An organosilicon-boron flame retardant, its preparation method and application

Abstract

This invention discloses an organosilicon-boron flame retardant, its preparation method, and its applications. This material exhibits excellent flame retardant properties and good light transmittance. The invention also provides a method for preparing this organosilicon-boron flame retardant, which is simple to operate, uses widely available raw materials, is low in cost, and can be applied to large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of flame retardant design technology, and in particular to a high-efficiency organosilicon boron flame retardant, its preparation method, and its application in the preparation of transparent polycarbonate composite materials. Background Technology

[0002] Polycarbonate (PC) is a transparent thermoplastic engineering plastic with excellent overall performance, possessing superior toughness, heat resistance, dimensional stability, and transparency. It is widely used in the electronics, automotive, and construction industries. While PC itself exhibits some flame-retardant properties, achieving a V-2 rating in the vertical burning UL-94 test, it produces severe dripping during combustion, posing a potential fire hazard. This significantly limits its practical application in electronics, electrical appliances, and automotive interiors where flame retardancy is crucial. Therefore, flame-retardant modification of PC is of paramount importance.

[0003] Flame retardant modification of PC mainly focuses on preparing flame-retardant PC by mechanical melt blending of flame retardants with the PC matrix. Commonly used flame retardants include phosphorus-based, sulfonic acid-based, and silicon-based flame retardants. However, in actual production, these flame retardants each have their own drawbacks. For example, phosphorus-based flame retardants require a large amount in PC and have poor compatibility with the PC matrix, which significantly reduces the transparency and mechanical properties of the composite material. Therefore, existing flame retardants for PC still suffer from serious problems such as low flame retardant efficiency, large addition requirements, and reduced transparency and mechanical properties of the composite material. Therefore, developing a flame retardant with minimal impact on the transparency and mechanical properties of PC and high flame retardant efficiency is of great significance.

[0004] In recent years, scholars have attempted to prepare flame retardants for transparent PC using organosilicon compounds. A Chinese patent document, "A Transparent Flame-Retardant PC Composite Material and Its Preparation Method," with the application number CN113878745A, discloses a transparent flame-retardant PC composite material prepared by mechanical melt blending of siloxane and PC. This method improves the flame-retardant properties of PC without affecting its transparency and mechanical properties, but requires a large amount of the compound. Summary of the Invention

[0005] This invention overcomes the problem of high addition amounts of flame retardants in traditional PC flame retardant modification leading to poor transparency and mechanical properties of composite materials, and provides a transparent PC flame retardant with low addition amounts and minimal impact on PC transparency and mechanical properties.

[0006] The present invention also provides a transparent flame-retardant composite material prepared by modifying PC with the above flame retardants, which has excellent flame retardant properties and good light transmittance.

[0007] The present invention also provides a method for preparing a flame retardant for transparent PC. This method is simple to operate, uses widely available raw materials, is low in cost, and can be applied to large-scale industrial production.

[0008] The present invention also provides a method for preparing a transparent flame-retardant PC composite material. This method has no special requirements for equipment, the process conditions are easy to control, and it can be applied to large-scale industrial production.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides an organosilicon-boron flame retardant of formula (I),

[0011]

[0012] Where R1 and R2 are independently methyl or phenyl, R3 is hydroxy or phenyl, and m1, m2, m3, ... m n Each of the following can be 5, 6, or 7, and n is an integer between 8 and 11.

[0013] Secondly, the present invention provides a method for preparing the organosilicon-boron flame retardant represented by formula (I) above, wherein the method comprises:

[0014] The dimethoxysilane monomer shown in formula (II) is dissolved in a first organic solvent, deionized water is added dropwise, the pH is adjusted to 2-4 (in one embodiment of the present invention, the pH is adjusted to 3), and the reaction is stirred for the first time at 50-90°C (preferably 70°C) for 2-6 hours (preferably 4 hours) to obtain reaction solution A;

[0015] In this step, dimethoxysilanes undergo hydrolysis in a solvent to form silanols, which can then undergo dehydration condensation to form linear oligomers A.

[0016] The organoboronic acid compound shown in formula (III) is dissolved in a second organic solvent to obtain an organoboronic acid compound solution; the organoboronic acid compound solution is added dropwise to the reaction solution A, and the reaction is stirred for a second time at 100-140°C (preferably 120°C) for 10-14 hours (preferably 12 hours); the resulting reaction solution B is post-treated to obtain the organosilicon-boron flame retardant shown in formula (I); the molar ratio of the dimethoxysilane monomer shown in formula (II) to deionized water is 1:1-5 (preferably 1:5); the molar ratio of the organoboronic acid compound shown in formula (III) to the dimethoxysilane monomer shown in formula (II) is 1:1-3 (preferably 1:1).

