Flame-retardant waterproof coiled material PE composite film and preparation method thereof

Abstract

The application discloses a kind of flame-retardant waterproof roll material PE composite film and preparation method thereof, belong to composite film technical field, aluminium hydroxide is chelated with zinc chloride and tin chloride under nitrogen, and polydopamine is coated, and zinc / tin composite flame retardant is obtained;Wood pulp fiber is pretreated with dimethylammonium hydrogen phosphate, urea and aminotri-methylene phosphonic acid high-temperature esterification, and phosphated cellulose is obtained, which is coated with polyaniline to obtain polyaniline coated phosphated cellulose;Zinc / tin composite flame retardant, phosphated cellulose and PE matrix are melt-blended, and then coated with the composite slurry of waterborne polyurethane and polyaniline coated phosphated cellulose mixture, and solidified to obtain a kind of flame-retardant waterproof roll material PE composite film;It has excellent mechanical properties, waterproofness and moisture and heat aging resistance, and is suitable for tunnel, basement and other harsh environments.

Description

Technical Field

[0001] This invention belongs to the field of composite membrane technology, specifically relating to a flame-retardant waterproof PE composite membrane and its preparation method. Background Technology

[0002] PE composite waterproof membrane is a waterproof material made primarily of polyethylene. It features high mechanical strength, aging resistance, strong puncture resistance, high coefficient of friction, flexibility, and corrosion resistance. It solves the problems of traditional single-material waterproof membranes, such as pure PE membranes which have high strength but poor flexibility and are prone to cracking at corners during construction, and EVA membranes which have good flexibility but insufficient strength and are prone to damage and leakage during construction. Neither of these two types of membranes can achieve both strength and toughness, leading to potential engineering hazards.

[0003] In recent years, building codes in various countries have raised the requirements for the flame retardancy rating of building materials, especially in places such as subways, tunnels, and high-rise buildings. Traditional waterproof membrane PE composite film cannot meet the new standards, which has led to the development of flame retardant composite film.

[0004] Flame-retardant waterproof membrane PE composite film is a composite material that combines flame-retardant properties and waterproof function. It is usually made by thermal bonding of a multi-layer co-extruded base film and needle-punched geotextile.

[0005] Chinese invention patent application CN 119610805A discloses a corrosion-resistant asphalt waterproof membrane and its preparation method. The method involves mixing petroleum asphalt, inorganic filler, and antioxidant in stages with heating and stirring, followed by the addition of SBS and a coupling agent to obtain the main layer material. Epoxy resin, ethylene-vinyl acetate copolymer, compatibilizer, and curing agent are then mixed in stages to obtain the corrosion-resistant layer material. Polyether polyol and flame retardant are stirred, dehydrated, and then reacted with isocyanate to obtain the flame-retardant layer material. Polyether ether ketone, epoxy-modified polyurethane, and compatibilizer are melt-blended to obtain the wear-resistant layer material.

[0006] The anti-corrosion layer, flame retardant layer, and wear-resistant layer materials are extruded by twin screws, pressed, cooled, crushed, and screened to form granules. The main layer material is extruded, calendered, cooled, and shaped. The flame retardant layer granules and wear-resistant layer granules are sprayed onto both sides of the main layer and calendered for the first time. Then, the anti-corrosion layer granules are sprayed onto the surface of the flame retardant layer and calendered for the second time to complete the overall composite. Finally, the material is cooled, shaped, corrected, and wound into a finished product.

[0007] However, in damp environments such as tunnels and basements, inorganic fillers are prone to absorbing moisture and expanding, which can cause stress cracking of the flame retardant layer, hydrolysis of ester groups in the polyurethane molecular chain, chain breakage, reduced strength, bulging and delamination, longitudinal cracks leading to leakage, and failure of flame retardant function. Summary of the Invention

[0008] The purpose of this invention is to solve the problem of decreased flame retardancy, waterproof durability and mechanical stability of waterproof PE composite membranes in humid environments, and to provide a flame retardant waterproof PE composite membrane and its preparation method.

[0009] This invention obtains a zinc / tin composite flame retardant by chelating aluminum hydroxide with zinc chloride and tin chloride under nitrogen and then coating it with polydopamine; pretreating wood pulp fibers with dimethylammonium hydrogen phosphate and urea and esterifying them at high temperature with aminotrimethylene phosphonic acid to obtain phosphorylated cellulose, which is then coated with polyaniline to obtain polyaniline-coated phosphorylated cellulose; melt-blending the zinc / tin composite flame retardant, phosphorylated cellulose, and PE matrix, then coating them with a composite slurry of waterborne polyurethane and polyaniline-coated phosphorylated cellulose, followed by silane coupling and isocyanate crosslinking, and curing to obtain a flame-retardant waterproof membrane PE composite film.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] A method for preparing a flame-retardant waterproof PE composite membrane includes the following steps:

[0012] Step 1: Mix polyethylene, ethylene-octene copolymer and benzoyl peroxide, add polyurethane prepolymer and bismuth isooctanoate, stir, then add zinc / tin composite flame retardant and phosphorylated cellulose, stir at 2000 rpm for 5-10 min, transfer to an extruder, stretch into a film at 140-160℃ to obtain a polyethylene-based film.

