阅读说明：本技术 一种石墨烯-纳米纤维素导电纸及其制备方法 (Graphene-nanocellulose conductive paper and preparation method thereof ) 是由 胡健 李海龙 陈俊君 于 2019-11-14 设计创作，主要内容包括：本发明提供一种石墨烯-纳米纤维素导电纸的制备方法及其制备的导电纸。所述制备方法包括以下步骤：将氧化石墨烯与纳米纤维素在水体系下均匀混合,使氧化石墨烯和纳米纤维素在水中的总质量浓度为0.5‰～2‰,调节pH＝3～10,在水热条件下反应,然后将反应后的产物进行分散,抽滤,干燥,即得；所述水热条件为：反应温度120℃～200℃,反应时间1h～15h；所述纳米纤维由木浆纤维经TEMPO/NaBr/NaClO氧化法制备。本发明的制备方法绿色、低成本、工艺简单、高效,制备得到的自支撑导电纸表面光滑平整、力学性能优良、电导率高、方阻低。(The invention provides a preparation method of graphene-nano cellulose conductive paper and the conductive paper prepared by the same. The preparation method comprises the following steps: uniformly mixing graphene oxide and nanocellulose in a water system, enabling the total mass concentration of the graphene oxide and the nanocellulose in water to be 0.5-2 per mill, adjusting the pH value to be 3-10, reacting under a hydrothermal condition, and then dispersing, filtering and drying a product after reaction to obtain the graphene oxide nano-cellulose nano-; the hydrothermal conditions are as follows: the reaction temperature is 120-200 ℃, and the reaction time is 1-15 h; the nano-fiber is prepared from wood pulp fiber by a TEMPO/NaBr/NaClO oxidation method. The preparation method disclosed by the invention is green, low in cost, simple in process and high in efficiency, and the prepared self-supporting conductive paper is smooth and flat in surface, excellent in mechanical property, high in conductivity and low in sheet resistance.)

1. A preparation method of graphene-nanocellulose conductive paper comprises the following steps:

uniformly mixing graphene oxide and nanocellulose in a water system, enabling the total mass concentration of the graphene oxide and the nanocellulose in water to be 0.5-2 per mill, adjusting the pH value to be 3-10, reacting under a hydrothermal condition, dispersing a product after reaction, performing suction filtration, and drying to obtain the graphene oxide nanocellulose.

2. The preparation method according to claim 1, wherein the oven dry mass ratio of the graphene oxide to the nanocellulose is 1: 0.7-1: 5;

preferably, the oven dry mass ratio of the graphene oxide to the nano-cellulose is 1: 0.7-1.1.

3. The production method according to claim 1 or 2, wherein the graphene oxide is a solid or a dispersion liquid.

4. The method of claim 1, wherein the hydrothermal conditions are: the reaction temperature is 120-200 ℃, and the reaction time is 1-15 h;

preferably, the hydrothermal reaction conditions are: the reaction temperature is 160-170 ℃, and the reaction time is 2-4 h.

5. The method according to claim 1, wherein the drying is natural air drying.

6. The method according to claim 1, wherein the product after the reaction is dispersed in water by one or both of a mechanical dispersion method and an ultrasonic dispersion method.

7. The method according to claim 1, wherein the nanocellulose is cellulose obtained by one or more of chemical, mechanical and biological treatment;

preferably, the chemical process is selected from the group consisting of a TEMPO oxidation process or an acid hydrolysis process;

preferably, the mechanical process is selected from the group consisting of a milling process or a high pressure homogenization process;

more preferably, the nano-cellulose is prepared by treating cellulose by a TEMPO oxidation method and a mechanical method;

preferably, the cellulose is from bleached hardwood pulp fibers or bleached softwood pulp fibers.

8. The method according to claim 7, wherein the nanocellulose is prepared by:

adding water into bleached hardwood pulp fibers or bleached softwood pulp fibers, stirring, then adding 0.1g/g of oven-dried NaBr, 0.015g/g of oven-dried TEMPO and 5-7 mmol/g of oven-dried NaClO into the suspension, adjusting the total mass percentage concentration of the reaction pulp to be 0.8-1%, adjusting the pH to 9.8-10, and reacting at room temperature; adjusting the pH value of the system to 9.8-10 by NaOH every 2-3 minutes in the reaction process, and finishing the oxidation reaction when the pH value of the reaction system is stabilized at 9.8-10 and is unchanged for more than 30 min; directly homogenizing the reacted mixed system for 4-10 times under high pressure of 80-100 bar to obtain the product;

