A bio-based flame retardant and its preparation method and application

Abstract

This invention belongs to the field of flame retardant technology, and discloses a bio-based flame retardant, its preparation method, and its application. This invention selects renewable bio-resources phytic acid and basic amino acids as part of the synthesized flame retardant. It further utilizes the reaction of metal salts with basic amino acids in solution to form a preliminary complex, which then rapidly forms a stable complex with phytic acid. This metal complex makes the flame-retardant char layer denser, thereby achieving anti-dripping properties. Therefore, the resulting bio-based flame retardant can be used to prepare flame-retardant polylactic acid composite materials with excellent mechanical properties and anti-dripping flame-retardant properties. The raw materials used in this invention, phytic acid and basic amino acids, are both renewable, biomass-derived organic compounds. The synthesized flame retardant is an environmentally friendly bio-based flame retardant with widely available and green raw materials, conforming to the theme of sustainable development. It can not only alleviate the oil shortage crisis but also protect the environment.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant technology, and more specifically relates to a bio-based flame retardant, its preparation method, and its application. Background Technology

[0002] With the increasing prevalence of environmental problems, bio-based materials have received widespread attention. Among them, polylactic acid (PLA) has become one of the most promising biomaterials in food packaging, agricultural films, and automotive interiors due to its excellent mechanical properties and biodegradability. However, PLA is highly flammable, and due to its low-branched structure, it is prone to softening during combustion, resulting in a flowing and dripping melt that can cause secondary disasters. This greatly limits its practical application in industries with high flame retardancy requirements. Therefore, flame retardant modification of PLA is crucial.

[0003] Currently, most flame-retardant modifications of PLA are physical additives, which involve mechanically blending flame retardants with PLA to obtain flame-retardant PLA composites. Commonly used flame retardants include halogenated, inorganic, and intumescent flame retardants. However, in actual production, all three types of flame retardants have problems such as requiring large amounts or producing toxic substances. For example, although inorganic flame retardants are non-toxic, their large addition to PLA significantly damages the mechanical properties of PLA, limiting their application. Organic flame retardants, especially phosphorus-based flame retardants, while having high flame-retardant efficiency and requiring low addition amounts, typically dissipate heat during combustion through molten droplets, which still poses a fire risk. Furthermore, most of these flame retardant raw materials are derived from non-renewable petroleum, seriously impacting the environmentally friendly development of PLA.

[0004] In recent years, scholars have attempted to introduce a synergistic flame-retardant system containing nitrogen, phosphorus, and transition metal elements to prepare environmentally friendly flame retardants. Chinese invention patent CN102153586A discloses a compound containing phosphorus, nitrogen, and transition metal elements and its preparation method. This invention prepares a coordination compound flame retardant containing phosphorus, nitrogen, and transition metals, which can effectively improve the char-forming properties of polymers, thereby delaying polymer combustion and exhibiting good flame-retardant effects. However, its high melting point prevents it from being uniformly dispersed within the PLA matrix, leading to a decrease in mechanical properties. Furthermore, this flame retardant cannot achieve anti-drip flame retardancy in PLA.

[0005] Therefore, how to provide a bio-based flame retardant with both excellent mechanical properties and high efficiency in preventing dripping and flame retardancy, as well as its preparation method and application, is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides a bio-based flame retardant, its preparation method and application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A bio-based flame retardant, the structure of which is shown in formula (I):

[0009]

[0010] in:

[0011] A is one of aluminum ions, magnesium ions, calcium ions, and zinc ions;

[0012] B is a basic amino acid found in biomass;

[0013] R represents the chain structure of the basic amino acid in the biomass, excluding the terminal group.

[0014] Preferably, B is one of histidine, lysine, and arginine.

[0015] Further preferred, B is arginine.

[0016] The beneficial effects of the above technical solution are: compared with the other two amino acids, arginine has a higher nitrogen content, which can produce more ammonia during combustion and has higher flame retardant efficiency in gas phase flame retardancy.

[0017] Further preferred, A is zinc ion.

[0018] The beneficial effects of the above technical solution are: zinc ions are often used in the flame retardancy of polyester, which can accelerate the thermal degradation of polymers, catalyze the dehydration and cross-linking between polymer chains and flame retardants, thereby producing a more continuous, dense and stable char layer.

