Preparation method of chemical crosslinking high-strength cellulose material and product of chemical crosslinking high-strength cellulose material

Abstract

The invention provides a preparation method of a chemical crosslinking high-strength cellulose material and a product thereof, the preparation method is as follows: cellulose fibers, ionic liquid and an aldehyde group crosslinking agent are mixed, and the ionic liquid can dissolve the fibers to expose more hydroxyls in cellulose molecules; meanwhile, the ionic liquid can be used as a catalyst to promote aldolization of aldehyde groups of aldehyde group molecules and hydroxyl groups of cellulose molecules to form strong chemical action bonds among the cellulose molecules, so that the interaction degree among the cellulose molecules is greatly improved, and finally, a high-strength cellulose material is prepared. The preparation process is simple, the raw materials are wide in source, and the prepared chemical crosslinking cellulose material is high in strength and wide in application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of green natural high-performance polymer materials, and particularly relates to a preparation method of a chemically crosslinked high-strength cellulose material and a product thereof.

Background Art

[0002] Cellulose, as a natural polymer with rich resources and renewable, is a biopolymer widely used in the field of materials. Due to its biodegradability, biocompatibility, low cost, renewability and mechanical properties, it is a good substitute for petroleum-based polymers, which has important and far-reaching significance for energy conservation and the achievement of low-carbon goals. Cellulose ion gel is a new material that combines the properties of a cellulose matrix and an ionic liquid. However, the formation of most cellulose ion gels mainly relies on weak physical interactions (mainly hydrogen bonding between cellulose molecules and between cellulose and ionic liquid), which limits the mechanical strength of cellulose ion gels and further restricts their practical applications under high loading conditions.

[0003] Chemical crosslinking connects molecular chains through covalent bonds to construct a molecular crosslinking network, which can significantly improve the mechanical properties of gel materials. The abundant hydroxyl groups in cellulose provide ideal active sites for chemical crosslinking modification, enabling the formation of a stable covalent bond network between cellulose molecules, regulating the microstructure of ion gels, and thus significantly improving the strength and toughness of cellulose ion gels. By adjusting factors such as the type, concentration and crosslinking time of crosslinking agents, and the density of crosslinking points, the mechanical strength of the gel can be precisely controlled. A higher crosslinking density can significantly increase the elastic modulus and tensile strength of the gel because the crosslinking points enhance the binding force between molecular chains and reduce the slippage or fracture of polymer chain segments. In addition, the uniformity of the crosslinking network also has an important impact on strength. Uniformly distributed crosslinking points help prevent local stress concentration and improve the overall mechanical properties of gel materials. In recent years, a series of important progress has been made in chemically crosslinked cellulose gels. For example, by introducing glutaraldehyde, epoxides and isocyanates to form permanent chemical bonds, the tensile strength and toughness of gel materials are significantly enhanced, enabling them to maintain a stable shape under high-stress environments;

[0004] By introducing dynamic covalent bonds (such as hydrazone bonds, thiol-ene bonds), it can not only improve the mechanical strength of the gel but also endow it with certain flexibility and self-healing ability; combining rigid networks and flexible networks, optimizing the distribution of crosslinking points, and constructing a stable and uniform crosslinking network enable the gel to have both high strength and high toughness, increasing the anti-deformation ability of the gel under tensile, compression, and shear conditions, avoiding the generation and propagation of cracks, and being applicable to impact-resistant application scenarios. For example, cellulose gels with a high crosslinking density show higher energy absorption ability during the stretching process.

[0005] During the chemical crosslinking process, adding a catalyst or initiator can effectively increase the rate of chemical reactions and improve the properties of gel materials. However, these additives also bring some drawbacks. For example, uneven distribution of the catalyst leads to insufficient or excessive local crosslinking reactions, affecting mechanical properties and functionality; the externally added catalyst or initiator makes it difficult to precisely control the reaction rate during the crosslinking reaction. If the reaction rate is too fast, it will cause uneven internal stress in the gel material, generating bubbles or by-products, which affect the chemical stability or biocompatibility of the material. Additionally, highly efficient catalysts or initiators are costly and may require special storage and handling conditions, especially increasing the manufacturing cost of the material. Particularly during large-scale production processes, it leads to an increase in the overall production cost of the gel material.

Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method and product of a chemically crosslinked high-strength cellulose material. This preparation method does not require additional catalysts, has low costs, a simple process, and the prepared cellulose ion gel has a high tensile strength. Moreover, the raw materials are environmentally friendly, renewable, and degradable, and do not cause pressure on the environment.

[0007] The present invention is implemented as follows:

[0008] A preparation method of a chemically crosslinked high-strength cellulose material, characterized by comprising the following steps:

[0009] (1) Add cellulose fibers to an ionic liquid and dissolve to prepare a cellulose solution; the dosage of the cellulose fibers is 1-6 wt% of the ionic liquid;

[0010] (2) Add an aldehyde crosslinking agent to the cellulose solution and stir to obtain a crosslinked cellulose mixed solution; the dosage of the aldehyde crosslinking agent is 10-70% wt of the cellulose fibers;

[0011] (3) Pour the mixed solution into a mold to prepare a chemically crosslinked high-strength cellulose ion gel at room temperature.

