Plastic material for flame-retardant food and preparation method of plastic material

Abstract

The invention discloses a plastic material for flame-retardant food and a preparation method of the plastic material, and the plastic material comprises the following raw materials in parts by weight: 80-100 parts of modified polypropylene, 3-5 parts of modified graphene, 5-10 parts of flame-retardant filler and 0.1-0.3 part of tetraphenylphosphorus bromide, amino groups on the side chain of the modified polypropylene and amino groups on the flame-retardant filler react with epoxy groups on the modified filler in the melt extrusion process of the raw materials to form cross-linked grids, the flame-retardant filler takes ammonium polyphosphate as a matrix, the surface of the flame-retardant filler is coated with modified polysiloxane, and the structure can reduce the water absorption of ammonium polyphosphate, so that after the plastic material is stored for a long time, the flame-retardant performance of the plastic material is improved. And during combustion, the flame-retardant filler is heated and decomposed to generate polyphosphoric acid and ammonia gas, the polyphosphoric acid catalyzes dehydration and carbonization of the base material and is matched with the modified filler, a compact carbon layer can be formed, generated phosphorus free radicals capture H and OH free radicals in combustion, a chain reaction is interrupted, and then the flame-retardant effect is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food plastic preparation, in particular to a flame-retardant plastic material for food and a preparation method thereof. BACKGROUND

[0002] With the improvement of people's awareness of food safety and health, new demands for packaging materials with higher flame-retardant requirements have been put forward in the market. In particular in the field of food packaging, although traditional plastic materials have the advantages of light weight, low cost, high transparency, etc., their flammability is a significant safety hazard, especially in a high-temperature environment, the burning rate is fast, and the toxic smoke generated is large, which not only affects the safety of food, but also may threaten the safety of consumers. To solve this problem, various flame-retardant plastic materials have emerged, but these materials often have the problem of poor comprehensive performance. For example, the flame-retardant effect will decrease or the flame-retardant substances will precipitate in a humid environment, resulting in a decrease in the flame-retardant effect. SUMMARY

[0003] The present application relates to the technical field of food plastic preparation, in particular to a flame-retardant plastic material for food and a preparation method thereof.

[0004] The object of the present application can be achieved by the following technical solutions:

[0005] A preparation method of a flame-retardant plastic material for food, specifically comprising the following steps:

[0006] Step A1: polypropylene material, maleic anhydride and dicumyl peroxide are added to a torque rheometer, and under the conditions of a rotation speed of 30-60 r / min, a temperature of 170-180℃ and a nitrogen atmosphere, they are melt-reacted for 10-15 min to obtain pretreated polypropylene; the pretreated polypropylene and ethylenediamine are added to the torque rheometer, and under the conditions of a rotation speed of 30-60 r / min and a temperature of 130-140℃, they are melt-reacted for 1.5-2 h to obtain modified polypropylene;

[0007] Step A2: carboxylated graphene is dispersed in ethanol, and under the conditions of a rotation speed of 300-500 r / min and a temperature of 60-70℃, deionized water and gamma-glycidoxypropyltrimethoxysilane are added and stirred for 3-5 h to obtain modified graphene;

[0008] Step A3: take the following weight parts of raw materials: modified polypropylene 80-100 parts, modified graphene 3-5 parts, flame retardant filler 5-10 parts and tetraphenyl phosphonium bromide 0.1-0.3 parts, add the raw materials into the twin-screw extruder, extrude and cool under the conditions of zone 1 temperature 140-150℃, zone 2 temperature 150-160℃, zone 3 temperature 160-165℃ and die temperature 160-170℃, to obtain a flame-retardant plastic material for food.

[0009] Further, the mass ratio of the polypropylene material, maleic anhydride and dicumyl peroxide in step A1 is 100:2:0.3, the mass ratio of the pretreated polypropylene and ethylenediamine is 100:0.5, and the model of the polypropylene material is Z30S.

[0010] Further, the amount of γ-glycidyl ether propyltrimethoxysilane used in step A2 is 2% of the mass of carboxylated graphene.

