Fireproof low-voltage wire cable and preparation method thereof

Abstract

The invention provides a fire-resistant low-voltage wire cable and a preparation method thereof, and belongs to the technical field of wire cables, the fire-resistant low-voltage wire cable comprises an internal cable core bundle and an outer sheath, the outer sheath is prepared from the following raw materials: a resin matrix, a composite flame retardant, a reinforcing filler and an anti-aging agent, the reinforcing filler is a glass fiber composite porous organic framework, the organic framework material is pretreated by an acrylic polymer, and the composite flame retardant is prepared by taking expanded graphite as a shell of a flame-retardant material and then performing hydroxylation modification by using a silicon source material. The preparation process is simple and suitable for industrial production, the prepared electric wire and cable outer sheath is good in environment friendliness, and through the combined action of the composite flame retardant and the reinforcing filler, the prepared outer sheath material has excellent fire resistance and flame retardance while keeping high mechanical strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of wire and cable, and particularly relates to a fire-resistant low-voltage wire and cable and a preparation method thereof. Background Art

[0002] The selection of wire and cable materials is not only related to the actual product life, but also related to the use safety. The outer sheath of the cable product is the direct protective layer against the external environment. At present, the development of high-performance fire-resistant cable sheaths has become a hot topic in the wire and cable industry and the field of scientific research.

[0003] Halogen polymer materials have good flame retardancy and are often used as sheath layer materials, which can keep the circuit of the finished cable intact during combustion. However, harmful halogen-containing gases will be generated during combustion, which will harm the environment and human health. Polyethylene (PE) materials have good environmental protection, high processing performance and mechanical strength. However, they have a high crystallinity, the material is too hard, and the flexibility and flame retardancy are poor, which cannot meet the requirements for direct use of flame-retardant cables.

[0004] In the prior art, inorganic flame retardant materials are used to blend and compound modify polyethylene. Without changing the original structure of the polymer molecular chain, it has the characteristics of simplicity, convenience and low cost, and can achieve the purpose of non-toxic flame retardancy. However, the flame retardant effect of the sheath layer material is directly related to the incorporation amount of the inorganic flame retardant. In order to obtain a good flame retardant effect, too much inorganic flame retardant is incorporated, resulting in poor fluidity during material mixing and molding. The incorporated inorganic flame retardant particles form many stress concentration points inside the sheath, reducing the mechanical properties of the optical cable sheath. It is a flame retardant characteristic obtained by sacrificing the mechanical properties of the optical cable sheath itself. Summary of the Invention

[0005] In order to solve the problems in the background art, the present invention provides a fire-resistant low-voltage wire and cable and a preparation method thereof, which can not only ensure the mechanical strength of the cable outer sheath, but also have excellent flame retardant performance.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A fire-resistant low-voltage wire and cable includes two parts: an internal cable core bundle and an outer sheath. The outer sheath is obtained by melt-extruding outer sheath pellets. The outer sheath pellets are prepared from the following raw materials: a resin matrix, a composite flame retardant, a reinforcing filler and an anti-aging agent. The reinforcing filler is a glass fiber composite porous organic framework, wherein the organic framework material is pretreated with an acrylic polymer. The composite flame retardant is a shell with expanded graphite as the flame retardant material, and then it is prepared by hydroxylation modification with a silicon source material.

[0007] Preferably, the preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 10 - 15 parts of dimethylimidazole, and 0.3 - 0.5 part of KH560 evenly, add 30 - 50 parts of DMF, stir evenly, add 0.1 - 0.2 part of triethylamine, and react for 6 - 10 h to obtain an organic framework; A2: Add 2.5 - 3.5 parts of an acrylic polymer and 0.2 - 0.3 part of p-toluenesulfonic acid to the organic framework obtained in step A1, mix evenly, and stir for 2 - 3 h under nitrogen protection to obtain a pretreated organic framework; A3: Add 0.5 - 0.7 part of methyltrimethoxysilane, 0.3 - 0.5 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 0.5 - 1 h, heat to 70 - 80 °C, let stand for 10 - 20 min, filter, wash, and dry to obtain a reinforcing filler; Preferably, the preparation of the composite flame retardant includes the following steps: B1: By weight, add 1 part of zinc borate, 0.5 - 0.8 part of magnesium hydroxide, and 0.1 - 0.2 part of surfactant to 40 - 60 parts of an ethanol solution with a concentration of 70 - 80%, perform ultrasonic treatment for 5 - 10 min to obtain a dispersion, add 4 - 6 parts of 100-mesh expanded graphite to the dispersion, and stir and mix at high speed to make a flame retardant precursor; B2: Place the flame retardant precursor obtained in step B1 in a water bath at 70 - 80 °C, add 0.8 - 1.2 parts of tetraethyl orthosilicate, keep stirring for 20 - 40 min, dropwise add 0.1 - 0.2 part of 0.5 mol / L ammonia water, stir for 2 - 3 h, let stand for 4 - 8 h, remove the solvent, dry, then place it in a tube furnace, heat to 300 - 400 °C under nitrogen protection, keep warm for 3 - 4 h, and cool to room temperature to obtain the composite flame retardant.

