Chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood and method of making same

Abstract

The application belongs to the technical field of wood modification, and particularly relates to chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood and a preparation method thereof. The preparation method of the chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood provided by the application adopts a layer-by-layer self-assembly impregnation mode, and fast-growing wood is respectively impregnated in a chitosan solution and a tea polyphenol solution, and after drying, the surface of the fast-growing wood is electrostatically adsorbed with chitosan and tea polyphenol to form a hydrophobic flame-retardant surface, so that a material with hydrophobic and flame-retardant double characteristics can be obtained without subsequent surface energy material or other flame retardant modification. Moreover, the preparation process and principle of the application are simple, the raw materials are widely sourced, green, environmentally friendly and renewable, the texture characteristics of the wood itself can be retained after modification, the color is natural and beautiful, and the application has extremely competitive industrialized production feasibility in the field of high-quality modified wood preparation.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wood modification, and particularly relates to chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood and a preparation method thereof. BACKGROUND

[0002] Wood is a renewable green environmental protection material and is widely used in furniture and buildings. Wood is a porous material mainly composed of cellulose, hemicellulose and lignin, and a large number of hydrophilic groups such as hydroxyl groups exist in the structures of the three main components, so that wood has strong hydrophilicity. After absorbing water, wood is prone to problems such as dimensional deformation, decay and discoloration.

[0003] By constructing a hydrophobic surface (structure), the wood can be endowed with a waterproof function and the self-cleaning ability of the wood surface can be effectively improved. At present, a hydrophobic surface is usually constructed in two ways: (1) constructing a micro-nano rough structure on the surface; and (2) modifying a low-surface-energy substance on the surface of a substrate. However, the conventional methods for constructing a hydrophobic surface have many problems in terms of preparation process, functionality and actual application, such as complex preparation process, expensive equipment and reagents, certain toxicity of reagents and single function.

[0004] Meanwhile, wood often has strong flammability due to its structural characteristics, and is prone to cause fire during use, thereby causing serious damage to human life and property safety. At present, flame retardants are usually used on the market to improve the flame-retardant effect and safety of wood. However, most of the existing wood flame retardants have problems such as poor biodegradability, generation of smoke or toxic gas, and high cost of raw materials.

[0005] Therefore, it is a key problem to be solved by the present application to provide a preparation method of a flame-retardant hydrophobic modified wood, which has more environmentally friendly raw materials, simple preparation method, low equipment requirement, low cost and industrial production feasibility. SUMMARY

[0006] In order to solve the problems of the prior art, the first object of the present application is to provide a preparation method of chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood, which has a simple preparation process, the raw materials are all biomass materials, the source is wide, it is green and environmentally friendly, renewable and low in cost, and the method uses an impregnation method to impregnate fast-growing wood in chitosan solution and tea polyphenol solution, so that modified wood with excellent flame-retardant and hydrophobic effect can be obtained by using the layer-by-layer self-assembly impregnation method.

[0007] The second object of the present application is to provide the chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood prepared by the above preparation method, which has excellent flame-retardant and hydrophobic effects, and retains the texture characteristics of the wood itself after modification, and has natural and beautiful color, and is suitable for industrial application of high-quality modified wood.

[0008] One of the objects of the present application is achieved by adopting the technical solution of:

[0009] A preparation method of chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood comprises the following steps:

[0010] Step (1): The fast-growing wood is immersed in a chitosan solution for treatment, and then taken out, washed and dried to obtain chitosan modified wood.

[0011] Step (2): The chitosan modified wood obtained in step (1) is immersed in a tea polyphenol solution for treatment, and then taken out, washed and dried to obtain chitosan-tea polyphenol modified wood.

[0012] Step (3): The chitosan-tea polyphenol modified wood obtained in step (2) is repeatedly immersed, washed and dried in the above steps (1) and (2) for 3-12 times to obtain the chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood.

[0013] As a further improved technical solution, in step (1), the fast-growing wood is one of fast-growing poplar wood, fast-growing eucalyptus wood and fast-growing pine wood.

[0014] As a further improved technical solution, in step (1), the fast-growing wood is washed and dried before being immersed in the chitosan solution for treatment.

[0015] As a further improved technical solution, in step (1), the concentration of the chitosan solution is 4-6 g / L, and the pH is 3-4; the deacetylation degree of chitosan used in the chitosan solution is ≥95%, and the viscosity is 100-200 mPa·s.

