Microcrystalline ptt resin and method for preparing the same

Abstract

This invention discloses a microcrystalline PTT resin and its preparation method. The invention relates to the field of PTT resin technology and includes the following raw materials in weight percentages: 60-80 wt% PTT resin, 9-15 wt% toughening filler, 10-25 wt% flame-retardant filler, and 0.01-0.05 wt% antioxidant. This microcrystalline PTT resin and its preparation method, through the addition of toughening filler, allows the three-dimensional network structure formed to interpenetrate or connect with the molecular chains of the PTT resin, acting as a "bridge" to more tightly bind the PTT molecular chains together. This significantly improves the tensile strength and hardness of the PTT resin, enabling it to withstand greater external forces without deformation or breakage. Furthermore, the toughening filler introduces rigid groups such as cyano groups into the product. These rigid groups restrict the movement of the PTT molecular chains, increase the inter-chain forces, further improve the rigidity and hardness of the PTT resin, and enhance the overall strength of the material.

Description

Technical Field

[0001] This invention relates to the field of PTT resin technology, specifically to a microcrystalline PTT resin and its preparation method. Background Technology

[0002] Polypropylene terephthalate (PTT), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT) all belong to the semi-aromatic polyester family. Each unit of PTT contains three methylene groups, and the macromolecules produce a "strange carbon effect" to form a helical arrangement. This allows PTT polyester fibers to overcome the rigidity of PET and the flexibility of PBT at the same time, and combine the advantages of both PET and PA.

[0003] Chinese Patent Publication No. CN104861159A discloses a method for preparing flame-retardant PTT polyester resin, characterized by including (1) preparing a prepolymer liquid containing phosphorus flame retardant; (2) preparing a nano flame retardant dispersion; (3) esterification reaction; and (4) condensation reaction. After water cooling and pelletizing, a flame-retardant PTT polyester resin is obtained. The beneficial effect of this invention is that the PTT polyester resin prepared by the synergistic modification and in-situ polymerization of phosphorus flame retardant and nano flame retardant not only has excellent flame retardant properties, but also has good mechanical properties, thermal properties and electrical properties. At the same time, the preparation process of this invention is simple, the procedures are simple, easy to operate, and highly practical, making it easy to promote and apply. However, the toughness of the PTT resin prepared by the above-mentioned prior art solution needs to be further improved. Therefore, this invention provides a microcrystalline PTT resin and its preparation method to solve the above-mentioned problems. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a microcrystalline PTT resin and its preparation method, thus solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution: a microcrystalline PTT resin, comprising the following raw materials by weight percentage: 60-80 wt% PTT resin, 9-15 wt% toughening filler, 10-25 wt% flame retardant filler, and 0.01-0.05 wt% antioxidant;

[0006] The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate];

[0007] The method for preparing the flame-retardant filler is as follows:

[0008] Ⅰ. Pour 6-10g of halloysite nanotube powder into a mixed solution of 90-100mL of ethylene glycol and 4.5-6g of polyethylene glycol-400, and sonicate for 1.5-2h.

[0009] II. Add 1.5-2.25g of ferric chloride hexahydrate and 0.3-0.56g of zinc chloride, and stir to react for 20-30 minutes;

[0010] Ⅲ. After the reaction is complete, add 2% sodium hydroxide solution dropwise until the pH of the system is 7;

[0011] IV. Heat to 180-200℃ and react for 8-10 hours. Filter the product and wash it with distilled water and ethanol alternately 3-5 times. Then, dry it in a drying oven at 50-60℃ for 10-12 hours. Then, place it in a tube furnace and calcine it at 280-300℃ for 3-4 hours at a rate of 8-10℃ / min.

[0012] V. Add 15-20 mL of dimethyl methyl phosphate and acetone, and sonicate for 30-50 min;

[0013] VI. Reduce the vacuum to -1.0 kPa and maintain it for 50-60 min, then stir under normal pressure for 20-30 min, and repeat the operation 3-4 times.

[0014] VII. After washing with ethanol and centrifuging, place in a drying oven at 55-65℃ for 6-8 hours to obtain flame-retardant filler.

