B1-grade halogen-free low-smoke flame-retardant special cable and preparation method thereof

Abstract

The present invention proposes a B1-class halogen-free, low-smoke, flame-retardant special cable and its preparation method. The cable comprises: a cable core formed by wrapping a control core and a power core, a flame-retardant filling rope, a wrapping layer, a flame-retardant tape layer, a total shielding layer, a ceramic fireproof layer, and an outer sheath. The present invention uses a cross-linked polyethylene sheath to form an outer layer of protection, a ceramic fireproof layer to form an intermediate shell flame-retardant insulation layer, and a flame-retardant tape layer combined with expandable graphite as an inner layer of buffer insulation, thereby achieving multiple flame-retardant insulation for the cable core, inhibiting the release of burning drips and toxic smoke with corrosion, and meeting and exceeding the B1-class flame-retardant requirements. By using low-smoke, halogen-free materials, the release of toxic gases can be reduced during combustion. At the same time, a double-layer hardness flame-retardant filling rope is twisted in the core to make the cable more round as a whole, and to allow the flame-retardant material to be fully filled into the cable core, achieving a better flame-retardant effect, and having certain buffering, compression resistance, torsional resistance, and fatigue resistance effects, thereby improving the mechanical properties of the cable.

Description

Technical Field

[0001] The present invention relates to the technical field of wires and cables, and in particular to a B1-class halogen-free, low-smoke, flame-retardant special cable. Background Art

[0002] B1-class flame-retardant cables are primarily used in locations with high fire, smoke, and fire safety requirements, such as high-rise buildings, rail transit stations, airports, bus stations, railway stations, hospitals, financial institutions, and other crowded public places. With the large-scale application of high-rise buildings, electrical equipment, automated production lines, and industrial control systems, B1-class flame-retardant wires and cables are increasingly appearing in engineering applications. They impose clear additional requirements on combustion (dripping), smoke release (smoke toxicity), and corrosiveness. In the event of a fire, they can effectively suppress the spread of flames, and during combustion, they do not release toxic gases (such as hydrogen halides) and generate low smoke, thus facilitating personnel evacuation and fire rescue efforts.

[0003] The design of B1-class halogen-free, low-smoke, flame-retardant cables aims to improve the stability and flame retardancy of the materials at high temperatures by using halogen-free or low-halogen materials such as polyolefins as the insulation and sheath materials of the cables, and by adding flame retardants such as aluminum hydroxide, and to reduce and eliminate the release of halogen gas (which is highly toxic). At the same time, through a compact design, the oxygen contact area is reduced, thereby reducing the combustion rate. However, with the increasing complexity of electrical equipment and the use of high-power electrical equipment in places such as high-altitude buildings, rail transit stations, airports, bus stations, railway stations, hospitals, and financial institutions, such as large-scale testing equipment (CT scanners, MRI scanners, radiotherapy systems, etc.), data centers, high-voltage power stations, and underground control centers, on the basis of meeting the basic B1-class flame retardancy, increasingly higher requirements are placed on the mechanical properties, electromagnetic shielding properties, mechanical fatigue resistance, low-smoke flame retardancy, and fire and temperature protection levels of the cables. The existing design method of using polyolefin in the sheath and insulation layer combined with flame retardants to improve the flame retardancy and smoke suppression performance is gradually becoming difficult to meet. Summary of the Invention

[0004] In view of the defects and shortcomings of the prior art, according to a first aspect of the present invention, a B1-class halogen-free, low-smoke, flame-retardant special cable is proposed, comprising:

[0005] The cable core comprises a control core and a power core twisted with copper wires, wherein the gaps between the control core, the power core and the wrapping layer are filled with flame-retardant filling ropes, and the control core, the power core and the flame-retardant filling ropes are wrapped with the wrapping layer so that their cross-section forms a circular shape to form the cable core;

[0006] A flame retardant tape layer is wrapped around the outer circumferential surface of the wrapping layer, and the surface where the flame retardant tape layer and the wrapping layer are in contact is covered with expanded graphite and then glued and wrapped with the wrapping layer to form a shape;

[0007] A total shielding layer, braided and wrapped around the outer circumferential surface of the flame retardant tape layer;

[0008] a ceramic fireproof layer formed by wrapping a ceramic fireproof silicone rubber composite tape around the outer circumferential surface of the overall shielding layer; and

[0009] An outer sheath, extruded and coated on the outer circumferential surface of the ceramic fireproof layer;

[0010] The flame retardant filling rope includes a flame retardant support core strip and a foamed flame retardant layer extruded outside the flame retardant support core strip, and the hardness of the foamed flame retardant layer is less than the hardness of the flame retardant support core strip;

[0011] The ceramic fireproof layer adopts a composite tape of flame retardant inorganic filler silicone rubber and glass fiber cloth, the thickness of the composite tape is 0.1mm to 1mm, and the heat release rate is less than 1.50g / cm 3 The density value of .