[0011] Further, the flame retardant filler is prepared by the following steps:

[0012] Step B1: mix phenylphosphoryl dichloride, glycerol and acetonitrile uniformly, react under the conditions of rotation speed 150-200r / min and temperature 80-85℃ for 8-10h to obtain intermediate 1, mix intermediate 1, acrylic acid, p-toluenesulfonic acid and toluene uniformly, react under the conditions of rotation speed 60-80r / min and temperature 110-115℃ for 6-8h to obtain intermediate 2, mix intermediate 2 and concentrated sulfuric acid uniformly, stir under the conditions of rotation speed 120-150r / min and temperature 0℃, add fuming nitric acid, warm up to 20-25℃, and react for 3-5h to obtain a modifier;

[0013] Step B2: mix tetramethylcyclotetrasiloxane, γ-aminopropyl methyl dimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water uniformly, protect with nitrogen, react under the conditions of rotation speed 120-150r / min and temperature 90-95℃ for 10-15h, warm up to 105-110℃, react for 2-3h to obtain polysiloxane, mix polysiloxane, modifier, chloroplatinic acid and DMF uniformly, protect with nitrogen, react under the conditions of rotation speed 150-200r / min and temperature 80-85℃ for 2-3h to obtain modified siloxane;

[0014] Step B3: mixing ammonium polyphosphate, modified polysiloxane and DMF, and reacting for 3-5 h at a rotation speed of 300-500 r / min and a temperature of 80-85 DEG C to obtain a pretreated filler, mixing the pretreated filler, zinc powder and DMF uniformly, stirring and adding concentrated hydrochloric acid at a rotation speed of 60-80 r / min and a temperature of 90-95 DEG C, and reacting for 3-4 h, then adjusting the pH value to 11-12 to obtain the flame-retardant filler.

[0015] Further, the molar ratio of phenylphosphonic dichloride and glycerol in step B1 is 1:1, the molar ratio of intermediate 1 and acrylic acid is 1:1, the amount of p-toluenesulfonic acid is 2% of the mass sum of intermediate 1 and acrylic acid, the amount ratio of intermediate 2, concentrated sulfuric acid and fuming nitric acid is 40 mmol:25 mL:43 mmol, the mass fraction of concentrated sulfuric acid is 98%, and the mass fraction of fuming nitric acid is 90%.

[0016] Further, the molar ratio of tetramethylcyclotetrasiloxane, gamma-aminopropyl methyl dimethoxy silane, hexamethyl disiloxane, tetramethyl ammonium hydroxide and deionized water in step B2 is 1:0.2:1:1.5:0.36, the molar ratio of Si-H bond on polysiloxane and modifier is 1:1, and the amount of chloroplatinic acid is 1 ‰ of the mass of the modifier.

[0017] Further, the mass ratio of ammonium polyphosphate and modified polysiloxane in step B3 is 1:3, the amount ratio of pretreated filler, zinc powder, DMF and concentrated hydrochloric acid is 15 g:16 g:200 mL:55 mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0018] The application has the following beneficial effects: the disclosed flame-retardant plastic material for food includes the following raw materials: modified polypropylene, modified graphene, flame-retardant filler and tetraphenyl phosphonium bromide, the modified polypropylene is prepared by treating polypropylene material with maleic anhydride, so that the maleic anhydride is covalently grafted onto the polypropylene chain through addition reaction to form a branched structure containing anhydride groups, and the pretreated polyethylene is prepared by reacting the pretreated polyethylene with ethylenediamine, so that the anhydride groups react with one amino group on the ethylenediamine to obtain the modified polypropylene.

[0019] The modified graphene is prepared by treating carboxylated graphene with gamma-glycidyl ether oxypropyl trimethoxysilane to graft epoxy groups on the surface.

