Flame-retardant PVC-C fire-fighting pipe and preparation method thereof

Abstract

The invention relates to the technical field of plastic pipelines, and particularly discloses a flame-retardant PVC-C fire-fighting pipe and a preparation method thereof. The flame-retardant PVC-C fire-fighting pipe is prepared from the following raw materials: 100 to 150 parts of PVC-C resin, 5 to 10 parts of CPE (Chlorinated Polyethylene) resin and 2 to 3 parts of zinc stearate. The composite material is prepared from the following components in parts by weight: 3-5 parts of calcium stearate, 1-3 parts of a processing aid, 0.5-1 part of a lubricant, 2-4 parts of a flame retardant, 5-10 parts of filler, 2-5 parts of modified aramid fibers, 1-5 parts of a nano toughening agent, 4-9 parts of an ethylene-octylene copolymer and 0.3-0.7 part of an antioxidant. The modified aramid fibers are aramid fibers which are modified by polydopamine and then grafted with polyethylene glycol monomethyl ether; the nano toughening agent is a nano boron nitride-polyether amine core-shell structure toughening agent. The fire-fighting pipe has the advantage of being high in low-temperature resistance, still has good toughness and strength in a low-temperature environment, and can meet the fire-fighting requirements in severe cold areas.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic pipe, more particularly, it relates to a flame-retardant PVC-C fire pipe and a preparation method thereof. BACKGROUND

[0002] As a kind of excellent performance fire pipe material, flame-retardant PVC-C fire pipe has been widely used in the market in recent years. PVC-C (chlorinated polyvinyl chloride) material has excellent flame retardant performance, high limiting oxygen index, and can extinguish immediately away from fire, effectively preventing flame spread and reducing fire risk. At the same time, it also has good heat resistance, can maintain stable performance at high temperature environment, and meets the use requirements of fire pipe in high temperature scene of fire. In addition, PVC-C fire pipe has strong chemical corrosion resistance, can resist the corrosion of various chemicals, has long service life, and is convenient to install and relatively low in cost. These advantages make it become a key component in the fire protection system of various buildings such as commercial buildings, residences and public facilities.

[0003] In the related art, a patent application file with publication number CN111690221A discloses a PVC-C pipe for fire engineering and a preparation method thereof. The pipe includes the following components by mass fraction: PVC-C resin 100 parts, stabilizer 5-8 parts, impact modifier 3-5 parts, processing aid 1-2 parts, internal lubricant 0.5-1 part, external lubricant 1-2 parts, flame retardant 2-4 parts, filler 5-10 parts, antioxidant 0.3-0.5 parts, ultraviolet absorber 0.2-0.5 parts and hindered amine light stabilizer 0.2-0.5 parts. The stabilizer includes calcium stearate, zinc stearate, beta-diketone and stearic acid modified hydrotalcite. The pipe has good processing performance and excellent mechanical properties, and can be applied to fire pipe.

[0004] However, in actual use, the fire pipe in the above-mentioned prior art still has defects. From the perspective of material performance, although PVC-C has many advantages, its molecular chain movement ability will significantly decrease under low temperature conditions, the interaction between molecules will increase, resulting in a significant decrease in material toughness and an increase in brittleness. When the external temperature decreases to a certain extent, the fire pipe is easily broken under the action of external force impact or internal water pressure change, which affects its use performance and service life. This not only affects the normal operation of the fire protection system, but also may cause serious consequences in emergency situations such as fire. Therefore, the fire pipe in the above-mentioned prior art has the defect of poor low temperature resistance, which cannot meet the fire protection needs in cold regions. SUMMARY

[0005] In order to improve the low temperature resistance of flame-retardant PVC-C fire pipe, the present application provides a flame-retardant PVC-C fire pipe and a preparation method thereof.

