A preparation method for softening and bending wood

Abstract

The present invention discloses a preparation method for softening and bending wood. The specific steps are as follows: (1) removing part of the lignin in the wood; (2) treating with N,N-dimethylacetamide and lithium chloride solution to cause the micro-nano fibers in the wood to swell and slide, and uniformly filling the hollow cell cavities in the wood; (3) washing the excess chemical solution with water; (4) drying the washed wood to a moisture content of 30%-100%, and then bending and deforming operations can be carried out; (5) drying and shaping the bent and deformed wood. The method of the present invention has a very significant effect on softening and bending wood. During the treatment process, not only the mechanical properties of the wood are not damaged, but on the contrary, they are increased several times, and the influence on the wood properties is small, with good stability, dense wood, not easy to fluff, and having a very high utilization value.

Description

Technical Field

[0001] The present invention relates to a preparation method for softening and bending wood, belonging to the technical fields of artificial microstructured materials and wood processing. Background Art

[0002] Wood comes from nature and is the most widely used traditional material composed of cellulose fibers. However, wood is a rigid material with poor plasticity. Under normal conditions, wood cannot be directly bent and shaped. If within the normal stress range, wood bends and deforms, but when the stress disappears, the wood returns to its original shape. When exceeding the elastic limit, the fibers on the tensile surface are broken and damaged. Therefore, it is very difficult to use wood as a curved member.

[0003] Since wood is a natural and environmentally friendly material, if wood can be made into a curved member, it will greatly expand the application range of wood. Currently, the main method to improve the bending processability of wood is to soften the wood. Common wood softening methods include physical methods such as hydrothermal treatment and high-frequency dielectric heating treatment. However, such methods will cause wood cracking and performance degradation, and the bending curvature of wood is limited.

[0004] The cell cavities in wood are hollow tubular structures, and their cell walls are composed of multi-level micro-nano fibers. When regulating the nano-cellulose fibers so that the cellulose fibers are evenly distributed in the hollow cell cavities, the cellulose crystalline regions are temporarily damaged, enabling the fibers to have space for sliding and free movement. Macroscopically, the wood obtains a certain plasticity and can be bent and shaped. However, the wood structure is complex and the fiber regulation is difficult, and the research still faces great challenges. Summary of the Invention

[0005] Aiming at the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide a preparation method for softening and bending wood.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A preparation method for softening and bending wood, comprising the following steps:

[0008] Step 1, removing part of the lignin: placing the wood in solution A and cooking it at high temperature to remove part of the lignin, and then washing the wood with clean water for later use;

[0009] Step 2, chemical treatment of the wood: treating the wood obtained in Step 1 with N,N-dimethylacetamide and lithium chloride solution to cause the micro-nano fibers in the wood to swell and slide, and evenly filling them in the hollow cell cavities of the wood;

[0010] Step 3, cleaning treatment: leaving the wood obtained in Step 2 to stand for 0.5 h - 24 h, then soaking it in water for 30 min - 24 h. After the wood is solidified, wash away the excess chemical solution with water;

[0011] Step 4, bending deformation: Dry the cleaned wood to a moisture content of 30%-100%, and then the bending deformation operation can be carried out.

[0012] Step 5, dry and shape the bent wood.

[0013] Further, in Step 1, the types of the wood include softwood and hardwood.

[0014] Further, in Step 1, the A solution is high-temperature steam, a sodium hydroxide / sodium sulfite mixed solution, a hydrogen peroxide solution, a sodium hypochlorite solution, or a safe combination of the above solutions.

[0015] Further, in Step 1, the removal content of lignin is 10%-99%.

[0016] Further, in Step 2, first activate the wood in an N,N-dimethylacetamide solution at 145-200°C for 30 minutes to 2 hours; then cool the above solution to 95-120°C, add lithium chloride, and the reaction time is 5 minutes to 2 hours; finally, let it stand for 1-24 hours.

[0017] Further, the mass ratio of lithium chloride to the N,N-dimethylacetamide solution is 1:8 to 1:12.

[0018] The present invention uses natural wood as raw material, and by regulating the position of micro-nano fibers in the wood and the interaction between fibers, enables the micro-nano fibers to slide so that the wood can be softened and bent. The advantages of the present invention are as follows:

[0019] (1) The plasticity of the wood is increased, making the wood bendable.

[0020] (2) During the softening process of the wood, no foreign substances are introduced. The composition of the softened wood remains unchanged compared with the original wood, and it is still composed of lignin, cellulose, and hemicellulose.

