Flame-retardant pearl wool and preparation method thereof

Abstract

The application discloses a kind of flame-retardant pearl wool and preparation method thereof, belong to polyethylene processing technical field, to solve the technical problem that mechanical property and flame-retardant property of pearl wool in prior art need to be further improved;The application comprises the following steps: secondary foaming is carried out to the flame-retardant pearl wool blank to obtain the flame-retardant pearl wool, by preparing modified inorganic flame retardant with a large number of double bonds, by gas phase polymerization to obtain light polyethylene, in the process of radiation crosslinking, modified inorganic flame retardant as radiation absorption center, promote light polyethylene and a large number of double bonds of flame-retardant crosslinking agent to produce a large number of free radicals to promote crosslinking reaction, as microwave absorption center in the process of pre-foaming makes pre-foaming more efficient and uniform, and in the process of butane foaming, porous structure as gas slow-release center, make foaming more complete, and synergistic cooperation with flame-retardant crosslinking agent improves the flame-retardant property of material.

Description

Technical Field

[0001] This invention relates to the field of pearl cotton preparation technology, specifically to a flame-retardant pearl cotton and its preparation method. Background Technology

[0002] The research and development of flame-retardant pearl cotton mainly revolves around improving mechanical properties and flame-retardant effects. Early pearl cotton mainly improved flame retardancy by adding halogenated flame retardants. Although it can effectively prevent the spread of flames, it releases toxic gases when burning, so it is not very environmentally friendly.

[0003] With technological advancements, phosphorus-based, nitrogen-based, and inorganic flame retardants were used in the mid-term, significantly reducing the emission of harmful gases and improving the flame retardant effect of the material. In terms of mechanical properties, the internal structure of pearl cotton was made more uniform by optimizing the foaming process, thereby enhancing its compressive strength and resilience.

[0004] Recent developments have focused on composite materials and high-efficiency flame retardant systems, combining different types of flame retardants to achieve higher flame retardant ratings while maintaining excellent mechanical properties. Future developments aim to further enhance the strength and environmental characteristics of materials, enabling them to have broader application prospects in packaging, construction, and automotive fields.

[0005] Existing technology CN116252453A discloses a method for processing flame-retardant pearl cotton, including adding low-density polyethylene and talc powder into a mixer. During mixing, the temperature of the mixer is 75-85℃. Then, carboxymethyl cellulose, chitosan phosphate, and flame retardant A are added, and the material temperature is controlled at 100-120℃ while stirring. Antistatic agent and anti-shrinkage agent are added into the mixer, and stirring continues at 100-120℃. Subsequently, monoglycerides are injected into the mixture using a high-pressure injection method, and then mixed. The mixture is then injected into the mixer with butane and nitrogen at a pressure of 1.3-1.4 MPa. The foaming agent mixed with nitrogen is injected into the mixer by high-pressure jet and mixed evenly. The mixture is then extruded through the die head and die to form pearl cotton. After cooling, traction, flattening and winding, pearl cotton is formed. Flame retardant a is mixed inside the pearl cotton to give the pearl cotton body a certain flame retardant effect, and flame retardant b is used to further increase the flame retardant effect of the pearl cotton surface against the outside world, so as to form a highly flame retardant pearl cotton material.

[0006] However, the aforementioned patent describes a process where low-density polyethylene (LDPE) and auxiliary materials are melt-blended and then directly introduced into the mixture with high-pressure butane gas to obtain foamed flame-retardant pearl cotton. The flame-retardant properties of the material are improved by adding flame retardants to the auxiliary materials and spraying the product with flame retardants. However, when low-density polyethylene and auxiliary materials are directly blended and then foamed with high-pressure butane, the significant polarity difference between the LDPE, organic auxiliary materials, and talc leads to poor mixing uniformity. This results in varying foaming difficulty at different locations, causing uneven foaming of the pearl cotton and resulting in differences in the mechanical properties of the material at different locations. Therefore, the mechanical properties of the material need further improvement.

[0007] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0008] The purpose of this invention is to provide a flame-retardant pearl cotton and its preparation method, which solves the technical problem that the mechanical properties and flame-retardant properties of pearl cotton in the prior art need to be further improved.

[0009] The objective of this invention can be achieved through the following technical solution: a method for preparing flame-retardant pearl cotton, comprising the following steps:

[0010] S1. Add inorganic porous flame retardant, 3-(methacryloyloxy)propyltrimethoxysilane, sodium hydroxide and deionized water to the reaction vessel, raise the temperature of the reaction vessel to 30-50℃, keep it at the temperature for 3-5 hours, and then the modified inorganic flame retardant is obtained after post-treatment.

[0011] The reaction principle for preparing modified inorganic flame retardants is as follows: under alkaline catalysis, a large number of hydroxyl groups on the surface of the inorganic porous flame retardant combine with the silanol structure generated by the hydrolysis of siloxane on 3-(methacryloyloxy)propyltrimethoxysilane, and dehydration yields the modified inorganic flame retardant.

[0012] S2. Under high temperature and high pressure conditions, ethylene gas is polymerized on the surface of a modified inorganic flame retardant under the initiation of azobisisobutyronitrile to prepare lightweight polyethylene.

[0013] S3. Light polyethylene, flame retardant crosslinking agent and auxiliary materials are added to a twin-screw extruder and melt extruded to obtain composite polyethylene;

[0014] S4. The composite polyethylene blank is placed in an electron beam irradiation device, and after electron radiation and post-treatment, flame-retardant pearl cotton blank is obtained.

