Flame-retardant degradable polyester material and preparation method thereof

Abstract

The invention relates to the technical field of polyester materials, and discloses a flame-retardant degradable polyester material and a preparation method thereof.The polyester material is formed by blending 65-80 parts by weight of aromatic polyester, 20-35 parts by weight of aliphatic polyester and 5-25 parts by weight of a polylactic acid-based flame retardant, the aromatic polyester is selected from polyethylene glycol terephthalate and the like, the aliphatic polyester is selected from polyethylene glycol terephthalate and the like, and the polylactic acid-based flame retardant is selected from polyethylene glycol terephthalate and the like. The aliphatic polyester comprises degradable components such as polylactic acid. According to the polylactic acid-based flame retardant, the compatibility between aliphatic polyester such as polylactic acid and aromatic polyester such as polyethylene glycol terephthalate is improved, the polylactic acid-based flame retardant has better mechanical properties, meanwhile, a main chain contains a large number of phosphamide groups, a nitrogen-phosphorus flame-retardant system is formed, and the flame retardance of a polyester material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyester materials, in particular to a flame-retardant degradable polyester material and a preparation method. BACKGROUND

[0002] Degradable polyesters such as polylactic acid, polyethylene terephthalate PET, polybutylene adipate terephthalate PBAT, polybutylene succinate-co-terephthalate PBST, etc. have good mechanical strength, are widely sourced and environmentally friendly, and are an ideal substitute for traditional non-biodegradable plastics, which are particularly important in alleviating environmental crises and mitigating resource shortages. However, these polyester materials have poor flame retardant effect and are prone to burning, and the addition of flame retardants can improve their flame retardant properties.

[0003] There are many types of flame retardants, including halogen-based, inorganic-based, organic phosphorus-based, nitrogen-based, etc. Among them, nitrogen-containing phosphorus flame retardants have unique nitrogen-phosphorus synergistic action mechanism, which has shown significant advantages in polyester material flame retardant modification, and has become an ideal choice for current industry focus. Through molecular design, nitrogen and phosphorus groups can be chemically combined with polyester segments (such as copolymerization introduction), avoiding the problem of easy agglomeration of inorganic flame retardants affecting the mechanical properties of the material, so that the polyester material after adding the flame retardant can still maintain good mechanical properties such as tensile strength.

[0004] Chinese invention patent with publication number CN109206871B discloses a flame-retardant toughened biodegradable polylactic acid material and a preparation method thereof, which melts and blends polylactic acid, unsaturated polyester, flame retardant and synergistic flame retardant to obtain a flame-retardant polylactic acid material, but 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 composites. SUMMARY

[0005] (I) Technical problems to be solved: In view of the deficiencies of the prior art, the present application provides a flame-retardant degradable polyester material and a preparation method, which ensures that the degradable polyester material has flame retardancy, and solves the problem of poor compatibility between aliphatic polyesters such as polylactic acid and aromatic polyesters, thereby improving the mechanical properties of the degradable polyester material.

[0006] (II) Technical solutions: Based on the above analysis, the present application provides a method for preparing a flame-retardant degradable polyester material, comprising the following steps: Step (1), at 0-5°C, add acetone, water, 100 parts by weight of cyanuric chloride, 33-34 parts by weight of ethanolamine to a flask, and dropwise add an aqueous solution of sodium hydroxide, 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) -phenyl phosphoramide, heat to 40-50°C, react for 1-2 hours, then add 62-69 parts by weight of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, heat to 100-110°C, condense and reflux to react for 12-18 hours, during the reaction, dropwise add an aqueous solution of sodium hydroxide, maintain the pH of the solution at 6.5-7, filter after cooling, wash with ethanol, and dry to obtain a nitrogen-phosphorus flame retardant. The reaction formula is: .

[0007] Step (2): 100 parts by weight of nitrogen-phosphorus flame retardant and toluene are added to a flask, and after stirring, 6-20 parts by weight of D, L-lactide and 0.03-0.1 parts by weight of stannous octoate as a catalyst are added. In a nitrogen atmosphere, the mixture is condensed and refluxed to react. The solution is poured into ethanol, filtered, washed with ethanol, and dried to obtain a polylactic acid-based flame retardant.

[0008] Step (3): 5-25 parts by weight of a polylactic acid-based flame retardant, 65-80 parts by weight of an aromatic polyester, and 20-35 parts by weight of an aliphatic polyester are mixed, added into a twin-screw extruder, blended, extruded, and pelletized to obtain a flame-retardant biodegradable polyester material.

