CN113549256A

CN113549256A - Degradable plastic produced based on waste plastic and preparation method thereof

Info

Publication number: CN113549256A
Application number: CN202110950396.6A
Authority: CN
Inventors: 段伟; 段朋朋; 段志豪
Original assignee: Jieshou Yunfeng Renewable Resources Co ltd
Current assignee: Jieshou Yunfeng Renewable Resources Co ltd
Priority date: 2021-08-18
Filing date: 2021-08-18
Publication date: 2021-10-26

Abstract

The invention relates to a degradable plastic produced based on waste plastics and a preparation method thereof, belonging to the technical field of waste plastics regeneration and comprising the following raw materials in parts by weight: 60-80 parts of clean waste plastic, 20-40 parts of polyethylene, 12-18 parts of modified starch, 5-7 parts of compatilizer, 1 part of lubricant and 4-6 parts of modified calcium carbonate; the preparation method of the degradable plastic based on waste plastic production comprises the following steps: adding the weighed raw materials into a stirring tank, mixing at the rotating speed of 50-80r/min for 10min, and transferring to a double-screw extruder for melting, extruding and granulating to obtain degradable plastic based on waste plastic production; by adding the modified starch and the modified calcium carbonate, the prepared composite plastic has biodegradability, reduces white pollution, has good mechanical property and oxidation resistance and has high application value.

Description

Degradable plastic produced based on waste plastic and preparation method thereof

Technical Field

The invention belongs to the technical field of waste plastic regeneration, and particularly relates to degradable plastic produced based on waste plastic and a preparation method thereof.

Background

As a novel chemical material, plastic is called as four large pillars in the material field together with steel, wood and cement. The plastic product has long degradation time period and is easy to generate white pollution, and a large amount of disposable non-degradable plastic products cause great negative effects on soil and environment, seriously damage the environment and harm human health.

Therefore, the urgent need of developing and popularizing environment-friendly biodegradable materials is to relieve the ecological pressure of the current environment, starch is one of the most potential natural biodegradable materials as a natural polymer which is rich in source, low in price, renewable and completely degradable, but starch has poor water resistance, and a large amount of hydroxyl exists in the intermolecular interaction of starch, so that the starch has strong polarity and strong acting force of hydrogen bonds, so that the starch has extremely poor fluidity when being heated and stressed, and is difficult to mold and process, and therefore, how to improve the water resistance of starch and the utilization rate of waste plastics is the technical problem which needs to be solved at present.

Disclosure of Invention

The invention aims to provide a degradable plastic produced based on waste plastics and a preparation method thereof, so as to solve the technical problems in the background.

The purpose of the invention can be realized by the following technical scheme:

a degradable plastic produced based on waste plastics comprises the following raw materials in parts by weight: 60-80 parts of clean waste plastic, 20-40 parts of polyethylene, 12-18 parts of modified starch, 5-7 parts of compatilizer, 1 part of lubricant and 4-6 parts of modified calcium carbonate;

the degradable plastic produced based on the waste plastic is prepared by the following steps:

and adding the weighed raw materials into a stirring tank, mixing at the rotating speed of 50-80r/min for 10min, and transferring to a double-screw extruder for melting, extruding and granulating to obtain the degradable plastic based on waste plastic production.

Further, the modified starch is prepared by the following steps:

step 1, adding 2-mercaptoethanol and toluene into a four-neck flask, stirring for 5min, controlling the reaction temperature to be 30-45 ℃ under the nitrogen atmosphere, sequentially dropwise adding a toluene solution of isophorone diisocyanate and dibutyltin dilaurate into the four-neck flask, stirring for reacting for 3-5h to obtain an intermediate 1, dropwise adding a mixed solution a of 4-amino-2, 6-di-tert-butylphenol, dibutyltin dilaurate and toluene into the intermediate 1, after dropwise adding, heating to 70-80 ℃, determining that NCO groups in a reaction solution react completely through FTIR (infrared Fourier transform infrared spectroscopy), stopping heating, removing toluene by rotary evaporation, washing for 3-5 times with methanol, and drying in an oven at 60 ℃ for 12h to obtain an intermediate 2, namely a hindered phenol graft;