[0015] The reaction principle for preparing flame-retardant pearl cotton preform is as follows: after electron radiation, a large number of free radicals are generated from the light polyethylene in the composite polyethylene and the large number of double bond structures in the flame-retardant crosslinking agent, and a polymerization reaction occurs, finally preparing the flame-retardant pearl cotton preform.

[0016] S5. The flame-retardant pearl cotton blank is foamed a second time to obtain flame-retardant pearl cotton.

[0017] Further, in step S1, the ratio of inorganic porous flame retardant, 3-(methacryloyloxy)propyltrimethoxysilane, sodium hydroxide, and deionized water is 6-8g:2-3g:0.3-0.5g:30-40mL. The post-treatment includes: after the reaction is completed, after the temperature of the reaction vessel drops to room temperature, the reaction liquid is filtered to collect the filter cake, and the filter cake is placed in a drying oven at 60℃ and vacuum dried until the filter cake reaches a constant weight to obtain the modified inorganic flame retardant; in step S3, the ratio of lightweight polyethylene, flame retardant crosslinking agent, and auxiliary materials is 80-100g:15-20g:15-30g, and the auxiliary materials include: heat stabilizer, lubricant, and antioxidant; in step S4, the post-treatment includes: after electron irradiation, the material is placed in a pulverizer and pulverized, and passed through a 40-80 mesh sieve to obtain the flame retardant pearl cotton blank.

[0018] Furthermore, in step S3, the ratio of heat stabilizer, lubricant, and antioxidant is 3-5g:6-10g:6-10g. The heat stabilizer is one or more of dibutyltin dilaurate, triphenyl phosphate, and epoxidized soybean oil; the lubricant is one or more of calcium stearate, zinc stearate, and polyethylene wax; the antioxidant is one or more of antioxidant 1010, triphenyl phosphite, and dilauryl sulfide; the temperatures of the eight temperature zones of the twin-screw extruder from the feed inlet to the discharge outlet are 160℃, 160℃, 165℃, 165℃, 175℃, 180℃, and 180℃ respectively; the main engine speed of the twin-screw extruder is 80-120 rpm, and the pressure is 100-150 bar.

[0019] Furthermore, in step S1, the preparation method of the inorganic porous flame retardant includes the following steps:

[0020] A1. Add ferric nitrate, aluminum nitrate and deionized water to the reaction vessel and stir for 10-15 min. Adjust the pH of the system to 8-10 with ammonia water at a concentration of 1-2 mol / L, add template agent and continue stirring for 5-10 min. Let stand for 16-24 h and then process to obtain anhydrous gel.

[0021] A2. The anhydrous gel was added to a tube furnace and calcined at high temperature to obtain a mixed metal oxide;

[0022] A3. Add the mixed metal oxides to a pulverizer and crush them, then pass them through a 100-200 mesh sieve to obtain an inorganic porous flame retardant.

[0023] The reaction principle for preparing inorganic porous flame retardants is as follows: under alkaline conditions, ferric nitrate and aluminum nitrate hydrolyze on the template agent to form a cross-linked gel structure. During high-temperature calcination, the template agent undergoes pyrolysis, causing the cross-linked structure to generate a porous structure, and finally, inorganic porous flame retardants are prepared.

[0024] Further, in step A1, the stirring speed of the reactor is 80-120 rpm, and the ratio of ferric nitrate, aluminum nitrate, deionized water and template agent is 5-6 g: 8-10 g: 40-50 mL: 8-10 g. The template agent is prepared by mixing polyethylene glycol and ethanol at a ratio of 1-2 mL: 10-15 mL. The post-treatment includes: after settling, the material is placed in a vacuum drying oven at 80°C and vacuum dried until the material reaches constant weight to obtain anhydrous gel. In step A2, the calcination operation includes: after nitrogen protection, the temperature of the tube furnace is increased to 500-600°C at a heating rate of 3-5°C / min, and the temperature is held for 1-2 hours. After natural cooling to room temperature, the mixed metal oxide is obtained.

[0025] Furthermore, in step S2, the high-pressure polymerization operation includes the following steps:

[0026] B1. Place the modified inorganic flame retardant and azobisisobutyronitrile in a reaction vessel and stir for 10-15 minutes at room temperature to obtain a prepolymer mixture;

[0027] B2. Place the prepolymer mixture in a high-pressure reactor, raise the temperature of the high-pressure reactor to 200-250℃, raise the pressure to 2000-3000psi, introduce ethylene, and polymerize at a constant temperature and pressure for 40-60 minutes to obtain lightweight polyethylene.

[0028] The reaction principle for preparing lightweight polyethylene is as follows: Under high temperature and high pressure, ethylene gas comes into contact with azobisisobutyronitrile, a free radical initiator inside the prepolymer mixture, and undergoes free radical polymerization reaction with a large number of double bonds on the surface of the modified inorganic flame retardant, ultimately producing lightweight polyethylene.

[0029] Furthermore, in step B1, the ratio of modified inorganic flame retardant to peroxydi-tert-butyl is 8-10g:1-2g, and the stirring speed of the reactor is 80-120rpm; in step B2, the ratio of prepolymer mixture to ethylene is 1g:4-5g.

[0030] Furthermore, in step S3, the preparation method of the flame retardant crosslinking agent includes the following steps:

[0031] C1. 2,4-Diamino-6-phenyl-1,3,5-triazine, isophthalaldehyde, triethylamine and N,N-dimethylformamide are added to a reaction vessel, the temperature of the reaction vessel is raised to 60-80℃, and the reaction is maintained for 2-4 hours. After post-treatment, an enamine polymer is obtained.

