Linear nitrogen-sulfur-containing polyborosiloxane as well as preparation method and application thereof

Abstract

The invention discloses linear nitrogen-sulfur-containing polyborosiloxane as well as a preparation method and application thereof. According to the technical scheme, a two-step method is innovatively adopted to precisely regulate and control the polymerization process: firstly, a functional flame-retardant unit is constructed through directional reaction of boric acid and a phenyl sulfonic acid compound with amino, then the functional flame-retardant unit is used as an active intermediate to be polymerized with hydroxyl-terminated silicone oil, controllable growth of molecular chains is achieved, and finally linear nitrogen-sulfur-containing polyborosiloxane is prepared. Only 0.2-0.4 wt% of nitrogen-sulfur-containing polyborosiloxane prepared by the preparation method disclosed by the invention is added, and the nitrogen-sulfur-containing polyborosiloxane has excellent effects of promoting PC charring and resisting molten drops, so that the polycarbonate composite material is good in thermal stability and high in carbon residue, passes a UL-94 V0 level test and an S2 needle flame test, and meanwhile, keeps excellent impact resistance.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology, specifically relating to a linear nitrogen-sulfur-containing polyboron siloxane, its preparation method, and its application. Background Technology

[0002] Polycarbonate (PC) exhibits certain flame-retardant properties in the UL-94 vertical burning test (LOI of 24%, reaching the V-2 level). However, with the increasing requirements for fire safety, its flammability and problems such as severe dripping and large smoke release during combustion have greatly limited its application in high-end fields such as aerospace and electronics. Therefore, the development of high-performance flame-retardant PC materials is of great significance and has broad prospects.

[0003] PC releases a large amount of CO2, phenolic derivatives and ether gases during combustion. In addition, PC has a low melt viscosity. Therefore, PC alone has insufficient ability to form char during combustion, which leads to PC dripping and the inability to self-extinguish.

[0004] Common flame retardants for polycarbonate include halogenated, silicon-based, boron-based, sulfonate-based, and phosphorus-based halogenated flame retardants. Halogenated flame retardants have good flame retardant effects and can achieve good flame retardant performance with relatively small amounts, effectively reducing the burning rate and flame spread of materials. However, they release large amounts of toxic gases and fumes during combustion, which are harmful to the environment and human health, and their use is gradually being banned.

[0005] The biggest advantage of sulfonate flame retardants is their high flame retardant efficiency and low dosage, which can improve flame retardant performance while basically maintaining the mechanical strength and other properties of the polycarbonate substrate. However, when used alone, their flame retardant efficiency is insufficient to achieve the UL-94 V-0 rating for thin-walled PC parts, or dripping may occur. Therefore, they usually need to be used in combination with other flame retardants. Furthermore, commonly used sulfonate flame retardants, due to their small molecular weight, are prone to precipitating in the PC substrate, resulting in poor material durability.

[0006] Furthermore, silicon-based flame retardants are characterized by being halogen-free, phosphorus-free, smoke-free, and non-toxic. At high temperatures, they easily migrate to the material surface, forming -Si-O- or -Si-C- structures, providing both heat insulation and flame retardancy. They also adsorb smoke and toxic gases generated during combustion, exhibiting characteristics of environmentally friendly flame retardants, thus gaining widespread industrial popularity. However, organosilicon compounds typically require compounding to achieve synergistic flame retardant effects; their flame retardant efficiency is limited when used alone, necessitating increased dosage to achieve the desired effect. Increasing the dosage not only raises costs but also easily degrades the material's mechanical properties. Boron-based compounds promote char formation but are prone to migration and have poor dispersibility. None of these flame retardants can achieve highly efficient flame retardancy of polycarbonate when added in small amounts alone. More importantly, the dripping phenomenon of PC still exists during combustion, often requiring compounding with anti-drip agents to achieve both flame retardancy and anti-drip effects. Research has found that if a Si-OB copolymer backbone can be introduced into the same polymer molecule simultaneously, and polarity and compatibility can be adjusted through nitrogen-containing sulfonate groups, a balance between highly efficient synergistic flame retardancy and thermal stability can be achieved. Therefore, it is of great significance to develop a nitrogen-sulfur polyboron siloxane flame retardant with a well-defined structure, controllable molecular weight, and good processing compatibility. Summary of the Invention

[0007] To address the technical bottlenecks of existing flame retardants, such as poor flame retardant performance and the difficulty in resolving dripping issues with compound formulations, this invention provides a groundbreaking linear nitrogen-sulfur-containing polyboron siloxane, its preparation method, and its applications. This innovative approach employs a two-step method for precise control of the polymerization process: first, functional flame-retardant units are constructed through the directional reaction of boric acid with an amino-containing phenylsulfonic acid compound; then, these units are used as active intermediates to polymerize with hydroxyl-terminated silicone oil, achieving controllable molecular chain growth, ultimately yielding the linear nitrogen-sulfur-containing polyboron siloxane. This material combines the heat resistance of organosilicon, the flame retardancy of boron-based materials, and the synergistic effect of nitrogen and sulfur, representing a novel, highly efficient, low-addition, environmentally friendly flame-retardant modified material.