[0012] As an optional embodiment, the control core includes a control conductor, a first insulating layer extruded on the outside of the control conductor, and a first shielding layer braided and wrapped on the outside of the first insulating layer, wherein the first insulating layer is a flame retardant foam insulating layer.

[0013] As an optional embodiment, the power line core includes a power conductor and a second insulation layer extruded outside the power conductor, wherein the second insulation layer is a polyolefin insulation layer.

[0014] As an optional embodiment, the overall shielding layer includes a plurality of cross-woven composite shielding fibers, wherein the composite shielding fibers include metal wires and semi-conductive fibers twisted together, and the hardness of the semi-conductive fibers is less than the hardness of the metal wires, so that when the composite shielding fibers are in a bent state, the metal wires can press the semi-conductive fibers.

[0015] As an optional implementation, the braiding density of the composite shielding fiber is set to 80% to 95%.

[0016] As an optional embodiment, the flame-retardant supporting core strip is a glass fiber bundle, and the foamed flame-retardant layer is a flame-retardant EVA foam that wraps the glass fiber bundle.

[0017] As an optional implementation manner, the thickness ratio of the flame retardant supporting core strip and the foamed flame retardant layer is set to 1:1-3.

[0018] As an optional implementation, the flame retardant tape layer is wrapped with polyurethane flame retardant tape or glass fiber fabric flame retardant tape.

[0019] As an optional embodiment, the expanded graphite has a median particle size of 10 μm to 200 μm, and a total coverage density on the surface of the flame retardant tape layer of 0.05 g / cm 2 ~0.5g / cm 2 .

[0020] As an optional embodiment, the outer sheath comprises a cross-linked polyethylene sheath.

[0021] The second aspect of the present invention provides a method for preparing a B1-class halogen-free, low-smoke, flame-retardant special cable, comprising the following steps:

[0022] Step 1: Prepare the cable core:

[0023] Step 1.1: Prepare a control core: Use a stranding machine to twist a plurality of twisted pairs of wires into a control core, use an extruder to extrude flame-retardant foam to coat the outside of the control core to form a first insulation layer, and then use a braiding machine to braid a layer of copper wire shielding onto the outside of the first insulation layer to form a first shielding layer. The control core, the first insulation layer, and the first shielding layer collectively form a control core;

[0024] Step 1.2: preparing a power line core: using a stranding machine to strand a plurality of annealed oxygen-free fine metal wires to form a power conductor core, using an extruder to extrude polyvinyl chloride to form a second insulation layer, so that the power conductor core and the second insulation layer are integrally formed into a power line core;

[0025] Step 1.3: preparing a flame-retardant filling rope: weaving glass fibers using a braiding machine to form a flame-retardant support core strip, and extruding flame-retardant foam using an extruder to form a foamed flame-retardant layer on the outer side of the flame-retardant support core strip, so that the flame-retardant support core strip and the foamed flame-retardant layer form a flame-retardant filling rope;

[0026] Step 1.4: twisting the control wire core, power wire core and flame retardant filling rope together using a twisting machine, and wrapping a polyester tape around the outside of the rope using a wrapping machine to form a wrapping layer, so that the cross section of the rope is circular to form a cable core.

[0027] Step 2: Wrapping a flame retardant tape layer: Wrapping a flame retardant tape with expanded graphite on the outside of the cable core using a wrapping machine. During the wrapping process, the expanded graphite is placed between the wrapping layer and the flame retardant tape to form a flame retardant tape layer.

[0028] Step 3, weaving the overall shielding layer: using a twisting machine to twist the metal wire and the semi-conductive fiber in a 1+N structure, with one of the semi-conductive fibers located in the center, to form a composite shielding fiber, and then using a braiding machine to weave multiple composite shielding fibers on the outside of the wrapped flame retardant tape layer into an overall shielding layer with an overlap density between 80% and 95%;

[0029] Step 4: Wrapping a ceramic fireproof layer: Using a composite tape made of flame-retardant inorganic filler silicone rubber and glass fiber cloth, wrap it around the outside of the braided shielding layer through a wrapping machine to form a ceramic fireproof layer;

[0030] Step 5, extruding an outer sheath: Extruding cross-linked polyethylene on the outside of the ceramic fireproof layer through an extrusion machine to form an outer sheath.