[0008] Preferably, the preparation of maleic anhydride grafted polyethylene includes the following; Mix low-density polyethylene (LDPE) resin, benzoyl peroxide, and polydimethylsiloxane evenly according to a mass ratio of 100:0.4 - 0.6:0.8 - 1.2, place it in the mixing zone of an extrusion device for melt mixing, then add maleic anhydride monomer to the mixing zone of the extrusion device, the addition amount of maleic anhydride monomer is 2 - 5% of the weight of the LDPE resin, introduce nitrogen into the mixing zone and the termination zone of the extrusion device, and extrude and pelletize to obtain maleic anhydride grafted polyethylene; Preferably, in step A2, the acrylic polymer is selected from one or a mixture of two of polyacrylic acid and polymethacrylic acid.

[0009] Preferably, the resin matrix is a premix of maleic anhydride grafted polyethylene and high-density polyethylene (HDPE) with a weight ratio of 3 - 5:10.

[0010] Preferably, by weight parts, the outer sheath granule comprises the following raw materials: 100 parts of resin matrix, 19 - 21 parts of composite flame retardant, 7.5 - 8.5 parts of reinforcing filler, and 1 - 2 parts of anti - aging agent.

[0011] Preferably, the anti - aging agent is one or a mixture of two or more of antioxidant 1010, antioxidant 1330, and antioxidant 168.

[0012] Preferably, the preparation process of the outer sheath granule is as follows: Mix all the raw materials evenly, add them into a twin - screw extruder, and under the conditions that the temperature of the first zone is 100 - 120 °C, the temperature of the second zone is 130 - 140 °C, the temperature of the third zone is 145 - 160 °C, the temperature of the fourth zone is 160 - 170 °C, the temperature of other zones is 175 - 185 °C, and the temperature of the die head is 185 - 195 °C, extrude, cool, and pelletize to obtain the outer sheath granule; A preparation method of a fire - resistant low - voltage wire and cable includes the following steps: Put the outer sheath granule into an extruder, carry out melt extrusion, and coat the outer sheath on the outside of the internal cable core bundle to obtain the fire - resistant low - voltage wire and cable.

[0013] This application has the following beneficial effects: 1. The present invention provides a fire - resistant low - voltage wire and cable and its preparation method. The preparation process is simple, suitable for industrial production. The outer sheath of the obtained wire and cable has good environmental protection performance. Through the combined action of the composite flame retardant and the reinforcing filler, the obtained outer sheath material has excellent fire - resistant and flame - retardant properties while maintaining high mechanical strength.

[0014] Maleic anhydride - grafted polyethylene is blended with high - density polyethylene to achieve the combination of rigidity and flexibility of the material. The polar groups are introduced through maleic anhydride grafting treatment, which enhances the interaction between polyethylene molecular chains, improves the interaction between the resin matrix, the composite flame retardant, and the reinforcing filler, increases the tensile strength of polyethylene, and improves the flame - retardant performance; The composite flame retardant uses porous expanded graphite as the carrier of the flame - retardant material, and then tetraethyl orthosilicate is introduced for modification treatment to achieve uniform dispersion of the flame - retardant material in the carrier and improve the flame - retardant performance of the composite flame retardant; The reinforcing filler is glass fiber - composite porous organic framework, which rapidly expands to form a porous carbonized layer when encountering fire. After pretreatment of the organic framework material with acrylic - type polymer, the dispersion ability of glass fiber can be improved, and its compatibility with the resin matrix can be enhanced, ultimately enhancing the mechanical properties of the outer sheath material.

[0015] The addition of tetraethyl orthosilicate in the composite flame retardant can introduce more hydroxyl groups, providing conditions for the bonding reaction with the acrylic groups in the reinforcing filler, enhancing the interaction between the flame retardant and the filler in the resin matrix, improving the interfacial bonding force and integrity of the material, and further improving the flame - retardant performance and tensile strength of the outer sheath material. Detailed implementation manners

[0016] The present application will be further described in detail below in conjunction with embodiments.

[0017] Unless otherwise specified, the raw materials in the embodiments and comparative examples of the present application are all commercially available.

