Methods for preparing composite communication cables and applications of the composite communication cables prepared therefrom

Abstract

This invention provides a method for preparing a composite communication cable, comprising the following steps: Step 1, covering the surface of a conductor substrate with an outer sheath, the conductor substrate including wires; Step 2, cooling the surface temperature of the outer sheath to below 60°C, spraying a fire-retardant slurry onto the surface of the outer sheath, and then drying the section covered with the fire-retardant slurry at a temperature of 70–85°C, the fire-retardant slurry forming a fire-retardant coating after drying; wherein the fire-retardant slurry contains soluble polytetrafluoroethylene and silicate. This method, by using a compound of silicate and soluble polytetrafluoroethylene, enables the coating to dry rapidly at lower ambient temperatures, thereby avoiding repeated sintering that could affect the coating's performance.

Description

Technical Field

[0001] This invention belongs to the field of communication cables, and particularly relates to a method for preparing composite communication cables and the composite communication cables prepared using the same method. Background Technology

[0002] Currently, multi-core communication cables on the market present the following problems: limited transmission function and simple structure; independent and isolated cores; low flame retardant and fire-resistant ratings, resulting in low fire safety; and the release of toxic gases during combustion, posing a significant risk of personal injury. Furthermore, with the rapid development of my country's cable industry, companies face increasing market competition, making cost control and R&D of new technologies key methods to enhance product competitiveness. Material costs constitute a large proportion of cable manufacturing costs; therefore, some companies use spraying to prepare coatings to achieve certain functionalities. However, the repeated sintering process used in spraying to dry the coating causes premature aging of the inner layer materials. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a combined communication cable and a method for preparing a combined communication cable using the same method, so as to improve the electrical performance, mechanical performance, flame retardancy, and non-toxicity of the combined communication cable.

[0004] According to one aspect of the present invention, a method for preparing a combined communication cable is provided, comprising the following steps: Step 1, covering the surface of a conductor substrate with an outer sheath, the conductor substrate comprising a conductor; Step 2, reducing the surface temperature of the outer sheath to below 60°C, spraying a fire-retardant slurry onto the surface of the outer sheath, and then drying the section covered with the fire-retardant slurry at a drying temperature of 70-85°C, wherein the fire-retardant slurry forms a fire-retardant coating after drying; wherein the fire-retardant slurry contains soluble polytetrafluoroethylene and silicate.

[0005] Preferably, the silicate includes at least one of potassium silicate, sodium silicate, lithium silicate, and ammonium silicate.

[0006] Soluble polytetrafluoroethylene (PTFE) possesses similar properties to PTFE, but when applying it in a spray coating process, it cannot be coated too thickly in one go, otherwise the coating is prone to pitting and sagging. Conventional techniques increase coating thickness through multiple sprays and repeated sintering, but repeated sintering may cause aging of the underlying coating layer, thus affecting its performance. This solution uses a compound of silicate and soluble PTFE, enabling the coating to dry rapidly at lower ambient temperatures, thereby avoiding the negative impact of repeated sintering on coating performance. Typically, silicate hydrolysis produces orthosilicic acid, which then undergoes dehydration condensation to form long-chain and silicon-oxygen network structures, resulting in a coating film that can effectively bond with the substrate. Furthermore, carbon dioxide in the air promotes this process. In summary, this invention, by using silicate in combination with PTFE, effectively optimizes the film-forming properties of PTFE. Silicate itself is low-cost, water-soluble, and does not produce volatile harmful gases, meeting the requirements of economic practicality and environmental friendliness.

[0007] Preferably, the fire-retardant slurry also contains fire-retardant particles, which include at least one of expanded graphite, nano-titanium dioxide, wollastonite, and mica.

[0008] Preferably, in the fire-retardant slurry, the proportion of fire-retardant particles is 6wt% to 19wt% by mass percentage.

