CN110607714A - A conductive heating food wrapping paper based on graphene/modified carbon nanotube/oxidized nanocellulose and its preparation method - Google Patents

Abstract

The invention relates to a conductive heating food wrapping paper based on graphene/modified carbon nanotube/oxidized nanocellulose and a preparation method thereof, belonging to the field of food wrapping paper in the papermaking industry. The conductive heating food wrapping paper of the present invention comprises packaging base paper, a conductive heating layer and a PLA coating layer stacked sequentially from bottom to top, wherein the conductive heating layer is made of graphene/modified carbon nanotubes/oxidized nanocellulose Made of conductive heating paint, the thickness of the conductive heating layer is 10-50μm, the resistance of the conductive heating layer is 50-500Ω, and the area of the conductive heating layer is 100-200cm ² . The surface of the modified carbon nanotube has more carboxyl groups, and the problem of poor dispersion of the carbon nanotube itself can be well improved through the modification. In addition, the food wrapping paper prepared by the invention can be energized by a 24v power supply to realize rapid heat preservation and heating of food, thereby ensuring food safety.

Description

A conductive heating based on graphene/modified carbon nanotubes/oxidized nanocellulose Food wrapping paper and preparation method thereof

technical field

The invention belongs to the field of food wrapping paper in the papermaking industry, in particular to a conductive heating food wrapping paper based on graphene/modified carbon nanotube/oxidized nanocellulose and a preparation method thereof.

Background technique

With the accelerated pace of life, irregular and unhealthy diet is a common problem for modern people. Although the development of the food delivery industry has solved the catering problem to a certain extent, due to the lack of supervision, health and safety issues also affect people's health. At present, the self-heating food packaging paper or container reported in the existing literature mainly realizes the heating of food through the chemical reaction of the attached heating pack. There are certain unsafe factors in the process, which may cause unexpected danger.

The working principle of conductive heating food packaging paper is mainly to prepare coatings with suitable physical properties such as resistance, and to further make a conductive heating coating layer on the food packaging base paper, and to convert electric energy into heat energy by electrifying the heating layer, and the temperature of the heating layer reaches Suitable temperature for heating food. The preparation of conductive heating food packaging paper mainly needs the following two core issues: 1) the development and preparation of conductive coatings, and the final prepared conductive heating layer is tightly combined with the base paper, with good adhesion and easy control of resistance; 2) The conductive heating layer is prepared by coating, and the appropriate coating process is confirmed in combination with the performance of the conductive coating.

For heating food, the most ideal state is that the heating temperature is maintained at around 90°C, which can keep the food in a good heating state. In addition, the heating rate of the wrapping paper directly affects the heating efficiency. The heating rate of conductive heating food wrapping paper after power-on and whether the final temperature is maintained at 90°C are the two main technical indicators to measure the heating performance. However, in the current related research, there are no relevant solutions reported in the literature.

Based on the above reasons, this application is proposed.

Contents of the invention

Aiming at the problems existing in the prior art, the object of the present invention is to provide a conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose and a preparation method thereof. The present invention mainly controls the coating composition, coating thickness, wrapping paper size, power supply voltage, etc., develops a feasible technology for regulating and controlling the temperature rise performance of conductive heating food wrapping paper, and establishes a systematic guiding scheme, which can prepare 80- The constant-temperature conductive heating layer with any target temperature within the range of 100°C, and the performance of high-efficiency heating, provide good conditions for heating food. In addition, graphene, oxidized nanocellulose and paper-based materials have good adhesion properties through hydrogen bonds and π-π bonds, and the conductive heating food packaging paper thus prepared can be used for Food heating.

In order to realize above-mentioned first object of the present invention, the technical scheme that the present invention adopts is as follows:

A conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose, comprising packaging base paper, a conductive heating layer and a PLA coating layer stacked sequentially from bottom to top, wherein the conductive heating layer is It is made of graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating, and the thickness of the conductive heating layer is 10-50 μm.

Further, in the above technical solution, the weight of the wrapping paper is 40-100g/m ² .

Further, in the above technical solution, the resistance of the conductive heating layer is 50-500Ω, and the area of the conductive heating layer is 100-200cm ² .

Further, in the above technical solution, the thickness of the PLA coating layer is 10-30 μm.

