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 present application relates to the technical field of plastic particles, in particular to a preparation method of flame-retardant polyester-containing plastic particles. BACKGROUND

[0002] In the field of plastic industry, polyester materials have a wide range of applications. However, there are some performance deficiencies in the actual use of polyester materials. On the one hand, polyester is prone to hydrolysis in a humid environment, and after absorbing moisture, it will cause its performance to decline, affecting the service life and stability of the material, which limits its application in some high-humidity environments. On the other hand, the mechanical strength of ordinary polyester materials cannot meet the demand in some application scenarios with high strength requirements, and needs to be further improved. In addition, polyester materials are usually flammable, which is a major safety hazard in many applications. In the combustion process, plastics are prone to chain reactions, causing the fire to spread rapidly, and generating a large amount of heat and toxic gases, posing a serious threat to life and property safety. Moreover, polyester materials exposed to ultraviolet light for a long time are prone to photoaging, which deteriorates the physical and chemical properties of the material, 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 prior art. In terms of flame retardation, some methods are to add traditional flame retardants, but there are problems such as unsatisfactory flame retardation effect, poor compatibility with polyester, etc., which may affect the mechanical properties and processing properties of the material. In terms of improving hydrolysis resistance and mechanical properties, more effective methods are needed to ensure the stability and strength of the material in complex environments. In terms of ultraviolet resistance, although there are some ultraviolet-resistant 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 retardation, and ultraviolet resistance. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of flame-retardant polyester-containing plastic particles to solve the problems in the prior art.

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

[0006] (1) Under the protection of nitrogen, 5-9 parts of esterified m-hydroxybenzoic acid, 30-54 parts of dimethylformamide, and 2-4 parts of triethylamine are mixed uniformly, cooled to-5-5℃, and 6-12 parts of vinyl phosphonic acid bis(2-chloroethyl ester)-dimethylformamide solution is added dropwise at a rate of 0.5 drops / s, and reacted for 4-8h under stirring at 80rpm to obtain a reaction liquid, which is post-treated to obtain a complexing agent;

[0007] (2) mixing 4-8 parts of the complexing agent, 7-14 parts of aluminum chloride, 32-64 parts of dichloromethane uniformly, adding 3.5-7.5 parts of 2,6-dihydroxytoluene under stirring at -5-5℃ and 120 rpm, reacting for 3-5 h to obtain a reaction solution, crystallizing, drying in an oven at 20-30℃ for 12-16 h to prepare the modified flame retardant;

[0008] (3) mixing 13-21 parts of the modified flame retardant, 35-58 parts of polyester, 2-6 parts of diphenyl phosphate uniformly, stirring at 160 rpm and 80-100℃ for 6-10 h, collecting the solid, washing with deionized water for 3 times, drying in an oven at 40-50℃ for 12-16 h to prepare the modified polyester;

[0009] (4) extruding and granulating 55-85 parts of the modified polyester, 5-9 parts of titanium dioxide, 1-3 parts of plasticizer through an extruder, cooling to prepare the flame-retardant polyester-containing plastic particles.

[0010] Further, the preparation step of the esterified m-hydroxybenzoic acid in step (1) is as follows: mixing 5-15 parts of m-hydroxybenzoic acid and 40-120 parts of methanol uniformly, adding 0.05-0.25 parts of 98wt% concentrated sulfuric acid at a rate of 1 drop / s, heating to 60-70℃, reacting for 3-5 h under stirring at 80 rpm to obtain a reaction solution, and post-treating to prepare the esterified m-hydroxybenzoic acid.

[0011] Further, the post-treating step is as follows: transferring the reaction solution to a separatory funnel, washing with 10 parts of saturated sodium carbonate aqueous solution, separating to obtain the organic phase, repeating for 3 times, drying with 2 parts of anhydrous magnesium sulfate for 2-4 min, and concentrating under a vacuum degree of -0.08 MPa and at 33℃ for 1-3 h.

[0012] Further, the content of the vinyl phosphonic acid bis(2-chloroethyl ester) in the vinyl phosphonic acid bis(2-chloroethyl ester)-dimethylformamide solution in step (1) is 20wt%.

[0013] Further, the post-treating step in step (1) is as follows: heating the reaction solution to 20-30℃, adjusting the pH of the solution to 7-7.5 with 2 mol / L sodium hydroxide aqueous solution, separating, taking the lower organic phase, adding 30-54 parts of water and 50-90 parts of ethyl acetate, extracting, taking the upper organic phase, drying with 2 parts of anhydrous magnesium sulfate for 2-4 min, and concentrating under a vacuum degree of -0.1 MPa and at 35℃ for 1-3 h.