[0006] The application provides a fire-fighting pipe made of PVC-C, which adopts the following technical scheme: The fire-fighting pipe made of PVC-C is made of raw materials with the following weight components: PVC-C resin 100-150 parts, CPE resin 5-10 parts, zinc stearate 2-3 parts, calcium stearate 3-5 parts, processing aid 1-3 parts, lubricant 0.5-1 part, flame retardant 2-4 parts, filler 5-10 parts, modified aramid fiber 2-5 parts, nano toughening agent 1-5 parts, ethylene-octene copolymer 4-9 parts and antioxidant 0.3-0.7 part; The modified aramid fiber is aramid fiber grafted with polyethylene glycol monomethyl ether after being modified by polydopamine; The nano toughening agent is a nano boron nitride-polyether amine core-shell structure toughening agent.

[0007] By adopting the above technical scheme, the PVC-C resin serves as a matrix and inherits the high flame retardancy and heat resistance of chlorinated polyvinyl chloride, which is the basis for realizing the function of the fire-fighting pipe. However, the inherent defect of the PVC-C resin is that the molecular chain movement ability decreases suddenly at low temperature, the intermolecular force increases, and the brittleness increases. Therefore, the CPE resin is introduced into the formula as an impact modifier. The elastomer characteristics of the CPE resin can form a dispersed phase in the PVC-C matrix to absorb impact energy, partially making up for the loss of toughness at low temperature. The surface of the traditional aramid fiber is inert, and the interface between the aramid fiber and the PVC-C matrix is weak, which is easy to cause brittle fracture due to interface debonding at low temperature. In the present application, a reactive interface is constructed by a polydopamine coating, and then a polyethylene glycol monomethyl ether flexible segment is grafted, forming a “rigid fiber-flexible transition layer” structure. At low temperature, the polyethylene glycol segment can still maintain the movement, and the impact energy can be absorbed by the segment curling. At the same time, the high strength characteristics of the aramid fiber can bridge the cracks and prevent crack propagation, solving the problem of low-temperature interface brittle fracture caused by traditional fiber toughening. The nano toughening agent has a rigid core of nano boron nitride, which changes the stress transfer path by using the stress dispersion effect of the lamellar structure of the nano boron nitride to avoid local stress concentration. The polyether amine flexible segment covalently grafted on the surface as a shell can still maintain the molecular chain movement at low temperature, forming an “elastic buffer layer” to absorb impact energy, thereby enhancing the toughness of the fire-fighting pipe at low temperature. The core-shell structure is connected by covalent bond to avoid phase separation, and the amino group of the polyether amine forms a hydrogen bond with the chlorine atom of the PVC-C, which significantly improves the interface compatibility. Through the compounding of multiple raw materials, the problems of poor molecular chain movement and insufficient toughness of the PVC-C at low temperature are solved, so that the fire-fighting pipe can still maintain excellent impact resistance in severe cold environments, meeting the low-temperature use requirements.

[0008] Optionally, the modified aramid fiber is prepared by the following method: The aramid fiber is dispersed in a Tris-HCl buffer solution, then dopamine hydrochloride is added, and the reaction is stirred for 8-12 hours to form a polydopamine coating aramid fiber, then the polydopamine coating aramid fiber is filtered, and then the polydopamine coating aramid fiber is immersed in a toluene solution of polyethylene glycol monomethyl ether at 60-70 DEG C for 4-6 hours, and after washing and drying, the modified aramid fiber is obtained.

[0009] By adopting the above technical solution, the modification method makes the aramid fiber not only transmit stress through the rigid skeleton at low temperature, but also absorb impact energy through the flexible chain segment, avoiding the defects of easy agglomeration and unstable toughening effect of the simple physical mixed fiber.

[0010] Optionally, the mass ratio of the aramid fiber to the Tris-HCl buffer solution is 1: (20-30), and the added amount of the dopamine hydrochloride is 5%-10% of the mass of the aramid fiber.

[0011] Optionally, the mass concentration of the toluene solution of polyethylene glycol monomethyl ether is 10%-15%, and the solid-liquid ratio of the aramid fiber to the toluene solution of polyethylene glycol monomethyl ether is 1: (10-15).

