Optical cable belting material with high flame retardance and high resistivity

Abstract

The invention relates to an optical cable belting material with high flame retardance and high resistivity, and belongs to the technical field of flame-retardant materials. The preparation method of the optical cable belting material comprises the step of coating the calcium carbonate powder and the intumescent flame retardant on a base material through vinyl acetate-ethylene copolymer emulsion and water to obtain the optical cable belting material. When the optical cable belting material is combusted, the calcium carbonate powder and the intumescent flame retardant are subjected to chemical reaction in flame combustion to form a calcium metaphosphate / carbonaceous composite flame-retardant coating, and the flame-retardant coating is constructed by embedding lamellar calcium metaphosphate continuous networks in a carbon layer. The calcium metaphosphate continuous network can control the combustion process of the composite coating, and the peak heat release rate and the smoke generation rate are remarkably reduced; and the expansion degree and the structural uniformity of the carbon residues are effectively improved, and a conductive path of a carbon layer is destroyed, so that the surface resistivity of the flame-retardant coating is improved. The preparation process is simple, the coating performance is excellent, and the coating is suitable for high-flame-retardant and high-resistivity optical cable belting materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame-retardant materials, and particularly relates to a high-flame-retardant and high-resistivity optical cable wrapping material. BACKGROUND

[0002] With the continuous advancement of infrastructure construction, optical cable systems are increasingly widely used in energy transmission and distribution, information communication, rail transportation and other fields, and higher requirements are put forward for their flame retardancy and insulation performance in extreme environments such as fire. In particular, in complex use scenarios such as high-voltage operation and wiring in narrow spaces, cable wrapping not only needs to have excellent flame retardant performance, but also must maintain good electrical insulation at high temperatures to prevent safety hazards such as short circuit and electrical breakdown.

[0003] Intumescent flame retardants are widely used in flame-retardant coating materials due to their advantages of being halogen-free, environmentally friendly, and efficient in smoke suppression. Previous studies have shown that intumescent flame retardants can effectively improve the structure and flame retardant performance of residual carbon when combined with various inorganic additives. For example, Hu et al. (Carbon, 2022, 187: 290-301) combined intumescent flame retardants with layered hydroxides or montmorillonite, which significantly improved the integrity and fire resistance of the carbon layer; Zhang et al. (Construction and Building Materials, 2025, 489: 142439) constructed a dense carbon layer generated by the synergistic effect of fly ash and phosphorus-nitrogen flame retardants to improve the flame retardant effect; other studies have introduced nano-zinc borate to form a glassy barrier to improve thermal stability and suppress smoke generation (Progress in Organic Coatings, 2018, 123: 82-98). Although the above studies have made some progress in flame retardant efficiency, there are still obvious shortcomings in high-temperature electrical insulation performance.

[0004] To address this problem, several patents have proposed improvement schemes, such as CN11865291A, which introduces carbon nanotubes to enhance the mechanical properties of residual carbon, but its electrical conductivity may compromise the insulation properties of the material; CN119192974A uses expandable graphite, but its large particle size and poor dispersibility result in uneven residual carbon structure; CN119220174A improves the temperature resistance of residual carbon, but does not effectively interrupt the conductive network, and the electrical insulation performance is still not ideal. In summary, current flame-retardant coatings based on intumescent flame retardant systems are difficult to balance the high surface resistivity of residual carbon while improving the combustion suppression ability, and cannot meet the core demand for electrical insulation of optical cable wrapping materials in fire conditions.

