Hydroxymethylated superfine lignin modified degradable mulching film and preparation method thereof

Abstract

The invention discloses a hydroxymethylated superfine lignin modified degradable mulching film and a preparation method thereof. The hydroxymethylated superfine lignin modified degradable mulching film comprises the following components in parts by weight: 60-89 parts of PBAT, 1-10 parts of PLA, 10-30 parts of hydroxymethylated superfine lignin, 0.1-5 parts of a plasticizer, 0.1-3 parts of a light stabilizer, 0.1-3 parts of an antioxidant, 0.1-5 parts of a lubricant and 0.1-5 parts of an anti-blocking agent. A preparation method of the hydroxymethylated superfine lignin comprises the following steps: filtering papermaking black liquor, adding the filtered papermaking black liquor and formaldehyde into a reaction kettle, fully reacting at 70-90 DEG C and 300-600 rpm for 2-5 hours, cooling to room temperature after the reaction is complete, and carrying out precipitation, filtering, drying and ultrasonic treatment to obtain the 20-300 nm hydroxymethylated superfine lignin. The papermaking black liquid is selected as the raw material, so that the raw material cost of the biodegradable mulching film is reduced. Besides, the aldehyde modifier reacts with lignin to form nanoscale hydroxymethylated superfine lignin, so that the dispersity and compatibility of the nanoscale hydroxymethylated superfine lignin in a degradable material are improved, the mechanical strength of the biodegradable mulching film is further improved, and the outdoor use time of the biodegradable mulching film can be prolonged.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a hydroxymethylated ultrafine lignin modified degradable mulch film and a preparation method thereof. Background Art

[0002] The mulch film, namely the ground covering film, is widely used in the planting of various crops, and can keep warm, preserve soil moisture, maintain the soil structure and increase the crop yield. In recent years, the mulch film has been popularized throughout the country and is used for more than 40 kinds of crops such as cotton, fruits and vegetables, etc., increasing the crop yield by 30% - 50% generally and increasing the value by 40% - 60%. However, the existing mulch film is mainly made of polyethylene (PE), which has a stable structure and is difficult to degrade. Long-term use will cause soil pollution and affect plant growth.

[0003] PBAT (copolymer of butylene adipate and butylene terephthalate) is a biodegradable material with good ductility and biodegradability, and is one of the popular materials in the current research and market application of biodegradable plastics. In addition, lignin, as a natural polymer compound, has high crystallinity and acid and alkali resistance, and is rich in sources and low in cost, and is considered to have great application potential in the field of biodegradable materials. The pulp and paper industry produces a large amount of lignin by-products every year, but the utilization rate of lignin is low.

[0004] However, there are some technical problems with PBAT and lignin in the field of biodegradable mulch films. On the one hand, the raw material prices of degradable plastics such as PBAT are relatively high, which limits their application. On the other hand, the compatibility between lignin and PBAT is poor. For example, in CN113278262, PBAT, PLA and lignin are used as the main materials, but the prepared biodegradable mulch film has low tensile properties. In addition, in CN114350057A, polyolefin is used as the main material, and starch and hydroxymethylated lignin are used as additives, but the polarity of the modified lignin is enhanced and its compatibility with polyolefin resin is poor, resulting in poor tensile properties of the prepared mulch film. Summary of the Invention

[0005] In order to overcome the problems in the prior art such as poor compatibility between lignin and PBAT and low tensile properties of the prepared biodegradable mulch film, the present invention provides a hydroxymethylated ultrafine lignin modified degradable mulch film and a preparation method thereof.