[0020] The flame-retardant filler is prepared by the following steps: taking phenylphosphoryl dichloride and glycerol as raw materials, reacting the chlorine atoms on the phenylphosphoryl dichloride with the hydroxyl groups on the glycerol to obtain an intermediate 1, reacting the intermediate 1 with acrylic acid to esterify the hydroxyl groups on the intermediate 1 with the carboxyl groups on the acrylic acid to obtain an intermediate 2, treating the intermediate 2 with fuming nitric acid to obtain a modifier, opening the ring of tetramethylcyclotetrasiloxane, and then hydrolyzing and condensing the opened ring with gamma-aminopropyl methyl dimethoxysilane, and finally capping the hydrolyzed and condensed product with hexamethyldisiloxane to obtain polysiloxane, reacting the polysiloxane with the modifier to make the Si-H bonds on the polysiloxane react with the double bonds on the modifier, obtaining modified polysiloxane, and reacting the modified polysiloxane with ammonium polyphosphate to make the amino groups on the modified polysiloxane ion exchange with the ammonium polyphosphate, so that the modified polysiloxane is grafted on the surface of the ammonium polyphosphate to form ammonium polyphosphate coated with modified polysiloxane, obtaining pretreated filler, and reducing the pretreated filler with zinc powder to reduce the nitro groups on the surface to amino groups, obtaining the flame-retardant filler.

[0021] During the raw material melt extrusion process, the amino groups on the side chains of the modified polypropylene and the amino groups on the flame-retardant filler react with the epoxy groups on the modified filler to form a crosslinked network, and the flame-retardant filler is coated with modified polysiloxane on the surface of the ammonium polyphosphate matrix. This structure can reduce the water absorption of ammonium polyphosphate, so that the plastic material can still maintain the flame-retardant effect after long-term storage. When burning, the flame-retardant filler decomposes to generate polyphosphoric acid and ammonia gas. The polyphosphoric acid catalyzes the dehydration and carbonization of the base material, and cooperates with the modified filler to form a dense carbon layer. The generated phosphorus free radicals capture H· and OH· free radicals in the combustion, interrupt the chain reaction, and thus achieve the flame-retardant effect. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present application will be described below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0023] Embodiment 1 is a preparation method of a flame-retardant plastic material for food, which specifically comprises the following steps:

[0024] Step A1: polypropylene material, maleic anhydride and dicumyl peroxide are added into a torque rheometer, and melt reaction is carried out under the conditions of a rotation speed of 30 r / min, a temperature of 170℃ and a nitrogen atmosphere for 10 min to obtain pretreated polypropylene. The pretreated polypropylene and ethylenediamine are added into the torque rheometer, and melt reaction is carried out under the conditions of a rotation speed of 30 r / min and a temperature of 130℃ for 1.5 h to obtain modified polypropylene.

[0025] Step A2: the carboxylated graphene was dispersed in ethanol, stirring at 300 r / min and 60℃, and then deionized water and γ-glycidyl ether propyl trimethoxysilane were added and reacted for 3h to obtain modified graphene;

[0026] Step A3: the raw materials were weighed as follows: 80 parts of modified polypropylene, 3 parts of modified graphene, 5 parts of flame-retardant filler, and 0.1 parts of tetraphenyl phosphonium bromide, and then the raw materials were added into a twin-screw extruder, and extruded and cooled under the conditions of zone 1 temperature of 140℃, zone 2 temperature of 150℃, zone 3 temperature of 160℃, and die temperature of 160℃ to obtain a flame-retardant plastic material for food.

[0027] The mass ratio of the polypropylene material, maleic anhydride and dicumyl peroxide in step A1 was 100:2:0.3, and the mass ratio of the pretreated polypropylene and ethylenediamine was 100:0.5, and the type of the polypropylene material was Z30S.

[0028] The amount of γ-glycidyl ether propyl trimethoxysilane used in step A2 was 2% of the mass of the carboxylated graphene.

