Fluoride-free anti-dripping functional flame retardant for polycarbonate as well as preparation method and application of fluorine-free anti-dripping functional flame retardant

Abstract

The invention belongs to the technical field of polymer flame retardance, and relates to a fluoride-free anti-dripping functional flame retardant for polycarbonate as well as a preparation method and application thereof, in the chemical structural formula of the fluoride-free anti-dripping functional flame retardant for polycarbonate, n is 5-20, and M is Li, Na, K, Rb or Cs; the preparation method comprises the following steps: mixing a metal salt solution of 2, 2 '-disulfonic acid benzidine with an acid-binding agent, dropwise adding a phenylphosphonic dichloride solution, continuing to stir and react after dropwise adding, heating after reaction, dropwise adding a diphenyl silanediol solution, continuing to react after dropwise adding, and finally performing post-treatment to obtain the fluoride-free anti-dripping functional flame retardant for polycarbonate. According to the application of the flame-retardant polycarbonate, polycarbonate and the fluoride-free anti-dripping functional flame retardant for polycarbonate are subjected to melt blending, so that the flame-retardant polycarbonate is prepared. The functional flame retardant disclosed by the invention integrates multiple functions of flame retardance, molten drop resistance, carbon formation enhancement and the like, and flame-retardant polycarbonate prepared from the functional flame retardant realizes no molten drop by virtue of a self-enhanced ceramic carbon layer.

Description

Technical Field

[0001] This invention belongs to the field of polymer flame retardant technology, and relates to a fluorine-free anti-drip functional flame retardant for polycarbonate, its preparation method and application. Background Technology

[0002] Polycarbonate, as an important amorphous thermoplastic engineering plastic, is widely used in high-end fields such as electronics, automobiles, construction, aerospace, and medicine due to its excellent impact strength, high transparency, good electrical insulation, dimensional stability, and heat resistance. However, although polycarbonate itself has a certain degree of self-extinguishing properties, it exhibits significant softening-melting characteristics during heating and combustion. Its carbonate bonds break at relatively low temperatures, generating phenols, aryl carbonates, and small molecules containing CO2, reducing melt strength. Because the decomposition products are difficult to form a dense and stable char layer, the condensed phase flame retardancy of polycarbonate is extremely weak; at the same time, its melt viscosity decreases rapidly during heating, making it highly susceptible to dripping with flames, leading to secondary ignition. Therefore, unmodified polycarbonate cannot meet the extremely stringent fire safety requirements of applications such as 5G communication equipment housings, high-speed rail interior parts, and high-rise building skylights.

[0003] Currently, the commonly used flame retardant systems for polycarbonate mainly include the following categories:

[0004] Halogenated flame retardants (such as brominated polystyrene, decabromodiphenyl ethane, etc.): Although they have high flame retardant efficiency, they release toxic and corrosive hydrogen halide gases and dioxin-like substances when burning, which do not meet the requirements of environmental regulations such as RoHS and REACH, and have been phased out in most high-end fields.

[0005] Phosphorus-based flame retardants (such as phosphate esters BDP and RDP): Although they are halogen-free systems, they usually need to be added at 5 to 10 wt% to achieve UL94-V0, and they are prone to migration and precipitation, reducing mechanical properties and transparency; more importantly, they are difficult to achieve UL94-V0 rating with a thickness of 1.5 mm, and cannot effectively suppress dripping.

[0006] Sulfonate flame retardants (such as potassium perfluorobutyl sulfonate PPFBS and potassium benzenesulfonylbenzenesulfonate KSS) are among the most efficient halogen-free flame retardants currently available for polycarbonate. They can achieve a UL94-V0 rating with an addition amount as low as 0.05–0.1 wt%. This is because sulfonates can produce significant flame-retardant effects through multiple pathways under high-temperature conditions:

[0007] Firstly, sulfonates readily undergo dehydration, aromatization, and cross-linking reactions in the condensed phase to form a dense, sulfur-containing carbon layer, which is beneficial for insulating heat and combustible gases.

[0008] Secondly, during the thermal decomposition of sulfonate, SOx or sulfur-containing free radical intermediates are generated, which inhibit the chain free radical reaction in the flame zone and significantly improve the oxygen index of the material. It belongs to a typical "gas phase-condensed phase" dual-effect flame retardant system.

[0009] Therefore, sulfonate flame retardants are considered important structural units for improving the flame retardant efficiency of polycarbonate, especially for increasing LOI and promoting char formation in the condensed phase.

[0010] However, most existing sulfonate flame retardants exist in the form of small molecule salts, which have poor compatibility with polycarbonate and are prone to problems such as migration, precipitation, and increased haze, especially in transparent materials.

