Lignin modified polyester-based antistatic composite material and preparation method thereof

Abstract

The invention belongs to the field of high polymer materials, and particularly relates to a lignin-modified polyester-based antistatic composite material and a preparation method thereof.The preparation method comprises the steps of lignin suspension preparation, raw material pulping, esterification reaction and condensation polymerization, the lignin suspension is obtained through ultrasonic-assisted dispersion esterification modified lignin or ball-milling nanocrystallization modified lignin, the lignin can be endowed with more excellent matrix compatibility and electrical conductivity by means of esterification or nanocrystallization modification and the like, and meanwhile, by combining improvement of a polycondensation process, the conductivity of the lignin can be improved. The prepared polyester material has a good antistatic effect under the condition of a small lignin addition amount, and also has the mechanical strength, thermal stability and environmental friendliness of the material. The composite material obtained by the invention is more suitable for multifunctional scenes such as bio-based and permanent electrostatic protection high polymer materials.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to a lignin-modified polyester-based antistatic composite material and a preparation method thereof. Background Art

[0002] Polymer materials are widely used in modern industry due to their light weight, low price, corrosion resistance and other characteristics. However, the inherent insulation of polymer materials generates static electricity, which has become one of the main problems restricting their applications. At the same time, as the basis for ensuring the application fields and service life of polymer materials, mechanical properties affect the comprehensive properties of polymer materials. Therefore, the research on preparing composite materials with both antistatic performance and good mechanical properties through antistatic enhancement modification has attracted wide attention. Static electricity accumulation not only causes damage to electronic devices, but also may lead to safety hazards such as fires or explosions. Reducing the resistivity of polymer materials to improve antistatic performance and the development of antistatic agents have become key research directions in materials science.

[0003] Lignin is rich in aromatic ring structures and has good thermal stability. Even under high-temperature processing conditions, it is not easily decomposed or denatured, which makes it suitable for some applications that require high temperature resistance. Moreover, it is widely sourced and inexpensive, and is usually used to improve the heat resistance of polymer materials. For example, patent text CN101921387A discloses a preparation method of a lignin-modified PET composite material, including the steps: (1) adding lignin, terephthalic acid, ethylene glycol, and zinc acetate into a reaction kettle according to the mass percentages of 0.5-5%, 50-80%, 20-50%, and 0.1-1% respectively for esterification reaction. Reaction conditions: temperature 200-280°C; pressure 0.1-0.6 Mpa; stirring speed 100-300 rpm; reaction time 2-6 hours; (2) carrying out polycondensation reaction on the esterification reaction product under vacuum conditions to obtain a lignin-modified PET composite material. Reaction conditions: temperature 220-260°C; pressure 0.015-0.03 Mpa; stirring speed 100-300 rpm; reaction time 2-6 hours; discharging material temperature 180-200°C. The heat resistance of PET materials is improved by adding lignin.

[0004] Then, in addition to improving the heat resistance of materials, lignin can also be used as a modifying material for antistatic composites. First of all, lignin is rich in aromatic ring structures and phenolic hydroxyl functional groups, endowing it with natural conductivity, enabling it to promote charge conduction to a certain extent. By compounding with conductive polymers or conductive fillers, the antistatic performance of materials can be significantly improved and static electricity accumulation can be reduced. In addition, lignin has good chemical stability and moisture resistance, and can maintain the stability of conductive performance in an environment with changing humidity, making the antistatic effect of the composite material durable and reliable. Moreover, lignin, as a natural source of biopolymer, is not only environmentally friendly and renewable, but also biodegradable, and has significant environmental advantages in replacing traditional petroleum-based or mineral fillers, meeting the concept of green and sustainable development.

[0005] However, there is currently little research on lignin antistatic composites, which may be due to: on the one hand, the lignin molecule contains hydroxyl groups, and the hydroxyl groups are prone to form intramolecular and intermolecular hydrogen bonds, making it easy to agglomerate and difficult to be uniformly dispersed in the polymer matrix. And the polymer materials usually lack functional groups that can form strong interactions with the hydroxyl groups of lignin, further exacerbating the interfacial compatibility problem. At the same time, the π-π interaction and hydrogen bond interaction between lignin molecules are very strong, resulting in serious self-agglomeration of lignin and very weak interaction force with the polymer interface. During the process of modifying PET composites, there are usually problems such as easy occurrence of faults due to interfacial compatibility problems with polymers or agglomeration due to the high polarity of lignin itself. It is difficult to obtain good uniform dispersion in the polymer matrix by simple stirring without surface treatment. This agglomeration phenomenon will lead to unstable performance in local areas and affect the overall performance of the material.

[0006] On the other hand: as a natural polymer material, the properties of lignin may be affected by various factors such as source, treatment method and storage conditions. The copolymerization and reaction of lignin with polyester raw materials involve various physical and chemical processes such as dissolution, diffusion, chemical reaction, etc. The complexity and uncontrollability of these processes may lead to an increase in processing difficulty and instability of the properties of the composite material, resulting in certain instability in the properties of lignin-modified polymer composites.

[0007] Therefore, it is necessary to improve the preparation of existing lignin composite antistatic materials, so that not only can the natural conductive characteristics and environmental advantages of lignin be fully exerted, but also the comprehensive requirements of high-performance antistatic materials in terms of conductivity, mechanical properties, stability and processability can be met. Summary of the Invention

[0008] In view of the deficiencies of the prior art, the present invention improves the preparation method of lignin-modified polyester-based antistatic composite materials. By using surface-modified lignin raw materials and polyester raw materials for compounding, and then using in-situ polymerization to prepare polyester, the process is adjusted during the preparation to enable the lignin to be evenly dispersed in the polyester matrix at a relatively low addition amount, thereby enhancing the interfacial bonding between the lignin and the matrix, giving play to the advantages of the natural macromolecular multi-hydroxy structure of the lignin material, and improving the construction of the conductive network.

