A method for preparing PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT

Abstract

This invention discloses a method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT, belonging to the field of biodegradable polymer reinforcement. It mainly addresses the problems of high dosage of reinforcing agents and insignificant reinforcing effects in current PBAT and its composite materials. The method involves pretreating and mechanically dissociating fiber raw materials to obtain carboxyethyl nanocellulose, which is then modified with advanced alkylamines and compounded with PBAT particles to obtain the masterbatch. This invention achieves significant reinforcing and toughening effects on PBAT and its composite materials even with a nanocellulose dosage of 0.1-2 wt%, which is beneficial for expanding its application range.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable polymer reinforcement, specifically relating to a method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT. Background Technology

[0002] With the increasing severity of "white pollution" caused by non-degradable plastic products, and the growing environmental awareness and promotion of sustainable development, the development and utilization of biodegradable polymer materials are considered a good solution to the problem. Polybutylene terephthalate (PBAT) possesses many advantages, including good flexibility, complete biodegradability, thermal stability, and good biocompatibility, making it one of the most promising environmentally friendly materials to replace traditional polymers. However, PBAT's low strength and low modulus significantly limit its applications.

[0003] To improve the strength of PBAT and its composites, various methods have been explored. For example, invention patent CN202110203802.2 discloses a modified ultrafine rice husk powder-reinforced PBAT fully degradable agricultural mulch film material and its preparation method. The ultrafine rice husk powder is modified with tung oil anhydride and octadecane. When the amount of ultrafine rice husk powder added is 5-20%, the tensile strength of the composite material increases from 20.0 MPa to 21.8 MPa, an increase of 9%. Invention patent CN202210658289.0 discloses a PBAT additive with both toughening, nucleation, and hydrolysis-resistant properties, its preparation method, and its application. The PBAT additive is obtained by heating phenylphosphonic acid, stearic acid, and aluminum hydroxide in the presence of xylene solvent. Adding 1% of this PBAT additive can increase the tensile strength of the PBAT material from 21.0 MPa to 25.7 MPa, an increase of 22.4%. Invention patent CN201910131302.5 discloses a graphene composite biomass-reinforced PBS / PBAT biodegradable composite material and its preparation method. When the amount of graphene composite biomass is 45% of PBAT, the tensile strength of the composite material increases from 49.0 MPa to 58 MPa, an increase of 18.4%. Invention patent CN201610813912.X discloses a modified bagasse-reinforced PBAT / starch fully biodegradable composite material, its preparation method, and its application. Using butyl methacrylate to modify bagasse, when the amount of modified bagasse is 16.7%, the tensile strength of the PBAT / starch composite material increases from 11.6 MPa to 14.5 MPa, an increase of 25%, and the elongation at break increases from 290% to 350%, an increase of 20.69%.

[0004] This shows that current methods for toughening and reinforcing PBAT and its composites still suffer from problems such as large amounts of reinforcing agents and insignificant reinforcing effects. Therefore, there is an urgent need to find a material that can significantly enhance and toughen PBAT with low dosage. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT, characterized by comprising the following steps:

[0008] (1) Pretreatment and mechanical dissociation: The fiber raw material is stirred evenly with a mixed aqueous solution of sodium hydroxide and acrylamide and reacted at a certain temperature for a period of time. The pulp is then washed with water until the pH value is neutral. The washed pulp is mechanically dissociated to obtain carboxyethyl nanocellulose.

[0009] (2) Modification: A certain amount of carbonyl activating reagent is added to the aqueous suspension of carboxyethyl nanocellulose. After stirring evenly, an ethanol solution of a higher alkylamine is added. The higher alkylamine is one or more of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine. The molar amount of the higher alkylamine is 1-7 times the content of carboxyethyl in the nanocellulose. The reaction pH is 5-7, the reaction temperature is 51-65℃, and the reaction time is 5-20h. The degree of substitution of the higher alkylamine in the modified nanocellulose is 0.1-0.5. Afterwards, the nanocellulose is washed by centrifugation with deionized water, ethanol, and dichloromethane to obtain the modified nanocellulose.

