Bio-based polyester and preparation method thereof

Abstract

The invention discloses bio-based polyester and a preparation method thereof, and belongs to the technical field of biomass resource utilization and bio-based polyester, and the bio-based polyester comprises the following components: deacetylated chitosan, aldehyde modified lignin, polybasic organic amine, polybasic aldehyde monomer, a catalyst, 1, 4-dioxane, methanol and deionized water. The method comprises the following steps: extracting chitosan from shrimp / crab shells, and exposing primary amino groups through alkali treatment; the method comprises the following steps: extracting lignin from coffee grounds, and grafting an aldehyde group with a polyaldehyde monomer; the aldehyde modified lignin and chitosan are subjected to Michael addition reaction and then are crosslinked with polyaldehyde monomers and polybasic organic amine to form a net structure, so that the film forming strength is improved. The environment burden caused by the coffee grounds and shrimp shells or crab shells is reduced, and meanwhile, a low-cost and environment-friendly bio-based polyester is provided for the field of coatings.

Description

Technical Field

[0001] The present invention belongs to the technical fields of biomass resource utilization and bio-based polyesters, and particularly relates to a bio-based polyester and a preparation method thereof. Background Art

[0002] In the mid-19th century, alkyd resins were synthesized in Germany. In 1912, General Electric Company in the United States made alkyd resins by condensing phthalic anhydride and glycerol to replace the electrical insulation material - shellac. In 1927, R.H. Keenle in the United States utilized the characteristic that the properties of resins vary depending on polybasic acids to develop a manufacturing method for alkyd resins suitable for various uses, especially using phthalic anhydride or maleic anhydride to manufacture resins for coatings, and the industrial production was carried out by General Electric Company in the same year. The output of alkyd resin coatings is very large, accounting for about 20% - 25% of the total coating industry. However, with the continuous development of the scale of human production and life, the global oil and natural gas resources are decreasing rapidly. It is predicted that the oil resources on the earth will be exhausted within 100 years. Green and renewable bio-based materials have become the most ideal alternative resources for oil and are also important new materials for the development of polymer chemical industry technology.

[0003] In the field of coating applications, bio-based materials, especially vegetable oils, have been widely used to prepare new types of green and environmentally friendly coatings. This is because vegetable oils have characteristics such as non-toxicity, low volatility, biodegradability, and abundant and easily available raw materials. Since the 19th century, a series of studies have been carried out on vegetable oil-based polymers. For example, after the triglycerides in vegetable oils are alcoholyzed with glycerol, monoglycerides are obtained for preparing alkyd resins; drying oils or fatty acids are first maleated and then subjected to a transesterification reaction with epoxy prepolymers to prepare fatty acid-modified epoxy coatings; after soybean oil is epoxidized, it is combined with acrylate to prepare epoxidized soybean oil acrylate resin; monoglyceride is also a polyol and can react with diisocyanates to prepare polyurethanes. Vegetable oils used for preparing water-based polyurethanes include sunflower oil, castor oil, rapeseed oil, soybean oil, etc.; tung oil forms a biodegradable coating directly after thermal cross-linking polymerization. However, the demand for vegetable oils as human food is also increasing continuously. Therefore, using vegetable oils as raw materials for alkyd resins results in relatively high production costs. Therefore, it is urgently needed to develop a new resin synthesis method using low-cost and green and environmentally friendly materials.

[0004] Coffee is one of the world's three major beverages. Between 2000 and 2012, global coffee production increased by nearly 17%. According to the International Coffee Organization, the global coffee industry processed about 9.6 million tons in 2017. In the coffee production steps such as roasting and brewing, more than 90% of the initial coffee dry mass is produced in the form of coffee grounds. The waste generated from coffee in coffee-producing countries accounts for more than 50% of the total fruit residues. Therefore, coffee grounds are a kind of agricultural and forestry waste with huge output. For this reason, coffee factories need to spend a certain cost to treat coffee grounds. Coffee grounds contain a large amount of lignin, and the dry weight ratio can reach more than 30wt%. Resource utilization of coffee grounds, especially its lignin, can not only reduce the pollution of coffee grounds to the environment, but also bring certain economic benefits.

[0005] Chitosan, also known as chitosan or chitin, is a polysaccharide extracted from the shells of marine crustaceans. It is the second largest bio-based green resource in the world, second only to cellulose. Chitosan and its derivatives can be used as reinforcing fillers for coatings, as well as synthetic raw materials for coating resins or as film-forming substances.

[0006] The two waste biomass are used as resources, and the lignin extracted from coffee grounds and the chitin extracted from shrimp or crab shells are modified by chemical modification. They are used as synthetic bio-based polyesters, which can not only reduce the pollution caused by their direct disposal, but also provide new alternative materials for bio-based polyesters, which has important scientific significance and practical application value. However, as far as we know, there are no relevant scientific reports by relevant scientists. Summary of the invention

[0007] The purpose of the present invention is to provide a bio-based polyester and a preparation method thereof, in particular, using agricultural and forestry wastes, namely coffee grounds and crab shells or shrimp shells as raw materials, extracting lignin and chitin from the coffee grounds and shrimp shells or crab shells respectively, modifying the lignin and chitin respectively by a chemical method, grafting aldehyde groups on the lignin molecular chain, exposing a large number of primary amino groups to the chitin molecular chain, and performing Michael addition on the two, further forming a network cross-linking with polyaldehydes and polyorganic amines, and improving the strength of the film. The present invention not only reduces the environmental burden brought by coffee grounds and shrimp shells or crab shells, but also provides a low-cost, green and environmentally friendly bio-based polyester for the coating field.

[0008] The specific technical solutions are as follows:

[0009] A bio-based polyester comprises the following components by weight: 20 to 30 parts of deacetylated chitin, 40 to 50 parts of aldehyde-modified lignin, 8 to 12 parts of polyvalent organic amines, 18 to 24 parts of polyvalent aldehyde monomers, 3 to 5 parts of catalysts, 10 to 20 parts of 1,4-dioxane, 8 to 12 parts of methanol and 40 to 60 parts of deionized water;

[0010] Among them, the chitosan is prepared by a method comprising the following steps:

[0011] S1 Pretreatment: The shrimp shells and crab shells are treated with hydrochloric acid, sodium hydroxide, and sodium hypochlorite in three steps to obtain purified chitin.