[0031] Compared with the existing technology, the B1-class halogen-free, low-smoke, flame-retardant special cable proposed in this invention has a cross-linked polyethylene sheath as an outer layer of protection, a ceramic fireproof layer as a middle layer to form a shell flame-retardant insulation, and a flame-retardant tape layer combined with expanded graphite as an inner layer of buffer insulation, achieving multiple flame-retardant insulation for the cable core, and excellently suppressing the release of burning drips and toxic smoke, as well as the surrounding corrosive media, meeting and exceeding the B1-class flame-retardant grade requirements. The use of low-smoke, halogen-free materials can reduce the release of toxic gases in the event of combustion. At the same time, the double-layer hardness flame-retardant filling rope twisted into the core not only makes the cable more rounded as a whole, but also allows the flame-retardant material to fully fill the cable core, achieving a better flame-retardant effect, and providing certain buffering, compression resistance, torsional fatigue resistance and other effects, thereby improving the mechanical properties of the cable.

[0032] The overall shielding layer, which is woven with metal wire and semi-conductive fiber in combination with composite shielding, not only has a good shielding effect, but also makes the overall shielding layer more flexible, and has a longer service life under bending and torsion conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the cross-sectional structure of a B1-class halogen-free, low-smoke, flame-retardant special cable shown in an embodiment of the present invention.

[0034] Figure 2 It is a partially enlarged schematic diagram of the shielding layer of the B1-class halogen-free, low-smoke, flame-retardant special cable shown in an embodiment of the present invention.

[0035] Figure 3 It is a schematic diagram of the cross-sectional structure of the composite shielding fiber in the B1-class halogen-free, low-smoke, flame-retardant special cable shown in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] In order to better understand the technical content of the present invention, specific embodiments are given below in conjunction with the accompanying drawings.

[0037] Example 1

[0038] Combine Figure 1As shown, the B1-class halogen-free low-smoke flame-retardant special cable according to an embodiment of the present invention includes: a cable core formed by winding a control core 10 and a power core 20, a flame-retardant filling rope 30, a wrapping layer 40, a flame-retardant tape layer 50, a total shielding layer 60, a ceramic fireproof layer 70 and an outer sheath 80.

[0039] Combine Figure 1 As shown, the cable core includes a control core 10 and a power core 20 twisted with copper wires. The gaps between the control core 10, the power core 20 and the sheathing layer 40 are filled with a flame retardant filling rope 30, and the control core 10, the power core 20 and the flame retardant filling rope 30 are wrapped by the sheathing layer 40 so that their cross-section forms a circular cable core.

[0040] The flame retardant tape layer 50 is wrapped around the outer circumferential surface of the wrapping layer 40 . The surface where the flame retardant tape layer 50 and the wrapping layer 40 are in contact is covered with expanded graphite and then glued and wrapped with the wrapping layer 40 to form a shape.

[0041] The overall shielding layer 60 is braided and coated on the outer circumferential surface of the flame retardant tape layer 50 .

[0042] The ceramic fireproof layer 70 is formed by wrapping a ceramic fireproof silicone rubber composite tape around the outer circumferential surface of the overall shielding layer 60 .

[0043] The outer sheath 80 is extruded and coated on the outer circumferential surface of the ceramic fireproof layer 70 .

[0044] As an optional embodiment, the flame retardant filling rope 30 includes a flame retardant support core strip 31 and a foamed flame retardant layer 32 extruded on the outside of the flame retardant support core strip 31 , and the hardness of the foamed flame retardant layer 32 is less than the hardness of the flame retardant support core strip 31 .

[0045] As an optional embodiment, the ceramic fireproof layer 70 is a composite tape made of flame-retardant inorganic filler silicone rubber and glass fiber cloth, the thickness of the composite tape is 0.1mm to 1mm, and the density is less than 1.50g / cm 3 The density value of .

[0046] As an optional embodiment, the control core 10 includes a control conductor 11, a first insulating layer 12 extruded outside the control conductor 11, and a first shielding layer 13 braided and wrapped outside the first insulating layer 12, wherein the first insulating layer 12 is a flame retardant foam insulating layer.

