Oil-resistant and high-temperature-resistant packaging paper and preparation method thereof

Abstract

The application belongs to the technical field of special paper, and discloses an oil-resistant and high-temperature-resistant packaging paper and a preparation method, which comprises the following steps: preparing nano silicon sol with a viscosity range of 30-50 cP as an inner immersion liquid; making base paper permeate and adsorb the inner immersion liquid to form micropores; coating a polytetrafluoroethylene emulsion coating on the pre-impregnated base paper, and performing calendering, drying, deviation correction, edge cutting and winding to obtain an oil-resistant and high-temperature-resistant packaging paper. By pre-impregnating silicon sol on the base paper to form fine pores and further coating polytetrafluoroethylene emulsion, a micron-level microconvex structure similar to a mountain peak is formed on the surface of the base paper, so that the coating layer has good hydrophobic and oleophobic effects, and the oil-resistant and high-temperature-resistant properties for packaging are ensured. Compared with the prior art, the oil-resistant and high-temperature-resistant packaging paper does not need to be treated by film coating, is stable in oil resistance and high-temperature resistance, has a shorter preparation process, and is suitable for batch production.

Description

Technical Field

[0001] This invention belongs to the field of specialty paper technology, specifically relating to an oil-resistant and high-temperature-resistant packaging paper and its preparation method. Background Technology

[0002] With the technological advancements in functional paper, its application in the packaging field is becoming increasingly widespread. Currently, some food packaging applications typically combine paper and plastic, utilizing the water and oxygen barrier properties of the plastic film for protection. For example, in frozen beverage packaging, a composite design is often used: an outer layer of polyethylene film, a middle layer of kraft paper, and an inner single-layer high-pressure polyethylene film. However, the introduction of plastic film also brings recycling and disposal issues, and this type of packaging paper generally has poor oil resistance and high-temperature resistance, making it unsuitable for microwave heating.

[0003] Depending on the application scenario, functional paper packaging requires good water resistance, oil resistance, high-temperature resistance, and safety and environmental protection. By endowing paper with water resistance, oil resistance, and fire resistance, functional paper can be used for food packaging, pharmaceutical packaging, cosmetic packaging, etc. Especially with the rapid development of ready-to-eat meals, self-heating processed foods, and takeout, the demand for paper packaging has increased rapidly. For example, silicone-coated paper has a three-layer structure: a base paper, a coating layer, and a silicone oil layer. Through silicone oil treatment, silicone-coated paper has high-temperature resistance, moisture resistance, and oil resistance, making it suitable for food packaging as well as for food heating, cooking, and baking. However, silicone-coated paper requires a coating pretreatment, introducing a barrier layer that is not heat-resistant. Furthermore, the bonding between silicone oil and the base paper is poor, posing a risk of leaching.

[0004] Chinese invention patent publication number CN115369682B discloses a method for preparing silicone paper and a product. The silicone paper prepared by directly coating silicone oil onto the base paper has general high temperature resistance, water and oil resistance, poor wet strength, and a risk of exudation. It can only be used for short-term food packaging and heat processing.

[0005] According to food packaging requirements, paper packaging must be able to protect food, prevent it from spoiling or being damaged during storage and transportation, prevent water and oil leakage, be heat-resistant, and for foods that are to be eaten directly, must not have any leaching contaminants.

[0006] Clearly, existing paper packaging has many uncontrollable factors, especially for the increasing number of self-heating packaging and takeaway food packaging, which have high requirements for oil resistance, exudation resistance, and high temperature stability. Summary of the Invention

[0007] In response to the current demand for oil-resistant and high-temperature-resistant packaging in self-heating food processing and food delivery, the present invention aims to provide an oil-resistant and high-temperature-resistant packaging paper and its preparation method. The core technology involves permeating the base paper with silica sol to form micropores, and then using these micropores as load pores to further coat a polytetrafluoroethylene (PTFE) coating, forming a coating with microscopic roughness, thereby achieving the technical effects of oil resistance and temperature resistance.

