Compound flame retardant for polycarbonate material as well as preparation method and application of compound flame retardant

Abstract

The invention discloses a compound flame retardant for a polycarbonate material as well as a preparation method and application of the compound flame retardant. The invention designs a conveniently prepared compound flame-retardant system, and the compound flame-retardant system is introduced into a polycarbonate matrix, so that the transparency of the polycarbonate matrix is reserved to the greatest extent, and the flame-retardant property of the material is remarkably improved. The flame-retardant system is introduced into a polycarbonate material according to the total addition amount not higher than 1 wt%, and after the flame-retardant system is added, the visible light transmittance of the polycarbonate is not lower than 80% of that before the flame-retardant system is added. And the polycarbonate material with the thickness of 3.2 mm can keep transparency and has flame retardant property at the same time.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology for polymer materials, specifically relating to a compound flame retardant for polycarbonate materials, its preparation method, and its application. Background Technology

[0002] Polycarbonate (PC) is widely used in fields with stringent requirements for comprehensive material performance, such as electronics, architectural lighting, optical devices, and transportation, due to its excellent mechanical strength, thermal stability, and high optical transparency. Transparency, as one of its key functional attributes, not only directly affects the visual appearance of products but also forms the basis of their core service performance in many applications. For example, in applications such as display panel protective covers, LED encapsulation lenses, and observation windows for high-speed trains or aircraft, the material must maintain high light transmittance (typically >85%) and low haze to ensure light transmission efficiency, image clarity, and operational safety.

[0003] However, PC is prone to melting and dripping during combustion, releasing a large amount of heat, which limits its application in applications requiring high flame retardancy and safety. Although halogenated flame retardants have high flame retardant efficiency, they release toxic and corrosive gases and persistent organic pollutants during combustion, and have been increasingly restricted by environmental regulations. In contrast, halogen-free flame retardant systems (such as phosphorus-based, silicon-based, and boron-based systems) are environmentally friendly, but often face problems such as low flame retardant efficiency, high addition amounts, and poor compatibility with the PC matrix in practical applications. Of particular note is that most halogen-free flame retardants, due to refractive index mismatch or the formation of microphase separation structures in the polymer matrix, induce significant light scattering effects, leading to decreased light transmittance and increased haze, severely impairing their optical properties and making it difficult to meet the technical requirements of high-end transparent products.

[0004] Therefore, the core challenge of current research lies in how to construct a low-addition-amount, highly compatible, and high-efficiency halogen-free flame-retardant system while maintaining the intrinsic high transparency of polycarbonate. Achieving this goal not only improves the flame-retardant safety of the material but also directly determines its sustainable application prospects in the field of high-value-added transparent engineering plastics. Against this backdrop, developing novel flame-retardant strategies that combine molecular-level dispersion capabilities, refractive index matching characteristics, and a synergistic flame-retardant mechanism between the condensed phase and the gas phase has become an important academic and technical direction for the functional modification of polycarbonate. Summary of the Invention

[0005] To address the problems existing in the prior art, this application proposes a compound flame retardant for polycarbonate materials, its preparation method, and its application.

[0006] By introducing silicon-oxygen bonds and boron-oxygen structures through the polycondensation reaction of silane coupling agents and boric acid, a powdered flame retardant with both organic compatibility and inorganic flame retardant properties is constructed. Then, by utilizing the char-promoting and drip-inhibiting effects of sulfonate small molecules during the thermal decomposition of polycarbonate, the powdered flame retardant is directly compounded with sulfonate compounds for the first time to form a convenient synergistic flame retardant system.

[0007] Furthermore, by introducing the compounded flame retardant into the polycarbonate matrix at an addition amount not exceeding 1 wt%, transparent flame retardancy can be achieved for polycarbonate materials with a thickness of 1.6-3.2 mm.

[0008] One of the technical solutions of the present invention is to provide a compound flame retardant for polycarbonate materials, comprising: a powdered flame retardant prepared by polycondensation reaction of a silane coupling agent and boric acid, and a sulfonate small molecule compound; wherein the silane coupling agent is selected from alkoxysilanes, aminosilanes, epoxysilanes, vinylsilanes, or any combination thereof; and the sulfonate small molecule compound is selected from aromatic sulfonates, aliphatic sulfonates, or mixtures thereof.