[0011] Meanwhile, although small molecule sulfonates have a good carbon-promoting effect, their effect on increasing melt viscosity and inhibiting dripping is limited, making it difficult to solve the problem of melt dripping during polycarbonate combustion from a mechanistic perspective. Commercially, 0.1-0.3 wt% of PTFE anti-dripping agent is often added externally to prevent dripping, but PTFE will cause a significant increase in haze of the product (>5%), which seriously damages optical properties, and the presence of halogen F element does not comply with environmental regulations such as RoHS and REACH.

[0012] Silicon-based flame retardants (such as polysiloxanes and POSS) can promote the formation of a SiO2 ceramic layer during combustion and improve the strength of the char layer. However, they have low flame retardant efficiency when used alone, require a large amount (>5wt%), and have poor compatibility with polycarbonate, which can easily lead to decreased transparency and processing difficulties.

[0013] In recent years, researchers have attempted to improve flame retardancy efficiency through multi-element synergistic strategies, as it is difficult for a single element to simultaneously satisfy the properties of polycarbonate such as transparency, flame retardancy, and anti-dripping.

[0014] Patent application CN120923792A discloses a silicon-phosphorus macromolecular flame retardant, a flame-retardant low-dielectric polycarbonate containing the flame retardant, and a method for preparing the same. The method involves mixing and dissolving dichloromethane, triethylamine, bisphenol containing an R-structure, and diaminopropyl-terminated siloxane to prepare solution A; dissolving isophthaloyl chloride and / or terephthaloyl chloride and phenylphosphodichloro in dichloromethane to prepare solution B; adding solution B dropwise to solution A and stirring to react, followed by end-capping treatment to prepare the silicon-phosphorus macromolecular flame retardant. However, it lacks sulfonic acid groups, resulting in weak catalytic charring ability of polycarbonate.

[0015] Patent CN114262347A discloses a phosphorus-containing, nitrogen-containing, and sulfonate-containing compound, its preparation method, and its applications. The method involves first sulfonating DOPO or its derivatives with a sulfonating agent to obtain a phosphorus-containing compound with sulfonic acid groups. This compound is then added to a nitrogen-containing compound containing carbon-carbon unsaturated groups. Finally, it undergoes neutralization or precipitation reactions with metal compounds and / or ammonia / amine compounds to obtain the phosphorus-containing, nitrogen-containing, and sulfonate-containing compound. However, the phosphorus-containing, nitrogen-containing, and sulfonate-containing compounds obtained by this method lack silicon, making it impossible to form a ceramicized carbon layer, and thus requiring an anti-drip agent.

[0016] Therefore, developing a novel polycarbonate flame retardant that combines high transparency, no dripping, low addition amount, and is free of halogens and PFAS is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0017] The purpose of this invention is to address the problems existing in the prior art and to provide a fluorine-free anti-drip functional flame retardant for polycarbonate, its preparation method, and its application.

[0018] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0019] A fluorine-free anti-drip functional flame retardant for polycarbonate, with the following chemical structural formula:

[0020]

[0021] Wherein, n is 5 to 20; if the value of n is less than 5, the relative molecular weight is too small and it is easy to migrate and precipitate; if the value of n is greater than 20, the relative molecular weight is too large and it is not conducive to dispersion; M is Li, Na, K, Rb or Cs.

[0022] As a preferred technical solution:

[0023] The above-mentioned fluorine-free anti-drip functional flame retardant for polycarbonate has a melting point of 170-200°C and an initial decomposition temperature of 400-425°C under a nitrogen atmosphere.

[0024] This invention also provides a method for preparing a fluorine-free anti-drip functional flame retardant for polycarbonate as described above, the preparation steps of which are as follows:

[0025] (a) Under nitrogen protection, the metal salt solution of 2,2'-bis(sulfonic acid) benzidine was mixed with an acid-binding agent, and phenylphosphonic dichloride solution was added dropwise at a rate of 0.1 to 0.5 mL / s at a temperature of 0 to 5 °C and a stirring speed of 200 to 300 rpm. After the addition was completed, the reaction was stirred for 2 to 4 hours.

[0026] (b) Heat the reaction system of step (a) to 40-80°C, and add diphenylsilanediol solution dropwise at a rate of 0.1-0.5 mL / s. After the addition is complete, continue the reaction for 2-4 hours.

[0027] (c) After post-treatment of the reaction system in step (b), a fluorine-free anti-drip functional flame retardant for polycarbonate is obtained;

[0028] The specific post-processing procedure is as follows: First, the reaction system of step (b) is poured into ice methanol at -25℃ to -30℃ and stirred at a speed of 400 to 600 rpm, so that the polymer in the reaction system precipitates out as a white precipitate. Then, the filter cake is obtained by suction filtration. Finally, the filter cake is washed three times each with dilute hydrochloric acid, deionized water and methanol to remove acid-binding agents, metal salts and unreacted monomers.