[0005] To solve the above problems, the application discloses application of a flame-retardant coating with a continuous calcium metaphosphate network in high-flame-retardant and high-resistivity optical cable wrapping material, which has the following two advantages: (1) the stacking and connection of calcium metaphosphate layers help to regulate the formation behavior of carbon layers, so that the combustion process is slower, more uniform and complete, the peak heat release rate and smoke generation rate are significantly reduced, and a compact and highly expanded residual carbon layer is formed; (2) calcium metaphosphate is obtained by the reaction of calcium carbonate and intumescent flame retardant in the combustion process, and the continuous network of calcium metaphosphate is inserted in the residual carbon layer, which destroys the continuous conductive path of the carbon layer, effectively improves the surface resistivity of the residual carbon layer of the coating, and significantly improves the electrical insulation performance. The technical path provides a new solution for realizing the optical cable wrapping material with high flame retardancy and high insulation. SUMMARY

[0006] The application proposes application of a flame-retardant coating with a continuous calcium metaphosphate network structure in high-flame-retardant and high-resistivity optical cable wrapping material to solve the problem that the existing optical cable wrapping material has poor compatibility between flame-retardant performance and electrical insulation performance in a fire environment. Calcium carbonate powder, intumescent flame retardant, vinyl acetate-ethylene copolymer emulsion and water are mixed in a certain proportion to prepare a uniformly dispersed coating, which is applied to the surface of a substrate such as glass cloth or mica cloth by dipping coating or wire bar coating, and a high-flame-retardant and high-resistivity optical cable wrapping material is formed after drying. The vinyl acetate-ethylene copolymer emulsion acts as a binder to effectively promote the uniform distribution and adhesion of the calcium carbonate powder and the intumescent flame retardant on the surface of the substrate. The optical cable wrapping material undergoes a chemical reaction during combustion to become a composite flame-retardant coating material with a continuous calcium metaphosphate network embedded in the carbon layer, which has good flame-retardant and electrical insulation performance.

[0007] To achieve the above object, the application adopts the following technical scheme: A high-flame-retardant and high-resistivity optical cable wrapping material, the preparation of the optical cable wrapping material comprising: applying calcium carbonate powder and intumescent flame retardant on a substrate through vinyl acetate-ethylene copolymer emulsion and water to obtain the optical cable wrapping material; when the optical cable wrapping material burns, the calcium carbonate powder and the intumescent flame retardant undergo a chemical reaction in the flame combustion to form a calcium metaphosphate / carbon composite flame-retardant coating, and the flame-retardant coating is constructed by embedding a continuous network of lamellar calcium metaphosphate in the carbon layer.

[0008] Further, the calcium carbonate powder is derived from one or more of chemical synthesis calcium carbonate, calcium-rich biomass such as shells, oyster shells, crab shells and shrimp shells. The calcium-rich biomass needs to be finely processed to obtain calcium carbonate powder, and the fine processing method is one or more of grinding and ball milling, preferably ball milling. The particle size of the fine powder is 1-20 microns.

[0009] Further, the intumescent flame retardant is composed of an acid source, a carbon source and a gas source, wherein the acid source is one or more of phosphoric acid, boric acid and ammonium polyphosphate, preferably ammonium polyphosphate; the carbon source is one or more of pentaerythritol, dipentaerythritol and starch, preferably pentaerythritol; and the gas source is one or more of melamine, ammonium bicarbonate and melamine phosphate, preferably melamine.

[0010] Further, the mass ratio of the acid source, the carbon source and the gas source in the intumescent flame retardant is (1-3):(1-2):(1-2), preferably 2:1:1.

[0011] Further, the mass ratio of the calcium carbonate powder, the intumescent flame retardant, the vinyl acetate-ethylene copolymer emulsion and water is (0.5-10):(1-10):(10-30):(10-30), and the solid content of the vinyl acetate-ethylene copolymer emulsion is greater than or equal to 54.4%.

[0012] Further, the coating method is one or more of dip coating and wire bar coating, and the corresponding coating conditions are 3-10 minutes / 1-4 times and 10-200 microns / 1-4 times, respectively.

[0013] Further, the combustion method is one or more of ethanol / methane / propane / butane flame combustion and electric heating combustion.

[0014] Further, the substrate is one or more of glass cloth and mica cloth.