[0009] The specific technical solution of the present invention is as follows:

[0010] In the first aspect of the present invention, a preparation method of a lignin-modified polyester-based antistatic composite material is provided, including the steps:

[0011] 1) Preparation of lignin suspension, and the lignin suspension is obtained by one of the following methods:

[0012] A: Mix dry lignin powder with a dispersant at a mass ratio of 1-1.5:1; use a twin-screw kneader to stir and mix at 60-130°C and 200-800 rpm; then raise the temperature to 140-160°C, add 0.5-3 wt% of zinc stearate based on the mass of the lignin powder and continue stirring and reacting. After the reaction ends, cool and collect the product, dry it, and add it to a solvent and use ultrasonic-assisted dispersion to prepare a lignin suspension; the dispersant can be at least one of β-propiolactone, γ-butyrolactone or ε-caprolactone;

[0013] B: Disperse lignin powder evenly in a solvent by ball milling to obtain a lignin suspension. After ball milling, the particle size of lignin in the lignin suspension is 10-500 nm; preferably, it can be 10-100 nm.

[0014] 2) Pulping of raw materials: Select and prepare at least one dibasic acid or its ester derivative and at least one diol as monomers of polyester, and add them to the lignin suspension obtained in step 1) for mixing and pulping;

[0015] 3) Esterification reaction: React the mixture of lignin, ester derivative of dibasic acid and diol obtained by pulping in step 2) in the presence of a catalyst to remove the alcohol generated by the reaction and generate an intermediate oligomer;

[0016] 4) Polycondensation reaction: After the esterification ends, add a stabilizer and a co-dispersant, and continue to heat the oligomer under reduced pressure for a pre-polycondensation reaction; then continue to carry out a final polycondensation reaction at a high temperature, and remove the remaining by-products and volatile impurities by further reducing the pressure to obtain the lignin-modified polyester-based antistatic composite material.

[0017] First, through esterification modification, nanometer ball milling modification, and physical means such as mechanical treatment and ultrasonic assistance, the polarity and dispersibility of lignin are regulated at the molecular level, endowing lignin with better matrix compatibility and conductivity, which can reduce the addition amount of lignin. At the same time, combined with the improvement of the polymerization process, the comprehensive performance of the polyester material can also be improved.

[0018] In some preferred embodiments, the lignin is one or a combination of kraft lignin, alkali lignin, delignified lignin, sodium lignosulfonate, calcium lignosulfonate, etc.

[0019] In some preferred embodiments, in step 1), the ball milling time is 12 to 144 h, and the rotation speed is 50 to 1200 rpm.

[0020] In some preferred embodiments, in the lignin suspension obtained in step 1), the solvent is one or a combination of water, ethanol, ethylene glycol, 1,3 - propanediol, isopropanol, 1,4 - butanediol, etc. This includes both the suspension prepared from the lignin obtained by esterification modification and the suspension obtained by ball milling nanometerization.

[0021] In the embodiments of the present invention, the polyester monomer synthesis raw materials include at least one dicarboxylic acid or its ester derivative, and at least one diol; wherein, the dicarboxylic acid or its ester derivative can be, for example, terephthalic acid or its dimethyl ester, isophthalic acid or its dimethyl ester or its dimethyl ester, naphthalenedicarboxylic acid or its dimethyl ester, bicyclo[2.2.1]hept - 5 - ene - 2,3 - dicarboxylic acid or its dimethyl ester, etc., and can be one or a combination of two or more of them; wherein the diol can be one or a combination of two or more of common diols such as ethylene glycol, 1,4 - cyclohexanedimethanol, isosorbide, etc.

[0022] Before the raw materials are beaten into pulp, the dicarboxylic acid or its ester derivative and the diol raw materials need to be dried, and they should be immediately taken for beating pulp after drying.

[0023] In some preferred embodiments, in step 2), according to the molar ratio, dicarboxylic acid or its ester derivative: diol = 1:1.1 - 1.6, and according to the mass ratio, dicarboxylic acid or its ester derivative: lignin = 100:0.01 - 1.5 ， 这里的木质素 is the lignin after being treated in step 1), the lignin after esterification modification in step 1) or the lignin after nanometerization.

[0024] In some preferred embodiments, in step 3), the esterification reaction conditions are: under nitrogen protection, the reaction temperature is 220 - 250 °C, the pressure is 0.3 - 0.4 MPa, and the reaction time is 2 - 5 h.

[0025] In some preferred embodiments, the polycondensation reaction conditions are:

[0026] Pre - polycondensation stage: Control the temperature at 240 - 270 °C, the low - vacuum reaction time is 50 - 70 min, gradually increase the pressure to - 40 kPa within 15 - 30 min, and then gradually increase the vacuum degree to 20 - 100 Pa within 25 - 45 min;

[0027] Final - polycondensation stage: Control the temperature at 265 - 285 °C, the vacuum degree is 20 - 100 Pa, the intrinsic viscosity of the final condensate is 0.6 - 1.2 dL / g, and the reaction time is usually 1 - 4 h.

[0028] In some preferred embodiments, the catalyst is one or a combination of antimony - based, titanium - based, germanium - based, and aluminum - based catalysts; by mass ratio, dibasic acid or its ester derivatives: catalyst = 100:0.01 - 0.1. For example, in some specific embodiments, the catalyst is antimony trioxide, etc.