[0009] Furthermore, in step (2), the temperature of the condensation reflux reaction is 110-120° C., and the time of the condensation reflux reaction is 24-36 hours.

[0010] Furthermore, in step (3), the temperature of each zone of the twin-screw extruder is 120°C-260°C, and the speed of the screw is 150-200 r / min.

[0011] Furthermore, in step (3), the aromatic polyester is one of polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate-adipate or polybutylene succinate-co-butylene terephthalate.

[0012] Furthermore, in step (3), the aliphatic polyester is polyglycolide or polylactic acid.

[0013] The present invention also provides a flame-retardant degradable polyester material prepared by the above preparation method.

[0014] (3) Beneficial technical effects: The amino group of ethanolamine acts as a nucleophilic center to replace the chlorine atom on cyanuric chloride to generate a monosubstituted product containing an -NH-CH2CH2-OH group. The amino groups at both ends of N,N'-bis(2-aminoethyl)-phenylphosphoramide sequentially attack the chlorine atom on the ring of the monosubstituted product. The substitution reaction process is repeated to gradually extend the molecular chain and gradually polymerize to form a nitrogen-phosphorus flame retardant. The hydroxyl group on the nitrogen-phosphorus flame retardant triggers the reaction grafting of D,L-lactide to finally synthesize the polylactic acid-based flame retardant of the present invention.

[0015] The polylactic acid-based flame retardant of the present invention contains polylactic acid chain segments and benzene ring structures in its molecules, wherein the polylactic acid chain segments have a high structural similarity with aliphatic polyesters such as polylactic acid, and the benzene ring structure forms a π-π conjugation with the aromatic ring structure of aromatic polyesters such as polyethylene terephthalate, which significantly enhances the interfacial bonding force with the aromatic polyester, so that the polylactic acid-based flame retardant can act as a compatibilizer, improve the compatibility between aromatic polyesters and aliphatic polyesters, and significantly improve the mechanical properties of the polyester material.

[0016] The main chain of the polylactic acid-based flame retardant of the present invention contains a large number of phosphoramide and triazine groups, forming a nitrogen-phosphorus flame retardant system. The phosphorus element can promote the formation of a dense carbon layer on the surface of the composite material in the early stage of combustion, effectively blocking the transfer of oxygen and heat to the interior of the material; the nitrogen element releases inert gases such as nitrogen when decomposed by heat, which can not only dilute the concentration of combustible gases in the combustion area, but also inhibit the continued progress of the combustion reaction by absorbing heat and cooling. The two work together to improve the flame retardant properties of the polyester material, thereby reducing the peak heat release rate and the total heat release. DETAILED DESCRIPTION

[0017] The present invention will be further described below with reference to specific examples, but the scope of the present invention is not limited thereto. Where specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, they are conventional products that can be purchased commercially.

[0018] The preparation method of N,N'-bis(2-aminoethyl)-phenylphosphoramide is as follows: 126g of ethylenediamine and 400mL of chloroform are added to a flask, 200mL of a chloroform solution containing 117g of phenylphosphonyl dichloride is added dropwise at 0°C, the mixture is stirred for 6h, and then filtered. The filtrate is extracted with a saturated sodium bicarbonate solution. After separation, the chloroform organic layer is distilled under reduced pressure and dried to obtain N,N'-bis(2-aminoethyl)-phenylphosphoramide, the structural formula of which is .

[0019] Example 1 This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, comprising the following steps: (1) At 0°C, add 55 mL of acetone, 30 mL of water, 30 g of cyanuric chloride, and 10.2 g of ethanolamine to a flask, and dropwise add a 20% by mass aqueous solution of sodium hydroxide, adjust the pH of the solution to 6.5, and react for 6 h. Then add 18.6 g (about 76.86 mmol) of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, heat to 50°C, and react for 1 h. Then add 18.6 g of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, heat to 110°C, and condense and reflux for 12 h. During the reaction, dropwise add an aqueous solution of sodium hydroxide to maintain the pH of the solution at 6.5. After cooling, filter, wash with ethanol, and dry to obtain a nitrogen-phosphorus flame retardant.

[0020] (2) Add 60g of nitrogen-phosphorus flame retardant and 700mL of toluene into a flask, stir and then add 3.6g of D, L-lactide and 18mg of catalyst stannous octoate. In a nitrogen atmosphere, heat to 115℃, condense and reflux for 24h, pour the solution into ethanol, filter and wash with ethanol, and vacuum dry at 80℃ to obtain a polylactic acid-based flame retardant.