[0015] The beneficial effects of the present application are as follows: The present application provides an application of a flame-retardant coating with a continuous calcium metaphosphate network in a high-flame-retardant and high-resistivity optical cable wrapping material. The optical cable wrapping material can construct a continuous calcium metaphosphate network structure under the action of flame combustion, has excellent flame-retardant performance and high surface resistivity, and is suitable for optical cables, cables and other occasions with high requirements for heat resistance and insulation. The beneficial effects of the present application are as follows: (1) the calcium carbonate powder used is widely available, which can be obtained by chemical synthesis or prepared by fine processing of calcium-based biomass (such as oyster shell and shell), realizing the resource utilization of biological solid waste; (2) under high temperature conditions, calcium carbonate can react with phosphate in the intumescent flame retardant to generate calcium metaphosphate, which destroys the continuity of the carbon network and improves the insulation; (3) the intumescent flame retardant releases acid source, carbon source and gas source under high temperature to generate an expanded loose carbon layer, which cooperates with the continuous calcium metaphosphate network structure to block heat and combustion spread, improving the flame-retardant effect; (4) the preparation process of the present application is simple and can be produced on a large scale. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 X-ray diffraction, scanning electron microscopy and transmission electron microscopy images of oyster shell powder; Figure 2 TGA data plot for Example 1, Comparative Example 1; Figure 3 Digital photos and SEM images for Example 2, Comparative Example 2; Figure 4 X-ray diffraction pattern for Example 2, Comparative Example 2. DETAILED DESCRIPTION

[0017] In order to make the content of the present application more convenient to understand, the technical solutions described in the present application will be further described below in conjunction with specific embodiments, but the present application is not limited to this. In the following examples and comparative examples, the calcium carbonate powder used is derived from the refinement of calcium-based biomass; the preparation method of the refined calcium-based biomass is as follows: oyster shells are selected as the calcium-based biomass, and the oyster shells are refined by ball milling to obtain calcium carbonate powder, and the particle size of the refined powder is 1-20 microns.

[0018] Example 1 Take 1 part by weight of calcium carbonate powder, 9 parts by weight of intumescent flame retardant (composed of ammonium polyphosphate, melamine, and pentaerythritol in a mass ratio of 2:1:1), 10 parts by weight of water, and 10 parts by weight of vinyl acetate-ethylene copolymer emulsion, and mix and stir uniformly.

[0019] Pour the mixed solution into a mold, and then freeze-dry to obtain a calcium carbonate / intumescent flame retardant / vinyl acetate-ethylene copolymer composite material.

[0020] Example 2 Take 1 part by weight of calcium carbonate powder, 9 parts by weight of intumescent flame retardant (composed of ammonium polyphosphate, melamine, and pentaerythritol in a mass ratio of 2:1:1), 10 parts by weight of water, and 10 parts by weight of vinyl acetate-ethylene copolymer emulsion, and mix and stir uniformly.

[0021] Pour the mixed solution into a mold, and then freeze-dry to obtain a calcium carbonate / intumescent flame retardant / vinyl acetate-ethylene copolymer composite material.

[0022] Under a heat radiation intensity of 50 kW / m 2 After 400 seconds, a calcium metaphosphate / carbon composite material is obtained by burning the above composite material through electric spark heating.

[0023] Example 3 Take 1 part by weight of calcium carbonate powder, 9 parts by weight of intumescent flame retardant (composed of ammonium polyphosphate, melamine, and pentaerythritol in a mass ratio of 2:1:1), 10 parts by weight of water, and 10 parts by weight of vinyl acetate-ethylene copolymer emulsion, and mix and stir uniformly.

[0024] The above solution was coated on the glass fiber cloth using a wire bar coater, with a coating parameter of 15 microns / time, and a dosage of 0.050 g / cm 2 to obtain a tape wrapping material coated with calcium carbonate / intumescent flame retardant / ethylene-vinyl acetate copolymer.

[0025] The above tape wrapping material was burned using an ethanol flame (temperature 600~700℃) for 5 minutes to obtain a tape wrapping material with a calcium metaphosphate / carbon composite coating.

[0026] Example 4 Calcium carbonate powder 1 part by weight, intumescent flame retardant 9 parts by weight (consisting of ammonium polyphosphate, melamine, and pentaerythritol mixed in a mass ratio of 2:1:1), water 10 parts by weight, and ethylene-vinyl acetate copolymer emulsion 10 parts by weight were mixed and stirred uniformly.