[0012] Further, the ionic liquid in step (1) is one of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium acetate.

[0013] Further, the dissolution time of the cellulose fibers in step (1) is 0.5 h to 2 h.

[0014] Further, the crosslinking agents in step (2) are one of acetaldehyde, glyoxal, glutaraldehyde, and dialdehyde polyethyleneglycol.

[0015] Further, the room temperature forming time of the mixed solution in step (3) is 1 h to 4 h.

[0016] Furthermore, a cellulose material prepared from the described chemically cross-linked high-strength cellulose material.

[0017] The present invention has the following advantages:

[0018] The present invention selects natural polymer material cellulose fiber widely distributed in nature as the matrix of the ion gel, and by introducing ionic liquid and aldehyde cross-linking agent, without adding a catalyst, uses the proton hydrogen of the ionic liquid to catalyze the cross-linking reaction between the reactive sites of cellulose hydroxyl groups and the aldehyde groups of the aldehyde cross-linking agent to construct a stable chemical cross-linking network, and prepares a high-strength chemically cross-linked cellulose material; it has the following advantages:

[0019] (1) The present invention uses renewable, degradable and resource-rich cellulose fiber as the solid matrix, which is of great significance for promoting the high-value application of cellulose.

[0020] (2) The high-strength chemically cross-linked cellulose constructs a stable cross-linking network through a simple chemical cross-linking process, effectively improving the strength of the cellulose material.

[0021] (3) The high-strength chemically cross-linked cellulose material can be finally prepared by a simple physical method, without adding an additional catalyst, with simple operation, laying a foundation for large-scale industrial production.

Specific Embodiments

[0022] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention. For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be purchased commercially.

[0023] Example 1:

[0024] (1) Add 6% (relative to the mass of the ionic liquid) cellulose fiber to the ionic liquid 1-allyl-3-methylimidazolium chloride, dissolve to prepare a cellulose solution. Add 70% wt (relative to the amount of cellulose used) glutaraldehyde cross-linking agent to the cellulose solution, stir to prepare a cross-linked cellulose mixed solution. Pour the mixed solution into a mold, defoam, and let it stand at room temperature for 4 h to prepare a chemically cross-linked high-strength cellulose material. Use a tensile machine to test the tensile properties of the material, take 10 points for testing, and the tensile strength is 10.82 ± 1.2 MPa, and the toughness is 2.8 ± 0.2 MJ / m 3 .

[0025] Control Example 1:

[0026] (1) 6% (relative to the mass of the ionic liquid) of cellulose fibers was added to water, but the cellulose could not dissolve, and no cellulose solution was prepared.

[0027] Comparative Example 2:

[0028] (1) 6% (relative to the mass of the ionic liquid) of cellulose fibers was added to the ionic liquid 1-allyl-3-methylimidazolium chloride and dissolved to prepare a cellulose solution. The mixed solution was poured into a mold, degassed, and left standing at room temperature for 4 h to prepare a chemically crosslinked high-strength cellulose material. The tensile properties of the material were tested using a tensile machine, and 10 points were tested. The tensile strength was 0.86 ± 0.09 MPa, and the toughness was 0.48 ± 0.07 MJ / m 3 。

[0029] Example 2:

[0030] (1) 1% (relative to the mass of the ionic liquid) of cellulose fibers was added to the ionic liquid 1-butyl-3-methylimidazolium chloride and dissolved to prepare a cellulose solution. 50% wt (relative to the amount of cellulose used) of an acetaldehyde crosslinking agent was added to the cellulose solution and stirred to prepare a crosslinked cellulose mixed solution. The mixed solution was poured into a mold, degassed, and left standing at room temperature for 3 h to prepare a chemically crosslinked high-strength cellulose material. The tensile properties of the material were tested using a tensile machine, and 10 points were tested. The tensile strength was 5.11 ± 0.7 MPa, and the toughness was 1.25 ± 0.03 MJ / m 3 。

[0031] Example 3:

[0032] (1) 2% (relative to the mass of the ionic liquid) of cellulose fibers was added to the ionic liquid 1-ethyl-3-methylimidazolium acetate and dissolved to prepare a cellulose solution. 30% wt (relative to the amount of cellulose used) of a dialdehyde polyethylene glycol crosslinking agent was added to the cellulose solution and stirred to prepare a crosslinked cellulose mixed solution. The mixed solution was poured into a mold, degassed, and left standing at room temperature for 2 h to prepare a chemically crosslinked high-strength cellulose material. The tensile properties of the material were tested using a tensile machine, and 10 points were tested. The tensile strength was 3.35 ± 0.1 MPa, and the toughness was 0.82 ± 0.04 MJ / m 3 。

[0033] Example 4:

[0034] (1) Add 4% (relative to the mass of the ionic liquid) cellulose fibers to the ionic liquid 1-allyl-3-methylimidazolium chloride and dissolve to obtain a cellulose solution. Add 10% wt (relative to the amount of cellulose used) glutaraldehyde crosslinking agent to the cellulose solution and stir to obtain a crosslinked cellulose mixed solution. Pour the mixed solution into a mold, defoam, and let it stand at room temperature for 1 h to prepare a chemically crosslinked high-strength cellulose material. Use a tensile testing machine to test the tensile properties of the material. Take 10 points for testing, and the tensile strength is 2.21 ± 0.02 MPa, and the toughness is 0.51 ± 0.002 MJ / m 3 .