[0015] A method for preparing microcrystalline PTT resin specifically includes the following preparation steps:

[0016] Step 1: Mix 0.24-0.5g of tetrabutyl titanate with 45-48g of 1,3-propanediol and stir until evenly dispersed;

[0017] Step 2: Add 55-60g of terephthalic acid and heat to 220-240℃, and react for 2-4 hours under normal pressure.

[0018] Step 3: Add 0.18-0.35g of antimony trioxide, continue heating the reaction, and after the reaction is complete, cool to room temperature to obtain microcrystalline PTT resin.

[0019] Preferably, the preparation method of the microcrystalline PTT resin further includes: adding toughening filler, flame retardant filler and antioxidant to the PTT resin, and extruding it into filaments through an extruder at an extrusion temperature of 190-210℃, and then cutting the extruded filaments into granules after cooling.

[0020] Preferably, in step three, the temperature is first raised to 220-240℃ and reacted for 30-45 minutes, at which point the vacuum degree is 60-80 kPa; then the temperature is raised to 260-270℃ and reacted for 3-3.5 hours, at which point the vacuum degree is 90-100 kPa.

[0021] Preferably, the toughening filler is prepared by:

[0022] S1. Under a nitrogen atmosphere, add 12-15g of tung oil acid, 10-15g of methyl tungate, 14-20g of acrylonitrile and 0.35-0.5g of potassium oleate to 80-100g of deionized water, heat the mixture in a water bath to 60-70℃, and react for 45-60min to obtain mixture A.

[0023] S2. Dissolve 0.25-0.4g of ammonium persulfate completely in 20mL of deionized water to prepare mixture B;

[0024] S3. Slowly add mixture B to mixture A and react for 8-10 hours;

[0025] S4. Add 6.5-10g of sodium chloride. After the reaction is complete, wash the reaction product 4-5 times with deionized water at 80-90℃, and then dry it in a vacuum oven at 65-75℃ until constant weight to obtain the toughening filler.

[0026] Preferably, the specific preparation method of the tung oil acid is as follows: 45-60g of tung oil is mixed evenly with 180-210mL of sodium hydroxide solution, the mixture is heated in a water bath to 70-80℃, and reacted for 2-3 hours. Then, 55-70mL of 5% hydrochloric acid is added, the reaction solution is poured into a separatory funnel and allowed to stand for separation. The upper layer product is taken and washed with deionized water until its pH is neutral. Then, it is rotary evaporated at a temperature of 70-80℃ to obtain tung oil acid.

[0027] Preferably, the sodium hydroxide solution is prepared by: pouring 12-17g of sodium hydroxide into a mixed solution of 200mL of ethanol and deionized water until completely dissolved; wherein the volume ratio of ethanol to deionized water is 1:1.

[0028] Preferably, the specific preparation method of the methyl tung oil is as follows: 15-20g of tung oil, 0.3-0.55g of methanol and 0.02-0.03g of potassium hydroxide are mixed, heated in a water bath to 65-75℃, and reacted for 1-1.5h. The reaction solution is poured into a separatory funnel and allowed to stand for separation. The upper liquid is taken and washed successively with sodium chloride aqueous solution and deionized water until its pH is neutral. Then, it is rotary evaporated at a temperature of 70-80℃ to obtain methyl tung oil.

[0029] Beneficial effects

[0030] This invention provides a microcrystalline PTT resin and its preparation method. Compared with the prior art, it has the following advantages:

[0031] (1) The microcrystalline PTT resin and its preparation method, through the addition of toughening fillers, enable the three-dimensional network structure formed by it to penetrate or connect with the molecular chains of PTT resin, playing a role similar to a "bridge", which makes the PTT molecular chains more tightly bonded together, thereby significantly improving the tensile strength and hardness of PTT resin, enabling it to withstand greater external forces without deformation or breakage. In addition, the toughening fillers introduce rigid groups such as cyano groups into the product. These rigid groups can restrict the movement of PTT molecular chains, increase the interaction force between molecular chains, further improve the rigidity and hardness of PTT resin, and enhance the overall strength of the material. Tung oil acid and methyl tung acid have long-chain fatty acid structures. After the reaction, their long carbon chain flexible segments will be inserted between the PTT resin molecular chains, increasing the flexibility and activity space of the molecular chains. When PTT resin is subjected to external impact, the molecular chains can absorb energy through relative sliding and deformation, thereby improving the toughness and impact resistance of the material and reducing brittleness.

