An environmentally friendly PVC composite material and its production method

Abstract

The present invention provides an environmentally friendly PVC composite material and its production method, belonging to the technical field of resin materials; its preparation process includes the following steps: adding waste cooking oil for reaction; reacting with terephthalic acid and adipic acid respectively and compounding; adding pentaerythritol to prepare an auxiliary heat stabilizer; adding isopropyl thiocyanate to modify multi-walled carbon nanotubes; adding phytic acid solution to prepare an environmentally friendly flame retardant; mixing and preparing the PVC composite material. The PVC composite material product obtained by mixing PVC resin with modified carbon nanotubes, composite environmentally friendly plasticizer, environmentally friendly heat stabilizer, auxiliary heat stabilizer and environmentally friendly flame retardant in the present invention, due to the unique tubular structure and high specific surface area of carbon nanotubes, has a special adsorption effect on harmful substances such as dioxins and polychlorinated biphenyls generated by the high-temperature pyrolysis of PVC, can effectively adsorb the harmful substances generated by the PVC material, thereby reducing the air pollution caused by harmful substances and achieving the purpose of green environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of resin materials, and particularly relates to an environmentally friendly PVC composite material and a production method thereof. Background Art

[0002] PVC material is a synthetic polymer material made from vinyl chloride monomers through a polymerization reaction. It has many excellent properties, such as chemical corrosion resistance, good water resistance, excellent electrical insulation performance, suitable mechanical strength and hardness, etc. According to the addition of different types and amounts of additives such as plasticizers, stabilizers, fillers, dyes, etc., PVC can be made into rigid or soft products.

[0003] However, PVC material is prone to thermal decomposition at high temperatures, generating substances harmful to the human body and the environment, such as hydrogen chloride, dioxins, and polychlorinated biphenyls, etc., thus causing environmental pollution. In addition, most of the existing traditional plasticizers are o-phenyl plasticizers, mainly including dioctyl phthalate, dioctyl terephthalate, and dihexyl phthalate, etc. Since they are usually long-chain aromatic compounds, their molecular structures are different from the chain structure of the PVC matrix. PVC is a linear polymer formed by the free radical polymerization of vinyl chloride monomers, with chlorine atoms and carbon atoms alternatingly distributed on its main chain, while the molecules of o-phenyl plasticizers contain benzene ring structures, with a large chemical structure difference from the PVC main chain, resulting in a lack of effective chemical bonding between the two, and further causing the o-phenyl plasticizers not to bind tightly to the PVC products. During use, leaching and evaporation will occur, and the materials will be directly diffused into the dust on the material surface through volatilization and leaching in liquids, etc., thus separating them from the materials and causing environmental pollution, with poor environmental friendliness.

[0004] Therefore, we need to propose an environmentally friendly PVC composite material capable of absorbing harmful substances generated by thermal decomposition and a production method thereof to reduce environmental pollution. Summary of the Invention

[0005] Aiming at the deficiencies existing in the prior art, the purpose of the present invention is to provide an environmentally friendly PVC composite material and a production method thereof.

[0006] An environmentally friendly PVC composite material includes the following components: 60 - 78 parts by weight of PVC resin, 25 - 35 parts by weight of modified carbon nanotubes, 8 - 10 parts by weight of composite environmentally friendly plasticizer, 6 - 8 parts by weight of environmentally friendly heat stabilizer, 1 - 3 parts by weight of auxiliary heat stabilizer, and 1 - 3 parts by weight of environmentally friendly flame retardant.

[0007] A production method of an environmentally friendly PVC composite material includes the following steps:

[0008] S1: Add waste cooking oil for reaction

[0009] Mix waste cooking oil with potassium hydroxide - methanol solution and heat - react, then react with formic acid, sulfuric acid and hydrogen peroxide, then react with carboxylic acid and tetrabutylammonium chloride, and finally reflux - react with acetic anhydride. After distillation, washing and drying, a bio - based precursor is obtained;

[0010] S2: React with terephthalic acid and adipic acid respectively and compound

[0011] Mix 3 / 4 of the above - mentioned precursor, terephthalic acid and tetrabutylammonium chloride to react to prepare plasticizer A, mix the remaining precursor, adipic acid and tetrabutylammonium chloride to react to prepare plasticizer B, and then mix and compound plasticizer A and plasticizer B to obtain an environmentally friendly plasticizer;

[0012] S3: Add pentaerythritol to prepare an auxiliary heat stabilizer

[0013] React maleic anhydride and 6 - amino - 1,3 - dimethyluracil, then take 2 / 3 of the product and react with zinc oxide to prepare an environmentally friendly heat stabilizer, and then dissolve the remaining product and mix it with pentaerythritol to react to obtain an auxiliary heat stabilizer;

[0014] S4: Add isopropyl thiocyanatoacetate to modify multi - walled carbon nanotubes

[0015] Add multi - walled carbon nanotubes to an aqueous hydrogen peroxide solution for the first treatment, then disperse them in a toluene solution of γ - aminopropyltriethoxysilane for the second treatment, and finally stir - mix them with isopropyl thiocyanatoacetate to react to obtain modified carbon nanotubes;

[0016] S5: Add phytic acid solution to prepare an environmentally friendly flame retardant

[0017] Dissolve piperazine and aqueous phytic acid in absolute ethanol respectively to prepare a piperazine solution and a phytic acid solution, then add the phytic acid solution to the piperazine solution, stir - react to prepare flame retardant additive A, then take 1 / 2 of the mass of flame retardant additive A and dry it at high temperature to prepare flame retardant additive B, and finally fully mix the two flame retardant additives to obtain an environmentally friendly flame retardant;

[0018] S6: Knead and prepare a PVC composite material

[0019] Add PVC resin, the above - mentioned modified carbon nanotubes, the above - mentioned composite environmentally friendly plasticizer, the above - mentioned environmentally friendly heat stabilizer, the above - mentioned auxiliary heat stabilizer and the above - mentioned environmentally friendly flame retardant into a high - speed mixer, stir - mix at high speed, then place it in a two - roll mill and knead at 150 - 160 °C for 20 - 30 min, then hot - press with a hot press for 8 - 10 min, and finally cold - press for 10 - 15 min to obtain a PVC composite material product.