[0029] In some preferred embodiments, the stabilizer is one or more of phosphoric acid, phosphorous acid, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, and triphenyl phosphite; the co - dispersant is one or more of silica, calcium carbonate, magnesium hydroxide, magnesium acetate, sodium silicate, magnesium stearate, zinc stearate, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylamide; by mass ratio, dibasic acid or its ester derivatives: stabilizer: co - dispersant = 100:0.01 - 0.1:0.05 - 0.25.

[0030] In the second aspect of the present invention, there is also provided a lignin - modified polyester - based antistatic composite material prepared by the described preparation method.

[0031] The beneficial effects of the present invention are:

[0032] Compared with the prior art, the present invention first regulates the polarity and dispersibility of lignin at the molecular level through esterification or nanometer - modification methods, as well as physical means such as mechanical treatment and ultrasonic assistance, endowing lignin with better matrix compatibility and conductivity, avoiding interfacial compatibility problems or agglomeration problems. At the same time, combined with the improvement of the polycondensation process, the prepared polyester material can have good antistatic effects with a relatively small amount of lignin added, and also takes into account the mechanical strength, thermal stability, and environmental friendliness of the material. The composite material obtained by the present invention is more suitable for multifunctional scenarios such as bio - based and permanent electrostatic - protection polymer materials. Specific Embodiments

[0033] The following specific examples are used to further illustrate the present invention, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0034] Example 1

[0035] This example provides an antistatic PET polyester material modified with lignin, which is prepared by the following steps:

[0036] (1) Lignin modification: Mix 50 g of dry kraft lignin powder with ε-caprolactone in a mass ratio of 1:1; Stir the mixture at a speed of 800 rpm and 90 °C for 40 min using a twin-screw kneader; Raise the temperature to about 150 °C, add 1 g of zinc stearate and continue stirring for 4 h; After the reaction is completed, cool and collect the product, and dry it to obtain modified lignin powder.

[0037] (2) Preparation of lignin dispersion: Take 5 g of the modified lignin powder prepared in step (1), add it to 100 g of ethylene glycol solvent and use ultrasonic-assisted dispersion to prepare a suspension dispersion for standby.

[0038] (3) Pulping of raw materials: Mix all the lignin dispersion prepared in step (2) with 1000 g of terephthalic acid (PTA) and 440 g of ethylene glycol (EG) at high speed to obtain a pre-reaction raw material slurry.

[0039] (4) Esterification reaction: In a 5 L stainless steel high-pressure reactor, add the raw material slurry and 0.7 g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 220 °C and 0.3 MPa for about 3.5 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0040] (5) Polycondensation reaction:

[0041] Pre-polycondensation: Add 0.5 g of triphenyl phosphite and 1.5 g of magnesium acetate. First, raise the temperature to 270 °C, gradually make the pressure in the reactor reach -40 kPa within 20 min, and then gradually make the vacuum degree in the reactor reach 100 Pa within 40 min. The reaction time is 60 min to complete the pre-polycondensation;

[0042] Final polycondensation: Continue to maintain a vacuum degree of 100 Pa, raise the temperature to 280 °C, and end the reaction when the intrinsic viscosity of the final condensate is 0.8 dL / g. The reaction time is about 1.5 h.

[0043] (6) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0044] Example 2

[0045] This example provides an antistatic PET polyester material modified with lignin, which is prepared by the following steps:

[0046] (1) Lignin modification: Mix 50 g of dry sodium lignosulfonate powder with ε-caprolactone in a mass ratio of 1.2:1; Stir the mixture with a twin-screw kneader at a speed of 800 rpm and 80 °C for 40 min; Raise the temperature to about 150 °C, add 1 g of zinc stearate and continue stirring for 4 h; After the reaction is completed, cool and collect the product, and dry it to obtain modified lignin powder.

[0047] (2) Preparation of lignin dispersion: Take 5 g of the modified lignin powder prepared in step (1), add it to a solvent of 200 g of ethylene glycol: water = 9:1, and use ultrasonic assistance for dispersion to prepare a suspension dispersion for standby.

[0048] (3) Pulping of raw materials: Mix all the lignin dispersion prepared in step (2) with 1000 g of terephthalic acid and 360 g of ethylene glycol at high speed to obtain a pre-reaction raw material slurry.

[0049] (4) Esterification reaction: In a 5 L stainless steel high-pressure reactor, add the raw material slurry and 0.6 g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 250 °C and 0.4 MPa for about 1 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0050] (5) Polycondensation reaction:

[0051] Pre-polycondensation: Add 0.5 g of triphenyl phosphite and 1.2 g of magnesium acetate. First, raise the temperature to 240 °C, and gradually increase the pressure in the reactor to -40 kPa within 25 min. Then, gradually increase the vacuum degree in the reactor to 100 Pa within 45 min. The reaction time is 70 min to complete the pre-polycondensation;

[0052] Final polycondensation: Continue to maintain a vacuum degree of 100 Pa, raise the temperature to 265 °C, and end the reaction when the intrinsic viscosity of the final condensate is 1.2 dL / g. The reaction time is about 3 h.

[0053] (6) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0054] Example 3

[0055] This example provides an antistatic PET polyester material modified with lignin, which is prepared by the following steps:

[0056] (1) Lignin modification: Mix 100 g of dry sodium lignosulfonate powder with ε-caprolactone in a mass ratio of 1:1; Stir the mixture with a twin-screw kneader at a speed of 600 rpm and 80 °C for 30 min; Raise the temperature to about 150 °C, add 1 g of zinc stearate and continue stirring for 3.5 h; After the reaction is completed, cool and collect the product, and dry it to obtain modified lignin powder.