[0012] S2 Deacetylation: The purified chitin is subjected to partial deacetylation treatment in a sodium hydroxide solution, NaBH4 is added, and the pH is adjusted to 3.0 - 4.0 to obtain the chitosan.

[0013] The aldehyde group - modified lignin is prepared by a method comprising the following steps:

[0014] S3 Pretreatment: The coffee grounds are soaked in n - hexane for defatting.

[0015] S4 Aldehyde group modification: The coffee grounds after the S3 treatment are mixed and stirred with polyaldehyde, 1,4 - dioxane, and hydrochloric acid, and heated under reflux to obtain crude aldehyde group - modified lignin.

[0016] S5 Collection and purification: The crude aldehyde group - modified lignin is mixed with 1,4 - dioxane and polyaldehyde monomer, neutralized with a NaHCO3 solution, then distilled under reduced pressure, filtered and washed, and the filter residue is air - dried to obtain the aldehyde group - modified lignin.

[0017] In some embodiments, the preparation method of the chitosan comprises the following steps:

[0018] S1 Pretreatment: The shrimp shells and crab shells are washed, dried, and crushed to obtain crude chitin. Take 100 - 300 g of crude chitin and soak it in 5 - 8 wt%, 300 - 500 mL of hydrochloric acid, react at 20 - 30 °C for 1 - 3 hours, filter, wash with water until neutral, take the filter residue, and dry it at 50 °C. Take 100 - 300 g of the dried chitin powder and soak it in 5 - 10 wt%, 100 - 300 mL of NaOH solution, react at 20 - 30 °C for 1 - 3 hours, filter, wash with water until neutral, take the filter residue, and dry it at 50 °C. Finally, take 100 - 300 g of the chitin after alkali treatment and drying, soak it in 0.3 - 0.9 wt% of NaClO solution, react at 20 - 30 °C for 1 - 3 hours, filter, wash with water until neutral, take the filter residue, and after drying at 50 °C, obtain purified chitin.

[0019] S2 Deacetylation: The purified chitin is subjected to partial de - etherification treatment in 30 - 40 w%, 200 - 400 mL of NaOH solution, and 0.5 - 1.5 g of NaBH4 is added, react at 80 - 90 °C for 1 - 3 hours, filter, wash with water until neutral, take the filter residue, and then drop 1 wt% acetic acid to adjust the pH to 3.0 - 4.0 to obtain the chitosan.

[0020] In some of these embodiments, the preparation method of the aldehyde group-modified lignin comprises the following steps:

[0021] S3 Pretreatment: Soak coffee grounds in n-hexane, with the mass-volume ratio of coffee grounds to n-hexane being 5 - 10 g:1 - 10 mL, react at 20 - 30 °C for 3 - 6 hours to obtain coffee grounds after impurity removal;

[0022] S4 Aldehyde group modification: By mass, put 30 - 50 parts of the coffee grounds treated in S3, 24 - 32 parts of polyaldehyde monomer, 35 - 45 parts of 1,4-dioxane, and 8 - 12 parts of hydrochloric acid into a reaction kettle and stir, heat to 100 - 110 °C, after reflux reaction for 2 - 3 hours; filter, and then wash successively with 1,4-dioxane and methanol until the washing liquid is colorless, collect the filter residue, dry it to obtain crude aldehyde group-modified lignin;

[0023] S5 Collection and purification: Add the crude aldehyde group-modified lignin, 1,4-dioxane, and polyaldehyde monomer into a reaction kettle and mix, then add NaHCO3 solution for neutralization, heat under reduced pressure to 40 - 50 °C, distill at a pressure of 50 - 60 mbar, filter the distilled solution, wash successively with 1,4-dioxane, methanol, and deionized water, collect the filter residue and air-dry it at 30 °C to obtain the aldehyde group-modified lignin; the mass ratio of the crude aldehyde group-modified lignin, 1,4-dioxane, and polyaldehyde is 40:10 - 18:8 - 12.

[0024] Specifically, the preparation method of the deacetylated chitin comprises the following steps:

[0025] S1 Pretreatment: Wash the collected shrimp and crab shells, dry them in the sun, and grind them into powder to obtain crude chitin. Then, soak 100 - 300 g of chitin in hydrochloric acid with a concentration of 5 - 8 wt% and a volume of 300 - 500 mL, react at a temperature of 20 - 30 °C and a stirring speed of 200 - 500 revolutions per minute for 1 - 3 hours, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C; Then, soak 100 - 300 g of the dried chitin powder in NaOH solution with a concentration of 5 - 10 wt% and a volume of 100 - 300 mL, react at a temperature of 20 - 30 °C and a stirring speed of 500 - 700 revolutions per minute for 1 - 3 hours, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C; Finally, soak 100 - 300 g of the alkali-treated and dried chitin in NaClO solution with a concentration of 0.3 - 0.9 wt%, react at a temperature of 20 - 30 °C and a stirring speed of 500 - 700 revolutions per minute for 1 - 3 hours, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C to obtain purified chitin;

[0026] S2 Deacetylation: Soak the purified chitin powder in NaOH solution with a concentration of 30 - 40 wt% and a volume of 200 - 400 mL for partial deacetylation treatment, and add 0.5 - 1.5 g of NaBH4, react at 80 - 90 °C and a stirring speed of 500 - 700 revolutions per minute for 1 - 3 hours, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and then drop 1 wt% acetic acid to adjust the pH value of the chitin suspension to 3.0 - 4.0 to obtain a deacetylated chitin solution, that is, deacetylated chitosan, and store it in a 4 °C environment for later use;

[0027] Specifically, the preparation method of the aldehyde group-modified lignin includes the following steps:

[0028] S3 Pretreatment: Soak coffee grounds in n-hexane, and the mass-volume ratio of coffee grounds to n-hexane is 5 - 10 g: 1 - 10 mL, react at 20 - 30 °C and a mechanical stirring speed of 200 - 500 revolutions per minute for 3 - 6 hours, filter to remove the filtrate to obtain the coffee grounds after impurity removal;

[0029] S4 Aldehyde group modification: By mass fraction, add 30 - 50 parts of coffee grounds after S3 treatment, 24 - 32 parts of polyaldehyde monomer, 35 - 45 parts of 1,4 - dioxane, and 8 - 12 parts of hydrochloric acid into the multi - functional reaction kettle in sequence. While stirring at a speed of 500 - 1000 revolutions per minute, heat the reactants to 100 - 110 °C and reflux for 2 - 3 hours. After the reaction, filter, and then wash with 1,4 - dioxane and methanol in sequence until the washing liquid becomes colorless to ensure complete removal of cellulose. Collect the filter residue, dry it, and obtain crude aldehyde - modified lignin.