[0029] Among them, the metal cation of the metal salt of 2,2'-bissulfonic acid benzidine is Li + Na + K + 、Rb + or Cs + The molar ratio of phenylphosphonodichloro, the metal salt of 2,2'-bis(sulfonic acid) benzidine, and diphenylsilanediol is 2–2.1:1:1.

[0030] The reaction equation for polycarbonate with a fluorine-free anti-dripping flame retardant is as follows:

[0031]

[0032] As a preferred technical solution:

[0033] As described above, the solvent for the phenylphosphonic dichloride solution and the diphenylsilanediol solution is the same. Since the solvent does not participate in the reaction but only serves as a carrier for the reactants and a medium for molecular diffusion, using the same solvent system can reduce the interference of interactions between molecules in different solvents and reduce the mass transfer resistance between reactant molecules and intermediates. Using different solvents may result in differences in the solubility of the products, leading to the dissolution loss of some products or difficulty in removing impurities. The solvent is N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide.

[0034] The metal salt solution of 2,2'-bissulfonic acid benzidine is obtained by dissolving 2,2'-bissulfonic acid benzidine in an alkaline solution; the alkaline solution is obtained by dissolving the hydroxide in deionized water; the hydroxide is LiOH, NaOH, KOH, RbOH or CsOH; the molar ratio of the hydroxide to 2,2'-bissulfonic acid benzidine is 2:1.

[0035] In the method described above, the acid-binding agent is an alkali metal hydroxide, alkali metal carbonate, or alkali metal bicarbonate; the molar amount of the acid-binding agent is 2 to 2.5 times the molar amount of phenylphosphonic dichloride.

[0036] In the method described above, the alkali metal hydroxide is LiOH, NaOH, KOH, RbOH, or CsOH, preferably KOH; the alkali metal carbonate is Li2CO3, Na2CO3, K2CO3, Rb2CO3, or Cs2CO3, preferably K2CO3; and the alkali metal bicarbonate is LiHCO3, NaHCO3, KHCO3, RbHCO3, or CsHCO3, preferably KHCO3.

[0037] The present invention also provides a method for preparing flame-retardant polycarbonate, wherein polycarbonate is melt-blended with a polycarbonate as described above using a fluorine-free anti-drip functional flame retardant to obtain flame-retardant polycarbonate.

[0038] As a preferred technical solution:

[0039] In the above-described method for preparing flame-retardant polycarbonate, the content of a fluorine-free anti-drip functional flame retardant in the flame-retardant polycarbonate is 0.5 wt% to 3 wt%.

[0040] The preparation method of flame-retardant polycarbonate as described above has a melting temperature of 260–320°C.

[0041] The flame-retardant polycarbonate prepared by the above-described method has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index higher than 30%, a light transmittance of more than 86%, and a haze of less than 1.5%.

[0042] The flame-retardant polycarbonate preparation method described above allows the flame-retardant polycarbonate resin to be further extruded or injection molded for use in preparing flame-retardant polycarbonate films, sheets, injection molded parts, etc.

[0043] Invention principle:

[0044] Polycarbonate is typically melt-processed at high temperatures of 260–320°C. Traditional small-molecule sulfonate flame retardants are prone to thermal decomposition, discoloration, and yellowing due to insufficient thermal stability. Furthermore, high-content small-molecule sulfonates are highly hydrophilic, easily migrating and precipitating under long-term service or humid environments, leading to a decrease in flame retardant performance and failure to meet requirements. On the other hand, sulfonate flame retardants and other flame retardants for polycarbonate usually require the addition of fluorinated PFAS and other anti-dripping agents to suppress dripping. However, fluorinated PFAS are increasingly subject to strict regulations and are restricted by RoHS, RECHA, and the Stockholm Convention. Therefore, there is an urgent need to develop fluorine-free anti-dripping flame retardants to replace them.

[0045] The present invention discloses a fluorine-free anti-drip functional flame retardant for polycarbonate, which uses phenylphosphonic dichloro as the backbone, with one end connected to benzidine disulfonic acid and the other end connected to diphenyldisilol, forming a multifunctional macromolecular structure that integrates phosphorus, sulfur and silicon as three flame retardant elements. In polycarbonate, it achieves high-efficiency flame retardancy and excellent anti-drip performance through the synergistic mechanism of condensed phase and gas phase.

[0046] In the condensed phase, the sulfonic acid groups in benzidine disulfonate pyrolyze at 300-500℃ to generate inert gases such as SO2, while efficiently catalyzing the Fries rearrangement and cross-linking reaction of polycarbonate, promoting the rapid formation of a dense aromatic char layer; the phenylphosphonoyl groups further enhance the char formation efficiency and char layer stability through dehydration and phosphorylation; while diphenylsilanol is oxidized at high temperature to generate SiO2 or PO-Si network, which is embedded in the organic char layer to construct an organic-inorganic hybrid protective layer with heat insulation and oxygen barrier functions, effectively preventing heat transfer and the escape of combustible gases.