preferably, the nanocellulose is prepared by the following method:

adding water into bleached hardwood pulp fibers or bleached softwood pulp fibers, stirring, then adding 0.1g/g of oven-dried pulp NaBr, 0.015g/g of oven-dried pulp TEMPO and 6mmol/g of oven-dried pulp NaClO into the suspension, adjusting the total mass percentage concentration of the reaction pulp to be 0.9%, adjusting the pH value to 9.8-10, and reacting at room temperature; adjusting the pH value of the system to 9.8-10 by NaOH every 2-3 minutes in the reaction process, and finishing the oxidation reaction when the pH value of the reaction system is stabilized at 9.8-10 and is unchanged for more than 30 min; and (3) directly homogenizing the reacted mixed system for 7-8 times at high pressure of 88-92 bar to obtain the product.

9. An electrically conductive paper produced by the production method according to any one of claims 1 to 8;

preferably, the conductive paper has a basis weight of 35 to 50g/m²And the thickness is 0.01-0.06 mm.

10. Use of the conductive paper of claim 9 or the conductive paper prepared by the preparation method of any one of claims 1 to 8 in an electromagnetic shielding material or an antistatic material.

Technical Field

The invention belongs to the technical field of papermaking, and particularly relates to flexible conductive paper.

Background

With the development of wearable and portable electronic devices, the research of flexible conductive materials with light weight, thinness and self-support has been more and more focused.

The raw material of the flexible conductive material comprises a matrix material and a conductive material. Graphene-nanocellulose conductive paper is a common flexible conductive material at present, wherein graphene is a conductive material, and nanofibers are a matrix and a reinforcing material.

The cellulose is widely applied to the matrix material of the flexible conductive material due to the advantages of natural degradability, low price, easy obtaining, environmental friendliness, large specific surface area and the like. The nano-cellulose (also called as cellulose nano-fiber) has the characteristics of high crystallinity, high strength, high specific surface area and the like, and also has the characteristics of light weight, biocompatibility and degradability, so that the nano-cellulose is of new interest as a matrix material in the field of preparing novel composite materials (including flexible conductive paper). Common methods for preparing nano-cellulose include mechanical methods, chemical methods, biological treatment methods and the like. However, since the nanocellulose has a large specific surface area and a large number of hydroxyl groups on the surface, it is difficult to disperse in an organic solvent. In addition, it is highly hydrophilic, and this hydrophilic tendency limits its use in composite materials. In order to improve its dispersibility in organic solvents, it is generally subjected to modification and surface activation. In recent years, researchers have found TEMPO (2,2,6, 6-tertramethylpiperadin-1-oxy, 2,2,6, 6-tetramethylpiperidine-1-oxyl)/NaBr/NaClO or TEMPO/NaClO₂The system can selectively oxidize cellulose primary alcohol hydroxyl in aqueous solution, thereby introducing negative charges such as carboxyl, aldehyde group and the like on the surface of the microfiber without changing fiber morphology and crystallinity, and leading the suspension to be more stable; and homogenizing the oxidized cellulose to obtain the TEMPO oxidized nano-cellulose. TEMPO oxidation reaction conditions are mild, operation is simple, cost is low, pollution is small, energy consumption in the preparation process of the nano-fiber is low, yield is high, and the obtained nano-fiber has the advantages of large length-diameter ratio and stable dispersion without aggregation in water (progress of preparation and application research of the TEMPO oxidized cellulose nano-fiber [ J]Material engineering. year 8, month 2015, volume 43, phase 8: 84-91). The invention patent application of publication No. CN109162141A (published 2019, 1, 8) discloses a nano conductive paper, a preparation method thereof and a capacitor, and discloses a nano conductive paper containing nano cellulose and electric conductionThe preparation method of the nano conductive paper of the material comprises the following steps of oxidizing and homogenizing broad-leaved wood pulp, eucalyptus wood pulp or softwood pulp by a TEMPO/NaBr/NaClO system to obtain the nano conductive paper; and uniformly mixing the nano-cellulose and the conductive material, carrying out vacuum filtration to obtain a nano-conductive film, then soaking the nano-conductive film in a mixed aqueous solution of choline chloride and urea, taking out and drying to obtain the nano-conductive paper.