[0008] Specifically, in order to achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A method for preparing oil-resistant and high-temperature-resistant packaging paper, characterized by the following specific preparation method:

[0010] (1) Pre-prepared inner impregnation solution: Detect the room temperature viscosity of nano silica sol and control the room temperature viscosity of nano silica sol to be 30-50 cP as the inner impregnation solution; if the viscosity is too high, add an appropriate amount of deionized water to reduce the viscosity; if the viscosity is too low, add a thickener to increase the viscosity; add the pre-prepared inner impregnation solution to the pre-impregnation tank.

[0011] (2) Inner impregnation base paper: The rolled base paper is loaded into the unwinding machine, the tension is adjusted to 5-10N, and the base paper is fed into the preimpregnation tank by the roller correction, so that the base paper can penetrate and absorb the inner impregnation liquid. The traction speed is 8-10m / min, and the excess inner impregnation liquid is removed by the pressure roller. The base paper is continuously fed into the tunnel oven, and the oven temperature is controlled at 150-200℃. After drying and curing, the preimpregnated base paper is obtained.

[0012] (3) Pre-coating solution: The polytetrafluoroethylene emulsion and dispersant are mixed at a mass ratio of 100:0.5-1 and dispersed evenly at high speed to obtain the coating solution;

[0013] (4) Coating: Unwind the prepreg base paper prepared in step (2), apply the coating liquid from step (3) to the prepreg base paper on both sides, calender, dry at 150-180℃, correct deviation, trim the edges, and roll to obtain an oil-resistant and high-temperature resistant packaging paper.

[0014] Preferably, the nano silica sol mentioned in step (1) is selected with a viscosity of 30-50 cP. If the viscosity is too low, the base paper will absorb a large amount of water during pre-impregnation, resulting in a decrease in wet strength and a reduction in the effective absorption of silica. If the viscosity is too high, it will affect the rapid absorption of silica sol by the base paper. The required viscosity can be adjusted by adding a small amount of tackifier, avoiding the need to add a large amount of deionized water to reduce viscosity or add a large amount of tackifier to increase viscosity.

[0015] Preferably, the thickener mentioned in step (1) is selected from water-soluble polyvinyl alcohol and hydroxypropyl cellulose ether.

[0016] More preferably, the average particle size of the nano-silica sol is 10-20 nm, which allows for good penetration into the base paper; the nano-silica sol has a silica content of 20-30% by mass and a sodium oxide content of ≤0.5%.

[0017] More preferably, the pH value of the nano-silica sol is 9-10. Alkaline silica sol has good fluidity and can fully penetrate and fill the base paper. The alkaline environment is more conducive to gelation and formation of micropores.

[0018] Preferably, the base paper used in step (2) is selected as 30-120g base paper.

[0019] Preferably, the linear pressure of the pressure roller in step (2) is controlled at 0.8-1 kg / cm; if the pressure is too high, the silica sol adsorbed by the base paper will be squeezed out; if the pressure is too low, the base paper surface will be covered with excessive silica sol, which will affect the subsequent processing.

[0020] Preferably, the moisture content of the prepreg base paper after drying in step (2) is controlled at 7-9% to ensure good flexibility of the prepreg paper. The base paper adsorbs silica sol and is cured by heat drying, which causes cross-linking between silica sol molecules to form good micropores. On the one hand, this helps to improve the high temperature resistance and heat preservation of the base paper; on the other hand, it forms micropores that can carry the coating liquid.

[0021] Preferably, the polytetrafluoroethylene emulsion in step (3) is a nano-polytetrafluoroethylene emulsion with a solid content of 40-50% by weight; the dispersant is selected from polyethoxylated fatty alcohol and dehydrated sorbitan ester.

[0022] Preferably, the coating in step (4) is applied by double-sided scraping, with a coating amount of 3-5 g / m² on one side.

[0023] This invention further provides an oil-resistant and high-temperature-resistant packaging paper prepared by the above method. By pre-impregnating the base paper with silica sol, a microporous support is formed, giving the base paper excellent high-temperature resistance. By dispersing and coating a polytetrafluoroethylene (PTFE) emulsion on the surface of the base paper, the PTFE solidifies in the micropores, forming a micron-scale micro-protrusion structure. The resulting coating has excellent hydrophobic and oleophobic effects and releases no harmful substances at high temperatures. When used for food packaging, water and oil are difficult to wet the packaging paper, providing excellent protection for the paper's wet strength. Simultaneously, the packaging paper of this invention exhibits excellent high-temperature resistance. It is suitable for applications requiring self-heating food processing, food takeaway packaging, meal trays, baking trays, frozen food packaging, pre-prepared food packaging, and various other packaging applications requiring oil resistance, temperature resistance, preservation of product aroma and taste, and prevention of oxidation and spoilage.

