Preparation method of lignin bio-based degradable plastic

Abstract

The invention relates to the technical field of degradable plastics, in particular to a preparation method of lignin bio-based degradable plastics. The method comprises the following steps: taking corn cob residues as a raw material, adopting alkali dissolution and filtration methods to obtain an alkali-soluble lignin solution, then adding 4-aminobenzoic acid and an epoxy cross-linking agent into the alkali-soluble lignin solution to carry out a cross-linking reaction, after the cross-linking reaction is finished, filtering, drying and crushing to obtain a cross-linking product, and blending the cross-linking product with polylactic acid to obtain the polylactic acid composite material. And granulating and forming to obtain the lignin bio-based degradable plastic. The lignin content in the lignin bio-based degradable plastic obtained by the method is high, and resource utilization of lignin is facilitated; meanwhile, the obtained plastic has good use performance and degradation performance, is beneficial to maintenance of soil fertility, is more beneficial to resource circulation and environmental protection, and has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of degradable plastics, and in particular to a method for preparing lignin bio-based degradable plastics. Background Art

[0002] With the further deployment of strengthening plastic pollution control in recent years, it is required to orderly ban and restrict the production, sale and use of some plastic products, actively promote recyclable, recyclable and degradable alternative products, increase the supply of green products, standardize the recycling of plastic waste, establish and improve management systems for all links, and effectively control plastic pollution in a strong, orderly and effective manner. Plastic pollution has been effectively controlled. Under the current "plastic restriction" background, the further development of degradable plastics has become inevitable.

[0003] Degradable plastics have basically the same performance as traditional plastics and are widely used. In natural environments (specific microorganisms, humidity, and temperature), they can be completely degraded into environmentally friendly substances in a relatively short period of time. In the current context of "plastic restriction", degradable plastics have become the "darling" of the plastics market in the past two years due to these advantages, and the entire degradable plastics industry has entered a blowout development stage from its infancy. Various degradable plastics, such as PLA, PBS, PBAT, and various composite materials are emerging in an endless stream, but among these materials, PLA and PBS polyesters are close to the performance of existing general-purpose plastics, have high market recognition, and are most in line with the current "plastic restriction" policy needs.

[0004] However, the existing polylactic acid degradable plastic (PLA) has great defects during use. Under natural conditions, it often takes more than half a year to be completely degraded. In practice, the degradation time can be as long as 2 to 3 years. This brings great limitations to the use of polylactic acid materials, restricts its wide application, and is also not conducive to environmental protection. Therefore, the present invention proposes a method for preparing a lignin bio-based degradable plastic, by compounding lignin with PLA, a lignin bio-based degradable plastic is obtained, which shows a good degradation effect when used. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a lignin bio-based degradable plastic, so as to solve the problem that the existing polylactic acid degradable plastic has a slow degradation rate and is not conducive to environmental protection.

[0006] To achieve the above object, the present invention adopts the following technical scheme: a method for preparing lignin bio-based degradable plastic, comprising the following steps:

[0007] S1, using xylose residue as raw material, dissolving and filtering with alkaline solution to obtain an alkaline solution of lignin;

[0008] S2, adding 4-aminobenzoic acid and an epoxy crosslinking agent to the alkaline solution in S1 to carry out a crosslinking reaction, filtering, drying, and crushing to obtain a crosslinked product;

[0009] S3, blending the cross-linked product obtained in S2 with polylactic acid, and then granulating and forming, to obtain lignin bio-based degradable plastic.

[0010] Furthermore, in S1, the xylose residue is the residue remaining after the xylose product is prepared using agricultural waste as raw material.

[0011] Furthermore, the agricultural waste includes corn cobs, bagasse and bamboo.

[0012] Furthermore, in the S1, the alkaline solution is a 5-10% sodium hydroxide solution, and the liquid-to-solid ratio of the volume of the alkaline solution to the absolute dry mass of the xylose residue is 5-10:1.

