High-temperature-resistant low-smoke zero halogen flame-retardant twisted-pair cable for building security system, and manufacturing method therefor

Abstract

The present invention relates to the technical field of cables, and provides a high-temperature-resistant low-smoke zero halogen flame-retardant twisted-pair cable for a building security system, and a manufacturing method therefor. Magnesium hydroxide is modified using a sol-gel method, and the surface of the magnesium hydroxide is coated with silicon dioxide, enabling the magnesium hydroxide to have an excellent hydration effect and a radical scavenging capability at a high temperature, thereby improving flame retardancy and smoke suppression performance. In addition, based on alkali lignin, a phosphorus-nitrogen structure and a phosphate ester group are introduced by means of the chemical modification using phosphonitrilic chloride trimer and triphenyl phosphate, and the thermal stability and carbonization capability of lignin are significantly enhanced under the catalytic action of titanium dioxide, thereby forming a dense carbonized protective layer to block oxygen and heat. Two flame-retardant materials are melted and mixed separately to finally obtain a low-smoke zero halogen flame-retardant cable. The cable material has both excellent flame retardancy and low smoke emission properties, and is suitable for building security systems having high security requirements.

Description

A high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems and its preparation method. Technical Field

[0001] This invention belongs to the field of cable technology and relates to a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems and its preparation method. Background Technology

[0002] Modern building security systems bear the important responsibility of ensuring building safety and the safety of people and property. However, traditional cables may pose several hidden dangers under extreme conditions such as fires: traditional cables are prone to combustion in fires, releasing large amounts of heat and accelerating the spread of fire; the halogen materials used in traditional cables produce toxic gases when burning, harming human health; and the large amount of smoke released during combustion hinders evacuation and rescue efforts. Therefore, there is a need to develop a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems and its preparation method. The method involves preparing modified magnesium hydroxide via a sol-gel method, introducing a silica coating layer on its surface to enhance flame retardancy and smoke suppression properties. Simultaneously, alkaline lignin is used as a raw material, modified with hexachlorocyclotriphosphazene and triphenyl phosphate to introduce phosphorus-nitrogen structures and phosphate groups. Furthermore, titanium dioxide is used to catalyze a carbonization reaction, enhancing the heat resistance and carbonization ability of the lignin, thereby meeting the needs of actual production.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] In a first aspect, the present invention provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, wherein the preparation method comprises:

[0006] Step S1: Under N2 atmosphere, 2,5-dihydroxybenzoic acid is dispersed in dimethyl sulfoxide and mixed evenly. Then, N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide are added and stirred continuously at the first stirring speed. The mixture is heated to the first temperature to fully react. After the reaction is completed, the mixture is washed and distilled to obtain product A.

[0007] Step S2: Add Mg(OH)2 and emulsifier to an ethanol aqueous solution, heat to a second temperature, add sodium hydroxide solution to adjust the pH to 10, add tetraethyl orthosilicate, and react fully at the second temperature. After the reaction is complete, wash and filter, and dry under vacuum at a third temperature to obtain modified Mg(OH)2.

[0008] Step S3: Modified Mg(OH)2 and triethylamine are dispersed in dimethyl sulfoxide. After heating to the second temperature, product A is added and reacted completely. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at the fourth temperature to obtain Mg(OH)2 flame retardant.

[0009] In step S4, under an N2 atmosphere, alkaline lignin is dissolved in N,N-dimethylformamide and stirred continuously at the second stirring speed. Pyridine is added and stirring continues to obtain a mixed solution. Hexachlorocyclotriphosphazene and triphenyl phosphate are dispersed separately in N,N-dimethylformamide and then added to the mixed solution. Metaphosphoric acid, melamine cyanurate and titanium dioxide are then added. The temperature is raised to the fourth temperature and stirred continuously at the second stirring speed. After the reaction is completed, the mixture is filtered and washed, and then dried thoroughly at the fifth temperature to obtain flame-retardant lignin.

[0010] Step S5: Mix Mg(OH)2 flame retardant, ethylene-vinyl acetate copolymer, vinyl silane and zinc stearate in proportion, and feed them into a twin-screw extruder. Melt and mix them at the sixth temperature to obtain the insulation layer material. Feed flame retardant lignin, low-density polyethylene, antioxidant 1010, UV-329 and zinc stearate into a second twin-screw extruder. Melt and mix them at the seventh temperature to obtain the sheath layer material. Coat the insulation layer material and the sheath layer material evenly onto the surface of the battery core in sequence. Then mechanically twist the two coated cables together to obtain a high-temperature resistant, low-smoke, halogen-free flame-retardant twisted pair cable for building security systems.

[0011] 2,5-Dihydroxybenzoic acid contains a carboxyl group and a benzene ring. The carboxyl group itself is a relatively stable functional group with low reactivity. N,N'-dicyclohexylcarbodiimide reacts with the carboxyl group of the carboxylic acid to form a carboxylic acid acyl intermediate, releasing dicyclohexylurea. This carboxylic acid acyl intermediate is more reactive than the original carboxyl group and readily reacts with other reactants. N-hydroxysuccinimide can form an N-hydroxysuccinimide ester with the generated carboxylic acid acyl intermediate, enhancing its reactivity and enabling it to undergo nucleophilic reactions with other compounds containing nucleophilic groups. Simultaneously, 2,5-dihydroxybenzoic acid and its derivatives contain a phenolic hydroxyl structure. The phenolic hydroxyl group has strong reducing properties and can neutralize free radicals by donating electrons. Free radicals are generated during fires and promote combustion reactions. By reacting with these free radicals, the phenolic hydroxyl group of 2,5-dihydroxybenzoic acid can effectively inhibit oxidation reactions, forming stable phenolic free radicals, thereby breaking the chain reaction of free radicals. This not only reduces oxidation reactions but also decreases the release of harmful gases during pyrolysis, reduces smoke production, slows down the thermal degradation of materials, and lowers the combustion rate in fires. Furthermore, under high-temperature conditions, compounds containing phenolic hydroxyl groups can interact with the matrix material through hydrogen bonding and π-π stacking, forming a more stable polymer network. The phenolic hydroxyl group, a group with a hydrogen bond donor, has a strong electron affinity. Phenolic hydroxyl molecules can form hydrogen bonds and interact with the molecular chains of other materials through these bonds, thereby enhancing the material's structure and properties. 2,5-Dihydroxybenzoic acid has an aromatic ring structure. Due to the presence of its electron cloud, aromatic rings have a strong π-π stacking ability; that is, benzene rings can attract each other through π-π interactions, forming a relatively stable structure, thus restricting the movement of molecular chains at high temperatures and enhancing the material's heat resistance.

