A water and oil repellent agent for coated bending-resistant paper, and a preparation method and application thereof

Abstract

This invention provides a coated water- and oil-repellent agent for foldable paper, its preparation method, and its application, belonging to the field of materials chemistry. The coated water- and oil-repellent agent for foldable paper of this invention comprises, by weight, the following components: 8-10 parts O-carboxymethyl chitosan; 1.5-4.5 parts nanocellulose; 1-3 parts nanocellulose crystals; 0.5-0.7 parts nano silica; 5-15 parts ammonium citrate buffer; 2-6 parts polycarbodiimide solution; 0.1-2 parts glycerol; and 40-100 parts water. This invention utilizes the cross-linking properties of polycarbodiimide with carboxyl groups and the esterification reaction of carboxyl and hydroxyl groups to form a cross-linked system on the paper surface. O-carboxymethyl chitosan provides oil resistance, while polycarbodiimide and nano silica provide water resistance, forming a surface water- and oil-repellent coating with minimal decrease in oil resistance after bending.

Description

Technical Field

[0001] This invention relates to the field of materials chemistry, specifically to a water- and oil-repellent agent for coated foldable paper, its preparation method, and its application. Background Technology

[0002] For a long time, fluorinated compounds, especially copolymers containing perfluoroalkyl groups, have been the "gold standard" for achieving highly efficient water and oil repellency. The principle behind this is the use of the extremely low surface energy of fluorocarbon chains to form a barrier on the fiber surface that is both hydrophobic and oleophobic. As early as 1978, a DuPont patent proposed a composition of a non-water-soluble fluorinated compound with film-forming polymers such as nitrocellulose for use as a barrier coating for paper and paperboard. However, with increasing concern about the environmental and health risks of perfluorinated and polyfluoroalkyl substances, the development of fluorine-free, environmentally friendly water and oil repellents has become the absolute mainstream in the industry.

[0003] Furthermore, paper products undergo folding and bending processes during use. If the water and oil repellent agent has poor bending resistance, it will crack at the bending point, causing the water and oil repellency to fail. Existing technologies disclose schemes for preparing water and oil repellent agents for paper using PLA, chitosan, and other raw materials, but these have the defect of insufficient bending stability, and the oil-repellent performance decreases significantly after bending. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a water- and oil-repellent agent for coated foldable paper, its preparation method, and its application. The water- and oil-repellent agent for coated foldable paper provided by this invention has good folding stability and retains its oil-repellent properties after bending.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a water- and oil-repellent agent for coated foldable paper, comprising the following components by weight: 8-10 parts of O-carboxymethyl chitosan; Nanocellulose 1.5~4.5 parts; 1-3 parts of nanocellulose crystals; 0.5-0.7 parts of nano-silica; 5-15 parts of ammonium citrate buffer solution; 2-6 parts of polycarbodiimide solution; Glycerin 0.1 to 2 parts; 40-100 parts water.

[0006] Preferably, the degree of substitution of the O-carboxymethyl chitosan is 0.6 to 1.2; and the degree of deacetylation of the chitosan used to prepare the O-carboxymethyl chitosan is ≥90%.

[0007] Preferably, the length of the nanocellulose is 1~10 μm; The length of the nanocellulose crystals is 100~500nm.

[0008] Preferably, the nano-silica is silane coupling agent modified nano-silica, and the particle size of the nano-silica is 10~50nm.

[0009] Preferably, the mass concentration of the polycarbodiimide solution is 20-30%, and the molecular weight of the polycarbodiimide is ≥5000.

[0010] This invention provides a method for preparing the above-mentioned water- and oil-repellent agent for coated foldable paper, comprising the following steps: Nanocellulose, nanocellulose crystals and the first part of water are mixed to obtain a nanocellulose-nanocellulose crystal dispersion. O-carboxymethyl chitosan, ammonium citrate buffer, nanocellulose-nanocellulose crystal dispersion, glycerol, nano silica, polycarbodiimide solution and the remaining water were mixed and dispersed to obtain a water- and oil-repellent agent for coated foldable paper.

[0011] Preferably, the mass ratio of the first portion of water to the remaining portion of water is 10~30:30~70; The dispersion process is ultrasonic treatment and / or homogenization treatment.

[0012] This invention provides the application of the above-mentioned water and oil repellent agent for coated foldable paper in packaging materials.