[0047] As an optional embodiment, the power line core 20 includes a power conductor 21 and a second insulation layer 22 extruded outside the power conductor 21 , wherein the second insulation layer 22 is a polyolefin insulation layer.

[0048] As an optional embodiment, the overall shielding layer 60 includes a plurality of cross-woven composite shielding fibers 61, the composite shielding fibers 61 include metal wires 611 and semi-conductive fibers 612 twisted together, and the hardness of the semi-conductive fibers 612 is less than the hardness of the metal wires 611, so that when the composite shielding fibers 61 are in a bent state, the metal wires 611 can press the semi-conductive fibers 612.

[0049] As an optional embodiment, the braiding density of the composite shielding fiber 61 is set to 80% to 95%.

[0050] As an optional embodiment, the flame-retardant supporting core strip 31 is a glass fiber bundle, and the foamed flame-retardant layer 32 is a flame-retardant EVA foam wrapped around the glass fiber bundle.

[0051] As an optional embodiment, the thickness ratio of the flame retardant supporting core strip 31 and the foamed flame retardant layer 32 is set to 1:1-3.

[0052] As an optional embodiment, the flame retardant tape layer 50 is wrapped with polyurethane flame retardant tape or glass fiber fabric flame retardant tape.

[0053] As an optional embodiment, the expanded graphite has a median particle size of 10 μm to 200 μm, and a total coverage density of 0.05 g / cm 2 ~0.5g / cm 2 .

[0054] As an alternative embodiment, the outer sheath 80 comprises a cross-linked polyethylene sheath.

[0055] Example 2

[0056] like Figures 1 to 3 As shown, combined with the B1-level halogen-free, low-smoke, flame-retardant special cable of the above embodiment 1, the specific design of the cable is further elaborated and illustrated in this embodiment.

[0057] The cable core adopts a 1+6 structure of twisted control core 10 and power core 20 to make the cable core structure more compact.

[0058] Combine Figure 1 As shown, the control core 10 includes a control conductor 11 , a first insulating layer 12 extruded outside the control conductor 11 , and a first shielding layer 13 braided and wrapped outside the first insulating layer 12 .

[0059] In a further design, the control conductor core 11 is formed by twisting a plurality of twisted pairs of wires together and is used for transmitting control signals.

[0060] The first insulating layer 12 includes a flame-retardant foam insulating layer, such as flame-retardant EVA foam, which not only has a good flame-retardant effect, but also has good insulation and elasticity. It can cooperate with the first shielding layer 13 on the outside to make the control core 10 more flexible. When the control core 10 is bent or twisted, the first shielding layer 13 can compress the space of the first insulating layer 12 inward, thereby releasing the stress of the first shielding layer 13 when bending, making the control core 10 resistant to bending and twisting, and improving the mechanical properties.

[0061] Combine Figure 1 The power line core 20 shown includes a power conductor 21 and a second insulation layer 22 extruded around the outside of the power conductor 21 .

[0062] The power conductor core 21 is formed by twisting together a plurality of annealed oxygen-free fine metal wires, and the second insulating layer 22 is a flexible insulating layer (core insulation is formed by extruding cross-linked polyethylene material).

[0063] Preferably, the control conductor 11 and the power conductor 21 are both made of annealed oxygen-free copper wire.

[0064] In a further design, after the power core 20 and the control core 10 are twisted together, the flame-retardant foam insulation layer filled in the control core 10 can also provide stress release space for the cable core to bend.

[0065] Furthermore, the flame retardant filling rope 30 filled in the cable core is wrapped with the wrapping layer 40 to make the cross section of the cable core circular. The wrapping layer 40 is made of polyester tape with a 25% to 40% overlap rate and is wrapped with a wrapping machine.

[0066] As an optional embodiment, the flame-retardant filling rope 30 includes a flame-retardant support core 31 and a foamed flame-retardant layer 32 extruded onto the outside of the flame-retardant support core 31. The flame-retardant support core 31 is made of glass fiber bundles, and the foamed flame-retardant layer 32 is flame-retardant EVA foam wrapped around the glass fiber bundles. The density of the flame-retardant support core 31 is greater than the density of the foamed flame-retardant layer 32, resulting in a lower hardness of the foamed flame-retardant layer 32 than the flame-retardant support core 31.