[0030] S5 Collection and purification: Add the crude aldehyde - modified lignin obtained in S4 into the multi - functional reaction kettle, add 1,4 - dioxane and polyaldehyde monomer in sequence, and then add NaHCO3 solution to neutralize the acid in the filter residue. Then use vacuum distillation to heat to 40 - 50 °C under a pressure of 50 - 60 mbar for distillation, distill out 1,4 - dioxane and unreacted polyaldehyde and collect and store them. Filter the distilled solution, wash with 1,4 - dioxane, methanol, and deionized water in sequence, collect the filter residue, and air - dry the filter residue at 30 °C to obtain purified aldehyde - modified lignin. The mass ratio of the crude aldehyde - modified lignin, 1,4 - dioxane, and polyaldehyde is 40:10 - 18:8 - 12.

[0031] In some embodiments, the polyamine is at least one of hexamethylenetetramine, ethylenediamine, hexamethylenediamine, and diphenylmethanediamine.

[0032] In some embodiments, the polyaldehyde monomer is at least one of glutaraldehyde, malondialdehyde, and succinaldehyde.

[0033] In some embodiments, the catalyst is at least one of tetraacetyltitanium, tetra - isopropyl titanate, and acetic acid.

[0034] The present invention also provides a preparation method of the above - mentioned bio - based polyester, and the preparation method of the bio - based polyester includes the following steps:

[0035] S6. Under the protection of nitrogen, add deacetylated chitin, aldehyde - modified lignin, 1,4 - dioxane, methanol, and deionized water into the reaction kettle, and stir until evenly mixed.

[0036] S7. Heat and keep warm, remove water by passing nitrogen, add polyamine, polyaldehyde monomer, and catalyst, and carry out heating and reflux reaction.

[0037] S8. Measure the viscosity after the reaction. When the viscosity is 8000 - 10000 cps / 25 °C, first disperse at high speed for 30 - 60 minutes, then disperse at low speed for 30 - 60 minutes, and finally cool down and filter to obtain the bio - based polyester.

[0038] In some of these embodiments, the method for preparing the bio-based polyester comprises the following steps:

[0039] S6: Add deacetylated chitin, aldehyde-modified lignin, 1,4-dioxane, methanol and deionized water into a reaction kettle, pass nitrogen and stir at 1000 - 2000 r / min for 10 - 30 minutes. After mixing evenly, continue to pass nitrogen for 5 minutes;

[0040] S7: Stop passing nitrogen, heat to 50 - 60 °C, keep warm for 1 hour, continue to pass nitrogen to remove free water, add polyamine, polyaldehyde monomer and catalyst, raise the temperature to 110 - 120 °C, and reflux for 3 - 6 hours, with the reaction water separated by a water separator;

[0041] S8: After reacting for 3 hours, measure the viscosity every 30 minutes. When the viscosity reaches 8000 - 10000 cps / 25 °C, set the stirring speed to 10000 - 12000 r / min for high-speed dispersion for 30 - 60 minutes, then set the stirring speed to 1000 - 1200 r / min for low-speed dispersion for 30 - 60 minutes, then cool down to 50 °C, and filter to obtain the bio-based polyester.

[0042] The present invention has the following advantages:

[0043] (1) Using agricultural and forestry waste, namely coffee grounds and shrimp or crab shells, as raw materials can not only reduce the environmental burden they bring, but also provide a low-cost and green bio-based polyester for the coating field, highly valorize the waste, and bring certain economic benefits;

[0044] (2) The formulation does not involve the use of organic solvents, and the bio-based polyester provided by the present invention in later use will not generate gases harmful to human health, which conforms to the green production concept;

[0045] (3) In the present invention, lignin and chitin are respectively modified by chemical methods, aldehyde groups are grafted onto the lignin molecular chain, a large number of primary amino groups are exposed on the chitin molecular chain, and Michael addition occurs between the two, further forming a network crosslinking with polyaldehyde and polyamine to improve the film-forming strength. Description of the Drawings

[0046] Figure 1 Scanning electron microscope images of deacetylated chitin prepared in Examples 1 - 3

[0047] Figure 2 Deacetylation degree titration curves of deacetylated chitin prepared in Examples 1 - 3 and chitin without deacetylation treatment;

[0048] Figure 3 Scanning electron microscope images of coffee grounds after being treated in Examples 6 - 8 and untreated coffee grounds;

[0049] Figure 4 Scanning electron micrographs of the aldehyde group-modified lignin prepared in Examples 9-11. Detailed implementation manners

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings, technical process steps, specific implementation conditions and materials in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0051] Example 1

[0052] The collected shrimp shells and crab shells were washed, dried in the sun and ground into powder to obtain crude chitin. Then, 100 g of chitin was soaked in 500 mL of hydrochloric acid with a concentration of 5 wt%, and reacted at a temperature of 30 °C and a stirring speed of 500 revolutions per minute for 3 hours. After filtration, it was washed with deionized water until the filtrate was neutral. The filter residue was taken and dried at a temperature of 50 °C. Then, 100 g of the dried chitin powder was soaked in 300 mL of NaOH solution with a concentration of 5 wt%, and reacted at a temperature of 30 °C and a stirring speed of 700 revolutions per minute for 3 hours. After filtration, it was washed with deionized water until the filtrate was neutral. The filter residue was taken and dried at a temperature of 50 °C. Finally, 100 g of the alkali-treated and dried chitin was soaked in a 0.3 wt% NaClO solution, and reacted at a temperature of 30 °C and a stirring speed of 700 revolutions per minute for 3 hours. After filtration, it was washed with deionized water until the filtrate was neutral. The filter residue was taken and dried at a temperature of 50 °C to obtain purified chitin. The purified chitin powder was soaked in 400 mL of NaOH solution with a concentration of 30 wt% for partial deacetylation treatment, and 0.5 g of NaBH4 was added. It was reacted at 90 °C and a stirring speed of 500 revolutions per minute for 3 hours. After filtration, it was washed with deionized water until the filtrate was neutral. The filter residue was taken, and then 1 wt% acetic acid was dropped in to adjust the pH value of the chitin suspension to 3.6 to obtain a deacetylated chitin solution, that is, deacetylated chitin. The results of scanning electron microscopy characterization are as Figure 1 shown in a. Chitosan has a fibrous structure, with a length of about 500 nm and a width of about 20 nm.