[0009] Preferably, the fire-retardant particles are composed of graphite and nano-titanium dioxide, wherein, calculated by mass ratio, the expanded graphite : nano-titanium dioxide ratio in the fire-retardant particles is (1-5):1. After graphite expands, it produces worm-like graphite particles, which have a certain flame-retardant effect. However, its expanded material has a low density, and combustible gases from the external environment may penetrate the fire-retardant coating through the gaps in the expanded material. This invention improves the flame-retardant effect of expanded graphite by adding nano-titanium dioxide. The nano-titanium dioxide is distributed in the pores of the expanded graphite. When a fire occurs around the cable, after the graphite absorbs heat and expands, the nano-titanium dioxide can adsorb combustible gases that the graphite cannot block, thereby slowing down the thermal degradation rate of the fire-retardant coating. Simultaneously, the nano-titanium dioxide can increase the initial decomposition temperature of the expanded graphite and promote the charring reaction.

[0010] Preferably, the fire-retardant particles are composed of wollastonite and mica, wherein, by mass ratio, the ratio of wollastonite to mica in the fire-retardant particles is (0.3-3):1. Both wollastonite and mica are silicate minerals with good insulating and heat-insulating properties. Both can form a dense ceramic layer after combustion. Furthermore, research has shown that smaller particle sizes of wollastonite and mica, in a certain proportion, improve the hardness and flame retardancy of the ceramic layer formed during combustion, thereby enhancing the flame retardancy of the base material.

[0011] Preferably, the fire-retardant particles are composed of expanded graphite, nano-titanium dioxide, wollastonite, and mica.

[0012] Preferably, in the fireproof slurry, the content of silicate is 61-77 wt%, the content of polytetrafluoroethylene is 14-24 wt%, the content of expanded graphite is 4-7 wt%, the content of nano-titanium dioxide is 1.5-4 wt%, the content of wollastonite is 1-3 wt%, and the content of mica is 1-3 wt%, calculated by mass percentage.

[0013] Preferably, in step one, the outer sheath is coated onto the surface of the conductor substrate by extrusion; during the extrusion molding of the outer sheath, the extrusion section is directly cooled to form the outer sheath, and then the section with the formed outer sheath on its surface is coated by the spraying operation in step two.

[0014] In another aspect, the present invention provides a combined communication cable, wherein the combined communication cable is prepared by the above-described method for preparing the combined communication cable.

[0015] Preferably, the thickness of the fire-retardant coating is less than 0.15 mm.

[0016] Preferably, the thickness of the fire-retardant coating is ≤0.1mm.

[0017] Preferably, the thickness / diameter of the filler is 1.0 to 3.0 mm.

[0018] Preferably, the thickness of the low-smoke halogen-free flame-retardant outer sheath is 1.0 to 2.0 mm.

[0019] Preferably, the outer sheath contains borax and antimony trioxide. Although antimony-based flame retardants were among the earliest flame retardants used, their individual application often fails to achieve good flame retardant effects. However, the combined use of borax and antimony trioxide has a synergistic effect, further enhancing their flame retardant performance.

[0020] Preferably, the outer sheath contains 4-7 wt% borax and 2-4 wt% antimony trioxide, calculated by mass percentage.

[0021] Preferably, the outer sheath also contains mesoporous silica. Mesoporous silica has a large specific surface area and abundant pore structure. This structural feature results in long and tortuous heat and mass transfer paths, thus mesoporous silica can act as a heat barrier. In addition, mesoporous silica can improve the thermal stability of the material, and because the amount added is small, it has little impact on the mechanical properties of the outer sheath.

[0022] Preferably, the mesoporous silica accounts for 2 to 4 wt% of the outer sheath, calculated by mass percentage.

[0023] Preferably, the outer sheath contains the following materials by weight percentage: 55-65 wt% polyethylene, 12-16 wt% modified brucite fiber, 4-7 wt% borax, 2-4 wt% zinc oxide, 2-4 wt% copper oxide, 2-4 wt% ferric oxide, 2-4 wt% antimony trioxide, and 2-4 wt% mesoporous silica. The modified brucite fiber refers to brucite fiber modified with a silane coupling agent. Polyethylene, as the matrix resin of the outer sheath, does not produce significant toxic gases or fumes when burned. The inorganic metal compounds generally exhibit a synergistic flame-retardant effect with various substances. In the above scheme, magnesium hydroxide, the main component of modified brucite fiber, can inhibit the temperature rise in the early stage of ignition by dehydration. In addition, the surface of brucite fiber contains abundant hydroxyl groups, which form Si-O-Mg bonds after modification with silane coupling agent. This can prevent the brucite fiber from agglomerating in the dispersion matrix, improve its dispersibility, and thus eliminate the adverse effects of the addition of brucite fiber on the mechanical properties of the outer sheath.