[0018] Example 1 A fire-resistant low-voltage wire and cable includes two parts: an internal cable core bundle and an outer sheath. The outer sheath pellets are put into an extruder for melt extrusion, and the outer sheath is coated on the outside of the internal cable core bundle to obtain the fire-resistant low-voltage wire and cable. The outer sheath pellets are prepared by extrusion granulation from the following raw materials: 100 parts of resin matrix, 20 parts of composite flame retardant, 8.5 parts of reinforcing filler, and 1.5 parts of antioxidant 1010, wherein the resin matrix is a premix of maleic anhydride grafted polyethylene and high-density polyethylene with a weight ratio of 4:10.

[0019] The specific preparation process of the outer sheath pellets is as follows: all the raw materials of the outer sheath are mixed evenly and added into a twin-screw extruder. Under the conditions of a temperature of 110°C in zone 1, 135°C in zone 2, 150°C in zone 3, 165°C in zone 4, 180°C in other zones, and a head temperature of 190°C, extrusion, cooling, and granulation are carried out to obtain the outer sheath pellets; The preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 12 parts of dimethylimidazole, and 0.4 part of KH560 evenly, add 40 parts of DMF, stir evenly, add 0.15 part of triethylamine, and react for 8 h to obtain an organic framework; A2: Add 3 parts of polymethacrylic acid and 0.25 part of p-toluenesulfonic acid to the organic framework in step A1, mix evenly, and stir for 3 h under nitrogen protection to obtain a pretreated organic framework; A3: Add 0.6 part of methyltrimethoxysilane, 0.4 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 1 h, heat to 75°C, let stand for 15 min, filter, wash, and dry to obtain the reinforcing filler; The preparation of the composite flame retardant includes the following steps: B1. By weight, add 1 part of zinc borate, 0.6 part of magnesium hydroxide, and 0.15 part of sodium dodecylsulfonate to 50 parts of an ethanol solution with a concentration of 75%, perform ultrasonic treatment for 5 min to obtain a dispersion liquid, add 5 parts of 100-mesh expanded graphite to the dispersion liquid, and stir and mix at high speed to prepare a flame retardant precursor; B2. Place the flame retardant precursor from step B1 in a 75°C water bath, add 1 part of tetraethyl orthosilicate, keep warm and stir for 30 min, dropwise add 0.15 part of 0.5 mol / L ammonia water, stir for 2 h, let stand for 8 h, remove the solvent, dry, then place it in a tube furnace, heat up to 350°C under nitrogen protection, keep warm for 4 h, and cool to room temperature to obtain the composite flame retardant; Preparation of maleic anhydride grafted polyethylene includes the following; Mix low-density polyethylene (LDPE) resin, benzoyl peroxide, and polydimethylsiloxane evenly according to a mass ratio of 100:0.5:1, place them in the mixing zone of the extrusion equipment for melt mixing, then add maleic anhydride monomer to the mixing zone of the extrusion equipment, and the addition amount of maleic anhydride monomer is 3% of the weight of the LDPE resin raw material. Pass nitrogen into the mixing zone and the termination zone of the extrusion equipment, extrude and pelletize to obtain maleic anhydride grafted polyethylene.

[0020] In the above materials, high-density polyethylene (HDPE), density: 0.953 g / cm 3 , melt index: 0.4 g / 10 min, tensile strength 23.7 MPa; low-density polyethylene (LDPE), density: 0.920 g / cm 3 , melt index: 5 g / 10 min, tensile strength 15.6 MPa; glass fiber size 1 - 3 mm.

