Preparation method of flame-retardant polyester-containing plastic particles

Abstract

The invention discloses a preparation method of flame-retardant polyester-containing plastic particles, and relates to the technical field of plastic particles. The modified flame retardant is tightly combined with secondary amine groups in polyester, so that the hydrolysis resistance and mechanical strength of the plastic are improved. According to the modified flame retardant, chlorine groups of vinylphosphonic acid bis (2-chloroethyl ester) and hydroxyl groups of m-hydroxybenzoic acid protected by ester groups react under the low-temperature condition, plastic particles can be promoted to be dehydrated into carbon in the presence of phosphate groups, continuous proceeding of a chain reaction during plastic combustion is prevented, the flame retardant performance is preliminarily achieved, an aromatized structure is assisted, and the flame retardant performance is improved. The formation of a low-permeability and high-continuity carbon layer is promoted, the transmission of combustible gas and heat is prevented, and the flame-retardant effect is further enhanced; after ester groups are removed from carboxyl, the carboxyl reacts with 2, 6-dihydroxytoluene to be combined to form a benzophenone structure, the anti-ultraviolet effect is achieved, the methyl is matched, the crystallization rate of plastic particles is increased, a more compact stacking structure is formed, and therefore the mechanical strength of the plastic particles is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of plastic particles, in particular to a method for preparing flame-retardant polyester-containing plastic particles. Background Art

[0002] Polyester materials are widely used in the plastics industry. However, polyester materials have some performance deficiencies in actual use. On the one hand, polyester easily hydrolyzes in humid environments, and after absorbing water, its performance deteriorates, affecting the material's service life and stability, which limits its application in some high-humidity environments. On the other hand, the mechanical strength of ordinary polyester materials cannot meet the requirements of certain applications with high strength requirements and needs to be further improved. In addition, polyester materials are generally flammable, which is a major safety hazard in many applications. During the combustion process, plastics easily trigger chain reactions, causing fires to spread rapidly, while also generating large amounts of heat and toxic gases, posing a serious threat to life and property safety. Moreover, polyester materials are prone to photoaging when exposed to ultraviolet light for a long time, which deteriorates the material's physical and chemical properties, further affecting its performance and appearance.

[0003] In order to improve these performance defects of polyester, a lot of research has been conducted in the existing technology. In terms of flame retardancy, some methods involve adding traditional flame retardants, but there are problems such as unsatisfactory flame retardancy and poor compatibility with polyester, which may affect the mechanical properties and processing performance of the material. In terms of improving hydrolysis resistance and mechanical properties, more effective methods are also needed to ensure the stability and strength of the material in complex environments. In terms of UV resistance, although there are some anti-UV additives, they often cannot simultaneously improve other properties, such as mechanical strength. Therefore, there is an urgent need for a new technical solution to comprehensively solve the performance problems of polyester materials in terms of hydrolysis resistance, mechanical strength, flame retardancy and UV resistance. Summary of the Invention

[0004] The object of the present invention is to provide a method for preparing flame retardant polyester-containing plastic particles to solve the problems existing in the prior art.

[0005] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing flame-retardant polyester-containing plastic particles, comprising the following preparation steps:

[0006] (1) Under nitrogen protection, 5-9 parts of esterified m-hydroxybenzoic acid, 30-54 parts of dimethylformamide, and 2-4 parts of triethylamine were mixed uniformly, cooled to -5-5°C, and 6-12 parts of vinylphosphonic acid bis(2-chloroethyl)-dimethylformamide solution were added dropwise at a rate of 0.5 drops / s. The mixture was stirred at 80 rpm for 4-8 hours to obtain a reaction solution, which was post-treated to obtain a composite agent;

