All-bamboo-based thermosetting plastics and their preparation methods and applications

Abstract

The present invention relates to the technical field of bamboo materials, and specifically relates to a fully bamboo-based thermosetting plastic, its preparation method and application. The fully bamboo-based thermosetting plastic comprises bamboo powder containing carbonyl and / or carboxyl groups, and the density of the fully bamboo-based thermosetting plastic is not less than 1.4 g / cm<supgt;3< / supgt>; in the bamboo powder containing carbonyl and / or carboxyl groups, the content of carbonyl and / or carboxyl groups is 1-5 mmol / g. In the fully bamboo-based thermosetting plastic of the present invention, carbonyl is modified on the basis of bamboo, and then obtained by hot pressing and curing, without other resins (such as gelling agents, reinforcing agents, etc.). The fully bamboo-based thermosetting plastic has excellent mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of bamboo materials, and particularly relates to a fully bamboo-based thermosetting plastic, a preparation method thereof, and an application thereof. Background Art

[0002] Petrochemical plastics have advantages such as good thermal stability, water resistance, stable mechanical strength, and easy production, and are widely used in the fields of construction, packaging, aviation, and electronics, and can be applied to medical instruments, 3D modeling, automobiles, household appliances, etc. However, most plastics have poor degradability and require hundreds of years to degrade, which brings serious environmental pollution problems to petrochemical plastics. Therefore, developing alternative materials with good environmental performance and biodegradability is considered an important way to solve the plastic pollution problem.

[0003] Bamboo grows fast, is renewable, and has high mechanical strength, and is a good substitute for materials such as wood, plastics, steel, and cement. Due to the small size and structure of bamboo, making corresponding plastic substitute products often requires compounding with high molecular polymers, such as bamboo-plastic composite materials, recombined bamboo, bamboo laminated lumber, etc. The polymer makes the small-size bamboo units into large-size products through gluing. However, the added high molecular polymers such as polypropylene, urea-formaldehyde resin, phenolic resin, etc. will bring new plastic pollution problems. At present, there are still problems such as poor water resistance and low mechanical strength in the production of bamboo-based biomass composite materials by adding active starch, lignin, etc.

[0004] The components of bamboo mainly consist of cellulose, hemicellulose, and lignin, and all three have a high activatable space. Some scholars have achieved plasticization modification of plant cellulose by etherification, esterification, cationic graft modification, or benzylation of plant fiber components. However, the reactivity of the groups of the plasticized fiber components is weak, and strong covalent bond binding cannot be formed after hot pressing, resulting in unsatisfactory water resistance and strength of the products. At the same time, some treatment systems have environmental problems such as the use of a large amount of organic toxic solvents and easy volatilization of activation agents. In addition, due to the special organizational structure of bamboo, such as high strength but poor permeability of bamboo fiber cells, thin cell walls of parenchyma cells and easy depolymerization, and a large amount of lipids and inorganic substances in bamboo green, there are currently few systematic solutions for the systematic and efficient and reasonable activation of bamboo components to prepare high-strength materials. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems in the prior art that a large amount of petroleum-based resins, toxic solvents, etc. are required, and to provide a fully bamboo-based thermosetting plastic, a preparation method thereof, and an application thereof. The fully bamboo-based thermosetting plastic has the advantages of high strength, water resistance, and degradability.

[0006] This application proposes a method for preparing a high-strength, water-resistant, and biodegradable all-bamboo-based thermosetting plastic without adding external substances. By using an aqueous activation system to specifically activate the bamboo cell structure units and combining with low-temperature hot pressing technology, efficient self-bonding of bamboo structure units is achieved. By degrading part of the lignin, the cellulose and hemicellulose in the bamboo cell wall are exposed. Then, an aqueous activation system is used to convert some of the hydroxyl groups in cellulose and hemicellulose into carbonyl groups (such as aldehyde groups or carboxyl groups). Through hot pressing, the density reaches 1.4 g / cm 3 or more, and then curing is carried out to obtain the final high-strength, water-resistant, and biodegradable all-bamboo-based thermosetting plastic.