[0021] (3) Mix 100g of polylactic acid-based flame retardant, 1600g of polyethylene terephthalate, and 400g of polylactic acid, and add them to a twin-screw extruder. The temperatures in zones 1-11 are 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C, and 260°C. The screw speed is 150r / min. Blend, extrude, and pelletize to obtain a flame-retardant biodegradable polyester material.

[0022] Example 2 This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, comprising the following steps: (1) At 5°C, add 50 mL of acetone, 35 mL of water, 30 g of cyanuric chloride, and 9.9 g of ethanolamine to a flask, and dropwise add a 20% by mass aqueous solution of sodium hydroxide, adjust the pH of the solution to 7, and react for 6 h. Then add 20.7 g of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, raise the temperature to 40°C, and react for 2 h. Then add 20.7 g of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, raise the temperature to 100°C, and condense and reflux to react for 18 h. During the reaction, dropwise add an aqueous solution of sodium hydroxide to maintain the pH of the solution at 7. After cooling, filter, wash with ethanol, and dry to obtain a nitrogen-phosphorus flame retardant.

[0023] (2) Add 60g of nitrogen-phosphorus flame retardant and 800mL of toluene into a flask, stir and add 12g of D, L-lactide and 60mg of catalyst stannous octoate. In a nitrogen atmosphere, heat to 120℃, condense and reflux for 36h, pour the solution into ethanol, filter and wash with ethanol, and vacuum dry at 75℃ to obtain a polylactic acid-based flame retardant.

[0024] (3) Mix 200g of polylactic acid-based flame retardant, 1500g of polybutylene succinate-co-butylene terephthalate, and 500g of polyglycolide, and add them to a twin-screw extruder. The temperatures in zones 1-11 are 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C, and 260°C. The screw speed is 180r / min. Blend, extrude, and pelletize to obtain a flame-retardant biodegradable polyester material.

[0025] Example 3 This embodiment provides a method for preparing a flame-retardant biodegradable polyester material, comprising the following steps: (1) At 3°C, add 50 mL of acetone, 35 mL of water, 30 g of cyanuric chloride, and 10.1 g of ethanolamine to a flask, and dropwise add a 20% by mass sodium hydroxide aqueous solution, adjust the pH of the solution to 7, and react for 5 h. Then add 20 g of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, raise the temperature to 45°C, and react for 2 h. Then add 20 g of N, N'-bis (2-aminoethyl) -phenyl phosphoramide, raise the temperature to 100°C, and condense and reflux for 16 h. During the reaction, dropwise add a sodium hydroxide aqueous solution to maintain the pH of the solution at 7. After cooling, filter, wash with ethanol, and dry to obtain a nitrogen-phosphorus flame retardant.

[0026] (2) Add 60g of nitrogen-phosphorus flame retardant and 900mL of toluene into a flask, stir and then add 6.8g of D, L-lactide and 40mg of catalyst stannous octoate. In a nitrogen atmosphere, heat to 110℃, condense and reflux for 30h, pour the solution into ethanol, filter and wash with ethanol, and vacuum dry at 70℃ to obtain a polylactic acid-based flame retardant.

[0027] (3) Mix 350g of polylactic acid-based flame retardant, 1400g of polybutylene terephthalate-adipate, and 600g of polylactic acid, and add them to a twin-screw extruder. The temperatures in zones 1-11 are 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C, and 260°C. The screw speed is 160r / min. Blend, extrude, and pelletize to obtain a flame-retardant biodegradable polyester material.

[0028] Example 4 The embodiment provides a preparation method of a flame-retardant degradable polyester material, and comprises the following steps. (1) at 5°C, 55 mL of acetone, 30 mL of water, 30 g of cyanuric chloride, 10 g of ethanolamine, and 20% by mass of sodium hydroxide aqueous solution are added into a flask, the pH of the solution is controlled to be 6.5, and reaction is carried out for 4 h; then 18.9 g of N,N'-bis(2-aminoethyl)-phenyl phosphorodiamide is added, the temperature is increased to 40°C, reaction is carried out for 1 h, 18.9 g of N,N'-bis(2-aminoethyl)-phenyl phosphorodiamide is additionally added, the temperature is increased to 105°C, and condensation reflux reaction is carried out for 15 h; in the reaction process, the aqueous solution of sodium hydroxide is added dropwise, the pH of the solution is maintained to be 6.5, and after cooling, filtration, ethanol washing and drying are carried out, a nitrogen-phosphorus flame retardant is obtained.

