NL2030477B1

NL2030477B1 - Underwater Elastic Cellulose Aerogel and Preparation Method and Application Thereof

Info

Publication number: NL2030477B1
Application number: NL2030477A
Authority: NL
Inventors: Wang Meng; Li Yong; Sun Peipei; Pang Huaipeng; Liu Guoran
Original assignee: Advanced Mat Institute Shandong Academy Of Sciences
Priority date: 2021-02-25
Filing date: 2022-01-08
Publication date: 2023-05-19
Also published as: NL2030477A; CN112898625A; CN112898625B

Abstract

The invention belongs to the field of cellulose aerogel preparation, and specifically provides 5 an underwater elastic cellulose aerogel, a preparation method and application thereof. The underwater elastic cellulose aerogel is cross - linked by nano cellulose and long - chain polymer. The preparation method includes the following steps: 1) dispersing nano cellulose raw materials in water, and processing by chemical oxidation and mechanical homogenization to obtain nano cellulose dispersion; 2) adding long - chain polymer, crosslinking agent and catalyst into the nano 10 cellulose dispersion in step 1), heating and stirring the mixed solution for a period of time to form a uniform dispersion, cooling the uniform dispersion, and freeze - drying in a mould to obtain an intermediate; and 3) placing the intermediate in an oven to react for a period of time to obtain the product. This disclosure solves the problem that cellulose aerogel is easily dispersed in water in the prior art, which limits the application of cellulose aerogel.

Description

Underwater Elastic Cellulose Aerogel and Preparation Method and Application Thereof

TECHNICAL FIELD

The invention belongs to the field of cellulose aerogel preparation, and specifically provides an underwater elastic cellulose aerogel, a preparation method and application thereof.

BACKGROUND

The descriptions here only provide background information related to the present disclosure rather than necessarily constitute this technique. Aerogel is a new material with continuous porous network structure, which has the advantages of high porosity, low thermal conductivity, large specific surface area and low density, and has very high potential application value in the fields of adsorption, heat insulation, catalysis and energy storage. Aerogels can be divided into organic aerogels, inorganic aerogels, carbon aerogels and hybrid aerogels according to their composition. Organic aerogel is a kind of aerogel with nanoporous network structure, which is prepared by sol - gel method and supercritical drying method with resorcinol/formaldehyde as precursor. Inorganic aerogels are mainly silica aerogels. Carbon aerogels is obtained by pyrolysis of organic aerogel as precursor in inert gas, which not only has the advantages of porosity of organic aerogel, but also has high conductivity.

Cellulose is one of the most abundant renewable polymers in nature, which has many advantages such as wide source, low cost as well as degradation, etc., and has attracted extensive attention at home and abroad. Cellulose aerogel prepared from cellulose as precursor is an important branch of cellulose application field. Cellulose aerogel is usually prepared by dissolving or dispersing cellulose to obtain homogeneous solution or dispersion of cellulose, and then freeze - drying or supercritical drying the solution to obtain flexible porous aerogel materials. In the prior art, the cellulose solution is added into an acidic solution to replace the cellulose solution after several times of freezing and thawing cycles, and the light high - strength cellulose aerogel is obtained by drying. In the prior art, a modified cellulose suspension is obtained by adding a modifier to cellulose for chemical modification, then dispersing the modified cellulose suspension in an organic solvent, forming a modified cellulose gel through moulding and drying, and finally preparing the multifunctional cellulose elastic aerogel through heat treatment of the modified cellulose gel.

In addition, it is found that the elasticity and strength of cellulose aerogel mainly come from the hydrogen bonds between cellulose chains. When cellulose aerogel is immersed in water, water molecules easily form hydrogen bonds with cellulose, which destroys the hydrogen bonds between the original fibres, resulting in the cellulose aerogel being easily dispersed in water, greatly limiting the application of cellulose aerogel.

SUMMARY

Aiming at the problem that cellulose aerogel is easily dispersed in water in the prior art, which limits the application of cellulose aerogel, the present disclosure provides a cellulose aerogel which can recover normally under water and a preparation method thereof.

In one or some embodiments of the present disclosure, an underwater elastic cellulose aerogel is provided, which is formed by crosslinking nano cellulose and long - chain polymer.

