Method for preparing all-bamboo composite material through surface layer dissolution connection method

Abstract

The invention discloses a method for preparing an all-bamboo composite material through a surface layer dissolution connection method, which comprises the following steps: immersing bamboo wood into an alkaline aqueous solution or hydrogen peroxide for treatment, taking out the bamboo wood, immersing the bamboo wood into an organic solvent for solvent exchange, immersing the bamboo wood subjected to solvent exchange into an ionic liquid and / or a deep eutectic solvent, and carrying out surface layer dissolution connection. After the bamboo is swelled, the surface layer is dissolved, the bamboo is taken out, the solvent in the bamboo is removed, the bamboo is subjected to hot pressing treatment, and the all-bamboo composite material is obtained. According to the treatment mode of the ionic liquid and / or the eutecticevaporate solvent, the tensile strength of the joints of the bamboos is remarkably improved through surface dissolution of cellulose, and the all-bamboo composite material with excellent physical performance is obtained. The preparation method provided by the invention not only improves the environmental protection performance and the processing efficiency of the all-bamboo composite material, but also obviously enhances the connection strength of the composite material, and opens up a new way for wide application of bamboo wood.

Description

Technical Field

[0001] The invention relates to the technical field of preparing all-bamboo composite materials, and in particular to a method for preparing the all-bamboo composite material by a surface dissolution connection method. Background Art

[0002] The increasingly serious problem of plastic pollution poses a huge threat to the natural environment and ecosystem, and people are urgently required to find more environmentally friendly and degradable materials to replace traditional plastics. Bamboo, as a renewable resource in nature, has shown great potential in replacing traditional plastic materials with its characteristics of rapid growth, abundant resources, and strong carbon fixation ability.

[0003] In this context, bamboo-plastic composite materials came into being. This material mainly uses bamboo fiber as the core raw material, and through composite processing with a polymer resin matrix, it has formed a new type of material with superior performance and wide application. However, although bamboo-plastic composite materials have partially replaced traditional plastics to a certain extent, they still rely on a certain proportion of plastic base materials and processing aids during the preparation process, which limits the further improvement of their environmental performance and has not completely gotten rid of their dependence on plastics.

[0004] Therefore, it is urgent to develop a new all-bamboo composite material to replace the existing bamboo-plastic composite material. This all-bamboo composite material should be completely based on bamboo itself, without adding any plastic components or other non-environmentally friendly additives, so as to ensure the environmental protection and sustainability of the material at the source. At the same time, the all-bamboo composite material should have high performance characteristics to meet the requirements of material performance in different fields. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a full-bamboo composite material by a surface dissolution connection method, which can achieve the dissolution of cellulose on the surface of bamboo and accurately control the dissolution process, and then use this surface dissolution connection technology to prepare a large-sized full-bamboo composite material.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for preparing a full-bamboo composite material by a surface dissolution connection method, comprising the following steps:

[0008] The bamboo material is immersed in an alkaline aqueous solution or hydrogen peroxide for treatment, taken out and immersed in an organic solvent for solvent exchange, the bamboo material after solvent exchange is immersed in an ionic liquid and / or a low eutectic solvent to make the bamboo material swell and then dissolve the surface layer, taken out and the solvent in the bamboo material is removed, and the bamboo material is subjected to heat pressing to obtain the all-bamboo composite material.

[0009] Furthermore, the bamboo material is more than one year old.

[0010] Furthermore, before the bamboo is immersed in an alkaline aqueous solution or hydrogen peroxide for treatment, the method also includes a step of pre-treating the bamboo. The specific operation of the pre-treatment is: cutting the fresh bamboo into required sizes and cleaning the surface impurities.

[0011] Furthermore, the alkaline aqueous solution is selected from one or more of a KOH aqueous solution, a NaOH aqueous solution, a NaClO aqueous solution and a Na2SO3 aqueous solution.

[0012] Furthermore, the concentration of the NaOH aqueous solution is 2-3 mol / L.

[0013] Furthermore, the concentration of the Na2SO3 aqueous solution is 0.3-0.4 mol / L.

[0014] Furthermore, the concentration of the hydrogen peroxide is 15%-30%.

