A flame-retardant biodegradable polyester material and its preparation method

Abstract

This invention relates to the field of polyester materials technology, and discloses a flame-retardant biodegradable polyester material and its preparation method. The polyester material of this invention is composed of 65-80 parts by weight of aromatic polyester, 20-35 parts by weight of aliphatic polyester, and 5-25 parts by weight of polylactic acid-based flame retardant. The aromatic polyester is selected from polyethylene terephthalate (PET), and the aliphatic polyester includes biodegradable components such as polylactic acid (PLA). The PLA-based flame retardant of this invention improves the compatibility between aliphatic polyesters such as PLA and aromatic polyesters such as PET, resulting in better mechanical properties. Simultaneously, the main chain contains a large number of phosphoramide groups, forming a nitrogen-phosphorus flame-retardant system, thereby improving the flame-retardant performance of the polyester material.

Description

Technical Field

[0001] This invention relates to the field of polyester materials technology, specifically to a flame-retardant biodegradable polyester material and its preparation method. Background Technology

[0002] Biodegradable polyesters such as polylactic acid (PLA), polyethylene terephthalate (PET), polybutylene terephthalate (PBAT), and polybutylene succinate-co-butylene terephthalate (PBST) possess good mechanical strength, are widely available, and are environmentally friendly, making them ideal alternatives to traditional non-biodegradable plastics. They are particularly important in alleviating the environmental crisis and reducing resource scarcity. However, these polyester materials have poor flame retardancy and are easily ignited. Adding flame retardants can improve their flame retardant properties.

[0003] Flame retardants are diverse, encompassing halogenated, inorganic, organophosphorus, and nitrogen-based categories. Among them, nitrogen-phosphorus flame retardants, with their unique nitrogen-phosphorus synergistic mechanism, exhibit significant advantages in the flame-retardant modification of polyester materials, making them an ideal choice that the industry is currently focusing on. Through molecular design, nitrogen and phosphorus groups can be chemically combined with polyester segments (such as through copolymerization), avoiding the problems of inorganic flame retardants' tendency to agglomerate and affect the mechanical properties of materials. This allows polyester materials with added flame retardants to still maintain good tensile strength and other mechanical properties.

[0004] Chinese invention patent CN109206871B discloses a flame-retardant, toughened, and biodegradable polylactic acid material and its preparation method. The method involves melt blending polylactic acid, unsaturated polyester, flame retardant, and synergistic flame retardant to obtain a flame-retardant polylactic acid material. However, this patent does not improve the compatibility between aliphatic polyesters such as polylactic acid and aromatic polyesters, which is not conducive to improving the mechanical properties of polyester composite materials. Summary of the Invention

[0005] (a) Technical problems to be solved:

[0006] To address the shortcomings of existing technologies, this invention provides a flame-retardant biodegradable polyester material and its preparation method. While ensuring the flame retardancy of the biodegradable polyester material, it solves the problem of poor compatibility between aliphatic polyesters such as polylactic acid and aromatic polyesters, thereby improving the mechanical properties of the biodegradable polyester material.

[0007] (II) Technical Solution:

[0008] Based on the above analysis, the present invention provides a method for preparing a flame-retardant biodegradable polyester material, comprising the following steps:

[0009] Step (1): At 0-5℃, add acetone, water, 100 parts by weight of cyanuric chloride, and 33-34 parts by weight of ethanolamine to a flask, and add an aqueous solution of sodium hydroxide dropwise to adjust the pH of the solution to 6.5-7. React for 4-6 hours, then add 62-69 parts by weight of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, raise the temperature to 40-50℃, and react for 1-2 hours. Then add another 62-69 parts by weight of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, raise the temperature to 100-110℃, and reflux for 12-18 hours. During the reaction, add an aqueous solution of sodium hydroxide dropwise to maintain the pH of the solution at 6.5-7. After cooling, filter, wash with ethanol, and dry to obtain the nitrogen-phosphorus flame retardant. The reaction formula is:

[0010] .

[0011] Step (2): Add 100 parts by weight of nitrogen-phosphorus flame retardant and toluene to a flask, stir, add 6-20 parts by weight of D,L lactide and 0.03-0.1 parts by weight of catalyst stannous octoate, reflux reaction in a nitrogen atmosphere, pour the solution into ethanol, filter, wash with ethanol, dry, and obtain polylactic acid-based flame retardant.