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

[0007] On the one hand, the present invention provides a hydroxymethylated ultrafine lignin modified degradable mulch film, which comprises the following components in parts by weight:

[0008] 60 - 89 parts of PBAT, 1 - 10 parts of PLA, 10 - 30 parts of hydroxymethylated ultrafine lignin, 0.1 - 5 parts of plasticizer, 0.1 - 3 parts of antioxidant, 0.1 - 3 parts of light stabilizer, 0.1 - 5 parts of lubricant, and 0.1 - 5 parts of antiblocking agent;

[0009] The hydroxymethylated ultrafine lignin is prepared by the following method: After filtering the papermaking black liquor, it is added to a reaction kettle together with formaldehyde, and reacted fully at 70 - 90 °C and 300 - 600 rpm for 2 - 5 h. After the reaction is complete, it is cooled to room temperature, and the hydroxymethylated ultrafine lignin is obtained through precipitation, filtration, drying, and ultrasonic treatment with a particle size of 20 - 300 nm.

[0010] As a further scheme of the present invention: The mass ratio of lignin to formaldehyde in the papermaking black liquor is (0.1 - 0.9):1;

[0011] And / or, in the papermaking black liquor, the content of lignin is 8 - 14%;

[0012] And / or, the precipitation step is: Pour the reaction solution into hot water at 60 - 100 °C, and while stirring, add an HCl solution with a concentration of 0.2 - 2 mol / L to fully precipitate the hydroxymethylated ultrafine lignin, and let it stand for 20 - 60 min.

[0013] In the present invention, the papermaking black liquor is the remaining black liquor after the paper mill extracts cellulose and hemicellulose.

[0014] As a further scheme of the present invention: The melt index of the PBAT < 5 g / 10 min, and the terminal carboxyl group < 20 Mol / t;

[0015] And / or, the melt index of the PLA < 5 g / 10 min.

[0016] As a further scheme of the present invention: The plasticizer is at least one of tributyl acetylcitrate, epoxidized soybean oil, and glycerol; preferably tributyl acetylcitrate and / or epoxidized soybean oil;

[0017] And / or, the light stabilizer is at least one of UV - 531, UV - 770, UV - 944, and UV - 783; preferably UV - 531 and / or UV - 944.

[0018] As a further scheme of the present invention: The antioxidant is at least one of antioxidant 168, 1010, 264, and 1076; preferably a compound of antioxidant 168 and 1010 with a mass ratio of 1:1;

[0019] And / or, the lubricant is at least one of stearic acid, butyl stearate, EBS, and ethylene bisstearamide; preferably stearic acid and / or EBS;

[0020] And / or, the antiblocking agent is at least one of silica, oleic acid amide and erucic acid amide; preferably oleic acid amide and / or erucic acid amide.

[0021] As a further aspect of the present invention: the weight parts of the PBAT are preferably 70-89 parts, such as 75 or 80 parts;

[0022] And / or, the weight parts of the PLA are preferably 3-10 parts, such as 5 parts;

[0023] And / or, the weight parts of the hydroxymethylated ultrafine lignin are preferably 5-20 parts, such as 15 parts or 20 parts;

[0024] And / or, the weight parts of the plasticizer are preferably 0.2-3 parts, such as 1.5 or 2 parts;

[0025] And / or, the weight parts of the antioxidant are preferably 0.2-3 parts, such as 0.5 part;

[0026] And / or, the weight parts of the light stabilizer are preferably 0.2-3 parts, such as 0.5 part;

[0027] And / or, the weight parts of the lubricant are preferably 0.2-3 parts, such as 1 part;

[0028] And / or, the weight parts of the antiblocking agent are preferably 0.2-3 parts, such as 1 part.

[0029] On the other hand, the present invention provides a preparation method of a hydroxymethylated ultrafine lignin modified degradable mulch film, which specifically includes the following steps:

[0030] (1) Add PBAT, PLA, hydroxymethylated ultrafine lignin, plasticizer, light stabilizer, antioxidant, lubricant and antiblocking agent into a high-speed mixer for mixing, stir at 70-200 °C for 20-120 min, cool after mixing evenly, and cool down to room temperature to obtain material A;

[0031] (2) Add material A into a parallel twin-screw extruder, and extrude under the action of 140-220 °C and shear force to obtain a biodegradable masterbatch B;

[0032] (3) Add material B into a single-screw blown film machine, and blow film at 110-200 °C to obtain the hydroxymethylated ultrafine lignin modified degradable mulch film.