[0007] To achieve the above object, in the first aspect of the present invention, an all-bamboo-based thermosetting plastic is provided. The all-bamboo-based thermosetting plastic includes bamboo powder containing carbonyl and / or carboxyl groups, and the density of the all-bamboo-based thermosetting plastic is not less than 1.4 g / cm 3 ;

[0008] In the bamboo powder containing carbonyl and / or carboxyl groups, the content of carbonyl and / or carboxyl groups is 1 - 5 mmol / g.

[0009] In the second aspect of the present invention, a method for preparing the all-bamboo-based thermosetting plastic of the present invention is provided. The method includes:

[0010] (1) Demineralizing the bamboo powder to obtain demineralized bamboo powder;

[0011] (2) Contacting the demineralized bamboo powder with a solution containing an oxidant to obtain bamboo powder containing carbonyl and / or carboxyl groups;

[0012] (3) Hot pressing the bamboo powder containing carbonyl and / or carboxyl groups until the density is not less than 1.4 g / cm 3 ;

[0013] (4) Curing the product obtained in step (3) to obtain the all-bamboo-based thermosetting plastic.

[0014] In the third aspect of the present invention, an application of the all-bamboo-based thermosetting plastic of the present invention as a rigid plastic with a glass transition temperature of 40 - 100 °C is provided.

[0015] Through the above technical solutions, the all-bamboo-based thermosetting plastic of the present invention has the following beneficial effects:

[0016] 1. The all-bamboo-based thermosetting plastic has excellent mechanical properties (for example, high strength, the tensile strength exceeds 30 MPa, and the flexural strength can reach up to 170 MPa at most).

[0017] 2. The all-bamboo-based thermosetting plastic has excellent water resistance. After 30 days of soaking test, the volume expansion rate is less than 1%.

[0018] 3. The all-bamboo-based thermosetting plastic can be repeatedly pressed 3 to 10 times and has good reusability.

[0019] 4. The all-bamboo-based thermosetting plastic can be biodegradable and will not cause pollution problems similar to those of petroleum-based plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a photo of untreated bamboo powder;

[0021] Figure 2 is a photo of bamboo powder containing carbonyl in Example 1;

[0022] Figure 3 is the all-bamboo-based thermosetting plastic of Example 1;

[0023] Figure 4 is a photo of the plate prepared in Comparative Example 1;

[0024] Figure 5 is a photo of the plate prepared in Comparative Example 2;

[0025] Figure 6 The all-bamboo-based thermosetting plastic product prepared by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The endpoints and any values disclosed in this article for a range are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0027] The first aspect of the present invention provides an all-bamboo-based thermosetting plastic, and the all-bamboo-based thermosetting plastic includes bamboo powder containing carbonyl and / or carboxyl, and the density of the all-bamboo-based thermosetting plastic is not less than 1.4 g / cm 3 ;

[0028] In the bamboo powder containing carbonyl and / or carboxyl, the content of carbonyl and / or carboxyl is 1 to 5 mmol / g.

[0029] In the present invention, in the all-bamboo-based thermosetting plastic, carbonyl groups are modified on the basis of bamboo, and then obtained through hot pressing and curing, without other resins (such as gelling agents, reinforcing agents, etc.). The all-bamboo-based thermosetting plastic has excellent mechanical properties (for example, relatively high strength, with a tensile strength exceeding 30 MPa and a flexural strength that can reach up to 170 MPa at most). The all-bamboo-based thermosetting plastic has excellent water resistance, and after 30 days of immersion test, the volume expansion rate is less than 1%. The all-bamboo-based thermosetting plastic can be repeatedly pressed 3 - 10 times and has good reusability. The all-bamboo-based thermosetting plastic can be biodegradable and will not cause pollution problems similar to those of petroleum-based plastics.