[0047] In the gas phase, the PO· and HPO· free radicals generated by the pyrolysis of phosphorus components can efficiently capture H· and OH· free radicals in the combustion chain reaction, interrupting flame propagation. Crucially, the PO-Si network structure significantly increases the melt viscosity of polycarbonate and forms a ceramic-like skeleton on the surface, effectively suppressing material softening and flow, thus solving the problem of secondary ignition of fusible droplets during polycarbonate combustion.

[0048] Different alkali metal cations, due to differences in ionic radius and charge density, affect the thermal stability, ion association behavior, and interaction with polycarbonate segments of sulfonates, thus exhibiting differences in char layer density, dispersion stability, and melt behavior. For example, lithium salt systems are conducive to forming dense char layers while maintaining material transparency; sodium salt systems balance dispersibility and structural stability; potassium salt systems can enhance melt viscoelasticity at high temperatures, thereby improving anti-dripping ability; rubidium salt systems, with their large ionic radius and low charge density, significantly enhance melt elasticity while maintaining good char formation ability; and cesium salt systems, due to their extremely low ion association and largest cation size, although initially exhibiting weaker char formation, can maximize high-temperature melt viscosity and structural integrity, endowing polycarbonate with non-dripping flame-retardant properties. Lithium salts are known for their high transparency, low smoke production, and excellent char formation ability, making them suitable for applications with stringent requirements for optical performance and smoke toxicity. Sodium and potassium salts achieve a good balance between transparency, flame retardancy, and processing stability, making them commonly used industrial solutions. Rubidium and cesium salts, on the other hand, significantly enhance melt strength due to their large ionic radii, enabling rapid self-extinguishing upon removal from the flame and the elimination of molten droplets.

[0049] Under the synergistic effect of the above functional groups, the polycarbonate in polycarbonate can achieve the UL94-V0 flame retardant rating with a very low addition amount (0.05-3wt%) of the fluorine-free anti-dripping functional flame retardant, and there is no dripping (especially suitable for thin-walled products with a thickness of 1.6mm or more).

[0050] Meanwhile, polycarbonate itself is an amorphous homogeneous material with a light transmittance of up to 89%. Adding flame retardants to polycarbonate often affects its optical properties, but the effect of adding high molecular weight polymer flame retardants on the material's transparency and haze depends on the degree of polymerization of the flame retardant: within the molecular weight range of 5–20 chain units, as the degree of polymerization increases, the flame retardant molecular chains become longer, their chain entanglement with the polycarbonate matrix is ​​enhanced, and their thermodynamic compatibility is significantly improved. This allows the flame retardant to be uniformly dispersed in polycarbonate at the nanoscale (<50 nm), effectively avoiding light scattering caused by micron-level phase separation or crystallization. Simultaneously, the flame retardant backbone is rich in aromatic rings and polar P=O, CN, and other groups that are similar to the structure or refractive index of polycarbonate, further reducing the interfacial refractive index difference, thereby maintaining high light transmittance (>87%) and low haze (<1.5%).

[0051] Beneficial effects:

[0052] (1) The non-fluorinated anti-dripping functional flame retardant for polycarbonate of the present invention integrates multiple functions such as flame retardancy, anti-dripping, and char reinforcement. The flame-retardant polycarbonate prepared with it achieves no dripping by relying on the self-reinforced ceramicized carbon layer, avoiding the haze increase and environmental hazards caused by the introduction of PTFE and PFAS substances, simplifying the composite material formulation system, and reducing the cost of raw materials and the complexity of the mixing process. In addition, its synthesis route adopts conventional polycondensation chemical reaction, the raw materials are readily available, the steps are simple, and the yield is high, making it suitable for large-scale industrial production.

[0053] (2) This invention not only solves the technical bottlenecks such as "low flame retardant efficiency, severe dripping, opacity and deterioration of mechanical properties" that are common in existing halogen-free flame retardant systems, but also makes great progress in environmental compliance, processing stability and industrialization feasibility, and has significant technological advancement, economic value and social benefits. Attached Figure Description

[0054] Figure 1 The infrared spectrum of the fluorine-free anti-dripping functional flame retardant for polycarbonate in Example 1 of the present invention;

[0055] Figure 2 The above is the 1H NMR spectrum of the fluorine-free anti-drip functional flame retardant for polycarbonate in Example 1 of this invention;

[0056] Figure 3 The TG curve of the fluorine-free anti-drip functional flame retardant for polycarbonate in Example 1 of this invention is shown.

[0057] Figure 4 This is a DSC diagram of the non-fluorine anti-drip functional flame retardant for polycarbonate in Example 1 of the present invention. Detailed Implementation

[0058] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0059] The general structural formula of the fluorine-free anti-drip functional flame retardant for polycarbonate prepared in the following embodiments is as follows:

[0060] In the formula, n is 5 to 20, and M is Li, Na, K, Rb, or Cs.