[0021] Example 2 A fire-resistant low-voltage wire and cable includes two parts: an internal cable core bundle and an outer sheath. Put the outer sheath pellet into an extruder for melt extrusion, and coat the outer sheath on the outside of the internal cable core bundle to obtain the fire-resistant low-voltage wire and cable. The outer sheath pellet is prepared by extrusion and pelletization from the following raw materials: 100 parts of resin matrix, 19 parts of composite flame retardant, 7.5 parts of reinforcing filler, and 1 part of antioxidant 1330, where the resin matrix is a premix of maleic anhydride grafted polyethylene and high-density polyethylene with a weight ratio of 3:10; The specific preparation process of the outer sheath pellet is as follows: Mix all the raw materials of the outer sheath evenly, add them to a twin-screw extruder, and extrude, cool, and pelletize under the conditions of a temperature of 100°C in zone 1, 130°C in zone 2, 145°C in zone 3, 160°C in zone 4, 175°C in other zones, and a head temperature of 185°C to obtain the outer sheath pellet; Preparation of the reinforcing filler includes the following steps: A1. Mix 10 parts of zinc nitrate hexahydrate, 10 parts of dimethylimidazole, and 0.3 part of KH560 evenly, add 30 parts of DMF, stir evenly, add 0.1 part of triethylamine, and react for 6 h to obtain the organic framework; A2: Add 2.5 parts of polymethacrylic acid and 0.2 parts of p-toluenesulfonic acid to the organic framework in step A1, mix evenly, stir for 2 h under nitrogen protection to obtain a pretreated organic framework; A3: Add 0.5 parts of methyltrimethoxysilane, 0.3 parts of sodium bicarbonate and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 0.5 h, heat to 70 °C, let stand for 20 min, filter, wash and dry to obtain a reinforcing filler; The preparation of the composite flame retardant includes the following steps: B1. By weight, add 1 part of zinc borate, 0.5 parts of magnesium hydroxide and 0.1 part of sodium dodecyl sulfonate to 40 parts of an ethanol solution with a concentration of 70%, perform ultrasonic treatment for 10 min to obtain a dispersion, add 4 parts of 100-mesh expanded graphite to the dispersion, and stir and mix at high speed to make a flame retardant precursor; B2. Place the flame retardant precursor in step B1 in a 70 °C water bath, add 0.8 parts of tetraethyl orthosilicate, keep warm and stir for 20 min, dropwise add 0.1 part of 0.5 mol / L ammonia water, stir for 2 h, let stand for 4 h, remove the solvent, dry and then place it in a tube furnace, heat to 300 °C under nitrogen protection, keep warm for 4 h, and cool to room temperature to obtain the composite flame retardant; The preparation of maleic anhydride grafted polyethylene includes the following content; Mix low density polyethylene (LDPE) resin, benzoyl peroxide and polydimethylsiloxane evenly according to a mass ratio of 100:0.4:0.8, place them in the mixing zone of an extrusion device for melt mixing, then add maleic anhydride monomer to the mixing zone of the extrusion device, and the addition amount of maleic anhydride monomer is 2% of the weight of the LDPE resin raw material. Pass nitrogen into the mixing zone and the termination zone of the extrusion device, extrude and pelletize to obtain maleic anhydride grafted polyethylene.

[0022] In the above materials, high density polyethylene (HDPE), density: 0.953 g / cm 3 , melt index: 0.4 g / 10 min, tensile strength 23.7 MPa; low density polyethylene (LDPE), density: 0.920 g / cm 3 , melt index: 5 g / 10 min, tensile strength 15.6 MPa; glass fiber size 1 - 3 mm.

[0023] Example 3 A fire-resistant low-voltage wire and cable, comprising two parts: an internal cable core bundle and an outer sheath. The outer sheath pellets are put into an extruder for melting and extrusion, and the outer sheath is coated on the outside of the internal cable core bundle to obtain the fire-resistant low-voltage wire and cable. The outer sheath pellets are prepared by extrusion granulation from the following raw materials: 100 parts of resin matrix, 21 parts of composite flame retardant, 8 parts of reinforcing filler, and 2 parts of antioxidant 168, wherein the resin matrix is a premix of maleic anhydride grafted polyethylene and high-density polyethylene with a weight ratio of 5:10; The specific preparation process of the outer sheath pellets is as follows: Mix all the raw materials of the outer sheath evenly, add them to a twin-screw extruder, and extrude, cool, and granulate under the conditions of a temperature of 120 °C in zone 1, 140 °C in zone 2, 160 °C in zone 3, 170 °C in zone 4, 185 °C in other zones, and a head temperature of 195 °C to obtain the outer sheath pellets; The preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 15 parts of dimethylimidazole, and 0.5 part of KH560 evenly, add 50 parts of DMF, stir evenly, add 0.2 part of triethylamine, and react for 10 h to obtain an organic framework; A2: Add 3.5 parts of polyacrylic acid and 0.3 part of p-toluenesulfonic acid to the organic framework in step A1, stir evenly under nitrogen protection for 3 h to obtain a pretreated organic framework; A3: Add 0.7 part of methyltrimethoxysilane, 0.5 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 1 h, heat to 80 °C, let stand for 10 min, filter, wash, and dry to obtain the reinforcing filler; The preparation of the composite flame retardant includes the following steps: B1. By weight, add 1 part of zinc borate, 0.8 part of magnesium hydroxide, and 0.2 part of sodium dodecyl sulfonate to 60 parts of an 80% ethanol solution, perform ultrasonic treatment for 8 min to obtain a dispersion, add 6 parts of 100-mesh expanded graphite to the dispersion, and stir and mix at high speed to prepare a flame retardant precursor; B2. Place the flame retardant precursor in step B1 in a water bath at 80 °C, add 1.2 parts of tetraethyl orthosilicate, keep stirring for 40 min, dropwise add 0.2 part of 0.5 mol / L ammonia water, stir for 3 h, let stand for 8 h, remove the solvent, dry, place in a tubular furnace, heat to 400 °C under nitrogen protection, keep warm for 3 h, and cool to room temperature to obtain the composite flame retardant; The preparation of maleic anhydride grafted polyethylene includes the following content; Mix low-density polyethylene (LDPE) resin, benzoyl peroxide, and polydimethylsiloxane evenly according to a mass ratio of 100:0.6:1.2, place them in the mixing zone of the extrusion equipment, conduct melt mixing, then add maleic anhydride monomer to the mixing zone of the extrusion equipment. The addition amount of maleic anhydride monomer is 5% of the weight of the LDPE resin raw material. Introduce nitrogen into the mixing zone and the termination zone of the extrusion equipment, and extrude and pelletize to obtain maleic anhydride-grafted polyethylene.