In one or some embodiments of the present disclosure, a preparation method of underwater elastic cellulose aerogel is provided, which includes the following steps: 1) dispersing nano cellulose raw materials in water, and obtaining nano cellulose dispersion liquid through chemical oxidation and mechanical homogenization treatment; 2) adding long - chain polymer, crosslinking agent and catalyst into the nano cellulose dispersion in step 1), heating and stirring the mixed solution to form a uniform dispersion, cooling the uniform dispersion, and freeze - drying the dispersion in a mould to obtain an intermediate; and 3) placing the intermediate in an oven to react for a period of time to obtain the product.

In one or some embodiments of the disclosure, the application of the underwater elastic cellulose aerogel or the preparation method of the underwater elastic cellulose aerogel in underwater stress recover is provided.

In one or some embodiments of the present disclosure, the application of the underwater elastic cellulose aerogel or the preparation method of the underwater elastic cellulose aerogel in underwater adsorption is provided.

In one or some embodiments of the disclosure, the application of the underwater elastic cellulose aerogel or the preparation method of the underwater elastic cellulose aerogel in wound haemostasis is provided.

One or some of the above technical solutions have the following advantages or beneficial effects: 1) the present disclosure compounded cellulose and polymer, and successfully prepared underwater super - elastic cellulose aerogel by adding crosslinking agent and catalyst to promote esterification and crosslinking reaction, effectively solving the problems of easy dispersion and poor elasticity of cellulose aerogel under water in the prior art, and broadening the application fields of cellulose aerogel, especially in the fields of underwater adsorption, haemostatic wound dressing and the like; and 2) the preparation process of aerogel in this disclosure does not need a complicated sol - gelation, which is relatively simple, easy to implement and operate. Besides, aerogel can be different size and shape without limited by raw materials, and thus can be prepared, processed or cut as required.

BRIEF DESCRIPTION OF THE FIGURES

The figures of the specification, which form a part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and the descriptions thereof are used to explain this disclosure rather than restrict this disclosure.

FIG. 1 is a scanning electron microscope image of cellulose aerogels of Comparative

Embodiment 2 and Embodiment 3, in which a is Embodiment 2 and b is Embodiment 3.

FIG. 2 is a compressed recover photograph of cellulose aerogel prepared in Embodiment 3 in air and under water.

FIG. 3 is the stress - strain curve of aerogel prepared in Embodiment 3 under water.

FIG. 4 is the stress - strain curve of aerogel prepared in Embodiment 3 under 50% strain for 100 cycles.

DESCRIPTION OF THE INVENTION

There will be clear and complete descriptions of the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure rather than all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in this field without making creative work are within the scope of this disclosure.

Preferably, the nano cellulose is one or a mixture of several kinds of softwood pulp board, hardwood pulp board and cotton; softwood pulp board is preferred; or, the long - chain polymer is one or a mixture of several of polyethylene glycol (PEG), polyvinyl alcohol (PVA), starch, polylactic acid (PLA) and carboxymethyl cellulose (CMC); polyethylene glycol or polyvinyl alcohol or a mixture of both is preferred.

In one or some embodiments of the present disclosure, a preparation method of underwater elastic cellulose aerogel is provided, which include the following steps: 1) dispersing nano cellulose raw materials in water, and processing by chemical oxidation and mechanical homogenization to obtain nano cellulose dispersion liquid; 2) adding long - chain polymer, crosslinking agent and catalyst into the nano cellulose dispersion in step 1), heating and stirring the mixed solution to form a uniform dispersion, cooling the uniform dispersion, and freeze - drying in a mould to obtain an intermediate; and 3) placing the intermediate in an oven to react for a period of time to obtain the product.

Preferably, in step 1), the mass fraction of cellulose dispersion is 0.1 - 1 wt%; or, in step 1), the ratio of cellulose to long - chain polymer is 1-5: 1-2;

preferably, the ratio of cellulose to long - chain polymer is 1- 1:1 - 2.

Preferably, in step 2}, the mixed solution is heated and stirred at 50 - 100°C; or, in step 2), the stirring time is 1-3 h; or, in step 3), the oven temperature is 40 - 80°C; 50°C is preferred; or, in step 3), the reaction time is 1 - 3 h; 2 h is preferred.