[0032] The reaction equation for preparing enamine polymers is as follows:

[0033]

[0034] The reaction principle for preparing enamine polymers is as follows: under alkaline conditions and high temperature catalysis, the amino group on 2,4-diamino-6-phenyl-1,3,5-triazine reacts with the aldehyde group on isophthalaldehyde, and finally the enamine polymer is prepared.

[0035] C2. Add the enamine polymer, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, aluminum chloride and dimethyl sulfoxide to the reactor, raise the temperature of the reactor to 30-50℃, keep the reaction at this temperature for 1-3 hours, and then perform post-treatment to obtain the phosphated enamine polymer.

[0036] The reaction equation for preparing the phosphorylated enamine polymer is as follows:

[0037]

[0038] In the formula:

[0039] The reaction principle for preparing phosphoenamine polymers is as follows: under the catalysis of Lewis acid, the phosphorus-hydrogen bond on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide undergoes a phosphorus-hydrogen addition reaction with the enamine bond on the enamine polymer, and finally phosphoenamine polymers are prepared.

[0040] C3. Phosphated enamine polymer, 4,4-diphenyl-2-cyclohexen-1-one, acetic acid and tetrahydrofuran are added to a reaction vessel. The temperature of the reaction vessel is raised to 40-50℃ and the reaction is maintained for 2-4 hours. The flame-retardant crosslinking agent is obtained after post-treatment.

[0041] The reaction equation for preparing the flame-retardant crosslinking agent is:

[0042]

[0043] In the formula:

[0044] The reaction principle for preparing flame-retardant crosslinking agent polymers is as follows: under the catalysis of acetic acid, the imino group on the phosphoryl amine polymer and the ketone group on 4,4-diphenyl-2-cyclohexen-1-one react to generate carbon-carbon double bonds, and finally the flame-retardant crosslinking agent is prepared.

[0045] Further, in step C1, the ratio of 2,4-diamino-6-phenyl-1,3,5-triazine, isophthalaldehyde, triethylamine, and N,N-dimethylformamide is 8-10 g: 3-5 g: 0.5-0.8 g: 40-50 mL. The post-treatment includes: after the reaction is complete, once the reaction vessel temperature has decreased to room temperature, the reaction solution is placed in a rotary evaporator at a water bath temperature of 80-100°C and distilled under reduced pressure until no liquid is collected, yielding the enamine polymer; in step C2, the ratio of phosphorylated enamine polymer, 4,4-diphenyl-2-cyclohexen-1-one, acetic acid, and tetrahydrofuran is 8-10 g: 4-6 g: 0.5-0.8 g: 40 mL. -50mL, post-processing includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, place the reaction solution in a rotary evaporator with a water bath temperature of 80-100℃, and distill under reduced pressure until no liquid is collected to obtain the phosphorinated enamine polymer; in step C3, the ratio of phosphorinated enamine polymer, 4,4-diphenyl-2-cyclohexen-1-one, acetic acid and tetrahydrofuran is 8-10g:2-4g:0.3-0.5g:50-60mL, post-processing includes: after the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, place the reaction solution in a rotary evaporator with a water bath temperature of 80-100℃, and distill under reduced pressure until no liquid is collected to obtain the flame retardant crosslinking agent.

[0046] Furthermore, in step S4, the operation of electron radiation is as follows: nitrogen gas is introduced into the electron radiation device at a flow rate of 15-20 L / min for protection, and the electron beam energy is set to 3-4 MeV, the power to 20-25 kW, the radiation dose to 200-250 kGy, and the conveyor belt speed to 1-3 m / min.

[0047] Furthermore, in step S5, the secondary foaming operation includes the following steps:

[0048] D1. Add the flame-retardant pearl cotton blank and toluene to a microwave generator with a power of 5-8kW and a power density of 2-4W / cm³. 3 The pre-foamed flame-retardant pearl cotton is obtained by heating it at a microwave frequency of 2.4-2.5 GH and a temperature of 100-120℃ until the solvent is removed.

[0049] D2. Add the pre-foamed flame-retardant pearl cotton to the high-pressure reactor, purge the air with nitrogen, raise the reactor temperature to 100-120℃, introduce butane into the reactor, control the pressure to 4-5MPa, keep it at the temperature for 40-60min, and then depressurize at a rate of 0.05-0.1MPa / s to obtain the flame-retardant pearl cotton.

[0050] The present invention also proposes a flame-retardant pearl cotton, which is obtained by processing a flame-retardant pearl cotton preparation method.

[0051] The present invention has the following beneficial effects:

[0052] 1. In the preparation of flame-retardant pearl cotton, this invention involves preparing a modified inorganic flame retardant with a large number of double bonds on its surface. Its porous structure serves as a base point for ethylene gas-phase polymerization. Lightweight polyethylene is obtained through gas-phase polymerization on its surface. A flame-retardant crosslinking agent is then prepared, which is melt-blended and extruded with the lightweight polyethylene and auxiliary materials to obtain composite polyethylene. During the radiation crosslinking process of the composite polyethylene, the modified inorganic flame retardant acts as a radiation absorption center, promoting the generation of numerous free radicals in the lightweight polyethylene and the flame-retardant crosslinking agent with a large number of double bonds, thus accelerating the crosslinking reaction. This results in a material with superior mechanical properties. During pre-foaming, it acts as a microwave absorption center, making pre-foaming more efficient and uniform. Furthermore, during supercritical fluid butane foaming, its porous structure acts as a gas release center, ensuring more complete foaming. In synergy with the flame-retardant crosslinking agent, it enhances the flame-retardant performance of the material, ultimately yielding flame-retardant pearl cotton with more complete and uniform foaming and stronger mechanical properties.