[0014] Further, the crystallizing step in step (2) is as follows: adding the reaction solution to 15-25 parts of methanol at a rate of 5 mL / min, stirring at 150 rpm for 30-40 min, and filtering to obtain the solid, which is washed with methanol for 3 times.

[0015] Further, the preparation step of the polyester in step (3) is: under the protection of nitrogen, 8-14 parts of hydrogenated bisphenol A and 10-16 parts of imino diacetic acid are mixed uniformly, and then polycondensation is carried out at 130-190 DEG C for 10-14 hours to obtain polyester with a molecular weight of 3500-5500.

[0016] Further, the plasticizer in step (3) is any one of ethyl phthalate citric acid tributyl ester, benzophenone tetrabutyl ester, and dibutyl phthalate.

[0017] Further, the parameters of the extruder in step (3) are: a material head temperature of 245-265 DEG C, a screw rotation speed of 195-215 r / min, an extrusion pressure of 20-26 MPa, a shearing rate of 220-240 s -1 .

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

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] The modified flame retardant is combined with the polyester in the present application, the unsaturated double bond in the flame retardant can be combined with the secondary amine group in the polyester closely, and the hydrophobic group in the molecular chain of the modified flame retardant can improve the hydrolysis resistance of the plastic, so that the plastic is not easy to absorb water in a humid environment, meanwhile, the grafting of the modified flame retardant introduces multiple rigid benzene ring structures into the molecular chain of the polyester, which can improve the mechanical strength of the plastic particles.

[0021] The modified flame retardant is prepared from vinyl phosphonic acid bis(2-chloroethyl ester), m-hydroxybenzoic acid and 2,6-dihydroxytoluene; the chlorine group of the vinyl phosphonic acid bis(2-chloroethyl ester) reacts with the hydroxyl group of the m-hydroxybenzoic acid protected by an ester group under low temperature conditions, the presence of the phosphoric acid group can promote the dehydration of the plastic particles to form 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, so as to prevent the continuation of the chain reaction of the plastic during combustion, preliminarily realize the flame retardant performance, assist the aromatic structure in the m-hydroxybenzoic acid, promote the formation of a low-permeability and high-continuity carbon layer, and prevent the transmission of flammable gas and heat, so as to effectively inhibit the diffusion and thermal degradation of the plastic particle combustion, and further strengthen the flame retardant effect; after the carboxyl group loses the ester group, it reacts and combines with 2,6-dihydroxytoluene to form a benzophenone structure, when the ultraviolet light is irradiated, the molecules move, the chelate ring formed by the carbonyl group in the benzophenone and the hydrogen bond breaks the hydrogen bond, converts the ultraviolet light energy into heat energy, and releases it back to the initial state, and then realizes the anti-ultraviolet effect, cooperates with the methyl group, improves the crystallization rate of the plastic particles, forms a more compact packing structure, and thus enhances the mechanical strength of the plastic particles. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0023] In order to more clearly illustrate the method provided by the present application, the following embodiments are described in detail. The test methods of various indexes of the prepared flame-retardant polyester-containing plastic particles in the following embodiments are as follows:

[0024] Tensile strength and elongation at break: the same mass of plastic particles of the examples and the comparative examples were taken to prepare 0.3 mm films, and the films were tested according to GB / T 13022.

[0025] Tensile strength and elongation at break after aging: the same mass of plastic particles of the examples and the comparative examples were taken to prepare 0.3 mm films, and the films were irradiated by a 6 kW xenon lamp with water spray at a water pressure of 0.12-0.15 MPa, and the periodical ultraviolet irradiation was carried out according to 120 minutes as one cycle, in which 18 minutes were simultaneous water spraying and light irradiation, and the other 120 minutes were light irradiation alone, and the total exposure irradiation time was 2000 hours. Then, the sample was placed in a room temperature environment for 20 hours, and the films were tested according to GB / T 13022.

[0026] Oxygen index: the same mass of plastic particles of the examples and the comparative examples were taken to prepare 0.3 mm films, and the films were tested according to GB / T 2406.

[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 was added dropwise at a rate of 1 drop / s, the temperature was raised to 60°C, and the reaction was carried out for 3 h under stirring at 80 rpm to obtain a reaction liquid. Then, the reaction liquid was transferred to a separatory funnel, washed with 10 parts of saturated sodium carbonate aqueous solution, and the organic phase was separated and repeatedly washed 3 times. After drying with 2 parts of anhydrous magnesium sulfate for 2 min, the esterified m-hydroxybenzoic acid was prepared by concentrating under a vacuum degree of-0.08 MPa at 33°C for 1 h.