[0017] In this step, phenylboronic acid undergoes dehydration condensation with linear oligomer A in reaction solution A to form linear polysiloborane. The letters in reaction solutions A and B are merely for distinguishing different stages of the reaction and for ease of description; they have no other special meaning.

[0018]

[0019] In formulas (I), (II), and (III), R1 and R2 are independently methyl or phenyl, R3 is hydroxyl or phenyl, and m1, m2, m3, ... m n Each of the following can be 5, 6, or 7, and n is an integer between 8 and 11.

[0020] In one embodiment of the invention, the pH was adjusted using 0.1 mol / L hydrochloric acid.

[0021] Organoboronic acid compounds, as boron-containing organic compounds, can improve the heat resistance and transparency of the matrix, have a certain char-forming ability, and possess great flame-retardant potential. Therefore, the flame retardant designed in this invention aims to achieve both flame-retardant properties for PC. By selecting silanes and organoboronic acid compounds with excellent compatibility with PC and flame-retardant potential as raw materials, a novel polysilicon-boron flame retardant suitable for transparent flame-retardant PC composites is prepared through a simple dehydration condensation reaction. Furthermore, this flame retardant is expected to produce transparent flame-retardant PC composites with good compatibility and excellent light transmittance.

[0022] Preferably, the dimethoxysilane monomer shown in formula (II) is dimethyldimethoxysilane, methylphenyldimethoxysilane or diphenyldimethoxysilane, preferably diphenyldimethoxysilane.

[0023] Preferably, the organoboronic acid compound represented by formula (III) is boric acid or phenylboronic acid, preferably phenylboronic acid.

[0024] Preferably, the molar ratio of the dimethoxysilane monomer shown in formula (II) to deionized water is 1:2.

[0025] The amount of deionized water added is crucial. Excessive deionized water (greater than 5 equivalents) will slow down the silane dehydration condensation reaction, while insufficient deionized water (less than 1 equivalent) will lead to incomplete silane hydrolysis. Preferably, the stirring speed for the first stirring reaction is 200-400 rpm, preferably 300 rpm.

[0026] Preferably, the stirring speed of the second stirring reaction is 200-400 rpm, and more preferably 300 rpm.

[0027] Preferably, the first organic solvent and the second organic solvent are each one of N,N-dimethylformamide and ethanol, or a mixture of the two, and preferably both are N,N-dimethylformamide.

[0028] Furthermore, the volume of the first organic solvent is 2 to 3 mL / g based on the mass of the dimethoxysilane monomer shown in formula (II); the volume of the second organic solvent is 2 to 3 mL / g based on the mass of the organoboronic acid compound shown in formula (III).

[0029] Further, the post-processing is as follows: the reaction solution B is added to deionized water to precipitate, filtered, and the resulting filter cake is washed with deionized water and vacuum dried to obtain the organosilicon-boron flame retardant shown in formula (I).

[0030] Thirdly, the present invention also provides the application of the organosilicon boron flame retardant shown in formula (I) above in the preparation of transparent flame-retardant polycarbonate composite materials.

[0031] Furthermore, the transparent flame-retardant polycarbonate composite material comprises the following components in the following mass percentages: 1-5% organosilicon boron flame retardant as shown in formula (I), and 95-99% polycarbonate.

[0032] Furthermore, the transparent flame-retardant polycarbonate composite material is prepared by the following method: the organosilicon boron flame retardant of formula (I) is melt-blended with polycarbonate and processed at 220-260°C for 10 min (in one embodiment of the present invention, it is processed at 250°C for 10 min) to obtain the transparent flame-retardant polycarbonate composite material.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The boron-containing organic compounds used in this invention can improve the heat resistance and transparency of the matrix, have good char-forming ability, and promote the improvement of flame retardant properties.

[0035] (2) The preparation method is simple and safe, without the use of toxic and harmful organic reagents, and the reaction conditions are mild, without the need for complex environments such as high temperature and high pressure, which can realize large-scale industrial production.

[0036] (3) The linear polysilane prepared by simple dehydration condensation reaction has excellent compatibility with PC materials and can effectively balance excellent mechanical properties, transparency and flame retardancy at low dosage.