Further, in the above technical solution, the packaging base paper is refined after mixing mixed wood pulp, AKD and cationic starch in a mass ratio of 1:0.01-0.03:0.01-0.04, and the refining concentration is controlled to 4-6%. It is 60-70°SR, and then it is made by fourdrinier paper machine.

Further, in the above technical scheme, the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating is composed of multilayer graphene, 9-anthracene formic acid modified carbon nanotube, dry oxidized nanocellulose (ToCN) and water, wherein: the mass ratio of the multilayer graphene, 9-anthracenecarboxylic acid modified carbon nanotubes, dry oxidized nanocellulose and water is 1:0.05-0.2:0.025-0.1:1-10.

Furthermore, in the above technical solution, the solid content of the conductive heating paint is preferably 20-50%.

Further, in the above technical scheme, the 9-anthracenecarboxylic acid modified carbon nanotubes are prepared by the following method: dissolving 9-anthracenecarboxylic acid in absolute ethanol according to the proportion to obtain an ethanol solution of 9-anthracenecarboxylic acid, and then dissolving the carbon The nanotubes are added into the ethanol solution of 9-anthracenecarboxylic acid, uniformly dispersed by ultrasonic at room temperature, and filtered to obtain non-covalent bond modified carbon nanotubes, that is, 9-anthracenecarboxylic acid modified carbon nanotubes.

Specifically, in the above technical solution, the normal temperature refers to natural room temperature conditions in four seasons, without additional cooling or heating treatment, and the normal temperature is generally controlled at 10-30°C, preferably 15-25°C.

Preferably, in the above technical solution, in the 9-anthracenecarboxylic acid ethanol solution, the concentration of 9-anthracenecarboxylic acid is 2-20g/L.

Preferably, in the above technical solution, the mass ratio of the carbon nanotubes to 9-anthracenecarboxylic acid is 1:2-20.

Preferably, in the above technical solution, the ultrasonic dispersion time is 20-40min.

The above-mentioned 9-anthracenecarboxylic acid modified carbon nanotubes in the present invention are specifically non-covalent bond modified carbon nanotubes. The above-mentioned modification mechanism is as follows: 9-anthracenecarboxylic acid is adsorbed on the surface of carbon nanotubes through π-π bonds, and the carboxyl group can make the modified carbon nanotubes have better dispersibility in the coating system.

Furthermore, in the above technical solution, the oxidized nanocellulose (ToCN) is made from cotton pulp by Tempo method.

The above-mentioned graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating of the present invention is obtained by the following method: multilayer graphene, 9-anthracene formic acid modified carbon nanotube, dry oxidized nanocellulose and Water is mixed according to the mass ratio of 1:0.05-0.2:0.025-0.1:1-10, and after ultrasonic dispersion, continue to stir evenly to obtain the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating .

Preferably, in the above technical solution, the stirring time is 30-60min.

The second object of the present invention is to provide the preparation method of the above-mentioned conductive heating food packaging paper based on graphene/modified carbon nanotubes/oxidized nanocellulose, specifically coating graphene/modified carbon nanotubes on the packaging base paper. The carbon nanotube/oxidized nanocellulose conductive heating coating is further coated with PLA after drying, dried, and finally cut to obtain the conductive heating food wrapping paper.

Preferably, in the above technical solution, the coating method is rod coating.

Each raw material component effect that the present invention adopts is as follows:

Graphene is the main component of conductive coatings, and its specific gravity determines the resistance of the conductive coating, which in turn affects the temperature rise performance of conductive heating food packaging paper; as the bonding force between pure graphene as a coating and paper is not ideal, this paper The invention uses oxidized nanocellulose as a binder. On the one hand, graphene can form a coating on paper. On the other hand, the specific gravity of oxidized nanocellulose can adjust the viscosity of the coating, making the coating performance easier to control; The function of the tube is to build more connection points between the graphene sheets, improve the overall electrical performance of the coating, and then improve the heating performance of the coating.

Compared with the prior art, the present invention relates to a conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose and its preparation method has the following beneficial effects:

(1) The oxidized nanocellulose and the paper substrate used in the present invention are all made of natural degradable plant fiber raw materials. Compared with the organic polymer film, this product has less pollution to the environment.