[0029] (2) 60 g of the nitrogen-phosphorus flame retardant, 850 mL of toluene, 7 g of D,L-lactide and 35 mg of a catalyst stannous octoate are added into a flask, the temperature is increased to 120°C under a nitrogen atmosphere, and condensation reflux reaction is carried out for 36 h; the solution is poured into ethanol, filtration is carried out, ethanol washing is carried out, and vacuum drying is carried out at 80°C, so that a polylactic acid-based flame retardant is obtained.

[0030] (3) 500 g of the polylactic acid-based flame retardant, 1300 g of polybutylene terephthalate and 700 g of polyglycolide are mixed, and are added into a double-screw extruder; the temperature of 1-11 zones is 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C and 260°C; the rotating speed of the screw is 200 r / min; blending, extrusion and granulation are carried out, so that the flame-retardant degradable polyester material is obtained.

[0031] Comparative Example 1 The comparative example provides a preparation method of a degradable polyester material, and comprises the following steps: (1) 1600 g of polyethylene terephthalate and 400 g of polylactic acid are mixed, and are added into a double-screw extruder; the temperature of 1-11 zones is 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C and 260°C; the rotating speed of the screw is 150 r / min; blending, extrusion and granulation are carried out, so that the degradable polyester material is obtained.

[0032] Comparative Example 2 The comparative example provides a preparation method of a degradable polyester material, and comprises the following steps: (1) At 0°C, add 55 mL of acetone, 30 mL of water, 30 g of cyanuric chloride, and 10.2 g of ethanolamine to a flask, and dropwise add a 20% by mass fraction of sodium hydroxide aqueous solution, adjust the pH of the solution to 6.5, and react for 6 h. Then add 4.61 g (76.86 mmol) of ethylenediamine, raise the temperature to 50°C, and react for 1 h. Then add another 4.61 g of ethylenediamine, raise the temperature to 110°C, and condense and reflux to react for 12 h. During the reaction, dropwise add sodium hydroxide aqueous solution to maintain the pH of the solution at 6.5. After cooling, filter, wash with ethanol, and dry to obtain a flame retardant.

[0033] (2) Add 60 g of flame retardant and 700 mL of toluene into a flask, stir, add 3.6 g of D, L-lactide and 18 mg of catalyst stannous octoate, heat to 115 ° C in a nitrogen atmosphere, condense and reflux for 24 hours, pour the solution into ethanol, filter, wash with ethanol, and vacuum dry at 80 ° C to obtain a polylactic acid-based flame retardant.

[0034] (3) Mix 100g of polylactic acid-based flame retardant, 1600g of polyethylene terephthalate, and 400g of polylactic acid, and add them to a twin-screw extruder. The temperatures in zones 1-11 are 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C, and 260°C. The screw speed is 150r / min. Blend, extrude, and pelletize to obtain a biodegradable polyester material.

[0035] Comparative Example 3 This comparative example provides a method for preparing a degradable polyester material, comprising the following steps: (1) 100 g of nitrogen-phosphorus flame retardant (prepared according to the method of Example 1), 1600 g of polyethylene terephthalate, and 400 g of polylactic acid were mixed and added to a twin-screw extruder. The temperatures in zones 1-11 were 120°C, 145°C, 160°C, 175°C, 180°C, 180°C, 170°C, 220°C, 250°C, 260°C, and 260°C. The screw speed was 150 r / min. The mixture was blended, extruded, and pelletized to obtain a biodegradable polyester material.

[0036] The degradable polyester materials prepared in the above examples and comparative examples were injection molded into strips using an injection molding machine, and the tensile properties were tested according to GB / T1040.1-2018 standard, as shown in Table 1.

[0037] The combustion performance of the material was tested by cone calorimeter with a thermal radiation power of 50kW / m 2 The sample size is 60mm×60mm×2mm.