[0032] (2) The microcrystalline PTT resin and its preparation method, by adding flame-retardant fillers, can play a nano-reinforcing role in PTT resin, hindering the slippage of PTT molecular chains, thereby improving the tensile strength, elastic modulus and other mechanical properties of PTT resin; and the flame-retardant fillers can be inserted between PTT molecular chains, increasing the flexibility and activity space of the molecular chains, so that when PTT resin is subjected to external impact, the molecular chains can absorb energy through relative sliding and deformation, thereby improving the toughness of the material and reducing brittleness; when PTT resin burns, the flame-retardant fillers can catalyze the dehydration and carbonization reaction of PTT molecular chains, promote the formation of a dense char layer, the char layer can cover the surface of the material, play a role in isolating oxygen and heat, preventing the spread of flame, reducing the burning rate, improving flame retardant performance, and at the same time can also play a physical barrier role, slowing down the burning speed, buying more time for the flame retardant process, and improving flame retardant performance.

[0033] (3) The microcrystalline PTT resin and its preparation method, in the process of preparing PTT resin, by staged heating and controlling the vacuum degree of the reaction, the reaction is made more stable and orderly, which is conducive to improving the quality and stability of the product, reducing the color change and impurity content of the product, and at the same time, it can more effectively extract small molecules such as water in the system, reduce the concentration of small molecules in the reaction system, reduce the probability of side reactions, ensure product quality, make the molecular structure of PTT resin more regular, and improve the crystallization performance, thereby improving the comprehensive performance of the product such as thermal stability and mechanical properties. Attached Figure Description

[0034] Figure 1 RT-IR images of halloysite nanotubes and flame-retardant fillers provided for this invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0036] In this technical solution, the sodium hydroxide solution is prepared by adding 15g of sodium hydroxide to a 200mL mixture of ethanol and deionized water until it is completely dissolved; wherein the volume ratio of ethanol to deionized water is 1:1.

[0037] Example 1

[0038] A method for preparing microcrystalline PTT resin specifically includes the following preparation steps:

[0039] Step 1: Mix 0.24g of tetrabutyl titanate with 45g of 1,3-propanediol and stir until evenly dispersed;

[0040] Step 2: Add 55g of terephthalic acid and heat to 220℃, and react for 2 hours under normal pressure.

[0041] Step 3: Add 0.18g of antimony trioxide, first heat to 220℃ and react for 30min, at which point the vacuum degree is 60kPa; then heat to 260℃ and react for 3h, at which point the vacuum degree is 90kPa. After the reaction is complete, cool to room temperature to obtain PTT resin.

[0042] Step 4: Add 14.95 wt% toughening filler, 25 wt% flame retardant filler, and 0.05 wt% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] to 60 wt% PTT resin, and extrude it into filaments at an extrusion temperature of 190°C. After cooling, cut the extruded filaments into granules.

[0043] The preparation method of the flame-retardant filler is as follows: 6g of halloysite nanotube powder is poured into a mixed solution of 90mL of ethylene glycol and 4.5g of polyethylene glycol-400, and ultrasonically treated for 1.5h; 1.5g of ferric chloride hexahydrate and 0.3g of zinc chloride are added, and the mixture is stirred for 20min; after the reaction is complete, 2% sodium hydroxide solution is added dropwise until the pH of the system is 7; the temperature is raised to 180℃, and the reaction is carried out for 8h. After filtration, the product is washed three times alternately with distilled water and ethanol, and then dried in a drying oven at 50℃ for 10h. Then, it is placed in a tube furnace and calcined at 280℃ for 3h at a rate of 8℃ / min; 15mL of dimethyl phosphate and acetone are added, and the mixture is ultrasonically treated for 30min; the vacuum degree is reduced to -1.0kPa and maintained for 50min, and then stirred under normal pressure for 20min. This cycle is repeated three times; the product is washed with ethanol, centrifuged, and then dried in a drying oven at 55℃ for 6h to obtain the flame-retardant filler.