[0010] (3) Preparation of masterbatch: Modified nanocellulose is dispersed in dichloromethane, PBAT particles are added, and the mixture is stirred until the particles are completely dissolved. After drying and granulation, PBAT / modified nanocellulose composite masterbatch is obtained. The dichloromethane vapor generated during the drying process is condensed and recovered.

[0011] The content of modified nanocellulose in the masterbatch is 5-40 wt%.

[0012] The fiber raw materials are at least one of bleached or unbleached softwood pulp, hardwood pulp, cotton pulp, bamboo pulp, wheat straw pulp, waste paper pulp, or wood flour, bamboo flour, plant straw, corn cob, and xylose waste residue, wherein the lumpy and powdered raw materials need to be crushed to a particle size of 40-80 mesh.

[0013] The mass concentration of the fiber raw material is 20-40%, preferably 25-35%; the amount of sodium hydroxide is 10-40% of the mass of the fiber raw material, preferably 10-20%; the amount of acrylamide is 10-30% of the mass of the fiber raw material, preferably 10-15%; the reaction temperature is 90-100℃, preferably 92-95℃; the reaction time is 0.5-2h, preferably 1-1.5h; and the carboxyethyl content of the material after reaction is 1.0-3.0 mmol / g, preferably 2.0-3.0 mmol / g.

[0014] The mechanical dissociation includes one or more combinations of disc milling, ball milling, bead milling, high-pressure homogenization, ultrasound, and microfluidics, and the resulting carboxyethyl cellulose nanoparticles have a diameter of less than 50 nm and an aspect ratio of greater than 100.

[0015] The carbonyl activating agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The molar amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1-5 times, preferably 2-3 times, the carboxyl ethyl content in the nanocellulose. The molar amount of N-hydroxysuccinimide is 0.2-1 times, preferably 0.25-0.5 times, the amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] 1. The present invention provides a method for preparing PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT. When the amount of nanocellulose is low, the tensile strength and elongation at break of PBAT and its composite material are significantly improved at the same time, and the reinforcing and toughening effect is very significant.

[0018] 2. The present invention provides a method for preparing PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT. By precisely controlling the pretreatment conditions, mechanical dissociation degree, modification reaction conditions, and masterbatch preparation process of the fiber raw materials, the obtained nanocellulose contains an appropriate amount of modified groups that are uniformly distributed on the cellulose chain. The morphology of the nanocellulose achieves the optimal aspect ratio and ensures the morphology maintenance and stability of the nanocellulose in subsequent processing. At the same time, it achieves full dispersion of nanocellulose in the masterbatch, PBAT, and their composite materials. Based on the superposition of these factors, it ultimately achieves a significant reinforcing and toughening effect on PBAT and its composite materials.

[0019] 3. The present invention provides a method for preparing PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT. By controlling various reaction conditions, a high carboxyl content and a high degree of substitution of higher alkylamines are obtained. At the same time, the amount of reagents used is small, the reaction time is short, and the reaction conditions are mild. This not only helps to reduce the preparation cost, but also helps to scale up industrial production, and also reduces environmental pollution. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to specific embodiments, but this is not intended to limit the present invention.

[0021] Example 1

[0022] (1) Pretreatment and mechanical dissociation: Bleached hardwood pulp was stirred evenly with a mixed aqueous solution of sodium hydroxide and acrylamide. The concentration of fiber raw material was 30%, the amount of sodium hydroxide was 20% of the mass of fiber raw material, the amount of acrylamide was 15% of the mass of fiber raw material, the reaction temperature was 95℃, and the reaction time was 1h. After the reaction, the pulp was washed with water until the pH value was neutral. The washed pulp was mechanically dissociated by fine grinding to obtain carboxyethyl nanocellulose with a carboxyethyl content of 2.5 mmol / g, a diameter of 50 nm, and an aspect ratio of 150.

[0023] (2) Modification: A certain amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added to an aqueous suspension of carboxyethyl cellulose nanoparticles. The molar amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was 3 times the carboxyethyl content in the nanoparticles, and the molar amount of N-hydroxysuccinimide was 0.25 times that of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. After stirring evenly, an ethanol solution of octadecylamine was added. The molar amount of octadecylamine was 3 times the carboxyethyl content in the nanoparticles. The reaction was carried out at a pH of 5.5-6.0 and a temperature of 56℃ for 12 h. Afterwards, the nanoparticles were washed by centrifugation with deionized water, ethanol, and dichloromethane, respectively, to obtain modified nanoparticles with a degree of substitution of octadecylamine of 0.3.