[0013] Step 2: Coat waterborne polyurethane and polyaniline with phosphorylated cellulose, stir at 2000 rpm for 8-10 min, then add isocyanate and 0.5 wt% glacial acetic acid, stir for 5-8 min, then add silane coupling agent KH550, and ultrasonically disperse to obtain composite slurry.

[0014] Step 3: The polyethylene base film is subjected to corona treatment to obtain a pretreated base film; the composite slurry is applied to the surface of the pretreated base film, pre-cured at 40-50℃ for 8-10 minutes, and then ultrasonically atomized with 0.1wt% acetic acid mist. After heating to 80-90℃ at 10℃ / min, it is deeply cured for 40-50 minutes and cooled to obtain a flame-retardant waterproof PE composite membrane.

[0015] Furthermore, the mass ratio of polyethylene, ethylene-octene copolymer, benzoyl peroxide, polyurethane prepolymer, bismuth isooctanoate, zinc / tin composite flame retardant, and phosphorylated cellulose is 45-50:5-10:0.5-1.0:15-20:0.3-0.5:18-22:2-4.

[0016] Furthermore, the ratio of waterborne polyurethane, polyaniline-coated phosphorylated cellulose, isocyanate, 0.5wt% glacial acetic acid, and silane coupling agent KH550 is 40-45g: 3-5g: 1.0-1.5g: 2-3mL: 0.6-1.0g.

[0017] Furthermore, the zinc / tin composite flame retardant is prepared by the following steps:

[0018] Aluminum hydroxide powder with a particle size of 200 nm and an aqueous ethanol solution were added to a reaction vessel, nitrogen gas was introduced, and the mixture was sonicated at 600-700 W for 20-30 min. Zinc chloride, tin chloride and dopamine hydrochloride were then added, and the mixture was stirred for 10-15 min. Tris(hydroxymethyl)aminomethane was added, and the pH was adjusted to 8.5. The mixture was stirred at 40-50 °C for 8-10 h. The mixture was washed 3-5 times by centrifugation with ethanol and then vacuum dried to obtain the zinc / tin composite flame retardant.

[0019] Furthermore, the ratio of aluminum hydroxide powder, ethanol aqueous solution, zinc chloride, tin chloride and dopamine hydrochloride is 25-30g: 500-600mL: 3.0-3.4g: 1.0-1.5g: 5-6g.

[0020] Furthermore, phosphorylated cellulose is prepared by the following steps:

[0021] Dimethylammonium hydrogen phosphate, urea, and deionized water are added to a reaction vessel and stirred for 20-30 minutes. Then, wood pulp fibers are added and stirred for 1-1.5 hours. The mixture is filtered, and the filter cake is dried at 60-70°C for 10-12 hours. The filter cake is then pulverized in the gas phase to obtain wood pulp fiber fragments. The wood pulp fiber fragments and aminotrimethylene phosphonic acid are added to an oil bath and stirred at 140-150°C for 30-40 minutes. The mixture is filtered, and the filter cake is washed with deionized water 3-5 times and dried to obtain phosphorylated cellulose.

[0022] Furthermore, the ratio of dimethylammonium hydrogen phosphate, urea, deionized water, and wood pulp fiber is 22-26g: 150-200g: 420-500mL: 15-20g.

[0023] Furthermore, the mass ratio of wood pulp fiber fragments to aminotrimethylenephosphonic acid is 12-15:1.2-1.5.

[0024] Furthermore, polyaniline-coated phosphorylated cellulose is prepared by the following steps:

[0025] Ammonium persulfate was added to a 0.3 mol / L phosphoric acid solution and stirred for 10-15 min to obtain an ammonium persulfate solution. Phosphorylated cellulose and a 0.2 mol / L phosphoric acid solution were added to a reaction vessel and ultrasonically dispersed for 30-40 min. Polyvinylpyrrolidone and sodium dodecylbenzenesulfonate were then added and stirred at 8-10℃ for 20-30 min. Aniline was added dropwise and stirred at 8-10℃ for 1-1.5 h. Ammonium persulfate solution was slowly added dropwise and reacted at 20-30℃ for 10-12 h. The mixture was ultrasonically washed 3-5 times with anhydrous ethanol and dried at 40-50℃ for 8-12 h to obtain polyaniline-coated phosphorylated cellulose.