[0053] Example 2

[0054] The collected shrimp shells and crab shells are washed, dried in the sun, and ground into powder to obtain crude chitin. Then, 200 g of chitin is soaked in hydrochloric acid with a concentration of 6 wt% and a volume of 400 mL, and reacted at a temperature of 25 °C and a stirring speed of 400 revolutions per minute for 2 hours. After filtration, it is washed with deionized water until the filtrate is neutral. The filter residue is taken and dried at a temperature of 50 °C. Then, 200 g of the dried chitin powder is soaked in a NaOH solution with a concentration of 8 wt% and a volume of 200 mL, and reacted at a temperature of 25 °C and a stirring speed of 600 revolutions per minute for 2 hours. After filtration, it is washed with deionized water until the filtrate is neutral. The filter residue is taken and dried at a temperature of 50 °C. Finally, 200 g of the alkali-treated and dried chitin is soaked in a NaClO solution with a concentration of 0.6 wt%, and reacted at a temperature of 25 °C and a stirring speed of 600 revolutions per minute for 2 hours. After filtration, it is washed with deionized water until the filtrate is neutral. The filter residue is taken and dried at a temperature of 50 °C to obtain purified chitin. The purified chitin powder is soaked in a NaOH solution with a concentration of 35 wt% and a volume of 300 mL for partial deacetylation treatment, and 1 g of NaBH4 is added. The reaction is carried out at 85 °C and a stirring speed of 600 revolutions per minute for 2 hours. After filtration, it is washed with deionized water until the filtrate is neutral. The filter residue is taken, and then acetic acid with a concentration of 1 wt% is dropped in to adjust the pH value of the chitin suspension to 4.0, that is, deacetylated chitin. The results of scanning electron microscopy characterization are as Figure 1 shown in a. Chitosan has a fibrous structure, with a length of about 600 nm and a width of about 22 nm.

[0055] Example 3

[0056] Wash the collected shrimp and crab shells, dry them in the sun, and grind them into powder to obtain crude chitin. Then, soak 300 g of chitin in 300 mL of hydrochloric acid with a concentration of 8 wt%, react at a temperature of 20 °C and a stirring speed of 200 revolutions per minute for 3 hours, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C; Then, soak 300 g of the dried chitin powder in 300 mL of NaOH solution with a concentration of 10 wt%, react at a temperature of 20 °C and a stirring speed of 500 revolutions per minute for 1 hour, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C; Finally, soak 300 g of the alkali-treated and dried chitin in 0.9 wt% NaClO solution, react at a temperature of 20 °C and a stirring speed of 500 revolutions per minute for 1 hour, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C to obtain purified chitin; Soak the purified chitin powder in 200 mL of NaOH solution with a concentration of 40 wt% for partial deacetylation treatment, add 1.5 g of NaBH4, react at 90 °C and a stirring speed of 500 revolutions per minute for 1 hour, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and then drop 1 wt% acetic acid to adjust the pH value of the chitin suspension to 3.0, that is, deacetylated chitin, and the results of scanning electron microscopy characterization are as Figure 1 shown in a. Chitosan has a fibrous structure, with a length of about 400 nm and a width of about 18 nm.

[0057] Example 4

[0058] Wash the collected shrimp and crab shells, dry them in the sun, and grind them into powder to obtain crude chitin. Then, soak 300 g of chitin in 300 mL of hydrochloric acid with a concentration of 8 wt%, react at a temperature of 20 °C and a stirring speed of 200 revolutions per minute for 3 hours, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C; Then, soak 300 g of the dried chitin powder in 300 mL of NaOH solution with a concentration of 10 wt%, react at a temperature of 20 °C and a stirring speed of 500 revolutions per minute for 1 hour, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C; Finally, soak 300 g of the alkali-treated and dried chitin in 0.9 wt% NaClO solution, react at a temperature of 20 °C and a stirring speed of 500 revolutions per minute for 1 hour, filter, wash with deionized water until the filtrate is neutral, take the filter residue, and dry it at a temperature of 50 °C to obtain purified chitin.

[0059] Example 5

[0060] Weigh accurately 0.2 g of chitin powder and chitin nanowhisker samples that have been dried to constant weight at 105 °C in a beaker using an electronic analytical balance. Then, prepare standard solutions of 0.1 mol / L HCl and 0.1 mol / L NaOH respectively. At 25 °C, first add 20 mL of HCl solution to the beaker and stir magnetically for 30 min to dissolve the sample. Subsequently, add 30 mL of deionized water. Insert the pH glass electrode on the Eco potentiometric titrator into the solution to be measured, and at the same time titrate with the prepared 0.1 mol / L NaOH solution. The instrument automatically records the change in the pH value of the solution during the titration process and the volume of the consumed NaOH standard solution. Plot the pH value of the solution against the titration volume of the NaOH standard solution to obtain the pH-V NaOH titration curve. Make the first derivative curve of the pH value against V NaOH to obtain the ΔpH-ΔV NaOH double inflection point titration curve. According to the definition of the degree of deacetylation, calculate the degree of deacetylation using the following formula:

[0061]

[0062] where, m 干重 is the mass of deacetylated chitin; V1 and V2 respectively represent the volumes consumed by 0.1 mol / L NaOH at the two inflection points; c represents the concentration of NaOH; the degree of deacetylation and the amino group content w NH2 are based on percentages, and each sample is tested three times and the average value is taken. The test results are as Figure 2 shown. The degrees of deacetylation of Example 1, Example 2, Example 3, and Example 4 are 38.9%, 42.6%, 46.7%, and 10.8% respectively. The results show that after deacetylation treatment, a large number of primary amino groups are exposed on the chitin molecular chain.

