Zero-dripping flame-retardant flexible cable and preparation method therefor

Abstract

The present invention relates to a zero-dripping flame-retardant flexible cable and a preparation method therefor. A zero-dripping flame-retardant sheath material in the zero-dripping flame-retardant flexible cable comprises the following components in percentages by weight: 10-30% of EVA, 1-10% of POE, 1-10% of LLDPE, 1-10% of HDPE, 1-10% of a compatilizer, 0.1-0.5% of an antioxidant, 20-50% of an inorganic flame retardant, 0.2-1% of carbon black, 0.5-1% of silicone, 0.15-0.5% of EBS, 0.01-0.6% of TAIC, 0.01-0.6% of silicone oil, and 1-5% of a char-forming agent. The inorganic flame retardant comprises 10-40% of magnesium hydroxide and 10-40% of aluminum hydroxide, ethylene-methacrylic acid is selected as the compatilizer, a hindered phenol antioxidant is selected as the antioxidant, and sepiolite is selected as the char-forming agent. A flame-retardant sheath prepared from the zero-dripping flame-retardant sheath material designed in the present application has excellent mechanical properties and flame-retardant properties, good flame-retardant effect, high strength of a carbon shell after combustion, and no dripping phenomenon.

Description

Zero-dripping flame-retardant flexible cable and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of cables, in particular to a zero-dripping flame-retardant flexible cable and a preparation method thereof. BACKGROUND

[0002] Flame-retardant cables refer to cables whose flame spreads only within a limited range after the fire source is removed, and the residual flame or residual burning self-extinguishes within a limited time. Due to the great difference in the flame retardancy of low-smoke halogen-free polyolefin materials with different properties, there are great differences in the smoke toxicity, dripping, heat release and other performances of the cables. Internationally, the European Union EN 13501-6 "Fire classification of construction products and building - Part 6: Classification of cable protection test data" standard classifies the flame-retardant performance of cables into seven grades of Aca, B1ca, B2ca, Cca, Dca, Eca and Fca according to multiple index data such as the burning heat value, flame spread, peak heat release rate and burning growth rate index. In addition, on this basis, additional performance grade recognition is also made according to three indexes of burning dripping / particulate matter (d), smoke generation grade (s) and corrosiveness (a) in the burning test. The domestic GB 31247 "Classification of cable and optical cable burning performance" also classifies the flame-retardant performance of cables into four grades of A, B1, B2 and B3 according to multiple index data such as the burning heat value, flame spread, peak heat release rate and smoke generation rate index. In addition, on this basis, additional performance grade recognition is also made according to three indexes of burning dripping / particulate matter (d), smoke toxicity grade (t) and corrosiveness (a) in the burning test. Therefore, the research and development of zero-dripping B1-grade high-flame-retardant flexible cable for communication power supply has the significance of meeting the current international expectations for flame-retardant cables.

[0003] The prior art all adopts high-flame-retardant sheath material to reduce the combustible content of the material, thereby reducing the total heat release amount, total smoke release amount and other indexes of the cable. However, such a formula can only ensure that the heat release performance of the cable does not exceed the standard, but cannot guarantee that the sheath or other structures do not fall off during burning, so the burning falling objects of the cable may ignite other objects during a fire, causing the fire to expand. SUMMARY

[0004] To solve the problems of the prior art, the present application provides a flame-retardant sheath material which has good flame-retardant effect and does not fall off during burning.

[0005] In a first aspect, the present application provides a zero-dripping flame-retardant sheath material, which comprises the following components in terms of weight percentage:

[0006] The inorganic flame retardant includes aluminum hydroxide and magnesium hydroxide, the magnesium hydroxide accounts for 10% to 40% of the total formula content by weight, the aluminum hydroxide accounts for 10% to 40% of the total formula content, the compatilizer is selected from ethylene-methacrylic acid, the antioxidant is selected from hindered phenol type antioxidant, and the charring agent is selected from meerschaum.

[0007] Further specifically, the silicone adopts solid silicone particles.

[0008] Further specifically, the content of the charring agent is 2% to 4.5%.

[0009] Further specifically, the content of the magnesium hydroxide is 15% to 25%, and the content of the aluminum hydroxide is 15% to 25%.

[0010] In a second aspect, the application provides a preparation method of the zero-dripping flame-retardant sheath material, including the following steps:

[0011] S1, EVA, POE, LLDPE, HDPE, compatilizer, antioxidant, inorganic flame retardant, carbon black, silicone, EBS, TAIC, silicone oil and charring agent are added into a stirrer in mass percentage to be fully mixed and uniform, to obtain a sheath material mixture;

[0012] S2, the sheath material mixture is sequentially subjected to a mixing process, a plasticizing process and an extrusion granulation process, to finally obtain the zero-dripping flame-retardant sheath material.