[0013] This invention provides a water- and oil-repellent slurry for coated foldable paper, comprising the following components by weight: 40-60 parts of water- and oil-repellent agent; 1-5 parts starch; 80-120 parts water; The water- and oil-repellent agent is the aforementioned water- and oil-repellent agent for coated, foldable paper.

[0014] This invention provides a water- and oil-repellent coated paper, comprising a paper substrate and a water- and oil-repellent slurry coated on the surface of the paper substrate, wherein the coating amount of the water- and oil-repellent slurry is 10~30 g / m². 2 .

[0015] This invention provides a coated water- and oil-repellent agent for foldable paper, comprising the following components by weight: 8-10 parts O-carboxymethyl chitosan; 1.5-4.5 parts nanocellulose; 1-3 parts nanocellulose crystals; 0.5-0.7 parts nano silica; 5-15 parts ammonium citrate buffer; 2-6 parts polycarbodiimide solution; 0.1-2 parts glycerol; and 40-100 parts water. This invention utilizes the cross-linking properties of polycarbodiimide with carboxyl groups and the esterification reaction of carboxyl and hydroxyl groups to form a cross-linked system on the paper surface. O-carboxymethyl chitosan provides oil resistance, while polycarbodiimide and nano silica provide water resistance, forming a water- and oil-repellent coating. Due to its cross-linking structure, the water- and oil-repellent coating of this invention exhibits stronger toughness and stability, with minimal decrease in oil resistance after bending. Specifically, in this invention, O-carboxymethyl chitosan is the main material providing water and oil resistance, and its structure itself possesses oil-repellent properties. Polycarbodiimide, acting as a crosslinking agent, can react with the carboxyl groups of O-carboxymethyl chitosan to form a crosslinked network structure, providing flexibility and flexural strength. Nanocellulose and nanocellulose crystals, with their nanoscale size, can fill the tiny pores in paper, reducing the permeability of water and oil. Nano-silica acts as a pore filler and enhances water repellency. The acidic citrate buffer solution provides stability to the water and oil repellent agent; furthermore, the carboxyl groups of citric acid in the buffer solution can react with polycarbodiimide to form a crosslinked network, further improving the flexural strength of the water and oil repellent agent. In this invention, the glycerol not only provides flexibility, but the hydroxyl groups in glycerol also undergo a certain esterification reaction with the carboxyl groups of citric acid, participating in the formation of a crosslinked network structure.

[0016] In this invention, polycarbodiimide, O-carboxymethyl chitosan, ammonium citrate buffer, and glycerol have a synergistic cross-linking effect. If only polycarbodiimide and O-carboxymethyl chitosan are used, a cross-linked network structure can also be formed, but the flexibility is somewhat poor. After adding ammonium citrate buffer and glycerol to the system, a more complex cross-linked network structure is formed. Its initial oil resistance will decrease slightly, but its flexibility and bending resistance will be improved. This is reflected in the fact that the oil resistance decreases less after bending and pressurization.

[0017] The results of the examples show that the water- and oil-repellent agent of the present invention requires a thin coating thickness of 14~16 g / m². 2 It can achieve a kit value of 9 for oil repellency. The water and oil repellent agent of this invention is fluorine-free, which has the advantage of being green and environmentally friendly. It also has excellent bending stability. After the bending test, the oil repellency decreases, but it can still maintain a kit value of 6 or higher for oil repellency. Detailed Implementation

[0018] This invention provides a water- and oil-repellent agent for coated foldable paper, comprising the following components by weight: 8-10 parts of O-carboxymethyl chitosan; Nanocellulose 1.5~4.5 parts; 1-3 parts of nanocellulose crystals; 0.5-0.7 parts of nano-silica; 5-15 parts of ammonium citrate buffer solution; 2-6 parts of polycarbodiimide solution; Glycerin 0.1 to 2 parts; 40-100 parts water.

[0019] The water- and oil-repellent agent for coated foldable paper provided by this invention, by weight percentage, comprises 8-10 parts of O-carboxymethyl chitosan, preferably 8.5-9.5 parts, more preferably 9 parts. In this invention, the degree of substitution of the O-carboxymethyl chitosan is preferably 0.6-1.2, more preferably 0.8-1.0; the degree of deacetylation of the chitosan used to prepare the O-carboxymethyl chitosan is preferably ≥90%, more preferably 92-95%. In this invention, the O-carboxymethyl chitosan contains carboxyl groups, which can react with a polycarbodiimide crosslinking agent to form a crosslinked structure.

