Flame-retardant and bend-resistant PVC wire duct and application thereof

Abstract

This invention discloses a flame-retardant and bend-resistant PVC cable tray and its application, belonging to the field of polymer materials technology. The cable tray comprises, by weight, 100 parts of polyvinyl chloride resin, 15-25 parts of a reactive flame-retardant and bend-resistant modifier, 4-6 parts of a calcium-zinc composite stabilizer, 0.5-1.0 parts of calcium stearate, 0.3-0.5 parts of zinc stearate, 0.2-0.5 parts of polyethylene wax, 1-4 parts of acrylate processing aids, 10-20 parts of light calcium carbonate, 2-4 parts of titanium dioxide, 1-2 parts of epoxidized soybean oil, and 0.1-0.5 parts of a silane hydrolysis condensation catalyst. The modifier used is prepared by reacting a phosphorus-boron-silicon flame retardant, polyether glycol, and aliphatic diisocyanate. This invention chemically anchors the phosphorus borosilicate flame-retardant structure into the polyurethane molecular chain and disperses it in the PVC matrix as a reactive modifier, achieving a synergistic coupling of multi-element flame retardancy and polyurethane toughening, which is suitable for building electrical wiring and communication cable laying scenarios.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a flame-retardant and bend-resistant PVC cable tray and its application. Background Technology

[0002] PVC cable trays are widely used in building electrical wiring and communication cable laying, and their flame-retardant properties are directly related to building fire safety. Pure rigid PVC resin has a chlorine content as high as about 56% and an intrinsic oxygen index of about 45%, exhibiting excellent self-extinguishing properties, extinguishing immediately upon removal of the flame. However, after adding plasticizers, modifiers, lubricants, and other organic additives, the flammability of the system increases significantly, and PVC still releases a large amount of smoke and toxic gases in a fire, thus requiring flame-retardant modification. Currently, industrial applications mostly use additive flame retardants, such as phosphate ester plasticizers or inorganic hydroxides. While phosphate ester plasticizers have good compatibility with the PVC matrix, their low molecular weight and high volatility make them prone to migration and precipitation during processing and use, leading to a decline in flame-retardant performance over time. Inorganic hydroxides, on the other hand, have poor compatibility with PVC and require large amounts to be effective.

[0003] With the increasing standards for building safety, the market urgently needs a PVC cable tray material that combines long-lasting flame retardancy, high toughness, and excellent bending resistance. However, existing technologies lack a reactive modification system that integrates phosphorus, boron, and silicon flame retardant elements with polyurethane toughening structures through chemical bonds and is suitable for the preparation of PVC cable trays. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a flame-retardant and bend-resistant PVC cable tray and its application. This cable tray uses polyvinyl chloride resin as the matrix, and achieves a synergistic improvement in flame retardancy and mechanical properties by adding a self-made reactive flame-retardant and bend-resistant modifier. The technical solution to achieve the purpose of this invention is as follows: A flame-retardant and bend-resistant PVC cable tray, by weight, comprises 100 parts of polyvinyl chloride resin, 15-25 parts of reactive flame-retardant and bend-resistant modifier, 4-6 parts of calcium-zinc composite stabilizer, 0.5-1.0 parts of calcium stearate, 0.3-0.5 parts of zinc stearate, 0.2-0.5 parts of polyethylene wax, 1-4 parts of acrylate processing aid, 10-20 parts of light calcium carbonate, 2-4 parts of titanium dioxide, 1-2 parts of epoxidized soybean oil, and 0.1-0.5 parts of silane hydrolysis condensation catalyst; wherein the reactive flame-retardant and bend-resistant modifier is an organosilicon-modified polyurethane with side-chain alkoxysilanes obtained by reacting a phosphorus-boron-silicon flame retardant, polyether glycol, and aliphatic diisocyanate.

[0005] Specifically, the aliphatic diisocyanate is selected from one or more of 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, and hexamethylene diisocyanate.

[0006] Specifically, the polyether glycol is selected from one or more of polytetrahydrofuran glycol, polypropylene glycol, and polyethylene glycol, and has a number average molecular weight of 1000-3000.

[0007] Specifically, the silane hydrolysis condensation catalyst is selected from one or more of dibutyltin dilaurate, tetrabutyl titanate, dibutyltin diacetate, and dioctyltin dilaurate. The preparation method of the reactive flame retardant and flexural modifier includes: reacting polyether glycol with aliphatic diisocyanate in an organic solvent to obtain isocyanate-terminated polyurethane prepolymer; then adding a phosphorus borosilicate flame retardant to carry out a chain extension reaction, removing the solvent, and obtaining the reactive flame retardant and flexural modifier.

[0008] The preparation method of the phosphorus-boron-silicon flame retardant includes the following steps: A dihydroxyarylphosphonoyl compound is reacted with an amino diol under dehydration conditions to obtain an amino intermediate containing a borate ester ring; the amino intermediate is then subjected to an amine-epoxy addition reaction with an epoxy silane compound to obtain a hydroxysilane intermediate; the hydroxysilane intermediate is then subjected to a ureation reaction with an isocyanate silane compound to generate a urea bond between the secondary amino group and the isocyanate group, thus obtaining a phosphorus borosilicate flame retardant.