[0020] Furthermore, S1 specifically includes the following steps:

[0021] S1.1: Add waste cooking oil and potassium hydroxide - methanol solution into the reactor at a mass ratio of (5 - 6):1, heat to 70 - 80 °C and keep the temperature, while stirring at a rate of 200 - 300 r / min for 2 - 3 h to carry out the esterification reaction;

[0022] S1.2: Add hydrochloric acid into the reactor until the pH value is 6.5 - 7.5, centrifuge for liquid - liquid separation, take the upper - layer product to the distiller, and carry out vacuum distillation at a temperature of 200 - 300 °C to obtain intermediate A;

[0023] S1.3: Add the above - mentioned intermediate A, formic acid and sulfuric acid into the reactor at a mass ratio of (18 - 22):(1 - 3):1, then add hydrogen peroxide, stir and react at 50 - 60 °C for 4 - 5 h, then centrifuge for liquid - liquid separation, remove the water layer, wash until the pH value is 6.5 - 7.5 to obtain intermediate B;

[0024] S1.4: Stir and mix the above - mentioned intermediate B, carboxylic acid and tetrabutylammonium chloride evenly at a mass ratio of (40 - 50):(25 - 35):1, then react at a temperature of 100 - 180 °C for 2 - 3 h, and then carry out vacuum distillation at a temperature of 200 - 250 °C to obtain intermediate C;

[0025] S1.5: Stir and mix the above - mentioned intermediate C and acetic anhydride at a molar ratio of 1:(2 - 4), and stir and reflux at a temperature of 50 - 60 °C for 2 - 3 h. After removing the remaining acetic anhydride by vacuum distillation, wash until the pH value is 6.5 - 7.5, and heat and dry at 70 - 80 °C with a rotary evaporator to obtain the bio - based precursor.

[0026] Further, S2 specifically includes the following steps:

[0027] S2.1: Uniformly mix 3 / 4 of the precursor prepared in step S1.5, terephthalic acid and tetrabutylammonium chloride at a mass ratio of (40 - 50):(5 - 7):1, and heat and react at a temperature of 160 - 180 °C for 3 - 5 h to obtain plasticizer A;

[0028] S2.2: Uniformly mix the remaining precursor prepared in step S1.5, adipic acid and tetrabutylammonium chloride at a mass ratio of (400 - 500):(45 - 55):1, and heat at a temperature of 140 - 150 °C for 5 - 6 h to obtain plasticizer B;

[0029] S2.3: Mix and compound the above - mentioned plasticizer A and plasticizer B at a mass ratio of (6 - 10):1 to obtain the composite environmentally friendly plasticizer.

[0030] Further, S3 specifically includes the following steps:

[0031] S3.1: Heat maleic anhydride to 80 - 90 °C, then add 6 - amino - 1,3 - dimethyluracil, stir and mix evenly, add tetrahydrofuran, stir and react for 4 - 5 h, then rotate to remove tetrahydrofuran to obtain a precursor product;

[0032] S3.2: Heat 2 / 3 of the above - mentioned precursor product to 110 - 120 °C, then add zinc oxide, stir and react for 3 - 4 h, after drying, obtain an environmentally friendly heat stabilizer;

[0033] S3.3: Stir and mix the remaining above - mentioned precursor product and tetrahydrofuran according to a solid - liquid ratio of 1 g:(15 - 25) mL, and heat to 150 - 160 °C to obtain a mixed solution;

[0034] S3.4: Add pentaerythritol to the above - mentioned mixed solution according to a solid - liquid ratio of 1 g:(40 - 45) mL, stir and react for 1 - 2 h, then rotate to evaporate and remove tetrahydrofuran, after drying, obtain an auxiliary heat stabilizer.

[0035] Furthermore, S4 specifically includes the following steps:

[0036] S4.1: Add multi - walled carbon nanotubes to an aqueous hydrogen peroxide solution according to a solid - liquid ratio of 1 g:(20 - 30) mL, ultrasonically treat for 20 - 30 min, then reflux and react at a temperature of 100 - 110 °C for 3 - 4 h, and then centrifuge at a rate of 8000 - 9000 r / min for 3 - 5 min to remove the supernatant to obtain once - treated carbon nanotubes;

[0037] S4.2: Disperse the above - mentioned once - treated carbon nanotubes evenly in a toluene solution of γ - aminopropyltriethoxysilane according to a solid - liquid ratio of 1 g:(30 - 40) mL, under the protection of nitrogen, stir at a constant temperature of 80 - 90 °C for 20 - 24 h, and centrifuge to obtain twice - treated carbon nanotubes;

[0038] S4.3: Ultrasonically disperse the above - mentioned twice - treated carbon nanotubes in N,N - dimethylformamide according to a solid - liquid ratio of 1 g:(20 - 30) mL, then add an equal volume of isopropyl thiocyanate, stir and react for 18 - 20 h, and centrifuge to obtain modified carbon nanotubes.

[0039] Furthermore, S5 specifically includes the following steps:

[0040] S5.1: Dissolve piperazine in absolute ethanol according to a solid - liquid ratio of 1 g:(10 - 15) mL, and dilute an aqueous phytic acid solution in absolute ethanol according to a volume ratio of 1:(1 - 3) to obtain a piperazine solution and a phytic acid solution;

[0041] S5.2: Add the phytic acid solution to the piperazine solution in a volume ratio of (1.2-1.4):1, stir and react for 3-4 hours, filter under reduced pressure, wash with anhydrous ethanol, and dry to obtain a flame retardant additive A;

[0042] S5.3: Take 1 / 2 of the mass of the flame retardant additive A and place it in a blast drying oven, and dry it at 220-240°C for 30-40 minutes to obtain flame retardant additive B;

[0043] S5.4: The flame retardant additive A and the flame retardant additive B are fully mixed and compounded to obtain an environmentally friendly flame retardant.

[0044] Furthermore, the potassium hydroxide-methanol solution is prepared by mixing potassium hydroxide and methanol in a mass ratio of (0.03-0.04):1.

[0045] Furthermore, the solid-liquid ratio of the intermediate A to the hydrogen peroxide is 1 g: (1.5-2.5) mL, and the concentration of the hydrogen peroxide is 35%.

[0046] Furthermore, the solid-liquid ratio of maleic anhydride, 6-amino-1,3-dimethyluracil and tetrahydrofuran is 1 g:(1.6-1.8) g:(20-30) mL, and the molar ratio of zinc oxide to the precursor product is 1:(2-3).

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] 1. The present invention comprises the following steps: mixing PVC resin with modified carbon nanotubes, composite environmentally friendly plasticizers, environmentally friendly heat stabilizers, auxiliary heat stabilizers and environmentally friendly flame retardants at high speed, kneading at high temperature, and hot pressing and cold pressing to obtain a PVC composite material product. Due to the unique tubular structure and high specific surface area of ​​the carbon nanotubes, the carbon nanotubes have a special adsorption effect on harmful substances such as dioxins and polychlorinated biphenyls generated by high-temperature pyrolysis of PVC, and can effectively adsorb harmful substances generated by PVC materials, thereby reducing the pollution of harmful substances to the air and achieving the purpose of green environmental protection.

[0049] 2. The present invention uses waste cooking oil as a raw material, obtains a bio-based precursor through a series of reactions, and then reacts the precursor with terephthalic acid and adipic acid respectively to obtain plasticizer A and plasticizer B. The environmentally friendly plasticizer formed by compounding the two plasticizers increases the polarity of the plasticizer molecules due to the introduction of benzene rings and ester bonds, thereby improving its compatibility with PVC resin, preventing leaching of the PVC matrix, and reducing the deterioration of the PVC composite material. Compared with traditional plasticizers, it is not only environmentally friendly, low in mobility and low in toxicity, but also has better thermal degradation stability, thereby improving the applicability of the PVC composite material and extending its service life.