[0016] As a further improved technical solution, in step (1), the immersion treatment time is 0.5-2 h.

[0017] As a further improved technical solution, in step (2), the concentration of the tea polyphenol solution is 1-10 g / L.

[0018] As a further improved technical solution, in step (2), the immersion treatment time is 0.5-2 h.

[0019] As a further improved technical solution, the number of repetitions is 4-9.

[0020] As a further improved technical solution, in step (1), step (2), the cleaning is performed by using water; and the drying temperature is 50-80 DEG C.

[0021] As a further improved technical solution, in step (1), step (2), the immersion treatment is performed at room temperature. In the present application, the room temperature generally refers to 15-35 DEG C.

[0022] The second object of the present application is achieved by the technical solution of:

[0023] A chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood prepared by the above preparation method.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] The preparation method of the chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood provided by the present application uses fast-growing wood as a base material, uses electrostatic force as a driving force to assemble positively charged chitosan polyelectrolyte and negatively charged tea polyphenol polyelectrolyte on the surface of the wood by using layer-by-layer self-assembly technology, and forms a modified film on the surface of the wood. The specific principle is that the surface of the wood is negatively charged, the wood is immersed in a positively charged chitosan solution, and the positively charged chitosan polycation is adsorbed on the surface of the wood by the action of positive and negative charges, so that the surface is positively charged. Then, the wood is immersed in a negatively charged tea polyphenol solution, and the negatively charged tea polyphenol polyanion is adsorbed on the surface of the wood, so that a layer of chitosan-tea polyphenol composite film is adsorbed on the surface of the wood. This is one layer of assembly, and the immersion is repeated several times to obtain modified wood with excellent flame-retardant and hydrophobic effects.

[0026] The chitosan-tea polyphenol modified wood prepared by the above method has a composite film adsorbed on the surface of the wood, which is composed of chitosan and tea polyphenol. In the modification process of the present application, chitosan and tea polyphenol are both natural degradable polyelectrolyte biomaterials, which are widely available, low in cost and high in safety. Moreover, the present application uses tea polyphenol for modification, which has a high carbon content, and chitosan has a high nitrogen content, so as to promote carbon formation during the wood combustion and pyrolysis process, play a heat and oxygen isolation role, inhibit the generation of flammable gas, and achieve the flame-retardant effect. At the same time, tea polyphenol is an aromatic compound containing a large number of side chains, and its pyrogallol / catechol has good effect in hydrophobic modification of materials.

[0027] In summary, the preparation method of this invention employs a layer-by-layer self-assembly impregnation process. Fast-growing wood is impregnated separately in a chitosan solution containing polycations and a tea polyphenol solution containing polyanions. After drying, the surface of the fast-growing wood forms a hydrophobic and flame-retardant surface through electrostatic adsorption of chitosan and tea polyphenols. This eliminates the need for subsequent modification with surface energy substances or other flame retardants, thus obtaining a material with both hydrophobic and flame-retardant properties. Furthermore, the preparation process of this invention uses water-based solvents, making the process and principle simple. The raw materials are widely available, environmentally friendly, and renewable, further improving the hydrophobic and flame-retardant properties of the wood. The modified wood retains its original texture and has a natural and aesthetically pleasing color. Simultaneously, the preparation process of this invention requires minimal equipment, making it highly competitive for industrial-scale production in the field of high-quality modified wood preparation. Attached Figure Description

[0028] Figure 1 This is a diagram of the exposed combustion test of the flame-retardant and hydrophobic modified wood prepared in Example 1 of the present invention;

[0029] Figure 2 This is a diagram of the exposed combustion test of the flame-retardant and hydrophobic modified wood prepared in Example 2 of the present invention;

[0030] Figure 3 This is a diagram of the exposed combustion test of the flame-retardant and hydrophobic modified wood prepared in Example 3 of the present invention;

[0031] Figure 4 The diagram shows the exposed burning test of the raw timber in Comparative Example 1.

[0032] Figure 5 The image shows the exposed combustion test results of chitosan-modified wood prepared in Comparative Example 2.

[0033] Figure 6 The water contact angle of the flame-retardant and hydrophobic modified wood surface obtained in Example 1 of this invention;

[0034] Figure 7 The water contact angle of the flame-retardant and hydrophobic modified wood surface obtained in Example 2 of this invention;

[0035] Figure 8 The water contact angle of the flame-retardant and hydrophobic modified wood surface obtained in Example 3 of this invention;

[0036] Figure 9 The water contact angle of the original wood surface in Comparative Example 1;

[0037] Figure 10 The water contact angle of the chitosan-modified wood surface obtained in Comparative Example 2 is shown. Detailed Implementation

[0038] In order to make the technical purposes, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the protection scope of the present application.