[0026] Furthermore, the ratio of ammonium persulfate to 0.3 mol / L phosphoric acid solution is 10-15 g : 80-120 mL.

[0027] Furthermore, the ratio of phosphorylated cellulose, 0.2 mol / L phosphoric acid solution, polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, aniline and ammonium persulfate solution is 3-5 g: 300-500 mL: 0.5-0.7 g: 0.2-0.4 g: 5-10 mL: 80-120 mL.

[0028] Furthermore, the polyethylene base film thickness is 0.5 mm, the wet coating film thickness is 150 μm, and the dry coating film thickness is 50 μm.

[0029] The beneficial effects of this invention are:

[0030] 1. This invention achieves a multifunctional integration of "flame retardancy, water resistance, and moisture stability" by constructing a synergistic system of zinc / tin composite flame retardant, cellulose phosphorylation, and polyaniline-coated cellulose phosphorylation. The zinc / tin composite flame retardant and cellulose phosphorylation form a gas-solid phase synergistic flame retardant effect. The rigid skeleton of cellulose phosphorylation is combined with the flexible conductive layer of polyaniline, improving tensile strength while maintaining elongation. The conductive network of polyaniline works in conjunction with the flame retardant to achieve dual protection against static electricity and fire. This design, through the synergy of "ceramicized barrier - fiber reinforcement - conductive network," gives the material excellent mechanical properties, water resistance, and resistance to damp heat aging, making it suitable for harsh environments such as tunnels and basements.

[0031] 2. The zinc / tin composite flame retardant of this invention involves chelating aluminum hydroxide with zinc chloride and tin chloride under nitrogen and then coating it with polydopamine. Aluminum hydroxide decomposes endothermally at high temperatures, releasing water vapor that dilutes the concentration of combustibles and oxygen. Simultaneously, the endothermic decomposition lowers the surface temperature of the material, slowing down the combustion process. The addition of zinc chloride and tin chloride further decomposes endothermally at high temperatures, and their decomposition products can react with free radicals generated by polymer combustion to achieve gas-phase flame retardancy. Zinc and tin ions can catalyze the breaking of polymer molecular chains and promote carbonization, forming a dense carbon layer that prevents heat and oxygen from being transferred to the interior. This flame retardant works synergistically with components such as cellulose phosphorylation and polyaniline-coated cellulose phosphorylation to further improve the overall flame retardant efficiency of the composite film through gas-phase and condensed-phase flame retardancy.

[0032] 3. The phosphorylated cellulose in this invention has good mechanical strength and flexibility. After phosphorylation modification, the phosphate groups on its molecular chain can form hydrogen bonds or chemical bonds with the polar groups in the polyethylene matrix and composite slurry, which enhances the interfacial bonding force, improves the tensile strength, tear resistance and other mechanical properties of the composite film, and reduces the material embrittlement problem caused by the addition of flame retardants. The phosphorylation treatment introduces polar phosphate groups on the surface of cellulose, which enhances its compatibility with the non-polar polyethylene matrix and water-based polyurethane slurry. The interaction between polar groups can reduce the aggregation of cellulose in the system, making it more uniformly dispersed in the matrix and ensuring the stability of the composite film performance.

[0033] 4. The polyaniline-coated cellulose phosphorylation in this invention has excellent chemical stability and antioxidant properties. The coating layer can protect cellulose phosphorylation from moisture, acid and alkali corrosion in the external environment, extending the service life of the composite film. Its conductivity may also help enhance the antistatic properties of the material and broaden the application scenarios. The coating structure of polyaniline can improve the rheological properties of the composite slurry, ensure the uniformity of coating, and form a dense coating with the curing process, further improving the waterproof sealing of the composite film and synergistically improving the overall waterproof performance with the pretreated base film. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments in 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.

[0035] Example 1: A method for preparing a flame-retardant waterproof PE composite membrane, comprising the following steps:

[0036] Step 1: Add 45g polyethylene, 5g ethylene-octene copolymer and 0.5g benzoyl peroxide to a high-speed mixer and stir at 110℃ for 3 minutes. Add 15g polyurethane prepolymer and 0.3g bismuth isooctanoate at 80℃ and stir for 3 minutes. Then add 18g zinc / tin composite flame retardant and 2g phosphorylated cellulose and stir at 2000rpm for 5 minutes. Transfer to an extruder and stretch into a film at 140℃ to obtain a polyethylene-based film.

[0037] By melt-blending and extruding substances such as polyurethane prepolymer, catalyst and initiator, the flame retardant is chemically bonded to the polymer matrix in situ, and the matrix resin is cross-linked, which improves mechanical strength, heat resistance and processing stability, and maximizes and prolongs the flame retardant efficiency.

