Graphite grade expandable polystyrene beads and process for their preparation

Abstract

The application provides a kind of graphite grade expandable polystyrene beads and its preparation process, belong to expandable polystyrene technical field, the preparation process includes steps: S1, according to weight fraction, 150-230 parts of deionized water is injected into reaction kettle, 0.5-1 parts of dispersion stabilizer is added, stirring, 100 parts of styrene, 3.3-3.8 parts of intercalation-modified double modified graphite, 0.3-0.35 parts of initiator and 0.9-1.1 parts of phosphorus-nitrogen system intumescent flame retardant are added, continue to stir, heat to 86-90 DEG C, constant temperature 7-9 h, obtain granular dispersion phase;S2, 5.6-6.2 parts of foaming agent is added to granular dispersion phase, temperature is raised to 120 DEG C, after continuous reaction 4.5-5.5 h, cooling, discharge, cleaning, filtration, the graphite grade expandable polystyrene beads are obtained;Intercalation-modified double modified graphite is prepared by surface modification of polybutylene succinate-1,3-propanediol ester from oxidized intercalation graphite.The application ensures that the product prepared has excellent thermal stability, and improves its flame retardance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of expandable polystyrene and particularly relates to graphite-grade expandable polystyrene beads and a preparation process thereof. BACKGROUND

[0002] Expandable polystyrene has excellent heat insulation performance, low water absorption, aging resistance, waterproof performance and low price, and is widely used as a heat insulation material in the field of energy-saving buildings. Graphite is an inorganic substance with black color and chemical composition of carbon, and has good chemical stability and can be used as refractory materials, conductive materials and wear-resistant lubricating materials. Natural graphite is mainly in the form of flake structure, which has excellent infrared reflection performance, and thus can be used to improve the heat conduction performance of materials. In order to further reduce the thermal conductivity of expandable polystyrene and improve its heat insulation performance, graphite can be added to prepare graphite-containing expandable polystyrene.

[0003] However, the surface of graphite contains a polymerization inhibitor group, such as a quinone group, which has a strong polymerization inhibition effect on the free radical polymerization of styrene. The greater the content of graphite, the more obvious the polymerization inhibition effect on the polymerization of styrene, the more obvious the inhibition effect on chain growth, and the lower the relative molecular mass of the product. With the increase of the amount of graphite added, the initial decomposition temperature of the prepared graphite-containing expandable polystyrene shows a downward trend, and the thermal stability decreases. SUMMARY

[0004] To solve the problems in the background art, the application provides graphite-grade expandable polystyrene beads and a preparation process thereof, which ensure that the product has excellent thermal stability and improves its flame retardance.

[0005] To achieve the above-mentioned purpose, in a first aspect, the application provides a preparation process of graphite-grade expandable polystyrene beads, which comprises the following steps:

[0006] S1, 150-230 parts of deionized water are injected into a reaction kettle according to the weight fraction, 0.5-1 part of a dispersion stabilizer is added, stirred, 100 parts of styrene, 3.3-3.8 parts of intercalation-modified double-modified graphite, 0.3-0.35 parts of an initiator and 0.9-1.1 parts of a phosphorus-nitrogen intumescent flame retardant are added, and continuous stirring is performed. Heating to 86-90℃, constant temperature for 7-9h, polymerization to generate polymer particles, to obtain a particle dispersion phase;

[0007] S2, 5.6-6.2 parts of a foaming agent are added to the particle dispersion phase obtained in S1, heated to 120℃, and continuously reacted for 4.5-5.5h, then cooled, discharged, washed and filtered, to obtain graphite-grade expandable polystyrene beads;

[0008] The intercalation-modification double modified graphite is prepared from the oxidized intercalation graphite through poly(1,3-propanediol succinate) surface modification.