[0044] The preparation method of the toughening filler is as follows:

[0045] (1) The specific preparation method of tung oil acid is as follows: 45g of tung oil is mixed with 180mL of sodium hydroxide solution, heated in a water bath to 70℃, reacted for 2h, then 55mL of 5% hydrochloric acid is added, the reaction solution is poured into a separatory funnel and allowed to stand for separation, the upper layer product is taken, and washed with deionized water until its pH is neutral, and then evaporated by rotary evaporation at 70℃ to obtain tung oil acid;

[0046] (2) The specific preparation method of methyl tung oil is as follows: 15g of tung oil, 0.3g of methanol and 0.02g of potassium hydroxide are mixed, heated to 65℃ in a water bath and reacted for 1h. The reaction solution is poured into a separatory funnel and allowed to stand for separation. The upper liquid is taken and washed with sodium chloride aqueous solution and deionized water in turn until its pH is neutral. Then it is evaporated by rotary evaporation at 70℃ to obtain methyl tung oil.

[0047] (3) Under nitrogen atmosphere protection, 12g of tung oil acid, 10g of methyl tung oil, 14g of acrylonitrile and 0.35g of potassium oleate were poured into 80g of deionized water, the water bath temperature was raised to 60℃ and the reaction was carried out for 45min to obtain mixture A; 0.25g of ammonium persulfate was completely dissolved in 20mL of deionized water to obtain mixture B; mixture B was slowly added to mixture A and the reaction was carried out for 8h; 6.5g of sodium chloride was added, and after the reaction was completed, the reaction product was washed 4 times with deionized water at 80℃, and then placed in a vacuum oven at 65℃ to dry to constant weight to obtain toughening filler.

[0048] Example 2

[0049] A method for preparing microcrystalline PTT resin specifically includes the following preparation steps:

[0050] Step 1: Mix 0.35g of tetrabutyl titanate with 46g of 1,3-propanediol and stir until evenly dispersed.

[0051] Step 2: Add 58g of terephthalic acid and heat to 230℃, and react for 3 hours under normal pressure.

[0052] Step 3: Add 0.22g of antimony trioxide, first heat to 230℃ and react for 35min, at which point the vacuum degree is 70kPa; then heat to 265℃ and react for 3.2h, at which point the vacuum degree is 95kPa. After the reaction is complete, cool to room temperature to obtain PTT resin.

[0053] Step 4: Add 12.98 wt% toughening filler, 17 wt% flame retardant filler, and 0.02 wt% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid] to 70 wt% PTT resin, and extrude it into filaments at an extrusion temperature of 200°C. After cooling, cut the extruded filaments into granules.

[0054] The preparation method of the flame-retardant filler is as follows: 8g of halloysite nanotube powder is poured into a mixed solution of 95mL ethylene glycol and 5g of polyethylene glycol-400, and ultrasonically treated for 1.8h; 2g of ferric chloride hexahydrate and 0.45g of zinc chloride are added, and the mixture is stirred for 25min; after the reaction is complete, 2% sodium hydroxide solution is added dropwise until the pH of the system is 7; the temperature is raised to 190℃, and the reaction is carried out for 9h. After filtration, the product is washed 4 times alternately with distilled water and ethanol, and then dried in a drying oven at 55℃ for 11h. Then, it is placed in a tube furnace and calcined at 290℃ for 4h at a rate of 9℃ / min; 18mL of dimethyl phosphate and acetone are added, and the mixture is ultrasonically treated for 40min; the vacuum degree is reduced to -1.0kPa and maintained for 55min, and then stirred under normal pressure for 25min. This cycle is repeated 4 times; after washing with ethanol, the mixture is centrifuged and then dried in a drying oven at 60℃ for 7h to obtain the flame-retardant filler.