[0038] Step 2: Add 40g of waterborne polyurethane and 3g of polyaniline-coated phosphorylated cellulose to the reactor and stir at 2000rpm for 8min. Then add 1.0g of isocyanate and 2mL of 0.5wt% glacial acetic acid and stir for 5min. Then add 0.6g of silane coupling agent KH550 and ultrasonically disperse to obtain the composite slurry.

[0039] Step 3: The polyethylene base film is subjected to corona treatment to obtain a pretreated base film; the composite slurry is applied to the surface of the pretreated base film, pre-cured at 40℃ for 8 minutes, ultrasonically atomized with 0.1wt% acetic acid mist, and then heated to 80℃ at 10℃ / min for 40 minutes for deep curing. After cooling, a flame-retardant waterproof membrane PE composite film is obtained.

[0040] By utilizing KH550 to achieve atomic-level bonding between inorganic fillers and organic matrix, and strong adhesion between coating and base film, and by cross-linking isocyanate to enhance the strength of coating body, flame-retardant waterproof membrane PE composite film is achieved with flame retardancy, smoke suppression, antistatic properties, strong adhesion and excellent mechanical properties.

[0041] Specifically, the zinc / tin composite flame retardant is prepared by the following steps:

[0042] 25g of aluminum hydroxide powder with a particle size of 200nm and 500mL of ethanol aqueous solution were added to a reaction vessel, nitrogen gas was introduced, and the mixture was sonicated at 600W for 20min. Then, 3.0g of zinc chloride, 1.0g of tin chloride and 5g of dopamine hydrochloride were added, and the mixture was stirred for 10min. Tris(hydroxymethyl)aminomethane was added, the pH value was adjusted to 8.5, and the mixture was stirred at 40℃ for 8h. The mixture was washed three times by centrifugation with ethanol and dried under vacuum to obtain the zinc / tin composite flame retardant.

[0043] By using alkaline catalysis to polymerize polydopamine in situ under nitrogen protection, a zinc / tin bimetallic chelate core-shell structure is constructed on the surface of aluminum hydroxide nanoparticles. Tin ions catalyze the graphitization of polydopamine, zinc ions suppress smoke, and polydopamine coating forms a superhydrophobic shell to reduce moisture absorption. The bimetallic chelate bonds resist damp heat aging, and the amount of additive required is halved compared to traditional flame retardants, thus reducing costs.

[0044] Specifically, phosphorylated cellulose is prepared by the following steps:

[0045] 22g of dimethylammonium hydrogen phosphate, 150g of urea, and 420mL of deionized water were added to a reaction vessel and stirred for 20min. Then, 15g of wood pulp fiber was added and stirred for 1h. The mixture was filtered, and the filter cake was dried at 60℃ for 10h and then pulverized in the gas phase to obtain wood pulp fiber fragments. 12g of wood pulp fiber fragments and 1.2g of aminotrimethylenephosphonic acid were added to an oil bath and stirred at 140℃ for 30min. The mixture was filtered, and the filter cake was washed three times with deionized water and dried to obtain phosphorylated cellulose.

[0046] By pretreating with dimethylammonium hydrogen phosphate / urea and then reacting at high temperature, hydrophilic wood pulp cellulose is converted into phosphorylated cellulose with hydrophobic and reactive sites. This improves the flame retardant properties of cellulose and enhances its compatibility and dispersibility in a hydrophobic polymer matrix.

[0047] Specifically, polyaniline-coated phosphorylated cellulose is prepared by the following steps:

[0048] 10 g of ammonium persulfate was added to 80 mL of 0.3 mol / L phosphoric acid solution and stirred for 10 min to obtain an ammonium persulfate solution. 3 g of phosphorylated cellulose and 300 mL of 0.2 mol / L phosphoric acid solution were added to a reaction vessel and ultrasonically dispersed for 30 min. Then, 0.5 g of polyvinylpyrrolidone and 0.2 g of sodium dodecylbenzenesulfonate were added and stirred at 8 °C for 20 min. 5 mL of aniline was added dropwise and stirred at 8 °C for 1 h. 80 mL of ammonium persulfate solution was slowly added dropwise and reacted at 20 °C for 10 h. The mixture was ultrasonically washed three times with anhydrous ethanol and dried at 40 °C for 8 h to obtain polyaniline-coated phosphorylated cellulose.

[0049] By using a low-temperature, in-situ, phosphoric acid-doped chemical oxidation polymerization process, a layer of polyaniline is coated on the surface of phosphorylated cellulose to form a composite material with phosphorylated cellulose as the core and polyaniline as the shell. This functional modification allows phosphorylated cellulose to not only retain its own flame-retardant properties, but also to have new effects such as flame-retardant enhancement, electrical conductivity and interface improvement brought by polyaniline.