(2) The conductive coating prepared by the present invention can adjust the viscosity of the coating through the addition of oxidized nanocellulose; and through the combination with the papermaking process, the processing technology of the product is mature and the cost is low; the coating prepared by the rod coating process Stable layer thickness, easy to produce wrapping paper with stable conductivity, and high production efficiency.

(3) The present invention has carried out 9-anthracene carboxylic acid modification to carbon nanotube, and this method is non-covalent bond modification method, has the advantage of high efficiency, low cost, and the carbon nanotube surface after modification has more carboxyl groups , the problem of poor dispersion of carbon nanotubes can be well improved by modification; modified carbon nanotubes, multi-layer graphene, and oxidized nanocellulose (containing more carboxyl groups) can form conductive coatings with excellent dispersibility. It is also beneficial to the improvement and control of the electrical conductivity of the product.

(4) the graphene that the present invention uses, oxidized nanocellulose and paper-based material three have good adhesion performance, and further carry out PLA coating treatment, and this PLA layer can play the purpose of water-proof and oil-proof, simultaneously It acts as a barrier between the food and the conductive paint, so that the food does not contact the conductive paint. The conductive heating food wrapping paper prepared in this way can be used for heating food under the condition of energization, and has no harm to food.

(5) The food packaging paper prepared by the present invention can be energized by a 24v power supply to realize rapid heat preservation and heating of food, and can ensure food safety and improve eating efficiency. It has great practical value and avoids potential hazards such as fires caused by lighting and heating.

Description of drawings

Figure 1 is a process flow chart for preparing conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose.

Fig. 2 is a mathematical model diagram of the relationship between the heating performance of the conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose of the present invention, the wrapping paper resistance and the size of the wrapping paper.

Fig. 3 is a schematic structural view of a four-edge-sealed package with different easy-tear line designs based on graphene/modified carbon nanotubes/oxidized nanocellulose conductive heating food wrapping paper according to the present invention.

Detailed ways

The present invention will be described in further detail below through examples of implementation. This implementation case is carried out on the premise of the technology of the present invention, and the detailed implementation and specific operation process are given to illustrate the inventiveness of the present invention, but the protection scope of the present invention is not limited to the following implementation cases.

From the information contained herein, various changes in the precise description of the invention will readily become apparent to those skilled in the art without departing from the spirit and scope of the appended claims. It should be understood that the scope of the present invention is not limited to the processes, properties or components defined, since these embodiments, as well as other descriptions, are only intended to illustrate certain aspects of the invention. In fact, various changes to the embodiments of the present invention that can be obviously made by those skilled in the art or related fields fall within the scope of the appended claims.

In order to better understand the present invention but not to limit the scope of the present invention, all figures representing dosage, percentage, and other numerical values used in this application should be understood as being modified by the word "about" in all cases. Accordingly, unless expressly indicated otherwise, the numerical parameters set forth in the specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At a minimum, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

The heating speed and the final maximum temperature of the conductive heating food wrapping paper of the present invention are mainly affected by the resistance of the heating layer. The smaller the resistance, the faster the temperature rise and the higher the maximum temperature that can be achieved. Coating thickness is one of the main factors affecting coating resistance, the greater the thickness, the lower the resistance. The present invention intends to control the thickness of the coating at 10-50 μm. If the thickness is too small, the temperature cannot meet the requirements, and if the thickness is too high, it will affect the softness and production cost.

The present invention mainly controls the coating composition, coating thickness, wrapping paper size, power supply voltage, etc., develops a feasible technology for regulating and controlling the temperature rise performance of conductive heating food wrapping paper, and establishes a systematic guiding scheme, which can prepare 80- The constant-temperature conductive heating layer with any target temperature within the range of 100°C has the performance of high-efficiency heating and provides good conditions for heating food.

The technical scheme for regulating the heating performance of the present invention: the resistance of the conductive heating layer is the best at 50Ω～500Ω, if the heating rate is too high, the heating rate will be slow, and the temperature cannot meet the requirements; if the heating rate is too low, the paper will burn; The cut wrapping paper should not be too large, 100-200cm ² and a square shape is the best; in order to improve the heating efficiency, the time to heat up to the ideal temperature should be as short as possible, which can be adjusted by reducing the aspect ratio and increasing the coating thickness . In addition, the following regulatory mathematical model (as shown in Figure 2) was obtained through a large amount of experimental data, where R is the resistance of the wrapping paper after cutting, A is the size of the wrapping paper, and ΔT is the difference between the maximum constant temperature and the initial temperature. Through this model, the resistance of the coating can be calculated by determining the size of the wrapping paper and the final desired temperature, and then the coating formula and coating process can be adjusted according to the resistance, so that the ideal formula and process can be determined efficiently .