[0027] The above solution was coated on the glass fiber cloth using a wire bar coater, with a coating parameter of 15 microns / time, and a dosage of 0.050 g / cm 2 to obtain a tape wrapping material coated with calcium carbonate / intumescent flame retardant / ethylene-vinyl acetate copolymer.

[0028] The above tape wrapping material was burned using an ethanol flame (temperature 600~700℃) for 5 minutes to obtain a tape wrapping material with a calcium metaphosphate / carbon composite coating.

[0029] Example 5 Calcium carbonate powder 1.5 parts by weight, intumescent flame retardant 8.5 parts by weight (consisting of ammonium polyphosphate, melamine, and pentaerythritol mixed in a mass ratio of 2:1:1), water 10 parts by weight, and ethylene-vinyl acetate copolymer emulsion 10 parts by weight were mixed and stirred uniformly.

[0030] The above solution was coated on the glass fiber cloth using a wire bar coater, with a coating parameter of 15 microns / time, and a dosage of 0.050 g / cm 2 to obtain a tape wrapping material coated with calcium carbonate / intumescent flame retardant / ethylene-vinyl acetate copolymer.

[0031] The above tape wrapping material was burned using an ethanol flame (temperature 600~700℃) for 5 minutes to obtain a tape wrapping material with a calcium metaphosphate / carbon composite coating.

[0032] Example 6 Calcium carbonate powder 2 parts by weight, intumescent flame retardant 8 parts by weight (consisting of ammonium polyphosphate, melamine, and pentaerythritol mixed in a mass ratio of 2:1:1), water 10 parts by weight, and ethylene-vinyl acetate copolymer emulsion 10 parts by weight were mixed and stirred uniformly.

[0033] The above solution was coated on the glass cloth using a wire bar coater, with a coating parameter of 15 microns / time, and a dosage of 0.05 g / cm 2 to obtain a tape wrapping material coated with calcium carbonate / intumescent flame retardant / ethylene-vinyl acetate copolymer.

[0034] The above tape wrapping material was burned using an ethanol flame (temperature 600-700°C) for 5 minutes to obtain a tape wrapping material with a calcium metaphosphate / carbon composite coating.

[0035] Comparative Example 1 Intumescent flame retardant 10 parts by weight (consisting of ammonium polyphosphate, melamine, and pentaerythritol mixed in a mass ratio of 2:1:1), water 10 parts by weight, and ethylene-vinyl acetate copolymer emulsion 10 parts by weight were mixed and stirred uniformly.

[0036] The mixed solution was poured into a mold, followed by freeze-drying, to obtain an intumescent flame retardant / ethylene-vinyl acetate copolymer composite material.

[0037] Comparative Example 2 Intumescent flame retardant 10 parts by weight (consisting of ammonium polyphosphate, melamine, and pentaerythritol mixed in a mass ratio of 2:1:1), water 10 parts by weight, and ethylene-vinyl acetate copolymer emulsion 10 parts by weight were mixed and stirred uniformly.

[0038] The mixed solution was poured into a mold, followed by freeze-drying, to obtain an intumescent flame retardant / ethylene-vinyl acetate copolymer composite material.

[0039] The above composite material was burned by electric spark heating at a thermal radiation intensity of 50 kW / m 2 for 400 seconds to obtain a carbon material.

[0040] Comparative Example 3 Intumescent flame retardant 10 parts by weight (consisting of ammonium polyphosphate, melamine, and pentaerythritol mixed in a mass ratio of 2:1:1), water 10 parts by weight, and ethylene-vinyl acetate copolymer emulsion 10 parts by weight were mixed and stirred uniformly.

[0041] The above solution was coated on the glass cloth using a wire bar coater, with a coating parameter of 15 microns / time, and a dosage of 0.05 g / cm 2 to obtain a tape wrapping material coated with intumescent flame retardant / ethylene-vinyl acetate copolymer.

[0042] The above tape wrapping material was burned using an ethanol flame (temperature 600-700°C) for 5 minutes to obtain a tape wrapping material with a carbon coating.