[0015] Furthermore, the bamboo material is immersed in an alkaline aqueous solution or hydrogen peroxide for treatment at a temperature of 20-100° C. for a time of 0.5-6 hours.

[0016] The purpose of treating bamboo by immersing it in an alkaline aqueous solution or hydrogen peroxide is to remove wax, pigment, tannin, chlorophyll, fatty acid, lignin and hemicellulose from the bamboo.

[0017] Furthermore, the organic solvent is selected from one or more of methanol, ethanol, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0018] Furthermore, the solvent exchange is performed for 0.1-4 h.

[0019] Furthermore, before taking out the bamboo material and immersing it in the organic solvent, the process also includes a step of using ethanol to wash away surface impurities.

[0020] The purpose of immersing bamboo in an organic solvent for solvent exchange is to exchange the water inside the bamboo and allow the organic solvent to enter the bamboo so as to cooperate with the subsequent mixed solution to swell and dissolve cellulose.

[0021] Furthermore, the ionic liquid is selected from one or more of 1-allyl-3-methylimidazolium chloride (AmimCl), 1-butyl-3-methylimidazolium chloride (BmimCl), 1-alkyl-3-methylimidazolium hexafluorophosphate and tetrabutylammonium hexafluorophosphate.

[0022] Furthermore, the 1-alkyl-3-methylimidazolium hexafluorophosphate is preferably [C4-C16mim]PF6.

[0023] Furthermore, the low eutectic solvent is selected from one or more of choline chloride-ethylene glycol (ChCl-EG), choline chloride-glycerol (ChCl-Gly) and urea-glycerol (U-Gly).

[0024] Furthermore, the bamboo material after solvent exchange is immersed in the ionic liquid and / or the low eutectic solvent at a temperature of 20-100° C. and a time of 5 min-4 h.

[0025] When a mixed solvent of an ionic liquid and a low eutectic solvent is used, the mass ratio of the ionic liquid to the low eutectic solvent is 1:(0.01-100).

[0026] The time of immersion in the mixed solvent of ionic liquid and deep eutectic solvent affects the degree of swelling and surface dissolution of bamboo, which in turn affects the tensile strength of its joints.

[0027] Furthermore, the specific operation of removing the solvent in the bamboo is: immersing the bamboo in water to exchange the solvent inside the bamboo.

[0028] Furthermore, the temperature of the hot pressing treatment is 20-120°C, the time is 3-60min, and the pressure is 0.1-5Mpa.

[0029] Beneficial effects of the present invention:

[0030] 1. The composite material obtained by the present invention is completely composed of bamboo materials. The all-bamboo composite material can be completely degraded under natural conditions. Compared with the existing bamboo-plastic composite materials, it has higher environmental protection.

[0031] 2. The present invention adopts the method of exchanging the internal moisture of bamboo with organic solvent, which not only significantly improves the drying efficiency of bamboo, effectively saves time cost, but also makes the surface of bamboo after treatment more soluble. This treatment method, in synergy with ionic liquid and deep eutectic solvent, further improves the solubility of bamboo, providing more favorable conditions for subsequent processing.

[0032] 3. The treatment method of the ionic liquid and / or low eutectic solvent in the present invention utilizes the surface dissolution of cellulose to significantly improve the tensile strength of the bamboo joints, thereby obtaining a full bamboo composite material with excellent physical properties.

[0033] 4. The preparation method provided by the present invention not only improves the environmental performance and processing efficiency of the all-bamboo composite material, but also significantly enhances the connection strength of the composite material, opening up a new way for the wide application of bamboo materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a real picture of natural bamboo cracking after natural drying.

[0035] Figure 2This is a physical picture of the bamboo material being overlapped up and down in Example 1.

[0036] Figure 3 This is a physical picture of the all-bamboo composite material prepared in Example 1.