Common conductive materials include nano silver wires, poly 3, 4-ethylenedioxythiophene, polystyrene sulfonate, graphene, carbon nanotubes, nanopowders of conductive metals, and the like. Graphene is the best material in the known substances at room temperature, and is widely applied to flexible conductive materials due to high electron mobility and high conductivity. As a two-dimensional sheet material with high specific surface area, the hydrophobicity of graphene and van der waals force existing between sheets enable the graphene to easily agglomerate, and uneven dispersion is caused; and the surface inertness of graphene makes it difficult to complex with other materials. Graphene Oxide (GO) can be well dispersed in water due to its large amount of oxygen-containing functional groups (e.g., hydrophilic groups such as hydroxyl, epoxy, carbonyl, and carboxyl groups), and thus can be sufficiently mixed with a matrix material (e.g., nanocellulose). However, the conductivity of graphene in an oxidized state is inferior to that in a reduced state, and therefore, after graphene oxide is mixed or compositely formed with a matrix material, graphene oxide needs to be reduced. The invention patent application of publication No. CN1077002628A (published 2018, 2, 16) discloses a high-conductivity conductive paper and a preparation method thereof, and the preparation method of the conductive paper comprises the following steps: obtaining surface-activated refined wood pulp fiber filaments by ultrasonic treatment and biological fermentation of wood pulp fibers, coating the wood pulp fibers with oxidized graphene by ultrasonic treatment, carrying out hydrothermal reduction (120-125 ℃ for 3-4 h) on glucose to obtain graphene-nano wood pulp fiber composite filaments, and finally mixing with resin for pulping and papermaking to obtain the high-conductivity conductive paper. The method comprises the steps of heating glucose water to reduce oxidized graphene; and the final formation of the conductive paper requires additional addition of resin as a binder. Also disclosed in patent application publication No. CN10184855A (published 2019, 8, 30) of "a breathable and water-washable composite flexible conductive paper, and a preparation method and an application thereof", the preparation method of the disclosed conductive paper is as follows: carrying out thermal reduction on cellulose paper with graphene oxide uniformly dispersed in fibers; the specific operation of the thermal reduction is as follows: 1) cutting the graphene oxide-cellulose composite paper into rectangles of 1-2 cm multiplied by 2-3 cm, and then sequentially spreading and clamping the rectangles between two glass sheets according to the interval of 0.5-1.5 cm; 2) placing the two glass sheets filled with the graphene oxide-cellulose composite paper in a tube furnace, heating to 200-400 ℃ at a speed of 4-8 ℃/min in an oxygen-isolated environment, preserving heat for 1.5-2.5 h, and cooling. The method for reducing the graphene oxide needs to add a reducing agent or is complex to operate, needs special equipment and is high in energy consumption.

Therefore, there is a need for improvement of the existing method to provide a green, low-cost, simple-process, and efficient method for preparing graphene-nanocellulose conductive paper.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a preparation method of graphene-nano cellulose conductive paper and the conductive paper prepared by the method. The preparation method disclosed by the invention is green, low in cost, simple in process and high in efficiency, and the prepared self-supporting conductive paper is smooth and flat in surface, excellent in mechanical property, high in conductivity and low in sheet resistance.

In order to realize the technical effects of the invention, the invention adopts the following technical scheme:

a preparation method of graphene-nanocellulose conductive paper comprises the following steps:

uniformly mixing graphene oxide and nanocellulose in a water system, enabling the total mass concentration of the graphene oxide and the nanocellulose in water to be 0.5-2 per mill, adjusting the pH value to be 3-10, reacting under a hydrothermal condition, dispersing a product after reaction, performing suction filtration, and drying to obtain the graphene oxide nanocellulose.

Preferably, the oven dry mass ratio of the graphene oxide to the nano-cellulose is 1: 0.7-1: 5.

More preferably, the oven dry mass ratio of the graphene oxide to the nano-cellulose is 1: 0.7-1.1.

Preferably, the graphene oxide may be a solid or a dispersion liquid.

Preferably, the hydrothermal conditions are: the reaction temperature is 120-200 ℃, and the reaction time is 1-15 h.

More preferably, the hydrothermal reaction conditions are: the reaction temperature is 160-170 ℃, and the reaction time is 2-4 h.

Preferably, the drying is natural air drying.

Preferably, the product after the reaction is dispersed in water by one or both of a mechanical dispersion method and an ultrasonic dispersion method.

Preferably, the nanocellulose is cellulose prepared by one or more of chemical, mechanical and biological processes.