[0012] By adopting the above technical solution, the above ratio makes the aramid fiber completely immersed in the solution, ensuring that the surface of each fiber can be uniformly grafted with a polyethylene glycol chain segment. If the solid-liquid ratio is too low, the fiber dispersion is insufficient, which can easily lead to uneven grafting; and if the solid-liquid ratio is too high, the solvent cost is increased. The thickness of the flexible transition layer of the grafted fiber is controllable under this parameter, the chain segment movement is more stable at low temperature, and the toughening effect is significantly improved.

[0013] Optionally, the nano-toughening agent is prepared by the following method: A. The nano-boron nitride is dispersed in N, N-dimethylformamide, ultrasonic stripping for 30-40 minutes, and then a silane coupling agent containing an epoxy group is added, and the reaction is stirred at 80-90 DEG C for 2-3 hours to obtain an epoxy-modified nano-boron nitride; B. The epoxy-modified nano-boron nitride, polyether amine, and anhydrous ethanol are added to a reaction kettle, and the reaction is carried out at 60-70 DEG C for 4-6 hours, and then the nano-toughening agent is obtained after centrifugal separation and vacuum drying.

[0014] By adopting the above technical solution, the silane coupling agent introduces an epoxy group, which undergoes ring-opening reaction with the amino group of the polyether amine to form a stable covalent bond, avoiding the problems of easy agglomeration of the nanoparticles and poor compatibility with the matrix in traditional physical mixing. The core-shell structure toughening agent prepared by this process can not only disperse stress through the boron nitride sheet at low temperature, but also buffer impact through the polyether amine chain segment, and the toughening effect is more durable.

[0015] Optionally, in step A, the mass ratio of the nano boron nitride and N, N-dimethylformamide is 1: (10-15), and the addition amount of the epoxy group-containing silane coupling agent is 5%-10% of the mass of the nano boron nitride.

[0016] Optionally, in step B, the mass ratio of the epoxy group-modified nano boron nitride, the polyether amine and the anhydrous ethanol is 1: (1.5-2.5): (20-30).

[0017] By adopting the above technical solution, the raw material ratio can promote the ring-opening reaction of the epoxy group and the amino group, and improve the grafting efficiency. The toughening agent prepared under the parameters is more uniformly dispersed in the PVC-C matrix, and the synergistic effect of the chain segment mobility and stress dispersion at low temperature is more significant.

[0018] Optionally, the lubricant includes pentaerythritol stearate and polyethylene wax with a mass ratio of 1: (1-1.5).

[0019] Optionally, the flame retardant is chlorinated paraffin; and the filler is at least one of nano calcium carbonate, talcum powder and montmorillonite.

[0020] By adopting the above technical solution, the filler is used to improve the pipe rigidity and dimensional stability, has a small particle size and is uniformly dispersed, and will not become a stress concentration point at low temperature. In cooperation with the toughening agent, the rigidity and toughness are balanced.

[0021] The application also provides a preparation method of the flame-retardant PVC-C fire-fighting pipe. The preparation method of the flame-retardant PVC-C fire-fighting pipe includes the following steps: S1, the PVC-C resin, the CPE resin, the zinc stearate, the calcium stearate, the antioxidant, the modified aramid fiber, the nano toughening agent, the ethylene-octene copolymer, the processing aid, the lubricant, the flame retardant and the filler are sequentially added to a high-speed mixer, mixed at 500-600 r / min for 3-5 min, and then mixed at 1000-1200 r / min until the material temperature reaches 95-105℃, and then unloaded and cooled to obtain a mixed material; S2, the mixed material is added to a double-screw extruder for extrusion, the barrel temperature is set to 170-185℃, the die head temperature is set to 185-195℃, the screw rotation speed is set to 200-250 r / min, and then the flame-retardant PVC-C fire-fighting pipe is obtained after vacuum sizing, water cooling and traction cutting.

[0022] The above preparation method first premixes at low speed and then mixes at high speed and high temperature, which can avoid the agglomeration of the modified aramid fiber and the nano toughening agent, and ensure that each component is uniformly distributed in the PVC-C matrix. The barrel temperature of 150-185℃ and the screw speed of 200-250r / min ensure that the material is fully plasticized, the vacuum sizing and water cooling can quickly fix the pipe structure, and avoid the residual internal stress caused by uneven cooling. The pipe prepared by the method has small fluctuation in low temperature performance and high batch stability.