[0009] Specifically, the dihydroxyarylphosphono compound is obtained by reacting arylphosphonodihalogen with hydroxyarylboronic acid in the presence of an acid-binding agent; the arylphosphonodihalogen is phenylphosphonodichloro; the hydroxyarylboronic acid is selected from 4-hydroxyphenylboronic acid and 3-hydroxyphenylboronic acid; and the acid-binding agent is triethylamine.

[0010] Specifically, the aminodiol is selected from one or more of 3-amino-1,2-propanediol, 2-amino-1,3-propanediol, 4-amino-1,2-butanediol, 2-amino-2-methyl-1,3-propanediol, and 2-amino-2-ethyl-1,3-propanediol; the epoxysilane compound is selected from 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-( The isocyanate silane compound is selected from one or more of 2,3-epoxypropoxy)propylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, and 3-glycidyl etheroxypropylmethyldimethoxysilane; the isocyanate silane compound is selected from one or two of propyltriethoxysilane and propyltrimethoxysilane.

[0011] A method for preparing a flame-retardant and bend-resistant PVC cable tray includes the following steps: S1. Premix: Polyvinyl chloride resin, reactive flame retardant and flexural modifier, calcium-zinc composite stabilizer, calcium stearate, zinc stearate, polyethylene wax, acrylate processing aids, light calcium carbonate, titanium dioxide, and epoxidized soybean oil are put into a high-speed mixer. The mixture is first stirred at low speed and then stirred at high speed until the material temperature rises to 100~110℃. It is then cooled to no higher than 40℃ to obtain the premix. S2. Extrusion Molding: The premixed material is added to a conical twin-screw extruder for extrusion molding. The barrel temperature is set as follows: feeding section 140~150℃, plasticizing section 160~170℃, homogenizing section 170~180℃, and die head and mold temperature 170~180℃. After vacuum shaping, cooling, and traction cutting, the profile is obtained. The catalyst solution is applied to the surface of the profile by spraying or impregnation. S3. Moisture crosslinking curing: The profile is placed under constant temperature and humidity conditions to allow the side-chain alkoxysilanes to hydrolyze and condense to form a siloxane crosslinking network, resulting in a flame-retardant and bend-resistant PVC cable tray.

[0012] Specifically, in step S2, the screw speed of the conical twin-screw extruder is 10~30 rpm, the traction speed is 0.5~2.0 m / min, the vacuum exhaust port is kept open, and the residence time of the material in the die head section does not exceed 1 min; in step S3, the constant temperature and humidity conditions are a temperature of 38~42℃, a relative humidity of 65~75%, and a standing time of 72~96 h.

[0013] Another objective of this invention is to protect the application of the flame-retardant and bend-resistant PVC trunking or the flame-retardant and bend-resistant PVC trunking prepared by the preparation method of the flame-retardant and bend-resistant PVC trunking in building electrical wiring and communication cable laying.

[0014] This invention achieves a synergistic coupling of multi-element flame retardancy and polyurethane toughening by chemically anchoring a phosphorus-boron-silicon flame retardant into the molecular chain of a polyurethane prepolymer and then dispersing it as a reactive modifier in the polyvinyl chloride matrix. In the gas phase, phosphorus decomposes upon heating to generate phosphorus-oxygen free radicals, which capture hydrogen and hydroxyl free radicals in the combustion chain reaction, inhibiting flame propagation. In the condensed phase, boron melts upon heating to form a glassy capping layer, isolating heat and oxygen transfer, and synergistically promoting the formation of a dense char layer with phosphorus. Silicon hydrolyzes and condenses during the moisture curing stage to form a three-dimensional siloxane crosslinking network, giving the material elastic recovery ability and improving bending resistance. Simultaneously, it undergoes a ceramic transformation during high-temperature combustion, stabilizing the char layer structure and preventing cracking and detachment. The polyether segments in the polyurethane soft segments provide low-temperature flexibility and high elongation, while the aliphatic isocyanate-derived hard segments form physical crosslinking points through hydrogen bonds, improving strength without sacrificing flexibility. The flame retardant is firmly embedded in the polyurethane backbone through urea bonds and urethane bonds, and then forms an elastic cross-linking domain in the modifier phase through a siloxane cross-linking network. It forms a good interfacial bond with the polyvinyl chloride body through dipole-dipole interactions and physical entanglement, so that the stress is evenly distributed during bending.