[0029] The flame-retardant filler was prepared by the following steps:

[0030] Step B1: phenylphosphoryl dichloride, glycerol and acetonitrile were uniformly mixed, and reacted for 8h at 150 r / min and 80℃ to obtain intermediate 1, intermediate 1, acrylic acid, p-toluenesulfonic acid and toluene were uniformly mixed, and reacted for 6h at 60 r / min and 110℃ to obtain intermediate 2, intermediate 2 and concentrated sulfuric acid were uniformly mixed, and reacted for 3h at 120 r / min and 0℃ by adding fuming nitric acid while stirring and heating to 20℃ to obtain a modifier;

[0031] Step B2: tetramethylcyclotetrasiloxane, γ-aminopropyl methyl dimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water were uniformly mixed, and reacted for 10h at 120 r / min and 90℃ under nitrogen protection, and then reacted for 2h at 105℃ to obtain polysiloxane, and then the polysiloxane, the modifier, chloroplatinic acid and DMF were uniformly mixed, and reacted for 2h at 150 r / min and 80℃ under nitrogen protection to obtain modified siloxane;

[0032] Step B3: Ammonium polyphosphate, modified polysiloxane and DMF were mixed and reacted for 3 h at 80 ℃ and 300 r / min to obtain a pretreated filler. The pretreated filler, zinc powder and DMF were mixed uniformly, and concentrated hydrochloric acid was added under stirring at 90 ℃ and 60 r / min. The pH value was adjusted to 11, and the reaction was carried out for 3 h to obtain a flame-retardant filler.

[0033] The molar ratio of phenylphosphonic dichloride to glycerol in step B1 was 1:1, the molar ratio of intermediate 1 to acrylic acid was 1:1, the amount of p-toluenesulfonic acid was 2% of the mass sum of intermediate 1 and acrylic acid, the amount ratio of intermediate 2, concentrated sulfuric acid and fuming nitric acid was 40 mmol:25 mL:43 mmol, the mass fraction of concentrated sulfuric acid was 98%, and the mass fraction of fuming nitric acid was 90%.

[0034] The molar ratio of tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water in step B2 was 1:0.2:1:1.5:0.36, the molar ratio of Si-H bond on polysiloxane to modifier was 1:1, and the amount of chloroplatinic acid was 1 ‰ of the mass of the modifier.

[0035] The mass ratio of ammonium polyphosphate to modified polysiloxane in step B3 was 1:3, and the amount ratio of pretreated filler, zinc powder, DMF and concentrated hydrochloric acid was 15 g:16 g:200 mL:55 mL, and the mass fraction of concentrated hydrochloric acid was 36%.

[0036] Example 2, a method for preparing a flame-retardant plastic material for food, specifically comprising the following steps:

[0037] Step A1: Polypropylene material, maleic anhydride and dicumyl peroxide were added to a torque rheometer and reacted for 13 min at 175 ℃ and 30 r / min under a nitrogen atmosphere to obtain pretreated polypropylene. The pretreated polypropylene and ethylenediamine were added to the torque rheometer and reacted for 1.8 h at 135 ℃ and 60 r / min to obtain modified polypropylene.

[0038] Step A2: Carboxylated graphene was dispersed in ethanol, and deionized water and γ-glycidoxypropyltrimethoxysilane were added under stirring at 500 r / min and 65 ℃, and the reaction was carried out for 4 h to obtain modified graphene.

[0039] Step A3: take the following weight parts of raw materials: modified polypropylene 90 parts, modified graphene 4 parts, flame-retardant filler 8 parts and tetraphenyl phosphonium bromide 0.2 parts, add the raw materials into a double screw extruder, extrude and cool under the conditions of zone 1 temperature 145℃, zone 2 temperature 155℃, zone 3 temperature 160℃ and die temperature 165℃, to obtain a flame-retardant plastic material for food.

[0040] The mass ratio of the polypropylene material, maleic anhydride and dicumyl peroxide in step A1 is 100:2:0.3, the mass ratio of the pretreated polypropylene and ethylenediamine is 100:0.5, and the model of the polypropylene material is Z30S.

[0041] The amount of the γ-glycidyl ether propyltrimethoxysilane in step A2 is 2% of the mass of the carboxylated graphene.