[0013] Furthermore, in the S2, the added amount of 4-aminobenzoic acid is 1 to 5% of the absolute dry mass of the xylose residue.

[0014] Furthermore, in the S2, the solid-liquid ratio of the absolute dry mass of the xylose residue to the volume of the added epoxy crosslinking agent is 1 to 3:1.

[0015] Furthermore, the epoxy cross-linking agent includes epichlorohydrin, ethylene oxide and propylene oxide.

[0016] Furthermore, in the S2, the temperature of the cross-linking reaction is 60-80° C., and the reaction time is 6-10 hours.

[0017] Furthermore, in the S2, the particle size of the cross-linked product after crushing is 50 to 200 meshes.

[0018] Furthermore, in the S3, the amount of the cross-linked product added is 20-30% of the amount of the polylactic acid added, and the particle size of the polylactic acid is 50-200 meshes.

[0019] Beneficial effects of the present invention:

[0020] 1. The method of the present invention can greatly increase the amount of lignin added to the plastic while ensuring the performance indicators of the obtained lignin bio-based degradable plastic, which is more conducive to the resource utilization of lignin;

[0021] 2. The lignin bio-based degradable plastic obtained by the method of the present invention has good performance, with a tensile strength of up to 52.18Mpa and an elongation at break of up to 58.3%, which can fully meet the use requirements; it also has good degradation performance, and can be degraded in only 2 to 3 months under natural light conditions; under natural conditions where the soil is completely covered, it can be degraded in only 6 to 8 months, and has broad application prospects;

[0022] 3. The lignin bio-based degradable plastic obtained by the method of the present invention degrades nitrogen during the natural degradation process, thereby helping to maintain soil fertility, making it more convenient for resource recycling and environmental protection. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0024] Example 1

[0025] A batch of corn cob xylose residue was taken from the factory and tested. The moisture content was 58.63%, the cellulose content in the dry material was 65.28%, the lignin content was 18.31%, the hemicellulose content was 8.14%, and the remainder was ash.

[0026] Take 100 g of the above-mentioned xylose residue and add it to a three-necked flask, the dry weight of the xylose residue is 41.37 g, and continue to add 200 mL of sodium hydroxide solution to the three-necked flask, the concentration of the sodium hydroxide solution is 2 mol / L; heat the water bath to 80°C, react at 300 rpm stirring intensity for 2 hours, filter out the residue after the reaction is completed, and obtain an alkaline solution of lignin.

[0027] The alkaline solution obtained above was transferred to a three-necked flask, heated to 70°C in a water bath, and then 1 g of 4-aminobenzoic acid was added thereto. After the addition was completed, stirring was carried out at 300 rpm for 10 min, and then 15 mL of epichlorohydrin was added to the three-necked flask, and the reaction was continued for 8 h. The mixture was filtered, washed, and dried to obtain a cross-linked product.

[0028] The obtained cross-linked product was crushed into 200 meshes and then used for later use.

[0029] Take 10 g of the crushed cross-linked product and mix it evenly with 40 g of polylactic acid, the particle size of the polylactic acid is 200 mesh, and then perform twin-screw extrusion granulation to obtain lignin bio-based degradable plastic.

[0030] Example 2

[0031] In this embodiment, ethylene oxide is used as the epoxy crosslinking agent, the obtained crosslinked product is crushed to 100 mesh, the particle size of polylactic acid is 100 mesh, and the rest is the same as in Embodiment 1, and finally a lignin bio-based degradable plastic is obtained.

[0032] Example 3

[0033] In this embodiment, propylene oxide is used as the epoxy crosslinking agent, the obtained crosslinked product is crushed into 50 mesh, the particle size of polylactic acid is 50 mesh, and the rest is the same as in Embodiment 1, and finally a lignin bio-based degradable plastic is obtained.

[0034] Comparative Example 1

[0035] In this comparative example, lignin and polylactic acid were directly mixed and granulated.