[0039] In the following examples, the raw materials or reagents involved are conventional materials or reagents in the art unless otherwise specified. Among them, in the following examples, the tea polyphenol used is purchased from Shanghai Maikelin Co., Ltd. (Shanghai, China), with a purity of 99% and a Cas number of 84650-60-2. The room temperature referred to in the present application generally refers to 15-35℃.

[0040] Example 1

[0041] This example provides a chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood, and the preparation method thereof comprises the following steps:

[0042] (1) Material preparation: after washing, the fast-growing poplar (size 120mm x 10mm x 1mm) is dried at a drying temperature of 60℃ to obtain pretreated fast-growing poplar;

[0043] Chitosan solution preparation: 1g of low viscosity chitosan (degree of deacetylation ≥95%, viscosity 100-200mPa·s) is dissolved in 200mL of deionized water, and 0.1mol / L of HCl solution is used to adjust the pH to 3-4. The solution is magnetically stirred until it is clear and transparent to obtain a chitosan solution with a concentration of 5g / L;

[0044] Tea polyphenol solution preparation: 0.2g of tea polyphenol (99%) is dissolved in 200mL of deionized water, and the solution is magnetically stirred until it is tea-brown to obtain a tea polyphenol solution with a concentration of 1g / L;

[0045] (2) The pretreated fast-growing poplar is first immersed in the chitosan solution (5g / L) for normal temperature impregnation treatment, and the impregnation time is 1h. Then it is repeatedly washed with deionized water and dried at 60℃. The dried fast-growing poplar is then immersed in the tea polyphenol solution (1g / L) for normal temperature impregnation treatment, and the impregnation time is 1h. After taking it out, it is repeatedly washed with deionized water and dried, and the drying temperature is 60℃. This is one cycle of impregnation. The above step (2) is repeated for cyclic impregnation, and the total cycle is 5 cycles to obtain the chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood of this example.

[0046] Example 2

[0047] This example provides a chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood, and the preparation method thereof comprises the following steps:

[0048] (1) Material preparation: the fast-growing poplar (size 120mm x 10mm x 1mm) was washed and dried, and the drying temperature was 60℃, to obtain the pretreated fast-growing poplar;

[0049] Chitosan solution preparation: 1g of low viscosity chitosan (degree of deacetylation ≥95%, viscosity 100-200mPa·s) was dissolved in 200mL of deionized water, 0.1mol / L HCl solution was used to adjust the pH to 3-4, and magnetic stirring was performed until the solution was clear and transparent, to obtain a chitosan solution with a concentration of 5g / L;

[0050] Tea polyphenol solution preparation: 2g of tea polyphenol (99%) was dissolved in 200mL of deionized water, and magnetic stirring was performed until the solution was tea-brown, to obtain a tea polyphenol solution with a concentration of 10g / L;

[0051] (2) The pretreated fast-growing poplar was first immersed in the chitosan solution (5g / L) for normal temperature immersion treatment, the immersion time was 1h, then it was repeatedly washed with deionized water and dried at 60℃; the dried fast-growing poplar was then immersed in the tea polyphenol solution (10g / L) for normal temperature immersion treatment, the immersion time was 1h, and after taking it out, it was repeatedly washed with deionized water and dried, and the drying temperature was 60℃, which was one cycle of immersion. The above step (2) was repeated for cyclic immersion, and the total cycle was 5 cycles, to obtain the chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood of the example.

[0052] Example 3

[0053] The example provides a chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood, and the preparation method comprises the following steps:

[0054] (1) Material preparation: the fast-growing poplar (size 120mm x 10mm x 1mm) was washed and dried, and the drying temperature was 60℃, to obtain the pretreated fast-growing poplar;

[0055] Chitosan solution preparation: 1g of low viscosity chitosan (degree of deacetylation ≥95%, viscosity 100-200mPa·s) was dissolved in 200mL of deionized water, 0.1mol / L HCl solution was used to adjust the pH to 3-4, and magnetic stirring was performed until the solution was clear and transparent, to obtain a chitosan solution with a concentration of 5g / L;

[0056] Tea polyphenol solution preparation: 1g of tea polyphenol (99%) was dissolved in 200mL of deionized water, and magnetic stirring was performed until the solution was tea-brown, to obtain a tea polyphenol solution with a concentration of 5g / L;