[0015] Beneficial effects

[0016] This invention provides a flame-retardant and bend-resistant PVC cable tray, with the following specific advantages: 1. Possesses synergistic flame retardant effect between gas phase and condensed phase. The reactive flame retardant and flexural modifier used in the cable tray contains a phenyl phosphonate structure. At high temperatures, the PO bond in the phosphorus-containing structure breaks, generating phosphorus-containing free radicals such as PO· and HPO·, which capture hydrogen free radicals and hydroxyl free radicals in the gas phase, interrupting the combustion chain reaction; the aromatic ring structure increases the thermal decomposition temperature, promotes the dehydration and char formation of polyvinyl chloride matrix, and forms a dense phosphorus-carbon layer on the surface of the cable tray, blocking the conduction of heat and combustible gases to the interior of the matrix.

[0017] 2. Possesses excellent condensed phase oxygen and heat insulation capabilities. The 1,3,2-dioxaborane structure contained in the modifier melts upon heating to form a boron trioxide glassy layer, which covers the outside of the phosphorus carbon layer, further isolating oxygen and heat; compared with linear boron esters, cyclic borate esters have relatively better hydrolytic stability and can maintain structural integrity under dry processing conditions, ensuring long-lasting flame retardant efficiency.

[0018] 3. Excellent load-bearing strength and stability of the expanded char layer. The urea bonds in the modifier can form strong hydrogen bonds between hard segments, improving the load-bearing strength and rigidity of the groove; during high-temperature combustion, the urea bonds decompose to produce non-combustible gases such as ammonia and carbon dioxide, diluting the oxygen concentration in the gas phase, while simultaneously promoting the expansion of the char layer to form a porous heat-insulating structure, enhancing the flame-retardant barrier effect.

[0019] 4. Good bending resistance and high-temperature residual carbon structure stability. The modifier side group triethoxysilane is hydrolyzed and condensed under moisture curing to construct a three-dimensional cross-linked network of siloxane, which acts as elastic cross-linking points to disperse bending stress and improve the bending resistance and elastic recovery performance of the cable tray. During high-temperature combustion, the siloxane is converted into a silicon dioxide ceramic layer, which works synergistically with the phosphorus carbon layer to form a dense barrier layer, inhibiting the cracking and peeling of the carbon layer and maintaining the structural integrity of the cable tray under fire conditions.

[0020] 5. Long-lasting flame retardant performance and good interfacial compatibility with the matrix. The secondary hydroxyl groups on the side of the modifier act as chain extension sites, reacting with the isocyanate-terminated polyurethane prepolymer to form urethane bonds, chemically anchoring the phosphorus-boron-silicon flame retardant structure to the polyurethane backbone; the urea bonds (NH) provide intermolecular hydrogen bonds, enhancing the cohesive force of the hard segments, inhibiting the migration and precipitation of flame retardants in the polyvinyl chloride matrix, and ensuring long-term flame retardant stability; the secondary hydroxyl groups and polar groups such as urethane and urea bonds can generate dipole-dipole interactions with the polyvinyl chloride molecular chains, improving the interfacial compatibility between the two phases and avoiding the decline in mechanical properties caused by phase separation.

[0021] 6. Excellent flexibility and low-temperature flexibility. The 4,4-diisocyanate dicyclohexylmethane-derived hard segments in the modifier form physical cross-linking points through hydrogen bonds, providing load-bearing strength; the polytetrahydrofuran soft segments endow the material with low-temperature flexibility and high elongation. The microphase separation structure of hard and soft segments dissipates energy during bending through shear bands and micro-region deformation mechanisms, improving the bending resistance of the wire groove.

[0022] 7. Stable flexibility over a wide temperature range, with excellent long-term service durability. The modifier polytetrahydrofuran soft segment contains ether bonds and methylene chains, resulting in a low glass transition temperature, which allows the wire groove to maintain high elasticity and flexibility over a wide temperature range. Moderate crystallization of this soft segment can reinforce the material without sacrificing flexibility, and its hydrolysis resistance is superior to that of polyester glycol, making it suitable for long-term use in humid environments.

[0023] 8. This invention achieves synergistic effects of phosphorus, boron, and silicon ternary flame-retardant elements through chemical bonding. It combines the polyurethane microphase separation structure with polyvinyl chloride body to form a good interface bond through dipole-dipole interaction and physical entanglement, taking into account flame retardant durability, high toughness, bending resistance and low temperature flexibility. It overcomes the technical defects of traditional additive flame-retardant PVC wire trough flame retardants, such as easy migration and difficulty in balancing flame retardancy and mechanical properties. Attached Figure Description

[0024] Figure 1 Synthetic route diagram for bisureoyltetrasilane phosphorus boron flame retardant 1.

[0025] Figure 2 The image shows the 1H NMR spectrum of bisureoyltetrasilane phosphorus boron flame retardant 1. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0028] The raw materials and equipment used in the embodiments and comparative examples are described below, where eq represents the equivalent amount: Polyvinyl chloride resin: Suspension polyvinyl chloride resin, SG-5 type, conforming to GB / T 5761-2018, commercially available.

[0029] Polytetrahydrofuran: molecular weight 1950~2050 g / mol, hydroxyl value 54.7~57.5 mg KOH / g, conforming to GB / T25254-2022, selected from BASF PolyTHF. ® 2000.