[0023] In summary, the present application has the following beneficial effects: 1. In the present application, a "rigidity-flexibility" multi-scale toughening system of modified aramid fiber and nano toughening agent is used, a reactive interface is constructed by a polydopamine coating and a polyethylene glycol monomethyl ether flexible segment is grafted, and a core-shell structure toughening agent is formed by taking nano boron nitride as a rigid core and polyether amine as a flexible shell, so that the effect of multi-path dissipation of impact energy at low temperature is obtained. The "rigid fiber-flexible transition layer" structure of the modified aramid fiber can absorb energy by curling of the polyethylene glycol segment at low temperature, and can bridge the cracks by using the high strength of aramid; the core-shell structure of the nano toughening agent disperses stress by slipping of the boron nitride sheet layer, and the polyether amine shell layer provides elastic buffer. The continuous phase of ethylene-octene copolymer is increased in flexibility to form a three-level toughening network, which solves the problem of brittle fracture caused by poor molecular chain mobility of PVC-C at low temperature, and thus effectively enhances the low temperature resistance of the fire hose.

[0024] 2. In the present application, a pentaerythritol stearate and polyethylene wax composite lubricating system is preferably used, which has a synergistic effect of reducing intermolecular friction of PVC-C by internal lubrication and reducing equipment friction by external lubrication, so that the raw materials are uniformly dispersed and the processing stability is improved. The pentaerythritol stearate ensures that the modified aramid fiber, nano toughening agent and other nano fillers are fully infiltrated in the melt, avoiding agglomeration caused by intermolecular friction; the polyethylene wax reduces the adhesion of the melt to the equipment, maintaining the stability of extrusion. This system effectively improves the uniformity of dispersion of the modified aramid fiber in the PVC-C matrix, and the nano toughening agent has no agglomeration phenomenon, solving the problem of uneven dispersion of fillers caused by single component of traditional lubricants, thereby avoiding brittle fracture caused by local stress concentration at low temperature. DETAILED DESCRIPTION

[0025] The present application will be further described in detail below in combination with examples.

[0026] Preparation example of modified aramid fiber Preparation example 1 The modified aramid fiber is prepared by the following method: 5 kg of short-cut aramid fibers were dispersed in 100 kg of Tris-HCl buffer solution, then 0.25 kg of dopamine hydrochloride was added, and the reaction was stirred for 8 h to form polydopamine-coated aramid fibers, then filtration was performed, and the filtered polydopamine-coated aramid fibers were immersed in 50 kg of a toluene solution of polyethylene glycol monomethyl ether with a mass concentration of 10%, and the reaction was carried out at 60°C for 4 h, and after washing and drying, modified aramid fibers were obtained.

[0027] Preparation Example 2 Modified aramid fibers were prepared by the following method: 5 kg of short-cut aramid fibers were dispersed in 120 kg of Tris-HCl buffer solution, then 0.4 kg of dopamine hydrochloride was added, and the reaction was stirred for 10 h to form polydopamine-coated aramid fibers, then filtration was performed, and the filtered polydopamine-coated aramid fibers were immersed in 60 kg of a toluene solution of polyethylene glycol monomethyl ether with a mass concentration of 12%, and the reaction was carried out at 65°C for 5 h, and after washing and drying, modified aramid fibers were obtained.

[0028] Preparation Example 3 Modified aramid fibers were prepared by the following method: 5 kg of short-cut aramid fibers were dispersed in 150 kg of Tris-HCl buffer solution, then 0.5 kg of dopamine hydrochloride was added, and the reaction was stirred for 12 h to form polydopamine-coated aramid fibers, then filtration was performed, and the filtered polydopamine-coated aramid fibers were immersed in 75 kg of a toluene solution of polyethylene glycol monomethyl ether with a mass concentration of 15%, and the reaction was carried out at 70°C for 6 h, and after washing and drying, modified aramid fibers were obtained.