[0037] Figure 4 The graph is a test result of tensile strength of joints of all-bamboo composite materials prepared in Example 1 and Comparative Examples 1-3; wherein a is Example 1, b is Example 2, c is Example 3, and d is Comparative Example 1. DETAILED DESCRIPTION

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0039] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0040] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0041] Example 1

[0042] A method for preparing a full bamboo composite material by a surface dissolution connection method comprises the following steps:

[0043] (1) Fresh bamboo was cut into pieces of 35 mm × 5 mm × 5 mm and the surface impurities were cleaned; 100 g of NaOH and 50.4 g of Na2SO3 were dissolved in 850 mL of deionized water and heated to 90°C using a magnetic stirrer to obtain an alkaline aqueous solution. The bamboo was then immersed in the alkaline aqueous solution and maintained at 90°C for 6 h. After the alkaline treatment was completed, the bamboo was taken out and rinsed with deionized water for multiple times.

[0044] (2) The bamboo was immersed in 400 mL of DMF for 2 h to exchange the water inside the bamboo into the solvent for subsequent treatment.

[0045] (3) 50 g of BmimCl and 50 g of U-Gly were added to a three-necked flask and heated to 100° C. using a magnetic stirrer to obtain a mixed solvent. The bamboo material from which water had been removed was immersed in the mixed solvent for 2 h to obtain a bamboo material with dissolved cellulose on the surface. The obtained bamboo material with dissolved cellulose on the surface was immersed in deionized water for 2 h to exchange the mixed solvent that had entered the interior of the cellulose.

[0046] (4) The upper and lower mold temperatures of the vulcanizer are set to 60°C, the exhaust times are set to 10 times, the pre-pressing time is set to 15 min, the pressurizing time is set to 15 min, the preset pressure is set to 3 MPa, the obtained bamboo material is overlapped and placed in the mold, and then placed in the vulcanizer for hot pressing treatment to obtain a full bamboo composite material.

[0047] Example 2

[0048] A method for preparing an all-bamboo composite material is basically the same as that of Example 1, except that in step (3), 50 g of BmimCl and 50 g of U-Gly are replaced by 100 g of BmimCl.

[0049] Example 3

[0050] A method for preparing an all-bamboo composite material is basically the same as Example 1, except that in step (3), 50 g of BmimCl and 50 g of U-Gly are replaced by 100 g of U-Gly.

[0051] Comparative Example 1

[0052] A method for preparing a full bamboo composite material comprises the following steps:

[0053] (1) Fresh bamboo was cut into pieces of 35 mm × 5 mm × 5 mm and the surface impurities were cleaned; 100 g of NaOH and 50.4 g of Na2SO3 were dissolved in 850 mL of deionized water and heated to 90°C using a magnetic stirrer to obtain an alkaline aqueous solution. The bamboo was then immersed in the alkaline aqueous solution and maintained at 90°C for 6 h. After the alkaline treatment was completed, the bamboo was taken out and rinsed with deionized water for multiple times.

[0054] (2) The bamboo was immersed in 400 mL of DMF for 2 h to exchange the water inside the bamboo into the solvent for subsequent treatment.

[0055] (3) 100 mL of deionized water was added to a three-necked flask and heated to 100° C. using a magnetic stirrer, and the dehydrated bamboo was immersed in the flask for 2 h.

[0056] (4) The upper and lower mold temperatures of the vulcanizer are set to 60°C, the exhaust times are set to 10 times, the pre-pressing time is set to 15 min, the pressurizing time is set to 15 min, the preset pressure is set to 3 MPa, the obtained bamboo material is overlapped and placed in the mold, and then placed in the vulcanizer for hot pressing treatment to obtain a full bamboo composite material.

[0057] Comparative Example 2

[0058] A method for preparing a full bamboo composite material comprises the following steps:

[0059] (1) Cut fresh bamboo into required sizes and clean the surface impurities; dissolve 100 g of NaOH and 50.4 g of Na2SO3 in 850 mL of deionized water, and heat to 90°C using a magnetic stirrer to obtain an alkaline aqueous solution. Then, immerse the bamboo in the alkaline aqueous solution and maintain the alkaline treatment at 90°C for 6 h. After the alkaline treatment is completed, take out the bamboo and rinse it with deionized water for multiple times.

[0060] (2) Place the alkali-treated bamboo in a ventilated place to dry naturally for 24 hours.