[0024] Preferably, the conductor matrix comprises a plurality of conductors and a filler, the filler filling the gaps between the conductors, and the filler comprising at least one of talc, antimony trioxide, iron oxide red, and clay. The filler contains flame-retardant particles, thereby improving not only the roundness of the cable's outer surface but also its flame-retardant properties.

[0025] Preferably, the combined communication cable includes a local Ethernet high-speed cable and a digital signal cable.

[0026] Preferably, the filler is composed of the following materials by mass percentage: 40-50 wt% styrene-butadiene-styrene copolymer, 7-13 wt% talc, 7-13 wt% antimony trioxide, 7-13 wt% iron oxide red, and 20-24 wt% clay.

[0027] In summary, compared with the prior art, the solution provided by this invention has the following beneficial effects:

[0028] (1) The prepared combined communication cable can transmit local Ethernet high-speed signals and digital signals;

[0029] (2) Most of the flame retardants used are inorganic flame retardants and do not contain halogens. Their good flame retardancy, low smoke and low toxicity can enhance the normal operation of the equipment and buy precious time for the safe evacuation of the people.

[0030] (3) Since the spraying process is a three-dimensional spraying process, the fireproof slurry can be sprayed onto the surface of the outer sheath quickly and evenly. This process can not only save operation time, but also save costs.

[0031] (4) The selected low-smoke halogen-free flame-retardant outer sheath material utilizes the property that modified magnesium hydroxide can be evenly dispersed in the matrix, thus improving the problem that excessive addition of magnesium hydroxide will affect the mechanical properties of the matrix.

[0032] (5) In addition, the low-smoke halogen-free flame-retardant outer sheath also utilizes the characteristics of mesoporous silica, which has a large specific surface area and an ordered pore structure (this structure makes the heat and mass transfer path long and tortuous, thus playing the role of heat barrier and mass barrier), to improve the flame-retardant performance of the outer sheath.

[0033] (6) The selected fireproof slurry formula utilizes potassium silicate, which can self-cur at room temperature, to improve the drying speed of the fireproof slurry and avoid the side effects on the underlying material after repeated sintering. In addition, the combination of soluble polytetrafluoroethylene and other flame-retardant particles greatly enhances the flame-retardant effect of this fireproof coating.

[0034] (7) The fireproof coating prepared can reach less than 0.15mm, and the required thickness can be achieved through process adjustment. In addition, it can significantly reduce enterprise costs.

[0035] Therefore, the method for preparing a combined communication cable disclosed in this invention and the combined communication cable prepared therefrom can meet the needs of densely populated, important places and enclosed spaces such as cinemas, commercial centers, large data exchange centers, and high-rise buildings, and have the characteristics of low smoke, low toxicity, high flame retardancy and multiple communication capabilities. Attached Figure Description

[0036] Figure 1 The combined communication cable prepared according to the present invention;

[0037] Labeling Explanation: 1. Center cable conductor; 2. Center cable insulation layer; 3. Low-smoke halogen-free flame-retardant outer sheath; 4. Outer cable conductor; 5. Outer cable insulation layer; 6. Filler; 7. Low-smoke halogen-free flame-retardant outer sheath; 8. Fire-retardant coating. Detailed Implementation

[0038] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0039] Example 1

[0040] Processing group 1A

[0041] 1. Selection of raw materials

[0042] The raw materials for this treatment group are shown in Table 1. Among the materials shown in Table 1: the silicate solution is of industrial grade purity, and the solution concentration is 20%; the soluble polytetrafluoroethylene is Daikin AC-5539; the modified brucite fiber is obtained by surface modification of brucite fiber with silane using silane coupling agent KH550.