[0053] 2. The modified inorganic flame retardant prepared by this invention has a significant promoting effect on the process of preparing flame-retardant pearl cotton. During the radiation crosslinking process, the modified inorganic flame retardant absorbs radiation and transfers its energy to the polyethylene matrix, thereby enhancing the local energy density. After absorbing radiation, the radiation absorbing material releases electrons or free radicals. These free radicals can promote the breaking of molecular chains in polyethylene and generate more active free radicals, thereby increasing the rate and degree of crosslinking reaction. This allows polyethylene and the flame-retardant crosslinking agent to be uniformly crosslinked throughout the material, forming a uniform crosslinking network, which gives the material higher mechanical properties and thermal stability.

[0054] During the pre-foaming process, the modified inorganic flame retardant acts as a microwave absorption center, improving microwave absorption efficiency, making the temperature distribution within the material more uniform, and enabling more uniform evaporation of the solvent toluene, forming a more uniform pore structure. During the secondary foaming process of supercritical fluid butane, the modified inorganic flame retardant acts as a gas release center, making the formed porous structure more uniform and stable through a slow-release effect. Through the improvement of the material's surface structure by the modified inorganic flame retardant and the micro-crosslinking of the flame retardant crosslinking agent, the mechanical properties of the material are ultimately significantly improved.

[0055] 3. In the process of preparing flame-retardant pearl cotton, this invention obtains a porous, lightweight modified inorganic flame retardant. Its surface, after modification with a silane coupling agent, contains numerous silicon-oxygen bonds and carbon-carbon double bonds. During the high-temperature, high-pressure gas-phase polymerization of polyethylene, the abundant porous structure of the modified inorganic flame retardant allows polyethylene to be adsorbed within its pores, resulting in polymerization on its pore structure and surface to obtain lightweight polyethylene. A flame-retardant crosslinking agent with a polymer structure is also prepared. During combustion, the inorganic crosslinking agent continuously decomposes to produce acidic substances, promoting the carbonization of the material. During the carbonization of the triazine ring, flame-retardant gases are continuously released, promoting the foaming of the molten carbon layer. Furthermore, the abundant porous structure of the modified inorganic flame retardant allows for the slow release of flame-retardant gases, enabling them to carry away more heat. Through synergistic effects, the flame-retardant performance of the pearl cotton is significantly improved. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 The image shows the SEM image of the modified inorganic flame retardant prepared in Example 3. Detailed Implementation

[0058] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment provides a method for preparing flame-retardant pearl cotton, including the following steps:

[0061] S1. Preparation of lightweight polyethylene

[0062] Weigh out 1.2 mL of polyethylene glycol and 12.0 mL of ethanol to prepare the template agent;

[0063] Weigh out 10.0g of ferric nitrate, 16.0g of aluminum nitrate and 80.0mL of deionized water and add them to the reaction vessel. Stir for 10 minutes at a stirring speed of 80rpm. Adjust the pH of the system to 8 using 1.0mol / L ammonia water. Add 16.0g of template agent and continue stirring for 5 minutes. Let stand for 16 hours. After standing, place the material in a vacuum drying oven at 80℃ and vacuum dry until the material reaches constant weight to obtain anhydrous gel.

[0064] Anhydrous gel was added to a tube furnace, and nitrogen gas was introduced for protection. The tube furnace was then heated to 500°C at a rate of 3°C / min, held at that temperature for 1 hour, and then naturally cooled to room temperature to obtain a mixed metal oxide.

[0065] The mixed metal oxides were added to a pulverizer and pulverized, then passed through a 100-mesh sieve to obtain an inorganic porous flame retardant.

[0066] Weigh out 14.0g of inorganic porous flame retardant, 5.4g of 3-(methacryloyloxy)propyltrimethoxysilane, 0.6g of sodium hydroxide and 72.0mL of deionized water and add them to the reaction vessel. Raise the temperature of the reaction vessel to 30℃ and keep it at that temperature for 3h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Place the filter cake in a drying oven at 60℃ and vacuum dry it until the filter cake reaches a constant weight to obtain the modified inorganic flame retardant.

[0067] Weigh out 18.0g of modified inorganic flame retardant and 3.2g of azobisisobutyronitrile and place them in a reaction vessel and stir at a stirring speed of 80rpm for 10min at room temperature to obtain a prepolymer mixture.

[0068] Weigh 20.0g of the prepolymer mixture and place it in a high-pressure reactor. Raise the temperature of the high-pressure reactor to 200℃ and the pressure to 2000psi. Introduce 80.0g of ethylene and polymerize at a constant temperature and pressure for 40min to obtain lightweight polyethylene.

[0069] S2. Preparation of composite polyethylene

[0070] Weigh out 16.0g of 2,4-diamino-6-phenyl-1,3,5-triazine, 8.0g of isophthalaldehyde, 1.2g of triethylamine and 80.0mL of N,N-dimethylformamide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 60℃ and keep it at that temperature for 2 hours. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 80℃. Distill under reduced pressure until no liquid is collected to obtain the enamine polymer.

[0071] Weigh out 18.0g of enamine polymer, 10.0g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1.2g of aluminum chloride and 80.0mL of dimethyl sulfoxide and add them to the reaction vessel. Raise the temperature of the reaction vessel to 30℃ and keep it at that temperature for 1h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 80℃. Distill under reduced pressure until no liquid is collected to obtain the enamine polymer.