[0008] One of the technical solutions of this invention is to provide a linear nitrogen-sulfur-containing polyboron siloxane, the main molecular chain of which is formed by alternating copolymerization of x siloxane units and boron units, as shown in the following chemical formula: Its repeating structural unit is (-Si(R1)(R2)-OB(-R3)-O-)X; the siloxane unit has substituents R1 and R2, the boron unit is -B(OH)3-, wherein R1 and R2 are independently selected from benzene ring, methyl, ethyl or vinyl, and x>5; the two hydroxyl groups of the boron unit undergo dehydration condensation with the hydroxyl groups of the siloxane unit respectively, and the boron atoms in the main chain are connected to the silicon-oxygen bond by the -B(O-)- bond to form a Si-OB covalent bond; the third hydroxyl group of the boron unit is replaced by R3, R3 is (MSO3-Ph-NH- or MSO3-NH-), introducing a "nitrogen-containing sulfonic acid group-metal salt" side chain; the metal ion M is K+ Na + Li + Ph has a benzene ring structure. Its number-average molecular weight Mn is (5 × 10⁻⁶). 3 ~8×10 4 ).

[0009] The second technical solution of the present invention is to provide a method for preparing the above-mentioned linear nitrogen-sulfur-containing polyboron siloxane, which includes the following steps: (1) under the conditions of 150~200℃ and -0.1~0.05MPa, boric acid compounds and aminosulfonates are subjected to solid-phase polycondensation reaction to obtain an intermediate; the molar ratio of the hydroxyl group of the boric acid compound to the amino group of the aminosulfonate compound is 1:0.1~1; (2) Cool down to 80-120℃, add hydroxyl-terminated silicone oil and catalyst, carry out polycondensation reaction, and finally obtain linear nitrogen-sulfur polyboron siloxane; the molar ratio of hydroxyl groups in the hydroxyl-terminated silicone oil to hydroxyl groups in the boric acid compound is controlled at 1:0.3-1.5.

[0010] Further, the boric acid compound mentioned in step 1 is boric acid; the aminophenyl sulfonic acid compound is one or more of potassium p-aminobenzenesulfonate, sodium p-aminobenzenesulfonate, potassium aminosulfonate, sodium aminosulfonate, lithium aminosulfonate, potassium 3,4-diaminobenzenesulfonate, sodium 3,4-diaminobenzenesulfonate, potassium 2,5-diaminobenzenesulfonate, and sodium 2,4-diaminobenzenesulfonate.

[0011] Further, the hydroxyl silicone oil in step 2 has a molecular weight of 500-20000, and its substituents are benzene rings, methyl, ethyl, vinyl, or a combination of all four; the catalyst is concentrated sulfuric acid, highly polymerized phosphoric acid containing 5 to 20 phosphoric acid units, or a mixture thereof.

[0012] Furthermore, the reaction time for the solid-phase condensation in step 1 is 1 to 2.5 h; during the reaction, the aminophenylsulfonic acid compound is added dropwise to the boric acid compound at a rate of 1 to 5 mL / min.

[0013] Furthermore, the reaction time of the polycondensation reaction described in step 2 is 0.5 to 4 hours.

[0014] The third technical solution of the present invention is to provide the application of the above-mentioned linear nitrogen-sulfur polyboron siloxane as a flame retardant. The flame retardant containing nitrogen-sulfur polyboron siloxane is heated and melted with polycarbonate and then hot-pressed to obtain a polycarbonate composite material. The content of nitrogen-sulfur polyboron siloxane in the polycarbonate composite material is 0.2~1.0wt%.

[0015] Furthermore, the heating and melting blending is performed using a torque rheometer at a processing temperature of 260°C, a processing time of 8-15 minutes, and a rotation speed of 50 r / min; the hot pressing is performed using a flat vulcanizing machine at a hot pressing temperature of 260°C and a pressure of 10 MPa. The polycarbonate composite material has a UL-94 vertical flammability rating of V-0.