[0012] Step (3): Mix 5-25 parts by weight of polylactic acid flame retardant, 65-80 parts by weight of aromatic polyester, and 20-35 parts by weight of aliphatic polyester, add them to a twin-screw extruder, blend, extrude, and pelletize to obtain flame-retardant biodegradable polyester material.

[0013] Furthermore, in step (2), the temperature of the reflux reaction is 110-120℃, and the time of the reflux reaction is 24-36h.

[0014] Furthermore, in step (3), the temperature of each zone of the twin-screw extruder is 120℃-260℃, and the screw speed is 150-200r / min.

[0015] Furthermore, in step (3), the aromatic polyester is one of polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate-adipate, or polybutylene succinate-co-butylene terephthalate.

[0016] Furthermore, in step (3), the aliphatic polyester is polyglycolic acid or polylactic acid.

[0017] The present invention also provides a flame-retardant biodegradable polyester material prepared by the above preparation method.

[0018] (III) Beneficial technical effects:

[0019] The amino group of ethanolamine acts as a nucleophilic center to replace the chlorine atom on cyanuric chloride, generating a monosubstituted product containing a -NH-CH2CH2-OH group. The amino groups at both ends of N,N'-bis(2-aminoethyl)-phenylphosphine diamide sequentially attack the chlorine atom on the ring of the monosubstituted product. By repeating the substitution reaction process, the molecular chain is gradually extended and polymerized to form a nitrogen-phosphorus flame retardant. The hydroxyl group on the nitrogen-phosphorus flame retardant initiates the D,L lactide reaction grafting, and finally synthesizes the polylactic acid-based flame retardant of this invention.

[0020] The polylactic acid-based flame retardant of the present invention contains polylactic acid segments and benzene ring structures in its molecule. The polylactic acid segments have a high structural similarity to aliphatic polyesters such as polylactic acid, and the benzene ring structure forms a π-π conjugation effect with the aromatic ring structure of aromatic polyesters such as polyethylene terephthalate, which significantly enhances the interfacial bonding force with aromatic polyesters. This allows the polylactic acid-based flame retardant to act as a compatibilizer, improve the compatibility between aromatic polyesters and aliphatic polyesters, and significantly improve the mechanical properties of polyester materials.

[0021] The polylactic acid-based flame retardant of the present invention contains a large number of phosphoramide and triazine groups in its main chain, forming a nitrogen-phosphorus flame retardant system. In the early stage of combustion, phosphorus can promote the formation of a dense carbon layer on the surface of the composite material, effectively blocking the transfer of oxygen and heat to the interior of the material. When nitrogen is heated and decomposed, it releases inert gases such as nitrogen, which can not only dilute the concentration of combustible gases in the combustion zone, but also inhibit the continued combustion reaction by absorbing heat and cooling down. The two work together to improve the flame retardant performance of polyester materials, thereby reducing the peak heat release rate and the total heat release. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are conventional products that can be purchased commercially.

[0023] The preparation method of N,N'-bis(2-aminoethyl)-phenylphosphine diamide is as follows: 126 g of ethylenediamine and 400 mL of chloroform are added to a flask. 200 mL of a chloroform solution containing 117 g of phenylphosphonic dichloride is added dropwise at 0 °C. The mixture is stirred for 6 h, then filtered. The filtrate is extracted with saturated sodium bicarbonate solution. After separation, the chloroform organic layer is distilled under reduced pressure and dried to obtain N,N'-bis(2-aminoethyl)-phenylphosphine diamide, with the structural formula [insert structural formula here]. .

[0024] Example 1

[0025] This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, including the following steps:

[0026] (1) At 0℃, 55mL of acetone, 30mL of water, 30g of cyanuric chloride, and 10.2g of ethanolamine were added to a flask, and a 20% sodium hydroxide aqueous solution was added dropwise to adjust the pH of the solution to 6.5. The reaction was allowed to proceed for 6h. Then, 18.6g (about 76.86mmol) of N,N'-bis(2-aminoethyl)-phenylphosphine was added, the temperature was raised to 50℃, and the reaction was allowed to proceed for 1h. Another 18.6g of N,N'-bis(2-aminoethyl)-phenylphosphine was added, the temperature was raised to 110℃, and the reaction was allowed to proceed under reflux for 12h. During the reaction, an aqueous solution of sodium hydroxide was added dropwise to maintain the pH of the solution at 6.5. After cooling, the solution was filtered, washed with ethanol, and dried to obtain a nitrogen-phosphorus flame retardant.