[0012] Hydration is one of the key mechanisms by which magnesium hydroxide exerts its flame-retardant effect at high temperatures. The structure of Mg(OH)₂ contains abundant hydroxyl groups. During heating, the water molecules released when Mg(OH)₂ decomposes form hydrates on the surface of magnesium oxide, increasing its thermal stability. When heat from the fire source is transferred to magnesium oxide, these hydrates are gradually released, providing a sustained cooling effect. This process not only reduces the temperature of the fire source but also inhibits oxidation reactions at high temperatures through evaporative cooling. The hydroxyl groups on the surface of Mg(OH)₂ can interact with emulsifiers, modifying the hydrophilicity of the magnesium hydroxide surface and improving its compatibility with other materials. Hexadecyltrimethylammonium bromide, with its hydrophilic amino groups and lipophilic alkyl chains in solution, can adsorb onto the surface of magnesium hydroxide, helping to improve the dispersibility of Mg(OH)₂. Simultaneously, by forming a charge-shielding layer and through hydrophobic interactions, hexadecyltrimethylammonium bromide can reduce the attractive forces between magnesium hydroxide particles, thereby preventing particle aggregation and ensuring its uniform dispersion in the solution. Tetraethyl orthosilicate hydrolyzes under alkaline conditions to form silanol groups. These silanol groups further undergo a condensation reaction with the hydroxyl groups on the surface of magnesium hydroxide. The resulting Si-O-Mg bonds are very stable, allowing a silicate layer to form on the surface of Mg(OH)₂, further improving its thermal stability and fire resistance. Furthermore, tetraethyl orthosilicate can react with itself to form silicon-oxygen chains, creating a three-dimensional silicon-oxygen network structure on the Mg(OH)₂ surface, further enhancing the thermal stability of magnesium hydroxide.

[0013] The modified Mg(OH)₂ surface possesses siloxy groups, which can undergo condensation reactions with the hydroxyl or phenolic hydroxyl groups in product A to form Mg–O–Si or Si–O–Si bonds. Triethylamine, acting as a basic catalyst, promotes the condensation reaction between the siloxy groups and hydroxyl groups, further cross-linking the modified Mg(OH)₂ in the matrix to form a stable cross-linked network. This cross-linked network restricts the thermal motion of molecular chains at high temperatures, thereby slowing down the decomposition rate of the material. Simultaneously, the cross-linked structure can better withstand high temperatures and inhibit heat conduction through enhanced thermal shielding. The phenolic hydroxyl groups in product A decompose at high temperatures, capturing free radicals in the flame and reducing the chain propagation of the combustion reaction. Mg(OH)₂ decomposes at high temperatures, releasing water vapor, diluting the oxygen concentration and cooling the combustion zone. The decomposition product (MgO) of Mg(OH)₂ forms a heat-insulating protective layer on the material surface, combining with the char layer formed by the decomposition of product A, enhancing the density and stability of the char layer. Aromatic rings promote the charring reaction during decomposition, thus forming a higher-quality char layer. The combination of these two factors gives the flame retardant both physical and chemical flame-retardant mechanisms, enhancing its flame-retardant effect.

[0014] Lignin contains a large number of phenolic hydroxyl and carboxyl groups. Hexachlorocyclotriphosphazene has a tricyclic structure, with each phosphorus atom connected by a nitrogen atom to form a closed ring. The chlorine atom on the phosphorus atom is the active center and can undergo nucleophilic substitution reaction. The phenolic hydroxyl group in lignin is a nucleophilic group that can attack the phosphorus atom in hexachlorocyclotriphosphazene, replacing the chloride ion on the phosphorus atom and generating a new chemical bond -P=N. The -P=N bond is a polar chemical bond with high chemical and thermal stability. The introduction of this structure not only increases the phosphorus content of lignin but also enhances the heat resistance of the material during combustion. At the same time, it can capture free radicals in the flame and inhibit the combustion chain reaction. Triphenyl phosphate consists of one phosphate group and three phenol groups. The hydroxyl or phenolic hydroxyl groups at the phosphate center are highly reactive and can undergo esterification with the hydroxyl groups of lignin. The phenolic hydroxyl groups of lignin act as nucleophiles, attacking the phosphorus atom in triphenyl phosphate, and the phenolic group is replaced to form a phosphate bond. The resulting phosphate bond has excellent thermal stability at high temperatures and can release phosphoric acid and its derivatives during combustion, promoting the formation of a char layer at high temperatures while preventing the release of flammable gases. Melamine cyanurate provides a high nitrogen content due to the cyanuric acid in it. The melamine moiety has excellent char-forming properties, forming a thermally stable nitrogen heterocyclic structure. During combustion, it decomposes and releases inert gases, which dilute oxygen and provide cooling. The phosphoric acid products and nitrogen heterocyclic structure can capture free radicals generated during combustion, inhibiting the combustion chain reaction. Simultaneously, the oxygen vacancies on the TiO2 surface can adsorb small molecular intermediates produced by lignin decomposition, lowering the activation energy of these intermediates and promoting dehydration, decarboxylation, or condensation reactions on the surface, accelerating the carbonization process and forming a dense char layer.