[0030] Acrylic ester processing aids: Acrylic ester copolymers, CAS 25852-37-3, commercially available.

[0031] Diureo-tetrasilane phosphorus boron flame retardant 1: Self-made, preparation method as follows: Under nitrogen protection, 2.2 eq of 4-hydroxyphenylboronic acid and 2.4 eq of anhydrous triethylamine were dissolved in dry tetrahydrofuran and stirred at -10 to 0 °C for 10 min. Then, 1.0 eq of phenylphosphonodichloro ... Å molecular sieves were stirred at 40 °C for 24 h. After the reaction, most of the N,N-dimethylformamide was removed by rotary evaporation at 70 °C and a vacuum of approximately 20 mmHg. Then, the mixture was dried at 80 °C and a vacuum of no more than 0.1 mmHg for 6 h to completely remove residual solvent and water, yielding bis(4-(4-(aminomethyl)-1,3,2-dioxaborhexacyclopentan-2-yl)phenyl)phenylphosphonate. Under nitrogen protection, 1.0 eq of the above bis(4-(4-(aminomethyl)-1,3,2-dioxaborhexacyclopentan-2-yl)phenyl)phenylphosphonate was dissolved in anhydrous toluene, and 2.05 eq of 3-(2,3-epoxypropoxy)propyltriethoxysilane was added. The reaction was carried out at 55 °C for 8 h. After the reaction, the mixture was dried at 120 °C and a vacuum of ≤1 Excess epoxysilane and toluene were removed by vacuum distillation under reduced pressure at mmHg until no fraction was distilled off, yielding a dihydroxy-disilane intermediate. Under strict nitrogen protection, 1.0 eq of the above dihydroxy-disilane intermediate was dissolved in dry N,N-dimethylformamide, and 2.05 eq of propyltriethoxysilane isocyanate was added. The mixture was reacted at 60°C for 6 h, and infrared monitoring showed that the intensity of the isocyanate peak no longer decreased. After the reaction, most of the N,N-dimethylformamide was removed by rotary evaporation at 60°C and a vacuum of approximately 20 mmHg. The residue was dissolved in a small amount of dry toluene and then slowly added dropwise to cold n-hexane that had been dried for more than 24 h using a 4 Å molecular sieve under vigorous stirring. A precipitate was formed, filtered, and collected. The precipitate was washed three times with cold n-hexane and dried under vacuum to obtain crude bisureotetrasilane phosphorus boron flame retardant 1. The crude bisureotetrasilane phosphorus boron flame retardant 1 was dissolved in dry toluene, and 10% (by weight) of activated carbon was added. The mixture was stirred at room temperature for 1 hour. h, filter to remove activated carbon, remove solvent from filtrate by vacuum distillation to obtain bisureoyltetrasilane phosphorus boron flame retardant 1, dispense in nitrogen-filled glove box, seal in brown glass bottle, and store at -20℃ protected from light.

[0032] Diureotetrasilane phosphorus-boron flame retardant 2: self-made. The preparation method is the same as that of diureotetrasilane phosphorus-boron flame retardant 1, except that 3-(2,3-epoxypropoxy)propyltriethoxysilane is replaced with 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and propyltriethoxyisocyanate is replaced with propyltrimethoxyisocyanate, while other conditions remain unchanged, thus obtaining diureotetrasilane phosphorus-boron flame retardant 2.

[0033] Diureodisilane phosphorus boron flame retardant 3: self-made. The preparation method is the same as that of diureotetrasilane phosphorus boron flame retardant 1, except that propyltriethoxysilane isocyanate is replaced with n-octyl isocyanate, while other conditions remain unchanged, thus obtaining diureodisilane phosphorus boron flame retardant 3.

[0034] Monoureodisilane phosphorus boron flame retardant 4: self-made. The preparation method is the same as that of bisureotetrasilane phosphorus boron flame retardant 1, except that phenylphosphonodichloride is replaced with diphenylphosphonodichloride, while other conditions remain unchanged, thus obtaining monoureodisilane phosphorus boron flame retardant 4.

[0035] Preparation Example Preparation Example 1 Reactive flame retardant and flexural modifier 1: Self-made, preparation method as follows: Under nitrogen protection, 1.0 eq of polytetrahydrofuran containing 2.0 eq of hydroxyl groups was dissolved in dry N,N-dimethylformamide and stirred at 60°C for 30 min. Then, 2.0 eq of 4,4'-diisocyanate dicyclohexylmethane containing 4.0 eq of isocyanate groups was added, and the mixture was reacted at 80°C for 4 h. Unreacted 4,4'-dicyclohexylmethane diisocyanate monomers were removed by vacuum distillation at 120°C and a vacuum degree not exceeding 0.5 mmHg for 2 h, yielding an isocyanate-terminated polyurethane prepolymer. The isocyanate-terminated polyurethane prepolymer was cooled to 60°C, and 1.0 eq of bisureoyltetrasilane phosphorus boron flame retardant 1 was added. 0.03% by weight of dibutyltin dilaurate was added as a catalyst, and the mixture was reacted at 60°C for 4 h. The temperature was then raised to 80°C for 2 h. h, under these conditions, the terminal isocyanate group preferentially reacts with the secondary hydroxyl group of the flame retardant side group to form an urethane bond to achieve chain extension. The urea bond NH mainly contributes to the intermolecular hydrogen bond enhancement. The amount of biuret generated is negligible. After the infrared monitoring of the isocyanate peak intensity no longer decreases, the solvent is removed at 80℃ and a vacuum degree not exceeding 0.1 mmHg until constant weight is obtained to obtain reactive flame retardant and bending resistance modifier 1.