[0027] (2) Add 60g of nitrogen-phosphorus flame retardant and 700mL of toluene to a flask, stir, add 3.6g of D,L lactide and 18mg of catalyst stannous octoate, heat to 115℃ in a nitrogen atmosphere, reflux for 24h, pour the solution into ethanol, filter, wash with ethanol, and dry under vacuum at 80℃ to obtain polylactic acid flame retardant.

[0028] (3) Mix 100g of polylactic acid flame retardant, 1600g of polyethylene terephthalate and 400g of polylactic acid, add them to a twin-screw extruder, and set the temperatures of zones 1-11 to 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃ and 260℃ respectively. Set the screw speed to 150r / min, blend, extrude and pelletize to obtain a flame-retardant biodegradable polyester material.

[0029] Example 2

[0030] This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, including the following steps:

[0031] (1) At 5℃, add 50mL of acetone, 35mL of water, 30g of cyanuric chloride and 9.9g of ethanolamine to a flask, and add 20% sodium hydroxide aqueous solution dropwise to adjust the pH of the solution to 7. React for 6h, then add 20.7g of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, heat to 40℃, react for 2h, then add another 20.7g of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, heat to 100℃, reflux for 18h. During the reaction, add sodium hydroxide aqueous solution dropwise to maintain the pH of the solution at 7. After cooling, filter, wash with ethanol, and dry to obtain nitrogen-phosphorus flame retardant.

[0032] (2) Add 60g of nitrogen-phosphorus flame retardant and 800mL of toluene to a flask, stir, add 12g of D,L lactide and 60mg of catalyst stannous octoate, heat to 120℃ in a nitrogen atmosphere, reflux for 36h, pour the solution into ethanol, filter and wash with ethanol, dry under vacuum at 75℃ to obtain polylactic acid flame retardant.

[0033] (3) Mix 200g of polylactic acid flame retardant, 1500g of polybutylene succinate-co-butylene terephthalate and 500g of polyglycolic acid, add them to a twin-screw extruder, and set the temperatures of zones 1-11 to 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃ and 260℃ respectively. The screw speed is 180r / min. Blend, extrude and pelletize to obtain a flame-retardant biodegradable polyester material.

[0034] Example 3

[0035] This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, including the following steps:

[0036] (1) At 3℃, add 50mL of acetone, 35mL of water, 30g of cyanuric chloride and 10.1g of ethanolamine to a flask, and add 20% sodium hydroxide aqueous solution dropwise to adjust the pH of the solution to 7. React for 5h, then add 20g of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, heat to 45℃, react for 2h, then add another 20g of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, heat to 100℃, reflux for 16h. During the reaction, add sodium hydroxide aqueous solution dropwise to maintain the pH of the solution at 7. After cooling, filter, wash with ethanol, and dry to obtain nitrogen-phosphorus flame retardant.

[0037] (2) Add 60g of nitrogen-phosphorus flame retardant and 900mL of toluene to a flask, stir, add 6.8g of D,L lactide and 40mg of catalyst stannous octoate, heat to 110℃ in a nitrogen atmosphere, reflux for 30h, pour the solution into ethanol, filter, wash with ethanol, and vacuum dry at 70℃ to obtain polylactic acid flame retardant.

[0038] (3) Mix 350g of polylactic acid flame retardant, 1400g of polybutylene terephthalate-adipate and 600g of polylactic acid, add them to a twin-screw extruder, and set the temperatures of zones 1-11 to 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃ and 260℃ respectively. The screw speed is 160r / min. Blend, extrude and pelletize to obtain a flame-retardant biodegradable polyester material.

[0039] Example 4

[0040] This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, including the following steps:

[0041] (1) At 5℃, add 55mL of acetone, 30mL of water, 30g of cyanuric chloride and 10g of ethanolamine to a flask, and add dropwise a 20% sodium hydroxide aqueous solution to adjust the pH of the solution to 6.5. React for 4h, then add 18.9g of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, heat to 40℃, react for 1h, then add another 18.9g of N,N'-bis(2-aminoethyl)-phenylphosphine diamide, heat to 105℃, reflux for 15h. During the reaction, add dropwise a sodium hydroxide aqueous solution to maintain the pH of the solution at 6.5. After cooling, filter, wash with ethanol, and dry to obtain nitrogen-phosphorus flame retardant.