[0013] Further specifically, in the extrusion granulation process, the sheath material mixture sequentially passes through four temperature zones with increasing temperature in the extruder, which are: a first zone 90℃, a second zone 110℃, a third zone 125℃ and a fourth zone 140℃.

[0014] In a third aspect, the application provides a zero-dripping flame-retardant flexible cable, the outermost layer of the cable is a flame-retardant sheath prepared from the zero-dripping flame-retardant sheath material.

[0015] Further specifically, the cable sequentially includes a cable conductor, an insulation layer wrapped outside the conductor, a cable wrapping and the flame-retardant sheath from inside to outside, and the insulation layer and the cable wrapping also have a flame-retardant filling material therebetween.

[0016] Further specifically, the flame-retardant filling material is a flame-retardant mineral material, and the flame-retardant mineral material is selected from at least one of basalt, magnesium oxide, aluminum oxide and silicon dioxide.

[0017] In a fourth aspect, the application provides a preparation method of a zero-dripping flame-retardant flexible cable, including the following steps:

[0018] T1, adopt the wire drawing machine to draw the conductor wire into the conductor monofilament with the diameter of 0.15mm~0.39mm, then adopt the annealing furnace to carry out annealing treatment to the conductor monofilament into the conductor monofilament with the breaking elongation of greater than or equal to 15%, after treatment, the conductor monofilament is stranded into a strand to obtain the cable conductor;

[0019] T2, adopt the extruder to uniformly extrude the insulating material on the outer surface of the stranded cable conductor;

[0020] T3, adopt the cabling and wire winding die to fill the flame-retardant filling material outside the cable conductor, and wind the cable winding on the outermost layer;

[0021] T4, adopt the extruder to extrude and melt the zero-dripping flame-retardant sheath material, then after shaping through the extrusion die, adopt the extrusion process to extrude and cover outside the cable winding to form the zero-dripping flame-retardant flexible cable.

[0022] The beneficial effects of the present application are:

[0023] 1, the cable inside the application is designed to adopt the soft conductor and the soft sheath of the multi-stranded stranding, increase the softness of the whole cable, can make the cable laying in a more narrow place. The mechanical properties of the traditional flame-retardant sheath are greatly reduced due to the addition of flame retardant, and the traditional flame-retardant sheath is more prone to cracking, and the component ratio in the present application is optimized and adjusted, so that the sheath has excellent flame-retardant performance and good softness.

[0024] 2, the application adopts the high-crust polyolefin sheath material, and the flame-retardant sheath made of the material does not fall off when the open flame power is less than 22kW, avoids the problem that the burning cable further ignites other objects, and can more effectively prevent the fire from expanding. Through formula design, the strength of the carbon shell formed after the fire is also improved, the carbon shell can resist slight vibration and wind below 6m / s, avoid the problem that the carbon shell after burning is broken or falls off under slight influence, and avoid the problem that the high-temperature carbon shell continues to ignite other objects.

[0025] 3, all materials in the cable designed in the application do not contain toxic substances such as arsenic or bromine compounds, which improves the safety of the cable to people and the environment; BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 is a structure schematic diagram of the zero-dripping flame-retardant flexible cable in the application.

[0027] In the figure: 1, cable conductor; 2, insulating layer; 3, flame-retardant filling material; 4, cable winding; 5, flame-retardant sheath. DETAILED DESCRIPTION

[0028] For the purposes of making the present application clear, the technical solutions and advantages are described below. The specific embodiments of the present application are described clearly and completely, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0029] In the formula designed in the present application, the main resin of the sheath material is composed of ethylene-vinyl acetate copolymer EVA, polyolefin elastomer POE, linear low density polyethylene LLDPE and high density polyethylene HDPE. In the main resin, with the help of the compatibilizer ethylene-methacrylic acid and the antioxidant hindered phenolic antioxidant BHA, the stable mixed inorganic flame retardant material aluminum hydroxide and magnesium hydroxide in the resin is enhanced, the overall flame retardant and smoke suppression performance of the resin sheath material is enhanced, and through the adjustment of the appropriate mass percentage, the overall mechanical strength and low temperature resistance of the material are maintained. The added carbon black and carbonizing agent sepiolite further improve the flame retardancy of the product, reduce the heat release rate, total heat release and smoke production rate, so that the flame retardant sheath meets high standards in all aspects. The cable designed in the present application meets the national B1 level flame retardant requirement, and has good mechanical properties, flame retardant properties and processing performance. The formula also adds lubricant ethylene bis-stearamide EBS, vulcanizing agent / crosslinking agent triallyl isocyanurate TAIC and silicone oil.