[0057] (2) Preparation of lignin dispersion: Take 10 g of the modified lignin powder prepared in step (1), add it to 200 g of a solvent with ethylene glycol: 1,4-butanediol = 9:1, and use ultrasonic assistance for dispersion to prepare a suspension dispersion for standby.

[0058] (3) Pulping of raw materials: Mix all the lignin dispersion prepared in step (2) with 980 g of terephthalic acid and 340 g of ethylene glycol at high speed for pulping to obtain a pre-reaction raw material slurry.

[0059] (4) Esterification reaction: Add the raw material slurry and 0.8 g of antimony trioxide into a 5 L stainless steel high-pressure reactor. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 230 °C and 0.4 MPa for about 3 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0060] (5) Polycondensation reaction:

[0061] Pre-polycondensation: Add 0.6 g of triphenyl phosphite and 2 g of magnesium acetate. First, raise the temperature to 260 °C, gradually increase the pressure in the reactor to -40 kPa within 20 min, and then gradually increase the vacuum degree in the reactor to 100 Pa within 40 min. The reaction time is 60 min to complete the pre-polycondensation;

[0062] Final polycondensation: Continue to maintain the vacuum degree of 100 Pa, raise the temperature to 280 °C, and the reaction time is 1.5 h. When the intrinsic viscosity of the final condensate reaches 0.8 dL / g, end the reaction.

[0063] (6) After the reaction, introduce nitrogen to extrude the melt, pelletize, and dry to obtain the polyester material.

[0064] Example 4

[0065] This example provides an antistatic PET polyester material modified with lignin, which is prepared by the following steps:

[0066] (1) Lignin modification: Mix 50 g of dry sodium lignosulfonate powder with ε-caprolactone at a mass ratio of 1.4:1; use a twin-screw kneader to stir the mixture at a speed of 700 rpm and 80 °C for 30 min; raise the temperature to about 150 °C, add 1 g of zinc stearate and continue to stir for 3.5 h; after the reaction ends, cool and collect the product, and dry to obtain the modified lignin powder.

[0067] (2) Preparation of lignin dispersion: Take 1 g of the modified lignin powder prepared in step (1), add it to 100 g of a solvent with ethylene glycol: 1,4-butanediol = 9:1, and use ultrasonic assistance for dispersion to prepare a suspension dispersion for standby.

[0068] (3) Pulping of raw materials: Mix all the lignin dispersion obtained in step (2) with 940 g of terephthalic acid, 50 g of isophthalic acid, and 430 g of ethylene glycol at high speed to obtain a pre-reaction raw material slurry.

[0069] (4) Esterification reaction: Add the raw material slurry and 0.8 g of antimony trioxide into a 5 L stainless steel autoclave. After purging the air in the autoclave with nitrogen, carry out the esterification reaction at 240 °C and 0.3 MPa for about 4 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0070] (5) Polycondensation reaction:

[0071] Pre-polycondensation: Add 0.6 g of triphenyl phosphite and 1.5 g of magnesium acetate. First, raise the temperature to 250 °C, and gradually increase the pressure in the autoclave to -40 kPa within 20 min. Then, gradually increase the vacuum degree in the autoclave to 100 Pa within 30 min. The reaction time is 50 min to complete the pre-polycondensation.

[0072] Final polycondensation: Continue to maintain the vacuum degree of 100 Pa, raise the temperature to 280 °C, and the reaction time is 1.5 h. When the intrinsic viscosity of the final condensate reaches 0.6 dL / g, end the reaction.

[0073] (6) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize, and dry to obtain the polyester material.

[0074] Example 5

[0075] This example provides an antistatic PET polyester material modified with lignin, which is prepared by the following steps:

[0076] (1) Lignin modification: Mix 50 g of dry sodium lignosulfonate powder with ε-caprolactone in a mass ratio of 1:1; use a twin-screw kneader to stir the mixture at a speed of 500 rpm and 90 °C for 30 min; raise the temperature to about 150 °C, add 1 g of zinc stearate and continue to stir for 4 h; after the reaction is completed, cool and collect the product, and dry to obtain the modified lignin powder.

[0077] (2) Preparation of lignin dispersion: Take 1 g of the modified lignin powder prepared in step (1), add it to a solvent of 100 g of ethylene glycol: isosorbide = 9:1, and use ultrasonic assistance for dispersion to prepare a suspension dispersion for standby.

[0078] (3) Pulping of raw materials: Mix all the lignin dispersion obtained in step (2) with 950 g of terephthalic acid, 50 g of naphthalenedicarboxylic acid, and 430 g of ethylene glycol at high speed to obtain a pre-reaction raw material slurry.

[0079] (4) Esterification reaction: In a 5L stainless steel high-pressure reactor, add the raw material slurry and 0.8g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 250°C and 0.3MPa for about 3h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0080] (5) Polycondensation reaction:

[0081] Pre-polycondensation: Add 0.6g of triphenyl phosphite and 1.5g of magnesium acetate. First, raise the temperature to 250°C, and gradually increase the pressure in the reactor to -40kPa within 20min. Then, gradually increase the vacuum degree in the reactor to 100Pa within 30min. The reaction time is 50min to complete the pre-polycondensation.

[0082] Final polycondensation: Continue to maintain the vacuum degree of 100Pa, raise the temperature to 280°C, and the reaction time is 1.5h. Wait until the intrinsic viscosity of the final condensate is 0.6dL / g to end the reaction.

[0083] (6) After the reaction is completed, purge with nitrogen to extrude the melt, pelletize, and dry to obtain the polyester material.