[0024] (3) Preparation of masterbatch: Modified nanocellulose is dispersed in dichloromethane, PBAT particles are added, and the mixture is stirred until the particles are completely dissolved. After drying and granulation, PBAT / modified nanocellulose composite masterbatch is obtained. The dichloromethane vapor generated during the drying process is condensed and recovered.

[0025] The modified nanocellulose content in the masterbatch is 20wt%. After the masterbatch is mixed evenly with PBAT particles and other additives, it is then extruded and injection molded into sheets. The modified nanocellulose content in the product is 0.5wt%. The tensile strength of the product increases from 22MPa to 36MPa, an increase of 63.6%, and the elongation at break increases from 610% to 950%, an increase of 55.7%.

[0026] Example 2

[0027] (1) Pretreatment and mechanical dissociation: Unbleached bamboo pulp was stirred evenly with a mixed aqueous solution of sodium hydroxide and acrylamide. The concentration of fiber raw material was 35%, the amount of sodium hydroxide was 15% of the mass of fiber raw material, the amount of acrylamide was 10% of the mass of fiber raw material, the reaction temperature was 92℃, and the reaction time was 1.5h. After the reaction, the pulp was washed with water until the pH value was neutral. The washed pulp was mechanically dissociated by bead milling to obtain carboxyethyl nanocellulose with a carboxyethyl content of 2.7mmol / g, a diameter of 40nm, and an aspect ratio of 180.

[0028] (2) Modification: A certain amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added to an aqueous suspension of carboxyethyl cellulose nanoparticles. The molar amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was 2.5 times the carboxyethyl content in the nanoparticles, and the molar amount of N-hydroxysuccinimide was 0.3 times that of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. After stirring evenly, an ethanol solution of hexadecylamine was added. The molar amount of hexadecylamine was 2.5 times the carboxyethyl content in the nanoparticles. The reaction was carried out at pH 5.5-6.0 and temperature 60℃ for 10 h. Afterwards, the nanoparticles were washed by centrifugation with deionized water, ethanol, and dichloromethane, respectively, to obtain modified nanoparticles with a hexadecylamine substitution degree of 0.4.

[0029] (3) Preparation of masterbatch: Modified nanocellulose is dispersed in dichloromethane, PBAT particles are added, and the mixture is stirred until the particles are completely dissolved. After drying and granulation, PBAT / modified nanocellulose composite masterbatch is obtained. The dichloromethane vapor generated during the drying process is condensed and recovered.

[0030] The modified nanocellulose content in the masterbatch is 25wt%. After the masterbatch is mixed with PBAT particles, starch and other additives, it is blow-molded into a film. The modified nanocellulose content in the product is 0.6wt%. The tensile strength of the product increases from 18MPa to 34MPa, an increase of 88.9%, and the elongation at break increases from 460% to 790%, an increase of 71.7%.

[0031] Example 3

[0032] (1) Pretreatment and mechanical dissociation: Unbleached wood powder of 60-80 mesh was stirred evenly with a mixed aqueous solution of sodium hydroxide and acrylamide. The concentration of fiber raw material was 40%, the amount of sodium hydroxide was 10% of the mass of fiber raw material, the amount of acrylamide was 10% of the mass of fiber raw material, the reaction temperature was 100℃, and the reaction time was 0.5h. After the reaction, the pulp was washed with water until the pH value was neutral. The washed pulp was mechanically dissociated by high pressure homogenization to obtain carboxyethyl nanocellulose with a carboxyethyl content of 3.0 mmol / g, a diameter of 30 nm, and an aspect ratio of 120.