[0061] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0062] Flame retardancy rating and dripping: The vertical method of GB / T 2408-2021 "Determination of Burning Performance of Plastics - Horizontal and Vertical Methods" was used to test the sample with a size of 125×13×3mm using a CZF-5 vertical burning tester. Methane was used as the ignition source gas (blue inner flame height 20±1mm). The sample was pretreated at 23±2℃ and 50±5% relative humidity for 48h. Two intermittent flame tests of 10±0.5 seconds were performed as specified in the standard. The burning time, dripping state and ignition of the degreased cotton were recorded to determine the flame retardancy rating and the presence or absence of dripping.

[0063] Limiting Oxygen Index (LOI): The limiting oxygen index (LOI) of a 120×13×4mm sample was determined using a JF-5 limiting oxygen index meter in accordance with ISO 4589-2 standard, with butane as the ignition source gas during the test.

[0064] Transmittance and haze: In accordance with GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics", a haze meter (model: TH110) was used to determine the transmittance of a 2mm thick sample. During the test, the measurement wavelength was 550nm. Each sample was tested in parallel 3 times, and the average value was taken as the final test result.

[0065] Example 1

[0066] A method for preparing flame-retardant polycarbonate, comprising the following steps:

[0067] (1) Prepare a metal salt solution of benzidine disulfonic acid;

[0068] First, KOH is dissolved in deionized water to obtain a 1 wt% alkaline solution. Then, 2,2'-disulfonic acid benzidine is dissolved in the alkaline solution to obtain a metal salt solution of 2,2'-disulfonic acid benzidine. The molar ratio of KOH to 2,2'-disulfonic acid benzidine is 2:1, and the metal cation of the metal salt of 2,2'-disulfonic acid benzidine is K. + ;

[0069] (2) Under nitrogen protection, the metal salt solution of 2,2'-bis(sulfonic acid) benzidine was mixed with KOH, and then phenylphosphonic dichloride solution (concentration of 50wt%, solvent of N,N-dimethylformamide) was added dropwise at a rate of 0.3 mL / s at a stirring speed of 250 rpm. After the addition was completed, the reaction was stirred for 3 h. The molar amount of KOH in step (2) was 2.3 times the molar amount of phenylphosphonic dichloride.

[0070] (3) Heat the reaction system of step (2) to 40°C, and add diphenylsilanediol solution (concentration of 15wt%, solvent of N,N-dimethylformamide) dropwise at a rate of 0.2mL / s. After the addition is completed, continue the reaction for 2h.

[0071] (4) First, pour the reaction system from step (3) into -25℃ ice-cold methanol and stir at 500 rpm to allow the polymer in the reaction system to precipitate as a white precipitate. Then, obtain a filter cake by vacuum filtration. Finally, wash the filter cake three times each with dilute hydrochloric acid, deionized water, and methanol to remove KOH, the metal salt of 2,2'-bis(sulfonic acid) benzidine, and unreacted monomers, thereby obtaining a fluorine-free anti-drip functional flame retardant for polycarbonate (its infrared spectrum is as follows). Figure 1 As shown, the proton NMR spectrum is as follows: Figure 2 (as shown);

[0072] In steps (2) to (4), the molar ratio of phenylphosphonodichloro, the metal salt of 2,2'-bis(sulfonic acid) benzidine and diphenylsilanediol is 2:1:1;

[0073] In the chemical structural formula of the prepared polycarbonate non-fluorine anti-dripping functional flame retardant, n is 8 and M is K;

[0074] Fluorine-free anti-drip functional flame retardants for polycarbonate (such as...) Figure 4 The melting point of (as shown) is 180.6℃, and the initial decomposition temperature under a nitrogen atmosphere (as shown) is... Figure 3 (As shown) is 404℃;

[0075] (5) Polycarbonate is melt-blended with a fluorine-free anti-drip functional flame retardant for polycarbonate to obtain flame-retardant polycarbonate; wherein the melting temperature is 275°C and the content of the fluorine-free anti-drip functional flame retardant for polycarbonate in the flame-retardant polycarbonate is 0.5wt%.

[0076] The final flame-retardant polycarbonate has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index of 34.5%, a light transmittance of 88%, and a haze of 1.4%.

[0077] Example 2

[0078] A method for preparing flame-retardant polycarbonate, comprising the following steps:

[0079] (1) Prepare a metal salt solution of benzidine disulfonic acid;

[0080] First, LiOH is dissolved in deionized water to obtain a 1 wt% alkaline solution. Then, 2,2'-bissulfonic acid benzidine is dissolved in the alkaline solution to obtain a metal salt solution of 2,2'-bissulfonic acid benzidine. The molar ratio of LiOH to 2,2'-bissulfonic acid benzidine is 2:1, and the metal cation of the metal salt of 2,2'-bissulfonic acid benzidine is Li. + ;

[0081] (2) Under nitrogen protection, the metal salt solution of 2,2'-bis(sulfonic acid) benzidine was mixed with Li2CO3, and then phenylphosphonic dichloride solution (concentration of 40wt%, solvent of N-methylpyrrolidone) was added dropwise at a rate of 0.1mL / s at a temperature of 2℃ and a stirring speed of 200rpm. After the addition was completed, the reaction was stirred for 2h. The molar amount of Li2CO3 was 2.1 times the molar amount of phenylphosphonic dichloride.