[0016] Polyborosiloxanes significantly improve the charring ability of PC by increasing the melt strength and participating in the formation of a ceramicized char layer. Polyborosiloxanes also have an expansion charring effect during combustion; therefore, adding approximately 3-8% is generally sufficient to achieve a UL-94 vertical burning V-0 rating. The flame retardant described in this invention, in addition to the flame retardant properties of polyborosiloxanes, also contains sulfonic acid groups, which can accelerate the cross-linking and charring of PC and the release of CO2 and H2O by promoting the isomerization and Fries rearrangement of PC. Through the synergistic effect of silicon, boron, and sulfur, the rapid charring ability and anti-dripping performance of PC composites are significantly improved. Only 0.4wt% of the addition is required to enable the material to pass the new national standard S2 needle flame test at a thickness of 1.5mm, effectively solving the problem that traditional flame retardants fail to meet standards due to dripping ignition of the underlying layer.

[0017] The advantages of this invention are as follows: The preparation method described herein brings unexpected technical effects. Through precise molecular design and process innovation, it achieves the synergistic integration of multiple flame-retardant elements such as boron, silicon, sulfur, and nitrogen. Its core breakthrough lies in overcoming the limitations of simple blending of traditional material elements—anchoring flame-retardant elements to the polymer backbone and side chains through covalent bonds. This fundamentally solves the problems of aggregation, migration, and flame-retardant efficiency decay caused by compatibility differences among multiple elements in existing technologies, constructing a technical barrier that is difficult to replicate through conventional compounding methods. Only an extremely low addition amount of 0.2-0.4 wt% is required to achieve multiple technological leaps in polycarbonate (PC) composite materials: not only are thermal stability and char residue significantly improved, easily passing the UL-94V0 flame retardant test, but also passing the S2 needle flame test, while maintaining excellent impact resistance. Attached Figure Description

[0018] Figure 1 The TGA spectra are for Example 1 and the PC composite material.

[0019] Figure 2 The image shows the S2 needle flame flaming test result of PC with flame retardant incorporated.

[0020] Figure 3 This is a vertical combustion diagram of Example 1.

[0021] Figure 4 This refers to the impact resistance of Example 1.

[0022] Figure 5The images show the vertical combustion patterns of Comparative Example 1 and Comparative Example 2. Detailed Implementation

[0023] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all figures are expressed in parts by weight and weight percentages.

[0024] Unless otherwise specified, all raw materials used in this invention are conventional commercially available products; and all methods used in this invention are conventional methods in the art, unless otherwise specified. The concentrated sulfuric acid used in this invention is sulfuric acid with a mass fraction greater than 70%.

[0025] The needle flame S2 test described in this invention is conducted in accordance with GB 4943.1-2022. The S.2 needle flame test is a mandatory requirement of the new national standard GB4943.1-2022 "Audio-visual, information technology and communication technology equipment - Part 1: Safety requirements", which was officially implemented in 2023 and aims to improve the fire safety performance of electronic products.

[0026] The test standard is as follows: Flame requirements: According to the requirements of GB / T 5169.5-2020 standard, the flame temperature should be able to increase from 100℃±5℃ to 700℃±3℃ within 23.5s±1s, and the gas that produces the flame should be propane or butane gas with a purity of not less than 95%. Burner standard: The burner that produces the flame should consist of a tube with a length of at least 35 mm, an orifice diameter of 0.5 mm ± 0.1 mm, and an outer diameter not exceeding 0.9 mm, and the height of the test flame should be adjustable to 12 mm ± 1 mm; Laying the bottom layer: Tightly wrap a layer of silk paper on a smooth white pine board about 10 mm thick, and place it 200 ± 5 mm below the test sample position where the needle flame is applied; Combustion time: The test needle flame of the sample is 60s, and the combustion time after the test needle flame is removed shall not exceed 30s (tb<30s). Drip restriction: No dripping material or dripping molten material must not ignite the underlying layer (such as absorbent cotton); Test environment: The test must be conducted in a shielded chamber at 23±2℃ and 50±5%RH, with a wind speed ≤0.2m / s, to avoid airflow interference with the test results.

[0027] The flame retardant rating of the plastics described in this invention decreases progressively from V-0, V-1, V-2 to HB: V-0: After two 10-second burning tests on the sample, the flame extinguishes within 30 seconds. No burning material should fall.

[0028] V-1: After two 10-second burning tests on the sample, the flame must extinguish within 60 seconds. No burning material should fall.

[0029] V-2: After two 10-second burning tests on the sample, the flame extinguishes within 60 seconds. Burning material may fall off.