[0015] As a preferred technical solution of the present invention, in step S1, the mass fraction of 2,5-dihydroxybenzoic acid is 5-10 parts, for example, it can be 5.0 parts, 5.5 parts, 6.0 parts, 6.5 parts, 7.0 parts, 7.5 parts, 8.0 parts, 8.5 parts, 9.0 parts, 9.5 parts or 10.0 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] In some optional instances, the dimethyl sulfoxide is in the range of 100-120 parts by mass, for example, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118 or 120 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] In some alternative instances, the N,N'-dicyclohexylcarbodiimide is in the range of 7-9 parts by mass, for example, 7.0, 7.2, 7.4, 7.6, 7.8, 8.0, 8.2, 8.4, 8.6, 8.8, or 9.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] In some alternative instances, the N-hydroxysuccinimide is present in parts by weight of 4-6 parts, for example, 4.0 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts, 5.0 parts, 5.2 parts, 5.4 parts, 5.6 parts, 5.8 parts, or 6.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0019] In some optional instances, the first stirring speed is 300-400 rpm, for example, it can be 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm or 400 rpm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0020] In some optional instances, the stirring time for the first stirring speed is 2-3 hours, for example, it can be 2.0 hours, 2.1 hours, 2.2 hours, 2.3 hours, 2.4 hours, 2.5 hours, 2.6 hours, 2.7 hours, 2.8 hours, 2.9 hours or 3.0 hours, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0021] In some alternative instances, the first temperature is 50-60°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C or 60°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0022] In some alternative instances, the reaction time at the first temperature is 4-5 hours, for example, 4.0 hours, 4.1 hours, 4.2 hours, 4.3 hours, 4.4 hours, 4.5 hours, 4.6 hours, 4.7 hours, 4.8 hours, 4.9 hours, or 5.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of the present invention, in step S2, the mass parts of Mg(OH)2 are 80-100 parts, for example, 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, 94 parts, 96 parts, 98 parts or 100 parts, but are not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] In some alternative examples, the emulsifier is cetyltrimethylammonium bromide in parts by weight of 2-5 parts, for example, 2.0 parts, 2.3 parts, 2.6 parts, 2.9 parts, 3.2 parts, 3.5 parts, 3.8 parts, 4.1 parts, 4.4 parts, 4.7 parts or 5.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some alternative instances, the ethanol-water solution is in the range of 400-500 parts by mass, for example, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490 or 500 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0026] In some alternative instances, the second temperature is 40-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0027] In some alternative examples, the sodium hydroxide solution has a mass fraction of 10-15 wt.%, for example, 10.0 wt.%, 10.5 wt.%, 11.0 wt.%, 11.5 wt.%, 12.0 wt.%, 12.5 wt.%, 13.0 wt.%, 13.5 wt.%, 14.0 wt.%, 14.5 wt.%, or 15.0 wt.%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some alternative instances, the tetraethyl orthosilicate is in the range of 25-35 parts by weight, for example, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34 or 35 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0029] In some alternative instances, the reaction time after the addition of tetraethyl orthosilicate is 4-5 h, for example, 4.0 h, 4.1 h, 4.2 h, 4.3 h, 4.4 h, 4.5 h, 4.6 h, 4.7 h, 4.8 h, 4.9 h, or 5.0 h, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0030] In some optional instances, the third temperature is 100-120°C, for example, it can be 100°C, 102°C, 104°C, 106°C, 108°C, 110°C, 112°C, 114°C, 116°C, 118°C or 120°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] In some optional instances, the vacuum drying time at the third temperature is 8-10 h, for example, it can be 8.0 h, 8.2 h, 8.4 h, 8.6 h, 8.8 h, 9.0 h, 9.2 h, 9.4 h, 9.6 h, 9.8 h or 10.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0032] As a preferred technical solution of the present invention, in step S3, the mass part of the modified Mg(OH)2 is 80-100 parts, for example, it can be 80 parts, 82 parts, 84 parts, 86 parts, 88 parts, 90 parts, 92 parts, 94 parts, 96 parts, 98 parts or 100 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] In some alternative instances, the triethylamine is in parts by weight of 1-2 parts, for example, 1.0 parts, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, or 2.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0034] In some optional instances, the dimethyl sulfoxide is in the range of 200-220 parts by weight, for example, 200 parts, 202 parts, 204 parts, 206 parts, 208 parts, 210 parts, 212 parts, 214 parts, 216 parts, 218 parts or 220 parts, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0035] In some alternative instances, the second temperature is 40-50°C, for example, it can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C or 50°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some alternative instances, the product A is 5-10 parts by mass, for example, 5.0 parts, 5.5 parts, 6.0 parts, 6.5 parts, 7.0 parts, 7.5 parts, 8.0 parts, 8.5 parts, 9.0 parts, 9.5 parts, or 10.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0037] In some alternative instances, the reaction time after the addition of product A is 4-6 h, for example, it can be 4.0 h, 4.2 h, 4.4 h, 4.6 h, 4.8 h, 5.0 h, 5.2 h, 5.4 h, 5.6 h, 5.8 h or 6.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] In some optional instances, the fourth temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In some optional instances, the drying time at the fourth temperature is 8-10 hours, for example, 8.0 hours, 8.2 hours, 8.4 hours, 8.6 hours, 8.8 hours, 9.0 hours, 9.2 hours, 9.4 hours, 9.6 hours, 9.8 hours, or 10.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0040] As a preferred technical solution of the present invention, in step S4, the mass fraction of the alkaline lignin is 20-30 parts, for example, it can be 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts or 30 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0041] In some optional instances, the N,N-dimethylformamide is in the range of 400-450 parts by weight, for example, 400 parts, 405 parts, 410 parts, 415 parts, 420 parts, 425 parts, 430 parts, 435 parts, 440 parts, 445 parts or 450 parts, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0042] In some optional instances, the second stirring speed is 200-300 rpm, for example, it can be 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm or 300 rpm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0043] In some optional instances, the stirring time for the second stirring speed is 20-30 min, for example, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] In some alternative instances, the pyridine is in the range of 40-50 parts by mass, for example, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0045] In some optional instances, the stirring time after the addition of pyridine is 10-20 min, for example, 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0046] In some optional instances, the hexachlorocyclotriphosphazene is in the range of 15-25 parts by weight, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 parts, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] In some alternative examples, the triphenyl phosphate is in the form of 10-15 parts by weight, for example, 10.0 parts, 10.5 parts, 11.0 parts, 11.5 parts, 12.0 parts, 12.5 parts, 13.0 parts, 13.5 parts, 14.0 parts, 14.5 parts or 15.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0048] In some alternative examples, the N,N-dimethylformamide used to dissolve hexachlorocyclotriphosphazene and triphenyl phosphate is in the range of 60-80 parts by weight, for example, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 80 parts by weight, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0049] In some alternative instances, the metaphosphoric acid is 10-15 parts by mass, for example, 10.0 parts, 10.5 parts, 11.0 parts, 11.5 parts, 12.0 parts, 12.5 parts, 13.0 parts, 13.5 parts, 14.0 parts, 14.5 parts, or 15.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0050] In some alternative instances, the melamine cyanurate is in the range of 5-10 parts by weight, for example, 5.0 parts, 5.5 parts, 6.0 parts, 6.5 parts, 7.0 parts, 7.5 parts, 8.0 parts, 8.5 parts, 9.0 parts, 9.5 parts, or 10.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0051] In some alternative examples, the titanium dioxide is 3-5 parts by mass, for example, 3.0 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4.0 parts, 4.2 parts, 4.4 parts, 4.6 parts, 4.8 parts or 5.0 parts, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0052] In some optional instances, the fourth temperature is 80-90°C, for example, it can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0053] In some optional instances, the second stirring speed is 200-300 rpm, for example, it can be 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm or 300 rpm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0054] In some optional instances, the stirring reaction time at the fourth temperature is 6-8 h, for example, it can be 6.0 h, 6.2 h, 6.4 h, 6.6 h, 6.8 h, 7.0 h, 7.2 h, 7.4 h, 7.6 h, 7.8 h or 8.0 h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0055] In some optional instances, the fifth temperature is 60-70°C, for example, it can be 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C or 70°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0056] In some optional instances, the drying time at the fifth temperature is 12-14 hours, for example, 12.0 hours, 12.2 hours, 12.4 hours, 12.6 hours, 12.8 hours, 13.0 hours, 13.2 hours, 13.4 hours, 13.6 hours, 13.8 hours, or 14.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0057] As a preferred technical solution of the present invention, in step S5, the mass fraction of the Mg(OH)2 flame retardant is 20-30 parts, for example, it can be 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts or 30 parts, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] In some alternative examples, the ethylene-vinyl acetate copolymer is in the range of 70-80 parts by weight, for example, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 or 80 parts, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0059] In some alternative instances, the vinylsilane is in the form of 2-3 parts by weight, for example, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, or 3.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0060] In some alternative instances, the zinc stearate is 1-2 parts by weight, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0061] In some optional instances, the sixth temperature is 160-180°C, for example, it can be 160°C, 162°C, 164°C, 166°C, 168°C, 170°C, 172°C, 174°C, 176°C, 178°C or 180°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0062] In some optional instances, the screw speed of the insulating layer material is 100-150 rpm, for example, 100 rpm, 105 rpm, 110 rpm, 115 rpm, 120 rpm, 125 rpm, 130 rpm, 135 rpm, 140 rpm, 145 rpm or 150 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0063] In some optional instances, the mixing time of the insulating layer material is 20-30 min, for example, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0064] In some optional instances, the flame-retardant lignin is in the range of 15-25 parts by weight, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0065] In some optional instances, the flame-retardant lignin is in the range of 15-25 parts by weight, for example, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0066] In some alternative instances, the low-density polyethylene is in the range of 75-85 parts by weight, for example, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84 or 85 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0067] In some alternative instances, the antioxidant 1010 is present in parts by weight of 2-3 parts, for example, 2.0 parts, 2.1 parts, 2.2 parts, 2.3 parts, 2.4 parts, 2.5 parts, 2.6 parts, 2.7 parts, 2.8 parts, 2.9 parts, or 3.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0068] In some alternative instances, the mass fraction of UV-329 is 1-2 parts, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0069] In some alternative instances, the zinc stearate is 1-2 parts by weight, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 parts, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0070] In some optional instances, the seventh temperature is 140-160°C, for example, it can be 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C or 160°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0071] In some optional instances, the screw speed of the sheath material is 100-150 rpm, for example, 100 rpm, 105 rpm, 110 rpm, 115 rpm, 120 rpm, 125 rpm, 130 rpm, 135 rpm, 140 rpm, 145 rpm or 150 rpm, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0072] In some optional instances, the mixing time of the sheath material is 20-30 min, for example, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0073] Secondly, the present invention provides a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, prepared according to the preparation method described in the first aspect.