[0042] (2) Add 60g of nitrogen-phosphorus flame retardant and 850mL of toluene to a flask, stir, add 7g of D,L lactide and 35mg of catalyst stannous octoate, heat to 120℃ in a nitrogen atmosphere, reflux for 36h, pour the solution into ethanol, filter and wash with ethanol, and dry under vacuum at 80℃ to obtain polylactic acid flame retardant.

[0043] (3) Mix 500g of polylactic acid flame retardant, 1300g of polybutylene terephthalate and 700g of polyethylene glycol, add them to a twin-screw extruder, and set the temperatures of zones 1-11 to 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃ and 260℃ respectively. The screw speed is 200r / min. Blend, extrude and pelletize to obtain a flame-retardant biodegradable polyester material.

[0044] Comparative Example 1

[0045] This comparative example provides a method for preparing a biodegradable polyester material, including the following steps:

[0046] (1) Mix 1600g of polyethylene terephthalate and 400g of polylactic acid, add them to a twin-screw extruder, set the temperatures of zones 1-11 to 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃, and 260℃, and set the screw speed to 150r / min. Blend, extrude, and pelletize to obtain biodegradable polyester material.

[0047] Comparative Example 2

[0048] This comparative example provides a method for preparing a biodegradable polyester material, including the following steps:

[0049] (1) At 0℃, add 55mL of acetone, 30mL of water, 30g of cyanuric chloride and 10.2g of ethanolamine to a flask, and add 20% sodium hydroxide aqueous solution dropwise to adjust the pH of the solution to 6.5. React for 6h, then add 4.61g (76.86mmol) of ethylenediamine, heat to 50℃, react for 1h, add another 4.61g of ethylenediamine, heat to 110℃, reflux for 12h. During the reaction, add sodium hydroxide aqueous solution dropwise to maintain the pH of the solution at 6.5. After cooling, filter, wash with ethanol, and dry to obtain the flame retardant.

[0050] (2) Add 60g of flame retardant and 700mL of toluene to a flask, stir, add 3.6g of D,L lactide and 18mg of catalyst stannous octoate, heat to 115℃ in a nitrogen atmosphere, reflux for 24h, pour the solution into ethanol, filter, wash with ethanol, and dry under vacuum at 80℃ to obtain polylactic acid flame retardant.

[0051] (3) Mix 100g of polylactic acid flame retardant, 1600g of polyethylene terephthalate and 400g of polylactic acid, add them to a twin-screw extruder, and set the temperatures of zones 1-11 to 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃ and 260℃ respectively. The screw speed is 150r / min. Blend, extrude and pelletize to obtain biodegradable polyester material.

[0052] Comparative Example 3

[0053] This comparative example provides a method for preparing a biodegradable polyester material, including the following steps:

[0054] (1) Mix 100g of nitrogen-phosphorus flame retardant (prepared according to the method of Example 1), 1600g of polyethylene terephthalate and 400g of polylactic acid, and add them to a twin-screw extruder. The temperatures of zones 1-11 are 120℃, 145℃, 160℃, 175℃, 180℃, 180℃, 170℃, 220℃, 250℃, 260℃ and 260℃ respectively. The screw speed is 150r / min. Blend, extrude and pelletize to obtain biodegradable polyester material.

[0055] The biodegradable polyester materials prepared in the above examples and comparative examples were injection molded into strips using an injection molding machine, and their tensile properties were tested according to GB / T1040.1-2018 standard, as shown in Table 1.

[0056] The combustion performance of the material was tested using a cone calorimeter, with a thermal radiation power of 50 kW / m². 2 The sample size is 60mm × 60mm × 2mm.

[0057] Table 1 Performance Tests of Flame-Retardant Biodegradable Polyester Materials

[0058]

[0059] Compared with Comparative Example 1, Example 1 incorporated a polylactic acid-based flame retardant. The polylactic acid-based flame retardant molecule contains polylactic acid segments and a benzene ring structure. The polylactic acid segments have a high structural similarity to aliphatic polyesters such as polylactic acid, and the benzene ring structure forms a π-π conjugation effect with the aromatic ring structure of aromatic polyesters such as polyethylene terephthalate, which significantly enhances the interfacial bonding force with aromatic polyesters. This allows the polylactic acid-based flame retardant to act as a compatibilizer, improving the compatibility between aromatic polyesters and aliphatic polyesters, and significantly improving the mechanical properties of the polyester material. Meanwhile, the main chain of polylactic acid-based flame retardant contains a large number of phosphoramide and triazine groups, forming a nitrogen-phosphorus flame retardant system. In the early stage of combustion, phosphorus can promote the formation of a dense carbon layer on the surface of the composite material, effectively blocking the transfer of oxygen and heat to the interior of the material. When nitrogen is heated and decomposed, it releases inert gases such as nitrogen, which can not only dilute the concentration of combustible gases in the combustion zone, but also inhibit the continued combustion reaction by absorbing heat and cooling down. The two work together to improve the flame retardant performance of polyester materials, thereby reducing the peak heat release rate and the total heat release.