[0009] Furthermore, the molar ratio of silane coupling agent to boric acid is (1-5):1.

[0010] Furthermore, the boric acid is orthoboric acid or its dehydrated derivative.

[0011] Furthermore, the mass ratio of the powdered flame retardant to the sulfonate small molecule compound is (1–9):(0.1–1).

[0012] The second technical solution of the present invention is to provide a flame-retardant polycarbonate material, including no more than 1 wt% of a compound flame retardant.

[0013] Furthermore, the thickness of the polycarbonate material is 1.6-3.2 mm.

[0014] The third technical solution of the present invention is to provide a method for preparing the above-mentioned compound flame retardant, comprising the following steps: (1) A condensation reaction is carried out between a silane coupling agent and boric acid in a solvent; (2) After the reaction is complete, the solvent is removed by rotary evaporation and dried to obtain a powdered flame retardant; (3) The powdered flame retardant is mixed with sulfonate small molecule compounds to obtain a compound flame retardant.

[0015] Furthermore, the polycondensation reaction is carried out at 60–120 °C.

[0016] Furthermore, the solvent is one of ethanol and diethylene glycol dimethyl ether.

[0017] Compared to the synthetic strategy of chemically grafting sulfonic acid groups onto the flame retardant backbone, the direct physical compounding scheme of powdered flame retardants and sulfonate compounds shows significant advantages in terms of process economy and matrix performance preservation. First, in terms of process convenience and cost control, direct compounding only requires simple physical blending, completely avoiding the multi-step organic synthesis (such as sulfonation, neutralization, and polycondensation reactions), expensive catalyst use, stringent reaction condition control, and complex solvent recovery and purification processes required by traditional chemical grafting. This not only significantly reduces equipment investment, energy consumption, and production costs, but also significantly shortens the production cycle, ensures batch stability, and facilitates large-scale scaling. Secondly, in terms of avoiding matrix performance degradation and processing risks, the sulfonates in the direct compound system exist independently in the form of small molecules, which can migrate to the combustion interface more quickly to exert catalytic char formation efficiency. At the same time, this strategy avoids problems such as polarity changes, decreased compatibility and thermal stability fluctuations that may be caused by the introduction of large grafted side chains. It effectively prevents material precipitation, frosting or processing degradation and discoloration caused by premature decomposition temperature. Thus, while achieving high flame retardancy, it retains the original high transparency, excellent impact strength and good melt flow of polycarbonate (PC) matrix to the greatest extent.

[0018] The advantages of this invention are: by designing a compound flame retardant and introducing it into a polycarbonate matrix, the flame retardant properties of the material are significantly improved while maximizing the transparency of the polycarbonate matrix. When introduced into polycarbonate materials at a total addition amount not exceeding 1 wt%, the polycarbonate still maintains a visible light transmittance of not less than 80% of that before the addition of the flame retardant system. This enables polycarbonate materials with a thickness of 1.6-3.2 mm to possess flame retardant properties while maintaining transparency. Attached Figure Description

[0019] Figure 1 Thermogravimetric analysis (TGA) of the powdered flame retardant prepared in Example 1.

[0020] Figure 2 This is a transparency test image from Example 1.

[0021] Figure 3 For pyrolysis performance analysis. Detailed Implementation

[0022] 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.

[0023] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0024] The embodiments of the present invention will be further described below with reference to several examples.

[0025] 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.

[0026] 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.

[0027] Example 1 (1) Tetraethyl orthosilicate and boric acid in a molar ratio of 2:1 were subjected to polycondensation reaction at 120 °C in diethylene glycol dimethyl ether solvent; (2) After the reaction is complete, the solvent is removed by rotary evaporation and dried to obtain a powdered flame retardant; (3) The powdered flame retardant and sodium dodecyl sulfonate are compounded in a mass ratio of 9:1, and 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, and 1.0wt% are added to PC for melt blending. The product is then extruded or injection molded to obtain a flame-retardant polycarbonate product with a thickness of 3.2mm.

[0028] like Figure 2 As shown, the transparency of polycarbonate with 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, and 1.0wt% flame retardant system added, respectively, is shown in figures 1-5. Even after adding the flame retardant system, the polycarbonate still maintains a visible light transmittance of no less than 80% of that before the addition, indicating good transparency. The polycarbonate with the 1.0wt% flame retardant system achieves VO flame retardancy.