[0020] Based on the mass fraction of O-carboxymethyl chitosan, the water- and oil-repellent agent for coated, bend-resistant paper provided by this invention comprises 1.5 to 4.5 parts of nanocellulose, preferably 2 to 4 parts, and more preferably 3 parts. In this invention, the nanocellulose is preferably cottonseed hull nanocellulose, the length of the nanocellulose is preferably 1 to 10 μm, more preferably 0.5 to 5 μm, further preferably 2 to 4 μm, and the diameter of the nanocellulose is preferably 2 to 20 nm, more preferably 5 to 10 nm.

[0021] Based on the mass fraction of O-carboxymethyl chitosan, the water- and oil-repellent agent for coated, fold-resistant paper provided by this invention comprises 1-3 parts of nanocellulose crystals, preferably 1.5-2.5 parts, and more preferably 2 parts. In this invention, the nanocellulose crystals are preferably cottonseed hull nanocellulose crystals, the length of the nanocellulose crystals is preferably 100-500 nm, more preferably 200-400 nm, and the diameter of the nanocellulose crystals is preferably 5-30 nm, more preferably 10-20 nm. In this invention, the nanocellulose and nanocellulose crystals work together to fill the tiny pores in the paper.

[0022] Based on the mass fraction of O-carboxymethyl chitosan, the water- and oil-repellent agent for coated foldable paper provided by the present invention comprises 0.5 to 0.7 parts of nano-silica, preferably 0.6 parts. In the present invention, the nano-silica is preferably silane coupling agent modified nano-silica, and the silane coupling agent is preferably γ-methacryloyloxypropyltrimethoxysilane. In the present invention, the particle size of the nano-silica is preferably 10 to 50 nm, more preferably 20 to 40 nm, and the nano-silica serves to fill pores and improve water repellency.

[0023] Based on the mass fraction of the O-carboxymethyl chitosan, the water- and oil-repellent agent for coated foldable paper provided by the present invention comprises 5-15 parts of ammonium citrate buffer, preferably 8-12 parts, and more preferably 10 parts. In the present invention, the pH value of the ammonium citrate buffer is preferably 3-6, more preferably 4-5; in the present invention, the preparation method of the ammonium citrate buffer preferably includes the following steps: Citric acid, ammonia, and water are mixed to obtain ammonium citrate buffer solution.

[0024] In this invention, the mass concentration of the ammonia water is preferably 25%, and the mass ratio of the citric acid, ammonia water and water is preferably (1~3):(0.7~2.1):(3~10), more preferably 1:0.7:3.3.

[0025] In this invention, the ammonium citrate buffer solution is acidic, providing stability to the water and oil repellent agent for coated foldable paper. The carboxyl groups of citric acid can also react with polycarbodiimide to participate in the formation of a cross-linked network. If pure citric acid is used instead of the ammonium citrate buffer solution, the stability will decrease.

[0026] Based on the mass fraction of O-carboxymethyl chitosan, the water- and oil-repellent agent for coated foldable paper provided by the present invention comprises 2-6 parts of a polycarbodiimide solution, preferably 3-5 parts, and more preferably 4 parts. In the present invention, the mass concentration of the polycarbodiimide solution is preferably 20-30%, more preferably 25%, and the molecular weight of the polycarbodiimide is preferably ≥5000, more preferably 5000-10000. In the present invention, the solvent of the polycarbodiimide solution is preferably water.

[0027] Based on the mass fraction of O-carboxymethyl chitosan, the water- and oil-repellent agent for coated foldable paper provided by the present invention comprises 0.1 to 2 parts of glycerol, preferably 0.5 to 1.8 parts, and more preferably 1 to 1.5 parts. In the present invention, the glycerol not only provides flexibility, but the hydroxyl groups in the glycerol may undergo a certain esterification reaction with the carboxyl groups of O-carboxymethyl chitosan and citric acid, participating in the formation of a cross-linked network structure.

[0028] Based on the mass fraction of O-carboxymethyl chitosan, the water- and oil-repellent agent for coated foldable paper provided by the present invention comprises 40 to 100 parts of water, preferably 50 to 80 parts, and more preferably 60 to 70 parts.