[0050] 3. The environmentally friendly heat stabilizer prepared from maleic anhydride, 6-amino-1,3-dimethyluracil and zinc oxide in the present invention does not contain heavy metal elements, so it has the characteristics of being non-toxic and environmentally friendly compared with traditional heavy metal lead and cadmium salt heat stabilizers. Moreover, after adding the auxiliary heat stabilizer, the anion in the uracil structure can absorb hydrogen chloride evolved from the thermal degradation of PVC, and at the same time replace the unstable allyl chloride atoms on the PVC carbon skeleton to form metal chlorides to prevent its own further thermal degradation. The polyol structure of the auxiliary heat stabilizer can inhibit the catalytic effect of zinc chloride on the dehydrochlorination of PVC during thermal degradation by complexing with metal chlorides, preventing the autocatalytic degradation of PVC, thereby further improving the thermal stability of the PVC composite material.

[0051] 4. In the present invention, multi-walled carbon nanotubes are added to an aqueous hydrogen peroxide solution for a first treatment, then uniformly dispersed in a toluene solution of γ-aminopropyltriethoxysilane for a second treatment, and finally reacted with isopropyl thiocyanate to graft chemical functional groups on the surface of the multi-walled carbon nanotubes, enhancing the interaction between the multi-walled carbon nanotubes and the PVC resin, thereby improving the dispersion of the multi-walled carbon nanotubes in the PVC resin to further improve the adsorption of harmful substances by the multi-walled carbon nanotubes.

[0052] 5. The bio-based flame retardant prepared from piperazine and phytic acid in the present invention has the characteristics of being environmentally friendly and non-toxic. After adding it as an environmentally friendly flame retardant to the PVC resin, it can not only effectively improve the flame retardant performance of the PVC composite material, but also, due to the high carbon content of the environmentally friendly flame retardant, cooperate with the acid source and gas source to play an expanding and covering flame retardant effect, while the modified carbon nanotubes can inhibit the heat and oxygen exchange between the polymer material and the outside world, enhancing the strength of the carbon layer formed during the combustion of the composite material. After adding the environmentally friendly flame retardant, it can produce a synergistic flame retardant effect with the modified carbon nanotubes to further improve the flame retardant performance of the PVC composite material. Detailed Embodiments

[0053] The following describes in detail an environmentally friendly PVC composite material and its production method provided by the present invention in combination with specific embodiments. At the same time, it is hereby explained that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments. For some well-known technologies, those skilled in the art can also adopt other alternative methods for implementation; moreover, the attached drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0054] Example 1

[0055] A production method of an environmentally friendly PVC composite material includes the following steps:

[0056] S1: Add waste cooking oil for reaction

[0057] Waste cooking oil and a potassium hydroxide-methanol solution prepared by mixing potassium hydroxide and methanol at a mass ratio of 0.03:1 are added to a reactor at a mass ratio of 5:1, heated to 70 °C and kept warm, and stirred at a rate of 200 r / min for 2 h for an esterification reaction. Then, hydrochloric acid is added to the reactor until the pH value is 6.5, and centrifuged for stratification. The upper-layer product is taken to a distiller and vacuum distilled at a temperature of 200 °C to obtain intermediate A. Subsequently, intermediate A, formic acid, and sulfuric acid are added to the reactor at a mass ratio of 18:1:1, and then hydrogen peroxide is added. The mixture is stirred and reacted at 50 °C for 4 h, then centrifuged for stratification, the water layer is removed, and washed until the pH value is 6.5 to obtain intermediate B. Among them, the solid-liquid ratio of intermediate A to hydrogen peroxide is 1 g:1.5 mL, and the concentration of hydrogen peroxide is 35%. Then, intermediate B, carboxylic acid, and tetrabutylammonium chloride are stirred and mixed evenly at a mass ratio of 40:25:1, and then reacted at a temperature of 100 °C for 2 h, and then vacuum distilled at a temperature of 200 °C to obtain intermediate C. Finally, intermediate C and acetic anhydride are stirred and mixed at a molar ratio of 1:2, and stirred and refluxed at a temperature of 50 °C for 2 h. After vacuum distilling to remove the remaining acetic anhydride, it is washed until the pH value is 6.5, and dried by heating with a rotary evaporator at 70 °C to obtain a bio-based precursor;

[0058] S2: React with terephthalic acid and adipic acid respectively and compound

[0059] 3 / 4 of the above-mentioned precursor, terephthalic acid, and tetrabutylammonium chloride are evenly mixed at a mass ratio of 40:5:1, and heated and reacted at a temperature of 160 °C for 3 h to obtain plasticizer A. The remaining above-mentioned precursor, adipic acid, and tetrabutylammonium chloride are evenly mixed at a mass ratio of 400:45:1, and heated at a temperature of 140 °C for 5 h to obtain plasticizer B. Then, plasticizer A and plasticizer B are mixed and compounded at a mass ratio of 6:1 to obtain a composite environmental protection plasticizer;

[0060] S3: Add pentaerythritol to prepare an auxiliary heat stabilizer

[0061] The maleic anhydride was heated to 80°C, and then 6-amino-1,3-dimethyluracil was added, and the mixture was stirred and mixed evenly. Tetrahydrofuran was added, and the mixture was stirred and reacted for 4 hours, wherein the solid-liquid ratio of maleic anhydride, 6-amino-1,3-dimethyluracil and tetrahydrofuran was 1g:1.6g:20mL, and then the tetrahydrofuran was removed by rotation to obtain a precursor product, and then 2 / 3 of the mass of the precursor product was heated to 110°C, and then zinc oxide was added, and the mixture was stirred and reacted for 3 hours. After drying, an environmentally friendly heat stabilizer was obtained, wherein the molar ratio of zinc oxide to the precursor product was 1:2, and then the remaining precursor product was stirred and mixed with tetrahydrofuran at a solid-liquid ratio of 1g:15mL, and heated to 150°C to obtain a mixed solution. Finally, pentaerythritol was added to the mixed solution at a solid-liquid ratio of 1g:40mL, and the mixture was stirred and reacted for 1 hour, and then the tetrahydrofuran was removed by rotary evaporation, and after drying, an auxiliary heat stabilizer was obtained;

[0062] S4: Modification of multi-walled carbon nanotubes by adding isopropylthioisocyanate

[0063] Multi-walled carbon nanotubes were added to a hydrogen peroxide aqueous solution at a solid-liquid ratio of 1g:20mL, ultrasonically treated for 20min, and then refluxed at a temperature of 100°C for 3h, and then centrifuged at a rate of 8000r / min for 3min, and the supernatant was removed to obtain a primary treated carbon nanotube, and then the primary treated carbon nanotube was uniformly dispersed in a toluene solution of γ-aminopropylethoxysilane at a solid-liquid ratio of 1g:30mL, and under the protection of nitrogen, the mixture was stirred at a constant temperature of 80°C for 20h, and centrifuged to obtain a secondary treated carbon nanotube, and then the secondary treated carbon nanotube was ultrasonically dispersed in N,N-dimethylformamide at a solid-liquid ratio of 1g:20mL, and an equal volume of isopropylthioisocyanate was added, stirred for reaction for 18h, and centrifuged to obtain a modified carbon nanotube;