[0050] The polyethylene base film has a thickness of 0.5 mm, the wet film coating thickness is 150 μm, and the dry film coating thickness is 50 μm.

[0051] Example 2: A method for preparing a flame-retardant waterproof PE composite membrane, comprising the following steps:

[0052] Step 1: Add 47.5g polyethylene, 7.5g ethylene-octene copolymer and 0.75g benzoyl peroxide to a high-speed mixer and stir at 115℃ for 4 minutes. Add 17.5g polyurethane prepolymer and 0.4g bismuth isooctanoate at 85℃ and stir for 4 minutes. Then add 20g zinc / tin composite flame retardant and 3g phosphorylated cellulose and stir at 2000rpm for 7.5 minutes. Transfer to an extruder and stretch into a film at 150℃ to obtain a polyethylene-based film.

[0053] Step 2: Add 42.5g of waterborne polyurethane and 4g of polyaniline-coated phosphorylated cellulose to the reactor and stir at 2000rpm for 9min. Then add 1.25g of isocyanate and 2.5mL of 0.5wt% glacial acetic acid and stir for 6.5min. Then add 0.8g of silane coupling agent KH550 and ultrasonically disperse to obtain the composite slurry.

[0054] Step 3: The polyethylene base film is subjected to corona treatment to obtain a pretreated base film; the composite slurry is applied to the surface of the pretreated base film, pre-cured at 45℃ for 9 minutes, ultrasonically atomized with 0.1wt% acetic acid mist, and then heated to 85℃ at 10℃ / min for 45 minutes for deep curing. After cooling, a flame-retardant waterproof membrane PE composite film is obtained.

[0055] Specifically, the zinc / tin composite flame retardant is prepared by the following steps:

[0056] 27.5 g of aluminum hydroxide powder with a particle size of 200 nm and 550 mL of ethanol aqueous solution were added to a reaction vessel, nitrogen gas was introduced, and the mixture was sonicated at 650 W for 25 min. Then, 3.2 g of zinc chloride, 1.25 g of tin chloride and 5.5 g of dopamine hydrochloride were added, and the mixture was stirred for 12.5 min. Tris(hydroxymethyl)aminomethane was added, the pH value was adjusted to 8.5, and the mixture was stirred at 45 °C for 9 h. The mixture was washed four times by centrifugation with ethanol and dried under vacuum to obtain the zinc / tin composite flame retardant.

[0057] Specifically, phosphorylated cellulose is prepared by the following steps:

[0058] 24g of dimethylammonium hydrogen phosphate, 175g of urea, and 460mL of deionized water were added to a reaction vessel and stirred for 25min. Then, 17.5g of wood pulp fiber was added and stirred for 1.25h. The mixture was filtered, and the filter cake was dried at 65℃ for 11h and then pulverized in the gas phase to obtain wood pulp fiber fragments. 13.5g of wood pulp fiber fragments and 1.35g of aminotrimethylenephosphonic acid were added to an oil bath and stirred at 145℃ for 35min. The mixture was filtered, and the filter cake was washed four times with deionized water and dried to obtain phosphorylated cellulose.

[0059] Specifically, polyaniline-coated phosphorylated cellulose is prepared by the following steps:

[0060] 12.5 g of ammonium persulfate was added to 100 mL of 0.3 mol / L phosphoric acid solution and stirred for 12.5 min to obtain an ammonium persulfate solution. 4 g of phosphorylated cellulose and 400 mL of 0.2 mol / L phosphoric acid solution were added to a reaction vessel and ultrasonically dispersed for 35 min. Then, 0.6 g of polyvinylpyrrolidone and 0.3 g of sodium dodecylbenzenesulfonate were added and stirred at 9 °C for 25 min. 7.5 mL of aniline was added dropwise and stirred at 9 °C for 1.25 h. 100 mL of ammonium persulfate solution was slowly added dropwise and reacted at 25 °C for 11 h. The mixture was ultrasonically washed four times with anhydrous ethanol and dried at 45 °C for 10 h to obtain polyaniline-coated phosphorylated cellulose.

[0061] The polyethylene base film has a thickness of 0.5 mm, the wet film thickness of the coating is 150 μm, and the dry film thickness of the coating is 50 μm.

[0062] Example 3: A method for preparing a flame-retardant waterproof PE composite membrane, comprising the following steps:

[0063] Step 1: Add 50g polyethylene, 10g ethylene-octene copolymer and 1.0g benzoyl peroxide to a high-speed mixer and stir at 120℃ for 5min. Add 20g polyurethane prepolymer and 0.5g bismuth isooctanoate at 90℃ and stir for 5min. Then add 22g zinc / tin composite flame retardant and 4g phosphorylated cellulose and stir at 2000rpm for 10min. Transfer to an extruder and stretch into a film at 160℃ to obtain a polyethylene-based film.