Preferably, the chemical oxidation and mechanical homogenization are TEMPO oxidation and high - pressure homogenization.

Preferably, the chemical oxidation and mechanical homogenization includes the following steps: oxidizing it by TEMPO oxidation system, heating up and reacting for a period of time under alkaline condition, and then preparing nano cellulose suspension by high - pressure homogenization method; further preferably, the reaction temperature is 20 - 30°C; further preferably, the reaction time is 3 - 8 h; further preferably, the reaction pH is 9 - 11; further, the TEMPO oxidation system is NaBr, TEMPO and NaCIO.

Preferably, the nano cellulose raw material is one or a mixture of several kinds of softwood pulp board, hardwood pulp board and cotton; softwood pulp board is preferred; or, the long - chain polymer is one or more of polyethylene glycol (PEG), polyvinyl alcohol (PVA), starch, polylactic acid (PLA) and carboxymethyl cellulose (CMC); polyethylene glycol or polyvinyl alcohol or their mixture is preferred.

In one or some embodiment of that present disclosure, a method for preparing an underwater elastic cellulose aerogel is provided, which includes the following steps: 1) dispersing a nano cellulose raw material in water, and carrying out treatment through chemical oxidation and mechanical homogenization to obtain a nano cellulose dispersion liquid; 2) adding a long chain high molecular polymer, a crosslinking agent and a catalyst into the nano cellulose dispersion liquid in the step 1), heating and stirring the mixed liquid for a period of time to form a uniform dispersion liquid, cooling the uniform dispersion liquid and then placing the uniform dispersion liquid in a mould for freeze - drying to obtain an intermediate; and 3) placing the intermediate in an oven for reaction for a period of time to obtain the product.

Preferably, in step 1), the mass fraction of cellulose dispersion is 0.1 - 1 wt%; or, in step 1), the ratio of cellulose to long - chain polymer is 1-5: 1-2; preferably, the ratio of cellulose to long - chain polymer is 1- 1:1 - 2.

Preferably, in step 2), the mixed solution is heated and stirred at 50 - 100°C; or, in step 2), the stirring time is 1 -3 h; or, in step 3), the oven temperature is 40 - 80°C; 50°C is preferred; or, in step 3), the reaction time is 1 - 3 h; 2 his preferred.

Preferably, the chemical oxidation and mechanical homogenization are TEMPO oxidation and high pressure homogenization; preferably, the chemical oxidation and mechanical homogenization include the following steps: oxidizing it by TEMPO oxidation system, heating up and reacting for a period of time under alkaline condition, and then preparing nano cellulose suspension by high - pressure homogenization method.

Further preferably, the reaction temperature is 20 - 30°C; 5 further preferably, the reaction time is 3 - 8 h; further preferably, the reaction pH is 9 - 11; further, the TEMPO oxidation system is NaBr, TEMPO and NaCIO.

Preferably, the nano cellulose raw material is one or a mixture of several kinds of softwood pulp board, hardwood pulp board and cotton; softwood pulp board is preferred; or, the long - chain polymer is one or more of polyethylene glycol (PEG), polyvinyl alcohol (PVA), starch, polylactic acid (PLA) and carboxymethyl cellulose (CMC); polyethylene glycol or polyvinyl alcohol or their mixture is preferred; or, the crosslinking agent is one or a mixture of tannic acid, citric acid and boric acid; citric acid is preferred, or, the catalyst is one or a mixture of several of phosphoric acid, nitric acid and hydrochloric acid; phosphoric acid is preferred.

In one or some embodiments of the disclosure, an application of the underwater elastic cellulose aerogel or a preparation method of the underwater elastic cellulose aerogel in underwater stress recover is provided.

In one or some embodiments of the present disclosure, an application of the underwater elastic cellulose aerogel or a preparation method of the underwater elastic cellulose aerogel in underwater adsorption is provided.

In one or some embodiments of the disclosure, an application of the underwater elastic cellulose aerogel or a preparation method of the underwater elastic cellulose aerogel in wound haemostasis is provided.