[0043] Table 1. Materials of each layer in a composite communication cable

[0044]

[0045]

[0046] 2. Preparation of composite communication cables

[0047] Step 1:

[0048] S1. The filler is mixed evenly in a high-speed mixer according to a certain ratio, and then melt-blended and extruded through a separate screw extruder to obtain filler 6. The temperature of the barrel section is 160℃, the screw speed is 60r / min, the temperature of the die section is 170℃, and the die temperature is 165℃.

[0049] S2. The center cable consists of a center cable conductor 1 and a center cable insulation layer 2 covering the center cable conductor 1. It uses 18 0.2mm... 2 The copper core wires are twisted in pairs to form nine pairs of wires. Two pairs are placed in the center, and seven pairs are twisted around these two pairs. This process of individual twisting followed by complete twisting forms the central cable conductor 1, used to transmit broadband network digital signals. A central cable insulation layer 2, made of polyethylene, is wrapped around the central cable conductor 1. The extrusion temperature of the central cable insulation layer 2 is controlled at 180℃, with the feeding zone temperature controlled at 160℃. The extruded outer diameter is 6.5mm, and the line speed is 30m / min. Four central cables are then... Figure 1 After being arranged sequentially, the cables are twisted together again and then extruded to form a 2mm thick low-smoke halogen-free flame-retardant outer sheath 3 around the four central cables. The raw materials for the low-smoke halogen-free flame-retardant outer sheath 3 are uniformly mixed in a high-speed mixer according to a specified ratio, and then melt-blended and extruded using a twin-screw extruder. The barrel temperature is 190℃, the screw speed is 20 r / min, and the die temperature is 185℃, with the die opening temperature at 180℃. The pipe is cooled in three stages using cooling water, with temperatures of 60℃, 50℃, and 40℃ respectively. Subsequently, to improve the uniformity of the finished product, the melt-blended extrusion temperature is 185℃, and the screw speed is 30 rpm.

[0050] S3. The outer cable consists of an outer cable conductor 4 and an outer cable insulation layer 5 covering the outer cable conductor 4. It uses 18 0.2mm...2 The copper core wires are twisted in pairs to form nine pairs of wires, with two pairs in the middle and seven pairs surrounding them, forming the outer cable conductor 4, used to transmit video, control, and data signals. To ensure flexibility, an outer cable insulation layer 5 is wrapped around the outer cable conductor 4, and the outer cable insulation layer 5 is made of cross-linked polyethylene. The extrusion temperature of the outer cable insulation layer 5 is controlled at 185℃, with the feeding zone temperature controlled at 170℃. The extruded outer diameter is 2.5mm, and the line speed is 50m / min. The outer cable and filler 6 are arranged around the four center cables and the low-smoke halogen-free flame-retardant outer sheath 3 at intervals, and then twisted together again. Subsequently, the same extrusion process is used to protect the center cables, the low-smoke halogen-free flame-retardant outer sheath 3, the outer cable, and the filler 6 with a 1.5mm thick low-smoke halogen-free flame-retardant outer sheath 7.

[0051] Step Two:

[0052] A fire-retardant coating 8 is applied to the surface of the low-smoke halogen-free flame-retardant outer sheath 7 using a three-dimensional spraying process. First, three nozzle groups are installed on the left and right sides above the cross-section of the cable covering the low-smoke halogen-free flame-retardant outer sheath 7, angled at 60° towards the surface of the sheath 7, with a distance of 2m between the nozzle groups. Then, a uniformly mixed fire-retardant slurry is injected into a 1.5mm diameter spray gun. After connecting the spray gun to an air compressor, the pressure is adjusted and stabilized at 0.4±0.05KPa, with the switch set to 1 / 4. The coating is then evenly applied to the surface of the low-smoke halogen-free flame-retardant outer sheath 7. To improve the insulation effect of the fire-retardant coating 8, the axis of the spray gun nozzle forms a 45° angle with the axis of the low-smoke halogen-free flame-retardant outer sheath 7. The distance from the nozzle to the surface of the low-smoke halogen-free flame-retardant outer sheath 7 is 180mm. The nozzle on the spray gun is aligned with the surface of the low-smoke halogen-free flame-retardant outer sheath 7 to be sprayed, forming the fire-retardant coating 8. It is then baked at 85℃ for 240 minutes to allow the fire-retardant coating 8 to better bond with the low-smoke halogen-free flame-retardant outer sheath 7. The thickness of the fire-retardant coating 8 is 0.1mm, and the surface of the fire-retardant coating 8 must be uniform. Finally, a combined communication cable is obtained. The prepared combined communication cable is as follows... Figure 1 As shown.