[0030] In the present invention, the carbonyl group is an aldehyde and / or a ketone.

[0031] The test standard for the carboxyl group content is shown in GB / T 10338 - 2008. For example: Take 0.1 g of freeze-dried bamboo powder and place it in a 250 mL conical flask, add 10 mL of 0.25 mol / L hydroxylamine hydrochloride (NH₂OH·HCl) solution, add 4 drops of thymol blue indicator, and then titrate with 0.1 mol / L NaOH solution. When the solution just turns blue and does not fade within 30 s, it is the titration end point (parallel titration 3 times). The calculation formula for the carboxyl group content is as follows:

[0032] C COOH =C NaOH (V sample -V control ) / (m*1000)*162*100%

[0033] In the formula:

[0034] C COOH ——The content of carboxyl group (-COOH), mmol / g;

[0035] C NaOH ——The concentration of the NaOH solution, 0.1 mol / L;

[0036] V sample ——The volume of the NaOH solution consumed by the DAWF powder, mL;

[0037] V control ——The volume of the NaOH solution consumed by the control group, mL;

[0038] m——The mass of the aldehyde-functionalized wood fiber, g;

[0039] 162——The molecular mass of the cellulose repeating unit, g / mol.

[0040] Carbonyl content: After additional oxidation of bamboo powder, the carbonyl groups in the bamboo powder are oxidized to carboxyl groups. For the bamboo powder before and after additional oxidation, the carboxyl content is calculated using the above-mentioned carboxyl content test method, and the carbonyl content is calculated based on the difference in carboxyl content of the bamboo powder before and after additional oxidation.

[0041] In the present invention, the step of additional oxidation of bamboo powder includes: mixing bamboo powder with a carboxyl group quantification with an oxidation reagent for oxidation. The oxidation reagent is a 2 wt% sodium chlorite aqueous solution with a pH of 4 - 5, and the oxidation time is 24 h.

[0042] In the bamboo powder containing carbonyl and / or carboxyl groups, the content of carbonyl and / or carboxyl groups is 1 - 3 mmol / g.

[0043] According to a preferred embodiment of the present invention, the density of the all - bamboo - based thermosetting plastic is 1.4 - 1.8 g / cm 3 .

[0044] According to a preferred embodiment of the present invention, the water absorption expansion rate of the all - bamboo - based thermosetting plastic is 0.1 - 5, preferably 0.5 - 2.5%.

[0045] According to a preferred embodiment of the present invention, the flexural strength of the all - bamboo - based thermosetting plastic is 30 - 180 Mpa.

[0046] According to a preferred embodiment of the present invention, the flexural modulus of the all - bamboo - based thermosetting plastic is 2 - 8 Gpa.

[0047] According to a preferred embodiment of the present invention, the tensile strength of the all - bamboo - based thermosetting plastic is 30 - 80 Mpa.

[0048] The second aspect of the present invention provides a method for preparing the all - bamboo - based thermosetting plastic described in the present invention, and the method includes:

[0049] (1) Demineralizing bamboo powder to obtain demineralized bamboo powder;

[0050] (2) Contacting the demineralized bamboo powder with a solution containing an oxidant to obtain bamboo powder containing carbonyl and / or carboxyl groups;

[0051] (3) Hot - pressing the bamboo powder containing carbonyl and / or carboxyl groups until the density is not lower than 1.4 g / cm 3 ;

[0052] (4) Curing the product obtained in step (3) to obtain an all - bamboo - based thermosetting plastic.

[0053] Through delignification treatment, the hydroxyl groups in the bamboo powder are exposed, enabling the hydroxyl groups to react with the oxidant, so that the bamboo powder containing carbonyl groups can be hot-pressed and cured to obtain a fully bamboo-based thermosetting plastic; according to a preferred embodiment of the present invention, in step (1), the lignin content in the delignified bamboo powder is 0-15 wt%.

[0054] In the present invention, there is no particular limitation on the particle size of the bamboo powder. According to a preferred embodiment of the present invention, the particle size of the bamboo powder is 10-400 mesh.