[0084] Example 6

[0085] This example provides a lignin-modified antistatic PET polyester material, which is prepared by the following steps:

[0086] (1) Lignin modification: Mix 50g of dry kraft lignin powder with ε-caprolactone in a mass ratio of 1:1; use a twin-screw kneader to stir the mixture at a speed of 400rpm and 90°C for 40min; raise the temperature to about 150°C, add 1g of zinc stearate and continue to stir for 4h; after the reaction is completed, cool and collect the product, dry to obtain the modified lignin powder.

[0087] (2) Preparation of lignin dispersion: Take 0.1g of the modified lignin powder prepared in step (1), add it to a solvent of 150g of ethylene glycol: isosorbide = 6:4, and use ultrasonic-assisted dispersion to prepare a suspension dispersion for standby.

[0088] (3) Raw material pulping: Mix all the lignin dispersion prepared in step (2) with 950g of terephthalic acid, 50g of naphthalenedicarboxylic acid, and 390g of ethylene glycol at high speed to obtain a pre-reaction raw material slurry.

[0089] (4) Esterification reaction: In a 5L stainless steel high-pressure reactor, add the raw material slurry and 0.8g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 220°C and 0.3MPa for about 3h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0090] (5) Polycondensation reaction:

[0091] Pre - polycondensation: Add 0.6 g of triphenyl phosphite and 1.5 g of zinc stearate. First, raise the temperature to 260 °C, and gradually increase the pressure in the reaction kettle to - 40 kPa within 20 min. Then, gradually increase the vacuum degree in the reaction kettle to 100 Pa within 30 min, with a reaction time of 50 min to complete the pre - polycondensation;

[0092] Final - polycondensation: Continue to maintain a vacuum degree of 100 Pa, raise the temperature to 280 °C, with a reaction time of 1 h. When the intrinsic viscosity of the final condensate reaches 1.0 dL / g, the reaction ends.

[0093] (6) After the reaction ends, introduce nitrogen to press out the melt, pelletize and dry to obtain the polyester material.

[0094] Example 7

[0095] This example provides a lignin - modified antistatic PET polyester material, which is prepared by the following steps:

[0096] (1) Lignin modification: Mix 50 g of dry delignified lignin powder with ε - caprolactone at a mass ratio of 1:1; use a twin - screw kneader to stir the mixture at a speed of 600 rpm and 80 °C for 40 min; raise the temperature to about 150 °C, add 1 g of zinc stearate and continue to stir for 4 h; after the reaction ends, cool and collect the product, and dry to obtain the modified lignin powder.

[0097] (2) Preparation of lignin dispersion: Take 1 g of the modified lignin powder prepared in step (1), add it to a solvent of 100 g of ethylene glycol: 1,4 - cyclohexanedimethanol = 8:2, and use ultrasonic - assisted dispersion to prepare a suspension dispersion for standby.

[0098] (3) Pulping of raw materials: Mix all the lignin dispersion prepared in step (2) with 950 g of terephthalic acid, 50 g of 2,5 - furandicarboxylic acid, and 440 g of ethylene glycol at high speed to obtain a pre - reaction raw material slurry.

[0099] (4) Esterification reaction: In a 5 L stainless - steel high - pressure reaction kettle, add the raw material slurry and 0.8 g of tetrabutyl titanate. After introducing nitrogen to displace the air in the kettle, carry out the esterification reaction at 220 °C and 0.3 MPa for about 3 h. When the water output reaches above the theoretical value, relieve the pressure to atmospheric pressure.

[0100] (5) Polycondensation reaction:

[0101] Pre - polycondensation: Add 0.6 g of triphenyl phosphite and 1.5 g of zinc stearate. First, raise the temperature to 260 °C, and gradually increase the pressure in the reaction kettle to - 40 kPa within 30 min. Then, gradually increase the vacuum degree in the reaction kettle to 100 Pa within 40 min, with a reaction time of 70 min to complete the pre - polycondensation;

[0102] Final polycondensation: Continue to maintain a vacuum of 100 Pa, raise the temperature to 270 °C, with a reaction time of 1.5 h, and end the reaction when the intrinsic viscosity of the final condensate is 1.0 dL / g.

[0103] (6) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0104] Example 8

[0105] This example provides a lignin-modified antistatic PET polyester material, which is prepared by the following steps:

[0106] (1) Lignin treatment: 10 g of dry sodium lignosulfonate powder is evenly dispersed in 100 g of ethylene glycol solvent by ball milling. The specific parameters of ball milling and dispersion are: ball milling time 72 h, rotation speed 800 rpm. After ball milling, in the obtained lignin dispersion liquid, the particle size of lignin is about 50 - 80 nm.

[0107] (2) Raw material pulping: Take 5 g of the lignin dispersion liquid prepared in step (1) (about containing 0.455 g of lignin) and mix it with 1000 g of terephthalic acid and 430 g of ethylene glycol at high speed to make a slurry of pre-reaction raw materials.

[0108] (3) Esterification reaction: In a 5 L stainless steel high-pressure reactor, add the raw material slurry and 0.8 g of antimony trioxide. After introducing nitrogen to displace the air in the reactor, carry out the esterification reaction at 250 °C and 0.3 MPa for about 2 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0109] (4) Polycondensation reaction:

[0110] Pre-polycondensation: Add 0.6 g of triphenyl phosphite and 1.5 g of magnesium acetate. First, raise the temperature to 260 °C, gradually increase the pressure in the reactor to -40 kPa within 20 min, and then gradually increase the vacuum in the reactor to 100 Pa within 30 min. The reaction time is 50 min to complete the pre-polycondensation;

[0111] Final polycondensation: Continue to maintain a vacuum of 100 Pa, raise the temperature to 280 °C, with a reaction time of 1 h, and end the reaction when the intrinsic viscosity of the final condensate is 1.0 dL / g.

