Flame-retardant polylactic acid containing vanillin-based flame retardant and preparation method of flame-retardant polylactic acid

Abstract

The invention belongs to the technical field of high polymer materials, and particularly discloses flame-retardant polylactic acid containing a vanillin-based flame retardant and a preparation method of the flame-retardant polylactic acid. The flame-retardant polylactic acid is prepared from the following components in parts by weight: 93.5 to 99 parts of polylactic acid, 0.5 to 6 parts of vanillin-based flame retardant and 0.5 part of antioxidant. The adopted bio-based flame retardant has a Schiff base structure and phosphorus element and is high in flame retardant efficiency, the main raw material vanillin adopted for synthesizing the vanillin-based flame retardant is reproducible and easy to obtain, the production process is simple, the sustainable development trend of materials is met, and the prepared vanillin-based flame retardant not only has efficient flame retardant efficiency, but also has good flame retardant effect. Moreover, the preparation process is non-toxic and environment-friendly, and the burden of the flame retardant on resources and the environment in synthesis and application can be effectively relieved.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and specifically discloses a flame retardant polylactic acid containing a vanillin-based flame retardant and a preparation method thereof. Background Art

[0002] As humans continue to pay attention to environmental protection and energy issues, bio-based materials have received widespread attention. At the same time, the development of bio-based polymer materials can reduce carbon emissions and is conducive to the realization of the "dual carbon goals". Polylactic acid (PLA), as an important bio-based polymer material, has been widely used in medicine, engineering, packaging and other fields due to its excellent mechanical properties, biodegradability, and renewable raw material sources.

[0003] In recent years, PLA has been increasingly popular in the fields of electronic and electrical equipment, automobiles, textiles, etc., and higher requirements have been placed on its flame retardant properties. Directly adding flame retardants is one of the simplest and most effective ways to improve the flame retardant properties of PLA. However, most of the flame retardants used in traditional polymer materials are halogen-containing flame retardants and inorganic flame retardants, but they have disadvantages such as being unfriendly to the environment, requiring large amounts of addition, and relying on petroleum resources. Therefore, bio-based phosphorus-containing flame retardants with environmental protection and high efficiency are one of the hot spots in the current research on flame retardant development.

[0004] Lignin is a natural polyphenol macromolecule, second only to cellulose in its storage volume in nature, and is considered to be the only biomass source that is expected to produce phenolic compounds on a large scale. Industrial lignin mainly comes from wastewater from the papermaking and pulping industry and byproducts of bioethanol production, most of which are used as fuel or directly discharged. The structural composition of lignin is complex, and it changes with changes in the biomass source, origin, extraction process, etc., making it difficult to ensure the stability of its composition and quality, which limits the effective utilization of lignin. However, due to the maturity and commercial use of the process for preparing vanillin from lignin, vanillin, as the only industrialized monophenol compound product derived from lignin, has received increasing attention in the field of bio-based flame-retardant polymer materials. However, vanillin itself lacks flame-retardant elements, and the flame-retardant effect of direct use is limited, making it difficult to meet the flame-retardant requirements of the material. At the same time, the thermal stability of vanillin is poor, and the initial degradation temperature (T 5％ ) Only 151℃ is difficult to meet the processing requirements of polymer materials, especially polylactic acid. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of traditional flame retardants' dependence on petrochemical resources, low flame retardant efficiency, environmental pollution, harm to human health, etc., to make fuller use of the commercial product derived from lignin - vanillin, and on this basis, introduce Schiff base structure and phosphorus element to obtain vanillin-based flame retardant, which is effectively used for flame retardant polylactic acid, to obtain a flame retardant polylactic acid material containing high-efficiency vanillin-based flame retardant, and realize the full bio-based flame retardant polylactic acid material.

[0006] In order to achieve the above-mentioned purpose, the flame retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant provided by the present invention has the following formula components by weight: 93.5 to 99 parts of polylactic acid, 0.5 to 6 parts of a high-efficiency vanillin-based flame retardant, and 0.5 part of an antioxidant.

[0007] The vanillin-based flame retardant used has the following structure as shown in the following formula:

[0008]

[0009] Among them, R is

[0010] n is 1, 3 or 5.