[0043] Performance Evaluation The cone calorimeter, surface resistivity and expansion degree of the prepared tape materials of the examples and comparative examples were tested, and the experimental steps were as follows: (1) Cone calorimeter A sample with a size of 100 mm x 100 mm x 4 mm was prepared, and a cone calorimeter test was performed on a cone calorimeter (FTT0007) according to the standard of ASTM E1354.

[0044] (2) Surface resistivity The surface resistance of the tape after burning was measured using a multimeter, and the surface resistivity was calculated according to the following formula.

[0045] In the formula, : surface resistivity; : surface resistance; : length of silver paste electrode; : distance of silver paste electrode.

[0046] (3) Expansion degree A sample with a size of 80 mm x 40 mm was prepared, and the surface of the sample was burned with an ethanol flame. The thickness of the coating was tested by an electronic vernier caliper, and the expansion degree was (thickness of residual carbon after burning - thickness of coating before burning) / thickness of coating before burning.

[0047] Test results Table 1. Comparison of cone calorimeter data of Example 1 and Comparative Example 1 Table 2. Comparison of surface resistivity and expansion degree of Examples 3-6 and Comparative Example 3 Result analysis The oyster shell was refined to obtain a powder, and the crystal phase of the powder was determined by X-ray diffraction. As shown in Figure 1 , the diffraction peaks of the powder correspond to the calcium carbonate standard card (CaCO3, PDF # 17-0763), Figure 1 , and Figure 1 , respectively, are scanning electron microscope and transmission electron microscope images, which show that the morphology is a flaky structure.

[0048] Figure 2 Table 1 and Table 2 are the test results of the composite coating prepared by Comparative Example 1 and Example 1 on the cone calorimeter. It can be seen that: (1) The peak heat release rate (PHRR) of Comparative Example 1 is 296 kW / m 2 , and the PHRR of Example 1 is significantly reduced to 135 kW / m 2The decrease was approximately 54.4%, indicating that the addition of calcium carbonate effectively suppressed the intense heat release during combustion. (2) The total heat release (THR) of Comparative Example 1 is 25.6 MJ / m 2 The THR of Example 1 increased slightly to 27.8 MJ / m³. 2 This indicates that calcium carbonate makes the combustion process of the composite coating more complete, thereby leading to an increase in THR; (3) Similarly, the total smoke production (TSP) of Example 1 was 4.54 m³. 2 Slightly higher than the TSP (4.37m) in Comparative Example 1. 2 But from Figure 2 Flue gas generation rate (SPR) and Figure 2 The trend of the TSP curve in Figure d shows that the flue gas release rate of Comparative Example 1 is faster and fluctuates more, while the flue gas release of Example 1 is more stable, which helps to improve the expansion degree of the residual char. This result also shows that calcium carbonate effectively regulates the combustion process of the composite material, making it slower, more uniform and more complete, thereby reducing PHRR and SPR and slightly increasing THR and TSP.

[0049] Figure 3 and Figure 4 The scanning electron microscope images and X-ray diffraction patterns of Example 2 and Comparative Example 2 show that: (1) The sample in Example 2 had uniformly expanded char residue, according to Figure 4 X-ray diffraction results indicate that the composition consists of calcium metaphosphate phase and carbon material. The formation of the calcium metaphosphate phase is due to the thermal decomposition of calcium carbonate and its reaction with the decomposition products of ammonium polyphosphate. Plate-like calcium metaphosphate is clearly visible in the residual carbon structure. Figure 3 The layers are interconnected and stacked to form a continuous calcium metaphosphate network, which can both suppress heat generation during combustion and cut off the conductive carbon layer to increase surface resistivity.

[0050] (2) Comparative Example 2 sample has a typical porous char structure. The pores are caused by non-flammable gases produced by the decomposition of melamine and ammonium polyphosphate. The pore size of Comparative Example 2 is larger and more uneven, which is due to the intense combustion of the intumescent flame retardant / vinyl acetate-ethylene copolymer composite material. From Figure 4 X-ray diffraction results indicate that the main component of the carbon residue is carbon material. Figure 3 Scanning electron microscopy images show that the carbon layer has high continuity, forming a good conductive path.