[0055] In the present invention, there is no particular limitation on the method for delignifying the bamboo powder. Any conventional delignification method in the art can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, in step (1), the method for delignifying the bamboo powder includes: mixing the bamboo powder with a delignifying solution for delignification.

[0056] In the present invention, the types of the delignifying solution that can be selected are relatively wide. According to a preferred embodiment of the present invention, the delignifying solution is selected from one of a 1%-5% sodium chlorite-acetic acid solution, a 1%-20% hydrogen peroxide solution, a 1%-5% sulfur dioxide solution, a solution containing 1%-10% sodium hydroxide and 2%-5% sodium sulfite, or a solution containing 1%-10% sodium hydroxide / 1%-8% hydrogen peroxide / 1%-8% sulfite. In the delignifying solution, the solute content is all by mass.

[0057] According to a preferred embodiment of the present invention, the delignification conditions include: the temperature is 60-80 °C, and the reaction time is 2-24 h.

[0058] In the present invention, there is no particular limitation on the dosage ratio of the bamboo powder to the delignifying solution, as long as the lignin content in the bamboo powder can be 0-15 wt%; according to a preferred embodiment of the present invention, the mass ratio of the bamboo powder to the delignifying solution is 1:5-40.

[0059] In the present invention, after the bamboo powder is mixed with the delignifying solution for delignification, it also includes washing and drying steps.

[0060] According to a preferred embodiment of the present invention, in the solution containing an oxidant, the oxidant is selected from one or more of periodate, 2,2,6,6-tetramethylpiperidine-n-oxide, dinitrogen tetroxide, hypochlorite, and oxygen base.

[0061] According to a preferred embodiment of the present invention, in the solution containing an oxidant, the solvent is selected from water and C1-C5 alcohols, preferably one or more of water, ethanol, and isopropanol.

[0062] According to a preferred embodiment of the present invention, in the solution containing an oxidant, the mass content of the oxidant is 1-10 wt%.

[0063] In the present invention, there is no particular limitation on the dosage ratio of delignified bamboo powder to the solution containing an oxidant, as long as it can oxidize the delignified bamboo powder to make the carbonyl and / or carboxyl content 1 - 5 mmol / g; according to a preferred embodiment of the present invention, the mass ratio of bamboo powder to the delignified solution is 1:5 - 30.

[0064] In the present invention, appropriate contact conditions are selected according to the type of oxidant; according to a preferred embodiment of the present invention, the contact conditions include: the temperature is 20 - 80 °C, and the reaction time is 1 - 48 h.

[0065] According to a preferred embodiment of the present invention, when the oxidant is an oxidant that is easily decomposed by light, contact and oxidation are carried out under light - free conditions.

[0066] In the present invention, the hot - pressing temperature required for preparing the all - bamboo - based thermosetting plastic is relatively low, not exceeding 120 °C; the hot - pressing time is relatively short, less than 10 min; according to a preferred embodiment of the present invention, in step (3), the hot - pressing conditions include: the temperature is 60 - 120 °C, and the pressure is 20 - 50 MPa; preferably, the hot - pressing time is 2 - 10 min.

[0067] According to a preferred embodiment of the present invention, in step (3), hot - press until the density is 1.4 - 1.8 g / cm 3 。

[0068] According to a preferred embodiment of the present invention, in step (3), before hot - pressing, it further includes adjusting the moisture content of the bamboo powder containing carbonyl and / or carboxyl to 10% - 150%.

[0069] According to a preferred embodiment of the present invention, in step (4), the curing conditions include: the temperature is 60 - 120 °C, and the curing time is 1 - 12 h.

[0070] The third aspect of the present invention provides an application of the all - bamboo - based thermosetting plastic described in the present invention as a rigid plastic with a glass transition temperature of 40 - 100 °C.

