Flame-retardant master batch for polypropylene and preparation method of flame-retardant master batch

Abstract

The invention belongs to the technical field of flame-retardant master batches, and particularly relates to a flame-retardant master batch for polypropylene and a preparation method thereof.The preparation method comprises the steps that tris (2-hydroxyethyl) isocyanurate is heated and molten, tetrabutyl titanate and DOPO-DPP are added into the molten tris (2-hydroxyethyl) isocyanurate, the mixture reacts for 3-4 h, melamine and cyanuric acid are added into the molten tris (2-hydroxyethyl) isocyanurate, the mixture reacts for 30 min, cooling and smashing are conducted, and a macromolecular flame retardant TDMC is obtained; the preparation method comprises the following steps: carrying out ester exchange reaction on 2, 4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonyl methoxy) phenyl]-1, 3, 5-triazine and 2, 2, 6, 6-tetramethyl piperidinol to prepare a free radical capturing agent; the polypropylene, the TDMC, the free radical scavenger and the zeolite are put into a high-speed mixer to be stirred and mixed, and then extrusion granulation is performed. The macromolecular flame retardant TDMC is adopted, the molecular weight of the macromolecular flame retardant TDMC is large, the water resistance is good, and the compatibility and damp-heat stability of the flame-retardant master batch in polypropylene are improved.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant masterbatch technology, specifically relating to a flame retardant masterbatch for polypropylene and its preparation method. Background Technology

[0002] Polypropylene (PP) is a non-polar, semi-crystalline thermoplastic polymer formed by the addition polymerization of propylene monomers. Due to its excellent mechanical properties, chemical resistance, and processability, it is widely used in electronics, construction, packaging, and medical fields. However, because its hydrocarbon backbone structure lacks flame-retardant elements, polypropylene is highly flammable and produces high-temperature droplets during combustion, severely limiting its application in scenarios with high safety requirements.

[0003] In the flame-retardant modification of polypropylene, commonly used flame retardants include halogenated flame retardants, inorganic filler flame retardants, silicone flame retardants, phosphorus flame retardants, and intumescent flame retardants. Among them, halogenated flame retardants, although possessing excellent gas-phase flame-retardant properties, release toxic and corrosive gases during combustion, and their use has been gradually restricted. In contrast, intumescent flame retardants, due to their halogen-free and environmentally friendly nature, efficient carbonization, and combined gas-phase and condensed-phase flame-retardant mechanisms, have become a key research direction in polypropylene flame retardancy.

[0004] Currently, intumescent flame retardants (IFR) are one of the commonly used flame retardant systems in polypropylene. They are usually a mixture of multiple components, including a char source, an acid source, and a gas source, in a certain proportion. However, due to the high polarity of IFR and the fact that PP is a non-polar polymer, the significant difference in polarity between the two may lead to the following problems: poor compatibility, uneven dispersion, and easy migration and precipitation upon contact with water. Summary of the Invention

[0005] The purpose of this invention is to provide a flame-retardant masterbatch for polypropylene and its preparation method, so as to solve the above-mentioned technical problems.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows: A method for preparing flame-retardant masterbatch for polypropylene includes the following steps: S1. Tris(2-hydroxyethyl) isocyanurate is heated and melted, and then tetrabutyl titanate and DOPO-DPP catalysts are added to it. The mixture is stirred and reacted at 160~165℃ for 3~4h. After the reaction is completed, melamine and cyanuric acid are added to it, and the mixture is stirred and reacted at 190~195℃ for 30min to obtain a viscous melt. After cooling and pulverizing, the macromolecular flame retardant TDMC is obtained. S2. A free radical scavenger was prepared by transesterification of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol. S3. 40-50 parts of polypropylene, 50-60 parts of TDMC, 10-15 parts of free radical scavenger and 3-5 parts of zeolite are loaded into a high-speed mixer and stirred and mixed. Then, the mixture is extruded and granulated to obtain flame retardant masterbatch for polypropylene. The extrusion temperature is 150-160℃.

