filler.

4. The fire-resistant cable according to claim 3, characterized in that: In step S1, the boron nitride is hexagonal boron nitride, cubic boron nitride or a mixture of the two.

5. The fire-resistant cable according to claim 3, characterized in that: In step S3, the magnesium oxide is one or a mixture of two or more of amorphous magnesium oxide, spherical magnesium oxide, and magnesium oxide whiskers.

6. The fire-resistant cable according to claim 3, characterized in that: In step S4, the mass ratio of modified boron nitride to modified magnesium oxide is 1:(1-4).

7. The fire-resistant cable according to claim 2, characterized in that: The preparation method of the insulating layer comprises the following steps: mixing polyphenylene sulfide, a toughening agent and a lubricant, and kneading them at 280-320°C for 15-20 minutes to obtain a reaction mixture; kneading a modified boron nitride / magnesium oxide composite filler and the reaction mixture at 300-320°C for 5-10 minutes, and granulating after cooling to obtain an insulating material; and extruding the insulating material on a conductor to form an insulating layer wrapping the conductor.

8. The fire-resistant cable according to claim 1, characterized in that: The shield is made of tinned annealed copper braid or aluminum braid.

9. The fire-resistant cable according to claim 1, characterized in that: The flame retardant layer is made of polyvinyl chloride.

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