wherein the dosage ratio of the 2-mercaptoethanol to the toluene solution of isophorone diisocyanate to the mixed solution a is 15 mmol: 10-13 g: 10 g: 10g of a mixture; the dosage ratio of isophorone diisocyanate to toluene in the toluene solution of isophorone diisocyanate is 15.5-16.5 mmol: 10g of a mixture; the using amount of the dibutyltin dilaurate is 1-4% of the mass of the isophorone diisocyanate; the mixed solution a was prepared from 4-amino-2, 6-di-tert-butylphenol, dibutyltin dilaurate and toluene in the following ratio of 15 mmol: 0.03-0.05 g: 10g of the mixture is obtained;

using toluene as a solvent, carrying out a chemical reaction on 2-mercaptoethanol and isophorone diisocyanate to obtain an intermediate 1, and carrying out a chemical reaction on the intermediate 1 and 4-amino-2, 6-di-tert-butylphenol to obtain an intermediate 2, namely a hindered phenol graft, wherein the reaction process is as follows:

step 2, adding the hindered phenol graft and tetrahydrofuran into a reaction kettle, magnetically stirring for 10min, heating to 65-70 ℃, dropwise adding a mixed solution b of methyl 3-hydroxy-2-methylenebutyrate, azodiisobutyronitrile and tetrahydrofuran, stirring for reaction for 3-4h after dropwise adding, after the reaction is finished, removing the tetrahydrofuran by rotary evaporation, transferring into methanol at 0 ℃ for oscillation, filtering after layering, washing a filter cake with deionized water for 3-5 times, and drying in an oven at 60 ℃ to constant weight to obtain an intermediate 3;

wherein the dosage ratio of the hindered phenol graft, tetrahydrofuran and the mixed solution b is 10 mmol: 25-32 mL: 10mL, wherein the using amount ratio of the methyl 3-hydroxy-2-methylen butyrate, the azobisisobutyronitrile and the tetrahydrofuran in the mixed solution b is 10 mmol: 6.8-10.2 mg: 10 mL;

carrying out addition reaction on-SH of the hindered phenol graft and an unsaturated carbon-carbon double bond of 3-hydroxy-2-methyl methylenebutyrate to obtain an intermediate 3, wherein the reaction process is as follows:

step 3, adding the intermediate 3, perfluoroalkyl alcohol, dibutyltin oxide and toluene into a reaction kettle, introducing nitrogen for protection, performing reflux reaction for 8-10h, performing rotary evaporation to remove the toluene after the reaction is finished, washing with anhydrous ether for 3 times, and performing freeze drying to constant weight to obtain an intermediate 4, namely a modifier;

wherein the dosage ratio of the intermediate 3, the perfluoroalkyl alcohol and the toluene is 20 mmol: 20.3-20.8 mmol: 56.4-61.7mL, wherein the dosage of dibutyltin oxide is 2-4% of the mass of the intermediate 3;

the intermediate 3 and perfluoroalkyl alcohol are subjected to ester exchange reaction to obtain an intermediate 4, namely a modifier, and the reaction process is as follows:

step 4, drying the pea starch in an oven at the temperature of 80 ℃ for 3-5h, cooling to room temperature, transferring to a reaction kettle, adding a modifier into the reaction kettle, stirring and mixing at the rotating speed of 500r/min for 5-10min, heating to 70 ℃, preserving heat, standing for 10h, adding polylactic acid, heating to 180 ℃, stirring at the rotating speed of 30-50r/min for 4-6h, and obtaining modified starch; wherein the mass ratio of the pea starch to the modifier to the polylactic acid is 100: 11-15: 20-25.