[0082] (3) Heat the reaction system of step (2) to 50°C, and add diphenylsilanediol solution (concentration of 20wt%, solvent of N-methylpyrrolidone) at a dropping rate of 0.1mL / s. After the addition is completed, continue the reaction for 3h.

[0083] (4) First, pour the reaction system of step (3) into -28℃ ice methanol and stir at 400 rpm so that the polymer in the reaction system precipitates out as a white precipitate. Then, filter cake is obtained by suction filtration. Finally, the filter cake is washed three times each with dilute hydrochloric acid, deionized water and methanol to remove Li2CO3, metal salt of 2,2'-bis(sulfonic acid) benzidine and unreacted monomers, and then a fluorine-free anti-drip functional flame retardant for polycarbonate is obtained.

[0084] In steps (2) to (4), the molar ratio of phenylphosphonic dichloride, the metal salt of 2,2'-bis(sulfonic acid) benzidine and diphenylsilanediol is 2.08:1:1;

[0085] In the chemical structural formula of the prepared polycarbonate non-fluorine anti-dripping functional flame retardant, n is 20 and M is Li;

[0086] The melting point of the fluorine-free anti-dripping functional flame retardant for polycarbonate is 170℃, and the initial decomposition temperature under nitrogen atmosphere is 400℃.

[0087] (5) Polycarbonate is melt-blended with a fluorine-free anti-drip functional flame retardant for polycarbonate to obtain flame-retardant polycarbonate; wherein the melting temperature is 280℃ and the content of the fluorine-free anti-drip functional flame retardant for polycarbonate in the flame-retardant polycarbonate is 1wt%.

[0088] The final flame-retardant polycarbonate has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index of 31.4%, a light transmittance of 89%, and a haze of 1.2%.

[0089] Example 3

[0090] A method for preparing flame-retardant polycarbonate, comprising the following steps:

[0091] (1) Prepare a metal salt solution of benzidine disulfonic acid;

[0092] First, NaOH is dissolved in deionized water to obtain a 1 wt% alkaline solution. Then, 2,2'-disulfonic acid benzidine is dissolved in the alkaline solution to obtain a metal salt solution of 2,2'-disulfonic acid benzidine. The molar ratio of NaOH to 2,2'-disulfonic acid benzidine is 2:1, and the metal cation of the metal salt of 2,2'-disulfonic acid benzidine is Na₂SO₄. + ;

[0093] (2) Under nitrogen protection, the metal salt solution of 2,2'-bis(sulfonic acid) benzidine was mixed with NaHCO3, and then phenylphosphonic dichloride solution (concentration of 45wt%, solvent of dimethyl sulfoxide) was added dropwise at a rate of 0.2 mL / s at a stirring speed of 225 rpm. After the addition was completed, the reaction was stirred for 2.5 h. The molar amount of NaHCO3 was 2.2 times the molar amount of phenylphosphonic dichloride.

[0094] (3) Heat the reaction system of step (2) to 60°C, and add diphenylsilanediol solution (concentration of 10wt%, solvent of dimethyl sulfoxide) at a dropping rate of 0.3mL / s. After the addition is completed, continue the reaction for 4h.

[0095] (4) First, pour the reaction system of step (3) into -30℃ ice methanol and stir at 500 rpm so that the polymer in the reaction system precipitates out as a white precipitate. Then, filter cake is obtained by suction filtration. Finally, the filter cake is washed three times each with dilute hydrochloric acid, deionized water and methanol to remove NaHCO3, metal salt of 2,2'-bis(sulfonic acid) benzidine and unreacted monomers, and then a fluorine-free anti-drip functional flame retardant for polycarbonate is obtained.

[0096] In steps (2) to (4), the molar ratio of phenylphosphonodichloro, the metal salt of 2,2'-bis(sulfonic acid) benzidine and diphenylsilanediol is 2.06:1:1;

[0097] In the chemical structural formula of the prepared polycarbonate non-fluorine anti-dripping functional flame retardant, n is 10 and M is Na;

[0098] The melting point of the fluorine-free anti-dripping functional flame retardant for polycarbonate is 178.4℃, and the initial decomposition temperature under nitrogen atmosphere is 411℃.