[0033] As a further aspect of the present invention: in step (1), the mixing temperature is 80 °C;

[0034] And / or, in step (1), the mixing time is 30 min;

[0035] And / or, in step (1), the rotation speed of the mixing is 300-600 rpm, preferably 400 rpm.

[0036] As a further solution of the present invention: in step (2), the extrusion temperature is 170 °C.

[0037] As a further solution of the present invention: in step (3), the blown film temperature is 160 °C.

[0038] The beneficial effects of the present invention are as follows:

[0039] The present invention selects paper-making black liquor as the raw material, reducing the raw material cost of the biodegradable mulch film. In addition, by reacting the aldehyde modifier with lignin, the present invention forms nano-scale hydroxymethylated ultrafine lignin, increasing its dispersibility and compatibility in the degradable material, thereby improving the mechanical strength of the biodegradable mulch film and further extending the outdoor use time of the biodegradable mulch film. Specific embodiments

[0040] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications. In addition, the reagents and raw materials used in the present invention are all commercially available. In the following examples and comparative examples, the lignin content in the paper-making black liquor is 12.5%; the melt index of PBAT is 3.8 g / 10 min, and the terminal carboxyl group is 18 Mol / t; the melt index of PLA is 4 g / 10 min.

[0041] Example 1

[0042] (1) Preparation method of hydroxymethylated ultrafine lignin:

[0043] After filtering the paper-making black liquor, it is added to the reaction kettle together with formaldehyde, where the lignin in the paper-making black liquor: formaldehyde = 0.4:1, and the reaction is carried out at 90 °C for 2 h, with a rotation speed of 500 rpm. After the reaction is complete, it is cooled to room temperature, and the reaction solution is poured into 60 °C hot water. While stirring, 1 mol / L HCl solution is added and stirred until hydroxymethylated ultrafine lignin precipitates. It is left standing for 20 min, filtered, dried and ultrasonically treated to obtain 20-300 nm hydroxymethylated ultrafine lignin.

[0044] (2) Preparation method of hydroxymethylated ultrafine lignin-modified degradable mulch film:

[0045] Step 1: Add PBAT, PLA, hydroxymethylated ultrafine lignin, plasticizer, light stabilizer, antioxidant, lubricant and opening agent into a high-speed mixer, and stir for 30 min under the condition of 100 °C; Place the mixed material in a cold mixing pot for cooling treatment until it reaches room temperature to obtain material A;

[0046] Step 2: Add the prepared material A into a parallel twin-screw extruder, and prepare biodegradable masterbatch B under the action of temperature and shear force, where the extruder temperature is 170 °C;

[0047] Step 3: Add material B into a single-screw blown film machine, and blow film to form biodegradable mulch film at a temperature of 110 °C. The types and dosages of components in the raw material composition of the biodegradable mulch film are shown in Table 1.

[0048] Table 1

[0049] Component Specific Component Dosage (parts by weight) PBAT PBAT 85 PLA PLA 5 Hydroxymethylated ultrafine lignin Hydroxymethylated ultrafine lignin 10 Plasticizer Tributyl acetylcitrate 1.5 Light stabilizer UV-531 0.5 Antioxidant 168 0.5 Lubricant Stearic acid 1.0 Anti-blocking agent Oleamide 1.0

[0050] Example 2

[0051] (1) Preparation method of hydroxymethylated ultrafine lignin:

[0052] Filter the papermaking black liquor and add it into a reaction kettle together with formaldehyde, where the lignin: formaldehyde in the papermaking black liquor is 0.1:1, react at 70 °C for 5 h, where the rotation speed is 300 rpm. After the reaction is complete, cool to room temperature, pour the reaction solution into 80 °C hot water, add 0.2 mol / L HCl solution while stirring and stir until hydroxymethylated ultrafine lignin precipitates, stand for 60 min, filter, dry and ultrasonically treat to obtain 20 - 300 nm hydroxymethylated ultrafine lignin.