[0057] (2) the pretreated fast-growing poplar is first immersed in a chitosan solution (5 g / L) for normal-temperature impregnation treatment for 1 h, then repeatedly washed with deionized water, and dried at 60°C; the dried fast-growing poplar is then immersed in a tea polyphenol solution (5 g / L) for normal-temperature impregnation treatment for 1 h, taken out, repeatedly washed with deionized water, and dried, with the drying temperature being 60°C, to form one cycle of impregnation. The above step (2) is repeated for cyclic impregnation, and the total cycle is 10 cycles, to obtain the chitosan-tea polyphenol modified flame-retardant hydrophobically modified wood of the example.

[0058] Comparative Example 1

[0059] The comparative example provides an unmodified wood, which uses fast-growing poplar of the same specification as that of Example 1, is washed, and then dried at 60°C to obtain the unmodified wood of Comparative Example 1.

[0060] Comparative Example 2

[0061] The comparative example provides a chitosan modified wood, and the preparation method thereof includes the following steps:

[0062] (1) material preparation: the fast-growing poplar (with a size of 120 mm x 10 mm x 1 mm) is washed and dried, with the drying temperature being 60°C, to obtain the pretreated fast-growing poplar;

[0063] chitosan solution preparation: 1 g of low-viscosity chitosan (degree of deacetylation ≥ 95%, viscosity 100-200 mPa·s) is dissolved in 200 mL of deionized water, 0.1 mol / L of HCl solution is used to adjust the pH to 3-4, and magnetic stirring is performed until the solution is clear and transparent, to obtain a chitosan solution with a concentration of 5 g / L;

[0064] (2) the pretreated fast-growing poplar is immersed in a chitosan solution (5 g / L) for normal-temperature impregnation treatment for 2 h, then repeatedly washed with deionized water, and dried at 60°C, to obtain the chitosan modified wood of the comparative example.

[0065] In addition, the scheme of only impregnating in a tea polyphenol solution, and the scheme of first impregnating in a tea polyphenol solution and then impregnating in a chitosan solution, cannot achieve effective modification of fast-growing wood after verification. Therefore, the present application does not set comparative examples for the two schemes.

[0066] Test Example 1, flame-retardant performance test

[0067] The wood prepared in Examples 1-3 and Comparative Examples 1-2 was subjected to vertical exposure combustion test, and the whole process was timed. The wood was applied with ignition source, and a flame of about 6 mm was covered on the top of the wood. The flame was removed after 15±1 s of ignition. The self-extinguishing time or combustion process of the wood of Examples 1-3 and Comparative Examples 1-2 was shown in Figures 1 to 5

[0068] As shown in Figure 1 , the chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood prepared in Example 1 was not easy to ignite, and self-extinguished after 14 s of removal of the flame. As shown in Figure 2 , the chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood prepared in Example 2 was not easy to ignite, and self-extinguished after 10.4 s of removal of the flame. As shown in Figure 3 , the chitosan-tea polyphenol modified flame-retardant hydrophobic modified wood prepared in Example 3 was not easy to ignite, and self-extinguished after 9.9 s of removal of the flame. As shown in Figure 4 , the combustion process of the wood of Comparative Example 1, which was not modified by chitosan and tea polyphenol, was fast and continuous. As shown in Figure 5 , the combustion process of the wood of Comparative Example 2, which was modified by chitosan only, was slower than that of Comparative Example 1, but still continuous.

[0069] Therefore, the chitosan and tea polyphenol self-assembled modified flame-retardant hydrophobic wood can significantly improve the flame-retardant performance of the wood, and the wood is more difficult to burn compared with the unmodified fast-growing wood. After the flame is removed, the flame becomes smaller, and self-extinguishes after a certain period of time. Therefore, the modified wood prepared by the chitosan and tea polyphenol impregnation modification can form a flame-retardant surface on the wood surface, and obtain a modified material with excellent flame-retardant performance.

[0070] Test Example Two, Hydrophobic Performance Test

[0071] The wood prepared in Examples 1-3 and Comparative Examples 1-2 was subjected to water contact angle test. The water contact angle test results of Examples 1-3 and Comparative Examples 1-2 were shown in Figures 6 to 10 and Table 1.