The use of conductive heating food wrapping paper: electrodes can be installed on the conductive heating layer to make the electrodes fully contact with the conductive heating layer, so that the conductive heating layer can be connected to the external power supply through wires and electrodes. In addition, the conductive heating layer can also be connected to an external power source through other methods well known to those skilled in the art. The external power supply can be a mobile power supply or a battery pack, and the conductive heating layer can be energized and heated. The voltage of the mobile power supply can be 12v or 24v.

In actual use, the conductive heating food wrapping paper is packaged with four edges (as shown in Figure 3), and a scribing machine is used to make easy-to-tear lines on the edges. After tearing, the paper itself can be used as a wire, fixed Electric heating can be realized at the positive and negative poles of mobile power supply or battery pack. The two different easy-tear wire designs on the left and right of Figure 3 can achieve different lengths of paper-based wires, which are convenient for specific applications. In addition, if the power supply itself is equipped with alligator clips, it is enough to directly heat the two ends of the wrapping paper diagonally.

In order to ensure food safety, in the present invention, the base paper is coated with conductive paint, and then coated with PLA. The PLA coating can serve the purpose of water and oil repellency, and at the same time, it acts as a barrier between the food and the paint, so that the food and the paint do not come into contact.

In order to ensure the use performance, the weight of the wrapping paper should be controlled at 40-100g/m ² , and the thickness of the PLA coating should be controlled at 10-30μm.

The heating performance of the conductive heating food wrapping paper of the present invention will be illustrated below through specific examples.

It should be further explained that 12v and 24v are commonly used outdoor power supply voltages, and the present invention can achieve ideal heating performance when used with 24v power supply voltage.

Example 1

A kind of conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose of the present embodiment includes packaging base paper, conductive heating layer and PLA coating layer stacked sequentially from bottom to top, wherein: the The weight of the wrapping paper is 40g/m ² , the resistance of the conductive heating layer is 58.1Ω, the area of the conductive heating layer is 200cm ² , the thickness of the conductive heating layer is 10 μm, and the thickness of the PLA coating layer is 10 μm; the conductive heating layer The layer is made of graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating; the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating has a solid content of 25%, which is determined by mass ratio The composition is 1:0.05:0.025:3.2 multilayer graphene, 9-anthracenecarboxylic acid modified carbon nanotubes, dry oxidized nanocellulose and water.

The specific preparation method of the conductive heating food wrapping paper described above in this embodiment is as follows:

(1) Preparation of packaging base paper

Mix the mixed wood pulp, AKD and cationic starch at a mass ratio of 1:0.025:0.02, and then use a fourdrinier paper machine to make food packaging base paper; wherein: the mixed wood pulp is made of softwood wood pulp with a mass ratio of 1:3 It is mixed with hardwood pulp and refined to form pulp, the refining concentration is controlled at 6%, and the beating degree is controlled at 65°SR.

(2) Preparation of conductive heating layer

(a) Prepare 100 mL of cotton pulp suspension with a mass concentration of 1%, add 0.1 g of sodium bromide and 0.02 g of tempo (2,2,6,6-tetramethylpiperidinyl oxygen free radical) reagent, stir well and then Add 5 mL of sodium hypochlorite solution with a concentration of 0.15 mol/L, and after mixing, adjust the pH value of the mixed solution to 10 with a diluted hydrochloric acid solution with a concentration of 0.1 mol/L to obtain a mixed reaction solution; then place the mixed reaction solution in The reaction was stirred in an ice-water bath for 6 h, and NaOH solution with a concentration of 0.1 mol/L was continuously added dropwise during the stirring process to maintain the pH value of the mixed reaction solution at 10. After the reaction, acidify with 0.1mol/L dilute hydrochloric acid solution for 3 to 4 hours, then centrifuge and wash with ethanol and deionized water for 3 times, and finally freeze-dry in a freeze-drying oven at -20°C for 24 hours to obtain Dry oxidized nanocellulose with carboxyl groups.