[0064] S5: Preparation of environmentally friendly flame retardant by adding phytic acid solution

[0065] Piperazine is dissolved in anhydrous ethanol at a solid-liquid ratio of 1g:10mL, and a phytic acid aqueous solution is diluted in anhydrous ethanol at a volume ratio of 1:1 to obtain a piperazine solution and a phytic acid solution. Subsequently, the phytic acid solution is added to the piperazine solution at a volume ratio of 1.2:1, and the mixture is stirred for reaction for 3 hours, filtered under reduced pressure, washed with anhydrous ethanol, and dried to obtain a flame retardant additive A. 1 / 2 of the mass of the flame retardant additive A is placed in a blast drying oven and dried at 220°C for 30 minutes to obtain a flame retardant additive B. Finally, the flame retardant additive A and the flame retardant additive B are fully mixed and compounded to obtain an environmentally friendly flame retardant.

[0066] S6: Mixing and preparing PVC composite materials

[0067] 60 parts by weight of PVC resin, 25 parts by weight of the above-mentioned modified carbon nanotubes, 8 parts by weight of the above-mentioned composite environmental plasticizer, 6 parts by weight of the above-mentioned environmental heat stabilizer, 1 part by weight of the above-mentioned auxiliary heat stabilizer, and 1 part by weight of the above-mentioned environmental flame retardant are added to a high-speed mixer and stirred at high speed. After mixing, it is placed in a two-roll mill and kneaded at 150 °C for 20 min, then hot-pressed with a hot press for 8 min, and finally cold-pressed for 10 min to obtain a PVC composite product.

[0068] Performance test:

[0069] 1. Take a PVC composite product with dimensions of 100 mm × 5 mm × 3 mm as a sample and place it in a crucible. Under a nitrogen atmosphere, use a thermogravimetric analyzer to test the thermal stability of the PVC composite product. Among them, the heating rate is 20 °C, the nitrogen flow rate is 50 mL / min, and the temperature detection range is 50 - 400 °C; at the same time, use an air dioxin sampler to collect the pyrolyzed gas, and then use a high-resolution gas chromatography-high-resolution mass spectrometry instrument to detect the content of dioxin and polychlorinated biphenyls in the collected gas. The results are shown in Table 1 below;

[0070] 2. Use a JF-5 type oxygen index tester to test the limiting oxygen index of the PVC composite product according to the ASTM D-2863 test standard. The sample size is 100 mm × 10 mm × 3 mm. The results are shown in Table 1 below.

[0071] Example 2

[0072] A production method of an environment-friendly PVC composite material includes the following steps:

[0073] S1: Add waste cooking oil for reaction

[0074] Waste cooking oil and a potassium hydroxide-methanol solution prepared by mixing potassium hydroxide and methanol at a mass ratio of 0.035:1 are added to a reactor at a mass ratio of 5.5:1, heated to 75 °C and kept warm, while stirring at a rate of 250 r / min for 2.5 h to carry out an esterification reaction. Then, hydrochloric acid is added to the reactor until the pH value is 7, followed by centrifugation for stratification. The upper-layer product is taken to a distiller and vacuum distilled at a temperature of 250 °C to obtain intermediate A. Subsequently, intermediate A, formic acid, and sulfuric acid are added to the reactor at a mass ratio of 20:2:1, and then hydrogen peroxide is added. The mixture is stirred and reacted at 55 °C for 4.5 h, followed by centrifugation for stratification to remove the aqueous layer and washing until the pH value is 7 to obtain intermediate B. Among them, the solid-liquid ratio of intermediate A to hydrogen peroxide is 1 g:2 mL, and the concentration of hydrogen peroxide is 35%. Then, intermediate B, carboxylic acid, and tetrabutylammonium chloride are stirred and mixed evenly at a mass ratio of 45:30:1, and then reacted at a temperature of 140 °C for 2.5 h. Then, it is distilled under reduced pressure at a temperature of 225 °C to obtain intermediate C. Finally, intermediate C and acetic anhydride are stirred and mixed at a molar ratio of 1:3, and stirred and refluxed at a temperature of 55 °C for 2.5 h. After distilling off the remaining acetic anhydride under reduced pressure, it is washed until the pH value is 7, and dried by heating with a rotary evaporator at 75 °C to obtain a bio-based precursor;

[0075] S2: React with terephthalic acid and adipic acid respectively and compound them

[0076] 3 / 4 of the above-mentioned precursor, terephthalic acid, and tetrabutylammonium chloride are uniformly mixed at a mass ratio of 45:6:1, and heated and reacted at a temperature of 170 °C for 4 h to obtain plasticizer A. The remaining above-mentioned precursor, adipic acid, and tetrabutylammonium chloride are uniformly mixed at a mass ratio of 450:50:1, and heated at a temperature of 145 °C for 5.5 h to obtain plasticizer B. Then, plasticizer A and plasticizer B are mixed and compounded at a mass ratio of 8:1 to obtain a composite environmentally friendly plasticizer;

[0077] S3: Add pentaerythritol to prepare an auxiliary heat stabilizer

[0078] The maleic anhydride was heated to 85°C, and then 6-amino-1,3-dimethyluracil was added, and the mixture was stirred and mixed evenly. Tetrahydrofuran was added, and the mixture was stirred and reacted for 4.5 hours, wherein the solid-liquid ratio of maleic anhydride, 6-amino-1,3-dimethyluracil and tetrahydrofuran was 1g:1.7g:25mL, and then the tetrahydrofuran was removed by rotation to obtain a precursor product, and then 2 / 3 of the mass of the precursor product was heated to 115°C, and then zinc oxide was added, and the mixture was stirred and reacted for 3.5 hours. After drying, an environmentally friendly heat stabilizer was obtained, wherein the molar ratio of zinc oxide to the precursor product was 1:2.5, and then the remaining precursor product was stirred and mixed with tetrahydrofuran at a solid-liquid ratio of 1g:20mL, and heated to 155°C to obtain a mixed solution. Finally, pentaerythritol was added to the mixed solution at a solid-liquid ratio of 1g:42.5mL, and the mixture was stirred and reacted for 1.5 hours, and then the tetrahydrofuran was removed by rotary evaporation, and after drying, an auxiliary heat stabilizer was obtained;

[0079] S4: Modification of multi-walled carbon nanotubes by adding isopropylthioisocyanate