[0064] Step 2: Add 45g of waterborne polyurethane and 5g of polyaniline-coated phosphorylated cellulose to the reactor and stir at 2000rpm for 10min. Then add 1.5g of isocyanate and 3mL of 0.5wt% glacial acetic acid and stir for 8min. Then add 1.0g of silane coupling agent KH550 and ultrasonically disperse to obtain the composite slurry.

[0065] Step 3: The polyethylene base film is subjected to corona treatment to obtain a pretreated base film; the composite slurry is applied to the surface of the pretreated base film, pre-cured at 50℃ for 10 min, ultrasonically atomized with 0.1wt% acetic acid mist, and then heated to 90℃ at 10℃ / min for 50 min for deep curing. After cooling, a flame-retardant waterproof membrane PE composite film is obtained.

[0066] Specifically, the zinc / tin composite flame retardant is prepared by the following steps:

[0067] 30g of aluminum hydroxide powder with a particle size of 200nm and 600mL of ethanol aqueous solution were added to a reaction vessel, nitrogen gas was introduced, and the mixture was sonicated at 700W for 30min. Then, 3.4g of zinc chloride, 1.5g of tin chloride and 6g of dopamine hydrochloride were added, and the mixture was stirred for 15min. Tris(hydroxymethyl)aminomethane was added, the pH was adjusted to 8.5, and the mixture was stirred at 50℃ for 10h. The mixture was washed 5 times by centrifugation with ethanol and dried under vacuum to obtain the zinc / tin composite flame retardant.

[0068] Specifically, phosphorylated cellulose is prepared by the following steps:

[0069] 26g of dimethylammonium hydrogen phosphate, 200g of urea, and 500mL of deionized water were added to a reaction vessel and stirred for 30min. Then, 20g of wood pulp fiber was added and stirred for 1.5h. The mixture was filtered, and the filter cake was dried at 70℃ for 12h and then pulverized in the gas phase to obtain wood pulp fiber fragments. 15g of wood pulp fiber fragments and 1.5g of aminotrimethylenephosphonic acid were added to an oil bath and stirred at 150℃ for 40min. The mixture was filtered, and the filter cake was washed 5 times with deionized water and dried to obtain phosphorylated cellulose.

[0070] Specifically, polyaniline-coated phosphorylated cellulose is prepared by the following steps:

[0071] 15g of ammonium persulfate was added to 120mL of 0.3mol / L phosphoric acid solution and stirred for 15min to obtain an ammonium persulfate solution. 5g of phosphorylated cellulose and 500mL of 0.2mol / L phosphoric acid solution were added to a reaction vessel and ultrasonically dispersed for 40min. Then, 0.7g of polyvinylpyrrolidone and 0.4g of sodium dodecylbenzenesulfonate were added and stirred at 10℃ for 30min. 10mL of aniline was added dropwise and stirred at 10℃ for 1.5h. 120mL of ammonium persulfate solution was slowly added dropwise and reacted at 30℃ for 12h. The mixture was ultrasonically washed 5 times with anhydrous ethanol and dried at 50℃ for 12h to obtain polyaniline-coated phosphorylated cellulose.

[0072] The polyethylene base film has a thickness of 0.5 mm, the wet film thickness of the coating is 150 μm, and the dry film thickness of the coating is 50 μm.

[0073] The raw materials used in Examples 1-3 of this application are all commercially available. For example, bismuth isooctanoate is selected from Shandong Xinghai Chemical Co., Ltd. (Xinghai Chemical); tris(hydroxymethyl)aminomethane is selected from Jinan Yucai Chemical Co., Ltd. (Yucai); dimethylammonium hydrogen phosphate is selected from Hubei Benof Chemical Technology Co., Ltd. (BNF); aminotrimethylenephosphonic acid is selected from Shandong Xuchen Chemical Technology Co., Ltd. (WY002); and aniline is selected from Dezhou Runheng Chemical Products Co., Ltd. (Runheng).

[0074] Comparative Example 1: The difference from Example 1 is that zinc chloride and tin chloride are not added in the process of preparing the zinc / tin composite flame retardant. The obtained flame retardant is used to replace the zinc / tin composite flame retardant in step one, while the other steps remain unchanged, to prepare a flame-retardant waterproof membrane PE composite film.

[0075] Comparative Example 2: The difference from Example 1 is that, in the process of preparing cellulose phosphorylation, aminotrimethylene phosphonic acid is not added, and wood pulp fiber fragments are used to replace the cellulose phosphorylation in the polyaniline-coated cellulose phosphorylation step, while the other steps remain unchanged, to prepare a flame-retardant waterproof PE composite membrane.