[0071] The application of the all - bamboo - based thermosetting plastic described in the present invention in place of rigid plastics (such as polypropylene plastics and polyethylene plastics) can obtain corresponding products by selecting appropriate molds and performing the above - mentioned hot - pressing and curing on the bamboo powder containing carbonyl and / or carboxyl.

[0072] The all - bamboo - based thermosetting plastic described in the present invention, as a rigid plastic with a glass transition temperature of 40 - 100 °C, can be used, for example, to prepare tableware, packaging materials, helmets, mobile phone cases, and computer cases, etc.

[0073] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0074] To illustrate the present invention more clearly, the following examples are listed, but the applicable situations of the present invention are not limited to the scope of the examples.

[0075] In the following examples, the flexural strength and flexural modulus were measured according to GB / T9341 - 2008, the tensile strength was measured according to GB / T1040.2 - 2006, and the water absorption expansion rate of the samples soaked in water for 10 days and the mass loss rate of samples buried in the ground for 120 days were measured.

[0076] The standard for lignin content determination is: GB / T 2677.8 - 1994.

[0077] Example 1

[0078] (1) Select bamboo powder of 40 - 60 mesh as shown in Figure 1 . According to the solid - liquid mass ratio of 1:20, cook it in a 5% sodium chlorite and acetic acid solution at 70 °C for 6 h, then wash it with clear water and dry it at 103 °C to obtain lignin - removed bamboo powder (lignin content is 0);

[0079] (2) Add the bamboo powder obtained in step (1) to a 5% sodium periodate solution according to the solid - liquid mass ratio of 1:16, and add isopropanol accounting for 1% of the total solution weight. React in a light - free environment for 5 h. The reacted sample is dried at 35 °C until the moisture content is 25% to obtain aldehyde - group - modified bamboo powder (as shown in Figure 2 ). In the bamboo powder, the aldehyde - group content is 4.1 mmol / g;

[0080] (3) Add the aldehyde - group - modified bamboo powder into a mold, and hot - press it at 90 °C and 20 MPa for 5 min to obtain a preliminary plasticized and cured material, and the material density is 1.65 g / cm 3 ;

[0081] (4) Put the preliminary plasticized and cured material into an oven and cure it at 100 °C for 2 h to obtain the final all - bamboo - based thermosetting plastic (as shown in Figure 3 ).

[0082] Test the flexural strength, tensile strength, flexural modulus, water absorption expansion rate and 120 - day buried mass loss rate of the all - bamboo - based thermosetting plastic, and the results are shown in Table 1.

[0083] Example 2

[0084] (1) Select bamboo powder with a mesh size of 40 - 60, and cook it in a solution of 2% sodium chlorite and acetic acid for 2 h according to a solid - liquid mass ratio of 1:20. Then wash it with clear water and dry it at 103 °C to obtain bamboo powder with partial lignin removal (lignin content is 8 wt%);

[0085] (2) Add the bamboo powder obtained in step (1) to a 5% sodium periodate solution according to a solid - liquid mass ratio of 1:16, and add isopropanol accounting for 1% of the total solution weight. React for 5 h in a light - free environment. Dry the reacted sample at 35 °C until the moisture content is 25% to obtain aldehyde - group - modified bamboo powder. The aldehyde - group content in the bamboo powder is 3.1 mmol / g;

[0086] (3) Add the aldehyde - group - modified bamboo powder into a mold, and hot - press it at 95 °C and 20 MPa for 5 min to obtain a preliminarily plasticized and cured material with a material density of 1.70 g / cm 3 ;

[0087] (4) Put the preliminarily plasticized and cured material into an oven and cure it at 100 °C for 2 h to obtain the final all - bamboo - based thermosetting plastic.

[0088] Test the flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 - day burial of the all - bamboo - based thermosetting plastic. The results are shown in Table 1.