[0067] In a preferred embodiment, the thickness ratio of the flame retardant support core strip 31 and the foamed flame retardant layer 32 is set to 1:1~3. In this way, the flame retardant support core strip 31 located in the inner layer plays a supporting and solidifying role, and the foamed flame retardant layer 32 combined with the outer layer can fill in the gap and fill the gap space, which not only makes the cable as a whole more round, but also allows the flame retardant material to be fully filled into the cable core, thereby playing a better flame retardant role.

[0068] Combined with attachment Figure 1As shown, the flame retardant tape layer 50 is wrapped around the outer circumferential surface of the wrapping layer 40 , and the surface where the flame retardant tape layer 50 and the wrapping layer 40 are in contact is covered with expanded graphite and then glued and wrapped with the wrapping layer 40 to form a shape.

[0069] As an example, the flame retardant tape layer 50 is wrapped with polyurethane flame retardant tape or glass fiber fabric flame retardant tape. The expanded graphite (also called expandable graphite) is selected with a median particle size of 10 μm to 200 μm, preferably 10 μm to 100 μm, and the total coverage density on the surface of the flame retardant tape layer 50 is 0.05 g / cm 2 ~0.5g / cm 2 .

[0070] Therefore, when the cable burns, the expanded graphite can expand rapidly in an instant after being heated, expanding the surface area and using its own worm-like structure to form a mutual interlocking, combining with the surface of the flame-retardant tape layer 50 to form an insulating layer, preventing further combustion and playing a flame-retardant role.

[0071] In an optional embodiment, the expanded graphite covering the surface of the flame-retardant tape layer 50 adopts a mismatch of particles in different particle size ranges, so that the graphene particles of different particle sizes form a complementary filling mosaic after expansion, and the small graphene particles can be filled into the gaps between the large graphene particles to form a denser flame-retardant insulation layer to prevent further combustion.

[0072] In a preferred embodiment of the present invention, the expanded graphite is prepared by mixing at least one Type I with at least one Type II. The median particle size of the Type I expanded graphite is between 10 μm and 50 μm, and the median particle size of the Type II expanded graphite is between 60 μm and 100 μm, forming a particle size mismatch distribution. The size staggered and dislocated distribution achieves better bonding, forming a buffer insulation to block combustion and improve flame retardancy.

[0073] It should be understood that in the embodiments of the present invention, the adhesive layer applied to the surface of the polyurethane or fiberglass fabric flame-retardant tape serves to adhere the expanded graphite powder. The adhesive layer is thin and can be made with a silicone rubber adhesive or acrylic adhesive with a high-temperature resistance range of approximately 200-250°C, achieving the same temperature resistance as the cross-linked polyethylene sheath. When exposed to high temperatures, such as in the case of a cable short circuit or fire, the tape gradually loses its effectiveness, allowing the expanded graphite to overcome its interlayer bonding strength and rapidly expand exponentially (up to 100-300 times) to form an insulating bond layer.

[0074] Combined with attachment Figure 1 As shown, the overall shielding layer 60 is braided and wrapped around the outside of the flame retardant tape layer 50. Figure 2 、 3As shown, the total shielding layer 60 includes a plurality of cross-woven composite shielding fibers 61, and the composite shielding fibers 61 include mutually twisted metal wires 611 and semi-conductive fibers 612, and the hardness of the semi-conductive fibers 612 is less than the hardness of the metal wires 611, so that when the composite shielding fibers 61 are in a bent state, the metal wires 611 can squeeze the semi-conductive fibers 612.

[0075] In some embodiments, the semi-conductive fiber 612 can be made of a conductive polymer material, such as polyaniline. The conductive polyaniline fiber prepared by chemical synthesis and spinning technology has good stability and conductivity. The metal wire 611 and the semi-conductive fiber 612 are twisted together and then mixed and woven to form the total shielding layer 60, which not only improves the shielding effect of the existing design using only metal wire weaving, but also makes the total shielding layer 60 softer as a whole.

[0076] Specifically, the metal wires 611 and the semi-conductive fibers 612 are twisted in a 1+N structure, and one of the semi-conductive fibers 612 is located at the center.

[0077] As an example, the braiding density of the composite shielding fiber 61 is set to 80% to 95%.

[0078] Therefore, the overall shielding layer 60 has the effect of significantly improving the shielding effectiveness of the inner control core 10 and the power core 20 and enhancing the reliability of signal transmission.