[0024] An oil-resistant and high-temperature-resistant packaging paper and its preparation method, compared with the existing technology, have the following advantages:

[0025] 1. The present invention forms micropores by pre-impregnating silica sol on base paper, and then coating it with polytetrafluoroethylene emulsion, thereby forming a micron-sized micro-protrusion structure similar to mountain peaks on the surface of the base paper. The resulting coating has good hydrophobic and oleophobic effects, ensuring oil barrier resistance and high temperature resistance for packaging.

[0026] 2. This invention pre-impregnates the base paper with silica sol, which protects the base paper and provides excellent high-temperature resistance. The resulting polytetrafluoroethylene coating is also heat-resistant and does not release harmful substances at high temperatures.

[0027] 3. Compared with the prior art, the present invention does not require coating treatment, is oil-resistant, high-temperature resistant and stable, has a simpler preparation process, and is suitable for mass production. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings:

[0029] Figure 1 This invention discloses a process flow for preparing oil-resistant and high-temperature resistant packaging paper (first step: impregnation of base paper, second step: coating).

[0030] Figure 2 This invention provides a schematic diagram of the structure of an oil-resistant and high-temperature resistant packaging paper. The base paper is formed by the infiltration of silica sol to form micropores, and polytetrafluoroethylene emulsion forms a film on the surface to form a micron-scale mountain-like structure.

[0031] Figure 3 : The effect of rapeseed oil wetting the paper in Example 1.

[0032] Figure 4 : The wetting effect of rapeseed oil on the paper surface in comparative experiment 2. Detailed Implementation

[0033] The following examples further describe the implementation process of the present invention, but are not intended to limit the scope of protection of the claims. Unless otherwise specified in the examples, all processes are performed under conventional conditions. In particular, according to the requirements of paper coating technology, it is necessary to reasonably control the doctor blade angle and doctor blade pressure to obtain a coating layer that meets quality requirements; furthermore, closed-loop tension control is used in the impregnation and coating processes to achieve constant tension during acceleration and deceleration, ensuring a highly uniform coating effect.

[0034] Example 1

[0035] (1) Pre-prepared inner impregnation solution: Select nano silica sol with a silica content of 25% by mass, the average particle size of the nano silica sol is 10-20nm, the sodium oxide content is ≤0.5%; the pH value is 10, the room temperature viscosity of the nano silica sol is 28cP, add 0.1% polyvinyl alcohol (brand 17-88) by mass of the nano silica sol and stir evenly to adjust the viscosity of the nano silica sol to 37cP, and add it to the pre-impregnation tank as the inner impregnation solution.

[0036] (2) Inner Impregnation Base Paper: A 45g roll of base paper is loaded into an unwinding machine, tension is adjusted to 10N, and the base paper is fed into a pre-impregnation tank via roller correction, allowing the base paper to absorb the inner impregnation liquid. The traction speed is 8m / min. Excess inner impregnation liquid is removed by pressure rollers, with the linear pressure of the pressure rollers controlled at 1kg / cm. The base paper is continuously fed into a tunnel-type drying oven, with the oven temperature controlled at 200℃. After drying and curing, the pre-impregnated base paper is obtained. The moisture content of the dried pre-impregnated base paper is controlled at 9% to ensure good flexibility. The base paper absorbs silica sol, which is then cured by heat drying, causing cross-linking between silica sol molecules to form good micropores. Figure 1 The first step in the simplified process flow diagram of the preparation process of medium-oil-resistant and high-temperature-resistant packaging paper clearly illustrates the process of impregnating the base paper.