[0007] As a further improvement, in step S1, the preparation method of DOPO-DPP is as follows: diaminodiphenyl sulfone, p-formylbenzoic acid and tetrahydrofuran solvent are mixed and stirred at 50~80℃ for 5~6h under a nitrogen atmosphere. After the reaction is completed, the reaction solution is cooled to room temperature, DOPO is added to it, and the reaction is stirred under a nitrogen atmosphere for 12~15h. After the reaction is completed, the mixture is filtered, and the filter cake is washed three times with tetrahydrofuran and dried to obtain DOPO-DPP.

[0008] As a further improvement, the molar ratio of diaminodiphenyl sulfone, p-formylbenzoic acid and DOPO is 0.8~1:2:2.

[0009] As a further improvement, in step S2, the preparation method of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl)-1,3,5-triazine] is as follows: S21. Mix cyanuric chloride, chlorobenzene and aluminum trichloride, stir and cool to 0~5℃, slowly add benzene and stir for 2h, then naturally heat to room temperature and stir for 12h, then heat to 50℃ and slowly add resorcinol, then heat to 75~80℃ and react for 5h. After the reaction is complete, remove chlorobenzene by azeotropic distillation, then cool to 60℃ and filter. Dry the precipitate and recrystallize to obtain 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. S22. Mix 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, butyl acetate, and potassium carbonate, stir, and heat to 60°C. Add ethyl chloroacetate dropwise over 2 hours. React at 60-65°C for 6 hours. Then, heat to 100°C and filter. Collect the filtrate, cool, and crystallize. Collect the solid, dry, and recrystallize to obtain 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine.

[0010] As a further improvement, the molar ratio of cyanuric chloride, benzene and resorcinol is 1:1.95 to 2:1.1, and the molar ratio of 4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine and ethyl chloroacetate is 1:1.1 to 1.2.

[0011] As a further improvement, in step S1, the molar ratio of tris(2-hydroxyethyl) isocyanurate, DOPO-DPP, melamine and cyanuric acid is 1:3:3:3.

[0012] As a further improvement, in step S2, the preparation method of the free radical scavenger is as follows: 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine, 2,2,6,6-tetramethylpiperidinol and the catalyst dibutyltin oxide are mixed, and then o-dichlorobenzene is added as a solvent. The mixture is reacted at 150~155℃ for 8 hours under nitrogen protection. After the reaction is completed, activated carbon is added for decolorization. After hot filtration, the filtrate is crystallized, and the solid is collected and recrystallized to obtain the free radical scavenger.

[0013] As a further improvement, the molar ratio of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol is 1:1 to 1.1.

[0014] The present invention also provides a flame-retardant masterbatch for polypropylene.

[0015] Due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: This invention provides a flame-retardant masterbatch for polypropylene and its preparation method. It utilizes the macromolecular flame retardant TDMC, which has a large molecular weight and good water resistance, improving the compatibility and hygrothermal stability of the flame-retardant masterbatch in polypropylene. During heating, melamine and cyanuric acid in TDMC separate and release gases such as ammonia. Subsequently, the ester bond between THEIC and DOPO-DPP breaks to form carboxylic acids and olefins. DOPO-DPP continues to exert its flame-retardant effect in both the gas and condensed phases upon heating. The generated olefins undergo diene addition, double bond shifting, and hydrogen atom migration during heating, generating various char precursors and corresponding fused ring structures, forming a black, viscous char skeleton with better flame-retardant properties.

[0016] In this invention, the macromolecular flame retardant TDMC exhibits higher thermal stability. The sulfur atoms in the DOPO-DPP structure are in their highest oxidation state, exhibiting strong electron-withdrawing ability. Furthermore, the benzene rings connected to the sulfone groups are in an oxidation-resistant state due to the lack of electrons, thus improving the overall thermal stability of the macromolecular flame retardant TDMC. Simultaneously, the multiple benzene ring structures in TDMC, after forming a char layer, possess high mechanical strength, enhancing the strength of the char layer. This prevents the char layer from becoming loose due to excessive expansion, allowing the formed char layer to expand further without weakening its strength.