[0072] Weigh out 18.0g of phosphorylated enamine polymer, 7.2g of 4-diphenyl-2-cyclohexen-1-one, 0.8g of acetic acid and 100.0mL of tetrahydrofuran and add them to the reaction vessel. Raise the temperature of the reaction vessel to 40℃ and keep it at that temperature for 2 hours. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 80℃. Distill under reduced pressure until no liquid is collected to obtain the flame retardant crosslinking agent.

[0073] Weigh out 96.0g of lightweight polyethylene, 18.0g of flame retardant crosslinking agent, 4.2g of dibutyltin dilaurate, 8.4g of polyethylene wax, and 8.4g of triphenyl phosphite and add them to a twin-screw extruder. The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 160℃, 160℃, 165℃, 165℃, 175℃, 180℃, and 180℃ respectively. The main motor speed of the twin-screw extruder is 80rpm and the pressure is 100bar. The composite polyethylene is obtained by melt extrusion.

[0074] S3. Preparation of flame-retardant pearl cotton

[0075] The composite polyethylene blank was placed in an electron beam irradiation device, and nitrogen gas was introduced into the electron radiation device at a flow rate of 15 L / min for protection. The electron beam energy was set to 3.0 MeV, the power to 20 kW, the radiation dose to 200 kGy, and the conveyor belt speed to 1 m / min. After the electron irradiation was completed, the material was placed in a pulverizer for crushing and passed through a 40-mesh sieve to obtain a flame-retardant pearl cotton blank.

[0076] Flame-retardant pearl cotton blank and toluene were added to a microwave generator with a power of 5kW and a power density of 2W / cm³. 3 The pre-foamed flame-retardant pearl cotton was obtained by heating it at a microwave frequency of 2.4 GH and a temperature of 100 ℃ until no solvent was extracted.

[0077] Pre-foamed flame-retardant pearl cotton is added to a high-pressure reactor, nitrogen is introduced to purge the air, the reactor temperature is raised to 100℃, butane is introduced into the reactor, the pressure is controlled at 4 MPa, the temperature is maintained for 40 minutes, and the flame-retardant pearl cotton is obtained after depressurization at a rate of 0.05 MPa / s.

[0078] Example 2

[0079] This embodiment provides a method for preparing flame-retardant pearl cotton, including the following steps:

[0080] S1. Preparation of lightweight polyethylene

[0081] Weigh out 2.0 mL of polyethylene glycol and 15.0 mL of ethanol to prepare the template agent;

[0082] Weigh out 12.0g of ferric nitrate, 18.0g of aluminum nitrate and 100.0mL of deionized water and add them to the reaction vessel. Stir for 15min at a stirring speed of 120rpm. Adjust the pH of the system to 10 using 2.0mol / L ammonia water. Add 16.0g of template agent and continue stirring for 10min. Let stand for 24h. After standing, place the material in a vacuum drying oven at 80℃ and vacuum dry until the material reaches constant weight to obtain anhydrous gel.

[0083] Anhydrous gel was added to a tube furnace, and nitrogen gas was introduced for protection. The tube furnace was then heated to 600°C at a rate of 5°C / min and held at that temperature for 2 hours. After natural cooling to room temperature, a mixed metal oxide was obtained.

[0084] The mixed metal oxides were added to a pulverizer and pulverized, then passed through a 200-mesh sieve to obtain an inorganic porous flame retardant.

[0085] Weigh out 16.0g of inorganic porous flame retardant, 5.4g of 3-(methacryloyloxy)propyltrimethoxysilane, 0.8g of sodium hydroxide and 80.0mL of deionized water and add them to the reaction vessel. Raise the temperature of the reaction vessel to 50℃ and keep it at that temperature for 5h. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Place the filter cake in a drying oven at 60℃ and vacuum dry it until the filter cake reaches a constant weight to obtain the modified inorganic flame retardant.

[0086] Weigh out 18.0g of modified inorganic flame retardant and 3.2g of azobisisobutyronitrile and place them in a reaction vessel and stir at a stirring speed of 120rpm for 15min at room temperature to obtain a prepolymer mixture.

[0087] Weigh 20.0g of the prepolymer mixture and place it in a high-pressure reactor. Raise the temperature of the high-pressure reactor to 250℃ and the pressure to 3000psi. Introduce 100.0g of ethylene and polymerize at a constant temperature and pressure for 60min to obtain lightweight polyethylene.

[0088] S2. Preparation of composite polyethylene

[0089] Weigh out 20.0g of 2,4-diamino-6-phenyl-1,3,5-triazine, 8.0g of isophthalaldehyde, 1.2g of triethylamine and 96.0mL of N,N-dimethylformamide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 80℃ and keep it at that temperature for 4h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 100℃. Distill under reduced pressure until no liquid is collected to obtain the enamine polymer.

[0090] Weigh out 18.0g of enamine polymer, 10.0g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1.2g of aluminum chloride and 100.0mL of dimethyl sulfoxide and add them to the reaction vessel. Raise the temperature of the reaction vessel to 30-50℃ and keep it at that temperature for 3h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 100℃. Distill under reduced pressure until no liquid is collected to obtain the enamine polymer.

[0091] Weigh out 18.0g of phosphorylated enamine polymer, 7.2g of 4-diphenyl-2-cyclohexen-1-one, 0.8g of acetic acid and 120.0mL of tetrahydrofuran and add them to the reaction vessel. Raise the temperature of the reaction vessel to 50℃ and keep it at that temperature for 4h. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 100℃. Distill under reduced pressure until no liquid is collected to obtain the flame retardant crosslinking agent.