[0037] (4) The transparent flame-retardant PC composite material prepared by the present invention has excellent flame-retardant effect. When the amount of flame retardant added is only 5wt%, the oxygen index can reach 34.8% and pass the V-0 level in the vertical burning test, which effectively improves its flame-retardant performance while maintaining excellent light transmission performance. Attached Figure Description

[0038] Figure 1 This is the Fourier transform infrared spectrum of the flame retardant in Example 1. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0040] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0041] Example 1

[0042] (1) Dissolve 14.66 g (0.06 mol) of diphenyldimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL (0.28 mol) of deionized water, adjust the pH to 3 with 0.1 mol / L HCl solution, heat at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A;

[0043] (2) Dissolve 7.32 g (0.06 mol) of phenylboronic acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. The mixture is heated at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0044] 2.5 g (5.0 wt%) of the flame retardant prepared in Example 1 was mixed with 47.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain the PC composite material.

[0045] Figure 1 This is the Fourier transform infrared spectrum of the flame retardant obtained in Example 1 of this invention. From... Figure 1 It can be seen from this that 2830cm -1 The peak at 3250 cm⁻¹ is attributed to the methoxy group in diphenyldimethoxysilane, while the disappearance of the methoxy group peak in polysilane indicates that dimethoxysilane has been completely hydrolyzed; -1 The peak at the position is attributed to the hydroxyl group in phenylboronic acid. The weakening of the hydroxyl peak in disiliborane indicates that the hydroxyl group of phenylboronic acid participated in the dehydration condensation reaction. The peaks attributed to the benzene ring of methoxysilane and the BO peak attributed to phenylboronic acid appear in polysiliborane, indicating the synthesis of polysiliborane flame retardants.

[0046] Example 2

[0047] (1) Dissolve 7.21 g (0.06 mol) of dimethyldimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL (0.28 mol) of deionized water, adjust the pH to 3 with 0.1 mol / L HCl solution, heat at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A;

[0048] (2) Dissolve 7.32 g (0.06 mol) of phenylboronic acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. The mixture is heated at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0049] 2.5 g (5.0 wt%) of the flame retardant prepared in Example 2 was mixed with 47.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain a PC composite material.

[0050] Example 3

[0051] (1) Dissolve 10.94 g (0.06 mol) of methylphenyl dimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL (0.28 mol) of deionized water, adjust the pH to 3 with HCl, and heat the mixture at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A;

[0052] (2) Dissolve 7.32 g (0.06 mol) of phenylboronic acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. The mixture is heated at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0053] 2.5 g (5.0 wt%) of the flame retardant prepared in Example 3 was mixed evenly with 47.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain a PC composite material.

[0054] Example 4

[0055] (1) Dissolve 14.66 g (0.06 mol) of diphenyldimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL (0.28 mol) of deionized water, adjust the pH to 3 with 0.1 mol / L HCl solution, heat at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A;

[0056] (2) Dissolve 2.47 g (0.06 mol) of boric acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. Heat the mixture at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0057] 2.5 g (5.0 wt%) of the flame retardant prepared in Example 4 was mixed evenly with 47.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain a PC composite material.

[0058] Example 5

[0059] (1) Dissolve 14.66 g (0.06 mol) of diphenyldimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL (0.28 mol) of deionized water, adjust the pH to 3 with 0.1 mol / L HCl solution, heat at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A;

[0060] (2) Dissolve 7.32 g (0.06 mol) of phenylboronic acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. The mixture is heated at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0061] 0.5 g (1.0 wt%) of the flame retardant prepared in Example 5 was mixed evenly with 49.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain a PC composite material.

[0062] Example 6

[0063] (1) Dissolve 14.66 g (0.06 mol) of diphenyldimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL (0.28 mol) of deionized water, adjust the pH to 3 with 0.1 mol / L HCl solution, heat at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A;

[0064] (2) Dissolve 7.32 g (0.06 mol) of phenylboronic acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. The mixture is heated at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0065] 1.5 g (3.0 wt%) of the flame retardant prepared in Example 6 was mixed with 48.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain the PC composite material.

[0066] Comparative Example 1

[0067] 14.66 g (0.06 mol) of diphenyldimethoxysilane was dissolved in 40 mL of N,N-dimethylformamide, followed by slow dropwise addition of 5 mL (0.28 mol) of deionized water. The pH was adjusted to 3 with HCl, and the reaction was carried out at 70 °C for 4 h with stirring at 300 rpm. The product was precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

[0068] 2.5 g (5.0 wt%) of the flame retardant prepared in Comparative Example 1 was mixed evenly with 47.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain the PC composite material.