[0021] (3) The strength performance of the wood itself is not weakened, but instead is increased several times. Compared with the traditional softening method, in which there is a certain loss in the wood strength while obtaining plasticity, the elastic limit, flexural modulus, fatigue limit, and plasticity of the wood prepared by the present invention are all significantly improved.

[0022] (4) The wood prepared by using the softening method of the present invention has a wide range of bending degrees, and can even be knotted and locked. The curved members with a wide curvature range and high strength greatly expand the application range of the wood. Description of the Drawings

[0023] Figure 1It is a scanning electron microscope photograph of the original wood that was directly bent and fractured without softening.

[0024] Figure 2 It is a scanning electron microscope photograph of the cross-section of the wood after softening.

[0025] Figure 3 It is a (a) schematic diagram and (b) physical photograph of the knotted wood after softening in Example 1.

[0026] Figure 4 It is a photograph of the curled wood softened prepared in Example 2.

[0027] Figure 5 It is a (a) photograph and (b) scanning electron microscope photograph of the folded wood softened prepared in Example 3.

[0028] Figure 6 It is a scanning electron microscope photograph of the bent wood softened prepared in Example 4.

[0029] Figure 7 It is a stress-strain curve graph of the longitudinal tensile strength of the wood in Example 1. Detailed implementation manners

[0030] The present invention provides a preparation method for softening and bending wood, which specifically includes the following steps:

[0031] (1) Treat the wood with an A treatment solution for 20 minutes to 72 hours to remove part of the lignin, and the removed lignin content is 10% - 99%. Lignin mainly exists between fibers and has the functions of connecting cells and fibers and providing rigid support for the wood. After removing part of the lignin, not only can the chemical bond between lignin and cellulose be destroyed, but also space is provided for the subsequent swelling and migration of cellulose fibers.

[0032] (2) Treat the wood obtained in step (1) with N,N-dimethylacetamide and lithium chloride solution to cause the nanofibers in the wood to swell and slide, and uniformly fill the hollow cell cavities in the wood.

[0033] The original wood structure before solution treatment is as Figure 1 shown. When the original wood is bent, it shows rigid characteristics, without plasticity and elasticity, and the wood is fractured and damaged, and cannot be made into a bent component. After the fibers swell and slide by solution treatment, at this time, the cell units in the wood have changed from a hollow tubular structure to a solid structure, and the whole wood forms a dense structure by the close arrangement of wood cell units. The wood cell units are solid structures composed of nanofibrils.

[0034] (3) Then leave the wood to stand for 0.5 h - 24 h, and then soak it in water for 30 min - 24 h. After the wood is solidified, wash off the excess chemical solution with water.

[0035] (4) Dry the washed wood to a moisture content of 30% - 100%, and then the bending deformation operation can be carried out.

[0036] (5) Finally, dry and shape the wood after bending deformation.

[0037] Example 1:

[0038] Put basswood with a height of 70 cm and a diameter of 1 mm into an aqueous solution of 2.0 mol / L sodium hydroxide and 0.03 mol / L sodium sulfite, cook for 10 hours, wash off the excess chemicals with water, and then dry. Then place it in an N,N - dimethylacetamide solution at 160 °C for 60 minutes, then cool to 110 °C, add a certain amount of lithium chloride, and the mass ratio of lithium chloride to N,N - dimethylacetamide solution = 1:8. React for 60 minutes, take it out, leave it to stand for 24 hours, immerse it in water for 10 hours, and then wash it repeatedly with deionized water. At this time, the wood can be bent and even knotted, and can be shaped by drying. The schematic diagram of the wood knotting is shown in Figure 1 , and it can be seen from Figure 6 that its longitudinal tensile strength is 430 MPa, which is nearly 7 times that of the original wood.

[0039] Example 2:

[0040] Cut the Scotch pine horizontally into a thickness of 3 mm and a diameter of 10 cm, put it into an aqueous solution of 2.0 mol / L sodium hydroxide and 0.03 mol / L sodium sulfite, cook for 10 hours, wash off the excess chemicals with water, and then dry. Then place it in an N,N - dimethylacetamide solution at 165 °C for 30 minutes, then cool to 120 °C, add a certain amount of lithium chloride, and the mass ratio of lithium chloride to N,N - dimethylacetamide solution = 1:9. React for 40 minutes, take it out, leave it to stand for 10 hours, take it out and immerse it in water for 5 hours, and then wash it repeatedly with deionized water. At this time, the wood can be bent and can be shaped by drying into Figure 4 as shown, and its longitudinal tensile strength is 423 MPa.

[0041] Example 3:

[0042] Place the basswood with a height of 15 cm and a diameter of 1.5 mm in an aqueous solution of 2.5 mol / L sodium hydroxide and 0.03 mol / L sodium sulfite, cook for 20 hours, wash with water to remove excess chemicals, and then dry. Then place it in an N,N-dimethylacetamide solution at 185 °C for 60 minutes, then cool to 110 °C, add a certain amount of lithium chloride, the mass ratio of lithium chloride to N,N-dimethylacetamide solution = 1:8, react for 60 minutes, take it out, let it stand for 10 hours, take it out and immerse it in water for 10 hours, and then wash it with deionized water multiple times. At this time, the wood can be bent and dried to be shaped into Figure 5 As shown, the wood can even be folded in half like paper, and the longitudinal tensile strength is 433 MPa.

[0043] Example 4:

[0044] Place the basswood with a height of 20 cm and a diameter of 1.5 mm in an aqueous solution of 2.5 mol / L sodium hydroxide and 0.03 mol / L sodium sulfite, cook for 10 hours, wash with water to remove excess chemicals, and then dry. Then place it in an N,N-dimethylacetamide solution at 175 °C for 60 minutes, then cool to 110 °C, add a certain amount of lithium chloride, the mass ratio of lithium chloride to N,N-dimethylacetamide solution = 1:8, react for 60 minutes, take it out, let it stand for 20 hours, take it out and immerse it in water for 20 hours, and then wash it with deionized water multiple times. At this time, the wood can be bent into a spiral spring shape (see the partial view of Figure 6 ), dried and shaped, and the longitudinal tensile strength is 417.5 MPa.

[0045] Example 5:

[0046] Place the basswood with a height of 2 cm, a width of 7 cm and a length of 7 cm in an aqueous solution of 2.5 mol / L sodium hydroxide and 0.03 mol / L sodium sulfite, cook for 6 hours, wash with water to remove excess chemicals, and then dry. Then place it in an N,N-dimethylacetamide solution at 165 °C for 30 minutes, then cool to 120 °C, add a certain amount of lithium chloride, the mass ratio of lithium chloride to N,N-dimethylacetamide solution = 1:8, react for 30 minutes, take it out, let it stand for 10 hours, take it out and immerse it in water for 10 hours, and then wash it with deionized water multiple times. At this time, the cross-cut wood can also be folded in half, dried and shaped, and the longitudinal tensile strength is 446.3 MPa.

Claims

1. A preparation method for softening and bending wood, characterized in that, the method comprises the following steps: Step 1, removing part of the lignin: Placing the wood in solution A for high-temperature cooking to remove part of the lignin, and washing the wood with clean water for standby; the solution A is high-temperature steam, a mixed solution of sodium hydroxide / sodium sulfite, a hydrogen peroxide solution, a sodium hypochlorite solution, or a safe combination of the above solutions; Step 2, chemical treatment of the wood: Treating the wood obtained in Step 1 with an N,N-dimethylacetamide and lithium chloride solution to cause the micro-nano fibers in the wood to swell and slide, and uniformly fill the hollow cell cavities in the wood. Specifically: first activating the wood in an N,N-dimethylacetamide solution at 145-200 °C for 30 minutes to 2 hours; then cooling the above solution to 95-120 °C, adding lithium chloride, and the reaction time is 5 minutes to 2 hours; finally standing for a period of time; Step 3, cleaning treatment: After standing the wood obtained in Step 2 for 0.5 h - 24 h, soaking it in water for 30 min - 24 h. After the wood is cured, washing off the excess chemical solution with water; Step 4, bending deformation: Drying the washed wood to a moisture content of 30% - 100%, and then the bending deformation operation can be carried out; Step 5, drying and shaping the bent wood.

2. The preparation method for softening and bending wood according to claim 1, characterized in that, in Step 1, the types of the wood include softwood and hardwood.

3. The preparation method for softening and bending wood according to claim 1, characterized in that, in Step 1, the removal content of the lignin is 10% - 99%.

4. The preparation method for softening and bending wood according to claim 1, characterized in that, the mass ratio of the lithium chloride to the N,N-dimethylacetamide solution is 1:8 - 1:

12.

5. The preparation method for softening and bending wood according to claim 1, characterized in that, the standing time is 1 - 24 hours.

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