[0007] (2) 4 to 8 parts of the composite agent, 7 to 14 parts of aluminum chloride, and 32 to 64 parts of dichloromethane were mixed uniformly, and 3.5 to 7.5 parts of 2,6-dihydroxytoluene were added under stirring at -5-5°C and 120 rpm, and the mixture was reacted for 3 to 5 hours to obtain a reaction solution, which was crystallized and dried in an oven at 20 to 30°C for 12 to 16 hours to obtain a modified flame retardant;

[0008] (3) 13 to 21 parts of a modified flame retardant, 35 to 58 parts of a polyester, and 2 to 6 parts of diphenylphosphoric acid were mixed uniformly, stirred at 160 rpm and 80 to 100° C. for 6 to 10 hours, the solid was collected, washed three times with deionized water, and dried in an oven at 40 to 50° C. for 12 to 16 hours to obtain a modified polyester;

[0009] (4) 55 to 85 parts of modified polyester, 5 to 9 parts of titanium dioxide, and 1 to 3 parts of plasticizer are extruded and pelletized through an extruder, and cooled to obtain flame-retardant polyester-containing plastic particles.

[0010] Furthermore, the preparation step of the esterified m-hydroxybenzoic acid in step (1) is as follows: 5 to 15 parts of m-hydroxybenzoic acid and 40 to 120 parts of methanol are uniformly mixed, 0.05 to 0.25 parts of 98 wt% concentrated sulfuric acid are added dropwise at a rate of 1 drop / s, the temperature is raised to 60 to 70°C, and the mixture is stirred at 80 rpm for 3 to 5 hours to obtain a reaction solution, which is then post-treated to obtain esterified m-hydroxybenzoic acid.

[0011] Furthermore, the post-treatment step is: transferring the reaction solution to a separatory funnel, washing with 10 parts of a saturated sodium carbonate aqueous solution, separating the organic phase, repeating 3 times, drying with 2 parts of anhydrous magnesium sulfate for 2 to 4 minutes, and concentrating at a vacuum degree of -0.08 MPa and 33°C for 1 to 3 hours.

[0012] Furthermore, the content of bis(2-chloroethyl)vinylphosphonate) in the bis(2-chloroethyl)vinylphosphonate-dimethylformamide solution in step (1) is 20 wt%.

[0013] Furthermore, the post-treatment step of step (1) is as follows: heating the reaction solution to 20-30° C., adjusting the pH of the solution to 7-7.5 with a 2 mol / L sodium hydroxide aqueous solution, separating the liquid, removing the lower organic phase, adding 30-54 parts of water and 50-90 parts of ethyl acetate, extracting, removing the upper organic phase, drying it over 2 parts of anhydrous magnesium sulfate for 2-4 minutes, and concentrating it at a vacuum degree of -0.1 MPa and 35° C. for 1-3 hours.

[0014] Furthermore, the crystallization step in step (2) is as follows: the reaction solution is added dropwise to 15 to 25 parts of methanol at a rate of 5 mL / min, stirred at 150 rpm for 30 to 40 minutes, the solid is filtered out, and washed with methanol three times.

[0015] Furthermore, the preparation step of the polyester in step (3) is as follows: under nitrogen protection, 8 to 14 parts of hydrogenated bisphenol A and 10 to 16 parts of iminodiacetic acid are uniformly mixed, and polycondensed at 130 to 190° C. for 10 to 14 hours to obtain a polyester with a molecular weight of 3500 to 5500.

[0016] Furthermore, the plasticizer in step (3) is any one of tributyl acetyl citrate, tetrabutyl pyromellitate, and dibutyl phthalate.

[0017] Furthermore, the parameters of the extruder in step (3) are head temperature 245-265°C, screw speed 195-215 r / min, extrusion pressure 20-26 MPa, shear rate 220-240 s -1 .