Embodiment 1

This embodiment provides a preparation method of underwater elastic cellulose aerogel, which includes the following steps: weigh 1 g of cotton and put it in a blender, add 50 ml of deionized water, pour the solution into a 250 ml beaker after evenly dispersing; add 40 ml of deionized water, 0.016 g TEMPO oxidant and 0.1 g of NaBr and stir them evenly, then slowly add 10 mmol NaCIO solution, stir and react the mixture for 5 hours at 25°C, and adjust the pH value of the reaction system to about 10 with 0.5 mol /l NaOH solution during the reaction. After the reaction, filter the mixture with a sand funnel, and adjust with a large amount of deionized water to neutrality to obtain

TEMPO oxidized cellulose. 1 wt% oxidized cellulose suspension is prepared, homogenized for 10 times in a high - pressure homogenizer under 100 MPa pressure, and then the concentration of oxidized cellulose suspension is adjusted to 0.5 wt%.

Add 1.2 g of citric acid and 1.2 ml of phosphoric acid into 100 ml of nano - cellulose suspension (0. 5 wt®%)}, stir the solution well, and then pour into a mould, freeze the sample in liquid nitrogen, freeze - dry for 48 h to obtain white cellulose aerogel; finally cross - link the white cellulose aerogel in 50°C oven for 2 h to obtain aerogel.

The test results show that the aerogel prepared in this embodiment can't form enough ester bonds due to the lack of high molecular polymer, which leads to that the cellulose aerogel is crushed and cannot recover after being compressed for 10 times under water with 50% stress.

Embodiment 2

The embodiment provides a preparation method of underwater elastic cellulose aerogel, which includes the following steps:

Weigh 1 g of softwood wood pulp board (Yinying Paper, content of a cellulose > 90%), put it in a stirrer, add 50 ml of deionized water, pour it into a 250 ml beaker after evenly dispersing; add 40 ml of deionized water, 0.016 g of TEMPO oxidant and 0.1 g of NaBr, and stir them evenly, then slowly add 10 mmol NaClO solution, stir and react the mixture for 5 hours at 25°C; during the reaction, 0.5 mol l NaOH solution is used to adjust the pH value of the reaction system to about 10. After the reaction, filter the mixture with a sand funnel, and adjust with a large amount of deionized water to neutrality to obtain TEMPO oxidized cellulose. 1 wt% oxidized cellulose suspension is prepared, homogenized for 10 times in a high - pressure homogenizer under 100 MPa pressure, and then the concentration of oxidized cellulose suspension is adjusted to 0.5 wt%.

A certain amount of PEG is added into 100 ml nano - cellulose suspension, in order to make the mass ratio of PEG to cellulose be 1:1, heat and stir the mixture at 95°C for 2 h until it is dissolved; then 1.2 g of citric acid and 1.2 ml of phosphoric acid are added and stirred evenly, then pour the solution into a mould, the sample is frozen in liquid nitrogen, freeze - dry for 48 h to obtain white cellulose aerogel, and then crosslink in 50°C oven for 2 h to obtain aerogel.

The test results show that hydrogen bonds are formed between cellulose, PEG and citric acid in the cellulose aerogel prepared in this embodiment; therefore, the cellulose aerogel can still recover to its original shape after being compressed for 10 times under water with 50% stress, and the recovery time is more than 5 s.

As shown in FIG. 1, the aerogel prepared in this embodiment is porous and has large surface and fine appearance.

Embodiment 3

This embodiment provides a preparation method of underwater elastic cellulose aerogel, which includes the following steps:

Weigh 1 g of softwood wood pulp board (Yinying Paper Company, content of a cellulose > 90%) and put it in a stirrer, add 50 ml of deionized water, pour it into a 250 ml beaker after evenly dispersing; add 40 ml of deionized water, 0.016 g of TEMPO oxidant and 0.1 g of sodium bromide and stir them evenly, then slowly add 10 mmol NaCIO solution, stir and react the mixture for 5 h at 25°C, and adjust the reaction process with 0.5 mol /I NaOH solution. After the reaction, filter the mixture with a sand funnel, and adjust with a large amount of deionized water to neutrality to obtain TEMPO oxidized cellulose. 1 wt% oxidized cellulose suspension is prepared, homogenized for 10 times in a high - pressure homogenizer under 100 MPa pressure, and then the concentration of oxidized cellulose suspension is adjusted to 0. 5 wt%.