[0055] The preparation method of the toughening filler is as follows:

[0056] (1) The specific preparation method of tung oil acid is as follows: 50g of tung oil is mixed with 200mL of sodium hydroxide solution, heated in a water bath to 75℃, reacted for 2.5h, then 60mL of 5% hydrochloric acid is added, the reaction solution is poured into a separatory funnel and allowed to stand for separation, the upper layer product is taken, and washed with deionized water until its pH is neutral, and then evaporated by rotary evaporation at 75℃ to obtain tung oil acid;

[0057] (2) The specific preparation method of methyl tung oil is as follows: 18g of tung oil, 0.45g of methanol and 0.03g of potassium hydroxide are mixed, heated to 70℃ in a water bath, and reacted for 1.2h. The reaction solution is poured into a separatory funnel and allowed to stand for separation. The upper liquid is taken and washed with sodium chloride aqueous solution and deionized water in sequence until its pH is neutral. Then, it is evaporated by rotary evaporation at 75℃ to obtain methyl tung oil.

[0058] (3) Under nitrogen atmosphere protection, 13g of tung oil acid, 14g of methyl tung oil, 17g of acrylonitrile and 0.45g of potassium oleate were poured into 90g of deionized water, the water bath temperature was raised to 65℃ and the reaction was carried out for 50min to obtain mixture A; 0.3g of ammonium persulfate was completely dissolved in 20mL of deionized water to obtain mixture B; mixture B was slowly added to mixture A and the reaction was carried out for 9h; 8.5g of sodium chloride was added, and after the reaction was completed, the reaction product was washed 5 times with deionized water at 85℃, and then dried in a vacuum oven at 70℃ to constant weight to obtain toughening filler.

[0059] Example 3

[0060] A method for preparing microcrystalline PTT resin specifically includes the following preparation steps:

[0061] Step 1: Mix 0.5g of tetrabutyl titanate with 48g of 1,3-propanediol and stir until evenly dispersed.

[0062] Step 2: Add 60g of terephthalic acid and heat to 240℃, and react for 4 hours under normal pressure.

[0063] Step 3: Add 0.35g of antimony trioxide, first heat to 240℃ and react for 45min, at which point the vacuum degree is 80kPa; then heat to 270℃ and react for 3.5h, at which point the vacuum degree is 100kPa. After the reaction is complete, cool to room temperature to obtain PTT resin.

[0064] Step 4: Add 9.95 wt% toughening filler, 10 wt% flame retardant filler, and 0.05 wt% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] to 80 wt% PTT resin, and extrude it into filaments at an extrusion temperature of 210°C. After cooling, cut the extruded filaments into granules.

[0065] The preparation method of the flame-retardant filler is as follows: 10g of halloysite nanotube powder is poured into a mixed solution of 100mL of ethylene glycol and 6g of polyethylene glycol-400, and ultrasonically treated for 2h; 2.25g of ferric chloride hexahydrate and 0.56g of zinc chloride are added, and the mixture is stirred for 30min; after the reaction is complete, 2% sodium hydroxide solution is added dropwise until the pH of the system is 7; the temperature is raised to 200℃, and the reaction is carried out for 10h. After filtration, the product is washed 5 times alternately with distilled water and ethanol, and then dried in a drying oven at 60℃ for 12h. Then, it is placed in a tube furnace and calcined at 300℃ for 4h at a rate of 10℃ / min; 20mL of dimethyl phosphate and acetone are added, and the mixture is ultrasonically treated for 50min; the vacuum degree is reduced to -1.0kPa and maintained for 60min, and then stirred under normal pressure for 30min. This cycle is repeated 4 times; after washing with ethanol, the mixture is centrifuged and then dried in a drying oven at 65℃ for 8h to obtain the flame-retardant filler.