[0030] Among them, the added carbonizing agent sepiolite is a naturally occurring hydrous magnesium silicate mineral, which belongs to a kind of clay mineral. It has a unique tubular structure, which is formed by the alternation of silicon-oxygen tetrahedron and magnesium-oxygen octahedron layer, and the chemical formula of sepiolite is: [(Mg, Al) 5Si8O 20 (OH)2(OH2)·4H2O]. When the cable burns, sepiolite itself plays a role as a framework, and can promote the carbonization of polymer resin, and form a dense carbon layer shell after burning. The carbon layer shell has a certain strength, which can ensure that the sheath does not drip after burning, and can effectively slow down or inhibit the expansion of burning. And the carbonized layer can cut off the overflow of flammable gas, inhibit the further heating of the polymer resin, hinder the flammable gas produced by the thermal decomposition of the polymer, thereby further improving the overall flame retardant effect.

[0031] The silicone added in the formula refers to an organosilicon compound containing a silicon-oxygen bond (Si-O), and the silicone added in the present application is a solid silicone particle. In the flame-retardant sheath material formula, the silicone can improve the wear resistance of the polymer, prolong the service life of the product; can improve the flexibility and elasticity of the polymer, so that it can also maintain good performance at low temperature; can improve the thermal stability of the polymer, so that it can also maintain performance at high temperature; can improve the surface performance of the polymer, such as improving the surface smoothness and anti-sticking of the formed sheath, reducing friction; can also improve the ultraviolet resistance of the polymer, prolonging its service life in outdoor environment.

[0032] The silicone oil added in the formula is a kind of linear polysiloxane with low molecular weight, usually colorless or light yellow transparent liquid, with excellent thermal stability and chemical stability, and good electrical insulation. In the flame-retardant sheath material formula, the silicone oil can be used as a lubricant for the polymer, reducing the friction between the polymer and other materials, improving its sliding property; can improve the flexibility of the polymer, so that it can also maintain good performance at low temperature; can improve the thermal stability of the polymer, so that it can also maintain performance at high temperature; can be used as a release agent for the polymer, reducing the adhesion of the polymer to the mold during molding, improving the production efficiency; when the polymer is blended with other materials, the silicone oil can be used as a compatibilizer to further improve the compatibility of the polymer with other materials. It can be used as a defoaming agent for the polymer to reduce the generation of bubbles and improve the quality of the product. It can be used as a softener for the polymer to improve the softness and hand feeling of the polymer.

[0033] In some specific embodiments, the EVA adopts a commercial model 7875S, the POE adopts a commercial model 5054D, the LLDPE adopts a commercial model 3210FB, the HDPE adopts a commercial model 3461, and the carbon black adopts a commercial model XP-983.

[0034] The present application provides a preparation method of a flame-retardant sheath material:

[0035] S1, according to the mass percentage, EVA, POE, LLDPE, HDPE, compatibilizer, antioxidant, inorganic flame retardant, carbon black, silicone, EBS, TAIC, silicone oil, and carbon forming agent are added into a stirrer, mixed thoroughly and uniformly to form a mixture.

[0036] S2, the mixture obtained in step S1 is sequentially subjected to a mixing process, a plasticizing process and an extrusion granulation process to obtain a flame-retardant sheath material. Preferably, a low compression ratio screw extruder with an L / D ratio not less than 20 and a compression ratio of 1:1.2 is used for extrusion granulation, and the extrusion temperatures of each section in the extruder are as follows: zone 1 90℃, zone 2 110℃, zone 3 125℃, zone 4 140℃, head 145℃ and die 145℃.

[0037] The following specific examples and their respective performance test results are listed in the above-mentioned method

[0038] Example 1:

[0039] EVA 28%, POE 5%, LLDPE 12%, HDPE 3%, compatibilizer 2%, antioxidant 0.1%, aluminum hydroxide 20%, magnesium hydroxide 22%, carbon black XP-983 0.5%, silicone 1%, EBS 0.8%, TAIC 0.2%, silicone oil 15 71%, char-forming agent 4.4%.

[0040] Example 2:

[0041] EVA 30%, POE 3%, LLDPE 10%, HDPE 10%, compatibilizer 2%, antioxidant 0.1%, aluminum hydroxide 20%, magnesium hydroxide 20%, carbon black XP-983 0.8%, silicone 1%, EBS 0.5%, TAIC 0.3%, silicone oil 15 70.3%, char-forming agent 2.0%.