[0029] Preparation Example of nano-toughening agent Preparation Example 4 Nano-toughening agent was prepared by the following method: A. 5 kg of nano-boron nitride was dispersed in 50 kg of N,N-dimethylformamide, and ultrasonic stripping was performed for 30 min, then 0.25 kg of silane coupling agent kh560 was added, and the reaction was stirred at 80°C for 2 h to obtain epoxy-modified nano-boron nitride; B. 5 kg of epoxy-modified nano-boron nitride, 7.5 kg of polyether amine, and 100 kg of absolute ethanol were mixed and added to a reaction kettle, and the reaction was carried out at 60°C for 4 h, then centrifugal separation and vacuum drying were performed to obtain a nano-toughening agent.

[0030] Preparation Example 5 Nano-toughening agent was prepared by the following method: A, 5 kg of nano boron nitride was dispersed in 60 kg of N, N-dimethylformamide, ultrasonic exfoliation for 35 min, then 0.4 kg of silane coupling agent kh560 was added, and the reaction was stirred at 85℃ for 2.5h to obtain epoxy modified nano boron nitride; B, 5 kg of epoxy modified nano boron nitride, 10 kg of polyether amine and 125 kg of anhydrous ethanol were mixed and added to the reaction kettle, and reacted at 65℃ for 5h, then centrifuged, vacuum dried to obtain a nano toughening agent.

[0031] Preparation Example 6 The nano toughening agent was prepared by the following method: A, 5 kg of nano boron nitride was dispersed in 75 kg of N, N-dimethylformamide, ultrasonic exfoliation for 40 min, then 0.5 kg of silane coupling agent kh560 was added, and the reaction was stirred at 90℃ for 3h to obtain epoxy modified nano boron nitride; B, 5 kg of epoxy modified nano boron nitride, 12.5 kg of polyether amine and 150 kg of anhydrous ethanol were mixed and added to the reaction kettle, and reacted at 70℃ for 6h, then centrifuged, vacuum dried to obtain a nano toughening agent.

[0032] Example Example 1 A flame-retardant PVC-C fire pipe was prepared by the following method:

[0033] A flame-retardant PVC-C fire pipe was prepared by the following method: S1, PVC-C resin, CPE resin, zinc stearate, calcium stearate, antioxidant, modified aramid fiber, nano toughening agent, ethylene-octene copolymer, processing aid, lubricant, flame retardant and filler were added to a high-speed mixer in turn, first mixed at 500r / min for 3min, then mixed at 1000r / min until the material temperature reached 95℃, unloaded and cooled to obtain a mixture; S2, the mixture was added to a twin-screw extruder for extrusion, the barrel temperature was set to 170℃, the die head temperature was 185℃, the screw speed was 200r / min, and after vacuum sizing, water cooling and traction cutting, a flame-retardant PVC-C fire pipe was obtained.

[0034] Example 2 A fire-fighting pipe of flame-retardant PVC-C is prepared by the following method, wherein the raw material components and the proportioning are shown in Table 1, the processing aid is ACR resin, the lubricant comprises pentaerythritol stearate and polyethylene wax with a mass ratio of 1:1.2, the flame retardant is chlorinated paraffin, the filler is talcum powder, the modified aramid fiber is the modified aramid fiber prepared in Preparation Example 2, the nano toughening agent is the nano toughening agent prepared in Preparation Example 4, and the ethylene-octene copolymer has an octene content of 30%.

[0035] A fire-fighting pipe of flame-retardant PVC-C is prepared by the following method, wherein the raw material components and the proportioning are shown in Table 1, the processing aid is ACR resin, the lubricant comprises pentaerythritol stearate and polyethylene wax with a mass ratio of 1:1.2, the flame retardant is chlorinated paraffin, the filler is talcum powder, the modified aramid fiber is the modified aramid fiber prepared in Preparation Example 2, the nano toughening agent is the nano toughening agent prepared in Preparation Example 4, and the ethylene-octene copolymer has an octene content of 30%. S1, the PVC-C resin, the CPE resin, zinc stearate, calcium stearate, the antioxidant, the modified aramid fiber, the nano toughening agent, the ethylene-octene copolymer, the processing aid, the lubricant, the flame retardant and the filler are sequentially added to a high-speed mixer, mixed at 550 r / min for 4 min, and then mixed at 1100 r / min until the material temperature reaches 100 DEG C, and then the material is discharged and cooled to obtain a mixture; S2, the mixture is added to a double-screw extruder for extrusion, the barrel temperature is set to 180 DEG C, the die head temperature is set to 190 DEG C, the screw rotation speed is set to 220 r / min, and after vacuum sizing, water cooling and traction cutting, a fire-fighting pipe of flame-retardant PVC-C is obtained.