[0018] Furthermore, the cooling conditions in step (3) are cooling air temperature of 14-18° C., wind speed of 0.7-1.1 m / s, wind pressure of 400-600 Pa, and cooling time of 15-25 min.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] The present invention combines a modified flame retardant with polyester. The unsaturated double bonds in the flame retardant can be tightly combined with the secondary amine groups in the polyester. With the assistance of the hydrophobic groups in the modified flame retardant molecular chain, the hydrolysis resistance of the plastic is improved, making it less likely to absorb moisture in a humid environment. At the same time, the grafting of the modified flame retardant introduces multiple rigid benzene ring structures into the polyester molecular chain, which can improve the mechanical strength of the plastic particles.

[0021] The modified flame retardant is made from bis(2-chloroethyl)vinylphosphonate), m-hydroxybenzoic acid, and 2,6-dihydroxytoluene. The chlorine group of bis(2-chloroethyl)vinylphosphonate reacts with the hydroxyl group of m-hydroxybenzoic acid protected by an ester group under low temperature conditions. The presence of the phosphate group can promote the dehydration of plastic particles into carbon, and the free radicals such as PO and PO2 generated by pyrolysis can quench active free radicals such as H and OH in the gas phase, thereby preventing the continuation of the chain reaction of the plastic during combustion, initially achieving flame retardant properties, assisting the aromatization structure in m-hydroxybenzoic acid, and promoting a low-permeability and highly continuous carbon layer. Formation, preventing the transfer of combustible gas and heat, thereby effectively inhibiting the diffusion of combustion and thermal degradation of plastic particles, further enhancing the flame retardant effect; after the carboxyl group removes the ester group, it reacts and combines with 2,6-dihydroxytoluene to form a benzophenone structure. When irradiated by ultraviolet light, the molecules undergo thermal motion, and the internal hydrogen bonds of the chelate ring formed by the carbonyl group and hydrogen bond in benzophenone are destroyed, converting the ultraviolet light energy into heat energy and releasing it back to its original state, thereby achieving an anti-UV effect. Combined with the methyl group, it increases the crystallization rate of plastic particles and forms a more compact stacking structure, thereby enhancing the mechanical strength of the plastic particles. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In order to more clearly illustrate the method provided by the present invention, the following examples are used to describe in detail the various index testing methods of the flame retardant polyester-containing plastic particles prepared in the following examples.

[0024] Tensile strength and elongation at break: The same mass of plastic particles of the embodiment and the comparative example were made into 0.3 mm films and tested in accordance with GB / T 13022.

[0025] Tensile strength and elongation at break after aging: The same mass of plastic particles from the examples and comparative examples was made into a 0.3 mm thick film and irradiated using a 6 kW xenon lamp and sprayed with water at a pressure of 0.12 to 0.15 MPa. The film was then irradiated with ultraviolet light for 120 minutes, with 18 minutes of simultaneous water spraying and light exposure and 120 minutes of light exposure alone, for a total of 2000 hours of exposure. The sample was then placed at room temperature for 20 hours and tested according to GB / T 13022.

[0026] Oxygen index: The same mass of plastic particles of the embodiment and the comparative example were made into 0.3 mm films and tested in accordance with GB / T2406.

[0027] Example 1: (1) 5 parts of m-hydroxybenzoic acid and 40 parts of methanol were uniformly mixed, 0.05 parts of 98 wt% concentrated sulfuric acid were added dropwise at a rate of 1 drop / s, the temperature was raised to 60°C, and the mixture was stirred at 80 rpm for 3 hours to obtain a reaction solution. The reaction solution was then transferred to a separatory funnel, washed with 10 parts of a saturated sodium carbonate aqueous solution, and the organic phase was separated. This was repeated 3 times, and the mixture was dried over 2 parts of anhydrous magnesium sulfate for 2 minutes, and then concentrated under a vacuum degree of -0.08 MPa at 33°C for 1 hour to obtain esterified m-hydroxybenzoic acid.