[0024] In the above materials, high-density polyethylene (HDPE), density: 0.953 g / cm 3 , melt index: 0.4 g / 10 min, tensile strength 23.7 MPa; low-density polyethylene (LDPE), density: 0.920 g / cm 3 , melt index: 5 g / 10 min, tensile strength 15.6 MPa; glass fiber size 1 - 3 mm.

[0025] Example 4 A fire-resistant low-voltage wire and cable includes two parts: an internal cable core bundle and an outer sheath. Put the outer sheath pellets into an extruder, conduct melt extrusion, and coat the outer sheath on the outside of the internal cable core bundle to obtain a fire-resistant low-voltage wire and cable. The outer sheath pellets are prepared by extrusion and pelletization from the following raw materials: 100 parts of resin matrix, 20 parts of composite flame retardant, 7.5 parts of reinforcing filler, and 1 part of antioxidant 1010, where the resin matrix is a premix of maleic anhydride-grafted polyethylene and high-density polyethylene with a weight ratio of 3:10; The specific preparation process of the outer sheath pellets is as follows: Mix all the raw materials of the outer sheath evenly, add them to a twin-screw extruder, and extrude, cool, and pelletize under the conditions of a temperature of 100 °C in zone 1, 130 °C in zone 2, 150 °C in zone 3, 170 °C in zone 4, 185 °C in other zones, and a head temperature of 190 °C to obtain the outer sheath pellets; The preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 10 parts of dimethylimidazole, and 0.5 part of KH560 evenly, add 30 parts of DMF, stir evenly, add 0.2 part of triethylamine, and react for 10 h to obtain an organic framework; A2: Add 3.5 parts of polymethacrylic acid and 0.2 part of p-toluenesulfonic acid to the organic framework in step A1, mix evenly, and stir for 2 h under nitrogen protection to obtain a pretreated organic framework; A3: Add 0.7 part of methyltrimethoxysilane, 0.3 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 1 h, heat to 70 °C, let stand for 10 min, filter, wash, and dry to obtain the reinforcing filler; The preparation of the composite flame retardant includes the following steps: B1. By weight, 1 part of zinc borate, 0.5 part of magnesium hydroxide, and 0.2 part of sodium dodecyl sulfonate are added to 40 parts of an ethanol solution with a concentration of 70%. After ultrasonic treatment for 5 min, a dispersion is obtained. Then, 6 parts of 100-mesh expanded graphite are added to the dispersion, and they are mixed by high-speed stirring to prepare a flame retardant precursor. B2. The flame retardant precursor prepared in step B1 is placed in an 80°C water bath, 1.2 parts of tetraethyl orthosilicate are added, and it is stirred while keeping warm for 30 min. Then, 0.1 part of 0.5 mol / L ammonia water is added dropwise, and it is stirred for 2 h. After standing for 8 h, the solvent is removed. After drying, it is placed in a tube furnace and heated to 300°C under nitrogen protection, kept warm for 4 h, and then cooled to room temperature to obtain a composite flame retardant. The preparation of maleic anhydride grafted polyethylene includes the following steps; Low-density polyethylene (LDPE) resin, benzoyl peroxide, and polydimethylsiloxane are mixed evenly according to a mass ratio of 100:0.4:1.2 and placed in the mixing zone of an extrusion device for melt mixing. Then, maleic anhydride monomer is added to the mixing zone of the extrusion device. The addition amount of maleic anhydride monomer is 5% of the weight of the LDPE resin raw material. Nitrogen is introduced into the mixing zone and the termination zone of the extrusion device, and extrusion granulation is carried out to obtain maleic anhydride grafted polyethylene.

[0026] In the above materials, high-density polyethylene (HDPE), density: 0.953 g / cm 3 , melt index: 0.4 g / 10 min, tensile strength 23.7 MPa; low-density polyethylene (LDPE), density: 0.920 g / cm 3 , melt index: 5 g / 10 min, tensile strength 15.6 MPa; glass fiber size 1 - 3 mm.