[0089] Example 3

[0090] (1) Select bamboo powder with a mesh size of 40 - 60, and cook it in a solution of 5% sodium chlorite and acetic acid for 2 h according to a solid - liquid mass ratio of 1:20. Then wash it with clear water and dry it at 103 °C to obtain bamboo powder with partial lignin removal (lignin content is 4 wt%);

[0091] (2) Add the bamboo powder obtained in step (1) to a mixed solution of 1% 2,2,6,6 - tetramethylpiperidine - N - oxide and 1% sodium chlorite according to a solid - liquid mass ratio of 1:16. React at 60 °C for 5 h. Dry the reacted sample at 35 °C until the moisture content is 25% to obtain carboxyl - group - modified bamboo powder. The carboxyl - group content in the bamboo powder is 2.3 mmol / g;

[0092] (3) Add the carboxyl - group - modified bamboo powder into a mold, and hot - press it at 100 °C and 20 MPa for 5 min to obtain a preliminarily plasticized and cured material with a material density of 1.70 g / cm 3 ;

[0093] (4) Put the preliminarily plasticized and cured material into an oven and cure it at 100 °C for 2 h to obtain the final all - bamboo - based thermosetting plastic.

[0094] The flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 days of underground burial of the all-bamboo-based thermosetting plastic were tested, and the results are shown in Table 1.

[0095] Example 4

[0096] (1) Select bamboo powder with a mesh size of 40 - 60 as shown in Figure 1 . Cook it in a 5% sodium chlorite and acetic acid solution for 6 h according to a solid-liquid mass ratio of 1:20, then wash it with clean water and dry it at 103 °C to obtain lignin-removed bamboo powder (lignin content is 0);

[0097] (2) Add the bamboo powder obtained in step (1) to a 2% dinitrogen tetroxide solution according to a solid-liquid mass ratio of 1:16 and react for 5 h. Adjust the moisture content of the reacted sample to 80% to obtain carboxylated bamboo powder, and the carboxyl content in the bamboo powder is 3.1 mmol / g;

[0098] (3) Add the aldehyde-functionalized bamboo powder to a mold and hot-press it at 90 °C and a pressure of 20 MPa for 5 min to obtain a preliminary plasticized and cured material, and the density of the material is 1.4 g / cm 3 ;

[0099] (4) Place the preliminary plasticized and cured material in an oven and cure it at 80 °C for 5 h to obtain the final all-bamboo-based thermosetting plastic.

[0100] The flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 days of underground burial of the all-bamboo-based thermosetting plastic were tested, and the results are shown in Table 1.

[0101] Comparative Example 1

[0102] (1) Select bamboo powder with a mesh size of 40 - 60 and hot-press it at 100 °C and a pressure of 20 MPa for 5 min to obtain densified bamboo powder;

[0103] Place the densified bamboo powder in an oven and dry it at 100 °C for 2 h to obtain the dried densified bamboo powder as shown in Figure 4 .

[0104] The flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 days of underground burial of the material were tested, and the results are shown in Table 1.

[0105] Comparative Example 2

[0106] According to the method of Example 1, the difference is that the lignin-removed bamboo powder was not carboxylated. Specifically:

[0107] (1) Select bamboo powder with a mesh size of 40 - 60, and cook it in a 5% sodium chlorite and acetic acid solution for 6 hours according to a solid - liquid mass ratio of 1:20. Then wash it with clean water and dry it at 103°C to obtain lignin - removed bamboo powder (lignin content is 0);

[0108] (2) Add the bamboo powder obtained in step (1) into a mold and hot - press it at 90°C and a pressure of 20 MPa for 5 minutes;

[0109] (3) Finally, dry it in an oven at 100°C for 2 hours, and the product is as Figure 5 shown.

[0110] Test the flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 - day burial of the material. The results are shown in Table 1.