[0009] Further, the preparation method of the intercalation-modification double modified graphite is as follows:

[0010] A1, the reactants 1,3-propanediol and succinic acid are placed in a three-necked flask at a molar ratio of 1:(1.1-1.2), a polymerization inhibitor is added, and pre-polycondensation is carried out at 180-190°C for 1.5-1.8h under nitrogen protection; a catalyst is added, and the temperature is raised to 220-225°C under vacuum to continue the reaction for 2-3h, and a climbing rod phenomenon appears; the product is dissolved in chloroform, purified by precipitation with cold methanol, and then dried under vacuum at 45-50°C to obtain poly(1,3-propanediol succinate);

[0011] A2, the oxidized intercalation graphite is dispersed in water, and after ultrasonic treatment for 1h, N,N-dimethylformamide is added, and water is removed under reduced pressure to obtain a graphite dispersion liquid;

[0012] A3, the poly(1,3-propanediol succinate) obtained in A1 is dissolved in the graphite dispersion liquid obtained in A2, and the mass ratio of poly(1,3-propanediol succinate) to oxidized intercalation graphite is (10-13):1; after stirring at room temperature for 24h, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine are added as a carboxyl activator to catalyze the esterification reaction; after stirring at room temperature for 72h, a reducing agent is added, and after reduction at 75-80°C for 22-24h, methanol is poured in for co-precipitation, and then dried to obtain the intercalation-modification double modified graphite.

[0013] Further, the preparation method of the oxidized intercalation graphite is as follows: 1g of natural flake graphite is placed in a beaker, 1.7-2.0g of concentrated nitric acid, 3.5-4.0g of perchloric acid, and 0.18-0.22g of potassium permanganate are added to the beaker, which is then sealed and placed in an ultrasonic environment at 25-30°C for 50-65min of reaction; then 1.8-2.2g of glacial acetic acid is slowly added to the beaker at 30-35°C, and the reaction is allowed to stand for 25-35min; then the obtained product is filtered, washed with water until the pH is 7, and then dried in an oven at 55-60°C for 24h to obtain the oxidized intercalation graphite.

[0014] Further, in A1, the mass of the polymerization inhibitor (p-hydroxyanisole) is 0.4-0.5% of the total mass of the reactants.

[0015] Further, in A1, the mass of the catalyst (tetrabutyl titanate) is 0.4-0.5% of the total mass of the reactants.

[0016] Further, in A2, the amount ratio of the oxidized intercalation graphite, water and N, N-dimethylformamide is 1g: (200-250) mL: (800-1000) mL.

[0017] Further, in A3, the mass ratio of the oxidized intercalation graphite, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine is 1: (0.9-1.1): (0.9-1.1).

[0018] Further, the phosphorus-nitrogen intumescent flame retardant is ammonium polyphosphate.

[0019] Further, the dispersion stabilizer is trimethylphenyl phosphate; the initiator is benzoyl peroxide; and the foaming agent is pentane.

[0020] In a second aspect, the present application provides a graphite-grade expandable polystyrene bead prepared by the above method.

[0021] The present application has the following beneficial effects:

[0022] The present application uses the intercalation-modified double modified graphite and the phosphorus-nitrogen intumescent flame retardant ammonium polyphosphate to prepare the graphite-grade expandable polystyrene bead, which has excellent thermal stability and flame retardancy, and the initial decomposition temperature is above 345.4℃ and the limiting oxygen index is above 42.1%.

[0023] The intercalation-modified double modified graphite is prepared by oxidizing intercalation graphite and polybutylene succinate-1,3-propanediol surface modification; in terms of thermal stability, the oxidizing intercalation treatment introduces oxygen-containing groups, partially destroys the quinone group structure, weakens the polymerization inhibition ability, and improves the dispersibility; the polybutylene succinate-1,3-propanediol surface modification treatment can cover / shield the residual quinone group or other polymerization inhibition groups on the surface of graphite, further inhibit the polymerization inhibition ability, and the polyester layer can also enhance the compatibility of graphite and polymer matrix, reduce the interface defects; the double modification synergistically inhibits the polymerization inhibition effect, optimizes the dispersibility, and synergistically improves the thermal stability (initial decomposition temperature).