[0053] (2) Preparation method of hydroxymethylated ultrafine lignin modified biodegradable mulch film:

[0054] Step 1: Add PBAT, PLA, hydroxymethylated ultrafine lignin, plasticizer, light stabilizer, antioxidant, lubricant and opening agent into a high-speed mixer, and stir for 20 min under the condition of 200 °C; Place the mixed material in a cold mixing pot for cooling treatment until it reaches room temperature to obtain material A;

[0055] Step 2: Add the prepared material A into a parallel twin-screw extruder, and prepare biodegradable masterbatch B under the action of temperature and shear force, where the extruder temperature is 140 °C;

[0056] Step 3: Add material B into a single-screw blown film machine, and blow film to form biodegradable mulch film at a temperature of 200 °C. The types and dosages of components in the raw material composition of the biodegradable mulch film are shown in Table 2.

[0057] Table 2

[0058] Component Specific Component Dosage (parts by weight) PBAT PBAT 75 PLA PLA 5 Hydroxymethylated ultrafine lignin Hydroxymethylated ultrafine lignin 20 Plasticizer Epoxidized soybean oil 1.5 Light stabilizer UV-783 0.5 Antioxidant 1010 0.5 Lubricant Stearic acid 1.0 Anti-blocking agent Erucamide 1.0

[0059] Example 3

[0060] (1) Preparation method of hydroxymethylated ultrafine lignin:

[0061] Filter the papermaking black liquor and add it to the reaction kettle together with formaldehyde, where the lignin: formaldehyde in the papermaking black liquor is 0.9:1. React at 80 °C for 3 h, with a rotation speed of 600 rpm. After the reaction is complete, cool to room temperature. Pour the reaction solution into water at 100 °C, and while stirring, add 2 mol / L HCl solution and stir until hydroxymethylated ultrafine lignin precipitates. Let it stand for 40 min, filter by suction, dry, and perform ultrasonic treatment to obtain 20 - 300 nm hydroxymethylated ultrafine lignin.

[0062] (2) Preparation method of hydroxymethylated ultrafine lignin modified degradable mulch film:

[0063] Step 1: Add PBAT, PLA, hydroxymethylated ultrafine lignin, plasticizer, light stabilizer, antioxidant, lubricant, and antiblocking agent to a high-speed mixer and stir at 80 °C for 120 min; Place the mixed material in a cold mixing pot for cooling treatment until it reaches room temperature to obtain material A;

[0064] Step 2: Add the prepared material A to a parallel twin-screw extruder and prepare biodegradable masterbatch B under the action of temperature and shear force, where the extruder temperature is 220 °C;

[0065] Step 3: Add material B to a single-screw blown film machine and blow film to form a biodegradable mulch film at 160 °C. The types and dosages of the components in the raw material composition of the biodegradable mulch film are shown in Table 3.

[0066] Table 3

[0067] Component Specific Component Dosage (parts by weight) PBAT PBAT 60 PLA PLA 10 Hydroxymethylated ultrafine lignin Hydroxymethylated ultrafine lignin 30 Plasticizer Tributyl acetylcitrate 2.0 Light stabilizer UV-531 0.5 Antioxidant 168:1010＝1:1 0.5 Lubricant Stearic acid 1.0 Anti-blocking agent Oleamide 1.0

[0068] Comparative Example 1

[0069] Step 1: Mix PBAT, PLA, lignin, silver / black masterbatch, plasticizer, light stabilizer, heat stabilizer, and antioxidant evenly to obtain a preliminary mixture;

[0070] Step 2: Add the preliminary mixture to the hopper of a twin-screw extruder and extrude and pelletize to obtain masterbatch;

[0071] Step 3: Blow film the masterbatch to form a silver-black two-color biodegradable agricultural film. The types and dosages of the components in the raw material composition of the biodegradable mulch film are shown in Table 4.