[0042] The flame-retardant filler is prepared by the following steps:

[0043] Step B1: mix phenylphosphoryl dichloride, glycerol and acetonitrile uniformly, react under the conditions of rotation speed 200r / min and temperature 83℃ for 9h to obtain intermediate 1, mix intermediate 1, acrylic acid, p-toluenesulfonic acid and toluene uniformly, react under the conditions of rotation speed 60r / min and temperature 115℃ for 7h to obtain intermediate 2, mix intermediate 2 and concentrated sulfuric acid uniformly, stir under the conditions of rotation speed 120r / min and temperature 0℃, add fuming nitric acid, heat to 25℃, and react for 4h to obtain a modifier;

[0044] Step B2: mix tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water uniformly, protect with nitrogen, react under the conditions of rotation speed 150r / min and temperature 90℃ for 13h, heat to 110℃, and react for 3h to obtain polysiloxane, mix the polysiloxane, the modifier, chloroplatinic acid and DMF uniformly, protect with nitrogen, react under the conditions of rotation speed 150r / min and temperature 85℃ for 2.5h to obtain modified siloxane;

[0045] Step B3: mix ammonium polyphosphate, modified polysiloxane and DMF under the conditions of rotation speed 300r / min and temperature 85℃ for 4h to obtain pretreated filler, mix the pretreated filler, zinc powder and DMF uniformly under the conditions of rotation speed 60r / min and temperature 95℃, stir and add concentrated hydrochloric acid, react for 3h, adjust the pH value to 11, and obtain a flame-retardant filler.

[0046] The molar ratio of phenylphosphonic dichloride and glycerol in step B1 is 1:1, the molar ratio of intermediate 1 and acrylic acid is 1:1, the amount of p-toluenesulfonic acid is 2% of the mass of intermediate 1 and acrylic acid, the amount ratio of intermediate 2, concentrated sulfuric acid and fuming nitric acid is 40 mmol:25 mL:43 mmol, the mass fraction of concentrated sulfuric acid is 98%, and the mass fraction of fuming nitric acid is 90%.

[0047] The molar ratio of tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water in step B2 is 1:0.2:1:1.5:0.36, the molar ratio of Si-H bond on polysiloxane and modifier is 1:1, and the amount of chloroplatinic acid is 1 ‰ of the mass of the modifier.

[0048] The mass ratio of ammonium polyphosphate and modified polysiloxane in step B3 is 1:3, the amount ratio of pretreated filler, zinc powder, DMF and concentrated hydrochloric acid is 15 g:16 g:200 mL:55 mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0049] Example 3, a preparation method of a flame-retardant plastic material for food, specifically comprising the following steps:

[0050] Step A1: polypropylene material, maleic anhydride and dicumyl peroxide are added into a torque rheometer, and under the condition of a rotation speed of 60 r / min and a temperature of 180℃ in a nitrogen atmosphere, melt reaction is carried out for 15 min to prepare pretreated polypropylene; the pretreated polypropylene and ethylenediamine are added into the torque rheometer, and under the condition of a rotation speed of 60 r / min and a temperature of 140℃, melt reaction is carried out for 2 h to prepare modified polypropylene;

[0051] Step A2: carboxylated graphene is dispersed in ethanol, and under the condition of a rotation speed of 500 r / min and a temperature of 70℃, deionized water and γ-glycidyl ether propyltrimethoxysilane are added and reacted for 5 h to prepare modified graphene;

[0052] Step A3: the following raw materials are weighed: 100 parts of modified polypropylene, 5 parts of modified graphene, 10 parts of flame-retardant filler and 0.3 parts of tetraphenylphosphonium bromide; the raw materials are added into a twin-screw extruder, and under the condition of a temperature of 150℃ in the first zone, a temperature of 160℃ in the second zone, a temperature of 165℃ in the third zone and a die temperature of 170℃, extrusion and cooling are carried out to prepare a flame-retardant plastic material for food.

[0053] The mass ratio of polypropylene material, maleic anhydride and dicumyl peroxide in step A1 is 100:2:0.3, the mass ratio of pretreated polypropylene and ethylenediamine is 100:0.5, and the type of polypropylene material is Z30S.