[0092] Weigh out 88.0g of lightweight polyethylene, 16.0g of flame retardant crosslinking agent, 8.0g of dibutyltin dilaurate, 8.0g of polyethylene wax, and 8.0g of triphenyl phosphite and add them to a twin-screw extruder. The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 160℃, 160℃, 165℃, 165℃, 175℃, 180℃, and 180℃ respectively. The main motor speed of the twin-screw extruder is 120rpm and the pressure is 150bar. The composite polyethylene is obtained by melt extrusion.

[0093] S3. Preparation of flame-retardant pearl cotton

[0094] The composite polyethylene blank was placed in an electron beam irradiation device, and nitrogen gas was introduced into the electron radiation device at a flow rate of 20 L / min for protection. The electron beam energy was set to 4 MeV, the power to 25 kW, the radiation dose to 250 kGy, and the conveyor belt speed to 3 m / min. After the electron radiation was completed, the material was placed in a pulverizer for crushing and passed through an 80-mesh sieve to obtain a flame-retardant pearl cotton blank.

[0095] Flame-retardant pearl cotton blank and toluene were added to a microwave generator with a power of 8kW and a power density of 4W / cm³. 3The pre-foamed flame-retardant pearl cotton was obtained by heating it at a microwave frequency of 2.5 GH and a temperature of 120 ℃ until no solvent was extracted.

[0096] Pre-foamed flame-retardant pearl cotton was added to a high-pressure reactor, nitrogen was introduced to purge the air, the reactor temperature was raised to 120°C, butane was introduced into the reactor, the pressure was controlled at 5 MPa, the temperature was maintained for 60 minutes, and the flame-retardant pearl cotton was obtained after depressurization at a rate of 0.1 MPa / s.

[0097] Example 3

[0098] This embodiment provides a method for preparing flame-retardant pearl cotton, including the following steps:

[0099] S1. Preparation of lightweight polyethylene

[0100] Weigh out 1.8 mL of polyethylene glycol and 12.0 mL of ethanol to prepare the template agent;

[0101] Weigh out 12.0g of ferric nitrate, 16.0g of aluminum nitrate and 100.0mL of deionized water and add them to the reaction vessel. Stir for 15min at a stirring speed of 100rpm. Adjust the pH of the system to 9 with 1.8mol / L ammonia water. Add 16.0g of template agent and continue stirring for 8min. Let stand for 20h. After standing, place the material in a vacuum drying oven at 80℃ and vacuum dry until the material reaches constant weight to obtain anhydrous gel.

[0102] Anhydrous gel was added to a tube furnace, and nitrogen gas was introduced for protection. The tube furnace was then heated to 600°C at a rate of 4°C / min, held at that temperature for 2 hours, and then naturally cooled to room temperature to obtain a mixed metal oxide.

[0103] The mixed metal oxides were added to a pulverizer and pulverized, then passed through a 150-mesh sieve to obtain an inorganic porous flame retardant.

[0104] Weigh out 16.0g of inorganic porous flame retardant, 5.4g of 3-(methacryloyloxy)propyltrimethoxysilane, 0.8g of sodium hydroxide and 72.0mL of deionized water and add them to the reaction vessel. Raise the temperature of the reaction vessel to 50℃ and keep it at that temperature for 2h. After the reaction is completed, wait for the temperature of the reaction vessel to drop to room temperature, filter the reaction liquid and collect the filter cake. Place the filter cake in a drying oven at 60℃ and vacuum dry it until the filter cake reaches a constant weight to obtain the modified inorganic flame retardant.

[0105] Weigh 18.0g of modified inorganic flame retardant and 3.6g of azobisisobutyronitrile and place them in a reaction vessel and stir at a stirring rate of 100rpm for 12min at room temperature to obtain a prepolymer mixture.

[0106] Weigh 20.0g of the prepolymer mixture and place it in a high-pressure reactor. Raise the temperature of the high-pressure reactor to 225℃ and the pressure to 2500psi. Introduce 90.0g of ethylene and polymerize at a constant temperature and pressure for 50min to obtain lightweight polyethylene.

[0107] S2. Preparation of composite polyethylene

[0108] Weigh out 18.0g of 2,4-diamino-6-phenyl-1,3,5-triazine, 8.4g of isophthalaldehyde, 1.2g of triethylamine and 90.0mL of N,N-dimethylformamide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 70℃ and keep it at that temperature for 3h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 90℃. Distill under reduced pressure until no liquid is collected to obtain the enamine polymer.

[0109] Weigh out 18.0g of enamine polymer, 10.8g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1.2g of aluminum chloride, and 100.0mL of dimethyl sulfoxide and add them to a reaction vessel. Raise the temperature of the reaction vessel to 30-50℃ and keep it at that temperature for 2 hours. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 90℃. Distill under reduced pressure until no liquid is collected to obtain the enamine polymer.

[0110] Weigh out 18.0g of phosphorylated enamine polymer, 7.2g of 4-diphenyl-2-cyclohexen-1-one, 0.8g of acetic acid and 100.0mL of tetrahydrofuran and add them to the reaction vessel. Raise the temperature of the reaction vessel to 50℃ and keep it at that temperature for 3h. After the reaction is complete, wait for the temperature of the reaction vessel to drop to room temperature, and place the reaction solution in a rotary evaporator with a water bath temperature of 90℃. Distill under reduced pressure until no liquid is collected to obtain the flame retardant crosslinking agent.

[0111] Weigh out 96.0g of lightweight polyethylene, 18.0g of flame retardant crosslinking agent, 4.2g of dibutyltin dilaurate, 8.4g of polyethylene wax, and 8.4g of triphenyl phosphite and add them to a twin-screw extruder. The temperatures of the eight temperature zones of the twin-screw extruder from the feed port to the discharge port are 160℃, 160℃, 165℃, 165℃, 175℃, 180℃, and 180℃ respectively. The main motor speed of the twin-screw extruder is 100rpm and the pressure is 125bar. The composite polyethylene is obtained by melt extrusion.