[0112] (5) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0113] Example 9

[0114] This example provides a lignin-modified antistatic PET polyester material, which is prepared by the following steps:

[0115] (1) Lignin treatment: 10 g of dry kraft lignin powder was evenly dispersed in 100 g of ethylene glycol solvent by ball milling. The specific parameters of ball milling dispersion were: ball milling time 96 h, rotation speed 700 rpm. After ball milling, in the obtained lignin dispersion, the lignin particle size was about 40 - 70 nm.

[0116] (2) Pulping of raw materials: 1.5 g of the lignin dispersion prepared in step (1) (about 0.14 g of lignin) was mixed and pulped at high speed with 950 g of terephthalic acid, 50 g of naphthalenedicarboxylic acid, and 430 g of ethylene glycol to obtain a pre-reaction raw material slurry.

[0117] (3) Esterification reaction: In a 5 L stainless steel high-pressure reactor, the raw material slurry and 0.8 g of antimony trioxide were added. After purging the air in the reactor with nitrogen, the esterification reaction was carried out at 240 °C and 0.4 MPa for about 3 h. When the water output reached above the theoretical value, the pressure was released to atmospheric pressure.

[0118] (4) Polycondensation reaction:

[0119] Pre-polycondensation: 0.6 g of triphenyl phosphite and 1.5 g of magnesium acetate were added. First, the temperature was raised to 260 °C, and the pressure in the reactor was gradually increased to -40 kPa within 20 min, and then the vacuum degree in the reactor was gradually increased to 100 Pa within 40 min. The reaction time was 60 min to complete the pre-polycondensation;

[0120] Final polycondensation: The vacuum degree of 100 Pa was continuously maintained, the temperature was raised to 270 °C, and the reaction time was 1.5 h. The reaction was terminated when the intrinsic viscosity of the final condensate reached 1.0 dL / g.

[0121] (5) After the reaction, nitrogen was introduced to extrude the melt, pelletize, and dry to obtain the polyester material.

[0122] Example 10

[0123] This example provides an antistatic PET polyester material modified with lignin, which is prepared by the following steps:

[0124] (1) Lignin treatment: 10 g of dry alkali lignin powder was evenly dispersed in 100 g of ethylene glycol solvent by ball milling. The specific parameters of ball milling dispersion were: ball milling time 96 h, rotation speed 700 rpm. After ball milling, in the obtained lignin dispersion, the lignin particle size was about 40 - 70 nm.

[0125] (2) Pulping of raw materials: 3 g of the lignin dispersion prepared in step (1) (about 0.27 g of lignin) was mixed and pulped at high speed with 950 g of terephthalic acid, 50 g of bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, 400 g of ethylene glycol, and 40 g of 1,4-cyclohexanedimethanol to obtain a pre-reaction raw material slurry.

[0126] (3) Esterification reaction: In a 5L stainless steel high-pressure reactor, add the raw material slurry and 0.8g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 230°C and 0.3MPa for about 5h. When the water output reaches above the theoretical value, relieve the pressure to atmospheric pressure.

[0127] (4) Polycondensation reaction:

[0128] Pre-polycondensation: Add 0.6g of triphenyl phosphite and 1.5g of magnesium acetate. First, raise the temperature to 260°C, and gradually increase the pressure in the reactor to -40kPa within 20min. Then, gradually increase the vacuum degree in the reactor to 100Pa within 30min. The reaction time is 50min to complete the pre-polycondensation.

[0129] Final polycondensation: Continue to maintain the vacuum degree of 100Pa, raise the temperature to 270°C, and the reaction time is 1.5h. Wait until the intrinsic viscosity of the final condensate is 1.0dL / g to end the reaction.

[0130] (5) After the reaction is completed, purge with nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0131] Example 11

[0132] This example provides a lignin-modified antistatic PET polyester material, which is prepared by the following steps:

[0133] (1) Lignin treatment: Make 10g of dry sodium lignosulfonate powder uniformly dispersed in 100g of ethylene glycol solvent by ball milling. The specific parameters of ball milling dispersion are: ball milling time 72h, rotation speed 800rpm. After ball milling, in the obtained lignin dispersion liquid, the lignin particle size is about 50 - 70nm.

[0134] (2) Raw material pulping: Take 10g of the lignin dispersion liquid prepared in step (1) (about containing 0.9g of lignin), 950g of terephthalic acid, 50g of isophthalic acid, 400g of ethylene glycol, and 40g of isosorbide, and mix and pulp them at high speed to obtain a pre-reaction raw material slurry.

[0135] (3) Esterification reaction: In a 5L stainless steel high-pressure reactor, add the raw material slurry and 0.8g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 220°C and 0.3MPa for about 5h. When the water output reaches above the theoretical value, relieve the pressure to atmospheric pressure.

[0136] (4) Polycondensation reaction:

[0137] Pre - polycondensation: Add 0.6 g of triphenyl phosphite and 1.5 g of magnesium acetate. First, raise the temperature to 260 °C, and gradually increase the pressure in the reaction kettle to - 40 kPa within 20 min. Then, gradually increase the vacuum degree in the reaction kettle to 100 Pa within 30 min. The reaction time is 50 min to complete the pre - polycondensation;

[0138] Final polycondensation: Continue to maintain the vacuum degree of 100 Pa, raise the temperature to 270 °C, and the reaction time is 1.5 h. Wait until the intrinsic viscosity of the final condensate is 1.0 dL / g to end the reaction.