[0011] The preparation method of the vanillin-based flame retardant of the present invention comprises the following steps:

[0012] (1) adding vanillin into a reactor containing anhydrous ethanol equipped with a reflux condenser and a stirrer, stirring with a magnetic stirrer until it is completely dissolved, then adding an aliphatic diamine and reacting at room temperature for 30 hours, washing the product, filtering and drying it to obtain an intermediate product (VS) containing a Schiff base structure;

[0013] Wherein, the aliphatic diamine is ethylenediamine, hexamethylenediamine or decanediamine, and the molar ratio of vanillin to the diamine is 2.1:1;

[0014] (2) Then, the intermediate product is added to a reaction bottle containing N'N-dimethylformamide, and magnetically stirred at room temperature until it is completely dissolved. Triethylamine is added, and then diphenoxyphosphoryl chloride or diphenylphosphoryl chloride is slowly added dropwise in an ice bath at 0-5°C. The addition is completed within 1 hour, and then the reaction is carried out at room temperature for 21 hours. The product is then filtered, rotary evaporated, washed, and dried to obtain a vanillin-based flame retardant containing a Schiff base structure and phosphorus element.

[0015] The molar ratio of the intermediate (VS), diphenoxyphosphoryl chloride or diphenylphosphoryl chloride and triethylamine is 1:2.1:2.2.

[0016] The present invention also provides a method for preparing a flame-retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant: first, the vanillin-based flame retardant, antioxidant 1010 and polylactic acid are mixed in proportion, and then melt-blended in an internal mixer to obtain the flame-retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant.

[0017] Compared with the prior art, the present invention has the following advantages: the flame-retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant prepared by the present invention has good flame retardant properties, the bio-based flame retardant used has a Schiff base structure and a phosphorus element, and has a high flame retardant efficiency, and the main raw material vanillin used for synthesizing the vanillin-based flame retardant is renewable and easy to obtain, the production process is simple, and it is easy to industrialize production, which is in line with the sustainable development trend of materials.

[0018] The vanillin-based flame retardant used in the present invention is derived from the commercial product vanillin derived from lignin, which is easily available and renewable, and can meet the sustainable development of materials. In addition, the bio-based monomer with a Schiff base structure on the flame retardant has little effect on the thermal stability of the base resin. When applied to polymers, it not only has a very high flame retardant efficiency, but also can achieve the flame retardant purpose by adding a small amount. In addition, the preparation process is non-toxic and environmentally friendly, and can effectively alleviate the burden of the flame retardant on resources and the environment during synthesis and application, and fully meets the conditions for processing and production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The infrared spectra of vanillin, the flame retardant intermediate prepared in Example 1 of the present invention, and the vanillin-based flame retardant;

[0020] Figure 2 The thermal weight loss curves of vanillin, the flame retardant intermediate prepared in Example 1 of the present invention, and the vanillin-based flame retardant in a nitrogen atmosphere. DETAILED DESCRIPTION

[0021] The following examples are further explanations of the present invention, but are not intended to limit the scope of the present invention. The polylactic acid used in the following examples is 4032D from Nature Works, USA; antioxidant 1010, Henan Wanshan New Material Technology Co., Ltd.; the main raw materials for the preparation of flame retardants are vanillin and ethylenediamine, both purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; diphenoxyphosphoryl chloride, Shanghai Lingfeng Chemical Reagent Co., Ltd.; hexamethylenediamine, Shanghai Ruidong Chemical Co., Ltd.; decanediamine, Shanghai Gaoming Chemical Co., Ltd.; triethylamine, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0022] Attached Figure 1 : The infrared spectra of vanillin, the flame retardant intermediate prepared in Example 1 of the present invention, and the vanillin-based flame retardant. As can be seen from the figure, compared with vanillin, the flame retardant intermediate has a higher infrared spectroscopy at 1667 cm -1 The characteristic absorption peak of C=O in the aldehyde group at 1633 cm -1 A new characteristic absorption peak appears at 3419 cm-1, corresponding to the C=N stretching vibration peak. Compared with the flame retardant intermediate, the vanillin-based flame retardant has a peak at 3419 cm-1. -1The characteristic absorption peaks corresponding to phenolic hydroxyl groups disappeared, and at the same time, -1 and 1087cm -1 New characteristic absorption peaks appear at 950cm -1 The characteristic absorption peak of POC also appeared. It can be seen that the vanillin-based flame retardant was successfully prepared.