[0030] HB: The lowest flame retardant rating in UL94 and CSA C22.2 No. 0.17 standards.

[0031] For samples 3 to 13 mm thick, the burning rate must be less than 40 mm per minute; for samples less than 3 mm thick, the burning rate must be less than 70 mm per minute; or the sample must extinguish before reaching the 100 mm mark.

[0032] The embodiments of the present invention will be further described below with reference to several examples.

[0033] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0034] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0035] Example 1 (1) Sodium 2,4-diaminobenzenesulfonate was added dropwise to boric acid at a rate of 1 mL / min. After mixing, a solid-phase condensation reaction was carried out at 150 °C and a negative pressure of -0.05 MPa for 2.5 h to obtain an intermediate. The molar ratio of the hydroxyl group of boric acid to the amino group of sodium 2,4-diaminobenzenesulfonate was 1:0.1.

[0036] (2) Cool to 80℃, add hydroxyl-terminated silicone oil with a molecular weight of 500 and 0.1mM concentrated sulfuric acid, and further carry out polycondensation reaction for 4 hours. Finally, linear nitrogen-sulfur-containing polyboron siloxane is obtained. The molar ratio of hydroxyl groups in the hydroxyl-terminated silicone oil to the hydroxyl groups in the boric acid is controlled at 1:0.3.

[0037] The obtained nitrogen-sulfur-containing polyboronsiloxane is In this formula, R1 is methyl, R2 is phenyl, and R3 is sodium 2,4-diaminobenzenesulfonate.

[0038] Nitrogen-sulfur polysiloxanes and polycarbonate were blended in a torque rheometer at 260°C for 8 minutes at a speed of 50 r / min. The resulting mixture was then hot-pressed using a flat vulcanizing machine at 260°C and 10 MPa to obtain a polycarbonate composite material. The contents of the nitrogen-sulfur polyboron-siloxanes in the polycarbonate composite material were 0.2 wt%, 0.3 wt%, and 0.4 wt%, respectively.

[0039] The TGA spectra of the nitrogen-sulfur-containing polyboron siloxane flame retardant and the PC composite material prepared in Example 1 are as follows: Figure 1 As shown, thermogravimetric analysis results indicate that although the initial thermal decomposition temperature (when mass loss reaches 5%) of the prepared nitrogen-sulfur-containing polyboron siloxane flame retardant is early, it remains very stable within the range of 200-450℃. Furthermore, the thermogravimetric analysis of the PC composite material shows that the thermal decomposition temperature decreases after the addition of the flame retardant. The flame retardant properties of the composite material were tested. The results are as follows. Figure 2 and 3 As shown, PC samples 1 and 2 (both 0.4 wt%) incorporating flame retardants passed the S2 needle flame test. The tested needle flame burning time was 60 s, and the burning time after the test needle flame was removed did not exceed 30 s (tb < 30 s), with no dripping material (such as...). Figure 2 As shown), and during vertical burning, the extinguishing time t1+t2<10s, and no burning material falls, passing the UL-94 V-0 flammability rating (as shown). Figure 3 (As shown).

[0040] Example 2 (1) Potassium 3,4-diaminobenzenesulfonate was added dropwise to boric acid at a rate of 5 mL / min. After mixing, solid-phase condensation reaction was carried out at 180℃ and a reaction negative pressure of -0.1 MPa for 1 h to obtain the intermediate. The molar ratio of the hydroxyl group of boric acid to the amino group of potassium 3,4-diaminobenzenesulfonate was 1:1.

[0041] (2) Cool to 120℃, add hydroxyl-terminated silicone oil with a molecular weight of 20,000 and 0.5 mM of high-polymerization-degree phosphoric acid, and further carry out polycondensation reaction for 0.5 h. Finally, linear nitrogen-sulfur-containing polyboron siloxane is obtained. The molar ratio of hydroxyl groups in the hydroxyl-terminated silicone oil to the hydroxyl groups in the boric acid compound is controlled at 1:1.5.

[0042] Nitrogen-sulfur-containing polysiloxanes and polycarbonate were blended in a torque rheometer at 260°C for 15 minutes at a speed of 50 r / min. The resulting mixture was then hot-pressed using a flat vulcanizing machine at 260°C and 10 MPa to obtain a polycarbonate composite material. The content of nitrogen-sulfur-containing polyboron-siloxanes in the polycarbonate composite material was 1 wt%.