[0080] Multi-walled carbon nanotubes were added to a hydrogen peroxide aqueous solution at a solid-liquid ratio of 1g:25mL, ultrasonically treated for 25min, and then refluxed at a temperature of 105°C for 3.5h, and then centrifuged at a rate of 8500r / min for 4min, and the supernatant was removed to obtain a primary treated carbon nanotube, and then the primary treated carbon nanotube was uniformly dispersed in a toluene solution of γ-aminopropylethoxysilane at a solid-liquid ratio of 1g:35mL, and under the protection of nitrogen, the mixture was stirred at a constant temperature of 85°C for 22h, and centrifuged to obtain a secondary treated carbon nanotube, and then the secondary treated carbon nanotube was ultrasonically dispersed in N,N-dimethylformamide at a solid-liquid ratio of 1g:25mL, and an equal volume of isopropylthioisocyanate was added, stirred for reaction for 19h, and centrifuged to obtain a modified carbon nanotube;

[0081] S5: Preparation of environmentally friendly flame retardant by adding phytic acid solution

[0082] Piperazine was dissolved in anhydrous ethanol at a solid-liquid ratio of 1 g:12.5 mL, and a phytic acid aqueous solution was diluted in anhydrous ethanol at a volume ratio of 1:2 to obtain a piperazine solution and a phytic acid solution. Subsequently, the phytic acid solution was added to the piperazine solution at a volume ratio of 1.3:1, stirred for reaction for 3.5 hours, filtered under reduced pressure, washed with anhydrous ethanol, and dried to obtain a flame retardant additive A. 1 / 2 of the mass of the flame retardant additive A was placed in a blast drying oven and dried at 230°C for 35 minutes to obtain a flame retardant additive B. Finally, the flame retardant additive A and the flame retardant additive B were fully mixed and compounded to obtain an environmentally friendly flame retardant.

[0083] S6: Mixing and preparing PVC composite materials

[0084] 69 parts by weight of PVC resin, 30 parts by weight of the above-mentioned modified carbon nanotubes, 9 parts by weight of the above-mentioned composite environmental protection plasticizer, 7 parts by weight of the above-mentioned environmental protection heat stabilizer, 2 parts by weight of the above-mentioned auxiliary heat stabilizer, and 2 parts by weight of the above-mentioned environmental protection flame retardant are added to a high-speed mixer and stirred at high speed. After mixing, it is placed in a two-roll plasticizer and kneaded at 155 °C for 25 min, then hot-pressed with a hot press for 9 min, and finally cold-pressed for 12.5 min to obtain a PVC composite product.

[0085] Then, performance testing is carried out with reference to the performance testing method in Example 1, and the results are shown in Table 1 below.

[0086] Example 3

[0087] A production method of an environment-friendly PVC composite material includes the following steps:

[0088] S1: Adding waste cooking oil for reaction

[0089] Waste cooking oil and a potassium hydroxide-methanol solution prepared by mixing potassium hydroxide and methanol in a mass ratio of 0.04:1 are added to a reactor in a mass ratio of 6:1, heated to 80 °C and kept warm, and stirred at a rate of 300 r / min for 3 h for esterification reaction. Then, hydrochloric acid is added to the reactor until the pH value is 7.5, centrifuged and layered, and the upper-layer product is taken to a distiller and vacuum distilled at a temperature of 300 °C to obtain intermediate A. Subsequently, intermediate A, formic acid, and sulfuric acid are added to the reactor in a mass ratio of 22:3:1, and then hydrogen peroxide is added, and the mixture is stirred and reacted at 60 °C for 5 h. Then, it is centrifuged and layered, the water layer is removed, and washed until the pH value is 7.5 to obtain intermediate B. Among them, the solid-liquid ratio of intermediate A to hydrogen peroxide is 1 g:2.5 mL, and the concentration of hydrogen peroxide is 35%. Then, intermediate B, carboxylic acid, and tetrabutylammonium chloride are stirred and mixed evenly in a mass ratio of 50:35:1, and then reacted at a temperature of 180 °C for 3 h, and then vacuum distilled at a temperature of 250 °C to obtain intermediate C. Finally, intermediate C and acetic anhydride are stirred and mixed in a molar ratio of 1:4, and stirred and refluxed at a temperature of 60 °C for 3 h. After vacuum distilling to remove the remaining acetic anhydride, it is washed until the pH value is 7.5, and dried by heating with a rotary evaporator at 80 °C to obtain a bio-based precursor;

[0090] S2: Reacting with terephthalic acid and adipic acid respectively and compounding

[0091] Mix 3 / 4 of the above-mentioned precursor, terephthalic acid, and tetrabutylammonium chloride in a mass ratio of 50:7:1 uniformly, and heat and react at a temperature of 180 °C for 5 h to obtain plasticizer A. Then mix the remaining above-mentioned precursor, adipic acid, and tetrabutylammonium chloride in a mass ratio of 500:55:1 uniformly, and heat at a temperature of 150 °C for 6 h to obtain plasticizer B. Then mix plasticizer A and plasticizer B in a mass ratio of 10:1 for compounding to obtain a composite environmental-friendly plasticizer;

[0092] S3: Add pentaerythritol to prepare an auxiliary heat stabilizer

[0093] Heat maleic anhydride to 90 °C, then add 6-amino-1,3-dimethyluracil, stir and mix evenly, add tetrahydrofuran, and stir and react for 5 h. Among them, the solid-liquid ratio of maleic anhydride, 6-amino-1,3-dimethyluracil, and tetrahydrofuran is 1 g:1.8 g:30 mL. Then rotate to remove tetrahydrofuran to obtain a precursor product. Then heat 2 / 3 of the mass of the precursor product to 120 °C, add zinc oxide, stir and react for 4 h, and after drying, obtain an environmental-friendly heat stabilizer. Among them, the molar ratio of zinc oxide to the precursor product is 1:3. Then stir and mix the remaining precursor product with tetrahydrofuran according to a solid-liquid ratio of 1 g:25 mL and heat to 160 °C to obtain a mixed solution. Finally, add pentaerythritol to the mixed solution according to a solid-liquid ratio of 1 g:45 mL, stir and react for 2 h, then rotate and evaporate to remove tetrahydrofuran, and after drying, obtain an auxiliary heat stabilizer;

[0094] S4: Add isopropyl thiocyanate to modify multi-walled carbon nanotubes

[0095] Add multi-walled carbon nanotubes to an aqueous hydrogen peroxide solution according to a solid-liquid ratio of 1 g:30 mL, ultrasonically treat for 30 min, then reflux and react at a temperature of 110 °C for 4 h, and then centrifuge at a rate of 9000 r / min for 5 min to remove the supernatant to obtain once-treated carbon nanotubes. Then disperse the once-treated carbon nanotubes evenly in a toluene solution of γ-aminopropyltriethoxysilane according to a solid-liquid ratio of 1 g:40 mL, and under the protection of nitrogen, stir at a constant temperature of 90 °C for 24 h, and centrifuge to obtain twice-treated carbon nanotubes. Subsequently, ultrasonically disperse the twice-treated carbon nanotubes in N,N-dimethylformamide according to a solid-liquid ratio of 1 g:30 mL, then add an equal volume of isopropyl thiocyanate, stir and react for 20 h, and centrifuge to obtain modified carbon nanotubes;