[0036] Preparation Example 2 Reactive flame retardant and flexural modifier 2: self-made. The preparation method is the same as that of reactive flame retardant and flexural modifier 1, except that bisureotetrasilane phosphorus boron flame retardant 1 is replaced with bisureotetrasilane phosphorus boron flame retardant 2, while other conditions remain unchanged, thus obtaining reactive flame retardant and flexural modifier 2.

[0037] Preparation Example 3 Reactive flame retardant and flexural modifier 3: self-made. The preparation method is the same as that of reactive flame retardant and flexural modifier 1, except that bisureotetrasilane phosphorus boron flame retardant 1 is replaced with bisureodisilane phosphorus boron flame retardant 3, while other conditions remain unchanged, thus obtaining reactive flame retardant and flexural modifier 3.

[0038] Preparation Example 4 Modifier 4: Self-made. The preparation method is the same as that of reactive flame retardant and flexural modifier 1. The difference is that the bisureotetrasilane phosphorus boron flame retardant 1 is replaced with monoureodisilane phosphorus boron flame retardant 4, while other conditions remain unchanged, thus obtaining modifier 4.

[0039] Examples and Comparative Examples Example 1

[0040] Flame-retardant and bend-resistant PVC cable tray 1: Self-made, preparation method as follows: By weight, 100 parts of polyvinyl chloride resin, 20 parts of the above-mentioned reactive flame retardant and flexural modifier, 1.5 parts of calcium-zinc composite stabilizer, 0.8 parts of calcium stearate, 0.4 parts of zinc stearate, 0.4 parts of polyethylene wax, 2 parts of acrylate processing aids, 15 parts of light calcium carbonate, 3 parts of titanium dioxide, and 1.5 parts of epoxidized soybean oil are sequentially added to a high-speed mixer. The mixture is first stirred at a low speed of 700 rpm for 2 minutes, then stirred at a high speed of 2000 rpm until the material temperature reaches 110°C. The material is then discharged and placed in a cooling mixer to cool to a temperature not exceeding 40°C, yielding a premix. The premix is ​​then added to a conical twin-screw extruder for extrusion molding. The barrel temperature is set as follows: feeding section 145°C, plasticizing section 165°C, homogenizing section 175°C, and die head and mold temperature 175°C. The residence time of the material in the die head section is strictly controlled to not exceed 1 minute. The screw speed is 30 rpm, and the traction speed is 1... At a speed of m / min, the vacuum exhaust port of the extruder is kept open. After vacuum shaping, circulating water cooling, and traction cutting, a profile is obtained. 0.2 parts of dibutyltin dilaurate solution are applied to the surface of the profile by spraying. The profile is placed in a constant temperature and humidity curing chamber, with the temperature controlled at 40℃ and the relative humidity at 70%. It is left to stand for 96 h to allow the side group triethoxysilane to hydrolyze and condense under the action of moisture to form a siloxane cross-linked network. After curing, it is left to stand at room temperature for 24 h to eliminate internal stress, and flame-retardant and bend-resistant PVC cable tray 1 is obtained.

[0041] Example 2

[0042] Flame-retardant and bend-resistant PVC cable tray 2: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable tray 1, except that the amount of reactive flame-retardant and bend-resistant modifier 1 is replaced with 15 parts, the amount of calcium-zinc composite stabilizer is replaced with 4 parts, the amount of calcium stearate is replaced with 0.5 parts, the amount of zinc stearate is replaced with 0.3 parts, the amount of polyethylene wax is replaced with 0.2 parts, the amount of acrylate processing aid is replaced with 1 part, the amount of light calcium carbonate is replaced with 10 parts, the amount of titanium dioxide is replaced with 2 parts, and the amount of epoxidized soybean oil is replaced with 1 part. All other conditions remain unchanged, thus obtaining flame-retardant and bend-resistant PVC cable tray 2.