(b) Dissolve 9-anthracene carboxylic acid in absolute ethanol, control the concentration of 9-anthracene carboxylic acid at 10g/L to obtain 9-anthracene carboxylic acid ethanol solution, then add carbon nanotubes to 9-anthracene carboxylic acid ethanol solution, and use ordinary ultrasonic Ultrasonic disperse with a disperser for 30 minutes, and filter to obtain non-covalent bond modified carbon nanotubes, that is, 9-anthracenecarboxylic acid modified carbon nanotubes; wherein: the mass ratio of the carbon nanotubes to 9-anthracenecarboxylic acid is 1:10.

(c) Mix the multi-layer graphene, 9-anthracenecarboxylic acid-modified carbon nanotubes, dry oxidized nanocellulose and water with a mass ratio of 1:0.05:0.025:3.2, and use an ordinary ultrasonic cleaning machine to sonicate for 10 minutes , continue to uniformly disperse with a mixer for 30 minutes to prepare a graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating, and the solid content of the conductive coating is 25%.

(3) Preparation of PLA coating layer

Use a bar coater to coat the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating prepared in step (2) on the food packaging base paper obtained in step (1), and then freeze-dry at -20 ° C Freeze-dry in the box for 2 hours, and obtain a conductive heating layer after drying; then further coat the surface of the conductive heating layer with PLA, continue to freeze-dry in a freeze-drying oven at -20°C for 2 hours, and finally cut it to obtain the conductive heating layer. Heat food wrappers.

The use of the conductive heating food wrapping paper prepared above in this example: use a 24v mobile power supply or battery pack to heat the conductive heating layer, which can increase the temperature of the food wrapping paper by 63.6°C. Under the condition of normal temperature of 22.5°C, the highest constant The temperature is 86.1°C.

Example 2

A kind of conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose of the present embodiment includes packaging base paper, conductive heating layer and PLA coating layer stacked sequentially from bottom to top, wherein: the The weight of the wrapping paper is 60g/m ² , the resistance of the conductive heating layer is 121.6Ω, the area of the conductive heating layer is 100cm ² , the thickness of the conductive heating layer is 20 μm, and the thickness of the PLA coating layer is 15 μm; the conductive heating layer The layer is made of graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating; the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating has a solid content of 20%, which is determined by mass ratio The composition is 1:0.1:0.05:4.5 multilayer graphene, 9-anthracenecarboxylic acid modified carbon nanotubes, dry oxidized nanocellulose and water.

The specific preparation method of the conductive heating food wrapping paper described above in this embodiment is as follows:

(1) Preparation of packaging base paper

Mix the mixed wood pulp, AKD and cationic starch in a mass ratio of 1:0.01:0.01, and then use a fourdrinier paper machine to make food packaging base paper; wherein: the mixed wood pulp is made of softwood pulp with a mass ratio of 1:1 It is mixed with hardwood pulp and refined to form pulp, the refining concentration is controlled at 4%, and the beating degree is controlled at 70°SR.

(2) Preparation of conductive heating layer

(a) Prepare 100 mL of cotton pulp suspension with a mass concentration of 1%, add 0.1 g of sodium bromide and 0.016 g of tempo (2,2,6,6-tetramethylpiperidinyl oxygen free radical) reagent, stir well and then Add 3 mL of sodium hypochlorite solution with a concentration of 0.25 mol/L, and after mixing, adjust the pH value of the mixed solution to 10 with a diluted hydrochloric acid solution with a concentration of 0.1 mol/L to obtain a mixed reaction solution; then place the mixed reaction solution in The reaction was stirred in an ice-water bath for 5 h, and NaOH solution with a concentration of 0.1 mol/L was continuously added dropwise during the stirring process to maintain the pH value of the mixed reaction solution at 10. After the reaction, acidify with 0.1 mol/L dilute hydrochloric acid solution for 3 to 4 hours, then centrifuge and wash with ethanol and deionized water for 3 times, and finally freeze-dry in a freeze-drying oven at -10°C for 36 hours to obtain Dry oxidized nanocellulose with carboxyl groups.