[0017] The macromolecular flame retardant TDMC can also improve the viscosity of the material after it is heated and melted, inhibit the migration of molten droplets to the surface of the matrix material, provide more time for the formation of the char layer, and prevent the molten droplets from dripping before the char layer is formed.

[0018] The free radical scavenger prepared in this invention can generate free radical scavengers while acting as a gas source, capturing free radicals generated during the thermal decomposition of polypropylene, thereby further improving the flame retardant properties of the flame retardant masterbatch. Attached Figure Description

[0019] Figure 1 These are the infrared spectra of the macromolecular flame retardants TDMC, THEIC, and DOPO prepared in Example 1; Figure 2 This is the infrared spectrum of the free radical scavenger prepared in Example 1. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0021] Example 1 A flame retardant masterbatch for polypropylene, comprising the following components by weight: 40 parts polypropylene, 50 parts TDMC, 10 parts free radical scavenger and 3 parts zeolite.

[0022] The preparation method of the above-mentioned flame retardant masterbatch for polypropylene includes the following steps: Preparation of S1 and DOPO-DPP; 0.8 mol diaminodiphenyl sulfone, 2 mol p-formylbenzoic acid and 250 mL tetrahydrofuran solvent were mixed and stirred at 50 °C for 6 h under a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature, and 2 mol DOPO was added. The reaction was stirred at a nitrogen atmosphere for 12 h. After the reaction was completed, the mixture was filtered, and the filter cake was washed three times with tetrahydrofuran at 5 °C and dried to obtain DOPO-DPP. The reaction equation is: ; ; S2, Preparation of macromolecular flame retardant TDMC; 0.4 mol of tris(2-hydroxyethyl) isocyanurate (THEIC) was heated and melted, and then 2.0 g of tetrabutyl titanate catalyst and 1.2 mol of DOPO-DPP were added. The mixture was stirred at 160 °C for 4 h. After the reaction was completed, 1.2 mol of melamine and 1.2 mol of cyanuric acid were added, and the mixture was stirred at 190 °C for 30 min to obtain a viscous melt. After cooling and pulverizing, the macromolecular flame retardant TDMC was obtained. The infrared spectra of the obtained macromolecular flame retardants TDMC, THEIC, and DOPO are as follows: Figure 1 As shown, the OH characteristic peak in THEIC disappears in TDMC, while in TDMC, the peak at 1735 cm⁻¹... -1 The characteristic peak of C=O appears at 1150 cm⁻¹. -1 The presence of the COC characteristic peak indicates the formation of an ester bond, and the peak is observed at 3407 cm⁻¹ in TDMC. -1 1544cm -1 The positions are -NH2 and -NH3 respectively. + The characteristic peak is at 1300 cm⁻¹. -1 The characteristic peak of P=O exists at 907 cm⁻¹. -1 The characteristic peaks of PO-Ph appear at 2435 cm⁻¹, while DOPO shows a peak at 2435 cm⁻¹. -1 The characteristic absorption peak of the PH bond at 1600 cm⁻¹ did not appear in the infrared spectrum of TDMC, nor was it observed at 1600 cm⁻¹. -1 ~1680cm -1 The characteristic peak of Schiff base appears at this location; Preparation of S3, 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine; 0.1 mol cyanuric chloride, 100 mL chlorobenzene, and 40 g aluminum trichloride were mixed and stirred, then cooled to 5 °C. 0.195 mol benzene was slowly added to the mixture, and the mixture was stirred for 2 h. The mixture was then naturally heated to room temperature and stirred for 12 h. The mixture was then heated to 50 °C and 0.11 mol resorcinol was slowly added. The mixture was then heated to 75 °C and reacted for 5 h. After the reaction was completed, chlorobenzene was removed by azeotropic distillation. The mixture was then cooled to 60 °C and filtered. The precipitate was dried and recrystallized in N,N-dimethylformamide to obtain 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. The reaction equation is: ; 0.05 mol of 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 90 mL of butyl acetate, and 8.0 g of potassium carbonate were mixed and stirred until the temperature reached 60 °C. 0.055 mol of ethyl chloroacetate was added dropwise over 2 hours. The mixture was reacted at 60 °C for 6 hours, then the temperature was raised to 100 °C and filtered. The filtrate was collected, cooled to 10 °C, and crystallized. The solid was collected, dried, and recrystallized in N,N-dimethylformamide to give 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine. The reaction equation is: ; S4. A free radical scavenger was prepared by transesterification of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol. Specifically, 0.02 mol of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine, 0.02 mol of 2,2,6,6-tetramethylpiperidinol and 0.4 g of dibutyltin oxide catalyst were mixed, and then 30 mL of o-dichlorobenzene solvent was added. The mixture was reacted at 150 °C for 8 h under nitrogen protection. After the reaction was completed, activated carbon was added for decolorization. The filtrate was then filtered hot and crystallized. The solid was collected and recrystallized in N,N-dimethylformamide to obtain a free radical scavenger. Infrared spectra of free radical scavengers are as follows Figure 2 As shown, in the free radical scavenger, at 3424 cm⁻¹ -1 There is an absorption peak for OH at 2855~2963 cm⁻¹. -1 An absorption peak for CH is present at 1759 cm⁻¹. -1 An absorption peak for C=O is present at 1348–1632 cm⁻¹. -1 Characteristic absorption peaks of triazine and benzene rings are present at 1179 cm⁻¹. -1 An absorption peak for CN is present at this location; S5. Polypropylene, TDMC, free radical scavenger and zeolite are loaded into a high-speed mixer and stirred and mixed, and then extruded and granulated. The extrusion temperature is 150℃. The specific method of extrusion granulation is the existing technology.