[0024] In terms of flame retardancy, the oxidizing intercalation treatment makes the graphite interlayer insert perchlorate and nitric acid intercalation, which decomposes to produce gas at high temperature, initiates the interlayer expansion of graphite, forms a loose and porous expanded structure, and can block the transmission of oxygen and heat, and inhibit the combustion chain reaction; the polybutylene succinate-1,3-propanediol surface modification treatment, polybutylene succinate-1,3-propanediol contains a large number of ester groups and carboxylic acid groups, which break the ester bond and release CO2 and other non-combustible gases when decomposed at high temperature; the residual Mn2+ of the oxidizing intercalation material such as KMnO4 can catalyze the decomposition of the polymer, and the residual quinone groups on the surface of graphite can also inhibit the polymerization of the polymer. +The application can catalyze the dehydration of polybutylene succinate to form carbon at high temperature, promote the formation of a dense carbon layer, and cooperatively build a multi-layer barrier structure to improve the flame retardancy.

[0025] In addition, ammonium polyphosphate is decomposed by heat to generate polyphosphoric acid and polyphosphoric acid, which catalyzes the dehydration of polybutylene succinate to form carbon; at the same time, NH3 and other non-combustible gases are released, which dilutes the oxygen concentration together with the gas released by graphite; the acidic product of ammonium polyphosphate can also react with metal ions (Mn 2+ ) in the graphite layer to generate manganese phosphate and other high-temperature-resistant ceramic phases, thereby enhancing the thermal stability and density of the carbon layer, and further achieving the effect of multiple synergistic improvement of flame retardancy. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 The initial decomposition temperature test data comparison trend chart of the products prepared in Examples 1-5 and Comparative Examples 1-7 of the application;

[0027] Fig. 2 The limiting oxygen index test data comparison trend chart of the products prepared in Examples 1-5 and Comparative Examples 1-7 of the application. DETAILED DESCRIPTION

[0028] The application will be further described in detail below in combination with the examples.

[0029] The raw materials of the examples and comparative examples of the application are all ordinary commercial products unless otherwise specified.

[0030] Example 1: (1) The preparation method of oxidized intercalated graphite is as follows: 1g of flake graphite is placed in a beaker, and 2.0g of concentrated nitric acid, 4.0g of perchloric acid and 0.2g of potassium permanganate are sequentially added to the beaker, which is then sealed and placed in an ultrasonic environment (frequency 40kHz, power density 0.5W / cm 2 ) at 28℃ for 60min; then 2.0g of ice acetic acid is added dropwise to the beaker at a rate of 1mL / min at 32℃, and the mixture is left to react for 30min; then the obtained product is filtered, washed with water until the pH is 7, and dried in an oven at 58℃ for 24h to obtain the oxidized intercalated graphite. The flake graphite (fixed carbon content≥99%) is of type 50 mesh and is purchased from Qingdao Risheng Graphite Co., Ltd.

[0031] (2) The preparation method of intercalation-modification double modified graphite is as follows:

[0032] A1. The reactants 1,3-propanediol and succinic acid were placed in a three-necked flask at a molar ratio of 1:1.15. The polymerization inhibitor p-hydroxyanisole was added, with the mass of p-hydroxyanisole being 0.45% of the total mass of the reactants. The mixture was prepolymerized at 185°C for 1.6 h under nitrogen protection. Tetrabutyl titanate was added as a catalyst, with the mass of tetrabutyl titanate being 0.45% of the total mass of the reactants. The mixture was heated to 222°C under vacuum (≤100 Pa) and the reaction was continued for 2.5 h. The stirring rod phenomenon (the stirring rod phenomenon is considered to occur when the stirring rod torque increases to 5 times the initial value) was observed. The product was dissolved in chloroform, purified by precipitation with cold methanol, and then dried under vacuum at 48°C to obtain poly(1,3-propanediol succinate).

[0033] A2. Disperse oxidized intercalated graphite in water, sonicate for 1 hour, add N,N-dimethylformamide, and remove water under reduced pressure to obtain a graphite dispersion. The ratio of oxidized intercalated graphite, water, and N,N-dimethylformamide is 1 g: 220 mL: 900 mL.

[0034] A3. The poly(1,3-propanediol) succinate obtained in A1 was dissolved in the graphite dispersion obtained in A2. The mass ratio of poly(1,3-propanediol) succinate to intercalated graphite oxide was 12:1. After stirring at 200 rpm for 24 h at room temperature, 1-ethyl-3-3-dimethylaminopropylcarbodiimide and 4-dimethylaminopyridine were added as carboxyl activators to catalyze the esterification reaction. The mass ratio of intercalated graphite oxide, 1-ethyl-3-3-dimethylaminopropylcarbodiimide and 4-dimethylaminopyridine was 1:1:1. After stirring at room temperature for 72 h, ascorbic acid, a reducing agent, was added. The mass of ascorbic acid was 4 times that of intercalated graphite oxide. After reduction at 78 °C for 23 h, methanol was added for co-precipitation, and the mixture was dried to obtain intercalated-modified double-modified graphite.