[0042] Comparative Example 1:

[0043] EVA 35%, POE 7%, LLDPE 10%, HDPE 5%, compatibilizer 2%, antioxidant 0.1%, aluminum hydroxide 15%, magnesium hydroxide 20%, carbon black XP-983 0.8%, silicone 1%, EBS 0.5%, TAIC 0.6%, silicone oil 15 70.6%, char-forming agent 2.4%.

[0044] The sheath material components of Examples 1, 2 and Comparative Example 1 were respectively prepared into flame-retardant sheaths according to the above-mentioned method, and were respectively subjected to elongation at break test, tensile strength test and residual carbon shell strength test after burning, and the performance test results are shown in the following table:

[0045] From the above performance test results, it can be seen that in Examples 1 and 2, the flame-retardant sheaths prepared according to the formula designed in the present application have excellent elongation at break and relatively high tensile strength, are relatively soft, have good toughness, and can adapt to external environment. The main components of the residual carbon shell after burning of the flame-retardant sheaths are the shell formed by the inorganic flame-retardant materials magnesium hydroxide, aluminum hydroxide and the char-forming agent sepiolite, and the residual carbon shell strength in Examples 1 and 2 is high and is not easy to be blown off by natural wind, while in Comparative Example 1, the content of resin EVA as the main burning material is relatively high, resulting in a larger proportion of combustible components in the outer sheath, and the carbon shell after burning is unstable, the carbon shell strength is low and is easy to break, and more dripping phenomenon occurs during the burning process.

[0046] The application provides a zero-dripping flame-retardant flexible cable, which comprises a cable conductor, an insulating layer wrapped outside the conductor, a cable wrapping and a flame-retardant sheath from inside to outside, and further comprises a flame-retardant filling material between the insulating layer and the cable wrapping. The flame-retardant filling material is a flame-retardant mineral material selected from at least one of basalt, magnesium oxide, aluminum oxide and silicon dioxide.

[0047] The application provides a preparation method of the zero-dripping flame-retardant flexible cable, which comprises the following steps.

[0048] T1, a Ф1.2 mm copper rod conductor wire is gradually stretched into a conductor monofilament with a diameter of 0.15 mm to 0.39 mm by using a wire drawing machine. Then the conductor monofilament is annealed by using a high-temperature annealing furnace at 580 ℃ to 600 ℃. In the annealing process, the crystal lattices broken by wire drawing in the conductor monofilament can be re-aggregated and arranged. After the annealing treatment, the breaking elongation of the conductor monofilament is greater than or equal to 15%. After the treatment, the conductor monofilament is stranded into a strand according to the mode of (1+6+12+18) to obtain a cable conductor. The stranding process can ensure that the stranded conductor has good softness, large bendability, stable structure when the core is bent, and will not cause plastic deformation of the conductor, greatly improves the softness and stability of the core, facilitates the processing, manufacturing and installation of the wire and cable, and can also avoid the problem of monofilament breakage and insulation layer puncture when the cable is bent at a small angle.

[0049] T2, low-smoke halogen-free polyolefin insulating material is uniformly extruded on the outer surface of the stranded cable conductor by using an extruder, wherein the oxygen index of the low-smoke halogen-free polyolefin is greater than or equal to 30%.

[0050] T3, a cable-forming and wire-forming die is used to fill the flame-retardant filling material outside the cable conductor, and a cable wrapping is wrapped on the outermost layer. The wrapping uses a silica gel mica composite tape, which is composed of 0.08 mm thick mica, 0.02 mm thick silica gel layer and 50 MPa glass fiber base cloth. During the wrapping, the mica is in the outermost layer, because the mica layer is dense and can completely resist the invasion of fire, which can further protect the internal wires. The silica gel layer is in the middle, and the silica gel can form a tubular protective shell after being heated, which can play a role in temperature isolation and ensure that the internal temperature of the cable core is much lower than the external temperature. The glass fiber base cloth is in the innermost layer, because the glass fiber cloth has high strength and can prevent the deformation of the cable core caused by the expansion of the internal material after being heated, that is, the sheath can be prevented from being damaged by the internal stress after the shell is formed.

[0051] T4, a zero-dripping flame-retardant sheath material is extruded and melted by using an extruder, and then is shaped by an extrusion die and is extruded on the outer surface of the cable wrapping by using an extrusion process. The extrusion process can expel the air between the cable core and the sheath, so that the sheath material is more tightly wrapped outside the cable core, forming a zero-dripping flame-retardant flexible cable.