[0028] (2) Under nitrogen protection, 5 parts of esterified m-hydroxybenzoic acid, 30 parts of dimethylformamide, and 2 parts of triethylamine were mixed uniformly, cooled to -5°C, and 6 parts of vinylphosphonic acid bis(2-chloroethyl)-dimethylformamide solution with a content of 20 wt% were added dropwise at a rate of 0.5 drops / s. The mixture was stirred at 80 rpm for 4 hours to obtain a reaction solution. The reaction solution was heated to 20°C, and the pH of the solution was adjusted to 7 with a 2 mol / L sodium hydroxide aqueous solution. The liquid was separated, the lower organic phase was taken, 30 parts of water and 50 parts of ethyl acetate were added, and the upper organic phase was taken. After drying with 2 parts of anhydrous magnesium sulfate for 2 minutes, it was concentrated at a vacuum degree of -0.1 MPa and 35°C for 1 hour to obtain a composite agent;

[0029] (3) 4 parts of the composite agent, 7 parts of aluminum chloride, and 32 parts of dichloromethane were mixed evenly, and 3.5 parts of 2,6-dihydroxytoluene were added under stirring at -5°C and 120 rpm. The reaction was carried out for 3 hours to obtain a reaction solution, which was added dropwise to 15 parts of methanol at a rate of 5 mL / min. The mixture was stirred at 150 rpm for 30 minutes. The solid was filtered and washed with methanol 3 times. It was placed in an oven at 20°C and dried for 12 hours to obtain a modified flame retardant.

[0030] (4) Under nitrogen protection, 8 parts of hydrogenated bisphenol A and 10 parts of iminodiacetic acid were mixed uniformly and polycondensed at 130°C for 10 hours to obtain a polyester with a molecular weight of 3500;

[0031] (5) 13 parts of a modified flame retardant, 35 to 58 parts of a polyester with a molecular weight of 3500, and 2 parts of diphenylphosphoric acid were mixed uniformly, stirred at 160 rpm and 80°C for 6 h, the solid was collected, washed three times with deionized water, and dried in an oven at 40°C for 12 h to obtain a modified polyester;

[0032] (6) 55 parts of modified polyester, 5 parts of titanium dioxide, and 1 part of tributyl acetyl citrate were mixed in a mixer at 290°C for 40 min, and then extruded through an extruder at a head temperature of 245°C, a screw speed of 195 r / min, an extrusion pressure of 20 MPa, and a shear rate of 220 s -1 The pellets were extruded and pelletized, and cooled for 15 minutes at a cooling air temperature of 14° C., a wind speed of 0.7 m / s, and a wind pressure of 400 Pa to obtain flame-retardant polyester-containing plastic pellets.

[0033] Example 2: (1) 10 parts of m-hydroxybenzoic acid and 80 parts of methanol were uniformly mixed, 0.15 parts of 98 wt% concentrated sulfuric acid were added dropwise at a rate of 1 drop / s, the temperature was raised to 65°C, and the mixture was stirred at 80 rpm for 4 hours to obtain a reaction solution. The reaction solution was then transferred to a separatory funnel, washed with 10 parts of a saturated sodium carbonate aqueous solution, and the organic phase was separated. This was repeated 3 times. After drying over 2 parts of anhydrous magnesium sulfate for 3 minutes, the mixture was concentrated under a vacuum degree of -0.08 MPa and 33°C for 2 hours to obtain esterified m-hydroxybenzoic acid.

[0034] (2) Under nitrogen protection, 7 parts of esterified m-hydroxybenzoic acid, 42 parts of dimethylformamide, and 3 parts of triethylamine were mixed uniformly, cooled to 0°C, and 8 parts of vinylphosphonic acid bis(2-chloroethyl)-dimethylformamide solution with a content of 20 wt% was added dropwise at a rate of 0.5 drops / s. The mixture was stirred at 80 rpm for 6 hours to obtain a reaction solution. The reaction solution was heated to 25°C, and the pH of the solution was adjusted to 7.25 with a 2 mol / L sodium hydroxide aqueous solution. The liquid was separated, the lower organic phase was taken, 42 parts of water and 70 parts of ethyl acetate were added, and the upper organic phase was taken. After drying over 2 parts of anhydrous magnesium sulfate for 3 minutes, the upper organic phase was concentrated at a vacuum degree of -0.1 MPa and 35°C for 2 hours to obtain a composite agent;