[0069] Comparative Example 2

[0070] 2.5 g of phenylboronic acid (5.0 wt%) was mixed evenly with 47.5 g of dried pure PC and then melt-blended in an internal mixer at 250 °C for 10 min to obtain the PC composite material.

[0071] Performance testing

[0072] The method for preparing test strips for the light transmittance and flame retardant properties of PC samples in this invention is as follows:

[0073] (1) Transmittance test strip: The sample with a size of 33mm×33mm×2mm was prepared by a fully automatic tablet press at 250℃ and 61bar.

[0074] (2) Vertical burning test strip: A strip with a size of 125mm×13mm×3mm was prepared by a fully automatic tablet press at 250℃ and 61bar.

[0075] (3) Limiting oxygen index test strips: The strips with dimensions of 120mm×7mm×3mm were prepared by a fully automatic tablet press at 250℃ and 61bar.

[0076] The test methods for light transmittance and flame retardant properties of PC samples are as follows:

[0077] (1) Transmittance / haze test: The transmittance and haze of the sample were tested using a UV-Vis spectrophotometer;

[0078] (2) Flame retardant performance test: The prepared PC samples were tested on a vertical combustion tester and an oxygen index tester, and the afterflame time and limiting oxygen index during the combustion of the samples were recorded.

[0079] The PC samples prepared in the above embodiments and comparative examples were tested for flame retardancy and light transmittance.

[0080] Table 1. Effects of flame retardants on the flame retardancy, transparency, and mechanical properties of PC materials.

[0081]

[0082] As shown in Table 1, the test results from Examples 1, 2, and 3 indicate that the oxygen index of the PC composite material significantly increases with the increase of the proportion of benzene rings in the siloxane. Furthermore, due to the good compatibility between benzene rings and PC, Example 1 exhibits the best transparency. Examples 1 and 4 show that the linear polysiloborane synthesized from the condensation polymerization of phenylboronic acid and siloxane has better compatibility with PC and a better flame-retardant effect. Examples 1, 5, and 6 demonstrate that with the increase of the amount of the novel flame retardant added, the oxygen index and vertical burning rating of the PC composite material significantly increase; however, with the increase of the added amount, the light transmittance of the composite material decreases to some extent.

[0083] As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, compared with PC with polysiloxane or phenylboronic acid added alone, the limiting oxygen index of PC composite material with the addition of the novel flame retardant polysiloxane is greatly improved, and it can maintain good transparency while meeting the flame retardant requirements. This proves that the polysiloxane flame retardant prepared in this invention has a great improvement on the flame retardant performance and transparency of PC.

[0084] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An organosilicon-boron flame retardant of formula (I), in, R1 and R2 are both phenyl groups, R3 is a phenyl group, and m1, m2, m3, ... m n Each of the following can be 5, 6, or 7, and n is an integer between 8 and 11.

2. The method for preparing the organosilicon-boron flame retardant of formula (I) as described in claim 1, characterized in that... The method is as follows: (1) Dissolve 14.66 g of diphenyldimethoxysilane in 40 mL of N,N-dimethylformamide, then slowly add 5 mL of deionized water, adjust the pH to 3 with 0.1 mol / L HCl solution, heat at 70 °C for 4 h with stirring at 300 rpm to obtain reaction solution A; (2) Dissolve 7.32 g of phenylboronic acid in 20 mL of N,N-dimethylformamide, and then slowly add it dropwise to product A. The mixture is heated at 120 °C for 12 h with stirring at 300 rpm. The product is precipitated in 1 L of deionized water, filtered, washed with deionized water, and dried in a vacuum oven to obtain the flame retardant.

3. The application of the organosilicone boron flame retardant of formula (I) as described in claim 1 or the organosilicone boron flame retardant prepared by the preparation method of claim 2 in the preparation of transparent flame-retardant polycarbonate composite materials, wherein the transparent flame-retardant polycarbonate composite material comprises the following components in the following mass percentages: 5% of the organosilicone boron flame retardant, 95% polycarbonate.

4. The application as described in claim 3, characterized in that: The transparent flame-retardant polycarbonate composite material is prepared by the following method: the appropriate amount of organosilicon boron flame retardant is melt-blended with polycarbonate and processed at 220-260℃ for 10 min to obtain the transparent flame-retardant polycarbonate composite material.

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