[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, 3 parts of triethylamine were mixed uniformly, cooled to 0℃, 8 parts of vinyl phosphonic acid bis(2-chloroethyl ester) with a content of 20wt% in vinyl phosphonic acid bis(2-chloroethyl ester)-dimethylformamide solution was added dropwise at a rate of 0.5 drops / s, and reacted for 6h under stirring at 80rpm. The reaction liquid was warmed to 25℃, the solution pH was adjusted to 7.25 with 2mol / L sodium hydroxide aqueous solution, and the lower organic phase was taken out, 42 parts of water and 70 parts of ethyl acetate were added for extraction, the upper organic phase was taken out, dried with 2 parts of anhydrous magnesium sulfate for 3min, and concentrated under vacuum at-0.1MPa and 35℃ for 2h to prepare a complexing agent;

[0035] (3) 6 parts of the complexing agent, 10.5 parts of aluminum trichloride, and 48 parts of dichloromethane were mixed uniformly, 5.5 parts of 2,6-dihydroxytoluene was added under stirring at 0℃ and 120rpm, and reacted for 4h to obtain a reaction liquid. The reaction liquid was added dropwise into 20 parts of methanol at a rate of 5mL / min, stirred at 150rpm for 35min, filtered to take out the solid, washed with methanol for 3 times, and dried in a 25℃ oven for 14h to prepare a modified flame retardant;

[0036] (4) Under nitrogen protection, 11 parts of hydrogenated bisphenol A and 13 parts of imino diacetic acid were mixed uniformly, and polycondensation was carried out at 160℃ for 12h to prepare a polyester with a molecular weight of 4500;

[0037] (5) 17 parts of the modified flame retardant, 46.5 parts of the polyester with a molecular weight of 4500, and 4 parts of diphenyl phosphate were mixed uniformly, stirred at 160rpm and 90℃ for 8h, the solid was collected, washed with deionized water for 3 times, and dried in a 45℃ oven for 14h to prepare a modified polyester;

[0038] (6) 70 parts of the modified polyester, 7 parts of titanium dioxide, and 2 parts of tetra butyl pyromellitate were mixed in a mixer at 300℃ for 50min, and then extruded through an extruder at a material head temperature of 255℃, a screw rotation speed of 205r / min, an extrusion pressure of 23MPa, and a shearing rate of 230s -1 The extruded material was cut into particles, cooled for 20min under a cooling wind temperature of 16℃, a wind speed of 0.9m / s, and a wind pressure of 500Pa to prepare flame-retardant polyester-containing plastic particles.

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

[0040] (2) 9 parts of esterified m-hydroxybenzoic acid, 54 parts of dimethylformamide, 4 parts of triethylamine were mixed uniformly under nitrogen protection, the temperature was lowered to 5°C, 12 parts of vinyl phosphonic acid bis(2-chloroethyl ester) solution with a content of 20wt% was added dropwise at a rate of 0.5 drop / s, and the reaction was carried out for 8h under stirring at 80rpm to obtain a reaction solution, then the reaction solution was warmed to 30°C, the pH of the solution was adjusted to 7.5 with 2mol / L sodium hydroxide aqueous solution, separated, and the lower organic phase was taken, 54 parts of water and 90 parts of ethyl acetate were added for extraction, the upper organic phase was taken, dried with 2 parts of anhydrous magnesium sulfate for 4min, and then concentrated under vacuum at-0.1MPa and 35°C for 3h to obtain a complexing agent;

[0041] (3) 8 parts of the complexing agent, 14 parts of aluminum trichloride, and 64 parts of dichloromethane were mixed uniformly, 7.5 parts of 2,6-dihydroxytoluene was added under stirring at 5°C and 120rpm, and the reaction was carried out for 5h to obtain a reaction solution, then the reaction solution was added dropwise to 25 parts of methanol at a rate of 5mL / min, stirred at 150rpm for 40min, filtered to obtain a solid, washed with methanol for 3 times, and dried in an oven at 30°C for 16h to obtain a modified flame retardant;

[0042] (4) 14 parts of hydrogenated bisphenol A and 16 parts of imino diacetic acid were mixed uniformly under nitrogen protection, and polycondensation was carried out at 190°C for 14h to obtain a polyester with a molecular weight of 5500;

[0043] (5) 21 parts of the modified flame retardant, 58 parts of the polyester with a molecular weight of 5500, and 6 parts of diphenyl phosphate were mixed uniformly, stirred at 160rpm and 100°C for 10h, the solid was collected, washed with deionized water for 3 times, and dried in an oven at 50°C for 16h to obtain a modified polyester;