[0036] Example 3 A fire-fighting pipe of flame-retardant PVC-C is prepared by the following method, wherein the raw material components and the proportioning are shown in Table 1, the processing aid is ACR resin, the lubricant comprises pentaerythritol stearate and polyethylene wax with a mass ratio of 1:1.2, the flame retardant is chlorinated paraffin, the filler is talcum powder, the modified aramid fiber is the modified aramid fiber prepared in Preparation Example 2, the nano toughening agent is the nano toughening agent prepared in Preparation Example 4, and the ethylene-octene copolymer has an octene content of 30%.

[0037] A fire-fighting pipe of flame-retardant PVC-C is prepared by the following method, wherein the raw material components and the proportioning are shown in Table 1, the processing aid is ACR resin, the lubricant comprises pentaerythritol stearate and polyethylene wax with a mass ratio of 1:1.2, the flame retardant is chlorinated paraffin, the filler is talcum powder, the modified aramid fiber is the modified aramid fiber prepared in Preparation Example 2, the nano toughening agent is the nano toughening agent prepared in Preparation Example 4, and the ethylene-octene copolymer has an octene content of 30%. S1, the PVC-C resin, the CPE resin, zinc stearate, calcium stearate, the antioxidant, the modified aramid fiber, the nano toughening agent, the ethylene-octene copolymer, the processing aid, the lubricant, the flame retardant and the filler are sequentially added to a high-speed mixer, mixed at 550 r / min for 4 min, and then mixed at 1100 r / min until the material temperature reaches 100 DEG C, and then the material is discharged and cooled to obtain a mixture; S2, the mixture is added to a double-screw extruder for extrusion, the barrel temperature is set to 180 DEG C, the die head temperature is set to 190 DEG C, the screw rotation speed is set to 220 r / min, and after vacuum sizing, water cooling and traction cutting, a fire-fighting pipe of flame-retardant PVC-C is obtained.

[0038] Table 1 Raw materials and proportioning of fire-fighting pipes in Examples 1-3 (kg)

[0039] Example 4 A fire-fighting pipe of flame-retardant PVC-C, which is different from Example 1 in that the nano-toughening agent used in this example is the nano-toughening agent prepared in Preparation Example 5.

[0040] Example 5 A fire-fighting pipe of flame-retardant PVC-C, which is different from Example 1 in that the nano-toughening agent used in this example is the nano-toughening agent prepared in Preparation Example 6.

[0041] Comparative Example Comparative Example 1 A PVC-C fire-fighting pipe is prepared according to the method in Example 1 of the patent application file with the publication number CN111690221A and the name of a PVC-C pipe for fire-fighting engineering and its preparation method.

[0042] Comparative Example 2 A fire-fighting pipe of flame-retardant PVC-C, which is different from Example 1 in that no CPE resin is added in this comparative example, and the difference is replaced by PVC-C resin.

[0043] Comparative Example 3 A fire-fighting pipe of flame-retardant PVC-C, which is different from Example 1 in that an equal amount of unmodified aramid fiber is used instead of modified aramid fiber in this comparative example.

[0044] Comparative Example 4 A fire-fighting pipe of flame-retardant PVC-C, which is different from Example 1 in that an equal amount of nano-boron nitride is used instead of nano-toughening agent in this comparative example.