(b) Dissolve 9-anthracene formic acid in absolute ethanol, control the concentration of 9-anthracene formic acid at 2g/L to obtain 9-anthracene formic acid ethanol solution, then add carbon nanotubes to the 9-anthracene formic acid ethanol solution, and use ordinary ultrasonic Ultrasonic disperse with a disperser for 30 minutes, and filter to obtain non-covalently modified carbon nanotubes, that is, 9-anthracenecarboxylic acid-modified carbon nanotubes; wherein: the mass ratio of the carbon nanotubes to 9-anthracenecarboxylic acid is 1:2.

(c) Mix the multi-layer graphene, 9-anthracenecarboxylic acid-modified carbon nanotubes, dry oxidized nanocellulose and water with a mass ratio of 1:0.1:0.05:4.5, and use an ordinary ultrasonic cleaning machine to sonicate for 20 minutes , and continue to uniformly disperse for 20 minutes with a mixer to prepare a graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating, and the solid content of the conductive coating is 20%.

(3) Preparation of PLA coating layer

Use a bar coater to coat the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating prepared in step (2) on the food packaging base paper obtained in step (1), and then freeze-dry at -20 ° C Freeze-dry in the box for 2 hours, and obtain a conductive heating layer after drying; then further coat the surface of the conductive heating layer with PLA, continue to freeze-dry in a freeze-drying oven at -20°C for 2 hours, and finally cut it to obtain the conductive heating layer. Heat food wrappers.

The use of the conductive heating food wrapping paper prepared above in this example: use a 24v mobile power supply or battery pack to heat the conductive heating layer, which can increase the temperature of the food wrapping paper by 60.8°C. At a room temperature of 25°C, the highest constant temperature can be achieved The temperature is 85.8°C.

Example 3

A kind of conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose of the present embodiment includes packaging base paper, conductive heating layer and PLA coating layer stacked sequentially from bottom to top, wherein: the The weight of the wrapping paper is 40g/m ² , the resistance of the conductive heating layer is 102.6Ω, the area of the conductive heating layer is 120cm ² , the thickness of the conductive heating layer is 50 μm, and the thickness of the PLA coating layer is 30 μm; the conductive heating layer The layer is made of graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating; the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating has a solid content of 50%, which is determined by mass ratio The composition is 1:0.2:0.1:1.3 multilayer graphene, 9-anthracenecarboxylic acid modified carbon nanotubes, dry oxidized nanocellulose and water.

The specific preparation method of the conductive heating food wrapping paper described above in this embodiment is as follows:

(1) Preparation of packaging base paper

Mix the mixed wood pulp, AKD and cationic starch in a mass ratio of 1:0.03:0.04, and then use a fourdrinier paper machine to make food packaging base paper; wherein: the mixed wood pulp is made of softwood pulp with a mass ratio of 1:4 It is mixed with hardwood pulp and refined to form pulp, the refining concentration is controlled at 4%, and the beating degree is controlled at 60°SR.

(2) Preparation of conductive heating layer

(a) Prepare 100 mL of cotton pulp suspension with a mass concentration of 1%, add 0.1 g of sodium bromide and 0.02 g of tempo (2,2,6,6-tetramethylpiperidinyl oxygen free radical) reagent, stir well and then Add 5 mL of sodium hypochlorite solution with a concentration of 0.15 mol/L, and after mixing, adjust the pH value of the mixed solution to 10 with a diluted hydrochloric acid solution with a concentration of 0.2 mol/L to obtain a mixed reaction solution; then place the mixed reaction solution in The reaction was stirred in an ice-water bath for 6 h, and NaOH solution with a concentration of 0.2 mol/L was continuously added dropwise during the stirring process to maintain the pH value of the mixed reaction solution at 10. After the reaction, acidify with 0.2 mol/L dilute hydrochloric acid solution for 3 to 4 hours, then centrifuge and wash with ethanol and deionized water for 3 times, and finally freeze-dry in a freeze-drying oven at -40°C for 10 hours to obtain Dry oxidized nanocellulose with carboxyl groups.

(b) Dissolve 9-anthracene formic acid in absolute ethanol, control the concentration of 9-anthracene formic acid at 20g/L to obtain 9-anthracene formic acid ethanol solution, then add carbon nanotubes to the 9-anthracene formic acid ethanol solution, and use ordinary ultrasonic Ultrasonic disperse with a disperser for 30 minutes, and filter to obtain non-covalently modified carbon nanotubes, that is, 9-anthracenecarboxylic acid-modified carbon nanotubes; wherein: the mass ratio of the carbon nanotubes to 9-anthracenecarboxylic acid is 1:20.