[0079] The ceramic fireproof layer 70 is formed by wrapping a ceramic fireproof silicone rubber composite tape around the outer circumferential surface of the total shielding layer 60. The ceramic fireproof layer 70 adopts a composite tape composed of flame-retardant inorganic filler silicone rubber and glass fiber cloth. The ceramic fireproof layer 70 can quickly form a dense and hard ceramic body at high temperature, which can effectively prevent the spread of flames. The ceramic body has good thermal insulation properties and can reduce the transfer of heat to the protected object or structure. Especially in the field of wires and cables, the ceramic fireproof layer 70 can ensure the smooth flow of power and communication lines in a fire, thereby winning precious time for people to escape and property rescue.

[0080] As an example, combined with Figure 1 The outer sheath 80 is a cross-linked polyethylene sheath, which is extruded and coated on the outside of the ceramic fireproof layer 70.

[0081] As a high-strength, high-heat-resistant, cold-resistant, water-resistant, and non-aging cable sheath material, the cross-linked polyethylene sheath is halogen-free, non-flammable, and produces less smoke when burned. It complies with fire protection standards such as UL94V0 and environmental protection standards such as ROHS and REACH.

[0082] The second aspect of the present invention provides a method for preparing a B1-class halogen-free low-smoke flame-retardant special cable, including preparing a cable core, wrapping a flame-retardant tape layer, braiding a general shielding layer, wrapping a ceramic fireproof layer, and extruding an outer sheath.

[0083] Step 1: preparing a cable core, specifically comprising the following steps:

[0084] Step 1.1: Prepare the control core 10: Use a stranding machine to twist a plurality of twisted pairs of wires into a control core 11. Use an extruder to extrude flame-retardant foam to coat the outside of the control core 11 to form a first insulating layer 12. Use a braiding machine to braid a layer of copper wire shielding onto the outside of the first insulating layer 12 to form a first shielding layer 13. The control core 11, first insulating layer 12, and first shielding layer 13 together form the control core 10.

[0085] Step 1.2: preparing the power line core 20: using a stranding machine to strand a plurality of annealed oxygen-free fine metal wires to form a power conductor core 21; using an extruder to extrude polyvinyl chloride to form a second insulating layer 22; and the power conductor core 21 and the second insulating layer 22 are integrally formed into the power line core 20;

[0086] Step 1.3: Prepare the flame-retardant filling rope 30: Use a braiding machine to weave glass fibers to form a flame-retardant support core strip 31, and use an extruder to extrude flame-retardant foam to form a foamed flame-retardant layer 32 on the outer side of the flame-retardant support core strip 31, so that the flame-retardant support core strip 31 and the foamed flame-retardant layer 32 form the flame-retardant filling rope 30;

[0087] Step 1.4 Twisting: Use a twisting machine to twist the prepared control core 10, power core 20 and flame retardant filling rope 30, and use a wrapping machine to wrap a polyester tape around the outside to form a wrapping layer 40, so that the cross section forms a circular cable core.

[0088] In this way, when the power line core 20 and the control line core 10 are twisted together, the flame-retardant foam insulation layer filled in the control line core 10 can also provide stress release space for the cable core bending. The flame-retardant filling rope 30 includes a flame-retardant support core strip 31 and a foamed flame-retardant layer 32 extruded on the outside of the flame-retardant support core strip 31. The flame-retardant support core strip 31 located in the inner layer plays a supporting and solidifying role, and the foamed flame-retardant layer 32 combined with the outer layer can fill in the gap and fill the gap space, which not only makes the cable as a whole more round, but also allows the flame-retardant material to be fully filled into the cable core, thereby playing a better flame-retardant role.

[0089] Step 2, wrapping the flame retardant tape layer 50: Use a wrapping machine to wrap the flame retardant tape with expanded graphite (using polyurethane flame retardant tape + propylene glue) on the outside of the cable core. During the wrapping process, the expanded graphite is placed between the wrapping layer 40 and the flame retardant tape to form a flame retardant tape layer 50, wherein the flame retardant tape layer 50 is wrapped with polyurethane flame retardant tape or glass fiber fabric flame retardant tape.

[0090] The expanded graphite has a median particle size of 10 μm to 200 μm. In this example, the expanded graphite with a median particle size of 100 μm is selected, and the total coverage density on the surface of the flame retardant tape layer 50 is 0.5 g / cm 2 When the cable burns, the expanded graphite expands rapidly upon exposure to heat, increasing its surface area and forming a worm-like structure that interlocks with each other, bonding to the surface of the flame-retardant tape layer 50 to form an insulating layer, preventing further combustion and providing a flame-retardant effect.