[0076] Comparative Example 3: The difference from Example 1 is that the preparation step of polyaniline-coated cellulose phosphorylation is omitted, and cellulose phosphorylation is used to replace the polyaniline-coated cellulose phosphorylation in step two. The remaining steps remain unchanged to prepare a flame-retardant waterproof PE composite membrane.

[0077] The flame-retardant waterproof membrane PE composite film prepared in Examples 1-3 and Comparative Examples 1-3 was bonded to the asphalt waterproof membrane substrate with cyanoacrylate adhesive. The thickness of the polyethylene film was 0.5 mm, the coating thickness was 50 μm, and the thickness of the asphalt waterproof membrane substrate was 2 mm. The prepared waterproof membrane was cut into 10 mm × 10 mm samples for performance testing.

[0078] According to GB / T 23457-2017, the tensile strength, elongation at maximum tensile strength, impermeability and flame retardancy of the test specimens were tested. After transferring the specimens to an oven and subjecting them to wet heat aging treatment at 70℃ and saturated water vapor for 180h, the tensile strength, elongation at maximum tensile strength, impermeability and flame retardancy of the test specimens were tested.

[0079] The results are shown in Table 1:

[0080] Table 1 Performance Test Results of Flame-Retardant Waterproof PE Composite Film

[0081] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Unaged tensile strength (N / 50mm) 705 714 722 687 630 655 Elongation without aging (%) 388 396 402 364 330 347 Non-aging and impermeable (0.3Mpa, 12h) impermeable impermeable impermeable impermeable impermeable impermeable Non-aging flame retardant rating B1 B1 B1 B2 B1 B1 Tensile strength after aging (N / 50mm) 688 696 702 594 578 578 Elongation after aging (%) 360 366 371 302 274 274 Water impermeability after aging (0.3 MPa, 12 h) impermeable impermeable impermeable impermeable Slight water permeability impermeable Flame retardancy rating after aging B1 B1 B1 B3 B2 B2

[0082] As can be seen from Table 1, the flame-retardant waterproof PE composite membranes prepared in Examples 1-3 are significantly better than those in Comparative Examples 1-3. The zinc / tin composite flame retardant forms a dense ceramic barrier layer during combustion, which improves the flame retardancy. Phosphorylated cellulose achieves a strong hydrophobic interface and works synergistically with the flame retardant. The polyaniline coating structure provides free radical quenching anti-aging and char layer reinforcement effects. The three work synergistically to achieve high flame retardancy, strong waterproofing and resistance to damp heat aging in the flame-retardant waterproof PE composite membrane.

[0083] In Comparative Example 1, the flame retardant rating deteriorated significantly after aging, possibly due to the failure of the ceramic barrier layer caused by the absence of zinc chloride and tin chloride. Zinc ions have the effect of catalyzing char formation and suppressing smoke, while tin ions can promote the formation of the ceramic barrier layer. If they are missing, the flame retardant mechanism degenerates into the endothermic decomposition of aluminum hydroxide alone, resulting in a decrease in the flame retardant effect. In humid environments, the polydopamine coating layer is prone to hydrolysis and cracking, and the residual char has a porous and loose structure, making the surface flame retardant easy to fall off.

[0084] In Comparative Example 2, the tensile strength and elongation before aging decreased significantly, and the water impermeability deteriorated after aging. This may be due to the lack of aminotrimethylene phosphonic acid for modification, and the failure to replace the hydrophilic hydroxyl groups of the wood pulp fiber with hydrophobic phosphonic acid groups. This resulted in poor compatibility between the fiber and polyurethane, agglomeration, and stress concentration points, which reduced the tensile strength and elongation. In a humid environment, the hydrophilic fiber absorbs moisture and swells, forming water molecule penetration channels, which greatly reduced the waterproof effect.