[0063] Example 6

[0064] Soak coffee grounds in n-hexane. The mass-volume ratio of coffee grounds to n-hexane is 5 g:1 mL. React at 20 °C with a mechanical stirring speed of 200 revolutions per minute for 6 hours. Filter to remove the filtrate to obtain coffee grounds after impurity removal.

[0065] Characterize the micro-morphologies of the original coffee grounds and the treated coffee grounds by scanning electron microscopy as Figure 3 shown. The surface of the coffee grounds before treatment has no pores and is filled with substances such as lipids and proteins, while the surface of the treated coffee grounds is honeycomb-like with a rich pore structure, indicating that substances such as lipids and proteins have been removed.

[0066] The contents of lignin (acid-insoluble lignin), cellulose, and hemicellulose in coffee grounds before and after treatment were determined according to GB / T 2677.8-947, GB / T 2677.10-19957, and the nitric acid-ethanol method, respectively. The measurement results are shown in Table 1, indicating that a large amount of lignin, cellulose, and hemicellulose were retained after treatment.

[0067] Table 1 Contents of lignin, cellulose, and hemicellulose in coffee grounds before and after treatment

[0068] Sample Name Lignin (%) Hemicellulose (%) Cellulose (%) Coffee Grounds before Treatment 30.3±1.5 51.5±0.5 18.2±0.8 Coffee Grounds after Treatment 28.9±0.5 51.6±0.7 20.5±0.5

[0069] Example 7

[0070] The coffee grounds were soaked in n-hexane at a mass-volume ratio of coffee grounds to n-hexane of 7 g:8 mL, reacted at 30 °C with a mechanical stirring speed of 300 revolutions per minute for 6 hours, and the filtrate was removed by filtration to obtain coffee grounds after impurity removal.

[0071] The microscopic morphology of the coffee grounds after treatment was characterized by scanning electron microscopy as Figure 3 shown. The surface of the treated coffee grounds was honeycombed with a rich pore structure, indicating that substances such as lipids and proteins were removed.

[0072] The contents of lignin (acid-insoluble lignin), cellulose, and hemicellulose in coffee grounds before and after treatment were determined according to GB / T 2677.8-947, GB / T 2677.10-19957, and the nitric acid-ethanol method, respectively. The measurement results are shown in Table 2, indicating that a large amount of lignin, cellulose, and hemicellulose were retained after treatment.

[0073] Table 2 Contents of lignin, cellulose, and hemicellulose in coffee grounds before and after treatment

[0074] Sample Name Lignin (%) Hemicellulose (%) Cellulose (%) Coffee Grounds before Treatment 30.3±1.5 51.5±0.5 18.2±0.8 Coffee Grounds after Treatment 30.5±1.09 52.7±1.27 17.3±0.9

[0075] Example 8

[0076] The coffee grounds were soaked in n-hexane at a mass-volume ratio of coffee grounds to n-hexane of 10 g:10 mL, reacted at 30 °C with a mechanical stirring speed of 200 revolutions per minute for 4 hours, and the filtrate was removed by filtration to obtain coffee grounds after impurity removal.

[0077] The microscopic morphologies of the original coffee grounds and the coffee grounds after treatment were characterized by scanning electron microscopy as Figure 3 shown. The surface of the coffee grounds before treatment had no pores and was filled with substances such as lipids and proteins, while the surface of the treated coffee grounds was honeycombed with a rich pore structure, indicating that substances such as lipids and proteins were removed.

[0078] The contents of lignin (acid-insoluble lignin), cellulose, and hemicellulose in coffee grounds before and after treatment were determined according to GB / T 2677.8-1994, GB / T 2677.10-1995, and the nitric acid-ethanol method, respectively. The measurement results are shown in Table 3, indicating that a large amount of lignin, cellulose, and hemicellulose were retained after treatment.

[0079] Table 3 Contents of lignin, cellulose, and hemicellulose in coffee grounds before and after treatment

[0080] Sample Name Lignin (%) Hemicellulose (%) Cellulose (%) Coffee Grounds before Treatment 30.3±1.5 51.5±0.5 18.2±0.8 Coffee Grounds after Treatment 29.5±0.77 49.8±0.56 21.7±1.2

[0081] Example 9

[0082] By mass fraction, 30 parts of coffee grounds treated in Example 6, 24 parts of glutaraldehyde, 35 parts of 1,4-dioxane, and 8 parts of hydrochloric acid were successively added to a multi-functional reaction kettle. With a stirring speed of 1000 revolutions per minute, the reactants were heated to 100 °C and refluxed for 3 hours; after the reaction, filtration was carried out, and then washed successively with 1,4-dioxane and methanol until the washing liquid became colorless to ensure complete removal of cellulose. The filter residue was collected and dried to obtain crude aldehyde-modified lignin; the obtained crude aldehyde-modified lignin was added to the multi-functional reaction kettle, and 1,4-dioxane and glutaraldehyde were successively added. The mass ratio of crude aldehyde-modified lignin, 1,4-dioxane, and glutaraldehyde was 40:10:8, and then a NaHCO3 solution was added to neutralize the acid in the filter residue; then, it was heated to 40 °C under a pressure of 50 mbar using vacuum distillation for distillation to distill out 1,4-dioxane and unreacted glutaraldehyde and collect and store them. The distilled solution was filtered and washed successively with 1,4-dioxane, methanol, and deionized water. The filter residue was collected and air-dried at 30 °C to obtain purified aldehyde-modified lignin, and scanning electron microscopy characterization was carried out. The results are as Figure 4 shown in a of the figure. The aldehyde-modified lignin is spherical, and the diameter distribution is 18 - 120 nm.