[0043] Comparative Example 1 The difference from Example 2 is that the molar ratio of the hydroxyl group of boric acid to the amino group of potassium 3,4-diaminobenzenesulfonate is 1:3. The results are as follows... Figure 5 As shown, during vertical combustion, the extinguishing time is t1+t2<10s, and molten droplets appear.

[0044] Comparative Example 2 The difference from Example 2 is that the molar ratio of the hydroxyl group of boric acid to the amino group of potassium 3,4-diaminobenzenesulfonate is 1:0.05. The results are as follows... Figure 5 As shown, during vertical combustion, the extinguishing time is t1+t2<10s, and molten droplets appear.

[0045] The above embodiments describe in detail the structure, features, and effects of the present invention. The above description is only a preferred embodiment of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall still fall within the scope of protection of the present invention if they do not exceed the scope covered by the specification.

Claims

1. A linear nitrogen-sulfur-containing polyboronsiloxane, characterized in that, The molecular backbone is formed by the alternating copolymerization of x siloxane units and boron units, and its repeating structural unit is (-Si(R1)(R2)-OB(-R3)-O-). X The siloxane unit has substituents R1 and R2, and the boron unit is -B(OH)3-, wherein R1 and R2 are independently selected from benzene ring, methyl, ethyl, or vinyl, and x > 5; the two hydroxyl groups of the boron unit undergo dehydration condensation with the hydroxyl groups of the siloxane unit, and the boron atoms in the main chain are connected to silicon-oxygen bonds by -B(O-)- bonds to form Si-OB covalent bonds; R3 is (MSO3-Ph-NH- or MSO3-NH-); the metal ion M is K + Na + Li + Ph has a benzene ring structure.

2. The linear nitrogen-sulfur-containing polyboronsiloxane according to claim 1, characterized in that, Number average molecular weight M n For (5×10) 3 ~8×10 4 ).

3. A method for preparing linear nitrogen-sulfur-containing polyboron siloxane as described in claim 1, characterized in that, The process includes the following steps: (1) under conditions of 150~200℃ and -0.1~0.05MPa, boric acid compounds and aminosulfonates are subjected to solid-phase polycondensation reaction to obtain an intermediate; the molar ratio of the hydroxyl group of the boric acid compound to the amino group of the aminosulfonate compound is 1:0.1~1. (2) Cool the intermediate to 80-120°C, add hydroxyl-terminated silicone oil and catalyst, and carry out polycondensation reaction to obtain linear nitrogen-sulfur polyboron siloxane; the molar ratio of hydroxyl groups in the hydroxyl-terminated silicone oil to hydroxyl groups in the boric acid compound is 1:0.3-1.

5.

4. The method according to claim 3, characterized in that, The boric acid compound mentioned in step 1 is boric acid; the aminophenyl sulfonic acid compound is one or more of the following: potassium p-aminobenzenesulfonate, sodium p-aminobenzenesulfonate, potassium aminosulfonate, sodium aminosulfonate, lithium aminosulfonate, potassium 3,4-diaminobenzenesulfonate, sodium 3,4-diaminobenzenesulfonate, potassium 2,5-diaminobenzenesulfonate, and sodium 2,4-diaminobenzenesulfonate.

5. The method according to claim 3, characterized in that, The hydroxyl-terminated silicone oil in step 2 has a molecular weight of 500-20000, and its substituents are benzene rings, methyl, ethyl, vinyl, or a combination of all four; the catalyst is concentrated sulfuric acid, phosphoric acid containing 5 to 20 phosphoric acid units, or a mixture thereof.

6. The method according to claim 3, characterized in that, The aminosulfonic acid compound described in step 1 is added dropwise to the boric acid compound at a rate of 1–5 mL / min.

7. The method according to claim 3, characterized in that, The reaction time for the polycondensation reaction in step 2 is 0.5 to 4 hours.

8. The application of the linear nitrogen-sulfur-containing polyboronsiloxane as described in claim 1 as a flame retardant, characterized in that, Nitrogen-sulfur polyboron siloxane is prepared by heating and melting it with polycarbonate, and then hot pressing it to obtain a polycarbonate composite material; the content of nitrogen-sulfur polyboron siloxane in the polycarbonate composite material is 0.2~1.0 wt%.

9. The application according to claim 8, characterized in that, The heating and melting blending is carried out using a torque rheometer at a processing temperature of 260°C, a processing time of 8-15 minutes, and a rotation speed of 50 r / min. The hot pressing is carried out using a flat vulcanizing machine at a hot pressing temperature of 260°C and a pressure of 10 MPa.

10. The application according to claim 8, characterized in that, The UL-94 vertical flammability rating of the polycarbonate composite material is V-0.

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