[0035] (3) 6 parts of the composite agent, 10.5 parts of aluminum chloride, and 48 parts of dichloromethane were mixed evenly, and 5.5 parts of 2,6-dihydroxytoluene were added under stirring at 0°C and 120 rpm. The reaction was carried out for 4 hours to obtain a reaction solution, which was added dropwise to 20 parts of methanol at a rate of 5 mL / min. The mixture was stirred at 150 rpm for 35 minutes. The solid was filtered and washed with methanol three times. It was placed in an oven at 25°C and dried for 14 hours to obtain a modified flame retardant.

[0036] (4) Under nitrogen protection, 11 parts of hydrogenated bisphenol A and 13 parts of iminodiacetic acid were mixed uniformly and polycondensed at 160°C for 12 hours to obtain a polyester with a molecular weight of 4500;

[0037] (5) 17 parts of modified flame retardant, 46.5 parts of polyester with a molecular weight of 4500, and 4 parts of diphenylphosphoric acid were mixed uniformly, stirred at 160 rpm and 90°C for 8 h, the solid was collected, washed with deionized water three times, and dried in an oven at 45°C for 14 h to obtain modified polyester;

[0038] (6) 70 parts of modified polyester, 7 parts of titanium dioxide and 2 parts of tetrabutyl pyromellitate were mixed in a mixer at 300°C for 50 min, and then extruded through an extruder at a head temperature of 255°C, a screw speed of 205 r / min, an extrusion pressure of 23 MPa and a shear rate of 230 s -1 The pellets were extruded and pelletized, and cooled for 20 minutes at a cooling air temperature of 16° C., a wind speed of 0.9 m / s, and a wind pressure of 500 Pa to obtain flame-retardant polyester-containing plastic pellets.

[0039] Example 3: (1) 15 parts of m-hydroxybenzoic acid and 120 parts of methanol were uniformly mixed, 0.25 parts of 98 wt% concentrated sulfuric acid were added dropwise at a rate of 1 drop / s, the temperature was raised to 70°C, and the mixture was stirred at 80 rpm for 5 hours to obtain a reaction solution. The reaction solution was then transferred to a separatory funnel, washed with 10 parts of a saturated sodium carbonate aqueous solution, and the organic phase was separated. This was repeated 3 times. After drying over 2 parts of anhydrous magnesium sulfate for 4 minutes, the mixture was concentrated under a vacuum degree of -0.08 MPa and 33°C for 3 hours to obtain esterified m-hydroxybenzoic acid.

[0040] (2) Under nitrogen protection, 9 parts of esterified m-hydroxybenzoic acid, 54 parts of dimethylformamide, and 4 parts of triethylamine were mixed uniformly, cooled to 5°C, and 12 parts of vinylphosphonic acid bis(2-chloroethyl)-dimethylformamide solution with a content of 20 wt% was added dropwise at a rate of 0.5 drops / s. The mixture was stirred at 80 rpm for 8 hours to obtain a reaction solution. The reaction solution was heated to 30°C, and the pH of the solution was adjusted to 7.5 with a 2 mol / L sodium hydroxide aqueous solution. The liquid was separated, the lower organic phase was removed, 54 parts of water and 90 parts of ethyl acetate were added, and the upper organic phase was taken. After drying with 2 parts of anhydrous magnesium sulfate for 4 minutes, it was concentrated at a vacuum degree of -0.1 MPa and 35°C for 3 hours to obtain a composite agent;

[0041] (3) 8 parts of the composite agent, 14 parts of aluminum chloride, and 64 parts of dichloromethane were mixed evenly, and 7.5 parts of 2,6-dihydroxytoluene were added under stirring at 5°C and 120 rpm. The reaction was carried out for 5 hours to obtain a reaction solution, which was added dropwise to 25 parts of methanol at a rate of 5 mL / min. The mixture was stirred at 150 rpm for 40 minutes. The solid was filtered and washed with methanol three times. It was placed in an oven at 30°C and dried for 16 hours to obtain a modified flame retardant.