[0027] Example 5 A fire-resistant low-voltage wire and cable includes two parts: an internal cable core bundle and an outer sheath. The outer sheath pellets are put into an extruder for melt extrusion, and the outer sheath is coated on the outside of the internal cable core bundle to obtain a fire-resistant low-voltage wire and cable. The outer sheath pellets are prepared by extrusion granulation from the following raw materials: 100 parts of resin matrix, 19 parts of composite flame retardant, 7.5 parts of reinforcing filler, and 2 parts of antioxidant 168. The resin matrix is a premix of maleic anhydride grafted polyethylene and high-density polyethylene with a weight ratio of 5:10; The specific preparation process of the outer sheath pellets is as follows: all the raw materials of the outer sheath are mixed evenly and added to a twin-screw extruder. Under the conditions of a temperature of 120°C in zone 1, 135°C in zone 2, 155°C in zone 3, 165°C in zone 4, 175°C in other zones, and a head temperature of 190°C, extrusion, cooling, and granulation are carried out to obtain the outer sheath pellets; The preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 10 parts of dimethylimidazole, and 0.3 part of KH560 evenly, add 50 parts of DMF, stir evenly, add 0.1 part of triethylamine, and react for 6 h to obtain an organic framework; A2: Add 3.5 parts of polyacrylic acid and 0.3 part of p-toluenesulfonic acid to the organic framework in step A1, mix evenly, and stir for 2 h under nitrogen protection to obtain a pretreated organic framework; A3: Add 0.5 part of methyltrimethoxysilane, 0.5 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 1 h, heat to 75 °C, let stand for 15 min, filter, wash, and dry to obtain a reinforcing filler; The preparation of the composite flame retardant includes the following steps: B1. By weight, add 1 part of zinc borate, 0.7 part of magnesium hydroxide, and 0.15 part of sodium dodecyl sulfonate to 40 parts of an 80% ethanol solution, perform ultrasonic treatment for 10 min to obtain a dispersion, add 5 parts of 100-mesh expanded graphite to the dispersion, and stir and mix at high speed to prepare a flame retardant precursor; B2. Place the flame retardant precursor in step B1 in a 70 °C water bath, add 1 part of tetraethyl orthosilicate, keep warm and stir for 40 min, dropwise add 0.15 part of 0.5 mol / L ammonia water, stir for 2 h, let stand for 4 h, remove the solvent, dry, place in a tubular furnace, heat to 350 °C under nitrogen protection, keep warm for 4 h, and cool to room temperature to obtain a composite flame retardant; The preparation of maleic anhydride grafted polyethylene includes the following: Mix low-density polyethylene (LDPE) resin, benzoyl peroxide, and polydimethylsiloxane evenly according to a mass ratio of 100:0.6:1.2, place them in the mixing zone of an extrusion device for melt mixing, then add maleic anhydride monomer to the mixing zone of the extrusion device, and the addition amount of maleic anhydride monomer is 4% of the weight of the LDPE resin raw material. Pass nitrogen into the mixing zone and the termination zone of the extrusion device, extrude and pelletize to obtain maleic anhydride grafted polyethylene.

[0028] In the above materials, high-density polyethylene (HDPE), density: 0.953 g / cm 3 , melt index: 0.4 g / 10 min, tensile strength 23.7 MPa; low-density polyethylene (LDPE), density: 0.920 g / cm 3 , melt index: 5 g / 10 min, tensile strength 15.6 MPa; glass fiber size 1 - 3 mm.

[0029] Comparative Example 1 The difference between this comparative example and Example 1 is only that in the raw materials of the outer sheath pellets, maleic anhydride grafted polyethylene is replaced by LDPE resin. The specific content is as follows. The outer sheath pellets are prepared by extrusion granulation from the following raw materials: 100 parts of resin matrix, 20 parts of composite flame retardant, 8.5 parts of reinforcing filler, and 1.5 parts of antioxidant 1010, where the resin matrix is a premix of LDPE resin and high-density polyethylene with a weight ratio of 4:10.

[0030] Comparative Example 2 The difference between this comparative example and Example 1 is only that in the preparation of the reinforcing filler, acrylic polymer is not added. The specific content is as follows. The preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 12 parts of dimethylimidazole, and 0.4 part of KH560 evenly, add 40 parts of DMF, stir evenly, add 0.15 part of triethylamine, and react for 8 h to obtain an organic framework. A2: Add 0.25 part of p-toluenesulfonic acid to the organic framework obtained in step A1 and mix evenly. Stir for 3 h under nitrogen protection to obtain a pretreated organic framework. A3: Add 0.6 part of methyltrimethoxysilane, 0.4 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 1 h, heat to 75 °C, let stand for 15 min, filter, wash, and dry to obtain the reinforcing filler.