[0072] Table 1

[0073] Test Group Number Initial water contact angle 60s water contact angle Example 1 128.4° 127.3° Example 2 138.1° 133.8° Example 3 141.4° 137.1° Comparative Example 1 60.8° 0° Comparative Example 2 101.2° 57.3°

[0074] As shown in Figures 6 to 10 ​As shown in Table 1, the modified wood of Example 1 has good hydrophobic property, the initial water contact angle is 128.4°, and the water contact angle maintained for 60s is 127.3°. The modified wood of Example 2 has good hydrophobic property, the initial water contact angle is 138.1°, and the water contact angle maintained for 60s is 133.8°. The modified wood of Example 3 has good hydrophobic property, the initial water contact angle is 141.4°, and the water contact angle maintained for 60s is 137.1°. The original wood without modification by chitosan and tea polyphenol in Comparative Example 1 is hydrophilic, the contact angle is 60.8°, and the water droplet is completely immersed after several seconds. The wood modified by chitosan only in Comparative Example 2 has unstable hydrophobic property, the initial contact angle is 101.2°, but the water contact angle of the modified wood is 57.3° after 60s of continuous measurement, which is hydrophilic.

[0075] Therefore, the fast-growing wood is immersed in the chitosan solution and the tea polyphenol solution respectively in the application, and the modified wood with excellent hydrophobic property can be obtained by the layer-by-layer self-assembly immersion method. Meanwhile, the excellent hydrophobic effect can be achieved without constructing the micro-nano rough structure on the surface of the wood or modifying the low surface energy material, and the long-term hydrophobic stability of the modified wood is better than that of Comparative Examples 1-2.

[0076] As described above, the preparation method of the chitosan-tea polyphenol modified flame-retardant and hydrophobic modified wood provided in the application adopts the layer-by-layer self-assembly immersion method, the fast-growing wood is immersed in the chitosan solution with poly-cation and the tea polyphenol solution with poly-anion respectively, and the surface of the fast-growing wood is electrostatically adsorbed with chitosan and tea polyphenol to form a hydrophobic and flame-retardant surface after drying, so that the material with hydrophobic and flame-retardant double characteristics can be obtained without subsequent modification by the low surface energy material or other flame retardants. The modified wood with excellent flame-retardant property and hydrophobic property double characteristics can be obtained by the simple immersion method in the application, the preparation process is simple, the raw material cost is low, the process is green and environmentally friendly, the requirement for the equipment used in the preparation process is low, the texture characteristics of the wood itself are retained after modification, the color is natural and beautiful, and the industrialized production feasibility is very competitive in the field of high-quality modified wood preparation.

Claims

1. A method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic wood, characterized in that, Includes the following steps: Step (1): The fast-growing wood is impregnated in a chitosan solution, then taken out, washed and dried to obtain chitosan-modified wood; Step (2): The chitosan-modified wood obtained in step (1) is impregnated in a tea polyphenol solution, then taken out, washed and dried to obtain chitosan-tea polyphenol-modified wood; Step (3): Take the chitosan-tea polyphenol modified wood obtained in step (2), and repeat the soaking, washing and drying steps in steps (1) and (2) above in sequence, repeating 3 to 12 times to obtain the chitosan-tea polyphenol modified flame retardant and hydrophobic modified wood.

2. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to claim 1, characterized in that, In step (1), the fast-growing timber is one of fast-growing poplar, fast-growing eucalyptus, and fast-growing pine.

3. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to claim 1, characterized in that, In step (1), the fast-growing wood is pre-washed and dried before being impregnated in the chitosan solution.

4. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to claim 1, characterized in that, In step (1), the concentration of the chitosan solution is 4~6 g / L and the pH is 3~4; the degree of deacetylation of the chitosan used in the chitosan solution is ≥95% and the viscosity is 100~200 mPa·s.

5. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to claim 1, characterized in that, In step (1), the immersion treatment time is 0.5~2h.

6. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to any one of claims 1 to 5, characterized in that, In step (2), the concentration of the tea polyphenol solution is 1~10g / L.

7. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to any one of claims 1 to 5, characterized in that, In step (2), the immersion treatment time is 0.5~2h.

8. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to any one of claims 1 to 5, characterized in that, The number of repetitions is 4 to 9.

9. The method for preparing chitosan-tea polyphenol-modified flame-retardant and hydrophobic modified wood according to any one of claims 1 to 5, characterized in that, In steps (1) and (2), the cleaning is done with water; the drying temperature is 50~80℃.

10. A chitosan-tea polyphenol-modified flame-retardant and hydrophobic wood prepared by the preparation method according to any one of claims 1 to 9.

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