[0045] Performance test 1. The fire-fighting pipes prepared in Examples 1-5 and Comparative Examples 1-4 are placed in a low-temperature box with a temperature setting of -30℃ for 24h, and then the low-temperature impact strength of the fire-fighting pipes prepared in Examples 1-5 and Comparative Examples 1-4 is tested according to GB / T14152-2001 "Test method for resistance to external impact of thermoplastic pipes". The higher the value, the better the low-temperature toughness. The results are shown in Table 2.

[0046] 2. The fire-fighting pipes prepared in Examples 1-5 and Comparative Examples 1-4 are placed in a low-temperature box with a temperature setting of -30℃ for 24h, and then the tensile strength and elongation at break of the fire-fighting pipes prepared in Examples 1-5 and Comparative Examples 1-4 are tested according to GB / T1040.3-2006 "Determination of tensile properties of plastics - Part 3". The higher the value, the better the ductility of the material at low temperature, and it is not easy to break. The results are shown in Table 2.

[0047] Table 2 Test results

[0048] In Examples 1-5, the low-temperature impact strength of Examples 1-5 is maintained at 13.2-14.1 kJ / m 2 , the tensile strength is between 57.79-58.62 MPa, and the elongation at break is 17.3%-18.7%, which are significantly better than Comparative Examples 1-4. Due to the use of the modified aramid fiber and the nano-toughening agent in the application, a multi-scale toughening system is used to construct a reactive interface and graft a polyethylene glycol monomethyl ether flexible segment through a polydopamine coating, and a core-shell structure toughening agent is formed by using nano-boron nitride as a rigid core and polyether amine as a flexible shell, thereby achieving the effect of impact energy multi-path dissipation at low temperature, and thus effectively enhancing the low-temperature performance of the fire hose.

[0049] The low-temperature impact strength of Comparative Example 1 is 7.4 kJ / m 2 , the tensile strength is 22.42 MP, and the elongation at break is 6.5%, which are significantly lower than the examples, indicating that the traditional PVC-C pipe material has a significant brittle fracture problem at low temperature, and cannot meet the fire protection needs in cold regions.

[0050] In the fire hose of Comparative Example 2, since CPE resin is not added, the low-temperature performance (impact strength 8.7 kJ / m 2 , tensile strength 35.27 MPa) is significantly worse than the examples, indicating that CPE resin as an impact modifier is indispensable, and its elastomer characteristics can absorb impact energy and compensate for the loss of low-temperature toughness, which is directly related to the synergistic effect of CPE and modified fiber and nano-toughening agent in the application.

[0051] In the fire hose of Comparative Example 2, since unmodified aramid fiber is directly used as the raw material, the low-temperature impact strength (9.6 kJ / m 2 ) and the tensile strength (40.36 MPa) of the fire hose are lower than the examples, indicating that the interface debonding problem caused by the inert surface of the unmodified fiber has not been solved, and the "rigid fiber-flexible transition layer" structure formed by the polydopamine-polyethylene glycol monomethyl ether grafting can still absorb energy through the flexible segment at low temperature, and can bridge the crack through the high strength of aramid, thereby significantly improving the interface bonding force.

[0052] Comparative Example 4 uses nano-boron nitride instead of nano-toughening agent, resulting in low-temperature performance (impact strength 9.3 kJ / m 2 , tensile strength 39.87 MPa) worse than the examples, indicating that pure nano-boron nitride cannot buffer the impact at low temperature due to the lack of a flexible shell, while the core-shell structure toughening agent of the application achieves a more efficient toughening effect through the elastic buffering of the polyether amine shell and the stress dispersion of the boron nitride core.

[0053] In summary, the application solves the low-temperature brittle fracture problem of PVC-C through the synergistic effect of the multi-scale toughening system, CPE resin impact modification and composite lubricating system, significantly improves the low-temperature resistance of the fire pipe, and meets the use demand in severe cold regions.

[0054] The specific embodiments are only an explanation of the application, and are not a limitation of the application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, but as long as the modifications are within the scope of the claims of the application, they are protected by the patent law.