[0091] Step 3, weaving the total shielding layer 60: Use a twisting machine to twist the metal wire 611 and the semi-conductive fiber 612 in a 1+N structure, and make one of the semi-conductive fibers 612 located in the center position, twisting them to form a composite shielding fiber 61, and then use a braiding machine to weave multiple composite shielding fibers 61 on the outside of the wrapped flame retardant tape layer 50 into a total shielding layer 60 with an overlap density between 80% and 95%. After twisting the metal wire 611 and the semi-conductive fiber 612, they are mixed and woven to form a total shielding layer 60.

[0092] Through this process, not only the shielding effect of the existing design using only metal wire braiding is improved, but also the overall shielding layer 60 is made softer. The overall shielding layer 60 has the effect of significantly improving the shielding effectiveness of the inner control line core 10 and the power line core 20 and enhancing the reliability of signal transmission.

[0093] Step 4, wrapping the ceramic fireproof layer 70: Use a composite tape made of flame-retardant inorganic filler silicone rubber and glass fiber cloth, and wrap it around the outside of the woven total shielding layer 60 through a wrapping machine to form a ceramic fireproof layer 70. The ceramic fireproof layer 70 can quickly form a dense and hard ceramic body at high temperature, which can effectively prevent the spread of flames.

[0094] Step 5, extruding the outer sheath 80: using an extrusion machine to extrude cross-linked polyethylene on the outside of the ceramic fireproof layer 70 to form the outer sheath 80.

[0095] While the present invention has been disclosed above with reference to preferred embodiments, this is not intended to limit the present invention. Persons skilled in the art will readily appreciate that various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A B1-class halogen-free, low-smoke, flame-retardant special cable, characterized in that: include: A cable core comprising a control core (10) twisted with copper wires, a power core (20) and a flame-retardant filling rope (30), wherein the control core (10), the power core (20) and the flame-retardant filling rope (30) are twisted and wrapped with a polyester tape on the outside to form a wrapping layer (40), thereby forming a cable core with a circular cross-section, and the flame-retardant filling rope (30) is filled in a gap between the control core (10), the power core (20) and the wrapping layer (40); A flame retardant tape layer (50) is wrapped around the outer circumferential surface of the wrapping layer (40), and the surface of the flame retardant tape layer (50) that is in contact with the wrapping layer (40) is covered with expanded graphite and then glued and wrapped with the wrapping layer (40) to form a shape; A total shielding layer (60) braided and wrapped around the outer circumferential surface of the flame-retardant tape layer (50); A ceramic fireproof layer (70) is formed by wrapping a ceramic fireproof silicone rubber composite tape around the outer circumferential surface of the overall shielding layer (60); as well as An outer sheath (80) is extruded and coated on the outer circumferential surface of the ceramic fireproof layer (70); The flame-retardant filling rope (30) comprises a flame-retardant supporting core strip (31) and a foamed flame-retardant layer (32) extruded on the outside of the flame-retardant supporting core strip (31), and the hardness of the foamed flame-retardant layer (32) is less than the hardness of the flame-retardant supporting core strip (31); The overall shielding layer (60) includes a plurality of cross-woven composite shielding fibers (61), the composite shielding fibers (61) including mutually twisted metal wires (611) and semi-conductive fibers (612), the metal wires (611) and semi-conductive fibers (612) being twisted in a 1+N structure, and one of the semi-conductive fibers (612) being located at a central position, the hardness of the semi-conductive fibers (612) being less than the hardness of the metal wires (611), so that when the composite shielding fibers (61) are in a bent state, the metal wires (611) can press the semi-conductive fibers (612); The ceramic fireproof layer (70) is a composite tape formed by calendering a flame-retardant inorganic filler silicone rubber and a glass fiber cloth. The thickness of the composite tape is 0.1 mm to 1 mm, and the composite tape has a strength of less than 1.50 g / cm 3 Density value; The flame retardant tape layer (50) is wrapped with polyurethane flame retardant tape or glass fiber fabric flame retardant tape, and the adhesive layer coated on the surface is used to adhere the powder of expanded graphite; the expanded graphite covered on the surface of the flame retardant tape layer (50) adopts a mismatch of particles with different particle size ranges, and the expanded graphite is prepared by mixing at least one type I and at least one type II, the median particle size of the type I expanded graphite is 10μm~50μm, and the median particle size of the type II expanded graphite is 60μm~100μm.