[0060] The flame retardant added in Comparative Example 2 does not contain a phosphoramide structure, resulting in poor flame retardant performance. Furthermore, it does not contain a benzene ring structure, leading to low interfacial bonding strength with aromatic polyesters. This makes it difficult to improve the compatibility between aromatic and aliphatic polyesters, resulting in low tensile strength and elongation at break of the polyester material.

[0061] The flame retardant in Comparative Example 3 did not have grafted polylactic acid molecular chains, resulting in very low compatibility with aliphatic polyesters. This made it difficult to improve the compatibility between aromatic polyesters and aliphatic polyesters, leading to lower tensile strength and elongation at break of the polyester material.

[0062] It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the invention. Furthermore, it should be understood that after reading the technical description of this invention, those skilled in the art can make various alterations, modifications, or variations to the invention, and all such equivalent forms also fall within the scope of protection defined by the appended claims.

Claims

1. A method for preparing a flame-retardant biodegradable polyester material, characterized in that, The method comprises the following steps: Step (1), at 0-5℃, add acetone, water, cyanuric chloride, ethanolamine into a flask, and drop sodium hydroxide aqueous solution to control the pH of the solution, react for 4-6h, then add N,N'-bis(2-aminoethyl)-phenyl phosphorodiamide, heat to 40-50℃, react for 1-2h, then add N,N'-bis(2-aminoethyl)-phenyl phosphorodiamide again, heat to 100-110℃, condense and reflux for 12-18h, drop sodium hydroxide aqueous solution to maintain the pH of the solution during the reaction, cool, filter, wash with ethanol, dry, and obtain the nitrogen-phosphorus flame retardant; Step (2), add the nitrogen-phosphorus flame retardant and toluene into a flask, stir, then add D,L lactide and catalyst stannous octoate, condense and reflux under nitrogen atmosphere, pour the solution into ethanol, filter, wash with ethanol, dry, and obtain the polylactic acid-based flame retardant; Step (3), mix the polylactic acid-based flame retardant, aromatic polyester and aliphatic polyester, add into a twin-screw extruder, blend, extrude, and pelletize to obtain the flame-retardant degradable polyester material; In step (2), the amount of the nitrogen-phosphorus flame retardant is 100 parts by weight, the amount of D,L lactide is 6-20 parts by weight, and the amount of catalyst stannous octoate is 0.03-0.1 parts by weight; In step (2), the condense and reflux temperature is 110-120℃, and the condense and reflux time is 24-36h; In step (1), the amount of cyanuric chloride is 100 parts by weight, the amount of ethanolamine is 33-34 parts by weight, and the amount of N,N'-bis(2-aminoethyl)-phenyl phosphorodiamide is 124-138 parts by weight.

2. The method for preparing a flame-retardant biodegradable polyester material according to claim 1, characterized in that, In step (1), the pH of the solution is controlled to 6.5-7, and the pH of the solution is maintained at 6.5-7.

3. The method for preparing a flame-retardant biodegradable polyester material according to claim 1, characterized in that, In step (3), the temperature of each zone of the twin-screw extruder is 120℃-260℃, and the screw rotation speed is 150-200r / min.

4. The method for preparing a flame-retardant biodegradable polyester material according to claim 1, characterized in that, In step (3), the amount of aromatic polyester is 65-80 parts by weight, the amount of aliphatic polyester is 20-35 parts by weight, and the amount of polylactic acid-based flame retardant is 5-25 parts by weight.

5. A process for the preparation of a flame retardant degradable polyester material as claimed in claim 4, wherein, The aromatic polyester is one of polyethylene terephthalate, polybutylene terephthalate, poly(butylene terephthalate-co-hexane adipate), or poly(butylene succinate-co-butylene terephthalate), and the aliphatic polyester is polyglycolide or polylactic acid.

6. A flame retardant degradable polyester material, characterized in that, Prepared according to the method of any one of claims 1-5.

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