[0083] Example 10

[0084] By mass parts, 40 parts of coffee grounds treated in Example 7, 38 parts of succinaldehyde, 40 parts of 1,4-dioxane, and 10 parts of hydrochloric acid were successively added into a multi-functional reaction kettle. While stirring at a speed of 800 revolutions per minute, the reactants were heated to 105 °C and refluxed for 2.5 hours; after the reaction ended, filtration was carried out, and then washed successively with 1,4-dioxane and methanol until the washing liquid was colorless to ensure complete removal of cellulose. The filter residue was collected and dried to obtain crude aldehyde-modified lignin; the obtained crude aldehyde-modified lignin was added into the multi-functional reaction kettle, and 1,4-dioxane and succinaldehyde were successively added. The mass ratio of the crude aldehyde-modified lignin, 1,4-dioxane, and succinaldehyde was 40:14:10. Then, a NaHCO3 solution was added to neutralize the acid in the filter residue; then, it was heated to 45 °C under a pressure of 55 mbar using vacuum distillation for distillation, and 1,4-dioxane and unreacted succinaldehyde were distilled out and collected and stored. The distilled solution was filtered, washed successively with 1,4-dioxane, methanol, and deionized water, the filter residue was collected, and the filter residue was air-dried at 30 °C to obtain purified aldehyde-modified lignin, and scanning electron microscopy characterization was carried out. The results are as Figure 4 shown in b in [reference], the aldehyde-modified lignin is spherical, and the diameter distribution is 50 - 140 nm.

[0085] Example 11

[0086] By mass parts, 50 parts of coffee grounds treated in Example 8, 32 parts of malonaldehyde, 45 parts of 1,4-dioxane, and 12 parts of hydrochloric acid were successively added into a multi-functional reaction kettle. While stirring at a speed of 500 revolutions per minute, the reactants were heated to 110 °C and refluxed for 2 hours; after the reaction ended, filtration was carried out, and then washed successively with 1,4-dioxane and methanol until the washing liquid was colorless to ensure complete removal of cellulose. The filter residue was collected and dried to obtain crude aldehyde-modified lignin; the obtained crude aldehyde-modified lignin was added into the multi-functional reaction kettle, and 1,4-dioxane and malonaldehyde were successively added. The mass ratio of the crude aldehyde-modified lignin, 1,4-dioxane, and malonaldehyde was 40:18:12. Then, a NaHCO3 solution was added to neutralize the acid in the filter residue; then, it was heated to 50 °C under a pressure of 60 mbar using vacuum distillation for distillation, and 1,4-dioxane and unreacted malonaldehyde were distilled out and collected and stored. The distilled solution was filtered, washed successively with 1,4-dioxane, methanol, and deionized water, the filter residue was collected, and the filter residue was air-dried at 30 °C to obtain purified aldehyde-modified lignin, and scanning electron microscopy characterization was carried out. The results are as Figure 4 shown in c in [reference], the aldehyde-modified lignin is spherical, and the diameter distribution is 40 - 220 nm.

[0087] Example 12

[0088] Prepare the silver ammonia solution, but pay attention to avoid adding excessive ammonia water, and the silver ammonia solution must be prepared and used immediately, and cannot be stored for a long time, otherwise explosive substances will be generated. Add the aldehyde group-modified lignin prepared in Examples 8, 9, and 10 to the silver ammonia solution, and carry out the silver mirror reaction at 100 °C. The silver ammonia solution is in excess to ensure that all the aldehyde groups of the modified lignin are consumed. Then filter the reaction solution, wash the filter residue with deionized water, collect the filtrate and make up the volume. Determine the silver ion content in the filtrate by adding sodium chloride, and then determine the aldehyde group content of the modified lignin. The formula is as follows:

[0089]

[0090] w 醛基 is the aldehyde group content of the aldehyde group-modified lignin, C1 and C2 are the concentrations of the original silver ammonia solution and the silver ions after volume making respectively, and V1 and V2 are the volumes of the original silver ammonia solution and the volume after volume making respectively. After testing, the aldehyde group contents of the aldehyde group-modified lignin prepared in Examples 9, 10, and 11 are 2.59 mmol g -1 、3.12 mmol g -1 and 3.45 mmol g -1 .

[0091] Example 13

[0092] In a multi-functional reaction kettle, according to the formula weight as shown in Table 4, add deacetylated chitin, aldehyde group-modified lignin, 1,4-dioxane, methanol and deionized water in sequence. While introducing nitrogen, stir at a speed of 1000 r / min for 30 minutes until the mixture is evenly mixed, and then continue to introduce nitrogen for 5 minutes; stop introducing nitrogen, heat up to 50 °C, keep warm for 1 hour, continue to introduce nitrogen to take out the water vapor and remove the free water. Then add hexamethylenetetramine, glutaraldehyde and tetraacetyl titanate in sequence, continue to heat up to 110 °C, start the polymerization reaction, and reflux for 6 hours. The water generated during the reaction is separated by a water separator; after the reaction for 3 hours, take samples every 30 minutes for viscosity testing. When the viscosity is 8000 cps / 25 °C, set the stirring speed to 10000 r / min for high-speed dispersion for 60 minutes, then set the stirring speed to 1000 r / min for low-speed dispersion for 30 minutes, and finally cool down to 50 °C, filter to obtain the bio-based polyester.

[0093] According to GB / T 6739-1996 "Pencil Test Method for Film Hardness", the strength of the bio-based polyester film prepared (cured at 120 °C for 1 hour) was tested by the manual method. The test results show that the film strength > B.

[0094] The water resistance of the prepared bio-based polyester was tested according to GB / T 1727-1992. After soaking for 48 hours, the water absorption rate was 15.9%.

[0095] The VOC of the prepared resin film was tested according to GB / T 23985-2009 "Determination of volatile organic compound (VOC) content in paints and varnishes - Difference method", and the result was VOC ≤ 49.

[0096] The ultraviolet resistance of the wood bio-based polyester was tested according to GBT 16422.3-1997. The experiment used type Ι fluorescent ultraviolet lamp, model UV-A340, and the exposure method was: radiation exposure at 60.0 ± 3 °C under the no-lamp standard for 8 hours, and then exposure at 50.0 ± 3 °C under the no-lamp standard for 4 hours. The results showed that the bio-based polyester prepared in this example had good stability to ultraviolet rays.

[0097] Table 4 Raw material ratio of alkyd resin synthesized in Example 13

[0098] Chitosan 20 parts Aldehyde-Modified Lignin 40 parts Hexamethylenetetramine 8 parts Glutaraldehyde 18 parts Tetraacetyltitanium 3 parts 1,4-Dioxane 10 parts Methanol 8 parts Deionized Water 40 parts

[0099] The chitosan used in the present invention was prepared in Example 1, and the aldehyde group-modified lignin was prepared in Example 9.