Further, the clean waste plastic is obtained by the following steps:

drying the waste PE plastic, the waste PC plastic and the waste polystyrene plastic in a 45 ℃ oven for 4-6h, then crushing and sieving with a 60-100 mesh sieve, and mixing the materials in ethanol, acetone and water according to a volume ratio of 1: 1: 1, ultrasonic cleaning, removing impurities, and drying at 45 ℃ to obtain clean waste plastics.

Further, the modified calcium carbonate is prepared by the following steps:

adding nano calcium carbonate, absolute ethyl alcohol and deionized water into a round bottom flask, performing ultrasonic dispersion for 20min at the frequency of 35-40kHz, adding a coupling agent KH-560, mixing for 20-40min at the rotation speed of 100-.

Further, the dosage ratio of the nano calcium carbonate, the absolute ethyl alcohol, the deionized water and the coupling agent KH-560 is 2-3 g: 55-58 mL: 25.3-32.7 mL: 3.3-4.2 mL.

Further, the lubricant is one or more of polyethylene wax, calcium stearate, magnesium stearate, butyl stearate and ethylene bis-stearamide which are mixed according to any proportion.

Further, the compatibilizer is an ethylene-acrylic acid copolymer.

Further, the screw rotation speed of the twin-screw extruder is 120rpm, the length-diameter ratio is 25: 1, the temperature of each section is: the first section is 165-175 ℃, the second section is 175-185 ℃, and the third section is 185-205 ℃.

The invention has the beneficial effects that:

1) the degradable plastic produced based on the waste plastic is prepared by taking clean waste plastic, polyethylene, modified starch, a compatilizer, a lubricant and modified calcium carbonate as raw materials through blending, melting, extruding and granulating, has biodegradability, reduces the generation of white pollution, has good mechanical property and oxidation resistance, and has high application value.

2) The invention firstly prepares the modifier through a series of chemical reactions, and then utilizes the modifier and polylactic acid to modify pea starch, overcomes the problem of poor water resistance of starch as a plastic raw material, and endows the starch with multiple functions, improves the utilization value of regenerated plastic, the modifier contains-OH, can interact with starch hydroxyl under the condition of high temperature, breaks the original interaction of starch, establishes a new hydrogen bond function, destroys the original polarity of starch molecules, achieves the plasticizing effect, the polylactic acid has good biodegradability, can improve the mechanical property and the heat resistance of the starch through blending treatment, contains a hindered phenol structure, can resist thermal-oxidative aging, introduces a thioether group with the function of hydroperoxide decomposition into the molecular chain of the modifier, plays the role of assisting oxidation resistance, and endows the modifier with biodegradability through the existence of an ester group, the carbon-fluorine bond energy in the fluoromethyl group is high, the cohesive energy density is small, the hydrophobicity of the modified starch is improved, and meanwhile, the modified starch has hydrophobicity, heat resistance, corrosion resistance, solvent resistance and weather resistance, so that the prepared degradable plastic has high hydrophobicity, corrosion resistance and oxidation resistance.

3) According to the invention, the coupling agent KH-560 is used for modifying the nano calcium carbonate to obtain the modified calcium carbonate, and the modified calcium carbonate is added into the plastic base material, so that on one hand, epoxy long chains grafted on the surface of the nano calcium carbonate can perform an open-loop reaction with hydroxyl groups in the modified starch to increase the internal crosslinking degree of the plastic base material, and on the other hand, the calcium carbonate plays a skeleton role in the plastic product to improve the heat resistance and the light-shielding property of the base material, reduce the size shrinkage rate of the plastic product and improve the size stability of the plastic product.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