[0112] S3. Preparation of flame-retardant pearl cotton

[0113] The composite polyethylene blank was placed in an electron beam irradiation device, and nitrogen gas was introduced into the electron radiation device at a flow rate of 18 L / min for protection. The electron beam energy was set to 4 MeV, the power to 24 kW, the radiation dose to 225 kGy, and the conveyor belt speed to 3 m / min. After the electron radiation was completed, the material was placed in a pulverizer for crushing and passed through an 80-mesh sieve to obtain a flame-retardant pearl cotton blank.

[0114] Flame-retardant pearl cotton blank and toluene were added to a microwave generator with a power of 7kW and a power density of 3W / cm³. 3 The pre-foamed flame-retardant pearl cotton was obtained by heating it at a microwave frequency of 2.5 GH and a temperature of 100 ℃ until no solvent was extracted.

[0115] Pre-foamed flame-retardant pearl cotton is added to a high-pressure reactor, nitrogen is introduced to purge the air, the reactor temperature is raised to 100℃, butane is introduced into the reactor, the pressure is controlled at 5MPa, the temperature is maintained for 50min, and the flame-retardant pearl cotton is obtained after depressurization at a rate of 0.08MPa / s.

[0116] Comparative Example 1

[0117] The difference between this comparative example and Example 3 is that the step of preparing the modified inorganic flame retardant in step S1 is omitted, and porous alumina is used to replace the modified inorganic flame retardant in an equal amount during the preparation of lightweight polyethylene.

[0118] Comparative Example 2

[0119] The difference between this comparative example and Example 3 is that the step of preparing the flame-retardant crosslinking agent in step S2 is omitted, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is used to replace the flame-retardant crosslinking agent in an equal amount during the preparation of the composite polyethylene.

[0120] Comparative Example 3

[0121] The difference between this comparative example and Example 3 is that the pre-foaming preparation of the flame-retardant pearl cotton blank in step S3 is omitted, and the flame-retardant pearl cotton blank is used to replace the pre-foamed flame-retardant pearl cotton in the process of making the flame-retardant pearl cotton.

[0122] Performance testing:

[0123] The vertical flammability ratings of the flame-retardant pearl cotton prepared in Examples 1-3 and Comparative Examples 1-3 were determined according to standard GB / T 2408-2021 "Determination of flammability of plastics - Horizontal and Vertical Methods".

[0124] Referring to standard BB / T 0066-2017 "Extruded Foamed Polyethylene Packaging Materials", the apparent density, tensile strength, tear strength, compressive strength and compression set of the flame-retardant pearl cotton prepared in Examples 1-3 and Comparative Examples 1-3 were tested. The specific data are shown in Table 1.

[0125] Table 1 - Performance test data of each sample

[0126]

[0127]

[0128] Data Analysis:

[0129] Comparative analysis of the data in Table 1 above shows that the flame-retardant pearl cotton prepared by this invention has a vertical flammability rating of V-0 and an apparent density of 16.3 kg·m³. -3 Tensile strength is 251 kPa, tear strength is 2.1 N·mm. -1 The compressive strength (40%) is 63 kPa and the compression permanent deformation rate (50%) is only 16%, all of which are better than the comparative example;

[0130] Data Explanation:

[0131] In the preparation of flame-retardant pearl cotton, this invention involves preparing a modified inorganic flame retardant with numerous double bonds on its surface. Its porous structure serves as a base for ethylene gas-phase polymerization, allowing for the polymerization of lightweight polyethylene on its surface via gas-phase polymerization. A flame-retardant crosslinking agent is then prepared, which is melt-blended and extruded with the lightweight polyethylene and auxiliary materials to obtain composite polyethylene. During the radiation crosslinking process of the composite polyethylene, the modified inorganic flame retardant acts as a radiation absorption center, promoting the generation of numerous free radicals between the lightweight polyethylene and the flame-retardant crosslinking agent with numerous double bonds, thus accelerating the crosslinking reaction. This results in a material with superior mechanical properties. During pre-foaming, it acts as a microwave absorption center, making pre-foaming more efficient and uniform. Furthermore, during supercritical fluid butane foaming, its porous structure acts as a gas release center, ensuring more complete foaming. In synergy with the flame-retardant crosslinking agent, it enhances the flame-retardant performance of the material, ultimately yielding flame-retardant pearl cotton with more complete and uniform foaming and stronger mechanical properties.