Preferably, the chemical process is selected from the group consisting of a TEMPO oxidation process or an acid hydrolysis process.

Preferably, the mechanical process is selected from a milling process or a high pressure homogenization process.

More preferably, the nanocellulose is cellulose prepared by TEMPO oxidation and mechanical treatment.

Preferably, the cellulose is from bleached hardwood pulp fibers or bleached softwood pulp fibers.

As a preferred scheme, the nano-cellulose is prepared by the following method:

adding water into bleached hardwood pulp fibers or bleached softwood pulp fibers, stirring, then adding 0.1g/g of oven-dried NaBr, 0.015g/g of oven-dried TEMPO and 5-7 mmol/g of oven-dried NaClO into the suspension, adjusting the total mass percentage concentration of the reaction pulp to be 0.8-1%, adjusting the pH to 9.8-10, and reacting at room temperature; adjusting the pH value of the system to 9.8-10 by NaOH every 2-3 minutes in the reaction process, and finishing the oxidation reaction when the pH value of the reaction system is stabilized at 9.8-10 and is unchanged for more than 30 min; and (3) directly homogenizing the mixed system after the reaction for 4-10 times at high pressure of 80-100 bar to obtain the product.

As a more preferable scheme, the nanocellulose is prepared by the following method:

adding water into bleached hardwood pulp fibers or bleached softwood pulp fibers, stirring, then adding 0.1g/g of oven-dried pulp NaBr, 0.015g/g of oven-dried pulp TEMPO and 6mmol/g of oven-dried pulp NaClO into the suspension, adjusting the total mass percentage concentration of the reaction pulp to be 0.9%, adjusting the pH value to 9.8-10, and reacting at room temperature; adjusting the pH value of the system to 9.8-10 by NaOH every 2-3 minutes in the reaction process, and finishing the oxidation reaction when the pH value of the reaction system is stabilized at 9.8-10 and is unchanged for more than 30 min; and (3) directly homogenizing the reacted mixed system for 7-8 times at high pressure of 88-92 bar to obtain the product.

Still another object of the present invention is to provide a conductive paper prepared by the above preparation method.

Preferably, the conductive paper has a basis weight of 35 to 50g/m²And the thickness is 0.01-0.06 mm.

In addition, the invention also provides application of the conductive paper in electromagnetic shielding materials or antistatic materials.

In this specification, if not specifically stated, the "water" is deionized water, distilled water, reverse osmosis water, or the like subjected to purification treatment.

According to the invention, the nanocellulose is degraded in the hydrothermal process to generate glycosyl groups such as glucose and the like to reduce graphene oxide, and the undegraded nanocellulose with high crystallinity is used as a reinforcing phase of the reduced composite paper, so that the paper is endowed with good flexibility and high strength, and the self-support of the conductive paper is realized. Therefore, the reduction of the oxidized graphene can be realized without adding a reducing agent or performing an additional reduction reaction.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the preparation method is simple, has low requirements on equipment and instruments, and is suitable for industrial production. The hydrothermal reduction reaction of the nano-cellulose and the graphene oxide can be carried out in common reaction equipment with a heating device without isolating air.

(2) The preparation process of the conductive paper does not need to add any binder, surfactant and reducing agent, and is green and pollution-free.

(3) The graphene-nano cellulose conductive paper prepared by the method has a smooth and flat surface, the maximum tensile stress is more than 3000MPa, the conductivity is more than 500S/m, and the sheet resistance is less than 60 omega/sq.

Drawings

The invention will be further described with reference to the accompanying drawings.

Fig. 1 is a photograph of a real object of the graphene-nanocellulose conductive paper prepared in example 2.

Fig. 2 is a photograph of the graphene-nanocellulose conductive paper prepared in example 2 bent 180 °.

Fig. 3 is an SEM image (magnification 15000 times) of the surface of the graphene-nanocellulose e-paper prepared in example 2.

Detailed Description

The invention is illustrated below with reference to specific examples. It will be understood by those skilled in the art that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention in any way.

The experimental procedures in the following examples are conventional unless otherwise specified. The raw materials and reagent materials used in the following examples are all commercially available products unless otherwise specified. Wherein, the purchase conditions of partial reagents and raw materials are as follows:

and (3) graphene oxide: an aqueous solution with the mass percent concentration of 0.5 percent; beijing carbon century science and technology Co., Ltd, specification model number CCTGO-203.

The water used in the examples below was deionized water.