[0029] In this invention, the preparation method of the water- and oil-repellent agent for coated foldable paper includes the following steps: Nanocellulose, nanocellulose crystals and the first part of water are mixed to obtain a nanocellulose-nanocellulose crystal dispersion. O-carboxymethyl chitosan, ammonium citrate buffer, nanocellulose-nanocellulose crystal dispersion, glycerol, nano silica and the remaining water were mixed and dispersed to obtain a water- and oil-repellent agent for coated foldable paper.

[0030] This invention involves mixing nanocellulose, nanocellulose crystals, and a first portion of water to obtain a nanocellulose-nanocellulose crystal dispersion. In this invention, based on the mass fraction of O-carboxymethyl chitosan, the mass fraction of the first portion of water is preferably 10-30 parts, more preferably 15-25 parts. This invention does not impose any special requirements on the mixing method; any mixing method well-known to those skilled in the art can be used, such as stirring.

[0031] This invention involves mixing O-carboxymethyl chitosan, ammonium citrate buffer, nanocellulose-nanocellulose crystal dispersion, glycerol, nano-silica, polycarbodiimide solution, and the remaining water, followed by dispersion treatment to obtain a water- and oil-repellent agent for coated, bend-resistant paper. In this invention, the mass ratio of the first portion of water to the remaining portion of water is preferably 10~30:30~70, more preferably 15~25:40~60. In this invention, the temperature of the remaining portion of water is preferably 40~50℃.

[0032] In this invention, the preferred method of mixing is: (1) First, mix O-carboxymethyl chitosan with the remaining water and stir to obtain a premixed solution; (2) Add ammonium citrate buffer, nanocellulose-nanocellulose crystal dispersion, glycerol, nano silica, and polycarbodiimide solution to the premixed solution while stirring.

[0033] In this invention, the stirring rate in steps (1) and (2) is preferably 500~2000 r / min, more preferably 800~1500 r / min.

[0034] In this invention, the power of the ultrasonic treatment is preferably 1000~1500W, more preferably 1200~1400W, and the time is preferably 30s~2min, more preferably 1min; the homogenization treatment is preferably 15~30MPa cycled 1~3 times.

[0035] This invention provides the application of the above-mentioned water and oil repellent agent for coated foldable paper in packaging materials.

[0036] This invention provides a water- and oil-repellent slurry for coated foldable paper, comprising the following components by weight: 40-60 parts of a water- and oil-repellent agent for coated foldable paper, preferably 45-55 parts, more preferably 50 parts; 1 to 5 parts of starch, preferably 2 to 4 parts, more preferably 3 parts; The water content is 80-120 parts, preferably 90-110 parts, and more preferably 95-100 parts.

[0037] In this invention, the gelatinization temperature of the starch is preferably 80~100℃, more preferably 90℃, and the gelatinization time is preferably 30~60min, more preferably 30~45min.

[0038] In this invention, the method for preparing the water- and oil-repellent slurry for coated foldable paper preferably includes the following steps: Starch and water are mixed to obtain a starch slurry; Add a water- and oil-repellent agent for coated foldable paper to the starch slurry, stir and mix to obtain a water- and oil-repellent slurry for coated foldable paper.

[0039] In this invention, the preferred temperature for mixing the starch and water is 90°C, and the preferred mixing time is 1 hour.

[0040] This invention provides a water- and oil-repellent coated paper, comprising a paper substrate and a water- and oil-repellent slurry coated on the surface of the paper substrate. The water- and oil-repellent slurry is the aforementioned water- and oil-repellent slurry for coated foldable paper, and the coating amount of the water- and oil-repellent slurry is preferably 10~30 g / m². 2 More preferably 14~21 g / m 2 Further preferred is 14~16 g / m 2 This invention does not have special requirements for the paper substrate; any paper substrate well-known in the art can be used. In this invention, the coating is preferably double-sided coating, and after coating, it is preferably dried and calendered. The drying temperature is preferably 90°C, and the calendering temperature is preferably 100°C.

[0041] The following detailed description, in conjunction with embodiments, illustrates the water- and oil-repellent agent for coated foldable paper provided by the present invention, its preparation method, and its application. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0042] Examples 1-9 The raw materials and dosages of the water- and oil-repellent agents for coated foldable paper in Examples 1-9 are shown in Table 1.

[0043] Table 1. Raw materials and dosage (parts by mass) of water- and oil-repellent agents for coated foldable paper in Examples 1-9.