[0100] Example 14

[0101] In a multi-functional reaction kettle, according to the formula weight as shown in Table 4, chitosan, aldehyde group-modified lignin, 1,4-dioxane, methanol and deionized water were added in sequence. While introducing nitrogen, stirring was carried out at a speed of 1500 r / min for 20 minutes until the mixture was evenly mixed, and then nitrogen was introduced continuously for 5 minutes; stop introducing nitrogen, heat up to 55 °C, keep warm for 1 hour, continue to introduce nitrogen to carry out the water vapor, remove the free water, and then add ethylenediamine, succinaldehyde and acetic acid in sequence, continue to heat up to 115 °C, start the polymerization reaction, and reflux for 4.5 hours. During this period, the water generated by the reaction was separated by a water separator; after the reaction for 3 hours, samples were taken every 30 minutes for viscosity testing. When the viscosity was 9000 cps / 25 °C, the stirring speed was set to 11000 r / min for high-speed dispersion for 45 minutes, and then the stirring speed was set to 1100 r / min for low-speed dispersion for 45 minutes. Finally, the temperature was lowered to 50 °C and filtered to obtain the bio-based polyester.

[0102] Table 5 Raw material ratio of alkyd resin synthesized in Example 14

[0103] Chitosan 25 parts Aldehyde-Modified Lignin 45 parts Polyorganic Amine 10 parts Polyaldehyde Monomer 21 parts Catalyst 4 parts 1,4-Dioxane 15 parts Methanol 10 parts Deionized Water 50 parts

[0104] The chitosan used in the present invention was prepared in Example 2, and the aldehyde group-modified lignin was prepared in Example 10.

[0105] According to GB / T 6739-1996 "Pencil Test Method for Film Hardness", the strength of the prepared bio-based polyester film (cured at 120 °C for 1 hour) was tested by the manual method. The test results showed that the film strength > B.

[0106] According to GB / T 23985-2009 "Determination of Volatile Organic Compounds (VOC) Content in Paints and Varnishes - Difference Method", the VOC of the prepared resin film was tested, and the result was VOC ≤ 51.

[0107] According to GB / T 1727-1992, the water resistance of the prepared bio-based polyester was tested. After soaking for 48 hours, the water absorption rate was 13.6%.

[0108] According to GBT 16422.3-1997, the ultraviolet resistance of the wood bio-based polyester was tested. The experiment used type Ι fluorescent ultraviolet lamp, model UV-A340. The exposure method was: radiation exposure at 60.0 ± 3 °C under the no-lamp standard for 8 hours, and then exposure at 50.0 ± 3 °C under the no-lamp standard for 4 hours. The results showed that the bio-based polyester prepared in this example had good stability to ultraviolet rays.

[0109] Example 15

[0110] In a multi-functional reaction kettle, according to the formula weight as shown in Table 4, deacetylated chitin, aldehyde-modified lignin, 1,4-dioxane, methanol and deionized water were added in sequence. While introducing nitrogen, stirring was carried out at a speed of 2000 r / min for 10 minutes until the mixture was evenly mixed, and then nitrogen was introduced continuously for 5 minutes; stop introducing nitrogen, heat up to 60 °C, keep warm for 1 hour, continue to introduce nitrogen to carry out the water vapor and remove free water, then hexamethylenediamine, malondialdehyde and tetraacetyl titanate were added in sequence, continue to heat up to 120 °C, start the polymerization reaction, and reflux for 3 hours. During this period, the water generated by the reaction was separated by a water separator; after reacting for 3 hours, samples were taken every 30 minutes for viscosity testing. When the viscosity was 10000 cps / 25 °C, the stirring speed was set to 12000 r / min for high-speed dispersion for 30 minutes, and then the stirring speed was set to 1200 r / min for low-speed dispersion for 30 minutes. Finally, the temperature was lowered to 50 °C and filtered to obtain the bio-based polyester.

[0111] Table 6 Raw material ratio of the alkyd resin synthesized in Example 15

[0112] Chitosan 20 - 30 parts Aldehyde-Modified Lignin 40 - 50 parts Hexamethylenediamine 8 - 12 parts Malonaldehyde 18 - 24 parts Tetra-isopropyl titanate 3 - 5 parts 1,4-Dioxane 10 - 20 parts Methanol 8 - 12 parts Deionized Water 40 - 60 parts

[0113] The deacetylated chitin used in the present invention was prepared in Example 3, and the aldehyde-modified lignin was prepared in Example 11.

[0114] According to GB / T 6739-1996 "Pencil Test Method for Film Hardness", the strength of the prepared bio-based polyester film (cured at 120 °C for 1 hour) was tested by the manual method, and the test results showed that the film strength > B.

[0115] According to GB / T 23985-2009 "Determination of Volatile Organic Compound (VOC) Content in Paints and Varnishes - Difference Method", the VOC of the prepared resin film was tested, and the result was VOC ≤ 54.

[0116] According to GB / T 1727-1992, the water resistance of the prepared bio-based polyester was tested. After soaking for 48 hours, the water absorption rate was 12.4%.

[0117] According to GBT 16422.3-1997, the ultraviolet resistance of the wood bio-based polyester was tested. The experiment used type Ι fluorescent ultraviolet lamp, model UV-A340, and the exposure method was: radiation exposure at 60.0 ± 3 °C under the no-lamp standard for 8 hours, and then exposure at 50.0 ± 3 °C under the no-lamp standard for 4 hours. The results showed that the bio-based polyester prepared in this example had good stability to ultraviolet rays.

[0118] All technicians should note that although the present invention has been described according to the above specific embodiments, the inventive concept of the present invention is not limited to this invention, and any modification using the inventive concept of the present invention will be included in the scope of protection of the patent right of this patent.

