Fireproof flame-retardant phenolic resin and preparation method thereof
By modifying lignin and montmorillonite, fire-retardant phenolic resin is prepared, which solves the problems of easy oxidation and poor toughness of traditional phenolic resins at high temperatures, improves its performance in a new generation of service environment, and expands the application range and molding efficiency.
Patent Information
- Application Number
- CN202510791762.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-13
- Publication Date
- 2025-08-15
AI Technical Summary
Traditional phenolic resins are prone to oxidation and pyrolysis at high temperatures, and have poor toughness, making them difficult to meet the thermodynamic performance requirements of the new generation of service environments, and their application range and molding efficiency are limited.
By depolymerizing alkali lignin in lithium bromide solution, depolymerized lignin is prepared and reacted with terminal amino polydimethylsiloxane, diethyl isonitrile methylphosphate, and glacial acetic acid to form modified lignin; reacting montmorillonite with isocyanate to produce modified montmorillonite; then polymerizing with phenol and paraformaldehyde to produce fire-resistant flame-retardant phenolic resin.
It improves the toughness, fire-retardant properties and anti-aging effects of phenolic resins, enhances tensile strength, and meets the thermodynamic performance requirements of the new generation of service environments.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of polymer materials, in particular to a fire-retardant phenolic resin and a preparation method thereof. Background Art
[0002] Phenolic resin is one of the earliest synthetic polymers, with a history of approximately 100 years. It is a condensation polymer synthesized from phenols and aldehydes through addition and condensation reactions under certain reaction conditions. It features low raw material costs and a simple synthesis process, as well as excellent thermal stability, dimensional stability, mechanical properties, and high carbon yield. It is widely used in ablative coatings, adhesives, and composite materials, and has become an indispensable polymer material in fields such as construction, machinery, aerospace, and defense. Among ablative polymer materials, phenolic resin is one of the most widely used. The development of the steel industry has led to the increased use of coated sand. The quality of the coated sand itself affects the quality of steel model production, and only high-quality coated sand can lay a solid foundation for high-quality steel model production. Coated sand is essentially sand coated with a layer of phenolic resin. During use, the coated sand is heated to melt the resin. External forces then fuse the sand and resin to form the desired pattern, which is then poured into molten iron to form the casting. Currently, the main use of coated sand is for casting castings, and its use is relatively single. Therefore, how to improve the application scope and molding efficiency of coated sand under the new development background has become an urgent problem to be solved by current coated sand production companies.
[0003] The molecular structure of traditional phenolic resins contains numerous phenolic hydroxyl groups and methylene structures, both of which are susceptible to thermal oxidation. Therefore, when the operating temperature of phenolic resin exceeds 250°C, the material will undergo oxidative thermal decomposition. Furthermore, in the synthesis reaction of phenolic resin, the phenolic hydroxyl group does not directly participate in the reaction, but merely changes its electronic state. Phenolic hydroxyl groups are unstable and are easily broken and formed into quinones due to environmental factors during use and storage. Furthermore, a large number of rigid benzene rings are connected only by methylene bridges, resulting in an excessive density of benzene rings in the phenolic resin network. The large steric hindrance and low degree of freedom of rotation of the connecting rods result in poor toughness of unmodified phenolic resins. However, with the rapid development of industry, the thermodynamic properties of composite materials based on traditional phenolic resins are difficult to meet the requirements of the next generation of service environments, and they need to be modified. Summary of the Invention
[0004] The object of the present invention is to provide a fire-retardant phenolic resin and a preparation method thereof, so as to solve the problems existing in the prior art.
[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:
[0006] A fire-retardant phenolic resin is prepared by polymerizing phenol with modified lignin, paraformaldehyde, and modified montmorillonite.
[0007] The modified lignin is prepared by subjecting depolymerized lignin to a multi-component reaction with amino-terminated polydimethylsiloxane, diethyl isocyanate methyl phosphate, and glacial acetic acid;
[0008] The depolymerized lignin is prepared by depolymerizing alkali lignin in a lithium bromide solution;
[0009] The modified montmorillonite is prepared by reacting isocyanate-modified montmorillonite with 3-aminopropyltriethoxysilane;
[0010] The isocyanate-modified montmorillonite is prepared by modifying montmorillonite with diisocyanate.
[0011] As an optimization, the diisocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate, and diphenylmethane diisocyanate.
[0012] As an optimization, the model of the amino-terminated polydimethylsiloxane is CM226.
[0013] A method for preparing a fire-retardant phenolic resin comprises the following steps:
[0014] (1) mixing alkali lignin and lithium bromide aqueous solution, ultrasonicating, heating, stirring and refluxing, cooling, filtering, washing and drying to obtain depolymerized lignin;
[0015] (2) mixing depolymerized lignin, amino-terminated polydimethylsiloxane, and methanol, stirring at room temperature, adding diethyl isocyanate methyl phosphate and glacial acetic acid, stirring at room temperature, filtering, washing, and drying to obtain modified lignin;
[0016] (3) dispersing montmorillonite in anhydrous toluene, stirring, adding isophorone diisocyanate and dibutyltin dilaurate, ultrasonicating, heating and stirring for reaction, washing, centrifuging, drying, grinding and sieving to obtain isocyanate-modified montmorillonite;
[0017] (4) dispersing the isocyanate-modified montmorillonite in anhydrous toluene, stirring, adding 3-aminopropyltriethoxysilane and dibutyltin dilaurate, ultrasonicating, heating and stirring to react, washing, centrifuging, drying, grinding and sieving to obtain modified montmorillonite;
[0018] (5) Phenol, modified lignin, pure water, and barium hydroxide octahydrate are mixed in a water bath, and paraformaldehyde is added in three times. The modified montmorillonite is added simultaneously with the second addition of paraformaldehyde. The mixture is heated and stirred for reaction, the pH is controlled, the temperature is raised for reaction, the water bath is removed, stirring is continued, and the system is cooled to 60° C. before discharging the material to obtain a fire-retardant phenolic resin.