[0044] In Examples 1-9, the degree of substitution of O-carboxymethyl chitosan was 0.9, and the degree of deacetylation of the chitosan raw material for preparing O-carboxymethyl chitosan was ≥90%. The length of cottonseed hull nanocellulose is 2~4μm and the diameter is 2~20nm; the length of cottonseed hull nanocellulose crystals is 200~400nm and the diameter is 5~30nm. The nano-silica is nano-silica with a surface modified by γ-methacryloxypropyltrimethoxysilane, and the particle size is 10~50nm; The polycarbodiimide solution contains 25% polycarbodiimide by mass and has a molecular weight ≥5000. Ammonium citrate buffer solution is prepared by mixing citric acid, 25% ammonia solution and water in a mass ratio of 1:0.7:3.3.

[0045] The preparation method of the water- and oil-repellent agent for coated folding paper in Examples 1-9 adopts the following steps: Cottonseed hull nanocellulose, cottonseed hull nanocellulose crystals and the first part of water were stirred and mixed to obtain a nanocellulose-nanocellulose crystal dispersion. O-Carboxymethyl chitosan was added to water at 50°C and dissolved by high-speed stirring at 1000 r / min to obtain a dispersion. While stirring, ammonium citrate buffer, cottonseed hull nanocellulose-nanocellulose crystal dispersion, glycerol, nano silica, and polycarbodiimide solution were slowly added. Then, the mixture was sonicated at 1400 W for 1 min to prepare a stable dispersion, thus obtaining a water- and oil-repellent agent.

[0046] Application examples The water- and oil-repellent agents prepared in Examples 1-9 were uniformly dispersed in starch paste. The preparation method was as follows: 3 parts starch and 97 parts water were mixed and stirred at 90°C for 1 hour to obtain starch paste. Then, 50 parts of the water- and oil-repellent agent were added, and the mixture was stirred and dispersed evenly to obtain a water- and oil-repellent slurry. The slurry was then coated on both sides of paper with a basis weight of 25 g / m². 2The thickness is 30 μm. The specific preparation method of the sample is as follows: first, a single-sided coating is applied and dried at 90℃, then the other side is coated and dried at 90℃, and finally calendered at 100℃ to obtain water- and oil-repellent coated paper. The coating amount is controlled at 14~16 g / m². 2 .

[0047] The water- and oil-repellent agents obtained in Examples 1-9 were applied according to Examples 1-9, with an untreated paper set up as a blank control. Oil resistance tests and oil resistance tests in folded areas were then performed. Oil resistance was evaluated using the Kit value, and water resistance was evaluated using the Cobb value. The national standard for the Kit value is GB / T 22805.2-2008, "Determination of Grease Resistance of Paper and Paperboard - Part 2: Surface Repulsion Method". The national standard for the Cobb value is GB / T 1540-2002, "Determination of Water Absorption of Paper and Paperboard - Cobb Method". The method for the oil resistance test in folded areas was as follows: the coated paper was folded in half sequentially, and a 1kg weight was applied to one folded area for 2 minutes. After unfolding and flattening, the oil resistance performance was tested at the fold. The data obtained were the average of three test groups, and the results are shown in Table 2.

[0048] Table 2. Water and oil repellency test results for application examples 1-9

[0049] As shown in Table 2, an initial Kit value of 6 or above can achieve a grade of 9, and a Kit value of 6 or above after bending can achieve a grade of 8. The optimized formulation has better bending resistance and oil resistance.

[0050] Using the water- and oil-repellent agent obtained in Example 1, a coating with a thickness of 9-11 g / m was prepared according to the same treatment method. 2 Application Example 10: Coating thickness is 19~21 g / m 2 Application Example 11: Coating thickness is 24~26 g / m 2 Application example 12, the test results of waterproof and oil-proof performance are shown in Table 3.

[0051] Table 3. Water and oil repellency test results for application examples 10-12

[0052] As can be seen from Table 3, a low coating thickness leads to a decrease in oil resistance, while a high coating thickness can increase the initial Kit value to level 10. However, the Kit value at a single bend remains at level 8, and there is no further improvement in bending resistance.

[0053] Comparative Example 1 By replacing the O-carboxymethyl chitosan in Example 1 with chitosan with a deacetylation degree of over 90%, and keeping other conditions unchanged, a water- and oil-repellent agent was obtained. Application Example 13 was prepared according to the method described in the application examples.

[0054] Comparative Example 2 By removing the polycarbodiimide from Example 1 while keeping other conditions unchanged, a water- and oil-repellent agent was prepared. Application Example 14 was prepared according to the method described in the application examples.