A certain amount of PVA (type 1788) is added into 100 ml of nano - cellulose suspension, in order to make the mass ratio of PVA to cellulose be 1:1; and heat and stir the mixture at 95°C for 2 h until it is dissolved. Add 1.2 g of CsHsO: and 1.2 ml of HsPO,, stir them well, then pour the solution into a mould, freeze the sample in liquid nitrogen, freeze - dry it for 48 h to obtain white cellulose aerogel, and then cross - link it in 50°C oven for 2 h to obtain aerogel.

Heating promotes the formulation of ester bond between cellulose, PVA and citric acid.

After testing, the aerogel prepared in this embodiment can recover to its original state after 80% stress compression under water, and the recovery time is less than 3s; after being compressed for 100 times under 50% stress, it can still return to its original shape, and the hysteresis loop area is small.

As shown in FIG. 1, the aerogel prepared in this embodiment is porous, with abundant surface area and good appearance.

As shown FIG. 2, the aerogel prepared in this embodiment has good compression recover effect in air and under water, and is suitable for underwater adsorption, haemostatic wound dressing, etc.

FIG. 3 is the underwater stress - strain curve of the aerogel prepared in this embodiment.

From the curve, the aerogel prepared in this embodiment has good underwater stress.

FIG. 4 is the stress - strain curve of the aerogel prepared in this embodiment for 100 cycles at 50% strain. From the curve, the aerogel prepared in this embodiment has good cycling performance and durability.

Embodiment 4

Weigh 1 g of softwood wood pulp board (Yinying Paper Company, content of a cellulose > 90%) and put it in a stirrer, add 50 ml of deionized water, pour the solution into a 250 ml beaker after evenly dispersing, add 40 ml of deionized water, 0.016 g of TEMPO oxidant and 0.1 g of sodium bromide and stir them evenly, then slowly add 10 mmol NaCIO solution, stir and react the mixture for 5 h at 25°C, and adjust with 0.5 mol /I NaOH solution during the reaction. After the reaction, filter the mixture with a sand funnel, and adjust with a large amount of deionized water to neutrality to obtain TEMPO oxidized cellulose. 1 wt% oxidized cellulose suspension is prepared, homogenized for 10 times in a high - pressure homogenizer under 100 MPa pressure, and then the concentration of oxidized cellulose suspension is adjusted to 0. 5 wt%.

A certain amount of PVA (type 1788) is added into 100 ml of nano - cellulose suspension, in order to make the mass ratio of PVA to cellulose be 2:1, and the mixture is heated and stirred at 95°C for 2 h until it is dissolved; then add 1.2 g of citric acid and 1.2 ml of phosphoric acid, stir well, then pour them into a mould, freeze the sample in liquid nitrogen, freeze - dry it for 48 h to obtain white cellulose aerogel, and then cross - link it in 50°C oven for 2 h to obtain aerogel.

The test results show that with the increase of PVA content, the cellulose aerogel prepared in this embodiment gradually hardens, and can't recover to its original shape after underwater compression.

Embodiment 5

Weigh 1 g of softwood wood pulp board (Yinying Paper, a cellulose > 90%), pour it into a 250 ml beaker, add 40 ml of deionized water, 0.016 g TEMPO oxidant and 0.1 g of sodium bromide, and stir them evenly; then slowly add 10 mmol NaCIO solution, stir and react the mixture for 5 hours at 25°C, and adjust the pH value of the reaction system to about 10 with 0.5 mol /l NaOH solution during the reaction. After the reaction, filter the mixture with a sand funnel, and adjust with a large amount of deionized water to neutrality to obtain TEMPO oxidized cellulose. 1 wt% oxidized cellulose suspension is prepared, homogenized for 10 times in a high - pressure homogenizer under 100 MPa pressure, and then the concentration of oxidized cellulose suspension is adjusted to 0. 5 wt%.

A certain amount of PVA (type 1788) is added into 100 ml of nano - cellulose suspension, in order to make the mass ratio of PVA to cellulose be 1:1, stirred and dissolved at 95°C for 2 h, then 1.2 g of CeHsO7 and 1.2 ml of HsPO, are added, stirred evenly, freeze - dry for 48 h, and then nano - cellulose aerogel is obtained without heating.