[0037] (3) Pre-coating solution: Mix nano polytetrafluoroethylene emulsion with a solid content of 40% and dispersant polyethoxylated fatty alcohol at a mass ratio of 100:0.5, disperse evenly at high speed, and obtain coating solution;

[0038] (4) Coating: Unwind the prepreg base paper prepared in step (2), apply the coating liquid from step (3) to both sides of the prepreg base paper, with a single-sided coating amount of 3 g / m², and obtain an oil-resistant and high-temperature resistant packaging paper after calendering, drying at 180°C, correction, edge trimming, and winding; Figure 1 The second step in the simplified process flow diagram of the preparation process of medium-oil resistant and high-temperature resistant packaging paper clearly illustrates the coating process.

[0039] Appendix Figure 2 This is a schematic diagram of the structure of an oil-resistant and high-temperature-resistant packaging paper, in which the base paper is formed by the infiltration of silica sol to form micropores, and polytetrafluoroethylene emulsion forms a film on the surface to form a micron-scale mountain structure.

[0040] Example 2

[0041] (1) Pre-prepared impregnation solution: Select nano-silica sol with a silica content of 20% by mass, an average particle size of 10-20nm, sodium oxide content ≤0.5%; pH value of 10, and the room temperature viscosity of nano-silica sol is measured to be 28cP. Add 0.05% by mass of hydroxypropyl cellulose ether to nano-silica sol and stir evenly to adjust the viscosity of nano-silica sol to 45cP. Use this as the impregnation solution to add to the pre-impregnation tank.

[0042] (2) Inner impregnation base paper: The 60g roll of base paper is loaded into the unwinding machine, the tension is adjusted to 10N, and the base paper is fed into the preimpregnation tank by the roller correction, so that the base paper can penetrate and absorb the inner impregnation liquid. The traction speed is 10m / min, and the excess inner impregnation liquid is removed by the pressure roller. The linear pressure of the pressure roller is controlled at 1kg / cm. The base paper is continuously fed into the tunnel oven, and the oven temperature is controlled at 200℃. After drying and curing, the preimpregnated base paper is obtained. The moisture content of the dried preimpregnated base paper is controlled at 9% to ensure the good flexibility of the preimpregnated paper. The base paper absorbs silica sol, and through heat curing, cross-linking occurs between silica sol molecules to form good micropores.

[0043] (3) Pre-coating solution: Mix nano polytetrafluoroethylene emulsion with a solid content of 40% and dehydrated sorbitan ester dispersant at a mass ratio of 100:0.5, disperse evenly at high speed, and obtain coating solution;

[0044] (4) Coating: Unwind the prepreg base paper prepared in step (2), apply the coating liquid from step (3) to both sides of the prepreg base paper, with a coating amount of 5 g / m2 on one side, and obtain an oil-resistant and high-temperature resistant packaging paper by calendering, drying at 180°C, correcting deviation, trimming, and winding.

[0045] Example 3

[0046] (1) Pre-prepared inner impregnation solution: Select nano silica sol with a silica content of 30% by mass, the average particle size of the nano silica sol is 10-20nm, the sodium oxide content is ≤0.5%; the pH value is 10, the room temperature viscosity of the nano silica sol is 66cP, add deionized water to adjust the viscosity to 50cP, and add it to the pre-impregnation tank as the inner impregnation solution.

[0047] (2) Inner impregnation base paper: The base paper in rolls weighing 30g is loaded into the unwinding machine, the tension is adjusted to 5N, and the base paper is fed into the preimpregnation tank by the roller correction, so that the base paper can penetrate and absorb the inner impregnation liquid. The traction speed is 10m / min, and the excess inner impregnation liquid is removed by the pressure roller. The linear pressure of the pressure roller is controlled at 0.8kg / cm. The base paper is continuously fed into the tunnel oven, and the oven temperature is controlled at 200℃. After drying and curing, the preimpregnated base paper is obtained. The moisture content of the dried preimpregnated base paper is controlled at 9% to ensure the good flexibility of the preimpregnated paper. The base paper absorbs silica sol, and through heat curing, cross-linking occurs between silica sol molecules to form good micro-fine particles.

[0048] (3) Pre-coating solution: Mix nano polytetrafluoroethylene emulsion with a solid content of 40% and dispersant polyethoxylated fatty alcohol at a mass ratio of 100:0.5, disperse evenly at high speed, and obtain coating solution;

[0049] (4) Coating: Unwind the prepreg base paper prepared in step (2), apply the coating liquid from step (3) to both sides of the prepreg base paper, with a coating amount of 4 g / m2 on one side, and obtain an oil-resistant and high-temperature resistant packaging paper by calendering, drying at 180°C, correcting deviation, trimming, and winding.