[0035] Example 5:

[0036] (1) Add 6% (relative to the mass of the ionic liquid) cellulose fibers to the ionic liquid 1-allyl-3-methylimidazolium chloride and dissolve to obtain a cellulose solution. Add 50% wt (relative to the amount of cellulose used) glutaraldehyde crosslinking agent to the cellulose solution and stir to obtain a crosslinked cellulose mixed solution. Pour the mixed solution into a mold, defoam, and let it stand at room temperature for 4 h to prepare a chemically crosslinked high-strength cellulose material. Use a tensile testing machine to test the tensile properties of the material. Take 10 points for testing, and the tensile strength is 6.75 ± 0.03 MPa, and the toughness is 1.5 ± 0.07 MJ / m 3 .

[0037] Example 6:

[0038] (1) Add 6% (relative to the mass of the ionic liquid) cellulose fibers to the ionic liquid 1-allyl-3-methylimidazolium chloride and dissolve to obtain a cellulose solution. Add 30% wt (relative to the amount of cellulose used) glutaraldehyde crosslinking agent to the cellulose solution and stir to obtain a crosslinked cellulose mixed solution. Pour the mixed solution into a mold, defoam, and let it stand at room temperature for 4 h to prepare a chemically crosslinked high-strength cellulose material. Use a tensile testing machine to test the tensile properties of the material. Take 10 points for testing, and the tensile strength is 4.78 ± 0.1 MPa, and the toughness is 0.98 ± 0.05 MJ / m 3 .

[0039] Example 7:

[0040] (1) Add 6% (relative to the mass of the ionic liquid) cellulose fibers to the ionic liquid 1-allyl-3-methylimidazolium chloride and dissolve to obtain a cellulose solution. Add 10% wt (relative to the amount of cellulose used) glutaraldehyde crosslinking agent to the cellulose solution and stir to obtain a crosslinked cellulose mixed solution. Pour the mixed solution into a mold, defoam, and let it stand at room temperature for 4 h to prepare a chemically crosslinked high-strength cellulose material. Use a tensile testing machine to test the tensile properties of the material. Take 10 points for testing, and the tensile strength is 3.31 ± 0.03 MPa, and the toughness is 0.71 ± 0.008 MJ / m 3 .

[0041] In summary, in the present invention, cellulose fibers, ionic liquids, and aldehyde-based crosslinking agents are mixed. The ionic liquid can dissolve the fibers to expose more hydroxyl groups of cellulose molecules; the ionic liquid can act as a catalyst to promote the acetal reaction between the aldehyde groups of aldehyde molecules and the hydroxyl groups of cellulose molecules, forming strong chemical bonds between cellulose molecules, greatly improving the degree of interaction between cellulose molecules, and finally preparing a high-strength cellulose material.

[0042] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that the specific embodiments we described are illustrative rather than used to limit the scope of the present invention. Equivalent modifications and changes made by those skilled in the art in accordance with the spirit of the present invention should be covered by the scope protected by the claims of the present invention.

Claims

1. A method for preparing a chemically cross-linked high-strength cellulose material, characterized in that: It includes the following steps: (1) Add cellulose fibers to ionic liquid and dissolve to prepare a cellulose solution; the dosage of the cellulose fibers is 1-6 wt% of the ionic liquid; (2) Add an aldehyde crosslinking agent to the cellulose solution and stir to obtain a crosslinked cellulose mixed solution; the dosage of the aldehyde crosslinking agent is 10-70 wt% of the cellulose fibers; (3) Pour the mixed solution into a mold to prepare a chemically crosslinked high-strength cellulose material at room temperature.

2. The method according to claim 1, wherein: The ionic liquid in step (1) is one of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium acetate.

3. The method according to claim 1, wherein: The dissolution time of the cellulose fibers in step (1) is 0.5 h to 2 h.

4. The method according to claim 1, wherein: The crosslinking agents in step (2) are one of acetaldehyde, glyoxal, glutaraldehyde, and dialdehyde poly(ethylene glycol).

5. The method according to claim 1, wherein: The room temperature forming time of the mixed solution in step (3) is 1 h to 4 h.

6. A cellulose material prepared from the chemically crosslinked high-strength cellulose material according to any one of claims 1-5.