[0023] Attached Figure 2 Table 1 shows the thermal weight loss curves of vanillin, the flame retardant intermediate prepared in Example 1 of the present invention, and the vanillin-based flame retardant in a nitrogen atmosphere. The relevant important thermal degradation parameters are shown in Table 1. As shown in Table 1, compared with vanillin, the vanillin-based flame retardant and the flame retardant intermediate have higher thermal stability and higher carbon residue, which can meet the processing requirements; at the same time, the temperature corresponding to the first maximum thermal degradation rate of the vanillin-based flame retardant (T max1 ) is significantly higher than that of vanillin and flame retardant intermediates, which is inseparable from its unique structural composition.

[0024] Table 1 Important thermal degradation parameter data of vanillin, flame retardant intermediates and vanillin-based flame retardants in nitrogen atmosphere

[0025]

[0026] Examples 1-5

[0027] According to the formula in Table 2, the vanillin-based flame retardant (VSEB or VSHB), antioxidant 1010 and polylactic acid (PLA) are first mixed uniformly in proportion, and then melt-blended by an internal mixer. The internal mixer temperature is set to 180°C and the speed is 30r / min to obtain a flame-retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant.

[0028] Among them, taking ethylenediamine as an example, the preparation method of the vanillin-based flame retardant is:

[0029] First, 0.0210 mol of vanillin was added to a reactor equipped with a reflux condenser and a stirrer containing 25 mL of anhydrous ethanol, and magnetically stirred until it was completely dissolved. Then, 0.0100 mol of ethylenediamine was added, and the reaction was carried out at room temperature for 30 hours. The product was washed, filtered and dried to obtain an intermediate product (VS) containing a Schiff base structure. Then, 0.00895 mol of the intermediate product was added to a reaction bottle containing 15 mL of N'N-dimethylformamide, and magnetically stirred at room temperature until it was completely dissolved. Then, 0.0199 mol of triethylamine was added, and then 0.0197 mol of diphenoxyphosphoryl chloride was slowly added dropwise under ice bath conditions of 0-5°C, and the dripping was completed within 1 hour. Then, the reaction was carried out at room temperature for 21 hours, and then the product was filtered, rotary evaporated, washed, and dried to obtain a vanillin-based flame retardant containing a Schiff base structure and a phosphorus element.

[0030] The preparation method of the vanillin-based flame retardant (VSHB) obtained by using 0.0100 mol of hexamethylenediamine as the diamine is the same as above.

[0031] The flame retardant performance test results of the obtained flame retardant polylactic acid material containing vanillin-based flame retardant are shown in Table 2.

[0032] Comparative Example 1

[0033] According to the formula in Table 2, antioxidant 1010 and polylactic acid (PLA) were first mixed uniformly according to a proportion, and then melt-blended in an internal mixer to obtain pure polylactic acid material.

[0034] The flame retardant properties test results of the obtained pure polylactic acid material are shown in Table 2.

[0035] Comparative Example 2

[0036] According to the formula in Table 2, the lignin-based flame retardant, antioxidant 1010 and polylactic acid (PLA) were first mixed uniformly according to the proportion, and then melt-blended by an internal mixer to obtain a flame-retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant.

[0037] Wherein, the preparation method of lignin-based flame retardant is as follows:

[0038] 18.0g of hydroxymethylated lignin was dispersed in 150mL toluene solution in a 250mL three-necked flask, ultrasonically dispersed for 1h, 36mL of silane coupling agent KH540 was added thereto, and the temperature was slowly raised to 110℃ under mechanical stirring, and refluxed for 16h. After the reaction was completed, it was cooled to room temperature, filtered, washed, and vacuum dried to constant weight to obtain the intermediate Lig-NH2; then 18.0gLig-NH2 was dispersed in 150mL toluene solution, 3.8g 4-(diethylamino) salicylaldehyde was added, ultrasonically dispersed for 1h, heated to 110℃, refluxed for 16h, and after the reaction was completed, the intermediate NLig was obtained by washing and drying; finally, 18.0g NLig and 3.5gDOPO were dispersed in 150mL anhydrous ethanol, refluxed at 50℃ for 10h, and after the reaction was completed, the target product, i.e., lignin-based flame retardant, was obtained by filtration, washing, and drying.

[0039] The flame retardant performance test results of the obtained flame retardant polylactic acid material containing lignin-based flame retardant are shown in Table 2.