[0019] This invention also provides a method for preparing the above-mentioned bio-based flame retardant, comprising the following steps:

[0020] (1) Under stirring at room temperature, ammonium polyphosphate is dissolved in a biomass alkaline amino acid aqueous solution with a mass fraction of 2% to 15% to obtain an ammonium polyphosphate solution;

[0021] (2) Dissolve the metal salt in a 2% to 10% phytic acid aqueous solution under stirring at room temperature to obtain a metal salt solution;

[0022] (3) Under stirring at room temperature, the ammonium polyphosphate solution obtained in step (1) is added dropwise to the metal salt solution in step (2). The resulting reaction solution is washed with water and dried to obtain a bio-based flame retardant.

[0023] The beneficial effects of the above technical solution are as follows: In this reaction process, renewable biological resources such as phytic acid and basic amino acids are selected as part of the synthetic flame retardant. Furthermore, the metal salt reacts with the basic amino acids in the solution to form a preliminary complex, which then rapidly forms a stable complex with the phytic acid. This metal complex makes the flame-retardant char layer denser, thereby achieving the purpose of preventing dripping. Therefore, the obtained bio-based flame retardant can be used to prepare flame-retardant polylactic acid composite materials that possess both excellent mechanical properties and anti-dripping flame-retardant properties.

[0024] Preferably, in the above-mentioned method for preparing a bio-based flame retardant, the molar ratio of ammonium polyphosphate, biomass basic amino acids, phytic acid, and metal salt is 1:0.5-5:0.01-0.1:0.5-10.

[0025] In a further preferred embodiment, in the above-mentioned method for preparing a bio-based flame retardant, the molar ratio of the ammonium polyphosphate to the biomass basic amino acid is 1:1.

[0026] Preferably, in the above-mentioned method for preparing a bio-based flame retardant, the mass fraction of the biomass alkaline amino acid aqueous solution is 2% to 15%; and the mass fraction of the phytic acid aqueous solution is 2% to 10%.

[0027] Preferably, in the above-mentioned method for preparing a bio-based flame retardant, the metal salt is selected from one of aluminum sulfate, aluminum chloride, magnesium chloride, calcium chloride, calcium sulfate, and zinc sulfate.

[0028] More preferably, in the above-mentioned method for preparing a bio-based flame retardant, the metal salt is zinc sulfate.

[0029] In a further preferred embodiment, in the above-mentioned method for preparing a bio-based flame retardant, the biomass basic amino acid is selected from one of histidine, lysine, and arginine.

[0030] In a further preferred embodiment, in the above-mentioned method for preparing a bio-based flame retardant, the basic amino acid of the biomass is arginine.

[0031] Preferably, in the above-mentioned method for preparing a bio-based flame retardant, the stirring speed in step (1) is 50 to 600 rpm.

[0032] More preferably, in the above-mentioned method for preparing a bio-based flame retardant, the stirring speed in step (1) is 500 rpm.

[0033] Preferably, in the above-mentioned method for preparing a bio-based flame retardant, the average rate of dripping in step (3) is 0.56-3.3 mL / min.

[0034] More preferably, in the above-mentioned method for preparing a bio-based flame retardant, the average rate of dripping in step (3) is 0.83 mL / min.

[0035] The present invention also provides the application of the above-mentioned bio-based flame retardant in the preparation of flame-retardant polylactic acid composite materials, characterized in that the flame-retardant polylactic acid composite material comprises the following components by mass fraction: 2-13% bio-based flame retardant, 2-13% intumescent flame retardant, and 85%-96% polylactic acid.

[0036] Preferably, the intumescent flame retardant is selected from one or two of ammonium polyphosphate, polyphosphazene, and melamine.

[0037] Preferably, the flame-retardant polylactic acid composite material is prepared by melting and blending a bio-based flame retardant, an intumescent flame retardant, and polylactic acid at 170–190°C for 7–10 min to obtain the flame-retardant polylactic acid composite material.

[0038] Preferably, the mass ratio of the bio-based flame retardant to the intumescent flame retardant is 1:0.2 to 5.