[0096] S5: Add phytic acid solution to prepare an environmental-friendly flame retardant

[0097] Dissolve piperazine in absolute ethanol according to a solid-liquid ratio of 1 g: 15 mL, and dilute the aqueous solution of phytic acid in absolute ethanol according to a volume ratio of 1:3 to obtain a piperazine solution and a phytic acid solution. Subsequently, add the phytic acid solution to the piperazine solution according to a volume ratio of 1.4:1, stir and react for 4 h, then perform vacuum filtration, wash with absolute ethanol and dry to obtain flame retardant additive A. Then, take 1 / 2 of the mass of flame retardant additive A and place it in a forced-air drying oven, dry at 240 °C for 40 min to obtain flame retardant additive B. Finally, fully mix and compound flame retardant additive A and flame retardant additive B to obtain an environmentally friendly flame retardant;

[0098] S6: Mix and prepare the PVC composite material

[0099] Add 78 parts by weight of PVC resin, 35 parts by weight of the above-mentioned modified carbon nanotubes, 10 parts by weight of the above-mentioned composite environmentally friendly plasticizer, 8 parts by weight of the above-mentioned environmentally friendly heat stabilizer, 3 parts by weight of the above-mentioned auxiliary heat stabilizer, and 3 parts by weight of the above-mentioned environmentally friendly flame retardant into a high-speed mixer, stir and mix at high speed, then place it in a two-roll mill, knead at 160 °C for 30 min, then hot press with a hot press for 10 min, and finally cold press for 15 min to obtain a PVC composite material product.

[0100] Then, refer to the performance test method in Example 1 for performance testing, and the results are shown in Table 1 below.

[0101] Table 1: Summary table of performance test results of Examples 1-3

[0102] Project Thermogravimetric loss rate (%) Content of harmful substances (μg / g) LOI (%) Example 1 78.6 0.51 28.9 Example 2 78.5 0.49 28.9 Example 3 78.2 0.48 29.2

[0103] Comparative Example 1

[0104] The difference between this comparative example and Example 1 is that step S4 is removed, and the modified carbon nanotubes in step S6 are removed. Then, refer to the performance test method in Example 1 to perform performance testing on the prepared PVC composite material, and the test results are shown in Table 2 below.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 1 is that step S4 is removed, and the modified carbon nanotubes in step S6 are replaced with an equal amount of unmodified multi-walled carbon nanotubes. Then, refer to the performance test method in Example 1 for performance testing, and the results are shown in Table 2 below.

[0107] Table 2: Comparative table of performance test results of Example 1 and Comparative Examples 1-2

[0108] Project Content of harmful substances (μg / g) Example 1 0.51 Comparative Example 1 20.63 Comparative Example 2 8.25

[0109] From the comparison of the performance tests of Comparative Examples 1-2 and Example 1, it can be seen that the harmful substance contents of Comparative Example 1 and Comparative Example 2 are 20.63 μg / g and 8.25 μg / g respectively, which are significantly greater than 0.51 μg / g in Example 1. Thus, it can be known that by mixing PVC resin with modified carbon nanotubes, composite environmental plasticizer, environmental heat stabilizer, auxiliary heat stabilizer and environmental flame retardant at high speed, then kneading at high temperature, and obtaining the PVC composite product after hot pressing and cold pressing. Due to the unique tubular structure and high specific surface area of carbon nanotubes, it has a special adsorption effect on harmful substances such as dioxins and polychlorinated biphenyls generated by the high-temperature pyrolysis of PVC, and can effectively adsorb the harmful substances generated by the PVC material, thereby reducing the air pollution caused by harmful substances and achieving the purpose of green environmental protection.

[0110] In addition, by adding multi-walled carbon nanotubes to an aqueous hydrogen peroxide solution for the first treatment, then uniformly dispersing them in a toluene solution of γ-aminopropyltriethoxysilane for the second treatment, and finally reacting with isopropyl thiocyanate, chemical functional groups are grafted onto the surface of the multi-walled carbon nanotubes, enhancing the interaction between the multi-walled carbon nanotubes and the PVC resin, thereby improving the dispersibility of the multi-walled carbon nanotubes in the PVC resin to further enhance the adsorption of harmful substances by the multi-walled carbon nanotubes.

[0111] Comparative Example 3

[0112] The difference between this comparative example and Example 1 is that steps S1 and S2 are removed, and the composite environmental plasticizer in step S6 is replaced with an equal amount of dioctyl phthalate plasticizer, and then the performance test is carried out with reference to the performance test method in Example 1, and the results are shown in Table 3 below.

[0113] Comparative Example 4

[0114] The difference between this comparative example and Example 1 is that plasticizer B in step S2 is removed, and the environmental plasticizer in step S6 is replaced with an equal amount of plasticizer A, and then the performance test is carried out with reference to the performance test method in Example 1, and the results are shown in Table 3 below.

[0115] Table 3: Comparison table of performance test results of Example 1 and Comparative Examples 3-4

[0116] Project Thermogravimetric loss rate (%) Example 1 78.6 Comparative Example 3 83.2 Comparative Example 4 80.5

[0117] From the comparison of the performance tests between Comparative Examples 3-4 and Example 1, it can be seen that the thermal weight loss rates of Comparative Example 3 and Comparative Example 4 are 83.2% and 80.5% respectively, both greater than 78.6% in Example 1. Thus, it can be known that by using waste cooking oil as a raw material, through a series of reactions to obtain a bio-based precursor, and then reacting the precursor with terephthalic acid and adipic acid respectively to prepare plasticizer A and plasticizer B, the environmentally friendly plasticizer formed by compounding the two plasticizers has increased the polarity of the plasticizer molecules due to the introduction of benzene rings and ester bonds, thereby improving its compatibility with PVC resin, preventing the leaching of the PVC matrix, reducing the deterioration of the PVC composite material. Compared with traditional plasticizers, it not only has the characteristics of environmental friendliness, low migration rate and low toxicity, but also has better thermal degradation stability, thus being able to improve the applicability of the PVC composite material and extend its service life.

[0118] Comparative Example 5

[0119] The difference between this comparative example and Example 1 is that step S3 is removed, and the environmentally friendly heat stabilizer and co-stabilizer in step S6 are removed, and then the performance test is carried out with reference to the performance test method in Example 1, and the results are shown in Table 4 below.

[0120] Comparative Example 6

[0121] The difference between this comparative example and Example 1 is that the co-stabilizer in step S6 is replaced with an equal amount of environmentally friendly heat stabilizer, and then the performance test is carried out with reference to the performance test method in Example 1, and the results are shown in Table 4 below.