[0019] As an optimization, the depolymerized lignin in step (1) is prepared by uniformly mixing 2 to 3 parts of alkali lignin and 10 to 12 parts of a 60 wt% lithium bromide aqueous solution, ultrasonically treating for 10 to 15 minutes, stirring and refluxing at 105 to 110° C. and 200 to 300 r / min for 2 to 2.5 hours, cooling in an ice-water bath, filtering, washing with pure water until neutral, and vacuum drying at 50 to 60° C. for 10 to 12 hours.
[0020] As an optimization, the reaction process of depolymerizing lignin in step (1) is as follows:
[0021]
[0022] As an optimization, the lithium bromide aqueous solution also contains 0.3 mol / L hydrochloric acid.
[0023] As an optimization, the modified lignin in step (2) is prepared by uniformly mixing 2 to 3 parts of depolymerized lignin, 1.5 to 2 parts of amino-terminated polydimethylsiloxane, and 15 to 20 parts of methanol, stirring at 200 to 300 r / min for 50 to 60 min at room temperature, adding 0.48 to 0.64 parts of diethyl isocyanate methyl phosphate and 0.17 to 0.23 parts of glacial acetic acid, stirring at 200 to 300 r / min for 22 to 24 h at room temperature, filtering, washing alternately with anhydrous ethanol and pure water for 3 to 4 times, and vacuum drying at 50 to 60°C for 10 to 12 h.
[0024] As an optimization, the reaction process of the modified lignin in step (2) is as follows:
[0025]
[0026] As an optimization, the isocyanate-modified montmorillonite in step (3) is prepared by dispersing 3 to 4 parts of montmorillonite in 25 to 30 parts of anhydrous toluene, stirring at 300 to 400 r / min for 30 to 40 min, adding 1.2 to 1.4 parts of isophorone diisocyanate and 0.018 to 0.022 parts of dibutyltin dilaurate, ultrasonicating for 30 to 40 min, stirring at 75 to 85° C. and 300 to 400 r / min for 6 to 7 h, washing with anhydrous toluene 3 to 4 times, centrifuging, vacuum drying at 70 to 80° C. for 10 to 12 h, grinding and passing through a 160-mesh sieve to obtain the obtained product.
[0027] As an optimization, the reaction process of the isocyanate-modified montmorillonite in step (3) is as follows:
[0028]
[0029] As an optimization, the montmorillonite is pretreated, and the pretreatment scheme is to grind it, pass it through a 160-mesh sieve, and dry it in a vacuum oven at 60-80° C. for 4-10 hours.
[0030] As an optimization, the modified montmorillonite in step (4) is prepared by dispersing 3 to 4 parts of isocyanate-modified montmorillonite in 25 to 30 parts of anhydrous toluene, stirring at 300 to 400 r / min for 30 to 40 min, adding 1.43 to 1.67 parts of 3-aminopropyltriethoxysilane and 0.021 to 0.025 parts of dibutyltin dilaurate, ultrasonicating for 30 to 40 min, stirring at 75 to 85° C. and 300 to 400 r / min for 14 to 16 h, washing with anhydrous toluene 3 to 4 times, centrifuging, vacuum drying at 70 to 80° C. for 10 to 12 h, grinding and passing through a 160-mesh sieve to obtain the obtained product.
[0031] As an optimization, the reaction process of the modified montmorillonite in step (4) is as follows:
[0032]
[0033] As an optimization, the fire-retardant phenolic resin in step (5) is prepared by mixing 14 to 16 parts of phenol, 1.5 to 1.8 parts of modified lignin, 0.7 to 0.8 parts of pure water, and 0.3 to 0.4 parts of barium hydroxide octahydrate in a water bath at 65 to 70°C in parts by mass, adding paraformaldehyde three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:(1.6 to 1.8), with an interval of 15 to 20 minutes between each addition, and adding 1.8 to 2.1 parts of modified montmorillonite simultaneously with the second addition of paraformaldehyde. The mixture is reacted at 70 to 80°C and 300 to 400 r / min for 2.5 to 3 hours, and a 30w% sodium hydroxide aqueous solution is used to control the pH between 9 and 10. The mixture is then heated to 93 to 95°C and reacted for 10 to 12 minutes. The water bath is removed, and stirring is continued at 200 to 300 r / min for 30 to 40 minutes. The system is cooled to 60°C and then discharged to obtain the obtained product.
[0034] As an optimization, the alkali lignin model is JYS1545.
[0035] As an optimization, the montmorillonite model is PGW and numbered as XFI44.
[0036] The invention discloses an application of a fire-resistant and flame-retardant phenolic resin in the preparation of coated sand.
[0037] Compared with the prior art, the present invention has the following beneficial effects:
[0038] When preparing the fire-retardant phenolic resin, the present invention comprises the following steps: firstly depolymerizing alkali lignin in a lithium bromide solution to obtain depolymerized lignin; then subjecting the depolymerized lignin to a multi-component reaction with amino-terminated polydimethylsiloxane, diethyl isocyanomethyl phosphate and glacial acetic acid to obtain modified lignin; then reacting montmorillonite with isophorone diisocyanate to obtain isocyanate-modified montmorillonite; then reacting the isocyanate-modified montmorillonite with 3-aminopropyltriethoxysilane to obtain modified montmorillonite; and finally polymerizing phenol with the modified lignin, paraformaldehyde and the modified montmorillonite to obtain the fire-retardant phenolic resin.
[0039] First, alkali lignin is degraded in lithium bromide molten salt hydrate, the phenolic hydroxyl content and the carbonyl content of the lignin side chain increase, and the reactivity of the alkali lignin is greatly improved to produce depolymerized lignin. The higher content of phenolic hydroxyl groups makes the depolymerized lignin have sufficient reactivity to replace phenol in the copolymerization reaction of phenolic resin, thereby reducing the amount of phenol used; the amino-terminated polydimethylsiloxane reacts with the carbonyl group on the depolymerized lignin side chain, and then the Ugi four-component reaction occurs in the presence of the isocyanate group on diethyl isocyanate methyl phosphate and the carboxyl group on glacial acetic acid, forming a unique α-amidoamide structure. structure, and successfully introduced flexible siloxane chain segments and flame-retardant phosphorus and silicon elements. Both ends of the flexible amino-terminated polydimethylsiloxane have amino functional groups. By adding excessive amounts of amino-terminated polydimethylsiloxane, one end of it reacts on the carbonyl group of the lignin side chain, and the other end can participate in the copolymerization reaction of phenolic resin, thereby making the modified lignin have more active sites to participate in the copolymerization reaction. In addition, phosphorus, nitrogen and silicon elements have a synergistic flame retardant effect, which avoids the decrease in heat-resistant and flame-retardant effects due to the improvement of the toughness of the phenolic resin, and the synergistic flame retardant effect also improves the flame retardant effect of the phenolic resin.