[0053] Treatment groups 2A to 5A refer to the formulations and methods provided in treatment group 1A to prepare composite communication cables. The silicates and soluble polytetrafluoroethylene in the fire-retardant slurry used in the formulations are used as variables as shown in Table 2. Except for the differences mentioned above, the operating steps for preparing composite communication cables in this treatment group are strictly consistent with those in treatment group 1A.

[0054] Table 2. Changes in silicate and soluble polytetrafluoroethylene in each treatment group and control group in Example 1.

[0055]

[0056] Example 2

[0057] This embodiment refers to the formula and method provided in processing group 2A to prepare a composite communication cable. Using the composition of fire-retardant particles in the fire-retardant slurry used in the composite communication cable formula as a variable, different processing groups are set up and sequentially labeled as: processing group 1B, processing group 2B, processing group 3B, processing group 4B, and processing group 5B. The specific variable settings for each processing group are shown in Table 3. Except for the above variables, the method used in this embodiment to prepare the composite communication cable is consistent with processing group 2A of embodiment 1.

[0058] Table 3. Composition (parts by mass) of fire-retardant mortar used in each treatment group in Example 2

[0059]

[0060]

[0061] Test case

[0062] 1. Participants

[0063] The combined communication cables prepared in Examples 1 and 2 were used as the test objects in this test example.

[0064] 2. Testing Method:

[0065] Conduct the tests according to the test items and corresponding test methods shown in Table 4.

[0066] Table 4. Test Items and Corresponding Test Methods

[0067]

[0068]

[0069] 3. Test Results and Analysis

[0070] The test results for this test case are shown in Table 5.

[0071] Table 5. Test results of each treatment group and control group in Example 1

[0072]

[0073]

[0074] Where “P” stands for Pass, meaning the test was passed, and “ / ” stands for Failed.

[0075] Table 5 shows the effects of silicate type and the ratio of silicate to soluble polytetrafluoroethylene on the fire-retardant coating. Compared to sodium silicate and potassium silicate, lithium silicate has poor thermal degeneration, resulting in poorer flame retardancy in the prepared composite communication cable. Sodium silicate, due to its lower modulus, is easily carbonized. The coating thickness variation indicates that the slurry formed by potassium silicate has better film-forming properties, allowing for faster drying during spraying and preventing slagging. Although the same process conditions were applied in different treatment groups, slagging inevitably affected the average thickness of the fire-retardant coating. Therefore, it can be concluded that the slurry formed by potassium silicate is inexpensive, has good film-forming properties, and good heat resistance.

[0076] Comparing groups 1 and 2 reveals that the flame-retardant properties of potassium silicate solution alone or the coating formed by soluble polytetrafluoroethylene alone are inferior to those of their combination. Different ratios of these solutions also result in varying flame-retardant properties; only a fire-retardant slurry formed at the appropriate ratio exhibits superior performance. In practical application, it has been observed that an inappropriate ratio—too thin—can lead to spots on the surface of the low-smoke halogen-free flame-retardant outer sheath 7; while too thick a ratio results in uneven spraying, with some areas thicker than others. Furthermore, this can significantly reduce the flame-retardant and abrasion-resistant properties of the prepared composite communication cable, possibly due to the uneven coating. Therefore, the test results show that potassium silicate aqueous solution and soluble polytetrafluoroethylene have a significant impact on the coating thickness and flame retardant properties. This may be because both potassium silicate and soluble polytetrafluoroethylene have excellent heat resistance. Generally, the heat resistance temperature of silicates is usually between 400℃ and 1000℃, while the long-term service temperature of soluble polytetrafluoroethylene is between -200℃ and 260℃. In addition, the coefficient of friction of soluble polytetrafluoroethylene is very small, which will affect the wear resistance of the coating.