[0050] Comparative Experiment 1

[0051] (1) Pre-prepared inner impregnation solution: Select nano silica sol with a silica content of 50% by mass, the average particle size of the nano silica sol is 10-20nm, the sodium oxide content is ≤0.5%; the pH value is 10, the room temperature viscosity of the nano silica sol is 85cP, add 0.1% polyvinyl alcohol (brand 17-88) by mass of the nano silica sol and stir evenly to adjust the viscosity of the nano silica sol to 100cP, and add it to the pre-impregnation tank as the inner impregnation solution.

[0052] (2) Inner impregnation base paper: The 45g roll of base paper is loaded into the unwinding machine, the tension is adjusted to 10N, and the base paper is fed into the preimpregnation tank by the roller correction, so that the base paper can penetrate and absorb the inner impregnation liquid. The traction speed is 8m / min, and the excess inner impregnation liquid is removed by the pressure roller. The linear pressure of the pressure roller is controlled at 1kg / cm. The base paper is continuously fed into the tunnel oven, and the oven temperature is controlled at 200℃. After drying and curing, the preimpregnated base paper is obtained.

[0053] (3) Pre-coating solution: Mix nano polytetrafluoroethylene emulsion with a solid content of 40% and dispersant polyethoxylated fatty alcohol at a mass ratio of 100:0.5, disperse evenly at high speed, and obtain coating solution;

[0054] (4) Coating: Unwind the prepreg base paper prepared in step (2), apply the coating liquid from step (3) to both sides of the prepreg base paper, with a coating amount of 3g / m2 on one side, and obtain an oil-resistant and high-temperature resistant packaging paper by calendering, drying at 180℃, correcting deviation, trimming, and winding.

[0055] Comparative Experiment 2

[0056] (1) Pre-coating solution: Mix nano polytetrafluoroethylene emulsion with a solid content of 40% and dispersant polyethoxylated fatty alcohol at a mass ratio of 100:0.5, disperse evenly at high speed to obtain coating solution;

[0057] (2) Coating: The 45g roll of base paper is loaded into the unwinding machine, and the coating liquid from step (1) is applied to both sides of the base paper. The coating amount on one side is 3g / m2. After calendering, drying at 180℃, correction, trimming, and winding, an oil-resistant and high-temperature resistant packaging paper is obtained.

[0058] Comparative test 3

[0059] (1) Pre-prepared inner impregnation solution: Select nano silica sol with a silica content of 25% by mass, the average particle size of the nano silica sol is 10-20nm, the sodium oxide content is ≤0.5%; the pH value is 10, the room temperature viscosity of the nano silica sol is 28cP, add 0.1% polyvinyl alcohol (brand 17-88) by mass of the nano silica sol and stir evenly to adjust the viscosity of the nano silica sol to 37cP, and add it to the pre-impregnation tank as the inner impregnation solution.

[0060] (2) Inner impregnation base paper: The 45g roll of base paper is loaded into the unwinding machine, the tension is adjusted to 10N, and the base paper is fed into the pre-impregnation tank through the roller correction, so that the base paper can penetrate and absorb the inner impregnation liquid. The traction speed is 8m / min, and the excess inner impregnation liquid is removed by the pressure roller. The linear pressure of the pressure roller is controlled at 1kg / cm. The base paper is continuously fed into the tunnel oven, and the oven temperature is controlled at 200℃. After drying and curing, a kind of oil-resistant and high-temperature resistant packaging paper is obtained.

[0061] Hydrophobic and oleophobic performance test:

[0062] The water contact angle and rapeseed oil contact angle of the samples in Examples 1-3 and Comparative Tests 1-3 are shown in Table 1.