[0042] (4) Under nitrogen protection, 14 parts of hydrogenated bisphenol A and 16 parts of iminodiacetic acid were mixed uniformly and polycondensed at 190°C for 14 hours to obtain a polyester with a molecular weight of 5500;

[0043] (5) 21 parts of modified flame retardant, 58 parts of polyester with a molecular weight of 5500, and 6 parts of diphenylphosphoric acid were mixed uniformly, stirred at 160 rpm and 100°C for 10 h, the solid was collected, washed three times with deionized water, and dried in an oven at 50°C for 16 h to obtain modified polyester;

[0044] (6) 85 parts of modified polyester, 9 parts of titanium dioxide, and 3 parts of dibutyl phthalate were mixed in a mixer at 310°C for 60 min, and then extruded through an extruder at a head temperature of 265°C, a screw speed of 215 r / min, an extrusion pressure of 26 MPa, and a shear rate of 240 s -1 The pellets were extruded and pelletized, and cooled for 25 minutes at a cooling air temperature of 18° C., a wind speed of 1.1 m / s, and a wind pressure of 600 Pa to obtain flame-retardant polyester-containing plastic pellets.

[0045] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that there is no step (5), and step (6) is changed to: 46.5 parts of polyester with a molecular weight of 4500, 17 parts of modified flame retardant, 7 parts of titanium dioxide, and 2 parts of tetrabutyl pyromellitate are mixed in a mixer at 300°C for 50 minutes, and then extruded through an extruder at a head temperature of 255°C, a screw speed of 205r / min, an extrusion pressure of 23MPa, and a shear rate of 230s -1 The pellets were extruded and pelletized, and cooled for 20 minutes at a cooling air temperature of 16° C., a wind speed of 0.9 m / s, and a wind pressure of 500 Pa to obtain flame-retardant polyester-containing plastic pellets. The remaining steps were the same as in Example 2.

[0046] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that steps (1) and (2) are omitted, and step (3) is changed to: 6 parts of m-hydroxybenzoic acid, 10.5 parts of aluminum chloride, and 48 parts of dichloromethane are mixed uniformly, and 5.5 parts of 2,6-dihydroxytoluene are added under stirring at 0°C and 120 rpm. The mixture is reacted for 4 hours to obtain a reaction solution, which is then added dropwise to 20 parts of methanol at a rate of 5 mL / min. The mixture is stirred at 150 rpm for 35 minutes, and the solid is filtered, washed three times with methanol, and dried in an oven at 25°C for 14 hours to obtain a modified flame retardant. The remaining steps are the same as those in Example 2.

[0047] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that steps (1) and (2) are omitted, and step (3) is changed to: 6 parts of bis(2-chloroethyl) vinylphosphonate), 10.5 parts of aluminum chloride, and 48 parts of dichloromethane are mixed uniformly, and 5.5 parts of 2,6-dihydroxytoluene are added under stirring at 0°C and 120 rpm. The mixture is reacted for 4 hours to obtain a reaction solution, which is then added dropwise to 20 parts of methanol at a rate of 5 mL / min. The mixture is stirred at 150 rpm for 35 minutes, and the solid is filtered, washed three times with methanol, and dried in an oven at 25°C for 14 hours to obtain a modified flame retardant. The remaining steps are the same as those in Example 2.