Claims

1. A bio-based polyester, characterized in that, By weight parts, it comprises the following components: 20-30 parts of chitosan, 40-50 parts of aldehyde-modified lignin, 8-12 parts of polyorganic amine, 18-24 parts of polyaldehyde monomer, 3-5 parts of catalyst, 10-20 parts of 1,4-dioxane, 8-12 parts of methanol and 40-60 parts of deionized water; Among them, the chitosan is prepared by a method including the following steps: S1 Pretreatment: The shrimp shells and crab shells are treated by hydrochloric acid, sodium hydroxide and sodium hypochlorite in three steps to obtain purified chitin; S2 Deacetylation: The purified chitin is partially deacetylated in a sodium hydroxide solution, NaBH4 is added, and the pH is adjusted to 3.0-4.0 to obtain the chitosan; The aldehyde-modified lignin is prepared by a method including the following steps: S3 Pretreatment: The coffee grounds are soaked in n-hexane for defatting treatment; S4 Aldehyde modification: The coffee grounds treated in S3 are mixed and stirred with polyaldehyde, 1,4-dioxane and hydrochloric acid, and heated under reflux to obtain crude aldehyde-modified lignin; S5 Collection and purification: The crude aldehyde-modified lignin is mixed with 1,4-dioxane and polyaldehyde monomer, neutralized with a NaHCO3 solution, then distilled under reduced pressure, filtered and washed, and the filter residue is air-dried to obtain the aldehyde-modified lignin.

2. The bio-based polyester according to claim 1, wherein The preparation method of the chitosan includes the following steps: S1 Pretreatment: The shrimp shells and crab shells are washed, dried and crushed to obtain crude chitin. Take 100-300 g of crude chitin, soak it in 5-8 wt%, 300-500 mL of hydrochloric acid, react at 20-30 °C for 1-3 hours, filter, wash with water until neutral, take the filter residue, and dry it at 50 °C; Take 100-300 g of the dried chitin powder and soak it in 5-10 wt%, 100-300 mL of NaOH solution, react at 20-30 °C for 1-3 hours, filter, wash with water until neutral, take the filter residue, and dry it at 50 °C; Finally, take 100-300 g of the chitin after alkali treatment and drying, soak it in 0.3-0.9 wt% of NaClO solution, react at 20-30 °C for 1-3 hours, filter, wash with water until neutral, take the filter residue, and after drying at 50 °C, obtain purified chitin; S2 Deacetylation: The purified chitin is partially de-etherified in 30-40 w%, 200-400 mL of NaOH solution, 0.5-1.5 g of NaBH4 is added, react at 80-90 °C for 1-3 hours, filter, wash with water until neutral, take the filter residue, and then drop 1 wt% acetic acid to adjust the pH to 3.0-4.0 to obtain the chitosan.

3. The bio-based polyester according to claim 1, wherein The preparation method of the aldehyde-modified lignin includes the following steps: S3 Pretreatment: The coffee grounds are soaked in n-hexane, and the mass-volume ratio of coffee grounds to n-hexane is 5-10 g: 1-10 mL, react at 20-30 °C for 3-6 hours to obtain the coffee grounds after impurity removal; S4 Aldehyde group modification: By mass parts, put 30 - 50 parts of coffee grounds after S3 treatment, 24 - 32 parts of polyaldehyde monomer, 35 - 45 parts of 1,4 - dioxane, and 8 - 12 parts of hydrochloric acid into a reaction kettle and stir. Heat to 100 - 110 °C and reflux for 2 - 3 hours; then filter, and wash successively with 1,4 - dioxane and methanol until the washing liquid is colorless. Collect the filter residue and dry it to obtain crude aldehyde - modified lignin; S5 Collection and purification: Add the crude aldehyde - modified lignin, 1,4 - dioxane, and polyaldehyde monomer into a reaction kettle and mix. Then add NaHCO3 solution for neutralization, and heat under reduced pressure to 40 - 50 °C. Distill at a pressure of 50 - 60 mbar, filter the distilled solution, wash successively with 1,4 - dioxane, methanol, and deionized water, and collect the filter residue and air - dry it at 30 °C to obtain the aldehyde - modified lignin; the mass ratio of the crude aldehyde - modified lignin, 1,4 - dioxane, and polyaldehyde is 40:10 - 18:8 - 12.

4. The bio-based polyester according to claim 1, wherein The polyamine is at least one of hexamethylenetetramine, ethylenediamine, hexamethylenediamine, and diphenylmethanediamine.

5. The bio-based polyester according to claim 1, characterized in that, The polyaldehyde monomer is at least one of glutaraldehyde, malondialdehyde, and succinaldehyde.

6. The bio-based polyester according to claim 1, characterized in that, The catalyst can be at least one of tetraacetyltitanium, tetra - isopropyl titanate, and acetic acid.

7. The preparation method of the bio-based polyester according to any one of claims 1 to 6, characterized in that, It includes the following steps: S6. Under the protection of nitrogen, add deacetylated chitin, aldehyde - modified lignin, 1,4 - dioxane, methanol, and deionized water into a reaction kettle and stir until evenly mixed; S7. Heat and keep warm, pass nitrogen to remove water, add polyamine, polyaldehyde monomer, and catalyst, and carry out heating and reflux reaction; S8. After the reaction, measure the viscosity. When the viscosity is 8000 - 10000 cps / 25 °C, first disperse at high speed for 30 - 60 minutes, then disperse at low speed for 30 - 60 minutes, and finally cool down and filter to obtain the bio - based polyester.

8. The preparation method of the bio-based polyester according to claim 7, wherein, It includes the following steps: S6: Add deacetylated chitin, aldehyde - modified lignin, 1,4 - dioxane, methanol, and deionized water into a reaction kettle, pass nitrogen and stir at 1000 - 2000 r / min for 10 - 30 minutes. After mixing evenly, continue to pass nitrogen for 5 minutes; S7: Stop passing nitrogen, heat to 50 - 60 °C, keep warm for 1 hour, continue to pass nitrogen to remove free water, add polyamine, polyaldehyde monomer, and catalyst, heat up to 110 - 120 °C, and reflux for 3 - 6 hours, and separate the reaction water with a water separator; S8: After reacting for 3 hours, measure the viscosity every 30 minutes. When the viscosity reaches 8000 - 10000 cps / 25 °C, set the stirring speed to 10000 - 12000 r / min and disperse at high speed for 30 - 60 minutes, then set the stirring speed to 1000 - 1200 r / min and disperse at low speed for 30 - 60 minutes, then cool down to 50 °C and filter to obtain the bio - based polyester.

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