[0043] Example 3

[0044] Flame-retardant and bend-resistant PVC cable trough 3: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable trough 1, except that the amount of reactive flame-retardant and bend-resistant modifier 1 is replaced with 25 parts, the amount of calcium-zinc composite stabilizer is replaced with 6 parts, the amount of calcium stearate is replaced with 1 part, the amount of zinc stearate is replaced with 0.5 parts, the amount of polyethylene wax is replaced with 0.5 parts, the amount of acrylate processing aid is replaced with 4 parts, the amount of light calcium carbonate is replaced with 20 parts, the amount of titanium dioxide is replaced with 4 parts, and the amount of epoxidized soybean oil is replaced with 2 parts. All other conditions remain unchanged, thus obtaining flame-retardant and bend-resistant PVC cable trough 3.

[0045] Example 4

[0046] Flame-retardant and bend-resistant PVC cable tray 4: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable tray 1, except that reactive flame-retardant and bend-resistant modifier 1 is replaced with reactive flame-retardant and bend-resistant modifier 2, while other conditions remain unchanged, thus obtaining flame-retardant and bend-resistant PVC cable tray 4.

[0047] Example 5

[0048] Flame-retardant and bend-resistant PVC cable tray 5: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable tray 1, except that the reactive flame-retardant and bend-resistant modifier 1 is replaced with reactive flame-retardant and bend-resistant modifier 3, while other conditions remain unchanged, thus obtaining flame-retardant and bend-resistant PVC cable tray 5.

[0049] Comparative Example 1 PVC cable tray 6: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable tray 1, except that the reactive flame-retardant and bend-resistant modifier 1 is replaced with modifier 4, while other conditions remain unchanged, to obtain PVC cable tray 6.

[0050] Comparative Example 2 PVC cable tray 7: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable tray 1, except that the reactive flame-retardant and bend-resistant modifier 1 is replaced with triphenyl phosphate, while other conditions remain unchanged, to obtain PVC cable tray 7.

[0051] Comparative Example 3 PVC cable tray 8: The preparation method is the same as that of flame-retardant and bend-resistant PVC cable tray 1. The difference is that 20 parts of reactive flame-retardant and bend-resistant modifier 1 are replaced with 16 parts of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and 4 parts of zinc borate. All other conditions remain unchanged to obtain PVC cable tray 8.

[0052] The following are the test methods for performance parameters involved in this invention: 1. Nuclear magnetic resonance hydrogen spectrum test: Characterization was performed using a nuclear magnetic resonance spectrometer (Bruker Avance III HD 600, 600MHz).

[0053] 2. Limiting oxygen index: Performed according to GB / T 2406.2-2009 "Determination of combustion behavior by oxygen index method for plastics - Part 2: Room temperature test", with sample size of 80 mm × 10 mm × 4 mm. Conditioning was performed according to GB / T 2918-2018 at a temperature of 23±2℃ and a relative humidity of 50±5% for no less than 40 h before testing.

[0054] 3. Vertical flammability rating: Performed according to GB / T 2408-2021 "Determination of flammability of plastics - Horizontal and Vertical Methods", with a sample size of 125 mm × 13 mm × 3 mm. Conditioning was performed according to GB / T 2918-2018 at a temperature of 23±2℃ and a relative humidity of 50±5% for no less than 40 h before testing.

[0055] 4. Tensile properties and elongation at break: Performed according to GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics", using type 1A dumbbell-shaped specimens with a thickness of 3~4 mm, tensile rate of 50 mm / min, and conditioning according to GB / T 2918-2018 at a temperature of 23±2℃ and a relative humidity of 50±5% for no less than 40 h before testing.

[0056] 5. Bending strength: Performed according to GB / T 9341-2008 "Determination of bending properties of plastics", with a sample size of 80 mm × 10 mm × 4 mm, a span of 64 mm, a test rate of 2 mm / min, and conditioning according to GB / T 2918-2018 at a temperature of 23±2℃ and a relative humidity of 50±5% for no less than 40 h before testing.

[0057] 6. Notched impact strength: Performed according to GB / T 1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test", with a specimen size of 80 mm × 10 mm × 4 mm, V-notch, and conditioning according to GB / T 2918-2018 at a temperature of 23±2℃ and a relative humidity of 50±5% for no less than 40 h before testing.

[0058] 7. Shore Hardness: Perform according to GB / T 2411-2008 "Determination of Indentation Hardness (Shore Hardness) of Plastics and Hard Rubber Using a Hardness Tester", using a Shore D hardness tester, with a sample thickness ≥6 mm (stacked if insufficient), and take the reading 15 s after the indenter contacts the sample. Conditioning should be performed according to GB / T 2918-2018, under conditions of 23±2℃ and 50±5% relative humidity for no less than 40 h before testing.

[0059] 8. Repeated Bending Performance: The test was conducted using a repeated bending tester according to GB / T 12586-2003, "Determination of Flexural Destructive Resistance of Rubber or Plastic Coated Fabrics". The grooved sample was fixed on a special fixture, and the bending radius was set to 10 mm and the frequency to 30 times / min. Repeated bending was performed at room temperature, and the number of bends at the point of sample breakage was recorded. Conditioning was performed according to GB / T2918-2018 at a temperature of 23±2℃ and a relative humidity of 50±5% for no less than 40 hours before testing.