[0074] Thirdly, the present invention provides a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for use in building security systems.

[0075] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0076] (1) Modified Mg(OH)2 decomposes at high temperature to release water vapor and absorb a large amount of heat, significantly reducing the surface temperature of the material. At the same time, the silicate coating on the surface forms a dense protective layer at high temperature, effectively isolating oxygen and heat and inhibiting flame spread. (2) The introduction of flame-retardant lignin with phosphorus-nitrogen structure allows the phosphoric acid derivative generated by the decomposition of hexachlorocyclotriphosphazene at high temperature to catalyze the carbonization of the material. Meanwhile, the gas released by the decomposition of nitrides plays a diluting role in the combustion zone. This synergistic effect of chemical reaction effectively interrupts the combustion chain reaction. (3) The flame-retardant lignin introduces phosphorus content through phosphoric acid esterification reaction. Combined with the catalytic effect of titanium dioxide, it rapidly carbonizes at high temperature to form a dense carbon layer, which not only insulates against heat and oxygen but also seals the release channels of volatile organic compounds, reducing smoke generation from the source. Attached Figure Description

[0077] Figure 1 is a flowchart of a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to Embodiments 1-6 of the present invention;

[0078] Figure 2 is a SEM image of the Mg(OH)2 flame retardant prepared in Example 1 of the present invention. Detailed Implementation

[0079] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein.

[0080] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products, and their brand names, specifications, and manufacturer information are as follows:

[0081] N2, purity ≥99%, Suzhou Chengan Gas Products Co., Ltd.;

[0082] 2,5-Dihydroxybenzoic acid, purity ≥99%, Shanghai Sanmei Chemical Co., Ltd.

[0083] Dimethyl sulfoxide, purity ≥99%, Zhuzhou Hansen Chemical Co., Ltd.;

[0084] N,N'-Dicyclohexylcarbodiimide, purity ≥99%, Zibo Tiantangshan Chemical Co., Ltd.;

[0085] N-hydroxysuccinimide, purity ≥99%, Hubei Hongfuda Biotechnology Co., Ltd.;

[0086] Mg(OH)2, purity ≥99%, Weifang Haililong Magnesium Industry Co., Ltd.;

[0087] Hexadecyltrimethylammonium bromide, purity ≥98%, Shandong Kerui Chemical Co., Ltd.;

[0088] Ethanol, purity ≥99%, Yonghua Chemical Co., Ltd.;

[0089] Sodium hydroxide, purity ≥99%, Tianjin Chengyuan Chemical Co., Ltd.

[0090] Tetraethyl orthosilicate, purity ≥99%, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0091] Triethylamine, purity ≥99%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0092] Alkaline lignin, purity ≥99%, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0093] N,N-Dimethylformamide, purity ≥99%, Shandong Aowei Chemical Co., Ltd.;

[0094] Pyridine, purity ≥99%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0095] Hexachlorocyclotriphosphazene, purity ≥99%, Shandong Zeshi New Material Technology Co., Ltd.;

[0096] Triphenyl phosphate, purity ≥99%, Zhangjiagang Yarui Chemical Co., Ltd.

[0097] Melamine cyanurate, purity ≥99%, Zhejiang Xusen Flame Retardant Co., Ltd.

[0098] Titanium dioxide, purity ≥99%, Henan Longxing Titanium Industry Technology Co., Ltd.;

[0099] Ethylene-vinyl acetate copolymer, purity ≥99%, Wenzhou Huatai Hot Melt Adhesive Co., Ltd.

[0100] Vinylsilane, purity ≥99%, Shandong Silicon Science New Materials Co., Ltd.

[0101] Zinc stearate, free fatty acids (calculated as stearic acid) ≤0.8%, Zanyu Technology Group Co., Ltd.

[0102] Low-density polyethylene, purity ≥99%, ExxonMobil Chemical;

[0103] Antioxidant 1010, purity ≥99%, Tianjin Lianlong New Material Co., Ltd.;

[0104] UV-329, purity ≥99%, Nanjing Milan Chemical Co., Ltd.;

[0105] All other raw materials can be purchased on the market.

[0106] Example 1

[0107] This embodiment provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, as shown in Figure 1. The preparation method specifically includes the following steps:

[0108] In step S1, under a N2 atmosphere, 7.3 parts of 2,5-dihydroxybenzoic acid were dispersed in 112 parts of dimethyl sulfoxide and mixed evenly. Then, 8.6 parts of N,N'-dicyclohexylcarbodiimide and 5.1 parts of N-hydroxysuccinimide were added, and the mixture was stirred continuously at 330 rpm for 2.6 h. The temperature was raised to 54 °C and the reaction was allowed to proceed for 4.3 h. After the reaction was completed, the product was washed and distilled to obtain product A.

[0109] In step S2, 87 parts of Mg(OH)2 and 3.8 parts of hexadecyltrimethylammonium bromide were added to 430 parts of an aqueous ethanol solution, the temperature was raised to 44°C, 12.3 wt.% sodium hydroxide solution was added to adjust the pH to 10, 29 parts of tetraethyl orthosilicate were added, and the mixture was reacted at 44°C for 4.2 h. After the reaction was completed, the mixture was washed and filtered, and then dried under vacuum at 108°C for 9.1 h to obtain modified Mg(OH)2.

[0110] Step S3: 84 parts of modified Mg(OH)2 and 1.6 parts of triethylamine are dispersed in 209 parts of dimethyl sulfoxide. After heating to 46°C, 7.2 parts of product A are added and reacted completely for 4.6 hours. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at 83°C for 8.7 hours to obtain Mg(OH)2 flame retardant.