[0040] Comparative Example 3

[0041] According to the formula in Table 2, the lignin-based flame retardant, antioxidant 1010 and polylactic acid (PLA) were first mixed uniformly according to the proportion, and then melt-blended by an internal mixer to obtain a flame-retardant polylactic acid material containing a high-efficiency vanillin-based flame retardant.

[0042] Among them, the preparation method of the lignin-based flame retardant is the same as the preparation method of the flame retardant in Comparative Example 2.

[0043] The flame retardant performance test results of the obtained flame retardant polylactic acid material containing lignin-based flame retardant are shown in Table 2.

[0044] Table 2 Formulation of flame retardant polylactic acid and its flame retardant performance test results

[0045]

[0046] Note: NR---No level

[0047] It can be seen from the flame retardant test results in Table 2 that after adding vanillin-based flame retardants (VSEB, VSHB), that is, Examples 1 to 5, the flame retardant properties of the flame retardant polylactic acid are significantly improved, and with the increase in the amount of addition, the limiting oxygen index (LOI) value continues to increase, wherein when the VSEB addition amount is 6%, the LOI value can reach 31.5%, and the U-94 vertical combustion reaches the V-0 level, especially the limiting oxygen index is significantly better than that of Comparative Example 3 (PLA / 20FRLig). In addition, under the condition that the VSEB addition amount is only 0.5%, the limiting oxygen index of the flame retardant polylactic acid (PLA / 0.5VSEB) is increased by 6 values ​​compared with Comparative Example 1 (PLA0), and the UL-94 vertical combustion is increased from NR to V-2 level, and is significantly higher than that of Comparative Example 2 (PLA / 10FRLig) with a LOI value of only 23.0%.

[0048] It can be seen that the vanillin-based flame retardant prepared by the present invention can be effectively used for flame retardant polylactic acid, and has good application prospects in the field of flame retardant polylactic acid.

Claims

1. A flame retardant polylactic acid containing a vanillin-based flame retardant, characterized in that: The flame retardant polylactic acid containing vanillin-based flame retardant is composed of 93.5-99 parts of polylactic acid, 0.5-6 parts of vanillin-based flame retardant, and 0.5 parts of antioxidant in parts by weight; the vanillin-based flame retardant has a structure shown in the following formula: Among them, R is n is 1, 3 or 5.

2. The flame retardant polylactic acid containing a vanillin-based flame retardant according to claim 1, characterized in that: The preparation method of the vanillin-based flame retardant comprises the following steps: (1) Add vanillin into a reactor containing anhydrous ethanol equipped with a reflux condenser and a stirrer, stir it magnetically until it is completely dissolved, then add an aliphatic diamine, react at room temperature for 30 hours, wash the product, filter and dry it to obtain an intermediate product VS containing a Schiff base structure; (2) The intermediate product is added to a reaction bottle containing N'N-dimethylformamide, and magnetically stirred at room temperature until it is completely dissolved. Triethylamine is added, and then diphenoxyphosphoryl chloride or diphenylphosphoryl chloride is added dropwise in an ice bath at 0-5°C. The addition is completed within 1 hour, followed by reaction at room temperature for 21 hours. The product is then filtered, rotary evaporated, washed, and dried to obtain a vanillin-based flame retardant containing a Schiff base structure and phosphorus element.

3. The flame retardant polylactic acid containing a vanillin-based flame retardant according to claim 2, characterized in that: In step (1), the aliphatic diamine is ethylenediamine, hexamethylenediamine or decanediamine.

4. The flame retardant polylactic acid containing a vanillin-based flame retardant according to claim 2, characterized in that: In step (1), the molar ratio of vanillin to diamine is 2.1:

1.

5. The flame retardant polylactic acid containing a vanillin-based flame retardant according to claim 2, characterized in that: In step (2), the molar ratio of the intermediate (VS), diphenoxyphosphoryl chloride or diphenylphosphoryl chloride and triethylamine is 1:2.1:2.

2.

6. A method for preparing a flame retardant polylactic acid containing a vanillin-based flame retardant according to claim 1, characterized in that: The preparation method comprises the following steps: mixing a vanillin-based flame retardant, an antioxidant 1010 and polylactic acid according to weight fractions, and then melt-blending the mixture in an internal mixer to obtain flame-retardant polylactic acid containing the vanillin-based flame retardant.

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