[0035] (3) A process for preparing graphite-grade expandable polystyrene beads, comprising the following steps:

[0036] S1. By weight, inject 200 parts of deionized water into the reactor, add 0.8 parts of the dispersion stabilizer tricresyl phosphate, stir at 240 rpm, then add 100 parts of styrene, 3.5 parts of intercalated-modified graphite, 0.32 parts of the initiator benzoyl peroxide and 1 part of the phosphorus-nitrogen intumescent flame retardant ammonium polyphosphate, continue stirring, heat to 88℃, maintain the temperature for 8 hours, polymerize to generate polymer particles, and obtain the particulate dispersion phase.

[0037] S2. Add 6 parts of foaming agent n-pentane to the particulate dispersion obtained in S1. The n-pentane is injected in liquid form at a pressure of 1 MPa through a high-pressure injector. The temperature is raised to 120°C and the reaction is continued for 5 hours. After cooling, the material is discharged, washed, and filtered to obtain graphite-grade expandable polystyrene beads.

[0038] Example 2: The difference between this example and Example 1 is that (1) the preparation method of the oxidized intercalated graphite is as follows: 1 g of natural flake graphite is placed in a beaker, 1.7 g of concentrated nitric acid, 3.5 g of perchloric acid and 0.18 g of potassium permanganate are added to the beaker, which is then sealed and placed in an ultrasonic environment at 25°C for 65 min of reaction; then 1.8 g of ice acetic acid is slowly added to the beaker at 30°C and reacted for 25 min; then the obtained product is filtered, washed with water until the pH is 7, and then dried in an oven at 55°C for 24 h to obtain the oxidized intercalated graphite.

[0039] (2) The preparation method of the intercalation-modification double modified graphite is as follows:

[0040] A1, the reactants 1,3-propanediol and succinic acid are placed in a three-necked flask at a molar ratio of 1:1.1, a polymerization inhibitor, p-hydroxyanisole, is added, the mass of p-hydroxyanisole is 0.4% of the total mass of the reactants, and pre-polycondensation is carried out at 180°C for 1.8 h under nitrogen protection; a catalyst, tetrabutyl titanate, is added, the mass of tetrabutyl titanate is 0.4% of the total mass of the reactants, and the temperature is raised to 220°C under vacuum for continued reaction for 2.78 h, during which a climbing rod phenomenon occurs; the product is dissolved in chloroform, purified by precipitation with cold methanol, and then dried under vacuum at 45°C to obtain poly(1,3-propanediol succinate).

[0041] A2, the oxidized intercalated graphite is dispersed in water, ultrasonic treatment is carried out for 1 h, N,N-dimethylformamide is added, and water is removed under reduced pressure to obtain a graphite dispersion. The dosage ratio of the oxidized intercalated graphite, water and N,N-dimethylformamide is 1 g:200 mL:800 mL.

[0042] A3, the poly(1,3-propanediol succinate) obtained in A1 is dissolved in the graphite dispersion obtained in A2, the mass ratio of poly(1,3-propanediol succinate) to oxidized intercalated graphite is 10:1, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine are added as carboxyl activators to catalyze the esterification reaction after stirring at room temperature for 24 h, the mass ratio of oxidized intercalated graphite, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine is 1:0.9:0.9, the reducing agent ascorbic acid is added after stirring at room temperature for 72 h, the mass of ascorbic acid is 4 times that of the oxidized intercalated graphite, and after reduction at 75°C for 24 h, the product is poured into methanol for co-precipitation and oven-dried to obtain the intercalation-modification double modified graphite.