[0039] As can be seen from the above technical solution, compared with the prior art, the present invention provides a bio-based flame retardant, its preparation method and application, which has the following beneficial effects:

[0040] (1) The raw materials used in this invention, phytic acid and basic amino acids, are renewable organic compounds derived from biomass. The synthesized flame retardant is an environmentally friendly bio-based flame retardant. The raw materials are widely available and environmentally friendly, which is in line with the theme of sustainable development. It can not only alleviate the crisis of oil shortage, but also protect the environment.

[0041] (2) The preparation method of the present invention is simple and safe. The solvent is only water, and there are no requirements for reaction temperature and reaction pressure. It can realize large-scale industrial production.

[0042] (3) This invention can effectively improve the flame retardant efficiency of flame retardants and the anti-drip properties of polylactic acid composites through the integrated reaction of alkaline amino acids, ammonium polyphosphate, phytic acid and metal compounds. It can also effectively reduce the melting point of flame retardants, so that they can be more uniformly dispersed in the polylactic acid matrix to improve mechanical properties.

[0043] (4) The flame-retardant polylactic acid composite material prepared by the present invention has obvious effects. By adjusting the ratio of intumescent flame retardant to product in the flame retardant, the flame-retardant polylactic acid composite material can obtain excellent flame retardant performance and anti-dripping performance at a low addition amount. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0045] Figure 1 This is an elemental analysis diagram of the bio-based flame retardant of Example 1 of the present invention.

[0046] Figure 2 A and B are scanning electron microscope images of ammonium polyphosphate and bio-based flame retardant from Example 1, respectively. Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Example 1

[0049] 5.0g of ammonium polyphosphate powder (4.1×10) -2 7.1 g arginine powder (4.1 × 10⁻⁶ mol) and 7.1 g arginine powder (4.1 × 10⁻⁶ mol) -2 Add 1.4 g of phytic acid (2.1 × 10⁻⁶ mol) to 92.9 mL of distilled water and stir at 500 rpm for 6 hours at room temperature until completely dissolved to obtain an ammonium polyphosphate solution; separately take 1.4 g of phytic acid (2.1 × 10⁻⁶ mol) -3 mol) and 9.6 g zinc sulfate heptahydrate (3.3 × 10⁻⁶) -2 Add mol) to 24 mL of distilled water and stir until completely dissolved to obtain a metal salt solution; add ammonium polyphosphate solution dropwise to the metal salt solution at an average rate of 0.83 mL / min, and continue stirring at room temperature for 2 h until the precipitate becomes a large gel block. Take the gel block, wash it three times with water, and dry it to obtain the bio-based flame retardant. Example 1: The structural formula of the bio-based flame retardant is as follows:

[0050]

[0051] 2.5g of the prepared bio-based flame retardant and 2.5g of ammonium polyphosphate were mixed evenly with 45.0g of polylactic acid and added to a mixer for melt blending. The processing temperature was 180℃ and the time was 9min to obtain the flame-retardant polylactic acid composite material.

[0052] Figure 1This is the XPS photoelectron spectrum of the bio-based flame retardant from Example 1. It contains peaks for five elements: C, O, P, Zn, and N, proving that the flame retardant does not contain sulfur (S) found in zinc sulfate after reaction, centrifugation, and washing. Specifically, the mass fractions of the five elements obtained are: C: 20.34 wt%, O: 37.13 wt%, P: 18.97 wt%, Zn: 13.85 wt%, and N: 9.71 wt%. Phytic acid contains P, C, and O; arginine contains C, O, and N; and zinc sulfate heptahydrate contains C, O, and Zn. The calculated ratio of ammonium polyphosphate:phytic acid:arginine:zinc sulfate heptahydrate is 7:0.2:3:4, demonstrating the successful synthesis of a bio-based flame retardant with excellent mechanical properties and high-efficiency anti-drip flame retardancy.

[0053] Figure 2 A and B are scanning electron microscope (SEM) images of ammonium polyphosphate and bio-based flame retardant from Example 1 of this invention, respectively. Ammonium polyphosphate is a rod-shaped solid with a particle size of about 20 μm and relatively uniform size; while the bio-based flame retardant is a blocky viscous solid. Under magnification, it can be observed that its surface has pores of varying sizes and unevenly distributed. The difference between the two is obvious, providing auxiliary evidence for the synthesis of the product.