[0048] Comparative Example 4: Comparative Example 4 differs from Example 2 in that step (3) is omitted and step (5) is modified as follows: 17 parts of the complexing agent, 46.5 parts of a polyester having a molecular weight of 4500, and 4 parts of diphenylphosphoric acid are uniformly mixed, stirred at 160 rpm and 90°C for 8 hours, the solid is collected, washed three times with deionized water, and dried in an oven at 45°C for 14 hours to produce a modified polyester. The remaining steps are the same as in Example 2.

[0049] Effect Examples

[0050] Table 1 below shows the performance analysis results of the flame retardant polyester-containing plastic particles obtained using Examples 1 to 3 of the present invention and Comparative Examples 1 to 4.

[0051] Table 1

[0052]

[0053] From the comparison of the experimental data of Examples 1, 2, and 3 with Comparative Example 1, it can be found that the modified flame retardant is combined with polyester, and the unsaturated double bonds in the flame retardant can be tightly combined with the two ends of the polyester to form ether bonds. At the same time, with the assistance of the hydrophobic groups in the modified flame retardant molecular chain, the hydrolysis resistance of the plastic is improved, and it is not easy to absorb moisture in a humid environment. With the grafting introduction of the modified flame retardant, multiple rigid benzene ring structures are introduced into the polyester molecular chain, which can improve the mechanical strength of the plastic particles. From the comparison of the experimental data of Examples 1, 2, and 3 with Comparative Example 2, it can be found that the chlorine group of vinylphosphonic acid bis(2-chloroethyl) reacts with the hydroxyl group of ester-protected m-hydroxybenzoic acid under low temperature conditions. The presence of the phosphate group can promote the dehydration of the plastic particles into carbon, and the free radicals such as PO and PO2 generated by pyrolysis can quench the active free radicals such as H and OH in the gas phase, thereby preventing the plastic from burning. The chain reaction continues during burning to achieve flame retardant properties; from the comparison of the experimental data of Examples 1, 2, and 3 with Comparative Example 3, it can be found that the aromatic structure in m-hydroxybenzoic acid can promote the formation of a low-permeability and high-continuity carbon layer, prevent the transfer of combustible gas and heat, and effectively inhibit the diffusion and thermal degradation of the combustion of plastic particles, thereby enhancing the realization of the flame retardant effect; from the comparison of the experimental data of Examples 1, 2, and 3 with Comparative Examples 3 and 4, it can be found that m-hydroxybenzoic acid reacts with 2,6-dihydroxytoluene to form a benzophenone structure. When irradiated with ultraviolet light, the molecules undergo thermal motion, and the intrinsic hydrogen bonds formed by the chelate ring of the carbonyl group and the hydrogen bond in the benzophenone are destroyed, converting the ultraviolet light energy into heat energy and releasing it back to its original state, thereby achieving an anti-ultraviolet effect, cooperating with the methyl group, increasing the crystallization rate of the plastic particles, forming a more compact stacking structure, and enhancing the mechanical strength of the plastic particles.

[0054] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims, not the foregoing description, and all variations within the meaning and range of equivalents of the claims are intended to be encompassed therein. Any reference in a claim should not be construed as limiting the claim to which it relates.