[0077] Table 6. Test results of each treatment group and control group in Example 2

[0078]

[0079]

[0080] The experimental results in Table 6 show that the fire-retardant particles synergistically enhance each other's flame-retardant effect. The comparative group demonstrates that even a single fire-retardant particle possesses certain flame-retardant properties. Specifically, the carbon layer formed by expanded graphite after combustion provides insulation, inhibiting heat transfer to the matrix; nano-titanium dioxide increases the oxygen index of the matrix material, allowing amorphous carbon particles formed in the burning matrix to adhere to the nano-titanium dioxide during combustion, thus forming a barrier carbon layer; wollastonite, a calcium metasilicate mineral, forms a complete and dense ceramic layer on the surface of combustion products; and mica, a layered silicate mineral, also forms a dense ceramic layer. In summary, these four types of fire-retardant particles each possess their unique fire-retardant effects and functions.

[0081] This invention further optimizes the flame retardancy of the fire-retardant coating 8 by utilizing the properties of fire-retardant particles. Expanded graphite and nano-titanium dioxide have a significant synergistic flame-retardant effect, possibly because graphite expands to form worm-like graphite, and its expanded material has a low density, making it difficult to effectively block external oxygen. The introduction of nano-titanium dioxide can improve the regularity of the char layer and adsorb oxygen that expanded graphite cannot block, thereby delaying the thermal degradation process of the material. Similarly, wollastonite and mica can both form ceramic layers after combustion. When used in combination in a certain proportion, they undergo a eutectic reaction, which can further improve the flame retardant effect of the matrix material.

[0082] In summary, the combined communication cable prepared by the method of this invention has low smoke density and low toxicity, and possesses excellent high-temperature resistance and mechanical properties, meeting the application requirements of densely populated, important, and enclosed spaces such as cinemas, commercial centers, large data exchange centers, and high-rise buildings. Furthermore, when the rated or maximum operating temperature of this combined communication cable is 105°C, its normal service life is over 15 years.

[0083] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention, but such modifications or substitutions are all within the scope of protection of the present invention.

Claims

1. A method of making a combined communications cable, Characterized in that The method comprises the following steps: Step one, covering an outer sheath on the surface of a conductor base, the conductor base comprising wires; Step two, the surface temperature of the outer sheath is reduced to below 60℃, the surface of the outer sheath is sprayed with fireproof slurry, then the section with the fireproof slurry on the surface is subjected to drying treatment, the drying temperature is 70-85℃, the fireproof slurry forms a fireproof coating after drying; wherein, according to mass percentage, the outer sheath contains the following materials: polyethylene 55-65wt%, modified brucite fiber 12-16wt%, borax 4-7wt%, zinc oxide 2-4wt%, copper oxide 2-4wt%, ferric oxide 2-4wt%, antimony trioxide 2-4wt%, mesoporous silica 2-4wt%, the modified brucite fiber refers to brucite fiber modified by silane coupling agent; The fireproof slurry contains soluble polytetrafluoroethylene and silicate.

2. The method for preparing the combined communication cable according to claim 1, characterized in that: The fireproof slurry further contains fireproof particles, the fireproof particles comprising at least one of expanded graphite, nano titanium dioxide, wollastonite and mica.

3. The method for preparing the combined communication cable according to claim 1, characterized in that: In the step one, the outer sheath is covered on the surface of the conductor base by extrusion; during the extrusion of the outer sheath, the extruded section is directly subjected to cooling operation to form the outer sheath, then the section with the formed outer sheath on the surface is subjected to the spraying operation of the step two.

4. A combined communications cable, characterized by: The combined communication cable is prepared by the method for preparing the combined communication cable according to any one of claims 1-3.

5. The combined communications cable of claim 4 wherein: The thickness of the fireproof coating is less than 0.15mm.

6. The combined communications cable of claim 4 wherein: The conductor base comprises a plurality of wires and a filler, the filler filling the interspaces between the wires, the filler comprising at least one of talcum powder, antimony trioxide, red iron oxide and clay.

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