[0043] Example 3: The difference between this example and Example 1 is that (1) the preparation method of the oxidized intercalated graphite is as follows: 1 g of natural flake graphite is placed in a beaker, 1.8 g of concentrated nitric acid, 3.8 g of perchloric acid and 0.22 g of potassium permanganate are added to the beaker, and then the beaker is sealed and placed in an ultrasonic environment at 30°C for 50 min; then 2.2 g of ice acetic acid is slowly added to the beaker at 35°C and reacted for 35 min; then the obtained product is filtered, washed with water until the pH is 7, and then dried in an oven at 60°C for 24 h to obtain the oxidized intercalated graphite.

[0044] (2) The preparation method of the intercalation-modified double modified graphite is as follows:

[0045] A1, the reactants 1,3-propanediol and succinic acid are placed in a three-necked flask in a molar ratio of 1:1.2, a polymerization inhibitor, p-hydroxyanisole, is added, the mass of p-hydroxyanisole is 0.5% of the total mass of the reactants, and pre-polycondensation is carried out at 190°C for 1.5 h under nitrogen protection; a catalyst, tetrabutyl titanate, is added, the mass of tetrabutyl titanate is 0.5% of the total mass of the reactants, and the temperature is raised to 225°C under vacuum for continuous reaction for 2.25 h, and a climbing rod phenomenon appears; the product is dissolved in chloroform, purified by precipitation with cold methanol, and then dried under vacuum at 50°C to obtain poly(1,3-propanediol succinate);

[0046] A2, the oxidized intercalated graphite is dispersed in water, ultrasonic treatment is carried out for 1 h, N,N-dimethylformamide is added, and water is removed under reduced pressure to obtain a graphite dispersion. The dosage ratio of the oxidized intercalated graphite, water and N,N-dimethylformamide is 1 g:250 mL:1000 mL.

[0047] A3, the poly(1,3-propanediol succinate) obtained in A1 is dissolved in the graphite dispersion obtained in A2, the mass ratio of poly(1,3-propanediol succinate) to oxidized intercalated graphite is 13:1, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine are added as carboxyl activators to catalyze the esterification reaction after stirring at room temperature for 24 h, the mass ratio of oxidized intercalated graphite, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine is 1:1.1:1.1, the reducing agent ascorbic acid is added after stirring at room temperature for 72 h, the mass of ascorbic acid is 4 times that of the oxidized intercalated graphite, and after reduction at 80°C for 22 h, the product is poured into methanol for co-precipitation and dried to obtain the intercalation-modified double modified graphite.

[0048] Example 4: The difference between this example and Example 1 is that (3) a preparation process of a graphite grade expandable polystyrene bead, which comprises the following steps:

[0049] S1, 150 parts of deionized water were injected into a reaction kettle, 0.5 parts of a dispersion stabilizer tricresyl phosphate was added, stirred, then 100 parts of styrene, 3.3 parts of intercalation-modified double modified graphite, 0.3 parts of an initiator benzoyl peroxide and 0.9 parts of a phosphorus-nitrogen intumescent flame retardant ammonium polyphosphate were added, continuous stirring, heated to 90℃, constant temperature for 8h, polymerization to generate polymer particles, to obtain the particle dispersion phase.

[0050] S2, 5.6 parts of a foaming agent n-pentane was added to the particle dispersion phase obtained in S1, heated to 120℃, after continuous reaction for 4.5h, cooled, discharged, washed, filtered, to obtain the graphite grade expandable polystyrene bead.

[0051] Example 5: The difference between this example and example 1 is that: (3) a preparation process of graphite grade expandable polystyrene bead, comprising the following steps:

[0052] S1, 230 parts of deionized water were injected into a reaction kettle, 1 part of a dispersion stabilizer tricresyl phosphate was added, stirred, then 100 parts of styrene, 3.8 parts of intercalation-modified double modified graphite, 0.35 parts of an initiator benzoyl peroxide and 1.1 parts of a phosphorus-nitrogen intumescent flame retardant ammonium polyphosphate were added, continuous stirring, heated to 90℃, constant temperature for 8h, polymerization to generate polymer particles, to obtain the particle dispersion phase.

[0053] S2, 6.2 parts of a foaming agent n-pentane was added to the particle dispersion phase obtained in S1, heated to 120℃, after continuous reaction for 5.5h, cooled, discharged, washed, filtered, to obtain the graphite grade expandable polystyrene bead.