[0085] In Comparative Example 3, the tensile strength and elongation decreased significantly after aging, which may be due to the lack of a polyaniline coating layer. Without polyaniline coating, the material loses its anodic protection ability, and the electrochemical corrosion rate is accelerated in a humid and hot environment. Free radicals cause the cellulose molecular chains to break, resulting in a decrease in tensile strength and elongation. Without the physical barrier effect of polyaniline, water molecules penetrate rapidly in a humid and hot environment, accelerating the hydrolysis of polyurethane ester bonds and causing the coating to chalk.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a flame-retardant waterproof PE composite membrane, characterized in that, Includes the following steps: Step 1: Mix polyethylene, ethylene-octene copolymer and benzoyl peroxide, add polyurethane prepolymer and bismuth isooctanoate, stir, then add zinc / tin composite flame retardant and phosphorylated cellulose, stir at 2000 rpm for 5-10 min, transfer to an extruder, stretch into a film at 140-160℃ to obtain a polyethylene-based film. In step one, the mass ratio of polyethylene, ethylene-octene copolymer, benzoyl peroxide, polyurethane prepolymer, bismuth isooctanoate, zinc / tin composite flame retardant, and phosphorylated cellulose is 45-50:5-10:0.5-1.0:15-20:0.3-0.5:18-22:2-4. The zinc / tin composite flame retardant is prepared by the following steps: aluminum hydroxide powder with a particle size of 200 nm and an aqueous ethanol solution are added to a reaction vessel, nitrogen gas is introduced, and the mixture is sonicated at 600-700 W for 20-30 min. Then zinc chloride, tin chloride and dopamine hydrochloride are added, and the mixture is stirred for 10-15 min. Tris(hydroxymethyl)aminomethane is added, the pH value is adjusted to 8.5, and the mixture is stirred at 40-50 °C for 8-10 h. The mixture is then washed 3-5 times by centrifugation with ethanol and vacuum dried to obtain the zinc / tin composite flame retardant. The phosphorylated cellulose is prepared by the following steps: adding dimethylammonium hydrogen phosphate, urea and deionized water into a reaction vessel, stirring for 20-30 min, then adding wood pulp fiber, stirring for 1-1.5 h, filtering, drying the filter cake at 60-70℃ for 10-12 h, and gas-phase pulverizing to obtain wood pulp fiber fragments. Wood pulp fiber fragments and aminotrimethylene phosphonic acid are added to an oil bath and stirred at 140-150℃ for 30-40 minutes. The mixture is then filtered, and the filter cake is washed 3-5 times with deionized water and dried to obtain phosphorylated cellulose. Step 2: Coat phosphorylated cellulose with waterborne polyurethane and polyaniline, stir at 2000 rpm for 8-10 min, then add isocyanate and 0.5 wt% glacial acetic acid, stir for 5-8 min, then add silane coupling agent KH550, and ultrasonically disperse to obtain composite slurry; In step two, the ratio of waterborne polyurethane, polyaniline-coated phosphorylated cellulose, isocyanate, 0.5wt% glacial acetic acid, and silane coupling agent KH550 is 40-45g: 3-5g: 1.0-1.5g: 2-3mL: 0.6-1.0g; The polyaniline-coated phosphoric acid cellulose is prepared by the following steps: ammonium persulfate is added to a 0.3 mol / L phosphoric acid solution and stirred for 10-15 min to obtain an ammonium persulfate solution; phosphoric acid cellulose and a 0.2 mol / L phosphoric acid solution are added to a reaction vessel and ultrasonically dispersed for 30-40 min; then polyvinylpyrrolidone and sodium dodecylbenzene sulfonate are added and stirred at 8-10℃ for 20-30 min; aniline is added dropwise and stirred at 8-10℃ for 1-1.5 h; ammonium persulfate solution is slowly added dropwise and reacted at 20-30℃ for 10-12 h; the mixture is ultrasonically washed 3-5 times with anhydrous ethanol and dried at 40-50℃ for 8-12 h to obtain polyaniline-coated phosphoric acid cellulose; Step 3: The polyethylene film is subjected to corona treatment to obtain a pretreated base film; The composite slurry is applied to the surface of the pretreated base film and pre-cured at 40-50℃ for 8-10 minutes. After ultrasonic atomization spraying of 0.1wt% acetic acid mist, the temperature is increased to 80-90℃ at 10℃ / min and then deeply cured for 40-50 minutes. After cooling, a flame-retardant waterproof PE composite membrane is obtained.

2. The method for preparing a flame-retardant waterproof PE composite membrane according to claim 1, characterized in that, The ratio of aluminum hydroxide powder, ethanol aqueous solution, zinc chloride, tin chloride and dopamine hydrochloride is 25-30g: 500-600mL: 3.0-3.4g: 1.0-1.5g: 5-6g.

3. The method for preparing a flame-retardant waterproof PE composite membrane according to claim 1, characterized in that, The ratio of dimethylammonium hydrogen phosphate, urea, deionized water and wood pulp fiber is 22-26g: 150-200g: 420-500mL: 15-20g; The mass ratio of the wood pulp fiber fragments to aminotrimethylene phosphonic acid is 12-15:1.2-1.

5.

4. The method for preparing a flame-retardant waterproof PE composite membrane according to claim 1, characterized in that, The ratio of ammonium persulfate to 0.3 mol / L phosphoric acid solution is 10-15 g: 80-120 mL; the ratio of phosphorylated cellulose, 0.2 mol / L phosphoric acid solution, polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, aniline, and ammonium persulfate solution is 3-5 g: 300-500 mL: 0.5-0.7 g: 0.2-0.4 g: 5-10 mL: 80-120 mL.

5. A flame-retardant waterproof PE composite membrane, characterized in that, It is prepared by the preparation method described in any one of claims 1-4.