[0072] Table 4

[0073] Component Specific Component Dosage PBAT PBAT 80 PLA PLA 10 Silver / black masterbatch PBAT silver / black masterbatch 5 Lignin Lignin 5 Plasticizer Epoxidized soybean oil 5 Light stabilizer UV-531 1 Heat stabilizer Calcium stearate 1 Antioxidant 1010 1

[0074] Comparative Example 2

[0075] The difference from Example 1 is only that (1) in the preparation method of hydroxymethylated ultrafine lignin, the mass ratio of lignin in papermaking black liquor to formaldehyde is 0.05:1, and hydroxymethylated lignin with a particle size of 200 - 500 mesh is prepared.

[0076] Comparative Example 3

[0077] The difference from Example 1 is only that (1) in the preparation method of hydroxymethylated ultrafine lignin, the reaction temperature is 100 °C, and hydroxymethylated lignin with a particle size of 800 - 1000 mesh is prepared.

[0078] Comparative Example 4

[0079] The difference from Example 1 is only that (1) in the preparation method of hydroxymethylated ultrafine lignin, the reaction time is 6 h, and hydroxymethylated lignin with a particle size of 900 - 2000 mesh is prepared.

[0080] Comparative Example 5

[0081] The difference from Example 1 is only that (1) in the preparation method of hydroxymethylated ultrafine lignin, the ultrasonic treatment operation is not carried out, and hydroxymethylated lignin with a particle size of 2000 - 3000 mesh is prepared.

[0082] Effect Example

[0083] Using a universal electronic tensile testing machine (Model KY8000C), in accordance with standards GB / T 1040.1 - 2018 and GB / T 1040.3 - 2006, the tensile load and nominal strain at break of the mulch films prepared in Examples 1 - 3 and Comparative Examples 1 - 5 were detected and analyzed.

[0084]

[0085]

[0086] Through the detection data of the above - mentioned examples and comparative examples, it can be clearly understood that in this application, by reacting formaldehyde with lignin to form nano - scale hydroxymethylated ultrafine lignin, its dispersibility and compatibility in the degradable material are increased, thereby improving the mechanical strength of the biodegradable mulch film, and further being able to extend the outdoor use time of the biodegradable mulch film.

[0087] Finally, it should also be noted that in the present invention, the terms "comprising", "including" or any other variants thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0088] Although the present disclosure has been disclosed above through the description of specific embodiments of the present disclosure, it should be understood that those skilled in the art can design various modifications, improvements or equivalents to the present disclosure within the spirit and scope of the appended claims. These modifications, improvements or equivalents should also be considered to be included within the scope claimed by the present disclosure.

Claims

1. A hydroxymethylated ultrafine lignin-modified degradable mulch film, characterized in that, It comprises components in the following parts by weight: 60 - 89 parts of PBAT, 1 - 10 parts of PLA, 10 - 30 parts of hydroxymethylated ultrafine lignin, 0.1 - 5 parts of plasticizer, 0.1 - 3 parts of light stabilizer, 0.1 - 3 parts of antioxidant, 0.1 - 5 parts of lubricant, and 0.1 - 5 parts of antiblocking agent; The hydroxymethylated ultrafine lignin is prepared by the following method: After filtering the papermaking black liquor, it is added into a reaction kettle together with formaldehyde, and reacted fully at 70 - 90 °C and 300 - 600 rpm for 2 - 5 h. After the reaction is complete, it is cooled to room temperature, and the hydroxymethylated ultrafine lignin is obtained through precipitation, filtration, drying, and ultrasonic treatment with a particle size of 20 - 300 nm.

2. The hydroxymethylated ultrafine lignin-modified degradable ground film according to claim 1, characterized in that, The mass ratio of lignin to formaldehyde in the papermaking black liquor is (0.1 - 0.9):1; and / or, in the papermaking black liquor, the content of lignin is 8 - 14%; and / or, the precipitation step is: Pour the reaction solution into hot water at 60 - 100 °C, add HCl solution with a concentration of 0.2 - 2 mol / L while stirring to fully precipitate the hydroxymethylated ultrafine lignin, and let it stand for 20 - 60 min.