[0054] Comparative example 1: The difference between this comparative example and example 1 is that: in the preparation process of graphite grade expandable polystyrene bead, 3.5 parts of intercalation-modified double modified graphite is replaced by 2.5 parts of flake graphite.

[0055] Comparative example 2: The difference between this comparative example and example 1 is that: in the preparation process of graphite grade expandable polystyrene bead, 3.5 parts of intercalation-modified double modified graphite is replaced by 3.5 parts of flake graphite.

[0056] Comparative example 3: The difference between this comparative example and example 1 is that: in the preparation process of graphite grade expandable polystyrene bead, 3.5 parts of intercalation-modified double modified graphite is replaced by 4.5 parts of flake graphite.

[0057] Comparative example 4: The difference between this comparative example and example 1 is that: in the preparation process of graphite grade expandable polystyrene bead, 3.5 parts of intercalation-modified double modified graphite is replaced by 2.5 parts of intercalation-modified double modified graphite.

[0058] Comparative Example 5: The difference between this comparative example and Example 1 is that in the preparation process of the graphite grade expandable polystyrene beads, 3.5 parts of the intercalation-modified double modified graphite is replaced by 4.5 parts of the intercalation-modified double modified graphite.

[0059] Comparative Example 6: The difference between this comparative example and Example 1 is that in the preparation process of the graphite grade expandable polystyrene beads, 3.5 parts of the intercalation-modified double modified graphite is replaced by 3.5 parts of the oxidized intercalation graphite (i.e. the polybutylene succinate-1,3-propanediol surface modification is deleted).

[0060] Comparative Example 7: The difference between this comparative example and Example 1 is that in the preparation process of the graphite grade expandable polystyrene beads, 3.5 parts of the intercalation-modified double modified graphite is replaced by 3.5 parts of the modified modified graphite (i.e. the oxidized intercalation graphite is replaced by flake graphite).

[0061] Test Example: Test objects: graphite grade expandable polystyrene beads prepared in Examples 1-5 and Comparative Examples 1-7. Test items: 1. thermal stability-initial decomposition temperature; 2. flame retardancy-limiting oxygen index. Test results: see Table 1.

[0062]

[0063] Result analysis: analysis of Examples 1-5 and combination of Table 1 data and Figs. 1-2 It can be seen that the graphite grade expandable polystyrene bead material prepared by the present application (Examples 1-5) has an initial decomposition temperature of 345.4°C or more and a limiting oxygen index of 42.1% or more, indicating that the product prepared by the present application has excellent thermal stability and flame retardancy.

[0064] Analysis of Examples 1 and Comparative Examples 1-7 and combination of Table 1 data and Figs. 1-2 By comparing Comparative Examples 1, 2 and 3, it can be seen that as the amount of graphite increases (from 2.5 parts to 3.5 parts and then to 4.5 parts), the flame retardancy (limiting oxygen index) of the graphite grade expandable polystyrene bead material prepared does not change much, but the thermal stability (initial decomposition temperature) shows a clear downward trend.

[0065] This is because, in terms of flame retardancy, the flame retardant effect of ordinary flake graphite mainly depends on physical barrier, and a higher addition amount (usually >10%) is required to show effective flame retardant effect. The addition amount of flake graphite in the low range will not bring obvious change in flame retardancy.

[0066] In terms of thermal stability, the graphite surface contains a polymerization inhibitor group such as a quinone group, which has a strong polymerization inhibition effect on the free radical polymerization of styrene. The greater the graphite content, the more obvious the polymerization inhibition effect on the polymerization of styrene, the more obvious the inhibition effect on chain growth, and the lower the relative molecular mass of the product. With the increase of the amount of graphite added, the initial decomposition temperature of the expandable polystyrene containing graphite prepared shows a downward trend, and the thermal stability decreases.

[0067] By comparing Comparative Example 4, Example 1 and Comparative Example 5, it can be seen that the graphite is prepared into the intercalation-modified double modified graphite of the application, which can simultaneously improve the thermal stability (initial decomposition temperature) and flame retardancy (limiting oxygen index) of the graphite grade expandable polystyrene bead material prepared. However, in terms of improvement of thermal stability (initial decomposition temperature), with the increase of the amount of intercalation-modified double modified graphite (from 2.5 parts to 3.5 parts and then to 4.5 parts), the improvement rate first increases and then decreases.