[0054] Example 2

[0055] The difference between Example 2 and Example 1 is that 9.6g of zinc sulfate heptahydrate (3.3×10) was used. -2 mol) was replaced with 11.1 g of aluminum sulfate octahydrate (3.3 × 10⁻⁶). -2 Under the same conditions (mol), a bio-based flame retardant was obtained. The structural formula of the bio-based flame retardant in Example 2 is as follows:

[0056]

[0057] 2.5g of the prepared bio-based flame retardant and 2.5g of ammonium polyphosphate were mixed with 45.0g of polylactic acid and then added to a mixer for melt blending. The processing temperature was 180℃ and the time was 9min to obtain the flame-retardant polylactic acid composite material.

[0058] Example 3

[0059] The difference between Example 3 and Example 1 is that 9.6g of zinc sulfate heptahydrate (3.3×10) was used. -2 Replace mol) with 3.4 g of anhydrous calcium chloride (3.3 × 10⁻⁶). -2 (mol), with other conditions remaining unchanged, a bio-based flame retardant was obtained. The structural formula of the bio-based flame retardant in Example 3 is as follows:

[0060]

[0061] 2.5g of the prepared bio-based flame retardant and 2.5g of ammonium polyphosphate were mixed with 45.0g of polylactic acid and then added to a mixer for melt blending. The processing temperature was 180℃ and the time was 9min to obtain the flame-retardant polylactic acid composite material.

[0062] Example 4

[0063] The difference between Example 4 and Example 1 is that 7.1g of arginine powder (4.1×10) was used. -2 Replace 6.0 g of lysine powder (4.1 × 10⁻⁶ mol) with 6.0 g of lysine powder (4.1 × 10⁻⁶ mol). -2 Under the same conditions (mol), a bio-based flame retardant was obtained. The structural formula of the bio-based flame retardant in Example 4 is as follows:

[0064]

[0065] 2.5g of the prepared bio-based flame retardant and 2.5g of ammonium polyphosphate were mixed with 45.0g of polylactic acid and then added to a mixer for melt blending. The processing temperature was 180℃ and the time was 9min to obtain the flame-retardant polylactic acid composite material.

[0066] Example 5

[0067] The difference between Example 4 and Example 1 is that 7.1g of arginine powder (4.1×10) was used. -2 The mol) was replaced with 6.4g histidine powder (4.1×10). -2 With the other conditions unchanged, a bio-based flame retardant was obtained by adding mol of the product.

[0068] The structural formula of the bio-based flame retardant in Example 5 is as follows:

[0069]

[0070] 2.5g of the obtained bio-based flame retardant and 2.5g of ammonium polyphosphate were mixed with 45.0g of PLA and then put into a mixer for melt blending at 180℃ for 9 minutes to obtain flame-retardant polylactic acid composite material.

[0071] Comparative Example 1

[0072] 5.0g of the bio-based flame retardant obtained in Example 1 was mixed evenly with 45.0g of PLA and then melt-blended in a mixer at a temperature of 180°C for 9 minutes to obtain the flame-retardant polylactic acid composite material.

[0073] Comparative Example 2

[0074] Mix 5.0g of ammonium polyphosphate and 45.0g of PLA evenly, and put them into a mixer for melt blending. The processing temperature is 180℃ and the time is 9min to obtain flame-retardant polylactic acid composite material.

[0075] Application Example 1

[0076] 4.0g of the bio-based flame retardant obtained in Example 1 and 1.0g of ammonium polyphosphate were mixed with 45.0g of PLA and then melt-blended in an internal mixer at a temperature of 180°C for 9 minutes to obtain the flame-retardant polylactic acid composite material.

[0077] Application Example 2

[0078] 1.0g of the bio-based flame retardant obtained in Example 1 and 4.0g of ammonium polyphosphate were mixed with 45.0g of PLA and then melt-blended in an internal mixer at a temperature of 180°C for 9 minutes to obtain the flame-retardant polylactic acid composite material.