[0023] Example 2 A flame retardant masterbatch for polypropylene, comprising the following components by weight: 50 parts polypropylene, 60 parts TDMC, 15 parts free radical scavenger and 5 parts zeolite.

[0024] The preparation method of the above-mentioned flame retardant masterbatch for polypropylene includes the following steps: Preparation of S1 and DOPO-DPP; 1 mol of diaminodiphenyl sulfone, 2 mol of p-formylbenzoic acid and 250 mL of tetrahydrofuran solvent were mixed and stirred at 80 °C for 5 h under a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature, and 2 mol of DOPO was added. The reaction was stirred at a nitrogen atmosphere for 15 h. After the reaction was completed, the mixture was filtered, and the filter cake was washed three times with tetrahydrofuran at 5 °C and dried to obtain DOPO-DPP. S2, Preparation of macromolecular flame retardant TDMC; 0.4 mol of tris(2-hydroxyethyl) isocyanurate was heated to melt, and then 2.0 g of tetrabutyl titanate catalyst and 1.2 mol of DOPO-DPP were added. The mixture was stirred at 165 °C for 3 h. After the reaction was completed, 1.2 mol of melamine and 1.2 mol of cyanuric acid were added, and the mixture was stirred at 195 °C for 30 min to obtain a viscous melt. After cooling and pulverizing, the macromolecular flame retardant TDMC was obtained. Preparation of S3, 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine; 0.1 mol cyanuric chloride, 100 mL chlorobenzene, and 40 g aluminum trichloride were mixed and stirred, then cooled to 0 °C. 0.2 mol benzene was slowly added to the mixture, and the mixture was stirred for 2 h. The mixture was then naturally heated to room temperature and stirred for 12 h. The mixture was then heated to 50 °C and 0.11 mol resorcinol was slowly added. The mixture was then heated to 80 °C and reacted for 5 h. After the reaction was completed, chlorobenzene was removed by azeotropic distillation. The mixture was then cooled to 60 °C and filtered. The precipitate was dried and recrystallized in N,N-dimethylformamide to obtain 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. 0.05 mol of 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 90 mL of butyl acetate, and 8.0 g of potassium carbonate were mixed and stirred until the temperature reached 60 °C. 0.06 mol of ethyl chloroacetate was added dropwise over 2 hours. The mixture was then reacted at 65 °C for 6 hours. The mixture was then heated to 100 °C and filtered. The filtrate was collected and cooled to 10 °C to crystallize. The solid was collected, dried, and recrystallized in N,N-dimethylformamide to give 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine. S4. A free radical scavenger was prepared by transesterification of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol. Specifically, 0.02 mol of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine, 0.022 mol of 2,2,6,6-tetramethylpiperidinol, and 0.4 g of dibutyltin oxide catalyst were mixed, and then 30 mL of o-dichlorobenzene solvent was added. The mixture was reacted at 155 °C for 8 h under nitrogen protection. After the reaction was completed, activated carbon was added for decolorization. The filtrate was then filtered hot and crystallized. The solid was collected and recrystallized in N,N-dimethylformamide to obtain a free radical scavenger. S5. Polypropylene, TDMC, free radical scavenger and zeolite are loaded into a high-speed mixer and stirred and mixed, then extruded and granulated at an extrusion temperature of 160℃.