[0111] In step S4, under a N2 atmosphere, 23 parts of alkaline lignin were dissolved in 410 parts of N,N-dimethylformamide and stirred continuously at 230 rpm for 23 min. Then, 43 parts of pyridine were added and stirring was continued for 14 min to obtain a mixed solution. 19 parts of hexachlorocyclotriphosphazene and 13 parts of triphenyl phosphate were dispersed in 68 parts of N,N-dimethylformamide respectively. After dispersion, they were added to the mixed solution. Then, 11.6 parts of metaphosphoric acid, 7.1 parts of melamine cyanurate and 4.2 g of titanium dioxide were added. The temperature was raised to 86 °C and the reaction was stirred continuously at 230 rpm for 6.8 h. After the reaction was completed, the mixture was filtered and washed, and then dried thoroughly at 63 °C for 13.4 h to obtain flame-retardant lignin.

[0112] In step S5, 21 parts of Mg(OH)2 flame retardant, 74 parts of ethylene-vinyl acetate copolymer, 2.2 parts of vinyl silane, and 1.6 parts of zinc stearate are mixed in proportion and fed into a twin-screw extruder. The mixture is melt-mixed at 168°C with a screw speed of 130 rpm for 22 minutes to obtain the insulation layer material. Then, 17 parts of flame-retardant lignin, 79 parts of low-density polyethylene, 2.4 parts of antioxidant 1010, 1.5 parts of UV-329, and 1.3 parts of zinc stearate are fed into a second twin-screw extruder. The mixture is melt-mixed at 146°C with a screw speed of 120 rpm for 22 minutes to obtain the sheath layer material. The insulation layer material and the sheath layer material are then uniformly coated onto the surface of the battery core. Finally, the two coated cables are mechanically twisted together to obtain a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems.

[0113] Figure 2 is a SEM image of the Mg(OH)2 flame retardant prepared in this embodiment.

[0114] Example 2

[0115] This embodiment provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, as shown in Figure 1. The preparation method specifically includes the following steps:

[0116] In step S1, under a N2 atmosphere, 5.9 parts of 2,5-dihydroxybenzoic acid were dispersed in 104 parts of dimethyl sulfoxide and mixed evenly. Then, 7.3 parts of N,N'-dicyclohexylcarbodiimide and 4.3 parts of N-hydroxysuccinimide were added, and the mixture was stirred continuously at 310 rpm for 2.2 h. The temperature was raised to 52 °C and the reaction was allowed to proceed for 4.1 h. After the reaction was completed, the product was washed and distilled to obtain product A.

[0117] In step S2, 82 parts of Mg(OH)2 and 2.5 parts of hexadecyltrimethylammonium bromide were added to 410 parts of an aqueous ethanol solution, the temperature was raised to 41°C, 11.6 wt.% sodium hydroxide solution was added to adjust the pH to 10, 26 parts of tetraethyl orthosilicate were added, and the mixture was reacted at 41°C for 4.5 h. After the reaction was completed, the mixture was washed and filtered, and then dried under vacuum at 103°C for 9.5 h to obtain modified Mg(OH)2.

[0118] Step S3: 87 parts of modified Mg(OH)2 and 1.3 parts of triethylamine are dispersed in 213 parts of dimethyl sulfoxide. After heating to 42°C, 6.1 parts of product A are added and reacted completely for 4.5 h. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at 86°C for 8.9 h to obtain Mg(OH)2 flame retardant.

[0119] In step S4, under a N2 atmosphere, 25 parts of alkaline lignin were dissolved in 420 parts of N,N-dimethylformamide and stirred continuously at 250 rpm for 26 min. Then, 42 parts of pyridine were added and stirring was continued for 12 min to obtain a mixed solution. 17 parts of hexachlorocyclotriphosphazene and 16 parts of triphenyl phosphate were dispersed in 64 parts of N,N-dimethylformamide respectively. After dispersion, they were added to the mixed solution. Then, 10.6 parts of metaphosphoric acid, 6.1 parts of melamine cyanurate and 3.2 g of titanium dioxide were added. The temperature was raised to 82 °C and the reaction was stirred continuously at 250 rpm for 6.4 h. After the reaction was completed, the mixture was filtered and washed, and then dried thoroughly at 66 °C for 12.6 h to obtain flame-retardant lignin.

[0120] In step S5, 23 parts of Mg(OH)2 flame retardant, 76 parts of ethylene-vinyl acetate copolymer, 2.5 parts of vinyl silane, and 1.2 parts of zinc stearate are mixed in proportion and fed into a twin-screw extruder. The mixture is melt-mixed at 164°C with a screw speed of 110 rpm for 26 minutes to obtain the insulation layer material. Then, 19 parts of flame-retardant lignin, 77 parts of low-density polyethylene, 2.2 parts of antioxidant 1010, 1.3 parts of UV-329, and 1.5 parts of zinc stearate are fed into a second twin-screw extruder. The mixture is melt-mixed at 151°C with a screw speed of 130 rpm for 24 minutes to obtain the sheath layer material. The insulation layer material and the sheath layer material are then uniformly coated onto the surface of the battery core. Finally, the two coated cables are mechanically twisted together to obtain a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems.

[0121] Example 3

[0122] This embodiment provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, as shown in Figure 1. The preparation method specifically includes the following steps:

[0123] In step S1, under a N2 atmosphere, 6.2 parts of 2,5-dihydroxybenzoic acid were dispersed in 108 parts of dimethyl sulfoxide and mixed evenly. Then, 7.6 parts of N,N'-dicyclohexylcarbodiimide and 4.7 parts of N-hydroxysuccinimide were added, and the mixture was stirred continuously at 370 rpm for 2.4 h. The temperature was raised to 56 °C and the reaction was allowed to proceed for 4.6 h. After the reaction was completed, the product was washed and distilled to obtain product A.

[0124] In step S2, 88 parts of Mg(OH)2 and 2.9 parts of hexadecyltrimethylammonium bromide were added to 430 parts of an aqueous ethanol solution, the temperature was raised to 46°C, 13.4 wt.% sodium hydroxide solution was added to adjust the pH to 10, 29 parts of tetraethyl orthosilicate were added, and the mixture was reacted at 46°C for 4.3 h. After the reaction was completed, the mixture was washed and filtered, and then dried under vacuum at 108°C for 8.3 h to obtain modified Mg(OH)2.

[0125] Step S3: 82 parts of modified Mg(OH)2 and 1.3 parts of triethylamine are dispersed in 208 parts of dimethyl sulfoxide. After heating to 44°C, 5.7 parts of product A are added and reacted completely for 4.8 hours. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at 82°C for 8.3 hours to obtain Mg(OH)2 flame retardant.

[0126] In step S4, under a N2 atmosphere, 22 parts of alkaline lignin were dissolved in 410 parts of N,N-dimethylformamide and stirred continuously at 260 rpm for 22 min. Then, 48 parts of pyridine were added and stirring was continued for 14 min to obtain a mixed solution. 19 parts of hexachlorocyclotriphosphazene and 12 parts of triphenyl phosphate were dispersed in 73 parts of N,N-dimethylformamide respectively. After dispersion, they were added to the mixed solution. Then, 11.7 parts of metaphosphoric acid, 6.8 parts of melamine cyanurate and 3.7 g of titanium dioxide were added. The temperature was raised to 85 °C and the reaction was stirred continuously at 260 rpm for 7.2 h. After the reaction was completed, the mixture was filtered and washed, and then dried thoroughly at 63 °C for 12.9 h to obtain flame-retardant lignin.