[0079] Comparative Example 3

[0080] 50.0g of PLA was put into a mixer for melt blending at a temperature of 180℃ for 9 minutes to obtain flame-retardant polylactic acid composite material.

[0081] The flame-retardant polylactic acid composite materials obtained in each embodiment and comparative example were tested for flame retardant properties, and the results are shown in Table 1.

[0082] Table 1 Vertical Combustion Test and Oxygen Index Test

[0083]

[0084] The above results indicate that the bio-based flame retardant with anti-dripping properties obtained in this invention can significantly improve the flame retardant performance of PLA composite materials. By adjusting the ratio of intumescent flame retardant to stable complex in the flame retardant, excellent flame retardant and anti-dripping properties of flame-retardant polylactic acid composite materials can be obtained at a lower addition amount.

[0085] The flame-retardant polylactic acid composite materials obtained in each embodiment and comparative example were subjected to tensile property tests, and the results are shown in Table 2.

[0086] Table 2 Tensile property test

[0087] serial number Tensile strength (MPa) Elongation at break (%) Example 1 61.0±1.5 11.4±2.4 Example 2 54.1±2.0 8.1±2.0 Example 3 58.6±2.4 10.8±2.7 Example 4 60.2±1.8 9.1±1.7 Example 5 57.2±1.3 9.4±1.3 Comparative Example 1 61.5±2.0 4.7±0.2 Comparative Example 2 44.4±0.5 7.6±1.7 Application Example 1 56.5±1.4 4.4±0.5 Application Example 2 46.2±1.1 6.3±0.5 Comparative Example 3 62.5±2.0 4.0±0.4

[0088] The above results show that the bio-based flame retardant obtained in this invention, which has both excellent mechanical properties and anti-dripping flame retardancy, can significantly improve the mechanical properties of PLA composite materials. By adjusting the ratio of intumescent flame retardant to stable complex in the flame retardant, the flame-retardant PLA composite material can have both excellent tensile strength and good tensile toughness.

[0089] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The solutions disclosed in the embodiments are described simply because they correspond to the methods disclosed in the embodiments; relevant parts can be found in the method section.

[0090] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bio-based flame retardant, characterized in that, The preparation method includes the following steps: (1) Under stirring at room temperature, ammonium polyphosphate is dissolved in an alkaline amino acid aqueous solution of biomass to obtain an ammonium polyphosphate solution; (2) Dissolve the metal salt in an aqueous phytic acid solution under stirring at room temperature to obtain a metal salt solution; (3) Under stirring at room temperature, the ammonium polyphosphate solution obtained in step (1) is added dropwise to the metal salt solution in step (2). The resulting precipitate is washed with water and dried to obtain a bio-based flame retardant. The molar ratio of ammonium polyphosphate, biomass basic amino acids, phytic acid, and metal salt is 1:0.5-5:0.01-0.1:0.5-10; The biomass alkaline amino acid aqueous solution has a mass fraction of 2% to 15%; the phytic acid aqueous solution has a mass fraction of 2% to 10%. The metal salt is selected from one of aluminum sulfate, aluminum chloride, magnesium chloride, calcium chloride, calcium sulfate, and zinc sulfate; The basic amino acid in the biomass is selected from one of histidine, lysine, and arginine.

2. Use of a bio-based flame retardant according to claim 1 for the preparation of a flame- retarded polylactic acid composite, characterized in that, The flame-retardant polylactic acid composite material is composed of the following components by mass fraction: 2-13% of the bio-based flame retardant as described in claim 1, 2-13% of the intumescent flame retardant, and 85%-96% of polylactic acid.

3. The application of a bio-based flame retardant according to claim 2 in the preparation of flame-retardant polylactic acid composite materials, characterized in that, The intumescent flame retardant is selected from one or two of ammonium polyphosphate, polyphosphazene, and melamine.

4. The application of the bio-based flame retardant according to claim 2 in the preparation of flame-retardant polylactic acid composite materials, characterized in that, The method for preparing the flame-retardant polylactic acid composite material is as follows: the bio-based flame retardant, the intumescent flame retardant and polylactic acid described in claim 1 are melt-blended at 170-190°C for 7-10 minutes to obtain the flame-retardant polylactic acid composite material.

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