[0038] Table 1 Performance test of flame retardant biodegradable polyester materials

[0039] Compared with Comparative Example 1, Example 1 adds a polylactic acid-based flame retardant containing a polylactic acid segment and a benzene ring structure in the molecule, wherein the polylactic acid segment has high structural similarity with 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, significantly enhancing the interfacial bonding force with aromatic polyesters, so that the polylactic acid-based flame retardant can play the role of a compatibilizer, improving the compatibility between aromatic polyesters and aliphatic polyesters, and significantly improving the mechanical properties of the polyester material. At the same time, the main chain of the polylactic acid-based flame retardant contains a large number of phosphoramide and triazine groups, forming a nitrogen-phosphorus flame-retardant system. Phosphorus elements can promote the formation of a dense carbon layer on the surface of the composite material at the initial stage of combustion, effectively blocking the transfer of oxygen and heat to the inside of the material; nitrogen elements release inert gases such as nitrogen gas when heated, which not only dilutes the concentration of flammable gases in the combustion area, but also inhibits the continuation of the combustion reaction by absorbing heat and reducing temperature, both of which improve the flame retardant properties of the polyester material, thereby reducing the peak heat release rate and total heat release.

[0040] The flame retardant added in Comparative Example 2 does not contain a phosphoramide structure, has poor flame retardant properties, and does not contain a benzene ring structure, so the interfacial bonding force with aromatic polyesters is low, making it difficult to improve the compatibility between aromatic polyesters and aliphatic polyesters, resulting in low tensile strength and elongation at break of the polyester material.

[0041] The flame retardant of Comparative Example 3 does not have a grafted polylactic acid molecular chain, and has low compatibility with aliphatic polyesters, making it difficult to improve the compatibility between aromatic polyesters and aliphatic polyesters, resulting in low tensile strength and elongation at break of the polyester material.

[0042] It should be understood that the use of these examples is only for the purpose of illustrating the present application and is not intended to limit the scope of protection of the present application. In addition, it should also be understood that after reading the technical content of the present application, those skilled in the art can make various modifications, modifications or variations to the present application, and all these equivalent forms also fall within the scope of protection defined by the claims attached hereto.

Claims

1. A method for preparing a flame-retardant degradable polyester material, characterized in that: The following steps are involved: Step (1), adding acetone, water, cyanuric chloride, and ethanolamine to a flask at 0-5°C, and dropping an aqueous solution of sodium hydroxide, adjusting the pH of the solution, reacting for 4-6 hours, then adding N, N'-bis (2-aminoethyl) -phenyl phosphoramide, heating to 40-50°C, reacting for 1-2 hours, then adding N, N'-bis (2-aminoethyl) -phenyl phosphoramide, heating to 100-110°C, condensing and refluxing for 12-18 hours, adding an aqueous solution of sodium hydroxide during the reaction process, maintaining the pH of the solution, filtering after cooling, washing with ethanol, and drying to obtain a nitrogen-phosphorus flame retardant; Step (2), adding nitrogen-phosphorus flame retardant and toluene into a flask, stirring, adding D, L-lactide and catalyst stannous octoate, condensing and refluxing in a nitrogen atmosphere, pouring the solution into ethanol, filtering, washing with ethanol, and drying to obtain a polylactic acid-based flame retardant; Step (3): mixing the polylactic acid-based flame retardant, aromatic polyester, and aliphatic polyester, adding the mixture into a twin-screw extruder, blending, extruding, and pelletizing to obtain a flame-retardant biodegradable polyester material.

2. The method for preparing a flame-retardant degradable polyester material according to claim 1, characterized in that: In the step (1), the amount of cyanuric chloride used is 100 parts by weight, the amount of ethanolamine used is 33-34 parts by weight, and the amount of N,N'-bis(2-aminoethyl)-phenylphosphoramide used is 124-138 parts by weight.

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

4. The method for preparing a flame-retardant degradable polyester material according to claim 1, characterized in that: In the step (2), the amount of 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 stannous octoate catalyst is 0.03-0.1 parts by weight.

5. The method for preparing a flame-retardant degradable polyester material according to claim 1, characterized in that: The temperature of the condensation reflux reaction in step (2) is 110-120° C., and the time of the condensation reflux reaction is 24-36 hours.

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

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

8. The method for preparing a flame-retardant degradable polyester material according to claim 7, characterized in that: The aromatic polyester is one of polyethylene terephthalate, polybutylene terephthalate, polybutylene terephthalate-adipate or polybutylene succinate-co-terephthalate, and the aliphatic polyester is polyglycolide or polylactic acid.

9. A flame retardant degradable polyester material, characterized in that: The flame retardant degradable polyester material is prepared according to the method for preparing the flame retardant degradable polyester material according to any one of claims 1 to 8.

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