[0127] In step S5, 25 parts of Mg(OH)2 flame retardant, 73 parts of ethylene-vinyl acetate copolymer, 2.2 parts of vinyl silane, and 1.4 parts of zinc stearate are mixed in proportion and fed into a twin-screw extruder. The mixture is melt-mixed at 168°C with a screw speed of 130 rpm for 20 minutes to obtain the insulation layer material. Then, 18 parts of flame-retardant lignin, 81 parts of low-density polyethylene, 2.6 parts of antioxidant 1010, 1.5 parts of UV-329, and 1.3 parts of zinc stearate are fed into a second twin-screw extruder. The mixture is melt-mixed at 154°C with a screw speed of 110 rpm for 27 minutes to obtain the sheath layer material. The insulation layer material and the sheath layer material are then uniformly coated onto the surface of the battery core. Finally, the two coated cables are mechanically twisted together to obtain a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems.

[0128] Example 4

[0129] This embodiment provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, as shown in Figure 1. The preparation method specifically includes the following steps:

[0130] In step S1, under a N2 atmosphere, 8.1 parts of 2,5-dihydroxybenzoic acid were dispersed in 118 parts of dimethyl sulfoxide and mixed evenly. Then, 8.5 parts of N,N'-dicyclohexylcarbodiimide and 5.3 parts of N-hydroxysuccinimide were added, and the mixture was stirred continuously at 340 rpm for 2.8 h. The temperature was raised to 52 °C and the reaction was allowed to proceed for 4.8 h. After the reaction was completed, the product was washed and distilled to obtain product A.

[0131] In step S2, 93 parts of Mg(OH)2 and 3.7 parts of hexadecyltrimethylammonium bromide were added to 420 parts of an aqueous ethanol solution, the temperature was raised to 49°C, 12.6 wt.% sodium hydroxide solution was added to adjust the pH to 10, 32 parts of tetraethyl orthosilicate were added, and the mixture was reacted at 49°C for 4.8 h. After the reaction was completed, the mixture was washed and filtered, and then dried under vacuum at 113°C for 9.4 h to obtain modified Mg(OH)2.

[0132] Step S3: 94 parts of modified Mg(OH)2 and 1.7 parts of triethylamine are dispersed in 216 parts of dimethyl sulfoxide. After heating to 47°C, 8.6 parts of product A are added and reacted completely for 5.1 h. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at 85°C for 9.2 h to obtain Mg(OH)2 flame retardant.

[0133] In step S4, under a N2 atmosphere, 24 parts of alkaline lignin were dissolved in 420 parts of N,N-dimethylformamide and stirred continuously at 210 rpm for 27 min. Then, 43 parts of pyridine were added and stirring was continued for 16 min to obtain a mixed solution. 22 parts of hexachlorocyclotriphosphazene and 16 parts of triphenyl phosphate were dispersed in 77 parts of N,N-dimethylformamide respectively. After dispersion, they were added to the mixed solution. Then, 13.4 parts of metaphosphoric acid, 7.6 parts of melamine cyanurate and 4.3 g of titanium dioxide were added. The temperature was raised to 88℃ and the reaction was stirred continuously at 210 rpm for 7.6 h. After the reaction was completed, the mixture was filtered and washed, and then dried thoroughly at 68℃ for 13.3 h to obtain flame-retardant lignin.

[0134] In step S5, 28 parts of Mg(OH)2 flame retardant, 72 parts of ethylene-vinyl acetate copolymer, 2.5 parts of vinyl silane, and 1.8 parts of zinc stearate are mixed in proportion and fed into a twin-screw extruder. The mixture is melt-mixed at 174°C with a screw speed of 140 rpm for 23 minutes to obtain the insulation layer material. Then, 20 parts of flame-retardant lignin, 80 parts of low-density polyethylene, 2.2 parts of antioxidant 1010, 1.6 parts of UV-329, and 1.8 parts of zinc stearate are fed into a second twin-screw extruder. The mixture is melt-mixed at 150°C with a screw speed of 130 rpm for 26 minutes to obtain the sheath layer material. The insulation layer material and the sheath layer material are then uniformly coated onto the surface of the battery core. Finally, the two coated cables are mechanically twisted together to obtain a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems.

[0135] Example 5

[0136] This embodiment provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, as shown in Figure 1. The preparation method specifically includes the following steps:

[0137] In step S1, under a N2 atmosphere, 7.0 parts of 2,5-dihydroxybenzoic acid were dispersed in 104 parts of dimethyl sulfoxide and mixed evenly. Then, 8.1 parts of N,N'-dicyclohexylcarbodiimide and 5.2 parts of N-hydroxysuccinimide were added, and the mixture was stirred continuously at 370 rpm for 2.3 h. The temperature was then raised to 56 °C and reacted completely for 4.3 h. After the reaction was completed, the product was washed and distilled to obtain product A.

[0138] In step S2, 90 parts of Mg(OH)2 and 4.1 parts of hexadecyltrimethylammonium bromide were added to 470 parts of an aqueous ethanol solution, the temperature was raised to 46°C, 13.0 wt.% sodium hydroxide solution was added to adjust the pH to 10, 31 parts of tetraethyl orthosilicate were added, and the mixture was reacted at 46°C for 4.4 h. After the reaction was completed, the mixture was washed and filtered, and then dried under vacuum at 110°C for 9.2 h to obtain modified Mg(OH)2.

[0139] Step S3: 88 parts of modified Mg(OH)2 and 1.3 parts of triethylamine are dispersed in 211 parts of dimethyl sulfoxide. After heating to 45°C, 8.3 parts of product A are added and reacted completely for 5.4 hours. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at 83°C for 9.4 hours to obtain Mg(OH)2 flame retardant.

[0140] In step S4, under a N2 atmosphere, 26 parts of alkaline lignin were dissolved in 440 parts of N,N-dimethylformamide and stirred continuously at 280 rpm for 22 min. Then, 41 parts of pyridine were added and stirring was continued for 13 min to obtain a mixed solution. 20 parts of hexachlorocyclotriphosphazene and 13 parts of triphenyl phosphate were dispersed in 71 parts of N,N-dimethylformamide respectively. After dispersion, they were added to the mixed solution. Then, 14.3 parts of metaphosphoric acid, 7.2 parts of melamine cyanurate and 3.2 g of titanium dioxide were added. The temperature was raised to 83 °C and the reaction was stirred continuously at 280 rpm for 7.2 h. After the reaction was completed, the mixture was filtered and washed, and then dried thoroughly at 64 °C for 12.6 h to obtain flame-retardant lignin.

[0141] In step S5, 22 parts of Mg(OH)2 flame retardant, 74 parts of ethylene-vinyl acetate copolymer, 2.6 parts of vinyl silane, and 1.3 parts of zinc stearate are mixed in proportion and fed into a twin-screw extruder. The mixture is melt-mixed at 170°C with a screw speed of 120 rpm for 28 minutes to obtain the insulation layer material. Then, 21 parts of flame-retardant lignin, 83 parts of low-density polyethylene, 2.5 parts of antioxidant 1010, 1.3 parts of UV-329, and 1.6 parts of zinc stearate are fed into a second twin-screw extruder. The mixture is melt-mixed at 155°C with a screw speed of 110 rpm for 24 minutes to obtain the sheath layer material. The insulation layer material and the sheath layer material are then uniformly coated onto the surface of the battery core. Finally, the two coated cables are mechanically twisted together to obtain a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems.