[0025] Example 3 A flame retardant masterbatch for polypropylene, comprising the following components by weight: 45 parts polypropylene, 55 parts TDMC, 13 parts free radical scavenger and 4 parts zeolite.

[0026] The preparation method of the above-mentioned flame retardant masterbatch for polypropylene includes the following steps: Preparation of S1 and DOPO-DPP; 0.9 mol diaminodiphenyl sulfone, 2 mol p-formylbenzoic acid and 250 mL tetrahydrofuran solvent were mixed and stirred at 65 °C for 5.5 h under a nitrogen atmosphere. After the reaction was completed, the reaction solution was cooled to room temperature, and 2 mol DOPO was added. The reaction was stirred at a nitrogen atmosphere for 13 h. After the reaction was completed, the mixture was filtered, and the filter cake was washed three times with tetrahydrofuran at 5 °C and dried to obtain DOPO-DPP. S2, Preparation of macromolecular flame retardant TDMC; 0.4 mol of tris(2-hydroxyethyl) isocyanurate was heated to melt, and then 2.0 g of tetrabutyl titanate catalyst and 1.2 mol of DOPO-DPP were added. The mixture was stirred at 163 °C for 3.5 h. After the reaction was completed, 1.2 mol of melamine and 1.2 mol of cyanuric acid were added, and the mixture was stirred at 193 °C for 30 min to obtain a viscous melt. After cooling and pulverizing, the macromolecular flame retardant TDMC was obtained. Preparation of S3, 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine; 0.1 mol cyanuric chloride, 100 mL chlorobenzene, and 40 g aluminum trichloride were mixed and stirred, then cooled to 3 °C. 0.198 mol benzene was slowly added to the mixture, and the mixture was stirred for 2 h. The mixture was then naturally heated to room temperature and stirred for 12 h. The mixture was then heated to 50 °C and 0.11 mol resorcinol was slowly added. The mixture was then heated to 78 °C and reacted for 5 h. After the reaction was completed, chlorobenzene was removed by azeotropic distillation. The mixture was then cooled to 60 °C and filtered. The precipitate was dried and recrystallized in N,N-dimethylformamide to obtain 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. 0.05 mol of 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, 90 mL of butyl acetate, and 8.0 g of potassium carbonate were mixed and stirred until the temperature reached 60 °C. 0.58 mol of ethyl chloroacetate was added dropwise over 2 hours. The mixture was then reacted at 63 °C for 6 hours. The mixture was then heated to 100 °C and filtered. The filtrate was collected and cooled to 10 °C to crystallize. The solid was collected, dried, and recrystallized in N,N-dimethylformamide to give 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine. S4. A free radical scavenger was prepared by transesterification of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol. Specifically, 0.02 mol of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine, 0.021 mol of 2,2,6,6-tetramethylpiperidinol and 0.4 g of dibutyltin oxide catalyst were mixed, and then 30 mL of o-dichlorobenzene solvent was added. The mixture was reacted at 153 °C for 8 h under nitrogen protection. After the reaction was completed, activated carbon was added for decolorization. The filtrate was then filtered hot and crystallized. The solid was collected and recrystallized in N,N-dimethylformamide to obtain a free radical scavenger. S5. Polypropylene, TDMC, free radical scavenger and zeolite are loaded into a high-speed mixer and stirred and mixed, then extruded and granulated at an extrusion temperature of 155℃.