[0111] Comparative Example 3

[0112] According to the method of Example 1, the difference is that the bamboo powder is not subjected to lignin - removal treatment. Specifically:

[0113] (1) Select bamboo powder with a mesh size of 40 - 60 and put it into a 5% sodium periodate solution according to a solid - liquid mass ratio of 1:16, and add 1% isopropanol based on the total weight of the solution. React in a light - free environment for 5 hours. The reacted sample is dried at 35°C until the moisture content is 25%. In the bamboo powder, the aldehyde group content is 0.2 mmol / g;

[0114] (2) Add the reacted bamboo powder into a mold and hot - press it at 90°C and a pressure of 20 MPa for 5 minutes;

[0115] (3) Finally, put it into an oven and dry it at 100°C for 2 hours.

[0116] Test the flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 - day burial of the material. The results are shown in Table 1.

[0117] Comparative Example 4

[0118] Polypropylene plastic

[0119] The plastic sheet is 50 cm long, 50 cm wide, and 3 mm thick, with a product number of AHD PP - C + H. Saw it into the required test sample size, and test the flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 - day burial of the material. The results are shown in Table 1.

[0120] Comparative Example 5

[0121] Polyethylene plastic

[0122] The plastic sheet is 50 cm in length, 50 cm in width, and 3 mm in thickness, with the product number AHD HDPE-50. It is sawn into the required test sample size, and the flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 days of underground burial of the test material are tested. The results are shown in Table 1.

[0123] Comparative Example 6

[0124] According to the method of Example 1, the difference is that in step (3), hot pressing makes the material density 1.3 g / cm 3 ; specifically:

[0125] (1) Select bamboo powder with a mesh size of 40-60, cook it in a 5% sodium chlorite and acetic acid solution for 6 h according to the solid-liquid mass ratio of 1:20, then wash it with clean water and dry it at 103 °C to obtain bamboo powder with lignin removed (lignin content is 0);

[0126] (2) Add the bamboo powder obtained in step (1) to a 5% sodium periodate solution according to the solid-liquid mass ratio of 1:16, and add isopropanol accounting for 1% of the total solution weight, and react in a lightless environment for 5 h. The reacted sample is dried at 35 °C until the moisture content is 25% to obtain aldehyde-functionalized bamboo powder, and the aldehyde group content in the bamboo powder is 4.2 mmol / g;

[0127] (3) Add the aldehyde-functionalized bamboo powder into a mold, and hot press it at 90 °C and a pressure of 20 MPa for 5 min to obtain a preliminarily plasticized and cured material. By controlling the mass of the sample added to the mold, the material density is 1.3 g / cm 3 ;

[0128] (4) Put the preliminarily plasticized and cured material into an oven and cure it at 100 °C for 2 h to obtain the final all-bamboo-based thermosetting plastic.

[0129] The flexural strength, tensile strength, flexural modulus, water absorption expansion rate, and mass loss rate after 120 days of underground burial of the all-bamboo-based thermosetting plastic are tested. The results are shown in Table 1.

[0130] Table 1

[0131]

[0132] Compared with Comparative Example 3, in Comparative Example 3, the bamboo powder was not treated to remove lignin. During the oxidation process, the oxide could not react with the hydroxyl groups of cellulose and hemicellulose, but mainly reacted with lignin, resulting in poor activity of the active groups, and thus the performance of the prepared sheet could not meet the processing requirements.

[0133] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A fully bamboo-based thermosetting plastic, characterized in that, The all-bamboo-based thermosetting plastic includes bamboo powder containing aldehyde groups or carboxyl groups, and the density of the all-bamboo-based thermosetting plastic is not less than 1.4 g / cm 3 ; In the bamboo powder containing aldehyde groups or carboxyl groups, the content of aldehyde groups or carboxyl groups is 1-5 mmol / g; The preparation method of the all-bamboo-based thermosetting plastic includes: hot-pressing bamboo powder containing aldehyde groups or carboxyl groups until the density is not lower than 1.4 g / cm 3 , and then curing to obtain the all-bamboo-based thermosetting plastic.