[0142] Example 6

[0143] This embodiment provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, as shown in Figure 1. The preparation method specifically includes the following steps:

[0144] In step S1, under a N2 atmosphere, 6.5 parts of 2,5-dihydroxybenzoic acid were dispersed in 108 parts of dimethyl sulfoxide and mixed evenly. Then, 8.3 parts of N,N'-dicyclohexylcarbodiimide and 5.0 parts of N-hydroxysuccinimide were added, and the mixture was stirred continuously at 320 rpm for 2.6 h. The temperature was then raised to 58 °C and reacted completely for 4.6 h. After the reaction was completed, the product was washed and distilled to obtain product A.

[0145] In step S2, 95 parts of Mg(OH)2 and 3.7 parts of hexadecyltrimethylammonium bromide were added to 450 parts of an aqueous ethanol solution, the temperature was raised to 48°C, 13.9 wt.% sodium hydroxide solution was added to adjust the pH to 10, 33 parts of tetraethyl orthosilicate were added, and the mixture was reacted at 48°C for 4.2 h. After the reaction was completed, the mixture was washed and filtered, and then dried under vacuum at 114°C for 8.6 h to obtain modified Mg(OH)2.

[0146] Step S3: 91 parts of modified Mg(OH)2 and 1.5 parts of triethylamine are dispersed in 216 parts of dimethyl sulfoxide. After heating to 47°C, 8.8 parts of product A are added and reacted completely for 4.7 h. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at 86°C for 9.2 h to obtain Mg(OH)2 flame retardant.

[0147] In step S4, under a N2 atmosphere, 22 parts of alkaline lignin were dissolved in 430 parts of N,N-dimethylformamide and stirred continuously at 240 rpm for 26 min. Then, 45 parts of pyridine were added and stirring was continued for 16 min to obtain a mixed solution. 19 parts of hexachlorocyclotriphosphazene and 16 parts of triphenyl phosphate were dispersed in 75 parts of N,N-dimethylformamide respectively. After dispersion, they were added to the mixed solution. Then, 12.3 parts of metaphosphoric acid, 8.2 parts of melamine cyanurate and 4.1 g of titanium dioxide were added. The temperature was raised to 85℃ and the reaction was stirred continuously at 240 rpm for 7.5 h. After the reaction was completed, the mixture was filtered and washed, and then dried thoroughly at 66℃ for 12.9 h to obtain flame-retardant lignin.

[0148] In step S5, 24 parts of Mg(OH)2 flame retardant, 77 parts of ethylene-vinyl acetate copolymer, 2.2 parts of vinyl silane, and 1.8 parts of zinc stearate are mixed in proportion and fed into a twin-screw extruder. The mixture is melt-mixed at 174°C with a screw speed of 150 rpm for 23 minutes to obtain the insulation layer material. Then, 23 parts of flame-retardant lignin, 81 parts of low-density polyethylene, 2.6 parts of antioxidant 1010, 1.4 parts of UV-329, and 1.7 parts of zinc stearate are fed into a second twin-screw extruder. The mixture is melt-mixed at 152°C with a screw speed of 120 rpm for 27 minutes to obtain the sheath layer material. The insulation layer material and the sheath layer material are then uniformly coated onto the surface of the battery core. Finally, the two coated cables are mechanically twisted together to obtain a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems.

[0149] Comparative Example 1

[0150] This comparative example provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems. The difference between this method and Example 1 is that the mass fraction of tetraethyl orthosilicate in step S2 is adjusted to 39 parts. Compared to Example 1, the mass fraction of tetraethyl orthosilicate increases by 10 parts. The increased mass fraction is then proportionally deducted from Mg(OH)2, hexadecyltrimethylammonium bromide, and the aqueous ethanol solution. Other process parameters and operating conditions are exactly the same as in Example 1.

[0151] Comparative Example 2

[0152] This comparative example provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems. The difference between this method and Example 1 is that the mass fraction of tetraethyl orthosilicate in step S2 is adjusted to 19 parts. Compared to Example 1, the mass fraction of tetraethyl orthosilicate is reduced by 10 parts. The reduced mass fraction is proportionally added to Mg(OH)2, hexadecyltrimethylammonium bromide, and an aqueous solution of ethanol. Other process parameters and operating conditions are exactly the same as in Example 1.

[0153] Comparative Example 3

[0154] This comparative example provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems. The difference between this method and Example 1 is that the mass fraction of hexachlorocyclotriphosphazene in step S4 is adjusted to 27 parts. Compared to Example 1, the mass fraction of tetraethyl orthosilicate is increased by 8 parts. The increased mass fraction is proportionally deducted from alkaline lignin, N,N-dimethylformamide, pyridine, triphenyl phosphate, metaphosphoric acid, melamine cyanurate, and titanium dioxide. Other process parameters and operating conditions are exactly the same as in Example 1.

[0155] Comparative Example 4

[0156] This comparative example provides a method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems. The difference between this method and Example 1 is that the mass fraction of hexachlorocyclotriphosphazene in step S4 is adjusted to 11 parts. Compared to Example 1, the mass fraction of tetraethyl orthosilicate is reduced by 8 parts. The reduced mass fraction is proportionally added to alkaline lignin, N,N-dimethylformamide, pyridine, triphenyl phosphate, metaphosphoric acid, melamine cyanurate, and titanium dioxide. Other process parameters and operating conditions are exactly the same as in Example 1.

[0157] The limiting oxygen index of the materials prepared in Examples 1-6 and Comparative Examples 1-4 was tested according to national standard GB / T 2406.2-2009; the flame retardant properties of the materials prepared in Examples 1-6 and Comparative Examples 1-4 were tested according to GB / T 2408-2021; and the maximum smoke density of the materials prepared in Examples 1-6 and Comparative Examples 1-4 was tested according to national standard GB / T 32129-2015. The test results are shown in Table 1.

[0158] Table 1. Test results of a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system in Examples 1-6 and Comparative Examples 1-4.

[0159] Stranded cable test results

[0160]

[0161] The data in the table show that Comparative Example 1 has a lower limiting oxygen index and flame retardant rating than Example 1, but a higher maximum smoke density (flameless). Comparative Example 2 has a lower limiting oxygen index and flame retardant rating than Example 1, but a higher maximum smoke density (flameless). This is because the excess tetraethyl orthosilicate in Comparative Example 1 may form an excessive silicate layer on the Mg(OH)2 surface, weakening the material's decomposition endothermic effect and moisture release capacity, thus reducing the material's flame retardant performance at high temperatures. Water vapor plays a role in diluting combustible gases during a fire; insufficient release will weaken the smoke suppression effect. In Comparative Example 2, insufficient tetraethyl orthosilicate results in incomplete silicate coverage, failing to adequately protect the Mg(OH)2 surface, reducing the refractory properties of Mg(OH)2, and consequently, the flame retardant performance of the material.