[0027] Example 4 A flame retardant masterbatch for polypropylene, comprising the following components by weight: 48 parts polypropylene, 53 parts TDMC, 11 parts free radical scavenger and 4 parts zeolite.

[0028] The preparation method of the flame-retardant masterbatch for polypropylene described above is the same as that in Example 1.

[0029] Example 5 A flame retardant masterbatch for polypropylene, comprising the following components by weight: 43 parts polypropylene, 58 parts TDMC, 11 parts free radical scavenger and 4 parts zeolite.

[0030] The preparation method of the flame-retardant masterbatch for polypropylene described above is the same as that in Example 1.

[0031] Comparative Example 1: A flame retardant masterbatch for polypropylene, comprising the following components by weight: 40 parts polypropylene, 50 parts TDMC and 3 parts zeolite.

[0032] In this comparative example, the preparation methods of TDMC and flame retardant masterbatch for polypropylene are the same as those in Example 1, the only difference being the different components used.

[0033] Comparative Example 2: A flame retardant masterbatch for polypropylene, comprising the following components by weight: 40 parts polypropylene, 10 parts free radical scavenger and 3 parts zeolite.

[0034] The preparation methods of the free radical scavenger and the flame retardant masterbatch for polypropylene in this comparative example are the same as those in Example 1, the only difference being the different components used.

[0035] Comparative Example 3 A flame retardant masterbatch for polypropylene, comprising the following components by weight: 40 parts polypropylene, 50 parts flame retardant and 3 parts zeolite.

[0036] The flame-retardant powder includes: 3 parts ammonium polyphosphate, 1 part pentaerythritol and 1 part melamine.

[0037] In this comparative example, the flame retardant powder was prepared by mechanically mixing ammonium polyphosphate, pentaerythritol, and melamine.

[0038] The preparation method of the flame retardant masterbatch in this comparative example is the same as that in Example 1.

[0039] The polypropylene obtained in Examples 1-5 and Comparative Examples 1-3 was used as flame retardant masterbatch to prepare composite material samples. Specifically, 88 wt% polypropylene and 12 wt% flame retardant masterbatch were mixed evenly and poured into a torque rheometer for melt blending to obtain composite material. The temperature in all three zones was 180℃, the mixing time was set to 8 min, and the speed was 50 rpm. Then, the composite material was hot-pressed into square samples of 100 mm × 100 mm × 3.2 mm. The hot-pressing pressure was 15 MPa, the temperature was 185℃, and the hot-pressing time was 15 min. The square samples were cut into composite material strips for testing. The obtained composite material strips were respectively named Example 1 Group, Example 2 Group, Example 3 Group, Example 4 Group, Example 5 Group, Comparative Example 1 Group, Comparative Example 2 Group, and Comparative Example 3 Group.

[0040] The flame-retardant masterbatch obtained in Comparative Example 3 was used as a flame retardant to prepare composite material samples. Specifically, 75 wt% polypropylene and 25 wt% flame-retardant masterbatch were used as Comparative Example 4.

[0041] The limiting oxygen index (LOI) of composite material specimens in Examples 1-5 and Comparative Examples 1-4 was tested according to standard GB / T 2406.2-2009. The LIO of the composite material specimens was tested. The specimen size was 100mm×6.5mm×3.2mm. The test results are shown in Table 1.