2. The B1-level halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The control wire core (10) comprises a control conductor (11), a first insulating layer (12) extruded on the outside of the control conductor (11), and a first shielding layer (13) braided and wrapped on the outside of the first insulating layer (12), wherein the first insulating layer (12) is a flame-retardant foam insulating layer.

3. The B1-class halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The power line core (20) comprises a power conductor (21) and a second insulation layer (22) extruded outside the power conductor (21), wherein the second insulation layer (22) is a polyolefin insulation layer.

4. The B1-class halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The braiding density of the composite shielding fiber (61) is set to 80%-95%.

5. The B1-level halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The flame-retardant supporting core strip (31) is a glass fiber bundle, and the foamed flame-retardant layer (32) is a flame-retardant EVA foam that wraps the glass fiber bundle.

6. The B1-level halogen-free, low-smoke, flame-retardant special cable according to claim 1 or 5, characterized in that: The thickness ratio of the flame-retardant supporting core strip (31) and the foamed flame-retardant layer (32) is set to 1:1-3.

7. The B1-level halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The flame retardant tape layer (50) is wrapped with polyurethane flame retardant tape or glass fiber fabric flame retardant tape.

8. The B1-level halogen-free, low-smoke, flame-retardant special cable according to claim 7, characterized in that: The total coverage density of the expanded graphite on the surface of the flame retardant tape layer (50) is 0.05 g / cm 2 ~0.5g / cm 2 .

9. The B1-level halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The outer sheath (80) comprises a cross-linked polyethylene sheath.

10. The method for preparing the B1-class halogen-free, low-smoke, flame-retardant special cable according to claim 1, characterized in that: The following steps are involved: Step 1: Prepare the cable core: Step 1.1: preparing a control core (10): using a twisting machine to twist a plurality of twisted pairs of wires into a control core (11); using an extruder to extrude flame-retardant foam to coat the outside of the control core (11) to form a first insulating layer (12); and then using a braiding machine to braid a layer of copper wire shielding to form a first shielding layer (13) on the outside of the first insulating layer (12); so that the control core (11), the first insulating layer (12) and the first shielding layer (13) form a control core (10) as a whole; Step 1.2: preparing a power line core (20): using a stranding machine to strand a plurality of annealed oxygen-free fine metal wires to form a power conductor core (21); using an extruder to extrude polyvinyl chloride to form a second insulating layer (22); and the power conductor core (21) and the second insulating layer (22) are integrally formed into a power line core (20); Step 1.3: preparing a flame-retardant filling rope (30): using a braiding machine to weave glass fibers to form a flame-retardant support core strip (31), and using an extruder to extrude flame-retardant foam to form a foamed flame-retardant layer (32) on the outer side of the flame-retardant support core strip (31), so that the flame-retardant support core strip (31) and the foamed flame-retardant layer (32) form a flame-retardant filling rope (30); Step 1.4: twisting: twisting the control wire core (10), the power wire core (20) and the flame-retardant filling rope (30) by a twisting machine, and wrapping a polyester tape around the outside to form a wrapping layer (40) by a wrapping machine, so that the cross section thereof is circular to form a cable core; Step 2, wrapping the flame retardant tape layer (50): using a wrapping machine to wrap the flame retardant tape with expanded graphite on the outside of the cable core, so that the expanded graphite is located between the wrapping layer (40) and the flame retardant tape through the wrapping process, thereby forming the flame retardant tape layer (50); Step 3, weaving the overall shielding layer (60): using a twisting machine to twist the metal wire (611) and the semi-conductive fiber (612) in a 1+N structure, with one of the semi-conductive fibers (612) located at the center, to form a composite shielding fiber (61), and then using a braiding machine to weave the plurality of composite shielding fibers (61) on the outside of the wrapped flame retardant tape layer (50) into an overall shielding layer (60) with an overlap density between 80% and 95%; Step 4, wrapping a ceramic fireproof layer (70): using a composite tape of flame-retardant inorganic filler silicone rubber and glass fiber cloth, wrapping it on the outside of the braided overall shielding layer (60) through a wrapping machine to form a ceramic fireproof layer (70); Step 5, extruding an outer sheath (80): using an extrusion machine to extrude cross-linked polyethylene on the outside of the ceramic fireproof layer (70) to form an outer sheath (80).

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