[0051] Table 2 is the surface resistivity and expansion degree comparison of the wrapping materials of Examples 3~6 and Comparative Example 3, it can be seen that: with the increase of the proportion of calcium carbonate in the formula, the surface resistivity of the sample is significantly improved, and the expansion degree gradually decreases. Among them, the surface resistivity of Example 6 is the highest, reaching 7.08*10 6 Ω, which is more than 18 times of that of Comparative Example 3, indicating that it has more excellent insulation performance; and the expansion degree of Example 3 is as high as 341.9%, which is significantly better than that of Comparative Example 3 (146.7%).

[0052] In summary, the application discloses the application of the flame-retardant coating with continuous calcium metaphosphate network in high-flame-retardant and high-resistivity optical / electrical cable wrapping materials. The calcium carbonate additive can make the composite coating burn more slowly, uniformly and completely, thereby forming a highly expanded structure. In addition, phase change occurs during the combustion of calcium carbonate, forming a continuous network of flaky calcium metaphosphate. Therefore, the highly expanded calcium metaphosphate / carbon composite coating material reduces the density and continuity of conductive carbon, significantly increases the surface resistivity of the residual carbon after combustion, and has a good application prospect in high-fire-safety optical / electrical cable wrapping materials.

[0053] The above is only the preferred embodiment of the application, and any equivalent changes and modifications made within the scope of the application should be included in the scope of the application.

Claims

1. A high flame retardant, high resistivity optical cable wrapping material, characterized in that, The preparation of the optical cable wrapping material comprises: applying calcium carbonate powder and intumescent flame retardant on the substrate through vinyl acetate-ethylene copolymer emulsion and water to obtain; when the optical cable wrapping material burns, the calcium carbonate powder and intumescent flame retardant chemically react to form a calcium metaphosphate / carbon composite flame-retardant coating in the flame combustion, and the flame-retardant coating is constructed by embedding a continuous network of lamellar calcium metaphosphate in a carbon layer.

2. A flame retardant, high resistivity optical cable wrapping material according to claim 1, wherein, The calcium carbonate powder is derived from chemical synthesis calcium carbonate or calcium-based biomass rich in calcium carbonate.

3. A flame retardant, high resistivity optical cable jacketing material according to claim 2, wherein The calcium-based biomass includes shells, oyster shells, crab shells and shrimp shells.

4. A flame retardant, high resistivity optical cable wrapping material according to claim 2, wherein The calcium-based biomass needs to be refined to obtain calcium carbonate powder, and the refinement method is one or more of grinding refinement and ball milling refinement, and the particle size of the refined powder is 1-20 microns.

5. A high flame retardant, high resistivity optical cable wrapping material according to claim 1, wherein, The intumescent flame retardant is composed of an acid source, a carbon source and a gas source, wherein the acid source is one or more of phosphoric acid, boric acid and ammonium polyphosphate; the carbon source is one or more of pentaerythritol, dipentaerythritol and starch; and the gas source is one or more of melamine, ammonium bicarbonate and melamine phosphate.

6. A flame retardant, high resistivity optical cable jacketing material according to claim 5, wherein, The mass ratio of the acid source, the carbon source and the gas source in the intumescent flame retardant is (1-3):(1-2):(1-2).

7. A high flame retardant, high resistivity optical cable wrapping material according to claim 1, wherein, The mass ratio of the calcium carbonate powder, the intumescent flame retardant, the vinyl acetate-ethylene copolymer emulsion and water is (0.5-10):(1-10):(10-30):(10-30).

8. A high flame retardant, high resistivity optical cable wrapping material according to claim 1, wherein, The solid content of the vinyl acetate-ethylene copolymer emulsion is >=54.4%.

9. A high flame retardant, high resistivity optical cable wrapping material according to claim 1, wherein, The coating method is one or more of dip coating and wire bar coating.

10. A high flame retardant, high resistivity optical cable wrapping material according to claim 1, wherein, The substrate is one or more of glass cloth and mica cloth.

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