[0031] Comparative Example 3 The difference between this comparative example and Example 1 is only that in the preparation of the composite flame retardant, tetraethyl orthosilicate is not added. The specific content is as follows. The preparation of the composite flame retardant includes the following steps: B1. By weight, add 1 part of zinc borate, 0.6 part of magnesium hydroxide, and 0.15 part of sodium dodecylsulfonate to 50 parts of an ethanol solution with a concentration of 75%, perform ultrasonic treatment for 5 min to obtain a dispersion, add 5 parts of 100-mesh expanded graphite to the dispersion, and stir and mix at high speed to prepare a flame retardant precursor. B2. Place the flame retardant precursor obtained in step B1 in a water bath at 75 °C, keep warm for 30 min, dropwise add 0.15 part of 0.5 mol / L ammonia water, stir for 2 h, let stand for 8 h, remove the solvent, dry, place it in a tubular furnace, heat to 350 °C under nitrogen protection, keep warm for 4 h, and cool to room temperature to obtain the composite flame retardant.

[0032] Comparative Example 4 The difference between this comparative example and Example 1 is only that in the preparation of the reinforcing filler, acrylic polymer is not added, and at the same time, in the preparation of the composite flame retardant, tetraethyl orthosilicate is not added either.

[0033] Effect Verification The outer sheath materials in Examples 1-5 and Comparative Examples 1-4 were used to make samples, and the mechanical properties and combustion performance were tested respectively: 1. Mechanical properties test: According to GB / T1040.2-2018, a universal tensile testing machine was used to test the tensile strength of each group of samples, where the sample shape was 1A type and the tensile speed was 100 mm / min; 2. Combustion performance test: The limiting oxygen index of each group of samples was tested in accordance with GB / T 2406.2-2009, and the vertical combustion grade of each group of samples was tested in accordance with GB / T2408-2021. The specific test results are shown in Table 1.

[0034] Tensile strength / Mpa Limiting oxygen index / % Vertical burning rating Example 1 40.6 31.5 V-0 Example 2 40.3 30.6 V-0 Example 3 40.4 30.9 V-0 Example 4 40.1 31.2 V-0 Example 5 39.8 31.0 V-0 Comparative example 1 36.4 29.4 V-0 Comparative example 2 34.3 30.7 V-0 Comparative example 3 38.6 25.5 V-1 Comparative example 4 29.2 24.1 V-2 Results Analysis By analyzing Examples 1-5 and Comparative Examples 1-4, and combining the data in Table 1, it can be seen that the fire-resistant low-voltage wire and cable outer sheath material provided by the present invention has a tensile strength of more than 39.8 MPa, a limiting oxygen index of more than 30.6%, a vertical combustion grade of V-0, and has excellent flame retardant properties and high mechanical strength. The specific analysis is as follows: Compared with Example 1, in Comparative Example 1, the maleic anhydride grafted polyethylene is replaced with LDPE resin in the raw material of the outer sheath granules, and the tensile strength of the outer sheath material obtained is reduced to a certain extent, indicating that the grafting treatment of maleic anhydride improves the mechanical strength of polyethylene by introducing polar groups.

[0035] Compared with Example 1, in Comparative Example 2, no acrylic polymer was added in the preparation of the reinforcing filler, and the tensile strength of the outer sheath material obtained was reduced to a certain extent, indicating that the acrylic polymer pre-treated the organic framework material, which can improve the dispersion ability of the glass fiber and enhance the mechanical strength of the outer sheath material; Compared with Example 1, in the preparation of the composite flame retardant, no ethyl orthosilicate was added, and the flame retardant properties of the prepared outer sheath material were significantly reduced, indicating that the addition of a silicon source for hydroxylation treatment can achieve uniform dispersion of the flame retardant material in the carrier, which can improve the flame retardant properties of the composite flame retardant; Compared with Example 1, in Comparative Example 4, no acrylic polymer was added in the preparation of the reinforcing filler, and no ethyl orthosilicate modification treatment was added in the preparation of the composite flame retardant. The tensile strength of the outer sheath material obtained was greatly reduced, and the flame retardant performance was also significantly reduced; It can be seen from comparative examples 2-4 and example 1 that pretreatment of the organic framework material with an acrylic polymer can enhance the mechanical strength of the outer sheath material, and adding a silicon source for hydroxylation treatment during the preparation of the flame retardant can improve the flame retardant properties of the composite flame retardant. At the same time, the two treatment methods can interact with each other, further improve the flame retardant properties, and jointly improve the mechanical properties of the material.

[0036] In addition, it should be noted that, for each of the specific technical features described in the above specific embodiments, they can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combinations.

[0037] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A fire-resistant low-voltage wire and cable, comprising two parts: an internal cable core bundle and an outer sheath, characterized in that, The outer sheath is prepared by melt-extruding outer sheath pellets, and the outer sheath pellets are prepared from the following raw materials: a resin matrix, a composite flame retardant, a reinforcing filler, and an anti-aging agent. The reinforcing filler is a glass fiber composite porous organic framework, wherein the organic framework material is pretreated with an acrylic polymer. The composite flame retardant is a shell with expanded graphite as the flame retardant material, and then is prepared by hydroxylation modification with a silicon source material.