[0029] Example 2 (1) 1,3-aminopropyltriethoxysilane in a molar ratio of 1:1 and boric acid were subjected to a polycondensation reaction at 100 °C in ethanol solvent; (2) After the reaction is complete, the solvent is removed by rotary evaporation and dried to obtain a powdered flame retardant; (3) The powdered flame retardant is mixed with sodium dodecylbenzenesulfonate at a mass ratio of 1:0.1 to obtain a transparent flame retardant system.

[0030] The obtained transparent flame-retardant system was melt-blended with polycarbonate resin at an addition rate of 0.7 wt%, and then extruded or injection molded to obtain a flame-retardant polycarbonate product with a thickness of 3.2 mm. The resulting material exhibits excellent flame-retardant properties while maintaining good transparency.

[0031] Example 3 (1) Vinyltrimethoxysilane with a molar ratio of 5:1 and boric acid were subjected to a polycondensation reaction in ethanol at 60°C; (2) After the reaction is complete, the solvent is removed by rotary evaporation and dried to obtain a powdered flame retardant; (3) The powdered flame retardant is mixed with sodium dodecyl sulfonate at a mass ratio of 2:1 to obtain a transparent flame retardant system.

[0032] The obtained transparent flame-retardant system was melt-blended with polycarbonate resin at an addition rate of 0.9 wt%, and then extruded or injection molded to obtain a flame-retardant polycarbonate product with a thickness of 1.6 mm. The resulting material exhibits excellent flame-retardant properties while maintaining good transparency.

[0033] Comparative Example 1 The polycarbonate resin is melt-blended with 1 wt% sodium dodecyl sulfonate, and then extruded or injection molded to obtain a flame-retardant polycarbonate product with a thickness of 3.2 mm.

[0034] Comparative Example 2 The polycarbonate resin is melt-blended with 1 wt% tetraethyl orthosilicate hydrolyzed with boric acid, and then extruded or injection molded to obtain a flame-retardant polycarbonate product with a thickness of 3.2 mm.

[0035] Comparative Example 3 The difference from Example 1 is that the obtained transparent flame retardant system is melt-blended with polycarbonate resin at an addition amount of 2wt%, and then extruded or injection molded.

[0036] from Figure 3 As can be seen, the total heat release of the comparative example is higher than that of the example, indicating that the flame-retardant modification of the example is successful and the fire safety is high.

[0037] 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 compound flame retardant for polycarbonate materials, characterized in that, A powdered flame retardant prepared by polycondensation of silane coupling agents and boric acid, and a sulfonate small molecule compound; wherein the silane coupling agent is selected from alkoxysilanes, aminosilanes, epoxysilanes, vinylsilanes or any combination thereof; and the sulfonate small molecule compound is selected from aromatic sulfonates, aliphatic sulfonates or mixtures thereof.

2. The compound flame retardant according to claim 1, characterized in that, The molar ratio of silane coupling agent to boric acid is (1–5):

1.

3. The compound flame retardant according to claim 1, characterized in that, The boric acid is orthoboric acid or its dehydrated derivative.

4. The compound flame retardant according to claim 1, characterized in that, The mass ratio of the powdered flame retardant to the sulfonate small molecule compound is (1–9):(0.1–1).

5. A flame-retardant polycarbonate material, characterized in that, It contains the compound flame retardant as described in claim 1, and the content is not higher than 1 wt%.

6. The polycarbonate material according to claim 5, characterized in that, The thickness of the polycarbonate material is 1.6-3.2 mm.

7. A method for preparing a compound flame retardant as described in claim 1, characterized in that, Includes the following steps: (1) A condensation reaction is carried out between a silane coupling agent and boric acid in a solvent; (2) After the reaction is complete, the solvent is removed by rotary evaporation and dried to obtain a powdered flame retardant; (3) The powdered flame retardant is mixed with sulfonate small molecule compounds to obtain a compound flame retardant.

8. The method according to claim 7, characterized in that, The polycondensation reaction was carried out at 60–120 °C.

9. The method according to claim 7, characterized in that, The solvent is one of ethanol and diethylene glycol dimethyl ether.

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