[0099] (5) Polycarbonate is melt-blended with a fluorine-free anti-drip functional flame retardant for polycarbonate to obtain flame-retardant polycarbonate; wherein the melting temperature is 270°C and the content of the fluorine-free anti-drip functional flame retardant for polycarbonate in the flame-retardant polycarbonate is 1.5wt%.

[0100] The final flame-retardant polycarbonate has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index of 32.3%, a light transmittance of 88%, and a haze of 1.3%.

[0101] Example 4

[0102] A method for preparing flame-retardant polycarbonate, comprising the following steps:

[0103] (1) Prepare a metal salt solution of benzidine disulfonic acid;

[0104] First, RbOH is dissolved in deionized water to obtain a 1 wt% alkaline solution. Then, 2,2'-disulfonic acid benzidine is dissolved in the alkaline solution to obtain a metal salt solution of 2,2'-disulfonic acid benzidine. The molar ratio of RbOH to 2,2'-disulfonic acid benzidine is 2:1, and the metal cation of the metal salt of 2,2'-disulfonic acid benzidine is Rb. + ;

[0105] (2) Under nitrogen protection, the metal salt solution of 2,2'-bis(sulfonic acid) benzidine was mixed with Rb2CO3, and then phenylphosphonic dichloride solution (concentration of 55wt%, solvent of N,N-dimethylformamide) was added dropwise at a rate of 0.4 mL / s at a stirring speed of 275 rpm. After the addition was completed, the reaction was stirred for 3.5 h. The molar amount of Rb2CO3 was 2.4 times the molar amount of phenylphosphonic dichloride.

[0106] (3) Heat the reaction system of step (2) to 70°C, and add diphenylsilanediol solution (concentration of 15wt%, solvent of N,N-dimethylformamide) dropwise at a rate of 0.4mL / s. After the addition is completed, continue the reaction for 2.5h.

[0107] (4) First, pour the reaction system of step (3) into -25℃ ice methanol and stir at 600 rpm so that the polymer in the reaction system precipitates out as a white precipitate. Then, filter cake is obtained by suction filtration. Finally, the filter cake is washed three times each with dilute hydrochloric acid, deionized water and methanol to remove the metal salts of Rb2CO3, 2,2'-bis(sulfonic acid) benzidine and unreacted monomers, and then a fluorine-free anti-drip functional flame retardant for polycarbonate is obtained.

[0108] In steps (2) to (4), the molar ratio of phenylphosphonodichloro, the metal salt of 2,2'-bis(sulfonic acid) benzidine and diphenylsilanediol is 2.04:1:1;

[0109] In the chemical structural formula of the prepared polycarbonate non-fluorine anti-dripping functional flame retardant, n is 6 and M is Rb;

[0110] The melting point of the non-fluorinated anti-dripping functional flame retardant for polycarbonate is 186.1℃, and the initial decomposition temperature under nitrogen atmosphere is 416℃.

[0111] (5) Polycarbonate is melt-blended with a fluorine-free anti-drip functional flame retardant for polycarbonate to obtain flame-retardant polycarbonate; wherein the melting temperature is 260℃ and the content of the fluorine-free anti-drip functional flame retardant for polycarbonate in the flame-retardant polycarbonate is 2wt%.

[0112] The final flame-retardant polycarbonate has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index of 33.1%, a light transmittance of 87%, and a haze of 1.3%.

[0113] Example 5

[0114] A method for preparing flame-retardant polycarbonate, comprising the following steps:

[0115] (1) Prepare a metal salt solution of benzidine disulfonic acid;

[0116] First, CsOH is dissolved in deionized water to obtain a 1 wt% alkaline solution. Then, 2,2'-disulfonic acid benzidine is dissolved in the alkaline solution to obtain a metal salt solution of 2,2'-disulfonic acid benzidine. The molar ratio of CsOH to 2,2'-disulfonic acid benzidine is 2:1, and the metal cation of the metal salt of 2,2'-disulfonic acid benzidine is CsOH. + ;

[0117] (2) Under nitrogen protection, the metal salt solution of 2,2'-bis(sulfonic acid) benzidine was mixed with CsHCO3, and then phenylphosphonic dichloride solution (60wt% concentration, dimethyl sulfoxide solvent) was added dropwise at a rate of 0.5 mL / s at a stirring speed of 300 rpm. After the addition was completed, the reaction was stirred for 4 h. The molar amount of CsHCO3 was 2.5 times the molar amount of phenylphosphonic dichloride.

[0118] (3) Heat the reaction system of step (2) to 80°C, and add diphenylsilanediol solution (concentration of 10wt%, solvent of dimethyl sulfoxide) at a dropping rate of 0.5mL / s. After the addition is completed, continue the reaction for 3.5h.

[0119] (4) First, pour the reaction system of step (3) into -30℃ ice methanol and stir at 450 rpm so that the polymer in the reaction system precipitates out as a white precipitate. Then, filter cake is obtained by suction filtration. Finally, the filter cake is washed three times each with dilute hydrochloric acid, deionized water and methanol to remove the metal salt of CsHCO3, 2,2'-bissulfonic acid benzidine and unreacted monomers, and then a fluorine-free anti-drip functional flame retardant for polycarbonate is obtained.