[0066] The preparation method of the toughening filler is as follows:

[0067] (1) The specific preparation method of tung oil acid is as follows: 60g of tung oil is mixed with 210mL of sodium hydroxide solution, heated in a water bath to 80℃, reacted for 3h, then 70mL of 5% hydrochloric acid is added, the reaction solution is poured into a separatory funnel and allowed to stand for separation, the upper layer product is taken, and washed with deionized water until its pH is neutral, and then evaporated by rotary evaporation at 80℃ to obtain tung oil acid;

[0068] (2) The specific preparation method of methyl tung oil is as follows: 20g of tung oil, 0.55g of methanol and 0.03g of potassium hydroxide are mixed, heated to 75°C in a water bath, and reacted for 1.5h. The reaction solution is poured into a separatory funnel and allowed to stand for separation. The upper liquid is taken and washed with sodium chloride aqueous solution and deionized water in sequence until its pH is neutral. Then, it is evaporated by rotary evaporation at 80°C to obtain methyl tung oil.

[0069] (3) Under nitrogen atmosphere protection, 15g of tung oil acid, 15g of methyl tungate, 20g of acrylonitrile and 0.5g of potassium oleate were poured into 100g of deionized water, the water bath temperature was raised to 70℃, and the reaction was carried out for 60min to obtain mixture A; 0.4g of ammonium persulfate was completely dissolved in 20mL of deionized water to obtain mixture B; mixture B was slowly added to mixture A and the reaction was carried out for 10h; 10g of sodium chloride was added, and after the reaction was completed, the reaction product was washed 5 times with deionized water at 90℃, and then dried in a vacuum oven at 75℃ to constant weight to obtain toughening filler.

[0070] Comparative Example 1

[0071] Compared with Example 1, the difference is that no toughening filler is added; everything else remains the same.

[0072] Comparative Example 2

[0073] Compared with Example 1, the difference is that no flame-retardant filler is added; everything else remains the same.

[0074] Comparative Example 3

[0075] Compared with Example 1, the difference is that step 3 is replaced by: adding 0.18g of antimony trioxide, heating to 260°C, reacting at normal pressure for 3 hours, and cooling to room temperature after the reaction is completed.

[0076] Performance testing:

[0077] Limiting oxygen index (LOI): The test was conducted using a J-3 oxygen index tester with a sample size of 80 mm × 10 mm × 3 mm. The results are shown in Table 1.

[0078] Impact strength test: The test was conducted using a drop hammer impact tester, and the sample size was 80mm×5mm×3mm; the results are shown in Table 1.

[0079] Tensile properties: The test was conducted using a universal testing machine with a sample size of 75mm × 5mm × 2mm; the results are shown in Table 1.

[0080] Table 1

[0081] LOT (%) <![CDATA[Impact strength (KJ / m 2 )]]> Tensile strength (MPa) Example 1 29.3 28.33 71.54 Example 2 28.9 27.97 70.32 Example 3 28.7 27.05 68.95 Comparative Example 1 28.2 19.67 57.38 Comparative Example 2 23.1 20.35 58.43 Comparative Example 3 28.5 24.55 64.83

[0082] like Figure 1 As shown, halloysite nanotubes at 3627 cm⁻¹ -1 and 3695cm -1 The characteristic peaks that appeared were caused by hydroxyl groups inside and between halloysite nanotubes, respectively. The FT-IR spectrum of the flame retardant filler not only showed strong characteristic peaks of halloysite nanotubes, but also some weaker new peaks, which is due to the adsorption of dimethyl methyl phosphate on the outside of halloysite nanotubes.

[0083] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0084] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A microcrystalline PTT resin, characterized in that, The raw materials include the following weight percentages: PTT resin 60-80wt%, toughening filler 9-15wt%, flame retardant filler 10-25wt%, and antioxidant 0.01-0.05wt%. The antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; The method for preparing the flame-retardant filler is as follows: Ⅰ. Pour 6-10g of halloysite nanotube powder into a mixed solution of 90-100mL of ethylene glycol and 4.5-6g of polyethylene glycol-400, and sonicate for 1.5-2h. II. Add 1.5-2.25g of ferric chloride hexahydrate and 0.3-0.56g of zinc chloride, and stir to react for 20-30 minutes; Ⅲ. After the reaction is complete, add 2% sodium hydroxide solution dropwise until the pH of the system is 7; IV. Heat to 180-200℃ and react for 8-10 hours. Filter the product and wash it with distilled water and ethanol alternately 3-5 times. Then, dry it in a drying oven at 50-60℃ for 10-12 hours. Then, place it in a tube furnace and calcine it at 280-300℃ for 3-4 hours at a rate of 8-10℃ / min. V. Add 15-20 mL of dimethyl methyl phosphate and acetone, and sonicate for 30-50 min; VI. Reduce the vacuum to -1.0 kPa and maintain it for 50-60 min, then stir under normal pressure for 20-30 min, and repeat the operation 3-4 times. VII. After washing with ethanol and centrifuging, place in a drying oven at 55-65℃ for 6-8 hours to obtain flame-retardant filler.