[0061] (3) 50 g of BmimCl and 50 g of U-Gly were added to a three-necked flask and heated to 100°C using a magnetic stirrer to obtain a mixed solvent. The naturally dried bamboo was immersed in the mixed solvent for 2 h to obtain a bamboo with dissolved cellulose on the surface. The obtained bamboo with dissolved cellulose on the surface was immersed in deionized water for 2 h to exchange the mixed solvent that entered the interior of the cellulose.

[0062] (4) The upper and lower mold temperatures of the vulcanizer are set to 60°C, the exhaust times are set to 10 times, the pre-pressing time is set to 15 min, the pressurizing time is set to 15 min, the preset pressure is set to 3 MPa, the obtained bamboo material is overlapped and placed in the mold, and then placed in the vulcanizer for hot pressing treatment to obtain a full bamboo composite material.

[0063] Figure 1 This is a real picture of natural bamboo cracking after natural drying.

[0064] Figure 2 This is a physical picture of the bamboo material being overlapped up and down in Example 1.

[0065] Figure 3 This is a physical picture of the all-bamboo composite material prepared in Example 1.

[0066] The tensile strength test of the joints of the all-bamboo composite materials prepared in Examples 1-3 and Comparative Examples 1-2 was performed by clamping the dried all-bamboo composite materials in the upper and lower clamps of a universal testing machine, and starting the testing machine to perform a tensile test.

[0067] The test results are as follows Figure 4As shown, it can be seen that the tensile strength of the joints of the all-bamboo composite material prepared in Example 1 is the best, which is better than the tensile strength of the joints of the all-bamboo composite material prepared by treating bamboo with two solvents alone. The tensile strength of the joints of the all-bamboo composite material obtained by using bamboo treated with DMF is also significantly higher than that of the all-bamboo composite material obtained by naturally drying bamboo. The joint condition of the all-bamboo composite material prepared in Comparative Example 2 was too poor after drying, so it was not subjected to a tensile test.

[0068] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a full bamboo composite material by surface dissolution connection method, characterized in that: The following steps are involved: The bamboo material is immersed in an alkaline aqueous solution or hydrogen peroxide for treatment, taken out and immersed in an organic solvent for solvent exchange, the bamboo material after solvent exchange is immersed in an ionic liquid and / or a low eutectic solvent to make the bamboo material swell and then dissolve the surface layer, taken out and the solvent in the bamboo material is removed, and the bamboo material is subjected to heat pressing to obtain the all-bamboo composite material.

2. The preparation method according to claim 1, characterized in that: The alkaline aqueous solution is selected from one or more of a KOH aqueous solution, a NaOH aqueous solution, a NaClO aqueous solution and a Na2SO3 aqueous solution.

3. The preparation method according to claim 1, characterized in that The bamboo is immersed in an alkaline aqueous solution or hydrogen peroxide for treatment at a temperature of 20-100°C and a time of 0.5-6 h.

4. The preparation method according to claim 1, characterized in that: The organic solvent is selected from one or more of methanol, ethanol, N,N-dimethylformamide and dimethyl sulfoxide.

5. The preparation method according to claim 1, characterized in that The solvent exchange was performed for 0.1-4 h.

6. The preparation method according to claim 1, characterized in that: The ionic liquid is selected from one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-alkyl-3-methylimidazolium hexafluorophosphate and tetrabutylammonium hexafluorophosphate.

7. The preparation method according to claim 1, characterized in that: The low eutectic solvent is selected from one or more of choline chloride-ethylene glycol, choline chloride-glycerol and urea-glycerol.

8. The preparation method according to claim 1, characterized in that The bamboo material after solvent exchange is immersed in the ionic liquid and / or the low eutectic solvent at a temperature of 20-100°C for a time of 5 min-4 h.

9. The preparation method according to claim 1, characterized in that: When a mixed solvent of an ionic liquid and a low eutectic solvent is used, the mass ratio of the ionic liquid to the low eutectic solvent is 1:(0.01-100).

10. The preparation method according to claim 1, characterized in that The temperature of the hot pressing treatment is 20-120°C, the time is 3-60 min, and the pressure is 0.1-5 Mpa.

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