This example prepares a modified starch by the following steps:

step 1, adding 15mmol of 2-mercaptoethanol and 10g of toluene into a four-neck flask, stirring for 5min, controlling the reaction temperature to be 30 ℃ under a nitrogen atmosphere, sequentially dropwise adding 10g of toluene solution of isophorone diisocyanate and dibutyltin dilaurate into the four-neck flask, stirring for reaction for 3h to obtain an intermediate 1, dropwise adding 10g of mixed solution a into the intermediate 1, heating to 70 ℃ after dropwise adding is finished, measuring NCO groups in reaction liquid through FTIR (Fourier transform infrared spectroscopy) to completely react, stopping heating, removing toluene through rotary evaporation, washing for 3 times with methanol, and drying for 12h in a 60 ℃ oven to obtain a hindered phenol graft; the dosage ratio of isophorone diisocyanate to toluene in the toluene solution of isophorone diisocyanate is 15.5 mmol: 10g of a mixture; the using amount of dibutyltin dilaurate is 1 percent of the mass of isophorone diisocyanate; the mixed solution a was prepared from 4-amino-2, 6-di-tert-butylphenol, dibutyltin dilaurate and toluene in the following ratio of 15 mmol: 0.03 g: 10g of the mixture is obtained;

step 2, adding 10mmol of hindered phenol graft and 25mL of tetrahydrofuran into a reaction kettle, magnetically stirring for 10min, heating to 65 ℃, dropwise adding 10mL of mixed solution b, stirring for reaction for 3h after dropwise adding, removing tetrahydrofuran by rotary evaporation after reaction, transferring into 0 ℃ methanol for oscillation, filtering after layering, washing a filter cake for 3 times by deionized water, and drying in a 60 ℃ oven to constant weight to obtain an intermediate 3; the using amount ratio of the 3-hydroxy-2-methylene butyric acid methyl ester, the azobisisobutyronitrile and the tetrahydrofuran in the mixed solution b is 10 mmol: 6.8 mg: 10 mL;

step 3, adding 20mmol of intermediate 3, 20.3mmol of perfluoroalkyl alcohol, dibutyltin oxide and 56.4mL of toluene into a reaction kettle, introducing nitrogen for protection, carrying out reflux reaction for 8 hours, carrying out rotary evaporation to remove toluene after the reaction is finished, washing for 3 times by using anhydrous ether, and carrying out freeze drying to constant weight to obtain an intermediate 4, namely a modifier, wherein the using amount of the dibutyltin oxide is 2% of the mass of the intermediate 3;

and 4, drying 100g of pea starch in an oven at 80 ℃ for 3h, cooling to room temperature, transferring to a reaction kettle, adding 11g of a modifier into the reaction kettle, stirring and mixing at a rotation speed of 500r/min for 5min, heating to 70 ℃, preserving heat, standing for 10h, adding 20g of polylactic acid, heating to 180 ℃, stirring at a rotation speed of 30r/min for 4h, and obtaining the modified starch.

Example 2

This example prepares a modified starch by the following steps:

step 1, adding 15mmol of 2-mercaptoethanol and 12g of toluene into a four-neck flask, stirring for 5min, controlling the reaction temperature to be 35 ℃ under a nitrogen atmosphere, sequentially dropwise adding 10g of toluene solution of isophorone diisocyanate and dibutyltin dilaurate into the four-neck flask, stirring for reacting for 4h to obtain an intermediate 1, dropwise adding 10g of mixed solution a into the intermediate 1, heating to 75 ℃ after dropwise adding is finished, measuring NCO groups in reaction liquid through FTIR (Fourier transform infrared spectroscopy) to completely react, stopping heating, removing toluene through rotary evaporation, washing for 4 times with methanol, and drying for 12h in a 60 ℃ oven to obtain a hindered phenol graft; the dosage ratio of isophorone diisocyanate to toluene in the toluene solution of isophorone diisocyanate is 15.8 mmol: 10g of a mixture; the using amount of the dibutyltin dilaurate is 2 percent of the mass of the isophorone diisocyanate; the mixed solution a was prepared from 4-amino-2, 6-di-tert-butylphenol, dibutyltin dilaurate and toluene in the following ratio of 15 mmol: 0.04 g: 10g of the mixture is obtained;

step 2, adding 10mmol of hindered phenol graft and 28mL of tetrahydrofuran into a reaction kettle, magnetically stirring for 10min, heating to 68 ℃, dropwise adding 10mL of mixed solution b, stirring for reaction for 3.5h after dropwise adding, transferring into methanol at 0 ℃ for oscillation after removing tetrahydrofuran by rotary evaporation after reaction is finished, filtering after layering, washing a filter cake for 4 times by deionized water, and drying in an oven at 60 ℃ to constant weight to obtain an intermediate 3; the using amount ratio of the 3-hydroxy-2-methylene butyric acid methyl ester, the azobisisobutyronitrile and the tetrahydrofuran in the mixed solution b is 10 mmol: 7.2 mg: 10 mL;

step 3, adding 20mmol of the intermediate 3, 20.5mmol of perfluoroalkyl alcohol, dibutyltin oxide and 58.1mL of toluene into a reaction kettle, introducing nitrogen for protection, carrying out reflux reaction for 9 hours, carrying out rotary evaporation to remove toluene after the reaction is finished, washing for 3 times by using anhydrous ether, and carrying out freeze drying to constant weight to obtain an intermediate 4, namely a modifier, wherein the using amount of the dibutyltin oxide is 3% of the mass of the intermediate 3;

and 4, drying 100g of pea starch in an oven at 80 ℃ for 4h, cooling to room temperature, transferring to a reaction kettle, adding 12g of a modifier into the reaction kettle, stirring and mixing at a rotation speed of 500r/min for 8min, heating to 70 ℃, preserving heat, standing for 10h, adding 23g of polylactic acid, heating to 180 ℃, stirring at a rotation speed of 40r/min for 5h, and obtaining the modified starch.

Example 3

This example prepares a modified starch by the following steps:

step 1, adding 15mmol of 2-mercaptoethanol and 13g of toluene into a four-neck flask, stirring for 5min, controlling the reaction temperature to be 45 ℃ under a nitrogen atmosphere, sequentially dropwise adding 10g of toluene solution of isophorone diisocyanate and dibutyltin dilaurate into the four-neck flask, stirring for reaction for 5h to obtain an intermediate 1, dropwise adding 10g of mixed solution a into the intermediate 1, heating to 80 ℃ after dropwise adding is finished, measuring NCO groups in reaction liquid through FTIR (Fourier transform infrared spectroscopy) to completely react, stopping heating, removing toluene through rotary evaporation, washing for 5 times with methanol, and drying for 12h in a 60 ℃ oven to obtain a hindered phenol graft; the dosage ratio of isophorone diisocyanate to toluene in the toluene solution of isophorone diisocyanate is 16.5 mmol: 10g of a mixture; the using amount of the dibutyltin dilaurate is 4 percent of the mass of the isophorone diisocyanate; the mixed solution a was prepared from 4-amino-2, 6-di-tert-butylphenol, dibutyltin dilaurate and toluene in the following ratio of 15 mmol: 0.05 g: 10g of the mixture is obtained;

step 2, adding 10mmol of hindered phenol graft and 32mL of tetrahydrofuran into a reaction kettle, magnetically stirring for 10min, heating to 70 ℃, dropwise adding 10mL of mixed solution b, stirring for reaction for 4h after dropwise adding, transferring into 0 ℃ methanol for oscillation after removing tetrahydrofuran by rotary evaporation after reaction, filtering after layering, washing a filter cake for 5 times by deionized water, and drying in a 60 ℃ oven to constant weight to obtain an intermediate 3; the using amount ratio of the 3-hydroxy-2-methylene butyric acid methyl ester, the azobisisobutyronitrile and the tetrahydrofuran in the mixed solution b is 10 mmol: 10.2 mg: 10 mL;