Claims

1. A flame-retardant PVC-C fire hose, characterized in that The raw material is made of the following weight components: PVC-C resin 100-150 parts, CPE resin 5-10 parts, zinc stearate 2-3 parts; calcium stearate 3-5 parts, processing aid 1-3 parts, lubricant 0.5-1 part, flame retardant 2-4 parts, filler 5-10 parts, modified aramid fiber 2-5 parts, nano toughening agent 1-5 parts, ethylene-octene copolymer 4-9 parts and antioxidant 0.3-0.7 parts; The modified aramid fiber is aramid fiber grafted with polyethylene glycol monomethyl ether after being modified by polydopamine; The nano toughening agent is a nano boron nitride-polyether amine core-shell structure toughening agent.

2. A fire-retardant PVC-C fire hose as claimed in claim 1, characterized in that: The modified aramid fiber is prepared by the following method: The aramid fiber is dispersed in a Tris-HCl buffer solution, then dopamine hydrochloride is added, and the mixture is stirred for 8-12 hours to form aramid fiber coated with a polydopamine coating, then filtered, and the aramid fiber coated with a polydopamine coating is immersed in a toluene solution of polyethylene glycol monomethyl ether and reacted at 60-70°C for 4-6 hours, then washed and dried to obtain the modified aramid fiber.

3. A fire-retardant PVC-C fire hose according to claim 2, characterized in that: The mass ratio of the aramid fiber to the Tris-HCl buffer solution is 1:(20-30), and the amount of dopamine hydrochloride added is 5%-10% of the mass of the aramid fiber.

4. A fire-retardant PVC-C fire hose as claimed in claim 2, characterized in that: The mass concentration of the toluene solution of polyethylene glycol monomethyl ether is 10%-15%, and the solid-liquid ratio of the aramid fiber to the toluene solution of polyethylene glycol monomethyl ether is 1:(10-15).

5. A fire-retardant PVC-C fire hose as claimed in claim 1, characterized in that: The nano toughening agent is prepared by the following method: A. Nano boron nitride is dispersed in N,N-dimethylformamide, ultrasonically exfoliated for 30-40 minutes, and then a silane coupling agent containing an epoxy group is added and stirred at 80-90°C for 2-3 hours to obtain epoxy-modified nano boron nitride; B. The epoxy-modified nano boron nitride, polyether amine and anhydrous ethanol are added to a reaction kettle and reacted at 60-70°C for 4-6 hours, then centrifuged and vacuum dried to obtain the nano toughening agent.

6. A fire-retardant PVC-C fire hose according to claim 5, characterized in that: In step A, the mass ratio of the nano boron nitride to N,N-dimethylformamide is 1:(10-15), and the amount of the silane coupling agent containing an epoxy group added is 5%-10% of the mass of the nano boron nitride.

7. A fire-retardant PVC-C fire hose as claimed in claim 5, characterized in that: In step B, the mass ratio of the epoxy-modified nano boron nitride, polyether amine and anhydrous ethanol is 1:(1.5-2.5):(20-30).

8. A fire-retardant PVC-C fire hose as claimed in claim 1, wherein: The lubricant includes pentaerythritol stearate and polyethylene wax in a mass ratio of 1:(1-1.5).

9. A fire-retardant PVC-C fire hose as claimed in claim 1, wherein: The flame retardant is chlorinated paraffin; and the filler is at least one of nano calcium carbonate, talcum powder and montmorillonite.

10. A process for the preparation of a fire-retardant PVC-C fire hose according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: S1. The PVC-C resin, CPE resin, zinc stearate, calcium stearate, antioxidant, modified aramid fiber, nano toughening agent, ethylene-octene copolymer, processing aid, lubricant, flame retardant and filler are sequentially added to a high-speed mixer, mixed at 500-600 r / min for 3-5 minutes, then mixed at 1000-1200 r / min until the material temperature reaches 95-105°C, and then the mixture is discharged and cooled to obtain a mixed material; S2, the mixture is added into a double screw extruder for extrusion, the barrel temperature is set to 170-185℃, the die head temperature is set to 185-195℃, the screw rotation speed is set to 200-250r / min, and after vacuum sizing, water cooling and traction cutting, the flame-retardant PVC-C fire-fighting pipe is obtained.

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