[0139] (5) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0140] Example 12

[0141] This example provides a lignin - modified antistatic PET polyester material, which is prepared by the following steps:

[0142] (1) Lignin treatment: Make 10 g of dry sodium lignosulfonate powder uniformly dispersed in 100 g of ethylene glycol solvent by ball - milling. The specific parameters of ball - milling dispersion are: ball - milling time 72 h, rotation speed 800 rpm. After ball - milling, in the obtained lignin dispersion liquid, the lignin particle size is about 50 - 70 nm.

[0143] (2) Raw material pulping: Take 50 g of the lignin dispersion liquid prepared in step (1) (about containing 4.5 g of lignin), 950 g of terephthalic acid, 50 g of isophthalic acid, and 380 g of ethylene glycol, and mix and pulp them at high speed to obtain the pre - reaction raw material slurry.

[0144] (3) Esterification reaction: In a 5 L stainless - steel high - pressure reaction kettle, add the raw material slurry and 0.8 g of antimony trioxide. After introducing nitrogen to displace the air in the kettle, carry out the esterification reaction at 220 °C and 0.3 MPa for about 4 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0145] (4) Polycondensation reaction:

[0146] Pre - polycondensation: Add 0.6 g of triphenyl phosphite and 1.5 g of magnesium acetate. First, raise the temperature to 260 °C, and gradually increase the pressure in the reaction kettle to - 40 kPa within 30 min. Then, gradually increase the vacuum degree in the reaction kettle to 100 Pa within 30 min. The reaction time is 60 min to complete the pre - polycondensation;

[0147] Final polycondensation: Continue to maintain the vacuum degree of 100 Pa, raise the temperature to 280 °C, and the reaction time is 1 h. Wait until the intrinsic viscosity of the final condensate is 1.0 dL / g to end the reaction.

[0148] (5) After the reaction is completed, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0149] Comparative Example 1

[0150] This example provides an ordinary polyester material without adding lignin, which is prepared by the following steps:

[0151] (1) Esterification reaction: In a 5L stainless steel high-pressure reactor, add 1000g of terephthalic acid (PTA), 540g of ethylene glycol (EG), and 0.7g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 220°C and 0.3MPa for about 3.5h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0152] (2) Polycondensation reaction: Add 0.5g of triphenyl phosphite and 1.5g of magnesium acetate, raise the temperature to 270°C, and gradually reduce the absolute pressure in the reactor to 100Pa within 60 minutes. Then continue the reaction until the intrinsic viscosity of the final condensate reaches 0.8dL / g to end the reaction, and the reaction time is about 3 hours.

[0153] (3) After the reaction, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0154] The difference from Example 1 is that modified lignin is not introduced into the polyester material.

[0155] Comparative Example 2

[0156] This comparative example provides a lignin-modified PET polyester material, which is prepared by the following steps:

[0157] (1) Preparation of lignin dispersion: Take 5g of dry kraft lignin powder, add it to 100g of ethylene glycol solvent and use ultrasonic-assisted dispersion to prepare a suspended dispersion for later use.

[0158] (2) Pulping of raw materials: Mix the prepared lignin dispersion with 1000g of terephthalic acid (PTA) and 440g of ethylene glycol (EG) at high speed to obtain a pre-reaction raw material slurry.

[0159] (3) Esterification reaction: In a 5L stainless steel high-pressure reactor, add the raw material slurry and 0.7g of antimony trioxide. After purging the air in the reactor with nitrogen, carry out the esterification reaction at 220°C and 0.3MPa for about 3.5h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0160] (4) Polycondensation reaction:

[0161] Pre-polycondensation: Add 0.5g of triphenyl phosphite and 1.5g of magnesium acetate, first raise the temperature to 270°C, gradually make the pressure in the reaction kettle reach -40kPa within 20min, and then gradually make the vacuum degree in the reaction kettle reach 100Pa within 40min. The reaction time is 60min to complete the pre-polycondensation;

[0162] Final polycondensation: Continue to maintain a vacuum of 100 Pa, raise the temperature to 280 °C, with a reaction time of 1.5 h. End the reaction when the intrinsic viscosity of the final condensate is 0.8 dL / g.

[0163] (5) After the reaction ends, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0164] The difference from Example 1 is that the lignin was not esterified and modified.

[0165] Comparative Example 3

[0166] This comparative example provides a lignin-modified PET polyester material, which is prepared by the following steps:

[0167] (1) Lignin modification: Mix 50 g of dry kraft lignin powder with ε-caprolactone in a mass ratio of 1:1; use a twin-screw kneader to stir the mixture at a speed of 800 rpm and 90 °C for 40 min; raise the temperature to about 150 °C, add 1 g of zinc stearate and continue to stir for 4 h; after the reaction ends, cool and collect the product, and dry it.

[0168] (2) Preparation of lignin dispersion: Take 5 g of the prepared modified lignin powder, add it to 100 g of ethylene glycol solvent and use ultrasonic-assisted dispersion to prepare a suspension dispersion for standby.

[0169] (3) Pulping of raw materials: Mix the prepared lignin dispersion with 1000 g of terephthalic acid (PTA) and 440 g of ethylene glycol (EG) at high speed to obtain a pre-reaction raw material slurry.

[0170] (4) Esterification reaction: In a 5 L stainless steel high-pressure reactor, add the raw material slurry and 0.7 g of antimony trioxide. After introducing nitrogen to displace the air in the reactor, carry out the esterification reaction at 220 °C and 0.3 MPa for about 3.5 h. When the water output reaches above the theoretical value, release the pressure to atmospheric pressure.

[0171] (5) Polycondensation reaction: Add 0.5 g of triphenyl phosphite and 1.5 g of magnesium acetate, raise the temperature to 270 °C, gradually reduce the absolute pressure in the reactor to 100 Pa within 60 minutes, and then continue the reaction. End the reaction when the intrinsic viscosity of the final condensate is 0.8 dL / g, and the reaction time is about 3 hours.