[0040] Secondly, montmorillonite is intercalated and modified under the strong reactivity of excess diisocyanate. The strong reactivity of isocyanate allows it to react with the hydroxyl groups on the surface of the montmorillonite layer, thereby expanding the interlayer spacing of the montmorillonite. The excessive addition of diisocyanate allows the montmorillonite to form isocyanate-terminated isocyanate-modified montmorillonite, which effectively improves the compatibility of montmorillonite with the polymer matrix. At the same time, the strong reactivity of isocyanate also makes subsequent modifications fully possible; the isocyanate-modified montmorillonite is then further modified with 3-aminopropyltriethoxysilane. In an anhydrous environment, the siloxane group is retained, while the amino group reacts with the isocyanate group under the action of the catalyst, thereby successfully introducing 3-aminopropyltriethoxysilane into the modified After the secondary modification of the surface of montmorillonite, the spacing between the montmorillonite flakes is further expanded. At the same time, the outward-facing siloxane groups give the modified montmorillonite a better dispersion ability. The modified montmorillonite can be fully dispersed in the phenolic resin matrix. The barrier property of its flakes allows it to effectively improve the fire retardant properties of the phenolic resin, and the filler effect can also improve the tensile strength of the phenolic resin. In the polymerization reaction of the phenolic resin, in the presence of water, the siloxane groups can be hydrolyzed into silanol groups and react with phenolic hydroxyl groups, thereby allowing the modified montmorillonite to be covalently bonded to the phenolic resin chain segments, further enhancing the dispersion and fixation effect of the modified montmorillonite in the phenolic resin, and reducing the local performance degradation caused by the migration of montmorillonite in the phenolic resin.
[0041] Finally, phenol is copolymerized with modified lignin, paraformaldehyde and modified montmorillonite. The modified lignin has a large number of phenolic hydroxyl and amino active groups that can participate in the polymerization reaction of phenolic resin, and at the same time brings siloxane flexible chain segments, which greatly improves the toughness of phenolic resin. The introduction of phosphorus, nitrogen and silicon flame retardant elements and the barrier effect of montmorillonite sheets form a synergistic effect, effectively avoiding the decrease in flame retardant performance caused by the enhanced toughness, and improving certain fire retardant properties; modified lignin can form a certain body structure in phenolic resin to improve tensile strength. Strength; In addition to reacting with phenolic hydroxyl groups to fix montmorillonite, the siloxane groups on the modified montmorillonite can also reduce the content of phenolic hydroxyl groups in the phenolic resin through this reaction. Because in the polymerization reaction of the phenolic resin, the phenolic hydroxyl group does not directly participate in the reaction, and the phenolic hydroxyl group is easily oxidized, resulting in performance degradation. Therefore, the content of phenolic hydroxyl groups is reduced through the bonding reaction between the siloxane groups and the phenolic hydroxyl groups, thereby improving the anti-aging effect of the prepared fire-retardant phenolic resin, slowing down the performance degradation caused by external factors, and thus increasing the service life. DETAILED DESCRIPTION
[0042] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.
[0043] The raw materials used in all the following examples and comparative examples are as follows:
[0044] Amino-terminated polydimethylsiloxane: model CM226, purchased from Jining Tangyi Chemical Co., Ltd.
[0045] Diisocyanate: isophorone diisocyanate;
[0046] Alkali lignin: Model JYS1545, purchased from Wuhan Jiyesheng Chemical Co., Ltd.
[0047] Montmorillonite: model PGW, number XFI44, purchased from Jiangsu Xianfeng Nanomaterial Technology Co., Ltd.
[0048] The montmorillonite used in all the following examples and comparative examples was pretreated. The pretreatment scheme was to grind it, pass it through a 160-mesh sieve, and dry it in a vacuum oven at 70° C. for 6 hours.
[0049] Example 1:
[0050] A method for preparing a fire-retardant phenolic resin, comprising the following steps:
[0051] (1) By weight, 2 parts of alkali lignin and 10 parts of a 60 wt% lithium bromide aqueous solution containing 0.3 mol / L hydrochloric acid were mixed uniformly, ultrasonicated for 10 min, stirred and refluxed at 105°C and 200 rpm for 2.5 h, cooled in an ice-water bath, filtered, washed with pure water until neutral, and vacuum dried at 50°C for 12 h to obtain depolymerized lignin;
[0052] (2) 2 parts of depolymerized lignin, 1.5 parts of amino-terminated polydimethylsiloxane, and 15 parts of methanol were mixed uniformly by weight, stirred at 200 r / min for 60 min at room temperature, 0.48 parts of diethyl isocyanate methyl phosphate and 0.17 parts of glacial acetic acid were added, and stirred at 200 r / min for 24 h at room temperature. The mixture was filtered, washed alternately with anhydrous ethanol and pure water for 3 times, and dried in vacuum at 50°C for 12 h to obtain modified lignin;
[0053] (3) 3 parts of montmorillonite were dispersed in 25 parts of anhydrous toluene, stirred at 300 r / min for 40 min, 1.2 parts of isophorone diisocyanate and 0.018 parts of dibutyltin dilaurate were added, ultrasonicated for 30 min, stirred at 75°C and 300 r / min for 7 h, washed with anhydrous toluene three times, centrifuged at 7000 rpm for 12 min, vacuum dried at 70°C for 12 h, ground and passed through a 160 mesh sieve to obtain isocyanate-modified montmorillonite;
[0054] (4) 3 parts of isocyanate-modified montmorillonite were dispersed in 25 parts of anhydrous toluene, stirred at 300 r / min for 40 min, 1.43 parts of 3-aminopropyltriethoxysilane and 0.021 parts of dibutyltin dilaurate were added, ultrasonicated for 30 min, stirred at 75°C and 300 r / min for 16 h, washed three times with anhydrous toluene, centrifuged at 7000 rpm for 12 min, vacuum dried at 70°C for 12 h, ground and sieved through a 160-mesh sieve to obtain modified montmorillonite;
[0055] (5) According to the mass fraction, 14 parts of phenol, 1.5 parts of modified lignin, 0.7 parts of pure water and 0.3 parts of barium hydroxide octahydrate were mixed uniformly in a water bath at 65°C. Polyformaldehyde was added three times at a molar ratio of phenolic hydroxyl group to aldehyde group of 1:1.6, with an interval of 15 minutes between each addition. When the polyformaldehyde was added for the second time, 1.8 parts of modified montmorillonite was added at 70°C and 300 r / min for 3 hours. During the reaction, the pH was controlled at 9 with a 30w% sodium hydroxide aqueous solution. The temperature was then raised to 93°C for 12 minutes. The water bath was removed and stirring was continued at 200 r / min for 40 minutes. The system was cooled to 60°C and then discharged to obtain a fire-retardant phenolic resin.