[0122] Table 4: Comparison table of performance test results of Example 1 and Comparative Examples 5-6

[0123] Project Thermogravimetric loss rate (%) Example 1 78.6 Comparative Example 5 92.9 Comparative Example 6 86.5

[0124] From the comparison of the performance tests between Comparative Examples 5-6 and Example 1, it can be seen that the thermal weight loss rates of Comparative Example 5 and Comparative Example 6 are 92.9% and 86.5% respectively, significantly greater than 78.6% in Example 1. Thus, it can be known that the environmentally friendly heat stabilizer prepared from maleic anhydride, 6-amino-1,3-dimethyluracil and zinc oxide has the characteristics of non-toxic environmental protection compared with traditional heavy metal lead and cadmium salt heat stabilizers because it does not contain heavy metal elements. And, after adding a co-stabilizer, since the anions in the uracil structure can absorb the hydrogen chloride evolved during the thermal degradation of PVC, and at the same time replace the unstable allyl chloride atoms on the PVC carbon skeleton to form metal chlorides to prevent its own further thermal degradation, while the polyol structure of the co-stabilizer can inhibit the catalytic effect of zinc chloride on the dehydrochlorination of PVC during thermal degradation through complexation with the metal chloride, preventing the autocatalytic degradation of PVC, thereby further improving the thermal stability of the PVC composite material.

[0125] Comparative Example 7

[0126] The difference between this comparative example and Example 1 is that step S5 is removed, and the environmentally friendly flame retardant in step S6 is removed, and then the performance test is carried out with reference to the performance test method in Example 1. The results are shown in Table 5 below.

[0127] Comparative Example 8

[0128] The difference between this comparative example and Example 1 is that the modified carbon nanotubes in step S6 are removed, and then the performance test is carried out with reference to the performance test method in Example 1. The results are shown in Table 5 below.

[0129] Table 5: Comparison table of performance test results of Example 1 and Comparative Examples 7 - 9

[0130] Project LOI (%) Example 1 28.9 Comparative Example 7 16.7 Comparative Example 8 22.6

[0131] From the comparison of the performance tests of Comparative Examples 7 - 8 and Example 1, it can be seen that the limiting oxygen indices (LOI) of Comparative Example 7 and Comparative Example 8 are 16.7% and 22.6% respectively, which are significantly lower than 28.9% of Example 1. It can be seen that the bio - based flame retardant prepared from piperazine and phytic acid has the characteristics of environmental protection and non - toxicity. After adding it as an environmentally friendly flame retardant to PVC resin, not only can the flame retardant performance of the PVC composite material be effectively improved, but also, due to the high carbon content of the environmentally friendly flame retardant, it cooperates with the acid source and gas source to play an expanding and covering flame retardant effect, while the modified carbon nanotubes can inhibit the heat and oxygen exchange between the polymer material and the outside world, enhance the strength of the carbon layer formed during the combustion of the composite material. After adding the environmentally friendly flame retardant, it can produce a synergistic flame retardant effect with the modified carbon nanotubes, further improving the flame retardant performance of the PVC composite material.

[0132] The above embodiments only illustrate the principles and effects of the present invention by way of example, and are not used to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An environmentally friendly PVC composite material, characterized in that: The components include: 60-78 parts by weight of PVC resin, 25-35 parts by weight of modified carbon nanotubes, 8-10 parts by weight of composite environmentally friendly plasticizer, 6-8 parts by weight of environmentally friendly heat stabilizer, 1-3 parts by weight of auxiliary heat stabilizer and 1-3 parts by weight of environmentally friendly flame retardant; The multi-walled carbon nanotubes are added to a hydrogen peroxide aqueous solution for a primary treatment, then dispersed in a toluene solution of γ-aminopropylethoxysilane for a secondary treatment, and finally stirred and mixed with isopropylthioisocyanate for reaction to obtain modified carbon nanotubes; The waste cooking oil is mixed with potassium hydroxide-methanol solution and heated for reaction, then mixed with formic acid, sulfuric acid and hydrogen peroxide for reaction, then mixed with carboxylic acid and tetrabutylammonium chloride for reaction, and finally mixed with acetic anhydride for reflux reaction, and after distillation, washing and drying, a bio-based precursor is obtained, 3 / 4 of the mass of the above precursor, terephthalic acid and tetrabutylammonium chloride are mixed for reaction to prepare plasticizer A, the remaining precursor, adipic acid and tetrabutylammonium chloride are mixed for reaction to prepare plasticizer B, and plasticizer A is mixed and compounded with plasticizer B to obtain a composite environmentally friendly plasticizer; Maleic anhydride and 6-amino-1,3-dimethyluracil are mixed and reacted, and then 2 / 3 of the mass of the product is reacted with zinc oxide to prepare an environmentally friendly heat stabilizer, and then the remaining product is dissolved and mixed with pentaerythritol to obtain an auxiliary heat stabilizer; Piperazine and phytic acid aqueous solutions are dissolved in anhydrous ethanol to prepare piperazine solution and phytic acid solution respectively, and then the phytic acid solution is added to the piperazine solution, and the flame retardant additive A is prepared by stirring the reaction, and then 1 / 2 of the mass of the flame retardant additive A is taken and dried at high temperature to prepare the flame retardant additive B, and finally the flame retardant additive A and the flame retardant additive B are fully mixed to obtain an environmentally friendly flame retardant.

2. The method for producing an environmentally friendly PVC composite material according to claim 1, characterized in that: The steps include: S1: Add waste cooking oil for reaction The waste cooking oil is mixed with a potassium hydroxide-methanol solution and heated for reaction, then mixed with formic acid, sulfuric acid and hydrogen peroxide for reaction, then mixed with carboxylic acid and tetrabutylammonium chloride for reaction, and finally mixed with acetic anhydride for reflux reaction, and after distillation, washing and drying, a bio-based precursor is obtained; S2: react with terephthalic acid and adipic acid respectively and compound 3 / 4 of the mass of the above precursor, terephthalic acid and tetrabutylammonium chloride are mixed and reacted to prepare plasticizer A, the remaining precursor, adipic acid and tetrabutylammonium chloride are mixed and reacted to prepare plasticizer B, and then plasticizer A and plasticizer B are mixed and compounded to obtain an environmentally friendly plasticizer; S3: Add pentaerythritol to prepare auxiliary heat stabilizer Maleic anhydride and 6-amino-1,3-dimethyluracil are mixed and reacted, and then 2 / 3 of the mass of the product is reacted with zinc oxide to prepare an environmentally friendly heat stabilizer, and then the remaining product is dissolved and mixed with pentaerythritol to obtain an auxiliary heat stabilizer; S4: Modification of multi-walled carbon nanotubes by adding isopropylthioisocyanate The multi-walled carbon nanotubes are added to a hydrogen peroxide aqueous solution for a primary treatment, then dispersed in a toluene solution of γ-aminopropylethoxysilane for a secondary treatment, and finally stirred and mixed with isopropylthioisocyanate for reaction to obtain modified carbon nanotubes; S5: Preparation of environmentally friendly flame retardant by adding phytic acid solution Dissolving piperazine and phytic acid aqueous solution in anhydrous ethanol to prepare piperazine solution and phytic acid solution respectively, then adding the phytic acid solution to the piperazine solution, stirring to react to prepare flame retardant additive A, then taking 1 / 2 of the mass of flame retardant additive A and drying at high temperature to prepare flame retardant additive B, and finally fully mixing flame retardant additive A and flame retardant additive B to obtain an environmentally friendly flame retardant; S6: Mixing and preparing PVC composite materials The PVC resin, the modified carbon nanotubes, the composite environmentally friendly plasticizer, the environmentally friendly heat stabilizer, the auxiliary heat stabilizer and the environmentally friendly flame retardant are added to a high-speed mixer and stirred at high speed, and then placed in a double-roller plasticator, mixed at 150-160° C. for 20-30 minutes, and then hot-pressed for 8-10 minutes with a hot press, and finally cold-pressed for 10-15 minutes to obtain a PVC composite material product.