step 3, adding 20mmol of the intermediate 3, 20.8mmol of perfluoroalkyl alcohol, dibutyltin oxide and 61.7mL of toluene into a reaction kettle, introducing nitrogen for protection, carrying out reflux reaction for 10 hours, carrying out rotary evaporation to remove toluene after the reaction is finished, washing for 3 times by using anhydrous ether, and carrying out freeze drying to constant weight to obtain an intermediate 4, namely a modifier, wherein the using amount of the dibutyltin oxide is 4% of the mass of the intermediate 3;

and 4, drying 100g of pea starch in an oven at 80 ℃ for 5 hours, cooling to room temperature, transferring to a reaction kettle, adding 15g of a modifier into the reaction kettle, stirring and mixing at a rotation speed of 500r/min for 10 minutes, heating to 70 ℃, preserving heat, standing for 10 hours, adding 25g of polylactic acid, heating to 180 ℃, stirring at a rotation speed of 50r/min for 6 hours, and thus obtaining the modified starch.

Example 4

A degradable plastic produced based on waste plastics comprises the following raw materials in parts by weight: 60 parts of clean waste plastic, 20 parts of polyethylene, 12 parts of modified starch in example 1, 5 parts of ethylene-acrylic acid copolymer, 1 part of polyethylene wax and 4 parts of modified calcium carbonate;

adding the weighed raw materials into a stirring tank, mixing for 10min at the rotating speed of 50r/min, transferring into a double-screw extruder for melting, extruding and granulating, wherein the rotating speed of screws of the double-screw extruder is 120rpm, and the length-diameter ratio is 25: 1, the temperature of the first section is 165 ℃, the temperature of the second section is 175 ℃, and the temperature of the third section is 185 ℃, so that the degradable plastic based on waste plastic production is obtained.

Wherein the clean waste plastic is obtained by the following steps:

drying the waste PE plastic, the waste PC plastic and the waste polystyrene plastic in a drying oven at 45 ℃ for 4 hours, then crushing and sieving by a 60-mesh sieve, and mixing the crushed materials with ethanol, acetone and water according to a volume ratio of 1: 1: 1, ultrasonic cleaning, removing impurities, and drying at 45 ℃ to obtain clean waste plastics.

The modified calcium carbonate is prepared by the following steps:

adding 2g of nano calcium carbonate, 55mL of anhydrous ethanol and 25.3mL of deionized water into a round-bottom flask, ultrasonically dispersing for 20min at the frequency of 35kHz, adding 3.3mL of coupling agent KH-560, mixing for 20min at the rotating speed of 100r/min, centrifuging, washing precipitates for 3 times by using distilled water, and finally drying in an oven at 68 ℃ to constant weight to obtain the modified calcium carbonate.

Example 5

A degradable plastic produced based on waste plastics comprises the following raw materials in parts by weight: 70 parts of clean waste plastic, 30 parts of polyethylene, 16 parts of modified starch of example 2, 6 parts of ethylene-acrylic acid copolymer, 1 part of polyethylene wax and 5 parts of modified calcium carbonate;

adding the weighed raw materials into a stirring tank, mixing for 10min at the rotating speed of 70r/min, transferring into a double-screw extruder for melting, extruding and granulating, wherein the rotating speed of screws of the double-screw extruder is 120rpm, and the length-diameter ratio is 25: 1, the temperature of the first section is 172 ℃, the temperature of the second section is 178 ℃, and the temperature of the third section is 190 ℃, so that the degradable plastic produced based on the waste plastic is obtained.

Wherein the clean waste plastic is obtained by the following steps:

drying the waste PE plastic, the waste PC plastic and the waste polystyrene plastic in a drying oven at 45 ℃ for 5 hours, then crushing and sieving by a 80-mesh sieve, and mixing the materials in ethanol, acetone and water according to a volume ratio of 1: 1: 1, ultrasonic cleaning, removing impurities, and drying at 45 ℃ to obtain clean waste plastics.