[0056] Example 2:
[0057] A method for preparing a fire-retardant phenolic resin, comprising the following steps:
[0058] (1) 2.5 parts of alkali lignin and 11 parts of a 60 wt% lithium bromide aqueous solution containing 0.3 mol / L hydrochloric acid were mixed uniformly, ultrasonicated for 12 min, stirred and refluxed at 108°C and 250 r / min for 2.2 h, cooled in an ice-water bath, filtered, washed with pure water until neutral, and vacuum dried at 55°C for 11 h to obtain depolymerized lignin;
[0059] (2) 2.5 parts of depolymerized lignin, 1.8 parts of amino-terminated polydimethylsiloxane, and 18 parts of methanol were mixed uniformly by weight, stirred at 250 r / min at room temperature for 55 min, 0.57 parts of diethyl isocyanate methyl phosphate and 0.21 parts of glacial acetic acid were added, and stirred at 250 r / min at room temperature for 23 h. The mixture was filtered, washed alternately with anhydrous ethanol and pure water for 3 times, and dried in vacuum at 55 °C for 11 h to obtain modified lignin;
[0060] (3) 3.5 parts of montmorillonite were dispersed in 28 parts of anhydrous toluene, stirred at 350 r / min for 35 min, 1.3 parts of isophorone diisocyanate and 0.02 parts of dibutyltin dilaurate were added, ultrasonicated for 35 min, stirred at 80°C and 350 r / min for 6.5 h, washed three times with anhydrous toluene, centrifuged at 7500 rpm for 11 min, vacuum dried at 75°C for 11 h, ground and passed through a 160 mesh sieve to obtain isocyanate-modified montmorillonite;
[0061] (4) 3.5 parts of isocyanate-modified montmorillonite were dispersed in 28 parts of anhydrous toluene, stirred at 350 r / min for 35 min, 1.55 parts of 3-aminopropyltriethoxysilane and 0.023 parts of dibutyltin dilaurate were added, ultrasonicated for 35 min, stirred at 80°C and 350 r / min for 15 h, washed three times with anhydrous toluene, centrifuged at 7500 rpm for 11 min, vacuum dried at 75°C for 11 h, ground and sieved through a 160-mesh sieve to obtain modified montmorillonite;
[0062] (5) According to the mass fraction, 15 parts of phenol, 1.65 parts of modified lignin, 0.75 parts of pure water and 0.35 parts of barium hydroxide octahydrate were mixed uniformly in a water bath at 68°C. Polyformaldehyde was added three times at a molar ratio of phenolic hydroxyl group to aldehyde group of 1:1.7, with an interval of 18 minutes between each addition. When the polyformaldehyde was added for the second time, 1.95 parts of modified montmorillonite was added at 75°C and 350 r / min for 2.8 hours. During the reaction, the pH was controlled at 9.5 with a 30w% sodium hydroxide aqueous solution. The temperature was then raised to 94°C for 11 minutes. The water bath was removed and stirring was continued at 250 r / min for 35 minutes. The system was cooled to 60°C and then discharged to obtain a fire-retardant phenolic resin.
[0063] Example 3:
[0064] A method for preparing a fire-retardant phenolic resin, comprising the following steps:
[0065] (1) By weight, 3 parts of alkali lignin and 12 parts of a 60 wt% lithium bromide aqueous solution containing 0.3 mol / L hydrochloric acid were mixed uniformly, ultrasonicated for 15 min, stirred and refluxed at 110°C and 300 rpm for 2 h, cooled in an ice-water bath, filtered, washed with pure water until neutral, and vacuum dried at 60°C for 10 h to obtain depolymerized lignin;
[0066] (2) 3 parts of depolymerized lignin, 2 parts of amino-terminated polydimethylsiloxane, and 20 parts of methanol were mixed uniformly by weight, stirred at 300 r / min at room temperature for 50 min, 0.64 parts of diethyl isocyanate methyl phosphate and 0.23 parts of glacial acetic acid were added, and stirred at 300 r / min at room temperature for 22 h. The mixture was filtered, washed alternately with anhydrous ethanol and pure water for 4 times, and dried in vacuum at 60°C for 10 h to obtain modified lignin;
[0067] (3) 4 parts of montmorillonite were dispersed in 30 parts of anhydrous toluene, stirred at 400 r / min for 30 min, 1.4 parts of isophorone diisocyanate and 0.022 parts of dibutyltin dilaurate were added, ultrasonicated for 30 min, stirred at 85°C and 400 r / min for 6 h, washed with anhydrous toluene 4 times, centrifuged at 8000 rpm for 10 min, vacuum dried at 80°C for 10 h, ground and passed through a 160 mesh sieve to obtain isocyanate-modified montmorillonite;
[0068] (4) 4 parts of isocyanate-modified montmorillonite were dispersed in 30 parts of anhydrous toluene, stirred at 400 r / min for 30 min, 1.67 parts of 3-aminopropyltriethoxysilane and 0.025 parts of dibutyltin dilaurate were added, ultrasonicated for 40 min, stirred at 85°C and 400 r / min for 14 h, washed with anhydrous toluene 4 times, centrifuged at 8000 rpm for 10 min, vacuum dried at 80°C for 10 h, ground and sieved through a 160-mesh sieve to obtain modified montmorillonite;
[0069] (5) According to the mass fraction, 16 parts of phenol, 1.8 parts of modified lignin, 0.8 parts of pure water and 0.4 parts of barium hydroxide octahydrate were mixed uniformly in a water bath at 70°C. Polyformaldehyde was added three times at a molar ratio of phenolic hydroxyl group to aldehyde group of 1:1.8, with an interval of 20 minutes each time. When the polyformaldehyde was added for the second time, 2.1 parts of modified montmorillonite were added at 80°C and 400 r / min for 2.5 hours. During the reaction, the pH was controlled at 10 with a 30w% sodium hydroxide aqueous solution. The temperature was then raised to 95°C for reaction for 10 minutes. The water bath was removed and stirring was continued at 300 r / min for 30 minutes. The system was cooled to 60°C and then discharged to obtain a fire-retardant phenolic resin.