The test results show that the ester bond between cellulose and PVA and citric acid molecules cannot be formed due to unheated, so the aerogel cellulose aerogel prepared in this embodiment has poor elasticity under water, and the recovery time is more than 10s when compressed by 50% stress under water.

With reference to Embodiments 1 - 5, only the underwater elastic cellulose aerogels prepared in Embodiment 2 and Embodiment 3 have short compression recovery time and good underwater elasticity. Obviously, the underwater elasticity can be satisfied only by the cooperation of all steps in this disclosure.

What has been disclosed above are only the preferred embodiments of this disclosure, and of course it cannot be used to limit the scope of rights of this disclosure.

Therefore, equivalent changes made according to the scope of patent application of this disclosure still fall within the scope of this disclosure.

Claims

CONCLUSIONS

An underwater elastic cellulose airgel characterized in that the underwater elastic cellulose airgel is formed by crosslinking nanocellulose and long chain polymer.

The underwater elastic cellulose airgel according to claim 1, characterized in that the nanocellulose is selected from various types of wood pulp - soft board, wood pulp - hard board and cotton; in that the long chain polymer is selected from polyethylene glycol (PEG), polyvinyl alcohol (PVA), starch, polylactic acid (PLA) and carboxymethyl cellulose (CMC).

A method for preparing underwater elastic cellulose airgel according to claim 1, comprising the following steps: - dispersing nanocellulose raw materials in water, and processing by chemical oxidation and mechanical homogenization to obtain a liquid nanocellulose dispersion; — adding long-chain polymer, cross-linking agent and a catalyst to the nanocellulose dispersion of step 1), heating and stirring the mixed solution to obtain a uniform dispersion, cooling the uniform dispersion, and freeze-drying in a mold to obtain an intermediate product ; — placing the intermediate in an oven to react for some time to obtain the product.

The method for preparing underwater elastic cellulose airgel according to claim 3, wherein the mass fraction of cellulose dispersion is 0.1 - 1 wt%; the ratio of cellulose to long chain polymer is 1-5:1-2; and the ratio of cellulose to long chain polymer is 1-1:1-2.

The method for preparing underwater elastic cellulose airgel according to claim 3, wherein in step 2) the mixed solution is heated and stirred at 50-100°C; the stirring time is 1-3 hours; the oven temperature is 40-80°C; and the reaction time 1 - 3 hours. is

The method for preparing underwater elastic cellulose airgel according to claim 3, wherein: - the chemical oxidation and the mechanical homogenization are TEMPO oxidation and high pressure homogenization; — the chemical oxidation and mechanical homogenization includes the following steps:

— oxidizing it by the TEMPO oxidation system, heating it up and reacting it for a while under alkaline conditions; wherein the TEMPO oxidation system contains NaBr, TEMPO and NaClO; wherein the reaction temperature is 20-30°C, the reaction time is 3-8 hours, and the pH of the reaction is 9-11; wherein the nanocellulose suspension is then prepared by a method of high pressure homogenization.

The method for preparing underwater elastic cellulose airgel according to claim 3, wherein - the nanocellulose raw material is selected from various kinds of wood pulp - soft board, wood pulp - hard board and cotton; - the long-chain polymer is selected from polyethylene glycol (PEG), polyvinyl alcohol (PVA), starch and polylactic acid (PLA); - the cross-linking agent is selected from tannic acid and citric acid; and - the catalyst is selected from phosphoric acid, nitric acid and hydrochloric acid.

Use of the underwater elastic cellulose airgel according to claim 1 or 2 or of a method for preparing underwater elastic cellulose airgel according to any one of claims 3 to 7 for providing underwater stress recovery.

Use of the underwater elastic cellulose airgel according to claim 1 or 2 or of a method for preparing underwater elastic cellulose airgel according to any one of claims 3 to 7 for providing underwater adsorption.

Use of the underwater elastic cellulose airgel according to claim 1 or 2 or of a method for preparing underwater elastic cellulose airgel according to any one of claims 3 to 7 in wound hemostasis.