[0042] Vertical burning tests were conducted on the composite material samples of Examples 1-5 and Comparative Examples 1-4 in accordance with standard GB / T 2408-2021 to test the UL-94 rating of the composite material samples. The sample size was 100mm×13mm×3.2mm. The test results are shown in Table 1.

[0043] Table 1. Results of vertical burning test and limiting oxygen index test of composite material specimens. ; As shown in Table 1, the flame retardant masterbatch of Examples 1-5 had the best flame retardant effect on polypropylene. The vertical burning test result of the composite material sample prepared by the flame retardant masterbatch of Comparative Example 3 was NR in UL-94. This is because the amount of flame retardant masterbatch added to the composite material sample of Comparative Example 3 was too small to achieve flame retardant performance. The flame retardant effect of the composite material sample of Comparative Example 4 was also good, indicating that the flame retardant masterbatch prepared by Comparative Example 3 needs to be added at a higher amount to achieve a better flame retardant effect. However, the LOI value of Comparative Example 4 was still lower than that of Examples 1-5.

[0044] Compared with Examples 1-5, the flame retardant effect of the composite material samples prepared by the flame retardant masterbatch of Comparative Example 1 and Comparative Example 2 was reduced to different degrees. The limiting oxygen index result of Comparative Example 2 was similar to that of Comparative Example 3. This is because no TDMC was added in Comparative Example 2, and the resulting composite material sample was extremely easy to burn.

[0045] The composite material samples of Examples 1-5 and Comparative Examples 1-3 were tested for resistance to damp heat. Specifically, the samples of each group were placed in a deionized water environment at 70°C for 168 hours for damp heat aging, and the samples after damp heat aging were tested for flame retardancy. The results are shown in Table 2.

[0046] Table 2. Vertical combustion test results and limiting oxygen index test results of composite material specimens after damp heat aging. ; As shown in Table 2, the flame retardant properties of the composite material samples in Examples 1-5 did not decrease significantly. The LOI of Examples 1-5 and Comparative Example 1 decreased by only about 5%, indicating that the flame retardant masterbatch prepared in Examples 1-5 has better compatibility with polypropylene, better hydrophobic properties, and will not precipitate under humid heat. However, the flame retardant properties of the composite material samples in Comparative Example 4 decreased significantly. This is because the flame retardant masterbatch prepared in Comparative Example 3 precipitated significantly after humid heat aging in polypropylene, making it unable to retard the polypropylene. This indicates that the flame retardant masterbatch prepared in this invention has higher humid heat resistance than existing ammonium polyphosphate intumescent flame retardants.

[0047] The flame retardant properties of the composite material specimens in Comparative Example 2 and Comparative Example 3 were similar to those before damp heat aging, and their flame retardant properties remained very poor.

[0048] The flame retardant masterbatches prepared in Example 1 and Comparative Examples 1-3 were subjected to thermal stability tests. The 5% decomposition temperature and the final residual mass percentage of the flame retardant masterbatches were recorded. The results are shown in Table 3.

[0049] Table 3. Thermal stability test results of flame retardant masterbatches in Example 1 and Comparative Examples 1-3 ; As can be seen from Table 3, the thermal stability of the flame retardant masterbatch of the present invention is higher than that of the existing ammonium polyphosphate intumescent flame retardant, mainly due to the higher thermal stability of the TDMC prepared by the present invention; the comparison of residual mass percentage shows that the flame retardant masterbatch of the present invention has better char-forming performance.