Claims

1. A method for preparing flame-retardant polyester-containing plastic particles, characterized in that: The method comprises the following preparation steps: (1) Under nitrogen protection, 5-9 parts of esterified m-hydroxybenzoic acid, 30-54 parts of dimethylformamide, and 2-4 parts of triethylamine were mixed uniformly, cooled to -5-5°C, and 6-12 parts of vinylphosphonic acid bis(2-chloroethyl)-dimethylformamide solution were added dropwise at a rate of 0.5 drops / s. The mixture was stirred at 80 rpm for 4-8 hours to obtain a reaction solution, which was post-treated to obtain a composite agent; (2) 4 to 8 parts of the composite agent, 7 to 14 parts of aluminum chloride, and 32 to 64 parts of dichloromethane were mixed uniformly, and 3.5 to 7.5 parts of 2,6-dihydroxytoluene were added under stirring at -5-5°C and 120 rpm, and the mixture was reacted for 3 to 5 hours to obtain a reaction solution, which was crystallized and dried in an oven at 20 to 30°C for 12 to 16 hours to obtain a modified flame retardant; (3) 13 to 21 parts of a modified flame retardant, 35 to 58 parts of a polyester, and 2 to 6 parts of diphenylphosphoric acid were mixed uniformly, stirred at 160 rpm and 80 to 100° C. for 6 to 10 hours, the solid was collected, washed three times with deionized water, and dried in an oven at 40 to 50° C. for 12 to 16 hours to obtain a modified polyester; (4) 55 to 85 parts of modified polyester, 5 to 9 parts of titanium dioxide, and 1 to 3 parts of plasticizer are extruded and pelletized through an extruder, and cooled to obtain flame-retardant polyester-containing plastic particles.

2. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The preparation step of the esterified m-hydroxybenzoic acid in step (1) is as follows: 5 to 15 parts of m-hydroxybenzoic acid and 40 to 120 parts of methanol are uniformly mixed, 0.05 to 0.25 parts of 98 wt% concentrated sulfuric acid are added dropwise at a rate of 1 drop / s, the temperature is raised to 60 to 70° C., and the mixture is stirred at 80 rpm for 3 to 5 hours to obtain a reaction solution, which is then post-treated to obtain esterified m-hydroxybenzoic acid.

3. The method for preparing flame-retardant polyester-containing plastic particles according to claim 2, characterized in that: The post-treatment steps are: transferring the reaction solution to a separatory funnel, washing with 10 parts of a saturated sodium carbonate aqueous solution, separating and taking the organic phase, repeating 3 times, drying with 2 parts of anhydrous magnesium sulfate for 2 to 4 minutes, and concentrating at a vacuum degree of -0.08 MPa and 33° C. for 1 to 3 hours.

4. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The content of bis(2-chloroethyl)vinylphosphonate) in the bis(2-chloroethyl)vinylphosphonate)-dimethylformamide solution in step (1) is 20 wt%.

5. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The post-treatment step of step (1) is as follows: heating the reaction solution to 20-30° C., adjusting the pH of the solution to 7-7.5 with a 2 mol / L sodium hydroxide aqueous solution, separating the liquid, removing the lower organic phase, adding 30-54 parts of water and 50-90 parts of ethyl acetate, extracting, taking the upper organic phase, drying it over 2 parts of anhydrous magnesium sulfate for 2-4 minutes, and concentrating it at a vacuum degree of -0.1 MPa and 35° C. for 1-3 hours.

6. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The crystallization step in step (2) is as follows: the reaction solution is added dropwise to 15 to 25 parts of methanol at a rate of 5 mL / min, stirred at 150 rpm for 30 to 40 minutes, the solid is filtered and washed with methanol three times.

7. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The preparation process of the polyester in step (3) is as follows: under nitrogen protection, 8 to 14 parts of hydrogenated bisphenol A and 10 to 16 parts of iminodiacetic acid are uniformly mixed, and polycondensed at 130 to 190° C. for 10 to 14 hours to obtain a polyester with a molecular weight of 3500 to 5500.

8. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The plasticizer in step (4) is any one of tributyl acetyl citrate, tetrabutyl pyromellitate, and dibutyl phthalate.

9. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The parameters of the extruder in step (4) are head temperature 245-265°C, screw speed 195-215 r / min, extrusion pressure 20-26 MPa, shear rate 220-240 s -1 .

10. The method for preparing flame-retardant polyester-containing plastic particles according to claim 1, characterized in that: The cooling conditions in step (4) are as follows: cooling air temperature of 14-18° C., wind speed of 0.7-1.1 m / s, wind pressure of 400-600 Pa, and cooling time of 15-25 min.

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