2. The all-bamboo-based thermosetting plastic according to claim 1, wherein in the bamboo powder containing aldehyde groups or carboxyl groups, the content of aldehyde groups or carboxyl groups is 1-3 mmol / g; and / or in the bamboo powder containing aldehyde groups or carboxyl groups, the lignin content is 0-15 wt%; and / or the water absorption expansion rate of the all-bamboo-based thermosetting plastic is 0.1-5%.

3. The all-bamboo-based thermosetting plastic according to claim 1 or 2, wherein, The water absorption expansion rate of the all-bamboo-based thermosetting plastic is 0.5-2.5%.

4. The all-bamboo-based thermosetting plastic according to claim 1, wherein the flexural strength of the all-bamboo-based thermosetting plastic is 30-180 Mpa; the flexural modulus of the all-bamboo-based thermosetting plastic is 2-8 Gpa; the tensile strength of the all-bamboo-based thermosetting plastic is 30-80 Mpa.

5. The all-bamboo-based thermosetting plastic according to claim 1, wherein the hot pressing conditions include: temperature is 60-120 °C, pressure is 20-50 MPa, and hot pressing time is 2-10 min; the curing conditions include: temperature is 60-120 °C, and curing time is 1-12 h.

6. The preparation method of the all-bamboo-based thermosetting plastic according to any one of claims 1-5, characterized in that, The method includes: (1) Delignifying the bamboo powder to obtain delignified bamboo powder; (2) Contacting the delignified bamboo powder with a solution containing an oxidant to obtain bamboo powder containing aldehyde groups or carboxyl groups; (3) Thermally press the bamboo powder containing aldehyde groups or carboxyl groups until the density is not less than 1.4 g / cm 3 ; (4) Curing the product obtained in step (3) to obtain an all-bamboo-based thermosetting plastic.

7. The preparation method according to claim 6, wherein the particle size of the bamboo powder is 10-400 mesh; and / or in step (1), in the delignified bamboo powder, the lignin content is 0-15 wt%.

8. The preparation method according to claim 6, wherein in step (1), the method for delignifying the bamboo powder includes: mixing the bamboo powder with a delignifying solution for delignification; the delignifying solution is selected from one of a sodium chlorite solution with a mass content of 1%-5%, a hydrogen peroxide solution with a mass content of 1%-20%, a sulfur dioxide solution with a mass content of 1%-5%, a solution containing 1%-10% sodium hydroxide and 2%-5% sodium sulfite, and a solution containing 1%-10% sodium hydroxide / 1%-8% hydrogen peroxide / / 1%-8% sulfite; the delignifying conditions include: temperature is 60-80 °C, and reaction time is 2-24 h.

9. The preparation method according to claim 6 or 7, wherein In step (2), in the solution containing an oxidant, the oxidant is selected from one or more of periodate, 2,2,6,6-tetramethylpiperidine-n-oxide, dinitrogen tetroxide, hypochlorite, and oxygen base; and / or the solvent is selected from water and C1-C5 alcohols; and / or the mass content of the oxidant is 1-10 wt%; and / or the contact conditions include: temperature is 20-80 °C, and reaction time is 1-48 h.

10. The preparation method according to claim 9, wherein, The solvent is one or more of water, ethanol, and isopropanol.

11. The preparation method according to claim 6, wherein in step (3), the hot pressing conditions include: temperature is 60-120 °C, pressure is 20-50 MPa, and hot pressing time is 2-10 min.

12. The preparation method according to claim 11, wherein, In step (3), hot press until the density reaches 1.4 - 1.8 g / cm 3 .

13. The preparation method according to claim 11, wherein, Before hot pressing in step (3), it also includes adjusting the moisture content of the bamboo powder containing aldehyde groups or carboxyl groups to 10%-150%.

14. The preparation method according to claim 6, wherein In step (4), the curing conditions include: the temperature is 60 - 120 °C, and the curing time is 1 - 12 h.

15. Use of the all-bamboo-based thermosetting plastic according to any one of claims 1 - 5 as a rigid plastic with a glass transition temperature of 40 - 100 °C.

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