[0050] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing flame-retardant masterbatch for polypropylene, characterized in that, Includes the following steps: S1. Tris(2-hydroxyethyl) isocyanurate is heated and melted, and then tetrabutyl titanate and DOPO-DPP catalysts are added to it. The mixture is stirred and reacted at 160~165℃ for 3~4h. After the reaction is completed, melamine and cyanuric acid are added to it, and the mixture is stirred and reacted at 190~195℃ for 30min to obtain a viscous melt. After cooling and pulverizing, the macromolecular flame retardant TDMC is obtained. S2. A free radical scavenger was prepared by transesterification of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol. S3. 40-50 parts of polypropylene, 50-60 parts of TDMC, 10-15 parts of free radical scavenger and 3-5 parts of zeolite are loaded into a high-speed mixer and stirred and mixed. Then, the mixture is extruded and granulated to obtain flame retardant masterbatch for polypropylene. The extrusion temperature is 150-160℃.

2. The method for preparing flame-retardant masterbatch for polypropylene according to claim 1, characterized in that, In step S1, the preparation method of DOPO-DPP is as follows: diaminodiphenyl sulfone, p-formylbenzoic acid and tetrahydrofuran solvent are mixed and stirred at 50~80℃ for 5~6h under a nitrogen atmosphere. After the reaction is completed, the reaction solution is cooled to room temperature, DOPO is added to it, and the reaction is stirred under a nitrogen atmosphere for 12~15h. After the reaction is completed, the mixture is filtered, and the filter cake is washed three times with tetrahydrofuran and dried to obtain DOPO-DPP.

3. The method for preparing flame-retardant masterbatch for polypropylene according to claim 2, characterized in that, The molar ratio of diaminodiphenyl sulfone, p-formylbenzoic acid and DOPO is 0.8~1:2:

2.

4. The method for preparing flame-retardant masterbatch for polypropylene according to claim 1, characterized in that, In step S2, the preparation method of the 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine is as follows: S21. Mix cyanuric chloride, chlorobenzene and aluminum trichloride, stir and cool to 0~5℃, slowly add benzene and stir for 2h, then naturally heat to room temperature and stir for 12h, then heat to 50℃ and slowly add resorcinol, then heat to 75~80℃ and react for 5h. After the reaction is complete, remove chlorobenzene by azeotropic distillation, then cool to 60℃ and filter. Dry the precipitate and recrystallize to obtain 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine. S22. Mix 2,4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine, butyl acetate, and potassium carbonate, stir, and heat to 60°C. Add ethyl chloroacetate dropwise over 2 hours. React at 60-65°C for 6 hours. Then, heat to 100°C and filter. Collect the filtrate, cool, and crystallize. Collect the solid, dry, and recrystallize to obtain 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine.

5. The method for preparing flame-retardant masterbatch for polypropylene according to claim 4, characterized in that, The molar ratio of cyanuric chloride, benzene, and resorcinol is 1:1.95 to 2:1.1, and the molar ratio of 4-diphenyl-6-(2,4-dihydroxyphenyl)-1,3,5-triazine and ethyl chloroacetate is 1:1.1 to 1.

2.

6. The method for preparing flame-retardant masterbatch for polypropylene according to claim 1, characterized in that, In step S1, the molar ratio of tris(2-hydroxyethyl) isocyanurate, DOPO-DPP, melamine and cyanuric acid is 1:3:3:

3.

7. The method for preparing flame-retardant masterbatch for polypropylene according to claim 1, characterized in that, In step S2, the preparation method of the free radical scavenger is as follows: 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine, 2,2,6,6-tetramethylpiperidinol and the catalyst dibutyltin oxide are mixed, and then o-dichlorobenzene is added as a solvent. The mixture is reacted at 150-155°C for 8 hours under nitrogen protection. After the reaction is completed, activated carbon is added for decolorization. After hot filtration, the filtrate is crystallized, and the solid is collected and recrystallized to obtain the free radical scavenger.

8. The method for preparing flame-retardant masterbatch for polypropylene according to claim 7, characterized in that, The molar ratio of 2,4-diphenyl-6-[2-hydroxy-4-(ethoxycarbonylmethoxy)phenyl]-1,3,5-triazine and 2,2,6,6-tetramethylpiperidinol is 1:1 to 1.

1.

9. The flame retardant masterbatch prepared by the method for preparing flame retardant masterbatch for polypropylene according to claim 1.

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