[0132] 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 specific implementations. 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 method for preparing flame-retardant pearl cotton, characterized in that, Includes the following steps: S1. Add inorganic porous flame retardant, 3-(methacryloyloxy)propyltrimethoxysilane, sodium hydroxide and deionized water to the reaction vessel, raise the temperature of the reaction vessel to 30-50℃, keep it at the temperature for 3-5 hours, and then the modified inorganic flame retardant is obtained after post-treatment. S2. Under high temperature and high pressure conditions, ethylene gas is polymerized on the surface of a modified inorganic flame retardant under the initiation of azobisisobutyronitrile to prepare lightweight polyethylene. S3. Light polyethylene, flame retardant crosslinking agent and auxiliary materials are added to a twin-screw extruder and melt extruded to obtain composite polyethylene; S4. The composite polyethylene blank is placed in an electron beam irradiation device, and after electron radiation and post-treatment, flame-retardant pearl cotton blank is obtained. S5. The flame-retardant pearl cotton blank is foamed twice to obtain flame-retardant pearl cotton. The preparation method of the inorganic porous flame retardant includes the following steps: A1. Add ferric nitrate, aluminum nitrate and deionized water to the reaction vessel and stir for 10-15 min. Adjust the pH of the system to 8-10 with ammonia water at a concentration of 1-2 mol / L, add template agent and continue stirring for 5-10 min. Let stand for 16-24 h and then perform post-treatment to obtain anhydrous gel. A2. The anhydrous gel was added to a tube furnace and calcined at high temperature to obtain a mixed metal oxide; A3. Add the mixed metal oxides to a pulverizer and pulverize them, then pass them through a 100-200 mesh sieve to obtain an inorganic porous flame retardant; The preparation method of the flame retardant crosslinking agent includes the following steps: C1. 2,4-Diamino-6-phenyl-1,3,5-triazine, isophthalaldehyde, triethylamine and N,N-dimethylformamide are added to a reaction vessel, the temperature of the reaction vessel is raised to 60-80℃, and the reaction is maintained for 2-4 hours. After post-treatment, an enamine polymer is obtained. C2. Add the enamine polymer, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, aluminum chloride and dimethyl sulfoxide to the reactor, raise the temperature of the reactor to 30-50℃, keep the reaction at this temperature for 1-3 hours, and then perform post-treatment to obtain the phosphated enamine polymer. C3. Phosphated enamine polymer, 4,4-diphenyl-2-cyclohexen-1-one, acetic acid and tetrahydrofuran are added to a reaction vessel. The temperature of the reaction vessel is raised to 40-50℃ and the reaction is maintained for 2-4 hours. The flame-retardant crosslinking agent is obtained after post-treatment.

2. The method for preparing flame-retardant pearl cotton according to claim 1, characterized in that, In step S1, the ratio of inorganic porous flame retardant, 3-(methacryloyloxy)propyltrimethoxysilane, sodium hydroxide, and deionized water is 6-8g:2-3g:0.3-0.5g:30-40mL; in step S3, the ratio of lightweight polyethylene, flame retardant crosslinking agent, and excipients is 80-100g:15-20g:15-30g, and the excipients include: heat stabilizer, lubricant, and antioxidant.

3. The method for preparing flame-retardant pearl cotton according to claim 1, characterized in that, In step A1, the stirring speed of the reactor is 80-120 rpm, and the ratio of ferric nitrate, aluminum nitrate, deionized water and template agent is 5-6 g: 8-10 g: 40-50 mL: 8-10 g. The template agent is prepared by mixing polyethylene glycol and ethanol at a ratio of 1-2 mL: 10-15 mL. In step A2, the high-temperature calcination operation includes: after nitrogen protection, the temperature of the tube furnace is increased to 500-600℃ at a heating rate of 3-5℃ / min, held for 1-2 hours, and then naturally cooled to room temperature to obtain the mixed metal oxide.

4. The method for preparing flame-retardant pearl cotton according to claim 1, characterized in that, In step S2, the high-pressure polymerization operation includes the following steps: B1. Place the modified inorganic flame retardant and azobisisobutyronitrile in a reaction vessel and stir for 10-15 minutes at room temperature to obtain a prepolymer mixture; B2. Place the prepolymer mixture in a high-pressure reactor, raise the temperature of the high-pressure reactor to 200-250℃, raise the pressure to 2000-3000psi, introduce ethylene, and polymerize at a constant temperature and pressure for 40-60 minutes to obtain lightweight polyethylene.

5. The method for preparing flame-retardant pearl cotton according to claim 1, characterized in that, In step C1, the ratio of 2,4-diamino-6-phenyl-1,3,5-triazine, isophthalaldehyde, triethylamine, and N,N-dimethylformamide is 8-10 g: 3-5 g: 0.5-0.8 g: 40-50 mL; in step C2, the ratio of phosphorylated enamine polymer, 4,4-diphenyl-2-cyclohexen-1-one, acetic acid, and tetrahydrofuran is 8-10 g: 4-6 g: 0.5-0.8 g: 40-50 mL; in step C3, the ratio of phosphorylated enamine polymer, 4,4-diphenyl-2-cyclohexen-1-one, acetic acid, and tetrahydrofuran is 8-10 g: 2-4 g: 0.3-0.5 g: 50-60 mL.

6. The method for preparing flame-retardant pearl cotton according to claim 1, characterized in that, In step S4, the operation of electron radiation is as follows: nitrogen gas is introduced into the electron radiation device at a flow rate of 15-20 L / min for protection, and the electron beam energy is set to 3-4 MeV, the power to 20-25 kW, the radiation dose to 200-250 kGy, and the conveyor belt speed to 1-3 m / min.

7. The method for preparing flame-retardant pearl cotton according to claim 1, characterized in that, In step S5, the secondary foaming operation includes the following steps: D1. Add the flame-retardant pearl cotton blank and toluene to a microwave generator with a power of 5-8kW and a power density of 2-4W / cm³. 3 Microwave frequency 2.4-2.5GH, temperature 100-120℃, heating until no solvent is discharged, to obtain pre-foamed flame-retardant pearl cotton; D2. Add the pre-foamed flame-retardant pearl cotton to the high-pressure reactor, purge the air with nitrogen, raise the reactor temperature to 100-120℃, introduce butane into the reactor, control the pressure to 4-5MPa, keep it at the temperature for 40-60min, and then depressurize at a rate of 0.05-0.1MPa / s to obtain the flame-retardant pearl cotton.

8. A flame-retardant pearl cotton, characterized in that, The flame-retardant pearl cotton is prepared using the method described in any one of claims 1-7.

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