3. The hydroxymethylated ultrafine lignin-modified degradable ground film according to claim 1, wherein The melt index of the PBAT < 5 g / 10 min, and the terminal carboxyl group < 20 Mol / t; and / or, the melt index of the PLA < 5 g / 10 min.

4. The hydroxymethylated ultrafine lignin-modified degradable ground film according to claim 1, wherein The plasticizer is at least one of tributyl acetylcitrate, epoxidized soybean oil, and glycerol; preferably tributyl acetylcitrate and / or epoxidized soybean oil; and / or, the light stabilizer is at least one of UV - 531, UV - 770, UV - 944, and UV - 783; preferably UV - 531 and / or UV - 944.

5. The hydroxymethylated ultrafine lignin-modified degradable ground film according to claim 1, wherein, The antioxidant is at least one of antioxidant 168, 1010, 264, and 1076; preferably a compound of antioxidant 168 and 1010 with a mass ratio of 1:1; and / or, the lubricant is at least one of stearic acid, butyl stearate, EBS, and ethylene bisstearamide; preferably stearic acid and / or EBS; and / or, the antiblocking agent is at least one of silica, oleic acid amide, and erucic acid amide; preferably oleic acid amide and / or erucic acid amide.

6. The hydroxymethylated ultrafine lignin-modified degradable ground film according to claim 1, wherein The parts by weight of the PBAT are preferably 70 - 89 parts, such as 75 or 80 parts; and / or, the parts by weight of the PLA are preferably 3 - 10 parts, such as 5 parts; and / or, the parts by weight of the hydroxymethylated ultrafine lignin are preferably 5 - 20 parts, such as 15 parts or 20 parts; and / or, the parts by weight of the plasticizer are preferably 0.2 - 3 parts, such as 1.5 or 2 parts; and / or, the parts by weight of the antioxidant are preferably 0.2 - 3 parts, such as 0.5 parts; and / or, the parts by weight of the light stabilizer are preferably 0.2 - 3 parts, such as 0.5 parts; and / or, the parts by weight of the lubricant are preferably 0.2 - 3 parts, such as 1 part; and / or, the parts by weight of the antiblocking agent are preferably 0.2 - 3 parts, such as 1 part.

7. The preparation method of the hydroxymethylated ultrafine lignin-modified degradable mulch film according to claims 1 to 6, characterized in that, Specifically, it includes the following steps: (1) Add PBAT, PLA, hydroxymethylated ultrafine lignin, plasticizer, light stabilizer, antioxidant, lubricant and anti-blocking agent into a high-speed mixer for mixing, stir at 70 - 200 °C for 20 - 120 min, cool after mixing evenly, and reduce the temperature to room temperature to obtain Material A; (2) Add Material A into a parallel twin-screw extruder, extrude under the action of 140 - 220 °C and shear force to obtain biodegradable masterbatch B; (3) Add Material B into a single-screw blown film machine, blow film at 110 - 200 °C to obtain the hydroxymethylated ultrafine lignin modified degradable mulch film.

8. The preparation method of the hydroxymethylated ultrafine lignin-modified degradable mulch film according to claim 7, characterized in that, In step (1), the mixing temperature is 80 °C; And / or, in step (1), the mixing time is 30 min; And / or, in step (1), the mixing rotation speed is 300 - 600 rpm, preferably 400 rpm.

9. The preparation method of the hydroxymethylated ultrafine lignin-modified degradable ground film according to claim 7, characterized in that, In step (2), the extrusion temperature is 170 °C.

10. The preparation method of the hydroxymethylated ultrafine lignin-modified degradable mulch film according to claim 7, characterized in that, In step (3), the blown film temperature is 160 °C.

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