[0070] Comparative Example 1:
[0071] The method for preparing the fire-retardant phenolic resin of Comparative Example 1 differs from that of Example 2 in that step (1) is omitted and step (2) is modified as follows: 2.5 parts of alkali lignin, 1.8 parts of amino-terminated polydimethylsiloxane, and 18 parts of methanol, by weight, are uniformly mixed, stirred at 250 r / min at room temperature for 55 min, 0.57 parts of diethyl isocyanate methyl phosphate and 0.21 parts of glacial acetic acid are added, stirred at 250 r / min at room temperature for 23 h, filtered, washed alternately with anhydrous ethanol and pure water three times, and vacuum dried at 55° C. for 11 h to obtain modified lignin. The remaining steps are the same as those of Example 2.
[0072] Comparative Example 2:
[0073] The preparation method of the fire-retardant phenolic resin of Comparative Example 2 differs from that of Example 2 in step (2). Step (2) is modified as follows: 2.5 parts of depolymerized lignin, 1.8 parts of amino-terminated polydimethylsiloxane, and 18 parts of methanol are uniformly mixed, stirred at 250 r / min at room temperature for 55 min, 0.37 parts of ethyl isocyanate and 0.21 parts of glacial acetic acid are added, and stirred at 250 r / min at room temperature for 23 h. The mixture is filtered, washed alternately with anhydrous ethanol and pure water three times, and vacuum-dried at 55° C. for 11 h to obtain modified lignin. The remaining steps are the same as those of Example 2.
[0074] Comparative Example 3:
[0075] The preparation method of the fire-retardant phenolic resin of Comparative Example 3 differs from that of Example 2 in step (2). Step (2) is modified as follows: 2.5 parts of depolymerized lignin, 0.32 parts of 1,4-butanediamine, and 18 parts of methanol, by weight, are uniformly mixed, stirred at 250 r / min at room temperature for 55 min, 0.57 parts of diethyl isocyanomethyl phosphate and 0.21 parts of glacial acetic acid are added, and stirred at 250 r / min at room temperature for 23 h. The mixture is filtered, washed alternately with anhydrous ethanol and pure water three times, and vacuum-dried at 55° C. for 11 h to obtain modified lignin. The remaining steps are the same as those of Example 2.
[0076] Comparative Example 4:
[0077] The method for preparing a fire-retardant phenolic resin in Comparative Example 4 differs from that in Example 2 in that step (2) is omitted and step (5) is modified as follows: 15 parts by mass of phenol, 1.65 parts of depolymerized lignin, 0.75 parts of pure water, and 0.35 parts of barium hydroxide octahydrate are uniformly mixed in a 68°C water bath, paraformaldehyde is added three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:1.7, each time with an interval of 18 minutes, 1.95 parts of modified montmorillonite is added simultaneously with the second addition of paraformaldehyde, and the mixture is reacted at 75°C and 350 rpm for 2.8 hours. During the reaction, the pH is controlled at 9.5 with a 30 w% aqueous sodium hydroxide solution, and the mixture is heated to 94°C for 11 minutes. The water bath is removed and stirring is continued at 250 rpm for 35 minutes. The system is cooled to 60°C before discharging, thereby obtaining a fire-retardant phenolic resin. The remaining steps are the same as those in Example 2.
[0078] Comparative Example 5:
[0079] The preparation method of the fire-retardant phenolic resin of Comparative Example 5 differs from that of Example 2 in that steps (1) and (2) are not performed, and step (5) is modified as follows: 15 parts by mass of phenol, 0.75 parts of pure water, and 0.35 parts of barium hydroxide octahydrate are mixed uniformly in a 68°C water bath, paraformaldehyde is added three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:1.7, each time with an interval of 18 minutes, 1.95 parts of modified montmorillonite is added simultaneously with the second addition of paraformaldehyde, and the mixture is reacted at 75°C and 350 rpm for 2.8 hours. During the reaction, the pH is controlled at 9.5 with a 30w% sodium hydroxide aqueous solution, and the mixture is heated to 94°C for 11 minutes. The water bath is removed and stirring is continued at 250 rpm for 35 minutes. The system is cooled to 60°C and then discharged to obtain the fire-retardant phenolic resin. The remaining steps are the same as those of Example 2.
[0080] Comparative Example 6:
[0081] The method for preparing the fire-retardant phenolic resin of Comparative Example 6 differs from that of Example 2 in that step (4) is omitted and step (5) is modified as follows: 15 parts by mass of phenol, 1.65 parts of modified lignin, 0.75 parts of pure water, and 0.35 parts of barium hydroxide octahydrate are uniformly mixed in a 68°C water bath, paraformaldehyde is added three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:1.7, each time with an interval of 18 minutes, 1.95 parts of isocyanate-modified montmorillonite is added simultaneously with the second addition of paraformaldehyde, and the mixture is reacted at 75°C and 350 rpm for 2.8 hours. During the reaction, the pH is controlled at 9.5 with a 30 w% sodium hydroxide aqueous solution, and the mixture is heated to 94°C for 11 minutes. The water bath is removed and stirring is continued at 250 rpm for 35 minutes. The system is cooled to 60°C before discharging, thereby obtaining the fire-retardant phenolic resin. The remaining steps are the same as those of Example 2.