[0120] In steps (2) to (4), the molar ratio of phenylphosphonodichloro, the metal salt of 2,2'-bis(sulfonic acid) benzidine and diphenylsilanediol is 2.02:1:1;

[0121] The chemical structural formula of the prepared polycarbonate non-fluorine anti-dripping functional flame retardant has n = 5 and M = Cs;

[0122] The melting point of the fluorine-free anti-dripping functional flame retardant for polycarbonate is 200℃, and the initial decomposition temperature under nitrogen atmosphere is 425℃.

[0123] (5) Polycarbonate is melt-blended with a fluorine-free anti-drip functional flame retardant for polycarbonate to obtain flame-retardant polycarbonate; wherein the melting temperature is 290°C and the content of the fluorine-free anti-drip functional flame retardant for polycarbonate in the flame-retardant polycarbonate is 3wt%.

[0124] The final flame-retardant polycarbonate has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index of 33.6%, a light transmittance of 87%, and a haze of 1.4%.

Claims

1. A fluorine-free anti-drip functional flame retardant for polycarbonate, characterized in that, The chemical structural formula is: Where n is 5 to 20; M is Li, Na, K, Rb or Cs.

2. The fluorine-free anti-drip functional flame retardant for polycarbonate according to claim 1, characterized in that, The melting point of the fluorine-free anti-drip functional flame retardant for polycarbonate is 170–200℃, and the initial decomposition temperature under nitrogen atmosphere is 400–425℃.

3. A method for preparing a fluorine-free anti-drip functional flame retardant for polycarbonate as described in claims 1-2, characterized in that, The preparation steps are as follows: (a) After mixing the metal salt solution of 2,2'-bissulfonic acid benzidine with an acid-binding agent, phenylphosphonic dichloride solution was added dropwise at a temperature of 0-5°C. After the addition was completed, the reaction was stirred for 2-4 hours. (b) Heat the reaction system of step (a) to 40-80°C, add diphenylsilanediol solution dropwise, and continue the reaction for 2-4 hours after the addition is complete; (c) After post-treatment of the reaction system in step (b), a fluorine-free anti-dripping functional flame retardant for polycarbonate is obtained; Among them, the metal cation of the metal salt of 2,2'-bissulfonic acid benzidine is Li + Na + K + 、Rb + or Cs + The molar ratio of phenylphosphonodichloro, the metal salt of 2,2'-bis(sulfonic acid) benzidine, and diphenylsilanediol is 2–2.1:1:

1.

4. The method according to claim 3, characterized in that, The solvent for the phenylphosphonic dichloride solution is the same as that for the diphenylsilanediol solution; the solvent is N,N-dimethylformamide, N-methylpyrrolidone, or dimethyl sulfoxide. The metal salt solution of 2,2'-bissulfonic acid benzidine is obtained by dissolving 2,2'-bissulfonic acid benzidine in an alkaline solution; the alkaline solution is obtained by dissolving the hydroxide in deionized water; the hydroxide is LiOH, NaOH, KOH, RbOH or CsOH; the molar ratio of the hydroxide to 2,2'-bissulfonic acid benzidine is 2:

1.

5. The method according to claim 3, characterized in that, The acid-binding agent is an alkali metal hydroxide, alkali metal carbonate, or alkali metal bicarbonate; the molar amount of the acid-binding agent is 2 to 2.5 times the molar amount of phenylphosphonic dichloride.

6. The method according to claim 5, characterized in that, Alkali metal hydroxides are LiOH, NaOH, KOH, RbOH, or CsOH; alkali metal carbonates are Li2CO3, Na2CO3, K2CO3, Rb2CO3, or Cs2CO3; alkali metal bicarbonates are LiHCO3, NaHCO3, KHCO3, RbHCO3, or CsHCO3.

7. A method for preparing flame-retardant polycarbonate, characterized in that, Flame-retardant polycarbonate is prepared by melt blending polycarbonate with a fluorine-free anti-drip functional flame retardant for polycarbonate as described in any one of claims 1 to 2.

8. The method for preparing flame-retardant polycarbonate according to claim 7, characterized in that, The content of fluorine-free anti-drip functional flame retardant in flame-retardant polycarbonate is 0.5wt% to 3wt%.

9. The method for preparing a flame-retardant polycarbonate according to claim 8, characterized in that, The melting temperature is 260–320℃.

10. The method for preparing a flame-retardant polycarbonate according to claim 9, characterized in that, The flame-retardant polycarbonate has a flame retardant rating of UL94-V0, is free of dripping, has a limiting oxygen index of over 30%, a light transmittance of over 86%, and a haze of less than 1.5%.

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