[0060] Table 1 Performance test results of the examples and comparative examples

[0061] As shown in Table 1, in Example 1, the phosphorus-boron-silicon ternary synergistic flame retardant system and the polyurethane toughening structure are integrated through chemical bonds. The flame retardant elements are uniformly dispersed in the polyvinyl chloride matrix and do not easily migrate. The siloxane crosslinking network gives the material excellent elastic recovery ability, thus achieving the highest flame retardant level. The mechanical strength and flexural life are both well-balanced and excellent, and the Shore hardness is moderate, taking into account both rigidity and toughness. In Example 2, due to the reduction in the amount of modifier, the total content of flame retardant elements is reduced, and the efficiency of gas-phase free radical capture and condensed phase char formation is slightly reduced, resulting in a corresponding decrease in the flame retardant level by one grade. However, the polyurethane soft segment still provides a good toughening effect, and the mechanical properties and flexural resistance remain at a good level. The hardness is slightly increased due to the reduction in toughening agent. Example 3 increased the amount of modifier, increased the content of phosphorus, boron, and silicon flame retardant elements, further improved the flame retardant efficiency in both the gas and condensed phases, and increased the crosslinking density of siloxanes. However, the excessive modifier caused the compatibility between the polyurethane polar segments and polyvinyl chloride to approach saturation, increasing the tendency for interfacial stress concentration. This resulted in a slight decrease in mechanical strength and flexural life compared to Example 1, and a decrease in hardness due to the increase in flexible segments. Example 4 used trimethoxysilane instead of triethoxysilane. Trimethoxysilane has higher hydrolytic condensation activity and a faster moisture crosslinking rate. The siloxane network density is similar to that of Example 1, so the overall performance and hardness are similar. Example 5 uses n-octyl isocyanate instead of isocyanate silane, halving the number of silane groups on the molecular side chain, making it difficult to form a dense three-dimensional siloxane crosslinking network. During combustion, there is no silicon ceramic layer to protect the char layer, thus the flame retardant performance is lower than in Example 1. However, the double urea bond structure still provides a certain hydrogen bond toughening effect, and its bending life is higher than that of the single urea structure in Comparative Example 1. However, due to the significantly insufficient density of the siloxane crosslinking network, its bending resistance is still far lower than that of Example 1, and the stability of the residual char structure at high temperatures is insufficient. Comparative Example 1 uses a flame retardant prepared with a monofunctional phosphonyl chloride. The number of borate ester rings, urea bonds, silane side groups, and secondary hydroxyl chain extension sites in the molecule is all halved, and it contains only one chain extension site, making linear chain extension impossible. The boron-silicon synergistic char formation efficiency and siloxane crosslinking density are insufficient, resulting in a flame retardant rating and bending resistance significantly inferior to the examples. It has higher hardness but insufficient toughness. Comparative Example 2 uses a traditional small-molecule phosphate flame retardant physically blended with polyvinyl chloride. The flame retardant has no chemical bond with the matrix and is prone to migration and precipitation when heated. Triphenyl phosphate is a small-molecule flame retardant plasticizer that melts at the processing temperature and plasticizes polyvinyl chloride. Although it increases the elongation at break, it weakens the intermolecular forces, resulting in a decrease in load-bearing strength and hardness. Moreover, its compatibility with polyvinyl chloride is limited, and it is prone to migration and exudation under bending stress and heat, resulting in the shortest bending fatigue life.Comparative Example 3 uses a physical compound of phosphorus-containing flame retardant compound and inorganic zinc borate. Although it has a certain synergistic flame retardant effect of phosphorus and boron, it lacks a polyurethane toughening structure and a siloxane cross-linking network. Stress concentration cannot be effectively dispersed, and its flame retardant and bending resistance are inferior to those of the embodiments of the present invention. The hardness is too high due to the introduction of the rigid aromatic ring structure of 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide and the stress concentration caused by poor compatibility with polyvinyl chloride. In addition, it lacks the toughening effect of polyurethane soft segments, and the material exhibits hard and brittle characteristics.

[0062] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame-retardant and bend-resistant PVC trunking, characterized in that, By weight, it comprises 100 parts of polyvinyl chloride resin, 15-25 parts of reactive flame retardant and flexural modifier, 4-6 parts of calcium-zinc composite stabilizer, 0.5-1.0 parts of calcium stearate, 0.3-0.5 parts of zinc stearate, 0.2-0.5 parts of polyethylene wax, 1-4 parts of acrylate processing aid, 10-20 parts of light calcium carbonate, 2-4 parts of titanium dioxide, 1-2 parts of epoxidized soybean oil, and 0.1-0.5 parts of silane hydrolysis and condensation catalyst; the reactive flame retardant and flexural modifier is an organosilicon modified polyurethane with side group containing alkoxysilane, obtained by reacting phosphorus borosilicate flame retardant, polyether glycol and aliphatic diisocyanate.