[0082] Comparative Example 7:
[0083] The preparation method of the fire-retardant phenolic resin of Comparative Example 7 differs from that of Example 2 in that steps (3) and (4) are not performed, and step (5) is modified as follows: 15 parts by mass of phenol, 1.65 parts of modified lignin, 0.75 parts of pure water, and 0.35 parts of barium hydroxide octahydrate are mixed uniformly in a 68°C water bath, paraformaldehyde is added three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:1.7, each time with an interval of 18 minutes, 1.95 parts of montmorillonite is added simultaneously with the second addition of paraformaldehyde, and the mixture is reacted at 75°C and 350 rpm for 2.8 hours. During the reaction, the pH is controlled at 9.5 with a 30w% sodium hydroxide aqueous solution, and the mixture is heated to 94°C for 11 minutes. The water bath is removed and stirring is continued at 250 rpm for 35 minutes. The system is cooled to 60°C and then discharged to obtain the fire-retardant phenolic resin. The remaining steps are the same as those of Example 2.
[0084] Comparative Example 8:
[0085] The preparation method of the fire-retardant phenolic resin of Comparative Example 8 differs from that of Example 2 in that steps (3) and (4) are not performed, and step (5) is modified as follows: 15 parts by mass of phenol, 1.65 parts of modified lignin, 0.75 parts of pure water, and 0.35 parts of barium hydroxide octahydrate are mixed uniformly in a 68°C water bath, paraformaldehyde is added three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:1.7, each time with an interval of 18 minutes, and the mixture is reacted at 75°C and 350 rpm for 2.8 hours. During the reaction, the pH is controlled at 9.5 with a 30w% sodium hydroxide aqueous solution, and the mixture is heated to 94°C for 11 minutes. The water bath is removed and stirring is continued at 250 rpm for 35 minutes. The system is cooled to 60°C and then discharged to obtain the fire-retardant phenolic resin. The remaining steps are the same as those of Example 2.
[0086] Sample preparation: The fire-retardant phenolic resin prepared in the above examples and comparative examples was mixed with hexamethylenetetramine in a mass ratio of 1:0.1 at 100°C, stirred at 200 r / min for 30 min, then poured into a mold preheated at 100°C, cured at 140°C for 4 h, continued to cure at 180°C for 4 h, and finally cured at 200°C for 2 h to prepare a sample.
[0087] Test Example 1:
[0088] Tensile strength test: Refer to GB / T 2567-2021 "Test method for properties of resin castings" to test the tensile strength of the specimen to evaluate its mechanical properties. The specimen size is prepared with reference to the tensile specimen size specified in the standard. The test is carried out at a test speed of 2mm / min, and the tensile strength is calculated. Each group is tested in parallel 5 times, and the average value is recorded.
[0089] Bending strength test: Refer to GB / T 2567-2021 "Test method for properties of resin castings" to test the bending strength of the specimen to evaluate its toughness. The specimen size is prepared with reference to the bending specimen size specified in the standard. The test is carried out at a test speed of 2mm / min, and the bending strength is calculated. Each group is tested in parallel 5 times, and the average value is recorded.
[0090] Anti-aging test: Prepare corresponding specimens with reference to the tensile strength test. Then, refer to GB / T 16422.3-2022 "Plastics Laboratory Light Source Exposure Test Methods Part 3: Fluorescent Ultraviolet Lamp" and subject the specimens to artificial accelerated aging for 10 days using a FR-1205-QUV UV aging tester. The tensile strength is then tested again, and the tensile strength retention rate is calculated. Repeat the test five times for each group of specimens, and the average value is recorded.
[0091] The results are shown in Table 1.
[0092] Table 1
[0093] Tensile strength / MPa Bending strength / MPa Tensile strength retention rate Example 1 45.78 81.85 86.47％ Example 2 46.23 82.61 87.19％ Example 3 45.96 82.37 86.22％ Comparative Example 1 34.68 44.55 83.44％ Comparative Example 2 45.38 81.27 85.64％ Comparative Example 3 44.56 67.44 85.35％ Comparative Example 4 38.29 52.18 84.24％ Comparative Example 5 33.72 42.52 83.12％ Comparative Example 6 41.95 76.45 54.59％ Comparative Example 7 38.44 71.98 45.92％ Comparative Example 8 36.79 67.58 40.24％
[0094] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 8 in Table 1, it can be found that the fire-retardant phenolic resin prepared in the present invention has good tensile strength, flexural strength, toughness and aging resistance.
[0095] By comparing the data in the table, the data of Comparative Example 1 show that the depolymerization of alkali lignin successfully reduces the molecular weight of lignin, improves its reactivity, increases the number of phenolic hydroxyl groups and side chain carbonyl groups, provides more sites for Ugi multi-component reactions, and can better participate in the polymerization reaction of phenolic resin, thereby effectively improving the tensile strength and flexural strength.
[0096] By comparing the data in the table, the data of Comparative Example 3 show that the introduction of amino-terminated polydimethylsiloxane introduces flexible siloxane segments into the modified lignin, and in the subsequent polymerization reaction of the phenolic resin, the flexible siloxane segments are introduced into the phenolic resin segments through the reaction of the active hydrogen of the amino group, formaldehyde, and the ortho-para positions of the phenolic hydroxyl group, thereby effectively improving the tensile strength and flexural strength, and greatly improving the mechanical properties and toughness.
[0097] By comparing the data in the table, the data of Comparative Example 4 shows that the multi-component reaction on the depolymerized lignin is successfully carried out, and the relevant groups are modified and introduced, thereby improving the tensile strength and flexural strength.
[0098] By comparing the data in the table, the data of Comparative Example 5 shows that the addition of modified lignin successfully replaced part of the phenol, and the depolymerization and multi-component reaction effectively improved the tensile strength and flexural strength.
[0099] By comparing the data in the table, the data of Comparative Example 6 show that 3-aminopropyltriethoxysilane was successfully introduced into isocyanate-modified montmorillonite to prepare modified montmorillonite. The interlayer spacing of the modified montmorillonite was further expanded, the dispersion effect was better, the tensile strength and flexural strength were improved, and the siloxane group successfully reacted with the phenolic hydroxyl group, thereby reducing the content of phenolic hydroxyl groups in the phenolic resin and improving the anti-aging performance.
[0100] By comparing the data in the table, the data of Comparative Example 7 show that the two-step modification of montmorillonite successfully expanded its interlayer spacing and improved its dispersion effect. Although the interlayer spacing of the isocyanate-modified montmorillonite is small, resulting in poor modification effect, it also improves some of the tensile strength, flexural strength and anti-aging properties.
[0101] By comparing the data in the table, the data of Comparative Example 8 show that the addition of modified montmorillonite is dispersed in the matrix through its flaky structure, successfully improving the tensile strength and full strength. At the same time, the two-step modification of montmorillonite successfully expands its interlayer spacing, improves the dispersion performance, and introduces siloxane groups. The siloxane groups undergo dehydration condensation with phenolic hydroxyl groups, which improves the fixation of the modified montmorillonite while reducing the content of phenolic hydroxyl groups in the phenolic resin and improving the anti-aging performance.
[0102] Test Example 2:
[0103] Flame retardant performance test: The flame retardant phenolic resin samples were tested for limiting oxygen index, UL 94 combustion grade, and residual carbon content to evaluate their flame retardant effect. The specific test methods are as follows:
[0104] Limiting oxygen index test: According to GB / T 2406.1-2008, the limiting oxygen index is tested using an oxygen index instrument. The sample size is 150mm×10mm×3mm. Five samples are tested in each group and the average value is recorded.
[0105] Vertical combustion test: The test was conducted using a vertical-horizontal combustion tester according to ASTM D3801-2010. Five specimens were tested in each group and the average value was recorded.
[0106] Residual carbon rate test: Cut the prepared sample into pieces and take 5-10 mg, and use TG-209F1 thermogravimetric analyzer to measure it in a nitrogen atmosphere. The heating rate is 20℃ / min and the termination temperature is 950℃. The residual carbon rate is recorded as the remaining mass percentage at the termination temperature. Five samples are tested in each group, and the average value is recorded.
[0107] The results are shown in Table 2.
[0108] Table 2
[0109] Limiting oxygen index UL94 rating Residual carbon rate Example 1 53.49％ V-0 67.83％ Example 2 53.68％ V-0 68.15％ Example 3 52.96％ V-0 67.76％ Comparative Example 1 42.67％ V-2 57.25％ Comparative Example 2 45.52％ V-1 63.44％ Comparative Example 3 49.34％ V-1 62.15％ Comparative Example 4 36.17％ V-2 54.25％ Comparative Example 5 39.27％ V-1 58.46％ Comparative Example 6 51.35％ V-0 65.48％ Comparative Example 7 49.27％ V-0 63.26％ Comparative Example 8 46.34％ V-1 59.59％
[0110] From the comparison of the experimental data of Examples 1 to 3 and Comparative Examples 1 to 8 in Table 2, it can be found that the fire-retardant phenolic resin prepared in the present invention has good flame retardant properties.
[0111] By comparing the data in the table, the data of Comparative Example 1 show that the depolymerization reaction of alkali lignin reduces the molecular weight of alkali lignin and increases the reaction activity, increases the content of phenolic hydroxyl groups and side chain carbonyl groups, provides more sites for Ugi multi-component reactions, thereby introducing more flame retardant elements such as phosphorus, nitrogen, and silicon, effectively improving the flame retardant properties, and phosphorus, nitrogen, and silicon elements all have the effect of promoting carbonization, thereby increasing the generation rate of the carbon layer, and the dense carbon layer has excellent flame retardant properties.
[0112] By comparing the data in the table, the data of Comparative Example 2 show that diethyl isocyanate methyl phosphate successfully participated in the Ugi multi-component reaction and was grafted onto the depolymerized lignin, introducing the flame retardant element phosphorus, thereby effectively improving the flame retardant properties and residual carbon rate.
[0113] By comparing the data in the table, the data of Comparative Example 3 show that the end-hydroxy polydimethylsiloxane successfully participated in the Ugi multi-component reaction and introduced a flexible siloxane segment, which contains a large amount of flame retardant element silicon, has a good effect of promoting carbonization, and can form a synergistic flame retardant effect with the flame retardant element phosphorus, further improving the flame retardant properties.
[0114] By comparing the data in the table, the data of Comparative Examples 4 and 5 show that when only depolymerized lignin is added, although the mechanical properties are improved, the flame retardant properties and carbonization properties are reduced. Due to the lack of flame retardant elements, the flame retardant properties are reduced.
[0115] By comparing the data in the table, the data of Comparative Example 6 shows that the use of 3-aminopropyltriethoxysilane to modify isocyanate-modified montmorillonite successfully further expands the interlayer spacing of montmorillonite and improves the dispersion properties of montmorillonite. The modified montmorillonite well dispersed in the phenolic resin effectively improves the flame retardant properties through the barrier effect of the flakes and the promotion of carbonization.
[0116] By comparing the data in the table, the data of Comparative Example 7 shows that the modification of montmorillonite by diisocyanate successfully expands the interlayer spacing of montmorillonite and improves its dispersibility. The modified montmorillonite well dispersed in the phenolic resin effectively improves the flame retardant properties through the barrier effect of the flakes and the promotion of carbonization.
[0117] By comparing the data in the table, the data of Comparative Example 8 shows that the addition of modified montmorillonite effectively improves the flame retardant properties through the barrier effect of its flakes and the promotion of carbonization.
[0118] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A fire-retardant phenolic resin, characterized in that: The fire-retardant phenolic resin is prepared by polymerizing phenol with modified lignin, paraformaldehyde and modified montmorillonite. The modified lignin is prepared by subjecting depolymerized lignin to a multi-component reaction with amino-terminated polydimethylsiloxane, diethyl isocyanate methyl phosphate, and glacial acetic acid; The depolymerized lignin is prepared by depolymerizing alkali lignin in a lithium bromide solution; The modified montmorillonite is prepared by reacting isocyanate-modified montmorillonite with 3-aminopropyltriethoxysilane; The isocyanate-modified montmorillonite is prepared by modifying montmorillonite with diisocyanate.
2. A fire-retardant phenolic resin according to claim 1, characterized in that: The diisocyanate is one of isophorone diisocyanate, hexamethylene diisocyanate, toluene diisocyanate and diphenylmethane diisocyanate.
3. A method for preparing a fire-retardant phenolic resin, characterized in that: The method comprises the following preparation steps: (1) mixing alkali lignin and lithium bromide aqueous solution, ultrasonicating, heating, stirring and refluxing, cooling, filtering, washing and drying to obtain depolymerized lignin; (2) mixing depolymerized lignin, amino-terminated polydimethylsiloxane, and methanol, stirring at room temperature, adding diethyl isocyanate methyl phosphate and glacial acetic acid, stirring at room temperature, filtering, washing, and drying to obtain modified lignin; (3) dispersing montmorillonite in anhydrous toluene, stirring, adding isophorone diisocyanate and dibutyltin dilaurate, ultrasonicating, heating and stirring for reaction, washing, centrifuging, drying, grinding and sieving to obtain isocyanate-modified montmorillonite; (4) dispersing the isocyanate-modified montmorillonite in anhydrous toluene, stirring, adding 3-aminopropyltriethoxysilane and dibutyltin dilaurate, ultrasonicating, heating and stirring to react, washing, centrifuging, drying, grinding and sieving to obtain modified montmorillonite; (5) Phenol, modified lignin, pure water, and barium hydroxide octahydrate are mixed in a water bath, and paraformaldehyde is added in three times. The modified montmorillonite is added simultaneously with the second addition of paraformaldehyde. The mixture is heated and stirred for reaction, the pH is controlled, the temperature is raised for reaction, the water bath is removed, stirring is continued, and the system is cooled to 60° C. before discharging the material to obtain a fire-retardant phenolic resin.
4. The method for preparing a fire-retardant phenolic resin according to claim 3, wherein: The depolymerized lignin in step (1) is prepared by uniformly mixing 2 to 3 parts of alkali lignin and 10 to 12 parts of a 60 wt% lithium bromide aqueous solution, ultrasonically treating for 10 to 15 minutes, stirring and refluxing at 105 to 110° C. and 200 to 300 r / min for 2 to 2.5 hours, cooling in an ice-water bath, filtering, washing with pure water until neutral, and vacuum drying at 50 to 60° C. for 10 to 12 hours.
5. The method for preparing a fire-retardant phenolic resin according to claim 3, wherein: The modified lignin in step (2) is prepared by uniformly mixing 2 to 3 parts of depolymerized lignin, 1.5 to 2 parts of amino-terminated polydimethylsiloxane, and 15 to 20 parts of methanol, stirring at 200 to 300 r / min for 50 to 60 minutes at room temperature, adding 0.48 to 0.64 parts of diethyl isonitrile methyl phosphate and 0.17 to 0.23 parts of glacial acetic acid, stirring at 200 to 300 r / min for 22 to 24 hours at room temperature, filtering, washing with anhydrous ethanol and pure water alternately for 3 to 4 times, and vacuum drying at 50 to 60°C for 10 to 12 hours.
6. The method for preparing a fire-retardant phenolic resin according to claim 3, wherein: The isocyanate-modified montmorillonite in step (3) is prepared by dispersing 3 to 4 parts of montmorillonite in 25 to 30 parts of anhydrous toluene, stirring at 300 to 400 r / min for 30 to 40 minutes, adding 1.2 to 1.4 parts of isophorone diisocyanate and 0.018 to 0.022 parts of dibutyltin dilaurate, ultrasonicating for 30 to 40 minutes, stirring at 75 to 85° C. and 300 to 400 r / min for 6 to 7 hours, washing with anhydrous toluene 3 to 4 times, centrifuging, vacuum drying at 70 to 80° C. for 10 to 12 hours, and grinding and passing through a 160-mesh sieve to obtain the obtained product.
7. The method for preparing a fire-retardant phenolic resin according to claim 6, wherein: The montmorillonite is pretreated, and the pretreatment scheme is to grind it, pass it through a 160-mesh sieve, and dry it in a vacuum oven at 60-80° C. for 4-10 hours.
8. The method for preparing a fire-retardant phenolic resin according to claim 3, wherein: The modified montmorillonite in step (4) is prepared by dispersing 3 to 4 parts of isocyanate-modified montmorillonite in 25 to 30 parts of anhydrous toluene, stirring at 300 to 400 r / min for 30 to 40 minutes, adding 1.43 to 1.67 parts of 3-aminopropyltriethoxysilane and 0.021 to 0.025 parts of dibutyltin dilaurate, ultrasonicating for 30 to 40 minutes, stirring at 75 to 85°C and 300 to 400 r / min for 14 to 16 hours, washing with anhydrous toluene 3 to 4 times, centrifuging, vacuum drying at 70 to 80°C for 10 to 12 hours, grinding and passing through a 160-mesh sieve to obtain the obtained product.
9. The method for preparing a fire-retardant phenolic resin according to claim 3, wherein: The fire-retardant phenolic resin in step (5) is prepared by uniformly mixing 14 to 16 parts of phenol, 1.5 to 1.8 parts of modified lignin, 0.7 to 0.8 parts of pure water, and 0.3 to 0.4 parts of barium hydroxide octahydrate in a water bath at 65 to 70° C., adding paraformaldehyde three times at a molar ratio of phenolic hydroxyl groups to aldehyde groups of 1:1.7, each time with an interval of 15 to 20 minutes, adding 1.8 to 2.1 parts of modified montmorillonite simultaneously with the second addition of paraformaldehyde, reacting at 70 to 80° C. and 300 to 400 r / min for 2.5 to 3 hours, controlling the pH value between 9 and 10 with a 30w% sodium hydroxide aqueous solution, heating to 93 to 95° C. and reacting for 10 to 12 minutes, removing the water bath, and continuing stirring at 200 to 300 r / min for 30 to 40 minutes. The system is cooled to 60° C. and then discharged to obtain the obtained product.
10. Use of the fire-retardant phenolic resin prepared by the method for preparing the fire-retardant phenolic resin according to any one of claims 3 to 9 in preparing coated sand.
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