The modified calcium carbonate is prepared by the following steps:

adding 2.5g of nano calcium carbonate, 56mL of anhydrous ethanol and 28.6mL of deionized water into a round-bottom flask, ultrasonically dispersing for 20min at the frequency of 38kHz, adding 3.7mL of coupling agent KH-560, mixing for 30min at the rotating speed of 150r/min, centrifuging, washing precipitates for 4 times by using distilled water, and finally drying in an oven at the temperature of 70 ℃ to constant weight to obtain the modified calcium carbonate.

Example 6

A degradable plastic produced based on waste plastics comprises the following raw materials in parts by weight: 80 parts of clean waste plastic, 40 parts of polyethylene, 18 parts of modified starch of example 3, 7 parts of ethylene-acrylic acid copolymer, 1 part of polyethylene wax and 6 parts of modified calcium carbonate;

adding the weighed raw materials into a stirring tank, mixing for 10min at the rotating speed of 80r/min, transferring into a double-screw extruder for melting, extruding and granulating, wherein the rotating speed of screws of the double-screw extruder is 120rpm, and the length-diameter ratio is 25: 1, the temperature of the first section is 175 ℃, the temperature of the second section is 185 ℃, and the temperature of the third section is 205 ℃, so that the degradable plastic produced based on the waste plastic is obtained.

Wherein the clean waste plastic is obtained by the following steps:

drying the waste PE plastic, the waste PC plastic and the waste polystyrene plastic in a drying oven at 45 ℃ for 6 hours, then crushing and sieving with a 100-mesh sieve, and mixing the materials in ethanol, acetone and water according to a volume ratio of 1: 1: 1, ultrasonic cleaning, removing impurities, and drying at 45 ℃ to obtain clean waste plastics.

The modified calcium carbonate is prepared by the following steps:

adding 3g of nano calcium carbonate, 58mL of absolute ethyl alcohol and 32.7mL of deionized water into a round-bottom flask, ultrasonically dispersing for 20min at the frequency of 40kHz, adding 4.2mL of coupling agent KH-560, mixing for 40min at the rotating speed of 200r/min, centrifuging, washing precipitates for 5 times by using distilled water, and finally drying in an oven at the temperature of 72 ℃ to constant weight to obtain the modified calcium carbonate.

Comparative example 1

The modified starch from example 4 was removed and the remaining raw materials and preparation were unchanged.

Comparative example 2

The modified calcium carbonate of example 5 was removed and the remaining raw materials and preparation were unchanged.

Comparative example 3

This comparative example is a starch-degradable plastic sold by Shuotai industries, Inc. of Dongguan.

The plastic pellets of examples 4 to 6 and comparative examples 1 to 3 were made into a plastic strip having a length of 76.2mm, a width of 25.4mm and a height of 3.2mm, and then subjected to a performance test:

firstly, water absorption: placing each group of samples in a drying box, drying at 50 ℃ for 24h, cooling at room temperature, initially weighing, immersing in distilled water, immersing for 24h, weighing again, recording weight change, calculating water absorption, wiping off surface water during weighing, and preferably wiping off water and weighing for no more than 2 minutes;

II, tensile test: the tensile strength test is an ASTM638 standard, the tensile speed is 50mm/min, the test piece is stretched in the stretching process until the test piece is broken, the maximum stretching force and the length change after the breaking are recorded, and the tensile strength and the breaking elongation are calculated;

thirdly, biodegradation rate: measuring the mass loss of the sample material after 60 days by adopting a soil burying method, and calculating the biodegradation rate of the sample material;

fourthly, aging resistance test: aging each group of samples in a 401A heat aging experiment box at 60 ℃ for 800h, and testing the elongation at break of the samples;

the test results are shown in table 1:

TABLE 1

As can be seen from Table 1, the degradable plastics prepared in examples 4-6 have lower water absorption, tensile strength, elongation at break, biodegradation rate and aging resistance than those of comparative examples 1-3, which shows that the degradable plastics prepared by the invention have higher hydrophobic property, better mechanical property and good oxidation resistance.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The foregoing is illustrative and explanatory only and is not intended to be exhaustive or to limit the invention to the precise embodiments described, and various modifications, additions, and substitutions may be made by those skilled in the art without departing from the scope of the invention or exceeding the scope of the claims.