[0033] (2) Modification: A certain amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide were added to an aqueous suspension of carboxyethyl cellulose nanoparticles. The molar amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was twice the carboxyethyl content in the nanoparticles, and the molar amount of N-hydroxysuccinimide was 0.2 times that of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride. After stirring evenly, an ethanol solution of tetradecylamine was added. The molar amount of tetradecylamine was twice the carboxyethyl content in the nanoparticles. The reaction was carried out at a pH of 5.5-6.0 and a temperature of 57℃ for 8 hours. Afterwards, the nanoparticles were washed by centrifugation with deionized water, ethanol, and dichloromethane, respectively, to obtain modified nanoparticles with a tetradecylamine substitution degree of 0.5.

[0034] (3) Preparation of masterbatch: Modified nanocellulose is dispersed in dichloromethane, PBAT particles are added, and the mixture is stirred until the particles are completely dissolved. After drying and granulation, PBAT / modified nanocellulose composite masterbatch is obtained. The dichloromethane vapor generated during the drying process is condensed and recovered.

[0035] The modified nanocellulose content in the masterbatch is 40wt%. After mixing the masterbatch with PBAT particles, calcium carbonate and other additives, it is then foamed and molded to prepare a foamed material. The modified nanocellulose content in the product is 0.8wt%. The tensile strength of the product increases from 45MPa to 71MPa, an increase of 57.8%, and the elongation at break increases from 450% to 690%, an increase of 53.3%.

[0036] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT, characterized in that, Includes the following steps: (1) Pretreatment and mechanical dissociation: The fiber raw material is stirred evenly with a mixed aqueous solution of sodium hydroxide and acrylamide and reacted at a certain temperature for a period of time. The pulp is then washed with water until the pH value is neutral. The washed pulp is mechanically dissociated to obtain carboxyethyl nanocellulose. (2) Modification: A certain amount of carbonyl activating reagent is added to the aqueous suspension of carboxyethyl nanocellulose. After stirring evenly, an ethanol solution of a higher alkylamine is added. The higher alkylamine is one or more of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine. The molar amount of the higher alkylamine is 1-7 times the content of carboxyethyl in the nanocellulose. The reaction pH is 5-7, the reaction temperature is 51-65℃, and the reaction time is 5-20h. The degree of substitution of the higher alkylamine in the modified nanocellulose is 0.1-0.

5. Afterwards, the nanocellulose is washed by centrifugation with deionized water, ethanol, and dichloromethane to obtain the modified nanocellulose. (3) Preparation of masterbatch: Modified nanocellulose is dispersed in dichloromethane, PBAT particles are added, and the mixture is stirred until the particles are completely dissolved. After drying and granulation, PBAT / modified nanocellulose composite masterbatch is obtained. The dichloromethane vapor generated during the drying process is condensed and recovered. The content of modified nanocellulose in the masterbatch is 5-40 wt%.

2. The method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT according to claim 1, characterized in that, In step (1), the fiber raw material is at least one of bleached or unbleached softwood pulp, broadleaf pulp, cotton pulp, bamboo pulp, wheat straw pulp, waste paper pulp or wood flour, bamboo flour, plant straw, corn cob, xylose waste residue, wherein the block and powder raw materials need to be crushed to a particle size of 40-80 mesh.

3. The method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT according to claim 1, characterized in that, In step (1), the mass concentration of the fiber raw material is 20-40%, the amount of sodium hydroxide is 10-40% of the mass of the fiber raw material, the amount of acrylamide is 10-30% of the mass of the fiber raw material, the reaction temperature is 90-100℃, the reaction time is 0.5-2h, and the carboxyethyl content of the material after the reaction is 1.0-3.0mmol / g.

4. The method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT according to claim 1, characterized in that, The mechanical dissociation in step (1) includes one or more of the following methods: disc milling, ball milling, bead milling, high-pressure homogenization, ultrasound, and microfluidics. The resulting carboxyethyl cellulose nanoparticles have a diameter of less than 50 nm and an aspect ratio of more than 100.

5. The method for preparing a PBAT / modified nanocellulose composite masterbatch for reinforcing and toughening PBAT according to claim 1, characterized in that, In step (2), the carbonyl activating agent is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and N-hydroxysuccinimide. The molar amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride is 1-5 times the carboxyethyl content in nanocellulose, and the molar amount of N-hydroxysuccinimide is 0.2-1 times that of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride.