A fully cellulose bulk material based on a three-dimensional entangled network of fibers and a method for producing the same

Abstract

This invention discloses a whole cellulose block material based on a three-dimensional entangled fiber network and its preparation method. The material is composed of natural plant fibers. By controlling the fiber structure, adjacent fibers are entangled and linked, forming a stable porous network structure in three-dimensional space. The preparation method of this invention is as follows: First, plant cellulose fibers are pretreated with a chemical solution to form a uniform paste, which is then poured into a mold for preliminary shaping. Next, a chemical solution is used to introduce the entangled fiber structure, followed by drying and water washing to remove residual chemicals. Finally, the material is dried to obtain a whole cellulose block material with structural stability and compression recovery. The whole cellulose block material prepared by this invention exhibits wet stability, dry strength and toughness, and compression recovery. It also features widely available raw materials, a simple preparation process, easy recovery of chemical solvents, and low cost, making it promising for applications in the field of sustainable functional materials.

Description

Technical Field

[0001] This invention relates to cellulose-based functional materials, specifically to a whole cellulose block material based on a three-dimensional entangled fiber network and its preparation method. Background Technology

[0002] Natural cellulose, as the most abundant natural polymer, possesses advantages such as renewability, biodegradability, and low cost, making it an important raw material for replacing petroleum-based plastics and developing sustainable functional materials. Currently, constructing all-cellulose materials using plant fibers has become a research hotspot. For example, patent CN112778578A discloses a plant plastic composed of micron-sized plant fibers, which uses low-temperature freezing treatment to bend and coil the fibers, forming a dense structure and obtaining a high-hardness, plastic-like block material. However, this type of material pursues high density and high hardness, and its dense structure lacks porosity, resulting in a lack of compressive resilience, and its stability in aqueous environments is not addressed.

[0003] Existing cellulose-based bulk materials generally suffer from the contradiction of high density resulting in a lack of resilience and porousness leading to low strength. Furthermore, most research focuses on composite materials or nanocellulose routes, which involve complex processes, high costs, and reliance on external binders or supports. In particular, achieving lightweight, high resilience, and wet stability in bulk materials without adding hydrophobic additives or nanofibers remains a pressing technical challenge in this field. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a lightweight, highly resilient, wet-state stable, additive-free, and low-cost all-cellulose block material based on a three-dimensional entangled fiber network and its preparation method, which solves the problems of existing cellulose blocks that are difficult to simultaneously achieve low density and high resilience, are prone to collapse in wet conditions, and rely on nano-processing or external binders, resulting in high costs and complex processes.

[0005] Technical solution: The all-cellulose block material based on a three-dimensional entangled fiber network described in this invention is composed of natural plant fibers, with adjacent fibers entangled and connected to form a stable porous network structure in three-dimensional space.

[0006] The recovery rate of the whole cellulose block material after mechanical compression of 50% is greater than 76%; preferably, it can reach more than 95%.

[0007] The density of the obtained whole cellulose blocks is 0.2~0.5 g·cm³. -3 The dry hardness is 30~55HD, the wet hardness is 10~35HD, the dry bending strength can reach 16.6MPa, and the dry compressive strength can reach up to 19.6MPa (50% deformation). It can be boiled in boiling water for more than 24 hours without collapsing, and it can remain stable without delamination under water impact.

[0008] The method for preparing all-cellulose block material based on a three-dimensional fiber entanglement network according to the present invention includes the following steps:

[0009] (1) Place the plant fiber in a room temperature alkaline / urea aqueous solution and stir until it becomes a paste to form a slurry. Pour the slurry into a mold and dry it under normal pressure.

[0010] (2) The molded blocks are placed in an alkaline solution for a period of time and then dried again;

[0011] (3) The block obtained in step (2) is placed in water to wash away residual chemicals and dried to obtain whole cellulose block.

[0012] Pretreatment with a room-temperature alkali / urea aqueous solution results in weaker and smoother interaction forces in the plant fibers under the alkali / urea system compared to pure water, leading to more uniform dispersion. Simultaneously, the fibers in the alkali / urea system have a higher water retention value, allowing them to "bind" a large amount of water and act as plasticizers. This ensures that the stress generated by water evaporation is evenly dispersed, reducing the probability of stress concentration during the drying process that could lead to crack initiation.

[0013] Preferably, the plant fiber can be at least one of herbaceous plant, woody plant, or vine plant fiber. The treatment temperature is room temperature, and the treatment time is 5-30 minutes.

[0014] Preferably, the plant fiber pulping method involves first mechanically treating it and then dispersing it in an alkaline / urea aqueous solution.

[0015] Preferably, the fiber solids content of the slurry is 3-10 wt%.

[0016] Preferably, the alkali in the alkali / urea aqueous solution can be one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0017] Preferably, the drying method includes various methods such as oven drying, natural drying, and freeze drying.

[0018] Preferably, step (1) involves drying to 50-80% of the initial moisture content.

[0019] Preferably, the alkali in step (2) can be one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide. More preferably, the alkali treatment is performed 1 to 5 times. Multiple treatments can make the fiber morphology more fully twisted and enhance the entanglement and linkage between fibers, thereby enabling the performance adjustment of the whole cellulose block material.

[0020] Preferably, step (2) involves drying until there is no liquid on the surface.

[0021] Preferably, step (3) involves rinsing in water until the final pH is neutral.

[0022] Preferably, the blocks cleaned in step (3) are dried to 1.2 to 1.5 times their initial plant fiber mass. Over-drying will lead to the breakdown of hydrogen bonds and a decrease in strength and wet-dry stability.

[0023] Preferably, all steps should use the same type of alkaline solution, which is beneficial for waste liquid recycling and treatment.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention induces three-dimensional entanglement of fibers through a unique room-temperature two-step alkali treatment process, and the prepared all-cellulose block material achieves lightweight (density 0.2~0.5 g·cm³) for the first time. -3 It exhibits excellent compression recovery properties (recovery rate >95% after 50% compression), does not disintegrate after boiling in water for 24 hours, and its dry and wet strength and impact toughness meet basic application requirements, showing significant application prospects in furniture, lightweight structures, and aquatic monitoring. Furthermore, the raw materials are readily available, easily degradable, and inexpensive; the operation steps are simple, reagent recovery is relatively easy, and its preparation has almost no size limitations, facilitating large-scale industrial production. Attached Figure Description

[0025] Figure 1 The whole cellulose block material prepared in Example 1.

[0026] Figure 2 The image shows a scanning electron microscope (SEM) image of the all-cellulose block material prepared in Example 1.

[0027] Figure 3 The bending strength of the all-cellulose block prepared in Example 1 is compared with that of the block in Comparative Example 1.

[0028] Figure 4 The compressive strength of the all-cellulose block prepared in Example 1 is compared with that of the block in Comparative Example 1.

[0029] Figure 5 This is a comparison of the water impact resistance of the all-cellulose block prepared in Example 1 and the block in Comparative Example 1.

[0030] Figure 6 The image shows the wetting recovery diagram of the all-cellulose block material prepared in Example 1 after mechanical compression of 50%. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings, embodiments, and comparative examples.

[0032] Example 1

[0033] Cotton cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (7wt% sodium hydroxide, 12wt% urea) and stirred until a paste was formed to form a slurry. The slurry contained 8wt% plant fiber. The resulting slurry was poured into a mold and dried in an oven (60℃, 8h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 20wt% sodium hydroxide solution for 15 minutes and then dried in an oven at 60℃ for 8h. The dried blocks were then washed in water to remove residual chemicals and dried again in an oven (60℃, 10h) until the initial plant fiber mass was 1.3 times, resulting in a whole cellulose block.

[0034] The actual image of the prepared whole cellulose block material is shown below. Figure 1 As shown, Figure 2 The scanning electron microscope (SEM) image of the surface of the all-cellulose block shows the presence of entangled cylindrical fibers. The density of the all-cellulose block is 0.25 g / cm³. 3 The dry hardness is 40HD, and the wet hardness is 25HD; the flexural strength before dry failure is 3.5MPa. A comparison of its flexural strength curve with the comparative example is shown below. Figure 3 The compressive strength at 50% deformation is 9.1 MPa. Its compressive strength curve is compared with that of the comparative example. Figure 4 .like Figure 5 As shown, its wet water impact resistance is significantly different from that of the untreated fiber block. Figure 6 This represents the 50% recovery of the compression deformation of the all-cellulose block material, with the thickness approaching 98% of the initial thickness. After recovery, the block material did not collapse.

[0035] Example 2

[0036] Cotton cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (7wt% sodium hydroxide, 12wt% urea) and stirred until a paste was formed to form a slurry. The slurry contained 9wt% plant fiber. The resulting slurry was poured into a mold and dried in an oven (60℃, 8h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in an 18wt% sodium hydroxide solution for 30 minutes and then dried in an oven at 60℃ for 8h. The dried blocks were then washed in water to remove residual chemicals and dried again in an oven (60℃, 9h) until the initial plant fiber mass was 1.4 times, resulting in whole cellulose blocks.

[0037] The density of this whole cellulose block is 0.50 g / cm³. 3 The dry hardness is 55HD, and the wet hardness is 32HD. The flexural strength before dry failure is 12.3MPa, and the compressive strength at 50% deformation is 18.3MPa. After 40% recovery from compression deformation, the thickness is close to 82% of the initial thickness, and the block material did not collapse after recovery.

[0038] Example 3

[0039] Cotton cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (7wt% sodium hydroxide, 12wt% urea) and stirred until a paste was formed to form a slurry. The slurry contained 7wt% plant fiber. The resulting slurry was poured into a mold and dried in an oven (60℃, 8h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 20wt% sodium hydroxide solution for 5 minutes and then dried in an oven at 60℃ for 8h. The dried blocks were then washed in water to remove residual chemicals and dried again in an oven (60℃, 8h) until the initial plant fiber mass was 1.5 times, resulting in whole cellulose blocks.

[0040] The density of this whole cellulose block is 0.26 g / cm³. 3 The dry hardness is 32HD, and the wet hardness is 10HD. The flexural strength before dry failure is 2.9MPa, and the compressive strength under 50% deformation is 6.6MPa. After 50% recovery of the compressive deformation, the thickness is close to 93% of the initial thickness, and the block does not collapse after recovery.

[0041] Example 4

[0042] Cotton cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (7wt% sodium hydroxide, 12wt% urea) and stirred until a paste was formed to form a slurry. The plant fiber solid content in the slurry was 7wt%. The resulting slurry was poured into a mold and dried in an oven (60℃, 8h, normal pressure) for preliminary shaping. The resulting shaped blocks were placed in a 20wt% sodium hydroxide solution for 20 minutes and then dried in an oven at 60℃ for 8h. The dried blocks were washed in water to remove residual chemicals and freeze-dried for 10h to 1.3 times the initial plant fiber mass to obtain whole cellulose blocks.

[0043] The density of this whole cellulose block is 0.31 g / cm³. 3 The dry hardness is 42HD, and the wet hardness is 29HD. The flexural strength before dry failure is 3.8MPa, and the compressive strength under 50% deformation is 9.3MPa. After 80% recovery of the compression deformation, the thickness is close to 92% of the initial thickness, and the block does not collapse after recovery.

[0044] Example 5

[0045] Rice straw cellulose fibers were placed in a mixed aqueous solution of potassium hydroxide / urea (7wt% potassium hydroxide, 12wt% urea) and stirred until a paste was formed to form a slurry with a plant fiber content of 6wt%. The resulting slurry was poured into a mold and dried in an oven (60℃, 8h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 15wt% potassium hydroxide solution for 15 minutes and then naturally dried at 25℃ for 24h. The dried blocks were then washed in water to remove residual chemicals and dried again in an oven (60℃, 10h) until the initial plant fiber mass was 1.3 times, resulting in whole cellulose blocks.

[0046] The density of this all-cellulose block is 0.22 g / cm³. 3 The dry hardness is 35HD, and the wet hardness is 21HD. The flexural strength before dry failure is 3.4MPa, and the compressive strength under 50% deformation is 7.5MPa. After 60% recovery of the compressive deformation, the thickness is close to 94% of the initial thickness, and the block does not collapse after recovery.

[0047] Example 6

[0048] Pine cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (0.5 wt% sodium hydroxide, 2 wt% urea) and stirred until a paste was formed. The plant fiber content was 3 wt%. The resulting paste was poured into a mold and dried in an oven (60°C, 8 h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 15 wt% sodium hydroxide solution for 10 minutes and dried in an oven at 60°C for 8 h. The dried blocks were then washed in water to remove residual chemicals and dried again in an oven (60°C, 8 h) until the initial plant fiber mass was 1.5 times, yielding whole cellulose blocks.

[0049] The density of this all-cellulose block is 0.20 g / cm³. 3 The dry hardness is 30HD, and the wet hardness is 14HD. The flexural strength before dry failure is 3.0MPa, and the compressive strength under 50% deformation is 6.8MPa. After 50% compression recovery, the thickness is close to 87% of the initial thickness, and no collapse occurs on the surface of the block after recovery.

[0050] Example 7

[0051] Poplar cellulose fibers were placed in a mixed aqueous solution of lithium hydroxide / urea (5 wt% lithium hydroxide, 12 wt% urea) and stirred until a paste was formed to form a slurry. The slurry contained 7 wt% plant fiber. The resulting slurry was poured into a mold and dried in an oven (60°C, 8 h, atmospheric pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 20 wt% lithium hydroxide solution for 15 minutes and then naturally dried at 25°C for 24 h. The dried blocks were then washed in water to remove residual chemicals and freeze-dried for 9 h to 1.4 times the initial plant fiber mass to obtain whole cellulose blocks.

[0052] The dry density of this whole cellulose block is 0.26 g / cm³. 3 The hardness is 38HD, and the wet hardness is 20HD. The flexural strength before dry failure is 3.1MPa, and the compressive strength under 50% deformation is 7.3MPa. After 70% recovery of the compression deformation, the thickness is close to 91% of the initial thickness, and the block does not collapse after recovery.

[0053] Example 8

[0054] Poplar cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (15wt% sodium hydroxide, 12wt% urea) and stirred until a paste was formed, with a plant fiber content of 10wt%. The resulting paste was poured into a mold and dried in an oven (60℃, 8h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 30wt% sodium hydroxide solution for 25 minutes and then dried in an oven at 60℃ for 8h. The dried blocks were then washed in water to remove residual chemicals and then naturally dried again (20℃, 24h) until the initial plant fiber mass was 1.2 times, yielding whole cellulose blocks.

[0055] The density of this whole cellulose block is 0.47 g / cm³. 3 The dry hardness is 51HD, and the wet hardness is 35HD. The flexural strength before dry failure is 16.6MPa, and the compressive strength under 50% deformation is 19.6MPa. After 60% recovery of the compressive deformation, the thickness is close to 76% of the initial thickness, and the block does not collapse after recovery.

[0056] Example 9

[0057] Ivy stem cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (10wt% sodium hydroxide, 12wt% urea) and stirred until a paste was formed, with a plant fiber content of 7wt%. The resulting paste was poured into a mold and dried in an oven (60℃, 8h, atmospheric pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 20wt% sodium hydroxide solution for 25 minutes, and then dried in an oven at 60℃ for 8h. This step was repeated twice. The dried blocks were then washed in water to remove residual chemicals and freeze-dried for 9h to 1.3 times the initial plant fiber mass to obtain whole cellulose blocks.

[0058] The density of this whole cellulose block is 0.43 g / cm³. 3 The dry hardness is 49HD, and the wet hardness is 33HD. The flexural strength before dry failure is 8.8MPa, and the compressive strength under 50% deformation is 15.1MPa. After 50% compression recovery, the thickness is close to 83% of the initial thickness, and slight cracks appear in the block after recovery.

[0059] Example 10

[0060] Ivy stem cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (7wt% sodium hydroxide, 10wt% urea) until a paste was formed, with a plant fiber content of 6wt%. The resulting paste was poured into a mold and dried in an oven (60℃, 8h, atmospheric pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 28wt% sodium hydroxide solution for 20 minutes, followed by drying in an oven at 30℃ for 12h. This step was repeated 3 times. The dried blocks were then washed in water to remove residual chemicals and freeze-dried for 10h to 1.4 times the initial plant fiber mass to obtain whole cellulose blocks.

[0061] The density of this whole cellulose block is 0.24 g / cm³. 3 The dry hardness is 39HD, and the wet hardness is 28HD. The flexural strength before dry failure is 6.5MPa, and the compressive strength under 50% deformation is 13.7MPa. After 50% compression recovery, the thickness is close to 96% of the initial thickness, and the block does not collapse after recovery.

[0062] Example 11

[0063] Cotton cellulose fibers were placed in a mixed aqueous solution of sodium hydroxide / urea (5 wt% sodium hydroxide, 12 wt% urea) and stirred until a paste was formed, with a plant fiber content of 7 wt%. The resulting paste was poured into a mold and dried in an oven (60°C, 8 h, normal pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 20 wt% sodium hydroxide solution for 15 minutes, and then dried in an oven at 70°C for 6 h. This step was repeated 3 times. The dried blocks were then washed in water to remove residual chemicals and naturally dried (20°C, 20 h) to 1.3 times the initial plant fiber mass to obtain whole cellulose blocks.