[0036] Take 10g of 100-mesh lignin and mix it with 200g of polylactic acid, where the particle size of the polylactic acid is 100 mesh. After mixing, twin-screw extrusion granulation is performed to obtain lignin-polylactic acid degradable plastic.

[0037] The properties of the plastics obtained in Examples 1-3 and Comparative Example 1 were tested, and the results are shown in the following table:

[0038] Table 1 Performance test table of the obtained degradable plastics

[0039]

[0040] It can be seen that with the increase of the amount of lignin used, the tensile strength of the obtained degradable plastic does not change much, indicating that under the condition of a higher amount of lignin added in the present invention, a product with excellent tensile strength performance can still be obtained. At the same time, the lignin bio-based degradable plastic obtained by the method of the present invention has a better elongation at break and is more convenient for application.

[0041] The plastics obtained in Examples 1-3 and Comparative Example 1 were subjected to degradation experiments, and the results are shown in the following table:

[0042] Table 2 Degradation performance test table of the obtained degradable plastics

[0043]

[0044] It can be seen that the lignin bio-based degradable plastic obtained in the present invention has good degradation performance. Under light conditions, the degradation rate is about twice that of Example 1. It has good biodegradability and is more conducive to environmental protection.

[0045] Under natural light conditions, the soil in Example 2 and Comparative Example 1 during the degradation process was tested; the total nitrogen content in the soil before degradation was 1.82 g / kg; on the 60th day of degradation, the total nitrogen content in the soil of Example 2 was 1.88 g / kg, and under the same conditions, the total nitrogen content in the soil of Comparative Example 1 was 1.79 g / kg; it can be seen that under the same conditions, the nitrogen element in the soil of Comparative Example 1 was lost to a certain extent, while the lignin bio-based degradable plastic obtained by the method of the present invention had a small increase in the nitrogen content, indicating that the lignin bio-based degradable plastic of the present invention plays a positive role in maintaining soil fertility.

[0046] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A method for preparing lignin bio-based degradable plastics, characterized in that: The following steps are involved: S1, using xylose residue as raw material, dissolving and filtering with alkaline solution to obtain an alkaline solution of lignin; S2, adding 4-aminobenzoic acid and an epoxy crosslinking agent to the alkaline solution in S1 to carry out a crosslinking reaction, filtering, drying, and crushing to obtain a crosslinked product; S3, blending the cross-linked product obtained in S2 with polylactic acid, and then granulating and forming, to obtain lignin bio-based degradable plastic.

2. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In S1, the xylose residue is the residue remaining after the xylose product is prepared using agricultural waste as raw materials.

3. The method for preparing a lignin bio-based degradable plastic according to claim 2, characterized in that: The agricultural waste includes corn cobs, bagasse and bamboo.

4. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In the S1, the alkaline solution is a 5-10% sodium hydroxide solution, and the liquid-to-solid ratio of the volume of the alkaline solution to the absolute dry mass of the xylose residue is 5-10:

1.

5. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In the S2, the added amount of 4-aminobenzoic acid is 1-5% of the absolute dry mass of the xylose residue.

6. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In the S2, the solid-liquid ratio of the absolute dry mass of the xylose residue to the volume of the added epoxy crosslinking agent is 1 to 3:

1.

7. The method for preparing a lignin bio-based degradable plastic according to claim 6, characterized in that: The epoxy crosslinking agent includes epichlorohydrin, ethylene oxide and propylene oxide.

8. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In the S2, the temperature of the cross-linking reaction is 60-80° C., and the reaction time is 6-10 hours.

9. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In the S2, the particle size of the cross-linked product after crushing is 50 to 200 meshes.

10. The method for preparing a lignin bio-based degradable plastic according to claim 1, characterized in that: In the above-mentioned S3, the amount of the cross-linked product added is 20-30% of the amount of the polylactic acid added, and the particle size of the polylactic acid is 50-200 meshes.

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