3. The method for producing an environmentally friendly PVC composite material according to claim 2, characterized in that: S1 specifically includes the following steps: S1.1: Add waste cooking oil and potassium hydroxide-methanol solution into the reactor at a mass ratio of (5-6): 1, heat to 70-80°C and keep warm, and stir at a rate of 200-300r / min for 2-3h to carry out esterification reaction; S1.2: Add hydrochloric acid to the reactor until the pH value is 6.5-7.5, centrifuge and separate the layers, take the upper layer product to a distiller, and perform vacuum distillation at a temperature of 200-300°C to obtain intermediate A; S1.3: The intermediate A, formic acid and sulfuric acid are added into a reactor in a mass ratio of (18-22): (1-3): 1, and then hydrogen peroxide is added. The mixture is stirred at 50-60°C for 4-5 hours, and then the layers are separated by centrifugation, the water layer is removed, and the mixture is washed until the pH value is 6.5-7.5 to obtain the intermediate B. S1.4: The intermediate B, carboxylic acid and tetrabutylammonium chloride are mixed uniformly in a mass ratio of (40-50): (25-35): 1, reacted at 100-180°C for 2-3h, and then distilled under reduced pressure at 200-250°C to obtain intermediate C; S1.5: The intermediate C and acetic anhydride are stirred and mixed in a molar ratio of 1: (2-4), and refluxed under stirring at a temperature of 50-60°C for 2-3h. The remaining acetic anhydride is removed by vacuum distillation, washed to a pH value of 6.5-7.5, and heated and dried at 70-80°C using a rotary evaporator to obtain a bio-based precursor.

4. The method for producing an environmentally friendly PVC composite material according to claim 3, characterized in that: S2 specifically includes the following steps: S2.1: 3 / 4 of the mass of the precursor prepared in step S1.5, terephthalic acid and tetrabutylammonium chloride are uniformly mixed in a mass ratio of (40-50): (5-7): 1, and heated at a temperature of 160-180°C for reaction for 3-5h to obtain plasticizer A; S2.2: The remaining precursor prepared in step S1.5, adipic acid and tetrabutylammonium chloride are uniformly mixed in a mass ratio of (400-500): (45-55): 1, and heated at a temperature of 140-150° C. for 5-6 hours to obtain plasticizer B; S2.3: The above plasticizer A and plasticizer B are mixed in a mass ratio of (6-10):1 to obtain a composite environmentally friendly plasticizer.

5. The method for producing an environmentally friendly PVC composite material according to claim 4, characterized in that: S3 specifically includes the following steps: S3.1: Heat maleic anhydride to 80-90°C, add 6-amino-1,3-dimethyluracil, stir to mix evenly, add tetrahydrofuran, stir to react for 4-5h, and then rotate to remove tetrahydrofuran to obtain a precursor product; S3.2: Heat 2 / 3 of the precursor product to 110-120°C, add zinc oxide, stir and react for 3-4h, and dry to obtain an environmentally friendly heat stabilizer; S3.3: Stir and mix the remaining precursor product and tetrahydrofuran at a solid-liquid ratio of 1 g: (15-25) mL, and heat to 150-160°C to obtain a mixed solution; S3.4: Add pentaerythritol to the above mixed solution at a solid-liquid ratio of 1g: (40-45)mL, stir and react for 1-2h, then remove tetrahydrofuran by rotary evaporation, and obtain the auxiliary heat stabilizer after drying.

6. The method for producing an environmentally friendly PVC composite material according to claim 5, characterized in that: S4 specifically includes the following steps: S4.1: Add multi-walled carbon nanotubes to a hydrogen peroxide aqueous solution at a solid-liquid ratio of 1 g: (20-30) mL, perform ultrasonic treatment for 20-30 min, then reflux the mixture at a temperature of 100-110°C for 3-4 h, and then centrifuge at a rate of 8000-9000 r / min for 3-5 min, remove the supernatant, and obtain a single-treatment carbon nanotube; S4.2: Disperse the primary treated carbon nanotubes uniformly in a toluene solution of γ-aminopropylethoxysilane at a solid-liquid ratio of 1 g: (30-40) mL, stir at a constant temperature of 80-90° C. for 20-24 h under the protection of nitrogen, and centrifuge to obtain secondary treated carbon nanotubes; S4.3: Ultrasonic disperse the above-mentioned secondary treated carbon nanotubes in N,N-dimethylformamide at a solid-liquid ratio of 1g: (20-30)mL, add an equal volume of isopropylthioisocyanate, stir the reaction for 18-20h, and centrifuge to obtain modified carbon nanotubes.

7. The method for producing an environmentally friendly PVC composite material according to claim 4, characterized in that: S5 specifically includes the following steps: S5.1: dissolve piperazine in anhydrous ethanol at a solid-liquid ratio of 1 g:(10-15) mL, and dilute the phytic acid aqueous solution in anhydrous ethanol at a volume ratio of 1:(1-3) to obtain a piperazine solution and a phytic acid solution; S5.2: Add the phytic acid solution to the piperazine solution in a volume ratio of (1.2-1.4): 1, stir and react for 3-4 hours, filter under reduced pressure, wash with anhydrous ethanol, and dry to obtain a flame retardant additive A; S5.3: Take 1 / 2 of the mass of the flame retardant additive A and place it in a blast drying oven, and dry it at 220-240°C for 30-40 minutes to obtain flame retardant additive B; S5.4: The flame retardant additive A and the flame retardant additive B are fully mixed and compounded to obtain an environmentally friendly flame retardant.

8. The method for producing an environmentally friendly PVC composite material according to claim 3, characterized in that: The potassium hydroxide-methanol solution is prepared by mixing potassium hydroxide and methanol in a mass ratio of (0.03-0.04):

1.

9. The method for producing an environmentally friendly PVC composite material according to claim 3, characterized in that: The solid-liquid ratio of intermediate A to hydrogen peroxide is 1 g: (1.5-2.5) mL, and the concentration of hydrogen peroxide is 35%.

10. The method for producing an environmentally friendly PVC composite material according to claim 5, characterized in that: The solid-liquid ratio of maleic anhydride, 6-amino-1,3 dimethyluracil and tetrahydrofuran is 1 g: (1.6-1.8) g: (20-30) mL, and the molar ratio of zinc oxide to the precursor product is 1: (2-3).