[0064] The density of this whole cellulose block is 0.44 g / cm³. 3 The dry hardness is 47HD, and the wet hardness is 31HD. The flexural strength before dry failure is 4.1MPa, and the compressive strength under 50% deformation is 9.4MPa. After 50% compression recovery, the thickness is close to 89% of the initial thickness, and the block does not collapse after recovery.

[0065] Example 12

[0066] Hemp cellulose fibers were placed in a mixed aqueous solution of lithium hydroxide / urea (7wt% lithium hydroxide, 12wt% urea) and stirred until a paste was formed to form a slurry with a plant fiber content of 7wt%. The resulting slurry was poured into a mold and dried in an oven (60℃, 8h, atmospheric pressure) for preliminary shaping. The resulting shaped blocks were then treated in a 22wt% lithium hydroxide solution for 15 minutes, dried in an oven at 60℃ for 8h, and then dried again after replacing the chemical solution with water for 3 hours (60℃, 6h). This step was repeated 4 times. The dried blocks were then washed in water to remove residual chemicals and freeze-dried for 12h to 1.2 times the initial plant fiber mass to obtain whole cellulose blocks.

[0067] The density of this whole cellulose block is 0.46 g / cm³. 3 The dry hardness is 50HD, and the wet hardness is 34HD. The flexural strength before dry failure is 5.7MPa, and the compressive strength under 50% deformation is 15.6MPa. After 50% compression recovery, the thickness is close to 82% of the initial thickness, and the block does not collapse after recovery.

[0068] Comparison Sample 1

[0069] Everything else was the same as in Example 1, except that the alkaline treatment in step (2) was not performed. The density of the resulting control sample fiber block was 0.2 g / cm³. 3 The dry hardness is 5-10 HD, and the wet hardness is 0 HD. The obtained comparative sample block has a flexural strength of 0.44 MPa and a compressive strength of 0.54 MPa (50% deformation) before dry failure. The corresponding strength curves are shown in the figure. Figures 3-4Its collapses under water impact conditions ( Figure 5 Example 1 did not collapse. After 50% compression and recovery, its thickness was close to 85% of the initial thickness, and the block did not collapse after recovery.

Claims

1. A whole cellulose block material based on a three-dimensional fiber entanglement network, characterized in that, The all-cellulose block material is composed of natural plant fibers, with adjacent fibers entangled and interconnected, forming a stable porous network structure in three-dimensional space; the all-cellulose block material has a recovery rate of more than 76% after 50% mechanical compression; the density of the all-cellulose block material is 0.2~0.5 g·cm³. -3 The dry hardness is 30~55HD, the wet hardness is 10~35HD, the dry flexural strength is 2.9~16.6MPa, the dry compressive strength at 50% deformation is 6.6~19.6MPa, it does not collapse after being boiled in boiling water for more than 24 hours, and it remains stable without delamination under water impact. The whole cellulose block is prepared by a method including the following steps: (1) plant fiber is placed in an alkaline / urea aqueous solution and stirred until it becomes a paste to form a slurry and poured into a mold and dried under normal pressure; (2) the shaped block obtained in step (1) is placed in an alkaline solution for treatment and dried again; (3) the block obtained in step (2) is placed in water to wash away residual chemical substances and dried to obtain the whole cellulose block. The alkali in the alkali / urea aqueous solution mentioned in step (1) is at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide, and the mass concentration of both alkali and urea is 0.5~15wt%. The alkaline solution mentioned in step (2) is at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide.

2. A method for preparing the all-cellulose block material according to claim 1, characterized in that, Includes the following steps: (1) Place the plant fiber in an alkaline / urea aqueous solution and stir until it becomes a paste to form a slurry. Pour the slurry into a mold and dry it under normal pressure. (2) The shaped block obtained in step (1) is placed in an alkaline solution for treatment and then dried again; (3) The block obtained in step (2) is placed in water to wash away residual chemicals and dried to obtain whole cellulose block.

3. The preparation method according to claim 2, characterized in that, The plant fiber mentioned in step (1) is at least one of herbaceous plant, woody plant, and vine plant fiber.

4. The preparation method according to claim 2, characterized in that, The fiber solids content of the pulp obtained in step (1) is 3~10wt%.

5. The preparation method according to claim 2, characterized in that, The concentration of the alkaline solution in step (2) is 15~30wt%, and the treatment time is 5~30 minutes.

6. The preparation method according to claim 2, characterized in that, After cleaning in step (3), the blocks are dried until the final block weight is 1.2 to 1.5 times the weight of the plant fiber used in step (1).

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