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

[0045] Comparative Example 1: Comparative Example 1 differs from Example 2 in that step (5) is omitted, 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 pyromellitic acid tetrabutyl ester are mixed in a mixer at 300℃ for 50 min, and then extruded through an extruder at a material head temperature of 255℃, a screw rotation speed of 205 r / min, an extrusion pressure of 23 MPa, and a shearing speed of 230 s -1 Extrusion and granulation, and then cooling for 20 min at a cooling air temperature of 16℃, an air speed of 0.9 m / s, and an air pressure of 500 Pa to obtain flame-retardant polyester-containing plastic particles. The remaining steps are the same as in Example 2.

[0046] Comparative Example 2: Comparative Example 2 differs from Example 2 in that steps (1) and (2) are omitted, and step (3) is changed to: 6 parts of m-hydroxybenzoic acid, 10.5 parts of aluminum trichloride, and 48 parts of dichloromethane are mixed uniformly, 5.5 parts of 2,6-dihydroxytoluene is added under stirring at 0℃ and 120 rpm, and the reaction is carried out for 4 h to obtain a reaction solution, the reaction solution is added dropwise to 20 parts of methanol at a rate of 5 mL / min, stirring is carried out at 150 rpm for 35 min, the solid is collected by filtration, washed with methanol for 3 times, and dried in an oven at 25℃ for 14 h to obtain a modified flame retardant. The remaining steps are the same as in Example 2.

[0047] Comparative Example 3: Comparative Example 3 differs from Example 2 in that steps (1) and (2) are omitted, and step (3) is changed to: 6 parts of vinyl phosphonic acid bis(2-chloroethyl ester), 10.5 parts of aluminum trichloride, and 48 parts of dichloromethane are mixed uniformly, 5.5 parts of 2,6-dihydroxytoluene is added under stirring at 0℃ and 120 rpm, and the reaction is carried out for 4 h to obtain a reaction solution, the reaction solution is added dropwise to 20 parts of methanol at a rate of 5 mL / min, stirring is carried out at 150 rpm for 35 min, the solid is collected by filtration, washed with methanol for 3 times, and dried in an oven at 25℃ for 14 h to obtain a modified flame retardant. The remaining steps are the same as in Example 2.

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

[0049] Effect Example

[0050] The performance analysis results of the flame-retardant polyester-containing plastic particles obtained by using Examples 1 to 3 and Comparative Examples 1 to 4 of the present application are shown in Table 1 below.

[0051] Table 1

[0052]

[0053] From the comparison of the experimental data of examples 1, 2, 3 and comparative examples 1, it can be found that the unsaturated double bond in the modified flame retardant can be combined with the two ends of the polyester to form an ether bond, and the hydrophobic group in the molecular chain of the modified flame retardant can improve the hydrolysis resistance of the plastic, which is not easy to absorb water in a humid environment. The grafting of the modified flame retardant introduces multiple rigid benzene ring structures into the molecular chain of the polyester, which can improve the mechanical strength of the plastic particles. From the comparison of the experimental data of examples 1, 2, 3 and comparative examples 2, it can be found that the reaction of the chlorine group of ethylene bis(2-chloroethyl) phosphinic acid and the hydroxyl group of m-hydroxybenzoic acid protected by ester group under low temperature conditions can promote the dehydration of plastic particles to 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 continuation of the chain reaction of the plastic during combustion, and achieving the flame retardant performance. From the comparison of the experimental data of examples 1, 2, 3 and comparative examples 3, it can be found that the aromatic structure in m-hydroxybenzoic acid can promote the formation of low-permeability and high-continuity carbon layer, prevent the transmission of flammable gas and heat, effectively inhibit the diffusion and thermal degradation of plastic particles during combustion, and strengthen the realization of flame retardant effect. From the comparison of the experimental data of examples 1, 2, 3 and comparative examples 3, 4, it can be found that the reaction and combination of m-hydroxybenzoic acid and 2, 6-dihydroxytoluene form a benzophenone structure. When ultraviolet light is irradiated, the molecules undergo thermal motion, the chelate ring formed by the carbonyl group in the benzophenone and the hydrogen bond breaks the hydrogen bond, converts the ultraviolet light energy into heat energy and releases it back to the original state, achieving the effect of resisting ultraviolet light. In combination with the methyl group, the crystallization rate of the plastic particles is improved, a more compact stacking structure is formed, and the mechanical strength of the plastic particles is enhanced.

[0054] It is obvious to a person skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any mark in the claims should not be regarded as limiting the involved claims.

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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