[0172] (6) After the reaction ends, introduce nitrogen to extrude the melt, pelletize and dry to obtain the polyester material.

[0173] The difference from Example 1 is that the steps of the polycondensation reaction are different.

[0174] The performance test results of the polyester samples obtained in each example and comparative example are shown in Table 1.

[0175] Table 1 Performance Comparison between Examples and Comparative Examples

[0176]

[0177] In summary, it can be seen that in the examples of the present invention, lignin is first modified by a dispersant or ball-milled and nano-modified, combined with physical means such as mechanical treatment and ultrasonic assistance to obtain a dispersed lignin suspension, and then in-situ polymerized with polyester raw materials to obtain a lignin-modified polyester composite material. Due to the modification treatment, the polarity and dispersibility of lignin are greatly improved, making it better compatible with the polyester matrix, avoiding interface compatibility problems or agglomeration problems. At the same time, combined with the improvement of the polycondensation process, the prepared polyester material can have good antistatic effects with a small amount of lignin addition, and the obtained material also has good mechanical strength, thermal stability, etc. The composite materials obtained in the examples of the present invention are more suitable for multifunctional scenarios such as bio-based and permanent electrostatic protection polymer materials.

[0178] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of this invention patent shall be subject to the appended claims.

Claims

1. A method for preparing a lignin-modified polyester-based antistatic composite material, characterized in that: The steps include: 1) Preparation of lignin suspension, wherein the lignin suspension is obtained by one of the following methods: A: Mix the dried lignin powder with a dispersant in a mass ratio of 1 to 1.5:1; use a twin-screw kneader at 60 to 130°C and 200 to 800 rpm to stir and mix; then heat to 140 to 160°C, add 0.5 to 3 wt% of zinc stearate by weight of the lignin powder and continue stirring to react, after the reaction is completed, cool and collect the product, dry it, add it to a solvent and use ultrasound to assist dispersion to prepare a lignin suspension; the dispersant is at least one of β-propiolactone, γ-butyrolactone or ε-caprolactone; B: The lignin powder is evenly dispersed in the solvent by ball milling to obtain a lignin suspension. After ball milling, the lignin particle size in the lignin suspension is 10 to 500 nm; 2) Raw material beating: selecting and preparing at least one dibasic acid or its ester derivative and at least one diol as monomers of polyester, adding them into the lignin suspension obtained in step 1) for mixing and beating; 3) Esterification reaction: subjecting the mixture of the pulped lignin, the ester derivative of the dibasic acid and the diol in step 2) to an esterification reaction in the presence of a catalyst, removing the alcohol produced by the reaction, and generating an intermediate product oligomer; 4) Polycondensation reaction: After the esterification is completed, stabilizers and dispersants are added, and the oligomers are continuously heated under reduced pressure to carry out a preliminary polycondensation reaction; then a final polycondensation reaction is continued at high temperature, and the remaining by-products and volatile impurities are removed by further reducing the pressure to obtain the lignin-modified polyester-based antistatic composite material.

2. The preparation method according to claim 1, characterized in that: The lignin is one or more combinations of kraft lignin, alkali lignin, dealkalized lignin, sodium lignin sulfonate, and calcium lignin sulfonate.

3. The preparation method according to claim 1, characterized in that: In step 1), the ball milling time is 12 to 144 hours, and the rotation speed is 50 to 1200 rpm.

4. The preparation method according to claim 1, characterized in that: The solvent of the lignin suspension obtained in step 1) is one or more combinations of water, ethanol, ethylene glycol, 1,3-propylene glycol, isopropanol, and 1,4-butanediol.

5. The preparation method according to claim 1, characterized in that: In the step 2), the molar ratio of dibasic acid or its ester derivative: diol is 1:1.1-1.6, and the mass ratio of dibasic acid or its ester derivative: lignin is 100:0.01-1.

5.

6. The preparation method according to claim 1, characterized in that: In the step 3), the esterification reaction conditions are: under nitrogen protection, the reaction temperature is 220-250° C., the pressure is 0.3-0.4 MPa, and the reaction time is 2-5 h.

7. The preparation method according to claim 1, characterized in that: The polycondensation reaction conditions are: Pre-condensation stage: control the temperature at 240-270°C, low vacuum reaction time at 50-70 minutes, gradually increase the pressure to -40 kPa within 15-30 minutes, and gradually increase the vacuum degree to 20-100 Pa within the next 25-45 minutes; Final polycondensation stage: temperature control at 265-285°C, vacuum degree at 20-100 Pa, and the intrinsic viscosity of the final polycondensation product at 0.6-1.2 dL / g.

8. The preparation method according to claim 1, characterized in that: The catalyst is a composite of one or more antimony-based, titanium-based, germanium-based and aluminum-based catalysts; in terms of mass ratio, the dibasic acid or its ester derivative: the catalyst = 100: 0.01-0.

1.

9. The preparation method according to claim 1, characterized in that: The stabilizer is one or more of phosphoric acid, phosphorous acid, dimethyl phosphate, trimethyl phosphate, triethyl phosphate, and triphenyl phosphite; the dispersant is one or more of silicon dioxide, calcium carbonate, magnesium hydroxide, magnesium acetate, sodium silicate, magnesium stearate, zinc stearate, polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, and polyacrylamide; in terms of mass ratio, the dibasic acid or its ester derivative: stabilizer: dispersant = 100: 0.01-0.1: 0.05-0.

25.

10. The lignin-modified polyester-based antistatic composite material prepared by the preparation method according to any one of claims 1 to 9.

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