[0055] Comparative Example 3 The amount of O-carboxymethyl chitosan in Example 1 was increased by 5 parts, for a total of 14 parts, and the amount of water was reduced by 5 parts, while other conditions remained unchanged, to prepare a water- and oil-repellent agent. Application Example 15 was prepared according to the method in the application examples.

[0056] Comparative Example 4 The amount of O-carboxymethyl chitosan in Example 1 was reduced by 5 parts, a total of 4 parts were added, and the amount of water was increased by 5 parts, while other conditions remained unchanged, to prepare a water- and oil-repellent agent. Application Example 16 was prepared according to the method in the application examples.

[0057] The test results of the waterproof and oil-repellent properties of Application Examples 13-16 are shown in Table 4.

[0058] Table 4. Water and oil repellency test results for application examples 13-16

[0059] As shown in Table 4, replacing O-carboxymethyl chitosan with chitosan significantly reduced the flexural resistance and oil repellency. Without polycarbodiimide participating in the formation of the cross-linking structure, the initial oil repellency decreased, and the flexural resistance and oil repellency also significantly decreased. Increasing the amount of O-carboxymethyl chitosan by 5 parts reduced the initial oil repellency, while decreasing the amount of O-carboxymethyl chitosan by 5 parts resulted in a substantial decrease in overall oil repellency.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A water- and oil-repellent agent for coated folding-resistant paper, characterized in that, Based on parts by weight, it includes the following components: 8-10 parts of O-carboxymethyl chitosan; Nanocellulose 1.5~4.5 parts; 1-3 parts of nanocellulose crystals; 0.5-0.7 parts of nano-silica; 5-15 parts of ammonium citrate buffer solution; 2-6 parts of polycarbodiimide solution; Glycerin 0.1 to 2 parts; 40-100 parts water; The degree of substitution of the O-carboxymethyl chitosan is 0.6~1.2; the degree of deacetylation of the chitosan used to prepare the O-carboxymethyl chitosan is ≥90%. The nanocellulose is cottonseed hull nanocellulose, and the length of the nanocellulose is 1~10μm; The nanocellulose crystals are cottonseed hull nanocellulose crystals, and the length of the nanocellulose crystals is 100~500 nm. The mass concentration of the polycarbodiimide solution is 20-30%, and the molecular weight of the polycarbodiimide is ≥5000; The pH value of the ammonium citrate buffer solution is 3-6.

2. The water- and oil-repellent agent for coated foldable paper according to claim 1, characterized in that, The nano-silica is silane coupling agent modified nano-silica, and the particle size of the nano-silica is 10~50nm.

3. The method for preparing the water- and oil-repellent agent for coated foldable paper according to claim 1 or 2, characterized in that, Includes the following steps: Nanocellulose, nanocellulose crystals and the first part of water are mixed to obtain a nanocellulose-nanocellulose crystal dispersion. O-carboxymethyl chitosan, ammonium citrate buffer, nanocellulose-nanocellulose crystal dispersion, glycerol, nano silica, polycarbodiimide solution and the remaining water were mixed and dispersed to obtain a water- and oil-repellent agent for coated foldable paper.

4. The preparation method according to claim 3, characterized in that, The mass ratio of the first portion of water to the remaining portion of water is 10~30:30~70; The dispersion process is a homogenization process.

5. The application of the water- and oil-repellent agent for coated foldable paper as described in claim 1 or 2, or the water- and oil-repellent agent for coated foldable paper prepared by the preparation method described in claim 3 or 4, in packaging materials.

6. A water- and oil-repellent slurry for coated foldable paper, characterized in that, Based on parts by weight, it includes the following components: 40-60 parts of water- and oil-repellent agent; 1-5 parts starch; 80-120 parts water; The water- and oil-repellent agent is the water- and oil-repellent agent for coated foldable paper as described in claim 1 or 2, or the water- and oil-repellent agent for coated foldable paper prepared by the preparation method described in claim 3 or 4.

7. A water- and oil-repellent coated paper, characterized in that, The paper substrate includes a water- and oil-repellent slurry coated on the surface of the paper substrate. The water- and oil-repellent slurry is the coated water- and oil-repellent slurry for foldable paper as described in claim 6, and the coating amount of the water- and oil-repellent slurry is 10~30 g / m². 2 .

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