[0068] This is because, in the low addition amount stage, the dispersion is insufficient, and the interface effect is limited, and the delay effect on the overall thermal decomposition path is weak; in the moderate addition amount stage, the network is formed, which significantly prolongs the diffusion path of volatile components during thermal decomposition, and the intercalation structure and the polyester coating layer better synergistically inhibit the heat and oxygen transfer, and the initial decomposition temperature increases greatly; in the excessive addition stage, the agglomeration effect begins to appear, and the interface is weakened. In summary, the improvement effect of the intercalation-modified double modified graphite on the thermal stability (initial decomposition temperature) shows a trend of first increasing and then decreasing with the increase of its amount, and the essence is the dynamic game result of dispersion degree-interface effect-agglomeration effect.

[0069] By comparing Comparative Example 6 and Comparative Example 7, it can be seen that the oxidation intercalation treatment of the flaky graphite alone can improve the thermal stability (initial decomposition temperature) and flame retardancy (limiting oxygen index) of the graphite grade expandable polystyrene bead material finally prepared; the surface modification treatment of the flaky graphite with polybutylene succinate-1,3-propanediol alone can also improve the thermal stability (initial decomposition temperature) and flame retardancy (limiting oxygen index) of the graphite grade expandable polystyrene bead material finally prepared; and the oxidation intercalation treatment of the flaky graphite first and then the surface modification treatment of the flaky graphite with polybutylene succinate-1,3-propanediol can produce a synergistic effect, which synergistically improves the thermal stability (initial decomposition temperature) and flame retardancy (limiting oxygen index) of the graphite grade expandable polystyrene bead material finally prepared.

[0070] This is because, in terms of thermal stability, the oxidation intercalation treatment introduces oxygen-containing groups, partially destroys the quinone group structure, reduces the polymerization inhibition ability, and improves the dispersibility; the polybutylene succinate surface modification treatment can cover / shield the residual quinone group or other polymerization inhibition groups on the surface of graphite, further inhibit the polymerization inhibition ability, and the polyester layer can also enhance the compatibility of graphite and the polymer matrix, reduce the interface defects; the double modification synergistically inhibits the polymerization inhibition effect, optimizes the dispersibility, and synergistically improves the thermal stability (initial decomposition temperature).

[0071] In terms of flame retardancy, the oxidation intercalation treatment makes the graphite intercalate intercalation of perchlorate and nitric acid, which decomposes to generate gas at high temperature, initiates the interlayer expansion of graphite, and forms a loose and porous expansion structure, which can block the transmission of oxygen and heat and inhibit the combustion chain reaction; the polybutylene succinate surface modification treatment contains a large number of ester groups and carboxylic acid groups, which decompose at high temperature to release CO2 and other non-combustible gases, and dilute the combustible gas concentration; the residual Mn2 + At high temperature, it can catalyze the dehydration of polybutylene succinate to form carbon, promote the formation of dense carbon layer, and synergistically build a multi-layer barrier structure to synergistically improve the flame retardancy. In addition, ammonium polyphosphate decomposes to generate polyphosphoric acid and polyphosphoric acid, which catalyze the dehydration of polybutylene succinate to form carbon; at the same time, NH3 and other non-combustible gases are released, which together with the gas released by graphite dilutes the oxygen concentration; the acidic product of ammonium polyphosphate can also react with metal ions (Mn 2+ ) in the graphite layer to generate manganese phosphate and other high-temperature-resistant ceramic phases, enhance the thermal stability and density of the carbon layer, and further achieve the effect of multiple synergistic improvement of flame retardancy.

[0072] In addition, it should be noted that various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction, and to avoid unnecessary repetition, various possible combinations are not described again by the present application.

[0073] Furthermore, various different embodiments of the present application can also be combined in any appropriate manner, as long as they do not deviate from the idea of the present application, and they should also be considered as disclosed by the present application.