[0063] Table 1:

[0064] Example 1 119.2 127.1 Example 2 122.6 129.9 Example 3 123.5 125.4 Comparative Experiment 1 126.4 135.7 Comparative Experiment 2 109.4 100.2 Comparative test 3 87.8 96.5

[0065] Through testing, this invention demonstrates that by pre-impregnating the base paper with silica sol to form micropores, and then further coating it with polytetrafluoroethylene emulsion, a micron-sized micro-protrusion structure resembling mountain peaks is formed on the surface of the base paper. This effectively prevents oil and water wetting, giving the base paper excellent hydrophobic and oleophobic properties. Figure 3 The image shows the wetting effect of rapeseed oil on the paper surface in Example 1. In contrast, the use of a single polytetrafluoroethylene coating (Comparative Example 2) is shown in the attached image. Figure 4 The image shows the wetting effect of rapeseed oil on paper; the oleophobic effect is significantly reduced.

[0066] Qualitative comparison test of high temperature resistance:

[0067] The samples from Examples 1-3 and Comparative Tests 1-3 were cut into 10×10cm samples, flattened, and placed at a high temperature of 220℃ for 5 minutes. The changes in the paper were observed, and the test results are shown in Table 2.

[0068] Table 2:

[0069]

[0070] Clearly, the base paper without effective silica sol penetration exhibits poor high-temperature resistance. In Comparative Experiment 1, the high viscosity of the silica sol prevented effective penetration into the base paper, resulting in rewinding at high temperatures. Obviously, penetrating the base paper with silica sol not only significantly improves high-temperature resistance but also, due to the formation of micropores, assists the polytetrafluoroethylene emulsion in forming a micro-convex coating, effectively preventing oil and water seepage, ultimately achieving the technical objective of oil and high-temperature resistance.

[0071] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing oil-resistant and high-temperature-resistant packaging paper, characterized in that, The specific preparation method is as follows: (1) Pre-prepared inner impregnation solution: The room temperature viscosity of the nano silica sol is tested and controlled to be 30-50 cP, which is used as the inner impregnation solution; if the viscosity is too high, an appropriate amount of deionized water is added to reduce the viscosity; if the viscosity is too low, a thickener is added to increase the viscosity; the pre-prepared inner impregnation solution is added to the pre-impregnation tank; the pH value of the nano silica sol is 9-10. (2) Inner impregnation base paper: The rolled base paper is loaded into the unwinding machine, the tension is adjusted to 5-10N, and the base paper is fed into the pre-impregnation tank through the roller correction, so that the base paper can penetrate and absorb the inner impregnation liquid. The traction speed is 8-10m / min, and the excess inner impregnation liquid is removed by the pressure roller. The base paper is continuously fed into a tunnel-type drying oven, and the oven temperature is controlled at 150-200℃. After drying, curing, and winding, the prepreg base paper is obtained. (3) Pre-coating solution: The polytetrafluoroethylene emulsion and dispersant are mixed at a mass ratio of 100:0.5-1 and dispersed evenly at high speed to obtain the coating solution; (4) Coating: Unwind the prepreg base paper prepared in step (2), apply the coating liquid from step (3) to the prepreg base paper on both sides, calender, dry at 150-180℃, correct deviation, trim the edges, and roll to obtain an oil-resistant and high-temperature resistant packaging paper.

2. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The thickener mentioned in step (1) is selected from water-soluble polyvinyl alcohol and hydroxypropyl cellulose ether.

3. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The average particle size of the nano-silica sol in step (1) is 10-20 nm; the nano-silica sol is selected with a silica content of 20-30% and a sodium oxide content of ≤0.5%.

4. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The base paper used in step (2) is selected to be 30-120g.

5. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The linear pressure of the pressure roller in step (2) is controlled at 0.8-1 kg / cm.

6. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: In step (2), the moisture content of the prepreg base paper after drying is controlled at 7-9%.

7. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The polytetrafluoroethylene emulsion mentioned in step (3) is a nano-polytetrafluoroethylene emulsion with a solid content of 40-50% by weight.

8. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The dispersant used in step (3) is selected from either polyethoxylated fatty alcohol or dehydrated sorbitan ester.

9. The method for preparing an oil-resistant and high-temperature-resistant packaging paper according to claim 1, characterized in that: The coating process described in step (4) involves double-sided scraping, with a single-sided coating amount of 3-5 g / m². 2 .

10. An oil-resistant and high-temperature resistant packaging paper, prepared by the method described in any one of claims 1-9.

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