(c) Mix the multi-layer graphene, 9-anthracenecarboxylic acid-modified carbon nanotubes, dry oxidized nanocellulose and water with a mass ratio of 1:0.2:0.1:1.3, and use an ordinary ultrasonic cleaning machine to sonicate for 20 minutes , continue to uniformly disperse with a mixer for 20 minutes to prepare a graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating, and the solid content of the conductive coating is 50%.

(3) Preparation of PLA coating layer

Use a bar coater to coat the graphene/modified carbon nanotube/oxidized nanocellulose conductive heating coating prepared in step (2) on the food packaging base paper obtained in step (1), and then freeze-dry at -20 ° C Freeze-dry in the box for 2 hours, and obtain a conductive heating layer after drying; then further coat the surface of the conductive heating layer with PLA, continue to freeze-dry in a freeze-drying oven at -20°C for 2 hours, and finally cut it to obtain the conductive heating layer. Heat food wrappers.

The use of the conductive heating food wrapping paper prepared above in this example: use a 24v mobile power supply or battery pack to heat the conductive heating layer, which can increase the temperature of the food wrapping paper by 60°C. The temperature is 83°C.

The above-mentioned conductive heating food wrapping paper developed by the present invention can be used for heating foods such as instant foods and homemade lunch boxes. The developed food packaging paper can be energized by 24v power supply to realize rapid heat preservation and heating of food, ensure food safety and improve eating efficiency.

Claims (10)

1. A conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose, characterized in that: comprising packaging base paper, conductive heating layer and PLA coating layer stacked sequentially from bottom to top, wherein, The conductive heating layer is made of graphene/modified carbon nanotube/oxidized nanocellulose conductive heating paint, and the thickness of the conductive heating layer is 10-50 μm. 2. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 1, characterized in that: the resistance of the conductive heating layer is 50-500Ω, and the conductive heating layer The area is 100-200 cm ² . 3. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 1, characterized in that: the weight of the wrapping paper is 40-100g/m ² , and the PLA The thickness of the coating layer is 10-30 μm. 4. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 1, characterized in that: said graphene/modified carbon nanotubes/oxidized nanocellulose conducts electricity The heating coating is composed of multilayer graphene, 9-anthracenecarboxylic acid modified carbon nanotubes, dry oxidized nanocellulose and water, wherein: the multilayer graphene, 9-anthracenecarboxylic acid modified carbon nanotubes, dry oxidized The mass ratio of nanocellulose to water is 1:0.05-0.2:0.025-0.1:1-10. 5. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 4, characterized in that: the solid content of the conductive heating coating is preferably 20-50%. 6. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 4, characterized in that: the 9-anthracenecarboxylic acid modified carbon nanotubes are prepared by the following method : Dissolve 9-anthracene carboxylic acid in absolute ethanol according to the proportioning ratio to obtain 9-anthracene carboxylic acid ethanol solution, then add carbon nanotubes to the 9-anthracene carboxylic acid ethanol solution, ultrasonically disperse at room temperature, and filter to obtain non-covalent Bond-modified carbon nanotubes, that is, 9-anthracenecarboxylic acid-modified carbon nanotubes. 7. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 6, characterized in that: in the ethanol solution of 9-anthracene formic acid, the concentration of 9-anthracene formic acid 2-20g/L. 8. The conductive heating food wrapping paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 6, characterized in that: the mass ratio of the carbon nanotubes to 9-anthracenecarboxylic acid is 1: 2-20. 9. The conductive heating food packaging paper based on graphene/modified carbon nanotubes/oxidized nanocellulose according to claim 1, characterized in that: the packaging base paper is made of mixed wood pulp, AKD and cationic starch by mass Ratio 1: 0.01-0.03: 0.01-0.04 Refining after mixing, controlling the refining concentration to 4-6%, beating degree to 60-70°SR, and then using fourdrinier paper machine to produce. 10. The preparation method of the conductive heating food wrapping paper based on graphene/modified carbon nanotube/oxidized nanocellulose according to claim 1, characterized in that: it is coated with graphene/modified on the packaging base paper After the carbon nanotube/oxidized nanocellulose conductive heating coating is dried, it is further coated with PLA, dried, and finally cut to obtain the conductive heating food wrapping paper.