2. The fire-resistant low-voltage wire and cable according to claim 1, characterized in that The preparation of the reinforcing filler includes the following steps: A1: Mix 10 parts of zinc nitrate hexahydrate, 10 - 15 parts of dimethylimidazole, and 0.3 - 0.5 part of KH560 evenly, add 30 - 50 parts of DMF, stir evenly, add 0.1 - 0.2 part of triethylamine, and react for 6 - 10 h to obtain an organic framework. A2: Add 2.5 - 3.5 parts of an acrylic polymer and 0.2 - 0.3 part of p-toluenesulfonic acid to the organic framework obtained in step A1, mix evenly, and stir for 2 - 3 h under nitrogen protection to obtain a pretreated organic framework. A3: Add 0.5 - 0.7 part of methyltrimethoxysilane, 0.3 - 0.5 part of sodium bicarbonate, and 1 part of glass fiber to the pretreated organic framework, stir at high speed for 0.5 - 1 h, heat to 70 - 80 °C, let stand for 10 - 20 min, filter, wash, and dry to obtain the reinforcing filler.

3. The fire-resistant low-voltage wire and cable according to claim 1, characterized in that The preparation of the composite flame retardant includes the following steps: B1: By weight, add 1 part of zinc borate, 0.5 - 0.8 part of magnesium hydroxide, and 0.1 - 0.2 part of a surfactant to 40 - 60 parts of an ethanol solution with a concentration of 70 - 80%, perform ultrasonic treatment for 5 - 10 min to obtain a dispersion liquid, and add 4 - 6 parts of 100-mesh expanded graphite to the dispersion liquid, stir and mix at high speed to prepare a flame retardant precursor. B2: Place the flame retardant precursor obtained in step B1 in a water bath at 70 - 80 °C, add 0.8 - 1.2 parts of tetraethyl orthosilicate, keep warm and stir for 20 - 40 min, dropwise add 0.1 - 0.2 part of 0.5 mol / L ammonia water, stir for 2 - 3 h, let stand for 4 - 8 h, remove the solvent, dry, then place it in a tubular furnace, heat to 300 - 400 °C under nitrogen protection, keep warm for 3 - 4 h, and cool to room temperature to obtain the composite flame retardant.

4. The fire-resistant low-voltage wire and cable according to claim 1, wherein, The preparation of maleic anhydride grafted polyethylene includes the following: Mix low-density polyethylene resin, benzoyl peroxide, and polydimethylsiloxane evenly according to a mass ratio of 100:0.4 - 0.6:0.8 - 1.2, place them in the mixing zone of an extrusion device for melt mixing, then add maleic anhydride monomer to the mixing zone of the extrusion device. The addition amount of maleic anhydride monomer is 2 - 5% of the weight of the low-density polyethylene resin. Pass nitrogen into the mixing zone and the termination zone of the extrusion device, and extrude and pelletize to obtain maleic anhydride grafted polyethylene.

5. The fire-resistant low-voltage wire and cable according to claim 1, characterized in that, In step A2, the acrylic polymer is selected from one or a mixture of two of polyacrylic acid and polymethacrylic acid.

6. The fire-resistant low-voltage wire and cable according to claim 1, characterized in that, The resin matrix is a premix of maleic anhydride grafted polyethylene and high-density polyethylene with a weight ratio of 3 - 5:

10.

7. The fire-resistant low-voltage wire and cable according to claim 1, wherein, By weight, the outer sheath pellets include the following raw materials: 100 parts of resin matrix, 19 - 21 parts of composite flame retardant, 7.5 - 8.5 parts of reinforcing filler, and 1 - 2 parts of anti-aging agent.

8. The fire-resistant low-voltage wire and cable according to claim 1, wherein, The anti-aging agent is one or more of antioxidant 1010, antioxidant 1330 and antioxidant 168 in admixture.

9. The fire-resistant low-voltage wire and cable according to claim 1, wherein The preparation process of the outer sheath granule is as follows: all raw materials are mixed evenly and added into a twin-screw extruder. Under the conditions that the temperature of the first zone is 100 - 120°C, the temperature of the second zone is 130 - 140°C, the temperature of the third zone is 145 - 160°C, the temperature of the fourth zone is 160 - 170°C, the temperatures of other zones are 175 - 185°C, and the temperature of the die head is 185 - 195°C, extrusion, cooling and pelletizing are carried out to obtain the outer sheath granule.

10. A preparation method of a fire-resistant low-voltage wire and cable for preparing the fire-resistant low-voltage wire and cable according to any one of claims 1-9, characterized in that, The preparation method includes the following steps: the outer sheath granule is put into an extruder for melt extrusion, and the outer sheath is coated on the outside of the internal cable core bundle to obtain a fire-resistant low-voltage wire and cable.