[0054] The amount of the γ-glycidyloxypropyltrimethoxysilane prepared in step A2 is 2% of the mass of the carboxylated graphene.

[0055] The flame-retardant filler is prepared by the following steps:

[0056] Step B1: uniformly mix phenylphosphonic dichloride, glycerol and acetonitrile, and react for 10 h at a rotation speed of 200 r / min and a temperature of 85°C to obtain intermediate 1; uniformly mix intermediate 1, acrylic acid, p-toluenesulfonic acid and toluene, and react for 8 h at a rotation speed of 80 r / min and a temperature of 115°C to obtain intermediate 2; uniformly mix intermediate 2 and concentrated sulfuric acid, and stir at a rotation speed of 150 r / min and a temperature of 0°C, and then add fuming nitric acid while the temperature is raised to 25°C, and react for 5 h to obtain a modifier;

[0057] Step B2: uniformly mix tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water, and protect under nitrogen, and react for 15 h at a rotation speed of 150 r / min and a temperature of 95°C, and then react for 3 h while the temperature is raised to 110°C to obtain polysiloxane; uniformly mix the polysiloxane, the modifier, chloroplatinic acid and DMF, and protect under nitrogen, and react for 3 h at a rotation speed of 200 r / min and a temperature of 85°C to obtain modified siloxane;

[0058] Step B3: mix ammonium polyphosphate, modified polysiloxane and DMF, and react for 5 h at a rotation speed of 500 r / min and a temperature of 85°C to obtain pretreated filler; uniformly mix the pretreated filler, zinc powder and DMF, and stir at a rotation speed of 80 r / min and a temperature of 95°C, and then add concentrated hydrochloric acid, and react for 4 h to obtain a flame-retardant filler.

[0059] The molar ratio of phenylphosphonic dichloride to glycerol in step B1 is 1:1, the molar ratio of intermediate 1 to acrylic acid is 1:1, the amount of p-toluenesulfonic acid is 2% of the mass of intermediate 1 and acrylic acid, the amount ratio of intermediate 2, concentrated sulfuric acid and fuming nitric acid is 40 mmol:25 mL:43 mmol, the mass fraction of concentrated sulfuric acid is 98%, and the mass fraction of fuming nitric acid is 90%.

[0060] The molar ratio of tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water in step B2 is 1:0.2:1:1.5:0.36, the molar ratio of Si-H bonds on the polysiloxane to the modifier is 1:1, and the amount of chloroplatinic acid is 1‰ of the mass of the modifier.

[0061] The mass ratio of ammonium polyphosphate and modified polysiloxane in step B3 is 1:3, and the ratio of the amount of pretreated filler, zinc powder, DMF and concentrated hydrochloric acid is 15g:16g:200mL:55mL, and the mass fraction of concentrated hydrochloric acid is 36%.

[0062] Comparative Example 1, this comparative example uses graphene instead of modified graphene compared with Example 1, and the rest of the steps are the same.

[0063] Comparative Example 2, this comparative example uses polypropylene material instead of modified polypropylene compared with Example 1, and the rest of the steps are the same.

[0064] Comparative Example 3, this comparative example uses 4-nitrostyrene instead of modifier compared with Example 1, and the rest of the steps are the same.

[0065] Comparative Example 4, this comparative example uses ammonium polyphosphate instead of flame-retardant filler compared with Example 1, and the rest of the steps are the same.

[0066] The plastic materials prepared in Examples 1-3 and Comparative Examples 1-3 are made into test samples with a size of 125mmx13mmx10mm, and the vertical burning grade is detected under the conditions of air humidity of 30%, 50% and 70% according to the standard of GB / T2408-2008, and the test results are shown in Table 1.

[0067] Table 1

[0068] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Air humidity 30% V0 V0 V0 V1 V1 V1 NR Air humidity 50% V0 V0 V0 V1 V1 V1 NR Air humidity 70% V0 V0 V0 V1 V1 V1 NR

[0069] From Table 1, it can be seen that the present application has good flame-retardant effect.