Claims

1. The degradable plastic produced based on the waste plastic is characterized by comprising the following raw materials in parts by weight: 60-80 parts of clean waste plastic, 20-40 parts of polyethylene, 12-18 parts of modified starch, 5-7 parts of compatilizer, 1 part of lubricant and 4-6 parts of modified calcium carbonate;

wherein, the modified starch is prepared by the following steps:

drying pea starch at 80 ℃, cooling to room temperature, transferring to a reaction kettle, adding a modifier, stirring and mixing, heating to 70 ℃, preserving heat and standing for 10 hours, adding polylactic acid, heating to 180 ℃, and stirring and reacting for 4-6 hours to obtain the modified starch.

2. The degradable plastic produced based on waste plastics as claimed in claim 1, wherein the modifier is prepared by the following steps:

step A1, mixing the hindered phenol graft and tetrahydrofuran, heating to 65-70 ℃, dropwise adding the mixed solution b, stirring for reacting for 3-4h, transferring to methanol at 0 ℃ after rotary evaporation, filtering, washing a filter cake, and drying to obtain an intermediate 3;

and A2, adding the intermediate 3, perfluoroalkyl alcohol, dibutyl tin oxide and toluene into a reaction kettle, performing reflux reaction for 8-10h under the protection of nitrogen, performing rotary evaporation, washing and drying to obtain the modifier.

3. The degradable plastic produced based on waste plastic according to claim 2, wherein the mixed solution b in the step a1 is prepared from methyl 3-hydroxy-2-methylbutanoate, azobisisobutyronitrile and tetrahydrofuran according to a ratio of 10 mmol: 6.8-10.2 mg: 10mL of the above-mentioned components were mixed.

4. The degradable plastic produced based on waste plastic as claimed in claim 2, wherein the amount of dibutyltin oxide used in the step A2 is 2-4% by mass of the intermediate 3.

5. The degradable plastic produced based on waste plastic as claimed in claim 2, wherein the hindered phenol graft is prepared by the following steps:

mixing 2-mercaptoethanol and toluene, controlling the temperature to be 30-45 ℃ in a nitrogen atmosphere, dropwise adding a toluene solution of isophorone diisocyanate and dibutyltin dilaurate, stirring and reacting for 3-5h to obtain an intermediate 1, dropwise adding a mixed solution a into the intermediate 1, heating to 70-80 ℃ after dropwise adding is finished, measuring NCO groups in a reaction solution, completely reacting, stopping heating, performing rotary evaporation, washing, and drying to obtain the hindered phenol graft.

6. The degradable plastic produced based on waste plastic according to claim 5, wherein the amount ratio of isophorone diisocyanate to toluene in toluene solution of isophorone diisocyanate is 15.5-16.5 mmol: 10 g.

7. The degradable plastic produced based on waste plastic according to claim 5, wherein the mixed solution a is prepared from 4-amino-2, 6-di-tert-butylphenol, dibutyltin dilaurate and toluene according to a ratio of 15 mmol: 0.03-0.05 g: 10g of the above-mentioned raw materials are mixed together.

8. The degradable plastic produced based on waste plastics as claimed in claim 1, wherein the modified calcium carbonate is prepared by the following steps:

carrying out ultrasonic dispersion on nano calcium carbonate, absolute ethyl alcohol and deionized water, adding a coupling agent KH-560, mixing, centrifuging, washing and drying to obtain the modified calcium carbonate.

9. The method for preparing the degradable plastic based on the waste plastic production according to the claim 1 is characterized by comprising the following steps:

and adding the weighed raw materials into a stirring tank, mixing, transferring into a double-screw extruder, and carrying out melting, extrusion and granulation to obtain the degradable plastic based on waste plastic production.