[0052] The zero-dripping flame-retardant flexible cable prepared by the above method is subjected to a combustion test, and the outer sheath can form a carbon shell after the cable encounters a flame with a power of 22 kW or less and high temperature, the carbon shell does not powder, does not break and does not fall off when the wind speed is less than or equal to 6 m / s, the carbon shell strength is greater than or equal to 4 MPa, the cable can resist the wind or heat wave with slight vibration, ensure that the carbon shell has a certain stress resistance under the condition of continuous flame, and effectively prevent the combustion range from expanding. The flame-retardant sheath of the outermost layer of the cable has an elongation at break greater than or equal to 180%, a tensile strength greater than or equal to 10.5 MPa, the material has good softness, the overall softness of the cable can be improved, the minimum bending radius of the cable is greater than or equal to 8 times the outer diameter of the cable, and the cable can be applied to various laying environments.

[0053] The embodiments of the present application are described in detail above, but the present application is not limited to the described embodiments. For those skilled in the art, various changes, modifications, replacements and variations of the embodiments can be made without departing from the principles and spirits of the present application, and still fall within the protection scope of the present application.

Claims

1. A zero-drip, flame-retardant jacketing compound characterized in that, comprising the following components in percent by weight: The inorganic flame retardant comprises aluminum hydroxide and magnesium hydroxide, the magnesium hydroxide accounts for 10-40% of the total formula content by weight, the aluminum hydroxide accounts for 10-40% of the total formula content by weight, the compatilizer is ethylene-methacrylic acid, the antioxidant is a hindered phenol antioxidant, and the charring agent is sepiolite.

2. The zero-drip, flame-retardant jacketing compound of claim 1, wherein, The silicone is a solid silicone particle.

3. The zero-drip, flame-retardant jacketing compound of claim 1, wherein, The content of the charring agent is 2-4.5%.

4. The zero-drip, flame-retardant jacketing compound of claim 1, wherein, The content of the magnesium hydroxide is 15-25%, and the content of the aluminum hydroxide is 15-25%.

5. A process for the preparation of a zero-dripping flame-retardant jacketing compound according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1, adding EVA, POE, LLDPE, HDPE, a compatilizer, an antioxidant, an inorganic flame retardant, carbon black, silicone, EBS, TAIC, silicone oil and a charring agent into a stirrer in a mass percentage to mix them evenly to obtain a sheath material mixture; S2, sequentially performing a mixing process, a plasticizing process and an extrusion granulation process on the sheath material mixture to finally obtain the zero-dripping flame-retardant sheath material.

6. The production method according to claim 5, wherein In the extrusion granulation process, the sheath material mixture sequentially passes through four temperature zones with increasing temperature in the extruder, which are: a first zone of 90°C, a second zone of 110°C, a third zone of 125°C and a fourth zone of 140°C.

7. A zero-drip, flame-retardant flexible cable, characterized in that, The outermost layer of the cable is a flame-retardant sheath prepared from the zero-dripping flame-retardant sheath material according to any one of claims 1-4.

8. The zero-drip, flame-retardant flexible cable of claim 7, wherein, The cable comprises, from inside to outside, a cable conductor, an insulation layer wrapped outside the cable conductor, a cable wrapping and the flame-retardant sheath, and the insulation layer and the cable wrapping are further provided with a flame-retardant filling material.

9. The zero-drip, flame-retardant flexible cable of claim 8, wherein, The flame-retardant filling material is a flame-retardant mineral material selected from at least one of basalt, magnesium oxide, aluminum oxide and silicon dioxide.

10. A process for the preparation of a zero-dripping, flame-retardant flexible cable according to any one of claims 7 to 9, characterized in that, The method comprises the following steps: T1, stretching a conductor wire into a conductor monofilament with a diameter of 0.15-0.39 mm by using a wire drawing machine, and then annealing the conductor monofilament in an annealing furnace to obtain a conductor monofilament with a breaking elongation of ≥15%, and then twisting the conductor monofilament into a strand to obtain a cable conductor; T2, uniformly extruding an insulation material on the outer surface of the stranded cable conductor by using an extruder; T3, filling a flame-retardant filling material around the cable conductor by using a cable forming and twisting die, and wrapping a cable wrapping on the outermost layer; T4, extruding and melting the zero-dripping flame-retardant sheath material by using an extruder, and then shaping the material by using an extrusion die, and then extruding the material around the cable wrapping by using an extrusion process to form a zero-dripping flame-retardant flexible cable.

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