[0162] Comparative Example 3 had a lower limiting oxygen index and flame retardant rating than Example 1, but a higher maximum smoke density (flameless). Comparative Example 4 had a lower limiting oxygen index and flame retardant rating than Example 1, but a higher maximum smoke density (flameless). This is because in Comparative Example 3, the chlorine atoms in hexachlorocyclotriphosphazene, under excess conditions, lead to excessive nucleophilic substitution reactions. This not only substitutes for the phenolic hydroxyl groups of lignin, but excess hexachlorocyclotriphosphazene may also trigger multi-step chlorination reactions, causing chlorination or ring-opening reactions of the aromatic rings, weakening its charring ability at high temperatures. Simultaneously, excess hexachlorocyclotriphosphazene may decompose during combustion, producing toxic fumes such as hydrogen chloride, thus increasing smoke production. In Comparative Example 4, insufficient hexachlorocyclotriphosphazene resulted in insufficient formation of new chemical bonds (-P=N), leading to inadequate chemical and thermal stability of the material. Furthermore, it could not effectively capture free radicals in the flame, inhibiting the combustion chain reaction and resulting in decreased flame retardant performance.

[0163] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, characterized in that, The preparation method is as follows: Step S1: Under N2 atmosphere, 2,5-dihydroxybenzoic acid is dispersed in dimethyl sulfoxide and mixed evenly. Then, N,N'-dicyclohexylcarbodiimide and N-hydroxysuccinimide are added and stirred continuously. The mixture is heated to the first temperature to react fully. After the reaction is completed, the mixture is washed and distilled to obtain product A. Step S2: Add Mg(OH)2 and emulsifier to an ethanol aqueous solution, heat to a second temperature, add sodium hydroxide solution to adjust the pH to 10, add tetraethyl orthosilicate, and react fully at the second temperature. After the reaction is complete, wash and filter, and dry under vacuum at a third temperature to obtain modified Mg(OH)2. Step S3: Modified Mg(OH)2 and triethylamine are dispersed in dimethyl sulfoxide. After heating to the second temperature, product A is added and reacted completely. After the reaction is completed, the mixture is cooled to room temperature, washed with anhydrous ethanol, and dried completely at the fourth temperature to obtain Mg(OH)2 flame retardant. In step S4, under an N2 atmosphere, alkaline lignin is dissolved in N,N-dimethylformamide and stirred continuously. Pyridine is added and stirring continues to obtain a mixed solution. Hexachlorocyclotriphosphazene and triphenyl phosphate are dispersed separately in N,N-dimethylformamide and then added to the mixed solution. Metaphosphoric acid, melamine cyanurate, and titanium dioxide are then added. The temperature is raised to the fourth temperature and the reaction is stirred continuously. After the reaction is completed, the mixture is filtered, washed, and dried thoroughly at the fifth temperature to obtain flame-retardant lignin. Step S5: Mix Mg(OH)2 flame retardant, ethylene-vinyl acetate copolymer, vinyl silane and zinc stearate in proportion, and feed them into a twin-screw extruder. Melt and mix them at the sixth temperature to obtain the insulation layer material. Feed flame retardant lignin, low-density polyethylene, antioxidant 1010, UV-329 and zinc stearate into a second twin-screw extruder. Melt and mix them at the seventh temperature to obtain the sheath layer material. Coat the insulation layer material and the sheath layer material evenly onto the surface of the battery core in sequence. Then mechanically twist the two coated cables together to obtain a high-temperature resistant, low-smoke, halogen-free flame-retardant twisted pair cable for building security systems.

2. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S1, The mass fraction of the 2,5-dihydroxybenzoic acid is 5-10 parts; The dimethyl sulfoxide has a mass fraction of 100-120 parts; The mass fraction of the N,N'-dicyclohexylcarbodiimide is 7-9 parts; The N-hydroxysuccinimide has a mass fraction of 4-6 parts; The first temperature is 50-60℃; The reaction time at the first temperature is 4-5 hours.

3. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S2, The mass fraction of Mg(OH)2 is 80-100 parts; The emulsifier is cetyltrimethylammonium bromide, with a mass fraction of 2-5 parts; The ethanol-water solution has a mass fraction of 400-500 parts, and the volume ratio of ethanol to deionized water is 3:

1. The second temperature is 40-50℃.

4. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S2, The sodium hydroxide solution has a mass fraction of 10-15 wt.%. The tetraethyl orthosilicate has a mass fraction of 25-35 parts; The reaction time after adding tetraethyl orthosilicate is 4-5 hours; The third temperature is 100-120℃; The vacuum drying time at the third temperature is 8-10 hours.

5. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S3, The modified Mg(OH)2 has a mass fraction of 80-100 parts; The triethylamine is present in 1-2 parts by weight; The dimethyl sulfoxide has a mass fraction of 200-220 parts; The second temperature is 40-50℃; The mass fraction of product A is 5-10 parts; The reaction time after the addition of product A is 4-6 hours; The fourth temperature is 80-90℃; The drying time at the fourth temperature is 8-10 hours.

6. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S4, The alkaline lignin has a mass fraction of 20-30 parts; The N,N-dimethylformamide has a mass fraction of 400-450 parts; The pyridine is present in a mass fraction of 40-50 parts; The stirring time after adding pyridine is 10-20 min; The hexachlorocyclotriphosphazene has a mass fraction of 15-25 parts; The triphenyl phosphate is present in 10-15 parts by mass. The mass fraction of N,N-dimethylformamide used to dissolve hexachlorocyclotriphosphazene and triphenyl phosphate is 60-80 parts.

7. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S4, The metaphosphoric acid is 10-15 parts by mass; The mass fraction of the melamine cyanurate is 5-10 parts; The titanium dioxide is present in 3-5 parts by weight; The fourth temperature is 80-90℃; The stirring reaction time at the fourth temperature is 6-8 hours; The fifth temperature is 60-70℃; The drying time at the fifth temperature is 12-14 hours.

8. The method for preparing a high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for a building security system according to claim 1, characterized in that, In step S5, The components of the insulating layer material are as follows by mass: 20-30 parts of Mg(OH)2 flame retardant, 70-80 parts of ethylene-vinyl acetate copolymer, 2-3 parts of vinylsilane, and 1-2 parts of zinc stearate. The sixth temperature is 160-180℃; The screw speed for the insulating layer material is 100-150 rpm, and the mixing time is 20-30 min; The components of the sheath material are as follows by weight: 15-25 parts flame retardant lignin, 75-85 parts low-density polyethylene, 2-3 parts antioxidant 1010, 1-2 parts UV-329, and 1-2 parts zinc stearate. The seventh temperature is 140-160℃; The screw speed for the sheath layer material is 100-150 rpm, and the mixing time is 20-30 min.

9. A high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable for building security systems, obtained by the preparation method according to any one of claims 1-8.

10. The application of the high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable prepared by the method according to any one of claims 1-8, characterized in that, The high-temperature resistant, low-smoke, halogen-free, flame-retardant twisted-pair cable is used in building security systems.

Images