Claims

1. A process for the preparation of graphite grade expandable polystyrene beads, characterized in that, It comprises the following steps: S1, according to the weight fraction, 150-230 parts of deionized water is injected into the reaction kettle, 0.5-1 parts of dispersion stabilizer is added, stirred, then 100 parts of styrene, 3.3-3.8 parts of intercalation-modified double modified graphite, 0.3-0.35 parts of initiator and 0.9-1.1 parts of phosphorus-nitrogen intumescent flame retardant are added, continuous stirring, heating to 86-90℃, constant temperature for 7-9h, the granular dispersion phase is obtained; S2, 5.6-6.2 parts of foaming agent is added to the granular dispersion phase obtained in S1, heated to 120℃, after continuous reaction for 4.5-5.5h, cooling, discharging, washing, filtering, the graphite grade expandable polystyrene beads are obtained; The intercalation-modified double modified graphite is prepared from oxidized intercalation graphite by polybutylene succinate-1,3-propanediol surface modification; The preparation method of the intercalation-modified double modified graphite is as follows: A1, the reactants 1,3-propanediol and succinic acid are placed in a three-necked flask at a molar ratio of 1:(1.1-1.2), a polymerization inhibitor is added, and the reaction is carried out at 180-190℃ for 1.5-1.8h under nitrogen protection; a catalyst is added, and the reaction is continued at 220-225℃ for 2-3h under vacuum; the product is dissolved in chloroform, precipitated and purified with cold methanol, and then dried in a vacuum oven at 45-50℃ to obtain polybutylene succinate-1,3-propanediol; A2, the oxidized intercalation graphite is dispersed in water, ultrasonic is added, N,N-dimethylformamide is added, and water is removed under reduced pressure to obtain a graphite dispersion liquid; A3, the polybutylene succinate-1,3-propanediol obtained in A1 is dissolved in the graphite dispersion liquid obtained in A2, the mass ratio of polybutylene succinate-1,3-propanediol to oxidized intercalation graphite is (10-13):1, stirring is carried out at room temperature for 24h, then 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylamino pyridine are added, stirring is carried out for 72h, then a reducing agent is added, reduction is carried out at 75-80℃ for 22-24h, then co-precipitation is carried out in methanol, and drying is carried out to obtain the intercalation-modified double modified graphite.

2. The process for the preparation of graphite grade expandable polystyrene beads according to claim 1, characterized in that, The preparation method of the oxidized intercalation graphite is as follows: 1g of flake graphite is placed in a beaker, 1.7-2.0g of concentrated nitric acid, 3.5-4.0g of perchloric acid and 0.18-0.22g of potassium permanganate are added to the beaker, and then the beaker is sealed and placed in an ultrasonic environment at 25-30℃ for 50-65min; then 1.8-2.2g of glacial acetic acid is added to the beaker at 30-35℃ and reacted for 25-35min; then the obtained product is filtered, washed with water until the pH is 7, and then dried in a 55-60℃ oven for 24h to obtain the oxidized intercalation graphite.

3. The process for the preparation of graphite grade expandable polystyrene beads according to claim 1, characterized in that, In A1, the mass of the polymerization inhibitor is 0.4-0.5% of the total mass of the reactants.

4. The process for the preparation of graphite grade expandable polystyrene beads according to claim 1, characterized in that, In A1, the mass of the catalyst is 0.4-0.5% of the total mass of the reactants.

5. The process for the preparation of graphite grade expandable polystyrene beads according to claim 1, characterized in that, In A2, the amount ratio of the oxidized intercalation graphite, water and N,N-dimethylformamide is 1g:(200-250)mL:(800-1000)mL.

6. The process for the preparation of graphite grade expandable polystyrene beads according to claim 2, characterized in that, In A3, the mass ratio of the oxidized intercalation graphite, 1-ethyl-3-3-dimethylaminopropyl carbodiimide and 4-dimethylaminopyridine is 1:(0.9-1.1):(0.9-1.1).

7. The process for the preparation of graphite grade expandable polystyrene beads according to claim 1, characterized in that, The phosphorus-nitrogen intumescent flame retardant is ammonium polyphosphate.

8. The process for the preparation of graphite grade expandable polystyrene beads according to claim 1, characterized in that, The dispersion stabilizer is trimethylphenyl phosphite; the initiator is benzoyl peroxide; and the foaming agent is pentane.

9. A graphite grade expandable polystyrene bead, characterized by, The preparation process of the graphite-grade expandable polystyrene beads is prepared by using the process as claimed in any one of claims 1-8.

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