2. A method for preparing microcrystalline PTT resin according to claim 1, characterized in that, Specifically, the preparation steps include the following: Step 1: Mix 0.24-0.5g of tetrabutyl titanate with 45-48g of 1,3-propanediol and stir until evenly dispersed; Step 2: Add 55-60g of terephthalic acid and heat to 220-240℃, and react for 2-4 hours under normal pressure. Step 3: Add 0.18-0.35g of antimony trioxide, continue heating the reaction, and after the reaction is complete, cool to room temperature to obtain PTT resin; The preparation method of the microcrystalline PTT resin also includes: adding toughening filler, flame retardant filler and antioxidant to the PTT resin, and extruding it into filaments through an extruder at an extrusion temperature of 190-210℃, and then cutting the extruded filaments into granules after cooling.

3. The method for preparing a microcrystalline PTT resin according to claim 2, characterized in that: In step three, the temperature is first raised to 220-240℃ and reacted for 30-45 minutes, at which point the vacuum degree is 60-80 kPa; then the temperature is raised to 260-270℃ and reacted for 3-3.5 hours, at which point the vacuum degree is 90-100 kPa.

4. The method for preparing a microcrystalline PTT resin according to claim 2, characterized in that: The toughening filler is prepared by: S1. Under a nitrogen atmosphere, add 12-15g of tung oil acid, 10-15g of methyl tungate, 14-20g of acrylonitrile and 0.35-0.5g of potassium oleate to 80-100g of deionized water, heat the mixture in a water bath to 60-70℃, and react for 45-60min to obtain mixture A. S2. Dissolve 0.25-0.4g of ammonium persulfate completely in 20mL of deionized water to prepare mixture B; S3. Slowly add mixture B to mixture A and react for 8-10 hours; S4. Add 6.5-10g of sodium chloride. After the reaction is complete, wash the reaction product 4-5 times with deionized water at 80-90℃, and then dry it in a vacuum oven at 65-75℃ until constant weight to obtain the toughening filler.

5. The method for preparing a microcrystalline PTT resin according to claim 4, characterized in that: The specific preparation method of the tung oil acid is as follows: 45-60g of tung oil is mixed evenly with 180-210mL of sodium hydroxide solution, and the mixture is heated in a water bath to 70-80℃ and reacted for 2-3 hours. Then, 55-70mL of 5% hydrochloric acid is added, and the reaction solution is poured into a separatory funnel and allowed to stand for separation. The upper layer product is taken and washed with deionized water until its pH is neutral. Then, it is rotary evaporated at a temperature of 70-80℃ to obtain tung oil acid.

6. The method for preparing a microcrystalline PTT resin according to claim 5, characterized in that: The sodium hydroxide solution is prepared by adding 12-17g of sodium hydroxide to a 200mL mixture of ethanol and deionized water until it is completely dissolved; wherein the volume ratio of ethanol to deionized water is 1:

1.

7. The method for preparing a microcrystalline PTT resin according to claim 4, characterized in that: The specific preparation method of the methyl tung oil is as follows: 15-20g of tung oil, 0.3-0.55g of methanol and 0.02-0.03g of potassium hydroxide are mixed and heated in a water bath to 65-75℃ for 1-1.5h. After the reaction solution is poured into a separatory funnel and allowed to stand for separation, the upper liquid is taken and washed successively with sodium chloride aqueous solution and deionized water until its pH is neutral. Then, it is rotary evaporated at a temperature of 70-80℃ to obtain methyl tung oil.

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