[0070] The above content is only an example and description of the concept of the present application, and those skilled in the art can make various modifications or supplements or use similar ways to replace the described specific examples, as long as they do not deviate from the concept of the present application or exceed the scope defined by the present claims, and should belong to the protection scope of the present application.

Claims

1. A method for preparing a flame-retardant plastic material for food, characterized by: The specific steps include: Step A1: adding polypropylene material, maleic anhydride and dicumyl peroxide into a torque rheometer and performing a melt reaction to obtain pretreated polypropylene; adding pretreated polypropylene and ethylenediamine into a torque rheometer and performing a melt reaction to obtain modified polypropylene; Step A2: dispersing the carboxylated graphene in ethanol, stirring, and adding deionized water and γ-glycidyloxypropyltrimethoxysilane to react to obtain modified graphene; Step A3: Weigh the following raw materials in parts by weight: 80-100 parts of modified polypropylene, 3-5 parts of modified graphene, 5-10 parts of flame retardant filler and 0.1-0.3 parts of tetraphenylphosphonium bromide, add the raw materials into a twin-screw extruder, extrude and cool to obtain a flame-retardant food plastic material.

2. The method for preparing a flame-retardant plastic material for food according to claim 1, characterized in that: The mass ratio of the polypropylene material, maleic anhydride and dicumyl peroxide described in step A1 is 100:2:0.3, and the mass ratio of the pretreated polypropylene and ethylenediamine is 100:0.

5.

3. The method for preparing a flame-retardant plastic material for food according to claim 1, wherein: The amount of γ-glycidyloxypropyltrimethoxysilane used in step A2 is 2% of the mass of the carboxylated graphene.

4. The method for preparing a flame-retardant plastic material for food according to claim 1, wherein: The flame retardant filler is prepared by the following steps: Step B1: Phenylphosphoryl dichloride, glycerol, and acetonitrile are mixed to react to obtain intermediate 1, intermediate 1, acrylic acid, p-toluenesulfonic acid, and toluene are mixed to react to obtain intermediate 2, intermediate 2 and concentrated sulfuric acid are mixed and stirred, and fuming nitric acid is added to react to obtain a modifier; Step B2: Tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water are uniformly mixed, nitrogen is introduced to protect the reaction, and polysiloxane is obtained. Polysiloxane, a modifier, chloroplatinic acid and DMF are uniformly mixed, nitrogen is introduced to protect the reaction, and modified siloxane is obtained. Step B3: ammonium polyphosphate, modified polysiloxane and DMF are mixed and reacted to prepare a pretreated filler, the pretreated filler, zinc powder and DMF are mixed and stirred, concentrated hydrochloric acid is added, the mixture is reacted, and the pH is adjusted to alkaline to prepare a flame retardant filler.

5. The method for preparing a flame-retardant plastic material for food according to claim 4, characterized in that: The molar ratio of phenylphosphoryl dichloride and glycerol in step B1 is 1:1, the molar ratio of intermediate 1 and acrylic acid is 1:1, and the amount ratio of intermediate 2, concentrated sulfuric acid and fuming nitric acid is 40mmol:25mL:43mmol.

6. The method for preparing a flame-retardant plastic material for food according to claim 4, characterized in that: The molar ratio of tetramethylcyclotetrasiloxane, γ-aminopropylmethyldimethoxysilane, hexamethyldisiloxane, tetramethylammonium hydroxide and deionized water in step B2 is 1:0.2:1:1.5:0.36, and the molar ratio of Si-H bonds on the polysiloxane to the modifier is 1:

1.

7. The method for preparing a flame-retardant plastic material for food according to claim 4, characterized in that: The mass ratio of ammonium polyphosphate and modified polysiloxane described in step B3 is 1:3, and the usage ratio of pretreated filler, zinc powder, DMF and concentrated hydrochloric acid is 15g:16g:200mL:55mL.

8. A flame-retardant plastic material for food, characterized by: Prepared according to any one of claims 1 to 7.