2. The flame retardant and bend resistant PVC conduit of claim 1, wherein, The aliphatic diisocyanate is selected from one or more of 4,4-diisocyanate dicyclohexylmethane, isophorone diisocyanate, and hexamethylene diisocyanate.

3. The fire-retardant, bend-resistant PVC conduit of claim 1, wherein, The polyether glycol is selected from one or more of polytetrahydrofuran glycol, polypropylene glycol, and polyethylene glycol, and has a number average molecular weight of 1000-3000.

4. The flame-retardant and bend-resistant PVC cable tray as described in claim 1, characterized in that, The preparation method of the reactive flame retardant and flexural modifier includes: reacting polyether glycol with aliphatic diisocyanate in an organic solvent to obtain isocyanate-terminated polyurethane prepolymer; then adding a phosphorus borosilicate flame retardant to carry out a chain extension reaction, removing the solvent, and obtaining the reactive flame retardant and flexural modifier.

5. The flame-retardant and bend-resistant PVC cable tray as described in claim 1, characterized in that, The preparation method of the phosphorus-boron-silicon flame retardant includes the following steps: A dihydroxyarylphosphonoyl compound is reacted with an amino diol under dehydration conditions to obtain an amino intermediate containing a borate ester ring; the amino intermediate is then subjected to an amine-epoxy addition reaction with an epoxy silane compound to obtain a hydroxysilane intermediate; the hydroxysilane intermediate is then subjected to a ureation reaction with an isocyanate silane compound to generate a urea bond between the secondary amino group and the isocyanate group, thus obtaining a phosphorus borosilicate flame retardant.

6. The flame-retardant and bend-resistant PVC cable tray as described in claim 5, characterized in that, The dihydroxyarylphosphonoyl compound is obtained by reacting arylphosphonoyl dihalogen with hydroxyarylboronic acid in the presence of an acid-binding agent; the arylphosphonoyl dihalogen is phenylphosphonoyl dichloro; the hydroxyarylboronic acid is selected from one or two of 4-hydroxyphenylboronic acid and 3-hydroxyphenylboronic acid; the acid-binding agent is triethylamine.

7. The flame-retardant and bend-resistant PVC cable tray as described in claim 5, characterized in that, The aminodiol is selected from one or more of 3-amino-1,2-propanediol, 2-amino-1,3-propanediol, 4-amino-1,2-butanediol, 2-amino-2-methyl-1,3-propanediol, and 2-amino-2-ethyl-1,3-propanediol; the epoxysilane compound is selected from 3-(2,3-epoxypropoxy)propyltriethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, and 3-(2,3-epoxypropoxy)propyltrimethoxysilane. The isocyanate silane compound is selected from one or more of the following: 3-epoxypropoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 5,6-epoxyhexyltriethoxysilane, and 3-glycidyl etheroxypropylmethyldimethoxysilane; wherein the isocyanate silane compound is selected from one or two of propyltriethoxysilane and propyltrimethoxysilane.

8. A method for preparing a flame-retardant and bend-resistant PVC cable tray as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Premix: Polyvinyl chloride resin, reactive flame retardant and flexural modifier, calcium-zinc composite stabilizer, calcium stearate, zinc stearate, polyethylene wax, acrylate processing aids, light calcium carbonate, titanium dioxide, and epoxidized soybean oil are put into a high-speed mixer. The mixture is first stirred at low speed and then stirred at high speed until the material temperature rises to 100~110℃. It is then cooled to no higher than 40℃ to obtain the premix. S2. Extrusion Molding: The premixed material is added to a conical twin-screw extruder for extrusion molding. The barrel temperature is set as follows: feeding section 140~150℃, plasticizing section 160~170℃, homogenizing section 170~180℃, and die head and mold temperature 170~180℃. After vacuum shaping, cooling, and traction cutting, the profile is obtained. The catalyst solution is applied to the surface of the profile by spraying or impregnation. S3. Moisture crosslinking curing: The profile is placed under constant temperature and humidity conditions to allow the side-chain alkoxysilanes to hydrolyze and condense to form a siloxane crosslinking network, resulting in a flame-retardant and bend-resistant PVC cable tray.

9. The method for preparing the flame-retardant and bend-resistant PVC cable tray as described in claim 8, characterized in that, In step S2, the screw speed of the conical twin-screw extruder is 10~30 rpm, the traction speed is 0.5~2.0 m / min, the vacuum exhaust port is kept open, and the residence time of the material in the die head section does not exceed 1 min; in step S3, the constant temperature and humidity conditions are a temperature of 38~42℃, a relative humidity of 65~75%, and a standing time of 72~96 h.

10. The application of the flame-retardant and bend-resistant PVC cable tray as described in any one of claims 1 to 7, or the flame-retardant and bend-resistant PVC cable tray prepared by the preparation method of the flame-retardant and bend-resistant PVC cable tray as described in any one of claims 8 to 9, in building electrical wiring and communication cable laying.

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